GB1303151A - - Google Patents

Abstract

1303151 Polypropylene strips BADISCHE ANILIN & SODA FABRIK AG 3 April 1970 [5 April 1969] 15883/70 Heading B5B [Also in Division C3] Strips of polypropylene are produced by extruding at a melt temperature of 180 to 360‹ C. a film or sheeting having a thickness of 0À03 to 4 mm. and a width of 150 to 3000 mm., cutting the film or sheeting longitudinally at a temperature of the material of 10 to 100 ‹C. into strips having a width of 2 to 70 mm. and drawing the strips monoaxially and longitudinally at a stretch ratio of 4:1 to 15:1 at a temperature of the material which is higher than 10‹ C. but lower than the crystallite melting point of the poly-propylene used wherein the polypropylene used in a mixture of: (a) 70 to 80% by weight of a polypropylene of which less than 1% by weight is soluble in toluene boiling at standard pressure, the ratio by weight of polypropylene to toluene being 5:95; and (b) 20 to 30% by weight of a polypropylene of which more than 99% by weight is soluble in toluene boiling at standard pressure, the ratio by weight of polypropylene to toluene being 5:95; with the provisos: (I) that the polypropylenes have substantially the same intrinsic viscosity and substantially the same molecular weight distribution (determined by the method of gel permeation chromatography) and (II) that the absolute values of the intrinsic viscosities (#) (measured in decahydronaphthalene at 130‹ C.) are always within the range of from 1 to 10, preferably 1À2 to 3À8. In the example the starting materials are: (A) a conventional finely powdered polypropylene consisting of a fraction soluble in boiling toluene and a fraction insoluble in boiling toluene. The intrinsic viscosities (#) (measured as stated above) are: insoluble fraction 3À6; soluble fraction 2À6: (B) a conventional different finely powdered polypropylene consisting of a fraction soluble in boiling toluene and a fraction insoluble in boiling toluene. The intrinsic viscosities (#) (measured as before) are: insoluble fraction 2À7; soluble fraction 1À6. The soluble fraction of polypropylene (A) and the insoluble fraction of polypropylene (B) are isolated by extraction with boiling toluene and these two fractionswhose molecular weight distributions (determined as stated above) are substantially the same-are homogenized with each other in the ratio by weight 25:75 at 220‹ C. The mixture obtained has crystallite melting point of about 160‹ C. Film having a thickness of 0À1 mm. and a width of 600 mm. as extruded from the polypropylene with conventional equipment at a melt temperature of 220‹ C., the film is cut longitudinally at a temperature of the material of 24‹ C. into strips having a width of 10 mm., and the strips are drawn longitudinally at a draw ratio of 7:1 and a temperature of 135‹ C.