# US 9,518,195 B2 · Biaxially stretched polyester film and method for producing same

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- Number: US 9,518,195 B2
- Document ID: US9518195B2
- Status: Granted
- Kind: B2
- Application number: 14/241,525
- Filed: 2012-09-03
- Published: 2014-07-10
- Granted: 2016-12-13
- Earliest claimed: 2011-09-06
- Assignees: Unitika Ltd.
- Applicants: Takayoshi Okuzu; Tomoharu Suzuki
- Inventors: Takayoshi Okuzu; Tomoharu Suzuki
- Web page: https://patentgrep.com/patent/US9518195B2

## CPC

- C09D 167/02: Polyesters derived from dicarboxylic acids and dihydroxy compounds (C09D167/06 takes precedence)
- B29C 48/0018: {combined with shaping by orienting, stretching or shrinking, e.g. film blowing (B29C48/0017 takes precedence)}
- B29C 55/12: biaxial
- C08J 5/18: Manufacture of films or sheets
- B29C 51/04: Combined thermoforming and prestretching, e.g. biaxial stretching
- B29K 2067/003: {PET, i.e. poylethylene terephthalate}
- B29K 2067/006: {PBT, i.e. polybutylene terephthalate}
- B29K 2105/0088: {Blends of polymers}
- C08G 63/183: Terephthalic acids
- C08J 2367/02: Polyesters derived from dicarboxylic acids and dihydroxy compounds; (C08J2367/06 takes precedence)
- Y10T 428/31681: Next to polyester, polyamide or polyimide [e.g., alkyd, glue, or nylon, etc.]
- Y10T 428/31786: Of polyester [e.g., alkyd, etc.]
- C09D: COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR (cosmetics A61K; processes for applying liquids or other fluent materials to surfaces, in general, B05D; staining wood B27K5/02; glazes or vitreous enamels C03C; natural resins, French polish, drying-oils, driers, turpentine, per se, C09F; polishing compositions other than French polish, ski waxes C09G; adhesives or use of materials as adhesives C09J; materials for sealing or packing joints or covers C09K3/10; materials for stopping leaks C09K3/12; processes for the electrolytic or electrophoretic production of coatings C25D)
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- B29K: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR {MOULDS, } REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A biaxially stretched polyester film, being a biaxially stretched film including a modified polybutylene terephthalate (modified PBT) and polyethylene terephthalate (PET), wherein a mass ratio (modified PBT/PET) between the modified PBT and PET is 20/80 to 5/95, the modified PBT is a PBT containing 5 to 20% by mass of a polytetramethylene glycol unit having a molecular weight of 600 to 4,000, the amount of tetrahydrofuran (THF) generated by heat treating the biaxially stretched film in a helium gas atmosphere at 180° C. for 30 minutes is 50 μg/g or less, and the biaxially stretched film has tear linearity in a lengthwise direction thereof.

## Claims

### Claim 1

A biaxially stretched polyester film, being a biaxially stretched film comprising a modified polybutylene terephthalate (modified PBT) and polyethylene terephthalate (PET), wherein a mass ratio (modified PBT/PET) between the modified PBT and PET is 20/80 to 5/95, the modified PBT is a PBT containing 5 to 20% by mass of a polytetramethylene glycol unit having a molecular weight of 600 to 4,000, an amount of tetrahydrofuran (THF) generated by heat treating the biaxially stretched film in a helium gas atmosphere at 180° C. for 30 minutes is 50 μg/g or less, and the biaxially stretched film has tear linearity in a lengthwise direction thereof.

### Claim 2 (depends on 1)

A biaxially stretched polyester film, wherein at least on one side of the biaxially stretched polyester film according to claim 1, at least one of aluminum, aluminum oxide and silicon oxide is vapor deposited, and the biaxially stretched polyester film has a gas barrier property and tear linearity.

### Claim 3 (depends on 1)

A method for producing the biaxially stretched polyester film according to claim 1, wherein a modified polybutylene terephthalate (modified PBT) including 5 to 20% by mass of a polytetramethylene glycol unit having a molecular weight of 600 to 4,000 and giving an amount of tetrahydrofuran (THF), generated by heat treating in a helium gas atmosphere at 180° C. for 30 minutes, of 800 μg/g or less and polyethylene terephthalate (PET) are mixed so as for a mass ratio (modified PBT/PET) between the modified PBT and PET to be 20/80 to 5/95, a film is formed from a resulting mixture and a formed film is stretched.