JP2017218582A - Extrusion expanded sheet and molded article thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an extrusion expanded sheet having excellent molding processability and suitable for high magnification, and a molded article capable of being obtained from the extrusion expanded sheet and having high expansion ratio.SOLUTION: There is provided an extrusion expanded sheet containing a styrenic copolymer and having thickness of 0.5 mm to 5.0 mm, the styrenic copolymer is a copolymer of a conjugated divinyl compound having number average molecular weight (Mn) of 850 to 100000 and one or more kind of monovinyl compound containing at least a styrenic compound, the content of the conjugated divinyl compound is 2.0×10to 4.0×10moles per 1 mole of the monovinyl compound, weight average molecular weight (Mw) of the styrenic copolymer is 200,000 to 500,000, and percentage with molecular weight of 2,000,000 or more is 0.3% to 6.0%.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an extruded foam sheet and a molded product thereof.

  Styrene-based resins are excellent in transparency, molding processability, and the like, and thus are widely used in molding materials and food packaging materials for home appliances, office machine products, sundries, and housing equipment. In particular, secondary molded products formed by thermoforming from polystyrene resin extruded foam sheets, for example, food packaging containers are used for various foods such as trays for meat, fish, side dishes, cup noodle containers, natto containers, etc. As a simple container, it is used for general purposes. In such a simple container formed by foaming a foamed sheet, a high magnification is achieved when the container is foamed for cost reduction. However, when the container is foamed at a high magnification, the strength of the product decreases, and problems such as breakage of the container when the container is wrapped are likely to occur. In order to solve this problem, by controlling the form of the foam cell during extrusion foam molding, and by increasing the thickness of the vacuum molded container (particularly the thickness of the fragile part), there is a device that maintains the container strength even when the magnification is increased. Has been. Further, a method using a styrene resin having a specific number of branches as a material for containers has been proposed.

  As such a method, for example, Patent Document 1 discloses an extruded foam sheet containing a vinyl aromatic hydrocarbon polymer composition having a high molecular weight by introducing a branched structure into the molecule using a specific branched polymer. Is described. Moreover, in patent document 2, when a uniaxial elongation viscosity is measured on the predetermined conditions of a base resin including the component derived from a polyfunctional vinyl aliphatic compound and a styrene monomer as a base resin, time-extension We focus on the ratio between the slope of the linear approximation line in the logarithmic plot of the viscosity curve and the slope of the linear approximation line in the above curve. Specifically, it is described that by making this ratio in the range of 2.0 to 6.0, weight reduction can be realized without deteriorating the physical properties of the container.

Japanese Patent Laying-Open No. 2015-083684 JP 2014-189964 A

  However, in Patent Documents 1 and 2 described above, reduction of defects in the extruded foam sheet due to the gel material is not sufficient, and further improvement in formability is required. In addition, since the gel-like substance may act as a defect in secondary molding in which an extruded foam sheet is processed into a molded product, a material suitable for further higher magnification is required.

  The present invention has been devised in view of such conventional circumstances, and an object of the present invention is to provide an extruded foam sheet suitable for increasing the magnification and having excellent moldability. Furthermore, another object of the present invention is to provide a molded article having a high expansion ratio obtained from the extruded foam sheet.

  As a result of diligent research to achieve the above object, the present inventors constituted a styrene copolymer with a predetermined conjugated divinyl compound and a predetermined monovinyl compound at an appropriate content ratio, and a styrene-based copolymer. By controlling the molecular weight and molecular weight distribution of the copolymer to an appropriate range, it was found that an extruded foam sheet having excellent molding processability and its molded product can be realized, and the present invention was completed. It came to do.

That is, the present invention is as follows.
[1]
An extruded foam sheet having a thickness of 0.5 mm to 5.0 mm containing a styrene copolymer,
The styrene copolymer is a copolymer of a conjugated divinyl compound having a number average molecular weight (Mn) of 850 to 100,000 and at least one monovinyl compound containing styrene, and the content of the conjugated divinyl compound is: The amount of the monovinyl compound is 2.0 × 10 ^{−6 to} 4.0 × 10 ⁻⁴ mol, and the styrene copolymer has a weight average molecular weight (Mw) of 200,000 to 500,000, and a molecular weight of 2,000,000. An extruded foam sheet having the above ratio of 0.3% to 6.0%.
[2]
Item 2. The extruded foam sheet according to Item 1, wherein the conjugated divinyl compound has a number average molecular weight (Mn) of 1,000 to 30,000.
[3]
Item 3. The extruded foam sheet according to Item 1 or Item 2, wherein the conjugated divinyl compound is a chain.
[4]
Item 4. The extruded foam sheet according to any one of Items 1 to 3, wherein at least one of the conjugated vinyl groups of the conjugated divinyl compound is located at a terminal of the conjugated divinyl compound.
[5]
The extruded foam sheet according to any one of items 1 to 4, wherein the ratio of the Z average molecular weight (Mz) to Mw of the styrene copolymer is 1.8 to 5.0.
[6]
The extruded foam sheet according to any one of items 1 to 5, wherein a ratio of the styrene copolymer having a molecular weight of 1,000,000 or more is 4.0% to 20.0%.
[7]
Item 7. The extruded foam sheet according to items 1 to 6, wherein the styrene copolymer has an initial rising strain of 0.2 to 1.3 and a maximum rising ratio of 1.2 to 4.0.
[8]
Item 8. The extruded foam sheet according to any one of Items 1 to 7, wherein the conjugated divinyl compound is (hydrogenated) polybutadiene-terminated di (meth) acrylate.
[9]
The secondary molded product of the extrusion foaming sheet as described in any one of items 1-8.

  The extruded foam sheet of the present invention exhibits excellent moldability even at a high expansion ratio. Furthermore, by molding the extruded foam sheet of the present invention, a molded product with few defects and a high magnification can be obtained efficiently.

It is the logarithmic graph which plotted Henkey distortion on the horizontal axis and the elongational viscosity on the vertical axis for the styrene copolymers obtained in Examples and Comparative Examples. It is the graph which plotted the expansion ratio on the horizontal axis and the deep drawability on the vertical axis for the extruded foam sheets obtained in Examples and Comparative Examples.

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

<Extruded foam sheet>
The extruded foam sheet of this embodiment is an extruded foam sheet having a thickness of 0.5 mm to 5.0 mm containing a styrene copolymer, and the styrene copolymer has a number average molecular weight (Mn) of 850 to 100,000. Of the conjugated divinyl compound and at least one monovinyl compound containing at least styrene, and the content of the conjugated divinyl compound is 2.0 × 10 ^{−6 to} 4.0 per mole of the monovinyl compound. × a ^{10 -4} mol, weight average molecular weight of the styrene-based copolymer (Mw) of a 200,000 to 500,000, the ratio of the molecular weight of 2,000,000 or more is 0.3% to 6.0%.

<Styrene copolymer>
According to this embodiment, it is possible to provide an extruded foam sheet suitable for increasing the magnification and having excellent moldability. Specifically, although not limited to theory, in the present embodiment, the molecular chain of the obtained styrenic copolymer is divided into a plurality of molecular chain portions mainly composed of a monovinyl compound, and between the molecular chain portions. It is easy to make the interval between the molecular chain portions a predetermined distance while forming with the portions derived from the conjugated divinyl compound linked to each other. That is, it is presumed that it is easy to introduce a portion having an “H” -shaped branched structure into the molecular chain of the styrene copolymer. In the styrene copolymer in the present embodiment, each molecular chain of the styrene copolymer is likely to be effectively entangled with each other (this effect is also referred to as “entanglement effect”), and therefore, the styrene copolymer. The molding processability can be improved. In the present embodiment, the content of the conjugated divinyl compound, and the molecular weight and molecular weight distribution of the styrene copolymer are within a predetermined range, so that the molding processability of the styrene copolymer is effectively improved, It is possible to effectively prevent the styrene copolymer from being gelled. Therefore, according to the present embodiment, it is possible to provide an extruded foam sheet having excellent molding processability even at a high foaming ratio, and an extruded foam sheet containing, for example, a styrene copolymer due to a small amount of gel substance. By secondary molding, it is possible to efficiently obtain a molded product with few defects and high magnification.

(Monovinyl compound)
The styrenic copolymer contained in the extruded foam sheet of this embodiment contains at least one monovinyl compound containing at least a styrenic compound as a monomer that forms the styrenic copolymer. The monovinyl compound may be composed of only a styrene compound (monomer) or may be composed of a compound having another monovinyl group copolymerizable with the styrene compound together with the styrene compound. The monovinyl compound is not particularly limited as long as it can be copolymerized with a styrene compound in addition to a styrene compound, and examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and cetyl (meth). Examples thereof include vinyl compounds such as acrylate and (meth) acrylonitrile, and dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, maleic anhydride, maleimide, and nucleus-substituted maleimide. Examples of the styrene compound include styrene, α-methyl styrene, paramethyl styrene, ethyl styrene, propyl styrene, butyl styrene, chlorostyrene, and bromostyrene, and styrene is preferable. Further, the content of the styrene compound is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, out of the total content of the monovinyl compound.

(Conjugated divinyl compound)
The conjugated divinyl compound in the present embodiment is 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 the present embodiment is preferably a chain rather than a network. The chain may be a straight chain or may have one or more side chains in the main chain. This is because when the conjugated divinyl compound is in a chain form, the molecular chain can be made to have a more linear shape, which tends to improve the entanglement effect. For example, the side chain preferably has 6 or less carbon atoms, and more preferably 4 or less carbon atoms.
The conjugated vinyl group in the conjugated divinyl compound can be at any position in the molecule, and at least one of the conjugated vinyl groups is preferably located at the terminal of the conjugated divinyl compound. Of the at least two conjugated vinyl groups, the two conjugated vinyl groups are more preferably located at different terminals in the molecule. When the conjugated divinyl compound is 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 are conjugated divinyl groups. When the conjugated vinyl group is located at the terminal, the polymerization reactivity can be increased.
When the conjugated divinyl compound is a chain and there are three or more conjugated vinyl groups, at least two of the three or more conjugated vinyl groups are preferably located at the terminal, and the remaining 1 More preferably, one or more conjugated vinyl groups are also located at the terminal.

  When the number of conjugated vinyl groups of the conjugated divinyl compound is large, the branch point increases, and there is a possibility that gelation is likely to occur in the process of recovering the reactor and raw material, and the transparency of the styrene copolymer is deteriorated, Reactor cleaning is required and productivity may be reduced. Therefore, the number of conjugated vinyl groups of the conjugated divinyl compound is preferably 5 or less, more preferably 4 or less, further preferably 3 or less, and particularly preferably 2 .

  If the conjugated vinyl group is present near the terminal, the reactivity with the monovinyl compound can be more effectively increased, and gelation can be more effectively suppressed. Therefore, in this embodiment, the “terminal” means in the molecular chain. Any part (end part) having a certain range including the position (atom) at the end of the molecular chain may be used. In other words, the conjugated vinyl group only needs to be positioned near the terminal, and a certain number of atoms may exist on the terminal side of the conjugated vinyl group. In the present embodiment, the “terminal” is not limited, but is preferably 20% or less of the extended chain length of the conjugated divinyl compound, more preferably 15% or less, and even more preferably 10% or less. Even more preferably 5% or less. Most preferably, the conjugated vinyl group constitutes the position (atom) that becomes the end of the molecule of the conjugated divinyl compound.

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

  In this embodiment, the number average molecular weight (Mn) of the conjugated divinyl compound is 850 to 100,000, preferably 1000 to 100,000, more preferably 1000 to 80000, 1000 to 60000, 1000 to 30000, and more preferably, For example, it is 1200-80000, 1200-60000, 1200-30000, More preferably, it is 1500-80000, 1500-60000, Especially preferably, it is 1500-30000. When the number average molecular weight (Mn) is less than 850, since the distance between the conjugated vinyl groups of the conjugated divinyl compound is short, the distance between the polymer chains bonded to the conjugated divinyl compound becomes short, and a sufficient entanglement effect cannot be obtained. Inferior to moldability. When the molecular weight exceeds 100,000, the distance between the conjugated vinyl groups of the conjugated divinyl compound becomes longer, and the reactivity of the conjugated vinyl group at the terminal is lowered (the molecular weight of the conjugated divinyl compound is large, so the terminal conjugated vinyl group reacts). Undesirably), the amount of high molecular weight components produced decreases, which is not preferable. In addition, 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, polyphenylene sulfide, and the like.

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

(Content of conjugated divinyl compound)
The content of the conjugated divinyl compounds in the present embodiment, monovinyl compound per mol 2.0 × ¹⁰ -6 ~4.0 × ^{10 -4} mol, preferably 5.0 × ¹⁰ -6 ~3.5 × ^{10 - The amount is 4} mol, more preferably 1.5 × 10 ^{−5 to} 3.0 × 10 ⁻⁴ mol, and still more preferably 2.0 × 10 ^{−5 to} 2.5 × 10 ⁻⁴ mol. When the content is less than 2.0 × 10 ⁻⁶ mol, the moldability is inferior. On the other hand, when the content exceeds 4.0 × 10 ⁻⁴ mol, a lot of gel material is generated, which causes a secondary molding failure.

(Molecular weight)
The weight average molecular weight (Mw) of the styrene copolymer used in the present embodiment is 200,000 to 500,000, preferably 220,000 to 480,000, more preferably 240,000 to 450,000. By setting the Mw of the styrene copolymer to 200,000 to 500,000, it is possible to improve the molding processability and fluidity by suppressing the generation of the gel material while ensuring the strength of the styrene copolymer. it can. The ratio of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) of the styrene copolymer of the present embodiment is preferably 1.8 to 5.0, more preferably 2.0 to 4.8, More preferably, it is 2.1-4.7. By setting the ratio of Mz to Mw of the styrene copolymer to be in the range of 1.8 to 5.0, it is possible to suppress the generation of the gel-like substance while ensuring the strength of the styrene copolymer, and more moldability. And can improve fluidity.

  In the styrene copolymer used in this embodiment, the weight average molecular weight (Mw) and the ratio of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) are determined when radically polymerizing the styrene monomer. In addition, it can be controlled by the type and amount of conjugated divinyl compound, reaction temperature, residence time, type and amount of polymerization initiator, type and amount of solvent, type and amount of chain transfer agent, and the like. More specifically, the control of the above weight average molecular weight (Mw) and the like is not limited. For example, in the production method: increase the addition amount of the polymerization initiator at the time of polymerization, and the polymerization reaction It can be controlled by lowering the temperature; reducing the amount of polymerization solvent used; and / or increasing the residence time during the polymerization. The combined molecular chain can have a desired shape, and the proportion of the high molecular weight component can be appropriately increased.

  The weight average molecular weight (Mw), the Z average molecular weight (Mz), the ratio of the molecular weight of 1 million or more, and the ratio of 2 million or more of the styrene copolymer are the differentials measured by gel permeation chromatography (GPC). It is the weight percentage of the molecular weight distribution.

(Ratio of high molecular weight component)
The ratio of the molecular weight of 2 million or more of the styrene copolymer used in the present embodiment is 0.3 to 6.0%, preferably 0.8 to 5.0%, and 1.4 to 4. More preferably, it is 8%. By setting the ratio of the molecular weight of 2 million or more in the range of 0.3 to 6.0%, the content of the gel substance can be very reduced. The ratio of the molecular weight of 1,000,000 or more is preferably 4.0 to 20.0%, more preferably 5.0 to 18.0%, and further preferably 5.0 to 15.0%. By setting the ratio of the molecular weight of 1 million or more in the range of 4.0 to 20.0%, it is possible to obtain a styrenic copolymer that is superior in molding processability and fluidity.
The ratio of the molecular weight of the styrene copolymer used in the present embodiment is the kind and amount of conjugated divinyl compound, reaction temperature, residence time, kind of polymerization initiator and The amount can be controlled by the addition amount, the type and amount of the solvent, the type and addition amount of the chain transfer agent, and the like. More specifically, the control of the ratio of the molecular weight of 2 million or more and the molecular weight of 1 million or more is not limited. For example, in the production method: increase the addition amount of the polymerization initiator during polymerization By lowering the polymerization reaction temperature; reducing the amount of polymerization solvent used; and / or increasing the residence time during polymerization. The ratio of the high molecular weight component, that is, the molecular weight of 2 million or more and the molecular weight of 1 million or more can be appropriately increased while reducing the ratio of the low molecular weight component of the styrene copolymer.

(Melt Mass Flow Rate (MFR))
The melt mass flow rate (MFR) of the styrenic copolymer used in this embodiment is preferably 0.5 to 8.0. More preferably, it is 0.6-5.0, Still more preferably, it is 0.7-4.0, Most preferably, it is 0.8-3.0. By setting the melt mass flow rate in the range of 0.5 to 8.0, a styrene copolymer having a better balance between moldability and fluidity can be obtained.

(Initial rise strain, maximum rise strain, and maximum rise ratio)
The strain at the beginning of the rising of the styrene copolymer used in the present embodiment is preferably 0.2 to 1.3, more preferably 0.3 to 1.1, and still more preferably 0.4 to 1. 0. In the specification of the present application, “rising at the beginning of rising” is a strain that causes strain hardening, and is an index of moldability. The smaller the strain at the beginning of the rise, in other words, the faster the rise, the strain hardening occurs from the time of low stretching, and the moldability is excellent, so the thickness of the secondary molded product may become more uniform, and the secondary molded product Can be thinned.

  The maximum rising ratio of the styrene copolymer used in 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. is there. In the present specification, “maximum rising ratio” means (extension viscosity in the nonlinear region of the maximum rising strain / extension viscosity in the linear region of the maximum rising strain), and “maximum rising strain” means that the elongation viscosity is the maximum. This means Henkey distortion. The maximum rise ratio is an index representing the degree of strain hardening at the maximum rise strain. The greater the maximum rise ratio, the greater the degree of strain hardening and the better the moldability. When the maximum rise ratio is 1.2 or more, the elongational viscosity increases when the strain is high, that is, when the resin is thinly stretched during molding, so that the thickness of the molded product becomes uniform and is broken during molding. There is a tendency to become difficult. A maximum rise ratio of 5.0 or less is preferable from the viewpoint of a balance between productivity and moldability because the elongational viscosity during molding does not become too high.

(Additives, etc.)
The styrene copolymer used in the present embodiment includes a rubber-reinforced aromatic vinyl resin such as HI-PS resin and MBS resin and an aromatic vinyl heat such as SBS as a component containing rubber if necessary. About 1% to 50% of a plastic elastomer may be contained. Further, in order to suppress thermal decomposition of the polymer in the step of recovering the unreacted monomer, for example, 2- [1- (2-hydroxy-3,5-di-t-phenylpentyl) ethyl] -4,6-di Processing stabilizers such as -t-phenylpentyl acrylate may be included. Further, higher fatty acids such as stearic acid, zinc stearate, calcium stearate, magnesium stearate and salts thereof, lubricants such as ethylene bisstearylamide, plasticizers such as liquid paraffin, and antioxidants may be contained. In addition, additives commonly used in the field of styrenic resins, for example, nucleating agents, flame retardants, colorants, etc. may be combined with styrene-based copolymers in a range that does not impair the purpose of this embodiment. Although it does not specifically limit as an additive, For example, colorants, such as nucleating agents, such as a talc, flame retardants, such as hexabromocyclododecane, titanium oxide, and carbon black. Further, styrene-based resin may be used as a pellet, and ethylene bisstearylamide, zinc stearate, magnesium stearate, or the like may be used as an external lubricant for the pellet.

  Antioxidants generally stabilize peroxide radicals such as hydroperoxy radicals generated during thermoforming or exposure to light, or decompose peroxides such as hydroperoxides generated. It is a possible ingredient. Although it does not specifically limit as antioxidant, For example, a hindered phenolic antioxidant and a peroxide decomposer are mentioned. The hindered phenol-based antioxidant can be used as a radical chain inhibitor, and the peroxide decomposer can decompose the peroxide generated in the system into more stable alcohols to prevent auto-oxidation. Examples of the hindered phenol antioxidant include, but are not limited to, 2,6-di-tert-butyl-4-methylphenol, styrenated phenol, n-octadecyl-3- (3,5-di- t-butyl-4-hydroxyphenyl) propionate, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2-t-butyl-6- (3-t-butyl-2-hydroxy-5- Methylbenzyl) -4-methylphenyl acrylate, 2- [1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6-di-t-pentylphenyl acrylate, 4,4 ′ -Butylidenebis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (3-methyl-6-tert-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 the peroxide decomposer include, but are not limited to, organic phosphorus peroxide decomposition such as trisnonylphenyl phosphite, triphenyl phosphite, and tris (2,4-di-t-butylphenyl) phosphite. As well as dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, pentaerythrityltetrakis (3-laurylthiopro Pionate), ditridecyl-3,3′-thiodipropionate, and organic sulfur peroxide decomposers such as 2-mercaptobenzimidazole. The addition amount of the antioxidant is preferably 0.01 parts by mass or more and 1 part by mass or less, and more preferably 0.1 parts by mass or more and 0.5 parts by mass with respect to 100 parts by mass of the styrene copolymer in the extruded foam sheet. It is below mass parts.

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

  Examples of brominated bisphenol-based 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-dibromoprol ether), tetrabromobisphenol S-bis (2,3-dibromo-2methylpropyl ether), tetrabromobisphenol F, tetrabromobisphenol F-bis (2,3-dibromopropyl ether), tetrabromobisphenol F-bis (2,3-dibromo-2methylpropyl ether) tetrabromobisphenol A-bis (allyl ether) , Tetrabromobisphenol A polycarbonate oligomer, and an epoxy group adduct of tetrabromobisphenol A oligomers and the like. Among brominated bisphenol-based flame retardants, in particular, tetrabromobisphenol A bis (2,3-dibromopropyl ether) and tetrabromobisphenol A-bis (2,3-dibromopropyl ether) are polystyrene. It is preferable because it is difficult to be decomposed during kneading with a resin and has a high flame-retardant effect and tends to be manifested. When tetrabromobisphenol A-bis (2,3-dibromopropyl ether) and tetrabromobisphenol A-bis (2,3-dibromo-2methylpropyl ether) are used in combination, flame retardancy and thermal stability are improved. It is more preferable because it tends to be excellent.

  The brominated flame retardant is preferably used in combination with a brominated isocyanurate-based flame retardant as a flame retardant aid. Examples of 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). ) Isocyanurate, mono (2,3,4-tribromobutyl) isocyanurate, di (2,3,4-tribromobutyl) isocyanurate, tris (2,3,4-tribromobutyl) isocyanurate, etc. Is mentioned. Among brominated isocyanurates, tris (2,3-dibromopropyl) isocyanurate is particularly preferable because it exhibits a very high flame retardant effect.

<Method for producing styrene-based copolymer>
(Polymerization process)
Examples of the polymerization method of the styrene copolymer used in the present embodiment include known styrene polymerization methods such as a bulk polymerization method, a solution polymerization method, and a suspension polymerization method. These polymerization methods may be batch polymerization methods or continuous polymerization methods, and are preferably continuous polymerization methods from the viewpoint of productivity. Examples of the continuous bulk polymerization method include, for example, a raw material solution containing monomers by adding and mixing a monovinyl compound, a conjugated divinyl compound having a conjugated vinyl group, and a solvent, a polymerization catalyst, and a chain transfer agent as necessary. To prepare. In a facility equipped with one or more reactors arranged in series and / or in parallel and a devolatilizer for a devolatilization step for removing volatile components such as unreacted monomers, the raw material solution is added. Examples of the method include continuous feeding and stepwise polymerization.

  Examples of the reactor include a complete mixing type reactor, a laminar flow type reactor, and a loop type reactor in which a part of the polymerization liquid is withdrawn while the polymerization proceeds. There is no restriction | limiting in particular in the order of the arrangement | sequence of these reactors.

  When polymerizing the styrenic copolymer used in the present embodiment, from the viewpoint of controlling the polymerization reaction, a polymerization initiator such as a polymerization solvent or an organic peroxide and a chain transfer agent may be used as necessary. Can do. The polymerization solvent is generally used for adjusting the polymerization rate, molecular weight and the like in continuous bulk polymerization and 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 molecular weight, and the like. It is preferably 3 to 20% by mass.

  When the polymerization raw material is polymerized in order to obtain the styrene copolymer used in the present embodiment, a polymerization initiator and a chain transfer agent can be contained in the polymerization raw material composition. The polymerization initiator is not particularly limited, but organic peroxides such as 2,2-bis (t-butylperoxy) butane, 1,1-bis (t-butylperoxy) cyclohexane, and n-butyl- Peroxyketals such as 4,4-bis (t-butylperoxy) valerate, dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, and dicumyl peroxide, acetyl peroxide, and isobutyryl peroxide Diacyl peroxides, peroxydicarbonates such as diisopropylperoxydicarbonate, peroxyesters such as t-butylperoxyacetate, ketone peroxides such as acetylacetone peroxide, and hydroperoxides such as t-butylhydroperoxide Mention may be made of the earth and the like. The polymerization initiator is preferably used in an amount of 0.005 to 0.08 mass% with respect to the styrene monomer. 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 styrene monomer.

  In this embodiment, it is preferable to add the phenol-based thermal deterioration inhibitor in the polymerization step or the devolatilization step, and after the polymerization step and before the devolatilization step. It is more preferable to add a phenol-based thermal deterioration inhibitor after the polymerization step, preferably immediately after the polymerization step and before the devolatilization step.

  Examples of the phenol-based thermal degradation inhibitor include 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate (trade names: Sumilizer GM, Sumitomo Chemical). 2- [1- (2-hydroxy-3,5-di-t-phenylpentyl) ethyl] -4,6-di-t-phenylpentyl acrylate (trade name: Sumilizer GS, manufactured by Sumitomo Chemical Co., Ltd.) ). The addition amount is 0.01 to 0.5% by mass, preferably 0.02 to 0.3% by mass, more preferably 0.03 to 0.2% by mass with respect to the styrene copolymer at the outlet of the final reactor. %.

  The production | generation of the monovinyl compound in a devolatilization process, its dimer, and a trimer can be more effectively suppressed as the addition amount of a phenol type thermal deterioration inhibitor is 0.01 mass% or more. On the other hand, even if the addition amount of the phenol-based thermal deterioration inhibitor is more than 0.5% by mass, the effect of suppressing the formation of the monovinyl compound and its dimer or trimer may not be sufficiently obtained. is there.

(Devolatilization process)
As the devolatilization device, for example, a normal devolatilization device such as a flash drum, a biaxial devolatilizer, a thin film evaporator, an extruder, etc. can be used. A volatile extruder is used. Examples of the arrangement of the devolatilizer include, for example, one using a vacuum devolatilization tank with a heater, one connected in series with two vacuum devolatilization tanks with a heater, and vacuum devolatilization with a heater. The thing etc. which connected the volatilization tank and the devolatilization extruder in series are mentioned. In order to reduce volatile components as much as possible, a vacuum devolatilization tank with a heater connected in two stages in series or a vacuum devolatilization tank with a heater and a devolatilization extruder connected in series is preferable. .

  The conditions for the devolatilization step are not particularly limited. For example, when the polymerization of the styrene copolymer is performed by bulk polymerization, the unreacted monovinyl compound is preferably 50% by mass in the styrene copolymer. In the following, the polymerization can be continued until more preferably 40% by mass or less. By devolatilization treatment, volatile components such as unreacted substances (monovinyl compounds) and / or solvents can be removed.

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

<Method for producing extruded foam sheet>
Examples of the method for producing an extruded foam sheet of the present embodiment include a method of melt-kneading and extruding the above-described styrenic copolymer together with other compounds, if necessary, using an extruder. A method is mentioned. First, the styrenic copolymer is melt-kneaded with an extruder connected to a circular die, and the melt-kneaded product is extruded in a foamed state through an annular opening provided in front of the circular die. Form a foam. Next, the foam is cooled while being stretched in the circumferential direction by being brought into sliding contact with the outer peripheral surface of the cooling mandrel having a diameter larger than the opening of the circular die, and is continuously cut and expanded along the extrusion direction. A commonly known method can be used.

As the foaming agent and foam nucleating agent at the time of extrusion foaming, commonly used substances can be used. Although it does not specifically limit as a foaming agent, For example, a butane, pentane, Freon, water, etc. are mentioned, A butane is suitable. Although it does not specifically limit as a foam nucleating agent, For example, a talc etc. can be used. The thickness of the extruded foam sheet of this embodiment is 0.5 mm to 5.0 mm, and the apparent density is preferably 50 g / L to 300 g / L. The basis weight of the extruded foam sheet of the present embodiment is preferably ^{80g / m 2 ~300g / m 2} . Extruded foam sheet of the present embodiment has a thickness of 0.5 mm to 5.0 mm, an apparent density of 50 g / to 300 g / L, it is preferable that a basis weight of ^{80g / m 2 ~300g / m 2} . A film may be laminated on the extruded foam sheet. As a kind of film, what is used for general polystyrene may be used.

<Molded product>
The molded product in the present embodiment is a secondary molded product manufactured using the extruded foam sheet of the present embodiment. The extruded foam sheet of the present embodiment is subjected to secondary molding by a conventionally known method such as vacuum molding, pressure molding, vacuum pressure molding, double-side vacuum molding, press molding, etc., so that a tray, a cup, a straw container, a natto container Or the like can be formed. As an example of the secondary molded product of the present embodiment, the extruded foam sheet of the present embodiment described above is used as a molding material, and the horizontal direction is the extrusion direction by a vacuum molding machine or the like. Examples include food tray containers having a depth of 5 to 36 cm and a depth of 1.1 to 3.4 cm, and food soups and bowls having a length of 3.5 to 20 cm, a width of 3.5 to 20 cm, and a depth of 2.0 to 20 cm. . Although the temperature conditions of vacuum forming are not limited to the following, the conditions of 120-150 degreeC are preferable normally.

  Hereinafter, although an embodiment of the present invention is described concretely with an example and a comparative example, the present invention is not limited to these examples.

<Measurement and evaluation method>
The measurement and evaluation method was performed based on the following method.

(1) Measurement of molecular weight Number average molecular weight (Mn) of conjugated divinyl compound, weight average molecular weight (Mw) of styrene copolymer, Z average molecular weight (Mz), ratio of molecular weight of 1 million or more, and molecular weight of 2 million or more The ratio and the number average molecular weight (Mn) of the conjugated divinyl compound were measured using gel permeation chromatography (GPC). Measurement was performed under the following conditions.
Device: Tosoh HLC-8220
Separation column: Two TOSOH TSK gel Super HZM-H (inner diameter 4.6 mm) connected in series Guard column: TSK guard column Super HZ-H manufactured by Tosoh
Measuring solvent: Tetrahydrofuran (THF)
Sample concentration: 5 mg of a measurement sample was dissolved in 10 mL of solvent and filtered with a 0.45 μm filter.
Injection volume: 10 μl
Measurement temperature: 40 ° C
Flow rate: 0.35 mL / min Detector: UV absorption detector (UV-8020, wavelength 254 nm)
To create a calibration curve, 11 types of TSK standard polystyrenes 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). A calibration curve was prepared using an approximate expression of a linear straight line.

(2) Measurement of melt mass flow rate (MFR) The melt mass flow rate of the styrene copolymer was measured under load conditions of 200 ° C. and 49 N in accordance with ISO 1133.

(3) Gel-like substance evaluation of solid sheet Using a 30 mmφ sheet extruder (manufactured by Soken Co., Ltd.), the styrene copolymer was extruded to prepare a sheet (solid sheet) having a thickness of 0.5 mm. Twenty test pieces were cut out to a size of 100 mm length × 100 mm width from the obtained sheet, and a gel-like substance having an average of a short diameter and a long diameter of 2 mm or more was visually measured. In the determination, the number of test pieces that contained the gel-like substance was “0” for 0-2 pieces, “◯” for 3-10 pieces, and “x” for 11 pieces or more.

(4) Measurement of initial rising strain, maximum rising strain, and maximum rising ratio The initial starting strain, maximum rising strain, and maximum rising ratio of the styrene-based copolymer were measured based on the following viscoelasticity measurements.
Device name: Viscoelasticity measuring device ARES-G2 (TA Instruments)
Measurement system: ARES-EVF option Test piece dimensions: Length 20mm, thickness 0.7mm, width 10mm
Elongation strain rate: 0.01 / second Temperature: 150 ° C
Measurement atmosphere: in nitrogen stream Preheating time: 2 minutes Pre-extension strain rate: 0.03 / second,
Pre-extension length: 0.295mm
Relaxation time after pre-extension: 2 minutes For the viscoelasticity measurement, the test piece was attached to a roller, and after the temperature was stabilized, the sample was left standing for the pre-heating time and pre-heated. After preheating was completed, pre-extension was performed under the above conditions. After pre-extension, it was allowed to stand for 2 minutes, and the stress produced by the pre-extension was relaxed and measured.

The maximum rising strain is the Henkey strain at which the extensional viscosity becomes maximum in the above viscoelasticity measurement.
In addition, the strain at the beginning of the rise was calculated by the following method. Based on the results obtained in the above viscoelasticity measurement, a logarithmic graph with common use is plotted with the Henkey strain plotted on the horizontal axis and the extensional viscosity plotted on the vertical axis. A power approximation curve was created as a region (for example, a broken line in FIG. 1). When strain hardening occurs, the actual extensional viscosity becomes higher than the extensional viscosity of the approximate straight line extrapolating this linear region. When the difference between the extensional viscosity in the non-linear region and the extensional viscosity in the linear region becomes 3% of the extensional viscosity in the non-linear region at the same Henkey strain, the Henkey strain starts to rise and is defined as the strain. The maximum rise ratio was calculated by (extension viscosity in the nonlinear region at the maximum rise strain / extension viscosity in the linear region at the maximum rise strain).

(5) Foam density Based on ISO10350, the foam density of the extruded foam sheet was measured. A hydrometer (SGM-220-60 measuring instrument) manufactured by Shimadzu Corporation was used as a measuring device.

(6) Foaming ratio The foaming ratio was calculated from the following formula using the foam density value (ρf) obtained in (5) above and the density (ρ) of the styrene copolymer.
Foaming ratio = ρ / ρf
(7) Deep drawability of extruded foam sheet For 100 parts by mass of styrene copolymer, 0.15 parts by mass of talc (average particle size 1.3 μm) as a foam nucleating agent and 4 liquefied butanes as a foaming agent A styrene resin composition was obtained by adding parts by mass. The styrene resin composition was extruded and foam-molded using an extrusion foaming machine equipped with a circular die having a diameter of 150 mm. The temperature of the resin melting zone of the extrusion foaming machine was adjusted to 200 to 230 ° C, the rotary cooler temperature was adjusted to 130 to 170 ° C, and the die temperature was adjusted to 145 ° 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 an extruded foam sheet having a sheet thickness of 1.4 mm and a width of 1000 mm.
The extruded foam sheet was allowed to stand for 20 days at 23 ± 3 ° C. and 50 ± 5% relative humidity. Thereafter, using a sheet container molding machine manufactured by Souken, the foamed sheet was sandwiched between the fixed frames of the sheet molding machine, the heater was set at an average temperature of 200 ° C., the ambient temperature was set at 130 ° C., and heated for 15 seconds. Next, the fixed frame was slid into a cup-shaped mold (temperature: 40 ° C.) having a diameter of 10 cm and a depth of 6 cm to perform vacuum forming, and 100 compacts were formed. It was visually confirmed whether or not tearing had occurred on the side surface of this molded body, and the number of molded bodies that could be molded without tearing was used as an index of deep drawability.

<Production example of conjugated divinyl compound>
The conjugated divinyl compounds 1, 5, and 6 were produced based on the following method.

(Conjugated divinyl compound 1)
In a reaction vessel having a capacity of 5 L equipped with a stirrer, a thermometer and a reflux condenser, 2742 g of polybutadiene alcohol at both ends (Mn: 1900), 379 g of methyl acrylate, 380 g of n-hexane, 0.8194 g of hydroquinone monomethyl ether, and 0.5533 g of 4-hydroxy-2,2,6,6-tetramethylpiperidine-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 moisture contained in this mixture was measured by the Karl Fischer method, and it was confirmed that the water content was 200 ppm or less. Thereafter, 1.36885 g of tetra-n-butyl titanate was added to the above mixture as a transesterification catalyst, and the resulting methanol was stirred out while distilling out of the reaction system under reflux of n-hexane, an azeotropic solvent. And reacted at a reaction temperature of 80 to 85 ° C. for 10 hours.

Next, the temperature in the reaction vessel is adjusted to 75 to 80 ° C., and concentrated at a reduced pressure of 70 to 2 kPa until 95% or more of the used methyl acrylate and n-hexane are distilled off. n-Hexane was recovered. To 2070 g of the obtained polybutadiene both-end diacrylate, 2000 g of toluene, 200 g of acetone, 20 g of ion-exchanged water, and hydrotalcite (composition formula Mg ₆ Al ₂ (OH) 16 CO ₃ .4H ₂ O) [Kyowa Chemical Co., Ltd.] Industrial Co., Ltd., trade name: KYOWARD 500PL] 20 g was added and treated at 75-80 ° C. for 2 hours. Next, by adjusting the temperature in the reaction vessel to 75 to 80 ° C. and concentrating at a reduced pressure of 90 to 35 kPa, 400 g of a mixed distillate of toluene, acetone and water is recovered, and the resulting concentrated solution is air. The catalyst and the adsorbent were separated by filtration under pressure, and the solvent was degassed at a temperature of 60 to 80 ° C. and a degree of vacuum of 30 to 0.8 kPa to obtain a conjugated divinyl compound 1.

  It was 99.3% when the conversion rate of the polybutadiene both terminal diacrylate of the conjugated divinyl compound 1 was measured by high performance liquid chromatography (HPLC). The number average molecular weight (Mn) in terms of polystyrene measured by GPC was 1900.

<Conjugated divinyl compound 5>
The conjugated divinyl compound 5 produced under the same conditions except that the molecular weight of the polybutadiene both-end alcohol was changed to Mn: 25000 had a conversion rate of polybutadiene both-end diacrylate of 99.5%. The number average molecular weight (Mn) in terms of polystyrene measured by GPC was 26000.

(Conjugated divinyl compound 6)
The conjugated divinyl compound 6 produced under the same conditions except that the molecular weight of the polybutadiene both-end alcohol was changed to Mn: 57000 had a conversion rate of polybutadiene both-end diacrylate of 99.2%. The number average molecular weight (Mn) in terms of polystyrene measured by GPC was 58,000.

<Examples of styrene copolymer and extruded foam sheet>
Example 1
80 parts by mass of styrene monomer, 20 parts by mass of ethylbenzene, 0.035 parts by mass of conjugated divinyl compound 1 (polybutadiene terminal acrylate Mn: 1900) (2.4 × 10 ⁻⁵ mol per 1 mol of styrene), polymerization started As an agent 1, 0.030 parts by mass of 2,2-bis (4,4-di-tertiary-butylperoxycyclohexyl) propane [manufactured by NOF Corporation: Pertetra A] was added to prepare a raw material solution. The prepared raw material solution was continuously supplied at 1.00 L / hour to a fully mixed first reactor having an internal volume of 6 L maintained at a temperature of 105 ° C. Subsequently, the polymerization solution from the first reactor was supplied to a plug flow type second reactor having an internal volume of 3 L. In the second reactor, the temperatures of the three zones were maintained at 119 ° C., 133 ° C., and 143 ° C., respectively, in the order in which the raw material solutions passed. In the second zone, 0.03 parts by mass of 1,1-di- (tertiary-butylperoxy) cyclohexane [manufactured by NOF Corporation: Perhexa C] was added as the polymerization initiator 2. Next, the polymerization solution from the second reactor was supplied to a vacuum degassing tank heated to a temperature of 240 ° C., volatile components such as unreacted monomers and solvents were removed, and after continuous operation for 72 hours, A styrene copolymer was obtained.

The production conditions and analysis results of the styrene copolymer are shown in Table 1. Conjugated divinyl compound 1 was synthesized by the method described in the production examples. The number average molecular weight (Mn) is a polystyrene equivalent value measured by GPC. The number of moles of the conjugated divinyl compound relative to 1 mole of styrene (monovinyl compound) is a value measured using ¹ H-NMR and ¹³ C-NMR. As a measuring device, JEOL-ECA500 manufactured by JEOL Ltd. was used. Chloroform-d1 was used as a solvent, and the tetramethylsilane resonance line was used as an internal standard.

  Examples 2 to 14 and 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 Tables 1 and 2, and the styrene copolymer Mw, Mz / Mw, molecular weight 100 The ratio of 10,000 or more, the ratio of molecular weight of 2 million or more, the strain at the beginning of rising, and the maximum rising ratio were controlled as shown in Tables 1 and 2.

In addition, the following were used for each conjugated divinyl compound, a polymerization initiator, and a thermal deterioration inhibitor listed in the table. In addition, the conjugated divinyl compounds 2 to 9, 11, and 12 have a conjugated vinyl group at both ends of the molecule.
Conjugated divinyl compound 2: polybutadiene diacrylate [manufactured by Sakai Kogyo Co., Ltd .: CN307] Mn: 3800
Conjugated divinyl compound 3: Polybutadiene-terminated acrylate [Osaka Organic Chemical Industry: BAC-45] Mn: 4800
Conjugated divinyl compound 4: urethane acrylate oligomer [manufactured by Sakai Kogyo Co., Ltd .: CN9014NS] Mn: 8000
Conjugated divinyl compound 7: Aromatic urethane acrylate [Sakai Kogyo Co., Ltd .: CN9782] Mn: 5200
Conjugated divinyl compound 8: Reaction product of (2,2 ′, 3,3 ′, 5,5′-hexamethylbiphenyl-4,4′-diol · 2,6-dimethylphenol polycondensate) and chloromethylstyrene [Mitsubishi Gas Chemical Co., Ltd .: OPE-2ST] Mn: 1200
Conjugated divinyl compound 9: 1,3-butylenediol dimethacrylate [manufactured by Wako Pure Chemical Industries, Ltd.] Mn: 226
Conjugated divinyl compound 10: NK ester A-GLY-20E [manufactured by Shin-Nakamura Chemical Co., Ltd.] Mn: 1295, the average number of conjugated vinyls in one molecule of conjugated divinyl compound 10 is 3.
Conjugated divinyl compound 11: Divinylbenzene [Wako Pure Chemical Industries, Ltd.] Mn: 130
Conjugated divinyl compound 12: Polyethylene glycol dimethacrylate [manufactured by Sigma-Aldrich] Mn: 750
Polymerization initiator 2: 1,1-di- (tertiary-butylperoxy) cyclohexane [manufactured by NOF Corporation: Perhexa C]
Thermal degradation inhibitor 1: 2- [1- (2-hydroxy-3,5-di-t-phenylpentyl) ethyl] -4,6-di-t-phenylpentyl acrylate [Sumitomo Chemical Co., Ltd .: Sumilyzer GS ]
Thermal degradation inhibitor 2: Octadecyl-3- (3,5-jetterybutyl-4-hydroxyphenyl) -propionate [Ciba Specialty Chemicals, Inc .: IRGANOX1076]

  Tables 1 and 2 summarize the measurement and evaluation results of Examples 2 to 14 and Comparative Examples 1 to 6. In addition, as for the styrene-type copolymer of Example 4, as shown in FIG. 1, it turns out that the strain hardening was expressed in the measurement of ARES-EVF.

As is clear from Tables 1 and 2 and FIG. 2, in Comparative Example 1 where the number of moles of the conjugated divinyl compound relative to 1 mole of the monovinyl compound is as small as 1.7 × 10 ⁻⁶ mole, in the measurement of viscoelasticity by ARES-EVF Strain hardening did not appear. Therefore, although the expansion ratio of the extruded foam sheet of Comparative Example 1 was relatively high, the deep drawability was low. In Comparative Example 2 where the number of moles of the conjugated divinyl compound relative to 1 mole of the monovinyl compound was 4.1 × 10 ⁻⁴ mole, stable data could not be obtained in the measurement of viscoelasticity by ARES-EVF. In addition, a large amount of THF-insoluble matter could not be measured during the GPC measurement. Furthermore, the melt mass flow rate (MFR) was small, and there were many gel-like substances of a sheet | seat. For these reasons, an extruded foam sheet of the styrene copolymer of Comparative Example 2 could not be prepared. In Comparative Examples 3 and 6 in which the number average molecular weight Mn of the conjugated divinyl compound was as small as 226 and 750, the strain at the beginning of the rise was large and the maximum rise ratio was small. Therefore, in the comparative examples 3 and 6, the deep drawability was considerably low. In Comparative Example 4, in which the ratio of the molecular weight of 2 million or more was increased to 6.39%, the strain started to rise and the gel substance was also large. For these reasons, an extruded foam sheet could not be prepared for the styrene copolymer of Comparative Example 4. In Comparative Example 5, in which the number average molecular weight Mn of the conjugated divinyl compound was as small as 130, the MFR was small and the sheet had many gel-like substances. Therefore, the deep-drawn formability of the extruded foam sheet of Comparative Example 5 was considerably low.

On the other hand, a styrene copolymer of a conjugated divinyl compound having a number average molecular weight (Mn) of 850 to 100,000 and at least one monovinyl compound containing at least a styrene compound, the ratio of the conjugated divinyl compound Is 2.0 × 10 ^{−6 to} 4.0 × 10 ⁻⁴ mol per mole of the monovinyl compound, and the styrenic copolymer has a weight average molecular weight (Mw) of 200,000 to 500,000, The ratio of the Z average molecular weight (Mz) to Mw is 1.8 to 5.0, the ratio of the molecular weight of 1 million or more is 4.0% to 20.0%, and the ratio of the molecular weight of 2 million or more is 0.00. The styrenic copolymers of Examples 1 to 14 that are 3% to 6.0% have less sheet-like gel material than the styrenic copolymers of Comparative Examples 1 to 6, and are further apparent from FIG. As in Example 1 It can be seen that the extruded foam sheets of ˜14 have a higher value of deep drawability than the extruded foam sheets of Comparative Examples 1-6 regardless of the foaming ratio.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this, In the range which does not deviate from the meaning of invention, it can change suitably.

  The extruded foam sheet of the present embodiment is easily subjected to molecular orientation during stretching of the foamed cell, and the strain hardening property works. Therefore, the secondary molded product of the deep-drawn container is excellent in the secondary moldability and has a high foaming ratio. Can be produced in Therefore, since a secondary molded product, for example, a foamed container can be obtained with a small amount of material, it can contribute to cost reduction of the product.

Claims (9)

An extruded foam sheet having a thickness of 0.5 mm to 5.0 mm containing a styrene copolymer,
The styrene copolymer is a copolymer of a conjugated divinyl compound having a number average molecular weight (Mn) of 850 to 100,000 and at least one monovinyl compound containing at least a styrene compound, and contains the conjugated divinyl compound. The amount is 2.0 × 10 ^{−6 to} 4.0 × 10 ⁻⁴ mol per mole of the monovinyl compound, and the weight average molecular weight (Mw) of the styrene copolymer is 200,000 to 500,000, An extruded foam sheet having a molecular weight of 2 million or more in a range of 0.3% to 6.0%.   The extruded foam sheet according to claim 1, wherein the conjugated divinyl compound has a number average molecular weight (Mn) of 1000 to 30000.   The extruded foam sheet according to claim 1 or 2, wherein the conjugated divinyl compound is a chain.   The extruded foam sheet according to any one of claims 1 to 3, wherein at least one of the conjugated vinyl groups of the conjugated divinyl compound is located at a terminal of the conjugated divinyl compound.   The extruded foam sheet according to any one of claims 1 to 4, wherein a ratio of a Z average molecular weight (Mz) to Mw of the styrene copolymer is 1.8 to 5.0.   The extruded foam sheet according to any one of claims 1 to 5, wherein a ratio of the styrene-based copolymer having a molecular weight of 1,000,000 or more is from 4.0% to 20.0%.   The extrusion foaming according to any one of claims 1 to 6, wherein the styrene-based copolymer has an initial rising strain of 0.2 to 1.3 and a maximum rising ratio of 1.2 to 5.0. Sheet.   The extruded foam sheet according to any one of claims 1 to 7, wherein the conjugated divinyl compound is (hydrogenated) polybutadiene-terminated di (meth) acrylate.   The secondary molded product of the extrusion foaming sheet as described in any one of Claims 1-8.

Images