Compositions: coating or plastic – Coating or plastic compositions – Inorganic materials only
Reexamination Certificate
2000-09-15
2004-09-14
Egwim, Kelechi C. (Department: 1713)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic materials only
C106S287350, C524S460000, C524S555000, C524S556000
Reexamination Certificate
active
06790272
ABSTRACT:
The present invention relates to pigment-comprising aqueous formulations which comprise at least one aqueous addition-polymer dispersion.
Pigmented formulations are employed widely in the form of coating compositions, especially emulsion paints, synthetic-resin-bound plasters (dispersion plasters), sealing compounds or filling compositions for purposes of architectural protection or decoration. Pigmented formulations generally include as their binder a film-forming polymer, at least one inorganic pigment and, if desired, one or more inorganic fillers/extenders, and customary auxiliaries. The quality of the coatings formed from pigmented formulations depends critically on the ability of the film-forming polymer to carry out uniform binding of the nonfilm-forming constituents, the pigments and the inorganic fillers.
A low pigment binding capacity leads to poor mechanical stability of the coating, which is manifested, for example, in a low wet abrasion resistance. The desire, however, is for high wet abrasion resistance, especially in the case of washable emulsion paints.
The pigment binding capacity of the binder plays a particularly important part in formulations having a moderate to high content of inorganic pigments and fillers/extenders. A characteristic parameter of the pigment content of a polymer-bound coating composition is the pigment volume concentration pvc. The pvc is usually defined as the percentage quotient of the overall volume of solid inorganic constituents (pigment+fillers/extenders) divided by the overall volume of the solid inorganic constituents and of the polymer particles of the aqueous binder polymer dispersion; see Ullmanns Enzyklopädie der technischen Chemie, 4th edition, volume 15, p. 668.
In the case of exterior applications in particular, the coating compositions should be stable to environmental influences such as sunlight, moisture and fluctuations in temperature. In addition, the coating composition must adhere well to a variety of substrates even when exposed to moisture, which again depends on the chosen binder polymer.
Another property dependent on the binder polymer is the blocking resistance of the coatings.
WO 93/11181 discloses titanium dioxide-containing formulations comprising, as dispersing auxiliaries, aqueous addition-polymer dispersions whose polymers include itaconic acid copolymerized in an amount of more than 1% by weight based on the weight of the addition polymer. The wet abrasion resistance of the dispersions disclosed therein leaves much to be desired.
EP-A-810 274 discloses binders for solvent-free coating compositions which may comprise acid-functional monomers copolymerized in an amount of up to 1% by weight based on the overall weight of the monomers to be polymerized.
The prior art binders are able to go only some of the way toward meeting the requirements that are placed on coating compositions.
It is an object of the present invention to provide pigmented formulations having a high pigment binding capacity and, therefore, high wet abrasion resistance. These properties must be ensured even at relatively high pigment volume concentrations, i.e., at pvc >40%. The formulations should also be stable on storage—that is, their viscosity should show little or no increase even on prolonged storage.
We have found that this object is achieved by using for the formulations binders based on aqueous addition-polymer dispersions whose polymers comprise from 0.1 to 1.5% by weight of itaconic acid in copolymerized form.
The present invention accordingly provides pigment-comprising aqueous formulations comprising
i) at least one copolymer P of ethylenically unsaturated monomers M in the form of an aqueous polymer dispersion which comprises from 0.1 to 1.5% by weight, based on the overall weight of the copolymer P, of itaconic acid as acidic monomer M1, its salts and/or its anhydride in copolymerized form, it being possible for up to 50% by weight of the itaconic acid to be replaced by another monomer having at least one acid group or one neutralized acid group, and has a glass transition temperature T
G
in the range from −10 to +50° C.,
ii) at least one inorganic pigment,
iii) if desired, inorganic fillers/extenders, and
iv) customary auxiliaries.
The monomers M of which the copolymer P is constructed preferably make up from 0.2 to 1.2% by weight, in particular from 0.2 to 1.0% by weight and, with particular preference, from 0.4 to 1.0% by weight. In an especially preferred embodiment the monomers M comprise from 0.5 to 0.9 and, specifically, from 0.5 to 0.8% by weight of itaconic acid as acidic monomer M1. Instead of itaconic acid it is also possible to employ its anhydride or its salts to prepare the copolymers P. A certain fraction of the itaconic acid, namely up to 50% by weight, but preferably not more than 25% by weight and in particular not more than 10% by weight, can be replaced by another monomer having at least one acid group; for example, by an ethylenically unsaturated carboxylic acid, such as acrylic acid or methacrylic acid, or by an ethylenically unsaturated sulfonic acid, an example being vinylsulfonic acid or its salts. Typical salts are the alkali metal and ammonium salts, preferably the sodium salts. Particular preference is given to employing itaconic acid as the sole acidic monomer (monomer M1).
Normally, the preparation of the copolymers P comprising itaconic acid takes place by free-radical addition polymerization of ethylenically unsaturated monomers M which in addition to itaconic acid include at least one further comonomer. Suitable comonomers are generally selected from vinylaromatic monomers, such as styrene, &agr;-methylstyrene, o-chlorostyrene or vinyl-toluenes, the vinyl esters of aliphatic C
1
-C
18
monocarboxylic acids, such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl hexanoate, vinyl 2-ethylhexanoate, vinyl decanoate, vinyl pivalate, vinyl laurate, vinyl stearate, and commercial monomers VEOVA® 5-11 (VEOVA® X is a tradename of Shell and stands for vinyl esters of &agr;-branched, aliphatic carboxylic acids having X carbon atoms, which are also referred to as versatic® X acids), and the esters of ethylenically unsaturated C
3
-C
8
mono- or dicarboxylic acids with C
1
-C
18
-, preferably C
1
-C
12
-and, in particular, C
1
-C
8
-alkanols or C
5
-C
8
-cycloalkanols. Examples of suitable C
1
-C
18
-alkanols are methanol, ethanol, n-propanol, i-propanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, n-hexanol, 2-ethylhexanol, lauryl alcohol and stearyl alcohol. Examples of suitable cyclolkanols are cyclopentanol and cyclohexanol. Particularly suitable esters are those of acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid or fumaric acid. The esters concerned are especially those of acrylic and/or methacrylic acid, such as methyl, ethyl, isopropyl, n-butyl, isobutyl, 1-hexyl, tert-butyl and 2-ethylhexyl (meth)acrylates, and also the esters of fumaric and maleic acid, examples being dimethyl fumarate, dimethyl maleate and di-n-butyl maleate. Also suitable are nitriles of &agr;,&bgr;-monoethylenically unsaturated C
3
-C
8
carboxylic acids, such as acrylonitrile or methacrylonitrile. It is also possible, furthermore, to employ C
4
-C
8
conjugated dienes, such as 1,3-butadiene, isoprene or chloroprene &agr;-olefins, such as ethylene, propene and isobutene, and vinyl chloride or vinylidene chloride as comonomers.
In addition to itaconic acid the monomers M preferably include from 50 to 99.9% by weight, based on the overall weight of the copolymer P, of at least one monomer M2 selected from the abovementioned vinylaromatic monomers, the abovementioned esters of ethylenically unsaturated C
3
-C
8
monocarboxylic acids with C
1
-C
12
-alkanols, and the vinyl esters of aliphatic C
1
-C
12
monocarboxylic acids. In a preferred embodiment of the present invention the monomers M2 are selected from the C
1
-C
12
-alkyl esters of acrylic acid and C
1
-C
12
-alkyl esters of methacrylic acid, especially methyl methacrylate, ethyl m
Baumstark Roland
Dersch Rolf
Roser Joachim
Zhao Cheng-Le
BASF - Aktiengesellschaft
Egwim Kelechi C.
LandOfFree
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