Biaxially oriented sheets, multilayer sheets, and molded products

Abstract

To provide a biaxially oriented sheet which does not contain a biomass plasticizer and reduces the burden on the environment during production. The present invention provides a biaxially oriented sheet containing a styrene-based resin derived from biomass.

Description

[Technical Field]

[0001] The present disclosure relates to biaxially oriented sheets, multilayer sheets, and molded articles. [Background technology]

[0002] Biaxially oriented sheets containing styrene-based resins are used for food packaging containers, etc. To reduce the environmental impact, the use of biomass raw materials in biaxially oriented sheets containing styrene-based resins has been investigated.

[0003] For example, Patent Document 1 discloses a styrene-based resin composition containing 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 characterized in that the total light transmittance of a 2 mm thick plate is 70% or more. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-057070 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 aims to reduce the environmental impact by using a biomass plasticizer together with a styrene-based polymer. However, when a biomass plasticizer is used, bleed-out may occur over time, resulting in poor appearance. Therefore, one aspect of the present disclosure aims to provide a biaxially oriented sheet that does not contain a biomass plasticizer and has a reduced environmental impact during production. [Means for solving the problem]

[0006] The present inventors have found that by using a biomass-derived styrene-based resin, it is possible to reduce the environmental impact of producing a biaxially oriented sheet without using a biomass plasticizer. In some aspects, the present disclosure provides the following [1] to

[11] . [1] A biaxially oriented sheet containing a biomass-derived styrene-based resin. [2] The biaxially oriented sheet according to [1], further comprising a styrene-based resin derived from a fossil fuel. [3] The biaxially oriented sheet according to [1] or [2], wherein the biaxially oriented sheet has a melt mass-flow rate of less than 5.5 g / 10 min. [4] The biaxially oriented sheet according to any one of [1] to [3], wherein the weight average molecular weight of the biaxially oriented sheet is 200,000 to 300,000. [5] The biaxially oriented sheet according to any one of [1] to [4], wherein the content of the biomass-derived styrene-based resin is 4.5 to 20 mass % based on the total mass of the biaxially oriented sheet. [6] The biaxially oriented sheet according to any one of [1] to [5], wherein the biomass-derived styrene-based resin has a biomass-derived characteristic content of 0.1 to 100% by mass. [7] The biaxially oriented sheet according to any one of [1] to [6], which is substantially free of plasticizers. [8] The biaxially oriented sheet according to any one of [2] to [7], wherein at least one of the biomass-derived styrene-based resin and the fossil fuel-derived styrene-based resin contains styrene as a monomer unit, and the styrene contains styrene derived from chemical recycling. [9] A multilayer sheet comprising a first layer made of the biaxially oriented sheet according to any one of [1] to [8] and a second layer provided on the first layer, wherein the second layer is an anti-fogging layer.

[10] The biaxially oriented sheet according to any one of [1] to [8] or the multilayer sheet according to [9], which is used for forming a food packaging container.

[11] A molded article obtained by molding the biaxially oriented sheet according to any one of [1] to [8] or the multilayer sheet according to [9] or

[10] . [Effects of the Invention]

[0007] According to one aspect of the present disclosure, there is provided a biaxially oriented sheet that does not contain a biomass plasticizer and that reduces the environmental impact of its production. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described in detail, but the present disclosure is not limited to the following embodiments.

[0009] The biaxially oriented sheet according to one embodiment contains a biomass-derived styrene-based resin. Because the biaxially oriented sheet according to one embodiment contains a biomass-derived styrene-based resin, the environmental impact of producing the biaxially oriented sheet is reduced.

[0010] Biomass-derived styrene resin (hereinafter also referred to as "styrene resin (A)") refers to a styrene resin to which biomass-derived characteristics have been assigned using the mass balance method. Here, the mass balance method refers to a method for allocating certain characteristics to a portion of a product based on the amount of raw material with a certain characteristic (e.g., biomass-derived raw material) mixed with other raw materials (e.g., petroleum-derived raw material) during the processing and distribution process from raw materials to the final product ("Bioplastics Introduction Roadmap" (established by the Ministry of the Environment, Ministry of Economy, Trade and Industry, Ministry of Agriculture, Forestry and Fisheries, and Ministry of Education, Culture, Sports, Science and Technology, January 2021)). The styrene resin (A) may actually be produced using biomass raw materials. In this case, the styrene resin (A) contains a biomass component.

[0011] According to the mass balance approach, biomass-derived characteristics can be assigned to individual products within a range according to the input amount of biomass-derived raw materials, regardless of the actual content of biomass components in each product. Certification systems are utilized to ensure the reliability of the assignment of biomass-derived characteristics. The styrene-based resin (A) may be a styrene-based resin certified by any certification system as a styrene-based resin assigned biomass-derived characteristics by the mass balance approach. Examples of certification systems include international certification systems such as ISCC PLUS, ISCC EU, RSB Global Advanced Products, and REDcert. The certification system may be one or more selected from the group consisting of ISCC PLUS, ISCC EU, RSB Global Advanced Products, and REDcert.

[0012] The biomass-derived characteristic ratio of the styrene-based resin (A) is greater than 0% by mass, and may be 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 5% by mass or more, 10% by mass or more, 30% by mass or more, 50% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, or may be 100% by mass or less. The biomass-derived characteristic ratio of the styrene-based resin (A) is, for example, 0.1 to 100% by mass. When the styrene-based resin (A) contains multiple types of styrene-based resins, the biomass-derived characteristic ratio of the styrene-based resin (A) refers to a weighted average value weighted by the mass of each styrene-based resin (A).

[0013] A styrene-based resin is a polymer containing mainly styrene-based monomers as monomer units. Examples of styrene-based resins include styrene-based resins modified with rubber (hereinafter also referred to as "rubber-modified styrene-based resins") and styrene-based resins not modified with rubber (hereinafter also referred to as "non-rubber-modified styrene-based resins"). The styrene-based resin (A) preferably contains a non-rubber-modified styrene-based resin. Hereinafter, the non-rubber-modified styrene-based resin that can be contained in the styrene-based resin (A) will also be referred to as "non-rubber-modified styrene-based resin (A1)."

[0014] The styrene monomer contained as a monomer unit in the non-rubber-modified styrene resin (A1) may be styrene (unsubstituted styrene) or a substituted styrene. Unsubstituted styrene refers to styrene having no substituents (styrene having no functional groups other than one vinyl group). Substituted styrene refers to styrene in which at least one of the hydrogen atoms on the benzene ring and the hydrogen atoms constituting the vinyl group in styrene has been substituted with a substituent such as an alkyl group or a halogen group.

[0015] Examples of substituted styrenes include alkylstyrenes, halogenated styrenes, nitrostyrene, acetylstyrene, and methoxystyrene.

[0016] The alkylstyrene may be, for example, an alkylstyrene having 1, 2, or 3 alkyl groups. Examples of alkylstyrenes having one alkyl group include α-alkylstyrenes such as α-methylstyrene, o-alkylstyrenes such as o-methylstyrene and o-ethylstyrene, m-alkylstyrenes such as m-methylstyrene and m-ethylstyrene, and p-alkylstyrenes such as p-methylstyrene, p-ethylstyrene, and p-tert-butylstyrene.

[0017] Examples of alkylstyrenes having two alkyl groups include 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, and 4,α-dimethylstyrene (1-methyl-4-isopropenylbenzene).An example of an alkylstyrene having three alkyl groups is 2,4,6-trimethylstyrene.

[0018] Examples of halogenated styrenes include fluorostyrene, chlorostyrene, dichlorostyrene, bromostyrene, dibromostyrene, and iodostyrene.

[0019] The non-rubber-modified styrene-based resin (A1) may contain, as a monomer unit, one or more of the above-mentioned styrene-based monomers. The non-rubber-modified styrene-based resin (A1) preferably contains, as a monomer unit, at least one of styrene and α-methylstyrene, more preferably styrene.

[0020] The content of styrene (styrene units) in the non-rubber-modified styrene-based resin (A1) may be 80 mass% or more, 90 mass% or more, 95 mass% or more, or 98 mass% or more, based on the total mass of the monomer units contained in the non-rubber-modified styrene-based resin (A1), and may be 100 mass% or less.

[0021] The non-rubber-modified styrene-based resin (A1) may contain only styrene-based monomers as monomer units, or may contain other monomers besides styrene-based monomers. The content of the styrene-based monomers may be 80% by mass or more, 90% by mass or more, 95% by mass or more, or 98% by mass or more, or 100% by mass or less, based on the total mass of the monomer units contained in the non-rubber-modified styrene-based resin (A1).

[0022] Examples of other monomers that can be contained as monomer units in the non-rubber-modified styrene-based resin (A1) include unsaturated carboxylic acids, unsaturated carboxylic acid esters, carboxylic acid anhydrides, vinyl carboxylates, and (meth)acrylonitrile.

[0023] Examples of unsaturated carboxylic acids include (meth)acrylic acid, fumaric acid, maleic acid, and itaconic acid. Examples of unsaturated carboxylic acid esters include (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, and n-butyl (meth)acrylate. Examples of carboxylic acid anhydrides include maleic anhydride. Examples of vinyl carboxylates include vinyl acetate. The non-rubber-modified styrene-based resin (A1) may contain one or more of these monomers as monomer units.

[0024] In the non-rubber-modified styrene-based resin (A1), the content of other monomers than the styrene-based monomer may be 0% by mass or more, and may be 10% by mass or less, 8% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less, based on the total mass of the monomer units contained in the non-rubber-modified styrene-based resin (A1).

[0025] The non-rubber-modified styrene-based resin (A1) may be a homopolymer or a copolymer. A homopolymer contains only one type of styrene-based monomer as a monomer unit. A copolymer may contain only two or more types of styrene-based monomer as a monomer unit, or may contain one or more types of styrene-based monomer and one or more other monomers. The non-rubber-modified styrene-based resin (A1) is preferably a homopolymer or copolymer containing only a styrene-based monomer as a monomer unit, and more preferably a homopolymer containing only one type of styrene-based monomer as a monomer unit (homopolymer of a styrene-based monomer). The homopolymer of a styrene-based monomer may be a homopolymer of styrene. A homopolymer of styrene is also called general-purpose polystyrene (GPPS).

[0026] The content of the non-rubber-modified styrene-based resin (A1) may be 70 mass% or more, 80 mass% or more, 90 mass% or more, 95 mass% or more, or 98 mass% or more, based on the total mass of the styrene-based resin (A), and may be 100 mass% or less.

[0027] The content of the non-rubber-modified styrene-based resin (A1) in the biaxially oriented sheet may be 0.5% by mass or more, 1% by mass or more, 2% by mass or more, 4% by mass or more, 6% by mass or more, or 8% by mass or more, based on the total mass of the biaxially oriented sheet. The content of the non-rubber-modified styrene-based resin (A1) in the biaxially oriented sheet may be 60% by mass or less, 50% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, 26% by mass or less, 22% by mass or less, 18% by mass or less, 15% by mass or less, or 12% by mass or less, based on the total mass of the biaxially oriented sheet. When the content of the non-rubber-modified styrene-based resin (A1) is within the above numerical range, the biaxially oriented sheet tends to have better transparency (the haze value of the biaxially oriented sheet can be reduced).

[0028] The styrene-based resin (A) may or may not contain a rubber-modified styrene-based resin. Hereinafter, the rubber-modified styrene-based resin that may be contained in the styrene-based resin (A) is also referred to as a "rubber-modified styrene-based resin (A2)." Details of the rubber-modified polystyrene-based resin (A2) may be the same as those of the rubber-modified polystyrene-based resin (B2) described below, except that biomass-derived properties are assigned using the mass balance method.

[0029] From the viewpoint of excellent moldability during production of a biaxially oriented sheet, the melt mass flow rate of the styrene-based resin (A) may be 1 g / 10 min or more, 2 g / 10 min or more, 2.2 g / min or more, or 2.5 g / 10 min or more, and may be 7 g / 10 min or less, 6.8 g / 10 min or less, 6.5 g / 10 min or less, 6.2 g / 10 min or less, 6 g / 10 min or less, 5.8 g / 10 min or less, 5.5 g / 10 min or less, 5.2 g / 10 min or less, 5 g / 10 min or less, 4.8 g / 10 min or less, 4.5 g / 10 min or less, 4.2 g / 10 min or less, 4 g / 10 min or less, 3.8 g / 10 min or less, 3.5 g / 10 min or less, 3.2 g / 10 min or less, or 3 g / 10 min or less. In this specification, the melt mass-flow rate refers to a value measured in accordance with JIS K7210:1999 at a test temperature of 200°C and a nominal load of 5.00 kg.

[0030] The number average molecular weight (Mn ) may be 50,000 or more, 70,000 or more, 90,000 or more, 95,000 or more, or 100,000 or more, and may be 200,000 or less, 170,000 or less, 150,000 or less, 130,000 or less, or 120,000 or less, from the viewpoints of excellent formability during production of the biaxially oriented sheet and excellent strength of the biaxially oriented sheet. n When is within the above numerical range, the biaxially oriented sheet has excellent strength even when made thin. Therefore, in a molded product (e.g., a container) using the biaxially oriented sheet, it is possible to reduce the amount of resin used while maintaining the strength of the molded product, which contributes to further reducing the environmental load.

[0031] Weight average molecular weight (M w From the viewpoints of achieving excellent formability during production of the biaxially oriented sheet and excellent strength of the biaxially oriented sheet, M may be 150,000 or more, 200,000 or more, 220,000 or more, 230,000 or more, 250,000 or more, or 260,000 or more, and may be 400,000 or less, 350,000 or less, 320,000 or less, 300,000 or less, or 295,000 or less. w When the M of the styrene-based resin (A) is within the above range, the biaxially oriented sheet has excellent strength even when made thin, and therefore, in a molded article (e.g., a container) using the biaxially oriented sheet, it is possible to reduce the amount of resin used while maintaining the strength of the molded article, which contributes to further reducing the environmental load. w may be, for example, 200,000 to 300,000.

[0032] Z-average molecular weight (M z From the viewpoints of excellent formability during production of the biaxially oriented sheet and excellent strength of the biaxially oriented sheet, M may be 300,000 or more, 350,000 or more, 380,000 or more, 390,000 or more, 400,000 or more, 410,000 or more, or 420,000 or more, and may be 600,000 or less, 550,000 or less, 520,000 or less, 500,000 or less, or 480,000 or less. z When is within the above numerical range, the biaxially oriented sheet has excellent strength even when made thin. Therefore, in a molded product (e.g., a container) using the biaxially oriented sheet, it is possible to reduce the amount of resin used while maintaining the strength of the molded product, which contributes to further reducing the environmental load.

[0033] Peak top molecular weight (M top From the viewpoints of achieving excellent formability during production of the biaxially oriented sheet and excellent strength of the biaxially oriented sheet, M may be 150,000 or more, 200,000 or more, 230,000 or more, 250,000 or more, 260,000 or more, or 280,000 or more, and may be 400,000 or less, 370,000 or less, 350,000 or less, 330,000 or less, or 320,000 or less. top M means the molecular weight at the point where the value on the vertical axis is maximum on the differential molecular weight distribution curve. top When is within the above numerical range, the biaxially oriented sheet has excellent strength even when made thin. Therefore, in a molded product (e.g., a container) using the biaxially oriented sheet, it is possible to reduce the amount of resin used while maintaining the strength of the molded product, which contributes to further reducing the environmental load.

[0034] Styrene-based resin (A) M w and M n Ratio to (M w / M n ) may be 1.5 or more, 2.0 or more, or 2.3 or more, and may be 3.0 or less, 2.8 or less, or 2.6 or less. z and M w Ratio to (M z / M w ) may be 1.0 or more, 1.3 or more, or 1.6 or more, and may be 2.5 or less, 2.2 or less, or 1.9 or less.

[0035] In this specification, M n , M w , M z , and M top is determined by GPC measurement under the following conditions: Apparatus: Tosoh Corporation, GPC "HLC-8320GPC" Column: Shodex KF404 x 3 Temperature: 40℃ Solvent: tetrahydrofuran Flow rate: 0.2ml / min Pressure: 10 MPa Detection: RI Sample preparation method: 120 mg of a sample was dissolved in 15 mL of tetrahydrofuran, and then filtered through a syringe filter (Millex (registered trademark) 0.45 μm, manufactured by Merck Millipore). Injection volume: 10μl Calibration curve: Using standard polystyrene (manufactured by Polymer Laboratories), the relationship between elution time and elution amount is converted into molecular weight to determine various average molecular weights.

[0036] Melt mass flow rate of non-rubber-modified styrene resin (A1), M n , M w , M z , M top , M w / M n , and M z / M w is the melt mass flow rate of the styrene resin (A), M n , M w , M z , M top , M w / M n , and M z / M w may be within the above-mentioned numerical range.

[0037] The content of the styrene-based resin (A) may be 0.5% by mass or more, 1% by mass or more, 2% by mass or more, 4% by mass or more, 4.5% by mass or more, 6% by mass or more, or 8% by mass or more, based on the total mass of the biaxially oriented sheet. The content of the styrene-based resin (A) may be 95% by mass or less, 90% by mass or less, 80% by mass or less, 60% by mass or less, 50% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, 26% by mass or less, 22% by mass or less, 20% by mass or less, 18% by mass or less, 15% by mass or less, or 12% by mass or less, based on the total mass of the biaxially oriented sheet. When the content of the styrene-based resin (A) is within the above numerical range, the biaxially oriented sheet tends to have better transparency (the haze value of the biaxially oriented sheet can be reduced). The content of the styrene-based resin (A) may be, for example, 4.5 to 20% by mass.

[0038] The biaxially oriented sheet may further contain a styrene-based resin derived from a fossil fuel (hereinafter also referred to as "styrene-based resin (B)"). When the biaxially oriented sheet contains the styrene-based resin (A) together with the styrene-based resin (B), the transparency of the biaxially oriented sheet can be further improved (the haze value can be reduced). The styrene-based resin (B) is a styrene-based resin produced only from raw materials derived from fossil fuels. In this specification, anything that corresponds to the styrene-based resin (A) does not correspond to the styrene-based resin (B).

[0039] The styrene-based resin (B) preferably contains a non-rubber-modified styrene-based resin. Hereinafter, the non-rubber-modified styrene-based resin that can be contained in the styrene-based resin (B) is also referred to as "non-rubber-modified styrene-based resin (B1)."

[0040] Examples of styrene-based monomers contained as monomer units in the non-rubber-modified styrene-based resin (B1) include those mentioned above as styrene-based monomers that can be contained in the non-rubber-modified styrene-based resin (A1). The non-rubber-modified styrene-based resin (B1) may contain, as a monomer unit, one or more of the above-mentioned styrene-based monomers. The non-rubber-modified styrene-based resin (B1) preferably contains, as a monomer unit, at least one of styrene and α-methylstyrene, and more preferably contains styrene.

[0041] The content of styrene (styrene units) in the non-rubber-modified styrene-based resin (B1) may be 80 mass% or more, 90 mass% or more, 95 mass% or more, or 98 mass% or more, based on the total mass of the non-rubber-modified styrene-based resin (B1), and may be 100 mass% or less.

[0042] The non-rubber-modified styrene-based resin (B1) may contain only a styrene-based monomer as a monomer unit, or may contain a monomer other than a styrene-based monomer. The content of the styrene-based monomer may be 80 mass % or more, 90 mass % or more, 95 mass % or more, or 98 mass % or more, or 100 mass % or less, based on the total mass of the monomer units contained in the non-rubber-modified styrene-based resin (B1).

[0043] Examples of other monomers that may be contained as monomer units in the non-rubber-modified styrene-based resin (B1) include those mentioned above as other monomers that may be contained in the non-rubber-modified styrene-based resin (A1). The non-rubber-modified styrene-based resin (B1) may contain one or more of the above-mentioned other monomers as monomer units. In the non-rubber-modified styrene-based resin (B1), the content of other monomers other than styrene-based monomers may be 0% by mass or more, and may be 10% by mass or less, 8% by mass or less, 5% by mass or less, 3% by mass or less, 2% by mass or less, 1.5% by mass or less, or 1% by mass or less, based on the total mass of monomer units contained in the non-rubber-modified styrene-based resin (B1).

[0044] The non-rubber-modified styrene-based resin (B1) may be a homopolymer or a copolymer. A homopolymer contains only one type of styrene-based monomer as a monomer unit. A copolymer may contain only two or more types of styrene-based monomer as a monomer unit, or may contain one or more types of styrene-based monomer and one or more other monomers. The non-rubber-modified styrene-based resin (B1) is preferably a homopolymer or copolymer containing only a styrene-based monomer as a monomer unit, and more preferably a homopolymer containing only one type of styrene-based monomer as a monomer unit (homopolymer of a styrene-based monomer). The homopolymer of a styrene-based monomer may be a homopolymer of styrene.

[0045] From the viewpoint of excellent moldability during production of a biaxially oriented sheet, the melt mass-flow rate of the non-rubber-modified styrene-based resin (B1) may be 2 g / 10 min or more, 2.2 g / min or more, 2.4 g / min or more, 2.6 g / 10 min or more, 2.8 g / 10 min or more, 3 g / 10 min or more, 3.2 g / 10 min or more, 3.4 g / 10 min or more, 3.5 g / 10 min or more, 3.6 g / min or more, 3.8 g / 10 min or more, or 4 g / min or more. 8g / 10 minutes or less, 7g / 10 minutes or less, 6.8g / 10 minutes or less, 6.6g / 10 minutes or less, 6.4g / 10 minutes or less, 6.2g / 10 minutes or less, 6g / 10 minutes or less, 5.8g / 10 minutes or less, 5.6g / It may be 10 minutes or less, 5.4g / 10 minutes or less, 5.2g / 10 minutes or less, 5g / 10 minutes or less, 4.8g / 10 minutes or less, 4.6g / 10 minutes or less, 4.5g / 10 minutes or less, or 4.4g / 10 minutes or less.

[0046] Non-rubber modified styrene resin (B1) M n From the viewpoints of achieving excellent formability during production of the biaxially oriented sheet and excellent strength of the biaxially oriented sheet, M may be 50,000 or more, 80,000 or more, 100,000 or more, or 120,000 or more, and may be 200,000 or less, 170,000 or less, 150,000 or less, or 130,000 or less. n When is within the above numerical range, the biaxially oriented sheet has excellent strength even when made thin. Therefore, in a molded product (e.g., a container) using the biaxially oriented sheet, it is possible to reduce the amount of resin used while maintaining the strength of the molded product, which contributes to further reducing the environmental load.

[0047] Non-rubber modified styrene resin (B1) M w From the viewpoints of achieving excellent formability during production of the biaxially oriented sheet and excellent strength of the biaxially oriented sheet, M may be 150,000 or more, 200,000 or more, 230,000 or more, 260,000 or more, or 280,000 or more, and may be 400,000 or less, 350,000 or less, 320,000 or less, 300,000 or less, or 295,000 or less. w When is within the above numerical range, the biaxially oriented sheet has excellent strength even when made thin. Therefore, in a molded product (e.g., a container) using the biaxially oriented sheet, it is possible to reduce the amount of resin used while maintaining the strength of the molded product, which contributes to further reducing the environmental load.

[0048] Non-rubber modified styrene resin (B1) M z From the viewpoints of achieving excellent formability during production of the biaxially oriented sheet and excellent strength of the biaxially oriented sheet, M may be 300,000 or more, 350,000 or more, 400,000 or more, 430,000 or more, or 460,000 or more, and may be 600,000 or less, 580,000 or less, 540,000 or less, 520,000 or less, or 500,000 or less. z When is within the above numerical range, the biaxially oriented sheet has excellent strength even when made thin. Therefore, in a molded product (e.g., a container) using the biaxially oriented sheet, it is possible to reduce the amount of resin used while maintaining the strength of the molded product, which contributes to further reducing the environmental load.

[0049] Non-rubber modified styrene resin (B1) M top From the viewpoints of achieving excellent formability during production of the biaxially oriented sheet and excellent strength of the biaxially oriented sheet, M may be 150,000 or more, 200,000 or more, 230,000 or more, 260,000 or more, or 280,000 or more, and may be 400,000 or less, 370,000 or less, 350,000 or less, or 330,000 or less. top When is within the above numerical range, the biaxially oriented sheet has excellent strength even when made thin. Therefore, in a molded product (e.g., a container) using the biaxially oriented sheet, it is possible to reduce the amount of resin used while maintaining the strength of the molded product, which contributes to further reducing the environmental load.

[0050] Non-rubber modified styrene resin (B1) M w and M n Ratio to (M w / M n ) may be 1.5 or more, 1.8 or more, or 2.2 or more, and may be 3.0 or less, 2.7 or less, or 2.4 or less. In addition, M of the non-rubber-modified styrene-based resin (B1) z and M w Ratio to (M z / M w ) may be 1.0 or more, 1.3 or more, or 1.6 or more, and may be 2.5 or less, 2.2 or less, or 1.9 or less.

[0051] The content of the non-rubber-modified styrene-based resin (B1) may be 70 mass% or more, 80 mass% or more, 90 mass% or more, 95 mass% or more, or 98 mass% or more, based on the total mass of the styrene-based resin (B), and may be 100 mass% or less, or 99 mass% or less.

[0052] The content of the non-rubber-modified styrene-based resin (B1) in the biaxially oriented sheet may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 85% by mass or more, and may be 100% by mass or less, 95% by mass or less, or 92% by mass or less, based on the total mass of the biaxially oriented sheet.

[0053] The mass ratio of the content of the non-rubber-modified styrene-based resin (A1) to the content of the non-rubber-modified styrene-based resin (B1) (content of non-rubber-modified styrene-based resin (A1) / content of non-rubber-modified styrene-based resin (B1)) may be 1 / 99 or more, 2 / 98 or more, 3 / 97 or more, 4 / 96 or more, 5 / 95 or more, 6 / 94 or more, 7 / 93 or more, 8 / 92 or more, 9 / 91 or more, or 10 / 90 or more, and may be 99 / 1 or less, 95 / 5 or less, 90 / 10 or less, 80 / 20 or less, 70 / 30 or less, 60 / 40 or less, 50 / 50 or less, 45 / 55 or less, 40 / 60 or less, 35 / 65 or less, 30 / 70 or less, or 25 / 75 or less.

[0054] The styrene-based resin (B) may contain a rubber-modified styrene-based resin. Hereinafter, the rubber-modified styrene-based resin that can be contained in the styrene-based resin (B) is also referred to as a "rubber-modified styrene-based resin (B2)." The rubber-modified styrene-based resin (B2) is a styrene-based polymer matrix in which rubber-like polymer particles are dispersed. The rubber-modified styrene-based resin may be, for example, a diene-based rubber-modified styrene-based resin containing a rubber-like diene-based polymer. The diene-based rubber-modified styrene-based resin is obtained, for example, by dissolving a rubber-like diene-based polymer in a styrene-based monomer and polymerizing (preferably graft polymerizing) the resulting mixture.

[0055] As the styrene-based monomer, for example, the styrene-based monomers described above as those that can be contained in the non-rubber-modified styrene-based resins (A1) and (B1) can be used. The above-mentioned monomers can be used alone or in combination of two or more. The rubber-modified styrene-based resin (B2) can be a rubber-modified polystyrene (HIPS) containing only styrene as the styrene-based monomer.

[0056] Examples of rubbery diene polymers that can be used include polymers of one or more conjugated 1,3-dienes (e.g., butadiene, isoprene, 2-chloro-1,3-butadiene, 1-chloro-1,3-butadiene, piperylene, etc.), butadiene-styrene copolymers, butadiene-acrylonitrile copolymers, and butadiene-styrene-acrylonitrile copolymers.

[0057] The content of the diene rubber component (hereinafter also simply referred to as "rubber component") may be 0.01% by mass or more, 0.02% by mass or more, 0.05% by mass or more, or 0.08% by mass or more, based on the total mass of the biaxially oriented sheet, and may be 3.0% by mass or less, 2.0% by mass or less, 1.5% by mass or less, 1.0% by mass or less, 0.8% by mass or less, 0.5% by mass or less, 0.3% by mass or less, or 0.1% by mass or less.

[0058] The rubber content of the biaxially oriented sheet, based on its total mass, can be measured by dissolving 0.25 g of the biaxially oriented sheet in 50 ml of chloroform, adding iodine monochloride to react with the double bonds in the rubber component, then adding potassium iodide to convert the remaining iodine monochloride to iodine, and back-titrating with sodium thiosulfate (iodine monochloride method). The analytical method is described, for example, in "(3) Rubber Content" on page 659 of "New Edition Polymer Analysis Handbook," edited by the Polymer Analysis Research Forum of the Japan Society for Analytical Chemistry, Kinokuniya Shoten (1995 edition), and can be used to measure the content.

[0059] The content of the rubber-modified styrene-based resin (B2) in the styrene-based resin (B) may be 0 mass% or more, 0.05 mass% or more, or 0.1 mass% or more, and may be 5.0 mass% or less, 3.0 mass% or less, 1.0 mass% or less, or 0.5 mass% or less, based on the total mass of the styrene-based resin (B).

[0060] The content of the styrene-based resin (B) may be 30% by mass or more, 50% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, or 85% by mass or more, based on the total mass of the biaxially oriented sheet. The content of the styrene-based resin (B) may be 99% by mass or less, 97% by mass or less, 95% by mass or less, 93% by mass or less, 91% by mass or less, or 90% by mass or less, based on the total mass of the biaxially oriented sheet. When the content of the styrene-based resin (B) is within the above numerical range, the biaxially oriented sheet tends to have better transparency (the haze value of the biaxially oriented sheet can be reduced).

[0061] The total content of the rubber-modified styrene-based resins in the biaxially oriented sheet (the total content of the rubber-modified styrene-based resin (A2) and the rubber-modified styrene-based resin (B2); the same applies below) may be 0.1 mass% or more, 0.3 mass% or more, 0.5 mass% or more, or 0.8 mass% or more, and may be 5.0 mass% or less, 3.0 mass% or less, 2.0 mass% or less, or 1.5 mass% or less, based on the total mass of the biaxially oriented sheet.

[0062] The mass ratio (total content of non-rubber-modified styrene-based resins / total content of rubber-modified styrene-based resins) of the total content of non-rubber-modified styrene-based resins in the biaxially oriented sheet (total content of the above non-rubber-modified styrene-based resins (A1) and non-rubber-modified styrene-based resins (B1); the same applies below) to the total content of rubber-modified styrene-based resins in the biaxially oriented sheet may be 95 / 5 or more, 96 / 4 or more, 97 / 3 or more, 98 / 2 or more, or 98.5 / 1.5 or more, and may be 99.9 / 0.1 or less, 99.7 / 0.3 or less, or 99.5 / 0.5 or less.

[0063] At least one of the styrene-based resin (A) and the styrene-based resin (B) contains styrene as a monomer unit, and the styrene may contain styrene derived from chemical recycling. The styrene derived from chemical recycling may be, for example, styrene obtained by thermal decomposition of a styrene-containing polymer.

[0064] The styrene-based resin (A) containing styrene as a monomer unit, and the styrene containing styrene derived from chemical recycling, may mean at least one of the following: the non-rubber-modified styrene-based resin (A1) containing styrene as a monomer unit, and the styrene containing styrene derived from chemical recycling; and the rubber-modified styrene-based resin (A2) containing styrene as a monomer unit, and the styrene containing styrene derived from chemical recycling.

[0065] Furthermore, the styrene-based resin (B) containing styrene as a monomer unit, and the styrene containing styrene derived from chemical recycling, may mean at least one of the following: the non-rubber-modified styrene-based resin (B1) containing styrene as a monomer unit, and the styrene containing styrene derived from chemical recycling; and the rubber-modified styrene-based resin (B2) containing styrene as a monomer unit, and the styrene containing styrene derived from chemical recycling.

[0066] The biaxially oriented sheet may further contain other components. Examples of other components include antioxidants, antigelling agents (e.g., polyoxyethylene alkyl ether (POE)), ultraviolet absorbers, light stabilizers, lubricants, plasticizers, colorants, antistatic agents, flame retardants, mineral oil, reinforcing fibers such as glass fiber, carbon fiber, and aramid fiber, and fillers such as talc, silica, mica, and calcium carbonate. The total content of other components may be, for example, 0% by mass or more and 1.0% by mass or less, based on the total mass of the biaxially oriented sheet.

[0067] The content of the plasticizer may be 5% by mass or less, 3% by mass or less, 1% by mass or less, 0.5% by mass or less, 0.3% by mass or less, or less than 0.1% by mass, based on the total mass of the biaxially oriented sheet, from the viewpoint of suppressing bleed-out in the biaxially oriented sheet and preventing poor appearance due to changes over time. The biaxially oriented sheet may be substantially free of plasticizer. In this specification, "substantially free of a certain component" means that the component is not contained at all, or that the component is contained only as an unavoidable impurity.

[0068] The biaxially oriented sheet may actually contain a biomass component. For example, when the styrene-based resin (A) contains a biomass component, the biaxially oriented sheet also contains a biomass component. The proportion of the biomass component (biomass ratio) in the biaxially oriented sheet is preferably 10 mass% or more, independently based on the total mass of the biaxially oriented sheet.

[0069] The thickness of the biaxially oriented sheet may be 0.1 mm or more, 0.15 mm or more, or 0.2 mm or more, and may be 0.7 mm or less, 0.5 mm or less, 0.4 mm or less, or 0.3 mm or less. The thickness of the biaxially oriented sheet may be, for example, 0.1 to 0.7 mm, or 0.1 to 0.3 mm.

[0070] The melt mass-flow rate of the biaxially oriented sheet may be 1 g / 10 min or more, 2 g / 10 min or more, 2.2 g / min or more, 2.4 g / min or more, 2.6 g / 10 min or more, 2.8 g / 10 min or more, 3 g / 10 min or more, 3.2 g / 10 min or more, 3.4 g / 10 min or more, 3.5 g / 10 min or more, 3.6 g / min or more, 3.8 g / 10 min or more, or 4 g / min or more, and may be 8 g / 10 min or less, 7 g / 10 min or less, 6.8 g / 10 min or less, or 8 g / 10 min or less. minutes or less, 6.6 g / 10 minutes or less, 6.4 g / 10 minutes or less, 6.2 g / 10 minutes or less, 6 g / 10 minutes or less, 5.8 g / 10 minutes or less, 5.6 g / 10 minutes or less, 5.5 g / 10 minutes or less, 5.4 g / 10 minutes or less, 5 .2g / 10min or less, 5g / 10min or less, 4.8g / 10min or less, 4.6g / 10min or less, 4.4g / 10min or less, 4.2g / 10min or less, 4g / 10min or less, or 3.8g / 10min or less.

[0071] The Mw of the biaxially oriented sheet may be 130,000 or more, 150,000 or more, 180,000 or more, 200,000 or more, 230,000 or more, or 250,000 or more, and may be 400,000 or less, 350,000 or less, 320,000 or less, 300,000 or less, 295,000 or less, 270,000 or less, or 260,000 or less. The Mw of the biaxially oriented sheet may be, for example, 200,000 to 300,000.

[0072] The stretching ratios of the biaxially oriented sheet in the MD (Machine Direction; sheet flow direction) and TD (Transverse Direction; direction perpendicular to the sheet flow direction) may be 1.9 times or more, 2.0 times or more, 2.3 times or more, or 2.4 times or more, and may be 4.0 times or less, 3.5 times or less, or 3.0 times or less. When the stretching ratio is equal to or greater than the above lower limit, the strength of the molded article is excellent. When the stretching ratio is equal to or less than the above upper limit, the formability of the biaxially oriented sheet is excellent. The MD stretching ratio and the TD stretching ratio may be the same or different.

[0073] When the MD stretching ratio of the biaxially oriented sheet is m and the TD stretching ratio is n, the areal stretching ratio represented by m×n may be 4 times or more, 5 times or more, or 6 times or more, and may be 16 times or less, 13 times or less, or 10 times or less.

[0074] The stretching ratio in this specification is calculated as the rate of change in a test piece of a biaxially stretched sheet before and after heating. Specifically, the stretching ratio is calculated by the following formula: Stretching ratio = Y / Z (unit [times]) In this formula, Y represents the length [mm] of a straight line drawn in MD or TD on a test piece of a biaxially oriented sheet before heating, and Z represents the length [mm] of the straight line after the test piece is allowed to stand for 60 minutes in an oven at a temperature 30°C higher than the Vicat softening point temperature of the biaxially oriented sheet measured in accordance with JIS K7206 and allowed to shrink. The MD stretch ratio can be calculated by drawing a straight line in MD, and the TD stretch ratio can be calculated by drawing a straight line in TD.

[0075] The heat shrinkage stress in the MD and TD of the biaxially oriented sheet may be independently 0.2 MPa or more, 0.3 MPa or more, 0.4 MPa or more, 0.5 MPa or more, or 0.6 MPa or more, and may be 1.0 MPa or less, 0.9 MPa or less, or 0.8 MPa or less.

[0076] The heat shrinkage stress of a biaxially oriented sheet is determined using the following method. First, a rectangular biaxially oriented sheet sample measuring 20 mm wide and 150 mm long is prepared. Next, both ends of the sample are gripped with chucks and heated to 130°C. The molecular orientation is relaxed by thermal motion, and the load applied to the chucks is measured as the sample thermally shrinks. The heat shrinkage stress is determined by dividing the maximum load by the cross-sectional area of ​​the sample. If the longitudinal direction of the sample is defined as the MD of the biaxially oriented sheet, the MD heat shrinkage stress can be determined. If the longitudinal direction of the sample is defined as the TD of the biaxially oriented sheet, the TD heat shrinkage stress can be determined. The heat shrinkage stress is an indicator of the degree of molecular orientation of the biaxially oriented sheet.

[0077] The MD heat shrinkage of the biaxially oriented sheet may be 40% or more, 50% or more, 55% or more, or 58% or more, and 80% or less, 70% or less, 65% or less, or 63% or less.The TD heat shrinkage of the biaxially oriented sheet may be 40% or more, 50% or more, 53% or more, or 55% or more, and 80% or less, 70% or less, 65% or less, or 63% or less.

[0078] The heat shrinkage of a biaxially oriented sheet in the MD and TD is determined by the following method. First, a 100 mm long straight line is drawn in the MD and TD on a test piece of the biaxially oriented sheet. The test piece is allowed to stand for 30 minutes in an oven at a temperature 30°C higher than the Vicat softening temperature of the sheet measured according to JIS K7206:2016, and then the length L of the straight line drawn in the MD is measured. MD [mm] and the length of the straight line drawn on TD L TD The heat shrinkage (%) in the MD and TD directions was calculated using the following formula. MD heat shrinkage (%) = {(100 - L MD ) / 100}×100 Heat shrinkage rate of TD (%) = {(100 - L TD ) / 100}×100

[0079] The biaxially oriented sheet can be produced by the following method. First, the raw materials, styrene-based resin (A), optionally used styrene-based resin (B), and optionally used optional components (for example, other components described above) are mixed (for example, melt-kneaded) and then molded (for example, extrusion molding or press molding) to obtain an unstretched sheet. Next, the unstretched sheet is stretched in two axial directions sequentially or simultaneously to obtain a biaxially oriented sheet. The unstretched sheet may be stretched while heated. The stretching temperature may be 90°C or higher, 100°C or higher, 110°C or higher, or 120°C or higher, and may be 150°C or lower, 140°C or lower, or 135°C or lower.

[0080] Suppliers of styrene resins that have obtained ISCC PLUS certification can issue and attach a Sustainability Declaration (SD), a document detailing the raw materials, to their products and pass it on to downstream users. When manufacturing biaxially oriented sheets, it is recommended to receive a Sustainability Declaration (SD) for styrene resin (A) and confirm that the supplier of styrene resin (A) holds a valid certification at the time of issuance of the SD.

[0081] Another embodiment of the present disclosure is a multilayer sheet including a layer made of the biaxially oriented sheet. The multilayer sheet includes a first layer made of the biaxially oriented sheet and a second layer disposed on the first layer. The multilayer sheet may further include a third layer disposed on the side of the first layer opposite the second layer, a fourth layer disposed on the second layer, etc. Examples of the second, third, and fourth layers include an anti-fogging layer containing an anti-fogging agent, a release layer containing a release agent (peeling agent), an anti-static layer containing an anti-static agent, a design layer (a layer for applying a pattern to the multilayer sheet) containing a colorant, an antibacterial layer containing an antibacterial agent, and a gas barrier layer containing a gas barrier material (e.g., an ethylene-vinyl alcohol copolymer) that suppresses the permeation of gases (such as oxygen).

[0082] The multilayer sheet can be produced, for example, by applying a coating liquid containing components appropriate for the purpose (anti-fogging agent, release agent (peeling agent), antistatic agent, colorant, antibacterial agent, gas barrier substance, etc.) to at least one surface of a biaxially stretched sheet to form a second layer, etc. The method for applying the coating liquid is not particularly limited, and may be a method using a roll coater, knife coater, gravure roll coater, etc., or may be spraying, dipping, etc.

[0083] The biaxially oriented sheet and multilayer sheet described above can be used, for example, to produce a molded article. The molded article may be, for example, a container, or a food packaging container (food pack) for storing food. The molded article may be, for example, a lid material for a food packaging container. The biaxially oriented sheet and the multilayer sheet may each independently be used to mold a food packaging container.

[0084] There are no particular limitations on the method for obtaining a molded article from a biaxially oriented sheet, and any method commonly used in the secondary molding of conventional biaxially oriented sheets can be used. For example, secondary molding can be performed by thermoforming methods such as vacuum molding and pressure molding. These methods are described, for example, in "Plastic Processing Technology Handbook" edited by the Society of Polymer Science, Nikkan Kogyo Shimbun (1995).

[0085] The biaxially oriented sheets, multilayer sheets, and molded articles described above may each independently be biomass-derived. That is, the biaxially oriented sheets, multilayer sheets, and molded articles may each independently be biaxially oriented sheets, multilayer sheets, or molded articles that have been assigned biomass-derived characteristics using a mass balance approach. The biaxially oriented sheets, multilayer sheets, and molded articles may each independently be certified under a certification system as biaxially oriented sheets, multilayer sheets, or molded articles that have been assigned biomass-derived characteristics. Examples of certification systems include the international certification systems described above. The certification system may be one or more selected from the group consisting of ISCC PLUS, ISCC EU, RSB Global Advanced Products, and REDcert.

[0086] If a biaxially oriented sheet, multi-layer sheet, or molded article has been certified with an international standard such as ISCC PLUS, the biaxially oriented sheet, multi-layer sheet, or molded article may be provided with a Sustainability Statement (SD). [Example]

[0087] The present disclosure will be described in more detail below based on examples, although the present disclosure is not limited to these examples.

[0088] <Material> In the examples and comparative examples, the following materials were used. A-1: Biomass-derived styrene resin (GPPS, ISCC PLUS certified as a styrene resin with a 100% biomass-derived characteristic allocation rate, "1450" manufactured by TPSC Asia Pte Ltd.) A-2: Biomass-derived styrene resin (GPPS, ISCC PLUS certified as a styrene resin with a 100% biomass-derived characteristic allocation rate, "Styrolution PS 158K" manufactured by INEOS Styrolution) B: Fossil fuel-derived styrene resin (GPPS, not assigned biomass-derived characteristics, "HRM61S" manufactured by Toyo Styrene Co., Ltd.) C: Fossil fuel-derived rubber-modified styrene resin (HIPS, not assigned biomass-derived characteristics, "H850N" manufactured by Toyo Styrene Co., Ltd.)

[0089] The melt mass-flow rate and molecular weight of each of A-1, A-2, and B were measured. The results are shown in Table 1. Test pieces consisting of only A-1, A-2, and B were also prepared using an injection molding machine, and their optical properties were investigated as described below. The results are shown in Table 1.

[0090] [Haze] The haze of each test piece was measured using a haze meter NDH5000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136:2000.

[0091] [Total light transmittance] The total light transmittance of each test piece was measured using a haze meter NDH5000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7361-1:1997.

[0092] [Solid refractive index] The refractive index of a test piece having a thickness of 2 mm was measured using an Abbe refractometer in accordance with JIS K 7142.

[0093] [Table 1]

[0094] <Production of biaxially oriented sheets> The materials of the types and amounts shown in Table 2 were melt-kneaded and extruded using a single-screw extruder (manufactured by Tanabe Plastics Machinery) with a screw diameter of 40 mm to obtain pellets. The extrusion temperature was 230°C, and the screw rotation speed was 90 RPM. The obtained pellets were melt-kneaded using an extruder (manufactured by Tanabe Plastics Machinery) with a screw diameter of 40 mm at an extrusion temperature of 230°C and a screw rotation speed of 90 RPM, and extruded through a T-die (width: 500 mm) to obtain an unstretched sheet with a thickness of 1.5 mm. The unstretched sheet was sequentially biaxially stretched 2.8 x 2.8 times at a stretching temperature of 125°C using a batch stretching machine (manufactured by Ever Sokki, SDR-507D) to obtain biaxially stretched sheets of each Example and Comparative Example. The thickness of each biaxially stretched sheet was as shown in Table 2. The rubber component content based on the total mass of the biaxially stretched sheet was 0.09% by mass.

[0095] <Degree of environmental impact reduction (proportion of biomass-derived components)> The content of biomass-derived components in the produced biaxially oriented sheet was calculated using the following formula. The results are shown in Table 2. If the content of biomass-derived components is greater than 0% by mass, it can be said that the environmental impact of producing the biaxially oriented sheet is reduced, and the higher the content of biomass-derived components, the better. Biomass-derived component content [%] = (Total content of biomass-derived materials / Total content of all materials) x 100

[0096] <Characteristics of biaxially oriented sheets> The physical properties of the biaxially oriented sheets produced in the Examples and Comparative Examples were examined as follows. The results are shown in Table 2. The thickness, melt mass-flow rate, and M w are also shown in Table 2.

[0097] [Thermal shrinkage stress] A biaxially oriented sheet was cut into a strip measuring 20 mm wide and 150 mm long to prepare a sample, with the longitudinal direction being the MD of the biaxially oriented sheet. Both ends of the sample were held with a chuck and submerged in a 130°C oil bath for heating. The load applied to the chuck was measured when the molecular orientation relaxed due to thermal motion and the sheet thermally shrunk. The MD heat shrinkage stress was calculated by dividing the maximum load by the cross-sectional area of ​​the sample. The TD heat shrinkage stress was calculated in the same manner as above, except that the longitudinal direction of the sample was defined as the TD of the biaxially oriented sheet. The heat shrinkage stress is an indicator of the degree of molecular orientation of the biaxially oriented sheet.

[0098] [Heat shrinkage rate] A 100 mm straight line is drawn in the MD and TD on a biaxially stretched sheet specimen. The specimen is left to stand for 30 minutes in an oven at a temperature 30°C higher than the Vicat softening temperature of the sheet measured according to JIS K7206:2016, and then the length L of the straight line drawn in the MD is measured. MD [mm] and the length of the straight line drawn on TD L TD The heat shrinkage (%) in the MD and TD directions was calculated using the following formula. MD heat shrinkage (%) = {(100 - LMD ) / 100}×100 Heat shrinkage rate of TD (%) = {(100 - L TD ) / 100}×100

[0099] [Haze] The haze of the biaxially stretched sheet was measured using a haze meter NDH5000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136:2000.

[0100] [Total light transmittance] The total light transmittance of the biaxially stretched sheet was measured using a haze meter NDH5000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7361-1:1997.

[0101] [Hue] The color of the biaxially stretched sheet was examined using a color difference meter (product name: "Spectrophotometer CM-2500d" manufactured by Konica Minolta, Inc.) Specifically, 16 biaxially stretched sheets (thickness: approximately 0.25 mm) were stacked to prepare a sheet sample with a thickness of approximately 4 mm, and the color of the sample was evaluated under the conditions of the SCI method.

[0102] [Tensile modulus and maximum tensile stress] A measurement sample was prepared by cutting a biaxially oriented sheet into the shape of a dumbbell No. 1 so that the longitudinal direction was the MD of the biaxially oriented sheet. The MD tensile modulus and tensile stress at break were measured according to ASTM D638 using an autograph (AGSX, manufactured by Shimadzu Corporation). The TD tensile modulus and tensile stress at break were also determined in the same manner as above, except that the longitudinal direction of the sample was the TD of the biaxially oriented sheet. The test environment was 23°C and 50% RH.

[0103] [Folding durability (MIT test)] A biaxially oriented sheet was cut into a 15 mm wide x 100 mm long strip so that the longitudinal direction of the biaxially oriented sheet was the MD of the biaxially oriented sheet, to prepare a sample. In accordance with JIS P8115:2001, the test piece was placed in an MIT folding fatigue tester (manufactured by Toyo Seiki Seisakusho, Ltd.). A bending test was performed at a test speed of 175 rpm, a bending angle of 90°, and a load of 1 kg, and the number of MD bendings until breakage was measured. Ten samples were tested, and the average value (average number of bendings) of the 10 samples was calculated. The average number of TD bendings until breakage was also calculated in the same manner as above, except that the longitudinal direction of the sample was the TD of the biaxially oriented sheet.

[0104] [Moldability] Using a hot plate molding machine (HPTA, manufactured by Wakisaka Engineering Co., Ltd.), lunch box lids (dimensions: length 241 mm × width 193 mm × height 28 mm) were molded under the following conditions: hot plate temperature: 123°C, mold temperature: 90°C, heating time: 2 seconds. The appearance of the molded lunch box lids was evaluated according to the following criteria. Good: No whitening due to surface roughness, good shape Defective: Whitening, raindrops, or defective shape due to rough surface (unable to be commercialized)

[0105] [Table 2]

Claims

1. A biaxially oriented sheet comprising a biomass-derived styrene-based resin.

2. 10. The biaxially oriented sheet of claim 1 further comprising a fossil fuel-derived styrene-based resin.

3. 3. The biaxially oriented sheet of claim 1 or 2, wherein the biaxially oriented sheet has a melt mass flow rate of less than 5.5 g / 10 min.

4. 3. The biaxially oriented sheet according to claim 1, wherein the weight average molecular weight of the biaxially oriented sheet is 200,000 to 300,000.

5. 3. The biaxially oriented sheet according to claim 1, wherein the content of the biomass-derived styrene-based resin is 4.5 to 20% by mass, based on the total mass of the biaxially oriented sheet.

6. The biaxially oriented sheet according to claim 1 or 2, wherein the biomass-derived styrene-based resin has a biomass-derived characteristic allocation rate of 0.1 to 100% by mass.

7. 3. The biaxially oriented sheet of claim 1 or 2, which is substantially free of plasticizers.

8. At least one of the biomass-derived styrene-based resin and the fossil fuel-derived styrene-based resin contains styrene as a monomer unit, 3. The biaxially oriented sheet of claim 2, wherein the styrene comprises chemically recycled styrene.

9. a first layer comprising the biaxially oriented sheet of claim 1; a second layer disposed on the first layer; and wherein the second layer is an anti-fogging layer.

10. The biaxially oriented sheet according to claim 1 or 2 or the multilayer sheet according to claim 9, which is used for forming a food packaging container.

11. A molded article obtained by molding the biaxially oriented sheet according to claim 1 or 2 or the multilayer sheet according to claim 9.

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