Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-02-07
2003-04-01
Wilson, D. R. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S328300, C525S328400, C525S355000, C525S369000, C525S378000, C525S379000
Reexamination Certificate
active
06541573
ABSTRACT:
The invention relates to a process for the elimination of formamide from polymers containing N-vinylformamide units by treatment of the polymers contaminated with formamide with acids or bases.
Polymers containing N-vinylformamide units are known. They are prepared by free-radical polymerization of N-vinylformamide, optionally in the presence of other monoethylenically unsaturated monomers which are copolymerizable therewith, cf. U.S. Pat. No. 4,421,602, EP-A-0374646, EP-A-0438744, EP-A-0473881, EP-A-0510246, U.S. Pat. No. 5,334,287, DE-A-19526626 and DE-A-19515943. The polymers can be prepared, for example, by polymerizing monomers by solution polymerization, precipitation polymerization or also by the process of water-in-oil emulsion polymerization. Polymers containing vinylformamide units are in many cases converted by treatment with bases or acids at relatively high temperatures with removal of the formyl group from the copolymerized vinylformamide units in polymers containing vinylamine units. Thus, for example, according to U.S. Pat. No. 4,421,602, homopolymers of N-vinylformamide are converted, with removal of from 10 to 90 mol % of the formyl groups, into polymers containing vinylamine and vinylformamide units. The removal of formyl groups from copolymers of N-vinylformamide using other ethylenically unsaturated monomers is known from EP-A-0216387. It takes place in the presence of acids or bases at from 20 to 100° C. Depending on the reaction conditions used, the reaction leads to partial or complete removal of formyl groups with formation of amino groups from the polymers containing vinylformamide groups. If the polymers contain formamide as impurity, during removal of the formyl groups from the polymers containing vinylformamide units, hydrolysis of the formamide also takes place, meaning that the polymers containing vinylamine units are virtually no longer contaminated with formamide.
U.S. Pat. No. 5,478,553 discloses the use of polymers containing N-vinylformamide units as conditioners and as setting compositions and gel formers for hair care. EP-A-0452758 describes the use of polymers containing N-vinylformamide units as auxiliary in cosmetic and pharmaceutical preparations. For such intended uses, however, the polymers must not contain any physiologically unacceptable impurities such as, for example, formamide. As a result of the preparation, N-vinylformamide contains formamide as impurity, which cannot easily be removed from the monomer using distillation. For this reason, the N-vinylformamide containing small amounts of formamide is polymerized. The problem following polymerization is then to purify the polymer from residual formamide.
It is an object of the present invention to provide a process for removing formamide from polymers containing N-vinylformamide units, the intention being for the N-vinylformamide units in the polymer to remain completely intact as far as possible.
We have found that this object is achieved by a process for the elimination of formamide from polymers containing N-vinylformamide units if polymers containing formamide are treated with from 1 to 2 mole-equivalents, based on 1 mole-equivalent of formamide, of an acid or a base under reaction conditions such that the N-vinylformamide units in the polymer undergo virtually no hydrolysis.
The polymers containing N-vinylformamide units can here be in the form of an aqueous solution, a solution in a water-soluble solvent or also in mixtures of water and a water-soluble solvent, an aqueous suspension or a water-in-oil emulsion. The polymer content in these systems is, for example, from 3 to 50% by weight, preferably from 5 to 30% by weight. The content of formamide in the polymer essentially depends on the amount of copolymerized N-vinylformamide. It is, for example, from 0.001 to 7.5% by weight, preferably from 0.01 to 3.0% by weight and in most cases from 0.02 to 0.5% by weight. Polymers containing N-vinylformamide units are known, for example, from the literature references given above in the prior art. The novel process can be used for all polymers which contain copolymerized N-vinylformamide. Suitable polymers are homo- and also copolymers of N-vinylformamide and also graft copolymers thereof. Suitable examples of possible comonomers for N-vinylformamide are other N-vinylcarboxamides, such as N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylformamide, N-vinyl-N-propylformamide, N-vinyl-N-isopropylformamide, N-vinyl-N-isobutylformamide, N-vinyl-N-methylpropionamide, N-vinyl-N-butylacetamide and N-vinyl-N-methylpropionamide.
Other suitable comonomers for N-vinylformamide are monoethylenically unsaturated carboxylic acids having from 3 to 8 carbon atoms and the water-soluble salts of these monomers. This group includes, for example, acrylic acid, methacrylic acid, dimethylacrylic acid, ethacrylic acid, maleic acid, citraconic acid, methylenemalonic acid, allylacetic acid, vinylacetic acid, crotonic acid, fumaric acid, mesaconic acid and itaconic acid. Of this group of monomers, preference is given to using acrylic acid, methacrylic acid, maleic acid or also mixtures of said carboxylic acids, in particular mixtures of acrylic acid and methacrylic acid. The unsaturated carboxylic acids can be polymerized either in free form or in partially or in completely base-neutralized form, e.g. using sodium hydroxide solution, potassium hydroxide solution, calcium hydroxide or ammonia.
Examples of other suitable comonomers are esters, amides and nitriles of said carboxylic acids. The acrylic and methacrylic esters are preferably derived from saturated, monohydric alcohols having from 1 to 4 carbon atoms or saturated dihydric alcohols containing from 2 to 4 carbon atoms. Examples of these esters are methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, propyl acrylate, isopropyl methacrylate and the esters of acrylic acid and methacrylic acid derived from isomeric butanols, for example hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxyisobutyl acrylate and hydroxyisobutyl methacrylate. Others which can be mentioned are acrylamide, methacrylamide, N,N-dimethylacrylamide, N-tert-butylacrylamide, acrylonitrile, methacrylonitrile, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate and the salts of the last-named monomers with carboxylic acids or mineral acids and also the quaternized products.
Other comonomers which can be used for the copolymerization of N-vinylformamide are vinylesters, such as vinyl formate, vinyl acetate and vinyl propionate. Also suitable are N-vinylpyrrolidone, N-vinylcaprolactam, 1-vinylimidazole, 2-methyl-1-vinylimidazole and 4-methyl-1-vinylimidazole, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, vinylphosphonic acid, allylphosphonic acid and diallyldimethylammonium chloride. It is of course also possible to use mixtures of said monomers.
Said comonomers can be present in copolymerized form, for example in an amount from 1 to 99 mol %, in the copolymers containing N-vinylformamide.
Moreover, homo- and copolymers of N-vinylformamide can be modified by carrying out the polymerization in the presence of compounds which have at least two ethylenically unsaturated nonconjugated double bonds in the molecule. The co-use of these monomers in the polymerization increases the molecular weight of the polymer. Examples of particularly suitable compounds are alkylenebisacrylamides such as methylenebisacrylamide and N,N′-acryloylethylenediamine, N,N′-divinylethyleneurea, N,N′-divinylpropyleneurea, ethylidenebis-3-(N-vinylpyrrolidone), N,N′-divinyldiimidazolyl-(2,2′)butane and 1,1′-bis(3,3′-vinylbenzimidazolin-2-one)-1,4-butane. Other suitable crosslinkers are, for example, alkylene glycol di(meth)acrylates such as ethylene glycol diacrylate, ethylene glycol dimethac
Mahr Norbert
Niessner Manfred
Rübenacker Martin
BASF - Aktiengesellschaft
Keil & Weinkauf
Wilson D. R.
LandOfFree
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