JP7639038B2 - Heat-resistant styrene resin, sheets and molded products - Google Patents

Description

The present invention relates to heat-resistant styrene-based resins, sheets, and molded articles.

Heat-resistant styrene resins have excellent heat resistance and are used as a raw material for packaging materials such as food containers and foam boards for home insulation. In particular, for packaging material applications, foam sheets of heat-resistant styrene resins are post-molded into various shapes, taking advantage of their excellent characteristics such as cushioning and insulation, and are widely used for food trays, lunch boxes, cups, etc. In recent years, there has been a demand for products to be thinner, lighter, and have a more diverse shape, and styrene resins with good appearance and excellent moldability are in demand.

As a method for obtaining such a resin, Patent Document 1 describes that a styrene-methacrylic acid copolymer resin composition having excellent heat resistance, no gel-like matter, and excellent melt viscoelastic properties during molding can be produced by introducing a copolymer of a monovinyl aromatic compound essentially containing styrene, methacrylic acid, and a solvent-soluble multifunctional vinyl copolymer.
Patent Document 2 also describes that by using a composition containing a styrene-methacrylic acid copolymer resin having a specific range of methacrylic acid amount, weight average molecular weight, proportion of components having a molecular weight of 1,000,000 or more, and melt tension, it is possible to obtain an extruded foam sheet that maintains impact resistance and heat resistance while eliminating the problem of powder generation, and a foamed container obtained by thermoforming the extruded foam sheet.

JP 2013-100433 A JP 2014-201708 A

However, it has been found that the copolymer described in Patent Document 1 is insufficient in moldability and there is room for further improvement. It has also been found that the copolymer resin described in Patent Document 2 is insufficient in moldability and there is room for further improvement.
In addition, when a foamed sheet of a heat-resistant styrene-based resin is subjected to secondary molding, a large number of moldings are performed at once, which causes variations in the degree of heating of the sheet. In the case of a heat-resistant styrene-based resin having a narrow range of molding conditions, the yield of molded products is reduced.

The present invention was devised in light of the above-mentioned conventional situation, and the object of the present invention is to provide a heat-resistant styrene-based resin, foamed and non-foamed sheets, and molded products that have excellent moldability, a wide range of molding conditions, and can be used to produce molded products such as sheets with good appearance.

The inventors have conducted intensive research to achieve the above object, and as a result have discovered that by controlling the degree of branching and gelation of the heat-resistant styrene resin, the content of components with absolute molecular weights of 1 to 5 million measured using a multi-angle light scattering detector (MALS), the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured using gel permeation chromatography (GPC), the ratio (Mz/Mw) of the z-average molecular weight (Mz) to the weight average molecular weight (Mw), and the Vicat softening temperature within appropriate ranges, it is possible to obtain a heat-resistant styrene resin that has excellent moldability, a wide range of molding conditions, and can be used to produce molded products such as sheets with good appearance, and has completed the present invention.

That is, the present invention is as follows.
[1] The degree of branching is 0.60 to 0.95,
The gel degree is 1.10 to 1.80,
The content of components having an absolute molecular weight of 1 million to 5 million as measured using a multi-angle light scattering detector (MALS) is 5.0 to 14.0%;
The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is 4.0 to 7.0;
the ratio of z-average molecular weight (Mz) to weight-average molecular weight (Mw) (Mz/Mw) is 2.0 to 5.0;
A heat-resistant styrene-based resin having a Vicat softening temperature of 105 to 130°C.
[2] The heat-resistant styrene-based resin according to [1] above, containing 2.0 to 17.0% by mass of a methacrylic acid monomer in 100% by mass of the heat-resistant styrene-based resin.
[3] The heat-resistant styrene-based resin according to [1] or [2] above, having a maximum rise ratio of 1.2 to 5.0.
[4] The heat-resistant styrene-based resin according to any one of [1] to [3] above, which has a peak top molecular weight (Mtop) measured by GPC of 100,000 to 180,000.
[5] A foamed sheet comprising the heat-resistant styrene-based resin according to any one of [1] to [4] above and having a thickness of 0.5 to 5.0 mm.
[6] A molded article comprising the foamed sheet according to [5] above.
[7] A non-foamed sheet comprising the heat-resistant styrene-based resin according to any one of [1] to [4] above.
[8] A molded article comprising the non-foamed sheet according to [7] above.

The present invention provides heat-resistant styrene-based resins, foamed and non-foamed sheets, and molded articles that have excellent moldability, a wide range of molding conditions, and can be used to produce molded articles such as sheets with good appearance.

The following describes an embodiment of the present invention (hereinafter, "the present embodiment"); however, the present invention is not limited to this embodiment.

{Heat-resistant styrene resin}
The heat-resistant styrene-based resin of the present embodiment has a branching degree of 0.60 to 0.95,
The gel degree is 1.10 to 1.80,
The content of components having an absolute molecular weight of 1 million to 5 million as measured using a multi-angle light scattering detector (MALS) is 5.0 to 14.0%;
The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is 4.0 to 7.0;
the ratio of z-average molecular weight (Mz) to weight-average molecular weight (Mw) (Mz/Mw) is 2.0 to 5.0;
It is characterized by having a Vicat softening temperature of 105 to 130°C.
According to the present embodiment, it is possible to provide a heat-resistant styrene-based resin that has excellent moldability, can be molded under a wide range of molding conditions, and can be used to produce molded products such as sheets having good appearance.

<Molecular weight of heat-resistant styrene resin>
The number average molecular weight (Mn) of the heat-resistant styrene-based resin of this embodiment is preferably 40,000 to 200,000, more preferably 50,000 to 180,000, and even more preferably 60,000 to 150,000.
The weight average molecular weight (Mw) of the heat-resistant styrene-based resin of the present embodiment is preferably 200,000 to 500,000, more preferably 220,000 to 480,000, and further preferably 240,000 to 450,000.
The heat-resistant styrene-based resin of the present embodiment preferably has a Z-average molecular weight (Mz) of 600,000 to 2,000,000, more preferably 700,000 to 1,800,000, and even more preferably 800,000 to 1,600,000.
By setting the content within the above range, it is possible to ensure the strength of the heat-resistant styrene-based resin, while suppressing the generation of gel-like substances, thereby improving the moldability and flowability.

The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the heat-resistant styrene-based resin of this embodiment is 4.0 to 7.0, preferably 4.2 to 6.5, more preferably 4.5 to 6.0, and even more preferably 4.7 to 5.9. If Mw/Mn is less than 4.0, the flowability may decrease, the moldability may decrease, and the molding condition range may become narrow. If Mw/Mn is more than 7.0, the amount of low molecular weight components may become extremely large, and the strength of the molded product may decrease.
In order to make the Mw/Mn ratio 4.0 to 7.0, for example, the reaction temperature during polymerization is increased in the order in which the reaction solution passes through, a chain transfer agent is used, the type of polymerization initiator is multifunctional (2, 3, 4 functional), and when a resin is produced by radical copolymerizing a monovinyl compound with a conjugated divinyl compound and/or a multi-branched vinyl compound, a conjugated divinyl compound or a multi-branched vinyl compound or both are added in an amount of preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ moles per mole of the total amount of the monovinyl compound. In addition, for example, in two reactors, polymerization is performed under conditions for polymerizing a low molecular weight component and conditions for polymerizing a high molecular weight component, respectively, and the two polymerization solutions are merged, or further polymerization is performed after merging. Conditions for polymerizing a 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 like. Conditions for polymerizing the high molecular weight component include, for example, a method of reducing the amount of solvent and lowering the polymerization temperature, a method of using a polyfunctional polymerization initiator, and a method of adding a conjugated divinyl compound or a multi-branched vinyl compound, or both, preferably in an amount of 2.0× ¹⁰ to 4.0× ¹⁰ moles per mole of the total amount of the monovinyl compounds.

The ratio (Mz/Mw) of the z-average molecular weight (Mz) to the weight-average molecular weight (Mw) of the heat-resistant styrene-based resin of this embodiment is 2.0 to 5.0, preferably 2.2 to 4.5, more preferably 2.5 to 4.0, and even more preferably 3.0 to 4.0. When Mz/Mw is less than 2.0, sufficient moldability may not be obtained. When Mz/Mw is more than 5.0, the flowability may decrease, moldability may decrease, the molding condition range may become narrow, the polymer component may become extremely large, the gel-like substance may increase, and the appearance of the molded product may deteriorate.
In order to make Mz/Mw 2.0 to 5.0, for example, there are 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 (2-, 3-, 4-functional) polymerization initiator, and a method of adding a conjugated divinyl compound or a polybranched vinyl compound or both of them, preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ moles per mole of the total amount of the monovinyl compound, when a resin is produced by radical copolymerizing a monovinyl compound with a conjugated divinyl compound and/or a polybranched vinyl compound. In addition, for example, there is a method of performing polymerization in two reactors under conditions for polymerizing a low molecular weight component and conditions for polymerizing a high molecular weight component, respectively, and then joining the two polymerization solutions, or a method of performing further polymerization after joining. Conditions for polymerizing a 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 like. Conditions for polymerizing the high molecular weight component include, for example, a method of reducing the amount of solvent and lowering the polymerization temperature, a method of using a polyfunctional polymerization initiator, and a method of adding a conjugated divinyl compound or a multi-branched vinyl compound, or both, preferably in an amount of 2.0× ¹⁰ to 4.0× ¹⁰ moles per mole of the total amount of the monovinyl compounds.

The peak top molecular weight (Mtop) of the heat-resistant styrene-based resin of this embodiment is preferably 100,000 to 250,000, more preferably 110,000 to 220,000, even more preferably 110,000 to 200,000, and most preferably 120,000 to 180,000. If Mtop is less than 100,000, the amount of low molecular weight components will be extremely large, and the strength of the molded product may decrease. If Mtop is more than 250,000, the flowability may decrease and the molding condition range may become narrow.
In order to set Mtop in the range of 100,000 to 180,000, for example, a method of using a chain transfer agent, or in the case of manufacturing by connecting a plurality of reactors in series, a method of increasing the reaction temperature during polymerization in the order in which the reaction solution passes through, or a method of adding a chain transfer agent and a polymerization initiator to a reactor at the latter stage. In addition, for example, a method of carrying out polymerization in two reactors under conditions for polymerizing a low molecular weight component and conditions for polymerizing a high molecular weight component, respectively, and then merging the two polymerization solutions, or a method of carrying out further polymerization after merging, is available. Conditions for polymerizing a 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 like. Conditions for polymerizing a high molecular weight component include, for example, a method of reducing the amount of solvent and lowering the polymerization temperature, a method of using a polyfunctional polymerization initiator, and a method of adding a conjugated divinyl compound or a multi-branched vinyl compound or both, preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ moles per mole of the total amount of monovinyl compounds.

In the present embodiment, the proportion of the heat-resistant styrene resin having a molecular weight of 1,000,000 or more is preferably 2.0 to 16.0%, more preferably 3.0 to 13.0%, and even more preferably 4.0 to 12.0%. By setting the proportion of the heat-resistant styrene resin having a molecular weight of 1,000,000 or more in the range of 2.0 to 16.0%, it is possible to obtain a heat-resistant styrene resin having excellent moldability and a wide range of molding conditions.
In order to make the proportion of molecular weights of 1 million or more 2.0 to 16.0%, when radically polymerizing a styrene-based monomer, it can be controlled by the type and amount of conjugated divinyl compound, reaction temperature, residence time, type and amount of polymerization initiator, type and amount of solvent, type and amount of chain transfer agent, etc. Specifically, the control of the above-mentioned proportion of molecular weights of 1 million or more, etc. is not limited, but can be controlled, for example, in the production method, by increasing the amount of polymerization initiator added during polymerization, lowering the polymerization reaction temperature, reducing the amount of polymerization solvent used, or lengthening the residence time during polymerization, and by doing so, in the obtained heat-resistant styrene-based resin, it is possible to reduce the low molecular weight component side and increase the high molecular weight component side while appropriately adjusting the proportion of molecular weights of 1 million or more.

In the present embodiment, the proportion of the heat-resistant styrene resin having a molecular weight of 2 million or more is preferably 1.0 to 5.0%, more preferably 1.5 to 4.5%, and even more preferably 2.0 to 3.9%. By setting the proportion of the heat-resistant styrene resin having a molecular weight of 2 million or more in the range of 1.0 to 5.0%, it is possible to obtain a heat-resistant heat-resistant styrene resin having excellent moldability and a wide range of molding conditions.
In order to make the proportion of molecular weights of 2 million or more 1.0 to 5.0%, when radically polymerizing a styrene-based monomer, it can be controlled by the type and amount of conjugated divinyl compound, reaction temperature, residence time, type and amount of polymerization initiator, type and amount of solvent, type and amount of chain transfer agent, etc. Specifically, the control of the above-mentioned proportion of molecular weights of 2 million or more, etc. is not limited, but can be controlled, for example, in the production method, by increasing the amount of polymerization initiator added during polymerization, lowering the polymerization reaction temperature, reducing the amount of polymerization solvent used, or lengthening the residence time during polymerization, and by doing so, in the obtained heat-resistant styrene-based resin, it is possible to reduce the low molecular weight component side and increase the high molecular weight component side while appropriately adjusting the proportion of molecular weights of 2 million or more.

By adjusting the Mw/Mn of the heat-resistant styrene-based resin to 4.0 to 7.0 and the Mz/Mw to 2.0 to 5.0, a heat-resistant styrene-based resin having better moldability and flowability can be obtained.
In the present disclosure, the number average molecular weight (Mn), weight average molecular weight (Mw), Z average molecular weight (Mz), and peak top molecular weight (Mtop) of the heat-resistant styrene-based resin are values measured using gel permeation chromatography (GPC).

<Content of components with absolute molecular weight of 1 million to 5 million>
In the heat-resistant styrene resin of this embodiment, the content of components having an absolute molecular weight of 1 million to 5 million is 5.0 to 14.0%, preferably 7.0 to 14.0%, and more preferably 9.0 to 14.0%. By setting the content of components having an absolute molecular weight of 1 million to 5 million in the range of 5.0 to 14.0%, a heat-resistant styrene resin having excellent moldability and little gel-like substance can be obtained.
In order to make the content of the component having an absolute molecular weight of 1,000,000 to 5,000,000 5.0 to 14.0%, for example, there are a method of using a polyfunctional polymerization initiator, a method of adding a conjugated divinyl compound, or a method of simultaneously adding a conjugated divinyl compound and a multi-branched vinyl compound. For example, when a heat-resistant styrene resin is obtained by radical copolymerization by optionally adding a conjugated divinyl compound and/or a multi-branched vinyl compound to a monovinyl compound, the amount of the conjugated divinyl compound and/or the multi-branched vinyl compound added is preferably 4.0×10 ⁻⁶ to 8.0×10 ⁻⁴ moles per vinyl group per mole of the total amount of the monovinyl compound (i.e., in the case of a conjugated divinyl compound having two vinyl groups, 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 to 100,000. In addition, in the production of styrene-based resins, there is a method in which the amount of solvent is reduced to 0 to 20% and the reaction temperature is set to 80 to 140°C.
In this disclosure, the content of components having an absolute molecular weight of 1 million to 5 million in the heat-resistant styrene-based resin is a value calculated using a multi-angle light scattering detector (MALS).

<Degree of branching>
The degree of branching of the heat-resistant styrene-based resin of this embodiment is 0.60 to 0.95, preferably 0.72 to 0.93, more preferably 0.75 to 0.92, and even more preferably 0.79 to 0.90. If the degree of branching is less than 0.60, the branching becomes too many and the molecular weight per branched chain becomes small, so that the number of entanglement points decreases, and entanglement may be unraveled under high strain, and sufficient moldability may not be obtained. If the degree of branching is more than 0.95, the branching is small and sufficient entanglement effect between polymer chains may not be obtained.
In order to make the degree of branching 0.60 to 0.95, for example, there are a method of using a polyfunctional polymerization initiator, a method of adding a conjugated divinyl compound, or a method of simultaneously adding a conjugated divinyl compound and a multi-branched vinyl compound. For example, when a heat-resistant styrene-based resin is obtained by radical copolymerization by optionally adding a conjugated divinyl compound and/or a multi-branched vinyl compound to a monovinyl compound, the amount of the conjugated divinyl compound and/or the multi-branched vinyl compound added is preferably 4.0×10 ⁻⁶ to 8.0×10 ⁻⁴ moles per vinyl group per mole of the total amount of the monovinyl compound (i.e., in the case of a conjugated divinyl compound having two vinyl groups, 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 to 100,000.
In the present disclosure, the degree of branching is a value calculated by the procedure described in the section [Examples] below.

<Gelation Degree>
The gelation degree of the heat-resistant styrene-based resin of this embodiment is 1.10 to 1.80, preferably 1.15 to 1.70, more preferably 1.20 to 1.65, and even more preferably 1.25 to 1.65. By setting the gelation degree in the range of 1.10 to 1.80, it is possible to suppress an increase in branching as the molecular weight increases, and therefore it is possible to reduce the amount of gel-like substances in the heat-resistant styrene-based resin. In addition, when the resin is retained for a long period of time in production equipment such as a reactor, it is possible to reduce the amount of gel-like substances generated, and therefore it is possible to improve productivity.
In order to make the gelation degree 1.10 to 1.80, for example, there are a method of using a polyfunctional polymerization initiator, a method of adding a conjugated divinyl compound, or a method of simultaneously adding a conjugated divinyl compound and a multi-branched vinyl compound. For example, when a heat-resistant styrene-based resin is obtained by radical copolymerization by optionally adding a conjugated divinyl compound and/or a multi-branched vinyl compound to a monovinyl compound, the amount of the conjugated divinyl compound and/or the multi-branched vinyl compound added is preferably 4.0×10 ⁻⁶ to 8.0×10 ⁻⁴ moles per vinyl group per mole of the total amount of the monovinyl compound (i.e., in the case of a conjugated divinyl compound having two vinyl groups, 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 to 100,000.
In the present disclosure, the gelation degree is a value calculated by the procedure described in the section [Examples] below.

<Melt Mass Flow Rate (MFR)>
The melt mass flow rate (MFR) of the heat-resistant styrene-based resin of this embodiment is preferably 0.5 to 5.0 g/10 min., more preferably 0.6 to 4.0 g/10 min., further preferably 0.7 to 3.5 g/10 min., and particularly preferably 0.8 to 3.0 g/10 min. By setting the melt mass flow rate in the range of 0.5 to 5.0 g/10 min., a heat-resistant styrene-based resin having excellent moldability and flowability can be obtained.
In order to achieve an MFR of 0.5 to 5.0 g/10 min, for example, there is a method in which the Mw/Mn of the heat-resistant styrene-based resin is set to 4.0 to 7.0 and the Mw is set to 200,000 to 500,000, or a method in which 0.01 to 10.0 mass% of a plasticizer such as liquid paraffin is added relative to 100 mass% of the heat-resistant styrene-based resin.
In this disclosure, the melt mass flow rate is a value measured in accordance with ISO 1133 at 200° C. and a load of 49 N.

<Maximum rise ratio>
The maximum rise ratio of the heat-resistant styrene resin of this embodiment is preferably 1.2 to 5.0, more preferably 1.3 to 4.8, and even more preferably 1.4 to 4.6. In this specification, the "maximum rise ratio" means (extensional viscosity in the nonlinear region of the maximum rise strain/extensional viscosity in the linear region of the maximum rise strain), and the "maximum rise strain" means the Hencky strain when the extensional viscosity is maximum. The maximum rise ratio is an index representing the degree of strain hardening at the maximum rise strain. The larger the maximum rise ratio, the larger the degree of strain hardening and the better the moldability. If the maximum rise ratio is less than 1.2, sufficient deep drawability cannot be obtained or the molding condition width tends to be narrow. If the maximum rise ratio is more than 5.0, the elongation viscosity during molding becomes too low, which is not preferable from the viewpoint of productivity.
In order to achieve a maximum rise ratio of 1.2 to 5.0, for example, the degree of branching may be set to 0.60 to 0.95 and the content of components having an absolute molecular weight of 1 to 5 million may be set to 5.0 to 14.0%.
In the present disclosure, the maximum rise ratio is a value calculated by the procedure described in the section [Examples] below.

<Total content of styrene dimer and trimer>
When the heat-resistant styrene resin of this embodiment is produced by radical polymerization of a styrene monomer, the total content of styrene dimers and trimers in the heat-resistant styrene resin is preferably 0.01 to 0.50% by mass, more preferably 0.01 to 0.25% by mass, and even more preferably 0.02 to 0.20% by mass, relative to 100% by mass of the heat-resistant styrene resin. By having the total content of styrene dimers and trimers be 0.01 to 0.50% by mass, it is possible to reduce eye plugs during secondary molding, improve the yield of molded articles with good appearance, or reduce the odor of molded articles.
In order to make the total content of styrene dimers and trimers 0.01 to 0.50% by mass relative to 100% by mass of the heat-resistant styrene resin, for example, there are a method of lowering the reaction temperature to 80 to 140° C. in order to reduce the amount generated during polymerization, and a method of adding 100 to 2000 ppm by mass of a polymerization initiator to generate many initiator radicals. In addition, there are a method of lowering the degree of vacuum to 50 kPa or less when devolatilizing unreacted monomers and solvents under vacuum, and a method of adding 100 to 3000 ppm by mass of a thermal decomposition inhibitor described later in order to reduce the amount generated due to heat or shearing of the molten resin.
In this disclosure, the total content of styrene dimer and trimer is a value measured using gas chromatography (GC).

<Vicat softening temperature>
The Vicat softening temperature of the heat-resistant styrene-based resin of this embodiment is preferably 105 to 130°C, more preferably 107 to 128°C, and even more preferably 109 to 127°C, from the viewpoint of the heat resistance temperature of the molded product.
In this disclosure, the Vicat softening temperature is a value measured in accordance with ISO 306 at a load of 49 N and a heating rate of 50° C./hour.
In order to adjust the Vicat softening temperature to 105 to 130° C., for example, a comonomer such as acrylic acid, methacrylic acid, or maleic anhydride that is copolymerizable with the monovinyl compound may be copolymerized in the heat-resistant styrene resin.

<Method for producing heat-resistant styrene-based resin>
The heat-resistant styrene resin of the present embodiment may contain a monovinyl compound and methacrylic acid as monomers, and may have a branched molecular structure. The heat-resistant styrene resin of the present embodiment may be produced, for example, by radical copolymerization of a monovinyl compound, a conjugated divinyl compound and/or a multi-branched vinyl compound, and methacrylic acid (the styrene resin may be branched).
Hereinafter, as an example, a method for producing a styrene-based resin by radical copolymerization of a monovinyl compound, a conjugated divinyl compound and/or a multi-branched vinyl compound, and methacrylic acid will be described in detail.

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

<Monovinyl compound content>
The content of the monovinyl compound in the heat-resistant styrene-based resin of the present embodiment is preferably 83.0 to 98.0 mass%, more preferably 85.0 to 97.5 mass%, and even more preferably 87.0 to 97.0 mass%, based on 100 mass% of the heat-resistant styrene-based resin, from the viewpoint of molding processability.

<Conjugated divinyl compounds>
The conjugated divinyl compound in this embodiment is preferably a compound having a number average molecular weight (Mn) of 850 to 100,000 and having at least two conjugated vinyl groups in the molecule.
In addition, the conjugated divinyl compound in this embodiment is preferably chain-like rather than mesh-like, and the main chain may or may not have a side chain. By being chain-like, the molecular chain can be made more linear, which tends to improve the entanglement effect. The side chain preferably has 6 or less carbon atoms, more preferably 4 or less carbon atoms.
Furthermore, the conjugated vinyl group in the conjugated divinyl compound can be located anywhere in the molecule, but it is preferable that the two conjugated vinyl groups among the at least two conjugated vinyl groups are located at different ends in the molecule. In addition, when the conjugated divinyl compound is chain-like, it is more preferable that the two conjugated vinyl groups are located at different ends of the main chain (i.e., it is more preferable that both ends of the main chain are conjugated divinyl groups). The polymerization reactivity can be increased by the conjugated vinyl groups being located at the ends.
Furthermore, when the conjugated divinyl compound is linear 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, and it is more preferable that all of the three or more conjugated vinyl groups are located at the terminals.
In addition, when the number of conjugated vinyl groups in the conjugated divinyl compound is large, the number of branching points increases, and gelation may easily occur in the process of recovering the reactor or raw materials, which may deteriorate the transparency of the styrene resin and require cleaning of the reactor or molding machine, resulting in reduced productivity. From these viewpoints, the number of conjugated vinyl groups possessed by the conjugated divinyl compound is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less. From the same viewpoint, it is particularly preferable that the number of conjugated vinyl groups of the conjugated divinyl compound is 2.
In this specification, the term "terminal" of a molecule includes not only the end position (atom) of the molecule but also a position adjacent to the end position of the molecule, and the adjacent position specifically means an end corresponding to about 20% of the extended chain length of the molecule. From the viewpoint of improving reactivity with a monovinyl compound and suppressing gelation, the conjugated vinyl group in the conjugated divinyl compound is more preferably located at an end corresponding to 15% of the extended chain length of the conjugated divinyl compound molecule, even more preferably located at an end corresponding to 10%, and even more preferably located at an end corresponding to 5%.

In this embodiment, the conjugated vinyl group is a group having an olefinic double bond copolymerizable with a monovinyl compound and a structure (such as, but not limited to, a carbonyl group, an aryl group, etc.) that forms a conjugated system with the olefinic double bond. Examples of the conjugated vinyl group include, but are not limited to, an acryloyl group and an aryl group substituted with a vinyl group, and examples of the structure having a conjugated vinyl group in a conjugated divinyl compound include, but are not limited to, a structure to which (meth)acrylate, urethane (meth)acrylate, aromatic vinyl, maleic acid, fumaric acid, etc. are added. The at least two conjugated vinyl groups may be the same or different from each other.

The number average molecular weight (Mn) of the conjugated divinyl compound of this embodiment is preferably 850 to 100,000, more preferably 1,000 to 80,000, even more preferably 1,200 to 80,000, even more preferably 1,500 to 60,000, and particularly preferably 1,500 to 30,000. 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 that the distance between the polymer chains bonded to the conjugated divinyl compound is short, and sufficient entanglement effect cannot be obtained, resulting in poor moldability. When the molecular weight exceeds 100,000, the distance between the conjugated vinyl groups of the conjugated divinyl compound is long, and the reactivity of the conjugated vinyl groups at the terminals decreases (the molecular weight of the conjugated divinyl compound is large, so that the conjugated vinyl groups at the terminals are less likely to react), and the amount of high molecular weight components produced may decrease.
In the present disclosure, the number average molecular weight (Mn) of a conjugated divinyl compound means the number average molecular weight (Mn) in terms of polystyrene measured by gel permeation chromatography (GPC).

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

Specific conjugated divinyl compounds include (hydrogenated) polybutadiene-terminated (meth)acrylate ("(hydrogenated)" refers to a compound that is hydrogenated or not hydrogenated, and the same applies below), terminal di(meth)acrylate compounds such as polyethylene glycol-terminated (meth)acrylate, polypropylene glycol-terminated (meth)acrylate, ethoxylated bisphenol A-terminated (meth)acrylate, and ethoxylated bisphenol F-terminated (meth)acrylate, as well as terminal urethane acrylate compounds such as (hydrogenated) 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 bonds of the repeating unit propylene glycol is determined so that the number average molecular weight (Mn) is 850 to 100,000. From the viewpoint of compatibility with styrene-based resins, the conjugated divinyl compound is preferably a (hydrogenated) polybutadiene-terminated (meth)acrylate, a polystyrene-terminated (meth)acrylate, or a polyphenylene ether-terminated divinyl. Note that "end" and "both ends" in the compound name mean that conjugated vinyl groups are located at both ends.

<Content of conjugated divinyl compounds>
The content of the conjugated divinyl compound in the styrene-based resin of this embodiment is preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ moles, more preferably 5.0×10 ⁻⁶ to 3.5×10 ⁻⁴ moles, even more preferably 1.5×10 ⁻⁵ to 3.0×10 ⁻⁴ moles, and even more preferably 2.0×10 ⁻⁵ to 2.5×10 ⁻⁴ moles per mole of the total amount of the monovinyl compound. If the content is less than 2.0×10 ⁻⁶ moles, sufficient entanglement between the polymers is difficult to occur, strain hardening is not expressed, or the degree of strain hardening is small, so that the thickness of the molded article is uneven, the molded article may break during molding, and the moldability may be poor. On the other hand, if the content exceeds 4.0×10 ⁻⁴ moles, gel-like substances are generated in large amounts, and the appearance of the molded article may be poor.
In the present disclosure, the content of the conjugated divinyl compound per mole of the total amount of the monovinyl compounds is a value measured using ¹ H-NMR and ¹³ C-NMR.

<Highly branched vinyl compounds>
In the multi-branched vinyl compound of the present embodiment, multi-branched means having one or more branched structures, and more specifically means having a star-shaped branched structure, a pom-pom-shaped branched structure, a graft-branched structure, or an H-shaped branched structure.
The number average molecular weight (Mn) of the multi-branched vinyl compound is preferably 850 to 100,000, more preferably 1,000 to 80,000, even more preferably 1,200 to 80,000, even more preferably 1,500 to 60,000, and particularly preferably 1,500 to 30,000. When 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 sufficient entanglement effect cannot be obtained, resulting in poor moldability. When the molecular weight exceeds 100,000, the distance between the vinyl groups is long, and the reactivity of the vinyl groups is reduced (the molecular weight of the multi-branched vinyl compound is large, so the terminal vinyl groups are less likely to react), and the amount of high molecular weight components produced may be reduced.
In the present disclosure, the number average molecular weight (Mn) of the hyperbranched vinyl compound is a value measured using gel permeation chromatography (GPC).

The multi-branched vinyl compound can be synthesized, for example, by the method described in JP-A-2016-113580 or JP-A-2016-113598. For example, there is a method of synthesizing a multi-branched vinyl compound by cationic polymerization of a divinyl aromatic compound such as divinylbenzene or diisopropenylbenzene, an aliphatic or alicyclic (meth)acrylate such as ethylene glycol di(meth)acrylate, a monovinyl compound such as styrene or ethylvinylbenzene, and a terminal modifier such as 2-phenoxyethyl methacrylate. In addition, there is a method of esterifying or adding a polymerizable double bond such as a vinyl group, for example, an isopropenyl group, to a polyhydric alcohol or polyester polyol having a multi-branched structure and multiple hydroxyl groups. Here, the polyhydric alcohol having a multi-branched structure and multiple hydroxyl groups is preferably an alcohol having 2 to 100 hydroxyl groups and 70 to 3000 carbon atoms.

<Content of hyperbranched vinyl compound>
The content of the multi-branched vinyl compound in the styrene-based resin of this embodiment is preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ moles, more preferably 5.0×10 ⁻⁶ to 3.5×10 ⁻⁴ moles, even more preferably 1.5×10 ⁻⁵ to 3.0×10 ⁻⁴ moles, and even more preferably 2.0×10 ⁻⁵ to 2.5×10 ⁻⁴ moles per mole of the total amount of the monovinyl compound. If the content is less than 2.0×10 ⁻⁶ moles, sufficient entanglement between the polymers is difficult to occur, strain hardening is not expressed, or the degree of strain hardening is small, so that the thickness of the molded article is uneven, the molded article may break during molding, and the moldability may be poor. On the other hand, if the content exceeds 4.0×10 ⁻⁴ moles, gel-like substances are generated in large amounts, and the appearance of the molded article may be poor.

<Methacrylic acid>
<Methacrylic acid content>
The content of methacrylic acid in the heat-resistant styrene-based resin of this embodiment is 2.0 to 17.0% by mass, preferably 2.5 to 15.0% by mass, and more preferably 3.0 to 13.0% by mass, based on 100% by mass of the heat-resistant styrene-based resin. If the content is less than 2.0% by mass, the heat resistance of the heat-resistant styrene-based resin may be low, and the heat resistance of the molded product may be low. If the content is more than 17.0% by mass, the methacrylic acid may condense intramolecularly or intermolecularly to generate a crosslinked superpolymer, which may cause the surface of the molded product to become rough or the product to be easily torn during molding.
In the present disclosure, the content of methacrylic acid in the heat-resistant styrene-based resin is a value measured using ¹ H-NMR or ¹³ C-NMR.

Additives, etc.
The heat-resistant styrene-based resin of the present embodiment may be a resin composition optionally containing additives, etc. For example, if necessary, the resin may contain about 1 to 50 mass % of a rubber-containing component such as a rubber-reinforced aromatic vinyl-based resin such as HIPS resin or MBS resin, an aromatic vinyl-based thermoplastic elastomer such as SBS, or a resin such as polyphenylene ether or polyamide.

In addition, the heat-resistant styrene-based resin may be further copolymerized with an additional monomer copolymerizable with a monovinyl compound, a conjugated divinyl compound, a multi-branched vinyl compound, and methacrylic acid, within a range that does not impair its physical properties. Examples of the copolymerizable monomer include methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate. These monomers may be used alone or in combination of two or more. The content of these additional monomers is preferably 2 to 20% by mass, more preferably 3 to 15% by mass, and even more preferably 4 to 10% by mass, based on 100% by mass of the heat-resistant styrene-based resin, from the viewpoint of the balance between heat resistance and chemical resistance.

In addition, the heat-resistant styrene resin may contain a processing stabilizer such as 2-[1-(2-hydroxy-3,5-di-t-phenylpentyl)ethyl]-4,6-di-t-phenylpentyl acrylate in order to suppress thermal decomposition of the polymer in the unreacted monomer recovery process. In addition, the heat-resistant styrene resin may contain a heat deterioration inhibitor such as 2-[1-(2-hydroxy-3,5-di-t-phenylpentyl)ethyl]-4,6-di-t-phenylpentyl acrylate, a higher fatty acid such as stearic acid, zinc stearate, calcium stearate, magnesium stearate, and the like, a lubricant such as ethylene bisstearylamide, a plasticizer such as liquid paraffin, and an antioxidant, in a range that does not impair the object of this embodiment. In addition, additives commonly used in the field of styrene resins, such as a nucleating agent, a flame retardant, a colorant, and the like, in a range that does not impair the object of this embodiment, may be added to the heat-resistant styrene resin in combination. The additives are not particularly limited, but examples thereof include nucleating agents such as talc, flame retardants such as hexabromocyclododecane, colorants such as titanium oxide and carbon black, etc. When the heat-resistant styrene-based resin is made into pellets, ethylene bisstearylamide, zinc stearate, magnesium stearate, etc. may be sprinkled on the pellets as an external lubricant for the pellets.
The heat-resistant styrene-based resin of the present embodiment can contain the additives by appropriately adding them during the production process of the heat-resistant styrene-based resin, or by melt-kneading the heat-resistant styrene-based resin and the above-mentioned additives, etc., using a known kneader such as a single-screw extruder, a twin-screw extruder, or a Banbury mixer after the production process.

Antioxidants are generally components that can stabilize peroxide radicals such as hydroperoxy radicals generated during thermoforming or exposure to light, or that can decompose the generated peroxides such as hydroperoxides. Antioxidants are not particularly limited, but examples include hindered phenol-based antioxidants and peroxide decomposers. Hindered phenol-based antioxidants act as radical chain inhibitors, and peroxide decomposers can decompose peroxides generated in the system into more stable alcohols to prevent autoxidation. Examples of the hindered phenol antioxidant include, but are not limited to, 2,6-di-t-butyl-4-methylphenol, stylenated 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 butylphenyl 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. Examples of peroxide decomposers include, but are not limited to, organic phosphorus peroxide decomposers such as trisnonylphenyl phosphite, triphenyl phosphite, and tris(2,4-di-t-butylphenyl)phosphite, as well as organic sulfur peroxide decomposers such as dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, pentaerythrityl tetrakis(3-laurylthiopropionate), ditridecyl-3,3'-thiodipropionate, and 2-mercaptobenzimidazole. The amount of antioxidant added is preferably 0.01 to 1 part by mass, more preferably 0.1 to 0.5 parts by mass, per 100 parts by mass of the heat-resistant styrene-based resin.

Flame retardants are not limited to the following, but from the viewpoint of flame retardancy and compatibility with styrene-based resins, examples include brominated flame retardants such as hexabromocyclododecane, brominated SBS block polymer, and 2,2-bis(4'(2",3"-dibromoalkoxy)-3',5'-dibromophenyl)-propane, as well as brominated bisphenol flame retardants.

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, and epoxy group adduct of tetrabromobisphenol A oligomer. Among the brominated bisphenol flame retardants, tetrabromobisphenol A bis(2,3-dibromopropyl ether) and tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) are particularly preferred because they are less likely to decompose when kneaded with polystyrene resins and tend to have a high flame retardant effect. The combined use of tetrabromobisphenol A-bis(2,3-dibromopropyl ether) and tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) is even more preferred because they tend to have excellent flame retardancy and thermal stability.

When using a brominated flame retardant, it is preferable to use a brominated isocyanurate flame retardant in combination as a flame retardant assistant. Examples of brominated isocyanurate flame retardants include, but are not limited to, mono(2,3-dibromopropyl)isocyanurate, di(2,3-dibromopropyl)isocyanurate, tris(2,3-dibromopropyl)isocyanurate, mono(2,3,4-tribromobutyl)isocyanurate, di(2,3,4-tribromobutyl)isocyanurate, tris(2,3,4-tribromobutyl)isocyanurate, and the like. Among the brominated isocyanurates, tris(2,3-dibromopropyl)isocyanurate is particularly preferable because it exhibits an extremely high flame retardant effect.

The content of the bromine-based 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 or less, and even more preferably 2 parts by mass or more and 8 parts by mass or less, relative to 100 parts by mass of the heat-resistant styrene-based resin. When the content is 0.1 parts by mass or more, sufficient flame retardancy tends to be ensured, and when the content is 10 parts by mass or less, sufficient moldability when producing a foamed sheet tends to be ensured.

The liquid paraffin may be selected from liquid paraffins specified in the Food Sanitation Act, standards for food, food additives, etc. Specific examples of this type of liquid paraffin include, but are not limited to, Krystal N52, Krystal N62, Krystal N72, Krystal N82, Krystal N122, Krystal N172, Krystal N262, Krystal N352, and Primol N542, which are commercially available from ExxonMobil Corporation. Other examples include Moresco White P-40, Moresco White P-55, Moresco White P-60, Moresco White P-70, Moresco White P-80, Moresco White 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 White P-300, Moresco White P-350, and Moresco White P-350P, all of which are commercially available from Matsumura Oil Research Institute Co., Ltd. Further examples include liquid paraffin 40-S, 60-S, 70-S, 80-S, 90-S, 100-S, 120-S, 150-S, 260-S, and 350-S, all of which are commercially available from Sanko Chemical Industry Co., Ltd. Also included is white mineral oil available from CK Witco Corporation.

The molecular weight of the liquid paraffin is usually defined by its kinetic viscosity. As the liquid paraffin in this embodiment, for example, one having a kinetic viscosity at 40° C. defined in the test method JIS K2283 in the range of 0.1 to 60 mm ² /sec can be used, and one having a kinetic viscosity of 1 to 40 mm ² /sec is preferred. The preferred weight average molecular weight of the liquid paraffin is in the range of 150 to 500, more preferably in the range of 180 to 450, and even more preferably in the range of 200 to 350. The weight average molecular weight is determined, for example, by using gas chromatography to obtain the weight average value of each molecular weight component of the liquid paraffin. When liquid paraffin in this viscosity range or this molecular weight range is used, the obtained heat-resistant styrene-based resin is plasticized to a greater extent, and the moldability of the heat-resistant styrene-based resin, for example, the surface gloss of a molded product, tends to be greatly improved, compared to liquid paraffins having a higher viscosity or a higher molecular weight. In addition, it is preferable to use liquid paraffin having a viscosity of 0.1 ^mm2 /sec or more or a weight average molecular weight of 150 or more, since this tends to effectively suppress mold contamination and bleeding onto the surface of the molded article during molding of the resulting heat-resistant styrene-based resin.

The content of liquid paraffin in the heat-resistant styrene resin is preferably less than 3.0 parts by mass, more preferably less than 1.0 parts by mass, and even more preferably less than 0.5 parts by mass, per 100 parts by mass of the heat-resistant styrene resin. By making the content of liquid paraffin less than 5.0 parts by mass, it is possible to obtain a molded product that has an excellent balance between secondary moldability, strength of the molded product, and heat resistance.

In addition, in this embodiment, it is preferable to add the heat deterioration inhibitor during the polymerization process or devolatilization process of the heat-resistant styrene-based resin, or after the polymerization process and before the devolatilization process. In particular, it is preferable to add the heat deterioration inhibitor after the end of the polymerization process (preferably immediately after) and before the devolatilization process. By adding the heat deterioration inhibitor, it is possible to stabilize the radicals generated by thermal decomposition and reduce the amount of thermal decomposition.

Examples of heat deterioration inhibitors include phenol-based heat deterioration inhibitors such as 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (product 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 (product name: Sumilizer GS, manufactured by Sumitomo Chemical Co., Ltd.), and 2,4-bis(octylthiomethyl)-6-methylphenol (product name: Irganox 1520L); hindered phenol-based antioxidants such as octadecyl-3-(3,5-tert-butyl-4-hydroxyphenyl)propionate and 4,6-bis(octylthiomethyl)-o-cresol; and phosphorus-based processing heat stabilizers such as tris(2,4-di-tert-butylphenyl)phosphite. These heat deterioration inhibitors may be used alone or in combination of two or more types as appropriate.

The content of the heat deterioration inhibitor is preferably 0.01 to 0.5 parts by mass, more preferably 0.02 to 0.3 parts by mass, and even more preferably 0.03 to 0.2 parts by mass, based on 100 parts by mass of the heat-resistant styrene-based resin at the final reactor outlet.
When the content of the thermal degradation inhibitor is 0.01 parts by mass or more, the generation of the monovinyl compound monomer and its dimer and trimer in the devolatilization step can be more effectively suppressed, whereas when the content of the thermal degradation inhibitor is more than 0.5 parts by mass, the effect commensurate with the content cannot be obtained.

The content of the above additives contained in the heat-resistant styrene-based resin is preferably 100 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the heat-resistant styrene-based resin.

<Polymerization process>
Examples of the polymerization method for the heat-resistant styrene-based resin of this embodiment include known styrene polymerization methods such as bulk polymerization, solution polymerization, and suspension polymerization. These polymerization methods may be batch polymerization or continuous polymerization, and continuous polymerization is preferable from the viewpoint of productivity. As a continuous bulk polymerization method, for example, a raw material solution containing monomers is prepared by adding and mixing a monovinyl compound, a conjugated divinyl compound and/or a multi-branched vinyl compound, methacrylic acid, etc., and, if necessary, a solvent, a polymerization catalyst, and a chain transfer agent. A method in which the raw material solution is continuously fed into a facility equipped with one or more reactors arranged in series and/or parallel and a volatilization device for a volatilization step for removing volatile components such as unreacted monomers, and polymerization is allowed to proceed stepwise, is exemplified.

Examples of reactors include complete mixing reactors, laminar flow reactors, and loop reactors in which a portion of the polymerization liquid is withdrawn while the polymerization is proceeding. There are no particular limitations on the order in which these reactors are arranged.

When polymerizing the heat-resistant styrene-based resin of this embodiment, a polymerization solvent, a polymerization initiator such as an organic peroxide, and a chain transfer agent can be used as necessary from the viewpoint of controlling the polymerization reaction. The 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, but 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 controlling gelation, improving productivity, increasing molecular weight, etc., it is usually preferably 1 to 50 mass % of the mixed solution composition of all monomers, polymers, solvents, etc. in the polymerization reactor, and more preferably 3 to 20 mass %.

When the polymerization raw materials are polymerized to obtain the heat-resistant styrene-based resin of this embodiment, a polymerization initiator and a chain transfer agent can be contained in the polymerization raw material composition. The polymerization initiator is not particularly limited, but examples thereof include organic peroxides, for example, peroxyketals such as 2,2-bis(t-butylperoxy)butane, 1,1-bis(t-butylperoxy)cyclohexane, and n-butyl-4,4-bis(t-butylperoxy)valerate, dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, and dicumyl peroxide, diacyl peroxides such as acetyl peroxide and isobutyryl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxyesters such as t-butylperoxyacetate, ketone peroxides such as acetylacetone peroxide, and hydroperoxides such as t-butyl hydroperoxide. The polymerization initiator is preferably used in an amount of 0.005 to 0.08% by mass relative to the monovinyl compound. The chain transfer agent is not particularly limited, but examples thereof include α-methylstyrene dimer, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-octyl mercaptan. The chain transfer agent is preferably used in an amount of 0.01 to 0.50% by mass relative to the monovinyl compound.

<Volatilization process>
As the volatilizing apparatus, for example, a conventional volatilizing apparatus such as a flash drum, a twin-screw volatilizing apparatus, a thin-film evaporator, an extruder, etc. can be used, and generally, a vacuum volatilizing tank with a heater or a volatilizing extruder, etc., is used. As the arrangement of the volatilizing apparatus, for example, one using only one vacuum volatilizing tank with a heater, one connecting two vacuum volatilizing tanks with a heater in series, and one connecting a vacuum volatilizing tank with a heater and a volatilizing extruder in series can be mentioned. In order to reduce the volatile components as much as possible, one connecting two vacuum volatilizing tanks with a heater in series or one connecting a vacuum volatilizing tank with a heater and a volatilizing extruder in series is preferred.

The conditions for the devolatilization step are not particularly limited. For example, when the polymerization of the heat-resistant styrene-based resin is carried out by bulk polymerization, the polymerization can be allowed to proceed until the final amount of unreacted monovinyl compound in the heat-resistant styrene-based resin is preferably 50% by mass or less, more preferably 40% by mass or less. The devolatilization process can remove volatile matters such as unreacted materials (monovinyl compounds) and/or solvents.

The temperature for the devolatilization process is usually about 190 to 280°C. The pressure for the devolatilization process is preferably 0.1 to 50 kPa, more preferably 0.13 to 13 kPa, even more preferably 0.13 to 7 kPa, and particularly preferably 0.13 to 1.3 kPa. Desirable methods for devolatilization include, for example, a method in which the pressure is reduced under heating, or devolatilization through an extruder designed to remove volatile components.

<Foam sheet>
The foamed sheet of the present embodiment is characterized by containing the heat-resistant styrene-based resin of the present embodiment and having a thickness of 0.5 to 5.0 mm.
The foamed sheet of the present embodiment has a thickness of 0.5 mm to 5.0 mm, and from the viewpoints of productivity and secondary formability of the sheet, it is preferably 0.7 to 4.5 mm, and more preferably 1.0 to 4.0 mm.
The foamed 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/ ^m2 .

The foam sheet of this embodiment may be multi-layered, for example, by further laminating a film. The type of film that can be used may be any type commonly used for polystyrene.

Regularly used substances can be used as the foaming agent and foam nucleating agent contained in the foam sheet of this embodiment. The foaming agent is not particularly limited, but examples include butane, pentane, fluorocarbons, and water, with butane being preferred. The foam nucleating agent is not particularly limited, but examples include talc.

<Residual amount of styrene monomer in foam sheet>
The residual amount of the 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 further preferably 30 to 200 ppm by mass, based on 100% by mass of the foam sheet. By having the residual amount of the styrene monomer be 10 to 500 ppm by mass, the odor of the foam sheet can be reduced.
In the present disclosure, the amount of remaining styrene monomer is a value measured using gas chromatography (GC).

<Method of manufacturing foam sheet>
The foamed sheet of the present embodiment can be produced by a commonly known method, for example, but not limited to, a method of melt-kneading and extruding the heat-resistant styrene-based resin of the present embodiment, a foaming agent, and a foam nucleating agent in an extruder, which is described in more detail below.
First, the heat-resistant styrene-based resin in this embodiment is melt-kneaded in an extruder connected to a circular die, and the melt-kneaded product is extruded in a foamed state from an annular opening provided in front of the circular die to form a cylindrical foam. Next, the foam is cooled while being stretched in the circumferential direction by sliding the foam against the outer circumferential surface of a cooling mandrel having a diameter larger than the opening of the circular die, and the foam is continuously cut and developed along the extrusion direction, using a commonly known method.

<Non-foam sheet>
The non-foamed sheet of the present embodiment is characterized by containing the heat-resistant styrene-based resin of the present embodiment described above.
The non-foamed sheet of the present embodiment preferably has a thickness of, for example, about 0.1 to 1.5 mm from the viewpoints of rigidity and thermoforming cycle.
The non-foamed sheet of the present embodiment may be formed only by ordinary roll stretching at a low stretching ratio. In particular, a sheet which is stretched by about 1.3 to 7 times with a roll and then stretched by about 1.3 to 7 times with a tenter is preferred in terms of strength.

The non-foamed sheet of this embodiment may be used in a multilayer structure with a styrene-based resin such as polystyrene resin, for example, a high-impact polystyrene made of a rubber component such as a styrene-butadiene block copolymer or polybutadiene, and may also be used in a multilayer structure with a resin other than the styrene-based resin. Examples of resins other than the styrene-based resin include PP resin, PP/PS resin, PET resin, and nylon resin.

<Method of manufacturing non-foamed sheet>
As a method for producing a non-foamed sheet, for example, a method using an apparatus in which the sheet is extruded using a single-screw or twin-screw extruder equipped with a T-die or circular die, and then taken up using a single-axis or biaxial stretching machine, can be used.

<Molded products>
The molded article of the present embodiment is characterized by comprising the foamed or non-foamed sheet of the present embodiment described above.
The molded product of the present embodiment can be formed into a secondary molded product such as a tray, a cup, a bowl container, a natto container, etc. by secondary molding the foamed sheet by a conventionally known method such as vacuum molding, pressure molding, vacuum pressure molding, double-sided vacuum molding, press molding, etc.
An example of a molded product of the present embodiment is a food tray container having a length of 5.5 to 21 cm, a width of 6.5 to 36 cm, and a depth of 1.1 to 3.4 cm, with the horizontal direction being the extrusion direction, formed by a vacuum forming machine using the foamed sheet of the present embodiment as a molding material. The temperature condition for vacuum forming is not particularly limited, but a condition of 120 to 150° C. is usually preferable.

As a molding method for obtaining the molded product of this embodiment, injection molding, extrusion molding, vacuum molding, compressed air 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 uses than ever before.

The following provides a detailed explanation of the present invention using examples and comparative examples, but the present invention is not limited to these examples.

Measurement and evaluation methods
The measurement and evaluation methods are as follows.

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

(2) Measurement of Contents of Methacrylic Acid and Methyl Methacrylate The contents (mass%) of methacrylic acid and methyl methacrylate in the heat-resistant styrene-based resin were determined by quantifying the resin composition from the integral ratio of the spectrum measured by a proton nuclear magnetic resonance ( ¹ H-NMR) measurement device.
Sample preparation: 30 mg of resin pellets were dissolved in 0.75 mL of d6-DMSO by heating at 60° C. for 4 to 6 hours.
Measuring equipment: JNM ECA-500 manufactured by JEOL Ltd.
Measurement conditions: measurement temperature 25° C., observation nucleus 1H, number of integrations 64, repetition time 11 seconds.

(3) Measurement of Molecular Weight The number average molecular weight (Mn) of the conjugated divinyl compound, the number average molecular weight (Mn), weight average molecular weight (Mw), Z average molecular weight (Mz), proportion of molecular weights of 1 million or more, proportion of molecular weights of 2 million or more, and peak top molecular weight (Mtop) of the heat-resistant styrene-based resin were measured by gel permeation chromatography (GPC) under the following conditions.
Equipment: Tosoh HLC-8220
Separation column: Two Tosoh TSK gel Super HZM-H (inner diameter 4.6 mm) connected in series Guard column: Tosoh TSK guard column Super HZ-H
Measurement solvent: tetrahydrofuran (THF)
Sample preparation: 5 mg of a measurement sample was dissolved in 10 mL of a solvent and filtered through a 0.45 μm filter.
Injection volume: 10 μL
Measurement temperature: 40°C
Flow rate: 0.35 mL/min Detector: Differential refractive index detector (RI-8020)
The calibration curve was created using 11 types of TSK standard polystyrene (F-850, F-450, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000) manufactured by Tosoh Corporation. The calibration curve was created using a linear approximation equation.

(4) Measurement of Melt Mass Flow Rate (MFR) The melt mass flow rate (g/10 min) of a heat-resistant styrene-based resin was measured in accordance with ISO1133 at 200° C. and a load of 49 N.

(5) Measurement of Vicat Softening Temperature The Vicat softening temperature (°C) of the heat-resistant styrene-based resin was measured in accordance with ISO 306. The load was 49 N. The heating rate was 50°C/hour.

(6) Measurement of Maximum Rise Ratio The maximum rise ratio of the heat-resistant styrene-based resin was measured based on the following viscoelasticity measurement.
Device name: Viscoelasticity measuring device ARES-G2 (manufactured by TA Instruments)
Measurement system: ARES-EVF option Test piece dimensions: length 20 mm, thickness 1.0 mm, width 10 mm
Elongation strain rate: 0.01/sec Temperature: 160°C
Measurement atmosphere: nitrogen gas flow Preheating time: 2 minutes Pre-elongation strain rate: 0.03/sec
Pre-extension length: 0.295 mm
Relaxation time after pre-stretching: 2 minutes For the viscoelasticity measurement, the test piece was attached to a roller, and after the temperature was stabilized at the measurement temperature, it was left to stand for the above pre-heating time and pre-heated. After the pre-heating was completed, pre-stretching was performed under the above conditions. After pre-stretching, it was left to stand for 2 minutes to relax the stress generated by the pre-stretching, and then the measurement was performed.

Based on the results of the above viscoelasticity measurements, a double common logarithmic graph was created with Hencky strain on the horizontal axis and extensional viscosity on the vertical axis, and a power approximation curve was created with the Hencky strain in the range of 0.5 to 0.8 as the linear region. When strain hardening occurs, the measured extensional viscosity becomes higher than the extensional viscosity on the approximation curve extrapolated from this linear region.
The maximum rise ratio was calculated by (extensional viscosity in the nonlinear region at maximum rise strain/extensional viscosity in the linear region at maximum rise strain), where the Hencky strain at which the extensional viscosity was maximum in the above viscoelasticity measurement was defined as the maximum rise strain.

(7) Measurement of Absolute Molecular Weight The absolute molecular weight of the heat-resistant styrene-based resin was measured using a multi-angle light scattering detector (MALS) under the following conditions (hereinafter, sometimes referred to as the "MALS method").
Equipment: Tosoh HLC-8220
Fractionation column: Two Shodex KF806-L columns connected in series Guard column: Shodex GPC KFG-4A
Measurement solvent: tetrahydrofuran (THF)
Sample concentration: 10 mg of a measurement sample was dissolved in 10 mL of a 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 (Tosoh Corporation, RI-8022)
MALS detector: Malvern Viscotek SEC-MALS 20
MALS detection angles: 12°, 20°, 28°, 36°, 44°, 52°, 60°, 68°, 76°, 84°, 90°, 100°, 108°, 116°, 124°, 132°, 140°, 148°, 156°, 164°
MALS detector temperature: 35°C
PS105K was used as a standard sample, and analysis was performed using analysis software OmniSEC5.1.
The content (%) of components with molecular weights of 1,000,000 to 5,000,000 was calculated from the obtained molecular weight and the ratio of dW/dlogM.

(8) Measurement of branching degree and gelation degree The branching degree and gelation degree of the heat-resistant styrene resin were measured and calculated by the above-mentioned MALS method. A graph was created with the horizontal axis representing log molecular weight and the vertical axis representing log radius of gyration. On this graph, a linear approximation line was created for linear polystyrene (PS245K) in the range of log molecular weight values of 5.0 to 6.0, and this was used as the reference value for linear polystyrene without a branched structure.
Here, the log radius of gyration values when the log molecular weight values are 6.0 and 6.5 are defined as <Rg6.0> and <Rg6.5>, respectively, and the <Rg6.0> and <Rg6.5> of PS245K are defined as <Rg6.0> ₂₄₅ and <Rg6.5> ₂₄₅ , respectively. Note that <Rg6.5> ₂₄₅ can be calculated from the extrapolated value of the approximation line.
The degree of branching is defined as: degree of branching = <Rg6.5>/<Rg6.5> _245. This degree of branching means how much the radius of gyration is smaller than that of linear polystyrene PS245K at an absolute molecular weight of 10 ^6.5 = 3,160,000, and the smaller the degree of branching, the more branched the target polymer is.
The gelation degree is defined as: gelation degree = (<Rg6.0>/<Rg6.0> ₂₄₅ )/(<Rg6.5>/<Rg6.5> ₂₄₅ ). This gelation degree represents the rate of change in the radius of gyration of the polymer when the absolute molecular weight is from ^106.0 to ^106.5 . In other words, it means the degree to which the branching increases as the molecular weight increases, and a higher gelation degree indicates that the branching increases as the molecular weight increases.

(9) Evaluation of deep drawing moldability of non-foamed sheet A heat-resistant styrene-based resin was extruded using a 30 mmφ sheet extruder (manufactured by Soken Co., Ltd.) to produce a sheet with a thickness of 0.5 mm. A test piece with a size of 250 mm length x 250 mm width was cut out from the obtained sheet, and a sheet container molding machine manufactured by Soken was used to sandwich the test piece between the fixed frame of the sheet molding machine, and the average temperature of the heater was set to 230 ° C., the atmospheric temperature was set to 120 ° C., and the test piece was heated for 20 seconds. Next, the fixed frame was slid into a bowl container mold (temperature 40 ° C.) with a diameter of 10 cm and a depth of 6 cm to perform vacuum molding, and 20 molded bodies were molded at a time. The side of this molded body was visually checked for tears, and the number of molded bodies that could be molded without tearing was used as an index of deep drawing moldability.

(10) Measurement of maximum moldable heating time of non-foamed sheet The heating time during deep drawing in (9) above was extended by 1 second from 20 seconds, and vacuum forming was performed without changing other conditions to mold 10 molded bodies at a time. As in (9), the heating time was extended until the number of moldable molded bodies by visual inspection was 7 or less. The maximum heating time at which 8 or more molded bodies were possible was defined as the maximum moldable heating time (seconds) of the sheet and measured.

(11) Evaluation of heat resistance of non-foamed extruded sheet A non-foamed stretched sheet having a thickness of 0.5 mm obtained by the method described in (9) above was immersed in a silicone oil bath at 105° C. for 30 minutes, and the shrinkage rate (%) of 5-fold stretching in the sheet extrusion direction was measured and evaluated according to the following criteria. A large shrinkage rate leads to a large deformation of the molded product, so a shrinkage rate of less than 3% is practically preferable.
◎: Shrinkage rate less than 3% ○: Shrinkage rate 3% to less than 6% ×: Shrinkage rate 6% or more

(12) Evaluation of deep drawing moldability of foamed sheet The foamed sheet was left at 23±3°C and 50±5% relative humidity for 20 days. Then, using a sheet container molding machine manufactured by Soken, the foamed sheet was sandwiched between the fixed frame of the sheet molding machine, the average temperature of the heater was set to 210°C, the atmospheric temperature was set to 140°C, and the sheet was heated for 15 seconds. Next, the fixed frame was slid into a cup-shaped mold (temperature 40°C) with a diameter of 10 cm and a depth of 3 cm or 6 cm, and vacuum molding was performed to mold 100 molded bodies. The side of the molded body was visually checked for tears, and the number of molded bodies that could be molded without tears was used as an index of deep drawing moldability.

(13) Measurement of maximum moldable heating time of foamed sheet During the deep drawing molding in (12) above, the heating time was extended by 1 second from 15 seconds, and vacuum molding was performed without changing other conditions, and 10 molded bodies were molded at a time. As in (12), visual inspection was performed, and the heating time was extended until the number of foamed sheets that could be molded into molded bodies was 7 or less. The maximum heating time at which 8 or more molded bodies could be molded was defined as the maximum moldable heating time (seconds) of the foamed sheet, and was measured.

(14) Evaluation of Appearance of Molded Products The gloss and roughness of the surface of the deep drawing molded products molded in (12) above were visually confirmed. Among 100 molded products, those that did not have dripping spots or uneven surfaces were judged to have good appearances, and the number of such molded products was used as an index for the appearance evaluation of the molded products.

"material"
In the examples and comparative examples, the following materials were used.

<Heat-resistant styrene resin>
<Monovinyl compounds>
Styrene: Styrene monomer [manufactured by Asahi Kasei Corporation]

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

<Conjugated divinyl compound 2>
Urethane acrylate oligomer [Tomoe Engineering Co., Ltd.: CN9014NS] Mn: 8000

<Conjugated divinyl compound 3>
Conjugated divinyl compound 3 was prepared according to the following method.
In a 10L reaction vessel equipped with a stirrer, a thermometer and a reflux condenser, 37522g of polybutadiene both-terminal alcohol (Mn: 26000), 379g of methyl acrylate, 380g of n-hexane, 0.8194g of hydroquinone monomethyl ether, and 0.5533g of 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl were charged. The mixture obtained was passed through a calcium chloride tube, while air was blown into the mixture, and reflux dehydration was performed at 80 to 85 ° C. 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, 1.3685g of tetra n-butyl titanate was added to the mixture as a transesterification catalyst, and the mixture was reacted for 10 hours at a reaction temperature of 80 to 85 ° C. while stirring and distilling the produced methanol out of the reaction system under the reflux of n-hexane, which is the azeotropic solvent.
Next, the temperature inside the reaction vessel was adjusted to 75-80°C, and the mixture was concentrated at a reduced pressure of 70-2 kPa until 95% or more of the methyl acrylate and n-hexane used were distilled out, and the excess methyl acrylate and n-hexane were recovered. 2000 g of toluene, 200 g of acetone, 20 g of ion-exchanged water, and 20 g of hydrotalcite (composition formula _Mg6Al2 (OH) _{16CO3.4H2O )} [manufactured by Kyowa Chemical Industry Co., Ltd., product name: Kyoward 500PL] as an ester exchange catalyst were added to 2070 g of _the obtained polybutadiene diacrylate, and the mixture was treated at 75-80°C for 2 hours. Next, the temperature inside the reaction vessel was adjusted to 75 to 80°C, and the mixture was concentrated at a reduced pressure of 90 to 35 kPa to recover 400 g of a mixed distillate of toluene, acetone and water. The resulting concentrated liquid was filtered under air pressure to separate the catalyst and adsorbent, and the solvent was degassed at a temperature of 60 to 80°C and a reduced pressure of 30 to 0.8 kPa to obtain a conjugated divinyl compound 3.
The conversion of the conjugated divinyl compound 3 to polybutadiene diacrylate at both ends was measured by high performance liquid chromatography (HPLC) and found to be 99.0%. The number average molecular weight (Mn) of the compound measured by GPC in terms of polystyrene was 26,000.

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

<Highly branched vinyl compounds>
<Multi-branched vinyl compound 1>
3.1 mol (399.4 g) of divinylbenzene, 0.7 mol (95.1 g) of ethylvinylbenzene, 0.3 mol (31.6 g) of styrene, 2.3 mol (463.5 g) of 2-phenoxyethyl methacrylate, and 974.3 g of toluene were charged into a 3.0 L reactor, and 42.6 g of boron trifluoride diethyl ether complex was added at 50 ° C. and reacted for 6.5 hours. After the polymerization reaction was stopped with a sodium bicarbonate solution, the oil layer was washed three times with pure water, and the reaction mixture was charged into a large amount of methanol at room temperature to precipitate a polymer. The obtained polymer was washed with methanol, filtered, 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 was 8000, the molar fraction of the structural unit (a1) containing a vinyl group derived from a divinyl compound was 0.44, the double bond (a2) derived from the terminal 2-phenoxyethyl methacrylate was 0.03, and the total molar fraction (a3) of both was 0.47. The radius of gyration of the polymer at a weight average molecular weight (Mw) of 8000 was 6.3 nm. The ratio of the radius of gyration of this polymer to the molar fraction of the double bond was 13.4, and compared with the radius of gyration of the linear type at a weight average molecular weight (Mw) of 8000 being 15 nm, it can be seen that the multi-branched vinyl compound 1 in this synthesis example has a branched structure.

<Multi-branched vinyl compound 2>
In a 2-liter flask equipped with a stirrer, a thermometer, a dropping funnel and a condenser, 50.5 g of ethoxylated pentaerythritol (ethylene oxide-added pentaerythritol) disclosed in JP 2016-113598 A and 1 g of _BF3 diethyl ether solution (50%) were added at room temperature and heated to 110 ° C. 450 g of 3-ethyl-3-(hydroxymethyl)oxetane was added slowly over 25 minutes while controlling the heat generated by the reaction. When the heat generation subsided, the reaction mixture was further stirred at 120 ° C. for 3 hours and then cooled to room temperature. The weight average molecular weight of the obtained hyperbranched polyether polyol was 3,000 and the hydroxyl value was 530.
50g of the hyperbranched polyether polyol obtained above, 13.8g of methacrylic acid, 150g of toluene, 0.06g of hydroquinone, and 1g of paratoluenesulfonic acid were added to a reactor equipped with a stirrer, a thermometer, and a condenser, and the mixture was stirred and heated under normal pressure while blowing 7% oxygen-containing nitrogen (v/v) into the mixture at a rate of 3mL/min. The heating amount was adjusted so that the amount of distillate in the decanter was 30g per hour, and heating was continued until the amount of dehydration reached 2.9g. After the reaction was completed, the mixture was cooled once, 36g of acetic anhydride and 5.7g of sulfamic acid were added, and the mixture was stirred at 60°C for 10 hours. Thereafter, in order to remove the remaining acetic acid and hydroquinone, the mixture was washed four times with 50g of 5% aqueous sodium hydroxide solution, and further washed once with 50g of 1% aqueous sulfuric acid solution and twice with 50g of water. To the obtained organic layer, 0.02 g of methoquinone was added, and the solvent was distilled off under reduced pressure while introducing 7% oxygen-containing nitrogen (v/v), to obtain 60 g of a multi-branched vinyl compound 2 having isopropenyl groups and acetyl groups. The weight average molecular weight of the obtained 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.

(Methacrylic acid, methyl methacrylate)
Methacrylic acid: Mitsubishi Gas Chemical Company, Inc. Methyl methacrylate: Asahi Kasei Corporation

Additives
・Heat deterioration inhibitor 1:
2-[1-(2-hydroxy-3,5-di-t-phenylpentyl)ethyl]-4,6-di-t-phenylpentyl acrylate [Sumitomo Chemical Co., Ltd.: Sumilizer GS]
Heat deterioration inhibitor 2:
Octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate [BASF Japan Ltd.: Irganox 1076]
Heat deterioration inhibitor 3:
Tris(2,4-di-tert-butylphenyl)phosphite [Irgafos 168, manufactured by BASF Japan Ltd.]

<others>
Polymerization initiator 1: 2,2-bis(4,4-di-tertiary-butylperoxycyclohexyl)propane [Pertetra A, manufactured by NOF Corporation]
Polymerization initiator 2: 1,1-di-(tertiary-butylperoxy)cyclohexane [Perhexa C, manufactured by NOF Corporation]
Chain transfer agent 1: α-methylstyrene dimer [NOFMER MSD, manufactured by NOF Corporation]
Ethylbenzene: manufactured by Wako Pure Chemical Industries, Ltd. Foaming nucleating agent: talc [manufactured by Matsumura Sangyo Co., Ltd.: High Filler #12]
・Blowing agent: Isobutane [Mitsui Chemicals]

Example 1
A raw material solution was prepared by adding 76.8 parts by mass of styrene, 20.0 parts by mass of ethylbenzene, 3.2 parts by mass of methacrylic acid, 0.14 parts by mass of the conjugated divinyl compound 1 obtained by the above-mentioned production method (3.9×10 ⁻⁵ mol per 1 mol of styrene), and 0.038 parts by mass of the polymerization initiator 1. The prepared raw material solution was continuously supplied at 0.73 L/hr to a 5.4 L complete mixing type first reactor maintained at a temperature of 101.5° C.
Next, 61.8 parts by mass of styrene, 35 parts by mass of ethylbenzene, 3.2 parts by mass of methacrylic acid, 0.15 parts by mass of chain transfer agent 1, and 0.05 parts by mass of polymerization initiator 2 were added to prepare a raw material solution to be supplied to the second reactor. The prepared raw material solution was continuously supplied at 0.2 L/hour to a plug-flow type second reactor having an internal volume of 1.5 L and in which the temperatures of three zones were maintained at 120° C., 128° C., and 133° C. in the order in which the raw material solution passed through.
Next, the polymerization solutions from the first reactor and the second reactor were joined and supplied to a plug-flow type third reactor having an internal volume of 3 L, in which the temperatures of four zones were maintained at 135, 155, 160, and 150° C. in the order in which the raw material solutions passed through. In addition, 0.14 parts by mass of heat deterioration inhibitor 1 was added to zone 3 of the third reactor. (In this example, the heat deterioration 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 230° C., where volatile components such as unreacted monomers and solvents were removed, and after 72 hours of continuous operation, a heat-resistant styrene-based resin for evaluation was obtained.
The solid content concentration was measured by drying the polymerization solution (after the third reactor and before the devolatilization step) at 215° C. under a reduced pressure of 2.5 kPa for 30 minutes and then calculating the solid content concentration according to the formula [(mass of sample after drying/mass of sample before drying)×100%].
To 100 parts by mass of the above heat-resistant styrene-based resin, 0.15 parts by mass of talc (average particle size 1.3 μm) was added as a foaming nucleating agent, and 4 parts by mass of liquefied isobutane was added as a foaming agent to obtain a foamed sheet raw material. The foamed sheet raw material was extruded and foamed using an extrusion foaming machine equipped with a circular die having a diameter of 150 mm. The temperature of the resin melting zone 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. The foam immediately after extrusion foaming was cooled with a cooling mandrel and cut with a cutter at one point on the circumference to obtain a foamed sheet having a thickness of 1.4 mm and a width of 1000 mm.
The production conditions and analysis results of Example 1 are shown in Table 1.

<Examples 2 to 13>
Examples 2 to 13 were carried out in the same manner as in Example 1 except that the conditions were changed as shown in Table 1, to obtain heat-resistant styrene-based resins and foamed sheets.
In the examples in which a polymerization initiator and a heat deterioration inhibitor were added in the third reactor, the polymerization initiator was added from zone 1 of the third reactor, and the heat deterioration inhibitor was added from zone 3 of the third reactor.
The measurement and evaluation results of Examples 2 to 13 are summarized in Table 1.

<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 heat-resistant styrene-based resins and foamed sheets.
In the comparative examples in which a polymerization initiator and a heat deterioration inhibitor were added in the third reactor, the polymerization initiator was added from zone 1 of the third reactor, and the heat deterioration inhibitor was added from zone 3 of the third reactor.
The measurement and evaluation results of Comparative Examples 1 to 5 are summarized in Table 1.

As is clear from Table 1, Comparative Examples 1 to 5, in which the ratios of Mw/Mn, Mz/Mw, and absolute molecular weight of 1 to 5 million are outside the specified range, had poor moldability and molding condition flexibility. Comparative Example 1, in which the Vicat softening temperature is lower than the specified range, had poor heat resistance. Furthermore, Comparative Examples 2 and 5, in which the Mw/Mn and gelation degree are outside the specified range, had insufficient appearance.

In contrast, the heat-resistant styrene resins of Examples 1 to 13, which have a branching degree of 0.60 to 0.95, a gelling degree of 1.10 to 1.80, a content of components with absolute molecular weights of 1 to 5 million of 5.0 to 14.0%, an Mw/Mn of 4.0 to 7.0, an Mz/Mw of 2.0 to 5.0, and a Vicat softening temperature of 105 to 130°C, are excellent in moldability, have a wide range of molding conditions, and produce molded products with good appearance.

The above describes an embodiment of the present invention, but the present invention is not limited to this and can be modified as appropriate without departing from the spirit of the invention.

The heat-resistant styrene resin of the present invention has excellent moldability, a wide range of molding conditions, and the ability to produce molded products such as sheets with good appearance. Taking advantage of these characteristics, it can be widely used, for example, as a molding material for home appliances, office equipment, miscellaneous goods, housing equipment, etc., and as a food packaging material, etc.

Claims (6)

A heat-resistant styrene-based resin comprising a radical copolymer of a monovinyl compound having a styrene-based compound, and a conjugated divinyl compound having at least two conjugated vinyl groups in the molecule and/or a multi-branched vinyl compound having one or more branched structures, wherein the content of the styrene-based compound in the monovinyl compound is 70 mol % or more of the content of the monovinyl compound,
The degree of branching is 0.60 to 0.95,
The gel degree is 1.10 to 1.80,
The content of components having an absolute molecular weight of 1 million to 5 million as measured using a multi-angle light scattering detector (MALS) is 5.0 to 14.0%;
The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is 4.0 to 7.0;
the ratio of z-average molecular weight (Mz) to weight-average molecular weight (Mw) (Mz/Mw) is 2.0 to 5.0;
The Vicat softening temperature is 105 to 130°C.
the styrene-based compound is styrene, α-methylstyrene, paramethylstyrene, ethylstyrene, propylstyrene, butylstyrene, chlorostyrene or bromostyrene;
the monovinyl compound is (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate or butyl (meth)acrylate;
In the case where the polybranched vinyl compound is contained, the following (a) , (b), and (c) are satisfied,
(a) the content of the multi-branched vinyl compound is 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ mol per mol of the total amount of the monovinyl compound;
(b) the multi-branched vinyl compound has a star-shaped branched structure, a pom-pom-shaped branched structure, a graft-branched structure, or an H-shaped branched structure;
(c) the number average molecular weight (Mn) of the hyperbranched vinyl compound is 1,500 to 100,000, and the weight average molecular weight (Mw) of the hyperbranched vinyl compound is 3,900 or more;
In the case where the conjugated divinyl compound is contained, the following (d) and (e) are satisfied:
(d) the content of the conjugated divinyl compound is 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ mol per 1 mol of the total amount of the monovinyl compounds;
(e) the number average molecular weight (Mn) of the conjugated divinyl compound is 4,800 to 58,000;
A heat-resistant styrene-based resin. The heat-resistant styrene-based resin according to claim 1 , which is any one of the following [2] to [4].
[2] The heat-resistant styrene-based resin contains 2.0 to 17.0% by mass of a methacrylic acid monomer in 100% by mass of the heat-resistant styrene-based resin.
[3] The maximum rise ratio is 1.2 to 5.0;
[4] The peak top molecular weight (Mtop) measured by GPC is 100,000 to 180,000. A foamed sheet comprising the heat-resistant styrene-based resin according to claim 1 or 2 and having a thickness of 0.5 to 5.0 mm. A molded article comprising the foamed sheet of claim 3 . A non-foamed sheet comprising the heat-resistant styrene-based resin according to claim 1 or 2 . A molded article comprising the non-foamed sheet of claim 5 .