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...
Patent
1996-09-30
2000-09-05
Reddick, Judy M.
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...
1621646, 1621647, 162166, 1621682, 1621683, 1621684, 1621685, 524555, C08L 3902
Patent
active
061144355
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the preparation of aqueous solutions of polymers containing vinylamine units, which solutions have a long shelf life, by hydrolysing polymers containing N-vinylcarboxamide units with acids in an aqueous medium and removing the carboxylic acids eliminated from the polymers from the aqueous polymer solution, and the use of the aqueous polymer solutions as dry and wet strength agents in papermaking.
EP-B-0 071 050 discloses linear, basic polymers which contain vinylamine and vinylformamide units. The polymers are prepared by homopolymerization of N-vinylformamide and subsequent partial elimination of formyl groups from the polymers with acids or bases. Formic acid is formed from the eliminated formyl groups as a by-product of the hydrolysis. However, formic acid cannot be distilled off alone from the aqueous polymer solution. The formic acid/water azeotropic mixture boils at 107.degree..
The polymers can also be solvolyzed in alcohols with acids. The by-products of the solvolysis, ie. formates, can be removed from the system, for example by distillation, during or after the hydrolysis. However, since the prior art distillation is carried out in the presence of alcohols and, for example, hydrochloric acid, considerable amounts of alkyl chlorides are formed.
EP-B-0 216 387 discloses the use of partially hydrolyzed copolymers which contain polymerized vinylamine units and are obtained from N-vinylformamide and monoethylenically unsaturated monomers selected from the group consisting of vinyl acetate, vinyl propionate, the C.sub.1 -C.sub.4 -alkyl vinyl ethers, N-vinylpyrrolidone and the esters, nitrites and amides of acrylic acid and methacrylic acid.
DE-A-17 20 737 discloses a process for the preparation of basic polymers, in which homo- or copolymers of N-vinyl-N-methylcarboxamides are subjected to an acidic hydrolysis at elevated temperature. This results in the formation of formic acid, which is removed by distillation. However, it is also possible to add methanol before or in the course of the hydrolysis and to esterify the eliminated formic acid to methyl formate and thus to remove it from the reaction mixture.
EP-A-185 935 discloses a process for the preparation of pulverulent, linear basic polymers which contain vinylamine units. Here, gaseous hydrogen halide is allowed to act on pulverulent polymers of N-vinylformamide in the presence of not more than 5% by weight, based on the polymer used, of water. The elimination of the formyl group can also be carried out in C.sub.1 -C.sub.4 -alcohols. Pulverulent vinylamine polymers and formates are obtained. However, an undesirable amount of alkyl chlorides is formed here.
EP-B-O 251 182 discloses vinylamine copolymers which, in addition to vinylamine units, also contain N-vinylformamide, acrylonitrile, acrylamide and, if required, acrylic acid units. These copolymers are prepared by copolymerizing N-vinylformamide and acrylonitrile and then modifying the formyl groups and, where relevant, the nitrile groups of the copolymers under acidic conditions. The modification of the formyl groups can be carried out in the presence of alcohol, said groups being separated off in the form of formates. If the modification is carried out using hydrochloric acid, alkyl chlorides are formed here too and must be disposed of.
Although the publications cited above point out that the formyl groups and polymers of N-vinylformamide can be separated off in the form of formates by treatment with acids in the presence of alcohols, not a single example of this is to be found. The aqueous polymer solutions have to date been neutralized after the hydrolysis and used together with the neutral salts formed, or the hydrolyzed polymers have been isolated by precipitation from the aqueous solution with, for example, acetone. Owing to the large amounts of acetone required for this purpose, based on polymer, such a method for isolating polymers is technically uneconomical.
As has also been found, the aqueous polymer solutions described in the prior art
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Kroner Michael
Nilz Claudia
Schuhmacher Rudolf
Stange Andreas
Winter Manfred
BASF - Aktiengesellschaft
Reddick Judy M.
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