Patent GB-1179436-A (GB)
Title: Helically Crimped Filamentary Materials
Inventor: CLARKE BARRY HENSON
IPC: D01F8/14
Filed: 1967-05-22
Abstract: 1,179,436. Composite filaments. IMPERIAL CHEMICAL INDUSTRIES Ltd. 13 May, 1968 [22 May, 1967], No. 23671/67. Heading B5B. [Also in Division D1] A composite filament possessing reversing helical crimp, characterized by a crimp index in the range 40% to 70% and 8 to 25 crimps per inch, comprises two synthetic polymers so distributed in the filament that it has along its length a cross-section made up of two distinct components arranged eccentrically, each component consisting of one of said polymers, and the two polymers being polyethylene terephthalates having different intrinsic viscosities and having values of birefringence which differ by an amount whereby the factor #IV. #BR. lies in the range 1À9 x 10<SP>-4</SP> to 3À3 x 10<SP>-3</SP>, where #IV is the difference in intrinsic viscosities and #BR is the difference in birefringence of the two components. Preferably, the factor #IV. #BR lies either in the range 2À9 x 10<SP>-4</SP> to 4À5 Î 10<SP>-4</SP>, or in the range 1À4 x 10<SP>-3</SP> to 2À1 x 10<SP>-3</SP>. Such filaments may be made into a filamentary non-woven structure, having a specific volume when uncompressed of at least 80 c.c.s. per gram and a specific volume when compressed under a load of 10 grams per centimeter of at least 30 c.c.s. per gram. The components of the filaments may be arranged either in a side-by-side structure or in a sheathcore structure, and the proportions of the polyethylene terephthalate components in the filament may vary between 80: 20 and 20: 80, but preferably the proportions are substantially equal. For the optimum performance of the filament, for example of 4 denier per filament, as a filling or stuffing material is preferred that the average number of crimps per inch is 13À5  2À5. Filaments having #IV. #BR values in the range 2À9 x 10<SP>-4</SP> to 2À5 x 10<SP>-4</SP> may be prepared from as-spun filaments having #IV. #BR s  values between about 9 x 10<SP>-5</SP> and 1À4 Î 10<SP>-4</SP> where #BR, is the difference in birefringence of the components of the as-spun filaments, by drawing a tow of as-spun continuous bicomponent filaments in steam, relaxing the filaments by releasing the tension on the tow to develop " spontaneous " crimp, and enhancing the crimp by heat treating the relaxed filament to develop " potential " crimp. Filaments having #IV. #BR values in the range 1À4 x 10<SP>-3</SP> to 2 x 10<SP>-3</SP> may be prepared from as-spun filaments having #IV. #BR s  values between about 4À3 x 10<SP>-4</SP> and 6À6 x 10<SP>-4</SP>, by using the crimping method of Specification 1,172,011, which method comprises drawing a tow of as-spun bicomponent continuous filaments, relaxing the tow while it contains at least 10% by weight of the liquid wetting agent to develop " spontaneous " crimp and heat treating the relaxed filaments to develop the " potential " crimp. In Example 1, composite filaments are made from polyethylene terephthalate chips of differing intrinsic viscosities by melt-spinning, the two components being in side-by-side relationship and in substantially equal proportions. After wind-up a tow comprising 16,000 of the spun bicomponent filaments is passed through a bath of water containing 2À0% by weight of a textile finishing agent and the tow then passed through a feed/ draw rolls system and drawn to a draw ratio of 3À9 times. After treatment to remove excess wetting agent, the tow is passed into an air ejector, to the outlet of which is connected a flexible tube, and conveyed to the brattice of a heat setting oven. Relaxation of the tow occurred within the flexible tube as the tension on the tow was reduced and crimp was developed simultaneously in the filaments. As the fully relaxed tow was deposited on the brattice it was observed that the tow had split up into several sub-tows, each containing many filaments crimped together in register. The tow was heat set in the oven at 135 C. for ten minutes and cut into 2-inch staple fibres to give fibres having a reversing helical crimp with an average crimp index of 58% and an average number of crimps of 15. In Example 2, composite filaments are made from polyethylene terephthalate chips of different intrinsic viscosities, and the polymer is melt-spun to bicomponent filaments with the components arranged in side-by-side relationship and in substantially equal proportions. After wind-up the tow comprising 12,600 of the spun bicomponent filaments is drawn to 3À33 times its original length. The tow is then treated as in the previous example to develop the crimp. The crimped tow is heat set at 145 C. for ten minutes, sprayed with a textile finishing agent, and cut into 2-inch staple fibres to give fibres having a reversing helical crimp with an average crimp index of 44% and an average number of crimps per inch of 14.