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
1999-03-29
2001-07-17
Wilson, Donald R. (Department: 1713)
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...
C524S823000, C524S825000, C524S820000, C526S209000, C526S210000, C526S319000, C526S303100, C526S317100
Reexamination Certificate
active
06262163
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field of the Invention
The invention relates to a process for preparing vinyl ester or vinyl ester-ethylene polymers in the form of their aqueous dispersions, and also to the use of the resultant dispersions as adhesives or textile binders.
2) Background Art
Aqueous synthetic resin dispersions and corresponding powders have for many years been indispensable additives for applications in the construction sector, for example for renders, mortars, reinforcement compositions, self-leveling compositions, tile adhesives, paints and composite thermal insulation systems. Especially for high-quality renders, there is constantly increasing use of binders which give properties such as better mechanical properties, better weathering resistance and lower susceptibility to soiling.
When highly hydrophobic properties are to be achieved, but with good water vapor permeability, as is the case with silicate renders, use is frequently made of synthetic resins made from hydrophobic monomers, such as vinyl chloride or styrene/butyl acrylate. Vinyl chloride is particularly attractive on cost grounds and its use has been popular in the past. For environmental reasons it is now undesirable. In addition, renders formulated with binders comprising vinyl chloride are highly sensitive to other additives required, such as thickeners or antifoams, and this means that the good hydrophobic properties are often lost when mixing specifications change, for example when there is a change in the type of antifoam. EP-A 217380 (U.S. Pat. No. 4,748,202), for example, describes dispersions comprising VC which are polymerized in the presence of a protective colloid that becomes completely dissolved during the polymerization.
WO 94/20556 (U.S. Pat. No. 5,708,093) recommends copolymerization of silanes to improve wet adhesion and to hydrophobicize aqueous coating compositions. The silanes are incorporated into the shell of core-shell polymers. A disadvantage here is the reduction in storage stability resulting from the incorporation of silane units.
EP-A 338486 describes a process for preparing core-shell polymers where these polymers are non-silanized and are prepared in the presence of a water-soluble protective colloid. The protective colloids used are very low-molecular-weight polymers which become completely dissolved during the polymerization. These dispersions are unsuitable for hydrophobicization in construction applications, because they do not give a lasting hydrophobicization independent of the mixing specification.
The object of the invention was to develop a dispersion which is attractive on cost grounds, environmentally accepted, i.e. free of vinyl chloride, and resistant to freezing and thawing, and whose properties in building applications, for example renders, are good and comparable with those of the vinyl chloride dispersions used hitherto, and which also has the advantage that the hydrophobic properties of the render formulation are less sensitive to changes within the other components.
SUMMARY OF THE INVENTION
The invention provides a process for preparing protective-colloid-stabilized vinyl ester or vinyl ester-ethylene polymers in the form of their aqueous dispersions by emulsion polymerization in the presence of one or more protective colloids, which comprises carrying out the polymerization in the presence of a hydrophobic but silane-free protective colloid based on (meth)acrylate polymers with from 80 to 95% by weight, based on the total weight of the copolymer, of acrylic or methacrylic esters of aliphatic alcohols having from 1 to 12 carbon atoms, and from 5 to 20% by weight, based on the total weight of the copolymer, of ethylenically unsaturated mono- or dicarboxylic acids, and with a glass transition temperature Tg of the copolymer of from 60 to 120° C., and with a Fikentscher K value of the copolymer of from 20 to 50.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred vinyl esters are vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethyl hexanoate, vinyl laurate, 1-methylvinyl acetate, vinyl pivalate and vinyl esters of alpha-branched monocarboxylic acids having from 5 to 11 carbon atoms, such as VeoVa9
R
, VeoVa10
R
, or VeoVa11
R
(Shell tradenames). Particular preference is given to vinyl acetate polymers or vinyl acetate copolymers with a proportion of from 1 to 25% by weight of olefinic comonomers, such as ethylene or propylene. In another particularly preferred embodiment, from 1 to 30% by weight of other vinyl esters may be copolymerized alongside vinyl acetate or alongside vinyl acetate and ethylene, for example vinyl 2-ethylhexanoate, vinyl laurate, 1-methylvinyl acetate, vinyl pivalate or vinyl esters of alpha-branched monocarboxylic acids having from 5 to 11 carbon atoms.
Other comonomers which may be copolymerized if desired are from 0.05 to 10.0% by weight, based on the total weight of the monomers, of comonomers selected from the class including ethylenically unsaturated mono- and dicarboxylic acids and amides of these, for example acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, acrylamide and methacrylamide; ethylenically unsaturated sulfonic acids and salts of these, preferably vinylsulfonic acid, 2-acrylamidopropanesulfonate and N-vinylpyrrolidone. The data in percent by weight are always based here on the total weight of the vinyl ester or vinyl ester-ethylene copolymer and in each case give 100% by weight in total.
Suitable protective colloids are based on (meth)acrylate polymers with, based on the total weight of the copolymer, from 80 to 95% by weight, preferably from 90 to 95% by weight, of units of acrylic or methacrylic esters of aliphatic alcohols having from 1 to 12 carbon atoms and from 5 to 20% by weight, preferably from 5 to 10% by weight, based on the total weight of the copolymer, of units of ethylenically unsaturated mono- or dicarboxylic acids, and with a glass transition temperature Tg of the copolymer of from 60 to 120° C., and with a Fikentscher K value of the copolymer of from 20 to 50.
Preferred (meth)acrylates for the protective colloid are methylacrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, tert-butyl acrylate, n-butyl methacrylate, tert-butyl methacrylate and 2-ethylhexyl acrylate. Particular preference is given to methyl acrylate, methyl methacrylate, n-butyl acrylate and 2-ethylhexyl acrylate.
Preferred ethylenically unsaturated carboxylic acids are acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid.
Other comonomers which may be copolymerized if desired are from 0.05 to 10.0% by weight, based on the total weight of the monomers, of comonomers selected from the class including ethylenically unsaturated carboxamides, such as acrylamide or methacrylamide, ethylenically unsaturated sulfonic acids and salts of these, preferably vinylsulfonic acid, 2-acrylamidopropanesulfonate, hydroxyfunctional comonomers, such as hydroxyethyl acrylate, and N-vinylpyrrolidone.
The most preferred copolymers are those of ethyl methacrylate, butyl acrylate and methacrylic or acrylic acid in the amounts given above.
The polymeric formulation of the protective colloid is selected in such a way as to give a glass transition temperature Tg of from 60 to 120° C. Preference is given to protective colloids with a Tg of from 60 to 90° C. The glass transition temperature Tg of the polymers can be determined in a known manner using differential scanning calorimetry (DSC). The Tg can also be approximated using the Fox equation. According to T. G. Fox, 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
is the proportion by weight (% 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 3rd Edition, J. Wiley & Sons, New York (1989).
The K value of the protective colloids is from 20 to 50, preferably from 30 to 40
Hannebaum Manfred
Kotschi Udo
Weitzel Hans-Peter
Burgess, Ryan & Wayne
Moran William R.
Wacker - Chemie GmbH
Wayne Milton J.
Wilson Donald R.
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