Multi-layer biaxially oriented film

Abstract

To provide a film which has both good heat resistance and good seal appearance, has good transparency and good stretchability, and is difficult to be delaminated (delamination).SOLUTION: A multilayer biaxially stretched film is obtained by laminating a layer A and a layer B, where the layer A is composed of a resin composition containing a specific 4-methyl-1-pentene-based polymer (A1) having a melting point (Tm) measured by DSC of 200-250°C and a specific 4-methyl-1-pentene copolymer (A2) which has a melting point (Tm) measured by DSC that is not observed and is within a range of 100-199°C, a content of the 4-methyl-1-pentene-based polymer (A1) in the layer A is 40 mass% or more and 85 mass% or less with respect to the total mass of the layer A, and a content of the 4-methyl-1-pentene copolymer (A2) is 15 mass% or more and 60 mass% or less with respect to the total mass of the layer A.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a multilayer biaxially stretched film, and more particularly to a multilayer biaxially stretched film useful for packaging films and the like.

Background Art

[0002] For resin products, metal products, glass products, etc. used for building materials and optics, it is common to attach a surface protection film to the surface to prevent surface scratches and foreign matter from entering during transportation, storage, and processing. The surface protection film is required to have various properties such as flexibility and mechanical properties, as well as various properties depending on the object to be protected, the purpose of protection, the use environment, etc. Therefore, the development of surface protection films has been promoted from various viewpoints. For example, a surface protection film mainly composed of a polyethylene component (Patent Document 1) and a surface protection film of a resin composition containing an oligomer of 4-methyl-1-pentene and 1-decene mainly composed of a polypropylene component have been studied (Patent Document 2).

[0003] Biaxially stretched polypropylene films are widely used as packaging and industrial material films because of their light weight, thermal stability, and excellent mechanical properties. However, when a biaxially stretched polypropylene film is used as a packaging film, it tends to shrink when heat-sealed, and further improvement has been desired.

[0004] In order to obtain a film with excellent heat resistance, various attempts have been made using a polymethylpentene polymer. For example, Patent Document 3 discloses using two types of polymethylpentene polymers having different melting points and using them in a wide range of applications such as films and hollow molded articles. However, Patent Document 3 does not show a multilayer biaxially stretched film in a specific form, and in particular, does not disclose an examination of the seal appearance during heat sealing when it is a multilayer biaxially stretched film.

[0005] Attempts have been made to combine a polypentene polymer with polypropylene. However, it is known that increasing the content of polypentene worsens biaxial stretchability and that delamination (interlayer separation) occurs in the case of multilayer films. Various attempts have been made to overcome these problems.

[0006] For example, Patent Document 4 discloses a multilayer biaxially stretched film including a base material layer containing polypentene and polypropylene and a seal layer containing polypropylene. Regarding this multilayer biaxially stretched film, it is also disclosed that delamination could be suppressed and that it has good releasability. However, in Patent Document 4, no examination has been made regarding the seal appearance during heat sealing for the multilayer biaxially stretched film.

[0007] Also, Patent Document 5 discloses a multilayer biaxially stretched film including a base material layer containing two types of polypentene polymers having different melting points and a seal layer containing polypropylene. However, the base material layer described in Patent Document 5 contains a polypentene polymer with a lower melting point as the main component. Also, in Patent Document 5, no examination has been made regarding the seal appearance during heat sealing for the multilayer biaxially stretched film.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0009] An object of the present invention is to provide a film that has good heat resistance, good seal appearance, good transparency, good stretchability, and is difficult to delaminate (interlayer delamination).

Means for Solving the Problems

[0010] As a result of intensive studies to solve the above problems, the present inventors have found that a multilayer biaxially stretched film having a layer containing a plurality of specific 4-methyl-1-pentene polymers having different melting points can solve the above problems, and have completed the present invention.

[0011] That is, the present invention relates to the following [1] to [9]. [1] A multilayer biaxially stretched film in which an A layer and a B layer are laminated, The A layer is composed of a resin composition containing a 4-methyl-1-pentene polymer (A1) and a 4-methyl-1-pentene copolymer (A2), In the A layer, the content of the 4-methyl-1-pentene polymer (A1) is 40% by mass or more and 85% by mass or less with respect to the total mass of the A layer, and the content of the 4-methyl-1-pentene copolymer (A2) is 15% by mass or more and 60% by mass or less with respect to the total mass of the A layer, And the 4-methyl-1-pentene polymer (A1) satisfies the following requirements (A1-I) to (A1-III), and the 4-methyl-1-pentene copolymer (A2) satisfies the following requirements (A2-I) to (A2-III), a multilayer biaxially stretched film: (A1-I) The content ratio of the structural unit (P1) derived from 4-methyl-1-pentene is 90 to 100 mol%, and the content ratio of the structural unit (Q1) derived from an α-olefin having 2 to 20 carbon atoms (excluding 4-methyl-1-pentene) is 0 mol% to 10 mol%. (A1-II) The melting point (Tm) measured by DSC is in the range of 200°C to 250°C. (A1-III) The intrinsic viscosity [η] measured in decalin at 135°C is 0.5 to 5.0 dl / g. (A2-I) The content rate of the structural unit (P2) derived from 4-methyl-1-pentene is 65 mol% or more and less than 96 mol%, and the content rate of the structural unit (Q2) derived from an α-olefin having 2 to 20 carbon atoms (excluding 4-methyl-1-pentene) is more than 4 mol% and 35 mol% or less. (A2-II) The melting point (Tm) measured by DSC is not observed or is in the range of 100°C to 199°C. (A2-III) The intrinsic viscosity [η] measured in decalin at 135°C is 0.5 to 5.0 dl / g. [2] For the multilayer biaxially stretched film according to [1] above, the value of the conversion content rate Y obtained by the following formula A is 3.0 mol% to 11.0 mol%: Y=(X Q1 ×W1+X Q2 ×W2) / (W1+W2+W O ) ··· Formula A In the above formula A, W1 is the content mass of the 4-methyl-1-pentene polymer (A1) in the resin composition constituting the A layer; W2 is the content mass of the 4-methyl-1-pentene Total polymer (A2) in the resin composition constituting the A layer; W O is the total content mass of resins that do not correspond to either the 4-methyl-1-pentene polymer (A1) or the 4-methyl-1-pentene copolymer (A2) in the resin composition constituting the A layer; X Q1 is the content rate (mol%) of the structural unit (Q1) in the 4-methyl-1-pentene polymer (A1); and, X Q2 is the content rate (mol%) of the structural unit (Q2) in the 4-methyl-1-pentene Total polymer (A2). [3] For the multilayer biaxially stretched film according to [1] or [2] above, the structural unit (Q2) is a structural unit derived from an α-olefin having 2 to 4 carbon atoms. [4] The B layer is the multilayer biaxially stretched film according to any one of [1] to [3] above, which contains polypropylene (B). [5] The B layer is the multilayer biaxially stretched film according to [4] above, which is composed of two or more layers. [6] The multilayer biaxially stretched film according to [5] above, wherein the two or more layers have the same composition. [7] The multilayer biaxially stretched film according to [5] above, wherein the two or more layers include a first layer and a second layer on the side opposite to the first layer when viewed from the A layer, and the polypropylene (B) constituting the first layer has a melting point equal to or higher than that of the polypropylene (B) constituting the second layer. [8] The multilayer biaxially stretched film according to any one of [1] to [7] above, which includes a layer structure composed of an A layer / B layer. [9] The multilayer biaxially stretched film according to any one of [1] to [8] above, which is a packaging film. [Advantages of the Invention]

[0012] According to the present invention, it is possible to provide a film that has both good heat resistance and good seal appearance, has good transparency, has good stretchability, and is difficult to delaminate (interlayer peeling) during biaxial stretching. [Embodiments for Carrying Out the Invention]

[0013] Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention.

[0014] Here, in this specification, the expression "polymer" is used in the meaning including homopolymers and copolymers unless otherwise specified. Also, in this specification, the numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0015] Also, in this specification, when referring to "structural unit derived from a monomer X" for a certain monomer X, it means the structural unit corresponding to the monomer X. For example, if the structure of the monomer X is R P R Q C=CR R R S then "structural unit derived from X" will have a structure represented by -CR P R Q -CR R R S -. For example, when referring to "structural unit derived from 4-methyl-1-pentene", it means the structural unit corresponding to 4-methyl-1-pentene (that is, the structural unit represented by -CH2-CH(-CH2CH(CH3)2)-). Also, when referring to "structural unit derived from propylene", it means the structural unit corresponding to propylene (that is, the structural unit represented by -CH2-CH(-CH3)-).

[0016] Also, in this specification, when referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, unless otherwise specified, it means the total amount of the multiple substances present in the composition.

[0017] The multilayer biaxially stretched film of the present invention is formed by laminating an A layer and a B layer. The A layer is composed of a resin composition containing a 4-methyl-1-pentene polymer (A1) and a 4-methyl-1-pentene copolymer (A2) (hereinafter also simply referred to as copolymer (A2)) having a melting point different from that of the 4-methyl-1-pentene polymer (A1). That is, the multilayer biaxially stretched film of the present invention is an A layer composed of a resin composition containing a 4-methyl-1-pentene polymer (A1) and a 4-methyl-1-pentene copolymer (A2) having a melting point different from that of the 4-methyl-1-pentene polymer (A1), a B layer and contains. Hereinafter, the A layer and the B layer will be described in detail, and then the layer structure and the film manufacturing method will be described.

[0018] <> In the multilayer biaxially stretched film of the present invention, the A layer functions as a heat-resistant layer. The A layer contains a 4-methyl-1-pentene polymer (A1) and a 4-methyl-1-pentene copolymer (A2) having a melting point different from that of the 4-methyl-1-pentene polymer (A1). In the A layer, the content of the 4-methyl-1-pentene polymer (A1) is 40% by mass or more and 85% by mass or less with respect to the total mass of the A layer, and the content of the 4-methyl-1-pentene copolymer (A2) is 15% by mass or more and 60% by mass or less with respect to the total mass of the A layer. The content of the 4-methyl-1-pentene polymer (A1) is preferably 50 to 85% by mass, more preferably 60 to 85% by mass, and still more preferably 70 to 85% by mass with respect to the total mass of the A layer. Also, the content of the 4-methyl-1-pentene copolymer (A2) is preferably 15 to 50% by mass, more preferably 15 to 40% by mass, and still more preferably 15 to 30% by mass with respect to the total mass of the A layer. When in the above range, it becomes possible to finely disperse the 4-methyl-1-pentene polymer (A1) in the A layer. Also, when the content of the 4-methyl-1-pentene polymer (A1) is at least the above lower limit value, the heat resistance of the A layer is excellent. When the content of the 4-methyl-1-pentene copolymer (A2) is at least the above lower limit value, the interlayer strength is excellent and delamination is difficult. On the other hand, when the content of the 4-methyl-1-pentene copolymer (A2) is at most the above upper limit value, the resulting multilayer biaxially stretched film has excellent heat resistance and good appearance after heat sealing.

[0019] Also, as described later, when both the polymer (A1) and the copolymer (A2) contain a specific amount or more of structural units derived from 4-methyl-1-pentene, the compatibility between the polymer (A1) and the copolymer (A2) is excellent, and it is considered that the gloss of the resulting film is excellent.

[0020] [4-Methyl-1-pentene polymer (A1)] Hereinafter, the 4-methyl-1-pentene polymer (A1), which is a component constituting the A layer, will be described. The 4-methyl-1-pentene polymer (A1) satisfies the following requirements (A1-I) to (A1-III).

[0021] <Requirement (A1-I)> The 4-methyl-1-pentene polymer (A1) contains 90 mol% to 100 mol% of a structural unit (P1) derived from 4-methyl-1-pentene (hereinafter, may be simply referred to as "structural unit (P1)" in this specification). Further, it contains a structural unit (Q1) (hereinafter, may be simply referred to as "structural unit (Q1)" in this specification) derived from an olefin having 2 to 20 carbon atoms (excluding 4-methyl-1-pentene) at a ratio of 0 mol% to 10 mol%. Note that the olefin having 2 to 20 carbon atoms is not limited to one type, and two or more types may be combined.

[0022] In other words, the content rate of the structural unit (P1) in the 4-methyl-1-pentene polymer (A1) (hereinafter, may be referred to as "X P1 ") is 90 to 100 mol%, and the content rate of the structural unit (Q1) (hereinafter, may be referred to as "X Q1 ") is 0 to 10 mol%.

[0023] Here, from the viewpoint of heat resistance, the 4-methyl-1-pentene polymer (A1) preferably contains 93 mol% or more of the structural unit (P1) derived from 4-methyl-1-pentene. On the other hand, the 4-methyl-1-pentene polymer (A1) contains 10 mol% or less, preferably 7 mol% or less, of the structural unit (Q1) derived from an olefin having 2 to 20 carbon atoms (excluding 4-methyl-1-pentene).

[0024] Examples of olefins having 2 to 20 carbon atoms that may be included in the 4-methyl-1-pentene polymer (A1) include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-eicosene, and the like. These olefins having 2 to 20 carbon atoms can be used alone or in combination of two or more. From the viewpoint of imparting an appropriate elastic modulus, flexibility, and ductility, olefins having 8 to 18 carbon atoms (for example, 1-octene, 1-decene, 1-tetradecene, 1-hexadecene, 1-heptadecene, and 1-octadecene) are preferred, and 1-decene, 1-hexadecene, and 1-octadecene are more preferred.

[0025] In addition, the 4-methyl-1-pentene polymer (A1) may contain structural units derived from a polymerizable compound (hereinafter also referred to as a polymerizable compound) other than 4-methyl-1-pentene and olefins having 2 to 20 carbon atoms (excluding 4-methyl-1-pentene) as long as the object of the present invention is not impaired.

[0026] Examples of such polymerizable compounds include vinyl compounds having a cyclic structure such as styrene, vinylcyclopentene, vinylcyclohexane, vinylnorbornane; vinyl esters such as vinyl acetate; unsaturated organic acids such as maleic anhydride or derivatives thereof; conjugated dienes such as butadiene, isoprene, pentadiene, 2,3-dimethylbutadiene; non-conjugated polyenes such as 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene, dicyclopentadiene, cyclohexadiene, dicyclooctadiene, methylenenorbornene, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene, 6-chloromethyl-5-isopropenyl-2-norbornene, 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,2-norbornadiene, etc.

[0027] In the 4-methyl-1-pentene polymer (A1) of the present invention, the units derived from the above polymerizable compounds may be contained in an amount of 10 mol% or less, preferably 5 mol% or less, more preferably 3 mol% or less, based on all the polymerizable compound structural units contained in the 4-methyl-1-pentene polymer (A1).

[0028] <Requirement (A1-II)> In the 4-methyl-1-pentene polymer (A1) of the present invention, the melting point (Tm) measured by DSC is in the range of 200 to 250°C, preferably 200°C to 245°C, more preferably 200°C to 240°C. The value of the melting point (Tm) is a value that changes depending on the stereoregularity of the polymer and the amount of α-olefin copolymerized, and it can be controlled and adjusted to a desired composition using the olefin polymerization catalyst described later. A polymer composition containing the 4-methyl-1-pentene polymer (A1) having a melting point (Tm) value within the above range is preferable from the viewpoint of heat resistance.

[0029] <Requirement (A1-III)> The 4-methyl-1-pentene polymer (A1) in the present invention has an intrinsic viscosity [η] measured in decalin at 135°C in the range of 0.5 to 5.0 dL / g.

[0030] Here, it is more preferable that the intrinsic viscosity [η] is in the range of 1.0 to 4.0 dL / g, and even more preferably in the range of 1.2 to 3.5 dL / g. The value of the intrinsic viscosity [η] can be adjusted by the amount of hydrogen added during polymerization when producing the 4-methyl-1-pentene polymer (A1).

[0031] The 4-methyl-1-pentene polymer (A1) with the value of the intrinsic viscosity [η] within the above range exhibits good fluidity during the production of resin compositions and various molding processes, has excellent stretchability, and also has good dispersibility in the 4-methyl-1-pentene copolymer (A2), which is preferable in terms of the appearance of the obtained multilayer biaxially stretched film.

[0032] <Method for Producing 4-Methyl-1-Pentene Polymer (A1)> The 4-methyl-1-pentene polymer (A1) may be produced by polymerizing olefins, or may be produced by thermally decomposing a high molecular weight 4-methyl-1-pentene polymer. Further, it may be purified by a method such as solvent fractionation that separates based on the difference in solubility in a solvent or molecular distillation that separates based on the difference in boiling point.

[0033] When producing by a polymerization reaction, for example, by adjusting the charged amounts of 4-methyl-1-pentene and, if necessary, the α-olefin to be copolymerized, the type of polymerization catalyst, the polymerization temperature, the amount of hydrogen added during polymerization, etc., the melting point, stereoregularity, molecular weight, etc. of the obtained 4-methyl-1-pentene polymer (A1) can be controlled. The method of producing by a polymerization reaction may be a known method. For example, it can be produced by a method such as a gas phase method, a solution method, or a slurry method using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. In addition to those produced as described above, the polymer (A1) may be a commercially available polymer such as TPX manufactured by Mitsui Chemicals, Inc.

[0034] [4-Methyl-1-pentene copolymer (A2)] The 4-methyl-1-pentene copolymer (A2) satisfies the following requirements (A2-I) to (A2-III).

[0035] [Requirement (A2-I)] The 4-methyl-1-pentene copolymer (A2) contains the structural unit (P2) derived from 4-methyl-1-pentene (hereinafter, may be simply referred to as "structural unit (P2)" in this specification) at a ratio of 65 mol% or more and less than 96 mol%, and the structural unit (Q2) derived from an α-olefin having 2 or more and 20 or less carbon atoms other than 4-methyl-1-pentene (hereinafter, may be simply referred to as "structural unit (Q2)" in this specification) at a ratio of more than 4 mol% and 35 mol% or less.

[0036] In other words, 4-methyl-1-pentene Total The content of the structural unit (P2) in the polymer (A2) (hereinafter, may be referred to as "X P2 ") is 65 mol% or more and less than 96 mol%, and the content of the structural unit (Q2) (hereinafter, may be referred to as "X Q2 ") is more than 4 mol% and 35 mol% or less.

[0037] The content of the structural unit (P2) is 65 mol% or more and less than 96 mol%, preferably 68 mol% or more and less than 92 mol%, more preferably 68 mol% or more and less than 90 mol%, and particularly preferably 80 mol% or more and less than 88 mol%.

[0038] Since the content of the structural unit (P2) is 65 mol% or more, it has excellent heat resistance, excellent compatibility with the polymer (A1), and excellent gloss of the resulting film. The content ratio of the constitutional unit (Q2) (when there are two or more constitutional units (Q2), the total content ratio of the two or more) is more than 4 mol% and 35 mol% or less, preferably more than 8 mol% and 32 mol% or less, more preferably more than 10 mol% and 30 mol% or less, and particularly preferably more than 12 mol% and 20 mol% or less.

[0039] When the content ratio of the constitutional unit (Q2) in the 4-methyl-1-pentene copolymer (A2) exceeds 4 mol%, the obtained laminated film has excellent interlayer strength and is difficult to delaminate. As the α-olefin having 2 or more and 20 or less carbon atoms other than 4-methyl-1-pentene that forms the constitutional unit (Q2), ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-hexadecene, 1-octadecene are preferable, and α-olefins having 2 to 4 carbon atoms, that is, ethylene, propylene, 1-butene are more preferable, and propylene is particularly preferable. In other words, the constitutional unit (Q2) is preferably a constitutional unit derived from an α-olefin having 2 to 4 carbon atoms, and particularly preferably a constitutional unit derived from propylene.

[0040] Also, when the polymer (A1) contains the constitutional unit (Q1), the constitutional unit (Q2) may be the same as or different from the constitutional unit (Q1). The 4-methyl-1-pentene copolymer (A2) may contain other constitutional units other than the constitutional unit (P2) derived from 4-methyl-1-pentene and the constitutional unit (Q2) derived from an α-olefin having 2 or more and 20 or less carbon atoms other than 4-methyl-1-pentene as long as the effects of the present invention are not impaired. The content ratio of the other constitutional units is, for example, 0 to 10 mol%.

[0041] Examples of the monomer that forms the other constitutional units include cyclic olefins, aromatic vinyl compounds, conjugated dienes, non-conjugated polyenes, functional vinyl compounds, hydroxyl group-containing olefins, halogenated olefins, and the like.

[0042] As the cyclic olefin, aromatic vinyl compound, conjugated diene, non-conjugated polyene, functional vinyl compound, hydroxyl group-containing olefin, and halogenated olefin, for example, the compounds described in paragraphs 0034 to 0041 of JP-A-2013-169685 can be used.

[0043] As the monomer forming the other structural unit, vinylcyclohexane and styrene are particularly preferable. When the 4-methyl-1-pentene copolymer (A2) contains the other structural unit, the other structural unit may be contained only in one kind, or may be contained in two or more kinds.

[0044] The value of the content ratio (mol%) of each structural unit in the 4-methyl-1-pentene copolymer (A2) 13 is measured by the measurement method using C-NMR, and the specific measurement method is as described in the Examples section.

[0045] <Requirement (A2-II)> The melting point (Tm) of the 4-methyl-1-pentene copolymer (A2) is not observed or is in the range of 100°C to 199°C, more preferably not observed or is in the range of 110°C to 180°C, still more preferably in the range of 110°C to 160°C, and particularly preferably in the range of 125°C to 150°C. That is, the difference between the 4-methyl-1-pentene copolymer (A2) and the 4-methyl-1-pentene polymer (A1) lies in the melting point (Tm). The melting point (Tm) of the 4-methyl-1-pentene copolymer (A2) is a value measured by the same method as the melting point (Tm) of the polymer (A1).

[0046] <Requirement (A2-III)> The intrinsic viscosity [η] of the 4-methyl-1-pentene copolymer (A2), measured at 135 °C in a decalin solvent, is 0.5 to 5.0 dl / g, preferably 0.5 dl / g to 3.5 dl / g, and more preferably 1.0 dl / g to 3.5 dl / g. When the intrinsic viscosity [η] of the 4-methyl-1-pentene copolymer (A2) is within the above range, it is preferable in terms of moldability.

[0047] The intrinsic viscosity [η] of the 4-methyl-1-pentene copolymer (A2) is a value measured by the same method as the intrinsic viscosity [η] of the polymer (A1). In addition to the above requirements (A2-I) to (A2-III), the 4-methyl-1-pentene copolymer (A2) preferably satisfies one or more of the following requirements.

[0048] <Requirement (A2-IV)> The molecular weight distribution (Mw / Mn) of the 4-methyl-1-pentene copolymer (A2) is preferably 1.0 to 3.5, and more preferably 1.1 to 3.0. The weight average molecular weight (Mw) of the 4-methyl-1-pentene copolymer (A2) is preferably 1×10 4 ~2×10 6 , and more preferably 1×10 4 ~1×10 6 from the viewpoint of the moldability of the layer composed of the composition. The weight average molecular weight (Mw) and the molecular weight distribution (Mw / Mn) of the 4-methyl-1-pentene copolymer (A2) are values calculated by the method described in the examples.

[0049] <Requirement (A2-V)> The melt flow rate (MFR) of the 4-methyl-1-pentene copolymer (A2), measured at 230 °C under a load of 2.16 kg in accordance with JIS K7210, is preferably 0.1 g / 10 min to 100 g / 10 min, more preferably 0.5 g / 10 min to 50 g / 10 min, and even more preferably 0.5 g / 10 min to 30 g / 10 min, from the viewpoint of the fluidity during molding of the composition.

[0050] <Method for producing 4-methyl-1-pentene copolymer (A2)> The 4-methyl-1-pentene copolymer (A2) can be synthesized by a conventionally known metallocene catalyst system, for example, by the methods described in International Publication No. 2005 / 121192, International Publication No. 2011 / 055803, International Publication No. 2014 / 050817, etc.

[0051] 〔Composition of A layer〕 As described above, the resin composition constituting the A layer of the multilayer biaxially stretched film of the present invention contains the 4-methyl-1-pentene polymer (A1) and the 4-methyl-1-pentene copolymer (A2) in a specific ratio.

[0052] In the present invention, when the A layer contains a specific amount of the 4-methyl-1-pentene copolymer (A2) in addition to the 4-methyl-1-pentene polymer (A1), the multilayer biaxially stretched film is flexible, has good stretchability, and is also excellent in heat resistance. Further, by configuring the A layer in such a manner, heat resistance is imparted, so that the seal appearance when the obtained multilayer biaxially stretched film is subjected to heat sealing is also excellent. For example, in the multilayer biaxially stretched film of the present invention, when the amount of the 4-methyl-1-pentene copolymer (A2) in the A layer is below a certain level, there is a tendency for less shrinkage when subjected to heat sealing. Further, the multilayer biaxially stretched film of the present invention has less shrinkage and higher transparency when subjected to heat sealing compared to a multilayer biaxially stretched film formed using a layer composed of a 4-methyl-1-pentene polymer (A1) and polypropylene instead of the A layer.

[0053] <Other components> The resin composition constituting the A layer may consist only of a 4-methyl-1-pentene polymer (A1) and a 4-methyl-1-pentene copolymer (A2). However, the resin composition may further contain other components (hereinafter, "other components") that do not correspond to either the 4-methyl-1-pentene polymer (A1) or the 4-methyl-1-pentene copolymer (A2). Examples of such "other components" include the "other resins" described below and the "additives" described later.

[0054] Other resins The resin composition constituting the A layer of the multilayer biaxially stretched film of the present invention may contain, within a range not impairing the object of the present invention, a resin that does not correspond to either the above-mentioned 4-methyl-1-pentene polymer (A1) or the 4-methyl-1-pentene copolymer (A2) (hereinafter, "other resin" in the section of "A layer"). As the other resin, for example, it is also possible to add polyolefin polymers such as polyethylene, poly-1-butene, styrene resins, and ethylene-α-olefin copolymers. When the resin composition constituting the A layer contains an "other resin", the amount of the "other resin" is preferably 0.01 to 5.0 parts by mass with respect to 100 parts by mass of the resin composition.

[0055] Here, in the present invention, the value of the conversion content Y obtained by the following formula A is preferably 3.0 mol% to 11.0 mol%, more preferably 3.5 mol% to 10.5 mol%, still more preferably 4.0 mol% to 10.0 mol%, and particularly preferably 4.5 mol% to 9.5 mol%: Y=(X Q1 ×W1+X Q2 ×W2) / (W1+W2+W O )···Formula A In the above formula A, W1 is the content mass of the 4-methyl-1-pentene polymer (A1) in the resin composition constituting the A layer; W2 is the 4-methyl-1-pentene in the resin composition constituting the A layerTotal Mass content of polymer (A2); W O is the total mass content of resins that do not correspond to the 4-methyl-1-pentene polymer (A1) or the 4-methyl-1-pentene copolymer (A2) in the resin composition constituting the A layer; X Q1 is the content ratio (mol%) of the constitutional unit (Q1) in the 4-methyl-1-pentene polymer (A1); and, X Q2 is the content ratio (mol%) of the constitutional unit (Q2) in the 4-methyl-1-pentene Total polymer (A2). When the value of the converted content ratio Y is within the numerical range, the stretchability and the appearance after heat sealing are excellent. In this specification, the converted comonomer content ratio Y may sometimes be referred to as "comonomer content (A1)+(A2)".

[0056] Here, when the resin composition constituting the A layer consists only of resin components, if the content ratio (mass%) of the 4-methyl-1-pentene polymer (A1) and the content ratio (mass%) of the 4-methyl-1-pentene copolymer (A2) in the resin composition are C1 and C2, respectively, then C1 = W1 / (W1 + W2 + W O ) × 100 C2 = W2 / (W1 + W2 + W O ) × 100 Therefore, the formula A can be expressed as the following formula B Y = (X Q1 × C1 + X Q2 × C2) / 100 ··· Formula B as well.

[0057] In addition, when the resin composition constituting the A layer does not contain "other resins", the W O becomes 0, and the above formula A becomes Y = (X Q1 × W1 + X Q2 × W2) / (W1 + W2) ··· Formula A' and is represented as such.

[0058] Additives In addition to the "other resin" or in place of the "other resin", the resin composition constituting the A layer of the multilayer biaxially stretched film of the present invention may further contain various additives within a range not impairing the object of the present invention. Examples of such various additives include weather stabilizers, heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, slip agents, antiblocking agents, antifogging agents, nucleating agents, lubricants, pigments, dyes, anti-aging agents, hydrochloric acid absorbers, inorganic or organic fillers, organic or inorganic foaming agents, crosslinking agents, crosslinking aids, adhesives, softeners, flame retardants, etc.

[0059] As the antioxidant, known antioxidants can be used. Specifically, hindered phenol compounds, sulfur-based antioxidants, lactone-based antioxidants, organic phosphite compounds, organic phosphonite compounds, or a combination of several of these can be used.

[0060] Examples of the lubricant include saturated or unsaturated fatty acids such as lauric acid, palmitic acid, oleic acid, and stearic acid, and their sodium, calcium, and magnesium salts, etc. These can be used alone or in combination of two or more. The blending amount of such a lubricant is usually preferably 0.1 to 3 parts by mass, more preferably 0.1 to 2 parts by mass, based on 100 parts by mass of the resin composition.

[0061] In the resin composition constituting the A layer in the present invention, a nucleating agent, which is a specific optional component, may be blended in order to further improve its moldability, that is, to increase the crystallization temperature and accelerate the crystallization rate. In this case, for example, the nucleating agent is a dibenzylidene sorbitol-based nucleating agent, a phosphate ester salt-based nucleating agent, a rosin-based nucleating agent, a benzoic acid metal salt-based nucleating agent, fluorinated polyethylene, sodium 2,2-methylenebis(4,6-di-t-butylphenyl) phosphate, pimelic acid or its salt, dicyclohexylamide 2,6-naphthalenedicarboxylate, etc., and the blending amount is not particularly limited, but it is preferably about 0.1 to 1 part by mass with respect to 100 parts by mass of the resin composition. There is no particular limitation on the blending timing, and it can be added during polymerization, after polymerization, or during molding. Among the other components of the various additives exemplified above, those generally used in the field to which the present invention pertains may be used, and their blending amounts may also be set as appropriate.

[0062] In addition to the various additives exemplified above, the resin composition can be further blended with other additives such as secondary antioxidants, natural oils, synthetic oils, waxes, etc. as necessary within a range that does not impair the object of the present invention. The blending amount of the other additives is not particularly limited, but it is usually 0 to 50 parts by mass, preferably 0 to 30 parts by mass, more preferably 0 to 10 parts by mass, and particularly preferably 0 to 1 part by mass with respect to 100 parts by mass of the resin composition.

[0063] When the A layer according to the present invention contains the "other components", the mass obtained by subtracting the "other components" from the total mass of the A layer is taken as 100% by mass, and the definitions of the content of the component (A1) (5 to 95% by mass) and the content of the component (A2) (5 to 95% by mass) are applicable.

[0064] ≪B layer≫ The B layer in the multilayer biaxially stretched film of the present invention is a layer provided to impart excellent mechanical properties, for example, excellent sealability, to the multilayer biaxially stretched film of the present invention. In a typical and preferred embodiment of the present invention, the B layer contains polypropylene (B). Here, when the B layer contains polypropylene (B), the B layer may consist of a single layer or may consist of two or more layers. When the B layer consists of two or more layers, the two or more layers may have the same composition or may be different from each other.

[0065] 〔Polypropylene (B)〕 The polypropylene (B) in the present invention is a known polymer mainly composed of propylene. Examples thereof include a propylene homopolymer, a propylene·α-olefin copolymer of propylene and an α-olefin other than propylene (such as a propylene random copolymer such as a propylene·ethylene copolymer, a propylene·1-butene copolymer, a propylene·ethylene·1-butene copolymer, a propylene block copolymer, or a mixture thereof). In this specification, when a polymer is said to be "mainly composed of" a certain constituent monomer X, it means that the polymer contains the most constituent units derived from X among all the constituent units. For example, a "polymer mainly composed of propylene" means a polymer that contains the most constituent units derived from propylene (that is, the constituent unit represented by -CH2-CH(-CH3)-) among all the constituent units. As polypropylene, isotactic polypropylene and syndiotactic polypropylene are preferably used, and it is preferable that the isotactic meso-pentad fraction (mmmm) or the syndiotactic meso-pentad fraction (rrrr) showing stereoregularity is 90% or more, more preferably 92% or more, and even more preferably 93% or more. When the stereoregularity is high, the crystallinity of the resin can be improved, and high thermal stability and mechanical properties can be imparted.

[0066] As the copolymerization ratio of the α-olefin in the propylene-α-olefin copolymer, it is preferably 5% by mass or less. Further, the propylene-α-olefin copolymer may be a random copolymer or a block copolymer, and may contain a nucleating agent (crystallization nucleating agent). The nucleating agent is not particularly limited, and examples include various inorganic compounds, various carboxylic acids or their metal salts, dibenzylidene sorbitol-based compounds, aryl phosphate-based compounds, cyclic polyvalent metal aryl phosphate-based compounds and mixtures with alkali metal salts of aliphatic monocarboxylic acids or basic aluminum lithium hydroxy carbonate hydrates, various polymer compounds, etc., such as α-nucleating agents. These crystallization nucleating agents can be used alone or in combination of two or more materials.

[0067] The MFR of the above polypropylene (B) can be measured according to JIS K7210. Specifically, under the measurement conditions of a temperature of 230°C and a load of 2.16 kg, it is preferably 0.5 to 25 g / 10 min, more preferably 1 to 15 g / 10 min, and even more preferably 2 to 10 g / 10 min. When the MFR of polypropylene (B) is within the above range, it is suitable for extrusion molding.

[0068] The ash content due to polymerization catalyst residues, etc. contained in polypropylene (B) is preferably as small as possible, preferably 50 ppm or less, in order to reduce minute foreign matters (fish eyes). More preferably, it is 40 ppm or less. By setting it to 50 ppm or less, minute foreign matters and defects are significantly reduced, and contamination when used in electronic component applications can be reduced.

[0069] When the B layer is composed of two or more layers, the two or more layers may include a first layer (hereinafter also referred to as the "B1 layer") and a second layer on the side opposite to the first layer as viewed from the A layer (hereinafter also referred to as the "B2 layer"). Here, the polypropylene (B) constituting the first layer (B1 layer) (hereinafter referred to as "polypropylene (B1)") and the polypropylene (B) constituting the second layer (B2 layer) (hereinafter referred to as "polypropylene (B2)") may be the same or different from each other.

[0070] When the polypropylene (B1) and the polypropylene (B2) are different from each other, the melting point of the polypropylene (B1) is preferably equal to or higher than the melting point of the polypropylene (B2). In one aspect of the present invention, the melting point of the polypropylene (B1) is the same as the melting point of the polypropylene (B2). However, depending on the use of the multilayer biaxially stretched film of the present invention, in some cases, it may be more preferable that the melting point of the polypropylene (B1) is higher than the melting point of the polypropylene (B2). In an exemplary aspect of the present invention, the polypropylene (B1) is a propylene homopolymer, and the polypropylene (B2) is the propylene random copolymer. However, the polypropylene (B1) is not limited to a propylene homopolymer as long as it has a melting point equal to or higher than the melting point of the polypropylene (B2), and may be a copolymer of propylene.

[0071] When the B layer contains polypropylene (B), the B layer may be a layer composed only of polypropylene (B), or may be a layer composed of a resin composition containing polypropylene (B). Here, various additives similar to those listed in the "additives" in the section of the "A layer", such as heat stabilizers, antioxidants, lubricants, chlorine scavengers, antistatic agents, etc., may be added to the resin composition forming the B layer. When the B layer is composed of two or more layers, the additives and their formulations that may be contained in the two or more layers may be the same or different from each other.

[0072] ≪Multilayer biaxially stretched film≫ The multilayer biaxially stretched film of the present invention includes the above A layer and the above B layer. In a typical embodiment, it includes a layer structure composed of an A layer / B layer. The multilayer biaxially stretched film of the present invention may have only a layer structure composed of an A layer / B layer, or may further include a C layer different from both the A layer and the B layer. Here, the B layer may be composed of a single layer or may be composed of two or more layers.

[0073] In one preferred embodiment of the present invention, the B layer is composed of a single layer (hereinafter referred to as the "B0 layer"). In this embodiment, the B0 layer functions as a seal layer. In this case, the multilayer biaxially stretched film of the present invention includes a two-layer structure composed of an A layer / B0 layer. In another preferred embodiment of the present invention, the B layer is composed of two or more layers. For example, the two or more layers may include the B1 layer and the B2 layer on the side opposite to the B1 layer as viewed from the A layer, as described above in the section of the "B layer". That is, the multilayer biaxially stretched film of the present invention may have a three-layer structure laminated in the order of A layer / B1 layer / B2 layer.

[0074] In the first embodiment of this aspect, the two or more layers constituting the B layer have the same configuration as each other. In this first embodiment, the two or more layers constituting the B layer function as a seal layer. In this first embodiment, the two or more layers can be regarded as constituting a single B layer as a whole. For example, the B1 layer and the B2 layer may be regarded as constituting the B0 layer as a whole.

[0075] Also, in the second aspect, the two or more layers constituting the B layer are different from each other. For example, the B1 layer and the B2 layer may be different depending on the presence or absence and type of components other than the polypropylene (B), or may be different depending on the type of the polypropylene (B). In one of the preferred embodiments of the present invention, the melting point of the polypropylene (B) constituting the B1 layer (i.e., the polypropylene (B1)) is equal to or higher than the melting point of the polypropylene (B) constituting the B2 layer (i.e., the polypropylene (B2)). In this aspect, the B2 layer functions as a seal layer. Note that the B1 layer may be composed of two or more layers having the same configuration as each other. Even in this case, the two or more layers that can constitute the B1 layer may be regarded as constituting one B1 layer as a whole.

[0076] Further, when the multilayer biaxially stretched film of the present invention further includes a C layer different from both the A layer and the B layer, the C layer is a component that does not correspond to the 4-methyl-1-pentene polymer (A1), the 4-methyl-1-pentene copolymer (A2), or the polypropylene (B), and can appropriately function as a seal layer, for example, a low-density polyethylene resin (LDPE), a medium-density polyethylene resin (MDPE), a linear low-density polyethylene resin (LLDPE), an ethylene-vinyl acetate copolymer (EVA), an ethylene-α-olefin copolymer, an ethylene-(meth)acrylic acid copolymer, or other ethylene-based resins, or a blend resin of polyethylene and polybutene. In this case, the multilayer biaxially stretched film of the present invention usually has a three-layer structure laminated in the order of A layer / B layer / C layer.

[0077] There is no particular limitation on the method for obtaining such a multilayer film. Usually, first, a base film (also referred to as a base sheet) in which an A layer, a B layer, and, if necessary, other layers are laminated is formed, and then the base film is biaxially stretched to obtain it. Examples of the method for forming the base film include a method of laminating on a surface layer film previously obtained by T-die forming or inflation forming by a known lamination method such as extrusion lamination or extrusion coating, and a method of laminating each film by dry lamination after independently forming a plurality of films. From the viewpoint of productivity, coextrusion molding in which a plurality of components are supplied to a multilayer extruder for molding is preferable.

[0078] The thickness of the film before stretching according to the present invention, that is, the base film, is not particularly limited, but is usually 100 μm to 1000 μm, preferably 150 to 800 μm, and more preferably 200 to 500 μm.

[0079] The thickness of one layer of the A layer in the base film is preferably 0.1 to 250% with respect to the thickness of the B layer, and more preferably 0.5 to 100%. When the multilayer biaxially stretched film of the present invention contains two or more A layers, the thicknesses of the respective A layers may be the same or different from each other.

[0080] The total thickness of the multilayer biaxially stretched film of the present invention is preferably 3 to 60 μm, more preferably 10 to 50 μm, and even more preferably 10 to 30 μm. By having the total thickness of the film be 3 to 60 μm, a film excellent in transparency, mechanical properties, and stretchability can be obtained.

[0081] The thickness of one layer of the A layer in the multilayer biaxially stretched film of the present invention is preferably 0.1 to 250% with respect to the thickness of the B layer, and more preferably 0.5 to 100%. When the multilayer biaxially stretched film of the present invention contains two or more A layers, the thicknesses of the respective A layers may be the same or different from each other.

[0082] ≪Method for manufacturing multilayer biaxially stretched film≫ Regarding the method of mixing each component to prepare resin composition pellets for the A layer or the B layer, various well-known methods can be adopted, such as multi-step polymerization methods, plast mills, Henschel mixers, V-blenders, ribbon blenders, tumblers, blenders, kneader extruders, etc. for mixing, or after mixing, using a single-screw extruder, twin-screw extruder, kneader, Banbury mixer, etc., for example, melting and kneading at 180 to 300 °C and then granulating or pulverizing. By this method, high-quality resin composition pellets in which each component and additive are uniformly dispersed and mixed can be obtained.

[0083] The base sheet for the multilayer biaxially stretched film of the present invention can be obtained by melt-extruding the above-mentioned resin composition pellets with the cylinder temperature usually in the range of 180 to 300 °C. To produce a multilayer biaxially stretched film from the base sheet, batch-type biaxial stretching, sequential biaxial stretching immediately after cast molding, or simultaneous biaxial stretching can be performed. In sequential biaxial stretching, the cast base sheet is maintained at 100 to 165 °C, passed between rolls with a speed difference, stretched 2 to 5 times in the flow direction, and immediately cooled to room temperature. Then, the film is guided to a tenter, stretched 5 to 10 times in the width direction at a temperature of 150 °C or higher, and then relaxed, heat-fixed, and wound up.

[0084] In the multilayer biaxially stretched film of the present invention, since the 4-methyl-1-pentene polymer (A1) and the 4-methyl-1-pentene copolymer (A2) are present with high affinity in the A layer, the 4-methyl-1-pentene polymer (A1) and the 4-methyl-1-pentene copolymer (A2) are less likely to drop off, and it has excellent antiblocking properties over a long period.

[0085] ≪Applications≫ Specific applications of the multilayer biaxially stretched film of the present invention can include, for example, the following general film applications. Packaging film; for example, food packaging film, stretch film, wrap film, shrink film, easy peel film, aluminum vapor-deposited film, PVDC-coated film, etc. Breathable film; for example, films used as disposable diapers, sanitary products, surgical gowns, surgical gloves, surgical down, house wrap (moisture-permeable and waterproof sheet), disposable warmers, household dehumidifiers, desiccants, oxygen absorbers, freshness retainers, composting sheets, disposable jumpsuits, etc. Rust-proof film; for example, films used for the transportation packaging, storage packaging, export packaging, etc. of automotive parts, knockdown parts, machines and machine parts, iron and chromium products, steel pipes, wire rods, bolts and nuts, bearings, molds, tools, cutting tools, construction tools, etc. Anti-fog film; for example, films for fruits and vegetables, processed foods, etc. Directional film; for example, films used for the spiral packaging of confectioneries, agricultural materials, laminate substrates, coin packaging, wire bundling materials, fruit and vegetable packaging, cardboard cutting tapes, refill containers for detergents, rice ball packaging, pillow packaging, stick packaging, boil-in-bag and retort packaging, fresh food packaging, infusion bags, etc. Self-cleaning film; for example, films used as road signs, general signs, billboards, window glass, road materials, side mirrors, etc. Separator; for example, battery separator, separator for lithium-ion batteries, electrolyte membrane for fuel cells, separator for adhesives and adhesives, etc. Stretched film; for example, films for film capacitors, capacitor films, capacitor films for fuel cells, etc. Semiconductor process films; for example, dicing tapes, back grinding tapes, die bonding films, films for polarizing plates, surface protection films; for example, protection films for polarizing plates, protection films for liquid crystal panels, protection films for optical components, protection films for lenses, protection films for electrical components and consumer electronics products, protection films for mobile phones, protection films for personal computers, masking films, protection films for touch panels, etc. Films for electronic components; for example, diffusion films, reflection films, radiation-resistant films, gamma-ray-resistant films, porous films, etc. Building material films; for example, window films for building materials, films for laminated glass, bulletproof materials, films for bulletproof glass, heat insulation sheets, heat insulation films, etc. Transfer films; for example, transfer films for automobiles and industries, transfer films for packaging, etc. Release films; for example, release films for flexible printed circuit boards (FPC), release films for ACM substrates, release films for rigid-flexible substrates, release films for advanced composite materials, release films for curing carbon fiber composites, release films for curing glass fiber composites, release films for curing aramid fiber composites, release films for curing nano composites, release films for curing filler-filled materials, release films for semiconductor encapsulation, release films for polarizing plates, release films for diffusion sheets, release films for prism sheets, release films for reflection sheets, cushion films for release films, release films for fuel cells, release films for various rubber sheets, release films for curing urethane, release films for curing epoxy (manufacturing process components such as metal bats and golf clubs), etc.

[0086] In a particularly preferred embodiment of the present invention, the multilayer biaxially stretched film of the present invention is a packaging film. When the multilayer biaxially stretched film of the present invention is used as a packaging film, the sheet appearance during heat sealing is excellent.

Examples

[0087] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In the examples, each physical property was measured as follows.

[0088] 〔Composition〕 The content (mol%) of 4-methyl-1-pentene and α-olefin in the polymer was 13 measured by C-NMR. The measurement conditions are as follows. · Measuring device: Nuclear magnetic resonance apparatus (ECP500 type, manufactured by JEOL Ltd.) · Observed nucleus: 13 C (125 MHz) · Sequence: Single pulse proton decoupling · Pulse width: 4.7 μs (45° pulse) · Repetition time: 5.5 s · Number of integration times: 10,000 times or more · Solvent: Orthodichlorobenzene / deuterated benzene (volume ratio: 80 / 20) mixed solvent · Sample concentration: 55 mg / 0.6 mL · Measurement temperature: 120 °C · Reference value of chemical shift: 27.50 ppm

[0089] 〔Limiting viscosity [η]〕 The limiting viscosity [η] of the polymer was measured at 135 °C in a decalin solvent using an Ubbelohde viscometer as the measuring device. Specifically, after dissolving about 20 mg of the powdery polymer in 25 ml of decalin, the specific viscosity η sp was measured in an oil bath at 135 °C using an Ubbelohde viscometer. After adding 5 ml of decalin to this decalin solution for dilution, the specific viscosity η sp was measured in the same manner as above. This dilution operation was repeated two more times, and the value of η sp / C when extrapolating the concentration (C) to 0 was determined as the limiting viscosity [η] (unit: dl / g) (see Equation 1 below). [η]=lim(η sp / C) (C→0) ··· Equation 1

[0090] 〔Melt flow rate (MFR)〕 The melt flow rate (MFR) of the polymer was measured in accordance with JIS K7210. For the polymer A1-1 obtained in Preparation Example 1 below and the polymer A1-2 obtained in Preparation Example 2 below, the measurement was carried out at 260 °C under a load of 5.0 kg. For the copolymer A2-1 obtained in Preparation Example 3 below and polypropylene, the measurement was carried out at 230 °C under a load of 2.16 kg. The unit is g / 10 min).

[0091] [Number average molecular weight (Mn), weight average molecular weight (Mw), molecular weight distribution (Mw / Mn)] The number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) were measured as follows using a gel permeation chromatograph Alliance GPC-2000 type manufactured by Waters. The separation columns were two TSKgel GNH6-HT and two TSKgel GNH6-HTL, the column size was 7.5 mm in diameter and 300 mm in length for all, the column temperature was 140 °C, o-dichlorobenzene (Wako Pure Chemical Industries) and 0.025 wt% of BHT (Takeda Pharmaceutical) as an antioxidant were used as the mobile phase, and it was moved at 1.0 ml / min. The sample concentration was 15 mg / 10 mL, the sample injection volume was 500 microliters, and a differential refractometer was used as the detector. For standard polystyrene with Mw < 1000 and Mw > 4×10 6 , those manufactured by Tosoh Corporation were used, and for 1000 ≤ Mw ≤ 4×10 6 , those manufactured by Pressure Chemical were used.

[0092] [Density] The density of the polymer was measured in accordance with JIS K7112 (density gradient tube method). This density (kg / m 3 ) was used as an index of lightness.

[0093] [Melting point (Tm)] The melting point (Tm) of the polymer was measured using a differential scanning calorimeter (DSC220C type, manufactured by Seiko Instruments Inc.) as the measuring device. About 5 mg of the polymer was sealed in an aluminum pan for measurement and heated from room temperature to 280 °C at 10 °C / min. To completely melt the polymer, it was held at 280 °C for 5 minutes and then cooled to -50 °C at 10 °C / min. After leaving it at -50 °C for 5 minutes, it was heated for the second time to 280 °C at 10 °C / min. The peak temperature (°C) in this second heating was defined as the melting point (Tm) of the polymer.

[0094] [Preparation Examples 1 and 2] Production of 4-methyl-1-pentene polymers A1-1 and A1-2 As Preparation Examples 1 and 2, two types of polymers corresponding to polymer (A1) were prepared. According to the polymerization methods described in Comparative Example 7 and Comparative Example 9 of International Publication No. 2006 / 054613, by changing the ratios of 4-methyl-1-pentene, 1-decene, 1-hexadecene, 1-octadecene, and hydrogen, 4-methyl-1-pentene polymers A1-1 and A1-2 (hereinafter, "polymer A1-1" and "polymer A1-2", respectively) having the physical properties shown in Table 1 were obtained as polymer (A1), respectively.

[0095] That is, polymer A1-1 is a polymer obtained by copolymerizing 4-methyl-1-pentene and 1-decene in the presence of a solid titanium catalyst component obtained by reacting magnesium chloride anhydride, 2-ethylhexyl alcohol, 2-isobutyl-2-isopropyl-1,3-dimethoxypropane (BPMP), and titanium tetrachloride as a polymerization catalyst, this solid titanium catalyst component, triethylaluminum, and hydrogen.

[0096] Also, polymer A1-2 is a polymer obtained by copolymerizing 4-methyl-1-pentene and an equimass mixture of 1-hexadecene and 1-octadecene in the presence of a solid titanium catalyst component obtained by reacting magnesium chloride anhydride, 2-ethylhexyl alcohol, 2-isobutyl-2-isopropyl-1,3-dimethoxypropane (BPMP), and titanium tetrachloride as a polymerization catalyst, this solid titanium catalyst component, triethylaluminum, and hydrogen.

[0097] [Preparation Example 3] 4-Methyl-1-pentene Total Production of Polymer A2-1 Into a 1.5 L SUS autoclave with a stirrer blade that had been sufficiently purged with nitrogen, 300 ml of n-hexane (dried over activated alumina under a dry nitrogen atmosphere) and 450 ml of 4-methyl-1-pentene were charged at 23°C. Then, 0.75 ml of a 1.0 mmol / ml toluene solution of triisobutylaluminum (TIBAL) was charged, and the stirrer was rotated.

[0098] Next, the autoclave was heated until the internal temperature reached 60°C, and pressurized with propylene so that the total pressure (gauge pressure) became 0.19 MPa. Subsequently, 0.34 ml of a toluene solution containing 1 mmol of methylaluminoxane in terms of Al and 0.01 mmol of diphenylmethylene(1-ethyl-3-t-butyl-cyclopentadienyl)(2,7-di-t-butyl-fluorenyl)zirconium dichloride, which had been prepared in advance, was pressured into the autoclave with nitrogen to initiate the polymerization reaction. During the polymerization reaction, the temperature was adjusted so that the internal temperature of the autoclave reached 60°C.

[0099] Sixty minutes after the start of polymerization, 5 ml of methanol was pressured into the autoclave with nitrogen to stop the polymerization reaction, and then the inside of the autoclave was depressurized to atmospheric pressure. After depressurization, acetone was added to the reaction solution while stirring the reaction solution to obtain a polymerization reaction product containing a solvent. Next, the obtained polymerization reaction product containing a solvent was dried at 130°C for 12 hours under reduced pressure to obtain 44.0 g of a powdery 4-methyl-1-pentene copolymer A2-1 (hereinafter, "copolymer A2-1") as a copolymer (A2). The measurement results of various physical properties are shown in Table 1.

[0100] [Table 1]

[0101] [Example 1] A three-layer biaxially stretched film laminated in the order of A layer / B1 layer / B2 layer was formed. First, as a resin composition for forming the A layer, a resin composition composed of 85 parts by mass of polymer A1-1 and 15 parts by mass of copolymer A2-1 was prepared. Specifically, polymer A1-1 and copolymer A2-1 were supplied to a biaxial extruder at a ratio of 85 parts by mass: 15 parts by mass and kneaded at 270 ° C to prepare a resin composition. The obtained resin composition was used as the raw material for the A layer.

[0102] Also, as the resin for forming the B1 layer and the B2 layer, Prime Polypro (registered trademark) F113G (homopolymer of propylene, density: 910 kg / m 3 , MFR (230 ° C, 2.16 kg load): 3.0 g / 10 min, manufactured by Prime Polymer Co., Ltd.) was used. In the following description, this Prime Polypro (registered trademark) F113G may be referred to as "polymer B".

[0103] The obtained resin composition and resin were used in a three-layer three-layer T-die sheet forming machine equipped with a T-die with a lip width of 330 mm, three hopper inlets and a 30 mmφ screw. The cylinder temperature of the A layer was 270 ° C, and the cylinder temperatures of the B1 layer and the B2 layer were 230 ° C. The die temperature was set to 270 ° C, and the melt-kneaded material was extruded from the T-die at a thickness of 250 μm (A layer 45 μm / B1 layer 190 μm / B2 layer 15 μm) and cast-molded to obtain the original film of Example 1. The thickness of each layer was calculated from the extrusion amount.

[0104] Next, using a batch-type biaxial stretching machine KARO IV manufactured by Brückner, under stretching conditions of a preheating temperature of 160 ° C, a preheating time of 30 seconds, a stretching temperature of 160 ° C, and a stretching speed of 300% / second, and heat setting conditions of 162 ° C and 60 seconds, the obtained original film was stretched 2.89 times in the machine direction (MD) and 5.2 times in the transverse direction (TD) to obtain a multilayer biaxially stretched film with a total film thickness of 17 μm. The evaluation results of the obtained multilayer biaxially stretched film are shown in Table 2-1 below. The specific test method is as follows.

[0105] <Uniformity after stretching> The multilayer biaxially stretched film obtained after multilayer biaxial stretching was visually inspected. If the surface was smooth and uniform, it was marked as ○; if there were non-uniform parts such as wrinkles, it was marked as ×.

[0106] <Delamination during stretching> The delamination between the A layer and the B1 layer and between the B1 layer and the B2 layer in the multilayer biaxially stretched film obtained after multilayer biaxial stretching was visually inspected to confirm the presence or absence of delamination. If there was no delamination, it was marked as ○; if there was delamination, it was marked as ×.

[0107] <Haze and total light transmittance> From the multilayer biaxially stretched film obtained after multilayer biaxial stretching, test pieces with a length of 80 mm and a width of 50 mm were taken, and in accordance with ASTM D1003, using a Haze Meter (manufactured by Nippon Denshoku Industries Co., Ltd., model: NDH - 20D, light source: D65), the haze value (unit: %) and the total transmitted light amount in the air were measured. This measurement was carried out at three arbitrary points in the multilayer biaxially stretched film respectively, and the average value of the data at these three points was taken as the measured value. Note that the total light transmittance was obtained by the following formula. Total light transmittance (%) = 100×(total transmitted light amount) / (incident light amount)

[0108] <Gloss> For the multilayer biaxially stretched film obtained after multilayer biaxial stretching, in accordance with JIS Z8741, the gloss was measured under the conditions of an incident angle of 60° and a receiving angle of 60°. This measurement was carried out at five arbitrary points in the multilayer biaxially stretched film respectively, and the average value of the data at these five points was taken as the glossiness.

[0109] <Shrinkage after heat sealing> A test piece with a length of 170 mm and a width of 50 mm was taken from the multilayer biaxially stretched film obtained after multilayer biaxial stretching. The length direction of the film was set as the direction corresponding to the flow direction in the film manufacturing process. Using a heat seal tester (Thermal Gradient Heat Seal Tester TP-701-G, manufactured by Tester Sangyo Co., Ltd.), under the conditions of an upper temperature of 180 °C, a lower temperature of 70 °C, a seal width of 5 mm, a seal pressure of 0.2 MPa, and a seal time of 1 second, the upper part (180 °C setting part) of the heat seal tester was set to be in contact with the A layer of the multilayer biaxially stretched film, and heat sealing was performed. At this time, the direction of the seal bar of the heat sealer was parallel to the width direction of the test piece, and the heating by the seal bar was performed over the entire width of the test piece. The shrinkage rate (%) was calculated by the following formula when the width of the test piece before heat sealing was L0 and the width of the test piece after heat sealing was L1. Shrinkage rate = (L0 - L1) / L0 × 100 (%)

[0110] [Examples 2 to 7, 10~12, Reference Examples 8, 9 13, Comparative Examples 1 to 8] Except for changing the types and blending ratios of the polymers constituting the resin composition for forming the A layer to those described in Tables 2-1 to 2-7 below and changing the thicknesses of each layer as described in Tables 2-1 to 2-7 below, a multilayer biaxially stretched film was obtained in the same manner as in Example 1. The evaluation results of the obtained multilayer biaxially stretched films are shown in Tables 2-1 to 2-7 below. Here, in Tables 2-1 to 2-7 below, the values described in the column of "Comonomer content (A1)+(A2)" represent the values of the converted comonomer content Y (mol%) obtained according to the following formula B1: Y = (X Q1 × C1 + X Q2 × C2) / 100 ··· Formula B1 In the above formula B1, C1 is the total content rate (mass%) of polymer A1-1 and polymer A1-2 in the resin composition constituting the above A layer, C2 is the content rate (mass%) of copolymer A2-1, X Q1is the total of the content rate (mol%) of the structural unit (Q1-1) derived from the comonomer in polymer A1-1 and the content rate (mol%) of the structural unit (Q1-2) derived from the comonomer in polymer A1-2, X Q2 is the content rate (mol%) of the structural unit (Q2-1) derived from the comonomer in copolymer A2-1.

[0111] [Table 2-1]

[0112] [Table 2-2]

[0113] [Table 2-3]

[0114] [Table 2-4]

[0115] [Table 2-5]

[0116] [Table 2-6]

[0117] [Table 2-7]

Claims

1. A multilayer biaxially stretched film in which layer A and layer B are laminated, wherein layer A is composed of a resin composition containing a 4-methyl-1-pentene polymer (A1) and a 4-methyl-1-pentene copolymer (A2), in the said layer A the content of the 4-methyl-1-pentene polymer (A1) is 60% by mass or more and 85% by mass or less with respect to the total mass of layer A, and the content of the 4-methyl-1-pentene copolymer (A2) is 15% by mass or more and 40% by mass or less with respect to the total mass of layer A, and the 4-methyl-1-pentene polymer (A1) satisfies the following requirements (A1-I) to (A1-III), the 4-methyl-1-pentene copolymer (A2) satisfies the following requirements (A2-I) to (A2-III), and a multilayer biaxially stretched film in which the value of the conversion content Y obtained by the following formula A is 3.0 mol% to 10.0 mol%: (A1-I) The content of the structural unit (P1) derived from 4-methyl-1-pentene is 90 to 100 mol%, and the content of the structural unit (Q1) derived from an α-olefin having 2 to 20 carbon atoms (excluding 4-methyl-1-pentene) is 0 mol% to 10 mol%. (A1-II) The melting point (Tm) measured by DSC is in the range of 200°C to 250°C. (A1-III) The intrinsic viscosity [η] measured in decalin at 135°C is 0.5 to 5.0 dl / g. (A2-I) The content of the structural unit (P2) derived from 4-methyl-1-pentene is 65 mol% or more and less than 96 mol%, and the content of the structural unit (Q2) derived from an α-olefin having 2 to 20 carbon atoms (excluding 4-methyl-1-pentene) exceeds 4 mol% and is 35 mol% or less. (A2-II) The melting point (Tm) measured by DSC is not observed or is in the range of 100°C to 199°C. (A2-III) The intrinsic viscosity [η] measured in decalin at 135°C is 0.5 to 5.0 dl / g. Y = (XQ1 × W1 + XQ2 × W2) / (W1 + W2 + WO) ··· Formula A In the said formula A, W1 is the content mass of the 4-methyl-1-pentene polymer (A1) in the resin composition constituting the said layer A; W2 is the content mass of the 4-methyl-1-pentene copolymer (A2) in the resin composition constituting the said layer A; WO is the total mass content of resins that do not correspond to either the 4-methyl-1-pentene polymer (A1) or the 4-methyl-1-pentene copolymer (A2) in the resin composition constituting the A layer; XQ1 is the content ratio (mol%) of the constitutional unit (Q1) in the 4-methyl-1-pentene polymer (A1); and XQ2 is the content ratio (mol%) of the constitutional unit (Q2) in the 4-methyl-1-pentene copolymer (A2).

2. The multilayer biaxially stretched film according to claim 1, wherein the constitutional unit (Q2) is a constitutional unit derived from an α-olefin having 2 to 4 carbon atoms.

3. The multilayer biaxially stretched film according to claim 1 or 2, wherein the B layer contains polypropylene (B).

4. The multilayer biaxially stretched film according to claim 3, wherein the B layer is composed of two or more layers.

5. The multilayer biaxially stretched film according to claim 4, wherein the two or more layers have the same constitution.

6. The multilayer biaxially stretched film according to claim 4, wherein the two or more layers include a first layer and a second layer on the side opposite to the first layer when viewed from the A layer, and the melting point of polypropylene (B) constituting the first layer is equal to or higher than the melting point of polypropylene (B) constituting the second layer.

7. The multilayer biaxially stretched film according to any one of claims 1 to 6, including a layer structure composed of an A layer / B layer.

8. The multilayer biaxially stretched film according to any one of claims 1 to 7, which is a packaging film.

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