JPWO2021070672A1 - Polyolefin film - Google Patents

Abstract

An object of the present invention is to provide a film having excellent transparency, slipperiness, and heat resistance. The crystallization temperature Tc ₀ obtained by measuring the film by DSC and externalizing the film is 110 ° C. or higher. The main purpose of the film is a polyolefin film having an in-plane phase difference of 400 nm or less and a dynamic friction coefficient μd of 0.7 or less after heating at 130 ° C. for 10 minutes.

Description

The present invention relates to a polyolefin film having excellent transparency, slipperiness, and heat resistance, which can be suitably used as a film for industrial materials.

Since polyolefin films are excellent in transparency, mechanical properties, electrical properties, etc., they are used in various applications such as packaging applications, mold release applications, tape applications, and electrical applications such as cable wrapping and capacitors. In particular, since it has excellent surface releasability and mechanical properties, it is suitably used as a releasable film or process film for various members such as plastic products, building materials, and optical members.

When it is used as a protective film or a cover film, it may be confirmed whether or not there is a defect in the adherend while it is attached to the adherend. At that time, if the transparency of the protective film or the cover film is low, it may be difficult to confirm the defects of the adherend. In particular, when used as a protective film for a retardation plate, not only transparency but also low retardation characteristics are required, and the required level has been increasing in recent years.

In general, when trying to increase the transparency, the film surface is also smoothed, so that the slipperiness is impaired, and wrinkles are less likely to occur during process transfer, and the flatness may be deteriorated. Further, when trying to increase the transparency, a method of lowering the crystallinity of the polyolefin resin is used. However, when the crystallinity is lowered, when the film is exposed to a high temperature environment, the low melting point portion of the film surface is partially melted, the coefficient of kinetic friction is increased, and the slipperiness may be further impaired. As described above, conventionally, it has been difficult to achieve both smoothness and slipperiness.

From the above, a film for industrial materials that satisfies the required characteristics is required to have transparency, slipperiness, and heat resistance.

As a film in which the in-plane retardation of the film is reduced, for example, Patent Document 1 describes an example in which the retardation is reduced by adding a polypropylene resin having a low melting point to the inner layer of the film. Further, as a film having improved slipperiness, for example, Patent Document 2 describes an example in which the cast temperature is raised, a large amount of β crystals are formed, and the surface is roughened to make the film slippery. Further, Patent Document 3 describes a film in which the phase difference is reduced by using a cyclic olefin resin.

International Publication No. 2015/129851 Japanese Unexamined Patent Publication No. 2001-247693 JP-A-2018-126909

However, the method described in Patent Document 1 described above has a problem that the film surface is smooth and the slipperiness is low, and particularly the slipperiness after high temperature heating is low and the flatness is insufficient. Further, in the method described in Patent Document 2, the surface roughness is high and the in-plane phase difference of the film is insufficient. Further, the method described in Patent Document 3 has problems that the film itself is brittle, handling is insufficient, and the cost is high.

Therefore, an object of the present invention is to solve the above-mentioned problems. That is, it is an object of the present invention to provide a polyolefin film having excellent transparency, slipperiness and heat resistance.

In order to solve the above-mentioned problems and achieve the object, the polyolefin film of the present invention has a crystallization temperature Tc ₀ of 110 ° C. or higher obtained by measuring the film by DSC and extrapolation point method, and the surface of the film. The inner phase difference is 400 nm or less, and the dynamic friction coefficient μd after heating at 130 ° C. for 10 minutes is 0.7 or less.

Since the polyolefin film of the present invention is excellent in transparency, heat resistance, and slipperiness, it can be widely and suitably used as a film for industrial materials.

This is an example of a graph showing the crystallization temperature T _{c0 of the polyolefin film.}

In the polyolefin film of the present invention, the film is measured by DSC, the crystallization temperature Tc ₀ determined by the extrapolation point method is 110 ° C. or higher, the in-plane retardation of the film is 400 nm or less, and the film is heated at 130 ° C. for 10 minutes. The subsequent dynamic friction coefficient μd is 0.7 or less. The polyolefin film refers to a film containing a polyolefin resin in an amount of more than 50% by mass and 100% by mass or less when all the components constituting the film are 100% by mass. Further, the polyolefin resin refers to a resin in which the olefin unit accounts for 100 mol%, which is more than 50 mol%, in all the constituent units constituting the resin.

_{The polyolefin film of the present invention has a crystallization temperature Tc 0} of 110 ° C. or higher, preferably 115 ° C. or higher, more preferably 118 ° C. or higher, further preferably 118 ° C. or higher, which is obtained by measuring the film with DSC and using an extrapolation point method. Is above 123 ° C. When Tc ₀ is less than 110 ° C., for example, coarse spherulites are formed during casting and the in-plane retardation becomes large, which makes it difficult to inspect the retardation characteristics of the adherend when used as a retardation protection film. May occur. In order to set Tc ₀ to 110 ° C. or higher, for example, the raw material composition of the polyolefin film is set in the range described later, and it is particularly preferable to add a raw material having a nucleating agent action, and among them, a branched chain polypropylene raw material may be added. preferable. It is also effective to adjust the amounts of the high molecular weight component and the low molecular weight component of the polypropylene resin used for the polyolefin film within a specific range. The upper limit of the crystallization temperature Tc ₀ is not particularly limited, but is substantially 135 ° C. The DSC means a differential scanning calorimeter.

In the polyolefin film of the present invention, the in-plane retardation of the film is 400 nm or less, preferably 300 nm or less, more preferably 200 nm or less, still more preferably 100 nm or less. If the in-plane retardation is larger than 400 nm, for example, when used as a retardation protection film, a problem may occur when inspecting the retardation characteristics in a state of being bonded to an adherend. In order to make the in-plane phase difference 400 nm or less, for example, the raw material composition of the polyolefin film is set to the range described later, and the film forming conditions are set to the range described later. By reducing the size of spherulites, lowering the extrusion temperature and the temperature of the cast drum to increase the cooling during casting, increasing the preheating temperature during longitudinal / horizontal stretching, and performing stretching at a low temperature, the film is uniformly stretched. It is effective to do. The lower limit of the in-plane phase difference is not particularly limited, but is substantially about 30 nm.

In the polyolefin film of the present invention, the coefficient of kinetic friction μd in the direction orthogonal to the main orientation direction after heat treatment at 130 ° C. for 10 minutes (hereinafter, also referred to as the main orientation orthogonal direction) is 0.7 or less. It is more preferably 0.6 or less, still more preferably 0.5 or less. The main orientation direction in the present invention is, in the film plane, when an arbitrary direction is 0 °, each direction forming an angle of 0 ° to 175 ° in 5 ° increments with respect to the arbitrary direction. When the Young's modulus is measured with, it means the direction showing the highest value. In the polyolefin film of the present invention, the direction parallel to the film forming direction of the polyolefin film is referred to as the film forming direction, the longitudinal direction or the MD direction, and the direction orthogonal to the film forming direction in the film surface is the width direction or TD. Called direction.

When the polyolefin film of the present invention is used as a protective film, it may go through various high temperature steps. For example, when it is used as a release film of a thermosetting resin, it may be heat-cured in a temperature range of about 120 to 150 ° C. after being bonded to the thermosetting resin. Further, when used as a film for a capacitor, radiant heat of 130 to 150 ° C. may be applied during metal sputtering. A method of lowering the crystallinity of a polyolefin film when smoothing the polyolefin film is well known. In such a case, when high temperature heat is applied, the low melting point resin portion of the surface layer melts and μd is reduced. It may be large. Since the μd after heating at 130 ° C. for 10 minutes is 0.7 or less, for example, when used as a release film or a film for a capacitor, wrinkles may be formed on the transport roll by passing through a high temperature process. It is possible to reduce winding misalignment when winding together with the adherend.

In order to reduce the μd after heating at 130 ° C. for 10 minutes to 0.7 or less, for example, the raw material composition of the polyolefin film is set to the range described later, and the film forming conditions are set to the range described later. It is effective to raise the temperature and perform stretching at a low temperature at a high magnification and uniformly at a high magnification, and to carry out heat treatment and relaxation after biaxial stretching within a range as described later. The lower limit of μd after heating at 130 ° C. for 10 minutes is not particularly limited, but is substantially about 0.1.

The polyolefin film of the present invention preferably has a breaking elongation at 130 ° C. in the direction orthogonal to the main orientation of the film of 100% or more. It is more preferably 110% or more, still more preferably 120% or more. When the breaking elongation at 130 ° C. is 100% or more, the breaking of the polyolefin film can be reduced, for example, in the transfer step in which high-temperature heat is applied as described above.

In order to set the elongation at break at 130 ° C. to 100% or more, for example, the raw material composition of the film is set within the range described later, and in particular, a raw material having a high crystallization temperature is used, and the preheating temperature during longitudinal / horizontal stretching is increased. It is effective to stretch the film at a low temperature at a high magnification and uniformly at a high magnification. The upper limit of the elongation at break at 130 ° C. is not particularly limited, but is substantially about 300%.

The polyolefin film of the present invention preferably has an internal haze (hereinafter, also simply referred to as haze) of 1.0% or less after heating at 130 ° C. for 10 minutes. It is more preferably 0.6% or less, still more preferably 0.3% or less. Since the haze after heating at 130 ° C. for 10 minutes is 1.0% or less, for example, when used as a protective film, the transparency of the protective film remains even after passing through the transfer step in which high temperature heat is applied as described above. It is maintained and the defects that occur when inspecting with a defect inspection machine in the state of being attached to the adherend are reduced.

Generally, in order to reduce the haze, a means for reducing the crystallinity of the polyolefin resin may be used. Therefore, a polyolefin resin having low stereoregularity may be used, or a copolymer having a low melting point may be added. However, when such a resin having a low melting point is used, the mobility of the amorphous portion in the polyolefin film becomes high, and when high temperature heat of 130 ° C. or higher is applied, additives such as antioxidants in the polyolefin are applied to the film. It may bleed out to the surface and impair transparency.

Based on the above points, in order to reduce the haze after heating at 130 ° C. to 1.0% or less, for example, the raw material composition of the film is set to the range described later, and the film forming conditions are set to the range described later, particularly crystallization. Using high temperature raw materials, reduce the spheres formed during casting, lower the extrusion temperature and the temperature of the cast drum to increase the cooling during casting, increase the preheating temperature during longitudinal / horizontal stretching, and stretch. It is effective to stretch the film uniformly at a low temperature. It is also effective to use a raw material having high stereoregularity and a low cold xylene-soluble portion (hereinafter, CXS) to enhance crystallinity, and to perform heat treatment and relaxation after longitudinal and transverse stretching. The lower limit of haze after heating at 130 ° C. for 10 minutes is not particularly limited, but is substantially about 0.05%.

In the polyolefin film of the present invention, it is preferable that the uneven orientation angle within a 10 cm square of the film is 3.0 ° or less. It is more preferably 2.5 ° or less, still more preferably 2.0 ° or less. When the unevenness of the orientation angle is 3.0 ° or less, it is possible to reduce problems that occur when inspecting the orientation angle, for example, in the state of being bonded to the adherend.

In order to make the unevenness of the orientation angle 3.0 ° or less, for example, the raw material composition of the film is set to the range described later, and the film forming conditions are set to the range described later. / It is effective to raise the preheating temperature at the time of lateral stretching, and to stretch the stretch at a low temperature at a high magnification and uniformly at a high magnification. The lower limit of the unevenness of the orientation angle is not particularly limited, but is substantially about 0.1%.

The thickness of the polyolefin film of the present invention is appropriately adjusted depending on the intended use and is not particularly limited, but is preferably 0.5 μm or more and 100 μm or less from the viewpoint of handleability. The upper limit of the thickness when used as a release film is more preferably 60 μm, further preferably 30 μm, and most preferably 16 μm. The lower limit is more preferably 4 μm, further preferably 8 μm, and most preferably 11 μm. Further, the upper limit of the thickness when used as a film for a capacitor is more preferably 15 μm, further preferably 8 μm, and most preferably 3 μm. The lower limit is more preferably 0.9 μm and even more preferably 1.5 μm. The thickness can be adjusted by adjusting the screw rotation speed of the extruder, the width of the unstretched sheet, the film forming speed, the stretching ratio, and the like within a range that does not deteriorate other physical properties.

Next, a resin or the like suitable for producing the polyolefin film of the present invention will be described, but the resin or the like constituting the polyolefin film of the present invention is not necessarily limited to this.

From the viewpoint of transparency and heat resistance, the polyolefin film of the present invention preferably contains polypropylene resin as a main component. In the present invention, the "main component" means that the ratio of the specific component to all the components is 50% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, still more preferable. Is 95% by mass or more and 100% by mass or less, more preferably 96% by mass or more and 100% by mass or less, particularly preferably 97% by mass or more and 100% by mass or less, and most preferably 98% by mass or more and 100% by mass or less. The polyolefin film of the present invention may contain only one kind of polypropylene resin, but preferably contains two or more kinds of polypropylene resins. When the film contains two or more components corresponding to polypropylene resin, if the total of these components is more than 50% by mass and 100% by mass or less, it is considered that "polypropylene resin is the main component". And.

The polypropylene resin is a polyolefin resin containing more than 50 mol% and 100 mol% or less of propylene units when all the constituent units constituting the molecular chain of the resin are 100 mol%. The polypropylene resin may be referred to as "polypropylene raw material" below.

The layer structure of the polyolefin film of the present invention is not particularly limited, and either a single layer or a laminated structure can be adopted, but from the viewpoint of satisfying different properties such as smoothness, slipperiness, and heat resistance. Therefore, it is preferable to have at least a surface layer (I) and a base layer (II). When the polyolefin film has a single-layer structure, it is preferable that the main component of the polyolefin film itself is polypropylene resin. When the polyolefin film has a laminated structure, it is preferable that the polyolefin film itself contains a polypropylene resin as a main component, and the main component of the base layer (II) described later is a polypropylene resin.

In the polyolefin film of the present invention, the content of the cyclic olefin resin in the film is preferably less than 2.0% by mass, assuming that the entire film is 100% by mass. It is more preferably less than 1.0% by mass, still more preferably less than 0.5% by mass. When the content of the cyclic olefin resin is less than 2.0% by mass, for example, even if a polypropylene resin having low compatibility with each other and a cyclic olefin resin are blended, the decrease in transparency of the polyolefin film is reduced. Further, since the cyclic olefin resin is brittle, when the content of the cyclic olefin resin is less than 2.0% by mass, it is possible to reduce breakage in a process in which tension is strong, and deterioration of handleability can be suppressed.

Hereinafter, the polypropylene resin (sometimes referred to as polypropylene raw material A) which is the main component of the polyolefin film of the present invention will be described.

The lower limit of the number average molecular weight (Mn) of the polypropylene raw material A is preferably 75,000, more preferably 80,000, and even more preferably 85,000, from the viewpoint of limiting the low molecular weight component to a certain amount or less. The upper limit of Mn is preferably 100,000, more preferably 94,000. Further, the lower limit of the Z + 1 average molecular weight (Mz + 1) is preferably 1.8 million, more preferably 2 million, from the viewpoint of containing a certain amount or more of the high molecular weight component. The upper limit of Mz + 1 is preferably 2.5 million, more preferably 2.2 million.

The melt flow rate (MFR) of the polypropylene raw material A is preferably in the range of 1 g / 10 minutes or more and 10 g / 10 minutes or less (230 ° C., 21.18 N load) from the viewpoint of film forming property and film strength. From the above viewpoint, the lower limit of MFR is more preferably 2 g / 10 minutes. The upper limit of MFR is more preferably 8 g / 10 minutes, further preferably 5 g / 10 minutes. In order to set the MFR to the above value, a method of controlling the average molecular weight or the molecular weight distribution is adopted. More specifically, a method of adjusting the hydrogen gas concentration at the time of polymerization, a method of appropriately selecting a catalyst and / or a co-catalyst, and a method of appropriately selecting a composition to control the molecular weight and molecular weight distribution of the polypropylene raw material are preferably adopted. NS. The lower the molecular weight, the higher the MFR, and the more low molecular weight components in the molecular weight distribution, the higher the MFR.

The melting point of the polypropylene raw material A is preferably 155 ° C. or higher, more preferably 160 ° C. or higher, still more preferably 165 ° C. or higher. When the melting point is 155 ° C. or higher, the heat resistance of the obtained polyolefin film becomes high. For example, when used as a release film, the film is formed even if it is subjected to a process of applying heat after being bonded to an adherend. The elongation in the tension direction due to the softening of the film is suppressed, and the deformation of the adherend is reduced.

The polypropylene raw material A preferably has a cold xylene-soluble portion (CXS) of 4% by mass or less and a mesopentad fraction of 0.90 or more in the polypropylene raw material A. By satisfying these conditions, deterioration of film forming stability, strength of the obtained polyolefin film, dimensional stability and heat resistance is reduced.

Here, CXS refers to a polyolefin component dissolved in xylene when the sample is completely dissolved in xylene and then precipitated at room temperature, which has low stereoregularity, low molecular weight, etc. It is considered that it corresponds to a component that is difficult to crystallize for the reason. If a large amount of such a component is contained in the resin, the thermal dimensional stability of the film may be inferior. Therefore, from the above viewpoint, CXS is preferably 3.5% by mass or less, more preferably 2.5% by mass or less, and further preferably 2.0% by mass or less. The lower the CXS, the more preferable, but the lower limit is about 0.1% by mass. CXS In such a range, a method of increasing the catalytic activity when obtaining the resin and a method of washing the obtained resin with a solvent or the olefin monomer itself can be used.

The mesopentad fraction of the polypropylene raw material A is preferably 0.94 or more, more preferably 0.96 or more, still more preferably 0.97 or more, and most preferably 0.98 or more. The mesopentad fraction is an index showing the stereoregularity of the polypropylene crystal phase measured by the nuclear magnetic resonance method (NMR method), and the higher the value, the higher the crystallinity, the higher the melting point, and the higher the temperature. This is preferable because it increases dimensional stability. The upper limit of the mesopentad fraction is not specified. In order to obtain a resin having such high stereoregularity, a method of washing the resin powder obtained with a solvent such as n-heptane, a method of appropriately selecting a catalyst and / or a co-catalyst, a method of appropriately selecting a composition, and the like are used. It is preferably adopted.

The polypropylene raw material A may contain other unsaturated hydrocarbon copolymerization components and the like as long as the object of the present invention is not impaired. Examples of the monomer components constituting such a copolymerization component include ethylene, propylene (in the case of a copolymerized blend), 1-butene, 1-pentene, 3-methylpentene-1, 3-methylbutene-1,1. -Hexene, 4-methylpentene-1,5-ethylhexene-1,1-octene, 1-decene, 1-dodecene, vinylcyclohexene, styrene, allylbenzene, cyclopentene, norbornene, 5-methyl-2-norbornene, etc. Can be mentioned.

The amount of the copolymerization component of the polypropylene raw material A is preferably 10 mol% or less. It is more preferably 5 mol% or less, still more preferably 3 mol% or less. The higher the content of the ethylene component, the lower the crystallinity and the easier it is to improve the transparency. However, if the content of the ethylene component exceeds 10 mol%, the strength of the film is lowered and the heat resistance is reduced. May decrease and the heat shrinkage rate may worsen. In addition, the resin may easily deteriorate during the extrusion process, and fish eyes may easily occur in the polyolefin film. The polyolefin film of the present invention may be a polypropylene resin different from the polypropylene raw material A (hereinafter referred to as polypropylene raw material B). There is.) Can be included. By containing the polypropylene raw material B, the low molecular weight component may act as a stretching aid during stretching, contributing to suppression of film rupture during stretching and reduction of physical characteristic spots.

The upper limit of the number average molecular weight (Mn) of the polypropylene raw material B is preferably 75,000, more preferably 7,000,000, and even more preferably 65,000, from the viewpoint of containing a certain amount or more of low molecular weight components. The lower limit of Mn is preferably 50,000, more preferably 55,000, and even more preferably 62,000. Further, the upper limit of the Z + 1 average molecular weight (Mz + 1) is preferably 2 million, more preferably 1.8 million, from the viewpoint of suppressing the high molecular weight component to a certain level or less. The lower limit of Mz + 1 is preferably 1.1 million, more preferably 1.3 million, and even more preferably 1.55 million. The Mn and Mz + 1 of the polypropylene raw material B are smaller than the Mn and Mz + 1 of the polypropylene raw material A.

The melt flow rate (MFR) of the polypropylene raw material B is preferably in the range of 3 g / 10 minutes or more and 11 g / 10 minutes or less (230 ° C., 21.18 N load) from the viewpoint of extrusion stability. The lower limit of the MFR of the polypropylene raw material B is more preferably 3.5 g / 10 minutes. The upper limit of the MFR of the polypropylene raw material B is more preferably 9 g / 10 minutes, still more preferably 8 g / 10 minutes. In order to set the MFR of the polypropylene raw material B to the above value, a method of controlling the average molecular weight or the molecular weight distribution is adopted. More specifically, a method of adjusting the hydrogen gas concentration at the time of polymerization, a method of appropriately selecting a catalyst and / or a co-catalyst, and a method of appropriately selecting a composition to control the molecular weight and molecular weight distribution of the polypropylene raw material B are preferably adopted. Will be done. The lower the molecular weight, the higher the MFR, and the more low molecular weight components in the molecular weight distribution, the higher the MFR.

The polyolefin film of the present invention may contain a branched polypropylene resin (hereinafter, may be referred to as a branched polypropylene raw material) in addition to the polypropylene raw material A and the polypropylene raw material B, both of which are linear. By containing the branched-chain polypropylene raw material, the formation of coarse spherulites at the time of casting is suppressed due to the effect of the nucleating agent, so that SPk and crystallite size can be reduced.

The MFR of the branched-chain polypropylene raw material is preferably 0.5 g / 10 minutes or more and 9 g / 10 minutes or less (230 ° C., 21.18 N load) from the viewpoint of extrusion stability. The lower limit of the MFR of the branched-chain polypropylene raw material is more preferably 2 g / 10 minutes, further preferably 6 g / 10 minutes. In order to set the MFR to the above value, a method of controlling the average molecular weight or the molecular weight distribution is adopted. More specifically, a method of adjusting the hydrogen gas concentration at the time of polymerization, a method of appropriately selecting a catalyst and / or a co-catalyst, and a method of appropriately selecting a composition to control the molecular weight and molecular weight distribution of the polypropylene raw material are preferably adopted. NS. The lower the molecular weight, the higher the MFR, and the more low molecular weight components in the molecular weight distribution, the higher the MFR.

The melt tension of the branched-chain polypropylene raw material is preferably 3 gf or more and 40 gf or less from the viewpoint of stretching uniformity. The lower limit of the melt tension is more preferably 4 gf, and even more preferably 6 gf. The upper limit is more preferably 30 gf and even more preferably 25 gf. In order to set the melt tension to the above value, a method of controlling the average molecular weight, the molecular weight distribution, the degree of branching in the polypropylene raw material, or the like is adopted. In particular, when it has a long chain branch, the melt tension can be dramatically increased, and it can be adjusted to a preferable value by adjusting the molecular chain of the long chain branch and the degree of branching.

A plurality of branched polypropylene raw materials such as Ziegler-Natta catalyst system and metallocene catalyst system are commercially available, but from the viewpoint of being used in combination with polypropylene raw material A and polypropylene raw material B, there are few low molecular weight components and high molecular weight components, and the molecular weight is small. A metallocene catalyst system with a narrow distribution is more preferable.

The polypropylene raw material A and the polypropylene raw material B used in the polyolefin film of the present invention, and the branched polypropylene raw material have various additives such as a crystal nucleating agent, an antioxidant, and a heat stabilizer, as long as the object of the present invention is not impaired. It can also contain a slip agent, an antistatic agent, an antiblocking agent, a filler, a viscosity modifier, an anticoloring agent and the like.

Among these, selection of the type and amount of the antioxidant is important from the viewpoint of bleed-out of the antioxidant. That is, the antioxidant is preferably a phenolic agent having steric hindrance, and at least one of them is a high molecular weight type having a molecular weight of 500 or more. Specific examples thereof include various examples. For example, 1,3,5-trimethyl-2,4,6-with 2,6-di-t-butyl-p-cresol (BHT: molecular weight 220.4). Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (eg, BASF's "Irganox"® 1330: molecular weight 775.2) or tetrakis [methylene-3 (3,5-di-) It is preferable to use t-butyl-4-hydroxyphenyl) propionate] methane (for example, "Irganox" (registered trademark) 1010 manufactured by BASF Corporation: molecular weight 1177.7) or the like.

The total content of these antioxidants is preferably in the range of 0.03 to 1.0 parts by mass with respect to the total amount of the polyolefin raw material. If the amount of the antioxidant is too small, the polymer may deteriorate in the extrusion process and the film may be colored, or the long-term heat resistance may be inferior. If there are too many antioxidants, the bleed-out of these antioxidants may reduce transparency. From the above viewpoint, the content of the antioxidant is more preferably 0.05 to 0.9 parts by mass, and particularly preferably 0.1 to 0.8 parts by mass.

A crystal nucleating agent can be added to the polyolefin raw materials A and B used in the polyolefin film of the present invention within a range not contrary to the object of the present invention. Further, it may contain a branched-chain polypropylene, and the branched-chain polypropylene already has an α-crystal or β-crystal crystal nucleating agent effect by itself, but another type of α-crystal nucleating agent (dibenzylidene sorbitols). , Sodium benzoate, etc.), β-crystal nucleating agent (amide compound such as potassium 1,2-hydroxystearate, magnesium benzoate, N, N'-dicyclohexyl-2,6-naphthalenedicarboxamide, quinacridone compound, etc.) Etc. are exemplified. However, if the above-mentioned other type of nucleating agent is excessively contained, it may cause a decrease in stretchability and a decrease in transparency and strength due to void formation, etc., so the content is usually 0.5% by mass with respect to the total amount of the polyolefin raw material. Parts or less, preferably 0.1 parts by mass or less, more preferably 0.05 parts by mass or less.

The polyolefin film of the present invention preferably does not contain organic particles and inorganic particles. Since the polypropylene resin that can be preferably used as the main component of the polyolefin film of the present invention has low affinity with organic particles and inorganic particles, the particles may fall off and contaminate the process or the product. Further, when coarse protrusions are formed by particles having high hardness, uneven transfer may occur to the resin layer of the optical member, and when used as a protective film or a base film for manufacturing of products requiring high quality such as display members. May cause quality deterioration. From the above viewpoint, it is preferable that the polyolefin film of the present invention does not contain lubricants such as organic particles and inorganic particles.

In the polyolefin film of the present invention, the ratio of the polypropylene raw material A, the polypropylene raw material B, and the branched-chain polypropylene raw material to the total amount of the resin component is preferably as follows. The polypropylene raw material A is preferably 50% by mass or more and 99.9% by mass or less from the viewpoint of film surface smoothness and mechanical strength. The lower limit of the proportion of the polypropylene raw material A is more preferably 60% by mass, further preferably 70% by mass. The upper limit is more preferably 99% by mass, further preferably 98% by mass. The proportion of the polypropylene raw material B is preferably 0.1% by mass or more and 50% by mass or less of the entire film. The lower limit of the proportion of the polypropylene raw material B is more preferably 0.5% by mass, further preferably 3% by mass. The upper limit is more preferably 30% by mass, further preferably 20% by mass. The ratio of the branched-chain polypropylene raw material is preferably 0.1% by mass or more and 30% by mass or less of the entire film. The lower limit of the proportion of the polypropylene raw material B is more preferably 0.2% by mass, further preferably 0.5% by mass, and most preferably 1.0% by mass. The upper limit is more preferably 20% by mass, further preferably 10% by mass.

In the polyolefin film of the present invention, it is preferable to add polypropylene raw material B or branched-chain polypropylene raw material, or both polypropylene raw material B and branched-chain polypropylene raw material to the above-mentioned polypropylene raw material A.

The polyolefin film of the present invention has a differential distribution value of 3% or more and 15% or less when the logarithmic molecular weight Log (M) is 4.0 in the molecular weight distribution curve measured by the gel permeation chromatograph method described later. preferable. When the logarithmic molecular weight Log (M) is 4.0 and the differential distribution value is less than 3%, there are few low molecular weight components that serve as lubricating components during stretching, and fractures may easily occur during stretching. If the differential distribution value when the logarithmic molecular weight Log (M) is 4.0 is larger than 15%, the heat resistance of the polyolefin film may decrease. From the above viewpoint, the lower limit of the differential distribution value when the logarithmic molecular weight Log (M) is 4.0 is more preferably 4% and further preferably 5%. When the logarithmic molecular weight Log (M) is 4.0, the upper limit of the differential distribution value is more preferably 13%, further preferably 10%.

The polyolefin film of the present invention preferably has a differential distribution value of 1% or more and 15% or less when the logarithmic molecular weight Log (M) is 6.1 in the molecular weight distribution curve measured by the gel permeation chromatograph method. When the logarithmic molecular weight Log (M) is 6.1 and the differential distribution value is less than 1%, there are few high molecular weight components that become tie molecules during stretching, and the uniformity during stretching may be inferior. When the differential distribution value when the logarithmic molecular weight Log (M) is 6.1 is larger than 15%, after winding the polyolefin film as a roll, the room temperature shrinkage over time becomes large and the flatness of the film roll is impaired. There is. From the above viewpoint, the lower limit of the differential distribution value when the logarithmic molecular weight Log (M) is 6.1 is more preferably 5%, further preferably 7%. When the logarithmic molecular weight Log (M) is 6.1, the upper limit of the differential distribution value is more preferably 13%, further preferably 11%.

The polyolefin film of the present invention is preferably biaxially stretched using the above-mentioned raw materials. The biaxial stretching method can be obtained by any of the simultaneous inflation biaxial stretching method, the simultaneous biaxial stretching method of the stenter, and the sequential biaxial stretching method of the stenter. Among them, the film forming stability, the thickness uniformity, and the film It is preferable to adopt the stenter sequential biaxial stretching method in terms of controlling high rigidity and dimensional stability.

Next, one aspect of the method for producing a polyolefin film of the present invention will be described by taking a polypropylene film having a two-kind, three-layer structure as an example, but the method for producing a polyolefin film of the present invention is not necessarily limited to this.

First, 80 parts by mass of polypropylene raw material A, 15 parts by mass of polypropylene raw material B, and 5 parts by mass of branched polypropylene raw material are dry-blended to form a single shaft for the base layer (II) (hereinafter, may be referred to as layer B). It is supplied to the extruder, and the polypropylene raw material B is supplied to the uniaxial extruder for the surface layer (I) (hereinafter, may be referred to as the A layer). After that, melt extrusion is performed at 200 to 280 ° C., more preferably 220 to 280 ° C., and even more preferably 240 to 270 ° C., respectively. Then, after removing foreign substances and modified polymers with a filter installed in the middle of the polymer tube, they are laminated with a multi-manifold type A layer / B layer / A layer composite T-die and discharged onto a casting drum for cooling. By solidifying, a laminated unstretched sheet having a layer structure of A layer / B layer / A layer is obtained. At this time, the laminated thickness ratio is preferably in the range of 1/8/1 to 1/60/1. Within the above range, the surface layer containing the polypropylene raw material A is thinly and uniformly formed on the film surface, the height uniformity of the protrusions formed during stretching is increased, and the formation of coarse protrusions can be suppressed.

The surface temperature of the casting drum is 10 to 50 ° C., preferably 10 to 40 ° C., more preferably 15 to 30 ° C., and even more preferably 15 to 20 ° C. Further, the layer structure may be a two-layer laminated structure of A layer / B layer. As the adhesion method to the casting drum, any of the electrostatic application method, the adhesion method using the surface tension of water, the air knife method, the press roll method, the underwater casting method, etc. may be used, but the flatness is good. The air knife method, which can control the surface roughness, is preferable. From the viewpoint of cooling the uncooled drum surface of the sheet on the casting drum, it is preferable to lower the air temperature of the air knife. The air temperature of the air knife is 10 to 50 ° C., preferably 10 to 40 ° C., more preferably 15 to 30 ° C., further preferably 20 to 25 ° C., and the blowing air speed is preferably 130 to 150 m / s. Further, it is preferable to appropriately adjust the position of the air knife so that air flows to the downstream side of the film formation so as not to cause vibration of the film. In the case of a two-type two-layer laminated structure of A layer / B layer, it is preferable that the A layer side is the casting drum side.

The obtained unstretched sheet is introduced into the longitudinal stretching step. In the longitudinal stretching step, first, a plurality of metal rolls kept at 80 ° C. or higher and 150 ° C. or lower, preferably 80 ° C. or higher and 130 ° C. or lower, more preferably 90 ° C. or higher and 130 ° C. or lower, still more preferably 100 ° C. or higher and 130 ° C. or lower are not formed. The stretched sheets were brought into contact with each other to be preheated, and the rolls provided with the peripheral speed difference were first stretched 1.1 to 3.0 times, more preferably 1.3 to 2.5 times in the longitudinal direction, and then subsequently. , 2.0 to 5.0 times, more preferably 3.0 to 4.5 times in the longitudinal direction, and cooled to room temperature. The stretching temperature of the first stage is 80 ° C. or higher and 130 ° C. or lower, preferably 90 ° C. or higher and 130 ° C. or lower, more preferably 100 ° C. or higher and 130 ° C. or lower, and the stretching temperature of the second stage is 130 ° C. or higher and 150 ° C. or lower. It is preferably 140 ° C. or higher and 150 ° C. or lower, and more preferably 145 ° C. or higher and 150 ° C. or lower. In the first half of the longitudinal stretching, the film is stretched at a low temperature and a high stress at a low magnification and then stretched at a high temperature at a stretch to obtain a highly uniform, highly oriented uniaxially stretched film that is uniformly oriented in the longitudinal direction over the entire width.

When the longitudinal stretching temperature of the first stage and the longitudinal stretching temperature of the second stage are significantly different, the film shrinks in the width direction when it comes into contact with a high-temperature stretching roll. At that time, the film shrinks unevenly, which may cause wrinkles in the flow direction. As a countermeasure, a ceramic roll was used as the stretching roll. On the ceramic roll, the film becomes slippery, and the film shrinks uniformly, so that the film can be stretched without wrinkles. If the total draw ratio of the two-stage stretching is less than 3.0 times, the orientation of the film becomes weak and the strength may decrease. Therefore, 3.0 times or more and 6.0 times or less are preferable, and 4.0 times or less. It is more preferably 5.5 times or more.

Next, both ends in the width direction are gripped with clips, the uniaxially stretched film is guided to the tenter, preheated, and then laterally stretched 7.0 to 13 times in the width direction. The preheating temperature is 165 to 180 ° C, more preferably 168 to 180 ° C, and even more preferably 170 to 180 ° C. The stretching temperature is 148 to 165 ° C, more preferably 148 to 160 ° C, and even more preferably 148 to 155 ° C. By increasing the preheating temperature by 5 ° C. or higher, preferably 8 ° C. or higher, more preferably 10 ° C. or higher with respect to the stretching temperature, highly oriented stretching can be performed uniformly over the entire width of the film, and the smoothness of the obtained polyolefin film can be improved. Is preferable.

In the subsequent heat treatment and relaxation treatment steps, while tension-grasping the width direction with a clip, relaxation is applied at a relaxation rate of 5 to 20%, more preferably 8 to 18%, still more preferably 11 to 18% in the width direction, and 160 ° C. Heat-fixed at a temperature of 180 ° C. or lower, preferably 165 ° C. or higher and lower than 180 ° C., more preferably 168 ° C. or higher and lower than 180 ° C., more preferably 170 ° C. or higher and lower than 180 ° C. As it is, it is guided to the outside of the tenter through a cooling step at 80 to 100 ° C., the clip at the end of the film is released, the edge of the film is slit in the winder step, and the film product roll is wound up. The heat treatment temperature is 5 ° C. or higher, more preferably 8 ° C. or higher, more preferably 10 ° C. or higher with respect to the transverse stretching temperature, thereby relaxing the residual stress in the film and lowering the heat shrinkage rate. be able to.

Further, when the polyolefin film coming out of the tenter passes through the migration, it is preferable to heat it with a hot roll from the viewpoint of heat resistance. The heating temperature is preferably 70 ° C. or higher, more preferably 80 ° C. or higher, further preferably 100 ° C. or higher, and particularly preferably 120 ° C. or higher. At a temperature of 140 ° C. or higher, the slipperiness of the hot roll and the polyolefin film is impaired, wrinkles may occur, and the flatness may deteriorate. Therefore, the upper limit is about 140 ° C. The heating time is preferably 0.2 seconds or longer, more preferably 0.4 seconds or longer. The upper limit of the heating time is not particularly limited, but from the viewpoint of productivity, the upper limit is about 2.0 seconds.

The polyolefin film obtained as described above can be used in various industrial applications such as packaging films, surface protective films, process films, sanitary products, agricultural products, construction products, medical products, and condenser films. Since it is particularly excellent in surface smoothness, it can be preferably used as a surface protective film, a process film, a mold release film, and a condenser film. Here, the surface protective film refers to a film having a function of being attached to an object such as a molded product or a film to prevent scratches and contamination generated during processing and transportation. A process film is a film that is attached to an object such as a molded product or film to prevent scratches and contamination that occur during manufacturing and processing, and is discarded when used as a final product. A mold release film has high mold releasability, is attached to an object such as a molded product or film, prevents scratches and contamination that occur during processing and transportation, and easily peels off when used as a final product. , A film having a function that can be discarded. The capacitor film refers to a film used for a film capacitor using a resin film as a dielectric.

Hereinafter, the present invention will be described in detail with reference to Examples. The characteristics were measured and evaluated by the following methods.

(1) Film thickness Measured using a micro-thickness meter (manufactured by Anritsu). The film was sampled in a 10 cm square, and 5 points were arbitrarily measured, and the average value was calculated.

(2) Crystallization temperature T _{c0 obtained by extrapolation point method}
Using a differential scanning calorimeter (EXSTAR DSC6220 manufactured by Seiko Instruments Inc.), a 3 mg polyolefin film was heated from 25 ° C. to 250 ° C. at 20 ° C./min in a nitrogen atmosphere and held for 5 minutes. Then, the temperature was lowered from 250 ° C. to 25 ° C. at 10 ° C./min. The same procedure was repeated 5 times, and the arithmetic mean value of the peak temperature of the heat generation curve obtained at the time of temperature decrease in each time was defined as T _c10 . Then, the polyolefin film sampled in the same manner was heated from 25 ° C. to 250 ° C. at 20 ° C./min and held for 5 minutes. Then, the temperature was lowered from 250 ° C. to 25 ° C. at 40 ° C./min. The same procedure was repeated 5 times, and the arithmetic mean value of the peak temperature of the heat generation curve obtained at the time of temperature decrease in each time was defined as T _c40 . Next, as shown in FIG. 1, the horizontal axis plots the _{temperature lowering rate, and the vertical axis plots the crystallization temperatures T c10} and T _c40 obtained at each temperature lowering rate, and a straight line is drawn from T _{c40 to T c10.} The crystallization temperature when the temperature was dropped to 0 ° C./min was _defined as T c0. In _{each measurement for measuring T c10} and T _c40 , when a plurality of peak temperatures could be observed, the temperature of the highest peak in the region of 80 ° C. to 130 ° C. was used as the peak temperature.

(3) Dynamic friction coefficient μd in the direction orthogonal to the main orientation after heat treatment at 130 ° C. for 10 minutes
A polyolefin film is cut into a width of 6.5 cm and a length of 12 cm, a test piece is sandwiched between papers, heated in an oven kept at 130 ° C. with no load, heated for 10 minutes, taken out, cooled at room temperature, and then Toyo Seiki ( Using a slip tester manufactured by Co., Ltd., the measurement was carried out at 25 ° C. and 65% RH according to JIS K 7125 (1999). The measurement was carried out in the directions orthogonal to the main orientation, and the different surfaces were overlapped with each other, that is, the front surface of one film and the back surface of the other film were overlapped with each other. The same measurement was performed 5 times for each sample, and the average value of the obtained values was calculated and used as the coefficient of dynamic friction (μd) of the sample. As for the main orientation direction, when an arbitrary direction is 0 ° in the film plane, the Young's modulus is set in each direction forming an angle of 0 ° to 175 ° in 5 ° increments with respect to the arbitrary direction. The direction showing the highest value when measured was defined as the main orientation direction.

The Young's modulus was measured by the following procedure. First, a sample was cut into a rectangle having a length (measurement direction) of 150 mm and a width of 10 mm. Tensile test using a tensile tester (Orientec "Tencilon" (registered trademark) UCT-100) at room temperature of 23 ° C and relative humidity of 65%, with an initial tensile chuck distance of 50 mm and a tensile speed of 300 mm / min. Was done. The F2 value is the value obtained by reading the load applied to the film when the sample is stretched by 2% (when the distance between chucks is 51 mm) and dividing by the cross-sectional area (film thickness x 10 mm) of the sample before the test. The slope of a straight line passing through the point used for measuring the F2 value was defined as Young's modulus.

(4) In-plane phase difference The in-plane phase difference of the polyolefin film with respect to a light beam having a wavelength of 548.3 nm was measured using an automatic birefringence meter (KOBRA-21ADH) manufactured by Oji Measurement Co., Ltd.

(5) Elongation at break in the direction orthogonal to the main orientation of the film at 130 ° C. Five samples with a width of 10 mm and a length of 50 mm (measurement direction) were cut out from the polyolefin film so that the direction orthogonal to the main orientation was the measurement direction. The test length was set to 20 mm by marking the positions from 15 mm to 15 mm. Next, the rectangular sample was set in a tensile tester (Orientech's "Tencilon" (registered trademark) UCT-100) with an initial chuck distance of 20 mm and heated in an oven heated to 130 ° C. for 1 minute. After that, a tensile test of the film was carried out at a tensile speed of 300 mm / min to obtain elongation (unit:%) and strength (unit: MPa) at the time when the sample broke. The measurement was performed 5 times, and the average value of the elongation at the time when the sample broke was calculated and used as the elongation at break (%).

(6) Internal haze after heat treatment at 130 ° C. for 10 minutes A polyolefin film was cut into a width of 3.0 cm and a length of 6.0 cm, and a test piece was sandwiched between papers in an oven kept at 130 ° C. with no load. After heating for 10 minutes, it was taken out and cooled at room temperature to prepare a sample. As a measuring device, a haze meter (HGM-2DP) manufactured by Suga Test Instruments Co., Ltd. was used. The value of the internal haze was determined in accordance with the provisions of JIS K7136 (2000) from the measured value of the haze when the film was immersed in a quartz cell having an optical path length of 1 cm in which the sample was filled with tetralin.

(7) Spots of orientation angle within 10 cm square of the film A polyolefin film was cut into a width of 10 cm and a length of 10 cm, and from the center of the cut sample, 11 points at 1 cm intervals in the film main orientation direction, and from the center of the film. A total of 21 points other than the central part of the film were set as measurement points at 1 cm intervals in the direction orthogonal to the main orientation of the film, and the orientation angles at each point were measured, and the unevenness of the orientation angle was obtained from the following formula. The orientation angle is measured using a phase difference measuring device (KOBRA-21ADH) manufactured by Oji Measuring Instruments Co., Ltd. so that the main orientation direction of the polyolefin film is the angle of 0 ° defined by this measuring device. It was installed in the device, and the clockwise inclination was + and the counterclockwise was-with respect to the film main orientation direction.
Orientation angle spot (%) = ((maximum orientation angle value-minimum orientation angle value) / average orientation angle value) × 100.

(8) Melting tension The measurement was carried out under the following conditions using an apparatus according to JIS K 7199 (1999).
・ Equipment: Capillograph with melt tension tester 1BPMD-i (manufactured by Toyo Seiki Co., Ltd.)
・ Temperature: 230 ℃ (using heat insulation chamber)
・ Dice: L = 8 (mm), D = 2.095 (mm)
-Extrusion speed: 20 mm / min-Collecting speed: 15.7 m / min-Sample mass: 15-20 g.

(9) Protruding peak height SPk, average roughness Sa, maximum height Sz
The measurement is performed using a scanning white interference microscope "VS1540" (manufactured by Hitachi High-Tech Science Co., Ltd., measurement conditions and device configuration will be described later), and the shooting screen is complemented (completely complemented) by the attached analysis software, and polynomials are used. After surface correction by a fourth-order approximation, the surface shape was determined by processing with a median filter (3 × 3 pixels).

The measurement was performed at each measurement position by determining a total of nine measurement positions according to the following procedure, starting from the intersection of the diagonal lines of the polyolefin film cut into a square of 5 cm × 5 cm. The surface was changed and the same measurement was repeated. Then, SPk, Sa, and Sz of each measurement position were obtained for each surface according to the above procedure, and the average value of SPk, Sa, and Sz was calculated for each surface. Of the obtained values, the smaller SPk value was adopted as the SPk value of the film.

<How to determine the measurement position>
Measurement 1: Position measurement of the start point 2: Position measurement 3.0 mm to the right of the start point 3: Position measurement 6.0 mm to the right of the start point 4: Position measurement 3.0 mm below the start point 5: 3 from the start point 0.0 mm below, 3.0 mm right position measurement 6: 3.0 mm below the start point, 6.0 mm right position measurement 7: Position measurement 6.0 mm below the start point 8: 6.0 mm below the start point, 3.0 mm right position measurement 9: 6.0 mm below the start point, 6.0 mm right position <Measurement conditions and device configuration>
Objective lens: 10x
Lens barrel: 1x
Zoom lens: 1x
Wavelength filter: 530nm white
Measurement mode: Wave
Measurement software: VS-Measure 10.0.4.0
Analysis software: VS-Viewer 10.0.3.0
Measurement area: 561.1 μm × 561.5 μm
Number of pixels: 1,024 x 1,024.

(10) Number average molecular weight Mn, Z + 1 average molecular weight Mz + 1, molecular weight distribution value The polyolefin film was dissolved by stirring at 165 ° C. for 30 minutes using 1,2,4-trichlorobenzene as a solvent. Then, the mixture was filtered using a 0.5 μm filter, the molecular weight distribution of the filtrate was measured, and the differential distribution values when the logarithmic molecular weight Log (M) was 4.0 and 6.1 were read.
In addition, the number average molecular weight of the sample and the Z + 1 average molecular weight were determined using the calibration curve of the molecular weight prepared using the following standard sample.
-Device: High-temperature GPC device (equipment No. HT-GPC-1, PL-220 manufactured by Polymer Laboratories)
・ Detector: Differential refractometer RI
-Column: Shodex HT-G (guard column)
Shodex HT-806M (2 pcs) (φ8.0 mm x 30 cm, manufactured by Showa Denko)
・ Flow velocity: 1.0 mL / min
-Column temperature: 145 ° C
・ Injection amount: 0.200 mL
-Standard sample: Tosoh monodisperse polystyrene, Tokyo Kasei divencil.

(11) Evaluation of transfer to an adherend A polyolefin film and a 20 μm-thick “Zeonoa film” (registered trademark) manufactured by Nippon Zeon Co., Ltd. were sampled into a square with a width of 100 mm and a length of 100 mm. Lay the smaller surface so that the "Zeonor film" (registered trademark) is in contact with each other, sandwich it between two acrylic plates (width 100 mm, length 100 mm), apply a load of 3 kg, and apply a load of 3 kg at 23 ° C. It was allowed to stand for 24 hours in an atmosphere. After 24 hours, the surface of "Zeonoa film" (registered trademark) (the surface in contact with the polyolefin film) was visually observed and evaluated according to the following criteria. When the SPk values on the front and back sides were the same, the surface having the smaller average surface roughness Sa value was used as the bonded surface. Further, when the value of Sa is the same on the front and back sides, the surface having the smaller maximum surface roughness Sz is used as the bonded surface.
A: It is clean and is the same as before the load was applied.
B: Weak unevenness is confirmed.
C: Strong unevenness is confirmed.

(12) Flatness of Film A polyolefin film having a width of 500 mm and a length of 200 m was wound around a core, heated in an oven at 60 ° C. for 7 days, taken out, cooled to room temperature, and then wound around a core. The film is unwound by 1 m, and free tension (a state in which the film hangs vertically due to its own weight) and 1 kg / m and 3 kg / m tensions are evenly and evenly applied to the entire width of the film, resulting in dents and waviness. It was visually confirmed whether or not there was a poor flatness such as.
S: There is no part with poor flatness due to free tension.
A: With free tension, there are some areas with poor flatness, and with tension of 1 kg / m width, it disappears.
B: Some parts with poor flatness can be seen with a tension of 1 kg / m width, and disappear with a tension of 3 kg / m width.
C: A part with poor flatness does not disappear even with a tension of 3 kg / m width.

(Polypropylene raw material, etc.)
For the production of the polyolefin films of Examples and Comparative Examples, polypropylene raw materials having a number average molecular weight (Mn) and a Z + 1 average molecular weight (Mz + 1) shown in Table 1 below were used. These values are values evaluated in the form of raw material resin pellets. Two kinds of raw materials were prepared as PP raw material A and two kinds of raw materials as PP raw material B. Further, as the branched chain polypropylene raw material 1, the following was used.
Polypropylene raw material 1 (PP1): Prime Polymer Co., Ltd. Polypropylene raw material 2 (PP2): Prime Polymer Co., Ltd. Polypropylene raw material 3 (PP3): Sumitomo Chemical Co., Ltd. Polypropylene raw material 4 (PP4): Prime Co., Ltd. Polymer branched chain polypropylene raw material 1 (branched PP1): Metallocene catalytic system branched branched polypropylene raw material (manufactured by Japan Polypropylene Corporation, melt tension: 13 gf)
Branched chain polypropylene raw material 2 (branched PP2): Metallocene catalytic system Branched chain polypropylene raw material (manufactured by Japan Polypropylene Corporation, melt tension: 5 gf)
Branched chain polypropylene raw material 3 (branched PP3): Ziegler-Natta catalytic system branched chain polypropylene raw material (manufactured by Basell, melt tension: 15 gf)
Low stereoregular polypropylene raw material: "L-MODU" (registered trademark) S901 manufactured by Idemitsu Kosan Co., Ltd.

Polypropylene raw material D: Polypropylene raw material 3 and 4-methyl-1-pentene polymer are supplied from a measuring hopper to a twin-screw extruder so as to have a ratio of 90:10 (mass ratio), and melt-kneaded at 260 ° C. A melted resin composition is discharged from a die in a strand shape, cooled and solidified in a water tank at 25 ° C., and cut into chips.
4-Methyl-1-pentene polymer: Mitsui Chemicals, Inc., MX004
1-Butene polymer: "Toughmer" (registered trademark) BL3450 (MFR = 12g / 10 minutes (load 21.18N, 230 ° C), structural unit derived from 1-butene: 87 mol%) manufactured by Mitsui Chemicals, Inc. ..

(Example 1)
As raw materials for the surface layer (I), polypropylene raw material 3 and polypropylene raw material D were dry-blended at 70:30 (mass ratio) and supplied to a single-screw extruder for the surface layer (I). As raw materials for the base layer (II), polypropylene raw material 2, polypropylene raw material 3, and branched chain polypropylene raw material 1 are dry-blended at a ratio of 70:26: 4 (mass ratio) and uniaxially extruded for the inner layer (II). Supplied to the machine. Each resin mixture is melt-extruded at 260 ° C., foreign matter is removed with a 20 μm cut sintering filter, and then the surface layer (I) / base layer (II) / is used with a feed block type A / B / A composite T-die. The surface layer (I) was laminated so as to have a thickness ratio of 1/20/1, discharged to a casting drum whose surface temperature was controlled at 22 ° C., and brought into close contact with the casting drum with an air knife. Then, the uncooled drum surface of the sheet on the casting drum was cooled by injecting compressed air at 22 ° C. at an air velocity of 140 m / s to obtain an unstretched sheet. Subsequently, the unstretched sheet was preheated to 108 ° C. with a ceramic roll, and stretched 1.5 times in the longitudinal direction between rolls at 108 ° C. provided with a peripheral speed difference as the first-stage stretching. Subsequently, as the second-stage stretching, a 3.4-fold stretching was performed in the longitudinal direction between the rolls at 146 ° C. Next, the obtained uniaxially stretched film was introduced into a tenter type stretching machine by gripping both ends in the width direction with clips, preheated at 173 ° C. for 3 seconds, and then stretched 9.2 times in the width direction at 152 ° C. The heat treatment was performed at 175 ° C. while giving 13% relaxation in the width direction. After that, it is guided to the outside of the tenter through a cooling step of 100 ° C., the clips at both ends in the film width direction are released, heated with a hot roll at 123 ° C. for 0.5 seconds, and then wound around a core to have a thickness of 15 μm. Polyolefin film was obtained. Table 2 shows the physical characteristics of the obtained film and the evaluation results.

(Examples 2 to 6, Comparative Examples 1 to 3)
A polyolefin film was obtained in the same manner as in Example 1 except that the raw material composition and film forming conditions of each layer were as shown in Table 2. At this time, the thickness was adjusted by adjusting the discharge amount at the time of extrusion and adjusting the speed of the casting drum. Table 2 shows the physical characteristics of the obtained film and the evaluation results. Regarding the mixing of the raw materials of the surface layer, in the surface layer (I) of Example 3 and Comparative Example 1, the polypropylene raw material 3 and the polypropylene raw material D were dry-blended at 70:30 (mass ratio) to be compared with Comparative Example 2. In the surface layer (I) of the above, the polypropylene raw material 3 and the polypropylene raw material D were dry-blended at an 80:20 (mass ratio). In the surface layer (I) and the base layer (II) of the other examples, each resin component was dry-blended at the ratio shown in Table 2 without using the polypropylene raw material D.

As described above, the polyolefin film of the present invention can be used in various industrial applications such as packaging films, surface protective films, process films, sanitary products, agricultural products, construction products, medical products, and condenser films. Since it is particularly excellent in surface smoothness, it can be preferably used as a surface protective film, a process film, a mold release film, and a condenser film.

In order to solve the above-mentioned problems and achieve the object, the polyolefin film of the present invention has a crystallization temperature Tc ₀ of 110 ° C. or higher obtained by measuring the film by DSC and externalizing point method, and the surface of the film. inner retardation is at 400nm or less, the dynamic friction coefficient μd after heating 130 ° C. 10 minutes Ri der 0.7, made mainly of polypropylene resin, and at least, have a surface layer (I), the base layer (II) and wherein the Rukoto such was.

In the polyolefin film of the present invention, the film is measured by DSC, the crystallization temperature Tc0 determined by the extrapolation point method is 110 ° C. or higher, the in-plane retardation of the film is 400 nm or less, and after heating at 130 ° C. for 10 minutes. The dynamic friction coefficient μd of is 0.7 or less. The polyolefin film refers to a film containing a polyolefin resin in an amount of more than 50% by mass and 100% by mass or less when all the components constituting the film are 100% by mass. Further, the polyolefin resin refers to a resin in which the olefin unit accounts for more than 50 mol% and 100 mol% or less in all the constituent units constituting the resin.

Melt tension of branched polypropylene material is preferably from the viewpoint of the stretching uniformity is at least 3 gf 40 gf or less. The lower limit of the melt tension is more preferably 4 gf, and even more preferably 6 gf. The upper limit is more preferably 30 gf and even more preferably 25 gf. In order to set the melt tension to the above value, a method of controlling the average molecular weight, the molecular weight distribution, the degree of branching in the polypropylene raw material, or the like is adopted. In particular, when it has a long chain branch, the melt tension can be dramatically increased, and it can be adjusted to a preferable value by adjusting the molecular chain of the long chain branch and the degree of branching.

In the polyolefin film of the present invention, the ratio of the polypropylene raw material A, the polypropylene raw material B, and the branched-chain polypropylene raw material to the total amount of the resin component is preferably as follows. The polypropylene raw material A is preferably 50% by mass or more and 99.9% by mass or less from the viewpoint of film surface smoothness and mechanical strength. The lower limit of the proportion of the polypropylene raw material A is more preferably 60% by mass, further preferably 70% by mass. The upper limit is more preferably 99% by mass, further preferably 98% by mass. The proportion of the polypropylene raw material B is preferably 0.1% by mass or more and 50% by mass or less of the entire film. The lower limit of the proportion of the polypropylene raw material B is more preferably 0.5% by mass, further preferably 3% by mass. The upper limit is more preferably 30% by mass, further preferably 20% by mass. The ratio of the branched-chain polypropylene raw material is preferably 0.1% by mass or more and 30% by mass or less of the entire film. The lower limit of the proportion of branched-chain polypropylene raw material is more preferably 0.2 mass%, more preferably 0.5 wt%, and most preferably 1.0% by mass. The upper limit is more preferably 20% by mass, further preferably 10% by mass.

In the subsequent heat treatment and relaxation treatment steps, while tension-grasping the width direction with a clip, relaxation is applied at a relaxation rate of 5 to 20%, more preferably 8 to 18%, still more preferably 11 to 18% in the width direction, and 160 ° C. Heat-fixed at a temperature of 180 ° C. or lower, preferably 165 ° C. or higher and lower than 180 ° C. , more preferably 168 ° C. or higher and lower than 180 ° C., more preferably 170 ° C. or higher and lower than 180 ° C., and tension-grasped in the width direction with a clip. As it is, it is guided to the outside of the tenter through a cooling step at 80 to 100 ° C., the clip at the end of the film is released, the edge of the film is slit in the winder step, and the film product roll is wound. The heat treatment temperature is 5 ° C. or higher, more preferably 8 ° C. or higher, more preferably 10 ° C. or higher with respect to the transverse stretching temperature, thereby relaxing the residual stress in the film and lowering the heat shrinkage rate. be able to.

(10) Number average molecular weight Mn, Z + 1 average molecular weight Mz + 1, molecular weight distribution value The polyolefin film was dissolved by stirring at 165 ° C. for 30 minutes using 1,2,4-trichlorobenzene as a solvent. Then, the mixture was filtered using a 0.5 μm filter, the molecular weight distribution of the filtrate was measured, and the differential distribution values when the logarithmic molecular weight Log (M) was 4.0 and 6.1 were read.
In addition, the number average molecular weight of the sample and the Z + 1 average molecular weight were determined using the calibration curve of the molecular weight prepared using the following standard sample.
-Device: High-temperature GPC device (equipment No. HT-GPC-1, PL-220 manufactured by Polymer Laboratories)
・ Detector: Differential refractometer RI
-Column: Shodex HT-G (guard column)
Shodex HT-806M (2 pcs) (φ8.0 mm x 30 cm, manufactured by Showa Denko)
・ Flow velocity: 1.0 mL / min
-Column temperature: 145 ° C
・ Injection amount: 0.200 mL
-Standard sample: Tosoh monodisperse polystyrene, Tokyo Kasei dibenzyl .

(Polypropylene raw material, etc.)
For the production of the polyolefin films of Examples and Comparative Examples, polypropylene raw materials having a number average molecular weight (Mn) and a Z + 1 average molecular weight (Mz + 1) shown in Table 1 below were used. These values are values evaluated in the form of raw material resin pellets. Two kinds of raw materials were prepared as PP raw material A and two kinds of raw materials as PP raw material B. Further, as the branched chain polypropylene raw material 1, the following was used.
Polypropylene raw material 1 (PP1): Made by Prime Polymer Co., Ltd. (Y-400GP)
Polypropylene raw material 2 (PP2): Made by Prime Polymer Co., Ltd. (F113G)
Polypropylene raw material 3 (PP3): manufactured by Sumitomo Chemical Co., Ltd. (WF836)
Polypropylene raw material 4 (PP4): Made by Prime Polymer Co., Ltd. (F-704NT)
Branched polypropylene material 1 (branch PP1): metallocene catalyst system branched polypropylene material ( "WAYMAX" (registered trademark) MFX6 Japan Polypropylene Corporation, melt tension: 13Gf)
Branched polypropylene material 2 (branch PP2): metallocene catalyst system branched polypropylene material ( "WAYMAX" (registered trademark) MFX3 Japan Polypropylene Corporation, melt tension: 5 gf)
Branched chain polypropylene raw material 3 (branched PP3): Ziegler-Natta catalytic system branched chain polypropylene raw material ( manufactured by PF-814 Basell, melt tension: 15 gf)
Low stereoregular polypropylene raw material: "L-MODU" (registered trademark) S901 manufactured by Idemitsu Kosan Co., Ltd.

Claims (13)

The film was measured by DSC, the crystallization temperature Tc ₀ determined by the extrapolation method was 110 ° C. or higher, the in-plane phase difference of the film was 400 nm or less, and the dynamic friction coefficient μd after heating at 130 ° C. for 10 minutes was 0. A polyolefin film that is 0.7 or less. The polyolefin film according to claim 1, wherein the breaking elongation in the direction orthogonal to the main orientation of the film at 130 ° C. is 100% or more. The polyolefin film according to claim 1 or 2, wherein the content of the cyclic olefin resin in the film is less than 2.0% by mass. The polyolefin film according to any one of claims 1 to 3, wherein the internal haze after heating at 130 ° C. for 10 minutes is 1.0% or less. The polyolefin film according to any one of claims 1 to 4, wherein the uneven orientation angle within a 10 cm square of the film is 3.0 ° or less. The polyolefin film according to any one of claims 1 to 5, which contains a polypropylene resin as a main component. The polyolefin film according to any one of claims 1 to 6, which comprises at least a surface layer (I) and a base layer (II). 7. Polyethylene film. 7. Polyethylene film. A surface protective film using the polyolefin film according to any one of claims 1 to 9. A process film using the polyolefin film according to any one of claims 1 to 9. A release film using the polyolefin film according to any one of claims 1 to 9. A film capacitor using the polyolefin film according to any one of claims 1 to 9.

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