JPH10119206A - Polyethylene-based multilayer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyethylene-based multilayer film in which blocking resistance and low-temperature heat-sealing properties are excellent and also transparency is excellent. SOLUTION: The polyethylene-based multilayer film is formed of three or more layers consisting of an inner layer, middle layers of at least one layer and an outer layer. The inner layer is formed of high pressure processed low density polyethylene (A) having specified density and MFR and/or straight chainlike low density polyethylene (B). In the middle layers, the middle layer adjacent to at least the inner layer is formed of a low density ethylene-α-olefin copolymer (C) which is obtained by copolymerizing ethylene and 3-20C α-olefin in the existence of a methallocene-based catalyst for olefin polymerization and has specified density and MFR. The outer layer is formed of polyethylene (D) having specified density and MFR. The ratio of layer thickness of the inner layer, the whole middle layer and the outer layer is 1/1.5-10/1-10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene-based multilayer film, and more particularly to a polyethylene-based multilayer film suitably used for applications such as a sealant substrate for a multilayer film and various multilayer film packaging materials.

[0002]

TECHNICAL BACKGROUND OF THE INVENTION A single-layer plastic film
Although it has various advantages, it was not always satisfactory in overall suitability including performance such as sealability, moisture resistance, gas barrier property, heat resistance, cold resistance, and printability.
As an improvement method, two or more single materials are laminated. Multilayer films obtained by such lamination are widely used as packaging films for foods, detergents, pharmaceuticals and the like.

One example of a multilayer film is a polyethylene-based multilayer film. For example, Japanese Patent Publication No. 6-10237
No. 5 discloses a polyethylene-based multilayer film having excellent low-temperature heat sealability and seal stability, and having good rigidity, lubricity, and anti-blocking properties.
90 to 0.910 g / cm ³ of ethylene and 4 carbon atoms
Copolymer layer with α-olefin (seal layer)
And (B) a copolymer layer of ethylene having a density of 0.915 to 0.960 g / cm ³ and an α-olefin having 3 to 20 carbon atoms, and (C) a density of 0.900 to 0.940 g / cm ^3. c
It describes a high-pressure polyethylene of m ³ and / or a polyethylene-based multilayer film laminated via a layer comprising a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms.

However, the density is 0.905 g / cm
^When an ethylene / α-olefin copolymer of ³ or less is used for forming the inner layer (seal layer), the blocking resistance decreases,
Further, if a large amount of an antiblocking agent is added to the ethylene / α-olefin copolymer in order to improve the blocking resistance, there is a problem that the inner layer becomes cloudy and the transparency is deteriorated.

[0005] Therefore, the appearance of a polyethylene-based multilayer film having excellent blocking resistance and low-temperature heat sealability and excellent transparency has been desired.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems associated with the prior art as described above, and to provide a polyethylene-based multilayer film having excellent blocking resistance and low-temperature heat sealability and excellent transparency. It is intended to provide.

[0007]

SUMMARY OF THE INVENTION The polyethylene multilayer film according to the present invention is a multilayer film having three or more layers comprising an inner layer, at least one intermediate layer, and an outer layer, wherein the inner layer has a density of 0.911.
0.925 g / cm ³ and a melt flow rate (ASTM D 1238, 190 ° C., load 2.16 kg) of 1.5 to 1
High-pressure low-density polyethylene (A) and / or linear low-density polyethylene (B) in the range of 0 g / 10 minutes
And at least an intermediate layer of the intermediate layer adjacent to the inner layer includes ethylene and α having 3 to 20 carbon atoms.
-An ethylene / α-olefin copolymer obtained by copolymerizing an olefin with a metallocene-based olefin polymerization catalyst and having a density of 0.860 to 0.905 g /
cm ³ and the melt flow rate (ASTM D 123
It is formed of a low-density ethylene / α-olefin copolymer (C) having a weight of 8,190 ° C and a load of 2.16 kg) in the range of 1.5 to 15 g / 10 minutes.
0.970 g / cm ³ and a melt flow rate (ASTM D 1238, 190 ° C., load 2.16 kg) of 1.5 to 1
It is made of polyethylene (D) in the range of 0 g / 10 minutes, and the ratio of the thickness of the inner layer, the entire intermediate layer, and the thickness of the outer layer is 1 / 1.5 to 10/1 to 10, And

[0008]

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the polyethylene-based multilayer film according to the present invention will be specifically described. The polyethylene-based multilayer film according to the present invention is a multilayer film of three or more layers including an inner layer, one or more intermediate layers, and an outer layer.

Inner Layer The inner layer of the polyethylene-based multilayer film according to the present invention is formed of high-pressure low-density polyethylene (A) and / or linear low-density polyethylene (B).

[High-Pressure Low-Density Polyethylene (A)] The high-pressure low-density polyethylene (A) used in the present invention is a polyethylene produced by subjecting ethylene to high pressure in the presence of a radical polymerization catalyst. Accordingly, a small amount of another vinyl monomer may be copolymerized.

The high-pressure low-density polyethylene (A) used in the present invention has a density (ASTM D 1505) of 0.911 to 0.911.
0.925 g / cm ³ , preferably 0.911 to 0.9
20 g / cm ³ , more preferably 0.911 to 0.9
It is in the range of 15 g / cm ³ . When the high-pressure method low-density polyethylene (A) having a density in the above range is used, a polyethylene-based multilayer film having excellent blocking resistance and low-temperature heat sealability can be obtained. If a small amount of an anti-blocking agent is added to the high-pressure low-density polyethylene (A), a polyethylene-based multilayer film having good transparency and excellent blocking resistance can be obtained.

The density is 2.16 at 190 ° C.
The strand obtained at the time of melt flow rate (MFR) measurement under a kg load is heat-treated at 120 ° C. for 1 hour, gradually cooled to room temperature over 1 hour, and measured with a density gradient tube.

The high-pressure low-density polyethylene (A) has a melt flow rate (MFR; ASTM D 1238,1).
90 ° C, load 2.16 kg) is in the range of 1.5 to 10 g / 10 min, preferably 2.0 to 5.0 g / 10 min. When a high-pressure low-density polyethylene (A) having a melt flow rate within the above range is used, neck-in during molding is reduced, and loss at the ear portion of the film is reduced. Also, high-speed molding can be performed.

[Linear low-density polyethylene (B)] The linear low-density polyethylene (B) used in the present invention is obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms. Can be

Examples of the α-olefin having 3 to 20 carbon atoms used for copolymerization with ethylene include propylene, 1-butene, 1-pentene, 1-hexene and 4-methyl-1-pentene. , 1-octene, 1-decene, 1-dodecene and the like. Among them, those having 4 to 10 carbon atoms
Α-olefins, especially α-olefins having 4 to 8 carbon atoms, are preferred.

The α-olefin as described above can be used alone,
Alternatively, two or more kinds can be used in combination. The linear low-density polyethylene (B) used in the present invention has a constitutional unit derived from ethylene of 50% by weight or more and less than 100% by weight, preferably 75-99% by weight, more preferably 80-95% by weight, particularly preferably Preferably 85 to 95% by weight
And the constituent unit derived from the α-olefin having 3 to 20 carbon atoms is 50% by weight or less, preferably 1 to
Desirably, it is present in an amount of 25% by weight, more preferably 5 to 20% by weight, particularly preferably 5 to 15% by weight.

The composition of the linear low-density polyethylene (B) is usually determined by measuring the ¹³ C-NMR spectrum of a sample obtained by uniformly dissolving about 200 mg of polyethylene in 1 ml of hexachlorobutadiene in a 10 mmφ sample tube at a measuring temperature of 12 mL.
0 ° C, measurement frequency 25.05 MHz, spectrum width 15
00Hz, pulse repetition time 4.2sec., Pulse width 6μ
It is determined by measuring under measurement conditions of sec.

The linear low-density polyethylene (B) used in the present invention has a density of 0.911 to 0.925 g / cm.
³ , preferably 0.911 to 0.920 g / cm ³ , more preferably 0.911 to 0.915 g / cm ³ . When a linear low-density polyethylene (B) having a density within the above range is used, a polyethylene-based multilayer film having excellent blocking resistance and low-temperature heat sealability can be obtained. If a small amount of an antiblocking agent is added to the linear low-density polyethylene (B), a polyethylene-based multilayer film having more excellent blocking resistance can be obtained while maintaining transparency.

The density is measured by the same method as described above. Also, the melt flow rate (MFR; ASTM D 1238,1) of this linear low density polyethylene (B)
90 ° C., load 2.16 kg) is in the range of 1.5 to 10 g / 10 min, preferably 1.5 to 8.0 g / 10 min. When a linear low-density polyethylene (B) having a melt flow rate within the above range is used, a film having excellent transparency and strength can be obtained.

The above-mentioned linear low-density polyethylene (B) can be produced by a conventionally known method, for example, using a Ziegler catalyst under medium to low pressure. [Other components] The high pressure method low density polyethylene (A)
And / or in the linear low density polyethylene (B),
If necessary, conventionally known anti-blocking agent, anti-fogging agent, anti-static agent, anti-oxidant, weather resistance stabilizer, heat stabilizer,
Additives such as lubricants can be blended within a range that does not impair the purpose of the present invention.

Specific examples of the antiblocking agent include natural silica, synthetic silica, zeolite, amorphous zeolite, diatomaceous earth, polyacrylate, polymethacrylate, and the like. Among them, zeolite, amorphous zeolite, natural silica and synthetic silica are preferably used.

The above antiblocking agent is usually used in an amount of 0.1 part by weight based on 100 parts by weight of the high-pressure low-density polyethylene (A) or the linear low-density polyethylene (B), or 100 parts by weight of the total of both components. 01 to 10 parts by weight, preferably 0.01 to 8 parts by weight, more preferably 0.0
It is used in a proportion of 1 to 5 parts by weight.

[0023] Among the intermediate layer of polyethylene-based multilayer film according to the intermediate layer present invention, the intermediate layer adjacent to at least the inner layer, the low density ethylene · alpha-olefin copolymer weight prepared by using a metallocene olefin polymerization catalyst It is formed by uniting (C).

[Low Density Ethylene / α-Olefin Copolymer (C)] The low density ethylene / α-olefin copolymer (C) used in the present invention can be obtained by adding ethylene to a metallocene-based olefin polymerization catalyst. Low-density ethylene / α-olefin copolymer (C1) or long-chain branched low-density ethylene / α-olefin random copolymer obtained by copolymerizing α-olefin having 3 to 20 carbon atoms Copolymer
(C2). As the low-density ethylene / α-olefin copolymer (C), a linear low-density ethylene / α-olefin copolymer (C1) and a long-chain branched low-density ethylene / α-olefin random copolymer (C2 ) Can be used in combination.

Examples of the α-olefin having 3 to 20 carbon atoms used for copolymerization with ethylene include propylene, 1-butene, 1-pentene, 1-hexene and 4-methyl-1-pentene. , 1-octene, 1-decene, 1-dodecene and the like. Among them, those having 3 to 10 carbon atoms
Α-olefins, especially α-olefins having 4 to 8 carbon atoms, are preferred.

The α-olefin as described above is used alone,
Alternatively, two or more kinds can be used in combination. The low-density ethylene / α-olefin copolymer (C) used in the present invention contains 50% by weight of structural units derived from ethylene.
Not less than 100% by weight, preferably 75 to 99% by weight,
More preferably 75 to 95% by weight, particularly preferably 8%
Present in an amount of 3 to 95% by weight;
-Not more than 50% by weight of structural units derived from olefins,
Preferably 1 to 25% by weight, more preferably 5 to 25%
Desirably, it is present in an amount of 5% by weight, particularly preferably 5 to 17% by weight.

The low-density ethylene α- used in the present invention
The olefin copolymer (C) has a density of 0.860 to 0.8.
905 g / cm ³ , preferably 0.880 to 0.905
g / cm ³ , more preferably 0.885 to 0.901
g / cm ³ . When the intermediate layer adjacent to the inner layer is formed of the low-density ethylene / α-olefin copolymer (C) having the density in the above range, the sealing property at the time of sealing is improved.

The density is measured by the same method as described above. Also, the low-density ethylene / α-olefin copolymer (C) has a melt flow rate (MFR; AS
TM D 1238, 190 ° C, load 2.16 kg) is 0.5 to 10 g /
It is in the range of 10 minutes, preferably 1.0 to 8.0 g / 10 minutes. When a low-density ethylene / α-olefin copolymer (C) having a melt flow rate within the above range is used, a film having excellent low-temperature heat sealability and excellent high-speed bag-making properties can be obtained.

Of the above low-density ethylene / α-olefin copolymers (C), linear low-density ethylene / α-olefin copolymers
The α-olefin copolymer (C1) is disclosed in, for example,
724, JP-A-6-136195, JP-A-6-136196, JP-A-6-207057, etc., containing a metallocene catalyst component, in the presence of a so-called metallocene-based olefin polymerization catalyst And ethylene and an α-olefin having 3 to 20 carbon atoms.

Such a metallocene-based catalyst generally contains at least one ligand having a cyclopentadienyl skeleton.
Metallocene catalyst component (a1) comprising a transition metal compound of Group IVB of the periodic table, organoaluminum oxy compound catalyst component (b), particulate carrier (c), and, if necessary, organoaluminum compound catalyst component (d ), An ionized ionic compound formed from the catalyst component (e).

As the metallocene catalyst component (a1) preferably used in the present invention, there is a transition metal compound of Group IVB of the periodic table having at least one ligand having a cyclopentadienyl skeleton. Examples of such a transition metal compound include a transition metal compound represented by the following general formula [I].

ML ¹ _x ... [I] In the formula, x is the valence of the transition metal atom M. M is a transition metal atom selected from Group IVB of the periodic table, and specifically, zirconium, titanium, and hafnium. Among them, zirconium is preferred.

L ¹ is a ligand which coordinates to the transition metal atom M, and at least one of these ligands L ¹
Is a ligand having a cyclopentadienyl skeleton.
As the ligand L ¹ having a cyclopentadienyl skeleton coordinated to the transition metal atom M as described above, specifically,
Examples thereof include an alkyl-substituted cyclopentadienyl group such as a cyclopentadienyl group, an indenyl group, a 4,5,6,7-tetrahydroindenyl group, and a fluorenyl group.
These groups may be substituted with a halogen atom, a trialkylsilyl group or the like.

When the compound represented by the above general formula [I] contains two or more groups having a cyclopentadienyl skeleton, two of the groups having a cyclopentadienyl skeleton are connected to each other by ethylene, propylene or the like. An alkylene group,
They may be bonded via a silylene group or a substituted silylene group such as a dimethylsilylene group, a diphenylsilylene group, or a methylphenylsilylene group.

As the organoaluminum oxy compound catalyst component (b), aluminoxane is preferably used. Specifically, methylaluminoxane, ethylaluminoxane, methylethylaluminoxane having a repeating unit represented by the formula -Al (R) O-, wherein R is an alkyl group, is usually about 3 to 50. Are used.

The particulate carrier (c) used in the preparation of the catalyst for olefin polymerization is an inorganic or organic compound and has a particle size of usually about 10 to 300 μm, preferably 20 to 200 μm. Solid.

As the inorganic carrier, a porous oxide is preferable. Specifically, SiO ₂ , Al ₂ O ₃ , MgO, Zr
O ₂ and TiO ₂ can be exemplified. Specific examples of the organoaluminum compound catalyst component (d) used as necessary in the preparation of the olefin polymerization catalyst include trialkylaluminums such as trimethylaluminum, dialkylaluminum halides such as dimethylaluminum chloride, and methylaluminum sesquichloride. And the like can be exemplified.

Examples of the ionized ionic compound catalyst component (e) include triphenylboron, MgCl ₂ , and Al described in US Pat. No. 5,321,106.
Lewis acids such as ₂ O ₃ and SiO ₂ —Al ₂ O ₃ ; ionic compounds such as triphenylcarbenium tetrakis (pentafluorophenyl) borate; carborane compounds such as dodecaborane and bis-n-butylammonium (1-carbedodeca) borate Is mentioned.

The linear low-density ethylene / α-olefin copolymer (C1) used in the present invention can be used in the presence of the above-mentioned olefin polymerization catalyst in the form of a gas phase, a slurry, or a solution. It can be obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms under various conditions in a liquid phase.

The long-chain branched ethylene / α-olefin random copolymer (C2) used in the present invention is prepared by reacting ethylene and carbon atoms in the presence of a metallocene-based olefin polymerization catalyst containing a specific metallocene compound. Α of Equations 3 to 20
-It can be prepared by random copolymerization with an olefin.

The metallocene olefin polymerization catalyst used here is not particularly limited except that it contains a metallocene catalyst component. For example, the following metallocene catalyst component (a2) and the above-mentioned organic aluminum oxy compound catalyst component ( b) and / or the ionized ionic compound catalyst component (e). Further, it may be formed from the metallocene catalyst component (a2) and the organic aluminum compound catalyst component (d) together with the organic aluminum oxy compound (b) and / or the ionized ionic compound catalyst component (e).

Examples of the metallocene catalyst component (a2) include compounds represented by the following general formula [II].

[0043]

Embedded image

In the formula, M is a transition metal atom of Group IVB of the periodic table, and specifically, titanium, zirconium,
Hafnium, particularly preferably zirconium. R ¹ is a hydrocarbon group having 1 to 6 carbon atoms.

R ² , R ⁴ , R ⁵ and R ⁶ may be the same or different and are each a hydrogen atom, a halogen atom or a hydrocarbon group having 1 to 6 carbon atoms similar to R ¹ . R ³ is an aryl group having 6 to 16 carbon atoms.
This aryl group has a halogen atom and a carbon atom number of 1 to 20.
May be substituted with a hydrocarbon group or an organic silyl group.

X ¹ and X ² are a hydrogen atom, a halogen atom, a hydrocarbon group having 1 to 20 carbon atoms, an oxygen-containing group or a sulfur-containing group. Y is a group having 1 to 20 carbon atoms.
A divalent hydrocarbon group, a divalent halogenated hydrocarbon group having 1 to 20 carbon atoms, a divalent silicon-containing group, a divalent germanium-containing group, and the like.

Such metallocene compounds are available from Journal
of Organometallic Chem. 288 (1985), pp. 63-67, European Patent Application Publication No. 0,320,762.

The ethylene / α-olefin random copolymer (C) obtained by the production method described in the above literature
2) is characterized in that the molecular weight distribution and the composition distribution are narrow, and there is a long chain branch, so that the melt tension is large.

[Other components] The above low-density ethylene α
-If necessary, additives such as conventionally known antiblocking agents, antifogging agents, antistatic agents, antioxidants, weather stabilizers, heat stabilizers and lubricants are added to the olefin copolymer (C). Can be blended within a range that does not impair the object of the present invention.

The specific examples and the amounts of the above antiblocking agents are the same as the specific examples and the amounts of the above antiblocking agents. When there are two or more intermediate layers, the intermediate layers other than the intermediate layer adjacent to the inner layer are resins having excellent transparency such as high-pressure low-density polyethylene and linear low-density polyethylene. It can be formed as long as it is not damaged.

Outer Layer The outer layer of the polyethylene-based multilayer film according to the present invention is formed of polyethylene (D).

The polyethylene (D) used in the present invention includes, for example, low density, medium density and high density ethylene homopolymers, low density, medium density and high density ethylene / α-olefin copolymers (the above high pressure And a linear low-density polyethylene (including the linear low-density polyethylene (B)). These polyethylenes can be used alone or in combination of two or more.

The polyethylene (D) used in the present invention
Has a density of 0.911 to 0.970 g / cm ³ , preferably 0.911 to 0.930 g / cm ³ , and more preferably 0.911 to 0.925 g / cm ³ .
When polyethylene (D) having a density in the above range is used,
A polyethylene-based multilayer film having excellent rigidity can be obtained.

The density of the polyethylene (D) is measured by the same method as described above. The polyethylene (D) has a melt flow rate (MFR; ASTM D 123).
8,190 ° C, load 2.16kg) is 0.01-10g / 10
Min, preferably in the range of 0.01 to 6 g / 10 min.
When polyethylene (D) having a melt flow rate within the above range is used, a film having excellent neck-in during molding and high-speed moldability can be obtained.

The polyethylene (D) having the above properties can be prepared by a conventionally known method for producing polyethylene. [Other components] Addition of conventionally known anti-blocking agents, anti-fogging agents, anti-static agents, anti-oxidants, weather stabilizers, heat stabilizers, lubricants and the like to the polyethylene (D) as necessary. Agents can be added within a range that does not impair the purpose of the present invention.

Specific examples of the antiblocking agent are as described above. The above antiblocking agent is used in an amount of usually 0.1 to 20 parts by weight, preferably 1 to 20 parts by weight, more preferably 5 to 20 parts by weight, based on 100 parts by weight of polyethylene (D). .

Multilayer Film In the polyethylene-based multilayer film according to the present invention,
The ratio of the thickness of each of the inner layer, the entire intermediate layer and the outer layer (inner layer /
Intermediate layer / outer layer) is 1 / 1.5 to 10/1 to 10,
Preferably it is 1 / 1.5 to 10/1 to 5.

The thickness of each layer of the polyethylene-based multilayer film varies depending on the specific application, but the thickness of the inner layer is usually 1 to 20 μm, preferably 1 to 10 μm, more preferably 1 to 5 μm. The thickness of the entire intermediate layer is usually 1.5 to 50 μm, preferably 1.5 to 30 μm.
μm, more preferably in the range of 5-30 μm, the thickness of the outer layer is usually 1-50 μm, preferably 1-30 μm
m, more preferably in the range of 3 to 30 μm, and the total thickness of these layers is usually 5 to 100 μm, preferably 10 to 60 μm, more preferably 20 to 60 μm.
m.

For example, when the total thickness of the multilayer film of three or more layers is 30 μm, examples of the thickness of the inner layer / the whole intermediate layer / the outer layer are 5 μm / 10 μm / 15 μm or 5 μm / 15 μm / 10 μm or 3 μm / 24 μm /
An example of a combination of 3 μm is given.

The polyethylene-based multilayer film according to the present invention can be heat-sealed at 100 ° C. using the inner layer as a sealing layer. Preparation of multilayer film The polyethylene-based multilayer film according to the present invention is a polyethylene-based resin used in each layer and the components such as the above-described additives are mixed as necessary, and then, water-cooled or air-cooled coextrusion inflation method, Alternatively, it can be prepared by laminating an inner layer, an intermediate layer and an outer layer by a casting method.

The polyethylene-based multilayer film according to the present invention as described above can be used for applications such as a sealant substrate for a multilayer film and various multilayer film packaging materials.
When using this multilayer film, the inner layer is used as a sealing surface.

When the polyethylene-based multilayer film according to the present invention is used as a sealant substrate for a multilayer film, an adhesive is applied to the surface of the outer layer, and the outer layer is pressed and laminated with another film. This lamination method is a so-called dry lamination method. Examples of the “other film” include plastic films such as polyamide, polyethylene terephthalate, polybutylene terephthalate, polypropylene, polyvinyl chloride, and polystyrene, aluminum foil, and paper.

[0063]

Industrial Applicability The polyethylene-based multilayer film according to the present invention has excellent blocking resistance and excellent transparency. Further, the polyethylene-based multilayer film according to the present invention is excellent in low-temperature heat-sealing properties, and can be heat-sealed at 100 ° C. using the inner layer as a sealing layer.

Therefore, the above-mentioned effects are obtained.
The polyethylene-based multilayer film according to the present invention is suitable for applications such as a sealant substrate for a multilayer film and various multilayer film packaging materials.

[0065]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

The multilayer films obtained in Examples and Comparative Examples were tested for low-temperature heat sealability (complete sealing temperature), transparency (haze), surface gloss (gloss), and blocking resistance (blocking strength). Was performed according to the following method. <Test Method> (1) Low Temperature Heat Sealability (Complete Seal Temperature) In accordance with JIS Z 1707, a peel test was performed while changing the heat seal temperature. In this test, the lowest heat-sealing temperature at which the heat-sealed portion was broken was defined as the complete sealing temperature. (2) Transparency (Haze) The haze, which is an index of the transparency of the film, is ASTM D
It was measured according to 1003. (3) Surface gloss (gloss) The gloss which is an index of the surface gloss of the film is ASTM.
It was measured according to D 523. (4) Blocking resistance (blocking strength) The blocking strength was measured in the following manner according to ASTM D1893-67.

In a constant temperature room at 50 ° C., a length of 150 mm × a width of 2
Two 00mm test pieces are superimposed and 10k
g / cm ² , left for 1 day, and then depressurized. Using a crosshead moving speed constant-type tensile tester (manufactured by Instron Co., Ltd.) on which a jig having a separation rod was set, M
The test piece blocked at 200 mm / min in the direction D was separated. The blocking strength (gf / cm) was determined by dividing the value (g) obtained by subtracting the weight of the film from the force required to separate the film by the width (cm) of the test piece. The resins and additives used in the examples and comparative examples are as follows. Linear low-density polyethylene (B) (1) Linear ethylene / 4-methyl-1-pentene copolymer (B-1) ・ Catalyst used in the production: Ziegler olefin polymerization catalyst ・ Ethylene content : 90% by weight · Density: 0.921 g / cm ³ · MFR (ASTM D 1238, 190 ° C, load 2.16 kg): 2.0
g / 10 minutes (2) Linear ethylene / 4-methyl-1-pentene copolymer (B-2) ・ Catalyst used in production: Ziegler-based olefin polymerization catalyst ・ Ethylene content: 87% by weight ・Density: 0.915 g / cm ³ · MFR (ASTM D 1238, 190 ° C, load 2.16 kg): 2.0
g / 10 minutes Low-density ethylene / α-olefin copolymer (C) (1) Low-density ethylene / 1-octene copolymer (C-1) ・ Catalyst used in production: Catalyst for metallocene olefin polymerization ethylene content: 80 wt% - ^{density: 0.895g / cm 3 · MFR (} ASTM D 1238,190 ℃, load 2.16 kg): 4.0
g / 10 minutes polyethylene (D) (1) Linear ethylene / 1-hexene copolymer (D-1) ・ Catalyst used in the production: catalyst for metallocene olefin polymerization ・ Ethylene content: 93% by weight ・Density: 0.928 g / cm ³ · MFR (ASTM D 1238, 190 ° C, load 2.16 kg): 1.8
g / 10 minutes Antiblocking agent (1) 90:10 weight ratio mixture of natural silica and linear ethylene / 4-methyl-1-pentene copolymer (B-1) (AB-10) slip agent ( 1) Erucamide and linear ethylene 4-methyl-1-
Mixture (SQ-3) of 97: 3 weight ratio with pentene copolymer (B-1)

[0068]

Examples 1 to 6 and Comparative Examples 1 to 9 Inner layer (seal layer)
The above-mentioned linear ethylene / 4-methyl-1-pentene copolymer (B-1) as a resin for forming, the above low-density ethylene / 1-octene copolymer (C-1) as a resin for forming an intermediate layer, and formation of an outer layer Using the above-mentioned linear ethylene / 1-hexene copolymer (D-1) as the resin for molding, a three-layer film having a layer constitution shown in Table 1 was molded by a water-cooled inflation molding method under the following conditions. . [Water-cooled inflation molding conditions] Molding machine: Water-cooled three-layer machine made by Placo Die diameter: 150 mm φ Lip width: 2.5 mm Molding temperature: 160 ° C Folding width: 220 mm Cooling water temperature: 25 ° C Sizing height: 350 mm Table 1 shows the physical properties of the film thus obtained.

[0069]

[Table 1]

[0070]

[Table 2]

[0071]

[Table 3]

Claims (1)

[Claims] 1. A multilayer film comprising at least three layers comprising an inner layer, at least one intermediate layer, and an outer layer, wherein said inner layer has a density in the range of 0.911 to 0.925 g / cm ³ , Rate (ASTM D 1238, 190 ℃, load 2.
16 kg) is made of high-pressure low-density polyethylene (A) and / or linear low-density polyethylene (B) in the range of 1.5 to 10 g / 10 minutes, and at least the inner layer of the intermediate layer The adjacent intermediate layer is an ethylene / α-olefin copolymer obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms in the presence of a metallocene-based olefin polymerization catalyst,
The density is in the range of 0.860 to 0.905 g / cm ³ and the melt flow rate (ASTM D 1238, 190 ° C, load 2.
16 kg) is formed of a low-density ethylene / α-olefin copolymer (C) in the range of 1.5 to 15 g / 10 minutes, and the outer layer has a density of 0.911 to 0.970 g / cm ^3. Melt flow rate (ASTM D 1238, 190 ℃, load 2.
16 kg) is formed of polyethylene (D) in the range of 1.5 to 10 g / 10 minutes, and the thickness ratio of the inner layer, the entire intermediate layer, and the outer layer is 1/1.
A polyethylene-based multilayer film having a ratio of 5-10 / 1 to 10.