GB1225824A - - Google Patents

Abstract

1,225,824. Making fibrous lace-like webs by film fibrillation. EASTMAN KODAK CO. 14 March, 1968 [20 March, 1967], No. 12367/68. Heading B5B. A fibrous product formed from an oriented film of a crystalline cellular thermoplastic synthetic organic material comprises a plurality of strands integrally connected with one another at points along their lengths, a plurality of fibrils integrally connected with one another and integral with and connecting adjacent strands between said points of connection, the strands and fibrils forming a lace-like web in which substantially all of the fibrils and strands have both their ends integral with and connected to the web whereby to provide less than 20 loose ends per square inch of web. The web may be twisted into cord-like form. The average diameter of the cells formed in the film may be not greater than the thickness of the film. The thickness of the film may be between 1À0 and 5À0 mils. The celular material may be a polyolefin such as polypropylene. The fibrous product may be made by melt extruding a mixture of the thermoplastic material and a small proportion (e.g. not exceeding 0À35% by weight) of a blowing agent to form a flat cellular film, stretching the film in the longitudinal direction at a draw ratio which is within the range of 3:1 to 15:1 and which is sufficiently high to render the film fibrillatable, and thereafter subjecting the oriented film to a fracturing force to separate the film into strands and fibrils. The stretching of the film may be effected in an oven maintained at a temperature within the range 300‹ to 375‹ F. The fibrillation of the film may be effected by subjecting the film to pulsating jets of air at 5-90 p.s.i. applied to both sides of the film at the same time.