Resin composition, masterbatch and sheet

Abstract

To provide a resin composition that achieves both of high impact resistance and high rigidity.SOLUTION: A resin composition contains a styrene-(meth)acrylic acid resin, polypropylene resin, polystyrenic resin, and hydrogenated styrene-butadiene resin.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a resin composition, a masterbatch for the resin composition, and a sheet. [Background technology]

[0002] In recent years, there has been an increasing tendency to require polymer materials to have conflicting properties such as heat resistance and moldability. Therefore, polymer alloys, which are blends of multiple resins, have been attracting attention in order to utilize the advantages and improve the disadvantages. For example, polystyrene-based resins are used in a wide range of fields such as automobile parts, electrical parts, lighting fixtures, and displays because of their excellent transparency, gloss, and moldability, but their applications are limited due to their low impact strength and heat resistance. Various polymer alloys, which are blends of such polystyrene-based resins with other resins such as polyphenylene ether-based resins (PPE), polyolefin-based resins, and styrene-acrylic acid copolymer resins (SMAA), have been studied.

[0003] For example, Patent Document 1 discloses a technique for blending trimming loss containing a polypropylene resin film and a heat-resistant polystyrene-based resin containing polyphenylene ether with virgin material (polyphenylene ether and polystyrene resin) and a compatibilizer, for the purpose of using waste materials such as losses resulting from cutting the ends of products in a later process as recycled raw materials. Patent Document 2 discloses a technique for blending a styrene-acrylic acid copolymer resin (SMAA) in a predetermined ratio with a polystyrene-based resin for the purpose of ensuring heat resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-40868 A [Patent Document 2] JP 2018-44086 A Summary of the Invention [Problem to be solved by the invention]

[0005] The technology of the above-mentioned Patent Document 1 uses polyphenylene ether, which has high compatibility with polystyrene resins, as a raw material, so compatibility between the resins is easy to ensure, but the improvement of impact strength, which is a disadvantage of polystyrene resins, is not considered. Furthermore, since the technology of Patent Document 1 focuses on the compatibility between polyphenylene ether, a compatibilizer, and polystyrene resins, its application is limited to recycled raw materials containing polyphenylene ether.

[0006] In addition, in the technology of Patent Document 2, polystyrene-based resins are blended with styrene-acrylic acid copolymer resin (SMAA) to improve the heat resistance, which is a drawback of polystyrene-based resins. However, since the compatibility between polystyrene-based resins and styrene-acrylic acid copolymer resin (SMAA) is low, the two undergo phase separation, resulting in a new problem of reduced impact strength. Therefore, the present invention is intended to solve the above problems, and has an object to provide a resin composition which has both excellent impact resistance and high rigidity. [Means for solving the problem]

[0007] As a result of intensive research into achieving the above object, the present inventors have found that the above problems can be solved by a resin composition containing a styrene-(meth)acrylic acid-based resin, a polypropylene-based resin, a polystyrene-based resin, and a hydrogenated styrene-butadiene-based resin, and have thus completed the present invention. That is, the present invention is as follows.

[0008] [1] The present invention is a resin composition comprising a styrene-(meth)acrylic acid-based resin, a polypropylene-based resin, a polystyrene-based resin, and a hydrogenated styrene-butadiene-based resin.

[0009] [2] In the present invention, the styrene-(meth)acrylic acid-based resin is preferably composed of a styrene-(meth)acrylic acid-methyl(meth)acrylate copolymer having 69 to 97 mass% of styrene monomer units, 3 to 16 mass parts of (meth)acrylic acid monomer units, and 0 to 15 mass% of methyl (meth)acrylate monomer units.

[0010] [3] In the present invention, the hydrogenated styrene-butadiene resin is preferably composed of a styrene-butadiene-styrene block copolymer in which a portion of the aliphatic double bonds is hydrogenated and one or more amino groups are introduced into at least one molecular chain.

[0011] [4] In the present invention, it is preferable to have a molten mixture containing a portion of the styrene-butadiene-styrene block copolymer and the styrene-(meth)acrylic acid-methyl(meth)acrylate copolymer that have been melt-kneaded in advance, and the polypropylene-based resin or the polystyrene-based resin that has been contacted with the molten mixture.

[0012] [5] In the present invention, at least a part of the resin selected from the group consisting of the styrene-(meth)acrylic acid-based resin, the polypropylene-based resin, and the polystyrene-based resin is preferably a resin derived from scraps of a resin molded product.

[0013] [6] In the present invention, it is preferable that the hydrogenated styrene-butadiene resin is contained in an amount of 3 to 15 parts by mass relative to a total of 100 parts by mass of 10 to 40% by mass of the styrene-(meth)acrylic acid resin, 45 to 87% by mass of the polypropylene resin, and 3 to 15% by mass of the polystyrene resin.

[0014] [7] In the present invention, it is preferable that the hydrogenated styrene-butadiene resin is contained in an amount of 3 to 15 parts by mass relative to a total of 100 parts by mass of 10 to 25% by mass of the styrene-(meth)acrylic acid resin, 2 to 5% by mass of the polypropylene resin, and 70 to 90% by mass of the polystyrene resin.

[0015] [8] The present invention provides a masterbatch used for preparing the resin composition according to any one of the above [1] to [7], A master batch comprising the hydrogenated styrene-butadiene resin and at least one resin selected from the group consisting of the styrene-(meth)acrylic acid resin, the polypropylene resin, and the polystyrene resin.

[0016] [9] The present invention relates to a sheet obtained from the resin composition according to any one of the above [1] to [7]. Effect of the Invention

[0017] According to the present invention, it is possible to provide a resin composition which combines excellent impact resistance with high rigidity.

[0018] According to the present invention, even in a system containing a styrene-(meth)acrylic acid-based resin that has low compatibility with a polystyrene-based resin, phase separation between the resins is suppressed, and a resin composition that combines excellent impact resistance and high rigidity can be provided.

[0019] According to the present invention, a resin composition that combines excellent impact resistance and high rigidity can be provided by reworking scraps containing a styrene-(meth)acrylic acid-based resin that has low compatibility with a polystyrene-based resin and suppressing phase separation between the resins. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a drawing showing a transmission electron microscope image of a sample formed using the resin composition of Comparative Example 1. [Diagram 2] FIG. 2 is a transmission electron microscope image of a sample formed using the resin composition of Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The following describes in detail an embodiment of the present invention (hereinafter referred to as the "present embodiment"); however, the present invention is not limited to the following description and can be implemented in various modified forms within the scope of its gist.

[0022] "Resin composition" The resin composition of the present embodiment contains a styrene-(meth)acrylic acid-based resin, a polypropylene-based resin, a polystyrene-based resin, and a hydrogenated styrene-butadiene-based resin. This makes it possible to provide a resin composition that has both excellent impact resistance and high rigidity. In particular, even in a system containing a styrene-(meth)acrylic acid-based resin that has low compatibility with a polystyrene-based resin, phase separation between the resins can be suppressed to provide a resin composition that has both excellent impact resistance and high rigidity, which is useful for recycling waste materials such as trimming loss.

[0023] Conventionally, for example, when a container is manufactured from a so-called heat-resistant PSP sheet containing a styrene-(meth)acrylic acid-based resin and a polystyrene-based resin, about 20% to 30% of the heat-resistant PSP sheet is left over depending on the shape of the container to be manufactured. As described above, since the styrene-(meth)acrylic acid-based resin has low compatibility with the polystyrene-based resin, the reality is that the about 20% to 30% of the leftover material cannot be reworked and is discarded. Therefore, as in the present invention, in an embodiment in which the resin composition as a whole contains a styrene-(meth)acrylic acid-based resin, a polypropylene-based resin, a polystyrene-based resin, and a hydrogenated styrene-butadiene-based resin, it has been confirmed that excellent impact resistance and high rigidity can be achieved by suppressing phase separation between the resins (=improving dispersibility). Therefore, in a preferred embodiment of the present invention, by using the leftover material or used material that was discarded after punching the container as a raw material for the resin composition, the leftover material or used material can be reused, so that waste can be reduced and the product can be recovered at a high yield relative to the raw material. Incidentally, the scraps or used materials that were discarded after punching out the containers can be collected by any conventionally known method such as manual dismantling or mechanical sorting. Each component will be described in detail below.

[0024] <Styrene-(meth)acrylic acid resin> The resin composition of the present embodiment contains a styrene-(meth)acrylic acid resin. The polystyrene resin composition contains a styrene-(meth)acrylic acid resin, which improves heat resistance. In particular, by using the composition in combination with a polystyrene resin (e.g., a rubber-modified polystyrene resin) and a hydrogenated styrene-butadiene resin, the dispersibility is improved, and a synergistic effect of achieving both excellent impact resistance and high rigidity is exhibited. In particular, even in a system containing a styrene-(meth)acrylic acid resin that has low compatibility with a polystyrene resin, the phase separation between the resins can be suppressed, and excellent impact resistance and high rigidity can be achieved at the same time, which is useful for a rework technique for recycling scraps such as trimming loss. As a result, scraps containing a styrene-(meth)acrylic acid resin that has low compatibility with a polystyrene resin may be used as a raw material.

[0025] The amount of the styrene-(meth)acrylic acid-based resin in the resin composition in this embodiment is 5 to 40 parts by mass, preferably 7 to 35 parts by mass, and more preferably 10 to 30 parts by mass, relative to 100 parts by mass of the total amount of the styrene-(meth)acrylic acid-based resin, the polypropylene-based resin, the polystyrene-based resin, and the hydrogenated styrene-butadiene-based resin.

[0026] In this specification, the "styrene-(meth)acrylic acid resin" is a copolymer essentially containing a styrene monomer unit and a (meth)acrylic acid monomer unit. The (meth)acrylic acid monomer is preferably at least one selected from the group consisting of a (meth)acrylic acid monomer unit and a (meth)acrylic acid ester monomer unit. These styrene-(meth)acrylic acid resins may be used alone or in combination of two or more.

[0027] In this specification, the term "styrene monomer unit" refers to a repeating unit derived from a styrene monomer, and more specifically, refers to a structural unit in which an unsaturated double bond in a styrene monomer is converted to a single bond through a polymerization reaction or a crosslinking reaction. The meaning of other "monomer units" is the same as that described above. The structure of the styrene-(meth)acrylic acid based resin may be either a random structure or a block structure, with a random copolymer being preferred.

[0028] The styrene-(meth)acrylic acid resin in the present invention is not particularly limited, and may be a commercially available or synthesized styrene-(meth)acrylic acid resin alone, or may be a material containing a styrene-(meth)acrylic acid resin. Therefore, the origin of the styrene-(meth)acrylic acid resin, which is the raw material of the resin composition of the present embodiment, is not limited. Examples of materials containing the styrene-(meth)acrylic acid resin include containers such as used food packaging products and food containers; electrical appliances such as microwave ovens, air conditioners, televisions, refrigerators, and washing machines; and used office automation equipment, as well as scraps (also called skeletons) generated during the manufacturing process.

[0029] In this embodiment, at least a part of the resin selected from the group consisting of styrene-(meth)acrylic acid-based resin, polypropylene-based resin, and polystyrene-based resin is preferably a resin derived from scraps of resin molded products. That is, a part of the resin constituting the resin composition of this embodiment may be recycled from scraps or used materials. In this embodiment, when the resin composition according to the present invention is produced for the purpose of recycling scraps or used materials, it may be produced by mixing the master batch described below with scraps or used materials.

[0030] The scraps or used materials in the present invention are not particularly limited as long as they contain styrene-(meth)acrylic acid-based resin and polystyrene-based resin, and the composition of the scraps varies depending on the type of scraps used (foam or biaxially oriented sheet), etc.

[0031] For example, a preferred example of the composition ratio of the scraps is a resin having 10 to 70 mass% styrene-(meth)acrylic acid resin (SMAA), 5 to 50 mass% rubber-modified polystyrene resin (HIPS), 10 to 40 mass% polystyrene (GPPS), and 1 to 20 mass% polypropylene relative to the total amount of the scraps (100 mass%).

[0032] Another preferred example of the composition ratio of the scraps is a resin having 40-65% by mass of styrene-(meth)acrylic acid resin (SMAA), 5-30% by mass of rubber modified polystyrene resin (HIPS), 10-26% by mass of polystyrene (GPPS), and 1-20% by mass of polypropylene relative to the total amount (100% by mass) of the scraps. Another preferred example of the composition ratio of the scraps is a resin having 85-99.5% by mass of styrene-(meth)acrylic acid resin (SMAA), and 0.5-15% by mass of rubber modified polystyrene resin (HIPS) relative to the total amount (100% by mass) of the scraps.

[0033] The styrene-(meth)acrylic acid resin (SMAA) contained in the waste material or used material usable in this embodiment preferably contains about 85 to 97% by mass of styrene monomer units and about 3 to 15% by mass of methacrylic acid monomer units. The weight average molecular weight (Mw) of the styrene-(meth)acrylic acid resin (SMAA) is preferably about 100,000 to 200,000.

[0034] The rubber-modified polystyrene resin (HIPS) contained in the scrap or used material usable in this embodiment may be one type or a mixture of two or more types, and the content of rubber-like polymer particles in the HIPS (= rubber amount) is preferably 4 to 15 mass%. The volume average particle diameter (D50) of the rubber-like polymer particles is preferably 0.7 to 3.0 μm. A preferred embodiment of the rubber-modified polystyrene resin (HIPS) contained in the scrap or used material usable in this embodiment is a mixture of two types of HIPS, one of which has a rubber amount of about 11 to 13% and a volume average particle diameter (D50) of about 0.8 to 1.5 μm, and the other HIPS has a rubber amount of about 5 to 7% and a volume average particle diameter (D50) of about 2 to 2.8 μm.

[0035] The weight average molecular weight (Mw) of the polystyrene (GPPS) contained in the scrap or used material usable in this embodiment is preferably about 80,000 to 350,000. More specifically, when the scrap contains rubber-modified polystyrene resin (HIPS), the weight average molecular weight (Mw) of the polystyrene (GPPS) is preferably 80,000 or more and 300,000 or less. On the other hand, when the scrap does not contain rubber-modified polystyrene resin (HIPS), the weight average molecular weight (Mw) of the polystyrene (GPPS) is preferably 200,000 or more and 350,000 or less.

[0036] The polypropylene contained in the scraps or used materials usable in this embodiment is preferably a propylene homopolymer, and the MFR of the propylene is preferably about 0.1-15.

[0037] In the present disclosure, the melt mass flow rate of the rubber-modified polystyrene resin is a value measured under conditions of 200° C. and a load of 5 kg in accordance with JIS K 7210-1.

[0038] Examples of the (meth)acrylic acid monomer used in the styrene-(meth)acrylic acid resin of the present invention include methacrylic acid, acrylic acid, maleic anhydride, maleic acid, fumaric acid, and itaconic acid.

[0039] The (meth)acrylic acid ester monomer used in the styrene-(meth)acrylic acid resin of the present invention is preferably a (meth)acrylic acid ester monomer having an alkyl chain having 1 to 6 carbon atoms as an ester substituent. The (meth)acrylic acid monomer is represented by the chemical formula (1): CH2=C(R 1 )-C(=O)-OR 2 In the case of the chemical formula (1), R 1 represents a hydrogen atom or a methyl group, R 2 represents a hydrogen atom or an ester substituent (a linear or branched alkyl group having 1 to 6 carbon atoms), where R 2 When the substituent is an ester, the (meth)acrylic acid monomer corresponds to a (meth)acrylic acid ester monomer.

[0040] The alkyl chain having 1 to 6 carbon atoms includes a linear, branched or cyclic alkyl group. Specific examples of the (meth)acrylic acid ester monomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, etc. Among these, from an industrial viewpoint, the (meth)acrylic acid ester monomer is preferably methyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, isobutyl (meth)acrylate, and t-butyl (meth)acrylate.

[0041] The styrene-based monomers used in the styrene-(meth)acrylic acid-based resin of the present invention include styrene, α-methylstyrene, α-methyl-p-methylstyrene, ο-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene, and t-butylstyrene, or styrene derivatives such as bromostyrene and indene. Styrene is particularly preferred from an industrial point of view. These styrene-based monomers can be used alone or in combination.

[0042] In the styrene-(meth)acrylic acid resin, the content of the styrene-based monomer unit in the entire styrene-(meth)acrylic acid resin is preferably 69 to 97% by mass, more preferably 69 to 94% by mass, even more preferably 74 to 91% by mass, and even more preferably 77 to 88% by mass. If the content of the styrene-based monomer unit is less than 69% by mass, the fluidity of the resin decreases, while if it exceeds 97% by mass, the methacrylic acid monomer unit and methyl methacrylate monomer unit described below cannot be present in desired amounts.

[0043] In the styrene-(meth)acrylic acid resin, the content of the acrylic acid monomer unit in the entire styrene-(meth)acrylic acid resin is preferably 3 to 16% by mass, more preferably 6 to 16% by mass, even more preferably 7 to 14% by mass, and even more preferably 9 to 13% by mass. (Meth)acrylic acid plays a role in improving heat resistance. If the content of the acrylic acid monomer unit is less than 3% by mass, the effect of improving heat resistance is insufficient, while if it exceeds 16% by mass, the amount of gelled matter in the resin increases, resulting in poor appearance, and also in a decrease in the fluidity and mechanical properties of the resin, which is not preferable.

[0044] In the styrene-(meth)acrylic acid resin, the content of the (meth)acrylic acid monomer unit in the entire styrene-(meth)acrylic acid resin is preferably 0 to 15% by mass, more preferably 2 to 12% by mass, and even more preferably 3 to 10% by mass. In a preferred embodiment of the styrene-(meth)acrylic acid resin, the content of the (meth)acrylic acid ester monomer unit in the entire styrene-(meth)acrylic acid resin is preferably 0 to 15% by mass, more preferably 2 to 12% by mass, and even more preferably 3 to 10% by mass. However, the total content of the (meth)acrylic acid monomer unit and the (meth)acrylic acid ester monomer unit in the entire styrene-(meth)acrylic acid resin is preferably 0 to 15% by mass, more preferably 2 to 12% by mass, and even more preferably 3 to 10% by mass. If the content exceeds 15% by mass, the fluidity of the resin decreases and the water absorption tends to increase, which is not preferable.

[0045] In the present invention, the styrene-(meth)acrylic acid-based resin is preferably composed of a styrene-(meth)acrylic acid-methyl(meth)acrylate copolymer having 81 to 97 mass % of styrene monomer units, 3 to 12 mass % of (meth)acrylic acid monomer units, and 0 to 7 mass % of methyl (meth)acrylate monomer units.

[0046] The (meth)acrylic acid ester monomer can be used to suppress the dehydration reaction of the (meth)acrylic acid monomer through intermolecular interaction with the (meth)acrylic acid monomer and to improve the mechanical strength of the resin. Furthermore, the (meth)acrylic acid ester monomer also contributes to improving the resin properties such as weather resistance and surface hardness.

[0047] In addition, when a (meth)acrylic acid monomer (unit) and a (meth)acrylic acid ester monomer (unit) are bonded side by side, if a high-temperature, high-vacuum devolatilizer is used, a dealcoholization reaction may occur under certain conditions, resulting in the formation of a six-membered cyclic acid anhydride. The styrene-(meth)acrylic acid resin of this embodiment may contain this six-membered cyclic acid anhydride, but since this reduces the fluidity, it is preferable that the amount of the six-membered cyclic acid anhydride produced is as small as possible.

[0048] In the present embodiment, a preferred example of the styrene-(meth)acrylic acid-based resin is a copolymer (A1) (hereinafter, copolymer (A1)) having a styrene-based monomer unit, a (meth)acrylic acid monomer unit, and a (meth)acrylic acid ester monomer unit. The copolymer (A1) is not particularly limited, and examples thereof include styrene-acrylic acid-methyl acrylate copolymer, styrene-acrylic acid-ethyl acrylate copolymer, styrene-acrylic acid-propyl acrylate copolymer, styrene-acrylic acid-isopropyl acrylate copolymer, styrene-acrylic acid-t-butyl acrylate copolymer, acrylic acid-n-butyl acrylate copolymer, acrylic acid-isobutyl acrylate copolymer, acrylic acid-s-butyl acrylate copolymer, styrene-acrylic acid-n-butyl acrylate copolymer, styrene-methacrylic acid-methyl acrylate copolymer, styrene-methacrylic acid-ethyl acrylate copolymer, styrene-methacrylic acid-propyl acrylate copolymer, styrene-methacrylic acid-isopropyl acrylate copolymer, copolymer, styrene-methacrylic acid-t-butyl acrylate copolymer, styrene-methacrylic acid-isobutyl acrylate copolymer, styrene-methacrylic acid-s-butyl acrylate copolymer, styrene-methacrylic acid-n-butyl acrylate copolymer, styrene-methacrylic acid-methyl methacrylate copolymer, styrene-methacrylic acid-ethyl methacrylate copolymer, styrene-methacrylic acid-propyl methacrylate copolymer, styrene-methacrylic acid-isopropyl methacrylate copolymer, styrene-methacrylic acid-t-butyl methacrylate copolymer, styrene-methacrylic acid-isobutyl methacrylate copolymer, styrene-methacrylic acid-s-butyl methacrylate copolymer, and styrene-methacrylic acid-n-butyl methacrylate copolymer.

[0049] In the present embodiment, another example of a preferred form of the styrene-(meth)acrylic acid based resin is a copolymer (hereinafter, copolymer (A2)) having a styrene based monomer unit and one or more kinds of (meth)acrylic acid ester monomer units as repeating units. The copolymer (A2) is not particularly limited, and examples thereof include styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-propyl acrylate copolymer, styrene-isopropyl acrylate copolymer, styrene-t-butyl acrylate copolymer, styrene-s-butyl acrylate copolymer, styrene-isobutyl acrylate copolymer, acrylic acid-n-butyl acrylate copolymer, styrene-methyl methacrylate-methyl acrylate copolymer, styrene-methyl methacrylate-ethyl acrylate copolymer, styrene-methyl methacrylate-propyl acrylate copolymer, styrene-methyl methacrylate-isopropyl acrylate copolymer, styrene-methyl methacrylate-t-butyl acrylate copolymer, styrene-methyl methacrylate-isopropyl acrylate copolymer, styrene-methyl methacrylate-t-butyl acrylate copolymer, styrene-methyl methacrylate-isobutyl acrylate copolymer, styrene-methyl methacrylate-s-butyl acrylate copolymer, and styrene-methyl methacrylate-n-butyl acrylate copolymer.

[0050] In the present embodiment, another example of a preferred form of the styrene-(meth)acrylic acid resin is a copolymer (hereinafter, copolymer (A3)) having a styrene monomer unit and one or more (meth)acrylic acid monomer units as repeating units. The copolymer (A3) is not particularly limited, but examples thereof include a styrene-acrylic acid copolymer, a styrene-methacrylic acid copolymer, and the like.

[0051] In the present embodiment, the copolymer having a styrene-based monomer unit and a (meth)acrylic acid-based monomer unit has a total ratio of the styrene-based monomer unit and the (meth)acrylic acid-based monomer unit to the total monomer units of the copolymer of preferably 95 mass% or more, more preferably 98 mass% or more.

[0052] The molecular weight or molecular weight distribution of the styrene-(meth)acrylic acid resin is not particularly limited, but the weight average molecular weight (Mw) is preferably from 10,000 to 500,000, and more preferably from 20,000 to 350,000. If the molecular weight is less than 10,000, the impact strength of the composition may decrease, and if it exceeds 500,000, the dispersibility of the styrene-(meth)acrylic acid resin in the composition decreases, and the mechanical strength, particularly the folding endurance, decreases. In the present invention, the weight average molecular weight is measured by the method described in the "Examples" section.

[0053] The melt mass flow rate of the styrene-(meth)acrylic acid based resin is preferably 0.3 to 7.0 g / 10 min, and particularly preferably 0.5 to 5.0 g / 10 min. The melt mass flow rate of the styrene-(meth)acrylic acid based resin is a value measured at 200° C. under a load of 5 kg in accordance with JIS K 7210-1.

[0054] In the present embodiment, the polymerization method of the styrene-(meth)acrylic acid-based resin is not particularly limited, but for example, a bulk polymerization method or a solution polymerization method can be suitably adopted as a radical polymerization method. The polymerization method mainly includes a polymerization step of polymerizing the polymerization raw materials (monomer components) and a devolatilization step of removing volatile matters such as unreacted monomers and polymerization solvent from the polymerization product. Hereinafter, an example of a method for polymerizing a styrene-(meth)acrylic acid-based resin that can be used in the present embodiment will be described. When the polymerization raw materials are polymerized to obtain a styrene-(meth)acrylic acid-based resin, a polymerization initiator and a chain transfer agent are typically contained in the polymerization raw material composition.

[0055] Examples of the polymerization initiator used in the polymerization of styrene-(meth)acrylic acid resin include organic peroxides, such as peroxyketals such as 2,2-bis(t-butylperoxy)butane, 1,1-bis(t-butylperoxy)cyclohexane, and n-butyl-4,4-bis(t-butylperoxy)valerate, dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, and dicumyl peroxide, diacyl peroxides such as acetyl peroxide and isobutyryl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxyesters such as t-butyl peroxyacetate, ketone peroxides such as acetylacetone peroxide, and hydroperoxides such as t-butyl hydroperoxide. Among them, 1,1-bis(t-butylperoxy)cyclohexane is preferred from the viewpoint of decomposition rate and polymerization rate.

[0056] Examples of the chain transfer agent used in the polymerization of styrene-(meth)acrylic acid-based resins include α-methylstyrene linear dimer, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-octyl mercaptan.

[0057] As a polymerization method for styrene-(meth)acrylic acid resin, solution polymerization using a polymerization solvent can be adopted as necessary. Examples of the polymerization solvent used include aromatic hydrocarbons, such as ethylbenzene, and dialkyl ketones, such as methyl ethyl ketone, and each of them may be used alone or in combination of two or more. Other polymerization solvents, such as aliphatic hydrocarbons, can be further mixed with aromatic hydrocarbons within a range that does not reduce the solubility of the polymerization product. These polymerization solvents are preferably used in an amount not exceeding 25 parts by mass relative to 100 parts by mass of the total monomers. If the polymerization solvent exceeds 25 parts by mass relative to 100 parts by mass of the total monomers, the polymerization rate is significantly reduced and the mechanical strength of the obtained resin tends to be significantly reduced. It is preferable to add the polymerization solvent at a ratio of 5 to 20 parts by mass relative to 100 parts by mass of the total monomers before polymerization, as this makes it easier to uniformize the quality and is also preferable in terms of polymerization temperature control.

[0058] In this embodiment, the apparatus used in the polymerization step for obtaining a styrene-(meth)acrylic acid-based resin is not particularly limited, and may be appropriately selected according to the polystyrene-based resin described below or a known polymerization method. For example, when bulk polymerization is adopted, a polymerization apparatus having one or more completely mixed reactors connected together can be used. There is also no particular limitation on the devolatilization step. When bulk polymerization is adopted, polymerization is continued until the unreacted monomer is preferably 50% by mass or less, more preferably 40% by mass or less, and a devolatilization treatment is performed by a known method to remove volatile matters such as the unreacted monomer. More specifically, for example, a normal devolatilization apparatus such as a flash drum, a twin-screw devolatilizer, a thin film evaporator, or an extruder can be used, but a devolatilization apparatus with a small retention portion is preferred. The temperature of the devolatilization treatment is usually about 190 to 280°C, more preferably 190 to 260°C. The pressure in the devolatilization treatment is usually about 0.13 to 4.0 kPa, preferably 0.13 to 3.0 kPa, and more preferably 0.13 to 2.0 kPa. Desirable devolatilization methods include, for example, a method of removing volatile matters by reducing pressure under heating, and a method of removing volatile matters through an extruder or the like designed for the purpose of removing volatile matters.

[0059] <Polypropylene resin> The resin composition of the present embodiment contains a polypropylene resin. In particular, even in a system containing a styrene-(meth)acrylic acid resin that has low compatibility with a polystyrene resin, the resins are prevented from phase-separating, and excellent impact resistance and high rigidity are achieved at the same time, making the composition useful in reworking techniques for recycling scraps such as trimming loss. For this reason, it is preferable to use scraps containing a polypropylene resin as a raw material.

[0060] In this embodiment, the polypropylene-based resin is not particularly limited, and may be a homopolymer of a propylene-based monomer, or a random polymer or block copolymer of propylene and other monomers. The polypropylene-based resin in the present invention includes a polypropylene-based resin having a linear structure (also called linear PP) and a polypropylene-based resin having a branched structure (also called branched PP). These propylene-based resins may be one type or a mixture of two or more types.

[0061] The partial structure of the polypropylene resin according to the present invention may have stereoregularity (tacticity). Specifically, the partial structure may have any of isotactic, syndiotactic, and atactic stereoregularity, or may have a plurality of blocks having any of these stereoregularities.

[0062] The content of the polypropylene resin in the resin composition of the present embodiment can be appropriately changed depending on the purpose of use. More specifically, in the case of a form in which the content of the polypropylene resin is high, the content of the polypropylene resin is 50 to 95 parts by mass, preferably 55 to 90 parts by mass, and more preferably 65 to 85 parts by mass, relative to 100 parts by mass of the total content of the styrene-(meth)acrylic acid resin, the polypropylene resin, the polystyrene resin, and the hydrogenated styrene-butadiene resin.

[0063] On the other hand, in the case where the content of the polypropylene-based resin is small, the content of the polypropylene-based resin is 1 part by mass or more and less than 50 parts by mass, preferably 3 to 45 parts by mass, and more preferably 5 to 40 parts by mass, relative to 100 parts by mass of the total content of the styrene-(meth)acrylic acid-based resin, the polypropylene-based resin, the polystyrene-based resin, and the hydrogenated styrene-butadiene-based resin.

[0064] For example, when emphasis is placed on heat resistance, hinge characteristics, low-temperature impact resistance, etc., the content of the polypropylene-based resin is 50 to 95 parts by mass, and preferably 60 to 95 parts by mass, per 100 parts by mass of the total content of the styrene-(meth)acrylic acid-based resin, the polypropylene-based resin, the polystyrene-based resin, and the hydrogenated styrene-butadiene-based resin.

[0065] For example, when emphasis is placed on dimensional stability, high synthesis, impact resistance, and the like, the content of the polypropylene-based resin is 1 to 50 parts by mass, and preferably 1 to 40 parts by mass, per 100 parts by mass of the total content of the styrene-(meth)acrylic acid-based resin, the polypropylene-based resin, the polystyrene-based resin, and the hydrogenated styrene-butadiene-based resin.

[0066] The polypropylene resin in this embodiment is not particularly limited, and may be a commercially available or synthesized polypropylene resin alone, or may be a material containing a polypropylene resin. Therefore, the origin of the polypropylene resin, which is the raw material of the resin composition of this embodiment, is not limited. Examples of materials containing the polystyrene resin include containers such as used food packaging products and food containers; electrical appliances such as microwave ovens, air conditioners, televisions, refrigerators, and washing machines; and used office automation equipment, as well as scraps (also called skeletons) generated during the manufacturing process.

[0067] The propylene-based monomer constituting the polypropylene-based resin is not particularly limited, but examples thereof include propylene homopolymers obtained by polymerizing only propylene, random copolymers obtained by copolymerizing a small amount of ethylene, and block copolymers in which rubber components are uniformly and finely dispersed in homo-random polymers. Propylene is particularly preferred from an industrial viewpoint. As the propylene-based monomer, these can be used alone or in combination.

[0068] The polypropylene resin in the present invention includes polypropylene, propylene-α-olefin random copolymers which are random copolymers of propylene and α-olefins, propylene-α-olefin block copolymers which are block copolymers of propylene and α-olefins, etc. The α-olefins used in the copolymers include ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc.

[0069] In this embodiment, the melt flow rate (MFR) of the propylene-based resin is easy to mold, and is preferably 0.1 g / 10 min or more, more preferably 0.3 g / 10 min or more. Also, it is preferably 15 g / 10 min or less, more preferably 12 g / 10 min or less. The melt mass flow rate (g / 10 min) of the polypropylene-based resin was measured under the conditions of 230° C. and a load of 2.16 kg, as shown in the Examples section.

[0070] <Polystyrene resin> The resin composition of the present embodiment contains a polystyrene-based resin. By containing a polystyrene-based resin, the rigidity of the entire composition is improved. In particular, even in a system containing a styrene-(meth)acrylic acid-based resin that has low compatibility with a polystyrene-based resin, phase separation between resins can be suppressed, and excellent impact resistance and high rigidity can be achieved at the same time, making the composition useful in rework technology for recycling scraps such as trimming loss. For this reason, it is preferable to use scraps containing a polystyrene-based resin as a raw material.

[0071] In this embodiment, the polystyrene-based resin may be a homopolymer of a styrene-based monomer, or a copolymer of a styrene-based monomer and another monomer (excluding a (meth)acrylic monomer) that is copolymerizable therewith, as necessary.

[0072] The polystyrene resin may also be a polystyrene resin having rubber polymer particles dispersed in a matrix of the polystyrene resin, in other words, a rubber-modified polystyrene resin obtained by polymerizing a styrene monomer in the presence of a rubber polymer.

[0073] The content of the polystyrene resin in the resin composition of the present embodiment can be appropriately changed depending on the purpose of use. More specifically, in the case of a form in which the content of the polystyrene resin is high, the content of the polystyrene resin is 50 to 95 parts by mass, preferably 55 to 90 parts by mass, and more preferably 65 to 85 parts by mass, relative to 100 parts by mass of the total content of the styrene-(meth)acrylic acid resin, the polypropylene resin, the polystyrene resin, and the hydrogenated styrene-butadiene resin.

[0074] On the other hand, in the case where the content of the polystyrene-based resin is small, the content of the polystyrene-based resin is 1 part by mass or more and less than 50 parts by mass, preferably 3 to 45 parts by mass, and more preferably 5 to 40 parts by mass, relative to 100 parts by mass of the total content of the styrene-(meth)acrylic acid-based resin, the polypropylene-based resin, the polystyrene-based resin, and the hydrogenated styrene-butadiene-based resin. When the polystyrene-based resin is present in the resin composition of the present embodiment, the heat resistance, mechanical properties, etc. of the molded article obtained from the resin composition can be ensured.

[0075] For example, when emphasis is placed on dimensional stability, high synthesis, impact resistance, and the like, the polystyrene-based resin is 50 to 95 parts by mass, and preferably 60 to 95 parts by mass, per 100 parts by mass of the total content of the styrene-(meth)acrylic acid-based resin, the polypropylene-based resin, the polystyrene-based resin, and the hydrogenated styrene-butadiene-based resin.

[0076] For example, when emphasis is placed on heat resistance, hinge characteristics, low-temperature impact resistance, and the like, the polystyrene-based resin is 1 to 50 parts by mass, and preferably 1 to 40 parts by mass, per 100 parts by mass of the total content of the styrene-(meth)acrylic acid-based resin, the polypropylene-based resin, the polystyrene-based resin, and the hydrogenated styrene-butadiene-based resin.

[0077] The polystyrene resin in this embodiment is not particularly limited, and may be a commercially available or synthesized polystyrene resin alone, or may be a material containing a polystyrene resin. Therefore, the origin of the polystyrene resin that is the raw material of the resin composition of this embodiment is not limited. Examples of materials that contain the polystyrene resin include containers such as used food packaging products and food containers; electrical appliances such as microwave ovens, air conditioners, televisions, refrigerators, and washing machines; and used office automation equipment, as well as scraps (also called skeletons) generated during the manufacturing process.

[0078] The styrene monomer constituting the polystyrene resin is not particularly limited, but examples thereof include styrene, α-methylstyrene, paramethylstyrene, ethylstyrene, propylstyrene, butylstyrene, chlorostyrene, bromostyrene, etc. From an industrial viewpoint, styrene is particularly preferred. As the styrene monomer, these can be used alone or in combination.

[0079] Further, the copolymer of another monomer (excluding (meth)acrylic acid monomers) copolymerizable with the styrene-based monomer is not particularly limited as long as it is copolymerizable with the styrene-based monomer.

[0080] The content of the styrene monomer unit in the polystyrene resin is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 97% by mass or more, when the total amount of the monomer units constituting the polystyrene resin is taken as 100% by mass. If the content is less than 70% by mass, the moldability and flowability of the resin, which are characteristics of the polystyrene resin, decrease, which is not preferable.

[0081] In addition, when the polystyrene resin is a copolymer of a styrene monomer and another copolymerizable monomer other than a (meth)acrylic acid monomer, the upper limit of the content of the styrene monomer unit in the polystyrene resin is preferably 98% by mass, more preferably 95% by mass. In addition, when the polystyrene resin is a homopolymer of a styrene monomer such as polystyrene, the polystyrene resin is preferably composed of a styrene monomer unit, but it is acceptable for the polystyrene resin to contain, for example, 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less of a monomer unit other than the styrene monomer unit.

[0082] When the polystyrene resin is a rubber-modified polystyrene resin, the content of the styrene monomer unit in the polystyrene resin excluding the rubber polymer is referred to.

[0083] The content of styrene monomer units and other monomer units in polystyrene resins copolymerized with other monomers was measured by measuring the resin with a nuclear magnetic resonance measurement device ( 1 It can be calculated from the integral ratio of the spectrum measured by 1 H-NMR.

[0084] When the polystyrene resin is a rubber-modified polystyrene resin, the rubber-like polymer may be polybutadiene, polyisoprene, natural rubber, polychloroprene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, or the like. Among them, polybutadiene or styrene-butadiene copolymer is preferable. As the polybutadiene, both high-cis polybutadiene having a high cis content and low-cis polybutadiene having a low cis content may be used. In addition, as the structure of the styrene-butadiene copolymer, both a random structure and a block structure may be used. One or more of these rubber-like polymers may be used.

[0085] The rubber-like polymer contained in the rubber-modified polystyrene-based resin may be one which encapsulates a polystyrene-based resin on the inside and has a polystyrene-based resin grafted on the outside.

[0086] Examples of such rubber-modified polystyrene resins include HIPS (high impact polystyrene), ABS resin (acrylonitrile-butadiene-styrene copolymer), AAS resin (acrylonitrile-acrylic rubber-styrene copolymer), AES resin (acrylonitrile-ethylene propylene rubber-styrene copolymer), etc. In addition, it is preferable to use scraps containing rubber-modified polystyrene resins.

[0087] The content of the rubber component contained in the rubber-modified polystyrene resin is not particularly limited, but is preferably 2 to 10 mass%, more preferably 2.5 to 8 mass%, based on 100 mass% of the rubber-modified polystyrene resin. If the content of the rubber component is less than 2 mass%, the impact resistance decreases and the molded product becomes easily cracked. Also, if the content of the rubber-like polymer exceeds 10 mass%, the mechanical strength and appearance tend to decrease. In the present disclosure, the content of the rubber component contained in the rubber-modified polystyrene resin is a value calculated using pyrolysis gas chromatography.

[0088] The average particle size of the rubber-like polymer dispersion particles contained in the rubber-modified polystyrene resin is not particularly limited, but is preferably 0.5 to 5.0 μm, more preferably 1.0 to 4.0 μm. If the average particle size of the rubber-like polymer dispersion particles is smaller than 0.5 μm, the resin composition tends to have difficulty in obtaining impact resistance, and if it is larger than 5.0 μm, the mechanical strength and appearance tend to be deteriorated.

[0089] In this disclosure, the average particle size of the dispersed particles of the rubber-like polymer contained in the rubber-modified polystyrene resin refers to the volume-based median size measured using a particle size distribution measuring device (Multisizer III, Beckman Coulter, Inc.) that employs the digital Coulter principle, as described in the Examples.

[0090] The weight average molecular weight (Mw) of the rubber-modified polystyrene resin is not particularly limited, but is preferably in the range of 50,000 to 400,000, and more preferably in the range of 80,000 to 350,000. If the weight average molecular weight is less than 50,000, the impact strength tends to decrease, and if it exceeds 400,000, the moldability tends to deteriorate.

[0091] In the present disclosure, the weight average molecular weight (Mw) of the rubber-modified polystyrene resin is a value measured by gel permeation chromatography (GPC), and more specifically, a value measured by the procedure described in the section [Examples] below.

[0092] The melt mass flow rate of the rubber-modified polystyrene resin is not particularly limited, but is preferably in the range of 1.0 to 20 g / 10 min, more preferably 1.5 to 16 g / 10 min. If it is lower than 1.0 g / 10 min, moldability decreases, and if it exceeds 20 g / 10 min, the appearance of the molded product tends to be poor.

[0093] In the present disclosure, the melt mass flow rate of the rubber-modified polystyrene resin is a value measured under conditions of 200° C. and a load of 5 kg in accordance with JIS K 7210-1. An example of a method for producing a rubber-modified polystyrene-based resin that can be used in the resin composition of the present embodiment will be described below.

[0094] In a typical embodiment, the rubber-modified polystyrene resin can be produced by a method including polymerizing a styrene monomer in the presence of a rubber-like polymer to form an island structure in which the rubber-like polymer is dispersed in the styrene polymer. There is no particular restriction on the polymerization method of the styrene monomer, and a solution in which rubber is dissolved in the styrene monomer can be used to carry out normal bulk polymerization, solution polymerization, suspension polymerization, etc. In addition, it is preferable to appropriately select and use a solvent and a chain transfer agent in order to adjust the melt flow rate. As the solvent, toluene, ethylbenzene, xylene, etc. can be used. The amount of the solvent used is not particularly limited, but is preferably in the range of 0 to 50 mass% with respect to the total amount of the polymerization raw material liquid (100 mass%). As the chain transfer agent, n-dodecyl mercaptan, t-dodecyl mercaptan, α-methylstyrene dimer, etc. are used, and α-methylstyrene dimer is preferred. The amount of the chain transfer agent used is preferably 0.01 to 2% by mass, more preferably 0.03 to 1% by mass, and even more preferably 0.05 to 0.2% by mass, based on 100% by mass of the total amount of the polymerization raw material liquid. The polymerization reaction temperature is preferably 80 to 200°C, and even more preferably 90 to 180°C. If the reaction temperature is 80°C or higher, the productivity is good and it is industrially appropriate, while if it is 200°C or lower, it is preferable because it is possible to avoid the production of a large amount of low molecular weight polymer. If the target molecular weight of the styrene-based polymer cannot be adjusted only by the polymerization temperature, it may be controlled by the amount of initiator, the amount of solvent, the amount of chain transfer agent, and the like. The reaction time is generally 0.5 to 20 hours, and preferably 2 to 10 hours. If the reaction time is 0.5 hours or more, the reaction proceeds well, while if it is 20 hours or less, the productivity is good and it is industrially appropriate.

[0095] In the above-mentioned production method, the particle size of the dispersed particles of the rubber-like polymer in the rubber-modified polystyrene-based resin can be controlled by the rotation speed of the stirrer in the reactor, the amount of the toluene-insoluble matter can be controlled by the amount of the initiator, and the swelling index of the toluene-insoluble matter with respect to toluene can be controlled by the temperature of the extruder in the recovery system.

[0096] The amount of the rubber-like polymer in the rubber-modified polystyrene resin can be controlled by adjusting the content of the rubber-like polymer in the raw material or the polymerization rate to a target content. In this embodiment, the rubber-modified polystyrene resin can be produced by the above-mentioned production method, but as another method, it can also be produced by mixing and diluting the rubber-modified polystyrene resin obtained by the above-mentioned production method with a polystyrene resin such as a polystyrene resin that does not contain a rubber-like polymer.

[0097] Examples of the organic peroxide used as a polymerization initiator include peroxyketals, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, peroxyesters, ketone peroxides, and hydroperoxides. As the polymerization solvent, ethylbenzene, toluene, xylene, etc. can be used.

[0098] In this embodiment, at any stage before or after the recovery step in producing the rubber-modified polystyrene-based resin, or at the stage of extruding or molding the rubber-modified polystyrene-based resin, various additives, for example, ultraviolet absorbers, light stabilizers, hindered phenol-based, phosphorus-based, sulfur-based and other antioxidants, lubricants, plasticizers such as liquid paraffin, antistatic agents, flame retardants, various dyes and pigments, fluorescent brightening agents, light diffusing agents, and selective wavelength absorbers may be added as necessary within a range that does not impair the object of the present invention.

[0099] <Hydrogenated styrene-butadiene resin> The resin composition of the present embodiment contains a hydrogenated styrene-butadiene resin. This can improve the mechanical strength of the molded body obtained by molding the resin composition. In addition, by being contained in the resin composition at a predetermined content together with the above-mentioned styrene-(meth)acrylic acid-based resin, the resin composition has high dispersibility and excellent impact resistance and rigidity. In particular, it has been confirmed that the mechanical strength of the resin composition as a whole is improved by adding the above-mentioned styrene-(meth)acrylic acid-based resin and hydrogenated styrene-butadiene-based resin to a resin composition containing a polystyrene-based resin and a polypropylene-based resin.

[0100] The hydrogenated styrene-butadiene resin refers to a styrene-butadiene copolymer which contains a conjugated diene and a styrene monomer unit as repeating units, and in which all or a part of the unsaturated bonds of the conjugated diene are hydrogenated.

[0101] In this embodiment, the content of the styrene monomer unit in the hydrogenated styrene-butadiene resin is preferably 10% by mass or more and 70% by mass or less, more preferably 20% by mass or more and 60% by mass or less. If the content of the styrene monomer unit is less than 10% by mass, the rigidity of the resin composition tends to decrease, whereas if the content of the styrene monomer unit is more than 70% by mass, the improvement in impact resistance tends to decrease.

[0102] In this embodiment, the hydrogenation rate of the double bonds based on the conjugated diene compound of the hydrogenated styrene-butadiene resin is preferably 80% or more, more preferably 90% or more. If the hydrogenation rate is less than 80%, the rigidity of the resin composition tends to decrease. The hydrogenation rate is as described in the Examples section. 1 H-NMR peak values ​​and their area ratios, 13 The carbon-carbon NMR peak values ​​were used to calculate the carbon-carbon NMR peak values.

[0103] In this embodiment, the content of the hydrogenated styrene-butadiene resin in the resin composition is 0.1 to 20 parts by mass, preferably 0.5 to 15 parts by mass, relative to 100 parts by mass of the total content of the styrene-(meth)acrylic acid resin, the polypropylene resin, the polystyrene resin, and the hydrogenated styrene-butadiene resin. By making the content 20 parts by mass or less, the strength of the molded article obtained from the resin composition can be further improved, and by making the content 0.1 parts by mass or more, the rigidity of the molded article obtained from the resin composition can be maintained.

[0104] In addition, when at least a portion selected from the group consisting of styrene-(meth)acrylic acid-based resins, polypropylene-based resins, and polystyrene-based resins is a resin derived from scraps of a resin molded product, in order to emphasize aspects such as heat resistance, hinge characteristics, and low-temperature impact resistance, it is preferable that the resin composition contains 3 to 15 parts by mass of the hydrogenated styrene-butadiene-based resin per 100 parts by mass of a resin composition containing 10 to 25% by mass of styrene-(meth)acrylic acid-based resin, 60 to 85% by mass of polypropylene-based resin, and 5 to 15% by mass of polystyrene-based resin.

[0105] In addition, when at least a portion selected from the group consisting of styrene-(meth)acrylic acid resin, polypropylene resin, and polystyrene resin is a resin derived from scraps of a resin molded product, in order to emphasize dimensional stability, high synthesis, impact resistance, and the like, it is preferable that the resin composition contains 3 to 15 parts by mass of the hydrogenated styrene-butadiene resin per 100 parts by mass of a resin composition containing 10 to 25% by mass of styrene-(meth)acrylic acid resin, 2 to 5% by mass of polypropylene resin, and 70 to 90% by mass of polystyrene resin.

[0106] In this embodiment, the hydrogenated styrene-butadiene resin is preferably a hydrogenated block copolymer obtained by hydrogenating a non-hydrogenated block copolymer containing a conjugated diene compound and a styrene monomer as repeating units. The conjugated diene compound is a diolefin having a pair of conjugated double bonds, and examples thereof include 1,3-butadiene and 2-methyl-1,3-butadiene (isoprene). Examples of the styrene monomer include styrene, α-methylstyrene, and divinylbenzene. The most common hydrogenated block copolymer is a hydrogenated block copolymer consisting of 1,3-butadiene and styrene, and is also called SEBS.

[0107] The hydrogenated styrene-butadiene resin of the present invention may have an amino group in the molecular chain constituting the resin. That is, the hydrogenated styrene-butadiene resin of the present invention is more preferably composed of a styrene-butadiene-styrene block copolymer in which a part of the aliphatic double bonds is hydrogenated and at least one amino group is introduced in at least one molecular chain. When the styrene-butadiene resin has an amino group in the polymer chain, it is considered that the interaction between the polymers is easily generated, and therefore the dispersibility of each component in the composition is further improved.

[0108] An example of the styrene-butadiene-styrene block copolymer is Tuftec (trade name MP10 or trade name P1000) manufactured by Asahi Kasei Chemicals Corp. The presence of the amine introduced into the polymer chain can be identified by a known method such as NMR or IR.

[0109] In addition, a preferred aspect of the present embodiment may be a form having a molten mixture containing a styrene-butadiene-styrene block copolymer and a styrene-(meth)acrylic acid resin (for example, a styrene-(meth)acrylic acid-methyl (meth)acrylate copolymer) that have been melt-kneaded in advance for the purpose of inducing an interaction such as a chemical bond with the styrene-(meth)acrylic acid resin, and a polypropylene resin and / or a polystyrene resin that has been brought into contact with the molten mixture.

[0110] That is, by mixing a molten mixture prepared by previously melt-mixing a styrene-butadiene-styrene block copolymer and a styrene-(meth)acrylic acid-based resin (e.g., a styrene-(meth)acrylic acid-methyl(meth)acrylate copolymer) with a polypropylene-based resin and / or a polystyrene-based resin, it is considered that the dispersibility of the styrene-(meth)acrylic acid-based resin in the resin composition is improved, or the compatibility of the styrene-(meth)acrylic acid-based resin with the polystyrene-based resin is improved, thereby making it possible to suppress phase separation between the resins.

[0111] In the present embodiment, the method for block copolymerizing a conjugated diene with a styrene-based monomer to produce a hydrogenated styrene-butadiene-based resin and the method for hydrogenating the resulting block copolymer can be any known method.

[0112] In the present embodiment, the weight average molecular weight of the hydrogenated styrene-butadiene resin is not particularly limited. For example, when emphasis is placed on moldability, the weight average molecular weight of the hydrogenated styrene-butadiene resin is preferably 600,000 or less. The weight average molecular weight of the hydrogenated styrene-butadiene resin is more preferably 70,000 to 500,000, and further preferably 80,000 to 400,000. On the other hand, when importance is attached to the impact resistance of the entire resin composition, the weight average molecular weight of the hydrogenated styrene-butadiene resin may be 600,000 or more.

[0113] In this embodiment, the hydrogenated styrene-butadiene resin may be modified with a compound having a functional group, such as a carboxyl group, an acid anhydride group, an isocyanate group, an epoxy group, a silanol group, or an alkoxysilane group. In this embodiment, the hydrogenated styrene-butadiene resin may be a commercially available product, such as Tuftec (product name) manufactured by Asahi Kasei Chemicals Corporation.

[0114] <Other ingredients> To the resin composition of the present embodiment, various general additives can be added to achieve known effects within the scope of the present invention. For example, mold release agents, lubricants, antioxidants, ultraviolet absorbers, plasticizers, dyes, pigments, antistatic agents, antifogging agents, various fillers, etc. can be added to achieve effects suited to the purpose. The amount of each of the above-mentioned various additives in the resin composition is preferably 1.0% by mass or less, more preferably 0.8% by mass or less, and even more preferably 0.5% by mass or less, relative to 100% by mass of the resin composition.

[0115] <Masterbatch for producing resin composition> In the present embodiment, at least a part of the resin selected from the group consisting of styrene-(meth)acrylic acid-based resin, polypropylene-based resin, and polystyrene-based resin may be recycled scrap or used material. In this case, when producing the resin composition according to the present embodiment, the master batch and the scrap or used material may be mixed to produce the resin composition.

[0116] The above-mentioned master batch is a master batch used for preparing the resin composition of the present invention, and preferably contains a hydrogenated styrene-butadiene-based resin and at least one resin selected from the group consisting of the styrene-(meth)acrylic acid-based resin, the polypropylene-based resin, and the polystyrene-based resin.

[0117] Since the master batch in this embodiment essentially contains a hydrogenated styrene-butadiene resin, it is possible to improve the dispersibility of different resins. In this embodiment, the master batch preferably contains 35 to 65 mass% of hydrogenated styrene-butadiene resin, 10 to 40 mass% of styrene-(meth)acrylic acid resin, 0 to 15 mass% of polypropylene resin, and 10 to 40 mass% of polystyrene resin, relative to the total amount (100 mass%) of the master batch, and more preferably contains 43 to 57 mass% of hydrogenated styrene-butadiene resin, 18 to 32 mass% of styrene-(meth)acrylic acid resin, 0 to 7 mass% of polypropylene resin, and 18 to 32 mass% of polystyrene resin.

[0118] <Method of producing resin composition> In this embodiment, the method for producing the resin composition is not particularly limited to the method of blending, melting, kneading, and granulating the styrene-(meth)acrylic acid resin, polypropylene resin, polystyrene resin, and hydrogenated styrene-butadiene resin, and any method commonly used in the production of resin compositions can be used. For example, the above components blended (mixed) in a drum tumbler, Henschel mixer, etc. are melted and kneaded using a Banbury mixer, single-screw extruder, twin-screw extruder, kneader, etc., and granulated using a rotary cutter, fan cutter, etc., to obtain a resin composition. The resin temperature during melting and kneading is preferably 180 to 240°C. In order to achieve a target resin temperature, it is preferable to set the cylinder temperature of the extruder, etc. to a temperature 10 to 20°C lower than the resin temperature. If the resin temperature is less than 180°C, mixing will be insufficient, which is not preferable. On the other hand, if the resin temperature exceeds 240°C, thermal decomposition of the resin will occur, which is not preferable.

[0119] A preferred method for producing the resin composition of the present invention includes the steps of mixing a hydrogenated styrene-butadiene resin and a styrene-(meth)acrylic acid resin in a mass ratio of 1:2 to 2:1, and then melt-kneading the mixture at 200 to 260° C. using a twin-screw extruder as necessary to prepare a molten mixture;

[0120] A step of preparing a resin mixture by mixing 100 parts by mass of chips obtained by crushing scraps or used materials of resin moldings and 100 to 2000 parts by mass of a material selected from the group consisting of polystyrene-based resins and polypropylene-based resins, which is a virgin material added as necessary; and mixing 1 to 20 parts by mass of the molten mixture with 100 parts by mass of the resin mixture to prepare a resin composition.

[0121] For the polystyrene-based resin and polypropylene-based resin used as the virgin material, the above descriptions of the polystyrene-based resin and polypropylene-based resin can be cited. As for the scraps or used materials of the resin moldings, the above description of the scraps or used materials can be used.

[0122] <Molded body> The molded body of this embodiment can be obtained by molding the resin composition of the embodiment according to the present invention. The molded body of this embodiment is not particularly limited as long as it is obtained by molding the resin composition of the embodiment according to the present invention, but it is preferable that the molded body has a part with a thickness of 1 mm or less. The above resin composition can be suitably used in the molded body having a part with a thickness of 1 mm or less.

[0123] The molded article of the present embodiment is not particularly limited, but is preferably a container or a sheet. The container of the present embodiment may be directly manufactured (molded) from the resin composition, or may be manufactured by further molding a sheet obtained by molding the resin composition. The sheet of the present embodiment can be used to manufacture (molde) not only containers but also other molded articles.

[0124] The sheet of the present embodiment is a non-foamed extruded sheet, and the thickness is not particularly limited, but can be, for example, 1.0 mm or less, and preferably 0.2 to 0.8 mm.

[0125] The sheet of the present embodiment may be a sheet formed only by ordinary low-ratio roll stretching, but from the viewpoint of strength, a sheet that is particularly preferably stretched about 1.3 to 7 times with a roll and then stretched about 1.3 to 7 times with a tenter.

[0126] The sheet of the present embodiment may be used in a multilayer with a styrene-based resin such as polystyrene resin, or may be used in a multilayer with a resin other than the styrene-based resin in addition to or instead of the layer of the styrene-based resin, etc. Examples of the resin other than the styrene-based resin include PP resin, PP / PS resin, PET resin, and nylon resin. The container of the present embodiment is a container obtained by injection blow molding using the above-mentioned resin composition, or a container obtained by molding the above-mentioned sheet.

[0127] Specifically, the container obtained by the injection blow molding of this embodiment is not particularly limited, but may be, for example, a container for storing or containing beverages such as lactic acid bacteria beverages and foods such as fermented milk, and the container may be a vertical cylindrical container having a flange surface at the opening and an opening at the top. The container may have a height of 50 to 120 mm, a diameter of 30 to 60 mm, and a thickness of 0.2 to 0.8 mm.

[0128] In addition, the container obtained by molding the above-mentioned sheet in this embodiment is not particularly limited, and examples thereof include a lid material for a lunch box or a container for storing side dishes, etc., molded from a sheet or a multilayer body containing the sheet.

[0129] In this embodiment, the manufacturing method for obtaining a molded body from the resin composition is not particularly limited, and can be manufactured by a known molding method, for example, extrusion molding or injection molding.Specific examples of extrusion molding include extrusion molding, calendar molding, blow molding, extrusion foam molding, profile extrusion molding, lamination molding, inflation molding, T-die film molding, sheet molding, vacuum molding, pressure molding, direct blow molding, etc.In addition, examples of injection molding include injection molding, RIM molding, injection foam molding, injection blow molding, injection stretch blow molding, etc.

[0130] In this embodiment, the method for producing a sheet among the molded products is not particularly limited, but examples thereof include a method in which the sheet is extruded using a single-screw or twin-screw extruder equipped with a T-die, and the sheet is taken up using a uniaxial or biaxial stretching machine. In the present embodiment, the method for producing the container by molding the sheet is not particularly limited, and examples thereof include vacuum molding.

[0131] In the present embodiment, the method for producing the container obtained by injection blow molding is not particularly limited, and can be a known method. Specifically, in injection blow molding, an intermediate body (e.g., a parison with a bottom) is first molded from a resin composition by injection molding, and then this intermediate body is transferred into a blow molding die while still attached to a core (male die for injection molding) in a softened state, and compressed air is sent from the core to inflate the intermediate body up to the inner wall surface of the blow molding die, thereby forming a hollow molded body (e.g., a container).

[0132] In the above molding method, the mold temperature is preferably 20 to 70°C, more preferably 25 to 65°C, and even more preferably 30 to 60°C, in the stage of blow molding the intermediate. The temperature of the rubber-modified polystyrene is preferably 180 to 280°C, and more preferably 200 to 260°C. The ratio of the volume of the container to the volume of the intermediate body (volume stretching ratio) is preferably 1.5 to 7 times, and more preferably 2 to 5 times. Although the embodiment of the present invention has been described above, the present invention is not limited to the above example and can be modified as appropriate. EXAMPLES

[0133] 1. "Method of evaluating resin characteristics" (1) Measurement of the content of each monomer unit in styrene-(meth)acrylic acid resin and each monomer unit in hydrogenated styrene-butadiene resin Nuclear magnetic resonance ( 1 The amount was quantified from the integral ratio of the spectrum measured by a 1 H-NMR device. Sample preparation: 75 mg of resin was dissolved in 0.75 mL of d1-chloroform. Measuring equipment: JEOL JNM ECA-500 Measurement conditions: Measurement temperature 60℃, observation nucleus 1 H, 32 times, 45 seconds

[0134] (2) Measurement of weight average molecular weight The weight average molecular weight (Mw) of the polystyrene resin was measured by gel permeation chromatography (GPC) under the following conditions. Equipment: Tosoh HLC-8220 Separation column: Two Tosoh TSK gel Super HZM-H (inner diameter 4.6 mm) connected in series Guard column: Tosoh TSK guard column Super HZ-H Measurement solvent: tetrahydrofuran (THF) Sample concentration: 5 mg of the measurement sample was dissolved in 10 mL of solvent and filtered through a 0.45 μm filter. Injection volume: 10μL Measurement temperature: 40℃ Flow rate: 0.35mL / min Detector: Ultraviolet absorption detector (Tosoh UV-8020, wavelength 254 nm) The calibration curve was created using 11 types of TSK standard polystyrene (F-850, F-450, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000) manufactured by Tosoh Corporation. The calibration curve was created using a linear approximation equation.

[0135] (3) Melt mass flow rate (MFR) measurement The melt mass flow rate (g / 10 min) of the produced polystyrene resin (composition) was measured in accordance with ISO1133 under conditions of 200° C. and a load of 5.00 kg. The melt mass flow rate (g / 10 min) of the polypropylene resin (composition) was measured in accordance with ISO1133 under conditions of 230° C. and a load of 2.16 kg.

[0136] (4) Measurement of Vicat softening temperature The Vicat softening temperature of the produced polystyrene resin composition was measured in accordance with ISO 306. The load was 50 N and the heating rate was 50° C. / h.

[0137] (5) Measurement of bending modulus The produced polystyrene resin composition was injection molded into an ISO type A test piece, and the flexural modulus was measured in accordance with ISO178.

[0138] (6) DuPont impact strength test DuPont impact strength was measured according to ASTM D 2974. A 0.4 mm thick test specimen was fixed in contact between a dart (weight 226.5 g) with a tip diameter of 9.5 mm and a support with a dent (dent diameter 9.6 mm). A 100 g weight was dropped onto the dart from an appropriate height (maximum 100 cm), and the energy (weight x drop height) at which a crack occurred was calculated from the 50% fracture height using the extrusion molded plate as the test specimen. The unit is kg cm. The test specimen was a 0.3 mm thick sheet extruded at 260°C using a 20 mm sheet extruder.

[0139] (7) Calculation of hydrogenation rate Using polymer samples taken at each step of the polymerization process of the modified block copolymer before hydrogenation and during the polymerization, 1 Measurements were performed by H-NMR. The vinyl bonds were calculated from the ratio of 1,4-bonds to 1,2-bonds after calculating the integral value per 1H of each bond type from the integral values ​​of the signals assigned to 1,4-bonds and 1,2-bonds. In addition, the hydrogenated polymer was used in the same manner as above, 1 The hydrogenation rate was measured by H-NMR. The hydrogenation rate was calculated by calculating the integral values ​​of the signals derived from the residual double bonds at 4.5 to 5.5 ppm and the signals derived from the hydrogenated conjugated dienes, and then calculating the ratio thereof.

[0140] 2. “Raw materials used” The raw materials used in the following Examples 1 to 7 and Comparative Examples 1 to 4 are as follows. As the styrene-(meth)acrylic acid-based resin (1), a styrene-methacrylic acid copolymer "G9001" manufactured by PS Japan Co., Ltd. (methacrylic acid monomer unit content 8% by mass, methyl methacrylate monomer unit content 0% by mass) was used.

[0141] As the styrene-(meth)acrylic acid-based resin (2), a styrene-methacrylic acid-methyl methacrylate copolymer (methacrylic acid monomer unit content: 11% by mass, methyl methacrylate monomer unit content: 5% by mass) called "MM290" manufactured by PS Japan Co., Ltd. was used.

[0142] The polypropylene resin (1) used was “Novatec PP FY6C” manufactured by Japan Polypropylene Corporation. The polystyrene resin (1) used was “PSJ-Polystyrene HIPS 475D” manufactured by PS Japan Co., Ltd. The polystyrene resin (2) used was “PSJ-Polystyrene HIPS H0103” manufactured by PS Japan Co., Ltd. The polystyrene resin (3) used was “PSJ-Polystyrene GPPS G9305” manufactured by PS Japan Co., Ltd. The hydrogenated styrene-butadiene resin (1) used was “Tuftec MP10 (amine-modified at one end of the molecular chain)” manufactured by Asahi Kasei Corporation. As the hydrogenated styrene-butadiene resin (2), “Tuftec P1500 (no modification at one end of the molecular chain)” manufactured by Asahi Kasei Corporation was used. As the styrene-butadiene-styrene block resin (1), "Tufprene 125" manufactured by Asahi Kasei Corporation was used.

[0143] The composition of the heat-resistant PSP (polystyrene paper) scraps was 55% by mass SMAA "G9001" manufactured by PS Japan Co., Ltd., 16% by mass HIPS, 16% by mass GPPS, and 13% by mass polypropylene.

[0144] 3. "Preparation of resin composition" <Preparation of molten mixture and resin mixture> <Preparation of Molten Mixture (1)> Hydrogenated styrene-butadiene resin (1) and styrene-(meth)acrylic acid resin (1) were mixed in a mass ratio of 1:1, and then melt-kneaded at 230°C in a 20 mm twin-screw extruder to prepare a molten mixture (1).

[0145] <Preparation of Molten Mixture (2)> A hydrogenated styrene-butadiene resin (1) and a styrene-(meth)acrylic acid resin (2) were mixed in a mass ratio of 1:1, and then melt-kneaded at 230°C in a 20 mm twin-screw extruder to prepare a molten mixture (2).

[0146] <Preparation of Molten Mixture (3)> The hydrogenated styrene-butadiene resin (2) and the styrene-(meth)acrylic acid resin (1) were mixed in a mass ratio of 1:1, and then melt-kneaded at 230°C in a 20 mm twin-screw extruder to prepare a molten mixture (3).

[0147] <Preparation of resin mixture (4)> Styrene-butadiene-styrene block copolymer (1) and styrene-(meth)acrylic acid resin (1) were mixed in a mass ratio of 1:1, and then melt-kneaded at 230°C in a 20 mm twin-screw extruder to prepare a resin mixture (4).

[0148] <Mixing with molten mixtures (1) to (3) or resin mixture (4)> The resin compositions of Examples 1 to 7 and the mixed compositions of Comparative Examples 1 to 4 were prepared by mixing the above-prepared molten mixtures (1) to (4) or resin mixture (4), scraps of resin moldings, and a polypropylene-based resin or a polystyrene-based resin as follows.

[0149] <<Example 1>> A resin composition (1) of Example 1 was prepared by mixing 10 parts by mass of the molten mixture (1) with 100 parts by mass of a mixture of 70% by mass of polypropylene-based resin (1) and 30% by mass of crushed chips of heat-resistant PSP (polystyrene paper) scraps.

[0150] <<Example 2>> A resin composition (2) of Example 2 was prepared by mixing 10 parts by mass of the molten mixture (1) with 100 parts by mass of a mixture of 80% by mass of polypropylene-based resin (1) and 20% by mass of crushed chips of heat-resistant PSP (polystyrene paper) scraps.

[0151] <<Example 3>> A resin composition (3) of Example 3 was prepared by mixing 16 parts by mass of the molten mixture (1) with 100 parts by mass of a mixture of 70% by mass of polypropylene-based resin (1) and 30% by mass of crushed chips of heat-resistant PSP (polystyrene paper) scraps.

[0152] <<Example 4>> A resin composition (4) of Example 4 was prepared by mixing 10 parts by mass of the molten mixture (3) with 100 parts by mass of a mixture of 70% by mass of polypropylene-based resin (1) and 30% by mass of crushed chips of heat-resistant PSP (polystyrene paper) scraps.

[0153] <<Example 5>> A resin composition (5) of Example 5 was prepared by mixing 10 parts by mass of the molten mixture (2) with 100 parts by mass of a mixture of 70% by mass of polypropylene-based resin (1) and 30% by mass of crushed chips of heat-resistant PSP (polystyrene paper) scraps.

[0154] <<Example 6>> A resin composition (6) of Example 6 was prepared by mixing 16 parts by mass of the molten mixture (1) with 100 parts by mass of a mixture of 70% by mass of polystyrene resin (1) and 30% by mass of crushed chips of heat-resistant PSP (polystyrene paper) scraps.

[0155] <<Example 7>> A resin composition (7) of Example 7 was prepared by mixing 24 parts by mass of the molten mixture (1) with 100 parts by mass of a mixture of 70% by mass of polystyrene resin (1) and 30% by mass of crushed chips of heat-resistant PSP (polystyrene paper) scraps.

[0156] <<Comparative Example 1>> A mixture (100 parts by mass) of 70% by mass of polypropylene resin (1) and 30% by mass of crushed chips of heat-resistant PSP (polystyrene paper) scraps was mixed with 2 parts by mass of the molten mixture (1) to prepare a mixed composition (1) of Comparative Example 1.

[0157] <<Comparative Example 2>> A mixture (100 parts by mass) of 70% by mass of polypropylene resin (1) and 30% by mass of crushed chips of heat-resistant PSP (polystyrene paper) scraps was mixed with 32 parts by mass of the molten mixture (1) to prepare a mixed composition (2) of Comparative Example 2.

[0158] <<Comparative Example 3>> A mixture (100 parts by mass) of 70% by mass of polypropylene resin (1) and 30% by mass of crushed chips of heat-resistant PSP (polystyrene paper) scraps was mixed with 10 parts by mass of resin mixture (4) to prepare a mixed composition (3) of Comparative Example 3.

[0159] <<Comparative Example 4>> A mixture (100 parts by mass) of 70% by mass of polystyrene resin (1) and 30% by mass of crushed chips of heat-resistant PSP (polystyrene paper) scraps was mixed with 2 parts by mass of the molten mixture (1) to prepare a mixed composition (4) of Comparative Example 4.

[0160] 4. "Production of Molded Products" The flexural modulus and Vicat softening temperature were evaluated using dumbbell-shaped molded pieces obtained by injection molding the resin compositions (1) to (7) prepared in Examples 1 to 16 and the mixed compositions prepared in Comparative Examples 1 to 4 under the injection conditions described below. In addition, the resin compositions (1) to (7) prepared in Examples 1 to 16 and the mixed compositions prepared in Comparative Examples 1 to 4 were molded under the extrusion conditions described below into sheets (thickness 0.3 mm) to perform DuPont impact tests.

[0161] <Injection molding> The obtained pellet-like styrene-based resin composition or resin composition was fed to an injection molding machine, EC60N, manufactured by Toshiba Machine Co., Ltd. The temperature of the resin melting zone was set to 180 to 220°C, and the resin was injected into a mold set to 50°C to obtain a dumbbell-shaped test piece having a thickness of 4 mm.

[0162] <Extrusion molding> The obtained pellet-like styrene resin composition or resin composition was fed to a sheet extruder with a screw diameter of 30 mm manufactured by Soken Co., Ltd. The temperature of the resin melting zone was set to 220 to 260°C, and the resin was melt-extruded from a T-die (coat hanger die) at a discharge rate of 10 kg / h, and then pressed against a cast roll and a touch roll set at 90°C to obtain a sheet with a width of 300 mm and a thickness of 0.3 mm. The results are shown in Tables 1-1, 1-2, and 2 below.

[0163] [Table 1-1]

[0164] [Table 1-2]

[0165] [Table 2]

[0166] 1 and 2 show transmission electron microscope images of molded articles formed using the resin compositions of Comparative Example 1 and Example 1, respectively. As is clear from a comparison between the image of Comparative Example 1 shown in Fig. 1 and the image of Example 1 shown in Fig. 2, the molded article using the resin composition of Example 1 has a smaller area of ​​the resin phase, which confirms that the components of the resin composition are well dispersed. [Industrial Applicability]

[0167] The present invention can provide a resin composition that suppresses phase separation between resins and achieves both excellent impact resistance and high rigidity, even in a system containing a styrene-acrylic acid copolymer resin (SMAA) that has low compatibility with polystyrene-based resins, and is therefore useful in the field of recycling waste materials such as trimming loss.

Claims

1. A resin composition comprising a styrene-(meth)acrylic acid-based resin, which is a copolymer essentially containing a styrene-based monomer unit and a (meth)acrylic acid-based monomer unit, a polypropylene-based resin, a polystyrene-based resin, and a hydrogenated styrene-butadiene-based resin, the content of the styrene-based monomer unit in the entire styrene-(meth)acrylic acid-based resin is 69 to 97% by mass, The polypropylene-based resin is an isotactic propylene homopolymer, The polystyrene-based resin is a homopolymer of a styrene-based monomer or a rubber-modified polystyrene-based resin, containing 70% by mass or more of a styrene-based monomer unit when the total amount of the monomer units constituting the polystyrene-based resin is taken as 100% by mass, The hydrogenated styrene-butadiene resin is a styrene-butadiene copolymer containing a conjugated diene and a styrene-based monomer unit as repeating units, the content of the styrene-based monomer unit being 10% by mass or more and 70% by mass or less, and in which all or a part of the unsaturated bonds of the conjugated diene are hydrogenated; The resin composition contains 3 to 15 parts by mass of the hydrogenated styrene-butadiene resin with respect to a total of 100 parts by mass of 10 to 40% by mass of the styrene-(meth)acrylic acid resin, 55 to 87% by mass of the polypropylene resin, and 3 to 15% by mass of the polystyrene resin.

2. A resin composition comprising a styrene-(meth)acrylic acid-based resin, which is a copolymer essentially containing a styrene-based monomer unit and a (meth)acrylic acid-based monomer unit, a polypropylene-based resin, a polystyrene-based resin, and a hydrogenated styrene-butadiene-based resin, the content of the styrene-based monomer unit in the entire styrene-(meth)acrylic acid-based resin is 69 to 97% by mass, The polystyrene-based resin is a homopolymer of a styrene-based monomer or a rubber-modified polystyrene-based resin, containing 70% by mass or more of a styrene-based monomer unit when the total amount of the monomer units constituting the polystyrene-based resin is taken as 100% by mass, The hydrogenated styrene-butadiene resin is a styrene-butadiene copolymer containing a conjugated diene and a styrene-based monomer unit as repeating units, the content of the styrene-based monomer unit being 10% by mass or more and 70% by mass or less, and in which all or a part of the unsaturated bonds of the conjugated diene are hydrogenated; The flexural modulus (MPa) measured according to ISO 178 is 1800-2250; The resin composition contains 3 to 15 parts by mass of the hydrogenated styrene-butadiene resin with respect to a total of 100 parts by mass of 10 to 40% by mass of the styrene-(meth)acrylic acid resin, 55 to 87% by mass of the polypropylene resin, and 3 to 15% by mass of the polystyrene resin.

3. The styrene-(meth)acrylic acid-based resin is composed of a styrene-(meth)acrylic acid-methyl(meth)acrylate copolymer having 69 to 97% by mass of styrene monomer units, 3 to 16% by mass of (meth)acrylic acid monomer units, and 0 to 15% by mass of methyl (meth)acrylate monomer units. The resin composition according to claim 1 or 2.

4. The hydrogenated styrene-butadiene resin is composed of a styrene-butadiene-styrene block copolymer in which a part of aliphatic double bonds is hydrogenated and one or more amino groups are introduced into at least one molecular chain. The resin composition according to any one of claims 1 to 3.

5. The resin composition according to claim 4, comprising a molten mixture containing a portion of the styrene-butadiene-styrene block copolymer and the styrene-(meth)acrylic acid-methyl (meth)acrylate copolymer that have been melt-kneaded in advance, and the polypropylene-based resin or the polystyrene-based resin that has been contacted with the molten mixture.

6. At least a part of the resin selected from the group consisting of the styrene-(meth)acrylic acid-based resin, the polypropylene-based resin, and the polystyrene-based resin is a resin derived from a scrap of a resin molded product. The resin composition according to any one of claims 1 to 5.

7. A masterbatch used for preparing the resin composition according to any one of claims 1 to 6, A master batch containing the hydrogenated styrene-butadiene resin and at least one resin selected from the group consisting of the styrene-(meth)acrylic acid resin, the polypropylene resin, and the polystyrene resin.

8. A sheet obtained from the resin composition according to any one of claims 1 to 6.

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