Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-08-01
2003-12-02
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S037000, C524S043000, C524S045000, C524S047000, C524S048000, C524S800000, C524S819000, C524S820000, C524S823000, C524S824000
Reexamination Certificate
active
06656983
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
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 as adhesive for porous substrates.
2. Background Art
WO-A 96/37551 discloses wood adhesives which comprise a mixture of a polymer containing hydroxyl groups, in particular polyvinyl alcohol, and a carboxyl-substituted styrene polymer, in particular styrene/butadiene latex, and a polyfunctional aziridine as the crosslinking agent for hydroxyl and carboxyl groups. When these polymers are used as wood adhesives, however, there is the disadvantage that, because of their high reactivity in the ready-to-use state, these cannot be used as storage-stable one-component systems.
JP-A 1/229085 (Derwent Abstract AN 89-312288) discloses wood adhesives which are composed of a chelating agent and a dissolved or dispersed adhesive. Polymer dispersions based on vinyl acetate, acrylate or styrene/butadiene, in addition to condensation resins, are mentioned here in particular as adhesives. These can optionally contain polyvinyl alcohol as a dispersing agent. Dibasic acids, such as oxalic or malonic acid, in addition to oxocarboxylic acids, and salts thereof, are mentioned as chelating agents.
JP-A 58/162645 (Derwent Abstract AN 83-805435) discloses adhesives for gluing porous materials, for example wood. The adhesives consist of a mixture of a vinyl acetate/ethylene copolymer dispersion and a styrene/butadiene latex modified with carboxyl groups, the dispersions mentioned being stabilized by emulsifiers. A problem with emulsifier-stabilized dispersions is their unsatisfactory resistance to water.
JP-A 60009970 discloses an adhesive composition for carpet bonding, containing glycine in order to prevent bubbling. The binder is again an emulsifier-stabilized latex with the drawback of unsatisfactory water resistance.
The invention was thus based on the object of providing adhesives which are distinguished by improved hydrophobicity and resistance to water compared with the known adhesives for porous materials, with a simultaneously good storage stability.
SUMMARY OF THE INVENTION
The invention relates to the use of vinylaromatic/1,3-diene copolymers, having a glass transition temperature Tg of −70° C. to +100° C., stabilized with protective colloids and in the form of their aqueous polymer dispersions or water-redispersible polymer powders as adhesives for porous substrates, the polymer dispersions and the polymer powders being obtained by emulsion polymerization of a mixture comprising
a) 20 to 80% by weight of one or more vinylaromatics,
b) 19.9 to 79.9% by weight of one or more 1,3-dienes,
c) 0.1 to 15% by weight of one or more comonomers from the group consisting of N-methylolacrylamide, N-methylolmethacrylamide and the N-(alkoxymethyl)-acrylamides and N-(alkoxymethyl)methacrylamides with a C
1
- to C
6
-alkyl radical, the data in % by weight adding up to 100% by weight,
in the presence of one or more protective colloids and with the exclusion of emulsifier, and optionally drying 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 content of comonomers a) and b) is preferably in each case 30 to 70% by weight, based on the total weight of the comonomers.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
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 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 optionally also 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 esters, and maleic anhydrides; and ethylenically unsaturated sulphonic acids and salts thereof, preferably vinylsulphonic acid and 2-acrylamido-2-methylpropanesulphonic acid. Further examples are pre-crosslinking comonomers, such as poly-ethylenically unsaturated comonomers, for example divinyl adipate, diallyl maleate, allyl methacrylate or triallyl cyanurate. 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 vinylmethyldialkoxy silanes, which can contain, for example, ethoxy and ethoxypropylene glycol ether radicals as alkoxy groups. Monomers with hydroxyl or CO groups, 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, may also be mentioned.
The choice of monomer and the choice of the weight contents of the comonomers is taken here such in general a glass transition temperature Tg of −70° C. to +100° C., preferably −50° C. to +50°, particularly preferably −20° C. to +20°, 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 in 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
, wherein x
n
represents the weight fraction (% by weight/100) of 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 cyclo-dextrins, celluloses and carboxymethyl, methyl, hydroxyethyl and hydroxypropyl derivatives thereof, poly(meth)acrylic acid, poly(meth)acrylamide, melamine-formaldehyde sulphonates and naphthalene-formaldehyde sulphonates.
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 (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. Examples of these are partly hydrolysed copolymers of vinyl acetate with hydrophobic comonomers, such as isopropenyl acetate, vinyl pivalate, vinyl ethylhexanoate, vinyl esters of saturated alpha-branched monocarboxylic acids having 5 or 9 to 11 C atoms, dialkyl maleates and dialkyl fumarates, such as diisopropyl maleate and diisopropyl fumarate, vinyl chloride, vinyl alkyl ethers, such as vinyl butyl ethers, and olefins, such as ethene and decene. The content of the hydrophobic units is preferably 0.1 to 10% by weight, based on the total weight of the partly hydrolysed polyvinyl acetate. Mixtures of the polyvinyl alcohols mentioned can also be employed.
The partly hydrolysed polyvinyl acetates with vinyl alcohol units and units of vinyl esters of alpha-branched carboxylic acids having 5 or 9 to 11 C atoms in the amounts mentioned are particularly preferred. Exampl
Härzschel Reinhard
Kohler Thomas
Mayer Theo
Schilling Bernd
Weitzel Hans-Peter
Brooks & Kushman P.C.
Cain Edward J.
Wacker-Chemie GmbH
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