JP6891562B2 - Heat-resistant, easily tearable multilayer film and packaging bag - Google Patents

Description

The present invention relates to an easily tearable multilayer film and a packaging bag. More specifically, the present invention is excellent in lateral tearability and impact resistance, and is excellent in lateral tearability and impact resistance even after heat and pressure sterilization. The present invention relates to a heat-resistant, easily tearable multilayer film and a packaging bag.

In recent years, due to the issue of final disposal of garbage, the recycling law, etc., containers used for food and drink, seasonings, chemicals, etc. are easily tearable packaging bags such as standing pouches and spout pouches that are not bulky and use less resin. It has changed to. The easily tearable packaging bag is manufactured by using a packaging laminate having an easy-opening property that can be easily cut without using a cutting tool.
On the other hand, in the field of food and beverage packaging, it has become common to fill the contents, heat-pressurize and sterilize them, and then freeze and refrigerate them. There has been a demand for packaging that can withstand.

The packaging laminate used in the easily tearable packaging bag uses a biaxially stretched film such as polyamide, polyester, or polypropylene as a base material, and ethylene and so-called HAO (higher α) are used as a heat-sealing layer resin on this base material. -An unstretched polyethylene system containing an ethylene / α-olefin copolymer (HAO-LLDPE) as a resin main component, which is a copolymer with C6 or higher α-olefin such as 1-hexene or 1-octene called (-olefin). A laminated resin has been used.

However, these packaging bags lose their easiness to tear because the heat-sealing layer resin is made strong. In order to improve such a defect, an attempt has been made to impart cutability by using a cyclic olefin resin. For example, an outer layer made of a specific polyethylene, an intermediate layer made of 60 to 90% by weight of a cyclic olefin resin and 10 to 40% by weight of a specific linear low-density polyethylene, and an inner layer made of a specific polyethylene density are arranged in this order. An easily tearable multilayer film (Patent Document 1) characterized by being laminated has been proposed.

Japanese Unexamined Patent Publication No. 2012-885

However, after filling the contents in the easily tearable multilayer film or the easily tearable packaging bag using the easily tearable multilayer film as the heat seal layer resin, heat and pressure treatment at more than 100 ° C. is performed for the purpose of sterilization. Then, there was a problem that the tearability was lost.
Further, if a resin having an excessively high density (for example, 0.945 g / cm ³ <) is used for the heat seal layer resin in order to improve the overall heat resistance, the impact resistance is lowered, and especially in food packaging. There was a problem that pinholes were generated during freezing and refrigerated distribution.
As described above, it is difficult to establish a packaging bag that has easy tearability even after heat and pressure treatment and can withstand freezing and refrigerating distribution, and its development has been required.

An object of the present invention is an easily tearable multilayer film and packaging having heat resistance, which is excellent in lateral tearability and impact resistance even after heat treatment, in view of the above-mentioned problems of the prior art. To provide a bag.

As a result of diligent studies to solve the above problems, the present inventors have a layer I containing a specific density of ethylene / α-olefin, a specific ethylene / α-olefin copolymer, and a specific glass transition point. It has been found that the above-mentioned problems can be solved by a multilayer film in which a second layer containing a cyclic olefin resin and a third layer containing an ethylene / α-olefin copolymer having a specific density are laminated in this order. Further studies have been made on these findings, and the present invention has been completed.

That is, according to the first invention of the present invention, the layer I (A) containing an ethylene / α-olefin copolymer (a1) having ^{a density of 0.931 to 0.945 g / cm 3 as a resin main component,} Ethylene / α-olefin copolymer (b1) having a density of 0.870 to 0.930 g / cm ³ was used in an amount of 10 to 80% by weight, and a cyclic olefin resin (b2) having a glass transition point of 105 ° C. or higher was used in an amount of 20 to 90. The second layer (B) containing% by weight and the ^third layer (C) containing an ethylene / α-olefin copolymer (c1) having a density of 0.931 to 0.945 g / cm 3 as a resin main component are Provided is an easily tearable multilayer film having heat resistance, which is characterized by being laminated in order.
According to the second invention of the present invention, in the first invention, the cyclic olefin resin (b2) is an ethylene / cyclic olefin copolymer, which is a heat-resistant, easily tearable multilayer film. Is provided.
According to the third invention of the present invention, in the second invention, the ethylene / cyclic olefin copolymer has an ethylene / cyclic olefin content ratio of 15 to 40/85 to 60 by weight. Provided is an easily tearable multilayer film having heat resistance, which is characterized by the above.
According to the fourth invention of the present invention, in any one of the first to third inventions, the cyclic olefin resin (b2) is contained in an amount of 5 to 30% by weight based on the entire film. An easily tearable multilayer film having heat resistance is provided.
According to the fifth invention of the present invention, in any one of the first to fourth inventions, the first layer has heat resistance that does not substantially contain a resin component having ^{a density greater than 0.945 g / cm 3.} An easily tearable multilayer film having is provided.
According to the sixth invention of the present invention, in any one of the first to fifth inventions, the second layer contains 30 to 60% by weight of a cyclic olefin resin (b2) having a glass transition point of 105 ° C. or higher. , An easily tearable multilayer film having heat resistance is provided.
According to the seventh invention of the present invention, in any one of the first to sixth inventions, the heat resistance is characterized in that ^{the density difference between (c1) and (b1) is 0.025 g / cm 3 or more.} An easily tearable multilayer film having a property is provided.
According to the eighth invention of the present invention, in any one of the first to seventh inventions, the heat resistance is further characterized in that the relationship between the densities of (c1) and (b1) satisfies the following formula 1. An easily tearable multilayer film having the above is provided.
Equation 1: −0.67 × (c1) Density +1.5
<(B1) Density
<-0.67 x (c1) density +1.54
According to the ninth invention of the present invention, in the first to eighth inventions, the Ermendorf tear strength measured according to JIS K7128-2 after the heat treatment is 1 to 30 N / mm in the lateral direction. A heat-resistant, easily tearable multilayer film is provided.
According to the tenth invention of the present invention, in any one of the first to ninth inventions, the thickness of the second layer (B) is 20 to 70% with respect to the entire film. , An easily tearable multilayer film is provided.
According to the eleventh invention of the present invention, there is provided a packaging material characterized by using the easily tearable multilayer film of any one of the first to tenth inventions.

According to the present invention, there are provided an easily tearable multilayer film and a packaging material having heat resistance, which are excellent in lateral tearability and impact strength, and excellent in lateral tearability even after heat treatment.

It is the schematic which shows the cross section of an example of the easily tearable multilayer film which has heat resistance of this invention.

Hereinafter, the heat-resistant easily tearable film and packaging material of the present invention will be described in detail for each item.
The heat-resistant easily tearable film of the present invention is a cyclic olefin system having a specific ethylene / α-olefin copolymer-containing layer I, a specific ethylene / α-olefin copolymer and a specific glass transition point. The second layer containing a resin and the third layer containing a specific ethylene / α-olefin copolymer are laminated in this order.
Further, the packaging material of the present invention is characterized by using the easily tearable film having heat resistance.

1. 1. Layers that have heat resistance and are easily tearable (1) Layer II The layer II in the film of the present invention is an ethylene / α-olefin copolymer (b1 ^{) having a density of 0.870 to 0.930 g / cm 3.} ) Containing 10 to 80% by weight and 20 to 90% by weight of a cyclic olefin resin (b2) having a glass transition point of 105 ° C. or higher, preferably ethylene α ^{having a density of 0.870 to 0.930 g / cm 3.} -Contains 30 to 77% by weight of the olefin copolymer (b1) and 23 to 70% by weight of the cyclic olefin resin (b2) having a glass transition point of 105 ° C. or higher, and more preferably 0.870 to 0% by weight. It is characterized by containing 40 to 70% by weight of an ethylene / α-olefin copolymer (b1) of 930 g / cm ³ and 30 to 60% by weight of a cyclic olefin resin (b2) having a glass transition point of 105 ° C. or higher. ..
If the content of the cyclic olefin resin (b2) having a glass transition point of 105 ° C. or higher in the second layer is less than 20% by weight, sufficient tearability may not be obtained, which is not preferable. Further, if the content of the cyclic olefin resin (b2) having a glass transition point of 105 ° C. or higher exceeds 90% by weight, the stability of bubbles may be lost during inflation film molding, which is not preferable.

(A) Ethylene / α-olefin copolymer (b1)
The ethylene / α-olefin copolymer (b1) used in the second layer of the heat-resistant easily tearable film of the present invention may be any one polymerized by a metallocene catalyst, a Ziegler catalyst, a Phillips catalyst, or the like. However, the density is in the range of ^{0.870 to 0.930 g / cm 3.} The density of the ethylene / α-olefin copolymer (b1) is preferably 0.880 to 0.920 g / cm ³ , and more preferably 0.890 to 0.910 g / cm ³ . If the density of the ethylene / α-olefin copolymer (b1) ^{is less than 0.870 g / cm 3} , the tearability may not be obtained after the heat treatment, which is not preferable. If the density exceeds 0.930 g / cm ³ , the impact resistance may be inferior, which is not preferable.
In the present invention, the density is a value measured based on JIS K6922-2. When a plurality of types of resins satisfying the conditions of density and content are used as the ethylene / α-olefin copolymer, the density value is an average value calculated based on the weight ratio of the plurality of types of resins. And.

(B) Cyclic olefin resin (b2)
The cyclic olefin resin (b2) used in the second layer of the heat-resistant easily tearable film of the present invention is, for example, a norbornene-based polymer having a glass transition point of 105 ° C. or higher, a vinyl alicyclic type. Examples thereof include a hydrocarbon polymer and a cyclic conjugated diene polymer. Among these, norbornene-based polymers are preferable. The norbornene-based polymer includes a ring-opened polymer of a norbornene-based monomer (hereinafter, also referred to as “COP”), a norbornene-based copolymer obtained by copolymerizing a norbornene-based monomer and an α-olefin such as ethylene. Coalescence (hereinafter, also referred to as "COC") and the like can be mentioned. Also, hydrogenated COP and COC can be used.
The COC includes linear monomers such as α-olefins such as ethylene, propylene, butene-1, penten-1, hexene-1, heptene-1, and octene-1, and cyclic monomers such as tetracyclododecene and norbornene. Examples thereof include a cyclic olefin copolymer obtained from. More specifically, the linear monomer and monocycloalkene and bicyclo [2.2.1] -2-heptene (norbornen) having 3 to 20 carbon atoms and their derivatives, tricyclo [4.3.0.12] , 5] -3-decene and its derivatives, tetracyclo [4.4.0.1.2.2.5.17,10] -3-dodecene and its derivatives, pentacyclo [6.5.1.13,6.02] , 7.09,13] -4-pentadecene and its derivatives, pentacyclo [7.4.0.12,5.19,12.08,13] -3-pentadecene and its derivatives, pentacyclo [8.4.0] .12, 5.19, 12.08, 13] -3-hexadecene and its derivatives, pentacyclo [6.6.1.13, 6.02, 7.09,14] -4-hexadecenes and their derivatives, hexacyclo [6.6.1.13, 6.110, 13.02, 7.09, 14] -4-heptadecene and its derivatives, heptacyclo [8.7.0.12, 9.14, 7.111, 17] .03, 8.012, 16] -5-eikosen and its derivatives, heptacyclo [8.7.0.13, 6.110, 17.112, 15.02, 7.011, 16] -4-eikosen And its derivative, heptacyclo [8.8.0.12, 9.14, 7.111, 18.03, 8.012, 17] -5-heneikosen and its derivative, octacyclo [8.8.0.12]. 9.14, 7.111, 18.113, 16.03, 8.012, 17] -5-docosen and its derivatives, nonacyclo [10.9.1.14, 7.113, 20.115, 18. 02, 10.03, 8.012, 21.014, 19] -Cyclic olefin copolymer composed of a copolymer with a cyclic olefin such as pentacocene and a derivative thereof can be mentioned. The linear monomer and the cyclic monomer may be used alone or in combination of two or more. Moreover, such a cyclic olefin copolymer can be used alone or in combination. Further, the COP and COC can be used in combination with the cyclic olefin resin (b2). In that case, different performances of COP and COC can be imparted.

In the present invention, the cyclic olefin resin (b2) is preferably COC because the dispersibility in polyethylene is improved. The COC is preferably an ethylene / cyclic olefin copolymer in which the linear monomer is ethylene. Furthermore, the cyclic monomer is preferably norbornene or the like.

Further, in the present invention, when the cyclic olefin resin (b2) is an ethylene / cyclic olefin copolymer, the content ratio of ethylene / cyclic olefin is 15 to 40/85 to 60 by weight. Is preferable. More preferably, it is 30 to 40/70 to 60. If ethylene is less than 15% by weight, the rigidity becomes too high, which may deteriorate inflation moldability and bag making suitability, which is not preferable. On the other hand, when ethylene is 40% by weight or more, sufficient tearability and rigidity may not be obtained, which is not preferable. When the content ratio is in this range, the rigidity, tearability, processing stability, and impact strength of the film are further improved, which is preferable.

The cyclic olefin resin (b2) has a glass transition point of 105 ° C. or higher. The temperature is preferably 110 ° C. or higher. The glass transition point of the cyclic olefin resin (b2) is preferably 140 ° C. or lower. When the content of the cyclic olefin is less than 60% by weight, the glass transition point may be lower than 105 ° C., for example, the easily tearable property cannot be obtained after the heat treatment at 120 ° C., and the barrier property of the aromatic component is lowered. , Sufficient rigidity may not be obtained, and the suitability for high-speed packaging machines may be inferior. On the other hand, if the content of the cyclic olefin is 85% by weight or more, the glass transition point becomes too high, and the melt moldability of the copolymer and the adhesiveness with the olefin resin may decrease, which is not preferable.
The weight average molecular weight of the cyclic olefin resin (b2) is preferably 5,000 to 500,000, more preferably 7,000 to 300,000.

The cyclic olefin resin (b2) is preferably contained in an amount of 20 to 70% by weight based on the entire easily tearable multilayer film. More preferably, it is 20 to 50% by weight. If it is less than 20% by weight, sufficient tearability may not be obtained, which is not preferable. On the other hand, if it is more than 70% by weight, the rigidity becomes too high, which may deteriorate the inflation moldability and the bag making suitability, which is not preferable.

As a commercially available product that can be used as the cyclic olefin resin (b2), examples of the ring-opening polymer (COP) of the norbornene-based monomer include "ZEONOR" manufactured by Nippon Zeon Corporation, and the norbornene-based monomer is used. Examples of the copolymer (COC) include "Apel" manufactured by Mitsui Kagaku Co., Ltd. and "TOPAS" manufactured by TICONA Corporation. In the present invention, TOPAS grade 7010F-600 is preferable because the content ratio of the norbornene-based monomer is in the above range, processability, and the like.
When the norbornene-based monomer is used for the cyclic olefin-based resin, the norbornene content is preferably 30 mol% or more and 70 mol% or less, more preferably 35 mol% or more and 65 mol% or less, and further preferably 36 mol% or more and 60 mol% or less. .. If the norbornene content is less than 30 mol%, easy tearing may not be obtained. Further, if it exceeds 70 mol%, the workability may be deteriorated.

(2) Layer I The layer I of the heat-resistant, easily tearable multilayer film of the present invention is made of an ethylene / α-olefin copolymer (a1) having ^{a density of 0.931 to 0.945 g / cm 3 as a resin.} Included as the main component. The density of the ethylene / α-olefin copolymer (a1) is preferably 0.933 to 0.940 g / cm ³ .
The ethylene / α-olefin copolymer (a1) may be polymerized by a metallocene catalyst, a Ziegler catalyst, a Phillips catalyst, or the like, but the density is 0.931 to 0.945 g / cm ³ . It is necessary. It is preferably 0.933 to 0.940 g / cm ³ . If the density is less ^{than 0.931 g / cm 3} , sufficient heat resistance cannot be obtained, and the performance may be affected, for example, the easy tearing property cannot be obtained after the heat treatment. On the other hand, if the density ^{exceeds 0.945 g / cm 3} , the impact strength may decrease.
In the present invention, the density is a value measured based on JIS K 6922-2.

The melt flow rate (MFR) of the ethylene / α-olefin copolymer (a1) is preferably 0.1 to 30 g / 10 minutes at 190 ° C. More preferably, it is 0.5 to 4.0 g / 10 minutes. If the MFR is less than 0.1 g / 10 minutes, problems such as poor melt flowability, difficulty in film processing, and a large motor load may occur, which is not preferable. On the other hand, if it exceeds 30 g / 10 minutes, the melt viscosity is too low, which may reduce the film-forming stability during film processing, which is not preferable.
In the present invention, the melt flow rate (MFR) is a melt flow rate value measured by JIS-K-7210.

Specifically, the ethylene / α-olefin copolymer (a1) preferably used in the present invention is as follows. That is, the α-olefin that copolymerizes with ethylene is copolymerized in an amount of 0.1 to 10 mol%, preferably 0.2 to 5 mol%, particularly preferably 0.3 to 4 mol%. Yes, the type of α-olefin is usually an α-olefin having 3 to 8 carbon atoms, and specifically, propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, 4-Methylpentene-1 can be mentioned.

The layer I may contain other resin components as long as the copolymer (a1) is contained as the resin main component. However, in order to make the impact resistance more sufficient, it is preferable that the resin component having ^{a density exceeding 0.945 g / cm 3 is substantially not contained.} Here, in the present specification, "containing as the main component of the resin" means that the content is the highest among all the components contained in the resin, and the content of the copolymer (a1) in the I layer is contained. The amount is preferably 50% by weight or more, more preferably 65% by weight or more, further preferably 80% by weight or more, and particularly preferably 90% by weight or more. Further, "substantially free" means that the content is 1% by weight or less, preferably 0.5% by weight or less, more preferably 0.1% by weight or less, and affects the physical properties of the entire resin composition. It means that the content is contained only to a certain extent or is below the detection limit, and is an amount that can be regarded as 0% by weight.

(3) Layer III The layer I of the heat-resistant, easily tearable multilayer film of the present invention is made of an ethylene / α-olefin copolymer (c1) having ^{a density of 0.931 to 0.945 g / cm 3 as a resin.} Included as the main component. The density of the ethylene / α-olefin copolymer (c1) is preferably 0.933 to 0.940 g / cm ³ .

The ethylene / α-olefin copolymer (c1) may be polymerized by a metallocene catalyst, a Ziegler catalyst, a Phillips catalyst, or the like, but the density is 0.931 to 0.945 g / cm ³ . It is necessary. It is preferably 0.933 to 0.940 g / cm ³ . If the density is less ^{than 0.931 g / cm 3} , sufficient heat resistance cannot be obtained, and the performance may be affected, for example, the easy tearing property cannot be obtained after the heat treatment. On the other hand, if the density ^{exceeds 0.945 g / cm 3} , the impact strength may decrease.
In the present invention, the density is a value measured based on JIS K 6922-2.

The melt flow rate (MFR) of the ethylene / α-olefin copolymer (c1) is preferably 0.1 to 30 g / 10 minutes at 190 ° C. More preferably, it is 0.5 to 4.0 g / 10 minutes. If the MFR is less than 0.1 g / 10 minutes, problems such as poor melt flowability, difficulty in film processing, and a large motor load may occur, which is not preferable. On the other hand, if it exceeds 30 g / 10 minutes, the melt viscosity is too low, which may reduce the film-forming stability during film processing, which is not preferable.
In the present invention, the melt flow rate (MFR) is a melt flow rate value measured by JIS-K-7210.

Specifically, the ethylene / α-olefin copolymer (c1) preferably used in the present invention is as follows. That is, the α-olefin that copolymerizes with ethylene is copolymerized in an amount of 0.1 to 10 mol%, preferably 0.2 to 5 mol%, particularly preferably 0.3 to 4 mol%. Yes, the type of α-olefin is usually an α-olefin having 3 to 8 carbon atoms, and specifically, propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, 4-Methylpentene-1 can be mentioned.

The third layer contains the copolymer (c1) as a resin main component, and may preferably contain other resin components as long as the relationship with the second layer described later is satisfied.

The first layer, the second layer and the third layer are an antifogging agent, an antistatic agent, a heat stabilizer, a nucleating agent, an antioxidant, a lubricant, an antiblocking agent, a mold release agent, an ultraviolet absorber, and a coloring agent. Etc. can be added as long as the object of the present invention is not impaired.

2. Layers I to III The layers I to III of the present invention are composed of a specific layer I / a specific layer II / a specific layer III, as described above. FIG. 1 shows a schematic cross-sectional view of an example of the easily tearable multilayer film of the present invention. 1 is the I layer, 2 is the II layer, and 3 is the III layer.
The thickness of the entire layers I to III is preferably 30 to 150 μm. When the thickness of the multilayer film is 30 μm or more, excellent secondary moldability can be obtained.

The thickness of the second layer of the first to third layers of the present invention is preferably 20 to 70% with respect to the entire easily tearable multilayer film. More preferably, it is 20 to 50%. That is, the thickness of the first layer / the second layer / the third layer can be about 1: 0.5: 1 to 1: 4: 1. If the second layer is thinner than 20%, sufficient tearability cannot be obtained, which is not preferable. On the other hand, if it is thicker than 70%, the rigidity becomes too high and the inflation moldability and bag making suitability are deteriorated, which is not preferable. If the second layer is in this range, it is excellent in tearability, is advantageous in terms of cost, and the transparency, tearability, and pinhole resistance of the easily tearable multilayer film having heat resistance are improved. preferable.

In the easily tearable multilayer film of the present invention, the first layer to the third layer are laminated in this order, and other layers known to those skilled in the art such as an adhesive layer between layers as long as the object of the present invention is not impaired. It may have a layer of.

The method for producing the layers I to III of the present invention is not particularly limited, but for example, the ethylene / α-olefin copolymer (a1) used for the layer I and ethylene used for the layer II (B). -The α-olefin copolymer (b1) and the cyclic olefin resin (b2) and the ethylene / α-olefin copolymer (c1) used for the third layer (C) are heated and melted by different extruders. After laminating in the order of layer I / layer II / layer III in a molten state by a method such as a coextrusion multilayer die method or a feed block method, the polymer is formed into a film by an inflation or a T-die chill roll method. Extrusion method can be mentioned. This coextrusion method is preferable because the thickness ratio of each layer can be adjusted relatively freely, and a multilayer film having excellent hygiene and excellent cost performance can be obtained.

3. 3. Relationship between Layer II and Layer III The density difference between the ethylene / α-olefin copolymer (c1) used for layer III of the present invention and the ethylene / α-olefin copolymer (b1) used for layer II is 0. .025g / cm ³ or more and preferably 0.028 g / cm ³ or more. If the density difference between (c1) used for the third layer and (b1) used for the second layer is ^{less than 0.025 g / cm 3} , there is a risk that heat resistance and impact may not be balanced, which is not preferable.

Further, it is preferable that the relationship between the densities of (c1) and (b1) satisfies the following formula 1, particularly formula 2.
Equation 1: −0.67 × (c1) Density +1.5
<(B1) Density
<-0.67 x (c1) density +1.54
Equation 2: −0.67 × (c1) Density +1.51
<(B1) Density
<-0.67 x (c1) density +1.53
If the density is −0.67 × (c1) density + 1.5 ≧ (b1) density, the impact resistance may be lacking, which is not preferable. On the other hand, if (b1) density ≤ −0.67 × (c1) density + 1.54, heat resistance may be lacking, which is not preferable.

4. Easy-to-tear multilayer film with heat resistance The heat-resistant easy-to-tear multilayer film of the present invention has Ermendorf's tear strength measured in accordance with JIS K7128-2 after heat treatment, 1 to 1 in each of the vertical and horizontal directions. It is preferably 30 N / mm or less. More preferably, it is 20 N / mm or less. In particular, it is preferable that the lateral direction satisfies this range.

5. Packaging Material Examples of the packaging material made of the heat-resistant, easily tearable film of the present invention include packaging bags and containers used for applications such as foods, chemicals, medical instruments, industrial parts, miscellaneous goods, and magazines. In particular, it is suitable for food packaging bags and packaging containers that are refrigerated / frozen and distributed after being heat-pressurized and sterilized.

Examples of the packaging bag include a packaging bag formed by heat-sealing the III layers of the easily tearable film of the present invention as a heat-sealing layer. Two pieces of the easily tearable film are cut out to the desired size of the packaging bag, and they are overlapped and heat-sealed on three sides to form a bag, and then the contents are removed from one side that is not heat-sealed. After filling, it can be used as a packaging bag by heat-sealing and sealing. It can also be used in the form of pillow packaging using one sheet of the easily tearable film. Further, it is also possible to form a packaging bag by superimposing and heat-sealing the third layer and another heat-sealable film. At that time, as another film to be used, a film such as LDPE or EVA having a relatively weak mechanical strength can be used. Further, a laminated film obtained by laminating a film such as LDPE or EVA and a stretched film having relatively good tearability, for example, a biaxially stretched polyethylene terephthalate film (OPET) or a biaxially stretched polypropylene film (OPP), is also used. Can be done.

Further, examples of the packaging container include a deep-drawn molded product (bottom material having an opening at the top) obtained by secondary molding the easily tearable film of the present invention, and a typical example of the packaging container is a blister pack. Bottom material can be mentioned. The lid material for sealing the bottom material may be any material as long as it can be heat-sealed with the bottom material, but since the lid material and the bottom material can be torn and opened at the same time, the easily tearable film of the present invention can be used as the lid material. It is preferable to use as.

Examples of the above-mentioned secondary molding method include a vacuum forming method, a compressed air forming method, a vacuum pressurized air forming method, and the like. Among these, vacuum forming is preferable because the film or sheet can be molded in-line on the packaging machine and the contents can be filled.

In the packaging material using the easily tearable film of the present invention, in order to weaken the initial tear strength and improve the opening property, any tear start portion such as V notch, I notch, perforation, microporous, etc. is formed in the seal portion. It is preferable to form.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto as long as it does not deviate from the gist thereof.
The measurement of various physical properties in the examples was performed according to the following procedure.

[Measuring method]
(1) Dirt Drop Impact (DDI) (Method A)
Measurements were performed in accordance with JIS K7124.
(2) Elmendorf tear strength The TD of the film was measured according to JIS K7128-2. In addition, MD is a flow direction (MD: Machine Direction), and TD is a value in a vertical direction (TD: Transverse Direction).
(3) Evaluation of Physical Properties after Heat-Pressure Sterilization The film was processed so as to have a length of 210 mm and a width of 140 mm to prepare a bag. It was filled with 400 g of water and sealed.
Using the water-filled film, heat-pressurization sterilization was performed under the conditions of 115 ° C.-30 minutes and 121 ° C.-30 minutes.
Separately, a bag not filled with water was prepared, and heat and pressure sterilization was performed in the same manner.
(3) -1 Evaluation of water-filled film (3) -1- (1) Elmendorf tear strength JIS K7128-2 was followed, and the TD of the film was measured.
(3) -1- (2) Evaluation of tearability by hand When opening the water-filled film, the bag was scratched with a cutter, and the openability was evaluated starting from that point. The evaluation was performed by tearing the TD of the film. Slowly and intermittently torn by hand to TD. Those that can be torn easily even if they are torn intermittently are marked with ○, and those that require force to tear and become difficult to tear immediately and cannot be torn intermittently are marked with ×.
(3) -1- (3) Evaluation of fusion state The case where fusion is not seen and can be easily peeled off is evaluated as 〇, and the case where there is fusion and cannot be easily peeled off is evaluated as x.
(3) -2 Evaluation of film not filled with water 〇 for cases where fusion is not seen and can be easily peeled off, △ for cases where it is heavy but can be peeled off with some force, and × for cases where it cannot be peeled off by fusion And said.

[Molding conditions and formability evaluation method for inflation film]
An inflation film was molded and evaluated under the following molding conditions using the following inflation film film forming machine (molding apparatus).
(3 types, 3 layers inflation molding machine)
Equipment: Inflation molding equipment (manufactured by PLACO Co., Ltd.)
Extruder screw diameter: outer layer (third layer) / intermediate layer (second layer) / inner layer (third layer)
= 50 mmφ / 55 mmφ / 50 mmφ
Die diameter: 200 mmφ
Extrusion amount: 49 kg / hr
Die lip gap: 3mm
Pick-up speed: 9m / min Blow-up ratio: 2.0
Molding resin temperature: Outer layer (third layer) / inner layer (third layer) 160 ° C, intermediate layer (second layer) 170 ° C
Film thickness: 80 μm
Cooling ring: Two-stage air cooling ring

[Raw materials used]
The raw materials used in Examples and Comparative Examples are as follows. The unit of density is g / cm ³ , and the unit of MFR is g / 10 min.
(1) Ethylene / α-olefin copolymer Novatec C6 "SF941" manufactured by Japan Polyethylene Corporation (PE (1))
Ethylene / α-olefin copolymer with a density of 0.936 ^{g / cm 3} and MFR of 2.0 g / 10 min (2) Ethylene / α-olefin copolymer Harmorex "NC595A" manufactured by Nippon Polyethylene (PE (2))
Ethylene / α-olefin copolymer with density 0.935 g / cm ³ , MFR 4.0 g / 10 min (3) Ethylene / α-olefin copolymer Harmorex "NF394N" manufactured by Japan Polyethylene Corporation (PE (3))
Ethylene / α-olefin copolymer with density 0.935 g / cm ³ and MFR 1.5 g / 10 min (4) Ethylene / α-olefin copolymer PE (4)
Ethylene / α-olefin copolymer with density 0.927 ^{g / cm 3} , MFR 3.6 g / 10 min (5) Ethylene / α-olefin copolymer PE (5)
Ethylene / α-olefin copolymer with density 0.932 ^{g / cm 3} , MFR 4.2 g / 10 min (6) Ethylene / α-olefin copolymer Harmorex "NF384A" manufactured by Japan Polyethylene Corporation (PE (6))
Ethylene / α-olefin copolymer with density 0.926 ^{g / cm 3} , MFR 1.7 g / 10 min (7) Ethylene / α-olefin copolymer Harmorex "NF324A" (PE (7)) manufactured by Nippon Polyethylene Co., Ltd.
Ethylene / α-olefin copolymer with density 0.906 ^{g / cm 3} , MFR 1.0 g / 10 min (8) High-pressure method low-density polyethylene Novatec LD "LF441B" (PE (8)) manufactured by Japan Polyethylene Corporation
Ethylene / α-olefin copolymer with density 0.924 ^{g / cm 3} , MFR 2.0 g / 10 min (9) High-pressure method low-density polyethylene Novatec LD "LF280" manufactured by Japan Polyethylene Corporation (PE (9))
Ethylene / α-olefin copolymer with density 0.928 ^{g / cm 3} and MFR 0.7 g / 10 min (10) Ethylene / α-olefin copolymer Novatec LL "UF320" manufactured by Japan Polyethylene Corporation (PE (10))
Ethylene / α-olefin copolymer with density 0.922 ^{g / cm 3} and MFR 0.9 g / 10 min (11) COC (1)
The product name TOPAS "7010F-600" is used.
Norbornene content 42 mol%, glass transition point 110 ° C
(12) COC (2)
The product name TOPAS "8007F-600" is used.
Norbornene content 36 mol%, glass transition point 78 ° C
(13) Slip agent masterbatch Kernel "KMB05S" manufactured by Japan Polyethylene Corporation (MB (1))
5 wt% slip agent masterbatch (14) Anti-blocking agent masterbatch Kernel "KMB16F" manufactured by Japan Polyethylene Corporation (MB (2))
Masterbatch of 16 wt% anti-blocking agent (15) Ethylene / α-olefin copolymer Engage "EG8200" manufactured by Dow Chemical Co., Ltd.
Ethylene / α-olefin copolymer with density 0.870 g / cm ^{3 and MFR 5 g / 10 min}

[Examples and Comparative Examples]
(Example 1)
As shown in Table 1, the first layer is a mixture of PE (1), PE (8), MB (1) and MB (2), and the second layer is PE (7), COC (1) and MB (1). An inflation film having a layer ratio of 1: 1: 1 was obtained by using the mixture and the third layer as a mixture of PE (1), PE (8), MB (1), and MB (2). The film thickness was 80 μm.
The film was evaluated for dirt drop impact (method A) and Elmendorf tear strength. Further, a bag filled with water was prepared, and after heat and pressure sterilization at 115 ° C. and 121 ° C., Elmendorf tear strength, manual tearability evaluation, and fusion state were evaluated. Further, a bag not filled with water was prepared, and the fused state was evaluated after heat treatment in the same manner. The evaluation results are shown in Table 1.

(Examples 2 to 8)
An inflation film was obtained in the same manner as in Example 1 with the formulation shown in Table 1, and its physical characteristics were evaluated. The evaluation results are shown in Table 1.

(Comparative Examples 1 to 5)
Inflation films were obtained in the same manner as in Examples 1 to 6 with the formulations shown in Table 2, and their physical characteristics were evaluated. The evaluation results are shown in Table 2.

[Evaluation]
As is clear from Table 1, the film having a specific layer structure, which is a specific matter of the present invention, has excellent impact strength and low tear strength even after heat treatment, and therefore has sufficient tearability. In Example 7 only, although wrinkles were generated in the film after heating and pressurizing at 121 ° C., it was shown that all the films had both impact strength and easy tearability after heating. In particular, by balancing the densities of each layer as in Examples 1 to 6, a film having a very excellent balance of required physical properties can be obtained.
On the other hand, Comparative Example 1 in which only ethylene / α-olefin copolymers (PE (4), PE (6), PE (7)) having ^{a density smaller than 0.931 g / cm 3 were used for the outer layer (third layer).} In and 4, fusion occurs in the bag after the treatment at 121 ° C.
Comparative Examples 2 and 5 in which the cyclic olefin resin (COC (2)) having a low glass transition point was used for the intermediate layer (second layer) did not have easy lateral tearability after the heat treatment.
Comparative Example 3 in which an ethylene / α-olefin copolymer (PE (2)) having a density greater than 0.930 g / cm ^{3 was used as the intermediate layer (second layer) has a weak impact strength.}

According to the present invention, there is provided a multilayer film having excellent tearability in the vertical and horizontal directions and excellent tearability even after heat treatment, and a packaging material using the same. Therefore, the easily tearable multilayer film of the present invention and the packaging material using the same can be used for foods, chemicals, medical instruments, industrial parts, miscellaneous goods, magazines, etc., especially after the introduction of the contents. It can be suitably used for applications such as heat treatment, and is very useful industrially. In particular, it is suitable for food packaging bags and packaging containers that are refrigerated / frozen and distributed after being heat-pressurized and sterilized.

1: Layer I 2: Layer II 3: Layer III

Claims (10)

Density ethylene · alpha-olefin copolymer 0.931~0.945g / cm ³ and (a1) the I layer comprising a resin main component (A), a density of 0.870~0.930g / cm ³ Layer II (B) and density containing 10 to 80% by weight of ethylene / α-olefin copolymer (b1) and 20 to 90% by weight of cyclic olefin resin (b2) having a glass transition point of 105 ° C. or higher. The heat resistance is characterized in that the third layer (C) containing an ethylene / α-olefin copolymer (c1) of 0.931 to 0.945 g / cm ^{3 as a resin main component is laminated in order.} Easy-to-tear multilayer film. The easily tearable multilayer film having heat resistance according to claim 1, wherein the cyclic olefin resin (b2) is an ethylene / cyclic olefin copolymer. The easily tearable property according to claim 2, wherein the ethylene / cyclic olefin copolymer has an ethylene / cyclic olefin content ratio of 15 to 40/85 to 60 by weight. Multilayer film. The easily tearable multilayer film having heat resistance according to any one of claims 1 to 3, wherein the cyclic olefin resin (b2) is contained in an amount of 5 to 30% by weight based on the entire film. The easily tearable multilayer film having heat resistance according to any one of claims 1 to 4, wherein the first layer ^{does not substantially contain a resin component having a density greater than 0.945 g / cm 3.} The easily tearable multilayer film having heat resistance according to any one of claims 1 to 5, wherein the second layer contains 30 to 60% by weight of a cyclic olefin resin (b2) having a glass transition point of 105 ° C. or higher. .. The easily tearable multilayer film having heat resistance according to any one of claims 1 to 6, wherein the density difference between (c1) and (b1) is 0.025 g / cm ^{3 or more.} Further, the easily tearable multilayer film having heat resistance according to any one of claims 1 to 7, wherein the relationship between the densities of (c1) and (b1) satisfies the following formula 1.
Equation 1: −0.67 × (c1) Density +1.5
<(B1) Density
<-0.67 x (c1) density +1.54 The easily tearable multilayer film having heat resistance according to any one of claims 1 to 8 , wherein the thickness of the second layer (B) is 20 to 70% with respect to the entire film. .. A packaging material comprising the easily tearable multilayer film having the heat resistance according to any one of claims 1 to 9.

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