JP6668065B2 - Biaxially stretch release film - Google Patents

Description

  The present invention relates to a biaxially stretched polypropylene-based film having excellent release properties. In particular, the present invention relates to a biaxially oriented polypropylene-based film which is excellent in releasability by containing a 4-methyl-1-pentene copolymer in a release layer and does not cause delamination during biaxial stretching. More specifically, the present invention relates to a biaxially oriented polypropylene film useful for a release film, a release liner, a separator film, and the like.

  In general, resin products, metal products, glass products, and the like for building materials and optics are provided with a surface protective film on their surfaces to prevent surface scratches and foreign matter from being introduced during transportation, storage, and processing. The surface protective film is required to have various properties depending on the protection target, protection purpose, use environment, and the like, in addition to properties such as flexibility and mechanical properties. For this reason, development of a surface protection film is being promoted from various viewpoints. For example, a surface protection film mainly composed of a polyethylene component and a surface protection film of a resin composition mainly containing a polypropylene component and containing an oligomer of 4-methyl-1-pentene and 1-decene have been studied. (Patent Document 2).

  Biaxially oriented polypropylene films are widely used as packaging and industrial material films because of their excellent light weight, thermal stability and mechanical properties. In particular, in recent years, it has been widely used as a non-silicone release material as a film for manufacturing electronic components, electronic substrate manufacturing processes, and thermosetting materials such as fiber-reinforced plastics, but further improvements have been demanded. . As a method of improving the releasability, for example, the release force can be further increased by blending a polymethylpentene polymer with polypropylene (Patent Documents 3 and 4). However, it is known that the biaxial stretching property is deteriorated by increasing the content of polymethylpentene, and in the case of a multilayer film, delamination is known. For example, an α-olefin copolymer is blended as a compatibilizer. Has been proposed (Patent Document 5).

  The present inventors have already disclosed a release film comprising a poly-4-methyl-1-pentene-based copolymer, which is excellent in releasability and has a relatively low moldable temperature, It has been confirmed that when the moldable temperature is lowered, there is no problem in practical use, but the film transparency tends to deteriorate (Patent Document 6).

  As described above, in recent years, in particular, the development of a film having excellent workability such as biaxial stretching, excellent appearance, and good releasability has been demanded.

JP-A-2006-116769 JP 2010-275340 A JP 2008-189995 A JP-A-7-070384 JP 2015-120331 A JP 2014-125496 A

  The present inventors provide a film having a low moldable temperature, excellent releasability, and excellent transparency, a surface protective film including the film, and a resin composition suitable for producing the film. With the goal.

The present inventors have conducted intensive studies to solve the above problems, and as a result, a biaxially stretched film containing a 4-methyl-1-pentene copolymer having specific physical properties can solve the above problems, and has a low moldable temperature. It has been found that even under the conditions, it is excellent in release property and transparency, and that the film can be stretched without causing the delamination phenomenon of the multilayer film sometimes encountered in the prior art, and has completed the present invention.
That is, the gist of the present invention is as follows.

{1} A biaxially stretched polypropylene film formed by laminating an A layer and a B layer,
A layer is composed of a resin composition containing 4-methyl-1-pentene copolymer (A1) and polypropylene (A2),
The content of the 4-methyl-1-pentene copolymer (A1) is 5% by mass or more and 95% by mass or less with respect to the total mass of the A layer, and the content of the polypropylene (A2) is A layer. Is from 5% by mass to 95% by mass with respect to the total mass of the compound (here, the total of the components (A1) and (A2) is 100% by mass), and the 4-methyl-1-pentene copolymer (A1) A film satisfying the following requirement [1].
[1] 96 mol% to 80 mol% of a structural unit derived from 4-methyl-1-pentene, and a structural unit derived from an olefin having 2 to 20 carbon atoms (excluding 4-methyl-1-pentene) The total sum is 4 to 20 mol% (provided that the total of the constitutional units derived from 4-methyl-1-pentene and the constitutional units derived from olefins having 2 to 20 carbon atoms is 100 mol%).

{2} The biaxially stretched polypropylene film according to claim 1, wherein the 4-methyl-1-pentene copolymer (A1) satisfies all of the following requirements [2] to [5].
[2] Intrinsic viscosity [η] measured in decalin at 135 ° C is 0.5 to 5.0 dl / g [3] Weight average molecular weight (Mw) and number average measured by gel permeation chromatography (GPC) molecular weight which is the ratio molecular weight distribution of the (Mn) (Mw / Mn) is 1.0 to 3.5 [4] melting point density was measured with a ^{825~860kg / m 3 [5] DSC} (Tm) Is in the range of 100 ° C to 199 ° C

  {3} The biaxially oriented polypropylene according to claim 1 or 2, wherein the 4-methyl-1-pentene copolymer (A1) has a melting point (Tm) measured by DSC in the range of 100 ° C to 180 ° C. the film.

  {4} The B layer is formed from a resin composition containing polypropylene (B1) which may be the same as or different from the polypropylene (A2). Biaxially oriented polypropylene film.

  The {5} layer configuration is a three-layer configuration of A layer / B layer / A layer or A layer / B layer / C layer (where C layer is a layer different from both A layer and B layer) The biaxially stretched film according to any one of claims 1 to 4, wherein

  According to the present invention, there is provided a biaxially stretched polypropylene film which does not generate delamination or the like during biaxial stretching and has excellent surface smoothness and releasability.

Hereinafter, specific embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and is implemented with appropriate modifications within the scope of the present invention. be able to. In this specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit and an upper limit.
Further, in the present specification, when referring to the amount of each component in the composition, when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified, a plurality of substances present in the composition Means the total amount of the substance.

  Hereinafter, the biaxially stretched release film containing the 4-methyl-1-pentene copolymer (A) according to the present invention will be described in detail.

  The biaxially stretched polypropylene-based film of the present invention is obtained by laminating an A layer and a B layer, and the A layer is formed from a resin composition containing a 4-methyl-1-pentene copolymer (A1) and a polypropylene (A2). It is configured. Hereinafter, the layer A and the layer B will be described in detail, and then the layer configuration and the film manufacturing method will be described.

≪A layer≫
The A layer contains a 4-methyl-1-pentene copolymer (A1) and polypropylene (A2).
[4-methyl-1-pentene copolymer (A1)]

Hereinafter, the 4-methyl-1-pentene copolymer (A1) will be described.
The 4-methyl-1-pentene copolymer (A1) contains a constitutional unit derived from 4-methyl-1-pentene in an amount of 96 mol% to 80 mol%, and has an olefin having 2 to 20 carbon atoms (4-methyl). -1 except for pentene) in a ratio of 4 mol% to 20 mol%. The olefin having 2 to 20 carbon atoms is not limited to one type, and two or more types may be selected. When a plurality of types are selected, the sum of the constituent units may satisfy the above range. .

  Here, from the viewpoints of heat resistance, transparency and moldability, the upper limit of the constitutional unit derived from 4-methyl-1-pentene is preferably 96 mol%, and preferably 95 mol%. More preferably, the content is more preferably 93 mol%. The lower limit of the structural unit derived from 4-methyl-1-pentene is preferably 80 mol%, more preferably 83 mol%, and more preferably 84 mol%. More preferred.

  On the other hand, the upper limit of the constitutional unit derived from an olefin having 2 to 20 carbon atoms (excluding 4-methyl-1-pentene) is preferably 20 mol%, more preferably 18 mol%. More preferably, the content is 17 mol%. The lower limit of the structural unit derived from an olefin having 2 to 20 carbon atoms (excluding 4-methyl-1-pentene) is preferably 4 mol%, and more preferably 5 mol%. More preferably, the content is more preferably 7 mol%. Here, the total of the constituent units of 4-methyl-1-pentene and an olefin having 2 to 20 carbon atoms is 100 mol%.

  By setting the ratio of the constitutional unit of 4-methyl-1-pentene and the olefin having 2 to 20 carbon atoms to be within the above range, the melting point of the obtained copolymer (A1) can be adjusted as in the above requirement [5]. Can be adjusted. Therefore, when producing a film comprising a layer containing the copolymer (A1), compared to a conventionally used 4-methyl-1-pentene polymer, particularly a 4-methyl-1-pentene homopolymer. To lower the molding temperature. Further, by setting the proportion of the structural unit within the above range, it is possible to maintain the heat resistance of the copolymer (A) at a high level.

  The 4-methyl-1-pentene copolymer (A1) has a structure derived from a 4-methyl-1-pentene structural unit chain and an olefin having 2 to 20 carbon atoms (excluding 4-methyl-1-pentene). It may be a block copolymer containing a block in which the same type of structural unit is continuous. From the viewpoint of transparency and moldability, a random copolymer of 4-methyl-1-pentene and an olefin having 2 to 20 carbon atoms is preferred.

  Examples of the olefin having 2 to 20 carbon atoms contained in the 4-methyl-1-pentene copolymer (A1) include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 3-methyl-1-. Preferred examples include butene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, and 1-eicosene.

  From the viewpoint of the physical properties of the obtained copolymer, ethylene, propylene, 1-butene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 1-octene, 1-decene, Hexadecene, 1-heptadecene and 1-octadecene are preferred, ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-hexadecene, 1-heptadecene and 1-octadecene are more preferred, and 1-octene is more preferred. , 1-decene, 1-hexadecene, 1-heptadecene and 1-octadecene are more preferred. Of these, α-olefins having 2 to 4 carbon atoms are preferable, and specific examples thereof include ethylene, propylene, and 1-butene.

  These olefins having 2 to 20 carbon atoms can be used alone or in combination of two or more. Further, propylene is most preferable from the viewpoint of copolymerizability and dispersibility.

  The 4-methyl-1-pentene copolymer (A1) is a mixture of 4-methyl-1-pentene and an olefin having 2 to 20 carbon atoms (4-methyl-1) as long as the object of the present invention is not impaired. -Excluding pentene), and may contain a structural unit derived from a polymerizable compound (hereinafter, also referred to as a polymerizable compound) other than a pentene.

  Examples of such a polymerizable compound include vinyl compounds having a cyclic structure such as styrene, vinylcyclopentene, vinylcyclohexane, and vinylnorbornane; vinyl esters such as vinyl acetate; unsaturated organic acids such as maleic anhydride or derivatives thereof. Conjugated dienes such as butadiene, isoprene, pentadiene and 2,3-dimethylbutadiene; 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-isopropylene Riden-2-norbol , 6-chloromethyl-5-isopropyl-2-norbornene, 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,2-norbornadiene and the like Non-conjugated polyenes.

  The 4-methyl-1-pentene copolymer (A1) according to the present invention includes all polymerizable compounds contained in the 4-methyl-1-pentene copolymer (A1) containing units derived from the polymerizable compound. It may be contained in an amount of 10 mol% or less, or 5 mol% or less and 3 mol% or less based on the compound structural unit.

  In the present invention, the intrinsic viscosity [η] of the 4-methyl-1-pentene copolymer (A1) measured in decalin at 135 ° C. is preferably 0.5 to 5.0 dL / g.

  Here, the intrinsic viscosity [η] is preferably in the range of 1.0 to 4.0 dL / g, and 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 copolymer (A1).

  The 4-methyl-1-pentene copolymer (A1) having an intrinsic viscosity [η] in the above range exhibits good fluidity during the production of a resin composition and various moldings, and also includes polypropylene and the like. The dispersibility in the thermoplastic resin (B) becomes good, and a molded article with beautiful appearance can be obtained.

  In the present invention, the molecular weight distribution, which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the 4-methyl-1-pentene copolymer (A1) measured by gel permeation chromatography (GPC). (Mw / Mn) is preferably from 1.0 to 3.5. Here, the molecular weight distribution (Mw / Mn) is preferably in the range of 1.0 to 3.5, and more preferably in the range of 1.5 to 3.0.

  The value of the molecular weight distribution (Mw / Mn) can be adjusted depending on the type of the olefin polymerization catalyst described later.

  The polymer composition containing the 4-methyl-1-pentene copolymer (A1) having a molecular weight distribution (Mw / Mn) in the above range tends to have a relatively low content of a low molecular weight component. . Therefore, the bleed out of the low molecular weight compound is small, the blocking property is reduced, and this is preferable from the viewpoint of overall film physical properties, particularly, mechanical strength and beautiful appearance.

  In the present invention, the molecular weight distribution (Mw / Mn), which is the ratio between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the 4-methyl-1-pentene copolymer (A1), is determined by gel permeation chromatography. This is a value calculated by a standard polystyrene conversion method using (GPC).

In the present invention, the density of the 4-methyl-1-pentene copolymer (A1) is preferably 825 to 860 kg / m ³ . Here, the density is preferably in the range of 830~855kg / ^{m 3,} more preferably in the range of 830~850kg / ^{m 3,} more preferably in the range of 830~845kg / ^{m 3.}

  The value of the density can be adjusted by selecting the type and the amount of the other α-olefin to be polymerized together with 4-methyl-1-pentene. The polymer composition containing the 4-methyl-1-pentene copolymer (A1) having a density value in the above range is preferable from the viewpoint of heat resistance and lightness. The density of the 4-methyl-1-pentene copolymer (A1) is a value measured according to JIS K7112 (density gradient tube method).

  In the present invention, the melting point (Tm) of the 4-methyl-1-pentene copolymer (A1) measured by DSC is preferably from 100 to 199 ° C, more preferably from 110 to 180 ° C. The temperature is more preferably in the range of 125 to 158 ° C, and particularly preferably in the range of 125 to 150 ° C. The value of the melting point (Tm) varies depending on the stereoregularity of the polymer and the amount of the α-olefin polymerized together, and is controlled and adjusted to a desired composition using an olefin polymerization catalyst described later. It is possible.

  The polymer composition containing the 4-methyl-1-pentene copolymer (A1) having a melting point (Tm) in the above range has a low stickiness, and has a good handling property from the viewpoint of moldability. preferable.

  The 4-methyl-1-pentene-based copolymer (A1) in the present invention can be obtained by subjecting 4-methyl-1-pentene and the above-mentioned specific α-olefin and, if necessary, the above polymerization in the presence of an olefin polymerization catalyst. Can be obtained by polymerizing a reactive compound.

Among the above-mentioned olefin polymerization catalysts, in producing the 4-methyl-1-pentene copolymer (A1), a preferred embodiment of the catalyst includes a metallocene catalyst.
Preferred metallocene catalysts include those described in WO 01/53369, WO 01/27124, JP-A-3-193796, JP-A-02-41303 or WO 2006/025540 and WO-A-2006 / 025540. Metallocene catalysts described in 2014/050817 and the like.

  The content of the 4-methyl-1-pentene copolymer (A1) in the film of the present invention is preferably from 5% by mass to 95% by mass, and more preferably from 10% by mass to 80% by mass, based on the total mass of the surface protective film. It is more preferably at most 10 mass%, more preferably at least 10 mass% and not more than 70 mass%. When the content is in the above range, the affinity to the polypropylene (A2) described later is high, and the 4-methyl-1-pentene copolymer (A1) can be finely dispersed in the system. When a film is produced using the resin composition, the 4-methyl-1-pentene copolymer (A1) is less likely to fall off, and the blocking resistance can be maintained for a long time. .

[Polypropylene (A2)]
The polypropylene (A2) in the present invention is a known polymer mainly composed of propylene. Examples of such a polymer include a propylene homopolymer and a propylene / α-olefin copolymer of propylene and an α-olefin other than propylene. (Random copolymer, block copolymer, propylene / ethylene copolymer, propylene / 1-butene copolymer, propylene / ethylene / 1-butene copolymer, or a mixture thereof). As the polypropylene, isotactic polypropylene and syndiotactic polypropylene are preferably used, and the isotactic mesopendad fraction (mmmm) or the syndiotactic mesopendad fraction (rrrr) exhibiting stereoregularity is 90% or more. Is preferably 92% or more, more preferably 93% or more. When the stereoregularity is high, the crystallinity of the resin is improved, and high thermal stability and mechanical properties can be imparted.

  The copolymerization ratio of the α-olefin in the propylene / α-olefin copolymer is preferably 5% by mass or less. 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 various inorganic compounds, various carboxylic acids or metal salts thereof, dibenzylidene sorbitol compounds, arylphosphate compounds, cyclic polyvalent metal arylphosphate compounds and aliphatic monocarboxylic acid alkalis Examples thereof include a mixture with a metal salt or basic aluminum / lithium / hydroxy / carbonate / hydrate, and an α-crystal nucleating agent such as various polymer compounds. These crystallization nucleating agents can be used alone or in combination of two or more.

  The MFR of the polypropylene (A2) can be measured according to JIS K7210. Specifically, it is preferably 0.5 to 25 g / 10 min, more preferably 1 to 15 g / 10 min, and more preferably 2 to 10 g / min under the measurement conditions of a temperature of 230 ° C. and a load of 2.16 kg load. More preferably, it is 10 minutes. When the MFR of the propylene-based polymer is in the above range, it is suitable for extrusion molding.

  The ash content due to the polymerization catalyst residue and the like contained in the polypropylene (A2) is preferably as small as possible, and is preferably 50 ppm or less in order to reduce minute foreign matters (fish eyes). More preferably, it is 40 ppm or less. By setting the content to 50 ppm or less, minute foreign matters and defects are significantly reduced, and contamination when used for electronic parts can be reduced.

  The content of the polypropylene (A2) in the film of the present invention is preferably from 5% by mass to 95% by mass, more preferably from 20% by mass to 90% by mass, and more preferably from 30% by mass, based on the total mass of the surface protective film. The content is more preferably 90% by mass or less. When the content is within the above range, the affinity for the 4-methyl-1-pentene copolymer (A1) is high, so that the 4-methyl-1-pentene copolymer (A1) is finely dispersed in the system. It becomes possible.

[Other resins]
The resin composition constituting the layer A of the biaxially stretched film of the present invention contains the above-mentioned 4-methyl-1-pentene copolymer (A1) and polypropylene (A2) as long as the object of the present invention is not impaired. ) May be included. As other resins, for example, a polyolefin-based polymer such as polyethylene, poly 1-butene, a styrene-based resin, and an ethylene / α-olefin copolymer can be added.

〔Additive〕
The resin composition constituting the layer A of the biaxially stretched film of the present invention contains a specific amount of a 4-methyl-1-pentene copolymer (A1) and a specific amount of polypropylene (A2), and further includes: Within the range that does not impair the object of the present invention, for example, weathering stabilizer, heat stabilizer, antioxidant, ultraviolet absorber, antistatic agent, antislip agent, antiblocking agent, antifogging agent, nucleating agent, lubricant, Contains various additives such as pigments, dyes, anti-aging agents, hydrochloric acid absorbents, inorganic or organic fillers, organic or inorganic foaming agents, crosslinking agents, crosslinking aids, adhesives, softeners, flame retardants, etc. It may be.

  In order to further improve the moldability of the resin composition constituting the layer A in the present invention, that is, to increase the crystallization temperature and increase the crystallization rate, a nucleating agent which is a specific optional component may be blended. Good. In this case, for example, the nucleating agent is a dibenzylidenesorbitol-based nucleating agent, a phosphate ester-based nucleating agent, a rosin-based nucleating agent, a metal benzoate-based nucleating agent, a fluorinated polyethylene, 2,2-methylenebis (4,6-di- Sodium t-butylphenyl) phosphate, pimelic acid and salts thereof, 2,6-naphthalene dicarboxylic acid dicyclohexylamide, and the like, and the mixing amount is not particularly limited. It is preferable to have about 1 to 1 part by mass. There is no particular limitation on the mixing timing, and the addition can be performed during polymerization, after polymerization, or during molding.

  In the resin composition, within a range that does not impair the object of the present invention, and further, if necessary, a secondary antioxidant, a heat stabilizer, a weather stabilizer, an antistatic agent, a slip agent, an antifogging agent, a lubricant, Dyes, pigments, natural oils, synthetic oils, waxes, fillers, hydrochloric acid absorbents, and other olefin polymers can be blended. Although the amount is not particularly limited, 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 more preferably 0 to 1 part by mass with respect to 100 parts by mass of the resin composition. Is particularly preferred.

  As the antioxidant, a known antioxidant can be used. Specifically, a hindered phenol compound, a sulfur-based antioxidant, a lactone-based antioxidant, an organic phosphite compound, an organic phosphonite compound, or a combination of several kinds thereof can be used.

  Examples of the lubricant include sodium, calcium, and magnesium salts of saturated or unsaturated fatty acids such as lauric acid, palmitic acid, oleic acid, and stearic acid. These may be used alone or as a mixture of two or more. it can. The amount of the lubricant is 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.

  As the slip agent, it is preferable to use amides of saturated or unsaturated fatty acids such as lauric acid, palmitic acid, oleic acid, stearic acid, erucic acid, and hevenic acid, or bisamides of these saturated or unsaturated fatty acids. Of these, erucamide and ethylenebisstearamide are particularly preferred. It is preferable that these fatty acid amides are usually added in the range of 0.01 to 5 parts by mass with respect to 100 parts by mass of the resin composition according to the present invention.

  When the layer A according to the present invention contains the optional components other than the component (A1) and the component (A2), the mass obtained by subtracting the optional components from the total mass of the layer A is defined as 100% by mass. The definition of the content of the component (A1) (5 to 95% by mass) and the definition of the content of the component (A2) (5 to 95% by mass) apply.

≫B layer≫
The layer B in the biaxially oriented polypropylene film of the present invention is a layer provided for imparting excellent mechanical properties to the biaxially oriented polypropylene film of the present invention. The B layer is formed from a resin composition containing polypropylene (B1). As the polypropylene (B1), for example, the same propylene-based polymer as the polypropylene (A2) used in the layer A can be mentioned. The polypropylene (A2) used for forming the A layer and the polypropylene (B1) used for forming the B layer may be the same or different, but may be the same from the viewpoint of adhesiveness. preferable.

  In addition, the same heat stabilizer, antioxidant, slip agent, chlorine scavenger, antistatic agent, etc. as those added to the resin composition forming the A layer are added to the resin composition forming the B layer. May be.

≪Biaxially stretched film≫
The layer structure of the biaxially stretched release film of the present invention includes a two-layer structure in which an A layer and a B layer are stacked, a three-layer structure in which an A layer / B layer / A layer is stacked in order, an A layer and a B layer. C layer different from any of the layers (for example, ethylene-modified isotactic polypropylene resin (random copolymer or block copolymer), composition containing atactic polypropylene, syndiotactic polypropylene, olefin-based polymer or styrene-based polymer, A three-layer structure in which a layer formed of an adhesive material exhibiting adhesiveness obtained from an acrylic polymer or the like) is laminated in the order of A layer / B layer / C layer. From the viewpoint of moldability during lamination, a two-layer structure of A layer / B layer or a three-layer structure of A layer / B layer / A layer is preferable.

  There is no particular limitation on the method of obtaining such a laminated film, but a method of laminating by a known lamination method such as extrusion lamination or extrusion coating on a surface layer film obtained in advance by T-die molding or inflation molding. Alternatively, a method of forming a plurality of films independently and then laminating each film by dry lamination may be mentioned, but from the viewpoint of productivity, co-extrusion in which a plurality of components are subjected to a multi-layer extruder and formed. Molding is preferred.

  Although the thickness of the film according to the present invention before stretching is not particularly limited, it is usually 300 μm to 1000 μm, preferably 300 to 800 μm, more preferably 350 to 500 μm as a raw sheet.

  The total thickness of the biaxially oriented polypropylene film of the present invention is preferably from 3 to 60 μm, more preferably from 10 to 50 μm, and still more preferably from 20 to 50 μm. When the total thickness of the film is 3 to 60 μm, a film having excellent mechanical properties and stretchability can be obtained. The thickness of one layer A is preferably 2 to 10%, more preferably 2 to 5%, of the thickness of one layer B. When the biaxially oriented polypropylene film of the present invention contains two or more A layers, the thickness of each A layer may be the same or different from each other.

  The tape peeling force of the biaxially oriented polypropylene film of the present invention at a peeling speed of 300 mm / min is preferably 7 N / 50 mm or less. More preferably, it is 1 to 6.5 N / 50 mm. The tape peeling force can be adjusted by the melting point and the amount of the 4-methylpentene-1 copolymer (A).

製造 Method of manufacturing biaxially stretched film≫
Various methods are known for preparing the resin composition pellets for the A layer or the B layer by mixing the respective components, for example, a multi-stage polymerization method, a plast mill, a Henschel mixer, a V-blender, a ribbon blender, a tumbler. , A method of mixing with a blender, a kneader-ruder or the like, or a method of melting and kneading at 180 to 250 ° C, for example, with a single-screw extruder, a twin-screw extruder, a kneader, a Banbury mixer, or the like, followed by granulation or pulverization. can do. By this method, high-quality resin composition pellets in which each component and additive are uniformly dispersed and mixed can be obtained.

  In the present invention, in particular, a masterbatch containing about 1 to 50 parts by mass of a 4-methyl-1-pentene copolymer (A1) in 100 parts by mass of polypropylene (A2) is prepared in advance, and then appropriately blended. It can also be used as the concentration of the predetermined 4-methyl-1-pentene copolymer (A1).

  The raw sheet for a biaxially stretched film of the present invention can be obtained by melt-extruding the resin composition pellets described above at a cylinder temperature of usually 180 to 300 ° C.

  In order to produce a biaxially stretched film from the raw sheet, a batch type biaxial stretching or a sequential biaxial stretching can be performed immediately after casting. In the successive biaxial stretching, the cast raw sheet is kept at 100 to 160 ° C, stretched 4 to 5 times in the flow direction between rolls provided with a speed difference, and immediately cooled to room temperature. Next, the film is guided to a tenter, stretched 5 to 10 times in the width direction at a temperature of 160 ° C. or higher, and then relaxed, heat-set, and wound up.

  The biaxially stretched film of the present invention has a 4-methyl-1-pentene-based copolymer because the 4-methyl-1-pentene-based copolymer (A1) has a high affinity with the polypropylene (A2). (A1) is less likely to fall off and has excellent blocking resistance over a long period of time.

≪Application≫
Specific applications of the biaxially oriented polypropylene film of the present invention include, for example, the following general film applications.

  Packaging film; for example, a food packaging film, a stretch film, a wrap film, a shrink film, an easy peel film, an aluminum vapor-deposited film, a PVDC coated film, and the like. Breathable films; for example, disposable diapers, sanitary products, surgical gowns, surgical gloves, surgical downs, house wraps (moisture permeable waterproof sheets), disposable warmers, household dehumidifiers, desiccants, oxygen absorbers, fresheners, compost Sheet, simple jumper, and the like. Anti-corrosion film; For example, transportation and packaging of automobile parts, knockdown parts, machinery and machine parts, iron and chrome products, steel pipes, wires, bolts and nuts, bearings, dies, tools, blades, cutting tools, building tools, etc. Storage packaging, export packaging, and the like. Antifogging films; for example, films for fruits and vegetables, films for processed foods, and the like.

Oriented film; twist packaging for confectionery, agricultural materials, laminate base, coin packaging, wire bundling material, fruit and vegetable packaging, cardboard cut tape, detergent refillable container, rice ball packaging, pillow packaging, stick packaging, boil and retort packaging, Water food packaging, infusion bags, and the like.
Self-cleaning film; for example, road signs, general signs, signboards, window glasses, road materials, side mirrors and the like.

Separator; for example, battery separator, lithium ion battery separator, fuel cell electrolyte membrane, adhesive / adhesive material separator, stretched film; for example, film capacitor film, capacitor film, fuel cell capacitor film,
Semiconductor process film; for example, dicing tape, back grind tape, die bonding film, polarizing plate film, surface protection film; for example, polarizing plate protection film, liquid crystal panel protection film, optical component protection film, lens protection film , Protective film for electrical parts and appliances, Protective film for mobile phones, Protective film for PC, Masking film, Protective film for touch panel,
Films for electronic members; for example, diffusion films, reflection films, radiation-resistant films, gamma-resistant films, porous films,
Building material films; examples include building material window films, laminated glass films, bulletproof materials, bulletproof glass films, heat shield sheets, heat shield films, and the like.

  Release film; for example, release film for flexible printed circuit board (FPC), release film for ACM substrate, release film for rigid flexible substrate, release film for advanced composite material, release film for curing carbon fiber composite material, Release film for curing glass fiber composite material, release film for curing aramid fiber composite material, release film for curing nano composite material, release film for curing filler filler, release film for semiconductor encapsulation, release film for polarizing plate Mold film, release film for diffusion sheet, release film for prism sheet, release film for reflective sheet, cushion film for release film, release film for fuel cell, release film for various rubber sheets, release for urethane curing Mold film, release film for epoxy curing (manufacturing process members such as metal bats and golf clubs, etc.), etc. And the like.

  Particularly preferred are a release film, a release liner or a separator film used for a surface protection film and an adhesive tape, and a carrier in the production of a composite material.

  Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples. In addition, each physical property was measured as follows in an Example.

〔composition〕
The contents (mol%) of 4-methyl-1-pentene and α-olefin in the polymer were measured by ¹³ C-NMR. The measurement conditions are as follows.

-Measuring device: Nuclear magnetic resonance device (ECP500, manufactured by JEOL Ltd.)
-Observation nucleus: ¹³ C (125 MHz)
・ Sequence: Single pulse proton decoupling ・ Pulse width: 4.7 μsec (45 ° pulse)
• Repetition time: 5.5 seconds • Number of integration: 10,000 or more • Solvent: mixed solvent of ortho-dichlorobenzene / deuterated benzene (volume ratio: 80/20) • Sample concentration: 55 mg / 0.6 mL
・ Measurement temperature: 120 ° C
-Reference value of chemical shift: 27.50 ppm

[Intrinsic viscosity [η]]
The intrinsic viscosity [η] of the polymer was measured at 135 ° C. in a decalin solvent using an Ubbelohde viscometer as a measuring device. Specifically, about 20 mg of the powdery copolymer was dissolved in 25 ml of decalin, and the specific viscosity η _sp was measured in an oil bath at 135 ° C. using an Ubbelohde viscometer. After the decalin solution was diluted by adding 5 ml of decalin, the specific viscosity η _sp was measured in the same manner as described above. This dilution operation was further repeated twice, and the value of η _sp / C when the concentration (C) was extrapolated to 0 was determined as the intrinsic viscosity [η] (unit: dl / g) (see the following formula 1). .
[Η] = lim (η _sp / C) (C → 0) Equation 1

[Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn)]
The weight average molecular weight (Mw) of the polymer and the molecular weight distribution (Mw / Mn) represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) are determined by gel permeation chromatography (GPC: Gel Permeation). It was calculated by a standard polystyrene conversion method using Chromatography). The measurement conditions are as follows.
-Measuring device: GPC (ALC / GPC 150-C plus type, integrated refractometer detector, Waters)
-Column: Two GMH6-HT (manufactured by Tosoh Corporation) and two GMH6-HTL (manufactured by Tosoh Corporation) are connected in series.-Eluent: o-dichlorobenzene-Column temperature: 140 ° C
・ Flow rate: 1.0 mL / min

[Melt flow rate (MFR)]
The melt flow rate (MFR: Melt Flow Rate) of the polymer was measured at 230 ° C. under a load of 2.16 kg according to ASTM D1238. The unit is g / 10 min). In addition, only the copolymer (A1-3) obtained in Preparation Example 3 was measured at 260 ° C. under a load condition of 5.0 kg.

〔density〕
The density of the polymer was measured according to JIS K7112 (density gradient tube method). This density (kg / m ³ ) was used as an index of lightness.

[Melting point (Tm) and glass transition temperature (Tg)]
The melting point (Tm) of the polymer was measured using a differential scanning calorimeter (DSC220C type, manufactured by Seiko Instruments Inc.) as a measuring device.

  About 5 mg of the copolymer was sealed in an aluminum pan for measurement and heated from room temperature to 200 ° C. at 10 ° C./min. In order to completely melt the copolymer, it was kept at 200 ° C. for 5 minutes, and then cooled at 10 ° C./min to −50 ° C. After 5 minutes at −50 ° C., a second heating was performed at 200 ° C. at 10 ° C./min. The peak temperature (° C.) at the second heating was defined as the melting point (Tm) of the copolymer, and the displacement point corresponding to the glass transition was defined as the glass transition temperature (Tg). The higher of the melting point (Tm) and the glass transition temperature (Tg) of the polymer was used as an index of heat resistance.

[Preparation Example 1] Production of 4-methyl-1-pentene copolymer (A1-1)
To a 1.5-liter SUS autoclave with stirring blades sufficiently purged with nitrogen, 300 ml of normal hexane (dried on activated alumina in a dry nitrogen atmosphere) and 450 ml of 4-methyl-1-pentene were charged at 23 ° C. . 0.75 ml of a 1.0 mmol / ml toluene solution of triisobutylaluminum (TIBAL) was charged into this autoclave, and the stirrer was turned. Next, the autoclave was heated to an internal temperature of 60 ° C. and pressurized with propylene so that the total pressure became 0.19 MPa (gauge pressure). Subsequently, 1 mmol of methylaluminoxane, which was prepared in advance, was converted to Al in terms of Al and diphenylmethylene (1-ethyl-3-t-butyl-cyclopentadienyl) (2,7-di-t-butyl-fluorenyl) zirconium. 0.34 ml of a toluene solution containing 0.01 mmol of dichloride was injected into the autoclave with nitrogen to initiate polymerization. During the polymerization reaction, the temperature was adjusted so that the internal temperature of the autoclave became 60 ° C. 60 minutes after the start of the polymerization, 5 ml of methanol was injected into the autoclave with nitrogen to terminate the polymerization, and the autoclave was depressurized to atmospheric pressure. Acetone was poured into the reaction solution with stirring.

  The powdery polymer containing the obtained solvent was dried at 100 ° C. under reduced pressure for 12 hours. The obtained polymer was 44.0 g, the 4-methyl-1-pentene content (abbreviated as 4MP1 in Table 1) in the polymer was 84.1 mol%, and the propylene content was 15.9 mol%. The melting point (Tm) of the polymer was 132 ° C., and the intrinsic viscosity [η] was 1.5 dl / g. Table 1 shows the results measured for various physical properties.

[Preparation Example 2] Production of 4-methyl-1-pentene copolymer (A1-2)
750 ml of 4-methyl-1-pentene was charged at 23 ° C. into a 1.5-liter SUS autoclave with stirring blades which had been sufficiently purged with nitrogen. 0.75 ml of a 1.0 mmol / ml toluene solution of triisobutylaluminum (TIBAL) was charged into the autoclave, and stirring was started.

  Next, the autoclave was heated to an internal temperature of 60 ° C., and pressurized with propylene so that the total pressure became 0.17 MPa (gauge pressure). Subsequently, 1 mmol of methylaluminoxane, which had been prepared in advance, was calculated as Al, and diphenylmethylene (1-ethyl-3-t-butyl-cyclopentadienyl) (2,7-di-t-butyl-fluorenyl) zirconium was used. 0.34 ml of a toluene solution containing 0.005 mmol of dichloride was injected into the autoclave with nitrogen to initiate polymerization. During the polymerization reaction, the temperature was adjusted so that the internal temperature of the autoclave became 60 ° C. 60 minutes after the start of polymerization, 5 ml of methanol was injected into the autoclave with nitrogen to terminate the polymerization, and the autoclave was depressurized to atmospheric pressure. Acetone was poured into the reaction solution with stirring.

The resulting powdery polymer containing the solvent was dried at 130 ° C. under reduced pressure for 12 hours. The weight of the obtained copolymer was 35.2 g, the 4-methyl-1-pentene content in the copolymer was 91.1 mol%, and the propylene content was 8.9 mol%. The Tm of the polymer was 178.2 ° C., the intrinsic viscosity [η] was 1.6 dl / g, and the density was 832 kg / m ³ . Table 1 shows the results measured for various physical properties.

[Preparation Example 3] Production of 4-methyl-1-pentene copolymer (A1-3) According to the method of Comparative Example 7 or Comparative Example 9 of International Publication WO 2006/054613, 4-methyl 1-pentene By changing the proportions of 1-decene and hydrogen, a 4-methyl-1-pentene copolymer (A1-3) having the physical properties shown in Table 1 was obtained. Table 1 shows the results measured for various physical properties.

[Example 1]
As a resin composition for forming the A layer, 10 parts by mass of a copolymer A1-1, polypropylene A2-1 (Prime Polypro (registered trademark) F113G, a homopolymer of propylene, density: 910 kg / m ³ , MFR (230 ° C. ): 3 g / 10 min, 90 parts by mass (produced by Prime Polymer Co., Ltd.) were mixed (dry-blended). The resin forming the layer B is the polypropylene A2-1 (Prime Polypro (registered trademark) F113G, a homopolymer of propylene, density: 910 kg / m ³ , MFR (230 ° C.): 3 g / 10 min, as polypropylene B1). ) Prime Polymer). The obtained mixture was set at a cylinder temperature of 240 ° C. and a die temperature of 240 using a three-type three-layer T-die sheet forming machine in which a T-die having a lip width of 330 mm was installed, and three hopper inlets and a 30 mm φ screw were installed. C., the melt-kneaded product was extruded from a T-die at a thickness of 500 μm, and cast to obtain a raw film of Example 1. In this example, the B layer was formed using two of the three hoppers, and the two-layer two-layer film of the A layer / B layer was formed.

Subsequently, using a batch type biaxial stretching machine KARO IV manufactured by Bruckner, a preheating temperature of 162 ° C., a preheating time of 2 minutes, a stretching temperature of 162 ° C., a stretching condition of a stretching speed of 100% / sec, a heat setting condition of 162 ° C. for 30 seconds The obtained raw film was stretched 5 times in the machine direction (MD) and 5 times in the width direction (TD) to obtain a biaxially stretched film having a total film thickness of 20 μm.
About the obtained biaxially stretched film, while confirming whether peeling (delamination) occurs between the film layers during stretching, the surface roughness of the obtained film and the releasability from the tape were evaluated and shown in Table 2. Was. The specific test method is as follows.

(Delamination during stretching)
The peeling between the film layers after the biaxial stretching was visually confirmed, and the presence or absence of delamination was confirmed.

(Surface roughness)
The surface roughness of the film was measured by a contact needle method in accordance with JIS B0601-1994, and the surface roughness was measured at a speed of 0.15 m / sec within a range of 150 mm in the TD direction. The obtained cross-sectional curve was calculated as Rz (μm) by least-squares straight line correction [Total haze (%)]
In accordance with ASTM D-1003, it was measured in the air with a digital turbidity meter (NDH-20D) manufactured by Nippon Denshoku Industries Co., Ltd.

(Peeling force evaluation)
The peeling force was measured according to the test method of the pressure-sensitive adhesive sheet (JIS Z0237-2000). An acrylic adhesive (Nitto Tape 31B, manufactured by Nitto Denko Corporation) was used as the adhesive. After leaving the test film and the adhesive tape cut to 50 mm width × 100 mm length in an environment of a temperature of 23 ° C. and a relative humidity of 50% for 1 hour, the adhesive film is passed back and forth with a rubber roll of about 2 kg while applying pressure. Affixed to a test plate.
After sticking, leave it in a constant environment at a temperature of 23 ° C. or 50 ° C. and a relative humidity of 50% for one day, and then peel it off in a 180 ° direction at a temperature of 23 ° C. and a relative humidity of 50% at a speed of 300 mm / min. The peeling force was measured.

[Example 2]
As a resin composition for forming the A layer, 30 parts by mass of a copolymer A1-1 and polypropylene A2-1 (Prime Polypro (registered trademark) F113G, a homopolymer of propylene, density: 910 kg / m ³ , MFR (230 ° C. ): 3 g / 10 min, 70 parts by mass (produced by Prime Polymer Co., Ltd.) was mixed (dry blended) with the same method as in Example 1 to obtain a biaxially stretched film of Example 2. Table 2 shows the evaluation results of the obtained biaxially stretched films.

[Example 3]
As the resin composition for forming the A layer, 70 parts by mass of a copolymer A1-1, polypropylene A2-1 (Prime Polypro (registered trademark) F113G, a homopolymer of propylene, density: 910 kg / m ³ , MFR (230 ° C. ): 3 g / 10 min, 30 parts by mass (produced by Prime Polymer Co., Ltd.) using a twin screw extruder BT-30 (screw system 30 mmφ, L / D = 46) manufactured by Plastic Engineering Laboratory Co., Ltd. A biaxially stretched film was obtained in the same manner as in Example 1, except that a resin composition granulated under the conditions of a set temperature of 270 ° C., a resin extrusion rate of 60 g / min, and 200 rpm was used. Table 2 shows the evaluation results of the obtained biaxially stretched films.

[Example 4]
As the resin composition for the A layer, 30 parts by mass of a copolymer A1-2 and polypropylene A2-1 (Prime Polypro (registered trademark) F113G, a homopolymer of propylene, density: 910 kg / m ³ , MFR (230 ° C.): A biaxially stretched film was obtained in the same manner as in Example 1 except that 3 g / 10 min and 40 parts by mass of Prime Polymer Co., Ltd.) were mixed (dry blended). Table 2 shows the evaluation results of the obtained biaxially stretched films.

[Comparative Example 1]
As a resin composition of the A layer, 30 parts by mass of a copolymer A1-3 and polypropylene (Prime Polypro (registered trademark) F113G, density: 910 kg / m ³ , MFR (230 ° C.): 3 g / 10 min, Prime Co., Ltd.) Polymer (polymer) and 70 parts by mass were mixed (dry-blended) in the same manner as in Example 1 to obtain a biaxially stretched film. Table 2 shows the evaluation results of the obtained biaxially stretched films.

[Comparative Example 2]
A biaxially stretched film was obtained in the same manner as in Example 1 using 100 parts by mass of polypropylene (Prime Polypro (registered trademark) F107, manufactured by Prime Polymer Co., Ltd.) for both the A layer and the B layer. Table 2 shows the evaluation results of the obtained biaxially stretched films.

From Examples 1 to 4 in Table 2, it can be seen that the biaxially stretched film of the present invention has excellent peelability without peeling between layers.
Comparing Examples 1 to 3 with the case in which the polypropylene resin (A2-1) is used for both the A layer and the B layer (Comparative Example 2), an example in which the copolymer (A-1) is blended in the A layer. In the case of 1 to 3, the peeling stress to the pressure-sensitive adhesive tape after biaxial stretching, that is, the releasability is good. Examples 2 and 4 and the case where a 4-methyl-1-pentene copolymer (A1-3) having a high content of 4-methyl-1-pentene and having a melting point of 200 ° C. or higher was used ( Compared with Comparative Example 1), when the 4-methyl-1-pentene copolymer (A1-1) or (A1-2) according to the present invention is used for the A layer, delamination at the time of stretching occurs. It can be seen that the surface roughness was also low.

The film according to the present invention is extremely excellent in releasability, maintains the same mechanical properties as a conventional biaxially stretched film, and has a lower temperature than a conventional 4-methyl-1-pentene (co) polymer. It can be obtained by molding. Thereby, it can be suitably used as a release film for an optical use, a building material use, an automobile part use, and the like, particularly, a non-silicone type release film, a release liner, a separator film, and a surface protection film.

Claims (4)

A biaxially oriented polypropylene-based film in which the A layer and the B layer are laminated,
A layer is composed of a resin composition containing 4-methyl-1-pentene copolymer (A1) and polypropylene (A2),
The B layer is formed from a resin composition containing the same polypropylene (B1) as the polypropylene (A2),
The content of the 4-methyl-1-pentene copolymer (A1) is 5% by mass or more and 95% by mass or less with respect to the total mass of the A layer, and the content of the polypropylene (A2) is A layer. Is from 5% by mass to 95% by mass with respect to the total mass of the compound (here, the total of the component (A1) and the component (A2) is 100% by mass), and the 4-methyl-1-pentene copolymer is used. (A1) A film satisfying the following requirement [1].
[1] 96 mol% to 80 mol% of a structural unit derived from 4-methyl-1-pentene, and a structural unit derived from an olefin having 2 to 20 carbon atoms (excluding 4-methyl-1-pentene) The total is 4 to 20 mol% (provided that the total of the constitutional units derived from 4-methyl-1-pentene and the constitutional units derived from olefins having 2 to 20 carbon atoms is 100 mol%). The biaxially stretched polypropylene film according to claim 1, wherein the 4-methyl-1-pentene copolymer (A1) satisfies all of the following requirements [2] to [5].
[2] Intrinsic viscosity [η] measured in decalin at 135 ° C is 0.5 to 5.0 dl / g [3] Weight average molecular weight (Mw) and number average measured by gel permeation chromatography (GPC) molecular weight which is the ratio molecular weight distribution of the (Mn) (Mw / Mn) is 1.0 to 3.5 [4] melting point density was measured with a ^{825~860kg / m 3 [5] DSC} (Tm) Is in the range of 100 ° C to 199 ° C   The biaxially stretched polypropylene film according to claim 1 or 2, wherein the 4-methyl-1-pentene copolymer (A1) has a melting point (Tm) measured by DSC in the range of 100C to 180C. The layer configuration is a three-layer configuration of A layer / B layer / A layer or A layer / B layer / C layer (here, the C layer is different from both the A layer and the B layer) The biaxially stretched film according to any one of claims 1 to 3 , characterized in that: