Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-07-14
2001-06-05
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S206000, C523S342000, C524S819000, C524S832000, C524S833000, C524S904000, C525S198000, C525S221000, C525S934000
Reexamination Certificate
active
06242512
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to redispersible polymer powders based on a mixture of a water-insoluble, film-forming polymer and a water-soluble atomizing protective colloid which can be deactivated by a change in pH. The invention furthermore relates to aqueous dispersions which can be prepared with the polymer powder.
BACKGROUND ART
Dispersion powders have been employed for many years, in particular in the building sector for modifying hydraulically setting systems with plastics, and in plasters, paints and adhesives. Substantial improvements in the properties of adhesion, abrasion resistance, scratch resistance and flexural strength are achieved by the addition or use of redispersible powders of plastics in such systems. The great advantage of dispersion powders over liquid polymer dispersions, which can likewise be employed as an alternative, is, inter alia, a high storage stability without additions of preservatives and the frost resistance of the pulverulent dry mixtures.
The dispersion powders known to date comprise water-soluble atomizing protective colloids which are added to the polymer dispersion to be dried, as a rule before the spray drying, and which are said to prevent premature film formation of the base polymer on which the dispersion powder is based, for example during spray drying, and which allow redispersion of the polymer powder in water.
Polyvinyl alcohols are chiefly employed as the protective colloids for this. Examples of these are described, for example, in DE-A 4030638 (U.S. Pat. No. 5,118,751) and in EP-A 149098 (U.S. Pat. No. 4,859,751). Dispersion powders which comprise water-soluble salts of phenolsulphonic acid-formaldehyde condensates as atomizing protective colloids are known from EP-A 407889 (U.S. Pat. No. 5,225,478). The use of naturally occurring substances such as dextrins or starch ethers as an atomizing protective colloid and the use of such dispersion powders in adhesives and hydraulically hardening binders is known from EP-A 134451. EP-A 467103 (U.S. Pat. No. 5,342,897) describes the preparation of dispersion powders by spray drying polymer dispersions which comprise water-soluble copolymers of unsaturated acids or anhydrides thereof and alkene or styrene.
The water-soluble protective colloids mentioned prevent premature film formation of the polymers during drying of the dispersion and first allow redispersion (i.e. substantial disintegration into the primary particles of the base dispersion) of the dry polymer powder in water. In many applications, however, the protective colloids employed in the known dispersion powders have an adverse effect on the properties of the products. Because of the protective colloid character of the water-soluble atomizing aids, when the already known dispersion powders are employed as binders in adhesives, for example, the adhesiveness thereof can be adversely influenced or destroyed entirely because of the content of atomizing protective colloid. In paints and plasters, permanently water-soluble atomizing protective colloids can severely impair resistance to water.
The invention was therefore based on the object of providing a dispersion powder composition which is redispersible in water and in which the action of the atomizing protective colloid employed can be eliminated in a controlled manner during use.
SUMMARY OF THE INVENTION
Surprisingly, it has now been found that this object can be achieved by the use of low molecular weight water-soluble polymers based on acrylic acid, methacrylic acid or maleic acid (anhydride) as the atomizing protective colloid.
The invention relates to a dispersion powder composition which is redispersible in water and comprises
a) a water-insoluble, film-forming base polymer having a glass transition temperature of −60° C. to +80° C. from the group consisting of homo- and copolymers of vinyl esters, acrylic acid esters, methacrylic acid esters, styrene and vinyl chloride, or a mixture of the base polymers mentioned,
b) 2 to 40% by weight, based on the base polymer, of a water-soluble atomizing protective colloid, and
c) 0 to 30% by weight, based on the total weight of polymeric constituents, of an antiblocking agent, characterized in that it comprises, as component b), non-neutralized homo- or copolymers of olefinically unsaturated mono- or dicarboxylic acids or anhydrides thereof, or partly neutralized homopolymers of olefinically unsaturated mono- or dicarboxylic acids or anhydrides thereof, or partly neutralized copolymers of olefinically unsaturated mono- or dicarboxylic acids or anhydrides thereof having an acid content of >80 mol % in the case of copolymers with C
3
- to C
12
-alkenes or styrene and an acid conteqt of 50 to 99 mol % in the case of the other copolymers, the molecular weight of the polymers mentioned being ≦250,000 g/mol, determined as the weight-average, and the pH of the aqueous redispersion of the dispersion powder composition being less than 4.5.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Vinyl ester homo- or copolymers which are suitable as component a) comprise one or more monomer units from the group consisting of vinyl esters of unbranched or branched carboxylic acids having 1 to 18 C atoms. Suitable (meth)acrylic acid ester polymers are homo- and copolymers of acrylic acid and methacrylic acid with unbranched or branched alcohols having 1 to 18 C atoms.
Preferred vinyl esters are vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, 1-methylvinyl acetate, vinyl pivalate and vinyl esters of &agr;-branched monocarboxylic acids having 5 or 9 to 10 C atoms, for example VV5
R
, VeoVa9
R
or VeoVa10
R
(trademarks of Shell Corp.). Vinyl acetate is particularly preferred.
Preferred methacrylic acid esters or acrylic acid esters are methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, methyl methacrylate, n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferred.
Examples of suitable vinyl ester polymers are:
vinyl ester homopolymers, such as vinyl acetate homopolymer;
vinyl ester/ethylene copolymers, such as vinyl acetate/ethylene copolymers having an ethylene content of 1 to 60% by weight;
vinyl ester/ethylene/vinyl chloride copolymers, such as vinyl acetate/ethylene/vinyl chloride copolymers having an ethylene content of 1 to 40% by weight and a vinyl chloride content of 20 to 80% by weight;
vinyl acetate copolymers with 1 to 50% by weight of one or more copolymerizable vinyl esters, such as vinyl laurate, vinyl pivalate, vinyl 2-ethylhexanoate or vinyl esters of an &agr;-branched carboxylic acid, in particular versatic acid vinyl ester (VeoVa9
R
, VeoVa10
R
), which optionally also comprise 1 to 40% by weight of ethylene; vinyl ester/acrylic acid ester copolymers with 30 to 90% by weight of vinyl ester, in particular vinyl acetate, and 1 to 60% by weight of acrylic acid ester, in particular n-butyl acrylate or 2-ethylhexyl acrylate, which optionally also comprise 1 to 40% by weight of ethylene;
vinyl ester/acrylic acid ester copolymers with 30 to 75% by weight of vinyl acetate, 1 to 30% by weight of vinyl laurate or vinyl esters of an a-branched carboxylic acid, in particular versatic acid vinyl ester, and 1 to 30% by weight of acrylic acid ester, in particular n-butyl acrylate or 2-ethylhexyl acrylate, which optionally also comprise 1 to 40% by weight of ethylene;
vinyl ester copolymers with esters of maleic acid or fumaric acid, such as the diisopropyl, di-n-butyl, di-t-butyl, di-ethylhexyl or methyl t-butyl ester, for example vinyl acetate copolymers with 10 to 60% by weight of one or more of the maleic/fumaric acid esters mentioned, which optionally also comprise ethylene or other copolymerizable vinyl esters, such as vinyl laurate or versatic acid vinyl ester.
Examples of suitable (meth)acrylic acid polymers are:
homopolymers of n-butyl acrylate or 2-ethylhexyl acrylate;
copolymers with 35 to 65% by weight of methyl methacrylate and 65 to 35% by weight of n-butyl acrylate and/or 2-ethylhexyl acrylate.
Figge Reiner
Weissgerber Rudolf
Zeh Harald
Burgess, Ryan & Wayne
Moran William R.
Wacker - Chemie GmbH
Wayne Milton J.
Yoon Tae H.
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