Associative thickener comprising acid monomer, associative monomer and nonionic monomer

The associative thickener according to any of the preceding claims, wherein the nonionic, copolymerizable monomers c) are selected from those of the general formula

• CH2═CYZ
• in which Y is H, CH3 or chlorine;
• Z is COOR, CONH2, CONHR, CONR2, C6H4R′, CN, Cl, —OCOR″ or CH═CH2;
• R is C1-C8-alkyl or C2-C8-hydroxyalkyl;
• R′ is H, Cl, Br or C1-C4 and R″ is C1-C8-alkyl.

The associative thickener according to any of the preceding claims, which is formed by free radical polymerization of

• a) from 25 to 55% by weight of at least one acid monomer selected from acrylic acid, methacrylic acid and a mixture thereof;
• b) from 0.1 to 5% by weight of at least one associative monomer of the general formula
• H2C═CR1—COO-(EO)n—R2
• in which R1 is hydrogen or methyl, n is a number from 10 to 40 and R2 is a C10- to C30-alkyl group,
• c) from 20 to 70% by weight of nonionic, copolymerizable monomers differing from a) and b) and selected from those of the general formula
• CH2═CYZ
• in which Y is H, CH3 or chlorine;
• Z is COOR, CONH2, CONHR, CONR2, C6H4R′, CN, Cl, —OCOR″ or CH═CH2;
• R is C1-C8-alkyl or C2-C8-hydroxyalkyl;
• R′ is H, Cl, Br or C1-C4 and R″ is C1-C8-alkyl,
• the initiator for the reaction of the reaction product after the polymerization being a redox initiator system, the oxidizing component used being at least one peroxide compound selected from hydrogen peroxide, organic peroxides and organic hydroperoxides, and the reducing component used being an inorganic or organic reducing agent.

A process for the preparation of an associative thickener according to any of the preceding claims, wherein a monomer mixture comprising

• a) at least one acid monomer selected from ethylenically unsaturated C3- to C8-carboxylic acids;
• b) at least one associative monomer of the general formula
• H2C═CR1—COO-(EO)n—(PO)m—R2
• in which R1 is hydrogen or methyl, n is a number of at least two, m is a number from zero to 50, EO is an ethylene oxide group, PO is a propylene oxide group and R2 is a C8-C30-alkyl group or a C8-C30-alkaryl group, and
• c) nonionic, copolymerizable monomers differing from a) and b) are subjected to free radical polymerization and the reaction product is reacted, after the polymerization, with initiators forming nonionic radicals.