Heat-resistant styrene resin, sheets and molded products

Abstract

An object of the present invention is 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 articles such as sheets with good appearance, a foamed or non-foamed sheet, and a molded article. [Solution] The heat-resistant styrene-based resin of the present invention has a degree of branching of 0.60 to 0.95, a degree of gelation of 1.1 to 1.8, a content of components having an absolute molecular weight of 1,000,000 to 5,000,000 of 5.0 to 14.0%, a ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) of 4.0 to 7.0, a ratio of z-average molecular weight (Mz) to weight-average molecular weight (Mw) of 2.0 to 5.0, and a Vicat softening temperature of 105 to 130°C. The foamed sheet of the present invention contains the above heat-resistant styrene-based resin and has a thickness of 0.5 to 5.0 mm. The non-foamed sheet of the present invention contains the above heat-resistant styrene-based resin. The molded article of the present invention is made of the above foamed or non-foamed sheet.

Description

[Technical field]

[0001] The present invention relates to a heat-resistant styrene-based resin, a sheet, and a molded article. [Background technology]

[0002] Heat-resistant styrene resins have excellent heat resistance and are used as raw materials for packaging materials such as food containers and foam boards for housing insulation, etc. In particular, for packaging material applications, foam sheets of heat-resistant styrene resins are post-molded into various shapes by 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 made thinner, lighter, and have more diverse shapes, and styrene resins with good appearance and excellent moldability are in demand.

[0003] 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 containing styrene as an essential component, 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 foam container obtained by thermoforming the extruded foam sheet. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-100433 A [Patent Document 2] JP 2014-201708 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, it has been found that the copolymer described in Patent Document 1 is insufficient in terms of 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 terms of 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.

[0006] The present invention has been devised in view of the above-mentioned conventional circumstances, and an object of the present invention is to provide a heat-resistant styrene-based resin which has excellent moldability, can be molded under a wide range of molding conditions, and can be used to produce molded articles such as sheets having good appearance, and which can be used to produce foamed and non-foamed sheets and molded articles. [Means for solving the problem]

[0007] In order to achieve the above object, the present inventors have conducted intensive research and have found that by controlling the branching degree, gelation degree, content of components having an absolute molecular weight of 1 million to 5 million measured using a multi-angle light scattering detector (MALS), ratio (Mw / Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) measured using gel permeation chromatography (GPC), ratio (Mz / Mw) of z average molecular weight (Mz) to weight average molecular weight (Mw), and Vicat softening temperature within appropriate ranges, it is possible to obtain a heat-resistant styrene-based resin that has excellent moldability, can be used under a wide range of molding conditions, and can be used to produce molded products such as sheets having good appearance, and has completed the present invention.

[0008] That is, the present invention is as follows. [1] The branching degree is 0.60 to 0.95; The gel degree is 1.10 to 1.80, The content of components with absolute molecular weights 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 using gel permeation chromatography (GPC) is 4.0 to 7.0; The ratio (Mz / Mw) of the z-average molecular weight (Mz) to the weight-average molecular weight (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, which contains 2.0 to 17.0% by mass of a methacrylic acid monomer based on 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 the above [1] to [3], which has a peak top molecular weight (Mtop) of 100,000 to 180,000 as measured by GPC. [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. Effect of the Invention

[0009] According to the present invention, it is possible to provide a heat-resistant styrene-based resin which has excellent moldability, can be molded under a wide range of molding conditions, and can be used to produce molded articles such as sheets having good appearance, as well as foamed and non-foamed sheets and molded articles. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention (hereinafter, referred to as "the present embodiment") will be described, but the present invention is not limited to the present embodiment.

[0011] {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 with absolute molecular weights 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 using gel permeation chromatography (GPC) is 4.0 to 7.0; The ratio (Mz / Mw) of the z-average molecular weight (Mz) to the weight-average molecular weight (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.

[0012] <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 further preferably 60,000 to 150,000. The heat-resistant styrene-based resin of the present embodiment preferably has a weight average molecular weight (Mw) of 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 and thereby improving the moldability and flowability.

[0013] The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the heat-resistant styrene resin of this embodiment is 4.0 to 7.0, preferably 4.2 to 6.5, more preferably 4.5 to 6.0, and further 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 following methods can be used: increasing the reaction temperature during polymerization in the order in which the reaction solution passes through the polymerization; using a chain transfer agent; using a polyfunctional (2-, 3-, or 4-functional) polymerization initiator; and, when a resin is produced by radical copolymerizing a monovinyl compound with a conjugated divinyl compound and / or a multi-branched vinyl compound, the conjugated divinyl compound or the multi-branched vinyl compound or both of them are preferably mixed in an amount of 2.0×10 per mole of the total amount of the monovinyl compound. -6 ~4.0×10 -4 mol of a conjugated divinyl compound or a multi-branched vinyl compound or both of them may be added. For example, in two reactors, polymerization may be 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 may be merged, or further polymerization may be 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 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 multifunctional polymerization initiator, a method of adding a conjugated divinyl compound or a multi-branched vinyl compound or both of them in an amount of preferably 2.0×10 per mole of the total amount of monovinyl compounds. -6 ~4.0×10 -4 There is a method of molar addition.

[0014] 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. If Mz / Mw is less than 2.0, sufficient molding processability may not be obtained. If Mz / Mw is more than 5.0, the flowability may decrease, molding processability may decrease, the molding condition range may become narrow, the polymer component may become extremely large, gel-like substances may increase, and the appearance of the molded product may deteriorate. In order to make the Mz / Mw ratio 2.0 to 5.0, for example, the following methods can be used: increasing the reaction temperature during polymerization in the order in which the reaction solution passes through the polymerization; using a chain transfer agent; using a polyfunctional (2-, 3-, or 4-functional) polymerization initiator; and, when a resin is produced by radical copolymerizing a monovinyl compound with a conjugated divinyl compound and / or a multi-branched vinyl compound, the conjugated divinyl compound or the multi-branched vinyl compound or both of them are preferably mixed in an amount of 2.0×10 per mole of the total amount of the monovinyl compound. -6 ~4.0×10 -4 mol of a conjugated divinyl compound or a multi-branched vinyl compound or both of them may be added. For example, in two reactors, polymerization may be 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 may be merged, or further polymerization may be 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 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 multifunctional polymerization initiator, a method of adding a conjugated divinyl compound or a multi-branched vinyl compound or both of them in an amount of preferably 2.0×10 per mole of the total amount of monovinyl compounds. -6 ~4.0×10 -4 There is a method of molar addition.

[0015] The heat-resistant styrene resin of the present embodiment preferably has a peak top molecular weight (Mtop) of 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 multiple 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 in the latter stage. 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 a method of further polymerization after merging is performed. 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 increasing the polymerization temperature, a method of using a chain transfer agent, etc. 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 multifunctional polymerization initiator, a method of adding a conjugated divinyl compound or a multi-branched vinyl compound or both to 1 mole of the total amount of monovinyl compounds, preferably 2.0 × 10 -6 ~4.0×10 -4 There is a method of molar addition.

[0016] In the present embodiment, the proportion of the heat-resistant styrene resin having a molecular weight of 1 million or more is preferably 2.0 to 16.0%, more preferably 3.0 to 13.0%, and further preferably 4.0 to 12.0%. By setting the proportion of the molecular weight of 1 million 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 reaction temperature of polymerization, reducing the amount of polymerization solvent used, lengthening the residence time during polymerization, etc., 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.

[0017] 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 molecular weight of 2 million or more in the range of 1.0 to 5.0%, 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 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, lengthening the residence time during polymerization, etc., 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.

[0018] 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 this 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).

[0019] <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 adjust the content of components having an absolute molecular weight of 1 to 5 million to 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 per vinyl group per mole of the total amount of the monovinyl compound. -6 ~8.0×10 -4 moles (i.e., in the case of a conjugated divinyl compound having two vinyl groups, preferably 2.0×10 -6 ~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 a styrene-based resin, there is a method in which the amount of the solvent is reduced to 0 to 20% and the reaction temperature is set to 80 to 140°C. In the present 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).

[0020] <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 much and the molecular weight per branched chain becomes small, so the number of entanglement points decreases, and entanglement is 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 adjust the branching degree to 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 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 per vinyl group per mole of the total amount of the monovinyl compound. -6 ~8.0×10 -4 moles (i.e., in the case of a conjugated divinyl compound having two vinyl groups, preferably 2.0×10 -6 ~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 this disclosure, the branching degree is a value calculated by the procedure described in the section [Examples] below.

[0021] <Gelling 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 a production facility 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 adjust the gelation degree to 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 resin is obtained by radical copolymerization of a monovinyl compound with an optional conjugated divinyl compound and / or a multi-branched vinyl compound, the amount of the conjugated divinyl compound and / or the multi-branched vinyl compound added is preferably 4.0×10 per vinyl group per mole of the total amount of the monovinyl compound. -6 ~8.0×10 -4 moles (i.e., in the case of a conjugated divinyl compound having two vinyl groups, preferably 2.0×10 -6 ~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.

[0022] <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 excellent in moldability and fluidity 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 at 200° C. and a load of 49 N in accordance with ISO1133.

[0023] <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 further preferably 1.4 to 4.6. In the present 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 more excellent 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 set the maximum rise ratio to 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 million 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.

[0024] <Total content of styrene dimer and trimer> When the heat-resistant styrene resin of the present 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 making the total content of styrene dimers and trimers 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 by heat or shearing of the molten resin. In the present disclosure, the total content of styrene dimer and trimer is a value measured using gas chromatography (GC).

[0025] <Vicat softening temperature> The heat-resistant styrene-based resin of this embodiment has a Vicat softening temperature of 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 article. 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.

[0026] <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.

[0027] <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, and styrene is 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.

[0028] <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.

[0029] <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. Here, 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%.

[0030] 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.

[0031] 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, so that 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).

[0032] The main chain structure of the conjugated divinyl compound of the present embodiment is not particularly limited, and examples thereof include polyolefins such as polyethylene, polypropylene, and polyisoprene, polystyrene, polybutadiene, hydrogenated polybutadiene, polyphenylene ether, polyester, and polyphenylene sulfide.

[0033] Specific examples of conjugated divinyl compounds include (hydrogenated) polybutadiene-terminated (meth)acrylate ("(hydrogenated)" refers to a compound that is hydrogenated or not hydrogenated. The same applies below.), polyethylene glycol-terminated (meth)acrylate, polypropylene glycol-terminated (meth)acrylate, ethoxylated bisphenol A-terminated (meth)acrylate, and ethoxylated bisphenol F-terminated (meth)acrylate, and other terminal di(meth)acrylate compounds, as well 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, and other terminal urethane acrylate compounds. For example, in the case of polypropylene glycol-terminated (meth)acrylate, the number of propylene glycol bonds in the repeating unit is determined so that the number average molecular weight (Mn) is 850 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" or "both ends" in the compound name means that conjugated vinyl groups are located at both ends.

[0034] <Content of conjugated divinyl compounds> The content of the conjugated divinyl compound in the styrene-based resin of the present embodiment is preferably 2.0×10 -6 ~4.0×10 -4 moles, more preferably 5.0 x 10 -6 ~3.5×10 -4 mole, more preferably 1.5×10 -5 ~3.0×10 -4 moles, and even more preferably 2.0×10 -5 ~2.5×10 -4 The mole content is 2.0 x 10 -6If the content is less than 4.0×10 mol, sufficient entanglement of the polymers is difficult to occur, and strain hardening does not occur, or the degree of strain hardening is small, so the molded product may have an uneven thickness or may break during molding, resulting in poor moldability. -4 If the content exceeds 1.0 mol, gel-like substances will be generated in large amounts, which may result in poor appearance of molded products. In the present disclosure, the content of the conjugated divinyl compound per mole of the total amount of the monovinyl compound is 1 H-NMR and 13 This is a value measured using C-NMR.

[0035] <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 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 vinyl groups is long, so that the reactivity of the vinyl groups decreases (the molecular weight of the multi-branched vinyl compound is large, so that the 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 the hyperbranched vinyl compound is a value measured using gel permeation chromatography (GPC).

[0036] The multi-branched vinyl compound can be synthesized by, for example, 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 a plurality of hydroxyl groups. Here, the polyhydric alcohol having a multi-branched structure and a plurality of hydroxyl groups is preferably an alcohol having 2 to 100 hydroxyl groups and having 70 to 3000 carbon atoms.

[0037] <Content of hyperbranched vinyl compound> The content of the multi-branched vinyl compound in the styrene-based resin of the present embodiment is preferably 2.0×10 -6 ~4.0×10 -4 moles, more preferably 5.0 x 10 -6 ~3.5×10 -4 mole, more preferably 1.5×10 -5 ~3.0×10 -4 moles, and even more preferably 2.0×10 -5 ~2.5×10 -4 The mole content is 2.0 x 10 -6 If the content is less than 4.0×10 mol, sufficient entanglement of the polymers is difficult to occur, and strain hardening does not occur, or the degree of strain hardening is small, so the molded product may have an uneven thickness or may break during molding, resulting in poor moldability. -4 If the content exceeds 1.0 mol, gel-like substances will be generated in large amounts, which may result in poor appearance of molded products.

[0038] <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 molded product to become easily broken during molding. In this disclosure, the content of methacrylic acid in the heat-resistant styrene-based resin is 1 H-NMR and 13 This is a value measured using C-NMR.

[0039] 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 an HIPS resin or an MBS resin, an aromatic vinyl-based thermoplastic elastomer such as SBS, or a resin such as polyphenylene ether or polyamide. 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 the physical properties of the resin. 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.

[0040] 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 process of recovering the unreacted monomer. 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 nucleating agents, flame retardants, colorants, etc., may be added to the heat-resistant styrene resin in a range that does not impair the object of this embodiment. 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.

[0041] An antioxidant is generally a component capable of stabilizing peroxide radicals such as hydroperoxy radicals generated during thermoforming or exposure to light, or decomposing the generated peroxides such as hydroperoxides. The antioxidant is not particularly limited, but examples thereof include hindered phenol-based antioxidants and peroxide decomposers. The hindered phenol-based antioxidant acts as a radical chain inhibitor, and the peroxide decomposer can decompose the 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, organophosphorus peroxide decomposers such as trisnonylphenyl phosphite, triphenyl phosphite, and tris(2,4-di-t-butylphenyl)phosphite, as well as organosulfur 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 the antioxidant added is preferably 0.01 to 1 part by mass, and more preferably 0.1 to 0.5 part by mass, based on 100 parts by mass of the heat-resistant styrene-based resin.

[0042] Examples of flame retardants include, but are not limited to, brominated flame retardants such as hexabromocyclododecane, brominated SBS block polymers, and 2,2-bis(4'(2",3"-dibromoalkoxy)-3',5'-dibromophenyl)-propane, as well as brominated bisphenol flame retardants, from the viewpoints of flame retardancy and compatibility with styrene-based resins.

[0043] Examples of the brominated bisphenol flame retardant 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 more preferred because they tend to have excellent flame retardancy and thermal stability.

[0044] When using a brominated flame retardant, it is preferable to use a brominated isocyanurate flame retardant as a flame retardant assistant. Examples of the brominated isocyanurate flame retardant 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, etc. Among the brominated isocyanurates, tris(2,3-dibromopropyl)isocyanurate is particularly preferable because it exhibits an extremely high flame retardant effect.

[0045] The content of the bromine-based flame retardant is preferably 0.1 to 10 parts by mass, more preferably 1 to 9 parts by mass, and even more preferably 2 to 8 parts by mass, relative to 100 parts by mass of the heat-resistant styrene-based resin. When the content is 0.1 part by mass or more, the flame retardancy tends to be sufficient, and when the content is 10 parts by mass or less, the moldability when producing a foamed sheet tends to be sufficiently good.

[0046] The liquid paraffin can be selected from liquid paraffins specified in, for example, the Food Sanitation Act, and standards for foods, additives, etc. Specific examples of this type of liquid paraffin include, but are not limited to, Krystoll N52, Krystoll N62, Krystoll N72, Krystoll N82, Krystoll N122, Krystoll N172, Krystoll N262, Krystoll N352, and Primol N542, all of 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.

[0047] The molecular weight of the liquid paraffin is usually determined by its kinetic viscosity. For example, the liquid paraffin in this embodiment has a kinetic viscosity of 0.1 to 60 mm at 40° C. as determined by the test method JIS K2283. 2 / sec range can be used, from 1 to 40 mm 2 / sec is preferred. The weight average molecular weight of the liquid paraffin is preferably 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 can be determined, for example, by using gas chromatography to calculate the weight average value of each molecular weight component of the liquid paraffin. When liquid paraffin in this viscosity range or in 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 the molded product, tends to be greatly improved, compared with liquid paraffin with a higher viscosity or a higher molecular weight. In addition, when the viscosity of the liquid paraffin is 0.1 mm, the heat-resistant styrene-based resin is more easily plasticized than when the viscosity of the liquid paraffin is 0.1 mm. 2 It is preferable to use liquid paraffin with a viscosity of 100 / s 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 product during molding of the resulting heat-resistant styrene-based resin.

[0048] 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, based on 100 parts by mass of the heat-resistant styrene resin. By making the content of liquid paraffin less than 5.0 parts by mass, a molded article having an excellent balance between secondary moldability, strength, and heat resistance of the molded article can be obtained.

[0049] In this embodiment, the heat deterioration inhibitor is preferably added in the polymerization step or the devolatilization step of the heat-resistant styrene resin, or after the polymerization step and before the devolatilization step. In particular, the heat deterioration inhibitor is preferably added after the end of the polymerization step (preferably immediately after) and before the devolatilization step. By adding the heat deterioration inhibitor, the radicals generated by thermal decomposition can be stabilized, and the amount of thermal decomposition can be reduced.

[0050] Examples of the heat deterioration inhibitor include phenol-based heat deterioration inhibitors such as 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, manufactured by Sumitomo Chemical Co., Ltd.), 2-[1-(2-hydroxy-3,5-di-t-phenylpentyl)ethyl]-4,6-di-t-phenylpentyl acrylate (trade name: Sumilizer GS, manufactured by Sumitomo Chemical Co., Ltd.), and 2,4-bis(octylthiomethyl)-6-methylphenol (trade name: Irganox 1520L); hindered phenol-based antioxidants such as octadecyl-3-(3,5-tertiary-butyl-4-hydroxyphenyl)propionate and 4,6-bis(octylthiomethyl)-o-cresol; and phosphorus-based processing heat stabilizers such as tris(2,4-di-tertiary-butylphenyl)phosphite. These heat deterioration inhibitors may be used alone or in combination of two or more kinds.

[0051] 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 further 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.

[0052] The content of the additive 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.

[0053] <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. In the 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.

[0054] Examples of the reactor include a complete mixing type reactor, a laminar flow type reactor, a loop type reactor in which a part of the polymerization liquid is withdrawn while the polymerization is proceeding, etc. There is no particular limitation on the order of arrangement of these reactors.

[0055] When polymerizing the heat-resistant styrene-based resin of the present 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% and more preferably 3 to 20 mass% with respect to the mixed solution composition of all monomers, polymers, solvents, etc. in the polymerization reactor.

[0056] 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, such as peroxyketals such as 2,2-bis(t-butylperoxy)butane, 1,1-bis(t-butylperoxy)cyclohexane, and n-butyl-4,4-bis(t-butylperoxy)valerate, dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, and dicumyl peroxide, diacyl peroxides such as acetyl peroxide and isobutyryl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxyesters such as t-butyl peroxyacetate, ketone peroxides such as acetylacetone peroxide, and hydroperoxides such as t-butyl hydroperoxide. The polymerization initiator is preferably used in an amount of 0.005 to 0.08% by mass based on 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 based on the monovinyl compound.

[0057] <Devolatilization process> As the volatilizing apparatus, for example, a typical 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 preferable.

[0058] The conditions for the devolatilization step are not particularly limited, and 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 the unreacted monovinyl compound in the heat-resistant styrene-based resin is preferably 50 mass % or less, more preferably 40 mass % or less. The devolatilization treatment can remove volatile matters such as the unreacted material (monovinyl compound) and / or the solvent.

[0059] The temperature for the devolatilization treatment is usually about 190 to 280° C. The pressure for the devolatilization treatment is preferably 0.1 to 50 kPa, more preferably 0.13 to 13 kPa, still more preferably 0.13 to 7 kPa, and particularly preferably 0.13 to 1.3 kPa. Desirable devolatilization methods include, for example, a method of devolatilization under reduced pressure while heating, or devolatilization through an extruder designed to remove volatile components.

[0060] <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 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 / m 2 It is preferable that:

[0061] The foamed sheet of the present embodiment may be multi-layered, for example, by further laminating a film, etc. As the type of film, any film generally used for polystyrene may be used.

[0062] The foaming agent and foam nucleating agent contained in the foam sheet of the present embodiment can be a commonly used substance. The foaming agent is not particularly limited, but examples thereof include butane, pentane, fluorocarbon, water, etc., and butane is preferred. The foam nucleating agent is not particularly limited, but examples thereof include talc, etc.

[0063] <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 making the residual amount of the styrene monomer 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).

[0064] <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 slidably contacted with the outer circumferential surface of a cooling mandrel having a diameter larger than that of the opening of the circular die, and the foam is continuously cut and developed along the extrusion direction, using a commonly known method.

[0065] <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 magnification. 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.

[0066] The non-foamed sheet of the present 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, or may be used in a multilayer structure with a resin other than the styrene-based resin, for example, a PP resin, a PP / PS resin, a PET resin, a nylon resin, etc.

[0067] <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.

[0068] <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 the 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 molding is not particularly limited, but a condition of 120 to 150°C is usually preferable.

[0069] As a molding method for obtaining the molded article of this embodiment, injection molding, extrusion molding, vacuum molding, pressure molding, extrusion foam molding, calendar molding, blow molding, etc. can be suitably used, and various molded articles can be obtained for a wider range of uses than before. EXAMPLES

[0070] Hereinafter, the embodiments of the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0071] Measurement and evaluation methods The measurement and evaluation methods are as follows.

[0072] (1) Measurement of the number of moles of conjugated divinyl compound per mole of styrene In heat-resistant styrene resins, the number of moles of conjugated divinyl compounds per mole of styrene (monovinyl compound) is: 1 H-NMR and 13 The measurements were performed using C-NMR. The measurement device used was a 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.

[0073] (2) Measurement of methacrylic acid and methyl methacrylate content The content (mass%) of methacrylic acid and methyl methacrylate in heat-resistant styrene resins was measured by proton nuclear magnetic resonance ( 1 The resin composition was determined quantitatively from the integral ratio of the spectrum measured by a 1 H-NMR measuring 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, accumulation number 64 times, repetition time 11 seconds.

[0074] (3) Molecular weight measurement 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 resin were measured using 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: 10μL Measurement temperature: 40℃ Flow rate: 0.35mL / 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.

[0075] (4) Melt mass flow rate (MFR) measurement The melt mass flow rate (g / 10 min) of the heat-resistant styrene resin was measured in accordance with ISO1133 at 200°C and a load of 49 N.

[0076] (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.

[0077] (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 20mm, thickness 1.0mm, width 10mm Elongation strain rate: 0.01 / sec Temperature: 160℃ Measurement atmosphere: Nitrogen gas flow Preheat time: 2 minutes Pre-stretch strain rate: 0.03 / sec, Pre-extension length: 0.295mm Relaxation time after pre-stretch: 2 minutes For the viscoelasticity measurement, the test piece was attached to a roller, and after the temperature stabilized at the measurement temperature, it was left to stand for the preheating time described above. After preheating, it was pre-extended under the above conditions. After pre-extension, it was left to stand for 2 minutes to relax the stress generated by the pre-extension, and then measured.

[0078] Based on the results of the 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 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 as (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.

[0079] (7) Measurement of absolute molecular weight The absolute molecular weight of the heat-resistant styrene-based resin was measured under the following conditions using a multi-angle light scattering detector (MALS) (hereinafter, sometimes referred to as the "MALS method"). Equipment: Tosoh HLC-8220 Separation column: Two Shodex KF806-L columns connected in series Guard column: Shodex GPC KFG-4A Measurement solvent: tetrahydrofuran (THF) Sample concentration: 10 mg of the measurement sample was dissolved in 10 mL of a solvent and filtered through a 0.45 μm filter. Injection volume: 100μL Measurement temperature: 40℃ Flow rate: 1.00mL / min Detector: Differential refractometer (Tosoh 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℃ PS105K was used as the standard sample, and analysis was performed using the analysis software OmniSEC5.1. The content (%) of components with molecular weights of 1 million to 5 million was calculated from the obtained molecular weight and the ratio of dW / dlogM.

[0080] (8) Measurement of branching degree and gelation degree The degree of branching and gelation of heat-resistant styrene resins were measured and calculated by the MALS method described above. A graph was created with the horizontal axis representing log molecular weight and the vertical axis representing log radius of gyration. A linear approximation line was created on this graph 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 when the log molecular weight is 6.0 and 6.5 is<Rg6.0> ,<Rg6.5> and PS245K<Rg6.0> ,<Rg6.5> respectively.<Rg6.0> 245 ,<Rg6.5> 245 It is defined as follows.<Rg6.5> 245 can be calculated from the extrapolated value of the approximation line. The degree of branching is:<Rg6.5> / <Rg6.5> 245 This branching degree is defined as the absolute molecular weight of 10 6.5 = 3.16 million, it indicates how much smaller the radius of gyration is compared to the linear polystyrene PS245K. The smaller the branching degree, the more branched the target polymer is. The degree of gelation is expressed as follows:<Rg6.0> / <Rg6.0> 245 ) / (<Rg6.5> / <Rg6.5> 245) This gelation degree is defined as the absolute molecular weight of 10 6.0 From 10 6.5 It represents the rate of change in the radius of gyration of a polymer over a period of time. In other words, it indicates the degree to which branching increases as the molecular weight increases. A higher degree of gelation indicates that branching increases as the molecular weight increases.

[0081] (9) Evaluation of deep drawing formability of non-foamed sheets A 30 mm diameter sheet extruder (manufactured by Soken Co., Ltd.) was used to extrude heat-resistant styrene resin to produce a sheet with a thickness of 0.5 mm. A test piece measuring 250 mm long x 250 mm wide was cut out from the obtained sheet, and the test piece was sandwiched between the fixed frame of a sheet container molding machine manufactured by Soken Co., Ltd., and heated for 20 seconds with the average heater temperature set to 230°C and the ambient temperature set to 120°C. 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, and vacuum molding was performed, forming 20 molded bodies at a time. The sides of these molded bodies were visually checked for tears, and the number of molded bodies that could be molded without tears was used as an index of deep drawing formability.

[0082] (10) Measurement of maximum moldable heating time for non-foamed sheet The heating time during deep drawing in (9) above was extended by 1 second from 20 seconds, while vacuum forming was performed without changing other conditions, and 10 molded bodies were molded at a time. As in (9), visual inspection was performed, and the heating time was extended until the number of molded bodies that could be molded was 7 or less. The maximum heating time at which 8 or more bodies could be molded was defined as the maximum moldable heating time (seconds) of the sheet, and was measured.

[0083] (11) Evaluation of heat resistance of non-foamed extruded sheets The non-foamed stretched sheet of 0.5 mm thickness 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% or more and less than 6% ×: Shrinkage rate 6% or more

[0084] (12) Evaluation of deep drawing formability of foam sheet The foamed sheet was left at 23±3°C and 50±5% relative humidity for 20 days. After that, the foamed sheet was sandwiched between the fixed frame of a sheet container molding machine manufactured by Soken Co., Ltd., and heated for 15 seconds with the average heater temperature set to 210°C and the ambient temperature set to 140°C. Next, the foamed sheet was slid together with the fixed frame 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 form 100 molded bodies each. The sides of the molded bodies were visually checked for tears, and the number of molded bodies that could be molded without tears was used as an index of deep drawing formability.

[0085] (13) Measurement of maximum moldable heating time for foam sheet During the deep drawing process in (12) above, the heating time was increased by 1 second from 15 seconds, while vacuum forming 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 increased until the number of foamed sheets that could be molded into molded bodies fell to 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.

[0086] (14) Evaluation of the appearance of molded products The gloss and roughness of the surface of the deep-drawn molded product molded in (12) above were visually confirmed. Among the 100 molded products, those that had no dripping spots or uneven surfaces were judged to have good appearances, and the number of such molded products was used as an index for evaluating the appearance of the molded products.

[0087] "material" In the examples and comparative examples, the following materials were used.

[0088] <Heat-resistant styrene resin> <Monovinyl compounds> Styrene: Styrene monomer [manufactured by Asahi Kasei Corporation]

[0089] <Conjugated divinyl compounds> Conjugated divinyl compounds 1 Polybutadiene terminal acrylate [Osaka Organic Chemical Industry Co., Ltd.: BAC-45] Mn: 4800

[0090] <Conjugated divinyl compound 2> Urethane acrylate oligomer [Tomoe Engineering: CN9014NS] Mn: 8000

[0091] Conjugated divinyl compounds 3 The 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, and air was blown into the mixture, followed by reflux dehydration at 80-85°C. The water content of the mixture was measured by the Karl Fischer method, and it was confirmed that the water content was 200ppm or less. Then, 1.3685g of tetra-n-butyl titanate was added to the mixture as an ester exchange catalyst, and the mixture was reacted for 10 hours at a reaction temperature of 80-85°C while stirring, while distilling the generated 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 70-2kPa 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. 2000g of toluene, 200g of acetone, 20g of ion-exchanged water, and 20g 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 2070g 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 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.

[0092] Conjugated divinyl compounds 4 The conjugated divinyl compound 4 was prepared according to the following method. Conjugated divinyl compound 4 was produced under the same conditions as conjugated divinyl compound 3, except that the molecular weight of the polybutadiene both-terminal alcohol was changed to Mn: 58000. The conversion rate of the polybutadiene both-terminal diacrylate was 98.5%. The number average molecular weight (Mn) measured by GPC in terms of polystyrene was 58000.

[0093] <Highly branched vinyl compounds> <Highly 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 poured into a large amount of methanol at room temperature to precipitate the 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.

[0094] <Highly 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 slowly added to this 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. In a reactor equipped with a stirrer, a thermometer, a Dean-Stark decanter equipped with a condenser and a gas inlet tube, 50 g of the hyperbranched polyether polyol obtained above, 13.8 g of methacrylic acid, 150 g of toluene, 0.06 g of hydroquinone, and 1 g of paratoluenesulfonic acid were added, 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 3 mL / min. The heating amount was adjusted so that the amount of distillate in the decanter was 30 g per hour, and heating was continued until the amount of dehydration reached 2.9 g. After the reaction was completed, the mixture was cooled once, 36 g of acetic anhydride and 5.7 g of sulfamic acid were added, and the mixture was stirred at 60 ° C for 10 hours. After that, in order to remove the remaining acetic acid and hydroquinone, the mixture was washed four times with 50 g of 5% sodium hydroxide aqueous solution, and further washed once with 50 g of 1% sulfuric acid aqueous solution and twice with 50 g 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 hyperbranched vinyl compound 2 having isopropenyl groups and acetyl groups. The weight average molecular weight of the obtained hyperbranched vinyl compound 2 was 3,900, and the introduction rates of isopropenyl groups and acetyl groups into the hyperbranched polyether polyol were 30 mol % and 62 mol %, respectively, based on the total hydroxyl groups.

[0095] <Methacrylic acid, methyl methacrylate> Methacrylic acid: Mitsubishi Gas Chemical Company, Inc. Methyl methacrylate: Asahi Kasei Corporation

[0096] 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 [BASF Japan Ltd.: Irgafos 168]

[0097] <others> Polymerization initiator 1: 2,2-bis(4,4-di-tertiary-butylperoxycyclohexyl)propane [NOF Corporation: Pertetra A] Polymerization initiator 2: 1,1-di-(tertiary-butylperoxy)cyclohexane [NOF Corporation: Perhexa C] Chain transfer agent 1: α-methylstyrene dimer [NOFMER MSD, manufactured by NOF Corporation] Ethylbenzene: Wako Pure Chemical Industries, Ltd. Foaming nucleating agent: Talc [Matsumura Sangyo Co., Ltd.: Hi-Filler #12] Foaming agent: Isobutane [Mitsui Chemicals]

[0098] <Example 1> 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 per mole of styrene) -5 A raw material solution was prepared by adding 0.038 parts by mass of polymerization initiator 1 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 complete mixing type first reactor having an internal volume of 5.4 L and 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 the formula [(sample mass after drying / sample mass before drying)×100%] after drying the polymerization solution (after the third reactor and before the devolatilization step) at 215° C. under reduced pressure of 2.5 kPa for 30 minutes. 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) as a foaming nucleating agent and 4 parts by mass of liquefied isobutane as a foaming agent were added 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.

[0099] <Examples 2 to 13> Examples 2 to 13 were carried out in the same manner as 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 where 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.

[0100] <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.

[0101] [Table 1]

[0102] As is clear from Table 1, in Comparative Examples 1 to 5, in which the ratios of Mw / Mn, Mz / Mw, and absolute molecular weight of 1 to 5 million were outside the prescribed range, the molding processability and molding condition range were poor. In addition, Comparative Example 1, in which the Vicat softening temperature was lower than the prescribed range, had low heat resistance. Furthermore, Comparative Examples 2 and 5, in which the Mw / Mn and gelation degree were outside the prescribed range, had insufficient appearance.

[0103] In contrast, the heat-resistant styrene-based resins of Examples 1 to 13, which have a branching degree of 0.60 to 0.95, a gelation degree of 1.10 to 1.80, a content of components with absolute molecular weights of 1 million to 5 million of 5.0 to 14.0%, Mw / Mn of 4.0 to 7.0, Mz / Mw of 2.0 to 5.0, and Vicat softening temperature of 105 to 130°C, are excellent in moldability, have a wide range of molding conditions, and produce molded articles with good appearance.

[0104] Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the spirit of the invention. [Industrial Applicability]

[0105] The heat-resistant styrene-based resin according to the present invention has excellent moldability, a wide range of molding conditions, and is capable of producing molded products such as sheets with good appearance. Taking advantage of these characteristics, the heat-resistant styrene-based resin can be widely used, for example, as a molding material for home appliances, office equipment, miscellaneous goods, housing equipment, etc., a food packaging material, etc.

Claims

1. 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 relative to 1 mole of the total amount of the monovinyl compound. －６ ~4.0 x 10 －４ is mole, (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 relative to 1 mole of the total amount of the monovinyl compounds. －６ ~4.0 x 10 －４ is mole, (e) the number average molecular weight (Mn) of the conjugated divinyl compound is 4,800 to 58,000; A heat-resistant styrene-based resin.

2. 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.

3. 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.

4. A molded article comprising the foamed sheet of claim 3.

5. A non-foamed sheet comprising the heat-resistant styrene-based resin according to claim 1 or 2.

6. A molded article comprising the non-foamed sheet of claim 5.

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