Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-05-11
2003-04-22
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S724000, C524S732000, C524S733000, C524S714000, C524S723000, C524S729000, C524S700000
Reexamination Certificate
active
06552120
ABSTRACT:
The invention relates to the use of vinylaromatic/1,3-diene copolymers stabilized with protective colloids and in the form of their aqueous polymer dispersions or water-redispersible polymer powders in building adhesive formulations, in particular those for tile adhesives and full thermal insulation adhesives.
Cement-based tile adhesives are currently prepared in large quantities and represent the standard. Using cement-based adhesives it is possible to prepare waterproof and frost-proof adhesives which, by modification with different amounts of polymer, can be adapted to suit the necessary requirements in respect of adhesion and flexibility. The addition of a polymer achieves a significant improvement in processing reliability, which has allowed the triumphant progress of one-component dry mortars.
A precondition for the use of polymers for modification of dry mortars is their existence as water-redispersible powders. Tile adhesive compositions with redispersible polymer powders based on vinyl ester and acrylic acid ester polymers are known from EP-A 722917. The use of hydrophobic polymers based on vinylaromatic/1,3-diene copolymers is not described therein.
DE-A 2148456 (GB-A 1407827) recommends aqueous dispersions of styrene/1,3-butadiene copolymers, which contain silanol groups to improve the wet adhesion and have been prepared in an emulsion polymerization process in the presence of emulsifiers, for aqueous building adhesive compositions. Because of the emulsifier content, emulsifier-stabilized dispersions show a reduced bonding force, in particular after wet storage. Although the wet adhesion of the emulsifier-containing dispersions can be improved by copolymerization of alkoxyvinylsilanes, in many cases the copolymerization of such relatively expensive comonomers is not desirable.
EP-B 182628 relates to the use of aqueous emulsions of carboxyl-functional and silanol-functional styrene-butadiene copolymers containing zinc-ammonium complexes as tile adhesives. A disadvantage here is that adhesives with a sufficient resistance to water can be obtained only by copolymerization of alkoxyvinylsilanes and in the presence of complex salts.
WO-A 97/38042 and DE-A 19710380 discloses redispersible powders based on carboxylated styrene/butadiene copolymers which have been prepared in the presence of emulsifier and are sprayed with a special mixture of polyvinyl alcohol and the salt of an addition product of sulfosuccinate and maleic acid. As with all conventional emulsifier-stabilized powders, a disadvantage is that no redispersible powders are obtained without the copolymerization of carboxyl-functional monomers and without the use of special spraying aids.
It was thus the object to provide building adhesives based on aqueous dispersions and water-redispersible powders of vinylaromatic/1,3-diene copolymers which, in the case of the powders, are also redispersible without the copolymerization of functional comonomers, and have good adhesive properties when used as building adhesives without the use of special agents.
The invention relates to the use of aqueous polymer dispersions or water-redispersible polymer powders based on vinylaromatic/1,3-diene copolymers stabilized with protective colloids in building adhesive formulations, the polymer dispersions and the polymer powders being obtained by emulsion polymerization of a mixture comprising at least one vinylaromatic and at least one 1,3-diene in the presence of one or more protective colloids, with exclusion of any emulsifier, and if appropriate drying of the aqueous polymer dispersion obtained by this process.
Suitable vinylaromatics are styrene and methylstyrene, and styrene is preferably copolymerized. Examples of 1,3-dienes are 1,3-butadiene and isoprene, and 1,3-butadiene is preferred. The copolymers in general comprise 20 to 80% by weight, preferably 30 to 70% by weight, of vinylaromatic and 20 to 80% by weight, preferably 30 to 70% by weight, of 1,3-diene, and they can optionally also contain further monomers, and the data in % by weight in each case add up to 100% by weight.
Up to 30% by weight, based on the total weight of the monomer phase, of further monomers which can be copolymerized with vinylaromatics and 1,3-dienes, such as ethylene, vinyl chloride, (meth)acrylic acid esters of alcohols having 1 to 15 C atoms or vinyl esters of unbranched or branched carboxylic acids having 1 to 15 C atoms, can also optionally be copolymerized. 0.05 to 10% by weight, based on the total weight of the monomer mixture, of auxiliary monomers can optionally also be copolymerized. Examples of auxiliary monomers are ethylenically unsaturated mono- and dicarboxylic acids, preferably acrylic acid, methacrylic acid, fumaric acid and maleic acid; ethylenically unsaturated carboxylic acid amides and nitriles, preferably acrylamide and acrylonitrile; mono- and diesters of fumaric acid and maleic acid, such as the diethyl and diisopropyl ester, and maleic anhydride; and ethylenically unsaturated sulfonic acids and salts thereof, preferably vinylsulfonic acid and 2-acrylamido-2-methylpropanesulfonic acid. Further examples are pre-crosslinking comonomers, such as poly-ethylenically unsaturated comonomers, for example divinyl adipate, diallyl maleate, allyl methacrylate or triallyl cyanurate, or post-crosslinking comonomers, for example acrylamidoglycolic acid (AGA), methylacrylamidoglycolic acid methyl ester (MAGME), N-methylolacrylamide (NMA), N-methylolmethacrylamide, allyl N-methylcarbamate or alkyl ethers, such as the isobutoxy ether, or esters of N-methylolacrylamide, of N-methylolmethacrylamide and of allyl N-meth-ylolcarbamate. Epoxide-functional comonomers, such as glycidyl methacrylate and glycidyl acrylate, are also suitable. Further examples are silicon-functional comonomers, such as acryloxypropyltri(alkoxy)- and methacryloxypropyltri(alkoxy)silanes, vinyltrialkoxy-silanes and vinylmethyldialkoxysilanes, which can contain as alkoxy groups, for example, ethoxy and ethoxypropylene glycol ether radicals. Monomers with hydroxyl or CO groups may also be mentioned, for example methacrylic acid and acrylic acid hydroxyalkyl esters, such as hydroxyethyl, hydroxypropyl or hydroxybutyl acrylate or methacrylate, and compounds such as diacetoneacrylamide and acetylacetoxyethyl acrylate or methacrylate.
The choice of monomers and the choice of the weight contents of the comonomers is made such that in general a glass transition temperature of Tg of −70° C. to +100° C., preferably −50° C. to +50° C., particularly preferably −20° C. to +40° C. results. The glass transition temperature Tg of the polymers can be determined in a known manner by means of differential scanning calorimetry (DSC.). The Tg can also be calculated beforehand by approximation by means of the Fox equation. According to Fox T. G., Bull. Am. Physics Soc. 1, 3, page 123 (1956): 1/Tg=x
1
/Tg
1
+x
2
/Tg
2
+. . . +x
n
/Tg
n
, where x
n
represents the weight fraction (% by weight/100) of the monomer n and Tg
n
is the glass transition temperature, in degrees Kelvin, of the homopolymer of monomer n. Tg values for homopolymers are listed in Polymer Handbook 2nd Edition, J. Wiley & Sons, New York (1975).
Suitable protective colloids are, for example, polyvinyl alcohols, polysaccharides in water-soluble form, such as starches (amylose and amylopectin), modified starches, such as starch ethers, for example hydroxyalkyl ether starches, dextrins and cyclodextrins, celluloses and carboxymethyl, methyl, hydroxyethyl and hydroxypropyl derivatives thereof, poly(meth)acrylic acid, poly(meth)acrylamide, melamine-formaldehyde sulfonates and naphthalene-formaldehyde sulfonates.
Polyvinyl alcohols having a degree of hydrolysis of 80 to 95 mol % and a Höppler viscosity in 4% strength aqueous solution of 1 to 30 mPas (Höppler method at 20° C., DIN 53015) are preferred. Hydrophobically modified polyvinyl alcohols with a degree of hydrolysis of 80 to 95 mol % and a Höppler viscosity in 4% strength aqueous solution of 1 to 30 mPas are also suitable
Härzschel Reinhard
Mayer Theo
Weitzel Hans-Peter
Brooks & Kushman P.C.
Nutter Nathan M.
Rajguru U. K
Wacker-Chemie GmbH
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