TREATMENT OF MICROPOROUS ELASTOMERIC POLYMERS

摘要

1294455 Microporous sheet material INMONT CORP 2 Dec 1969 [2 Dec 1968] 58798/69 Headings C3C and C3R Microporous sheet material consisting essentially of thermoplastic elastomeric polymer material free from preformed fibrous sheet material and having a thickness of 0-63 to 2À5 mm., is treated by heating the sheet at a temperature below the collapse temperature (i.e. the temperature at which the sheet loses its porous structure) of the sheet and within 40‹ C. of the collapse temperature to cause the sheet to shrink at least 5% in area in the plane of the sheet. The microporous sheet may be prepared by conventional processes, a number of which are described, and suitably consists of a thermoplastic polyurethane optionally blended with up to 40% by weight of another polymer, e.g. a vinyl chloride polymer or a copolymer of a conjugated diolefin and acrylonitrile. The heat treatment may be carried out before or after the microporous sheet is subjected to a finishing operation, such as treatment of the upper surface with fine droplets of a solvent and heating to partly collapse the microporous structure along the surface and form a thin fused polymer skin thereon. The heat treatment is effected on the unreinforced sheet which must be free to shrink in its planar direction. Varying increases in density can be achieved according to heating conditions. The heat treatment may be carried out in a stream of hot air, e.g. in a convection oven, whilst the sheet is supported horizontally, or the sheet may be hung vertically. Both before and after the heat treatment the sheet should permit the passage of water vapour. The treated microporous sheet material may be used for the preparation of shoe uppers.