Spinning of artificial fibers and films

Реферат: Artificial filaments and films are produced by forming an aqueous dispersion of at least 20% by weight of thermoplastic organic polymeric material, the dispersed polymer particles having p an average size below about 2 microns and being formed by emulsion polymerization using an acid-sensitive emulsifier and a free radical polymerization initiator and the pH of the dispersion being at least 7, extruding the dispersion into an aqueous coagulating bath having a pH of not over 4,1, and preferably below 1, removing the filaments or films thereby formed from the bath, heating the filaments or films to dry them and bring them to such a temperature above their apparent second order transition temperature as to cause the particles to coalesce, and then stretching the filaments or films. The polymeric material consists of one or more thermoplastic copolymers each of which meets the following requirements. (1) It consists of units corresponding to monomers containing a single CH2 = C < group, there being present at least 5% by weight of two different types of units of which one type contains groups having atoms other than carbon and hydrogen. (2) It consists of predominantly linear molecules which are capable of orientation and have a number average molecular weight of 20,000 to 1,000,000 or more as determined by osmosis. (3) It has an apparent second order transition temperature between 30 DEG C. and 150 DEG C. as determined by a described method. (4) It is capable of being formed by emulsion polymerization to give an aqueous dispersion in which the copolymer particles have an average size below about 2 microns. The monomers may be esters, ethers, amides, nitriles or cyclic compounds having a single CH2 = C < group, the preferred esters, nitriles and amides being of the acrylic type. Thus there may be used esters of acrylic or methacrylic acid with aliphatic, cycloaliphatic, aryl, aryl-aliphatic or heterocyclic alcohols free of polymerizable unsaturated linkages. There may also be used as one of the co-monomers esters of itaconic acid with alcohols of the above types. Vinyl esters of monocarboxylic acids can be used but are less desirable. Amides of acrylic and methacrylic acids having an N-substituent and reactivity towards stabilizing agents are also suitable. Vinyl ethers containing alcohol residues of the kinds specified above, vinyl chloride, vinylidene chloride, styrene and vinyltoluene may also be used. Copolymers containing a major proportion of acrylonitrile or methacrylonitrile and 5 to 50% of at least one other polymerizable monomer may be used for the production of filaments. The emulsifier may be an alkali-metal, ammonium or amine salt of a fatty acid or of a long-chain hydroxyalkanoic, epoxyalkanoic or cyanoalkanoic acid and is preferably a soap. Other "acid-sensitive" emulsifiers which may be used are octylphenoxyethyl sodium sulphate, sodium diisobutylphenoxy-ethoxyethyl sulphate, and polyethers having the general formula alkylphenyl (OC2H4)x CH2O (C2H4O)y R in which x represents an integer from 1 to 3, y represents an integer from 4 to about 60, and R represents a hydrocarbon group of 1-7 carbon atoms, including alkyl, alkenyl, benzyl and phenyl groups. The indicated alkyl group of the alkyl phenyl may have 6-18 carbon atoms. Instead of the alkylphenyl group the polyether may contain an alkyl group of 8 or more carbon atoms, preferably 12-24 carbon atoms. Another type of acid-sensitive emulsifier which may be used has the general formula Rx SCH2(OC2H4)z. OR in which Rx represents an alkyl group of 8-24 carbon atoms, z is an integer from 8 to about 60 and R is a hydrocarbon group such as methyl, butyl, allyl, phenyl or benzyl. Yet another type has the formula Rx COCH2 (OC2H4)z OR, where Rx is a hydrocarbon group of 7-24 carbon atoms and z and R are as above. A method is described for determining whether the emulsifiers are sufficiently acid-sensitive to be suitable. The proportion of emulsifier used may be from a few tenths per cent up to about 10% of the weight of the co-monomers. The polymerization initiator may be one of the peroxidic or azo initiators or actinic light. A list of suitable initiators is given. The spinning dispersion may contain a "fusion aid", i.e. a liquid organic compound which is a solvent for the dispersed polymer and has a favourable distribution coefficient towards the polymer in a polymer-water system. A method of determining the suitability of a liquid for use as a fusion aid is described. The liquid should be volatile at the highest temperatures at which the filaments are processed after leaving the coagulating bath, and it may be present in a proportion of 1-40%, usually 10-20%, by weight of the polymer. The coagulating bath preferably contains about 1-10% of a water-soluble acid, such as hydrochloric, phosphoric, sulphuric, oxalic, formic, acetic, citric, or lactic acid, or an alkanesulphonic or arylsulphonic acid, and a small proportion of a water-soluble salt of a metal having a valency of 2 or more, e.g. a salt of iron, aluminium, tin, cobalt, nickel or zinc. The coagulating bath is usually maintained at a temperature above the second order transition temperature of the copolymer, e.g. at 50-105 DEG C. After removal from the bath, the products may be water-washed and thereafter are passed through a heated drying zone which may be at 60-400 DEG C., preferably 100-250 DEG C. Filaments are usually stretched at 70-300 DEG C. by 50-2,000%, preferably 700-1,200%. If the polymers of which the products are composed contain reactive groups, the products, at any stage of the process after their formation, may be treated with reagents such as hexamethylene diisocyanate or diisothiocyanate; decamethylene, phenylene, propylene or butylene diisocyanate, phenylene diisothiocyanate, triisocyanatobutane, triisocyanatobenzene, polycarboxylic acids or their anhydrides or acid halides, e.g. succinic, pimelic, azelaic, sebacic, citric, tricarballylic and polyacrylic acids, or polyamines such as ethylenediamine. Mutually reactive groups may be present or developed within the copolymer, e.g. ureido groups. Instead of using different mutually reactive copolymers, a mixture of two different homopolymers, or a mixture of a homopolymer and a copolymer, may be used, a mixture of aqueous dispersions of the polymers being extruded into the acid coagulating bath. In an example, 0,15 part of phenylcyclohexane hydroperoxide as a 10% solution in toluene is added to an emulsion of 70 parts of acrylonitrile and 30 parts of 3,3,5-trimethyl cyclohexyl acrylate in 200 parts of water to which has been added 6 parts of aqueous 2% ferrous sulphate heptahydrate, 4% of sodium ethylenediaminotetracetate adjusted to pH 4 with aqueous 0,5 N-sulphuric acid, 2 1/4 parts of the potassium soap of coconut oil fatty acids and 0,6 part of sodium formaldehyde sulphoxylate. 2H2O, the pH of the solution having been adjusted to 10,5 with 0,5 N sodium hydroxide, and the monomers are allowed to copolymerize at a controlled temperature of 35-40 DEG C. in half an hour to form a copolymer having a second order transition temperature of about 120 DEG C. and a particle size below 0,1 micron in diameter. The dispersion is wet-spun into an aqueous 4% hydrogen chloride solution containing 0,6% of ferric chloride and maintained at 86 DEG C. The bundle of filaments formed (immersion in bath 3 inches) is withdrawn from the bath, washed slightly with water at room temperature and passed over a metal surface at 260 DEG C. to dry the filaments and cause the filament particles to coalesce. The resulting yarn is stretched over rolls about 600% while being heated to about 170 DEG C. In other examples the same procedure is followed but 20 parts of adiponitrile, alpha-methyl-succinonitrile, nitromethane, or phenylacetonitrile or 10 parts of succinonitrile are added to the polymerization charge before the addition of the hydroperoxide. In further examples the monomers used in the preparation of the copolymer dispersions are: (1) 60 parts of acrylonitrile and 40 parts of p-tert-octylphenoxyethyl acrylate; (2) 80 parts of acrylonitrile and 20 parts of 2-acryloxyxnorcamphane; (3) 70 parts of acrylonitrile, 20 parts of 2-n-butoxyethyl acrylate and 10 parts of N-isopropenyl-4, 4-dimethyl-oxazoline; (4) 70 parts of acrylonitrile and 30 parts of 5-acryloxy-3,a,4, 7,7a-tetrahydro-4,7-methanoindene; (5) 87 parts of methyl methacrylate and 13 parts of ethyl acrylate; (6) 70 parts of acrylonitrile, 20 parts of 3,3,5-trimethylcyclohexyl acrylate and 10 parts of vinyl pyrrolidone; (7) 70 parts of acrylonitrile, 25 parts of 3,3,5-trimethylcyclohexyl acrylate, and 5 parts of 2-(dimethylamino)ethyl methacrylate or of methacrylamide; (8) 45 parts of ethyl acrylate, 45 parts of acrylonitrile, and 10 parts of beta-ureidoisobutyl vinyl ether, or of glycidyl methacrylate; and (9) 50 parts of ethyl acrylate, 45 parts of acrylonitrile and 5 parts of epsilonureidopentyl vinyl ether.