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
2001-08-09
2003-06-03
Cain, Edward J. (Department: 1714)
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...
C524S557000, C524S560000, C524S561000, C524S563000, C524S564000, C524S005000
Reexamination Certificate
active
06573326
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to thickeners based on vinyl alcohol copolymers, and also to the use of these, in particular in compositions used in the building trades.
2. Background Art
Mixtures of lime hydrate and of cement are used for the masonry, rendering, troweling, bonding and restoration work carried out by the construction industry. Water-soluble polymers are added to the mixtures of lime hydrate and of cement to improve their workability and water-retention properties, with the intention of achieving very good workability and preventing the compositions of lime hydrate and of cement from losing water prior to setting on highly absorbent substrates. Premature loss of water leads to inadequate hardening or development of cracks in the construction material. The water-soluble polymers usually added are non-ionic cellulose ethers, such as methyl cellulose (MC), hydroxyethyl cellulose (HEC), methyl hydroxyethyl cellulose (MHEC), or methyl hydroxypropyl cellulose (MHPC).
For the purposes of the present invention, cellulose ethers are cellulose derivatives produced by the action of alkylating agents on cellulose in the presence of bases. Examples of alkylating agents are ethylene oxide, dimethyl sulfate, methyl chloride and methyl iodide. The only industrial method of preparing methyl celluloses is the reaction of alkali celluloses with methyl chloride, in the presence or absence of organic solvents, a process which generates toxicological concerns. The resultant cellulose ether therefore contains methanol, dimethyl ether, and relatively large amounts of sodium chloride as by-products. NaCl in particular can lead to corrosion problems in applications in the construction sector, and complicated purification processes therefore have to be used for its removal.
In applications in many other fields, cellulose ethers compete with entirely synthetic polymers, such as associative polyurethane thickeners, polyacrylates, polyamines, and polyamides, and also with naturally occurring water-soluble polymers, such as agar agar, tragacanth, carrageen, gum arabic, alginates, starch, gelatine, and casein. However, there have hitherto been no alternatives to cellulose ether for the workability and water-retention required for lime hydrate or cement-based compositions, in particular in cement-type systems with their high pH and high electrolyte content. A disadvantage of the cellulose ethers usually used in cement-type construction applications, in particular hydroxyethyl methyl cellulose, is that there is sometimes a considerable delay in cement setting. Although polyvinyl alcohols are known constituents of cement-type compositions, they are used only in a relatively low-molecular-weight form which cannot have any significant thickening effect. Although higher-molecular-weight polyvinyl alcohol polymers would be expected to have thickening properties, these polymers exhibit difficulties of low cold-water solubility and poor workability associated with this low solubility.
U.S. Pat. No. 5,565,027 discloses polyvinyl alcohols modified with hydroxyaldehydes used as cement plasticizers in cement-type systems. EP-A 272012 describes the use of vinyl alcohol copolymers as thickeners in aqueous systems such as emulsion paints, the copolymers containing not only vinyl alcohol units but also acrylic ester units having at least two ethylene oxide units in the ester radical. JP-A 10/087937 describes an improvement in the mechanical strength of cement-containing construction materials via addition of polyvinyl alcohol or of vinyl alcohol copolymers with defined solubility in aqueous Ca(OH)
2
solution. The vinyl alcohol copolymers contain carboxyl units, sulfonate units and N-vinyl units.
JP-A 08/319395 describes the use of a composition made from alkali metal acetate salt and a vinyl alcohol copolymer having acetylacetone units as a thickener for polymer emulsions. JP-A 08/269132 describes fine-particle size, pulverulent vinyl alcohol homo- or copolymers with a defined proportion of syndiotactic, rather than the usual atactic, conformation, for improving the water-resistance of compositions modified with the same. JP-B 54-27382 describes a process for thickening copolymer dispersions based on carboxyl-functionality copolymers, where partially hydrolyzed polyvinyl alcohol is added. EP-A 458328 describes a thickener system intended for water-containing construction materials and composed of a combination of cellulose ether, polyvinyl alcohol and borax, its action being based on complex formation between polyvinyl alcohol and borax.
SUMMARY OF THE INVENTION
It was an object of the invention to provide an entirely synthetic water-soluble polymer which acts as a thickener in formulations used in civil engineering, and in particular in cement-type formulations, which produces formulations displaying excellent workability and mechanical properties, but which does not have the abovementioned disadvantages.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
The invention provided thickeners based on fully or partially hydrolyzed vinyl alcohol copolymers with a molecular weight Mw greater than 100,000, obtainable by hydrolyzing vinyl acetate copolymers which, besides vinyl acetate units, also contain comonomer units which derive from one or more comonomers selected from the group consisting of 1-(C
1-5
)-alkylvinyl esters of C
1-5
carboxylic acids, allyl esters, vinyl esters of alpha-branched C
5-12
carboxylic acids having from 5 to 12 carbon atoms, and C
1-18
-alkyl (meth)acrylates, and in the form of their aqueous solution or in powder form. As is common in polymer chemistry, polymers may be described in terms of their constituent monomers without using language such as “units derived from” those monomers. Thus, a polymer derived from vinyl acetate monomer may be described as a vinyl acetate polymer even though once polymerized, the polymer will not contain vinyl acetate moieties.
The preferred 1-alkylvinyl ester is isopropenyl acetate. Preferred vinyl esters of alpha-branched carboxylic acids are those of alpha-branched carboxylic acids having from 9 to 11 carbon atoms, and particular preference is given to vinyl esters of alpha-branched carboxylic acids having 10 carbon atoms (VeoVa10, trade name of Shell). Preferred acrylic and methacrylic esters are those of C
1-10
alcohols. Particular preference is given to methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, and 2-ethylhexyl methacrylate. From 0.05 to 2% by weight of auxiliary monomers, based on the total weight of the monomer mixture, may also be copolymerized. Examples of auxiliary monomers are ethylenically unsaturated mono- and dicarboxylic acids, preferably acrylic acid, methacrylic acid, fumaric acid, crotonic acid or maleic acid; ethylenically unsaturated carboxamides and ethylenically unsaturated carbonitriles, preferably acrylamide or acrylonitrile; cyclic carboxamides, such as N-vinylpyrrolidone and N-vinyl-&egr;-caprolactam, and ethylenically unsaturated carboxylic anhydrides, preferably maleic anhydride.
The degree of hydrolysis of the partially or fully hydrolyzed vinyl alcohol copolymers is generally from 75 to 100 mol %; in the case of “fully hydrolyzed” vinyl alcohol copolymers it is preferably from 97.5 to 100 mol %, more preferably from 98 to 99.5 mol %; and in the case of partially hydrolyzed vinyl alcohol copolymers it is preferably from 80 to 95 mol %, more preferably from 86 to 90 mol %. The proportion of comonomer units is from 0.1 to 50% by weight, preferably from 0.3 to 15% by weight, and most preferably from 0.5 to 6% by weight, based in each case on the total weight of the vinyl alcohol copolymer.
Particular preference is given to vinyl alcohol copolymers obtainable by hydrolyzing vinyl acetate copolymers having from 0.3 to 15% by weight of isopropenyl acetate, vinyl esters of alpha-branched C
9-11
carboxylic acids, methyl, ethyl, butyl or 2-ethylhexyl acrylate, or 2-ethylhexyl methacrylate, or methyl methacrylate. Particular preference
Bacher Andreas
Bauer Werner
Dietrich Ulf
Kayser Bernd
Mayer Theo
Brooks & Kushman P.C.
Cain Edward J.
Wacker-Chemie GmbH
LandOfFree
Thickeners based on vinyl alcohol copolymers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Thickeners based on vinyl alcohol copolymers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thickeners based on vinyl alcohol copolymers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3089155