Multilayer stretched film

Abstract

[Problem] To provide a multilayer stretched film that exhibits an excellent balance between luster, rigidity, longitudinal tear strength, and sag and has excellent recyclability. [Solution] A multilayer stretched film that combines five layers of ethylene-based polymers having respectively different melt flow rates and densities. Also provided is a laminate in which the multilayer stretched film is used as a base material, and another plastic film, a metal foil of aluminum or the like, paper, cellophane, and the like, are laminated.

Description

Multilayer oriented film

[0001] The present invention relates to a multilayer stretched film, and more particularly to a multilayer stretched film that is excellent in recyclability and has excellent gloss, rigidity, and strength, all of which are well-balanced.

[0002] Films made from various resins are used as base materials for packaging materials, and the properties required for all-PE films include excellent gloss, rigidity, and strength. From the perspective of rigidity, high-density polyethylene (HDPE) is a suitable resin, but its longitudinal tear strength may be insufficient.

[0003] Therefore, if HDPE with a low melt flow rate (MFR) is used to increase the longitudinal tear strength, the gloss may be insufficient, and if the density of the base film is high, sagging may occur, resulting in an unsatisfactory appearance.

[0004] In view of these problems, the present invention is based on the discovery that by forming a multilayer film with different MFRs (high MFR HDPE layer / low MFR HDPE layer) and by using a layer with a lower density than the high MFR HDPE layer in combination, the overall density (average density) can be kept low, and a multilayer stretched film can be obtained that is well-balanced in terms of gloss, rigidity, longitudinal tear strength, and sagging, and that also has excellent recyclability.

[0005] The gist of the present invention is as follows.

[0006] [1] The melt flow rate (MFR, 190 ° C, 2.16 kg load) measured in accordance with JIS K 7210 is 0.5 g / 10 min or more and 10 g / 10 min or less, and the density measured in accordance with JIS K7112 is 940 kg / m 3 a layer (a1) containing as a main component an ethylene polymer (A1) having a melt flow rate (MFR, 190°C, 2.16 kg load) measured in accordance with JIS K 7210 of 0.01 g / 10 min or more and less than 0.5 g / 10 min, and a density measured in accordance with JIS K 7112 of 940 kg / m 3a layer (a2) containing as a main component an ethylene polymer (A2) having a melt flow rate (MFR, 190°C, 2.16 kg load) measured in accordance with JIS K 7210 of 0.01 g / 10 min or more and less than 50 g / 10 min, and a density measured in accordance with JIS K 7112 of 940 kg / m 3 a layer (b) containing as a main component an ethylene polymer (B) having a melt flow rate (MFR, 190°C, 2.16 kg load) measured in accordance with JIS K 7210 of 0.01 g / 10 min or more and less than 0.5 g / 10 min, and a density measured in accordance with JIS K 7112 of 940 kg / m 3 a layer (a3) ​​containing as a main component an ethylene polymer (A3) having a melt flow rate (MFR, 190°C, 2.16 kg load) measured in accordance with JIS K 7210 of 0.5 g / 10 min or more and 10 g / 10 min or less and a density measured in accordance with JIS K 7112 of 940 kg / m 3 and a layer (a4) containing as a main component an ethylene polymer (A4) having an average density of 931 kg / m 3 Above, 948kg / m 3 A multilayer stretched film that is:

[0007] [2] The multilayer stretched film according to the above [1], characterized in that the stretching ratio is 2 times or more.

[0008] [3] The multilayer stretched film according to [1] or [2] above, having a thickness of 5 μm to 1000 μm.

[0009] [4] The multilayer stretched film according to any one of [1] to [3] above, characterized in that it has a gloss of 30% or more, an elastic modulus (MD direction) of 2000 MPa or more, and a tear strength (MD direction) of more than 0.5 N.

[0010] [5] A laminate comprising the multilayer stretched film according to any one of [1] to [4].

[0011] [6] A packaging material comprising the laminate according to [5] above.

[0012] [7] The method for producing a multilayer stretched film according to any one of [1] to [4] above, wherein the film is stretched when or after being formed into a raw film by melt coextrusion.

[0013] According to the present invention, it is possible to obtain a multilayer stretched film that is well-balanced in terms of gloss, rigidity, longitudinal tear strength, and sagging, and also has excellent recyclability.

[0014] The multilayer stretched film of the present invention will be described in more detail below.

[0015] The multilayer stretched film of the present invention has at least the following five layers in the following order:

[0016] Layer (a1) is a layer containing an ethylene polymer (A1) as a main component, Layer (a2) is a layer containing an ethylene polymer (A2) as a main component, Layer (b) is a layer containing an ethylene polymer (B) as a main component, Layer (a3) ​​is a layer containing an ethylene polymer (A3) as a main component, and Layer (a4) is a layer containing an ethylene polymer (A4) as a main component. Ethylene-Based Polymer The ethylene-based polymers used in these layers are all polymers containing ethylene as a main component, and examples thereof include ethylene homopolymers and copolymers of ethylene and an α-olefin having 3 to 20 carbon atoms.

[0017] Examples of α-olefins having 3 to 20 carbon atoms include 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 mixtures thereof may also be used. The α-olefin is preferably a compound having 4, 6, or 8 carbon atoms or a mixture thereof, such as 1-butene, 1-hexene, 1-octene, or a mixture thereof.

[0018] When the ethylene polymer in any of the layers is a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, the α-olefin content is desirably selected within the range of usually 30 mol % or less, preferably 20 mol % or less, and more preferably 15 mol % or less. Within this range, the flexibility and heat resistance of the layer containing it are improved.

[0019] In the ethylene-based polymer used in the present invention, the polymerization method of ethylene or a monomer containing ethylene is not particularly limited, and can be carried out by a conventionally known method. The polymerization temperature and polymerization pressure are appropriately adjusted depending on the polymerization method and polymerization apparatus. The polymerization apparatus is also not particularly limited, and a conventionally known apparatus can be used.

[0020] The polymerization method can also be appropriately selected depending on the type of the target ethylene polymer, for example, differences in density and branching such as high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), and linear low density polyethylene (LLDPE).

[0021] For example, the polymerization is carried out in one stage or in two or more stages by any of gas phase polymerization, slurry polymerization, solution polymerization, and high pressure ionic polymerization using a multi-site catalyst such as a Ziegler catalyst or a Phillips catalyst, or a single-site catalyst such as a metallocene catalyst.

[0022] When a multi-site catalyst such as a Ziegler catalyst or a Phillips catalyst is used, an ethylene polymer having excellent moldability can be obtained.

[0023] The Ziegler catalyst may be any of those generally known as Ziegler catalysts used in coordination polymerization, such as catalysts containing a titanium compound and an organoaluminum compound, catalysts consisting of a titanium halide compound and an organoaluminum compound, and catalysts consisting of a solid catalyst component containing titanium, magnesium, chlorine, or the like and an organoaluminum compound.

[0024] Examples of such catalysts include a catalyst comprising a catalyst component (a) obtained by reacting a titanium compound with a reaction product of an alcohol pre-treated anhydrous magnesium dihalide and an organometallic compound, and an organometallic compound (b); a catalyst comprising a catalyst component (A) obtained by reacting magnesium metal with an organic hydroxide compound or an oxygen-containing organic compound such as magnesium, an oxygen-containing organic compound of a transition metal, and an aluminum halide, and an organometallic compound catalyst component (B); and a catalyst comprising a solid catalyst component (A) obtained by reacting (i) metallic magnesium with at least one member selected from an organic hydroxide compound, an oxygen-containing organic compound of magnesium, and a halogen-containing compound, (ii) at least one member selected from an oxygen-containing organic compound of a transition metal and a halogen-containing compound, and (iii) a silicon compound with (iv) an aluminum halide compound, and an organometallic compound catalyst component (B).

[0025] Phillips catalysts have been known for some time, and include, for example, catalyst systems containing chromium compounds such as chromium oxide, and specifically, 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.

[0026] The monomers constituting the ethylene-based polymer used in the present invention may contain a biomass-derived monomer (ethylene and / or an α-olefin). The monomers constituting the ethylene-based polymer may contain only biomass-derived monomers, or may contain both biomass-derived monomers and fossil fuel-derived monomers.

[0027] Biomass-derived monomers are monomers derived from any renewable natural raw materials and their residues, including those derived from plants or animals, including fungi, yeast, algae, and bacteria, and contain carbon. 14 C isotope 10 -12 The biomass carbon concentration (pMC) measured in accordance with ASTM D 6866 is usually about 100 (pMC). The biomass-derived monomer can be obtained by a conventionally known method.

[0028] It is preferable that the ethylene polymer used in the present invention contains a biomass-derived monomer from the viewpoint of reducing the environmental load (mainly greenhouse gas reduction). As long as the polymer production conditions, such as the polymerization catalyst, polymerization temperature in the polymerization process, etc., are the same, even if the raw material monomer contains a biomass-derived monomer, 14 C isotope 10 -12 ~10 -14 Other than the proportion of ethylene in the polymer, its molecular structure is the same as that of ethylene polymers made from fossil fuel-derived monomers, and its performance is therefore said to be the same.

[0029] The monomers constituting the ethylene-based polymer used in the present invention may contain a chemically recycled monomer (ethylene or further an α-olefin). The monomers constituting the ethylene-based polymer may be only chemically recycled monomers, or may contain chemically recycled monomers and fossil fuel-derived monomers and / or biomass-derived monomers.

[0030] Chemically recycled monomers are obtained by conventionally known methods. It is preferable that the ethylene polymer used in the present invention contains a chemically recycled monomer from the viewpoint of reducing the environmental load (mainly waste reduction). Even if the raw material monomer contains a chemically recycled monomer, the chemically recycled monomer is a monomer obtained by depolymerizing or thermally decomposing a polymer such as waste plastics to return it to a monomer unit such as ethylene, or a monomer produced using such a monomer as a raw material. Therefore, if the polymer production conditions, such as the polymerization catalyst, polymerization process, and polymerization temperature, are equivalent, the molecular structure is equivalent to that of an ethylene polymer made from a fossil fuel-derived monomer. Therefore, the performance is also considered to be unchanged.

[0031] The molecular weight distribution of the ethylene polymer is not particularly limited, but the molecular weight distribution (expressed as the ratio of weight average molecular weight: Mw to number average molecular weight: Mn: Mw / Mn) is preferably as follows:

[0032] Molecular weight distribution (Mw / Mn) of the ethylene polymer (A1) and the ethylene polymer (A4): Preferably 2 to 15, more preferably 2 to 12, even more preferably 2 to 9, and among these, preferably 2 to 7. When the Mw / Mn is within this range, an excellent balance between transparency and moldability is achieved.

[0033] The molecular weight distribution (Mw / Mn) of the ethylene polymer (A2) and the ethylene polymer (A3) is preferably at least 2, more preferably at least 4, even more preferably at least 10, of which preferably at least 20, even more preferably at least 30, and particularly preferably at least 35. When the Mw / Mn is within this range, a stretched film having excellent tear strength can be obtained.

[0034] Molecular weight distribution (Mw / Mn) of the ethylene polymer (B): Preferably, the molecular weight distribution is at least 2 and less than 100. When the molecular weight distribution is within this range, an excellent balance between strength and moldability is achieved.

[0035] This molecular weight distribution (Mw / Mn) can be measured by gel permeation chromatography (GPC), and more specifically, it can be measured by the method described in the examples of the present application.

[0036] The polyethylene polymer may be used alone or in combination with two or more other polymers, including other ethylene polymers.

[0037] The ethylene polymer may contain, as needed, at least one of various additives that are added to general polyolefin resin compositions, such as a weather stabilizer, a heat stabilizer, an antistatic agent, an antifogging agent, an antiblocking agent, a slip agent, a lubricant, a pigment, a dripping agent, and a nucleating agent, within the scope of the present invention.

[0038] Next, each layer will be described. [Layer (a1)] The layer (a1) is a layer containing an ethylene polymer (A1) as a main component.

[0039] The ethylene polymer (A1) has an MFR (190° C., 2.16 kg load) of 0.5 g / 10 min or more and 10 g / 10 min or less.

[0040] The lower limit is preferably 0.55 g / 10 min or more, more preferably 0.6 g / 10 min or more, and even more preferably 0.8 g / 10 min or more.

[0041] The upper limit is preferably 8 g / 10 min or less, more preferably 7 g / 10 min or less, even more preferably 6 g / 10 min or less, and among these, preferably 3 g / 10 min or less.

[0042] When the MFR of the ethylene polymer (A1) is within this range, transparency and extrudability are obtained.

[0043] The density is 940 kg / m 3 Preferably, it is 941 kg / m or more. 3 More preferably, 942 kg / m 3 More preferably, 946 kg / m 3 Furthermore, the upper limit is usually 970 kg / m 3 or less, preferably 969 kg / m 3 More preferably, 962 kg / m or less. 3 The following is the result.

[0044] If the density is within the above range, appropriate stiffness and strength can be obtained.

[0045] The density is a value measured in accordance with JIS K7112 (density gradient tube method).

[0046] [Layer (a2)] The layer (a2) is a layer containing an ethylene polymer (A2) as a main component. The ethylene polymer (A2) has an MFR (190°C, 2.16 kg load) of 0.01 g / 10 min or more and less than 0.5 g / 10 min. The lower limit is preferably 0.025 g / 10 min or more, more preferably 0.06 g / 10 min or more.

[0047] The upper limit is preferably less than 0.45 g / 10 min, more preferably 0.40 g / 10 min or less, and even more preferably 0.35 g / 10 min or less.

[0048] When the MFR of the ethylene polymer (A2) is within this range, appropriate strength and extrudability can be obtained.

[0049] The density is 940 kg / m 3 Preferably, it is 941 kg / m or more. 3 More preferably, 942 kg / m 3 More preferably, 946 kg / m 3 Furthermore, the upper limit is usually 970 kg / m 3 or less, preferably 969 kg / m 3 More preferably, 968 kg / m or less. 3 More preferably, it is 962 kg / m or less. 3 The following is the result.

[0050] If the density is within the above range, appropriate stiffness and strength can be obtained.

[0051] The density is a value measured in accordance with JIS K7112 (density gradient tube method).

[0052] [Layer (b)] Layer (b) is a layer containing an ethylene polymer (B) as a main component. The ethylene polymer (B) has an MFR (190°C, 2.16 kg load) of 0.01 g / 10 min or more and less than 50 g / 10 min. The lower limit is preferably 0.1 g / 10 min or more, more preferably 0.2 g / 10 min or more, even more preferably 0.3 g / 10 min or more, and of these, preferably 0.5 g / 10 min or more.

[0053] The upper limit is preferably 30 g / 10 min or less, more preferably 20 g / 10 min or less, even more preferably 12 g / 10 min or less, of which 5 g / 10 min or less is more preferable, and of which 3 g / 10 min or less is even more preferable, and particularly preferably 2.5 g / 10 min or less.

[0054] If the MFR of the ethylene polymer (B) is within this range, appropriate strength and extrudability can be obtained.

[0055] The density is 940 kg / m 3 Preferably less than 935 kg / m 3 More preferably, 930 kg / m or less. 3 More preferably, it is 925 kg / m or less. 3or less, and among these, 920 kg / m is preferable. 3 or less, and more preferably 915 kg / m 3 or less, and particularly preferably 910 kg / m 3 The following is the result.

[0056] Furthermore, the lower limit is usually 880 kg / m 3 or more, preferably 885 kg / m 3 More preferably, 890 kg / m 3 More preferably, 895 kg / m 3 or more, and preferably 900 kg / m 3 That's all.

[0057] If the density is within the above range, appropriate stiffness and strength can be obtained.

[0058] The density is a value measured in accordance with JIS K7112 (density gradient tube method).

[0059] [Layer (a3)] The layer (a3) ​​is a layer containing an ethylene polymer (A3) as a main component. The ethylene polymer (A3) has an MFR (190°C, 2.16 kg load) of 0.015 g / 10 min or more and less than 0.5 g / 10 min. The lower limit is preferably 0.025 g / 10 min or more, more preferably 0.06 g / 10 min or more.

[0060] The upper limit is preferably 0.45 g / 10 min. or less.

[0061] When the MFR of the ethylene polymer (A3) is within this range, appropriate strength and extrudability can be obtained.

[0062] The density is 940 kg / m 3 Preferably, it is 941 kg / m or more. 3 More preferably, 942 kg / m 3 More preferably, 946 kg / m 3 Furthermore, the upper limit is usually 970 kg / m 3 or less, preferably 969 kg / m 3 More preferably, 968 kg / m or less. 3More preferably, it is 962 kg / m or less. 3 The following is the result.

[0063] If the density is within the above range, appropriate stiffness and strength can be obtained.

[0064] The density is a value measured in accordance with JIS K7112 (density gradient tube method). [Layer (a4)] The layer (a4) is a layer containing an ethylene polymer (A4) as a main component.

[0065] The ethylene polymer (A4) has an MFR (190° C., 2.16 kg load) of 0.5 g / 10 min or more and 10 g / 10 min or less.

[0066] The lower limit is preferably 0.55 g / 10 min or more, more preferably 0.6 g / 10 min or more, and even more preferably 0.8 g / 10 min or more.

[0067] The upper limit is preferably 8 g / 10 min or less, more preferably 7 g / 10 min or less, even more preferably 6 g / 10 min or less, and among these, preferably 3 g / 10 min or less.

[0068] When the MFR of the ethylene polymer (A4) is within this range, transparency and extrudability are obtained.

[0069] The density is 940 kg / m 3 Preferably, it is 941 kg / m or more. 3 More preferably, 942 kg / m 3 More preferably, 946 kg / m 3 Furthermore, the upper limit is usually 970 kg / m 3 or less, preferably 969 kg / m 3 More preferably, 962 kg / m or less. 3 The following is the result.

[0070] If the density is within the above range, appropriate stiffness and strength can be obtained.

[0071] The density is a value measured in accordance with JIS K7112 (density gradient tube method).

[0072] [Multilayer stretched film] The multilayer stretched film of the present invention has five layers, in this order: Layer (a1) a layer containing an ethylene polymer (A1) as a main component, Layer (a2) a layer containing an ethylene polymer (A2) as a main component, Layer (b) a layer containing an ethylene polymer (B) as a main component, Layer (a3) ​​a layer containing an ethylene polymer (A3) as a main component, and Layer (a4) a layer containing an ethylene polymer (A4) as a main component, and the multilayer stretched film has an average density of 931 kg / m 3 Above, 948kg / m 3 The following is the result.

[0073] The lower limit is preferably 935 kg / m 3 More preferably, 936 kg / m 3 More preferably, 937 kg / m 3 The upper limit is preferably 946 kg / m 3 More preferably, 944 kg / m or less. 3 The following is the result.

[0074] If the average density is within this range, the occurrence of sagging can be prevented, and a multilayer stretched film with excellent appearance can be obtained.

[0075] In each of these layers, the proportion of the ethylene polymer as the main component is preferably 90% by mass or more.

[0076] In the multilayer stretched film of the present invention, the polymer composition of the layers (a1) and (a4) may be the same, and similarly, the polymer composition of the layers (a2) and (a3) ​​may be the same.

[0077] The formulation of additives such as stabilizers in each of these layers may be the same or different.

[0078] The thickness of the multilayer stretched film of the present invention is usually 5 μm or more and 1,500 μm or less. The lower limit is preferably 6 μm or more, more preferably 8 μm or more. The upper limit is preferably 1,000 μm or less, more preferably 200 μm or less, and even more preferably 80 μm or less.

[0079] If the thickness of the multilayer stretched film is 5 μm or more, it can maintain an appropriate strength depending on the application.

[0080] Furthermore, if the thickness of the multilayer stretched film is 200 μm or less, it is suitable for use as a variety of packaging materials and is easy to handle when used as a base material for such applications.

[0081] The thickness of each layer of the multilayer stretched film of the present invention is usually from 0.3 μm to 150 μm, but may be changed depending on the application and desired functions of the multilayer stretched film.

[0082] The thickness ratio of each layer (thickness ratio of layer (a1): layer (a2): layer (b): layer (a3): layer (a4)) is generally 0.02-5: 0.04-5: 0.04-5: 0.04-5: 0.02-5, preferably 0.04-5: 0.1-5: 0.1-5: 0.1-5: 0.04-5.

[0083] When the thickness ratio of each layer is within the above range, a good balance of rigidity, strength, and heat resistance is achieved.

[0084] Among the multilayer stretched films of the present invention, those having particularly excellent performance can also be obtained that have a gloss of 30% or more, particularly 35% or more, and even more particularly 40% or more.

[0085] Furthermore, it is possible to obtain an excellent multilayer stretched film having an elastic modulus (in the MD direction) of 2000 MPa or more, particularly 2200 MPa or more, and further particularly 2500 MPa or more.

[0086] Furthermore, it is possible to obtain an excellent multilayer film having a tear strength (in the MD direction) of 0.5 N or more, preferably 1.0 N or more, further preferably 2.0 N or more, and particularly preferably 2.5 N or more.

[0087] The multilayer stretched film of the present invention can be produced by various methods, but a common method is to stretch the film during or after it is formed by melt coextrusion.

[0088] For film formation by melt coextrusion, known methods such as the T-die method, inflation method, etc. Among them, a five-layer film (unstretched) formed by melt coextrusion is stretched to form the multilayer stretched film of the present invention.

[0089] The stretching method is not limited, and includes both uniaxial stretching and biaxial stretching.

[0090] An example of uniaxial stretching is a method in which a roll stretching machine is used, and after preheating with a preheating roll, uniaxial stretching is performed in the MD direction (take-up speed direction) by changing the rotation speed ratio of two or more rolls. From the viewpoint of improving production efficiency, it is preferable to preheat the raw sheet to be stretched and then immediately uniaxially stretched in the MD direction. In uniaxial stretching, uniaxial stretching is performed, but there may also be some accompanying stretching in a direction different from the uniaxial direction. This is because, depending on the stretching equipment used, even if uniaxial stretching is attempted, substantial stretching may occur in a direction different from the uniaxial direction.

[0091] Examples of biaxial stretching include sequential biaxial stretching, simultaneous biaxial stretching, multi-stage stretching, etc. Examples include a method of simultaneous or sequential biaxial stretching in the longitudinal and transverse directions by a tenter method, and a method of simultaneous biaxial stretching in the longitudinal and transverse directions by a tubular method.

[0092] The stretched film may be annealed as needed, for example by contacting the stretched sheet with a heated roll.

[0093] The stretching ratio in at least one direction is generally 1.5 times or more, preferably 2 times or more, and more preferably 2.5 times or more. The upper limit of the stretching ratio is not particularly limited, but is preferably less than 20 times, more preferably less than 18 times, and more preferably less than 6 times.

[0094] If the stretching ratio is within the above range, rigidity and strength can be obtained.

[0095] The stretching temperature is adjusted to an appropriate temperature depending on the melting point of the ethylene copolymer in each layer of the multilayer stretched film, the stretching ratio, the stretching speed, etc. In the case of multistage stretching, such as sequential biaxial stretching, the stretching temperature may be set to successively higher temperatures. The stretching temperature is usually in the range of 70°C to 130°C.

[0096] The elastic modulus in the MD direction (take-up speed direction) of the multilayer stretched film of the present invention is preferably 1600 MPa or more, more preferably 1700 MPa or more, and even more preferably 2000 MPa or more. The upper limit of the elastic modulus is generally 8000 MPa or less. The multilayer stretched film has sufficient rigidity required for its wide range of applications.

[0097] The multilayer stretched film of the present invention can be used in a variety of applications, such as as a base material or a stiffness-modifying layer for packaging materials.

[0098] [Laminate] The laminate of the present invention is characterized by including a layer made of the multilayer stretched film of the present invention. The laminate of the present invention may have a plurality of layers made of the multilayer stretched film of the present invention. The multilayer stretched film of the present invention is preferably used as a substrate in the laminate.

[0099] Examples of other layers in the laminate of the present invention include other plastic films, metal foils such as aluminum foil, paper, cellophane, and the like.

[0100] By laminating other layers onto the multilayer stretched film of the present invention to form a laminate, various additional functions can be imparted to the film, such as by co-extrusion with a barrier resin (e.g., EVOH, Ny, etc.) or an adhesive resin (e.g., Admer, etc.) or by coating the surface layer (e.g., a vapor-deposited film).

[0101] The vapor-deposited film may be made of a metal or an inorganic oxide. Examples of metals constituting the metal vapor-deposited film include aluminum, chromium, tin, nickel, copper, silver, gold, and platinum. Examples of metal oxides include aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, and barium oxide.

[0102] Examples of plastic films include thermoplastic resin plastic films such as polyolefins such as crystalline polypropylene, crystalline propylene-ethylene copolymer, crystalline polybutene-1, crystalline poly-4-methylpentene-1, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), and ionically cross-linked olefin copolymer (ionomer); polyamides such as nylon 6 and nylon 66; polyesters such as polyethylene terephthalate (PET) and polytetramethylene terephthalate; and polyacetals such as various polycarbonates.

[0103] In producing the laminate of the present invention comprising the substrate of the multilayer stretched film of the present invention and the other layers described above, an adhesive or an anchoring agent may be interposed between the layers as needed. Also, a metal oxide or the like may be vapor-deposited on the entire surface or a part of the surface, or an ink layer may be provided.

[0104] There are no particular limitations on the method for laminating other layers onto the base layer, and examples thereof include a method of directly laminating the layers by extrusion lamination or the like, an ozone treatment in which the layers are treated in an oxidizing atmosphere (e.g., a gas (air, etc.) containing oxygen, particularly ozone), or a method of laminating the layers via an adhesive by dry lamination or the like.

[0105] The thickness of the laminate is generally about 8 μm to 2000 μm.

[0106] The thickness of the other layer is usually about 3 to 1000 μm. The lower limit of the thickness of the other layer is preferably 4 μm or more, more preferably 6 μm or more. The upper limit is preferably 600 μm or less, more preferably 500 μm or less.

[0107] The laminate of the present invention is widely used in various applications, and is particularly suitable for use as a packaging material. [Packaging Material] The packaging material of the present invention comprises the multilayer stretched film of the present invention. In particular, for example, a packaging material made of the laminate of the present invention is suitable for packaging various products and parts. Such a packaging material can be produced, for example, by overlapping the laminates of the present invention so that at least some of their edges are in contact with each other and integrating them by heat sealing.

[0108] The packaging material of the present invention can be used in a wide range of applications, for example, for packaging various products and parts such as daily necessities, machine parts, electrical parts, food, beverages, and pharmaceuticals.

[0109] Next, the present invention will be described based on examples, etc., but the present invention is not limited to these examples. [Measurement methods] In the following examples, etc., the physical properties of the raw materials and films were measured as follows. <Gross [unit: %]> Measured according to the method specified in JIS Z 8741. <Elastic modulus [unit: MPa]> Dumbbells of a size conforming to JIS K6781 were punched out from the film in the film take-up direction (MD) to prepare test specimens.

[0110] The test piece was set in the air chuck of a universal testing machine so that the MD was the tensile direction, and a tensile test was performed with a chuck distance of 80 mm and a tensile speed of 200 mm / min. The slope of the initial stress versus displacement was taken as the modulus of elasticity. <Tear Strength [Unit: N]> A cut was made in the test piece in the film's take-up direction (MD), and the Elmendorf tear strength was measured using an Elmendorf tear tester manufactured by Toyo Seiki Seisaku-sho, Ltd., in accordance with JIS K7128-2. <Puncture Strength [Unit: N]> A tool with a tip diameter of 1 / 4 inch was used to pierce the test piece at a test speed of 200 mm / min, and the force required to penetrate the sample was measured. <Sagging> The flatness of the film was evaluated according to the following criteria.

[0111] Evaluation criteria: ◯: Sagging becomes less noticeable when the multilayer stretched film is lightly stretched. ×: Sagging is observed in the multilayer stretched film, and remains even when lightly stretched.

[0112] [Raw Materials] The following raw materials were used in the examples. 3300F: Ethylene-based polymer (trade name: Hi-Zex (registered trademark) 3300F (manufactured by Prime Polymer Co., Ltd.)), MFR: 1.1 g / 10 min, density: 949 kg / m 3 ) 3600F: ethylene polymer (trade name: Hi-Zex (registered trademark) 3600F (manufactured by Prime Polymer Co., Ltd.), MFR: 1.0 g / 10 min, density: 958 kg / m 3 SP0510: Ethylene-based polymer (trade name: Evolue (registered trademark) SP0510 (manufactured by Prime Polymer Co., Ltd.), MFR: 1.3 g / 10 min, density: 904 kg / m 3 )

[0113] Production Example 1 3300F and SP0510 in a ratio of 50% by mass:50% by mass were melt-kneaded at 200° C. in an extruder to obtain an ethylene polymer composition (hereinafter referred to as “composition c3”).

[0114] Example 1, Comparative Examples 1 to 6 (Production of Multilayer Unstretched Film) Co-extrusion molding was carried out with the layer structure shown in Table 1 to obtain a multilayer unstretched film having a thickness of 125 μm.

[0115] (Production of Stretched Film) The obtained unstretched film was uniaxially stretched in the machine direction (MD) at a stretching ratio of 5 times using a heated roll at the stretching temperature shown in Table 1 to obtain a uniaxially stretched film with a thickness of 25 μm. The elastic modulus, tear strength, and heat shrinkage of the obtained stretched film were measured. The measurement results are shown in Table 1.

[0116]

Claims

1. The melt flow rate (MFR, 190°C, 2.16 kg load) measured in accordance with JIS K 7210 is 0.5 g / 10 min or more and 10 g / 10 min or less, and the density measured in accordance with JIS K7112 is 940 kg / m 3 a layer (a1) containing as a main component an ethylene polymer (A1) having a melt flow rate (MFR, 190°C, 2.16 kg load) measured in accordance with JIS K 7210 of 0.01 g / 10 min or more and less than 0.5 g / 10 min, and a density measured in accordance with JIS K7112 of 940 kg / m 3 a layer (a2) containing as a main component an ethylene polymer (A2) having a melt flow rate (MFR, 190°C, 2.16 kg load) measured in accordance with JIS K 7210 of 0.01 g / 10 min or more and less than 50 g / 10 min, and a density measured in accordance with JIS K7112 of 940 kg / m 3 a layer (b) containing as a main component an ethylene polymer (B) having a melt flow rate (MFR, 190°C, 2.16 kg load) measured in accordance with JIS K 7210 of 0.01 g / 10 min or more and less than 0.5 g / 10 min, and a density measured in accordance with JIS K7112 of 940 kg / m 3 a layer (a3) ​​containing as a main component an ethylene polymer (A3) having a melt flow rate (MFR, 190°C, 2.16 kg load) measured in accordance with JIS K 7210 of 0.5 g / 10 min or more and 10 g / 10 min or less and a density measured in accordance with JIS K7112 of 940 kg / m 3 and a layer (a4) containing as a main component an ethylene polymer (A4) having an average density of 931 kg / m 3 Above, 948kg / m 3 A multilayer oriented film as follows:

2. The multilayer stretched film according to claim 1, characterized in that the stretching ratio is 2 times or more.

3. The multilayer stretched film according to claim 1, which has a thickness of 5 μm to 1000 μm.

4. The multilayer stretched film according to claim 1, characterized in that it has a gloss of 30% or more, an elastic modulus (in the MD direction) of 2000 MPa or more, and a tear strength (in the MD direction) of more than 0.5 N.

5. A laminate comprising the multilayer stretched film of claim 1.

6. A packaging material comprising the laminate according to claim 5.

7. A method for producing a multilayer stretched film according to any one of claims 1 to 4, characterized in that the film is stretched when or after the raw film is formed by melt coextrusion.