Document 6BMaZ9bqw68nVRE01OdO6O2rd

e prunin'" being piesenlcd by The General Tire & llulil'ti Company for the 'ra'^oT .A. 1 ,Ch. K. in thin one day seminar ia concerned only with M'olyvinyl Chloride, Mannforture and Technology.* The importante of this plastic in the United States is evidenced h\ a consumption now approuching neaily (wo In I I ion unda per year, We have attempted to set up the day's program to raciv you rough the early history of PVC, present day technology, including vinvl r^dai.monomer synthesis, polymerization theory, anti plant scale manufacturing polyvinyl chloride resin. Some of the technology used to pruduce useful end odii^tn.is discussed. We have tried to meite this presentation, which imludea proprietary engineering data, the- moat up-to-date and comprehensive treatit of this subject mallei available. jteral Tire entered the plastica fabrication field in the earlv 1950's on a rge' scale by acquisition of several manufacturing facilitica located in ioj Eennsylvania, and Massachuaetta. Theae facilities made General Tire the largest calender operator for vinyl in thu United Slates. Products 'T^,3Sltnuf*etuTed in these plastic plsnts include calendered, printed, and embossed . supported and unsupported vinyl film and sheeting for the home furnishings, , - .ferine, shoe, and automotive arceaaory industries'. A new plant in Columbus, Mississippi, u mullimillion dollar inveatment in plastic operstiona, went on stream late .in 1963. .4 .' In 1954, General Tire built a plant at Ashtabula, Ohio, to produce vinyl '* chloride from acetylene and hydrochloric arid and to produce polyvinyl chloride resins by the suspension polymerisation method. This plant ia now undergoing its third major ekpanaion. Gene ml Tire is thus veiricatly integrated in the vinyl field from monomer synthesis through pulymer11 a11 on and, finally, is a supplier of ait types of plastic end products or accessories In several major industries. General Tire's capabilities in pluttii fabrication, in addition to vinyl upp11 catinna, include reinforced polyester plastics, thermoplastic nd products, and poly urethane plastic foam for all kinds of cushioning appI i ca( 1 ona. t Sr i* 1 .. i ucc 013288 III STUBY OK POLY.VINY Vi n.c I list t4|{^wr^cri^a*|<er-jyj#iu44*#4iA a ted by.itfe*bJ^*p**viny 14* or "vinyl rt?|i iv P.9iY*i"Y'44<jlSri<1*?* <*'-KiK- i?i# produce)! on a global basis iin.l 1.1 niriirMd under many t milt iu#t iiich Yinylu#*;. Gruni, C.orvic VwnJur, Vi nnoi, Pliovir, Muivinol, Opal oil, ' anf Genera I'Ti rt* s Vygens. lb it PVF. liar risen l.o such an import mil place m lhi` economies ol several nations i due lo a great deal .if technical work done in ibis field. The nerd of a rubber substitute as well aa urtilicial leather mid aiiulhrr rellnloid si art ed i, be reseaicii i'i iinmuiiv. With the advent of the war, England lilnO' ai rr,puied In find a rubber substitute, particularly for the wire and inble industry. The development of special forma of the poLymera such aa plaatisolv during the later war years led to the coating of textiles for the manufacturer of leatberlike cloth pioducta. By the end of the war, good plaslisol polymers were available and from 1948 the standard types of PVC suspension, emulsion, polymers and copolymers were being made in increaaing tonnage. The period 1950-1955 throughout the world saw the development of unproved polymers.- Fallowing this period, major price reductions' were made and this, together with the improved polymers for special appIii atinna and implored process techniques, have all contributed to the amaaing growth in onsoinpLion over the paat twenty years. The early beginnings can be traced back to 1835 when M. V. Hegnault*** published his findings on Lhe reaction of an alcoholic solution of caustic potash'on the ethylene dihalidea to yield the monomer vinyl chloride according *o the following equal ion: cH2Gi-ai2oi koh ~> ai2 - an:i <- im> kci He also observed that when the mixture was allowed to aland for a Lime, and siiharquent1y heated and exposed to sunlight, a white precipitate formed. Several ruviava^* have covered in considerable detail the development of polyvinylchloride. M. Kaufmen*''' presents an i nl e r:a t I ng review n| the development of polyvinylchloride in Fngland. Almost 40 years later. IH72, Oi . E. Baumann*** published hia observations that vinyl bromide as well i.i vinyl chloride in sealed tubes exposed to sunlight, thatiged from liquids to 1igbl-roI ored solids. He also observed that these materials were extremely chemically resistant to acids, alkalies, and solvents. The next significant steps are described in papers by 1. Oarromislensky.*^'* ** * The first ne, published in 1912, >m entitled "Concerning the Structure ol Polymerized Vinyl Bromide and Its Rubber." He observed the reaction nf ultraviolet light on the polymerization of vinyl chlotide and vinyl bromide to yield three different modifications, and on the tiusis of their so I nb i I 11 it-, b>diviJcd them into alpha, beta, and gamma forms and considered that the degree of |>o1ymerization was the highest with the most insoluble or gamme form. The most insolnhle or gamma isomer was called Kaupren bromide and Kuupreu chloride, and served' for the basis of determining the cryoscnpic molecular weight and resulted in the empiriral formula {C^ll.^altr(6) or {(.'32**48^ 1$^ which showed that Iti vinyl halides had been definitely combined. %4i 1- UCC 013289 40 C3^HCl' ji.` -- . l6_.l##^IB^-*C32H4gBr16. + V `'4 Ai .iIkmii <(n: same time, 1912, Osi rum i s l en sky anil others^' applied foi a Itruisli Patent entitled *A I'lun'ss fot Obtaining lliihhcr or hiiutlur NiI^uik i-s from Polymerized Vinyl llromide or Polymerized Vinyl Chloride and Their Mnliyl Homo log-. " It was stated lhat the po1ymerited vinyl chloride or vinyl bromide is ideal ual in all its piuperties with the chloride or bromide of the "Ihil ml i i or " i libber fi. They also noted the uctiou of sunlight and the al-seme 111 oxygen in nr re 1 e r at i ng this rearlion. It was observed that the po 1 vm- r i rat i m, run I d easily be effected in solution, in bromoben acne, toluene, xyli'ii" or r a r bo n disulfide. l.ater Ost roisl * 1 ensky ' *" ' received u pal nil on a pine ess for obtaining vinyl chloride from acetylene. Also in 1929, he received a llritishfa tool * 1 1 * 'The Preparation of PVC and the Application of Plasticizers silt li as dn hIorhenaene,. chlorinated naphthalene in order to work the material into plastic masses and films. In I9I'2, f, Klatte**"* was issued u German Paient for 'The Synthesis of Vinyl Chloride by ihe Reaction of HCl and Acetylene.* In an analogous reaction, be likewise made vinyl' acetate. These syntheses still today are the main onca for the commercial production of these monomers. Klutte and others^*'*' obtained a Patent for the 'Processing und Preparation of Horny Materials, Fi Iras, Synthetic Fibers, l.ucquers, and Working of I'laaiic Materials.' They also recognised at this time tliar, with or without additives, through pressure or with solvents, PVC could he softened or dissolved so that it could lie worked into a desirable shape or form. In l'<28, three groups working independently developed vinyl chloride cnpolymeiH. The use of vinyl acetate as a copolymer in the. po I vme r i z at I on of vinyl <blorid>' greatly ini-loused t.he use of the vinyl polymers lierniisi- i* solved the proiesuiog difficulties of the straight homopolymera. The three groups: E. W. MmP * from Carbide and Carbon, Voss und l)i okhaiiser ^ from I. G. Fa rben i ndust i i , and W. K. I.awson from DuPont,* ^ all obtained patents on their processes. A little later, W. L. Semon^*^^ iliscloaed that a ruhlie.r-I I ke gel stiioture inuld be obtained by intimately mixing a high boiling point material like tr i 1 ol v Ipbosphal e into the polymer. Th i a was I .-iter I'nljnaed by oibei plasLicizcis anil resulted in a product culled *Koro sea I " * * and has served as a basis for the development of thin new claas of materials. The first commercial polymerization process of vinyl chloride resulting ftOm technical unplications is credited t.o Lawson and Worm /. of F,. I. DuPont deNemnurs* who, in the year 1928, showed that peroxide catalysis si,rb us ozone, benzoyl peroxide sad barium peroxide could lie used. In the earlier patents only the action of light and heal were described. The fhtPont process could likewise be used in organic solvents. The application of emulsion processes for vinyl t-Moride polymerizations resulted in a rapid development of PVC preparation ami applications. Thioldext emulsion po l yme r i r at. I on process of vinyl rhiocidc is that of Marks Fikentscher, Hongslenherg, and V. Sysich.^*** A further Silvnnrc was the I. G. process of (tapper! and Wick*^ for 'Cont inuous Emulsion I'ol ymeri zut ion. " -2- . t--*>, .*' UCC 013290 The effect -of oxygen op air on ihe^eourae of' the polymeriration was later tecogntzed by Schunfeld. .* * Tlii* oldest suspension process, although not using vinyl (hloride, appears to Le Lli.tl of Crawford and MrGrutli, * who developed a suspension process for* a scries of Ji.ryj >ii| vinyl caters. The first, suspension I'VC resins were made by l)r. Ileig*-'^ l-.** 0| Wucker-Chemie in 1035 in which he employed partially saponified polyvinyl acetate (polyvinyl alcohol) as the protective colloid. In the suspension process, the PVC is formed in polymeriration into a granular powder in on easily.filterable form. 'Ztf? * The future oI PVC as well us the past is linked to the appropriate balance of rrscarth and development. Kurther expansion and growth ol the PVt. industry is dependent on a greater knowledge of .ill basic behavior and improved processing t echo l ijue-s. Where me industry now stands in this country is shown in the following Table* 1 slid 2 of monomer and polyvinyl chloride resin production Capacities, Table 1 Estimated Vinyl Monomer, U. S. Capacity, 1964 B. K. Goodrich Union Carbide Kt Kyi Corporation Dow Chemical Teiincco (Cary Chemical) Allied Chemical Monochem (Burden A ti. S. Hubber) Monsanto Diamond Alkali Goodyear Cumberland Chemical iAircu) General Tire American Chemical Capacity-Mi I lions of Pounds Annually too 2#0 240 200 170 150 150 ISO 00 45 60 .10 40 2025 3- ucc 013291 Capacily*MiJlioim of Pounds Anrniu 11 y___ B. F. (ioodritli Union Carbide Monsanto Chemical Caty Chemical Firestone Tire A Butiber Diamond Alkali Air Deduct ion II. S. (lubber Goodyear IT re & Rubber Borden Chemical Thompson Chemical General Tim A Rubber Pontusute Cnntpany Dow Chemical Escambia Chemical Atlantic Re fining Atlantic Tubing Keysor Chemical Great American Plaalica American Chemical Rubber Corporation of America Mniiieaota Mining A Manufacturing .125 275 150 I 10 125 120 115 110 80 80 65 55 50 40 40 25 25 25 IS 12 10 5 1887 l.i terature References (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) M. V. Ileguault, Liebigs Ann. Chem. 1_5 (JB35) 85 c. E. Selli ldkneeiit, "Vinyl and Related Polymers,* Wiley and Sons (1952) F. Knim-r, "Po 1 y v i ny I rli I ir i d and V i tiy 1 eh I nr i d-Mi .srhpo I ymer i a ate, * Springer-Ver1ug (1V5II Karl Krelyelrr and (iVnrg Wick, "Kuntatoff-llandbuch" Hand II Toil l, Karl Hanaer-Vr 1 ag (|9f>3) M. Kaufman, *The First Century of Plastics," P. 74, Plastics Institute, London, 1983 K. Ruumsnn Liebigs Ann. Chem. 163 ( 1872) 312 1. Ostrumisiensky, ,1. ilusa. I'hys. Chem. Gea. U ( 1912) 204-239, die Zentral, 1912, 1, I9h0 I. Ostromislenaky, .1. Russ. Phv. Chem. fin, 4B^ (1918), 1132-5), Chem Zentrsl, 1923, IV, 806 B. P. No. 8299 (Oatromtslensky and Others) (1912) U.S.P. No. 1.54!,174 (Ostromialenaky) (1925) B, P. No. 255,837 l()nt romi slenskv) ( 1925) O.R.P. No, 278,249 F. Klatte (1912) D.R.P. No. 281,877 F. Klatte (1913) U.S.P. No. 1,935,577 K. W. Reid (1920) -4- - O' ucc 013292 vc ? -rafc*-"' (15) lift(17) do) (19) (JO) (21) (22) (23) (24) (25) 177 Vdis arf ii.s.p^-jio.f.i.-a&juiJU II. >o/'^7!fwTlw1. *t*(1935) )vU928) ii.s.p:1 No. t). P. No. 319, S$1 Lawaott^a "rnti (1928) li.S.P. No. 2,068,424 Mark, Fikentarher, Hmgnlenberg, and Susith () (1. Karben ind.) (1937) D. H.P. No. 679,897 lUppert and Wick (1936 U..S.P. No. 2,168,808 Schonfeld (H. F. Goodrich) (1937)' U.,l.s.p. No. 2,108,044 Crawford and McGrath, IC1 (1933) D IIP. No. 750,428 Her# (Wacker-Chemie) (1935) D.R.P. No. 7.55,028 Derg (Wacker-Cheiaie) (1935) W #" *.ak' ,, 44 5 ucc 013293 4 piiwi^p.ipi m i" mi vHEumpp11 Min w ii mmmmK/*- I t jun I'UKUHV UK KJLYMKH1 7AT10N - -V. Hus |>,.|.cr i ^ an ii.troini i ion lu po 1 ymer *ut i on terminology as applied m the KituMi, ami n*>( linn i :iina ii.v-lved in the synthesis nl m.w rouio I ecu 1 en. The jhi1 r n i a i i mi will In- .ii a gt-iit-rul nature to help von bolter umlrr mi and the in l 1 -I I hi; |< r i s t-n l a t i mi - wliuh deal spec i f i r a I 1 y with t bo i (iraimTi'I d I preparation o f |.o I y v i nv I Ii i o i 1 ill-. Do I i n i t ion I'd I ihi: r s ait- Ii i (<!i mo 1 i-i u I a i weight materials i i-nsiil iii|i of ilia ins nl many i- piating -H, 11--. tin- p i,iii3.s r omii-it i tig sm.li units t iiuinomi-1 s ) into a chain ii culled poly fun i i nit ion. Through the process of po l yiucr i rut i on, a Variety of i i- ai tiii- g n so *, Ii,|uiJs, ami solids are converted into high Molecular weight muli-r i a Is which have been found to have unique physical properties of commercial i important I- an shown in Table I. There are two mum classes of react ions which are responsible lor the format ion nl tliL-dr. useful materials, po i y c.onden s u t i on and additinn polymerisation. The Similarities of these two classes of reactions arc- that they hutli lead to the formal ion nl long chains. The differences are based on the reactions involved, *hn!i are dependent on the type of monomer employed, t'o I y i ntidens at i on reactions protret! in a stepwise fashion involving iutermolecu 1 ar rondeuaation of dis similar functional groups, e.g., esterification to produce Dai ron. Addition polymeriration is a fast chain reaction involving monomers having one functional group such aa carboil-carhon double bonds to produce such materials as poly ethylene, In addition polynieriration, an active center rather than an organic functional group is responsible for the growth of the chain. Polymer molecules are formed from the beginning of the reaction nnd almost no species intermediate between monomer and high molecular weight polymer are found. The. ayntliesis of polymeric chains having molecular weights of several million are possible in addition polymerisation. There are three different types of active centers which can provide mechanisms of addition polymenration. These are: Free Medicals n (ial ions H0 Aniona M Suspension Polymeritation The traditional avenues by which monomers are converted t.o polymeis by a free radical mechanism are: -1- iiT-yvn^ ucc 013294 o to O vi iK.li.E ethylk.se HH c *C 1 HH V1NVL CHLORIDE HH 1t c =C 1 H Ci ACRYLONITRILE HH 1 C -c 1 H cs VINYL ACETATE HH I c *c 1 H0 1 C =0 STYRENE HK l1 c *c HA 0 BUTADIENE H It ii C.; C tI H CH I CH- Ai>f-n P-rl.iMFB rut i It F Cut 1 ETHU I.NE ti H It li h H it H tl H H H H M j ij -- c -- C -- C -- C -- c-- c -- c-- C -- C --C -- c -- C -- c --c-- 1 il 11 J H H It H H H H H H H H HH POLYVINYL CHLORIDE HHH 1 t1 -- c --c--c 1J H Ci H H H H It H H K it H H 1\ C -- c-- c -- c -- C - --- ^ --*"* C -- L -- c 1l1l1 Cl :t Cl 11 Cl H Cl H Cl H H 1 Cl POLYACRYLONITRILE HHHHHKHH H H HHHH -- C --C--C -- C -- c-- C ---C -- C -- C --C -- C --c ---C cs1 h CS II CS H CN tl CS H H CN H CLN POLYVINYL ACETATE It H H H K1 H Ht H H H H Ki H H -- C -- C --C -- C-- c-- C -- c -- C --c --C--C --c -- c --C -- i H 0 H 0 H 0 1 H 01 h I 0 1 H 0 1 H 0 C=0 CO CO c=o CO CO CO CH- A <A CH3 A A <A POLYSTYRENE HHHH iiii -- c --c --c --c H POLYBLTADIENE H H It H i i> -- c -- C-- ( -- c- 11,. H at H H I CH- ti HH H iii C --C --c ii CH H t CH- H H HH i i t ti i -C.; =C -c --c--c-- II I H CH H I CH- Str Pfii'.'li i' U. LSES l. i 11.MS 2. TURING i ife ' t 3. MOLDED OBJECTS ^ 4. ELECTRICAL IN^LLAT^ 1 SHEE1S 2. PlfOS.SOH.APH HECOR(^j 3. COPOLYMER ITH VINYIl* ACE FATE TO HAKE FLOcft COVF.RINGS. LATEX PAINT#, Fit. I. FIBFHS, F.li. , ORLON, * acrilan 1. CHE*INC GLAI 2. ADHESIVES 3. TEXTILE COATINGS 4. TO MAKE POLYVINYL ALCOHOL >(OS TREATMENT H1TH AtKALI MOLDED OBJECTS ELECTRICAL IN'LLATliA COPOLYMER *ITH BITVDIESE T MAKE lil\A-S AND ,',R-S Rl BRLV TO vu.i lON-EXUiANCE HE"IN' <0\ I REATX!KM *1TH SlLFLRIf AC 11 ' 1 RENA niBBER C V; i mmm m >! n v mm ihilk Cn 1) u,t r i tat I on \ pot ytuiT i ut iuii system iDiiUiiiiti|[ only Monomer and an initialing sprites. (!, ."v. i ui uni Polymerization \ |i Initn it.niiin system i n which the monomer is polymerized in the pirsenec ii f n sulvent. (,. Knnisi"n Polymerization '['hi'. I y me r i is t i on system is distinguished by tin* fuel Unit tin monomer is solubilized in water by a soap into mirmscoptr particles lulled nu relies, to form a stable colloidal emulsion. The |iulyim-n mum rest lion is initiated in llie micelles. The final product is an emulsified polymer system nailed a latex. 0. Suspension t'ul ymeri sal ion The dispersed monomer phase in waLer is of macroscopic aiae and is the site uf rlie pulymerisat ion reaction. The final product is in the form of beads. The (lencra 1 Tire A Hubber Company employs the suspension polymerisation process fur tin.' commercial preparation of polyvinyl chloride. I'nl ymer i sat i uu of a monomer in sospensi mi is achieved by dispersing the mnnuiner in the form of smalt droplets in a non solvent medium (usually wain 1 by strong medium cal agitation .mil subjecting ibis monomer suspension to polymerising conditions. Tim size of the suspended monomer droplets ran be viirlrd over a wide range (0.01 - 0.S cm) and IS dependent Oil the monomer-to-waler ratio, the cate of mcclian11al agitation and the iuterfacial tension of the monomer droplets (width can be controlled by suspension stabilisers). The meclianits of forming suspensions of insoluble monomers in an aqueous system is illustrated .schematically in Kiguie I. Mechanical ugitation subjects the monomer to a viscous drag causing elongation lo a thread-like form with sub sequent degeneration into drops. Simultaneously, through I he rever.se pi ness of i in 1rat cure, the dtops tend to revert to the original mouomerir mass. In a simple medianics 1 suspension under a constant overall rate of shear, a dyuamit equilibrium is quickly eatablished. Clusters of globules held together by wenk residual forces, but not fused, tend in disperse under (lie disruptive stress of un agitated system. Kfieclive nil' face-act i vt* agents will de fl occu 1 at e these aggregates. With the ousel, (if po I yme r i t at I on and the HCiompery i ng increase in viscosity within the monomer droplets, there is greater resistance to distortion of droplets due to viscous drag but, uufoituu in ** Iy, u greater tendency toward aggregation through collisions with neighboring globules. The latter phenomenon is inmimtzcd by suspension stabilisers which are s.lc tivcly adsorbed at the interface forming u protective film of moleiuluc ptoportions. This is illustrated schematically by the enlarged dioplel in figure I supporting an adsorbed film of a suspension stabilizer. The mechanism of polymerization in suspension is I undaraeni aiIy identical to the other modes of poIymeri hition processes already ment ioned. * :i - ucc 013296 nnpw MUi M\l',. DiAUHAM <>l' STACKS r,K ni M'i'.HSION IN >l'.SI,h.VSlUN I'OI.YMKHI/ATION HlU \ . MtlMiMI-.H 5 {c 5-8 w 5' -o-5 - A(!l I ATIO.N ( Si IK Ml I )- to COAI.K.SCKNCK ! IN I KIlKAt I At. ' TKNMON f <j o( ^ o .i O I j.STAH I l.l/.tilt CI O O Q i o O () o O O / llowet ei , thr kinetic* oi pu 1 ywer t tat i on of vinyl chloride varies greatly with tin- process employed except ill the cases of the bulk snd suspension lyilrm line they are virtually identical. Tree H'l11 nI A free radical can be defined as a molecular species having an odd number of electrons, consequen1. Iy an unpaired electron. Such molecular species do not normally have a formal electronic charge as represented above for cations or unions. Free radicals can be produced in a number of ways including thermal or photoili.-mical decomposition of such compounds as: a. Organic Peroxides Benzoyl Peroxide OO _ C-O-O-Ca -- ^j) * -(^jj * 2 t2 b. llydrnperox i dea Cumene Hydroperoxide ai, CH, IJ ^ ^ -- C -- 0 - OH 4 ^ ^ -C -- 0' + OH ai. CH, -\- *<-/ ucc 013297 c. A to Compound;* Aaobisisobulyronitr i le monomer unit <o initiate the pulymeritation reaction. Primary fire radicals air Iras stable and nurr reactive than secondary free radicals, which are in turn less stable than tertiary free radicals. Phenyl radicals a2 JL([Hi) are more reactive than bensyl radicals ( )> end allyl radicals ^ <Ql (CI|2 =* CJl - Cllj ') are so stabilised that they are quite unreactive. Polymer list ion of Vinyl Monomers by free Hadicals It has been established that the scheme of reactiona ia as follows: The radicel ia generated thermally or by radiation and initiatea polymer 1taiion by adding to the monomer. The new radical formed grows by successive additions of monomer molecules to form polymer chein radicel. This polymer radical ceases to grow when two radicals interact and ere rendered inactive. Thera are also other ways in which a polymer radical can react. The polymer molecule nn attack a monomer in aucli a way aa to transfer the radical activity to the moiiumer but not add it to the chain. This is called chain transfer to monomer. Another reaction can occur when one polymer radical attacks another polymer radical or an inactive polymer chain and transfers its radical activity. This will result in branches being formed on the backbone of e polymer chain. When auch reactions occur to a high degree, c.rosalinked molecules are formed. . Chain transfer of a polymer molecule to monomer is very prevalent in vinyl chloride potymeriset ion as we will see later. Meciiatii sw of Free Uadi cal Po 1 ymer 1 rat 1 on of Vinyl Monomers All addition polymerisation reactions have three basic mechanistic steps in common, whether the reaction is carried out in bulk in the presence of a solvent or in a heterogeneous system such as anemulsion or suspension. These steps are: (a) Initiation, (b) Propagation, and (c) Termination. When a free radical is generated in the presence of a moiiumer, the radical will attack the double bond of the monomer in the following way: R H I radical source) R * CH4n * OI f X energy 2 H (free radical) >1 R - CH2 - C l X -5 UCC 013298 Hfp -a* 4* the r mi teal atproaches the double bond of the inyl aonoaer, one of the bonds Splits into two radical*: .* * N. H ` -> CII-> * ~v (31 i X The attacking t.idical combines with one of the electron* foraing bond, end e new free radical results. H : cji (1 I X Tbia then ia the initiation atop: The attack of a free radical on a aonoaer molecule. The propagation step is very aimilar in that the new radical foraed in the initiation atep attack* a second aonoaer unit and tha radical ia now propagated along a chain by successive aonoaer addition*. li ^ CH2 C i X H i CH2 " C HM Ii R . die C - die - C * I "I XX R - ch2 HH II - c - ch2 - c * ii XX + a ai2 H > "C i X -> R (dl2 H i - C) - ch2 i+n X II I -c t X Terainetion of the propagation atep can occur in a nuaber of way*. a. Two free radical chain* aay siapiy coabine. H H H H| R - (CH2 - C) - CH2 - c * c - ch2 - tc - ai2) ft - 'K X t1 XX X1 y 7 11 H Hi H | R - (CH2 - C) - Ctt2 - C C * CH2 (C - CHj) * ft or *X X l XX 1 X y -6- ucc 013299 b. A disproportionation reaction nay occur- in which r.aaa one of the polymer ch ain s will have an unaaturated end group: H H II l H | K - (Clb, - C) - at 2 - C + C - ch2 - (C - Cll2) - R i* i XX Xv HH R - (Clio - C) i* Pin4 . Oi2 X VC 1 X = CH (C - Pl2) y - R c. The polymer chain may transfer ita radical to a aonoarr unit. fl il iI R - (CIU - C) - CHo - c t* II I ch2 c I X - H I r - (ch2 * r) - ch2 ai2 + ch2 - c Tins is the generalixed mechanisn of free radical addition polyneriration. Vinyl chloride is thought to deviate slightly in the termination steps. It is known that transfer plays a very large part in the polyneritation of vinyl chloride, and lienee it seems likely thst any termination by monomer will take the form of a degradalive transfer reaction. Pie first step is probably the abatraction of a chlorine atom from the.monomer . R - Cll2 - Ql* * CH2 3 CH Cl Cl R - CH2 - CHCl2 + CH2 " Ctl* The CHn = CH* radical may initial# the polymerisation of vinyl chloride sod thus constitute a true Chain transfer step of polymer to monomer. IT it dimerites, butadiene will he formed which would then act sa a chain terminator because when the butadiene.is attacked by e polyvinyl chloride radical, the resulting species would be a resonance stabilised allyl radical. The stability of this al lyl - radical ia auch thst i.t will not initiate poly merisation of vinyl chloride monomer. n - ui2 - cnci- ch2 * en - cii - ch2 -* h - ch2 * aici - a2 - ch - ai * ch2 r - ai2 - aici - ch2 - ai * pi - ch2- Another way in which the vinyl radical may disappear ia by combination with a growing radical. in effect, each degradative chain transfer would then stop two chains: H - CH2 - CHC1* + Ut2 - CH' - R - CH2CHC1 - CH - CJ12. -7- UCc 013300 Tins .si met ..in is t lie same us is formed if mutual termination of the growing i.uiiiui i iki'i plate by a ill sproport ionation i eat Lion, and would not be expected to lake -iny further part in the polymerization reaction: u - ui . - ciui * h - ch2 oici -* a - an - cnci2 + h - cji -- ui2 Tin- Ai t .1:1 e-iuriii of Monomer Hulls in I In* C.liatn In tlie previous section on the mechani sia of pulymeri zation, the initiation step was shown t - be an attack of a free radical on the double bond of the monomer. There are two ways ill which this may ociur. II I r - ai2 - c x 11 1 r - ai - c 11 x 11 As is generally true in Tree radical reactions, the reaction leading to the more stable piciduct will be favored. The occurrence of either reaction cxiluaively would lead to a head to tail structure in which the substituent (X) wuiiid be on alternating carbon atoms. - CIU - CH * CM., - C1I - Ole - CM - 41 `I "l XXX Alternate possibilities are head-to-head, tail-to-tail structures, - ch, - iOf - ail -- bio - ciio* - ai - ai - ui2 - ;x x ; ; ;x J I____________ -_____ _ J x or a random structure containing both arrangements. The possibility of ob taining a regular head-to-head, tail-to-tail structure exclusively is quite remote, but it appears that an occasional monomer unit may enter the chain in a reverse manner to provide a single head-to-head, tail-to-tail linkage. The question of orientation of vinyl chloride units in polyvinyl chloride has bien resolved by treating the polymer with tine. The head-to-head structure would leave an unsaturated polymer while the. head-to-tail structure would yield cy*. Iopropane rings3. - Cllu - Ol t - al i - ch2 - ai2 - C11 H - CI M - ai2 - - Cl Cl Cl Cl * Ulu - r = CM - ch2 - CM2 - CII - CH - ch2 - -8- UCC 013301 - ('ll*; - iJl <Jl12 - 1'lf - ~l | a c.i iJ12 * Lll - CHo * CH - CJIj * (31 * "1 "I I ci ci ci - din ci 12 /\ /\ -m , - < ti - ai - ch2 - oh - ai2 - ai - ai -- -1 ci Sinn* only Sl-8b per rent, of the chlorine could be removed, this fits the theoret ;c.n 1 < a l<.ti 1 si iaim for head-to-lai1 polymer. The theo1 cl 1c u1 calculations are based on statistically derived probabilities for pairs of chlorine groups in a chain which might react with eiich oilier to form rn.g closures. The calculated values are that 86.47 per cent oi the chlorine groups will react in pairs and that 13.53 per cent will bu isolated. ,<J Kinetics of 1m listed Polymerisation Initiation u I addition po 1 ymer i rat i on 111 the presence of an initiator 1 may be considered in two steps. 1. The decomposition of the initiator into free raJicals. R' where *kj* 11 the rate constant for the decomposition step. 2. The addition of a monomer unit to form a chain radical Mj. R- * M ka ------- > Mj* hee *k#* is the rate constant for the attack of an initiator radical on u monomer unit. The growth or propagation of a polymer chain is the repetitive step of the monomer radical attacking available monomer. "r V M m2- M V M S -> UP - A. -> M2' 3' All of the propagation stepa are shown with the same rate constant 'k.' because rudical reactivity ia presumed to be independent of chein length and dependent only on the nature of the monomer radical. 9- UCC 013302 The termTItaCioii step involves the mutuaF rad>tralij^lj^eithy^jjombi nation ocmd-ispropj - V' * V Wtc 7 *^( x + y) V V ktd Mx My the setivity of two 'k, * and *k. * represent the rate constant of termination by combin.ition and Lc 1 d disproportionation respectively. W no* have the fundamental equations shewing the various kinetic steps occurring in free radical polymerisation except for chain transfer, which will be treated s,,. . The rate equations of the three basic polymer!aetion steps can now be written in terma of the concentrations of the spacies'imvolved. Bate of Initiation * Vj * (d lM* 1) * .2 < dt ' - v. This equation simply states that the rate;of.pdfymur radicala formed with time is aqua^;ti>'.:the concentration of the initiatorMjJ timea the rate which the initiator decomposes. The efficiency factor '('fpEveepreaents the fraction of the radical* formed that initiate polymerisation-- Rate of Termination =* v^ * - (d jM*]) " 2 kt [H* ] < ( dt )t The rate of termination of polymerisation aa given in the above equation states thul the rate f disappearance of free radical chain apecies is equal to the square of the radical concentration. The rate eonatant *k^* in this esse represents all modes of radical annihilation where two radicala are involved. We now have the rate equations for the initiation and termination of polymeric radicals. At an early stage of polymerisation tht rates of radical formation and termination become constant and equal to each other. When this happens, a steady state condition is established. The ua* of the steady state assumption enables us to calculate the overall rate relationships of polymerisation to initiator and monomer concentration. 2 f kd [I] - 2 kt LlH2 (f hd [1])* - t*- J ( kt ) i* - 10 - US UCC 013303 The ifiiuiit.ity i,M` j is. the Ntuudv uu roiiti-Hirat ion of radicals *1Iiich, when i ij n *. uuit.l in t ti** kmrtu ntf 4* uprc mi i on for the propagation at op of i he tio 1 i f .it i'in . gives us the following relationship' Hale uf Propagul i on " -d [Mj = ^p |M] IM* J ill. - -.1 ,Mj Jl k(1 If k,, Ul)!i t|j kt I'li,is i.li i: .<*<.i*LI rdi i* uf fri'c ridicjl polymeri itilion should lie, in the enr 1 v ugi'M, pi opiirl i oim l in tin* si|uure rout, corn-rut rat i on of the initi atm. In lit* bovi; roiiii1ioii, llie overall rate in shown tn be proportional I o the first power of the monomer conrent rat i on. This will be true if the effi r. i riii-| factor If) ia independent of the monomer concent rut ion whiih wuulil r 1-1(0 1 re if) in be i.earl/ one. It the efficiency factor ia low, then (f) may I e pro|iort lonsl to the monomer concentrtion and this would make the overall rate expression j VpH.C |M j .1 - d! prnport i onal to the threo halve* power of the aonoac r concentrat ion. In order to observe the experimental verification of these theorel ica'I kinetics, a per rent converainn (dilatometer reading) vs. time plot te firal obtained as shown in Figure 2 in obtain the rate of polymerisation. H(.IIHE 2. IIH.YMKH12ATlON OF MN fL CHI.OIUDE IN 11IF PHKSENCK OF SOI.VKNTS F( niF. FOLYMKH 100 - 11 ucc 013304 Tli e vnr i nl i on of I he run- >1 ;m 1 yum v i net i on with vinyl ehlnriJe p unreiit rst t on as tielAiaiftp-l it. titruhy.-liofnron solvent ft constuni inmuui cuiui-i-lil ration U', 11' sto- ii.'jbuiyionit'ri 1. ) i v shown in Kjpure 3. The slope ol (h tine shows thuL the iie nf po I vwi*' r i tuii on is relste^ to the ilifri- halve* povje r of the nmniiraor ron-i ntutliin*. The urtuul slope a* tie t c t in I lii il hv l In me l hoi! of I rn st si|iiiiiv wjs l.iiin.1 iii I"- I - M*. t Uil'lili .1 VARIATION Oh' RA+K WITII VINYI CHUHWDK CONCENTRATION - 12 - u ucc 013305 i'ltfiii-f i i.m i |i I tit showing the relationship ofil^itw of polymerixati on to ..i:vi;.g initiator concentration at constant aanoay concentration. Thr slope o{ Ui.- lint: for points obtained na ing ''WfcrihydVtmlren containing p roxides, ns determined by t.lie method of least squares* i^-.0.45. That for pm reside free tutrahydrtiinrnn is 0.49. In this case, as shown in the theoretical rate i'vp; i".sion previously, the rate of polymer^ aation is dependent on 1 he square mol i .'iii' cut i iiti on of the initiator concentration. FIGURE X. VARIATION OF RATE WITH SENSITIZER CONT.KNTRATH1N l-aio-bis-e|fcloh*aane nitrile) l.h " 1.4 - I 1.2 O 1.0 -d*r o o 0.8 1.7 1.9 0.1 i.ooio initiator! OONCN. 0.3 __ L 0. Thus far, wo hove shown that the polymerisation of vinyl chloride >ie a free radical Mechanism in a solvent for the polymer* i.e., tetrahvdrofu ran. fulIowa the predicted theoretical kinetic scheme. However, when vinyl ddji ride is polymerised in a medio in which the polymer is not soluble, auch ; in the case of suapenaion polymeriaation, deviations from the predicted eoretleal kinetics are observed. . 13 + ucc 013306 '' '1 *'1 ja'`li*'l,l`JI <*' I *!ii<-r i tut urn of Vinyl Cht^ritfc . U- ucc 013307 l( nof the concentration of bentoy 1 peroxide is kept constant, nd the temper* uiuro i varied, it is found that the ritte increases markedly i tit increaae in temperature. This will be apparent from Figure 6 which huw* the course of tii<t p<>i voter i cati on >( vinyl chloride! catalyzed by 0.115 mot ben joy 1 peroxide at temperatures of 33, 47, 61, and 75#C. FIGURE (>. EFFECT OF TEMPERATURE ON THE POLYMERIZATION OF VINYL CHLORIDE CATALYZED UY 0.115 MM. * BENZOYL PEROXIDE (*s4i GuCi The polymer i zet ion thus appears to be a^ltocst a 1 y t i c over the rat ( of catalyat concentration from 0.025 to 1.0 mol % benioyl peroxide, and over range of temperature from 33 to 75C. Decree of Polymerization An indiration of the way in which the degree of pulymerizai.ion varies with the mode and ronditiona of preparation of t^ie polymer can be obtained by deter mining the relative viscosities of dilute solution# of tlm polyaier. The equivalent viacosity. A, is defined as the ratio (lnqr).'er, wIh-ic n, i the relative viscosity of the solution and c' the concentration f tlic .solution in monomoles per litre. It was shown tfiat for viuvl chloride polymer* *.< - flA,,c1 ) where A-Q is the limiting equivalent viscosity for zero concent nil t on and 0 is s constant which was found to be of low velue; thus fur very dilute solutions we have A o' Furthermore, they showed that An is proportion i I i n t lie molecular weight. The value of the function (log q.t'r, where S * the concentration of the solution in g. of (polymer per 100 ml. of solution will. - IS - ucc 013308 I;ii ii i. o hr (irojior l i urn* 1 In (.lie Macular weight of the polyaer. in Tali 11- 2'ili;u there m I lirouiitioul :li<- itjrtil.li)ii. It it TABLE 2 VARIATION Of DEGREE OK POLYMERIZATION WITH PERCENTAGE polymerizatidn. in hie polymerization ok vinyl chloride, CA f MAZED HY 0.1.2!) MOL. PERCENTAGE HENZOYL PEROXIDE. AT 47"!: gr Polymerisation (logg, >. 4. 5 *.o 20.0 33.0 46.5 04.0 88.0 i 0.41 0.41 0.41 0.41 0.41 0.41 0.39 Hir concentr at ion Ir) of the polymer solutions, used in the above axperiaenle. i* 0.25 g. of polymer per LOO ml. of tetrajhydrofurun. Mimtlar result* ere obtained if vinyl chloride in polymerized tli tli e pre'senew of 10 mol. % dibutyl phthelate and 0.50 mdl. * benzoyl peroxide, 'fhe degree of polymerisation in thie case, however, in Somewhat lower than when iibutyl phihalate ia abeeut from the ayatem. It n interesting to note th t no marked mcreiiae in rate of polymerication, or in degree of polymerisation w.is ob* xerved, although the polymerizing mixture at -3-6--%- ,--po,lymerisa-t-i-o---n- w- an a firm gel, from which the vinyl chloride eacaped very slowly, even when eft at room temperature; the results are shown in Tnbljo 3. TABLE 3 VARIATION OF DEGREE OF POLYMERIZATION WITH PERCENTAGE PuI.YMKMIZATION FOR VINYL CHLORIDE CATALYZE HY 0.5 MOL. PERCENTAGE HENZOYL PEROXIDE, lift THE PRESENCE OF 20 MOL. PERCENTAGE DHMITYL PltTUAUTF. AT 47C Percentage Polymerisation (loggp 1 (< 3.6 8.4 15.0 26.0 35.0 46.3 66. S 85.0 0.28 0.29 0.34 0.33 0.30 0.29 0.28 0. 29 - 16 UCC 013309 rVinvl L ti t < r 1 o e . i-ateiyxed by 0.115 mol. % bcnaoyl peroxide pol rited at vii:..h:,h t .MiperttUiree to an extent of about!T0% polyneritat ion. To e 4 give* u i: >:ufisun of the degrtH of polymerization at temperature* from _ to 85C. It is situ ill at at 85C the value of the .average molecular weight t a about une-thi ni of t he value obtained at 33C. TABLE 4 EFFECT OF TEMPERATURE ON HIE DEGREE OF POLYMER IZATION ruture, C (log7r)/c 33 0.68 47 0.45 61 0. .19 75 0.28 85 0.22 The variation of degree of polymeriaation with cetalyat concentration waa dt-Lei-mined fur polymeriiatioua of vinyl clhloride at *7C. The concentration of Imiunyl peroxide wan varied from 0.008 to 2 mol. %, oil polymer!aetionn being atopped at about 10% conversion of the monomer to the polymer It it aeen from Figure 7 that the degree pf polymeriaation variea inly Slightly over a wide range of cetelyet concentration. At concentration* higher then 0.5 moi. %, however, the everege noleculer weight heronee nuch morn dependent on the concentretion of the cetelyat. At very high catalyst concentration it tanda toward the familiar invnrsn proportionality bntween the average molecular weight and the concentretion of the cetelyet. FIGURE 7. EFFECT OF CHANGE IN CATALYST CONCENTRATION 0ft HIE AVERAGE MOLECUI.AH WEIGHT 1.8 r 1.6 1.2 2.0 To" LOG (CONCENTHATION OF Ba202) I 17 i i ucc 013310 Summary l. When vinyl chloride is polymerised in"thu ptfearuce of a so tv rut tor the polymer, the theoretical polymerisation kinetics are obeyed. i.vj, tlie rate of polymerisation is proportional to the square root of the initiator lorn cntrul mu ami to tlir three-halves power of the monomer omeni r at i on. flit- plot of per cent j.o l ymer i tat i on versus time, Figure 2, .show.vjn lint-si' relationship in the curly stages of the polymerisation reaction. 2. Whereae increasing the rate of poly men net ion by either mcressn| K the initiator i onirnl i at l on or temperature ija expected to reduce t lie molec u1 a r weight of tlie polymer foimed, it ta shown that in the ease of vi I f.lilonde thsl the chain transfer effect is very strong in that initiator <j onivntration had very little effect on the molecular weight, whereas, the t>-mj> erature effect waa very pronounced, , 3. When vinyl chloride is polymerised in bujlk, an auto acceleration la noted which begins in the initial atagea of tl^e polymerisation reactioli. This auto accelerated effect ia alao noted when inaufficient .solvent la present to aolvate all of the polymer formed aa indicated in Figure 2, iit the caae of a email amount of dibutyl phthnlnte. Periode of acceleration are ala exhibited in the polymerisation of monodora which are solvents for their polymers. This so-called 'gel effect* does not appoar until letl-r stages of the reaction whan th system has become viscous, and so diffitb from the period of ncceleretion which, in thf polymerisation of vinyl chloride, occurs from the very beginning of the reaction end ia closely asuoriuted with the aeperetion of the solid polymer phase. Again, in the pIymerisatiou of vinyl chloride, the average molecule^ weight of the polymer furmed during the reaction remains constant, hut with monomers which give rise to the 'gel effect,* it increaae* with increaa^ in rate of polymerisati mi. The 'gel effect* has been explained aa due a reduction in the rate of the termination raaction, resulting from tha great increase in m:iiy of the medium, probably supplemented by the coiling of the growing polymer chains. - ia ucc 013311 HEFKPKttCKS ('. H. Wiuatow and W. Metreyeh, Industrial and Engineering Cheetst ry. Page HOB, (May 1951) G. M. Hurnett and W. W. Wright, Proceeding* of the floyel Society of London Series A 221, Pages 28-36 (1954) i. C. S. Marvel, J. II. Sample end M. F. Roy, J.A.C.S. 61 . Page 3211 ( 1939) i. P. Flory, J.A.C.S.oJ_, Page 1318 ( 1939) s. y, T. Wall, J.A.C.S. 62^ Page 803 (1940) and J.A.C.S. 63, Page 8 21 (1441) I 0. H. Stadia, J.A.C.S. 63, Page 1479 (1941) 7. W. t. Ilengough and R. G. W. Norriah, Proceedings of the Royel So ciety of London, .Serin* A 200, Page 301 (1950) j - 19 ucc 013312 m i i I. I I !! < "Hi, li.iii-t.il Tin- Suspension I'nKess" will bo (oiicerned itli tit sits pen a i on in'll.nj I,it pui vmi-rt/. i HR vinyl chloride: with lilt technuIog1 al advam es iniido in tin* past lot* year* and their effrcls on plant design: 11 h the c>* i st. i UK f.n i | it mu and planned expaneioh of (letieral Tire's A*hl abula plant; .mil tin* exacting i|iiutily conttol and product I mp lov onion t S of V ygen tea his. Sunt* I^Vt, when tin* Ashlubula plant first t ami1 on stream, impoi lmil ddvanies liuyr In*on made in nearly every pliase of I'Vl' production. The r cjsult has been a i o ii s t a tit mode rn i ml i on to remuiii economically i ompet i Li ve. I I . Snspens i on l*n I vmer i z at I on A. Se1ei 11 on Tlir Ashtabula plant * designed to wake suspension type pc lyviuyl r Ii I o ii de (I'VC) for the following reasons' 1. The tieneral Tire A Itubber Company had u considerable internal demand for suspension l*VC'.. 2. The polymer obtained from a suspension system is reluti vely free of impurities and consei|ucnl I y wore stable aa opposed Iu tmulsion polymers which invariably contain emulsifier and other residuea. If. Her i pe The reeipe given below is typical of that used throughout the industry to make suspension I'VC. Vinyl (ih I ot i de Water, Mi nnnii'il Alperox II (luuroyl peroxide) til v*nn I `,0-42 (polyvinyl alcohol) I*nrta by We 100 200 0. I 0. I ght (lie vuriouM prodiiicis may use a' different iuiliHtor, s dff emit colImd. or even a dilfeii-ul water to mo no me I ratio; however, all a u spellsum |'V(i recipes rout sin monomer, fniivr, n free radical in itialor and a protective <olio id. The type of mitintor and the colloid used in the recipe muat be cboarn with extreme care. The choice of initiator is determined by it* ability to produce un acceptable polymerization rale aud not Ieave|re*iduea in the polymer that have a detrimental effeil on heat sisbil y, I'hr (hoi, c of colloid is govetoed by several Tartul'S Fi rat . the i ul old .should aid to stabilizing the inouiimec droplets winch in turn become p lymei particles, A good colloid must ptotcii I lie pa|rl.icle from agglomerati g and at the same time should m I n i w i /1: buildup of polymer in the r esc to Aa with the initiator, the colloid should not i m|> i r heats tain 111 y. l,'urlher, since I he major portion ol the I'VC produced is plaaLtcized, the oI 1oid film which remains on tin* particles should not interfere with tlie absorption o f plasticizer. I UCC 013313 r. >" b 1 e Oi;i r :i t e r i I i e s Hu- MipL.is i s tit' (be ioUiiir.il progi'iim ut Ashtabula litis been to i out nil Ij l il ! A 4* 1 KH. mo I o it l il r weight it l st r i but i oil, purliel" si if .lisjtll- bill, i u|. .ii|ti [..ilynei puliiN. The mo I e< u 1 a r we i ght of I'Vll ;) t \ mo r s iI "> ion* trolled bv i In* |>ti I \ mi-1 i > .i i i on li mpel atnie. The highei i In- reaction tempera In I , t lie towel i " lilt- Hid I I III til' WO I Kill. Molecular weight ills 1.1 i but i >u i .hi bo oil i ml <ilIn i fin|io'ut uro programming; tli.it. is [in I v i.e r i- i nil |I.I I I ol tin- ih.ilge .it one temperature, t lionhilng i Ii[r I lie I eni|ie I m. ill o us often ns n.i 1`s.s.n v l.i obtain .1 dr .s i r ed j >nn I cr u I <t I weight <11 a I. r I b.i I i on. pHi'liele s i . o .1 i s I I-1 bn I I oil is tout rolled by I he .iiniiiint of ttilloid irh.tTged l.o tin. reactoi .mil tin' i s |.t* of agitation usotl during the rid. lion. I'olymet puritv run bo .ml i o I led by taking extreme pre-eum i mis that foreign materials are : i t i nl induced into the produrt hioJ by washim; the product prior in drying. I), Beget ton t.lmi ut ter i si i c <tn.l Ik'Mitii Hutu Tin! Mechanism of flee radical pol ymeri /.Jt Ion involving I ormu 1.1 on, I" "I*uguliou .md lerwiiiiitiiiii bus been enverod previously. Full length polymer molecules uro |iiosoiit in every sti'p ol the I'VC icuilnm. I In- lull, of po 1 vme rt tut ion o I .i suspension system follows the prcilicle .1 p ropoi t i oti.i 111 y involving 'be square root of the initiator .ouieiit r.iturn. Typu ul curves ol lime versus If conversion of it vinyl ihlot I de polymeritulion reset ion uie shown in Figure I. FUJUIIK I. UKAITIUN I'HOFII.K UIMI'AIIISON .n ucc 013314 mtmm I'lii- lime period ill whuh im reartion occurs, I'llRlBDItlv I 1*1 I I'd .lie indue- ! uiu period, i* one in *liieh the rmnlmii l> inhibited. THi!' pe r i od jrini's from the | re sem i* of very smull truces of i mpur 1l1e. I nhilittors , omlii in* mill nctive tenters of pu 1 ymeri mtion or with the ini i a tor. ? ! TUv min. ow it mi 11 at nr* p i ue 11 c u11 v eliminate lhe induction p nod nud hi.11 i,i ,i 11. ,i line.ii rule through gre.|t. portion of the re*iii i. A eom |i ,i e i'inn of i lie reii'linii prolilr of the early 1950`s with a ly it ru l re ,ii i mu iniiny ii shown in Figure I. The effect thin mlvani e h ts hud upon plant design will l"* eonsiili-reil in detail in a Inter sm lion. The muimer in whir.h pressure changes with extent of convernm i is i 11 uslruled in Figure 2. l fiUf- FIUUHK 2. PRESSURE VS. % CONVERSION j 12.1 too PRESSURE IP S IA i all _L Ml 70 #0 CONVERSION <f*> -3* ; 90 100 ucc 013315 Figure 2 shows that there is a useful relationship between pres jure mid extent of conversion in the interval fro 70% to 100% conversion. Below 70% conversion, the rate of reaction in be roughly rstimateJ by the temperature differential between the bitch anti the jacket cooli ng witter, This tcflipcrulure differential be<ones greater as polymerisation progress cs indicsling an at re 1i at i ng rat-' of fiot ymeri tat ion up to about 70% conversion. j 111. The Basil Unit Opt- rat ions j Kur iL'BKoiid previously discussed. PV(1 is to he produced by raaition in suspension of water ami is to be sold as fine, dry particles ranging in sice from 75-2.rn'l mi irons (about bO-JUU U.S. mesh) with the majority at about ihO microns. The ur.lt operations of fluid flop, heal transfer, mixing, centrifu gation, drying and solids handling are immediately recognised. Most chemical reactions are nut ecoitomtcally feasible to run to completion so that an ef ficient design must consider vapor recovery methods. The auxiliary storage operations are defined by the design of thy major equipment. A preliminary block diagram is shown in Figure 3. The immediate design problem is to determine whether a continuous or balch-wijze reaction should be pursued. HEACT10N UKAT THAN.SFKH KIUIIHK 3. I'HKI.IMINAHY BLOCK DIAUHAM VABOH HKVKRY CKNTMI FI KiATI ON MIXING A. Batch Vs. Continuous Heart ion At the time of this writing, no commercial producing plant is llnown to he uarng a tontinuoua suspension technique. However, the advantages of a continuous system are sufficient to warrant close investigation, Bntit this time, there have been three major stumbling blocks to continuous polymeritstion. Unless the first vessel or zone has sufficient hold-up time for particle formation (coiaplation of the induction period), it la difficult to maintain proper part it Ie-site control. Secondly, PVC has a pronounced tendency to adhere to even the most polished surfaces. The pumping of a partially polymerized slurry at low velority results in plugged lines necessitating frequent clesn-out. Last, a aeriona quality problem - the formation of "fish-eyes' which are hardened, solid particles so named for their apprarance in a calendered sheet, and incapable of absorbing plasticizer or pigment - is observed when reaction vi asela begin to get dirty. -4- ucc 013316 A put.cnt on rou 11 mi on h polymerization granted to General Tire" utilizes only three reactors but takes advantage of maximum conversion rates to alnmsi double the output of batchwixe production. It is known that the polymer nation rate of VC1 increases to a maximum at 70% conversion. At that point, pressure drop occurs and the polymerization rate fella off. In this patent, two reactors are continuously operating at the peak rate while the third serves in a `clean-np* capacity. A sketih of the process as outlined in the patent is shown in figure 4. The relatively large volume hold-up in the first vessel* allows sufficient Lime for particle formation, and extended runs have shown that the number of fish eyes did not increase with the time ul' r esc Hon. It is concluded that continuous suspension reactions are feasible from a quality standpoint. The problem of line plugging has not been resolved. B. Continuous Dewatering and Prying Continuous dewatering and drying techniques have been used since the inception of PVC manufacture becauae of an advantage in good quality (uiiLrol and inherently economic operation. With large slurry hold tanks, several reactor batches can be blended, reducing batch-to-batch variances and providing a buffer zone between the variable reactor production rates and the constant rale dewatering and drying procedure. I'i press Pcacrtpt ton This section will very briefly describe thr existing Ashtabula PVC production process. Each of the manufacturing steps mentioned will be discussed in detail in Section IV, Design Criteria. Vinyl chloride monomer is pumped from a field storage tank to a weigh scale in the polymer area, and a weighed amount is then added to the reactor. The preheated process water is added after the monomer. A weighed amount of the colloid solution is pumped into the reactor along with the process water. Other ingredients are added through a charge bomb located on the lop of each reactor. The reactants are agitated and the temperature of the reaction ia controlled by regulating the temperature of the water in the jacket. The reaction is terminated when the desired conversion ia obtained as indicated by a specific pressure. The batch is then dropped to one of three agitated dump tanks. In the dump tank the unrearted monomer is stripped from the polymer slurry (75% water and 25% PVC) through a water sealed vacuum pump and is re turned to the monomer area for purification and reuse. The stripped slurry ia pumped to alurry storage tanka where it is blended before being pumped to the ream finishing area. Fn the resin finishing area, the alurry ia de-watered in a continuous solid-bowl horizontal centrifuge. The resin, after dewatering, con tains about 25% moisture as it ia fed by a screw conveyor into a rotary drier. The dried product is then sieved and packaged. -5- ucc 013317 ife' Klll. Itl i. iIIK U NI lUI, UMTlNUOUs SYSTEM APPROX. AMOUNT MONOMFH IKM.YMKR WATKH T I31F P 150 PSIG 30 70 100 TO HfcC.OVKRY TO CKNTHIHHiK OH Fll.TKH KUSH CHAMBKH -6- UCC 013318 IV. DESIGN CRITERIA A. Reactor l. Design Considerations The reactor is the focal poinL in producing PVC and ita design is a subject for close study. We must consider materials of construe* lion, productive cycles, heat transfer, and optimum ailing., The subject of sgitation, although not a separate operation, will be considered in the nest section. a. Materials of Construction There are two typea of reactors in use for producing suspension PVC - stainless steel and glass-lined. The stainless reactors give superior heat transfer, while experience has taught that they also afford a surface on which polymerisation will readily take place. A metal surface, even highly polished, is irregular enough to provide surfaces which become polymerisation sites. Once a site is provided, the polymer builds up rapidly to a large site and haud-c1eaning is required. The presence of reactor scale has a direct relation to the number of fish-eyes produced in a batch. Wall deposits also drop the heat transfer rate sharply. This combination of poor product quality due to fish-eyes and the reduction of heat transfer necessitates fre quent reactor clean-out. With spray nosslea installed at the top of the reactor and a flush given after every polymerisation, several batches can be produced before cleaning a glass-lined vessel. With stainless reactors, cleaning is more frequent and store difficult. The expense of cleaning that la incurred dictates the use of glass-lined vessels. In a similar fashion, the agita tor and agitator shaft are subject to build-up and the use of glass-coated equipment ia preferred. b. Siting Glass-lined autoclaves are available in various sixes with some large vessels of 10,000 gallons and above. Beyond 5,000 gallons, pressure requirements are important in determining the maximum site attainable. In PVC polymeritat ion, the highest pressure attained is due to the equilibrium vapor preasure of VC1. At 150F,, pressure of 151 paig is experienced. A safety range must exist in which relief valves can operate. A 200 pai rated vessel is the minimum consistent with safety. c. Productive Cycles For the production of 75 million pounds per year of PVC, the number of reactors needed will depend on the reactor site, re actor loading, equipment downtime, yields, and reaction cycle. It will be assumed that reactor loadings are a constant 90% of nominal reactor capacity, that clean-out time does not very with -7- UCC 013319 iMlP size, thut equipment downtime due to malfunctions is constant ,,ver a year's time, and that reaction cycles are identical for dll reuctm sites if sufficient batch cooling ia available* The following tycle calculation, baaed on plant experience, can be made: Table l Typical Cycle Calculation i'repu i'a L i on fur Charging lie ad ion Time Drop and flush Time Scheduling and Turn-Around 0.S hr*./batch 13.0 hrs./batch 0.5 hr*./batch 2.0 hra./batch 16.0 hra./hatch Reactor ('.leaning and Maintenance tiijui pineut Malfunctiona Plant .Shutdown 2.0 hra./batch 200.0 hrs./yr. 14.0 daya/yr. CR ' the number of batches per year in a aingle reactor lb C,, 2 C plnfi ilnys x it li i x,*l - p4 day a a 24 hrsTI - 200 hi " j_ vr. day J [_ Yr* dayj yr. <'. - 457 balchea per reactor per year The following table can now be made: Table 2 Number of Reactors Needed Nominal Reactor Cap. (Gal.) A**uuieti l.odti i iig fCinl. ) * MVC Ch urged 1 PVC Produced At 95% Yield * l*VC Produced Per Heactur-Yr. No. f Reactors For 75 x 106 #/Yi 2,000 3,000 4,000 5,000 1,800 2.700 3,600 4. 500 5,094 7,641 10,188 12,735 4,839 7,259 9,679 12,098 2.21 x 10b 3.32 x 10* 4.42 x 10* 5.53 x I06 34 23 17 14 d. Heat Transfer A glass-lined reactor used for PVC polymerisation exhibits an average overall heat transfer coefficient of 4b HTH hr.ft."F Tlie heat uf poIymeritat ion of vinyl chlorida ia approximately 650 imi/4 (H * -650 HTIJ/#). At its maximum, experience has shown the reaction to attain 16% conversion per hour at 72% total conversion. <l) -8 UCC 013320 l!s i ui< I lie at* figures, ; he heat liberated per unit volume cun be equated lo the reactor jacket temperature arul heat transfer area: Heat Liberated at Maximum Conversion Hate V Volume p - Density of monomer-water mixture = 7.88 f/gel. Q Heat liberated per hour Q = pVAIt a *t. % reacting per unit time --------- ---------- (tl) -- 7.88 mix x V x 650 DTP x 0. 16 _J_ x 100 # VCI gel. IVCI hr. 282 I Mix = 290. b V Bill hr. gal. Heat Tranaferred Through the Hcactor Walla 0 * UAAl - 46 AAt ........................ (Ill) Equating 0-46 AAt * 290.6 V ...................... (IV) V 3 46At gal, A 290.6 fiT* For various fluid coolant temperaturea, the following table reaulta: Table 3 V/A Ratioa for Varioua t'a at llll^F Batch Temperature Average Cooling Water Temperature 70F 60F 50F 40F 30F Average At Acruaa the Heactor Wall 60 70 80 90 100 46At 2760 3220 3680 4140 4600 V/A 9. S 11.1 12.7 14.2 15.8 By plotting the reactor1 nominal capacity va. the heat tranafer area and by uaing the values obtained above for parameters, the neceaaary cooling water temperature can be obtained (Figure 5). ucc 013321 HEAT TRANSFER AREA (F T . ** - i TV * -**_J ,,V_- / * t^TJliUlU&A. . RhArnm NOMINAL CAPACITY VS. IIKAT thansfkm ahka .J The 70F water from a cooling tower will not maintain control over the batch if the only heat transfer surface available in the jacket wall. Accordingly, methods for extending the heat transfer area have been investigated. Thear lake the form of external heat, exchangers through whirli the slurry ia rerirni* lated or reflux rnndensrrs mounted on top of the reactora which continually condenae VC.l vapors. The former method hee proved 10 . ucc 013322 f' i 1 '4 ' * "' * impractical. If external pumping velocity is high, the resin particle site is disturbed; "and if the-pumping velocity is low, plugged lines result, , * Early work with reflux condensers was concerned with the effect an product quality and the efficiency of heat transfer. The results were heartily encouraging with respect to product quality, and overall heat transfer coefficients in excess of 100 BTU/hr.F sq. ft. were reported. But so the condensers were used on larger vessels, serious fouling problems were noted. It was determined that cleaning would be excessive and that Maintenance coats would offset any capital advantages over refrigerated water. , Optimum Siting Assuming that glass*lined reactors aunt bo used, that they are available in varioua sites, and that cooling costs will change aoMowkat with varying voluoe to area ratios, the optiouo reactor site (200 pai) can be deternined on'the basis of bars equipsent costa. The following table can bo prepared: Table 4 Reactor F.auipment Coats for 75 s 10* #/Yr. Nominal Reactor Capacity F.O.B. Coat of Reactor and Agitator (per reactor) Instrumenta tion Coats (per reactor) No. of Reactors F.O.B. Cost For Reactors, Agitators, And InstrU' mentation 2,000 gal. 3,000 gal. 4,000 gal. 5.000 gal. >20,500 13) 25,200 28,400 35,000 53,100 3,100 3,100 3.100 34 5802,400 23 650.900 17 535,500 14 533,400 The coat of cooling equipMeat can be found by aaauaing a ached* uling rate. The peak load is normally 16* conversion per hour and the aooinal load 9* conversion per hour. Further aaaune that the 16* figure is based on the total monomer charged, the 9* figure ia baaed on 95* yield, and that all reactors are on a 16-hour cycle with a 3-hour nonproductive time. - 11 - uec 013323 i1** Table S Refrigeration fhity Norm nal Realtor Capactty (gal. ) 1 PVC Produced Per Batch 1 PVC Produced At Peak Rate/llr. f PVC Produced At Avg. Rate/Hr. No. Heactora Idle No. Reactors At Peak Rata 2,000 3,000 4,000 5,000 4,839 7,259 9,679 12,098 815 1,223 1,630 2,038 436 653 891 1 ,089 6. 4 4.3 3.2 2.6 2. 1 1.4 1.0 0.9 No. Heactors At Nominal Hal e Peak Heat Load HTII/Hr. Average Heat Load HTU/Hir. Total Heat Load nrnj/Hr Total Load in Tons of Refrigeration 25.5 17.3 12.8 10.5 11.1 * 10 11.1 * 10' 10.6 a 105 11.9 x 10S 7.22 a 10* 7.34 a 106 7.42 a 106 7.44 a IQ6 8. 33 a IQ6 8.45 a 106 8.53 a 10* 8.56 a 10* 694 704 711 713 Combining the refrigeration load with the temperature require* meats of Figure 5, the refrigeration equipment coata caa be estimated. Table 6 Coat of Cooling Equipment Nominal Hesc tor Capecity Tons of Refrigeration Temperature Required Refrigeration Equipment Coat, F.O.B. 2,000 gal. 3,000 4,000 5,000 694 704 711 713 50F 40F 40F 40F $50,000 66,000 67,000 68,000 Uaing Tablea 4 and 5, the equipment coata (F.O.B.) for refrigera tion and reactors ia known. A plot of the combined coata is ahoen in Figure 6. The presented curse indicates a bread ainiam between 4,000 and 5.000 gallon reactors. For a 6,000 gallon reactor, fabrication coata would riae steeply, causing the formation of a very definite minimum. . 12 - uec 013324 \ * _*- t, V m K1GIJHK 6. BARK COSTS VS. REACTOR SIZE v^/ 2, Abtbiil l)iin The Ashtabula PVC. Plant of The General Tiro & Rubber Conpany naa designed anti constructed in 1954 by Scientific Design Conpany. Tb original plan calked for a 24 Million pound por year polyncr facility utilixing ton 3.500 gallon reactors arrnnged in loo banka of fivo reactors each. Reactor cooling wee provided by a cooling tower and via generally aucceaaful with the 20*24 hour reaction tinea obtained with 1954 technology. All reactors were glaaa-lined. By 1956, the deataud for PVC caused General Tire to eapand tha polyaer area by 50*. A new line of five reactors was added. In 13 - ucc 013325 the past several years, both the demand for PVC and the technology of manufacture huve advaiued. New catalyst system* have lowered reaction times to 10-<6 hours (depending on the product! and mar kets littve expanded. B. Agitation 1. Design ('on aide rat i ons The size of a particle made by the suspension method is a function of the protective colloid and the fluid regime. The agitation variables are primarily: a. Agit ator speed. b. Impeller size and design. c. Number of baffles and their design. d. Material of construction. The notarial of construction follows the requirements laid down in the reactor design. Theoretical aspects of impeller design, baffling requirements, and motor si sing have been investigated by numerous workers since 1880. A complete equation, describing the geometry of the system, impeller Reynold's number, vortexing effect (Froude number) and baffling would include some ten dimensionless groups.^ It is possible, following the method of Rushton,^ to scale up an important variable if at least two smaller systems, geometrically similar, are used. In practice, it is common to scale up using trial and error tech niques based on the commercial designs available. Initial pilot investigations at General Tire dealt with a variety of impeller and baffle designs. The tubular finger baffle was found most suited to PVC operations. Fi ve *1 Ion reactor studies on the anchor, turbine, 45 marine screw and three-bladed perpendicular blades led to the conclusion that the speed of agitation and type of agitator had a decided effect on the particle (Figure 7). 1 H * average p a r tic le s iz e ------------- (..AUGER - 14 - ucc Only with Lin; murine screw agitator did particle site continue to decrease with increased speed. The optimum particle site distri bution is also related to the agitator design. The sane result was obtained in the 3,500 gal. reactors by using a three-blade retreating blade impeller which does not hare the deep vortex and. large baffling requirements of the Marine screw system. It is postulated that both the aucceaaful ayatena hare en action resembling a centrifugal pump. The liquid ie pul led-downward and against the reactor sides, then fluwa up the walls and down for a repeat cycle. Thia gives very satisfactory heat tranafer and with the retreat blade system there is minimal scale formation. After the reaction is complete, the suspension ia emptied through a transfer line to a receiver tank for unreacted monomer removal. If high speed agitation is msintained, this operation is slowed greatly by the creation of a vortex. Cassation of agitation will result in phase separation and complete pluggiog of the reector outlet valve. The solution is to equip all reactora with twospeed agitators, the lower speed ueed only while transferring. 2. Ashtabula Design Hie Ashtabula plant presently has two-speed, 1$ H.P., retreating blade agitators. The original ten reactora were equipped with.a single, three-finger wall baffle. Ik* five reectore added in 1956 have been successfully run with a single smell blade baffle. The same recipe in the two types of reactora will produca a slightly different resin particle. C. Recovery System 1. Peaian Considerations The reaction for Vinyl resins attain* an average 95% conversion in the reactor. The importance of the recovery syetem cen be shown by a simple example; Assume 75 x 10* lb /yr. production; then the unreacted monomer with no recovery at 95% convoraion would be: 75 x 106 Iba./yr* - 75 x 106 Iba./yr. - 3.9 x 106 Iba./yr. 0.95 At current market prices (Bd/)b.), .this represents: SO.08 x 3.9 x 10* - 8312,000 Obviously the recovery system ie no small part of the overall profit pictura. Vinyl chloride ia nearly insoluble in water, and the bulk of the unreaCted monomer ia in a dispersed state within the water phmse or in the vapor phase over the batch. Since VC1 exhibits a volume 15 MPMRI m 6' - all i-i ullage of 35% during polymerization and the reucturs are not S. fully lauded initially, the vapor in the free apace is considerable (pressure is 30 to 50 pat*). To leaser extent, some residual monomer (about 0.4% of the amount charged) is solvated in t.he resin particle. The unreacted monomer is difficult to remove from the I'VC particles because diffusion of monomer through the psrticle is lime-lemperulure dependent. Simple vacuum flashing suffices to remove the free monomer at a rate dependent un the sire of the vacuum pump and recovery rompressor and the hatch temperature. The latter will drop off sharply unless the heal of vaporiiat ion is continually replaced. This heal may be supplied in a variety of ways but, if the boiler feed water is suffi i: ient1y pure, it is best to inject live steam into the batch. This must be carefully done to avoid product degradation but gives the added advantage of intimately contacting the polymer, leading to a lowered residual VC1 level within the particle. The drop tanks must be.fully agitated to prevent phase separation and mual be rated for full vacuum and a minimum uf 100 paig. Since they are the site of only a minor amount of polymerixation, at sin less vessels are satisfactory. To reduce liquid entrainment in the recovery system due to foaming, the veeeele should be at least 30% larger thun the reactors. The number of drop tanks is selected no that there will be no production scheduling holdups between batches. Since the completion of s PVC batch reaction is determined by pressure drop and not by time control, some latitude must be allowed and it in most economi cal to provide an adequate number of drop tanka. Baaed on plant experience, a single butch can be transferred into a drop tank in one-half hour, stripped in one hour, and tranafrrred from the drop tank in one-half hour. for a system of N reactors operating st 16 hours turn-around per reactor and scheduled churging, there will be one batch available for monomer removal every N/16 hours. The number of drop tanks would then be given by the equation: No. Tanks = Stripping time (hr./batch) x Prod. Bate (batchea/hr.) ........................ (V) No. Tanka * 2.0 In i. * N_ botches = batch lo hr. 8 The conclusion is readied that one drop tank is needed for every eight reactors. This analysis does not allow for batch-to-batch variations in cycle time. For these reasons, e safer figurr would be one drop tank for every six reactors. The physical arrangement of equipment may also help determine the number of drop tanks needed per reactor. The general layout of a dump tank-recovery system is given in Figure 8. u - 16 - ucc 013328 f l HUMP TANK V - 17 - ucc 013329 Using the enthalpy curves for VC1 (Figure 9), the heet duty for the recovery condenser can be calculated. The storage conditions for VC1 are normally 80F and equilibrium vapor pressure. I- I tiliHE 9. ENTHALPY OF VCt ENTHALPY IB T li'# ) - 16 - ucc 013330 2. * Aghtittbula Design ee- ** ` Thc Ashtabula recovery ytf cgaaiats of three duep tanka. i** "f s 7,000 gal- "d one of 5,000 glV%iapacity. Each haa a vacuum poop and recovery coapreasor feeding a coaaoa recovery condenser. The yaten ia given in Figure 10. FUiliHE 10. ASHTABULA RECOVERY SYSTEM SI .11HUY .NILAM . v....*, ***'. ....+4*M* t> compressors - 19 - f.l v UCC 013331 Si II i' ng ' 1. I)p x i iii I .mi w i ilc r al i on A-. dr fined in i h i s sell i mi, storage will mean the raw mouumer being tipltl (nr (.ii I vnn: i i /. ui i uimI the rem lor slurry being helil fur con tinuous diying- The volume of the former la ileteiatineii by the .in ii i c e of mo nome i It.e.. is it being continually produced, is it being shipped in, oi n combination), anil by the rate of* production. Murrv storage is determined by the number of different products being pni.Jiji ed simultaneously, the number of drying lines, mid quality luiittol. .Several hutches should be blended before drying to assure produei uniformity in day-to-day operation. 2. Ashtabula Design 4. Monomer .Storage The original design foi Ashtabula constated of three monomer tanks of I1),000 gal. capacity each. Two were 304 al sinless clod, and the third made of carbon steel. The stainless tanka were to hold purchased and produced monomer for feed to the reactors. The srbon steel tank received recovered monomer and served as a feed vessel to the monomer refining column. Iron contamination is removed in the refining step and the stainless tanks were to prevent any iron from being picked up after I he refilling step. It was soon rounJ necessary to use a tank in eon | unr 11 on with tile conlinuonn monomer production. Tina led to the purchase of a fooith, carbon steel, tank. Time proved that the choice of 301 stuinless clad tanks for Ash I aim I a-pIodni el moiemer whs unfortunate. Trace ipiuulities of f(Ct and water led to extensive corrosion problems and iron pickup in the monomer. The existing 304 stainless steel clad tanks have been repaiied, and a glass-lined vessel is being purchased in the current expansion. b. Slurry Storage The slurry .storage tanks ("til end" tanks) of the original Ashtabula design consisted of three 15,000 gal. 304 stainless steel tnnks. Continuous agitation is provided to prevent phase sepnrutinn. The tiaiisfer lines ere constantly re circulated to prevent line plugging and to further increase the blending efficiency when the tanka are-not feeding the dryers. During the 50T plant expansion of 19S6, two more 15.000 gal. tanks were added, and three more are being installed with the current expansion. IV.:. i i. I>esir,n i'-onst .if i nl i ana Slurry Iron. storage contain* an average of 25$ PVC. with actual v,,ln,.:, y a t y i ttf; with the baste recipe, reactor wash, and water al.lei in laiililnte penning. All .water used < n i In* prurea* * ilr i .in i/.cl. A i unil> i nut ion tethnii|ue uf ilew.il e.r i ug and ilryuiK is le.piired lor l'Vi;. The method beat suited is a eontinuous ..olidbowl centrifugal separation with the solids discharge feeding din > tty into the drying systea. I.tili/ing this, .c ami .ml products ran he .onsiatentIy colic en t r at d to 76$ - 77$ solids before curling the dryer. figure 1) illualrutes a noumerc i a l centrifuge tonmonly u seii. KKil'HK 11. (XJhKKHClAl. CKNOUmiK Sl.WUlY IN lUM.IlAlhd IIOWI. OUTAll. A|Kh rtiNi) ni.nii - 21 - ucc 013333 A fir.I pip.- iniieing along the bori xonl.al axis of tin: . e.ntt t luge ill st i` i but <'< t lir slurry. ..The plow mechanism rnUtr. in tin" ".urne ilirfriii.it as the i-r-w i but'eL a rtsdured speed, thus conveying solids Lo tl.n small end of the bowl where they are discharged. Normal Ln.wl i .'till i .*n .11 speeds range from 2000 Ri'M and above for small units, down to sOM Hl'M on large ones. Liquid level (the *pond") is mu i n i a . ue.J by a.lj ii s Linen l of the outlet dams. Ilotli the depth of the pond and Lhe angle of the bowl relative to tin- Imr i runta I axis is important to the efficiency of operation. The deeper the pond, the more efficient the phase separation (less solids nt u r t i :t 1 in the effluent). Correspondingly, the deeper the pond, tin- mure moisture in the wet cake disrharge. The former means less loss of product to the plunt, while the latter means an overload of the drying system with subsequent reduction in produc tion rates. The net effect of the bowl configuration is to .hange the ehurecicristics of the curve relating feed rate to diet barge moisture r .intent. Elertrical giade rosins requiring low ion content for msulstion application* me easily handled in commercial erntrifcges with the use nl u dei.miced wash water technique. Dei united water is intro duced into the icntnluge, and is brought, in contact with the resin through the rlinniing action of the blnde. iluth the volume of wash water and the water temperature have an effect on the removal of soluble ions. With 12UK process water, the experimental wash water efficiency is given iu Figure 12. 2. Ashtabula Design Ashtabula has two driers rated for 25 million pounds per year each. I'Inns huve been laid to install a third lino will, its attendant eentnlug.il dewatering system. The two existing driers each have two centrifuges developing 7b0xG at 1750 Hl'M with a feed of 4000 l/lti . "it each line. Ilascd on the drying rapacity being in stalled, it is desired to maintain 5000 f/lir. on stanJard reams. The specific centrifuge design for economic plant operation depends on the two factors mentioned previously, e.g., on the sum of the effluent losses and on t.he variable coat of drying for differing wet Cake moistures. F. Dryers 1, Design Considerations 'Die piime considerations in drying PVC are to avoiJ product degradation and lo obtain low moisture content. At ebout I50F degradation of the product will occur, resulting in discoloration of a milieJ sheet. In addition, PVC. is subject to a cumulative "heat, history"; the length of time at moderately elevated temper atures will affect quality. This necessitates the use of cocurrent drying system or one in which exposure time of the polymer - 22 - UCC 013334 i mmm wawn FIGURE 12. WASH WATER EFFICIENCY WV~li WATER RATIO ` BASED ON " WATER IN CENTRIR'OE CAKE* - 23 - UCC 013335 tn heat it ini hi m i .ed. Tlii? two types I n use foe PVC an* rotary and Hash. Tlie rotary drier is used by General Tire. As 11 ' atm I a ties I nil Tli 1954 A.slit jIiu 1 a design consisted of a single 10' diameter x 30 1 long stainless steel, mturceiu rotary drier, rated for 25 Million pounds a vest. A finned-tube lie at exchanger delivered approximately 1 x 10*' HTU/hr. tu the air stream. At normal operating rates, some 1,000 dry pounds could be produced per hour at. an overall thermal efficiency of uboul 50%. During the 50% plant expansion of 1956 a second, identical drier was installed. This pushed the drying capacity to 50 million pounds a year. With further reactor expansion planned to put plant capacity to 75 million pounds per year, a third will be re quired. Accoidingly, the existing system was completely evaluated. The following data and Figure Id are extracts from a General Tire report bearing on factors affecting drier capacities. F1G1IHF. 13. DfllKH SAMPl.K POINT AND HAFFLK LOCATION I i INl.KT OUTLKT SAMPl.K POINTS I, 2 AND I l.uO.ATKD AT 28.3%, 54.3%, AND 90.0% OK DiliKH I.KM.IH. Table 7 No. 1 Drier Fraction of Drier !) . 283 . 543 Air Temperature 300 209 200 Solid Temperature 120 102 108 Solid Moisture: Wet Reals 24. 3 17.9 8.2 Dry Reaia 32.2 21.8 9.0 Humidity .009 .0203 . 0343 Wet Bulb Temp. 108 102 107.5 Air Rate Through Drier - 54,800 lb s./hr. Velocity Within Drier - 198 ft ./min. Heut Input by Coils - 3,060, 000 BTlI-hr. Slurry Feed Rate (dry h a a i a | - 4,350 lbs . /hr. .60 160 112 0.3 0.3 .0443 112.3 t. 13 146 136 0.25 0.25 .0443 107 - 24 - ucc 013336 l-'iniv the prcrcd 1nq data, the dVcrnll volumetric lical.-i fun*tiT was dts-hjyymiMd Chemical hnguieer's II ji.iitiuuk, Mi i r<i Kd iliuu, p. 831 and Fourth KJition, p. 20-19; (VII q^ - Total heat tranaferred, MU/hr. l!^ * VuluMctt ic heat transfer coefficient, Iflll,Mir . Ft. ^"F lAt). *. True mean temperature difference between hut g> and Material, F ______ At)* _____ r. -9t (Al)p ------ I -- *t -- ........................ IMI/ 9t (At). q - lie at i rana.ferred to wet Material while heating to the air wet-bulb leap.. BTII/hr. qv a l.atenl heat tranaferred to the Material while aoiature in being evaporated at constant trap.. UTU/hr. qa a Sensible heat transferred to the dry Material while beating it to the discharge leap., BTU/hr. q^ - Total lieat transferred in the drier. HTU/hr. (At), Mean Leap, difference between the eir and the Material at constant leap., "F <At>H Mean teap. difference between the air and the materiel while heating to its discharge temp., F IAllp Mean temp, difference between the air and the material while heating to the wet-bulb temp., F Kvalnation of Equation VII (I'VC.I 0.25 imj #-bF Cp (H20l - 1.0 BTU * F Solids Leap, - I20"F inlet, lJh,,F outlet Air temp. - 300F inlet, I46'>l"' outlet Air wet-bulh Imp. I07F Dry product production rate - 4,350 I/hr. Water content of feed 24.3% Con atari t drying rate period - 20% to 1% moisture Hast a - I hour Total moiatnre in feed - 4.350 - 4,350 - 1,400 1.0 - 0.243 lbs. UCC 013337 mmamm wmm \ \ ('"t. )l.v( \ * (4,350 X * U.2S) Alp r* 'w (107-120) . ( 1,400 x 1.00) % - -1.23 x io4 mu *| V (m,, Ml * |f .-`UMl - .01 x 11,400 x 1,030 1. <10-. 757 '1. 1.13 v IOf,tV11 - (m< j, )|VC. Ats " (0.2$ x 4,,350) (136-107) 3. IS x io4 imi 'It " ^1 1 ti ** wL of evaporation of unit eady* si ate moisture removal Ignoring the laat ter*: q .3.23 * IO4 v 1.13 a 106 + 3.15 * I04 qt - 1.13* I06 imi Air trmp. at 1n1rt Air temp, at beginning of constant drying prviotl (20% noisturt) Air tfinpi at *"nd of conilint drying period 11% mointure) Air temp, at drier exit Material initial temp. Material constant drying temp. (wet bulb) Material final temp. Symliu 1 Value tai 300F TA2 TA3 TA4 TM! T||(2 TM3 230F I95F 146F 120F 107F 136F (At>,, - Taj i Tal. - TM, i Tm2 22 (At )n . 300 230 - 120 " If -1 1 15 lF (At) v T^vjr^ * T|h2 (At), e_l_9^ * 107 106F (At, ' rA3 rA4 ' rM2 * TMU (At) " 195 .1--1 ` 107 * 136 -------1-------- 49 F - 26 - UCC 013338 !______ ,, .3,23 x IQ4 (At) 1.13 x 10b x 151 * 1. U x 106 1.13 * 10" x 106 3.15 X IQ4 1.13 x 10 -49 \ (At)_m . 9.81 x 10*3 (At),, - 102F Evaluation of Equation VI qt - U. V .(At), Drier is 10' diao. x 30' long V -wr2l -*<S)2 x 30 - 2.36 x 103 ft.3 U. - q. - 1 -1-3 x 106 BTU/hr. V fAtl, 2.36 X 103 ft.3 x 102F U_ - 4.70 BTU_____ ft.3hr.F The above result *aa compared to the correlation of Friedman and Marshall:^ Comparison With Fricdman-Marahal1 Correlation U, . 20 G*16 D ...................... (VUI) where G - air aaia velocity, lba./hr.ft.2 - 54,800 lbs./hr. D - drier diaai., ft. - 10 ft. U - 20 (54.800)016 - 5.70 BTU 10 ( 25* ) hr. ft. 3"F The Friedman-Merahall equation ia admittedly only an approxioation but it doea show a fairly good correlation with the rotary dnera in uae at the Aahtabula plant. G. Separation of the Product froai Air 1. Design Coneideration* The product oay be discharged froai a rotary drier either directly from the lower end with the uae of a breeching ring, or it oay bo intentionally entrained in the-exit gases by reatricting the exit area and thereby increasing the air velocity. The latter Method is aoat coanaon because (t) the breeching ring method ia not highly efficient, since it requires a backup filter for the exhaust air, and (2) entrainaient allows convenient conveying to any point in the plant. The fluidised particles oust then be separated from the eir stream for packaging or storage. - 27 - UCC 013339 All* separkb.* n ilem ci. li v .* i* I II> .11 l y been of three tvpc.y: 111 C t * 11, nr bag fillers, (2) 1 yi 1 .'iii* si-|..!r.ii urs, or (3) u combination of cyr lonwaud cloth filtcis. The primary design criteria is overall collection efficiency. tfii the loss of one-tenth 0/ one per cent of the product in a 75 mil lion pound plant represents a loss of II2,IK10 per yt-ur. The various melliods of recovery are discussed below, along with their characteristic limitations. a. The Hag Kilter Fro* tieneial's experience, s bug filter maintains an average 90.9&H collection efficiency in retaining PVC particles. A typical installation is shown in Figure H. FIttJHE M. HAG FILTER With this device th>' inlet air, laden with PVC particles, is ditr1huled *tnto s header feeding the interior of several ruws of bags. A partiul vacuum is laai-nlained on the exterior of the hugs, pulling the air out to the atmosphere. Moat of the I'VC drops to bins hi low, hut some PVC particles are left clinging to the interior and must be removed. This is accom plished with the use of a blow-buck ring mounted on a movable turriuge. Tim carri.ge continually traverses the length of the hag with small jets of uir shaking the PVC loose to drop in the bin below. A rotating star valve maintains an air seal while allowing the free-flowing polymer granule* to pass through. 1'heie are several disadvantage* to the b*g filter. Relatively high capital and operating costa are combined with operetional limitations which peviudicatly produce low-grade product. The f 1 Iter media (cniroionjy Orion) plugs and can only bn opened by more violent means than the blow-bark ringa. Successive re lease and re-ostablialiment of the vacuum on the exterior of the* * 28 ucc 013340 m 1> a^s sill cause firmly adhering RVC to drop off. The product garnered tn this manner is primarily "fines'-(smaller than 270 mesh I and is designated as off-specification material. This method is not successful indefinitely end bsg replacement is frequent. Continual wear on the cloth from the mechanical rurnugc leads to eventual rupturing, further raiaing maintenance coats and the loss of top grade product. b. Cyclone Separator l'lie cyclone separator operatea with no moving parta, is inexpen sive and relatively free of maintenance. Collection efficiencies have not been theoretically correlated to the degree of accuracy needed for firm design, necessitating experimental work. Such work hits been done at the Ashtabula plant. The coarser resins could be collected at au efficiency of 99.93%t while the finer resins were.gathered aL efficiencies ranging down to 99.4*. By using two or mure small-diameter cyclones in parallel, it is estimated that a liigb collection efficiency can ba achieved. The system is shown in Figure IS. FIGURE 15. DUAL CYCLONE COLLECTOR AIR AIR e. Combiner ion of Cyclone snd Cloth Filter Various combinstions of cyclone filters with clesnup cloth filters exist. One such srrsngement is given in Figure 16. In this sepsrstor, the incoming stresm enters a conical sepa rator where the majority of particles settle by the cyclone desrcelersting effect. Above the cyclone chamber are rows of cloth filters with a partial vacuum maintained on the inside. The air stream, rising up the center of the chamber, it drawn through the cloth to the asmosphere. The entrained product is retained on the outside of the cloth. The filter is cleaned by regulated pulses of air striking the neck which sets up a sinusoidal pattern violent enough to loosen adhering perticlea. The system has the high collection efficiency ot the sock filter without great attandant machanical difficulties. - 29 - UCC 013341 ! 1U:IU\ I <. UJMHI NATION KILTER 2. Ashtabula Design The original Ashtabula design consisted of s bag filter identical to tlie type described above. During the 19S6 expansion, an addi tional bng filter unit was installed eith the nee drying line. Since that time, cyclone separators have been improved and in the third drying line it is planned to seitch to the use of cyclones. - 30 - UCC 013342 il. Screen i*ng 1. ^'Desigl^Consideratiorta After the product is obtained in a free-flowing granular for*, quulity considerations dictate careful screening. This operation serves the dual purpose of removing foreign object* and oversite particle*. The operation is accomplished by the use of a series of vibrating semens which automatically dump screened material into a storage bin. It is possible to design an arrangement which will give several c l assi11cat iona of the product. 2. Ashtabula Design At the discharge of the hag filters there are two vibrating, triple-deck screens. All ovrrsiae particles aiuat pass over all the screens before being discharged into a holding bin. Product obtained in this manner is designated off-specification and sold at a lower price. This method his been quite satisfactory and will be duplicated on the new drying line. 1. Dry Polymer Handling 1. Design Considers!ions After screening classification, the dry polymer is ready for packaging and shipment. In the past, the operations of begging, palletising, and loading have been areas largely neglected by chemical engineers. But in high-volume products, packaging and handling contribute significantly to manufacturing costs; In the last twenty years, new methods for transporting PVC to the consumer have been steadily .-merging, supplanting to a considerable extent the standard SO lb. bug. The most economical shipping mathod is by railroad hopper car* winch reduces filling, handling, storage, and container cosIh by two-thirJa. The use of these new methods has completely changed the process flow after the screening operation. Figure 17 illustrates the typical installation common a few years ago. FIGline 17. BAGGING STATION UCC 013343 i Dry pdl^ni'r i a tli sdiurged from the sifter into a hopper fitted with a bugging machine,-. Hie new bulk handling Methods utilizing pn<: uni a t,*t c conveying have changed this procedure radically. PVC fluidited with small quantities of air can be Moved rapidly to and from storage. Automated bagging station* operating at noninai spn-il^ of 20 bags/min. perform the operaliona of bagging, closing, pui1et 111ng, and movement to the warehouse. Manpower is required only to remove the loaded palleta. Bulk storage ailoa atore the various renins for ahipment by railcar and truck. A typical inutuI 1ni ioii utilizing bulk storage, bulk loading, and automatic bagging is shown in figure IS. FIGURE 18. HULK HANDLING 2. Ashtabula Design The General Tire plant warn originally set up for one bagging opera tion at the diacherge of the bag filters. The SOX expansion of 1956 duplicated the original installation and allowed continuous bagging of two product lines siMultsneoualy. Realising the econoMica of the new bulk shipment methods end their convenience to the customer. General Tire he* laid plans for the installation of atorage nilos and bulk loading equipment. An automated bugging machine used in conjunction with e bulk atorage silo will allow all bagging to be none in abort prrieda at time. V. Ashtabula Operations A. Standard Products The Ashtabula, Ohio, plant has been producing PVC resins since 1954. Trade-named "Vygen," these PVC raaina are a basic raw material in the production of many plaatic products, bath consumer end industrial. - 32 - V UCC 013344 There ttnuiil lie many advantages, to both the manufacturer and the con* Humcr, of making a single, aL1-purpose vinyl ream that would be suitable for all app1icationa. However, due to the number of method* of processing and end products, thi* ia impoaaible. No single type of resin could possibly .'.pan the variety of specification* required by the industry. Hence, our research and development efforts are continu ally directed towards developing and manufacturing a family of special* lied vinyl resin* to meet the requirements of the processor. While (he Vygen resins sere designed for various types of processes and uses, they sll have the following essential characteristics: .Superior heat stability Excellent 1 tght stabi 1 ity Minimum of gelled particles Consistency of performance. Dependable quality B. Quality We feel thet quality and consistency of performance are th# most impor tant attributes of our Vygen resins. Thea* are maintained by careful control of the raw materials, process conditions controlled by modern instrumentation, and by nn extensive and .exacting in-procesa and finished product quality control program, A brief description of our quality control program and facilities includes the following: I 1, Pipeline Raw Materials <and HC1) are metered and sampled aa they enter the plant. Tests for purity ure run, some on a con tinuous basis, so that at any time we can predict and set the gee flow ratio to our vinyl chloride producing reactors. In addition, a C-jHo purificalion system is in continuous operation to increase the efficiency and life of the monomer reactor catalyst beds. 1, Other Haw Materials are sampled as they enter the plant and must be released by the QusliLy Control group before being used in production. 3. Vinyl Chloride Monomer quality is csrefully gauged by e system f process control instrumentation and frequent sampling at intermedi ate and final check-points. Chromatographic analysis of refined vinyl chloride is accomplished before the material is released for production use and contaminant levels in the psrts-psr-mi11 ion rang* are readily detected. 4. The Water used in the suspension polymerisation phase must be extremely pure. An efficient water treatment system consisting of carbon filters and deionisers ia used and process water is continuously monitored for conductivity. 5. Polymer qua Iity is initially controlled by monomer purity and the proper selection of other polymerisation ingredients and conditions. Accurate weighing or metering of all recipe materials is accomplish**! 33 - ucc 013345 into a clean, putgcd (><i i ymf i zul. mu kettle ituti prm i batch teinperiiLuti- iiiiiltdl IS inn i nt j i ned ig pimliiii- (.lie desired polymer. A polymer sampling si liedu 1 c is in I'ffflci lo moke sure t. lit* pi minted PV(. has die mi rrd properties (inliiiisic viscosity, bulk density, fish eyes, particle size distribution, etc.). 0. Tlie l*n 1 yme r Dew a t e r i ng and Drying Conditions are established and r on l r o 11 eil iii piodnce tin* desired low sioiature content and to be sure the resin is nut burned during the drying operation. Frequent i(wo*hour) samples of the drier polymer are taken and tested for din panicles, per tent of moisture, end bulk density, and a test for ftsli eyes is run three times per day. 7, The finished Product Testing Program la placed into effect after the resin i * bagged into convenient lot sues (usually 100,000 lbs.), hut before it is shipped to the consumer. This extensive program is ihe final quality check and must be accomplished before shipment. Tests run on each lot include: Intrinsic Viscosity Bulk Density 1U asLif I let Take-Up Irreversible Plasticiser Take-Up (Blotter Heeine) % Moisture Conductivity - (Electrical grade reeine) pll (Electrical grade resins) Mi 11 Stabi 1 ily Clarity Kish Eyes (Celled particles) Foreign Particles (Dirt) Particle .Size Distribution Press Stability In addition, spetial tests such as blended reain funnel flow, color drift and rheological (melt flow) studies are conducted ea the situation warrants. Vygen resins have become well known throughout the trsde as being the most reproducible from lot to lot of all the PVC resins menufsetured. This consistency of performance is accomplished by raw material purity and selection, an extensive and vigorous m-process testing scheme, s highly autoDiHled and accurate system of process control instrumentstion and a comprehensive finished produet resin testing program. This combination of factors is responsible for the reputation of quality that the Vyijcn "family of resins" hss come to enjoy. C. Productivity end Yields Continued efforts to increase plsnt efficiency and productivity have been made at the Ashtabula plant in order to meet the increasing demand for Vygen resins and to maintain our competitive position in the industry. These efforts have been rewarded in excellent fashion, and have resulted in increasing our production from 36 million pounds - 34 - UCC 013346 m t in ; y 5*# to an estimated SO null tun pound* this year *iih no major capital cxpun.ln.urc. Durum Uus same time period, tlie plant yield increased .1.5%. In .il.iitimi, a S'2 million programmed expansion program *** announced on May 14, l`<64, which is expected to increase production of the plant by an estimated 50%. This expansion will include the installation of a new .hying line, increased polymenration rapacity, and improved bulk handling facilities. 35 - UCC 013347 Him IQGHAPtlY 1. H. Coliling, l*o I ymi* r s .mil Remus, I). Van Nostrand Company, Inc., New York, 1939 2. 11. S. Patent 1,125,533. March 17, 1964 J. 11. Cli il ton, Cnit Knmneerina in the Process Industries. McGraw-Hill Book Company, I tic:. , New York, 19(iO 4. II, C. Itauman, fundamental a of Coat Knaineertns in the Chemical Industry. Ileinhold Publishing C.urp. , New York, 1964 5. It. L. Dates, P. L. Fundy, H. R. Corpatein, 'An Examination of Some Geometric Parameters of Impeller Power,* Presentation at Mixing Symposium, Chicago Meeting A. l.Cli.E. , December 3, 1962 6. J. II. Ruahton, Chemical Engineering Progress. Vol. 47, 485 (1951) 7. Friedman and Marshall, Chemical Engineering Progress. Vol 45, 482 (1949) 8. E. 0. Ayers and A. . Rhodes, Chemical Engineering. September 16. 1963, p. 157 o - 36 . KJ ucc 013348 l Aimie.Al'KJN AND APPLICATIONS t . 1 lit llijuill (.III Tlie cri'v i nu.H papers have described how polyvinyl chloride ts obtained as u g i >i o n 11* i powder. In tins .state, PVC has very limited use and the con version of I'VC into commercial products depends upon its modification through compounding. The many compositions obtainable from PVC are highly adaptable to a number of cpt`1 ut i ons wh 11 h convert the mute.riula into usable products. Most I'VC pro Jin. is lire oht at nrd by calendering, extrusion, snd coating techniques. Oilier conversion methods .such as blow molding, compression molding, injec tion molding, and fluidized bed are used to s lesser degree. The molecular weight of the resin, compounding, processing, and finishing all contribute to the performance and appearance of the final product. The great variety of end uses for PVC make it one of America's most thriving and expanding industries. PVC, more than any other polymer, ta aynonomoua wi tb veraati 1 ity. 11. End Use Applications In I Oil 2, PVC became the world's first billion pound plastic. Figure 1 shows the sales volumes of the various classifications of viuyl for 1962 and 1961. 1l ran be seen from the curves that calendering and extrusion i npt.urcs the bulk of the market. Poundage for 1963 was greater then in 1%2 in every classification except mi seel I aneouH, nml the total increase fur the one year period is 19%. Indications are that 1964 will ahow a similst i in reuse over 1963 and PVC seems headed toward a two billion pound market in t.lir near future. As PVC. has grown in volume, the price has dropped accordingly, further si i elern11ng the pi,,stirs imiusiry's interest in the material. The current low pi ire of lnr/lb. cont ributes toward making PVC one of the firat materi als roii.ii ilefcl when product ion of a new plsstir article is being planned. Though ill,* 1.40 specific gravity of the imp 1 as t i c i ir d renin ia relatively high, the pound-volume costs of the plasticized compounds are much morn 1 Hvonhl r. This poundage is not consumed as a single product nr sppI ir.it.ion. PVC has widespread utility in products ranging in stiffness from rigid sheet for' construction applications to flexible film for food snipping. This extreme difference in end product application is possible hersusn the basic vinyl polymer ran bn solvated by plasticisers over n range of concentrations. Alt of these PVC compounds are thermoplastic in 'hnnicter and acquire at snme critical elevated temperature a rubber-like consistency. Therefore, it is not surprising t.ltnt in the early days p I ns t. i e i * ed vinyl rompounds were reuverted or formed to shape on equipment found in the rubber industry. Experience soon demonstrated that, calendering, tubing, extruding, nnd pressing machines for rubber were inefficient, for making quality vinyl products. These same typns of converting machines weie modified in basic cngineeiing design, temperature range, and automatic control in order'to manufacture vinyl end-productn to extremely close dimensional tolerances. -1* ucc 013349 SUBTOTAL USAGE OF P\C RESIN (000,000 OF LBS.) GRAND TOTAL IN BILLION LBS. ucc 013350 ill. PVi: llcuit Type* ' * 4 &m'.e * ^ As out 1ined earlier, the basic polyvinyl wjorida can be polymerised or cupolymerited by suspension, emulsion, origolutilintechniquee. For the purposes of this psper, the emphasis willbepleced on the suspension type of resin. PVC polymer cun be made in s wide range of chain lengths or molecular weights. For control end identification purposes, the molecular weight is rhursrterited by the polymer's intrinsic viscosity in a solvrnt solution. The higher molecular weight polymers possess higher tensile strength and hardness, better resistance to floe at elevated temperatures, and improved solvent resistance, when compared to their lower molecular weight humologs. Tab1e 1 Effect of Molecular Weight on PVC Properties Resin Vygen 8S Vygen 10S Vygen 110 Vygen 120 Molecular Weight* Intrinsic Viscoaity 74,000 .80 83,000 .93 93,000 1.03 107,000 1.18 Tensile Strength, pat** Ultimate Elongetion, V* Tensile Stress at 100X Elongation, psi** Shore A Hardness, 0 Sec. 10 Sec. 2160 230 1290 VI 80 2490. 300 1400 91 80 2730 340 1420 91 81 2890 350 1460 92 82 Formuletiou Resin - 100 parts OOP - SO parts Ba-Cd Stsb i1iser - 2 parts i * 0. J. Mead and H. M. Punas, J. American Chemical Society, 64, 277, (1942) ** asTM 0-412-61T In a typical formulation using SO parts of dioctyl phthaiate (DOF) plas ticiser per hundred parts of rrsin and reaine of differing intrinsic viscosity ranging from 0,80 to 1.18, it can be seen that the tensile strength, elon gation at break, and Shore A hardness increase with inrressing molecular weight. Figuruu 2 and .1 show these points graphically. - 3- ucc 013351 FIGUIU: 2 EFFECT OK MOi.tC-U.AIV WEIGHT ON TENSILE STRENGTH TENSILE STRENGTH, PSI FIGURE 3. EFFECT OF MOLECULAR WEIGHT ON ELONGATION 4* * ucc 013352 IV. Conversion of Rcain u ProJuct A. Compounding 1. StabiIiration Very few polymers inherently possess outstanding heat or light resistance on lung term exposure, and polyvinyl chloride is no exception. The science of PVC degradation in veil established and. although complicated, is known to involve the loss of a chlorine and a hydrogen utoia from adjacent carbon atoms on the backbone chain. Strong alkali promotes this loss of hydrogen chloride. A slightly alkaline mctullic salt will act aa an acid acceptor and prevent further generation of IIC1 along the polymer chein. Lead aalta auch as basic lead carbonate or lead silicate were the earli est stabilisers used in polyvinyl chloride. Lead atabiliaera are still used in eloctrical insulation where the servica specifications require up to a 105C temperature rating. Organo-tin compounds auch as dibutyl tin dilaurate or tin naleate are liquid at processing temperatures and can be dispersed through the PVC compound more readily than solid metallic aalta. They also protect the polymer by ssturating the double bond created wherever HCI ia lost in the firat stage of decomposition. A major advance in atabiIixation was the discovery that organocadmium compounda are synergised in their stabilising action by companion barium organic compounds. These systems ere readily dispersed end have limited solubility in plasticized PVC compounds end nuke possible haxe-free products of good clarity and color. 2. PIsSticilet ion It vii stated previously that polyvinyl chloride resins sre capable of being compounded into a wide variety of products having different degrees of flexibility nnd hardness. This great versatility ia possibla because of the softening action of plasticisers on the hard horny resin. In general, the degree of softness of the com pound will be in direct proportion to the plsaticizer-restn ratio. By varying this ratio, a wide range of PVC properties can be achieved. The chemical function of a plasticiser in dependent upon the preaence of polar groups in its molecular structure. Thin polarity allowa the piasticiier molecules to be inserted between PVC resin molecules, neutralising the Van der Waul nr secondary valence bonds. This weakening of the Van drr Waal forces creates localised flexible areas intermingled with resin strength areas. The combination re sults in n strong, vet plinble, polymer. There is evidence that the plasticiser swells the amorphous regions and that the small regions of crystallitan are unattached nr un affected by the plasticiser. This situation is unique to polyvinyl -6- ucc 013353 IV. Conversion of Hesiu to Product. A. Compounding 1. Stabilisation Very few polymers inherently possena outstanding heat or light resistance on long term exposure, and polyvinyl chloride is no exception. The acience of PVC degradation ia well established and, although complnoted, ia known to involve the loas of a chlorine and a hydrogen atom from adjacent carbon atoms on the backbone chain. Strong alkali promotes this loss of hydrogen chloride. A slightly alkaline metallic salt will act as an acid acceptor and prevent further generation of I1C1 along the polymer chain. Lead salts such as basic lead carbonate or lead silicate were the earli* eat atabiliaers used in polyvinyl chloride. Lead stabilisers are still used in electrical insulation where the service specifications require up to a I05C temperature rating. Organo'tin compounds such as dibutyl tin dilaurate or tin maleate are liquid at processing temperatures and can be dispersed through the PVCcompound more readily than solid metallic salts. They also protect the polymer by saturating the double bond created wherever HC1 ia lost in the first stage of decomposition. A major advance in stabi1ication wee the discovery that organocadmium compounds are aynergited in their stebilixing action by companion barium organic compounds. These systems are readily dispersed and have limited solubility is plasticised PVC compounds and make possible liaxe*free products of good clarity'and color. 2. Plaaticitut ion It was stated previously that polyvinyl chloride reaina are capable of being compounded into wide variety of products having different degrees of flexibility and hardness. This grrst versatility is possible because of the softening action of plasticisers on the hard horny resin. In general, the degreo of softness of the cn pound will be in direct proportion .to the piastici*er*resin ratio. By varying this ratio, a wide range of PVC properties can be achieved. The chemical function of a plasticiser ia dependent upon the prenence of polar groupa in its molecular structure. This polarity allows the plasticiser molecules to bn inserted between PVC resin molecules, neutralising the Van der Vast or secondary valence bonds. This weakening of the Vnn iler fill forces creates localised flexible areaa intermingled with resin strength areas. The combination re* suits in a strong, vet pliable, polymer. There is evidence that the plasticiser swells the amorphous regions and that the smell regions of crystallites are unattached or unaffected by the plasticiser. This situation ia unique to polyvinyl -6- ucc 013354 I || lull dr, ll (III- i- r c >1L i un til prodm Is which art- flexible willio.it bring weak, .Hi- i i-.-. i I i flit willmut being snappy, air linin' 11-,il In-r I i k c fli.in iiibli'iv, have siul.ii-1- slip without tuik, .mil have good iiliiasiiin resistance, (oiimuMi, i jl pimini Ls ol will, i s f ur lory durability require that the Mil wnt 01 p 1 ns. l i i-1 l i ng ii,,ui have tout? term permanence, The p I ast.i i i irr s li u ii I d to- at least as permanent as the properly stabilized resin. To he permanent, the plasticizer must either be ii true solvent Oi lie .issue i ated with a true solvent fur l lie I'VC. i,.sin. The plasticizer must resist oxidutioii both during pio.'xsiiig and during long i etui in-use aping for periods up tu five or manyears. Its affinity to tile resin must be greater than In iurrigu substances which would normally contact the I'Ve product ill set VICO. For uplin I siery, these aiibstuneea would include reaiatanee to Wilkin* into clothing, dual or dirt, ami soapy water washing. It must have u very low volatility to eliminate evaporation. It should be odorless and colorless in order to liavo widespread utility. When the material in question meets these specifications to a practical degree, it. becomes known as s primary HVC pLusticiter. Qidinar!ly, a plasticizer wilt be a high molecular weight ester formed by the revrlimi of an aliphatic alcohol of eight to twelve carbon chain length with an acid which may be either phthalic, azelaic, adipic, ot sebaric. Polymeric forma of esters are usually tu the 21|UO>SOOO molecular weight range. These pIast1Citers are used where special permanence is required. IM nstit: izers sre commonly liquids with viscosities which may be as low as a light oil or as thick as honey. They vary widely in thnir efficiency in f lex i b i I i z i iig the I'VCresin and the particular proper ties contributed in the PVT product. For this reason, it is iommon practice in blend a mixture of plasticizers in nhLain a compromise of their individual assets mid defects. It is this type of blending that makes vinvl product* so versatile. Figures 5, 6, anil 7 show the effect of IKK1 plasticizer (di-oetyl phtlialate) concent r at i on on < lie tensile sttcngt.h, elongation, and Shore A Hardness of a Vygrn 120 formulation. Wheie exceptional pci nisiirnce or d i mens I onu I stability is dekisnJed, chemically bound copolymers mid physical polymer l.leuds provide the answer. Nitrile ruhlier lbutadicue' m-ryI onitt11r) can be used, although its poor color limits it to dark colored applications. Other polymers used for modification sre chlorinated polyethylene, acrylics, and acrylonitri lc*bitndiene*sLyrriir (AILS) resins. 7 POINDS SQUARE fNC.lt MOI llE > KHT.'CT OK HOP i.KVKL ON TENS!1.K STRENGTH UIOO 0n O L'000 O o _L .10 -------- 1---------- 1______ I_______1______ L 40 SO l.O i PARTS OOP/ 100 PART'S VVtiKN 120 PI WIRE to. EKKECT OK OOP I.KVKL ON KI.ONGATION 400 3001- O" 200 JL TO ----------1---------- 1---------- 1---------- 1______ IL II) r>0 SO -I______ I 70 PARTS IK1P/I00 PARIS VVGKN 120 PE8 CENT i l l > 8 - ucc 013356 I H.UiE 7. MHCT OK OOP LEVEL ON SHORE A HARDNESS SHORE A HARDNESS, 10 SET. 3. Lubrication Vinyl is procesaed and forced by metallic part* which may be a aet of rolls, a fuming die, a mold, or some other device. During this prot i-ssing, the vinyl aiuat adhere to the aetal an that the plastic draws in, fills, and flows with the forming surfaces. However, this adhesion must not be great enough to cause distortion when the article is removed frost these octal surfaces. Adequate parting is obtained by including in the cosipound trace quantities of lubricants that art as metal release agents. The release agents are soluble to only a limited degree in the vinyl compound at the processing temperatures. Thus, minute particles of the release agent are deposited on the hot metal surfaces and form a acmicontinuoua costing. Excessive quantities of the release agent should be avoided to prevent exudation on ths finished PVC surface. Exudation of lubricant appears after processing and ia not only unsightly, but can interfere with the* application of decorative finishes or subsequent dielectric heat.aealing. Stearic acid ia a common release egent, but metallic stearates, waxes, or poly ethylene have been used. Proper technology in the use of lubricants is an important factor in successful'production of vinyl products. A. Pigmentation The growing use of PVC has been due in part to the color possibilities of the plastic. -9- ucc 013357 mrnimmm m 1*19 Au Lomu11 w und hoiisciio Id upholstery ere presently made ill high mylc mini's to mutch or contrast with any color scheme. I'VC sheeting having superior durability is produced in colors and tex tures whi<.h offer unlimited creative styling possibilities to the designer. The pigments used must be acid resistant, stable to the processing temperatures up to 400K, nonmigratory, and light stable. The pigments sre dispersed to a fine particle aixe by grinding in a three-roll paint mill with part of the plaaticiier. Satiafactory pigments include titanium dioxide, phthaiocyanine blues and greens, and high tint nirbon blacks. Killers are often used for cost reduction. Finely divided calcium carbonate is must often used, but clay, aabeatoa, and other fillers are common. Certain electrical properties sre improved through the use of fillers. Flame resistance is bolstered through the incorporation of antimony trioxide and phoaphate plaaticiler*. Klectrical properties are improved with the addition of calcined clay. Processes and Fabrication 1. Pryhiending A I'VC compound initially is a heterogeneous mixture of the many components. The major ingredients are a PVC resin powder and liquid plaaticiter which must solvate the resin. The solvation rate of this type of system is time and temperature dependent. The most economical method of eolvoting the resin is through the use of inexpensive mixing equipment with Large capacities. Thu a, large stainless steel chambers jacketed for heating are used to churn, tumble, or agitate three to five thousand pounds of Lhe compound. At this stage, only the colorant is omitted. The temper ature is maintained at 160 to 200F for about an hour. This equip ment is often a ribbon blender. 2. Uanburying Part of the presolvated resin-plaaticixer masterbatch from the pre blender, together with the pigment paste, is fused into a homogeneous mass in an intensive shear internal mixer such as a Banbury. This machine consiata of a two cylindered stator containing two powered rotors. Their operation ia such that the plaatie compound ia sheared against and around the stator's surfaces. The stators and/or the rotors are heated to raise the temperature of the vinyl compound to its fusing temperature between 300-350F. A plunger retains the compound within the chambers and a sliding door in the bottom of the chambers allows tbe fused homogeneous compound to be discharged. The capacity of production site Banburya for the vinyl industry varies from a 110 to a 600 lb. batch delivered on five minute cycles. 3. Milling Normally, a Banbury batch is delivered to one or store 60* to 90" wide two-roll mills designed for high temperature operation. The - 10 - v'-v-t' J UCC 013358 I li I t'r in I (1 I'll (I I I I mi nf lit*- mill I: ( I ) t <1 I lee l hr p I n -.1 ; , n I entrapped air whipped in l> v a h i speed Uaubury; (2) i o i.iing * l* (i l ai.lt *f,o a controlled l emperut urc (anil, the i e I ore, a constant plustic viscosity); ami ( \) u> deliver tin* plastic in a r i Mum of predetermined a i t| t It ami gunge of thickness. This ribbon tuck may In- led tlirri-tly to n calender or.in extruder in practically an ideal pliislii statu, or il way lip partially cooled and fed tu a Jii'i't or pel lei iter to make a reserve compound inventory for fut ure prnccssiup. Ca I Cllilr r 1 ll A large percentage of tlie uhove mi 11-prep* red vinyl plastic com pound is fed to a calender which converts iltc crudely slmpvd ribbon into continuous lengths of film, sheeting, or coating for a sub strate (t.e., woven cloth, knit fabrics, or paper, etc.) of surprisingly arc unite widths and thicknesses. For esasiple, a modern plastic calender is capable of delivering aO.OOlR" gauge film with a maximum variation in gauge of L 11,0001". Normally, film of this gauge can be more einnomical 1y produced by ml rustan, since a two million dollar calender train must have a high poundage output to justify its capital investment. A modern calender engineered for handling plaatica haa four caal chilled iron rolls mounted in a L type frame so that the influences of lorces on any mm roll enn affect only one adjacent roll. A roll with a working face of bb* width will be from 20* to 24* in diameter while a 9t>* width roll face will have from 30" tu 3d* in diBmeier. This calender will be automated both to control the gauge of the film uud also to emboss, cool, and delivci the film to the packaging unit. These di-vi-.-s and their controls in the calender train repre sent mi investment' of a million dollars. The output production of a calender is dependent upon the gauge of the plastic delivered and generally falls in the range of 2000 to 3000 lbs. per hour for a 66* width machine. The ordinary plastic <ulonder produces film between 0.003* slid O.OOS* gauges to be used for raincoats, shower or window curtains, aprons, baby pants, food covers, uud similar arlicles. Film be tween O.OOS* and 0.010* gauges is used for inflatable toys, air mattresses, industrial protective covering, and electrical tape. Sheeting between 0.016* and 0.022* is used for novelty purposes such t* ladies handbags, belts, wallets', and briefcases. All of these gauges are used for coating fabrics or paper that are widely used in upholstery, rainwear, apparel, boat decking, shoe trimmings, book covers, and many other uses. Table 2 shown a typical formulation for a General Purpose Film. - 11 - UCC 013359 Til bio i Typical I'VC'KofftlflTalion liriur.il Purimao Flint Part. v Ho sin: Plasticizer*: I'rui imm iik uid: St ulii 1 i zcr: Vygcn 110 IX1P Crcsyl diphenyl phosphate Monomerir epoxy plasticizer Stearic acid Hu-tsl 100,00 37.U0 B.00 5. IK) O.Jfi 2,00 S. Kx I i u si mi A second method foi shaping * molten plaatic into a desired shape is with jn extruder. This device consists of a smooth bore cylinder with a close titling worm strew rotating inside the cylinder. PVU comfiouiti) as inld pellets, cold dry blended powder, or hot mill ribbon is fed lo the extruder. It is homogeneously mixed and brought to its proper working visrosity for nltimnte forming by the mechanical energy of the screw mid the heut provided by the controlled temperature cylinder or barrel. The changed pitch of the screw at its end alters the screw's function from maaticuting and mixing to that of s positive displacement pump. The orifice or die mounted at the head of the screw ia similar in simpe to the desired product. The shaped extrudale is drawn in a measured degree from the die to the cooling medium, usually water. The die must be designed in such a fashion as to compensate for the change in dimensions and shape that this pull or draft exerts mi tin* hot extrudale, 'The extruder cun form flat film, sheeting, and coated products simi lar to the products of a calender and, in addition, make hollow articles and complex shupes impossible to obtain from a calender. It is considerably less costly to install, but ban only a small fraction of the capacity of a calender. Film as thin as ! mil can be extruded by the blown film technique, A tube with a wall thickness of 0.012* is extruded. As the tube of hot plastic issues from the extruder, air is introduced inside the tube in sufficient quanttiv to expand lliu plastic to a 72* diameter cylinder. This simuItanemiHty widens the film and reduces the gauge of the wall thickness. The percentage gauge tolerance of this film is far greater than the L Ti" allowable for calendered film, but it ie adequate for film used in packaging applications. An alternate procedure to blown film ia the use of a slit die with dimensions approximately equal tn that of the film desired. This die requires a high degree of engineering sophistication to produce uniform flow of the I'VC plastic across wide widths snd especially to prevent any aert.ional areas in the flow of the I'VC plastic tlisi are slaw moving or 'dead.* This latter condition can lead to - 12 V' ucc 013360 The cxtiudcr in used fur making film, aonofilumenl atrip*, rod*, tubing, hone hiuI profile shapes such as refrigerator gasketing. Table i shows a lypu.nl PV(1 refrigerutur gasket compound. Table 3 Extruded Wefrigeratnr Gasket Parts He*In: Plasticiitis; Filler: Stabi 1 i irr: Processing aid: Vygen 120 Polymeric epoxy plasticiser Polymeric plasticiser Calcium carbonate. Ba-Cd Lubricant 100.00 10.00 80.00 25.00 1.50 0.25 The extruder ia the umvc rail device used' for. PVC coating of elec* tricat wire. In this 1st ter application, thn coppar wira ia preheated, passed through u croaa head on the extruder and carefully centered ijt a circular at ream of'extrudiug plastic so that an even coating surrounds the wir e. The wire ia pulled et a constant rata of speed and actually aid a the production rate of the extruder in aaaiating the flow of the plastic. A croas head is e device for changing the flow of the plastic to a right angta with its noreal flow. The capacity of an extruder ia rated by Lhe diameter of its cylin* der. Extruders are available in a range from 1%" to 12* with the 2M*. 4X\ and 6* the most popular sixes. Their output cepeciliea are about 175,500, und 1000 pounds per hour, respectively. The technology of the action of various thermoplastic materials during extrusion has received intenaive study during the past five years and many plastics have had their behaviour reduced to mothemalical terms. For example, screw design has been keyed to specific therm plastic compositions and the proper ratio of the length of the acre* to its diameter (L/D) has been established. Plastic extruders nor* molly have an L/D of at lenst 20/1 and often ere 30/1. As in the case of calendering, the process of cooling the extrudate and handling during poatforming are highly developed operations which affect the surface characteristics, clarity, flatness, shspe, and gauge of the product. Pieid Vinyl Rigid PVC contains only a small amount of plasticiser or none et all. Too types of rigid PVC are available. Type 1 possesses - 13 - V* **" at iniiaeiinameii' '*' ~' -ai* ucc 013361 '<* ?* > sjai6^: i^tf|^c*heiiucal reai stance, physical properties, heat n, and >eather.rreaistance. Type 2 has slightly lower and physical p^i^p.nrtien but has better iaipact reaistams^ ^up 'td 20 tinea that of Type 1. Tile iapect strength is provided by inclusion of nitrile rubbers or Modifying resins, along with stabilisers, fillers, and additives. Fabrication of Type 2 is easier and surface defects are less of a problem. Types l and 2 PVC are used in electrical conduit, pipe, ton* atruction panels, tank linings, velvet and skylights, and Many other rigid applications. Table 4 shows the effect of molecular weight and resin modifier oil the physical properties of rigid PVC. The use of the AOS resin provides s substantisl increase in inpact resiatancc. Table 4 Effect of Molecular Height end Modify ins Resin on Rigid PVC Properties -1.1. -fk-'-lT r* " Resin. S Vygen 6$ Vygen 05 Vygen 120 AflS* `n . ,' O'. 70 0.80' 1.18 hL too - 2. * 100 - _3_ 100 4_ * 70 * 30 - 70' 30 Properties Tensile Strength, pai Flexural Strength, pal Flexural Moduluu, pat 7,750 7.7T5 7.850 6,150 6,250 11,750 12,000 12,500 9,225 9,600 4.2 x 10s 4.2 x 10s 4.4 x I05 3.3 x 105 3.6 x 10s Notched Ixod'o 77P, ft. 1 fa./in. 0.44 0.50 0.80 14.0 18.0 Meat Distortion 0 264 pai . c 10 mi 1 deflection 69 69 75 66 72 60 mil deftecLion 75 76 80 74 78 Rockwell *R* Hardness 115 ns 116 107 108 *' Acrylonitrile-Butadiene-Styrene re*in b. Vinyl Foam Vinyl fois nay be prepared fron auapensinn renin by extrusion. Nitrogen' compounds which decompose under heat are used to provide the gan needed for expansion. The decomposition temper* ature is adjustable by e post expansion technique. In thin process, the material is extruded et a temporalure below the blowing agent decomposition temperature; subsequent expansion - 14 * ucc 013362 i1 f**- -'flfj.'W.,- ,, -.-a *^iu of tlit* foun in acitMipuwSc . density .h seven pounds "Hg\ Minimum practical * t by post expansion. 1^ High density (40 lb./cuevljl W) closed cell foam mmf& in* produced by direct e lowing of the compound witimi lIh* barrel of the extruder. Expansion occurs upon the (.mergence of the compound fro* the extruder head. ; Clossd cell vinyl foams arw.glao made from blends of vinyl and nitrile rubber. The proper relationship must be maintained between the i ure of the nitrile and the decomposition of the blowing agent, since the curing nitrile supports the cellular matrix. Too tupid a cure leada to ruptured cells; too slow a cure results in lost gas, giving, high densities. Proper balancing of the system gives densities aa low as four to six . pounds per cubic foot. 6. Blow Molding ' >, * .H***$i' ... ' -y ^ i7>Blow molding is a we 11 -occepted^proCeaiT for the production of plastic bottles especially, but the UBetOf iiny'l iu this process in tbe U.3.A. lies not reached the volump- which' it enjoys in Europe. The slower growth of blown W. bottles in this country lias been duo to a luck uf atabilizera which wilLpermit clarity of tbe finished bottle and still pass the toxicity requirements of the Food end Drug Administretion. Blowtl-l'VC bottles do show superior properties to polyethylene types. In addition to high'clarity and.good.ol1 resistance, PVC bottles Have .1/10 the oxygen permeability of similar PE bolt lea. Due to the high rigidity of PVC, thinner walla can be used. An extruder is the source of tbe prepared hot plaatic compound for blow molding. In thia process cylinder of hot plastic falls in a vertical position below the extruder head and between the opening of a split mold. The split mold closes to pinch the ends of the plastic, making a scaled tube. A hypodermic needle pene* tratea the interior of the sealed tube, and pressurised air is injected to expend the sealed tube until it fills the mold cavity. The cold or relatively cold mold ennverta the plastic to its hsrdened condition in s few seconds. The mold opene end dischsrges the molded object, end the cycle repeets itself automatically. The formed object may be a waste basket, (in automobile arm rest, or s part of a toy doll, although PVC bottles have one of the most interesting possibilities for future laarknLs. This is an intricate art requiring extremely accurate control of the temperature, (i.e., viscosity) of the PVC compound. Clarity is achieved through proper compounding, and ia based mainly on the stabiliser used, although the chilling rate of the hot article, particularly bottles, is also important. A rapid chill usually improves the clarity. Some degree of clarity is lost due |y> the increased molecular weight needed for impact strength. - IS - -v* ,*** * *' : ucc 013363 'V- -JS. However, these material* give less protect i uii ot processing temper atures than liii* ha r i mu-'uditi t mu and tin types. The aui cess of I'VC blow molding in Kurnpe is dot' lu the one of ill-octyl tin compounds, wliirh are an yi niim c i* I. ah I n in this country. Am morn acceptable * t ahi I i curs are developed, a large market, will be created for I'VC bottle* where other t heritiop I uh i cm are unaccept able. Fhe future should see 1'V(`. bottles used t.u package gasoline, motor and mineral Oils, polishes end insecticides, cosmetics, per fumes, disinfectant*, detergents, foods, and soft drinks. 7. Compression Molding The noUiti of plionogmfilt plwyer record* convttae l.trge tonnage of vi iiyl,,. compounds for compression molding of l.heir disks. They use s loir motwculsr weight hosnipuIymer or copolymer-resin for this purpose end-the application is a specialised industry. Clear rigid shcfefcinga* windows for instrument panels, flexible clear sheeting1;**-, rear window* in automobiles nnd novelty application*. 8. Injection Molding I'VC compounds are used to a limited extent in injection molded part*. The rotsting pleat testing screw plunger type of machine is definitelY-preferred in promising vinyl. 9. Fluidised Bed Coatings The fluidised bed coating technique is excellent for coating intricate metallic parts. This can he done with n powder blend containing all plastici*er, pigments, and stabilisers. The more popular and successful method is to fuse the powder blend end to then pulverise it into u fine powder. The costing technique is to heat the part to be coated to s temper ature in r.xcess of 150F. The he need part is then suspended in an environment of the powdered resin blend which is fluidised with a stream of air. The thickness of the fused layers can be controlled very accurately, Ih-peatcd dippings cun build up thirk and uniform costings. 10'. Cot;our__FermiTMt Irregular formed part a, such * automotive crash pada, are usually made from flat sheet* which are po*tformed to- the de.sircd shape. The most common procedure is to use the vacuum forming system. In this technique the flat sheeting is softened by radiant heat to the forming temperature. The preheated sheet in them placed over Id i O' . ..u-n ii dlikfi jini.mai asai-r'M ucc 013364 ` r" * ". te*'m&fif, uwiftrii i fcuLt. prc^t-re c auses. I J heat rapidly arfdV$ * later. I^MfhV>in the mold and the atmospheric inyl sheettg to flow anil Till the cod' ^h^Jewltl t-i colil, the vinyl sheet loses F^N^ftthd' from the mold a minute or two An alternative type of molding to varuum In distort the hot vinyl sheeting into a is equipped with holes for the escape of Tlte use of matched male and female molds the cloM'si .1 i men si on a 1 tolerance. forming uses air pressure Female mold providing it nir entrapped in the molds, results in products with i I. As semi11 y of PVC. Products PVC products arc readily cut to aiae in multiple layers by the commonly employed motor driven circular knives or by cutting with pattern sheped dies. Dielectric heat scaling is often used to seal PVC films and fleaiblm sheets. In the process, the PVC to be joined is placed between tw electrode sealing bars which transmit e high frequency current to the PVC uud inert the required pressure on it. Meat provided by friction from shifting of the polar chains within the material . causes the films to flow- together sud seal. The resultant seams have bond strengths equal to the strength of the goods. The use of recommended solvent cements to make assemblies is as sat is fee lory as dielectric sealing and are used for large objects such as in tent-making or swismiing pools. Fabric backed or sup ported PVC products are sewn with thread as in upholstery assembly. C. Decorative Effects a high percentage of vinyl resin products are consumer items and depend* ent upon their attractive surface appearance and style to sell. These effects sre obtained by either embossing or printing the colored.surface, or both. 1. Embossing Embossing of tbe plastic is achieved using steel rolls engraved with impressions that will give e pleasing appearance. These rolls sre mounted over rubber backup rolls in the calender or extruder trein an close to the forming orifice as possible. At this loca tion, the plastic sheet is in its ideal rheological condition to form' into and permanently retain the configuration of the delicate engraving pattern of the embossing roll. 2. Printing The majority of automotive upholstery is currently finished in metnllic effects across the entire surfsce. These chrome tones cannot be obtained directly from the calender since the aluminum flake dors not have an opportunity to "leaf* an it does in a highly - 17 - UCC 013365 Till' ; print iV. I I ii i sll must, t i`;Tm 1 qu*. be from a colored so I oli on The fabric is subsequently osi ({ dried Design print falls i n i i *n rlassfi. ITicre arc the delicate and subtle shadings usmiciatcd with high grade leather effects and the gaudy and often mill 11 - cu I or effects of houseware and apparel malerisis, These arc nl.so .i,>|ilted on rotogravure print machines equipped with print rolls having the appropriate dcaign engraved into their surface. At tunc*, print machines must have up to right stations applying different colors which print in register to make D. a , flower- reproJuc lion. T:', Mi aiwl ftoceaaing of Plastiaol lies ins ' ?V V' So fATJfV diMimsMed how PVC suspension produced pounddd^B^processed. I'lastisul resins are handled t resina are cum* and .processed in an entirely.di'fferent manner. I'lustisol compounds are made so that whenblended with a liquid plasticiser, the mixture is in tb^^o^^bd^h fluid. fl ast are often termed "stir-in resins," for a common method of blendisalisuI resin formulstion is the use of a simple gilatrfr.4 )(i* shear mixer* ore, quite common, although practically any methott'by. which`the ream can he dispersed uniformly in the plasticiser and/or-solventa ia acceptable. In thtt blending process, the liquids in a formulation are charged to a vese'et^an-il agitated until mixed. Then the plaatiaol resin and other powders'.are, added gradually under agitation until all materials are charged- and a uniform liquid, called a *pl listisol,* in produced. When organic solvents are included in the fonaiiiatton, the liquid is termed an "organosol." The solvent* .ire used us viscosity reducing agents. The rheology of these liquid systems is quite critical, since they ire processed by aiethoda whore the flowubility must be closely controlled. Plestisoi* are used in the following wsys: I. Dio Coating A widely used process i* dip costing. In this process, an article, web as a wire dish drainer, is dipped into the plamtiaol and re moved. The coating is then fused onto the dipped article in forced draft oveaa. When an organosol is used, the heating of the article muse be carried out in two nlagra. The first stage constats of evaporation of the solvent under low heat; the nerond stage consists of fuaion of the vinyl. In this way, surface imperfections due to boiling solvent during fusion nre eliminated. Usually, a solvent recovery system ia installed in plants using organosols for reasons of economy. In n variation of this process, cotton gloves an metal hands are dip cosrrd in order to impart chemtral protection and solvent resistance to work glove*. Articles too large for dip coating may be aprsyed with plnatiaol and subsequently fused. m -Wf*- 'as \W*'*I . Id . ucc 013366 , /' "J 2. SI ilfli Motili m S| i.shewn!ding ii. in sense refers* proTWfeft of dip- coaling, in litis process lit* pi asLi sot^jef poured into attested Mold.' The mo lit is then inverted and only-* coating of the gelled vinyl remain* in ih* molil. Fusion unit stripping of the article from the muld Lomiilfir ihe process. Hoots are made by such technique. The main itst ric11 on of slush molding is that the article must liuve at least one si(cubic opening to the interior to perai t- f i I l ing uiitl cmptviug the mold of plastisol. .1. Hot .it i olio 1 Mo 1 d 1 ng HotuLionul molding is ouch like slush molding, except that there need be no opening in the article for the introduction of plastisol. It is used for complex shapes like dolls' heads, arms, etc. It ia also used for play hall*, football*, and basketball*. In Lhe tech* tuque, a quantity of ploaLisol ia pourad into a mold, the mold ia closed and rotated in three dimenaiona while heat ia uaed to fuae the formulation inside. Temperatures must be controlled so a to permit oven fusion and uniforai flow characteristics. 4. 1'VC Foam* t'VC foams aie easily prepared from plastisol*. Either a chemical which decompoacs under heat or a mechanical entrapment of gas may be used. The plastisol is often laid down as a thin coating over another vinyl layer which may or may not be fused. When blown, the combination is effectively used as an insulating material resembling leather for use in outerwear. The areas of cushioning and inaulating err more often captured by urethane* or polystyrenes. , o'Sw aMMUfUti 19 . ucc 013367 I 'Hi t I.Vi'l''. ut1'. S* . Si--. .i, Vim-' tlr<iii>, IWinliulil, New \nrk, I95B In i.lk- > if. , Tn! v hi liivfiili, \invl Polymers. Wiley and Sn, New j i. l-ifii ,r,|i Kim-- ! ('.. . Drurra* nK f Plamjic Mutcrinls. Reinhold, flow Vork, nVi 4. Hope, Dwight, IMuntic Mnlerjjla, Cuodheert-Wi Icux Co., Chicago, 1956 5. Ki.t i-1 r,, n.| mill .1. \t. Till.. I-. II IJI .Ifvfri.i-ii'l4a lV_J-.i-musll,ili,dI.1I... II.., .a. MdIo.u..nn, ,iIh1 uIIQ9I 6ia.0ftl urn uf Therwnplwnt it .Shrel.. f>. Sin.oiulu, llvi lmi t Itumacv, Son rei Hunk of t)hc Now PIH* tic a. Rainhotil, New Vork, 1959 7. Frudou, Joel iMitur .', Mmirw 1*1 untie a Kijryclopi-diu for )964, Vol *1/ No. I A, Hi tdi elh l'rea. I'm*. llriiiol, Connect i i u l, 1963 B. SPI Plaatica Kngineei i ng DiinJbook, 1960 - 20 ucc 013368 HIM m