Flexible wrapping material

Claim 2

A FLEXIBLE LAMINATED, HEAT-SEALABLE WRAPPING MATERIAL PARTICULARLY SUITABLE FOR USE IN THE PACKAGING OF FOOD PRODUCTS AND OTHER PRODUCTS WHICH ARE TO BE MAINTAINED IN HERMETICALLY SEALED RELATIONSHIP TO THE ATMOSPHERE, AND IN WHICH THE PACKAGE IS OF THE NONCONFORMING TYPE WHEREBY THE WRAPPING MATERIAL MAY BE SUBJECTED TO CONSIDERABLE FLEXING AND BENDING WHICH IS CONDUCIVE TO FLEX CRACKING OF THE MATERIAL AND THE DEVELOPMENT OF PINHOLES THEREIN, SAID MATERIAL BEING CHARACTERIZED BY ITS RESISTANCE TO FLEX CRACKING AND PINHOLE DEVELOPMENT, AND BY ITS IMPERVIOUSNESS TO GAS AND MOISTURE, COMPRISING A CELLOPHANE SHEET, COATED WITH A LAYER OF A VINYLIDENE CHLORIDE COPOLYMER, AND SENDWICHED BETWEEN AND BONDED ON ONE SIDE TO A POLYMERIC LAYER HAVING GOOD HEAT-SEAL STRENGTH, AND BONDED ON THE OTHER SIDE, BY A LAYER O BONDING MATERIAL, TO A BIAXIALLY ORIENTED POLYPROPYLENE SHEET TREATED ON ITS INNER FACE TO FACILITATE BONDING SO THAT SAID POLYPROPYLENE SHEET FORMS ONE SURFACE OF SAID LAMINATED MATERIAL, AND SAID POLYMERIC LAYER FORMS THE OPPOSITE SURFACE OF SAID MATERIAL, SAID POLYMERIC LAYER BEING HEAT-SEALABLE AT A TEMPERATURE SUBSTANTIALLY BELOW THE MELTING POINT OF SAID POLYPROPYLENE SHEET, AND SAID POLYMERIC LAYER BEING SELECTED FROM A GROUP CONSISTING OF POLYETHYLENE AND ETHYLENE-VINYL ACETATE COPOLYMRS,

Claim 3

A wrapping material in accordance with claim 1 in which the polymeric layer forming one surface of the sheet is low density polyethylene.

Claim 4

A wrapping material in accordance with claim 1 in which the polypropylene and cellophane sheets are bonded together by means of polyethylene.

Claim 5

A wrapping material in accordance with claim 3 in which the polyethylene bonding material is an extrusion-laminated layer between the polypropylene sheet and the cellophane sheet and the polymeric layer is a polyethylene extrustion-coated layer on the cellophane sheet.

Claim 6

A wrapping material in accordance with claim 1 in which the cellophane sheet has a thickness of the order of about 0.8 mil, the polymeric layer has a thickness of the order of about 1.5 mils, and the polypropylene has a thickness of the order of about 0.5 mil.

Claim 7

A wrapping material in accordance with claim 4 in which the polyethylene has a density of about 0.910 to about 0.930 and a melt index above 4.

Claim 8

A wrapping material in accordance with claim 1 in which the polymeric layer is an ethylene-vinyl acetate copolymer bonded to the cellophane sheet by extrusion coating said polymeric layer containing vinyl acetate within the range of 0.5% to 26% by weight.

Claim 9

A wrapping material in accordance with claim 1 in which the polymeric layer is a preformed film, glue-laminated to the cellophane sheet.

Claim 10

A wrapping material in accordance with claim 4 in which the polypropylene sheet has a thickness of about 0.25 to 1.5 mils, the thickness of the cellophane sheet is such as to weigh about one pound per 25,000 square inches, the thickness of the polyethylene lamination between the polypropylene and cellophane is 0.3 to 2 mils and the thickness of the extrusion-coated polyethylene layer is 0.5 to 4 mils.

Claim 11

A flexible, laminated, heat-sealable wrapping material particularly suitable for use in the packaging of food products and other products which are to be maintained in hermetically sealed relationship to the atmosphere, and in which the package is of the nonconforming type whereby the wrapping material may be subjected to considerable flexing and bending which is conducive to flex cracking of the material and the development of pinholes therein, said material being characterized by its resistance to flex cracking and pinhole development, and by its imperviousness to gas and moisture, consisting essentially of, and bonded together and in the order specified (1) a biaxially oriented polypropylene sheet having its inner face treated for receptivity to a polymeric bonding material, (2) a polymeric bonding material, (3) cellophane coated on at least one side with a vinylidene chloride copolymer, and (4) a heat-sealable polymeric material bonded to the coated cellophane and having a melting point substantially below the melting point of said polypropylene sheet, said heat-sealable, polymeric material being selected from a group consisting of polyethylene and ethylene-vinyl acetate copolymers.

Claim 12

A flexible, laminated, heat-sealable wrapping material particularly suitable for use in the packaging of food products and other products which are to be maintained in hermetically sealed relationship to the atmosphere, and in which the package is of the nonconforming type whereby the wrapping material may be subjected to considerable flexing and bending which is conducive to flex cracking of the material and the development of pinholes therein, said material being characterized by its resistance to flex cracking and pinhole development, and by its imperviousness to gas and moisture, consisting essentially of, and bonded together and in the order specified (1) a biaxially oriented polypropylene sheet having its inner face treated for receptivity to a polymeric bonding material, (2) a polymeric bonding material, (3) cellophane coated on at least one side with a vinylidene chloride copolymer, and (4) a heat-sealable polymeric material bonded to the coated cellophane and having a melting point substantially below the melting point of said polypropylene sheet, said heat-sealable, polymeric material being selected from a group consisting of polyethylene and ethylene-vinyl acetate copolymers.

Claim 13

A wrapping material as set forth in claim 10, in which the polymeric bonding material between the polypropylene and the cellophane is polyethylene.

Claim 14

A wrapping material as set forth in claim 10, in which the heat-sealable polymeric material is a polyethylene having a density of about 0.914 to about 0.925.

Claim 15

A wrapping material as set forth in claim 10, in whiCh the polypropylene sheet has a film thickness between 0.25 and 1.5 mils, the polymeric bonding material has a thickness between 0.3 and 2 mils, the cellophane layer has a thickness on the order of about 0.8 mil, and the heat-sealable polymeric material has a thickness of from 0.5 to 4 mils.

Claim 16

A flexible, laminated, heat-sealable wrapping material particularly suitable for use in the packaging of food products and other products which are to be maintained in hermetically sealed relationship to the atmosphere, and in which the package is of the nonconforming type whereby the wrapping material may be subjected to considerable flexing and bending which is conducive to flex cracking of the material and the development of pinholes therein, said material being characterized by its resistance to flex-cracking and pinhole development, and by its imperviousness to gas and moisture, comprising a cellophane sheet, coated with a layer of vinylidene chloride copolymer, and sandwiched between and bonded of one side to a polymeric layer having good heat-seal strength, and bonded on the other side, by a layer of bonding material, to a heat-set biaxially oriented polypropylene sheet treated on its inner face to facilitate bonding so that said polypropylene sheet forms one surface of said laminated material, and said polymeric layer forms the opposite surface of said material, said polymeric layer being heat-sealable at a temperature substantially below the melting point of said polypropylene sheet, and said polymeric layer being selected from a group consisting of polyethylene and ethylene-vinyl acetate copolymers.

Claim 17

A flexible, laminated, heat-sealable wrapping material particularly suitable for use in the packaging of food products and other products which are to be maintained in hermetically sealed relationship to the atmosphere, and in which the package is of the nonconforming type whereby the wrapping material may be subjected to considerable flexing and bending which is conducive to flex cracking of the material and the development of pinholes therein, said material being characterized by its resistance to flex-cracking and pinhole development, and by its imperviousness to gas and moisture, comprising a cellophane sheet, coated with a layer of vinylidene chloride copolymer, and sandwiched between and bonded of one side to a polymeric layer having good heat-seal strength, and bonded on the other side, by a layer of bonding material, to a heat-set biaxially oriented polypropylene sheet treated on its inner face to facilitate bonding so that said polypropylene sheet forms one surface of said laminated material, and said polymeric layer forms the opposite surface of said material, said polymeric layer being heat-sealable at a temperature substantially below the melting point of said polypropylene sheet, and said polymeric layer being selected from a group consisting of polyethylene and ethylene-vinyl acetate copolymers.

Claim 18

A wrapping material in accordance with claim 14, in which a polymeric layer forming one surface of the sheet is low density polyethylene.

Claim 19

A wrapping material in accordance with claim 14, in which the polypropylene and cellophane sheets are bonded together by means of polyethylene.

Claim 20

A wrapping material in accordance with claim 16, in which the polyethylene bonding material is an extrusion-laminated layer between the polypropylene sheet and the cellophane sheet and the polymeric layer is a polyethylene extrusion-coated layer on the cellophane sheet.

Claim 21

A wrapping material in accordance with claim 14, in which the cellophane sheet has a thickness of the order of about 0.8 mil, the polymeric layer has a thickness of the order of about 1.5 mils, and the polypropylene has a thickness of the order of about 0.5 mil.

Claim 22

A wrapping material in accordance with claim 17, in which the polyethylene has a density of about 0.910 to about 0.930 and a melt index above four.

Claim 23

A wrapping material in accordance with claim 14, in which the polymeric layer is an ethylene-vinyl acetate copolymer bonded to the cellophane sheet by extrusion coating said polymeric layer containing vinyl acetate within the range of 0.5 to 26% by weight.

Claim 24

A wrapping material in accordance with claim 14, in which the polymeric layer is a preformed film, glue-laminated to the cellophane sheet.

Claim 25

A wrapping material in accordance with claim 17, in which the polypropylene sheet has a thickness of about 0.25 to 1.5 mils, the thickness of the cellophane sheet is such as to weigh about one pound per 25,000 square inches, the thickness of the polyethylene lamination between the polypropylene and cellophane is 0.3 to 2 mils and the thickness of the extrusion-coated polyethylene layer is 0.5 to 4 mils.