Patent GB-1390693-A (GB)
Title: Method of processing a heat-shrinkable sheet-like material
IPC: D06C23/00
Filed: 1973-01-01
Abstract: 1390693 Random patterned film MITSUBISHI RAYON CO Ltd 1 Jan 1973 79/73 Heading B5B [Also in Division D1] A heat-shrinkable sheet-like material 2 is inserted under a tension not exceeding its shrinkage stress at the temperature employed between a first heating device 3 maintained at a temperature higher than that at which the material 2 begins to shrink and a second device 4 which may be a heating device or a non- heating device, which controls the rising of the material, spaced from the device 3 by a distance greater than the thickness of the sheet material 2 while bringing the material 2 into contact at least with the device 3, without positive pressing thereto, to heat the material 2, whereby random solid heat shrinkage pattern is produced thereon. The heat shrinkage stress is determined by fixing a sample having a width of 1 cm. and a length of 10 cm. at both ends and holding it vertically in a dry box including a heater and fan. The temperature is raised and the stress which occurs on the material is measured by a strain gauge attached to the top of the sample and is expressed in grams per cm. The material 2 may comprise a heat shrinkable thermoplastic substance only or a mixture of a major proportion of the thermoplastic substance with a minor proportion of a non-heatshrinkable material obtained by mixing or blending the components in a spinning, weaving, knitting or sheet-forming operation (e.g. a film, paper, or woven, non-woven or knitted fabric). Specified thermoplastic substances are polyesters, polyamides, polyolefins, polyvinyl alcohol, polyacrylonitride, polyvinyl chloride, polyvinylidene chloride and polyurea in such a form as fibres of films. Specified non-heatshrinkable materials are cotton, flax, wool, silk, viscose rayon, cuprammonium rayon, and cellulose acetate. Preferably, the material 2 has a specific volume of not more than 5 cm.<SP>3</SP>/g. and a maximum heat shrinkage stress under dry heat of at least 0À10 W g./cm., where W is the weight in grams of the material per square meter. The material 2 may have a dye applied thereto, e.g. a disperse dye, cationic dye, acid dye or reactive dye. In one embodiment, Fig. 2, the material 2 passes from delivery rollers 1 under low tension into contact with a heated roller 3 and passes through a space of predetermined size between the roller 3 and a second roller 4 which may or may not be heated. The patterned material 5 is taken up under low tension by rollers 6. In a modification, Fig. 3 (not shown), the material passes between five pairs of rollers of which at least one roller of each pair is heated. The gap between the rollers of each pair becomes progressively smaller in the direction of advance of the material. In another embodiment, Fig. 4, the material 22 passes between a roller 27 and rollers 23, 24, 25, 26 spaced therefrom by a distance K. If the roller 27 is heated, the rollers 23, 24, 25, 26 may or may not be heated but if the roller 27 is not heated, the rollers 23, 24, 25, 26 are heated. In a further embodiment, Fig. 5, the material passes between rollers 32, 34, 36 and corresponding plates 33, 35, 37, at least the roller or the plate of each pair being heated. The gap between the members of each pair becomes smaller in the direction of advance of the material. In a still further embodiment, Fig. 6, the material passes downwardly between pairs of rollers 42 and 43, 44 and 45, 46 and 47 and 48 and 49 of which at least one roller of each pair must be heated and the gap between the rollers of each pair becomes progressively smaller. In a further embodiment, Fig. 7, non-heated belts 55, 57, 59 co-operate with heated rollers 54, 56, 58, respectively. The gap between the members of each pair becoming progressively smaller. In other embodiments (all not shown), differential heat shrinkage patterns are produced by a pair of rollers of which one, at least, is heated and one is provided with (a) a longitudinal groove (76) in its periphery, Fig. 13, (b) notched portions (82), Fig. 15, (c) a longitudinal protruding portion (88), Fig. 17, (d) annular protrusions (93), Fig. 19, (e) eccentric rings (98) at each end thereof, Fig. 21, (f) circular projections, Fig. 24, (g) a polygonal cross-section, Fig. 27, or (h) an elliptical cross-section, Fig. 30. The material may be dyed, printed, etched, embossed or calendered before or after heat shrinking or may be a laminate comprising a fabric layer and a fabric, foam or film layer. Subsequently, the material may be heated further under longitudinal or transverse tension to remove the bulges and produce a planar pattern.