# US 5,702,784 A · Polypropylene heat shrinkable film

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- Number: US 5,702,784 A
- Document ID: US5702784A
- Status: Granted
- Kind: A
- Application number: 08/712,675
- Filed: 1996-09-13
- Granted: 1997-12-30
- Earliest claimed: 1993-09-03
- Assignees: Gunze Limited
- Inventors: Masayuki Nishimura; Kiyoshi Sogabe; Hiroyuki Tanaka; Shinji Arai
- Web page: https://patentgrep.com/patent/US5702784A

## CPC

- C08L 23/16: Ethylene-propylene or ethylene-propylene-diene copolymers
- B29C 48/10: flexible, e.g. blown foils
- C08J 5/18: Manufacture of films or sheets
- C08L 23/10: Homopolymers or copolymers of propene
- C08L 23/142: {at least partially crystalline copolymers of propene with other olefins}
- B29C 48/0018: {combined with shaping by orienting, stretching or shrinking, e.g. film blowing (B29C48/0017 takes precedence)}
- B29C 48/0019: {combined with shaping by flattening, folding or bending}
- B29C 48/0022: {combined with cutting}
- B29K 2995/0049: Heat shrinkable
- C08J 2323/08: Copolymers of ethene (C08J2323/16 takes precedence)
- C08J 2323/14: Copolymers of propene (C08J2323/16 takes precedence)
- C08L 23/20: having four to nine carbon atoms
- Y10S 428/91: Product with molecular orientation
- Y10T 428/1328: Shrinkable or shrunk [e.g., due to heat, solvent, volatile agent, restraint removal, etc.]
- Y10T 428/1331: Single layer [continuous layer]
- C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06)
- 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
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

The heat shrinkable film includes at least one of an ethylene-propylene random copolymer and an ethylene-propylene-butene random copolymer and a propylene-butene copolymer of low crystallinity, which is biaxially stretched simultaneously by a ratio of 2.0-3.5 times for each of the machine direction and the transverse direction by a wet heating method. The film preferably has a tensile elongation at breaking of more than 200%, and a heat shrinking ratio of more than 8% for each of the machine direction and the transverse direction when it is immersed in glycerine at 80.degree. C. for 30 sec. Since the file is excellent in tensile elongation and has satisfactory heat shrinkability at low temperature, it is suitable as a film for use in an automatic L-bar sealer in which a tensile elongation at breaking is an important factor.

## Claims

### Claim 1

A polypropylene heat shrinkable mono-layer film consisting essentially of a blend of propylene-butene copolymer and at least one polymer selected from the group consisting of an ethylene-propylene random copolymer and an ethylene-propylene-butene random polymer, said heat shrinkable film resulting from simultaneous biaxial stretching in a tubular state at a stretching ratio of from 2.0 to 3.5 times in each of the machine direction and the transverse direction under wet heating wherein the tensile elongation at breaking of the film is more than 200%, the tensile modulus of elasticity of the film is less than 9 kg/mm.sup.2 and the film shrinks more than 8% in both the machine and the transverse direction when said film is immersed for 30 seconds in 80.degree. C. glycerine.

### Claim 2 (depends on 1)

The polypropylene heat shrinkable mono-layer as defined in claim 1, wherein the ethylene content in said ethylene-propylene random copolymer is from 1 to 20 mol %, the ethylene content in said ethylene-propylene-butene random copolymer is from 0.5 to 10 mol %, the butene content in said ethylene-propylene-butene random copolymer is from 0.5 to 10 mol %, the propylene content in said propylene-butene copolymer of low crystallinity is form 40 to 98 mol % and the butene content in said propylene-butene copolymer of low crystallinity is from 60 to 2 mol %.

### Claim 3 (depends on 1)

A polypropylene heat shrinkable mono-layer as defined in claim 1, wherein the propylene-butene copolymer of low crystallinity is mixed at a ratio of 1 to 95 parts by weight based on 100 parts by weight of at least one of the ethylene-propylene random copolymer and the ethylene-propylene-butene random copolymer.