Patent GB-684972-A (GB)
Title: Method for improving polyamides containing hydroxyl groups
IPC: C08G69/44
Filed: 1950-04-06
Abstract: Polyamides derived from specified materials and having hydroxyl groups side-linked to the main chain are subjected to heating above 50 DEG  C., preferably above 100 DEG  C. for several hours or days to produce a polymer of improved tensile strength and resistance to solvents, water and heat.  The polyamides are made from polyamide-forming constituents including an hydroxy amino acid, hydroxy-dicarboxylic acid, or hydroxy-diamine.  In examples: (1) a ,a 1-dihydroxy adipic acid (for preparation see Group IV (b)) in methanolane is mixed with hexamethylene diamine, also in methanol, with stirring and cooling.  After purification of the resulting salt by recrystallization it is heated in a nitrogen atmosphere to 195 DEG C. for 2 1/2 hours.  Water loss is 115 per cent of the theoretical for linear condensation, indicating that the lateral OH groups have partly reacted.  The product may be cold drawn and are insoluble in the usual solvents for polyamides.  After heating for 100 hours at 155-160 DEG  C. in an inert atmosphere the polyamide becomes insoluble in all solvents, the tensile strength increases by 50 per cent, and the polymer is capable of being dyed.  Comparable figures are given for tensile strength before heating, after heating and after ageing without heat for 3 and 6 months; (2) 0.79 per cent 11 amino-10 hydroxy-undecanoic acid and 99.21 per cent 11 amino-undecanoic acid (molar proportions), are condensed at 215 DEG C. for 6 hours in nitrogen.  Threads drawn at 170 DEG  C. in a nitrogen atmosphere are aged at 170 DEG  C. for various times and the tensile strengths of the aged fibres compared with that of the untreated fibre; (3) fibres of polyamides from 11-N-ethanol-amino-undecanoic acid and 11-amino-undecanoic acid, with various small proportions of the former, are aged at 145-150 DEG  C. and the tensile strengths compared with those of the untreated fibres.ALSO:a ,a 1-Dihydroxy adipic acid is prepared by reacting adipic acid with thionyl chloride, and brominating the resulting acid chloride with excess bromine.  The product is emulsified in water with cooling and the resulting brominated acid (melting-point about 180 DEG  C.) drained and washed with water.  The acid is then suspended in water and accurately neutralized with caustic soda at the boiling-point.  Copper sulphate in aqueous solution is then added to cause crystallization of copper a ,a 1-dihydroxy adipate.  This is suspended in water and treated with hydrogen sulphide and the acid obtained by evaporation, after filtering to remove precipitated copper sulphide.  The acid is purified by crystallization from dioxane solution by adding chloroform.  Hexamethylene diammonium a ,a 1-dihydroxy adipate is obtained by adding a solution of the a ,a 1-dihydroxy adipic acid in methanol to hexamethylene diamine, also in methanol, with vigorous cooling and agitation, the salt tending to remain in the supersaturated state.  The salt can be purified by precipitation with ethanol from a solution in a methanol/water mixture (m.p. 158-162 DEG  C.).  The salt may be condensed (see Group IV (a)) to give a polyamide.