JP2002210895A - Easily tearable composite film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easily tearable composite film which is excellent in balance among impact resistance, transparency, heat-seal properties, and easy tearability, can be processed to make a bag as a packaging material for food, etc., makes hygienic packaging possible, and can be opened easily by being pulled horizontally by weak force. SOLUTION: In the composite film, the first layer of linear low density polyethylene (A), the second layer of an ionomer resin (B), and the third layer of the linear low density polyethylene resin (A) are laminated in turn. The linear low density polyethylene which forms the first and third layers is an ethylene-α-olefin copolymer prepared by using a metallocene catalyst for polymerizing olefins and has a density of 0.905-0.950 g/cm3 and a melt flow rate of 0.5-4.0 g/10 min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easily tearable (composite) film having good impact resistance and excellent tearability and suitable for use in tear-open packaging bags such as outer bags.

[0002]

2. Description of the Related Art Conventionally, when packaging an article with a film, the film is heat-sealed. At that time, it is known to use a film in which a heat seal layer made of a polyolefin-based thermoplastic resin such as polyethylene becomes a surface layer.

In such packaging, it is necessary that the film and the joint between the films have sufficient strength so as not to be broken at the time of distribution, but at the same time, conflicting performances that the film can be easily opened by hand are required. Is done. For example, in the case of food packaging materials, especially packaging materials for confectionery bags such as crackers, the heat-sealed portion of the packaging material is pulled open by hand, but if the heat-sealing strength is high, it becomes difficult to open. However, if the heat seal strength is too low, it cannot be used as a packaging material. Therefore, in a bag-like packaging material, it is required to appropriately control the heat sealing strength. Conventionally, high-density polyethylene is used as a resin for forming a thin film or forming a second layer (intermediate layer) of a three-layer laminated film. A method using a resin is employed.

[0004] However, the film obtained by such a method is not yet sufficient in terms of balance of impact resistance, transparency, heat sealability and easy tearability. Therefore, the present inventors have studied diligently, and used linear low-density polyethylene produced by gas phase polymerization using a metallocene-based olefin polymerization catalyst as a resin for forming the first and third layers, In addition, they have found that by using an ionomer resin as the resin for forming the second layer, a composite film having an excellent balance of impact resistance, transparency, heat sealability and tearability can be obtained. Reached.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an easily tearable composite film which is suitably used as a material for various packaging materials and has an excellent balance of impact resistance, transparency, heat sealability and tearability. I have.

[0006]

SUMMARY OF THE INVENTION The easily tearable composite film according to the present invention comprises a first layer composed of a linear low-density polyethylene (A), a second layer composed of an ionomer resin (B), and a linear low-density polyethylene. The third layer made of the resin (A) is a composite film laminated in this order, and the linear low-density polyethylene (A) forming the first layer and the third layer is a metallocene-based olefin polymerization catalyst. Is an ethylene / α-olefin copolymer prepared using
TM D 1505) is 0.905 to 0.950 g / cm ³ , and has a melt flow rate (MFR; ASTM D 1238,190).
C., load 2.16 kg) is 0.5 to 4.0 g / 10 min.

[0007] The linear low-density polyethylene (A) is
(I) Endotherm measured by differential scanning calorimeter (DSC)
Temperature (Tm (° C)) and density at the maximum peak position in the curve
(D (g / cm^Three)) Satisfies the relationship expressed by Tm <400 × d−248, and (ii) n-decane at room temperature.
Soluble component amount ratio (W (% by weight)) and density (d (g / cm^Three ))
When MFR ≦ 10 g / 10 min, W <80 × exp (−100 (d−0.88)) + 0.1 When MFR> 10 g / 10 min, W <80 × (MFR-9)^0.26× exp (−100 (d−
0.88)) + 0.1 is preferably satisfied.

Such a linear low-density polyethylene (A) satisfies the above-mentioned relationships (i) and (ii), and further has (iii) a melt tension at 190 ° C. (MT (g)); Melt flow rate (MFR (g / 1
0 minutes)) satisfies the relationship expressed by MT ≦ 2.2 × MFR− ^0.84 , and (iv) 190 ° C. of the molten polymer.
The fluidity index (F) defined by the shear rate when the shear stress reaches 2.4 × 10 ⁶ dyne / cm ² at
I (1 / sec)) and the melt flow rate (MFR (g / 1)
0 minutes)) and a linear low-density polyethylene (A) satisfying the relationship of FI <75 × MFR.
1) and (i) and (ii), and (v) the melt tension at 190 ° C. (MT
(g)) and melt flow rate (MFR (g / 10 minutes))
Is a linear low-density polyethylene (A) satisfying the relationship expressed by MT> 2.2 × MFR- ^0.84.
2) is preferred.

[0009] When more excellent moldability is required, linear low-density polyethylene (A2) is suitable. Above all, while satisfying the above-mentioned relationships (i), (ii) and (v), (vi) the melt polymer at 190 ° C.
The fluidity index (F) defined by the shear rate when the shear stress reaches 2.4 × 10 ⁶ dyne / cm ² at
I (1 / sec)) and the melt flow rate (MFR (g / 1)
0 min)) is particularly suitable for the linear low-density polyethylene satisfying the relationship of FI> 75 × MFR.

In the composite film according to the present invention, the first layer and / or the third layer comprising the linear low-density polyethylene (A) has a tensile stress at break (ASTM D 638) of usually 20 to 20.
It is 45 MPa.

[0011]

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the easily tearable composite film according to the present invention will be specifically described. The easily tearable composite film according to the present invention comprises a first layer composed of a linear low-density polyethylene (A), a second layer composed of an ionomer resin (B), and a linear low-density polyethylene (A). Are laminated in this order.

In this specification, when a packaging bag is prepared, the inner surface layer of the composite film is referred to as an inner layer, the outer surface layer is referred to as an outer layer, and the first layer of the composite film is referred to as an inner layer. The layer is referred to as an outer layer, and the second layer is referred to as an intermediate layer. First Layer and Third Layer The first layer (inner layer) and the third layer (outer layer) constituting the surface layer of the easily tearable composite film according to the present invention are formed from linear low-density polyethylene (A). I have.

The linear low density polyethylene (A) used in the present invention is obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms in the presence of a metallocene olefin polymerization catalyst. It is an ethylene / α-olefin copolymer. As the α-olefin having 3 to 20 carbon atoms used for copolymerization with ethylene, specifically,
Propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene and the like. Among these, those having 3 to 1 carbon atoms
Zero 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 linear low-density polyethylene (A) 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 75-95% by weight, particularly Preferably 83 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 25% by weight, particularly preferably 5 to 17% by weight.

The composition of the linear low-density polyethylene is usually about 200 mg of the copolymer in a sample tube of 10 mmφ per meter.
of a sample uniformly dissolved in 1 l of hexachlorobutadiene
^{The 13} C-NMR spectrum is determined by measuring at a measurement temperature of 120 ° C., a measurement frequency of 25.05 MHz, a spectrum width of 1500 Hz, a pulse repetition time of 4.2 sec., And a pulse width of 6 μsec.

The linear low-density polyethylene (A) used in the present invention usually has a density (d; ASTM D 1505) of 0.9.
05 to 0.950 g / cm ³ , preferably 0.910 to 0.950 g / cm ³
0.940 g / cm ³ , more preferably 0.915 to
It is in the range of 0.930 g / cm ³ . Also, the melt flow rate (MF) of this linear low density polyethylene (A)
R; ASTM D 1238, 190 ° C, load 2.16 kg) is usually 0.5
To 4.0 g / 10 min, preferably 1.0 to 3.0 g / 1
0 minutes, more preferably in the range of 1.0 to 2.0 g / 10 minutes.

The linear low-density polyethylene (A) used in the present invention has the following properties: (i) the temperature (T) at the maximum peak position in an endothermic curve measured by a differential scanning calorimeter (DSC);
m (° C.)) and density (d (g / cm ³ )) are Tm <400 × d-248, preferably Tm <450 × d-296, more preferably Tm <500 × d-343, and particularly preferably Tm < 550 × d-392, and (ii) n-decane soluble component content ratio (W (% by weight)) and density (d (g / cm ³ )) at room temperature
When MFR ≦ 10 g / 10 min, W <80 × exp (−100 (d−0.88)) + 0.1, preferably W <60 × exp (−100 (d−
0.88)) + 0.1 more preferably W <40 × exp (−100 (d−
0.88)) + 0.1 When MFR> 10 g / 10 min, W <80 × (MFR-9) ^0.26 × exp (−100 (d−
0.88)) + 0.1 is preferably satisfied.

The linear low-density polyethylene (A) satisfying the above-mentioned relationship (i) has a lower Tm with respect to the density. Therefore, when compared to a low-density polyethylene having the same density but not satisfying this relationship, Excellent heat sealability.
The relationship between the temperature (Tm) at the maximum peak position of the endothermic curve measured by a differential scanning calorimeter (DSC) and the density (d),
Then, it can be said that the linear low-density polyethylene (A) in which the n-decane soluble component amount ratio (W) and the density (d) have the above relationship has a narrow composition distribution.

The maximum peak position temperature (Tm) in an endothermic curve measured by a differential scanning calorimeter (DSC)
(° C)), about 5 mg of a sample was packed in an aluminum pan, and 10 ° C /
The temperature is raised to 200 ° C. in minutes, the temperature is maintained at 200 ° C. for 5 minutes, then the temperature is lowered to room temperature at 10 ° C./min, and then determined by an endothermic curve when the temperature is raised at 10 ° C./min. The measurement is performed using a DSC-7 device manufactured by PerkinElmer.

The amount (W) of the n-decane-soluble component at room temperature was determined for the sample (ethylene / α-olefin copolymer).
After adding about 3 mg to 450 ml of n-decane and dissolving at 145 ° C., the solution was cooled to 23 ° C. (room temperature), and then filtered to remove the n-decane insoluble portion in the filtrate.
It is determined by collecting the decane-soluble part, dividing the weight of the n-decane-soluble part by the weight of the first sample, and multiplying the obtained value by 100.

The ethylene / α-olefin copolymer (A) described above is disclosed in, for example, JP-A-9-183816, JP-A-9-235424, and JP-A-9-235.
426, JP-A-10-195263, JP-A-10-182866, JP-A-10-19337
7, JP-A-9-95572, JP-A-10-95572
JP-A-251334, JP-A-10-251335, Japanese Patent Application No. 10-58636, and Japanese Patent Application No. 10-58636.
In the presence of a so-called metallocene-based olefin polymerization catalyst containing a metallocene catalyst component described in the specification of Japanese Patent No.
And α-olefins.

Such a metallocene olefin polymerization catalyst is usually a metallocene catalyst component comprising a transition metal compound of Group IVB of the Periodic Table having at least one ligand having a cyclopentadienyl skeleton; It is formed from a compound catalyst component and, if necessary, a carrier, an organoaluminum compound catalyst component, and an ionized ionic compound catalyst component.

For details of the metallocene olefin polymerization catalyst and the method for producing the ethylene / α-olefin copolymer (A), see, for example, JP-A-9-183816, JP-A-9-235424, and 235
426, JP-A-10-195263, JP-A-10-182866, JP-A-10-19337
7, JP-A-9-95572, JP-A-10-95572
JP-A-251334, JP-A-10-251335, Japanese Patent Application No. 10-58636, and Japanese Patent Application No. 10-58636.
-370575.

In the present invention, among the above-mentioned linear low-density polyethylenes (A), while satisfying the above-mentioned relationships (i) and (ii), further, (iii) the melt tension at 190 ° C. (MT (g) ) And melt flow rate (MFR)
(g / 10 minutes)) and the relationship MT ≦ 2.2 × MFR ^−0.84 is satisfied, and (iv) 190 ° C. of the molten polymer
The fluidity index (F) defined by the shear rate when the shear stress reaches 2.4 × 10 ⁶ dyne / cm ² at
I (1 / sec)) and the melt flow rate (MFR (g / 1)
0 minutes)) and a linear low-density polyethylene (A) satisfying the relationship of FI <75 × MFR.
1) and (i) and (ii), and (v) the melt tension at 190 ° C. (MT
(g)) and melt flow rate (MFR (g / 10 minutes))
Is a linear low-density polyethylene (A) satisfying the relationship expressed by MT> 2.2 × MFR- ^0.84, more preferably MT> 2.5 × MFR- ^0.84.
2) is preferably used.

Particularly when more excellent moldability is required, a linear low-density polyethylene (A2) having a long chain branch is suitable. Among them, while satisfying the above-mentioned relationships (i), (ii) and (v), (vi) the shear stress of the molten polymer at 190 ° C. is 2.4 × 10 ⁶
The flowability index (FI (1 / sec)) defined by the shear rate when reaching dyne / cm ² and the melt flow rate (MFR (g / 10 min)) are: FI> 75 × MFR A linear low-density polyethylene satisfying the relationship of FI> 80 × MFR is particularly suitable.

The above-mentioned melt tension (MT) is determined by measuring the stress when the molten polymer is stretched at a constant speed. That is, the measurement of the melt tension (MT) is performed by using granulated pellets of the copolymer as a measurement sample,
Using an MT measuring device manufactured by Toyo Seiki Seisaku-sho, resin temperature 190 ° C., extrusion speed 15 mm / min, winding speed 10
~ 20m / min, nozzle diameter 2.09mmφ, nozzle length 8
mm.

The liquidity index (FI (1 /
Seconds)), the shear stress at 190 ° C. is 2.4 × 10 ⁶ d
It is determined by extruding the sample from the capillary while changing the shear rate when reaching yne / cm ² , and measuring the rate corresponding to a predetermined stress. That is, using a capillary flow characteristic tester manufactured by Toyo Seiki Seisaku-sho, Ltd., the resin temperature was 190 ° C., and the shear stress range was 5 × 10 ^{4 to} 3 × 10 ^6.
It is measured at about dyne / cm ² . The measurement is performed by changing the nozzle diameter as follows according to the MFR (g / 10 minutes) of the sample to be measured.

When MFR> 10 0.7 mm When 10 ≧ MFR> 3 1.0 mm When 3 ≧ MFR> 0.8 2.0 mm When 0.8 ≧ MFR ≧ 0.1 3.0 mm In the present invention Is that the linear low-density polyethylene (A) forming the first layer and the linear low-density polyethylene (A) forming the third layer may be completely the same or may have different physical properties. It may be a low density polyethylene (A).

The above linear low-density polyethylene (A1)
Are disclosed in, for example, JP-A-9-183816,
In the presence of a so-called metallocene-based olefin polymerization catalyst containing a metallocene catalyst component described in JP-A-235424 and the like, ethylene and α- having 3 to 20 carbon atoms are used.
It can be produced by copolymerizing with an olefin.

The linear low-density polyethylene (A)
2) is described in, for example, JP-A-9-235426, JP-A-10-195263, and JP-A-10-18286.
6, JP-A-10-193377, JP-A-9
-95572, JP-A-10-251334, JP-A-10-251335, Japanese Patent Application No. 10-5
In the presence of a so-called metallocene-based olefin polymerization catalyst containing a metallocene catalyst component described in Japanese Patent Application No. 8636 and Japanese Patent Application No. 10-370575, ethylene and α having 3 to 20 carbon atoms are used. -It can be produced by copolymerizing with an olefin.

The first layer (inner layer) and the third layer (outer layer) constituting the easily tearable composite film according to the present invention comprise:
Since it is formed from the above-mentioned metallocene linear low-density polyethylene (A), it is excellent in transparency, heat sealability and tearability. In the linear low-density polyethylene (A) used in the present invention, if necessary,
Conventionally known additives such as an anti-blocking agent, an antistatic agent, an antioxidant, a weather resistance stabilizer, a heat stabilizer, and a lubricant can be blended within a range that does not impair the object of the present invention.

Second Layer The second layer constituting the easily tearable composite film according to the present invention.
The layer (intermediate layer) is formed from the ionomer resin (B). Ionomer resin (B) used in the present invention
Is a thermoplastic resin having an olefin as a main component and obtained by introducing an ionic bond (crosslinking) between long chains, for example, copolymerizing ethylene and (meth) acrylic acid to obtain Na,
It is a resin obtained by crosslinking with metal ions such as K, Mg and Zn. Such an ionomer resin (B) is commercially available, for example, under the trade name of Surlyn.

Since the second layer constituting the easily tearable composite film according to the present invention is formed of the ionomer resin (B), it has excellent transparency and elasticity, and
It has excellent interlayer adhesion with the first and third layers made of the linear low-density polyethylene resin (A). In the ionomer resin (B) used in the present invention, if necessary, conventionally known additives such as an antiblocking agent, an antistatic agent, an antioxidant, a weather resistance stabilizer, a heat stabilizer, and a lubricant may be added. It can be blended within a range that does not impair the object of the invention.

Composite Film The easily tearable composite film according to the present invention comprises a first layer composed of the above-mentioned linear low density polyethylene (A), a second layer composed of the ionomer resin (B), and a linear low density polyethylene (A). And a third layer made of high density polyethylene (A). The thickness of the easily tearable composite film according to the present invention is not particularly limited, but is usually 60 to 120 μm. The first layer (inner layer) and the second layer
The thickness ratio between the layer (intermediate layer) and the third layer (outer layer) is usually
4: 3: 4 to 4: 12: 4.

The easily tearable composite film according to the present invention has a tensile stress at break (ASTM D 638) of the first layer and / or the third layer comprising linear low density polyethylene (A) of 30 to 45 MPa. Is preferred. The composite film according to the present invention has an Elmendorf tear strength (ASTM D 1922) of usually 100 in the TD direction (lateral direction).
~ 200 N / cm, the dart impact strength (A
STM D 1709) is usually 800 g or more, and haze (ASTM
D1330) is usually 20% or less.

Preparation of Composite Film The easily tearable composite film according to the present invention can be prepared by a conventionally known method. For example, a linear low density polyethylene (A), an ionomer resin (B) and a linear It can be prepared by coextruding with low density polyethylene (A), joining and cooling.

[0037]

The easily tearable composite film according to the present invention comprises a first layer comprising a metallocene linear low density polyethylene (A) having a specific density and MFR, and a second layer comprising an ionomer resin (B). Layer and a third layer made of a metallocene linear low-density polyethylene (A) specially having a density and MFR, so that it has impact resistance, transparency, heat sealability and easy tearability. Excellent balance. Therefore, bag making can be performed as a packaging material for foods and the like, and sanitary packaging is enabled.
Then, it can be easily opened by pulling left and right with a weak force. The composite film having such an effect is suitably used as a packaging material for dry food products such as confectionery, sanitary goods packaging, electronic component packaging, various mechanical parts, and the like.

[0038]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.
The Elmendorf tear strength, dirt pact strength, haze, and tensile break strength of the films in Examples and Comparative Examples were determined according to the following test methods. (1) Elmendorf tear strength Elmendorf tear strength was determined by conducting a tear strength test in accordance with ASTM D1922. (2) Dart Impact Strength Dart impact strength was determined by performing an impact test in accordance with ASTM D 1709 (38.1 mm in dirt tip diameter). (3) Haze Haze was measured according to ASTM D1330. (4) Tensile breaking strength Tensile breaking strength was measured according to ASTM D 638.

[0039]

[Production Example 1] <Linear low-density polyethylene (M-LLD)
Production of PE (1)) [Preparation of catalyst] Silica 10 dried at 250 ° C. for 10 hours
kg after suspending with 154 liters of toluene.
Cooled to ° C. Thereafter, a toluene solution of methylaminooxane (Al = 1.33 mol / liter) 57.5.
One liter was added dropwise over one hour. At this time, the temperature in the system is set to 0
C. Subsequently, the reaction was carried out at 0 ° C. for 30 minutes.
The temperature was raised to 95 ° C. over 1.5 hours, and the reaction was carried out at that temperature for 20 hours. Thereafter, the temperature was lowered to 60 ° C., and the supernatant was removed by a decantation method. After the solid component thus obtained was washed twice with toluene, toluene 100
Resuspended in liters. Bis (1-methyl-3
16.8 L of a toluene solution of -n-butylcyclopentadienyl) zirconium dichloride (Zr = 27.0 mmol / L) was dropped at 80 ° C over 30 minutes, and further reacted at 80 ° C for 2 hours. Thereafter, the supernatant was removed and washed twice with hexane to obtain a solid catalyst containing 3.5 mg of zirconium per gram.

[Preparation of Preliminary Polymerization Catalyst] To 87 liters of hexane containing 2.5 mol of triisobutylaluminum, 870 g of the solid catalyst obtained above and 260 g of 1-hexene were added, and the ethylene was preliminarily prepared at 35 ° C. for 5 hours. By performing the polymerization, a prepolymerized catalyst in which 10 g of polyethylene was prepolymerized per 1 g of the solid catalyst was obtained.

[Polymerization] Using a continuous fluidized bed gas phase polymerization apparatus, ethylene and 1-hexene were copolymerized at a total pressure of 20 kg / cm ² -G and a polymerization temperature of 80 ° C. 0.33 mmol of zirconium atom-converted prepolymerized catalyst prepared above
l / h, 10 mmol /
h, and ethylene, 1-hexene, hydrogen, and nitrogen were continuously supplied to maintain a constant gas composition during the polymerization (gas composition; 1-hexene / ethylene =
0.02, hydrogen / ethylene = 10.5 × 10 ⁻⁴ , ethylene concentration = 70%).

The obtained linear low-density polyethylene (M-
The yield of LLDPE (1)) is 60 kg / hr,
The density (d) is 0.928 g / cm ³ and the MFR (AS
TM D1238, 190 ° C, load 2.16 kg) was 1.6 g / 10 min, the temperature (Tm) at the maximum peak position of the endothermic curve measured by DSC was 122 ° C, and the decane soluble component ratio at room temperature (Tm). W) is 0.40% by weight;
Was 1.5 g, and the fluidity index (FI) was 100 sec ^-1 . From these numerical values, the value of the following equation is obtained as follows. 1) Relational expression between Tm and d; 400 × d−248 = 123.2 2) Relational expression between W and d; 80 × exp (−100 (d−0.88)) + 0.1 = 0.9
8 3) Relational expression between MT and MFR; 2.2 × MFR ^-0.84 = 1.5 4) Relational expression between FI and MFR; 75 × MFR = 120

[0043]

Example 1 The linear low-density polyethylene (M-LLDPE (1)) obtained in Production Example 1 was coated with an outer layer having a thickness of 25 μm each.
As inner layer, melt flow rate (ASTM D 1238, 190 ℃,
Load 2.16kg) is 1.2g / 10min, density (ASTM D 1505)
A composite film having an intermediate layer having a thickness of 50 μm using an ionomer resin (trade name: Himilan ^™ 1601, manufactured by DuPont-Mitsui Polychemicals Co., Ltd.) having a die diameter of 100 mmφ and a lip gap of 2.5 m is 0.940 g / cm ^3.
Using a three-layer die of mφ, an extruder having an ESP (specific energy) of 0.2 kw / kg and a Q / N (discharge rate per screw rotation) of 0.05 kg / rpm,
A blown multilayer film was formed at a swelling ratio of 2.0.

With respect to the composite film obtained as described above, Elmendorf tear strength, dirt pact strength,
Haze and tensile strength at break were measured according to the test methods described above. Table 1 shows the results.

[0045]

Example 2 A composite film was obtained in the same manner as in Example 1, except that the thicknesses of the outer layer and the inner layer were 33 μm and the thickness of the intermediate layer was 34 μm. With respect to the obtained composite film, Elmendorf tear strength, dirt pact strength, haze and tensile strength at break were measured in accordance with the above test methods. Table 1 shows the results.

[0046]

Comparative Example 1 In Example 1, the resin for forming the outer layer and the inner layer was a linear low-density polyethylene (M-LLDPE).
Instead of (1)), the melt flow rate (ASTM D 123
8,190 ° C, load 2.16kg) 0.6g / 10min, density (AST
A composite film was obtained in the same manner as in Example 1 except that a high-pressure low-density polyethylene (HP-LDPE) having an MD 1505) of 0.921 g / cm ³ was used.

With respect to the obtained composite film, Elmendorf tear strength, dirt pact strength, haze and tensile strength at break were measured in accordance with the above test methods. Table 1 shows the results.

[0048]

Comparative Example 2 In Example 1, a Ziegler-based olefin polymerization catalyst was used in place of an ionomer resin as a resin for forming an intermediate layer, and a melt flow rate (ASTM D 1238, 190 ° C., load 2.16 kg) was used. ) Is 0.6 g /
10 minutes, density (ASTM D 1505) 0.958 g / cm ³
Except for using high-density polyethylene (HDPE), a composite film was obtained in the same manner as in Example 1.

With respect to the obtained composite film, Elmendorf tear strength, dirt pact strength, haze and tensile strength at break were measured in accordance with the above test methods. Table 1 shows the results.

[0050]

[Table 1]

As is clear from the comparison between Example 1 and Example 2 and Comparative Example 1 in Table 1, the outer layer and the inner layer were formed of a metallocene linear low-density polyethylene so that the impact strength and It is possible to obtain a highly transparent easily tearable composite film having improved tensile strength. Also,
As is clear from comparison between Example 1, Example 2 and Comparative Example 2, by forming the intermediate layer with an ionomer resin, the impact strength and the tensile strength were improved, and a highly transparent easily tearable composite was obtained. It is possible to obtain a film.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4F100 AK63A AK63C AK70B BA03 BA06 BA10A BA10C BA15 EH20 GB15 JA06A JA06C JA13A JA13C JJ05A JJ05C JK02A JK02C JK03 JK10 JL08A JL08C YY00A04 AQA AQA DAA 4A FA10 JA58

Claims (6)

[Claims] 1. A first layer comprising a linear low density polyethylene (A), a second layer comprising an ionomer resin (B),
A third layer made of a linear low-density polyethylene resin (A) is a composite film laminated in this order, and the linear low-density polyethylene (A) forming the first layer and the third layer is: An ethylene / α-olefin copolymer prepared using a metallocene-based olefin polymerization catalyst, having a density (d; ASTM D 1505) of 0.905 to 0.9.
50 g / cm ³ and a melt flow rate (MFR; A
STM D 1238, 190 ℃, load 2.16kg) is 0.5 ~ 4.0
g / 10 minutes, the easily tearable composite film. 2. The method according to claim 1, wherein said linear low-density polyethylene (A) has an endotherm measured by a differential scanning calorimeter (DSC).
Temperature (Tm (° C)) and density at the maximum peak position in the curve
(D (g / cm^Three)) Satisfies the relationship expressed by Tm <400 × d-248, and (ii) the amount of n-decane-soluble component at room temperature (W (weight)
%)) And density (d (g / cm^Three )), When MFR ≦ 10 g / 10 min, W <80 × exp (−100 (d−0.88)) + 0.1 When MFR> 10 g / 10 min, W <80 × (MFR-9) )^0.26× exp (−100 (d−
(0.88)) + 0.1.
Easy tearing composite film. 3. The linear low-density polyethylene (A) comprises:
Further, (iii) the melt tension at 190 ° C. (MT (g)) and the melt flow rate (MFR (g / 10 minutes)) satisfy the relationship expressed by MT ≦ 2.2 × MFR− ^0.84 , iv) 190 ° C of the molten polymer
Fluidity index (F) defined by the shear rate at which the shear stress reaches 2.4 × 10 ⁶ dyne / cm ²
I (1 / sec)) and the melt flow rate (MFR (g / 1)
0 minutes)) and a linear low-density polyethylene (A) satisfying the relationship of FI <75 × MFR.
The easily tearable composite film according to claim 2, wherein 1) is satisfied. 4. The linear low-density polyethylene (A) comprises:
Further, (v) the melt tension at 190 ° C. (MT (g))
And a melt flow rate (MFR (g / 10 min)) satisfying the relationship of MT> 2.2 × MFR− ^0.84.
The easily tearable composite film according to claim 2, wherein the composite film is (2). 5. The linear low-density polyethylene (A2)
And (vi) a fluidity index (FI (1 / sec)) defined by the shear rate at which the shear stress of the molten polymer at 190 ° C. reaches 2.4 × 10 ⁶ dyne / cm ^2.
And the melt flow rate (MFR (g / 10 min)) satisfies the relationship of FI> 75 × MFR. The easily tearable composite film according to claim 4, wherein 6. The tensile stress at break (AS) of the first layer and / or the third layer comprising the linear low density polyethylene (A).
The tearable composite film according to any one of claims 1 to 5, wherein TMD 638) is 20 to 45 MPa.