Polypropylene resin composition

Abstract

To provide a biaxial oriented film including the layer of polypropylene resin composition comprising all of such characteristics that (1) there is a mat feeling, that is, haze is large; (2) irregularity is not recognized in the mat feeling, that is, homogeneity is high; (3) there is no fish eye, namely appearance defect; and (4) heat resistance of a heat-sealing part and other portions is high.SOLUTION: A polypropylene resin composition (X) included in a biaxial oriented film includes polypropylene resin (A), propylene-based copolymer (B) (except the above resin (A) and so on), high density polyethylene (C) and low density polyethylene (D), and has a specific composition.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a polypropylene resin composition, and more particularly to a biaxially oriented polypropylene film having a matte feel. [Background technology]

[0002] A method is known in which a biaxially stretched film with a matte finish is obtained by inserting a layer containing a polypropylene resin blended with inorganic fine particles such as silica, talc, or calcium carbonate. Patent documents 1 and 2 disclose a method of obtaining a biaxially stretched film with a matte finish by using a propylene-ethylene block copolymer without using inorganic particles. Patent documents 3, 4, and 5 disclose a method of obtaining a biaxially stretched film with a matte finish by using a polypropylene resin blended with high density polyethylene and low density polyethylene. Such matte biaxially oriented films have excellent design properties and are therefore used for packaging materials, the non-adhesive surfaces of adhesive films, and the like. However, there has not yet been provided a biaxially oriented film having a matte finish that contains a polypropylene-based resin layer, which (1) has a high haze, (2) has no unevenness in the matte finish, (3) is free of fish eyes, and (4) has high heat resistance in the heat-sealed areas and other areas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-184683 A [Patent Document 2] JP 2011-252081 A [Patent Document 3] Japanese Patent Application Publication No. 7-233291 [Patent Document 4] JP 2003-213069 A [Patent Document 5] JP 2011-194588 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure aims to provide a biaxially oriented film including a layer of a polypropylene resin composition, which has all of the following characteristics: (1) a matte finish, i.e., high haze; (2) no unevenness in the matte finish, i.e., high homogeneity; (3) no fisheyes, i.e., no appearance defects; and (4) high heat resistance in the heat-sealed portions and other portions. [Means for solving the problem]

[0005] The inventors have achieved the above object by the following aspects.

[0006] A first aspect of the present disclosure includes: (i) a polypropylene resin (A) having an MFR of 0.3 to 40 g / 10 min; (ii) a propylene-based copolymer (B) having an MFR of 5 to 15 g / 10 min (excluding the polypropylene resin; the same applies below), (iii) a high-density polyethylene (C) having an MFR of 0.01 to 0.4 g / 10 min; and (iv) A polypropylene resin composition (X) containing a low-density polyethylene (D) having an MFR of 0.1 to 0.6 g / 10 min. Here, the composition of the polypropylene resin composition is When the total weight of polypropylene resin (A), propylene copolymer (B), high density polyethylene (C) and low density polyethylene (D) is 100, (i) the weight of the polypropylene resin (A) is 15 to 30, (ii) the weight of the propylene copolymer (B) is 20 to 35; (iii) the weight of the high-density polyethylene (C) is 20 to 45 (iv) The weight of low-density polyethylene (D) is limited to 5 to 30.

[0007] The second embodiment of the present disclosure is the first embodiment, in which the propylene-based copolymer (B) is a propylene-ethylene random copolymer or a propylene-ethylene-1-butene random copolymer.

[0008] A third aspect of the present disclosure is the first aspect, wherein the production process for the low density polyethylene (D) is a high pressure process.

[0009] A fourth aspect of the present disclosure is the first aspect, wherein the difference between the melting point of the polypropylene resin (A) and the melting point of the propylene-based copolymer (B) is 20 to 45°C.

[0010] A fifth aspect of the present disclosure is a biaxially stretched film comprising a layer of the composition according to any one of the first to fourth aspects.

[0011] A sixth aspect of the present disclosure is a biaxially stretched film having a surface layer of the composition according to any one of the first to fourth aspects.

[0012] A seventh aspect of the present disclosure is the biaxially stretched film according to the fifth or sixth aspect, having a total haze of 70% or more. Effect of the Invention

[0013] A biaxially stretched film including a layer that is a composition according to any one of the first to fourth embodiments satisfies all of the following characteristics: (1) high haze, i.e., high matte finish; (2) no unevenness in the matte finish, i.e., high homogeneity; (3) low appearance defects such as no fish eyes or cracks; and (4) high heat resistance in the heat-sealed portions and other portions, i.e., high heat resistance. A film including a layer having the composition according to any one of the fifth to seventh embodiments also satisfies all of the above (1) to (4). Therefore, the biaxially oriented films including layers that are the compositions of embodiments 1 to 4 and the biaxially oriented films of embodiments 5 to 7 have unexpected effects that were not observed in biaxially oriented films including layers of conventional polypropylene resin compositions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The polypropylene resin composition (X) of the present disclosure is characterized in that the components satisfying the above requirements (A) to (D) are blended in specific ratios.

[0015] In a layer made by mixing polypropylene resin, propylene-based copolymer, high density polyethylene and low density polyethylene in a specific ratio, the high density polyethylene and low density polyethylene crystallize before the polypropylene resin and propylene-based copolymer during biaxial stretching in film production. As a result, the areas in the layer where the total amount of high density polyethylene and low density polyethylene is high become convex parts, and the areas in the layer where the total amount of polypropylene resin and propylene-based copolymer is high become concave parts. The convex parts and the concave parts diffuse light. This gives the film a matte feel.

[0016] [Components] 1. Polypropylene resin (A) The polypropylene resin refers to a propylene-α-olefin random copolymer in which the propylene monomer content in the polymer exceeds 98% by weight, a propylene homopolymer, and a mixture of these. For the sake of productivity, high haze, high uniformity, no appearance defects, and high heat resistance in the heat-sealed portions and other portions, the polypropylene resin is preferably a propylene homopolymer. The monomers of the polypropylene resin other than propylene may be one or more α-olefins. The α-olefins include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 3-methyl-1-butene, 4-methyl-1-pentene, 2-methyl-1-pentene, 2-methyl-1-hexene, and the like. In order to impart a matte feel to the polypropylene resin obtained by polymerizing a monomer component other than propylene, the α-olefin monomer is preferably ethylene or an α-olefin having 4 to 20 carbon atoms, more preferably ethylene or an α-olefin having 4 to 10 carbon atoms, and even more preferably ethylene or 1-butene.

[0017] (1) Melting point of polypropylene resin For improving the matte finish, heat resistance, homogeneity and productivity, the melting point of the polypropylene resin (A) is preferably from 155 to 170°C, more preferably from 160 to 165°C.

[0018] (2) MFR of polypropylene resin From the viewpoints of preventing defects in appearance of the product, improving the design of the product, the productivity of the product, and / or the heat resistance of the product, the MFR of the polypropylene resin is preferably 0.3 to 40 g / 10 min, more preferably 0.3 to 30 g / 10 min, and even more preferably 0.3 to 25 g / 10 min.

[0019] Those skilled in the art can purchase or prepare the above polypropylene resins.

[0020] 2. Propylene-based copolymer The propylene-based copolymer is a propylene-α-olefin random copolymer and a mixture of propylene-α-olefin random copolymers. The mixture may include a molten blend obtained by melt-kneading a propylene-α-olefin random copolymer, and a multi-stage polymer produced by a multi-stage polymerization method. In view of productivity, high haze, high homogeneity, no appearance defects, and high heat resistance in the heat-sealed portion and other portions, the monomer components of the propylene-based copolymer other than propylene are preferably ethylene and an α-olefin having 4 to 20 carbon atoms, more preferably ethylene or an α-olefin having 4 to 10 carbon atoms, and further preferably ethylene or 1-butene. Monomers of the propylene-based copolymer other than propylene may be ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 3-methyl-1-butene, 4-methyl-1-pentene, 2-methyl-1-pentene, 2-methyl-1-hexene, and the like, and mixtures thereof.

[0021] Melting point of propylene copolymer From the viewpoints of durability and good matte feel of the product, the melting point of the propylene-based copolymer is preferably from 125 to 140°C, and more preferably from 125 to 135°C.

[0022] (2) MFR of propylene copolymer The MFR of the propylene-based copolymer is preferably from 5 to 15 g / 10 min, more preferably from 5 to 10 g / 10 min, and further preferably from 5 to 8 g / 10 min. From the viewpoint of productivity, the MFR is preferably 5 g / 10 min or more, and from the viewpoint of preventing the occurrence of fish eyes, the MFR is preferably 15 g / 10 min or less. In order to solve the problems of the present invention, the difference between the melting point of the polypropylene resin and the melting point of the propylene-based copolymer is preferably 20 to 45°C, more preferably 30 to 45°C, and even more preferably 40 to 45°C.

[0023] 3.High density polyethylene The monomers for high density polyethylene are ethylene and mixtures of ethylene and alpha-olefins. For the sake of productivity, high haze, high homogeneity, no appearance defects, and high heat resistance in the heat-sealed portion and other portions, the α-olefin component which is the monomer of the high-density polyethylene is preferably an α-olefin having 3 to 20 carbon atoms, more preferably an α-olefin having 3 to 10 carbon atoms, and further preferably propylene and 1-butene. In addition to ethylene, the monomer of the high-density polyethylene may be propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 3-methyl-1-butene, 4-methyl-1-pentene, 2-methyl-1-pentene, 2-methyl-1-hexene, and the like, or a mixture thereof.

[0024] (1) Density of high-density polyethylene From the viewpoint of the high haze expression effect of the polypropylene resin composition and the prevention of the occurrence of fish eyes, the density of the high-density polyethylene, which is a component of the polypropylene resin composition, is 0.935 to 0.970 g / cm 3 is preferable, and 0.940 to 0.965 g / cm3 is more preferred. The density can be decreased by increasing the ratio of the α-olefin having 3 to 20 carbon atoms to be copolymerized with ethylene, whereas the density can be increased by increasing the ratio of ethylene. Here, the density is a measured value according to the D method (density gradient tube) of JIS K7112:1999.

[0025] (2) MFR of high-density polyethylene In order to suppress the occurrence of fish eyes and to achieve a rough surface that gives a matte feel, the MFR of the high-density polyethylene is preferably 0.01 g / 10 min to 0.4 g / 10 min, and more preferably 0.02 to 0.35 g / 10 min. Such high density polyethylene is commercially available to those skilled in the art.

[0026] 4. Low density polyethylene The monomers for low density polyethylene are ethylene and mixtures of ethylene and alpha-olefins. In order to achieve the object of the present invention, the low density polyethylene is preferably produced by a high pressure process. For the sake of productivity, high haze, high homogeneity, no appearance defects, and high heat resistance in the heat-sealed portion and other portions, the α-olefin component which is the monomer of the low-density polyethylene is preferably an α-olefin having 3 to 20 carbon atoms, more preferably an α-olefin having 3 to 10 carbon atoms, and further preferably propylene and 1-butene. In addition to ethylene, the monomer of the low-density polyethylene may be propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 3-methyl-1-butene, 4-methyl-1-pentene, 2-methyl-1-pentene, 2-methyl-1-hexene, and the like, or a mixture thereof.

[0027] (1) Density of low-density polyethylene From the viewpoint of the effect of expressing high haze in the polypropylene resin composition and preventing the occurrence of fish eyes, the density of the low-density polyethylene, which is a component of the polypropylene resin composition, is 0.910 to 0.935 g / cm3 is preferable, and 0.915 to 0.930 g / cm 3 is more preferred. Here, the density of the low-density polyethylene can be adjusted in the same manner as for the high-density polyethylene, and the density can be measured in the same manner as for the high-density polyethylene.

[0028] (2) MFR of low-density polyethylene In order to suppress the occurrence of fish eyes and to achieve a rough surface that gives a matte feel, the MFR of the low-density polyethylene is preferably from 0.1 to 0.6 g / 10 min, and more preferably from 0.1 to 0.45 g / 10 min. Such low density polyethylene is commercially available to those skilled in the art.

[0029] 5. Proportion of components in polypropylene resin composition (X) In order to solve the problems of the present invention, when the total weight of the polypropylene resin (A), the propylene-based copolymer (B), the high-density polyethylene (C) and the low-density polyethylene (D) in the polypropylene resin composition (X) is taken as 100, the weight of the polypropylene resin (A) is preferably 15 to 30, and more preferably 20 to 30. In order to solve the problems of the present invention, when the total weight of the polypropylene resin (A), the propylene-based copolymer (B), the high-density polyethylene (C) and the low-density polyethylene (D) in the polypropylene resin composition (X) is taken as 100, the propylene-based copolymer (B) is preferably 20 to 35, more preferably 20 to 30. In order to solve the problems of the present invention, when the total weight of the polypropylene resin (A), the propylene-based copolymer (B), the high-density polyethylene (C) and the low-density polyethylene (D) in the polypropylene resin composition (X) is taken as 100, the weight of the high-density polyethylene (C) is preferably 20 to 45, and more preferably 40 to 45. In order to solve the problems of the present invention, when the total weight of the polypropylene resin (A), the propylene-based copolymer (B), the high-density polyethylene (C) and the low-density polyethylene (D) in the polypropylene resin composition (X) is taken as 100, the weight of the low-density polyethylene (D) is preferably 5 to 30, and more preferably 5 to 10.

[0030] 6.Other Ingredients The polypropylene resin composition (X) of the present invention may contain additives for synthetic resins, such as antioxidants, ultraviolet absorbers, neutralizing agents, nucleating agents, light stabilizers, antistatic agents, lubricants, antiblocking agents, odor absorbents, antibacterial agents, pigments, inorganic and organic fillers, and other additives.

[0031] In order to prevent deterioration of the polypropylene resin, the content of the antioxidant in the polypropylene resin composition (X) is preferably from 100 to 10,000 ppm, more preferably from 200 to 5,000 ppm, and even more preferably from 300 to 3,000 ppm, calculated on a weight basis.

[0032] In order to prevent weathering deterioration of the polypropylene resin, the content of the ultraviolet absorber in the polypropylene resin composition (X) is preferably 100 to 10,000 ppm, more preferably 200 to 5,000 ppm, and even more preferably 300 to 3,000 ppm, calculated on a weight basis.

[0033] In order to protect members that come into contact with the polypropylene resin, the content of the neutralizing agent in the polypropylene resin composition (X) is preferably 100 to 10,000 ppm, more preferably 200 to 5,000 ppm, and even more preferably 300 to 3,000 ppm, calculated on a weight basis.

[0034] In order to improve the physical properties and design properties of the polypropylene resin, the content of the nucleating agent in the polypropylene resin composition (X) is preferably 100 to 10,000 ppm, more preferably 200 to 5,000 ppm, and even more preferably 300 to 3,000 ppm, calculated on a weight basis.

[0035] In order to prevent weathering deterioration of the polypropylene resin, the content of the light stabilizer in the polypropylene resin composition (X) is preferably 100 to 10,000 ppm, more preferably 200 to 5,000 ppm, and even more preferably 300 to 3,000 ppm, calculated on a weight basis.

[0036] For preventing static electricity of the polypropylene resin, the content of the antistatic agent in the polypropylene resin composition (X) is preferably 500 to 50,000 ppm, more preferably 1,000 to 30,000 ppm, and even more preferably 5,000 to 15,000 ppm, calculated on a weight basis.

[0037] In order to impart lubricity to the polypropylene resin, the content of the lubricant in the polypropylene resin composition (X) is preferably from 100 to 10,000 ppm, more preferably from 200 to 5,000 ppm, and even more preferably from 300 to 3,000 ppm, calculated on a weight basis.

[0038] In order to impart blocking resistance to the polypropylene resin, the content of the antiblocking agent in the polypropylene resin composition (X) is preferably 100 to 10,000 ppm, more preferably 200 to 5,000 ppm, and even more preferably 300 to 3,000 ppm, calculated on a weight basis.

[0039] For preventing odors from polypropylene resins, the content of the odor adsorbent in the polypropylene resin composition (X) is preferably 1,000 to 100,000 ppm, more preferably 5,000 to 80,000 ppm, and even more preferably 10,000 to 50,000 ppm, calculated on a weight basis.

[0040] In order to impart antibacterial properties to the polypropylene resin, the content of the antibacterial agent in the polypropylene resin composition (X) is preferably from 1000 to 50000 ppm, more preferably from 2000 to 40000 ppm, and even more preferably from 5000 to 30000 ppm, calculated on a weight basis.

[0041] In order to impart design properties to the polypropylene resin, the content of the pigment in the polypropylene resin composition (X) is preferably from 1,000 to 50,000 ppm, more preferably from 2,000 to 40,000 ppm, and even more preferably from 5,000 to 30,000 ppm, calculated on a weight basis.

[0042] In order to impart rigidity to the polypropylene resin, the content of the inorganic filler in the polypropylene resin composition (X) is preferably from 1,000 to 50,000 ppm, more preferably from 2,000 to 40,000 ppm, and even more preferably from 3,000 to 30,000 ppm, calculated on a weight basis.

[0043] In order to improve homogeneity, to have large haze, to have small variation in haze depending on the observation point, to have no fisheyes, and to impart heat resistance to the heat-sealed parts and other parts, the content of polyethylene in the polypropylene resin composition (X) is preferably 50,000 to 500,000 ppm, more preferably 100,000 to 480,000 ppm, and further preferably 150,000 to 450,000 ppm, calculated by weight.

[0044] In order to improve homogeneity, to have large haze, to have small variation in haze depending on the observation point, to have no fisheyes, and to impart heat resistance to the heat-sealed parts and other parts, the total content of additives for synthetic resins in the polypropylene resin composition (X) is preferably 100 to 5000 ppm, more preferably 200 to 4000 ppm, and further preferably 300 to 3000 ppm, calculated on a weight basis.

[0045] [Method for producing pellets of polypropylene resin composition and film thereof] Those skilled in the art may prepare pellets of the polypropylene resin composition and then prepare a film of the polypropylene resin composition from the pellets. Those skilled in the art may also prepare a film directly from the polypropylene resin composition in a molten state without preparing pellets of the polypropylene resin composition. One skilled in the art may incorporate additives into polypropylene powder to create a film.

[0046] A person skilled in the art can prepare pellets of the polypropylene resin composition (X) of the present disclosure by mixing and homogenizing the polypropylene resin (A), the propylene-based copolymer (B), the high-density polyethylene (C), the low-density polyethylene (D) and other necessary components in a mixing device, and subsequently melt-kneading the mixture in a kneader at a temperature range of 190 to 260°C.

[0047] Those skilled in the art may feed a mixture of pellets of polypropylene resin (A), propylene-based copolymer (B), high-density polyethylene (C), low-density polyethylene (D) and other necessary components into a main hopper, melt the mixture, and feed the mixture to a film extrusion machine to make a film. Those skilled in the art may feed pellets of some of the components of the polypropylene resin composition into a main hopper and melt the mixture, and subsequently feed pellets or powder of the remaining components into one or more side feeds and knead the mixture, and then prepare pellets or feed the mixture to a film extrusion machine to make a film.

[0048] It is preferable to add and knead the components by side feeding as described above, since this is expected to result in homogeneous dispersion of the components of the polypropylene resin composition, i.e., improvement in the quality of the film.

[0049] The mixing equipment includes a Henschel mixer (trade name), a V blender, a ribbon blender, and a tumbler blender. The kneading machine may be a single screw extruder, a multi-screw extruder, a kneader, a Banbury mixer, or the like.

[0050] [Film forming method] Those skilled in the art can prepare a film of the polypropylene resin composition (X) of the present disclosure by known melt extrusion film formation methods. The film can be produced by a T-die casting method for unstretched films, a uniaxially stretched film or a biaxially stretched film that is hot-stretched after casting, or an inflation method that cools the film in water or in the air. For the sake of productivity, and because it has high haze, high uniformity, no appearance defects, and high heat resistance in the heat-sealed parts and other parts, biaxial stretching is preferred as the method for producing the film.

[0051] The film may be a single layer or a multilayer. For productivity, and because it has high haze, high uniformity, no appearance defects, and high heat resistance in the heat-sealed portion and other portions, the film is preferably a multilayer.

[0052] In the multilayer film of the present disclosure, layers other than the polypropylene resin composition may be composed of a propylene-ethylene block copolymer, a propylene homopolymer, a propylene-ethylene random copolymer, a propylene-ethylene-1-butene random copolymer, a styrene-based elastomer, or a mixture thereof.

[0053] By using the polypropylene resin composition of the present invention described above, the film of the present disclosure can provide a film having a rough surface due to the presence of irregular asperities and having an excellent matte feel due to high haze. Specifically, the multilayer film of the present invention is obtained by melt extrusion of the polypropylene resin composition of the present invention described above, and has a total haze of 70% or more at a thickness of 20 μm, and the number of fish eyes, which are appearance defects caused by polymer gels, on the long side of the film is 1 m or less. 2 It is preferable that the number of the particles is 5 or less per layer. The multilayer film of the present invention is preferably obtained by melt extrusion film formation using the polypropylene resin composition of the present invention described above in at least one layer. For productivity, and for achieving high haze, high homogeneity, no appearance defects, and high heat resistance in the heat-sealed portion and other portions, the thickness of the film is preferably 5 to 200 μm, more preferably 10 to 100 μm.

[0054] To improve processability, the surface of the film of the present disclosure may be subjected to a discharge treatment such as corona and / or plasma, a flame treatment, or an ozone treatment. EXAMPLES

[0055] The present invention is not limited to the examples only. [Method of measuring physical properties] The physical properties and analytical values ​​of each item in the detailed description of the present invention and the examples were measured according to the following methods.

[0056] (1) Melting point (unit: °C) Using a differential scanning calorimeter (DSC), the temperature was first raised to 200°C to erase the thermal history, then the temperature was lowered to 40°C at a rate of 10°C / min, and then measured again at a rate of 10°C / min. The temperature at the top of the endothermic peak was taken as the melting point.

[0057] (2) MFR (unit: g / 10 min) The MFR of polypropylene resin was measured under the following conditions in accordance with JIS K7210:1999, Annex A, Table 1, Condition M. Test temperature: 230℃ Nominal load: 2.16kg Die shape: diameter 2.095mm, length 8.000mm The MFR of polyethylene was measured under the following conditions in accordance with JIS K7210:1999, Annex A, Table 1, Condition D. Test temperature: 190℃ Nominal load: 2.16kg Die shape: diameter 2.095mm, length 8.000mm

[0058] (3) Film haze (unit: %) After the film was left to stand for 24 hours or more under an atmosphere of 23°C and 50% RH, the haze was measured at 4 points per example according to JIS-K7136, and the average of these measurements was taken as the "total haze (%)." The higher the obtained value, the more opaque it was, and a value of 70% or more indicated excellent matte feel.

[0059] (4)Homogeneity The film was visually evaluated for unevenness in the matte finish. Good: No unevenness in the matte finish is observed. ×: Unevenness in the matte finish is observed. When the rating was ◯, the film was evaluated to have high uniformity.

[0060] (5) Heat resistance of heat-sealed parts The heat resistance of the heat-sealed portion was evaluated as follows. Equipment: Tester Sangyo Co., Ltd. "TP-701-B HEAT SEAL TESTER" Sealing temperature: 140℃ Sealing pressure: 1.0kg / cm 2 (0.10MPa) Sealing time: 1 second Seal bar: 1cm x 20cm Two sheets of the films described in the Examples and Comparative Examples were stacked and inserted into a seal bar, and the seal was made under the above-mentioned conditions, and the change in the matte feel of the sealed portion was visually evaluated. ◯: No difference in matte feel was observed when compared with areas other than the heat sealed area. ×: A difference in matte feel was observed in comparison with the portion other than the heat sealed portion. In the case of ◯, the film was judged to have high heat resistance.

[0061] (7) Fisheyes on film (unit: pieces / m 2 ) The number of fisheyes with a long side of 0.2 mm or more was visually counted for five rectangular films with a thickness of 20 μm and dimensions of MD 300 mm × TD 400 mm. Here, MD is the distance parallel to the flow direction during film extrusion molding, and TD is the distance perpendicular to said direction. Area 1 m 2 The number of winning fish eyes was counted. The more fisheyes there are, the worse the appearance is.

[0062] (8) Surface roughness of the film After conditioning the film for 24 hours or more in an atmosphere of 23°C and 50% RH, the center plane average value (hereinafter referred to as "Ra") at a cutoff of 0.25 mm was measured for the contact surface with the cooling roll immediately after the die during film forming in accordance with JIS B-0601. The larger the Ra, the greater the unevenness of the film surface, and therefore the deeper the matte feel.

[0063] [Resin used] The various resins used in the examples and comparative examples are listed below. [Polypropylene resin (A)] A-1: Made by Japan Polypropylene Corporation, product name Novatec (registered trademark) PP, grade name EA9HD Propylene homopolymer produced by Ziegler-Natta catalyst Melting point: 165℃, MFR (230℃, 2.16kg load) = 0.4g / 10min A-2: Made by Japan Polypropylene Corporation, product name Novatec (registered trademark) PP, grade name FL203D Propylene homopolymer produced by Ziegler-Natta catalyst Melting point 162, MFR (230℃, 2.16kg load) = 3g / 10min A-3: Made by Japan Polypropylene Corporation, product name Novatec (registered trademark) PP, grade name SA3B Propylene homopolymer produced by Ziegler-Natta catalyst Melting point: 162℃, MFR (230℃, 2.16kg load) = 10g / 10min A-4: Made by Japan Polypropylene Corporation, product name Novatec (registered trademark) PP, grade name SA2EA Propylene homopolymer produced by Ziegler-Natta catalyst Melting point: 162℃, MFR (230℃, 2.16kg load) = 16g / 10min A-5: Made by Japan Polypropylene Corporation, product name Novatec (registered trademark) PP, grade name SA04M Propylene homopolymer produced by Ziegler-Natta catalyst Melting point: 161℃, MFR (230℃, 2.16kg load) = 40g / 10min A-6: Made by Japan Polypropylene Corporation, product name Novatec (registered trademark) PP, grade name SA06GA Propylene homopolymer produced by Ziegler-Natta catalyst Melting point: 161℃, MFR (230℃, 2.16kg load) = 60g / 10min

[0064] [Propylene-based copolymer (B)] B-1: Made by Japan Polypropylene Corporation, product name Wintech (registered trademark), grade name WFX4M Metallocene-catalyzed propylene-ethylene random copolymers Melting point: 125℃, MFR (230℃, 2.16kg load) = 7g / 10min B-2: Made by Japan Polypropylene Corporation, product name Novatec (registered trademark) PP, grade name FX4GF Propylene-ethylene-1-butene random copolymers produced by Ziegler-Natta catalyst Melting point: 126℃, MFR (230℃, 2.16kg load) = 5g / 10min

[0065] [High density polyethylene (C)] C-1: Manufactured by Keiyo Polyethylene Co., Ltd., product name KEIYO Polyethylene (registered trademark), grade name B5514 Density 0.953g / cm 3 , MFR (190℃, 2.16kg load) = 0.35g / 10min C-2: Manufactured by Keiyo Polyethylene Co., Ltd., product name KEIYO Polyethylene (registered trademark), grade name FX503 Density 0.950g / cm 3 , MFR (190℃, 2.16kg load) = 0.04g / 10min C-3: Made by Japan Polyethylene Co., Ltd., product name Novatec (registered trademark) HD, grade name HY430 Density 0.956g / cm 3 , MFR (190℃, 2.16kg load) = 0.8g / 10min

[0066] [Low density polyethylene (D)] D-1: Made by Japan Polyethylene Co., Ltd., product name Novatec (registered trademark) LD, grade name LF128 Density 0.922g / cm 3 , MFR (190℃, 2.16kg load) = 0.25g / 10min D-2: Made by Japan Polyethylene Co., Ltd., product name Novatec (registered trademark) LD, grade name LF443 Density 0.924g / cm 3 , MFR (190℃, 2.16kg load) = 1.5g / 10min

[0067] Examples 1 to 9 and Comparative Examples 2 to 7 [Pelletization of polypropylene resin composition (X)] The pellets of the polypropylene resin (A), propylene-based copolymer (B), high-density polyethylene (C), and low-density polyethylene (D) described above are mixed and homogenized in a tumbler in the ratios shown in Table 1, and then melt-kneaded at 230°C in a twin-screw extruder having a diameter of 35 mm to obtain pellets of polypropylene resin composition (X). The kneading machine used here was a 35 mm diameter co-rotating twin screw kneader manufactured by Toshiba Machine Co., Ltd., with a screw rotation speed of 250 rpm and a feeder rotation speed of 50 rpm.

[0068] [Forming method for biaxially oriented polypropylene film] The resin temperatures of both were 240°C, and the polypropylene resin composition (X) was melt extruded to form the first and third layers, and A-2 (Novatec (registered trademark) PP FL203D (propylene-based polymer, MFR 3.0 g / 10 min, melting point 162°C) manufactured by Japan Polypropylene Corporation) was melt extruded to form the middle layer, and then quenched with a cooling roll at 30°C to produce a two-kind, three-layer raw sheet. The sheet was stretched in a longitudinal direction by a stretching machine with the roll temperature adjusted to 110° C. to obtain a biaxially stretched film. Therefore, the layer of the biaxially stretched film is necessarily the polypropylene resin composition (X).

[0069] The longitudinal stretching machine and the transverse stretching machine are as follows. Biaxially stretched film forming machine (stenter): Manufactured by Mitsubishi Heavy Industries Extrusion conditions: Extrusion temperature: 240°C, die width: 300mm, lip opening: 2.0mm Stretching conditions: cooling roll temperature: 30°C, cooling roll speed: 3 m / min, longitudinal (MD) stretching ratio: 5 times, Transverse (TD) stretch ratio: 8 times, take-off speed: 15 m / min Film thickness: 20 μm. However, the thickness of the first layer made of polypropylene resin composition (X) and the third layer made of polypropylene resin composition (X) is 3 μm. The physical properties of the obtained biaxially stretched film are shown in Table 2.

[0070] [Table 1]

[0071] [Consideration of the results of the Examples and Comparative Examples] From Examples 1 to 9 in Table 1, it can be seen that the film having a layer of polypropylene resin composition (X) is a biaxially stretched polypropylene film and has all the following characteristics: (1) it has a matte finish, i.e., it has high haze; (2) the matte finish is even, i.e., it has high homogeneity; (3) it has no fisheyes, i.e., it has no appearance defects; and (4) the heat resistance of the heat-sealed parts and other parts is high. None of the films of Comparative Examples 2 to 7 satisfied all of the characteristics (1) to (4).

Claims

1. (1) (i) A polypropylene resin (A) having an MFR of 0.3 to 40 g / 10 min, measured in accordance with JIS K7210:1999, Annex A, Table 1, Condition M, at a test temperature of 230° C., a nominal load of 2.16 kg, and a die shape of 2.095 mm in diameter and 8.000 mm in length; (ii) A propylene-based copolymer (excluding the above polypropylene resin (A)) (B) having an MFR of 5 to 15 g / 10 min, measured in accordance with JIS K7210:1999, Annex A, Table 1, Condition M, at a test temperature of 230° C., a nominal load of 2.16 kg, and a die shape of diameter 2.095 mm and length 8.000 mm; (iii) High-density polyethylene (C) having an MFR of 0.01 to 0.4 g / 10 min and a density of 0.940 to 0.970 g / cm 3 , measured in accordance with JIS K7210:1999, Annex A, Table 1, Condition D, at a test temperature of 190° C., a nominal load of 2.16 kg, and a die shape of diameter 2.095 mm and length 8.000 mm; (iv) A low-density polyethylene (D) having an MFR of 0.1 to 0.6 g / 10 min and a density of 0.910 to 0.935 g / cm 3 , measured in accordance with JIS K7210:1999, Annex A, Table 1, Condition D, at a test temperature of 190° C., a nominal load of 2.16 kg, and a die shape of diameter 2.095 mm and length 8.000 mm; (2) When the total amount of polypropylene resin, propylene copolymer, high density polyethylene and low density polyethylene is 100% by weight, (i) the polypropylene resin (A) is 15 to 30% by weight, (ii) the propylene-based copolymer (B) is 20 to 35% by weight, (iii) the high-density polyethylene (C) is 35 to 45% by weight, (iv) The low-density polyethylene (D) is 5 to 30% by weight. Polypropylene resin composition

2. The polypropylene resin composition according to claim 1, wherein the propylene-based copolymer (B) is a propylene-ethylene random copolymer or a propylene-ethylene-1-butene random copolymer.

3. The polypropylene resin composition according to claim 1, wherein the low-density polyethylene (D) is produced by a high-pressure process.

4. 2. The polypropylene resin composition according to claim 1, wherein the difference between the melting point of the polypropylene resin (A) and the melting point of the propylene-based copolymer (B) is 20 to 45° C.

5. A biaxially oriented film comprising a layer which is any one of the compositions of claims 1 to 4.

6. 6. The biaxially stretched film according to claim 5, which has a surface layer of any one of the compositions according to claims 1 to 4.

7. 6. The biaxially stretched film of claim 5, having a total haze of 70% or more.

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