Resin composition containing copolymer, method for producing same and molded article

Abstract

The present invention provides a resin composition which contains a copolymer that has less odor and comprises a styrene monomer unit and a (meth)acrylate ester monomer unit, and which has excellent safety, productivity and injection moldability for cosmetic and food packaging applications, while forming a molded article that has excellent hue and light resistance.　The present invention provides a resin composition which contains a copolymer that comprises a styrene monomer unit and a (meth)acrylate ester monomer unit, and which is characterized in that: the sum of the contents of unreacted monomers is 2,000 ppm by mass or less; the sulfur content is more than 0 ppm by mass but not more than 150 ppm by mass; and the degree of yellowing of an injection molded plate of 2 mm t is 0.6 or less.

Description

[Technical Field]

[0001] The present invention relates to a resin composition containing a copolymer including a styrene-based monomer unit and a (meth)acrylic acid ester-based monomer unit, which has excellent safety and productivity for use in cosmetics and food packaging, injection moldability, and the color and light resistance of molded products, and has little odor. [Background technology]

[0002] Styrenic resins, typified by polystyrene, are excellent in color, rigidity, moldability, etc., and are also inexpensive, making them useful for household goods, toys, housing materials for office equipment, food packaging containers, etc. In particular, they have been widely used for food packaging containers and other applications because they are non-toxic and safe materials with excellent processing properties, such as sheet processing, foaming properties, and vacuum forming properties. Patent Documents 1 to 3 disclose that productivity, appearance, and odor during molding of a copolymer containing styrene-based monomer units and (meth)acrylic acid ester-based monomer units can be improved by reducing the amount of unreacted monomer remaining in the copolymer, the amount of by-produced styrene dimer and styrene trimer, and the amount of sulfur contained in the copolymer due to a sulfur-based chain transfer agent to a predetermined level or less. They also disclose that the use of a polyfunctional organic peroxide or two or more monofunctional organic peroxides as an essential component of the polymerization initiator ensures that a sufficient amount of polymerization initiator is present in the high conversion region, suppressing the formation of styrene dimer and trimer, and preventing a large amount of residual monomer and a decrease in productivity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-26616 A [Patent Document 2] JP 2001-31046 A [Patent Document 3] JP 2002-212233 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a resin composition containing a copolymer including a styrene-based monomer unit and a (meth)acrylic acid ester-based monomer unit, which has excellent safety and productivity for use in cosmetics and food packaging, injection moldability, and the color and light resistance of molded products, and which has little odor. [Means for solving the problem]

[0005] As a result of investigations by the present inventors, it has been found that, by adjusting the total content of unreacted monomers, the sulfur content, and the yellowness index (YI) of a 2 mmt injection-molded plate in a copolymer containing styrene-based monomer units and (meth)acrylic acid ester-based monomer units to fall within predetermined ranges, it is possible to obtain a resin composition containing a copolymer containing styrene-based monomer units and (meth)acrylic acid ester-based monomer units, which has excellent safety and productivity for cosmetic and food packaging applications, injection moldability, and the transparency and light resistance of molded products, and which has little odor. That is, the present invention provides: (1) A resin composition comprising a copolymer containing a styrene-based monomer unit and a (meth)acrylic acid ester-based monomer unit, The total content of unreacted monomers is 2000 ppm by mass or less, The sulfur content is more than 0 ppm by mass and 150 ppm by mass or less, The yellowness index of a 2mm injection molded plate is 0.6 or less. A resin composition comprising: (2) The resin composition according to (1), wherein the reciprocal of the product of the total content of the unreacted monomers and the sulfur content multiplied by 100,000 (100,000 / (the total content of the unreacted monomers × the sulfur content)) is 0.5 to 8.0. (3) The resin composition according to (1) or (2), wherein the ratio of the total content of the unreacted monomers to the sulfur content (total content of the unreacted monomers / sulfur content) is 8 to 50. (4) The resin composition according to any one of (1) to (3), which satisfies the following relationship when the yellowness index of a 2 mm injection-molded plate is A and the yellowness index of the plate after 360 hours of ultraviolet irradiation at an irradiation intensity of 60 W / m is B: BA<0.8 (5) The resin composition according to any one of (1) to (4), having an MFR value of 1 g / 10 min to 5 g / 10 min under conditions of a test temperature of 200° C. and a nominal load of 5 kg. (6) The resin composition according to any one of (1) to (5), wherein 100% by mass of the copolymer contains 20% by mass to 80% by mass of styrene-based monomer units and 20% by mass to 80% by mass of (meth)acrylic acid ester monomer units. (7) The resin composition according to any one of (1) to (6), wherein the styrene-based monomer unit is styrene and the (meth)acrylic acid ester monomer unit is methyl methacrylate. (8) The resin composition according to any one of (1) to (7), having a sulfur content of 30 ppm by mass or more. (9) The total content of the styrene-based monomer units and the (meth)acrylic acid ester-based monomer units contained in 100% by mass of the copolymer is more than 96% by mass. The resin composition according to any one of (1) to (8). (10) The copolymer further comprises other copolymerizable monomer units, the content of the other copolymerizable monomer units is 0 to 10% by mass relative to 100% by mass of the total of the styrene-based monomer units, the (meth)acrylic acid ester-based monomer units, and the other copolymerizable monomer units; The other copolymerizable monomer units are acrylic acid, acrylonitrile, methacrylonitrile, Lu, The resin composition according to any one of (1) to (8), wherein the maleimide is at least one selected from the group consisting of phenylmaleimide and cyclohexylmaleimide. (11) A method for producing a polymerizable composition comprising a styrene-based monomer and a (meth)acrylic acid ester-based monomer, The method for producing a resin composition according to any one of (1) to (10), wherein in the polymerization step, a linear alkyl mercaptan chain transfer agent and an α-methylstyrene dimer chain transfer agent are used in combination. (12) The method for producing a resin composition according to (11), wherein the ratio of the amount of the linear alkyl mercaptan chain transfer agent to the amount of the α-methylstyrene dimer chain transfer agent is 0.08 to 0.25. (13) An injection-molded article using the resin composition according to any one of (1) to (10). (14) A housing for a home appliance or a container for food, stationery, or cosmetics, using the injection-molded article according to (13). Regarding. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a resin composition containing a copolymer including a styrene-based monomer unit and a (meth)acrylic acid ester-based monomer unit, which has excellent safety and productivity for use in cosmetics and food packaging, injection moldability, and the color and light resistance of molded products, and has little odor. DETAILED DESCRIPTION OF THE INVENTION

[0007] <Terminology> In the present specification, for example, the expression "A to B" means A or more and B or less.

[0008] The following describes in detail the embodiments of the present invention. The present invention is not limited to these, and various modifications are possible without departing from the spirit of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an invention independently.

[0009] <Copolymer containing styrene-based monomer units and (meth)acrylic acid ester-based monomer units> The copolymer containing styrene-based monomer units and (meth)acrylic acid ester-based monomer units according to this embodiment contains monomer units derived from the styrene-based monomer and the (meth)acrylic acid ester-based monomer. In this specification, the copolymer containing styrene-based monomer units and (meth)acrylic acid ester-based monomer units may be simply referred to as "copolymer P." Furthermore, copolymer P according to this embodiment may contain copolymerizable monomer units other than the styrene-based monomer units and the (meth)acrylic acid ester-based monomer units, as long as the effects of the present invention are not impaired. The monomer units constituting the copolymer P according to this embodiment will be described below.

[0010] <Styrene-based monomer unit> The styrene-based monomer unit is a structural unit of the copolymer P derived from a styrene-based monomer used in copolymerization. Examples of the styrene-based monomer include styrene, α-methylstyrene, and styrene in which a portion of the benzene nucleus is substituted with an alkyl group. In one embodiment, among these, styrene is preferred from the viewpoints of rigidity and moldability. These styrene-based monomers may be used alone or in combination of two or more.

[0011] Copolymer P according to this embodiment preferably contains 20 to 80% by mass of styrene-based monomer units per 100% by mass of copolymer P. More preferably, it contains 30 to 70% by mass, and even more preferably 35 to 55% by mass. Specifically, for example, it preferably contains 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80% by mass, and may be within a range between any two of the values ​​exemplified here. If the amount of styrene-based monomer units is less than 30% by mass, molding processability may be insufficient, while if it exceeds 70% by mass, the color may be insufficient. The content of styrene-based monomer units in copolymer P is calculated from the mass of the styrene-based monomer relative to the mass of all monomers used in polymerization. It can also be calculated by, for example, H-NMR measurement of the obtained copolymer P. When a styrene-based monomer unit is used in combination, the content of the styrene-based monomer unit means the total amount of the styrene-based monomer units used in combination.

[0012] <(Meth)acrylic acid ester monomer unit> The (meth)acrylic acid ester monomer unit is a structural unit of the copolymer P derived from the (meth)acrylic acid ester monomer used in copolymerization. Examples of the (meth)acrylic acid ester monomer unit include methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate, and acrylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate, and decyl acrylate. In one embodiment, methyl methacrylate is preferred among these in terms of cost, color, and heat resistance. These (meth)acrylic acid ester monomers may be used alone or in combination of two or more.

[0013] Copolymer P according to this embodiment preferably contains 20 to 80% by mass of (meth)acrylic acid ester-based monomer units per 100% by mass of copolymer P. More preferably, it contains 30 to 70% by mass, and even more preferably 45 to 65% by mass. Specifically, for example, it preferably contains 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80% by mass, and may be within a range between any two of the values ​​exemplified here. If the amount of (meth)acrylic acid ester-based monomer units is less than 40% by mass, the color and surface strength may be insufficient. If it exceeds 70% by mass, the water absorption rate, deformation rate (water absorption), and moldability may be insufficient. The content of (meth)acrylic acid ester-based monomer units in copolymer P is calculated from the mass of the (meth)acrylic acid ester-based monomer relative to the mass of all monomers used in polymerization. Alternatively, the calculation can be performed by, for example, 1H-NMR measurement of the obtained copolymer P. When (meth)acrylic acid ester-based monomer units are used in combination, the content of the (meth)acrylic acid ester-based monomer units means the total amount of the (meth)acrylic acid ester-based monomer units used in combination.

[0014] <Other copolymerizable monomer units> The copolymer P according to this embodiment may optionally contain other copolymerizable monomer units other than the styrene-based monomer units and the (meth)acrylic acid ester-based monomer units, as long as the effects of the present invention are not impaired. Examples of other copolymerizable monomer units include acrylic acid, acrylonitrile, and methacrylonitrile. Lu, Examples of the copolymerizable monomer units include phenylmaleimide and cyclohexylmaleimide. These other copolymerizable monomer units may be used alone or in combination of two or more. The content of the other copolymerizable monomer units is preferably 0 to 10% by mass, and more preferably 8% by mass or less, relative to 100% by mass of the total of the styrene-based monomer units, the (meth)acrylic acid ester-based monomer units, and the other copolymerizable monomer units.

[0015] In the copolymer P according to this embodiment, the total content of styrene-based monomer units and (meth)acrylic ester-based monomer units contained in 100% by mass of the copolymer P is preferably more than 96% by mass, and more preferably 98% by mass or more. In one embodiment, the copolymer P is composed essentially of styrene-based monomer units and (meth)acrylic ester-based monomer units. Note that "composed essentially of styrene-based monomer units and (meth)acrylic ester-based monomer units" means that other components may be contained only to the extent that the effects of the present invention are not impaired by other components than the styrene-based monomer units and (meth)acrylic ester-based monomer units. Typically, the total content of styrene-based monomer units and (meth)acrylic ester-based monomer units contained in 100% by mass of the copolymer P is in the range of 100.0 to 99.5% by mass. The other components are not limited to those exemplified as the other copolymerizable monomer units described above. When other components are used in combination, the content of the other components means the total amount of the other components used in combination.

[0016] In the copolymer P according to this embodiment, the content of methacrylic acid monomer units contained in 100% by mass of the copolymer P is preferably less than 4% by mass, and more preferably less than 2% by mass.

[0017] <Unreacted Monomer in Resin Composition> The resin composition according to this embodiment may contain a portion of the monomers used in copolymerization of the copolymer P as unreacted monomers. The total content of unreacted monomers contained in the resin composition according to this embodiment is 2000 ppm by mass or less, preferably 1800 ppm by mass or less, and more preferably 1600 ppm by mass or less. Specifically, for example, 2000, 1800, 1600, 1400, 1200, 1000, 800, 600, or 500 ppm by mass is preferable, and may be within a range between any two of the values ​​exemplified here. If the total content of unreacted monomers exceeds 2000 ppm by mass, mold contamination may be significant when molding using the resin composition, reducing productivity, or when the molded product is used in a container, the unreacted monomers may leach into the contents of the container, compromising safety.

[0018] The content of unreacted monomers in the resin composition can be measured by an internal standard method using, for example, gas chromatography. In addition, when a styrene-based monomer, and / or a (meth)acrylic acid ester-based monomer, and / or other copolymerizable monomer units are used in combination, the content of unreacted monomer means the total amount of these monomers used in combination. The content of unreacted monomers in the resin composition can be controlled, for example, by adjusting the type and amount of chain transfer agent used during polymerization of copolymer P. It can also be controlled by adjusting the devolatilization conditions after obtaining copolymer P or the ratio of monomers used during polymerization of copolymer P.

[0019] <Sulfur content of resin composition> The resin composition according to this embodiment may contain sulfur due to the sulfur-based chain transfer agent used in copolymerization of the copolymer P. The sulfur content in the resin composition according to this embodiment is more than 0 ppm by mass and not more than 150 ppm by mass, preferably not less than 30 ppm by mass, and more preferably not less than 40 ppm by mass. Specifically, for example, the sulfur content is preferably 0.1, 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or 150 ppm by mass, and may be within a range between any two of the values ​​exemplified here. When the sulfur content is 150 ppm by mass or less, odor is sufficiently reduced. In addition, although it is ideal not to use a sulfur-containing chain transfer agent, when a chain transfer agent such as α-methylstyrene dimer is used, the chain transfer efficiency is poor and the chain transfer agent remains, which adversely affects the physical properties of the resin, making this practically difficult.

[0020] The sulfur content of the resin composition can be measured, for example, by using a flat plate of the resin composition and quantifying the sulfur by a fluorescence method in X-ray analysis. The sulfur content of the resin composition can be controlled, for example, by adjusting the type and amount of the chain transfer agent used during polymerization of the copolymer P.

[0021] <Yellowness YI> The yellowness index (YI) of a 2 mm injection-molded plate obtained from the resin composition according to this embodiment is 0.6 or less, preferably 0.55 or less, and more preferably 0.50 or less. Specifically, for example, it is preferably 0.1, 0.2, 0.3, 0.4, 0.5, or 0.6, and may be within a range between any two of the values ​​exemplified here. If the yellowness index (YI) is 0.6 or less, there are advantages in that the molded product has excellent hue and good colorability.

[0022] The yellowness index (YI) of a 2 mmt injection-molded plate obtained from the resin composition can be measured, for example, by a color difference meter (Σ-80 manufactured by Nippon Denshoku Industries Co., Ltd.). The yellowness index (YI) of a 2 mm injection-molded plate obtained from the resin composition can be controlled, for example, by adjusting the type and amount of chain transfer agent used in the polymerization of copolymer P. It can also be controlled by adjusting the type and ratio of monomers used in the polymerization of copolymer P and the devolatilization conditions of the obtained copolymer P.

[0023] <Change in yellowness ΔYI> When the yellowness index (YI) of a 2 mm injection-molded plate obtained from the resin composition according to this embodiment is A, and the yellowness index (YI) of the plate after 360 hours of ultraviolet irradiation at an irradiation intensity of 60 W / m is B, it is preferable that the following relationship be satisfied. BA<0.8 The BA value is more preferably less than 0.75, and even more preferably less than 0.70. If the BA value is less than 0.8, the film has good resistance to ultraviolet light, is less likely to yellow, and maintains excellent optical properties, particularly when used or stored outdoors. The BA value can be controlled, for example, by adjusting the type and amount of a chain transfer agent used in the polymerization of copolymer P. It can also be controlled by the type and ratio of monomers used in the polymerization of copolymer P, and the use of a stabilizer.

[0024] <Relationship between the total content of unreacted monomers and the sulfur content> In the resin composition according to this embodiment, the reciprocal of the product of the total content of unreacted monomers and the sulfur content multiplied by 100,000 (100,000 / (total content of unreacted monomers × sulfur content)) is preferably 0.5 to 8.0, more preferably 0.8 to 7.5, and even more preferably 1.0 to 2.5. Specifically, for example, the value is preferably 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.3, 1.4, 1.5, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, or 8.0, and may be within a range between any two of the values ​​exemplified here. If the value of (100000 / (total content of unreacted monomers×sulfur content)) is within this range, an excellent balance between odor reduction and safety in cosmetic and food packaging applications is achieved. The value of (100,000 / (total content of unreacted monomers × sulfur content)) can be controlled, for example, by adjusting the type and amount of chain transfer agent used in the polymerization of copolymer P. It can also be controlled by adjusting the type and ratio of monomers used in the polymerization of copolymer P and the devolatilization conditions of the obtained copolymer P.

[0025] <Proportion of unreacted monomer content to total sulfur content> In the resin composition according to this embodiment, the ratio of the total content of unreacted monomers to the sulfur content (total content of unreacted monomers / sulfur content) is preferably 8 to 50, more preferably 10 to 40, and even more preferably 20 to 30. Specifically, for example, it is preferably 8, 10, 15, 20, 25, 30, 35, 40, or 50, and may be within a range between any two of the numerical values ​​exemplified here. If the ratio of the content of unreacted monomers to the total sulfur content is within this range, an excellent balance between odor reduction and safety in cosmetic and food packaging applications is achieved. The ratio of the content of unreacted monomers to the total sulfur content can be controlled, for example, by adjusting the type and amount of chain transfer agent used during polymerization of copolymer P. It can also be controlled by adjusting the devolatilization conditions of the obtained copolymer P.

[0026] <Melt mass flow rate (MFR) value> The resin composition according to this embodiment preferably has an MFR value of 1 to 5 g / 10 min, more preferably 1.5 to 4 g / 10 min, and even more preferably 1.8 to 3 g / 10 min, under conditions of a test temperature of 200°C and a nominal load of 5 kg. Specifically, for example, 1, 2, 3, 4, or 5 g / 10 min is preferred, and the MFR value may be within a range between any two of the values ​​exemplified here. If the MFR value is within this range, the fluidity is good and the molding processability is excellent. The resin composition according to this embodiment preferably has an MFR value of 70 to 110 g / 10 min, 75 to 100 g / 10 min, and more preferably 80 to 95 g / 10 min, under conditions of a test temperature of 240°C and a nominal load of 10 kg. Specifically, for example, 70, 75, 80, 85, 90, 95, 100, or 110 g / 10 min is preferred, and the MFR value may be within a range between any two of the values ​​exemplified here. An MFR value within this range results in good fluidity and excellent moldability.

[0027] The MFR value is a value measured in accordance with JIS K-7210 at 200°C and 5 kg or 240°C and 10 kg. The MFR value can be controlled, for example, by adjusting the type and amount of chain transfer agent used in the polymerization of copolymer P to adjust the molecular weight of copolymer P. It can also be controlled by adjusting the type and ratio of monomers used in the polymerization of copolymer P.

[0028] <Method for producing a copolymer containing styrene-based monomer units and (meth)acrylic acid ester-based monomer units> The copolymer P according to this embodiment is obtained by polymerizing a styrene-based monomer and a (meth)acrylic acid ester-based monomer, and is preferably produced by radical polymerization. Specifically, it may be produced by suspension polymerization, bulk polymerization, solution polymerization, or the like, with suspension polymerization being preferred. Suspension polymerization allows for easy removal of heat generated by polymerization and allows polymerization up to a high conversion range, thereby efficiently suppressing unreacted monomers.

[0029] <Polymerization solvent> As the polymerization solvent, for example, alkylbenzenes such as benzene, toluene, ethylbenzene and xylene, ketones such as acetone and methyl ethyl ketone, aliphatic hydrocarbons such as hexane and cyclohexane, etc. can be used.

[0030] <Polymerization initiator> The polymerization initiator is preferably a radical polymerization initiator, and examples of commonly known and commonly used initiators include peroxyketals such as 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(t-butylperoxy)butane, 2,2-di(4,4-di-t-butylperoxycyclohexyl)propane, and 1,1-di(t-amylperoxy)cyclohexane; hydroperoxides such as cumene hydroperoxide and t-butyl hydroperoxide; alkyl peroxides such as t-butyl peroxyacetate and t-amylperoxyisononanoate; t-butylcumyl peroxide, di-t-butyl peroxide, dicumyl peroxide, and di-t-hexyl peroxide. peroxyesters such as t-butylperoxyacetate, t-butylperoxybenzoate, and t-butylperoxyisopropyl monocarbonate; peroxycarbonates such as t-butylperoxyisopropyl carbonate and polyethertetrakis(t-butylperoxycarbonate); N,N'-azobis(cyclohexane-1-carbonitrile), N,N'-azobis(2-methylbutyronitrile), N,N'-azobis(2,4-dimethylvaleronitrile), and N,N'-azobis[2-(hydroxymethyl)propionitrile]; and the like, and these can be used alone or in combination of two or more.

[0031] <Chain transfer agent> When copolymerizing the copolymer P according to this embodiment, a chain transfer agent may be added during the polymerization to adjust the molecular weight. Examples of such a chain transfer agent include sulfur-based chain transfer agents, α-methylstyrene dimer, and terpinolene. These chain transfer agents may be used alone or in combination of two or more.

[0032] <Sulfur-based chain transfer agents> Examples of sulfur-based chain transfer agents include linear alkyl mercaptan chain transfer agents, branched alkyl mercaptan chain transfer agents, aromatic mercaptans, and ethylene thioglycol. Examples of linear alkyl mercaptan chain transfer agents include n-dodecyl mercaptan, n-octyl mercaptan, n-decyl mercaptan, n-hexyl mercaptan, and n-butyl mercaptan. Examples of branched alkyl mercaptan chain transfer agents include t-dodecyl mercaptan, sec-dodecyl mercaptan, and isobutyl mercaptan. From the viewpoint of chain transfer effect and the amount of sulfur components generated in the copolymer P, n-dodecyl mercaptan is preferred. These sulfur-based chain transfer agents may be used alone or in combination of two or more. Sulfur-based chain transfer agents can cause sulfur components derived from the sulfur-based chain transfer agent to be generated in the resin composition.

[0033] <α-methylstyrene dimer> The α-methylstyrene dimer does not cause the generation of sulfur components derived from sulfur-based chain transfer agents in the resin composition.

[0034] In the method for producing copolymer P according to this embodiment, it is preferable to use a linear alkyl mercaptan chain transfer agent and an α-methylstyrene dimer chain transfer agent in combination in the step of polymerizing a styrene monomer and a (meth)acrylic acid ester monomer. By using the chain transfer agents in combination, it is possible to achieve a balance between odor reduction and safety in cosmetics and food packaging applications.

[0035] In the method for producing copolymer P according to this embodiment, in the step of polymerizing a styrene monomer and a (meth)acrylic acid ester monomer, the ratio of the amount of linear alkyl mercaptan chain transfer agent added to the amount of α-methylstyrene dimer chain transfer agent added is preferably 0.08 to 0.25, more preferably 0.08 to 0.20, and even more preferably 0.10 to 0.20. Specifically, for example, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, or 0.25 is preferred, and the ratio may be within a range between any two of the values ​​exemplified here. When the ratio of the amount of linear alkyl mercaptan chain transfer agent added to the amount of α-methylstyrene dimer chain transfer agent added is within this range, the balance between odor reduction and safety in cosmetic and food packaging applications is even better. When a linear alkyl mercaptan chain transfer agent is used in combination, the amount of linear alkyl mercaptan chain transfer agent added means the total amount of these linear alkyl mercaptan chain transfer agents used in combination.

[0036] <Resin composition containing a copolymer containing styrene-based monomer units and (meth)acrylic acid ester-based monomer units> The resin composition according to this embodiment may contain known additives such as antioxidants, lubricants, mold release agents, plasticizers, pigments, dyes, foaming agents, foam nucleating agents, inorganic fillers, antistatic agents, and sliding agents, as needed. It may also be used in combination with known resins such as GP-PS (general-purpose polystyrene), HI-PS (high-impact polystyrene), MBS (methyl methacrylate-butadiene-styrene copolymer) resin, AS (acrylonitrile-styrene copolymer) resin, ABS (acrylonitrile-butadiene-styrene copolymer) resin, PE (polyethylene), PP (polypropylene), and PPO (polyphenylene oxide).

[0037] The resin composition according to this embodiment can be made into an injection-molded article by a known method. The obtained injection-molded article can be used as a housing for a home appliance or a container for food, stationery, cosmetics, etc. [Example]

[0038] Examples and comparative examples are provided below to explain specific embodiments of the present invention in more detail. The present invention is not limited to the following examples. Note that "%" is based on mass. First, the evaluation methods used in the present invention are described below.

[0039] (1) Measurement of monomer units: A sample was prepared by dissolving the resin composition in deuterated chloroform, and the monomer unit composition in copolymer P was calculated from the area ratio of the spectral peaks attributable to each monomer unit using 13C-NMR. (2) Measurement of unreacted monomer: The amount of residual monomer was measured by precisely weighing 0.2 g of the resin composition, dissolving it in 10 ml of tetrahydrofuran containing p-diethylbenzene as an internal standard, and using a capillary gas chromatograph under the following conditions. Capillary gas chromatograph: GC-4000 (GL Sciences Inc.) Column: GS Science InertCap WAX, inner diameter 0.25 mm, length 30 m, film thickness 50 μm Injection temperature: 180℃ Column temperature: 60℃~170℃ Detector temperature: 210℃ Split ratio: 5 / 1 (3) Measurement of sulfur content: Using a 2 mm injection molded plate obtained from the resin composition under molding conditions of a cylinder temperature of 230°C and a mold temperature of 60°C, sulfur was quantified by the fluorescent method of X-ray analysis. (4) Measurement of yellowness index (YI) of 2mm injection molded plate: A 2mm thick portion of the plate was injection molded under molding conditions of a cylinder temperature of 230°C and a mold temperature of 60°C. YI (yellowness index) was measured by the transmittance method in a constant temperature and humidity chamber at a temperature of 23°C and a humidity of 50% using a color difference meter Σ-80 manufactured by Nippon Denshoku Industries Co., Ltd., in accordance with JIS K7105 (unit: -). (5) Calculation of yellowing index (ΔYI) before and after irradiation: Using 2 mm injection-molded plates obtained from the resin composition under molding conditions of a cylinder temperature of 230°C and a mold temperature of 60°C, a 500-hour weather resistance test was conducted in accordance with JASO M351 using an accelerated weather resistance tester (Atlas Xenon Weather Meter Ci4000 manufactured by Toyo Seiki Seisakusho, using Type S borosilicate filters for both input and output). ΔYI before and after irradiation was calculated according to the above-mentioned YI measurement method. (6) MFR value: The MFR value of the obtained resin composition was measured in accordance with JIS K-7210 at 200°C and 5 kg or at 240°C and 10 kg. (7) Safety and productivity in food and cosmetic packaging applications: A 2 mm thick plate obtained by injection molding under molding conditions of a cylinder temperature of 230°C and a mold temperature of 60°C was immersed in an 8% ethanol solution and heated at about 50°C for about 24 hours, or immersed in n-heptane and heated at about 50°C for about 30 minutes. After removing the plate, the solution was evaporated to dryness and the weight of the residue was measured. The amount of elution per unit area of ​​the plate (mg / cm) was then calculated. 2 ) and evaluated safety for food and cosmetic packaging applications according to the following criteria. Note that a large amount of elution also serves as an indicator of productivity, as a large amount of elution will result in increased contamination of the mold during molding. ○ (Excellent): 0.01 mg / cm 2 Less △(Good):0.01~0.3mg / cm 2 Within the range × (inferior): 0.3 mg / cm 2 more (8) Resistance to yellowing due to ultraviolet rays: For 2 mm thick plates obtained by injection molding under molding conditions of a cylinder temperature of 230°C and a mold temperature of 60°C, the yellowing index (ΔYI) before and after irradiation was used as an index to evaluate the resistance to yellowing due to ultraviolet rays according to the following criteria. ○ (Excellent): ΔYI<0.7 △(Good): 0.7≦ΔYI≦1.2 × (inferior): ΔYI>1.2 (9) Moldability: Using an injection molding machine (Toshiba Machine IS-50EPN) under molding conditions of a cylinder temperature of 230°C and a mold temperature of 40°C, three-stage plates with each stage being 40 mm x 40 mm and thicknesses of 1 mm, 2 mm, and 3 mm were injection molded, and the moldability was evaluated according to the following criteria. 〇 (Excellent): Can be easily injection molded without any particular problems. △ (Good): The molded product has some flashing or other appearance defects, but can be molded. × (poor): The molded product has noticeable defects in appearance such as flash, burns, and flow marks, but is still moldable, or the mold cannot be completely filled and no molded product can be obtained. (10) Odor: Five test pieces (10mm x 10mm, 4mm thick) obtained by injection molding under molding conditions of a cylinder temperature of 230°C and a mold temperature of 60°C were placed in a glass container, sealed with aluminum foil, and left for 10 hours. After that, the aluminum foil was removed, and the odor was smelled and evaluated using the sensory test criteria below. ○ (Excellent): Almost none △(Good): Some × (poor): Strange odor

[0040] Example 1 Styrenic resins were produced by continuous solution polymerization using a radical polymerization method. A complete mixing tank was used as the first reactor, and a plug flow reactor with a static mixer was used as the second reactor. They were connected in series to form the polymerization process. The first reactor had a capacity of 30 L, and the second reactor had a capacity of 12 L. A raw material solution containing 35 parts by mass of styrene, 53 parts by mass of methyl methacrylate, and 12 parts by mass of ethylbenzene was prepared and continuously fed to the polymerization process at a flow rate of 8.0 kg / hr. Additionally, 0.015 parts by mass of t-butylperoxyisopropyl monocarbonate as a polymerization initiator, 0.038 parts by mass of n-dodecyl mercaptan as a chain transfer agent, and 0.42 parts by mass of α-methylstyrene dimer were continuously added to the raw material solution feed line. The temperature of the first reactor was adjusted to 135°C, and the temperature of the second reactor was adjusted to a gradient along the flow direction, with the temperature adjusted to 130°C at the middle and 145°C at the outlet. The polymer concentration at the polymerization outlet was 65%, and the conversion of styrene and methyl methacrylate was 72%. The polymer solution continuously removed from the reactor was fed to a vacuum devolatilizer with a preheater to separate unreacted styrene, methyl methacrylate, ethylbenzene, etc. The temperature of the preheater was adjusted so that the polymer temperature in the devolatilizer was 240°C, and the pressure in the devolatilizer was 1 kPa. The polymer was extracted from the vacuum devolatilizer using a gear pump, extruded into a strand, cooled with cooling water, and then cut to obtain pellet-shaped copolymers. Table 1 (Tables 1-1 and 1-2) shows the formulation of the resin composition and the analysis and evaluation results.

[0041] <Example 2> The same procedure as in Example 1 was carried out, except that the 0.038 part by mass of n-dodecyl mercaptan and 0.42 part by mass of α-methylstyrene dimer were changed to 0.04 part by mass of n-dodecyl mercaptan and 0.40 part by mass of α-methylstyrene dimer. Table 1 (Table 1-1 to Table 1-2) shows the formulation of the resin composition and the analysis and evaluation results.

[0042] Example 3 The same procedure as in Example 1 was carried out, except that the 0.038 part by mass of n-dodecyl mercaptan and 0.42 part by mass of α-methylstyrene dimer were changed to 0.04 part by mass of n-dodecyl mercaptan and 0.35 part by mass of α-methylstyrene dimer. Table 1 (Table 1-1 to Table 1-2) shows the formulation of the resin composition and the analysis and evaluation results.

[0043] Example 4 The same procedure as in Example 1 was carried out, except that the 0.038 part by mass of n-dodecyl mercaptan and 0.42 part by mass of α-methylstyrene dimer were changed to 0.04 part by mass of n-dodecyl mercaptan and 0.30 part by mass of α-methylstyrene dimer. Table 1 (Table 1-1 to Table 1-2) shows the formulation of the resin composition and the analysis and evaluation results.

[0044] <Example 5> The same procedure as in Example 1 was carried out, except that the 0.038 part by mass of n-dodecyl mercaptan and 0.42 part by mass of α-methylstyrene dimer were changed to 0.05 part by mass of n-dodecyl mercaptan and 0.25 part by mass of α-methylstyrene dimer. Table 1 (Table 1-1 to Table 1-2) shows the formulation of the resin composition and the analysis and evaluation results.

[0045] Example 6 The same procedure was carried out as in Example 2, except that the 40 parts by mass of styrene and 60 parts by mass of methyl methacrylate in Example 2 were changed to 54 parts by mass of styrene and 46 parts by mass of methyl methacrylate. Table 1 (Table 1-1 to Table 1-2) shows the formulation of the resin composition and the analysis and evaluation results.

[0046] Example 7 The same procedure as in Example 1 was carried out, except that the amounts of n-dodecyl mercaptan and α-methylstyrene dimer were changed from 0.038 parts by mass of n-dodecyl mercaptan and 0.42 parts by mass of α-methylstyrene dimer to 0.07 parts by mass of n-dodecyl mercaptan and 0.40 parts by mass of α-methylstyrene dimer. Table 1 (Table 1-1 to Table 1-2) shows the formulation of the resin composition and the analysis and evaluation results.

[0047] Example 8 The same procedure as in Example 1 was carried out, except that the 0.038 part by mass of n-dodecyl mercaptan and 0.42 part by mass of α-methylstyrene dimer were changed to 0.10 part by mass of n-dodecyl mercaptan and 0.50 part by mass of α-methylstyrene dimer. Table 1 (Table 1-1 to Table 1-2) shows the formulation of the resin composition and the analysis and evaluation results.

[0048] Example 9 The same procedure as in Example 1 was carried out, except that the 0.038 part by mass of n-dodecyl mercaptan and 0.42 part by mass of α-methylstyrene dimer were changed to 0.01 part by mass of n-dodecyl mercaptan and 0.25 part by mass of α-methylstyrene dimer. Table 1 (Table 1-1 to Table 1-2) shows the formulation of the resin composition and the analysis and evaluation results.

[0049] Example 10 The same procedure as in Example 1 was carried out, except that the amounts of n-dodecyl mercaptan and α-methylstyrene dimer were changed from 0.038 parts by mass of n-dodecyl mercaptan and 0.42 parts by mass of α-methylstyrene dimer to 0.11 parts by mass of n-dodecyl mercaptan and 0.05 parts by mass of α-methylstyrene dimer. Table 1 (Table 1-1 to Table 1-2) shows the formulation of the resin composition and the analysis and evaluation results.

[0050] Example 11 The same procedure as in Example 1 was carried out, except that 0.038 parts by mass of n-dodecyl mercaptan and 0.42 parts by mass of α-methylstyrene dimer were used instead of 0.11 parts by mass of n-dodecyl mercaptan and 0.42 parts by mass of α-methylstyrene dimer. Table 1 (Table 1-1 to Table 1-2) shows the formulation of the resin composition and the analysis and evaluation results.

[0051] Example 12 The same procedure as in Example 1 was carried out, except that the 0.038 part by mass of n-dodecyl mercaptan and 0.42 part by mass of α-methylstyrene dimer were changed to 0.02 part by mass of n-dodecyl mercaptan and 0.30 part by mass of α-methylstyrene dimer. Table 1 (Table 1-1 to Table 1-2) shows the formulation of the resin composition and the analysis and evaluation results.

[0052] Example 13 The same procedure as in Example 1 was carried out, except that the 0.038 part by mass of n-dodecyl mercaptan and 0.42 part by mass of α-methylstyrene dimer in Example 1 were changed to 0.02 part by mass of n-dodecyl mercaptan and 0.40 part by mass of α-methylstyrene dimer. Table 1 (Table 1-1 to Table 1-2) shows the formulation of the resin composition and the analysis and evaluation results.

[0053] Example 14 The same procedure as in Example 1 was carried out, except that the 0.038 part by mass of n-dodecyl mercaptan and 0.42 part by mass of α-methylstyrene dimer were changed to 0.01 part by mass of n-dodecyl mercaptan and 0.20 part by mass of α-methylstyrene dimer. Table 1 (Table 1-1 to Table 1-2) shows the formulation of the resin composition and the analysis and evaluation results.

[0054] <Comparative Example 1> The same procedure as in Example 1 was carried out, except that the 0.038 part by mass of n-dodecyl mercaptan and 0.42 part by mass of α-methylstyrene dimer in Example 1 were replaced with 0.20 part by mass of n-dodecyl mercaptan, and no α-methylstyrene dimer was used. Table 2 shows the formulation of the resin composition and the analysis and evaluation results.

[0055] <Comparative Example 2> The same procedure as in Example 1 was carried out, except that the 0.038 part by mass of n-dodecyl mercaptan and 0.42 part by mass of α-methylstyrene dimer in Example 1 were replaced with 0.30 part by mass of n-dodecyl mercaptan, and no α-methylstyrene dimer was used. Table 2 shows the formulation of the resin composition and the analysis and evaluation results.

[0056] <Comparative Example 3> The same procedure as in Example 1 was carried out, except that the 0.038 part by mass of n-dodecyl mercaptan and 0.42 part by mass of α-methylstyrene dimer in Example 1 were replaced with 0.54 part by mass of α-methylstyrene dimer, and no n-dodecyl mercaptan was used. Table 2 shows the formulation of the resin composition and the analysis and evaluation results.

[0057] <Comparative Example 4> The same procedures as in Example 1 were carried out, except that the 0.038 part by mass of n-dodecyl mercaptan and 0.42 part by mass of α-methylstyrene dimer in Example 1 were replaced with 0.60 part by mass of t-dodecyl mercaptan, and no α-methylstyrene dimer was used. Table 2 shows the formulation of the resin composition and the analysis and evaluation results.

[0058] <Comparative Example 5> The same procedures as in Example 1 were carried out, except that the 0.038 part by mass of n-dodecyl mercaptan and 0.42 part by mass of α-methylstyrene dimer were replaced with 0.15 part by mass of t-dodecyl mercaptan and 0.15 part by mass of α-methylstyrene dimer. Table 2 shows the formulation of the resin composition and the analysis and evaluation results.

[0059] <Comparative Example 6> The same procedures as in Example 6 were carried out, except that the 0.04 part by mass of n-dodecyl mercaptan and 0.40 part by mass of α-methylstyrene dimer in Example 6 were replaced with 0.25 part by mass of t-dodecyl mercaptan, and no α-methylstyrene dimer was used. Table 2 shows the formulation of the resin composition and the analysis and evaluation results.

[0060] <Comparative Example 7> The same procedure was carried out as in Example 1, except that the 40 parts by mass of styrene and 60 parts by mass of methyl methacrylate in Example 12 were changed to 79 parts by mass of styrene and 21 parts by mass of methyl methacrylate. Table 2 shows the formulation of the resin composition and the analysis and evaluation results.

[0061] [Table 1-1]

[0062] [Table 1-2]

[0063] [Table 2]

[0064] From the results in Table 1 (Table 1-1 to Table 1-2) and Table 2, it can be seen that the resin compositions according to the examples are excellent in safety and productivity for cosmetic and food packaging applications, injection moldability, and the hue and light resistance of molded articles, and have little odor. Furthermore, because the yellowness index before UV irradiation and the change in yellowness index before and after UV irradiation are small, they are suitable for applications in environments where UV exposure may occur. On the other hand, it can be seen that the resin compositions according to the comparative examples are inferior in one or more aspects of safety and productivity for cosmetic and food packaging applications, injection moldability, the hue and light resistance of molded articles, and odor. Furthermore, when the yellowness index before UV irradiation or the change in yellowness index before and after UV irradiation are large, they are not suitable for applications in environments where UV exposure may occur. [Industrial Applicability]

[0065] The resin composition of the present invention, which contains the copolymer P containing styrene-based monomer units and (meth)acrylic acid ester-based monomer units, is safe and productive for use in cosmetics and food packaging, has excellent injection moldability, and produces molded articles with excellent color and light resistance, and has little odor. The resin composition of the present invention can be mixed with other resins to form a resin composition, and can be suitably used as an injection-molded article for housings for home appliances or containers for food, stationery, cosmetics, etc., and has industrial applicability.

Claims

1. A resin composition comprising a copolymer including a styrene-based monomer unit and a (meth)acrylic acid ester-based monomer unit, The total content of unreacted monomers is 2000 ppm by mass or less, The sulfur content is more than 0 ppm by mass and 150 ppm by mass or less, The yellowness of a 2 mm injection-molded plate is 0.6 or less; It is characterized by the fact that The copolymer contains 50% by mass to 70% by mass of the styrene-based monomer unit relative to 100% by mass of the copolymer.

2. 2. The resin composition according to claim 1, wherein the reciprocal of the product of the total content (ppm by mass) of the unreacted monomers and the sulfur content (ppm by mass) multiplied by 100,000 (100,000 / (the total content (ppm by mass) of the unreacted monomers × the sulfur content (ppm by mass))) is 0.5 to 8.

0.

3. The resin composition according to claim 1, wherein the ratio of the total content of the unreacted monomers to the sulfur content (the total content of the unreacted monomers / the sulfur content) is 8 to 50.

4. 2. The resin composition according to claim 1, wherein the yellowness index of a 2 mm injection-molded plate is A, and the yellowness index of the plate after 360 hours of ultraviolet irradiation at an irradiation intensity of 60 W / m is B, satisfying the following relationship: B-A<0.8

5. 2. The resin composition according to claim 1, wherein the MFR value is 1 g / 10 min to 5 g / 10 min under conditions of a test temperature of 200° C. and a nominal load of 5 kg.

6. The resin composition according to claim 1, wherein 100% by mass of the copolymer contains 20% by mass to 50% by mass of (meth)acrylic acid ester monomer units.

7. 2. The resin composition according to claim 1, wherein the styrene-based monomer unit is styrene and the (meth)acrylic acid ester monomer unit is methyl methacrylate.

8. The resin composition according to claim 1, having a sulfur content of 30 ppm by mass or more.

9. the total content of the styrene-based monomer units and the (meth)acrylic acid ester-based monomer units contained in 100% by mass of the copolymer is more than 96% by mass; The resin composition according to claim 1.

10. the copolymer further comprises other copolymerizable monomer units, the content of the other copolymerizable monomer units is 0 to 10% by mass relative to 100% by mass of the total of the styrene-based monomer units, the (meth)acrylic acid ester-based monomer units, and the other copolymerizable monomer units; 2. The resin composition according to claim 1, wherein the other copolymerizable monomer unit is at least one selected from the group consisting of acrylic acid, acrylonitrile, methacrylonitrile, phenylmaleimide, and cyclohexylmaleimide.

11. The method includes a step of polymerizing a styrene-based monomer and a (meth)acrylic acid ester-based monomer, The method for producing a resin composition according to any one of claims 1 to 10, wherein in the polymerization step, a linear alkyl mercaptan chain transfer agent and an α-methylstyrene dimer chain transfer agent are used in combination.

12. The method for producing a resin composition according to claim 11, wherein the ratio of the amount of the linear alkyl mercaptan chain transfer agent added to the amount of the α-methylstyrene dimer chain transfer agent added is 0.08 to 0.

25.

13. An injection-molded article using the resin composition according to any one of claims 1 to 10.

14. A housing for a home appliance or a container for food, stationery, or cosmetics, using the injection-molded article according to claim 13.

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