JP7520178B2 - Heat-resistant styrene resin composition, extruded sheet, molded product - Google Patents

Description

The present invention relates to a heat-resistant styrene-based resin composition that is excellent in heat resistance, appearance, extrusion moldability, and deep drawability during vacuum molding, non-foamed and foamed extruded sheets formed using the heat-resistant styrene-based resin composition, and molded products formed using the extruded sheets.

Styrene-methacrylic acid resins have excellent heat resistance and are relatively inexpensive, so they are widely used in food containers for boxed lunches and prepared foods, packaging materials, foam boards for residential insulation, and diffusion panels for LCD televisions that contain diffusion agents. In recent years, with the spread of commercial microwave ovens in convenience stores and other places, and the shortening of microwave oven operating times, higher output appliances (which tend to reach higher temperatures in a shorter time) are being used. For this reason, resins with higher heat resistance and excellent moldability are desired. In addition, for food containers, due to the increasing complexity of shapes associated with design and the increase in size of containers (area and depth) due to the increase in contents, resins with improved mechanical strength such as brittleness and deep drawability during vacuum molding compared to conventional products are desired.

Patent Document 1 describes how, by using a resin composition that is a mixture of a copolymer resin with a specific composition of styrene-methacrylic acid and a specific resin as a reinforcing agent, it is possible to obtain a resin that has high heat resistance, mechanical strength, and appearance, and is excellent in deep drawability during vacuum molding.

JP 2018-90753 A

However, when using the resin composition of the conventional technology described above to produce a molded product, the mold used may become dirty if multiple moldings are performed, and the molded product obtained may not have a sufficiently good appearance.

Under these circumstances, the problem that the present invention aims to solve is to provide a heat-resistant styrene-based resin composition that has excellent properties such as heat resistance, mechanical strength, extrusion moldability, and deep drawability during vacuum molding, and that can suppress mold contamination and produce molded products with sufficiently good appearance, non-foamed and foamed extruded sheets formed using the heat-resistant styrene-based resin composition, and molded products formed using the extruded sheets.

In view of the above problems, the present inventors have conducted intensive research and repeated experiments, and as a result have found that the above problems can be solved by using a resin composition having high heat resistance and specific properties, which is obtained by mixing (a) a copolymer resin of a specific composition of styrene-methacrylic acid, (b) a specific resin as a reinforcing agent, i.e., an MBS resin (b) obtained by grafting a copolymer mainly composed of methyl methacrylate monomer units and styrene monomer units onto rubber-like particles containing butadiene monomer units, and (c) a styrene-based resin having a specific molecular weight, in a specific ratio, and thereby completing the present invention.
That is, the present invention is as follows.

[1]
The heat-resistant styrene-based resin composition contains (a) a copolymer resin which is a styrene-methacrylic acid copolymer, (b) an MBS resin obtained by grafting a copolymer mainly composed of methyl methacrylate monomer units and styrene monomer units onto rubber particles containing butadiene monomer units, and (c) a styrene-based resin having a weight average molecular weight of 200,000 to 2,000,000,
the content of the copolymer resin (a) is 83 to 99 mass%, the content of the MBS resin (b) is 0.9 to 12 mass%, and the content of the styrene-based resin (c) is 0.1 to 5.0 mass%, relative to 100 mass% of the total mass of the copolymer resin (a), the MBS resin (b), and the styrene-based resin (c);
The copolymer resin (a) contains 84 to 96% by mass of styrene monomer units and 4 to 16% by mass of methacrylic acid monomer units, when the total of the styrene monomer units and the methacrylic acid monomer units is 100% by mass,
The Vicat softening temperature is 106°C or higher,
A heat-resistant styrene-based resin composition having a branching degree of 0.60 to 0.95 and a gelation degree of 1.10 to 1.60.
[2]
The heat-resistant styrene-based resin composition according to [1], wherein the total content of styrene monomer units contained in the heat-resistant styrene-based resin composition is 80 mass% or more.
[3]
The heat-resistant styrene-based resin composition according to [1] or [2], wherein the total content of a styrene dimer and a styrene trimer is 0.6 mass% or less, and the content of a styrene monomer is 700 mass ppm or less, relative to 100 mass% of a total mass of the heat-resistant styrene-based resin composition.
[4]
The heat-resistant styrene-based resin composition according to any one of [1] to [3], wherein the copolymer resin (a) has a weight average molecular weight of 100,000 to 350,000.
[5]
The heat-resistant styrene-based resin composition according to any one of [1] to [4], wherein the butadiene monomer unit content in the MBS resin (b) is 50% by mass or more, the mass composition ratio of methyl methacrylate to styrene in the MBS resin (b) is 30/70 to 70/30, and the styrene monomer unit content in the MBS resin (b) is 3 to 35% by mass.
[6]
The heat-resistant styrene-based resin composition according to any one of [1] to [5], further comprising a rubber-modified styrene-based resin (d) in an amount of 30 mass% or less based on 100 mass% of the total mass of the heat-resistant styrene-based resin composition, and the rubber-modified styrene-based resin (d) has a rubber particle diameter of 0.5 to 5.0 μm.
[7]
The heat-resistant styrene-based resin composition according to any one of [1] to [6], further comprising an aliphatic primary alcohol having 14 or more carbon atoms and a freezing point of -10°C or lower in an amount of 0.02 to 1.0 parts by mass, relative to 100% by mass of the total mass of the heat-resistant styrene-based resin composition.
[8]
An extruded sheet formed using the heat-resistant styrene-based resin composition according to any one of [1] to [7].
[9]
A foamed extruded sheet formed using the heat-resistant styrene-based resin composition according to any one of [1] to [7].
[10]
A molded product formed using the non-foamed extruded sheet according to [8] or the foamed extruded sheet according to [9].

The present invention provides a heat-resistant styrene-based resin composition that has excellent properties such as heat resistance, mechanical strength, extrusion moldability, and deep drawability during vacuum molding, and that can suppress mold contamination and produce molded products with sufficiently good appearance; non-foamed and foamed extruded sheets formed using the heat-resistant styrene-based resin composition; and molded products formed using the extruded sheets.

The following describes in detail the form for carrying out the present invention (hereinafter, referred to as the "present embodiment"). Note that the present invention is not limited to the following embodiment, and can be carried out in various modifications within the scope of the gist of the invention.

(Heat-resistant styrene-based resin composition)
The heat-resistant styrene-based resin composition of the present embodiment contains a copolymer resin (a) which is a styrene-methacrylic acid copolymer, an MBS resin (b) which is obtained by grafting a copolymer mainly composed of methyl methacrylate monomer units and styrene monomer units onto rubber-like particles containing butadiene monomer units, and a styrene-based resin (c) having a weight-average molecular weight of 200,000 to 2,000,000. In the heat-resistant styrene-based resin composition of the present embodiment, the content of the copolymer resin (a) is 83 to 99 mass%, the content of the MBS resin (b) is 0.9 to 12 mass%, and the content of the styrene-based resin (c) is 0.1 to 5.0 mass%, relative to 100 mass% of the total mass of the copolymer resin (a), the MBS resin (b), and the styrene-based resin (c). In this embodiment, the copolymer resin (a) contains 84 to 96% by mass of styrene monomer units and 4 to 16% by mass of methacrylic acid monomer units, when the total of the styrene monomer units and the methacrylic acid monomer units is taken as 100% by mass. Furthermore, the heat-resistant styrene-based resin composition of this embodiment has a Vicat softening temperature of 106° C. or higher, a branching degree of 0.60 to 0.95, and a gelling degree of 1.10 to 1.60 (hereinafter, the heat-resistant styrene-based resin composition of this embodiment may be simply referred to as the "resin composition of this embodiment").

<Copolymer Resin (a)>
In the resin composition of the present embodiment, the content of the copolymer resin (a), which is a styrene-methacrylic acid copolymer, is 83 to 99 mass%, preferably 85 to 98 mass%, more preferably 87 to 98 mass%, and even more preferably 89 to 97 mass%, relative to 100 mass% of the total mass of the copolymer resin (a), the MBS resin (b), and the styrene-based resin (c).
If the content is less than 83% by mass, the amount of MBS resin (b) and styrene-based resin (c) used increases, which makes foaming difficult due to gas escape during foaming, and the physical properties of the resulting foam tend to deteriorate. In addition, the rigidity of the resulting molded product tends to decrease, and the appearance of the sheet or the like tends to deteriorate. Furthermore, the content of the styrene monomer unit contained in the heat-resistant styrene-based resin composition decreases, which tends to decrease the adhesion of the resulting molded product to the laminate film. On the other hand, if the content exceeds 99% by mass, the amount of MBS resin (b) used decreases, which makes it difficult to obtain a sufficient effect of improving mechanical strength, and the amount of styrene-based resin (c) used decreases, which makes it difficult to obtain a sufficient effect of improving deep drawability during vacuum molding of the resulting extruded sheet.

In the copolymer resin (a), when the total of the styrene monomer units and the methacrylic acid monomer units is 100% by mass, the content of the styrene monomer units is 84 to 96% by mass, preferably 86 to 94% by mass, and more preferably 87 to 91% by mass. If the content is less than 84% by mass, the fluidity of the resin decreases, while if it exceeds 96% by mass, the desired amount of the methacrylic acid monomer units described below cannot be present, and the effects of the methacrylic acid monomer units described below cannot be obtained.

In the resin composition of this embodiment, the methacrylic acid monomer units play a role in improving heat resistance. When the total of the styrene monomer units and the methacrylic acid monomer units in the copolymer resin (a) is taken as 100% by mass, the content of the methacrylic acid monomer units is 4 to 16% by mass, preferably 6 to 14% by mass, and more preferably 9 to 13% by mass. If this content is less than 4% by mass, the effect of improving heat resistance is insufficient, while if it exceeds 16% by mass, the amount of gelled matter in the resin increases, resulting in poor appearance and a decrease in the fluidity and mechanical properties of the resin, which is not preferable.

Generally, styrene-methacrylic acid resins are almost always produced on an industrial scale by radical polymerization, but as described in the aforementioned Patent Documents 1 and 2, various alcohols may be added to the polymerization system to suppress the gelling reaction during the devolatilization process.

The contents of the styrene monomer unit and the methacrylic acid monomer unit in the copolymer resin (a) according to the present invention can be determined from the integral ratio of the spectrum measured by a proton nuclear magnetic resonance ( ¹ H-NMR) measuring device.

The copolymer resin (a) may optionally contain monomer units other than styrene monomer units and methacrylic acid monomer units within a range that does not impair the effects of the present invention, for example, preferably in a range of 10 mass% or less, more preferably 3 mass% or less, when the total content of all monomer units constituting the copolymer resin (a) is taken as 100 mass%, but typically consists of styrene monomer units and methacrylic acid monomer units.

In this embodiment, the Vicat softening temperature of the copolymer resin (a) is preferably 106 to 135°C, more preferably 108 to 130°C, and even more preferably 110 to 125°C. When the Vicat softening temperature is 106 to 135°C, a resin with a better balance between heat resistance and fluidity can be obtained.

In this embodiment, the weight average molecular weight of the copolymer resin (a) is preferably 100,000 to 350,000, more preferably 120,000 to 300,000, and even more preferably 140,000 to 250,000. When the weight average molecular weight is 100,000 to 350,000, a resin having an excellent balance between mechanical strength and fluidity is obtained, and the inclusion of gel is reduced.
In the present disclosure, the weight average molecular weight is a value obtained by gel permeation chromatography in terms of standard polystyrene.

The melt mass flow rate of the copolymer resin (a) at 200° C. is preferably 0.3 to 3.0 g/10 min, more preferably 0.4 to 2.5 g/10 min, and even more preferably 0.4 to 2.0 g/10 min.
A melt mass flow rate of 0.3 g/10 min or more is preferred from the viewpoint of fluidity, and a melt mass flow rate of 3.0 g/10 min or less is preferred from the viewpoint of mechanical strength of the resin.
In this disclosure, the melt mass flow rate is a value measured in accordance with ISO 1133 at 200° C. and a load of 49 N.

The polymerization method for the copolymer resin (a) according to the present invention is not particularly limited, but as a radical polymerization method, a bulk polymerization method or a solution polymerization method can be preferably adopted. The polymerization method mainly comprises a polymerization step of polymerizing the polymerization raw materials (monomer components) and a devolatilization step of removing volatile matters such as unreacted monomers and polymerization solvent from the polymerization product.
The polymerization method for the copolymer resin (a) according to the present invention will be described below.

When the polymerization raw materials are polymerized to obtain the copolymer resin (a) according to the present invention, a polymerization initiator and a chain transfer agent are typically contained in the polymerization raw material composition.

Examples of polymerization initiators include organic peroxides, for example, peroxyketals such as 2,2-bis(t-butylperoxy)butane, 1,1-bis(t-butylperoxy)cyclohexane, and n-butyl-4,4-bis(t-butylperoxy)valerate, dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, and dicumyl peroxide, diacyl peroxides such as acetyl peroxide and isobutyryl peroxide, peroxydicarbonates such as diisopropyl peroxydicarbonate, peroxyesters such as t-butylperoxyacetate, ketone peroxides such as acetylacetone peroxide, and hydroperoxides such as t-butyl hydroperoxide. From the viewpoints of decomposition rate and polymerization rate, 1,1-bis(t-butylperoxy)cyclohexane is particularly preferred.

Examples of chain transfer agents include α-methylstyrene linear dimer, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-octyl mercaptan.

As the polymerization method, solution polymerization using a polymerization solvent can be adopted as necessary.
The polymerization solvent to be used includes aromatic hydrocarbons such as ethylbenzene, dialkyl ketones such as methyl ethyl ketone, etc., each of which may be used alone or in combination of two or more. Other polymerization solvents such as aliphatic hydrocarbons may be further mixed with the aromatic hydrocarbons within a range that does not decrease the solubility of the polymerization product.
The polymerization solvent is preferably used in an amount not exceeding 25 parts by mass relative to 100 parts by mass of the total monomers. If the amount of the polymerization solvent exceeds 25 parts by mass relative to 100 parts by mass of the total monomers, the polymerization rate is significantly decreased and the mechanical strength of the obtained resin tends to be significantly decreased. It is preferable to add the polymerization solvent in an amount of 5 to 20 parts by mass relative to 100 parts by mass of the total monomers before polymerization, because this makes it easier to achieve uniform quality and is also preferable in terms of controlling the polymerization temperature.

The apparatus used in the polymerization step for obtaining the copolymer resin (a) according to the present invention is not particularly limited, and may be appropriately selected according to the polymerization method for styrene-based resins.
For example, in the case of bulk polymerization, a polymerization apparatus having one or more completely mixed reactors connected together can be used. There is also no particular restriction on the devolatilization step. In the case of bulk polymerization, polymerization is continued until the final amount of unreacted monomer is preferably 50 mass% or less, more preferably 40 mass% or less, and devolatilization treatment is performed by a known method to remove volatile matters such as unreacted monomer. For example, a conventional devolatilization apparatus such as a flash drum, a twin-screw devolatilizer, a thin film evaporator, or an extruder can be used, but a devolatilization apparatus with a small retention portion is preferred.
The temperature for the devolatilization treatment is usually about 190 to 280° C., and more preferably 190 to 260° C. The pressure for the devolatilization treatment is usually about 0.13 to 4.0 kPa, preferably 0.13 to 3.0 kPa, and more preferably 0.13 to 2.0 kPa. Desirable devolatilization methods include, for example, a method of removing volatile matters by reducing pressure under heating, and a method of removing volatile matters through an extruder or the like designed for the purpose of removing volatile matters.

<MBS resin (b)>
In the resin composition of the present embodiment, the MBS resin ( The content of b) is preferably 0.9 to 12 mass% relative to 100 mass% of the total mass of the copolymer resin (a), the MBS resin (b), and the styrene-based resin (c), It is more preferably 2 to 11 mass %, and even more preferably 3 to 10 mass %.
Here, the copolymer to be grafted onto the rubber-like particles containing butadiene monomer units is mainly composed of methyl methacrylate monomer units and styrene monomer units, and the total monomer content of the copolymer to be grafted is This means that the ratio of the total of the methyl methacrylate monomer units and the styrene monomer units to the total of the copolymer units is 92% by mass or more. This ratio is preferably 94% by mass or more, and more preferably 96% by mass or more. % or more. In the case where a monomer unit other than the methyl methacrylate monomer and the styrene monomer is contained, such a monomer unit may be, for example, a butyl acrylate monomer. Butyl acrylate monomer The inclusion of such a binder is preferable since it improves the fluidity, but if the content is too high, the heat resistance is likely to decrease.
By using the MBS resin (b), a resin composition excellent in improving mechanical strength can be obtained. However, if the amount used is less than 0.9 mass %, the improvement in mechanical strength tends to be low. If it exceeds 100% by mass, the butadiene monomer unit content in the resin composition will be so high that foaming will become difficult due to gas escape during foam molding, and the physical properties of the resulting foam will tend to deteriorate. The rigidity of the obtained molded article tends to decrease, and the appearance of the sheet or the like tends to deteriorate.

The content of butadiene monomer units in MBS resin (b) is preferably 50 to 90% by mass, more preferably 60 to 85% by mass, and even more preferably 65 to 80% by mass. The higher the butadiene monomer unit content, the greater the improvement in mechanical strength with a small amount of addition, and the less the decrease in heat resistance, which is preferable. On the other hand, if the butadiene monomer unit content is too high, the content of the graft copolymer mainly composed of methyl methacrylate monomer units and styrene monomer units will decrease, and compatibility with copolymer resin (a) will decrease, tending to deteriorate the sheet appearance.

In the MBS resin (b), the composition ratio of the methyl methacrylate monomer units to the styrene monomer units is preferably in the range of 30/70 to 70/30, more preferably in the range of 35/65 to 65/35. When the composition ratio is in the range of 30/70 to 70/30, compatibility with the copolymer resin (a) is good, which is advantageous in terms of mechanical strength and sheet appearance.

In MBS resin (b), the content of styrene monomer units is preferably 3 to 35 mass%, more preferably 5 to 30 mass%, and even more preferably 7 to 23 mass%.

<Styrene-based resin (c)>
In the resin composition of the present embodiment, the content of the styrene-based resin (c) having a weight average molecular weight of 200,000 to 2,000,000 is 0.1 to 5.0 mass%, preferably 0.3 to 3.0 mass%, and more preferably 0.5 to 2.0 mass%, relative to 100 mass% of the total mass of the copolymer resin (a), the MBS resin (b), and the styrene-based resin (c).
By using the styrene-based resin (c), the melt tension of the resin composition of this embodiment is improved, and the molding stability during extrusion molding of the sheet and the deep drawability during vacuum molding of the extruded sheet are significantly improved. In addition, if the resin composition contains a copolymer resin having a weight average molecular weight of 1,000,000 or more, which is a copolymer of methyl methacrylate monomer units and butyl acrylate monomer units, at the above content, the mold staining and appearance are not sufficient (it is presumed that the high molecular weight component of the copolymer may decompose due to heat history caused by shear stress during melt kneading when producing the resin composition, and the decomposition product may affect the mold staining and appearance), but by using the styrene-based resin (c), the risk of decomposition of the high molecular weight component during melt kneading when producing the resin composition can be reduced, so that mold staining can be suppressed and the appearance can be improved.
Furthermore, if the content is less than 0.1% by mass, the melt tension is not improved, and therefore the effects of improving molding stability and deep drawability cannot be obtained. If the content exceeds 5.0% by mass, the melt tension is too high, and the fluidity is reduced, making extrusion molding difficult.

<Molecular weight distribution>
The styrene-based resin (c) of this embodiment has a weight average molecular weight (Mw) of 200,000 to 2,000,000, more preferably 300,000 to 500,000, even more preferably 250,000 to 1,000,000, and particularly preferably 300,000 to 600,000. By having a weight average molecular weight (Mw) of 200,000 or more, it is possible to improve the molding stability during extrusion molding of the sheet and the deep drawability during vacuum molding of the extruded sheet, and by having a weight average molecular weight (Mw) of 2,000,000 or less, it is possible to further suppress the content of high molecular weight components, so that even if shear stress occurs during the production of the resin composition, decomposition products can be reduced, mold contamination can be suppressed, and the appearance can be improved.
The number average molecular weight (Mn) of the styrene-based resin (c) is preferably from 50,000 to 200,000, more preferably from 55,000 to 150,000, and particularly preferably from 60,000 to 120,000.

The styrene-based resin (c) of this embodiment preferably has a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 3.0 to 7.0, more preferably 4.0 to 6.5, and particularly preferably 4.7 to 6.0. If the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is less than 3.0, the content of high molecular weight components is low, and deep drawing formability may be insufficient. If Mw/Mn is more than 7.0, the content of low molecular weight components becomes extremely high, and the strength of the molded product may decrease.
In order to make the Mw/Mn of the styrene-based resin (c) 3.0 to 7.0, for example, there are a method of increasing the reaction temperature during polymerization in the order in which the reaction solution passes through, a method of using a chain transfer agent, a method of using a polyfunctional (2-, 3-, 4-functional) polymerization initiator, and a method of adding a conjugated divinyl compound or a polybranched vinyl compound or both of them, preferably 2.0×10 −6 to 4.0× ^{10 −4 moles} per mole of the total amount of the monovinyl compound, when a resin is produced by radical copolymerizing a monovinyl compound with a conjugated divinyl compound and/or a polybranched vinyl compound. In addition, for example, there is a method of performing polymerization in two reactors under conditions for polymerizing a low molecular weight component and conditions for polymerizing a high molecular weight component, respectively, and then joining the two polymerization solutions, or a method of performing further polymerization after joining. Conditions for polymerizing a low molecular weight component include, for example, a method of shortening the residence time in the reactor, a method of increasing the amount of solvent and raising the polymerization temperature, a method of using a chain transfer agent, and the like. Conditions for polymerizing the high molecular weight component include, for example, a method of reducing the amount of solvent and lowering the polymerization temperature, a method of using a polyfunctional polymerization initiator, a method of adding a conjugated divinyl compound or a multi-branched vinyl compound or both, preferably in an amount of 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ mol per mol of the total amount of the monovinyl compound, and a method of adding a styrene-based resin (c) whose molecular weight has been controlled by anionic polymerization or cationic polymerization to a solution, or kneading with an extruder.

In addition, the styrene-based resin (c) of this embodiment preferably has a ratio (Mz/Mw) of the z-average molecular weight (Mz) to the weight-average molecular weight (Mw) of 1.8 to 6.0, more preferably 2.0 to 5.5, and particularly preferably 2.5 to 5.0. By making the ratio (Mz/Mw) of the z-average molecular weight (Mz) to the weight-average molecular weight (Mw) 1.8 or more, molding processability can be improved, and by making (Mz/Mw) 6.0 or less, the content of high molecular weight components can be further suppressed, so that decomposition products can be reduced, mold fouling can be suppressed, and the appearance can be improved.
In order to obtain the Mz/Mw of the styrene-based resin (c), for example, there are a method of increasing the reaction temperature during polymerization in the order in which the reaction solution passes through, a method of using a chain transfer agent, a method of using a polyfunctional (2-, 3-, 4-functional) polymerization initiator, and a method of adding a conjugated divinyl compound or a polybranched vinyl compound or both of them, preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ moles per mole of the total amount of the monovinyl compound, when a resin is produced by radical copolymerizing a monovinyl compound with a conjugated divinyl compound and/or a polybranched vinyl compound. In addition, for example, there is a method of performing polymerization in two reactors under conditions for polymerizing a low molecular weight component and conditions for polymerizing a high molecular weight component, respectively, and then joining the two polymerization solutions, or a method of performing further polymerization after joining. Examples of conditions for polymerizing a low molecular weight component include a method of shortening the residence time in the reactor, a method of increasing the amount of solvent and raising the polymerization temperature, and a method of using a chain transfer agent. Conditions for polymerizing the high molecular weight component include, for example, a method of reducing the amount of solvent and lowering the polymerization temperature, a method of using a polyfunctional polymerization initiator, a method of adding a conjugated divinyl compound or a multi-branched vinyl compound or both, preferably in an amount of 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ mol per mol of the total amount of the monovinyl compound, and a method of adding a styrene-based resin (c) whose molecular weight has been controlled by anionic polymerization or cationic polymerization to a solution, or kneading with an extruder.

<Degree of branching>
The branching degree of the styrene-based resin (c) of this embodiment is preferably 0.60 to 0.95, more preferably 0.62 to 0.92, even more preferably 0.65 to 0.90, and even more preferably 0.65 to 0.85. If the branching degree 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 the entanglement may be unraveled at high strain, and sufficient moldability may not be obtained. If the branching degree is more than 0.95, the branching is small, and sufficient entanglement effect between polymer chains cannot be obtained, and sufficient deep drawing moldability cannot be obtained.
In order to make the degree of branching 0.60 to 0.95, 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 styrene-based resin (c) is obtained by radical copolymerization by optionally adding a conjugated divinyl compound and/or a multi-branched vinyl compound to a monovinyl compound, the amount of the conjugated divinyl compound and/or the multi-branched vinyl compound added is preferably 4.0×10 ⁻⁶ to 8.0×10 ⁻⁴ moles per vinyl group per mole of the total amount of the monovinyl compound (i.e., in the case of a conjugated divinyl compound having two vinyl groups, it is preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ ). The number average molecular weight (Mn) of the conjugated divinyl compound and the multi-branched vinyl compound is preferably 850 to 100,000.
In the present disclosure, the degree of branching is a value calculated by the procedure described in the section [Examples] below.

<Gelling degree>
The gel degree of the styrene-based resin (c) of this embodiment is preferably 1.10 to 1.60, more preferably 1.12 to 1.55, even more preferably 1.15 to 1.50, and even more preferably 1.18 to 1.45. By setting the gel degree in the range of 1.10 to 1.60, 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 material in the resin composition. 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 material generated, and therefore it is possible to improve productivity.
In order to make the gelation degree 1.10 to 1.60, 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 styrene-based resin (c) is obtained by radical copolymerization by optionally adding a conjugated divinyl compound and/or a multi-branched vinyl compound to a monovinyl compound, the amount of the conjugated divinyl compound and/or the multi-branched vinyl compound added is preferably 4.0×10 ⁻⁶ to 8.0×10 ⁻⁴ moles per vinyl group per mole of the total amount of the monovinyl compound (i.e., in the case of a conjugated divinyl compound having two vinyl groups, it is preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ ). The number average molecular weight (Mn) of the conjugated divinyl compound and the multi-branched vinyl compound is preferably 850 to 100,000.
In the present disclosure, the gelation degree is a value calculated by the procedure described in the section [Examples] below.

<Melt mass flow rate>
The melt mass flow rate (MFR) of the styrene-based resin (c) of this embodiment measured under conditions of 200 ° C. and 49 N load is preferably more than 1.0 g / 10 min and 10 g / 10 min or less, more preferably more than 1.5 g / 10 min and 10 g / 10 min or less, even more preferably more than 2.0 g / 10 min and 8.0 g / 10 min or less, even more preferably more than 2.5 g / 10 min and 6.0 g / 10 min or less, and particularly preferably more than 2.5 g / 10 min and 5.0 g / 10 min or less. By making it more than 1.0 g / 10 min, mold contamination can be suppressed and the molded article obtained from the resin composition can have a sufficiently good appearance. In addition, by making it 10 g / 10 min or less, the strength of the molded article of the resin composition containing the styrene-based resin (c) can be maintained.
In this disclosure, the melt mass flow rate is a value measured at 200° C. and a load of 49 N in accordance with ISO 1133.

In order to set the melt mass flow rate (MFR) in the above range, for example, a method of broadening the molecular weight distribution of the styrene-based resin (c) (Mw/Mn is set to 3.0 to 7.0), a method of adding 0.01 to 10.0 mass% of a plasticizer such as liquid paraffin relative to 100 mass% of the styrene-based resin (c), or a method of lowering the glass transition temperature of the styrene-based resin (c) can be mentioned. In addition, it can be adjusted by the reaction temperature and residence time of the polymerization process, the type, amount, and location of addition of the polymerization initiator, the type, amount, and location of addition of the chain transfer agent, and the type and amount of the solvent used during polymerization.

<Peak top molecular weight (Mtop)>
The styrene-based resin (c) of this embodiment preferably has a peak top molecular weight (Mtop) measured by gel permeation chromatography (GPC) of 80,000 to 300,000, more preferably 90,000 to 250,000, and particularly preferably 100,000 to 200,000. If Mtop is less than 80,000, the content of low molecular weight components increases, and the strength of the sheet or molded product may decrease. If Mtop exceeds 300,000, the flowability decreases, so that the molding elongation tends to deteriorate, and deep drawing formability may decrease. The Mtop of the styrene-based resin (c) can be adjusted by the reaction temperature and residence time of the polymerization step, the type and amount of polymerization initiator, the type and amount of chain transfer agent, and the type and amount of solvent used during polymerization.

<Content of components with molecular weight of 1 million or more>
In the styrene-based resin (c) of the present embodiment, the content of components having a molecular weight of 1,000,000 or more is preferably 7.0% by mass or more, more preferably 7.5 to 12.0% by mass, and particularly preferably 8.0 to 10.0% by mass, based on 100% by mass of the styrene-based resin.
By making the content of components having a molecular weight of 1,000,000 or more 7% by mass or more, moldability can be improved, while by making the content 12.0% by mass or less, the appearance can be improved.
The molecular weight ratio of the styrene-based resin (c) can be adjusted by the reaction temperature and residence time in the polymerization step, the type and amount of the polymerization initiator, the type and amount of the solvent used during polymerization, and the type and amount of the chain transfer agent.
For example, there is 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 styrene-based resin (c) is obtained by radical copolymerization by optionally adding a conjugated divinyl compound and/or a multi-branched vinyl compound to a monovinyl compound, the amount of the conjugated divinyl compound and/or the multi-branched vinyl compound added is preferably 4.0×10 ⁻⁶ to 8.0×10 ⁻⁴ moles per vinyl group relative to 1 mole of the total amount of the monovinyl compound (i.e., in the case of a conjugated divinyl compound having two vinyl groups, it is preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ ). The number average molecular weight (Mn) of the conjugated divinyl compound and the multi-branched vinyl compound is preferably 850 to 100,000. In addition, in the production of the styrene-based resin (c), there is a method of reducing the amount of solvent to 0 to 20% and setting the reaction temperature to 80 to 140° C. Also, there is a method in which a styrene-based resin (c) whose molecular weight has been controlled by anionic polymerization or cationic polymerization is added to the solution, or kneaded in an extruder.

<Content of components with molecular weight of 2 million or more>
In the styrene-based resin (c) of this embodiment, the proportion of components having a molecular weight of 2,000,000 or more is preferably 2% by mass or more, more preferably 2.3 to 5.0% by mass, and particularly preferably 2.5 to 4.0% by mass.
By making the content of components having a molecular weight of 2,000,000 or more 2% by mass or more, moldability can be improved, while by making the content 5.0% by mass or less, a product with good appearance can be molded.
The molecular weight ratio of the styrene-based resin (c) can be adjusted by the reaction temperature and residence time in the polymerization step, the type and amount of the polymerization initiator, the type and amount of the solvent used during polymerization, and the type and amount of the chain transfer agent.
For example, there is 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 styrene-based resin (c) is obtained by radical copolymerization by optionally adding a conjugated divinyl compound and/or a multi-branched vinyl compound to a monovinyl compound, the amount of the conjugated divinyl compound and/or the multi-branched vinyl compound added is preferably 4.0×10 ⁻⁶ to 8.0×10 ⁻⁴ moles per vinyl group relative to 1 mole of the total amount of the monovinyl compound (i.e., in the case of a conjugated divinyl compound having two vinyl groups, it is preferably 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ ). The number average molecular weight (Mn) of the conjugated divinyl compound and the multi-branched vinyl compound is preferably 850 to 100,000. In addition, in the production of the styrene-based resin (c), there is a method of reducing the amount of solvent to 0 to 20% and setting the reaction temperature to 80 to 140° C. Also, there is a method in which a styrene-based resin (c) whose molecular weight has been controlled by anionic polymerization or cationic polymerization is added to the solution, or kneaded in an extruder.

<Maximum rise ratio>
The styrene-based resin (c) of the present embodiment preferably has a maximum rise ratio of 1.1 to 4.0, more preferably 1.2 to 3.0, and further preferably 1.1 to 2.5.
In this specification, the term "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 term "maximum rise strain" means the Hencky strain at which 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 greater the degree of strain hardening and the better the moldability.
Therefore, if the maximum rise ratio is 1.1 or more, the elongational viscosity becomes high at high strain, that is, when the resin is stretched thin during molding, so that the molded product tends to have a uniform wall thickness and is less likely to break during molding. If the maximum rise ratio is 4.0 or less, the elongational viscosity during molding does not become too high, which is preferable from the viewpoint of the balance between productivity and moldability.

<Raw materials and production method of styrene-based resin (c)>
The styrene-based resin (c) of the present embodiment is not particularly limited, but can be obtained, for example, by radical copolymerization of a monovinyl compound with a conjugated divinyl compound and/or a multi-branched vinyl compound (the molecular chain can be made branched).
Hereinafter, as an example, a method for producing the styrene-based resin (c) by radical copolymerization of a monovinyl compound with a conjugated divinyl compound and/or a multi-branched vinyl compound will be described in detail.

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

<<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-based resin (c) or require cleaning of the reactor or molding machine, resulting in reduced productivity. From these viewpoints, the number of conjugated vinyl groups possessed by the conjugated divinyl compound is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less. From the same viewpoint, it is particularly preferable that the number of conjugated vinyl groups of the conjugated divinyl compound is 2.
In this specification, the term "terminal" of a molecule includes not only the end position (atom) of the molecule but also a position adjacent to the end position of the molecule, and the adjacent position specifically means an end corresponding to about 20% of the extended chain length of the molecule. From the viewpoint of improving reactivity with a monovinyl compound and suppressing gelation, the conjugated vinyl group in the conjugated divinyl compound is more preferably located at an end corresponding to 15% of the extended chain length of the conjugated divinyl compound molecule, even more preferably located at an end corresponding to 10%, and even more preferably located at an end corresponding to 5%.

In this embodiment, the conjugated vinyl group is a group having an olefinic double bond copolymerizable with a monovinyl compound and a structure that forms a conjugated system with the olefinic double bond (for example, but not limited to, a carbonyl group, an aryl group, etc.). 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. Note that at least two conjugated vinyl groups may be the same or different from each other.

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

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

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

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

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

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

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

<<Polymerization process>>
The polymerization method of the styrene-based resin (c) of this embodiment may be, for example, a known styrene polymerization method such as a bulk polymerization method, a solution polymerization method, or a suspension polymerization method. These polymerization methods may be batch polymerization methods or continuous polymerization methods, and continuous polymerization methods are preferable from the viewpoint of productivity. As a continuous bulk polymerization method, for example, a monovinyl compound, a conjugated divinyl compound having a conjugated vinyl group, and if necessary, a solvent, a polymerization catalyst, a chain transfer agent, etc. are added and mixed to prepare a raw material solution containing monomers. 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, may be mentioned.

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

When polymerizing the styrene-based resin (c) of this embodiment, a polymerization solvent 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 preferable that the composition in the polymerization reactor is 1 to 50 mass%, and more preferably 3 to 40 mass%.

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

In this embodiment, the styrene-based resin (c) is preferably polymerized using a combination of a polyfunctional polymerization initiator and a monofunctional polymerization initiator. The monofunctional polymerization initiator is preferably added to a reactor in which the polymerization rate of the monovinyl compound exceeds 40%, or added simultaneously with a chain transfer agent.

<<Volatilization 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 preferred.

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

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

<Rubber-modified styrene-based resin (d)>
The rubber-modified styrene-based resin (d) in this embodiment is a styrene-based resin matrix in which rubber polymer particles are dispersed, and can be produced by polymerizing a styrene-based monomer in the presence of the rubber polymer.
In the resin composition of the present embodiment, the rubber-modified styrene-based resin (d) can be used by blending with the copolymer resin (a).

In addition to styrene, examples of styrene monomers constituting styrene resins include α-methylstyrene, α-methyl-p-methylstyrene, ο-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene, and t-butylstyrene, or styrene derivatives such as bromostyrene, chlorostyrene, and indene. From an industrial viewpoint, styrene is particularly preferred. These styrene monomers can be used alone or in combination. Although it is not excluded that the styrene resin further contains monomer units other than the above styrene monomer units within a range that does not impair the effects of the present invention, the styrene resin typically consists of styrene monomer units.

As the rubber-like polymer, polybutadiene, polyisoprene, natural rubber, polychloroprene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, etc. can be used, but from an industrial point of view, polybutadiene and styrene-butadiene copolymer are preferred. As the polybutadiene, both high-cis polybutadiene with a high cis content and low-cis polybutadiene with a low cis content can be used. In addition, as the structure of the styrene-butadiene copolymer, both a random structure and a block structure can be used. These rubber-like polymers can be used alone or in combination. Also, saturated rubber obtained by hydrogenating butadiene rubber can be used.

The content of the rubber-modified styrene-based resin (d) is preferably 30% by mass or less, more preferably 27% by mass or less, and even more preferably 25% by mass or less, based on 100% by mass of the total mass of the resin composition.
The resin composition contains the rubber-modified styrene-based resin (d), which can improve the mechanical strength of the resin composition. When the content is 30 mass % or less, the butadiene monomer unit content of the resin composition does not become too high, which can prevent the difficulty of foaming due to gas escape during foam molding, suppress the decrease in rigidity caused by the inclusion of butadiene, and prevent the deterioration of the physical properties of the obtained foam.
On the other hand, from the viewpoint of obtaining a good effect of improving mechanical strength, the content of the rubber-modified styrene-based resin (d) is preferably 3 mass% or more, more preferably 5 mass% or more, relative to 100 mass% of the total mass of the resin composition.

The rubber content in the rubber-modified styrene-based resin (d) is preferably 7 to 15% by mass, more preferably 9 to 14% by mass. When the rubber content is 7% by mass or more, the mechanical strength can be improved in blending with the copolymer resin (a), and by increasing the blend ratio of the rubber-modified styrene-based resin (d), the mechanical strength is improved while the heat resistance is not significantly reduced, which is preferable. On the other hand, when the rubber content is 15% by mass or less, the viscosity of the polymerization system does not become too high when producing the rubber-modified styrene-based resin (d), and the operation can be prevented from becoming difficult, and the rubber particle size can be easily refined. Furthermore, when the copolymer resin (a) and the rubber-modified styrene-based resin (d) are blended, the decrease in mechanical strength or the appearance of the product due to poor dispersion of the rubber component can be prevented.
In this disclosure, rubber content is measured by the procedure described in the Examples section or by a method that would be understood by one of ordinary skill in the art to be equivalent thereto.

The rubber component in the rubber-modified styrene-based resin (d) can be present as rubber particles in the resin composition. In this case, the rubber particle size is preferably 0.5 to 5.0 μm, more preferably 0.7 to 4.0 μm, and even more preferably 1.0 to 3.0 μm.
When the rubber particle size is 0.5 μm or more, the mechanical strength of the resin composition is good. When the rubber particle size is 5.0 μm or less, the appearance of the resin composition is good. The rubber-modified styrene-based resin (d) is obtained by polymerizing a styrene-based monomer in a reactor equipped with a stirrer in the presence of a rubber-like polymer, and the rubber particle size can be adjusted by the number of revolutions of the stirrer, the molecular weight of the rubber-like polymer used, etc.
In the present disclosure, the rubber particle size is a value measured from a cross-sectional observation image taken with a transmission electron microscope.

The melt mass flow rate of the rubber-modified styrene-based resin (d) at 200° C. may be preferably 0.5 to 18.0 g/10 min, more preferably 1.0 to 16.0 g/10 min, and even more preferably 1.0 to 14.0 g/10 min.
If the melt mass flow rate is within the range of 0.5 to 18.0 g/10 min, the copolymer has good mixability with the copolymer resin (a) and MBS (b) and also has good mechanical strength.
In this disclosure, the melt mass flow rate is a value measured in accordance with ISO 1133 at a temperature of 200° C. and a load of 49 N.

The method for producing the rubber-modified styrene-based resin (d) is not particularly limited, but it can be produced by bulk polymerization (or solution polymerization) in which a styrene-based monomer (and solvent) is polymerized in the presence of a rubber-like polymer, or bulk-suspension polymerization in which the reaction transitions to suspension polymerization during the course of the reaction, or emulsion graft polymerization in which a styrene-based monomer is polymerized in the presence of a rubber-like polymer latex. In bulk polymerization, it can be produced by continuously supplying a mixed solution containing a rubber-like polymer, a styrene-based monomer, and, if necessary, an organic solvent, an organic peroxide, and/or a chain transfer agent to a polymerization apparatus consisting of a complete mixing reactor or a tank reactor connected in series with multiple tank reactors.

In this embodiment, the swelling index of the toluene insoluble matter of the rubber-modified styrene-based resin (d) is preferably 8.0 to 14.0, more preferably 9.0 to 13.0, and even more preferably 9.5 to 12.5.
When the swelling index of the toluene insoluble matter of the rubber-modified styrene-based resin (d) is 8.0 to 14.0, a resin having excellent mechanical strength can be obtained.
In this disclosure, the swelling index of the toluene insoluble matter is a value measured by the procedure described in the Examples section or a procedure that would be understood by one of ordinary skill in the art to be equivalent thereto.

The characteristics of the resin composition of this embodiment are described below.

The content of the styrene monomer unit contained in the resin composition of the present embodiment is preferably 80% by mass or more, more preferably 83% by mass or more, and even more preferably 85% by mass or more.
If the content of the styrene monomer unit is 80% by mass or more, the adhesion between the sheet or container and the laminate film is good, and peeling of the laminate film during use of the sheet or container can be prevented. The content of the styrene monomer unit can be achieved by adjusting the content of the styrene monomer unit in the copolymer resin (a), MBS resin (b), styrene-based resin (c), and rubber-modified styrene resin (d) used, as well as the mixing ratio of these resins.

The resin composition of this embodiment has a Vicat softening temperature of 106 to 130°C, preferably 108 to 125°C, and more preferably 110 to 125°C.
If the Vicat softening temperature is 106°C or higher, the deformation of the sheet or container is small even when immersed in boiling water or heated in a microwave oven, and the sheet or container is favorable. On the other hand, if the Vicat softening temperature exceeds 130°C, the moldability during extrusion molding or vacuum molding tends to decrease. A Vicat softening temperature of 106°C or higher can be achieved by adjusting the Vicat softening temperatures of the copolymer resin (a), MBS resin (b), styrene-based resin (c), and rubber-modified styrene resin (d) used, as well as the mixing ratio of these resins.
In this disclosure, the Vicat softening temperature is a value measured at a load of 49 N in accordance with ISO 306.

The resin composition of the present embodiment has a melt mass flow rate of 0.6 to 3.0 g/10 min, preferably 0.8 to 2.5 g/10 min, and more preferably 1.0 to 2.5 g/10 min.
If the melt mass flow rate is 0.6 g/10 min or more, the moldability during extrusion molding or vacuum molding is good. On the other hand, if the melt mass flow rate exceeds 3.0 g/10 min, the deep drawability during vacuum molding and the mechanical strength of the molded product tend to decrease. The melt mass flow rate of 0.6 g/10 min can be achieved by adjusting the melt mass flow rates of the copolymer resin (a), MBS resin (b), styrene-based resin (c), and rubber-modified styrene resin (d) used, as well as the mixing ratio of these resins.
In this disclosure, the melt mass flow rate is a value measured in accordance with ISO 1133 at a temperature of 200° C. and a load of 49 N.

The resin composition of the present embodiment preferably has a branching degree of 0.60 to 0.95, more preferably 0.62 to 0.92, even more preferably 0.65 to 0.90, and even more preferably 0.65 to 0.85. If the branching degree is less than 0.60, sufficient moldability may not be obtained. If the branching degree is more than 0.95, sufficient deep drawability may not be obtained.
The branching degree can be adjusted to satisfy the above range by using a resin having an appropriate branching degree as the styrene-based resin (c) in the resin composition.
In the present disclosure, the degree of branching is a value calculated by the procedure described in the section [Examples] below.

<Gelation Degree>
The resin composition of this embodiment preferably has a gelation degree of 1.10 to 1.60, more preferably 1.12 to 1.55, even more preferably 1.15 to 1.50, and even more preferably 1.18 to 1.45. By setting the gelation degree in the range of 1.10 to 1.60, it is possible to reduce the amount of gel-like substance in the resin composition. In addition, when the resin composition is retained in a production facility for a long period of time, the amount of gel-like substance generated can be reduced, and therefore productivity can be improved.
The gelation degree can be adjusted to satisfy the above range by using a resin having an appropriate gelation degree as the styrene-based resin (c) in the resin composition.
In the present disclosure, the gelation degree is a value calculated by the procedure described in the section [Examples] below.

The method of mixing the copolymer resin (a), MBS resin (b), styrene resin (c), and any rubber-modified styrene resin (d) is not particularly limited, but examples include mixing and pelletizing in an extruder or the like, and then using the resulting pellets to produce a sheet or foam by sheet extrusion or foam extrusion, or directly feeding the copolymer resin (a), MBS resin (b), styrene resin (c), and any rubber-modified styrene resin (d) into a sheet extruder or foam extruder in a specified ratio to directly produce a sheet or foam.

In the resin composition of this embodiment, when the total mass of the resin composition is 100 mass%, the total content of styrene dimer and styrene trimer is preferably 0.6 mass% or less, and more preferably 0.5 mass% or less.
If the total content of styrene dimer and styrene trimer is 0.6 mass% or less, for example, in injection molding, adhesion of styrene dimer and styrene trimer to a mold is significantly reduced, transfer of the styrene dimer and styrene trimer to a molded product is significantly reduced, and defective appearance is significantly improved; in extrusion molding of a sheet or the like, the amount of styrene dimer and styrene trimer precipitating on a die is significantly reduced, transfer to a sheet is significantly reduced, and defective appearance is significantly improved; further, the need for cleaning the mold and the die outlet can be reduced, thereby improving productivity.
In the present disclosure, the contents of styrene dimer and styrene trimer can be measured by gas chromatography.

In the resin composition of this embodiment, when the total mass of the resin composition is 100 mass%, the content of the styrene monomer is preferably 700 mass ppm or less, more preferably 600 mass ppm or less, and even more preferably 500 mass ppm or less. If the content of the styrene monomer is 700 mass ppm or less, the odor around the die outlet during sheet extrusion is improved, and the color tone of the resin is also improved.
In the present disclosure, the content of styrene monomer can be measured by gas chromatography.

<Aliphatic primary alcohol>
The resin composition of the present embodiment may contain an aliphatic primary alcohol, preferably one having 14 or more carbon atoms, and more preferably one having a freezing point of -10°C or lower.
The incorporation of an aliphatic primary alcohol is effective in suppressing a gelling reaction caused by a dehydration reaction of methacrylic acid, as described in the above-mentioned Patent Document 1 , and it is particularly desirable to add an aliphatic primary alcohol to the system during the production of the copolymer resin (a).

In particular, alcohols with less than 14 carbon atoms tend to volatilize easily and have a reduced effect in inhibiting the gelling reaction when a high vacuum is applied to remove low-volatile components such as residual monomers or moisture during the production of copolymer resin (a) or during sheet extrusion, and therefore aliphatic primary alcohols with a larger carbon number are more preferable.

Furthermore, among the aliphatic primary alcohols having 14 or more carbon atoms, aliphatic primary alcohols having a freezing point of −10° C. or lower are preferred because, when a high vacuum is created for the purpose of removing low-volatile components such as moisture and residual monomers, the alcohol is less likely to precipitate in a condenser or the like and is less likely to reduce the degree of vacuum.
Examples of the aliphatic primary alcohol having 14 or more carbon atoms and a freezing point of −10° C. or lower include iso-type aliphatic primary alcohols having 14 or more carbon atoms (described later).

In this disclosure, the content of aliphatic primary alcohols can be measured by gas chromatography.

Specific examples of the aliphatic primary alcohol used in the present embodiment will be described below.
Examples of aliphatic primary alcohols having 14 or more carbon atoms include n-myristic alcohol having 14 carbon atoms, n-palmitic alcohol having 16 carbon atoms, and n-stearyl alcohol having 18 carbon atoms.
Further, examples of iso-type aliphatic primary alcohols having 14 or more carbon atoms that can have a freezing point of 10° C. or less include isotetradecanol having 14 carbon atoms, isohexadecanol having 16 carbon atoms, isooctadecanol having 18 carbon atoms, and isoeicosanol having 20 carbon atoms. Specific examples of such isotetradecanol include isotetradecanol having 14 carbon atoms, isohexadecanol having 16 carbon atoms, isooctadecanol having 18 carbon atoms, and isoeicosanol having 20 carbon atoms. Examples of the alcohol include octanol, 2-hexyl-1-decanol, 5,7,7-trimethyl-2-(1,3,3-trimethylbutyl)-1-octanol, 8-methyl-2-(4-methylhexyl)-1-decanol, 2-heptyl-1-undecanol, 2-heptyl-4-methyl-1-decanol, and 2-(1,5-dimethylhexyl)-(5,9-dimethyl)-1-decanol. Of these, isooctadecanol having 18 carbon atoms is particularly preferred from an industrial viewpoint.

When using an aliphatic primary alcohol having a freezing point of −10° C. or lower and a carbon number of 14 or more, the amount of such an aliphatic primary alcohol added is preferably 0.02 to 1.0 part by mass, more preferably 0.04 to 0.8 part by mass, and even more preferably 0.06 to 0.6 part by mass, relative to 100% by mass of the total mass of the heat-resistant styrene-based resin composition.
Under the alcohol addition conditions where the amount added is 0.02 parts by mass or more, the gelation reaction is effectively inhibited during the devolatilization step in the production of the copolymer resin (a) or during sheet extrusion. On the other hand, under the addition conditions where the amount added is 1.0 parts by mass or less, the gelation reaction is effectively inhibited, while the amount of the aliphatic primary alcohol remaining in the resin composition is not too large, so that the heat resistance of the resin is not significantly reduced, and mold deposits are not easily generated during molding, which is preferable.

<<Additives, etc.>>
The heat-resistant styrene-based resin composition of the present embodiment may optionally contain additives, for example, a processing stabilizer such as 2-[1-(2-hydroxy-3,5-di-t-phenylpentyl)ethyl]-4,6-di-t-phenylpentyl acrylate may be contained in order to suppress thermal decomposition of the polymer in the unreacted monomer recovery step. Also, a heat deterioration inhibitor such as 2-[1-(2-hydroxy-3,5-di-t-phenylpentyl)ethyl]-4,6-di-t-phenylpentyl acrylate, higher fatty acids and salts thereof such as stearic acid, zinc stearate, calcium stearate, magnesium stearate, lubricants such as ethylene bisstearylamide, plasticizers such as liquid paraffin, antioxidants, etc. may be contained in combination within a range that does not impair the object of the present embodiment. In addition, additives commonly used in the field of styrene resins, such as flame retardants, colorants, ultraviolet absorbers, release agents, various fillers, etc., may be combined and contained in the styrene resin composition within a range that does not impair the purpose of this embodiment. The additives are not particularly limited, but examples include flame retardants such as hexabromocyclododecane, colorants such as titanium oxide and carbon black, etc. In addition, when the heat-resistant styrene resin composition is made into pellets, ethylene bisstearylamide, zinc stearate, magnesium stearate, etc. may be sprinkled on the pellets as an external lubricant for the pellets.

Antioxidants are generally components that can stabilize peroxide radicals such as hydroperoxy radicals generated during thermoforming or exposure to light, or that can decompose the generated peroxides such as hydroperoxides. Antioxidants are not particularly limited, but examples include hindered phenol-based antioxidants and peroxide decomposers. Hindered phenol-based antioxidants act as radical chain inhibitors, and peroxide decomposers can decompose peroxides generated in the system into more stable alcohols to prevent autoxidation. Examples of the hindered phenol antioxidant include, but are not limited to, 2,6-di-t-butyl-4-methylphenol, stylenated phenol, n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenyl butylphenyl acrylate, 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), alkylated bisphenol, tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, and 3,9-bis[2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxyspiro[5.5]undecane. Examples of peroxide decomposers include, but are not limited to, organic phosphorus peroxide decomposers such as trisnonylphenyl phosphite, triphenyl phosphite, and tris(2,4-di-t-butylphenyl)phosphite, as well as organic sulfur peroxide decomposers such as dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, pentaerythrityl tetrakis(3-laurylthiopropionate), ditridecyl-3,3'-thiodipropionate, and 2-mercaptobenzimidazole. The amount of antioxidant added is preferably 0.01% by mass or more and 1% by mass or less, more preferably 0.1% by mass or more and 0.5% by mass or less, based on 100% by mass of the heat-resistant styrene-based resin composition.

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

Brominated bisphenol flame retardants include, but are not limited to, tetrabromobisphenol A, tetrabromobisphenol A-bis(2,3-dibromopropyl ether), tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol S, tetrabromobisphenol S-bis(2,3-dibromopropyl ether), tetrabromobisphenol S-bis(2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol F, tetrabromobisphenol F-bis(2,3-dibromopropyl ether), tetrabromobisphenol F-bis(2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol A-bis(allyl ether), tetrabromobisphenol A polycarbonate oligomer, and epoxy group adduct of tetrabromobisphenol A oligomer. Among the brominated bisphenol flame retardants, tetrabromobisphenol A bis(2,3-dibromopropyl ether) and tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) are particularly preferred because they are less likely to decompose during kneading of the heat-resistant styrene-based resin composition and tend to have a high flame retardant effect. The combined use of tetrabromobisphenol A-bis(2,3-dibromopropyl ether) and tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) is even more preferred because they tend to have excellent flame retardancy and thermal stability.

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

The content of the bromine-based flame retardant is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 1 part by mass or more and 9 parts by mass or less, and even more preferably 2 parts by mass or more and 8 parts by mass or less, relative to 100 parts by mass of the total of components (a), (b), (c), and optional (d) in the styrene-based resin composition. When the content is 0.1 parts by mass or more, sufficient flame retardancy tends to be ensured, and when the content is 10 parts by mass or less, sufficient moldability when producing a foamed sheet tends to be ensured.

The liquid paraffin may be selected from liquid paraffins specified in the Food Sanitation Act, standards for food, food additives, etc. Specific examples of this type of liquid paraffin include, but are not limited to, Krystal N52, Krystal N62, Krystal N72, Krystal N82, Krystal N122, Krystal N172, Krystal N262, Krystal N352, and Primol N542, which are commercially available from ExxonMobil Corporation. Other examples include Moresco White P-40, Moresco White P-55, Moresco White P-60, Moresco White P-70, Moresco White P-80, Moresco White P-85, Moresco White P-100, Moresco White P-120, Moresco White P-150, Moresco White P-200, Moresco White P-230, Moresco White P-260, Moresco White P-300, Moresco White P-350, and Moresco White P-350P, all of which are commercially available from Matsumura Oil Research Institute Co., Ltd. Further examples include liquid paraffin 40-S, 60-S, 70-S, 80-S, 90-S, 100-S, 120-S, 150-S, 260-S, and 350-S, all of which are commercially available from Sanko Chemical Industry Co., Ltd. Also included is white mineral oil available from CK Witco Corporation.

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

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

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

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

The content of the heat deterioration inhibitor is preferably 0.01 to 0.5 mass %, more preferably 0.02 to 0.3 mass %, and further preferably 0.03 to 0.2 mass %, based on 100 mass % of the heat-resistant styrene-based resin composition.
When the content of the heat deterioration inhibitor is 0.01 mass% or more, the generation of the monomer of the monovinyl compound and its dimer and trimer in the devolatilization process of each component in the resin composition can be more effectively suppressed. On the other hand, even if the content of the heat deterioration inhibitor is more than 0.5 parts by mass, it becomes difficult to obtain an effect commensurate with the content.

The resin composition of the present embodiment may further contain an additional resin.
Examples of the additional resin include general polystyrene, styrene-methacrylic acid-methyl methacrylate copolymer resin, styrene-butadiene random copolymer elastomer, polyphenylene ether, and the like.

In the resin composition of this embodiment, the total content of the copolymer resin (a), the MBS resin (b), and the styrene-based resin (c) is preferably 96% by mass or more, more preferably 97% by mass or more, and even more preferably 98% by mass or more, based on 100% by mass of the total mass of the resin composition, from the viewpoint of obtaining the above-mentioned effects of these resins well. On the other hand, the total content of the copolymer resin (a), the MBS resin (b), and the styrene-based resin (c) is preferably 99.8% by mass or less, more preferably 99.5% by mass or less, and even more preferably 99.0% by mass or less, based on 100% by mass of the total mass of the resin composition, from the viewpoint of obtaining the desired effects of other components such as those exemplified above.

<<Method for producing styrene-based resin composition>>
The styrene-based resin composition of the present embodiment is not particularly limited, but can be obtained, for example, by a method of melt-kneading the copolymer resin (a), the MBS resin (b), the styrene-based resin (c) and the above-mentioned additives using a known kneader such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, etc. The above-mentioned additives may be appropriately added in the production process of the copolymer resin (a), the MBS resin (b) and the styrene-based resin (c).

(Extruded sheet)
The extruded sheet of the present embodiment contains the resin composition of the present embodiment described above, and is an extruded sheet formed using the resin composition of the present embodiment described above, and may be either a non-foamed extruded sheet or a foamed extruded sheet.
The extruded sheet can be produced by any commonly known method.

A method for producing a non-foamed extruded sheet includes extruding the material with a single-screw or twin-screw extruder equipped with a T-die and then taking off the sheet with a uniaxial or biaxial stretching machine, while a method for producing a foamed extruded sheet includes using an extrusion foam molding machine equipped with a T-die or circular die.

When forming a foamed extrusion sheet, the foaming agent and foam nucleating agent used during extrusion foaming may be any of those commonly used. The foaming agent may be butane, pentane, fluorocarbons, carbon dioxide, water, etc., with butane being preferred. Additionally, the foam nucleating agent may be talc, etc.

In the foamed extruded sheet, the thickness is preferably 0.5 to 5.0 mm, the apparent density is preferably 50 to 300 g/L, and the basis weight is preferably 80 to 300 g/ ^m2 .

The foam extruded sheet may be used in a multilayer structure with a styrene-based resin such as polystyrene resin, for example, a styrene-butadiene block copolymer, high-impact polystyrene (high-impact polystyrene) made of a rubber component such as polybutadiene, etc.
The foamed extruded sheet may be used in a multi-layered form with a resin other than the styrene-based resin, such as polypropylene (PP) resin, PP/polystyrene (PS) resin, polyethylene terephthalate (PET) resin, nylon resin, etc.

On the other hand, in the case of a non-foamed extruded sheet, the thickness is preferably, for example, about 0.1 to 5.0 mm from the viewpoints of rigidity and thermoforming cycle.
The non-foamed extruded sheet may be a sheet formed only by ordinary low-magnification roll stretching, but in particular, a sheet that has been 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 from the viewpoint of strength.

The non-foamed extruded sheet may be used in the form of a multilayer with a styrene-based resin such as polystyrene resin, for example, a styrene-butadiene block copolymer or high impact polystyrene made of a rubber component such as polybutadiene.
The non-foamed extruded sheet may be used in the form of a multi-layer with a resin other than the styrene-based resin, such as PP resin, PP/PS resin, PET resin, nylon resin, etc.

(Molding)
The molded article of the present embodiment can be formed using the non-foamed extruded sheet or the foamed extruded sheet of the present embodiment described above.
In this embodiment, a foamed extruded sheet or a multilayer body containing the same can be molded by, for example, vacuum forming, pressure forming, vacuum pressure forming, match mold forming, etc. to produce a container such as a tray. Also, in this embodiment, a non-foamed extruded sheet or a multilayer body containing the same can be molded by, for example, vacuum forming to produce a lid material for a lunch box or a container for storing side dishes, etc.

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

The resin compositions, extruded sheets, molded products, etc. in the examples and comparative examples were evaluated using the following analytical and measurement methods.

(1) Measurement of the contents (mass%) of styrene monomer units and methacrylic acid monomer units in copolymer resin (a), and calculation of the content (mass%) of styrene monomer units in the resin composition The resin composition of copolymer resin (a) was quantified based on the integral ratio of the spectrum measured by a proton nuclear magnetic resonance ( ¹ H-NMR) measurement device. The content (mass%) of styrene monomer units in the resin composition was calculated from the results of such quantification. Detailed conditions and procedures were as follows:
Sample preparation: 30 mg of resin pellets were dissolved in 0.75 mL of d ₆ -DMSO by heating at 60° C. for 4 to 6 hours.
・Measuring equipment: JNM ECA-500 manufactured by JEOL Ltd.
Measurement conditions: Measurement temperature 25°C, observation nucleus 1H, number of integrations 64, repetition time 11 seconds.
Spectral assignments: For the assignments of the spectra measured in dimethylsulfoxide deuterated solvent, the peaks at 0.5 to 1.5 ppm are hydrogen atoms of the α-methyl groups of methacrylic acid and six-membered cyclic acid anhydrides, the peaks at 1.6 to 2.1 ppm are hydrogen atoms of the methylene groups of the polymer main chain, and the peak at 12.4 ppm is hydrogen atoms of the carboxylic acid of methacrylic acid. The peaks at 6.5 to 7.5 ppm are hydrogen atoms of the aromatic rings of styrene. Note that the content of six-membered cyclic acid anhydrides in the resins of the present examples and comparative examples is low, so quantification is usually difficult with this measurement method.

(2) Measurement of Vicat Softening Temperature (° C.) The Vicat softening temperature (° C.) of a resin and a resin composition was measured in accordance with ISO 306 under a load of 49 N.

(3) Measurement of Molecular Weight The number average molecular weight (Mn), weight average molecular weight (Mw), Z average molecular weight (Mz), Mw/Mn, Mz/Mw, peak top molecular weight (Mtop), and content of a predetermined molecular weight component of a resin or resin composition 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 concentration: 5 mg of a measurement sample was dissolved in 10 mL of a solvent and filtered through a 0.45 μm filter.
Injection volume: 10 μL
Measurement temperature: 40°C
Flow rate: 0.35 mL/min Detector: Ultraviolet absorption detector (Tosoh UV-8020, wavelength 254 nm)
The calibration curve was created using 11 types of TSK standard polystyrene (F-850, F-450, F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000) manufactured by Tosoh Corporation. The calibration curve was created using a linear approximation equation.

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

(5) Measurement of Branching Degree and Gelling Degree The branching degrees and gelling degrees of the styrene-based resin (c) and the resin composition were calculated by measuring the absolute molecular weight using a multi-angle light scattering detector (MALS) (hereinafter, sometimes referred to as the "MALS method") as described below.
Apparatus: Malvern GPCmax
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 a measurement sample was dissolved in 10 mL of a solvent and filtered through a 0.45 μm filter.
Injection volume: 100 μL
Measurement temperature: 40°C
Flow rate: 1.00 mL/min Detector: differential refractometer (Malvern TDA305)
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: 40°C
PS105K was used as a standard sample, and analysis was performed using the linear equation of Berry plot with analysis software OmniSEC5.1.
After the measurement was performed by the above-mentioned MALS method, a graph was created with the horizontal axis representing log molecular weight and the vertical axis representing log radius of gyration. On this graph, a linear approximation line was created for linear polystyrene (PS245K) in the range of log molecular weight values of 5.0 to 6.0, and this was used as the reference value for linear polystyrene without a branched structure.
Here, the log radius of gyration values when the log molecular weight values are 6.0 and 6.5 are defined as <Rg6.0> and <Rg6.5>, respectively, and the <Rg6.0> and <Rg6.5> of PS245K are defined as <Rg6.0> ₂₄₅ and <Rg6.5> ₂₄₅ , respectively. Note that <Rg6.5> ₂₄₅ can be calculated from the extrapolated value of the approximation line.
The degree of branching is defined as follows: degree of branching = <Rg6.5>/<Rg6.5> _245. This degree of branching means how small the radius of gyration is relative to the linear polystyrene PS245K at an absolute molecular weight of 10 ^6.5 = 3,160,000, and the smaller the degree of branching, the more branched the target polymer is.
The gelation degree is defined as follows: gelation degree = (<Rg6.0>/<Rg6.0> ₂₄₅ )/(<Rg6.5>/<Rg6.5> ₂₄₅ ). This gelation degree represents the rate of change in the radius of gyration of the polymer when the absolute molecular weight is from 10 ^6.0 to 10 ^6.5 . In other words, it means the degree to which the branching increases as the molecular weight increases, and a higher gelation degree indicates that the branching increases as the molecular weight increases.

(6) Measurement of Maximum Rise Ratio The maximum rise ratio of the styrene-based resin (c) was measured based on the following viscoelasticity measurement.
Device name: Viscoelasticity measuring device ARES-G2 (manufactured by TA Instruments)
Measurement system: ARES-EVF option Test piece dimensions: length 20 mm, thickness 0.7 mm, width 10 mm
Elongation strain rate: 0.01/sec Temperature: 150°C
Measurement atmosphere: nitrogen gas flow Preheating time: 2 minutes Pre-elongation strain rate: 0.03/sec
Pre-extension length: 0.295 mm
Relaxation time after pre-stretching: 2 minutes For the viscoelasticity measurement, the test piece was attached to a roller, and after the temperature was stabilized at the measurement temperature, it was left to stand for the above pre-heating time and pre-heated. After the pre-heating was completed, pre-stretching was performed under the above conditions. After pre-stretching, it was left to stand for 2 minutes to relax the stress generated by the pre-stretching, and then the measurement was performed.

From the results of the viscoelasticity measurements, a double logarithmic graph was created with Hencky strain on the horizontal axis and extensional viscosity on the vertical axis, and a power-approximated linear region line was created with the Hencky strain in the range of 0.2 to 0.5 as the linear region. When strain hardening occurs, the actual extensional viscosity becomes larger than the extensional viscosity of the approximation curve extrapolated from this linear region.
The maximum rise ratio was calculated by (extensional viscosity in the nonlinear region at the maximum rise strain/extensional viscosity of the approximate straight line extrapolated from the linear region at the maximum rise strain), where the Hencky strain at which the extensional viscosity was maximum in the above viscoelasticity measurement was defined as the maximum rise strain.

(7) Measurement of Styrene Dimer and Styrene Trimer Content (% by mass) The styrene dimer and styrene trimer contents (% by mass) in a resin (100% by mass) or in a resin composition (100% by mass) were measured under the following conditions and by the following procedure.
Sample preparation: 1.0 g of resin or resin composition was dissolved in 10 mL of methyl ethyl ketone, and then 3 mL of methanol containing a standard substance (triphenylmethane) was added to reprecipitate the polymer component, and the supernatant was collected and used as the measurement solution.
Measurement conditions: Instrument: Agilent 6850 series GC system Detector: FID
Column: HP-1 (100% dimethylpolysiloxane) 30 m, film thickness 0.25 μm, 0.32 mm diameter
Injection volume: 1 μL (splitless)
Column temperature: 40°C for 1 minute, increase temperature to 320°C at 20°C/min, and hold at 320°C for 10 minutes. Injection port temperature: 250°C.
Detector temperature: 280°C
Carrier gas: Helium

(8) Measurement of Rubber Particle Size (μm) The rubber particle size (μm) of the rubber-modified styrene-based resin (d) was measured by taking a photograph using a transmission electron microscope by the ultrathin section method, measuring the particle sizes of 1,000 particles in the photograph, and calculating the size from the following formula.
Rubber particle diameter = Σni × Di ⁴ / Σni × Di ³
(In the formula, ni is the number of rubber particles having a particle diameter Di, where Di is the average value of the major axis and minor axis of the particle.)

(9) Measurement of swelling index of toluene insoluble matter 1 g of rubber-modified styrene-based resin (d) was weighed out in a precipitation tube (this mass was designated as W1), 20 mL of toluene was added, and the mixture was shaken at 23°C for 2 hours, and then centrifuged for 60 minutes at 10°C or less and 45100G (20000 rpm) in a centrifuge (himac, CR-20 (rotor: R20A2) manufactured by Hitachi, Ltd.). The precipitation tube was slowly tilted at about 45 degrees, and the supernatant liquid was removed by decantation. The insoluble matter (which is in a state accompanied by toluene) was conditioned for 5 minutes in a desiccator containing silica gel with a relative humidity of 20 to 60%, and the mass was weighed out (this mass was designated as W2), followed by vacuum drying for 1 hour at 160°C and 3 kPa or less, and then cooled to room temperature in the desiccator, and the mass of the toluene insoluble matter was weighed out (this mass was designated as W3). The swelling index of the toluene-insoluble matter was then calculated by the following formula.
Swelling index of toluene insoluble matter=(W2/W3)

(10) Measurement of rubber content 0.25 g of the rubber-modified styrene-based resin (d) was dissolved in 50 mL of chloroform, and iodine monochloride was added to react with the double bonds in the rubber component. Potassium iodide was then added to convert the remaining iodine monochloride to iodine, and the mixture was back-titrated with sodium thiosulfate (iodine monochloride method). Using this method, the mass of the rubber contained in the rubber-modified styrene-based resin (d) (this mass is designated as W4) was measured, and the rubber content (mass%) in the rubber-modified styrene-based resin was calculated from this value and the mass of the rubber-modified styrene-based resin (d) (this mass is designated as W1) according to the following formula:
Rubber content in rubber-modified styrene resin = W1 x W4/100

(11) Measurement of Styrene Monomer Content (ppm by mass) The styrene monomer content (ppm by mass) in a resin composition (100% by mass) was measured under the following conditions and by the following procedure.
Sample preparation: 1.0 g of the resin composition was dissolved in 25 mL of dimethylformamide containing a standard substance (cyclopentanol).
Measurement conditions: Equipment: Shimadzu Gas Chromatography GC-14Bpf
Column: SUS 3 mmφ x 3 m (packed column)
Packing material: Liquid phase → PEG-20M 25%, carrier → Chromosorb W (AW) 60-80 mesh Column temperature: 110°C
Inlet temperature: 220℃
Detector temperature: 220°C
Carrier gas: Nitrogen

(12) Measurement of Aliphatic Primary Alcohol Content (Parts by Mass) The aliphatic primary alcohol content (parts by mass) in the resin composition was measured under the following conditions and procedures.
Sample preparation: 0.5 g of the resin composition was dissolved in 20 mL of methyl ethyl ketone.
Measurement conditions: Equipment: Shimadzu Gas Chromatography GC2010
Column: DB-WAX 30 m, 0.25 mm φ, df = 0.5 μm
Temperature: 100°C → 5°C/min to 130°C → 10°C/min to 180°C → 12 minutes at 180°C → 20°C/min to 220°C → 20 minutes at 220°C

(13) Measurement of Melt Mass Flow Rate (MFR) (g/10 min) The resin and the resin composition were molded by an injection molding machine (EC60N, manufactured by Toshiba Machine Co., Ltd.) at a cylinder temperature of 230°C, a mold temperature of 45°C, an injection pressure of 80 MPa, and an injection speed of 26 mm/s to obtain ISO mold type A test pieces.
The runner portion of the obtained test piece was cut, and the melt mass-flow rate (g/10 min) was measured at 200° C. and a load of 49 N in accordance with ISO 1133.

(14) Measurement of Charpy impact strength (kJ/m ² ) For the test pieces obtained in (13) above, the Charpy impact strength (kJ/m ² ) was measured without a notch in accordance with ISO179.

(15) Measurement of flexural strength (MPa) The flexural strength (MPa) of the test pieces obtained in (13) above was measured in accordance with ISO 178.

(16) Measurement of bending deflection (mm) For the test pieces obtained in (13) above, bending deflection (mm) was measured by measuring the maximum deflection amount during the bending strength measurement in (15) above.

(17) Determination of mold staining The resin composition was injected into a rectangular mold of 150 x 150 x 2.5 mm for 5.0 seconds. After 70 shots, injection molding was stopped for 15 minutes and the mold was cooled. The mold surface corresponding to the tip of the molded body after cooling was visually observed to confirm the degree of mold staining. Then, injection molding was repeated up to 700 shots while checking the degree of mold staining as described above. Molding was performed at a mold temperature of 20°C and a resin temperature of 260°C. The number of times mold staining first occurred was used as an index of mold staining.
When the components of the deposits on the mold were measured by gas chromatography using the procedure described above, it was found that the majority of the deposits were styrene dimers and styrene trimers, with only a small amount of the alcohol that had been kneaded into the resin.

(18) Measurement of impact strength (kgf cm) of non-foamed extruded sheet A non-foamed stretched sheet of a predetermined thickness was prepared using the resin composition as follows. Using a 30 mmφ single-screw sheet extruder manufactured by Soken Co., Ltd., the resin composition was extruded at a resin melting zone setting temperature of 220 to 230°C, a T-die temperature setting of 240°C, and a discharge rate of 7 kg/hour to produce sheets with thicknesses of 0.5 mm and 0.7 mm. Furthermore, for the 0.7 mm thick sheet, a biaxial stretching device EX6-S1 manufactured by Toyo Seiki Co., Ltd. was used, and the sheet was heated at 150°C for 10 minutes, and then stretched 5 times in the extrusion direction of the sheet and 1.5 times in the direction perpendicular to the extrusion direction of the sheet to produce a sheet of about 0.1 mm.
The impact strength (kgf·cm) of the non-foamed stretched sheet having a thickness of 0.1 mm prepared as described above was measured using a film impact tester A121807502 manufactured by Toyo Seiki Seisakusho.

(19) Evaluation of heat resistance of non-foamed extruded sheet A non-foamed stretched sheet having a thickness of 0.1 mm obtained by the method described in (18) above was immersed in a silicone oil bath at 105° C. for 30 minutes, and the shrinkage rate (%) at 5-fold stretching in the sheet extrusion direction was measured and evaluated according to the following criteria. A large shrinkage rate leads to large deformation of the molded product, so a shrinkage rate of less than 3% is practically preferable.
◎: Shrinkage rate less than 3% ○: Shrinkage rate 3% to less than 6% ×: Shrinkage rate 6% or more

(20) Evaluation of Appearance of Non-foamed Extruded Sheet Three sheets measuring 8 cm x 20 cm were cut out from the 0.1 mm-thick non-foamed stretched sheet obtained by the method described in (18) above. The total number of gel particles, which are foreign bodies with an average diameter of 1 mm or more, expressed as [major axis + minor axis]/2, and the number of dripping patterns on the surfaces of the three sheets was used as an evaluation index for appearance.

(21) Deep drawability evaluation during vacuum forming of non-foamed extruded sheet:
Using a cup-shaped mold with an opening diameter of 8 cm, a bottom diameter of 4 cm, and a depth of 10 cm, a 0.5 mm-thick non-foamed sheet obtained by the method described in (18) above was preheated at a heater temperature of 250° C. in the heating zone for a heating time of 27 seconds, and then vacuum-molded 20 times. The number of pieces that could be molded according to the shape of the mold was used as an index of deep drawability. Incidentally, pieces that could be molded according to the shape but were partially whitened or torn were included as pieces that could not be molded.

(22) Measurement of impact strength (kgf cm) of foamed extrusion sheet A non-foamed stretched sheet of a predetermined thickness was prepared using the resin composition as follows. A sheet of 0.18 mm in thickness was produced using a compression molding machine manufactured by Soken Co., Ltd. The sheet was impregnated with liquefied carbon dioxide gas at 10 mPa for 30 minutes in an autoclave, and then heated at 117°C for an appropriately adjusted time to produce a foamed extrusion sheet of about 10 times its original size.
The foamed extruded sheet having a thickness of 0.4 mm prepared as described above was measured for impact strength (kgf·cm) using a film impact tester A121807502 manufactured by Toyo Seiki Seisakusho.

Next, the resin components used to produce the resin compositions of the examples and comparative examples will be described.
[Copolymer resin (a)]
[Resin a-4]
A polymerization raw material composition liquid consisting of 71.0 parts by mass of styrene, 7.5 parts by mass of methacrylic acid, 6.5 parts by mass of methyl methacrylate, 15.0 parts by mass of ethylbenzene, and 0.025 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane was continuously supplied at a rate of 1.1 L/hour to a 4-L complete mixing type reactor, then to a polymerization apparatus consisting of a 2-L laminar flow type reactor, and then to a devolatilizer connected to a single-screw extruder for removing volatile matters such as unreacted monomers, polymerization solvent, etc., to prepare a resin.
The polymerization reaction conditions in the polymerization step were a polymerization temperature of 125° C. in the complete mixing reactor and a polymerization temperature of 120 to 142° C. in the laminar flow reactor. The devolatilized unreacted gas was condensed in a condenser through which a coolant of −5° C. was passed, and recovered as an unreacted liquid.
The polymer content in the final polymerization solution was measured by the formula [(mass of sample after drying/mass of sample before drying)×100%] after drying the polymerization solution at 215° C. for 30 minutes under reduced pressure of 2.5 kPa, and was found to be 65.3% by mass. The weight average molecular weight was 210,000 (210,000).
The composition and properties of the resulting resin are shown in Table 1.

[Resins a-1 to a-3]
The composition, polymerization temperature conditions, etc. were adjusted so as to obtain the resin properties shown in Table 1, and a copolymer resin (a) was obtained in the same manner as in the case of resin a-4.
The composition and properties of the resulting resin are shown in Table 1.

[MBS resin (b)]
As MBS resin (b) in which a copolymer of methyl methacrylate monomer units, styrene monomer units and a small amount of butyl acrylate is grafted onto rubber particles consisting of butadiene monomer units, Mitsubishi Rayon Co., Ltd. Metablen C-223A (butadiene monomer unit content: 70% by mass, total content of methyl methacrylate monomer unit and styrene monomer unit: 29% by mass, methyl methacrylate monomer/styrene monomer content: 29% by mass) manufactured by The monomer composition ratio was 1/1, and the butyl acrylate monomer unit was 1%).

[Styrene-based resin (c)]
[Resin c-1]
A raw material solution to be supplied to the first reactor was prepared by adding 84 parts by mass of styrene monomer, 16 parts by mass of ethylbenzene, 0.14 parts by mass (3.6×10 ⁻⁵ moles per mole of styrene) of a conjugated divinyl compound (polybutadiene terminated acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., BAC-45, Mn: 4800)), and 0.038 parts by mass of a polymerization initiator 1 (2,2-bis(4,4-di-tertiary-butylperoxycyclohexyl)propane (manufactured by NOF Corporation, Pertetra A)). The prepared raw material solution was continuously supplied at 0.73 L/hour to a completely mixed first reactor having an internal volume of 5.4 L and maintained at a temperature of 100° C.
Next, 68 parts by mass of styrene monomer, 32 parts by mass of ethylbenzene, 0.5 parts by mass of chain transfer agent 1 (α-methylstyrene dimer (NOFMER MSD, manufactured by NOF Corporation)), and 0.07 parts by mass of polymerization initiator 2 (1,1-di-(tertiary-butylperoxy)cyclohexane (PERHEXA C, manufactured by NOF Corporation)) were added to prepare a raw material solution to be supplied to the second reactor. The prepared raw material solution was continuously supplied at 0.23 L/hour to a plug-flow type second reactor having an internal volume of 1.5 L and having three zones whose temperatures were maintained at 115° C., 120° C., and 110° 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 the joined polymerization solution was 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 120° C., 127° C., 133° C., and 133° C. in the order in which the raw material solutions passed through. In zone 1 of the third reactor, 0.0365 parts by mass of a polymerization initiator 3 (t-butylperoxyisopropyl carbonate (Perbutyl I, manufactured by NOF Corporation)) was added. In addition, in zone 3 of the third reactor, 0.1 parts by mass of thermal degradation inhibitor 1 (2-[1-(2-hydroxy-3,5-di-t-phenylpentyl)ethyl]-4,6-di-t-phenylpentyl acrylate (Sumitomo Chemical Co., Ltd., Sumilizer GS)), 0.07 parts by mass of thermal degradation inhibitor 2 (octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate (BASF Japan Ltd., Irganox 1076)), and 0.07 parts by mass of thermal degradation inhibitor 3 (tris(2,4-di-tert-butylphenyl)phosphite (BASF Japan Ltd., Irgafos 168)) were added. (In this production example, the polymerization initiator and the chain transfer agent were added from zone 1 of the third reactor, and the thermal degradation inhibitor was added from zone 3 of the third reactor.)
Next, the polymerization solution from the third reactor was supplied to a vacuum degassing tank heated to a temperature of 240° C., where volatile components such as unreacted monomers and solvents were removed, and after 72 hours of continuous operation, a styrene-based resin for evaluation was obtained.
The composition and properties of the resulting resin are shown in Table 2.

[Resin c-2]
Resin c-2 was polymerized in the same manner as Resin c-1, except that the composition was changed as shown in Table 2. The multi-branched vinyl compound used in the polymerization of Resin c-2 was synthesized by the method described later, and was added when preparing the raw material solution to be supplied to the reactor.
The composition and properties of the resulting resin are shown in Table 2.

<Highly branched vinyl compounds>
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 thereto over 25 minutes while controlling the heat generated by the reaction. When the heat generation subsided, the reaction mixture was further stirred at 120 ° C. for 3 hours and then cooled to room temperature. The weight average molecular weight of the obtained hyperbranched polyether polyol was 3,000 and the hydroxyl value was 530.
50g of the hyperbranched polyether polyol obtained above, 13.8g of methacrylic acid, 150g of toluene, 0.06g of hydroquinone, and 1g of paratoluenesulfonic acid were added to a reactor equipped with a stirrer, a thermometer, and a condenser, and the mixture was stirred and heated under normal pressure while blowing 7% oxygen-containing nitrogen (v/v) into the mixture at a rate of 3mL/min. The heating amount was adjusted so that the amount of distillate in the decanter was 30g per hour, and heating was continued until the amount of dehydration reached 2.9g. After the reaction was completed, the mixture was cooled once, 36g of acetic anhydride and 5.7g of sulfamic acid were added, and the mixture was stirred at 60°C for 10 hours. Thereafter, in order to remove the remaining acetic acid and hydroquinone, the mixture was washed four times with 50g of 5% aqueous sodium hydroxide solution, and further washed once with 50g of 1% aqueous sulfuric acid solution and twice with 50g of water. 0.02g of methoquinone was added to the obtained organic layer, and the solvent was distilled off under reduced pressure while introducing 7% oxygen-containing nitrogen (v/v), to obtain 60g of a multi-branched vinyl compound having isopropenyl groups and acetyl groups. The weight-average molecular weight of the obtained multi-branched vinyl compound was 3,900, and the introduction rates of isopropenyl groups and acetyl groups into the multi-branched polyether polyol were 30 mol% and 62 mol%, respectively, based on the total hydroxyl groups.

[Resin c-3]
For comparison with resins c-1 and c-2, an acrylic resin (Metablen P-531A, manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight: 4,500,000) was used.

[Resin c-4]
For comparison with resins c-1 and c-2, polystyrene (manufactured by Tosoh Corporation, F-288, weight average molecular weight: 2,110,000) was used.

[Rubber-modified styrene-based resin (d)]
[Resin d-1]
A rubber-modified styrene-based resin was produced using a polymerization apparatus in which three laminar flow reactors (1.5 liters) equipped with stirrers were connected in series and a two-stage vented extruder was arranged behind them. 82 parts by mass of styrene, 12 parts by mass of ethylbenzene, 6.7 parts by mass of Asahi Kasei Corporation's Diene (registered trademark) 55 as a rubber component, and 0.02 parts by mass of 1,1-bis(t-butylperoxy)cyclohexane were charged into a raw material tank equipped with a stirrer, and the rubber component was dissolved with a stirrer. Then, this raw material solution was supplied to the reactor at a volume of 0.75 liters/hr, and polymerization was performed at a temperature of 110 to 120°C in the first stage reactor, a temperature of 120 to 130°C in the second stage reactor, and a temperature of 140 to 150°C in the third stage reactor. In addition, the extruder temperature was 210 to 240°C, the degree of vacuum was 3 kPa, and the total solid content in the polymerization liquid discharged from the final reactor was 77.9% by mass. The rubber particle size was controlled by adjusting the rotation speed of the agitator of the first-stage laminar flow reactor to 115 rpm.
The composition and properties of the resulting resin are shown in Table 3.

[Resin d-2, d-3]
Various conditions were adjusted so as to obtain the resin properties shown in Table 3, and a rubber-modified styrene-based resin (d) was obtained in the same manner as for resin d-1.
In order to obtain the rubber particle diameters shown in Table 3, the rotational speeds of the stirrers in the first-stage laminar flow reactors for resins d-2 and d-3 were adjusted to 200 rpm and 250 rpm, respectively.

[Aliphatic primary alcohol]
Fine Oxocol 180 (freezing point: -30°C or lower) (manufactured by Nissan Chemical Industries, Ltd.), which is an isoaliphatic primary alcohol, was used.

Next, the methods for producing the resin compositions of the examples and comparative examples will be described.
[Reference Example 1 ]
As shown in Table 4, 96.5% by mass of resin a-1 as copolymer resin (a) was mixed with 3% by mass of MBS (b) and 0.5% by mass of resin c-1 as styrene-based resin (c). Further, Fine Oxocol 180 as an isoaliphatic primary alcohol was added in an amount of 2 parts by mass per 100 parts by mass of the total mass of the copolymer resin (a), the MBS resin (b), and the copolymer resin (c), and then extruded with a twin-screw extruder to prepare resin pellets.
The alcohol content (mass %) in the resin composition shown in Table 4 below is a value determined by quantitatively measuring the resin composition after extrusion by gas chromatography.

[Examples 2 to 5]
The copolymer resin (a), MBS (b), styrene-based resin (c), and optionally rubber-modified styrene-based resin (d) were mixed in the same manner as in Example 1, except that the composition ratios were as shown in Table 4. After further adding an isoaliphatic primary alcohol, the mixture was extruded with a twin-screw extruder to prepare resin pellets. The evaluation results are shown in Table 4 below.
The sheet stretching temperature and the foaming temperature of the liquefied carbon dioxide-containing sheet were increased or decreased by the difference in Vicat softening temperature from Example 1.

[Comparative Examples 1 to 4]
The copolymer resin (a), MBS (b), styrene-based resin (c), and rubber-modified styrene-based resin (d) were mixed and further added with an isoaliphatic primary alcohol in the same manner as in Example 1, except that the composition ratio was as shown in Table 4. The resin pellets were prepared by extruding with a twin-screw extruder. The evaluation results are shown in Table 4 below.
The sheet stretching temperature and the foaming temperature of the liquefied carbon dioxide-containing sheet were increased or decreased by the difference in Vicat softening temperature from Example 1.
In Comparative Example 1, the styrene-based resin (c) was not added, and as a result, the sheet broke during vacuum molding of the non-foamed sheet, and a vacuum molded product could not be obtained, as compared with Example 1. In Comparative Examples 2 and 3, the resin c-3 containing a high molecular weight component was used instead of the styrene-based resin (c), which made mold staining more likely to occur and also deteriorated the appearance. In Comparative Example 4, the resin c-4 containing a high molecular weight component was used instead of the styrene-based resin (c), which made mold staining more likely to occur and also deteriorated the appearance.

The heat-resistant styrene-based resin composition of the present invention is used to produce non-foamed and foamed extruded boards and sheets, as well as molded products such as food containers and packaging materials produced by secondary processing of these, which have excellent heat resistance, mechanical strength, appearance, extrusion moldability, and deep drawability during vacuum molding. Furthermore, the heat-resistant styrene-based resin composition of the present invention can be widely used as a raw material for molded products produced by injection molding or the like, for electrical product parts, toys, miscellaneous goods, daily necessities, and various industrial parts, and plays a major role in the industrial world. In addition, the heat-resistant styrene-based resin composition of the present invention can suppress mold contamination when producing molded products by injection molding or the like, and therefore molded products can be produced efficiently.

Claims (8)

a copolymer resin (a) which is a styrene-methacrylic acid copolymer; an MBS resin (b) which is obtained by grafting a copolymer mainly composed of methyl methacrylate monomer units and styrene monomer units onto rubber-like particles containing butadiene monomer units; and a styrene resin (c) which has a weight average molecular weight of 200,000 to 2,000,000 and contains 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, and in which the content of the styrene-based compound in the monovinyl compound is 70 mol % or more of the content of the monovinyl compound,
the content of the copolymer resin (a) is 83 to 99 mass%, the content of the MBS resin (b) is 0.9 to 12 mass%, and the content of the styrene-based resin (c) is 0.1 to 5.0 mass%, relative to 100 mass% of the total mass of the copolymer resin (a), the MBS resin (b), and the styrene-based resin (c);
The copolymer resin (a) contains 84 to 96% by mass of styrene monomer units and 4 to 16% by mass of methacrylic acid monomer units, when the total of the styrene monomer units and the methacrylic acid monomer units is 100% by mass,
The Vicat softening temperature is 110 to 125°C .
The degree of branching is 0.60 to 0.95, and the degree of gelation is 1.10 to 1.60,
the styrene-based compound is styrene, α-methylstyrene, paramethylstyrene, ethylstyrene, propylstyrene, butylstyrene, chlorostyrene or bromostyrene;
The monovinyl compound is methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, cetyl (meth)acrylate, (meth)acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, maleic anhydride, maleimide, or nucleus-substituted maleimide;
In the case where the polybranched vinyl compound is contained, the following (1) and (2) are satisfied,
(1) The content of the multi-branched vinyl compound is 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ mol per 1 mol of the total amount of the monovinyl compound.
(2) The number average molecular weight (Mn) of the hyperbranched vinyl compound is 850 to 100,000.
In the case where the conjugated divinyl compound is contained, the following (3) and (4) are satisfied:
(3) The content of the conjugated divinyl compound is 2.0×10 ⁻⁶ to 4.0×10 ⁻⁴ mol per 1 mol of the total amount of the monovinyl compounds.
(4) A heat-resistant styrene-based resin composition, characterized in that the conjugated divinyl compound has a number average molecular weight (Mn) of 850 to 100,000. The heat-resistant styrene resin composition according to claim 1, wherein the total content of styrene dimer and styrene trimer is 0.6 mass% or less, and the content of styrene monomer is 700 mass ppm or less, relative to 100 mass% of the total mass of the heat-resistant styrene resin composition. The heat-resistant styrene-based resin composition according to claim 1 or 2, wherein the butadiene monomer unit content in the MBS resin (b) is 50% by mass or more, the mass composition ratio of methyl methacrylate and styrene in the MBS resin (b) is 30/70 to 70/30, and the styrene monomer unit content in the MBS resin (b) is 3 to 35% by mass. The heat-resistant styrene-based resin composition further contains a rubber-modified styrene-based resin (d) in an amount of 30% by mass or less based on 100% by mass of the total mass of the heat-resistant styrene-based resin composition, and the rubber-modified styrene-based resin (d) has a rubber particle diameter of 0.5 to 5.0 μm;
The heat-resistant styrene-based resin composition according to any one of claims 1 to 3, wherein the rubber-modified styrene-based resin (d) is a resin in which rubber-like polymer particles are dispersed in a styrene-based resin matrix, and the styrene-based resin is composed of styrene, α-methylstyrene, α-methyl-p-methylstyrene, ο-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, ethylstyrene, isobutylstyrene, t-butylstyrene, bromostyrene, chlorostyrene, or indene. The heat-resistant styrene-based resin composition according to any one of claims 1 to 4, further comprising an aliphatic primary alcohol having 14 or more carbon atoms and a freezing point of -10°C or lower in an amount of 0.02 to 1.0 parts by mass relative to 100% by mass of the total mass of the heat-resistant styrene-based resin composition. An extruded sheet formed using the heat-resistant styrene-based resin composition according to any one of claims 1 to 5. A foamed extruded sheet formed using the heat-resistant styrene-based resin composition according to any one of claims 1 to 5 . A molded product formed using the extruded sheet according to claim 6 or the foamed extruded sheet according to claim 7.