| 摘要 |
1,075,487. Thermoplastic open network sheet; laminates. T. J. SMITH & NEPHEW Ltd. Nov. 19, 1965 [Nov. 20, 1964], No. 47397/64. Headings B5B and B5N. Open network structures are formed by biaxially stretching a sheet of thermoplastic material having a plurality of non-connected depressions in at least one surface. The biaxial stretching is sufficient to cause the sheet to become permanently set in an expanded state; various depression-bounding portions of fullthickness sheet material become elongated and attenuated; and the area of each depression is expanded, becomes thinner and splits to form network openings. The sheet may be composite, e.g. a laminate of two different thermoplastic materials. The depressions may be, e.g. circular, elliptical, polygonal, re-entrant or otherwise, or annular; various different shapes may be used on one surface; they may be convergent downwardly from the open end, and their bases may be concave, pointed or stepped. They may be arranged in rows. Depressions, preferably of the same shape, may be formed on both surfaces in axial alignment. Interconnecting portions formed across the openings may be removed by flaming or blowing with a hot gas. The depressions are formed by embossing rollers. After the network structures have been formed, they may be further stretched in two directions. |
