| 摘要 |
1,248,265. Rupturing cellular film. W. R. GRACE & CO. 10 June, 1969 [18 June, 1968], No. 29463/69. Heading B5B. [Also in Divisions C3 and D1] A non-woven fabric is made by drawing a tubular foamed sheet 30 of thermoplastic material over a conical mandrel 31 so as to stretch the cell walls and rupture them, drawing being effected at the "hardening-orientation" temperature of the material. This temperature is defined as that at which the material achieves orientation but no longer stretches as a film, instead pulling apart to leave a rupture. The mandrel may be a cylindrical frusto-cone 40 with the frustrum adjacent the die-outlet. To the base may be attached a cylindrical tubecollapsing mandrel which tapers gradually and uniformly to a flattened edge (as in Fig. 1A) adjacent nip-rolls 41, 42. The tube may be cooled after extrusion with fluid blown from a ring 25, and the mandrel may be internally cooled, e.g. via pipes 32, 33. Tubes of polypropylene and polybutene-1 are exemplified. The product may be heat-shrinkable by up to 25% in the longitudinal and transverse directions. |
