Patent GB-1006727-A (GB)
Title: Preparation of cross-linked cellulose products
IPC: D01F2/10
Filed: 1962-11-29
Abstract: 1,006,727. Cross-linked regenerated cellulose filamentary materials. ROHM & HAAS CO. Nov. 29, 1962 [Dec. 5, 1961; Oct. 16, 1962], No. 45231/62. Heading B5B. Cross-linked regenerated cellulose films and filaments are made by (A) adding at least one amide selected from the group consisting of N - methylolacrylamide N - methylolmethacrylamide and the (C 1 -C 4 ) alkyl ethers thereof to an alkaline solution of viscose or cuprammonium cellulose to form therein a modified cellulosic compound; (B) extruding the solution containing the modified cellulosic compound into a coagulating bath to form a film or filamentary product; (C) regenerating the modified cellulosic compound to a modified regenerated cellulose; (D) stretching the regenerated product at least in a longitudinal direction; and (E) heating the stretched product in the presence of an acidic catalyst so that the substituted amido groups therein undergo reaction and a cross-linked product is formed. The modified cellulosic compound may be formed by adding 0À15 to 0À60 mols. of amide per glucose unit in the viscose or cuprammonium cellulose. N-alkoxymethylacrylamides specified include N-methoxymethyl-, N-ethoxymethyl - N - isopropoxymethyl-, and N - tert.- butoxymethylacrylamides. From 1-25% by weight of N-substituted amide monomer, based on the weight of cellulose in the spinning solution, may be used, especially 5-10% by weight, and the amide is preferably added shortly before spinning so as to minimize hydrolysis. Coagulating baths of conventional compositions are used. Thus the amide-treated viscose having a sodium chloride salt test of 3-6, containing 6-9% caustic soda and having a ball fall viscosity of 35 secs. at 18‹ C., may be extruded into a coagulating bath containing 7-13.5% sulphuric acid, 18-28% anhydrous sodium sulphate and if desired, 0À1-5% anhydrous zinc sulphate, or an amide treated cuprammonium cellulose solution containing 3À8% cellulose and 30 gms. ammonia per litre may be extruded into an aqueous 4% caustic soda bath. Stretching may be effected immediately after the product leaves the coagulating and/or regenerating bath while the films or filaments are submerged in or sprayed with hot water or other heated aqueous baths which may contain acids or salts, and may amount to 70-100% of the original length of the products. After stretching, the product is purified in known manner, e.g. viscose products are washed, desulphurized, bleached and lubricated and before drying, the stretched product is heated in the presence of an acid catalyst or a substance yielding an acidic catalyst to effect cross-linking by reaction of methylol or alkoxymethyl groups with the hydroxyl groups of the cellulose, e.g. at least 220‹ F. for at least 30 sees., preferably at 220-350‹ F. for 30 secs.- 5 mins. The catalyst may be applied as a bath or spray of an aqueous solution of ¢-3% by weight concentration. Specified catalysts include ammonium chloride, monobasic and dibasic ammonium phosphates, oxalic, lactic, citric, tartaric, formic, acetic, propionic, boric and succinic acids, and salts of amines, e.g. 2-amino-2-methyl-propanol-1, with acids, e.g. hydrochloric and sulphuric acids. Products containing only 1% of amide show reduced water-retention and reduced swelling or shrinking on exposure to water, while products containing 5-10% by weight of amide show greatly improved resistance to shrinkage and creasing or wrinkling. U.S.A. Specifications 2,173,005 and 2,858,185 are referred to.