WO2020196602A1

WO2020196602A1 - Polypropylene film

Info

Publication number: WO2020196602A1
Application number: PCT/JP2020/013262
Authority: WO
Inventors: 岡田一馬; 大倉正寿; 山中康平
Original assignee: 東レ株式会社
Priority date: 2019-03-28
Filing date: 2020-03-25
Publication date: 2020-10-01
Also published as: CN113490704A; CN113490704B; JPWO2020196602A1; TW202102592A; KR20210148096A; TWI824130B

Abstract

A polypropylene film according to the present invention has a thermal shrinkage force at 140°C of 400 mN or less in both a main orientation axis direction and a direction perpendicular thereto, and a Young's modulus of 1.8 GPa or more in both the main orientation axis direction and the direction perpendicular thereto.　Provided is a polypropylene film having excellent thermal resistance and quality.

Description

Polypropylene film

The present invention relates to a polypropylene film having excellent shrinkage characteristics at high temperatures, mechanical strength at high temperatures, heat resistance, productivity, and quality.

Polypropylene film has excellent transparency, mechanical properties, electrical properties, etc., so it is used in various applications such as packaging, mold release, tape, cable wrapping, and electrical applications such as 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.

The required characteristics of the release film are appropriately set depending on the intended use, but one of the ways to use it is to attach it to an adherend and then heat it to a high temperature of 140 to 150 ° C, such as an oven or an oven. May go through the process. In such cases, PET films with excellent heat resistance have often been used, but PET films have poor mold releasability and may not satisfy the required characteristics, and have excellent heat resistance and releasability. Film may be required.

If the shrinkage force at high temperature is large, it may peel off from the adherend or curl when it is attached to the adherend and passes through the heating process. In particular, polypropylene has a low melting point of about 160 ° C., and it is very difficult to suppress a shrinkage force of about 140 to 150 ° C.

As a means for heat resistance, for example, Patent Document 1 describes an example in which the heat treatment temperature is extremely high and the orientation is relaxed to reduce the shrinkage force at 120 ° C. Further, Patent Documents 3 and 4 describe an example in which the heat shrinkage rate is lowered by raising the heat treatment temperature in the relaxation treatment and relaxing the orientation. Further, Patent Document 2 describes an example in which the heat shrinkage rate is lowered by lowering the molecular weight of the polypropylene raw material. Further, Patent Document 5 describes an example in which the contraction force at 140 ° C. is lowered by making the relaxation rate after lateral stretching extremely large.

Generally, in order to reduce the shrinkage force, a method of lowering the orientation of the polypropylene film is used, but if the mechanical strength of the polypropylene film at high temperature is low, a problem may occur. For example, when adhesive coating is applied to a polypropylene film and the adhesive layer is dried in a high-temperature oven, quality problems such as wrinkles may occur. Further, Patent Document 5 describes an example in which the contraction force at 140 ° C. is lowered by making the relaxation rate after lateral stretching extremely large.

From the above, it is required to reduce the shrinkage force at high temperature and maintain the mechanical strength at high temperature, but in general, when trying to increase the mechanical strength at high temperature, the orientation of the polypropylene film is adjusted. It is necessary to increase it, and when the orientation is relaxed, a contraction force is generated, and the contraction force may increase. That is, the contraction force and the mechanical strength are in a trade-off relationship, and it is difficult to achieve both.

Japanese Unexamined Patent Publication No. 2003-041017 Japanese Unexamined Patent Publication No. 2014-051657 JP-A-2017-125184 International Publication No. 2016/006578 International Publication No. 2014/148547

However, the methods described in Patent Documents 1 and 3 have a problem that the mechanical strength is low and wrinkles are formed when the polypropylene film and the adhesive film are transported at a high temperature. Further, the methods described in Patent Documents 2 and 4 have problems such as high heat shrinkage at high temperature, peeling from the adherend, and curling. Further, the method described in Patent Document 5 has a problem that the rigidity of the film at a high temperature is low, the film stretches in the flow direction when the adhesive film is conveyed at a high temperature, and the width shrinkage becomes large.

Therefore, the subject of the present invention is to solve the above-mentioned problems. That is, it is an object of the present invention to provide a polypropylene film which is excellent in mechanical strength at room temperature and high temperature despite its low heat shrinkage force and can be suitably used as a release film in a high temperature environment.

In order to solve the above-mentioned problems and achieve the object, the polypropylene film of the present invention has a heat shrinkage force at 140 ° C. in both the main orientation axis direction and the direction orthogonal to the main orientation axis direction of 400 mN or less, and the main orientation axis. The Young's modulus in both the direction and the direction orthogonal to the direction is 1.8 GPa or more.

Despite its low heat shrinkage, the polypropylene film of the present invention has excellent mechanical strength at room temperature and high temperature, and can be suitably used as a release film in a high temperature environment.

The polypropylene film of the present invention has a heat shrinkage force of 400 mN or less at 140 ° C. in both the main orientation axis direction and the direction orthogonal to the main orientation axis direction, and the Young's modulus in both the main orientation axis direction and the direction orthogonal to the main orientation axis direction is 1. It is 8 GPa or more.

The heat shrinkage force at 140 ° C. in the direction of the main orientation axis and in the direction orthogonal to the main orientation axis is more preferably 350 mN or less, further preferably 100 mN or less, still more preferably 95 mN or less, and most preferably 30 mN or less. is there. When the heat shrinkage force at 140 ° C. in the main orientation axis direction and the direction orthogonal to it exceeds 400 mN in at least one of them, it may be peeled off from the adherend due to shrinkage when it is bonded to the adherend and passed through the heating step. , Curls may occur. The lower limit of the heat shrinkage force at 140 ° C. in the main orientation axis direction and the direction orthogonal to the main orientation axis direction is not particularly limited, but is substantially -100 mN. Here, the heat shrinkage force means a heat shrinkage force in a width of 4 mm, and the measurement thereof can be performed by the method shown in the examples.

The main orientation axis direction in the present invention is 15 °, 30 °, 45 °, 60 °, 75 °, 90 ° with respect to the longitudinal direction when the longitudinal direction is 0 ° in the film plane. , 105 °, 120 °, 135 °, 150 °, 165 °, the direction showing the highest value when Young's modulus is measured in each direction. Here, in the polypropylene film of the present invention, the "longitudinal direction" is the direction corresponding to the flow direction in the film manufacturing process (hereinafter, may be referred to as "MD"), and the "width direction" is the above-mentioned film. It is a direction orthogonal to the flow direction in the manufacturing process (hereinafter, may be referred to as "TD"). When the film sample has a shape such as a reel or a roll, the film winding direction can be said to be the longitudinal direction. On the other hand, in the case of a film in which it is not clear from the appearance of the film which direction corresponds to the flow direction in the film manufacturing process, for example, a line is drawn in 15 ° increments with reference to an arbitrary straight line on the film plane. A slit-shaped film piece is sampled in parallel with each line, the Young ratio is obtained with a tensile tester, and the direction in which the maximum Young ratio is given is regarded as the main orientation axis direction. Details will be described later, but if the sample width is less than 150 mm and the Young's modulus cannot be determined with a tensile tester, the crystal orientation of the α crystal (110) plane of the polypropylene film by wide-angle X-ray is measured as follows. , The film length and width directions are based on the following criteria. That is, X-rays are incident in the direction perpendicular to the film surface, and the crystal peak at 2θ = about 14 ° (α crystal (110) plane) is scanned in the circumferential direction, and the diffraction intensity of the obtained diffraction intensity distribution is obtained. The highest direction is the main orientation axis direction.

The Young's modulus in the main orientation axis direction and the direction orthogonal to the main orientation axis direction is more preferably 2.0 GPa or more, and further preferably 2.3 GPa or more. When the Young's modulus in the main orientation axis direction and the direction orthogonal to the main orientation axis is less than 1.8 GPa in at least one of them, the polypropylene film is adhesively coated and the adhesive layer is dried in a high temperature oven when wrinkles are formed. There is. The upper limit of Young's modulus in the direction of the main orientation axis and the direction orthogonal to the main orientation axis direction is not particularly limited, but is substantially about 10 GPa.

In order to set the values of the heat shrinkage force at 140 ° C. and the Young's modulus in the main orientation axis direction and the direction orthogonal to the main orientation axis direction in the above range, the raw material composition of the film should be in the range described later, and the film forming conditions should be in the range described later. In particular, a raw material having high crystallinity, a low cold xylene-soluble portion, and a high melting point was used, and the preheating roll temperature during longitudinal stretching was set within the range described later to make the crystalline state before stretching uniform. Above, highly oriented stretching is effective.

The polypropylene film of the present invention preferably has a temperature of 116 ° C. or higher, more preferably 124 ° C. or higher, and even more preferably 124 ° C. or higher when the heat shrinkage force is 20 mN or higher in the main orientation axis direction and the direction orthogonal to the main orientation axis direction. Both are 132 ° C. or higher, most preferably 142 ° C. or higher. When the temperature at which the heat shrinkage force is 20 mN or more is less than 116 ° C. in at least one of the main orientation axis direction and the direction orthogonal to the main orientation axis direction, due to shrinkage when the material is bonded to the adherend and passes through the heating step. It may come off from the adherend or curl. The upper limit of the temperature when the heat shrinkage force becomes 20 mN or more is not particularly limited, but is substantially about 160 ° C. In order to set the temperature value when the heat shrinkage force is 20 mN or more in the above range, the raw material composition of the film is set in the range described later, and the film forming conditions are set in the range described later, and in particular, it is highly crystalline and cold. Use a raw material with a low xylene-soluble part and a high melting point, set the preheating roll temperature during longitudinal stretching to the range described later, homogenize the crystal state before stretching, and perform the heat treatment step after transverse stretching. It is effective to moderately promote the relaxation of the film.

In the polypropylene film of the present invention, the maximum point stress at 120 ° C. in both the main orientation axis direction and the direction orthogonal to the main orientation axis direction is preferably 80 MPa or more, more preferably both 100 MPa ° C. or higher, and further preferably 120 MPa or higher. .. When the maximum point stress at 120 ° C. is less than 80 MPa in at least one of the main orientation axis direction and the direction orthogonal to it, the polypropylene film is adhesively coated and the adhesive layer is dried in a high temperature oven. Wrinkles may occur. The upper limit of the maximum point stress is not particularly limited, but is substantially about 300 MPa. In order to set the maximum point stress in the above range, the raw material composition of the film is set in the range described later, and the film forming conditions are set in the range described later. In particular, it is highly crystalline, has a low cold xylene-soluble portion, and has a high melting point. It is preferable to use a raw material, set the preheating roll temperature at the time of longitudinal stretching within the range described later, homogenize the crystal state before stretching, and then perform highly oriented stretching. Further, it is preferable that the heat treatment temperature after lateral stretching and the relaxation rate are set in the ranges described later, and the orientation of the film is not relaxed more than necessary.

The polypropylene film of the present invention preferably has a maximum protrusion roughness St on at least one side of 2000 nm or more, more preferably 4000 nm or more, and further preferably 6000 nm or more. If the St on both sides of the film is less than 2000 nm, the releasability when peeling from the adherend is insufficient, and the adherend may be deformed or ruptured. The upper limit of St is not particularly limited, but is substantially about 30,000 nm. In order to set St to the above range, 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. In particular, the casting temperature is raised and β crystals are formed in the unstretched film in the casting step. It is effective to do.

The polypropylene film of the present invention preferably has a thickness unevenness in the main orientation axis direction of less than 6.0%, more preferably less than 4.0%, and further preferably less than 2.0%. If the thickness unevenness in the main orientation axis direction is 6.0% or more, it becomes difficult to attach the adherend to the adherend neatly, and the adherend may be peeled off or air biting may be mixed. .. The lower limit of the thickness unevenness in the main orientation axis direction is not particularly limited, but is substantially about 0.1%. In order to set the thickness unevenness in the main orientation axis direction within the above range, the raw material composition of the film is set to the range described later, the film forming conditions are set to the range described later, and in particular, the preheating and stretching temperature during transverse stretching are set to the range described later. It is effective to adjust to and increase the lateral stretching ratio.

The polypropylene film of the present invention preferably has a heat shrinkage force of 95 mN or less at 140 ° C. in the direction orthogonal to the main orientation axis direction, more preferably 60 mN or less, still more preferably 30 mN or less, and most preferably 10 mN or less. When the heat shrinkage force at 140 ° C. in the direction orthogonal to the main orientation axis direction exceeds 95 mN, the shrinkage causes peeling or curling from the adherend when it is attached to the adherend and passes through the heating step. It may happen. The lower limit of the heat shrinkage force at 140 ° C. in the direction orthogonal to the main orientation axis direction is not particularly limited, but is substantially −100 mN. In order to set the heat shrinkage force at 140 ° C. in the direction orthogonal to the main orientation axis direction within the above range, 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 longitudinal stretching. It is effective to set the preheating roll temperature at that time in the range described later, make the crystal state before stretching uniform, and then perform highly oriented stretching. In addition, it is more effective to set the preheating temperature and stretching temperature at the time of lateral stretching within the range described later, raise the preheating temperature to a high temperature, preheat the polypropylene film uniformly, and perform high stress stretching at a temperature lower than the preheating temperature. Is.

The polypropylene film of the present invention has a value obtained by multiplying the Young's ratio (GPa) at 120 ° C. in the direction orthogonal to the main orientation axis direction by the film thickness (μm) at 1.5 (GPa · μm) or more. It is preferably 3.0 (GPa · μm) or more, more preferably 4.0 (GPa · μm) or more, and most preferably 5.5 or more. The value obtained by multiplying the Young's modulus at 120 ° C. in the direction orthogonal to the main orientation axis direction by the film thickness has a high correlation with the rigidity of the film in a high temperature environment, and the value is less than 1.5. In some cases, the film being conveyed may stretch in the flow direction and the width of the film may shrink significantly when the film is bonded to the adherend and passed through the heating step. The upper limit of the value obtained by multiplying the Young's modulus at 120 ° C. in the direction orthogonal to the main orientation axis direction by the thickness of the film is not particularly limited, but is substantially about 30. In order to set the value obtained by multiplying the Young ratio at 120 ° C. in the direction orthogonal to the main orientation axis direction by the thickness of the film in the above range, the raw material composition of the film should be in the range described later, and the film forming conditions should be set. The range to be described later, in particular, the preheating roll temperature at the time of longitudinal stretching is the range to be described later, and after homogenizing the crystal state before stretching, highly oriented stretching, the preheating at the time of transverse stretching, and the stretching temperature are the ranges to be described later. It is effective that the film is uniformly preheated at a high temperature, highly oriented and stretched at a low temperature, the relaxation rate is not too large, and the orientation is not relaxed too much.

The polypropylene film of the present invention has a laminated structure of two or more layers, and at least one layer contains 50 polypropylene having a cold xylene-soluble portion (CXS) of 3.5% or less based on 100% by mass of the whole layer. It is preferable that the layer contains by mass% or more and 100% by mass or less, a more preferable content is 70% by mass or more and 100% by mass or less, a further preferable content is 90% by mass or more and 100% by mass or less, and the most preferable content is 95. It is 100% by mass or more and 100% by mass or less. Here, CXS refers to a polyolefin component dissolved in xylene when the sample is completely dissolved in xylene and then precipitated at room temperature, for reasons such as low stereoregularity and low molecular weight. It is considered that it corresponds to a component that is difficult to crystallize. If a large amount of such a component is contained in the resin, the thermal dimensional stability of the film may be inferior. Therefore, the CXS of polypropylene contained in the polypropylene film of the present invention is more preferably 2.0% or less, further preferably 1.5% or less. When the polypropylene film has a laminated structure of two or more layers and the content of polypropylene having a CXS of 3.5% or less in at least one layer is less than 50% by mass, the mechanical strength of the polypropylene film at a high temperature is insufficient. As a result, for example, when a polypropylene film is adhesively coated and the adhesive layer is dried in a high temperature oven, wrinkles may occur. Further, in a laminated structure of two or more layers, when polypropylene having a CXS of more than 3.5% is contained in 50% by mass or more and 100% by mass or less in at least one layer, the heat shrinkage force becomes large and the polypropylene is bonded to the adherend. When passing through the heating step, it may be peeled off from the adherend or curled due to shrinkage. The lower limit of CXS of at least one layer is not particularly limited, but is substantially about 0.1%. In order to set CXS in the above range, it is effective to set the raw material composition of the film in the range described later, and in particular, to use a polypropylene raw material having a low CXS.

The polypropylene film of the present invention is not particularly limited in whether it has a single-layer structure or a laminated structure as long as it contains polypropylene, but as described above, the polypropylene film of the present invention has a laminated structure of two or more layers. Therefore, at least one layer is preferably a layer containing 50% by mass or more and 100% by mass or less of polypropylene having a CXS of 3.5% or less. The layer containing 50% by mass or more and 100% by mass or less of polypropylene having a CXS of 3.5% or less is preferably the thickest layer among the layers having a laminated structure. In particular, it is preferable that the inner layer having a three-layer structure is a layer containing 50% by mass or more and 100% by mass or less of polypropylene having a CXS of 3.5% or less.

The polypropylene film of the present invention has a laminated structure of two or more layers, and at least one layer is heated from 25 ° C. to 250 ° C. at 20 ° C./min by a differential scanning calorimeter DSC, and then from 250 ° C. to 25 ° C. The crystallization peak temperature (Tc) when the temperature is lowered at 20 ° C./min is preferably 110 ° C. or higher, more preferably 112 ° C. or higher, and further preferably 114 ° C. or higher. Tc has a correlation with the ease of crystallization, and the higher the Tc, the easier it is to crystallize. The polypropylene film crystallizes to form spherulites when solidified on a cooling drum after melt extrusion. The higher the Tc, the more dense spherulites are generated on the unstretched sheet, and the protrusions on the surface shape of the film after biaxial stretching become finer accordingly. The higher the Tc, the more preferable, from the viewpoint of obtaining a surface in which the protrusions having good releasability are obtained without dent transfer to the adherend. The upper limit of Tc is not particularly limited, but is substantially about 125 ° C. In order to set Tc in the above range, the raw material composition of the film is set in the range described later, and it is particularly effective to use branched-chain polypropylene or a polypropylene raw material having a high molecular weight. In order to obtain the value of Tc, it is necessary to separate the polypropylene film into each layer and evaluate each layer. However, when it is difficult to separate into each layer, the polypropylene film is evaluated as a whole and the value is regarded as a representative value.

The thickness of the polypropylene film of the present invention is appropriately adjusted depending on the intended use and is not particularly limited, but it is preferably 0.5 μm or more and 100 μm or less from the viewpoint of handleability. In order to take advantage of such characteristics, the thickness is more preferably 1 μm or more and 40 μm or less, further preferably 1 μm or more and 30 μm or less, and most preferably 6 μm or more and 30 μm or less. 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, the raw material of the polypropylene film of the present invention will be described, but the present invention is not necessarily limited to this.

The polypropylene film of the present invention is not particularly limited in whether it has a single-layer structure or a laminated structure as long as it contains polypropylene, but as described above, the polypropylene film of the present invention has a laminated structure of two or more layers. Therefore, at least one layer is preferably a layer containing 50% by mass or more and 100% by mass or less of polypropylene having a CXS of 3.5% or less. In order to obtain a polypropylene film having such a layer (a layer containing 50% by mass or more and 100% by mass or less of polypropylene having a CXS of 3.5% or less), a raw material having a CXS of 3.5% or less (hereinafter, As a raw material, polypropylene having a CXS of 3.5% or less is preferably used as the polypropylene raw material A). The CXS of the polypolopylene raw material A is more preferably 2.0% or less, still more preferably 1.5% or less. The content of the polypropylene raw material A is preferably 50% by mass or more, more preferably 70% by mass or more, and 90% by mass or more, when the layer containing the polypropylene raw material A is 100% by mass. It is more preferably 95% by mass or more, and most preferably 95% by mass or more. In order to obtain a polypropylene raw material satisfying such CXS, 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.

Further, as the polypropylene raw material A, homopolypropylene is preferably used from the viewpoint of strength and heat resistance.

The polypropylene raw material A preferably has a melting point of 155 ° C. or higher, more preferably 160 ° C. or higher, and even more preferably 165 ° C. or higher. When the melting point is less than 155 ° C., the heat resistance is poor, and when the product is bonded to the adherend and passed through the heating step, it may be peeled off from the adherend or curled due to shrinkage.

The polypropylene raw material A preferably has a mesopentad fraction of 0.94 or more, and more preferably 0.97 or more. The mesopentad fraction is an index showing the stereoregularity of the polypropylene crystal phase measured by nuclear magnetic resonance spectroscopy (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 cocatalyst, a method of appropriately selecting a composition, and the like are used. It is preferably adopted.

Further, as the polypropylene raw material A, the melt flow rate (MFR) is more preferably 1 to 10 g / 10 minutes (230 ° C., 21.18 N load), and more preferably 1 to 8 g / 10 minutes (230 ° C., 21. 18N load), and particularly preferably in the range of 4 to 8g / 10 minutes (230 ° C., 21.18N load) from the viewpoint of film forming property and film strength. In order to set the melt flow rate (MFR) to the above value, a method of controlling the average molecular weight or the molecular weight distribution is adopted.

The polypropylene raw material A may contain a copolymerization component of other unsaturated hydrocarbons or the like as long as the object of the present invention is not impaired, or may be blended with a polymer. Examples of the monomer components constituting such copolymerization components and blends 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 and the like can be mentioned. From the viewpoint of dimensional stability, the copolymerization amount or the blend amount is preferably less than 1 mol% in the copolymerization amount and less than 10% by mass in the blend amount.

The content of the ethylene component contained in the polypropylene raw material A is preferably 10% by mass or less. It is more preferably 5% by mass or less, still more preferably 3% by mass 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% by mass, the strength is lowered or the heat resistance is lowered to heat. The shrinkage rate may worsen. In addition, the resin may easily deteriorate during the extrusion process, and fish eyes may easily occur in the film. The polyolefin raw material used for the polypropylene film of the present invention contains various additives as long as the object of the present invention is not impaired. For example, a crystal nucleating agent, an antioxidant, a heat stabilizer, a slip agent, an antistatic agent, an antiblocking agent, a filler, a viscosity modifier, an antioxidant and the like can be contained.

Among these, selection of the type and amount of antioxidant is important from the viewpoint of bleed-out of 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, Inc., molecular weight 1177.7) or the like. The total content of these antioxidants is preferably in the range of 0.03 to 1.0% by mass with respect to the total amount of the polyolefin raw material. If the amount of antioxidant is too small, the polymer may deteriorate in the extrusion process, the film may be colored, or the long-term heat resistance may be poor. If too much antioxidant is used, bleed-out of these antioxidants may reduce transparency. A more preferable content is 0.05 to 0.9% by mass, and particularly preferably 0.1 to 0.8% by mass.

Further, it is preferable that the polypropylene film of the present invention has at least one layer containing branched chain polypropylene. The content of the branched-chain polypropylene in the layer containing the branched-chain polypropylene resin is preferably 0.05 to 10% by mass when the entire layer is 100% by mass. The crystallization peak temperature (Tc) of the polypropylene film is raised, the spherulite size generated in the cooling process of the melt-extruded resin sheet is controlled to be small, and the sharp height difference of the film surface unevenness after biaxial stretching is reduced. From the viewpoint of forming fine surface irregularities, the lower limit of the content of the branched polypropylene resin is more preferably 0.5% by mass or more, still more preferably 1% by mass or more. On the other hand, the upper limit of the content of the branched chain polypropylene resin is more preferably 8% by mass or less, still more preferably 5% by mass or less.

Further, a crystal nucleating agent can be added to the polypropylene raw material used for the polypropylene film of the present invention within a range not contrary to the object of the present invention. α-crystal nucleating agents (dibenzylideneacetone sorbitols, sodium benzoate, etc.), β-crystal nucleating agents (potassium 1,2-hydroxystearate, magnesium benzoate, N, N'-dicyclohexyl-2,6-naphthalenecarboxamide, etc. Amide compounds, quinacridone compounds, etc.) are exemplified. However, since excessive addition of the above-mentioned other type of nucleating agent may cause a decrease in stretchability and a decrease in transparency and strength due to void formation, etc., the addition amount is usually 0.5% by mass or less, preferably 0.1. It is preferably mass% or less, more preferably 0.05 mass% or less.

The polypropylene 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 polypropylene film of the present invention will be described as an example, but the present invention is not necessarily limited thereto.

First, 80 parts by mass of the polypropylene raw material A and 20 parts by mass of the branched polypropylene raw material are dry-blended and supplied to a single-screw extruder for the B layer (base layer (II)), and the polypropylene raw material A is supplied to the A layer (surface layer (surface layer (II)). It is supplied to the single-screw extruder for I)), and melt extrusion is performed at 200 to 280 ° C., more preferably 220 to 280 ° C., and even more preferably 240 to 270 ° C. 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, discharged onto a casting drum, and A. 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, at least one layer having a CXS of 3.5% or less and a layer having a Tc of 112 ° C. or higher is formed, and the film is excellent in heat resistance and mechanical strength at high temperature. Can be obtained.

Further, the surface temperature of the casting drum is preferably 40 to 120 ° C., preferably 60 to 120 ° C., and more preferably 80 to 110 ° C. Further, a two-layer laminated structure of A layer / B layer may be used. 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 as the adhesion method to the casting drum, but the flatness is good. The air knife method, which is capable of controlling the surface roughness, is preferable. The air temperature of the air knife is preferably 40 to 100 ° C., and the blown 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.

The obtained unstretched sheet is introduced into the longitudinal stretching step. In the longitudinal stretching step, first, the unstretched sheet is brought into contact with a plurality of metal rolls kept at 10 ° C. or higher and 160 ° C. or lower, preferably 140 ° C. or higher and 158 ° C. or lower, and more preferably 145 ° C. or higher and 155 ° C. or lower to preheat them. After stretching 4 to 8 times in the longitudinal direction between the rolls provided with the peripheral speed difference, the mixture is cooled to room temperature. The stretching temperature is 100 ° C. or higher and 150 ° C. or lower, preferably 100 ° C. or higher and 140 ° C. or lower, and more preferably 110 ° C. or higher and 130 ° C. or lower. By heating to a high temperature in the preheating step of longitudinal stretching, β crystals in the unstretched film are transferred to α crystals, and the crystal state in the polypropylene film can be made uniform. Further, by lowering the stretching temperature to a lower temperature than the preheating temperature, stretching can be performed with high stress. In this way, by making the crystal state in the polypropylene film uniform and stretching with high stress in the longitudinal stretching step, it is possible to obtain a polypropylene film having excellent mechanical strength at high temperature and low heat shrinkage. .. The draw ratio is preferably 3 times or more and 6 times or less, and more preferably 4 times or more and 5.5 times or less.

Next, guide the longitudinally uniaxially stretched film to the tenter, grasp the end of the film with a clip, preheat it, and then laterally stretch it 7 to 13 times in the width direction. At this time, the preheating temperature is raised, the polypropylene film is uniformly preheated, and the polypropylene film is stretched under high stress at a temperature lower than the preheating temperature to obtain a polypropylene film having excellent mechanical strength at high temperatures and low heat shrinkage. be able to. From this, the preheating temperature is 165 to 180 ° C, more preferably 170 to 180 ° C, and even more preferably 173 to 180 ° C. The transverse stretching temperature is 155 to 170 ° C, more preferably 155 to 165 ° C, and even more preferably 155 to 160 ° C.

In the subsequent heat treatment and relaxation treatment step, while tension-grasping the width direction with a clip, relaxation is applied at a relaxation rate of 2 to 20%, more preferably 8 to 18%, still more preferably 10 to 15% in the width direction, and 140 ° C. Heat-fixed at a temperature of 140 ° C. or higher and lower than 160 ° C., and guided to the outside of the tenter through a cooling step at 80 to 100 ° C. while tension-grasping in the width direction with a clip. Release the clip, slit the film edge in the winder process, and wind up the film product roll. When the heat treatment is performed at a high temperature of 170 ° C. or higher, the orientation of the polypropylene film is relaxed, which may lead to a decrease in mechanical strength. In particular, the decrease in mechanical strength in the high temperature range becomes remarkable. Further, if the relaxation treatment is performed at a relaxation rate of 20% or more, the orientation of the polypropylene film is relaxed, which may lead to a decrease in mechanical strength. In particular, the decrease in mechanical strength in the high temperature range becomes remarkable.

The polypropylene film obtained as described above can be used for various purposes such as packaging films, surface protective films, process films, sanitary products, agricultural products, construction products, medical products, etc., but especially for surface smoothness. Since it is excellent, it can be preferably used as a surface protective film, a process film, and a release film, and particularly preferably as a release film.

Next, an example in which the polypropylene film of the present invention is used as a coating base material (base material film) for an adhesive film will be described. The polypropylene film of the present invention can be an adhesive film having an adhesive layer on at least one side thereof.

The pressure-sensitive adhesive used for the pressure-sensitive adhesive layer in the pressure-sensitive adhesive film of the present invention is not particularly limited, and rubber-based, vinyl polymerization-based, condensation polymerization-based, thermosetting resin-based, silicone-based, and the like can be used. Among these, examples of the rubber-based pressure-sensitive adhesive include a butadiene-styrene copolymer system, a butadiene-acrylonitrile copolymer system, and an isobutylene-isoprene copolymer system. Examples of the vinyl polymerization type pressure-sensitive adhesive include an acrylic type, a styrene type, a vinyl acetate-ethylene copolymer system, and a vinyl chloride-vinyl acetate copolymer system. Further, as the condensation polymerization type pressure-sensitive adhesive, a polyester type can be mentioned. Further, examples of the thermosetting resin-based adhesive include an epoxy resin-based adhesive and a urethane resin-based adhesive.

Among these, an acrylic adhesive is preferably used in consideration of excellent transparency, weather resistance, heat resistance, moisture heat resistance, substrate adhesion, and the like. Specific examples of such acrylic pressure-sensitive adhesives include "SK Dyne" (registered trademark) 1310, 1435, SK Dyne 1811L, SK Dyne 1888, SK Dyne 2094, SK Dyne 2096, SK Dyne 2137, SK manufactured by Soken Kagaku Co., Ltd. Preferable examples include Dyne 3096 and SK Dyne 1852.

Further, it is preferable to use a curing agent together with the acrylic pressure-sensitive adhesive. Specific examples of the curing agent include toluene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylene diisocyanate, and diphenylmethane-4 in the case of isocyanate. -4'-diisocyanate, diphenylmethane-2-4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4-4'-diisocyanate, dishikiurohexylmethane-2-4'-diisocyanate , Lysine isocyanate and the like. The mixing ratio of the curing agent is 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the pressure-sensitive adhesive. If it is less than 0.1 parts by mass, the pressure-sensitive adhesive layer is not sufficiently cured in the drying furnace, and lining may occur. If it exceeds 10 parts by mass, the excess curing agent may be transferred to the substrate or gasified at a high temperature to cause contamination.

Further, the acrylic pressure-sensitive adhesive may be appropriately added with an antioxidant, an ultraviolet absorber, a silane coupling agent, a metal deactivator, etc., depending on the material of the adherend (glass or functional film). ..

The pressure-sensitive adhesive film using the polypropylene film of the present invention preferably has a pressure-sensitive adhesive layer thickness d of 2.0 μm or less. It is more preferably 1.5 μm or less, still more preferably 1.0 μm or less. If the thickness d of the adhesive layer exceeds 2.0 μm, the slipperiness between the back surface of the base film and the surface of the adhesive layer may deteriorate and winding may become difficult. In addition, the adhesive layer may not be sufficiently dried in the drying oven, resulting in lining. “Bleed” means that after applying a solution of an adhesive layer on one side of a base film, it is dried and cured in a drying furnace, and the adhesive film of the present invention is wound into a roll without passing through a release film. Later, when the adhesive film is unwound during use, a part of the adhesive layer is transferred to the back surface of the base film. A known technique can be used for the method of setting the thickness of the adhesive layer in the above range, and it can be controlled by adjusting the solid content concentration of the solution of the adhesive layer and the coating thickness in various coating methods. If the thickness of the adhesive layer is too thin, stable coating may be difficult, or the adhesive strength may be too low to adhere to the adherend. Therefore, the lower limit is about 0.1 μm.

The adhesive film using the polypropylene film of the present invention preferably has a 180 ° peeling force of 200 mN / 25 mm or less after being attached to an acrylic plate. The peeling force is more preferably 100 mN / 25 mm or less, still more preferably 80 mN / 25 mm or less. If the peeling force exceeds 200 mN / 25 mm, the slipperiness between the back surface of the base film and the surface of the adhesive layer deteriorates, which may make winding difficult or line-off may occur. In order to set the peeling force in the above range, the composition and thickness of the adhesive layer are set in the range described later, and the raw material composition and film forming conditions of the film are set in the range described later, and the surface roughness of the base film is controlled. Is effective. If the peeling force is less than 10 mN / 25 mm, the adhesive film may peel off during transportation after bonding with the adherend, so the lower limit is about 10 mN / 25 mm.

Next, the method for manufacturing the adhesive layer will be described, but the method is not necessarily limited to this.

First, prepare a coating agent for the adhesive layer. The coating agent can be used by dissolving the above-mentioned additives such as a pressure-sensitive adhesive and a curing agent in a solvent. The solvent can be appropriately adjusted depending on the drying temperature of the coater, the viscosity of the coating material, and the like. Specific examples thereof include methanol, ethanol, isopropyl alcohol, n-butanol, tert-butanol, ethylene glycol monomethyl ether, and 1 At least one solvent selected from -methoxy-2-propanol, propylene glycol monomethyl ether, cyclohexanone, toluene, ethyl acetate, butyl acetate, isopropyl acetone, methyl ethyl ketone, methyl isobutyl ketone, diacetyl acetone and acetyl acetone can be used.

The solid content concentration in the coating material is appropriately selected depending on the viscosity of the coating material and the thickness of the adhesive layer, but is preferably 5 to 20% by mass.

Next, the above-mentioned base film is conveyed to the coater, and the coating agent for the adhesive layer is applied. Here, the surface to be coated with the adhesive layer may be either surface of the base film, but the coated surface may be pretreated with a corona treatment or the like in advance to improve the wettability with the coating agent. preferable. On the other hand, it is preferable not to perform pretreatment such as corona treatment on the back surface of the base film in order to improve releasability. The coating method (coating method) is not particularly limited, and existing coating methods such as a metabar method, a doctor blade method, a gravure method, a die method, a knife method, a reverse method, and a dip method can be adopted. However, as described above, the thickness of the adhesive layer is as thin as 2.0 μm or less, and the gravure method or the reverse method is preferable from the viewpoint of stably obtaining the thin coating layer.

After applying the coating agent for the adhesive layer to the base film, guide it to a drying furnace and remove the solvent in the coating agent to obtain an adhesive film. The drying temperature here is appropriately set depending on the heat resistance of the base film and the boiling point of the solvent, but is preferably 60 to 170 ° C. If the temperature is lower than 60 ° C., the adhesive layer may not be sufficiently cured and betrayed may occur. If it exceeds 170 ° C., the base film may be deformed and the flatness may be deteriorated. The drying time is preferably 15 to 60 seconds. If it is less than 15 seconds, the adhesive layer may not be sufficiently cured and betrayed may occur. If it exceeds 60 seconds, the productivity will decrease, which is not preferable.

The dried adhesive film is wound with a winder without attaching a release film or the like to the adhesive surface to obtain an adhesive film roll. The pressure-sensitive adhesive film of the present invention has the above-mentioned structure, so that the pressure-sensitive adhesive layer is sufficiently cured and the slipperiness between the back surface of the base film and the surface of the pressure-sensitive adhesive layer is good. Therefore, the pressure-sensitive adhesive film is wound without a release film. Even if it is taken, there is no problem such as line-up or wrinkles during winding, and a high-quality adhesive film roll can be obtained.

The adhesive film of the present invention obtained as described above can be used for various purposes such as packaging film, surface protective film, process film, sanitary product, agricultural product, building product, medical product, etc., but particularly on the surface. Since it is excellent in smoothness, it can be preferably used as a surface protective film or a process film.

Further, since the polypropylene film of the present invention is excellent in heat resistance and quality, it can be preferably used as a release film that requires extremely high quality in optical members and semiconductor manufacturing processes.

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 to obtain an average value.

(2) Using the temperature TMA (manufactured by SII Nanotechnology Co., Ltd./model TMA / SS6100) when the heat shrinkage force and heat shrinkage force are 20 mN or more, the measurement direction (main orientation axis direction) under the following conditions. And the direction perpendicular to it) the heat shrinkage curve was measured.

(A) Sample: Width 4 mm x length 20 mm
(B) Temperature program: Temperature rise from 30 ° C at a heating rate of 10 ° C / min <heat shrinkage force>
The heat shrinkage force (mN) at 140 ° C. was read from the heat shrinkage force curve. The measurement was performed 3 times and the average was calculated.

<Heat shrinkage start temperature>
In the above heat shrinkage curve, the temperature at which the heat shrinkage becomes 20 mN in the heating process was read. The measurement was performed 3 times and the average was calculated.

(3) Young's modulus The Young's modulus was measured at 23 ° C. and 65% RH using a film strength elongation measuring device (AMF / RTA-100) manufactured by Orientec Co., Ltd. The sample was cut into a size of measurement direction (main orientation axis direction and direction orthogonal to it): 25 cm, direction perpendicular to the measurement direction: 1 cm, stretched at an original length of 100 mm and a tensile speed of 300 mm / min, and the Young ratio was JIS. -Measured according to the method specified in Z1702 (1994).

(4) Young's modulus at 120 ° C. Young's modulus at 120 ° C. is chucked into an oven heated to 120 ° C. using a film strength elongation measuring device (AMF / RTA-100) manufactured by Orientec Co., Ltd. After charging for 1 minute, the film was subjected to a tensile test at a tensile speed of 300 mm / min. The sample is cut into a size of 25 cm in the measurement direction (orthogonal direction of the main orientation axis) and 1 cm in the direction perpendicular to the measurement direction, stretched at an original length of 100 mm and a tensile speed of 300 mm / min, and specified in JIS-Z1702 (1994). It was measured according to the above method.

(5) Maximum point stress at 120 ° C The maximum point stress at 120 ° C is determined in an oven heated to 120 ° C using a film strength elongation measuring device (AMF / RTA-100) manufactured by Orientec Co., Ltd. The film was subjected to a tensile test at a tensile speed of 300 mm / min after being charged together with the chuck and heated for 1 minute. The load value at the time of sample breakage is read, and the value obtained by dividing by the cross-sectional area (film thickness x width (10 mm)) of the sample before the test is calculated as the stress of breaking strength, and the measurement is performed 5 times for each sample, and the average value thereof. It was evaluated in. The value measured in (1) above was used as the film thickness used for calculating the breaking strength.

(6) Maximum protrusion roughness (St)
The measurement was performed using Ryoka System Co., Ltd. VertScan2.0 R5300GL-Lite-AC, and the surface shape was obtained by surface-correcting the photographed screen by polynomial fourth-order approximation using the attached analysis software. The maximum protrusion roughness (St) indicates the difference between the maximum height value (Peek) and the minimum height value (Valley) in the measurement region. The measurement conditions are as follows. The measurement was performed on both sides of the film at n = 3 (number of measurements = 3 times), and the average value of each surface was obtained and adopted as St on each surface. The larger value of the St values on both sides of the film is shown in the table.
Manufacturer: Ryoka System Co., Ltd. Device name: VertScan2.0 R5300GL-Lite-AC
Measurement conditions: CCD camera SONY HR-57 1/2 inch objective lens: 5x
Intermediate lens: 0.5x
Wavelength filter: 530nm white
Measurement mode: Wave
Measurement software: VS-Measure Version 5.5.1
Analysis software: VS-Viewer Version 5.5.1
Measurement area: 1.252 mm x 0.939 mm.

(7) Thickness unevenness A polypropylene film was prepared, the film was cut into a width of 10 mm, and 20 points were measured at intervals of 50 mm in the main orientation axis direction. The average value of the obtained 20 points of data is calculated, the difference between the maximum value and the minimum value (absolute value) is calculated, and the value obtained by dividing the absolute value of the difference between the minimum value and the maximum value by the average value is the main component of the film. The thickness was uneven in the axis of orientation. The measurement was carried out in an atmosphere of 23 ° C. and 65% RH using a contact-type electronic micrometer manufactured by Anritsu Co., Ltd. (K-312A type).

(8) Crystallization peak temperature (Tc)
Using a differential scanning calorimeter (EXSTAR DSC6220 manufactured by Seiko Instruments Inc.), each layer of 3 mg polypropylene film was heated from 25 ° C. to 250 ° C. at 20 ° C./min and held for 5 minutes in a nitrogen atmosphere. Then, the temperature is lowered from 250 ° C. to 25 ° C. at 20 ° C./min. The peak temperature of the heat generation curve obtained at the time of this temperature decrease was defined as the crystallization temperature (Tc) of the polypropylene film. When a plurality of peak temperatures could be observed, the highest temperature in the region of 80 ° C. to 130 ° C. was defined as the crystallization temperature (Tc) of the polypropylene film.

(9) Curl evaluation after heating Polypropylene film and "Zeonoa film" (registered trademark) manufactured by Nippon Zeon Co., Ltd. with a thickness of 40 μm were sampled into a square with a width of 100 mm and a length of 100 mm, and the A side of the polypropylene film and the "Zeonoa film" were sampled. Put them in contact with each other, sandwich them between two acrylic plates (width 100 mm, length 100 mm), apply a load of 2 kg, let stand for 1 hour in an atmosphere of 23 ° C, and then oven at 120 ° C. After heating for 1 hour in the film, the bonded sample was taken out. The Zeonoa film side was placed on the floor, and the height of the curled bonded sample was measured with a ruler and evaluated according to the following criteria.

S: The height of the curled bonded sample is less than 5 mm.
A: The height of the curled bonded sample is 5 mm or more and less than 10 mm.
B: The height of the curled bonded sample is 10 mm or more and less than 15 mm.
C: The height of the curled bonded sample is 15 mm or more.

(10) Flatness of Adhesive Film with Adhesive Layer An adhesive film having an adhesive layer with a width of 500 mm wound around a core is unwound by 1 m, and free tension (a state in which the film hangs vertically due to its own weight) and a film width. Tensions of 1 kg / m and 3 kg / m were uniformly applied to the entire surface, and the presence or absence of poor flatness such as wrinkles and dents was visually confirmed.

S: There is no part with poor flatness due to free tension.
A: With free tension, there are spots with poor flatness, and with tension of 1 kg / m width, it disappears.
B: With a tension of 1 kg / m width, there are some areas with poor flatness, and with a tension of 3 kg / m width, it disappears.
C: A part with poor flatness does not disappear even with a tension of 3 kg / m width.

(9) Width shrinkage of adhesive film having an adhesive layer After applying a coating agent for an adhesive layer to a polypropylene film having a width of 500 mm, it is guided to a drying furnace at 100 ° C. and conveyed at a tension of 200 N for 30 seconds during the coating. The solvent was removed to obtain an adhesive film. The width of the polypropylene film and the width of the adhesive film were measured with a measure, and the width shrinkage ratio was calculated based on the following formula.

Width shrinkage rate (%) = (500-adhesive film width) / 500 x 100
Based on the calculated width shrinkage rate, evaluation was made according to the following criteria.

S: The width shrinkage rate is less than 0.5%.
A: The width shrinkage rate is 0.5% or more and less than 1.0%.
B: The width shrinkage rate is 1.0% or more and less than 2.0%.
C: The width shrinkage rate is 2.0% or more.

(Example 1)
As a raw material for the surface layer (I), 98.5 parts by mass of a homopolypropylene raw material A (MFR: 7.5 g / 10 minutes, melting point: 163 ° C., CXS: 1.0%) manufactured by Sumitomo Chemical Co., Ltd. 1.5 parts by mass of the nutter-catalyzed branched-chain polypropylene raw material B (Profax PF-814) is dry-blended and supplied to a single-screw extruder for the surface layer (I) as a raw material for the inner layer (II). , 98.5 parts by mass of homopolypropylene raw material C (MFR: 4.0 g / 10 minutes, melting point: 166 ° C., CXS: 1.7%) manufactured by Prime Polymer Co., Ltd., and the above-mentioned branched polypropylene B. 5 parts by mass dry blended and supplied to a single-screw extruder for the inner layer (II) layer, melt-extruded at 260 ° C., and after removing foreign matter with a 20 μm cut sintering filter, feed block type A / It was laminated with a B / A composite T-die at a thickness ratio of 1/10/1, discharged to a casting drum whose surface temperature was controlled at 102 ° C., and brought into close contact with the casting drum with an air knife to obtain an unstretched sheet. Subsequently, the sheet was preheated to 155 ° C. using a ceramic roll, and stretched 4.0 times in the longitudinal direction of the film between rolls at 148 ° C. provided with a peripheral speed difference. Next, the end was gripped by a clip and introduced into a tenter type stretching machine, preheated at 180 ° C. for 5 seconds, stretched 9.6 times at 170 ° C., and at 167 ° C. while giving 14% relaxation in the width direction. A heat treatment was performed, and then the film was guided to the outside of the tenter through a cooling step of 100 ° C., the clip at the end of the film was released, and the film was wound around a core to obtain a polypropylene film having a thickness of 25 μm. Table 1 shows the physical properties of the obtained film and the evaluation results.

(Example 2)
Homopolypropylene raw material D (MFR: 3.0 g / 10 minutes, melting point: 164 ° C, CXS: 3.3%) manufactured by Prime Polymer Co., Ltd. 90 parts by mass, 4-Methyl-1-manufactured by Mitsui Chemicals, Inc. Raw materials are supplied from the measuring hopper to the twin-screw extruder so that 10 parts by mass of the penten-based polymer "MX004" (melting point: 230 ° C.) is mixed at this ratio, melt-kneaded at 260 ° C., and from the die in a strand shape. It was discharged, cooled and solidified in a water tank at 25 ° C., and cut into chips to obtain a polypropylene raw material (1). As a raw material for the surface layer (I), 98 parts by mass of the homopolypropylene raw material C and 2 parts by mass of the polypropylene raw material (1) are dry-blended and supplied to a single-screw extruder for the surface layer (I). As a raw material for the inner layer (II), 98.5 parts by mass of the homopolypropylene raw material C and 1.5 parts by mass of the branched polypropylene raw material B are dry-blended to form a single shaft for the inner layer (II). It is supplied to a uniaxial extruder, melt-extruded at 260 ° C., foreign matter is removed with a 20 μm cut sintering filter, and then a 1/12/1 thickness ratio is used with a feed block type A / B / A composite T-die. And discharged to a casting drum whose surface temperature was controlled at 93 ° C., and brought into close contact with the casting drum with an air knife to obtain an unstretched sheet. Subsequently, the sheet was preheated to 153 ° C. using a ceramic roll, and stretched 4.9 times in the longitudinal direction of the film between the rolls at 128 ° C. provided with a peripheral speed difference. Next, the end was gripped by a clip and introduced into a tenter type stretching machine, preheated at 179 ° C. for 5 seconds, stretched 9.5 times at 173 ° C., and at 148 ° C. while giving 11% relaxation in the width direction. A heat treatment was performed, and then the film was guided to the outside of the tenter through a cooling step of 100 ° C., the clip at the end of the film was released, and the film was wound around a core to obtain a polypropylene film having a thickness of 25 μm. Table 1 shows the physical properties of the obtained film and the evaluation results.

(Example 3)
As a raw material for the surface layer (I), 98 parts by mass of the homopolypropylene raw material A and 2 parts by mass of the polypropylene raw material (1) are dry-blended and supplied to a single-screw extruder for the surface layer (I). As a raw material for the inner layer (II), 70 parts by mass of the homopolypropylene raw material C and 30 parts by mass of the homopolypropylene raw material A are dry-blended and supplied to a single-screw extruder for the inner layer (II) layer. Melt extrusion is performed at 250 ° C., foreign matter is removed with a 20 μm cut sintered filter, and then laminated with a feed block type A / B / A composite T-die at a thickness ratio of 1/8/1, and the surface is heated to 58 ° C. The material was discharged to a temperature-controlled casting drum and brought into close contact with the casting drum with an air knife to obtain an unstretched sheet. Subsequently, the sheet was preheated to 144 ° C. using a ceramic roll, and stretched 4.4 times in the longitudinal direction of the film between rolls at 138 ° C. provided with a peripheral speed difference. Next, the end was gripped with a clip and introduced into a tenter type stretching machine, preheated at 176 ° C for 5 seconds, stretched 8.8 times at 167 ° C, and at 163 ° C while giving 9% relaxation in the width direction. A heat treatment was performed, and then the film was guided to the outside of the tenter through a cooling step of 100 ° C., the clip at the end of the film was released, and the film was wound around a core to obtain a polypropylene film having a thickness of 25 μm. Table 1 shows the physical properties of the obtained film and the evaluation results.

(Example 4)
As a raw material for the surface layer (I), 95.7 parts by mass of the homopolypropylene raw material D, 2.3 parts by mass of the branched polypropylene raw material B, and 2 parts by mass of the polypropylene raw material (1) are dry-blended. It is supplied to a single-screw extruder for the surface layer (I), and 97.7 parts by mass of the homopolypropylene raw material D and 2.3 parts by mass of the branched polypropylene raw material B as raw materials for the inner layer (II). The parts are dry-blended and supplied to a single-screw extruder for the inner layer (II) layer, melt-extruded at 250 ° C., and after removing foreign matter with a 20 μm-cut sintering filter, feed block type A / It was laminated with a B / A composite T-die at a thickness ratio of 1/10/1, discharged to a casting drum whose surface temperature was controlled at 110 ° C., and brought into close contact with the casting drum with an air knife to obtain an unstretched sheet. Subsequently, the sheet was preheated to 159 ° C. using a ceramic roll, and stretched 4.1 times in the longitudinal direction of the film between rolls at 125 ° C. provided with a peripheral speed difference. Next, the end was gripped by a clip and introduced into a tenter type stretching machine, preheated at 180 ° C. for 5 seconds, stretched 10.2 times at 175 ° C., and at 140 ° C. while giving 14% relaxation in the width direction. A heat treatment was performed, and then the film was guided to the outside of the tenter through a cooling step of 100 ° C., the clip at the end of the film was released, and the film was wound around a core to obtain a polypropylene film having a thickness of 25 μm. Table 1 shows the physical properties of the obtained film and the evaluation results.

(Example 5)
As a raw material for the surface layer (I), 98.5 parts by mass of the homopolypropylene raw material C and 1.5 parts by mass of the branched polypropylene raw material B are dry-blended to form a single shaft for the surface layer (I). Supply to a uniaxial extruder, 100 parts by mass of the homopolypropylene raw material C as a raw material for the inner layer (II) is supplied to a uniaxial uniaxial extruder for the inner layer (II) layer, and melt extrusion is performed at 250 ° C. After removing foreign matter with a 20 μm cut sintered filter, laminate with a feed block type A / B / A composite T-die at a thickness ratio of 1/10/1 to make a casting drum whose surface temperature is controlled at 65 ° C. It was discharged and brought into close contact with the casting drum with an air knife to obtain an unstretched sheet. Subsequently, the sheet was preheated to 152 ° C. using a ceramic roll, and stretched 4.6 times in the longitudinal direction of the film between rolls at 132 ° C. provided with a peripheral speed difference. Next, the end was gripped by a clip and introduced into a tenter type stretching machine, preheated at 177 ° C for 5 seconds, stretched 6.8 times at 169 ° C, and at 170 ° C while giving 16% relaxation in the width direction. A heat treatment was performed, and then the film was guided to the outside of the tenter through a cooling step of 100 ° C., the clip at the end of the film was released, and the film was wound around a core to obtain a polypropylene film having a thickness of 25 μm. Table 1 shows the physical properties of the obtained film and the evaluation results.

(Example 6)
As a raw material for the surface layer (I), 95 parts by mass of the homopolypropylene raw material D and 5 parts by mass of a metallocene catalytically branched branched polypropylene raw material (WAYMAX MFX3 manufactured by Japan Polypropylene Corporation) are dry-blended to form the surface layer (I). 100 parts by mass of the homopolypropylene raw material D as a raw material for the inner layer (II) is supplied to the single-screw extruder for the inner layer (II), and the temperature is 250 ° C. After removing foreign matter with a 20 μm-cut sintered filter, laminate with a feed block type A / B / A composite T-die at a thickness ratio of 1/10/1, and set the surface temperature to 55 ° C. It was discharged to a controlled casting drum and brought into close contact with the casting drum with an air knife to obtain an unstretched sheet. Subsequently, the sheet was preheated to 146 ° C. using a ceramic roll, and stretched 4.4 times in the longitudinal direction of the film between the rolls at 133 ° C. provided with a peripheral speed difference. Next, the end was gripped by a clip and introduced into a tenter type stretching machine, preheated at 176 ° C for 5 seconds, stretched 7.8 times at 166 ° C, and at 153 ° C while giving 11% relaxation in the width direction. A heat treatment was performed, and then the film was guided to the outside of the tenter through a cooling step of 100 ° C., the clip at the end of the film was released, and the film was wound around a core to obtain a polypropylene film having a thickness of 7 μm. Table 1 shows the physical properties of the obtained film and the evaluation results.

(Comparative Example 1)
A polypropylene resin (MFR: 2.0 g / 10 minutes) having a copolymerization composition of 98.4 parts by mass of a propylene component and 1.6 parts by mass of an ethylene component is supplied to a uniaxial extruder and sheeted from a T die at 280 ° C. After being extruded into a shape and cooled and solidified on a cooling roll at 60 ° C., it was longitudinally stretched 4.4 times by a heating roll stretching machine set at 141 ° C., and then 9.2 times laterally stretched by a tenter stretching machine set at 162 ° C. The film was stretched, transversely stretched, and then heat-treated at 170 ° C. to obtain a 30 μm polypropylene-based film. Table 1 shows the physical properties of the obtained film and the evaluation results.

(Comparative Example 2)
"Novatec SA4L" (MFR = 5.0 / 10 minutes) manufactured by Japan Polypropylene Corporation is supplied to a single-screw single-screw extruder, extruded into a sheet from a T-die at 250 ° C, and cooled with a cooling roll at 30 ° C. After solidification, it is vertically stretched 4.5 times at 135 ° C., then both ends are clipped, guided into a hot air oven, preheated at 169 ° C., stretched 8.2 times at 160 ° C., and then 6 Heat treatment was performed at 168 ° C. while relaxing at a relaxation rate of 0.7% to obtain a 4 μm polypropylene film. Table 1 shows the physical properties of the obtained film and the evaluation results.

(Comparative Example 3)
75 parts by mass of the homopolypropylene raw material D and 25 parts by mass of calcium carbonate particles (manufactured by Sankyo Flour Milling Co., Ltd., 2480K, particle diameter: 6 μm) are dry-blended to create a single-screw melt extruder for the inner layer (II). The homopolypropylene raw material D is supplied to a single-screw melt extruder for the surface layer (I), melt-extruded at 240 ° C., and after removing foreign substances with an 80 μm-cut sintering filter, a feed block type The particles were laminated with a B / A / B composite T-die at a thickness ratio of 1/50/1, and discharged to a cast drum whose surface temperature was controlled at 30 ° C. to obtain a cast sheet. Next, the film was preheated to 140 ° C. using a plurality of ceramic rolls and stretched 4.6 times in the longitudinal direction of the film. Next, the end portion was gripped by a clip and introduced into a tenter type stretching machine, preheated at 165 ° C. for 3 seconds, and then stretched 8.0 times at 160 ° C. In the subsequent heat treatment step, heat treatment is performed at 160 ° C while giving 10% relaxation in the width direction, and then the film is guided to the outside of the tenter through a cooling step at 130 ° C, the clip at the end of the film is released, and the film is wound around the core. A polypropylene film having a thickness of 25 μm was obtained. Table 1 shows the physical properties of the obtained film and the evaluation results.

(Comparative Example 4)
99.7 parts by mass of the homopolypropylene raw material A, and 0.3 of N, N'-dicyclohexyl-2,6-naphthalene dicarboxyamide (NU-100, manufactured by Shin Nihon Rika Co., Ltd.), which is a β crystal nucleating agent. Biaxial from the measuring hopper so that 0.1 parts by mass of each of IRGANOX (registered trademark) 1010 and IRGAFOS (registered trademark) 168 manufactured by Ciba Specialty Chemicals, which are antioxidants, are mixed in this ratio by mass. The raw material was supplied to an extruder, melt-kneaded at 300 ° C., discharged from a die in a strand shape, cooled and solidified in a water tank at 25 ° C., and cut into chips to obtain a polypropylene raw material (2).

The homopolypropylene raw material D is supplied to a single-screw melt extruder for the inner layer (II) layer, and the polypropylene raw material (2) is supplied to a single-screw melt extruder for the surface layer (I) layer at 240 ° C. After melt extrusion and removing foreign matter with a 60 μm cut sintered filter, the cast drum is laminated with a feed block type A / B composite T-die at a thickness ratio of 8/1, and the surface temperature is controlled at 90 ° C. A cast sheet was obtained by ejection. Then, the film was preheated to 125 ° C. using a plurality of ceramic rolls and stretched 4.6 times in the longitudinal direction of the film. Next, the end portion was gripped by a clip and introduced into a tenter type stretching machine, preheated at 165 ° C. for 3 seconds, and then stretched 8.0 times at 160 ° C. In the subsequent heat treatment step, heat treatment is performed at 160 ° C while giving 10% relaxation in the width direction, and then the film is guided to the outside of the tenter through a cooling step at 130 ° C, the clip at the end of the film is released, and the film is wound around the core. A polypropylene film having a thickness of 15 μm was obtained. Table 1 shows the physical properties of the obtained film and the evaluation results.

(Comparative Example 5)
As a raw material for the surface layer (I), 98.5 parts by mass of the homopolypropylene raw material A and 1.5 parts by mass of the branched polypropylene raw material B are dry-blended to form a single shaft for the surface layer (I). It is supplied to a uniaxial extruder, and 98.5 parts by mass of the homopolypropylene raw material C and 1.5 parts by mass of the branched polypropylene raw material B are dry-blended as raw materials for the inner layer (II), and the inner layer ( II) Supply to a single-screw single-screw extruder for layers, melt-extrude at 250 ° C., remove foreign matter with a 20 μm-cut sintering filter, and then use a feed block type A / B / A composite T-die. The polypropylene was laminated at a thickness ratio of 1/10/1, discharged to a casting drum whose surface temperature was controlled at 35 ° C., and brought into close contact with the casting drum with an air knife to obtain an unstretched sheet. Subsequently, the sheet was preheated to 153 ° C. using a ceramic roll, and stretched 3.7 times in the longitudinal direction of the film between rolls at 148 ° C. provided with a peripheral speed difference. Next, the end was gripped with a clip and introduced into a tenter type stretching machine, preheated at 180 ° C. for 5 seconds, stretched 7.2 times at 178 ° C., and at 170 ° C. while giving 16% relaxation in the width direction. A heat treatment was performed, and then the film was guided to the outside of the tenter through a cooling step of 100 ° C., the clip at the end of the film was released, and the film was wound around a core to obtain a polypropylene film having a thickness of 25 μm. Table 1 shows the physical properties of the obtained film and the evaluation results.

(Comparative Example 6)
As a linear polypropylene, 100 parts by mass of a polypropylene resin manufactured by Prime Polymer Co., Ltd., which has a mesopentad fraction of 98.5% and a melt mass flow rate (MFR) of 2.6 g / 10 minutes, and a branched polypropylene made by Basell Co., Ltd. 0.5 parts by mass of resin (high melt tension polypropylene Profax PF-814 mesopentad fraction 91.0%) is blended and supplied to an extruder at a temperature of 250 ° C., and the resin temperature is 250 ° C. from a T-shaped slit die to form a sheet. The molten sheet was melt-extruded and solidified by cooling on a casting drum having a diameter of 1 m held at 90 ° C. at an air knife temperature of 90 ° C. and an air speed of 140 m / s. Next, the sheet was gradually preheated to 140 ° C., continuously maintained at a temperature of 145 ° C., passed between rolls provided with a peripheral speed difference, and stretched 4.8 times in the longitudinal direction. At that time, a radiation heater (output 3.5 kW) was used in the stretched portion to supplement the amount of heat and stretch. Subsequently, the film was led to a tenter, stretched 10 times in the width direction at a stretching temperature of 160 ° C., and then relaxed in three stages with a total relaxation rate of 23% in the width direction. (The first stage is 12.0%, the second stage is 9.0%, and the third stage is 3.9%.) The heat treatment is performed at a heat fixing temperature of 150 ° C. and a cooling temperature of 140 ° C., and then at room temperature. The mixture was rapidly cooled for 5 seconds to obtain a biaxially oriented polypropylene film having a film thickness of 3.0 μm. Table 1 shows the physical properties of the obtained film and the evaluation results.

Note that the "direction orthogonal to the main orientation axis" in the table means a direction orthogonal to the direction of the main orientation axis.

As described above, the polypropylene film of the present invention can be used for various purposes such as packaging films, release films, process films, sanitary products, agricultural products, building products, and medical products. In particular, since it is excellent in heat resistance, mechanical strength, releasability, and quality, it can be preferably used as a releasable film or process film that passes through a high temperature process after being bonded to an adherend.

Claims

A polypropylene film in which the heat shrinkage force at 140 ° C. in the main orientation axis direction and the direction orthogonal to the main orientation axis direction is 400 mN or less, and the Young's modulus in the main orientation axis direction and the direction orthogonal to the main orientation axis direction is 1.8 GPa or more. ..
The polypropylene film according to claim 1, wherein the temperature at which the heat shrinkage force is 20 mN or more in the main orientation axis direction and the direction orthogonal to the main orientation axis direction is 116 ° C. or more.
The polypropylene film according to any one of claims 1 and 2, wherein the maximum point stress at 120 ° C. in the main orientation axis direction and the direction orthogonal to the main orientation axis direction is 80 MPa or more.
The polypropylene film according to any one of claims 1 to 3, wherein the maximum protrusion roughness St on at least one side is 2000 nm or more.
The polypropylene film according to any one of claims 1 to 4, wherein the thickness unevenness in the main orientation axis direction is less than 6.0%.
The polypropylene film according to any one of claims 1 to 5, wherein the heat shrinkage force at 140 ° C. in the direction orthogonal to the main orientation axis direction is 95 mN or less.
Claims 1 to 1, wherein the value obtained by multiplying the Young's modulus (GPa) at 120 ° C. in the direction orthogonal to the main orientation axis direction by the film thickness (μm) is 1.5 (GPa · μm) or more. The polypropylene film according to any one of 6.
The polypropylene film according to any one of claims 1 to 7, wherein the thickness of the film is 6 μm or more.
Claim 1 is a laminated structure of two or more layers, wherein at least one layer contains 50% by mass or more and 100% by mass or less of polypropylene having a cold xylene soluble portion (CXS) of 3.5% or less. 8. The polypropylene film according to any one of 8.
In a laminated structure of two or more layers, at least one layer was heated at 20 ° C./min from 25 ° C. to 250 ° C. by a differential scanning calorimeter DSC, and then lowered at 20 ° C./min from 250 ° C. to 25 ° C. The polypropylene film according to any one of claims 1 to 9, wherein the crystallization peak temperature (Tc) is 110 ° C. or higher.
An adhesive film having an adhesive layer on at least one side of the polypropylene film according to any one of claims 1 to 10.
A release film using the polypropylene film according to any one of claims 1 to 10.