Patent GB-654513-A (GB)
Title: Improvements in or relating to a new or improved method for insolubilising artificial filaments, threads, fibres and the like filamentary products
IPC: D01D10/04
Filed: 1948-05-28
Abstract: Artificial filamentary products, obtained by spinning aqueous alkaline solutions of vegetable globulins or phospho-proteins into acidified saline coagulating baths, are insolubilized by treatment in a "relaxing solution" followed by treatment in aqueous formaldehyde solution containing not less than 240 grams sodium chloride per litre, having a pH value between 4 and 7 and at a temperature not exceeding 80 DEG  C., and finally by treatment in a strongly-acidified aqueous formaldehyde solution containing per litre 250-325 grams sulphuric acid and 370-480 grams sodium sulphate, the solution being at a raised temperature, e.g. 70-98 DEG  C.  The last solution preferably contains 30-130 grams of sodium chloride also. The relaxing solution consists of a concentrated aqueous solution of sodium chloride, free from formaldehyde, which may also contain a small proportion of sodium sulphate and/or a small proportion of sulphuric acid and which has a pH value of 4-7.  This solution greatly reduces the longitudinal contractility of the coagulated filaments and is advantageously at a temperature of 10-40 DEG  C., preferably 15-25 DEG  C.  The coagulated filamentary products in the form of a continuous travelling tow may be insolubilized under non-tensioning conditions by passing the tow through a succession of two liquids each containing 240-320 grams sodium chloride, less than 60 grams sodium sulphate and less than 3 grams of sulphuric acid per litre, the first of these two liquids being a relaxing solution free from formaldehyde and preferably at a temperature of 15-25 DEG  C., and the second liquid having a pH of 4-7, and containing 10-20 grams of formaldehyde per litre and being preferably at a temperature of 25-80 DEG  C.  The tow is subsequently treated in a third liquid containing per litre 30-130 grams of sodium chloride, 370-480 grams of sodium sulphate, 250-325 grams of sulphuric acid and 10-20 grams of formaldehyde and preferably at a temperature of 70-98 DEG  C.  In the example, a coagulated tow obtained by extruding an aqueous alkaline solution of ground nut globulin into an aqueous sodium sulphate sulphuric acid coagulating bath is stretched between godets and treated with a solution containing 290 gm./l. sodium chloride, 30 gm./l. sodium sulphate and 0.5 gm./l. sulphuric acid at 20 DEG  C., contained in the trough of a ring trough according to the method described in Specification 623,460, the tow being deposited in a zig-zag manner in the ring trough.  The tow is then taken up from the ring trough, mangled between squeeze rolls and stretched between two godets.  The tow is now treated in a solution containing 300 gm./l. sodium chloride, 24 gm./l. sodium sulphate, 1 gm./l. sulphuric acid and 15 gm./l. formaldehyde at 55 DEG  C. contained in the trough of a second ring trough and again according to the method described in Specification 623,460.  The tow after leaving the ring trough is mangled between squeeze rolls and passed over a godet and through a vertical helical coil through which flows a treating liquor consisting of 75 gm./l. sodium chloride, 420 gm./l. sodium sulphate, 300 gm./l. sulphuric acid and 12 gm./l. formaldehyde at 90 DEG  C. On leaving the outlet of the coil the tow is washed and dried. Specification 597,497 also is referred to.