Resin composition and molded article

Abstract

To provide a resin composition capable of obtaining a molded article having excellent mechanical strength (tensile strength and elongation) and a good appearance.SOLUTION: A resin composition comprises a polyethylene-based resin, talc having an average particle diameter of 0.7 μm to 6.0 μm as determined from results of measurement of a specific surface area by an air permeability method in accordance with JIS M-8511, a zinc fatty acid having a carbon number of 15 to 20, and a fatty acid having a carbon number of 15 to 20. The mass ratio of the polyethylene-based resin to the talc is from 60:40 to 93:7, the content of the zinc fatty acid is from 0.05 mass% to 0.60 mass%, the content of the fatty acid is from 0.1 mass% to 1.2 mass%, and the mass ratio of the zinc fatty acid to the fatty acid is from 1:1 to 1:2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition and a molded article using the same. [Background technology]

[0002] Polyethylene resins are used in a variety of applications due to their ease of molding and excellent mechanical properties, etc. For example, they are processed into films or bags by inflation molding or the like.

[0003] Here, it has been proposed to add various fillers and additives to polyethylene resins in order to improve the mechanical strength and processability of molded articles made from polyethylene resins (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-200108 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-020556 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional polyethylene resin compositions have had problems such as insufficient mechanical strength, such as tensile strength and elongation, of the resulting molded articles, and poor appearance.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a resin composition that can be used to obtain a molded article having excellent mechanical strength (tensile strength, elongation) and good appearance, and a molded article containing the same. [Means for solving the problem]

[0007] The present inventors have conducted extensive research into the above-mentioned problems and have found that by incorporating a polyethylene resin, talc having a predetermined average particle size, a fatty acid zinc salt, and a fatty acid in predetermined amounts or predetermined ratios, the tensile strength and elongation of the resulting molded article are significantly improved, and the appearance of the molded article is also improved.

[0008] The present invention provides the following resin composition. [1] A resin composition comprising a polyethylene resin, talc having an average particle size of 0.7 μm or more and 6.0 μm or less, as determined from the results of measuring the specific surface area by an air permeability method in accordance with JIS M-8511, a fatty acid zinc salt having 15 to 20 carbon atoms, and a fatty acid having 15 to 20 carbon atoms, wherein the mass ratio of the polyethylene resin to the talc is 60:40 to 93:7, the content of the fatty acid zinc salt is 0.05% by mass or more and 0.60% by mass or less, the content of the fatty acid is 0.1% by mass or more and 1.2% by mass or less, and the mass ratio of the fatty acid zinc salt to the fatty acid is 1:1 to 1:2.

[0009] [2] The resin composition according to [1], wherein the polyethylene resin comprises a high-density polyethylene having a melt mass-flow rate of 0.025 g / 10 min or more and 0.045 g / 10 min or less at 190°C under a load of 2.16 kg, as measured in accordance with JIS K 6922-1:2018, and a linear low-density polyethylene having a melt mass-flow rate of 0.5 g / 10 min or more and 1.5 g / 10 min or less at 190°C under a load of 2.16 kg, as measured in accordance with JIS K 6922-1:2018, and the mass ratio of the high-density polyethylene to the linear low-density polyethylene is 92:8 to 98:2.

[0010] [3] The resin composition according to [1] or [2], further comprising 0.2% by mass or more and 0.9% by mass or less of a polyethylene wax.

[0011] [4] The resin composition according to any one of [1] to [3], wherein the talc has an apparent density of 0.05 g / ml or more and 0.30 g / ml or less, measured in accordance with JIS K5101-12-1:2001.

[0012] [5] The resin composition according to any one of [1] to [4], wherein the mass ratio of the polyethylene resin to the talc is 67:33 to 93:7.

[0013] The present invention provides the following molded article. [6] A molded article comprising the resin composition according to any one of [1] to [5] above.

[0014] [7] The molded product according to [6], which is an inflation molded product.

[0015] [8] The molded article according to [6] or [7], wherein the degree of orientation of the talc is 2 or more. [Effects of the Invention]

[0016] According to the present invention, there are provided a resin composition which has excellent mechanical strength (tensile strength, elongation) and can be used to produce a molded article having a good appearance, and a molded article containing the same. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic cross-sectional view of a molded article made of a resin composition according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] As described above, conventional resin compositions containing polyethylene resins have had problems such as insufficient mechanical strength (tensile strength, elongation) of the resulting molded articles and poor appearance, etc. The reasons for this are not clear, but are presumed to be as follows.

[0019] In conventional molded products made from compositions containing resin and inorganic particles, spherical or irregularly shaped inorganic particles are randomly dispersed in a resin binder, with some of the particles protruding from the resin surface. This is likely to result in unevenness on the surface of the molded product, which is thought to contribute to poor appearance. Furthermore, when force is applied to a molded product containing such randomly dispersed inorganic particles, the inorganic particles do not deform, but only the resin deforms. This tends to result in large localized stresses around the inorganic particles (resin), which can easily cause cracks in the resin in these areas. Further application of force is thought to cause the cracks to connect and fracture the molded product. Furthermore, cracks in the resin tend to cause the inorganic particles to fall off, which is also thought to reduce the mechanical strength of the molded product.

[0020] On the other hand, in the resin composition of the present invention, when a molded article is produced, the talc tends to orient substantially parallel to the surface of the molded article. Talc generally has a flat shape. It is believed that applying a large force to a resin composition containing talc during molding (e.g., stretching at a high magnification below the Vicat softening temperature) can orient the talc in one direction, but molding without applying a large force will not orient the talc. However, in the resin composition of the present invention, talc can be oriented in a molded article without applying a large force. One reason for this is that the resin composition of the present invention has an appropriate average talc particle size and a specific talc-to-resin ratio. In the resin composition of the present invention, talc moves appropriately in the molten resin. Therefore, even with a relatively small force applied during molding, the talc is thought to orient in a specific direction. Another reason is that the resin composition contains a specific ratio of fatty acid zinc and fatty acid. The fatty acid zinc and fatty acid tend to interact with the sides of the flat talc. Therefore, it is believed that when the resin composition is molded, the presence of the fatty acid zinc salt and the fatty acid makes it easier to hold adjacent talc particles parallel to each other at an appropriate distance.

[0021] Thus, when talc is oriented in a fixed direction (usually parallel to the surface of the molded article) within the molded article, unevenness on the surface of the molded article is unlikely to occur. Therefore, it is likely to have an excellent appearance. Furthermore, talc having the above average particle size has a large contact area with the resin. Therefore, even if force is applied to the molded article, it is unlikely to fall off from the molded article. Furthermore, since the talc is oriented in a fixed direction, force is easily applied uniformly throughout the molded article, and localized force is unlikely to be applied to the resin. In addition, the high aspect ratio of talc can keep peeling (defects) formed at the interface between the talc and the resin when strain occurs small. As a result, it is believed that the mechanical strength (tensile strength and elongation) of molded articles obtained from the resin composition is good. Note that if the average particle size of talc is excessively small, there is little difference between spherical and irregular particles, while if the average particle size of talc is excessively large, orientation becomes difficult or the particles protrude from the surface of the molded article, making it difficult to achieve the above-mentioned effects.

[0022] Hereinafter, one embodiment of the present invention will be described in detail. However, the present invention is not limited to this embodiment. Furthermore, in this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0023] 1.Resin composition The resin composition of the present embodiment contains a polyethylene resin, talc, a specific zinc salt of a fatty acid, and a specific fatty acid.

[0024] 1-1.Polyethylene resin The polyethylene resin in the present invention may be any resin that contains at least a portion of repeating units derived from ethylene (ethylene component units). The resin composition may contain only one type of polyethylene resin, or may contain two or more types. The polyethylene resin may be an ethylene homopolymer or a copolymer of ethylene and another monomer. When the polyethylene resin is a copolymer, the total amount of ethylene component units in the polyethylene resin is preferably 50% by mass or more relative to the mass of the polyethylene resin. Furthermore, the raw material for the polyethylene resin is not particularly limited, and may be derived from petroleum or plants. Furthermore, the polyethylene resin may be synthesized or commercially available.

[0025] Examples of ethylene homopolymers include high density polyethylene (HDPE): 0.942 g / cm 3 Polyethylene with a density of 0.930 g / cm or more, medium density polyethylene: 0.930 g / cm 3 More than 0.942g / cm 3 Low-density polyethylene (LDPE), polyethylene with a density less than 0.910 g / cm 3 More than 0.930g / cm 3 Polyethylene with a density of less than 0.911 g / cm, linear low-density polyethylene (LLDPE) 3 More than 0.940g / cm 3 Linear polyethylene and ultra-low density polyethylene (ULDPE) with a density of less than 0.910 g / cm 3 Polyethylenes having densities less than 1000 MPa are included.

[0026] Examples of copolymers of ethylene with other monomers include ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, metal salts of ethylene-methacrylic acid copolymer (ionomer), ethylene-acrylic acid alkyl ester copolymer, ethylene-methacrylic acid alkyl ester copolymer, maleic acid-modified polyethylene, etc.

[0027] Among the above, the resin composition preferably contains at least one of a high-density polyethylene having an MFR (190°C, 2.16 kg load) according to JIS K 6922-1:2018 (ISO17855-1) of 0.025 g / 10 min or more and 0.045 g / 10 min or less, and a linear low-density polyethylene having an MFR (190°C, 2.16 kg load) according to JIS K 6922-1:2018 (ISO17855-1) of 0.5 g / 10 min or more and 1.5 g / 10 min or less, and more preferably contains both. Note that in this specification, the term "MFR" refers to melt mass-flow rate.

[0028] When the resin composition contains high-density polyethylene satisfying the above MFR and linear low-density polyethylene satisfying the above MFR, the mass ratio thereof (high-density polyethylene:linear low-density polyethylene) is preferably 92:8 to 98:2, more preferably 95:5 to 97:3. When the ratio of high-density polyethylene to linear low-density polyethylene is within this range, the mechanical strength of the obtained molded article tends to be increased. In addition, the moldability of the resin composition tends to be improved.

[0029] The amount (total amount) of polyethylene resin in the resin composition may be in the range of 60:40 to 93:7 in terms of the mass ratio of polyethylene resin to talc (described later), and this mass ratio is more preferably 70:30 to 88:12. When the mass ratio of polyethylene resin to talc is within this range, the talc is more likely to be oriented in the molded article, as described above. Furthermore, the amount (total amount) of polyethylene resin relative to the total amount of the resin composition is preferably 60% by mass or more and 93% by mass or less, more preferably 70% by mass or more and 85% by mass or less. When the amount of polyethylene resin is within this range, the elongation of the resulting molded article is further improved.

[0030] 1-2.Talc Talc is a natural mineral known as "hydrated magnesium silicate" and is expressed by the chemical formula 4SiO2·3MgO·H2O. Its chemical composition varies slightly depending on its origin, but theoretically it is expressed as SiO2: 64.4% by mass, MgO: 31.8% by mass, and loss on ignition (water) 4.7% by mass. The resin composition may contain talc from multiple sources.

[0031] The talc may contain impurities to the extent that the object and effect of this embodiment are not impaired. Examples of impurities include quartz, dolomite, magnesite, chlorite, etc. However, the amount of these impurities is preferably 30% by mass or less, more preferably 20% by mass or less, based on the total amount of talc. The amount and type of impurities can be identified by X-ray diffraction or X-ray fluorescence analysis.

[0032] Here, the average particle diameter of talc, as determined from the results of measuring the specific surface area by the air permeability method in accordance with JIS M-8511, should be 0.7 μm or more and 6.0 μm or less, and more preferably 1.0 μm or more and 5.0 μm or less. An example of an instrument for measuring the specific surface area by the air permeability method is the specific surface area measuring device SS-100 manufactured by Shimadzu Corporation. As mentioned above, when the average particle diameter of talc is within this range, the talc is easily oriented within the molded article. As mentioned above, talc usually has a flat structure. The aspect ratio (length and thickness) is not particularly limited as long as the above average particle diameter is satisfied.

[0033] The apparent density of the talc, measured in accordance with JIS K 5101-12-1:2004, is preferably 0.05 g / ml or more and 0.30 g / ml or less, and more preferably 0.15 g / ml or more and 0.25 g / ml or less. When the apparent density of the talc is within this range, the elongation of the resulting molded article is likely to be further increased.

[0034] The total amount of talc may be any amount that satisfies the mass ratio of the talc to the polyethylene resin. However, the total amount of talc in the resin composition is preferably 7% by mass or more and 40% by mass or less, and more preferably 12% by mass or more and 30% by mass or less. When the talc content is within this range, the mechanical strength of the resulting molded product is further increased.

[0035] 1-3. Fatty acid zinc The fatty acid zinc salt contained in the resin composition is a salt of zinc and a fatty acid having 15 to 20 carbon atoms. The fatty acid constituting the fatty acid zinc salt may be a monovalent fatty acid or a polyvalent fatty acid, but is preferably a monovalent fatty acid. Furthermore, the fatty acid may be a saturated fatty acid or an unsaturated fatty acid, but is preferably a saturated fatty acid from the viewpoint of ease of interaction with the polyethylene resin and talc.

[0036] Specific examples of the fatty acid zinc salt include zinc palmitate and zinc stearate. The resin composition may contain only one type of fatty acid zinc salt, or may contain two or more types.

[0037] The mass ratio of the fatty acid zinc salt to the fatty acid described below in the resin composition may be 1:1 to 1:2, and more preferably 1:1.3 to 1:1.7. When the mass ratio of the fatty acid zinc salt to the fatty acid is within this range, the orientation of the talc becomes even better.

[0038] The content of the fatty acid zinc salt relative to the total amount of the resin composition may be 0.05% by mass or more and 0.60% by mass or less, and more preferably 0.10% by mass or more and 0.40% by mass or less. If the amount of fatty acid zinc salt is 0.05% by mass or more, the fatty acid zinc salt is more likely to interact with talc. On the other hand, if the content of fatty acid zinc salt is 0.60% by mass or less, the fatty acid zinc salt is less likely to bleed out from the molded product.

[0039] 1-4.Fatty acid The fatty acid contained in the resin composition is a fatty acid having 15 to 20 carbon atoms. The fatty acid may be a monovalent fatty acid or a polyvalent fatty acid, but is preferably a monovalent fatty acid. The fatty acid may be a saturated fatty acid or an unsaturated fatty acid, but is preferably a saturated fatty acid from the viewpoint of ease of interaction with the polyethylene-based resin and talc. The carbon number of the fatty acid is preferably small compared to the carbon number of the fatty acid constituting the fatty acid zinc, and the difference is preferably 2 or less, more preferably 0.

[0040] Specific examples of the fatty acid include palmitic acid, stearic acid, and mixtures thereof. The resin composition may contain only one type of fatty acid, or may contain two or more types of fatty acids.

[0041] The content of the fatty acid relative to the total amount of the resin composition may be from 0.1 to 1.2% by mass, and preferably from 0.2 to 0.8% by mass, which allows the fatty acid to easily interact with talc.

[0042] 1-5.Polyethylene wax The resin composition of the present embodiment may further contain a polyethylene wax. The polyethylene wax may be a wax containing polyethylene as a main component, and may contain more than 50% by mass of polyethylene, but preferably contains 80% by mass or more, and more preferably 90% by mass or more of polyethylene.

[0043] The melting point of the polyethylene wax is not particularly limited, but is preferably 70°C or higher and 150°C or lower, and more preferably 80°C or higher and 130°C or lower. When the melting point of the polyethylene wax is within this range, the molding processability of the resin composition is improved. The melting point is a value measured in accordance with JIS K7121.

[0044] The weight-average molecular weight of the polyethylene wax is not particularly limited, and is preferably from 1,000 to 10,000, and more preferably from 1,500 to 9,000. When the weight-average molecular weight of the polyethylene wax is within this range, the polyethylene wax is less likely to bleed out from the resin composition or molded article.

[0045] The polyethylene wax may be a commercially available product, examples of which include the POLYWAX series manufactured by NuCera Solutions, the Hiwax series manufactured by Mitsui Chemicals, Inc., the Excelex series manufactured by Mitsui Chemicals, Inc., and the Sanwax series manufactured by Sanyo Scientific Co., Ltd.

[0046] The amount of polyethylene wax relative to the total amount of the resin composition is preferably 0.2% by mass or more and 0.9% by mass or less, and more preferably 0.3% by mass or more and 0.7% by mass or less. When the amount of polyethylene wax is 0.2% by mass or more, the polyethylene wax tends to improve the moldability of the resin composition. On the other hand, when the amount of polyethylene wax is 0.9% by mass or less, the polyethylene wax is less likely to bleed out from the resin composition and molded products.

[0047] 1-6.Other ingredients The resin composition may further contain components other than those described above, provided that the purpose and effect of this embodiment are not impaired. Examples of such components include paraffin oil, plasticizer, colorant, antioxidant, flame retardant, foaming agent, and flow adjuster.

[0048] The paraffin oil is not particularly limited as long as it is liquid at 23° C., and any known paraffin oil can be used. Paraffin oil is, for example, a linear or branched hydrocarbon having 14 to 30 carbon atoms, but may also contain cyclic hydrocarbons (naphthenes) or aromatic hydrocarbons.

[0049] Examples of plasticizers include triethyl citrate, acetyl triethyl citrate, dibutyl phthalate, diaryl phthalate, dimethyl phthalate, diethyl phthalate, dioctyl phthalate, di(2-ethylhexyl) phthalate, di-2-methoxyethyl phthalate, dibutyl tartrate, o-benzoyl benzoate, diacetin, epoxidized soybean oil, etc. The resin composition may contain these alone or in combination.

[0050] The colorant may be any of known organic or inorganic pigments or dyes. Specific examples of colorants include organic pigments such as azo, anthraquinone, phthalocyanine, quinacridone, isoindolinone, diosadin, perinone, quinophthalone, and perylene pigments, and inorganic pigments such as ultramarine, titanium oxide, titanium yellow, iron oxide (red iron oxide), chromium oxide, zinc white, and carbon black. The resin composition may contain these pigments alone or in combination.

[0051] Examples of antioxidants include phosphorus-based antioxidants, phenol-based antioxidants, and pentaerythritol-based antioxidants. The resin composition may contain these antioxidants alone or in combination. Phosphorus-based antioxidant stabilizers, more specifically, phosphorus-based antioxidant stabilizers such as phosphite esters and phosphate esters, are preferably used. Examples of phosphite esters include triesters, diesters, and monoesters of phosphorous acid, such as triphenyl phosphite, trisnonylphenyl phosphite, and tris(2,4-di-t-butylphenyl) phosphite.

[0052] Examples of the phosphate ester include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris(nonylphenyl)phosphate, and 2-ethylphenyldiphenyl phosphate.

[0053] Examples of phenolic antioxidants include α-tocopherol, butylhydroxytoluene, sinapyl alcohol, vitamin E, n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2-t-butyl-6-(3'-t-butyl-5'-methyl-2'-hydroxybenzyl)-4-methylphenylacrylate, 2,6-di-t-butyl-4-(N,N-dimethylaminomethyl)phenol, 3,5-di-t-butyl-4-hydroxybenzylphosphonate diethyl ester, and tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxymethyl]methane.

[0054] The flame retardant is not particularly limited, but may be, for example, a halogen-based flame retardant or a non-phosphorus-based halogen-based flame retardant such as a phosphorus-based flame retardant or a metal hydrate. The resin composition may contain one or more of these.

[0055] Examples of halogen-based flame retardants include halogenated bisphenol compounds such as halogenated bisphenylalkanes, halogenated bisphenylethers, halogenated bisphenylthioethers, and halogenated bisphenylsulfones, as well as bisphenol-bis(alkyl ether) compounds such as brominated bisphenol A, brominated bisphenol S, chlorinated bisphenol A, and chlorinated bisphenol S. Examples of phosphorus-based flame retardants include aluminum tris(diethylphosphinate), bisphenol A bis(diphenylphosphate), triarylisopropyl phosphate, cresyl di-2,6-xylenyl phosphate, and aromatic condensed phosphate esters. Examples of metal hydrates include aluminum trihydrate, magnesium dihydroxide, and combinations thereof.

[0056] The flame retardant may be combined with a flame retardant aid. Examples of the flame retardant aid include antimony oxides such as antimony trioxide and antimony pentoxide, zinc oxide, iron oxide, aluminum oxide, molybdenum oxide, titanium oxide, calcium oxide, and magnesium oxide.

[0057] The foaming agent is not particularly limited as long as it is a compound that can generate bubbles when mixed with or injected under pressure into a resin composition that has been molten in a melt kneader. Examples of foaming agents include those that change phase from solid to gas to generate bubbles, those that change phase from liquid to gas to generate bubbles, and gas itself.

[0058] Examples of blowing agents include aliphatic hydrocarbons such as propane, butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane; halogenated hydrocarbons such as chlorodifluoromethane, difluoromethane, trifluoromethane, trichlorofluoromethane, dichloromethane, dichlorofluoromethane, dichlorodifluoromethane, chloromethane, chloroethane, dichlorotrifluoroethane, dichloropentafluoroethane, tetrafluoroethane, difluoroethane, pentafluoroethane, trifluoroethane, dichlorotetrafluoroethane, trichlorotrifluoroethane, tetrachlorodifluoroethane, and perfluorocyclobutane; inorganic gases such as carbon dioxide, nitrogen, and air; and water.

[0059] The foaming agent may contain an active ingredient of the foaming agent together with a carrier resin. Examples of the carrier resin include crystalline olefin resins such as crystalline propylene. Examples of the active ingredient include bicarbonates. Among these, bicarbonates are preferred. A foaming agent concentrate containing a crystalline polypropylene resin as the carrier resin and bicarbonates as the thermal decomposition type foaming agent is preferred.

[0060] Known flow control agents can also be used, including peroxides such as dialkyl peroxides, for example, 1,4-bis[(t-butylperoxy)isopropyl]benzene.

[0061] Examples of antistatic agents include fatty acid diethanolamides such as lauryl diethanolamide and stearyl diethanolamide; and hydroxyl group-containing compounds such as alcohol amine compounds. Alcohol amines, such as monoethanolamine, diethanolamine, and triethanolamine, are particularly preferred. Two or more types of antistatic agents can also be used in combination. These antistatic agents may be supported on calcium silicate, calcium carbonate, or the like. The number of carbon atoms in the acyl group of the fatty acid diethanolamide is preferably 8 to 22, in order to achieve sufficient antistatic effect.

[0062] 1-7. Shape of resin composition The shape of the resin composition of the present invention is not particularly limited, and can be any shape, such as particulate, pellet, or block. When the resin composition is in pellet form, the shape of the pellet is not particularly limited, and may be any shape, such as cylindrical, spherical, or oval sphere. The size is also not particularly limited, and is selected appropriately depending on the shape. For example, in the case of spherical pellets, the diameter may be 1 to 10 mm. In the case of oval sphere pellets, the major axis may be about 1 to 10 mm, and the aspect ratio may be about 0.1 to 1.0. In the case of cylindrical pellets, the diameter may be about 1 to 10 mm, and the height may be about 1 to 10 mm.

[0063] 1-8.Method for producing resin composition The method for producing the resin composition is not particularly limited. It is sufficient that the polyethylene resin, talc, fatty acid zinc salt, and fatty acid, as well as other components as necessary, can be mixed. These may be mixed simultaneously, or only a portion may be mixed first and the rest may be mixed later. Examples of mixing methods include melt kneading. The apparatus used for melt kneading is not particularly limited, and a general extruder, kneader, Banbury mixer, etc. can be used. From the viewpoint of obtaining a resin composition with a particularly uniform composition, kneading with a twin-screw kneader is preferred.

[0064] 2. Molded products By molding the above-described resin composition, a molded article containing the resin composition can be obtained.

[0065] The molding method is not particularly limited, and may be any of inflation molding, extrusion molding, injection molding, foam injection molding, injection compression molding, blow molding, press molding, calendar molding, vacuum molding, etc. As described above, when producing a molded article using the above resin composition, talc can be oriented within the molded article without applying a large force. For example, in inflation molding, molding is performed at a relatively high temperature, i.e., while the resin is in a molten state. Therefore, when distortion occurs during molding, the stress applied to the particles within the resin composition is small, and it is generally considered difficult to orient the particles. However, the above resin composition can orient the talc in the desired direction even when inflation molding is performed. Therefore, the above resin composition is very useful as a resin composition for inflation molding.

[0066] 1 is a schematic cross-sectional view showing a molded article 10 according to one embodiment of the present invention. As shown in Fig. 1, the molded article 10 includes a matrix phase 11 of the polyethylene resin and talc 12, and the talc 12 is oriented approximately parallel to the surface of the molded article.

[0067] The degree of orientation of the talc within the molded article 10 is not particularly limited, but is preferably, for example, 2 or more. When the degree of orientation is 2 or more, the surface smoothness of the molded article 10 is significantly improved, and the mechanical strength thereof is also likely to be increased. The degree of orientation is more preferably 4 or more. The upper limit of the degree of orientation is not particularly limited, but can be, for example, 7 or less.

[0068] The degree of orientation of talc within molded article 10 can be determined from an SEM image obtained by observing the cross section of molded article 10 with an SEM. Specifically, the SEM image is subjected to a two-dimensional Fourier transform to obtain a two-dimensional Fourier image. The pixel intensity for each angular direction of the obtained Fourier image is calculated. This is plotted with the horizontal axis representing the angular direction (orientation angle) and the vertical axis representing the pixel intensity to obtain a power spectrum. The plot of the obtained power spectrum is then elliptically approximated, and the ratio of the pixel intensity at the peak of the obtained approximation curve (intensity at orientation angle 1) to the pixel intensity in the direction perpendicular to the peak direction (intensity at angle 2, which is 90 degrees subtracted from orientation angle 1) is calculated, and this can be used to calculate the "degree of orientation."

[0069] Evaluating the degree of orientation using the power spectrum obtained by two-dimensional Fourier transform is a common method for calculating the orientation direction of fibrous materials in composite materials (Reference: CE Ayres, BS Jha, H. Meredith, JR Bowman, GL Bowlin, SC Henderson, DG Simpson, Journal of Biomaterials Science, Polymer Edition. 2008, 19(5), 603-621.).

[0070] The degree of orientation can be adjusted by the shape of the talc (the average particle size described above), the ratio of the amount of polyethylene resin to the amount of talc, etc. Furthermore, when the molded product is molded by inflation molding, the degree of orientation can also be adjusted by the blow-up ratio, etc.

[0071] The shape and use of molded articles containing the resin composition are not particularly limited. For example, they can be used for films, sheets, containers (food containers, etc.), daily necessities, automobile parts, electrical and electronic parts, various consumables, etc. Examples of inflation-molded articles include films, sheets, and bags (shopping bags, etc.). The thickness of the inflation-molded article is not particularly limited, but is preferably about 7 μm to 200 μm, and more preferably about 10 μm to 100 μm. [Example]

[0072] The present invention will be described in detail based on examples, but the present invention is not limited to these examples.

[0073] 1. Material Preparation In the following examples and comparative examples, the following materials were used.

[0074] (polyethylene) HDPE: High-density polyethylene (MFR (190°C, 21.6 kg): 10 g / 10 min according to JIS K 6922-1 (ISO 1133)) LLDPE: Linear low-density polyethylene (MFR (190°C, 2.16 kg): 1.0 g / 10 min according to JIS K 6922-1 (ISO 1133))

[0075] (talc or calcium carbonate) Talc A: Average particle size calculated from the specific surface area measured by the air permeability method in accordance with JIS M-8511: 0.7 μm, apparent density: 0.1 g / ml Talc B: Average particle size determined from the specific surface area measurement results using the air permeability method in accordance with JIS M-8511: 6.0 μm, apparent density: 0.2 g / ml Talc C: Average particle size determined from the specific surface area measurement results using the air permeability method in accordance with JIS M-8511: 0.3 μm, apparent density: 0.05 g / ml Talc D: Average particle size determined from specific surface area measurement results using the air permeability method in accordance with JIS M-8511: 8.0 μm, apparent density: 0.4 g / ml Calcium carbonate: Average particle size determined from specific surface area measurement results using the air permeability method in accordance with JIS M-8511: 6.0 μm, apparent density: 0.5 g / ml The average particle size was calculated from the results of measuring the specific surface area by the air permeability method according to JIS M-8511 using a specific surface area measuring device "SS-100" manufactured by Shimadzu Corporation. The apparent density was measured in accordance with JIS K5101-12-1:2001.

[0076] (others) Zinc stearate stearic acid Wax: Polyethylene wax

[0077] 2. Preparation of resin composition and production of molded products (1) Preparation of resin composition Polyester resin, talc, zinc stearate, stearic acid, and wax were charged into a Parker HK-25D co-rotating twin-screw kneading extruder (φ25 mm, L / D=41) in the mass ratios shown in Tables 1 and 2. The mixture was melt-kneaded at a cylinder temperature of 230°C and then extruded into strands. The extruded resin composition was then cooled and cut to obtain pellets of the resin composition.

[0078] (2) Preparation of inflation film The pellets of the resin composition were extruded into a 30 μm-thick film using an inflation molding machine extrusion line equipped with an extruder, die, and inflation / cooling section. The temperature in each section of the extruder was set to 180°C to 220°C. The screw (diameter 30 mm, L / D ratio: 30) inside the extruder rotated at 20 rpm. The die was a 60 mm circular die with a die gap of 1.2 mm. The blow-up ratio (BUR) in the inflation / cooling section was set to 2.5.

[0079] 3. Evaluation The physical properties of the resin compositions and molded articles obtained above were evaluated by the following methods. The results are shown in Tables 1 and 2.

[0080] (1) Degree of orientation The cross section of the obtained inflation film was observed using a scanning electron microscope (SEM) to obtain an SEM image. The obtained SEM image was then subjected to a two-dimensional Fourier transform to obtain a two-dimensional Fourier image. In the obtained two-dimensional Fourier image, the pixel intensity for each angular direction was calculated and plotted with the angle (orientation angle) on the horizontal axis and the pixel intensity on the vertical axis to obtain a power spectrum. The plot of the obtained power spectrum was subjected to an elliptical approximation, and the ratio of the pixel intensity at the peak of the obtained approximation curve (intensity at orientation angle 1) to the pixel intensity in the direction perpendicular to the peak direction (intensity at angle 2, which is 90 degrees subtracted from orientation angle 1) was calculated as the "degree of orientation."

[0081] The degree of orientation was evaluated according to the following criteria. A: The degree of orientation is 2 or more B: The degree of orientation is 1.5 or more and less than 2 C: The degree of orientation is 1.2 or more and less than 1.5 D: The degree of orientation is less than 1.2

[0082] (2) Molding processability The ease of molding (ease of inflation molding) of each resin composition was evaluated by visually observing the blown state in the inflation / cooling section and according to the following criteria. A: Very easy to blow dry B: I can blow dry without any problems. C: A little difficult to blow, but not a problem for practical use D: Difficult to blow, practically problematic level

[0083] (3) Appearance of molded product The appearance of the resulting inflation film was visually observed and evaluated according to the following criteria. A: The surface is smooth with almost no irregularities and has a good appearance. B: The surface is smooth and has a good appearance with few irregularities. C: There are some unevenness on the surface, but it is not a problem for practical use. D: The surface is uneven and is at a level that is problematic for practical use.

[0084] (4) Mechanical strength (tensile strength) and elongation at break Dumbbell-shaped test pieces were prepared from the obtained inflation film in accordance with JIS K7161-2:2014. The tensile strength and elongation at break of the test pieces were measured in accordance with JIS K7161-2:2014 using an autograph AG-100kNXplus (Shimadzu Corporation) under conditions of 23°C and 50% RH. The test speed was 50 mm / min.

[0085] The tensile strength was evaluated based on the following criteria. A: Tensile strength is 50 MPa or more B: Tensile strength is 40 MPa or more and less than 50 MPa C: Tensile strength is 30 MPa or more and less than 40 MPa D: Tensile strength is less than 30 MPa

[0086] The elongation at break was evaluated according to the following criteria. A: The elongation at break is 150% or more before the test B: Elongation at break is 100% or more and less than 150% C: Elongation at break is 50% or more but less than 100% D: Elongation at break is less than 50% The elongation at break is a value calculated by the following formula. Elongation = (gauge length after test - gauge length before test) / gauge length before test x 100

[0087] [Table 1]

[0088] [Table 2]

[0089] [Consideration] As shown in Table 2, when inflation molding was performed using a resin composition containing calcium carbonate (Comparative Example 2), the mechanical strength and elongation at break were not improved compared to when no inorganic particles were added (Comparative Example 1). In addition, calcium carbonate is a nearly spherical particle, so orientation did not occur.

[0090] In contrast, when the average particle size determined from the results of measuring the specific surface area by the air permeability method in accordance with JIS M-8511 was 0.7 μm or more and 6.0 μm or less, the degree of orientation of talc in the obtained inflation film was 2 or more (Examples 1 to 8).In this case, the mechanical strength and elongation of the film were good, and the appearance of the film was also excellent.

[0091] On the other hand, when the average particle size of the talc was outside the above range, the molding processability was reduced, the surface became uneven, and the degree of orientation of the talc was reduced (for example, Comparative Examples 5 and 6). When the degree of orientation of the talc was reduced, the mechanical strength and elongation were not good.

[0092] Furthermore, even when the average particle size of the talc was 0.7 μm or more and 6.0 μm or less, the degree of orientation decreased when zinc stearate and stearic acid were not contained or when the amounts thereof were not within the specified ranges (Comparative Examples 3 and 4). [Industrial Applicability]

[0093] The resin composition of the present invention can provide inflation-molded articles having excellent mechanical strength (tensile strength, elongation) and good appearance, and is therefore useful in the production of various industrial products. [Explanation of symbols]

[0094] 10 Molded products 11 Matrix phase of polyethylene resin 12 Talc

Claims

1. A polyethylene resin, Talc having an average particle size of 0.7 μm or more and 6.0 μm or less, as determined from the results of measuring the specific surface area by an air permeability method in accordance with JIS M-8511; a zinc fatty acid having 15 to 20 carbon atoms; a fatty acid having 15 to 20 carbon atoms; Including, a mass ratio of the polyethylene resin to the talc is 60:40 to 93:7; The content of the fatty acid zinc is 0.05% by mass or more and 0.60% by mass or less, The content of the fatty acid is 0.1% by mass or more and 1.2% by mass or less, The content mass ratio of the fatty acid zinc and the fatty acid is 1:1 to 1:

2. Resin composition.

2. The polyethylene resin is A high-density polyethylene having a melt mass flow rate of 0.025 g / 10 min or more and 0.045 g / 10 min or less at 190 ° C. and a load of 2.16 kg, as measured in accordance with JIS K 6922-1:2018; and a linear low-density polyethylene having a melt mass flow rate of 0.5 g / 10 min or more and 1.5 g / 10 min or less at 190°C and a load of 2.16 kg, as measured in accordance with JIS K 6922-1:2018; the mass ratio of the high-density polyethylene to the linear low-density polyethylene is 92:8 to 98:2; The resin composition according to claim 1.

3. Further containing 0.2% by mass or more and 0.9% by mass or less of a polyethylene wax, The resin composition according to claim 1.

4. The talc has an apparent density measured in accordance with JIS K5101-12-1:2001 of 0.05 g / ml or more and 0.30 g / ml or less. The resin composition according to claim 1.

5. The mass ratio of the polyethylene resin to the talc is 67:33 to 93:

7. The resin composition according to claim 1.

6. The resin composition according to any one of claims 1 to 5, Molded products.

7. It is an inflation molding product. The molded article according to claim 6.

8. The degree of orientation of the talc is 2 or more. The molded article according to claim 6.

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