Resin composition and molded article thereof

Abstract

Provided are: a resin composition that contains eggshell powder, that has excellent tensile elastic modulus and tensile elongation at break, and that has superior moldability; and a molded article of the resin composition.　This resin composition contains eggshell powder (A), a polystyrene-based resin (B), and an additive (C). The proportion of the eggshell powder (A) is 20 parts by mass or more with respect to 100 parts by mass of the total of the eggshell powder (A) and the polystyrene-based resin (B). The additive (C) includes at least one compound selected from a fatty acid amide (c1), a fatty acid sodium (c2), and a fatty acid ester (c3). The total contained amount of the fatty acid amide (c1), the fatty acid sodium (c2), and the fatty acid ester (c3) with respect to the total mass of the additive (C) is more than 50 mass%. The contained amount of the additive (C) is not more than 10 parts by mass with respect to 100 parts by mass of the total of the eggshell powder (A) and the polystyrene-based resin (B).

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, automobile interior materials, toys, and the like are generally molded by injection molding or the like. Among these, polystyrene-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 polystyrene-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 polystyrene-based resin derived from fossil resources.

[0004] In response to these demands, the present inventors investigated the possibility of creating a resin composition with less environmental impact by replacing the inorganic filler blended in a polystyrene-based resin composition with biomass-derived eggshell powder. However, they found that polystyrene-based resin compositions containing eggshell powder tend to have reduced mechanical strength, such as tensile modulus and tensile elongation at break, making it difficult to achieve the desired physical properties. Furthermore, thermoplastic resins for injection molding are required to have appropriate fluidity from the standpoints of mold filling and moldability, but such compositions are prone to reduced fluidity and poor moldability.

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-119048 Summary of the Invention

[0006] The present invention has been made in view of the above circumstances, and aims to provide a resin composition containing eggshell powder that has a good tensile modulus and tensile elongation at break and also has excellent moldability, and a molded article made from the resin composition.

[0007] As a result of extensive research into the above-mentioned problems, the present inventors discovered that by blending a certain amount of an additive containing a specific compound as a main component with respect to the total amount of eggshell powder and polystyrene-based resin, a resin composition that is excellent in tensile modulus and tensile elongation at break and also has good moldability can be obtained, leading to the completion of the present invention. That is, the present invention has the following aspects. [1] Contains eggshell powder (A), polystyrene resin (B), and additive (C), The ratio of the eggshell powder (A) to a total of 100 parts by mass of the eggshell powder (A) and the polystyrene-based resin (B) is 20 parts by mass or more, The additive (C) comprises at least one compound selected from fatty acid amide (c1), fatty acid sodium (c2), and fatty acid ester (c3), and the total content of the fatty acid amide (c1), the fatty acid sodium (c2), and the fatty acid ester (c3) relative to the total mass of the additive (C) is more than 50 mass%, and the content of the additive (C) relative to a total of 100 parts by mass of the eggshell powder (A) and the polystyrene-based resin (B) is 10 parts by mass or less. [2] The resin composition according to [1], wherein the ratio of the eggshell powder (A) to the total of 100 parts by mass of the eggshell powder (A) and the polystyrene-based resin (B) is 70 parts by mass or less. [3] The resin composition according to [1] or [2], wherein the resin composition has an MFR of 4.0 g / 10 min or more at 200°C under a load of 5 kg. [4] The resin composition according to [1] or [2], wherein the resin composition has an MFR of 4.0 g / 10 min or more at 220°C under a load of 10 kg. [5] The resin composition according to any one of [1] to [3], wherein the polystyrene-based resin (B) comprises at least one resin selected from a general-purpose polystyrene resin (b1) and an impact-resistant polystyrene resin (b2), and a styrene-butadiene copolymer resin (b3). [6] The resin composition according to [1], [2], [4] or [5], wherein the polystyrene-based resin (B) contains an acrylonitrile-butadiene-styrene copolymer resin (b4). [7] The resin composition according to any one of [1] to [6], wherein the eggshell powder (A) has an average particle size of 3 to 50 μm. [8] The resin composition according to any one of [1] to [7], which is for injection molding. [9] A molded article comprising the resin composition according to any one of [1] to [8].

[0008] According to the present invention, it is possible to provide a resin composition containing eggshell powder, which has a good tensile modulus and tensile elongation at break and also has excellent moldability, and a molded article made from the resin composition. 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 the present embodiment comprises eggshell powder (A), a polystyrene-based resin (B), and an additive (C), wherein the proportion of the eggshell powder (A) is 20 parts by mass or more relative to 100 parts by mass of the eggshell powder (A) and the polystyrene-based resin (B) combined; the additive (C) comprises at least one compound selected from fatty acid amide (c1), fatty acid sodium salt (c2), and fatty acid ester (c3); the combined content of the fatty acid amide (c1), fatty acid sodium salt (c2), and fatty acid ester (c3) relative to the total mass of the additive (C) exceeds 50% by mass; and the content of the additive (C) is 10 parts by mass or less relative to 100 parts by mass of the eggshell powder (A) and the polystyrene-based resin (B) combined. The resin composition according to this embodiment has a good tensile modulus and elongation at break, and also has excellent moldability. Furthermore, since it contains a certain amount of eggshell powder, which is a biomass-derived material, it has a lower environmental impact than conventional polystyrene-based resin compositions.

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

[0012] In one embodiment, the proportion of the (A) component 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, relative to 100 parts by mass of the total of the (A) component and the (B) component. From the viewpoint of compounding the resulting resin composition, it is preferable that the proportion be 70 parts by mass or less, relative to 100 parts by mass of the total of the (A) component and the (B) component. That is, the proportion of the (A) component, relative to 100 parts by mass of the total of the (A) component and the (B) component, 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 proportion of the (A) component may be 20 to 50 parts by mass, or 20 to 55 parts by mass, relative to 100 parts by mass of the total of the (A) component and the (B) component.

[0013] In one embodiment, the average particle size of the eggshell powder (A) is preferably 3 to 50 μm, more preferably 3 to 40 μm, and even more preferably 4 to 30 μm. In one embodiment, the average particle size of the eggshell powder (A) may be 10 to 50 μm, 10 to 30 μm, or 3 to 15 μm. When a powder with a smaller average particle size is used as the eggshell powder (A), the viscosity of the resulting resin composition tends to increase, which may result in a decrease in flowability during molding. Furthermore, the dispersibility of the eggshell powder (A) in the resin composition tends 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 (A) with an average particle size greater than 50 μm is blended as the eggshell powder (A), the resin tends to break easily, which may make it difficult to obtain the desired tensile elongation at break. The average particle size of the eggshell powder (A) can be measured using a particle size distribution analyzer according to the "sieving method."

[0014] In one embodiment, the density (g / cm 3 ) of the eggshell powder (A) 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 the eggshell powder (A) in the resin composition may be 10 to 70 mass % or 30 to 60 mass % relative to the total mass of the resin composition.

[0016] Eggshell powder (A) 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 (A) 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 eggshell powder (A) can then be obtained by classification using a sieve with an appropriate mesh size.

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

[0018] In one embodiment, the resin composition may contain an inorganic filler other than component (A). Examples of inorganic fillers other than component (A) 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 component (A) and the aforementioned inorganic fillers are used in combination, it is preferable that the total amount of component (A) and the inorganic filler does not exceed 70 parts by mass per 100 parts by mass of the total of components (A) and (B). Note that, from the viewpoint of easily achieving both a high tensile modulus and tensile elongation at break and moldability, eggshell powder (A) alone may be contained as the inorganic filler.

[0019] <Polystyrene resin (B)> The resin composition according to the present embodiment contains a polystyrene-based resin (B). The proportion of the polystyrene-based resin (B) is 80 parts by mass or less relative to 100 parts by mass of the total of the components (A) and (B). In one embodiment, the proportion of the component (B) 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 containing a smaller amount of the component (B), the proportion of the component (B) may be 30 to 50 parts by mass relative to 100 parts by mass of the total of the components (A) and (B).

[0020] In this specification, the term "polystyrene-based resin (B)" refers to a polymer containing a monomer unit derived from an aromatic vinyl compound. The polystyrene-based resin (B) 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 polystyrene resin (B) is preferably 10,000 to 500,000, and more preferably 100,000 to 300,000. When the Mw of the polystyrene resin (B) is within the above range, the flowability is likely to be good. The Mw of the polystyrene resin (B) refers to a value calculated by GPC (gel permeation chromatography) in terms of polystyrene. When the polystyrene resin (B) is a mixture, the Mw refers to a value calculated by measuring the mixture by GPC.

[0026] In one embodiment, the polystyrene resin (B) preferably contains at least one resin selected from a general-purpose polystyrene resin (b1) and an impact-resistant polystyrene (b2), and a styrene-butadiene copolymer resin (b3). From the viewpoint of easily achieving a balance between the tensile modulus and the tensile elongation at break, the general-purpose polystyrene resin (b1) may be combined with the styrene-butadiene copolymer resin (b3). From the viewpoint of obtaining a resin composition with a superior tensile modulus, the impact-resistant polystyrene (b2) may be combined with the styrene-butadiene copolymer resin (b3).

[0027] 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 (B) 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 a conjugated diene rubber is preferred, and an acrylonitrile-styrene-butadiene copolymer (b4) is more preferred.

[0028] (General-purpose polystyrene resin (b1)) General-purpose polystyrene resin (b1) (hereinafter sometimes referred to as "component (b1)") is a styrene homopolymer, a resin abbreviated as "GPPS." When component (B) contains component (b1), the tensile modulus tends to be good. In one embodiment, the weight average molecular weight (Mw) of component (b1) may be 10,000 to 500,000 or 100,000 to 300,000 from the viewpoint of fluidity. The Mw of component (b1) refers to a value calculated in terms of polystyrene by gel permeation chromatography (GPC).

[0029] When component (B) contains component (b1), the proportion of component (b1) in component (B) is preferably 20 to 95 mass %, more preferably 30 to 80 mass %, based on the total mass of component (B) from the viewpoint of tensile modulus. Furthermore, the proportion of component (b1) in the resin composition may be 10 to 80 mass %, or 10 to 60 mass %, based on the total mass of the resin composition.

[0030] (High impact polystyrene (b2)) High impact polystyrene (b2) (hereinafter sometimes referred to as "component (b2)") is a graft polymer obtained by graft polymerizing a rubbery polymer with a styrene monomer, and is a resin abbreviated as "HIPS." When component (B) contains component (b2), the impact strength (impact resistance) of the resulting molded article is likely to be improved. In one embodiment, the weight average molecular weight (Mw) of component (b2) may be 100,000 to 250,000 or 130,000 to 200,000 from the viewpoint of fluidity. The Mw of component (b2) refers to a value calculated in terms of polystyrene by gel permeation chromatography (GPC). In one embodiment, the proportion of the rubbery polymer (proportion of the rubber component) in component (b2) is preferably 1 to 15 mass%, more preferably 2 to 14 mass%, and even more preferably 3 to 13 mass%, relative to the total mass of component (b2). The proportion of the rubber polymer in component (b2) (proportion of rubber component) may be 1 to 10 mass%, 2 to 8 mass%, or 3 to 6 mass% relative to the total mass of component (b2). The proportion of the rubber component in component (b2) may be calculated from the amount charged when preparing component (b2), or may be measured using the same method as the "amount of conjugated diene" described below.

[0031] When component (B) contains component (b2), the proportion of component (b2) in component (B) is preferably 10 to 90 mass %, more preferably 50 to 85 mass %, based on the total mass of component (B) from the viewpoint of flowability. Furthermore, the proportion of component (b2) in the resin composition may be 5 to 75 mass %, or may be 10 to 60 mass %, based on the total mass of the resin composition.

[0032] (Styrene-butadiene copolymer resin (b3)) Styrene-butadiene copolymer resin (b3) (hereinafter sometimes referred to as "component (b3)") is a copolymer resin obtained by polymerizing a monomer mixture containing styrene and butadiene. Examples of component (b3) 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, component (b3) preferably contains a styrene-butadiene (SB) copolymer, from the viewpoint of more easily improving brittleness due to high loading of filler containing eggshell powder.

[0033] In one embodiment, the weight average molecular weight (Mw) of component (b3) is preferably 100,000 to 200,000, and more preferably 120,000 to 180,000. When the Mw of component (b3) is within the above range, compatibility with component (b1) and / or component (b2) tends to be good. Note that the Mw of component (b3) refers to a value calculated using GPC (gel permeation chromatography) in terms of polystyrene.

[0034] In one embodiment, the proportion of component (b3) in component (B) is preferably 5 to 80 mass %, more preferably 20 to 70 mass %, relative to the total mass of component (B) from the viewpoint of improving brittleness. The proportion of component (b3) in the resin composition may be 5 to 30 mass %, or may be 10 to 25 mass %, relative to the total mass of the resin composition.

[0035] In one embodiment, from the viewpoint of making it easier to adjust the tensile modulus of the resin composition, the amount of conjugated diene in component (b3) 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 component (b3). The "amount of conjugated diene" refers to the amount of butadiene contained in component (b3). The amount of conjugated diene may be a value calculated from the amount of butadiene charged when preparing component (b3), or may be a value measured by potentiometric titration using iodine monochloride, potassium iodide, and sodium thiosulfate standard solutions.

[0036] (Acrylonitrile-butadiene-styrene copolymer (b4)) Examples of the acrylonitrile-butadiene-styrene copolymer (b4) include, but are not limited to, a mixture of a copolymer of styrene and acrylonitrile and polybutadiene; a graft polymer obtained by graft polymerizing styrene and acrylonitrile onto polybutadiene; a melt mixture of the copolymer and the graft polymer; and a melt mixture of a copolymer of butadiene and acrylonitrile and the copolymer.

[0037] In one embodiment, from the viewpoint of improving brittleness, the proportion of component (b4) in component (B) may be 30 to 100 mass%, 40 to 100 mass%, or 50 to 90 mass%, relative to the total mass of component (B).Furthermore, the proportion of component (b4) in the resin composition may be 30 to 80 mass%, or 40 to 80 mass%, relative to the total mass of the resin composition.

[0038] In one embodiment, from the viewpoint of making it easier to adjust the tensile modulus of the resin composition, the amount of conjugated diene in component (b4) is preferably 5 to 40 mass%, more preferably 7 to 30 mass%, and particularly preferably 10 to 25 mass%, relative to the total mass of component (b4). The "amount of conjugated diene" refers to the amount of butadiene contained in component (b4), and, like component (b3), may be a value calculated from the amount of butadiene charged, or may be a value measured by potentiometric titration using iodine monochloride, potassium iodide, and sodium thiosulfate standard solutions.

[0039] In one embodiment, when component (B) contains at least one resin selected from components (b1) and (b2), and component (b3), the total amount of components (b1), (b2), and (b3) in component (B) may be 50 to 100 mass% or 60 to 100 mass% based on the total mass of component (B). When the total amount of components (b1), (b2), and (b3) in component (B) is within the above range, a resin composition with good tensile modulus and flowability is easily obtained.

[0040] Component (B) may contain components (other components) other than components (b1) to (b4). Examples of other components include styrene-based thermoplastic elastomers other than components (b3) and (b4) (for example, copolymers such as styrene-isoprene (SI) and styrene-isoprene-styrene (SIS), as well as hydrogenated copolymers thereof). These may be used alone or in combination of two or more. When component (B) contains other components, their content is preferably 30% by mass or less relative to the total mass of component (B).

[0041] <Additive (C)> The resin composition according to this embodiment contains an additive (C). The additive (C) contains at least one compound selected from fatty acid amide (c1), fatty acid sodium salt (c2), and fatty acid ester (c3), and the total content of the compounds (c1), (c2), and (c3) relative to the total mass of the additive (C) is more than 50 mass%. In this embodiment, the additive (C) contains the aforementioned compound as a main component. The content of additive (C) in the resin composition according to this embodiment is 10 parts by mass or less, based on 100 parts by mass of the total of components (A) and (B). By combining such additive (C) with components (A) and (B), a resin composition having good tensile elongation at break and tensile modulus, as well as excellent moldability, is obtained.

[0042] In one embodiment, the content of additive (C) may be 9 parts by mass or less, 8 parts by mass or less, or 7 parts by mass or less, relative to 100 parts by mass of the total of components (A) and (B). The lower limit of the content of additive (C) 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. That is, the content of additive (C) may be 0.5 to 10 parts by mass, 0.5 to 9 parts by mass, 0.5 to 8 parts by mass, 1 to 8 parts by mass, or 1 to 6 parts by mass, relative to 100 parts by mass of the total of components (A) and (B).

[0043] (Fatty acid amide (c1)) In this embodiment, the additive (C) may contain a fatty acid amide (c1) (hereinafter, sometimes referred to as "compound (c1)"). The fatty acid amide (c1) is a compound having an amide group represented by "R1-C(=O)-N-" in its structure. The term "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 (c1) in this embodiment does not include polymers such as aliphatic polyamides, typified by nylon-6.

[0044] The R1 is a hydrocarbon group which may have a substituent. "Optionally substituted" means that one or more hydrogen atoms in the hydrocarbon group may be substituted with a substituent. R1 is preferably an alkyl group having two 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 amide (c1) as long as it achieves the effects of the present invention, but from the viewpoint of compatibility with component (B), it is preferable that the fatty acid amide is 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. Specifically, 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 compound (c1) 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 improving extrusion with the resin and facilitating improved moldability, it is preferable that the compound (c1) contains a saturated fatty acid bisamide having 10 or more carbon atoms.

[0045] (Sodium fatty acid (c2)) In this embodiment, the additive (C) can contain a fatty acid sodium salt (c2). The fatty acid sodium salt (c2) (hereinafter sometimes referred to as "compound (c2)") 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 salt (c2) as long as it achieves the effects of the present invention. In one embodiment, from the viewpoint of more easily improving compatibility with component (B) and more easily obtaining a resin composition having excellent tensile elongation at break, it is preferable to use a sodium salt of a higher fatty acid 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. 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 (c2) may be a mixture of the above-mentioned sodium salts of higher fatty acids having 10 to 20 carbon atoms.

[0046] (Fatty acid ester (c3)) In this embodiment, the additive (C) can contain a fatty acid ester (c3). The fatty acid ester (c3) (hereinafter sometimes referred to as "compound (c3)") is an ester containing a fatty acid group represented by "R3-C(=O)O-" in its structure. In one embodiment, the fatty acid ester (c3) 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.

[0047] In a preferred embodiment, the higher fatty acid ester may include a glycerin fatty acid ester. Examples of glycerin fatty acid esters 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. Among these, it is preferable to include hydroxystearic acid glyceride, as this makes it easier to improve the compatibility between the eggshell powder and the resin component and makes it easier to obtain a resin composition with superior tensile elongation at break.

[0048] In one embodiment, from the viewpoint of making it easier to obtain better tensile elongation at break, the additive (C) preferably contains fatty acid sodium salt (c2).

[0049] In the resin composition according to this embodiment, the total content of the compounds (c1) to (c3) in the additive (C) is more than 50% by mass, may be more than 50% by mass and not more than 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, based on the total mass of the additive (C).

[0050] In one embodiment, the additive (C) may contain other additives in addition to the aforementioned compounds (c1) to (c3). 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.

[0051] (plasticizer) In one embodiment, the additive (C) may further contain a plasticizer. The combined use of at least one compound selected from compounds (c1), (c2), and (c3) with a plasticizer facilitates the production of a resin composition with a low static friction coefficient while maintaining good ranges of mechanical properties such as tensile modulus and tensile elongation at break, as well as moldability. Such a resin composition also tends to have good abrasion resistance. Here, "abrasion resistance" may refer to the resistance of a molded article having a joint to wear during repeated joining.

[0052] Examples of plasticizers 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, it is preferable to include at least one plasticizer selected from synthetic polymer plasticizers, particularly silicone oil and silicone rubber.

[0053] (i) Silicone oil The silicone oil is not particularly limited, and known silicone oils can be used. In one embodiment, examples of silicone oils include dimethylpolysiloxane, methylphenylsiloxane, methylhydrogenpolysiloxane, and modified products thereof. These may be used alone or in combination of two or more. Among these, it is preferable to include dimethylpolysiloxane, from the viewpoint of easily obtaining a resin composition with better 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 at a test temperature of 37.8°C or 40°C using a Cannon-Fenske viscometer in accordance with, for example, JIS K 2283:2000, "5. Kinematic viscosity test method."

[0054] (ii) Silicone rubber The silicone rubber is a rubber containing polyorganosiloxane rubber. The silicone rubber is not particularly limited, and for example, a silicone / acrylic composite rubber obtained by combining polyorganosiloxane rubber or polyorganosiloxane with polyalkyl(meth)acrylate rubber may be used. The "silicone / acrylic composite rubber" refers to a composite rubber obtained by gradually adding and polymerizing various monomers when polymerizing two or more types of monomers that constitute the rubber. Among these, the silicone / acrylic composite rubber may be contained from the viewpoint of easily obtaining a resin composition with better abrasion resistance.

[0055] When additive (C) contains a plasticizer, the content of the plasticizer in additive (C) can be appropriately adjusted within a range of 50% by mass or less, relative to the total mass of additive (C). In one embodiment, the content of the plasticizer in additive (C) may be 0.3 to 3.0 parts by mass, 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 100 parts by mass of the total of components (A) and (B). When the content of the plasticizer is within the above range, the plasticizer is less likely to bleed out, and wear resistance is also likely to be improved.

[0056] The additive (C) may contain other components in addition to the above-mentioned plasticizer, for example, it may further contain an ultraviolet absorber, a light stabilizer, an antioxidant, a lubricant, and the like.

[0057] 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.

[0058] 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. .

[0059] 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.

[0060] The proportion of additives other than the plasticizers in additive (C) can be adjusted as appropriate to within a range of 50% by mass or less, based on the total mass of additive (C). In one embodiment, the proportion is preferably 40% by mass or less, and more preferably 30% by mass or less, based on the total mass of additive (C). Note that in a resin composition according to this embodiment containing a certain amount of eggshell powder, additive (C) may contain only compounds (c1) to (c3), from the viewpoint of maintaining physical properties such as tensile elongation at break within a favorable range.

[0061] <Other thermoplastic resins> The resin composition according to this embodiment may contain a thermoplastic resin other than the polystyrene-based resin (B) (another 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.

[0062] <Characteristics of resin composition> In one embodiment, the resin composition preferably has an MFR of 4.0 g / 10 min or more at 200°C under a 5 kg load. A resin composition with an MFR of 4.0 g / 10 min or more (200°C under a 5 kg load) tends to have better moldability. The MFR of the resin composition (200°C under a 5 kg load) may be 4.5 g / 10 min or more, 5.0 g / 10 min or more, 6.0 g / 10 min or more, or 10.0 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). A resin composition with an MFR of 4.0 g / 10 min or more (200°C under a 5 kg load) is easily obtained when the resin composition (B) contains at least one resin selected from the resins (b1) and (b2) and the resin (b3).

[0063] In one embodiment, the resin composition may have an MFR of 4.0 g / 10 min or more at 220°C under a 10 kg load, 4.5 g / 10 min or more, 5.0 g / 10 min or more, 6.0 g / 10 min or more, or 10.0 g / 10 min or more. The MFR (220°C under a 10 kg load) of the resin composition may also be measured according to JIS K 7210-2:2014 (ISO 133-2:2011). A resin composition having an MFR (220°C under a 10 kg load) of 4.0 g / 10 min or more is easily obtained when the resin composition contains the component (b4) as the component (B).

[0064] In one embodiment, the tensile modulus of the resin composition, measured according to ASTM-D638, may be 1,000 MPa or more, 1,200 MPa or more, or 1,500 MPa or more. The upper limit of the tensile modulus is preferably less than 1,800 MPa. That is, the tensile modulus of the resin composition is preferably 1,000 MPa or more and less than 1,800 MPa. Furthermore, the tensile elongation at break of the resin composition, measured according to ASTM-D638, may be 15% or more, 20% or more, or 50% or more. The resin composition according to this embodiment contains a certain amount or more of eggshell powder (A) and has a good tensile modulus and tensile elongation at break. Furthermore, it also has good moldability.

[0065] Resin compositions containing eggshell powder tend to have reduced mechanical strength, such as tensile modulus and tensile elongation at break. The present inventors investigated the reasons for this and found that eggshell powder has poor adhesion to resin components, making it difficult to achieve desired tensile properties. After further intensive research, the present inventors surprisingly found that blending a certain amount of additive (C) containing specific compounds (c1) to (c3) as its main components tends to improve adhesion between the eggshell powder and resin components, thereby improving the tensile elongation at break of the resulting resin composition.

[0066] [Method of producing resin composition] The resin composition according to this embodiment can be produced by melt-kneading the eggshell powder (A), the polystyrene resin (B), the additive (C), and, if necessary, other components. Specifically, the components (A) to (C) are each placed in a twin-screw extruder, melt-kneaded at a temperature of 200 to 250°C, and then extruded into strands to prepare a pellet-shaped resin composition.

[0067] [Application] As described above, the resin composition according to this embodiment has a good tensile modulus and tensile elongation at break, and also has excellent moldability. Therefore, it can be suitably used as a resin composition for injection molding. However, the use of the resin composition according to this embodiment is not limited to injection molding.

[0068] [Molded products] The molded article according to this embodiment contains the resin composition described above. Preferably, it is obtained by injection molding the resin composition according to this embodiment. The molded article according to this embodiment has excellent tensile modulus and tensile elongation at break. Furthermore, since the molded article according to this embodiment contains a certain amount of eggshell powder, it is an environmentally friendly molded article. The molded article according to this embodiment can be used for stationery, furniture, building materials, tableware, containers, gardening materials, toys, etc. [Example]

[0069] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following description. [Preparation of eggshell powder (A-1)] 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 separating 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 (A-1). When the density of the obtained eggshell powder (A-1) 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. Furthermore, the obtained powder was classified to obtain eggshell powder (A-1) with an average particle diameter of 10 μm.

[0070] [Production of Polystyrene Resin (B)] [Production of General-Purpose Polystyrene Resin (b1-1)] 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, 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) (b1-1). When the Mw of the obtained (b1-1) component was measured using GPC under the following conditions, it was 167,000. [GPC Measurement Conditions] Apparatus: Manufactured by Shodex Corporation, product name "Shodex SYSTEM-21" Column: PLgel MIXED-B Measurement temperature: 40 °C Solvent: Tetrahydrofuran Flow rate: 1.0 mL / min Detection method: RI Sample concentration: 0.2 mass% Injection volume: 100 μL Calibration curve: Standard polystyrene (manufactured by Polymer Laboratories)

[0071] [Production of Impact-Resistant Polystyrene Resin (b2-1)] 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 a strand, and then passed through a water tank to pelletize, yielding impact-resistant polystyrene resin (b2-1). The rubber content of the resulting (b2-1) component was 4.8% by mass. Furthermore, the Mw of the (b2-1) component, measured under the same conditions as for the (b1-1) component, was 210,000.

[0072] <Production of styrene-butadiene copolymer resin (b3-1)> A styrene-butadiene block copolymer resin was prepared as component (b3-1). 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 then 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 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 block copolymer resin (b3-1). The amount of conjugated dienes in the obtained component (b3-1) calculated from the amount of charged monomer was 28 mass %.

[0073] <Acrylonitrile-butadiene-styrene copolymer resin (b4-1)> The following was used as the (b4-1) component: (b4-1) Component: acrylonitrile-butadiene-styrene copolymer resin (manufactured by Denka Co., Ltd., product name "Denka ABS GR-3000").

[0074] [Additive (C)] The following was used as additive (C): Compound (c1): ethylene bisstearic acid amide (manufactured by Kao Corporation, product name "Kaowax EB-FF"). Compound (c2): Miyoshi Oil & Fats Co., Ltd., product name "Tankal MH" (a mixture of sodium fatty acids with a mass ratio of lauric acid: myristic acid: palmitic acid: stearic acid: oleic acid = 3:2:40:15:30). Compound (c3): 1,2-hydroxystearic acid triglyceride (manufactured by Dainichi Chemical Industry Co., Ltd., product name "OHG"). <Other additives> Plasticizer 1: silicone oil (dimethylpolysiloxane, manufactured by Shin-Etsu Chemical Co., Ltd., product name "KF-96 350CS", kinematic viscosity (25°C): 350 mm 2 / s). Plasticizer 2: silicone / acrylic composite rubber (manufactured by Mitsubishi Chemical Corporation, product name "Metabrene (registered trademark) SX-005"). Zinc stearate: manufactured by Nitto Kasei Kogyo Co., Ltd., product name "Zn-St". Polyethylene wax: manufactured by Mitsui Chemicals, Inc., product name "Excelex (registered trademark) T". Stearic acid: manufactured by NOF Corporation, product name "Stearic acid Sakura".

[0075] [Example 1] As the polystyrene resin (B), 30 parts by mass of the component (b1-1), 20 parts by mass of the component (b2-1), and further 50 parts by mass of eggshell powder (A-1) (average particle diameter 10 μm) were blended. After blending 1 part by mass of the compound (c1) with respect to 100 parts by mass in total of the components (A) and (B), using a twin-screw extruder (manufactured by Toshiba Machine Co., Ltd., product name "TEM35-B"), melt-kneading was performed at 200°C and 350 rpm, and then extrusion was performed in a strand shape at a discharge rate of 20 kg / hr to obtain a pelletized resin composition. When the MFR of the obtained pellets was measured under the following conditions, it was 6.7 g / 10 min. Further, the obtained pellets were formed into a plate shape with a thickness of 0.40 mm using a hot press (manufactured by Tester Sangyo Co., Ltd., product name "SA-303"), and the tensile modulus of elasticity, tensile elongation at break, and impact strength were evaluated by the following methods. The results are shown in Table 1.

[0076] <MFR and Molding Property Evaluation> Measurement was carried out in accordance with the standards of JIS K 7210-2:2014 (ISO 133-2:2011) under the conditions of 200°C and 5 kg load or 220°C and 10 kg load. Further, the molding property was evaluated in accordance with the following evaluation criteria, and if it was above good evaluation, it was considered that the effect of the present invention was exhibited. (Evaluation Criteria) Excellent: MFR (200°C, 5 kg load) or MFR (220°C, 10 kg load) is 10.0 g / 10 min or more. Good: MFR (200°C, 5 kg load) or MFR (220°C, 10 kg load) is 4.0 g / 10 min or more and less than 10.0 g / 10 min. Unacceptable: MFR (200°C, 5 kg load) or MFR (220°C, 10 kg load) is less than 4.0 g / 10 min.

[0077] <Method for measuring tensile modulus> Measurements were made in accordance with ASTM-D638 using an autograph (Shimadzu Corporation, product name "AGS-X"). Specifically, a measurement sample was prepared by cutting out a No. 1 dumbbell shape from a 0.40 mm thick plate sample, and the tensile modulus of the measurement sample was measured at a measurement temperature of 23°C and a humidity of 50% at a tension speed of 5 mm / min. Evaluation was made according to the following evaluation criteria, and a rating of good or better was deemed to demonstrate the effects of the present invention. (Evaluation criteria) Excellent: Tensile modulus of elasticity is 1,200 MPa or more but less than 1,800 MPa. Good: Tensile modulus of elasticity is 800 MPa or more but less than 1,200 MPa. Unacceptable: Tensile modulus of elasticity is less than 800 MPa or more than 1,800 MPa.

[0078] <Method for measuring tensile elongation at break> Measurements were made 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 made according to the following evaluation criteria, and a result of satisfactory or better was deemed to demonstrate the effects of the present invention. (Evaluation criteria) Excellent: Tensile elongation at break is 40% or more. Good: Tensile elongation at break is 25% or more and less than 40%. Acceptable: Tensile elongation at break is 15% or more but less than 25%. Unacceptable: Tensile elongation at break is less than 15%.

[0079] <Impact Strength> The impact strength was measured using a film impact tester (manufactured by Yasuda Seiki) in accordance with ASTM-D3420. 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 also performed according to the following evaluation criteria. (Evaluation criteria) Excellent: Impact strength is 2.0 J / mm or more. Good: Impact strength is 1.5 J / mm or more and less than 2.0 J / mm. Unacceptable: Impact strength less than 1.5J / mm.

[0080] [Examples 2 to 20 and Comparative Examples 1 to 7] Resin compositions were prepared in the same manner as in Example 1, except that the formulations of the resin compositions were as shown in Tables 1 and 2. Pellets were prepared in the same manner as in Example 1, and the MFR was measured. The resin compositions were then molded into plates in the same manner as in Example 1, and the tensile modulus, tensile elongation at break, and impact strength were measured. The results are shown in Tables 1 and 2.

[0081] [Table 1]

[0082] [Table 2]

[0083] As shown in Tables 1 and 2, the resin compositions of Examples 1 to 20, which fulfilled the configuration of this embodiment, had good values ​​for tensile modulus and tensile elongation at break. They also had good moldability. On the other hand, the resin composition of Comparative Example 1, which did not contain additive (C), had insufficient tensile elongation at break and poor moldability. Furthermore, the resin compositions of Comparative Examples 2 to 4, which contained additive (C) but did not contain compounds (c1) to (c3), had lower tensile elongation at break than the resin composition of Comparative Example 1. They also had poor moldability. Furthermore, the resin compositions of Comparative Examples 5 to 7, in which the total amount of compounds (c1) to (c3) in additive (C) was 50% by mass or less, had good moldability but poor tensile elongation at break. These results demonstrate that the resin composition of this embodiment has good tensile modulus and tensile elongation at break, and is also excellent in moldability. The resin composition of this embodiment contains a certain amount of eggshell powder, which reduces the environmental impact. [Industrial Applicability]

[0084] The resin composition according to this embodiment has a good tensile modulus and elongation at break, and is also excellent in moldability. Therefore, it can be suitably used as a resin composition for injection molding. Furthermore, the molded article according to this embodiment has a good tensile modulus and elongation at break, and contains a certain amount of eggshell powder, so it is an environmentally friendly molded article. Such molded articles can be used for stationery, furniture, building materials, tableware, containers, gardening materials, toys, and other applications.

Claims

1. The composition contains eggshell powder (A), a polystyrene resin (B), and an additive (C), a ratio of the eggshell powder (A) to a total of 100 parts by mass of the eggshell powder (A) and the polystyrene-based resin (B) is 20 parts by mass or more, the additive (C) comprises at least one compound selected from fatty acid amides (c1), fatty acid sodium salts (c2), and fatty acid esters (c3), the total content of the fatty acid amides (c1), fatty acid sodium salts (c2), and fatty acid esters (c3) relative to the total mass of the additive (C) is more than 50 mass%, and the content of the additive (C) is 10 parts by mass or less relative to a combined total of 100 parts by mass of the eggshell powder (A) and the polystyrene-based resin (B).

2. 2. The resin composition according to claim 1, wherein a ratio of the eggshell powder (A) to a total of 100 parts by mass of the eggshell powder (A) and the polystyrene-based resin (B) is 70 parts by mass or less.

3. The resin composition according to claim 1 or 2, wherein the resin composition has an MFR of 4.0 g / 10 min or more at 200° C. under a load of 5 kg.

4. The resin composition according to claim 1 or 2, wherein the resin composition has an MFR of 4.0 g / 10 min or more at 220°C under a load of 10 kg.

5. The polystyrene-based resin (B) comprises at least one resin selected from a general-purpose polystyrene resin (b1) and an impact-resistant polystyrene resin (b2), and a styrene-butadiene copolymer resin (b3). The resin composition according to claim 1 or 2.

6. The resin composition according to claim 1 or 2, wherein the polystyrene resin (B) contains an acrylonitrile-butadiene-styrene copolymer resin (b4).

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

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

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

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