Patent GB-1328878-A (GB)
Title: Latex composition
Inventor: SEINER J A
IPC: C09D17/00
Filed: 1970-12-11
Abstract: 1328878 Film-forming latex polymer compositions and cellular opaque films PPG INDUSTRIES Inc 11 Dec 1970 [22 June 1970(2)] 58845/70 Headings C3C and C3P A latex composition which forms continuous opaque films comprises an aqueous continuous phase having dispersed therein particles of coalescable polymer (i.e. a polymer which, either alone or in the presence of coalescing aids, forms a continuous film at the temperature of use), said composition containing a non-solvent for said coalescable polymer in an amount and of sufficiently low volatility as to produce, upon first removing water from said continuous phase and secondly removing said non-solvent, a continuous, non-porous, microcellular and opaque film having minute, discrete and substantially closed voids. A non-porous film having a plurality of minute closed microcellular voids is produced by applying to a substrate a composition of the type described above, removing water from the applied composition while at the same time controlling the entrapment of the non-solvent by the dispersed polymeric substance to an extent sufficient to form a coalesced film of the polymeric material having entrapped therein minute droplets of non- solvent, and thereafter removing the non- solvent. The coalescable polymer may be a non-film-former, marginal film-former or good film-former, and the entrapment of the non- solvent may be controlled (a) by controlling the temperature during water removal so that the polymer is above its glass transition temperature, (b) by adding good film formers, coalescers, plasticizers and/or polymer thickeners to increase flow; this method applies to marginal film formers, and to non-film formers, although in this case the film may have small discontinuous areas, (c) by adding flow-inhibiting agents where the polymer is a good film former; flow-inhibiting agents may be added to marginal film-formers, but the film may have small discontinuous areas, (d) by adding one or more non-film-formers and/or marginal filmformers where the polymer is a good film-former or (e) by using a non-solvent of sufficiently low volatility such that the film is essentially tack-free prior to evaporation of the non- solvent; this method is applied to good filmformers, and the non-solvent generally substantially boils above 400 F. The non-solvent may be odourless mineral spirits, high-flash aliphatic naphtha, naphthenic mineral oil, neat's foot oil, pine oil, phenyl cyclohexane, triethylbenzene, phenylpropane, dicyclohexylamine, isoamyl bromide, trichloropropane, methylbenzylketone or allyl butyrate. The composition may also contain pigments, dyes, fluorescent materials, and/or optical brighteners. The polymer may be a homopolymer or copolymer of vinyl esters of saturated carboxylic acids (e.g. acetic and propionic), alkyl or aryl esters of unsaturated carboxylic acids (e.g. acrylates, methacrylates, maleates and fumarates), unsaturated hydrocarbons, vinyl halides, unsaturated nitriles, unsaturated amides or unsaturated carboxylic acids, alkyd resins, phenolic resins, epoxy resins, polyurethanes, aminoplast resins or naturally occurring materials such as rubber, shellac or casein. The opacifying pigment may be titanium dioxide, basic carbonate white lead, basic sulphate white lead, basic silicate white lead, zinc oxide, leaded zinc oxide, zinc sulphide, lithopone, titanated lithopone or antimony oxide. In the examples the polymer is (1) a non-film-forming copolymer of methyl methacrylate (65%)/ ethylacrylate (35%); (2) a good film-forming copolymer of ethylacrylate (66%)/methyl methacrylate (32%)/methacrylic acid (2%); (3) a marginal film-former obtained by mixing latices of the polymers in Examples (1) and (2); (4) a marginal film-forming butadiene/styrene copolymer; (5)-(8) and (10)-(12) a good filmforming vinyl acetate (75%)/dibutyl maleate (25%) copolymer; (9) a non-film forming acrylic polymer; (13) to (16) a good film-forming copolymer of methyl methacrylate (43%)/ butyl acrylate (55%)/methacrylic acid (2%).