Adhesive polymer latex

Claim 1

An aqueous based pressure sensitive adhesive having improved shear properties comprising a latex of a polymer having a Tg less than about 0° C., formed by emulsion polymerizing a monomeric mixture selected from the group comprising: (a) (i) from about 60-99.5 weight percent of a C 1-8 alkyl or alkanol ester of acrylic or methacrylic acid; or a mixture thereof and (ii) from 0.5 to about 40 weight percent of a C 3-9 ethylenically unsaturated acid; and (iii) from 0 up to about 5 weight percent of an amide of a C 3-9 ethylenically unsaturated acid which amide may be unsubstituted or substituted at the nitrogen atom by a C 1-8 alkyl or alkanol radical; a C 3-9 ethylenically unsaturated aldehyde; or an anhydride of a C 4-8 ethylenically unsaturated dicarboxylic acid; or a mixture thereof; (b) (i) from about 0 to about 60 weight percent of a vinyl aromatic monomer which may be unsubstituted or substituted by a C 1-4 alkyl radical or a chlorine or bromine atom; (ii) from 40 to 99 weight percent of a mixture comprising 100 to 50 weight percent of a C 4-8 conjugated diolefin and 0 to 50 weight percent of a C 1-8 alkyl or alkanol, or a C 2-8 alkenyl or alkenol ester of a C 3-9 ethylenically unsaturated acid; (iii) from about 0.5 to 10 weight percent of a C 3-9 ethylenically unsaturated acid; and (iv) from 0 up to about 5 weight percent of an amide of a C 3-9 ethylenically unsaturated acid which amide may be unsubstituted or substituted at the nitrogen atom by a C 1-8 alkyl or alkanol radical; a C 3-9 ethylenically unsaturated aldehyde; or an anhydride of a C 4-8 ethylenically unsaturated dicarboxylic acid; or a mixture thereof; and (c) (i) from about 1 to about 40 weight percent of a C 2-4 monoolefin monomer; (ii) from about 60 to 99.5 weight percent of a C 1-8 alkyl or alkanol ester of a C 3-12 ethylenically unsaturated carboxylic acid or a C 2-8 alkenyl or alkenol ester of a C 1-12 saturated carboxylic acid or a mixture thereof; and (iii) from about 0.5 to 10 weight percent of a C 3-9 ethylenically unsaturated acid; and (iv) from 0 up to about 5 weight percent of an amide of a C 3--9 ethylenically unsaturated acid which amide may be unsubstituted or substituted at the nitrogen atom by a C 1-8 alkyl or alkanol radical; a C 3-9 ethylenically unsaturated aldehyde; or an anhydride of a C 4-8 ethylenically unsaturated dicarboxylic acid or a mixture thereof; which has been adjusted to a pH of equal to or greater than about 6 with an agent selected from hydroxides and salts of lithium, sodium, potassium and a mixture thereof.