| 摘要 |
1,211,510. Hollow thermoplastic filament. BARMAG BARMER MASCHINENFABRIK A.G. 13 May, 1969 [22 May, 1968], No. 24229/69. Heading B5B. A strand (defined as a monofilament having a diameter of from 0À8 mm. to 8 mm. in a stretched state) of thermoplastic synthetic resin has a continuous coaxial cavity of uniform cross-section whose area constitutes from 0À2% to 15% of the total cross-sectional area of the strand. Preferably the strand is of circular cross-section, and the cross-sectional area of the cavity constitutes from 0À5% to 10% of the total cross-sectional area. The strand is made by extrusion from a monofilament die in which a fine hollow tube is coaxially arranged, the interior of the tube communicating with the external atmosphere. Typically the internal diameter of the die is 8-10 mm. and the external diameter of the tube is 1-2À5 mm. The extruded hollow monofilament is cooled in a liquid bath, e.g. water at between 20‹ and 50‹ C., placed some 60-80 mm. from the die, and is then stretched in a hot air zone. The draw ratio is adjusted to produce the required cavity area proportion, typical draw ratios being 1: 7 and 1: 4. Specified materials are polypropylene and polyamide 6. |
