| 摘要 |
1,064,358. Polypropylene films; sheets and tapes. SIGNODE CORPORATION. March 29, 1965 [July 27, 1964], No. 13278/65. Headings B5A and B5B. Abrasion-resistant polypropylene films, sheets or tapes are made by working crystallizable polypropylene to obtain planar orientation of the macromolecular chains and flash-heating the surface whereby fusion of the surface layer is effected. A sheet may be reduced to an intermediate thickness by calendering and chill rolls, and an orientated sheet produced therefrom by use of mill rolls or mill rolls coupled with a longitudinal stretching process. In one embodiment, an extruded polypropylene sheet (# inch thick) is cold-rolled to an intermediate thickness of 2-7 times the final thickness, compressed between rolls maintained at 100‹-250‹ F. by a cascade of heated oil and stretched at substantially the temperature of the compression rolls to produce an orientated sheet of 0À01-0À1 inch in thickness, which is flash-heated on at least one surface to 375-525‹ F. to form a fused surface layer 1 to 3 mils. thick. Heating may be effected by impingement of gas flames, contacting with gas-heated rollers or a hot flat iron or by radiant heat. The final sheet may be slit to produce strap. |
