Antistatic, low temperature heat sealable polypropylene composite film and process for production thereof

• US 4,117,193 A
• Filed: 04/13/1977
• Issued: 09/26/1978
• Est. Priority Date: 07/22/1976
• Status: Expired due to Term

• Current Assignee: Honshu Seishi Kabushiki Kaisha
• Original Assignee: Honshu Seishi Kabushiki Kaisha
• Inventors: Kawamura, Takashi, Shibata, Kaoru, Tsuchiya, Mikio
• Primary Examiner(s): Ansher, Harold
• Application Number:
  US05/787,143
• Time in Patent Office: 531 Days
• Field of Search: 428/332, 428/339, 428/474, 428/515, 428/516, 428/523, 428/539, 428/910, 156/163, 156/164, 156/229, 156/244, 156/272, 156/244.11, 156/244.17
• US Class Current: 428/339
• CPC Class Codes: B32B 2038/0028 Stretching, elongating
• CPC Class Codes: B32B 2250/02 2 layers
• CPC Class Codes: B32B 2250/242 All polymers belonging to those covered by group B32B27/32
• CPC Class Codes: B32B 2264/102 Oxide or hydroxide
• CPC Class Codes: B32B 2270/00 Resin or rubber layer containing a blend of at least two different polymers
• CPC Class Codes: B32B 2307/21 Anti-static
• CPC Class Codes: B32B 2307/31 Heat sealable
• CPC Class Codes: B32B 2307/516 mono-axially
• CPC Class Codes: B32B 2307/518 bi-axially
• CPC Class Codes: B32B 2307/732 Dimensional properties
• CPC Class Codes: B32B 2307/746 Slipping, anti-blocking, low friction
• CPC Class Codes: B32B 2310/14 Corona, ionisation, electrical discharge, plasma treatment
• CPC Class Codes: B32B 2323/04 Polyethylene
• CPC Class Codes: B32B 2323/043 HDPE, i.e. high density polyethylene
• CPC Class Codes: B32B 2323/10 Polypropylene
• CPC Class Codes: B32B 2439/70 Food packaging
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/16 specially treated, e.g. irradiated
• CPC Class Codes: B32B 27/18 characterised by the use of special additives
• CPC Class Codes: B32B 27/20 using fillers, pigments, thixotroping agents
• CPC Class Codes: B32B 27/32 : comprising polyolefins comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30
• CPC Class Codes: B32B 38/0008 : Electrical discharge treatment, e.g. corona, plasma treatment; wave energy or particle radiation heat treatment B32B38/0036
• CPC Class Codes: C08J 2323/10 : Homopolymers or copolymers of propene
• CPC Class Codes: C08J 2423/00 : Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
• CPC Class Codes: C08J 7/0427 : with only one layer of a composition containing a polymer binder with more layers C08J7/042
• CPC Class Codes: C08L 23/06 : Polyethene
• CPC Class Codes: C08L 2666/04 : Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
• CPC Class Codes: C09J 123/06 : Polyethene
• CPC Class Codes: C09J 123/0815 : Copolymers of ethene with aliphatic 1-olefins
• CPC Class Codes: Y10S 428/91 : Product with molecular orientation
• CPC Class Codes: Y10T 428/269 : including synthetic resin or polymer layer or component
• CPC Class Codes: Y10T 428/31757 : Polymer of monoethylenically unsaturated hydrocarbon
• CPC Class Codes: Y10T 428/31913 : Monoolefin polymer
• CPC Class Codes: Y10T 428/31938 : Polymer of monoethylenically unsaturated hydrocarbon

Abstract

There is disclosed a novel composite film prepared by melt extrusion laminating a polymer blend composition comprising a low-crystalline resin of an ethylene-butene copolymer and a polyolefin resin having incorporated therein a lubricant and an anti-blocking agent onto a surface or surfaces of a uniaxially stretched polypropylene film followed by stretching the laminate film in the direction perpendicular to the direction in which said polypropylene has been stretched and optionally subjecting the resulting film to corona discharge treatment. The composite film thus made provides an excellent packaging material because of its improved antistatic, lubricating and anti-blocking properties in addition to its heat sealability feasible at lower temperatures than prior art materials.

Claims

1. An antistatic, low-temperature heat-sealable polypropylene composite film which comprises:

(a) a substrate layer of a uniaxially stretched film of a polymer composition comprising a propylene homopolymer or a propylene copolymer containing a small amount of an alpha-olefin, said polymer composition having incorporated therein (i) a lubricant, (ii) an anti-blocking agent, and (iii) an antistatic agent; and

(b) a lamination layer or layers of a polymer blend composition comprising a low-crystalline resin of an ethylene-butene copolymer and a polyolefin resin laminated on at least one surface of said substrate layer, said polymer blend composition having incorporated therein (i) a lubricant and (ii) an anti-blocking agent,

said composite film having been stretched, after lamination, in a direction perpendicular to the direction in which said substrate layer has been stretched.

2. The composite film of claim 1 which has been subjected to corona discharge treatment after the final stretching.

3. The composite film of claim 2 in which the corona discharge treatment has been carried out until the surface tension of the treated surface reaches 35-45 dynes/cm.

4. The composite film of claim 2 in which the corona discharge treatment has been carried out until the surface tension of the treated surface reaches 37-40 dynes/cm.

5. The composite film of claim 1 in which said polypropylene in the uniaxially stretched film substrate layer is selected from the group consisting of a propylene homopolymer and a propylene copolymer containing up to 5% by weight of ethylene.

6. The composite film of claim 1 in which said polyolefin resin in the polymer blend in the lamination layer is a high density polyethylene.

7. The composite film of claim 1 in which said ethylene-butene copolymer in the polymer blend in the lamination layer is a copolymer comprising 50-99% by weight of ethylene and 50-1% by weight of butene.

8. The composite film of claim 1 in which said ethylene-butene copolymer in the polymer blend in the lamination layer is a copolymer comprising 90-99% by weight of ethylene and 10-1% by weight of butene.

9. The composite film of claim 1 in which said polymer blend in the lamination layer comprises 20-60% by weight of the ethylene-butene copolymer and 80-40% by weight of the polyethylene.

10. The composite film of claim 1 in which said polymer blend in the lamination layer comprises 25-45% by weight of the ethylene-butene copolymer and 75-55% by weight of the polyethylene.

11. The composite film of claim 1 having a thickness in the region of 10-60 microns.

12. The composite film of claim 1 having a thickness in the region of 15-50 microns.

13. The composite film of claim 1 having a thickness in the region of 20-30 microns.

24. The composite film of claim 1, wherein the lubricant is a fatty acid amide in an amount of from 0.2 to 1 percent by weight.

25. The composite film of claim 1, wherein the anti-blocking agent is silica in an amount of from 0.1-0.5 percent by weight.

14. A process for the production of an antistatic, low-temperature heat-sealable polypropylene composite film which comprises the steps of:

melt extrusion laminating a polymer blend composition comprising (a) a polymer blend of (i) a low-crystalline resin of an ethylene-butene copolymer and (ii) a polyolefin resin; and

(b) additives;

(i) a lubricant and (ii) an anti-blocking agent;

onto at least one surface of a uniaxially stretched polypropylene film prepared by uniaxially stretching a polymer composition comprising (a) a propylene homopolymer or a propylene copolymer containing a small amount of an alpha-olefin and (b) additives;

(i) a lubricant, (ii) an anti-blocking agent and (iii) an antistatic agent; and

then

stretching the resulting laminate film in the direction perpendicular to the direction in which said polypropylene film has been stretched.

15. The process of claim 14 which includes an additional step of subjecting the biaxially stretched film to corona discharge treatment.

16. The process of claim 15 in which the corona discharge treatment is carried out until the surface tension of the treated surface reaches 35-45 dynes/cm.

17. The process of claim 15 in which the corona discharge treatment is carried out until the surface tension of the treated surface reaches 37-40 dynes/cm.

18. The process of claim 14 in which said polypropylene in the uniaxially stretched film substrate layer is selected from the group consisting of a propylene homopolymer and a propylene copolymer containing up to 5% by weight of ethylene.

19. The process of claim 14 in which said polyolefin resin in the polymer blend in the lamination layer is a high density polyethylene.

20. The process of claim 14 in which said ethylene-butene copolymer in the polymer blend in the lamination layer is a copolymer comprising 50-99% by weight of ethylene and 50-1% by weight of butene.

21. The process of claim 14 in which said ethylene-butene copolymer in the polymer blend in the lamination layer is a copolymer comprising 90-99% by weight of ethylene and 10-1% by weight of butene.

22. The process of claim 14 in which said polymer blend in the lamination layer comprises 20-60% by weight of the ethylene-butene copolymer and 80-40% by weight of the polyethylene.

23. The process of claim 14 in which said polymer blend in the lamination layer comprises 25-45% by weight of the polyethylene.

26. The process of claim 14, wherein the lubricant is a fatty acid amide in an amount of from 0.2 to 1 percent by weight.

27. The process of clam 14, wherein the anti-blocking agent is silica in an amount of from 0.1-0.5 percent by weight.