JP6930866B2 - Styrene-based resin composition, foamed sheet, molded product, manufacturing method - Google Patents

Description

The present invention relates to a styrene-based resin composition, a method for producing the same, a foamed sheet containing the styrene-based resin composition, and a molded product composed of the foamed sheet.

Since styrene resin is excellent in transparency and moldability, it is widely used as a molding material for home appliances, office machine products, miscellaneous goods, housing equipment, and food packaging materials. In recent years, thinning, weight reduction, and diversification of shapes of products have been required, and styrene resins having a good appearance and excellent molding processability are required. Further, in the secondary molding of an extruded sheet of styrene resin, since a large number of moldings are performed at one time, the degree of heating of the sheet varies, and the yield of the molded product is poor with the styrene resin having a narrow molding condition range. There is a problem. It is known that a method of adding an ultra-high molecular weight component to a styrene resin is effective as a method of improving the molding processability of an extruded sheet of a styrene resin or the like.

As such a method, Patent Document 1 describes the slope of the first-order approximate straight line of the non-linear region in the logarithmic plot of the time-extensional viscosity curve when the uniaxial extensional viscosity of the polystyrene-based resin composition is measured under predetermined conditions. We are paying attention to the ratio of the linear region to the slope of the linear approximation straight line in the curve. Specifically, by setting this ratio in the range of more than 2.0 and 6.0 or less under the conditions of a temperature of 160 ° C. and a constant strain rate of 0.1 / sec, weight reduction is realized without deteriorating the physical properties of the container. It is stated that it can be done. Further, in Patent Document 2, the melt mass flow rate of the styrene resin, the total amount of the styrene dimer and the trimmer, the peak molecular weight (Mtop), the Z average molecular weight (Mz), the degree of branching, and the content of the low molecular weight saturated hydrocarbon are specified. It is stated that a styrene resin foam sheet having less odor and an excellent balance of strength, secondary moldability, and drawdown resistance can be obtained by setting the range.

Japanese Unexamined Patent Publication No. 2014-189764 Japanese Unexamined Patent Publication No. 2016-11580

However, in Patent Document 1, when the uniaxial extensional viscosity of the polystyrene-based resin composition is measured under predetermined conditions, the slope of the first-order approximate straight line in the non-linear region in the logarithmic plot of the time-extensional viscosity curve and the linear region in the above curve. It is stated that the ratio of the slope of the first-order approximation curve to the slope is within a specific range, but it was found that the reduction of gel-like substances was not sufficient and there was room for further improvement. Further, in the styrene resin described in Patent Document 2, since a multi-branched vinyl compound is used to introduce a multi-branched structure, the reduction of gel-like substances is not sufficient, and there is room for further improvement. Do you get it.
Therefore, the present invention has been devised in view of such conventional circumstances, and an object of the present invention is a styrene-based resin composition having excellent molding processability, a wide range of molding conditions, and a small amount of gel-like substances. It is to provide things.

As a result of diligent research to achieve the above object, the present inventors have measured the degree of branching, the degree of gelation, and the absolute molecular weight of the styrene resin composition using a multi-angle light scattering detector (MALS). Using the content of 10,000 to 5 million components, the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) measured using gel permeation chromatography (GPC) (Mw / Mn), and GPC. We have found that by controlling the measured peak top molecular weight (Mtop) within an appropriate range, it is possible to realize a styrene-based resin composition having excellent molding processability, a wide range of molding conditions, and a small amount of gel-like substance. It came to be completed.

That is, the present invention is as shown below.
[1] The degree of branching is 0.70 to 0.94, and the degree of branching is 0.70 to 0.94.
The degree of gelation is 1.00 to 1.25,
The content of the component having an absolute molecular weight of 1 million to 5 million measured using a multi-angle light scattering detector (MALS) is 10.0 to 15.0%.
The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is 3.0 to 5.0.
A styrene-based resin composition having a peak top molecular weight (Mtop) measured using GPC of 100,000 to 180,000.
[2] The styrene resin composition according to [1], which has a maximum rising ratio of 1.2 to 5.0.
[3] The method according to [1] or [2], wherein the total residual amount of the styrene dimer and the trimer is 0.01 to 0.30% by mass with respect to 100% by mass of the styrene resin composition. Styrene-based resin composition.
[4] A foamed sheet containing the styrene resin composition according to any one of [1] to [3] and having a thickness of 0.5 to 5.0 mm.
[5] A molded product comprising the foamed sheet according to [4].
[6] The method for producing a styrene resin composition according to any one of [1] to [3], which comprises using continuous solution polymerization or continuous bulk polymerization.

According to the present invention, it is possible to provide a styrene-based resin composition having excellent molding processability, a wide range of molding conditions, and a small amount of gel-like substance.

It is a figure which shows the log-log graph which plotted the Henky strain on the horizontal axis, and the extensional viscosity on the vertical axis about the styrene resin composition obtained in Example and Comparative Example.

Hereinafter, embodiments of the present invention (hereinafter referred to as “the present embodiment”) will be described, but the present invention is not limited to the present embodiment.

<< Styrene-based resin composition >>
The styrene-based resin composition of the present embodiment has a branching degree of 0.70 to 0.94 and a gelation degree of 1.00 to 1.25, and uses a multi-angle light scattering detector (MALS). The content of the measured absolute molecular weight of 1 million to 5 million is 10.0 to 15.0%, and the weight average molecular weight with respect to the number average molecular weight (Mn) measured by gel permeation chromatography (GPC). The ratio (Mw / Mn) of (Mw) is 3.0 to 5.0, and the peak top molecular weight (Mtop) measured by GPC is 100,000 to 180,000.

The degree of branching, the degree of gelation, the content of components having an absolute molecular weight of 1 to 5 million measured using MALS, and the Mw / Mn and peak top molecular weights measured using GPC of the styrene resin composition of the present embodiment. By controlling (Mtop) to an appropriate range as described above, it is possible to provide a styrene-based resin composition having excellent molding processability, a wide range of molding conditions, and a small amount of gel-like substance.
Although not limited to theory, the styrene-based resin composition of the present embodiment has the degree of branching, the content of components having an absolute molecular weight of 1 to 5 million measured using MALS, and Mw / Mn and Mw / Mn measured using GPC. By controlling the peak top molecular weight (Mtop) in an appropriate range, the moldability at the time of extrusion is improved, the range of molding conditions is widened, and the gelation degree is controlled in an appropriate range to achieve gelation. It is thought that it makes it possible to be suppressed.
The degree of branching, the degree of gelation, the content of the component having an absolute molecular weight of 1 to 5 million measured using MALS, and the Mw / Mn and peak top molecular weight measured using GPC of the styrene resin composition of the present embodiment. (Mtop) is, for example, when a monovinyl compound is radically polymerized to obtain a styrene-based resin composition, the content of the conjugated divinyl compound which may be optionally contained, the polymerization reaction temperature, and the inside of the polymerization reactor. It can be controlled by the residence time, the type and amount of the polymerization initiator, the type and amount of the solvent used at the time of polymerization, and the like.

The styrene-based resin composition of the present embodiment contains, for example, a styrene-based resin and optionally additives and the like.

Since the styrene-based resin composition of the present embodiment has excellent molding processability and a small amount of gel-like substance, a foamed sheet having an excellent appearance and a molded product thereof can be obtained, and various molded products can be obtained in a wider range of applications than before. be able to.

<Molecular weight of styrene resin composition>
The number average molecular weight (Mn) of the styrene resin composition of the present embodiment is preferably 50,000 to 200,000, more preferably 60,000 to 180,000, still more preferably 70,000 to 150,000. Is.
The weight average molecular weight (Mw) of the styrene resin composition of the present embodiment is preferably 200,000 to 500,000, more preferably 220,000 to 480,000, and even more preferably 240,000 to 450,000. ..
The Z average molecular weight (Mz) of the styrene resin composition of the present embodiment is preferably 600,000 to 2,000,000, more preferably 700,000 to 1.8 million, and even more preferably 800,000 to 1.6 million.

The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the styrene resin composition of the present embodiment is 3.0 to 5.0, preferably 3.2 to 4.8. It is more preferably 3.5 to 4.7, still more preferably 3.7 to 4.6. When Mw / Mn is smaller than 3.0, the fluidity may be lowered, the molding processability may be lowered, or the molding condition width may be narrowed. When Mw / Mn is larger than 5.0, the number of low molecular weight components becomes extremely large, and the strength of the molded product may decrease.
In order to set Mw / Mn to 3.0 to 5.0, for example, there are many methods of increasing the reaction temperature at the time of polymerization in the order in which the reaction solution passes, a method of using a chain transfer agent, and a large number of types of polymerization initiators. A method of making it functional (2, 3, or 4 functional), when a resin is produced by radically copolymerizing a monovinyl compound with a conjugated divinyl compound and / or a multi-branched vinyl compound, the conjugated divinyl compound or the multi-branched vinyl compound or the same thereof. There is a method in which both are preferably added in an ^{amount of 2.0 × 10 -6 to} 4.0 × 10 ^-4 mol with respect to 1 mol of the total amount of the monovinyl compound. Further, for example, in two reactors, there is a method of polymerizing a low molecular weight component and a method of polymerizing a high molecular weight component, respectively, and merging the two polymerization solutions, or a method of further polymerizing after the merging. .. Conditions for polymerizing the low molecular weight component include, for example, a method of shortening the residence time in the reactor, a method of increasing the amount of the solvent and raising the polymerization temperature, a method of using a chain transfer agent, and the like. The 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 conjugated divinyl compound, a polybranched vinyl compound, or both. , There is a method of adding ^{2.0 × 10 -6 to} 4.0 × 10 ^-4 mol, preferably 2.0 × 10 -6 to 4.0 × 10 -4 mol, with respect to 1 mol of the total amount of the monovinyl compound.

The peak top molecular weight (Mtop) of the styrene resin composition of the present embodiment is 100,000 to 180,000, preferably 110,000 to 180,000, more preferably 110,000 to 170,000, and further preferably 120,000 to 160,000. Is. When Mtop is smaller than 100,000, the number of low molecular weight components becomes extremely large, and the strength of the molded product may decrease. If the Mtop is larger than 180,000, the fluidity may decrease and the molding condition range may be narrowed.
In order to set the Mtop in the range of 100,000 to 180,000, for example, in the case of a method using a chain transfer agent or in the case of manufacturing by connecting a plurality of reactors in series, the reaction solution passes through the reaction temperature at the time of polymerization. There is a method of increasing the value in the order of increasing the amount, and a method of adding a chain transfer agent and a polymerization initiator to the reactor in the subsequent stage. Further, for example, in two reactors, there is a method of polymerizing a low molecular weight component and a method of polymerizing a high molecular weight component, respectively, and merging the two polymerization solutions, or a method of further polymerizing after the merging. .. Conditions for polymerizing the low molecular weight component include, for example, a method of shortening the residence time in the reactor, a method of increasing the amount of the solvent and raising the polymerization temperature, a method of using a chain transfer agent, and the like. The 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 conjugated divinyl compound, a polybranched vinyl compound, or both. , There is a method of adding ^{2.0 × 10 -6 to} 4.0 × 10 ^-4 mol, preferably 2.0 × 10 -6 to 4.0 × 10 -4 mol, with respect to 1 mol of the total amount of the monovinyl compound.

By setting the Mw / Mn of the styrene resin composition to 3.0 to 5.0 and the Mtop to the range of 100,000 to 180,000, a styrene resin composition having more excellent molding processability and fluidity can be obtained. Be done.
In the present disclosure, gel permeation chromatography (GPC) is used for the number average molecular weight (Mn), weight average molecular weight (Mw), Z average molecular weight (Mz), and peak top molecular weight (Mtop) of the styrene resin composition. It is a value measured by.

<Contents of components with an absolute molecular weight of 1 to 5 million>
In the styrene resin composition of the present embodiment, the content of the component having an absolute molecular weight of 1 million to 5 million is 10.0 to 15.0%, preferably 11.0 to 14.5%, and more preferably 12. It is .0 to 14.0%. By setting the content of the component having an absolute molecular weight of 1 million to 5 million in the range of 10.0 to 15.0%, a styrene resin composition having excellent molding processability and a small amount of gel-like substance can be obtained.
In order to set the content of the component having an absolute molecular weight of 1 million to 5 million to 10.0 to 15.0%, for example, a method using a polyfunctional polymerization initiator, a method of adding a conjugated divinyl compound, or a conjugate There is a method of adding a divinyl compound and a multi-branched vinyl compound at the same time. For example, when a styrene-based resin composition is obtained by optionally adding a conjugated divinyl compound and / or a multi-branched vinyl compound to a monovinyl compound and radically copolymerizing the monovinyl compound, the conjugated divinyl compound and / or the multi-branched vinyl compound can be obtained. ^{The amount added is preferably 4.0 × 10 -6 to} 8.0 × 10 ^-4 mol per vinyl group with respect to 1 mol of the total amount of the monovinyl compound (that is, conjugated divinyl having two vinyl groups). In the case of a compound, 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. Further, in the production of the styrene resin, there is a method of reducing the amount of the solvent to 0 to 20% and setting the reaction temperature to 80 to 140 ° C.
In the present disclosure, the content of the component having an absolute molecular weight of 1 million to 5 million in the styrene resin composition is a value calculated by using a multi-angle light scattering detector (MALS).

<Bifurcation degree>
The degree of branching of the styrene resin composition of the present embodiment is 0.70 to 0.94, preferably 0.72 to 0.93, more preferably 0.75 to 0.92, and even more preferably 0.79. ~ 0.90. If the degree of branching is less than 0.70, there will be too many branches and the molecular weight per branched chain will be small, so the number of entanglement points will be small, the entanglement will be unwound at high strain, and sufficient formability will be achieved. It may not be obtained. When the degree of bifurcation is larger than 0.94, there are few bifurcations, and a sufficient entanglement effect between the polymer chains may not be obtained.
In order to set the degree of branching to 0.70 to 0.94, a method using a polyfunctional polymerization initiator, a method of adding a conjugated divinyl compound, or a method of adding a conjugated divinyl compound and a polybranched vinyl compound at the same time. There is. For example, when a styrene-based resin composition is obtained by optionally adding a conjugated divinyl compound and / or a multi-branched vinyl compound to a monovinyl compound and radically copolymerizing the monovinyl compound, the conjugated divinyl compound and / or the multi-branched vinyl compound can be obtained. ^{The amount added is preferably 4.0 × 10 -6 to} 8.0 × 10 ^-4 mol per vinyl group with respect to 1 mol of the total amount of the monovinyl compound (that is, conjugated divinyl having two vinyl groups). In the case of a compound, 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 [Example] described later.

<Degree of gelation>
The degree of gelation of the styrene resin composition of the present embodiment is 1.00 to 1.25, preferably 1.01 to 1.15, more preferably 1.01 to 1.12, and even more preferably 1. It is 01 to 1.10. By setting the degree of gelation in the range of 1.00 to 1.25, it is possible to suppress the increase in branching as the molecular weight increases, so that the gel-like substance in the styrene resin composition can be reduced. In addition, the amount of gel-like substance produced when staying in a production facility such as a reactor for a long period of time can be reduced, so that the productivity can be improved.
In order to set the gelation degree to 1.00 to 1.25, a method using a polyfunctional polymerization initiator, a method of adding a conjugated divinyl compound, or a method of adding a conjugated divinyl compound and a polybranched vinyl compound at the same time is added. There is a way. For example, when a styrene-based resin composition is obtained by optionally adding a conjugated divinyl compound and / or a multi-branched vinyl compound to a monovinyl compound and radically copolymerizing the monovinyl compound, the conjugated divinyl compound and / or the multi-branched vinyl compound can be obtained. ^{The amount added is preferably 4.0 × 10 -6 to} 8.0 × 10 ^-4 mol per vinyl group with respect to 1 mol of the total amount of the monovinyl compound (that is, conjugated divinyl having two vinyl groups). In the case of a compound, 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 gelation is a value calculated by the procedure described in the section [Example] described later.

<Melt Mass Flow Rate (MFR)>
The melt mass flow rate (MFR) of the styrene resin composition of the present embodiment is preferably 0.5 to 5.0 g / 10 minutes. It is more preferably 0.6 to 4.0 g / 10 minutes, still more preferably 0.7 to 3.5 g / 10 minutes, and particularly preferably 0.8 to 3.0 g / 10 minutes. By setting the melt mass flow rate in the range of 0.5 to 5.0 g / 10 minutes, a styrene resin composition having excellent molding processability and fluidity can be obtained.
In order to set the MFR to 0.5 to 5.0 g / 10 minutes, for example, a method in which the Mw / Mn of the styrene resin composition is set to 3.0 to 5.0 and the Mw is set to 250,000 to 500,000. Alternatively, there is a method of adding a plasticizer such as liquid paraffin in an amount of 0.01 to 10.0% by mass based on 100% by mass of the styrene resin composition.
In the present disclosure, the melt mass flow rate is a value measured at 200 ° C. and a load of 49 N in accordance with ISO1133.

<Maximum rise ratio>
The maximum rising ratio of the styrene resin composition of the present embodiment is preferably 1.2 to 5.0, more preferably 1.3 to 4.8, and even more preferably 1.4 to 4.6. In the present specification, the "maximum rising ratio" means (extensional viscosity of the nonlinear region of the maximum rising strain / the extensional viscosity of the linear region of the maximum rising strain), and the "maximum rising strain" means the maximum extensional viscosity. It means the henky strain when it becomes. The maximum rising ratio is an index showing the degree of strain hardening at the maximum rising strain. The larger the maximum rise ratio, the greater the degree of strain hardening and the better the moldability. If the maximum rise ratio is less than 1.2, sufficient deep drawing moldability tends not to be obtained, or the molding condition width tends to be narrowed. If the maximum rising ratio is larger than 5.0, the extensional viscosity during molding becomes too low, which is not preferable from the viewpoint of productivity.
In order to set the maximum rising ratio to 1.2 to 5.0, for example, the degree of branching is 0.70 to 0.94, and the content of the component having an absolute molecular weight of 1 million to 5 million is 10.0 to 15.0. There is a way to set it to%.
In the present disclosure, the maximum rise ratio is a value calculated by the procedure described in the section [Example] described later.

<Total residual amount of styrene dimer and trimer>
When the styrene-based resin composition of the present embodiment is produced by radically polymerizing a styrene-based monomer, the total residual amount of the styrene dimer and the trimer in the styrene-based resin composition is preferable. Is 0.01 to 0.30% by mass, more preferably 0.01 to 0.25% by mass, and further preferably 0.02 to 0.20% by mass with respect to 100% by mass of the styrene resin composition. be. When the total residual amount of the styrene dimer and trimer is 0.01 to 0.30% by mass, the amount of rheumatism during the secondary molding is reduced, and the yield of the molded product having a good appearance is improved. It also makes it possible to reduce the odor of the molded product.
In order to make the total residual amount of the styrene dimer and trimer 0.01 to 0.30% by mass with respect to 100% by mass of the styrene resin composition, for example, in order to reduce the amount produced during polymerization. There are a method of lowering the reaction temperature to 80 to 140 ° C. and a method of adding 100 to 2000 mass ppm of the polymerization initiator to generate a large number of initiator radicals. Further, in order to reduce the amount generated by heat or shearing of the molten resin, a method of reducing the degree of vacuum when vacuum devolatile of unreacted monomers and solvents to 50 kPa or less, and a thermal decomposition inhibitor described later of 100 to 3000 are used. There is a method of adding mass ppm.
In the present disclosure, the total residual amount of the styrene dimer and the trimer is a value measured by using gas chromatography (GC).

<Styrene resin>
<Manufacturing method of styrene resin>
Examples of the method for producing the styrene-based resin of the present embodiment include a method for producing a monovinyl compound by radical copolymerizing a conjugated divinyl compound and / or a multi-branched vinyl compound.
Hereinafter, as an example, a method for producing a styrene resin by radical copolymerizing a monovinyl compound with a conjugated divinyl compound and / or a multi-branched vinyl compound will be described in detail.

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

<Conjugated divinyl compound>
The conjugated divinyl compound in the present 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.
Further, the conjugated divinyl compound in the present embodiment is preferably in the form of a chain rather than in the form of a network, and the main chain may or may not have a side chain. This is because the chain shape allows the molecular chain to have a more linear shape, which tends to improve the entanglement effect. The side chain preferably has 6 or less carbon atoms, and more preferably 4 or less carbon atoms.
Further, the conjugated vinyl group in the conjugated divinyl compound can be positioned arbitrarily in the molecule, but at least two of the two conjugated vinyl groups are located at different ends in the molecule. Is preferable. When the conjugated divinyl compound is in the form of a chain, it is more preferable that the two conjugated vinyl groups are located at different ends of the main chain (that is, both ends of the main chain become conjugated divinyl groups). It is more preferable to have it). The polymerization reactivity can be enhanced by locating the conjugated vinyl group at the terminal.
Further, when the conjugated divinyl compound is chain-like and has three or more conjugated vinyl groups, it is preferable that two of the three or more conjugated vinyl groups are located at the terminals. More preferably, all three or more conjugated vinyl groups are located at the ends.
If 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 and the raw material, resulting in deterioration of the transparency of the styrene resin. In addition, it may be necessary to clean the reactor and molding machine, which may reduce productivity. From these viewpoints, the number of conjugated vinyl groups contained in the conjugated divinyl compound is preferably 5 or less, more preferably 4 or less, and further preferably 3 or less. From the same viewpoint, it is particularly preferable that the conjugated divinyl compound has two conjugated vinyl groups.
Here, in the present specification, the "terminal" of a molecule includes not only the position (atom) at the end of the molecule but also the position close to the position at the end of the molecule. Specifically means an end corresponding to about 20% of the stretched chain length of the molecule. The conjugated vinyl group in the conjugated divinyl compound is located at the end corresponding to 15% of the stretched chain length of the conjugated divinyl compound molecule from the viewpoint of improving the reactivity with the monovinyl compound and suppressing gelation. Is more preferable, and it is more preferably located at the end portion corresponding to 10%, and further preferably located at the end portion corresponding to 5%.

In the present embodiment, the conjugated vinyl group includes an olefinic double bond copolymerizable with a monovinyl compound and a structure (for example, a carbonyl group, an aryl group, etc.) that forms a conjugated system with the olefinic double bond. It is a group having. The conjugated vinyl group is not particularly limited, and examples thereof include an acryloyl group and an aryl group substituted with a vinyl group, and the structure having a conjugated vinyl group in the conjugated divinyl compound is not particularly limited, for example. , (Meta) acrylate, urethane (meth) acrylate, aromatic vinyl, maleic acid, fumaric acid and the like are also added. The at least two conjugated vinyl groups may be the same or different from each other.

The number average molecular weight (Mn) of the conjugate divinyl compound of the present embodiment is preferably 850 to 100,000, more preferably 1000 to 80000, still more preferably 1200 to 80000, still more preferably 1500 to 60000, and particularly preferably. It is 1500 to 30000. When the number average molecular weight (Mn) is less than 850, the distance between the conjugated vinyl groups of the conjugated divinyl compound is short, so that the distance between the polymer chains bonded to the conjugated divinyl compound is short, and a sufficient entanglement effect cannot be obtained. , May be inferior in molding processability. When the molecular weight exceeds 100,000, the distance between the conjugated vinyl groups of the conjugated divinyl compound becomes long, and the reactivity of the conjugated vinyl group at the terminal decreases (because the molecular weight of the conjugated divinyl compound is large, the conjugated vinyl group at the terminal reacts. It becomes difficult to do so), and the amount of high-molecular-weight components produced may decrease.
In the present disclosure, the number average molecular weight (Mn) of the conjugated divinyl compound means the polystyrene-equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC).

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

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

<Contents of conjugated divinyl compound>
The content of the conjugated divinyl compound in the styrene resin of the present embodiment is preferably 2.0 × 10 ^{-6 to} 4.0 × 10 ^-4 mol, more preferably 5.0, based on 1 mol of the total amount of the monovinyl compound. × 10 ^{-6 to} 3.5 × 10 ^-4 mol, more preferably 1.5 × 10 ^{-5 to} 3.0 × 10 ^-4 mol, even more preferably 2.0 × 10 ^{-5 to} 2.5 × ^10-4 mol. When the content is ^{less than 2.0 × 10-6} mol, sufficient entanglement between the polymers is unlikely to occur, strain curing does not occur, or the degree of strain curing is small, so that the wall thickness of the molded product is not sufficient. The molded product may be uniform or the molded product may be torn during molding, resulting in inferior molding processability. On the other hand, when the content exceeds 4.0 × 10 ^-4 mol, a large amount of gel-like substance is generated, and the appearance of the molded product may be deteriorated.
In the present disclosure, the content of the conjugated divinyl compound with respect to 1 mol of the total amount of the monovinyl compound is a value measured using ^{1 1} H-NMR and ^{13 C-NMR.}

<Multi-branched vinyl compound>
In the multi-branched vinyl compound of the present embodiment, multi-branching means having one or more branched structures, and more specifically, a star-shaped branched structure, a pompon-shaped branched structure, a graft branched structure, and the like. It means that it has an H-shaped branch structure.
The number average molecular weight (Mn) of the polybranched vinyl compound is preferably 850 to 100,000, more preferably 1000 to 80000, still more preferably 1200 to 80000, even more preferably 1500 to 60000, and particularly preferably 1500 to 30000. Is. 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 a sufficient entanglement effect cannot be obtained, resulting in molding processability. May be inferior. When the molecular weight exceeds 100,000, the distance between the vinyl groups becomes long, the reactivity of the vinyl group decreases (the large molecular weight of the multi-branched vinyl compound makes it difficult for the terminal vinyl group to react), and the high molecular weight component The amount of production may decrease.
In the present disclosure, the number average molecular weight (Mn) of the polybranched vinyl compound is a value measured by gel permeation chromatography (GPC).

The multi-branched vinyl compound can be synthesized, for example, by the method described in JP-A-2016-113580 and JP-A-2016-11358. For example, divinyl aromatic compounds such as divinylbenzene and diisopropenylbenzene, aliphatic and alicyclic (meth) acrylates represented by ethylene glycol di (meth) acrylate, and styrene, ethylvinylbenzene and the like. There is a method for synthesizing a multi-branched vinyl compound by cationically polymerizing a monovinyl compound and a terminal modifier such as 2-phenoxyethyl methacrylate. Further, a method of esterifying or adding a polymerizable double bond such as a vinyl group, for example, an isopropenyl group to a polyhydric alcohol or polyester polyol having a multi-branched structure and having a plurality of hydroxyl groups can be mentioned. .. Here, the polyhydric alcohol having a multi-branched structure and having a plurality of hydroxyl groups is preferably an alcohol having 2 to 100 hydroxyl groups and 70 to 3000 carbon atoms.

<Content of multi-branched vinyl compound>
The content of the multi-branched vinyl compound in the styrene-based resin of the present embodiment is preferably 2.0 × 10 ^{-6 to} 4.0 × 10 ^-4 mol, more preferably 5. 0 × 10 ^{-6 to} 3.5 × 10 ^-4 mol, more preferably 1.5 × 10 ^{-5 to} 3.0 × 10 ^-4 mol, even more preferably 2.0 × 10 ^{-5 to} 2.5 × 10 ^-4 mol. When the content is ^{less than 2.0 × 10-6} mol, sufficient entanglement between the polymers is unlikely to occur, strain curing does not occur, or the degree of strain curing is small, so that the wall thickness of the molded product is not sufficient. The molded product may be uniform or the molded product may be torn during molding, resulting in inferior molding processability. On the other hand, when the content exceeds 4.0 × 10 ^-4 mol, a large amount of gel-like substance is generated, and the appearance of the molded product may be deteriorated.

<Polymerization process>
Examples of the polymerization method of the styrene resin of the present embodiment include known styrene polymerization methods such as a massive polymerization method, a solution polymerization method, and a suspension polymerization method. These polymerization methods may be a batch polymerization method or a continuous polymerization method, and are preferably continuous polymerization methods 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, a solvent, a polymerization catalyst, a chain transfer agent, etc., if necessary, are added and mixed, and a raw material solution containing monomers is added. To prepare. The raw material solution is placed in a facility equipped with one or more reactors arranged in series and / or in parallel and a devolatilizer for a volatilization step of removing volatile components such as unreacted monomers. Examples thereof include a method of continuously feeding and gradually advancing the polymerization.

Examples of the reactor include a completely mixed reactor, a laminar reactor, and a loop reactor that extracts a part of the polymerization solution while advancing the polymerization. The order of arrangement of these reactors is not particularly limited.

When polymerizing the styrene resin of the present embodiment, a polymerization solvent can be used if necessary from the viewpoint of controlling the polymerization reaction. The polymerization solvent is generally used for adjusting the polymerization rate, molecular weight, etc. in continuous bulk polymerization or continuous solution polymerization. The polymerization solvent is not particularly limited, and examples thereof include alkylbenzenes such as benzene, toluene, ethylbenzene, and xylene, ketones such as acetone and methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and cyclohexane. The amount of the polymerization solvent used is not particularly limited, but is usually 1 to 50% by mass as the composition in the polymerization reactor from the viewpoints of controlling gelation, improving productivity, increasing the molecular weight, and the like. It is preferably 3 to 40% by mass, and more preferably 3 to 40% by mass.

Further, when the polymerization raw material is polymerized in order to obtain the styrene resin of the present 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 is an organic peroxide, for example, 2,2-bis (t-butylperoxy) butane, 1,1-bis (t-butylperoxy) cyclohexane, and n-butyl-. Peroxyketals such as 4,4-bis (t-butylperoxy) valerate, dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, and dicumyl peroxide, acetyl peroxide, isobutyryl peroxide, etc. Diacyl peroxides, peroxydicarbonates such as diisopropylperoxydicarbonate, peroxyesters such as t-butylperoxyacetate, ketone peroxides such as acetylacetone peroxide, and hydroperoxides such as t-butylhydroperoxide. Can be done. The polymerization initiator is preferably used in an amount of 0.005 to 0.08% by mass based on the monovinyl compound. The chain transfer agent is not particularly limited, and examples thereof include α-methylstyrene dimer, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-octyl mercaptan. The chain transfer agent is preferably used in an amount of 0.01 to 0.50% by mass based on the monovinyl compound.

<Devolatile process>
As the volatilization device, for example, a normal volatilization device such as a flash drum, a twin-screw volatilizer, a thin film evaporator, or an extruder can be used, and generally, a vacuum volatilization tank equipped with a heater or a devolatilizer can be used. A volatile extruder or the like is used. As the arrangement of the devolatilizer, for example, a vacuum devastation tank with a heater is used in only one stage, a vacuum devastation tank with a heater is connected in two stages in series, and a vacuum devastation tank with a heater is connected. An example is one in which a volatilization tank and a devolatilization extruder are connected in series. In order to reduce the volatile components as much as possible, it is preferable that a vacuum devastation tank with a heater is connected in two stages in series, or a vacuum devolatilization tank with a heater and a devolatilization extruder are connected in series. ..

The conditions of the devolatilization step are not particularly limited. For example, when the polymerization of the monovinyl compound is carried out by bulk polymerization, the unreacted monovinyl compound is preferably 50% by mass, more preferably 40% by mass in the styrene resin. Polymerization can proceed until it becomes mass% or less. By the devolatile treatment, unreacted substances (monovinyl compounds) and / or volatile components such as solvents can be removed.

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

The content of the styrene resin in the styrene resin composition is preferably 50% by mass or more, preferably 50% by mass or more.
70% by mass or more is more preferable.

<Additives, etc.>
The styrene-based resin composition of the present embodiment may optionally contain an additive or the like, and for example, a rubber-reinforced aromatic such as HIPS resin or MBS resin as a rubber-containing component, if necessary. It may contain about 1 to 50% by mass of an aromatic vinyl-based thermoplastic elastomer such as a vinyl-based resin or SBS. In addition, the styrene resin composition is, for example, 2- [1- (2-hydroxy-3,5-di-t-phenylpentyl) ethyl, in order to suppress the thermal decomposition of the polymer in the step of recovering the unreacted monomer. ] -4,6-Di-t-Phenylpentyl acrylate and other processing stabilizers may be included. In addition, thermal deterioration inhibitors such as 2- [1- (2-hydroxy-3,5-di-t-phenylpentyl) ethyl] -4,6-di-t-phenylpentyl acrylate, stearic acid, zinc stearate. , Higher fatty acids such as calcium stearate and magnesium stearate and salts thereof, lubricants such as ethylenebisstearylamide, plasticizers such as liquid paraffin, antioxidants and the like in combination within a range that does not impair the object of the present embodiment. You may. In addition, additives commonly used in the field of styrene-based resins, such as flame retardants and colorants, may be combined and contained in the styrene-based resin composition as long as the object of the present embodiment is not impaired. The additive is not particularly limited, and examples thereof include a flame retardant such as hexabromocyclododecane and a colorant such as titanium oxide and carbon black. When the styrene resin is used as pellets, ethylene bisstearylamide, zinc stearate, magnesium stearate or the like may be sprinkled on the pellets as an external lubricant for the pellets.

Antioxidants are generally capable of stabilizing peroxide radicals such as hydroperoxy radicals generated during thermoforming or light exposure, or decomposing peroxides such as hydroperoxide produced. It is an ingredient that can be produced. The antioxidant is not particularly limited, and examples thereof include a hindered phenolic antioxidant and a peroxide decomposing agent. The hindered phenolic antioxidant can be used as a radical chain inhibitor, and the peroxide decomposition agent can decompose the peroxide produced in the system into more stable alcohols to prevent autoxidation. The hindered phenolic antioxidant is not limited to the following, but is limited to 2,6-di-t-butyl-4-methylphenol, stylenate phenol, and n-octadecyl-3- (3,5-di-). t-butyl-4-hydroxyphenyl) propionate, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-) Methylbenzyl) -4-methylphenyl acrylate, 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6-di-t-pentylphenyl acrylate, 4,4' − Butylidenebis (3-methyl-6-t-butylphenol), 4,4'-thiobis (3-methyl-6-t-butylphenol), alkylated bisphenol, tetrakis [methylene-3- (3,5-di-) t-butyl-4-hydroxyphenyl) propionate] methane, and 3,9-bis [2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) -propionyloxy] -1,1 -Dimethylethyl] -2,4,8,10-tetraoxyspiro [5.5] undecane and the like. The peroxide decomposing agent is not limited to the following, but organic phosphorus-based peroxide decomposition such as trisnonylphenylphosphine, triphenylphosphine, and tris (2,4-di-t-butylphenyl) phosphite. Agents, as well as dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, pentaerythrityl tetrakis (3-laurylthiopro) Pionate), ditridecyl-3,3'-thiodipropionate, and organic sulfur peroxide degrading agents such as 2-mercaptobenzimidazole. The amount of the antioxidant added is preferably 0.01 part by mass or more and 1 part by mass or less, and more preferably 0.1 part by mass or more and 0.5 part by mass with respect to 100 parts by mass of the styrene resin in the styrene resin composition. It is less than a part by mass.

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

The brominated bisphenol flame retardant is not limited to the following, but for example, 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 Examples thereof include A polycarbonate oligomer and an 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 effective. Is preferable because it is difficult to decompose during kneading with a polystyrene resin, has a high flame retardant effect, and tends to be easily exhibited. When tetrabromobisphenol A-bis (2,3-dibromopropyl ether) and tetrabromobisphenol A-bis (2,3-dibromo-2 methylpropyl ether) are used in combination, flame retardancy and thermal stability are achieved. It is more preferable because it tends to be superior.

When using a brominated flame retardant, it is preferable to use a brominated isocyanurate flame retardant together as a flame retardant aid. Brominated isocyanurate flame retardants include, but are not limited to, mono (2,3-dibromopropyl) isocyanurate, di (2,3-dibromopropyl) isocyanurate, and tris (2,3-dibromopropyl). Propyl) isocyanurate, mono (2,3,4-tribromobutyl) isocyanurate, di (2,3,4-tribromobutyl) isocyanurate, tris (2,3,4-tribromobutyl) isocyanurate, etc. Can be mentioned. 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 part by mass or more and 10 parts by mass or less, and more preferably 1 part by mass or more and 9 parts by mass with respect to 100 parts by mass of the styrene-based resin in the styrene-based resin composition. It is 2 parts by mass or less, more preferably 2 parts by mass or more and 8 parts by mass or less. When it is 0.1 part by mass or more, flame retardancy tends to be sufficiently secured, and when it is 10 parts by mass or less, the moldability at the time of producing a foamed sheet tends to be sufficiently good. ..

The liquid paraffin can be selected from, for example, liquid paraffin defined by standards such as the Food Sanitation Law, foods, and additives. Specific examples of this type of liquid paraffin include, but are not limited to, Cristol N52, Cristol N62, Cristol N72, Cristol N82, Cristol N122, Cristol N172, and chestnut commercially available from ExxonMobil. Examples include Stall N262, Cristol N352, and Plymall N542. In addition, Moresco White P-40, Moresco White P-55, Moresco White P-60, Moresco White P-70, Moresco White P-80, and More, which are commercially available from Matsumura Oil Research Corp. Sco 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 Examples thereof include White P-300, Moresco White P-350, and Moresco White P-350P. Furthermore, liquid paraffin 40-S, 60-S, 70-S, 80-S, 90-S, 100-S, 120-S, 150-S, 260-S commercially available from Sanko Chemical Industry Co., Ltd. , 350-S and the like. Furthermore, white mineral oil commercially available from CK Witco Corporation can be mentioned.

The molecular weight of the liquid paraffin is usually defined by the kinematic viscosity. The liquid paraffin in the present embodiment, for example, a kinematic viscosity of 40 ° C. which is defined by the test method JIS K2283 is able to use a range of 0.1~60mm ² / sec, the 1~40mm ² / sec Is preferable. 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 further preferably in the range of 200 to 350. The weight average molecular weight is determined by taking the weight average value of each molecular weight component of liquid paraffin using, for example, gas chromatography. When liquid paraffins in this viscosity range or this molecular weight range are used, the obtained styrene-based resin composition is greatly plasticized as compared with liquid paraffins having a higher viscosity or a higher molecular weight, and the moldability of the styrene-based resin composition is increased. For example, there is a tendency to greatly improve the surface gloss of a molded product. The use of liquid paraffin having a viscosity of 0.1 mm ² / sec or more or a weight average molecular weight of 150 or more effectively prevents mold contamination and bleeding on the surface of the molded product during the molding process of the obtained styrene resin composition. It is preferable because it tends to be suppressed.

The content of the liquid paraffin in the styrene resin composition is preferably less than 3.0 parts by mass, more preferably less than 1.0 part by mass, and further preferably less than 1.0 part by mass with respect to 100 parts by mass of the styrene resin. It is less than 0.5 parts by mass. When the content of liquid paraffin is less than 5.0 parts by mass, a molded product having an excellent balance between secondary moldability, strength and heat resistance of the molded product can be obtained.

Further, in the present embodiment, it is preferable to add the heat deterioration inhibitor in the polymerization step or the devolatilization step of the styrene resin composition, and after the polymerization step and before the volatilization step. In particular, it is preferable to add a thermal deterioration inhibitor after the completion of the polymerization step (preferably immediately after) and before the volatilization step. By adding a thermal deterioration inhibitor, radicals generated by thermal decomposition can be stabilized and the amount of thermal decomposition can be reduced.

Examples of the heat deterioration inhibitor include 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenylacrylate (trade name: Sumilyzer GM, manufactured by Sumitomo Chemical Co., Ltd.). ), 2- [1- (2-Hydroxy-3,5-di-t-phenylpentyl) ethyl] -4,6-di-t-phenylpentyl acrylate (trade name: Sumilyzer GS, manufactured by Sumitomo Chemical Co., Ltd.), Phenolic thermal degradation inhibitors such as 2,4-bis (octylthiomethyl) -6-methylphenol (trade name: Irganox 1520L) and octadecyl-3- (3,5-tersary butyl-4-hydroxyphenyl) propionate. , 4,6-Bis (octylthiomethyl) -o-cresol and other hindered phenolic antioxidants, tris (2,4-diterly butylphenyl) phosphite and other phosphorus-based processing heat stabilizers, etc. Can be mentioned. These heat deterioration inhibitores may be used individually or in combination of two or more.

The content of the heat deterioration inhibitor is preferably 0.01 to 0.5 parts by mass, more preferably 0.02 to 0 parts by mass with respect to 100 parts by mass of the styrene resin in the styrene resin composition at the outlet of the final reactor. .3 parts by mass, more preferably 0.03 to 0.2 parts by mass.
When the content of the heat deterioration inhibitor is 0.01 parts by mass or more, the formation of the monomer of the monovinyl compound and its dimer or trimer in the volatilization step can be more effectively suppressed. can. On the other hand, even if the content of the heat deterioration inhibitor is increased to more than 0.5 parts by mass, the effect commensurate with the content cannot be obtained.

<< Manufacturing method of styrene resin composition >>
The styrene-based resin composition of the present embodiment is, for example, a styrene-based resin obtained by radical polymerization of the above-mentioned monovinyl compound and a conjugated divinyl compound and / or a multi-branched vinyl compound by the above-mentioned production method, and the above-mentioned additive. Etc. can be obtained by a method of melt-kneading using a known kneader such as a single-screw extruder, a twin-screw extruder, or a Banbury mixer. The styrene resin composition of the present embodiment may be produced by appropriately adding the above-mentioned additives and the like in the above-mentioned production process of the styrene resin.

《Effervescent sheet》
The foamed sheet of the present embodiment contains the styrene resin composition of the present embodiment and has a thickness of 0.5 to 5.0 mm. Further, the foamed sheet of the present embodiment preferably has an apparent density of 50 to 300 g / L and a basis weight of 80 to 300 g / m ² .
The foamed sheet of the present embodiment may have a film laminated on the sheet. As the type of film, those used for general polystyrene can be used.
According to the foamed sheet of the present embodiment, a molded product having a good appearance can be obtained.

As the foaming agent and the foaming nucleating agent contained in the foaming sheet of the present embodiment, commonly used substances can be used. The foaming agent is not particularly limited, and examples thereof include butane, pentane, chlorofluorocarbon, and water, and butane is preferable. The effervescent nucleating agent is not particularly limited, and examples thereof include talc and the like.

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

<< Manufacturing method of foam sheet >>
The method for producing the foamed sheet of the present embodiment can be carried out by using a commonly known method. For example, although not particularly limited, a method of melt-kneading and extruding the styrene resin composition, the foaming agent, and the foam nucleating agent in the present embodiment with an extruder can be mentioned, and more details thereof are as follows.
First, the styrene resin composition of the present embodiment is melt-kneaded with an extruder connected to the circular die, and the melt-kneaded product is foamed from the annular opening provided in front of the circular die. Extrude in the state to form a cylindrical foam. Next, the foam is slidably contacted with the outer peripheral surface of a cooling mandrel having a diameter larger than the opening of the circular die to be cooled while being stretched in the circumferential direction, and this is continuously cut and developed along the extrusion direction. A commonly known method can be used.

"Molding"
The molded product in this embodiment is a secondary molded product of the foamed sheet of this embodiment. By secondary molding the foam sheet of the present embodiment by a conventionally known method such as vacuum molding, pressure molding, vacuum pressure molding, double-sided vacuum molding, press molding, etc., a tray, a cup, a bowl container, a natto container, etc. It is possible to form a secondary molded product of.
As an example of the secondary molded product of the present embodiment, the foamed sheet of the present embodiment is used as a molding material, and a vacuum molding machine is used to push out the foam sheet in the horizontal direction from 5.5 to 21 cm in length and 6.5 to 36 cm in width. Examples thereof include food tray containers having a depth of 1.1 to 3.4 cm. The temperature condition for vacuum forming is not particularly limited, but is usually preferably 120 to 150 ° C.

As a molding method, injection molding, extrusion molding, vacuum molding, pressure molding, extrusion foam molding, calendar molding, blow molding and the like can be preferably used, and various molded products can be obtained in a wider range of applications than before.

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

<< Measurement and evaluation method >>
The measurement and evaluation methods are as follows.

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

(2) Measurement of Molecular Weight The number average molecular weight (Mn), weight average molecular weight (Mw), Z average molecular weight (Mz), Mw / Mn, and peak top molecular weight (Mtop) of the styrene resin composition are determined by gel permeation chromatography (Mn). It was measured under the following conditions using GPC).
Equipment: Tosoh HLC-8220
Sorting column: Two Tosoh TSK gel Super HZM-H (inner diameter 4.6 mm) connected in series Guard column: Tosoh TSK guard volume Super HZ-H
Measuring solvent: tetrahydrofuran (THF)
Sample concentration: 5 mg of the 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 velocity: 0.35 mL / min Detector: Ultraviolet absorption detector (UV-8020 manufactured by Tosoh, wavelength 254 nm)
To create a calibration curve, 11 types of TSK standard polystyrene manufactured by Tosoh (F-850, F-450, F-128, F-80, F-40, F-20, F-10, F-4, F-2) , F-1, A-5000) was used. A calibration curve was created using an approximate expression of a linear straight line.

(3) Measurement of Absolute Molecular Weight The absolute molecular weight of the styrene resin composition was measured using a multi-angle light scattering detector (MALS) under the following conditions (hereinafter, may be referred to as "MALS method"). ..
Equipment: Tosoh HLC-8220
Sorting column: Two Shodex KF806-L connected in series Guard column: Shodex GPC KFG-4A
Measuring solvent: tetrahydrofuran (THF)
Sample concentration: 10 mg of the measurement sample was dissolved in 10 mL of a solvent and filtered through a 0.45 μm filter.
Injection volume: 100 μL
Measurement temperature: 40 ° C
Flow velocity: 1.00 mL / min Detector: Differential refractometer (RI-8022 manufactured by Tosoh Corporation)
MALS detector: Viscotek SEC-MALS 20 manufactured by Malvern
MALS detection angles: 12 °, 20 °, 28 °, 36 °, 44 ° 52 °, 60 °, 68 °, 76 °, 84 °, 90 °, 100 °, 108 °, 116 °, 124 °, 132 ° , 140 °, 148 °, 156 °, 164 °
MALS detector temperature: 35 ° C
PS105K was used as a standard sample, and analysis was performed using the analysis software OmniSEC 5.1.
From the obtained molecular weight and the ratio of dW / dlogM, the content (%) of the component having a molecular weight of 1 million to 5 million was calculated.

(4) Measurement of Branching Degree and Gelling Degree The branching degree and gelling degree of the styrene resin composition were calculated by measuring by the above-mentioned MALS method. A graph was created in which the horizontal axis was log molecular weight and the vertical axis was log radius of gyration. In this graph, for linear polystyrene (NBS706), a linear approximate straight line with a log molecular weight value in the range of 5.0 to 6.0 was created, and this was used as a reference value for linear polystyrene having no branched structure. And said.
Here, the values of log radius of gyration when the values of log Molecular weight are 6.0 and 6.5 are defined as <Rg6.0> and <Rg6.5>, respectively, and <Rg6.0> of NBS706, <Rg6.5> is defined as <Rg6.0> _{NBS and <Rg6.5> NBS, respectively.} The <Rg6.5> _NBS can be calculated from the extrapolated value of the approximate straight line.
The degree of bifurcation is defined as the degree of bifurcation = <Rg6.5> / <Rg6.5> _NBS. The degree of branching, the absolute molecular weight ^{106.5 = 3.16} million, it is meant whether the rotation radius with respect NBS706 a linear polystyrene becomes how smaller and the degree of branching is small, the target polymer Indicates that it is branched.
The degree of gelation is defined as the degree of gelation = (<Rg6.0> / <Rg6.0> _NBS ) / (<Rg6.5> / <Rg6.5> _NBS ). This degree of gelation represents the rate of change in the radius of gyration of the polymer from an absolute molecular weight of ^{106.0 to 106.5.} That is, it means how many branches increase as the molecular weight increases, and it means that the larger the degree of gelation, the more branches increase as the molecular weight increases.

(5) Measurement of Melt Mass Flow Rate (MFR) The melt mass flow rate (g / 10 minutes) of the styrene resin composition was measured under a load condition of 200 ° C. and 49 N in accordance with ISO1133.

(6) Measurement of maximum rise ratio The maximum rise ratio of the styrene resin composition was measured based on the following viscoelasticity measurement.
Device name: Viscoelasticity measuring device ARES-G2 (manufactured by TA Instruments)
Measurement system: ARES-EVF option Specimen dimensions: Length 20 mm, Thickness 0.7 mm, Width 10 mm
Elongation strain rate: 0.01 / sec Temperature: 150 ° C
Measurement atmosphere: In a nitrogen stream Preheating time: 2 minutes Preliminary extension strain rate: 0.03 / sec,
Preliminary extension length: 0.295 mm
Relaxation time after pre-stretching: 2 minutes In the viscoelasticity measurement, the test piece was attached to a roller, and after the temperature became stable at the measured temperature, the test piece was allowed to stand for the above preheating time and preheated. After the completion of preheating, pre-stretching was performed under the above conditions. After the pre-stretching, the mixture was allowed to stand for 2 minutes to relieve the stress generated by the pre-stretching and measured.

From the results obtained by the above viscoelasticity measurement, a log-log graph was created in which Henky strain was plotted on the horizontal axis and extensional viscosity was plotted on the vertical axis, and the range of Henky strain of 0.2 to 0.5 was set as the linear region. A linear region straight line of the power approximation was created (for example, the broken line in FIG. 1). When strain hardening occurs, the actual extensional viscosity becomes larger than the extensional viscosity of the approximate curve extrapolating this linear region.
The maximum rising ratio is an approximate straight line extrapolating the extensional viscosity of the non-linear region at the maximum rising strain / the linear region at the maximum rising strain, with the Henky strain at the maximum elongation viscosity in the above viscoelasticity measurement as the maximum rising strain. The extensional viscosity of) was calculated.
FIG. 1 shows a log-log graph in which the styrene-based copolymers obtained in Examples and Comparative Examples are plotted with the horizontal axis as the henky strain and the vertical axis as the extensional viscosity.

(7) Measurement of Total Residual Amount of Styrene Dimer and Trimer The total residual amount (mass ppm) of styrene dimer and trimer in the styrene resin composition is determined by the following conditions and procedures. So I measured it.
-Sample preparation: After dissolving 1.0 g of a styrene resin composition in 10 mL of methyl ethyl ketone, 3 mL of methanol containing a standard substance (triphenylmethane) was added to reprecipitate the polymer component, and a supernatant was collected and used as a measurement solution. ..
-Measurement conditions Equipment: Agilent 6850 series GC system Detector: FID
Column: HP-1 (100% dimethylpolysiloxane) 30 m, film thickness 0.25 μm, 0.32 mmφ
Injection volume: 1 μL (splitless)
Column temperature: Hold at 40 ° C for 1 minute → Heat up to 320 ° C at 20 ° C / min → Hold at 320 ° C for 10 minutes Injection temperature: 250 ° C
Detector temperature: 280 ° C
Carrier gas: helium

(8) Evaluation of Gel-like Material of Sheet A styrene resin composition was extruded using a 30 mmφ sheet extruder (manufactured by Soken Co., Ltd.) to prepare a sheet having a thickness of 0.5 mm. Twenty test pieces were cut out from the obtained sheet to a size of 100 mm in length × 100 mm in width, and a gel-like substance having an average of 2 mm or more in minor axis and major axis was visually measured. Judgment was made when the number of test pieces containing the gel-like substance was 0 to 2, "⊚", 3 to 10 was "○", and 11 or more was "x".

(9) Evaluation of Deep Drawing Formability of Sheet A styrene resin composition was extruded using a 30 mmφ sheet extruder (manufactured by Soken Co., Ltd.) to prepare a sheet having a thickness of 0.5 mm. Twenty test pieces were cut out from the obtained sheet to a size of 250 mm in length × 250 mm in width, and the sheet was sandwiched between the fixed frames of this sheet molding machine using a sheet container molding machine manufactured by Soken, and the average temperature of the heater was 220. The temperature was set to 110 ° C. and the atmospheric temperature was set to 110 ° C., and the mixture was heated for 20 seconds. Next, 20 molded bodies were molded by sliding the fixed frame together with a mold (temperature 40 ° C.) of a bowl container having a diameter of 10 cm and a depth of 10 cm for vacuum molding. It was visually confirmed whether or not tearing occurred on the side surface of the molded body, and the number of molded bodies that could be molded without tearing was used as an index of deep drawing moldability.

(10) Measurement of maximum moldable heating time of sheet The heating time during deep drawing in (9) above is increased from 20 seconds to 1 second by 1 second, and vacuum forming is performed without changing other conditions to obtain a molded product. 10 pieces were molded at a time. In the same manner as in (9), the heating time was extended until the number of molded bodies that could be molded was 7 or less. The maximum heating time at which 8 or more sheets could be molded was defined as the maximum moldable heating time (seconds) of the sheet, and was measured.

(11) Evaluation of Appearance of Molded Product The gloss and rough skin condition of the surface of the deep-drawn molded product molded in (10) above were visually confirmed. Of the 100 molded products, the molded product in which no dripping spots or uneven surface was confirmed was judged to be a molded product having a good appearance, and the number of the molded products was used as an index for evaluating the appearance of the molded product. bottom.

(12) Measurement of Residual Amount of Styrene Monomer in Foam Sheet The residual amount (mass ppm) of styrene monomer in the foam sheet was measured by a gas chromatography method under the following measurement conditions. 1 g of the foamed sheet was dissolved in 25 mL of dimethylformamide to prepare a measurement sample.
Measurement condition detection method: FID
Equipment: Shimadzu GC14B
Column: CHROMAPACK CP WAX 52CB
100m, film thickness 2μm, 0.52mmφ
Column temperature: The temperature was maintained at 110 ° C. for 10 minutes, the temperature was raised to 130 ° C. at 15 ° C./min, and the temperature was maintained at 130 ° C. for 2 minutes.
Injection port temperature: 150 ° C
Detector temperature: 150 ° C
Carrier gas: helium

(13) Evaluation of Deep Drawing Formability of Foam Sheet The foamed sheet was left to stand at 23 ± 3 ° C. and a relative humidity of 50 ± 5% for 20 days. Then, using a sheet container molding machine manufactured by Soken, the foamed sheet was sandwiched between the fixed frames of the sheet molding machine, the average temperature of the heater was set to 200 ° C., the atmospheric temperature was set to 130 ° C., and the mixture was heated for 15 seconds. Next, vacuum molding was performed by sliding the fixed frame together with a cup-shaped mold (temperature 40 ° C.) having a diameter of 10 cm and a depth of 3 cm or 6 cm, and 100 molded bodies were molded at a time. It was visually confirmed whether or not tearing occurred on the side surface of the molded body, and the number of molded bodies that could be molded without tearing was used as an index of deep drawing moldability.

(14) Measurement of maximum moldable heating time of foamed sheet During deep drawing molding in (13) above, the heating time is extended from 15 seconds to 1 second, and vacuum molding is performed without changing other conditions. The bodies were molded 10 pieces at a time. Similar to (13), the heating time was extended until the number of foamed sheets that could be molded into the molded product was 7 or less. The maximum heating time during which eight or more compacts could be molded was defined as the maximum moldable heating time (seconds) of the foamed sheet and measured.

(15) Foaming Magnification of Foamed Sheet The foaming ratio (times) of the foamed sheet was calculated by the following formula using the value of the foam density (ρf) and the density of the styrene resin composition (ρ).
Foaming magnification = ρ / ρf
As for the foam density, the foam density of the foam sheet was measured based on ISO10350. As a measuring device, a hydrometer (SGM-220-60 measuring device) manufactured by Shimadzu Corporation was used.

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

<Styrene resin>
<Monovinyl compound>
Styrene: Styrene monomer [manufactured by Asahi Kasei Corporation]

<Conjugated divinyl compound>
<Conjugated divinyl compound 1>
Conjugated divinyl compound 1 was produced based on the following method.
In a 5 L reaction vessel equipped with a stirrer, a thermometer and a reflux condenser, 2742 g of polybutadiene double-ended alcohol (Mn: 1900), 379 g of methyl acrylate, 380 g of n-hexane, 0.8194 g of hydroquinone monomethyl ether, and 4 0.5533 g of -hydroxy-2,2,6,6-tetramethylpiperidin-N-oxyl was charged. While passing the obtained mixture through a calcium chloride tube, air was blown into the mixture, and reflux dehydration was performed at 80 to 85 ° C. The water content of this mixture was measured by the Karl Fischer method, and it was confirmed that the water content was 200 ppm or less. Then, as a transesterification catalyst, 1.3685 g of tetra n-butyl titanate was added to the above mixture, and the produced methanol was distilled off from the reaction system under reflux of n-hexane, which is an azeotropic solvent, while stirring. The reaction was carried out at a reaction temperature of 80 to 85 ° C. for 10 hours.
Next, the temperature inside the reaction vessel was adjusted to 75 to 80 ° C., and the mixture was concentrated at a reduced pressure of 70 to 2 kPa until 95% or more of the methyl acrylate and n-hexane used were distilled off to remove excess methyl acrylate. n-Hexane was recovered. To the resulting polybutadiene both ends diacrylate 2070 g, toluene 2000 g, acetone 200 g, ion exchanged water 20g, and hydrotalcite (formula _{Mg 6 Al 2 (OH) 16CO} 3 · 4H 2 O) [manufactured by Kyowa Chemical as an ester exchange catalyst 20 g of [Kyoward 500PL] manufactured by Kogyo Co., Ltd. was added, and the mixture was treated at 75 to 80 ° C. for 2 hours. Next, the temperature inside the reaction vessel was adjusted to 75 to 80 ° C., and the mixture was concentrated at a reduced pressure of 90 to 35 kPa to recover 400 g of a mixed distillate of toluene, acetone and water, and the obtained concentrated solution was air-conditioned. The catalyst and the adsorbent were separated by filtration under pressure, and the solvent was further degassed at a temperature of 60 to 80 ° C. and a reduced pressure of 30 to 0.8 kPa to obtain a conjugated divinyl compound 1.
The conversion rate of the polybutadiene biterminal diacrylate of the conjugated divinyl compound 1 was measured by high performance liquid chromatography (HPLC) and found to be 99.3%. The polystyrene-equivalent number average molecular weight (Mn) measured by GPC was 1900.

Conjugated divinyl compound 2: Polybutadiene diacrylate [Made by Tomoe Kogyo Co., Ltd .: CN307] Mn: 3800
Conjugated divinyl compound 3: Polybutadiene terminal acrylate [Osaka Organic Chemical Industry Co., Ltd .: BAC-45] Mn: 4800
Conjugated divinyl compound 4: Urethane acrylate oligomer [manufactured by Tomoe Kogyo Co., Ltd .: CN9014NS] Mn: 8000

<Conjugated divinyl compound 5>
Conjugated divinyl compound 5 was produced based on the following method.
The conjugated divinyl compound 5 produced under the same conditions as in the case of the conjugated divinyl compound 1 except that the molecular weight of the polybutadiene double-ended alcohol was changed to Mn: 25000 had a conversion rate of 99.5% of the polybutadiene double-ended diacrylate. rice field. The polystyrene-equivalent number average molecular weight (Mn) measured by GPC was 26000.

<Conjugated divinyl compound 6>
Conjugated divinyl compound 6 was produced based on the following method.
The conjugated divinyl compound 6 produced under the same conditions as in the case of the conjugated divinyl compound 1 except that the molecular weight of the polybutadiene double-ended alcohol was changed to Mn: 57000 had a conversion rate of 99.2% of the polybutadiene double-ended diacrylate. rice field. The polystyrene-equivalent number average molecular weight (Mn) measured by GPC was 58,000.

Conjugated divinyl compound 7: Aromatic urethane acrylate [Made by Tomoe Kogyo Co., Ltd .: CN9782] Mn: 5200
Conjugated divinyl compound 8: 1,3-butylenediol dimethacrylate [manufactured by Wako Pure Chemical Industries, Ltd.] Molecular weight: 226
Conjugated divinyl compound 9: NK ester A-GLY-20E [manufactured by Shin-Nakamura Chemical Industry Co., Ltd.] Molecular weight: 1295, the average number of conjugated vinyl in one molecule of conjugated divinyl compound 9 is 3.
Conjugated divinyl compound 10: Divinylbenzene [manufactured by Wako Pure Chemical Industries, Ltd.] Molecular weight: 130

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

<Multi-branched vinyl compound 2>
In a 2 liter flask equipped with a stirrer, a thermometer, a dropping funnel and a condenser, at room temperature, 50.5 g of pentaerythritol ethoxylated (pentaerythritol with ethylene oxide added) disclosed in JP-A-2016-113598, BF ₃ diethyl ether 1 g of the solution (50%) was added and heated to 110 ° C. To this, 450 g of 3-ethyl-3- (hydroxymethyl) oxetane was slowly added over 25 minutes while controlling the exotherm caused by the reaction. When the exotherm 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 multi-branched polyether polyol was 3,000, and the hydroxyl value was 530.
In a reactor equipped with a Dean-Stark decanter equipped with a stirrer, a thermometer, a condenser and a gas introduction tube, 50 g of the above-mentioned multi-branched polyether polyol, 13.8 g of methacrylic acid, 150 g of toluene, 0.06 g of hydroquinone, and para 1 g of toluene sulfonic acid was added, and the mixture was stirred under normal pressure and heated while blowing 7% oxygen-containing nitrogen (v / v) into the mixed solution at a rate of 3 mL / min. The heating amount was adjusted so that the amount of the distillate in the decanter was 30 g per hour, and heating was continued until the dehydrated amount reached 2.9 g. After completion of the reaction, the mixture was cooled once, 36 g of acetic anhydride and 5.7 g of sulfamic acid were added, and the mixture was stirred at 60 ° C. for 10 hours. Then, in order to remove the remaining acetic acid and hydroquinone, the cells were washed 4 times with 50 g of a 5% aqueous sodium hydroxide solution, once with 50 g of a 1% aqueous sulfuric acid solution, and twice with 50 g of water. 0.02 g of methquinone was added to the obtained organic layer, and the solvent was distilled off while introducing 7% oxygen-containing nitrogen (v / v) under reduced pressure to obtain a polybranched vinyl compound 2 having an isopropenyl group and an acetyl group. 60 g was obtained. The weight average molecular weight of the obtained multi-branched vinyl compound 2 is 3,900, and the introduction rates of isopropenyl groups and acetyl groups into the multi-branched polyether polyol are 30 mol% and 62 mol%, respectively, with respect to the total hydroxyl groups. Met.

<Additive>
Thermal deterioration inhibitor 1: 2- [1- (2-hydroxy-3,5-di-t-phenylpentyl) ethyl] -4,6-di-t-phenylpentyl acrylate [Sumitomo Chemical Co., Ltd .: Sumilyzer GS] ]

<others>
Polymerization Initiator 1: 2,2-Bis (4,5-Ditershally-Butyl Peroxycyclohexyl) Propane [NOF CORPORATION: Pertetra A]
Polymerization Initiator 2: 1,1-Di- (Turshary-Butyl Peroxy) Cyclohexane [NOF CORPORATION: Perhexa C]
Chain transfer agent 1: α-methylstyrene dimer [NOF: NOFMER MSD]
Effervescent nucleating agent: Talc (manufactured by Matsumura Sangyo Co., Ltd., product name "High Filler # 12"
Foaming agent: Isobutane: Made by Mitsui Chemicals, Inc.

<Example 1>
80 parts by mass of styrene monomer, 20 parts by mass of ethylbenzene, 0.031 parts by mass of the conjugated divinyl compound 1 obtained by the above-mentioned production method (2.1 × ^10-5 mol with respect to 1 mol of styrene), polymerization initiation 0.025 parts by mass of Agent 1 was added to prepare a raw material solution to be supplied to the first reactor. The prepared raw material solution was continuously supplied at 0.6 L / hour to a completely mixed first reactor having an internal volume of 5.4 L maintained at a temperature of 102 ° C.
Next, a raw material solution to which 80 parts by mass of styrene monomer, 20 parts by mass of ethylbenzene, 0.35 parts by mass of chain transfer agent 1 and 0.023 parts by mass of polymerization initiator 2 are added and supplied to the second reactor. Was adjusted. The prepared raw material solution was placed in a plug-flow type second reactor having an internal volume of 1.5 L in which the temperatures of the three zones were maintained at 122, 127, and 115 ° C. in the order in which the raw material solution passed, and 0.17 L / hour. Supplied continuously at.
Then, the polymerization solutions from the first reactor and the second reactor were merged, and the temperatures of the four zones were maintained at 126, 139, 140, and 140 ° C. in the order in which the raw material solutions passed, and the internal volume was 3 L. It was supplied to the plug-flow type third reactor. In Zone 1 of the third reactor, 0.03 parts by mass of the polymerization initiator 2 was added. Further, in zone 3 of the third reactor, 0.1 part by mass of the heat deterioration inhibitor 1 was added.
Then, the polymerization solution from the third reactor was supplied to a vacuum degassing tank heated to a temperature of 240 ° C. to remove volatile components such as unreacted monomers and solvents, and evaluated after 72 hours of continuous operation. A styrene-based resin composition for use was obtained.
To 100 parts by mass of the above styrene resin composition, 0.15 parts by mass of talc (average particle size 1.3 μm) was added as a foaming nucleating agent, and 4 parts by mass of liquefied butane was added as a foaming agent to prepare a foamed sheet raw material. Obtained. Using an extrusion foaming machine equipped with a circular die having a diameter of 150 mm, the foamed sheet raw material was extruded and foamed. The temperature of the resin melting zone of the extruder was adjusted to 200 to 230 ° C, the temperature of the rotary cooler was adjusted to 130 to 170 ° C, and the temperature of the die was adjusted to 135 to 155 ° C. The foam immediately after extrusion foaming was cooled with a cooling mandrel and cut with a cutter at one point on the circumference to obtain a foam sheet having a thickness of 1.4 mm and a width of 1000 mm.
Table 1 shows the production conditions and analysis results of Example 1.

<Examples 2 to 13>
Examples 2 to 13 were carried out in the same manner as in Example 1 except that the conditions were changed as shown in Table 1, to obtain a styrene resin composition and a foamed sheet.
The measurement and evaluation results of Examples 2 to 13 are summarized in Table 1.
As shown in FIG. 1, it can be seen that the styrene resin composition of Example 4 exhibited strain hardening in the measurement of ARES-EVF.

<Comparative Examples 1 to 6>
Comparative Examples 1 to 6 were carried out in the same manner as in Example 1 except that the conditions were changed as shown in Table 1, to obtain a styrene resin composition and a foamed sheet.
Table 1 summarizes the measurement and evaluation results of Comparative Examples 1 to 6.

As is clear from Table 1, Mw / Mn is as small as 2.8 and the degree of branching is as large as 0.95. Comparative Example 1 and Mtop are as large as 276,000 and contain components having an absolute molecular weight of 1 million to 5 million. In Comparative Example 2 in which the amount was as low as 9.3%, the maximum rising ratio measured by ARES-EVF was 1.00, and strain hardening did not occur. Further, in Comparative Examples 3, 5 and 6, which had high gelation degrees of 1.56, 1.29 and 1.34, respectively, there were many gel-like substances on the sheet. Further, in Comparative Example 4 in which the degree of branching was as high as 0.97, the maximum moldable heating time was short and the molding condition range was narrow.

On the other hand, the degree of bifurcation is 0.70 to 0.94,
The degree of gelation is 1.00 to 1.25,
The content of the component having an absolute molecular weight of 1 million to 5 million measured using a multi-angle light scattering detector (MALS) is 10.0 to 15.0%.
The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is 3.0 to 5.0.
The styrene resin compositions of Examples 1 to 13 having a peak top molecular weight (Mtop) of 100,000 to 180,000 measured using GPC have appropriate properties with less gel-like substance on the sheet. It can be seen that the molding processability is excellent and the molding condition range is wide.

Although the embodiments of the present invention have been described above, the present invention is not limited to this, and can be appropriately changed without departing from the spirit of the invention.

Since the styrene-based resin composition according to the present invention has excellent molding processability, a wide range of molding conditions, and a small amount of gel-like substances, it can be used as a molding material for home appliances, office machine products, miscellaneous goods, housing equipment, etc. It can be widely used.

Claims (6)

The degree of bifurcation is 0.70 to 0.94,
The degree of gelation is 1.00 to 1.25,
The content of the component having an absolute molecular weight of 1 million to 5 million measured using a multi-angle light scattering detector (MALS) is 10.0 to 15.0%.
The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is 3.0 to 5.0.
A styrene-based resin composition having a peak top molecular weight (Mtop) measured using GPC of 100,000 to 180,000. The styrene resin composition according to claim 1, wherein the maximum rising ratio is 1.2 to 5.0. The styrene resin composition according to claim 1 or 2, wherein the total residual amount of the styrene dimer and trimer is 0.01 to 0.30% by mass with respect to 100% by mass of the styrene resin composition. thing. A foamed sheet containing the styrene resin composition according to any one of claims 1 to 3 and having a thickness of 0.5 to 5.0 mm. A molded product, which comprises the foamed sheet according to claim 4. The method for producing a styrene resin composition according to any one of claims 1 to 3, wherein continuous solution polymerization or continuous bulk polymerization is used.

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