GB960067A - Process for preparing filamentary microtapes of labyrinthian cross-section and product - Google Patents

Abstract

960,067. Microtapes. DOW CHEMICAL CO. May 15, 1961 [May 19, 1960 (4); Jan. 24, 1961 (2)], No. 17624/61. Heading B5B. A continuous length of tape of thermoplastic polymeric material is converted into a filamentlike microtape by passage through a confined channel (suitable cross-sections being shown in Figs. 1-5) which effects curling (Fig. 8) or folding (Fig. 9) of the edges of the tape; the edges of the tape and at least one fold may be enclosed in the microtape (Fig. 17). Up to 10 layers may be similarly treated to form a laminated microtape. The polymeric material may be a polymer of vinylidene chloride, ethylene, propylene, isobutylene, vinyl chloride, styrene, hexamethylene adipamide, or ethyleneterephthalate, rubber hydrochloride, cellulose acetate, methyl cellulose, or hydroxypropyl methyl cellulose. Various copolymers of vinylidene chloride are specified. The starting tape may be cast or extruded and may be slit from a wider tape. It may be provided with a thermoplastic coating and may be passed through a bath of a finishing agent, e.g. a lubricant. It may be 20-125 microns thick and 2.5-25 mm. wide. The microtape may have a denier of 100-3000, a ratio of apparent to true density of 0.5-0.9, and a ratio of width to thickness of 2-30. The channel may be in a grooved shoe or rotating roll and may be of decreasing width. A steel roll coated with PTFE may be used. The microtape is preferably withdrawn from the grooved shoe at an angle # (Fig. 14) equal to 15-30 degrees. Unfused material may be fused just before or simultaneously with formation of the microtape. Molecular orientation by stretching may be effected before, during or after formation of the microtape. A microtape may be formed from a fused polyolefin tape at a temperature of 45-70‹ C. at a stretch ratio of 3-9, stretched at a temperature of 150- 165‹ C. at a stretch ratio of 1-3, and relaxed at a temperature of 10‹ C. below the orienting temperature at a stretch ratio of 0.9-0.95. Examples are given.