Liquid emulsion polymers useful as pH responsive thickeners for aqueous systems

A liquid emulsion polymer useful as a pH responsive thickener for aqueous compositions comprising an aqueous emulsion copolymer of:

• A. about 15-60 weight percent based on total monomers of at least one C.sub.3 -C.sub.8 .alpha.,.beta.-ethylenically unsaturated carboxylic acid monomer of the formula:
• ##STR10## where R is H and R' is H, C.sub.1 -C.sub.4 alkyl, or --CH.sub.2 COOX;
• R is --COOX and R' is H or --CH.sub.2 COOX;
• or,
• R is CH.sub.3 and R' is H;
• and
• X is H or C.sub.1 -C.sub.4 alkyl;
• B. about 15-80 weight percent of at least one nonionic, copolymerizable C.sub.2 -C.sub.12 .alpha.,.beta.-ethylenically unsaturated monomer of the formula:
• CH.sub.2 .dbd.CYZ (II)
• where
• Y is H and Z is --COOR, --C.sub.6 H.sub.4 R', CN, Cl, ##STR11## or --CH.dbd.CH.sub.2 ;
• Y is CH.sub.3 and Z is --COOR, --C.sub.6 H.sub.4 R', CN or --CH.dbd.CH.sub.2 ;
• or
• Y and Z are Cl;
• and
• R is C.sub.1 -C.sub.8 alkyl or C.sub.2 -C.sub.8 hydroxyalkyl;
• R' is H, Cl, Br, or C.sub.1 -C.sub.4 alkyl;
• and
• R" is C.sub.1 -C.sub.8 alkyl;
• and
• C. about 1-30 weight percent based on total monomers of at least one nonionic vinyl surfactant ester of the formula:
• ##STR12## where R is H or CH.sub.3, each R' is C.sub.1 -C.sub.2 alkyl,
• R" is C.sub.8 -C.sub.20 alkyl or C.sub.8 -C.sub.16 alkylphenyl,
• n is an average number from about 6-100 and m is an average number from about 0-50 provided that n.gtoreq.m and .SIGMA.(n+m) is about 6-100;
• said polymer being stable as an aqueous colloidal dispersion at a pH lower than about 5.0 but becoming an effective thickener for aqueous systems upon adjustment to a pH of about 5.5-10.5 or higher.