Resin composition and molded article

Abstract

Provided are a resin composition that has excellent fluidity and excellent molded article strength, and a molded article that includes the resin composition.　The present invention provides a resin composition that includes eggshell powder and a thermoplastic resin that includes a general-purpose polystyrene (A) having a weight average molecular weight of 300,000 or less, a styrene-based thermoplastic elastomer (B), and an impact-resistant polystyrene (C), the eggshell powder content being 5-75% by mass with respect to the total mass of the eggshell powder and the thermoplastic resin. The thermoplastic resin preferably includes 30-90% by mass of the general-purpose polystyrene (A) having a weight average molecular weight of 300,000 or less, 5-60% by mass of the styrene-based thermoplastic elastomer (B), and 5-30% by mass of the impact-resistant polystyrene (C) with respect to the total mass of the general-purpose polystyrene (A) having a weight average molecular weight of 300,000 or less, the styrene-based thermoplastic elastomer (B), and the impact-resistant polystyrene (C).

Description

[Technical Field]

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

[0002] In recent years, environmental issues such as global warming have become a focus of attention, and attempts have been made to use naturally derived materials as inorganic fillers in resin compositions. For example, Patent Document 1 describes the use of natural ground calcium carbonate as a filler material in extrusion coating materials. Patent Document 2 describes the use of seashell powder or eggshell powder as the calcium carbonate (CaCO3) contained in non-PVC eraser compositions. Patent Document 3 describes the use of inorganic particle aggregates containing eggshell-derived inorganic waste in a resin composition manufacturing method in which inorganic particle aggregates are kneaded with resin raw materials.

[0003] [Patent Document 1] Special Publication No. 2018-516159 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-212978 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-256260 Summary of the Invention

[0004] When molding resin molded products by injection molding, it is necessary to use a resin with excellent fluidity to improve mold filling. Natural materials such as eggshells discolor and emit odors when heated at high temperatures, so a resin with excellent fluidity at low temperatures is preferred to enable injection molding at low temperatures. Polystyrene resin is a typical thermoplastic resin, and because it is transparent, moldable, and inexpensive, it is widely used in various fields such as home appliance parts, automotive interior materials, building materials, food containers, and toys. However, when polystyrene resin is highly filled with filler, the fluidity of the resin at low temperatures tends to decrease, and the strength (especially impact strength) of the resulting molded product tends to decrease. The decreased fluidity leads to a decrease in the mold filling ability during injection molding. The decreased strength of the molded product makes it more susceptible to breakage when subjected to impact.

[0005] An object of the present invention is to provide a resin composition having excellent fluidity and excellent molded article strength, and a molded article containing the resin composition.

[0006] The present inventors discovered that by using three specific types of styrene-based resins as the thermoplastic resin, it is possible to obtain a resin composition that has excellent flowability and produces molded articles with excellent strength, even when containing eggshell powder, and this discovery led to the completion of the present invention.

[0007] The present invention has the following aspects. [1] Eggshell powder, (A) general-purpose polystyrene having a weight average molecular weight of 300,000 or less; (B) a styrene-based thermoplastic elastomer, and (C) High-impact polystyrene a thermoplastic resin comprising Including, A resin composition, wherein the content of the eggshell powder is 5 to 75 mass % based on the total mass of the eggshell powder and the thermoplastic resin. [2] The thermoplastic resin is, relative to the total mass of (A) general-purpose polystyrene having a weight average molecular weight of 300,000 or less, (B) a styrene-based thermoplastic elastomer, and (C) high-impact polystyrene, (A) 30 to 90% by mass of general-purpose polystyrene having a weight-average molecular weight of 300,000 or less, (B) 5 to 60% by mass of a styrene-based thermoplastic elastomer, and (C) 5 to 30 mass% of high-impact polystyrene The resin composition according to [1], [3] The resin composition according to [1] or [2], wherein the eggshell powder has an average particle size of 2 to 70 μm. [4] The resin composition according to any one of [1] to [3], wherein (B) the styrene-based thermoplastic elastomer contains a styrene-butadiene block copolymer. [5] (B) styrene-based thermoplastic elastomer and (C) high-impact polystyrene contain a conjugated diene component, The resin composition according to any one of [1] to [4], wherein the content of the conjugated diene component in the resin composition is 15 mass% or less relative to the total mass of the eggshell powder and the thermoplastic resin. [6] The resin composition according to any one of [1] to [5], wherein the resin composition has a melt flow rate of 15 g / 10 min or more at 200°C under a load of 5 kg. [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, it is possible to provide a resin composition having excellent fluidity and excellent molded article strength, and a molded article containing the resin composition. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described in detail below, but the scope of the present invention is not limited to the embodiment described herein, and various modifications can be made without departing from the spirit of the present invention. Furthermore, when multiple upper and lower limit values ​​are described for a specific parameter, any of these upper and lower limit values ​​can be combined to form a suitable numerical range. The expression "X to Y" indicating a numerical range means "X or more and Y or less." When a specific description given for one embodiment also applies to other embodiments, that description may be omitted in other embodiments.

[0010] [Resin composition] The resin composition according to this embodiment contains eggshell powder and (A) a general-purpose polystyrene having a weight-average molecular weight of 300,000 or less, (B) a styrene-based thermoplastic elastomer, and (C) a thermoplastic resin containing high-impact polystyrene, and the content of eggshell powder is 5 to 75 mass% based on the total mass of the eggshell powder and the thermoplastic resin.

[0011] Because the resin composition contains (A) a general-purpose polystyrene having a weight-average molecular weight of 300,000 or less, (B) a styrene-based thermoplastic elastomer, and (C) a thermoplastic resin containing high-impact polystyrene, it is possible to obtain a resin composition that has excellent fluidity at low temperatures (e.g., 200°C or less) and excellent molded article strength (impact strength), even when containing eggshell powder as an inorganic filler. Because of its excellent fluidity at low temperatures, injection-molded articles can be produced with good mold filling even at low temperatures. As a result, discoloration and odor generation during injection molding can be prevented. Because the molded articles have excellent strength, breakage of the molded articles when impacted can be suppressed. Because eggshell powder is contained as an inorganic filler, naturally derived materials can be utilized, and waste materials such as food waste can be effectively utilized, thereby contributing to reducing environmental impact.

[0012] <Eggshell powder> The eggshell powder may be made from any suitable raw material, provided that it is made from powdered eggshells, but eggshells from animals are preferred, and eggshells from chickens are more preferred. From the perspective of further reducing the environmental load, eggshells made from waste materials are preferred, and food waste may also be used as the raw material.

[0013] The content of eggshell powder is 5 to 75% by mass, preferably 8 to 73% by mass, and more preferably 10 to 70% by mass, based on the total mass of the eggshell powder and the thermoplastic resin. In one embodiment, the content of eggshell powder based on the total mass of the eggshell powder and the thermoplastic resin may be 10 to 50% by mass or 50 to 70% by mass. By having the content of eggshell powder in the range of 5 to 75% by mass based on the total mass of the eggshell powder and the thermoplastic resin, it is possible to reduce the environmental impact and, when combined with the thermoplastic resin described below, to achieve both excellent fluidity and excellent molded product strength.

[0014] The resin composition according to this embodiment can achieve both excellent fluidity and excellent molded product strength, even when the content of eggshell powder is high. In one embodiment, the content of eggshell powder can be 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more, based on the total mass of the resin composition. In another embodiment, the content of eggshell powder can be 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more, based on the total mass of the eggshell powder and the thermoplastic resin.

[0015] In one embodiment, the content of eggshell powder is preferably 5 to 350 parts by mass, more preferably 8 to 300 parts by mass, even more preferably 10 to 300 parts by mass, and particularly preferably 10 to 250 parts by mass, relative to 100 parts by mass of the thermoplastic resin.

[0016] In one embodiment, the average particle size of the eggshell powder is preferably 2 to 70 μm, more preferably 3 to 65 μm, and even more preferably 4 to 60 μm, from the viewpoint of further improving fluidity and dispersibility. The average particle size of the eggshell powder can be adjusted according to the "sieving method," and can be evaluated by measuring the laser diffraction and scattering state under wet conditions using water as a dispersion medium with a particle size distribution analyzer.

[0017] In one embodiment, the density of the eggshell powder (g / cm 3) is preferably 1.5 to 3.0 g / cm from the viewpoint of the content ratio of eggshell membrane. 3 and more preferably 1.7 to 2.8 g / cm 3 and more preferably 2.0 to 2.7 g / cm 3 is.

[0018] 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.

[0019] Commercially available eggshell powders can also be used, such as those manufactured by Green Techno 21 Co., Ltd. under the trade name "GT-26" and those manufactured by Kewpie Egg Co., Ltd. under the trade name "Calhope (registered trademark)."

[0020] In one embodiment, the resin composition may contain an inorganic filler other than eggshell powder, provided that the effects of the present invention are not impaired. Examples of inorganic fillers other than eggshell powder include inorganic fillers derived from minerals such as calcium carbonate, talc, and zeolite; inorganic fillers derived from biominerals such as pearls, seashells, eggshells, bones, and the exoskeletons of crustaceans; and inorganic fillers such as glass fibers and glass beads.

[0021] When eggshell powder and the aforementioned inorganic filler are used in combination, the total content of the eggshell powder and the inorganic filler is preferably adjusted to a range not exceeding 75% by mass relative to the total mass of the eggshell powder and the thermoplastic resin. From the viewpoint of more easily achieving the effects of combined use with the thermoplastic resin described below, the content of eggshell powder in the inorganic filler is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and particularly preferably 98% by mass or more, relative to the total mass of the inorganic filler. In one embodiment, the inorganic filler can be configured to consist solely of eggshell powder.

[0022] <Thermoplastic resin> The thermoplastic resin includes (A) a general-purpose polystyrene having a weight-average molecular weight of 300,000 or less (hereinafter simply referred to as "(A) general-purpose polystyrene"), (B) a styrene-based thermoplastic elastomer, and (C) a high-impact polystyrene. By including three types of styrene-based resins, namely (A) general-purpose polystyrene, (B) a styrene-based thermoplastic elastomer, and (C) a high-impact polystyrene, the thermoplastic resin can be made into a resin composition that exhibits excellent flowability and molded product strength, even when containing eggshell powder. In this disclosure, "styrene-based" means that the resin contains a monomer unit derived from an aromatic vinyl compound.

[0023] In one embodiment, the content of the thermoplastic resin is preferably 25 to 95% by mass, more preferably 27 to 92% by mass, and even more preferably 30 to 90% by mass, based on the total mass of the eggshell powder and the thermoplastic resin. In one embodiment, the total content of the eggshell powder and the thermoplastic resin in the resin composition is preferably 90% by mass or more, and more preferably 95% by mass or more.

[0024] ((A) General-purpose polystyrene) General-purpose polystyrene, also known as GPPS, is a styrene homopolymer. (A) The weight-average molecular weight (Mw) of the general-purpose polystyrene is 300,000 or less, preferably 100,000 to 250,000, and more preferably 160,000 to 250,000. If the weight-average molecular weight (Mw) of the general-purpose polystyrene exceeds 300,000, it becomes difficult to achieve both excellent fluidity and excellent molded product strength in a resin composition containing eggshell powder. The weight average molecular weight (Mw) is a value calculated in terms of polystyrene by gel permeation chromatography (GPC) using a differential refractive index method.

[0025] In one embodiment, the content of (A) general-purpose polystyrene is preferably 30 to 90 mass%, more preferably 35 to 85 mass%, even more preferably 38 to 83 mass%, and particularly preferably 40 to 80 mass%, based on the total mass of (A) general-purpose polystyrene, (B) styrenic thermoplastic elastomer, and (C) high-impact polystyrene, from the viewpoint of further improving the fluidity of the resin composition at low temperatures. The content of (A) general-purpose polystyrene is preferably 18 to 55 mass parts, more preferably 20 to 50 mass parts, based on 100 mass parts of the total of the eggshell powder and the thermoplastic resin. In one embodiment, (A) the content of general-purpose polystyrene (X A ) of (B) styrene-based thermoplastic elastomer content (X B ) and (C) the content of high-impact polystyrene (X C ) to the total mass ratio [X A / (X B +X C )] is preferably 0.43 to 9.00, more preferably 0.67 to 4.00, from the viewpoint that it becomes easier to achieve both excellent fluidity and excellent strength of the molded product.

[0026] ((B) Styrene-based thermoplastic elastomer) (B) The styrene-based thermoplastic elastomer is a block copolymer of an aromatic vinyl compound and a conjugated diene, and a polymer obtained by partially or completely hydrogenating the block copolymer.

[0027] Examples of aromatic vinyl compounds include styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, ethylstyrene, and pt-butylstyrene, and it is preferable to include at least one selected from these. The aromatic vinyl compounds may be used alone or in combination of two or more. In one embodiment, it is preferable that the aromatic vinyl compound includes styrene.

[0028] Examples of conjugated dienes include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene, and it is preferable to include at least one selected from these. One type of conjugated diene may be used alone, or two or more types may be used in combination. In one embodiment, it is preferable that the conjugated diene includes 1,3-butadiene and / or isoprene.

[0029] Specific examples of (B) styrene-based thermoplastic elastomers include block copolymers such as styrene-butadiene (SB), styrene-isoprene (SI), styrene-butadiene-butylene (SBB), styrene-butadiene-isoprene (SBI), styrene-butadiene-styrene (SBS), styrene-butadiene-butylene-styrene (SBBS), styrene-isoprene-styrene (SIS), 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, the styrene-based thermoplastic elastomer preferably includes a styrene-butadiene copolymer.

[0030] In one embodiment, the content of the conjugated diene component in the (B) styrene-based thermoplastic elastomer is preferably 10 to 50 mass%, more preferably 15 to 40 mass%, even more preferably 18 to 35 mass%, and particularly preferably 20 to 30 mass%, based on the total mass of the (B) styrene-based thermoplastic elastomer. The content of the conjugated diene component may be a value calculated from the amount of the conjugated diene charged, or may be a value measured by potentiometric titration using iodine monochloride, potassium iodide, and sodium thiosulfate standard solutions.

[0031] In one embodiment, the weight average molecular weight (Mw) of the (B) styrene-based thermoplastic elastomer is preferably 100,000 to 200,000, and more preferably 120,000 to 180,000. The method for measuring the weight average molecular weight (Mw) is the same as the method for measuring the weight average molecular weight (Mw) of the (A) general-purpose polystyrene.

[0032] In one embodiment, the content of (B) styrene-based thermoplastic elastomer is preferably 5 to 60 mass%, more preferably 8 to 55 mass%, even more preferably 10 to 53 mass%, and particularly preferably 10 to 50 mass%, based on the total mass of (A) general-purpose polystyrene, (B) styrene-based thermoplastic elastomer, and (C) high-impact polystyrene, from the viewpoint of further increasing the strength of the molded article. The content of (B) styrene-based thermoplastic elastomer is preferably 1 to 35 mass parts, more preferably 5 to 30 mass parts, based on 100 mass parts of the total of the eggshell powder and the thermoplastic resin. In one embodiment, the content of (B) styrene-based thermoplastic elastomer (X B ) of (A) general-purpose polystyrene content (X A ) and (C) the content of high-impact polystyrene (X C ) to the total mass ratio [X B / (X A +X C )] is preferably 0.05 to 1.50, more preferably 0.11 to 1.00, from the viewpoint of making it easier to achieve both excellent fluidity and excellent strength of the molded product.

[0033] ((C) High impact polystyrene) High-impact polystyrene, also known as rubber-modified styrene resin or HIPS, is a polymer in which styrene monomer is graft-polymerized onto a rubber-like elastomer primarily composed of a conjugated diene. By including (C) high-impact polystyrene in the thermoplastic resin in addition to the (A) general-purpose polystyrene and (B) styrene-based thermoplastic elastomer, a resin composition containing a specified amount of eggshell powder can achieve both excellent fluidity and excellent molded product strength.

[0034] Examples of conjugated dienes include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene, and it is preferable to use at least one selected from these. In one embodiment, the conjugated diene is preferably 1,3-butadiene. In one embodiment, the rubber-like elastomer is preferably a rubbery polymer containing 1,3-butadiene.

[0035] In one embodiment, the content of the conjugated diene component in the high-impact polystyrene (C) is preferably 1 to 30% by mass, more preferably 3 to 20% by mass, and even more preferably 5 to 15% by mass, based on the total mass of the high-impact polystyrene (C). The content of the conjugated diene component may be a value calculated from the amount of the conjugated diene charged, or may be a value measured by potentiometric titration using iodine monochloride, potassium iodide, and sodium thiosulfate standard solutions.

[0036] In one embodiment, the content of the high-impact polystyrene (C) is preferably 5 to 30 mass%, more preferably 8 to 28 mass%, even more preferably 10 to 25 mass%, and particularly preferably 10 to 20 mass%, based on the total mass of the (A) general-purpose polystyrene, the (B) styrene-based thermoplastic elastomer, and the (C) high-impact polystyrene, from the viewpoint of more easily achieving both excellent fluidity and excellent molded product strength. The content of the high-impact polystyrene (C) is preferably 1 to 15 mass parts, more preferably 3 to 10 mass parts, based on 100 mass parts of the total of the eggshell powder and the thermoplastic resin. In one embodiment, (C) the content of high impact polystyrene (X C ) of (A) general-purpose polystyrene content (X A ) and (B) the content of styrene-based thermoplastic elastomer (X B ) to the total mass ratio [X C / (X A +X B)] is preferably 0.05 to 0.43, and more preferably 0.11 to 0.25, from the viewpoint that it becomes easier to achieve both excellent fluidity and excellent strength of the molded product.

[0037] In one embodiment, (C) the content of high impact polystyrene (X C ) of (A) general-purpose polystyrene content (X A ) to the mass ratio value (X C / X A ) is preferably 0.10 to 0.40, more preferably 0.11 to 0.35, and even more preferably 0.13 to 0.33, from the viewpoint of making it easier to achieve both excellent fluidity and excellent strength of the molded product.

[0038] In one embodiment, (C) the content of high impact polystyrene (X C ) of (B) styrene-based thermoplastic elastomer content (X B ) to the mass ratio value (X C / X B ) is preferably 0.10 to 1.10, more preferably 0.15 to 1.05, and even more preferably 0.20 to 1.00, from the viewpoint of making it easier to achieve both excellent fluidity and excellent strength of the molded product.

[0039] The thermoplastic resin may contain a thermoplastic resin other than the above-mentioned (A) general-purpose polystyrene, (B) styrene-based thermoplastic elastomer, and (C) high-impact polystyrene. In one embodiment, from the viewpoint of easily obtaining a resin composition having superior tensile modulus and impact strength (particularly impact strength), the thermoplastic resin may contain a polymer containing monomer units derived from the aromatic vinyl compound, monomer units derived from unsaturated nitrile compounds, and a rubbery polymer (conjugated diene rubber, a copolymer of a conjugated diene and an aromatic vinyl compound, an ethylene-propylene copolymer rubber, etc.). As such a polymer, a copolymer of acrylonitrile, styrene, and conjugated diene rubber is preferred, and an acrylonitrile-butadiene-styrene copolymer is more preferred. In one embodiment, the total content of (A) general-purpose polystyrene, (B) styrene-based thermoplastic elastomer, and (C) high-impact polystyrene in the thermoplastic resin is preferably 90% by mass or more, and more preferably 95% by mass or more, based on the total mass of the thermoplastic resin. In one embodiment, the thermoplastic resin can be composed solely of (A) general-purpose polystyrene, (B) styrene-based thermoplastic elastomer, and (C) high-impact polystyrene.

[0040] <Additives> In one embodiment, the resin composition may contain, as necessary, other additives such as ultraviolet absorbers, light stabilizers, antioxidants, lubricants, plasticizers, colorants, antistatic agents, flame retardants, and mineral oils, as well as reinforcing fibers such as glass fibers, carbon fibers, and aramid fibers, within the scope of not impairing the effects of the present invention. These may be used alone or in combination of two or more.

[0041] In one embodiment, the resin composition may contain one or more selected from fatty acid amides, fatty acid sodium salts, and fatty acid esters, as needed, to enhance mechanical properties such as tensile modulus, within a range that does not impair the effects of the present invention. In one embodiment, the content of one or more selected from fatty acid amides, fatty acid sodium salts, and fatty acid esters is preferably 0.1 to 5 parts by mass, and more preferably 1 to 3 parts by mass, per 100 parts by mass of the total of the eggshell powder and the thermoplastic resin.

[0042] In one embodiment, the resin composition may contain silicone oil as needed, as long as the effects of the present invention are not impaired. In one embodiment, the content of silicone oil is preferably 0.1 to 1 part by mass, more preferably 0.1 to 0.5 parts by mass, per 100 parts by mass of the total of the eggshell powder and the thermoplastic resin.

[0043] <Physical properties of resin composition> In one embodiment, the content of the conjugated diene component in the resin composition is preferably 15% by mass or less, more preferably 1 to 12% by mass, and even more preferably 1 to 10% by mass, based on the total mass of the eggshell powder and the thermoplastic resin, from the viewpoint of further increasing the strength of the molded article. The content of the conjugated diene component in the resin composition can be adjusted to a desired value by adjusting the content of the conjugated diene component in the (B) styrene-based thermoplastic elastomer and the content of the conjugated diene component in the (C) high-impact polystyrene. The content of the conjugated diene component may be a value calculated from the amounts of conjugated diene charged in the (B) styrene-based thermoplastic elastomer and the (C) high-impact polystyrene, or a value measured by potentiometric titration using iodine monochloride, potassium iodide, and sodium thiosulfate standard solutions.

[0044] In one embodiment, the melt flow rate (MFR) of the resin composition at 200°C under a 5 kg load is preferably 15 g / 10 min or more, more preferably 17 g / 10 min or more, and even more preferably 20 g / 10 min or more. By making the melt flow rate of the resin composition at 200°C under a 5 kg load 15 g / 10 min or more, the resin composition can have excellent fluidity at lower temperatures. The melt flow rate of the resin composition is a value measured in accordance with the standard JIS K 7210-2:2014 (ISO 1133-2:2011).

[0045] [Method of producing resin composition] The resin composition can be produced by melt-kneading eggshell powder with a thermoplastic resin containing (A) general-purpose polystyrene, (B) a styrene-based thermoplastic elastomer, and (C) high-impact polystyrene, and other components added as needed. Specifically, the components are fed into 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.

[0046] [Application] The resin composition has excellent flowability and produces molded articles with excellent strength. Therefore, the resin composition 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.

[0047] [Molded products] The molded article according to this embodiment includes the resin composition described above. The molded article is preferably obtained by injection molding the resin composition described above. The molded article is molded using the resin composition having excellent flowability described above, and therefore has high mold filling properties. The molded article includes the resin composition described above, and therefore has excellent strength (particularly impact strength). The molded article includes a certain amount of eggshell powder, and therefore has a low environmental impact. The molded article can be used for applications such as parts for home appliances, automobile interior materials, building materials, food containers, toys, stationery, furniture, containers, and gardening materials. In one embodiment, the molded article can be used as a molded article for automobile interior materials, building materials, food containers, or toys.

[0048] In one embodiment, the Charpy impact strength of the molded article is preferably 5 kJ / m 2 More preferably, 10 kJ / m 2 The Charpy impact strength is a value measured in accordance with JIS K 7111-1:2012.

[0049] The molded article can be produced by any known molding method, and among these, injection molding is preferred. [Example]

[0050] The present invention will be explained in more detail below by showing examples, but the interpretation of the present invention is not limited to these examples.

[0051] [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 eggshell. 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. Furthermore, the obtained powder was classified to obtain eggshell powder with an average particle size of 4 μm (density: 2.6 g / cm 3 ). In the same manner, eggshell powders of 10 μm (density: 2.6 g / cm 3 ), 30 μm (density: 2.6 g / cm 3 ), and 60 μm (density: 2.6 g / cm 3 ) were obtained respectively. The average particle size was measured by the laser diffraction / scattering method under wet conditions with water as the dispersion medium using a particle size distribution measuring device (manufactured by Beckman Coulter, "LS13-320").

[0052] [(A) Preparation of General-Purpose Polystyrene] (Production Example 1: Preparation of General-Purpose Polystyrene (GPPS-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 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 styrene (GPPS-1). When the weight average molecular weight (Mw) of the obtained GPPS-1 was measured using GPC under the following conditions, it was 160,000. <Measurement Conditions of GPC> Apparatus: Manufactured by Shodex Co., Ltd., 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)

[0053] (Production Example 2: Preparation of General-Purpose Polystyrene (GPPS-2)) In Production Example 1, a homopolymer of styrene (GPPS-2) was obtained in the same manner as in Production Example 1, except that the reaction time was extended to 10 hours. When the weight-average molecular weight (Mw) of the obtained GPPS-2 was measured under the same conditions as in Production Example 1 using GPC, it was 250,000.

[0054] [(B) Preparation of Styrenic Thermoplastic Elastomer] (Production Example 3: Preparation of Styrene-Butadiene Block Copolymer (SBC-1)) 500.0 kg of cyclohexane and 75.0 g of tetrahydrofuran (THF) were placed in a reaction vessel, and 1,000 mL of a 10 mass% cyclohexane solution of n-butyllithium was added thereto as a polymerization initiator solution, and the temperature was maintained at 30°C. Then, 20.0 kg of styrene was added, and styrene was anion-polymerized. At that time, the internal temperature rose to 35°C. After the styrene was completely consumed, 58.0 kg of 1,3-butadiene and 64.0 kg of styrene were added simultaneously. After the styrene and 1,3-butadiene were completely consumed, the internal temperature of the reaction system was lowered to 75°C, and 60.0 kg of styrene was added in one portion to complete the polymerization. Finally, all the polymerization active ends were deactivated with water to obtain a polymerization solution containing a styrene-butadiene copolymer having a polystyrene block and a tapered block of styrene and butadiene. This polymerization solution was devolatilized to obtain a pelletized styrene-butadiene block copolymer (SBC-1) using an extruder. The conjugated diene amount calculated from the monomer charge amount of the obtained SBC-1 was 29 mass%. When the melt flow rate of the obtained SBC-1 was measured according to the standard of JIS K 7210-2:2014 (ISO 1133-2:2011) under the conditions of 200°C and a load of 5 kg, it was 7 g / 10 min.

[0055] (Production Example 4: Preparation of styrene-butadiene block copolymer (SBC-2)) A styrene-butadiene block copolymer (SBC-2) was obtained in the same manner as in Production Example 3, except that the amount of 1,3-butadiene was 48 kg. The amount of conjugated dienes in the obtained SBC-2, calculated from the amount of monomer charged, was 24 mass%. The melt flow rate of the obtained SBC-2, measured under the same conditions as in Production Example 3, was 18 g / 10 min.

[0056] (C) Preparation of high-impact polystyrene (Production Example 5: Preparation of high impact polystyrene (HIPS-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 40°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 reactant was then extracted from the devolatilizer tank using a gear pump, passed through a die plate to form a strand, and then pelletized in a water tank to obtain high-impact polystyrene (HIPS-1). The rubber content (conjugated diene content) of the resulting HIPS-1, calculated from the amount of monomer charged, was 5% by mass.

[0057] (Production Example 6: Preparation of high impact polystyrene (HIPS-2) High impact polystyrene (HIPS-2) was obtained in the same manner as in Production Example 5, except that the rubber polymer was used in an amount of 10.6% by mass relative to the total mass of the polymerization raw materials. The rubber component content (conjugated diene component content) of the obtained HIPS-2 calculated from the charged amount of monomer was 10% by mass.

[0058] (Production Example 7: Preparation of high impact polystyrene (HIPS-3) High impact polystyrene (HIPS-3) was obtained in the same manner as in Production Example 5, except that the rubber polymer was used in an amount of 11.7% by mass relative to the total mass of the polymerization raw materials. The rubber component content (conjugated diene component content) of the obtained HIPS-3 calculated from the charged amount of monomer was 11% by mass.

[0059] [Additives] The additives used in the following examples and comparative examples are as follows: Ethylene bis(stearic acid amide) (EBS): Kao Wax "EB-FF" (Kao Corporation) Sodium fatty acid: "Tankal MH" (Miyoshi Oil & Fats Co., Ltd.) Silicone oil: "KF-96 350CS" (Shin-Etsu Chemical Co., Ltd.)

[0060] [Example 1] GPPS-1 (25 parts by mass per 100 parts by mass of the total of eggshell powder and thermoplastic resin), SBC-1 (20 parts by mass per 100 parts by mass of the total of eggshell powder and thermoplastic resin), HIPS-1 (5 parts by mass per 100 parts by mass of the total of eggshell powder and thermoplastic resin), and eggshell powder (50 parts by mass per 100 parts by mass of the total of eggshell powder and thermoplastic resin, average particle size 30 μm) were melt-mixed with EBS (1 part by mass per 100 parts by mass of the total of eggshell powder and thermoplastic resin), sodium fatty acid (3 parts by mass per 100 parts by mass of the total of eggshell powder and thermoplastic resin), and silicone oil (0.5 parts by mass per 100 parts by mass of the total of eggshell powder and thermoplastic resin) using a twin-screw extruder (TEM35-B) at 200°C, 350 rpm, and a discharge rate of 20 kg / h. The mixture was extruded into strands and pelletized.

[0061] [Examples 2 to 9, Comparative Examples 2 to 7] Pellets were prepared in the same manner as in Example 1, except that the eggshell powder, (A) general-purpose polystyrene, (B) styrene-based thermoplastic elastomer, and (C) high-impact polystyrene shown in Table 1 were blended in the amounts shown in Table 1.

[0062] [Comparative Example 1] Eggshell powder, (A) general-purpose polystyrene, (B) styrene-based thermoplastic elastomer, and (C) high-impact polystyrene were blended in the amounts shown in Table 1, and an attempt was made to pelletize them in the same manner as in Example 1. However, some of the eggshell powder adhered to the surface of the resin, making it impossible to fill it into the resin.

[0063] [Measurement and Evaluation] The following items were measured and evaluated, and the results are shown in Table 1. (Melt flow rate: MFR) The MFR of the pellets obtained in the examples and comparative examples was measured at 200°C under a load of 5 kg in accordance with the standard JIS K 7210-2:2014 (ISO 1133-2:2011). The fluidity was evaluated according to the following evaluation criteria. A rating of B or higher is considered to be excellent in fluidity. (Evaluation criteria) A: MFR is 20g / 10min or more B: MFR is 15g / 10min or more and less than 20g / 10min C: MFR is less than 15g / 10min or cannot be measured

[0064] (Charpy impact strength) The pellets obtained in the examples and comparative examples were each molded into a type A dumbbell-shaped tensile test piece using an injection molding machine (JSW-140AD) at a cylinder temperature of 220°C to obtain a test piece. Using this test piece, the Charpy impact strength was measured in accordance with JIS K 7111-1:2012. The strength was evaluated according to the following evaluation criteria. A rating of B or higher was considered to be excellent in strength. A: Charpy impact strength is 10kJ / m 2 End B: Charpy impact strength is 5kJ / m 2 More than 10kJ / m 2 less than C: Charpy impact strength is 5kJ / m 2 Less than or not measurable In Table 1, "impossible to measure" in Comparative Example 3 means that the molded article was too soft to stand on its own and the Charpy impact strength test could not be carried out.

[0065] (comprehensive evaluation) A comprehensive evaluation was carried out according to the following evaluation criteria: A rating of B or higher was judged to have achieved both excellent fluidity and excellent molded product strength. A: Both MFR and Charpy impact strength are evaluated as A B: The lower of MFR and Charpy impact strength is rated B. C: The lower of MFR and Charpy impact strength is C

[0066] [Table 1]

[0067] As shown in Table 1, the resin compositions of Examples 1 to 9, which contain a predetermined amount of eggshell powder and at least (A) general-purpose polystyrene having a weight-average molecular weight of 300,000 or less, (B) a styrene-based thermoplastic elastomer, and (C) a thermoplastic resin containing high-impact polystyrene, all have an MFR of 15 g / 10 min or more at 200°C under a 5 kg load, and have excellent fluidity at low temperatures. All have a Charpy impact strength of 5 kJ / m 2 As a result, the molded product has excellent strength. In contrast, the resin compositions of Comparative Examples 2 to 7 do not contain at least one of (A) general-purpose polystyrene having a weight-average molecular weight of 300,000 or less, (B) a styrene-based thermoplastic elastomer, and (C) high-impact polystyrene as the thermoplastic resin, and therefore are unable to achieve both excellent fluidity and excellent molded product strength.The resin composition of Comparative Example 1 contains more than 75 mass% of eggshell powder relative to the total mass of the resin composition, and some of the eggshell powder adhered to the surface of the resin, making it impossible to fill the entire amount of eggshell powder into the resin (kneading was not possible). [Industrial Applicability]

[0068] The resin composition according to this embodiment has excellent fluidity and excellent molded product strength, and therefore has industrial applicability as parts for home appliances, interior materials for automobiles, building materials, food containers, toys, stationery, furniture, containers, gardening materials, and the like.

Claims

1. Eggshell powder and (A) a general-purpose polystyrene having a weight-average molecular weight of 300,000 or less; (B) a styrene-based thermoplastic elastomer, and (C) High-impact polystyrene a thermoplastic resin comprising Including, the content of the eggshell powder is 5 to 75% by mass based on the total mass of the eggshell powder and the thermoplastic resin, The thermoplastic resin is, relative to the total mass of (A) general-purpose polystyrene having a weight average molecular weight of 300,000 or less, (B) a styrene-based thermoplastic elastomer, and (C) high-impact polystyrene, (B) containing 5 to 44 mass% of a styrene-based thermoplastic elastomer; Resin composition.

2. The thermoplastic resin is, relative to the total mass of (A) general-purpose polystyrene having a weight average molecular weight of 300,000 or less, (B) a styrene-based thermoplastic elastomer, and (C) high-impact polystyrene, (A) 30 to 90% by mass of general-purpose polystyrene having a weight-average molecular weight of 300,000 or less, and (C) 5 to 30% by mass of high-impact polystyrene The resin composition according to claim 1 , comprising:

3. The resin composition according to claim 1 or 2, wherein the eggshell powder has an average particle size of 2 to 70 μm.

4. 3. The resin composition according to claim 1, wherein the styrene-based thermoplastic elastomer (B) comprises a styrene-butadiene block copolymer.

5. (B) the styrene-based thermoplastic elastomer and (C) the high-impact polystyrene contain a conjugated diene component, 3. The resin composition according to claim 1, wherein the content of the conjugated diene component in the resin composition is 15% by mass or less with respect to the total mass of the eggshell powder and the thermoplastic resin.

6. The resin composition according to claim 1 or 2, wherein the resin composition has a melt flow rate of 15 g / 10 min or more at 200° C. under a load of 5 kg.

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.

Images