JP7706232B2 - Heat-sealable laminated film - Google Patents

Description

The present invention relates to a polyethylene laminate film, and more specifically, to a laminate film that is suitable for use as a packaging film, has excellent lamination strength with the outer layer film and blocking resistance, and also reduces the environmental impact by using a plant-derived resin.

Packaging bags made by heat-sealing plastic multilayer films are widely used to store various contents such as food, beverages, detergents, shampoos, and cosmetics. As the film constituting the inner layer that becomes the heat-sealed part of such plastic multilayer films, various polyethylene-based laminated films with a three-layer structure consisting of a heat-sealing layer, an intermediate layer, and a laminate layer with a base film (base layer) on the outer side have been proposed (see, for example, Patent Document 1). These laminated films were designed to have suitable properties in terms of seal strength, impact resistance, blocking resistance, etc., but in recent years, there has been a demand for improved laminate strength with the outer layer film and further improved blocking resistance.

JP 2005-14461 A

In view of the above technical background, the object of the present invention is to provide a polyethylene-based laminated film suitable for use in packaging bags and the like, which has excellent lamination strength with the outer layer film and excellent blocking resistance while maintaining excellent properties such as seal strength and impact resistance.

Means for Solving the Problems The inventors of the present invention have, as a result of intensive research, found that in a laminate film having a heat-sealing layer, an intermediate layer, and a laminate layer, each of which contains a petroleum-derived linear low-density polyethylene, by adding a biomass-derived linear low-density polyethylene to at least one of these layers, the laminate strength can be significantly improved and the blocking resistance can also be improved, thereby completing the present invention.
That is, the present invention provides:
[1]
A laminated film having (A) a heat-sealing layer, (B) an intermediate layer, and (C) a laminate layer, each of which contains a petroleum-derived linear low-density polyethylene, wherein at least one of the (A) heat-sealing layer, (B) the intermediate layer, and (C) the laminate layer contains at least 3% or more of a plant-derived biomass linear low-density polyethylene;
Regarding.

Below, [2] to [6] are each a preferred aspect or embodiment of the present invention.
[2]
(C) The laminate film according to [1], wherein the laminate layer contains at least 3% or more of plant-derived biomass linear low-density polyethylene.
[3]
The laminate film according to [1] or [2], wherein the heat of fusion ΔH at 0° C. to 130° C. calculated from a melting curve obtained by DSC measurement is 135 to 164 J/g.
[4]
The laminate film according to any one of [1] to [3], wherein the molecular weight distribution Mw/Mn of the plant-derived biomass linear low density polyethylene is 3.5 or more.
[5]
The laminate film according to any one of [1] to [4], which has a base layer (D) on the side of the laminate layer (C) directly or via an adhesive layer.
[6]
A packaging bag comprising the laminate film according to any one of [1] to [5].

The laminated film of the present invention maintains the excellent properties of conventional polyethylene laminated films, such as seal strength and impact resistance, while significantly improving lamination strength and reducing the environmental impact of its production, etc. It combines highly valuable properties in practical use at a high level that goes beyond the limits of conventional technology, and can be suitably used in a variety of applications, including packaging bags.

The present invention is a laminate film having (A) a heat-sealable layer, (B) an intermediate layer, and (C) a laminate layer, each of which contains a petroleum-derived linear low-density polyethylene, wherein at least one of the (A) heat-sealable layer, (B) intermediate layer, and (C) laminate layer contains at least 3% or more of plant-derived biomass linear low-density polyethylene.
That is, the laminated film of the present invention contains petroleum-derived linear low-density polyethylene in each of (A) the heat-sealing layer, (B) the intermediate layer, and (C) the laminate layer.
The laminated film of the present invention contains a predetermined amount of plant-derived biomass linear low density polyethylene in at least one layer of (A) the heat sealable layer, (B) the intermediate layer, and (C) the laminate layer.

Petroleum-derived linear low-density polyethylene The petroleum-derived linear low-density polyethylene used in the present invention is a homopolymer of ethylene produced using petroleum as a raw material, or a copolymer of ethylene and an α-olefin produced using petroleum as a raw material, and may be synthesized by a known production method.

As the α-olefin, a compound having 3 to 20 carbon atoms can be used, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 4-methyl-1-pentene, 4-methyl-1-hexene, etc., or a mixture of these may be used. The α-olefin is preferably a compound having 4, 6, or 8 carbon atoms or a mixture of these, such as 1-butene, 1-hexene, 1-octene, or a mixture of these.

The petroleum-derived linear low density polyethylene may be a commercially available product, for example, 2040F (C6-LLDPE, MFR: 4.0, density: 0.918 g/cm ³ ) manufactured by Ube Maruzen Polyethylene Co., Ltd. can be used.

The petroleum-derived linear low density polyethylene preferably has a density of 0.905 to 0.935 g/cm ³ , more preferably 0.915 to 0.930 g/cm ³ , and preferably has an MFR of 0.5 to 6.0 g/10 min, more preferably 2.0 to 4.0 g/10 min.

The molecular weight distribution of petroleum-derived linear low-density polyethylene (expressed as the ratio of weight average molecular weight: Mw to number average molecular weight: Mn: Mw/Mn) is preferably in the range of 1.5 to 4.0, and more preferably in the range of 1.8 to 3.5. This Mw/Mn can be measured by gel permeation chromatography (GPC).

Petroleum-derived linear low-density polyethylene has one or more sharp peaks as determined from an endothermic curve measured with a differential scanning calorimeter (DSC) at a heating rate of 10°C/min, and the maximum temperature of the peak, i.e., the melting point, is preferably in the range of 95 to 140°C, and more preferably in the range of 105 to 130°C.

Petroleum-derived linear low-density polyethylene can be produced by a conventional production method using a conventional catalyst, including a multi-site catalyst such as a Ziegler catalyst, or a single-site catalyst such as a metallocene catalyst. From the viewpoint of obtaining linear low-density polyethylene that has a narrow molecular weight distribution and can be formed into a high-strength film, it is preferable to use a single-site catalyst.

The single-site catalyst is a catalyst capable of forming a uniform active species, and is usually prepared by contacting a metallocene transition metal compound or a nonmetallocene transition metal compound with an activating cocatalyst. Compared to multi-site catalysts, single-site catalysts have a uniform active site structure, and are therefore preferred because they can polymerize polymers with high molecular weights and highly uniform structures. As a single-site catalyst, it is particularly preferred to use a metallocene catalyst. A metallocene catalyst is a catalyst that contains each of the catalytic components of a transition metal compound of Group IV of the periodic table that contains a ligand having a cyclopentadienyl skeleton, a cocatalyst, and if necessary, an organometallic compound and a carrier.

In the above-mentioned transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, the cyclopentadienyl skeleton is a cyclopentadienyl group, a substituted cyclopentadienyl group, or the like. The substituted cyclopentadienyl group has at least one substituent selected from 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, a halosilyl group, or the like. The substituted cyclopentadienyl group may have two or more substituents, and the substituents may be bonded to each other to form a ring, such as an indenyl ring, a fluorenyl ring, an azulenyl ring, or a hydrogenated product thereof. The rings formed by bonding the substituents to each other may further have substituents.

In the transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, the transition metal may be zirconium, titanium, hafnium, etc., with zirconium and hafnium being particularly preferred. The transition metal compound usually has two ligands having a cyclopentadienyl skeleton, and it is preferred that the ligands having the cyclopentadienyl skeleton are bonded to each other via a bridging group. Examples of the bridging group include alkylene groups having 1 to 4 carbon atoms, silylene groups, substituted silylene groups such as dialkylsilylene groups and diarylsilylene groups, and substituted germylene groups such as dialkylgermylene groups and diarylgermylene groups. The substituted silylene group is preferred.

In transition metal compounds of Group IV of the periodic table, representative ligands other than those having a cyclopentadienyl skeleton include hydrogen, hydrocarbon groups having 1 to 20 carbon atoms (alkyl groups, alkenyl groups, aryl groups, alkylaryl groups, aralkyl groups, polyenyl groups, etc.), halogens, metaalkyl groups, metaaryl groups, etc.

The above-mentioned transition metal compounds of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton can be used as a catalyst component, either alone or in a mixture of two or more kinds.

The co-catalyst refers to a catalyst that can effectively use the above-mentioned transition metal compound of Group IV of the periodic table as a polymerization catalyst, or can balance the ionic charge in a catalytically activated state. Examples of the co-catalyst include benzene-soluble aluminoxanes of organoaluminum oxy compounds and benzene-insoluble organoaluminum oxy compounds, ion-exchangeable layered silicates, boron compounds, ionic compounds consisting of cations with or without active hydrogen groups and non-coordinating anions, lanthanoid salts such as lanthanum oxide, tin oxide, and phenoxy compounds containing fluoro groups.

The transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton may be used supported on an inorganic or organic carrier, preferably an inorganic or organic porous oxide, specifically _ion -exchangeable layered silicate such as _{montmorillonite} , _SiO2 , _Al2O3 , MgO, _ZrO2 , _TiO2 , _B2O3 , CaO, ZnO, BaO, _ThO2 , or mixtures thereof.

Furthermore, examples of organometallic compounds that may be used as necessary include organoaluminum compounds, organomagnesium compounds, and organozinc compounds. Of these, organoaluminum compounds are preferably used.

The petroleum-derived linear low-density polyethylene may be used alone or in combination of two or more types. It may also be used together with other polymers, including other ethylene-based polymers.

The petroleum-derived linear low-density polyethylene may be blended with various known additives that are usually added to olefin polymers, such as antioxidants, weather stabilizers, antistatic agents, antifogging agents, antiblocking agents, slip agents, etc., as necessary, within the scope of the present invention.

Plant-derived biomass linear low-density polyethylene The plant-derived biomass linear low-density polyethylene used in the present invention is a linear low-density polyethylene obtained by polymerizing ethylene produced using plants as the raw material.
In the present invention, the plant-derived biomass linear low-density polyethylene is a linear low-density polyethylene obtained by polymerizing a monomer containing ethylene derived from biomass as described below.
Therefore, except that it is produced by polymerizing monomers containing ethylene derived from biomass, it preferably has similar physical properties to conventional linear low density polyethylene.
For example, the "linear low density polyethylene" in the present application is preferably an ethylene (co)polymer having 10 to 30 SCBs (side chains having 1 to 5 carbon atoms, also called "short chain branches") per 1,000 carbon atoms.

The plant-derived biomass linear low-density polyethylene may be a commercially available product, for example, a product manufactured and sold by Braskem Co., Ltd. Specifically, the brand name: SLH218 can be preferably used.
The plant-derived biomass linear low density polyethylene used in the present invention is obtained by polymerizing a monomer containing ethylene derived from biomass. The biomass-derived ethylene is preferably obtained by the following production method, but is not limited thereto. Since biomass-derived ethylene is used as the raw material monomer, the polymerized linear low density polyethylene is derived from biomass. Note that the raw material monomer of the linear low density polyethylene does not have to contain 100% by mass of biomass-derived ethylene, and may contain ethylene that is not derived from biomass or raw material monomers other than ethylene.

The method for producing biomass ethylene, which is the raw material for plant-derived biomass linear low-density polyethylene, is not particularly limited, and can be obtained by a conventionally known method. An example of a method for producing biomass ethylene is described below.

Biomass ethylene can be produced using biomass-derived ethanol as a raw material. In particular, it is preferable to use biomass-derived fermented ethanol obtained from plant raw materials. There are no particular limitations on the plant raw material, and any conventionally known plant can be used. Examples include corn, sugarcane, beet, and manioc.

In the present invention, the fermented ethanol derived from biomass refers to ethanol produced by contacting a culture solution containing a carbon source obtained from a plant raw material with an ethanol-producing microorganism or a product derived from its crushed material, and then purifying the ethanol. Conventionally known methods such as distillation, membrane separation, and extraction can be applied to purify ethanol from the culture solution. For example, a method of adding benzene, cyclohexane, etc., and removing water by azeotropy or membrane separation can be used.
In order to obtain biomass ethylene, further advanced purification may be carried out at this stage, for example, to reduce the total amount of impurities in the ethanol to 1 ppm or less.

A catalyst is usually used when obtaining ethylene by the dehydration reaction of ethanol, but the catalyst is not particularly limited and any conventionally known catalyst can be used. From the viewpoint of the process, a fixed bed flow reaction is advantageous because it is easy to separate the catalyst from the product, and for example, γ-alumina is preferable.
Since this dehydration reaction is an endothermic reaction, it is usually carried out under heating conditions. As long as the reaction proceeds at a commercially useful reaction rate, the heating temperature is not limited, but is preferably 100° C. or higher, more preferably 250° C. or higher, and even more preferably 300° C. or higher. There is no particular upper limit, but from the viewpoint of energy balance and equipment, it is preferably 500° C. or lower, more preferably 400° C. or lower.
The reaction pressure is not particularly limited, but is preferably equal to or higher than atmospheric pressure in order to facilitate the subsequent gas-liquid separation. From an industrial perspective, a fixed bed flow reaction is preferred because it is easy to separate the catalyst, but a liquid phase suspension bed, a fluidized bed, etc. may also be used.

In the dehydration reaction of ethanol, the yield of the reaction depends on the amount of water contained in the ethanol supplied as a raw material. In general, when performing a dehydration reaction, it is preferable to have no water, considering the efficiency of removing water. However, in the case of the dehydration reaction of ethanol using a solid catalyst, it has been found that the amount of other olefins, especially butene, produced tends to increase if water is not present. This is probably because the presence of a small amount of water makes it difficult to suppress ethylene dimerization after dehydration. The lower limit of the allowable water content is 0.1 mass% or more, preferably 0.5 mass% or more. There is no particular upper limit, but from the viewpoint of material balance and heat balance, it is preferably 50 mass% or less, more preferably 30 mass% or less, and even more preferably 20 mass% or less.

By carrying out the dehydration reaction of ethanol in this manner, a mixture of ethylene, water and a small amount of unreacted ethanol is obtained, but since ethylene is in a gaseous state at room temperature below about 5 MPa, water and ethanol can be removed from this mixture by gas-liquid separation to obtain ethylene. This method may be performed by any known method.
The ethylene obtained by the gas-liquid separation is further distilled. The distillation method, operation temperature, residence time, etc. are not particularly limited, except that the operation pressure at this time is normal pressure or higher.

When the raw material is biomass-derived fermented ethanol, the resulting ethylene contains trace amounts of carbonyl compounds such as ketones, aldehydes, and esters, which are impurities mixed in during the ethanol fermentation process, as well as carbon dioxide, which is their decomposition product, and nitrogen-containing compounds such as amines and amino acids, which are enzyme decomposition products and impurities, as well as ammonia, which is their decomposition product. These trace amounts of impurities may be problematic in the production and use of polyethylene, so they may be removed by purification. The purification method is not particularly limited, and can be performed by a conventionally known method. An example of a suitable purification operation is an adsorption purification method. The adsorbent used is not particularly limited, and conventionally known adsorbents can be used. For example, a material with a high surface area is preferable, and the type of adsorbent is selected depending on the type and amount of impurities in the ethylene obtained by the dehydration reaction of biomass-derived fermented ethanol.

Caustic water treatment may also be used in combination as a method for purifying impurities in ethylene. If caustic water treatment is used, it is preferable to carry it out before adsorption purification. In that case, it is necessary to carry out a moisture removal treatment after the caustic treatment and before adsorption purification.

The monomers that are the raw materials for plant-derived biomass linear low-density polyethylene may further contain ethylene and/or α-olefins derived from fossil fuels, or may further contain α-olefins derived from biomass.

The above α-olefins are not particularly limited in the number of carbon atoms, but those with 3 to 20 carbon atoms can usually be used, and butylene, hexene, or octene is preferable. This is because butylene, hexene, or octene can be produced by polymerizing ethylene, a raw material derived from biomass. In addition, by including such α-olefins, the linear low-density polyethylene obtained by polymerization has alkyl groups as a branched structure, making it more flexible than a simple straight-chain polyethylene.

In terms of environmental impact, it is preferable that the linear low-density polyethylene is a copolymer of ethylene and an α-olefin derived from ethylene. This is because, by using ethylene, which is a raw material derived from biomass, it is theoretically possible to produce it from components derived from 100% biomass.

The biomass-derived ethylene concentration in the linear low-density polyethylene (hereinafter sometimes referred to as "biomass degree") is a value obtained by measuring the content of biomass-derived carbon by radiocarbon ( ^14C ) measurement. Carbon dioxide in the atmosphere contains a certain proportion of ^14C (105.5 pMC), and it is known that the ^14C content in plants that grow by absorbing carbon dioxide in the atmosphere, such as corn, is also about 105.5 pMC. It is also known that fossil fuels contain almost no ^14C . Therefore, the proportion of biomass-derived carbon can be calculated by measuring the proportion of ^14C contained in the total carbon atoms in the linear low-density polyethylene. In the present invention, when the content of ^14C in the linear low-density polyethylene is _P14C , the content of biomass-derived carbon _Pbio can be calculated as follows.
P _bio (%) = P _14C /105.5×100

In the biomass linear low density polyethylene used in the present invention, theoretically, if all the raw materials for the polyethylene are biomass-derived ethylene and α-olefins derived therefrom, the concentration of biomass-derived ethylene will be 100%, and the biomass degree of the biomass-derived linear low density polyethylene will be 100%. In addition, the concentration of biomass-derived ethylene in fossil fuel-derived polyethylene produced only from raw materials derived from fossil fuels will be 0%, and the biomass degree of the fossil fuel-derived polyethylene will be 0%.

In the present invention, the biomass linear low density polyethylene does not need to be 100% biomass. If even a part of the biomass linear low density polyethylene is made from raw materials derived from biomass, the amount of fossil fuel used can be reduced compared to conventional methods.

In the biomass linear low density polyethylene used in the present invention, the polymerization method of the monomer containing ethylene derived from biomass is not particularly limited, and can be carried out by a conventionally known method. The polymerization temperature and polymerization pressure are suitably adjusted depending on the polymerization method and polymerization apparatus. The polymerization apparatus is also not particularly limited, and a conventionally known apparatus can be used.
For example, the polymerization method of a monomer containing ethylene described below can be applied.

The polymerization method for biomass linear low density polyethylene can be appropriately selected depending on the density and branching of the desired linear low density polyethylene. For example, it is preferable to use a multi-site catalyst such as a Ziegler catalyst or a Phillips catalyst, or a single-site catalyst such as a metallocene catalyst, as the polymerization catalyst, and to carry out the polymerization in one stage or in two or more stages by any of the methods of gas phase polymerization, slurry polymerization, solution polymerization, and high pressure ion polymerization.

From the viewpoint of obtaining a biomass linear low density polyethylene having a broad molecular weight distribution and excellent flexibility and moldability, it is preferable to use a multi-site catalyst such as a Ziegler catalyst or a Phillips catalyst.
Preferred Ziegler catalysts may be those generally known as Ziegler catalysts used in the coordination polymerization of ethylene and α-olefins, and examples thereof include catalysts containing a titanium compound and an organoaluminum compound, such as catalysts consisting of a titanium halide compound and an organoaluminum compound, and catalysts consisting of a solid catalyst component consisting of titanium, magnesium, chlorine, etc., and an organoaluminum compound. More specifically, examples of such catalysts include a catalyst comprising a catalyst component (a) obtained by reacting a reaction product of an alcohol pretreatment product of anhydrous magnesium dihalide and an organometallic compound with a titanium compound, and an organometallic compound (b); a catalyst comprising a catalyst component (A) obtained by reacting magnesium metal with an organic hydroxide compound or an oxygen-containing organic compound such as magnesium, an oxygen-containing organic compound of a transition metal, and an aluminum halide, and a catalyst component (B) of an organometallic compound; and a catalyst comprising a solid catalyst component (A) obtained by reacting (i) metallic magnesium with at least one member selected from an organic hydroxide compound, an oxygen-containing organic compound of magnesium, and a halogen-containing compound, (ii) at least one member selected from an oxygen-containing organic compound of a transition metal and a halogen-containing compound, or (iii) a silicon compound with (iv) an aluminum halide compound, and an organometallic compound catalyst component (B).

The Phillips catalyst may be any of those generally known as Phillips catalysts used in the coordination polymerization of ethylene and α-olefins, such as a catalyst system containing a chromium compound such as chromium oxide. Specific examples include catalysts in which a chromium compound such as chromium trioxide or chromate ester is supported on a solid oxide such as silica, alumina, silica-alumina, or silica-titania.

There are no particular limitations on the density of the plant-derived biomass linear low-density polyethylene, but it is preferably 0.905 to 0.935 g/cm ³ , more preferably 0.915 to 0.930 g/cm ³ .
The MFR of the plant-derived biomass linear low density polyethylene is not particularly limited, but from the viewpoint of moldability, etc., it is preferably 0.3 to 15.0 g/10 min, more preferably 1.0 to 12.0 g/10 min, even more preferably 1.5 to 10.0 g/10 min, and particularly preferably 2.0 to 9.0 g/10 min.

There are no particular limitations on the molecular weight distribution of the plant-derived biomass linear low-density polyethylene, but from the standpoint of flexibility, moldability, etc., the molecular weight distribution (expressed as the ratio of weight average molecular weight: Mw to number average molecular weight: Mn: Mw/Mn) is preferably 3.5 or more, more preferably 3.8 to 9.0, and even more preferably in the range of 4.0 to 8.6. This Mw/Mn can be measured by gel permeation chromatography (GPC), and more specifically, for example, it can be measured by the method described in the examples of this application.

Furthermore, the plant-derived biomass linear low-density polyethylene has one or more sharp peaks as determined from an endothermic curve measured with a differential scanning calorimeter (DSC) at a heating rate of 10°C/min, and the maximum temperature of the peak, i.e., the melting point, is preferably in the range of 95 to 140°C, and more preferably in the range of 100 to 135°C.

The plant-derived biomass linear low-density polyethylene may be used alone or in a mixture of two or more types. It may also be used together with other polymers, including other ethylene-based polymers (whether or not they are plant-derived).

The plant-derived biomass linear low-density polyethylene can be blended with various known additives that are usually added to olefin polymers, such as antioxidants, weather stabilizers, antistatic agents, anti-fogging agents, anti-blocking agents, slip agents, etc., as necessary, within the scope of the present invention.

The laminated film of the present invention has (A) a heat-sealing layer, (B) an intermediate layer, and (C) a laminate layer, which will be described below.
The (A) heat-sealing layer, the (B) intermediate layer, and the (C) laminate layer all contain the above-mentioned petroleum-derived linear low-density polyethylene. By the (A) heat-sealing layer, the (B) intermediate layer, and the (C) laminate layer all containing the above-mentioned petroleum-derived linear low-density polyethylene, the lamination strength between the layers can be made sufficient. This is also advantageous in terms of the productivity and cost of the laminate film.

(A) heat-sealing layer When forming a packaging bag using the laminated film of the present invention, the (A) heat-sealing layer constituting the laminated film of the present invention is often the innermost layer and is fused to other films. For this reason, it is preferable to use a resin with a low melting point so as to obtain high sealing strength. For example, the ethylene content of the petroleum-derived linear low-density polyethylene is set low, so that the melting point of the (A) heat-sealing layer can be lowered. More specifically, the ethylene content of the petroleum-derived linear low-density polyethylene is preferably 10% by mass or less, more preferably 7% by mass or less, and preferably 5% by mass or less.

In cases where the ethylene content of the petroleum-derived linear low density polyethylene must be increased due to the strength of the film, the necessity of using materials common to other layers, etc., a resin with a low melting point may be added to the heat seal layer (A). In addition, in cases where a plant-derived biomass linear low density polyethylene is added to the heat seal layer (A), a plant-derived biomass linear low density polyethylene with a low melting point may be added.
Examples of other low melting point resins include relatively low density ethylene polymers such as high pressure low density polyethylene and ethylene-α-olefin random copolymers; aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, aromatic hydrocarbon resins, polyterpene resins, rosins, styrene resins, coumarone-indene resins and other tackifying resins.

From the viewpoint of heat sealability, etc., the content of petroleum-derived linear low-density polyethylene in the heat-sealable layer (A) is preferably 50% by mass or more, more preferably 55 to 99% by mass, and particularly preferably 65 to 95% by mass.

The thickness of the heat-sealing layer (A) is not particularly limited, but from the viewpoint of heat sealability, etc., it is preferably 5 μm or more, and more preferably 10 μm or more.
On the other hand, from the viewpoint of film strength, etc., the thickness is preferably 30 μm or less, and more preferably 20 μm or less.
In the heat-sealing layer, various known additives that are usually added to polyolefins, such as antiblocking agents, slip agents, antioxidants, weather stabilizers, antistatic agents, antifogging agents, etc., can be blended as necessary within the scope of the present invention.
Examples of the anti-blocking agent include silica, talc, silica, clay, calcium carbonate, synthetic zeolite, starch, aluminum oxide, acrylic resin, methacrylic resin, silicone resin, and polytetrafluoroethylene resin.
Examples of slip agents include various amides such as palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, oleyl palmitamide, stearyl palmitamide, methylene bisstearylamide, methylene bisoleylamide, ethylene bisoleylamide, and ethylene biserucic acid amide; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; and hydrogenated castor oil.

(B) Intermediate Layer Among the layers constituting the laminated film of the present invention, the (A) heat-sealing layer is preferably designed to obtain an appropriate seal strength, and the (C) laminate layer is preferably designed in consideration of the lamination strength between the (D) base layer, etc., whereas the (B) intermediate layer is relatively less restricted in this respect, and can be designed with priority given to imparting the desired physical properties and performance, such as mechanical properties, to the entire laminated film of the present invention. In this case, the thickness of the (B) intermediate layer is preferably made larger than the thickness of the (A) heat-sealing layer and the thickness of the (C) laminate layer, and is particularly preferably made larger than the sum of the thicknesses of the (A) heat-sealing layer and the (C) laminate layer.
More specifically, the thickness of the intermediate layer (B) is preferably 10 μm or more, more preferably 15 μm or more, and particularly preferably 30 μm or more.
On the other hand, from the viewpoint of heat sealability, the thickness of the intermediate layer (B) is preferably 150 μm or less, more preferably 130 μm or less, and even more preferably 100 μm or less.

For example, from the viewpoint of realizing high mechanical strength for the entire laminate, it is preferable to use a resin having high mechanical strength at a high ratio in the intermediate layer (B). For example, it is preferable to select a petroleum-derived linear low-density polyethylene having a high molecular weight and a narrow molecular weight distribution, and further set its content at a high level.
From this viewpoint, the content of the petroleum-derived linear low-density polyethylene in the (B) intermediate layer is preferably 50% by mass or more, more preferably 75 to 100% by mass, even more preferably 85 to 100% by mass, and particularly preferably 90 to 100% by mass.
The molecular weight distribution of the petroleum-derived linear low density polyethylene is preferably 4.0 or less, and particularly preferably 3.0 or less. Similarly, the molecular weight of the petroleum-derived linear low density polyethylene is preferably 20,000 or more, more preferably 25,000 or more, even more preferably 50,000 or more, and particularly preferably 70,000 or more.

From the viewpoint of improving the flexibility and impact strength of the entire laminate, it is preferable to use a resin having high flexibility and impact strength at a high ratio in the intermediate layer (B). For example, a resin having high flexibility and impact strength can be selected as the petroleum-derived linear low-density polyethylene, and its content can be set to be high.
Furthermore, by adding an elastomer or rubber component to the intermediate layer (B), the flexibility and impact strength of the intermediate layer (B) can be improved, and the flexibility and impact strength of the entire laminate can be improved. Examples of the elastomer or rubber component include an ethylene-propylene copolymer, an ethylene-butene copolymer, and an ethylene-propylene-butene copolymer, and the amount of the elastomer or rubber component added can be 1 to 30% by mass, and preferably 5 to 10% by mass.

(C) Laminate Layer The (C) laminate layer constituting the laminate film of the present invention can be laminated with other layers including the (D) substrate layer described below, as necessary or desired.
Therefore, it is preferable to design the laminate layer (C) taking into consideration the lamination strength between it and other layers.
From this viewpoint, it is preferable to appropriately select the petroleum-derived linear low-density polyethylene in the (C) laminate layer from one having excellent affinity with other layers including the (D) base material layer, and the content thereof is preferably 40 to 99 mass%, particularly preferably 70 to 95 mass%.
In order to further improve the laminate strength between the (C) laminate layer and other layers, the surface of the (C) laminate layer (the surface opposite to the surface to be laminated with the (B) intermediate layer) may be subjected to a corona treatment, a roughening treatment, or the like.

On the other hand, from the viewpoint of preventing blocking during storage of the laminate film of the present invention, the laminate layer (C) may contain an anti-blocking agent.
As the blocking inhibitor, powdered silica, preferably synthetic silica, etc. can be suitably used. From the viewpoint of uniformly dispersing powdered silica in the (C) laminate layer, powdered silica can be dispersed in a resin that is highly compatible with the petroleum-derived linear low-density polyethylene that constitutes the (C) laminate layer, for example, in low-density polyethylene, to form a master batch, and then the master batch can be added to the petroleum-derived linear low-density polyethylene.In addition, slip agent (lubricant) can be blended into the laminate layer as necessary within a range that does not impair the object of the present invention.
Examples of slip agents include various amides such as palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, oleyl palmitamide, stearyl palmitamide, methylene bisstearylamide, methylene bisoleylamide, ethylene bisoleylamide, and ethylene biserucic acid amide; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; and hydrogenated castor oil.

There is no particular restriction on the thickness of the laminate layer (C). From the viewpoint of lamination processability, the thickness is preferably 5 μm or more, and particularly preferably 10 μm or more.
On the other hand, from the viewpoint of film strength, etc., the thickness is preferably 30 μm or less, and particularly preferably 20 μm or less.

Any of the (A) heat-sealing layer, (B) intermediate layer, and (C) laminate layer may contain various additives and fillers other than the petroleum-derived linear low-density polyethylene (and, if present, the plant-derived biomass linear low-density polyethylene), such as heat stabilizers, antioxidants, light stabilizers, antistatic agents, antiblocking agents, lubricants, nucleating agents, flame retardants, pigments, dyes, calcium carbonate, barium sulfate, magnesium hydroxide, mica, talc, clay, antibacterial agents, and antifogging agents, as long as they do not violate the objectives of the present invention. Furthermore, other thermoplastic resins, thermoplastic elastomers, rubbers, hydrocarbon resins, petroleum resins, and the like may be added to the extent that they do not violate the objectives of the present invention.

The laminated film of the present invention has a heat-sealing layer (A), an intermediate layer (B), and a laminate layer (C), each of which contains a petroleum-derived linear low-density polyethylene. In the laminated film of the present invention, the laminate layer (C) and the heat-sealing layer (A) are preferably laminated via the intermediate layer (B), but other layers may also be present.

The laminated film of the present invention can be produced by various known film forming methods, such as a method of forming films to be the (C) laminate layer, the (B) intermediate layer, and the (A) heat-sealing layer in advance, and then laminating the films together to produce a laminated film, a method of using a multilayer die to obtain a multilayer film consisting of the (B) intermediate layer and the (A) heat-sealing layer, and then extruding the (C) laminate layer onto the (B) intermediate layer surface to produce a laminated film, a method of using a multilayer die to obtain a multilayer film consisting of the (C) laminate layer and the (B) intermediate layer, and then extruding the (A) heat-sealing layer onto the (B) intermediate layer surface to produce a laminated film, or a method of using a multilayer die to obtain a laminated film consisting of the (C) laminate layer, the (B) intermediate layer, and the (A) heat-sealing layer.

As the film forming method, various known film forming methods, specifically, a T-die cast film forming method and an inflation film forming method can be adopted.
The laminated film of the present invention and each of the layers constituting the laminated film may be a non-stretched film (unstretched film) or a stretched film.

There is no particular limitation on the thickness of each layer of the laminated film of the present invention, but it is usually 3 μm or more, preferably 5 to 150 μm, and more preferably in the range of 5 to 90 μm.
The thickness of the laminated film of the present invention is not particularly limited, but is usually 20 μm or more, preferably 25 μm or more, more preferably 30 μm or more from the viewpoint of ensuring practical strength, etc. On the other hand, from the viewpoint of having practical flexibility even after being laminated with the (D) base layer, for example, the thickness is usually 200 μm or less, preferably 180 μm or less, more preferably 150 μm or less.

The laminated film of the present invention contains 3% by mass or more of plant-derived biomass linear low-density polyethylene in at least one layer of (A) the heat-sealing layer, (B) the intermediate layer, and (C) the laminate layer.
By containing 3% by mass or more of plant-derived biomass linear low-density polyethylene in at least one layer of (A) heat-sealing layer, (B) intermediate layer, and (C) laminate layer, the laminate film of the present invention realizes a remarkable technical effect that the laminate strength with the (D) substrate layer described below is significantly improved while maintaining the excellent properties of conventional polyethylene-based laminate films such as mechanical strength, blocking resistance, etc. Moreover, despite the significant improvement in the laminate strength with the multiple layers, surprisingly, the blocking resistance between the laminate films of the present invention can be maintained at the same level as that of conventional products.

The content of the plant-derived biomass linear low-density polyethylene is preferably 6% by mass or more, and particularly preferably 12% by mass or more.
There is no particular upper limit on the amount of plant-derived biomass polyethylene contained.

The laminated film of the present invention may contain 3% by mass or more of plant-derived biomass linear low-density polyethylene in at least one of the (A) heat-sealing layer, (B) intermediate layer, and (C) laminate layer. However, it is particularly preferable that all of the (A) heat-sealing layer, (B) intermediate layer, and (C) laminate layer contain 3% by mass or more of plant-derived biomass linear low-density polyethylene, since this has a large effect of improving the laminate strength.

The content of the plant-derived biomass linear low density polyethylene can be appropriately increased or decreased, for example, by adjusting the blending of the resin composition when producing each layer.
The content of plant-derived biomass linear low density polyethylene in each layer of the film after production can be calculated, for example, by measuring the content of biomass-derived carbon in the film by radiocarbon ( ¹⁴ C) measurement and from this measurement result and the content of biomass-derived carbon in the plant-derived biomass linear low density polyethylene.

The laminate film of the present invention contains plant-derived biomass linear low-density polyethylene in at least one layer of (A) the heat-sealing layer, (B) the intermediate layer, and (C) the laminate layer, thereby reducing the amount of fossil fuels used in the production and reducing the environmental burden.
The biomass degree of the laminated film can be calculated by averaging the biomass degree of each layer weighted by the weight of each layer.
The biomass degree of the laminated film can be appropriately increased or decreased by adjusting the biomass degree of each layer, and the biomass degree of each layer can be appropriately increased or decreased by adjusting the biomass degree of the resin used in each layer and the amount used.
The biomass degree of the laminated film of the present invention is more preferably 5% by mass or more, and particularly preferably 10% by mass or more.
The higher the biomass ratio of the laminated film of the present invention, the better. There is no particular upper limit, but in relation to the physical properties and costs of the film, the biomass ratio is usually 60% by mass or less, and in many cases 30% by mass or less.

The heat of fusion ΔH of the laminated film of the present invention at 0° C. to 130° C., calculated from a melting curve obtained by DSC measurement, is preferably 135 to 164 J/g.
When the heat of fusion ΔH at 0° C. to 130° C. is within the above range, the laminate strength between the laminate film and the base layer can be improved more effectively.
The measurement of the melting curve by DSC and the calculation of the heat of fusion ΔH from 0° C. to 130° C. from the melting curve can be carried out by a conventionally known method, and more specifically, for example, can be carried out by the method described in the Examples of the present application.
As described above, the heat of fusion ΔH at 0° C. to 130° C. is preferably 135 to 164 J/g, and particularly preferably 140 to 164 J/g.
The heat of fusion ΔH at 0° C. to 130° C. can be reduced by lowering the crystallinity of the film by adding a component other than the petroleum-derived linear low-density polyethylene, etc. As a component other than the petroleum-derived linear low-density polyethylene, it is preferable to add biomass polyethylene derived from plants, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-propylene-butene copolymer, etc.

The melting point of the laminated film of the present invention, which corresponds to the maximum peak in the melting curve obtained by DSC measurement, is preferably higher than 114°C.
When the value corresponding to the maximum peak is within the above range, the laminate strength between the laminate film and the base material layer can be improved more effectively.
The melting point is more preferably 115° C. or higher, and particularly preferably 116° C. or higher.

The laminated film of the present invention may be a stretched film or a non-stretched film.
From the viewpoint of improving mechanical properties, a stretched film is preferred, and a biaxially stretched film is particularly preferred.
As the biaxial stretching, a method such as sequential biaxial stretching, simultaneous biaxial stretching, or multi-stage stretching is appropriately adopted.
The conditions for biaxial stretching may be those for producing a known biaxially stretched film. For example, in the case of a sequential biaxial stretching method, the longitudinal stretching temperature is set to 100° C. to 145° C., the stretching ratio is set to a range of 4 to 7 times, the transverse stretching temperature is set to 150° C. to 190° C., and the stretching ratio is set to a range of 8 to 11 times.

(D) Base layer If desired, the laminated film of the present invention can be laminated with a (D) base layer at its (C) lamination layer. In the present invention, a remarkable effect is realized in that the lamination strength with the base layer (D) is greatly improved.
The laminate strength can be measured by a conventionally known method. More specifically, for example, the laminate (C) layer of the laminate is laminated with the base layer (D), then cut into a sample strip with a width of 15 mm, and peeled between the base layer (D) and the laminate at a tensile speed of 100 mm/min, and the strength of the tensile peeled surface can be measured to evaluate the strength. More specifically, the laminate strength can be measured by the method described in the examples of the present application. The laminate strength in this case is preferably 3 (N/15 mm) or more, and particularly preferably 5 (N/15 mm) or more.

There are no particular limitations on the base layer (D), and for example, a film that is normally used for plastic packaging bags can be suitably used.
Preferred materials for the (D) base layer include plastic films composed of thermoplastic resins such as polyolefins, such as crystalline polypropylene, crystalline propylene-ethylene copolymer, crystalline polybutene-1, crystalline poly-4-methylpentene-1, low-, medium-, or high-density polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), and ionically crosslinked olefin copolymer (ionomer); aromatic vinyl copolymers, such as polystyrene and styrene-butadiene copolymer; halogenated vinyl polymers, such as polyvinyl chloride and vinylidene chloride resin; nitrile polymers, such as acrylonitrile-styrene copolymer and acrylonitrile-styrene-butadiene copolymer; polyamides, such as nylon 6, nylon 66, and para- or meta-xylylene adipamide; polyesters, such as polyethylene terephthalate (PET) and polytetramethylene terephthalate; various polycarbonates; and polyacetals, such as polyoxymethylene. In addition, when the contents to be packaged are sensitive to oxygen, the above film may be provided with a film vapor-deposited with a metal oxide or the like, a film coated with an organic compound, or a layer made of ethylene vinyl alcohol copolymer (EVOH) resin.
Plastic films made of these materials may be used in an unstretched, uniaxially stretched, or biaxially stretched state.

As the (D) base layer, these plastic films can be used as a single layer or as a laminate of two or more types. Also, one or more types of these plastic films can be laminated with a metal foil such as aluminum, paper, cellophane, etc.
Preferred examples of the (D) substrate layer include a single-layer film made of a stretched nylon film or a stretched polyester film, a two-layer film made of a polyolefin film such as low-density polyethylene or polypropylene laminated with PET, and a three-layer film made of a PET/nylon/polyethylene laminate. When producing these laminated films, an adhesive or an anchoring agent can be interposed between the layers as necessary. An ink layer expressing a design can also be provided.

The method for laminating the (D) base material layer on the (C) laminate layer is not particularly limited, but for example, the (D) base material layer can be directly laminated on the (C) laminate layer by extrusion lamination, etc. Also, the (D) base material layer may be laminated on the (C) laminate layer via an adhesive by dry lamination, etc. As the adhesive, a normal adhesive such as a urethane adhesive, an acid-modified polyolefin adhesive, a polyester adhesive, a polyether adhesive, or a polyamide adhesive can be used.
The thickness of the base layer (D) can be set arbitrarily, but is usually selected within the range of 5 to 50 μm, preferably 10 to 30 μm.

The laminate film of the present invention and a laminate film obtained by laminating a base layer (D) onto the laminate layer (C) of the laminate film of the present invention are preferably used in various applications, and are particularly suitable for use as packaging materials.
When used as a packaging material, the laminated films can be heat-sealed to each other or to another film at the heat-sealing layer (A) to form a packaging bag.
The laminate film of the present invention, in which the (D) base layer is laminated on the (C) laminate layer, has strong laminate strength and rarely peels off during production and use, and is therefore suitable for use as a packaging material in a wide range of applications in combination with various (D) base layers.
There are no particular limitations on the contents to be stored in a packaging bag using the laminated film of the present invention, but it is particularly suitable for storing liquids such as fresh produce, cooked foods, liquid medicines, toiletries such as liquid detergents and fabric softeners, or liquid foods such as concentrated coffee, or powders such as powdered detergents, sugar, pepper, and salt.

The present invention will be specifically described below with reference to examples and comparative examples. Note that the present invention is not limited in any way by the following examples.

The physical properties and characteristics in the examples and comparative examples were evaluated by the following methods.
(1) Molecular weight distribution (Mw/Mn)
After pretreatment of a polymer sample under the following conditions, the molecular weight was measured by GPC, and the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) was taken as the molecular weight distribution.
i) Pretreatment A sample (30 mg) was added with 20 mL of mobile phase for GPC measurement (o-dichlorobenzene) and dissolved by shaking at 145° C. The resulting solution was hot-filtered through a sintered filter having a pore size of 1.0 μm and used for GPC measurement.
ii) GPC
Apparatus: Tosoh Corporation, gel permeation chromatograph HLC-8321
Column: Tosoh Corporation, inner diameter 7.5 mm x 30 cm, 4 columns (TSKgel GMH6-HT: 2 columns, and TSKgel GMH6-HTL: 2 columns)
)
Column temperature: 140 ° C.
Detector: differential refractometer Flow rate: 1 mL/min
Sampling interval: 0.5 seconds (2) Melting point and heat of fusion Using a TA Instruments Q100 differential scanning calorimeter (DSC), about 5 mg of a sample was precisely weighed out, and a thermal melting curve was measured in accordance with JIS K7121 under conditions of a nitrogen gas inflow rate of 50 ml/min from 25° C. to 200° C. at a heating rate of 10° C./min. From the obtained thermal melting curve, the melting point (Tm) and the heat of crystalline fusion of the sample were determined.

(3) Blocking Strength: According to ASTM D1893-67, the blocking strength was measured by overlapping the heat-sealable layers (A) of the laminated film.

(4) Laminate strength A nylon film (manufactured by Toyobo Co., Ltd., product name: Harden) having a thickness of 15 microns was used as the (D) substrate layer. An adhesive (manufactured by Mitsui Chemicals, Inc., Takelac/Takenate=A310/A3 mixed in ethyl acetate) was applied to the surface of the (C) laminate layer side of the sample laminate, and the (D) substrate layer was bonded by hand lamination. A sample was cut into a strip shape with a width of 15 mm, and a trigger for peeling was formed between the sample laminate and the (D) substrate layer, and then the substrate and the sealant were peeled off using a Tensilon universal material testing machine (manufactured by A&D Co., Ltd.), and the strength of the tensile peel surface was measured at a tensile speed of 100 mm/min, which was taken as the laminate strength (N/15 mm).

(Comparative Example 1)
The components constituting each layer were fed to separate extruders in the formulations shown in Table 1, and a laminate film having (A) a heat-sealing layer, (B) an intermediate layer, and (C) a laminate layer, each having the resin composition shown in Table 1, was produced by a T-die method, with the layer configuration also shown in Table 1. Since no plant-derived biomass linear low-density polyethylene was used, the biomass degree was 0% by mass.
The prepared films were evaluated for melting point, heat of fusion, blocking strength, and lamination strength. The results are shown in Table 1.

(Examples 1 to 8)
Except for changing the resin composition as shown in Table 1, such as using a plant-derived biomass linear low-density polyethylene, a laminated film was produced in the same manner as in Comparative Example 1, and the melting point, heat of fusion, blocking strength, and lamination strength were evaluated. The results are shown in Table 1.

Details of each of the constituent components indicated by abbreviations in the resin composition column in Table 1 are as follows.
・LLDPE
Petroleum-derived linear low-density polyethylene MFR (2.16 kg, 190°C): 2.3 g/10 min
Density: 918kg/ ^m3
Molecular weight distribution (Mw/Mn): 2.52
・BioPE
Plant-derived biomass linear low-density polyethylene MFR (2.16 kg, 190°C): 2.3 g/10 min
Density: 916kg/ ^m3
Molecular weight distribution (Mw/Mn): 4.12

The laminate film of the present invention maintains the excellent properties of conventional polyethylene-based laminate films, while at the same time significantly improving the lamination strength with the outer layer film in particular, and reducing the environmental impact during its production, etc., and thus combines at a high level properties that are of great practical value. It is particularly suitable for use in applications such as packaging bags, and has high applicability in various industrial fields such as agriculture, food processing, distribution, and restaurant serving.

Claims (5)

A laminate film (I) having (A) a heat seal layer, (B) an intermediate layer, and (C) a laminate layer, each of which contains a petroleum-derived linear low density polyethylene,
(C) the laminate layer contains 12% by mass or more of plant-derived biomass linear low-density polyethylene ;
The heat of fusion ΔH at 0° C. to 130° C. calculated from a melting curve obtained by DSC measurement of the laminated film (I) is 135 to 164 J/g;
The melting point corresponding to the maximum peak in the melting curve obtained by DSC measurement of the laminated film (I) is more than 114°C; and
The biomass content of the laminated film consisting of the (A) heat-sealing layer, the (B) intermediate layer, and the (C) laminate layer is 5 to 10.2% by mass;
The above laminated film (I) . The laminated film (I) according to claim 1, wherein the heat sealable layer (A) and/or the intermediate layer (B) further contain at least 3% by mass of a plant-derived biomass linear low density polyethylene. The laminate film (I) according to claim 1 or 2, wherein the molecular weight distribution Mw/Mn of the plant-derived biomass linear low-density polyethylene is 3.5 or more. The laminate film (I) according to any one of claims 1 to 3, which has a substrate layer (D) on the side of the laminate layer (C) directly or via an adhesive layer. A packaging bag comprising the laminate film (I) according to any one of claims 1 to 4.