Method for preparing cationic latexes

DETAILED DESCRIPTION That which is claimed is: 1.
A method for preparing a cationic structured-particle latex comprising the steps of reacting at a temperature from about 0.
degree.
to about 80.
degree.
C a water-stable, nonionic, sulfide nucleophile which is capable of diffusing through aqueous media and a low molecular weight acid which ionizes at pH values below about 10 with a latex of copolymer particles having epoxide groups bound to the copolymer at or near the particle surface; said epoxide groups being present in an amount of at least about 0.
01 milliequivalent per gram of copolymer in the latex; whereby sulfonium cationic groups are chemically bound to the particles at or near the particle surface.
2.
The method of claim 1 in which the reaction is carried out until the sulfonium cationic groups are present in an amount from about 0.
01 to about 0.
5 milliequivalent per gram of copolymer.
3.
The method of claim 1 in which the acid is a lower aliphatic carboxylic acid.
4.
The method of claim 3 in which the acid is acetic acid.
5.
The method of claim 1 in which the latex of copolymer particles having epoxide groups is a structured-particle latex of copolymer particles consisting of a nonionic, organic polymer core having adhered thereto a thin layer of a water-insoluble copolymer of (a) an ethylenically unsaturated, non-ionic monomer which is devoid of an epoxide group and (b) a non-ionic, ethylenically unsaturated, epoxide monomer; the amount of the epoxide groups in the copolymer being from about 0.
01 to about 1.
4 milliequivalents per gram of copolymer.
6.
The method of claim 1 in which the latex of copolymer particles having epoxide groups bound to the copolymer at or near the particle surface also has bound epoxide groups throughout the particles.
7.
The method of claim 1 in which the epoxide groups are provided by copolymerized glycidyl methacrylate.
8.
The method of claim 1 in which the sulfide nucleophile is a compound having the formula R.
sub.
1-- S--R.
sub.
2 wherein R.
sub.
1 and R