Patent GB-1279269-A (GB)
Title: Production of acrylic composite filaments having latent helical crimps
IPC: D02J1/22
Filed: 1969-11-26
Abstract: 1279269 Composite polyacrylonitrile filament JAPAN EXLAN CO Ltd 26 Nov 1969 [26 Nov 1968] 57956/69 Heading B5B Composite polyacrylonitrile filaments having helical crimps are produced by wet spinning at least two aqueous spinning solutions into an aqueous coagulating bath are solutions containing a high shrinking component which contains from 85 to 94% by weight of acrylonitrile and forms the inner portion of the helical crimp and the other solution containing a low shrinking component in which the acrylonitrile content is greater than that in the high shrinking component and subjecting the formed filaments to stretching, drying and relaxation heat treatment which treatment causes the filaments to become crimped, which process comprises withdrawing the filaments from the relaxation heat treatment step and applying to the filaments at a temperature (T) a tension (F) which satisfies the equation in a range of 353#T#372 or the equation in a range of 333#T#353 in which F is the tension (in mg./d.) applied, AN is the acrylonitrile content (1%) in the high shrinking component, T is the temperature (‹K) and D is the filament denier of the composite filament produced, which heat and tension is sufficient to partially or completely remove the crimp from the filaments but is insufficient to deprive the filaments of their latent crimp. The relaxation heat treatment may be conducted at 105- 140‹ C. whilst the water content of the filaments is maintained at greater than 150% based upon the dry weight of the filaments. In an example, a copolymer of 91 parts by weight of acrylonitrile, 9 of methyl acrylate and 0À5 part of sodium methallyl-sulphonate and a copolymer of 89 parts acrylonitrile, 11 parts methyl acrylate and 0À5 part of sodium methallylsulphonate are separately dissolved in respective 49% aqueous solutions of sodium thiocyanate to prepare spinning solutions each containing 10% by weight of the copolymer. The solutions are supplied at the same rate to a spinning apparatus as described in the Applicant's British Patent No. 954,274 and extruded into an 8% aqueous solution of sodium thiocyanate maintained at a temperature of - 3‹ C. The composite filaments thereby formed are washed with water, stretched at a stretch ratio of 9:1 and dried in air having a dry-bulb temperature of 120‹ C. and a wet-bulb temperature of 78‹ C. The dried composite filaments are then continuously passed through a relaxation heat-treating apparatus shown in Fig. 4 in which after having been contacted with warm water to give them a water content of 200% (based on the weight of the dry filaments) they are treated with saturated steam at 120‹ C. for 3 minutes in the apparatus while being free to shrink, whereby they develop helical crimps, withdrawn from the apparatus and immediately passed under a predetermined tension through a body of water maintained at a predetermined temperature. At a temperature of 50‹ C. the tension used is 21,000 mg./denier and at 99‹ C. 12 mg./denier. The filaments are thereafter dried with air at 80‹ C., treated with boiling water for 10 minutes while free to shrink to develop helical crimps and dried in air at 70‹ C. The heat relaxing apparatus shown in Fig. 4 has an inlet sealing mechanism 12 and outlet sealing mechanism. The dried composite filaments introduced through the mechanism 12 are guided into the main body 50 of a pressure vessel 10 by feeding rollers 16 and 18. The dried composite filaments flow down along an inclined shoot 22 together with a stream of warm water supplied through an inlet 24. The filaments are thereby caused to absorb water, e.g. 200% based on the weight of the dry filaments. The filaments are then guided on to a coarse screen endless travelling belt conveyer 52 and are moved towards the body 50 while being heattreated in a relaxed state, completely free from tension, by saturated steam introduced through inlet ports 100, whereby the filaments become crimped. The crimped filaments are withdrawn from the discharge end of the conveyer 57 over a guide rod 53, cage roller 54, guide rod 56 and tension controlling rods 58 adjustably mounted in an outlet water cylinder 66. During their upward passage through a column of hot water contained in the cylinder 66, the crimped filaments are subjected to a tension which stretches them and thereby reduces the crimp frequency of the filaments to a greater or lesser extent depending upon the tension applied to the filaments and the temperature of the water in the cylinder 66. Hot water is supplied to the cylinder 66 through inlet 62 and a water seal 64. Part of the water overflows from the water seal through a port 60 into the chamber 50 of the pressure vessel 10 forming a layer 120 therein and the remainder of the water is forced upwards through the cylinder 66 and discharged therefrom through the sealing mechanism 14, the water seal 68 and the overflow outlet 70. The water in the layer 120 in the chamber 50 is drained off through the valved discharge pipes 72 and 74. The tension and the temperature to which the crimped filaments are subjected in the cylinder 66 are adjusted in accordance with the mathematical equations of the invention and the filaments are withdrawn from the cylinder 66 through the outlet sealing means 14 by the co-operating pinch rolls 82 and 84.