Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-10-05
2003-03-04
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S393000, C524S561000, C524S731000, C524S733000
Reexamination Certificate
active
06528590
ABSTRACT:
The present invention relates to novel aqueous copolymer dispersions, to processes for preparing them and to their use in particular in elastic coatings.
EP-A-0 458 144 discloses aqueous synthetic resin dispersions whose synthetic resins contain in copolymerized form not only monomers such as acrylic or methacrylic esters, styrene and vinyl esters, monoethylenically unsaturated acetophenone derivatives and/or benzophenone derivatives but also at least one unsaturated ketone or one aldehyde, and also comprise a compound containing at least two acid hydrazide groups, and are obtained by free-radical emulsion polymerization. These synthetic resin dispersions are recommended for coating, adhesive bonding, sealing, and impregnating.
The use of relatively expensive monoethylenically unsaturated acetophenone derivatives and/or benzophenone derivatives, and of unsaturated ketone derivatives and/or aldehyde derivatives and a compound containing at least two acid hydrazide groups which is added subsequently, means that the corresponding synthetic resin is itself relatively expensive. A disadvantage of these synthetic resins is that films thereof, despite attaining high values of elongation at break, lack sufficient resilience following a defined extension, either through application of a defined weight or following extension by a defined distance, and remain, accordingly, in the extended state. A further disadvantage of coatings comprising these synthetic resins is that they frequently prove to be of poor stability to water exposure a short time following their application to the substrate, and exhibit high water absorption. Furthermore, these coatings in many cases exhibit a strong tendency toward reemulsification and/or blistering after brief exposure to water vapor.
EP-A-0 599 676 discloses aqueous polymer dispersions whose synthetic resins include not only monomers such as acrylic or methacrylic esters and styrene but also monoethylenically unsaturated acetophenone derivatives and/or benzophenone derivatives and also have an oxygen-reactive dicyclopentadienyl group. These synthetic resin dispersions are recommended for elastic coatings.
Disadvantages of these binders are that the process of crosslinking of paint films of these binders is relatively slow to proceed, and the paint lacks adequate elasticity in the sense of resilience following cracking-induced extension of the paint. Furthermore, stark differences may arise in the properties of a coating based on such synthetic resins depending on whether it is applied to the sun-facing side of a building or to an area not exposed to the sun. Furthermore, during the preparation of the synthetic resin dispersions by means of free-radical polymerization, allylic double bonds have an inhibiting action and so hinder the preparation of these dispersions.
EP-A-0 778 296 relates to aqueous polymer dispersions whose synthetic resins contain in copolymerized form not only monomers such as acrylic or methacrylic esters but also methylstyrene or other alkyl-substituted styrenes and, optionally, acrylonitrile. These synthetic resin dispersions are recommended as binders for elastic coatings and sealing compounds.
Disadvantages of these binders are that the process of crosslinking of paint films of these binders is relatively slow to proceed under the influence of light, and the paint lacks adequate elasticity in the sense of resilience following cracking-induced extension of the paint. Furthermore, stark differences may arise in the properties of a coating based on such synthetic resins depending on whether it is applied to the sun-facing side of a building or to an area not exposed to the sun. A further disadvantage of coatings with these synthetic resins is that they are in many cases of poor stability to water exposure shortly after application to the substrate. Furthermore, these coatings in many cases exhibit a strong tendency toward reemulsification and/or toward blistering following brief exposure to water vapor. The use of acrylonitrile in these binders results, moreover, both in a readiness toward yellowing and in poor stability of the coatings with respect to basic substrates owing to hydrolysis of the acrylonitrile group in the copolymer, which leads to a greatly increased sensitivity to water.
It was an object of the present invention, therefore, to develop a synthetic resin which features, in the coating, both low water absorption and particularly low reemulsifiability following treatment with water vapor, in combination with good elongation at break and good relaxation following defined extension.
This object is achieved by an aqueous copolymer dispersion consisting essentially of
A) an aqueous dispersion of a copolymer having a solids fraction of from 20 to 65% by weight, said copolymer being composed of
a) from 40 to 99.9% by weight, preferably from 65 to 85% by weight, of at least one ester of a,p-monoethylenically unsaturated carboxylic acids containing 3 to 6 carbon atoms and alkanols containing 1 to 18 carbon atoms and from 0 to 40% by weight, preferably from 15 to 35% by weight, of at least one vinylaromatic compound (monomers a),
b) from 0.05 to 10% by weight of at least one &agr;,&bgr;-monoethylenically unsaturated mono- or dibasic acid containing 3 to 8 carbon atoms, and/or anhydrides thereof, and from 0 to 10% by weight of at least one &agr;,&bgr;-monoethylenically unsaturated carboxamide which contains 3 to 8 carbon atoms and can be substituted once or twice on the nitrogen by alkyl ether sulfates, alkyl sulfates, alkanols or alkyls containing up to 5 carbon atoms (monomers b),
c) from 0.05 to 10% by weight of at least one monoethylenically unsaturated crosslinking monomer (monomers c), and
d) from 0 to 30% by weight of at least one other copolymerizable monoethylenically unsaturated monomer (monomers d), in copolymerized form,
the weight fractions of the monomers a, b, c and d being chosen within the stated limits such that a synthetic resin composed of these monomers alone would have a glass transition temperature in the range from −50 to 35° C., preferably from −40 to 10° C. and, with particular preference, from −30 to −10° C.,
B) from 0 to 10% by weight, preferably from 0.02 to 2% by weight, based on the copolymer A, of benzophenone, acetophenone, one or more acetophenone derivatives or benzophenone derivatives without an ethylenically unsaturated group, or a mixture thereof,
C) from 0.3 to 10% by weight, based on the copolymer A, of emulsifiers, and
D) from 0 to 5% by weight, preferably from 0.05 to 5% by weight, based on the copolymer A, of protective colloids.
The compounds used as esters of &agr;,&bgr;-monoethylenically unsaturated carboxylic acids containing 3 to 6 carbon atoms and alkanols containing 1 to 18 carbon atoms are preferably the esters of acrylic and/or methacrylic acid. Of these, particular importance is attached to the esters of methanol, of ethanol, of the propanols, of the butanols, of the pentanols, of 2-ethylhexanol, of isooctanol, of n-decanol and of n-dodecanol. Preferred vinylaromatic compounds are styrene, methylstyrene, ethylstyrene, dimethylstyrene, diethylstyrene and trimethylstyrene, particular preference being given to styrene.
The compounds used as &agr;,&bgr;-monoethylenically unsaturated mono- or dibasic acids containing 3 to 8 carbon atoms are preferably &agr;,&bgr;-monoethylenically unsaturated carboxylic acids and their water-soluble derivatives; with particular preference, acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, fumaric acid and maleic acid, and their anhydrides. Also suitable, furthermore, are the amides and monoamides of these acids, preference among these being given to acrylamide and methacrylamide and also their N-substituted derivatives such as N,(N′-di)methyl(meth)acrylamide, N,(N′-di)ethyl(meth)acrylamide and N,(N′-di)isopropyl(meth)acrylamide. Methacrylamide is particularly preferred. Acrylamide derivatives which are substituted once or twice on the nitrogen by alkyl, alkanol, alkyl sulfate or alkyl ether
Beyer Dierk
De Almeida Carvalho Susana Maria
Kuropka Rolf
Renisch Volker
Asinovsky Olga
Bisulca Anthony A.
Clariant GmbH
Seidleck James J.
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