Surfactant-free acrylic plastisols and organosols compositions

#1. Field of the Invention

#This invention relates to nonaqueous acrylic resin dispersions and particularly to acrylic resin plastisols and organosols. This invention also relates to acrylic resin dispersions containing photopolymerizable ethylenically unsaturated compounds.

#2. Description of the Prior Art

#The invention will be illustrated by the examples that follow, wherein parts and percentages are by weight unless otherwise noted. Data on the inherent viscosity of polymers (.eta..sub.inh) refer to the inherent viscosities of solutions of 0.25 g polymer in 50 ml solvent, either chloroform or 50/50 (by volume) chloroform/methanol, measured at 25.degree. C. with a No. 50 Cannon-Fenske viscometer. Particle size values are mean particle diameters determined by inspection of photomicrographs or electron micrographs. Dispersion viscosities, reported in centipoises (cp.), were measured with a Brookfield RVT viscometer with a No. 5 spindle. All monomers used in the examples, either to make the acrylic polymers or to serve as photopolymerizable monomers in photosensitive compositions, were commercially available polymerizationgrade monomers containing conventional amounts of polymerization inhibitors. Dyes are identified, in some instances, by C.I. name and number as given in "Colour Index", Third Edition, The Society of Dyers and Colourists, Bradford, Yorkshire, England (1971). Performance of photosensitive elements was measured in part by exposing them through a conventional graphic arts resolution guide, i.e., a series of transparent parallel lines of known width in a nontransparent background, and a series of transparent converging lines separated by nontransparent spacing areas of known width, then removing the unpolymerized composition from the unexposed areas. Performance is expressed in the examples in terms of the minimum width of polymerized parallel lines that could be faithfully reproduced, and of the minimum spacing that could be obtained without plugging between polymerized converging lines. Filters and sieves are identified in terms of mesh (number of openings per inch) and sieve opening (mm or .mu.m) according to Table 21-16 on page 21-51 of Perry, "Chemical Engineers' Handbook", Fourth Edition, McGraw-Hill Book Company, New York (1963).

#To a solution of 0.4 g ammonium persulfate in 200 g of water was added 18 ml of a solution of 1.09 g dodecyl mercaptan and 10.0 g methacrylic acid in 100 g methyl methacrylate. The suspension was stirred vigorously under nitrogen and heated to 80.degree.-85.degree. C. At 30-minute intervals, there was added 25 ml of the methyl methacrylate/methacrylic acid/dodecyl mercaptan solution and 112 ml of a solution of 0.2 g ammonium persulfate in 450 g water. Thirty minutes after the fourth such addition, the reactor was opened to air and cooled to room temperature. The latex that had been produced was evaporated at 55.degree.-66.degree. C. under nitrogen with stirring, and the residual powder was ground in a mortar, passed through a 40-mesh (.about.0.38 mm) sieve, and held for 3 days in a closed container over concentrated ammonium hydroxide. The powder was soluble at room temperature in chloroform and 1,1,2-trichloromethane; partly soluble, swollen and agglomerated in methylene chloride, 1,2-dichloroethane, trichloroethylene and 1,2,3-trichloropropane. It was swollen but insoluble in methyl chloroform, perchloroethylene and carbon tetrachloride. It was insoluble and not swollen in hexane.

#A plastisol was prepared by mixing equal parts by weight of the powder, prepared by just described, with dibutyl phthalate. The resultant soft translucent paste was spread at 1 mm thickness on glass and coalesced by heating for five minutes at 120.degree. C. to give a clear, dry, soft, pliable film.