Resin composition and molded article thereof

Abstract

The present invention provides: a styrene resin composition which has a low environmental load and good wear resistance; and a molded article of this styrene resin composition.　The present invention provides a resin composition which contains an eggshell powder and a styrene resin, wherein: the content of the eggshell powder is 20 parts by mass or more relative to a total of 100 parts by mass of the eggshell powder and the styrene resin; and the coefficient of static friction is not less than 0.3 but less than 1.0.

Description

[Technical Field]

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

[0002] In recent years, in an effort to build a sustainable society, biomass-containing resin compositions that combine thermoplastic resins derived from fossil resources such as petroleum with biomass-derived materials have been studied. For example, Patent Document 1 proposes a thermoplastic resin composition that incorporates biomass powder, such as wood flour or bamboo powder, as a filler. From the perspective of waste utilization, it has also been considered to replace the calcium carbonate powder that is incorporated into thermoplastic resin compositions as an inorganic filler with eggshell powder, seashell powder, or the like. Such biomass-containing resin compositions have attracted attention as resin compositions with a lower environmental impact because increasing the proportion of biomass-derived materials can reduce the proportion of thermoplastic resins derived from fossil resources.

[0003] Resin products used in home appliances, automotive interior materials, toys, and the like are generally molded by injection molding or the like. Among these, styrene-based resins are widely used in the above-mentioned applications as thermoplastic resins for injection molding because of their excellent transparency, moldability, and low cost. Even for styrene-based resin compositions that can be used in these various applications, there is a demand for replacing them with biomass-derived materials and reducing the amount of styrene-based resin derived from fossil resources.

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-119048 Summary of the Invention

[0005] In response to such demands, the inventors of the present application produced a resin composition with less environmental impact by replacing the inorganic filler blended in a styrene-based resin composition with eggshell powder derived from biomass, and investigated its physical properties.

[0006] When an injection-molded article was produced using a styrene-based resin composition containing eggshell powder, it was found that if the molded article had a fitting portion, repeated fitting easily caused wear. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a styrene-based resin composition which has a low environmental impact and excellent abrasion resistance, and a molded article thereof.

[0007] As a result of extensive research into the above-mentioned problems, the inventors of the present application discovered that the abrasion resistance of the eggshell powder-containing styrene-based resin composition can be improved by setting the static friction coefficient at a certain level or less, and thus completed the present invention. That is, the present invention has the following aspects. [1] A resin composition containing eggshell powder and a styrene-based resin, wherein the content of the eggshell powder is 20 parts by mass or more per 100 parts by mass of the total of the eggshell powder and the styrene-based resin, and the static friction coefficient is 0.3 or more and less than 1.0. [2] The resin composition according to [1], wherein the resin composition contains 0.3 to 3.0 parts by mass of a plasticizer relative to 50 parts by mass of the eggshell powder. [3] The resin composition according to [2], wherein the plasticizer comprises at least one selected from silicone oil and silicone-based rubber. [4] The resin composition according to any one of [1] to [3], wherein the styrene-based resin comprises at least one selected from general-purpose polystyrene and high-impact polystyrene, and a styrene-butadiene copolymer. [5] The resin composition according to any one of [1] to [4], which contains less than 10 parts by mass of an additive per 100 parts by mass of the total of the eggshell powder and the styrene-based resin, and has an MFR of 15 g / 10 min or more at 200°C and a 5 kg load. [6] The resin composition according to any one of [1] to [5], wherein the eggshell powder has an average particle size of 3 to 50 μm. [7] The resin composition according to any one of [1] to [6], which is for injection molding. [8] A molded article comprising the resin composition according to any one of [1] to [7].

[0008] According to the present invention, there are provided a styrene-based resin composition which has a low environmental impact and good abrasion resistance, and a molded article thereof. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described in detail below. The present invention is not limited to the following embodiment, and can be implemented by making appropriate modifications within the scope that does not impair the effects of the present invention. When a specific explanation given for one embodiment also applies to other embodiments, that explanation may be omitted in other embodiments. In this specification, the expression "X to Y" indicating a numerical range means "not less than X and not more than Y."

[0010] [Resin composition] The resin composition according to this embodiment contains eggshell powder and a styrene-based resin, and is characterized by having a static friction coefficient of 0.3 or more and less than 1.0, with the content of the eggshell powder being 20 parts by mass or more per 100 parts by mass of the total of the eggshell powder and the styrene-based resin. The resin composition according to this embodiment has good abrasion resistance. Furthermore, because it contains a certain amount of eggshell powder, which is a biomass-derived material, it also has a lower environmental impact than conventional styrene-based resin compositions. The resin composition of this embodiment also has good tensile modulus, tensile elongation at break, and moldability, and therefore can also be used for injection molding.

[0011] <Eggshell powder> The resin composition according to this embodiment contains eggshell powder. The content of the eggshell powder is 20 parts by mass or more relative to 100 parts by mass of the total of the eggshell powder and the styrene-based resin. In this specification, the "eggshell powder" is not particularly limited as long as it is made from powdered eggshells. However, from the viewpoint of effective utilization of waste, it is preferable that the raw material contains chicken eggshells.

[0012] In one embodiment, the content of eggshell powder in the resin composition may be 30 parts by mass or more, 40 parts by mass or more, or 50 parts by mass or more, based on 100 parts by mass of the total of the eggshell powder and the styrene-based resin. From the viewpoint of compounding the resulting resin composition, the content is preferably 70 parts by mass or less, based on 100 parts by mass of the total of the eggshell powder and the styrene-based resin. That is, the proportion of eggshell powder in 100 parts by mass of the total of the eggshell powder and the styrene-based resin may be 20 to 70 parts by mass, 30 to 70 parts by mass, 40 to 70 parts by mass, or 50 to 70 parts by mass. In one embodiment, the content of eggshell powder may be 20 to 50 parts by mass, based on 100 parts by mass of the total of the eggshell powder and the styrene-based resin.

[0013] In one embodiment, the average particle size of the eggshell powder is preferably 3 to 50 μm, more preferably 3 to 40 μm, and even more preferably 4 to 30 μm. When a powder with a smaller average particle size is used as the eggshell powder, for example, the plasticizer contained in the resin composition may not be sufficiently absorbed and may bleed out. The dispersibility of the eggshell powder in the resin composition is also likely to decrease. On the other hand, if the average particle size is too large, it becomes difficult to obtain a molded product with the desired strength and flexibility. In particular, when eggshell powder with an average particle size greater than 50 μm is blended as the eggshell powder, the resin may be prone to breakage, making it difficult to obtain the desired tensile elongation at break. The average particle size of the eggshell powder can be measured using a particle size distribution analyzer according to the "sieving method."

[0014] In one embodiment, the density of the eggshell powder (g / cm 3 ) is 2.0 to 3.0 g / cm 3 is preferably 2.0 to 2.8 g / cm 3 More preferably, it is 2.3 to 2.7 g / cm 3 It is particularly preferred that:

[0015] In one embodiment, the proportion of eggshell powder in the resin composition may be 10 to 70% by mass, or 30 to 60% by mass, relative to the total mass of the resin composition.

[0016] Eggshell powder can be prepared by a conventionally known manufacturing method. For example, eggshells may be pulverized by a known method and then classified to obtain eggshell powder having a desired average particle size. Specifically, after removing the eggshell membrane from the eggshell, the eggshell is dried. The eggshell is then pulverized using a pulverizer or the like to obtain eggshell powder. The resulting pulverized product is then classified using a sieve with an appropriate mesh size to obtain eggshell powder.

[0017] Alternatively, commercially available eggshell powder may be used, such as "GT-26" manufactured by Green Techno 21 Co., Ltd., or "Calhope (registered trademark)" manufactured by Kewpie Egg Corporation.

[0018] In one embodiment, the resin composition may contain an inorganic filler other than eggshell powder. Examples of inorganic fillers other than eggshell powder include inorganic fillers derived from minerals such as calcium carbonate, talc, and zeolite; and inorganic fillers derived from biominerals other than eggshell powder. Note that "biominerals" refer to minerals produced by living organisms, such as pearls, seashells, eggshells, bones, and the exoskeletons of crustaceans. When eggshell powder and the aforementioned inorganic fillers are used in combination, it is preferable that the total amount of eggshell powder and the inorganic filler does not exceed 70 parts by mass per 100 parts by mass of the total of eggshell powder and styrene-based resin. Note that, from the viewpoint of easily achieving both tensile modulus and tensile elongation at break and moldability, eggshell powder alone may be contained as the inorganic filler.

[0019] <Styrene-based resin> The resin composition according to this embodiment contains a styrene-based resin. The content of the styrene-based resin is 80 parts by mass or less relative to 100 parts by mass of the total of the eggshell powder and the styrene-based resin. In one embodiment, the content of the styrene-based resin may be 30 to 80 parts by mass, 60 to 80 parts by mass, or 50 to 80 parts by mass. From the viewpoint of obtaining a resin composition with a lower content of the styrene-based resin, the content of the styrene-based resin may be 30 to 50 parts by mass relative to 100 parts by mass of the total of the eggshell powder and the styrene-based resin.

[0020] In this specification, the term "styrene-based resin" refers to a polymer containing a monomer unit derived from an aromatic vinyl compound. The styrene-based resin according to this embodiment may include a polymer of an aromatic vinyl compound, a copolymer of an aromatic vinyl compound and a compound copolymerizable with an aromatic vinyl compound, or a polymer obtained by polymerizing these in the presence of a rubber polymer.

[0021] Examples of aromatic vinyl compounds include styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, ethylstyrene, and pt-butylstyrene. These may be used alone or in combination of two or more. Among these, it is preferable to use styrene.

[0022] Examples of compounds copolymerizable with aromatic vinyl compounds include methacrylic acid esters such as methyl methacrylate and ethyl methacrylate, unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile, acid anhydrides such as maleic anhydride, etc. These may be used alone or in combination of two or more.

[0023] The mass proportion of the copolymerizable compound is preferably 20% by mass or less, and more preferably 15% by mass or less, based on the total amount (100% by mass) of the aromatic vinyl compound and the copolymerizable compound.

[0024] Examples of rubbery polymers include conjugated diene rubber, copolymers of conjugated dienes and aromatic vinyl compounds, ethylene-propylene copolymer rubbers, etc. More specific examples include polybutadiene, styrene-butadiene random copolymers, styrene-butadiene block copolymers, and polymers obtained by hydrogenating some or all of these.

[0025] In one embodiment, the weight average molecular weight (Mw) of the styrene resin is preferably 10,000 to 500,000, and more preferably 100,000 to 300,000. When the Mw of the styrene resin is within the above range, the flowability is likely to be good. The Mw of the styrene resin refers to a value calculated in terms of polystyrene by GPC (gel permeation chromatography).

[0026] In one embodiment, the styrene-based resin preferably includes at least one selected from general-purpose polystyrene and high-impact polystyrene, and a styrene-butadiene copolymer. In one embodiment, from the viewpoint of easily obtaining a resin composition having superior tensile modulus and impact strength (particularly impact strength), the polystyrene resin may contain a polymer containing monomer units derived from the aromatic vinyl compound, monomer units derived from the unsaturated nitrile compounds, and the rubbery polymer. As such a polymer, a copolymer of acrylonitrile, styrene, and conjugated diene rubber is preferred, and an acrylonitrile-butadiene-styrene copolymer is more preferred.

[0027] (general-purpose polystyrene resin) General-purpose polystyrene resin is a styrene homopolymer and is a resin expressed as "GPPS." When the styrene-based resin contains general-purpose polystyrene resin, the tensile modulus tends to be good. In one embodiment, the mass average molecular weight (Mw) of the general-purpose polystyrene resin may be 10,000 to 500,000 or 100,000 to 300,000 from the viewpoint of fluidity. The Mw of the general-purpose polystyrene resin refers to a value calculated in terms of polystyrene by GPC (gel permeation chromatography).

[0028] In one embodiment, the proportion of the general-purpose polystyrene resin in the styrene resin is preferably 20 to 95 mass %, more preferably 30 to 80 mass %, relative to the total mass of the styrene resin from the viewpoint of tensile modulus of elasticity. The proportion of the general-purpose polystyrene resin in the resin composition may be 10 to 85 mass %, or 10 to 60 mass %, relative to the total mass of the resin composition.

[0029] (high impact polystyrene) High impact polystyrene is a graft polymer obtained by graft polymerizing a rubbery polymer with a styrene monomer, and is a resin abbreviated as "HIPS." When a styrene-based resin contains high impact polystyrene, the impact strength tends to be good. In one embodiment, the mass average molecular weight (Mw) of the high impact polystyrene may be 100,000 to 250,000 or 130,000 to 200,000 from the viewpoint of fluidity. The Mw of the high impact polystyrene refers to a value calculated in terms of polystyrene by gel permeation chromatography (GPC).

[0030] In one embodiment, the proportion of high impact polystyrene in the styrene resin is preferably 10 to 90 mass %, more preferably 50 to 85 mass %, relative to the total mass of the styrene resin, from the viewpoint of improving brittleness through high filler loading. The proportion of high impact polystyrene in the resin composition may be 10 to 75 mass %, or 10 to 60 mass %, relative to the total mass of the resin composition.

[0031] (styrene-butadiene copolymer resin) Styrene-butadiene copolymer resins are copolymer resins obtained by polymerizing a monomer mixture containing styrene and butadiene. Examples of styrene-butadiene copolymer resins include block copolymers such as styrene-butadiene (SB), styrene-butadiene-butylene (SBB), styrene-butadiene-isoprene (SBI), styrene-butadiene-styrene (SBS), styrene-butadiene-butylene-styrene (SBBS), and styrene-butadiene-isoprene-styrene (SBIS), as well as hydrogenated block copolymers thereof. These may be used alone or in combination of two or more. Of these, from the viewpoint of improving brittleness through high filler loading, it is preferable that the styrene-butadiene copolymer resin contains a styrene-butadiene (SB) copolymer.

[0032] In one embodiment, the mass average molecular weight (Mw) of the styrene-butadiene copolymer resin is preferably 100,000 to 200,000, and more preferably 120,000 to 180,000. When the Mw of the styrene-butadiene copolymer resin is within the above range, compatibility with general-purpose polystyrene resins and / or high-impact polystyrene tends to be good. The Mw of the styrene-butadiene copolymer resin refers to a value calculated in terms of polystyrene by GPC (gel permeation chromatography).

[0033] In one embodiment, the proportion of the styrene-butadiene copolymer resin in the styrene-based resin is preferably 8 to 60 mass %, more preferably 10 to 50 mass %, relative to the total mass of the styrene-based resin from the viewpoint of improving brittleness. The proportion of the styrene-butadiene copolymer resin in the resin composition may be 3 to 45 mass %, or may be 5 to 35 mass %, relative to the total mass of the resin composition.

[0034] In one embodiment, from the viewpoint of easily adjusting the tensile modulus of elasticity of the resin composition, the amount of conjugated diene in the styrene-butadiene copolymer resin is preferably 5 to 40 mass%, more preferably 6 to 30 mass%, and particularly preferably 8 to 28 mass%, relative to the total mass of the styrene-butadiene copolymer resin. The "amount of conjugated diene" refers to the amount of butadiene contained in the styrene-butadiene copolymer resin. The amount of conjugated diene may be a value calculated from the amount of butadiene charged when preparing the styrene-butadiene copolymer resin, or may be a value measured by potentiometric titration using iodine monochloride, potassium iodide, and sodium thiosulfate standard solutions.

[0035] In one embodiment, the total amount of the general-purpose polystyrene resin and / or high-impact polystyrene and the styrene-butadiene copolymer resin may be 50 to 100% by mass or 60 to 100% by mass relative to the total mass of the styrene-based resin. When the total amount of the general-purpose polystyrene resin and / or high-impact polystyrene and the styrene-butadiene copolymer resin in the styrene-based resin is within the above range, a resin composition having good tensile modulus and flowability is easily obtained.

[0036] The styrene-based resin may contain components (other components) other than general-purpose polystyrene resin, high-impact polystyrene, and styrene-butadiene copolymer resin. Examples of other components include styrene-based thermoplastic elastomers other than styrene-butadiene copolymer resin (for example, block copolymers such as styrene-isoprene (SI) and styrene-isoprene-styrene (SIS), as well as hydrogenated block copolymers thereof). These may be used alone or in combination of two or more. When the styrene-based resin contains other components, the amount is preferably 30% by mass or less relative to the total mass of the styrene-based resin.

[0037] <Plasticizer> In one embodiment, the resin composition preferably contains a plasticizer. The content of the plasticizer is preferably 0.3 to 3.0 parts by mass, or alternatively 0.3 to 2.5 parts by mass, 0.3 to 2.0 parts by mass, or 0.3 to 1.5 parts by mass, relative to 50 parts by mass of the eggshell powder. By setting the content of the plasticizer to 0.3 parts by mass or more, an increase in the static friction coefficient of the resin composition is suppressed, and by setting the content to 3.0 parts by mass or less, bleeding out of the plasticizer is suppressed. In one embodiment, the content of the plasticizer is preferably 0.3 to 3.0 parts by mass relative to 100 parts by mass of the total of the eggshell powder and the styrene-based resin. In another embodiment, the content of the plasticizer may be 0.3 to 2.5 parts by mass, 0.3 to 2.0 parts by mass, or 0.3 to 1.5 parts by mass. Examples of the plasticizer include process oils such as paraffinic and naphthenic, liquid paraffin and other paraffins, waxes, synthetic polymer plasticizers such as silicone oil and silicone rubber, and ester plasticizers such as phthalic acid, adipic acid, sebacic acid, and phosphoric acid. Of these, synthetic polymer plasticizers, particularly plasticizers selected from silicone oil and silicone rubber, are preferred.

[0038] (silicone oil) As the silicone oil, known silicone oils can be used, but silicone oils selected from the viewpoints of heat resistance, transparency, etc. may be used. As the silicone oil, for example, dimethylpolysiloxane, methylphenylsiloxane, methylhydrogenpolysiloxane, and modified products thereof may be used. These may be used alone or in combination of two or more. Among these, it is preferable to contain dimethylpolysiloxane from the viewpoint of easily obtaining a resin composition having excellent abrasion resistance. In a preferred embodiment, the dimethylsiloxane is a silicone oil having a kinematic viscosity at 25°C of 100 to 500 mm 2 The kinematic viscosity can be measured, for example, in accordance with JIS K 2283:2000, "5. Kinematic viscosity test method," using a Cannon-Fenske viscometer at a test temperature of 37.8°C or 40°C.

[0039] (silicone rubber) Silicone-based rubber is rubber containing polyorganosiloxane rubber. The silicone-based rubber is a silicone / acrylic composite rubber that combines polyorganosiloxane rubber or polyorganosiloxane with polyalkyl(meth)acrylate rubber. The silicone / acrylic composite rubber is a rubber obtained by polymerizing two or more constituent monomers in stages, rather than simply polymerizing them.

[0040] <Additives> In one embodiment of the present invention, the resin composition contains an additive. The content of the additive is preferably 10 parts by mass or less, but may be 9 parts by mass or less, 8 parts by mass or less, or 7 parts by mass or less, per 100 parts by mass of the total of the eggshell powder and the styrene-based resin. The lower limit of the content of the additive is not particularly limited as long as the effects of the present invention are achieved, and may be 0.5 parts by mass or more, or 1 part by mass or more.

[0041] (compound) In this embodiment, the additive contains a compound selected from fatty acid amides, fatty acid sodium salts, and fatty acid esters as a main component. Here, "containing a compound as a main component" means that the total content of the compound in the additive exceeds 50% by mass relative to the total mass of the additive. By combining such an additive with eggshell powder and a styrene-based resin, a resin composition is obtained that has good tensile elongation at break, tensile modulus, and excellent moldability. The compound has a fatty acid group represented by "RC(=O)-" in its structure, where R is a hydrocarbon group that may have a substituent. "May have a substituent" means that one or more hydrogen atoms in the hydrocarbon group may be substituted with a substituent. By including such a compound as a main component, a resin composition with particularly good tensile elongation at break can be obtained.

[0042] In this embodiment, the fatty acid amide is a compound having an amide group represented by "R1-C(=O)-N-" in its structure. "Fatty acid amide" includes primary amides, secondary amides, tertiary amides, and those having two or more nitrogen atoms in one molecule. On the other hand, the fatty acid amide in this embodiment does not include polymers such as aliphatic polyamides typified by nylon-6. R1 is a hydrocarbon group which may have a substituent, and is preferably an alkyl group having 2 or more carbon atoms which may have a substituent, or an alkenyl group which may have a substituent. There are no particular limitations on the type of fatty acid amide as long as it achieves the effects of the present invention. However, from the viewpoint of compatibility with styrene-based resins, a higher fatty acid amide in which R1 is an alkyl group having 10 or more carbon atoms which may have a substituent, or an alkenyl group which may have a substituent is preferred. Specific examples include saturated fatty acid monoamides such as lauric acid amide, palmitic acid amide, stearic acid amide, and behenic acid amide; unsaturated fatty acid monoamides such as oleic acid amide and erucic acid amide; substituted amides such as N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl erucic acid amide; methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene biscapric acid amide, and ethylene biscapric acid amide. Examples of the bisamide include saturated fatty acid bisamides such as ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, and N,N'-distearyl adipic acid amide; and unsaturated fatty acid bisamides such as ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, and N,N'-dioleyl adipic acid amide. These may be used alone or in combination of two or more. Among these, from the viewpoint of extrusion with resin, it is preferable to use saturated fatty acid bisamides having 10 or more carbon atoms.

[0043] In this embodiment, the fatty acid sodium salt is a compound represented by "R2-C(=O)-O-Na," where R2 can be exemplified as R1, and is preferably an alkyl group having 2 or more carbon atoms, which may have a substituent, or an alkenyl group, which may have a substituent. There are no particular limitations on such fatty acid sodium salts as long as they achieve the effects of the present invention. However, from the viewpoint of compatibility with styrene-based resins, sodium salts of higher fatty acids in which R2 is an alkyl group having 10 or more carbon atoms, which may have a substituent, or an alkenyl group, which may have a substituent, are preferred. Specific examples include sodium salts of higher fatty acids having 10 to 20 carbon atoms, such as sodium laurate, sodium myristate, sodium palmitate, sodium oleate, and sodium stearate. These may be used alone or in combination of two or more. That is, the fatty acid sodium salt may be a mixture of the aforementioned sodium salts of higher fatty acids having 10 to 20 carbon atoms.

[0044] In this embodiment, the fatty acid ester is an ester containing the aforementioned fatty acid group. In one embodiment, the fatty acid ester is preferably a higher fatty acid ester obtained by reacting a higher fatty acid having 10 or more carbon atoms with a polyhydric alcohol. The higher fatty acid is preferably an alkyl or alkenyl group having 10 or more carbon atoms, which may have a substituent. In addition, examples of the polyhydric alcohol include dihydric to hexahydric polyhydric alcohols such as ethylene glycol, glycerin, 1,2,4-butanetriol, diglycerin, pentaerythritol, sorbitol, erythritol, and hexanetriol.

[0045] In a preferred embodiment, the higher fatty acid ester may include a glycerin fatty acid ester. Examples of the glycerin fatty acid ester include lauric acid monoglyceride, lauric acid diglyceride, lauric acid triglyceride, palmitic acid monoglyceride, palmitic acid diglyceride, palmitic acid triglyceride, stearic acid monoglyceride, stearic acid diglyceride, stearic acid triglyceride, stearic acid tetraglyceride, hydroxystearic acid monoglyceride, hydroxystearic acid diglyceride, hydroxystearic acid triglyceride, and hydroxystearic acid tetraglyceride. These may be used alone or in combination of two or more. Among these, from the viewpoint of compatibility with eggshell materials, it is preferable to include hydroxystearic acid glyceride.

[0046] In one embodiment, from the viewpoint of more easily obtaining a better tensile elongation at break, the compound preferably contains a fatty acid amide and / or a fatty acid sodium salt.

[0047] In one embodiment, the proportion of the compound in the additive may be greater than 50% by mass to 100% by mass, may be 55 to 100% by mass, may be 60 to 100% by mass, or may be 65 to 100% by mass, relative to the total mass of the additive.

[0048] In one embodiment, the additives may contain other additives in addition to the above-mentioned compounds. Examples of other additives include other compounds such as ultraviolet absorbers, light stabilizers, antioxidants, lubricants, plasticizers, colorants, antistatic agents, flame retardants, mold release agents, and mineral oils; and reinforcing fibers such as glass fibers, carbon fibers, and aramid fibers. These may be used alone or in combination of two or more.

[0049] Examples of ultraviolet absorbers include 2-(5'-methyl-2'-hydroxyphenyl)benzotriazole, 2-(5'-t-butyl-2'-hydroxyphenyl)benzotriazole, 2-[2'-hydroxy-3',5'-bis(α,α-dimethylbenzyl)phenyl]benzotriazole, 2-(3',5'-di-t-butyl-2'-hydroxyphenyl)benzotriazole, 2-(3'-t-butyl-5'-methyl-2'-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3',5'-di-t-butyl-2'-hydroxyphenyl)benzotriazole, Benzotriazole-based ultraviolet absorbers such as 2-(3',5'-di-t-amyl-2'-hydroxyphenyl)benzotriazole, 2-[3'-(3”,4”,5”,6”-tetrahydrophthalimidomethyl)-5'-methyl-2'-hydroxyphenyl]benzotriazole, and 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol]; 2-ethoxy-2'-ethyl oxalic acid bisanilide, 2-ethoxy-5-t-butyl oxalic acid anilide-based ultraviolet absorbers such as 2-ethyl-2'-ethyl oxalic acid bisanilide and 2-ethoxy-4'-isodecylphenyl oxalic acid bisanilide; benzophenone-based ultraviolet absorbers such as 2-hydroxy-4-n-octoxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, and 2-hydroxy-4-methoxy-2'-carboxybenzophenone; Examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers; salicylic acid-based ultraviolet absorbers such as phenyl salicylate, pt-butylphenyl salicylate, and p-octylphenyl salicylate; cyanoacrylate-based ultraviolet absorbers such as 2-ethylhexyl-2-cyano-3,3'-diphenylacrylate and ethyl-2-cyano-3,3'-diphenylacrylate; and titanium oxide-based ultraviolet stabilizers such as rutile titanium oxide, anatase titanium oxide, alumina, silica, titanium oxide treated with a surface treatment agent such as a silane coupling agent or a titanium-based coupling agent.These may be used alone or in combination of two or more.

[0050] Examples of light stabilizers include bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, dimethyl succinate·1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, and poly[[6,(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl] [(2,2,6,6-tetramethyl-4-piperidyl)imino]-hexamethylene-[(2,2,6,6-tetramethyl-4-piperidyl)imino]], 1-[2-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine, etc. These may be used alone or in combination of two or more.

[0051] Examples of antioxidants include triethylene glycol bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, pentaerythrityl tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl) Phenolic antioxidants such as 2,2-bis(4-methyl-6-t-butylphenol)propionate, 2,2-thiobis(4-methyl-6-t-butylphenol) and 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene; ditridecyl-3,3'-thiodipropionate, dilauryl-3,3'-thiodipropionate, ditetradecyl-3,3'-thiodipropionate, distearyl-3,3' -thiodipropionate, dioctyl-3,3'-thiodipropionate, and other sulfur-based antioxidants; trisnonylphenyl phosphite, 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl)phosphite, (tridecyl)pentaerythritol diphosphite, bis(octadecyl)pentaerythritol diphosphite, bis(di-t-butylphenyl)pentaerythritol diphosphite, bis Examples of such antioxidants include phosphorus-based antioxidants such as (di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, dinonylphenyl octyl phosphonite, tetrakis(2,4-di-t-butylphenyl)1,4-phenylene-diphosphonite, tetrakis(2,4-di-t-butylphenyl)4,4'-biphenylene-diphosphonite, and 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene. These may be used alone or in combination of two or more.

[0052] The proportion of other additives in the additives is less than 50% by mass, preferably 40% by mass or less, and more preferably 30% by mass or less, based on the total mass of the additives. In the resin composition according to this embodiment, which contains a certain amount of eggshell powder, blending additives other than the compound may result in a decrease in physical properties such as tensile elongation at break. In this case, it is preferable that the additive contain only the compound.

[0053] The resin composition according to the present invention may contain a thermoplastic resin other than a styrene-based resin (an other thermoplastic resin). However, from the viewpoint of obtaining a resin composition with a low resin content, it is preferable that the resin composition does not contain any other thermoplastic resin.

[0054] In this embodiment, the static friction coefficient of the resin composition is 0.3 or more and less than 1.0, preferably 0.5 or more and less than 0.8, and more preferably 0.6 or more and less than 0.75. A static friction coefficient of 0.3 or more prevents loose fitting in a molded article having a fitting portion, and a static friction coefficient of less than 1.0 improves wear resistance. The static friction coefficient of the resin composition can be measured using a friction and wear analyzer (e.g., Kyowa Interface Science, TS501) in accordance with JIS K7125. Here, good abrasion resistance means, for example, that the abrasion resistance is rated B or higher in the abrasion resistance evaluation in the following examples.

[0055] In one embodiment, the MFR of the resin composition at 200°C under a 5 kg load is preferably 15.0 g / 10 min or more. If the MFR (200°C under a 5 kg load) of the resin composition is 15.0 g / 10 min or more, the moldability tends to be better. The MFR (200°C under a 5 kg load) of the resin composition may be 15.0 g / 10 min or more, 20.0 g / 10 min or more, or 22.0 g / 10 min or more. The MFR of the resin composition can be measured according to JIS K 7210-2:2014 (ISO 133-2:2011).

[0056] In one embodiment, the tensile modulus of the resin composition, measured according to ASTM-D638, may be 1000 MPa or more, or 1500 MPa or more. The tensile elongation at break of the resin composition, measured according to ASTM-D638, may be 20% or more, or 50% or more. The resin composition according to this embodiment contains a certain amount or more of eggshell powder, yet has a good tensile modulus and tensile elongation at break. It also has good moldability.

[0057] In resin compositions containing eggshell powder, mechanical properties such as tensile elongation at break may be reduced due to factors such as poor adhesion between the resin and eggshell powder. However, by blending a certain amount of an additive containing a compound as its main component, the tensile elongation at break of the resulting resin composition can be improved.

[0058] [Method of producing resin composition] The resin composition according to this embodiment can be produced by melt-kneading eggshell powder, a styrene-based resin, and, if necessary, other components such as a plasticizer or additives. Specifically, the components are each placed in a twin-screw extruder, melt-kneaded at a temperature of 200 to 250°C, and then extruded in the form of strands to prepare a pellet-shaped resin composition.

[0059] [Application] As described above, the resin composition according to this embodiment has good abrasion resistance. Therefore, it can be suitably used for manufacturing molded articles having a portion requiring abrasion resistance, such as containers having fitting portions, assembly kits, etc. Of course, the use of the resin composition according to this embodiment is not limited to manufacturing containers having fitting portions, assembly kits, etc.

[0060] [Molded products] The molded product according to this embodiment contains the resin composition described above. Preferably, it is obtained by molding the resin composition according to this embodiment. In the molded product according to this embodiment, wear due to friction between the molded products is suppressed. Further, since the molded product according to this embodiment contains a certain amount of eggshell powder, it is a molded product with a low environmental load. The molded product according to this embodiment can be applied to uses such as stationery, furniture, building materials, tableware, containers, gardening materials, toys, and the like.

Examples

[0061] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited by the following description. [Preparation of eggshell powder] After washing chicken eggshells with water, they were put into a hot air dryer for drying treatment. The dried eggshells were put into a stirring and separation tank, and stirred while applying high-pressure water to separate and remove the egg membrane inside the eggshells. Then, the eggshells from which the egg membrane had been separated and removed were put back into the hot air dryer and dried at 90 to 120 °C for 6 hours. The dried eggshells were pulverized using a pulverizer to obtain eggshell powder. When the density of the obtained eggshell powder was measured using a densitometer (manufactured by Shimadzu Corporation, product name "Dry Automatic Densitometer AccuPic II 1340"), it was 2.6 g / cm 3 It was. Further, the obtained powder was classified to obtain eggshell powder with an average particle size of 10 μm.

[0062] [Production of styrene resin] [Production of general-purpose polystyrene resin (GPPS)] 70.4 kg of pure water and 300 g of tricalcium phosphate were added to a polymerization kettle with an internal volume of 200 L and stirred. Then, 80.0 kg of styrene and 267.2 g of benzoyl peroxide were added and sealed, and reacted at 100 °C for 6 hours. After the reaction was completed, the reaction product was cooled, neutralized, dehydrated, and dried to obtain a homopolymer of polystyrene (GPPS). When the Mw of the obtained general-purpose polystyrene resin was measured using GPC under the following conditions, it was 167,000. [Measurement conditions of GPC] Apparatus: Manufactured by Shodex Co., Ltd., product name "Shodex SYSTEM-21" Column: PLgel MIXED-B Measurement temperature: 40℃ Solvent: tetrahydrofuran Flow rate: 1.0mL / min Detection method: RI Sample concentration: 0.2% by mass Injection volume: 100μL Calibration curve: Standard polystyrene (Polymer Laboratories)

[0063] <Production of High Impact Polystyrene (HIPS)> Low-cis polybutadiene rubber (manufactured by Asahi Kasei Corporation, trade name "Diene 55AS") was used as the rubber polymer. This rubber polymer (5.3% by mass based on the total mass of the polymerization raw materials) and styrene were dissolved in ethylbenzene (5% by mass based on the total mass of the polymerization raw materials) as a solvent to prepare the polymerization raw materials. Furthermore, 0.1 parts by mass of an antioxidant for rubber polymers (manufactured by Ciba-Geigy Japan, trade name "Irganox (registered trademark) 1076") was added to the polymerization raw materials. This polymerization raw material was fed at 12.5 kg / hr into a 14 L jacketed reactor (R-01) equipped with an anchor-type stirring blade with a blade diameter of 0.285 m. The reaction temperature was 140°C, and the rotation speed was 2.17 sec. -1 The mixture was stirred at 20°C for polymerization, yielding a polymer solution. The resulting polymer solution had a polymerization rate of 25%. This polymer solution was introduced into two 21 L jacketed plug flow reactors arranged in series. In the first plug flow reactor (R-02), the jacket temperature was adjusted so that the reaction temperature was 120 to 140°C in the direction of the polymer solution flow. In the second plug flow reactor (R-03), the jacket temperature was adjusted so that the reaction temperature had a gradient of 130 to 160°C in the direction of the polymer solution flow. The polymerization rate at the outlet of R-02 was 50%, and the polymerization rate at the outlet of R-03 was 70%. Here, the polymerization rate is a value calculated using the following formula (1): Polymerization rate (%) = [(amount of polymer produced) / {(amount of charged monomer) + (amount of solvent)}] × 100 (1) The resulting polymer solution was heated to 230°C and then transferred to a devolatilizer tank at a vacuum of 5 torr, where the unreacted monomer and solvent were separated and recovered. The reaction product was then extracted from the devolatilizer tank using a gear pump, passed through a die plate to form strands, and then pelletized in a water tank to obtain high-impact polystyrene. The rubber content of the resulting high-impact polystyrene was 4.8% by mass. The Mw of the high-impact polystyrene, measured under the same conditions as for general-purpose polystyrene resin, was 210,000.

[0064] <Production of styrene-butadiene copolymer resin (SBC)> A styrene-butadiene block copolymer resin was prepared as a styrene-butadiene copolymer resin. First, 500.0 kg of cyclohexane and 75.0 g of tetrahydrofuran (THF) were placed in a reaction vessel. 1,000 mL of a 10% by mass solution of n-butyllithium in cyclohexane was added as a polymerization initiator solution and maintained at 30°C. 20.0 kg of styrene was added to allow anionic polymerization of styrene. During this process, the internal temperature rose to 35°C. After complete consumption of the styrene, 56 kg of 1,3-butadiene and 64 kg of styrene were added simultaneously. After complete consumption of the styrene and 1,3-butadiene, the internal temperature of the reaction system was lowered to 75°C, and an additional 60.0 kg of styrene was added all at once to complete the polymerization. Finally, all active polymerization terminals were deactivated with water to obtain a polymerization solution containing a styrene-butadiene copolymer having a polystyrene block and a tapered styrene-butadiene block. This polymerization solution was devolatilized and pelletized using an extruder to obtain the block copolymer. The amount of diene in the resulting styrene-butadiene copolymer calculated from the amount of charged monomer was 28 mass %.

[0065] [Plasticizer] The following plasticizers were used: Plasticizer (1): Silicone oil (Shin-Etsu Chemical Co., Ltd., product name "KF-96 350CS") Plasticizer (2): Metablen (manufactured by Mitsubishi Chemical Corporation, product name "Metablen SX-005")

[0066] [Additives] The following additives were used: <Compound> Compound (1): fatty acid amide (EBS: ethylene bisstearic acid amide (manufactured by Kao Corporation, product name "Kaowax EB-FF")). Compound (2): Sodium fatty acid (manufactured by Miyoshi Oil & Fats Co., Ltd., product name "Tankal MH" (a mixture of sodium fatty acid with a mass ratio of lauric acid:myristic acid:palmitic acid:stearic acid:oleic acid=3:2:40:15:30)).

[0067] [Example 1] 40 parts by weight of HIPS, 10 parts by weight of SBC, 50 parts by weight of eggshell powder, 1 part by weight of EBS, 2 parts by weight of fatty acid sodium salt, and 1 part by weight of silicone oil were melt-kneaded using a twin-screw extruder (Shibaura Machine Co., Ltd., TEM35-B) at 200°C, 350 rpm, and a discharge rate of 20 kg / h, and extruded into strands and pelletized. The resulting pellets had a MFR of 15.8 g / 10 min at 200°C and a 5 kg load. The resulting pellets were molded using a hot press (Tester Sangyo Co., Ltd., SA-303), and the static friction coefficient, abrasion resistance, tensile modulus, tensile elongation at break, and impact strength were evaluated using the following methods. The results are shown in Table 1.

[0068] <Method for measuring the static friction coefficient> Measurements were made in accordance with JIS K7125 using a friction and wear analyzer (TS501, manufactured by Kyowa Interface Science Co., Ltd.). Specifically, a plate-shaped sample with a thickness of 0.40 mm was cut out to a shape of 30 mm x 100 mm to prepare a measurement sample and evaluate it. Evaluation was also made according to the following evaluation criteria, with a rating of B or higher being considered a pass. (Evaluation criteria) A: The static friction coefficient is 0.30 or more and less than 0.70. B: Static friction coefficient is 0.70 or more and less than 1.00. C: The static friction coefficient is less than 0.30 or greater than 1.00.

[0069] <Wear resistance evaluation> Using an injection molding machine (manufactured by Nippon Steel Works, Ltd., model JSW-140AD), a sealed container with a fitting portion (a sealed container formed by fitting a container body and a lid) was molded at a molding temperature of 200°C and a mold temperature of 80°C. After manually opening and closing the fitting portion of the molded product 30 times, the state of the fitting portion was observed. (Evaluation Criteria) A: No change in the fitting portion B: Some powdering and loose fit C: Powdering and unable to fit

[0070] <MFR and Molding Property Evaluation> Measured according to the standard of JIS K 7210-2:2014 (ISO 133-2:2011) under the conditions of 200°C and 5 kg load. Also, the molding property was evaluated according to the following evaluation criteria, and a B evaluation or above was considered qualified. (Evaluation Criteria) A: MFR is 20.0 g / 10 min or more. B: MFR is 15.0 g / 10 min or more and less than 20.0 g / 10 min. C: MFR is less than 15.0 g / 10 min.

[0071] <Method for Measuring Tensile Modulus> Measured according to ASTM-D638 using an autograph (manufactured by Shimadzu Corporation, product name "AGS-X"). Specifically, a plate-shaped sample with a thickness of 0.40 mm was cut out in the shape of dumbbell No. 1 to prepare a measurement sample, and the tensile modulus of the measurement sample was measured at a measurement temperature of 23°C, a humidity of 50%, and a tensile speed of 5 mm / min. Evaluation was carried out according to the following evaluation criteria, and a B evaluation or above was considered qualified. (Evaluation Criteria) A: Tensile modulus is 1200 MPa or more and less than 1800 MPa. B: Tensile modulus is 800 MPa or more and less than 1200 MPa. C: Tensile modulus is less than 800 MPa or 1800 MPa or more.

[0072] <Method for Measuring Tensile Elongation at Break> Measurements were performed in accordance with ASTM-D638 using an autograph (Shimadzu Corporation, product name "AGS-X"). Specifically, a measurement sample was prepared by cutting a 0.40 mm thick plate sample into the shape of a No. 1 dumbbell, and the tensile elongation at break of the sample was measured at a measurement temperature of 23°C and a humidity of 50% at a tension rate of 5 mm / min. Evaluation was performed according to the following evaluation criteria, with a rating of B or higher being considered a pass. (Evaluation criteria) A: Tensile elongation at break is 15% or more. B: Tensile elongation at break is 10% or more and less than 15%. C: Tensile elongation at break is less than 10%.

[0073] <Method for measuring impact strength> Measurements were made in accordance with ASTM-D3420 using a film impact tester (manufactured by Yasuda Seiki Co., Ltd.). Specifically, a plate-shaped sample with a thickness of 0.40 mm was cut into a 70 mm x 70 mm measurement sample, and the impact strength was measured. Evaluation was made according to the following evaluation criteria, with a rating of B or higher being considered a pass. (Evaluation criteria) A: Impact strength is 2.0J / mm or more. B: Impact strength is 1.5J / mm or more and less than 2.0J / mm. C: Impact strength is less than 1.5J / mm.

[0074] [Examples 2 and 3 and Comparative Example 1] Resin compositions were prepared in the same manner as in Example 1, except that the formulation of the resin compositions was as shown in Table 1. Pellets were prepared in the same manner as in Example 1, and the MFR was measured. Furthermore, the resin compositions were molded into plates in the same manner as in Example 1, and the static friction coefficient, abrasion resistance, tensile modulus, tensile elongation at break, and impact strength were evaluated. The results are shown in Table 1.

[0075] [Table 1]

[0076] As shown in Table 1, the resin compositions of Examples 1 to 3, which satisfy the configuration of this embodiment, had static friction coefficients that were within an appropriate range. Furthermore, they also received good evaluations in the abrasion resistance test. On the other hand, the resin composition of Comparative Example 1 did not have a static friction coefficient that was within an appropriate range, and did not receive good evaluations in the abrasion resistance test. From these results, it was found that the resin composition of this embodiment had a static friction coefficient that was within a suitable range, and exhibited good abrasion resistance. Furthermore, the resin composition of this embodiment contains a certain amount of eggshell powder, which reduces the environmental impact. [Industrial Applicability]

[0077] INDUSTRIAL APPLICABILITY The present invention can provide a styrene-based resin composition that has little environmental impact and excellent abrasion resistance, and a molded article thereof, and has industrial applicability.

Claims

1. A resin composition comprising eggshell powder and a styrene-based resin, wherein the content of the eggshell powder is 40 parts by mass or more relative to 100 parts by mass of the total of the eggshell powder and the styrene-based resin, the resin composition has a static friction coefficient of 0.3 or more and less than 1.0, the styrene-based resin contains a styrene-butadiene copolymer, and the amount of conjugated diene in the styrene-butadiene copolymer is 5 to 40% by mass relative to the total mass of the styrene-butadiene copolymer.

2. The resin composition according to claim 1, wherein the resin composition contains 0.3 to 3.0 parts by mass of a plasticizer relative to 50 parts by mass of the eggshell powder.

3. The resin composition according to claim 2 , wherein the plasticizer comprises at least one selected from silicone oil and silicone-based rubber.

4. The resin composition according to claim 1 or 2, wherein the styrene-based resin comprises at least one selected from general-purpose polystyrene and high-impact polystyrene.

5. 3. The resin composition according to claim 1, wherein the resin composition comprises less than 10 parts by mass of an additive per 100 parts by mass of the total of the eggshell powder and the styrene-based resin, and has an MFR value of 15 g / 10 min or more at 200°C and a 5 kg load.

6. The resin composition according to claim 1 or 2, wherein the eggshell powder has an average particle size of 3 to 50 μm.

7. The resin composition according to claim 1 or 2, which is for injection molding.

8. A molded article comprising the resin composition according to claim 1 or 2.

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