GB1142821A - Improvements in or relating to hollow polypropylene filaments and fibres - Google Patents

Abstract

1,142,821. Making hollow polypropylene fibres. L. COSTELLO, G. SHAW, and J. C. LEWIS. 17 May, 1966 [18 May, 1965], No. 21954/66. Heading B5B. [Also in Division A4] Hollow unoriented polypropylene filaments are passed through a heated orientation zone at a temperature such that they may be stretched to 2 to 4À5 times their initial length thereby orienting them and are then treated in a heated annealing zone at a temperature and for a period of time such that the elongation at break of the filaments at room temperature is at least 60%, in the case of a homopolymer of propylene, and at least 40%, in the case of a copolymer of propylene. The term " polypropylene " is defined as including propylene homopolymer and copolymer of propylene wherein polymerized propylene is present in a major proportion, as in polyallomers such as propylene-ethylene copolymers. The preferred filaments are isotactic polypropylene filaments and crystalline polyallomer filaments. The term isotactic polypropylene is defined as meaning polypropylene comprising crystallizable isotactic molecules and up to 15% of amorphous, non-crystallizable macromolecules. The stretching of the filaments may be carried out by means of feed and draw roll at 203‹ to 284‹ F. The stretched filament may be allowed to shrink from 1 to 10% during the subsequent annealing or heat-setting step which may be effected at 280‹ to 310‹ F., preferably for 1 hour at 300‹ F. The preferred filaments of the invention range in diameter from 0À008 to 0À050 inch and may be cut to form staple fibres suitable for use in the manufacture of brushes.