Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Patent
1983-03-30
1985-10-29
Ives, Patricia C.
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
428409, 428910, 428522, 264240, 249 95, B32B 2730, B29C 1704, B22D 1904
Patent
active
045500576
ABSTRACT:
A tough acrylic sheet having a smooth surface and a thickness of 1 to 10 mm, which is composed of methacrylate polymer having a weight average molecular weight of at least 1,000,000 and being biaxially oriented at an area stretch ratio of at least 3 and has a maximum orientation release stress of at least 20 kg/cm.sup.2. The acrylic sheet is prepared by a method wherein an acrylic resin blank having a surface area of at least 400 cm.sup.2 is heated at a temperature higher than the glass transition temperature of the resin but lower than the melting point of the resin so that the ratio of the viscosity of the resin in the surface layer portion to the viscosity of the resin in the core portion is smaller than 0.8; the heated resin blank is placed in a flat clamping mold heated to the temperature of the surface layer portion of the resin blank or a temperature close thereto, a high compressive force of at least 45 kg per cm.sup.2 of the resin blank is applied in the state where a lubricant is present between the resin blank and the clamping mold, to thereby stretch the resin blank biaxially; the mold is cooled to solidify the stretched product; and then the product is taken out from the mold. At the step of heating the mold, the mold is preferably held substantially in non-contact with a cooling die plate, and, at the clamping and cooling steps, the mold is preferably held in contact with the cooling die plate.
REFERENCES:
patent: 2918696 (1959-12-01), Bottoms et al.
patent: 3388035 (1968-06-01), Mattimoe et al.
patent: 3632841 (1972-01-01), Fortin
patent: 4278723 (1981-07-01), Moench et al.
Asahi Kasei Kogyo Kabushiki Kaisha
Ives Patricia C.
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