Biaxially oriented polyethylene film

Claim 2

A biaxially stretched polyethylene film whose main component is a linear low density polyethylene (A) as mentioned below.

Claim 3

A biaxially stretched polyethylene film which is formed from a composition comprising, as main components 100 parts by weight of the sum of 90 to 60 % by weight of a linear low density polyethylene (A) as mentioned below and 10 to 40 % by weight of an ethylene-a-olefin copolymer (B) as mentioned below and 0.5 to 3.0 parts by weight of a surfactant composition (D) as mentioned below.

Claim 4

A biaxially stretched polyethylene film which is formed from a composition comprising, as main components 100 parts by weight of the sum of 90 to 60 % by weight of a linear low density polyethylene (A) as mentioned below and 10 to 40 % by weight of an ethylene-a-olefin copolymer (B) as mentioned below and 0.5 to 3.0 parts by weight of a surfactant composition (D) as mentioned below.

Claim 5

A biaxially stretched polyethylene film which comprises: an intermediate layer formed from a composition comprising, as a main component, a linear low density polyethylene (A) as mentioned below and the innerest layer and the outerest layer formed from a composition comprising, as main components, 100 parts by weight of the sum of 20 to 60 % by weight of an ethylene-a-olefin copolymer (B) as mentioned below and 80 to 40 % by weight of a linear low density polyethylene (C) as mentioned below and 0.5 to 3.0 parts by weight of a surfactant composition (D) as mentioned below; the thickness of the intermediate layer accounting for 60 % of all layers and the thicknesses of the innerest layer and the outerest layer being at least 1 u.m, respectively. (A) a linear low density polyethylene having a density of 0.870 to 0.930 g/cm 3 and a melt flow index of 0.1 to 10 g/10 minutes, and showing, in measurement of a melting point by a differential scanning calorimeter, a main peak temperature (Tma) within the range of 118 ± 5°C in a melting curve obtained when after a temperature of the polyethylene is kept at 190°C for 30 minutes, the temperature is dropped down to 20° C at a cooling rate of 100° C/minute and subsequently raised at a heating rate of 10° C/minute (hereinafter referred to as "melting curve after rapidly cooling") and showing a temperature difference between Tma and Tmb of at least 3°C wherein Tmb is a main peak temperature in a melting curve obtained when after the temperature of the polyethylene is kept at 190°C for 30 minutes, the temperature is dropped down to 20 C at a cooling rate of 10° C/minute and subsequently raised at a heating rate of 10° C/minute (hereinafter referred to as "melting curve after gradually cooling") (lowered melting point polyethylene in rapidly cooling) (B) an ethylene-a-olefin copolymer having a density of 0.870 to 0.900 g/cm 3 , a melt index of 0.1 to 20 g/10 minutes and a melting point according to DSC of 50° to 100°C (low melting point polyethylene copolymer) (C) a linear low density polyethylene having a density of 0.890 to 0.930 g/cm 3 and a melt flow index of 0.1 to 10 g/10 minutes (widely used linear low density polyethylene) (D) a composition comprising at least one surfactant selected from the group consisting of glycerol fatty acid esters, polyglycerol fatty acid esters, sorbitan fatty acid esters, polyethylene glycol fatty acid esters, alkyl diethanol amides, polyoxyethylene alkyl amines and polyoxyethylene alkyl ethers (surfactant composition)

Claim 6

A biaxially stretched polyethylene film which comprises: an intermediate layer formed from a composition comprising, as a main component, a linear low density polyethylene (A) as mentioned below and the innerest layer and the outerest layer formed from a composition comprising, as main components, 100 parts by weight of the sum of 20 to 60 % by weight of an ethylene-a-olefin copolymer (B) as mentioned below and 80 to 40 % by weight of a linear low density polyethylene (C) as mentioned below and 0.5 to 3.0 parts by weight of a surfactant composition (D) as mentioned below; the thickness of the intermediate layer accounting for 60 % of all layers and the thicknesses of the innerest layer and the outerest layer being at least 1 u.m, respectively. (A) a linear low density polyethylene having a density of 0.870 to 0.930 g/cm 3 and a melt flow index of 0.1 to 10 g/10 minutes, and showing, in measurement of a melting point by a differential scanning calorimeter, a main peak temperature (Tma) within the range of 118 ± 5°C in a melting curve obtained when after a temperature of the polyethylene is kept at 190°C for 30 minutes, the temperature is dropped down to 20° C at a cooling rate of 100° C/minute and subsequently raised at a heating rate of 10° C/minute (hereinafter referred to as "melting curve after rapidly cooling") and showing a temperature difference between Tma and Tmb of at least 3°C wherein Tmb is a main peak temperature in a melting curve obtained when after the temperature of the polyethylene is kept at 190°C for 30 minutes, the temperature is dropped down to 20 C at a cooling rate of 10° C/minute and subsequently raised at a heating rate of 10° C/minute (hereinafter referred to as "melting curve after gradually cooling") (lowered melting point polyethylene in rapidly cooling) (B) an ethylene-a-olefin copolymer having a density of 0.870 to 0.900 g/cm 3 , a melt index of 0.1 to 20 g/10 minutes and a melting point according to DSC of 50° to 100°C (low melting point polyethylene copolymer) (C) a linear low density polyethylene having a density of 0.890 to 0.930 g/cm 3 and a melt flow index of 0.1 to 10 g/10 minutes (widely used linear low density polyethylene) (D) a composition comprising at least one surfactant selected from the group consisting of glycerol fatty acid esters, polyglycerol fatty acid esters, sorbitan fatty acid esters, polyethylene glycol fatty acid esters, alkyl diethanol amides, polyoxyethylene alkyl amines and polyoxyethylene alkyl ethers (surfactant composition)

Claim 7

The biaxially stretched polyethylene films of Claims 2 and 3 which are characterized in that said surfactant composition is at least one surfactant selected from the group consisting of polyglycerol fatty acid esters, sorbitan fatty acid esters, polyethylene glycol fatty acid esters and alkyl ethanol amines.

Claim 8

The biaxially stretched polyethylene films of Claims 1 to 3 which are characterized in that the endothermic area within the range of Tma ± 5°C accounts for at lest 15 % of the total endothermic area.

Claim 9

The biaxially stretched polyethylene films of Claims 1 to 3 which are characterized in that a thickness variation is less than 8 %.

Claim 10

The biaxially stretched polyethylene films of Claims 1 to 3 which are characterized in that an area shrinkage is at least 20 % at 90 C.

Claim 11

The biaxially stretched polyethylene films of Claims 2 and 3 which are characterized in that a tensile stress at 50 %-elongation is not more than 500 kg/cm 2 .

Claim 12

The biaxially stretched polyethylene films of Claims 2 and 3 which are characterized in that an elastic restorations after 1 minute from 30 %-elongation in the machine direction and the transverse direction of the film heat-shrinked in an area shrinkage of 15 % at 90 C are at least 90 % respectively.

Claim 13

A process for preparing a biaxially stretched polyethylene film which is characterized in that a composition comprising, as main components, 100 parts by weight of the sum of 90 to 60 % by weight of the above-mentioned linear low density polyethylene (A) and 10 to 40 % weight of the above-mentioned ethylene-a-olefin copolymer (B), and 0.5 to 3.0 parts by weight of the above-mentined surfactant composition (D) is melt-extruded and solidified by rapidly cooling, and the obtained non-stretched film is stretched in a temperature resion where an orientation can be induced by stretching under conditions such that a tensile strength represented by the formula (1) is 30 ≦ S ≦ 170 kgicm 2 Formula (1) S = Q wherein p is an internal pressure of a bubble (kg/cm 2 ), d is an inside diameter of a bubble (cm) and t is a film thickness (cm).

Claim 14

A process for preparing a biaxially stretched polyethylene film which is characterized in that a composition comprising, as main components, 100 parts by weight of the sum of 90 to 60 % by weight of the above-mentioned linear low density polyethylene (A) and 10 to 40 % weight of the above-mentioned ethylene-a-olefin copolymer (B), and 0.5 to 3.0 parts by weight of the above-mentined surfactant composition (D) is melt-extruded and solidified by rapidly cooling, and the obtained non-stretched film is stretched in a temperature resion where an orientation can be induced by stretching under conditions such that a tensile strength represented by the formula (1) is 30 ≦ S ≦ 170 kgicm 2 Formula (1) S = Q wherein p is an internal pressure of a bubble (kg/cm 2 ), d is an inside diameter of a bubble (cm) and t is a film thickness (cm).

Claim 15

A process for preparing a biaxially stretched polyethylene film which is characterized in that a composition comprising, as a main component, the above-mentioned linear low density polyethylene (A) which is to be formed into an intermediate layer and a composition comprising, as main components, 100 parts by weight of the sum of 20 to 60 % by weight of the above-mentioned ethylene-a-olefin copolymer (B) and 80 to 40 % by weight of the above-mentioned linear low density polyethylene (C) and 0.5 to 3.0 parts by weight of the above-mentioned surfactant composition (D) are melt-coextruded so that a thickness of the intermediate layer accounts for at least 60 % of all of the layers and so that thicknesses after post-processing, a stretching step of the innerest layer and the outerest layer are at least 1 µm, respectively and solidified by rapidly cooling, and the obtained non-stretched film is stretched in a temperature resion where an orientation can be induced by stretching under conditions such that a tensile strength represented by the above-mentioned formula (1) is 30 ≦S ≦ 170 kg/ cm 2.

Claim 16

A process for preparing a biaxially stretched polyethylene film which is characterized in that a composition comprising, as a main component, the above-mentioned linear low density polyethylene (A) which is to be formed into an intermediate layer and a composition comprising, as main components, 100 parts by weight of the sum of 20 to 60 % by weight of the above-mentioned ethylene-a-olefin copolymer (B) and 80 to 40 % by weight of the above-mentioned linear low density polyethylene (C) and 0.5 to 3.0 parts by weight of the above-mentioned surfactant composition (D) are melt-coextruded so that a thickness of the intermediate layer accounts for at least 60 % of all of the layers and so that thicknesses after post-processing, a stretching step of the innerest layer and the outerest layer are at least 1 µm, respectively and solidified by rapidly cooling, and the obtained non-stretched film is stretched in a temperature resion where an orientation can be induced by stretching under conditions such that a tensile strength represented by the above-mentioned formula (1) is 30 ≦S ≦ 170 kg/ cm 2.