| 摘要 |
964,406. Spinning polypropylene. IMPERIAL CHEMICAL INDUSTRIES Ltd. Feb. 18, 1963 [Feb. 27, 1962], No. 7636/62. Heading B5B. Isotactic polypropylene filaments having a spontaneously developed helically crimped form are produced by melt spinning the polymer at such a temperature and at such a throughput and the intrinsic viscosity of the polymer being such that the intrinsic viscosity of the spun yarn is in the range 1.0 to 3.0, preferably 1.5 to 2.5, and that the birefringence of the spun yarn is between 10 x 10<SP>-3</SP> and 25 x 10<SP>-3</SP> and thereafter allowing the yarn to relax freely. The spun yarn may be drawn 1.2 to 4.0 times its original length before being allowed to relax. The stretched yarn thereafter being allowed to relax freely and quickly. The polymer before melt spinning may have an intrinsic viscosity between 1.0 and 6.0. The spinning temperature may be between 165‹ C. and 320‹ C. The relaxed helically crimped yarn may be maintained in the relaxed state at 100‹ to 140‹ C. for a further period of, for example, 20 minutes, to stabilize the crimp. When a drawing step is used the temperature of the heated pin, roller or other device whereon drawing takes place may be adjusted to a temperature within the range about 10‹ C. to about 140‹ C. The preferred drawing temperature is within the range of about 80‹ C. to about 100‹ C. Specifications 810,023 and 818,100 are referred to. |
