Latexes vinyl-acrylic

An acrylate modified vinyl chloride - vinylidene chloride latex copolymer (Haloflex 202) has been developed in our laboratory (1,2) specifically for the preparation of water-borne anti-corrosive primer paints. This carefully designed copolymer, hereafter... 

Although acidic paint formulations based on the chlorine-containing vinyl acrylic latex copolymer give excellent anti-corrosive performance, they do exhibit two unusual features not present in the corresponding alkaline formulations ... 

Substrates, Paints and Coatings. Both flash rusting and underfilm darkening studies exployed a white, pH 4.5, primer formulation (see Appendix), designated as Standard, based upon Haloflex 202, a chlorine-containing vinyl acrylic latex. A zinc phosphate free formulation, designated as Non-Standard, of pH6 was prepared by substitution of zinc phosphate for barytes. The comparison paints were a commercial butyl acrylate-methyl methacrylate water borne primer, formulated at pH 9, and a solvent based chlorinated rubber primer. 

Primer Formulation Based on Chlorine Containing Vinyl Acrylic Latex... 

Product Vinyl acetate, butyl acrylate, and vinyl neodecanoate (60/15.3/24.7[w/w]) latex polymer... 

The formation of coagulum is observed in all types of emulsion polymers (i) synthetic rubber latexes such as butadiene-styrene, acrylonitrile-butadiene, and butadiene-styrene-vinyl pyridine copolymers as well as polybutadiene, polychloroprene, and polyisoprene (ii) coatings latexes such as styrene-butadiene, acrylate ester, vinyl acetate, vinyl chloride, and ethylene copolymers (iii) plastisol resins such as polyvinyl chloride (iv) specialty latexes such as polyethylene, polytetrafluoroethylene, and other fluorinated polymers (v) inverse latexes of polyacrylamide and other water-soluble polymers prepared by inverse emulsion polymerization. There are no major latex classes produced by emulsion polymerization that are completely free of coagulum formation during or after polymerization. 

Surfactant Interactions in Polyvinyl Acetate and Poly (vinyl acetate-butyl acrylate) Latexes... 

The second objective is to verify experimentally the predicted relationship between polymer polarity and surfactant adsorption by studying the adsorption of a non ionic surfactant that shows a saturation type isotherm behavior on vinyl acrylic latexes of varying polarity. 

In order to achieve the above objectives, three vinyl acrylic latexes of varying butyl acrylate content have been prepared and cleaned1 for use in the study. Several anionic and nonionic surfactants commonly usod in emulsion polymerization have been used to investigate the effects of surfactant structure and polymer composition on the solubilization process. Polarity of latex surface estimated from contact angle measurements have been used to study the effect of polymer polarity on surfactant adsorption. 

Figure 3. Thickening of vinyl acrylic latexes in the presence of NaLS ( 1) ((O) PVAC ho mo polymer (J ) 70/30 VA/BA copolymer)...

ANIONIC SURFACTANTS STUDIED IN VINYL ACRYLIC LATEXES 07)... 

Formation of solubilized surfactant-latex complexes can influence the properties and performance of vinyl acrylic latexes prepared with NaLS and other penetrating type anionic surfactants. Such complexes seem to affect glass transition temperature and film coalescence process (12). 

Our results on the interactions of anionic surfactants in vinyl acrylic latexes can be summarized as follows ... 

Lower molecular weight (300-800) anionic surfactants such as NaLS and Alipal EP-110 adsorb at a vinyl acrylic latex in a complex C-type adsorption isotherm, leading to penetration and solubilization of latex. 

Polarity of Vinyl Acrylic Latex and Surfactant Adsorption Contact angle measurements, dispersion and polar contribution to latex film surface tension and polarity of polymer calculated according to the method of Kaelble (10) of the three latex films are whown in Table V. It is seen that the polarity of the latex film decreases with increase in butyl acrylate content of the vinyl acrylic co-polymer. The polarity of the 70/30 (VA/BA) latex is very similar to that of the polybutyl acrylate homopolymer estimated to be about 0.21 (1). ... 

ADSORPTION OF IGEPAL CO-630 ON VINYL ACRYLIC LATEX OF DIFFERENT POLARITY (17)... 

It is seen that the adsorption of Igepal CO-630 at the three latex/water interfaces decreases with increase in polarity of the vinyl acrylic latex surface. Explanation for such a decrease in surfactant adsorption at a polymer/water interface with increase in polymer polarity has been discussed in detail elsewhere (1). Briefly, increased polarity of the polymer lowers the interfacial free energy of the polymer latex/water interface and this, in turn, reduces the free energy of adsorption for a simple saturation type adsorption process of a surfactant at a latex surface in aqueous media. Such a lowering in free energy of surfactant adsorption at a polymer latex/water interface with increase in polymer polarity leads to the observed results, namely, decrease in the adsorption of Igepal CO-630 with polarity increase of the VA/BA latex particle. 

The polarity and adsorption data discussed above reveal some interesting aspects of the surface chemistry of vinyl acrylic latex surfaces. It is quite likely that the polarity of the latex films, expecially of the two co-polymers, determined by contact angle measurements may not correspond exactly with their respective latex surfaces in the dispersed state due to reorientation of polymer chains during film formation. But the surfactant adsorption data shows clearly that the three latex surfaces in their dispersed state do exhibit varying polarity paralleling the trend found from contact angle measurements. The result also shows that the surface of the co-polymer latex surface is a mixture of vinyl acetate and acrylate units. This result is somewhat unexpected in a vinyl acrylic latex, prepared by a batch... 

Figure 5. Effect of polymer polarity on the adsorption of Igepal CO-630 surfactant at vinyl acrylic latex/water interface ( 1)...

In agreement with our earlier studies (1,15), the adsorption results of Igepal CO-630 on the three vinyl acrylic latexes show that the area per molecule of surfactant can be related to the polarity of polymer surface. Further, the results show that one can employ the techniques discussed above to characterize the polarity of co-polymer latex surfaces. 

It is also shown that the adsorption of non-ionic surfactants at a vinyl acrylic latex/water interface that exhibit a saturation type isotherm can be related to the polarity of the polymer surface, in agreement with earlier sufactant adsorption studies. 

The coating durability of organolead-treated southern pine in exterior exposure was reported (144), Significant improvement in the durability of a vinyl-acrylic latex and an alkyd paint on treated wood was demonstrated. Improved durability appeared to be independent of the type or concentration of the organolead-treated compounds. 

A recipe to synthesize a vinyl acrylic latex for paint formulation is shown in Table 8. 

Today, the latex paint industry produces primarily acrylic and vinyl-acrylic (vinyl acetate-acrylic copolymer) paints. The vinyl-acrylic latexes are used most commonly in interior flat paints, while the acrylic latexes are used most frequently with exterior paints and interior gloss or semigloss paints. In 1981, approximately 30-40 million worth of cellulose ethers was sold to the paint industry to produce over 1 billion gallons of paint in the United States (36). 

---