JP2023086825A - Styrenic resin composition, foam sheet and food container - Google Patents

Abstract

To provide a styrenic resin composition excellent in a balance between moldability and recyclability, a foam sheet, and a food container.SOLUTION: A styrenic resin composition has a melt mass flow rate (MFR) measured on conditions of 200°C and 49 N of 1.0-5.0 g/10 min, the total content of a styrene dimer and a trimer of more than 2,500 μg/g and a melt-tension value (MT) measured at 190°C of 40-80 gf, and contains 7.0-15.0 mass% of a component having a molecular weight of 1,000,000 or more in 100 mass% of the styrenic resin composition. A foam sheet contains the styrenic resin composition. A food container contains the foam sheet.SELECTED DRAWING: None

Description

The present invention relates to a styrenic resin composition, a foamed sheet and a food container.

Styrene-based resins are excellent in transparency, moldability, etc., and are therefore widely used as molding materials for home appliances, office equipment, sundries, housing equipment, etc., and food packaging materials. In recent years, there has been a demand for thin-walled, lightweight products and diversification of shapes, and styrene resins with excellent molding processability are in demand.

JP 2014-227459 A

By the way, in the above styrene resins, in addition to moldability, from the viewpoint of reducing manufacturing costs and considering the environment, scraps generated during the molding process and used molded products can be recycled more easily. There is a demand for recyclability such that the resin can be recycled and the physical properties of the resin after recycling do not deteriorate.

As a conventional technique, in Patent Document 1, by using a foaming styrene resin composition containing a high molecular weight polymer obtained by polymerizing a solvent-soluble polyfunctional vinyl copolymer having a branched structure and a vinyl monomer, Techniques have been disclosed for providing a foamed sheet that is excellent in strength and secondary moldability and that exhibits little deterioration in physical properties even when recycled materials are blended.
However, it has been found that the styrene-based resin composition described in Patent Document 1 is not sufficient in moldability and recyclability, and there is room for further improvement.

Accordingly, an object of the present invention is to provide a styrenic resin composition, a foamed sheet and a food container which are excellent in balance between moldability and recyclability.

In order to achieve the above object, the present inventors have made intensive studies and found that the melt mass flow rate (MFR), the total content of styrene dimer and trimer, the melt tension value (MT), and the content of components with a molecular weight of 1,000,000 or more The inventors have found that a styrenic resin composition having an excellent balance between molding processability and recyclability can be realized by setting the content within a predetermined range, and have completed the present invention.
That is, the present invention is as follows.

[1] The melt mass flow rate (MFR) measured under the conditions of 200° C. and 49 N load is 1.0 to 5.0 g/10 min, the total content of styrene dimer and trimer is more than 2500 μg/g, and 190 The melt tension value (MT) measured at ° C. is 40 to 80 gf, and the content of components having a molecular weight of 1,000,000 or more is 7.0 to 15.0% by mass in 100% by mass of the styrene resin composition. A styrenic resin composition characterized by
[2] The styrenic resin composition of [1] above, wherein the content of components having a molecular weight of 2,000,000 or more is 1.2 to 5.0% by mass in 100% by mass of the styrenic resin composition.
[3] The styrenic resin composition of [1] or [2] above, wherein the ratio (Mz/Mw) of z-average molecular weight (Mz) to weight-average molecular weight (Mw) is from 1.8 to 6.0.
[4] The styrenic resin composition according to any one of [1] to [3] above, which has a maximum rise ratio of 1.1 to 4.0.
[5] The styrenic resin composition of any one of [1] to [4] above, which has a degree of branching of 0.60 to 0.95.
[6] The styrenic resin composition of any one of [1] to [5] above, which has a degree of gelation of 1.10 to 1.60.
[7] A foamed sheet comprising the styrenic resin composition of any one of [1] to [6] above.
[8] A food container comprising the foamed sheet of [7] above.

ADVANTAGE OF THE INVENTION According to this invention, the styrenic resin composition, foam sheet, and food container which are excellent in moldability and recyclability balance can be provided.

Embodiments of the present invention (hereinafter referred to as "present embodiments") will be described below, but the present invention is not limited to these embodiments.

<<Styrene resin composition>>
The styrene-based resin composition of the present embodiment has a melt mass flow rate (MFR) of 1.0 to 5.0 g/10 minutes measured under a load of 49 N at 200° C., and a total content of styrene dimers and trimers of 2500 μg/ g, the melt tension value (MT) measured at 190° C. is 40 to 80 gf, and the content of the component having a molecular weight of 1,000,000 or more is 7.0 to 15.0 g in 100% by mass of the styrene resin composition. It is 0% by mass. Thereby, the moldability and recyclability of the polystyrene-based resin composition can be well balanced.

<Melt mass flow rate>
The styrene resin composition of the present embodiment has a melt mass flow rate (MFR) of 1.0 to 5.0 g/10 minutes, preferably 1.1 to 4, measured under conditions of 200° C. and 49 N load. 0 g/10 min, more preferably 1.2 to 3.0 g/10 min, even more preferably 1.5 to 2.5. When the MFR is 1.0 g/10 minutes or more and the total content of styrene dimer and trimer is within a predetermined range as described later, the styrene resin composition is relatively easy to flow, so recycling is possible. can improve sexuality. In addition, when the MFR is 5.0 g/10 minutes or less, the strength of the styrene-based resin composition molded article can be maintained.
In the present disclosure, melt mass flow rate is a value measured at 200° C. and a load of 49 N in accordance with ISO1133.

In order to make the melt mass flow rate (MFR) in the above range, for example, a method of widening the molecular weight distribution of the styrene resin composition (Mw / Mn is 2.0 to 6.0), liquid paraffin, etc. A method of adding 0.01 to 10.0% by mass of a plasticizer to 100% by mass of the styrene resin composition, and a method of lowering the glass transition temperature of the styrene resin composition. In addition, depending on the reaction temperature, residence time, type of polymerization initiator, addition amount, and addition location of polymerization initiator, type, addition amount, and addition location of chain transfer agent, and type and amount of solvent used during polymerization. can be adjusted.

<Total Content of Styrene Dimer and Trimer>
The styrene-based resin composition of the present embodiment has a total content of styrene dimer and trimer of more than 2500 μg/g, preferably more than 3000 μg/g, more preferably more than 3500 μg/g. By making the total content of styrene dimer and trimer exceed 2500 μg / g, when recycling the styrene resin composition, moldings of the styrene resin composition (products using the styrene resin composition and manufacturing processes When melting offcuts, etc. generated in , it melts and flows quickly, so it can be suppressed from being excessively exposed to heat. As a result, it is possible to reduce deterioration of the resin during recycling, so that recyclability can be improved.
The upper limit of the total content of styrene dimer and trimer is not particularly limited from the above point of view. or less, more preferably 6000 μg/g or less, and even more preferably 5000 μg/g or less.

Here, the styrene dimer includes 2,4-diphenyl-1-butene, 1,3-diphenylpropane and 1,2-diphenylcyclobutane, and the styrene trimer includes 2,4,6-triphenyl- 1-hexene, 1,3,5-triphenylcyclohexane, 1-phenyl-4-(1″-phenylethyl)tetralin.
The total content of styrene dimer and trimer is the total content of these compounds.

Styrene dimers and trimers are known to be produced as by-products in the polymerization process for producing styrene-based resins and thermal decomposition in the devolatilization process or the like. Since by-products in the polymerization process are generated by thermally initiated radicals, the formation of dimers and trimers can be suppressed by polymerizing using a large amount of a polymerization initiator or by polymerizing at a low temperature. Conversely, in order to increase the styrene dimer and trimer by-produced in the polymerization step, there are a method of raising the polymerization temperature and a method of increasing the concentration of styrene monomer in the polymerization solution. In addition, in the devolatilization process, the thermal history of the devolatilization process is reduced, or the hindered phenol-based antioxidant described later is added in the polymerization process or the devolatilization process to suppress the formation of dimers and trimers due to thermal decomposition. can do. Conversely, in the devolatilization process, thermal decomposition can be accelerated and the content of dimers and trimers can be increased by increasing the polymer temperature, increasing the shearing force in an extruder or the like, or increasing the residence time. can be done.
In the present disclosure, the total content of styrene dimers and trimers is a value measured using gas chromatography (GC).

<Melt tension value (MT)>
The styrenic resin composition of the present embodiment has a melt tension value (MT) measured at 190° C. of 40 to 80 gf, preferably 40 to 70 gf, more preferably 40 to 60 gf. When the melt tension value is 80 gf or less, the secondary molding processability and drawdown resistance of the foam sheet obtained from the styrene-based resin composition can be improved. Secondary molding workability can be improved.

The method of controlling the melt tension value (MT) to be within the above range is a method in which the content of components having a molecular weight of 1,000,000 or more is 7.0% by mass or more in 100% by mass of the styrenic resin composition, and the molecular weight is 200. A method of making the content of 10,000 or more components 2.0% by mass or more in 100% by mass of the styrene resin composition. 8 to 6.0 can be mentioned. Reaction temperature, residence time, type and amount of polymerization initiator, type and amount of solvent used during polymerization, type and amount of chain transfer agent are selected so that the melt tension value (MT) is within the above range. , and can be controlled by appropriately adjusting the type and amount of the additive.
Other methods include, for example, a method of using a polyfunctional polymerization initiator, a method of adding a conjugated divinyl compound, or a method of adding a conjugated divinyl compound and a multi-branched vinyl compound at the same time. For example, when obtaining a styrenic resin composition by optionally adding a conjugated divinyl compound and/or a multibranched vinyl compound to a monovinyl compound and radically copolymerizing them, the conjugated divinyl compound and/or the multibranched vinyl compound The amount added is preferably 4.0×10 ⁻⁶ to 8.0×10 ⁻⁴ mol per vinyl group with respect to 1 mol of the total amount of the monovinyl compound (i.e., conjugated divinyl compound having two vinyl groups). In the case of compounds, it is preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ ). The number average molecular weight (Mn) of the conjugated divinyl compound and the multi-branched vinyl compound is preferably 850-100,000. Also, in the production of styrenic resin, there is a method in which the amount of solvent is reduced to 0-20% and the reaction temperature is 80-140°C. Further, for example, there is a method in which polymerization is performed in two reactors under conditions for polymerizing a low-molecular-weight component and a condition for polymerizing a high-molecular-weight component, respectively, and the two polymerization solutions are merged, or a method in which polymerization is further performed after the confluence. . Conditions for polymerizing the low-molecular-weight component include, for example, a method of shortening the residence time in the reactor, a method of increasing the amount of solvent and raising the polymerization temperature, a method of using a chain transfer agent, and the amount of initiator added. and the like. Conditions for polymerizing the high-molecular-weight component include, for example, a method of reducing the amount of solvent and the polymerization temperature, a method of using a polyfunctional polymerization initiator, a method of using a conjugated divinyl compound and/or a multi-branched vinyl compound, and the like. , preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ mol per 1 mol of the total amount of the monovinyl compound. There is also a method of adding a styrenic resin composition whose molecular weight is controlled by anionic polymerization or cationic polymerization to the solution or kneading with an extruder.

<Peak top molecular weight (Mtop)>
The styrene resin composition of the present embodiment preferably has a peak top molecular weight (Mtop) of 80,000 to 300,000, more preferably 90,000 to 250,000, as measured by gel permeation chromatography (GPC). It is preferably 100,000 to 200,000, and particularly preferably 100,000 to 200,000. If the Mtop is less than 80,000, the strength of molded articles such as foamed sheets will be low. Further, when Mtop exceeds 300,000, the fluidity is lowered and the molding elongation is deteriorated. For example, deep drawing molding of the foam sheet becomes difficult. The Mtop of the styrenic resin composition is adjusted according to the reaction temperature and residence time in the polymerization process, the type and amount of polymerization initiator added, the type and amount of chain transfer agent used, and the type and amount of solvent used during polymerization. be able to.

<Content of Component with Molecular Weight of 1,000,000 or More>
In the styrene resin composition of the present embodiment, the content of components having a molecular weight of 1,000,000 or more is 7.0% by mass to 15.0% by mass in 100% by mass of the styrene resin composition. 5. % to 14.0% by mass, more preferably 8.0 to 13.0% by mass, and particularly preferably 8.5 to 11.0% by mass.
When the content of the component having a molecular weight of 1,000,000 or more is 7.0% by mass or more, the moldability can be improved in combination with the melt tension value being within the predetermined range as described above. In addition, when the content is 15.0% by mass or less, the appearance can be improved.
The molecular weight ratio of the styrenic resin composition is adjusted according to the reaction temperature and residence time in the polymerization process, the type and amount of polymerization initiator added, the type and amount of solvent used during polymerization, and the type and amount of chain transfer agent. be able to.
Further, for example, there is a method of using a polyfunctional polymerization initiator, a method of adding a conjugated divinyl compound, or a method of adding a conjugated divinyl compound and a multi-branched vinyl compound at the same time. For example, when obtaining a styrenic resin composition by optionally adding a conjugated divinyl compound and/or a multi-branched vinyl compound to a monovinyl compound and performing radical copolymerization, the conjugated divinyl compound and/or the multi-branched vinyl compound The amount added is preferably 4.0×10 ⁻⁶ to 8.0×10 ⁻⁴ mol per vinyl group with respect to 1 mol of the total amount of the monovinyl compound (that is, conjugated divinyl compound having two vinyl groups). In the case of compounds, it is preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ ). The number average molecular weight (Mn) of the conjugated divinyl compound and the multi-branched vinyl compound is preferably 850-100,000. Also, in the production of styrenic resin, there is a method in which the amount of solvent is reduced to 0-20% and the reaction temperature is 80-140°C. Further, there is a method of adding a styrenic resin composition whose molecular weight is controlled by anionic polymerization or cationic polymerization to a solution or kneading with an extruder.

<Content of components with a molecular weight of 2,000,000 or more>
In the styrene resin composition of the present embodiment, the proportion of components having a molecular weight of 2,000,000 or more is preferably 1.2 to 5.0% by mass in 100% by mass of the styrene resin composition, more preferably 1 .5 to 4.8% by mass, particularly preferably 2.0 to 4.5% by mass.
When the content of the component having a molecular weight of 2,000,000 or more is 1.2% by mass or more, moldability can be further improved. In addition, when the content is 5.0% by mass or less, a product with a better appearance can be molded.
The molecular weight ratio of the styrenic resin composition is adjusted according to the reaction temperature and residence time in the polymerization process, the type and amount of polymerization initiator added, the type and amount of solvent used during polymerization, and the type and amount of chain transfer agent. be able to.
Further, for example, there is a method of using a polyfunctional polymerization initiator, a method of adding a conjugated divinyl compound, or a method of adding a conjugated divinyl compound and a multi-branched vinyl compound at the same time. For example, when obtaining a styrenic resin composition by optionally adding a conjugated divinyl compound and/or a multibranched vinyl compound to a monovinyl compound and radically copolymerizing them, the conjugated divinyl compound and/or the multibranched vinyl compound The amount added is preferably 4.0×10 ⁻⁶ to 8.0×10 ⁻⁴ mol per vinyl group with respect to 1 mol of the total amount of the monovinyl compound (i.e., conjugated divinyl compound having two vinyl groups). In the case of compounds, it is preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ ). The number average molecular weight (Mn) of the conjugated divinyl compound and the multi-branched vinyl compound is preferably 850-100,000. Also, in the production of styrenic resin, there is a method in which the amount of solvent is reduced to 0-20% and the reaction temperature is 80-140°C. There is also a method of adding a styrenic resin composition whose molecular weight is controlled by anionic polymerization or cationic polymerization to the solution or kneading with an extruder.

<Molecular weight distribution>
The styrene resin composition of the present embodiment preferably has a weight average molecular weight (Mw) to number average molecular weight (Mn) ratio (Mw/Mn) of 2.0 to 6.0, preferably 4.0 to 6.0. .0 is more preferred, and 4.7 to 6.0 is particularly preferred. If the ratio (Mw/Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) is less than 2.0, the flowability is lowered, the molding processability is lowered, and the width of molding conditions is narrowed. There is When Mw/Mn is more than 6.0, the amount of low-molecular-weight components is extremely increased, and the strength of the molded product may be lowered.
In order to set the Mw/Mn of the styrene resin to 2.0 to 6.0, for example, a method of increasing the reaction temperature during polymerization in the order that the reaction solution passes through, a method of using a chain transfer agent, a polymerization initiator is polyfunctional (2-, 3-, or 4-functional), or when a monovinyl compound and a conjugated divinyl compound and/or a multi-branched vinyl compound are radically copolymerized to produce a resin, a conjugated divinyl compound or a multi-branched vinyl compound There is a method of adding preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ mol of the vinyl compound or both per 1 mol of the total amount of the monovinyl compound. Further, for example, there is a method in which polymerization is performed in two reactors under conditions for polymerizing a low-molecular-weight component and a condition for polymerizing a high-molecular-weight component, respectively, and the two polymerization solutions are merged, or a method in which polymerization is further performed after the confluence. . Conditions for polymerizing the low-molecular-weight components include, for example, a method of shortening the residence time in the reactor, a method of increasing the amount of solvent and raising the polymerization temperature, and a method of using a chain transfer agent. Conditions for polymerizing the high-molecular-weight component include, for example, a method of reducing the amount of solvent and the polymerization temperature, a method of using a polyfunctional polymerization initiator, a method of using a conjugated divinyl compound and/or a multi-branched vinyl compound, and the like. , preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ mol per 1 mol of the total amount of the monovinyl compound. There is also a method of adding a styrenic resin composition whose molecular weight is controlled by anionic polymerization or cationic polymerization to the solution or kneading with an extruder.

In addition, the styrene resin composition of the present embodiment preferably has a ratio (Mz/Mw) of the z-average molecular weight (Mz) to the weight-average molecular weight (Mw) of 1.8 to 6.0, preferably 2.0 ∼5.5 is more preferable, and 2.5 to 5.0 is particularly preferable. Moldability can be improved by setting the ratio (Mz/Mw) of the z-average molecular weight (Mz) to the weight-average molecular weight (Mw) to 1.8 or more, and setting (Mz/Mw) to 6.0 or less. By doing so, fluidity can be improved.
In order to obtain the Mz/Mw of the styrene-based resin composition, for example, a method of increasing the reaction temperature during polymerization in the order in which the reaction solution passes through, a method of using a chain transfer agent, a method of using a polyfunctional ( di-, tri-, or tetra-functional), or when producing a resin by radical copolymerization of a monovinyl compound and a conjugated divinyl compound and/or a multi-branched vinyl compound, the conjugated divinyl compound and/or the multi-branched vinyl compound are used. , preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ mol per 1 mol of the total amount of the monovinyl compound. Further, for example, there is a method in which polymerization is performed in two reactors under conditions for polymerizing a low-molecular-weight component and a condition for polymerizing a high-molecular-weight component, respectively, and the two polymerization solutions are merged, or a method in which polymerization is further performed after the confluence. . Conditions for polymerizing the low-molecular-weight components include, for example, a method of shortening the residence time in the reactor, a method of increasing the amount of solvent and raising the polymerization temperature, and a method of using a chain transfer agent. Conditions for polymerizing the high-molecular-weight component include, for example, a method of reducing the amount of solvent and the polymerization temperature, a method of using a polyfunctional polymerization initiator, a method of using a conjugated divinyl compound and/or a multi-branched vinyl compound, and the like. , preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ mol per 1 mol of the total amount of the monovinyl compound. There is also a method of adding a styrenic resin composition whose molecular weight is controlled by anionic polymerization or cationic polymerization to the solution or kneading with an extruder.

The number average molecular weight (Mn) of the styrene resin composition is preferably 50,000 to 200,000, more preferably 55,000 to 150,000, and more preferably 60,000 to 100,000. 00000 is particularly preferred.

<Maximum Rise Ratio>
The styrenic resin composition of the present embodiment preferably has a maximum rise ratio of 1.1 to 4.0, more preferably 1.2 to 3.0, still more preferably 1.1 to 2.0. 5.
In the present specification, the “maximum rise ratio” means (elongation viscosity in the nonlinear region of the maximum rise strain/elongational viscosity in the linear region of the maximum rise strain), and the “maximum rise strain” refers to the elongation viscosity is the Henky strain when is maximum. The maximum rise ratio is an index representing the degree of strain hardening at the maximum rise strain. The greater the maximum rise ratio, the greater the degree of strain hardening and the better the moldability.
Therefore, when the maximum rise ratio is 1.1 or more, the elongational viscosity increases at high strain, that is, when the resin is stretched thinly during molding, so that the thickness of the molded product becomes uniform and the molding It tends to break easily at times. When the maximum rise ratio is 4.0 or less, the extensional viscosity during molding does not become too high, which is preferable from the viewpoint of the balance between productivity and moldability.

<Degree of branching>
The degree of branching of the styrenic resin composition of the present embodiment is preferably 0.60 to 0.95, more preferably 0.62 to 0.92, still more preferably 0.65 to 0.90, and still more It is preferably 0.65 to 0.85. If the degree of branching is less than 0.60, the number of branches becomes too large and the molecular weight per branched chain becomes small, so the number of entanglement points decreases, and the entanglement is loosened at high strain, resulting in sufficient moldability. may not be obtained. If the degree of branching is more than 0.95, the number of branches is small, and a sufficient entanglement effect between polymer chains may not be obtained.
In order to adjust the degree of branching to 0.60 to 0.95, a method of using a polyfunctional polymerization initiator, a method of adding a conjugated divinyl compound, or a method of adding a conjugated divinyl compound and a multi-branched vinyl compound at the same time. There is For example, when obtaining a styrenic resin composition by optionally adding a conjugated divinyl compound and/or a multibranched vinyl compound to a monovinyl compound and radically copolymerizing them, the conjugated divinyl compound and/or the multibranched vinyl compound The amount added is preferably 4.0×10 ⁻⁶ to 8.0×10 ⁻⁴ mol per vinyl group with respect to 1 mol of the total amount of the monovinyl compound (i.e., conjugated divinyl compound having two vinyl groups). In the case of compounds, it is preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ ). The number average molecular weight (Mn) of the conjugated divinyl compound and the multi-branched vinyl compound is preferably 850-100,000.
In the present disclosure, the degree of branching is a value calculated by the procedure described in the "Example" section below.

<Gelling degree>
The degree of gelation of the styrenic resin composition of the present embodiment is preferably 1.10 to 1.60, more preferably 1.12 to 1.55, still more preferably 1.15 to 1.50, and more It is more preferably 1.18 to 1.45. By setting the degree of gelation in the range of 1.10 to 1.60, it is possible to suppress the increase in branching as the molecular weight increases, so that the amount of gelatinous substances in the styrenic resin composition can be reduced. In addition, since the amount of gel-like substance that is produced during long-term retention in a production facility such as a reactor can be reduced, productivity can be improved.
In order to adjust the degree of gelation to 1.10 to 1.60, a method of using a polyfunctional polymerization initiator, a method of adding a conjugated divinyl compound, or a method of adding a conjugated divinyl compound and a multi-branched vinyl compound at the same time. There is a way. For example, when obtaining a styrenic resin composition by optionally adding a conjugated divinyl compound and/or a multibranched vinyl compound to a monovinyl compound and radically copolymerizing them, the conjugated divinyl compound and/or the multibranched vinyl compound The amount added is preferably 4.0×10 ⁻⁶ to 8.0×10 ⁻⁴ mol per vinyl group with respect to 1 mol of the total amount of the monovinyl compound (i.e., conjugated divinyl compound having two vinyl groups). In the case of compounds, it is preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ ). The number average molecular weight (Mn) of the conjugated divinyl compound and the multi-branched vinyl compound is preferably 850-100,000.
In the present disclosure, the degree of gelation is a value calculated by the procedure described in the "Examples" section below.

<Styrene resin>
<Raw material and manufacturing method of styrene resin>
The styrene-based resin of the present embodiment is not particularly limited, but can be obtained, for example, by radical copolymerization of a monovinyl compound and a conjugated divinyl compound and/or a multi-branched vinyl compound (the styrene-based resin is branched). be able to).
As an example, a method for producing a styrenic resin by radical copolymerization of a monovinyl compound and a conjugated divinyl compound and/or a multi-branched vinyl compound will be described in detail below.

<Monovinyl compound>
The monovinyl compound in the present embodiment may consist of only a styrene compound (monomer), or may consist of a styrene compound and a compound having another monovinyl group copolymerizable with the styrene compound. The monovinyl compound is not particularly limited as long as it can be copolymerized with a styrene compound other than a styrene compound. Examples include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and cetyl (meth). Examples include vinyl compounds such as acrylates and (meth)acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, maleic anhydride, maleimide, and nuclear-substituted maleimide. Examples of styrene compounds include styrene, α-methylstyrene, paramethylstyrene, ethylstyrene, propylstyrene, butylstyrene, chlorostyrene and bromostyrene, with styrene being preferred.
The content of the styrene compound is preferably 50 mol% or more, more preferably 70 mol% or more, and still more preferably 90 mol% or more of the monovinyl compound content.

<Conjugated divinyl compound>
The conjugated divinyl compound in the present embodiment preferably has a number average molecular weight (Mn) of 850 to 100,000 and has at least two conjugated vinyl groups in the molecule.
Moreover, the conjugated divinyl compound in the present embodiment is preferably chain-like rather than network-like, and the main chain may or may not have a side chain. This is because the chain shape allows the molecular chain to have a more linear shape, thereby tending to improve the entanglement effect. The side chain preferably has, for example, 6 or less carbon atoms, and more preferably 4 or less carbon atoms.
Furthermore, the conjugated vinyl groups in the conjugated divinyl compound can be located anywhere in the molecule, but two of the at least two conjugated vinyl groups are located at different ends in the molecule. is preferred. Further, when the conjugated divinyl compound is chain-like, the two conjugated vinyl groups are more preferably located at different ends of the main chain (that is, both ends of the main chain are conjugated divinyl groups). is preferred). Polymerization reactivity can be enhanced by locating the conjugated vinyl group at the terminal.
Furthermore, when the conjugated divinyl compound is chain-shaped and has three or more conjugated vinyl groups, it is preferable that two of the three or more conjugated vinyl groups are located at the terminals. More preferably, all three or more conjugated vinyl groups are terminally located.
In addition, when the number of conjugated vinyl groups in the conjugated divinyl compound is large, the number of branch points increases, and gelation may easily occur in the reactor and in the process of collecting raw materials, resulting in deterioration of the transparency of the styrene resin. Also, the reactor and molding machine need to be cleaned, which may reduce productivity. From these points of view, the number of conjugated vinyl groups in the conjugated divinyl compound is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less. From the same point of view, it is particularly preferable that the conjugated divinyl compound has two conjugated vinyl groups.
Here, in this specification, the term "terminal" for a molecule includes not only the most terminal position (atom) of the molecule, but also a position adjacent to the most terminal position of the molecule, and the adjacent position and specifically means an end corresponding to about 20% of the extended chain length of the molecule. The conjugated vinyl group in the conjugated divinyl compound should be located at the end corresponding to 15% of the extended chain length of the conjugated divinyl compound molecule from the viewpoint of improving reactivity with the monovinyl compound and suppressing gelation. is more preferably located at the edge corresponding to 10%, and even more preferably at the edge corresponding to 5%.

In the present embodiment, the conjugated vinyl group means an olefinic double bond that can be copolymerized with a monovinyl compound, and a structure that forms a conjugated system with the olefinic double bond (eg, but not limited to, a carbonyl group, an aryl group, etc.). is a group having The conjugated vinyl group is not particularly limited, but examples thereof include an acryloyl group and an aryl group substituted with a vinyl group. The structure having a conjugated vinyl group in the conjugated divinyl compound is not particularly limited, but for example , (meth)acrylates, urethane (meth)acrylates, aromatic vinyls, maleic acid, fumaric acid, and the like. At least two conjugated vinyl groups may be the same or different.

The number average molecular weight (Mn) of the conjugated divinyl compound of the present embodiment is preferably 850 to 100,000, more preferably 1,000 to 80,000, still more preferably 1,200 to 80,000, still more preferably 1,500 to 60,000, and particularly preferably 1500 to 30000. When the number average molecular weight (Mn) is less than 850, the distance between the conjugated vinyl groups of the conjugated divinyl compound is short, so the distance between polymer chains bonded to the conjugated divinyl compound is shortened, and a sufficient entanglement effect cannot be obtained. , may be inferior in moldability. When the molecular weight exceeds 100,000, the distance between the conjugated vinyl groups of the conjugated divinyl compound increases, and the reactivity of the terminal conjugated vinyl groups decreases (because the conjugated divinyl compound has a large molecular weight, the terminal conjugated vinyl groups react). difficult to remove), and the amount of high-molecular-weight components produced may decrease.
In the present disclosure, the number average molecular weight (Mn) of the conjugated divinyl compound means the polystyrene equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC).

The main chain structure of the conjugated divinyl compound of the present embodiment is not particularly limited, and examples thereof include polyolefins such as polyethylene, polypropylene, and polyisoprene, polystyrene, polybutadiene, hydrogenated polybutadiene, polyphenylene ether, polyester, polyphenylene sulfide, and the like. .

Specific conjugated divinyl compounds include (hydrogenated) polybutadiene-terminated (meth)acrylate (“(hydrogenated)” refers to a hydrogenated or non-hydrogenated compound. The same shall apply hereinafter.), polyethylene terminal di(meth)acrylate compounds such as glycol-terminated (meth)acrylates, polypropylene glycol-terminated (meth)acrylates, ethoxylated bisphenol A-terminated (meth)acrylates, and ethoxylated bisphenol F-terminated (meth)acrylates, and (hydrogenated) Examples include terminal urethane acrylate compounds such as polybutadiene-terminated urethane acrylate, polyethylene glycol-terminated urethane acrylate, polypropylene glycol-terminated urethane acrylate, ethoxylated bisphenol A-terminated urethane acrylate, and ethoxylated bisphenol F-terminated urethane acrylate. For example, in the case of polypropylene glycol-terminated (meth)acrylate, the number of propylene glycol bonds in the repeating unit is determined so that the number average molecular weight (Mn) is 850-100,000. The conjugated divinyl compound is preferably a (hydrogenated) polybutadiene-terminated (meth)acrylate, a polystyrene-terminated (meth)acrylate, or a polyphenylene ether-terminated divinyl from the viewpoint of compatibility with the styrene resin. In addition, "end" and "both ends" in the compound names mean that the conjugated vinyl groups are located at both ends.

<Conjugated divinyl compound content>
The content of the conjugated divinyl compound in the styrene resin of the present embodiment is preferably 2.0×10 ⁻⁶ to 4.0×10 ^{−4 mol, more preferably 5.0×10 −4} mol, per 1 mol of the total amount of monovinyl compounds. ×10 ⁻⁶ to 3.5×10 ⁻⁴ mol, more preferably 1.5×10 ⁻⁵ to 3.0×10 ⁻⁴ mol, still more preferably 2.0×10 ⁻⁵ to 2.5× 10 ⁻⁴ mol. If the content is less than 2.0 × 10 ^-6 mol, sufficient entanglement between polymers is difficult to occur, and strain hardening does not occur or the degree of strain hardening is small, so the thickness of the molded product is inadequate. It may be uniform, or the molded product may break during molding, resulting in poor moldability. On the other hand, when the content exceeds 4.0×10 ⁻⁴ mol, a large amount of gel-like substance is generated, and the appearance of the molded product may become poor.
In the present disclosure, the content of the conjugated divinyl compound with respect to 1 mol of the total amount of monovinyl compounds is a value measured using ¹ H-NMR and ¹³ C-NMR.

<Multi-branched vinyl compound>
In the multi-branched vinyl compound of the present embodiment, the term "multi-branched" means having one or more branched structures, and more specifically includes a star-shaped branched structure, a pom-pom-shaped branched structure, a grafted branched structure, It means having an H-type branched structure.
The number average molecular weight (Mn) of the multi-branched vinyl compound is preferably 850 to 100000, more preferably 1000 to 80000, still more preferably 1200 to 80000, still more preferably 1500 to 60000, particularly preferably 1500 to 30000. is. If the number average molecular weight (Mn) is less than 850, the distance between the vinyl groups is short, so the distance between the polymer chains bonded to the conjugated divinyl compound is short, and a sufficient entanglement effect cannot be obtained, resulting in poor moldability. may be inferior. When the molecular weight exceeds 100,000, the distance between the vinyl groups increases, the reactivity of the vinyl groups decreases (because the molecular weight of the multi-branched vinyl compound is large, the terminal vinyl groups are less likely to react), and the high-molecular-weight component becomes less reactive. Production may decrease.
In the present disclosure, the number average molecular weight (Mn) of the multi-branched vinyl compound is a value measured using gel permeation chromatography (GPC).

The multi-branched vinyl compound can be synthesized, for example, by the methods described in JP-A-2016-113580 and JP-A-2016-113598. For example, divinyl aromatic compounds such as divinylbenzene and diisopropenylbenzene, aliphatic and alicyclic (meth)acrylates represented by ethylene glycol di(meth)acrylate, and styrene and ethylvinylbenzene. There is a method of synthesizing a multi-branched vinyl compound by cationic polymerization of a monovinyl compound and a terminal modifier such as 2-phenoxyethyl methacrylate. Further, a method of esterifying or adding a polymerizable double bond such as a vinyl group such as an isopropenyl group to a polyhydric alcohol or polyester polyol having a multi-branched structure and having a plurality of hydroxyl groups can be mentioned. . Here, the polyhydric alcohol having a multi-branched structure and a plurality of hydroxyl groups is preferably an alcohol having 2 to 100 hydroxyl groups and 70 to 3,000 carbon atoms.

<Content of hyperbranched vinyl compound>
The content of the multi-branched vinyl compound in the styrene resin of the present embodiment is preferably 2.0×10 ⁻⁶ to 4.0×10 ^{−4 mol, more preferably 5.0×10 −4} mol, per 1 mol of the total amount of monovinyl compounds. 0×10 ⁻⁶ to 3.5×10 ⁻⁴ mol, more preferably 1.5×10 ⁻⁵ to 3.0×10 ⁻⁴ mol, still more preferably 2.0×10 ⁻⁵ to 2.5 ×10 ⁻⁴ mol. If the content is less than 2.0 × 10 ^-6 mol, sufficient entanglement between polymers is difficult to occur, and strain hardening does not occur or the degree of strain hardening is small, so the thickness of the molded product is inadequate. It may be uniform, or the molded product may break during molding, resulting in poor moldability. On the other hand, when the content exceeds 4.0×10 ⁻⁴ mol, a large amount of gel-like substance is generated, and the appearance of the molded product may become poor.

<Polymerization process>
Examples of the method for polymerizing the styrene-based resin of the present embodiment include known styrene polymerization methods such as bulk polymerization, solution polymerization, and suspension polymerization. These polymerization methods may be batch polymerization methods or continuous polymerization methods, and from the viewpoint of productivity, continuous polymerization methods are preferred. As a continuous bulk polymerization method, for example, a monovinyl compound, a conjugated divinyl compound having a conjugated vinyl group, and optionally a solvent, a polymerization catalyst, a chain transfer agent, etc. are added and mixed to obtain a raw material solution containing monomers. to prepare. The raw material solution is added to a facility equipped with one or more reactors arranged in series and/or in parallel and a devolatilization device for a devolatilization step for removing volatile components such as unreacted monomers. A method in which the polymerization is progressed stepwise by continuously feeding is exemplified.

Examples of the reactor include a complete mixing reactor, a laminar flow reactor, and a loop reactor from which a portion of the polymerization solution is withdrawn while the polymerization proceeds. There is no particular restriction on the order of arrangement of these reactors.

When polymerizing the styrenic resin of the present embodiment, a polymerization solvent can be used as necessary from the viewpoint of controlling the polymerization reaction. A polymerization solvent is generally used to adjust the polymerization rate, molecular weight, etc. in continuous bulk polymerization or continuous solution polymerization. The polymerization solvent is not particularly limited, and examples thereof include alkylbenzenes such as benzene, toluene, ethylbenzene and xylene, ketones such as acetone and methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and cyclohexane. The amount of the polymerization solvent used is not particularly limited, but from the viewpoint of control of gelation, improvement of productivity, increase of molecular weight, etc., it is usually 1 to 50% by mass as a composition in the polymerization reactor. is preferred, and 3 to 40% by mass is more preferred.

Moreover, when polymerizing raw materials for obtaining the styrene-based resin of the present embodiment, the raw material composition for polymerization may contain a polymerization initiator such as an organic peroxide and a chain transfer agent. The polymerization initiator is not particularly limited, but organic peroxides such as 2,2-bis(t-butylperoxy)butane, 1,1-bis(t-butylperoxy)cyclohexane, and n-butyl- peroxyketals such as 4,4-bis(t-butylperoxy)valerate; dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide and dicumyl peroxide; acetyl peroxide and isobutyryl peroxide; diacyl peroxides, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxyesters such as t-butyl peroxyacetate, ketone peroxides such as acetylacetone peroxide, and hydroperoxides such as t-butyl hydroperoxide. can be done. It is preferable to use 0.005 to 0.08% by mass of the polymerization initiator based on the monovinyl compound. The chain transfer agent is not particularly limited, but examples include α-methylstyrene dimer, n-dodecylmercaptan, t-dodecylmercaptan, and n-octylmercaptan. The chain transfer agent is preferably used in an amount of 0.01 to 0.50% by mass based on the monovinyl compound.

In addition, in the method for producing a styrene-based resin according to the present embodiment, the reaction temperature is set stepwise in the polymerization step, and the reaction temperature difference is preferably 40° C. or more, more preferably 50° C. or more. Furthermore, when polymerizing in parallel using a plurality of reactors, and then combining the respective polymerization solutions polymerized in parallel and polymerizing in one reactor, the reaction temperature is the lowest among the polymerization reactions performed in parallel. It is preferable that the temperature difference from the highest reaction temperature in the polymerization reaction performed by merging is 40° C. or more, more preferably 50° C. or more.

<Volatilization process>
As the devolatilization device, for example, a flash drum, a twin-screw devolatilizer, a thin film evaporator, an extruder, or other ordinary devolatilization device can be used. A volatilization extruder or the like is used. The arrangement of the devolatilization apparatus includes, for example, one using only one vacuum devolatilization tank with a heater, one in which two vacuum devolatilization tanks with heaters are connected in series, and a vacuum devolatilization tank with a heater. For example, a volatilization tank and a devolatilization extruder are connected in series. In order to reduce volatile components as much as possible, it is preferable to connect two vacuum devolatilizing tanks with heaters in series, or to connect a vacuum devolatilizing tank with heaters and a devolatilizing extruder in series. .

Conditions for the devolatilization step are not particularly limited. Polymerization can be allowed to proceed until the content becomes less than or equal to mass %. Volatile matter such as unreacted substances (monovinyl compound) and/or solvent can be removed by the devolatilization treatment.

The temperature of the devolatilization treatment is usually about 190 to 280°C. The pressure of the devolatilization treatment is preferably 0.1 to 50 kPa, more preferably 0.13 to 13 kPa, still more preferably 0.13 to 7 kPa, and particularly preferably 0.13 to 1.3 kPa. As the devolatilization method, desirably, for example, a method of devolatilizing by reducing the pressure under heating, or devolatilization through an extruder or the like designed to remove volatile components.

The styrenic resin composition of the present embodiment contains, for example, a styrenic resin and optional additives described later. The content of the styrene-based resin in the styrene-based resin composition is preferably 50% by mass or more, more preferably 70% by mass or more.

<Additives, etc.>
The styrenic resin composition of the present embodiment may optionally contain additives and the like. It may contain about 1 to 50% by mass of a vinyl resin or an aromatic vinyl thermoplastic elastomer such as SBS. In addition, the styrenic resin composition, for example, 2-[1-(2-hydroxy-3,5-di-t-phenylpentyl)ethyl ]-4,6-di-t-phenylpentyl acrylate may also be included. In addition, heat deterioration inhibitors such as 2-[1-(2-hydroxy-3,5-di-t-phenylpentyl)ethyl]-4,6-di-t-phenylpentyl acrylate, stearic acid, zinc stearate , Calcium stearate, higher fatty acids such as magnesium stearate and salts thereof, lubricants such as ethylene bisstearylamide, plasticizers such as liquid paraffin, antioxidants, etc. may In addition, additives commonly used in the field of styrenic resins, such as flame retardants and colorants, may be combined in the styrenic resin composition within a range that does not impair the purpose of the present embodiment. Examples of additives include, but are not particularly limited to, flame retardants such as hexabromocyclododecane, and coloring agents such as titanium oxide and carbon black. When styrene-based resin is used as pellets, the pellets may be coated with ethylenebisstearylamide, zinc stearate, magnesium stearate, or the like as an external lubricant for the pellets.

Antioxidants generally stabilize peroxide radicals such as hydroperoxy radicals generated during thermoforming or by exposure to light, or decompose generated peroxides such as hydroperoxides. It is an ingredient that can Examples of antioxidants include, but are not limited to, hindered phenol-based antioxidants and peroxide decomposers. The hindered phenol-based antioxidant acts as a radical chain inhibitor, and the peroxide decomposer decomposes the peroxide generated in the system into more stable alcohols to prevent autoxidation. Hindered phenolic antioxidants include, but are not limited to, 2,6-di-t-butyl-4-methylphenol, styrenated phenol, n-octadecyl-3-(3,5-di- t-butyl-4-hydroxyphenyl)propionate, 2,2′-methylenebis(4-methyl-6-t-butylphenol), 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' -butylidenebis(3-methyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), alkylated bisphenol, tetrakis[methylene-3-(3,5-di- t-butyl-4-hydroxyphenyl)propionate]methane and 3,9-bis[2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)-propionyloxy]-1,1 -dimethylethyl]-2,4,8,10-tetraoxyspiro[5.5]undecane and the like. Peroxide decomposers include, but are not limited to, organophosphorus peroxide decomposers such as trisnonylphenyl phosphite, triphenyl phosphite, and tris(2,4-di-t-butylphenyl)phosphite. and dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, pentaerythrityl tetrakis (3-laurylthiopropionate pionate), ditridecyl-3,3′-thiodipropionate, and organic sulfur peroxide decomposers such as 2-mercaptobenzimidazole. The amount of the antioxidant to be added is preferably 0.01 part by mass or more and 1 part by mass or less, more preferably 0.1 part by mass or more and 0.5 part by mass with respect to 100 parts by mass of the styrene resin in the styrene resin composition. Part by mass or less.

The flame retardant is not limited to the following, but from the viewpoint of flame retardancy and compatibility with styrene resins, for example, hexabromocyclododecane, brominated SBS block polymer, and 2,2-bis(4'( brominated flame retardants such as 2″,3″-dibromoalkoxy)-3′,5′-dibromophenyl)-propane, and brominated bisphenol flame retardants.

Examples of brominated bisphenol flame retardants include, but are not limited to, tetrabromobisphenol A, tetrabromobisphenol A-bis(2,3-dibromopropyl ether), tetrabromobisphenol A-bis(2,3-dibromo -2 methylpropyl ether), tetrabromobisphenol S, tetrabromobisphenol S-bis(2,3-dibromopropyl ether), tetrabromobisphenol S-bis(2,3-dibromo-2 methylpropyl ether), tetrabromobisphenol F, Tetrabromobisphenol F-bis(2,3-dibromopropyl ether), Tetrabromobisphenol F-bis(2,3-dibromo-2-methylpropyl ether) Tetrabromobisphenol A-bis(allyl ether), Tetrabromobisphenol A polycarbonate oligomer, epoxy group adduct of tetrabromobisphenol A oligomer, and the like. Among the brominated bisphenol flame retardants, especially tetrabromobisphenol A bis(2,3-dibromopropyl ether) and tetrabromobisphenol A-bis(2,3-dibromo-2 methylpropyl ether) is preferable because it is difficult to decompose when kneaded with a polystyrene resin and tends to exhibit a high flame retardant effect. Combined use of tetrabromobisphenol A-bis(2,3-dibromopropyl ether) and tetrabromobisphenol A-bis(2,3-dibromo-2methylpropyl ether) improves flame retardancy and thermal stability. It is more preferable because it tends to be excellent.

When using a brominated flame retardant, it is preferable to use a brominated isocyanurate flame retardant together as a flame retardant aid. Brominated isocyanurate flame retardants include, but are not limited to, mono(2,3-dibromopropyl)isocyanurate, di(2,3-dibromopropyl)isocyanurate, and tris(2,3-dibromo propyl)isocyanurate, mono(2,3,4-tribromobutyl)isocyanurate, di(2,3,4-tribromobutyl)isocyanurate, tris(2,3,4-tribromobutyl)isocyanurate, etc. are mentioned. Among brominated isocyanurates, tris(2,3-dibromopropyl)isocyanurate is particularly preferred because it exhibits an extremely high flame retardant effect.

The content of the brominated flame retardant is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 1 part by mass or more and 9 parts by mass with respect to 100 parts by mass of the styrene resin in the styrene resin composition. It is not more than 2 parts by mass, and more preferably 2 parts by mass or more and 8 parts by mass or less. When the amount is 0.1 parts by mass or more, flame retardancy tends to be sufficiently ensured, and when the amount is 10 parts by mass or less, moldability tends to be sufficiently good when producing a foam sheet. be.

The above liquid paraffin can be selected from, for example, liquid paraffins stipulated by the Food Sanitation Law, standards for foods, additives, and the like. Specific examples of this type of liquid paraffin include, but are not limited to, Crystal N52, Crystal N62, Crystal N72, Crystal N82, Crystal N122, Crystal N172, and Crystal which are commercially available from ExxonMobil. Stall N262, Crystal N352, Primol N542 and the like. In addition, Moresco White P-40, Moresco White P-55, Moresco White P-60, Moresco White P-70, Moresco White P-80, Moresco White P-80, Moresco White P-40, Moresco White P-55, Moresco White P-80, which are commercially available from Matsumura Oil Laboratory Co., Ltd. SCOWHITE P-85, MORESCO WHITE P-100, MORESCO WHITE P-120, MORESCO WHITE P-150, MORESCO WHITE P-200, MORESCO WHITE P-230, MORESCO WHITE P-260, MORESCO Examples include White P-300, Moresco White P-350, Moresco White P-350P, and the like. Furthermore, liquid paraffin 40-S, 60-S, 70-S, 80-S, 90-S, 100-S, 120-S, 150-S, 260-S commercially available from Sanko Kagaku Kogyo Co., Ltd. , 350-S and the like. Also included is white mineral oil commercially available from CK Witco Corporation.

The molecular weight of the liquid paraffin is usually defined by kinematic viscosity. As the liquid paraffin in the present embodiment, for example, one having a kinematic viscosity at 40° C. defined by the test method JIS K2283 in the range of 0.1 to 60 mm ^{2 /} sec can be used. things are preferred. The weight average molecular weight of liquid paraffin is preferably in the range of 150-500, more preferably in the range of 180-450, even more preferably in the range of 200-350. The weight average molecular weight can be obtained by taking the weight average value of each molecular weight component of liquid paraffin using, for example, gas chromatography. When liquid paraffin having this viscosity range or molecular weight range is used, the obtained styrenic resin composition is greatly plasticized compared to liquid paraffin having a higher viscosity or a higher molecular weight, and the moldability of the styrenic resin composition is improved. , for example, tends to greatly improve the surface gloss of molded articles. The use of liquid paraffin with a viscosity of 0.1 mm ² /sec or more or a weight average molecular weight of 150 or more effectively prevents mold contamination and bleeding onto the molded product surface during molding of the obtained styrene resin composition. It is preferred because it tends to suppress.

The content of liquid paraffin in the styrene resin composition is preferably less than 3.0 parts by mass, more preferably less than 1.0 parts by mass, and still more preferably It is less than 0.5 parts by mass. When the content of liquid paraffin is less than 5.0 parts by mass, it is possible to obtain a molded article having excellent balance between secondary molding processability, strength and heat resistance of the molded article.

Further, in the present embodiment, it is preferable to add the heat deterioration inhibitor in the polymerization step or the devolatilization step of the styrene-based resin composition, or after the polymerization step and before the devolatilization step. In particular, it is preferable to add the thermal deterioration inhibitor after (preferably immediately after) the polymerization step and before the devolatilization step. By adding a thermal degradation inhibitor, it is possible to stabilize radicals generated by thermal decomposition and reduce the amount of thermal decomposition.

As the heat deterioration inhibitor, for example, 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, manufactured by Sumitomo Chemical Co., Ltd. ), 2-[1-(2-hydroxy-3,5-di-t-phenylpentyl)ethyl]-4,6-di-t-phenylpentyl acrylate (trade name: Sumilizer GS, manufactured by Sumitomo Chemical Co., Ltd.), Phenolic heat deterioration inhibitors such as 2,4-bis(octylthiomethyl)-6-methylphenol (trade name: Irganox 1520L) and octadecyl-3-(3,5-tert-butyl-4-hydroxyphenyl) propionate , 4,6-bis(octylthiomethyl)-o-cresol and other hindered phenol-based antioxidants, tris (2,4-di-tert-butylphenyl) phosphite and other phosphorus-based processing heat stabilizers, etc. can be mentioned. These heat deterioration inhibitors may be used either singly or in combination of two or more.

The content of the heat deterioration inhibitor is preferably 0.01 to 0.5 parts by mass, more preferably 0.02 to 0, per 100 parts by mass of the styrene resin in the styrene resin composition at the exit of the final reactor. .3 parts by mass, more preferably 0.03 to 0.2 parts by mass.
By setting the content of the heat deterioration inhibitor to 0.01 to 0.5 parts by mass, the content of the dimer trimer can be appropriately adjusted.

<<Method for producing styrene resin composition>>
The styrene-based resin composition of the present embodiment includes, for example, a styrene-based resin obtained by radically polymerizing the above-described monovinyl compound, a conjugated divinyl compound and/or a multi-branched vinyl compound by the above-described production method, and the above-described additive. and the like can be obtained by a method of melt-kneading using a known kneader such as a single-screw extruder, a twin-screw extruder, and a Banbury mixer. The styrene-based resin composition of the present embodiment may be manufactured by appropriately adding the above-described additives and the like in the manufacturing process of the styrene-based resin described above.

《Foam sheet》
The foam sheet of the present embodiment contains the styrene-based resin composition of the embodiment of the present invention, and can have a thickness of 0.5 to 5.0 mm. The foam sheet of the present embodiment preferably has an apparent density of 50 to 300 g/L and a basis weight of 80 to 300 g/m ² .
The foamed sheet of this embodiment may be laminated with a film on the sheet. As for the type of film, those used for general polystyrene can be used.
According to the foamed sheet of the present embodiment, it is possible to obtain a molded article that is excellent in moldability of the sheet and excellent in recyclability.

For the foaming agent and foaming nucleating agent contained in the foamed sheet of the present embodiment, commonly used substances can be used. The foaming agent is not particularly limited, but examples thereof include butane, pentane, freon, and water, with butane being preferred. Examples of the foam nucleating agent include, but are not particularly limited to, inorganic powders such as talc, calcium carbonate, and clay, with talc being preferred.

<Amount of residual styrene monomer in foamed sheet>
The residual amount of styrene monomer in the foam sheet of the present embodiment is preferably 10 to 500 ppm by mass, more preferably 20 to 300 ppm by mass, and still more preferably 30 to 200 mass ppm relative to 100% by mass of the foam sheet. mass ppm. When the residual amount of the styrene monomer is 10 to 500 ppm by mass, the odor of the foam sheet can be reduced.
In the present disclosure, the residual amount of styrene monomer is a value measured using gas chromatography (GC).

<<Method for manufacturing foam sheet>>
The method for producing the foamed sheet of the present embodiment can be carried out using a commonly known method. For example, although not particularly limited, a method of melt-kneading the styrenic resin composition, foaming agent, and foaming nucleating agent in the present embodiment with an extruder and extruding the mixture is described in more detail below.
First, an extruder connected to a circular die melts and kneads the styrene-based resin composition in the present embodiment, and the melt-kneaded product is foamed from an annular opening provided in front of the circular die. extruded in situ to form a cylindrical foam. Next, the foam is cooled while being stretched in the circumferential direction by being brought into sliding contact with the outer peripheral surface of a cooling mandrel having a larger diameter than the opening of the circular die, and is continuously cut along the extrusion direction to develop. A commonly known method can be used.

《Non-foam sheet》
The non-foamed sheet of the present embodiment contains the styrene-based resin composition of the embodiment of the present invention and has a thickness of 1 μm or more and 5 mm or less.
In this embodiment, the non-foamed sheet may be multilayered with a film or sheet on the sheet. As the type of resin for multilayering, those used for general polystyrene can be used.
According to the non-foamed sheet of the present embodiment, it is possible to obtain a molded article that is excellent in moldability of the sheet and excellent in recyclability.

<<Manufacturing method of non-foam sheet>>
In this embodiment, the method of manufacturing the non-foamed sheet can be an old term that uses a commonly known method. The styrenic resin composition may be produced by any conventionally known molding method, including, but not limited to, inflation molding, extrusion molding, melt-kneading, extrusion through a die, and compression molding. . In the present embodiment, the conditions for producing the extruded sheet containing the styrenic copolymer are not particularly limited, but the resin temperature is preferably in the range of 150 to 250°C.

"Molding"
The molded article in this embodiment can be a secondary molded article of the foamed sheet or non-foamed sheet of the embodiment of the present invention. A molded article can be obtained by subjecting the foamed sheet or non-foamed sheet of the above-described embodiments to secondary molding by a conventionally known method such as vacuum forming, pressure forming, vacuum pressure forming, double-sided vacuum forming, and press molding. can. Examples of molded articles obtained from non-foamed sheets include secondary molded articles such as trays, cups, rice bowl containers, and natto containers. A secondary molded product such as a container for containing.
As an example of the secondary molded product of this embodiment, the foamed sheet of this embodiment is used as a molding material, and is extruded by a vacuum molding machine with the horizontal direction as the extrusion direction. Food tray containers with a depth of 1.1 to 3.4 cm can be mentioned. Although the temperature conditions for vacuum molding are not particularly limited, 120 to 150° C. is usually preferred.

As a molding method, injection molding, extrusion molding, vacuum molding, air pressure molding, extrusion foam molding, calendar molding, blow molding, etc. can be suitably used, and various molded products can be obtained for a wider range of applications than before.

EXAMPLES Hereinafter, embodiments of the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

《Measurement and evaluation method》
Measurement and evaluation methods are as follows.

(1) Measurement of number of moles of conjugated divinyl compound contained per 1 mole of styrene The number of moles of the conjugated divinyl compound contained per 1 mole of styrene in the styrene-based resin composition was measured using ¹ H-NMR and ¹³ C-NMR. bottom. As a measuring device, JEOL-ECA500 manufactured by JEOL Ltd. was used. Chloroform-d1 was used as solvent and the resonance line of tetramethylsilane was used as internal standard.

(2) Measurement of Melt Mass Flow Rate (MFR) The melt mass flow rate (g/10 minutes) of the styrene-based resin composition was measured under conditions of 200° C. and 49 N load according to ISO1133.

(3) Measurement of Total Content of Styrene Dimer and Trimer The total remaining amount of styrene dimer and trimer (mass ppm) in the styrene resin composition was measured under the following conditions and procedures.
・Sample preparation: After dissolving 1.0 g of the styrene resin composition in 10 mL of methyl ethyl ketone, 3 mL of methanol containing a standard substance (triphenylmethane) was added to reprecipitate the polymer component, and the supernatant was collected and used as a 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 mmφ
Injection volume: 1 μL (splitless)
Column temperature: Hold at 40°C for 1 minute → Heat up to 320°C at 20°C/min → Hold at 320°C for 10 minutes Inlet temperature: 250°C
Detector temperature: 280°C
Carrier gas: helium

(4) Melt Tension The melt tension (g) of the styrene-based resin composition was measured under the following conditions.
Device name: Capillary rheometer RH10 (manufactured by Malvern)
Measurement temperature: 190°C
Extrusion speed: 20 mm/min Take-up speed: 3.1 m/min Drying conditions: The styrene-based resin composition was dried at 80°C for 3 hours before measurement.
cylinder diameter 15mm,
capillary die length: L=16 mm,
Capillary die diameter: D = 1 mm (L/D = 16)
Under the above measurement conditions, the range in which the load was stable was averaged to obtain the melt tension value. If the strand breaks during take-off or if the coefficient of variation of the load exceeds 10%, the measurement cannot be performed.

(5) Measurement of molecular weight Number average molecular weight (Mn), weight average molecular weight (Mw), Z average molecular weight (Mz), Mz/Mw, Mw/Mn, peak top molecular weight (Mtop), predetermined molecular weight component of styrene resin composition The content of was measured under the following conditions using gel permeation chromatography (GPC).
Apparatus: Tosoh HLC-8220
Separation column: Two TSK gel Super HZM-H manufactured by Tosoh (inner diameter 4.6 mm) connected in series Guard column: TSK guard column Super HZ-H manufactured by Tosoh
Measurement solvent: tetrahydrofuran (THF)
Sample concentration: 5 mg of a sample to be measured was dissolved in 10 mL of solvent and filtered through a 0.45 μm filter.
Injection volume: 10 μL
Measurement temperature: 40°C
Flow rate: 0.35 mL / min Detector: UV absorption detector (Tosoh UV-8020, wavelength 254 nm)
To create a calibration curve, 11 types of Tosoh 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) were used. A calibration curve was created using a first-order linear approximation formula.

(6) Measurement of Branching Degree and Gelation Degree The branching degree and gelation degree of the styrene-based resin composition were calculated by measuring the absolute molecular weight as follows.
The absolute molecular weight of the styrene-based resin composition was measured using a multi-angle light scattering detector (MALS) under the following conditions (hereinafter sometimes referred to as "MALS method").
Apparatus: GPCmax manufactured by Malvern
Fractionation column: Two Shodex KF806-Ls connected in series Guard column: Shodex GPC KFG-4A
Measurement solvent: tetrahydrofuran (THF)
Sample concentration: 10 mg of a sample to be measured was dissolved in 10 mL of solvent and filtered through a 0.45 μm filter.
Injection volume: 100 μL
Measurement temperature: 40°C
Flow rate: 1.00 mL/min Detector: Differential refractometer (TDA305 manufactured by Malvern)
MALS detector: Viscotek SEC-MALS 20 manufactured by Malvern
MALS detection angle: 12°, 20°, 28°, 36°, 44°, 52°, 60°, 68°, 76°, 84°, 90°, 100°, 108°, 116°, 124°, 132° , 140°, 148°, 156°, 164°
MALS detector temperature: 40°C
PS105K was used as a standard sample, and the analysis was performed using the analysis software OmniSEC5.1 using the linear equation of the Berry plot.

After the measurement by the MALS method, a graph was prepared with log molecular weight on the horizontal axis and log radius of gyration on the vertical axis. In this graph, for linear polystyrene (PS245K), a linear approximation line is created in the range of 5.0 to 6.0 for the log molecular weight, and this is used as the reference value for linear polystyrene without a branched structure. and
Here, the values of log radius of gyration when the values of log molecular weight are 6.0 and 6.5 are defined as <Rg6.0> and <Rg6.5>, respectively, and <Rg6.0> of PS245K, <Rg6.5> is defined as <Rg6.0> ₂₄₅ and <Rg6.5> ₂₄₅ respectively. <Rg6.5> ₂₄₅ can be calculated from the extrapolated value of the approximate straight line.
The degree of branching is defined as degree of branching=<Rg6.5>/<Rg6.5> ₂₄₅ . This degree of branching means how small the radius of gyration is relative to PS245K, which is linear polystyrene, at an absolute molecular weight of 10 ^6.5 = 3,160,000. It represents a branch.
The degree of gelation is defined as degree of gelation=(<Rg6.0>/<Rg6.0> ₂₄₅ )/(<Rg6.5>/<Rg6.5> ₂₄₅ ). The degree of gelation represents the rate of change in the radius of gyration of the polymer from absolute molecular weight 10 ^6.0 to 10 ^6.5 . In other words, it means how much branching increases as the molecular weight increases.

(7) Vicat softening temperature The Vicat softening temperature (°C) of the styrene-based resin composition was measured according to JIS K7206. The load was 49N, and the heating rate was 50°C/h.

(8) Measurement of maximum rise ratio The maximum rise ratio of the styrene-based resin composition was measured based on the following viscoelasticity measurement.
Device name: Viscoelasticity measuring device ARES-G2 (manufactured by TA Instruments)
Measurement system: ARES-EVF option Specimen dimensions: length 20 mm, thickness 0.7 mm, width 10 mm
Elongation strain rate: 0.01/sec Temperature: 150°C
Measurement atmosphere: in nitrogen stream Preheating time: 2 minutes Pre-elongation strain rate: 0.03/sec,
Pre-stretched length: 0.295mm
Relaxation time after pre-stretching: 2 minutes For viscoelasticity measurement, the test piece was attached to a roller, and after the temperature was stabilized at the measurement temperature, the specimen was allowed to stand still for the above preheating time and preheated. After preheating, pre-stretching was performed under the above conditions. After pre-stretching, it was allowed to stand still for 2 minutes to relax the stress generated by the pre-stretching and measured.

From the results obtained from the above viscoelasticity measurements, create a log-log graph plotting the Henky strain on the horizontal axis and the extensional viscosity on the vertical axis. A linear region straight line of exponential approximation was constructed. When strain hardening occurs, the actual elongational viscosity becomes larger than the elongational viscosity of the approximation curve extrapolated from this linear region.
The maximum rise ratio is obtained by taking the Henky strain at the maximum elongational viscosity in the above viscoelasticity measurement as the maximum rise strain, (the elongation viscosity in the nonlinear region at the maximum rise strain / the approximate straight line extrapolating the linear region at the maximum rise strain elongational viscosity).

(9) Evaluation of Sheet Deep Drawability A 30 mmφ sheet extruder (manufactured by Soken Co., Ltd.) was used to extrude the styrene-based resin composition to prepare a sheet with a thickness of 0.5 mm. From the obtained sheet, 20 test pieces with a size of 250 mm in length × 250 mm in width were cut out, and a sheet container molding machine manufactured by Soken Co., Ltd. was used. ° C., the ambient temperature was set to 110° C., and heating was performed for 20 seconds. Next, the fixed frame was slid into a bowl container mold (temperature: 40° C.) having a diameter of 10 cm and a depth of 10 cm, and vacuum forming was performed to form 30 deep-drawn formed bodies. It was visually confirmed whether or not the sides of the molded body were torn, and the number of molded bodies that could be molded without tearing was used as an index of moldability.

(10) Measurement of the maximum moldable heating time of the sheet The heating time during the deep draw forming in (9) above is extended from 20 seconds to 1 second at a time, vacuum forming is performed without changing other conditions, and a formed body is obtained. 10 pieces were molded. As in (9), the heating time was extended until the number of compacts that could be molded decreased to 7 or less. The maximum heating time during which 8 or more sheets could be molded was defined as the maximum molding possible heating time (seconds) of the sheet and measured.

(11) Evaluation of Deep Drawability of Foam Sheet The foam sheet was allowed to stand at 23±3° C. and a relative humidity of 50±5% for 20 days. After that, using a sheet container molding machine manufactured by Soken Co., Ltd., the foamed sheet was sandwiched between the fixed frames of the sheet molding machine, and the average temperature of the heater was set to 200° C. and the atmospheric temperature was set to 130° C. for 15 seconds. Next, the fixed frame was slid into a cup-shaped mold (temperature: 40°C) having a diameter of 10 cm and a depth of 3 cm or 6 cm, and vacuum forming was performed to form 100 formed bodies. The side faces of the molded body were visually checked for tearing, and the number of molded bodies that could be molded without tearing was used as an index of deep drawability.

(12) Measurement of the maximum moldable heating time of the foam sheet At the time of deep draw molding in (11) above, the heating time is extended from 15 seconds to 1 second at a time, and vacuum molding is performed without changing other conditions. 10 bodies were molded. As in (11), the heating time was extended until the number of foamed sheets that could be formed into a molded body decreased to 7 or less. The maximum heating time during which 8 or more moldings could be molded was defined as the maximum molding possible heating time (seconds) of the foamed sheet, and measured.

(13) Recyclability Using a twin-screw extruder (manufactured by Nakatani Kikai Co., Ltd.: AS20-2), the temperature of the three zones in the screw is controlled to 180, 200, and 220 ° C. in the order in which the resin passes. Three push extrusions were performed. The molecular weights of the styrenic resin composition before extrusion and the styrenic resin composition after being extruded three times were measured by the above GPC.
Regarding the molecular weight obtained by measurement, the ratio of components with a molecular weight of 50,000 or less in the styrene resin composition before extrusion to the ratio of components with a molecular weight of 50,000 or less in the styrene resin composition after extrusion three times. (“ratio of components with a molecular weight of 50,000 or less after three extrusions”/“ratio of components with a molecular weight of 50,000 or less before extrusion”) was used as an index of recyclability.

"material"
The following materials were used in Examples and Comparative Examples.

<Styrene resin>
<Monovinyl compound>
Styrene monomer [manufactured by Asahi Kasei]
Butyl acrylate [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.]

<Conjugated divinyl compound>
<Conjugated divinyl compound 1>
Polybutadiene-terminated acrylate [manufactured by Osaka Organic Chemical Industry Co., Ltd.: BAC-45] Mn: 4800

<Conjugated divinyl compound 2>
Urethane acrylate oligomer [manufactured by Tomoe Industry: CN9014NS] Mn: 8000

<Conjugated divinyl compound 3>
Conjugated divinyl compound 3 was produced according to the following method.
37522 g of polybutadiene double-ended alcohol (Mn: 26000), 379 g of methyl acrylate, 380 g of n-hexane, 0.8194 g of hydroquinone monomethyl ether, and 4 -Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl 0.5533 g was charged. The obtained mixture was dehydrated under reflux at 80 to 85°C by blowing air into the mixture while passing it through a calcium chloride tube. The water content in this mixture was measured by the Karl Fischer method, and it was confirmed that the water content was 200 ppm or less. Thereafter, 1.3685 g of tetra-n-butyl titanate was added as a transesterification catalyst to the above mixture, and the resulting methanol was distilled out of the reaction system under reflux of the azeotropic solvent, n-hexane, while stirring. and a reaction temperature of 80-85° C. for 10 hours.
Next, the temperature in the reaction vessel is adjusted to 75 to 80° C., and the mixture is concentrated at a reduced pressure of 70 to 2 kPa until 95% or more of the methyl acrylate and n-hexane used is distilled off, and excess methyl acrylate is removed. n-Hexane was recovered. To 2070 g of the resulting polybutadiene both-ended diacrylate, 2000 g of toluene, 200 g of acetone, 20 g of ion-exchanged water, and hydrotalcite (composition formula Mg ₆ Al ₂ (OH) 16CO _{3.4H 2} O) as a transesterification catalyst [Kyowa Chemical Kogyo Co., Ltd., trade name: Kyoward 500PL] was added, and the mixture was treated at 75 to 80°C for 2 hours. Next, the temperature in the reaction vessel is adjusted to 75 to 80° C., and concentration is performed at a reduced pressure of 90 to 35 kPa to recover 400 g of a mixed distillate of toluene, acetone and water. The catalyst and adsorbent were separated by filtration under pressure, and the solvent was degassed at a temperature of 60-80° C. and a reduced pressure of 30-0.8 kPa to obtain a conjugated divinyl compound 3.
The conversion rate of polybutadiene both-terminated diacrylate of conjugated divinyl compound 3 was measured by high performance liquid chromatography (HPLC) and found to be 99.0%. In addition, the polystyrene equivalent number average molecular weight (Mn) measured by GPC was 26,000.

<Conjugated divinyl compound 4>
Conjugated divinyl compound 4 was produced according to the following method.
Conjugated divinyl compound 4, which was produced under the same conditions as for conjugated divinyl compound 3, except that the molecular weight of the alcohol at both ends of polybutadiene was changed to Mn: 58000, had a conversion rate of diacrylate at both ends of polybutadiene of 98.5%. rice field. Further, the number average molecular weight (Mn) in terms of polystyrene measured by GPC was 58,000.

<Multi-branched vinyl compound>
<Multi-branched vinyl compound 1>
Divinylbenzene 3.1 mol (399.4 g), ethylvinylbenzene 0.7 mol (95.1 g), styrene 0.3 mol (31.6 g), 2-phenoxyethyl methacrylate 2.3 mol (463.5 g) , 974.3 g of toluene was charged into a 3.0 L reactor, 42.6 g of boron trifluoride diethyl ether complex was added at 50° C., and the reaction was allowed to proceed for 6.5 hours. After stopping the polymerization reaction with a sodium bicarbonate solution, the oil layer was washed with pure water three times, and the reaction mixture was poured into a large amount of methanol at room temperature to precipitate a polymer. The obtained polymer was washed with methanol, separated by filtration, dried and weighed to obtain 372.5 g of multi-branched vinyl compound 1.
The weight average molecular weight (Mw) of this multi-branched vinyl compound 1 is 8000, the mole fraction of the structural unit (a1) containing a vinyl group derived from the divinyl compound is 0.44, and the terminal 2-phenoxyethyl methacrylate-derived The double bond (a2) was 0.03, and the total molar fraction (a3) of both was 0.47. The radius of inertia of the polymer with a weight average molecular weight (Mw) of 8000 was 6.3 nm. The ratio of the radius of gyration of the present polymer to the mole fraction of double bonds is 13.4, and the radius of gyration of the linear weight average molecular weight (Mw) of 8000 is 15 nm. It can be seen that the multi-branched vinyl compound 1 in Synthesis Example has a branched structure.

<Multi-branched vinyl compound 2>
In a 2-liter flask equipped with a stirrer, thermometer, dropping funnel and condenser, at room temperature, 50.5 g of ethoxylated pentaerythritol (ethylene oxide-added pentaerythritol) disclosed in JP-A-2016-113598, BF ₃ diethyl ether 1g of solution (50%) was added and heated to 110°C. To this, 450 g of 3-ethyl-3-(hydroxymethyl)oxetane was slowly added over 25 minutes while controlling the heat generated by the reaction. After the exotherm subsided, the reaction mixture was further stirred at 120° C. for 3 hours and then cooled to room temperature. The resulting multi-branched polyether polyol had a weight average molecular weight of 3,000 and a hydroxyl value of 530.
In a reactor equipped with a Dean-Stark decanter equipped with a stirrer, a thermometer, a condenser and a gas inlet tube, 50 g of the multi-branched polyether polyol obtained above, 13.8 g of methacrylic acid, 150 g of toluene, 0.06 g of hydroquinone, para 1 g of toluenesulfonic acid was added, and the mixed solution was stirred and heated under normal pressure while blowing 7% oxygen-containing nitrogen (v/v) into the mixed solution at a rate of 3 mL/min. The amount of heating was adjusted so that the amount of distillate in the decanter was 30 g per hour, and heating was continued until the amount of dewatering reached 2.9 g. After completion of the reaction, the mixture was cooled once, 36 g of acetic anhydride and 5.7 g of sulfamic acid were added, and the mixture was stirred at 60° C. for 10 hours. After that, in order to remove the remaining acetic acid and hydroquinone, it was washed four times with 50 g of a 5% aqueous sodium hydroxide solution, once with 50 g of a 1% aqueous sulfuric acid solution, and twice with 50 g of water. 0.02 g of methoquinone was added to the obtained organic layer, and the solvent was distilled off under reduced pressure while introducing 7% oxygen-containing nitrogen (v/v) to obtain a hyperbranched vinyl compound 2 having an isopropenyl group and an acetyl group. 60 g was obtained. The weight-average molecular weight of the resulting multi-branched vinyl compound 2 was 3,900, and the introduction rates of isopropenyl groups and acetyl groups into the multi-branched polyether polyol were 30 mol% and 62 mol%, respectively, based on the total hydroxyl groups. Met.

<Additive>
・ Thermal deterioration inhibitor 1: 2-[1-(2-hydroxy-3,5-di-t-phenylpentyl)ethyl]-4,6-di-t-phenylpentyl acrylate [manufactured by Sumitomo Chemical Co., Ltd.: Sumilizer GS]
· Thermal degradation inhibitor 2: octadecyl-3-(3,5-di-tertiary-butyl-4-hydroxyphenyl)-propionate [manufactured by BASF Japan Ltd.: Irganox 1076]
・ Thermal deterioration inhibitor 3: Tris (2,4-di-tertiary-butylphenyl) phosphite [manufactured by BASF Japan Ltd.: Irgafos 168]

<others>
・Polymerization initiator 1: 2,2-bis (4,4-di-tertiary-butylperoxycyclohexyl) propane [manufactured by NOF Corporation: Pertetra A]
・Polymerization initiator 2: 1,1-di-(tertiary-butylperoxy)cyclohexane [manufactured by NOF Corporation: Perhexa C]
-Chain transfer agent 1: α-methylstyrene dimer [NOFMER MSD manufactured by NOF CORPORATION]

<Example 1>
84 parts by mass of styrene monomer, 16 parts by mass of ethylbenzene, 0.14 parts by mass of the above-described conjugated divinyl compound 1 (3.6 × 10 ^-5 mol per 1 mol of styrene), 0.038 parts of polymerization initiator 1 Parts by mass were added to prepare a raw material solution to be supplied to the first reactor. The prepared raw material solution was continuously fed at a rate of 0.73 L/hour to a complete mixing type first reactor having an internal volume of 5.4 L maintained at a temperature of 101.5°C.
Next, 68 parts by mass of styrene monomer, 32 parts by mass of ethylbenzene, 0.15 parts by mass of chain transfer agent 1, and 0.05 parts by mass of polymerization initiator 2 are added, and the raw material solution supplied to the second reactor. adjusted. 0.2 L/ fed continuously over time.
Next, the polymerization solutions from the first reactor and the second reactor were combined, and the temperatures of the four zones were kept at 135, 155, 160, and 150°C in the order in which the raw material solutions passed through, and the internal volume was 3 L. It was fed to a plug flow third reactor. In zone 3 of the third reactor, 0.14 parts by mass of heat deterioration inhibitor 1 was added. (In this example, the polymerization initiator was added from zone 1 of the third reactor, and the thermal degradation inhibitor was added from zone 3 of the third reactor.)
Next, the polymerization solution from the third reactor was supplied to a vacuum degassing tank heated to a temperature of 240° C. to remove volatile components such as unreacted monomers and solvents. A styrene resin composition for was obtained.
Furthermore, to 100 parts by mass of the above styrene resin composition, 0.15 parts by mass of talc (average particle diameter 1.3 μm) as a foaming nucleating agent and 4 parts by mass of liquefied butane as a foaming agent are added to form a foamed sheet. got the raw material. Using an extrusion foaming machine equipped with a circular die with a diameter of 150 mm, the foam sheet raw material was extruded and foam-molded. The resin melting zone temperature of the extrusion foaming machine was adjusted to 200 to 230°C, the rotary cooler temperature to 130 to 170°C, and the die temperature to 135 to 155°C. A foam sheet having a thickness of 1.4 mm and a width of 1000 mm was obtained by cooling the foam immediately after extrusion and foaming with a cooling mandrel and cutting it with a cutter at one point on the circumference.
Table 1 shows the production conditions and analysis results of Example 1.

<Examples 2 to 11>
Examples 2 to 11 were carried out in the same manner as in Example 1 except that the conditions were changed as shown in Table 1 to obtain styrenic resin compositions. Table 1 summarizes the measurement and evaluation results of Examples 2 to 11.

<Comparative Examples 1 to 5>
Comparative Examples 1 to 5 were carried out in the same manner as in Example 1 except that the conditions were changed as shown in Table 1 to obtain styrenic resin compositions. Table 1 summarizes the measurement and evaluation results of Comparative Examples 1 to 5. In Comparative Example 2, the butyl acrylate monomer as a raw material was added to the raw material solution together with other raw materials when preparing the raw material solution.

As is clear from Table 1, in Comparative Example 5, the melt mass flow rate (MFR) measured under the conditions of 200° C. and 49 N load was as small as 0.8 g/10 min, and the recyclability was low. Moreover, in Comparative Examples 1 to 3, in which the total content of styrene dimer and trimer was 2500 ppm or less, the recyclability was low. Furthermore, in Comparative Example 3 in which the melt tension value (MT) was 39.7 gf, the deep drawability of the sheet and the foamed sheet was low, and the moldability was low. In addition, in Comparative Examples 3 and 4 in which the content of the component having a molecular weight of 1,000,000 or more was 4.2% by mass and 5.8% by mass, the deep drawability of the sheet and foamed sheet was low, and the moldability was low. .

On the other hand, the melt mass flow rate (MFR) measured under the conditions of 200 ° C. and 49 N load is 1.0 to 5.0 g / 10 minutes, the total content of styrene dimer and trimer is more than 2500 μg / g, The melt tension value (MT) measured at 190° C. is 40 to 80 gf, and the content of components having a molecular weight of 1,000,000 or more is 7.0 to 15.0% by mass in 100% by mass of the styrene resin composition. , the styrenic resin compositions of Examples 1 to 11 are found to have an excellent balance between moldability and recyclability.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the gist of the invention.

The styrenic resin composition according to the present invention has an excellent balance between moldability and recyclability, and therefore can be widely used as a molding material for home appliances, office equipment, miscellaneous goods, housing equipment, food packaging materials, and the like.

Claims (1)

The melt mass flow rate (MFR) measured under the conditions of 200° C. and 49 N load is 1.0 to 5.0 g/10 minutes,
The total content of styrene dimer and trimer is more than 2500 μg / g,
Melt tension value (MT) measured at 190 ° C. is 40 to 80 gf,
A styrenic resin composition, characterized in that the content of components having a molecular weight of 1,000,000 or more is 7.0 to 15.0% by mass in 100% by mass of the styrenic resin composition.