KR20220080081A - polyolefin film - Google Patents

Abstract

The object is to provide a film excellent in transparency, lubricity, and heat resistance, the film is measured by DSC, and the crystallization temperature Tc ₀ obtained by the extrapolation method is 110° C. or more, and the in-plane retardation of the film is 400 nm or less, , a polyolefin film having a kinetic friction coefficient μd of 0.7 or less after heating at 130° C. for 10 minutes is used as the main paper.

Description

polyolefin film

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

Since the polyolefin film is excellent in transparency, mechanical properties, electrical properties, etc., it is used for various uses, such as a packaging use, a mold release use, a tape use, cable wrapping, and electrical use including a capacitor|condenser. In particular, since it is excellent in surface releasability and mechanical properties, it is used suitably as a film for release of various members, such as a plastic product, a building material, and an optical member, and a process film.

When using as a protective film or a cover film, the presence or absence of the defect of a to-be-adhered body may be confirmed, bonding to a to-be-adhered body. In that case, when transparency of a protective film or a cover film is low, it may become difficult to confirm the fault of a to-be-adhered body. In particular, when using as a protective film for retardation plate, not only transparency but low retardation characteristic is calculated|required, and the level of the request|requirement is gradually increasing in recent years.

Generally, when trying to improve transparency, since the film surface also becomes smooth, lubricity may be impaired, planarity may deteriorate, such as becoming easy to enter a wrinkle at the time of process conveyance. Moreover, when it is going to improve transparency, the method of reducing the crystallinity of polyolefin resin is used. However, when crystallinity is lowered, when the film is exposed to a high-temperature environment, the low-melting-point portion of the film surface partially melts, the kinetic friction coefficient rises, and the lubricity may be further impaired. As described above, conventionally, it has been difficult to achieve both smoothness and lubricity.

In view of the above, a film having both transparency, lubricity, and heat resistance is required for a film for industrial materials that satisfies the required characteristics.

As a film in which the in-plane retardation of a film was reduced, the example in which the retardation was reduced by adding polypropylene resin of a low melting point to the inner layer of a film is described in patent document 1, for example. Moreover, as a film which improved lubricity, the example which made lubricity by making a casting temperature high, forming a beta crystal abundantly, and roughening is described in patent document 2, for example. Moreover, in patent document 3, the film which reduced retardation by using cyclic olefin resin is described.

International Publication No. 2015/129851 Japanese Patent Laid-Open No. 2001-247693 Japanese Patent Laid-Open No. 2018-126909

However, in the method described in Patent Document 1 described above, there was a problem in that the film surface was smooth, the lubricity was low, and the lubricity was particularly low after high-temperature heating and the planarity was insufficient. Moreover, in the method of patent document 2, surface roughness was high and the in-plane retardation of a film was inadequate. Moreover, in the method of patent document 3, there existed a problem that the film itself was soft, handling was inadequate, and cost was high.

Then, the subject of this invention consists in solving the above-mentioned problem. That is, to provide a polyolefin film excellent in transparency, lubricity, and heat resistance.

In order to solve the above problems and achieve the object, the polyolefin film of the present invention has a crystallization temperature Tc ₀ determined by measuring the film by DSC and an extrapolation method is 110° C. or more, and the in-plane retardation of the film is 400 nm or less, and the coefficient of kinetic friction μd after heating at 130° C. for 10 minutes is characterized as 0.7 or less.

The polyolefin film of this invention is excellent in transparency, heat resistance, and lubricity, and can be used conveniently as a film for industrial materials widely.

BRIEF DESCRIPTION OF THE DRAWINGS It is an example of the graph which shows the crystallization temperature T _c0 of a polyolefin film.

The polyolefin film of the present invention has a crystallization temperature Tc ₀ of 110° C. or higher determined by measuring the film by DSC and an extrapolation method, an in-plane retardation of the film is 400 nm or less, and a coefficient of kinetic friction μd after heating at 130° C. for 10 minutes is 0.7 or less. A polyolefin film means the film which contains 100 mass % or less of polyolefin resin more than 50 mass %, when all the components which comprise a film are 100 mass %. In addition, polyolefin resin means resin which has more than 50 mol% and 100 mol% of the olefin unit which occupies for all the structural units which comprise 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 123°C or higher by measuring the film by DSC and using an extrapolation method. ℃ or higher. When Tc ₀ is less than 110 ° C., for example, coarse spheroids are formed at the time of casting, and the in-plane retardation becomes large, and when used as a retardation protective film, a problem may arise in the inspection of the retardation characteristics of the adherend. In order to set Tc ₀ to 110 ° C. or higher, for example, it is preferable to add a raw material having a nucleating action in the range described below for the raw material composition of the polyolefin film, and especially, it is preferable to add a branched polypropylene raw material. . Moreover, it is also effective to adjust the quantity of the high molecular weight component and low molecular weight component of the polypropylene resin used for a polyolefin film to specific ranges. Although the upper limit in particular of crystallization temperature Tc ₀ is not restrict|limited, It is substantially about 135 degreeC. In addition, DSC is the meaning of a differential scanning calorimeter.

In the polyolefin film of this invention, the in-plane retardation of a film is 400 nm or less, 300 nm or less is preferable, 200 nm or less is more preferable, 100 nm or less is still more preferable. When the in-plane retardation is larger than 400 nm, for example, when it is used as a retardation protective film, a problem may arise when inspecting the retardation characteristics in a state bonded to an adherend. In order to make the in-plane retardation 400 nm or less, for example, the raw material composition of the polyolefin film is set to a range described later, and the film forming conditions are set to a range described later, and a raw material having a particularly high crystallization temperature is used, and formed at the time of casting. It is effective to uniformly stretch by reducing the spherulite, lowering the extrusion temperature and the temperature of the cast drum, increasing cooling during casting, increasing the preheating temperature during longitudinal/horizontal stretching, and stretching at a low temperature. to be. The lower limit of the in-plane retardation 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 (hereinafter, sometimes referred to as the main orientation orthogonal direction) after heat treatment at 130°C for 10 minutes is 0.7 or less. More preferably, it is 0.6 or less, More preferably, it is 0.5 or less. In addition, when an arbitrary direction is 0° in the film plane with the main orientation direction in the present invention, each of which forms an angle of 0° to 175° at intervals of 5° with respect to the arbitrary direction When the Young's modulus is measured in the direction, it refers to the direction showing the highest value. In addition, in the polyolefin film of the present invention, the direction parallel to the direction in which the polyolefin film is formed is called the film forming direction, the longitudinal direction or the MD direction, and the direction orthogonal to the film forming direction in the film plane is called the width direction or the TD direction. .

When using the polyolefin film of this invention as a protective film, it may pass through various high temperature processes. For example, when using as a release film of a thermosetting resin, after bonding to a thermosetting resin, it may be made to thermoset in the temperature range of about 120-150 degreeC. Moreover, when using as a film for capacitor|condensers, 130-150 degreeC radiant heat may be applied at the time of metal sputtering. A method for reducing crystallinity of a polyolefin film when smoothing a polyolefin film is well known, but in such a case, when high-temperature heat is applied, the low-melting-point resin portion of the surface layer melts and μd becomes large in some cases. When 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 capacitors, wrinkles are entered on the conveyance roll by passing through a high-temperature process, or when winding with an adherend Winding deviation and the like can be reduced.

In order to make 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 a range described later, and film forming conditions are set to a range described later, and in particular, increase the preheating temperature at the time of vertical/horizontal stretching , it is effective to carry out the stretching at a low temperature at a high magnification and uniformly high magnification stretching, and heat treatment and relaxation after biaxial stretching in the ranges 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.

It is preferable that the breaking elongation of the polyolefin film of this invention in the direction orthogonal to the film main orientation in 130 degreeC is 100 % or more. More preferably, it is 110 % or more, More preferably, it is 120 % or more. When the elongation at break at 130°C is 100% or more, for example, in the conveyance process to which the high-temperature heat as mentioned above is applied, the fracture|rupture of a polyolefin film can be reduced.

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

As for the polyolefin film of this invention, it is preferable that the internal haze (Hereinafter, it may simply call a haze) after heating at 130 degreeC for 10 minutes is 1.0 % or less. More preferably, it is 0.6 % or less, More preferably, it is 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 is maintained even after passing through the conveying process to which high-temperature heat is applied as described above, The problem that occurs when inspecting with a defect inspection machine in a state bonded to the complex is reduced.

Generally, in order to reduce a haze, the means which reduces the crystallinity of polyolefin resin may be used. Therefore, a polyolefin resin with low stereoregularity may be used, or a copolymer with a low melting|fusing point may be added. However, when such a low-melting-point resin is used, the mobility of the amorphous portion in the polyolefin film is increased, and when high-temperature heat of 130° C. or higher is applied, additives such as antioxidants in the polyolefin bleed out on the film surface, and the transparency is impaired. there may be cases

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

As for the polyolefin film of this invention, it is preferable that the nonuniformity of the orientation angle within 10 cm square of a film is 3.0 degrees or less. More preferably, it is 2.5 degrees or less, More preferably, it is 2.0 degrees or less. When the nonuniformity of an orientation angle is less than 3.0 degrees, the problem which arises when test|inspecting an orientation angle in the state joined with a to-be-adhered body, for example can be reduced.

In order to make the nonuniformity of orientation angle 3.0 degrees or less, for example, make the raw material composition of a film into the range mentioned later, and make film forming conditions into the range mentioned later, especially use a raw material with a high crystallization temperature, and longitudinal/horizontal stretching It is effective to increase the preheating temperature at the time and to perform stretching at a low temperature at a high magnification and uniformly at a high magnification. Although the lower limit in particular of the nonuniformity of an orientation angle is not restrict|limited, It is substantially about 0.1 %.

Although the thickness of the polyolefin film of this invention is adjusted suitably according to a use, and limitation in particular is not carried out, It is preferable from a viewpoint of handling property that they are 0.5 micrometer or more and 100 micrometers or less. As for the upper limit of the thickness at the time of using as a release film, 60 micrometers is more preferable, 30 micrometers is still more preferable, and 16 micrometers is the most preferable. As for a lower limit, 4 micrometers is more preferable, 8 micrometers is still more preferable, and 11 micrometers is the most preferable. Moreover, as for the upper limit of the thickness at the time of using as a film for capacitors, 15 micrometers is more preferable, 8 micrometers is still more preferable, and 3 micrometers is the most preferable. As for a minimum, 0.9 micrometer is more preferable, and 1.5 micrometers is still more preferable. Thickness can be adjusted by the screw rotation speed of an extruder, the width|variety of an unstretched sheet|seat, film forming speed, a draw ratio, etc. within the range which does not reduce other physical properties.

Next, although resin etc. suitable for manufacture of the polyolefin film of this invention are demonstrated, resin etc. which comprise the polyolefin film of this invention are not necessarily limited to this.

It is preferable that the polyolefin film of this invention has a polypropylene resin as a main component from a viewpoint of transparency and heat resistance. In the present invention, the "main component" means that the proportion of a specific component in all components is 50 mass% or more and 100 mass% or less, more preferably 90 mass% or more and 100 mass% or less, still more preferably 95 mass% It is 100 mass % or more, More preferably, 96 mass % or more and 100 mass % or less, Especially preferably, it is 97 mass % or more and 100 mass % or less, Most preferably, it is 98 mass % or more and 100 mass % or less. Moreover, although the polyolefin film of this invention may contain only 1 type of polypropylene resin, it is preferable that 2 or more types of polypropylene resins are included. When two or more types of components corresponding to polypropylene resin are contained in the film, if these components are added up to more than 50 mass % and 100 mass % or less, it shall be regarded as "consisting of polypropylene resin as a main component".

A polypropylene resin means polyolefin resin which contains more than 50 mol% of propylene units and 100 mol% or less when all the structural units which comprise the molecular chain of resin are 100 mol%. In addition, about a polypropylene resin, it may be called "polypropylene raw material" hereafter.

The polyolefin film of the present invention is not particularly limited in terms of its layer structure, and may have either a single layer or a laminated structure, but from the viewpoint of satisfying different properties such as smoothness, lubricity, heat resistance, ), it is preferable to have 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 a polypropylene resin. When the polyolefin film has a laminated structure, it is preferable that the polyolefin film itself has a polypropylene resin as a main component, and that the main component of the base layer (II) to be described later is a polypropylene resin.

When the polyolefin film of this invention makes the whole film 100 mass %, it is preferable that content rate of the cyclic olefin resin in a film is less than 2.0 mass %. More preferably, it is less than 1.0 mass %, More preferably, it is less than 0.5 mass %. When the content rate of cyclic olefin resin is less than 2.0% by mass, for example, even if it blends a mutually low polypropylene resin and cyclic olefin resin, the transparency fall of a polyolefin film is reduced. Moreover, since cyclic olefin resin is soft, when the content rate of cyclic olefin resin is less than 2.0 % by mass, the fall of handling property, such as being able to reduce the fracture|rupture in the process of sharpening strongly in tension|tensile_strength, is also suppressed.

Hereinafter, the polypropylene resin used as a main component in the polyolefin film of this invention, (it may be referred to as polypropylene raw material A.) is demonstrated.

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 still more preferably 8.5 million from the viewpoint of limiting the low molecular weight component to a fixed amount or less. 100,000 are preferable and, as for the upper limit of Mn, 9.4 million are more preferable. Moreover, 1.8 million is preferable from a viewpoint of containing a high molecular weight component fixed or more, and, as for the minimum of Z+1 average molecular weight (Mz+1), 2 million is more preferable. 2.5 million is preferable and, as for the upper limit of Mz+1, 2.2 million is more preferable.

The melt flow rate (MFR) of the polypropylene raw material A is preferably in the range of 1 g/10 min or more and 10 g/10 min or less (230°C, 21.18 N load) from the viewpoints of film formability and film strength. From the above viewpoint, the lower limit of MFR is more preferably 2 g/10 min. The upper limit of MFR is more preferably 8 g/10 min, and still more preferably 5 g/10 min. In order to make MFR into said value, the method of controlling an average molecular weight, molecular weight distribution, etc. are employ|adopted. More specifically, a method of adjusting the hydrogen gas concentration during polymerization, a method of controlling the molecular weight or molecular weight distribution of the polypropylene raw material by appropriately selecting a catalyst and/or a promoter, and selecting a composition are preferably employed. do. By making molecular weight low, MFR becomes high, and in molecular weight distribution, MFR becomes high, so that there are many low molecular weight components.

It is preferable that melting|fusing point of polypropylene raw material A is 155 degreeC or more, More preferably, it is 160 degreeC or more, More preferably, it is 165 degreeC or more. When the melting point is 155 ° C. or higher, the heat resistance of the polyolefin film obtained is high, for example, when used as a release film, even if it passes through a process in which heat is applied after bonding with an adherend, in the tension direction due to softening of the film Elongation is suppressed, and deformation of the adherend is reduced.

The polypropylene raw material A preferably has a cold xylene soluble part (CXS) in the polypropylene raw material A of 4 mass % or less, and it is preferable that the mesopentad fraction is 0.90 or more. By satisfying these, the film-forming stability, the intensity|strength of the polyolefin film obtained, dimensional stability, and the fall of heat resistance are reduced.

Here, CXS refers to a polyolefin component that is dissolved in xylene when the sample is completely dissolved in xylene and then precipitated at room temperature, which is a component that is difficult to crystallize due to low stereoregularity and low molecular weight. I think there is. When many of these components are contained in resin, the thermal dimensional stability of a film may be inferior. Therefore, from the said viewpoint, it is preferable that CXS is 3.5 mass % or less, 2.5 mass % or less is more preferable, More preferably, it is 2.0 mass % or less. Although it is so preferable that CXS is low, about 0.1 mass % is a minimum. In order to set CXS in such a range, the method of increasing the catalytic activity at the time of obtaining resin, and the method of washing|cleaning the obtained resin with a solvent or olefin monomer itself can be used.

It is preferable that the mesopentad fraction of polypropylene raw material A is 0.94 or more, More preferably, it is 0.96 or more, More preferably, it is 0.97 or more, Most preferably, it is 0.98 or more. The mesopentad fraction is an index indicating the crystalline stereoregularity of polypropylene measured by nuclear magnetic resonance (NMR). The higher the value, the higher the crystallinity, the higher the melting point, and the higher the dimensional stability at high temperature. desirable. There is no particular restriction on the upper limit of the mesopentad fraction. In order to obtain a resin with high stereoregularity as described above, a method of washing the resin powder obtained in a solvent such as n-heptane, a method of selecting a catalyst and/or a cocatalyst, and a method of appropriately selecting a composition are preferably employed. .

As polypropylene raw material A, you may contain the copolymerization component etc. by another unsaturated hydrocarbon in the range which does not impair the objective of this invention. As a monomer component constituting this copolymerization component, for example, 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-ethyl hexene-1, 1-octene, 1-decene, 1-dodecene, vinylcyclohexene, styrene, allylbenzene, cyclopentene, norbornene, 5-methyl-2-norbornene Nen etc. are mentioned.

It is preferable that the amount of copolymerization components of the polypropylene raw material A is 10 mol% or less. More preferably, it is 5 mol% or less, More preferably, it is 3 mol% or less. The higher the content of the ethylene component, the lower the crystallinity and the easier to improve the transparency. However, when the content of the ethylene component exceeds 10 mol%, the strength of the film decreases, or the heat resistance decreases and the heat shrinkage deteriorates. There are cases. Moreover, resin deteriorates easily in an extrusion process, and it may become easy to generate|occur|produce the fish eye in a polyolefin film.

The polyolefin film of the present invention may contain a polypropylene resin different from the polypropylene raw material A (hereinafter, may be referred to as the polypropylene raw material B). By including the polypropylene raw material B, a low molecular weight component may act as an extending|stretching aid at the time of extending|stretching, and may contribute to film breakage suppression at the time of extending|stretching and reduction of physical property nonuniformity.

As for the upper limit of the number average molecular weight (Mn) of the polypropylene raw material B, from a viewpoint of containing a low molecular-weight component fixed or more, 75,000 is preferable, 7.0 million is more preferable, and 6.5 million is still more preferable. 50,000 are preferable, as for the minimum of Mn, 5.5 million is more preferable, and 6.2 million is still more preferable. Moreover, from a viewpoint of suppressing a high molecular weight component to fixed or less, 2 million is preferable, and, as for the upper limit of Z+1 average molecular weight (Mz+1), 1.8 million is more preferable. 1.1 million is preferable, as for the minimum of Mz+1, 1.3 million is more preferable, and 1.55 million is still more preferable. Moreover, Mn and Mz+1 of the polypropylene raw material B become smaller than Mn and Mz+1 of the polypropylene raw material A.

It is preferable from the viewpoint of extrusion stability that the melt flow rate (MFR) of the polypropylene raw material B is in the range of 3 g/10 min or more and 11 g/10 min or less (230°C, 21.18 N load). As for the minimum of MFR of the polypropylene raw material B, 3.5 g/10min is more preferable. The upper limit of the MFR of the polypropylene raw material B is more preferably 9 g/10 min, still more preferably 8 g/10 min. In order to make MFR of the polypropylene raw material B into said value, the method of controlling an average molecular weight, molecular weight distribution, etc. are employ|adopted. More specifically, a method of adjusting the hydrogen gas concentration during polymerization, a method of controlling the molecular weight and molecular weight distribution of the polypropylene raw material B by appropriately selecting a catalyst and/or a cocatalyst, and selecting a composition are preferable. are hired By making molecular weight low, MFR becomes high, and in molecular weight distribution, MFR becomes high, so that there are many low molecular weight components.

The polyolefin film of the present invention may contain a branched polypropylene resin (hereinafter, sometimes referred to as a branched polypropylene raw material) in addition to the linear polypropylene raw material A and polypropylene raw material B. By including the branched polypropylene raw material, by the nucleating effect, coarse spheroid formation at the time of casting is suppressed, so SPk and crystallite size can be made small.

The MFR of the branched polypropylene raw material is preferably 0.5 g/10 min or more and 9 g/10 min or less (230°C, 21.18 N load) from the viewpoint of extrusion stability. The lower limit of the MFR of the branched polypropylene raw material is more preferably 2 g/10 min, and still more preferably 6 g/10 min. In order to make MFR into said value, the method of controlling an average molecular weight, molecular weight distribution, etc. are employ|adopted. More specifically, a method of adjusting the hydrogen gas concentration during polymerization, a method of controlling the molecular weight or molecular weight distribution of the polypropylene raw material by appropriately selecting a catalyst and/or a promoter, and selecting a composition are preferably employed. do. By making molecular weight low, MFR becomes high, and in molecular weight distribution, MFR becomes high, so that there are many low molecular weight components.

The melt tension of the branched 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, still more preferably 6 gf. 30 gf is more preferable and, as for an upper limit, 25 gf is still more preferable. In order to make melt tension into said value, the method of controlling an average molecular weight, molecular weight distribution, the degree of branching in a polypropylene raw material, etc. are employ|adopted. In particular, in the case of having long-chain branching, the melt tension can be remarkably increased, and by adjusting the molecular chain of the long-chain branching and the degree of branching, it can be adjusted to a preferable value.

Branched polypropylene raw materials are commercially available in a plurality of Ziegler-Natta catalyst systems and metallocene catalyst systems, but from the viewpoint of using in combination with polypropylene raw material A and polypropylene raw material B, low molecular weight components and high molecular weight components are small, A metallocene catalyst system with a narrow molecular weight distribution is more preferable.

To the polypropylene raw material A, polypropylene raw material B, and branched polypropylene raw material used for the polyolefin film of the present invention, various additives, for example, crystal nucleating agent, antioxidant, heat stabilizer, within the scope not impairing the object of the present invention , a slip agent, an antistatic agent, an antiblocking agent, a filler, a viscosity modifier, an anti-coloring agent, and the like.

Among these, selection of the type of antioxidant and the amount to be added is important from the viewpoint of bleed-out of the antioxidant. That is, as such an antioxidant, it is a phenol-type thing which has steric hindrance, and it is preferable that at least 1 sort(s) has a molecular weight 500 or more high molecular weight type thing. Specific examples thereof include various ones, for example, 1,3,5-trimethyl-2,4,6-tris(2,6-di-t-butyl-p-cresol (BHT: molecular weight 220.4) and 3,5-di-t-butyl-4-hydroxybenzyl)benzene (for example, "Irganox" (registered trademark) 1330 manufactured by BASF: molecular weight 775.2) or tetrakis [methylene-3 (3,5-di-t) -Butyl-4-hydroxyphenyl) propionate] methane (for example, "Irganox" (trademark) 1010 by BASF Corporation: molecular weight 1177.7) etc. is used together is preferable.

The total content of these antioxidants is preferably in the range of 0.03 to 1.0 parts by mass based on the total amount of the polyolefin raw material. When there are too few antioxidants, a polymer may deteriorate in an extrusion process, a film may be colored, or long-term heat resistance may be inferior. When there are too many antioxidants, transparency may fall by the bleed-out of these antioxidants. From the said viewpoint, content with more preferable antioxidant is 0.05-0.9 mass parts, Especially preferably, it is 0.1-0.8 mass parts.

A crystal nucleating agent can be added to the polyolefin raw material A and B used for the polyolefin film of this invention in the range which does not go against the objective of this invention. Further, branched polypropylene may be contained, and the branched polypropylene already has an α-table or β-tablet crystal nucleating effect by itself, but a different α-tablet nucleating agent (dibenzylidene sorbitol, sodium benzoate, etc.), β-tablet Nucleating agents (amide-based compounds such as 1,2-hydroxystearate, magnesium benzoate, N,N'-dicyclohexyl-2,6-naphthalenedicarboxamide, and quinacridone-based compounds) and the like are exemplified. However, if the nucleating agent of the above type is contained excessively, since it may cause a decrease in transparency or strength due to a decrease in stretchability or void formation, etc., the content is usually 0.5 parts by mass or less, preferably based on the total amount of the polyolefin raw material. It is 0.1 mass part or less, More preferably, it is 0.05 mass part or less.

It is preferable not to contain an organic particle and an inorganic particle in the polyolefin film of this invention. Since the polypropylene resin which can be preferably used as a main component of the polyolefin film of this invention has low affinity with organic particle|grains and inorganic particle, particle|grains may fall off and a process or a product may be contaminated. In addition, when coarse protrusions are formed by particles with high hardness, irregularities may be transferred to the resin layer of the optical member, and when used as a protective film for products requiring high quality such as display members or a base film for manufacturing, a cause of quality deterioration There are cases when this From the above viewpoint, the polyolefin film of the present invention preferably does not contain a lubricant such as organic particles or inorganic particles.

The polyolefin film of this invention WHEREIN: It is preferable that the ratio which the polypropylene raw material A, the polypropylene raw material B, and the branched polypropylene raw material occupies with respect to the resin component whole quantity is the following. As for the polypropylene raw material A, 50 mass % or more and 99.9 mass % or less are preferable from a viewpoint of the surface smoothness of a film, and a mechanical strength. As for the lower limit of the ratio for which the polypropylene raw material A occupies, 60 mass % is more preferable, and its 70 mass % is still more preferable. 99 mass % is more preferable, and, as for an upper limit, 98 mass % is still more preferable. As a ratio for the polypropylene raw material B, 0.1 mass % or more and 50 mass % or less are preferable in the whole film. As for the lower limit of the ratio for which the polypropylene raw material B occupies, 0.5 mass % is more preferable, and its 3 mass % is still more preferable. 30 mass % is more preferable, and, as for an upper limit, 20 mass % is still more preferable. As a ratio for which the branched polypropylene raw material occupies, in the whole film, 0.1 mass % or more and 30 mass % or less are preferable. The lower limit of the proportion of the polypropylene raw material B is more preferably 0.2 mass %, still more preferably 0.5 mass %, and most preferably 1.0 mass %. 20 mass % is more preferable, and, as for an upper limit, 10 mass % is still more preferable.

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

The polyolefin film of the present invention preferably 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 chromatography method described later. When the logarithmic molecular weight Log(M) is 4.0, when the differential distribution value is less than 3%, there are few low molecular weight components used as lubricating components at the time of extending|stretching, and it may become easy to fracture|rupture at the time of extending|stretching. When the differential distribution value in case logarithmic molecular weight Log(M) is 4.0 becomes larger than 15 %, the heat resistance of a polyolefin film may fall. 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%, still more preferably 5%. As for the upper limit of the differential distribution value in case logarithmic molecular weight Log(M) is 4.0, it is more preferable that it is 13 %, and it is more preferable that it is 10 %.

The polyolefin film of the present invention preferably has a differential distribution value of 1% or more and 15% or less in the molecular weight distribution curve measured by the gel permeation chromatography method when the logarithmic molecular weight Log(M) is 6.1. When the logarithmic molecular weight Log(M) is 6.1, when the differential distribution value is less than 1%, there are few high molecular weight components used as tie molecules at the time of stretching, and the uniformity at the time of stretching may be poor. When the differential distribution value when the logarithmic molecular weight Log(M) is 6.1 becomes larger than 15%, after the polyolefin film is wound up as a roll, the normal temperature shrinkage over time becomes large, and the planarity of the film roll may be impaired. 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%, still more preferably 7%. As for the upper limit of the differential distribution value when logarithmic molecular weight Log(M) is 6.1, it is more preferable that it is 13 %, and it is more preferable that it is 11 %.

It is preferable that the polyolefin film of this invention is biaxially stretched using the raw material mentioned above. As a method of biaxial stretching, it can be obtained by any of the inflation simultaneous biaxial stretching method, the stenter simultaneous biaxial stretching method, and the stenter sequential biaxial stretching method. Among them, film forming stability, thickness uniformity, high rigidity and dimensions of the film From the viewpoint of controlling stability, it is preferable to employ a stenter successive biaxial stretching method.

Next, although one aspect of the manufacturing method of the polyolefin film of this invention is demonstrated as an example of the polypropylene film of 2 types and 3 layer structure, the manufacturing method of the polyolefin film of this 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 shorten the base layer (II) (hereinafter, sometimes referred to as B layer). It is supplied to an extruder, and the polyolefin raw material B is supplied to the single screw extruder for surface layer (I) (Hereinafter, it may be called A-layer.). Thereafter, melt extrusion is performed at 200 to 280°C, more preferably 220 to 280°C, still more preferably 240 to 270°C, respectively. Then, after removing foreign substances or modified polymers with a filter installed in the middle of the polymer tube, stacked in a multi-manifold type A-layer/B-layer/A-layer composite T-die, discharged on a casting drum and cooled and solidified, A A laminated unstretched sheet having a layer structure of layer/layer B/layer A is obtained. At this time, the lamination thickness ratio is preferably in the range of 1/8/1 to 1/60/1. By setting it as the said range, the surface layer containing polypropylene raw material A is formed thinly and uniformly on the film surface, the height uniformity of the projections formed at the time of extending|stretching increases, and formation of coarse projections can be suppressed.

Further, the casting drum has a surface temperature of 10 to 50°C, preferably 10 to 40°C, more preferably 15 to 30°C, still more preferably 15 to 20°C. In addition, the layer structure is not cared about as a two-layer laminated structure of A-layer/B-layer. As a method of adhesion to the casting drum, any of an electrostatic application method, an adhesion method using the surface tension of water, an air knife method, a press roll method, an underwater casting method, etc. may be used, but the flatness is good and the surface roughness can be controlled. The air knife method 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 velocity is preferably 130 to 150 m/s . Moreover, in order not to generate|occur|produce vibration of a film, it is preferable to adjust the position of an air knife appropriately so that air may flow to a film forming downstream. In addition, in the case of the two types, two-layer lamination structure of A-layer/B-layer, it is preferable to make the A-layer side into the casting drum side.

The obtained unstretched sheet|seat is introduce|transduced into a longitudinal stretch process. In the longitudinal stretching process, first a plurality of metal rolls maintained at 80°C or more and 150°C or less, preferably 80°C or more and 130°C or less, more preferably 90°C or more and 130°C or less, still more preferably 100°C or more and 130°C or less. The unstretched sheet is preheated by contacting the sheet, and between the rolls provided with the circumferential speed difference, it is first stretched in the longitudinal direction by 1.1 to 3.0 times, more preferably by 1.3 to 2.5 times, and then continuously by 2.0 to 5.0 times in the longitudinal direction, more Preferably it extends|stretches 3.0-4.5 times, and cools to room temperature. The stretching temperature of the first stage is 80°C or more and 130°C or less, preferably 90°C or more and 130°C or less, more preferably 100°C or more and 130°C or less, and the stretching temperature of the second stage is 130°C or more and 150°C or less, preferably Preferably, it is 140 degreeC or more and 150 degrees C or less, More preferably, it is 145 degrees C or more and 150 degrees C or less. In the first half of longitudinal stretching, low magnification stretching at low temperature and high stress, followed by stretching at high temperature at once, is uniformly oriented in the longitudinal direction over the entire width to obtain a highly oriented uniaxially oriented film with high uniformity.

When the longitudinal stretching temperature of the first stage and the longitudinal stretching temperature of the second stage differ greatly, the film contracts in the width direction when it comes into contact with a hot stretching roll. In that case, a film may shrink|contract unevenly, and the wrinkle of a flow direction may enter. As a countermeasure, a ceramic roll was used for the stretching roll. On the ceramic roll, the film becomes slippery, and the film can be stretched without wrinkles by shrinking it uniformly. The total draw ratio of the two-stage stretching is preferably 3.0 times or more and 6.0 times or less, and more preferably 4.0 times or more and 5.5 times or less from the viewpoint that the orientation of the film may be weakened and the strength may be lowered if it is less than 3.0 times.

Next, the both ends in the width direction are gripped with clips to guide the uniaxially stretched film to a tenter, and after preheating, it is transversely stretched 7.0 to 13 times in the width direction. Preheating temperature is 165-180 degreeC, More preferably, it is 168-180 degreeC, More preferably, it is 170-180 degreeC. Moreover, extending|stretching temperature is 148-165 degreeC, More preferably, it is 148-160 degreeC, More preferably, it is 148-155 degreeC. With respect to the stretching temperature, by raising the preheating temperature to 5°C or more, preferably 8°C or more, more preferably 10°C or more, high-oriented stretching is possible uniformly over the entire width of the film, and smoothness of the polyolefin film obtained preferred in

In the subsequent heat treatment and relaxation treatment process, while tensioning in the width direction with a clip and giving relaxation at a relaxation rate of 5 to 20%, more preferably 8 to 18%, more preferably 11 to 18% in the width direction, 160 ° C or more and 180 ° C or less, preferably 165 ° C or more and less than 180 ° C, more preferably 168 ° C or more and less than 180 ° C, even more preferably at a temperature of 170 ° C or more and less than 180 ° C. It guides to the outside of the tenter through the cooling process at 80-100 degreeC with tension holding, the clip of the film edge part is released, the film edge part is slit in a winder process, and the film product roll is wound up. The heat treatment temperature is 5 ° C. or higher with respect to the transverse stretching temperature, more preferably 8 ° C. or higher, and still more preferably 10 ° C. or higher. .

Moreover, it is preferable from a heat resistance viewpoint to heat with a hot roll when the polyolefin film which came out from a tenter passes through a moving part. The heating temperature is preferably 70°C or higher, more preferably 80°C or higher, still more preferably 100°C or higher, and particularly preferably 120°C or higher. At the temperature of 140 degreeC or more, the lubricity of a hot roll and a polyolefin film is impaired, and an upper limit is about 140 degreeC at the point that wrinkles may enter and planarity may deteriorate. 0.2 second or more is preferable and, as for heating time, 0.4 second or more is more preferable. Although the upper limit in particular of a heating time is not restrict|limited, From a viewpoint of productivity, about 2.0 second is an upper limit.

The polyolefin film obtained as described above can be used in various industrial applications such as packaging films, surface protection films, process films, sanitary products, agricultural products, building products, medical products, and capacitor films. From this, it can use suitably as a surface protection film, a process film, the film for mold release, and the film for capacitor|condensers. Here, the surface protection film refers to a film having a function of being affixed to a target object such as a molded article or a film, and having a function of preventing scratches and contamination generated during processing or transport. Process film refers to a film that is adhered to a target object such as a molded article or a film to prevent scratches or contamination generated during manufacturing or processing, and discarded when used as a final product. A release film has a high releasability, is attached to a molded object or a film, etc. to prevent scratches and contamination occurring during processing or transportation, and has a function of easily peeling and discarding when used as a final product. film that has The film for capacitors refers to a film used for a film capacitor using a resin film as a dielectric.

Example

Hereinafter, the present invention will be described in detail by way of Examples. In addition, the characteristic measured and evaluated by the following method.

(1) Film thickness

It measured using the microthickness meter (made by Anritsu Corporation). The film was sampled at 10 cm square, and arbitrarily 5 points were measured, and the average value was calculated|required.

(2) Crystallization temperature T _c0 obtained by the extrapolation point method

Using a differential scanning calorimeter (EXSTAR DSC6220 manufactured by Seiko Instruments), 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. Subsequently, the temperature was decreased 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 exothermic curve obtained at the time of temperature fall in each time was made into T _c10 . Then, the polyolefin film similarly sampled separately was heated up at 20 degreeC/min from 25 degreeC to 250 degreeC, and it hold|maintained for 5 minutes. Subsequently, the temperature was decreased 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 exothermic curve obtained at the time of temperature fall in each time was made into T _c40 . Next, as shown in FIG. 1 , the crystallization temperatures T _c10 and T _c40 obtained by the temperature decrease rate on the abscissa axis and the temperature decrease rate on the ordinate axis are plotted, and a straight line is drawn from T _c40 to T _c10 , and the temperature decrease rate is 0° C. The crystallization temperature when extrapolated to /min was taken as T _c0 . In addition, in each measurement for the measurement of T _c10 and T _c40 , when a plurality of peak temperatures can be observed, the highest peak temperature in the region of 80°C to 130°C was used as the peak temperature.

(3) Coefficient of kinetic friction μd in the direction perpendicular to the main orientation after heat treatment at 130° C. for 10 minutes

A polyolefin film was cut to a width of 6.5 cm and a length of 12 cm, and the test piece was sandwiched between paper and heated in an oven kept at 130° C. under zero load, heated for 10 minutes, and then taken out after cooling at room temperature, Toyo Seiki ( It measured at 25 degreeC and 65 %RH according to JISK7125 (1999) using the slip tester manufactured by Co., Ltd. In addition, the measurement was performed by overlapping other surfaces in the direction orthogonal to main orientation, ie, overlapping so that the surface of one film and the back surface of the other film might contact. The same measurement was performed 5 times per one sample, the average value of the obtained values was computed, and it was set as the kinetic friction coefficient (micrometer) of the said sample. In addition, as for the main orientation direction, when an arbitrary direction is 0° in the film plane, the Young's modulus was measured in each direction forming an angle of 0° to 175° at intervals of 5° with respect to the arbitrary direction. In this case, the direction showing the highest value was set as the main orientation direction.

In addition, the measurement of Young's modulus was performed by the following procedure. First, it cut out into the rectangle of length (measurement direction) 150 mm x width 10 mm, and set it as the sample. Using a tensile tester (“Tensilon” (registered trademark) UCT-100 manufactured by Orientec Co., Ltd.), in an atmosphere at room temperature of 23° C. and a relative humidity of 65%, the initial tensile distance between chucks was 50 mm, and the tensile speed was 300 mm/min. A tensile test was performed. The load applied to the film when the sample is elongated by 2% (when the distance between chucks becomes 51 mm) is read, and the value divided by the cross-sectional area (film thickness × 10 mm) of the sample before the test is taken as the F2 value, the origin and the slope of the straight line passing through the point used to measure the F2 value was defined as the Young's modulus.

(4) In-plane phase difference

The in-plane retardation with respect to the light ray with a wavelength of 548.3 nm was measured for the polyolefin film using the automatic birefringent meter (KOBRA-21ADH) manufactured by Oji Keisoku Co., Ltd. product.

(5) Elongation at break in the direction perpendicular to the main orientation of the film at 130°C

From the polyolefin film, 5 samples with a width of 10 mm and a length of 50 mm (measurement direction) are cut out from the polyolefin film so that the direction orthogonal to the main orientation is the measurement direction, and marks are placed at positions 15 mm from both ends to give a sample length of 20 mm did Next, a rectangular sample was set in a tensile tester (“Tensilon” (registered trademark) UCT-100 manufactured by Orientec Co., Ltd.) at an initial chuck distance of 20 mm, heated in an oven heated to 130° C. for 1 minute, and then the tensile rate A tensile test of the film was performed at 300 mm/min, and the elongation (unit: %) and strength (unit: MPa) at the time the sample was fractured were obtained. The measurement was performed 5 times, the average value of elongation at the time when the sample fracture|ruptures was computed, and it was set as the fracture|rupture elongation (%).

(6) Internal haze after heat treatment at 130°C for 10 minutes

A polyolefin film was cut out to 3.0 cm in width and 6.0 cm in length, and the test piece was sandwiched between paper and heated in an oven kept at 130° C. under zero load, after heating for 10 minutes, and cooled at room temperature to obtain a sample. As a measuring apparatus, the Suga Chemical Co., Ltd. product haze meter (HGM-2DP) was used. The value of the internal haze was calculated|required based on the prescription|regulation of JISK7136 (2000) from the haze measurement value at the time of measuring and immersing the film in the quartz cell of 1 cm optical path length filled with tetralin.

(7) Non-uniformity of orientation angle within 10 cm square of film

A polyolefin film was cut to a width of 10 cm and a length of 10 cm, and from the center of the cut sample, 11 points at an interval of 1 cm in the film main orientation direction and 10 points other than the film center at an interval of 1 cm in the film central direction orthogonal to the film main orientation. A total of 21 points was taken as a measurement point, the orientation angle in each point was measured, and the nonuniformity of orientation angle was calculated|required from the following formula. In addition, the measurement of the orientation angle uses the retardation measuring apparatus (KOBRA-21ADH) manufactured by Oji Keisoku Kikini Co., Ltd., and it is installed in the apparatus so that the main orientation direction of the polyolefin film becomes the angle 0° defined by this measuring apparatus. and the clockwise inclination with respect to the film main orientation direction was + and the counterclockwise direction was -.

Non-uniformity of orientation angle (%)=((Maximum orientation angle- Minimum orientation angle value)/Average orientation angle value)×100.

(8) melt tension

The measurement was performed under the following conditions using the apparatus according to JISK7199 (1999).

- Apparatus: Capyrograph 1BPMD-i with melt tension tester (manufactured by Toyo Seiki Co., Ltd.)

·Temperature: 230℃ (using a thermal chamber)

Die: L=8 (mm), D=2.095 (mm)

·Extrusion speed: 20mm/min

·Take-up speed: 15.7m/min

· Sample mass: 15 to 20 g.

(9) Projected peak height SPk, average roughness Sa, maximum height Sz

Measurement is performed using a scanning white interference microscope "VS1540" (manufactured by Hitachi High-Tech Sciences, Ltd., measurement conditions and device configuration will be described later), and the shooting screen is supplemented (completely supplemented) with the included analysis software, After surface correction in polynomial quadratic approximation, the surface shape was obtained by processing with a median filter (3×3 pixels).

The measurement was performed at each measurement position by making the intersection point of the diagonal of the polyolefin film cut into the square shape of 5 cm x 5 cm as a starting point, and determining a total of 9 measurement positions according to the following procedure. The same measurement was repeated by changing the side. Then, according to the said procedure, SPk, Sa, and Sz of each measurement position were calculated|required for each surface for each surface, and the average value of SPk, Sa, Sz was computed for each surface. Among the obtained values, the smaller SPk value was adopted as the SPk value of the film.

<Measurement position determination method>

Measurement 1: Position of the starting point

Measurement 2: Position 3.0 mm to the right of the starting point

Measurement 3: Position 6.0 mm right from the starting point

Measurement 4: Position 3.0 mm below the starting point

Measurement 5: Position 3.0 mm down and 3.0 mm to the right of the starting point

Measurement 6: Position 3.0 mm down and 6.0 mm to the right of the starting point

Measurement 7: Position 6.0 mm below the starting point

Measurement 8: Position 6.0 mm down and 3.0 mm to the right of the starting point

Measurement 9: Position 6.0 mm down and 6.0 mm to the right of the starting point

<Measurement conditions and device configuration>

Objective Lens: 10x

barrel: 1x

Zoom Lens: 1x

Wavelength filter: 530nm white

Measurement mode: Wave

Measurement software: VS-Measure 10.0.4.0

Analysis software: VS-Viewer10.0.3.0

Measurement area: 561.1 μm × 561.5 μm

Number of pixels: 1,024×1,024.

(10) Number average molecular weight Mn, Z+1 Average molecular weight Mz+1, molecular weight distribution value

The polyolefin film was dissolved by using 1,2,4-trichlorobenzene as a solvent and stirring at 165°C for 30 minutes. Then, it filtered using a 0.5 micrometer filter, the molecular weight distribution of the filtrate was measured, and the differential distribution value at the time of logarithmic molecular weight Log(M) of 4.0 and 6.1 was read.

Moreover, the number average molecular weight and Z+1 average molecular weight of the sample were calculated|required using the analytical curve of the molecular weight created using the following standard sample.

Device: High-temperature GPC device (device No.HT-GPC-1, PL-220 manufactured by Polymer Laboratories)

Detector: differential refractive index detector RI

·Column: Shodex HT-G (Guard Column)

Shodex HT-806M (2 pcs.) (φ 8.0mm×30cm, manufactured by Showa Denko)

·Flow rate: 1.0mL/min

·Column temperature: 145℃

・Injection amount: 0.200mL

·Standard sample: Monodisperse polystyrene manufactured by Tosoh Corporation, dibenzyl manufactured by Tokyo Kasei.

(11) Transcription evaluation to an adherend

A polyolefin film and a 20 µm-thick "Zeonoa Film" (registered trademark) manufactured by Nippon Zeon Co., Ltd. were sampled in a square of 100 mm in width and 100 mm in length, and the surface of the polyolefin film with the smaller SPk and "Zeo" Noah film" (registered trademark) was overlapped so that they contacted, it was sandwiched between two acrylic plates (width 100 mm, length 100 mm), a load of 3 kg was applied, and it was left still in an atmosphere of 23 degreeC for 24 hours. After 24 hours, the surface (surface to which the polyolefin film was in contact) of "Zeonoa Film" (registered trademark) was visually observed and evaluated according to the following criteria. In addition, when the value of SPk of front and back was the same, the surface with a smaller value of average surface roughness Sa was made into the bonding surface. Furthermore, when the value of Sa was the same value in the front and back, the surface of the smaller one of the maximum surface roughness Sz was made into the joint surface.

A: Clean, same as before loading.

B: Weak irregularities are confirmed.

C: A strong unevenness|corrugation is confirmed.

(12) Planarity of the film

A polyolefin film with a width of 500 mm and a length of 200 m is wound on a core, taken out after heating in an oven at 60° C. for 7 days, cooled to room temperature, and only 1 m of a polyolefin film with a width of 500 mm wound on the core is unwound, Pre-tension (the state of being hung vertically due to the weight of the film) and 1kg/m and 3kg/m of tension uniformly applied to the entire width of the film without unevenness. The presence or absence was visually confirmed.

S: There is no point of flatness defect by pre-tension.

A: Points with poor planarity are seen with pre-tension, and disappear with tension of 1 kg/m width.

B: A point of poor planarity is seen with a tension of 1 kg/m width, and disappears with a tension of 3 kg/m width.

C: The point where the flatness defect does not disappear even with a tension of 3 kg/m width.

(Polypropylene raw material, etc.)

The polypropylene raw material which has a number average molecular weight (Mn) and Z+1 average molecular weight (Mz+1) shown in following Table 1 was used for manufacture of the polyolefin film of an Example and a comparative example. In addition, these values are the 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 were prepared as PP raw material B. In addition, as the branched polypropylene raw material 1, the following were used.

Polypropylene raw material 1 (PP1): Made by Prime Polymer Co., Ltd.

Polypropylene Raw Material 2 (PP2): Made by Prime Polymer Co., Ltd.

Polypropylene raw material 3 (PP3): Sumitomo Chemical Co., Ltd.

Polypropylene raw material 4 (PP4): Made by Prime Polymer Co., Ltd.

Branched polypropylene raw material 1 (branched PP1): metallocene catalyst-based branched polypropylene raw material (Nippon Polypro Co., Ltd., melt tension: 13 gf)

Branched polypropylene raw material 2 (branched PP2): metallocene catalyst-based branched polypropylene raw material (Nippon Polypro Co., Ltd., melt tension: 5 gf)

Branched polypropylene raw material 3 (branched PP3): Ziegler-Natta catalyst-based branched polypropylene raw material (Basell, melt tension: 15 gf)

Low stereoregularity polypropylene raw material: Idemitsu Kosan Co., Ltd. product, "L-MODU" (registered trademark) S901.

Polypropylene raw material D: Polypropylene raw material 3 and 4-methyl-1-pentene polymer are supplied from a metering hopper to a twin-screw extruder so as to be 90:10 (mass ratio), melt-kneaded at 260°C, and melted resin The composition was discharged from the die on the strand, solidified by cooling in a water bath at 25°C, and cut into chips.

4-methyl-1-pentene polymer: Mitsui Chemicals Co., Ltd. product, MX004

1-butene polymer: Mitsui Chemicals Co., Ltd. "Tapmer" (registered trademark) BL3450 (MFR=12 g/10 min (load 21.18 N, 230°C), 1-butene-derived structural unit: 87 mol%) .

(Example 1)

As a raw material for the surface layer (I), the polypropylene raw material 3 and the 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 a raw material for the base layer (II), the polypropylene raw material 2, the polypropylene raw material 3 and the branched polypropylene raw material 1 were dry blended at a ratio of 70:26:4 (mass ratio) in a single screw extruder for the inner layer (II). supplied For each resin mixture, melt extrusion was performed at 260 ° C., and foreign matter was removed with a sintered filter having a cut of 20 μm. It laminated|stacked so that the surface layer (I) might become a thickness ratio of 1/20/1, and it discharged to the casting drum which controlled the surface temperature at 22 degreeC, and made it adhere to the casting drum with an air knife. Then, on the uncooled drum surface of the sheet|seat on a casting drum, 22 degreeC pneumatic air was blown off, it was made to blow at the air velocity of 140 m/s, and it cooled, and obtained the unstretched sheet|seat. Subsequently, the unstretched sheet was preheated to 108°C with a ceramic roll, and as the first stage of stretching, stretching was performed 1.5 times in the longitudinal direction between rolls at 108°C with a circumferential speed difference. Then, as 2nd stage extending|stretching, the 3.4-times extending|stretching was performed in the longitudinal direction between rolls at 146 degreeC. 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, stretched 9.2 times in the width direction at 152° C., and 13% relaxation in the width direction Heat treatment was performed at 175 ° C. 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, and after heating for 0.5 seconds with a hot roll at 123° C. got the film. Table 2 shows the physical properties and evaluation results of the obtained film.

(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, thickness adjustment was performed by adjustment of the discharge amount at the time of extrusion, or speed adjustment of a casting drum. Table 2 shows the physical properties and evaluation results of the obtained film. In addition, about the raw material mixing of the surface layer, in the surface layer (I) of Example 3 and Comparative Example 1, by dry blending the polypropylene raw material 3 and the polypropylene raw material D at 70:30 (mass ratio), the surface layer of Comparative Example 2 In (I), it was carried out by dry blending the polypropylene raw material 3 and the polypropylene raw material D at 80:20 (mass ratio). In the surface layer (I) and the base layer (II) of another example, the polypropylene raw material D was not used, and each resin component was dry-blended in the ratio of Table 2.

As described above, the polyolefin film of the present invention can be used for various industrial uses, such as packaging films, surface protection films, process films, sanitary products, agricultural products, construction products, medical products, and capacitor films. From the viewpoint of being excellent, it can be preferably used as a surface protection film, a process film, a film for mold release, and a film for capacitors.

Claims (13)

The film is measured by DSC, the crystallization temperature Tc ₀ obtained by the extrapolation method is 110 ° C or more, the in-plane retardation of the film is 400 nm or less, and the coefficient of kinetic friction μd after heating at 130 ° C for 10 minutes is 0.7 or less, Polyolefin film. The polyolefin film according to claim 1, wherein the elongation at break in a direction perpendicular to the main orientation of the film at 130°C is 100% or more. The polyolefin film of Claim 1 or 2 whose content rate of the cyclic olefin resin in a film is less than 2.0 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 non-uniformity of the orientation angle within 10 cm square of the film is 3.0 degrees or less. The polyolefin film according to any one of claims 1 to 5, comprising a polypropylene resin as a main component. The polyolefin film according to any one of claims 1 to 6, which has at least a surface layer (I) and a base layer (II). The method according to any one of claims 1 to 7, wherein in the molecular weight distribution curve measured by the gel permeation chromatography method, the differential distribution value when the logarithmic molecular weight Log(M) is 4.0 is 3% or more and 15% or less, polyolefin film. The method according to any one of claims 1 to 8, wherein in the molecular weight distribution curve measured by the gel permeation chromatography method, the differential distribution value when the logarithmic molecular weight Log(M) is 6.1 is 1% or more and 15% or less, polyolefin film. The surface protection film using the polyolefin film in any one of Claims 1-9. Process film using the polyolefin film in any one of Claims 1-9. The film for mold release using the polyolefin film in any one of Claims 1-9. The film capacitor using the polyolefin film in any one of Claims 1-9.

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