GB785631A - A process for the production of shaped articles from elastomeric polymers containing reactive groups - Google Patents

Abstract

Shaped articles, e.g. filaments or films, are made by introducing a solution or emulsion of a synthetic elastomeric polymer containing reactive groups into a coagulating bath which contains an agent capable of reacting with the reactive groups of the polymer to give cross-linking, removing the coagulate so formed from the bath, and finally drying it. Suitable elastomeric polymers consist essentially of linear carbon chains to which are linked 0.005-0.6 mols. by weight per 100 parts by weight of the polymer of reactive groups such as carbonyl, carboxyl, sulphonic acid, amide, or basic groups, preferably basic groups containing nitrogen. These groups may be introduced by copolymerizing 15-99 per cent of such monomers as acrylic or methacrylic acid esters of aliphatic alcohols containing at least 4 and preferably 8-14 carbon atoms, vinyl alkyl ethers in which the alkyl group contains 1-8 carbon atoms, and butadiene and its homologues and derivatives, with such carbonyl-containing compounds as acrolein, a -substituted acroleins, vinyl alkyl ketones or methyl isopropenyl ketone, or acids such as acrylic or methacrylic acid, sorbic acid, maleic or fumaric acid or their monoesters, or amides such as acrylamide, a -methacrylamide, a -isopropylacrylamide, or a -chloracrylamide, or heterocyclic nitrogen bases such as 2-vinyl pyridine or sulphonic acids such as vinyl sulphonic acid. The monomers containing the reactive groups may be present in quantities of 0.5-50 per cent by weight of the monomer mixture. Other polymerizable compounds such as styrene, acrylonitrile, acrylic or methacrylic acid esters of alcohols having 1-3 carbon atoms, vinyl chloride, and 1 : 1-dichlorethylene, and small amounts (preferably 0.001-1 per cent by weight of the monomer mixture) of polyfunctional monomers containing at least two active olefinic non-conjugate double bonds, such as divinyl benzene, esters of polyhydric alcohols or phenols with unsaturated acids, di-vinyl ether, or divinyl sulphone may be incorporated. Other suitable copolymerizable compounds which contain reactive groups present in "masked" form, from which they may be liberated by hydrolysis, include acrylic and methacrylic alkyl esters, vinylsulphonic alkyl esters, unsaturated nitriles such as acrylonitrile, and such amides as have already been mentioned. Copolymers containing carboxyl groups are preferred. The monomers may be polymerized in bulk, in solution in solvents such as benzene, chlorobenzene, 2 : 4-dichlorobenzene, or ketones such as methyl ethyl ketone or emulsified with alkali metal salts of paraffin sulphonates, in the presence of catalysts, e.g. azo-dinitriles, per-compounds, redox systems, and especially with aliphatic sulphinic acid salts, and modifiers such as n-dodecyl mercaptan and diisopropyl xanthogen disulphide. The polymerization may be stopped by adding hydroquinone or sodium hydrosulphite and unreacted monomer stripped by steam distillation. The solutions should contain 8-40, preferably 10-20, per cent by weight of polymers. Stabilizers such as phenyl-b -naphthylamine or phenols should also be included in the case of butadiene polymers. The reactive agent present in the coagulating bath, in the case of copolymers containing carbonyl groups, may be a polyamine or polyamide, such as polyalkylene polyamines and diamides of dibasic aliphatic and aromatic carboxylic acids. A water-soluble hydroxide or salt of a polyvalent metal is suitable for carboxyl-containing copolymers. Other suitable cross-linking agents for such copolymers include compounds containing at least two epoxy groups, such as diglycidyl trimethylolpropane, diglycidyl glycerol, b ,b - di - (glycidyloxyphenyl) - propane and diglycidyl aniline, which are all preferably used in alcoholic solution. Copolymers containing amide groups may be reacted with aliphatic or aromatic aldehydes or with such formaldehyde-yielding compounds as hexamethylene tetramine, the sodium salt of a -hydroxymethane sulphinic acid, dimethylol urea or hexamethylol melamine, while copolymers containing basic nitrogen groups may be reacted with polybasic acids such as oxalic, maleic, citric, itaconic, fumaric, succinic, glutaconic, adipic, tartaric, 1 : 3-benzenedisulphonic or 1 : 5-naphthalene-disulphonic acid. The coagulating bath should contain the cross-linking agent in a proportion sufficient to react with at least 10 per cent of the reactive groups in the copolymer in a solvent such as water or an alcohol such as methanol or ethanol. Preferably, the cross-linking agent is present in an amount at least chemically equivalent to the reactive groups present in the copolymers, and to ensure this the cross-linking agent should comprise 1-50 per cent of the bath. In addition, the bath may also contain coagulating agents, for instance strong electrolytes such as metallic salts, in concentrations of 1-30 per cent. The pH value of the bath should be within the range 4-10, depending on the cross-linking agent used, and its temperature should be 20-70 DEG C. Thickening agents such as polyvinyl alcohol, salts of polyacrylic acid, alginic acid or carboxymethyl cellulose may also be present. After leaving the coagulating bath, the coagulate may be washed with water or alcohol at 20-70 DEG C. and finally dried at 50-150 DEG C., preferably at 90-120 DEG C. Although the process is particularly suitable for the production of threads or filaments, tubular films may also be produced by the use of annular nozzles, or alternatively the copolymer may be cast on to a mould which rotates in the coagulating bath to produce a film. The copolymer emulsions to be spun may also include natural or synthetic rubber latices or plastic emulsions, fillers, plasticizers, resins, dyes, pigments, solvents or other high polymers. Numerous examples are given. German Specification 750,330 and U.S.A. Specification 2,581,464 are referred to.