| abstract |
1307951 Stretching foamed sheets; laminates TEIJIN Ltd 30 April 1971 [28 July 1970] 12512/71 Headings B5B and B5N [Also in Division C3] A molten thermoplastic polymer is extruded in admixture with a foaming agent through a die of 0À2-1À0 mm. width, the resulting foam sheet is quenched below the polymer glass transition temperature within 5 mm. of leaving the die, and the quenched sheet is drawn at a ratio between the maximum possible without breakage of the sheet and one third of this value, whereby a fibrous sheet is obtained having numerous cracks running in one direction. A plurality of such sheets may be superposed with their cracks parallel, subjected to tension transverse to the cracks to open them, e.g. to 3-15 times their width, and finally pressed at a temperature below the softening point of the lowest melting component, whereby a laminate is obtained. A vinyl acetate binder may be incorporated into the laminate. Other sheetmaterials may be included in the laminate. In examples, sheets of polystyrene, polycarbonate, nylon-6 or polyethylene-2,6-napthalate containing 1% talc are extruded using N 2 or CO 2 as foaming agent. In Ex. 6 two laminates, each of 240 polystyrene sheets, are superposed with a polycarbonate film between them, and the whole integrated by pressure at 80 C. In Ex. 7, a 240-sheet laminate as above is adhered to an asbestos sheet with vinyl acetate. |