Styrene resin composition and process for producing the same

Abstract

An object of the present invention is to provide a styrene-based resin composition containing a styrene-based resin having an increased molecular weight while ensuring productivity during polymerization, and a method for producing the same.SOLUTION: The styrene resin composition of the present invention contains a styrene resin (a), an alcohol (b) having 4 to 15 carbon atoms, and a solvent (c) other than the alcohol (b), wherein the content of the alcohol (b) is 10 ppm by mass or more with respect to 100% by mass of the resin composition, and the ratio of the content of the alcohol (b) to the content of the solvent (c) (content of alcohol (b) / content of solvent (c)) is 0.5 or more. The method for producing a styrene resin composition of the present invention includes a step of polymerizing the styrene resin (a) under the condition that the content of the alcohol (b) in the polymerization solution is 15% by mass or more with respect to 100% by mass of the total content of the alcohol (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 have excellent heat resistance, transparency, moldability, and rigidity, and are relatively inexpensive, and are therefore widely used in food container and packaging materials for boxed lunches, prepared meals, and other foods, foam boards for residential insulation, diffusion plates for televisions, etc. Generally, higher strength is required of 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] Japanese Patent Application Laid-Open No. 2002-3531 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, the molecular weight of a styrene-based resin can generally be controlled during polymerization by adjusting conditions such as 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 a styrene-based resin can be improved by, for example, lowering the polymerization temperature, reducing the amount of initiator added, or extending the polymerization time. However, while these methods can improve the molecular weight of the styrene-based resin obtained by polymerization, they also reduce the productivity of the styrene-based resin (e.g., the amount of styrene-based resin obtained relative to the amount charged during polymerization (reactor polymer ratio)). Therefore, there is a problem in that it is difficult to simultaneously achieve both productivity and strength improvement through high molecular weight. Furthermore, the obtained styrene-based resin is further processed, such as by melting, for use in desired applications. To solve the above problem, it is also important to maintain the molecular weight even after such 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] The present inventors have conducted extensive research in light of the above problems and have found a method for improving the productivity during polymerization and the molecular weight of a resin in a styrene-based resin composition that is polymerized so as to contain a specific alcohol content and a specific solvent and alcohol content ratio, thereby completing the present invention. That is, the present invention is as follows.

[0007] [1] A styrene-based resin composition comprising a styrene-based resin (a), an alcohol (b) having 4 to 15 carbon atoms, and a solvent (c) 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 [1] above, wherein the styrene-based resin (a) contains 70% or more of a styrene-based monomer unit. [3] The styrene-based resin composition according to [1] or [2] above, 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 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 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 items [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). [Effects 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 INVENTION

[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 various modifications can be made within the scope of the gist of the present invention.

[0010] [Styrene-based resin composition] The styrene-based resin composition in this embodiment comprises a styrene-based resin (a), an alcohol (b) having 4 to 15 carbon atoms, and a solvent (c) other than the alcohol (b), wherein the content of the alcohol (b) is 10 ppm by mass or more relative to 100% by 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 allows a styrene-based resin with a high molecular weight to be obtained while ensuring productivity during polymerization. Hereinafter, 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 polymerized in the presence of a rubber component to be rubber-modified. The rubber component is preferably a rubbery polymer, and examples of the rubbery polymer include polybutadiene, polyisoprene, natural rubber, polychloroprene, styrene-butadiene copolymer, and acrylonitrile-butadiene copolymer. Among these, polybutadiene or styrene-butadiene copolymer is preferred. Both high-cis polybutadiene with a high cis content and low-cis polybutadiene with a low cis content can be used as the polybutadiene. The styrene-butadiene copolymer may have either a random structure or a block structure. One or more of these rubbery polymers can be used. Saturated rubber obtained by hydrogenating butadiene rubber can also 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-based monomer is not particularly limited, but examples thereof include styrene, α-methylstyrene, paramethylstyrene, ethylstyrene, propylstyrene, butylstyrene, chlorostyrene, bromostyrene, etc. Styrene is particularly preferred from an industrial viewpoint. These styrene-based monomers can be used alone or in combination.

[0014] The copolymer of another monomer copolymerizable with a styrene-based monomer is not particularly limited as long as it is copolymerizable with a styrene-based 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-ethylhexyl (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-based compound, and more preferably to contain methacrylic acid.

[0015] The content of styrene-based monomer units 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 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 undesirable. When the styrene resin (a) is a copolymer of a styrene monomer and another monomer copolymerizable therewith, the upper limit of the content of styrene monomer units in the styrene resin (a) is preferably 98% by mass, more preferably 95% by mass. When the styrene resin (a) is a homopolymer of a styrene monomer such as polystyrene, the styrene resin (a) preferably consists of styrene monomer units, but it is acceptable for the styrene resin (a) to contain, for example, 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less of monomer units other than the styrene monomer units.

[0016] The content of styrene-based monomer units and other monomer units in the styrene-based resin (a) when other monomers are copolymerized is measured by subjecting the resin to a nuclear magnetic resonance measurement apparatus ( 1It can be calculated from the integral ratio of the spectrum measured by 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 in terms of polystyrene 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 and containing one or more hydroxyl groups, and may contain heteroatoms such as oxygen or nitrogen in the carbon chain, and may contain bonds other than single bonds, such as double bonds, triple bonds, ester bonds, or amide bonds in the carbon chain. It is preferable that alcohols (b) be present in the polymerization solution when polymerizing the styrene-based resin (a). However, alcohols having 3 or fewer carbon atoms have low solubility in the styrene-based resin (a), causing polymer precipitation and making stable production difficult. Furthermore, alcohols having 16 or more carbon atoms tend to remain in molded articles, etc., when molding a styrene-based resin composition, resulting in a decrease in the heat resistance temperature of the resulting molded article. Furthermore, to reduce the amount of residual alcohols having 16 or more carbon atoms, molding must be performed at high temperatures, which reduces the molecular weight of the styrene-based resin (a). Furthermore, the alcohols produce an odor during molding, etc., reducing workability.

[0019] The alcohols (b) are not particularly limited, and 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, 6-methyl-1-pent ... alcohol, 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, allyl alcohols, and the like.

[0020] As the alcohol (b), alcohols having 4 to 14 carbon atoms are preferred, and alcohols having 5 to 12 carbon atoms are particularly preferred, from the viewpoints of solubility in styrene-based resins, heat resistance, suppression of molecular weight reduction during processing, and low odor during molding. 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 cloudiness, while 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 to decrease, the molecular weight to decrease 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 resulting styrene-based resin (a). Specifically, when polymerizing the styrene-based resin (a), by polymerizing the styrene-based resin (a) so that a certain amount of alcohols (b) is present in the solvent, the molecular weight of the styrene-based resin (a) can be improved without conditions that would reduce productivity in resin polymerization. Usually, after polymerizing the styrene-based resin (a), the polymerization solution containing the remaining monomer, alcohols (b), and a solvent (c) described below is devolatilized. Devolatilization under normal conditions ensures that the content of alcohols (b) is 10 ppm or more, and the molecular weight of the styrene-based resin (a) at the time of polymerization can be maintained even after the devolatilization step.

[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. However, from the viewpoint of good appearance and heat resistance, 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 below (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, when 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, 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 a styrene-based resin (a), the molecular weight of the styrene-based resin (a) can be improved by polymerizing the styrene-based resin (a) in the presence of alcohols (b) in a solvent (c). However, if the polymerization solvent (total of alcohols (b) and solvent (c)) in the polymerization solution contains a large amount of solvents (c) other than alcohols (b), the effect of improving the molecular weight by alcohols (b) is reduced. However, by polymerizing the styrene-based resin (a) so that the ratio of the content of alcohols (b) to the content of solvent (c) in the styrene-based resin composition (after polymerization of the styrene-based 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 fully obtained. As described above, after polymerizing 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 alcohols (b) having 4 to 15 carbon atoms to the resin composition, but it is preferable to add them to the polymerization solution during polymerization of the styrene-based resin (a).

[0025] <Solvents (c) other than alcohols (b)> 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 may be, for example, a polymerization solvent that can be used when polymerizing a styrene-based resin. Specific examples include 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. Each of these may be used alone or in combination of two or more.

[0026] The boiling point of solvent (c) is preferably 100° C. or higher and 230° C. or lower, more preferably 120° C. or higher and 200° C. or lower. A boiling point lower than 100° C. is undesirable from the viewpoint of reactor pressure, while a boiling point higher than 230° C. is undesirable because it cannot be sufficiently removed in the devolatilization step, which may result in a decrease in the heat resistance of the resin composition, a decrease in molecular weight during processing, and odor. Furthermore, other organic solvents, such as alcohols or polyoxyethylene derivatives, can be mixed in as long as the solubility of the polymerization product is not impaired.

[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 even more preferably 10 to 200 ppm. By being in this range, appropriate polymerization can be facilitated during the production of the styrene-based resin (a), and the resin composition can be prevented from being reduced in heat resistance, reduced in molecular weight during processing, or causing odor, etc.

[0028] <Other ingredients> Various additives commonly used in styrene-based resins can also be added to the styrene-based resin composition of this embodiment to achieve known effects. Examples include stabilizers, antioxidants, UV absorbers, lubricants, release agents, plasticizers, antiblocking agents, antistatic agents, antifogging agents, and mineral oil. Reinforcing materials such as styrene-butadiene block copolymers and MBS resins may also be added to the extent that they do not impair physical properties. While there are no particular restrictions on the blending method, examples include a method in which the additives are added during polymerization, or a method in which the additives are mixed in a blender after polymerization and before melt-kneading, followed by melt-kneading in an extruder or Banbury mixer.

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

[0030] In this 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 also 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 ISO 306 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-based 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 even more preferably 1.5 to 2.5 g / 10 min. By setting the melt flow rate to 0.5 g / 10 min or more, the composition can be easily discharged from the reactor, and by setting it to 4.5 g / 10 min or less, a styrene-based resin composition with excellent strength can be obtained.

[0033] In this embodiment, the content of the monomers constituting the styrene-based resin (a) present in the styrene-based resin composition is preferably 1000 ppm or less, more preferably 800 ppm or less, and even more preferably 600 ppm or less, based on 100% by mass of the styrene-based resin composition. By keeping the total amount of monomers including the styrene monomer at 1000 ppm or less, the odor around the die outlet during sheet extrusion using the styrene-based 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-based 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 comprises a polymerization step of polymerizing polymerization raw materials (monomer components) and a devolatilization step of removing volatile components such as unreacted monomers and polymerization solvents (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 materials are 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-butyl peroxyacetate; ketone peroxides such as acetylacetone peroxide; and hydroperoxides such as t-butyl hydroperoxide. From the viewpoints of decomposition rate and polymerization rate, 1,1-bis(t-butylperoxy)cyclohexane is particularly preferred.

[0036] During polymerization of the styrene-based resin (a), a chain transfer agent may be used as needed. 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-based resin (a), styrene dimers and trimers may be produced. The amount of styrene dimers and trimers produced varies depending on the polymerization initiation method, i.e., whether an organic peroxide or an azo-based polymerization initiator is used as the polymerization initiator, or whether thermal initiation alone is used. The amount of styrene dimers and trimers produced is lowest when an organic peroxide is used and highest when thermal initiation alone is used. Styrene dimers and trimers can cause problems such as adhesion of eye discharge to the die outlet during extrusion in an extruder or to the mold during injection molding. Therefore, the use of an organic peroxide is the most preferred polymerization initiation method. The total amount of styrene dimers and trimers in 100% by mass of the styrene-based resin composition is preferably as low as possible, more preferably 0.7% by mass or less, and even more preferably 0.6% by mass or less. Examples of the dimer and trimer of styrene 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 alcohols (b) and solvent (c) described above. 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, per 100 parts by mass of all monomers constituting the styrene-based resin (a). If the amount of polymerization solvent exceeds 25 parts by mass per 100 parts by mass of all monomers, the polymerization rate tends to decrease and the mechanical strength of the resulting resin tends to decrease. If the amount is less than 3 parts by mass, it may become difficult to control heat removal during polymerization. Adding the solvent in a ratio of 3 to 25 parts by mass per 100 parts by mass of all monomers is preferred in terms of facilitating uniform quality and controlling the polymerization temperature.

[0039] Furthermore, in this embodiment, when polymerizing the styrene-based resin (a), it is preferable to polymerize under the following conditions, with respect to the content of the alcohols (b) relative to the total content of the alcohols (b) and the solvent (c) (100% by mass): That is, the content of the alcohols (b) relative to the total content of the alcohols (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 alcohols (b) relative to the total content of the alcohols (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 content of alcohols (b) in the solution components (including alcohols (b), solvent (c), unreacted monomers, etc.) excluding the polymer component when the devolatilization step is carried out after the polymerization step is preferably 5% by mass or more. By carrying out polymerization so as to achieve such a content, the molecular weight can be further increased 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 complete mixing type reactor or a plurality of connected reactors can be used.

[0042] In this embodiment, there are no particular limitations on the devolatilization step that follows the polymerization step of polymerizing the styrene-based resin (a). When the polymerization step is carried out by bulk polymerization, the polymerization step is continued until the final unreacted monomer content is preferably 50% by mass or less, more preferably 40% by mass or less. Then, in the devolatilization step, devolatilization treatment is carried out by a known method to remove volatile components such as unreacted monomer. For example, a conventional 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 area is preferred. The devolatilization temperature is usually about 150 to 280°C, preferably 160 to 260°C, and more preferably 160 to 240°C. By setting the devolatilization temperature to 150°C or higher, unreacted styrene monomer can be efficiently removed, and by setting it to 280°C or lower, reduction in molecular weight due to thermal decomposition of the styrene-based resin (a) can be suppressed. The pressure in the devolatilization treatment is usually about 0.13 to 4.0 kPa, preferably 0.13 to 3.0 kPa, and more preferably 0.13 to 2.0 kPa. 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 setting the residence time in the devolatilization step to less than 2.0 hours, it is possible to prevent the decomposition of the styrene-based resin (a) from progressing, resulting in a decrease in molecular weight and an increase in the monomer content of the composition. Desirable devolatilization methods include, for example, a method in which volatile components are removed by reducing the pressure under heating, and a method in which volatile components are removed through an extruder or the like designed for the purpose of devolatilization. [Example]

[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 resins and extruded sheets in the examples and comparative examples were analyzed and evaluated as follows.

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

[0045] (2) Measurement of weight-average molecular weight The weight average molecular weight (Mw) of the styrene-based resin was measured using gel permeation chromatography (GPC) under the following conditions. Equipment: Tosoh HLC-8220 Separation column: Two TSK gel Super HZM-H (inner diameter 4.6 mm) manufactured by Tosoh Corporation 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 in accordance with ISO1133 under conditions of 200°C and a load of 49N.

[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 when the mass of the styrene-based resin composition was taken as 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 component. 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) 30 m, Film thickness: 0.25 μm, 0.32 mm diameter 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 determination at the die exit When a styrene resin composition was used to extrude a sheet using a 30 mmφ short-screw sheet extruder, the odor at the die outlet was checked and rated according to the following evaluation criteria. 〇: Almost no smell ×: Smelled

[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 solution directly removed from the reactor during the polymerization reaction, drying it under reduced pressure of 2.0 kPa or less for 15 minutes in a vacuum dryer heated to 230°C, and then weighing the mass thereof 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 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, NOF Corporation, trade name: Perhexa® C) was continuously fed at a rate of 0.72 kg / h into a 3.6-liter complete mixing reactor. Furthermore, to remove volatile components such as unreacted monomers and polymerization solvent, the liquid was continuously fed sequentially into a two-stage devolatilization apparatus consisting of a devolatilization tank (170°C, 1.5 kPa) equipped with a heat exchanger and a single-screw extruder (230°C, 1.5 kPa). The polymerization temperature in the complete mixing reactor was 142°C. The devolatilized unreacted gas was condensed in a condenser using a -5°C refrigerant and recovered as an unreacted liquid, and the polymer was recovered as resin pellets. The polymer content in the polymerization solution discharged from the reactor was measured by (sample mass after drying / sample mass before drying x 100%) after drying the polymerization solution at 230°C under reduced pressure of 0.3 kPa for 15 minutes, and was found to be 65.8 mass%. 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] Styrenic 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 produce 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, compared to Example 4, the alcohol used was changed from 2-ethylhexanol to 2-propanol (C3), but the solubility of the polymerization product was poor, resulting in precipitation, and a styrene-based resin could not be obtained.

[0055] Comparative Example 6 A styrene-based resin composition was prepared under the same conditions as in Example 1, except for the changes shown in Table 2. In Comparative Example 6, the alcohol used was changed from 2-ethylhexanol to isostearyl alcohol (C18), resulting in an inferior Vicat softening temperature compared to 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, resulting in an inferior result in terms of odor as well (evaluation result: ×).

[0056] Comparative Example 7 When the residence time for devolatilization was extended under the conditions of Comparative Example 6 to reduce residual alcohols, the thermal decomposition of the styrene resin progressed, 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) to the content of solvent (c) was lower than in 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) to the content of solvent (c) was lower than in 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 compromising productivity or heat resistance. Therefore, the styrene resin composition of the present invention can be widely used in extrusion molding for non-foamed sheets and foamed sheets, food packaging containers using these, and molded products by injection molding (electrical appliance parts, toys, daily necessities, various industrial parts), and will play a major role in the industrial world.

Claims

[Claim 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.

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