JP6579430B2 - Laminated body and package using the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a laminate, and more specifically, a laminate comprising a polyethylene film substrate having both surfaces irradiated with an electron beam, and a polyethylene film layer having at least one surface not irradiated with an electron beam, and a package using the laminate. About the body.

  A film made of a polyethylene resin has moderate flexibility, is excellent in transparency, moisture resistance, chemical resistance, and the like, and is inexpensive, and thus is used in various packaging materials. In particular, since the melting point of polyethylene is somewhat different depending on the type, it is generally about 100 to 140 ° C., so that it is generally used as a sealant film in the field of packaging materials.

  On the other hand, compared to other thermoplastic resins, polyethylene resin is inferior in heat resistance and insufficient in strength, so when used as a packaging material, heat resistance and strength such as polyester film and nylon film It is used as a laminate that laminates a resin film with excellent polyethylene film and a polyethylene film side, and the end of the laminate can be heat sealed so that the polyethylene film side is the inside of the package, so that a package can be produced. (For example, JP-A-2005-104525).

  By the way, in recent years, with the increasing demand for the construction of a recycling society, attempts have been made to recycle and use packaging materials. However, a laminate in which different types of resin films are bonded together is difficult to separate for each type of resin, and there is a problem that it is not suitable for recycling.

JP 2005-104525 A

  The present inventors have now found that polyethylene near the film surface irradiated with an electron beam can be cured or crosslinked by irradiating the polyethylene film with an electron beam. Furthermore, if a polyethylene film irradiated with such an electron beam is used as a base material, and a polyethylene film that is not irradiated with an electron beam is bonded to the laminated body to form a laminate, a different type of resin film that has been used in conventional packaging It was replaced with the laminated body which laminated | stacked together, and the package body can be produced only with a polyethylene film, and the knowledge that the package body suitable for recycling can be obtained was acquired. The present invention is based on this finding.

  Accordingly, an object of the present invention is to provide a laminate in which a package can be produced only with a polyethylene film, instead of a laminate film in which different types of resin films used in a conventional package are bonded together. Another object of the present invention is to provide a package using such a laminate.

  The laminate according to the present invention comprises a polyethylene film substrate and a polyethylene film layer, the polyethylene film substrate is irradiated with an electron beam on both sides, and comprises polyethylene and a crosslinking agent. , At least one surface is not irradiated with an electron beam.

  In the laminate according to the present invention, the polyethylene is selected from the group consisting of low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, and a copolymer of ethylene and another monomer. It is preferable that there is at least one.

  Moreover, in the laminated body by this invention, it is preferable that content of the crosslinking agent in the said polyethylene film base material is 1-49 mass%.

  In the laminate according to the present invention, the cross-linking agent is preferably a styrene elastomer, an ethylene-acrylate copolymer, or an ethylene-acrylate ester-glycidyl methacrylate.

  In the laminate according to the present invention, the polyethylene film substrate and the polyethylene film layer may be dry-laminated so that the surface of the polyethylene film layer that is not irradiated with an electron beam is the outermost surface. preferable.

  Moreover, in the laminated body by this invention, it is preferable that the said polyethylene film base material is a laminated film base material which consists of two or more polyethylene films.

  Moreover, in the laminated body by this invention, it is preferable that the dose of an electron beam is 10-1000 kGy.

  Moreover, in the laminated body by this invention, it is preferable that the acceleration voltage of an electron beam is 30-300 kV.

  Moreover, in the laminated body by this invention, it is preferable that the gel fraction of a polyethylene film base material is 20 to 80%.

  Moreover, in the laminated body by this invention, it is preferable to further provide a barrier film between the said polyethylene film base material and the said polyethylene film layer.

  Moreover, the packaging body by another aspect of this invention is a packaging body which consists of an above described laminated body, Comprising: The surface side where the electron beam irradiation of the said polyethylene film layer with which the said laminated body is equipped is heat-sealed. It is characterized by.

  According to the present invention, by irradiating the polyethylene film substrate constituting the laminate with an electron beam, the polyethylene in the film irradiated with the electron beam can be cured or crosslinked. Since the polyethylene film surface whose crosslink density is higher than that of ordinary polyethylene by electron beam irradiation is improved in heat resistance and strength, it can satisfy the physical properties required for the outer layer of the package. Moreover, since the laminated body by this invention is equipped with the polyethylene film layer by which at least one surface is not irradiated with an electron beam, ie, heat seal property and a softness | flexibility, the package can be produced.

It is a section schematic diagram of a layered product by one embodiment of the present invention. It is a section schematic diagram of a layered product by one embodiment of the present invention. It is a section schematic diagram of a layered product by one embodiment of the present invention.

<Laminate>
The laminate according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a laminate 10 of the present invention in one embodiment. The laminate 10 is provided with a polyethylene film substrate 1 that is irradiated with an electron beam on both sides, and a polyethylene film layer 2 that is not irradiated with an electron beam on both sides. Moreover, in one Embodiment, as shown in FIG. 2, the laminated body 10 is equipped with the polyethylene film base material 1 by which the electron beam was irradiated to both surfaces, and the polyethylene film layer 2 by which the electron beam was not irradiated on one side. Become. At this time, it is preferable to laminate | stack so that the surface of the polyethylene film layer which is not irradiated with an electron beam may turn into an outermost surface. When the surface of the polyethylene film layer that is not irradiated with the electron beam is the outermost surface, the heat sealability of the laminate can be maintained. Moreover, in one Embodiment, as shown in FIG. 3, as for the laminated body, the barrier film | membrane 3 may be provided between both the polyethylene film base materials 1 and the polyethylene film layer 2. As shown in FIG.

<Polyethylene film substrate>
The polyethylene film substrate provided in the laminate according to the present invention comprises polyethylene and a crosslinking agent, and both surfaces thereof are irradiated with an electron beam. The polyethylene film substrate may be a single layer or a laminated film substrate composed of a plurality of polyethylene films. When the laminate is provided with such a polyethylene film substrate, the heat resistance and strength of the surface of the laminate are improved, and physical properties required as an outer layer of a package or the like can be satisfied.

  The reason why the crosslink density of polyethylene differs depending on whether or not the electron beam is irradiated is not clear, but is considered as follows. That is, when a polyethylene film is irradiated with an electron beam, a carbon-hydrogen bond in polyethylene near the film surface is cut, and a radical is generated at the cut bond end. The generated radicals are considered to come into contact with other polyethylene molecular chains due to the molecular motion of the molecular chains, pull out hydrogen atoms and bond with carbon atoms in the polyethylene molecular chains, resulting in the formation of a crosslinked structure. .

  Polyethylene films usually tend to shrink when heated, but dimensional stability tends to improve as the crosslink density increases. For this reason, polyethylene films with different crosslink densities on the front and back surfaces curl like a bimetal when heated. Therefore, as a simple method for confirming that the crosslinking density is different between the front and back surfaces of the polyethylene film, it can be confirmed by heating the polyethylene film irradiated with the electron beam only on one side.

In addition, using the fact that the crosslinked part does not dissolve in the solvent, immerse the polyethylene film substrate in an organic solvent such as methyl ethyl ketone, dry the insoluble film remaining without dissolution, measure the mass, and before dissolving The crosslink density can also be examined by calculating the gel fraction from the mass of the polyethylene film substrate and the insoluble film after drying. Specifically, first, the polyethylene film substrate Xg is wrapped with a Yg stainless wire mesh, heated and immersed in a solvent, and the polyethylene film substrate wrapped with the stainless wire mesh is taken out. Subsequently, this is vacuum-dried and the mass (Zg) of the polyethylene film base material wrapped with the stainless steel wire mesh after drying is measured. And a gel fraction can be measured from following formula (1).
Gel fraction (% by mass) = (Z−Y) / X × 100 (1)

  The gel fraction of the polyethylene film substrate is preferably 20 to 80%, more preferably 30 to 80%, and further preferably 40 to 80%.

  The polyethylene film substrate according to the present invention comprises polyethylene and a crosslinking agent. When a polyethylene film base material contains a crosslinking agent in addition to polyethylene, a higher crosslinking density can be realized, and heat resistance can be further improved.

As polyethylene, one or more types of different density and branching such as high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), and linear low density polyethylene (LLDPE) are used. Can be used as a mixture. In general, high density polyethylene has a density of 0.940 g / cm ³ or more, medium density polyethylene has a density of 0.925 to 0.940 g / cm ³ , and low density polyethylene has a density of 0. .Less than 925 g / cm ³

  The above-described polyethylene having different density and branching can be obtained by appropriately selecting the polymerization method. For example, as a polymerization catalyst, using a multi-site catalyst such as a Ziegler-Natta catalyst or a single site catalyst such as a metallocene catalyst, by any of gas phase polymerization, slurry polymerization, solution polymerization, and high-pressure ion polymerization, It is preferable to carry out by one stage or two or more stages.

  The above single-site catalyst is a catalyst that can form a uniform active species, and is usually adjusted by bringing a metallocene transition metal compound or a nonmetallocene transition metal compound into contact with an activation cocatalyst. . The single site catalyst is preferable because the active site structure is uniform as compared with the multisite catalyst, and a polymer having a high molecular weight and a high degree of uniformity can be polymerized. As the single site catalyst, it is particularly preferable to use a metallocene catalyst. The metallocene-based catalyst is a catalyst containing a transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, a cocatalyst, and if necessary, an organometallic compound, and each catalyst component of the support. is there.

  In the group IV transition metal compound containing a ligand having a cyclopentadienyl skeleton, the cyclopentadienyl skeleton is a cyclopentadienyl group, a substituted cyclopentadienyl group, or the like. . Examples of substituted cyclopentadienyl groups include hydrocarbon groups having 1 to 30 carbon atoms, silyl groups, silyl substituted alkyl groups, silyl substituted aryl groups, cyano groups, cyanoalkyl groups, cyanoaryl groups, halogen groups, haloalkyl groups, halosilyl groups. It has at least one substituent selected from a group and the like. The substituted cyclopentadienyl group may have two or more substituents, and the substituents are bonded to each other to form a ring, such as an indenyl ring, a fluorenyl ring, an azulenyl ring, and a hydrogenated product thereof. It may be formed. Rings formed by bonding substituents to each other may further have substituents.

  In the group IV transition metal compound containing a ligand having a cyclopentadienyl skeleton, examples of the transition metal include zirconium, titanium, hafnium, and particularly zirconium and hafnium are preferable. The transition metal compound usually has two ligands having a cyclopentadienyl skeleton, and each ligand having a cyclopentadienyl skeleton is preferably bonded to each other via a bridging group. Examples of the bridging group include substituted silylene groups such as alkylene groups having 1 to 4 carbon atoms, silylene groups, dialkylsilylene groups and diarylsilylene groups, dialkylgermylene groups and diarylgermylene groups. Preferably, it is a substituted silylene group. The transition metal compound of Group IV of the Periodic Table containing a ligand having a cyclopentadienyl skeleton can use one or a mixture of two or more as a catalyst component.

  The co-catalyst is one that can effectively make the above-mentioned group IV transition metal compound as a polymerization catalyst, or can neutralize ionic charges in a catalytically activated state. Co-catalysts include benzene-soluble aluminoxanes of organoaluminum oxy compounds, benzene-insoluble organoaluminum oxy compounds, ion-exchange layered silicates, boron compounds, active hydrogen group-containing or non-containing cations and non-coordinating anions. And lanthanoid salts such as lanthanum oxide, tin oxide, phenoxy compounds containing a fluoro group, and the like.

The group IV transition metal compound containing a ligand having a cyclopentadienyl skeleton may be used by being supported on an inorganic or organic compound carrier. The support is preferably a porous oxide of an inorganic or organic compound, specifically, an ion-exchange layered silicate such as montmorillonite, SiO ₂ , Al ₂ O ₃ , MgO, ZrO ₂ , TiO ₂ , B ₂ O. _3, CaO, ZnO, BaO, and the like or mixtures thereof ThO _2. Furthermore, examples of the organometallic compound used as necessary include organoaluminum compounds, organomagnesium compounds, and organozinc compounds. Of these, organic aluminum is preferably used.

  A copolymer of ethylene and another monomer can also be used. Examples of the ethylene copolymer include a copolymer composed of ethylene and an α-olefin having 3 to 20 carbon atoms. Examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene, 3-methyl-1-butene, 4-methyl-1-pentene, 6-methyl- Examples include 1-heptene. Moreover, as long as the object of the present invention is not impaired, it may be a copolymer with vinyl acetate, acrylate ester or the like.

  Moreover, in this invention, it may replace with ethylene obtained from a fossil fuel and may use the polyethylene which used ethylene derived from biomass as the raw material. Since such biomass-derived polyethylene is a carbon-neutral material, it can be made into a package with less environmental impact. Such polyethylene derived from biomass can be produced, for example, by a method described in JP2013-177531A. Moreover, you may use the biomass-derived polyethylene resin (for example, green PE marketed from Brasschem etc.) marketed.

  As the crosslinking agent, styrene-based elastomers such as styrene-polyisoprene elastomer, styrene-polybutadiene elastomer, styrene-polyisoprene-butadiene random copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene -Ethylene-acrylate copolymers such as butyl acrylate copolymer, ethylene-acrylic acid ester-glycidyl methacrylate, etc.

  The content of the crosslinking agent in the polyethylene film substrate is preferably 1 to 49% by mass, more preferably 10 to 40% by mass, and still more preferably 15 to 35% by mass. If content of a crosslinking agent is in the said numerical range, the heat resistance and intensity | strength of a polyethylene film base material can be improved further.

  The polyethylene film substrate can be obtained by melting the resin composition comprising at least the above-described polyethylene resin and a crosslinking agent, and forming the film by a melt extrusion method such as inflation molding or T-die molding. . For example, it is supplied to a melt extruder heated to a temperature not lower than the melting point (Tm) of polyethylene to a temperature of Tm + 120 ° C., melts the resin composition, is extruded into a cylindrical shape from a die such as an annular die, and the extruded cylinder It can shape | mold by sending air to a shaped object, forming a bubble, and pressurizing this with a roller.

  A laminated film substrate can also be produced by bonding two polyethylene film substrates together by a dry lamination method using an adhesive or the like, and then irradiating an electron beam. Further, in order to omit the adhesive application step and the bonding step, a resin composition containing polyethylene and a cross-linking agent, and polyethylene or a resin composition having a different composition are coextruded from an inflation film forming machine or the like, A laminated film substrate can also be produced by performing electron beam irradiation. Furthermore, a polyethylene film is formed by extrusion coating a molten polyethylene or a resin composition having a different composition on a polyethylene film substrate made of a resin composition, and then a laminated film is formed by performing electron beam irradiation. A substrate can be manufactured.

  Although the thickness of a polyethylene film base material is arbitrary according to the use, it is about 5 micrometers-200 micrometers normally, Preferably it is about 5 micrometers-100 micrometers. The thickness can be appropriately adjusted depending on the screw rotation speed of the melt extruder, the rotation speed of the cooling roll, and the like.

  When forming a film into a polyethylene film substrate, for example, film processability, heat resistance, weather resistance, mechanical properties, dimensional stability, antioxidant properties, slip properties, mold release properties, flame retardancy, Various plastic compounding agents and additives can be added for the purpose of improving and modifying moldability, electrical characteristics, strength, etc. The amount of addition is from a very small amount to several tens of percent. Depending on the purpose, it can be added arbitrarily. Common additives include, for example, antioxidants, ultraviolet absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, modifying resins, and the like.

  The polyethylene film base material with which the laminated body by this invention is provided can be obtained by irradiating an electron beam from both surfaces of the said polyethylene film base material, and improving the crosslinking density of both surfaces. Moreover, an electron beam may be irradiated from one surface, the polyethylene film base material may be penetrated by the electron beam, and not only the irradiated surface but also the crosslink density on the surface opposite to the irradiated surface may be improved. The electron beam irradiation energy varies depending on the intended use of the package, but the higher the electron beam irradiation energy, the greater the amount of radicals generated and the easier it is to form a crosslinked structure, but the higher the irradiation energy. If it is too large, the molecular chain of polyethylene will be cleaved too much, and film properties such as strength will be significantly reduced.

  The electron beam dose is preferably in the range of 10 to 2000 kGy, more preferably 20 to 1000 kGy, and the acceleration voltage of the electron beam is preferably in the range of 30 to 300 kV, more preferably 50 to 300 kV, and particularly preferably 50 to 250 kV. Further, the irradiation energy of the electron beam is preferably 20 to 750 keV, more preferably 25 to 400 keV, further preferably 30 to 300 keV, and particularly preferably 20 to 200 keV.

  As the electron beam irradiation apparatus, conventionally known ones can be used. For example, a curtain type electron irradiation apparatus (LB1023, manufactured by I Electron Beam Co., Ltd.) or a line irradiation type low energy electron beam irradiation apparatus (EB-ENGINE, Hamamatsu Photonics). In particular, a line irradiation type low energy electron beam irradiation device (EB-ENGINE, manufactured by Hamamatsu Photonics Co., Ltd.) can be used preferably.

  The oxygen concentration in the electron beam irradiation apparatus is preferably 500 ppm or less, and more preferably 100 ppm or less. By performing electron beam irradiation under such conditions, generation of ozone can be suppressed, and radicals generated by electron beam irradiation can be suppressed from being deactivated by oxygen in the atmosphere. it can. Such a condition can be achieved, for example, by setting the inside of the apparatus to an inert gas (nitrogen, argon, etc.) atmosphere.

  Since the polyethylene film easily undergoes thermal shrinkage, the electron beam irradiation is preferably performed simultaneously with cooling using a cooling drum or the like.

  Moreover, after a polyethylene film base material is laminated | stacked through a polyethylene film layer and an adhesive agent, you may irradiate an electron beam from the polyethylene film base material side.

<Polyethylene film layer>
The polyethylene film layer provided in the laminate according to the present invention comprises a polyethylene film, and at least one surface thereof is not irradiated with an electron beam. When the laminate includes such a layer, different physical properties (for example, strength, heat resistance, heat sealability) between the base material and the layer provided on the base material while using the same material (polyethylene) Etc.) can be made into different laminates.

  As the polyethylene film layer on which at least one surface is not irradiated with the electron beam, the same film as the above-described polyethylene film can be used. Therefore, since the same polyethylene is used, recycling can be easily performed.

  Although the thickness of a polyethylene film layer is arbitrary according to the use, it is about 15-100 micrometers normally, Preferably it is about 20-200 micrometers, More preferably, it is about 25-160 micrometers. In the production of the polyethylene film, the thickness of the base material can be appropriately adjusted by changing the screw rotation speed of the melt extruder or the rotation speed of the cooling roll.

  The polyethylene film substrate and the polyethylene film layer can be produced by bonding by a dry lamination method using an adhesive or the like. However, in order to omit the adhesive coating process and the bonding process, the polyethylene film By extrusion coating a molten polyethylene resin on the substrate, a laminate can be produced simultaneously with the formation of the polyethylene film layer.

  Moreover, when a polyethylene film layer is a film layer by which one side was irradiated with the electron beam, it is preferable to laminate | stack with a polyethylene film base material so that the surface which is not irradiated with the electron beam of a polyethylene film layer may become an outermost surface.

<Barrier film>
The laminate according to the present invention may include a barrier film between the polyethylene film substrate and the polyethylene film layer, if desired. The barrier film can be formed by depositing a metal foil such as an aluminum foil, or a metal such as aluminum, or an inorganic oxide such as aluminum oxide or silicon oxide on the surface of the polyethylene film layer. As a vapor deposition method, a conventionally known method can be employed. For example, a physical vapor deposition method (Physical Vapor Deposition method, PVD method) such as a vacuum vapor deposition method, a sputtering method, or an ion plating method, or a plasma chemical vapor deposition method. And chemical vapor deposition (chemical vapor deposition, CVD) such as thermal chemical vapor deposition and photochemical vapor deposition. In addition, when manufacturing the film which consists of a transparent laminated body used for the packaging material, a vacuum vapor deposition method is mainly used and a plasma chemical vapor deposition method is also used partially.

In addition, for example, a composite film composed of two or more vapor-deposited films of different kinds of inorganic oxides can be formed by using both physical vapor deposition and chemical vapor deposition. The degree of vacuum deposition chamber, before ^introduction of oxygen 10 ^-2 to 10 -8 mbar approximately, in ^particular, is preferably about 10 ^-3 to 10 -7 mbar, in the post-oxygen ^{introduction,} 10 -1 to 10 ^{- About 6} mbar, especially about 10 ⁻² to 10 ⁻⁵ mbar is preferable. The amount of oxygen introduced varies depending on the size of the vapor deposition machine. For the oxygen to be introduced, an inert gas such as argon gas, helium gas, or nitrogen gas may be used as a carrier gas as long as there is no problem. As a conveyance speed of a film, about 10-800 m / min, especially about 50-600 m / min are preferable.

  In the present invention, the surface of the deposited film formed as described above may be subjected to oxygen plasma treatment. The amount of oxygen introduced for the oxygen plasma treatment varies depending on the size of the vapor deposition apparatus, but is usually about 50 sccm to 2000 sccm, and particularly preferably about 300 sccm to 800 sccm. Here, sccm means the average amount of oxygen introduced (cc) per minute in the standard state (STP: 0 ° C., 1 atm). For the oxygen to be introduced, an inert gas such as argon gas, helium gas, or nitrogen gas may be used as a carrier gas as long as there is no problem. By performing such treatment on the deposited film (barrier film), the adhesion when the polyethylene film substrate is bonded to the barrier film formed on the polyethylene film layer is improved. These are merely examples, and the present invention is not limited to those obtained by these methods.

  To produce a laminate having a barrier film, a polyethylene film is formed by forming a barrier film on a polyethylene film substrate as described above, and then extrusion-coating a molten polyethylene resin on the barrier film. A laminate can be produced simultaneously with the film formation of the layers.

<Packaging body>
The packaging body according to the present invention is a polyethylene film when the above-described laminate is formed by irradiating a polyethylene film substrate on both sides with an electron beam on the outside, a polyethylene film layer on the inside, and one side of the polyethylene film layer with an electron beam. It can be manufactured by folding the layers so that the surface not irradiated with the electron beam is on the inside, and then heat-sealing the ends. Depending on the sealing method, for example, side seal type, two-side seal type, three-side seal type, four-side seal type, envelope-attached seal type, palm-attached seal type (pillow seal type), pleated seal type, flat bottom seal type, square bottom seal Various types of packaging bodies can be manufactured by heat-sealing by a heat-sealing form such as a mold, a gusset mold, and the like. In addition, for example, a self-supporting packaging bag (standing pouch) is also possible. As a heat sealing method, for example, a known method such as a bar seal, a rotary roll seal, a belt seal, an impulse seal, a high frequency seal, or an ultrasonic seal can be used.

  According to the present invention, the strength and dimensions required for the outer film of the package is that the polyethylene film substrate irradiated with the electron beam included in the laminate is a laminate made of only one kind of material (that is, polyethylene). Since the physical properties such as stability can be satisfied and the heat-sealability of the polyethylene film layer on which at least one surface is not irradiated with an electron beam is maintained, it can be suitably used as a packaging film. Moreover, since a package can be manufactured using the laminated body which consists only of 1 type of material, recycling of a material can be performed easily after use of a package.

  Examples The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

<Example 1>
Dry blend of linear low density polyethylene (manufactured by Prime Polymer Co., Ltd., trade name: Evolue SP2020) and styrene elastomer (Kuraray Co., Ltd., trade name: Hibler 7125) in a mass ratio of 4: 1 Thus, a resin composition was obtained.

  The resin composition and linear low density polyethylene (manufactured by Prime Polymer Co., Ltd., trade name: Evolue SP2020) were coextruded 1: 1 by inflation film formation to obtain a laminated film. The thickness of the obtained laminated film was 60 μm.

From the surface of the layer made of the resin composition of the laminated film obtained as described above, an electron beam irradiation device (line irradiation type low energy electron beam irradiation device EES-L-DP01, manufactured by Hamamatsu Photonics Co., Ltd.) is used. An electron beam was irradiated under the following conditions to obtain a polyethylene laminated film having both surfaces irradiated with an electron beam.
Voltage: 110 kV
Current: 1mA
Irradiation dose: 650 kGy
In-device oxygen concentration: 100 ppm or less

  After electron beam irradiation, the surface of the polyethylene laminated film made of linear low-density polyethylene is changed to a 60 μm-thick linear low-density polyethylene film (trade name: Rix L6100, manufactured by Toyobo Co., Ltd.). A laminate was obtained by dry lamination via a urethane adhesive (trade name: RU-40 / curing agent H-4, manufactured by Rock Paint Co., Ltd.).

<Example 2>
In Example 1, a laminate was obtained in the same manner as in Example 1 except that the electron beam irradiation dose was changed to 430 kGy.

<Example 3>
A low-density polyethylene (trade name: LD2420H, product name: LD2420H) is dry blended with a styrene elastomer (Kuraray Co., Ltd., product name: Hibura 7311) at a mass ratio of 3: 2, and a resin composition is obtained. Got.

  The resin composition and low density polyethylene (manufactured by PTT, trade name: LD2420H) were coextruded 1: 1 by inflation film formation to obtain a laminated film. The thickness of the obtained laminated film was 60 μm.

  From the surface of the layer made of the resin composition of the laminated film obtained as described above, an electron beam irradiation device (line irradiation type low energy electron beam irradiation device EES-L-DP01, manufactured by Hamamatsu Photonics Co., Ltd.) is used. Then, an electron beam was irradiated under the same conditions as in Example 1 to obtain a polyethylene laminated film in which both surfaces were irradiated with an electron beam.

  After electron beam irradiation, the surface of the polyethylene laminated film made of low-density polyethylene is changed to a 60 μm-thick linear low-density polyethylene film (trade name: Rix L6100, manufactured by Toyobo Co., Ltd.). A laminate was obtained by dry lamination via a product (trade name: RU-40 / hardening agent H-4, manufactured by Rock Paint Co., Ltd.).

<Example 4>
In Example 3, a laminate was obtained in the same manner as in Example 3 except that the electron beam irradiation dose was changed to 430 kGy.

<Example 5>
Linear low density polyethylene (manufactured by Prime Polymer Co., Ltd., trade name: Evolue SP2020) and ethylene-methyl acrylate copolymer (trade name: LOTRYL18MA02, manufactured by Arkema Co., Ltd.) are used in a mass ratio of 4: 1. Dry blending was performed to obtain a resin composition.

  The resin composition and linear low density polyethylene (manufactured by Prime Polymer Co., Ltd., trade name: Evolue SP2020) were coextruded 1: 1 by inflation film formation to obtain a laminated film. The thickness of the obtained laminated film was 60 μm.

  From the surface of the layer made of the resin composition of the laminated film obtained as described above, an electron beam irradiation device (line irradiation type low energy electron beam irradiation device EES-L-DP01, manufactured by Hamamatsu Photonics Co., Ltd.) is used. Then, an electron beam was irradiated under the same conditions as in Examples, and a polyethylene laminated film having both surfaces irradiated with an electron beam was obtained.

  After electron beam irradiation, the surface of the polyethylene laminated film made of linear low-density polyethylene is changed to a 60 μm-thick linear low-density polyethylene film (trade name: Rix L6100, manufactured by Toyobo Co., Ltd.). A laminate was obtained by dry lamination via a urethane adhesive (trade name: RU-40 / curing agent H-4, manufactured by Rock Paint Co., Ltd.).

<Example 6>
In Example 5, a laminate was obtained in the same manner as Example 5 except that the electron beam irradiation dose was changed to 430 kGy.

<Example 7>
Dry blend of linear low density polyethylene (manufactured by Prime Polymer Co., Ltd., trade name: Evolue SP2020) and styrene elastomer (Kuraray Co., Ltd., trade name: Hibler 7125) in a mass ratio of 9: 1 Thus, a resin composition was obtained.

  The resin composition was extruded into an inflation film to obtain a polyethylene film. The thickness of the obtained polyethylene film was 60 μm.

  From one surface of the polyethylene film obtained as described above, an electron beam irradiation apparatus (line irradiation type low energy electron beam irradiation apparatus EES-L-DP01, manufactured by Hamamatsu Photonics Co., Ltd.) was used. An electron beam was irradiated under the same conditions to obtain a polyethylene film with both surfaces irradiated with the electron beam.

  After electron beam irradiation, the polyethylene film is converted into a 60 μm-thick linear low-density polyethylene film (manufactured by Toyobo Co., Ltd., trade name: Rix L6100), a two-component curable urethane adhesive (manufactured by Rock Paint Co., Ltd.) A laminate was obtained by dry lamination via a trade name: RU-40 / curing agent H-4).

<Example 8>
In Example 7, a laminate was obtained in the same manner as in Example 7 except that the electron beam irradiation dose was changed to 430 kGy.

<Comparative Example 1>
A linear low density polyethylene (manufactured by Prime Polymer Co., Ltd., trade name: Evolue SP2020) was formed by inflation film to obtain a polyethylene film having a thickness of 120 μm.

  This polyethylene film is converted into a 60 μm-thick linear low-density polyethylene film (trade name: Rix L6100, manufactured by Toyobo Co., Ltd.), a two-component curable urethane adhesive (manufactured by Rock Paint Co., Ltd., product name: RU). -40 / Hardening agent H-4) was used for dry lamination to obtain a laminate.

<Comparative Example 2>
A laminate was obtained in the same manner as in Example 1 except that the electron beam was not irradiated.

<Comparative Example 3>
From one surface of the polyethylene film obtained in Comparative Example 1, an electron beam irradiation device (line irradiation type low energy electron beam irradiation device EES-L-DP01, manufactured by Hamamatsu Photonics Co., Ltd.) is used as in Example 1. The film was irradiated with an electron beam to obtain a polyethylene film with both surfaces irradiated with an electron beam.

  After the electron beam irradiation, this polyethylene film is converted into a 60 μm-thick linear low-density polyethylene film (manufactured by Toyobo Co., Ltd., trade name: Rix L6100), a two-component curable urethane adhesive (manufactured by Rock Paint Co., Ltd.). , Trade name: RU-40 / curing agent H-4) to obtain a laminate.

<Heat sealability evaluation>
(Appearance evaluation)
Each film of Examples 1-8 and Comparative Examples 1-3 was cut into 10 cm × 10 cm to prepare three sample pieces. This sample piece was folded in half so that the surface on which the electron beam was not irradiated, that is, the dry-laminated linear low-density polyethylene film side was inside, using a heat seal tester, the temperature was 180 ° C., A region of 1 cm × 10 cm was heat-sealed under conditions of a pressure of 1 kgf / cm ² and 1 second. The remaining two sample pieces were similarly heat-sealed except that the temperature was changed to 190 ° C. and 200 ° C.

The appearance of the obtained sample pieces after heat sealing was visually evaluated. The evaluation criteria were as follows.
○: Even when heat sealed at 200 ° C., the surface is not melted and there is no problem in appearance. Δ: When heat sealed at 190 ° C., the surface is melted and there is a problem in appearance. X: When heat sealed at 180 ° C., the surface is melted and there is a problem in appearance. The evaluation results are as shown in Table 1 below.

(Seal strength)
Further, the heat-sealed sample piece was cut into a strip shape with a width of 15 mm, and both ends that were not heat-sealed were gripped by a tensile tester, and peel strength (N / 15 mm under the conditions of speed 300 mm / min and load range 50 N) ) Was measured. The measurement results were as shown in Table 1 below.

<Gel fraction>
Samples were prepared by cutting each laminate of Examples 1 to 6 and Comparative Examples 1 and 2 to 1 g, wrapped with 5 g of 400 mesh stainless steel wire mesh, and immersed in 100 ml of xylene at 120 ° C. for 24 hours. . Then, after vacuum-drying the sample piece wrapped with the stainless steel wire mesh at 80 ° C. for 16 hours, the mass was measured to obtain the gel fraction.

Claims (10)

A laminate comprising a polyethylene film substrate and a polyethylene film layer,
The polyethylene film substrate is irradiated with an electron beam on both sides, and comprises polyethylene and a crosslinking agent,
The polyethylene film substrate and the polyethylene film layer are dry-laminated so that the surface of the polyethylene film layer that is not irradiated with an electron beam is the outermost surface,
The polyethylene film layer has a structure in which an electron beam does not reach at least a surface opposite to the polyethylene film substrate side .   2. The polyethylene according to claim 1, wherein the polyethylene is at least one selected from the group consisting of low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, and a copolymer of ethylene and another monomer. The laminated body of description.   Content of the crosslinking agent in the said polyethylene film base material is a laminated body of Claim 1 or 2 which is 1-49 mass%.   The laminate according to any one of claims 1 to 3, wherein the crosslinking agent is a styrene-based elastomer, an ethylene-acrylate copolymer, or an ethylene-acrylate ester-glycidyl methacrylate. The laminate according to any one of claims 1 to 4 , wherein the polyethylene film substrate is a laminated film substrate composed of two or more polyethylene films. The laminated body as described in any one of Claims 1-5 whose dose of the said electron beam is 10-2000 kGy. The laminate according to any one of claims 1 to 6 , wherein an acceleration voltage of the electron beam is 30 to 300 kV. The laminate according to any one of claims 1 to 7 , wherein the polyethylene film base has a gel fraction of 20 to 80%. The laminate according to any one of claims 1 to 8 , further comprising a barrier film between the polyethylene film substrate and the polyethylene film layer. A package comprising a laminate according to any one of claims 1 to 9, the surface side, which is not an electron beam irradiation of the polyethylene film layer, wherein the laminate comprises becomes heat bonded, packaging .