Heat-shrinkable composite laminate film and process for preparing the same

Claim 2

A heat-shrinkable composite laminate film comprising an intermediate layer of a copolymer of vinylidene chloride, an outer layer of an olefin resin, another outer layer of a polyamide and two adhesive layers respectively disposed between the intermediate layer and the two outer layers, the adhesive layers being at least one resinous material selected from the group consisting of a modified copolymer obtained by modifying a copolymer of ethylene and a vinyl carboxylate or an acrylic ester with an ethylenically unsaturated carboxylic acid or an acid anhydride thereof and a polymeric material obtained by further modifying said modified copolymer with a metal compound.

Claim 3

A heat-shrinkable composite laminate film according to claim 1, wherein the thickness of the intermediate layer is 3 to 30 micrometers, the thickness of each of the two outer layers is 5 to 50 micrometers, respectively and the thickness of each of ! the two adhesive layers is not less than 1 micrometer and below 5 micrometers.

Claim 4

A heat-shrinkable composite laminate film according to claim 1, wherein the heat-shrinkage thereof in the direction parallel to the take-up direction of preparing the film, and the heat-shrinkage thereof in the direction perpendicular to the take-up direction are larger than 15 % at 90°C, respectively.

Claim 5

A heat-shrinkable composite laminate film according to claim 1, wherein said copolymer of vinylidene chloride is a copolymer comprising 65 to 95 % by weight of vinylidene chloride units and 5 to 35 % by weight of units of a comonomer copolymerizable with vinylidene chloride.

Claim 6

A heat-shrinkable composite laminate film according to claim 1, wherein said olefin resin is one member selected from the group consisting of high-density polyethylene, middle-density polyethylene, low-density polyethylene, a copolymer of ethylene and vinyl acetate, a copolymer of ethylene and an acrylic ester, polypropylene, a copolymer of ethylene and propylene, a copolymer of ethylene and an alpha-olefin other than propylene and an ionomer.

Claim 7

A heat-shrinkable composite laminate film according to claim 1, wherein said polyamide is one member selected from the group consisting of nylon 6, nylon 6-6, nylon 6-66, nylon 6-10 and nylon 12.

Claim 8

A heat-shrinkable composite laminate film according to claim 1, wherein said modified copolymer is prepared by modifying a copolymer of ethylene and a vinyl carboxylate or an acrylic ester with an ethylenically unsaturated carboxylic acid selected from the group consisting of acrylic acid, methacrylic acid, maleic acid and fumaric acid, and an acid anhydride thereof.

Claim 9

A heat-shrinkable composite laminate film according to claim 1 or 7, wherein the content of the ethylenically unsaturated carboxylic acid in the modified copolymer is 0.01 to 10 % by weight.

Claim 10

A heat-shrinkable composite laminate film according to claim 1, wherein said polymeric material has been prepared by further modifying said modified copolymer with the metal compound selected from the group consisting of alkali metal salts, alkali metal oxides, alkaline earth metal salts and alkaline earth metal oxides.

Claim 11

A heat-shrinkable composite laminate film according to claim 1 or 7, wherein the content of metal in said polymeric material is 0.02 to 10 mol %.

Claim 12

A process for preparing a heat-shrinkable composite laminate- film, comprising the steps of simultaneously melt-coextruding a copolymer of vinylidene chloride as an intermediate layer, an olefin resin as an outer layer, a polyamide as another outer layer and an adhesive material as two adhesive layers respectively disposed between the intermediate layer and each of two outer layers, the adhesive layer being selected from the group consisting of a modified copolymer obtained by modifying a copolymer of ethylene and a vinyl carboxylate or an acrylic ester with an ethylenically unsaturated carboxylic acid or an acid anhydride thereof and a polymeric material obtained by further modifying said modified copolymer with a metal compound, while laminating the five layers within a circular die, or melt-extruding a copolymer of vinylidene chloride as an intermediate layer, an olefin resin as an outer layer and adhesive material as the two adhesive layers, and a layer of polyamide from a circular die, respectively and laminating a four-layer tubular composite laminate film comprising the outer layer of the olefin resin, the adhesive layer, intermediate layer and the adhesive layer, and the film of polyamide still in molten state, and subjecting the thus obtained 5-layer tubular composite laminate to simultaneous biaxial stretching by sliding said tubular composite laminate along the external circumpherential surface of a conical inner mandrel provided with the central position of the bottom of said circular die and by pulling said tubular composite laminate into the longitudinal direction while cooling said tubular composite laminate by hot water at a temperature in the range of from the secondary transition point of said polyamide to a temperature of higher" than the secondary transition point by 20°C.

Claim 13

A process for preparing a heat-shrinkable composite laminate- film, comprising the steps of simultaneously melt-coextruding a copolymer of vinylidene chloride as an intermediate layer, an olefin resin as an outer layer, a polyamide as another outer layer and an adhesive material as two adhesive layers respectively disposed between the intermediate layer and each of two outer layers, the adhesive layer being selected from the group consisting of a modified copolymer obtained by modifying a copolymer of ethylene and a vinyl carboxylate or an acrylic ester with an ethylenically unsaturated carboxylic acid or an acid anhydride thereof and a polymeric material obtained by further modifying said modified copolymer with a metal compound, while laminating the five layers within a circular die, or melt-extruding a copolymer of vinylidene chloride as an intermediate layer, an olefin resin as an outer layer and adhesive material as the two adhesive layers, and a layer of polyamide from a circular die, respectively and laminating a four-layer tubular composite laminate film comprising the outer layer of the olefin resin, the adhesive layer, intermediate layer and the adhesive layer, and the film of polyamide still in molten state, and subjecting the thus obtained 5-layer tubular composite laminate to simultaneous biaxial stretching by sliding said tubular composite laminate along the external circumpherential surface of a conical inner mandrel provided with the central position of the bottom of said circular die and by pulling said tubular composite laminate into the longitudinal direction while cooling said tubular composite laminate by hot water at a temperature in the range of from the secondary transition point of said polyamide to a temperature of higher" than the secondary transition point by 20°C.

Claim 14

A process according to claim 11, wherein a copolymer of vinylidene chloride as an intermediate layer, an olefin resin as an outer layer, a polyamide as another outer layer and two adhesive layers respectively disposed between the intermediate layer and each of two outer layers, the adhesive layer being selected from the group consisting of a modified copolymer obtained by modifying a copolymer of ethylene and a vinyl carboxylate or an acrylic ester with an ethylenically unsaturated carboxylic acid or an acid anhydride thereof and a polymeric material obtained 'by further modifying said-modified copolymer with a metal compound are simultaneously melt-coextruded while laminating the five layers within a circular die. I

Claim 15

A process according to claim 11, wherein the temperature of said conical inner mandrel is controlled within the range of from 30 to 80°C by a heating medium.

Claim 16

A process according to claim 11, wherein said tubular composite laminate is subjected to simultaneous biaxial stretching so that the stretch ratio in the direction of taking-up of the thus stretched tubular composite laminate and the stretch ratio in the direction perpendicular to the direction of taking-up of the thus stretched tubular composite laminate are respectively in a range of 1.5 to 5.

Claim 17

A process according to claim 11, wherein said tubular composite laminate in a molten state is cooled to a temperature of higher than the crystallization temperature of said polyamide by 5 to 10°C so as to maintain said tubular composite laminate substantially in a non-crystalline state in advance of subjecting said tubular composite laminate in a molten state to cooling treatment with hot water at a temperature in the range of from the secondary transition point of said polyamide to a temperature of higher than the secondary transition point by 20°C.

Claim 18

A process according to claim 11, wherein hot water is sprayed onto said tubular composite laminate so as to cool said tubular composite laminate in a molten state to a stretching temperature between the crystallization temperature and the secondary transition point of said polyamide at a cooling velocity of larger than 50°C/sec.

Claim 19

A process according to claim 11, wherein after simultaneously biaxially stretching 5-layer tubular composite laminate film, thus stretched tubular composite laminate film is subjected to relaxation-treatment between two pairs of pinch rolls the rotatory speed of the former pair of pinch rolls being the same or a little smaller as compared to that of the latter pair of said pinch rolls and optionally, an amount of air being enclosed in said stretched tubular composite laminate between said two pairs of pinch rolls.

Claim 20

A process according to claim 17, wherein said relaxation-treatment is carried put in an atmosphere at a temperature of 40 to 100°C.

Claim 21

A process according to claim 11, wherein said simultaneously biaxially stretched tubular composite laminate is cooled to a temperature of lower than the secondary transition point of said polyamide by spraying water at 5 to 30°C.

Claim 22

A process according to claim 11, wherein after simultaneously biaxially stretching said tubular composite laminate by sliding along the external circumferential surface of the conical inner mandrel, subsequently subjecting the thus stretched tubular composite laminate to simultaneous biaxial stretching by inflating the tubular composite laminate and by pulling down said tubular composite laminate.

Claim 23

A process according to claim 11 or 20, wherein the thickness of said intermediate layer is 3 to 30 micrometers, the thickness of each of the two outer layers is 5 to 50 micrometers and the thickness of the adhesive layer is not less than 1 micrometer and below 5 micrometers.

Claim 24

A process according to claim 11 or 20, wherein the heat-shrinkage of said heat-shrinkable composite laminate film in the direction of baking-up and that in the direction perpendicular to the direction of taking-up are respectively higher than 15 % at 90°C.

Claim 25

A process according to claim 11, wherein said copolymer of vinylidene chloride is a copolymer of 65 to 95 % by weight of vinylidene chloride and 5 to 35 % by weight of units of a copolymer copolymerizable with vinylidene chloride.

Claim 26

A process according to claim 11, wherein said olefin resin is one member selected from the group consisting of high-density polyethylene, middle-density polyethylene, low-density polyethylene, a copolymer of ethylene and vinyl acetate, a copolymer of ethylene and an acrylic ester, polypropylene, a copolymer of ethylene and propylene, a copolymer of ethylene and alphasolefin other than propylene and an ionomer.

Claim 27

A process according to claim 11, wherein said polyamide is one member selected from the group consisting of nylon 6, nylon 6-6, nylon 6-66, nylon 6-10 and nylon 12.

Claim 28

A process according to claim 11, wherein said modified copolymer has been prepared by modifying a copolymer of ethylene and a vinyl carboxylate or an acrylic ester with an ethylenically unsaturated carboxylic acid selected from the group consisting of acrylic acid, methacrylic acid, maleic acid and fumaric acid, or an acid anhydride thereof.

Claim 29

A process according to claim 11 or 26, wherein the content of the ethylenically unsaturated carboxylic acid in the modified copolymer is 0.01 to 10 % by weight.

Claim 30

A process according to claim 11, wherein said polymeric material has been prepared by further modifying said modified copolymer with a metal compound selected from the group consisting of alkali metal salts, alkali metal oxides, alkaline earth metal salts and alkaline earth metal oxides.

Claim 31

A process according to claim 11 or 28, wherein the content of metal(s) in said polymeric material is 0.02 to 10 mol %.