Preparation of polymer dispersions which form block-resistant films

• US 4,654,397 A
• Filed: 12/02/1985
• Issued: 03/31/1987
• Est. Priority Date: 12/01/1984
• Status: Expired due to Term

• Current Assignee: BASF AG (BASF SE)
• Original Assignee: BASF AG (BASF SE)
• Inventors: Melan, Michael, Wistuba, Eckehardt, Matthaei, Lothar, Mueller-Mall, Rudolf
• Primary Examiner(s): Michl, Paul R.
• Application Number:
  US06/803,164
• Time in Patent Office: 484 Days
• Field of Search: 524/559, 524/561, 524/562, 524/460, 524/555, 526/318.2, 526/318.44, 526/318.45
• US Class Current: 524/460
• CPC Class Codes: C08F 2/26 anionic
• CPC Class Codes: C08F 285/00 Macromolecular compounds obtained by polymerising monomers on to preformed graft polymers
• CPC Class Codes: C09D 151/00 Coating compositions based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds based on ABS polymers C09D155/02; Coating compositions based on derivatives of such polymers

Abstract

A process for the preparation of aqueous polymer dispersions which have a low film-forming temperature but still give films having a high block resistance, and the use of these polymer dispersions as binders for coating materials.

Claims

1. A process for the preparation of an aqueous polymer dispersion which has a low film-forming temperature and forms films having a high block resistance, by multistage emulsion polymerization of predominant amounts of monoolefinically unsaturated monomers A, whose homopolymers have a glass transition temperature of from 0°

to -72°

C., with monoolefinically unsaturated monomers B, whose homopolymers have a glass transition temperature of from 80°

to 140°

C., from 0.2 to 6% by weight, based on the total amount of monomers, of monoolefinically unsaturated monomers C which possess carboxyl and/or carboxamide groups, and from 0 to 10% by weight, based on the total amount of monomers, of olefinically unsaturated monomers D which effect cross-linking, wherein first

(a) from 1 to 10% by weight of a monomer mixture (I) consisting of

from 75 to 98 parts by weight of monomer A,

from 2 to 25 parts by weight of monomer B,

from 0.5 to 10 parts by weight of monomer C and

from 0 to 10 parts by weight of monomer D

are initially taken and polymerized in 0.5-4% strength aqueous emulsion in the presence of from 0.1 to 2% by weight, based on the total amount of monomers (in monomer mixtures I and II), of an anionic emulsifier and from 0 to 1% by weight, based on the total amount of monomers, of a nonionic emulsifier, and in the presence of a water-soluble free radical polymerization initiator, then

(b) the remainder of the monomer mixture (I) is fed in at the rate at which the emulsion polymerization progresses, and finally, when the addition of the monomer mixture (I) is complete,

(c) a monomer mixture (II) which consists of

from 75 to 98 parts by weight of monomer B,

from 2 to 25 parts by weight of monomer A,

from 0 to 10 parts by weight of monomer C,

from 0 to 10 parts by weight of monomer D and/or

from 0 to 15 parts by weight of monoolefinically unsaturated ureido compounds or tertiary amino compounds

is added at the rate at which it is consumed, while the emulsion polymerization is continued, the amount of monomer mixture (I) being from 40 to 65% by weight, based on the total amount of the two monomer mixtures, monoolefinically unsaturated carbonyl compounds being used as monomers D, the monomer mixtures (I) and (II) being fed into the polymerization vessel as such or in the form of an aqueous emulsion, so that the resulting aqueous polymer dispersion has a polymer content of from 40 to 60% by weight, based on the polymer dispersion, and a content of anionic emulsifiers of from 0.5 to 3% by weight, based on the polymer, and, when the polymer contains monomer D as copolymerized units, a hydrazide of an aliphatic dicarboxylic acid is added to the ready-prepared polymer dispersion in an amount of from 0.5 to 1 mole per mole of carbonyl monomer.

2. An aqueous polymer dispersion prepared by the process of claim 1.