Method for producing styrene resin, styrene resin, and molded article

Abstract

Provided is a method for producing a styrene resin that can contribute to a reduction in the carbon footprint.　The present invention provides a method for producing a styrene resin that includes a polymerization step. In the polymerization step, a raw material monomer containing a styrene monomer (B) is polymerized. The styrene monomer (B) has a sustainable ratio assigned using the mass balance method of 0.1-100%.

Description

Method for producing styrene-based resin, styrene-based resin and molded product

[0001] The present invention relates to a method for producing a styrene-based resin, a styrene-based resin, and a molded article thereof.

[0002] Plastic products are essential materials for society, but the generation of greenhouse gases throughout their life cycle, from manufacturing to disposal and recycling, is an issue. For this reason, we have developed a method to measure the CO2 emissions of greenhouse gases throughout the entire life cycle of plastic products, from manufacturing to disposal and recycling. ２ Efforts are being made to reduce the carbon footprint.

[0003] One method for reducing carbon footprints is to convert the raw material monomers of plastic products from conventional fossil fuel-derived monomers to biomass-derived monomers. For example, Patent Document 1 discloses a method for producing polyolefins using ethylene or α-olefins derived from ethanol obtained from biomass raw materials as raw material monomers. Furthermore, Patent Document 2 discloses a method for producing a conjugated diene copolymer obtained by polymerizing biobutadiene derived from bioethanol.

[0004] International Publication No. 2009 / 070858 Japanese Patent Application Laid-Open No. 2013-249379

[0005] However, although methods for deriving styrene-based monomers from biomass-derived alcohols have been intensively investigated, they have not yet been industrialized, and it has been difficult to produce styrene-based resins that can contribute to reducing carbon footprints using styrene-based monomers derived from biomass-derived alcohols. Furthermore, deriving styrene-based monomers from biomass-derived alcohols requires additional steps and equipment, which makes it difficult to provide a useful means from the perspective of reducing carbon footprints.

[0006] The present invention has been made in view of the above problems, and provides a method for producing a styrene-based resin that can contribute to reducing carbon footprints. The present invention also provides a styrene-based resin that can contribute to reducing carbon footprints, and a molded article obtained by molding a styrene-based resin composition containing the styrene-based resin.

[0007] According to the present invention, the following inventions are provided. [1] A styrene-based resin having structural units derived from a styrene-based monomer, the styrene-based monomer including a styrene-based monomer (B), and having a sustainable ratio of 0.0001 to 100% as allocated using a mass balance method. [2] The styrene-based resin according to [1], wherein the styrene-based monomer includes a fossil fuel-derived styrene-based monomer (A). [3] The styrene-based resin according to [1] or [2], having structural units derived from a monomer (C), the monomer (C) including at least one selected from the group consisting of a (meth)acrylic acid ester monomer, a vinyl cyanide monomer, an α,β-ethylenically unsaturated carboxylic acid, and an imide. [4] The styrene-based resin according to any one of [1] to [3], having a weight-average molecular weight (Mw) of 50,000 to 400,000. [5] The styrene-based resin according to any one of [1] to [4], having a melt mass-flow rate (MFR) of 0.1 to 30.0 g / 10 min at 200°C under a load of 49 N, as measured in accordance with JIS K7210. [6] A molded article obtained by molding a styrene-based resin composition containing the styrene-based resin according to any one of [1] to [5]. [7] A method for producing a styrene-based resin, comprising a polymerization step, in which raw material monomers including a styrene-based monomer (B) are polymerized, and the styrene-based monomer (B) has a sustainable ratio of 0.1 to 100% allocated using a mass balance method. [8] The method for producing a styrene-based resin according to [7], wherein the raw material monomers include a fossil fuel-derived styrene-based monomer (A). [9] The method for producing a styrene-based resin according to [7] or [8], wherein the raw material monomer includes a monomer (C), and the monomer (C) includes at least one selected from the group consisting of a (meth)acrylic acid ester-based monomer, a vinyl cyanide monomer, an α,β-ethylenically unsaturated carboxylic acid, and an imide.

[10] The method for producing a styrene-based resin according to [8] or [9], wherein the content of the styrene-based monomer (B) in the raw material monomers is 0.1 to 99.9 mass% relative to 100 mass% of the total of the raw material monomers.

[11] The method for producing a styrene-based resin according to any one of [7] to

[10] , wherein bio-circular styrene and / or circular styrene is used as the styrene-based monomer (B) in the polymerization step.

[0008] As a result of intensive investigations, the present inventors have found that the above-mentioned problems can be solved by using, as raw material monomers in the production of a styrene-based resin, a styrene-based monomer derived from a fossil fuel and a styrene-based monomer whose sustainable ratio is equal to or greater than a predetermined amount, which is allocated by employing a mass balance method, and have thereby completed the present invention.

[0009] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an invention independently.

[0010] <Styrene-based resin> The styrene-based resin of the present invention is a polymer obtained by polymerizing raw material monomers containing at least a styrene-based monomer (B). The raw material monomers may contain a fossil fuel-derived styrene-based monomer (A) and may further contain a monomer (C) copolymerizable with the styrene-based monomer. That is, the styrene-based resin of the present invention may be a copolymer having a structural unit derived from a styrene-based monomer and a structural unit derived from the monomer (C). Furthermore, the styrene-based resin of the present invention may be a copolymer having a structural unit derived from a monomer other than the monomers (A), (B), and (C).

[0011] The fossil fuel-derived styrene monomer (A) is a styrene monomer obtained from petroleum, coal, natural gas, shale gas, etc., which are obtained from the liquefied and gasified remains of animals and plants that have been decomposed under pressure by sediment and geothermal heat over hundreds of millions of years. １４Since more time has passed than the half-life of the C isotope, which is 5,700 years, in the elemental analysis of fossil fuel-derived styrene monomer (A), １４ C is not detected. In the present invention, the fossil fuel-derived styrene-based monomer (A) is a non-sustainable monomer, and does not include sustainable monomers such as circular styrene, which will be described later.

[0012] The styrene monomer (B) is a styrene monomer having a sustainable ratio assigned using the mass balance method. The mass balance method is a technique in which, when raw materials with different properties are mixed, a certain characteristic is arbitrarily assigned to a portion of the product to be produced depending on the amount of raw material having that characteristic added. In the present invention, the styrene monomer (B) is a monomer produced by mixing sustainable raw materials and fossil fuel-derived raw materials using conventional equipment and production methods, and has an arbitrary sustainable ratio assigned depending on the amount of sustainable raw materials added.

[0013] For example, if 40 parts by mass of biomass-derived sustainable raw materials and 60 parts by mass of fossil fuel-derived raw materials are input to produce 10 products of styrene-based monomer (B) with a biomass component content of approximately 40% by mass, the actual biomass component content in all products is approximately 40% by mass. However, the sustainable ratio of any four of the 10 products can be set to 100%, and the sustainable ratio of the remaining six can be set to 0%. Thus, the sustainable ratio may differ from the actual biomass component content of each individual product and is an indicator of the contribution of each product to reducing the carbon footprint of the entire industry. Note that the sustainable ratio can be arbitrarily assigned to each product within a range depending on the amount of sustainable raw materials input, and is not limited to 0% or 100% as described above. In one embodiment, the sustainable ratio of the styrene-based monomer (B) is preferably 0.1 to 100%, more preferably 1 to 100%, and even more preferably 10 to 100%. Specifically, the sustainable ratio may be, for example, 0.1, 0.5, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100%, or may be within a range between any two of the values ​​exemplified here. If the sustainable ratio is too small, the contribution to reducing the carbon footprint of the entire industry will be insufficient.

[0014] Examples of sustainable raw materials include unused biomass such as corn, sugarcane, rapeseed, sunflower, palm, soybean, rice, wheat, willow, and poplar; biomass-derived waste and residues such as rice straw, wheat straw, thinning materials, oil extraction residue, tall oil, UC oil, and food waste; and non-biomass-derived materials such as recyclable plastics. In this specification, "biomass-derived sustainable raw materials" includes unused biomass and biomass-derived waste and residues. Note that the carbon in biomass-derived sustainable raw materials is １４ Contains a certain amount of C isotope.

[0015] In this specification, styrene-based monomers (B) produced using unused biomass, biomass-derived waste or residue, and recyclable non-biomass-derived materials are defined as biostyrene, biocircular styrene, and circular styrene, respectively. In the present invention, the styrene-based monomer (B) may be any of these, but from the viewpoints of avoiding competition for food, stable procurement, effective utilization of unnecessary materials, etc., non-edible biocircular styrene and / or circular styrene are preferred.

[0016] The styrene-based monomer (B) is preferably produced by a supplier that has obtained international certification regarding sustainability and carbon, such as ISCC EU certification or ISCC PLUS certification. In this case, the traceability of the styrene-based monomer (B) is guaranteed, and the carbon footprint reduction effect of using the styrene-based monomer (B) becomes clearer.

[0017] For example, ISCC PLUS certification ensures traceability through a chain of custody (CoC), a system that combines certification of the manufacturing site and the raw materials, ensuring traceability by identifying where the raw materials originated and the routes they were subsequently collected, processed, transported, and remanufactured. For this reason, ISCC PLUS-certified suppliers of styrene monomer (B) can issue and attach a Sustainability Declaration (SD), a document detailing the raw materials, to each product delivery and pass it on to downstream users. This enables the management of material movements and information as a set in the production of styrene resins, ensuring traceability. In the production of styrene resins, it is preferable to confirm that the supplier of styrene monomer (B) holds a valid certification at the time the SD is issued after receiving the SD.

[0018] Examples of styrene-based monomers including the fossil fuel-derived styrene-based monomer (A) and the styrene-based monomer (B) include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, ethylstyrene, p-t-butylstyrene, α-methylvinyltoluene, dimethylstyrene, bromostyrene, and dibromostyrene. These can be used alone or in combination of two or more. In one embodiment, it is preferable to use styrene as the styrene-based monomer.

[0019] The monomer (C) preferably includes at least one selected from the group consisting of (meth)acrylic acid ester monomers, vinyl cyanide monomers, α,β-ethylenically unsaturated carboxylic acids, and imides. The content of the structural units derived from the monomer (C) in the styrene-based resin is not particularly limited, but in one embodiment, it can be 1 to 99 mass% relative to 100 mass% of the styrene-based resin. Specific examples of this content include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 99 mass%, and may be within a range between any two of the values ​​exemplified here.

[0020] Examples of the (meth)acrylic acid ester monomer include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate; (meth)acrylic acid aryl esters such as phenyl (meth)acrylate and benzyl (meth)acrylate; (meth)acrylic acid cycloalkyl esters such as cyclohexyl (meth)acrylate, 4-t-butylcyclohexyl (meth)acrylate, tricyclodecanyl (meth)acrylate, and adamantyl (meth)acrylate; glycidyl (meth)acrylate; and dicyclopentadienyl (meth)acrylate. These may be used alone or in combination of two or more. In one embodiment, the (meth)acrylic acid ester monomer is preferably a (meth)acrylic acid alkyl ester, and more preferably methyl methacrylate.

[0021] Examples of the vinyl cyanide monomer include acrylonitrile and methacrylonitrile, which can be used alone or in combination of two or more. In one embodiment, the vinyl cyanide monomer is preferably acrylonitrile.

[0022] Examples of α,β-ethylenically unsaturated carboxylic acids include monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, and isocrotonic acid; dicarboxylic acids and anhydrides thereof such as maleic acid (anhydride), fumaric acid, and itaconic acid (anhydride); and dicarboxylic acid monoalkyl esters such as monomethyl maleate, monoethyl maleate, monobutyl maleate, mono-2-ethylhexyl maleate, monomethyl fumarate, monoethyl fumarate, monobutyl fumarate, mono-2-ethylhexyl fumarate, monomethyl itaconate, monoethyl itaconate, monobutyl itaconate, and mono-2-ethylhexyl itaconate. These can be used alone or in combination of two or more. In one embodiment, the α,β-ethylenically unsaturated carboxylic acid is preferably methacrylic acid and / or maleic acid (anhydride).

[0023] Examples of imides include maleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-butylmaleimide, N-pentylmaleimide, N-hexylmaleimide, N-octylmaleimide, N-dodecylmaleimide, N-isopropylmaleimide, N-isobutylmaleimide, N-sec-butylmaleimide, N-tert-butylmaleimide, N-cyclopropylmaleimide, N-cyclobutylmaleimide, N-cyclohexylmaleimide, and N-phenylmaleimide, and these can be used alone or in combination of two or more. In one embodiment, the imide is preferably N-phenylmaleimide.

[0024] In one embodiment, the raw material monomer for the styrene-based resin preferably contains a (meth)acrylic acid ester monomer as the monomer (C). The styrene-based resin is preferably a copolymer containing 5 to 95% by mass of structural units derived from styrene-based monomers and 5 to 95% by mass of structural units derived from (meth)acrylic acid ester monomers, more preferably a copolymer containing 10 to 90% by mass of structural units derived from styrene-based monomers and 10 to 90% by mass of structural units derived from (meth)acrylic acid ester monomers, even more preferably a copolymer containing 15 to 85% by mass of structural units derived from styrene-based monomers and 15 to 85% by mass of structural units derived from (meth)acrylic acid ester monomers, and particularly preferably a copolymer containing 20 to 65% by mass of structural units derived from styrene-based monomers and 35 to 80% by mass of structural units derived from (meth)acrylic acid ester monomers. The content of the structural units derived from styrene-based monomers is, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95% by mass, and may be within a range between any two of the numerical values ​​exemplified herein. Furthermore, the content of the structural units derived from (meth)acrylic acid ester-based monomers is, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95% by mass, and may be within a range between any two of the numerical values ​​exemplified herein. By setting the content of the structural units derived from styrene-based monomers or the structural units derived from (meth)acrylic acid ester-based monomers within such ranges, the resulting film has excellent hue and transmittance, and can reduce costs and carbon footprint.

[0025] The weight average molecular weight (Mw) of the styrene resin is preferably 50,000 to 400,000, more preferably 100,000 to 350,000, specifically, for example, 50,000, 100,000, 150,000, 200,000, 250,000, 300,000, 350,000, or 400,000, and may be within a range between any two of the values ​​exemplified herein. Furthermore, the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the styrene resin is preferably 1.0 to 3.5, more preferably 1.5 to 3.0, specifically, for example, 1.0, 1.5, 2.0, 2.5, 3.0, or 3.5, and may be within a range between any two of the values ​​exemplified herein. By setting the weight average molecular weight (Mw) or the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the styrene resin within such ranges, when molding the styrene resin, it is possible to achieve both strength and moldability of the molded body. If the weight average molecular weight (Mw) is too small, the strength of the molded product tends to be insufficient, and if it is too large, the moldability may decrease. Also, if the ratio (Mw / Mn) of the number average molecular weight (Mn) is too small, the moldability tends to decrease, and if it is too large, the strength of the molded product may decrease. The weight average molecular weight (Mw) can be measured by gel permeation chromatography (GPC), as described in the following examples.

[0026] The styrene-based resin of the present invention can be widely used in light guide plates and diffusion plates for home appliance components and liquid crystal display panels, food packaging containers, etc. However, when used in molding optical products such as light guide plates, the content of the polymerization inhibitor is preferably 0 to 10 ppm. Here, ppm refers to the concentration based on the mass of the total raw material monomers. The polymerization inhibitor may be contained in the raw material monomers of the styrene-based resin, and specific examples include t-butylcatechol (TBC) and 6-tert-butyl-2,4-xylenol (TBX). In one embodiment, the polymerization inhibitor is preferably TBC and / or TBX. The content of TBC in the styrene-based resin is preferably 0 to 10 ppm, more preferably 0 to 5 ppm. The TBC content may be, for example, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 ppm, or may be within a range between any two of the values ​​exemplified here.

[0027] The TBX content in the styrene-based resin is preferably 0 to 10 ppm, more preferably 0 to 5 ppm. Specifically, the TBX content may be, for example, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 ppm, and may be within a range between any two of the values ​​exemplified here. By setting the TBC and TBX contents within these ranges, a styrene-based resin with excellent hue and transmittance can be obtained. The TBC and TBX contents can be measured by gas chromatography mass spectrometry (GC / MS), as described in the following examples.

[0028] The melt mass flow rate (MFR) of the styrene-based resin can be measured in accordance with JIS K 7210. The MFR measured in accordance with JIS K 7210 under conditions of a temperature of 200°C and a load of 49 N is preferably 0.1 to 30.0 g / 10 min, and more preferably 0.2 to 25.0 g / 10 min. Specific examples of this MFR include 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, and 30 g / 10 min, and may be within a range between any two of the values ​​exemplified here. If the MFR is too small, molding stability tends to decrease, and if the MFR is too large, the strength of the molded article tends to be insufficient.

[0029] <Styrene-Based Resin Composition> The styrene-based resin composition of the present invention contains at least the styrene-based resin of the present invention, and may contain any one or more of a phenol-based antioxidant, a phosphorus-based antioxidant, and a phosphorus-phenol-based antioxidant, within a range that does not impair the properties of the present invention.

[0030] The phenolic antioxidant is an antioxidant that has a phenolic hydroxyl group in its basic skeleton and is not a phosphate ester (or phosphate ester). Examples of the phenolic antioxidant include octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate], pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 4,6-bis(octylthiomethyl)-o-cresol, hexa ... Methylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxyphenylmethyl)-2,4,6-trimethylbenzene, 4,4',4''-(1-methylpropanyl-3-ylidene)tris(6-tert-m-cresol), 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1 ,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)hexahydro-1,3,5-triazine-2,4,6-trione, 2,6-di-tert-butyl-4-(4, Examples of such esters include 6-bis(octylthio)-1,3,5-triazin-2-ylamine)phenol, 4,4'-thiobis(6-tert-butyl-3-methylphenol), 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, and 2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl acrylate. These may be used alone or in combination of two or more.

[0031] The phosphorus-based antioxidant is a (phosphite) ester that does not have a phenolic hydroxyl group in its basic skeleton, and is preferably a phosphite ester that is a trivalent phosphorus compound. Specific examples of the phosphorus-based antioxidant include tris(2,4-di-tert-butylphenyl)phosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane, 2,2'- Examples of such phosphorus compounds include methylenebis(4,6-di-tert-butyl-1-phenyloxy)(2-ethylhexyloxy)phosphorus, tris[2-[[2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxaphosphine-6-yl]oxy]ethyl]amine, bis(2,4-bis(1,1-dimethylethyl)-6-methylphenyl)ethyl ester phosphorous acid, tetrakis(2,4-di-tert-butylphenyl)(1,1biphenyl)-4,4'-diylbisphosphonite, and tris(nonylphenyl)phosphite. These may be used alone or in combination of two or more.

[0032] The phosphorus-phenol-based antioxidant is a phosphite ester having a phenolic hydroxyl group in its basic skeleton, preferably a phosphite ester, which is a trivalent phosphorus compound having a phenolic hydroxyl group in its basic skeleton. Examples of the phosphorus-phenol-based antioxidant include 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepine.

[0033] Furthermore, the styrene-based resin composition of the present invention may contain, within the scope not impairing the properties of the present invention, a release agent such as a sulfur-based antioxidant, a lactone-based antioxidant, a hindered amine-based light stabilizer, an ultraviolet absorber, an antistatic agent, a hydrophilic additive, liquid paraffin (mineral oil), polyethylene wax, microcrystalline wax, a bluing agent, a higher fatty acid such as lauric acid, myristic acid, palmitic acid, or stearic acid, a higher fatty acid amide such as stearamide, erucic acid amide, or ethylene bisstearamide, a higher fatty acid glyceride such as lauric acid monoglyceride, palmitic acid monoglyceride, stearic acid monoglyceride, or behenic acid monoglyceride, or a higher alcohol such as myristyl alcohol, cetyl alcohol, or stearyl alcohol.

[0034] <Method for producing styrene-based resin> A method for producing a styrene-based resin according to one embodiment includes a polymerization step. In the polymerization step, raw material monomers including a styrene-based monomer (B) are polymerized. The styrene-based monomer (B) has a sustainable ratio of 0.1 to 100% allocated using a mass balance method. The styrene-based monomer (B) is preferably non-edible bio-circular styrene and / or circular styrene.

[0035] The raw material monomer used in the polymerization step may contain a fossil fuel-derived styrene-based monomer (A) or a monomer (C) copolymerizable with the styrene-based monomer. The monomer (C) preferably contains at least one selected from the group consisting of (meth)acrylic acid ester-based monomers, vinyl cyanide monomers, α,β-ethylenically unsaturated carboxylic acids, and imides.

[0036] The polymerization method for the styrene resin in the polymerization step includes known styrene polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. In terms of quality and productivity, bulk polymerization and / or solution polymerization are preferred, and continuous polymerization is preferred. As the solvent, for example, (alkyl)benzenes such as benzene, toluene, ethylbenzene, and xylene, ketones such as acetone and methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and cyclohexane can be used.

[0037] During polymerization of the styrene-based resin, polymerization aids such as a polymerization initiator, a chain transfer agent, a crosslinking agent, and other polymerization aids may be used as necessary. The polymerization initiator is preferably a radical polymerization initiator, and examples of commonly used initiators include peroxyketals such as 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(t-butylperoxy)butane, 2,2-di(4,4-di-t-butylperoxycyclohexyl)propane, and 1,1-di(t-amylperoxy)cyclohexane, hydroperoxides such as cumene hydroperoxide and t-butyl hydroperoxide, alkyl peroxides such as t-butyl peroxyacetate and t-amylperoxyisononanoate, t-butylcumyl peroxide, di-t-butyl peroxide, dicumyl peroxide, and di-t-hexyl peroxide. peroxyesters such as t-butylperoxyacetate, t-butylperoxybenzoate, and t-butylperoxyisopropyl monocarbonate; peroxycarbonates such as t-butylperoxyisopropyl carbonate and polyethertetrakis(t-butylperoxycarbonate); N,N'-azobis(cyclohexane-1-carbonitrile), N,N'-azobis(2-methylbutyronitrile), N,N'-azobis(2,4-dimethylvaleronitrile), and N,N'-azobis[2-(hydroxymethyl)propionitrile]; and the like, and these can be used alone or in combination of two or more. Examples of the chain transfer agent include aliphatic mercaptans such as n-dodecyl mercaptan and tert-dodecyl mercaptan, aromatic mercaptans, thiocarboxylic acids such as thioglycolic acid and mercaptopropionic acid, polyfunctional mercaptans in which the hydroxyl group of a polyhydric alcohol such as ethylene glycol, tetraethylene glycol, neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, and sorbitol is esterified with thioglycolic acid or mercaptopropionic acid, pentaphenylethane, α-methylstyrene dimer, and terpinolene.Among these, at least one selected from the group consisting of aliphatic mercaptans, aromatic mercaptans, thiocarboxylic acids, and polyfunctional mercaptans is preferred because it allows for easy molecular weight adjustment.

[0038] In the case of continuous polymerization, the styrene-based resin can be produced by a method including a polymerization step, a devolatilization step, and a granulation step.

[0039] First, in the polymerization step, a known complete mixing tank type agitation tank or tower type reactor is used, and the polymerization reaction is controlled by adjusting the polymerization temperature etc. so as to achieve the target molecular weight, molecular weight distribution and reaction conversion rate.

[0040] The polymerization solution containing the polymer that has undergone the polymerization process is transferred to the devolatilization process, where unreacted monomers and polymerization solvent are removed. The devolatilization process is composed of a vacuum devolatilization tank equipped with a heater or a devolatilization extruder equipped with a vent. The molten polymer that has undergone the devolatilization process is transferred to the granulation process. In the granulation process, the molten resin is extruded in the form of strands through a multi-hole die and processed into pellets using the cold cut method, the in-air hot cut method, or the underwater hot cut method.

[0041] The contents of TBC and TBX in the styrene-based resin can be adjusted at the start of polymerization of the styrene-based resin and in the subsequent devolatilization step, etc.

[0042] From the viewpoint of reducing carbon footprint and cost, the content of the styrene-based monomer (B) relative to the total 100% by mass of the raw material monomers used in the polymerization step is preferably 0.1 to 100% by mass. When the raw material monomers contain a monomer other than the styrene-based monomer (B), the content of the styrene-based monomer (B) is preferably 0.1 to 99.9% by mass, more preferably 1 to 99% by mass, and even more preferably 10 to 90% by mass. Specific examples include 0.1, 0.5, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 99.9% by mass, and may be within a range between any two of the values ​​exemplified here.

[0043] From the viewpoint of traceability, it is preferable to produce a styrene-based resin using a styrene-based monomer (B) produced by a supplier that has obtained international certification related to sustainability and carbon, such as ISCC EU certification or ISCC PLUS certification. It is also preferable to use the styrene-based monomer (B) after confirming that the supplier of the styrene-based monomer (B) holds a valid certification at the time of issuance of the SD.

[0044] In the production of the styrene-based resin, the styrene-based monomer (B) having a sustainable ratio assigned by adopting the mass balance method is used, and therefore the styrene-based resin produced by the above method can also be assigned a sustainable ratio by adopting the mass balance method. The sustainable ratio of the styrene-based resin according to the present invention is defined by the following formula: Sustainable ratio (%) of styrene-based resin = Sustainable ratio (%) of styrene-based monomer (B) × Content (% by mass) of styrene-based monomer (B) relative to 100% by mass of the total of raw material monomers used in the polymerization step / 100

[0045] When a monomer other than the styrene-based monomer (B) contained in the raw material monomers has a sustainable ratio, the sustainable ratio (%) of the styrene-based resin can be calculated as the sum of the sustainable ratio (%) of each monomer x the content (mass%) of each monomer / 100.

[0046] In one embodiment, the sustainable ratio of the styrene-based resin is preferably 0.0001 to 100%, more preferably 0.0001 to 99.9%, even more preferably 0.001 to 99%, and particularly preferably 0.01 to 90%. Specific examples of the sustainable ratio of the styrene-based resin include 0.0001, 0.001, 0.01, 0.1, 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 99, 99.9, and 100%, and may be within a range between any two of the values ​​exemplified here. By setting the sustainable ratio of the styrene-based resin within this range, it is possible to reduce costs and contribute to reducing the carbon footprint across the industry.

[0047] In general, the derivation of biomass-derived alcohols tends to be costly, and the sales price of the styrene-based monomer obtained through such derivation is expected to be high. Therefore, when producing a styrene-based resin using such a styrene-based monomer, it is considered necessary to appropriately adjust the biomass content of the styrene-based resin product, taking into account the price of the styrene-based resin product, market needs, etc. One method for adjusting the biomass content is, for example, mixing a polymer obtained by polymerizing a styrene-based monomer derived from a biomass feedstock with a polymer obtained by polymerizing a conventional styrene-based monomer derived from a fossil fuel. However, this method requires an additional mixing step and the necessary equipment, which not only results in high costs but also raises concerns about increased environmental impact. Furthermore, the physical properties of a polymer obtained from a styrene-based monomer derived from a biomass feedstock are not necessarily the same as those of a polymer obtained from a conventional styrene-based monomer derived from a fossil fuel. In particular, when these physical properties differ significantly, there is a risk that the desired physical properties of a styrene-based resin cannot be obtained. On the other hand, according to the method for producing a styrene-based resin of the present invention, a styrene-based resin having physical properties equivalent to those of conventional fossil fuel-derived styrene-based resins and a sustainable ratio that can contribute to reducing the carbon footprint can be produced while keeping costs down.

[0048] <Method for producing styrene-based resin composition and molding method> The styrene-based resin produced as described above can be mixed with other components such as an antioxidant as needed using a known method such as melt kneading to produce a styrene-based resin composition. The content of the styrene-based resin in 100% by mass of the styrene-based resin composition can be, for example, 90% by mass or more and 100% by mass or less, more preferably more than 90% by mass and 100% by mass or less, and can be appropriately adjusted depending on the purpose. When the content of the styrene-based resin is 100% by mass, the above-mentioned mixing is not necessary.

[0049] When the content of the styrene-based resin is 100% by mass, the sustainable ratio of the styrene-based resin composition is the same as the sustainable ratio of the styrene-based resin. Furthermore, when a component other than the styrene-based resin contained in the styrene-based resin composition has a sustainable ratio, the sustainable ratio (%) of the styrene-based resin composition can be calculated as the sum of the sustainable ratio (%) of each component × the content (% by mass) of each component / 100.

[0050] The molding method of the styrene-based resin composition is not particularly limited, and known molding methods such as press molding, extrusion molding, injection molding, injection blow molding, blow molding, and profile extrusion molding can be used. Other examples include a method in which the composition is combined with various foam molding techniques to form a foamed molded article, and a method in which the composition is molded into a sheet or film using a T-die sheet extruder, a biaxial stretching processing device, or an inflation processing device. When the molded article is a sheet, it may be a single layer, or it may be used as at least one of the outer layers or only the inner layer of a multilayer sheet. By replacing part or all of a molded article made from a conventional styrene-based resin composition with a molded article made from the styrene-based resin composition of the present invention, the carbon footprint can be reduced.

[0051] <Provision of styrene-based resin products and molded articles> The styrene-based resin or styrene-based resin composition (hereinafter referred to as "styrene-based resin product") manufactured by the above-described manufacturing method can be provided with the issuance of a Sustainability Declaration (SD) if the manufacturing base has already obtained international certification such as ISCC PLUS. Furthermore, the issuance of an SD guarantees the traceability of products such as molded articles manufactured using the styrene-based resin product, making it possible to provide them as products that can contribute to reducing carbon footprints based on international certification systems.

[0052] The present invention will be described in more detail below with reference to examples, but these examples are merely illustrative and are not intended to limit the scope of the present invention.

[0053] 1. Evaluation Methods The physical properties of the styrene-based resins in each of the Examples and Comparative Examples were evaluated by the following methods.

[0054] <Melt Mass Flow Rate (MFR)> The melt mass flow rate was measured in accordance with JIS K 7210 under conditions of a temperature of 200°C and a load of 49N.

[0055] <Contents of TBC and TBX in Styrenic Resin> 0.2 g of styrene-based resin was dissolved in a small amount of THF, and then 200 μL of BSTFA (M,O-bis(trimethylsilyl)trifluoroacetamide) was added to carry out a trimethylsilyl derivatization treatment. The volume was adjusted to 10 mL with THF, and the supernatant separated by centrifugation was measured by gas chromatography mass spectrometry (GC / MS) under the following conditions. A calibration curve prepared in advance was used to determine the concentrations. GC device: 7890A manufactured by Agilent Co. Column: DB-5ms (0.25 mm i.d. x 30 m) manufactured by Agilent Co., Ltd. Liquid phase film thickness 0.25 μm Column temperature: 50°C (1 min) → (20°C / min temperature increase) → 320°C (6.5 min) Total 20 min Inlet : 300℃, 1.5mL / min, (split ratio 1:5) Injection volume: 1μL MS device: Agilent 5975C Interface temperature: 320℃ MS detection conditions: SIM measurement TBC (m / z 295 for quantitative, m / z 310 for confirmation)

[0056] <Weight-average molecular weight (Mw)> The weight-average molecular weight (Mw) was measured using gel permeation chromatography (GPC) under the following conditions: GPC model: Shodex GPC-101 manufactured by Showa Denko K.K. Column: PLgel 10 μm MIXED-B manufactured by Polymer Laboratories, Inc. Mobile phase: tetrahydrofuran Sample concentration: 0.2% by mass Temperature: oven 40°C, injection port 35°C, detector 35°C Detector: differential refractometer The molecular weight was calculated as a polystyrene-equivalent molecular weight by calculating the molecular weight at each elution time from the elution curve of monodisperse polystyrene.

[0057] <Average Transmittance and YI Value> The average transmittance and YI value were measured according to the following procedure. Using pellets of a styrene-based resin, injection molding was performed at a cylinder temperature of 190°C and a mold temperature of 40°C to produce a plate-shaped molded product measuring 115 mm x 80 mm x 3 mm thick. For the plate-shaped molded product obtained above, the spectral transmittance was measured at wavelengths of 350 nm to 800 nm at an optical path length of 115 mm for incident light of 20 x 1.6 mm and a spread angle of 0° using a UV-visible spectrophotometer V-670 manufactured by JASCO Corporation, and the YI value at a field of view of 2° under C light source was calculated according to JIS K7105. The average transmittance (total light transmittance) was calculated as the average of the spectral transmittances at wavelengths of 380 to 780 nm.

[0058] 2. Examples and Comparative Examples [Example 1] A polymerization process was carried out by connecting a first reactor, which was a complete mixing type stirred tank, and a second reactor, which was a plug flow type reactor equipped with a static mixer, in series, to produce a styrene-based resin. The volumes of the first reactor and the second reactor were 30 liters and 12 liters, respectively. The raw material composition was 50% by mass of biocircular styrene (manufactured by Shell Chemicals, ISCC PLUS certified, sustainable ratio: 100%, TBC concentration 10 μg / g), 40% by mass of methyl methacrylate (TBX concentration 7 μg / g), and 10% by mass of ethylbenzene. At the inlet of the first reactor, the polymerization initiator was 100 ppm of t-butylperoxyisopropyl monocarbonate (manufactured by NOF Corporation: Perbutyl I), and the chain transfer agent was 150 ppm of n-dodecyl mercaptan (manufactured by Arkema Inc.). The raw material solution was then continuously supplied at 8.0 kg / h to the first reactor, which was set at 135°C. The resulting polymerization solution was then continuously supplied to the second reactor, where the polymerization was completed. The monomer conversion was 70%. In the second reactor, a temperature gradient was applied along the direction of flow, adjusting the temperature to 135°C in the middle section and 145°C at the outlet. Subsequently, the polymer-containing solution continuously removed from the second reactor was introduced into a vacuum devolatilizer tank equipped with a preheater, consisting of two stages in series. The temperature of the preheater was adjusted so that the resin temperature was 240°C, and unreacted styrene and ethylbenzene were separated at a pressure of 0.8 kPa. The resin was extruded into strands through a multi-hole die, and the strands were cooled, cut, and pelletized using a cold-cut method. The resulting styrene-based resin had a styrene content of 54% by mass, a methyl methacrylate content of 46% by mass, an MFR of 2.5 g / 10 min, a weight-average molecular weight (Mw) of 186,000, a TBC content of 2.5 ppm, a TBX content of 0.6 ppm, a YI value of 1.7, an average transmittance of 88%, and a sustainability ratio of 54%.

[0059] Example 2 A styrene-based resin was produced in the same manner as in Example 1, except that the raw material composition was changed to 20% by mass of fossil fuel-derived styrene, 30% by mass of biocircular styrene, 40% by mass of methyl methacrylate, and 10% by mass of ethylbenzene. The obtained styrene-based resin had a styrene content of 54% by mass, a methyl methacrylate content of 46% by mass, an MFR of 2.5 g / 10 min, a weight-average molecular weight (Mw) of 186,000, a TBC content of 2.5 ppm, a TBX content of 0.6 ppm, a YI value of 1.7, an average transmittance of 88%, and a sustainability ratio of 32%.

[0060] [Example 3] A styrene-based resin was produced in the same manner as in Example 1, except that the raw material composition was changed to 36 mass% biocircular styrene, 54 mass% methyl methacrylate, and 10 mass% ethylbenzene, and n-dodecyl mercaptan was changed to 1,000 ppm. The styrene content of the obtained styrene-based resin was 40 mass%, the methyl methacrylate content was 60 mass%, the MFR was 1.9 g / 10 min, the weight-average molecular weight (Mw) was 120,000, the TBC content was 1.4 ppm, the TBX content was 1.2 ppm, the YI value was 1.5, the average transmittance was 89%, and the sustainability ratio was 40%.

[0061] [Example 4] A styrene-based resin was produced in the same manner as in Example 1, except that the raw material composition was changed to 9% by mass of fossil fuel-derived styrene, 27% by mass of biocircular styrene, 54% by mass of methyl methacrylate, and 10% by mass of ethylbenzene, and the n-dodecyl mercaptan was changed to 1,000 ppm. The styrene content of the obtained styrene-based resin was 40% by mass, the methyl methacrylate content was 60% by mass, the MFR was 1.9 g / 10 min, the weight-average molecular weight (Mw) was 120,000, the TBC content was 1.4 ppm, the TBX content was 1.2 ppm, the YI value was 1.5, the average transmittance was 89%, and the sustainability ratio was 30%.

[0062] [Example 5] A styrene-based resin was produced in the same manner as in Example 1, except that the raw material composition was changed to 73 mass% biocircular styrene, 17 mass% methyl methacrylate, and 10 mass% ethylbenzene, and n-dodecyl mercaptan was changed to 100 ppm. The styrene content of the obtained styrene-based resin was 80 mass%, the methyl methacrylate content was 20 mass%, the MFR was 1.7 g / 10 min, the weight-average molecular weight (Mw) was 250,000, the TBC content was 2.8 ppm, the TBX content was 0.5 ppm, the YI value was 4.5, the average transmittance was 83%, and the sustainability ratio was 80%.

[0063] Comparative Example 1 A styrene-based resin was produced in the same manner as in Example 1, except that the raw material composition was changed to 50 mass% of fossil fuel-derived styrene, 40 mass% of methyl methacrylate, and 10 mass% of ethylbenzene. The obtained styrene-based resin had a styrene content of 54 mass%, a methyl methacrylate content of 46 mass%, an MFR of 2.5 g / 10 min, a weight-average molecular weight (Mw) of 186,000, a TBC content of 2.5 ppm, a TBX content of 0.6 ppm, a YI value of 1.7, an average transmittance of 88%, and a sustainability ratio of 0%.

[0064] From the results of the Examples and Comparative Examples, it can be seen that the styrene-based resins of Examples 1 to 5, which use biocircular styrene, were produced using the same equipment and method as the styrene-based resin of Comparative Example 1, which uses only fossil fuel-derived styrene and methyl methacrylate, and have physical properties (MFR, Mw) equivalent to those of the styrene-based resin of Comparative Example 1, as well as a sustainability ratio that can contribute to reducing the carbon footprint. Producing styrene-based resin compositions and molded articles using these styrene-based resins can contribute to reducing the carbon footprint while suppressing costs. Furthermore, the styrene-based resins of Examples 1 to 5 have excellent hue and transmittance because the TBC and TBX contents are equivalent to those of Comparative Example 1, making them particularly suitable as materials for optical molded articles such as light guide plates.

Claims

1. A styrene-based resin having structural units derived from a styrene-based monomer, the styrene-based monomer including a styrene-based monomer (B), and having a sustainable ratio of 0.0001 to 100% as determined by the mass balance method.

2. A styrene-based resin according to claim 1, wherein the styrene-based monomer comprises a fossil fuel-derived styrene-based monomer (A).

3. A styrene-based resin according to claim 1, comprising a structural unit derived from a monomer (C), wherein the monomer (C) comprises at least one selected from the group consisting of (meth)acrylic acid ester monomers, vinyl cyanide monomers, α,β-ethylenically unsaturated carboxylic acids, and imides.

4. The styrene-based resin according to claim 1, having a weight average molecular weight (Mw) of 50,000 to 400,000.

5. The styrene-based resin according to claim 1, wherein the melt mass flow rate (MFR) measured in accordance with JIS K 7210 at 200°C under a load of 49 N is 0.1 to 30.0 g / 10 min.

6. A molded article obtained by molding a styrene-based resin composition containing the styrene-based resin according to any one of claims 1 to 5.

7. A method for producing a styrene-based resin, comprising a polymerization step, wherein raw material monomers including a styrene-based monomer (B) are polymerized in the polymerization step, and the styrene-based monomer (B) has a sustainable ratio of 0.1 to 100% allocated using a mass balance method.

8. A method for producing a styrene-based resin according to claim 7, wherein the raw material monomer includes a fossil fuel-derived styrene-based monomer (A).

9. A method for producing a styrene-based resin according to claim 8, wherein the raw material monomer includes a monomer (C), and the monomer (C) includes at least one selected from the group consisting of (meth)acrylic acid ester monomers, vinyl cyanide monomers, α,β-ethylenically unsaturated carboxylic acids, and imides.

10. A method for producing a styrene-based resin according to claim 8 or 9, wherein the content of the styrene-based monomer (B) in the raw material monomers is 0.1 to 99.9 mass% relative to 100 mass% of the total of the raw material monomers.

11. A method for producing a styrene-based resin according to any one of claims 7 to 9, wherein in the polymerization step, bio-circular styrene and / or circular styrene is used as the styrene-based monomer (B).