Heat-fusible laminate film

Abstract

To provide a heat-fusible laminate film which is suitably used for a lid material of a resin coat paper container, can achieve adequate heat sealability between a resin coat paper container and the laminate film, and is also excellent in film formation property.SOLUTION: A laminate film has (A) a seal layer, (B) a core layer and (C) a laminate layer, where (A) the seal layer contains polypropylene and an ethylene-1-butene copolymer, (B) the core layer and (C) the laminate layer each contains linear low-density polyethylene, and the content of the ethylene-1-butene copolymer of (A) the seal layer is 35-70 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a heat-sealable laminated film, and more specifically to a heat-sealable laminated film that is suitably used as a lid material for resin-coated paper containers, and is particularly capable of achieving appropriate heat-seal performance with resin-coated paper containers, as well as having excellent film-forming properties. [Background technology]

[0002] Paper containers have become commonplace as containers for various foods such as yogurt and other dairy products, natto, and instant noodles, in response to the demand for clearer printing due to the diversification of designs and to address environmental issues during disposal. These paper containers are usually coated on the inside with various resins such as polyethylene for purposes such as water resistance, and it has been proposed to use a laminated film with a sealing layer as a lid material in order to heat-seal the resin coating layer of these resin-coated paper containers (see, for example, Patent Document 1).

[0003] In recent years, the demands on the performance of resin-coated paper containers have increased even further. There is a need for lid materials that can achieve appropriate heat-sealing performance with resin-coated paper containers, more specifically, sufficient heat-sealing strength at relatively low temperatures, and that can be peeled off from the paper container without causing paper peeling during opening. Furthermore, from the perspective of production efficiency and storage convenience, there is a need to suppress film sticking to the rolls during film formation due to tackiness, and to appropriately prevent film blocking. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-058642 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In view of the above technical background, the present invention aims to provide a heat-sealable laminated film that is suitable for use as a lid material for resin-coated paper containers, and in particular can achieve appropriate heat-seal performance with respect to resin-coated paper containers, as well as having excellent film-forming properties. [Means for solving the problem]

[0006] As a result of diligent research, the present inventors have found that in a laminated film having (A) a seal layer, (B) a core layer, and (C) a laminate layer, wherein the (A) seal layer contains polypropylene and ethylene-1-butene copolymer, and the (B) core layer and (C) laminate layer each contain linear low-density polyethylene, by setting the content of the ethylene-1-butene copolymer in the (A) seal layer to a specific range, it is possible to achieve appropriate heat seal performance with resin-coated paper containers as well as excellent film-forming properties, thus completing the present invention. In other words, the present invention is [1] A laminated film having (A) a sealing layer, (B) a core layer, and (C) a laminate layer, (A) The seal layer contains polypropylene and ethylene-1-butene copolymer, (B) The core layer and (C) the laminate layer each contain linear low-density polyethylene. (A) The present invention relates to a laminated film in which the content of the ethylene-1-butene copolymer in the sealing layer is 35 to 70% by mass.

[0007] Hereinafter, [2] to [4] are all preferred embodiments or models of the present invention. [2] The density of the ethylene-1-butene copolymer is 850 to 910 kg / m³. 3 The laminated film described in [1]. [3] The laminated film according to [1] or [2], wherein the polypropylene is homopolypropylene. [4] A laminated film according to any one of [1] to [3], used for sealing polyethylene resin-coated paper containers. [Effects of the Invention]

[0008] The laminated film of the present invention possesses properties that are of high practical value, such as the ability to achieve appropriate heat-sealing performance with resin-coated paper containers and excellent film-forming properties, at a level that surpasses the limitations of conventional technology, and can be suitably used in various applications, including food packaging. [Modes for carrying out the invention]

[0009] The present invention relates to a laminated film having (A) a sealing layer, (B) a core layer, and (C) a laminate layer, (A) The seal layer contains polypropylene and ethylene-1-butene copolymer, (B) The core layer and (C) the laminate layer each contain linear low-density polyethylene. (A) The laminated film wherein the content of the ethylene-1-butene copolymer in the sealing layer is 35 to 70% by mass. In other words, the laminated film of the present invention contains linear low-density polyethylene in its (B) core layer and (C) laminate layer, and polypropylene and a specific amount of ethylene-1-butene copolymer in its (A) seal layer. The details of each of these components will be described below.

[0010] polypropylene The polypropylene used in at least the (A) sealing layer of the laminated film of the present invention is a resin that is generally manufactured and sold under the names polypropylene, propylene polymer, or propylene-based polymer, and typically has a density of 890-930 kg / m³. 3It is a homopolymer of propylene (homopolypropylene) of a certain degree or a propylene copolymer, that is, a copolymer derived from at least one or more comonomers selected from other small amounts of α-olefins together with propylene. In the present invention, either homopolypropylene or a propylene copolymer may be used, but it is preferable to use homopolypropylene. When it is a copolymer, it may be a random copolymer or a block copolymer, but a block copolymer is particularly preferable. Examples of other α-olefins in the case of a propylene copolymer include α-olefins such as ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, and 4-methyl-1-pentene, where the number of carbon atoms in ethylene and the α-olefin is about 4 to 20. Such other α-olefins may be copolymerized alone or in combination of two or more α-olefins.

[0011] Among these polypropylenes, from the balance of the heat resistance of the obtained laminated film and the usability with the (A) heat-sealing layer, etc., a propylene polymer having a melting point based on a differential scanning calorimeter (DSC) in the range of 110 to 170 °C, particularly 115 to 165 °C, is preferably used.

[0012] In the present invention, as long as the polypropylene used has the ability to form a film, whether it is used alone or in a blend with other resins such as an ethylene-based polymer, an ethylene·α-olefin random copolymer, and a tackifying resin, its melt flow rate (MFR) is not particularly limited. However, from the viewpoint of extrusion processability, etc., the melt flow rate (MFR) (ASTM D1238, 230 °C, 2160 g load) is usually in the range of 0.01 to 100 g / 10 min, preferably 0.1 to 70 g / 10 min.

[0013] In the present invention, two or more polypropylenes can also be used in combination.

[0014] The polypropylene used in the present invention can be produced by various known production methods, specifically, for example, using an olefin polymerization catalyst such as a Ziegler-Natta catalyst or a single-site catalyst. In particular, it can be produced using a single-site catalyst. A single-site catalyst is a catalyst in which the active sites are uniform (single-site), and examples thereof include a metallocene catalyst (so-called Kaminsky catalyst) and a Brookhart catalyst. A metallocene catalyst is a catalyst composed of a metallocene-based transition metal compound and at least one compound selected from the group consisting of an organoaluminum compound and a compound that reacts with the metallocene-based transition metal compound to form an ion pair, and it may be supported on an inorganic substance.

[0015] In polypropylene, various additives such as inorganic fillers such as silica and talc, antioxidants, weather stabilizers, antistatic agents, antifogging agents, antiblocking agents, slip agents, and pigments can be blended as long as they do not contravene the object of the present invention.

[0016] Ethylene-1-butene copolymer

[0017] The ethylene-1-butene copolymer used in at least the (A) seal layer of the laminated film of the present invention is a copolymer having a structural unit derived from ethylene and a structural unit derived from 1-butene. The ethylene-1-butene copolymer only needs to have a structural unit derived from ethylene and a structural unit derived from 1-butene, and it may have other structural units, or it may be composed only of a structural unit derived from ethylene and a structural unit derived from 1-butene without having other structural units.

[0018] When the ethylene-1-butene copolymer has other structural units in addition to the structural unit derived from ethylene and the structural unit derived from 1-butene, there are no particular restrictions on the other structural units, and structural units derived from monomers copolymerizable with ethylene and 1-butene can be appropriately used. Other constituent units that can be used include those derived from α-olefins other than propylene, such as propylene, 1-pentene, 1-hexene, and 4-methyl-1-pentene, and those derived from non-conjugated dienes, such as 1,4-hexadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene.

[0019] There are no particular restrictions on the density of ethylene-1-butene copolymers, but it is typically 850 to 910 kg / m³. 3 The load is preferably 855 to 908 kg / m³. 3 The density is preferably 860 to 906 kg / m³. 3 Therefore, from the viewpoint of appropriately realizing the effects of the present invention, the density is 906 kg / m³. 3 It is preferable to use materials with a density classified as so-called modifiers or rubber, as described below.

[0020] There are no particular restrictions on the melting point of the ethylene-1-butene copolymer, but it is usually 100°C or lower, preferably 98°C or lower, and particularly preferably 96°C or lower.

[0021] There are no particular restrictions on the MFR of the ethylene-1-butene copolymer, but the MFR measured at 230°C and a 2.16 kg load is usually 0.1 to 80 g / min, preferably 0.2 to 70 g / min, and particularly preferably 0.3 to 60 g / min.

[0022] Ethylene-1-butene copolymers can be produced by known polymerization methods using known olefin polymerization catalysts. Examples include slurry polymerization, solution polymerization, bulk polymerization, and gas-phase polymerization using complex catalysts such as Ziegler-Natta catalysts, metallocene complexes, and non-metallocene complexes. Furthermore, the various catalysts and manufacturing methods described and illustrated in the following method for producing linear low-density polyethylene can also be used as appropriate in the production of ethylene-1-butene copolymer.

[0023] Linear low-density polyethylene In the present invention, as the linear low density polyethylene used in at least the (B) core layer and the (C) laminate layer, those generally known as linear low density polyethylene in the technical field can be appropriately used. As such linear low density polyethylene, a copolymer of ethylene and an α-olefin can be used, and those synthesized by a production method using a known catalyst such as a Ziegler catalyst or a metallocene catalyst can be used.

[0024] As the α-olefin, compounds having 3 to 20 carbon atoms can be used. For example, 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. can be mentioned, and mixtures thereof may also be used. The α-olefin is preferably a compound having 4, 6 or 8 carbon atoms or a mixture thereof, and is 1-butene, 1-hexene, 1-octene or a mixture thereof. However, it is also possible to increase the amount of ethylene in the polymerization step to produce an α-olefin, and in this case, it is also possible to produce substantially only ethylene as a raw material.

[0025] The linear low density polyethylene may be a commercially available product. For example, 2040F (C6-LLDPE, MFR: 4.0, density: 918 kg / m 3 ) manufactured by Ube Maruzen Polyethylene Co., Ltd., Evolue (registered trademark) manufactured by Prime Polymer Co., Ltd., etc. can be used.

[0026] The density of the linear low density polyethylene is preferably 890 to 940 kg / m 3 and more preferably 900 to 930 kg / m 3 is. The density of the linear low density polyethylene can be appropriately adjusted by adjusting the comonomer content, and can also be appropriately adjusted by selecting and preparing polymerization conditions such as a catalyst and a polymerization temperature.

[0027] The MFR (Metal Flow Rate) of linear low-density polyethylene (at 190°C, 2160g load) is preferably 0.1 to 15g / 10min, more preferably 0.5 to 12g / 10min, and particularly preferably 0.7 to 11g / 10min. The molecular weight-free polymer (MFR) of linear low-density polyethylene (at 190°C and 2160g load) can be adjusted as appropriate by conventionally known methods, such as by adjusting polymerization conditions like polymerization temperature or by introducing molecular weight modifiers.

[0028] Linear low-density polyethylene can be produced by conventionally known manufacturing methods using conventionally known catalysts, including multi-site catalysts such as Ziegler catalysts and single-site catalysts such as metallocene catalysts. From the viewpoint of obtaining linear low-density polyethylene that can form a high-strength film with a narrow molecular weight distribution, it is preferable to use a single-site catalyst.

[0029] The single-site catalyst described above is a catalyst capable of forming a uniform active species, and is usually prepared by contacting a metallocene transition metal compound or a non-metallocene transition metal compound with an activation co-catalyst. Single-site catalysts are preferred over multi-site catalysts because they have a more uniform active site structure, allowing for the polymerization of polymers with high molecular weight and high uniformity. As a single-site catalyst, metallocene catalysts are particularly preferred. A metallocene catalyst is a catalyst comprising a transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, a co-catalyst, an organometallic compound if necessary, and each catalytic component of a support.

[0030] In the transition metal compounds of Group IV of the periodic table containing the ligand having the cyclopentadienyl skeleton described above, the cyclopentadienyl skeleton is a cyclopentadienyl group, a substituted cyclopentadienyl group, etc. The substituted cyclopentadienyl group has at least one substituent selected from hydrocarbon groups having 1 to 30 carbon atoms, silyl groups, silyl-substituted alkyl groups, silyl-substituted aryl groups, cyano groups, cyanoalkyl groups, cyanoaryl groups, halogen groups, haloalkyl groups, halosilyl groups, etc. The substituted cyclopentadienyl group may have two or more substituents, and the substituents may bond to each other to form a ring, forming an indenyl ring, a fluorenyl ring, an azlenyl ring, or a hydrogenated version thereof. The ring formed by the bonding of substituents may further have substituents on each other.

[0031] In a transition metal compound of Group IV of the periodic table containing a ligand having a cyclopentadienyl skeleton, examples of the transition metal include zirconium, titanium, and hafnium, with zirconium and hafnium being particularly preferred. The transition metal compound usually has two ligands having a cyclopentadienyl skeleton, and it is preferable that each ligand having a cyclopentadienyl skeleton is bonded to each other by a bridging group. Examples of bridging groups 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. A substituted silylene group is preferred.

[0032] In transition metal compounds of Group IV of the periodic table, typical 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, and metaaryl groups.

[0033] The transition metal compounds of Group IV of the periodic table containing the ligand having the cyclopentadienyl skeleton described above can be used as catalyst components, either individually or as a mixture of two or more.

[0034] Co-catalysts are those that can effectively utilize the transition metal compounds of Group IV of the periodic table mentioned above as polymerization catalysts, or that can balance the ionic charge of the catalytically activated state. Examples of co-catalysts include benzene-soluble aluminoxanes and benzene-insoluble organoaluminum oxy compounds, ion-exchangeable layered silicates, boron compounds, ionic compounds consisting of cations containing or not containing active hydrogen groups and non-coordinating anions, lanthanide salts such as lanthanum oxide, tin oxide, and phenoxy compounds containing fluoro groups.

[0035] Transition metal compounds of Group IV of the periodic table containing ligands having a cyclopentadienyl skeleton may be used by being supported on an inorganic or organic compound support. A porous oxide of an inorganic or organic compound is preferred as the support, specifically an ion-exchangeable material such as montmorillonite. Examples include layered silicates, SiO2, Al2O3, MgO, ZrO2, TiO2, B2O3, CaO, ZnO, BaO, ThO2, etc., or mixtures thereof.

[0036] Further organometallic compounds that may be used as needed include organoaluminum compounds, organomagnesium compounds, and organozinc compounds. Of these, organoaluminum compounds are preferred.

[0037] From the viewpoint of obtaining linear low-density polyethylene with a broad molecular weight distribution and excellent flexibility and moldability, it is preferable to use multi-site catalysts such as Ziegler catalysts and Phillips catalysts. Preferred Ziegler catalysts are those commonly known as Ziegler catalysts used in the coordination polymerization of ethylene and α-olefins, such as catalysts containing titanium compounds and organoaluminum compounds. Examples include catalysts composed of titanium halide compounds and organoaluminum compounds, and catalysts composed of solid catalyst components such as titanium, magnesium, and chlorine, and organoaluminum compounds. Examples of such catalysts include catalysts comprising a catalyst component (ai) obtained by reacting an alcohol pretreatment product of an anhydrous magnesium dihalide with an organometallic compound, and an organometallic compound (bi); catalysts comprising a catalyst component (aii) obtained by reacting magnesium metal with an organic hydroxide or oxygen-containing organic compound such as magnesium, an oxygen-containing organic compound of a transition metal, and an aluminum halide, and an organometallic compound catalyst component (bii); and catalysts comprising (i) metallic magnesium and at least one selected from organic hydroxides, oxygen-containing organic compounds of magnesium, and halogen-containing compounds; (ii) at least one selected from oxygen-containing organic compounds of transition metals and halogen-containing compounds; (iii) a reaction product obtained by reacting a silicon compound with (iv) an aluminum halide compound, and an organometallic compound catalyst component (biii).

[0038] Furthermore, the Phillips catalyst can be any generally known Phillips catalyst used in the coordination polymerization of ethylene and α-olefins, such as a catalyst system containing chromium compounds like chromium oxide. Specifically, examples include catalysts in which chromium compounds such as chromium trioxide and chromate esters are supported on solid oxides such as silica, alumina, silica-alumina, and silica-titania.

[0039] (A) sealing layer The (A) seal layer constituting the laminated film of the present invention is often fused to other components such as resin-coated paper containers when forming packaging films, packaging bags, etc., using the laminated film of the present invention. For this reason, it is preferable to use a low-melting-point resin to obtain high seal strength. Preferred examples of low-melting-point resins include ethylene polymers such as high-density polyethylene, 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, and tackifying resins such as coumarone-indene resins. In particular, high seal strength can be achieved by using polypropylene and ethylene-1-butene copolymers, especially ethylene-1-butene copolymers, that have low melting points to constitute the (A) seal layer.

[0040] As described above, the (A) seal layer contains polypropylene and ethylene-1-butene copolymer. (A) The content of ethylene-1-butene copolymer in the seal layer is 35 to 70% by mass. (A) The content of ethylene-1-butene copolymer in the seal layer is preferably 35 to 60% by mass, and particularly preferably 35 to 50% by mass. (A) By having an ethylene-1-butene copolymer content of 35% by mass or more in the sealing layer, the laminated film of the present invention can achieve high heat seal strength with other components such as resin-coated paper containers. Furthermore, high lamination strength can also be achieved with the (B) core layer containing linear low-density polyethylene. (A) By having an ethylene-1-butene copolymer content of 70% by mass or less in the sealing layer, the laminated film of the present invention suppresses sticking to the roll during film formation due to film tackiness, and also appropriately prevents film blocking. (A) Details of the ethylene-1-butene copolymer used in the sealing layer are as described above.

[0041] (A) There are no particular restrictions on the polypropylene content in the sealing layer, but from the viewpoint of heat seal strength with other components such as resin-coated paper containers or lamination strength with the core layer, it is preferably 20 to 60% by mass, and particularly preferably 30 to 60% by mass. (A) Details of the polypropylene used in the sealing layer are as described above.

[0042] (A) There are no particular restrictions on the thickness of the seal layer, but from the viewpoint of ease of opening, it is preferable to have a thickness of 0.5 μm or more, and particularly preferable to have a thickness of 0.8 μm or more. On the other hand, from the viewpoint of preventing stringing, etc., it is preferable that the thickness be 20.0 μm or less, and particularly preferable that it be 15.0 μm or less.

[0043] From the viewpoint of preventing blocking when storing the laminated film of the present invention, (A) the sealing layer may contain a blocking inhibitor. As an anti-blocking agent, powdered silica, preferably synthetic silica, etc., can be suitably used. From the viewpoint of uniformly dispersing the powdered silica in the (A) seal layer, the powdered silica may be dispersed in a resin with excellent miscibility with the ethylene-1-butene copolymer constituting the (A) seal layer, for example in low-density polyethylene, to form a masterbatch, and then the masterbatch may be added to the ethylene-1-butene copolymer.

[0044] (B) Core layer The (B) core layer constituting the laminated film of the present invention contains linear low-density polyethylene. By containing linear low-density polyethylene in the (B) core layer, the laminated film of the present invention can be given excellent properties such as transparency, flexibility, and lightness. Furthermore, by containing linear low-density polyethylene in the (B) core layer, high lamination strength can be achieved between the (A) seal layer, which contains ethylene-1-butene copolymer, which is also an ethylene-based resin, and the (C) laminate layer, which also contains linear low-density polyethylene. (B) The content of linear low-density polyethylene in the core layer is preferably 60% by mass or more, more preferably 70% by mass or more, and particularly preferably 80% by mass or more.

[0045] Of the layers constituting the laminated film of the present invention, (A) the seal layer is preferably designed to obtain appropriate seal strength, and (C) the laminate layer is preferably designed considering the laminate strength between it and (D) the base layer, etc., whereas (B) the core layer has relatively few such constraints, so it can be designed with priority given to imparting desired physical properties and performance to the entire laminated film of the present invention, such as mechanical properties. In this case, it is preferable that the thickness of (B) the core layer be greater than the thickness of (A) the seal layer and the thickness of (C) the laminate layer, and it is particularly preferable that it be greater than the sum of the thicknesses of (A) the seal layer and (C) the laminate layer. Specifically, it is preferable that the thickness ratio of each layer be seal layer / core layer / laminate layer = 7±4% / 75±10% / 18±6%. Furthermore, the thickness of the core layer (B) is preferably 10 to 85 μm, and more preferably in the range of 15 to 80 μm.

[0046] (C) Laminate layer The laminate layer (C) constituting the laminated film of the present invention contains linear low-density polyethylene. By containing linear low-density polyethylene in the laminate layer (C), the laminated film of the present invention can be given excellent properties such as transparency, flexibility, and lightness. Furthermore, by containing linear low-density polyethylene in the laminate layer (C), high lamination strength can be achieved between it and the core layer (B), which also contains linear low-density polyethylene. (C) The content of linear low-density polyethylene in the laminate layer is preferably 60% by mass or more, more preferably 70% by mass or more, and particularly preferably 80% by mass or more.

[0047] (C) The laminate layer can be laminated with other layers, including the base layer (D) described below, as necessary or desired. Therefore, it is preferable that the (C) laminate layer be designed taking into consideration the lamination strength between it and other layers, including the (D) base layer. For example, it is preferable to use the same material as other layers, including the (D) base layer, and therefore it is preferable to use polyethylene-based, polypropylene-based, polyester-based materials, etc., which are commonly used for the (D) base layer. Furthermore, in order to further improve the lamination strength between other layers, (C) the surface of the laminate layer (the surface opposite to the surface laminated with (B) the core layer) may be treated with corona treatment, roughening treatment, or the like.

[0048] From the viewpoint of preventing blocking when storing the laminated film of the present invention, (C) the laminate layer may contain a blocking inhibitor. As an anti-blocking agent, powdered silica, preferably synthetic silica, etc., can be suitably used. From the viewpoint of uniformly dispersing the powdered silica in the (C) laminate layer, the powdered silica may be dispersed in a resin with excellent miscibility with the linear low-density polyethylene constituting the (C) laminate layer, for example, in low-density polyethylene to form a masterbatch, and then the masterbatch may be added to the petroleum-derived linear low-density polyethylene.

[0049] (C) There are no particular restrictions on the thickness of the laminate layer, but it is preferably 1 to 20 μm, and more preferably in the range of 3 to 15 μm.

[0050] (A) The seal layer, (B) the core layer, and (C) the laminate layer may contain various additives and fillers, 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, antifogging agents, etc., as long as they do not contradict the objectives of the present invention. Furthermore, thermoplastic resins, thermoplastic elastomers, rubbers, hydrocarbon resins, petroleum resins, etc., other than the essential resin components mentioned above may be blended in a manner that does not contradict the objectives of the present invention.

[0051] Laminated film As described above, the laminated film of the present invention has (A) a seal layer, (B) a core layer, and (C) a laminate layer. In the laminated film of the present invention, preferably the (C) laminate layer and the (A) seal layer are laminated via the (B) core layer, but other layers may also be present.

[0052] In manufacturing the laminated film of the present invention, various known film forming methods can be employed, such as a method in which films to be (C) laminate layer, (B) core layer, and (A) seal layer are formed separately in advance, and then the films are bonded together to form a laminated film; a method in which a multilayer film consisting of a (B) core layer and an (A) seal layer is obtained using a multilayer die, and then the (C) laminate layer is extruded onto the (B) core layer surface to form a laminated film; a method in which a multilayer film consisting of a (C) laminate layer and a (B) core layer is obtained using a multilayer die, and then the (A) seal layer is extruded onto the (B) core layer surface to form a laminated film; or a method in which a laminated film consisting of a (C) laminate layer, a (B) core layer, and an (A) seal layer is obtained using a multilayer die.

[0053] Furthermore, various known film forming methods can be used as the film forming method in the production of the laminated film of the present invention, specifically, the T-die-cast film forming method and the inflation film forming method. The laminated film of the present invention and each of its constituent layers may be an unstretched film (unoriented film) or a stretched film.

[0054] The thickness of the laminated film of the present invention is not particularly limited, but from the viewpoint of ensuring practical strength, it is 5 μm or more, preferably 10 μm or more, and more preferably 15 μm or more. On the other hand, from the viewpoint of having practical flexibility even after being laminated with, for example, the (D) substrate layer, it is usually 100 μm or less, preferably 90 μm or less, and more preferably 80 μm or less.

[0055] The laminated film of the present invention may be a stretched film or an unstretched film, but from the viewpoint of manufacturing cost and flexibility, an unstretched film is preferred. From the viewpoint of improving mechanical properties, a stretched film is preferable, and a biaxially oriented film is particularly preferable. Biaxial stretching can be performed using methods such as sequential biaxial stretching, simultaneous biaxial stretching, or multi-stage stretching, as appropriate. As for the conditions for biaxial stretching, known manufacturing conditions for biaxially oriented films include, for example, in the sequential biaxial stretching method, the longitudinal stretching temperature is in the range of 100°C to 145°C, the stretching ratio is in the range of 4 to 7 times, the transverse stretching temperature is in the range of 150 to 190°C, and the stretching ratio is in the range of 8 to 11 times.

[0056] (D) Base material layer If desired, the laminated film of the present invention can be laminated with the (D) substrate layer in its (C) laminate layer.

[0057] (D) There are no particular restrictions on the base layer; for example, a film commonly used for plastic packaging can be suitably used. Preferred materials for the (D) base layer include, for example, plastic films made from thermoplastic resins such as various polyethylenes, crystalline polypropylene, crystalline propylene-ethylene copolymers, crystalline polybutene-1, crystalline poly-methylpentene-1, low-, medium-, or high-density polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), and ion-crosslinked olefin copolymers (ionomers); aromatic vinyl copolymers such as polystyrene and styrene-butadiene copolymers; 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, para, or metaxylylene adipamide; polyesters such as polyethylene terephthalate (PET) and polytetramethylene terephthalate; various polycarbonates; and polyacetals such as polyoxymethylene. Furthermore, if the contents to be packaged are sensitive to oxygen, a film with a metal oxide or the like deposited on it, a film coated with an organic compound, or a layer made of ethylene vinyl alcohol copolymer (EVOH) resin may be provided on the above-mentioned film. Plastic films made from these materials can be used unstretched, uniaxially oriented, or biaxially oriented.

[0058] (D) These plastic films can be used as a base layer, either as a single layer or as a laminate of two or more types. Alternatively, one or more of these plastic films can be laminated with metal foil such as aluminum, paper, cellophane, etc. Preferred (D) base layers include, for example, a single-layer film made of stretched nylon film or stretched polyester film, a two-layer film made by laminating a polyolefin film such as low-density polyethylene or polypropylene with PET, and a three-layer film made by laminating PET / nylon / polyethylene. When manufacturing these laminated films, adhesives and anchoring agents may be interposed between each layer as needed. An ink layer for expressing the design may also be provided.

[0059] There are no particular restrictions on the method of laminating the (D) base material layer onto the (C) laminate layer, but for example, the (D) base material layer can be directly laminated onto the (C) laminate layer by extrusion lamination or the like. Alternatively, the (D) base material layer may be laminated onto the (C) laminate layer via an adhesive by dry lamination or the like. As the adhesive, ordinary adhesives such as urethane adhesives, acid-modified polyolefin adhesives, polyester adhesives, polyether adhesives, and polyamide adhesives can be used. (D) The thickness of the substrate layer can be set arbitrarily, but is usually selected from the range of 5 to 1000 μm, preferably 9 to 100 μm.

[0060] The laminated film of the present invention, and the laminated film obtained by laminating a (D) substrate layer onto a (C) laminate layer of the laminated film of the present invention, are preferably used in various applications and are particularly suitable for use as packaging materials.

[0061] A preferred example of such packaging material is a lid material. Specifically, the laminated film of the present invention, and the laminated film obtained by laminating a base material layer (D) onto the laminate layer (C) of the laminated film of the present invention, can be used as a lid material in which the seal layer (A) is used as the innermost layer of the container. The laminated film of the present invention can achieve appropriate heat-seal performance with respect to the resin-coated paper container, and is therefore particularly suitable for use as a lid material for resin-coated paper containers. When used as a container lid, the laminated film of the present invention may be used as is, or it may be printed on it. Furthermore, it may be laminated with a printed or unprinted (D) base layer to form a lid. Depending on the application, it may also be cut in advance to match the shape of the container to form a lid. When used as a container lid, it is preferable to use it laminated with a (D) base layer.

[0062] The laminated film of the present invention can form a heat-seal layer by heat-sealing the (A) seal layer to various adherends. Resin-coated paper containers are particularly preferred as such adherends. Examples of resins used for the resin coating of resin-coated paper containers include polyethylene, polypropylene, polystyrene, polyester, polycarbonate, and polyvinyl chloride, but polyethylene is particularly preferred. Resin-coated paper containers can be in various shapes, such as trays, cups, bottles, films, and sheets. The laminated film of the present invention, and the laminated film obtained by laminating a base material layer (D) onto the laminate layer (C) of the laminated film of the present invention, have excellent opening properties, and when used as a lid material for resin-coated paper containers, they can effectively suppress the occurrence of paper peeling.

[0063] There are no particular restrictions on the contents that can be stored in packaging containers such as resin-coated paper containers, but they can be preferably used for packaging food, pharmaceuticals, medical devices, daily necessities, and general merchandise. Taking advantage of the excellent heat-seal properties of the laminated film of the present invention, it is particularly suitable for use in packaging containers for liquids such as food. [Examples]

[0064] The present invention will be described in detail below with reference to examples and comparative examples. However, the present invention is not limited in any way to the following examples.

[0065] The physical properties and characteristics of the examples / comparative examples were evaluated by the following methods. (1) Heat seal strength The laminated films produced in each example / comparative example were bonded to a 12 μm thick biaxially oriented polyethylene terephthalate film on the (C) laminate layer side using hand lamination to create sample films (50 mm x 60 mm). A test piece (50mm x 30mm) was cut from the side of a heat-insulating embossed paper container SMP-900E-2 manufactured by Tokan Kogyo Co., Ltd. The sample film described above was placed on the test piece, and heat-sealed for 1.0 second using a precision heat sealer (manufactured by Tester Sangyo Co., Ltd.) at a temperature of 160°C or 180°C and a pressure of 0.2 MPa with a 5mm wide sealing bar. After cooling, a 15mm wide test piece was cut from the heat-sealed sample, and the maximum load was measured by peeling it in the 180-degree direction on a universal tensile testing machine (manufactured by A&D Co., Ltd.) at a tensile speed of 500mm / min in a constant temperature room of 23°C and 50%RH, and the heat seal strength (N / 15mm) was determined. The delamination surface was observed, and the delamination state was evaluated according to the following criteria. ○: The delamination was due to cohesive peeling, and no paper peeling occurred from the paper container. △: The paper peeled off due to cohesive delamination, resulting in partial paper peeling from the paper container. (2) Film formability The film-forming properties of the laminated films produced in each example / comparative example were confirmed during film formation. ○: There were no problems with film formation, and a laminated film was obtained. ×: The laminated film was sticky, causing it to adhere to the roll and block between the films, making sample collection impossible.

[0066] Details of each component of the resins used in the examples / comparative examples are as follows. • Linear low-density polyethylene-1 (LLDPE-1) Density: 931kg / m 3 MFR (2.16kg, 190℃): 2.1g / 10min Melting point: 123℃ • Linear low-density polyethylene-2 ​​(LLDPE-2) Density: 924kg / m 3 MFR (2.16kg, 190℃): 3.8g / 10min Melting point: 120℃ • Homopolypropylene (h-PP) Density: 910kg / m 3 MFR (2.16kg, 230℃): 7.0g / 10min Melting point: 161℃ • Ethylene-1-butene copolymer (EBR) Density: 885kg / m 3 MFR (2.16kg, 210℃): 2.9g / 10min. • Linear low-density polyethylene-based antiblocking agent (LLDPE-based AB agent) • A mixture of linear low-density polyethylene and synthetic zeolite. Density: 913kg / m 3 MFR (2.16kg, 190℃): 3.8g / 10min Melting point: 113℃

[0067] (Example 1) The components constituting each layer were supplied to separate extruders according to the formulations shown in Table 1, and a 50 μm thick three-layer co-extruded laminate film consisting of (A) seal layer / (B) core layer / (C) laminate layer was manufactured by the T-die method. The thickness ratio of each layer was (A) seal layer:(B) core layer:(C) laminate layer = 11:60:29. The resulting laminated film was used to evaluate its seal strength, peelability, and film-forming properties. Film-forming properties were also evaluated during the manufacturing process of the laminated film. The results are shown in Table 1.

[0068] (Examples 2 to 6 and Comparative Example 1) (C) A laminated film was prepared and evaluated in the same manner as in Example 1, except that the composition of the sealing layer was changed to that shown in Table 1. The results are shown in Table 1. In Comparative Example 1, the film-forming properties were poor, so it was not possible to obtain a sample to evaluate the heat seal strength.

[0069] [Table 1] [Industrial applicability]

[0070] The laminated film of the present invention possesses properties of high practical value, such as the ability to achieve appropriate heat-sealing performance with resin-coated paper containers and excellent film-forming properties, making it suitable for various applications including food containers and having high applicability in various fields of industry such as food, distribution, restaurants, healthcare, nursing, caregiving, and accommodation.

Claims

1. A laminated film having (A) a seal layer, (B) a core layer, and (C) a laminate layer, (A) the sealing layer contains polypropylene and ethylene-1-butene copolymer, (B) the core layer and (C) the laminate layer each contain linear low-density polyethylene; (A) The above laminate film, wherein the content of the ethylene-1-butene copolymer in the seal layer is 35 to 70 mass %.

2. The density of the ethylene-1-butene copolymer is 850 to 910 kg / m ３ The laminated film according to claim 1, wherein

3. The laminated film according to claim 1 or 2, wherein the polypropylene is a homopolypropylene.

4. The laminated film according to claim 1 or 2, which is used to seal polyethylene resin-coated paper containers.