JPH1171483A - Ethylene polymer composition and easily unsealable sealing material prepared therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin compsn. which gives a sealing material easily unsealable by compounding an ethylene polymer, a block copolymer, and a hydrocarbon resin-based or terpene resin-based tackifying resin, each in a specified amt. SOLUTION: This compsn. comprises 40-80 pts.wt. ethylene polymer, 5-40 pts.wt. A-B-A type block copolymer, and 5-30 pts.wt. hydrocarbon resin-based or terpene resin-based tackifying resin. If necessary, an antioxidant, a heat stabilizer, an antistatic agent, a lubricant, etc., are incorporated into the compsn. The ethylene polymer is selected from among a low-density polyethylene, a copolymer of ethylene and 3-12C α-olefin and a copolymer of ethylene and a polar monomer having a polar monomer content of 15 wt.% or lower. In the A-B-A type block copolymer, A is a styrene polymer block and B is an alkylene polymer block, and the block copolymer is obtd. by hydrogenating a styrene-butadiene-styrene block copolymer or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ethylene polymer composition exhibiting excellent sealing properties and easy-opening properties for various materials, and an easy-opening sealing material comprising the composition. More specifically, the present invention relates to an ethylene polymer composition suitable as a sealing material such as polyester, polyacrylonitrile-based polymer, styrene polymer, polyvinyl chloride and the like, and an easily-openable sealing material comprising the composition.

[0002]

2. Description of the Related Art Plastic containers provided with easy-open lids are widely used as containers for various foods and drinks and pharmaceuticals. The easy-opening sealing material used for the sealing layer of such a lid material is required to have a wide heat sealing temperature range, obtain stable sealing strength, and be easily opened. Depending on the material and size of the container,
Since the required seal strength is different, various easy-open seal materials have been proposed and used in the past.

[0003] Conventionally, polypropylene, polyvinyl chloride, polystyrene, and the like have been widely used as container materials. Therefore, many easy-opening materials suitable for containers made of these materials are already known. However, practically excellent easy-opening materials have not been found for amorphous polyester containers, which have recently attracted attention as heat-resistant containers. That is, among the easily-openable sealing materials proposed in the past, there are many materials having a wide heat-sealing temperature range and an appropriate sealing strength as compared with amorphous polyester. However, the sealing surface of the amorphous polyester container may be crystallized due to sealing or other heat history, and in such a case, the sealing strength of the conventionally proposed easy-open sealing material is significantly reduced. found. For this reason, the seal strength varies, or the adhesion during transportation or storage is left uneasy.

Further, stretched polyethylene terephthalate (O-PET), which is excellent in heat resistance and strength, is used as a packaging base material and a molding container, and is excellent in heat resistance, is used for a microwave oven container and the like. Crystalline polyethylene terephthalate (C-PET), excellent in heat resistance and gas barrier properties, polyethylene naphthalate used in semi-retorted foods, etc., polyacrylonitrile polymer excellent in gas barrier properties, used in miso containers, etc. At present, there is no excellent easy-opening sealing material except for a hot-melt adhesive having a low softening point.

[0005]

SUMMARY OF THE INVENTION For this reason, the present inventor has:
A sealing material having a wider heat-sealing temperature range than amorphous polyester, exhibiting an appropriate sealing strength, and exhibiting the same sealing characteristics even when crystallization of the polyester occurred was studied. as a result,
The following ethylene polymer composition was found to have such properties. Furthermore, it has been found that such an ethylene polymer composition has excellent easy-opening sealing performance with respect to the above-mentioned O-PET and other materials. Accordingly, an object of the present invention is to provide an ethylene polymer composition which is an excellent easy-open seal material for an amorphous polyester packaging material. Another object of the present invention is to provide an ethylene polymer composition which is an excellent easy-open seal material even for other polyester materials and polyacrylonitrile polymers.

[0006]

According to the present invention, there is provided an ethylene polymer of 40 to 80 parts by weight, an ABA type block copolymer (A is a polystyrene block, and B is an alkylene copolymer block). The present invention relates to an ethylene polymer composition comprising 5 parts by weight and 5 to 30 parts by weight of a hydrocarbon resin-based tackifying resin or a terpene resin-based tackifying resin. The present invention also provides
The present invention relates to an easily-openable sealing material comprising the ethylene polymer composition.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The ethylene polymer which is a component of the ethylene polymer composition of the present invention is a polymer containing ethylene as a main component, and is composed of polyethylene, ethylene and α.
-Selected from olefin copolymers or copolymers of ethylene and polar monomers.

As the polyethylene, there are high-density polyethylene, medium-density polyethylene, and low-density polyethylene, and it is particularly preferable to use low-density polyethylene produced by a high-pressure method. If too much high-density polyethylene or medium-density polyethylene is used, high sealing strength may not be obtained.

[0009] copolymers of ethylene and α- olefin in the present invention, for convenience referred to as a density of 0.930 g / cm ³ or less, those exceeding 0.930 g / cm ³ can alternatively density polyethylene in the basis of the density Included in high density polyethylene. As the ethylene / α-olefin copolymer, those produced by using either a multi-site catalyst or a single-site catalyst can be used. Although it differs slightly depending on the catalyst system used,
Density of 0.870 g / cm ³ or more, preferably 0.88
So-called linear low-density polyethylene of 0 g / cm ³ or more,
It is preferable to use those in a region called ultra-low density polyethylene, plastomer or the like.

[0010] The α-olefin constituting the ethylene copolymer has about 3 to 12 carbon atoms, especially 4 to
It is preferable to use about ten. In particular,
Examples thereof include 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, and 4-methyl-1-pentene.

Most preferably, the density is 0.880 to 0.910 g / cm, made with a single site catalyst.
^{3. The} copolymer is preferably used so as to contain at least one copolymer, particularly preferably at least 10% by weight, of a copolymer having a plastomer region of 0.885 to 0.905 g / cm ³ .

Next, the copolymer of ethylene and a polar monomer has a polar monomer content of 30% by weight or less, preferably 20% by weight or less, more preferably 15% by weight or less. When only the polymer having a high polar monomer content is used as the ethylene-based polymer, when the composition is used as a heat seal material for the polyester, there is a large difference in the seal strength between the case where the polyester is amorphous and the case where the polyester is crystalline. It is not preferable because of the tendency, and in such a case, it is desirable to use together with polyethylene or an ethylene / α-olefin copolymer. In any case, when the ethylene-polar monomer copolymer is used, the average polar monomer concentration in the ethylene-based polymer component is 15% by weight or less,
The content is preferably adjusted to 10% by weight or less, particularly preferably 5% by weight or less.

Specific examples of the polar monomer include vinyl esters such as vinyl acetate, and unsaturated carboxylic acids such as methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, isooctyl acrylate and methyl methacrylate. Examples include esters, acrylic acid, methacrylic acid, unsaturated carboxylic acids such as maleic anhydride, carbon monoxide and the like. Of these, the use of vinyl acetate is most preferred.

Considering workability, seal strength, etc., these ethylene-based polymers are 190 ° C., 2160 g
Melt flow rate under load is 0.1 to 500 g
It is desirable to use a material having a viscosity of / 10 minutes, particularly 1 to 150 g / 10 minutes.

In the ABA type block copolymer used as the other component of the composition of the present invention, A is a styrene polymer block, B is an alkylene copolymer block, specifically, ethylene / butene copolymer. It is a polymer block or an ethylene / propylene copolymer block. Such a block copolymer is obtained by hydrogenating a butadiene polymer unit or an isoprene polymer unit of a styrene-butadiene-styrene block copolymer or a styrene-isoprene-styrene block copolymer. Generally, SEBS is used. Alternatively, it is called SEPS. Here, the styrene polymer block content is 8 to 50% by weight, preferably 10 to 40% by weight. Further, it is preferable to use one having a melt flow rate of 0.1 to 500 g / 10 min, particularly 1 to 100 g / 10 min at 230 ° C. and a load of 2160 g.

In the composition of the present invention, a tackifier resin is used in addition to the ethylene polymer and the ABA type block copolymer. As the tackifying resin, a hydrocarbon resin-based tackifying resin or a terpene resin selected from aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, aromatic hydrocarbon resins, styrene resins, cumarone / indene resins, etc. A system tackifying resin is used.

Examples of the aliphatic hydrocarbon resin include polymers mainly containing C ₄ -C ₅ mono- or diolefins such as butene-1, isobutylene, butadiene, 1,3-pentadiene, isoprene and piperylene. Is mentioned. Examples of alicyclic hydrocarbon resins include Svent C ₄
-C ₅ fraction in the resin the diene component were polymerized after cyclization dimerization of the cyclic monomer is polymerized resins, such as resins obtained by nuclear hydrogenation of aromatic hydrocarbon resins include, such as cyclopentadiene Can be Examples of aromatic hydrocarbon resins include:
Examples thereof include resins mainly containing C _{9 to} C ₁₀ vinyl aromatic hydrocarbons such as vinyltoluene, indene and α-methylstyrene. Styrene-based hydrocarbon resins include polymers such as styrene, vinyltoluene, α-methylstyrene, and isopropenyltoluene.

Examples of the terpene resin include α-pinene polymer, β-pinene polymer, dipentene polymer, terpene-phenol copolymer, α-pinene-phenol copolymer, hydrogenated terpene resin and the like. Can be

Of these, the use of hydrogenated resins such as hydrogenated aromatic hydrocarbon resins and hydrogenated terpene resins is particularly preferred.

In the present invention, the mixing ratio of the ethylene polymer, the block copolymer and the tackifying resin is such that when the total amount thereof is 100 parts by weight, the ethylene polymer is 40 to 80 parts by weight; Preferably 50 to 75 parts by weight, 5 to 40 parts by weight of the block copolymer, preferably 1
The range is from 0 to 30 parts by weight, and the amount of the tackifier resin is from 5 to 30 parts by weight, preferably from 10 to 20 parts by weight.

If the amount of the block copolymer is less than the above range, the amorphous polyester is crystallized, so that the sealing strength is reduced to a small extent.
On the other hand, when the amount exceeds the above range, the amount of heptane extractables becomes too large, so that it cannot be used for oily foods.

When the amount of the tackifier resin is too small, the sealing strength is too low. However, when the amount is excessively used, the oil resistance and processability of the composition are impaired. You.

The polymer composition of the present invention may contain optional additives in addition to the above three essential components. Examples of such additives include an antioxidant, a heat stabilizer, a light stabilizer, an antistatic agent, a lubricant, and a colorant. In particular, it is desirable to incorporate a lubricant in order to improve the processability of the composition. Such lubricants include fatty acid amides, high molecular weight polyethylene glycols,
Examples include hydrogenated castor oil, silica, and the like.

Such a lubricant is used in an amount of 100 parts by weight based on the total amount of the above three essential components and 100 parts by weight in the case of an organic compound lubricant.
It is effective to add about 1 to 10000 ppm, and in the case of an inorganic compound lubricant such as silica, about 0.1 to 3% by weight. The use of the lubricant is advantageous in that the polymer composition of the present invention can be used to prevent blocking between films and sticking to a metal roll in an extrusion coating process on a substrate, and also to enhance workability in a post-process such as rewinding. Have.

The polymer composition of the present invention has a melt flow rate (190 ° C., 2
160 g load) 1 to 400 g / 10 min, especially 1 to 15
It is desirable to adjust so as to be 0 g / 10 minutes.

Since the ethylene polymer composition of the present invention has the same heat sealing property as that of the amorphous polyester and the crystalline polyester, the amorphous polyester packaging material such as a cup, When used as a sealing layer for a lid material or a cover material of a tray or the like, a seal excellent in sealing property and easy opening property can be performed, and even if polyester is crystallized, stable sealing strength can be obtained.

The polymer composition of the present invention may also contain other polyester materials such as drawn polyethylene terephthalate, crystalline polyethylene terephthalate, polytetramethylene terephthalate and polyethylene naphthalate, and polyacrylonitrile-based polymers such as acrylonitrile and nitrile rubber. What is known as BAREX (trade name) obtained by graft polymerization of acrylic acid ester, styrene-based polymer such as polystyrene and high-impact polystyrene, polyvinyl chloride, etc.
It has an excellent easy-opening sealing property of exhibiting an appropriate sealing strength.

The composition of the present invention can be used as a single layer for the above applications, and can be used as a heat seal layer laminated on a substrate. Such a substrate is a stretched or unstretched film, for example, polyester such as polyethylene terephthalate, polyamide, polypropylene, polyethylene, ethylene / vinyl acetate copolymer, ethylene / unsaturated carboxylic acid ester copolymer. Coal, ethylene / unsaturated carboxylic acid copolymer or its ionomer, ethylene / vinyl alcohol copolymer, paper, aluminum foil, aluminum, silica, alumina, etc. vapor-deposited film, gas barrier material such as polyvinylidene chloride and polyvinyl alcohol Can be exemplified. These substrates may be a single layer or a laminate of two or more layers.

In particular, a laminated substrate comprising a polyolefin resin such as polyethylene, polypropylene, an ethylene / unsaturated carboxylic acid copolymer, an ionomer and another substrate is formed, and the ethylene polymer of the present invention is provided on the polyolefin resin side. By laminating the composition, a heat seal layer can be easily formed on the surface of various substrates.

Here, the lamination of the ethylene polymer composition and the substrate is carried out by a tandem extrusion lamination method in which the polyolefin resin and the ethylene polymer composition are continuously extruded and laminated on the substrate, and the polyolefin resin and the ethylene polymer composition are laminated. It can be carried out by a known method such as a method of coextruding and laminating a product, a sandwich extrusion laminating method of a polyolefin resin between a substrate and an ethylene polymer composition film, and the like. In laminating the base material and the polyolefin-based resin, it is effective to use an adhesive as necessary.

[0031]

According to the present invention, it is possible to provide a polymer composition having good sealing properties and low-temperature sealing properties, a wide temperature range for heat sealing, appropriate sealing strength, and excellent easy-opening properties. . Such a polymer composition is useful as a lid material or a cover material for various amorphous polyester packages utilizing the above-mentioned properties. The polymer composition of the present invention can also be used as an easily-openable seal material such as various other polyester materials, polyacrylonitrile-based polymers, styrene-based polymers, and polyvinyl chloride. Further, it can be used as a sealing material such as polyethylene, polypropylene, polyolefin such as poly-4-methyl-1-pentene, and polycarbonate.

[0032]

EXAMPLES Examples and comparative examples are described below to explain the effects of the present invention. The composition and physical properties of the raw material resin for preparing the ethylene polymer composition used in Examples and Comparative Examples are as follows.

(1) Ethylene polymer (1-1) Ethylene / vinyl acetate copolymer

(1-2) Ethylene / 1-octene copolymer polymerized in the presence of a single-site catalyst Density: 895 kg / m ³ MFR: 4.0 g / 10 min

(1-3) Linear low-density polyethylene "Ultzex 152" manufactured by Mitsui Petrochemical Industries, Ltd.
0 L "Density: 915 kg / m ³ MFR: 2.0 g / 10 min

(1-4) Low crystallinity ethylene / α-olefin copolymer “Tuffmer A4085” manufactured by Mitsui Petrochemical Industry Co., Ltd. Density: 890 kg / m ³ MFR: 3.6 g / 10 min

(2) ABA block copolymer

(3) Tackifying Resin "Alcon AM-1" manufactured by Arakawa Chemical Co., Ltd. Alicyclic hydrocarbon resin having a ring and ball method softening point of 115 ° C. (nuclear hydrogenated resin of aromatic hydrocarbon resin)

Example 1 40 parts by weight of an ethylene / vinyl acetate copolymer, 20 parts by weight of a single-site catalyst ethylene / α-olefin copolymer, 20 parts by weight of an ABA type block copolymer, tackification 100 parts by weight of a composition comprising 20 parts by weight of a resin, 0.2 parts by weight of erucamide, 0.1 parts by weight of polyethylene glycol, and 1 part by weight of silica
The mixture to which parts by weight were added was melt-mixed with a single screw extruder under the condition of a resin temperature of 150 ° C. to prepare an ethylene polymer composition (A).

The pellets of the polymer composition (A) were mixed with 5
Using an extruder having a diameter of 0 mm, an inflation film having a thickness of 30 μm was formed at a resin temperature of 160 ° C., and the inflation film and stretched PET (thickness of 12 μm) were prepared in advance.
m) / a low-density polyethylene film (thickness: 20 μm) was sandwich-coated with a high-pressure low-density polyethylene of 20 μm on the surface of a two-layered flexible material polyethylene film to obtain a laminated material.

Next, the heat sealability of the obtained laminate to the amorphous polyester and crystalline polyester sheets was measured by the following method. Using a heat sealer, the laminated material was converted to an amorphous polyester sheet (300 μm).
m) and the above-mentioned amorphous polyester sheet was heat-sealed with a crystalline polyester sheet crystallized by treating at 120 ° C. × 40 minutes in a vacuum chamber, and then under a condition of 23 ° C. × 50% RH. After aging for one day,
The heat seal strength was measured (N / 15 mm). Heat sealing conditions Temperature 120, 140, 160 ° C Pressure 0.2MPs Time 1 second The results are shown in Table 1.

Example 2 The composition of the polymer was as follows: 40 parts by weight of an ethylene / vinyl acetate copolymer, 30 parts by weight of a low-crystalline ethylene / α-olefin copolymer, and an ABA block copolymer. A mixture obtained by blending 10 parts by weight of the coalesced resin and 20 parts by weight of the tackifier resin and other additives in the same amount as in Example 1 was melt-mixed in the same manner as in Example 1 to obtain an ethylene polymer composition. A product (B) was prepared. From this composition, a laminated material was prepared in the same manner as in Example 1, and the heat sealability of the amorphous polyester and the crystalline polyester sheet was measured. The results are shown in Table 1.

[Embodiment 3] In Embodiment 2, AB-
An ethylene polymer composition (C) was prepared in the same manner as in Example 2 except that an ABA type block copolymer was used instead of the A type block copolymer. A laminated material was prepared in the same manner as described above, and the physical properties were measured. Table 1 shows the results.

Comparative Example 1 An ABA type block copolymer was not blended, and 40 parts by weight of an ethylene / vinyl acetate copolymer and 40 parts by weight of a low crystalline ethylene / α-olefin copolymer 40
Composition 1 comprising only 20 parts by weight of a tackifier resin and 1 part by weight
A mixture obtained by adding 0.2 parts by weight of erucamide, 0.1 part by weight of polyethylene glycol, and 1 part by weight of silica to 00 parts by weight was melt-mixed in the same manner as in Example 1,
A laminate was prepared from the obtained ethylene polymer composition in the same manner as in Example 1, and the heat sealability of the amorphous polyester and the crystalline polyester sheet was measured in the same manner as in Example 1. The results are shown in Table 3.

Example 4 An ethylene polymer composition prepared in the same manner as in Example 1 except that the ethylene / vinyl acetate copolymer was used instead of the ethylene / vinyl acetate copolymer (Example 4) D) Create a laminate from
Physical properties were measured. Table 2 shows the results.

[Comparative Example 2] Composition 10 comprising 80 parts by weight of an ethylene / vinyl acetate copolymer and 20 parts by weight of a tackifying resin without blending an ABA type block copolymer
A mixture prepared by adding 0.3 parts by weight of erucamide, 0.1 parts by weight of polyethylene glycol, and 4 parts by weight of silica to 0 parts by weight was melt-mixed in the same manner as in Example 1 to prepare an ethylene polymer. A laminated material was prepared from the united composition, and the physical properties were measured. The results are shown in Table 3.

Comparative Example 3 80 parts by weight of an ethylene / vinyl acetate copolymer, without adding a tackifier resin, ABA
Composition 1 consisting of only 20 parts by weight of mold block copolymer
A blend of 0.2 part by weight of erucamide and 0.1 part by weight of polyethylene glycol with respect to 00 parts by weight was melt-mixed in the same manner as in Example 1 to prepare an ethylene polymer composition. A laminated material was prepared in the same manner as in Example 1, and the physical properties were measured. The results are shown in Table 3.

Example 5 The composition of the polymer was as follows: 40 parts by weight of linear low-density polyethylene, 20 parts by weight of a single-site catalytic ethylene / α-olefin copolymer, ABA
20 parts by weight of the mold block copolymer and 20 parts by weight of the tackifier resin, and other additives were blended in the same amount as in Example 1 and melt-mixed in the same manner as in Example 1 to prepare. A laminated material is prepared from the ethylene polymer composition (E) thus obtained,
Physical properties were measured. The results are shown in Table 2.

Example 6 The compounding composition of the polymer was 60 parts by weight of a single-site catalyst ethylene / α-olefin copolymer, 20 parts by weight of an ABA type block copolymer, and 20 parts by weight of a tackifying resin. And the other additives were as in Example 1.
A laminate was prepared in the same manner as in Example 1 from the ethylene polymer composition (F) prepared by melt-mixing the blend obtained in the same amount as in Example 1, and the physical properties were determined. It was measured. The results are shown in Table 2.

As shown in Tables 1 and 2, the polymer composition of the present invention is a sealing material having good sealing properties and excellent openability for both amorphous and crystalline polyester sheets. On the other hand, a polymer composition containing no ABA type block copolymer does not provide a good sealing strength with respect to a crystalline polyester sheet, and a polymer composition containing no tackifier resin does not. Good seal strength cannot be obtained for any of the amorphous polyester sheet and the crystalline polyester sheet.

[0051]

[Table 1] (Seal strength unit: N / 15mm)

[0052]

[Table 2]

[0053]

[Table 3] (Seal strength unit: N / 15mm)

[Examples 7 to 15] The ethylene polymer composition (A) obtained in Example 1 and a density of 0.921 g / c
m ³ , melt flow rate 3g / 10min.
Co-extruded blown film having a thickness ratio of 13/74/13 and a thickness of 30 μm by three-layer co-extrusion so that the -methyl-1-pentene copolymer serves as both outer layers and the intermediate layer serves as an equal blend layer of both. It was created.

Next, the low-density polyethylene surface of the laminated film composed of stretched PET (thickness: 12 μm) / low-density polyethylene (thickness: 20 μm) and the ethylene-4-methyl-1-pentene copolymer surface of the three-layer coextruded film Was sandwiched with 20 μm of low-density polyethylene to obtain a laminated material.

As the ethylene polymer composition, (A)
Instead of using the ethylene polymer compositions (E) and (F) obtained in Examples 5 and 6, similar laminates were obtained.

Using a heat sealer, the ethylene polymer composition surface of the laminate was heat-sealed to the adherend sheet made of various polymers shown in Table 4, and the heat seal strength was measured (N / 15 mm). ). Heat sealing conditions Temperature 140, 160, 180 ° C Pressure 0.2MPs Time 1 second The results are shown in Table 5.

[0058]

[Table 4]

[0059]

[Table 5]

[Example 16] Using crystalline polyethylene terephthalate as an adherend sheet, the laminate was heat-sealed in the same manner as in Examples 1 to 15, and the heat seal strength immediately after sealing was measured. Separately, after heat sealing,
Heat seal strength was measured for a sample immersed in hot water at 90 ° C. for 30 minutes and left for 5 days. Table 6 shows the results.

[0061]

[Table 6]

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Claims (7)

[Claims] 1. An ethylene polymer of 40 to 80 parts by weight, A
-BA type block copolymer (A is a polystyrene block, B is an alkylene copolymer block) 5 to 40 parts by weight and a hydrocarbon resin-based tackifying resin or a terpene resin-based tackifying resin is 5 to 30 parts by weight. Ethylene polymer composition. 2. The ethylene-based polymer is a low-density polyethylene, an ethylene / α-olefin copolymer and an ethylene / α-olefin copolymer.
2. The method according to claim 1, which is selected from polar monomer copolymers.
A composition as described. 3. The composition according to claim 1, wherein the tackifying resin is a hydrogenated resin. 4. An easily-openable sealing material comprising the ethylene polymer composition according to claim 1. 5. The easy-open seal material according to claim 4, which is used for an adherend selected from polyester, polyacrylonitrile-based polymer, styrene polymer and polyvinyl chloride. 6. The easy-open seal material according to claim 5, wherein the polyester is selected from amorphous polyethylene terephthalate, crystalline polyethylene terephthalate, stretched polyethylene terephthalate, polytetramethylene terephthalate and polyethylene naphthalate. 7. The easy-open seal material according to claim 4, which is used by being laminated on a base material containing a polyolefin-based resin layer.