Highly-oriented stretchable multilayer film and process for producing the same

Claim 2

A multilayer oriented film having excellent sealability and stretchability, and showing high strength and high elongation, which comprises at least the following three layers : (1) a base layer (M layer) containing primarily a specific mixed composition selected from the group of polymer compositions consisting of (A) + (B) + (C), (A) + (B) and (B) + (C), (A) being at least one polymer selected from a low density polyethylene, or a copolymer of ethylene with a monomer selected from a vinyl ester monomer, an aliphatic unsaturated mono-carboxylic acid or an alkyl ester of said mono-carboxylic acid or the derivatives of said copolymer; (B) being a soft elastomer having a Vicat softening point of 60 °C or lower; (C) being at least one polymer selected from crystalline polypropylenes and crystalline polybutenes-1, at least one such M layer being provided adjacent to the core layer as defined below, (2) a core layer (H layer) as inside layer comprising primarily a polymer selected from (C); and (3) a surface layer (S layer) containing at least one polymer selected from said polymer (A), soft elastomer (B), crystalline 1,2-polybutadiene or a soft ionomer resin from ethylenic copolymer, said film having a stress on 100 % elongation of from 100 to 600 (g/cm-width) on an average value in the longitudinal and transverse directions.

Claim 3

A multilayer oriented film according to Claim 1, wherein the polymer (A) comprises at least one selected from the group consisting of ethylene-vinyl acetate copolymers, ethylene-acrylate copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylate copolymers, ethylene-methacrylic acid copolymers and ethylene copolymer ionomer resins.

Claim 4

A multilayer oriented film according to Claim 1 or 2, wherein the soft elastomer (B) is a copolymer elastomer comprising 90 to 20 mole % of ethylene and at least one a-olefin selected from the group consisting of a-olefins having 3 to 12 carbon atoms.

Claim 5

A multilayer oriented film according to Claim 1 or Claim 3, wherein the soft elastomer (B) is a copolymer elastomer having a Vicat softening point of 50°C or lower and a crystallinity of 30 % or lower.

Claim 6

A multilayer oriented film according to Claim 1 or Claim 3, wherein the soft elastomer (B) is a copolymer containing further a small amount of a polyene copolymerized therein in addition to ethylene and a-olefin.

Claim 7

A multilayer oriented film according to Claim 1, Claim 3 or Claim 5, wherein the soft elastomer (B) is a thermoplastic copolymer elastomer having a melt index of 0.1 to 10 and the a-olefin in the soft elastomer (B) is selected from propylene and butene-1.

Claim 8

A multilayer oriented film according to any of the Claims 1 to 6, having a mixed composition with the ratios of respective components satisfying the following relationships: 0.90 > B/(A+B) > 0.05, or 0.90 > B/(B+C) > 0.30, or 0.90 > B/(A+B) > 0.05 and 2.0 > C/(A+B) > 0.05.

Claim 9

A multilayer oriented film according to any of the Claims 1 7, wherein the base layer (M layer) is composed mainly of a mixed composition of (A) + (B) + (C).

Claim 10

A multilayer oriented film according to Claim 1 or Claim 8, wherein the base layer (M layer) contains 1 to 30 wt. % of a carrier (AS agent) in addition to (A) + (B) + (C).

Claim 11

A multilayer oriented film according to Claim 9, wherein the carrier (AS agent) is at least one selected from the group consisting of alicyclic saturated hydrocarbon resins, rosins, petroleum resins, terpene resins, cumarone resins or modified products thereof, atactic polypropylenes (APP), 1,2-polybutadiene, ethylene-vinyl acetate copolymers with high vinyl acetate content.

Claim 12

ll. A multilayer oriented film according to any of the Claims 1 to 10,wherein the base layer contains at least one selected from anti-fogging agents and plasticizers in a total amount of 1 to 10 wt. %.

Claim 13

A multilayer oriented film according to any of the Claims 1 to 1 1,wherein the base layer (M layer) comprises 20 to 90 %, the skin layer (S layer) 5 to 40 % and the core layer (H ! layer) 5 to 40 % of the total thickness, respectively.

Claim 14

A multilayer oriented film according to any of the Claims 1'to 12,consisting of at least five layers of S layer/M la y er/H la y er/M l ayer/S layer.

Claim 15

A multilayer oriented film according to any of the Claims 1 to 12,consisting of at least five layers of S layer/H layer/M layer/H layer/S layer.

Claim 16

1 5. A multilayer oriented film according to any of the Claims 1 14,having a stress on 200 % elongation of 200 to 1,000 g/cm-width as an average value in the longitudinal and transverse directions.

Claim 17

A process for producing an oriented stretchable multilayer oriented film comprising at least three layers of: (1) a base layer (M layer) containing primarily a specific mixed composition selected from the group of polymer compositions consisting of (A) + (B) + (C), (A) + (B) and (B) + (C), (A) being at least one polymer selected from a low density polyethylene, or a copolymer of ethylene with a monomer slected from a vinyl ester monomer, an aliphatic unsaturated mono-carboxylic acid or an alkyl ester of said mono-carboxylic acid the derivatives of said copolymer; (B) being a soft elastomer having a Vicat softening point of 60 °C or lower; (C) being at least one polymer selected from crystalline polypropylenes and crystalline polybutenes-1, at least one such M layer being provided adjacent to the core layer as defined below, (2) a core layer (H layer) as inside layer comprising primarily a polymer selected from (C); and (3) a surface layer ( S layer) containing at least one polymer selected from said polymer (A), soft elastomer (B), crystalline 1,2-polybutadiene or a soft ionomer resin from ethylenic copolymer, said film having a stress on 100 % elongation of from 100 to 600 (g/cm-width) on an average value in the longitudinal and transverse directions, which process comprises melting and kneading the respective resins, extruding through a multilayer die so as to have an arrangement as defined above, quenching the extrudate to prepare a tubular or flat raw film, which film is then subjected to, as such or after heating to 100 °C or lower, to cold stretching to a stretching degree in area ratio of 4-times to 30-times at a stretching temperature within the range of from 30 to 80 °C, followed by shrinkage to 5 to 50 % (area ratio) by heating to a temperature range of from 40 to 90 °C to modify the oriented stress.

Claim 18

A process for producing an oriented stretchable multilayer oriented film comprising at least three layers of: (1) a base layer (M layer) containing primarily a specific mixed composition selected from the group of polymer compositions consisting of (A) + (B) + (C), (A) + (B) and (B) + (C), (A) being at least one polymer selected from a low density polyethylene, or a copolymer of ethylene with a monomer slected from a vinyl ester monomer, an aliphatic unsaturated mono-carboxylic acid or an alkyl ester of said mono-carboxylic acid the derivatives of said copolymer; (B) being a soft elastomer having a Vicat softening point of 60 °C or lower; (C) being at least one polymer selected from crystalline polypropylenes and crystalline polybutenes-1, at least one such M layer being provided adjacent to the core layer as defined below, (2) a core layer (H layer) as inside layer comprising primarily a polymer selected from (C); and (3) a surface layer ( S layer) containing at least one polymer selected from said polymer (A), soft elastomer (B), crystalline 1,2-polybutadiene or a soft ionomer resin from ethylenic copolymer, said film having a stress on 100 % elongation of from 100 to 600 (g/cm-width) on an average value in the longitudinal and transverse directions, which process comprises melting and kneading the respective resins, extruding through a multilayer die so as to have an arrangement as defined above, quenching the extrudate to prepare a tubular or flat raw film, which film is then subjected to, as such or after heating to 100 °C or lower, to cold stretching to a stretching degree in area ratio of 4-times to 30-times at a stretching temperature within the range of from 30 to 80 °C, followed by shrinkage to 5 to 50 % (area ratio) by heating to a temperature range of from 40 to 90 °C to modify the oriented stress.

Claim 19

A process for producing a multilayer oriented film according to Claim 16, wherein the raw film is heated at a temperature of 85 °C or lower and stretching is effected under heating at a temperature of 35 to 70 °C without melting the crystal components of the resins which are the main components for the base layer (M layer), the skin layer (S layer) and the core layer (H layer), respectively.

Claim 20

A process for producing a multilayer oriented film according to Claim 16, wherein the oriented stress is modified by permitting the stretched film to be shrunk to a shrinkage of from 10 to 40 % (area ratio) at a temperature of from 45 to 80 °C.