Patent GB-534698-A (GB)
Title: Treatment of synthetic polyamide filaments, fabrics, films and other articles, to improve their resilience and other properties
IPC: C08G69/50
Filed: 1939-09-13
Abstract: 534,698. Artificial filaments, films etc.; treating textiles with liquids ; resinous condensation &c. products. IMPERIAL CHEMICAL INDUSTRIES, Ltd. Sept. 13, 1939, No. 25698. Convention date, Sept. 14, 1938. [Classes 2 (ii), 2 (iii), and 15 (ii)] [Also in Group VIII] Yarns, bristles, fabrics, ribbons, films, sheets, or other articles formed from fibre-forming synthetic polyamides are subjected to the action of formaldehyde or a substance capable of liberating formaldehyde. The polyamides may be obtained from monoamino monocarboxylic acids or their amide forming derivatives, or from diamines by reaction with dicarboxylic acids or amide forming derivatives of dibasic carboxylic acids. The formaldehyde treatment increases the power of filaments, bristles, and the like to recover their shape after deformation, and increases their resistance to deterioration in the presence of ultra-violet light. Treatment of crimped polyamide fibres improves the permanency of the crimp. The stiffness of bristles may be increased. Waterrepellency may be imparted to fabrics or yarns particularly when the formaldehyde-liberating substance contains a long chain aliphatic radical e.g. methylol stearamide, or when the fabric is impregnated first with stearamide and then with formaldehyde and is subse-, quently dried and baked. The intrinsic viscosity of the polyamides is increased by heating with aqueous formaldehyde. Yarns or fabrics which have been treated with formaldehyde or the equivalent may be used in the production of stockings or flags. Polyamide bristles so treated may be used for the production of surgical sutures, fishing lines, or brushes. During the formaldehyde treatment the pH of the reaction medium is preferably not allowed to be below 3.0. In an example, melt-spun polyhexamethylene adipamide yarn is cold drawn while wet with water and dried in relaxed condition so as to become crimped. The yarn is immersed in an aqueous solution of formaldehyde containing ammonium chloride as catalyst and then allowed to crimp by being dried in relaxed condition. - It is then baked at 150C. The treatment imparts a high degree of crimp retentivity. Cold drawn polyamide bristles are conditioned by immersion in boiling water and then heated in a sealed vessel at 100 C. for one day with a slightly acid formaldehyde solution containing potassium hydrogen phthalate. The bristles have a high power of recovery from deformation. Cold drawn polyamide bristles are heated in a sealed vessel with dimethylol urea and water and then washed and dried. Yarn is treated similarly and is found to have increased resistance to degradation by ultra-violet light e.g. from a carbon arc. Crepe de Chine type fabric made of polyamide yarn is impregnated with sodium phosphate, dried, immersed in a solution of methylol stearamide in ethyl alcohol, dried, and baked. The treated fabric is water repellent. Formaldehyde derivatives which may be used include hexamine, methylol mercaptan, methylol ureides, methylol amines, and hydroxymethyl ethers. Phthalic, boric, or formic acid, or sodium acetate, borate, or bisulphate may be used as catalyst. The reaction may be carried out in water, alcohols, ketones, or other non- solvents, and it may be effected at raised temperature and pressure. Specified polyamides are polypentamethylene sebacamide, polydecamethylene adipamide, poly-p-xylylene sebacamide, polycaprolactam, and poly-11- amino undecanoic acid. Interpolymers e.g. one prepared from hexamethylene diamine, decamethylene diamine, adipic, and sebacic acid and polymers such as that obtained from adipic acid, hexamethylene diamine, and #- hydroxydecanoic acid may be used. The polyamide may contain plasticizers, pigments, delustrants, oils, and resins. It may contain phenol or urea which reacts with the formaldehyde when the polyamide articles are treated with this reagent. The process may be applied to mixed yarns and fabrics. Specification 461,237 is referred to.