Document bar1MQKOoZqgpyZ3BnrjNQxKy

3 < /-2 > b /? 3 .c E. I. DU PONT DE NEMOURS & COMPANY 256 VANDERPOOL STREET NEWARK, NEW JERSEY Serial No. KN-54-33 Copy No. / NEWARK PLANT PIGMENT COLOR RESEARCH REPORT t it l e: nmm d is p e r s io n in p o l t v ih x l a c e t a t e l a t e x p a in t . i Period Covered JULY - OCTOBER, 1954 CHARGE: A-IIC-321 FILE: DATE, H/26/54 HJ 44*7 Copy to? #1 Numerical File, 2 - Research File . 3 * Library File (173.< 4 - J. S Tully/A. Slog* i: A. IT. A* F. Brisssolara Spengeman 3: J. A. FTedrickaon, Wilmington H. Arnoul 9 - j# h . Bailey if: 1* Booge/I. Jf. Krchma, Wilmington H. 4. McLain, Wif * 12 - P. J. Monahan (X lei 8: Extra Extra 15 - Extra Serial No. KN-54-33 Copy No. / NEWARK PLANT PIGMENT COLOR RESEARCH REPORT PROGRESS REPORT TITLES PIGMENT DISPERSION IN POLOTTL ACETATE LATEX PAINT* PERIOD COVERED? JOLT, 1954 - OCTOBER, 1954* CHARGE! A-IIC-321 SUBMITTED BT? APPROVED BXt Ml SGSKIffS&S 11/11/% DATE ISSUED: DUP050070032 KH-5W3 --I** mmmmt Until recently, the major emphasis in the latex saint field has been on the "rubber-base" paints based on plasticised polysty and styrene-butadiene copolymers. latex paints based on pol: acetate or polyacrylate water-disperalona are non increase in particularly for exterior paint use# The problem of pimaeat dispersion has prom to be somewhat of a drawback in the application of polyvinyl acetate (F7A) for latex paints* The dispersion considerations are complicated by the fact that optimum pigment dispersion must be effected at a pH lower than that prevalent in the rubber-base or polyacrylate paint systems* The latter are distinctly on the alkaline side and unlike polyvinyl acetate systems , do not experience a pH drift downward* Whereas our current line of anlonically die is completely unsatisfactory in PVA P, YW-694-P. at least two and pa RW-704-P, and RW-706- in such systems* Acc en to determine tbs critical factors invc pension lyvinyl acetate systems and to develop a suite f dispei colors for use in these paint systems* A complete line of pigment colors, tentatively selected on the basis of durability as being suitable for use in exterior paint applications has bean modified by surface treatment with selected non-ionic agents to facilitate their dispersion in polyvinyl acetate paint systems* It has been further demonstrated that such non-ionically dispersed colors will perform satisfactorily in typical butadisne-iiyfSae systems, and in acrylic paint systems* There is evidence that tho presence of suitable non-ionic protective colloids* present either in the dispersed pigment paste or in.|fce paint formulation, will further stabilise the pigment dispersion* if A practical plant process for the manufacture of non-ionically dispersed pigment pastes has not been developed in this work* Rather, a principle has been demonstrated which should enable the development of as complete line of non-ionically dispersed pastes for general niS in water emulsion paint systems including polyvinyl acetate, butadienestyrene, and the acrylics. DfiBHt Poor pigment dispersion in polyvinyl acetate emulsion p is evidenced by t!he increased color strength obtained when the wet# DUP050070033 KN-54-33 -2- tacky paint film la vigorously finger-rubbed to dryness* Several possible mechanisms of pigment flocculation were Investigated: 1) Pigment migration into the dibutyl phthalate which serves as a non-solvent plasticiser for polyvinyl acetate# A CPC toner paste (H-623) was flushed into dibutyl phthalate and this was then need to tint a typical exterior white formulation (Newport w-C)* Poor strength and seme flocculation versus a control were obtained* wetting and poor dispanpion ^pls^es^s^: ` `a serves as a paint tMckner and protective BW-372-P disperses very poorly into a methyl cellulose gel {2% 4000 ope) such as ie used in the paint formulation* When 3*2 parte of methyl cellulate were gsllfd in the presence of 200 , parte of BW-372-P (no additional water added) and the slue gel eo formed used to tint a white formulation, poor strength and severe flocculation versus a control were observed* Either the methyl cellulose is not completely dispersed within the paint system or the pigment, originally well water-dispersed as BW-372-P, is "floe wit! the methyl cellulose gel in this concentrated medium. Attempts to disperse TiCfc together with B-372~P in Metboesl by gelling the latter in the presence of the blue and white pigments offered no advantage over a control* Substitution of casein for Hsthoeel in a tint base formulation did not offer any advantage with respect to pigasnt flocculation# However, when Btf-372-P was dispersed in a relatively lam amount of water and the diluted dispersion subsequently gelled with methyl cellulose, a good pigment dispersion was obtained in the paint formulation as evidenced by a relatively small amount of "flocculation** The use of a non-ionic surface agent (water-insoluble Tergitol NP-14) in the paint formulation in conjunction with the above variation gave evidence of still greater pigment strength* 3) Treatment of BW-372-P (Baxad-dispersed CPC Slum) with a series of non-ionic surface active products of diffsrsnt hydrophyMe-bydrophobie balance showed some evidence that the water-insoluble members of thl r modify': ' colloids L\ Pigment incompatibility with polyvinyl acetate due to coating of the latter with water-soluble polyvinyl alcohol used as a protective colloid for the FVAi Much as polyvinyl alcohol is used in the production of resists to prevent dyes from adhering to fabrics, the possibility that it prevents the adherence of organic pigments to polyvinyl acetate was DUP050070034 KH-54-33 considered. 5) Pigment flocculation resulting from the relatively low pl!*s of polyvinyl acetate systems. Whereas a technique has been devised which assures fair dispersion of BW-372-P in a methyl cellulose gel with a consequent improvement in dispersion in a polyvinyl acetate paint system. optimum dispersion is not achieved in this manner* It is spsculstsd that tha non-ionic methyl cellulose serves as s protective colloid for the anionically dispersed CPC pigment. and preserves Its state of dispersion in the acidic polyvinyl acetate paint system. CPC Blue (B-623) ,was dispersed in the recommended exterior white PVA paint formulation (W-8) employing Slvacet $1-900 PVA emulsion, to give products essentially free of flocculation as shown by the finger rub tsst. Freedom from flocculation is further evident in greater color strength. Other paint properties have not been evaluated. N-623 (aqueous paste of solvent-ground LB/CPC} was treated with two series of non-ionic surfactants (8 Igepala and 5 Tergitols), eucoeesive members of which have a different hydrophyllic-hydrophobic balance. An essentially orderly increase in dispersion is obtained as evidanced by paint strength and freedom from flocculation. Zgepal CO-610 and CO-630. and Tergitol BP-27 and BPZ yield the beet paints. The above agents are adjacent to each other within their respective series and all are in the same range of hydrophylliclty. The best products are superior to those obtained using BW-372-P (Baxad dispersed CPC Blue) as the color source, or versus an absolute control using Daxad as the dispersing agent. The latter gives a product fully equal to BW-372-P which confirms its value as a control. It is significant that tbs most effective agents in these series are not the most hydrophyllic. In an arbitrary range of hydro* phyllicity from 43 to 81. the most effective agents for this application are in the region 6l to 63* A variety of other surface-active agents have been tested and several have been found to be equal or superior to BW-372-P (or a Daxad control) although not equal to the beet acting Tergitols or Igepals. (Emulphor EL-719, Sterox CD. Tamol 731# and TrltonX-1007. Ammonium caseinate yielded a product essentially equal to the best. The technique described above with reference to the optimum non-ionic dispersion of CPC was smiled to a complete lime of pigment colors, tentatively eslscted on tha basis of durability as being suitable for use in exterior paint applications. These eolors were modified by surface treatment to facilitate their dispersion in polyvinyl acetate paint systems* The respective toner pastes wars treated by ball milling with two aerite of non-ionic surfactants, the successive members of Which have a different hydrophilic-hydrophobic balance. An orderly DUP050070035 KN-54-33 -*4- progression of dispersion was observed* Optimum dispersion is evidenced by freedom from flocculation (finger rub test) and greater pigment strength* In addition to the non-ionic agents, ammonium caseinate, and Broad 11103 (anionic agent) were included in each aeries. The latter was used so as to confirm the behavior of tbs current line of dispersed pastes which are pressured for the most part by ths use of analogous surface agents* In ell cases* evaluation was mads in ths Newportrecommended W-g exterior white formulation which incorporates du Pont** Elvacet 61-900 PVA emulsion* Paint properties other than strength or flocculation resistance wars not evaluated* Ths results are tabulated in table I. All of the dispersed pastes described contain approximately 15-20$ pigment toner* and 25$ of surface agent based on ths toner present* The agents were incorporated by milling with the toner paste for 72 hours in a 1/2 pt* glass iar containing glass beads* To determine the effectiveness of homogenisation (in lieu of milling) for the purpose of incorporating the surface agent* Green GX paste (%764) was homogenised (one minute recirculation at 5*000 pel* Sif unit) with 5, 15 and 25$ amounts of Igepal CO-530 end CO-elO, respectively* The 25$ products were superior strengthwise, although equal flocculationwise, to the 72 hour milled controls* Increased strength and flocculation resistance was evident with the higher amounts of agent* Initial attempts to prepare a TiQg white dispersion using non-ionic agents exclusively yielded products slightly superior to the W-g exterior white control* Excellent dispersion of non-ionically dispersed CPC was obtained in the Litter Laboratories white formulation* which usee Polyco*a polyvinyl sestets emulsion and which employs non-ionic dispersants for the white* The W-g formulation uses both anionic and non-ionic dispersants* Non-ionically dispersed CPC Blue yielded s wholly non flocculating tint in a typical Dow butadiene-styrene latex formulation and in a typical acrylic emulsion paint formulation* Ths flocculationresistance was at least equal to that observed with the present dispersed pasts for latex paint, BK-372-P* There is some evidence that anionically treated colors* (BW-372-P, TT-674-P, TT-5gO-P) can be rendered more effective* diapsrsion- wise* in a PVA aysteabyapplying a protective colloid or watsr-insolU^e surface active agent (e*g* feethoeel, Igepal CO-430* Tergitol HP-14)* In either ease* a protective coating is applied to ths faioaieaUy dispersed color which renders it* at leasttemporarily* Immune to the effects of the acidic polyvinyl acetate system* The very effective action of ammonium caseinate presumably arises from its dual roll as pigment dispersant and protective colloid. Ammonium caseinate should DUP050070036 DUP050070037 KR-54-33 prow to bo an excellent dispersant in a buffered PITA or other latex apeteas as should the use of a protective colloid (or less eater-soluble surface agents, e.g. Tergitol NP-14, Igepal CO-430, etc#) In conjunction with the reeaanended non-ionic dispersants. As has been intioated previously, the soot effective non-ionic agents for plgnent dispersion in P?A ayetema are not the meet hydrophilic but rather those which exhibit a limited solubility in the system. Under the latter condition, the agent presumably migrates to an inter face and facilitate* micelle formation. NB-1514 jc i- DUP050070038 APPBHDIX X. KH-54-33 "TiFure" R-610 men* 325 Mash Waterground 2% Methoeel 4000 cp. Solution P 1 P-12p0 A - 10$ solution Reduction (a) Water ,, % Eamlphor BL-719 ' (b) Ethyl Carbltol Water 20$ Dowicide A solution {c)Elvacet 21-900 Dibutyl Phtbalate Lb./IQO Gal. 246.0 41.0 laf. 5 2.0 12*2 176.7 2*2 '1:1 11.5 356.0 ,29*0 ioif*2 jaj,^{b)j {e| preaixed solutions designated Eaulphor SLA Initial Consistency (KU) l IU Gallon Weitfit (actual)* PVCi 27$ DUP050070039 COPT APPENDIX II B. X. du Pont do Nemours & Co Incorporated PIGMENTS DEPARTMENT MiMQRANDOM FOR FILS ec; J* Booge/X. J Krehma Pigraents-Wilmington Filo NEWARK, NEW JERSEY AUGUST 9, 1954 Report of visit to the Electrochemicalfs Department, Niagara Falls, N. Y, with 0. F. Lane, August 3, 1954* PURPOSE: To acquaint the writer with the nature of polyvinyl acetate emulsion paint systems, the mechanism of pigmented film formation, the experiences of Slcnem in their efforts to prevent the apparent flocculation of pigment colors in such systems. R. D. Smmick D. A. Swalheim Polyvinyl acetate emulsion paint films form by coalescence of the plasticised PVA particles as a consequence of water evaporation* The film forms by collapse so that* for the most part, the polyvinyl acetate and the other paint constituents retain the. same relative positions in the dried film as in the wet emulsion paint. To minimise pigment flocculation in the final film, therefore, it is necessary to effect the optimum dispersion of the pigments, both white and colored, in the emulsion paint system. Photomicrographs of the original paints and semi-dry and dry paint films indicated that flocculation of the white pigment is a condition present in the original paint and no additional flocculation occurs on drying. Rubbing the seal-dry film gives better dispersion of the white by breaking up the floes. If the colored pigment is held inside the white pigment floes, such rubbing treatment would release it from the hiding white pigment and thus give a darker color. Electronmicrographs of paint films deposited from paints diluted 1 to 25 with water indicated that the titanium dioxide was flocculated and in each ease it was flocculated around the polyvinyl acetate particles. In DUP050070040 some instance, only a portion of the floe was in direct contact with the PVA particle. These restate indicate the need either for better initial dispersion of the whit pigment or, if the initial dispersion is adequate, modifiers which will pretent the flocculation of the white pigment as the other paint ingredients are added. Elchea has investigated the use of surface active agents rather extensively (Progress Report ~ Slchem NF-54~$1) in attempts to find a completely satisfactory solution to the problem of flocculation of colored or^nic pigments in light tints and conclude that improvement in this respect will probably have to come from variations or improve ments in the method of preparation of the paints with their present Slvacet $1-900 vehicle. The latter was originally developed for use as an adhesive rather than as a paint vehicle. Elchera is currently developing a PVA vehicle for paint use which incorporates a polyvinyl acetate of smaller particle size. Initial evaluations show such formulations to fee superior with respect to water resistance, and pigment flocculation tendencies as compared to the present vehicles. F. F. EHRICH CHEMICAL DIVISION DUP050070041 COPT a p p e n d ix in HR. J. A. FREDRICKSON WILMINGTON oos J. S. Bo o m. Wilmington J. N. Tuliy/A. Siegel A* A. Brisaolara D. B. Killian. Wi Pigments-Wilaington W F* Spengeman/O. F. Lane mmw. NEW JBRSBI No v ember 12, 1954 Aa per your request, we are Hating below the non-ionic surface-active agents which ware found to be effective in dispersing pigment colors in polyvinyl acetate paint systems* We understand that attempts will be made to substitute such agents for the anionic agent currently used in the W-8 exterior white formulation. .Igepal 00-610 Igepal CO-630 Tergitol BP-27 Tergitol EPX The preferred agents are Igepal C0-6lQ<Antara Chemicals Division, General Dyestuffs Corp.) and Tergitol NP-27 (Carbide and Carbon Corp.}. The possibility that one such agent can displace both the Emulphor and the Tamol in the W-g formulation la suggested* It might be of interest to investigate the entire homologous Igepal series {8 members) or th# Tergitol series (5 members) so a# to determine the org&nophilic-hydrophillc balance required for optimum dispersion. The work with pigment colors showed an essentially 1 orderly progression of dispersion with a maximum dispersion shown by ^ F* F* ENRICH CHEMICAL DIVISION DUP050070042