Resin composition and molded article comprising same

Abstract

To provide a resin composition capable of obtaining a molded article having excellent mechanical strength and good appearance even when formed into a thin molded article.SOLUTION: The resin composition contains a thermoplastic resin and a calcium carbonate particle group. A ratio of a mass of the calcium carbonate particle group to a total mass of the thermoplastic resin and the calcium carbonate particle group is 20% by mass or more and 40% by mass or less, and the calcium carbonate particle group contains hexagonal plate-shaped calcium carbonate particles in a particle number of 80% or more with respect to a total particle number of the calcium carbonate particle group.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, resin compositions in which inorganic powder such as calcium carbonate powder is filled into a thermoplastic resin have been known (for example, Patent Document 1). For example, calcium carbonate powder is generally spherical. Molded articles obtained by molding such resin compositions are used for various purposes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-220234 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the conventional resin compositions described above, the mechanical strength (tensile strength and elongation) of the molded articles obtained may be insufficient, or the surface condition may be deteriorated, resulting in poor appearance.

[0005] In particular, for example, plastic bags made of thin films with a thickness of 30 μm or less tend to lack mechanical strength and have poor appearance, which can cause problems when used. Therefore, it is desirable to be able to increase the mechanical strength and suppress poor appearance even in thin molded products.

[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 from which a molded article having excellent mechanical strength and good appearance can be obtained, even when formed into a thin molded article, and a molded article containing the same. [Means for solving the problem]

[0007] The present invention relates to the following resin composition and molded article. [1] A resin composition comprising a thermoplastic resin and calcium carbonate particle groups, wherein the ratio of the mass of the calcium carbonate particle groups to the total mass of the thermoplastic resin and the calcium carbonate particle groups is 20% by mass or more and 40% by mass or less, and the calcium carbonate particle groups contain hexagonal plate-shaped calcium carbonate particles in a number of 80% or more of the total number of particles in the calcium carbonate particle groups. [2] The resin composition according to [1], wherein the ratio of the mass of the calcium carbonate particle groups to the total mass of the thermoplastic resin and the calcium carbonate particle groups is 20 mass % or more and less than 40 mass %. [3] The resin composition according to [1] or [2], wherein, in the hexagon of the hexagonal plate-like calcium carbonate particle, the length of the longest diagonal among the three diagonals connecting each vertex to the third vertex from that vertex is 1.0 to 1.5 times the length of the shortest diagonal. [4] The resin composition according to [3], wherein the length of the longest diagonal line is 10 μm or more and 25 μm or less. [5] The resin composition according to [3], wherein the length of the longest diagonal line is 20 to 40 times the thickness of the hexagonal plate-like calcium carbonate particles. [6] The resin composition according to any one of [1] to [5], wherein the thermoplastic resin contains a polyolefin-based resin. [7] The resin composition according to [6], wherein the polyolefin resin comprises at least one of a polyethylene resin and a polypropylene resin. [8] The resin composition according to any one of [1] to [7], wherein the hexagonal plate-like calcium carbonate particles are composed of precipitated calcium carbonate. [9] A molded article comprising the resin composition according to any one of [1] to [8].

[10] The molded article according to [9], wherein the molded article is a film, a sheet or a bag.

[11] The molded article according to

[10] , wherein the molded article is an inflation molded article.

[12] The molded article according to

[10] or

[11] , wherein the degree of orientation of the hexagonal plate-like calcium carbonate particles is 1.5 or more. [Effects of the Invention]

[0008] According to the present invention, there are provided a resin composition from which a molded article having excellent mechanical strength and good appearance can be obtained even when formed into a thin molded article, and a molded article containing the same. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1A is a schematic plan view illustrating the shape of a hexagonal plate-like calcium carbonate particle, and FIG. 1B is a schematic perspective view. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a molded article made of a resin composition according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present inventors have found that by using a calcium carbonate particle group containing hexagonal plate-shaped calcium carbonate particles in a predetermined ratio as the calcium carbonate powder to be filled into a resin composition, it is possible to significantly increase the mechanical strength, smooth the surface, and improve the appearance even in the case of a thin molded product.

[0011] The reason for this is not clear, but is presumed to be as follows. Hexagonal plate-shaped calcium carbonate particles can be packed at a higher density than spherical or scaly calcium carbonate particles. Furthermore, the surfaces of the hexagonal plate-shaped calcium carbonate particles are likely to be oriented in the direction of stretching, for example, when the resin composition is stretched during the molding process. As a result, the resulting molded product is thought to have high mechanical strength, minimal surface irregularities, and a good appearance.

[0012] An embodiment of the present invention will be described in detail below. However, the present invention is not limited to this embodiment. In addition, in this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits.

[0013] 1.Resin composition The resin composition of the present embodiment contains a thermoplastic resin and calcium carbonate particles.

[0014] In the resin composition, the mass ratio of calcium carbonate particle groups to the total mass of the thermoplastic resin and calcium carbonate particle groups is 20% by mass or more and 40% by mass or less, preferably 20% by mass or more and less than 40% by mass, and more preferably 20% by mass or more and 30% by mass or less. When the mass ratio of calcium carbonate particle groups is equal to or more than the lower limit, the calcium carbonate particles are likely to be well oriented, thereby further improving the appearance and mechanical strength (particularly tensile strength) of the molded article. On the other hand, when the mass ratio of calcium carbonate particle groups is equal to or less than the upper limit, even in the case of a thin molded article, deterioration in tensile elongation and flexibility due to an excessive proportion of calcium carbonate particles can be further suppressed.

[0015] 1-1.Thermoplastic resin The type of thermoplastic resin is not particularly limited, and examples thereof include thermoplastic resins such as polyolefin resins, poly(meth)acrylic acid (esters), polyvinyl acetate, polyacrylonitrile, polystyrene, ABS resins, polycarbonate, polyamide, polyvinyl alcohol, petroleum hydrocarbon resins, and coumarone-indene resins; and elastomers such as styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-butadiene-ethylene copolymers, styrene-isoprene-ethylene copolymers, acrylonitrile-butadiene copolymers, and fluorine-based elastomers. Among these, polyolefin resins are preferred from the viewpoints of mechanical strength and moldability.

[0016] That is, the thermoplastic resin preferably contains a polyolefin-based resin. Specifically, the amount of polyolefin-based resin in the thermoplastic resin is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The thermoplastic resin may contain only one type of polyolefin-based resin, or may contain two or more types.

[0017] Polyolefin resins are resins whose main component is an olefin-derived structural unit, and the amount of the olefin-derived structural units relative to all structural units constituting the polyolefin resin is 50% by mass or more. The polyolefin resin may be a homopolymer of one type of olefin, a copolymer of two or more types of olefins, or a copolymer of one or more types of olefins with one or more other monomers (monomers other than olefins). The amount of the olefin-derived structural units in the polyolefin resin is preferably 75% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more.

[0018] Examples of olefins include ethylene and α-olefins having 3 to 10 carbon atoms, and specific examples thereof include ethylene, propylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1-heptene, 4-methylpentene-1, 3-methyl-1-hexene, and 1-octene. The polyolefin resin may contain only one type of structural unit derived from these, or may contain two or more types.

[0019] Examples of other monomers include diene monomers such as 1,4-hexadiene, 1,6-octadiene, 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, dicyclopentadiene (DCPD), ethylidene norbornene (ENB), norbornadiene, and 5-vinyl-2-norbornene; acid (or acid anhydride)-modified olefins such as maleic anhydride-modified olefins; and (meth)acrylates such as methyl (meth)acrylate. The polyolefin resin may contain only one type of structural unit derived from these, or may contain two or more types.

[0020] The polyolefin resin is preferably at least one of a polypropylene resin and a polyethylene resin, and the polypropylene resin or the polyethylene resin may be a virgin resin, a recycled resin, or a mixture thereof.

[0021] In this specification, the term "polypropylene resin" refers to a resin containing 50% by mass or more of structural units derived from propylene, and includes propylene homopolymers and copolymers of propylene with other monomers (propylene copolymers). Propylene homopolymers include isotactic, syndiotactic, atactic, hemiisotactic, and linear or branched polypropylenes exhibiting various stereoregularities. The stereoregularity of propylene is 13 The propylene copolymer can be identified by C-NMR or the like. The propylene copolymer may be a random copolymer or a block copolymer. The propylene copolymer may be a binary copolymer of propylene and another monomer, or a multi-component copolymer of propylene and two or more other monomers. Examples of preferred copolymerization components (other monomers) include ethylene, α-olefins having 4 or more carbon atoms, tetrafluoroethylene, vinyl acetate, etc. In this embodiment, the polypropylene-based resin is preferably a propylene homopolymer or a propylene copolymer containing less than 5 mass % of structural units derived from other monomers.

[0022] In this specification, the term "polyethylene resin" refers to a resin containing 50% by mass or more of ethylene-derived structural units, and includes ethylene homopolymers and copolymers of ethylene with other monomers (ethylene copolymers). 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 3The ethylene copolymer may be a binary copolymer of ethylene and another monomer, or a multi-component copolymer of ethylene and two or more other monomers. Examples of preferred copolymerization components (other monomers) include vinyl acetate and α-olefins having 3 or more carbon atoms. In this embodiment, the polyethylene resin is preferably an ethylene homopolymer or an ethylene copolymer containing less than 5% by mass of structural units derived from other monomers.

[0023] In particular, for thin molded products such as shopping bags, the polyolefin resin preferably contains a polyethylene resin, more preferably a high-density polyethylene. The MFR (190°C, 2.16 kg load) of the high-density polyethylene according to JIS K 6922-1:2018 (ISO17855-1) is not particularly limited, but is preferably, for example, 0.01 g / 10 min or more and 3.0 g / 10 min or less.

[0024] The content of the thermoplastic resin in the resin composition is not particularly limited, but is preferably 57% by mass or more and 80% by mass or less, more preferably 65% ​​by mass or more and 78% by mass or less, and even more preferably 70% by mass or more and 76% by mass or less, relative to the total amount of the resin composition. When the content of the thermoplastic resin is equal to or greater than the lower limit, even in the case of a thin molded article, the decrease in tensile elongation and flexibility caused by an excessive proportion of calcium carbonate particles can be further suppressed. When the content of the thermoplastic resin is equal to or less than the upper limit, the proportion of calcium carbonate particles is equal to or greater than a predetermined value, and therefore the appearance and mechanical strength (particularly tensile strength) of the molded article can be further improved.

[0025] 1-2. Calcium carbonate particles The calcium carbonate particle group contains hexagonal plate-shaped calcium carbonate particles, the number of which is 80% or more of the total number of particles in the calcium carbonate particle group. The hexagonal plate-shaped calcium carbonate particles are vaterite crystals (hexagonal crystals). The hexagonal plate-shaped refers to a shape that is approximately hexagonal in plan view, with the length of one side of the hexagon being 10 times or more the thickness. Compared to spherical calcium carbonate particles or scaly calcium carbonate particles, hexagonal plate-shaped calcium carbonate particles are easily packed at high density and are easily oriented, for example, by stretching during the molding process. Molded articles of resin compositions containing such calcium carbonate particles have a smooth surface and high mechanical strength. The number of hexagonal plate-shaped calcium carbonate particles in the calcium carbonate particle group is preferably 90% or more, more preferably 95% or more of the total number of particles in the calcium carbonate particle group.

[0026] FIG. 1A is a schematic plan view illustrating the shape of a hexagonal plate-like calcium carbonate particle, and FIG. 1B is a schematic perspective view.

[0027] In the hexagonal shape of a hexagonal plate-like calcium carbonate particle, the length (lmax) of the longest of the three diagonals connecting each vertex to the vertex three vertices from that vertex is preferably 1.0 to 1.5 times, more preferably 1.0 to 1.2 times, the length (lmin) of the shortest diagonal (see FIG. 1A ). Here, the diagonal connecting a vertex to the vertex three vertices from that vertex refers to the longer of the diagonals drawn from that vertex. In FIG. 1A , the three diagonals connecting each vertex to the vertex three vertices from that vertex are diagonals L1, L2, and L3, of which L1 (or L2) is the longest diagonal and L3 is the shortest. Hereinafter, the term "diagonal" used in this specification refers to the three diagonals connecting each vertex to the vertex three vertices from that vertex. When the ratio of the length of the longest diagonal line (lmax) to the length of the shortest diagonal line (lmin) is within the above range, the hexagonal shape of the calcium carbonate particles becomes closer to a regular hexagon, and therefore the particles can be packed more densely in the resin composition and more easily oriented, thereby further improving the mechanical strength (particularly tensile strength) and appearance.

[0028] The length of the longest diagonal line (lmax) is not particularly limited, but is preferably, for example, 10 μm or more and 25 μm or less. When the length of the longest diagonal line is 10 μm or more, the calcium carbonate particles have a sufficient size, which makes it easier to orient them and improves the appearance. When the length of the longest diagonal line is 25 μm or less, the calcium carbonate particles are less likely to break during molding and are more likely to maintain their hexagonal plate shape, which makes it possible to maintain better mechanical strength. From the same perspective, the length of the longest diagonal line is more preferably 12 μm or more and 18 μm or less.

[0029] The length of the longest diagonal line (lmax) is preferably 20 to 40 times the thickness (t) of the hexagonal plate-like calcium carbonate particles (see FIG. 1B). When the length of the longest diagonal line is 20 times or more the thickness of the hexagonal plate-like calcium carbonate particles, the size of the hexagonal plate-like calcium carbonate particles becomes larger, thereby further improving the mechanical strength and appearance of the resin composition. When the length of the longest diagonal line is 40 times or less the thickness of the hexagonal plate-like calcium carbonate particles, the calcium carbonate particles are less likely to break during molding, thereby further maintaining the mechanical strength (particularly tensile strength) of the resin composition. From the same viewpoint, the length of the longest diagonal line is more preferably 25 to 30 times the thickness of the hexagonal plate-like calcium carbonate particles.

[0030] The shape of the hexagonal plate-like calcium carbonate particles can be observed using a scanning electron microscope (SEM). From the obtained SEM image, 100 hexagonal plate-like calcium carbonate particles are randomly selected, and for each, the lengths of the longest and shortest of the three diagonals mentioned above are measured, and the average values ​​are taken as a representative value. Furthermore, the thickness of each hexagonal plate-like calcium carbonate particle is measured, and the average value is taken as a representative value. Furthermore, the ratio of the number of hexagonal plate-like calcium carbonate particles to the total number of particles in the calcium carbonate particle group can also be determined by the image analysis.

[0031] The calcium carbonate may be so-called light calcium carbonate, which is prepared by a synthetic method, or so-called heavy calcium carbonate, which is obtained by mechanically crushing and classifying a natural raw material containing CaCO as a main component, such as limestone. Of these, light calcium carbonate is preferred from the viewpoint of easier preparation into a hexagonal plate shape.

[0032] The shape of the hexagonal plate-like calcium carbonate particles can be adjusted by the production conditions of the calcium carbonate particles. For example, calcium carbonate particles can be produced through the following steps: 1) introducing carbon dioxide into a calcium-containing solution containing a calcium compound (e.g., calcium hydroxide) to prepare a calcium carbonate suspension; 2) further introducing carbon dioxide into the calcium carbonate suspension to prepare a saturated calcium bicarbonate solution in which calcium carbonate is dissolved; and 3) heating the saturated calcium bicarbonate solution to decarbonate and crystallize calcium carbonate. The shape of the hexagonal plate-like calcium carbonate particles can be adjusted by adjusting the degree of supersaturation and pH of the saturated solution in step 2) and the rate of temperature rise in step 3). For example, the lower the degree of supersaturation, the higher the pH, and the slower the rate of temperature rise, the easier it is to obtain a hexagonal plate-like shape closer to a regular hexagon.

[0033] Specifically, the pH of the calcium bicarbonate saturated solution in step 2) can be, for example, 7.0 or higher, preferably 7.4 or higher. The upper limit of the pH is not particularly limited, but can be, for example, 8.0 or lower. The degree of supersaturation of the calcium bicarbonate saturated solution can be, for example, 30 or lower, preferably 20 or lower. The degree of supersaturation is defined as (Ci-Cs) / Cs (Ci: initial calcium bicarbonate concentration, Cs: initial calcium carbonate solubility).

[0034] The rate of temperature rise of the saturated calcium bicarbonate solution in step 3) can be, for example, 5 to 15°C / min. The heating temperature may be any temperature that allows decarbonation, and can be, for example, 90 to 120°C.

[0035] In this embodiment, the calcium carbonate particles may be a powder made from concrete sludge, steel slag, carbide slag, waste concrete, coal ash, biomass ash, incineration ash, waste gypsum, alkaline wastewater, etc., or may be a powder made from steel slag and / or carbide slag. That is, these calcium-containing waste materials may be used as the calcium compound (calcium source) used in the production of the calcium carbonate particles.

[0036] In this way, calcium-containing waste, such as steel slag or carbide slag, or calcium extracted from the waste, is reacted with carbon dioxide, which causes the greenhouse effect, to prepare calcium carbonate particle groups, thereby reducing the environmental load.

[0037] Here, the calcium carbonate particles may be surface-modified or may not be surface-modified. From the viewpoint of improving dispersibility, the calcium carbonate particles are preferably surface-modified. Examples of methods for surface modification of calcium carbonate particles include physical modification methods using plasma treatment or the like, and chemical modification methods using coupling agents, surfactants, or the like. Examples of coupling agents that can be used in chemical modification methods include silane coupling agents and titanium coupling agents. Any of anionic, cationic, nonionic, and amphoteric surfactants can be used as the surfactant, and examples thereof include higher fatty acids, higher fatty acid esters, higher fatty acid amides, and higher fatty acid salts.

[0038] The content of calcium carbonate particles in the resin composition is not particularly limited, but is preferably 17% by mass or more and 40% by mass or less, more preferably 22% by mass or more and 35% by mass or less, and even more preferably 24% by mass or more and 30% by mass or less, relative to the total amount of the resin composition. When the content of calcium carbonate particles is equal to or greater than the lower limit, the appearance and mechanical strength (particularly tensile strength) of the molded article can be further improved. When the content of calcium carbonate particles is equal to or less than the upper limit, even in the case of a thin molded article, a decrease in tensile strength and elongation due to an excessive proportion of calcium carbonate particles can be further suppressed.

[0039] 1-3.Other ingredients The resin composition may further contain other components in addition to those described above, provided that the purpose and effect of the present embodiment are not impaired. Examples of other components in addition to those described above include lubricants, plasticizers, colorants, antioxidants, flame retardants, foaming agents, and flow adjusters.

[0040] Examples of lubricants include fatty acid-based lubricants such as stearic acid, hydroxystearic acid, complex stearic acid, and oleic acid; fatty alcohol-based lubricants; aliphatic amide-based lubricants such as stearamide, oxystearamide, oleylamide, erucylamide, ricinoleamide, behenamide, methylolamide, methylenebisstearamide, methylenebisstearobenamide, bisamic acids of higher fatty acids, and complex amides; aliphatic ester-based lubricants such as n-butyl stearate, methyl hydroxystearate, polyhydric alcohol fatty acid esters, saturated fatty acid esters, and ester waxes; and fatty acid metal soap-based lubricants such as zinc stearate and magnesium stearate.

[0041] 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-benzoylbenzoic acid ester, diacetin, epoxidized soybean oil, etc. The resin composition may contain these alone or in combination.

[0042] The colorant may be any of known organic pigments, inorganic pigments, or dyes. Specific examples of colorants include organic pigments such as azo-based, anthraquinone-based, phthalocyanine-based, quinacridone-based, isoindolinone-based, dioxazine-based, perinone-based, quinophthalone-based, and perylene-based pigments; and inorganic pigments such as ultramarine, titanium yellow, and chromium oxide. The resin composition may contain these pigments alone or in combination.

[0043] 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 antioxidants, more specifically, phosphorus-based antioxidants 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.

[0044] Examples of phosphate esters include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, tris(nonylphenyl)phosphate, 2-ethylphenyldiphenyl phosphate, and the like.

[0045] 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.

[0046] 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 these flame retardants alone or in combination.

[0047] 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.

[0048] The flame retardant may also be combined with a flame retardant synergist. Examples of the flame retardant synergist include antimony oxides such as antimony trioxide and antimony pentoxide, and other known flame retardant synergists.

[0049] The foaming agent is not particularly limited as long as it is a compound that can generate bubbles when mixed or injected into a composition that is in a molten state 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.

[0050] 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.

[0051] 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.

[0052] Known fluidity modifiers can also be used. Examples of fluidity modifiers include peroxides such as dialkyl peroxides, for example, 1,4-bis[(t-butylperoxy)isopropyl]benzene. Depending on the type of thermoplastic resin used, these peroxides can also function as crosslinking agents. In particular, when the thermoplastic resin (polyolefin resin) has a diene-derived structural unit, the diene may be crosslinked by the peroxide.

[0053] 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.

[0054] The total amount of other components in the resin composition is not particularly limited, but can be, for example, 3% by mass or less, preferably 0.1% by mass or more and 2% by mass or less, based on the total amount of the resin composition.

[0055] 1-4. Shape of resin composition The shape of the resin composition is not particularly limited, and can be any shape such as particles, pellets, or blocks. When the resin composition is in the form of pellets, the shape of the pellets is not particularly limited, and can 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 can be about 1 to 10 mm, and the aspect ratio can be about 0.1 to 1.0. In the case of cylindrical pellets, the diameter can be about 1 to 10 mm, and the height can be about 1 to 10 mm.

[0056] 1-5.Method for producing resin composition The method for producing the resin composition is not particularly limited. Any method is sufficient as long as it can sufficiently mix the above-mentioned thermoplastic resin, calcium carbonate particles, and other components as necessary, and the resin composition can be prepared, for example, by melt kneading. In this case, all components may be mixed and then melt kneaded, or only some of the components may be melt kneaded first and the remaining components may be kneaded later. The device for performing melt kneading is not particularly limited, and a general extruder, kneader, Banbury mixer, etc. can be used. In particular, from the viewpoint of obtaining a resin composition with a uniform composition, kneading with a twin-screw kneader is preferred.

[0057] 2. Molded products By molding the above-described resin composition, a molded article containing the resin composition can be obtained.

[0058] 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, and the like.

[0059] The shape of the molded product is not particularly limited, and may be, for example, a film, a sheet, or a bag. The film, sheet, or bag may be further stretched.

[0060] The thickness of the film or sheet is not particularly limited, but can be, for example, 1 μm or more and 5000 μm or less, preferably 7 μm or more and 200 μm or less, more preferably 10 μm or more and 100 μm or less, and even more preferably 10 μm or more and 30 μm or less.

[0061] For example, thin films or bags can be molded by inflation molding. That is, the molded product may be an inflation molded product. The resin composition can be appropriately stretched during molding by inflation molding or the like, thereby allowing the hexagonal plate-like calcium carbonate particles to be well oriented. This allows for the production of molded products that have excellent mechanical strength (especially tensile strength) and good appearance, even when they are thin.

[0062] FIG. 2 is a schematic cross-sectional view showing a molded article 10 according to one embodiment of the present invention.

[0063] 2, the molded article 10 includes a thermoplastic resin matrix phase 11 and a plurality of hexagonal plate-shaped calcium carbonate particles 12 (calcium carbonate particle groups). The hexagonal plate-shaped calcium carbonate particles 12 are stretched appropriately during the molding process, so that their surfaces are oriented along the surface of the molded article (along the stretching direction), thereby making it possible to smooth the surface of the molded article 10 and increase its mechanical strength (particularly tensile strength).

[0064] The degree of orientation of the hexagonal plate-like calcium carbonate particles in a molded article of the resin composition is not particularly limited, but is preferably, for example, 1.5 or more. When the degree of orientation is 1.5 or more, the hexagonal plate-like calcium carbonate particles are highly oriented, so that the molded article has a smooth surface and high mechanical strength (especially tensile strength). From the same viewpoint, the degree of orientation of the hexagonal plate-like calcium carbonate particles is more preferably 2 or more. The upper limit of the degree of orientation is not particularly limited, but can be, for example, 5 or less.

[0065] The degree of orientation of the hexagonal plate-like calcium carbonate particles can be determined from an SEM image obtained by observing the cross section of the molded article with an SEM. Specifically, a two-dimensional Fourier transform is performed on the SEM image to obtain a two-dimensional Fourier image. The pixel intensity for each angular direction of the obtained Fourier image is calculated. This is then 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 fitted to an ellipse, and the ratio of the pixel intensity at the peak of the fitted 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."

[0066] 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.).

[0067] The degree of orientation can be adjusted by the shape of the hexagonal plate-like calcium carbonate particles, molding conditions, stretching conditions, etc. For example, the degree of orientation tends to be high when the ratio of the length of the longest diagonal to the length of the shortest diagonal among the three diagonals of the hexagonal plate-like calcium carbonate particles is close to 1 or when the length of the longest diagonal is increased. Furthermore, when a molded product is molded by inflation molding, the degree of orientation tends to be high when the blow-up ratio is increased. Furthermore, when a molded film or sheet is stretched, the degree of orientation tends to be high when the stretch ratio is increased.

[0068] For example, when molding by inflation molding, the blow-up ratio (BUR) in the inflation and cooling section is preferably 1.5 to 6.0. When the molded film or sheet is stretched, the stretching ratio in the longitudinal direction can be, for example, 2.5 to 5.0, preferably 3.0 to 4.5.

[0069] The uses of the molded article are not particularly limited. For example, the molded article can be used as bags such as garbage bags, plastic bags, food storage bags, and shopping bags, containers such as food containers, daily necessities, automobile parts, electric and electronic parts, various consumables, and the like. [Example]

[0070] The present invention will be described in detail based on examples, but the present invention is not limited to these examples.

[0071] 1. Material Preparation 1-1.Thermoplastic resin PE (high-density polyethylene, HF313 manufactured by Japan Polyethylene Corporation, MFR (190°C, 21.6 kg) = 0.05 g / 10 min)

[0072] 1-2. Preparation of calcium carbonate particles [Preparation of CC-1] (Preparation of calcium-containing solution) Commercially available Portland cement was prepared as the calcium source. 800 g of the calcium source was mixed with 3200 mL of ion-exchanged water and stirred to obtain a suspension of the calcium source. The suspension was then filtered using a solid-liquid separator to obtain a calcium-containing solution. The amount of calcium in the resulting calcium-containing solution was measured using inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0073] (Preparation of calcium carbonate suspension) The pH of the calcium-containing solution was adjusted to 7.0 or higher. Carbon dioxide gas passed through a glass filter was then introduced into the calcium-containing solution to crystallize calcium carbonate, thereby obtaining a calcium carbonate suspension.

[0074] (Preparation of calcium bicarbonate suspension) Carbon dioxide was further introduced into the calcium carbonate suspension to dissolve calcium carbonate, thereby preparing a calcium bicarbonate saturated solution. The pH of the calcium bicarbonate saturated solution was adjusted to 7.5. The degree of supersaturation of the calcium bicarbonate saturated solution (Ci-Cs) / Cs (Ci: initial calcium bicarbonate concentration, Cs: initial calcium carbonate solubility) was adjusted to 20.

[0075] (recrystallization) The calcium bicarbonate saturated solution was heated to 100°C at a rate of 10°C / min to decarbonate, thereby recrystallizing calcium carbonate.

[0076] (collect) After the recrystallization, suction filtration was carried out to recover the solid content, thereby obtaining calcium carbonate particle groups CC-1 containing hexagonal plate-shaped calcium carbonate particles.

[0077] [Preparation of CC-2 to CC-8] By adjusting the degree of supersaturation of the calcium bicarbonate saturated solution, pH, the rate of temperature rise for decarbonation, etc., calcium carbonate particle groups CC-2 to CC-8 with different hexagonal plate shapes were obtained.

[0078] [Preparation of CC-9] By adjusting the degree of supersaturation of the calcium bicarbonate saturated solution, pH, and the heating rate for decarbonation, calcium carbonate particle group CC-9 containing calcium carbonate particles of various shapes was obtained.

[0079] [SEM observation] The shapes of the particles contained in the obtained calcium carbonate particle group were observed using a scanning electron microscope (SEM). Among them, 100 hexagonal plate-shaped calcium carbonate particles were selected, and the shapes of each were analyzed by image analysis. The lengths of the longest and shortest diagonals among the three diagonals connecting each vertex of the hexagon with the third vertex from that vertex were measured and averaged. The thickness of each hexagonal plate was also measured and averaged. The ratio of the number of hexagonal plate-shaped calcium carbonate particles to the total number of particles in the calcium carbonate particle group was also calculated.

[0080] [CC-10] Bihoku Funka Kogyo calcium bicarbonate powder (no surface treatment), average particle size: 2.2 μm

[0081] The average particle size of the calcium carbonate particle group CC-8 was calculated from the measurement results of the specific surface area by the air permeability method in accordance with JIS M-8511 using a specific surface area measuring device "SS-100 Model" manufactured by Shimadzu Corporation.

[0082] Table 1 shows the physical properties of the calcium carbonate particles CC-1 to CC-10. [Table 1]

[0083] 1-3.Other ingredients Lubricant (stearic acid, manufactured by Kao Corporation)

[0084] 2. Preparation and evaluation of resin compositions [Examples 1 to 9, Comparative Examples 1 to 4] (1) Preparation of resin composition The high-density polyethylene, calcium carbonate particles, and lubricant were fed into a Parker HK-25D co-rotating twin-screw kneading extruder (φ25 mm, L / D=41) in the mass ratios shown in Table 2. The mixture was melt-kneaded at a cylinder temperature of 230°C and then extruded into a strand shape. The extruded resin composition was then cooled and cut to obtain pellets of the resin composition.

[0085] (2) Preparation of inflation film The pellets of the resin composition were extruded into a 20 μm thick blown 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 to 220°C. The rotation speed of the screw (diameter 30 mm, L / D ratio: 30) in the extruder was set to 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.

[0086] [evaluation] The resulting inflation film was evaluated as follows.

[0087] (1) Tensile strength and elongation at break A dumbbell-shaped test piece was prepared from the obtained inflation film in accordance with JIS K7161-2: 2014. The dumbbell-shaped test piece was oriented so that the MD direction was the longitudinal direction. The tensile strength and elongation at break of the test specimens were measured in the MD direction using an autograph AG-100kNXplus (Shimadzu Corporation) at 23°C and 50% RH in accordance with JIS K7161-2:2014. The test speed was 50 mm / min.

[0088] The tensile strength was evaluated based on the following criteria. A: Tensile strength is 40 MPa or more B: Tensile strength is 35 MPa or more and less than 40 MPa C: Tensile strength is 25 MPa or more and less than 35 MPa D: Tensile strength is less than 25 MPa

[0089] The elongation at break was evaluated according to the following criteria. A: Elongation at break is 250% or more B: Elongation at break is 200% or more and less than 250% C: Elongation at break is 150% or more and less than 200% D: Elongation at break is less than 150% 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

[0090] (2) Degree of orientation The cross section of the obtained sheet (cross section along the MD direction) was observed using a scanning electron microscope (SEM) to obtain an SEM image. The obtained SEM image was 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 horizontal axis representing the angle (orientation angle) and the vertical axis representing the pixel intensity 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, and this was used to calculate the "degree of orientation."

[0091] The degree of orientation was evaluated according to the following criteria. A: The degree of orientation is 1.5 or more. B: The degree of orientation is 1.3 or more and less than 1.5 C: The degree of orientation is 1.2 or more and less than 1.3 D: The degree of orientation is less than 1.2

[0092] (3) Appearance The surface condition of the obtained sheet was visually observed and evaluated based on 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.

[0093] The evaluation results of Examples 1 to 9 and Comparative Examples 1 to 4 are shown in Table 2.

[0094] [Table 2]

[0095] [Consideration] As shown in Table 2, the film of Comparative Example 1, which contains calcium carbonate particles CC-10, the majority of which have a spherical particle shape, has low tensile strength and poor appearance. The film of Comparative Example 2, which contains calcium carbonate particles CC-9, the majority of which have a mixture of spherical and scaly particle shapes, also has low tensile strength and elongation at break, and poor appearance. Furthermore, Comparative Example 4, which contains a low content of calcium carbonate particles relative to the total amount of thermoplastic resin and calcium carbonate particles, has low tensile strength, while Comparative Example 3, which contains a high content of calcium carbonate particles, has a reduced elongation at break.

[0096] In contrast, the films of Examples 1 to 9, in which the content ratio of the thermoplastic resin to the calcium carbonate particles was within a predetermined range and the calcium carbonate particles were mainly hexagonal plate-shaped, all had high tensile strength and elongation at break, and also had good appearance. [Industrial Applicability]

[0097] The resin composition of the present invention can provide molded articles having excellent mechanical strength and good appearance, even when they are thin, and is therefore useful in the fields of manufacturing various industrial products. [Explanation of symbols]

[0098] 10 Molded products 11 Thermoplastic resin matrix phase 12 Hexagonal plate-shaped calcium carbonate particles

Claims

1. The composite material includes a thermoplastic resin and calcium carbonate particles, a ratio of the mass of the calcium carbonate particle groups to the total mass of the thermoplastic resin and the calcium carbonate particle groups is 20% by mass or more and 40% by mass or less, the calcium carbonate particle group contains hexagonal plate-shaped calcium carbonate particles in a number of 80% or more of the total number of particles of the calcium carbonate particle group, Resin composition.

2. a ratio of the mass of the calcium carbonate particle groups to the total mass of the thermoplastic resin and the calcium carbonate particle groups is 20 mass% or more and less than 40 mass%; The resin composition according to claim 1.

3. In the hexagon of the hexagonal plate-like calcium carbonate particle, the length of the longest diagonal among three diagonals connecting each vertex to the third vertex from the hexagonal vertex is 1.0 to 1.5 times the length of the shortest diagonal. The resin composition according to claim 1.

4. The length of the longest diagonal line is 10 μm or more and 25 μm or less. The resin composition according to claim 3.

5. the length of the longest diagonal line is 20 to 40 times the thickness of the hexagonal plate-like calcium carbonate particles; The resin composition according to claim 3.

6. The thermoplastic resin includes a polyolefin resin. The resin composition according to claim 1.

7. The polyolefin resin includes at least one of a polyethylene resin and a polypropylene resin. The resin composition according to claim 6.

8. The hexagonal plate-shaped calcium carbonate particles are composed of light calcium carbonate. The resin composition according to claim 1.

9. The resin composition according to any one of claims 1 to 8 is included. Molded products.

10. The molded article is a film, a sheet, or a bag. The molded article according to claim 9.

11. The molded article is an inflation molded article. The molded article according to claim 10.

12. The degree of orientation of the hexagonal plate-like calcium carbonate particles is 1.5 or more. The molded article according to claim 10.

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