Process for producing thermoformable polypropylene films and sheets
AssigneeMobil Oil Corporation
InventorsPeter Breidt, Jr., John R. Wagner, Jr.
Life of this patent
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Abstract
A process for thermoforming thermo-plastics including a random copolymer of polypropylene and polyethylene. The process including stretching in at least one direction, a film or sheet containing polypropylene and polyethylene random copolymer to partially orient the sheet sufficiently as to reduce sag during thermoforming and thermoforming the stretched sheet.
Claims19
A process for producing a polyolefin sheet for thermoforming with minimal sag, comprising the steps of:
- (a) providing a polyolefin sheet, said sheet produced from a resin selected from the group consisting of random copolymers of propylene monomer and ethylene monomer and mixtures of homopolymers of propylene and random copolymers of propylene monomer and ethylene monomer;
- and
- (b) stretching said sheet in at least one direction to obtain a partial orientation of a degree effective to minimize sag when thermoforming said sheet;
- wherein said ethylene monomer of said random copolymer is present in an amount effective to minimize sag when thermoforming said sheet.
A method of thermoforming a partially oriented polyolefin sheet, comprising the steps of:
- (a) providing a partially oriented polyolefin sheet said sheet produced from a resin selected from the group consisting of random copolymers of propylene monomer and ethylene monomer and mixtures of homopolymers of propylene and random copolymers of propylene monomer and ethylene monomer, said sheet oriented to a degree effective to minimize sag while conducting steps (b) through (d);
- (b) subjecting said sheet to a temperature sufficient to permit deformation thereof;
- (c) deforming the so-treated sheet to a predetermined shape;
- and
- (d) while so-deformed cooling the same to cause retention of said shape.
A process for producing a thermoformable polyolefin film, comprising the steps of:
- (a) providing a polyolefin film, said film produced from a resin selected from the group consisting of random copolymers of propylene monomer and ethylene monomer and mixtures of homopolymers of propylene and random copolymers of propylene monomer and ethylene monomer;
- and
- (b) stretching said film in at least one direction to obtain a partial orientation of a degree effective to minimize sag when thermoforming said film;
- wherein said ethylene monomer is present in an amount effective to minimize sag when thermoforming said sheet.
A method of thermoforming a partially oriented polyolefin film comprising the steps of:
- (a) providing a partially oriented polyolefin film said film produced from a resin selected from the group consisting of random copolymers of propylene monomer and ethylene monomer and mixtures of homopolymers of propylene and random copolymers of propylene monomer and ethylene monomer, said film oriented to a degree effective to minimize sag while conducting steps (b) through (d);
- (b) subjecting said film to a temperature sufficient to permit deformation thereof;
- (c) deforming the so-treated film to a predetermined shape;
- and
- (d) while so-deformed cooling the same to cause retention of said shape.
Dependencies are inferred from the claim text.