JP6969160B2 - Polyethylene press film and packaging material using it - Google Patents

Description

The present invention relates to a polyethylene co-pressing film, and more particularly, a polyethylene co-pressing film comprising a polyethylene film base material which is an electron beam irradiation layer and a polyethylene film layer having a heat-sealing property, and a packaging material using the same. Regarding.

A film made of polyethylene (hereinafter, simply referred to as "polyethylene film") has appropriate flexibility, is excellent in transparency, moisture resistance, chemical resistance, etc., and is inexpensive, so that it can be used as various packaging materials. in use. In particular, since the melting point of polyethylene is about 100 to 140 ° C., although it varies slightly depending on the type, it is generally used as a sealant film in the field of packaging materials.

On the other hand, compared to other thermoplastic resins, polyethylene is inferior in heat resistance and insufficient in strength. Therefore, when used as a packaging material, the heat resistance and strength of polyester films, nylon films, etc. It is used as a laminate made by laminating an excellent resin film and a polyethylene film, and the packaging material can be produced by heat-sealing the end of the laminate so that the polyethylene film side is inside the packaging material. (For example, Japanese Patent Application Laid-Open No. 2005-104525).

By the way, in recent years, with the increasing demand for the construction of a sound material-cycle society, attempts have been made to recycle and use packaging materials. However, there is a problem that it is difficult to separate each type of resin in the laminated body in which different kinds of resin films are laminated as described above, and it is not suitable for recycling.

Japanese Unexamined Patent Publication No. 2005-104525

In a previous application (Japanese Patent Application No. 2015-21395), the present inventors have proposed a laminate comprising a polyethylene film irradiated with an electron beam and a polyethylene film having a heat-sealing property. By irradiating the polyethylene film with an electron beam, its heat resistance and strength can be improved, so that the packaging material can be produced only with polyethylene.

However, in the laminate produced as described above, although the polyethylene film having heat-sealing property is not directly irradiated with the electron beam, the influence of the electron beam passing through the polyethylene film irradiated with the electron beam is exerted. Since it is exposed to some extent, active radicals (for example, hydroper radicals) are likely to be generated by being exposed to the action of light or heat during storage, and as a result, the heat sealability may be deteriorated. , There was room for improvement.
Furthermore, the present inventors have recently found that the laminated body produced by irradiating with an electron beam tends to decrease its breaking strength over time.

Then, the present inventors surprisingly prevent the heat sealability and the breaking strength from being remarkably lowered with time by containing a hydride amine-based antioxidant in the polyethylene film irradiated with the electron beam. I found that I could do it.

Therefore, an object of the present invention is to provide a polyethylene co-pressing film capable of producing a packaging material only by a polyethylene film, which can prevent deterioration of heat-sealing property and breaking strength over time. Is. Another object of the present invention is to provide a packaging material using this polyethylene co-pressing film.

The polyethylene co-pressing film of the present invention comprises a polyethylene film base material and a polyethylene film layer.
The polyethylene film substrate is an electron beam irradiation layer containing polyethylene and a hydride-based antioxidant.
The polyethylene film layer contains polyethylene and is characterized in that the outer surface has a heat-sealing property.

In the above embodiment, the content of the hydride-based antioxidant in the polyethylene film substrate is preferably 1% by mass or more and 30% by mass or less.

In the above embodiment, the polyethylene film substrate preferably contains low density polyethylene and / or linear low density polyethylene as polyethylene.

In the above embodiment, it is preferable to further provide a morphologically stable layer containing medium-density polyethylene and / or high-density polyethylene between the polyethylene film base material and the polyethylene film layer.

In the above embodiment, the polyethylene film layer preferably contains medium density polyethylene.

The packaging material of the present invention is made of the above-mentioned polyethylene co-pressing film, and is characterized in that the polyethylene film layer is located inside the packaging material.

According to the present invention, a polyethylene co-pressing film capable of producing a packaging material using only polyethylene, and a polyethylene co-pressing film capable of preventing deterioration of heat sealability and breaking strength over time, and thereby. The manufactured packaging material can be provided.

It is sectional drawing of the polyethylene co-pressing film by one Embodiment of this invention. It is sectional drawing of the polyethylene co-pressing film by one Embodiment of this invention. It is sectional drawing of the polyethylene co-pressing film by one Embodiment of this invention.

Aspects for carrying out the invention

<Polyethylene press film>
The polyethylene co-pressing film according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of the polyethylene co-pressing film 10 of the present invention in one embodiment. The polyethylene co-pressing film 10 includes a polyethylene film base material 1 which is an electron beam irradiation layer and a polyethylene film layer 2.
Further, in one embodiment, as shown in FIG. 2, the polyethylene co-pressed film 10 includes a morphologically stable layer 3 between the polyethylene film base material 1 and the polyethylene film layer 2. The shaded area in the figure represents a portion where the crosslink density is improved by being irradiated with an electron beam.

The thickness of the polyethylene joint pressing film is preferably 10 μm or more and 300 μm or less, more preferably 30 μm or more and 200 μm or less, and further preferably 50 μm or more and 200 μm or less.

Hereinafter, each layer constituting the polyethylene co-pressed film will be described in detail.

<Polyethylene film base material>
The polyethylene film substrate included in the polyethylene co-pressing film according to the present invention is a layer containing polyethylene and a hydride-based antioxidant, and is a layer irradiated with an electron beam (hereinafter, simply referred to as an “electron beam irradiation layer”). Is.
When the polyethylene co-pressing film is provided with such a polyethylene film base material, the heat resistance and strength of the surface of the polyethylene co-pressing film can be improved, and the physical properties required as an outer layer of a packaging material or the like can be satisfied. ..
In the present invention, the electron beam irradiation layer is not only a layer in which the crosslink density of one side (the surface corresponding to the outer layer of the packaging material) is improved by irradiation with an electron beam (see FIG. 1), but also a polyethylene film group. Includes materials with improved crosslink density on both sides (see FIG. 3).

The reason why the crosslink density of polyethylene changes depending on the presence or absence of electron beam irradiation is not clear, but it is considered as follows. That is, when the polyethylene film is irradiated with an electron beam, the carbon-hydrogen bond in the polyethylene near the film surface is broken, and a radical is generated at the cut bond end. It is considered that the generated radicals come into contact with other polyethylene molecular chains due to the molecular motion of the molecular chains, extract hydrogen atoms and bond with carbon atoms in the polyethylene molecular chains, and as a result, a crosslinked structure is formed. ..

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

In addition, taking advantage of the fact that the crosslinked portion does not dissolve in the solvent, the polyethylene film substrate is immersed in an organic solvent such as methyl ethyl ketone, the insoluble film remaining undissolved is dried, and then the mass is measured before dissolution. 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 base material Xg is wrapped in a Yg stainless steel wire mesh, heated and immersed in a solvent, and the polyethylene film base material wrapped in the stainless steel wire mesh is taken out. Next, this is vacuum-dried, and the mass (Zg) of the polyethylene film base material wrapped in the dried stainless wire mesh is measured. Then, the gel fraction can be measured from the following formula (1).
Gel fraction (% by mass) = (ZY) / X × 100 (1)

The gel fraction of the polyethylene film base material is preferably 10% or more and 80% or less, more preferably 20% or more and 80% or less, and further preferably 30% or more and 80% or less.

Examples of polyethylene contained in the polyethylene film substrate include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE). The polyethylene film base material may contain two or more kinds of these polyethylenes.
Among these, low-density polyethylene and linear low-density polyethylene are preferable because the cross-linking reaction occurs satisfactorily and heat resistance, strength and the like can be improved more remarkably.
In the present invention, density of 0.87 g / cm ³ or more, 0.91 g / cm ³ or less of polyethylene of low density polyethylene, density of 0.92 g / cm ³ greater, 0.96 g / cm ³ or less of polyethylene Is referred to as medium-density polyethylene, and ^{polyethylene having a density of more than 0.96 g / cm 3} is referred to as high-density polyethylene.

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

The above-mentioned single-site catalyst is a catalyst capable of forming a uniform active species, and is usually prepared by contacting a metallocene-based transition metal compound or a non-metallocene-based transition metal compound with an activation co-catalyst. .. A single-site catalyst is preferable because it has a uniform active site structure as compared with a multi-site catalyst, and can polymerize a polymer having a high molecular weight and a high uniformity structure. As the single-site catalyst, it is particularly preferable to use a metallocene-based 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, an organic metal compound if necessary, and each catalyst component of the carrier. be.

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

In the transition metal compound of Group IV of the Periodic Table containing a ligand having a cyclopentadienyl skeleton, examples of the transition metal include zirconium, titanium and hafnium, and zirconium and hafnium are particularly preferable. The transition metal compound usually has two ligands having a cyclopentadienyl skeleton, and the ligands having each cyclopentadienyl skeleton are preferably bonded to each other by a cross-linking group. Examples of the cross-linking group include a substituted silylene group such as an alkylene group having 1 to 4 carbon atoms, a silylene group, a dialkylsilylene group and a diarylcyrylene group, a substituted gelmilene group such as a dialkylgelmylene group and a diarylgelmylene group and the like. It is preferably a substituted silylene group. The above-mentioned transition metal compound of Group IV of the Periodic Table containing a ligand having a cyclopentadienyl skeleton can have one or a mixture of two or more as a catalytic component.

As the co-catalyst, the transition metal compound of Group IV of the Periodic Table can be effectively used as a polymerization catalyst, or the ionic charge in a catalytically activated state can be equalized. As co-catalysts, benzene-soluble aluminoxane of organic aluminum oxy compounds, benzene-insoluble organic aluminum oxy compounds, ion-exchangeable layered silicates, boron compounds, cations containing or not containing active hydrogen groups and non-coordinating anions can be used. Examples thereof include ionic compounds, lanthanoid salts such as lanthanum oxide, tin oxide, and phenoxy compounds containing a fluoro group.

The transition metal compound of Group IV of the Periodic Table containing a ligand having a cyclopentadienyl skeleton may be used by being carried on a carrier of an inorganic or organic compound. As the carrier, a porous oxide of an inorganic or organic compound is preferable, and specifically, an ion-exchangeable layered silicate such as montmorillonite, SiO ₂ , Al ₂ O ₃ , MgO, ZrO ₂ , TiO ₂ , B ₂ O. ₃ , CaO, ZnO, BaO, ThO _2, etc. or a mixture thereof can be mentioned. Further, examples of the organometallic compound used as necessary include organoaluminum compounds, organomagnesium compounds, organozinc compounds and the like. Of these, organoaluminum is preferably used.

Further, in the present invention, polyethylene includes a copolymer of ethylene and other monomers in addition to HDPE, MDPE, LDPE and LLDPE. Examples of the ethylene copolymer include a copolymer composed of ethylene and an α-olefin having 3 to 20 carbon atoms, and examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene and 1-pentene. 1-Hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 3-methyl-1-butene, 4-methyl-1-pentene, 6-methyl- 1-Heptene and the like can be mentioned. Further, a copolymer with vinyl acetate, acrylic acid ester, etc. may be used as long as the object of the present invention is not impaired.

Further, in the present invention, polyethylene derived from biomass may be used as a raw material instead of ethylene obtained from fossil fuel. Since such biomass-derived polyethylene is a carbon-neutral material, it can be used as a packaging material with even less environmental impact. Such biomass-derived polyethylene can be produced, for example, by a method as described in Japanese Patent Application Laid-Open No. 2013-177531. Further, a commercially available biomass-derived polyethylene resin (for example, green PE commercially available from Braskem) may be used.

The polyethylene film base material contains a hydride amine-based antioxidant, which can prevent deterioration of the heat-sealing property and breaking strength of the polyethylene co-pressed film irradiated with an electron beam over time.
Examples of the hindered amine antioxidants include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate and bis (N-methyl-2,2,6,6-tetramethyl-4-piperidyl). Sevacate, N, N'-bis (2,2,6,6-tetramethyl-4-piperidyl) -1,6-hexamethylenediamine, 2-methyl-2- (2,2,6,6-tetramethyl) -4-piperidyl) Amino-N- (2,2,6,6-tetramethyl-4-piperidyl) propionamide, tetrakis (2,2,6,6-tetramethyl-4-piperidyl) (1,2,2 3,4-Butanetetracarboxylate, poly [{6- (1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diyl} {(2,2,6) , 6-Tetramethyl-4-piperidyl) imino} Hexamethyl {(2,2,6,6-tetramethyl-4-piperidyl) imino}]], Poly [(6-morpholino-1,3,5-triazine-2) , 4-diyl) {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethine {(2,2,6,6-tetramethyl-4-piperidyl) imino}], with dimethyl succinate Polycondensate with 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine, N, N'-4,7-tetrakis [4,6-bis {N-butyl -N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino} -1,3,5-triazine-2-yl] -4,7-diazadecan-1,10-diamine and the like. Be done.
The polyethylene film substrate may contain two or more of the above-mentioned hydride-based antioxidants.

The content of the hydride-based antioxidant in the polyethylene film substrate is preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 20% by mass or less, and 5% by mass. It is more preferably% or more and 10% by mass or less.
By setting the content of the light stabilizer within the above numerical range, the transparency of the polyethylene film substrate can be maintained, and the heat sealability and breaking strength of the polyethylene co-pressed film can be more significantly prevented from deteriorating over time. Can be done.

Further, a phenol-based antioxidant, an amine-based antioxidant, a phosphorus-based antioxidant, a sulfur-based antioxidant, a hydroxylamine-based antioxidant, and the like may be contained as long as the effects of the invention are not impaired.

Polyethylene film substrate has film processability, heat resistance, weather resistance, mechanical properties, dimensional stability, antioxidant properties, slipperiness, releasability, flame retardancy, antifungal properties, electrical properties, strength, etc. Various plastic compounding agents, additives and the like can be contained for the purpose of improving and modifying others. Further, the amount to be added may be from a very small amount to several tens of percent, depending on the purpose. Examples of general additives include fillers, cross-linking agents, reinforcing agents, antistatic agents, pigments, modifying resins and the like.

The thickness of the polyethylene film base material is arbitrary depending on the intended use, but is usually about 5 μm or more and 200 μm or less, preferably about 5 μm or more and 100 μm or less. 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.

<Polyethylene film layer>
The polyethylene film layer provided in the laminate according to the present invention is made of a polyethylene film, and the outer surface (the surface opposite to the side on which the polyethylene film base material is provided) has at least heat-sealing property.
By providing such a layer, the polyethylene co-pressed film has different physical properties (for example, strength, etc.) between the polyethylene film base material and the layer provided on the polyethylene film base material while using the same material (polyethylene). Laminates having different heat resistance, heat sealability, etc.) can be used.

In the polyethylene film layer, the outer surface (the surface opposite to the side on which the polyethylene film base material is provided) may have at least heat-sealing properties, and the electron beam with respect to the surface on which the polyethylene film base material is provided. As a result of the irradiation, the cross-linking density of the polyethylene film layer on the substrate side may be improved (see FIG. 3). With such a configuration, the heat resistance and strength of the polyethylene co-pressed film can be further improved.

As the polyethylene film layer, high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ethylene copolymer, polyethylene-derived polyethylene, etc. are used as polyethylene. Including. Among these, low-density polyethylene, medium-density polyethylene and linear low-density polyethylene are preferable from the viewpoint of heat-sealing property. Further, from the viewpoint of preventing deterioration of heat-sealing property due to electron beam irradiation, medium-density polyethylene is preferable.
The polyethylene film layer may contain two or more types of the above-mentioned polyethylene.

Further, the polyethylene film layer may contain the above-mentioned antioxidant, and preferably contains a hydride amine-based antioxidant.

The thickness of the polyethylene film layer is arbitrary depending on its use, but is usually about 5 μm or more, about 200 μm, preferably about 10 μm or more, about 200 μm or less, more preferably about 15 μm or more, about 160 μm or less.

<Morphologically stable layer>
In one embodiment, the polyethylene co-pressed film of the present invention may include a morphologically stable layer containing medium density polyethylene and / or high density polyethylene between the polyethylene film base material and the polyethylene film layer. By providing the polyethylene co-pressing film with a morphologically stable layer, it is possible to prevent the polyethylene co-pressing film from being melted and thinned due to heat sealing during the production of the packaging material.
The morphologically stable layer may be one that has been irradiated with an electron beam or one that has not been irradiated with an electron beam.

Further, the morphologically stable layer may contain the above-mentioned antioxidant, and preferably contains a hydride amine-based antioxidant.

The thickness of the morphologically stable layer is arbitrary depending on the intended use, but is usually about 5 μm or more and 100 μm or less, preferably about 10 μm or more and 80 μm or less, and more preferably about 10 μm or more and 60 μm or less.

<Barrier membrane>
The polyethylene co-pressing film according to the present invention may be provided with a barrier film between arbitrary layers, if desired. The barrier film can be formed by depositing a metal such as aluminum or an inorganic oxide such as an aluminum oxide or a silicon oxide on the surface of a polyethylene film layer or the like, in addition to a metal foil such as an aluminum foil. As the vapor deposition method, a conventionally known method can be adopted, for example, a 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. , Chemical vapor deposition method, CVD method and the like, such as thermochemical vapor deposition method and photochemical vapor deposition method. When producing a film made of a transparent laminate used as a packaging material, a vacuum vapor deposition method is mainly used, and a plasma chemical vapor deposition method is also partially used.

Further, for example, both the physical vapor deposition method and the chemical vapor deposition method can be used in combination to form a composite film composed of two or more layers of vapor-filmed films of different kinds of inorganic oxides. The degree of vacuum deposition chamber, before ^introduction of oxygen 10 -2 mbar or ^more, the degree 10 -8 mbar or less, in ^particular, 10 -3 mbar or ^more, or less extent preferably 10 -7 mbar, in the post-oxygen introduction, It ^{is preferably 10 -1} mbar or more and 10 ^-6 mbar or less, particularly preferably 10 ^-2- mbar or more and 10 ^-5 mbar or less. The amount of oxygen introduced differs depending on the size of the vapor deposition machine and the like. As the oxygen to be introduced, an inert gas such as argon gas, helium gas, or nitrogen gas may be used as the carrier gas within a range that does not hinder. The transport speed of the film is preferably about 10 m / min or more and 800 m / min or less, particularly preferably about 50 m / min or more and 600 m / min or less.

Further, in the present invention, the surface of the vapor-filmed 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 machine and the like, but is usually about 50 sccm or more and 2000 sccm or less, and particularly preferably about 300 sccm or more and 800 sccm or less. Here, sccm means the average amount of oxygen introduced per minute (cc) in the standard state (STP: 0 ° C., 1 atm). As the oxygen to be introduced, an inert gas such as argon gas, helium gas, or nitrogen gas may be used as the carrier gas within a range that does not hinder. By performing such a treatment on the vapor-filmed film (barrier membrane), the adhesion when the polyethylene film base material is bonded to the barrier film formed on the polyethylene film layer or the like is improved. These are examples, and the present invention is not limited to those obtained by these methods.

<Manufacturing method of polyethylene co-press film>
The method for producing a polyethylene co-extruded film of the present invention is a resin composition for a polyethylene film base material, a resin composition for a polyethylene film layer, and a desired resin composition by a melt coextrusion molding method such as an inflation extrusion molding method or a T-die extrusion molding method. This includes a step of heating and melting the resin composition for a morphologically stable layer and extruding it, and a step of irradiating the molded product with an electron beam.
Further, the method for producing a polyethylene co-pressed film of the present invention may include a step of printing on the polyethylene co-pressed film.

A conventionally known electron beam irradiation device can be used for electron beam irradiation on a molded product, for example, a curtain type electron irradiation device (LB1023, manufactured by i-Electron Beam Co., Ltd.), a line irradiation type low energy electron beam. Examples thereof include an irradiation device (EB-ENGINE, manufactured by Hamamatsu Photonics Co., Ltd.), a drum roll type electron beam irradiation device (EZ-CURE, manufactured by Eye Electron Beam Co., Ltd.) and the like.

The dose of the electron beam irradiated to the polyethylene film substrate is preferably in the range of 10 kGy or more and 2000 kGy or less, and more preferably in the range of 20 kGy or more and 1000 kGy or less. By setting the dose of the electron beam within the above numerical range, it is possible to improve the crosslink density of the polyethylene film substrate while maintaining the heat-sealing property of the polyethylene film layer.
The acceleration voltage of the electron beam is preferably in the range of 30 kV or more and 300 kV or less, more preferably in the range of 50 kV or more and 300 kV or less, and further preferably in the range of 50 kV or more and 250 kV or less. By setting the acceleration voltage of the electron beam in the above numerical range, it is possible to improve the crosslink density of the polyethylene film base material while maintaining the heat-sealing property of the polyethylene film layer.
The irradiation energy of the electron beam is preferably in the range of 20 keV or more and 750 keV or less, more preferably in the range of 25 keV or more and 500 keV or less, further preferably in the range of 30 keV or more and 400 keV or less, and more preferably 20 keV or more. , 200 keV or less is particularly preferable. By setting the irradiation energy of the electron beam within the above numerical range, it is possible to improve the crosslink density of the polyethylene film base material while maintaining the heat-sealing property of the polyethylene film layer.

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

Since the polyethylene film is prone to heat shrinkage, it is preferable to irradiate the electron beam with a cooling drum or the like at the same time as cooling.

<Packaging material>
In the packaging material according to the present invention, the above-mentioned polyethylene co-pressed film is folded in half so that the polyethylene film base material is located on the outside and the polyethylene film layer is located on the inside (content side), and the edges and the like thereof are overlapped. It can be manufactured by heat-sealing.
Further, it can be manufactured by superimposing two polyethylene co-pressed films so that the polyethylene film layers face each other and heat-sealing the end portions thereof.
For example, side seal type, two-way seal type, three-way seal type, four-way seal type, envelope-attached seal type, gassho-attached seal type (pillow seal type), fold-attached seal type, flat-bottom seal type, square-bottom seal type, gusset type. , And others can be heat-sealed to produce various forms of packaging materials. In addition, for example, a self-supporting packaging bag (standing pouch) or the like 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, and an ultrasonic seal can be used.

The printing method for the polyethylene co-pressed film is not particularly limited, and for example, a printing method such as an inkjet method, a gravure printing method, an offset printing method, a flexographic printing method, a thermal transfer method, or a hot stamp (foil stamping) can be used.

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

<Example 1>
Linear low-density polyethylene (density: 0.904 g / cm ² , manufactured by Dow Chemical Japan Co., Ltd., trade name: AFFINITY1881G) and a hydride-based antioxidant (manufactured by BASF Co., Ltd., trade name: Chimassorob). 2020 FDL) was mixed to obtain a resin composition for a polyethylene film substrate. The content of the hydride-based antioxidant was 5% by mass with respect to 100% by mass of the total mass of the resin composition.

The resin composition for a polyethylene film base material obtained as described above is used as a resin composition for a morphologically stable layer made of medium-density polyethylene (density: 0.926 g / cm ² , manufactured by Dow Chemical Japan Co., Ltd.). Name: Doulex 2098P) and a resin composition for a polyethylene film layer made of medium-density polyethylene (density: 0.924 g / cm ² , manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumikasen F208-3) are extruded by inflation. Coextruded with a film at a ratio of 1: 3: 1 to obtain a molded product. The thickness of the obtained molded product was 50 μm.

From the surface of the layer made of the resin composition for the polyethylene film substrate of the molded product obtained as described above, the following using an electron beam irradiation device (line irradiation type irradiation device EZ-CURE, manufactured by Iwasaki Electric Co., Ltd.) Irradiation with an electron beam under the conditions of (1) was carried out to obtain a polyethylene co-pressed film.
Voltage: 100kV
Irradiation dose: 260 kGy
Oxygen concentration in the device: 100ppm or less Line speed: 25m / min

<Example 2>
The content of the hydride-based antioxidant in the resin composition for polyethylene film base material is changed to 2.5% by mass, and the hydroxylamine-based antioxidant is changed to 100% by mass of the resin composition for polyethylene film base material. On the other hand, a polyethylene co-pressed film was obtained in the same manner as in Example 1 except that the film was contained so as to be 2.5% by mass.

<Comparative Example 1>
A polyethylene co-pressed film was obtained in the same manner as in Example 1 except that the hydride-based antioxidant was not added to the resin composition for a polyethylene film substrate.

<Comparative Example 2>
A polyethylene co-pressed film was obtained in the same manner as in Example 1 except that the electron beam was not irradiated.

<Breaking strength test>
In the above Examples and Comparative Examples, three dumbbell-shaped sample pieces having a width of 5 mm were prepared from the polyethylene co-pressed film immediately after production.
This sample piece was gripped by a tensile tester, and the breaking strength (N) was measured under the conditions of a speed of 300 mm / min and a load range of 50 N (see JIS Z7102). The measurement results are as shown in Table 1 below.

<Heat sealability evaluation>
(Seal strength (immediately after manufacturing))
In the above Examples and Comparative Examples, the polyethylene co-pressed film immediately after production was cut into 10 cm × 10 cm to prepare three sample pieces.
This sample piece is folded in half so that the layer made of the resin composition for the polyethylene film layer is on the inside, and using a heat seal tester, the temperature is 180 ° C., the pressure is 1 kgf / cm ² , and the pressure is 1 cm for 1 second. An area of × 10 cm was heat-sealed.
Cut the sample piece after heat sealing into strips with a width of 15 mm, grasp both ends that were not heat sealed with a tensile tester, and obtain peel strength (N / 15 mm) under the conditions of a speed of 300 mm / min and a load range of 50 N. It was measured. The measurement results are as shown in Table 1 below.
The polyethylene co-pressing film obtained in Comparative Example 2 was melted during heat sealing, and the sealing strength could not be measured.

(Seal strength (6 months later))
The polyethylene co-pressed films obtained in the above Examples and Comparative Examples were stored at 40 ° C. and a relative humidity of 75% for 6 months, and then cut into 10 cm × 10 cm pieces to prepare three sample pieces. This sample piece is folded in half so that the layer made of the resin composition for the polyethylene film layer is on the inside, and using a heat seal tester, the temperature is 180 ° C., the pressure is 1 kgf / cm ² , and the pressure is 1 cm for 1 second. An area of × 10 cm was heat-sealed.
Cut the sample piece after heat sealing into strips with a width of 15 mm, grasp both ends that were not heat sealed with a tensile tester, and obtain peel strength (N / 15 mm) under the conditions of a speed of 300 mm / min and a load range of 50 N. It was measured. The measurement results are as shown in Table 1 below.
The polyethylene co-pressing film obtained in Comparative Example 2 was melted during heat sealing, and the sealing strength could not be measured.

Claims (4)

A polyethylene co-press film for packaging materials whose one side is heat-sealed.
With a polyethylene film substrate and a polyethylene film layer ,
The polyethylene film substrate is an electron beam irradiation layer containing at least one polyethylene selected from the group consisting of low density polyethylene and linear low density polyethylene and a hindered amine-based antioxidant.
The polyethylene film layer contains medium-density polyethylene, and the outer surface is a heat-sealed side, which is a polyethylene co-pressing film. The polyethylene co-pressing film according to claim 1, wherein the content of the hindered amine-based antioxidant in the polyethylene film base material is 1% by mass or more and 30% by mass or less. The polyethylene co-pressing film according to claim 1 or 2 , further comprising a morphologically stable layer containing medium-density polyethylene and / or high-density polyethylene between the polyethylene film base material and the polyethylene film layer. A packaging material made of the polyethylene co-pressed film according to any one of claims 1 to 3.
A packaging material, characterized in that the polyethylene film layer is located inside the packaging material.

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