Resin composition and molded body

Abstract

To improve compatibility between a polylactic acid and a styrenic resin.SOLUTION: A resin composition contains a polylactic acid (A), a styrenic resin (B) and a compatibilizing agent (C), wherein the compatibilizing agent (C) is a polymer having a first polymer part and a second polymer part, the first polymer part is composed of a polyester-based polymer, and the second polymer part is composed of a polymer different from the first polymer part and has a constitutional unit derived from a (meth)acrylate monomer.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a resin composition and a molded article. [Background technology]

[0002] Conventionally, attempts have been made to mix multiple resins to achieve functions or improve performance that cannot be achieved with a single resin. However, since many combinations of resin types are incompatible, the performance or function of the composite is often lower than that of a single resin. Therefore, compatibilizers are added to improve the compatibility of multiple resin types.

[0003] Patent Document 1 discloses a polylactic acid-based thermoplastic resin composition that contains a styrene-based resin, a polylactic acid resin, and a styrene-based copolymer, the styrene-based copolymer being composed of an alkyl (meth)acrylate monomer and an aromatic vinyl monomer. Patent Document 2 discloses a resin composition that is a blend of an aromatic vinyl-based resin, a thermoplastic resin, and a copolymer of a vinyl-based resin portion and a polyester resin portion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-167404 [Patent Document 2] Japanese Patent Application Publication No. 10-219074 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the styrene copolymer described in Patent Document 1 has room for improvement in terms of its function as a compatibilizer between polylactic acid and styrene resins. In addition, the copolymer described in Patent Document 2 is unclear in terms of its effect on compatibility with styrene resins when the thermoplastic resin is polylactic acid.

[0006] An object of one aspect of the present invention is to provide a resin composition or the like that can improve the compatibility between polylactic acid and a styrene-based resin. [Means for solving the problem]

[0007] In order to solve the above problems, a resin composition according to one embodiment of the present invention is a resin composition comprising polylactic acid (A), a styrene-based resin (B), and a compatibilizer (C), wherein the compatibilizer (C) is a polymer having a first polymer portion and a second polymer portion, the first polymer portion being composed of a polyester-based polymer, and the second polymer portion being composed of a polymer different from the first polymer portion, and having a structural unit derived from a (meth)acrylate monomer. Effect of the Invention

[0008] According to one embodiment of the present invention, it is possible to provide a resin composition or the like that can improve the compatibility between polylactic acid and a styrene-based resin. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment of the present invention will be described in detail below. In this specification, "A to B" indicating a numerical range means "A or more and B or less" unless otherwise specified. Note that the following description is one embodiment of the present invention, and the present invention is not limited to the following configuration.

[0010] A resin composition according to an embodiment of the present invention is a resin composition containing polylactic acid (A), a styrene-based resin (B), and a compatibilizer (C). The resin composition according to an embodiment of the present invention may further contain a polymer (D). The compatibilizer (C) has a first polymer portion and a second polymer portion. The first polymer portion is composed of a polyester-based polymer, and the second polymer portion is composed of a polymer different from the first polymer portion, and has a structural unit derived from a (meth)acrylate monomer.

[0011] The use of such a compatibilizer (C) can improve the compatibility between the polylactic acid (A) and the styrene-based resin (B), thereby reducing phase separation between the polylactic acid (A) and the styrene-based resin (B).

[0012] [1. Polylactic acid (A)] Polylactic acid (A) is a polyester resin in which lactic acid is polymerized through ester bonds. Polylactic acid (A) may contain only one of the optical isomers L-lactic acid (L form) and D-lactic acid (D form), or both. When polylactic acid (A) contains both L-lactic acid and D-lactic acid, polylactic acid (A) may be a mixture of a polymer having only L-lactic acid as a constituent unit and a polymer having only D-lactic acid as a constituent unit. Polylactic acid (A) may also be a polymer having both L-lactic acid and D-lactic acid as constituent units.

[0013] Polylactic acid (A) can be synthesized from biological materials and is a material that contributes to carbon neutrality compared to resins made from petroleum or other raw materials. In addition, polylactic acid (A) is biodegradable and has a small environmental impact when disposed of. By containing such polylactic acid (A), the resin composition according to one embodiment of the present invention can reduce greenhouse gas emissions throughout the entire product cycle. This effect also contributes to the achievement of, for example, Goal 12 of the Sustainable Development Goals (SDGs) advocated by the United Nations, "Ensure sustainable consumption and production patterns."

[0014] [2. Styrene-based resin (B)] The styrene resin (B) is a resin obtained by polymerization of styrene. Examples of the styrene resin (B) include polystyrene, high impact polystyrene (HIPS), and acrylonitrile-butadiene-styrene copolymer (ABS). The styrene resin (B) may be a recycled material.

[0015] The high-impact polystyrene may be a resin containing a component such as rubber in polystyrene. For example, a high-impact polystyrene containing a rubber component in a styrene homopolymer may be suitably used. Examples of the rubber component include polybutadiene, styrene-butadiene copolymer, polyisoprene, and butadiene-isoprene copolymer. The rubber component may be a rubber component that is dispersed independently in the form of particles in polystyrene that is the matrix resin, or rubber particles may be graft-polymerized to polystyrene and dispersed in the form of particles.

[0016] [3. Compatibilizer (C)] The compatibilizer (C) according to one embodiment of the present invention is a polymer having a first polymer portion and a second polymer portion, the first polymer portion being composed of a polyester polymer, and the second polymer portion being composed of a polymer different from the first polymer portion. The second polymer portion has a structural unit derived from a (meth)acrylate monomer.

[0017] In one embodiment of the present invention, the polymer having a first polymer portion and a second polymer portion may be a polymer in which the first polymer portion and the second polymer portion are covalently bonded to each other. In another embodiment of the present invention, the polymer also includes a complex in which the first polymer portion and the second polymer portion are not covalently bonded to each other and the first polymer portion is encapsulated or enclosed by the second polymer portion.

[0018] An example of a polymer in which a first polymer portion and a second polymer portion are covalently bonded is a block copolymer having a first polymer portion and a second polymer portion. Also, an example of a polymer in which a first polymer portion is encapsulated or enveloped by a second polymer portion is a polymer having a core-shell structure composed of a core portion and a shell portion. A core-shell structure is a structure in which a portion called a core is encapsulated in a portion called a shell. A polymer having a core-shell structure may be one in which the core portion contains one of the first polymer portion and the second polymer portion, and the shell portion contains the other of the first polymer portion and the second polymer portion.

[0019] Among them, the compatibilizer (C) is preferably a polymer having a core-shell structure, with the first polymer portion constituting the shell portion of the core-shell structure. That is, the compatibilizer (C) is preferably a polymer having a core-shell structure, with the first polymer portion constituted by a polyester polymer constituting the shell portion, and the second polymer portion constituted by a polymer different from the first polymer portion constituting the core portion. Below, a preferred embodiment of the compatibilizer (C) having the core-shell structure will be described in detail as a representative example.

[0020] <3-1. First polymer portion> As described above, the first polymer portion is composed of a polyester polymer. In one aspect of the present invention, the polyester polymer means a polymer composed of a structural unit containing an ester bond as a repeating unit. The polyester polymer may be synthesized, for example, by a polycondensation reaction between a dicarboxylic acid component and a diol component.

[0021] Although the function of the first polymer portion is not particularly limited, it is believed that the first polymer portion is composed of a polyester-based polymer, thereby improving the affinity with the polyester resin polylactic acid (A). As a result, it is believed that the compatibility between the polylactic acid (A) and the styrene-based resin (B) is improved by the compatibilizer (C).

[0022] The dicarboxylic acid is not particularly limited, and examples thereof include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and alicyclic dicarboxylic acids. Examples of such aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, 2,5-norbonanedicarboxylic acid, 1,4-naphthalic acid, 1,5-naphthalic acid, 4,4-oxybenzoic acid, fumaric acid, maleic anhydride, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, tetrahydrophthalic anhydride, tetrahydroterephthalic acid, 5-sodium sulfoisophthalic acid, 5-lithium sulfoisophthalic acid, trimellitic anhydride, and pimellitic anhydride.

[0023] The diol component is not particularly limited, and examples thereof include ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, triethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, cyclohexanedimethanol, an ethylene oxide adduct of bisphenol A, a propylene oxide adduct of bisphenol A, an ethylene oxide and propylene oxide adduct of bisphenyl A, an ethylene oxide adduct and propylene oxide adduct of hydrogenated bisphenol A, polytetramethylene glycol, polyethylene glycol, polypropylene glycol and modified products thereof, and sodium sulfobutanediol.

[0024] Two or more kinds of dicarboxylic acid components may be used, and similarly, two or more kinds of diol components may be used.

[0025] The first polymer portion may be composed of a plurality of polymers each having a plurality of different structural units. In this case, the structural units may be any of those exemplified as the structural units of the first polymer portion.

[0026] The mass average molecular weight of the first polymer portion is not particularly limited, but is preferably 3000 or more, more preferably 5000 or more, and particularly preferably 7000 or more, in terms of powder handling properties. On the other hand, in order to reduce the increase in viscosity when a matrix resin is added, the mass average molecular weight is preferably 200,000 or less, more preferably 100,000 or less, and particularly preferably 50,000 or less. The mass average molecular weight can be measured by gel permeation chromatography (GPC).

[0027] The glass transition temperature of the first polymer portion is not particularly limited, but in order to ensure powder recoverability, it is preferably 40° C. or higher, more preferably 45° C. or higher, and even more preferably 50° C. or higher. On the other hand, in order to avoid pulverization of the powder, the glass transition temperature is preferably 150° C. or lower, more preferably 130° C. or lower, and even more preferably 100° C. or lower.

[0028] <3-2. Second polymer portion> The second polymer portion is composed of a polymer different from the first polymer portion and has a constitutional unit derived from a (meth)acrylate monomer. The second polymer portion has a constitutional unit derived from a (meth)acrylate monomer, and thus the tensile elongation of an article molded from the resin composition is improved.

[0029] In addition, the second polymer portion preferably has a structural unit other than the structural unit derived from the (meth)acrylate monomer, and such a structural unit is preferably a component having excellent affinity with the styrene-based resin (B). Specifically, it is preferable that at least a part of the structural units of the second polymer portion is the same as at least a part of the structural units constituting the styrene-based resin (B).

[0030] Regarding the (meth)acrylate monomer-derived constituent unit constituting the second polymer portion, examples of the (meth)acrylate monomer include methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, propyl acrylate, 2-ethylhexyl acrylate, glycidyl acrylate, propyl methacrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, phenyl acrylate, phenyl methacrylate, hydroxyethyl acrylate, 4-hydroxybutyl acrylate, benzyl acrylate, benzyl methacrylate, polyalkylene glycol monoacrylate, polyalkylene glycol monomethacrylate, and methacrylic acid. Among these, methyl methacrylate, butyl acrylate, glycidyl methacrylate, polyalkylene glycol monomethacrylate, and methacrylic acid are preferred from the viewpoint of tensile elongation of the molded article.

[0031] The content of the structural unit derived from the (meth)acrylate monomer relative to 100 parts by mass of the second polymer portion is preferably 1 part by mass or more, while the upper limit is not particularly limited and is, for example, 100 parts by mass or less. More preferably, it is 3 parts by mass or more. With such a configuration, the compatibility between the polylactic acid (A) and the styrene-based resin (B) can be improved by the compatibilizer (C), and the tensile elongation of the molded article can also be improved.

[0032] Examples of the structural units constituting the second polymer portion other than the structural units derived from the (meth)acrylate monomer include structural units derived from aromatic vinyl monomers. When the structural units constituting the second polymer portion contain structural units derived from aromatic vinyl monomers, the affinity between the second polymer portion and the styrene-based resin (B) is improved. As a result, it is expected that the compatibility between the polylactic acid (A) and the styrene-based resin (B) will be improved.

[0033] The structural unit constituting the second polymer portion is more preferably a structural unit derived from an aromatic vinyl monomer having a six-membered monocyclic structure, and even more preferably a structural unit derived from styrene which may have a substituent. The structural unit derived from styrene which may have a substituent includes a structural unit derived from styrene or a structural unit derived from α-methylstyrene, and among these, a structural unit derived from styrene is particularly preferred.

[0034] The content of the constituent unit derived from the aromatic vinyl monomer relative to 100 parts by mass of the second polymer portion is not particularly limited to a lower limit, and is, for example, 0 parts by mass or more. On the other hand, the upper limit is preferably 99 parts by mass or less. More preferably, it is 98 parts by mass or less. With this configuration, the compatibility between the polylactic acid (A) and the styrene-based resin (B) can be improved by the compatibilizer (C), and the tensile elongation of the molded article can also be improved.

[0035] The second polymer portion may further have other structural units. There is no particular limit to the content of the other structural units relative to 100 parts by mass of the second polymer portion, but it is preferably 50 parts by mass or less in order to further improve the compatibility between the polylactic acid (A) and the styrene-based resin (B). It is more preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and on the other hand, it is 0 parts by mass or more.

[0036] The second polymer portion may be composed of a plurality of polymers composed of a plurality of different structural units. In this case, the structural units may be any of those exemplified as the structural units of the second polymer portion.

[0037] The content of the first polymer portion relative to 100 parts by mass in total of the first polymer portion and the second polymer portion is preferably 20 parts by mass or more and 70 parts by mass or less. Also, it is more preferably 25 parts by mass or more and 60 parts by mass or less, and more preferably 30 parts by mass or more and 50 parts by mass or less. With this configuration, the compatibility between the polylactic acid (A) and the styrene-based resin (B) can be effectively improved by the compatibilizer (C).

[0038] <3-3. Manufacturing method of compatibilizer (C)> The method of producing the compatibilizer (C) when it has a core-shell structure is not particularly limited, and it can be produced by a known method such as suspension polymerization, solution polymerization, or emulsion polymerization. Among them, from the viewpoint of ease of production, it is preferable to produce it by emulsion polymerization. That is, it is preferable that the compatibilizer (C) is a polymer obtained by emulsion polymerization of the monomer component constituting the second polymer portion in the presence of the polymer constituting the first polymer portion finally obtained. In addition, when carrying out emulsion polymerization, the monomer component may be added and polymerized at once by batch polymerization, or may be added stepwise by dropwise polymerization.

[0039] More specifically, a monomer component constituting the second polymer portion can be added to a solution in which the polymer constituting the first polymer portion is dispersed in an arbitrary solvent, emulsified using various mixers, and a polymerization initiator can be added to polymerize.

[0040] A solution in which the polymer constituting the first polymer portion is dispersed in an arbitrary solvent can be obtained, for example, by adding the polymer to one or more solvents such as water, various alcohols such as isopropyl alcohol, ethanol, and methanol, acetone, methyl ethyl ketone, and diethyl ether, and stirring while applying shear. The proportion of the polymer constituting the first polymer portion in the dispersion solution is preferably 10% by mass or more in view of excellent dispersibility, and is preferably 50% by mass or less in view of handleability taking into account the viscosity of the dispersion solution.

[0041] When the monomer component constituting the second polymer portion is added to a solution in which the polymer constituting the first polymer portion is dispersed in an arbitrary solvent, a surfactant may be further added. Examples of the surfactant include anionic surfactants, cationic surfactants, and neutral surfactants. One type of surfactant may be used alone, or two or more types may be used in combination.

[0042] As the polymerization initiator, those generally used for radical polymerization can be used. Specific examples thereof include persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate; oil-soluble azo compounds such as azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), and 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile; 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-azobis{2-methyl-N-[2-(1-hydroxyethyl)]propionamide}, 2,2'-azobis{2-methyl-N-[2-(1 water-soluble azo compounds such as 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] and its salts, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] and its salts, 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane} and its salts, 2,2'-azobis(2-methylpropynamidine) and its salts, and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]; and organic peroxides such as benzoyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, t-butyl peroxy-2-ethylhexanoate, and t-butyl peroxyisobutyrate. The polymerization initiator may be used alone or in combination of two or more kinds.

[0043] Preferred radical polymerization methods in one embodiment of the present invention include, for example, a method in which polymerization is carried out using a water-soluble polymerization initiator, and a method in which polymerization is carried out by a redox reaction using an organic peroxide and a reducing agent such as ferrous sulfate or isoascorbic acid.

[0044] The amount of the polymerization initiator used is preferably 0.05 to 1.0 parts by mass relative to 100 parts by mass of the total of the monomer components constituting the second polymer portion, and more preferably the lower limit is 0.1 parts by mass or more and the upper limit is 0.3 parts by mass or less. When a peroxide-based polymerization initiator is used, it can be used as a redox-based polymerization initiator in combination with a reducing agent. The amount of the reducing agent used is preferably 0.0001 to 1 part by mass relative to 100 parts by mass of the total of the monomer components constituting the second polymer portion.

[0045] Furthermore, the polymerization of the monomer components constituting the second polymer portion may be carried out using a known chain transfer agent as a molecular weight regulator, such as n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, or α-methylstyrene dimer.

[0046] The reaction temperature is not particularly limited, but is usually from 45° C. to 80° C. The reaction time is not particularly limited, but is usually from 30 minutes to 300 minutes.

[0047] The latex of the compatibilizer (C) obtained by emulsion polymerization can be dried by spray drying or freeze drying, or coagulated, to recover it as a polymer powder. Among these, drying or coagulation by spray drying is preferred.

[0048] When drying is performed by the spray drying method, it is preferable to spray the latex of the compatibilizer (C) onto fine droplets and then dry them by applying hot air to them. Any device such as a rotating disk type, a pressure nozzle type, or a two-fluid nozzle type may be used as a device for generating droplets.

[0049] When the latex of the compatibilizer (C) is dried by applying hot air, the hot air temperature is preferably 100° C. or higher and 200° C. or lower. When the hot air temperature is 100° C. or higher, the latex can be sufficiently dried, and when the hot air temperature is 200° C. or lower, thermal decomposition of the obtained powder can be reduced.

[0050] When coagulation is performed, the latex of the compatibilizer (C) is put into hot water in which a coagulant is dissolved, and the compatibilizer (C) is salted out and separated, purified, coagulated, and made wet, which is then dehydrated and dried. Examples of the coagulant include inorganic salts such as aluminum chloride, aluminum sulfate, sodium sulfate, magnesium sulfate, sodium nitrate, and calcium acetate, and acids such as sulfuric acid, with calcium acetate being particularly preferred. These coagulants may be used alone or in combination of two or more, but when used in combination, it is preferable to select a combination that does not form a water-insoluble salt. For example, the combination of calcium acetate with sulfuric acid or its sodium salt is not preferable because it forms a water-insoluble calcium salt.

[0051] It is common technical knowledge that the polymerization mode of the first polymer portion and the second polymer portion of the compatibilizer (C) changes depending on the manufacturing method thereof, but it is difficult to specify what the polymerization mode is. For example, the polymerization mode of the compatibilizer (C) obtained by emulsion polymerization of the monomer component constituting the second polymer portion in the presence of the polymer constituting the first polymer portion is different from that of the compatibilizer (C) obtained by other methods, and it is considered that the structure or characteristics are different. However, it is technically impossible or almost impractical to specify the structure or characteristics so that such differences are clear.

[0052] [4. Polymer (D)] The resin composition according to one aspect of the present invention preferably further contains a polymer (D). The polymer (D) has a polymer (D1) portion having a crosslinked structure and a polymer (D2) portion having a structural unit (d2) derived from an alkyl (meth)acrylate.

[0053] (4-1. Polymer (D1)) The polymer (D1) used in the resin composition according to one embodiment of the present invention is preferably an acrylic rubber component in terms of compatibility with polylactic acid (A). The acrylic rubber component contains one or more monomers containing alkyl (meth)acrylate as structural units (d1), and the monomer may contain a monomer having two or more unsaturated bonds in the molecule in an amount of 20% by weight or less. Furthermore, the monomer may contain various vinyl monomers such as aromatic alkenyl compounds such as styrene, α-methylstyrene, and vinyltoluene, cyanide vinyl compounds such as acrylonitrile and methacrylonitrile, methacrylic acid-modified silicone, and fluorine-containing vinyl compounds in an amount of 30% by weight or less.

[0054] The alkyl (meth)acrylate used is not particularly limited, and examples thereof include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, ethoxyethoxyethyl acrylate, methoxytripropylene glycol acrylate, 4-hydroxybutyl acrylate, lauryl methacrylate, stearyl methacrylate, etc. These alkyl (meth)acrylates may be used alone or in combination of two or more.

[0055] The "monomer having two or more unsaturated bonds in the molecule" serves as a crosslinking agent or a graft crosslinking agent, and examples of the crosslinking agent include ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, divinylbenzene, and silicones such as polyfunctional methacrylic group-modified silicones. Examples of the graft crosslinking agent include allyl methacrylate, triallyl cyanurate, and triallyl isocyanurate. Allyl methacrylate can also be used as a crosslinking agent. These crosslinking agents and graft crosslinking agents are used alone or in combination of two or more.

[0056] The polymer (D1) may contain one or more of the above-mentioned acrylic rubber components. The polymer (D1) preferably has a glass transition temperature of 10°C or lower. When the polymer (D1) has such a glass transition temperature, the obtained impact strength modifier is preferably capable of imparting higher impact resistance. Here, the glass transition temperature of the polymer is measured as the maximum point of Tan δ measured by a dynamic mechanical property analyzer (hereinafter, DMA).

[0057] The method for producing the polymer (D1) is not particularly limited, but it may be usually emulsion polymerization, or if necessary, forced emulsion polymerization. Here, any known surfactant such as anionic, nonionic, or cationic surfactant may be used as the emulsifier or dispersion stabilizer. If necessary, a mixture of them may be used, but it is preferable to use a combination of an emulsifier with a high micelle forming ability and an emulsifier with a low micelle forming ability.

[0058] The particle size of the polymer (D1) is not particularly limited, but the median particle size measured by a laser diffraction method is preferably 50 to 2000 nm, more preferably 100 to 500 nm, and even more preferably 100 to 300 nm. When the particle size is 2000 nm or less, the impact resistance is excellent when added to a matrix resin. When the particle size is 50 nm or more, the impact resistance is excellent when added to a matrix resin.

[0059] (4-2. Polymer (D2)) The polymer (D2) contains a structural unit (d2) derived from an alkyl (meth)acrylate. Examples of the structural unit (d2) derived from an alkyl (meth)acrylate include vinyl monomers such as methacrylic acid esters, such as methyl methacrylate and 2-ethylhexyl methacrylate, and acrylic acid esters, such as methyl acrylate, ethyl acrylate, and n-butyl acrylate, which may be used alone or in combination of two or more. From the viewpoint of excellent polymerizability, the structural unit (d2) is preferably a structural unit derived from methyl methacrylate.

[0060] The polymer (D2) may contain other structural units (d3) as necessary. Examples of the other structural units (d3) include aromatic vinyl and conjugated diene monomers. The proportion of the other structural units (d3) in the total structural units of the polymer (D2) is not particularly limited, but is preferably 0 to 20% by weight.

[0061] The ratio of the polymer (D1) portion to the polymer (D2) in the polymer (D) is 70 to 95% by weight, preferably 75 to 90% by weight, based on 100% by weight of the total of the polymer (D1) portion and the polymer (D2) portion. When the polymer (D1) portion is 95% by weight or less, the dispersibility of the resulting polymer (D) in the resin tends to be excellent. On the other hand, when it is 70% by weight or more, the impact resistance tends to be excellent.

[0062] The polymer (D) may be a core-shell type polymer in which the polymer (D1) portion is the core and the polymer (D2) portion is the shell, or may be a core-shell type polymer in which the polymer (D2) portion is the core and the polymer (D1) portion is the shell. In terms of further improving impact resistance, the polymer (D) is preferably a core-shell type polymer in which the polymer (D1) portion is the core and the polymer (D2) portion is the shell.

[0063] Polymer (D) is obtained by adding a structural unit (d2) derived from an alkyl (meth)acrylate to a latex of polymer (D1) and polymerizing it in one or multiple stages by radical polymerization. Polymer (D) is obtained as particles by pouring this graft copolymer latex into hot water in which an acid such as sulfuric acid or hydrochloric acid, or a metal salt such as calcium chloride, calcium acetate, or magnesium sulfate is dissolved, salting out, coagulating, separating, and recovering. At this time, salts such as sodium carbonate or sodium sulfate may be used in combination. Polymer (D) can also be obtained by a direct drying method such as a spray drying method.

[0064] [5. Resin composition] The resin composition according to one embodiment of the present invention includes polylactic acid (A), a styrene-based resin (B), and a compatibilizer (C). The content of the compatibilizer (C) is not particularly limited relative to 100 parts by mass of the total of the polylactic acid (A) and the styrene-based resin (B), but is preferably 0.1 parts by mass or more and 20 parts by mass or less, and more preferably 3 parts by mass or more and 20 parts by mass or less. If the proportion of the compatibilizer (C) is 0.1 parts by mass or more, the compatibility between the polylactic acid (A) and the styrene-based resin (B) is further improved, and if it is 20 parts by mass or less, the processability during production of the resin composition is excellent.

[0065] The resin composition according to one embodiment of the present invention may further include a polymer (D). In this case, the upper limit of the content of the polymer (D) is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, when the total of the polylactic acid (A) and the styrene-based resin (B) is 100% by mass. If the content of the polymer (D) is 50% by mass or less relative to the total of 100% by mass of the polylactic acid (A) and the styrene-based resin (B), the moldability is improved and the appearance of the molded product is excellent. Furthermore, the lower limit of the content of the polymer (D) is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, when the total of the polylactic acid (A) and the styrene-based resin (B) is 100% by mass. If the content of the polymer (D) is 1% by mass or more relative to the total of 100% by mass of the polylactic acid (A) and the styrene-based resin (B), the improvement of mechanical properties by the polymer (D) is effectively exhibited.

[0066] The resin composition according to one embodiment of the present invention may further contain other components. For example, known auxiliary agents may be blended as necessary to impart functionality or improve properties. Examples of such auxiliary agents include flame retardants, anti-dripping agents, antioxidants, UV absorbers, light stabilizers, release agents, lubricants, sliding agents, colorants, fluorescent brighteners, phosphorescent pigments, fluorescent dyes, and antistatic agents.

[0067] The method for producing the resin composition according to one embodiment of the present invention is not particularly limited, but the resin composition can be produced by mixing or melt-kneading the polylactic acid (A), the styrene-based resin (B) and the compatibilizer (C) in the form of powder. For mixing or melt-kneading, for example, a Henschel mixer, a Banbury mixer, a single-screw extruder, a twin-screw extruder, a two-roll machine, a kneader, a Brabender, or the like is used.

[0068] 6. Molded body The resin composition according to one embodiment of the present invention can be molded into a molded article. The resin composition according to one embodiment of the present invention may be mixed with other materials and then molded into a molded article. That is, the molded article may contain the resin composition according to one embodiment of the present invention.

[0069] The shape of the molded product is not particularly limited, and may be various shapes such as a resin plate, a sheet, a film, a cable, a fiber, an irregular shape, etc. As a molding method for the molded product, a known method can be used, and examples thereof include compression molding, transfer molding, injection molding, blow molding, vacuum molding, extrusion molding, lamination molding, and calendar molding.

[0070] [7. Summary] As described above, the present invention has the following aspects.

[0071] The resin composition according to aspect 1 of the present invention is a resin composition comprising polylactic acid (A), a styrene-based resin (B) and a compatibilizer (C), wherein the compatibilizer (C) is a polymer having a first polymer portion and a second polymer portion, the first polymer portion being composed of a polyester-based polymer, and the second polymer portion being composed of a polymer different from the first polymer portion and having a structural unit derived from a (meth)acrylate monomer.

[0072] In the resin composition according to aspect 2 of the present invention, in the aspect 1, the content of the structural unit derived from the (meth)acrylate monomer per 100 parts by mass of the second polymer portion may be 1 part by mass or more.

[0073] The resin composition according to aspect 3 of the present invention may be the same as that according to aspect 1 or 2, wherein the compatibilizer (C) has a core-shell structure, the first polymer portion constitutes a shell portion of the core-shell structure, and the second polymer portion constitutes a core portion of the core-shell structure.

[0074] The resin composition according to aspect 4 of the present invention, in any one of aspects 1 to 3, may have a content of the first polymer portion in the compatibilizer (C) of 20 parts by mass or more and 70 parts by mass or less, relative to 100 parts by mass of the total of the first polymer portion and the second polymer portion.

[0075] The resin composition according to aspect 5 of the present invention may be the resin composition according to any one of aspects 1 to 4, wherein the compatibilizer (C) is obtained by emulsion polymerization of a monomer component constituting the second polymer portion in the presence of a polymer constituting the first polymer portion.

[0076] The resin composition according to aspect 6 of the present invention, in any one of aspects 1 to 5, may have a content of the compatibilizer (C) of 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the total of the polylactic acid (A) and the styrene-based resin (B).

[0077] A molded article according to a seventh aspect of the present invention comprises the resin composition according to any one of the first to sixth aspects. EXAMPLES

[0078] An embodiment of the present invention will now be described with reference to the following examples. In the examples, "parts" refers to "parts by mass."

[0079] <Tensile modulus, tensile stress, tensile elongation> A tensile test was carried out using a Tensilon universal testing machine (model name "RTC-1250A-PL", manufactured by Orientec Co., Ltd.) in accordance with JIS K7139 to measure the tensile modulus, tensile stress and tensile elongation of the molded body.

[0080] <Impact properties> The impact resistance was evaluated by measuring the Charpy strength of a molded product with a thickness of 4 mm at at least either 23°C or 0°C in accordance with JIS K7111.

[0081] (Production Example 1) As an aqueous dispersion solution of the polymer (hereinafter also referred to as "first polymer") constituting the first polymer portion, 300 parts of Nichigo Polyester (registered trademark) WR-905 (manufactured by Mitsubishi Chemical Corporation: solid content 20%), 50 parts of styrene (St), 45 parts of methyl methacrylate (MMA), and 5 parts of butyl acrylate (BA) as radical polymerizable monomers, and 3 parts of normal octyl mercaptan (manufactured by Tokyo Chemical Industry Co., Ltd.) as a chain transfer agent were mixed and emulsified with a homomixer to obtain a pre-emulsion liquid of the radical polymerizable monomer. The radical polymerizable monomer constitutes the second polymer portion.

[0082] The obtained pre-emulsion liquid and 180 parts of deionized water were added to a flask equipped with a stirrer, a reflux condenser, and a temperature control device, and the temperature was raised to 50°C while nitrogen bubbling was performed under the condition of a flow rate of 200 mL per minute, and the temperature was maintained for 1 hour. 0.7 parts of Percumyl (registered trademark) P (manufactured by NOF Corp.) as a polymerization initiator, 0.002 parts of ferrous sulfate as a reducing agent, 0.006 parts of sodium ethylenediaminetetraacetate (EDTA), 0.3 parts of sodium formaldehyde sulfoxylate, and 10 parts of deionized water were added, and the nitrogen flow was switched to initiate polymerization. After 1 hour, the temperature was raised to 60°C, and the mixture was maintained for 2 hours and then cooled to obtain a latex of compatibilizer C1 according to one embodiment of the present invention. The obtained latex of compatibilizer C1 was added to 460 parts of deionized water containing 5 parts by mass of calcium acetate, coagulated, washed with water, dehydrated, and dried to obtain compatibilizer C1 in the form of powder.

[0083] (Examples 2 to 9) Compatibilizers C2 to C6 and C9 according to an embodiment of the present invention and compatibilizers C7 and C8 according to comparative examples were obtained by the same production method as in Production Example 1, except that the amount of the first polymer used, the type of radical polymerizable monomer, and the copolymerization amount were changed as shown in the following Table 1. In Production Examples 2 to 9, at least one of styrene (St), butyl acrylate (BA), methyl methacrylate (MMA), polypropylene glycol monomethacrylate (Blenmer (registered trademark) PP-800 manufactured by NOF Corporation) and methacrylic acid (MAA) was used as the radical polymerizable monomer.

[0084] Example 1 65 parts of polylactic acid (PLA, manufactured by NatureWorks: Ingeo (registered trademark) Biopolymer 3001D), 35 parts of high impact polystyrene (HIPS, manufactured by Toyo Styrene Co., Ltd.: Toyo Styrol (registered trademark) H350), and 5 parts of the compatibilizer C1 manufactured in Manufacturing Example 1 were placed in a polyethylene bag. The polyethylene bag was shaken well by hand to blend by hand, and then the mixture was melt-kneaded at 230°C using a twin-screw extruder (manufactured by Toshiba Machine Co., Ltd., product name: TEM35B), and the extruded strand was cut to obtain pellets.

[0085] The obtained pellets were molded using an injection molding machine (Toshiba Machine Co., Ltd., product name: IS100EN) at a molding temperature of 230°C and a mold temperature of 60°C to produce a dumbbell-shaped molded body with a thickness of 4 mm in accordance with JIS K7139 and JIS K7111, thereby obtaining a molded body according to Example 1. A tensile test and an impact test were carried out on the molded body. The tensile modulus of the molded body in the tensile test was 2.1 GPa, the tensile stress was 31 MPa, and the tensile elongation was 15.7%. The result of the impact test was 2.4 kJ / m at 23°C. 2 , 2.2 kJ / m at 0°C 2 It was.

[0086] (Examples 2 to 10) Molded articles were obtained and evaluated in the same manner as in Example 1, except that the ratio of polylactic acid (A) and styrene-based resin (B) and the type of compatibilizer (C) used were changed as shown in Table 2 below.

[0087] (Examples 11 and 12) Except for changing the types and ratios of polylactic acid (A) and styrene-based resin (B) as shown in Table 2 below and further adding polymer (D), molded bodies were obtained and evaluated in the same manner as in Example 1. Here, Toyo Styrol GP MW1C, D manufactured by Toyo Styrene Co., Ltd. was used as the styrene-based resin (B), and Metablen W-600A manufactured by Mitsubishi Chemical Corporation was used as the polymer (D).

[0088] Comparative Example 1 A resin composition and a molded article were produced in the same manner as in Example 1, except that the polymer C1 obtained in Production Example 1 was not added, to obtain a molded article according to Comparative Example 1. A tensile test and an impact test were carried out on the molded article. The tensile modulus of the molded article in the tensile test was 2.0 GPa, the tensile stress was 28 MPa, and the tensile elongation was 3.8%. The result of the impact test was 1.9 kJ / m at 23°C. 2 , 2.0 kJ / m at 0°C 2 It was.

[0089] (Comparative Examples 2 to 4) Molded articles were obtained and evaluated in the same manner as in Example 1, except that the ratio of polylactic acid (A) and styrene-based resin (B) and the type of compatibilizer (C) used were changed as shown in Table 2 below.

[0090] (Comparative Examples 5 to 7) Molded articles were obtained and evaluated in the same manner as in Example 11, except that the compatibilizer (C) was not used and the proportion of the polymer (D) was changed as shown in Table 2 below.

[0091] [Table 1]

[0092] [Table 2]

[0093] Compared with Comparative Example 1 in which no compatibilizer was used, Examples 1 to 6 and 10 in which the compatibilizer according to one aspect of the present invention was used showed improved impact resistance. In the tensile test, the tensile elongation to break and the tensile stress improved while maintaining the tensile modulus. This is because the compatibility between polylactic acid and the styrene-based resin improved by adding the compatibilizer according to one aspect of the present invention.

[0094] The same thing is shown in a comparison between systems in which the mixing ratio of polylactic acid and styrene-based resin is changed, that is, Comparative Example 2 and Examples 7 to 9.

[0095] Furthermore, the same thing is shown in a comparison of the systems in which the mixing ratio of polylactic acid and styrene-based resin was changed and polymer (D) was added, that is, Examples 11 and 12 and Comparative Examples 5 to 7.

[0096] Furthermore, in Comparative Example 3, in which compatibilizer C7, which does not have a structural unit derived from a (meth)acrylate monomer in the second polymer portion of the compatibilizer, was used, the tensile modulus and tensile elongation were inferior to those of Comparative Example 2, in which no compatibilizer was used.

[0097] Furthermore, Comparative Example 4, in which the compatibilizer C8 not containing the first polymer portion was used, showed inferior impact resistance, tensile modulus, and tensile elongation compared to Comparative Example 2, in which no compatibilizer was used.

[0098] As a reference example, a molded article was obtained and evaluated in the same manner as in Example 1, except that polybutylene terephthalate (PBT, manufactured by Mitsubishi Chemical Corporation, Novaduran 5010R5) was used instead of polylactic acid (A) and the proportions of polybutylene terephthalate and styrene-based resin (B) were changed as shown in Table 3 below. In a resin composition containing polybutylene terephthalate and a styrene-based resin, Reference Example 2, which used compatibilizer C5, did not show much improvement in impact resistance and tensile properties compared to Reference Example 1, which did not use a compatibilizer.

[0099] [Table 3] [Industrial Applicability]

[0100] In the resin composition according to one embodiment of the present invention, the polyester resin (A) and the polyolefin resin (B) are well compatible with each other, and therefore the resin composition has excellent tensile elongation when molded into a molded product. Such molded products can be suitably used as molded products obtained by recycling automobile, motorcycle, and ship parts, electrical and electronic parts, office appliance parts, miscellaneous goods, fibers, films, and molded products, and molded products useful in other fields.

Claims

1. A resin composition comprising polylactic acid (A), a styrene-based resin (B), and a compatibilizer (C), the compatibilizer (C) is a polymer having a first polymer portion and a second polymer portion, The first polymer portion is composed of a polyester-based polymer, A resin composition, wherein the second polymer portion is composed of a polymer different from the first polymer portion and has a structural unit derived from a (meth)acrylate monomer.

2. The resin composition according to claim 1 , wherein a content of the structural unit derived from the (meth)acrylate monomer relative to 100 parts by mass of the second polymer portion is 1 part by mass or more.

3. 2. The resin composition according to claim 1, wherein the compatibilizer (C) has a core-shell structure, the first polymer portion constitutes a shell portion of the core-shell structure, and the second polymer portion constitutes a core portion of the core-shell structure.

4. 2. The resin composition according to claim 1, wherein a content of the first polymer portion in the compatibilizer (C) is 20 parts by mass or more and 70 parts by mass or less with respect to a total of 100 parts by mass of the first polymer portion and the second polymer portion.

5. The resin composition according to claim 1, wherein the compatibilizer (C) is obtained by emulsion polymerization of a monomer component constituting the second polymer portion in the presence of a polymer constituting the first polymer portion.

6. The resin composition according to claim 1, wherein the content of the compatibilizer (C) is 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the total of the polylactic acid (A) and the styrene-based resin (B).

7. A molded article comprising the resin composition according to any one of claims 1 to 6.

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