Styrenic resin composition and molded article thereof

Abstract

To provide a styrene-based resin composition which reduces the environmental load by using a biomass raw material, and reduces die contamination during injection molding, but yet has excellent mechanical strength, the styrene-based resin composition exhibiting high fluidity, and a molded product thereof.SOLUTION: The present disclosure discloses a styrene-based resin composition which contains a styrene-based polymer (A) and a biomass plasticizer (B) of more than 5 mass% to 15 mass% or less, with a biomass carbon ratio (pMC%) of 10% or more. A plate of 2 mm thick including the styrene-based resin composition has a total light transmittance of 70% or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a styrene-based resin composition and a molded article made of the styrene-based resin. [Background technology]

[0002] Styrene-based resins are used for a wide range of purposes due to their moldability and mechanical strength. Styrene-based resins in particular have a high level of transparency and are used in a wide range of applications, including miscellaneous goods, transparent food containers, packaging materials, and office equipment. In addition, biomass raw materials have been attracting attention from the viewpoint of reducing the environmental load, and the development of composite materials of styrene-based resins and naturally derived raw materials is being promoted. For example, Patent Document 1 discloses a styrene-based resin composition containing rubber-modified polystyrene, polylactic acid, and a thermoplastic elastomer containing a styrene monomer unit. In addition, Patent Document 2 discloses a styrene-based resin composition containing plant-derived polyethylene and a compatibilizer.

[0003] In the field of styrene resins, particularly in the field of injection molding applications, resins exhibiting high fluidity have been required as materials in recent years in order to reduce the residual strain that occurs in molded products during cooling after injection molding. It is known that mechanical strength improves when residual strain is reduced, so that mechanical strength can be expected to improve by increasing the fluidity of resins. In general, a large amount of liquid paraffin is used as a plasticizer to increase the fluidity of resins. For example, Patent Document 3 discloses a method for producing a rubber-modified styrene resin that has an excellent balance between surface impact resistance, rigidity, and fluidity. On the other hand, as a technique for increasing the fluidity of resins by other methods, for example, Patent Document 4 discloses a method for producing a styrene resin with high fluidity and low mold adhesion by adjusting the molecular weight or molecular weight distribution without adding liquid paraffin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-199652 A [Patent Document 2] JP 2020-193274 A [Patent Document 3] Japanese Patent Application Publication No. 10-251355 [Patent Document 4] JP 2017-222770 A Summary of the Invention [Problem to be solved by the invention]

[0005] The technology of the above Patent Document 1 considers a polymer alloy of polylactic acid, which has a relatively high melting point and toughness among plant-derived biodegradable polymers, and a styrene-based resin, but since the compatibility of polylactic acid with styrene-based resins is very low, there is a problem that it is difficult to design a product that satisfies the mechanical properties required in the market, such as impact resistance or elasticity. In addition, since polylactic acid is incompatible with styrene-based resins, the transparency of the polymer alloy as a whole is impaired. Furthermore, there is also a problem that it is difficult to recycle waste materials containing polylactic acid and styrene-based resins.

[0006] The technology of Patent Document 2 above studies a polystyrene-based resin containing plant-derived polyethylene and a compatibilizer. However, since polystyrene and polyethylene have low compatibility, it is difficult to maintain high transparency even when a compatibilizer is used.

[0007] The technology of the above-mentioned Patent Document 3 is a method for producing a rubber-modified styrene-based resin with an excellent balance of surface impact resistance, rigidity, and fluidity, but since a large amount of liquid paraffin is used, low boiling point components volatilize during injection molding, resulting in a large amount of volatile components during molding, which results in new problems such as mold contamination during molding or contamination of molded products. In the technology of the above-mentioned Patent Document 4, a styrene-based resin with high fluidity and low adhesion of low molecular weight substances to the mold is considered, but since the molecular weight of the resin is low, it is difficult to design a product without reducing the Charpy impact strength or rigidity of the molded product. In addition, biomass raw materials, which have been attracting attention in recent years for the purpose of reducing the environmental load, are not used. For this reason, the techniques of the above Patent Documents 1 to 4 do not consider highly transparent resins that exhibit high fluidity, high mechanical strength, and reduced mold fouling. Therefore, an object of the present disclosure is to provide a styrene-based resin composition and a molded article thereof that use biomass raw materials to reduce the environmental load, cause less mold contamination during injection molding, and have high fluidity and high mechanical strength and are highly transparent. [Means for solving the problem]

[0008] In view of the above problems, the present inventors have conducted intensive research and repeated experiments, and as a result, have found that the above problems can be solved by using a styrene-based resin composition containing a styrene-based polymer (A) and a predetermined amount of a biomass plasticizer (B) having a high boiling point and a biomass carbon ratio (pMC%) of 10% or more, and have completed the present inventions [1] to [6] below. [1] A styrene-based resin composition comprising: a styrene-based polymer (A); and a biomass plasticizer (B) having a biomass carbon ratio (pMC%) of 10% or more and a weight ratio of more than 5% by mass and not more than 15% by mass, the weight ratio being 10% or more. The total light transmittance of a 2 mm-thick plate is 70% or more. [2] The styrene-based resin composition according to [1], wherein the SP value of the biomass plasticizer (B) is 7.0 to 11.0. [3] The styrene-based resin composition according to [1] or [2], wherein the styrene-based resin composition has a toluene-insoluble content of 3% or less. [4] The styrene-based resin composition according to any one of [1] to [3], wherein the styrene-based polymer (A) is contained in an amount of 85 to 94.9 mass% based on the entire styrene-based resin composition, and the content of styrene-based monomer units in the styrene-based polymer (A) based on the total amount of the styrene-based polymer (A) is 80 mass% or more. [5] The styrene-based resin composition according to any one of [1] to [4], wherein the styrene-based resin composition (A) contains one or more types selected from the group consisting of liquid paraffin and fatty acid-based compounds as the biomass plasticizer (B) having a biomass carbon ratio (pMC%) of 10% or more. [6] The styrene-based resin composition according to any one of [1] to [5], wherein the styrene-based resin composition (A) contains 0.001 ppm to 10 ppm of a bluing agent. [7] A molded article obtained by injection molding the styrene-based resin composition according to any one of [1] to [6]. Effect of the Invention

[0009] According to the present invention, it is possible to provide a transparent styrene-based resin composition which reduces the environmental load, causes less mold contamination during molding, and has high fluidity and high mechanical strength, and a molded article made of the styrene-based resin composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The following describes in detail an embodiment of the present invention (hereinafter referred to as the "present embodiment"); however, the present invention is not limited to the following description and can be implemented in various modified forms within the scope of its gist.

[0011] [Styrene-based resin composition] The styrene-based resin composition of the present embodiment contains a styrene-based polymer (A) and more than 5 mass % and not more than 15 mass % of a biomass plasticizer (B) having a biomass carbon ratio (pMC ratio) of 10% or more. In other words, the styrene-based resin composition of the present embodiment contains more than 5 mass % and 15 mass % or less of the styrene-based polymer (A) and the biomass plasticizer (B) relative to the entire styrene-based resin composition (100 mass %). A 2 mm thick plate obtained from the styrene-based resin composition has a total light transmittance of 70% or more. This makes it possible to provide a transparent styrene-based resin composition which reduces the environmental load, has high flowability and high mechanical strength, and causes little mold contamination during injection molding.

[0012] <Styrene-Based Polymer (A) (hereinafter also referred to as Component (A))> The styrene-based resin composition in this embodiment contains a styrene-based polymer (A). In this embodiment, the content of the styrene-based polymer (A) is preferably 85.0 to 95.0 mass%, more preferably 86.0 to 94.5 mass%, and further more preferably 87.0 to 94.0 mass%, based on the entire styrene-based resin composition (100 mass%).

[0013] In this embodiment, the monomer constituting the styrene-based polymer (A) essentially contains a styrene-based monomer (a), and may contain a vinyl-based monomer (b) copolymerizable with the styrene-based monomer (a) as necessary. Among the monomers constituting the styrene polymer (A), the content of the styrene monomer (a) is preferably 50 to 100 mass%, more preferably 60 to 100 mass%, further preferably 70 to 100 mass%, further more preferably 80 to 100 mass%, and further more preferably 90 to 100 mass%. The content of the styrene monomer (a), i.e., the content of the styrene monomer unit (a), can be measured by proton nuclear magnetic resonance ( 1 It can be calculated from the integral ratio of the spectrum measured by a H-NMR spectrometer. 1 When quantification is difficult using H-NMR measurement, quantification is performed using infrared spectroscopy (FTIR). Examples of the styrene monomer (a) include, in addition to styrene, α-methylstyrene, α-methyl p-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene, and t-butylstyrene, or styrene derivatives such as bromostyrene and indene. Styrene is particularly preferred. These styrene monomers can be used alone or in combination.

[0014] In the present embodiment, the vinyl monomer (b) is not particularly limited, but examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, etc. These unsaturated carboxylate ester monomers may be used alone or in combination of two or more.

[0015] In this embodiment, polystyrene is a homopolymer obtained by polymerizing a styrene-based monomer (a), and generally available ones can be appropriately selected and used. In addition to styrene, the styrene-based monomer (a) constituting polystyrene includes α-methylstyrene, α-methyl-p-methylstyrene, ο-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene, and t-butylstyrene, or styrene derivatives such as bromostyrene and indene. Styrene is particularly preferred from an industrial viewpoint. One or more of these styrene-based monomers (a) can be used. Polystyrene typically consists of styrene-based monomer (a) units, although it is not excluded that the polystyrene further contains monomer units other than the above-mentioned styrene-based monomer (a) units within a range that does not impair the effects of the present invention. In the present embodiment, the styrene polymer (A) is preferably prepared by controlling the SP value between the styrene polymer (A) and the biomass plasticizer (B) having a biomass carbon ratio (pMC ratio) of 10% or more so as to be within a predetermined range. Therefore, for example, the type of monomer unit constituting the styrene polymer (A), the content of the styrene monomer (a), or the content of the vinyl monomer (b) may be adjusted depending on the SP value of the biomass plasticizer (B) used. This allows the biomass plasticizer (B) to be dispersed more uniformly in the composition, thereby further improving the mechanical strength.

[0016] In this embodiment, the weight average molecular weight (Mw) of the styrene-based polymer (A) is preferably 100,000 to 400,000, more preferably 120,000 to 350,000, and even more preferably 140,000 to 300,000. When the weight average molecular weight (Mw) is 100,000 to 400,000, a resin having a better balance between mechanical strength and fluidity is obtained, and the amount of gel contamination is small. The weight average molecular weight (Mw) is a value obtained by using gel permeation chromatography and converting it into a standard polystyrene equivalent. In addition, the styrene-based polymer (A) in this embodiment preferably contains less than 1.0 mass% of a rubber-like polymer (e.g., polybutadiene, polybutadiene containing polystyrene, polyisoprene, natural rubber, polychloroprene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer) or a structural unit having a conjugated diene structure, relative to the total amount (100 mass%) of the styrene-based polymer (A).

[0017] In this embodiment, it is preferable that the styrene polymer (A) or the styrene resin composition of this embodiment does not substantially contain a vinyl cyanide monomer such as an acrylonitrile monomer unit or a methacrylonitrile monomer unit. Specifically, the vinyl cyanide monomer is preferably contained in an amount of 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less, based on the total amount of the vinyl monomer (b).

[0018] In this embodiment, the polymerization method of the styrene-based polymer (A) is not particularly limited, but for example, a bulk polymerization method or a solution polymerization method can be suitably adopted as a radical polymerization method. The polymerization method mainly includes a polymerization step of polymerizing the polymerization raw materials (monomer components) and a devolatilization step of removing volatile matters such as unreacted monomers and polymerization solvent from the polymerization product.

[0019] Hereinafter, an example of a method for polymerizing the styrene-based polymer (A) that can be used in the present embodiment will be described. When the polymerization raw materials are polymerized to obtain the styrene-based polymer (A), a polymerization initiator and a chain transfer agent are typically contained in the polymerization raw material composition. Examples of the polymerization initiator used in the polymerization of the styrene-based polymer (A) include organic peroxides, for example, peroxyketals such as 1,1-bis(t-butylperoxy)cyclohexane (Perhexa C), 2,2-bis(t-butylperoxy)butane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane (Pertetra A), and n-butyl-4,4-bis(t-butylperoxy)valerate, dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, and dicumyl peroxide, diacyl peroxides such as acetyl peroxide and isobutyryl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxyesters such as t-butyl peroxyacetate, ketone peroxides such as acetylacetone peroxide, and hydroperoxides such as t-butyl hydroperoxide. From the viewpoints of decomposition rate and polymerization rate, 1,1-bis(t-butylperoxy)cyclohexane is particularly preferred. It is preferably added in an amount of 0.005 to 0.08% by mass based on the total amount of monomers. Examples of the chain transfer agent used in the polymerization of the styrene-based polymer (A) include mercaptans such as α-methylstyrene linear dimer, n-dodecyl mercaptan, t-dodecyl mercaptan, 1-phenyl-2-fluorene, dipentene, and chloroform, terpenes, halogen compounds, terpenes such as terpinolene, etc. The amount of the chain transfer agent used is not particularly limited, but it is generally preferable to add about 0.005 to 0.3% by weight based on the monomer.

[0020] As a polymerization method for the styrene-based polymer (A), solution polymerization using a polymerization solvent can be adopted as necessary. Examples of the polymerization solvent used include aromatic hydrocarbons, such as ethylbenzene, and dialkyl ketones, such as methyl ethyl ketone, and each of them may be used alone or in combination of two or more. Other polymerization solvents, such as aliphatic hydrocarbons, can be further mixed with aromatic hydrocarbons as long as the solubility of the polymerization product is not reduced. These polymerization solvents are preferably used in an amount not exceeding 25 parts by mass relative to 100 parts by mass of the total monomers. If the amount of the polymerization solvent exceeds 25 parts by mass relative to 100 parts by mass of the total monomers, the polymerization rate is significantly reduced and the mechanical strength of the resin obtained tends to be significantly reduced. It is preferable to add the polymerization solvent at a ratio of 5 to 20 parts by mass relative to 100 parts by mass of the total monomers before polymerization, as this makes it easier to uniformize the quality and is also preferable in terms of controlling the polymerization temperature.

[0021] In this embodiment, the apparatus used in the polymerization step for obtaining the styrene-based polymer (A) is not particularly limited, and may be appropriately selected according to the polymerization method of the styrene-based resin. For example, when bulk polymerization is adopted, a polymerization apparatus having one or more completely mixed reactors connected thereto can be used. There is also no particular limit to the devolatilization step. For example, when bulk polymerization is adopted, polymerization is continued until the unreacted monomer is finally reduced to preferably 50% by mass or less, more preferably 40% by mass or less, and devolatilization treatment is performed by a known method in order to remove volatile matters such as the unreacted monomer. More specifically, for example, a normal devolatilization apparatus such as a flash drum, a twin-screw devolatilizer, a thin film evaporator, an extruder, etc. can be used, but a devolatilization apparatus with a small retention portion is preferred. The temperature of the devolatilization treatment is usually about 190 to 280°C, more preferably 190 to 260°C. The pressure of the devolatilization treatment is usually about 0.13 to 4.0 kPa, preferably 0.13 to 3.0 kPa, more preferably 0.13 to 2.0 kPa. As a method for removing volatile matters, for example, a method of removing volatile matters by reducing pressure under heating, or a method of removing volatile matters through an extruder or the like designed for the purpose of removing volatile matters is preferable.

[0022] <Biomass plasticizer (B) (hereinafter also referred to as component (B))> The styrene-based resin composition in this embodiment contains a biomass plasticizer (B). The biomass plasticizer (B) has a biomass carbon ratio (pMC%) of 10% or more. If the biomass carbon ratio (pMC%) is within the above range, the amount of fossil fuel used can be reduced, and therefore a styrene-based resin composition that can reduce the environmental load can be provided. In this embodiment, the lower limit of the biomass carbon ratio (pMC%) is preferably 10% or more, more preferably 25% or more, even more preferably 50% or more, and even more preferably 75% or more. In this embodiment, the content of the biomass plasticizer (B) is more than 5% by mass and not more than 15% by mass relative to the total amount (100% by mass) of the styrene-based resin composition. The lower limit of the content of the biomass plasticizer (B) is more than 5.0% by mass, preferably 5.3% by mass or more, more preferably 5.5% by mass or more, even more preferably 5.8% by mass or more, even more preferably 6.0% by mass or more, even more preferably 6.3% by mass or more, even more preferably 6.5% by mass or more. The upper limit of the content of the biomass plasticizer (B) is 15% by mass or less, preferably 14% by mass or less, more preferably 13% by mass or less. On the other hand, if the content of the biomass plasticizer (B) is too small, the fluidity decreases, so that short shots tend to occur during injection molding, and the injection moldability decreases. In particular, in a molded body having a complex shape or a molded body having a thin wall portion, the higher the content of the biomass plasticizer (B), the less likely the short shots are to occur, and the better the injection moldability. If the content of the biomass plasticizer (B) is too high, the amount of volatile components increases, resulting in increased mold fouling. The biomass plasticizer (B) is preferably uniformly dispersed in the styrene-based resin composition. More specifically, it is preferably not an external lubricant (e.g., a lubricant insoluble in a polymer melt) that forms a monolayer of the biomass plasticizer (B) on the surface of the styrene-based resin composition. Examples of a method for uniformly dispersing the biomass plasticizer (B) in the styrene-based resin composition include a method of kneading the styrene-based polymer (A) and the biomass plasticizer (B) in an extruder, and a method of including the biomass plasticizer (B) in the polymerization raw material composition when polymerizing the polymerization raw material.

[0023] In this specification, the biomass carbon ratio (pMC%) refers to the carbon concentration (mass ratio) of biomass-derived components. More specifically, it refers to the radiocarbon ( 14 C) Obtained by the measurement method 14 The value of the radioactive carbon ( 14 C) The measurement method is as follows: 14 C, and biomass (or biological) carbon is the same as the atmospheric carbon at the time of growth. 14 By utilizing the carbon absorption of biomass materials (or living organisms), 14 This is a method to estimate the biomass carbon ratio (pMC%) from the C ratio. Therefore, the C contained in the total carbon atoms in the plasticizer of this embodiment 14 By measuring the ratio of carbon derived from biomass, the ratio of carbon derived from biomass can be calculated. In the present invention, the biomass carbon ratio (pMC%) is calculated by the following formula (1) using the method described in the Examples section below. Formula (1): Biomass carbon ratio (pMC%) = ( 14 C Plasticizer / 12 C plasticizer) / ( 14 C standard material / 12 C standard material)×100 In addition, oxalic acid (SRM4990) was used as the standard substance, and the AMS method was used to measure 14 C Plasticizer / 12 C plasticizer) / ( 14 C standard material / 12C standard material) was calculated.

[0024] The weight average molecular weight (Mw) of the biomass plasticizer of this embodiment is preferably 200 to 7500, more preferably 300 to 5000, and further preferably 400 to 3000. When the weight average molecular weight (Mw) of the biomass plasticizer is 200 to 7500, a styrene-based resin composition having a better balance between mechanical strength and fluidity is obtained, and the amount of gel contamination is small. The weight average molecular weight (Mw) is a value obtained by using gel permeation chromatography and converting it into standard polystyrene, as described in the Examples section below.

[0025] The biomass plasticizer in this embodiment refers to a plasticizer that uses a biomass material as part or all of the raw material, and refers to a plasticizer with a biomass carbon ratio (pMC%) of 10% or more. The biomass plasticizer in this embodiment uses a plant-derived biomass material as at least part of the raw material and has a biomass carbon ratio (pMC%) of 10% or more, and is preferably a vegetable oil, a mixture of vegetable oil and mineral oil, or a polyester-based plasticizer, and more preferably a natural vegetable oil, a modified vegetable oil, a mixture of natural vegetable oil and mineral oil, a mixture of modified vegetable oil and mineral oil, a mixture of natural vegetable oil, modified vegetable oil and mineral oil, or a polyester-based plasticizer. In this specification, vegetable oil is a general term for oils and fats derived from plants, and includes natural vegetable oils and modified vegetable oils.

[0026] In this embodiment, the biomass plasticizer may be modified vegetable oil. The modified vegetable oil refers to a compound made from vegetable oil, and more specifically, a part of a hydrocarbon oil of plant origin is modified with a functional group, and the vegetable oil is preferably modified with an epoxy group, an amino group, or an ester bond. The vegetable oil includes a triester of glycerin and a fatty acid, a fatty acid monoester obtained by adding a monoalcohol to a vegetable oil and subjecting it to an ester exchange reaction, a fatty acid monoester obtained by subjecting a fatty acid to an esterification reaction with a monoalcohol, and an ether derived from a fatty acid. In the present embodiment, it is preferable that the modified group (epoxy group, amino group, or ester bond functional group) of the modified vegetable oil does not substantially polymerize with other components (including the styrene resin (A)) or with the modified vegetable oil itself in the styrene resin composition. In addition, in the present embodiment, it is preferable that the modification rate of the modified vegetable oil per 1 g of the modified vegetable oil is 1 mmol% to 50 mmol%. The modification rate of the modified vegetable oil is as described in the Examples below. 1 Calculated by H-NMR measurement.

[0027] Specific examples of the natural vegetable oil include cottonseed oil, tung oil, shea oil, alfalfa oil, poppy seed oil, pumpkin oil, winter squash oil, millet oil, barley oil, quinoa oil, rye oil, kukui oil, passionflower oil, shea butter, aloe vera oil, sweet almond oil, peach kernel oil, soybean oil, cashew oil, peanut oil, avocado oil, baobab oil, borage oil, broccoli oil, calendula oil, camellia oil, canola oil, carrot oil, safflower oil, and linseed oil. Included are hemp oil, rapeseed oil, cottonseed oil, coconut oil, pumpkin seed oil, wheat germ oil, jojoba oil, lily oil, macadamia oil, corn oil, medfoam oil, monoi oil, hazelnut oil, apricot kernel oil, walnut oil, olive oil, evening primrose oil, palm oil, blackcurrant seed oil, kiwi seed oil, grapeseed oil, pistachio oil, musk rose oil, sesame oil, soybean oil, sunflower oil, castor oil, watermelon oil or mixtures of these oils. In this embodiment, the modified vegetable oil may be an oil obtained by hydrogenating the above-listed natural vegetable oils (e.g., hydrogenated castor oil); an oil obtained by epoxidizing the above-listed natural vegetable oils (e.g., modified epoxidized oil); or an oil obtained by amminating the above-listed natural vegetable oils (e.g., modified aminated oil). The modified epoxidized oil includes oils in which the epoxy functional group is ring-opened, such as hydroxylated modified soybean oil, oils that have been directly hydroxylated in advance, and cashew oil-based polyols.

[0028] Specific examples of the biomass plasticizer (B) of this embodiment include palm oil, epoxidized soybean oil, epoxidized linseed oil, polyoxyethylated castor oil, polyoxyethylated hardened castor oil, oleic acid ester, or lauric acid ester, and examples thereof include "Polysizer W-1810-BIO" and "Epo-cizer" manufactured by DIC Corporation; "Newsizer 510R" and "Newsizer 512" manufactured by NOF Corporation; "Pionin D Series" manufactured by Takemoto Oil Co., Ltd.; and "Multi-Ace 20 (S)" and "Refined Palm Oil (S)" manufactured by Nisshin Oillio Group, Ltd.

[0029] In this embodiment, the viscosity of the vegetable oil (including natural vegetable oil and modified vegetable oil) at 50° C. is preferably 1000 mPa·s or less, more preferably 10 to 1000 mPa·s, and even more preferably 20 to 800 mPa·s.

[0030] The melting point of the biomass plasticizer (B) in this embodiment is preferably -30 to 80°C, more preferably -25 to 77°C, even more preferably -22°C to 74°C, even more preferably -18°C to 70°C, even more preferably -15°C to 67°C, even more preferably -10°C to 64°C, even more preferably -8°C to 61°C, and particularly preferably -3°C to 58°C. When the melting point of the biomass plasticizer (B) is in the range of -30 to 80°C, the compatibility with the polymer matrix phase of the rubber-modified styrene-based resin (A) is further improved, and the biomass plasticizer (B) is easily dispersed in the styrene-based resin composition. In addition, when the melting point of the biomass plasticizer (B) is lower than -30°C, the amount of volatile components increases, and mold fouling tends to increase. When the melting point of the biomass plasticizer (B) is higher than 80°C, it is difficult to melt, making it difficult to add the biomass plasticizer (B).

[0031] In this embodiment, the SP value of the styrene-based polymer (A) and the SP value of the biomass plasticizer (B) ((cal / cm 3 ) 1 / 2) is preferably less than ±2.5, more preferably less than ±2.3, even more preferably less than ±2.0, even more preferably less than ±1.8, even more preferably less than ±1.5, even more preferably less than ±1.3, and particularly preferably less than ±1.0. If the difference between the SP value of the styrene-based polymer (A) and the SP value of the biomass plasticizer (B) is ±2.5 or more, the two become difficult to be compatible with each other. As a result, the biomass plasticizer (B) becomes difficult to disperse uniformly in the styrene-based resin composition, and the mechanical strength of the entire styrene-based resin composition and the total light transmittance of the molded product tend to decrease. One preferred aspect of the present embodiment is a composition comprising a styrene-based polymer (A) and a biomass plasticizer (B), and the SP value of the styrene-based polymer (A) and the SP value of the biomass plasticizer (B) ((cal / cm 3 ) 1 / 2 ) is less than ±2.5, and the total light transmittance of a 2 mm thick plate is 70% or more. The SP value of the styrene polymer (A) in this embodiment is 7 to 11 (cal / cm 3 ) 1 / 2 ), and more preferably 7.5 to 10 ((cal / cm 3 ) 1 / 2 ), and more preferably 8.0 to 9.5 ((cal / cm 3 ) 1 / 2 ), and even more preferably 8.0 to 9.0 ((cal / cm 3 ) 1 / 2 ). In addition, the SP value of the biomass plasticizer (B) in this embodiment is 7.0 to 11.0 ((cal / cm 3 ) 1 / 2 ), and more preferably 7.5 to 10.0 ((cal / cm 3 ) 1 / 2 ), and even more preferably 7.7 to 9.5 ((cal / cm 3 ) 1 / 2 ), and even more preferably 7.9 to 9.0 ((cal / cm 3 ) 1 / 2 ). The solubility parameter (SP value) specified in this embodiment is calculated using the cohesive energy density function shown in the following formula. SP value ((cal / cm 3 ) 1 / 2 )=(△E / V) 1 / 2 Formula (1) (△E is the intermolecular cohesive energy (heat of vaporization), V is the total volume of the mixture, and △E / V is the cohesive energy density.) In addition, the change in heat quantity due to mixing, ΔHm, is expressed by the following formula using the SP value. △Hm=V(δ1-δ2) · Φ1 · Φ2 ··· Formula (2) (δ1 indicates the SP value of the solvent, δ2 indicates the SP value of the solute, Φ1 indicates the volume fraction of the solvent, and Φ2 indicates the volume fraction of the solute.) According to the above equations (1) and (2), the closer the values ​​of δ1 and δ2 are, the smaller ΔHm becomes and the smaller the Gibbs free energy becomes, so that molecules with a small difference in SP values ​​have a higher affinity with each other. In this specification, the SP value is calculated by comparing the solubility of the resin with various solvents with known SP values, and calculating the SP value of the unknown resin from the SP value of the most compatible solvent, specifically, by using a turbidimetric titration method. In this embodiment, the value calculated by calculation from the monomer composition is mainly used.

[0032] The toluene insoluble content of the styrene resin composition is preferably less than 3% by mass, more preferably less than 1% by mass. The toluene insoluble content is measured by the method described in the Examples section below.

[0033] In this embodiment, examples of mineral oils include atmospheric residual oils obtained by atmospheric distillation of crude oils such as paraffinic crude oil (including liquid paraffin), intermediate base crude oil, and naphthenic crude oil; distillate oils obtained by vacuum distillation of these atmospheric residual oils; mineral oils obtained by subjecting the distillate oils to one or more refining processes such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining; and mineral oils obtained by isomerizing wax (GTL wax) produced by the Fischer-Tropsch process or the like. These mineral oils may be used alone or in combination of two or more kinds. In this embodiment, when a mixture of vegetable oil and mineral oil is used as the biomass plasticizer (B), there is no particular limitation as long as the biomass carbon ratio (pMC ratio) of the entire biomass plasticizer (B) is 10% or more. For example, it is preferable to mix 10 to 100 parts by mass, and more preferably 10 to 50 parts by mass, per 100 parts by mass of vegetable oil. The amount of mineral oil added is preferably 0.01% by mass to 5.0% by mass, more preferably 0.01% by mass to 4.5% by mass, even more preferably 0.01% by mass to 4.0% by mass, even more preferably 0.01% by mass to 3.5% by mass, even more preferably 0.01% by mass to 3.0% by mass, even more preferably 0.01% by mass to 2.5% by mass, even more preferably 0.01% by mass to 2.0% by mass, even more preferably 0.01% by mass to 1.5% by mass, even more preferably 0.01% by mass to 1.0% by mass, and even more preferably 0.01 to 0.5% by mass, relative to the total amount (100% by mass) of the styrene-based resin composition.

[0034] In this embodiment, preferred aspects of the biomass plasticizer (B) having a biomass carbon ratio (pMC%) of 10% or more include one or more types of vegetable oil alone; or a mixed oil containing one or more types of vegetable oil and one or more types selected from the group consisting of liquid paraffin and fatty acid compounds. When the mixed oil is used as the biomass plasticizer (B), it is preferable that the mixed oil contains vegetable oil and 0.01% to 3.0% by mass of liquid paraffin, or vegetable oil and 25 ppm to 5000 ppm of a fatty acid compound, or alternatively vegetable oil and 0.01% to 3.0% by mass of liquid paraffin and 25 ppm to 5000 ppm of a fatty acid compound. When the vegetable oil, liquid paraffin, and aliphatic compound are mixed in the above contents, a styrene-based resin composition having excellent flowability and mold release properties can be obtained. When the biomass plasticizer (B) is a mixed oil, the amount of each component contained in the biomass plasticizer (B) can be determined by the method described in the Examples section below. When the viewpoint of reducing the environmental load is emphasized, the biomass plasticizer (B) is preferably a single vegetable oil, which is one or more kinds of vegetable oil. On the other hand, when the viewpoint of color and fluidity of the molded body is particularly emphasized, the biomass plasticizer (B) is preferably a mixed oil of one or more kinds of vegetable oil and liquid paraffin. When the content of vegetable oil is increased, the color of the resin tends to become yellow, and it may be necessary to add a large amount of bluing agent to adjust the color, but since liquid paraffin is colorless and transparent, it is possible to improve the fluidity without affecting the color of the resin. In addition, when the viewpoint of releasability of the molded body is particularly emphasized, the biomass plasticizer (B) is preferably a mixed oil of one or more kinds of vegetable oil and a fatty acid compound.

[0035] In this embodiment, the styrene-based resin composition preferably contains a bluing agent. This allows the color tone to be adjusted. Since most biomass plasticizers (B) with a biomass carbon ratio (pMC%) of 10% or more are yellowish, the styrene-based resin composition of this embodiment containing more than 5% by mass of the biomass plasticizer (B) with a biomass carbon ratio (pMC%) of 10% or more tends to be yellowish. This makes it difficult to use the composition as a transparent material for food such as a lunch box lid or an optical material (e.g., a light guide plate). However, since the bluing agent allows the color tone to be adjusted, the effect of adjusting the color tone is particularly exhibited when the content of the biomass plasticizer (B) is in the range of more than 5% by mass.

[0036] The fatty acid compound may be a fatty acid compound or a fatty acid metal salt compound, etc. Specific examples include ethylene bis-stearamide, stearic acid, stearate, zinc bis-stearate, calcium stearate, magnesium stearate, etc. The amount of the fatty acid compound added is preferably 0.1 ppm to 15,000 ppm, more preferably 1 ppm to 10,000 ppm, even more preferably 5 ppm to 9,000 ppm, even more preferably 10 ppm to 8,000 ppm, even more preferably 15 ppm to 7,000 ppm, even more preferably 20 ppm to 6,000 ppm, and even more preferably 25 ppm to 5,000 ppm, relative to the total amount (100 mass%) of the styrene resin composition. When molding styrene resins by injection molding or extrusion molding, fatty acid compounds may be added. In particular, when moldings with complex shapes or thin-walled parts are to be obtained, it may be necessary to add a compound with releasability (fatty acid compounds or liquid paraffin) to prevent cracks or deformations in the molded product when it is released from the mold. The method of addition includes melt-kneading the compound with releasability into the resin, or sprinkling the compound with releasability in powder form on the resin pellets as an external lubricant. When added as an external lubricant, it also acts as a lubricant to reduce friction between the screw and the resin during molding or kneading, improving processability. Two or more types of compounds with releasability may be used in combination.

[0037] In this embodiment, it is preferable to add an anthraquinone-based compound as a bluing agent to adjust the color tone depending on the application. When the bluing agent has an anthraquinone skeleton, a hydrogen abstraction reaction by an excited carbonyl or electron transfer from anions occurs, making it easier to adjust the color tone (=yellowness is easier to suppress). Therefore, an anthraquinone-based compound having an electron-withdrawing group for the anthraquinone skeleton is particularly preferable. In this embodiment, by adding an anthraquinone-based compound as a bluing agent, a molded product having a color tone and appearance required for some applications can be obtained. For example, in applications such as food cutlery and toys where the color tone of the molded product is important, it is necessary to use a styrene-based resin composition with reduced yellowness of the resin. In this embodiment, the amount of the bluing agent added is preferably 0.001 ppm to 10 ppm, more preferably 0.01 ppm to 5.0 ppm, more preferably 0.03 ppm to 3.0 ppm, even more preferably 0.05 ppm to 2.5 ppm, even more preferably 0.08 ppm to 2.2 ppm, even more preferably 0.1 ppm to 2.0 ppm, and even more preferably 0.12 ppm to 1.8 ppm, relative to the total amount (100 mass%) of the styrene-based resin composition. If the amount is within the above range, it is possible to obtain a molded product with excellent appearance by suppressing the yellowness of the resin. Note that two or more kinds of bluing agents may be used in combination.

[0038] <Optional addition ingredients> In addition to the above components (A) and (B), the styrene-based resin composition of the present embodiment may contain optional components such as known additives and processing aids, as necessary, within the scope of not impairing the effects of the present invention. As these optional components, a release agent, a flame retardant, a dispersant, an antioxidant, a weathering agent, an antistatic agent, a filler, an antiblocking agent, a colorant, a surface treatment agent, an antibacterial agent, and an anti-eye discharge agent (an anti-eye discharge agent such as silicone oil described in JP 2009-120717 A, a monoamide compound of a higher aliphatic carboxylic acid, and a monoester compound obtained by reacting a higher aliphatic carboxylic acid with a monohydric to trihydric alcohol compound), etc. may be added. In this embodiment, the styrene-based resin composition may contain a known flame retardant (a phosphorus-based flame retardant, a halogen-based flame retardant such as a bromine-based flame retardant). However, from the viewpoint of the possibility of generating gas such as hydrogen bromide by reaction with the biomass plasticizer (B) contained in the styrene-based resin composition, the content of the halogen-based flame retardant is preferably less than 3 mass%, more preferably less than 1 mass%, based on the total amount (100 mass%) of the styrene-based resin composition.

[0039] It is preferable that the styrene-based resin composition in this embodiment does not contain any metal, except for unavoidable impurities. More specifically, the metal content is preferably less than 3 mass% and more preferably less than 1 mass% relative to the total amount (100 mass%) of the styrene-based resin composition. In this embodiment, the dispersant may be a fatty acid ester compound, a polyethylene glycol compound, a terpene compound, a rosin compound, a fatty acid amide, a fatty acid compound, or a fatty acid metal salt compound. Examples of the antioxidant include phenol-based compounds, phosphorus-based compounds, and thioether-based compounds. The total content of the above-mentioned optional added components may be 0.05 to 5% by mass based on the entire styrene-based resin composition.

[0040] The styrene-based resin composition of the present embodiment may consist essentially of only the component (A), the component (B), and any optional additional components, or may consist of only the components (A) and (B), or only the components (A), (B), and any optional additional components. The phrase "consisting essentially of only the component (A), the component (B), and any optional additional components" means that 95 to 100 mass% (preferably 98 to 100 mass%) of the total amount of the styrene-based resin composition is the component (A) and the component (B), or the component (A), the component (B), and any optional additional components. The styrene-based resin composition of the present embodiment may contain inevitable impurities in addition to the component (A), the component (B), and any optional additional components, as long as the effects of the present invention are not impaired.

[0041] When modified vegetable oil is used as the biomass plasticizer (B) contained in the styrene-based resin composition of this embodiment, the content of the hydroxyl group-containing compound is preferably less than 3 mass%, more preferably less than 1 mass%, relative to the total amount (100 mass%) of the styrene-based resin composition. The hydroxyl group-containing compound of this embodiment refers to a compound having a hydroxyl group in the polymer, such as (meth)acrylic acid, maleic acid, or phthalic acid. If the hydroxyl group-containing compound is 3 mass% or more, it reacts with the modified vegetable oil and gelation occurs, resulting in a decrease in moldability or a negative effect of deteriorating the appearance of the injection molded product. When natural vegetable oil is used as the biomass plasticizer contained in the styrene-based resin composition, the amount of the hydroxyl group-containing compound is not specified.

[0042] [Physical properties of styrene-based resin composition] <Total light transmittance (%)> The total light transmittance (%) of the styrene resin composition of this embodiment is 70% or more, preferably 75% or more, more preferably 80% or more, and even more preferably 85% or more. If the total light transmittance (%) of the styrene resin composition is 80% or more, for example, the content of rubber polymer particles contained in the styrene resin composition is 3% by mass or less based on the entire styrene resin composition, or the styrene resin composition can be used for transparent food containers, packaging materials, or office automation equipment applications that require transparency. The specific method of preparing the test specimen used to measure the total light transmittance (%) of the styrene resin composition complies with K7361-1, and it is confirmed that the test specimen has no defects such as scratches, bubbles, bumps, adhesion of dirt and grease, and adhesion of adhesives from protective materials. In addition, the surface of the test specimen is free of voids and particles visible to the naked eye. When preparing the test specimen by injection molding, if necessary depending on the condition of the surface of the mold used, it may be polished to a mirror finish using abrasive paper, a stick grindstone, loose abrasive grains, etc. The method for measuring the total light transmittance (%) in the present disclosure and the method for preparing a test piece used in the method for measuring the total light transmittance (%) are as described in the Examples section below. <Melt Mass Flow Rate (MFR)> The melt mass flow rate (measured under conditions of 200°C and 49N load) of the styrene-based resin composition of this embodiment is 3.0 to 60 (g / 10 min), preferably 3.5 to 50 (g / 10 min), more preferably 4.0 to 40 (g / 10 min), and even more preferably 4.5 to 35 (g / 10 min). If the MFR of the styrene-based resin composition is lower than 3.0, the fluidity decreases, short shots tend to occur during injection molding, and injection moldability decreases. In order to increase the MFR of the styrene-based resin composition to more than 60, a large amount of plasticizer is required, which increases the amount of volatile components during injection molding, and there is a risk of mold fouling becoming worse. In the present disclosure, the melt mass flow rate was measured in accordance with ISO 1133. When the melt mass flow rate of the styrene-based resin composition of the present embodiment is within the above range, the fluidity of the entire composition can be maintained at a high level, thereby reducing mold contamination during molding. <Vicat softening temperature> The Vicat softening temperature of the styrene-based resin composition of this embodiment is preferably 50°C to 105°C, more preferably 60°C to 95°C, and further preferably 65°C to 90°C. If the Vicat softening temperature of the styrene-based resin composition is high, the flowability decreases, and short shots tend to occur during injection molding, resulting in a decrease in injection moldability. In addition, if the Vicat softening temperature of the styrene-based resin composition is low, the amount of plasticizer increases, which may cause mold fouling to worsen. In this disclosure, the Vicat softening temperature (°C) was measured in accordance with ISO 306 under a load of 49N.

[0043] [Injection molded products] A commonly known method can be used for producing an injection molded product using the styrene-based resin composition of the present embodiment as a raw material. The temperature of the molding machine is preferably 150°C to 300°C, more preferably 160°C to 260°C, and even more preferably 180°C to 240°C. If the temperature of the molding machine is higher than 300° C., the styrene resin composition will undergo thermal decomposition, which is undesirable, whereas if it is lower than 150° C., the composition will not be moldable due to its high viscosity, which is undesirable.

[0044] Molded articles, particularly injection molded articles (including injection compression) containing the styrene-based resin composition of the present embodiment are suitably used for office automation equipment such as copiers, fax machines, personal computers, printers, information terminals, refrigerators, vacuum cleaners, and microwave ovens, home appliances, housings and various parts of electric and electronic equipment, interior and exterior materials for automobiles, construction materials, foam insulation materials, insulating films, and the like. EXAMPLES

[0045] Hereinafter, the embodiments of the present invention will be described in more detail based on examples and comparative examples, but the present invention is not limited to these examples in any way.

[0046] <Measurement and evaluation methods> The physical properties of the resin compositions and injection molded articles obtained in each of the Examples and Comparative Examples were measured and evaluated according to the following methods.

[0047] (1) Measurement of weight average molecular weight of styrene polymer (A) and biomass plasticizer (B) used in the examples and comparative examples The weight average molecular weights of the styrene-based polymer (A) and the biomass plasticizer (B) were measured under the following conditions and procedures. Sample preparation: 5 mg of the measurement sample was dissolved in 10 mL of tetrahydrofuran and filtered through a 0.45 μm filter. Measurement conditions Equipment: TOSOH HLC-8220GPC (Gel Permeation Chromatography) Column: Two SHODEX GPC KF-606M columns connected in series Guard column: SHODEX GPC KF-G 4A Temperature: 40℃ Carrier: THF 0.50mL / min Detector: RI, UV: 254 nm Calibration curve: Eleven types of TSK standard polystyrene (F-850, F-450, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000) manufactured by Tosoh Corporation were used to create the calibration curve. The calibration curve was created using a third-order linear approximation equation.

[0048] (2) Melt mass flow rate (MFR) The melt mass flow rate (g / 10 min) of the styrene-based resin composition used in the examples and comparative examples was measured in accordance with ISO 1133 (200° C., load 49 N).

[0049] (3) Measurement of Vicat softening temperature (℃) The Vicat softening temperature (° C.) of the styrene-based resin compositions used in the present examples and comparative examples was measured in accordance with ISO 306 under a load of 49 N.

[0050] (4) Measurement of toluene insoluble content (%) of styrene resin composition The toluene insoluble portion of the styrene resin composition was measured as follows. 1.00 g of the styrene resin composition was weighed out in a precipitation tube (this mass was designated as W1), 20 milliliters of toluene was added, and the mixture was shaken at 23°C for 1 hour, and then centrifuged for 60 minutes at 4°C, 20,000 rpm, and 45,100×G in a centrifuge (manufactured by Sakuma Seisakusho Co., Ltd., SS-2050A rotor: 6B-N6L). The precipitation tube was slowly tilted at about 45 degrees, and the supernatant liquid was decanted off. The mass of the insoluble portion containing toluene was weighed out, and the mixture was vacuum-dried at 160°C and 3 kPa or less for 1 hour, cooled to room temperature in a desiccator, and then the mass of the toluene insoluble portion was weighed out (this mass was designated as W2). The toluene insoluble content (%) of the styrene-based resin composition was calculated using the following formula. Toluene insoluble content of styrene resin composition (%) = W2 / W1 × 100

[0051] (5) Measurement method for biomass carbon percentage (pMC%) The biomass carbon ratio (pMC%) of the biomass plasticizer (B) is calculated based on the radioactive carbon (14 C) Measurement method: Using the following formula (1), AMS method ( 14 C Plasticizer / 12 C plasticizer) / ( 14 C standard material / 12 C standard material) was calculated. Formula (1): Biomass carbon ratio (pMC%) = ( 14 C Plasticizer / 12 C plasticizer) / ( 14 C standard material / 12 C standard material)×100 In addition, oxalic acid (SRM4990) was used as the standard substance. The biomass carbon ratio in the styrene-based resin composition was calculated in the same manner as above.

[0052] (6) Determination of biomass plasticizer content The amount of the biomass plasticizer in the styrene-based resin composition used in the examples and comparative examples was determined by the following method. (6-1) Creating a calibration curve Vegetable oil (glycerin fatty acid ester) was dissolved in deuterated chloroform (containing 1% TMS) containing 2-dimethoxyethane as an internal standard substance. 1 H-NMR measurements were performed. Taking the TMS peak as the standard at 0 ppm, a peak derived from the protons bonded to the carbon adjacent to the ester group of the vegetable oil was detected at δ4.0-4.4 ppm, and a peak derived from 1,2-dimethoxymethane was detected at 3.4-3.6 ppm. The peak area derived from vegetable oil was calculated by setting the peak area derived from 1,2-dimethoxymethane as 1. By repeating this procedure while changing the concentration of vegetable oil, a calibration curve of vegetable oil concentration was created. (6-2) Quantification The pellet-shaped styrene-based resin composition obtained in the Examples or Comparative Examples was dissolved in deuterated chloroform (containing 1% TMS), 1 H-NMR measurement was performed, and the vegetable oil content in the styrene-based resin composition was quantified using the above calibration curve. In the above method, when other peaks overlap with the peak of the internal standard and quantitative determination is difficult, an appropriate substance may be used as the internal standard, as appropriate. Furthermore, vegetable oils can also be quantified using the peak derived from triglycerides detected at 5.0 to 5.5 ppm. When the biomass plasticizer (B) is a mixed oil of vegetable oil and ethylene bis-stearamide and / or zinc stearate and / or liquid paraffin, the content of the vegetable oil is determined by the above method, and the content of the ethylene bis-stearamide and / or zinc stearate and / or liquid paraffin is determined separately. The ethylene bis-stearamide and / or zinc stearate and / or liquid paraffin are quantitatively determined by liquid chromatography, GC-MS, 1 H-NMR or 13 Identification, quantification, and molecular weight measurement can be performed using various analytical devices such as C-NMR.

[0053] (7) Calculation of denaturation rate For styrene-based resins containing modified vegetable oils, the following procedure was used: 1 It is possible to calculate the degree of modification of modified vegetable oils using H-NMR. 1 g of the pellet-like styrene resin composition obtained in the Examples or Comparative Examples was placed in a 20 mL screw bottle, and 10 mL of methyl ethyl ketone was added. The pellets were then completely dissolved using a shaker, and 5 mL of methanol was added, causing the styrene resin composition to precipitate as an insoluble component in the solution. The insoluble portion was then removed, and the solution portion was placed in a recovery flask, which was then evacuated for 2 hours using an evaporator to volatilize the methyl ethyl ketone and methanol. The liquid (vegetable oil) remaining in the recovery flask was then added to deuterated chloroform (containing 1% TMS), and 1 H-NMR measurement was performed. With TMS as the standard at 0 ppm, a peak derived from the epoxy group was confirmed at δ2.8-3.2 ppm, and a peak derived from the proton bonded to the carbon adjacent to the ester group of the vegetable oil was confirmed at δ4.0-4.4 ppm. The epoxy modification rate was calculated from the area ratio of the above two peaks.

[0054] (8) Charpy impact test The styrene-based resin composition was injection-molded at 220° C. in accordance with JIS K 7152 to prepare a specimen, and the Charpy impact strength was measured in accordance with JIS K 7111-1.

[0055] (9-1) Injection moldability-1 In the evaluation of the injection moldability of the examples and comparative examples, a 2 mm plate was molded using an injection molding machine, EC60N, manufactured by Toshiba Machine Co., Ltd., at a cylinder temperature of 210°C, a mold temperature of 45°C, and an injection pressure of 45 MPa. The evaluation was based on the following criteria. 〇: Can be molded without problems Short: A short shot (9-2) Injection moldability-2 In the evaluation of the injection moldability of the examples and comparative examples, the minimum injection pressure at which molding was possible without short shots was evaluated when a 2 mm plate was molded at a cylinder temperature of 220°C and a mold temperature of 45°C using an injection molding machine EC60N manufactured by Toshiba Machine Co., Ltd. In this evaluation, the lower the injection pressure at which molding is possible, the more complex the molded product or the molded product having a thin wall portion can be molded at a relatively low cylinder temperature without short shots. By being able to mold at a low cylinder temperature, the cooling time is shortened, the molding cycle is shortened, volatile components are reduced, and mold staining is less likely to occur.

[0056] (10) Demoldability of injection molded products The evaluation of demoldability was judged based on the degree of damage caused by the magnitude of demold resistance inside the molded product when the molded product was removed during injection molding. Specifically, a box-shaped molded product with an external dimension of 50 mm length, 90 mm width, 40 mm depth, and 2 mm thickness and a mold with two 1 mm thick ribs spaced 30 mm apart on the horizontal position was used. Injection molding was performed using a molding machine J100E-P (manufactured by Nippon Steel Corporation) at a temperature of 210°C and a mold temperature of 45°C. The evaluation of demoldability was based on the degree of damage caused inside the molded product during demolding according to the following criteria. : No scratches occurred. Good: Small, dot-like scratches can be seen in the corners inside the molded product. △: Slight linear scratches of 2 mm or less can be seen in the corners inside the molded product. ×: A linear scratch larger than 2 mm can be seen in the corner inside the molded product.

[0057] (11) Mold contamination during injection molding When a styrene resin composition was prepared into an injection-molded piece at 220°C in accordance with JIS K 7152, the mold fouling was evaluated using the number of shots until deposits were confirmed on the mold after continuous molding as an index. If the number of shots until deposits were confirmed on the mold was less than 100, the mold would need to be cleaned more frequently, which would decrease productivity, so a number of 100 or more was considered acceptable.

[0058] (12) Calculation of SP value The SP value of each material used in the Examples and Comparative Examples was calculated by turbidimetric titration with reference to literature values ​​or "J. Appl. Polym. Sci., 12, 2359 (1968)".

[0059] (13) Measurement of total light transmittance and color difference (I) Preparation conditions of test specimen The obtained styrene-based resin composition was injection molded under the following conditions using a mold for plate molding to prepare a plate having a thickness of 2 mm, and then a sheet body was prepared. Molding machine: Toshiba Machine Co., Ltd. EC60N Cylinder temperature: 220℃ Injection pressure: 45MPa, Injection time: 10 seconds Cooling time: 15 seconds, mold temperature: 45℃ (II) Measurement conditions for total light transmittance The total light transmittance (%) of the test piece sheet prepared above was measured in accordance with JIS K7361-1. (III) Measurement conditions for YI (Yellow Index) The test piece sheet thus prepared was used to measure YI (yellow index) in accordance with JIS K7105.

[0060] The materials used in the examples and comparative examples are as follows. (modified vegetable oil) [Biomass plasticizer (B)] Epoxidized soybean oil (product name "Newsizer 510R" (NOF Corporation), weight average molecular weight (Mw = 1500), biomass carbon ratio (pMC%) 100%, melting point: 5°C, SP value: 9.0 ((cal / cm 3 ) 1 / 2 ), epoxy modification rate: 5 mmol per 1 g (natural vegetable oil) Palm oil (product name "Multi-Ace 20(S)" (Nisshin Oillio Group Co., Ltd.), weight average molecular weight (Mw = 1000), biomass carbon ratio (pMC%) 100%, melting point: 22°C, SP value (calculated by the Hansen method, distance from the origin in the three-component coordinate system of dispersion force term (δD), polar term (δP), and hydrogen bond term (δH)): 8.2 ((cal / cm 3 ) 1 / 2 )) Castor hydrogenated oil (product name: Castor hydrogenated oil (Ito Oil Mills, Ltd.), weight average molecular weight (Mw=1000), biomass carbon ratio (pMC%): 100%, melting point: 85°C, SP value (calculated by the Hansen method, and represents the distance from the origin in the three-component coordinate system of the dispersion force term (δD), polar term (δP), and hydrogen bond term (δH)): 10.1 ((cal / cm 3 ) 1 / 2 ))

[0061] [others] (liquid paraffin) Liquid paraffin, product name "PS350S" (manufactured by Sanko Chemical Industry Co., Ltd.), weight average molecular weight (Mw=250), biomass carbon ratio (pMC%) 0%, pour point: -12.5℃ (Polylactic acid) Polylactic acid, product name "LX175" (Total Corbinion PLA), biomass carbon ratio (pMC%) 100%, melting point: 155°C, SP value: 10.3 (cal / cm 3 ) 1 / 2 (Bluing agent) Bluing agent, product name "Plast Violet 8840" (manufactured by Arimoto Chemical Co., Ltd.) (Release agent / lubricant) Ethylene bis(stearic acid amide), product name "Kao Wax EB-FF" (manufactured by Kao Corporation) Zinc stearate, product name "Daiwax ZP" (manufactured by Dainichi Chemical Industry Co., Ltd.)

[0062] [Method of producing styrene-based resin composition] [Example 1] (Production method of styrene-based resin composition (PS-1)) A polymerization liquid in which 91.2% by mass of styrene, 4.0% by mass of ethylbenzene, and 4.8% by mass of Multiace 20 (S) (manufactured by Nisshin Oillio Group, Ltd.) were mixed and dissolved was continuously charged at 0.78 L / Hr into a 1.5-liter laminar flow reactor-1 equipped with a stirrer and capable of temperature control in three zones, and the temperature was adjusted to 119°C / 124°C / 128°C. The stirrer rotation speed was 80 rpm. The reaction rate at the reactor outlet was 30%. The reaction liquid was then sent to a 1.5-liter laminar flow reactor-2 equipped with an agitator connected in series with the laminar flow reactor-1 and capable of temperature control in three zones. The agitator was set to 40 revolutions per minute, and the temperature was set to 130°C / 132°C / 134°C. The reaction liquid was then sent to a 1.5-liter laminar flow reactor-3 equipped with an agitator and capable of temperature control in three zones. The agitator was set to 10 revolutions per minute, and the temperature was set to 144°C / 147°C / 149°C. The polymer solution continuously discharged from the polymerization reactor (laminar flow reactor-3) was pelletized after devolatilization under a reduced pressure of 0.8 kPa using an extruder equipped with a vacuum vent. The temperature of the extruder was set to 220°C. Thereafter, 0.3 ppm of Plast Violet 8840 (manufactured by Arimoto Chemical Co., Ltd.) was added to the obtained pellets in the styrene-based resin composition, which was melt-kneaded using an extruder and then pelletized. Furthermore, 70 ppm of Daiwax ZP (manufactured by Dainichi Chemical Industry Co., Ltd.) was added to the obtained pellets to produce a styrene-based resin composition (PS-1). The polymer matrix phase of the styrene-based resin composition (PS-1) contained polystyrene, and the SP value of the polystyrene was 8.6 (cal / cm 3 ) 1 / 2The above-mentioned various evaluations were then carried out on the obtained styrene-based composition of Example 1. The evaluation results are shown in Table 2-1.

[0063] [Examples 2 to 20] <Styrene-based resin compositions (PS-2) to (PS-7), (PS-15) to (PS-27), and (PS-29)> Styrenic resin compositions (PS-2) to (PS-7), (PS-15) to (PS-25) and (PS-29) were produced in the same manner as for the styrene resin composition (PS-1), except that the polymerization conditions were changed as shown in Tables 1-1 to 1-3. For the styrene resin composition (PS-26), Multiace 20 (S) (manufactured by Nisshin Oillio Group Co., Ltd.) was added to the styrene resin composition (PS-8) (GPPS not containing biomass plasticizer) described later so that the content was 12 mass%, and Plast Violet 8840 was added at 0.8 ppm and kneaded with a twin-screw extruder. After pelletizing, 70 ppm of Daiwax ZP (manufactured by Dainichi Chemical Industry Co., Ltd.) was added to the obtained pellets to produce (PS-26). In addition, the styrene-based resin composition (PS-27) was prepared by adding Multiace 20 (S) (manufactured by Nisshin Oillio Group, Ltd.) to styrene-acrylonitrile (KIBISAN (registered trademark) PN-117C (CHI-MEI product)) so that the content was 6 mass%, adding 0.3 ppm of Plast Violet 8840, kneading with a twin-screw extruder, and then adding 70 ppm of Daiwax ZP (manufactured by Dainichi Chemical Industry Co., Ltd.). The above-mentioned various evaluations were performed on the obtained styrene-based compositions of Examples 2 to 20. The evaluation results are shown in Tables 2-1 to 2-2.

[0064] [Comparative Examples 1 to 8] <Styrene-based resin compositions (PS-8) to (PS-14) and (PS-28) Styrenic resin compositions (PS-8) to (PS-14) and (PS-28) were produced in the same manner as the styrene-based resin composition (PS-1), except that the polymerization conditions were changed as shown in Tables 1-1 and 1-2. When PS-14 was produced, the polybutadiene rubber used was Diene 55 manufactured by Asahi Kasei Chemicals Corporation. The styrene-based resin composition (PS-28) was produced by adding polylactic acid (PLA) to the styrene-based resin composition (PS-8) so that the amount was 6% by mass, and kneading the mixture with a twin-screw extruder. The obtained styrene-based compositions of Comparative Examples 1 to 8 were subjected to the various evaluations described above. The evaluation results are shown in Table 2-3.

[0065] [Table 1-1]

[0066] [Table 1-2]

[0067] [Table 2-1]

[0068] [Table 2-2]

[0069] [Table 2-3] [Industrial Applicability]

[0070] The present invention provides a styrene-based resin composition which reduces the environmental load and has excellent mechanical strength, and an injection-molded article made of the styrene-based resin composition. The molded article obtained from the styrene-based resin composition can be suitably used for miscellaneous goods, toys, home appliance parts, industrial materials, etc.

Claims

1. Contains a styrene-based polymer (A) and a biomass plasticizer (B) having a biomass carbon ratio (pMC%) of 10% or more and more than 5% by mass and not more than 15% by mass, A styrene-based resin composition, characterized in that a total light transmittance of a 2 mm thick plate is 70% or more.

2. The styrene-based resin composition according to claim 1, wherein the SP value of the biomass plasticizer (B) is 7.0 to 11.

0.

3. 3. The styrene-based resin composition according to claim 1, wherein the toluene-insoluble matter content of the styrene-based resin composition is 3% or less.

4. 3. The styrene-based resin composition according to claim 1, wherein the styrene-based polymer (A) is contained in an amount of 85 to 94.9% by mass based on the entire styrene-based resin composition, and a content of a styrene-based monomer unit in the styrene-based polymer (A) based on the total amount of the styrene-based polymer (A) is 80 mass% or more.

5. 3. The styrene-based resin composition according to claim 1 or 2, wherein the styrene-based resin composition (A) contains, in the biomass plasticizer (B) having a biomass carbon ratio (pMC%) of 10% or more, one or more selected from the group consisting of liquid paraffin and fatty acid-based compounds.

6. 3. The styrene-based resin composition according to claim 1, further comprising 0.001 ppm to 10 ppm of a bluing agent relative to the styrene-based resin composition (A).

7. A molded article obtained by injection molding the styrene-based resin composition according to claim 1 or 2.

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