Styrene 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, retains excellent mechanical strength, and excels in moldability into a biaxially stretched sheet, releasability during molding, and sheet appearance, the styrene-based resin composition having high transparency, 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 0.1 mass% to 5.0 mass% 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 resin composition and a molded article made of the styrene resin.

Background Art

[0002] Styrene resins are used in a wide variety of applications due to their moldability and mechanical strength. In particular, styrene resins with high transparency have a wide range of applications such as miscellaneous goods, transparent food containers, packaging materials, and OA equipment. Also, from the perspective of reducing environmental impact, biomass raw materials have attracted attention, and the development of composite materials of styrene resins and natural-derived raw materials has been promoted. For example, Patent Document 1 discloses a styrene resin composition containing rubber-modified polystyrene, polylactic acid, and a styrene monomer unit elastomer. Further, Patent Document 2 discloses a styrene resin composition containing plant-derived polyethylene and a compatibilizer.

[0003] Since styrene resins are transparent and have excellent rigidity, in recent years, not only biaxially stretched sheets and molded articles obtained by secondary processing of biaxially stretched sheets, but also injection molded articles are widely used in food container applications. In biaxially stretched sheets and injection molded articles using styrene resins, if the fluidity or mold release property of the styrene resin is low, there are problems such as a decrease in productivity and deterioration of thickness unevenness. On the other hand, when the fluidity of the styrene resin is high, drawdown is likely to occur during sheet molding, and the sheet moldability deteriorates. Therefore, the balance between the fluidity and mold release property of the entire composition is important. For example, in order to control the fluidity of styrene resins, there is a method of adding liquid paraffin. Patent Document 3 discloses an example in which liquid paraffin is added to a highly branched styrene resin. As another technique for controlling the fluidity of resins, there is a method of adjusting the molecular weight and molecular weight distribution of the resin. For example, Patent Document 4 discloses a styrene resin composition having fluidity suitable for biaxially stretched sheets by adjusting the molecular weight and molecular weight distribution of a styrene-methacrylic acid copolymer.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-199652 [Patent Document 2] Japanese Patent Application Laid-Open No. 2020-193274 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-100430 [Patent Document 4] Japanese Patent No. 6389574 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] In the technology of the above Patent Document 1, 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 is being studied. However, since the compatibility of polylactic acid with the styrene-based resin is very low, there is a problem that it is difficult to conduct a product design that satisfies mechanical properties such as impact resistance or stretchability required in the market. In addition, since polylactic acid shows incompatibility with the styrene-based resin, the transparency of the entire polymer alloy is impaired. Furthermore, there is also a problem that it is difficult to recycle waste materials containing polylactic acid and the styrene-based resin.

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

[0007] The technology of the above Patent Document 3 is studying a highly branched styrene-based resin composition excellent in biaxially stretchable sheet formability and productivity. However, since liquid paraffin is added, it is considered that the sheet appearance deteriorates due to bleed-out and generation of volatile gases during molding. In the technology of Patent Document 4 mentioned above, the molecular weight of the styrene-methacrylic acid copolymer is adjusted to control the fluidity, and a styrene-based resin composition excellent in biaxially stretched sheet moldability and productivity is studied. However, since the molecular weight is relatively low to increase the fluidity, there is a concern that the mechanical strength may decrease. When obtaining an injection molded article, or a biaxially stretched sheet and a molded article obtained by secondary processing of the biaxially stretched sheet, depending on the shape and molding conditions of the molded article, the mold release property of the molded article from the mold becomes important for increasing productivity. However, in Patent Documents 1 to 4 mentioned above, the mold release property of the molded article during molding has not been studied. Further, in Patent Documents 3 to 4, biomass raw materials, which have been attracting attention in recent years for the purpose of reducing environmental load, are not used. Therefore, in the technologies of Patent Documents 1 to 4, a resin having high mechanical strength, excellent mold release property during molding, moldability into a biaxially stretched sheet, and high transparency in sheet appearance, and a plasticizer using a biomass raw material have not been studied. Therefore, an object of the present disclosure is to provide a styrene-based resin composition and a molded article thereof that have high transparency, excellent mold release property during molding, moldability into a biaxially stretched sheet, and sheet appearance, while reducing the environmental load by using a biomass raw material and maintaining high mechanical strength.

Means for Solving the Problems

[0008] In view of the above problems, the present inventor conducted intensive research and repeated experiments, and as a result, by using a styrene-based resin composition containing a styrene-based polymer (A) and a biomass plasticizer (B) having a high boiling point and a biomass carbon ratio (pMC%) of 10% or more in a predetermined amount, it was found that the above problems can be solved, and the present invention of the following [1] to [8] was completed. [1] A styrene-based resin composition comprising a styrene-based polymer (A) and 0.1% by mass to 5.0% by mass of a biomass plasticizer (B) having a biomass carbon ratio (pMC) of 10% or more, and having a total light transmittance of 70% or more for a 2 mm thick plate. [2] The styrene-based resin composition according to [1], having a Vicat softening temperature of 85°C or higher. [3] The SP value of the biomass plasticizer is 7.5 to 10.5, and the difference in the SP values between the styrenic polymer (A) and the biomass plasticizer (B) is less than 2.0. The styrenic resin composition according to [1] or [2]. [4] The toluene-insoluble content of the styrenic resin composition is 3% by mass or less. The styrenic resin composition according to any one of [1] to [3]. [5] The content of the styrenic polymer (A) is 95.0 to 99.9% by mass based on the entire styrenic resin composition, and the content of the styrenic monomer unit contained in the styrenic polymer (A) is 50% by mass or more based on the total amount of the styrenic polymer (A). The styrenic resin composition according to any one of [1] to [4]. [6] The biomass plasticizer (B) is a mixture of a vegetable oil and a moldability adjusting compound for adjusting moldability. The moldability adjusting compound is contained in the range of 0.01 to 5% by mass based on the entire styrenic resin composition (A). The moldability adjusting compound is one or more selected from the group consisting of liquid paraffin and fatty acid-based compounds. The styrenic resin composition according to any one of [1] to [5]. [7] The styrenic resin composition (A) contains a bluing agent in an amount of 0.001 ppm to 10 ppm. The styrenic resin composition according to any one of [1] to [6]. [8] A molded article comprising the styrenic resin composition according to any one of [1] to [7].

Advantages of the Invention

[0009] According to the present disclosure, it is to provide a transparent styrenic resin composition that reduces environmental impact, maintains high mechanical strength, and is excellent in mold release properties, formability into a biaxially stretched sheet, and sheet appearance during molding, and a biaxially stretched sheet molded article comprising the styrenic resin composition.

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. However, the present invention is not limited to the following description and can be implemented with various modifications within the scope of the gist thereof.

[0011] [Styrene resin composition] The styrene resin composition of the present embodiment contains a styrene polymer (A) and 0.1 to 5.0% by mass of a biomass plasticizer (B) having a biomass carbon ratio (pMC ratio) of 10% or more. In other words, the styrene resin composition of the present embodiment contains 0.1 to 5.0% by mass of the styrene polymer (A) and the biomass plasticizer (B) with respect to the entire styrene resin composition (100% by mass). The total light transmittance of a 2-mm-thick plate obtained from the above styrene resin composition is 70% or more. Thereby, it is possible to provide a transparent styrene resin composition having reduced environmental impact, good fluidity and high mechanical strength, excellent injection moldability, formability into a biaxially stretched sheet, and sheet appearance, and a biaxially stretched sheet molded body made of the styrene resin composition.

[0012] [Styrene polymer (A) (hereinafter also referred to as component (A))] The styrene resin composition in the present embodiment contains a styrene polymer (A). In the present embodiment, the content of the styrene polymer (A) is 95.0 to 99.9% by mass, preferably 96.0 to 99.7% by mass, more preferably 96.5 to 99.7% by mass, and even more preferably 97.0 to 99.5% by mass with respect to the entire styrene resin composition (100% by mass).

[0013] In the present embodiment, as the monomer constituting the styrene polymer (A), a styrene monomer (a) is essential, and optionally, a vinyl monomer (b) copolymerizable with the styrene monomer (a) may be included. Of the monomers constituting the styrene-based polymer (A), the content of the styrene-based monomer (a) is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, still more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass. The content of the styrene-based monomer (a), that is, the content of the styrene-based monomer unit (a), can be determined from the integration ratio of the spectrum measured with a proton nuclear magnetic resonance ( 1 1H-NMR) measuring instrument. Also, 1 when quantification is difficult by 1H-NMR measurement, quantification is performed by Fourier transform infrared spectroscopy (FTIR) measurement. Examples of the styrene-based monomer (a) include, in addition to styrene, α-methylstyrene, α-methyl-p-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene, and styrene derivatives such as t-butylstyrene or bromostyrene and indene. Styrene is particularly preferred. These styrene-based monomers can be used alone or in combination of two or more.

[0014] In the present embodiment, the vinyl-based monomer (b) is not particularly limited, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, and the like. These unsaturated carboxylic acid ester monomers can be used alone or in combination of two or more.

[0015] In this embodiment, polystyrene is a homopolymer obtained by polymerizing styrene monomer (a), and a generally available one can be appropriately selected and used. As the styrene monomer (a) constituting polystyrene, in addition to styrene, styrene derivatives such as α-methylstyrene, α-methyl-p-methylstyrene, ο-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene, and t-butylstyrene or bromostyrene and indene can be mentioned. Styrene is particularly preferred from an industrial perspective. These styrene monomers (a) can be used alone or in combination of two or more. Polystyrene is not excluded from further containing monomer units other than the above styrene monomer (a) units as long as the effects of the present invention are not impaired, but typically consists of styrene monomer (a) units. As a preferred form of the styrene-based polymer (A) in this embodiment, it is preferable to control the SP value of the styrene-based polymer (A) and the biomass plasticizer (B) having a biomass carbon ratio (pMC ratio) of 10% or more to be within a predetermined range. Therefore, for example, depending on the SP value of the biomass plasticizer (B) used, the type of monomer unit constituting the styrene-based polymer (A), the content of the styrene monomer (a), or the content of the vinyl monomer (b) may be adjusted. As a result, the biomass plasticizer (B) in the composition is likely to be uniformly dispersed, so the mechanical strength is further improved.

[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 with an excellent balance between mechanical strength and fluidity can be obtained, and the mixing of gel substances is also small. The weight average molecular weight (Mw) is a value obtained by gel permeation chromatography in terms of standard polystyrene. In addition, the styrenic polymer (A) in the present embodiment preferably contains a rubbery polymer (for example, polybutadiene, polybutadiene encapsulating polystyrene, polyisoprene, natural rubber, polychloroprene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer) or a structural unit having a conjugated diene structure in an amount of less than 1.0% by mass based on the total amount (100% by mass) of the styrenic polymer (A).

[0017] In the present embodiment, it is preferable that the styrenic polymer (A) or the styrenic resin composition of the present embodiment does not substantially contain vinyl cyanide-based monomers such as acrylonitrile monomer units and methacrylonitrile monomer units. Specifically, the vinyl cyanide-based 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-based monomer (b).

[0018] In the present embodiment, the polymerization method of the styrenic polymer (A) is not particularly limited. For example, as a radical polymerization method, a bulk polymerization method or a solution polymerization method can be preferably employed. The polymerization method mainly includes a polymerization step of polymerizing a polymerization raw material (monomer component) and a devolatilization step of removing volatile components such as unreacted monomers and polymerization solvents from the polymerization product.

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

[0020] As a polymerization method of the styrene-based polymer (A), solution polymerization using a polymerization solvent can be employed as necessary. Examples of the polymerization solvent used include aromatic hydrocarbons such as ethylbenzene, and dialkyl ketones such as methyl ethyl ketone. Each of them may be used alone, or two or more of them may be used in combination. 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 a range not exceeding 25 parts by mass with respect to 100 parts by mass of the total monomers. When the polymerization solvent exceeds 25 parts by mass with respect to 100 parts by mass of the total monomers, the polymerization rate is significantly reduced, and the mechanical strength of the resulting resin tends to decrease significantly. It is preferable to add it at a ratio of 5 to 20 parts by mass with respect to 100 parts by mass of the total monomers before polymerization, as the quality is easily homogenized and it 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 employed, a polymerization apparatus in which one or a plurality of completely mixed reactors are connected can be used. Also, there are no particular restrictions on the devolatilization step. For example, when bulk polymerization is employed, the polymerization is advanced until the unreacted monomer finally becomes preferably 50% by mass or less, more preferably 40% by mass or less, and the volatile components such as such unreacted monomers are removed by a known method for devolatilization treatment. More specifically, for example, ordinary devolatilization apparatuses such as a flash drum, a twin-screw devolatilizer, a thin-film evaporator, and an extruder can be used, but a devolatilization apparatus with fewer residence parts is preferable. 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 the devolatilization method, for example, a method of removing volatile components by reducing the pressure under heating and a method of removing them through an extruder or the like designed for the purpose of removing volatile components are desirable.

[0022] <Biomass plasticizer (B) (hereinafter also referred to as component (B)).> The styrene resin composition in this embodiment contains a biomass plasticizer (B). And the content of the biomass plasticizer is 0.1% by mass to 5.0% by mass, preferably 0.3% by mass to 4.0% by mass, more preferably 0.3% by mass to 3.5% by mass, and even more preferably 0.5% by mass to 3.0% by mass. When the amount of the biomass plasticizer is 5% by mass or more, the Vicat softening temperature is lower than 85°C, which is not suitable for stretch sheet applications and food packaging applications. Also, when the amount of the biomass plasticizer is less than 0.1% by mass, there is a concern that the fluidity decreases, resulting in deterioration of thickness unevenness during molding. Moreover, when the fluidity decreases, there is a concern that the productivity will drop. Furthermore, there is also a concern that the mold release property of the molded body will deteriorate.

[0023] The biomass carbon ratio (pMC%) in this specification indicates the carbon concentration (mass ratio) of biomass-derived components. More specifically, it is the value of the carbon-14 content obtained by the measurement method of radioactive carbon-14 ( 14 C) in accordance with ASTM-D6866. The measurement method of the radioactive carbon-14 ( 14 C) utilizes the fact that fossil fuels do not contain 14 C and that biomass (or biological) -derived carbon absorbs 14 C in the atmosphere during the growth period, and is a method for estimating the biomass carbon ratio (pMC%) from the 14 C ratio in the carbon contained in the biomass material (or biological). 14 C ratio in the carbon contained in the biomass material (or biological). Therefore, by measuring the proportion of 14 C contained in all carbon atoms in the plasticizer of this embodiment, the proportion of biomass-derived carbon 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 in plasticizer / 12 C in plasticizer) / ( 14 C in standard substance / 12 C in standard substance) × 100 In addition, oxalic acid (SRM4990) was used as the reference material, and ([ 14 14 C plasticizer / 12 C plasticizer) / ( 14 C reference material / 12 C reference material) was calculated.

[0024] The weight average molecular weight (Mw) of the biomass plasticizer of the present embodiment is preferably from 200 to 7500, more preferably from 300 to 5000, and still more preferably from 400 to 3000. When the weight average molecular weight (Mw) of the biomass plasticizer is from 200 to 7500, a styrenic resin composition excellent in the balance between mechanical strength and fluidity can be obtained, and the incorporation of gel substances is also small. The weight average molecular weight (Mw) is a value obtained in terms of standard polystyrene using gel permeation chromatography as described in the Examples section below.

[0025] The biomass plasticizer (B) in the present embodiment refers to a plasticizer using a biomass material as part or all of the raw material, and a plasticizer having a biomass carbon ratio (pMC%) of 10% or more. The biomass plasticizer of the present embodiment uses a plant-derived biomass material as at least part of the raw material, and is a plasticizer having a biomass carbon ratio (pMC%) of 10% or more, and is preferably a vegetable oil, a mixture of a vegetable oil and a mineral oil, or a polyester-based plasticizer, and more preferably a natural vegetable oil, a modified vegetable oil, a mixture of a natural vegetable oil and a mineral oil, a mixture of a modified vegetable oil and a mineral oil, a mixture of a natural vegetable oil, a modified vegetable oil and a mineral oil, or a polyester-based plasticizer. Note that the vegetable oil in this specification is a general term for plant-derived fats and oils, and includes natural vegetable oils and modified vegetable oils. In the present embodiment, from the viewpoint of adjusting the balance between releasability and fluidity to improve the moldability, the biomass plasticizer (B) is preferably a mixture of a vegetable oil and a moldability adjusting compound for adjusting the moldability. As a preferred form of the biomass plasticizer (B) of the present embodiment, it is preferably a mixture of 50 to 99.99% by mass of vegetable oil and 0.01 to 50% by mass of a moldability adjusting compound in the whole biomass plasticizer (B). In the whole biomass plasticizer (B), it is preferably a mixture of 75 to 99.99% by mass of vegetable oil and 0.01 to 25% by mass of a moldability adjusting compound. More preferably, it is a mixture of 85 to 99.99% by mass of vegetable oil and 0.01 to 15% by mass of a moldability adjusting compound. Even more preferably, it is a mixture of 90 to 99.99% by mass of vegetable oil and 0.01 to 5% by mass of a moldability adjusting compound. With the preferred composition ratio of the above biomass plasticizer (B), a biomass content of 50% or more can be maintained, so a higher environmental load reduction effect can be expected. Among them, a mixture in which the vegetable oil is 85% to 99.99% by mass, the liquid paraffin is 1% to 15% by mass, and the fatty acid-based compound is 0.1 to 5% by mass is preferred. By adding the moldability adjusting compound to the styrene resin composition, effects such as an increase in fluidity and an improvement in the mold release property of the molded body from the mold can be imparted, and productivity can be improved. Also, the addition amount of the moldability adjusting compound is preferably 0.01% to 5.0% by mass, more preferably 0.01% to 4.0% by mass, even more preferably 0.01% to 3.0% by mass, even more preferably 0.01% to 2.5% by mass, even more preferably 0.01% to 2.0% by mass, even more preferably 0.01% to 1.5% by mass, even more preferably 0.01% to 1.2% by mass, even more preferably 0.01% to 1.0% by mass, even more preferably 0.01% to 0.5% by mass, and even more preferably 0.01 to 0.3% by mass with respect to the total amount (100% by mass) of the styrene resin composition. As the moldability adjusting compound, it is preferably one or more selected from the group consisting of liquid paraffin and fatty acid-based compounds. As the fatty acid compound, a fatty acid compound, a fatty acid metal salt compound, or the like can be used. Specifically, for example, ethylene bisstearamide, stearic acid, zinc bisstearate stearate, calcium stearate, magnesium stearate, and the like can be mentioned. In this embodiment, the addition amount of the fatty acid compound is preferably 0.1 ppm to 15000 ppm, more preferably 1 ppm to 10000 ppm, even more preferably 5 ppm to 9000 ppm, even more preferably 10 ppm to 8000 ppm, even more preferably 15 ppm to 7000 ppm, even more preferably 20 ppm to 6000 ppm, even more preferably 25 ppm to 5000 ppm, based on the total amount (100% by mass) of the styrenic resin composition. When obtaining a molded product by injection molding or extrusion molding, a fatty acid compound may be added to the styrenic resin. In particular, when obtaining a molded product with a complex shape or a molded product having a thin-walled portion, it may be necessary to add a fatty acid compound so that the molded product does not crack or deform during demolding. The addition methods include a method of melt-kneading the fatty acid compound into the resin and a method of sprinkling the fatty acid compound in powder form as an external lubricant onto the resin pellets. When added as an external lubricant, it also has the effect of a lubricant that reduces the friction between the screw and the resin during molding and kneading processing and improves processability. Note that two or more kinds of fatty acid compounds may be used in combination. When emphasizing the viewpoint of reducing environmental impact, the biomass plasticizer (B) is preferably a single vegetable oil which is one or more kinds of vegetable oils. On the other hand, when particularly emphasizing the viewpoint of fluidity, the biomass plasticizer (B) is preferably a mixed oil of one or more kinds of vegetable oils and liquid paraffin. Further, when emphasizing the viewpoint of the demoldability of the molded body, the biomass plasticizer (B) is preferably a mixed oil of one or more kinds of vegetable oils and a fatty acid compound. Note that, as the quantification method of each component contained in the biomass plasticizer (B) when the biomass plasticizer (B) is a mixed oil, the method described in the column of Examples described later can be used.

[0026] In this embodiment, a biomass plasticizer may use a modified vegetable oil. The modified vegetable oil refers to a compound made from a vegetable oil. More specifically, it is a part of a hydrocarbon-based oil of plant origin modified by a functional group, and it is preferable that the vegetable oil is modified by an epoxy group, an amino group, or an ester bond. Examples of the vegetable oil include a triester of glycerin and a fatty acid, a fatty acid monoester obtained by adding a monoalcohol to a vegetable oil and performing a transesterification reaction, a fatty acid monoester obtained by esterifying a fatty acid and a monoalcohol, and an ether derived from a fatty acid. In this embodiment, it is preferable that the modification group (epoxy group, amino group, or functional group of an ester bond) of the modified vegetable oil does not substantially polymerize with other components (including the styrene-based resin (A)) or with other modified vegetable oils in the styrene-based resin composition. Further, in this 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 above-mentioned modified vegetable oil is as described in the examples below 1 It is calculated by the H-NMR measurement method.

[0027] Specific examples of the natural vegetable oil include, for example, cottonseed oil, castor oil, shea oil, alfalfa oil, poppy oil, pumpkin oil, winter squash oil, cereal oil, barley oil, quinoa oil, rye oil, kukui oil, asparagus oil, shea butter, aloe vera oil, sweet almond oil, peach kernel oil, soybean oil, cashew oil, peanut oil, avocado oil, baobab oil, lulidisa oil, broccoli oil, nasturtium oil, camellia oil, canola oil, carrot oil, safflower oil, flaxseed oil, rapeseed oil, cottonseed oil, coconut oil, pumpkin seed oil, wheat germ oil, jojoba oil, lily oil, macadamia oil, corn oil, meadowfoam oil, monoi oil, hazelnut oil, apricot kernel oil, walnut oil, olive oil, evening primrose oil, palm oil, blackcurrant seed oil, kiwi seed oil, grape seed oil, pistachio oil, jasmine oil, sesame oil, soybean oil, sunflower oil, castor oil, watermelon oil, or a mixture of these oils. In this embodiment, the modified vegetable oil includes oils obtained by hydrogenating the above-exemplified natural vegetable oils (e.g., hydrogenated castor oil); oils obtained by epoxidizing the above-exemplified natural vegetable oils (e.g., modified epoxidized oil); and oils obtained by aminating the above-exemplified natural vegetable oils (e.g., modified aminated oil). The modified epoxidized oil includes oils in which the epoxy functional group of soybean oil modified with hydroxide or the like has been ring-opened, oils directly hydroxylated in advance, and polyols based on cashew nut oil.

[0028] Specific examples of the biomass plasticizer (B) of this embodiment include, for example, palm oil, epoxidized soybean oil, epoxidized linseed oil, polyoxyethylenated castor oil, polyoxyethylenated hydrogenated castor oil, oleic acid ester, or lauric acid ester, such as "Polysizer W-1810-BIO" and "Epoxysizer" manufactured by DIC Corporation; "New Sizer 510R" and "New Sizer 512" manufactured by NOF Corporation;; "Pionin D series" manufactured by Takemoto Yushi Co., Ltd.; "Multi Ace 20(S)" and "Refined Palm Oil (S)" manufactured by Nisshin Oillio Group Co., Ltd.

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

[0030] In this embodiment, the melting point of the biomass plasticizer (B) is preferably -30 to 80 °C, more preferably -25 to 77 °C, still 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 more likely to be dispersed in the styrene-based resin composition. Also, when the melting point of the biomass plasticizer (B) is lower than -30 °C, the volatile components increase, and there is a tendency for mold fouling to increase. When the melting point of the biomass plasticizer (B) is higher than 80 °C, it is difficult to melt, making the addition operation difficult.

[0031] In this embodiment, the difference between 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, still more preferably ±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. When 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, it becomes difficult for the two to be compatible. As a result, it is difficult for the biomass plasticizer (B) to be uniformly dispersed in the styrene-based resin composition, and the mechanical strength of the entire styrene-based resin composition tends to decrease. One of the preferred embodiments of this embodiment contains the styrene-based polymer (A) and the biomass plasticizer (B), and the difference between 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. Also, the SP value of the styrene-based polymer (A) in this embodiment is 7 to 11 (cal / cm 3 ) 1 / 2) is preferably, more preferably 7.5 to 10 ((cal / cm 3 ) 1 / 2 ) and even more preferably 8.0 to 9.5 ((cal / cm 3 ) 1 / 2 ), still more preferably 8.0 to 9.0 ((cal / cm 3 ) 1 / 2 ). Further, the SP value of the biomass plasticizer (B) in the present embodiment is 7.0 to 11.0 ((cal / cm 3 ) 1 / 2 ) is preferably, more preferably 7.5 to 10.0 ((cal / cm 3 ) 1 / 2 ), still more preferably 7.7 to 9.5 ((cal / cm 3 ) 1 / 2 ), still more preferably 7.9 to 9.0 ((cal / cm 3 ) 1 / 2 ). The solubility parameter (SP value) defined in the present embodiment is calculated using the function of the cohesive energy density shown in the following formula. SP value ((cal / cm 3 ) 1 / 2 ) = (△E / V) 1 / 2 Formula (1) (△E represents the intermolecular cohesive energy (heat of vaporization), V represents the total volume of the mixed solution, and △E / V represents the cohesive energy density.) Further, the heat quantity change △Hm due to mixing is represented by the following formula using the SP value. △Hm = V(δ1 - δ2)·Φ1·Φ2 ··· Formula (2) (δ1 represents the SP value of the solvent, δ2 represents the SP value of the solute, Φ1 represents the volume fraction of the solvent, and Φ2 represents the volume fraction of the solute.) From the above formulas (1) and (2), the closer the values of δ1 and δ2 are, the smaller △Hm becomes, and the Gibbs free energy becomes smaller. Therefore, those with a smaller difference in SP values have higher affinity. As a method for obtaining the SP value in this specification, the solubility of the resin in various solvents with known SP values is compared, and the SP value of the unknown resin is calculated from the SP value of the solvent that is most compatible. Specifically, it is calculated using the turbidity titration method. In this embodiment, a value obtained mainly by calculation from the monomer composition is used.

[0032] In this embodiment, examples of the mineral oil include atmospheric residue obtained by atmospheric distillation of crude oils such as paraffinic crude oil (including liquid paraffin), intermediate-base crude oil, and naphthenic crude oil; distillate oil obtained by vacuum distillation of these atmospheric residues; mineral oil obtained by subjecting the distillate oil to one or more purification treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining; mineral oil obtained by isomerizing wax (GTL wax) produced by the Fischer-Tropsch method or the like. These mineral oils may be used alone or in combination of two or more. In this embodiment, when using a mixture of vegetable oil and mineral oil 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 preferably mixed in an amount of 10 to 100 parts by mass, more preferably 10 to 50 parts by mass, based on 100 parts by mass of the vegetable oil. The addition amount of the mineral oil is preferably 0.01% by mass to 5.0% by mass, more preferably 0.01% by mass to 4.0% by mass, even more preferably 0.01% by mass to 3.0% 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 1.2% by mass, even more preferably 0.01% by mass to 1.0% by mass, even more preferably 0.01% by mass to 0.5% by mass, and even more preferably 0.01% by mass to 0.3% by mass, based on the total amount (100% by mass) of the styrenic resin composition. The quantification and identification of the liquid paraffin in this embodiment can be confirmed by methods common to those skilled in the art. For example, fragments of the styrene resin composition or a molded article of the composition are dissolved in a solvent that dissolves the matrix resin, such as tetrahydrofuran, to prepare a solution. Then, while stirring this solution with a stirrer, a small amount of n-hexane is added dropwise to precipitate the polymer matrix and the rubbery polymer. Thereafter, the filtrate filtered through a glass filter is evaporated to dryness, then made up to a fixed volume with n-hexane, passed through a polytetrafluoroethylene membrane filter, and then separated by liquid chromatography to calculate the content of liquid paraffin in the composition or molded article. Further, for the analysis of liquid paraffin, identification, quantification, and measurement of the molecular weight can be performed using various analyzers such as pyrolysis GC-MS, 1 1H-NMR or 13 13C-NMR.

[0033] The content of the toluene-insoluble matter in the styrene resin composition is preferably 3% by mass or less, more preferably less than 1% by mass. The toluene-insoluble matter content is measured by the method described in the Examples section below.

[0034] <Optional additive component> In addition to the above components (A) and (B), the styrene resin composition of this embodiment may be added with optional additive components such as known additives and processing aids, etc., as long as the effects of the present invention are not impaired. These optional additive components include a moldability adjusting compound composed of the above liquid paraffin and fatty acid-based compound, a release agent, a flame retardant, a dispersant, an antioxidant, a weathering agent, an antistatic agent, a filler, an antiblocking agent, a colorant, a blooming inhibitor, a surface treatment agent, an antibacterial agent, an anti-eye varnish agent (such as the silicone oil, monoamide compound of a higher aliphatic carboxylic acid, and monoester compound obtained by reacting a higher aliphatic carboxylic acid with a monohydric to trihydric alcohol compound described in JP-A-2009-120717) and the like. In the present embodiment, the styrene resin composition may contain a known flame retardant (phosphorus-based flame retardant, halogen-based flame retardant such as bromine-based). However, from the viewpoint of fear of generation of gases such as hydrogen bromide due to the reaction with the biomass plasticizer (B) contained in the styrene resin composition, the content of the halogen-based flame retardant is preferably less than 3% by mass, more preferably less than 1% by mass, based on the total amount (100% by mass) of the styrene resin composition. In the present embodiment, by adding a moldability adjusting compound composed of liquid paraffin and a fatty acid compound to the styrene resin composition, an effect of increasing fluidity and an effect of improving the releasability of the molded body from the mold can be imparted, and productivity can be improved.

[0035] In the present embodiment, depending on the application, it is preferable to add an anthraquinone-based compound as a bluing agent to adjust the color tone. When the bluing agent has an anthraquinone skeleton, a hydrogen abstraction reaction by an excited carbonyl or an electron transfer from anions occurs, making it easier to adjust the color tone (= easier to suppress yellowness). Therefore, an anthraquinone-based compound having an electron-withdrawing group with respect to the anthraquinone skeleton is particularly preferable. In the present embodiment, by adding a bluing agent which is an anthraquinone-based compound, a molded body having a color tone and appearance required in some applications can be obtained. For example, when the styrene resin composition of the present embodiment is formed into a biaxially stretched sheet and used as a lid for a food packaging container, it is necessary to suppress the yellowness of the resin so that the food in the packaging container does not look yellowish. The addition amount of the bluing agent is preferably 0.001 ppm to 10 ppm, more preferably 0.01 ppm to 5.0 ppm, still 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 with respect to the total amount (100% by mass) of the styrene resin composition. Within the above addition amount range, it becomes possible to obtain a molded article with excellent appearance by suppressing the yellowness of the resin. Incidentally, two or more types of bluing agents may be used in combination. Since many of the biomass plasticizers (B) having a biomass carbon ratio (pMC%) of 10% or more are yellowish, the styrene resin composition of the present embodiment containing up to 5% by mass of the biomass plasticizer (B) having a biomass carbon ratio (pMC%) of 10% or more tends to be yellowish. As a result, it becomes difficult to use it for transparent materials for foods such as lids of lunch boxes or optical materials (for example, light guide plates). However, by containing a bluing agent, the color tone can be adjusted.

[0036] The styrene resin composition in the present embodiment preferably does not contain metal except for unavoidable impurities. More specifically, the metal content is preferably less than 3% by mass, and more preferably less than 1% by mass with respect to the total amount (100% by mass) of the styrene resin composition. In the present embodiment, as the dispersant, a fatty acid ester compound, a polyethylene glycol compound, a terpene compound, a rosin compound, a fatty acid amide, a fatty acid compound, a fatty acid metal salt, or the like can be used. Examples of the antioxidant include phenolic compounds, phosphorus compounds, thioether compounds, and the like. The total content of the above optional components may be 0.01 to 5% by mass with respect to the entire styrene resin composition.

[0037] As the moldability adjusting compound, as described above, liquid paraffin, a fatty acid compound, a fatty acid metal salt compound, or the like can be used.

[0038] The styrene resin composition of this embodiment may substantially consist only of component (A), component (B), and optional components. Further, it may consist only of component (A) and component (B), or only of component (A), component (B), and optional components. "Substantially consisting only of component (A), component (B), and optional components" means that 95 to 100% by mass (preferably 98 to 100% by mass) of the total amount of the styrene resin composition is component (A) and component (B), or component (A), component (B), and optional components. Note that the styrene resin composition of this embodiment may contain unavoidable impurities in addition to component (A), component (B), and optional components as long as the effects of the present invention are not impaired.

[0039] When a modified vegetable oil is used as the biomass plasticizer (B) contained in the styrene resin composition of this embodiment, the content of the hydroxyl group-containing compound is preferably less than 3% by mass, and more preferably less than 1% by mass, based on the total amount (100% by mass) of the styrene 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, and phthalic acid. When the hydroxyl group-containing compound is 3% by mass or more, it reacts with the modified vegetable oil and causes gelation, resulting in a decrease in moldability or an adverse effect such as deterioration of the appearance of the injection molded product. When a natural vegetable oil is used as the biomass plasticizer contained in the styrene resin composition, the amount of the hydroxyl group-containing compound is not specified.

[0040] [Physical properties of styrene 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. When the total light transmittance (%) of the styrene resin composition is 80% or more, for example, the content of particles (for example, particles of a rubbery polymer having an average particle diameter of 1.0 to 5.0 μm) contained in the styrene resin composition is set to 3% by mass or less based on the entire styrene resin composition, or it is within a range where it can be used for transparent food containers, packaging materials, or OA equipment applications that require transparency. Further, by using the biomass plasticizer (B) of this embodiment as a specific vegetable oil such as palm oil, epoxidized soybean oil, epoxidized linseed oil, polyoxyethylenated castor oil, oleic acid ester, or lauric acid ester, or by making the SP value of the biomass plasticizer (B) of this embodiment less than 10, the blend state within the composition changes, so the total light transmittance (%) of the styrene resin composition can be adjusted to a desired value (for example, 70% or more). The specific method for producing the test piece used for measuring the total light transmittance (%) of the styrene resin composition complies with K7361-1, and it is confirmed that the test piece has no defects such as scratches, bubbles, impacts, dust or grease adhesion, and further no adhesion of adhesives from protective materials. Also, it is assumed that there are no voids or particles visible to the naked eye on the surface of the test piece. When producing the test piece by injection molding, if necessary according to the state of the mold surface used, mirror polishing may be appropriately performed using abrasive paper, stick grindstones, free abrasive grains, etc. The method for measuring the total light transmittance (%) and the method for producing the test piece used for the method for measuring the total light transmittance (%) in the present disclosure are as described in the column of the examples below.

[0041] <Melt mass flow rate (MFR)> The melt mass flow rate (MFR) of the styrene resin composition of this embodiment is 1.0 to 9.0, preferably 1.5 to 8.0, more preferably 1.8 to 7.0, even more preferably 2.0 to 6.5, and even more preferably 2.2 to 6.0. When the MFR is less than 1.0, the productivity of the sheet decreases. Also, thickness unevenness of the sheet is likely to occur. When the MFR is higher than 9.0, it is necessary to lower the molecular weight of the resin or increase the amount of plasticizer. When the molecular weight of the resin decreases, there is a risk of a decrease in mechanical strength. Also, when the amount of plasticizer increases, there is a risk that the Vicat softening temperature will decrease and it will be difficult to provide the required heat resistance. Also, when the MFR increases, there is a concern that drawdown will occur during sheet forming. <Vicat softening temperature> The Vicat softening temperature of the styrene resin composition of this embodiment is 85°C or higher, preferably 85°C to 105°C, more preferably 87°C to 103°C, and even more preferably 90°C to 101°C. When the Vicat softening temperature is less than 85°C, it becomes difficult to provide the heat resistance required for biaxially stretched sheets and food packaging applications. Also, when the Vicat softening temperature exceeds 105°C, the fluidity of the resin decreases, so the productivity of the sheet decreases. Also, thickness unevenness of the sheet is likely to occur.

[0042] [Injection molded article] As a method for manufacturing an injection molded article using the styrene resin composition of this embodiment as a raw material, a generally known method can be used. 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. When the temperature of the molding machine is higher than 300°C, the styrene resin composition undergoes thermal decomposition, which is not preferable. On the other hand, when it is lower than 150°C, molding cannot be performed due to high viscosity, which is not preferable. [Biaxially stretched sheet] As a method for manufacturing a biaxially stretched sheet using the styrene resin composition of this embodiment as a raw material, a generally known method can be used. The molding temperature of the molding machine is preferably 180°C to 280°C, more preferably 200°C to 260°C, and even more preferably 210°C to 250°C. The biaxially stretched sheet can be secondary formed by a thermoforming method such as a vacuum forming method or a pressure air forming method. As applications of the formed product of the biaxially stretched sheet of the present invention, there are various containers, which are mainly used for food packaging containers and the like.

Examples

[0043] Hereinafter, embodiments of the present invention will be described in more detail based on examples and comparative examples, but the present invention is not limited by these examples at all.

[0044] <Measurement and Evaluation Methods> The physical property measurement and evaluation of the resin compositions and biaxially stretched sheets obtained in each example and comparative example were carried out based on the following methods.

[0045] (1) Measurement of the weight average molecular weight of the styrene-based polymer (A) and the biomass plasticizer (B) used in the examples and comparative examples The weight average molecular weight of the styrene-based polymer (A) and the biomass plasticizer (B) was 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 were connected in series Guard column: SHODEX GPC KF-G 4A Temperature: 40 °C Carrier: THF 0.50 mL / min Detector: RI, UV: 254 nm Calibration curve: For the preparation of the calibration curve, eleven types of TSK standard polystyrenes (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. The calibration curve was created using a third-order linear approximation formula.

[0046] (2) Melt mass flow rate (MFR) The melt mass flow rate (g / 10 min) of the styrene resin compositions used in the examples and comparative examples was measured in accordance with ISO 1133 (200 °C, load 49 N).

[0047] (3) Measurement of Vicat softening temperature (°C) The Vicat softening temperature (°C) of the styrene resin compositions used in this example and comparative examples was measured at a load of 49 N in accordance with ISO 306.

[0048] (4) Measurement of the content (%) of toluene-insoluble matter in the styrene resin composition The toluene-insoluble matter in the styrene resin composition was measured as follows. 1.00 g of the styrene resin composition was precisely weighed into a precipitation tube (this mass is designated as W1), 20 milliliters of toluene was added, and the mixture was shaken at 23 °C for 1 hour. Then, it was centrifuged at a temperature of 4 °C, a rotation speed of 20,000 rpm, and a centrifugal acceleration of 45,100 × G for 60 minutes using a centrifuge (manufactured by Sakuma Seisakusho, model SS-2050A, rotor: 6B-N6L). The precipitation tube was slowly tilted to about 45 degrees, and the supernatant was removed by decantation. The mass of the insoluble matter containing toluene was precisely weighed. Subsequently, it was vacuum dried at 160 °C under a pressure of 3 kPa or less for 1 hour, cooled to room temperature in a desiccator, and then the mass of the toluene-insoluble matter was precisely weighed (this mass is designated as W2). The content (%) of toluene-insoluble matter in the styrene resin composition was determined by the following formula. Content (%) of toluene-insoluble matter in the styrene resin composition = W2 / W1 × 100

[0049] (5) Method for measuring the biomass carbon ratio (pMC%) The biomass carbon ratio (pMC%) of the biomass plasticizer (B) was calculated by the AMS method using the following formula (1) according to the radiocarbon ( 14 C) measurement method in accordance with ASTM-D6866 ( 14 C plasticizer / 12 C plasticizer) / ( 14 C standard substance / 12 C standard substance). Formula (1): Biomass carbon ratio (pMC%) = ( 14 C plasticizer / 12 C plasticizer) / ( 14 C standard substance / 12 C standard substance) × 100 In addition, oxalic acid (SRM4990) was used as the standard substance.

[0050] (6) Quantification of biomass plasticizer content The quantification of the amount of biomass plasticizer in the styrene resin compositions used in the examples and comparative examples was measured by the following method. (6-1) Calibration curve preparation Vegetable oil (glycerin fatty acid ester) was dissolved in deuterated chloroform (containing 1% TMS) containing 2-dimethoxyethane as an internal standard substance, 1 and 1H-NMR measurement was performed. When the peak of TMS was used as a reference of 0 ppm, a peak derived from a proton bonded to a carbon adjacent to the ester group of the vegetable oil was detected at δ 4.0 to 4.4 ppm, and a peak derived from 1,2-dimethoxymethane was detected at 3.4 to 3.6 ppm. The peak area derived from the vegetable oil was calculated when the peak area derived from 1,2-dimethoxymethane was set to 1. By changing the concentration of the vegetable oil and performing this operation, a calibration curve of the vegetable oil concentration was prepared. (6-2) Quantification The pelletized styrene resin composition obtained in the example or comparative example was dissolved in deuterated chloroform (containing 1% TMS), 1 1H-NMR measurement was performed, and the vegetable oil content in the styrene resin composition was quantified by using the above calibration curve. In the above method, when other peaks overlap with the peak of the internal standard substance and it is difficult to quantify, an appropriate substance may be used as the internal standard substance as appropriate. In addition, the vegetable oil can also be quantified by the peak derived from triglyceride detected at 5.0 to 5.5 ppm. When the biomass plasticizer (B) is a mixed oil of vegetable oil and a moldability adjusting compound, the content of the vegetable oil is determined by the above method, and the content of the moldability adjusting compound is separately determined for quantification. The moldability adjusting compound is liquid chromatography, GC-MS, 1 1H-NMR or13 Identification, quantification, and molecular weight measurement can be performed using various analytical instruments such as C-NMR.

[0051] (7) Calculation of the modification rate For styrene resins containing modified vegetable oil, the following procedure is used 1 It is possible to calculate the modification rate of the modified vegetable oil by H-NMR. 1 g of the pelletized styrene resin composition obtained in the examples or comparative examples was placed in a screw bottle with a volume of 20 mL, and 10 mL of methyl ethyl ketone was added. Then, after completely dissolving the pellets with a shaker, 5 mL of methanol was added, and the styrene resin composition was precipitated as an insoluble component in the solution. Next, the insoluble part was removed, the solution part was placed in an eggplant flask, and vacuumed for 2 hours with an evaporator to volatilize methyl ethyl ketone and methanol. Then, the liquid (vegetable oil) remaining in the eggplant flask was added to deuterated chloroform (containing 1% TMS), 1 H-NMR measurement was performed. When TMS was used as a reference of 0 ppm, a peak derived from an epoxy group was confirmed at δ 2.8 - 3.2 ppm, and a peak derived from a proton bonded to a carbon adjacent to the ester group of the vegetable oil was confirmed at δ 4.0 - 4.4 ppm. From the peak area ratio of these two peaks, the epoxy modification rate was calculated.

[0052] (8) Measurement of the thickness of the biaxially stretched sheet From the styrene resin compositions produced in the examples and comparative examples, a sheet with a thickness of 0.95 - 1.05 mm was produced using a 25 mmφ single-screw sheet extruder manufactured by Soken. A sheet with a size of 8 cm × 8 cm was cut out from the produced sheet. The cut-out sheet was simultaneously biaxially stretched under the following conditions using a biaxial stretching device (EX6-S1) manufactured by Toyo Seiki to produce a biaxially stretched sheet. The thickness of the stretched sheet was measured using a micro gauge. Stretching temperature: Vicat softening temperature + 20°C Stretching speed: 170% Stretching ratio: 2.0 times

[0053] (9) Measurement of the impact strength (kgf·cm) of the biaxially stretched sheet The impact strength of the sheet produced by the method described in (8) above was measured using a film impact tester (A121807502) manufactured by Toyo Seiki Seisaku-sho, Ltd.

[0054] (10) Appearance evaluation of the sheet Using a 25 mmφ single-screw sheet extruder manufactured by Soken-sha, a sheet with a thickness of 0.3 mm was produced, and the number of foreign matters, bubbles, and transparent or opaque deposits with an average diameter of 1 mm or more in (major axis + minor axis) / 2 within 5 m of the sheet was counted.

[0055] (11) Release property of the biaxially stretched sheet The above biaxially stretched sheet was cut into 3 cm × 3 cm pieces, and 20 pieces were made by sandwiching them between two 5 mm sheet metals made of pre-hardened steel and fixing them with clips. After heating in an oven at 130°C for 5 minutes, the sheet was peeled off from the sheet metal. At that time, the number of sheet samples that did not separate from the sheet metal was used as an index of the release property. As a result of this evaluation, the smaller the number of samples that did not separate from the sheet metal, the better the release property.

[0056] (12) Thickness uniformity of the biaxially stretched sheet As one of the indexes of the formability of the biaxially stretched sheet, the thickness uniformity of the biaxially stretched sheet was evaluated by the following method. For nine intersection points when three straight lines were drawn in a grid pattern at 5 cm intervals in the longitudinal and transverse directions on the sheet produced by the method described in (8) above, the thickness was measured with a micro gauge. The same thickness measurement was performed on three sheets, and the sheet thickness uniformity was evaluated by the number of points outside the range of 0.23 to 0.27 mm among the total 27 points.

[0057] (13) Release property of injection molded product The evaluation of the release property was determined by the degree of damage caused by the release resistance generated inside the molded product when taking out the molded product during injection molding. Specifically, a box-shaped molded product with an outer shape of 50 mm in length, 90 mm in width, 40 mm in depth, and 2 mm in wall thickness, and a mold having two ribs with a thickness of 1 mm at intervals of 30 mm in the horizontal position was used. Injection molding was carried out using a molding machine J100E-P (manufactured by Nippon Steel Works, Ltd.) at a temperature of 220 °C and a mold temperature of 45 °C. The evaluation of the release property was performed according to the following criteria based on the degree of damage during release that occurred inside the molded product. ◎: No damage occurs at all. 〇: Slight damage can be confirmed in a dot shape at the corner part inside the molded product. △: Slight linear damage of 2 mm or less can be confirmed at the corner part inside the molded product. ×: Linear damage larger than 2 mm can be confirmed at the corner part inside the molded product.

[0058] (14) Calculation of SP value The SP values of each material used in the examples and comparative examples were calculated by the turbidity titration method with reference to the literature values or "J. Appl. Polym. Sci., 12, 2359 (1968)".

[0059] (15) Measurement of total light transmittance and YI (I) Conditions for preparing test pieces Using a mold for flat molded products, an injection molded product of a styrene resin composition obtained under the following conditions was used to produce a flat plate with a thickness of 2 mm to produce a sheet body. Molding machine: EC60N manufactured by Toshiba Machine Co., Ltd. Cylinder temperature: 220 °C Injection pressure: 45 MPa, injection time: 10 seconds Cooling time: 15 seconds, mold temperature: 45 °C (II) Measurement conditions for total light transmittance Using the sheet body of the test piece prepared above, the total light transmittance (%) was measured in accordance with JIS K7361-1. (III) Measurement conditions for YI (Yellow Index) Using the sheet body of the test piece prepared above, the YI (Yellow Index) was measured in accordance with JIS K7105.

[0060] Each material used in the examples and comparative examples is as follows. (Modified vegetable oil) [Biomass plasticizer (B)] Epoxidized soybean oil (product name "New Sizer 510R" (manufactured by 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)" (manufactured by Nisshin Oillio Group Ltd.), weight average molecular weight (Mw = 1000), biomass carbon ratio (pMC%) 100%, melting point: 22 °C, SP value (calculated value by Hansen method, distance from the origin in the three-component coordinates of the dispersion force term (δD), polar term (δP) and hydrogen bond term (δH)): 8.2 ((cal / cm 3 ) 1 / 2 )) Castor oil (product name "Castor oil" (manufactured by Ito Shoyu Co., Ltd.), weight average molecular weight (Mw = 1000), biomass carbon ratio (pMC%) 100%, melting point 85 °C, SP value (calculated value by Hansen method, represents the distance from the origin in the three-component coordinates 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 °C (Polylactic acid) Polylactic acid, product name "LX175" (manufactured by Total Corbinion PLA), biomass carbon ratio (pMC%) 100%, melting point: 155 °C, SP value: 10.3 (cal / cm 3 ) 1 / 2 (Anthraquinone-based bluing agent) Bluing agent, product name "Plast Viоlet8840" (manufactured by Arimoto Chemical Co., Ltd.) Bluing agent, product name "Plast Blue8580" (manufactured by Arimoto Chemical Co., Ltd.) (Fatty acid-based compound, fatty acid metal salt-based compound) Ethylene bisstearamide, product name "KAO-WAX EB-FF" (manufactured by Kao Corporation) Zinc stearate, product name "DAIWA-WAX ZP" (manufactured by Dainichi Chemical Industry Co., Ltd.)

[0062] [Method for producing styrenic resin composition] [Example 1] (Method for producing styrenic resin composition (PS-1)) A polymerization solution prepared by mixing and dissolving 93.05% by mass of styrene, 6.5% by mass of ethylbenzene, 0.4% by mass of Multi Ace 20(S) (manufactured by Nisshin Oillio Group, Ltd.), and 0.05% by mass of liquid paraffin was continuously charged at 0.78 liters / hr into a 1.5-liter laminar flow reactor-1 equipped with a stirrer and capable of temperature control in 3 zones, and the temperature was adjusted to 123 °C / 128 °C / 132 °C. The rotation speed of the stirrer was set at 80 revolutions per minute. The reaction rate at the reactor outlet was 30%. Subsequently, the reaction solution was sent to a 1.5-liter laminar flow reactor-2 equipped with a stirrer and connected in series with laminar flow reactor-1 and capable of temperature control in 3 zones. The stirring speed of the stirrer was set at 40 revolutions per minute, and the temperature was set at 133 °C / 135 °C / 137 °C. Subsequently, the reaction solution was sent to a 1.5-liter laminar flow reactor-3 equipped with a stirrer and capable of temperature control in 3 zones. The rotation speed of the stirrer was set at 10 revolutions per minute, and the temperature was set at 147 °C / 150 °C / 152 °C. The polymer solution continuously discharged from the coincidence reactor (laminar flow reactor - 3) was devolatilized and pelletized under a reduced pressure of 0.8 kPa using an extruder with a vacuum vent. The temperature of the extruder was set at 220°C. Subsequently, 0.2 ppm of Plast Violet 8840 (manufactured by Yuhon Chemical Co., Ltd.) was added to the obtained pellets in the styrene resin composition, and after melt-kneading with an extruder, it was pelletized. Further, 100 ppm of Daiwax ZP (manufactured by Dainichi Chemical Industry Co., Ltd.) was added to the obtained pellets to produce a styrene resin composition (PS-1). The polymer matrix phase of the styrene resin composition (PS-1) contains polystyrene, and the SP value of the polystyrene is 8.6 (cal / cm 3 ) 1 / 2 . Then, various evaluations described above were performed on the obtained styrene resin composition of Example 1. The evaluation results are shown in Table 2-1.

[0063] 〔Examples 2 to 29〕 <Styrene resin compositions (PS-2) to (PS-15), (PS-24) to (PS-35) and (PS-21) to (PS-22) Styrene resin compositions (PS-2) to (PS-15), (PS-24) to (PS-35) were produced in the same manner as the styrene resin composition (PS-1), except that the coincidence conditions were changed as shown in Tables 1-1 to 1-3 below. Also, for the styrene resin composition (PS-21), palm oil was added to the styrene resin composition (PS-16) (GPPS without plasticizer) so that it contained 1% by mass, and further 0.05% by mass of liquid paraffin and 0.2 ppm of Plast Violet 8840 were added. After kneading with a twin-screw extruder and pelletizing, 100 ppm of Daiwax ZP (manufactured by Dainichi Chemical Industry Co., Ltd.) was added to the obtained pellets to prepare it. Similarly, for the styrene resin composition (PS-22), palm oil was added to KIBISAN (registered trademark) PN-117C (CHI-MEI product) so that it contained 1% by mass, and further 0.05% by mass of liquid paraffin and 0.2 ppm of Plast Violet 8840 were added. After kneading with a twin-screw extruder, 100 ppm of Daiwax ZP (manufactured by Dainichi Chemical Industry Co., Ltd.) was added to prepare it. For the obtained styrene resin compositions of Examples 2 to 17, the above various evaluations were conducted. The evaluation results are shown in Tables 2-1 to 2-3.

[0064] 〔Comparative Examples 1 to 6〕 <Styrene resin compositions (PS-16) to (PS-20) and (PS-23)> Styrene resin compositions (PS-16) to (PS-20) were produced in the same manner as the styrene resin composition (PS-1), except that the polymerization conditions were changed as shown in Table 1-2 below. For the styrene resin composition (PS-23), PLA was added to the styrene resin composition (PS-16) so that it contained 2% by mass, and further 0.05% of liquid paraffin and 0.2 ppm of Plast Violet 8840 were added. After kneading with a twin-screw extruder, 100 ppm of Daiwax ZP (manufactured by Dainichi Chemical Industry Co., Ltd.) was added to prepare it. It was prepared by kneading with a twin-screw extruder. Then, for the obtained styrene resin compositions of Comparative Examples 1 to 6, the above various evaluations were conducted. The evaluation results are shown in Table 2-4.

[0065]

Table 1-1

[0066]

Table 1-2

[0067]

Table 1-3

[0068]

Table 2-1

[0069]

Table 2-2

[0070]

Table 2-3

[0071]

Table 2-4

Industrial Applicability

[0072] The present invention provides a highly transparent styrene resin composition that reduces environmental load, maintains high mechanical strength, and has excellent formability into a biaxially stretched sheet and sheet appearance by using biomass raw materials, and a biaxially stretched sheet made of the styrene resin composition. The biaxially stretched sheet obtained from the styrene resin composition can be suitably used for food packaging containers and the like by secondary processing.

Claims

1. A styrenic polymer (A) and 0.1% to 5.0% by mass of a biomass plasticizer (B) having a biomass carbon ratio (pMC) of 10% or more, wherein the content of the styrenic polymer (A) is 95.0 to 99.9% by mass based on the entire styrenic resin composition, and the content of the styrenic monomer unit contained in the styrenic polymer (A) is 50% by mass or more based on the total amount of the styrenic polymer (A), the biomass plasticizer (B) is any one of natural vegetable oils, hydrogenated oils, modified epoxidized oils or modified aminated oils, A styrenic resin composition characterized in that the total light transmittance of a 2-mm-thick plate is 70% or more.

2. The styrenic resin composition according to claim 1, having a Vicat softening temperature of 85°C or higher.

3. The styrenic resin composition according to claim 1 or 2, wherein the SP value of the biomass plasticizer is 7.5 to 10.5, and the difference in the SP values between the styrenic polymer (A) and the biomass plasticizer (B) is less than 2.

0.

4. The styrenic resin composition according to claim 1 or 2, wherein the toluene-insoluble content of the styrenic resin composition is 3% by mass or less.

5. The biomass plasticizer (B) is a mixture of a vegetable oil and a formability-adjusting compound for adjusting the formability, and the formability-adjusting compound is contained in the range of 0.01 to 5% by mass based on the entire styrenic resin composition (A), The styrenic resin composition according to claim 1 or 2, wherein the formability-adjusting compound is one or more selected from the group consisting of liquid paraffin and fatty acid-based compounds.

6. The styrenic resin composition according to claim 1 or 2, containing 0.001 ppm to 10 ppm of a bluing agent with respect to the styrenic resin composition (A).

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

Images