Styrene resin composition, extruded sheet and molded article

Abstract

To provide a styrenic resin composition that is excellent in heat resistance, appearance and moldability, an extruded sheet including the same, and a molded article obtained by secondary molding of the extruded sheet.SOLUTION: A styrenic resin composition includes a styrene copolymer (A) having an unsaturated carboxylic acid monomer unit and a styrenic monomer unit, a styrene oligomer (B) having a styrenic monomer unit, and a radical scavenger (C). Relative to the styrene copolymer (A) 100 pts.mass, the unsaturated carboxylic acid monomer unit contained in the styrene copolymer (A) is 2-15 pts.mass; the content of the styrene oligomer (B) is 0.05-0.4 pts.mass; and the content of the radical scavenger (C) is 0.001-0.1 pt.mass.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a styrenic resin composition, an extrusion sheet formed using the styrenic resin composition, and a molded article formed by secondary molding of the extrusion sheet.

Background Art

[0002] Styrene-unsaturated carboxylic acid resins typified by styrene-methacrylic acid copolymer resins are excellent in heat resistance, transparency, and rigidity, and are inexpensive. Therefore, they are widely used as packaging materials for food containers such as lunch boxes and prepared foods, foamed boards for heat insulating materials in houses, diffusion plates for liquid crystal TVs containing diffusing agents, etc. In particular, due to the recent spread of high-power microwave ovens used for business purposes such as convenience stores, they are used as containers and lid materials that do not undergo thermal deformation even at the temperature during cooking in a high-power microwave oven. On the other hand, with the improvement of the heat resistance of styrene-unsaturated carboxylic acid resins, the viscosity becomes high in the same molding temperature range as general styrenic resins, and the moldability deteriorates. Therefore, the molding temperature has to be increased.

[0003] And, due to the increase in the molding temperature, the by-production during the polymerization of styrene-unsaturated carboxylic acid resins and the volatilization or bleed-out of high-boiling oligomer components generated by thermal decomposition during molding are promoted. The volatilized high-boiling oligomer components quickly aggregate on the take-up roll, and dirt due to the high-boiling components accumulates on the take-up roll. When the dirt accumulated on the take-up roll increases, the dirt is transferred to the transparent sheet, causing surface clouding and leading to a deterioration in the quality of the transparent sheet. Therefore, especially during the production of transparent sheets, it is necessary to remove the dirt on the take-up roll at regular intervals. Therefore, a method for suppressing the generation of oligomers during the polymerization and molding of styrene-unsaturated carboxylic acid resins has been demanded.

[0004] For example, Patent Document 1 discloses a method for suppressing the generation of oligomers during polymerization by producing a styrene-methacrylic acid resin under relatively low-temperature conditions by suspension polymerization in water.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-12734 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] In the method of Patent Document 1 above, although the oligomers generated during polymerization are suppressed, the oligomers generated during molding are not suppressed, and as a result, it was insufficient to suppress the clouding of the obtained transparent sheet. Further, by suppressing the oligomer component during polymerization too much, the plasticizing effect by the oligomers was reduced, and the molding temperature tended to increase. Furthermore, when the molding temperature increases, there also arises a problem that a transparent sheet used for a lid material of a food container or the like is yellowed and the appearance is impaired.

[0007] Therefore, the problem to be solved by the present invention is to provide a styrene resin composition excellent in heat resistance, appearance and moldability, an extruded sheet using the same, and a molded article obtained by secondarily molding the extruded sheet. [Means for Solving the Problems]

[0008] As a result of intensive studies in view of the above problems, the present inventor added a radical scavenger to a styrene-unsaturated carboxylic acid resin at a specific ratio in the latter half of polymerization to suppress the generation of oligomers during polymerization, and further by setting the content of the radical scavenger in the resin composition within a specific range, the generation of oligomers during molding is also suppressed, and a styrene resin composition excellent in heat resistance, appearance and moldability, an extruded sheet using the same, and a molded article (for example, a container) obtained by secondarily molding the extruded sheet were successfully realized, and the present invention was completed. That is, the present invention is as follows.

[0009] [1] A styrene resin composition comprising a styrene copolymer (A) having an unsaturated carboxylic acid monomer unit and a styrene monomer unit, a styrene oligomer (B) having a styrene monomer unit, and a radical scavenger (C), wherein With respect to 100 parts by mass of the styrene copolymer (A), the content of the unsaturated carboxylic acid monomer unit contained in the styrene copolymer (A) is 2 to 15 parts by mass, the content of the styrene oligomer (B) is 0.05 to 0.4 parts by mass, and the content of the radical scavenger (C) is 0.001 to 0.1 parts by mass. A styrene resin composition characterized by that.

[0010] [2] The styrene resin composition according to [1], further containing 0.001 to 0.08 parts by mass of ethylbenzene with respect to 100 parts by mass of the styrene copolymer (A).

[0011] [3] The styrene copolymer (A) has the following general formula (1)

Chemical formula

[0012] [4] The styrene resin composition according to any one of [1] to [3], further containing 0.001 to 1 part by mass of a monohydric alcohol having 16 or more carbon atoms with respect to 100 parts by mass of the styrene copolymer (A).

[0013] [5] The radical scavenger (C) has the following general formula (2)

Chemical formula

[0014] [6] The styrene resin composition according to any one of [1] to [5], which contains 0.5 to 5 parts by mass of a rubber-modified polystyrene (D) with respect to 100 parts by mass of the styrene copolymer (A).

[0015] [7] The styrene resin composition according to any one of [1] to [6], which contains 0 to 0.6 parts by mass of a conjugated diene monomer unit with respect to 100 parts by mass of the styrene copolymer (A).

[0016] [8] The styrene resin composition according to any one of [1] to [7], which further contains 0.001 to 0.5 parts by mass of a liquid paraffin (E) with respect to 100 parts by mass of the styrene copolymer (A).

[0017] [9] A non-foamed extruded sheet having the styrene resin composition according to any one of [1] to [8].

[0018]

[10] A foamed extruded sheet having the styrene resin composition according to any one of [1] to [8].

[0019]

[11] A molded article formed using the non-foamed extruded sheet according to [9] or the foamed extruded sheet according to

[10] .

Advantages of the Invention

[0020] According to the present invention, a styrene resin composition excellent in heat resistance, appearance, and moldability can be provided. According to the present invention, it is possible to provide an extruded sheet excellent in heat resistance, appearance, and impact resistance, and a lid material for a lunch box container that can be cooked in a microwave oven.

Mode for Carrying Out the Invention

[0021] Hereinafter, embodiments for carrying out 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 embodiments, and various modifications can be made within the scope of the gist thereof.

[0022] [Styrene-based Resin Composition] The styrene-based resin composition of the present embodiment is a styrene-based resin composition having a styrene copolymer (A) having an unsaturated carboxylic acid monomer unit and a styrene-based monomer unit, a styrene oligomer (B) having a styrene-based monomer unit, and a radical scavenger (C), and when the total amount of the styrene copolymer (A) is 100 parts by mass, the content of the unsaturated carboxylic acid monomer unit contained in the styrene copolymer (A) is 2 to 15 parts by mass, the content of the styrene oligomer (B) is 0.05 to 0.4 parts by mass, and the content of the radical scavenger (C) is 0.001 to 0.1 parts by mass. It is to provide a styrene-based resin composition (hereinafter sometimes simply referred to as a resin composition).

[0023] [Styrene Copolymer (A)] In the present embodiment, the styrene copolymer (A) has a styrene-based monomer unit and an unsaturated carboxylic acid monomer unit as essential components, and when the content of the unsaturated carboxylic acid monomer unit is 100 parts by mass of the total content of all monomer units constituting the styrene copolymer (A) (= the total amount of the styrene copolymer (A)), it is a copolymer (hereinafter also simply referred to as copolymer (A)) having a content of 2 to 15 parts by mass. The styrene copolymer (A) is excellent in heat resistance as compared with a styrene homopolymer because an unsaturated carboxylic acid monomer unit is introduced into the polymer chain. In addition, the styrene copolymer (A) in the present embodiment may contain other monomer units in addition to styrene-based monomer units and unsaturated carboxylic acid monomer units. As the other monomer units, (meth)acrylate monomer units are preferable.

[0024] <<Styrene-based monomer>> In the above styrene copolymer (A), when the total content of all monomer units constituting the styrene copolymer (A) is 100 parts by mass, the content of the styrene-based monomer units is preferably 85 to 98 parts by mass, more preferably 80 to 96 parts by mass, and still more preferably 82 to 91 parts by mass. If the content is less than 70 parts by mass, it will cause a decrease in fluidity. If it is more than 98 parts by mass, it will be difficult to contain a desired amount of the unsaturated carboxylic acid described below, and the effect of improving heat resistance by the unsaturated carboxylic acid cannot be sufficiently obtained.

[0025] The styrene-based monomer that forms styrene-based monomer units by polymerization is not particularly limited. For example, styrene, α-methylstyrene, β-methylstyrene, paramethylstyrene, orthomethylstyrene, metamehylstyrene, chlorostyrene, bromostyrene, etc. can be mentioned. Particularly from an industrial perspective, styrene and α-methylstyrene are preferable, and styrene is more preferable. These styrene-based monomers can be used alone or in a mixture of two or more.

[0026] <<Unsaturated carboxylic acid monomer>> In the above styrene copolymer (A), the unsaturated carboxylic acid monomer unit plays a role in improving heat resistance. When the total content of all monomer units constituting the styrene copolymer (A) is 100 parts by mass, the content of the unsaturated carboxylic acid monomer unit is 2 to 15 parts by mass, preferably 3 to 14 parts by mass, more preferably 4 to 13 parts by mass, even more preferably 5 to 12 parts by mass, and even more preferably 6 to 11 parts by mass. If this content is less than 2 parts by mass, the effect of improving heat resistance is insufficient. On the other hand, when the content of the unsaturated carboxylic acid monomer unit exceeds 15 parts by mass, it is not preferable because the amount of gelified matter in the resin increases, bubbles are generated during molding due to an increase in water absorption rate, and the viscosity becomes too high during production.

[0027] Examples of the unsaturated carboxylic acid monomer in this embodiment include acrylic acid and methacrylic acid. Particularly from an industrial perspective, as the unsaturated carboxylic acid monomer, these may be used alone or in a mixture of two or more. As the unsaturated carboxylic acid monomer, methacrylic acid, which has a large effect of improving heat resistance, is particularly preferable.

[0028] <<(meth)acrylate monomer unit>> In a preferred aspect of this embodiment, the styrene copolymer (A) may contain a (meth)acrylate monomer unit in addition to the styrene-based monomer unit and the unsaturated carboxylic acid monomer unit described above. The (meth)acrylate monomer unit is preferably a (meth)acrylate monomer unit having an ester substituent with 6 to 12 carbon atoms. Thereby, a resin composition excellent in fluidity can be obtained. The (meth)acrylate monomer unit having an ester substituent with 6 to 12 carbon atoms is preferably a monomer unit represented by the following general formula (1). [Chemical formula] (In the above general formula (1), R 1 represents a hydrogen atom or a methyl group, and R 2 represents an ester substituent, and the ester substituent R 2represents an alkyl group having 6 to 12 carbon atoms. * represents a bond with another atom.)

[0029] In addition, the ester substituent having 6 or more and 12 or less carbon atoms means an alkyl group represented by R 2 (which has 6 or more and 12 or less carbon atoms and is a linear, branched or cyclic alkyl group). When the styrene copolymer (A) of the present embodiment is a terpolymer or higher copolymer, the content of the (meth)acrylate monomer unit having an ester substituent having 6 or more and 12 or less carbon atoms in the styrene copolymer (A) is preferably 0.05 parts by mass or more, more preferably 0.05 parts by mass to 5 parts by mass, based on 100 parts by mass of the total amount of monomer units contained in the styrene copolymer (A). If it is less than 0.05 parts by mass, the effect of improving fluidity cannot be sufficiently obtained, and if it exceeds 5 parts by mass, the heat resistance is significantly impaired.)

[0030] <<Other monomers>> The styrene copolymer (A) according to the present invention may have monomer units other than the above-described styrene-based monomer units, unsaturated carboxylic acid monomer units, and (meth)acrylate monomer units having an ester substituent having 6 or more and 12 or less carbon atoms as an optional component. That is, in the present embodiment, as long as it is copolymerizable with the styrene-based monomer and / or the unsaturated carboxylic acid monomer, it may be copolymerized with monomers other than the above two monomers without particular limitation as long as the effects of the invention are not impaired. Examples thereof include methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, (n-octyl) methacrylate, and (2-ethylhexyl) methacrylate, acrylic acid esters such as methyl acrylate, ethyl acrylate, propyl acrylate, (n-butyl) acrylate, and (t-butyl) acrylate, maleic anhydride, maleic acid, fumaric acid, itaconic acid, (meth)acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, maleimide, and nucleus-substituted maleimide. In particular, methyl methacrylate is preferable because it improves the transparency and strength of the resin by copolymerization.)

[0031] In the styrene copolymer (A) according to the present invention, the contents of styrene monomer units, unsaturated carboxylic acid monomer units, (meth)acrylic acid ester monomer units having an ester substituent with 6 to 12 carbon atoms which are optional components, and other monomer units can be determined from the integration ratios of the spectra measured by a proton nuclear magnetic resonance ( 1 1H-NMR) measuring instrument, respectively.

[0032] The weight average molecular weight (Mw) of the styrene copolymer (A) according to the present invention is preferably 100,000 to 400,000, more preferably 120,000 to 320,000. When the weight average molecular weight is 100,000 to 350,000, a resin excellent in the practicality of the 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 conversion.

[0033] The number average molecular weight (Mn) of the styrene copolymer (A) according to the present invention is preferably 30,000 to 200,000, more preferably 40,000 to 170,000. When the number average molecular weight is 30,000 to 200,000, a resin excellent in the practicality of the balance between impact strength and fluidity can be obtained. The number average molecular weight can be measured by gel permeation chromatography in terms of polystyrene standard conversion.

[0034] <Production method of styrene copolymer (A)> The production method of the styrene copolymer (A) of this embodiment will be described below. The production method of the styrene copolymer (A) of the present invention includes a step of preparing a mixed solution by mixing a styrene monomer, an unsaturated carboxylic acid monomer, a solvent, and, if necessary, other monomers (such as (meth)acrylic acid ester monomer units having an ester substituent with 6 to 12 carbon atoms), an initiator, a step of polymerizing the mixed solution, a step of adding a radical scavenger (C) described later, and a step of recovering the reaction product. The polymerization method of the styrene copolymer (A) is not particularly limited, but for example, a radical polymerization method, and among them, a bulk polymerization method or a solution polymerization method can be preferably adopted. Specifically, the polymerization method mainly includes a polymerization step of polymerizing a polymerization raw material (monomer component) and a devolatilization step of removing volatile components such as unreacted monomers and polymerization solvents from the polymerization product.

[0035] Hereinafter, the polymerization of the styrene copolymer (A) according to this embodiment will be described. In this embodiment, when polymerizing the polymerization raw material to obtain the styrene copolymer (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, n-butyl-4,4-bis(t-butylperoxy)valerate, dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, diacyl peroxides such as acetyl peroxide, isobutyryl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxy esters 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, among them, 1,1-bis(t-butylperoxy)cyclohexane is preferred.

[0036] A chain transfer agent can also be used as needed during the polymerization of the styrene copolymer (A). Examples of the chain transfer agent include, for example, α-methylstyrene linear dimer, n-dodecyl mercaptan, t-dodecyl mercaptan, n-octyl mercaptan, and the like.

[0037] As the polymerization method of the styrene copolymer (A), solution polymerization using a polymerization solvent can be employed. As the polymerization solvent, aromatic solvents such as toluene, ethylbenzene, propylbenzene, and butylbenzene are preferred, and a solvent system in which the solubility of the styrene copolymer (A) is adjusted by combining polar solvents such as alcohols or ketones as needed may also be used. In this embodiment, the polymerization solvent is preferably used in the range of 3 to 35 parts by mass, more preferably 5 to 30 parts by mass, based on 100 parts by mass in total of all the monomers and the solvent constituting the styrene copolymer (A). If the amount of the polymerization solvent exceeds 35 parts by mass, the polymerization rate decreases and the molecular weight of the resulting resin also decreases, so the mechanical strength of the resin tends to decrease. On the other hand, if the amount of the polymerization solvent is less than 3 parts by mass, it may be difficult to control heat removal during polymerization. Adding in a proportion of 3 to 35 parts by mass based on 100 parts by mass of all the monomers is preferable in terms of easy homogenization of quality and also in terms of controlling the polymerization temperature. When using a monohydric alcohol as the polymerization solvent, it is preferably added in a proportion of 1 to 10 parts by mass based on 100 parts by mass in total of all the monomers and the solvent.

[0038] The apparatus used in the polymerization step for obtaining the styrene copolymer (A) according to the present invention is not particularly limited and may be appropriately selected according to a general polymerization method for styrene-based resins. For example, in the case of bulk polymerization, a polymerization apparatus in which one or a plurality of completely mixed reactors are connected can be used. Also, there is no particular limitation on the devolatilization step. In the case of bulk polymerization, the polymerization is advanced until the unreacted monomer finally becomes preferably 50% by mass or less, more preferably 40% by mass or less.

[0039] At the stage where the monomer has been sufficiently polymerized, that is, at the stage where the unreacted monomer is 50% by mass or less, by adding the radical scavenger (C) described below, the amount of the styrene oligomer described below can be produced to be within an appropriate range.

[0040] In order to remove volatile components such as unreacted monomers, devolatilization is carried out by a known method. For example, ordinary devolatilization apparatuses such as a flash drum, a twin-screw devolatilizer, a thin-film evaporator, and an extruder can be used, but a devolatilization apparatus with less residence part is preferred. The temperature of the devolatilization treatment is usually about 190 to 280°C, and more preferably 190 to 260°C from the viewpoint of decomposition inhibition. 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. As the devolatilization method, for example, a method of removing volatile components by reducing the pressure under heating and a method of removing them through an extruder or the like designed for the purpose of removing volatile components are desirable.

[0041] <Styrene oligomer (B)> In this embodiment, the styrene oligomer (B) is a general term for a group of compounds composed of styrene dimers and trimers generated by side reactions of styrene monomers or thermal decomposition of polymers when polymerizing or melt-processing the styrene copolymer (A). By appropriately containing it in the composition, a plasticizing effect of improving fluidity can be expected. When the plasticizing effect is improved, the molding temperature can be reduced, so that yellowing of the molded product can be suppressed and excellent appearance can be ensured. Therefore, the styrene oligomer (B) plays an important role in a styrene-based resin composition with improved heat resistance and reduced fluidity. On the other hand, if there is too much styrene oligomer (B), the amount of volatiles during molding increases, causing contamination of the die and mold and cloudiness of the transparent sheet. Therefore, it is important to contain the styrene oligomer (B) in the composition within an appropriate range in the present invention.

[0042] In this specification, the content of the styrene oligomer (B) represents the total content of styrene dimers and trimers formed from styrene monomers. When the content of the styrene copolymer (A) in the styrene resin composition of the present invention is 100 parts by mass, the content of the styrene oligomer (B) in the styrene resin composition is 0.05 to 0.4 parts by mass, preferably 0.08 to 0.3 parts by mass, more preferably 0.09 to 0.25 parts by mass, and even more preferably 0.1 to 0.2 parts by mass. If it is less than 0.05 parts by mass, the effect of improving fluidity becomes poor, resulting in easy yellowing. If it exceeds 0.4 parts by mass, it will contaminate the die, mold, and sheet winding roll during molding, and also cause a decrease in heat resistance. Especially when manufacturing a transparent sheet, if the winding roll is contaminated, the stain derived from the styrene oligomer (B) on the roll will be transferred to the transparent sheet, causing cloudiness. In particular, by setting the content of the styrene oligomer (B) to 0.1 to 0.2 parts by mass, a styrene resin composition excellent in the balance of fluidity, low contamination property, and heat resistance can be obtained.

[0043] Specific compounds of the above-mentioned styrene dimers and trimers include, as dimers, 2,4-diphenyl-1-butene, cis-1,2-diphenylcyclobutane, trans-1,2-diphenylcyclobutane, and the like. As trimers, 2,4,6-triphenyl-1-hexene, 1,3,5-triphenylcyclohexane, 1e-phenyl-4a-(2-phenylethyl)tetralin, 1e-phenyl-4e-(1-phenylethyl)tetralin, and the like can be mentioned.

[0044] The quantification of the styrene oligomer (B) in the styrene resin composition of this embodiment can be carried out by the gas chromatography method described later.

[0045] <<Radical scavenger (C)>> In this embodiment, the radical scavenger (C) plays a role in appropriately adjusting the content of the styrene oligomer (B) in the styrene resin composition.

[0046] As the content in the styrene resin composition, when the content of the styrene copolymer (A) is 100 parts by mass, it is 0.001 to 0.1 part by mass, preferably 0.003 to 0.08 part by mass, more preferably 0.005 to 0.06 part by mass, still more preferably 0.007 to 0.04 part by mass, even more preferably 0.010 to 0.035 part by mass, and most preferably 0.013 to 0.030 part by mass. If it is less than 0.001 part by mass, the reduction effect of the styrene oligomer (B) cannot be sufficiently obtained. If it exceeds 0.1 part by mass, not only cannot the oligomer reduction ability with respect to the addition amount be sufficiently obtained, but also the radical scavenger (C) itself may cause contamination of the winding roll and cloudiness of the transparent sheet, so attention is required. In particular, by setting the content of the radical scavenger (C) to 0.013 to 0.030 part by mass, a resin composition excellent in the balance between the suppression of the above-described oligomer generation and the suppression of the appearance of the molded product due to the bleed-out of the radical scavenger (C) can be obtained.

[0047] Specific examples of the radical scavenger (C) include octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 3,9-bis[2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane, ethylene bis(oxyethylene) bis[3-(5-t-butyl-4-hydroxy-m-tolyl)propionate], 4-t-butylcatechol, 4,6-bis(octylthiomethyl)-o-cresol, 4,6-bis[(dodecylthio)methyl]-o-cresol, 2,4-dimethyl-6-(1-methylpentadecyl)phenol, pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], DL-α-tocopherol, 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate, 4,4'-thiobis(6-t-butyl-3-methylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 4,4'-butylidenebis(3-methyl-6-t-butylphenol), bis-[3,3-bis-(4'-hydroxy-3'-t-butylphenyl)-butanoic acid]-glycol ester, 6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-t-butyldibenz[d,f][1,3,2]-dioxaphosphepine, 4-methoxyphenol, 2-methoxyphenol, and the like.

[0048] In particular, when the radical scavenger (C) has an ester-type chemical structure represented by the following general formula (2), the effect of reducing the oligomer amount is high. Particularly preferred is 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl acrylate.

Chemical formula

[0049] The quantification in the composition of the radical scavenger (C) can be carried out by the gas chromatography method described below.

[0050] [Rubber-modified polystyrene (D)] As a preferred embodiment of the present embodiment, the styrenic resin composition preferably contains a rubber-modified polystyrene (D). When the styrenic resin composition in the present embodiment emphasizes impact resistance, a rubber-modified polystyrene (D) may be further added.

[0051] In this specification, the rubber-modified polystyrene (D) is a rubbery polymer containing conjugated diene monomer units such as polybutadiene, and a styrenic monomer or other monomers are graft-polymerized while applying shear with a stirring blade or the like, and is represented by particles of a rubbery polymer having graft chains dispersed as particles of a rubbery polymer in a resin composed of a matrix resin.

[0052] The rubber-modified polystyrene (D) improves the strength of the entire styrenic resin composition, particularly prevents cracking during winding when sheet molding, and also has the effect of preventing blocking between sheets by imparting an appropriate surface roughness with the particles of the rubbery polymer.

[0053] As the content of the rubber-modified polystyrene (D) in the resin composition, when the content of the styrene copolymer (A) is 100 parts by mass, it is preferably 0.5 to 5.0 parts by mass, more preferably 0.7 to 4.5 parts by mass, and even more preferably 1.0 part by mass to 3.5 parts by mass. By setting it to 0.5 parts by mass or more, the effect of improving the strength of the resin composition can be obtained, and when it is 5.0 parts by mass or more, the transparency is impaired.

[0054] The method of adding the rubber-modified polystyrene (D) is not particularly limited, but preferably melt-kneading with an extruder. For melt-kneading, it may be used by mixing with the styrene copolymer (A) in a dry blend at the time of molding, or it may be melt-kneaded in advance with the styrene copolymer (A) using an extruder different from the molding machine.

[0055] - Rubber-like polymer - As the rubber-like polymer in the rubber-modified polystyrene (D), polybutadiene, polyisoprene, natural rubber, polychloroprene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, etc. can be used. From an industrial perspective, polybutadiene and styrene-butadiene copolymers are preferred. For polybutadiene, high-cis polybutadiene with a high cis content, low-cis polybutadiene with a low cis content, or both can be used. As the structure of the styrene-butadiene copolymer, it may be a random structure, a block structure, or a combination thereof. These rubber-like polymers may be used alone or in combination of two or more. Saturated rubber obtained by hydrogenating butadiene-based rubber can also be used. In particular, when emphasizing the appearance (suppression of yellowing), the total content of (meth)acrylonitrile monomer units in the styrene-based resin composition of the present invention is preferably 2% by mass or less, more preferably 1.5% by mass or less, still more preferably 0.6% by mass or less, even more preferably 0.5% by mass or less, and even more preferably 0.4% by mass or less with respect to the total amount (100% by mass) of the styrene-based resin composition.

[0056] -Conjugated diene monomer unit- In the present specification, the conjugated diene monomer unit is a diolefin having a pair of conjugated double bonds among the monomer units constituting the rubber-like polymer. For example, 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, etc. can be mentioned. The content of the conjugated diene monomer unit in the rubber-modified polystyrene (D) and the resin composition can be measured by the procedure described in the Examples section below or a method equivalent thereto.

[0057] The content of the conjugated diene monomer unit in the rubber-modified polystyrene (D) is preferably 2 to 15% by mass, more preferably 3 to 14% by mass, and even more preferably 4 to 13% by mass with respect to the total amount of the rubber-modified polystyrene (D).

[0058] In the styrene resin composition of the present invention, the total content of conjugated diene monomer units is preferably 0 to 1.0 part by mass, more preferably more than 0 and 1.0 part by mass or less, still more preferably 0.005 to 0.8 part by mass, even more preferably 0.010 to 0.6 part by mass, and most preferably 0.030 to 0.4 part by mass with respect to 100 parts by mass of the content of the styrene copolymer (A) in the styrene resin composition. In particular, by setting the total content of conjugated diene monomer units to 0.01 part by mass or more, the strength improvement effect and blocking prevention effect by the addition of the rubber-modified polystyrene (D) and other additives can be obtained highly, and by setting it to 0.6 part by mass or less, a resin composition excellent in transparency can be obtained. In particular, when the object is to provide a styrene resin composition excellent in heat resistance, appearance, transparency and moldability, or when the object is to provide an extruded sheet excellent in heat resistance, appearance, transparency and impact resistance and a lid material for a lunch box container that can be cooked in a microwave oven, the total content of conjugated diene monomer units in the styrene resin composition of the present invention is 0.4 part by mass or less with respect to 100 parts by mass of the content of the styrene copolymer (A) in the styrene resin composition, which is particularly preferable. The total content of the above conjugated diene monomer units refers to the total amount of conjugated diene monomer units, including not only the conjugated diene monomer units that can be contained in the essential components, the styrene copolymer (A) and the styrene oligomer (B), but also the conjugated diene monomer units that can be contained in the optional components, the rubber-modified polystyrene (D) and other additives such as MBS rubber.

[0059] - Rubber particle size - The rubber-like polymer in the rubber-modified polystyrene (D) preferably exists as rubber particles in the styrene resin composition. In this case, the average particle diameter of the particles of the rubber-like polymer (hereinafter also referred to as the rubber particle diameter) is preferably 0.3 to 9.0 μm, more preferably 0.4 to 6.0 μm, and still more preferably 0.5 to 3.0 μm. When the rubber particle diameter is 0.3 μm or more, the mechanical strength of the resin composition is good. Further, when the rubber particle diameter is 9.0 μm or less, the transparency and appearance of the resin composition are good. The rubber-modified polystyrene-based (D) is obtained by polymerizing a styrene-based monomer in a reactor equipped with a stirrer in the presence of a rubber-like polymer, and the rubber particle diameter can be adjusted by the rotation speed of the stirrer, the molecular weight of the rubber-like polymer used, etc. In the specification, the average particle diameter of the rubber-like polymer is a value measured from a cross-sectional observation image by a transmission electron microscope.

[0060] - Swelling index - In the present invention, the swelling index of the toluene-insoluble matter of the rubber-modified polystyrene (D) is preferably 8.0 to 14.0, and the mass ratio of the toluene-insoluble matter to the rubber content in the toluene-insoluble matter (toluene-insoluble matter / rubber content in the toluene-insoluble matter) is preferably 1.5 to 4.0. This swelling index is more preferably 9.0 to 13.0, still more preferably 9.5 to 12.5, and the ratio of the toluene-insoluble matter / rubber content in the toluene-insoluble matter is more preferably 2.0 to 3.5, still more preferably 2.5 to 3.5. When the swelling index of the toluene-insoluble matter of the rubber-modified styrene resin (b) is 8.0 to 14.0 and the ratio of the toluene-insoluble matter / rubber content in the toluene-insoluble matter is 1.5 to 4.0, a resin excellent in mechanical strength can be obtained. In the present disclosure, the swelling index of the toluene-insoluble matter and the ratio of the toluene-insoluble matter / rubber content in the toluene-insoluble matter are values measured by the procedure described in the Examples section or a procedure equivalent thereto as understood by those skilled in the art.

[0061] The melt flow rate of the rubber-modified polystyrene (D) at 200 °C can preferably be 0.5 to 20.0, more preferably 1.0 to 18.0, and still more preferably 2.0 to 16.0. If the melt flow rate is in the range of 0.5 to 20.0, the miscibility with the styrene copolymer (A) is good and the mechanical strength is also good. In the present disclosure, the melt flow rate is a value measured at 200 °C and a load of 49 N in accordance with ISO 1133.

[0062] - Method for producing rubber-modified polystyrene (D)- The method for producing the rubber-modified polystyrene (D) is not particularly limited, but bulk polymerization (or solution polymerization) in which a styrene monomer (and a solvent) is polymerized in the presence of a rubber-like polymer, or bulk-suspension polymerization that shifts to suspension polymerization during the reaction, or emulsion graft polymerization in which a styrene monomer is polymerized in the presence of a rubber-like polymer latex can be used for production. In bulk polymerization, a mixed solution containing a rubber-like polymer, a styrene monomer, and, if necessary, an organic solvent, an organic peroxide, and / or a chain transfer agent is continuously supplied to a polymerization apparatus configured by connecting a completely mixed reactor or a tank reactor and a plurality of tank reactors in series, whereby it can be produced.

[0063] <Liquid paraffin (E)> As a preferred embodiment of the present embodiment, the styrene resin composition preferably further contains a liquid paraffin (E). The styrene resin composition containing the liquid paraffin (E) exhibits an effect of improving fluidity, an effect of improving the strength of the sheet-shaped product, and an effect of reducing cracking during winding.

[0064] When the amount of the liquid paraffin (E) contained in the styrene resin composition is based on 100 parts by mass of the styrene copolymer (A), it is preferably 0.005 to 0.5 parts by mass, more preferably 0.010 to 0.4 parts by mass, and still more preferably 0.015 to 0.3 parts by mass. If it is less than 0.005 parts by mass, the effect of improving fluidity cannot be obtained, and if it is 0.5 parts by mass or more, it causes a decrease in heat resistance.

[0065] The liquid paraffin (E) used in the present invention may be referred to as white mineral oil, mineral oil, MO, white mineral oil, etc. in addition to liquid paraffin depending on the degree of purification and business practices.

[0066] The liquid paraffin (E) is preferably one having a naphthene component ratio of 20% or more, more preferably 30% or more by the n-d-M ring analysis method, because it has excellent compatibility with the styrene copolymer (A). The n-d-M ring analysis method is a composition test method for high-boiling petroleum fractions, and is a method (ASTM D3238) for obtaining the aromatic ring ratio (%Ca), naphthene ring ratio (%Cn), and paraffin chain ratio (%Cp) in the oil by determining the refractive index (n), density (d), and molecular weight (M). From the viewpoint of the color of the product, the polycyclic aromatic component in the white mineral oil needs to be 3% or less, preferably 0.5% or less. In liquid paraffin, the aromatic ring is usually 0%.

[0067] It is effective to have few low-boiling components in the liquid paraffin (E) in order to avoid the problem of volatile components during extrusion molding. The 5% distillation temperature is preferably 400 °C or higher in terms of the value converted from the reduced-pressure distillation method or gas chromatography method of JIS K2254 to normal pressure.

[0068] The kinematic viscosity of the liquid paraffin (E) is preferably in a viscosity range in which the above low-boiling components are few, and which effectively lowers the Vicat softening temperature and is easy to handle. The range of 40 to 120 mm 2 2 / s at 40 °C is preferred, and more preferably 60 to 80 mm2 / s.

[0069] The method of adding the liquid paraffin (E) is not particularly limited, and examples include a method of adding the liquid paraffin (E) in the polymerization step, and a method of kneading using a known kneader such as a single-screw extruder, a twin-screw extruder, or a Banbury mixer. In particular, it is preferable to add it during the production of the styrene copolymer (A) because the dispersibility is improved. The quantification and identification of the liquid paraffin (E) in the present embodiment can be easily confirmed by a method common to those skilled in the art. For example, a styrene resin composition or a fragment of a molded article of the composition is dissolved in a solvent that dissolves the matrix resin, such as tetrahydrofuran, to prepare a solution. Then, while stirring this solution with a stirrer, n-hexane is added dropwise little by little to precipitate the matrix resin and the rubber-like polymer. After that, the filtrate filtered through a glass filter is evaporated to dryness, then made up to a fixed volume with n-hexane, passed through a membrane filter made of polytetrafluoroethylene, and separated by liquid chromatography to calculate the content of liquid paraffin in the composition or the molded article. Also, for the analysis of liquid paraffin, identification, quantification, and molecular weight measurement can be performed using various analyzers such as pyrolysis GC-MS, 1 1H-NMR or 13 13C-NMR.

[0070] <Monohydric alcohols having 16 or more carbon atoms> As a preferred embodiment of the present embodiment, the styrene resin composition preferably contains a monohydric alcohol having 16 or more carbon atoms. Alcohols having 15 or fewer carbon atoms have high volatility, and when molding or the like is performed, odor is generated by the alcohol and workability is reduced. However, it has been confirmed that by increasing the number of carbon atoms to 16 or more, the volatility is lowered and abnormal odor during molding or the like is suppressed. In this embodiment, by containing a monohydric alcohol having 16 or more carbon atoms, the effect of suppressing the formation of a gelled product during molding around 250°C is achieved, and a molded product with excellent appearance can be obtained. The monohydric alcohol is an alcohol having 16 or more carbon atoms containing one hydroxyl group, and 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. The number of carbon atoms is preferably 16 or more, more preferably 17 or more, and even more preferably 18 or more and 50 or less. The monohydric alcohol may be contained in the styrene resin composition. Therefore, the monohydric alcohol may remain in the styrene resin composition as the final product by allowing the monohydric alcohol to be present (or added) in the polymerization solution used when polymerizing the styrene copolymer (A), or may be contained by mixing in an extruder or in a solvent after the polymerization of the styrene copolymer (A). In this embodiment, when emphasizing the viewpoint of molding around 200°C or suppressing turbidity, it is preferable to select an alcohol having 5 to 13 carbon atoms, and when emphasizing the viewpoint of molding around 250°C or suppressing odor, it is preferable to select an alcohol having 16 or more carbon atoms.

[0071] The boiling point of the monohydric alcohol having 16 or more carbon atoms is preferably 260°C or higher, more preferably 270°C or higher, and even more preferably 290°C or higher. If the boiling point of the monohydric alcohol is less than 260°C, the volatility becomes high, and there is a tendency for a strange odor to occur during molding or the like.

[0072] In the styrene resin composition according to the present invention, the content of the monohydric alcohol having 16 or more carbon atoms is preferably 0.001 to 1.0 part by mass, more preferably 0.03 to 1.0 part by mass, still more preferably 0.05 to 0.7 part by mass, and even more preferably 0.08 to 0.4 part by mass when 100 parts by mass of the styrene copolymer (A) is used. If the content is less than 0.001 part by mass, the gel suppression effect during molding around 250 °C will decrease. If it exceeds 1.0 part by mass, the remaining amount in the resin will increase, resulting in a strong odor or a significant decrease in heat resistance, and the heat resistance increasing effect due to methacrylic acid modification will become poor.

[0073] The monohydric alcohol having 16 or more carbon atoms is not particularly limited. For example, 1-hexadecanol, isohexadecanol, 1-octadecanol, 5,7,7-trimethyl-2-(1,3,3-trimethylbutyl)-1-octanol, isooctadecanol, 1-isoicosanol, 8-methyl-2-(4-methylhexyl)-1-decanol, 2-heptyl-1-undecanol, 2-heptyl-4-methyl-1-decanol, 2-(1,5-dimethylhexyl)-(5,9-dimethyl)-1-decanol, or polyoxyethylene alkyl ethers, etc. can be mentioned.

[0074] The above polyoxyethylene alkyl ethers are preferably compounds represented by the following general formula (3). R-O-(CH 2 -CH 2 -O) X -H ···(3) (In the above general formula (3), R is an alkyl group having 12 to 20 carbon atoms, X is the average addition number of ethylene oxide, and is an integer of 1 to 15.) As a specific example of the polyoxyethylene alkyl ether, Emulgen 109P manufactured by Kao Corporation is particularly preferred.

[0075] <<Ethylbenzene>> As a preferred embodiment of the present embodiment, the styrenic resin composition preferably further contains ethylbenzene. By appropriately containing ethylbenzene, a further improvement effect in fluidity is expected. When the content of the styrene copolymer (A) in the styrenic resin composition is 100 parts by mass, the content of ethylbenzene is preferably in the range of 0.001 to 0.08 parts by mass. By setting it to 0.001 parts by mass or more, an improvement effect in fluidity can be obtained, and by setting it to 0.08 parts by mass or less, odors can be prevented. As a method for adding ethylbenzene, a method of adding it during the polymerization of each resin is preferred.

[0076] [[Other Components]] In addition to the above, the styrenic resin composition of the present embodiment may contain various additives generally used in general styrenic resins or polystyrene-containing compositions in order to achieve known effects. Examples of such various additives include stabilizers, antioxidants, ultraviolet absorbers, lubricants, mold release agents, plasticizers, antiblocking agents, antistatic agents, antifogging agents, mineral oils, and the like. Also, reinforcing materials such as styrene-butadiene block copolymers or MBS resins may be added within a range that does not impair the physical properties. There is no particular regulation regarding the blending method. For example, a method of adding and polymerizing during polymerization, or a method of premixing the additives with a blender before melt-kneading after polymerization and then melt-kneading with an extruder or a Banbury mixer, etc. can be mentioned.

[0077] In the present embodiment, various additives can be added to the styrenic resin composition as described above. Although the content of the styrenic resin in the styrenic resin composition is not particularly limited, it is preferably 95% by mass or more, more preferably 97% by mass, and even more preferably 99% by mass or more.

[0078] [Physical Properties of Styrenic Resin Composition] The physical properties of the styrenic composition in the present embodiment will be described below. In this embodiment, the Vicat softening temperature of the styrene resin composition is preferably 105°C or higher, more preferably 115°C or higher. By setting it at 105°C or higher, sheets and containers applicable to heat cooking in a general microwave oven of around 500 W can be obtained, and by setting it at 115°C or higher, it can withstand heat cooking in a high-output commercial microwave oven of 1000 W or higher placed in convenience stores, etc. The Vicat softening temperature can be measured in accordance with ISO306 under the conditions of a load of 50 N and a temperature rising rate of 50°C / h.

[0079] In this embodiment, the melt flow rate of the styrene resin composition at 200°C is preferably in the range of 0.5 to 5.0 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 at 0.5 g / 10 min or higher, good moldability can be obtained, and by setting it at 4.5 g / 10 min or lower, a resin with excellent strength can be obtained.

[0080] In this embodiment, the haze degree of the styrene resin composition, that is, the haze in a 2-mm plate, is preferably 20% or less, more preferably 15%, and even more preferably 10% or less. In particular, by setting it at 10% or less, a molded product with extremely excellent transparency can be obtained when molded into a sheet or a container. In this embodiment, the method for producing the 2-mm plate used in the method for measuring haze and the method for measuring haze are such that the styrene resin composition is injection molded into a 2-mm plate under the conditions described in the column of Examples below.

[0081] [Manufacturing method of styrene resin composition] The styrene resin composition of this embodiment can be produced by melt-kneading each component by any method. For example, methods of using alone or in combination a high-speed stirrer typified by a Henschel mixer, a batch kneader typified by a Banbury mixer, a single-screw or twin-screw continuous kneader, a roll mixer, etc. can be mentioned. The heating temperature during kneading is usually selected in the range of 180 to 260°C. Also, a radical scavenger and / or liquid paraffin, etc. may be added during the production of the styrene copolymer (A) or the rubber-modified polystyrene. [Molded article] The styrene resin composition of this embodiment can be used to produce a molded article by the above melt-kneading molding machine or by using the pellets of the obtained styrene resin composition as a raw material by an injection molding method, an injection compression molding method, an extrusion molding method, a blow molding method, a press molding method, a vacuum molding method, a foam molding method, etc.

[0082] [Extruded sheet] Another aspect of the present invention provides an extruded sheet formed using the styrene resin composition of the present invention described above. The extruded sheet may be either non-foamed or foamed. As a method for manufacturing the extruded sheet, a commonly known method can be used. As a method for manufacturing a non-foamed extruded sheet, a method of using a short-axis or twin-screw extrusion molding machine equipped with a T-die and a device for taking up the sheet with a uniaxial or biaxial stretching machine, etc. can be used, and as a method for manufacturing a foamed extruded sheet, a method of using an extrusion foam molding machine equipped with a T-die or a circular die, etc. can be used.

[0083] [Foamed extruded sheet]< When forming a foamed extruded sheet, substances commonly used as a foaming agent and a foaming nucleating agent during extrusion foaming can be used. As the foaming agent, butane, pentane, Freon, carbon dioxide, water, etc. can be used, and butane is preferable. Also, as the foaming nucleating agent, talc, etc. can be used.

[0084] The foamed extruded sheet preferably has a thickness of 0.5 mm to 5.0 mm, a bulk density of 50 g / L to 300 g / L, and a basis weight of 80 g / m2 ~300 g / m 2 It is preferably so. The foamed extrusion sheet of the present invention may be made into multiple layers by, for example, further laminating a film or the like. The type of film to be used may be the same as those used for general polystyrene.

[0085] <Non-foamed extrusion sheet> The thickness of the non-foamed sheet is preferably about 0.1 to 1.0 mm, for example, from the viewpoints of rigidity and thermoforming cycle. Also, the uniaxial sheet may be formed only by normal low magnification roll stretching, and for the biaxially stretched sheet, it is preferable in terms of strength to stretch it about 1.3 to 7 times in the flow direction (MD) with a roll and then stretch it about 1.3 to 7 times in the vertical direction (TD) with a tenter. Further, the non-foamed sheet may be used in a multilayer with a styrenic resin such as a known polystyrene resin. Moreover, it may be used in a multilayer with a resin other than the styrenic resin. Examples of the resin other than the styrenic resin include PET resin, nylon resin, and the like.

[0086] Another aspect of the present invention provides a molded article formed using the non-foamed extrusion sheet or the foamed extrusion sheet of the present invention described above. The foamed extrusion sheet or the multilayer body containing the same can be molded, for example, by vacuum forming to produce a container such as a tray. Also, the non-foamed extrusion sheet can be molded, for example, by vacuum forming to produce a lid material for a bento or a container for putting side dishes or the like.

Examples

[0087] Next, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The analysis and evaluation methods of the resin, extrusion sheet, etc. in the Examples and Comparative Examples are as follows.

[0088] [Characteristics evaluation of each resin material and styrenic resin composition used in Examples and Comparative Examples] (1) Measurement of weight average molecular weight The weight average molecular weight (Mw) of each resin material and each resin composition used in the examples and comparative examples was measured under the following conditions using gel permeation chromatography (GPC). Measuring instrument: HLC-8220 manufactured by Tosoh Corporation Separation column: Two TSK gel Super HZM-H (inner diameter 4.6 mm) manufactured by Tosoh Corporation were connected in series Guard column: TSK guard column Super HZ-H manufactured by Tosoh Corporation Measuring solvent: Tetrahydrofuran (THF) Sample concentration: 5 mg of the measurement sample was dissolved in 10 mL of the solvent and filtered through a 0.45 μm filter. Injection volume: 10 μL Measuring temperature: 40 °C Flow rate: 0.35 mL / min Detector: Ultraviolet absorption detector (UV-8020 manufactured by Tosoh Corporation, wavelength 254 nm) For the preparation of the calibration curve, eleven types of TSK standard polystyrene manufactured by Tosoh Corporation (F-850, F-450, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000) were used. The calibration curve was prepared using a first-order linear approximation formula.

[0089] (2) Measurement of melt mass flow rate (MFR) The melt mass flow rate (g / 10 min) of each resin composition used in the examples and comparative examples was measured under the load conditions of 200 °C and 49 N in accordance with ISO 1133.

[0090] (3) Measurement of Vicat softening temperature The Vicat softening temperature of each resin and resin composition used in the examples and comparative examples was measured in accordance with ISO 306. The load was 50 N and the heating rate was 50 °C / h.

[0091] (4) Measurement of the content of alcohols in the resin composition The content of monohydric alcohols having 16 or more carbon atoms and ethylbenzene was measured under the following conditions using gas chromatography. Sample preparation: 1.0 g of the resin material was dissolved in 5 mL of methyl ethyl ketone, and then 5 mL of hexane containing the standard substance (p - diethylbenzene) was added to reprecipitate the polymer component. The supernatant was collected and used as the measurement solution. Measuring instrument: Agilent 6850 Series GC System Detector: FID Column: HP - 1 (100% dimethylpolysiloxane), 30 m Film thickness 0.25 μm, 0.32 mm φ Injection volume: 1 μL (splitless) Column temperature: Hold at 40°C for 2 minutes → Heat up to 320°C at 20°C / min → Hold at 320°C for 15 minutes Injector temperature: 250°C Detector temperature: 280°C Carrier gas: Helium

[0092] (5) Measurement of the content of conjugated diene monomer units The content of conjugated diene monomer units was measured by pyrolysis GC. Sample preparation: The styrene - based resin composition was dissolved in chloroform at 5 mass%, applied to a 20 μl pyrolysis foil, and vacuum - dried at 80°C for 24 hours. Measurement conditions: Py - GC Instrument: Curie point injector manufactured by Japan Analytical Industry Co., Ltd. Pyrolysis foil temperature: 590°C High - frequency irradiation time: 10 seconds GC: Instrument: HP - GC - 6890 manufactured by Agilent Technologies Column: HP - 5MS 30 m, film thickness 0.25 mm, 0.25 mm φ Column temperature: Hold at 50°C for 5 minutes, heat up at 10°C / min, and from 100°C Heat up at 70°C / min and hold at 300°C for 10 minutes. Injector temperature: 300°C Detector temperature: 300°C Split ratio: 1 / 20 Carrier gas: Helium Detection method: MSD

[0093] (6) Average particle diameter of rubber particles in rubber-modified polystyrene The average particle diameter (μm) of rubber particles in rubber-modified polystyrene (hereinafter referred to as HIPS resin) was determined for 200 rubber-like elastomer particles observed by cross-sectional observation using a transmission electron microscope according to the following formula: Average particle diameter = Σ(ni × Di 4 ) / Σ(ni × Di 3 ) {In the formula, ni is the number of rubber-like elastomer particles having a particle diameter Di, and Di is the average value of the major axis and minor axis of the rubber-like elastomer particles.} It was calculated by

[0094] (7) Measurement of swelling index of toluene-insoluble matter in HIPS resin 1 g of HIPS resin was precisely weighed (W1) into a precipitation tube, 20 milliliters of toluene was added, and the mixture was shaken at 23°C for 2 hours. Then, it was centrifuged at 10°C or lower and 20,000 rpm for 60 minutes using a centrifuge (himac, CR-20 (rotor: R20A2), manufactured by Hitachi, Ltd.). The precipitation tube was slowly tilted to about 45 degrees, and the supernatant was removed by decantation. The mass of the toluene-containing insoluble matter was precisely weighed (W2) and vacuum dried at 160°C and 3 kPa or less for 1 hour. After the dried toluene-insoluble matter was cooled to room temperature in a desiccator, its mass was precisely weighed (W3). The swelling index of the toluene-insoluble matter and the toluene-insoluble matter were determined by the following formulae. Toluene-insoluble matter (mass%) = ((W3) / (W1)) × 100 Swelling index of toluene-insoluble matter = (W2 / W3)

[0095] (8) Measurement of haze (haze of 2 mm plate) The resin compositions prepared in the examples and comparative examples were molded into 2 mm plates under the following conditions by injection molding (EC60N, manufactured by Toshiba Machine Co., Ltd.), and the haze was measured using a haze meter (NDH-2000, manufactured by Nippon Denshoku Industries Co., Ltd.), and the n3 average was taken as the value. 2 mm plate molding conditions Molding Machine: EC60N manufactured by Toshiba Machine Co., Ltd. Cylinder Temperature: 220 - 240 - 220 - 200 °C Measurement: 45 mm Pressure Holding Switching: 10 mm Injection Time: 10 seconds Cooling Time: 15 seconds Injection Speed: 23 mm / second Pressure Holding Speed: 23 mm / second Pressure Holding Time: 10 seconds Mold Temperature: 45 °C Note that the above molding conditions are for reference only. Each condition, including temperature and pressure holding, may be finely adjusted as required.

[0096] [Characteristics Evaluation of Sheet Molding] (8) Appearance Judgment of Extruded Sheet Using the styrene resin compositions of the examples and comparative examples, after continuously extruding the sheet for 3 hours with a 30 mmφ short-axis sheet extruder, five sheets with a size of 10 cm × 20 cm were cut out from the 0.3 mm thick sheet. The number of gel-like substances and bubbles, which are foreign matters with an average diameter of (major axis + minor axis) / 2 on the surface of the five sheets being 0.5 mm or more, was counted, and the yellowness was evaluated visually. The appearance was judged according to the following criteria. ○: No yellowness visually and the number of gel-like substances and bubbles is 2 or less △: No yellowness visually and the number of gel-like substances and bubbles is 3 - 9 ×: No yellowness visually and the number of gel-like substances and bubbles is 10 or more Y: Level where yellowness is visually recognized

[0097] (9) Film Impact of Batch Biaxially Oriented Sheet Using a press molding machine, press plates with a thickness of 1.2 - 1.6 mm were prepared from the styrene resin compositions of the examples and comparative examples. Sheets with a size of 10 cm × 10 cm were cut out from the prepared plates. The cut-out sheets were simultaneously biaxially oriented under the following conditions using a biaxial orientation device (EX6 - S1) manufactured by Toyo Seiki to prepare biaxially oriented sheets with a thickness of approximately 0.2 mm. Orientation Temperature: Vicat softening temperature of the resin composition + 20 - 30 °C, Orientation Speed: 170% Elongation ratio: 2.5 times The obtained sheet was cut into 8 cm × 8 cm, and the film impact was measured using a film impact tester (No. 195) manufactured by Toyo Seiki, and the n8 average was used as the value.

[0098] (10) Heat resistance of the batch biaxially stretched sheet Using a press molding machine, press plates with a thickness of 1.2 to 1.6 mm were produced from the styrene resin compositions of the examples and comparative examples. Sheets with a size of 10 cm × 10 cm were cut out from the produced plates. The cut sheets were simultaneously biaxially stretched under the following conditions using a biaxial stretching device (EX6-S1) manufactured by Toyo Seiki to produce biaxially stretched sheets with a thickness of about 0.2 mm. Stretching temperature: Vicat softening temperature of the resin composition + 20 to 30 °C, Stretching speed: 170% Elongation ratio: 2.5 times The stretched sheets obtained under the above molding conditions were placed in an oven set at 110 °C for 60 minutes, and then the deformation of the container was visually observed, and the following evaluation was made on the heat resistance from the thermal deformation. ○: No deformation ×: Dimensional change (3% or more)

[0099] (11) Stain on the winding roll (moldability) After extruding a sheet of about 250 μm continuously for 10 hours with a 30 mmφ single-screw sheet extruder, the stain on the winding roll was visually confirmed, and the roll stain was evaluated according to the following criteria. ○: Not stained at all. △: It seems not to be stained at first glance, but when the roll is wiped with a cloth, the wiped part can be seen. ×: Clearly stained. In this specification, the stain on the winding roll is evaluated as an example of an index of moldability.

[0100] (12) Haze of the 250 μm sheet after 8-hour extrusion (cloudiness) Regarding the transparent sheet at the 8-hour mark when a sheet with a thickness of approximately 250 μm was extruded continuously for 8 hours using a 30 mmφ single-screw sheet extruder, the haze at 250 μm of the above sheet was measured using a haze meter (NDH-2000) manufactured by Nippon Denshoku Industries Co., Ltd., and the n3 average was taken as the value.

[0101] The following specific manufacturing examples will be described for the examples and comparative examples. In this example, a composition was produced using rubber-modified polystyrenes d-1 to d-3 having the following properties.

[0102] [Table 1]

[0103] [Example 1] A polymerization raw material composition liquid consisting of 73.0 parts by mass of styrene, 5.8 parts by mass of methacrylic acid, 17.2 parts by mass of ethylbenzene, 3.0 parts by mass of 2-ethyl-1-hexanol, Fine Oxocol 180 (a monohydric alcohol with 18 carbon atoms) manufactured by Nissan Chemical Industries, Ltd., and 0.05 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane was prepared and supplied to a completely mixed reactor for the polymerization process. At the outlet of the completely mixed reactor, Sumilizer GS manufactured by Sumitomo Chemical Co., Ltd. was added and stirred to a ratio of 0.1 part by mass per 100 parts by mass of the polymerization reaction composition liquid, and then continuously supplied to a devolatilization device connected to a single-screw extruder for removing volatile components such as unreacted monomers and polymerization solvents. The temperature of the single-screw extruder was set at 200 - 250°C and the pressure at 10 torr to devolatilize the volatile components such as unreacted monomers and polymerization solvents. The devolatilized volatile components were condensed in a condenser through which a refrigerant at -5°C was passed, recovered as an unreacted liquid, and the styrene-based resin composition was recovered as resin pellets 1. The physical properties of the resin composition obtained by the above analysis method are shown in Table 2-1 below. Next, using the obtained resin pellet product 1 and the pellet of d-1 having the composition shown in Table 1 above as the rubber-modified polystyrene (D), they were dry blended so that the mass ratio of resin pellet product 1 / d-1 was 100 / 1.5, and sheet molding was continuously performed for 10 hours using a short-axis sheet extruder to produce an extruded sheet (A). Then, for the extruded sheet (A), appearance determination, soiling of the winding roll, and each evaluation of the haze of a 250-μm sheet after 8 hours of extrusion were performed according to the above evaluation method. The results are shown in Table 2-1 below. Also, in the same manner as above, after dry blending so that the mass ratio of resin pellet product 1 / rubber-modified polystyrene (D) (d-1) was 100 / 1.5, melt kneading was performed using a twin-screw extruder, and then the press-molded product was batch biaxially stretched to produce an extruded sheet (B). Then, for the extruded sheet (B), film impact and heat resistance were evaluated according to the above evaluation method.

[0104] [Examples 2 to 19] Styrene resin compositions and extruded sheets (A) and (B) were obtained in the same manner as in Example 1 except that the conditions were changed as shown in Table 2-1 below.

[0105] [Comparative Example 1] A resin composition was obtained in the same manner as in Example 1 except that the polymerization conditions were changed as shown in Table 2-2 below. When a styrene homopolymer was used instead of the styrene copolymer (A), the heat resistance of the extruded sheet decreased.

[0106] [Comparative Example 2] A resin composition was obtained in the same manner as in Example 1 except that the polymerization conditions were changed as shown in Table 2-2 below. When an excessive amount of Sumilyzer GS was added as the radical scavenger (C), the soiling of the winding roll and the haze of the sheet after 10 hours of extrusion deteriorated.

[0107] [Comparative Example 3] A resin composition was obtained in the same manner as in Example 1 except that the polymerization conditions were changed as shown in Table 2-2 below. When no radical scavenger (C) was added, the amount of oligomers increased, and the soiling of the winding roll and the haze of the sheet after 10 hours of extrusion deteriorated.

[0108] [Comparative Example 4] A resin composition was obtained in the same manner as in Example 1 except that the polymerization conditions were changed as shown in Table 2-2 below. Compared with Example 2, the fluidity decreased due to the decrease in the amount of oligomer. Due to the decrease in the fluidity of the entire composition, the molding temperature of the extruded sheet (A) increased, and the sheet showed a yellowish color at a visually recognizable level.

[0109]

Table 2-1

[0110]

Table 2-2

[0111] In addition, in Tables 2-1 and 2-2, “at the reactor outlet” for the “timing of adding the radical scavenger” means that after the polymerization step of the styrene copolymer (A) is completed and it exits the reactor, the radical scavenger is added between the polymerization step and the devolatilization step, and “before the reactor” means that the radical scavenger is added before the polymerization of the styrene copolymer (A).

Industrial Applicability

[0112] The styrene resin of the present disclosure is excellent in heat resistance, appearance, and moldability. Therefore, the styrene resin composition of the present invention can be widely used in non-foamed sheets or foamed sheets by extrusion molding, food packaging containers using them, or molded products by injection molding (electrical product parts, toys, daily necessities, various industrial parts, containers), etc., and plays a great role in the industrial field.

Claims

1. A styrenic resin composition comprising a styrene copolymer (A) having an unsaturated carboxylic acid monomer unit and a styrene monomer unit, a styrene oligomer (B) having a styrene monomer unit, and a radical scavenger (C), wherein the radical scavenger (C) is selected from the group consisting of methoxyphenol, t-butylcatechol, and the following general formula (2): 【Chemical 1】 (In the above general formula (2), X1 and X2 each independently represent a hydrogen atom, a halogen atom, or a substituted or unsubstituted aromatic ring, and L1 and L2 each independently represent a single bond or an alkylene group having 1 to 23 carbon atoms, and one or more methylene groups in the alkylene group may be substituted with -CH=CH- so as not to be adjacent to each other.) and is selected from the group consisting only of compounds represented by when the styrene copolymer (A) is 100 parts by mass, the content of the unsaturated carboxylic acid monomer unit contained in the styrene copolymer (A) is 2 to 15 parts by mass, the content of the styrene oligomer (B) is 0.05 to 0.4 parts by mass, and the content of the radical scavenger (C) is 0.001 to 0.1 parts by mass, wherein the styrene oligomer (B) is a styrene dimer or a styrene trimer which is any one of 2,4-diphenyl-1-butene, cis-1,2-diphenylcyclobutane, trans-1,2-diphenylcyclobutane, 2,4,6-triphenyl-1-hexene, 1,3,5-triphenylcyclohexane, 1e-phenyl-4a-(2-phenylethyl)tetralin, or 1e-phenyl-4e-(1-phenylethyl)tetralin. A styrenic resin composition characterized by that.

2. The styrenic resin composition according to claim 1, further containing 0.001 to 0.08 parts by mass of ethylbenzene with respect to 100 parts by mass of the styrene copolymer (A).

3. The styrene copolymer (A) has the following general formula (1): [Chemical 2] (In the above general formula (1), R １ represents a hydrogen atom or a methyl group, and R ２ is an ester substituent and represents an alkyl group having 6 to 12 carbon atoms.) The styrene resin composition according to claim 1 or 2, further containing 0.05 parts by mass or more of a (meth)acrylic acid ester monomer unit represented by the formula per 100 parts by mass of the styrene copolymer (A).

4. The styrenic resin composition according to any one of claims 1 to 3, further containing 0.001 to 1 part by mass of a monohydric alcohol having 16 or more carbon atoms with respect to 100 parts by mass of the styrene copolymer (A).

5. The styrenic resin composition according to any one of claims 1 to 4, further containing 0.5 to 5 parts by mass of a rubber-modified polystyrene (D) with respect to 100 parts by mass of the styrene copolymer (A).

6. The styrenic resin composition according to any one of claims 1 to 5, containing 0 to 0.6 parts by mass of a conjugated diene monomer unit with respect to 100 parts by mass of the styrene copolymer (A).

7. The styrenic resin composition according to any one of claims 1 to 6, further containing 0.001 to 0.5 parts by mass of liquid paraffin (E) with respect to 100 parts by mass of the styrene copolymer (A).

8. An unfoamed extruded sheet having the styrenic resin composition according to any one of claims 1 to 7.

9. A foamed extruded sheet having the styrenic resin composition according to any one of claims 1 to 7.

10. A molded article formed using the unfoamed extruded sheet according to claim 8 or the foamed extruded sheet according to claim 9.

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