JPH09136389A - Multilayer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To makes it possible to heat seal and to incorporate the performance of excellent low-temperature flexing resistance and heat resistance in a multilayer film. SOLUTION: This multilayer film comprises both outer layers containing ethylene and 3-12C α-olefin and containing ethylene-α-olefin copolymer (a) and having a density of 0.915 to 0.945g/cm<3> , a melt flow rate of 0.1 to 20g/10min, and the highest melting peak temperature by a differential scanning calorimeter of 110 deg.C or higher, and an intermediate layer having a density of 0.880 to 0.920g/cm<3> , a melt flow rate of 0.5 to 20g/10min, and number-average-molecular- weight measured by a GPC method of 50,000 to 150,000 and containing ethylene-α-olefin copolymer (b).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a multi-layer film having at least three layers. More specifically, the present invention relates to a multilayer film composed of at least three layers, which is excellent in low temperature bending resistance and heat resistance.

[0002]

2. Description of the Related Art Most of packaging materials are ethylene resins such as polyethylene, ethylene / α-olefin copolymers, ethylene / vinyl acetate copolymers and ionomers because of their excellent heat-sealing property and hot tack property. Is used as a heat seal layer. However, these films have some problems. For example, the ethylene-vinyl acetate copolymer has poor heat resistance and oil resistance, and the ethylene / α-olefin copolymer has poor heat resistance in the low density region and poor low temperature bending resistance in the high density region. To compensate for these drawbacks, multi-layer or mixed methods are used. For example, Japanese Examined Patent Publication No. 4-59140 discloses a multi-layer film consisting of at least three layers having a density of 0.900 to 0.940 g / cm ^{3 and} a linear ethylene / α-olefin copolymer of 10 to 95% by weight, and A layer composed of a resin composition prepared by mixing 1 to 30 parts by weight of a low crystalline α-olefin copolymer with 100 parts by weight of a resin mixture composed of 90 to 5% by weight of high-density polyethylene as an intermediate layer, and a linear chain Disclosed is a multi-layered film in which both outer layers are layers made of an ethylene / α-olefin copolymer and / or an ethylene-based polymer having a density of 0.900 to 0.940 g / cm ^{3 made} of a high-pressure low-density polyethylene. . However, this multilayer film is not satisfactory in cold resistance such as low temperature bending resistance.

Also, several laminated films have been proposed for the same purpose as a packaging material made of only a polyolefin resin. For example, Japanese Examined Patent Publication (Kokoku) No. 3-213343 discloses a resin composition obtained by mixing 100 parts by weight of high-density polyethylene and 10 to 200 parts by weight of an ethylene-α-olefin copolymer in a multilayer film composed of at least three layers. Is disclosed as a middle layer, and at least one of both outer layers made of an ethylene-α-olefin copolymer is a layer made of a resin composition containing a high-pressure polyethylene, and a multilayer film is disclosed. ,
Although it has excellent heat resistance and heat sealability, it is not satisfactory in low temperature bending resistance. In addition, Japanese Patent Publication No. 62-10532 relating to a single layer film, ethylene.
A composition containing an α-olefin copolymer and a low-crystallinity ethylene / α-olefin copolymer has proposed a film having excellent flex resistance, but it was not sufficiently satisfactory in heat resistance. .

When used as a food packaging material, mechanical strength such as impact strength, tensile strength and tear strength,
In addition to rigidity, low temperature heat sealability and hot tack, food hygiene is required. In order to satisfy the performance required for materials at present with the diversification of packaging forms,
In many cases, the ethylene polymer is laminated on another suitable film. For example, films such as stretched polyamide and polyethylene terephthalate are often used as a base material for packaging materials, but strength, rigidity, heat resistance, and
Although it is excellent in many aspects such as gas barrier property and safety and hygiene property, it has a defect that heat seal property is inferior. On the other hand, the polyolefin-based resin film has a good heat-sealing property by itself, but is inferior to the above-mentioned base film in terms of strength, rigidity and heat resistance. In general,
These laminating methods are used to complement the drawbacks of both.

[0005]

DISCLOSURE OF THE INVENTION The present invention is intended to provide a multilayer film suitable for various packaging materials such as food packaging materials, and more specifically, a multilayer film excellent in low temperature bending resistance and heat resistance. The aim is to get a film.

[0006]

Means for Solving the Problems As a result of intensive studies to solve these problems, the present inventors have found that in a multilayer film composed of at least three layers, a specific ethylene
By laminating a layer containing an α-olefin copolymer as both outer layers and a layer containing a specific ethylene / α-olefin copolymer different from the above as an intermediate layer, low temperature bending resistance and heat resistance can be obtained. It was found that a multi-layer film having excellent properties can be obtained, and the present invention was completed.

That is, the present invention provides a multi-layer film comprising at least three layers with ethylene and 3 to 12 carbon atoms.
Of α-olefin, and has a density of 0.915 to 0.94
5 g / cm ³ , melt flow rate 0.1 to 20 g / 1
0 min, the maximum melting peak temperature by differential scanning calorimeter was 11
It is 0 ° C or higher and the amorphous content at 100 ° C is 0.
Ethylene / α-olefin copolymer (a) having 8 or less
The layer containing is both outer layers, ethylene and carbon number 3-12
Composed of α-olefins with a density of 0.880 to 0.92
0 g / cm ³ , melt flow rate 0.5 to 20 g / 1
0 minutes, the number average molecular weight measured by GPC method is 50,
000 to 150,000, and the molecular weight distribution represented by the ratio of weight average molecular weight / number average molecular weight is 1.8 to 3.
0, the maximum melting peak temperature by differential scanning calorimeter is 50 ℃
Ethylene / α- observed in the range above 110 ° C
It is intended to provide a multi-layer film having a layer containing the olefin copolymer (b) as an intermediate layer.
Hereinafter, the present invention will be described in detail.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An ethylene / α-olefin copolymer (a) is used as both outer layers constituting the multilayer film of the present invention. The ethylene / α-olefin copolymer (a) is a copolymer composed of ethylene and an α-olefin having 3 to 12 carbon atoms. As the α-olefin, specifically, propylene, butene-1, pentene-
1,4-methylpentene-1, hexene-1, heptene-1, octene-1, nonene-1, decene-1, dodecene-1, etc., and mixtures thereof may be mentioned. Of these, α-olefins having 3 to 8 carbon atoms such as propylene, butene-1, 4-methylpentene-1, hexene-1, 4-methylhexene-1, octene-1 are preferable. Further, carbon number of 6 such as hexene-1 and octene-1
The α-olefin of 8 is more preferable. The content of α-olefin in the ethylene / α-olefin copolymer is 1 to 20.
Preferably it is mol%.

The production of the ethylene / α-olefin copolymer (a) for both outer layers is not particularly limited, and generally ethylene and α-olefin are used to contain at least a transition metal by an ionic polymerization method. In the presence of a solid catalyst component and a co-catalyst component consisting of an organoaluminum compound, the temperature is usually 30 to 300 ° C. and normal pressure to 3000 kg.
/ Cm ² , in the presence or absence of solvent, gas-solid, liquid-
It is polymerized and produced in a solid or homogeneous liquid phase.

Examples of the solid catalyst component containing a transition metal include titanium compounds such as chromium oxide, molybdenum oxide, titanium trichloride, titanium tetrachloride, titanium tetrachloride-alkylaluminum and titanium tetrachloride-magnesium chloride compounds. A magnesium compound- (alkyl chloride) alkylaluminum compound and the like can be mentioned. Examples of the organoaluminum compound are represented by the general formula R ′ _m AlX _3-m (wherein R ′ is a hydrocarbon group, X is halogen, and 1 ≦ m ≦ 3), and (C ₂ H ₅ ) ₂ AlCl, (C _{4
H 9) 2 AlCl, (C} 6 H 13) 2 AlCl, (C 2 H 5) 1.
₅ AlCl _1.5 , (C ₄ H ₉ ) _1.5 AlCl _1.5 , (C ₆
H ₁₃ ) _1.5 AlCl _1.5 , C ₂ H ₅ AlCl ₂ , C ₄ H ₉
AlCl ₂ , C ₆ H ₁₃ AlCl _{2 and the} like can be mentioned.

An ethylene / α-olefin copolymer (b) is used as the intermediate layer constituting the multilayer film of the present invention. The ethylene / α-olefin copolymer (b) is a copolymer composed of ethylene and an α-olefin having 3 to 12 carbon atoms. As an α-olefin,
The same ones as those used for the ethylene / α-olefin copolymer (a) of both outer layers are used. Further, the content of α-olefin contained in the copolymer is preferably 1 to 40 mol%.

In the production of the ethylene / α-olefin copolymer (b) used as the intermediate layer constituting the multilayer film of the present invention, the presence of a metallocene catalyst or a Ziegler catalyst is generally carried out by a coordination ionic polymerization method. Under normal temperature of 30 to 300 ° C., normal pressure to 3000 kg /
cm ² , in the presence or absence of solvent, gas-solid, liquid-
It is manufactured under a solid or homogeneous liquid phase.

The metallocene compound may be a composite catalyst system of a compound having a specific structure containing a transition metal and an organoaluminum compound, and the Ziegler catalyst may be a composite catalyst system of a vanadium compound and an organoaluminum compound.

The metallocene catalyst is represented by the general formula R ¹ _k
R ² _l R ³ _m R ⁴ _n M (wherein M is zirconium, titanium, hafnium or vanadium, R ¹ is a group having a cycloalkadienyl skeleton, and R ² , R ³ and R ⁴ are cycloalkaline). A group having a dienyl skeleton, an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom or hydrogen, and k and l are integers of 1 or more, m or n
Is 0 or more and k + l + m + n = 4. ), Specifically, a catalyst system composed of a compound mainly containing a transition metal compound containing a ligand having a cycloalkadienyl skeleton and an organoaluminum oxide compound.

Examples of the transition metal compound containing a ligand having a cycloalkadienyl skeleton include bis (cyclopentadienyl) diethyl zirconium, bis (pentamethylcyclopentadienyl) zirconium and bis (cyclopentadienyl). Dichlorozirconium, bis (cyclopentadienyl) monochloride monohydride, bis (indenyl) zirconium monochloride monohydride, bis (indenyl) zirconium dichloride,
Ethylenebis (indenyl) dimethylzirconium, ethylenebis (indenyl) methylzirconium chloride, ethylenebis (indenyl) zirconium dichloride, ethylenebis (4,5,6,7-tetrahydro-1)
-Indenyl) zirconium dichloride, ethylenebis (4,5,6,7-tetrahydro-1-indenyl) dimethylzirconium, ethylenebis (4-methyl-1-)
Examples thereof include indenyl) zirconium dichloride and ethylenebis (2,3-dimethyl-1-indenyl) zirconium dichloride. Among these, biscyclopentadienyldimethyl zirconium and bispentadienyl zirconium dichloride are preferable.

Examples of the organic aluminum oxide compound include tetramethyldialuminoxane, tetraethyldiaminoxane, tetrabutyldialuminoxane, tetrahexyldialuminoxane, methylaluminoxane, ethylaluminoxane, butylaluminoxane and hexylaluminoxane. Of these, methylaluminoxane is preferable.

Compound of vanadium compound and organoaluminum
As a vanadium compound in a catalyst system consisting of
Is, for example, the general formula VO (OR)_nX_3-n(However, R is charcoal
A hydrogen halide group, X is a halogen, and a number of 0 ≦ n ≦ 3 is shown. )
, VOCl_Three, VO (OCH_Three) Cl_Two, VO
(OCH_Three)_TwoCl, VO (OCH_Three)_Three , VO (OC_Two H
_Five) Cl_Two, VO (OC_Two H_Five)_Two Cl, VO (OC_Two H_Five)
_Three , VO (OC_Three H₇) Cl _Two, VO (OC_Three H₇)_Two C
l, VO (OC_Three H₇)_Three , VO (OisoC_Three H₇) Cl
_Two, VO (OisoC_Three H₇)_TwoCl, VO (OisoC
_Three H₇)_Three, Or a mixture thereof. this
Of these compounds, compounds represented by 0 ≦ n ≦ 1 are particularly
preferable.

Examples of the organic aluminum compound include
General formula R '_mAlX_3-m(However, R'is a hydrocarbon group, X
Represents a halogen and a number 1 ≦ m ≦ 3. ),
(C _Two H_Five)_Two AlCl, (C_Four H₉)_Two AlCl, (C₆ 
H₁₃)_TwoAlCl, (C_Two H_Five) _1.5 AlCl_1.5, (C_Four 
H₉)_1.5 AlCl_1.5, (C₆ H₁₃)_1.5AlCl_1.5,
C_Two H_Five AlCl_Two, C_Four H₉ AlCl_Two, C₆ H₁₃A
lCl_TwoAnd the like. More preferred in the present invention
In order to exert the effect, 1 ≦ m ≦ 2 is satisfied.
, Especially (C_Two H_Five)_1.5 AlCl_1.5Is preferred.

Further, by combining a halogenated ester with a catalyst system comprising these vanadium compound and organoaluminum compound, an ethylene / α-olefin copolymer having a narrower molecular weight distribution and a uniform composition distribution can be obtained. it can. The halogenated ester is represented by the general formula R "COOR '" (where R "is an organic group obtained by substituting a part or all of hydrogen atoms of a hydrocarbon group having 1 to 20 carbon atoms with halogen, R". Is a hydrocarbon group having 1 to 20 carbon atoms), and is preferably a compound in which all the substituents of R "are chloro substituted, such as perchlor crotonic acid ester. Is ethyldichloroacetate, methyltrichloroacetate, ethyltrichloroacetate, methyldichlorophenylacetate, ethyldichlorophenylacetate, methylperchlorcrotonate, ethylperchlorcrotonate,
Examples thereof include propyl perchlor crotonate, isopropyl perchlor crotonate, phenyl perchlor crotonate, and the like.

The ethylene / α-olefin copolymer (a) of both outer layers constituting the multilayer film of the present invention has a density in the range of 0.915 to 0.945 g / cm ³ , and a density of 0.915 g / cm ^3. If it is less than ³ cm ³ , the amorphous content exceeds 0.8, the heat resistance is lowered, and the performance which is not satisfactory for the purpose of the present invention cannot be obtained. On the other hand, when it exceeds 0.945 g / cm ³ , the low temperature bending resistance of the obtained multilayer film is deteriorated.

The ethylene / α-olefin copolymer (b) of the intermediate layer of the present invention has a density of 0.880 to 0.920 g.
/ Cm ³ , preferably 0.885 to 0.910 g / cm
^When the density is in the range of ³ and the density is less than 0.880 g / cm ³ , the n-hexane soluble content of the finally obtained multilayer film increases, which causes food hygiene problems and lacks heat resistance. The properties of the multilayer film are not satisfactory. On the other hand, when it exceeds 0.920 g / cm ³ , the low temperature bending resistance of the obtained multilayer film deteriorates.

Further, the melt flow rate (MFR) of the ethylene / α-olefin copolymer in both the outer layer and the intermediate layer constituting this multilayer film is measured by the method specified in Condition 4 of Table-1 of JIS-K7210. To be done. The MFR of the ethylene / α-olefin copolymer (a) in both outer layers is in the range of 0.1 to 20 g / 10 minutes. MFR is 0.1
When it is less than g / 10 minutes, in order to obtain the multilayer film of the present invention, the pressure of the extruder is increased during the extrusion process, and the extrusion processability is significantly reduced, while the MFR is 20 g / 1.
If it exceeds 0 minutes, take-up surging tends to occur during extrusion processing, which is not preferable in terms of film-forming property, and the flex resistance of the obtained multilayer film decreases.

The MFR of the ethylene / α-olefin copolymer (b) in the intermediate layer is 0.5 to 20 g / 10 minutes, G
The number average molecular weight measured by the PC method is 50,000-
150,000. When the MFR is less than 0.5 g / 10 min or the number average molecular weight is more than 150,000, an extruder resin is used when the finally obtained composition is extruded to obtain the multilayer film of the present invention. The pressure becomes large and the extrudability is deteriorated. On the other hand, MFR is 20g
/ 10 minutes or a number average molecular weight of 50,000
When it is less than 0, take-off surging is likely to occur during extrusion processing, which is not preferable in terms of film-forming property, and inferior bending resistance cannot be obtained as a satisfactory multilayer film. Furthermore, GP of ethylene / α-olefin copolymer (b)
The molecular weight distribution represented by the ratio of weight average molecular weight / number average molecular weight measured by the C method is 1.8 to 3.0. If this value is less than 1.8, molding will be difficult due to an increase in motor load during extrusion molding, and if it exceeds 3.0, molding processability will improve, but satisfactory heat seal strength and hot tack strength will be obtained. I can't.

The maximum melting peak temperature of the ethylene-α-olefin copolymer is obtained by measuring the calorific value of fusion based on JIS K7122 using a Perkin Elmer 7 type DSC device (differential scanning calorimeter). The measuring method conforms to K7121 3- (2). In the ethylene / α-olefin copolymer (a) of the outermost layer, the temperature of the highest melting peak among the one or more endothermic peaks present in the endothermic curve determined by the above method is 110 ° C. or higher, preferably Present above 115 ° C.
It is particularly preferable that the number of endothermic peaks is plural.

It is also important that the ethylene / α-olefin copolymer (a) has an amorphous fraction at 100 ° C. of 0.8 or less. The amorphous content at 100 ° C. is calculated by the following formula. F = (Fa) + {([Delta] H100 / [Delta] Hs) * (1-Fa)} where F: Amorphous fraction at 100 [deg.] C. Fa = 1-([Delta] Hs / [Delta] Hu): Amorphous fraction at 40 [deg.] C [Delta] Hs: Sample Heat of fusion (J / g) ΔH100: Cumulative heat of fusion at a temperature of 100 ° C (J / g
g) ΔHu: heat of fusion of polyethylene equilibrium crystal (292.
9 J / g) If the maximum peak temperature of the endothermic peaks is less than 110 ° C. or if the amorphous fraction exceeds 0.8, the heat resistance is poor,
When a four-sided sealed bag in which two films are stacked is subjected to high-temperature filling, which is generally performed for the purpose of sterilization, heat fusion occurs between the films, resulting in poor filling suitability and poor bending resistance.

In the ethylene / α-olefin copolymer (b) of the intermediate layer of the present invention, it is the temperature of the highest melting peak among the endothermic peaks present in one or a plurality of endothermic curves determined by the above method. , The temperature is more than 50 ℃ 110 ℃
It is important to exist below. Preferably 60 to 1
It is in the range of 08 ° C, more preferably 75 to 105 ° C. The number of endothermic peaks may be plural, but it is particularly preferable that only one is present.

In order to produce the multilayer film of the present invention, the technique of the coextrusion method can be generally used by using an inflation film production apparatus or a T die film production apparatus.

The outer layers of the ethylene / α-olefin copolymer constituting the multilayer film of the present invention have a thickness of 2 to
It is 30μ. The thickness of the intermediate layer is preferably 0.5 to 20 times, especially 2 to 10 times the total thickness of both outer layers.

The multi-layer film of the present invention utilizes the outstanding balance of low temperature bending resistance, heat resistance and mechanical properties, rigidity, etc., and is laminated with other base materials to provide a gas barrier property. It is also possible to obtain a box film.

The substrate to be laminated with the multilayer film of the present invention can be selected from any polymer capable of forming a film. Examples of the polymer capable of forming a film include nylon 6, nylon 66, nylon 11,
Polyamide resin such as nylon 12, polyethylene terephthalate, polyester resin such as polybutylene terephthalate, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, polyethylene, ethylene / vinyl acetate copolymer, ethylene / methacrylic acid Ester copolymer, ethylene / acrylic acid ester copolymer,
Gas barriers from ethylene / methacrylic acid copolymer, ethylene / acrylic acid copolymer, polyolefin resin such as ionomer, polyvinylidene chloride, polyvinyl chloride, polystyrene, polyvinyl alcohol, ethylene / vinyl alcohol copolymer, etc. , Printability,
It can be selected in consideration of transparency, rigidity, adhesiveness and the like according to the purpose of forming the composite film. The substrate may be uniaxially or biaxially stretched when the substrate is stretchable, particularly when the properties of the film are improved by stretching such as polyamide resin, polyester resin, polypropylene and the like.

As a method for producing a laminated film obtained by laminating the multilayer film of the present invention and the above-mentioned substrate, known methods such as a dry laminating method, an extrusion laminating method and a sand laminating method can be adopted. It is also possible to laminate nylon having a gas barrier property or an ethylene / vinyl alcohol copolymer by a coextrusion method.

In the outer layer and the intermediate layer containing the ethylene / α-olefin copolymer constituting the multilayer film of the present invention, a metal such as calcium stearate is added, if necessary, in order to further improve the physical properties of the multilayer film. Neutralizers such as soap and hydrotalcite, 2,6-
Di-t-butyl-p-cresol (BHT), tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane (IRGA
NOX 1010) and n-octadecyl-3- (4'-
A phenolic stabilizer represented by hydroxy-3,5'-di-t-butylphenyl) propionate (IRGANOX 1076), bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite and tris (2). , 4-di-t-butylphenyl) phosphite and the like, phosphite-based stabilizers, lubricants typified by higher fatty acid amides and higher fatty acid esters, and having 8 to 8 carbon atoms.
An antistatic agent such as glycerin ester of 22 fatty acid, sorbitan acid ester, polyethylene glycol ester, and an antiblocking agent typified by silica, calcium carbonate, talc, and the like are added.

[0033]

Hereinafter, the present invention will be described based on examples.
The present invention is not limited to these examples.

First, methods for measuring physical property values in the following examples and comparative examples will be described. (1) Density (d) According to the method specified in JIS K6760. 100
After annealing for 1 hour in water at ℃, the density was measured. Annealing was not performed for the density of the copolymer (b) of 0.910 or less. (2) Melt flow rate (MFR) According to the method specified in JIS K6760. (3) Maximum melting peak temperature (Tm) For the measurement, a differential scanning calorimeter (DSC) DSC-7 manufactured by Perkin Elmer was used. About 10 mg of a test piece cut out from a sheet with a thickness of about 0.5 mm prepared by hot pressing was put in a sample pan for DSC measurement, and 150 ° C. in DSC.
Was pre-melted for 5 minutes, the temperature was lowered to 40 ° C. at 5 ° C./minute, the temperature was kept for 5 minutes, and then the temperature was raised to 150 ° C. at a rate of 5 ° C./minute to obtain a thermogram. When there are multiple melting peaks, the highest value was taken as the highest melting peak temperature.

(4) Amorphous fraction F. C. Stehling and P.M. Meka,
J. Appl. Polym. Sci. , 51, 105
Based on the method described in the literature of (1994), the maximum melting peak temperature was determined to be 100 using a thermogram.
The amorphous content at ° C was calculated by the following formula. F = (Fa) + {([Delta] H100 / [Delta] Hs) * (1-Fa)} where F: Amorphous fraction at 100 [deg.] C. Fa = 1-([Delta] Hs / [Delta] Hu): Amorphous fraction at 40 [deg.] C [Delta] Hs: Sample Heat of fusion (J / g) ΔH100: Cumulative heat of fusion (J / g) at a temperature of 100 ° C. ΔHu: Heat of fusion of polyethylene equilibrium crystals (292.
9 J / g)

(5) Low-temperature flex resistance It was measured as follows based on ASTM F392-74 (1987). Sample (282.6mm x 220m
m) is attached to a fixed head having a diameter of 88.9 mm and an operating head (a head-to-face distance of 177.8 mm), and the operating head has a stroke of 152.4 mm. 6mm straight ahead,
A reciprocal twisting motion was applied in an atmosphere of −30 ° C. for 5000 times at a speed of 40 times / min. A solution prepared by dissolving 0.4% methylene blue in a 10% ethyl alcohol aqueous solution was applied onto a sample placed on a filter paper with a roller, and spots of methylene blue generated on the filter paper were counted and used as a pinhole number. A large number of pinholes indicates poor low temperature bending resistance.

(6) Heat resistance Two sheets of film were stacked and heated using a heat sealer manufactured by Tester Sangyo Co., Ltd. under the conditions of a seal bar width of 10 mm, a sealing surface pressure of 1.0 kg / cm ² and a heating time of 120 seconds. The temperature of the seal bar was changed by 5 ° C. and heated in the same manner. From this, a test piece with a width of 15 mm was cut out in a direction perpendicular to the heating surface, and 200 mm was cut using a Shopper type tensile tester.
The 180 ° peel strength was measured at a speed of mm / min. The heat resistance is such that the peel strength measured under the above conditions is 0.2 kg /
The minimum temperature (heat fusion development temperature) when the width exceeds 15 mm is shown. The higher this temperature is, the better the heat resistance is, and it is preferably 100 ° C. or higher. The following were used as the samples used in this example.

Both outer layers: ethylene / α-olefin copolymer (a) (1) copolymer 1 ethylene-1-butene random copolymer (d = 0.91)
9 g / cm ³ , MFR = 0.8 g / 10 min, Tm = 12
2 ° C.) (2) Copolymer 2 Ethylene-1-hexene random copolymer (d = 0.9
25 g / cm ³ , MFR = 0.8 g / 10 minutes, Tm = 1
22 ° C.) (3) Copolymer 3 Ethylene-1-hexene random copolymer (d = 0.9
25 g / cm ³ , MFR = 0.5 g / 10 min, Tm = 1
21 ° C.) (4) Copolymer 4 Ethylene-1-hexene random copolymer (d = 0.9
12 g / cm ³ , MFR = 0.8 g / 10 minutes, Tm = 1
17 ° C.) In the above ethylene / α-olefin copolymer, copolymer 1 was produced by a gas phase polymerization method using a solid Ziegler-Natta catalyst. Copolymers 2 to 4 were produced by a high pressure ionic polymerization method using a similar catalyst.

Intermediate layer: ethylene / α-olefin copolymer (b) (1) Copolymer 5 Ethylene-1-hexene random copolymer (d = 0.9)
06 g / cm ³ , MFR = 1.9 g / 10 minutes, Tm = 9
6 ° C., Mn = 97,000, Mw / Mn = 2.1) (2) Copolymer 6 Ethylene-1-butene random copolymer (d = 0.89)
5 g / cm ³ , MFR = 1.7 g / 10 min, Tm = 84
C, Mn = 98200, Mw / Mn = 2.0) (3) Copolymer 7 Ethylene-1-hexene random copolymer (d = 0.8)
95 g / cm ³ , MFR = 1.7 g / 10 min, Tm = 8
4 ° C., Mn = 98200, Q = 2.0) (4) Copolymer 8 Ethylene-1-butene random copolymer (d = 0.88)
7 g / cm ³ , MFR = 0.6 g / 10 min, Tm = 72
C, Mn = 120,000, Mw / Mn = 2.0) (5) Copolymer 9 Ethylene-1-butene random copolymer (d = 0.90)
9 g / cm ³ , MFR = 2.0 g / 10 min, Tm = 11
9 ° C., Mn = 72800, Mw / Mn = 3.7) In the above ethylene / α-olefin copolymer, copolymers 5, 7 and 8 are vanadium-based homogeneous catalysts, and copolymer 6 is a metallocene-based catalyst. Was produced by a solution polymerization method. Copolymer 9 uses a solid Ziegler-Natta catalyst,
It was produced by a high pressure ionic polymerization method.

Examples 1 to 5 and Comparative Examples 1 to 5 Samples constituting both outer layers and intermediate layers shown in Tables 1 to 3 were manufactured by Placo Co. having an extruder of 50 mmφ3 units, a die diameter of 150 mmφ and a die slit width of 2.0 mm. Blow-up ratio (BU
R) A multilayer film having a thickness of 2.5 and a thickness of 80 μm was formed. The molding temperature is 190 ° C when the MFR of the sample is in the range of 0.5 to 1.2, and 16 when the MFR of the sample is in the range of 1.7 to 3.
It was set to 0 ° C. The evaluation results are shown in Tables 1 to 3.

Comparative Examples 6 to 10 Pellets of each copolymer shown in Tables 4 and 5 were mixed with a tumble mixer to prepare samples. The processing conditions were the same as in Example 1 except that the extruding ratio of each layer was an outer layer / intermediate layer / inner layer = 1/2/1, and a type 1 three-layer 80 μ film was used. The evaluation results are shown in Tables 4 and 5.

[0042]

[Table 1] ─────────────────────────────────── Example 1 Example 2 Example 3 Example 3 4 ─────────────────────────────────── Both outer layers Copolymer (a) Copolymer 1 Copolymer Polymer 2 Copolymer 3 Copolymer 2 Density g / cm ³ 0.919 0.925 0.925 0.925 MFR g / 10 min 0.8 0.8 0.5 0.8 Maximum melting peak temperature ℃ 122 122 121 122 Amorphous fraction% 0.74 0.68 0.67 0.68 Thickness μ 20 20 10 10 ───────────────────────── ─────────── Intermediate layer Copolymer (b) Copolymer 5 Copolymer 6 Copolymer 5 Copolymer 7 Density g / cm ³ 0.906 0.895 0.906 0 .895 MFR g / 10 min 1.9 1 7 1.9 1.7 Mn 97000 98200 97000 98200 Mw / Mn 2.1 2.0 2.1 2.0 Maximum melting peak temperature ℃ 96 84 96 84 Number of peaks by DSC 1 1 1 1 1 Thickness μ 40 40 60 60 ─────────────────────────────────── Number of pinholes 22 21 18 15 Heat resistance ℃ 109 117 117 117 117 ───────────────────────────────────

[0043]

[Table 2] ─────────────────────────────────── Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 ─────────────────────────────────── Both outer layers Copolymer (a) Copolymer 3 Copolymer Polymer 4 Copolymer 1 Copolymer 2 Density g / cm ³ 0.925 0.912 0.919 0.925 MFR g / 10 min 0.5 0.8 0.8 0.8 0.8 Maximum melting peak temperature ℃ 121 117 122 122 Amorphous fraction% 0.67 0.84 0.74 0.68 Thickness μ 5 20 80 80 ───────────────────────── ─────────── Intermediate layer Copolymer (b) Copolymer 8 Copolymer 5 None None Density g / cm ³ 0.887 0.906 ─── ─── MFR g / 10 Min 0.6 1.9 ─── ─── Mn 120,000 97000 ─────── Mw / Mn 2.0 2.1 ────── Maximum melting peak temperature ℃ 72 96 ─────── Number of peaks by DSC 11 1 ─────── Thickness μ 70 40 ────────────────────────────────────────── Number of pinholes 9 10 38 60 Heat resistance ℃ 115 90 90 109 117 ────────────────────────────────────

[0044]

[Table 3]

[0045]

[Table 4] ───────────────────────────── Comparative Example 6 Comparative Example 7 Comparative Example 8 ───────── ───────────────────── Copolymer (a) Copolymer 1 Copolymer 2 Copolymer 3 Density g / cm ³ 0.919 0.925 0.925 MFR g / 10 min 0.8 0.8 0.5 Maximum melting peak temperature ℃ 122 122 121 121 Amorphous fraction% 0.74 0.68 0.67 Blending amount Weight part 50 50 60 Copolymer ( b) Copolymer 5 Copolymer 6 Copolymer 7 Density g / cm ³ 0.906 0.895 0.895 MFR g / 10 min 1.9 1.7 1.7 Mn 97000 98200 98200 Mw / Mn 2 1 2.0 2.0 Maximum melting peak temperature ℃ 96 84 84 Number of peaks by DSC 1 1 1 Compounding amount Weight part 50 50 40 Mixture Density g / cm ³ 0.913 0.910 0.909 MFR g / 10min 1.3 1.2 0.90 Thickness μ 80 80 80 ──────────────────── ────────── Number of pinholes 25 7 3 Heat resistance ℃ 95 82 93 93 ─────────────────────────── ──

[0046]

[Table 5]

[0047]

As described above in detail, according to the present invention, it is possible to provide a multilayer film which can be heat-sealed and has excellent low temperature bending resistance and heat resistance. Further, the multilayer film of the present invention is particularly suitable for packaging liquid foods such as vinegar, liquor and soy sauce, and liquid fertilizers. Furthermore, the multilayer film of the present invention is also most suitable for bag-in-box.

Claims (4)

[Claims] 1. A multilayer film comprising at least three layers, comprising ethylene and an α-olefin having 3 to 12 carbon atoms, having a density of 0.915 to 0.945 g / cm ³ , and a melt flow rate of 0.1 to 20 g / 10. And a layer containing the ethylene / α-olefin copolymer (a) having a maximum melting peak temperature of 110 ° C. or higher by a differential scanning calorimeter and an amorphous fraction at 100 ° C. of 0.8 or less. The outer layer is composed of ethylene and an α-olefin having 3 to 12 carbon atoms, has a density of 0.880 to 0.920 g / cm ³ , a melt flow rate of 0.5 to 20 g / 10 minutes, and a number average molecular weight measured by a GPC method. Is 50,000 to 150,000
0, the molecular weight distribution represented by the ratio of weight average molecular weight / number average molecular weight is 1.8 to 3.0, and the maximum melting peak temperature by a differential scanning calorimeter is observed in the range of 50 ° C or higher and lower than 110 ° C. A multi-layer film comprising a layer containing an ethylene / α-olefin copolymer (b) as an intermediate layer. 2. An ethylene / α-olefin copolymer (b)
2. The multilayer film according to claim 1, wherein only one endothermic peak by the differential scanning calorimeter is present. 3. An ethylene / α-olefin copolymer (b)
Is obtained by polymerizing in the presence of a metallocene catalyst. 4. A multilayer film according to claim 1, which is for a bag-in-box.