Process for producing stable latex.

摘要

The subject invention discloses a process for producing a neutralized latex that is useful in the manufacture of water reducible coatings which comprises: (1) free radical aqueous emulsion polymerizing at a pH of less than about 3.5, a monomer mixture which comprises based on 100 weight percent monomers: (a) from about 45 to about 85 weight percent vinyl aromatic monomers, (b) from about 15 to about 50 weight percent of at least one alkyl acrylate monomer, and (c) from about 1 to about 6 weight percent of at least one unsaturated carbonyl compound; in the presence of about 0.5 to 4.0 phm at least one phosphate ester surfactant; in the presence of about 0.5 to 4.0 phm of at least one water insoluble nonionic surface active agent to produce a latex; and in the presence of at least one seed polymer which is comprised of repeat units which are derived from about 45 to about 85 weight percent vinyl aromatic monomers, from about 15 to about 50 weight percent alkyl acrylate monomers, and from about 1 to about 6 weight percent unsaturated carbonyl compounds; and (2) neutralizing the latex with ammonia to a pH which is within the range of about 7 to about 10.5 to produce the neutralized latex. In the practice of this invention, it is highly preferred to utilize styrene as the vinyl aromatic monomer, to utilize N-butyl acrylate as the alkyl acrylate monomer and to utilize a combination of acrylic acid and methacrylic acid as the unsaturated carbonyl compound component. It is highly desirable to adjust the pH of the polymerization medium as the polymerization proceeds by the addition of ammonia to maintain a pH of at least about 2. n