Document GK5rwQrpb7ovJN5kDoY6r24mY

25 most important starting materials of the plastics Industry. <1) Process Descriptions1'**3*5***7 Vinyl chloride la presently produced by 10 companies in 15 plants in the United States (including Puerto Rico),as shovn in Table 1. Until the late 1950's, VC was generally produced from acetylene and hydrogen chloride* Sines that time, the process Involving oxychlorlnation of ethylene has increasingly replaced the Acetylene route in this country, so that presently 13 plants with almost 92 percent of the cipaelty ere using the ethylene route. Acetylene Route - In this process, vinyl chloride is produced by the catalytic hydroehlorlnatlon of acetylene, usually with mereurle chloride ee the eetelyst. The acetylene and the hydrogen chloride are first passed through a drying tovar and then mixed in a chamber packed with activated charcoal* This mixture is then passed through several hundred vertical tubes in which the catalyst is packed* The temperature of these tubes Is controlled to ranges which permit the reaction to take place. The product gases are then purified to vinyl chloride by water and alkaline scrubbing, drying, and finally fractional distillation using decreasad pressure and permitting the VC to boll* Host of the variations In this process arise from the use of different catalysts or mixtures of catalysts* Use of this route in the United States has been decreasing due to the greater efficiency of large scale plants using the oxychlorlnation process. AP00043116 / Comany Allied Chemical Corporation American Chemical, Inc. B. F. Goodrich Chemical Company Continental Oil Comanv Dow Chemical Company Ethyl Corporation Monochem. Inc. PPG Industries Shell Chemical Co. Tenneco Chemicals, Inc* Table 1 Tlnvl Chloride Monomer Producers Location nominal Capacity (MM lb.) Baton Rouge, La. Vatson, Calif. Calvert City, Ky. Lake Charles. La. Freeport, Texas Oyster Creek, Texas Plaquemine, La. Baton Rouge, La. Houston, Texas Geismar. La. take Charles, La. Guayanllla, P. R. Beer Park, Texas Horco, La. Houston, Texas 300 170 1,000 625 180 >700 340 270 150 350 300 500 1,200 1,000 255 7,340 Process Direct and oxychlorlnatlon H nM tf H Direct chlorination tv Direct end oxychlorlnatlon Acetvlene Direct and oxychlorlnatlon it Acetylene ti Sources: See Bibliography, references la 2, 3, 4. NOk AP00043117 Ethylene Rout* - Ethylene can be directly chlorinated to produce vinyl chloride; however, difficulties with that technique have led to VC production from ethylene through the intermediate formation of 1,2-dichloroethane (also called ethylene dichloride). Several plants in the United States, Japan, and Europe use this process, also known as the oxychlorlnatlon proeese. There are severel variations of this process which have demonstrated commercial feasibility* Dlffsrencas among thase generally arise in the amount of recycling or In materials used es catalysts* The basic ateps Involve combining chlorine with ethylene to fora ethylene dichloride (EDC), oxyhydsochlorlnatlng ethylene to fora EDO, and pyrolyalng EDC to form vinyl chloride and hydrogen chloride. The EDC thus comes from two sources: chlorine combined with ethylene In a liquid phase reaction with a dlssdlved catalyst, and ethylene combined with hydrogen chloride and oxygen In e vapor phase reaction with a catalyst. The crude ZDC from these two units ! combined with EDC recycled from the cracking unit end la then purified by distillation. The second major operation Involves thermal cracking In the presence of a catalyst to form vinyl chloride and anhydrous hydrogen chloride from the EDC. The resultant effluent is then separated by fractionation Into vinyl chloride. Hydrogen chloride la passed back to the oxychlorination unit, and unreacted EDC la recycled. (2) Worker Exposure3* 8> 18 Vinyl chloride la produced in outdoor plants, and hence the build-up of vinyl chloride in any area Is less then whet is observed at locations In subsequent processing involving the AP00043118 28 monomer or polymer. The job categories of workers at VC production plants ere shown In Table 2.' No data la currently available to show how many people nationwide are employed In these plants In each category. At the OSHA hearing on February 15, 1974, the Manufacturing Chemists Association estimated that 1,500 people are employed in monomer production* However, Information presented by PPG Industries and the Shell Chemical Company gives a substantially different picture. PPG indicated that It employe between 2 end 4 workers par million tons of stated capacity at Its plants, while Shell Indicated between 26 and 40 workers psr million tons of stated capacity at Its planes* The difference between the two probably indicates that each type of process (and perhaps each plant) differs In the number end type of workers required. An estimate of the number of workers of each type la necessary for any characterisation of tha total hazard, since data presented to OSHA and at the public hearing indicate different peak and tlae-welghted-average concentrations for different categories. The oajor sources of exposure during normal exposure are judged to be: o SaspUng and analysis of vinyl chloride for quality control; o Loading of vinyl chloride for shipping; o Entry of vinyl chloride containing vessels for maintenance and repair work; and o Laaka of vinyl chloride In the process area. i AP00043119 29 Table 2 Job Categories of Workers Vinyl Chloride Plants Control Operator Distillation Operator GDC Operator Electrician Inetrumenc Technician Laboratory Technician Laborer Loading Operator Maintenance Worker Material Controller Millwright OXY Operator Plpeflttar Quality Control Specialist Saaple Man Shift Supervisor Tank Tarn Operator VCM Operator AP00043120 30 Some sampling data indicat* peak concentrations ovr 200 ppm for laboratory technicians* over ISO ppm for loading operators, and near 50 ppm for quality control specialists. Time-weighted averages are generally vail below 50 ppm* Since no information in sampling time and method or analytical mtchod are given* the data cannot ba uaed to estimate the worker's exposure to VC. 2. Production of Vinyl Chloride Polymer and Copolymer Resins Virtually all vinyl ehlorlda produced in the United States is used to manufacture vinyl ehlorlda homopolymare and vinyl chloride eopolymerlsed with such monomers es vinyl acetate* vlnylldene chloride* and acrylates. Generlcally* these homopolymere and copolymers ere known as polyvinyl chloride (PVC) retina. They are generally In the form of powders* which* sftsr compounding with a variety of additives* ere processed in several ways to producers large variety of plastic or resinous end products. The resins ere produced by 22 companies in 36 plants In the United States* as shown in Table 3* which also indicates the capacity of each plant. As Indicated in the references* this list is current to mld-1972; changes in company ovnarship* additional plant openings* and Increased capacities are likely to have occurred since that time. Host commercial resins have molecular weights between 30*000 and 120*000* the weight being a determinant of tha resin's processing and performance characteristics. These characteristics are also affected by the specific additives with which the reelns are compounded. Since theoretical results do not definitively Indicate AP00043121 Table 3 I Vinyl Chloride Polymer and Copolymer Resin Producers Nameplate Capacity smum Ale tmdueti A Chemicals, Ine. American Chemical Corporation B. F. Goodrich Chealcal Co* Borden, Inc. Continental Oil Co* Diamond Shamrock Corporation Ethyl Corporation Firestone Tire & Rubber Co* Calvert City, Ky. Pensacola, Fla. Long Beach, Calif. Avon Lake, Ohio Henry, 111. Long Beach, Calif. Louisville, Ky. Pedrlcktovn, H.J. Illlopolla, 111. Leominster, Maaa. Aberdeen, Hiss. Oklahoma City, Okla. Delaware City, Del. Deer Park, Texas Baton Rouge, La. Perryvllle, Md. Pottstovn, Fa. 120 v 50^ 125 125 125 125 275 130 285 285 220 80 250 250 180 130 140 Genetal Tire & Rubber Co. Goodyear Tire & Rubber Co. Greet American Chealcal Corp. Hooker Chenleal Corporation Ashtabula, Ohio Niagara Palls, N.T. Plaquemlne, La.Fitchburg, Hasa. Burlington, N.J. Hicksvllie, N.T. 100 100 100 40 180 10 Keysor Century Corporation Saugus, Calif. 35 Monsanto Company Springfield, Mass. 150 National Starch & Chealcal Corp. Meredosla, 111. 10 Fantasote Coapany Passaic, N.J. 120 i Point Pleasant, V. Ve. 120 AP00043122 Table 3 (conc'd) Vinyl Chloride Polymer and Copolymer Resin Producer Company Location Baseplate Capacity AM U>.) Roblntech* Inc. Stauffer Chemical Company Tenneco Chemicals, Inc Thoapaon Plastics Conpany Union Carbide Corporation Unlroyal* Inc. Painsville, Ohio Delaware City* Del. Burlington* R.J. Flealngtoo* N.J. Assonet, Mass. Sooth Charleston* If. Vs. Texas City* Texaa Palnsvllle* Ohio 220 160 165 60 150 120 200 140 Sources: See bibliography references 2, 12, 13, 14. i i AP00043123 uK 33 t u. what mixture* will give rise to vhat properties, formulation end processing Is largely e natter of experience. Four basic processes are employed la polymerization or eopolyaerlzatlons bulk, suspension, emulsion, and solution polymerisation The bulk process is a dry process requiring no vater, euapandlng agents, or emulsifiers; the other three processes requlrt water, solvents, or other liquids, but they are similar enough that they can be used in the seme equipment. Polymerization of monomers is initiated by free radicals produced from peroxides, azo compounds, and persulfates by thermal decomposition. The race of polymerization and the molecular weight distribution of the resin ars largely determined by the temperature of the reaction end the concentration of Initiators. CD Process Descriptions 1*12,13,13 In the United States, approximately 78 percent of PVC resins i le produced by suspension polymerization, 13 percent by solution polymerization, 6 percent by bulk polymerization, and 3 percent by i solution polymerization. The bulk polymerization process is relatively nev and has been taking an increasing proportion of - the production of PVC resins in recent years. Suspension Polymerization - This process is essentially a batch process generally carried out in glass-lined reactors having a capacity of 2,000-6,000 U.S. gallons. Monomer soluable initiators, such as lauroyl, deesnoyl, and benzoyl peroxides are AP00043124 34 dissolved in liquid monomer dispersed la vster to form s suspension. The reactor is first charged with the required amount of deionized vster. Then the dispersant, a buffer, and the Initiator are added. Oxygen is then evacuated from the reactor, and the vinyl chloride and any comonomer are fed in. Agitation (to lncreasa the degree of dispersion) Is begun, end the contents of the reactor ara brought up to the polymerization temperature (45-40*0. When the polymer* Ixatlon has been completed (efter 10 to 16 hours), the contents of the reactor are dumped Into a large vessel where excess vinyl chloride is recovered for distillation and reuae. The PVC slurry Is then blended In another vessel with other batches to reduce small variations, and dewatered by a superdecanter or continuous centrifuge to yield a polymer cake containing about 20 percent moisture. The polymer Is then dried in a flash dryer, and the polymer particles are separated by passage through a cyclone separator, from which it Is ecreened and sent to storage. Emulsion Polymerization * This process is very similar to the suepension process, and Is used primarily to produce very fine particles. There are two primary differences: (1) Usually two emulsifying agents, one solubls in water and one in the monomer, ere used to prevent the coalescence of.polymer particles; and (2) the polymer is separated from the water by spray drying. Evan though this process is more costly, it is Important to users who need PVC in liquid form. This type of polymer has tha ability to form a paste when combined with a plasticizer. In some cases, the slurry is not dried, instead it *s used subsequently in the latex form. i AP00043125 35 Bulk Polymerization - In tbia. proceae, vinyl chloride la polymerized without the addition of othr liquids In the presence of s free-radical initiator. The rssultlng polymer is Insoluble In the monomer, and the rate of polymerization increases with increasing conversion. This acceleration can be induced by the addition of preformed polymer. For this reason, e portion of a day's supply of monomer la pumped into e prapolymerizer, stainless-ateel clad vaaaal. The reaction products from this stage serve as seed for the polymerization continued In e second Step. The mixture from the prepolymerlzer, together with an equal amount of fresh monomer, are transferred into an autoclave equipped with slowly rotating agitator blades, where the reaction la Induced by high pressures. The reaction medium le essentially powdery. After the monomer has been converted, unreacted monomer is removed by e vacuum end recovered in e recycle condenser. The resin la transferred to a resin receiver, end fines ere collected in e duet separator and removed through a manhole. The output of bulk processing plants is said to ba more than twice that of good suspension plants of comparable size. This factor will probably lead to a greater use of bulk polymerization during ensuring years. Solution Polymerization - This process is used exclusively for the production of copolymers of vinyl chloride with vinyl acetate. The mixed monomers ere dissolved in an organic solvent in a stirred autoclave heeted to 40*C. The reectlon in the autoclave haa the same eutocatalytic characteristic ae that occurring In bulk AP00043126 36 polymerization. In this case, however, the phase separation, arising from'the formation of a concentrated polymer base, leads to decrease In the rats of polymerization. The contents of the autoelave are passed through a filter press to retain the polymer, and the filtrate is recycled. The filtered polymer (in the filter prase) is then veehed, during vhich e certain amount of unpolymerized vinyl chloride la recovered by fractional distillation. (2) Worker Exposure 16 The total number of workers engaged in ell eepecte of the production of 2VC resins has been eetlmeted as 5,000. The validity of this figure Is suspect, sines an Industrial byglane survey conducted in 1969 examined over 5,000 workers at a time when PVC production was approximately half of the current level. A small proportion of those workers were engaged In operations other then reeln production; In addition, the productivity of these workers has probably increased substantially since 1969 in view of elgnifleant technological changes, such ss the introduction of the bulk polymerization procees. Therefore, the number of workers has probably Increased substantially beyond 5,000, but In all likelihood la still significantly leaa than 10,000. Soma of the job classifications of workers involved in resin production with potential exposure to VC are shown In Table 4, Since no estimates of the personnel distribution in these categories is available, end since exposure varies according to job category, no estimate of the total industry exposure to vinyl chloride can be made. AP00043127 37 Table 4 Job Categories of Worker* Production of PVC Resina Bagging and shipping operator Catalyst makeup man Dryer operator Ganaral laborer, custodial Laboratory technician Maintenance personnel Monomer maintenance personnel Monomer operator Monomer recovery operator Monomer supervisor Polymer supervisor Reactor cleaner Reector operator Slurry blender Utilities operator Warehouse personnel i AP00043128 38 Vary little information i available as to the lavel of exposure faced by different workers* The Industrial hygiene survey mentioned above performed no air analyses. However* the Information available does tend to Indicate that exposure to VC Is greater In realn producing plants than in those synthesising the monomer. The areas of greatest exposure In a FVC plant are judged to be the following: o Unloading of Incoming vinyl chloride; o Reactor cleaning; o Entry of vinyl chlorlda containing vaaaala for maintenance and repair work; o Entry of PVC storage silos; o Shipping or packaging of FVC; and o leaks of vinyl chloride In the process area. Ho definitive measurements have been made to ascertain the relative exposure In these areas. From the little data available. It appears that reactor cleaners are likely to have the greatest exposure. Operators of the polymerisation process equipment, those involved in unloading or transferring the monomer, and maintenance personnel, respectively, have successively lower exposures to VC. Other personnel are likely to be exposed to much lower levels. Reactor cleaning posea a special hazard. During tha reaction, the polymer, with entrapped monomer, bullda up on the surface of the reactor, so that cleaning aftar several batches is usually required. In the past, moat of this cleaning was performed by hand AP00043129 39 using a scraper end chisel. Air analyses have shovn chat VC concentrations In the reactor prior to ventilation reach 3,000 ppm. After ventilation has been completed and the worker begins the scraping* concentrations between 50 and 100 ppm may easily be released in the scraping. Air analyses have shown concentrations of 600 to 1*000 ppm of VC close to the hand. Since these studies were completed* the industry has moved to greater use of water-jet or organic-solvent cleaning. The status of the exposure levels when the reactor Is opened for cleaning is not known. 1, 12, 15, 17 3. Compounding of PVC Resina with Addltlvaa In moat applications PVC is used with one or more specific additives to enable processing and converting the compound into final products. The additives which are used depend on the Initial form of the resin* the type of processing to ba used, and the daaired application. Resins are classified as general purpose (made by any of the techniques described in the previous section) and dispersion (made primarily by emulsion polymerization). With the addition of a plasticizer, the general purpose resins are further classified into plasticized resins and unplasticized* or rigid* resins. The dispersion resins* or latexes* may also be plasticized for ultimate use as plastlsols or organosols* or they may be chlorinated for ultimate proceaalng similar to that used ian general purpose resins. To these basic resins, other additives may be compounded according to particular requirements. These AP00043130 40 additives ere usually categorized as follows: o Plasticizers, to Increase realn flexibility, softness, and elongation, and in some eases, to extend the beslc resin; o Heat stabilizers, to prevent discoloration during the processing of resin compounds; o Fillers, ssssntlslly to rsducs costs, but sometimes to produce opacity, specific electrical properties, resistance to ultraviolet light, realetance to blocking, improved dryblending properties, end other properties; o Pigments and dves. to eolor PVC resin compounds; o Processing aide, to facilitate the achievement of certain processing objectives, such ee increased processing rates, lover processing temperatures, Improved fusion, and reduced surface gloss| o Impact modifiers.for rigid resins, to protect against brittle fracture; o Lubricants* to reduce friction of melts with the surfaces of processing machinery and molds; o Light stabilizers, to prevent PVC degradation'"from continuous exposure to sunlight; O Fungicides, to inhibit the vulnerability of compounded PVC to attack by microorganisms; i AP0004313I 41 o Mama retardant*, to preserve the nonflammability of FTC introduced by the uee of flammable plasticizers; o Antietatic agents, to improve electrical conductivity; o Antioxidants, to provide protection in high-temperature application*; and o Foaming agents, to influence cell structure for resins expanded into foams. Compounding of these additives with FTC resins may take place in a plant producing the basic resin, in s plant designed for the purpose of compounding alone, or in a plant vhlch also processes the compounded resins. Trade publications identify approximately 200 companies supplying chlorinated, plasticized, or rigid PTC or copolymer reeins. The accuracy and completeness of Chase listings cannot bo appraised at this time. The purpose of the compounding stage la to ensure that the additives are fully dispersed in the PVC resins to yield a homogeneous material suitable for further processing. The compound may be in povder or granular form. The latter can ba obtained only by heating vhlch converts the compound into granules or pellets. The granulated compound is used ee the feedstock for subsequent extrusion and molding processes. The powder AP00043\32 42 blends esn bs fed dirsccly into fabrication equipment so chat the PTC resin needs to be heated only once and thus requires fever additives* (1) Process Descriptions A vide variety of compounding equipment la currently available; the majority of such equipment accepts tha resin and tha various additives in dry form* Frequently} the resin is prsalxsd with several additives before being used In processing the compounded PVC* The order la which specific compounding equipment is used depends on the requirements that the PTC must meet* Two-Roll Will - The materiel is fed in the fora of powder blend to two rolls eepereted by a small gap In which it la kneaded at a taaparaturs of 150-160*C and stripped off as a continuous band aftar about 10 minutes. The strip of material la then granulated into small cubes auitabla for use in an extruder. Banbury Mixer - Tha mixer consists of a Jacketed mixing chamber fitted with rotors rotating in opposite directions. Material la mixed in batches under pressure and heat to produce a fully fused and kneaded mixture* This mixture is discharged in a doughlike mass which must be converted into Bheet form for AP00043133 43 granulation. Th* material la fad into a two-roll mill for thla purpose. The uaa of Banbury mixers nay lead to significant variation batwaan batches. Thla variation Is reduced In soma caaaa by the use of automatic weighing and feeding systems for Injection of the various materials to be mixed. Continuous Mixers - Thla type of mixing is designed to increase consistency between batches by providing a continuous fsad operation. These mixers requirs greater care to ensure that a homogeneous mlxturs is obtained. The types of squlpaent used ere basically single or twin-screw extruders, modified to Increase the working of the materiel. The compound may be heated, fed directly to calenders, extruded through e die plate for granulation, or extruded through a die with a dle-face cutter for granulation. Multiscrew Compounders - Since a twin-screw extruder is suitable for FVC compounding, this type of equipment has been adapted. The primary variation from extruders la tha development of screw sections and kneading discs which esn be changed to meet the specific requirements of the material being compounded. High-Speed Mixers - Injection molding and extrusion equipment has bean modified to accept PVC powder blends. To i AP00043 i 34 44 ensure satisfactory processing, the blends are nixed In a high-speed mixer in which'heat is generated by friction. The production of the proper blends must be carried out very carefully using this type of equipment. Wet Granulation - In this process, the PVC is used directly from the polymerizer while still in an aqueous dispersion. The additives are first introduced into the granulating vessel. The plasticiser, along with some of the stabilizer and lubricants, however, la mixed separately and then fed into the granulator. Finally, the compounded resin particles are rapidly plasticized, and the compound la produead in tha form of granules which are easily sspsratsd from the suspension. This process is limited to polymer manufacture, since It la not economically feasible to redlsparss the polymer once it hee been dried out. of Plastlsols - FVC pastes can be produced using paddle-type mixers, such as the vertical paddle mixer, the vertical planetary mixer, or the horlzonal Z-blade mixer. These mixers can be operated under a vacuum. The PVC resin is Introduced into the mixer along with sufficient plasticizer to fora a paste. Other Ingredients are then incorporated slowly and at low temperatures until a smooth homogeneous paste Is obtained. (2) Worker Exposure The PVC resin and the compounds involvsd in the processing at this stage contain residual amounts of vinyl chloride in concentrations which may be ea high as 3,000 ppm. The basic resin. AP00043135 43 if scored for some time in begs or drms, will release an amount of the monomer inside the container which would be released to tb* elr upon the opening of the conteiner. During the compounding, the mixing operation* ney cause an additional release of the nonomer entrained In the polymer. The extent to which the monomer escapee haa not bean adequately studied, since a significant problem was not known to be present. Soma initial environmental studies have shown levels in the workroom air to be below 1 ppm; however, level# inalde certain types of mixers have been measured at 460 ppm. These etudlee do not conclusively establish that workers engaged in compounding are not exposed to concentrations In excess of 1 ppm. No studies have as yet been made to determine the relationship between the concentration in the workplace air and the residual vinyl chloride In the FVC resin or compound. , The numbers and types of workers exposed to vinyl chloride during these compounding operations are not known. It la assumed that the greatest concentrations of vinyl chloride are present in storage rooms where the FVC resins ere kept prior to processing. However, Industrial hygiene studies have not yet been conducted to determine where the greatest concentrations are to be found. 4. Fabrication of End Products from FVC Compounds** ^ The popularity of polyvinyl chloride arises from lea adaptability to many types of processing for the production of a AP00043136 46 wide variety of products. These processes have not been developed specifically for PVC, and so equipment may possibly be employed with a variety of plasties compounds. The importance of PVC lies in the ease with which it is processed and the characteristics of the final products. Through processing( PVC resins are converted after all additives have been introduced into products which are subjected to no further chemical processing. The products of this stage say be flnel products (such as pipes), components of othtr equipment (such as wires), or sieterlels for other industries (such es films and sheats for packaging). Thus, products made at this stage may ba subjectad to further processing, but such products would no longer be designated as PVC. Tha number of firms engaged in this type of processing is not known, but has been estimated to be between 4,000 and 20,000, ranging in else from a fev people with simple equipment: to large plane* involving many people. (1) Process Descriptions PVC compound processing In this stage is marked by heating the compound and subjecting it to pressure In order to put it Into the desired form. The types of equipment and the temperature used for these processes depend on the form and tha characteristics of the raw material. Thus, for example, plasticized compounds can be processed more easily than rigid compounds, since it is possible to use temperatures between 140 and 160*C rather than between 185 end 190*C. < AP00043137 47 Extrusion - Both plasticised and rigid PVC formulation# can ba extruded into a variety of shape#. The compound la generally processed from either powder blends or granulated material using single or twin-screw extruders. Determination of the temperatures and other characteristics such as rate at which the extrusion is carried out can only be accomplished by careful experimentation. Extrusion performance depends quite significantly on the additives, particularly lubricants, combined with the PVC resin. Extrusion is used primarily to produce wire and cable insulation, rigid pipe and tubing, blown film, and unplastlclzed PVC sheet. Ini action Molding - Generally, low-molacular-welght PVC resins In the form of granular or powder blends may be used in screw-type injection molding machines. The rotation of the screw produces a homogeneous melt which Is then injected into a mold at high pressures. Blow Holding - This process Is generally limited to the production of bottles, mostly from powdar blends but with some use of granular compounds. Moat of the equipment used in this process forms a parlson, a partially formed mass of material still in plastic form, by continuous extrusion or by the use of e reciprocating-screv system. The parlson is then blown into the proper mold. Compression Molding - This technique is used primarily for processing rigid PVC compounds into phonographic records. Usually, AP00043138 41 * copolymftr of vlayl chloride aad vinyl acetate is used to produca a low-viacoaity malt. Thia malt la nixed and fused, passed to ft two-roll sill from which it it stripped, and then eoBprftftftloa molded in rtcord pr at high pressure. The Initial compound can also be la pellet fora from which a preaeaeured molten extrudete la preaaed in a mold. Thia. technique ia alao eha only method used to (Manufacture thick, high-quality, rigid ahaat. Calendaring - This tachnlqua ia used extensively for the production of flexible and rigid PVC film and cheating. It Is usually uaad In conjunction with the mixing of additives rather than as e aeperete stage in processing PVC* Pellets ox powder ere fed directly to the hot rolls of the calender. The resulting molten material is carried through finishing rolls to produce rigid eheets or material laminated to substrate* Plaatiaol Processing (Coating) - In thia processing, a PVC pests resin is coetsd on various substrates such as fabrics, sheet steal, and papas. Several types of equipment may be used to accomplish the coating. The paste resin is generally fed to a device which appliea the PVC to the substrate, either one or several times to achieve the desired thlckaeaa. The material is then passed through a heating oven to produce complete fusion of tha PVC. AP00043139 49 Plastisol Proceeeint CMolding Methods) Several methods say bt employed.to mold a PVC pasta resin into a desired shape. A measured amount of paste say be charged into a sold. The sold la rotated to cause the resin to gravitate to Its vails where It Is fused to form a uniform thickness. The paste resin may also be poured into a sold where it is fused. Low-pressure injection molding is also used to produce PVC shoe soles. Poems - Flexible or rigid PVC foams can bs produced by subjecting PVC resin convtreed into a plastisol to mechanical ox chemical bloving. The plastisol is mixed vith an inert gee or elr which la then fed through spray nozzles under carefully controlled conditions to produce e slowly expanding foam. The plastisol Is whisked and the resulting froth is stabilized. Either of these mixtures is then subjected to heat while being calendered) extruded or molded so that it is fused in the daelred form. (2) Worker Exposure The numbers and types of workers exposed to vinyl chloride in this fabricating stage art not known. The extent to which vinyl chloride Is released froiPthe raw materials used is also not known* although It would seem that the amount released would depend on the amount of the residuum still present in PVC compounds. The products fabricated in this stage also contain soma amounts of vinyl chloride, but the rate o migration Is deemed to be sufficiently small so that no detectable amount is present in workroom AP00043140 so lr. Further studies nust be conducted to determine the extent to vhleh writers la fabricating pleats ere exposed to vinyl chloride. i AP00043141 51 BIBLIOGRAPHY 1. C. A, Brighton, J. L. Benton, G, C Marks, and J. P. Dux la N. M. Blkales, ad,, Encyclopedia of Polymer Science end Technology, Volume 14, Intereelence Publishers, e division of Joha Wiley & Sons, Inc., New York, 1971, pp. 305*483. 2. D. P. Keene, R. B. Stobeugh, end P. L. Townsend, "Vinyl chloride: how, where, who * future," Hydrocerbon Processing, February 1973, pp. 99*110. 3 Statement of R. J. Reynolds, Shell Chemical Company, et OSHA hearing oa February 15, 1974. 4. "Tight monomer supply plagues PVC producers," Chemical and Engineering Hews, Hey 28, 1973, pp* 6*7* 5* D. W. P, Herdle in A. Standee, ed., Kirk-Othmer Encyclopedia of Chemical Technology, 2nd ed.. Volume 5, Xateradence Publishers, a division of John Wiley & Sons, Zac., New York, 1964, pp. 171*178. 6. "Production processes for vinyl chloride," Hydrocarbon Processing, November 1971, pp. 220-223. 7. L. P* Albright, "Manufacture of vinyl chloride," Chemical Engineering, April 10, 1967, pp. 219*226. 6. Division of Health Standarde, Office of Standards Development, OSHA, "Industrial Hygiene Survey Report on Vinyl Chloride and Polyvinyl Chloride Manufacturing Facilities," March 1974. 9. Steteaeat of V. K. Rowe, Dow Chemical Company, at OSHA hearing on February 16, 1974, Appendix II. 10. Statement of the Manufacturing Chemists Association at OSHA hearing on February 15, 1974. U. Statement of PPG Industries, Inc. at OSHA hearing on February 15, 1974. 12. H. E. Frey, "Polyvinyl chloride resins," Chemical Economic Handbook, Stanford Research Institute, Menlo Park, California September 1973. AP00043142 52 13. M. J. R. Cantov la A. Standen, ed< Klrk-Othaer Encyclopedia of Chemical Technology, 2nd ed., volume 21, ^ntereeience Publishers, a division of John Wiley 6 Sons, Inc,, New York, 1970, pp. 369-412. 14. United States Tariff Commission, "Preliminary Report on U.S. Production of Selected Synthetic Organic Chemicals, November, December, and Cumulative Totals, 1973,11 Washington, D.C., February 6, 1974. 15. "PVC," Plastics Engineering, December 1973, pp. 23-40. 16. W. A. Cook, P. M. Clever, B. D. Oilman, and H. J. Magnuson, "Occupational acroostaelysia: IX. An Industrial hygiana survey," Archives of Environmental Health, Volume 22, January 1971, pp. 74-82* 17. R. J. Gallueh, "Polyvinyl chloride," Plastics World, August 20, 1973, pp. 66-67, 149-152, AP00043143 S3 V. THE PROPOSED STANDARD In response to the health hazard# of vinyl chloride that have recently become known, the Occupational Safety and Health Administration haa developed proposed standard (Appendix B). This chapter briefly describes the provisions of the proposed stsadsrd. Applicability of Proposed Standard The propoael applies to any company manufacturing or using vinyl chloride or polyvinyl chloride which releases detectable amounts of vinyl chloride. Detectable levels ere defined as those measurable by a method capable of detecting 1 ppm with an accuracy of i SO percent. Saw polyvinyl chloride resin end the many compounds made from this resin specifically for molding* calendering extrusion* or other similar processes are considered to have the potential for releasing detectable levels of vinyl chloride. If the PVC compounded Tesla contains a large proportion of unreacted monomer* Its handling end heating will release some pert of that monomer. Operations handling fabricated products made from polyvinyl chloride, entirely or In parts are specifically exluded from the standard* since the release of monomer from such products has not been demonstrated. The proposed standard specifies that fabricated products Include such Items as film, sheet, block, bar, and extrusion stock. 4 AP00043144