| 摘要 |
1,126,321. Wet spinning polyvinyl alcohol filaments. KURASHIKI RAYON K.K. 7 Feb., 1967 [8 Feb., 1966; 15 March, 1966 (2); 5 April, 1966], No. 5729/67. Heading B5B. Polyvinyl alcohol filaments are produced by wet spinning an aqueous solution of polyvinyl alcohol into a coagulating bath which is an aqueous solution of an inorganic salt and which is at a temperature above 55‹ C. and subjecting the filaments to cooling immediately after their being withdrawn from the bath, the cooling being effected at a temperature at least 30‹ C. below the temperature of the coagulating bath, and thereafter drawing the filaments in one or more stages at a draw ratio of not less than 4 : 1 and preferably not less than 6 : 1. The cooling may be effected by means of cold water and/or a cooled organic liquid, a cooled gas or cooling rolls. The concentration of the spinning solution may depend upon the average degree of polymerization of the polyvinyl alcohol used, the ranges of concentration being 20 to 50%, 15 to 45%, 10 to 40% and 8 to 35% corresponding to ranges of average D.P.s of 1000 to 1500, 1500 to 2000, 2000 to 3000 and 3000 to 5000 respectively. The organic cooling liquids which may be used include alcohols such as methanol and ethanol, acetone, esters, ethers and benzene. When a mixture of water and an organic liquid is used, the latter should be miscible with water. The salt present in the coagulating bath may be sodium, ammonium or zinc sulphate, sodium chloride or sodium carbonate. Two or more of these may be used conjointly. When sodium sulphate is used, the conjoint use therewith of potassium sulphate gives especially satisfactory results. In an example, a 15% aqueous solution of PVA of average DP 3000 is extruded into an aqueous solution of sodium sulphate at 80‹ C. and the filaments thereby formed are withdrawn from the coagulating bath, passed through water at 10‹ C., drawn by means of rolls at a draw ratio of 2 : 1 and further drawn at a draw ratio of 2 : 1 while wet with an aqueous solution of sodium sulphate at 60‹ C., the total draw ratio being 4 : 1. The filaments are then dried and drawn at a temperature of 235‹ C. and a draw ratio of 3 : 1, the overall draw ratio thus being 12 : 1. The filaments are thereafter heat set at 240‹ C. while being allowed to shrink 20%. |
