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
1996-08-23
2001-12-18
Reddick, Judy M. (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...
C524S503000, C525S056000, C525S057000, C525S061000, C526S202000, C526S219500
Reexamination Certificate
active
06331587
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for the preparation of vinyl ester polymer dispersions which are stabilized with protective colloids and have a high solids content, to the so-prepared dispersions, and to the use of these dispersions, or of the dispersible dispersion powders obtainable therefrom by spray drying, for example, for modifying building materials.
2. Description of Related Art
For economic reasons, dispersions having the highest possible solids content should be prepared. However, this requirement has not been met to date for all types of dispersion. Thus, dispersions which are based on vinyl ester/(meth)acrylate and are stabilized with protective colloids tend toward dilatancy at high solids contents.
The use of cationic azo initiators in the preparation of emulsifier-stabilized dispersions is known in principle. DE-A 32 39 091 describes a process for the preparation of cationic styrene or acrylic ester latices in the presence of cationic comonomers using a cationic azo compound as an initiator. The solids content of the dispersions described in the examples is a maximum of 41% by weight.
U.S. Pat. No. 4,489,192 relates to curable cationic polymer lattices which are based on vinyl esters and monomers containing cationic quaternary ammonium groups and are prepared in the presence of a water-soluble cationic azo initiator, an aminothiol salt, and cationic and/or nonionic emulsifiers.
A publication by K. Sakota and T. Okaya (J. Appl. Polym. Sci. 20, 1725 (1976)) reports on the preparation of cationic polystyrene latices, 2,2′-azobis(2-amidino-propane) hydrochloride being employed as an initiator. Stable latices are obtained only if the cationic emulsifier dodecylpyridinium chloride is added or in the case of copolymerization with the cationic monomer dimethyl-aminoethyl methacrylate hydrochloride. The solids content of the dispersions described is less than 25% by weight.
SUMMARY OF THE INVENTION
An object of the present invention was to provide a process for the preparation of polymer dispersions which comprise vinyl esters and are stabilized with protective colloids. It is also an object of the invention to provide such dispersions and methods of using them.
These objects have been achieved by using water-soluble, cationic azo initiators. In particular, in accordance with the present invention there is provided a process for the preparation of a dispersion which comprises a homopolymer or copolymer of vinyl ester and is stabilized with a protective colloid that comprises polymerization of monomers comprising at least one vinyl ester of a linear or branched monocarboxylic acid having 2 to 12 carbon atoms and optionally further monomers which can be copolymerized with the vinyl ester, by use of a water-soluble cationic azo initiator in the presence of a protective colloid, at a preferred polymerization temperature of 40 to 90° C.
In accordance with further objects of the invention, there is provided a polymer dispersion which is stabilized with a protective colloid and has a solids content of at least 45% by weight, obtained by the process described above.
Further objects, features, and advantages of the present invention will become apparent from the detailed description of preferred embodiment that follows.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention relates to a process for the preparation of dispersions which comprise homo- or copolymeric vinyl esters and are stabilized with protective colloids, by polymerization of at least one vinyl ester and optionally further monomers which are copolymerizable with this vinyl ester, by means of water-soluble cationic azo initiators.
Any desired water-soluble cationic azo initiator or mixture thereof can be used. Preferred water-soluble cationic azo initiators in the context of the invention include azoamidine compounds, for example 2,2′-azobis(2-methylpropionamidine) dihydrochloride, 2,2′-azobis(2-methyl-N-phenylpropionamidine) dihydrochloride, 2,2′-azobis[N-(4-chlorophenyl)-2-methylpropionamidine] di-hydrochloride, 2,2′-azobis[N-(4-hydroxyphenyl)-2-methyl-propionamidine]dihydrochloride, 2,2′-azobis[N-(4-amino-phenyl)-2-methylpropionamidine]tetrahydrochloride, 2,2′-azobis[2-methyl-N(phenylmethyl)propionamidine]dihydrochloride, 2,2′-azobis[2-methyl-N-2-propenylpropionamidine]dihydrochloride, 2,2′-azobis[N-(2-hydroxy-ethyl)2-methylpropionamidine]dihydrochloride, 2,2′-azobis[2(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2′-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 2,2′-azobis[2-(4,5,6,7-tetrahydro-1H-1,3-diazepin-2-yl)propane]dihydrochloride, 2,2′-azobis[2-(3,4,5,6-tetrahydropyrimidin-2-yl)propane]dihydrochloride, 2,2′-azobis[2-(5-hydroxy-3,4,5,6-tetrahydropyrimidin -2-yl)propane]dihydrochloride and 2,2′-azobis {2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane}dihydrochloride.
2,2′-azobis(2-methylpropionamidine) dihydrochloride is particularly preferably used as the initiator.
The initiator is employed in initiating effective amounts, and preferably is employed in an amount of 0.05 to 2% by weight, in particular of 0.1 to 1% by weight, based on the total amount of the monomers.
Useful monomers for the process according to the invention are the known vinyl esters, in particular vinyl esters of linear and branched monocarboxylic acids having 2 to 12 carbon atoms. Examples include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl 2-ethylhexanoate, and vinyl esters of Versatic® acid 9, 10 or 11 (&agr;,&agr;-dialkyl-branched monocarboxylic acids, Shell Chemie). The content of vinyl esters is preferably at least 50% by weight, in particular 70 to 90% by weight, based on the total amount of monomers employed.
Any monomer that is polymerizable with vinyl esters can be used as optional comonomers. Suitable comonomers include ethylene and esters of acrylic acid or methacrylic acid with an alcohol containing 1 to 12 carbon atoms, for example, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, n-hexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, n-octyl methacrylate, and 2-ethylhexyl methacrylate. The content of these comonomers is preferably up to 50% by weight, in particular 5 to 30% by weight, based on the total amount of monomers employed.
Furthermore, monoolefinically unsaturated monocarboxylic acids and dicarboxylic acids, for example acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, and mono- and diesters of the dicarboxylic acids, for example maleic acid monomethyl ester and maleic acid mono-2-ethylhexyl ester, and also salts of the above mentioned acids, can be employed. The content of these comonomers is preferably up to 5% by weight, in particular 0.1 to 5% by weight, based on the total amount of monomers employed.
The process according to the invention may be preferably carried out in the complete absence of cationic comonomers, exclusively in the presence of vinyl esters or of vinyl esters and exclusively comonomers from the group consisting of neutral and anionic monomers.
Polyvinyl alcohol is preferably employed as the protective colloid, generally in an amount of 2 to 15% by weight, preferably 4 to 12% by weight, based on the total amount of the monomers. The degree of polymerization of the polyvinyl alcohol is preferably 200 to 3500, in particular between 500 and 3000. The degree of hydrolysis is preferably 80 to 98 mol %, preferably 88 mol %, in particular 85 to 95 mol %.
Further examples of suitable protective colloids include etherified cellulose derivatives, for example hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, starches which are water-soluble or degraded by hydr
Clariant GmbH
Heller Ehrman White & McAuliffe LLP
Reddick Judy M.
LandOfFree
Polyvinyl ester dispersions and methods for their preparation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyvinyl ester dispersions and methods for their preparation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyvinyl ester dispersions and methods for their preparation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2597892