Styrenic resin composition and production method of the same

Abstract

To provide a styrenic resin composition having a styrenic resin of which the molecular weight is increased while securing productivity during polymerization, and a production method of the styrenic resin composition.SOLUTION: The styrenic resin composition of the present invention includes: a styrene resin (a); alcohols having 4 to 15 carbons (b); and a solvent (c) other than the alcohols (b), a content of the alcohols (b) is 10 mass ppm or larger relative to 100 mass% of the resin composition, a ratio of the content of the alcohols (b) relative to a content of the solvent (c) (content of the alcohols (b) / content of the solvent (c)) is 0.5 or more. The production method of the styrenic resin composition of the present invention comprises a step of polymerizing the styrenic resin (a) under the condition that a content of the alcohols (b) of polymerization solution is 15 mass% or more relative to a total content 100 mass% of the alcohols (b) and the solvent (c).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a styrene-based resin composition and a method for producing the same. [Background technology]

[0002] Styrene-based resins are excellent in heat resistance, transparency, moldability, and rigidity, and are relatively inexpensive, and therefore are widely used in food container packaging materials such as boxed lunches and prepared foods, foam boards for residential insulation, television diffusion panels, etc. Generally, higher strength is required for styrene-based resins, and it is known that the higher the molecular weight of a styrene-based resin, the better its strength (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-3531 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, the molecular weight of the styrene resin can generally be controlled by adjusting the conditions during polymerization, such as the polymerization temperature, polymerization time, amount of solvent, type and amount of initiator, and type and amount of chain transfer agent. Specifically, the molecular weight of the styrene resin can be improved, for example, by lowering the polymerization temperature, reducing the amount of initiator, or extending the polymerization time. However, these methods can improve the molecular weight of the styrene resin obtained by polymerization, but the productivity of the styrene resin (for example, the amount of styrene resin obtained relative to the amount charged during polymerization (reactor polymer rate)) is reduced. Therefore, there was a problem that it was difficult to simultaneously satisfy both productivity and strength improvement by high molecular weight. In addition, the obtained styrene resin is further processed by melting, etc. for use in a desired application, but in solving the above problem, it was also essential that the molecular weight be maintained even after the processing.

[0005] Therefore, the problem to be solved by the present invention is to provide a styrene-based resin composition having a styrene-based resin with an increased molecular weight while ensuring productivity during polymerization, and to provide a method for producing a styrene-based resin composition that can obtain such a resin composition. [Means for solving the problem]

[0006] Means for Solving the Problems The present inventors have conducted intensive research in view of the above problems and have found a method for increasing the productivity during polymerization and the molecular weight of a resin in a styrene-based resin composition polymerized so as to contain a specific alcohol content and a specific content ratio of a solvent and an alcohol, thereby completing the present invention. That is, the present invention is as follows.

[0007] [1] A styrene-based resin composition comprising: (a) a styrene-based resin; (b) an alcohol having 4 to 15 carbon atoms; and (c) a solvent other than the alcohol (b), The content of the alcohol (b) is 10 ppm by mass or more relative to 100% by mass of the resin composition, A styrene-based resin composition, characterized in that the ratio of the content of the alcohols (b) to the content of the solvent (c) (content of alcohols (b) / content of solvent (c)) is 0.5 or more. [2] The styrene-based resin composition according to the above [1], wherein the content of styrene-based monomer units contained in the styrene-based resin (a) is 70% or more. [3] The styrene-based resin composition according to the above [1] or [2], wherein the content of styrene-based monomer units contained in the styrene-based resin (a) is 90 mass% or more. [4] The styrene-based resin composition according to any one of the above [1] to [3], wherein the styrene-based resin (a) is a homopolymer of a styrene-based monomer. [5] The styrene-based resin composition according to any one of the above [1] to [4], which has a melt flow rate of 0.5 to 4.5 g / 10 min. [6] The styrene-based resin composition according to any one of the above [1] to [5], which has a Vicat softening temperature of 100° C. or higher. [7] A method for producing a styrene-based resin composition according to any one of the above [1] to [6], comprising a step of polymerizing the styrene-based resin (a) under conditions in which the content of the alcohol (b) in the polymerization solution is 14 mass% or more relative to 100 mass% of the total content of the alcohol (b) and the solvent (c). Effect of the Invention

[0008] According to the present invention, it is possible to provide a styrene-based resin composition having a styrene-based resin with an increased molecular weight while ensuring productivity during polymerization, and to provide a method for producing such a resin composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention (hereinafter, referred to as "the present embodiment") will be described in detail. Note that the present invention is not limited to the following embodiment, and can be modified in various ways within the scope of the gist of the present invention.

[0010] [Styrene-based resin composition] The styrene-based resin composition in this embodiment is characterized in that it contains a styrene-based resin (a), an alcohol (b) having 4 to 15 carbon atoms, and a solvent (c) other than the alcohol (b), and the content of the alcohol (b) is 10 mass ppm or more relative to 100 mass% of the resin composition, and the ratio of the content of the alcohol (b) to the content of the solvent (c) (content of the alcohol (b) / content of the solvent (c)) is 0.5 or more. This makes it possible to obtain a styrene-based resin having a high molecular weight while ensuring productivity during polymerization. In the following, the alcohols (b) having 4 to 15 carbon atoms will also be referred to simply as alcohols (b), and the solvents (c) other than the alcohols (b) will also be referred to simply as solvents (c).

[0011] <Styrene-based resin (a)> In this embodiment, the styrene-based resin composition contains a styrene-based resin (a). The styrene-based resin (a) may be a homopolymer of a styrene-based monomer, or a copolymer of a styrene-based monomer and, if necessary, another monomer copolymerizable therewith.

[0012] The styrene-based resin (a) may be modified to rubber by polymerization in the presence of a rubber component. The rubber component is preferably a rubber-like polymer, and examples of the rubber-like polymer include polybutadiene, polyisoprene, natural rubber, polychloroprene, styrene-butadiene copolymer, and acrylonitrile-butadiene copolymer. Among them, polybutadiene or styrene-butadiene copolymer is preferable. As the polybutadiene, both high-cis polybutadiene having a high cis content and low-cis polybutadiene having a low cis content can be used. As the structure of the styrene-butadiene copolymer, both a random structure and a block structure can be used. One or more of these rubber-like polymers can be used. Also, saturated rubber obtained by hydrogenating butadiene rubber can be used. Examples of such rubber-modified styrene-based resins include HIPS (high impact polystyrene), ABS resin (acrylonitrile-butadiene-styrene copolymer), AAS resin (acrylonitrile-acrylic rubber-styrene copolymer), and AES resin (acrylonitrile-ethylene propylene rubber-styrene copolymer).

[0013] The styrene monomer is not particularly limited, but examples thereof include styrene, α-methylstyrene, paramethylstyrene, ethylstyrene, propylstyrene, butylstyrene, chlorostyrene, bromostyrene, etc. From an industrial viewpoint, styrene is particularly preferred. As the styrene monomer, these can be used alone or in combination.

[0014] The copolymer of other monomers copolymerizable with the styrene monomer is not particularly limited as long as it is copolymerizable with the styrene monomer, and examples thereof include vinyl compounds such as methacrylic acid, acrylic acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, cetyl (meth)acrylate, 2-ethyl-hexyl (meth)acrylate, and (meth)acrylonitrile, as well as dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, maleic anhydride, maleimide, and nucleus-substituted maleimide. Among these, it is preferable to contain a vinyl compound, and more preferably to contain methacrylic acid.

[0015] The content of the styrene-based monomer unit in the styrene-based resin (a) is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 97% by mass or more, when the total amount of the monomer units constituting the styrene-based resin is taken as 100% by mass. If the content is less than 70% by mass, the moldability and flowability of the resin, which are characteristics of the styrene-based resin, decrease, which is not preferable. In addition, when the styrene-based resin (a) is a copolymer of a styrene-based monomer and another monomer copolymerizable therewith, the upper limit of the content of the styrene-based monomer unit in the styrene-based resin (a) is preferably 98% by mass, more preferably 95% by mass. In addition, when the styrene-based resin (a) is a homopolymer of a styrene-based monomer such as polystyrene, the styrene-based resin (a) is preferably composed of a styrene-based monomer unit, but it is permissible that the styrene-based resin (a) contains, for example, 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less of a monomer unit other than the styrene-based monomer unit.

[0016] The content of styrene monomer units and other monomer units in the styrene resin (a) when other monomers are copolymerized is measured by subjecting the resin to a nuclear magnetic resonance measurement device ( 1It can be calculated from the integral ratio of the spectrum measured by 1 H-NMR.

[0017] In this embodiment, the weight average molecular weight (Mw) of the styrene resin (a) is preferably 100,000 to 400,000, and more preferably 130,000 to 350,000. When the weight average molecular weight is 100,000 to 400,000, a resin having an excellent balance between impact strength and fluidity can be obtained. The weight average molecular weight can be measured by gel permeation chromatography using polystyrene as the standard.

[0018] <Alcohols having 4 to 15 carbon atoms (b)> In this embodiment, the styrene-based resin composition contains an alcohol (b) having 4 to 15 carbon atoms. The alcohol (b) is an alcohol having 4 to 15 carbon atoms containing one or more hydroxyl groups, which may contain a heteroatom such as oxygen or nitrogen in the carbon chain, and may contain a bond other than a single bond, such as a double bond, a triple bond, an ester bond, or an amide bond, in the carbon chain. It is preferable that the alcohol (b) is present in the polymerization solution when the styrene resin (a) is polymerized, but alcohols having 3 or less carbon atoms have low solubility in the styrene resin (a), so that polymer precipitation occurs, making stable production difficult. In addition, alcohols having 16 or more carbon atoms tend to remain in molded products, etc., when molding using a styrene resin composition, and for example, the heat resistance temperature of the obtained molded product decreases. In addition, in order to reduce the amount of the alcohols having 16 or more carbon atoms remaining, molding at high temperatures is required, and in this case, the molecular weight of the styrene resin (a) decreases due to the high temperature. Or, during molding, etc., the alcohol generates an odor, which reduces workability.

[0019] The alcohols (b) are not particularly limited, but examples thereof include n-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-hexanol, 2-hexanol, 3-hexanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 4-methyl-1-pentanol, 2-methyl-2-pentanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 3-methyl-3-pentanol, 2,2-dimethyl-1-butanol, 2,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 3,3-dimethyl-2-butanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 4-heptanol, 1-octanol, 2-ethyl-1-hexanol, 6-methyl-1-heptanol, 7-methyl-1-hexanol, 8-methyl-1-hexanol, 9-methyl-1-hexanol, 10-methyl-1-hexanol, 11-methyl-1-hexanol, 12-methyl-1-hexanol, 13-methyl-1-hexanol, 14-methyl-1-hexanol, 15-methyl-1-hexanol, 16-methyl-1-hexanol, 17-methyl-1-hexanol, 18-methyl-1-hexanol, 19-methyl-1-hexanol, 20-methyl-1-hexanol, 21-methyl-1-hexanol, 22-methyl-1-hexanol, 23-methyl-1-hexanol, 24-methyl-1-hexanol, 25-methyl-1-hexanol, 26-methyl-1-hexanol, 27-methyl-1- nol, 2-methylheptan-2-ol, 1-nonanol, 3-methyloctan-3-ol, 1-decanol, 1-undecanol, 1-dodecanol, 1-tridecanol, 1-tridecanol, 1-tetradecanol, 1-pentadecanol, 1-methoxy-2-propanol, 2-aminoethanol, 6-amino-hexanol, 2-(methylamino)ethanol, diethanolamine, 1,3-diamino-2-propanol, 2-(ethylthio)ethanol, 2-(propylthio)ethanol, cyclohexanol, benzyl alcohol, ethylene glycol, propylene glycol, glycerin, 3-methyl-3-buten-1-ol, 3-hydroxy-3-methyl-1-butene, polyethylene glycol monoethers, and allyl alcohols.

[0020] As the alcohol (b), from the viewpoints of solubility in styrene-based resins, heat resistance, suppression of molecular weight reduction during processing, and low odor during molding, alcohols having 4 to 14 carbon atoms are preferred, and alcohols having 5 to 12 carbon atoms are particularly preferred. The boiling point of the alcohol (b) is preferably from 100° C. to 290° C., more preferably from 120° C. to 260° C., and even more preferably from 130° C. to 230° C. If the boiling point of the alcohol (b) is less than 100° C., it tends to cause resin turbidity, and if it exceeds 290° C., the amount of alcohol remaining in the resin composition increases, which may cause the heat resistance of the resin composition, a decrease in molecular weight during processing, and an odor during molding.

[0021] In this embodiment, the content of the alcohols (b) in 100% by mass of the styrene-based resin composition is 10 ppm or more, preferably 30 ppm or more, and more preferably 50 ppm or more. By making the content of the alcohols (b) in the styrene-based resin composition 10 ppm or more, it is possible to ensure productivity during polymerization of the styrene-based resin (a) in the styrene-based resin composition while improving the molecular weight of the obtained styrene-based resin (a). Specifically, when the styrene resin (a) is polymerized, the polymerization is performed so that a certain amount of alcohols (b) is present in the solvent, thereby making it possible to improve the molecular weight of the styrene resin (a) without setting conditions that would reduce productivity in resin polymerization. Usually, after the polymerization of the styrene resin (a), the polymerization solution containing the remaining monomer, alcohols (b), and the solvent (c) described below is devolatilized. By devolatilizing under normal conditions, the content of alcohols (b) becomes 10 ppm or more, and the molecular weight of the styrene resin (a) at the time of polymerization can be maintained even after the devolatilization process.

[0022] From the viewpoint of improving the molecular weight of the styrene-based resin (a) in the styrene-based resin composition, the upper limit of the content of the alcohols (b) in the styrene-based resin composition is not particularly limited. From the viewpoint of good appearance and heat resistance, however, the content of the alcohols (b) in the styrene-based resin composition is preferably 700 ppm or less, more preferably 500 ppm or less, even more preferably 300 ppm or less, and still more preferably 200 ppm or less.

[0023] In this embodiment, the ratio of the content of alcohols (b) to the content of solvent (c) described later (content of alcohols (b) / content of solvent (c)) is 0.5 or more, preferably 1.0 or more, and more preferably 3.0 or more. As described above, the content of alcohols (b) is 10 ppm or more, and the ratio of the content of alcohols (b) to the content of solvent (c) is 0.5 or more, so that the molecular weight of the styrene-based resin (a) can be increased without impairing productivity during production, and a resin composition with excellent strength can be obtained. Specifically, when polymerizing the styrene resin (a), the molecular weight of the styrene resin (a) can be improved by polymerizing the styrene resin (a) in the presence of alcohols (b) in the solvent (c), but if the polymerization solvent (total of alcohols (b) and solvent (c)) in the polymerization solution contains a large amount of solvent (c) other than alcohols (b), the effect of improving the molecular weight by alcohols (b) is reduced. However, by polymerizing the styrene resin (a) so that the ratio of the content of alcohols (b) to the content of solvent (c) in the styrene resin composition (after polymerization of the styrene resin (a)) (content of alcohols (b) / content of solvent (c)) is 0.5 or more, the effect of improving the molecular weight by alcohols (b) can be sufficiently obtained. As described above, after polymerization of the styrene-based resin (a), the polymerization solution is usually devolatilized. By devolatilizing under normal conditions, the ratio of the content of the alcohol (b) to the content of the solvent (c) in the polymerization solution is maintained even after the devolatilization step.

[0024] There are no particular limitations on the method for adding the alcohol (b) having 4 to 15 carbon atoms to the resin composition, but it is preferable to add it to the polymerization solution during polymerization of the styrene-based resin (a).

[0025] <Solvents other than alcohols (b) (c)> In this embodiment, the styrene-based resin composition contains a solvent (c) other than the alcohols (b). The solvent (c) is not particularly limited, but for example, a polymerization solvent that can be used when polymerizing a styrene-based resin can be used, and specifically, aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene, ketones such as acetone and methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and cyclohexane can be mentioned. Each of them may be used alone or in combination of two or more.

[0026] The boiling point of the solvent (c) is preferably 100° C. or more and 230° C. or less, more preferably 120° C. or more and 200° C. or less. If the boiling point is less than 100° C., this is not preferred from the viewpoint of the reactor pressure, and if the boiling point is more than 230° C., this is not preferred because it cannot be sufficiently removed in the devolatilization step, which may cause a decrease in the heat resistance of the resin composition, a decrease in molecular weight during processing, and odor, etc. In addition, other organic solvents, such as alcohols and polyoxyethylene derivatives, can be mixed within a range that does not impair the solubility of the polymerization product.

[0027] In the present embodiment, the content of the solvent (c) in 100% by mass of the styrene-based resin composition is preferably 5 to 500 ppm, more preferably 10 to 300 ppm, and further preferably 10 to 200 ppm. By being in this range, appropriate polymerization during the production of the styrene-based resin (a) can be facilitated, and the deterioration of the heat resistance of the resin composition, the decrease in molecular weight during processing, the cause of odor, etc. can be prevented.

[0028] <Other ingredients> The styrene-based resin composition of the present embodiment may also contain various additives that are generally used in styrene-based resins in order to achieve known effects. Examples of such additives include stabilizers, antioxidants, ultraviolet absorbers, lubricants, release agents, plasticizers, antiblocking agents, antistatic agents, antifogging agents, and mineral oils. Reinforcing materials such as styrene-butadiene block copolymers and MBS resins may also be added to the extent that they do not impair the physical properties. There are no particular restrictions on the method of blending, but examples include a method in which the additives are added during polymerization and polymerized, and a method in which the additives are mixed in advance in a blender before melt-kneading after polymerization, and then melt-kneaded in an extruder, Banbury mixer, or the like.

[0029] In this embodiment, various additives can be added to the styrene-based resin composition as described above. The content of the styrene-based resin (a) in the styrene-based resin composition is not particularly limited, but is preferably 95 mass% or more, more preferably 97 mass% or more, and even more preferably 99 mass% or more.

[0030] In the present embodiment, alcohols other than the above alcohols (c) can also be added to the styrene-based resin composition as long as the effects of the present invention are not impaired.

[0031] <Physical properties of styrene-based resin composition> In this embodiment, the Vicat softening temperature of the styrene-based resin composition is preferably 100° C. or higher. By setting the Vicat softening temperature in this range, the composition can be suitably used as a food packaging material that comes into contact with hot water. The Vicat softening temperature can be measured in accordance with ISO306 under conditions of a load of 50 N and a heating rate of 50° C. / h.

[0032] In this embodiment, the melt flow rate of the styrene resin composition is preferably in the range of 0.5 to 4.5 g / 10 min, more preferably 1.0 to 3.5 g / 10 min, and further preferably 1.5 to 2.5 g / 10 min. By making the melt flow rate 0.5 g / 10 min or more, the composition can be discharged well from the reactor, and by making it 4.5 g / 10 min or less, a styrene resin composition with excellent strength can be obtained.

[0033] In this embodiment, the content of the monomer constituting the styrene resin (a) present in the styrene resin composition is preferably 1000 ppm or less, more preferably 800 ppm or less, and even more preferably 600 ppm or less, when the styrene resin composition is 100% by mass. By making the total amount of monomers including the styrene monomer 1000 ppm or less, the odor around the die outlet during sheet extrusion using the styrene resin composition of this embodiment is improved. The color tone of the resin is also improved. The remaining amount of each monomer constituting the styrene resin (a) can be measured by gas chromatography.

[0034] <Method of producing styrene-based resin composition> The styrene-based resin composition of the present embodiment can be obtained through the production (polymerization) of a styrene-based resin (a). The polymerization method for the styrene-based resin (a) is not particularly limited, but for example, a radical polymerization method, among which a bulk polymerization method or a solution polymerization method can be preferably used. Specifically, the polymerization method mainly includes a polymerization step of polymerizing polymerization raw materials (monomer components) and a devolatilization step of removing volatile matters such as unreacted monomers, polymerization solvent (including alcohols (b) and solvent (c)) from the polymerization product. The polymerization method according to this embodiment will be described below.

[0035] In this embodiment, when the polymerization raw material is polymerized to obtain the styrene-based resin (a), a polymerization initiator is typically contained in the polymerization raw material composition. Examples of the polymerization initiator include organic peroxides, such as peroxyketals such as 2,2-bis(t-butylperoxy)butane, 1,1-bis(t-butylperoxy)cyclohexane, and n-butyl-4,4-bis(t-butylperoxy)valerate, dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, and dicumyl peroxide, diacyl peroxides such as acetyl peroxide and isobutyryl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxyesters such as t-butylperoxyacetate, ketone peroxides such as acetylacetone peroxide, and hydroperoxides such as t-butyl hydroperoxide. From the viewpoint of decomposition rate and polymerization rate, 1,1-bis(t-butylperoxy)cyclohexane is particularly preferred.

[0036] When polymerizing the styrene resin (a), a chain transfer agent may be used as necessary. Examples of the chain transfer agent include α-methylstyrene linear dimer, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-octyl mercaptan.

[0037] During polymerization of the styrene resin (a), styrene dimers and trimers may be produced. The amount of styrene dimers and trimers produced varies depending on the method of polymerization initiation, that is, between using an organic peroxide or an azo-based polymerization initiator as a polymerization initiator, or between thermal initiation alone. The amount of styrene dimers and trimers produced is the smallest when an organic peroxide is used, and the largest when thermal initiation alone is used. Styrene dimers and trimers may cause problems such as adhesion of eye mucus to the die outlet during extrusion in an extruder, or adhesion of eye mucus to a mold during injection molding. Therefore, the use of an organic peroxide is the most preferable polymerization initiation method. The total amount of styrene dimers and trimers in 100% by mass of the styrene resin composition is preferably as small as possible, more preferably 0.7% by mass or less, and even more preferably 0.6% by mass or less. Examples of the styrene dimer and trimer include 1,3-diphenylpropane, 2,4-diphenyl-1-butene, 1,2-diphenylcyclobutane, 1-phenyltetralin, 2,4,6-triphenyl-1-hexene, and 1-phenyl-4-(1'-phenylethyl)tetralin.

[0038] The polymerization method may be solution polymerization using a polymerization solvent, such as the above-mentioned alcohols (b) and solvent (c). In this embodiment, the polymerization solvent (including the above-mentioned alcohols (b) and solvent (c)) is preferably used in the range of 3 to 25 parts by mass, more preferably 5 to 20 parts by mass, relative to 100 parts by mass of all monomers constituting the styrene-based resin (a). If the polymerization solvent exceeds 25 parts by mass relative to 100 parts by mass of all monomers, the polymerization rate tends to decrease and the mechanical strength of the obtained resin tends to decrease. If the amount is less than 3 parts by mass, it may be difficult to control the heat removal during polymerization. Adding the polymerization solvent in a ratio of 3 to 25 parts by mass relative to 100 parts by mass of all monomers is preferable in terms of making the quality uniform and controlling the polymerization temperature.

[0039] In this embodiment, when polymerizing the styrene-based resin (a), the content of the alcohol (b) relative to the total content of the alcohol (b) and the solvent (c) (100% by mass) is preferably polymerized under the following conditions. That is, the content of the alcohol (b) relative to the total content of the alcohol (b) and the solvent (c) (100% by mass) is preferably 14% by mass or more, more preferably 17% by mass or more, even more preferably 20% by mass or more, and particularly preferably 25% by mass or more. If the content of the alcohol (b) relative to the total content of the alcohol (b) and the solvent (c) is 14% by mass or more, a molecular weight increase effect can be obtained during polymerization, and a styrene-based resin with excellent strength can be obtained.

[0040] In this embodiment, the polymerization solution in which the devolatilization step is carried out after the polymerization step is preferably one in which the content of alcohols (b) in the solution components excluding the polymer component (including alcohols (b), solvent (c), unreacted monomers, etc.) is 5% by mass or more. By carrying out polymerization to obtain such a content, it is possible to obtain a more effective molecular weight increase during polymerization, and a styrene-based resin with excellent strength can be obtained.

[0041] In this embodiment, the apparatus used in the polymerization step for obtaining the styrene-based resin (a) is not particularly limited and may be appropriately selected according to the polymerization method of the styrene-based resin (a). For example, in the case of bulk polymerization, a polymerization apparatus having one or more completely mixed reactors connected together may be used.

[0042] In this embodiment, there is no particular restriction on the devolatilization step following the polymerization step of polymerizing the styrene-based resin (a). When the polymerization step is carried out by bulk polymerization, the polymerization step is carried out until the final amount of unreacted monomer is preferably 50% by mass or less, more preferably 40% by mass or less, and then, in the devolatilization step, devolatilization is carried out by a known method to remove volatile matters such as unreacted monomer. For example, a normal devolatilization device such as a flash drum, a twin-screw devolatilizer, a thin film evaporator, or an extruder can be used, but a devolatilization device with a small retention portion is preferred. The temperature of the devolatilization treatment is usually about 150 to 280°C, preferably 160 to 260°C, and more preferably 160 to 240°C. By setting the devolatilization temperature at 150°C or higher, unreacted styrene monomer can be efficiently removed, and by setting the devolatilization temperature at 280°C or lower, the molecular weight reduction due to thermal decomposition of the styrene-based resin (a) can be suppressed. The pressure of the devolatilization treatment is usually about 0.13 to 4.0 kPa, preferably 0.13 to 3.0 kPa, and more preferably 0.13 to 2.0 kPa. The residence time in the devolatilization step is usually less than 2.0 hours, preferably less than 1.5 hours, and more preferably less than 1.2 hours. By making the residence time in the devolatilization step less than 2.0 hours, the decomposition of the styrene-based resin (a) progresses, and it is possible to prevent a decrease in molecular weight and an increase in the monomer content of the composition. As a devolatilization method, for example, a method of removing volatile matters by reducing pressure under heating, and a method of removing volatile matters through an extruder or the like designed for the purpose of removing volatile matters are desirable. EXAMPLES

[0043] The present invention will now be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The methods for analyzing and evaluating the resins and extruded sheets in the examples and comparative examples are as follows.

[0044] (1) Measurement of the content of styrene monomer units and other monomer units in styrene resins The content of styrene monomer units and other monomer units in styrene resins was measured by nuclear magnetic resonance ( 1The amount was quantified from the integral ratio of the spectrum measured by a 1 H-NMR device. Sample preparation: 75 mg of resin was dissolved in 0.75 mL of d1-chloroform. Measuring equipment: JEOL JNM ECA-500 Measurement conditions: Measurement temperature 60℃, observation nucleus 1 H, 32 times, 45 seconds

[0045] (2) Measurement of weight average molecular weight The weight average molecular weight (Mw) of the styrene-based resin was measured by gel permeation chromatography (GPC) under the following conditions. Equipment: Tosoh HLC-8220 Separation column: Two Tosoh TSK gel Super HZM-H (inner diameter 4.6 mm) connected in series Guard column: Tosoh TSK guard column Super HZ-H Measurement solvent: tetrahydrofuran (THF) Sample concentration: 5 mg of the measurement sample was dissolved in 10 mL of solvent and filtered through a 0.45 μm filter. Injection volume: 10μL Measurement temperature: 40℃ Flow rate: 0.35mL / min Detector: Ultraviolet absorption detector (Tosoh UV-8020, wavelength 254 nm) The calibration curve was created using 11 types of TSK standard polystyrene (F-850, F-450, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000) manufactured by Tosoh Corporation. The calibration curve was created using a linear approximation equation.

[0046] (3) Melt mass flow rate (MFR) measurement The melt mass flow rate (g / 10 min) of the styrene-based resin composition was measured under conditions of 200° C. and a load of 49 N in accordance with ISO1133.

[0047] (4) Measurement of Vicat softening temperature The Vicat softening temperature of the styrene-based resin composition was measured in accordance with ISO 306. The load was 50 N and the heating rate was 50° C. / h.

[0048] (5) Measurement of styrene monomer, alcohol and solvent content The contents of the styrene-based monomer, alcohols and solvent were measured by gas chromatography, assuming the mass of the styrene-based resin composition to be 100% by mass. Sample preparation: 2.0 g of resin was dissolved in 20 mL of methyl ethyl ketone, and then 5 mL of methanol containing a standard substance (triphenylmethane) was added to reprecipitate the polymer components. The supernatant was collected and used as the measurement solution. Measurement conditions Equipment: Agilent 6850 Series GC system Detector: FID Column: HP-1 (100% dimethylpolysiloxane) 30m, Film thickness: 0.25μm, 0.32mmφ Injection volume: 1 μL (splitless) Column temperature: 40°C for 2 minutes → Raise to 320°C at 20°C / min → Hold at 320℃ for 15 minutes Inlet temperature: 250℃ Detector temperature: 280℃ Carrier gas: Helium

[0049] (6) Odor assessment at the die exit When a styrene-based resin composition was used for sheet extrusion using a 30 mmφ short-screw sheet extruder, the odor at the die outlet was confirmed and rated according to the following evaluation criteria. 〇: Almost no smell ×: Smell was felt

[0050] (7) Calculation of polymer productivity The polymer productivity during the production of the styrene-based resin was determined by calculating the amount of polymer produced per unit time using the following formula. {Reactor polymer rate (mass%)} × {Reaction liquid supply rate (kg / h)} = {Polymer productivity (kg / h)} The reactor polymerization rate was calculated by weighing the mass of the polymer liquid directly discharged from the reactor during the polymerization reaction, drying the polymer liquid for 15 minutes under a reduced pressure of 2.0 kPa or less in a vacuum dryer heated to 230°C, and then weighing the mass of the polymer liquid using the following formula. [{After drying under reduced pressure (g)} / {Before drying under reduced pressure (g)}] x 100 = {Reactor polymer rate (mass%)}

[0051] Examples and comparative examples will be described below. [Example 1] A polymerization raw material composition liquid consisting of 85.5 parts by mass of styrene, 10.5 parts by mass of ethylbenzene, 4.0 parts by mass of 2-ethyl-1-hexanol, and 0.025 parts by mass of 1,1-di(t-butylperoxy)cyclohexane (PHC, manufactured by NOF Corp., trade name: Perhexa (registered trademark) C) was continuously fed at a rate of 0.72 kg / hour to a complete mixing type reactor having a capacity of 3.6 liters, and further to a two-stage volatilization apparatus connected to a volatilization tank (170 ° C, 1.5 kPa) having a heat exchanger and a single screw extruder (230 ° C, 1.5 kPa) in order to remove volatile matters such as unreacted monomers and polymerization solvents. The polymerization temperature of the complete mixing reactor was set to 142 ° C. The volatilized unreacted gas was condensed in a condenser through which a refrigerant of -5 ° C was passed, and was recovered as an unreacted liquid, and the polymer content was recovered as resin pellets. The polymer content in the polymerization solution discharged from the reactor was 65.8% by mass, as measured by (mass of sample after drying / mass of sample before drying×100%) after drying the polymerization solution at 230° C. under reduced pressure of 0.3 kPa for 15 minutes. The physical properties obtained by the above-mentioned analytical methods are shown in Table 1.

[0052] [Examples 2 to 13] In Examples 2 to 13, styrene-based resin compositions were prepared in the same manner as in Example 1, except that the conditions were changed as shown in Table 1.

[0053] [Comparative Examples 1 to 4, 8 to 9] Styrene-based resin compositions were prepared in the same manner as in Example 1, except that the conditions were changed as shown in Table 2. In Comparative Examples 1 to 4 and 7 to 8, the effect of increasing the molecular weight was not obtained because the alcohol (b) was not contained in the composition.

[0054] [Comparative Example 5] An attempt was made to prepare a styrene-based resin composition under the same conditions as in Example 1, except that the conditions were changed as shown in Table 2. In Comparative Example 5, as compared with Example 4, the alcohol used was changed from 2-ethylhexanol to 2-propanol (C3), which resulted in poor solubility in the polymerization product and precipitation, making it impossible to obtain a styrene-based resin.

[0055] [Comparative Example 6] A styrene-based resin composition was prepared under the same conditions as in Example 1, except that the conditions were changed as shown in Table 2. In Comparative Example 6, the alcohol used was changed from 2-ethylhexanol to isostearyl alcohol (C18), as compared with Example 4, and the Vicat softening temperature was inferior to that of Comparative Example 4. Furthermore, in the examples and comparative examples other than Comparative Example 6, the odor evaluation showed that almost no odor was detected (evaluation result: ○), whereas in Comparative Example 6, the amount of remaining volatile components including alcohol was large, and the result was also inferior in terms of odor (evaluation result: ×).

[0056] [Comparative Example 7] When the residence time for devolatilization was extended to reduce the residual alcohol under the conditions of Comparative Example 6, the thermal decomposition of the styrene-based resin proceeded, and the effect of increasing the molecular weight by the alcohol was not obtained.

[0057] [Comparative Example 10] A styrene-based resin composition was prepared under the same conditions as in Example 1, except that the conditions were changed as shown in Table 2. In Comparative Example 10, the ratio of the content of alcohols (b) / the content of solvent (c) was low compared to Example 2, and a sufficient molecular weight increasing effect could not be confirmed.

[0058] [Comparative Example 11] As shown in Table 2, a styrene-based resin composition was prepared by changing the temperature conditions of Comparative Example 2 so as to obtain a weight average molecular weight equivalent to that of Example 4. In Comparative Example 10, a styrene-based resin composition having a molecular weight similar to that of Example 4 was obtained, but the productivity was lower than that of Example 4.

[0059] [Comparative Examples 12 and 13] A styrene-based resin composition was prepared under the same conditions as in Example 1, except that the conditions were changed as shown in Table 2. In Comparative Example 12, the ratio of the content of alcohols (b) / the content of solvent (c) was low compared to Comparative Example 11, and a sufficient molecular weight increasing effect could not be confirmed.

[0060] [Table 1]

[0061] [Table 2] [Industrial Applicability]

[0062] The styrene resin composition obtained by the present invention has excellent strength without impairing productivity and heat resistance. Therefore, the styrene resin composition of the present invention can be widely used in non-foamed sheets and foamed sheets by extrusion molding, food packaging containers using them, and molded products by injection molding (electrical product parts, toys, daily necessities, various industrial parts), and plays a major role in the industrial world.

Claims

1. A styrene-based resin composition comprising: (a) a styrene-based resin having a content of 80% by mass or more and 95% by mass or less of styrene-based monomer units; (b) an alcohol having 4 to 12 carbon atoms; and (c) a solvent other than the alcohol (b), The solvent (c) is an aromatic hydrocarbon having a boiling point of 100° C. or more and 230° C. or less, The content of the alcohol (b) is 10 ppm by mass or more based on 100% by mass of the resin composition, The content of the solvent (c) is 5 to 500 ppm by mass relative to 100% by mass of the resin composition; a ratio of the content of the alcohols (b) to the content of the solvent (c) (content of the alcohols (b) / content of the solvent (c)) is 0.5 or more; The content of monomers including styrene monomer constituting the styrene-based resin (a) is 800 ppm by mass or less, The melt flow rate measured in accordance with ISO 1133 is 1.5 to 4.5 g / 10 min. The styrene-based resin composition contains 0.1 to 10 parts by weight of organic crosslinked particles (B) having a weight average particle diameter of 1.0 to 10 μm. A styrene-based resin composition comprising:

2. A styrene-based resin composition as described in claim 1, wherein the content of styrene-based monomer units contained in the styrene-based resin (a) is 90 mass% or more.

3. The styrene-based resin composition according to claim 1 or 2, wherein the styrene-based resin (a) is a homopolymer of a styrene-based monomer, a rubber-modified styrene-based resin, or a copolymer of a styrene-based monomer and another copolymerizable monomer, and the copolymer of the other copolymerizable monomer is any one of methacrylic acid, acrylic acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, cetyl (meth)acrylate, 2-ethyl-hexyl (meth)acrylate, (meth)acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, maleic anhydride, maleimide, and nucleus-substituted maleimide.

4. A styrene-based resin composition described in any one of claims 1 to 3, having a weight average molecular weight of 213,000 or more and 400,000 or less.

5. A styrene-based resin composition described in any one of claims 1 to 4, having a Vicat softening temperature of 100°C or higher.

6. A polymerization step of polymerizing the styrene-based resin (a) under conditions in which the content of the alcohols (b) in the polymerization solution is 14 mass% or more relative to the total content of the alcohols (b) and the solvent (c), which is 100 mass%; a devolatilization step of removing volatile matters such as unreacted monomers and the polymerization solvent (containing the alcohols (b) and the solvent (c)) from the polymerization product obtained by the polymerization step; The method for producing a styrene-based resin composition according to any one of claims 1 to 5, comprising: