Producing method of a thermoplastic resin sheet and producing apparatus therefor

A method of producing a thermoplastic resin sheet, using a producing apparatus in which a driven metallic endless belt having a mirror face on a surface thereof is wound on and extends between a first cooling roller covered with an elastic member and a second cooling roller spaced from the first cooling roller, and a third cooling roller having a mirror face on a surface thereof and touching the first cooling roller through a molten thermoplastic resin sheet and the metallic endless belt to hold the molten thermoplastic resin sheet pressed against the metallic endless belt are provided, the method comprising the steps of:

• extruding the molten thermoplastic resin sheet and applying the resin sheet into an area between the first and third cooling rollers to approximately simultaneously touch the metallic endless belt and the third cooling roller and to be compressed by the first cooling roller and the third cooling roller;
• maintaining the temperature of the face of the metallic endless belt at less than 50 degrees Celsius by cooling the endless belt with the first and second cooling rollers;
• maintaining the temperature of the surface of the third cooling roller at less than 50 degrees Celsius;
• advancing the molten thermoplastic resin sheet into a nip width between the metallic endless belt and the third cooling roller;
• touch-rolling and cooling the molten thermoplastic resin sheet between the first and third cooling rollers, the elastic member being elastically deformed by a pressing force between the first and third cooling rollers;
• and
• touch-rolling the molten thermoplastic sheet, as the sheet advances and travels downstream beyond the first cooling roller, between only the third cooling roller and the metallic belt, wherein the thermoplastic resin sheet has a temperature of less than 50° C. before the resin sheet leaves the surface of the third cooling roller.

A method of producing a thermoplastic resin sheet, using a producing apparatus in which a driven metallic endless belt having a mirror face on a surface thereof is provided and wound on and extends between an elastic member cooling roller covered with an elastic member about a circumference thereof and a metallic endless belt supporting cooling roller, and a mirrored face cooling roller having a mirrored face on a surface about a circumference thereof and capable of applying a pressing force to the elastic member cooling roller through a molten thermoplastic resin sheet pressed against the metallic endless belt, the method comprising the steps of:

• extruding a molten thermoplastic resin sheet from a T-die of an extruder;
• applying the molten thermoplastic resin sheet into an area between the elastic member cooling roller supporting the metallic endless belt and the mirrored face cooling roller so that the molten thermoplastic resin sheet touches the metallic endless belt and the mirrored face cooling roller approximately simultaneously;
• maintaining the temperature of the face of the metallic endless belt at less than 50 degrees Celsius by the elastic member cooling roller cooling the endless belt;
• maintaining the temperature of the mirrored face of the mirrored face cooling roller at less than 50 degrees Celsius;
• advancing the molten thermoplastic resin sheet between the metallic endless belt and the mirrored face cooling roller, to touch-roll and cool the molten thermoplastic resin sheet therebetween, the elastic member of the elastic member cooling roller being deformed by the pressing force between the elastic member cooling roller and the mirrored face cooling roller;
• and
• advancing the thermoplastic resin sheet beyond the area where the mirrored face cooling roller contacts the resin sheet, wherein the thermoplastic resin sheet has a temperature of less than 50 degrees Celsius, the mirrored face cooling roller is free from contact with other rollers or contact with other rollers through the thickness of the metallic endless belt, except for the elastic member cooling roller.