Patent GB-986550-A (GB)
Title: Process for the production of highly elastic shaped elements
IPC: D06M15/564
Filed: 1962-08-10
Abstract: Highly elastic filaments, films and coatings are made by spin-drying, casting or coating a solution comprising a reaction product of a polyacetal with a molecular weight of 400-4000 containing the recurring atomic grouping -O-CHR-O-(in which R is a hydrogen atom or an alkyl or alkenyl group), or such a polyacetal which has been reacted with a less than equivalent quantity of diisocyanates to increase the chain length, with an excess of polyisocyanate, based on the hydroxyl groups contained in the acetal, together with water, a polyhydric alcohol, an aminoalcohol, an amine, hydrazine or a substituted hydrazine as a chain extender, the quantity of the chain extender being substantially equivalent to the remaining NCO groups, while removing the solvent after completion of the reaction. Preferably the polyacetal is linear and has a softening point below 60 DEG  C. Desirably, the polyacetal has a molecular weight of 500-2000 and is liquid.  The polyacetals may be made in known manner from polyhydric alcohols and aliphatic aldehydes, e.g. from formaldehyde or paraformaldehyde and hexanediol, methylhexanediol, heptanediol, octanediol, decanediol, xylylene glycol, bis-hydroxyethylcyclohexane or hydroxyethylation products of the said dialcohols.  The glycols may be used individually or in admixture with one another.  Hydroxyl group-containing polyesters of molecular weight below about 500 made from polycarboxylic acids (e.g. adipic, methyladipic, sebacic and isophthalic acids) zand polyalcohols (e.g. hexane-diol, methylhexane-diol and b hydroxyethyoxy hexanol), if desired in the presence of triols, may be reacted with formaldehyde to yield acetals.  Polyethers and polythioethers may also be used for the production of the acetal, e.g. 4,41-dihydroxydibutyl ether or higher ethers of butylene glycol, as well as polyhydroxy ethers of molecular weight below about 500 obtained from hexanediol, methylhexanediol, xylylene glycol, and bishydroxy -methylcyclohexane, either alone or in admixture.  Suitable isocyanates include 1,5 - naphthylene-, 1,3 - phenylene-, 1,4 - phenylene-, 2,4-toluylene-, and 2,6-toluylene diisocyanates and isomeric mixtures of 2,4- and 2,6-toluylene diisocyanates, 4,41-diphenylmethane-, 4-41-diphenyl dimethylmethane, 4-41-diphenyl-, 4,4 - o - tolidine-, 2,4,6 - trialkyl - 1,3phenylene diisocyanates as well as 1,6-hexane and 1,4-cyclohexane diisocyanates.  Trifunctional isocyanates, e.g. thio phosphoric acid4,41,-411 -triisocyanate can also be used in admixture with these diisocyanates.  Specified chain extenders for the polyacetal-isocyanates include water, glycols, e.g. butanediol and 1,4-dihydroxyethoxybenzene, amino alcohols, e.g. b -aminoethanol and q -aminopropanol, polyvalent amines, e.g. ethylene diamine, N,N1dimethyl ethylene diamine, propylene-1,3-diamine, hexane-1,6-diamine, cyclohexane-1,4diamine, piperazine, 2,5-dimethyl-piperazine, 4-41-diaminodiphenyl methane, 4-41-diaminodiphenylsulphone and 3,31-dichlorbenzidine, as well as hydrazine or substituted hydrazines, e.g. N,N1-bis-hydroxyethyl hydrazine.  The OH:NCO ratio is preferably 1:1.3 to 3.5, advantageously 1:1.5 to 2.2 and the reaction period 15 minutes-150 hours, especially 30 minutes-3 hours, at temperatures of 40-150 DEG C., especially 70-130 DEG  C., the solvent or solvent mixture being distilled off during reaction so that the solution becomes a liquid melt.  Fresh or additional solvent is then added for the reaction with the chain-extender. Suitable solvents are dimethyl formamide, dimethyl acetamide, dimethyl sulphoxide, tetramethyl urea, dioxane, tetrahydrofuran, chlorobenzene, ethyl acetate, methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone, and mixtures thereof. Reaction of the chainextender with the polyacetal isocyanate takes place in solution, the chain-extender preferably being supplied in solution form, at temperatures from - 20 DEG  C. to 150 DEG  C., in particular between - 10 DEG  C. and 30 DEG  C. when using diamines and hydrazines and above 30 DEG  C. when using dialcohols, the quantity of chainextender being substantially equivalent to the NCO groups of the polyacetal isocyanate.  Various techniques are described for effecting the mixing of the polyacetal isocyanate reaction product with the chain extender solution to form a spinning solution or emulsion, from which filaments are obtained by dry- or set-spinning, and films by casting.  Products so made are stable to acid and alkaline hydrolytic agents and have a good resistance to ageing and light.  Filaments so made are elastic, resistant to solvents used in chemical cleaning and have a good fatigue resistance to repeated stretching.  Specification 919,146 is referred to.