TW202235285A - Laminate film - Google Patents

Abstract

An object of the present invention is to provide an olefin-based polymer film that has desired properties of a film, such as recyclability, mechanical strength, and stretchability, at a high level and can be produced relatively easily at a low cost. A solution to such object is a laminate film having an intermediate layer (A) containing an ethylene-based polymer and a surface layer (B) containing a propylene-based polymer formed on one side or both sides of the intermediate layer (A). In the DSC curve obtained by repeating temperature rise and fall twice at a rate of 10℃ / min, the first temperature fall observes a half-width of the crystallization peak of 3.0℃ or higher at 110℃ or higher and 125℃ or lower; the second temperature rise has a melting point Tm₁ of 135℃ or higher and 165℃ or lower and a melting point Tm₂ of 125℃ or higher and lower than 135℃.

Description

laminated film

The present invention relates to a laminated film, more specifically to a laminated film having high-grade recyclability and mechanical strength as preferred properties of the film, and a manufacturing method thereof.

Olefin-based polymer films such as ethylene polymer film are widely used in containers, packaging, and substrates due to their excellent flexibility, light weight, processability, gas and liquid barrier properties, and cost. , Substrates and other uses.

In recent years, from the standpoint of reducing environmental load, etc., the plastic materials used for these films have been required to be recyclable. When recycling, it is preferable that the plastic material is composed of a single polymer, that is, a mono-material.

On the other hand, stretching of olefin-based polymer films is widely performed from the standpoint of film strength, thinness, and the like. However, it is difficult to say that the stretching processability of a film composed only of an ethylene-based polymer is excellent, and a solution to this is examined. For example, in Patent Document 1, by changing the degree of crosslinking of the polyethylene resin sheet in the thickness direction, the elongation processability at low temperature can be improved particularly. However, the production steps of a film in which the degree of crosslinking is changed in the thickness direction are complicated and disadvantageous in terms of cost, and crosslinking is not expected from the viewpoint of recyclability.

Therefore, there is a demand for an olefin-based polymer film that has high-grade recyclability, mechanical strength, and elongation processability as preferred properties of the film, and can be produced relatively easily and at low cost.

[Prior Art Literature]

[Patent Document]

Patent Document 1: Japanese Patent Application Laid-Open No. 61-74819.

In view of the above-mentioned technical background, the purpose of the present invention is to provide an olefin-based polymer film, which has high-grade recyclability, mechanical strength, elongation processability, etc. Low cost manufacturing.

The inventors of the present invention tried hard to examine, and as a result, found that a laminated film can solve the above-mentioned problems. The skin layer (B) of the polymer, and the laminated film has a specific DSC heat absorption/release pattern, thereby completing the present invention.

That is, the present invention relates to the following.

[1] A laminated film comprising: an intermediate layer (A) containing an ethylene-based polymer, and a skin layer (B) containing a propylene-based polymer formed on one or both sides of the intermediate layer (A); the laminated layer In the DSC curve obtained by repeating the heating and cooling of the film twice at 10°C/min, the half-width of the crystallization peak observed in the first cooling process above 110°C and below 125°C is greater than 3.0°C. In the second heating process, there is a melting point Tm ₁ of 135°C to 165°C, and a melting point Tm ₂ of 125°C to less than 135°C.

Below, [2] to [7] are all one of the preferred aspects or an implementation form of the present invention.

[2] The laminated film according to [1], wherein the ethylene-based polymer has a crystal fusion heat ΔH of 180 to 240 J/g in the first cooling step of the DSC curve.

[3] The laminated film according to [1] or [2], wherein the skin layer (B) is formed on one side of the intermediate layer (A), and the skin layer (B) is provided on the opposite side to the skin layer (B). The surface layer (C) containing vinyl polymer.

[4] The laminated film according to any one of [1] to [3], wherein the thickness of the skin layer (B) accounts for 5 to 60% of the total thickness of the film (except when the skin layer (B) exists in For both sides of the middle layer (A), it is the sum of the thicknesses of the two skin layers (B)).

[5] The laminated film according to [3] or [4], wherein, before stretching, from "the center of the middle layer (A) or the center of the middle layer (A) and the surface layer (C)" to "with The distance to the interface of the skin layer (B) is 0.1 to 1.0 mm.

[6] The laminated film according to any one of [1] to [5], which is a stretched laminated film.

[7] The laminated film according to [6], wherein the stretching ratio is 2 times×2 times or more.

The laminated film of the present invention has high-grade recyclability, mechanical strength, elongation processability, etc. as the preferred properties of the film, and can be manufactured relatively easily and at low cost, can reduce environmental load, and is suitable for packaging Films and other applications where conventional olefin-based polymer films have been used.

The present invention is a laminated film comprising: an intermediate layer (A) containing an ethylene-based polymer, and a skin layer (B) containing a propylene-based polymer formed on one or both sides of the intermediate layer (A); the laminated layer In the DSC curve obtained by repeating the temperature rise and fall twice at 10°C/min, the half-width of the crystallization peak observed at 110°C to 125°C in the first cooling cycle is greater than 3.0°C. In the second heating process, there is a melting point Tm ₁ of 135°C to 165°C, and a melting point Tm ₂ of 125°C to less than 135°C.

That is, the easy-open film system of the present invention has an intermediate layer (A) containing an ethylene-based polymer, and a skin layer (B) containing a propylene-based polymer.

middle layer (A)

The intermediate layer (A) constituting the laminated film of the present invention contains an ethylene-based polymer.

The intermediate layer (A) only needs to contain an ethylene-based polymer. Therefore, it may contain components other than ethylene-based polymers, or may be completely composed of ethylene-based polymers without containing components other than ethylene-based polymers.

The intermediate layer (A) may contain only one type of ethylene-based polymer, or may contain a combination of two or more types of ethylene-based polymers.

vinyl polymer

Preferred examples of the aforementioned ethylene-based polymers include: homopolymers of ethylene, ethylene as the main monomer and at least one α- Copolymers of olefins, ethylene/vinyl acetate copolymers, their saponified products, and ionic polymers, etc. Specifically, polyethylene, ethylene/propylene copolymer, ethylene/1-butene copolymer, ethylene/1-pentene copolymer, ethylene/1-hexene copolymer, ethylene/4-methyl-1 - Pentene copolymers, ethylene/1-octene copolymers, etc., are copolymers of ethylene as the main monomer and at least one α -olefin with 3 to 8 carbon atoms. In these copolymers, the ratio of α -olefin is preferably 1 to 15 mol%.

In the ethylene-based polymer, if the ratio of the constituent units derived from ethylene exceeds 50 mol%, it can be distinguished from the propylene-based polymer described later in terms of this feature.

The density of the aforementioned ethylene-based polymer is preferably from 0.910 to 0.970 g/cm ³ , more preferably from 0.940 to 0.965 g/cm ³ . Heat sealability can be improved by making this density 0.910 g/cm< ³ > or more. Moreover, processability, toughness, and transparency can be improved by making this density 0.970g/cm< ³ > or less.

Among these ethylene-based polymers, the melting point measured by differential scanning calorimeter (DSC) is preferably 125 to 135° C. from the viewpoint of the balance between elongation and heat resistance of the obtained laminated film, more Preferably it is in the range of 128 to 133°C.

In addition, specific examples of the aforementioned ethylene-based polymers include ethylene polymers manufactured and sold under the name of polyethylene. Specifically, high-pressure low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE) are preferred, and linear low-density polyethylene and high-density polyethylene are more preferred. Ethylene, especially high density polyethylene.

High-density polyethylene (HDPE) suitable for the aforementioned ethylene-based polymers can be ethylene homopolymers or copolymers of ethylene and α -olefins.

The melt flow rate (hereinafter referred to as MFR) of the high-density polyethylene measured at 190°C under a load of 21.18N according to JIS K 6922-1 is preferably 0.1 to 15 g/10 minutes, more preferably 0.5 to 10.0 g/10 minutes , and more preferably 1.0 to 5.0 g/10 minutes.

When the MFR is within the above range, the load on the extruder during molding can be reduced and the molding stability can be improved, which is preferable.

The high-density polyethylene suitable for this embodiment has a density of preferably 940 to 970 kg/m ³ , more preferably 945 to 970 kg/m ³ , and more preferably 950 to 965 kg/m 3 according to JIS K 6922-1 ³ .

When the density is in the above-mentioned range, the heat resistance of the film is improved without deforming the film due to heat treatment, and the decrease in transparency is reduced, which is preferable.

The above-mentioned high-density polyethylene is preferably substantially linear. For example, when classified by molecular weight, it is preferable to have 0.14 or less per 1,000 carbons in the main chain in the part where Mn is 100,000 or more. Long chain branches.

The above-mentioned high-density polyethylene (B) preferably has Mw/Mn in the range of 3.0 to 40.0, more preferably in the range of 5.0 to 30.0.

When the molecular weight distribution is within the above-mentioned range, formability is favorable and transparency is improved, which is preferable.

Moreover, since transparency improves when Mn is 25000 or more, it is preferable.

In this embodiment, suitable high-density polyethylene can be obtained from commercial products, for example: (trade name) Nipolon Hard 5700, 8500, 8022 manufactured by TOSOH Co., Ltd.; (trade name) manufactured by Prime Polymer Co., Ltd. (trade name) ) HI-ZEX 3300F, etc.

In addition, in the present embodiment, the high-density polyethylene suitable for use can be produced by a production method such as a slurry method, a solution method, or a gas phase method, for example. When producing this high-density polyethylene, it can generally be produced by the following process: using "a Ziegler catalyst composed of a solid catalyst component containing magnesium and titanium and an organoaluminum compound", "a catalyst composed of a Metallocene catalysts composed of organotransition metal compounds of ene derivatives and compounds that react with them to form ionic complexes and/or organometallic compounds", "vanadium-based catalysts", etc., using the catalysts to make ethylene Homopolymerization or copolymerization of ethylene and α -olefins is carried out. As long as the α -olefin is generally called an α -olefin, examples include: propylene, butene-1, hexene-1, octene-1, 4-methyl-1-pentene, etc., having 3 to 3 carbon atoms. 12 alpha -olefins. Copolymers of ethylene and α -olefin include, for example, ethylene/hexene-1 copolymers, ethylene/butene-1 copolymers, ethylene/octene-1 copolymers, and the like.

The above-mentioned linear low-density polyethylene is usually a copolymer of ethylene and α -olefin, and can be synthesized by a known production method.

α -Olefins can use compounds with 3 to 20 carbon atoms, 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., and their mixtures can also be used. The α -olefin is preferably a compound having 4, 6 or 8 carbon atoms or a mixture thereof, that is, 1-butene, 1-hexene, 1-octene or a mixture thereof.

In particular, α -olefin may be produced by polymerizing ethylene in the polymerization step, and in this case, it can be produced substantially using only ethylene as a raw material.

Commercially available linear low-density polyethylene can be used, for example, 2040F (C6-LLDPE, MFR: 4.0, density: 0.918 g/cm ³ ) manufactured by UBE-MARUZEN POLYETHYLENE Co., Ltd., and manufactured by Prime Polymer Co., Ltd. can be used. The (trade name) Evolue SP2040, etc.

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

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

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

The above-mentioned single-site catalyst refers to a catalyst capable of forming a uniform active species, which is usually adjusted by contacting a metallocene transition metal compound or a non-metallocene transition metal compound with an activation co-catalyst. Compared with multi-site catalysts, single-site catalysts have a uniform active point structure, so they can polymerize high molecular weight and uniform A polymer with a high-strength structure is preferred. The single-site catalyst is preferably a metallocene-based catalyst. Metallocene-based catalysts include "a transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, a co-catalyst, an organic metal compound if necessary, and various catalyst components of a carrier" catalyst.

In the transition metal compound of Group IV of the Periodic Table having a ligand having a cyclopentadienyl skeleton, the cyclopentadienyl skeleton refers to cyclopentadienyl, substituted cyclopentadienyl, and the like. The substituted cyclopentadienyl group has a hydrocarbon group selected from 1 to 30 carbons, a silyl group, a silyl-substituted alkyl group, a silyl-substituted aryl group, a cyano group, a cyanoalkyl group, and a cyanoaryl group. At least one substituent of group, halo group, haloalkyl group, halosilicon group, etc. The substituted cyclopentadienyl may have two or more substituents, or the substituents may be bonded to each other to form a ring, and may form an indene ring, an oxene ring, an azulene ring, hydrogenated forms thereof, and the like. A ring formed by bonding substituents to each other may further have substituents.

Among the transition metal compounds of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, examples of the transition metal include zirconium, titanium, hafnium, etc., preferably zirconium and hafnium. The transition metal compound usually contains two ligands having a cyclopentadienyl skeleton, and each ligand having a cyclopentadienyl skeleton is preferably bonded to each other via a crosslinking group. In addition, the crosslinking group can include: alkylene group with 1 to 4 carbon atoms; silylene group; substituted silylene group such as dialkylsilylene group and diarylsilylene group; dialkylgermanium group Substituted germanyl groups such as diaryl germanyl, diaryl germanyl, etc. Preferred are substituted silylene groups.

Among the transition metal compounds of Group IV of the periodic table, the representative examples of the ligands other than the ligands having the cyclopentadienyl skeleton include: hydrogen, hydrocarbon groups (alkyl, alkenyl) having 1 to 20 carbons, , aryl, alkylaryl, aralkyl, polyalkenyl, etc.), halogen, meta-alkyl, meta-aryl, etc.

Among the transition metal compounds of Group IV of the Periodic Table containing a ligand having a cyclopentadienyl skeleton, one type or a mixture of two or more types may be used as a catalyst component.

A catalyst promoter refers to a transition metal compound in Group IV of the above-mentioned periodic table that can function as a polymerization catalyst, or that can balance the ionic charge in a catalytically activated state. Co-catalysts include: benzene-soluble aluminoxane (aluminoxane) or benzene-insoluble organoaluminum oxy-compounds, ion-exchange phyllosilicates, boron compounds, with or without active hydrogen Ionic compounds composed of radical cations and non-coordinating anions, lanthanide salts such as lanthanum oxide, tin oxide, phenoxy compounds containing fluorine groups, etc.

A transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton can be supported on a carrier of an inorganic or organic compound. The support is preferably porous oxides of inorganic or organic compounds, specifically, ion-exchanged phyllosilicates 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 their mixtures.

Moreover, organometallic compounds used further as needed include organoaluminum compounds, organomagnesium compounds, organozinc compounds, and the like. Among them, organoaluminum is preferably used.

The middle layer (A) may contain components other than the above-mentioned ethylene-based polymers, for example, polymers other than ethylene-based polymers, oligomers, and heat-resistant stabilizers (antioxidants) may be formulated as needed or within the scope not contrary to the purpose of the present invention. , weathering stabilizer, UV absorber, lubricant, slip agent, nucleating agent, anti-caking agent, antistatic agent, anti-fogging agent, pigment, dye, etc., as well as talc, silicon dioxide, diatomaceous earth, etc. Fillers etc.

These additional components may be prepared in the vinyl polymer in advance, or may be added when forming the intermediate layer (A) from the vinyl polymer.

The thickness of the intermediate layer (A) is not particularly limited, but is preferably at least 10 μm, more preferably at least 13 μm, particularly preferably at least 15 μm, from the viewpoint of film strength and the like.

On the other hand, the thickness of the intermediate layer (A) is preferably at most 500 μm, more preferably at most 300 μm, particularly preferably at most 100 μm, from the viewpoint of flexibility and economical efficiency.

When stretching is performed in the production process of the laminated film of the present invention, the thickness of the layer corresponding to the intermediate layer (A) before stretching is preferably 0.2 to 1.94 mm, particularly preferably 0.4 to 1.9 mm.

The thickness of the intermediate layer (A) can be appropriately adjusted by adjusting stretching conditions such as stretching magnification, layer thickness before stretching, and distance between lips of a machine forming the layer before stretching.

Also, when stretching is carried out in the manufacturing process of the laminated film of the present invention, before stretching, from "the center of the middle layer (A) or the center of the middle layer (A) and the surface layer (C)" to "with the skin layer (B) ) to the interface" is preferably from 0.1 to 1.0 mm, more preferably from 0.1 to 0.97 mm, and most preferably from 0.25 to 0.95 mm.

Regarding the distance from "the center of the middle layer (A) or the center of the middle layer (A) and the surface layer (C)" to "the interface with the skin layer (B)", it can be calculated by the thickness of each layer before stretching , Adjust the distance between the die lips of the machine that forms the layer before stretching, etc., and adjust it appropriately.

epidermis (B)

The intermediate layer (B) constituting the laminated film of the present invention contains a propylene-based polymer.

The skin layer (B) may contain components other than the propylene polymer as long as it contains the propylene polymer, or may be completely composed of the propylene polymer without containing the components other than the propylene polymer.

The skin layer (B) may contain only one kind of propylene-based polymer, or may contain a combination of two or more kinds of propylene-based polymers.

Propylene polymer

As far as the propylene polymer is concerned, resins generally produced and sold under the name of polypropylene can be used, and generally propylene homopolymers or propylene copolymers (that is, made ^of A copolymer composed of propylene and a small amount of at least one comonomer selected from α -olefins, etc.).

In the case of a copolymer, it may be a random copolymer or a block copolymer. Examples of other α -olefins in this propylene copolymer include ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, and 4-methyl-1-pentene Ethylene and α -olefins with about 4 to 20 carbon atoms. Such other α -olefins may be used alone or in combination of two or more α -olefins to be copolymerized. Also, the presence of comonomers other than alpha -olefins is not excluded.

A propylene-based polymer can be distinguished from an ethylene-based polymer by making the ratio of the structural unit derived from propylene 50 mol% or more. The ratio of the constituent units derived from propylene is preferably at least 80 mol%, particularly preferably at least 90 mol%.

Since the ratio of the structural unit derived from propylene is 50 mol% or more, the ratio of the structural unit derived from a comonomer may be less than 50 mol%. In general polypropylene, the ratio of constituent units derived from a comonomer is usually 25 mol% or less. In the case of a random copolymer, it is preferably at most 10 mol%, particularly preferably at most 7 mol%. In the case of a block copolymer, it is preferably at most 20 mol%, particularly preferably at most 15 mol%.

Among these propylene-based polymers, it is preferred that the melting point measured by a differential scanning calorimeter (DSC) be 135 to 165° C. (especially It is a propylene-based polymer in the range of 137 to 163°C), especially a homopolypropylene or a propylene/ α -olefin random copolymer.

The melt flow rate (MFR) (ASTM D1238, 230°C, 2160g load) of the propylene-based polymer used for the skin layer (B) is not particularly limited, but it is usually 0.01 to 100g from the viewpoint of elongation processability, etc. /10 minutes, preferably in the range of 0.1 to 70 g/10 minutes.

The propylene-based polymer (a) can be produced by various known production methods, specifically, it can be produced using a catalyst for olefin polymerization such as a Ziegler-Natta catalyst or a single-site catalyst. Especially can make Manufactured with a single point catalyst. A single-site catalyst is a catalyst with a uniform active point (single site), such as a metallocene catalyst (also known as a Kaminsky catalyst) or a Brookhart catalyst. The metallocene catalyst is composed of "metallocene transition metal compound" and "at least one compound selected from the group consisting of an organoaluminum compound and a compound that reacts with the above metallocene transition metal compound to form an ion pair" The catalyst can also be carried on inorganic matter.

Surface layer (C)

The laminated film of the present invention is a laminate having "an intermediate layer (A) containing an ethylene-based polymer" and "a skin layer (B) containing a propylene-based polymer formed on one or both sides of the intermediate layer (A)" It is enough to be a film, and may or may not have another layer, especially if the skin layer (B) is formed on only one side of the middle layer (A), it is preferable to have a layer on the side opposite to the skin layer (B). Surface layer (C) containing vinyl polymer.

By providing the surface layer (C), it is preferable because functions such as improving lamination strength can be imparted.

The thickness of the surface layer (C) is not particularly limited, preferably 0.1 to 10 μm , particularly preferably 1 to 5 μm .

Based on the thickness of the middle layer (A), the thickness of the surface layer (C) is preferably 1 to 30% of the middle layer (A), particularly preferably 5 to 20%.

The surface layer (C) is not limited as long as it contains an vinyl polymer. Therefore, there are cases where the surface layer (C) is made of the same material as that of the middle layer (A), but when there are two or more layers containing vinyl polymers, "more than the middle layer (A) The "layer located on the outside and constituting the surface" corresponds to the surface layer (C).

Details such as the type and physical properties of the vinyl polymer in the surface layer (C) are the same as those described above for the intermediate layer (A).

laminated film

The laminated film of the present invention is a film having the above-mentioned intermediate layer (A) and skin layer (B). In the laminated film of the present invention, the intermediate layer (A) and the skin layer (B) are preferably directly laminated, but other layers may be present therebetween.

Examples of other layer systems include an adhesive layer, a gas barrier layer, and the like, but are not limited thereto.

In the laminated film of the present invention, the thickness of the skin layer (B) (but when the skin layer (B) exists on both sides of the middle layer (A), it is the sum of the thicknesses of the two skin layers (B)) is preferably the thickness of the film. 5 to 60% of the total thickness.

By making the thickness of the skin layer (B) account for more than 5% of the total film thickness, stretching processability can be improved, and stable stretching can be performed at a high stretching ratio. From this point of view, the thickness of the epidermis (B) (except when the epidermis (B) exists on both sides of the middle layer (A), then the sum of the thicknesses of the two epidermis (B)) is preferably the total thickness of the film. More than 5% of the thickness, preferably more than 10%.

By setting the thickness of the skin layer (B) to 60% or less of the total thickness of the film, the film of the present invention can be excellent in recyclability. From this point of view, the thickness of the epidermis (B) (except when the epidermis (B) exists on both sides of the middle layer (A), then the sum of the thicknesses of the two epidermis (B)) is preferably the total thickness of the film. Less than 30% of the thickness, preferably less than 10%.

When the laminated film of the present invention is stretched, the ratio of the thickness of the skin layer (B) to the total thickness of the film is almost the same before and after stretching, but if there is a difference before and after stretching, it is preferably the one after stretching. The ratio is within the above range.

The ratio of the thickness of the skin layer (B) to the total thickness of the film can be properly adjusted by adjusting the thickness of each layer before stretching, and can also be adjusted by adjusting the distance between the die lips when manufacturing each layer before stretching Adjust and adjust appropriately.

The laminated film of the present invention can be formed by various known film forming methods, for example: After forming the films of the middle layer (A) and the skin layer (B) (two layers when there are two layers) in advance, the films are bonded together. The method of making a laminated film; after using a multi-layer mold to obtain a laminated film composed of an intermediate layer (A) and a skin layer (B), the A method of extruding another layer of skin layer (B) on the surface of the middle layer (A) to form a laminated film; or, using a multi-layer die for co-extrusion to obtain a layer of skin layer (B), middle layer (A) and The method of the laminated film composed of the skin layer (B), etc.

Also, various known film forming methods can be used as the film forming method, specifically, a T-die casting film forming method, an air-filled film forming method, and the like can be used.

Since the laminated film of the present invention is excellent in stretching processability, it is preferably stretched for the purpose of producing a film, improving mechanical strength, improving transparency, and the like. Preferably, biaxial stretching is performed. The stretching ratio is not particularly limited, but it is preferably 2 times×2 or more in the case of biaxial stretching.

For biaxial stretching, methods such as sequential biaxial stretching, simultaneous biaxial stretching, and multistage stretching can be appropriately used.

The conditions for biaxial stretching can be the production conditions of known biaxially stretched films. For example, in the sequential biaxial stretching method, it can be listed: the longitudinal stretching temperature is 100°C to 145°C and the stretching ratio is 3 to 7 times. The temperature is 120 to 180° C. and the elongation ratio is in the range of 3 to 11 times.

The total thickness of the laminated film of the present invention is not particularly limited. From the viewpoint of ensuring practical strength, etc., when stretched, it is usually 15 μm or more after stretching, preferably 18 μm or more, more preferably 20 μm or more. μ m or more. On the other hand, it is usually 500 μm or less, preferably 300 μm or less, more preferably 100 μm or less from the viewpoint of sufficient flexibility depending on the application.

When the laminated film of the present invention is stretched, the total thickness before stretching is preferably 0.3 to 2.5 mm, particularly preferably 0.5 to 2.0 mm.

The laminated film of the present invention is heated from -50°C to 200°C at a heating rate of 10°C/min under the conditions of a sample weight of about 5.0 mg and a nitrogen flow rate of 50 ml/min according to JIS K 7121. Keep at 200°C for 10 minutes, and then repeat the cooling and heating under the same conditions for one time. The DSC curve has a specific heat absorption/radiation pattern. More specifically, the DSC curve obtained from the above conditions satisfies the following conditions:

． In the first cooling cycle, the half-width of the crystallization peak observed above 110°C and below 125°C is greater than 3.0°C; and

． In the second heating process, it has a melting point Tm ₁ of not less than 135°C and not more than 165°C, and a melting point Tm ₂ of not less than 125°C but less than 135°C.

In the first cooling process, the half-width of the crystallization peak observed at 110°C to 125°C is greater than 3.0°C, so that the crystallization during stretching can be properly suppressed, and the stretching processability can be improved. good.

In the first cooling process, the half width of the crystallization peak observed at 110°C to 125°C is preferably 3.0°C or higher, more preferably 3.5°C or higher.

In the first cooling process, the half width of the crystallization peak observed at 110°C to 125°C has no particular upper limit, but it is usually 10.0°C or less, more preferably 5.0°C or less.

The half-width of the crystallization peak in the first cooling process can be determined by comparing the type of ethylene polymer, propylene polymer, or the skin layer made of propylene polymer with respect to the entire film layer. The thickness ratio etc. shall be changed and adjusted appropriately.

The laminated film of the present invention has a melting point Tm ₁ of not less than 135°C and not more than 165°C, and a melting point Tm ₂ of not less than 125°C but less than 135°C in the second heating process.

Since it has the melting points Tm ₁ and Tm ₂ mentioned above, the laminated film of the present invention is suitable for heat-sealing processing.

In the laminated film composed of only ethylene polymers, because the difference between the melting point of the outermost layer of the film and the sealing layer is small, it has been pointed out that the outermost layer will melt and fuse to the heat-sealing rod during heat sealing. question.

The laminated film of the present invention has the above-mentioned melting points Tm ₁ and Tm ₂ , especially higher Tm ₁ , so that thermal fusion of the outermost layer (skin layer (B)) can be suppressed during heat sealing. For example, when it is used for a food packaging bag, it can realize a food packaging bag excellent in bag-making suitability, so it is preferable.

The melting point Tm ₁ is preferably from 135 to 165°C, more preferably from 137 to 160°C.

The melting point Tm ₁ can be appropriately adjusted by adjusting the type, physical properties, content, and the like of the propylene-based polymer contained in the skin layer (B).

The melting point Tm ₂ is preferably from 120 to 135°C, more preferably from 125 to 133°C.

The melting point Tm ₂ can be appropriately adjusted by adjusting the type, physical properties, content, etc. of the vinyl polymer contained in the intermediate layer (A).

In addition, in the above-mentioned DSC curve, the ethylene-based polymer contained in the intermediate layer (A) preferably has a heat of crystal fusion ΔH (converted to 100% ratio of the ethylene-based polymer) of 180 to 240 J/g in the first heating cycle. .

The heat of fusion ΔH (J/g) of the overall crystallization of the laminated film can be observed in the above DSC curve, so the ΔH of the melting peak of the ethylene polymer is divided by the content ratio of the ethylene polymer (PE monomer material ratio), and The heat of fusion of the crystals of the ethylene-based polymer was obtained (converted to an ethylene-based polymer ratio of 100%).

It is preferable that the heat of crystal fusion ΔH of the ethylene-based polymer contained in the intermediate layer (A) in the first heating process be in the above-mentioned range, since the ethylene-based polymer can be stretched efficiently.

The heat of fusion ΔH of crystallization of the ethylene polymer contained in the intermediate layer (A) in the first heating process is more preferably 180 to 240 J/g, particularly preferably 190 to 230 J/g.

The crystal fusion heat ΔH of the ethylene polymer in the first cooling step can be appropriately adjusted by adjusting the type of ethylene polymer contained in the intermediate layer (A) or physical properties such as crystallinity.

As described above, the laminated film of the present invention is excellent in elongation processability, so a high modulus of elasticity can be realized by the laminated film of the present invention.

When the laminated film of the present invention is stretched, after stretching, when the modulus of elasticity in the MD direction (machine direction) is T1, and the modulus of elasticity in the TD direction (transverse direction) is T2, the value of T1+T2 It is preferably at least 1500 (MPa), more preferably at least 1600 (MPa), still more preferably at least 1800 (MPa), and most preferably at least 2000 (MPa).

The value of T1+T2 has no special upper limit, as long as it can be manufactured with materials and manufacturing methods obtained at a reasonable cost, it is usually below 4500MPa, most of which are below 3500MPa.

The elastic modulus of the laminated film can be measured by conventionally known methods in this technical field, more specifically, it can be measured by cutting out a strip-shaped sample from the laminated film and performing a tensile test. For example, it can be measured by the method described in the examples of this specification.

The laminated film of this embodiment has a high modulus of elasticity, so it is suitable for use in packaging bags and the like, for example. A packaging bag using such a laminated film having such a high modulus of elasticity has high rigidity, so that a packaging bag with a good appearance can be realized when displaying products.

In this embodiment, the shape of the packaging bag is not particularly limited, and conventionally known packaging bags can be used appropriately. The preferred examples include: three-seal bag, four-seal bag, pillow bag, gusset bag (gazette bag), standing pouch, etc. Among them, it is especially suitable for gusset bags or stand-up bags that require standing.

Also, the high elastic modulus of this embodiment is preferable because it contributes to excellent processability in lamination steps, printing steps, and the like.

When "the temperature at which the heat-sealing strength becomes 1.0 (N/15mm) or higher" is used as the fusion temperature, the fusion temperature of the laminated film of the present invention is preferably 140°C or higher, more preferably 150°C or higher, and most preferably 160°C above.

The heat-sealing strength and heat fusion temperature of the laminated film can be measured by conventionally known methods in this technical field. More specifically, the laminated body can be obtained by "heat-sealing with the adherend film at a specific heat-sealing temperature. From the obtained Cut out a 15mm wide sample of the laminate, and conduct a peel test to measure it. For example, it can be measured by the method described in the examples of this specification.

The laminated film of the present invention uses ethylene-based polymers and propylene-based polymers with excellent transparency, and the transparency can be further improved by stretching, so it can easily achieve high transparency, for example, it is suitable for food packaging bags, etc. use. The food packaging bag of this embodiment has high practical value because of its high transparency, which makes the printing and the appearance of the contents better.

From the viewpoint of printed appearance, the content of the food packaging bag of this embodiment is not particularly limited. The food packaging bag of this embodiment is especially suitable for desserts and other contents that consumers want to see.

On the other hand, for food packaging bags that contain contents (such as snacks or small dried fish, etc.) that are easily crushed due to impact during transportation, etc., and do not want consumers to see their contents, it may not be very suitable. However, it is often printed on the packaging bag at this time, so the food packaging bag of this embodiment with excellent printing appearance can still be used publicly.

The transparency of the laminated film of the present invention can be evaluated by haze. The haze is preferably at most 10%, more preferably at most 8%, and more preferably at most 5%.

The haze of the laminated film can be measured by conventionally known methods, more specifically, it can be measured by the method described in the Examples of this specification.

When the laminated film of the present invention is used in food packaging bags, it is preferable to use a laminated film with high tear-openability. Here, examples of the form of the packaging bag include three-seal bags, four-seal bags, pillow bags, gusset bags, and stand-up pouches.

More specifically, in the laminated film of this embodiment, when the tear strength in the MD direction (machine direction) is T1 (mN), and the tear strength in the TD direction is T2 (mN), T1+T2 The value is preferably 1000 (mN) or less, more preferably 400 (mN) or less, particularly preferably 200 (nM) or less.

The tear strength of the laminated film can be measured by a known method in the technical field, more specifically, it can be measured using a light-load tear tester. For example, it can be measured by the method described in the examples of this specification.

There is no particular lower limit for the tear strength of the laminated film. From the standpoint of preventing unexpected rupture, the value of T1+T2 is preferably 10 (mN) or more, more preferably 20 (mN) or more.

The laminated film of the present invention can have high-level recyclability, mechanical strength, stretching processability, etc. as the preferred properties of the film, and can be suitable for various applications where olefin-based polymer films have been used in the past. For example, it can be suitable for packaging materials for fresh food, processed food, daily necessities, sanitary products, pharmaceuticals, etc., electrical and electronic materials, surface protection materials for various components, etc., especially more suitable for packaging materials.

When using the laminated film of the present invention as a packaging material, for example, the laminated film itself can be folded in half and sealed on three sides, or two laminated films can be sealed on four sides to form a package. Also, a laminated film, or a cover material obtained by laminating the laminated film and a base material, etc., may be heat-sealed with various container bodies such as cups to form a package.

A preferred example of such a package can include: a container body composed of "the above-mentioned cover material" and "containing at least one of polypropylene, polyethylene terephthalate, and polybutylene terephthalate". "Packaging container composed of.

The storage contents in the packaging container are not particularly limited, and are preferably used for packaging of food, pharmaceuticals, medical devices, daily necessities, and miscellaneous goods.

(Example)

Hereinafter, the present invention will be specifically described with reference to Examples/Comparative Examples. In addition, this invention is not limited to a following example.

Evaluation of physical properties and characteristics in Examples/Comparative Examples was performed by the following methods.

(1) Maximum elongation ratio

According to the layer constitution shown in Table 1, a stretched raw material film with a thickness of 1mm formed by laminating the middle layer (A) and the skin layer (B) was produced.

Using a batch-type biaxial stretching machine, the stretched raw film obtained is at the temperature shown in Table 1 (122°C to 166°C, with an interval of 4°C) at the same vertical and horizontal magnification at intervals of 0.5 times to 2 times in length and width x 2 times to 9 The range of times × 9 times is extended, and the "maximum magnification that can be extended without the clip falling off or breaking" is taken as the maximum elongation magnification at the extension temperature.

(2) Haze

For the stretched film obtained at the stretching temperature and stretching ratio shown in Table 2, the haze of one sheet and the haze of four sheets were measured in accordance with JIS K 7136 using a haze meter (NDH5000 manufactured by Nippon Denshoku Industries, Ltd.) Spend. The measured value is the average value of 5 times.

(3) modulus of elasticity

From the stretched film obtained at the stretching temperature and stretching ratio shown in Table 2, a strip-shaped film (length: 150 mm, width: 15 mm) was cut out in the longitudinal direction (MD) and transverse direction (TD) as a test piece, and used A tensile tester (RTG1210 manufactured by A&D Co., Ltd.) was used to conduct a tensile test under the conditions of a distance between chucks of 100 mm and a crosshead speed of 5 mm/min, and the modulus of elasticity (MPa) was obtained. The measured value is the average value of 5 times.

(4) Tear strength

Using a light-load tear tester manufactured by Toyo Seiki Seisakusho Co., Ltd., under the conditions of a measurement temperature of 23±3°C and a measurement humidity of 50±5%RH, the elongation obtained by the elongation temperature and elongation ratio shown in Table 2 were respectively measured. Tear strength of film in MD direction and TD direction.

(5) Heat seal strength

Change the heat-sealing temperature between the stretched films obtained from the stretching temperature and stretching ratio shown in Table 2 in the range of 120°C to 190°C, use a sealing rod with a width of 10mm, and seal with a pressure of 0.2MPa for 1 second. Allow to cool, and prepare the sample for measurement. Cut a test piece with a width of 15 mm from the sample, peel off the heat-sealed part at a crosshead speed of 300 mm/min, and use its strength as the heat-seal strength (N/15mm) at the heat-sealing temperature.

"The temperature at which the heat-sealing strength becomes 1.0 N or more" was used as the fusion temperature of the stretched film.

(6)DSC curve

Differential scanning calorimeter (DSC) uses Q100 manufactured by TA Instruments, and cuts out and accurately weighs about 5 mg of the sample from the stretched film obtained by the stretching temperature and stretching ratio shown in Table 2. According to JIS K 7121, the nitrogen flow Under the condition of 50ml/min, heat up from -50°C to 200°C at a heating rate of 10°C/min, then keep it at 200°C for 10 minutes, then repeat the temperature down and temperature up once under the same conditions to obtain the DSC curve According to this, the melting point (°C), the heat of crystal fusion ΔH (J/g), the half-width (°C) of the crystallization peak, etc. are determined.

The details of each constituent component such as the resin used in the examples/comparative examples are as follows.

． HDPE (High Density Polyethylene)

Density: 950kg/m ³ .

MFR: 1.1 g/10 minutes.

Melting point: 131°C.

． h-PP (homopolypropylene)

Density: 900kg/m ³ .

MFR: 3.0 g/10 minutes.

Melting point: 161°C.

． r-PP1 (3-element random polypropylene 1)

Density: 900kg/m ³ .

MFR: 7g/10 minutes.

Melting point: 139°C.

． r-PP2 (3-element random polypropylene 2)

Density: 900kg/m ³ .

MFR: 5.0 g/10 minutes.

Melting point: 128°C.

． r-PP3 (metallocene binary random polypropylene)

Density: 900kg/m ³ .

MFR: 7.0 g/10 minutes.

Melting point: 125°C.

(Example 1)

Homopolypropylene (h-PP) as a material constituting the skin layer (B) and high-density polyethylene (HDPE) as a material constituting the middle layer (A) are supplied to separate extruders. Formed into a 3-layer co-extruded film with a thickness ratio of skin layer (B)/intermediate layer (A)/skin layer (B) of 30.0:40.0:30.0 and a total thickness of 1.0 mm by molding to produce stretched raw film.

Using the obtained stretched raw material film, the maximum stretching ratio was evaluated according to the method described above. The results are shown in Table 1.

Next, the stretched raw film was stretched 7×7 times at 158°C, and the haze, elastic modulus, tear strength, and HS strength of the obtained stretched film were evaluated according to the above method, and the DSC curve was measured. The results are shown in Table 2.

(Example 2 to 5)

Except changing the thickness ratios of the skin layer (B)/intermediate layer (A)/skin layer (B) as shown in Table 1, the stretched raw material film was produced in the same manner as in Example 1, and the maximum stretching ratio was evaluated. . The results are shown in Table 1.

Next, a stretched film was produced from the stretched raw film in the same manner as in Example 1, and the haze, elastic modulus, tear strength, and HS strength were evaluated, and the DSC curve was measured. The results are shown in Table 2.

(Example 6)

Homopolypropylene (h-PP) as the material constituting the skin layer (B), high-density polyethylene (HDPE) as the material constituting the middle layer (A), and high density polyethylene (HDPE) as the material constituting the surface layer (C) Density polyethylene (HDPE) is supplied to individual extruders and formed by T-die method so that the thickness ratio of skin layer (B)/middle layer (A)/surface layer (C) is 5.0:90.0:5.0 and 3-layer co-extruded film with a total thickness of 1.0mm to make stretched raw film.

Using the obtained stretched raw material film, the maximum stretching ratio was evaluated according to the method described above. The results are shown in Table 1.

Next, the stretched raw film was stretched 6×6 times at 126°C, and the haze, elastic modulus, tear strength, and HS strength of the obtained stretched film were evaluated according to the above-mentioned method, and the DSC curve was measured. The heat sealing is performed by laminating the homopolypropylenes of the skin layer (B) together. The results are shown in Table 2.

(Example 7)

Except for using ternary random polypropylene (r-PP1) as the material constituting the skin layer (B), a stretched raw material film was produced in the same manner as in Example 4, and the maximum stretching ratio was evaluated. The results are shown in Table 1.

Next, a stretched film was produced from the stretched raw film in the same manner as in Example 1, and the haze, elastic modulus, tear strength, and HS strength were evaluated, and the DSC curve was measured. The results are shown in Table 2.

Next, the stretched raw film was stretched 7×7 times at 130° C., and the haze, elastic modulus, tear strength, and HS strength of the obtained stretched film were evaluated according to the above-mentioned method, and the DSC curve was measured. The results are shown in Table 2. In addition, the half-width of the first cooling process described in Table 2 is the peak of 117.3° C. among the two peaks.

(Embodiment 8)

The positions of the skin layer (B) and the surface layer (C) were exchanged, and as the material constituting the skin layer (B), ternary random polypropylene (r-PP1) was used, except that it was the same as in Example 6 The stretched raw material film was produced in the same way, and the maximum stretching ratio was evaluated. The results are shown in Table 1.

(Example 9 and 10)

As the material constituting the skin layer (B), ternary random polypropylene (r-PP2) or metallocene binary random polypropylene (r-PP3) was used, and it was produced in the same manner as in Example 7. The raw film was stretched, and the maximum stretching ratio was evaluated. The results are shown in Table 1.

(comparative example 1)

High-density polyethylene (HDPE) as a material constituting the surface layer (C) and high-density polyethylene (HDPE) as a material constituting the middle layer (A) are supplied to separate extruders, and the T-die Formed into a 3-layer co-extruded film with a thickness ratio of surface layer (C)/intermediate layer (A)/surface layer (C) of 5.0:90.0:5.0 and a total thickness of 1.0 mm to produce an extended raw film.

Using the obtained stretched raw material film, the maximum stretching ratio was evaluated according to the method described above. The results are shown in Table 1.

The stretching processability of the above-mentioned stretched raw material film is poor, and a stretched film cannot be formed. Therefore, the high-density polyethylene was supplied to the extruder, and formed by the T-die method so that the thickness ratio of the surface layer (C)/intermediate layer (A)/surface layer (C) was 5.0:90.0:5.0 and the layer For a non-stretched film with a thickness of about 20 μm , evaluate the haze, elastic modulus, tear strength, and HS strength according to the above method, and measure the DSC curve. The results are shown in Table 2.

[Table 1]

[Table 2]

(Industrial Utilization)

The laminated film system of the present invention can have both recyclability, mechanical strength, elongation processability, etc. as the preferred properties of the film at a high level, and can be manufactured more easily and at low cost, so it can reduce environmental load, and It is suitable for various applications where olefin-based polymer films have been used in the past, such as packaging films, and is highly applicable in various fields such as electrical and electronic industries, pharmaceutical industries, agriculture, food processing, distribution, and catering.

Claims (7)

A laminated film comprising: an intermediate layer (A) containing an ethylene-based polymer, and a skin layer (B) containing a propylene-based polymer formed on one or both sides of the intermediate layer (A); In the DSC curve obtained by repeating the heating and cooling twice at 10°C/min, the half-width of the crystallization peak observed in the first cooling stroke above 110°C and below 125°C is greater than 3.0°C, In the second heating process, it has a melting point Tm ₁ of not less than 135°C and not more than 165°C, and a melting point Tm ₂ of not less than 125°C but less than 135°C. The laminated film according to claim 1, wherein the crystalline fusion heat ΔH of the ethylene-based polymer in the first cooling step of the DSC curve is 180 to 240 J/g. The laminated film according to claim 1 or 2, wherein a skin layer (B) is formed on one side of the intermediate layer (A), and an ethylene-based polymer layer is provided on the opposite side of the skin layer (B). The surface layer of the object (C). The laminated film as described in any one of claims 1 to 3, wherein the thickness of the skin layer (B) accounts for 5 to 60% of the total thickness of the film, but when the skin layer (B) exists in the middle layer (A) When both sides, the thickness of the aforementioned epidermis (B) is then the sum of the thicknesses of the two epidermis (B). The laminated film according to claim 3 or 4, wherein, before stretching, from the center of the middle layer (A) or the center of the middle layer (A) and the surface layer (C) to the interface with the skin layer (B) The distance is 0.1 to 1.0mm. The laminated film according to any one of claims 1 to 5, which is a stretched laminated film. In the laminated film according to claim 6, the elongation ratio is 2 times×2 times or more.