Thermoformable, multi-layer plastic sheet having gas barrier properties

• US 4,681,797 A
• Filed: 09/19/1985
• Issued: 07/21/1987
• Est. Priority Date: 09/26/1984
• Status: Expired due to Fees

• Current Assignee: Spartech Plastics, Inc. (Spartech LLC)
• Original Assignee: Cobelplast NVSA
• Inventors: Van Iseghem, Augustinus E. M.
• Primary Examiner(s): Buffalow, Edith
• Application Number:
  US06/777,797
• Time in Patent Office: 670 Days
• Field of Search: 428/516, 428/517, 428/349, 428/518, 428/522, 428/520, 428/212, 156/245
• US Class Current: 428/212
• CPC Class Codes: B32B 2307/724 Permeability to gases, adsorption
• CPC Class Codes: B32B 2323/10 Polypropylene
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/304 comprising vinyl halide (co)polymers, e.g. PVC, PVDC, PVF, PVDF
• CPC Class Codes: B32B 27/32 comprising polyolefins comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30
• CPC Class Codes: B32B 7/12 using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/2826 Synthetic resin or polymer
• CPC Class Codes: Y10T 428/31913 Monoolefin polymer
• CPC Class Codes: Y10T 428/31917 Next to polyene polymer
• CPC Class Codes: Y10T 428/3192 Next to vinyl or vinylidene chloride polymer
• CPC Class Codes: Y10T 428/31928 Ester, halide or nitrile of addition polymer
• CPC Class Codes: Y10T 428/31935 Ester, halide or nitrile of addition polymer

Abstract

A thermoformable, multi-layer plastic sheet with gas barrier properties is disclosed having an inner gas barrier layer, a glue layer applied to either side of the gas barrier layer and layers of a polyolefin composition bonded to the glue layers. To increase the tensile strength of the sheet during heating for the purpose of thermoforming, a second polyolefin layer is bonded to at least one of the two polyolefin layers, the second polyolefin layer having a lower melt index than the layer of the polyolefin composition beneath it.

Claims

1. A thermoformable, multi-layer plastic sheet having gas barrier properties, the sheet comprising an inner extrudable gas barrier layer, a glue layer applied to either side of the gas barrier layer, each of the glue layers having layers of a first polyolefin composition bonded to it and at least one of the two first polyolefin layers being bonded to a second polyolfin layer which has a lower melt index than the layer of the first polyolefin composition underneath.

2. The sheet in accordance with claim 1, wherein the first polyolefin composition layer has a melt index (ASTM D-1238-Condition L) of about 1.5 to about 10 g/min at 230°

C. and the second polyolefin layer has a melt index of less than 1.5 g/min at 230°

C.

3. The sheet of claim 1, wherein the glue layer is comprised of an ethylene/vinyl acetate copolymer.

4. The sheet of claim 1, wherein the gas barrier layer is a vinylidene chloride polymer.

5. The sheet of claim 1, wherein the first polyolefin layer is a propylene block copolymer.

6. The sheet of claim 1 wherein the second layer is a polypropylene copolymer.

7. The sheet of claim 1, wherein each outer polyolefin layer comprises about 30 to about 60 percent of the total thickness of the sheet.