| 摘要 |
<p>1305653 Producing polypropylene yarns by fibrillation BADISCHE ANILIN- & SODAFABRIK AG 3 April 1970 [5 April 1969] 15887/70 Addition to 1303151 Heading B5B A process for producing polypropylene yarns comprises extruding polypropylene at a melt temperature of 180‹ to 360‹ C. to form a film or sheeting having a thickness of 0À03 to 4 mm. which is then either cut longitudinally at 10‹ to 100‹ C. into strips and the strips drawn monoaxially and longitudinally at a draw ratio of 4:1 to 15:1 at a temperature between 10‹ C. and the crystallite melting point of the polypropylene used, or the film or sheeting is drawn monoaxially and longitudinally as specified above before it is cut longitudinally into strips at 10‹ to 100‹ C. In either case the strips are mechanically fabricated to form yarns having a mean denier of 1 to 100. In a third modification of the process the melt extruded product may be a strip, film or sheeting having a thickness of 0À03 to 4 mm. and after having been drawn monoaxially and longitudinally under the conditions specified above is mechanically fibrillated to form yarns having a mean denier of 1 to 100, the step (in the case of a film or sheeting) of cutting the drawn product longitudinally into strips before fibrillation being omitted, In all three modifications of the process the polypropylene used is a mixture of 70 to 80% by weight of a polypropylene of which less than 1% by weight is soluble in toluene boiling at standard pressure, and 20 to 30% by weight of a polypropylene of which more than 99% by weight is soluble in toluene boiling at standard pressure, the polypropylene/toluene weight ratio being in both cases 5:95. The two polypropylenes have substantially the same intrinsic viscosity and molecular weight distributions, and their intrinsic viscosities [#] (measured in decahydronapthalene at 130‹ C.) are within the range of from 1 to 10; especially 1À2 to 3À8. In an example, a mixture of 25 parts by weight of a polypropylene soluble in boiling toluene and having an intrinsic viscosity of 2À6 and 75 parts by weight of a polypropylene insoluble in boiling toluene and having an intrinsic viscosity of 2À7, the mixture having a crystallite melting point of about 160‹ C. is melt extruded at a melt temperatrue of 220‹ C. to form a film 0À1 mm. thick and 600 mm. wide. The film is cut longitudinally at 25‹ C. into strips 10 mm. wide and the strips are drawn monoaxially and longitudinally at a stretch ratio of 7:1 and a temperature of 135‹ C. The strips are then fibrillated mechanically to form yarns having a mean denier of about 20.</p> |
