Teijin Limited

Isao Hamana

Shiro Kumakawa

Hirofumi Yoshikawa

Yoshio Fujiwara

A filament, fiber and yarn consisting of a naphthalate polyester containing at least 85 mol % of ethylene-2,6-naphthalate units and having an intrinsic viscosity of 0.3 to 1.0, said filament, fiber and yarn having a diffraction intensity ratio (R) between a Bragg reflection angle 2.THETA. = 18.7.degree. and 2.THETA. = 15.6.degree., as determined by the X-ray diffraction method, being in the range of 0.15 to 1.73. Electrically insulating material can be produced by heat-treating a fabric consisting mainly of the above naphthalate polyester fibers.

Novel naphthalate polyester fibers, and their end uses

Textured polyester yarn is prepared from multifilament yarn composed of a synthetic linear ethylene terephthalate polyester by draw-texturing at a draw ratio of 1.05 - 1.30X, using a heat-setting temperature of about 170.degree. - 240.degree.. Feed yarn for said draw-texturing process has (a) a break elongation of 40 - 80%, (b) a density of above 1.371 g/cm.sup.3, and (c) a boil-off shrinkage of less than 8%. Said feed yarn is prepared by modified melt spinning of the foregoing polyester at a speed of about 3000 - 5000 meters per minute.

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Ibaraki, Japan

Isao Hamana