JP2016180038A - Expandable composite resin particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide expandable composite resin particles capable of producing an expandable composite resin molded article that has excellent retention of a forming agent and expandability, mechanical properties such as rigidity, fire resistance, and a high fusion rate of foaming particles.SOLUTION: Expandable composite resin particles 1 contain a composite resin 2 containing an ethylene-based resin and a styrene-based resin, a physical foaming agent, and a bromine-based flame retardant. The composite resin 2 is produced by impregnation polymerization of a styrene-based monomer of 400-1,900 pts.mass with respect to the ethylene-based resin of 100 pts.mass. The ethylene-based resin is composed of an ethylene-vinyl acetate copolymer and/or a mixture of polyvinyl acetate and linear low-density polyethylene, and is mainly composed of the linear low-density polyethylene. The composite resin 2 has a content of 0.2-5 mass% of a vinyl acetate component derived from the ethylene-vinyl acetate copolymer and/or the polyvinyl acetate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to expandable composite resin particles containing a flame retardant.

  Expanded particle molded bodies are used in a wide range of applications such as packaging materials, building materials, and vehicle members, taking advantage of their excellent buffering properties, lightweight properties, vibration proofing properties, soundproofing properties, heat insulation properties, and the like. The foamed particle molded body is generally manufactured using foamable resin particles. Specifically, first, resin particles are impregnated with an organic physical foaming agent such as propane, butane, and pentane to produce expandable resin particles. Next, the foamed resin particles are obtained by foaming the expandable resin particles by heating or the like, and then the foamed particles are fused to each other in a mold to obtain a foamed particle molded body. As the resin component constituting the foamed particle molded body, styrene resins such as polystyrene and olefin resins such as polypropylene and polyethylene are mainly used, but in recent years, composite resins of polyolefin resins and styrene resins (hereinafter simply referred to as “resin components”). "Composite resin") is attracting attention.

  The foamed particle molded body containing the composite resin (hereinafter appropriately referred to as “foamed composite resin molded body”) is, for example, a foamed particle molded body containing styrene-based resin (hereinafter appropriately referred to as “foamed PS resin molded body”). Compared to, it is excellent in resilience, oil resistance, etc., so it is used as a packaging material for precision parts and heavy products. In addition, since the foamed composite resin molded article has sufficient rigidity and cushioning properties, it is widely used as automobile members such as bumpers and floor spacers. However, the foamed composite resin molded body has a drawback that it is easy to burn.

Therefore, a technique for imparting flame retardancy to the foamed composite resin molded body has been developed. Specifically, for example, when the expansion ratio of the styrene-modified ethylene resin foam molded article is Y times and the amount of the combustible foaming agent remaining in the molded article is X wt%, X ² × Y ≦ 5 A technique for maintaining the remaining amount of foaming agent and the expansion ratio in a specific relationship has been proposed (see Patent Document 1).
In addition, a method has been proposed in which expanded particles using a styrene-modified olefin-based resin as a base resin, using tetrabromocyclooctane or tris (2,3-dibromopropyl) isocyanurate as a flame retardant (Patent Literature). 2-4).

Japanese Patent No. 2806512 Japanese Patent No. 3093551 Japanese Patent No. 3093552 JP 2006-257150 A

  The foamed composite resin molded body has excellent rigidity and can be reduced in weight compared to the foamed olefin resin molded body, but further weight reduction is desired due to the recent increase in awareness of environmental problems. Although it is possible to improve the rigidity of the foamed composite resin molded article by increasing the ratio of the styrene resin in the composite resin, in this case, the flame retardancy of the foamed composite resin molded article is lowered. On the other hand, if the expansion ratio is increased for weight reduction, the flame retardancy of the foamed composite resin molded product is lowered. A method to improve the flame retardancy by increasing the blending amount of the flame retardant can be considered, but excessive increase of the flame retardant may reduce the fusion rate between the foam particles in the foam composite resin molded product, There is a possibility that the rigidity and resilience of the resin molded body may be lowered.

  The present invention has been made in view of such a background, and is excellent in retention and foamability of the foaming agent, and also excellent in mechanical properties such as rigidity, but excellent in flame retardancy, and between the expanded particles. An object of the present invention is to provide expandable composite resin particles capable of obtaining a foamed composite resin molded body having a high fusion rate.

One aspect of the present invention is an expandable composite resin particle containing a composite resin of an ethylene-based resin and a styrene-based resin, a physical foaming agent, and a brominated flame retardant,
The composite resin is formed by impregnating and polymerizing 400 to 1900 parts by mass of a styrene monomer with respect to 100 parts by mass of the ethylene resin.
The ethylene-based resin is composed of an ethylene-vinyl acetate copolymer and / or a mixture of polyvinyl acetate and linear low density polyethylene, and the linear low density polyethylene as a main component,
The foamable composite resin particle is characterized in that the content of the vinyl acetate component derived from the ethylene-vinyl acetate copolymer and / or polyvinyl acetate in the composite resin is 0.2 to 5% by mass. .

  The foamable composite resin particles use a composite resin containing the ethylene resin having the predetermined composition and the styrene resin as a base resin, and the vinyl resin component is contained in the composite resin at the predetermined ratio. The foamable composite resin particles contain a brominated flame retardant. Therefore, the foamable composite resin particles have a high blending ratio of the styrene monomer to the ethylene resin as described above, and even if the ratio of the styrene resin in the composite resin is high, compared with the foamable composite resin particles that have been produced conventionally. Thus, expanded particles exhibiting excellent flame retardancy can be obtained. Furthermore, since the expanded particles obtained from the expandable composite resin particles can exhibit high flame retardancy even when the expansion ratio is increased, it is possible to produce a lightweight and excellent expanded composite resin molded body. It becomes possible. Furthermore, the foamable composite resin particles exhibit excellent foamability, and the obtained foamed particles are also excellent in fusion property, so that it is possible to produce a foamed composite resin molded product having a high fusion rate between the foamed particles. It becomes possible.

  The composite resin is formed by impregnating and polymerizing 400 to 1900 parts by mass of a styrene monomer with respect to 100 parts by mass of the ethylene resin, and the expandable composite resin particles have a high ratio of the styrene resin. Therefore, by using the expandable composite resin particles, it is possible to obtain a foamed composite resin molded body having high rigidity. Furthermore, the expandable composite resin particles are excellent in retention of the foaming agent. Therefore, the expandable composite resin particles enable simplification of the storage temperature condition and extension of the storage period in a state of being put in a sealed container. As a result, it can be stored for a long period of time at room temperature, for example, while maintaining sufficient foaming power in a sealed container. Therefore, the foamable composite resin particles need not be foamed within a short time after the production of the expandable composite resin particles, and can be transported and stored in a state where the foamable composite resin particles are not bulky. And the said foamable composite resin particle can show the outstanding foamability.

The figure which shows the transmission electron microscope photograph in the center part cross section of the expandable composite resin particle in Example 1. FIG. The figure which shows the transmission electron micrograph in the center part cross section of the expandable composite resin particle in Example 10. FIG. The figure which shows the transmission electron micrograph in the center part cross section of the expandable composite resin particle in Example 12. FIG. The figure which shows the transmission electron micrograph in the center part cross section of the expandable composite resin particle in the comparative example 3. FIG.

Next, a preferred embodiment of the expandable resin particle will be described.
The foamable composite resin particles are foamed to produce composite resin foamed particles (also simply referred to as “foamed particles”), and further, these foamed particles are molded in-mold to obtain a foamed composite resin molded body. Can be used to manufacture.

  The foamable composite resin particles contain a composite resin of an ethylene resin and a styrene resin, and the composite resin is obtained by impregnating and polymerizing 400 to 1900 parts by mass of a styrene monomer with respect to 100 parts by mass of the ethylene resin. Become. When the styrene monomer is less than 400 parts by mass, the characteristics of the styrene resin in the composite resin may be impaired, and the rigidity of the foamed composite resin molded body obtained using the foamable composite resin particles may be reduced. is there. On the other hand, when the styrene monomer exceeds 1900 parts by mass, the characteristics of the ethylene resin in the composite resin are impaired, and the toughness and restorability of the foamed composite resin molded body obtained using the foamable composite resin particles are reduced. Etc. may be reduced. From the same viewpoint, the amount of the styrene monomer relative to 100 parts by mass of the ethylene resin is preferably 410 to 850 parts by mass, and more preferably 420 to 650 parts by mass.

  The ethylene-based resin is composed of an ethylene-vinyl acetate copolymer and / or a mixture of polyvinyl acetate and linear low-density polyethylene, and has the linear low-density polyethylene as a main component. The content of linear low density polyethylene in the ethylene-based resin can be, for example, 50% by mass or more, preferably 75% by mass or more, and more preferably 80% by mass or more.

The ethylene-based resin is mainly composed of linear low density polyethylene. Therefore, the foamable composite resin particles are excellent in foamability as described above, and can improve the toughness of the foamed composite resin molded body obtained by foam-molding the foamable composite resin particles. As the linear low density polyethylene, those using a metallocene polymerization catalyst are preferable. The linear low density polyethylene is a copolymer of ethylene and an α-olefin such as 1-butene and 1-hexene, and means a density (g / cm ³ ) of 0.910 to 0.925. .

  The melt mass flow rate (MFR 190 ° C., load 2.16 kg) of the linear low density polyethylene is preferably 0.5 to 4.0 g / 10 minutes, and 1.0 to 3.0 g / 10 minutes from the viewpoint of foamability. Is more preferable. The MFR (190 ° C., load 2.16 kg) of the linear low density polyethylene is a value measured by the condition code D based on JIS K7210 (1999). As a measuring device, a melt indexer (for example, model L203 manufactured by Takara Kogyo Co., Ltd.) can be used.

  Moreover, it is preferable that melting | fusing point (Tm) of a linear low density polyethylene is 80 to 115 degreeC. In this case, the ethylene resin can be sufficiently impregnated with the styrene monomer during the production of the expandable composite resin particles, and the suspension system can be prevented from becoming unstable during the polymerization. As a result, by using the foamable composite resin particles, it is possible to obtain a foamed composite resin molded article that combines the excellent mechanical properties of the styrene resin and the excellent tenacity of the ethylene resin at a higher level. Become. From the same viewpoint, the melting point (Tm) of the ethylene-based resin is more preferably 85 to 110 ° C. The melting point (Tm) of the linear low density polyethylene can be measured by differential scanning calorimetry (DSC) based on JIS K7121 (1987).

  The ethylene-based resin is composed of an ethylene-vinyl acetate copolymer and / or a mixture of polyvinyl acetate and linear low-density polyethylene, and the ethylene-vinyl acetate copolymer and / or polyvinyl acetate in the composite resin. The content of the derived vinyl acetate component is 0.2 to 5% by mass. When the content of the vinyl acetate component is less than 0.2% by mass, the flame retardant property of the foamed composite resin molded article obtained using the foamable composite resin particles may be insufficient. On the other hand, when the content of the vinyl acetate component exceeds 5% by mass, foamability may be reduced. From the same viewpoint, the content of the vinyl acetate component is preferably 0.2 to 3.5% by mass, more preferably 0.3 to 1% by mass, and 0.5 to 0.8% by mass. % Is even more preferred.

  The reason why flame retardancy is particularly excellent when the content of the vinyl acetate component is in the specific range is presumed as follows. That is, in the expandable composite resin particles, in order to adjust the content of the vinyl acetate component, the ethylene-vinyl acetate copolymer and / or polyvinyl acetate is included in the expandable composite resin particles. Since ethylene-vinyl acetate copolymer and / or polyvinyl acetate can supply hydrogen to radicals generated during the decomposition of the polymer, it is considered that the decomposition rate of the polymer can be slowed. As a result, since the component (the volatile low-molecular compound generated by the decomposition of the polymer) that continues to burn is reduced, the foamed composite resin molded article may exhibit further excellent flame retardancy as described above. It is considered possible.

  As a method of adjusting the content of the vinyl acetate component in the expandable composite resin particles, there is a method of adjusting the compounding amount by previously blending an ethylene-vinyl acetate copolymer or polyvinyl acetate into an ethylene-based resin. The ethylene-vinyl acetate copolymer is a polymer obtained by copolymerizing ethylene and vinyl acetate by, for example, high-pressure radical polymerization. The ethylene-vinyl acetate copolymer generally has a long-chain polyethylene chain branch and a short-chain branch structure derived from vinyl acetate. Polyvinyl acetate (vinyl acetate resin) can be obtained, for example, by radical polymerization of vinyl acetate.

  As described above, the foamable composite resin particles are excellent in retention of the foaming agent because the composite resin having a high styrene resin content is used as the base resin. The bead life of the expandable composite resin particles is preferably 0.2 or more, more preferably 0.5 or more, and even more preferably 1 or more. The method for measuring the bead life will be described later in Examples.

  Moreover, when the foamable composite resin particles are actually stored for a long period of time and then expanded to obtain composite resin foam particles, it is possible to reduce the variation in the apparent density of the composite resin foam particles. Furthermore, the composite resin foam particles obtained in this way have good in-mold moldability. Therefore, the foamed composite resin molded body obtained using the composite resin foamed particles is excellent in appearance and fusion property between the foamed particles. In addition, the foamed composite resin molded body has little variation in mechanical properties and can exhibit not only the excellent rigidity provided by the styrene resin, but also the excellent toughness provided by the ethylene resin.

  The morphology of the composite resin in the foamable composite resin particles includes a morphology in which an ethylene resin forms a continuous phase and a styrene resin forms a dispersed phase (sea-island structure), and a morphology in which an ethylene resin and a styrene resin form a co-continuous phase. (Sea / sea structure) or a morphology (island sea structure) in which an ethylene-based resin forms a dispersed phase (island phase) and a styrene-based resin forms a continuous phase (sea phase).

  The composite resin in the foamable composite resin particles should have a morphology in which the ethylene-based resin forms a continuous phase and a styrene-based resin forms a dispersed phase (sea-island structure), or a morphology in which an ethylene-based resin and a styrene-based resin form a co-continuous phase. Is preferred. In this case, superior toughness and resilience can be obtained compared to the morphology (island sea structure) in which the ethylene-based resin forms a dispersed phase (island phase) and the styrene-based resin forms a continuous phase (sea phase). . More preferably, the morphology (sea island structure) in which the ethylene-based resin forms a continuous phase and the styrene-based resin forms a dispersed phase is preferable. In this case, toughness can be further improved. In such a sea-island structure, a number of dispersed phases made of styrene resin are dispersed in a continuous phase made of ethylene resin.

  In the foamable composite resin particles, the content of the residual styrene monomer is preferably 500 ppm or less (including 0). In this case, a foamed composite resin molding suitable as a low VOC (volatile organic compound) vehicle member or a building member can be obtained. The residual styrene monomer content in the foamable composite resin particles is more preferably 400 ppm or less (including 0), more preferably 300 ppm or less (including 0), and 100 ppm or less (including 0). Even more preferably.

  The ethylene-based resin is a mixture of 75 to 95% by weight of linear low density polyethylene and 5 to 25% by weight of ethylene-vinyl acetate copolymer (provided that the linear low density polyethylene and ethylene-vinyl acetate copolymer The total amount with the polymer is preferably 100% by mass). In this case, the foamable composite resin particles are more excellent in foamability, and the flame retardancy of the foamed composite resin molded body obtained by foam-molding the foamable composite resin particles can be further improved. From the same viewpoint, the ethylene-based resin is more preferably composed of 80 to 90% by mass of linear low density polyethylene and 10 to 20% by mass of ethylene-vinyl acetate copolymer.

  Moreover, it is preferable that content of the vinyl acetate component in an ethylene-vinyl acetate copolymer is 25-50 mass%. In this case, the foamable composite resin particles exhibit more excellent foamability, and the flame retardancy of the foamed composite resin molded body obtained by foam-molding the foamable composite resin particles can be further improved. From the same viewpoint, the content of the vinyl acetate component in the ethylene-vinyl acetate copolymer is more preferably 30 to 50% by mass.

  The MFR of the ethylene-vinyl acetate copolymer and the MFR of polyvinyl acetate are preferably 1 to 120 g / 10 min (190 ° C., load 2.16 kg). In this case, the fusing property of the foamed composite resin molded body obtained by foam-molding the foamable composite resin particles can be further improved, and the toughness of the foamed composite resin molded body can be further improved. From the same viewpoint, the MFR of the ethylene-vinyl acetate copolymer and the MFR of the polyvinyl acetate (190 ° C., load 2.16 kg) are more preferably 2 to 30 g / 10 min, and 2 to 10 g / 10 min. More preferably.

  The composite resin is formed by impregnating and polymerizing a styrene monomer with respect to the ethylene resin. Styrene (styrene monomer) can be used as the styrene monomer (styrene monomer), but not only styrene but also a monomer copolymerizable therewith can be used. In the present specification, styrene constituting the styrene resin in the composite resin and a monomer copolymerizable with styrene added as necessary may be collectively referred to as a styrene monomer. The amount of styrene used in a total of 100% by mass of the styrenic monomer is preferably 50% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more.

Examples of the monomer copolymerizable with styrene include the following styrene derivatives and other vinyl monomers.
Examples of styrene derivatives include α-methyl styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-ethyl styrene, 2,4-dimethyl styrene, p-methoxy styrene, pn-butyl styrene, p. -T-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4,6-tribromostyrene, divinylbenzene, styrene sulfonic acid, sodium styrene sulfonate and the like. These may be used alone or in combination of two or more.

Examples of the other vinyl monomers include acrylic acid esters, methacrylic acid esters, vinyl compounds containing hydroxyl groups, vinyl compounds containing nitrile groups, organic acid vinyl compounds, olefin compounds, diene compounds, halogenated vinyl compounds, Examples thereof include vinylidene halide compounds, maleimide compounds, acrylic acid, methacrylic acid and the like.
Examples of the acrylate ester include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate.
Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate.
Examples of the vinyl compound containing a hydroxyl group include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.
Examples of the vinyl compound containing a nitrile group include acrylonitrile and methacrylonitrile.
Examples of the organic acid vinyl compound include vinyl acetate and vinyl propionate.
Examples of the olefin compound include ethylene, propylene, 1-butene, and 2-butene.
Examples of the diene compound include butadiene, isoprene, chloroprene and the like.
Examples of the vinyl halide compound include vinyl chloride and vinyl bromide.
Examples of the vinylidene halide compound include vinylidene chloride.
Examples of maleimide compounds include N-phenylmaleimide and N-methylmaleimide.
These vinyl monomers may be used alone or in combination of two or more.

  Specific examples of the styrene resin in the composite resin include polystyrene, rubber-modified polystyrene, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, acrylonitrile-ethylenepropylene rubber-styrene copolymer, and styrene-acrylic acid ester. Examples thereof include a copolymer, a styrene-methacrylic acid ester copolymer, a styrene-acrylic acid copolymer, a styrene-methacrylic acid copolymer, and a styrene-α-methylstyrene copolymer. The styrenic resin may be present alone or in combination of two or more.

  In the case of a morphology in which the styrene resin in the composite resin constitutes the dispersed phase, the styrene resin is composed of a styrene homopolymer and a copolymer of styrene and an acrylate ester from the viewpoint of good foamability. It is preferable. When producing expandable composite resin particles, it is preferable to use styrene and butyl acrylate from the viewpoint of foamability, as in the examples described later. In this case, the content of the butyl acrylate component in the composite resin is preferably 0.5 to 10% by mass, more preferably 1 to 8% by mass, and 2 to 5% by mass. Is more preferable.

  Moreover, it is preferable that the weight average molecular weights of styrene resin are 100,000-600,000. In this case, shrinkage at the time of foaming of the foamable composite resin particles can be further prevented. Furthermore, when the composite resin foam particles obtained after foaming are molded in the mold, the fusion property between the composite resin foam particles can be further improved. As a result, the dimensional stability of the foamed composite resin molded product can be further improved. From the same viewpoint, the weight average molecular weight of the styrene-based resin is more preferably 150,000 to 550,000, and further preferably 200,000 to 500,000. A method for measuring the weight average molecular weight of the styrene resin will be described later in Examples.

  The glass transition temperature (Tg) of the styrene resin is preferably 85 ° C to 100 ° C. In this case, the foamability of the foamable composite resin particles can be further improved, and shrinkage during foaming can be prevented. Furthermore, at the time of in-mold molding of the composite resin foam particles obtained after foaming, the fusion property between the composite resin foam particles can be further improved, and the dimensional stability of the foam composite resin molded body can be further improved. .

  The glass transition temperature (Tg) of the styrene resin can be measured, for example, as follows. Specifically, first, 1.0 g of expandable composite resin particles is placed in a 150 mesh wire net bag. Next, about 200 ml of xylene is placed in a 200 ml round flask, and the sample placed in the wire mesh bag is set in a Soxhlet extraction tube. Heat with a mantle heater for 8 hours to extract Soxhlet. The extracted xylene solution is dropped into 600 ml of acetone, decanted, and the supernatant is evaporated to dryness under reduced pressure to obtain a styrene resin as an acetone-soluble component. With respect to 2 to 4 mg of the obtained styrenic resin, a heat flux differential scanning calorimetry is performed by JIS K7121 (1987) using a DSC measuring instrument (Q1000) manufactured by TA Instruments. And glass transition temperature (Tg) can be calculated | required as a midpoint glass transition temperature of the DSC curve obtained on the conditions of a heating rate of 10 degree-C / min.

  Examples of the brominated flame retardant include 2,2-bis (4- (2,3-dibromo-2-methylpropoxy) -3,5-dibromophenyl) propane, bis [3,5-dibromo-4- ( 2,3-dibromopropoxy) phenyl] sulfone, 2,2-bis (4- (2,3-dibromopropoxy) -3,5-dibromophenyl) propane, triallyl isocyanurate hexabromide, brominated butadiene polymer Etc.

  The brominated flame retardant is preferably a brominated butadiene polymer. In this case, it is possible to obtain expandable composite resin particles having more excellent flame retardancy with a small addition amount. Furthermore, expandable composite resin particles with a smaller amount of residual styrene-based monomer can be obtained. Examples of the brominated butadiene-based polymer include those disclosed in JP 2009-516019 A and JP 2012-512942 A, for example. These brominated butadiene polymers are produced by brominating butadiene polymers.

  The brominated butadiene polymer is preferably a block copolymer, a random copolymer, or a graft copolymer containing a component unit of a styrene monomer (hereinafter referred to as “butadiene- It is also referred to as “brominated product of styrene copolymer”), and is more preferably a block copolymer of a polystyrene polymer block and a brominated polybutadiene block.

  Examples of the styrene monomer in the brominated butadiene polymer include styrene, brominated styrene, chlorinated styrene, 2-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, and α-methylstyrene. it can. Among these, styrene, 4-methylstyrene, α-methylstyrene, or a mixture thereof is preferable, and styrene is more preferable.

  The bromine content in the brominated butadiene-based polymer is preferably 60% by mass or more, and more preferably 63% by weight or more, from the viewpoint of imparting flame retardancy. The bromine content can be determined based on JIS K7392 (2009).

  A bromide of a butadiene-styrene block copolymer, which is a typical brominated butadiene polymer, can be represented by the following general formula (1). In the general formula (1), X, Y, and Z are positive integers. The block copolymer in the general formula (1) is a triblock copolymer, but may be a diblock copolymer.

  The brominated product of such a butadiene-styrene block copolymer is produced, for example, by brominating a styrene-butadiene block copolymer. Preferable examples of brominated butadiene-styrene block copolymers include commercially available products such as “Emerald 3000” manufactured by Chemtura and “FR122P” manufactured by ICL-IP.

  The weight average molecular weight in terms of polystyrene of the brominated butadiene-based polymer is preferably 1,000 or more and 300,000 or less, more preferably 10,000 or more and 200,000 or less, and further preferably 100,000 or more and 150,000 or less.

  It is preferable that the compounding quantity of a brominated flame retardant is 0.5-4.5 mass parts with respect to 100 mass parts of said composite resins. In this case, expandable composite resin particles having an excellent balance between flame retardancy and foamability can be obtained. Furthermore, when the brominated flame retardant is a brominated product of a butadiene-styrene copolymer, expandable composite resin particles having a smaller amount of residual styrene monomer can be obtained. The blending amount of the brominated flame retardant is more preferably 0.8 to 3 parts by mass with respect to 100 parts by mass of the composite resin from the viewpoint of flame retardancy and the amount of residual styrene monomer. Even more preferably 5 parts by weight.

  Moreover, in order to improve the thermal stability of a brominated flame retardant, a thermal stabilizer such as an epoxy compound or an antioxidant can be used in combination. The epoxy compound has a property of capturing HBr derived from bromine desorbed from the brominated flame retardant at the time of extrusion processing of core particles composed of an ethylene-based resin, which will be described later. By using this property, a styrene resin by HBr is used. Decomposition can be suppressed. As the epoxy compound, a bisphenol type epoxy compound, a novolac type epoxy compound, or the like can be used. More specifically, for example, commercially available products such as “F2200HM” manufactured by ICL-IP, “EPICLON series” manufactured by DIC, and “Araldite ECN1280” manufactured by HUNTUMAN can be exemplified. These epoxy compounds can be used alone or in combination of two or more. It is preferable that the usage-amount of an epoxy compound is 1-30 mass parts with respect to 100 mass parts of brominated flame retardants, and it is more preferable that it is 5-20 mass parts.

  Moreover, as said antioxidant, a phenolic antioxidant, a hindered amine antioxidant, a phosphite antioxidant, etc. can be used. These antioxidants can be used alone or in combination of two or more. The antioxidant has a property of capturing halogen radicals and halogen ions generated by decomposition of the brominated butadiene-based polymer during the extrusion process of core particles described later. Utilizing this property, the antioxidant can suppress a decrease in molecular weight and coloring of the styrene resin. From such a viewpoint, it is preferable to use a phenol-based antioxidant and a phosphite-based antioxidant in combination as the antioxidant.

It is preferable that the compounding quantity of antioxidant is 0.2-20 mass parts with respect to 100 mass parts of brominated flame retardants, and it is more preferable that it is 1-15 mass parts.
In addition to the above-described epoxy compound and antioxidant, other stabilizers can be used in combination. Examples of such stabilizers include metal soaps, organotin compounds, lead compounds, hydrotalcite, polyhydric alcohols, β-ketones, and sulfur compounds.

  The degree of swelling in methyl ethyl ketone at a temperature of 23 ° C. of the mixed insoluble matter of xylene insoluble matter when the foamable composite resin particles are soxhlet extracted with xylene and the acetone insoluble matter contained in the xylene solution after the soxhlet extraction is 1.25 The above is preferable. The reason is as follows.

  In general, in expanded particles made of a composite resin of an ethylene-based resin and a styrene-based resin and a molded body thereof, rigidity increases as the ratio of the styrene-based resin increases, but resilience during compression decreases. On the other hand, when the expandable composite resin particles contain a composite resin exhibiting the above specific swelling degree, the expanded particles obtained by using the expandable composite resin particles and the molded product thereof are due to an increase in the proportion of the styrene resin. Restorability during compression can be greatly improved while maintaining rigidity. Therefore, when the degree of swelling is 1.25 or more as described above, the rigidity and the restorability can be improved to a higher level. From the same viewpoint, the degree of swelling is more preferably 1.5 or more, further preferably 2 or more, and even more preferably 3.5 or more. Further, the degree of swelling is preferably approximately 10 or less, and more preferably 5 or less. The swelling degree of the composite resin foamed particles and the foamed composite resin molded body obtained using the foamable composite resin particles is also preferably in the same range as the foamable composite resin particles.

  Moreover, when the degree of swelling is not less than the predetermined value, the reason why the rigidity and the restoring property are excellent as described above is presumed as follows. The degree of swelling (degree of swelling) when an ethylene-based resin is immersed in an organic solvent has a correlation with the crosslinked structure (three-dimensional network structure) of the resin, and the finer the network, the lower the amount of organic solvent absorbed. , The degree of swelling decreases. On the other hand, non-crosslinked ethylene-based resins hardly swell in methyl ethyl ketone at a temperature of 23 ° C. That is, as described above, the xylene-insoluble matter (crosslinked ethylene resin component) of the composite resin constituting the expandable composite resin particles and the acetone insoluble matter (crosslinked ethylene resin that has passed through the mesh) in the xylene-soluble matter. Component, uncrosslinked ethylene resin component, and ethylene resin component obtained by graft polymerization of styrene monomer). This means that the ethylene resin constituting the resin contains a large amount of a cross-linked three-dimensional network structure with a coarse ethylene resin component. Then, the crosslinked ethylene-based resin component having a three-dimensional network structure with a coarse network easily stretches moderately while foaming composite resin particles, so that a foam film having high strength is formed. Inferred. Furthermore, when the composite resin foamed particles are compressed, the ethylene resin in the composite resin is flexible and sufficiently deformable, so even if the ratio of the styrene resin in the composite resin is high, the foamed foam bubbles It is assumed that the closed cell structure can be maintained without breaking the membrane. That is, by using the foamable composite resin particles having a swelling degree in the above specific range, composite resin foam particles and foamed composite resin molded bodies having a higher level of rigidity and restorability can be obtained. The method for measuring the degree of swelling of the expandable composite resin particles in methyl ethyl ketone at a temperature of 23 ° C. will be described later in Examples.

  Further, in the foamable composite resin particles, it is preferable that the weight ratio of xylene-insoluble matter by Soxhlet extraction is 50% or less (including 0). In this case, the foamability of the foamable composite resin particles can be further improved. Further, the weight ratio of xylene-insoluble matter is more preferably 45% or less (including 0), and further preferably 40% or less (including 0). In this case, the rigidity and restorability of the foamed composite resin molded body formed by foaming the foamable composite resin particles can be further improved. It is preferable that the weight ratio of the xylene-insoluble matter in the composite resin foam particles and the foam composite resin molded body is also in the same range as the above-described foamable composite resin particles. A method for measuring the weight ratio of the insoluble component in xylene in the foamable composite resin particles will be described later in Examples.

  The expandable composite resin particles contain a physical foaming agent. As a physical foaming agent, it is preferable to use a C3-C6 saturated hydrocarbon compound, for example. In this case, the retention of the foaming agent of the foamable composite resin particles and the foaming power during molding can be further improved. Furthermore, the fusion property between the foamed particles in the foamed composite resin molded body can be further improved. Examples of such saturated hydrocarbon compounds include propane, n-butane, isobutane, cyclobutane, n-pentane, isopentane, neopentane, cyclopentane, n-hexane, cyclohexane, and the like. These foaming agents can be used alone or in a mixture of two or more.

  The physical foaming agent is preferably composed of 30 to 80% by mass of isobutane and 20 to 70% by mass of other hydrocarbons having 4 to 6 carbon atoms. However, the total amount of isobutane and other hydrocarbons having 4 to 6 carbon atoms is 100% by mass. By adjusting the ratio of isobutane and other hydrocarbons having 4 to 6 carbon atoms as described above, the foaming composite resin particles can be sufficiently impregnated with the physical foaming agent, and the foaming agent in the foaming composite resin particles Can be further improved. From the same viewpoint, the proportion of isobutane in the physical foaming agent is more preferably 40 to 75% by mass.

  Moreover, it is preferable that content of the foaming agent in an expandable composite resin particle is 3-10 mass%. In this case, the foamability of the foamable composite resin particles can be further improved, and shrinkage during foaming can be prevented. Furthermore, at the time of in-mold molding of the composite resin foam particles obtained after foaming, the fusion property between the composite resin foam particles can be further improved, and the dimensional stability of the foam composite resin molded body can be improved. More preferably, the content of the physical foaming agent is 4 to 9% by mass.

Next, the manufacturing method of an expandable composite resin particle is demonstrated.
First, core particles made of an ethylene-based resin are suspended in an aqueous medium to prepare a suspension. A styrenic monomer is then added to the suspension. The core particles can be impregnated with the styrenic monomer, polymerized, and the particles can be impregnated with a foaming agent to produce expandable composite resin particles.

  When the core particles are impregnated with a styrene monomer and polymerized, the entire amount of styrene monomer can be added in one batch, but the use of a styrene monomer as in the dispersion step and the modification step described later. For example, the amount can be divided into a first monomer and a second monomer, and these monomers can be added at different times. As in the latter case, by adding the styrene monomer separately, it is possible to prevent the resin particles from condensing during polymerization.

  Moreover, as a method of blending the brominated flame retardant into the expandable composite resin particles, there are a method of dissolving in a styrene monomer to be added and a method of kneading in advance into core particles made of an ethylene resin. A method of impregnating the composite resin particles with a brominated flame retardant can also be employed. Preferably, a method of kneading a brominated flame retardant in an ethylene resin in advance is preferable. In this case, compared with the case where the brominated flame retardant is dissolved in the styrene monomer, the brominated flame retardant is easily contained in the foamable composite resin particles, and the flame retardancy is superior with a small amount of addition. It becomes possible to produce expandable composite resin particles having the following characteristics. In addition, compared with the case where the brominated flame retardant is dissolved in the styrene monomer, there is less opportunity for the flame retardant and the styrene monomer to contact with each other, so that the polymerization inhibition by the brominated flame retardant is less likely to occur. The amount of residual styrenic monomer can be further reduced.

  The expandable composite resin particles can be produced, for example, by performing the following dispersion step, modification step, and impregnation step. In the dispersion step, a first monomer and a polymerization initiator are added to a suspension in which core particles mainly composed of an ethylene-based resin are suspended in an aqueous medium, and the first monomer is added to the suspension. To disperse. In the modification step, when the suspension is heated and the melting point of the ethylene-based resin in the core particles is Tm, the second monomer is added at a temperature of (Tm-10) to (Tm + 30) ° C. It is continuously added to the suspension over an addition time, and the core particles are impregnated with a styrene monomer and polymerized.

  The seed ratio of the first monomer (the mixing ratio (mass ratio) of the first monomer to the core particles is preferably 0.5 or more. In this case, the foamable composite resin particles are prevented from being flattened. From the same viewpoint, the seed ratio of the first monomer is more preferably 0.7 or more, and more preferably 0.8 or more from the same viewpoint. In addition, the seed ratio of the first monomer is preferably 1.5 or less, which suppresses polymerization before the styrenic monomer is sufficiently impregnated into the core particles. In this case, the styrenic monomer can be stabilized, and the generation of a resinous mass can be suppressed.From the same viewpoint, the seed ratio of the first monomer is 1. 3 or less Is more preferably 1.2 or less, and the range of the seed ratio of the first monomer is determined from all combinations of the above-described preferred ranges, more preferred ranges, and further preferred ranges for the upper and lower limits. Can do.

  The addition temperature of the first monomer is preferably less than (Tm-10) ° C. Moreover, it is preferable that the addition temperature of a 2nd monomer exists in the range of (Tm-10) degreeC-(Tm + 30) degreeC. When the addition temperature of the first monomer and the second monomer is within this range, the suspension system can be further stabilized, and the generation of resin lumps can be more effectively suppressed. The addition temperature of the second monomer is more preferably (Tm-5) ° C. to (Tm + 10) ° C. In addition, Tm means melting | fusing point of the ethylene-type resin component which comprises a core particle.

  Further, in the impregnation step, assuming that the glass transition temperature of the resulting styrene resin is Tg (° C.), the polymerization of the styrene monomer and / or the temperature within the range of (Tg−10) to (Tg + 40) ° C. Alternatively, the resin particles are impregnated with a physical foaming agent after polymerization to obtain expandable composite resin particles.

  By performing the dispersion step, the modification step, and the impregnation step, it is possible to obtain the expandable composite resin particles having excellent foaming agent retention and foamability. In addition, a foamed composite resin molded body obtained by foaming the foamable composite resin particles is excellent in rigidity and toughness. Hereinafter, each process in the manufacturing method of the said expandable composite resin particle is demonstrated.

The expandable composite resin particles having a degree of swelling in the predetermined range can be obtained by adjusting the production conditions as follows. In particular,
(1) Impregnating the styrene-based monomer impregnated into the core particles containing the ethylene-based resin in a plurality of times, and relatively increasing the addition ratio of the styrene-based monomer (first monomer) impregnated first, Polymerizing the first monomer by relatively reducing the ratio of the polymerization initiator to one monomer;
(2) using t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, or the like as a polymerization initiator, which has a lower hydrogen abstraction ability than dicumyl peroxide as an initiator,
(3) controlling the polymerization state of the styrenic monomer at the initial stage in the impregnation polymerization by dissolving the polymerization initiator only in the first monomer and polymerizing.
As a result, it is difficult to increase the crosslink density in the ethylene-based resin, and it becomes possible to produce expandable composite resin particles having a degree of swelling within the predetermined range. Under the production conditions that have been studied in the past, dicumyl peroxide having a small ratio of the styrene monomer (first monomer) impregnated into the core particles containing the ethylene resin and having a high hydrogen abstraction ability as a polymerization initiator is used. Since the polymerization initiator is dividedly added to the first monomer and the second monomer, it is considered that the crosslinking density in the ethylene-based resin becomes too high and the degree of swelling becomes low.

  In the dispersion step, the core particles can be suspended in an aqueous medium containing, for example, a suspending agent, a surfactant, a water-soluble polymerization inhibitor and the like to prepare a suspension. In the dispersion step, the first monomer and the polymerization initiator are added to the suspension.

  The core particles can contain additives such as a bubble adjusting agent, a pigment, a slip agent, and an antistatic agent. The core particles can be produced by blending an ethylene-based resin and a dispersion diameter expanding agent added as necessary, melt-kneading, and then finely pulverizing. Melt kneading can be performed by an extruder. At this time, in order to perform uniform kneading, it is preferable to perform extrusion after mixing the resin components in advance. Mixing of each resin component can be performed using mixers, such as a Henschel mixer, a ribbon blender, a V blender, a ladyge mixer, for example.

  In addition, in order to improve the foam retainability and foam moldability, and further to achieve a foamed composite resin molded body with superior strength while maintaining the tenacity characteristic of the ethylene resin, an ethylene resin and It is preferable to uniformly disperse the thermoplastic resin (dispersion diameter expanding agent for the styrene resin phase) for controlling the morphology with the styrene resin in the ethylene resin of the core particles. Therefore, it is preferable to perform melt kneading using a high dispersion type screw such as a dalmage type, a Maddock type, and a unimelt type, or a twin screw extruder.

  The dispersion diameter enlarging agent has an action of expanding the styrene resin phase formed by impregnation polymerization of styrene monomer to the core particles. Examples of such a dispersion diameter expanding agent include one selected from acrylonitrile-styrene copolymer, rubber-modified polystyrene, ABS resin, and AES resin, or a mixture of two or more of these. An acrylonitrile-styrene copolymer is preferable. The amount of acrylonitrile component in the acrylonitrile-styrene copolymer is preferably 20 to 40% by mass.

  10-1000 nm is preferable and, as for the dispersion diameter of the dispersion diameter expansion agent disperse | distributed to the ethylene-type resin of a core particle, 10-500 nm is more preferable. The dispersion diameter of the dispersion diameter-enlarging agent is an average value of the equivalent circle diameters of the phase composed of the dispersion diameter-enlarging agent in the cross section of the core particle.

  The melt mass flow rate (MFR (200 ° C., load 5 kg)) of the dispersion diameter expanding agent is preferably 1 g / 10 min to 20 g / 10 min, and more preferably 2.5 g / 10 min to 15 g / 10 min. . The MFR (200 ° C., load 5 kg) of the dispersion diameter expanding agent is a value measured by the condition code H based on JIS K7210 (1999). As a measuring device, a melt indexer (for example, model L203 manufactured by Takara Kogyo Co., Ltd.) can be used.

The content of the dispersion diameter-enlarging agent in the core particles is preferably 1 to 10 parts by mass, more preferably 3 to 7 parts by mass with respect to 100 parts by mass of the ethylene-based resin constituting the core particles.
If the content of the dispersion diameter-enlarging agent is within the above range, the morphology in which the ethylene resin forms a continuous phase and the styrene resin forms a dispersed phase (sea-island structure) or the co-continuous phase of the ethylene resin and the styrene resin (sea It becomes easy to form a morphology indicating a sea structure), and the foaming agent holding performance of the expandable composite resin particles can be further improved. Also, from the viewpoint of maintaining a higher level of toughness and strength of the foamed composite resin molded body obtained by foaming the foamable composite resin particles and molding in-mold, the content of the dispersion diameter expanding agent is set in the above range. It is preferable.

  Moreover, in order to adjust the bubble size of the foamed composite resin foamed particles, a bubble regulator can be added to the core particles. As a bubble regulator, organic substances, such as higher fatty acid bisamide and higher fatty acid metal salt, or an inorganic substance can be used, for example. In the case of using an organic foam regulator, the blending amount is preferably in the range of 0.01 to 2 parts by mass with respect to 100 parts by mass of the resin component used for the core particles. Moreover, when using an inorganic bubble regulator, it is preferable to make the compounding quantity into the range of 0.1-5 mass parts with respect to 100 mass parts of resin components used for a core particle.

  The refinement of the core particles can be performed by a strand cut method, a hot cut method, an underwater cut method, or the like. Any other method can be used as long as the desired particle size can be obtained. When the particle diameter of the core particles is too small, the retention of the foaming agent may be reduced. On the other hand, if the particle size is too large, the particle size of the expanded particles after foaming also becomes large, and the filling property to the mold may be lowered during in-mold molding. Therefore, the particle diameter of the core particle is preferably 0.1 to 3.0 mm, more preferably 0.3 to 1.5 mm. In the case of using an extruder, for example, the resin is extruded from a hole having a diameter in the range of approximately the particle diameter, and the particle is obtained by cutting the length to obtain core particles having a predetermined particle diameter by changing the cutting speed. The diameter can be adjusted.

  The particle diameter of the core particle can be measured as follows. That is, the core particles are observed with a micrograph, the maximum diameter of each core particle is measured for 200 or more core particles, and the arithmetic average value of the measured maximum diameters is defined as the particle diameter of the core particles.

The core particles are usually suspended in an aqueous medium to form a suspension. Dispersion in the aqueous medium can be performed using, for example, a closed container equipped with a stirrer. Examples of the aqueous medium include deionized water.
The core particles are preferably dispersed in an aqueous medium together with a suspending agent. Examples of the suspending agent include tricalcium phosphate, hydroxyapatite, magnesium pyrophosphate, magnesium phosphate, aluminum hydroxide, ferric hydroxide, titanium hydroxide, magnesium hydroxide, barium phosphate, calcium carbonate, magnesium carbonate. Fine particulate inorganic suspending agents such as barium carbonate, calcium sulfate, barium sulfate, talc, kaolin and bentonite can be used. Moreover, organic suspension agents such as polyvinyl pyrrolidone, polyvinyl alcohol, ethyl cellulose, and hydroxypropyl methyl cellulose can also be used. Preferred are tricalcium phosphate, hydroxyapatite, and magnesium pyrophosphate. These suspending agents can be used alone or in combination of two or more.

  The amount of the suspending agent used is 0.05 to 10 parts by mass in solid content with respect to 100 parts by mass of the suspension polymerization aqueous medium (all water in the system including water such as the reaction product-containing slurry). Is preferred. More preferably, 0.3-5 mass parts is good. When the amount of the suspending agent is too small, it becomes difficult to suspend and stabilize the styrene monomer, and there is a possibility that a lump of resin is generated. On the other hand, when there are too many suspending agents, not only manufacturing cost will increase, but there exists a possibility that particle size distribution may spread.

  A surfactant can be added to the suspension. As the surfactant, for example, an anionic surfactant, a nonionic surfactant, a cationic surfactant, an amphoteric surfactant, and the like can be used.

  The above-mentioned surfactants can be used alone or in combination. Preferably, an anionic surfactant is used. More preferably, it is an alkylsulfonic acid alkali metal salt (preferably a sodium salt) having 8 to 20 carbon atoms. Thereby, the suspension can be sufficiently stabilized. In addition, an electrolyte made of an inorganic salt such as lithium chloride, potassium chloride, sodium chloride, sodium sulfate, sodium nitrate, sodium carbonate, sodium bicarbonate or the like can be added to the suspension as necessary.

  In addition, in order to obtain a foamed composite resin molded body having better toughness and mechanical strength, it is preferable to add a water-soluble polymerization inhibitor to the suspension. As the water-soluble polymerization inhibitor, for example, sodium nitrite, potassium nitrite, ammonium nitrite, L-ascorbic acid, citric acid and the like can be used. The water-soluble polymerization inhibitor is difficult to impregnate into the core particles and dissolves in an aqueous medium. Therefore, polymerization of the styrenic monomer impregnated in the core particles is performed, but the vicinity of the surface of the core particle being absorbed by the microparticles made of the styrenic monomer in the aqueous medium not impregnated in the core particle and the core particle. Polymerization of the styrene monomer can be suppressed. As a result, the amount of the styrene resin on the surface of the expandable composite resin particles can be controlled to be small, and it is assumed that the retention of the foaming agent can be further improved. The addition amount of the water-soluble polymerization inhibitor is preferably 0.001 to 0.1 parts by mass with respect to 100 parts by mass of the aqueous medium (referring to all water in the system including water such as the reaction product-containing slurry). 0.005-0.06 mass part is more preferable.

  In order to uniformly polymerize the styrene monomer in the core particles, the core particles are impregnated with the styrene monomer and polymerized. In this case, the ethylene resin may be cross-linked with the polymerization of the styrene monomer. In the polymerization of the styrene monomer, a polymerization initiator is used, and a crosslinking agent can be used in combination as necessary. Moreover, when using a polymerization initiator and / or a crosslinking agent, it is preferable to previously dissolve the polymerization initiator and / or the crosslinking agent in a styrene monomer.

  As a polymerization initiator, what is used for the suspension polymerization method of a styrene-type monomer can be used. For example, a polymerization initiator that is soluble in a styrene monomer and has a 10-hour half-life temperature of 50 to 120 ° C. can be used. Examples of the polymerization initiator include cumene hydroxy peroxide, dicumyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxybenzoate, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t -Organic peroxides such as amylperoxy-2-ethylhexyl carbonate, hexylperoxy-2-ethylhexyl carbonate, and lauroyl peroxide can be used. As the polymerization initiator, an azo compound such as azobisisobutyronitrile can be used. These polymerization initiators can be used alone or in combination of two or more. In addition, t-butylperoxy-2-ethylhexanoate is preferable from the viewpoint of easily adjusting the degree of swelling and reducing the residual styrene monomer.

  It is also possible to dissolve the polymerization initiator in a solvent and impregnate the core particles. Examples of the solvent for dissolving the polymerization initiator include aromatic hydrocarbons such as ethylbenzene and toluene, and aliphatic hydrocarbons such as heptane and octane. The polymerization initiator is preferably used in an amount of 0.01 to 3 parts by mass with respect to 100 parts by mass of the styrene monomer.

  Further, as the crosslinking agent, it is preferable to use a substance that does not decompose at the polymerization temperature but has a 10 hour half-life temperature that is 5 to 50 ° C. higher than the polymerization temperature. Specifically, for example, peroxides such as dicumyl peroxide, 2,5-t-butyl perbenzoate, and 1,1-bis-t-butyl peroxycyclohexane can be used. A crosslinking agent can be used individually or in combination of 2 or more types. It is preferable that the compounding quantity of a crosslinking agent is 0.1-5 mass parts with respect to 100 mass parts of styrene-type monomers. In addition, the same compound can also be employ | adopted as a polymerization initiator and a crosslinking agent.

  Moreover, a bubble regulator can be added to the styrene monomer or solvent. Examples of the air conditioner include aliphatic monoamide, fatty acid bisamide, polyethylene wax, and methylene bisstearic acid. As the aliphatic monoamide, for example, oleic acid amide, stearic acid amide or the like can be used. As the fatty acid bisamide, for example, ethylene bis stearic acid amide can be used. The bubble regulator is preferably used in an amount of 0.01 to 2 parts by mass with respect to 100 parts by mass of the styrene monomer.

  Moreover, a plasticizer, an oil-soluble polymerization inhibitor, a flame retardant, a dye, etc. can be added to a styrene-type monomer as needed. As the plasticizer, for example, fatty acid esters, acetylated monoglycerides, fats and oils, hydrocarbon compounds and the like can be used. Examples of fatty acid esters that can be used include glycerin tristearate, glycerin trioctoate, glycerin trilaurate, sorbitan tristearate, sorbitan monostearate, and butyl stearate. Moreover, as an acetylated monoglyceride, glycerol diacetomonolaurate etc. can be used, for example. As fats and oils, hardened beef tallow, hardened castor oil, etc. can be used, for example. As a hydrocarbon compound, cyclohexane, a liquid paraffin, etc. can also be used, for example. As the oil-soluble polymerization inhibitor, for example, para-t-butylcatechol, hydroquinone, benzoquinone and the like can be used.

  Next, in the reforming step, heating of the suspension after the dispersing step is started. When the melting point of the ethylene-based resin in the core particle is Tm, the second monomer is continuously added into the suspension at a temperature of (Tm-10) to (Tm + 30) ° C. over a predetermined addition time. Add to. As a result, the core particles are impregnated with the styrene monomer and polymerized.

  The mixing of the core particles and the styrene monomer is adjusted so that the ratio of the styrene monomer is 400 to 1900 parts by mass with respect to 100 parts by mass of the ethylene resin contained in the core particles. The ratio of the styrene monomer to 100 parts by mass of the ethylene resin is preferably 410 to 850 parts by mass, and more preferably 420 to 650 parts by mass.

  Moreover, in the said modification | reformation process, although superposition | polymerization temperature changes with kinds of polymerization initiator to be used, 60-105 degreeC is preferable. Moreover, although a crosslinking temperature changes with kinds of crosslinking agent to be used, 100-150 degreeC is preferable.

  Next, in the impregnation step, the resin particles are impregnated with a foaming agent (physical foaming agent) during and / or after the polymerization of the styrene monomer to obtain expandable composite resin particles. That is, the impregnation of the foaming agent in the impregnation step can be performed during or after the polymerization of the styrene monomer. Specifically, the foaming agent is impregnated into the resin particles by press-fitting the foaming agent into a container containing the resin particles during or after polymerization.

  The impregnation temperature of the blowing agent is preferably in the range of (Tg-10) to (Tg + 40) ° C., where Tg is the glass transition temperature of the styrene resin. When the impregnation temperature of the foaming agent is less than (Tg-10) ° C., there is no problem when foaming the foamable composite resin particles immediately, but when foaming after storage or transportation in an atmosphere at room temperature or higher, There is a possibility that the retention of the foaming agent is lowered. Further, the plasticization becomes insufficient, and a load is applied when foaming the foamable composite resin particles, and the closed cell ratio may be lowered in the foamed composite resin molded body obtained after foam molding. This is because the phase of the ethylene resin that is easily impregnated with the physical foaming agent is impregnated with the foaming agent, but the styrene resin phase is not sufficiently impregnated with the foaming agent, and the physical foaming agent is easily dissipated. It is presumed that the physical foaming agent escapes from the phase. On the other hand, when the impregnation temperature of the physical foaming agent exceeds (Tg + 40) ° C., the foamable composite resin particles may be condensed during the foaming agent impregnation. More preferably, the impregnation temperature of the blowing agent is within the range of (Tg-5) ° C. to (Tg + 25) ° C.

  Further, after impregnation with the foaming agent, the foamable composite resin particles can be dehydrated and dried, and the surface coating agent can be coated as necessary. Examples of the surface coating agent include zinc stearate, stearic acid triglyceride, stearic acid monoglyceride, and castor oil. Moreover, an antistatic agent etc. can also be used as a functional surface coating agent. The amount of the surface coating agent added is preferably 0.01 to 2 parts by mass with respect to 100 parts by mass of the expandable composite resin particles.

The foamed composite resin particles can be obtained by heating the foamed composite resin particles with a heating medium to cause foaming. Specifically, the foamable composite resin particles can be foamed by introducing a heating medium such as steam into a pre-foaming machine supplied with the foamable composite resin particles. Incidentally, the bulk density of the composite resin foamed particles obtained after foaming is preferably from 16~200kg / m ^3, and more preferably 20 and 100 kg / m ^3. Moreover, a foamed composite resin molded body can be obtained by molding the composite resin foamed particles in a mold by a known molding means. Preferably the apparent density of the expanded composite resin molded article obtained after the molding is 16~200kg / m ^3, and more preferably 20 and 100 kg / m ^3.

Below, the Example and comparative example of an expandable composite resin particle are demonstrated.
Example 1
In this example, expandable composite resin particles according to the example are prepared, and composite resin foam particles and a foamed composite resin molded body are prepared using the same. Hereinafter, the manufacturing method of the expandable composite resin particles of this example will be described.

(1) Production of core particles Linear low-density polyethylene ("Nipolon Z HF210K" manufactured by Tosoh Corporation) obtained by polymerization using a metallocene polymerization catalyst, and ethylene having a vinyl acetate (VA) component content of 46% by mass Vinyl acetate copolymer (EVA; “Evaflex EV45LX” manufactured by Mitsui DuPont Polychemical Co., Ltd.) and acrylonitrile-styrene copolymer (AS; “AS-XGS, manufactured by Denki Kagaku Kogyo Co., Ltd., weight average molecular weight: 10. 90,000, acrylonitrile component amount: 28% by mass, MFR (200 ° C., 5 kgf): 2.8 g / 10 min) and brominated product of butadiene-styrene block copolymer (“Emerald 3000” manufactured by Chemtura) , Polystyrene equivalent weight average molecular weight Mw = 130,000, bromine content = 65 mass%) 10 parts by mass of “EPICLON N680” manufactured by DIC as an agent, 5 parts by mass of “Irganox 1010” manufactured by BASF, 5 parts by mass of “PEP36” manufactured by ADEKA, and manufactured by Daihachi Chemical Co., Ltd. as a plasticizer A flame retardant masterbatch (concentration of brominated product of butadiene-styrene block copolymer: 80.5% by mass) prepared by melting and kneading 4.16 parts by mass of “TPP” was prepared.
Then, 18 kg of the linear low density polyethylene, 2 kg of the ethylene-vinyl acetate copolymer, 1 kg of the acrylonitrile-styrene copolymer, and 3.08 kg of the master batch of the flame retardant described above were mixed with a Henschel mixer (Mitsui Mitsui). Kako Koki Co., Ltd .; Model FM-75E) and mixed for 5 minutes to obtain a resin mixture.
Next, the resin mixture was melt-kneaded at an extruder maximum setting temperature of 250 ° C. using an extruder (Icage Co., Ltd .; Model MS50-28; 50 mmφ single screw extruder, Maddock type screw), and cut in water. Were cut into an average of 0.5 mg / piece to obtain core particles (ethylene-based resin core particles).

(2) Production of Expandable Composite Resin Particles 1000 g of deionized water was added to an autoclave with an internal volume of 3 L equipped with a stirrer, and 6.0 g of sodium pyrophosphate was further added. Thereafter, 12.9 g of powdered magnesium nitrate hexahydrate was added and stirred at room temperature for 30 minutes. This produced the magnesium pyrophosphate slurry as a suspending agent. Next, 1.25 g of sodium lauryl sulfonate (10 mass% aqueous solution) as a surfactant, 0.15 g of sodium nitrite as a water-soluble polymerization inhibitor, and 90 g of core particles were added to this suspension (dispersion). Process).

  Next, 2.58 g of t-butylperoxy-2-ethylhexyl monocarbonate (“Perbutyl E” manufactured by NOF Corporation) as a polymerization initiator was dissolved in the first monomer (styrene monomer). Then, the dissolved material was added to the suspension in the autoclave while stirring at a stirring speed of 500 rpm (dispersing step). Note that a mixed monomer of 75 g of styrene and 15 g of butyl acrylate was used as the first monomer. Next, after the air in the autoclave was replaced with nitrogen, the temperature increase was started, and the temperature was increased to 100 ° C. over 1 hour 30 minutes. After the temperature increase, the temperature was maintained at 100 ° C. for 1 hour. Thereafter, the stirring speed was lowered to 450 rpm, and the temperature was maintained at 100 ° C. for 1 hour. Thereafter, the temperature was raised to 105 ° C. over 7 hours (reforming step). When 1 hour had passed since the temperature reached 100 ° C., 320 g of styrene as the second monomer (styrene monomer) was added into the autoclave over 5 hours.

  Next, the temperature was raised to 125 ° C. over 2 hours, and the temperature was kept at 125 ° C. for 5 hours. Thereafter, the mixture was cooled to a temperature of 90 ° C. over 1 hour, the stirring speed was lowered to 400 rpm, and the temperature was kept at 90 ° C. for 3 hours. When the temperature reaches 90 ° C., about 20 g of pentane (a mixture of about 80% by mass of normal pentane and about 20% by mass of isopentane) and 65 g of butane (a mixture of about 20% by mass of normal butane and about 80% by mass of isobutane) are used as blowing agents. It was added into the autoclave over 1 hour (impregnation step). Further, the temperature was raised to 105 ° C. over 2 hours, kept at 105 ° C. for 5 hours, and then cooled to 30 ° C. over about 6 hours.

  After cooling, the contents were taken out, and nitric acid was added to dissolve the magnesium pyrophosphate adhering to the surface of the resin particles. Then, it dehydrated and washed with a centrifuge, and the water adhering to the surface was removed with an airflow drying device to obtain expandable composite resin particles. 0.008 parts by mass of N, N-bis (2-hydroxyethyl) alkylamine as an antistatic agent is added to 100 parts by mass of the resulting expandable composite resin particles, and further 0.12 parts by mass of zinc stearate. Part, 0.04 parts by mass of glycerol monostearate, and 0.04 parts by mass of glycerol distearate.

  The polymerization conditions for the expandable composite resin particles of this example are shown in Table 1 below. Specifically, Table 1 shows the composition of the ethylene resin and the blending amount of the styrene monomer with respect to 100 parts by mass of the ethylene resin. In addition, as composition of ethylene resin, content of linear low density polyethylene (mLL), content of ethylene-vinyl acetate copolymer (EVA), acetic acid in ethylene-vinyl acetate copolymer (EVA) Content of vinyl (VA) component, content of polyvinyl acetate (PVA), MFR of ethylene-vinyl acetate copolymer (EVA) or polyvinyl acetate (PVA) are shown. In addition, the mass ratio of the ethylene-based resin to the styrene-based resin (ethylene-based resin / styrene-based resin) and the content of the vinyl acetate (VA) component in the foamable composite resin particles are shown in Table 1 described later. Furthermore, for the foamable composite resin particles, the morphology of the composite resin, the bead life, the foaming agent content, the residual styrene monomer content (R-SM), the degree of swelling, the weight ratio of xylene insolubles, the weight of the styrene resin The average molecular weight (Mw) was examined as follows, and the results are shown in Table 1 described later.

"Morphology of composite resin"
The cross section of the central part of the expandable composite resin particles was observed with a transmission electron microscope (TEM), and the morphology of the composite resin was examined. As the transmission electron microscope, JEM1010 manufactured by JEOL Ltd. was used. A TEM photograph (10,000 magnifications) of the expandable composite resin particles of this example is shown in FIG. As shown in FIG. 1, in the composite resin, the dark gray portion is an ethylene resin phase, and the light gray portion is a styrene resin phase. As shown in the figure, the expandable composite resin particle 1 of this example contains a composite resin 2 of an ethylene resin and a styrene resin. The composite resin 2 includes a continuous phase 21 made of an ethylene resin and a dispersed phase 22 made of a styrene resin dispersed in the continuous phase 21. That is, the composite resin 2 in the foamed resin particle 1 of this example shows a sea-island morphology in which the ethylene-based resin is the continuous phase 21 and the styrene-based resin is the dispersed phase 22. Although not shown, the composite resin 2 is impregnated with a physical foaming agent and a brominated flame retardant. As a result of the observation, the case where the ethylene-based resin formed a continuous phase and the styrene-based resin formed a dispersed phase as in this example was evaluated as “Umijima”, and the ethylene-based resin and the styrene-based resin were mutually The case where a continuous phase is formed (in the case of a co-continuous phase) is evaluated as “sea and sea.” The case where an ethylene resin forms a dispersed phase and a styrene resin forms a continuous phase is ".

"Bead Life"
The foamable composite resin particles were allowed to stand for a predetermined time in an open state at a temperature of 23 ° C. to dissipate the foaming agent from the foamable composite resin particles. Thereafter, the expandable composite resin particles were expanded by heating at a heating steam temperature of 107 ° C. for 270 seconds to obtain expanded particles. Next, the expanded particles were dried at a temperature of 23 ° C. for 24 hours. Next, the bulk density (kg / m ³ ) of the foamed particles after drying was measured. For the bulk density (kg / m ³ ), prepare a 1 L graduated cylinder, fill the foamed particles up to the 1 L mark in an empty graduated cylinder, measure the mass (g) of the expanded particles per liter, and unit Obtained by conversion. The standing time (days) during which foamed particles having a bulk density of 33 kg / m ³ were obtained, ie, the standing time (days) until foamed particles having a bulk density of 33 kg / m ³ were not obtained was defined as the bead life.

"Foaming agent content"
First, the foamable composite resin particles were dehydrated and washed with a centrifuge, and the water adhering to the surface of the foamable composite resin particles was removed with an airflow drying device. Next, the foamable composite resin particles were dissolved in dimethylformamide (DMF). The content of the added foaming agent was measured by gas chromatography of the lysate, and the content of each component was summed up. Specifically, the quantitative determination of the blowing agent by gas chromatography was performed according to the following procedure.
First, about 5 g of cyclopentanol was precisely weighed to the third decimal place in a 100 mL volumetric flask (the weight at this time was set to Wi), and DMF was added to make a total of 100 mL. This DMF solution was further diluted 100 times with DMF to obtain an internal standard solution. Next, about 1 g of the expandable composite resin particles to be measured was precisely weighed to the third decimal place, and the weight at this time was defined as Ws (g). A precisely weighed sample of expandable composite resin particles was dissolved in about 18 mL of DMF, and 2 mL of the internal standard solution was accurately added to the lysate using a whole pipette. 1 μL of this solution was collected with a microsyringe and introduced into gas chromatography to obtain a chromatogram. The peak area of each foaming agent component and internal standard was determined from the obtained chromatogram, and the concentration of each component was determined by the following equation.
Concentration of each component (mass%) = [(Wi / 10000) × 2] × [An / Ai] × Fn ÷ Ws × 100
here,
Wi: Weight of cyclopentanol when the internal standard solution was prepared (g)
Ws: weight of sample dissolved in DMF (g)
An: Peak area of each foaming agent component at the time of gas chromatographic measurement Ai: Peak area of the internal standard substance at the time of gas chromatographic measurement Fn: Correction coefficient of each foaming agent component obtained from a calibration curve prepared in advance The above gas chromatographic analysis The conditions were as follows.
Equipment used: Gas chromatograph GC-6AM manufactured by Shimadzu Corporation
Detector: FID (hydrogen flame ionization detector)
Column material: Glass column with an inner diameter of 3 mm and a length of 5000 mm Column filler: [Liquid phase name] FFAP (free fatty acid), [Liquid phase impregnation rate] 10 mass%, [Carrier name] Diatomaceous earth Comasorb W for gas chromatography, [Carrier Particle size] 60/80 mesh, [carrier treatment method] AW-DMCS (washing, baking, acid treatment, silane treatment), [filling amount] 90 mL
Inlet temperature: 250 ° C
Column temperature: 120 ° C
Detector temperature: 250 ° C
Carrier gas: N ₂ , flow rate 40 ml / min

"Styrene monomer content (R-SM)"
First, the foamable composite resin particles were frozen and pulverized with an analysis mill manufactured by IKA so that the particle diameter was about 100 μm. About 1 g of pulverized material was collected, dissolved in 25 ml of dimethylformamide, and the content of styrenic monomer was measured by gas chromatography. The measurement conditions for gas chromatography are as follows. Equipment used: Gas chromatograph GC-9A manufactured by Shimadzu Corporation, column filler: [liquid phase name] PEG-20M, [liquid phase impregnation rate] 25% by weight, [carrier particle size] 60/80 mesh, carrier treatment Method], column material: glass column having an inner diameter of 3 mm and length of 3000 mm, carrier gas: N ₂ , detector: FID (hydrogen flame ionization detector), quantification: internal standard method.

"Swelling degree"
First, about 1 g of expandable composite resin particles were collected, and their weight (W ₀ ) was weighed to the fourth decimal place and placed in a 150 mesh wire mesh bag. Next, about 200 ml of xylene was placed in a round flask having a capacity of 200 ml, and the sample placed in the wire mesh bag was set in a Soxhlet extraction tube. Soxhlet extraction was performed by heating with a mantle heater for 8 hours. After the extraction, it was cooled by air cooling. After cooling, the wire mesh was taken out from the extraction tube, and the sample together with the wire mesh was washed with about 600 ml of acetone. Next, acetone was volatilized and dried at a temperature of 120 ° C. The sample collected from the wire net after this drying is “xylene-insoluble matter”. The xylene solution after the Soxhlet extraction was put into 600 ml of acetone. And the component which is not melt | dissolved in acetone was isolate | separated and collect | recovered by filtering using the filter paper of 5 types A prescribed | regulated to JISP3801, and the recovered material was evaporated to dryness under reduced pressure. The obtained solid is “acetone-insoluble matter”.
The weight (W _a ) of the mixed insoluble part of “xylene insoluble part” and “acetone insoluble part” obtained by these operations was measured to the fourth decimal place. In other examples and comparative examples, when the weight of the mixed insoluble component is less than 0.2 g, the above operation is repeated to obtain a sufficient amount of the mixed insoluble component. Insoluble matter was obtained. Next, the mixed insoluble matter was immersed in 50 ml of methyl ethyl ketone and left at a temperature of 23 ° C. for 24 hours. Thereafter, the mixed insoluble matter was taken out from methyl ethyl ketone, and after lightly wiping with filter paper, the weight (W _b ) of the mixed insoluble matter was measured to the fourth decimal place. Then, based on the weight (W _a , W _b ) of the mixed insoluble matter before and after immersion in methyl ethyl ketone, the degree of swelling S was determined by the following formula (I). In addition, the swelling degree of the composite resin foamed particles and the foamed composite resin molded body, which will be described later, is the same as the above method except that the specimens cut out from the composite resin foamed particles or the foamed composite resin molded body are used as samples, respectively. And measured.
S = W _b / W _a (I)

"Weight ratio of xylene (XY) insoluble matter"
First, the weight (W ₁ ) obtained by subtracting the weight of the foaming agent contained in the foamable composite resin particles from the weight (W ₀ ) of the foamable composite resin particles measured by the degree of swelling was obtained. Further, the weight (W ₂ ) of the xylene-insoluble matter obtained by the measurement of the degree of swelling was measured. The ratio of xylene insolubles is the ratio of weight (W ₂ ) to weight (W ₁ ) (W ₂ / W ₁ ; percentage (%)).

"Weight average molecular weight of styrene resin (Mw)"
First, Soxhlet extraction was performed in the same manner as described above. The extracted xylene solution was dropped into 600 ml of acetone, followed by decantation and evaporation under reduced pressure. As a result, a styrene resin was obtained as an acetone-soluble component. The weight average molecular weight of the styrene resin was measured by a gel permeation chromatography (GPC) method (mixed gel column for polymer measurement) using polystyrene as a standard substance. Specifically, using a measuring device (HLC-8320GPC EcoSEC) manufactured by Tosoh Corporation, eluent: tetrahydrofuran (THF), flow rate: 0.6 ml / min, sample concentration: 0.1 wt%, column: TSK guard column It measured on the measurement conditions of connecting SuperH-Hx1 piece and TSK-GEL SuperHM-Hx2 piece in series. That is, the weight average molecular weight was obtained by dissolving a styrene resin in tetrahydrofuran, measuring by gel permeation chromatography (GPC), and calibrating with standard polystyrene.

(3) Preparation of Composite Resin Expanded Particles Next, expanded particles having a bulk density of 25 kg / m ³ were prepared using the expandable composite resin particles obtained as described above. Specifically, first, the foamable composite resin particles were placed in a 30 L atmospheric pressure batch foaming machine, and steam was supplied into the foaming machine. As a result, the expandable composite resin particles were expanded to a bulk density of 25 kg / m ³ to obtain composite resin expanded particles having a bulk expansion ratio of 40 times. The bulk density (kg / m ³ ) of the composite resin foam particles can be measured by the same operation as the bulk density of the foam particles in the above-described method for evaluating the bead life of the foamable composite resin particles. The mass of the expanded particles per 1 L of bulk volume determined by this operation was defined as the bulk density (kg / m ³ ) of the composite resin expanded particles. The bulk foaming ratio of the foamed particles is calculated from the formula 1000 / bulk density (kg / m ³ ).

(4) Production of foamed composite resin molded body (composite resin foamed particle molded body) First, the composite resin foamed particles obtained as described above were aged at room temperature for 1 day. Next, using a mold molding machine (DSM-0705VS manufactured by DABO Co., Ltd.), the composite resin foam particles are formed into a 300 mm × 75 mm × 25 mm rectangular shaped molded body and a 340 mm × 270 mm × 25 mm box shaped molded body. Molded. The obtained molded body was dried at a temperature of 40 ° C. for 1 day, and further cured at room temperature for 1 day or more.
In this way, composite resin foamed particles having a bulk density of 25 kg / m ³ were molded to obtain a foamed composite resin molded body having an expansion ratio of 40 times. The expansion ratio of the foamed composite resin molded product is calculated by the following equation (II) by calculating the apparent density (kg / m ³ ) by dividing the mass of the molded product by its volume.
Foaming ratio (times) = 1000 / apparent density (kg / m ³ ) (II)

  Next, for the foamed composite resin molded body, the fusion rate (%), 50% compression stress (kPa), flame retardancy (mm / min), compression set (%), swelling degree, and residual styrene-based monomer Content (R-SM) (ppm) was measured as follows. The results are shown in Table 1.

"Fusion rate"
The fracture surface of the foamed composite resin molded body was observed, and the number of foam particles peeled off at the interface with the foam particles fractured internally was measured. Next, the ratio of the internally broken foam particles to the total number of foam particles peeled at the interface and the foam particles peeled at the interface was calculated, and the value expressed as a percentage was defined as the fusion rate (%).

"50% compressive stress"
A plate-shaped test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm was cut out from the rectangular parallelepiped foamed composite resin molded article, and a compression test was performed on the test piece according to JIS K 7220 (2006). The compressive stress when the compressive strain is 50% is 50% compressive stress (kPa).

"Flame retardance"
A rectangular parallelepiped test piece having a size of 340 mm × 102 mm × 12.7 mm was cut out from the box-shaped foamed composite resin molded body. Using this test piece, FMVSS No. defined in JIS D 1201 was used. The burning rate (mm / min) was measured according to the burning test of 302. This measurement was performed on three test pieces to determine the arithmetic average value of the burning rates. And the flame retardance was evaluated according to the following criteria. That is, the case where the burning speed is 80 mm / min or less is evaluated as “A”, the case where it exceeds 80 mm / min but is 100 mm / min or less is evaluated as “B”, and the case where it exceeds 100 mm / min is defined as “C”. evaluated. The results are shown in Table 1 below. In Table 1, the numbers in parentheses shown together with the evaluation results of flame retardancy are the burning rates (mm / min). In particular, those showing self-extinguishing properties are described as self-extinguishing in parentheses. did.

"Compression set"
A plate-shaped test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm was cut out from the rectangular parallelepiped foamed composite resin molding, and the test piece was measured according to JIS K 6767 (1999).

"Swelling degree"
The measurement was performed in the same manner as the above-mentioned expandable composite resin particles except that a test piece cut out from the foamed composite resin molded body was used as a sample.

"Styrene monomer content (R-SM)"
First, a sample piece of about 1 g was cut out from a rectangular parallelepiped foamed composite resin molded body. Next, this sample piece was dissolved in 25 ml of dimethylformamide, and the content of the styrenic monomer was measured by gas chromatography under the same conditions as R-SM of the expandable composite resin particles.

(Example 2)
In this example, the ethylene-vinyl acetate copolymer having a vinyl acetate component content of 46% by mass and the ethylene-acetic acid having a vinyl acetate component content of 42% by mass used in the production of the core particles in Example 1 were used. Expandable composite resin particles were produced in the same manner as in Example 1 except that the copolymer was changed to “Ultrasen 760” manufactured by Tosoh Corporation.

Example 3
In this example, the ethylene-vinyl acetate copolymer having a vinyl acetate component content of 46% by mass used in the preparation of the core particles in Example 1 was used, and the ethylene-acetic acid having a vinyl acetate component content of 25% by mass. Expandable composite resin particles were produced in the same manner as in Example 1 except that the copolymer was changed to “Ultrasen 640” manufactured by Tosoh Corporation.

Example 4
In this example, the ethylene-vinyl acetate copolymer having a vinyl acetate component content of 46% by mass and the ethylene-acetic acid content having a vinyl acetate component content of 32% by mass used in the preparation of the core particles in Example 1 was used. Expandable composite resin particles were prepared in the same manner as in Example 1 except that the copolymer was changed to “Ultrasen 750” manufactured by Tosoh Corporation.

(Example 5)
In this example, the ethylene-vinyl acetate copolymer having a vinyl acetate component content of 46% by mass used in the production of core particles in Example 1 was used, and the ethylene-acetic acid content having a vinyl acetate component content of 70% by mass. Expandable composite resin particles were produced in the same manner as in Example 1 except that the copolymer was changed to “Soabrene DH” manufactured by Nippon Synthetic Chemical Co., Ltd.

(Example 6)
In this example, except that the ethylene-vinyl acetate copolymer used in the production of the core particles in Example 1 was changed to polyvinyl acetate (“Sacnol SN-09T” manufactured by Denki Kagaku Kogyo Co., Ltd.). In the same manner as in Example 1, expandable composite resin particles were produced.

(Example 7)
In this example, the amount of linear low density polyethylene used in the production of the core particles in Example 1 was changed from 18 kg to 19 kg, and the amount of ethylene-vinyl acetate copolymer used was changed from 2 kg to 1 kg. Except for the points described above, expandable composite resin particles were produced in the same manner as in Example 1.

(Example 8)
In this example, the amount of linear low density polyethylene used in the production of core particles in Example 1 was changed from 18 kg to 15 kg, and the amount of ethylene-vinyl acetate copolymer used was changed from 2 kg to 5 kg. Except for the points described above, expandable composite resin particles were produced in the same manner as in Example 1.

Example 9
In this example, the amount of linear low density polyethylene used in the preparation of the core particles in Example 1 was changed from 18 kg to 10 kg, and the amount of ethylene-vinyl acetate copolymer was changed from 2 kg to 10 kg. Except for the points described above, expandable composite resin particles were produced in the same manner as in Example 1.

(Example 10)
In this example, the amount of core particles used in the production of expandable composite resin particles in Example 1 was changed from 90 g to 110 g, and a mixed monomer of 95 g of styrene and 15 g of butyl acrylate was used as the first monomer. In the same manner as in Example 1, except that 280 g of styrene was used as the second monomer, expandable composite resin particles were produced.

(Example 11)
In this example, the amount of the flame retardant masterbatch used in the preparation of the core particles in Example 1 was changed from 3.08 kg to 8 kg. Further, the amount of the core particles used in the production of the expandable composite resin particles in Example 1 was changed from 90 g to 70 g, a mixed monomer of 55 g of styrene and 15 g of butyl acrylate was used as the first monomer, and the second 360 g of styrene was used as a monomer. Except for these points, expandable composite resin particles were produced in the same manner as in Example 1.

(Example 12)
In this example, the amount of the flame retardant masterbatch used in the production of the core particles in Example 1 was changed from 3.08 kg to 21 kg. Further, the amount of the core particles used in the production of the expandable composite resin particles in Example 1 was changed from 90 g to 50 g, a mixed monomer of styrene 35 g and butyl acrylate 15 g was used as the first monomer, and the second 400 g of styrene was used as a monomer. Except for these points, expandable composite resin particles were produced in the same manner as in Example 1.

(Example 13)
In this example, the amount of flame retardant masterbatch used in the production of core particles in Example 1 was changed from 3.08 kg to 1.44 kg. Further, the amount of the core particles used in the production of the expandable composite resin particles in Example 1 was changed from 90 g to 85 g, a mixed monomer of 70 g of styrene and 15 g of butyl acrylate was used as the first monomer, and the second 330 g of styrene was used as a monomer. Except for these points, expandable composite resin particles were produced in the same manner as in Example 1.

(Comparative Example 1)
In this example, the amount of linear low density polyethylene used in the production of the core particles in Example 1 was changed from 18 kg to 20 kg, and the amount of ethylene-vinyl acetate copolymer used was changed to 0 kg. Also, the amount of flame retardant master batch used was changed from 3.08 kg to 6.93 kg. Furthermore, the amount of the core particles used for producing the expandable composite resin particles in Example 1 was changed from 90 g to 100 g, a mixed monomer of 85 g of styrene and 15 g of butyl acrylate was used as the first monomer, and the second 300 g of styrene was used as a monomer. Except for these points, expandable composite resin particles were produced in the same manner as in Example 1.

(Comparative Example 2)
In this example, the amount of the flame retardant masterbatch used in the production of the core particles in Example 1 was changed from 3.08 kg to 12.5 kg. Further, the amount of the core particles used in the production of the expandable composite resin particles in Example 1 was changed from 90 g to 115 g, a mixed monomer of 100 g of styrene and 15 g of butyl acrylate was used as the first monomer, and the second 270 g of styrene was used as a monomer. Except for these points, expandable composite resin particles were produced in the same manner as in Example 1.

(Comparative Example 3)
In this example, the amount of the flame retardant masterbatch used in the production of the core particles in Example 1 was changed from 3.08 kg to 20 kg. Further, the amount of the core particles used in the production of the expandable composite resin particles in Example 1 was changed from 90 g to 30 g, and a mixed monomer of 15 g of styrene and 15 g of butyl acrylate was used as the first monomer. 440 g of styrene was used as a monomer. Except for these points, expandable composite resin particles were produced in the same manner as in Example 1.

(Comparative Example 4)
In this example, the amount of core particles used in the production of expandable composite resin particles in Example 1 was changed from 90 g to 145 g, and a mixed monomer of 130 g of styrene and 15 g of butyl acrylate was used as the first monomer. 210 g of styrene was used as the second monomer. Except for these points, expandable composite resin particles were produced in the same manner as in Example 1.

(Comparative Example 5)
In this example, the amount of linear low-density polyethylene used in the preparation of the core particles in Example 1 was changed from 18 kg to 19 kg, and the ethylene-vinyl acetate copolymer having a vinyl acetate component content of 46 mass% was used. The polymer was changed to an ethylene-vinyl acetate copolymer ("Ultrasen 626" manufactured by Tosoh Corporation) with a vinyl acetate component content of 15% by mass, except that the amount used was changed from 2 kg to 1 kg. In the same manner as in Example 1, expandable composite resin particles were produced.

(Comparative Example 6)
In this example, the amount of linear low-density polyethylene used in the preparation of the core particles in Example 1 was set to 0, and an ethylene-vinyl acetate copolymer having a vinyl acetate component content of 46% by mass was obtained by adding acetic acid. An ethylene-vinyl acetate copolymer having a vinyl component content of 70% by mass (same as Example 1 except that the content was changed to “Soabrene DH” manufactured by Nippon Synthetic Chemical Co., Ltd. and the amount used was changed to 20 kg. Thus, expandable composite resin particles were produced.

(Results of Examples and Comparative Examples)
About the expandable composite resin particle produced in Examples 2-13 and Comparative Examples 1-6, the examination result similar to Example 1 is shown in Tables 1-3. As representative examples of the morphology of the composite resin, the results (TEM photographs) of Example 10, Example 12, and Comparative Example 3 in addition to Example 1 (see FIG. 1) described above are shown in FIGS. As shown in FIG. 2-4, the same code | symbol as FIG. 1 shows the structure similar to FIG. 1, and refers the description to precede. In addition, although illustration is abbreviate | omitted, morphology was investigated also with the transmission electron microscope similar to Example 1 also about the other Example and the comparative example. Further, using the foamable composite resin particles prepared in Examples 2 to 13 and Comparative Examples 1 to 6, foamed composite resin molded bodies were prepared in the same manner as in Example 1. And the examination result similar to Example 1 is shown in Table 1-Table 3 about a foaming composite resin molding.

  As is known from Tables 1 and 2, as in Examples 1 to 13, the ratio of the ethylene resin and the styrene resin (the ratio of the styrene monomer to the ethylene resin) was adjusted, and the ethylene resin As an ethylene-vinyl acetate copolymer and / or a mixture of polyvinyl acetate and linear low density polyethylene, a resin mainly composed of linear low density polyethylene is used, and the vinyl acetate component By adjusting the content and the like, expandable composite resin particles excellent in retention of foaming agent and foamability can be obtained. And by using these foamable composite resin particles, it is possible to obtain a foamed composite resin molded article that is excellent in flame retardancy, has a high fusion rate between the foamed particles, and has high rigidity and resilience. In particular, as the ethylene resin, by using a resin mainly composed of linear low density polyethylene and further containing an ethylene-vinyl acetate copolymer and / or polyvinyl acetate, the content of the styrene resin in the composite resin It can be seen that even if the amount is increased, it is possible to realize foamable composite resin particles that are excellent in flame retardancy, have a high fusion rate between foamed particles, and can produce a foamed composite resin molded body having high rigidity and resilience. . Moreover, even if the content of the styrene resin in the composite resin is increased by using a specific flame retardant as in Examples 1 to 13 and adjusting the amount to a predetermined range, the residual styrene monomer An increase in the amount can be suppressed. As a result, expandable composite resin particles with a small amount of residual styrene monomer can be obtained.

  On the other hand, in the expandable composite resin particles of Comparative Example 1 and Comparative Example 2, the ethylene-based resin does not contain an ethylene-vinyl acetate copolymer and / or polyvinyl acetate but contains a vinyl acetate component. Absent. For this reason, the foamable composite resin particles of Comparative Example 1 have insufficient flame retardancy of the foamed composite resin molded article, although the content of the flame retardant is relatively large. Further, when the content of the flame retardant was further increased as compared with Comparative Example 1 as in Comparative Example 2, the flame retardancy was improved, but the amount of residual styrene monomer was increased. Furthermore, the fusion rate between the foamed particles was lowered, and the restoration property of the foamed composite resin molded article was impaired.

  In the foamable composite resin particles of Comparative Example 3, since the amount of the styrene monomer to be impregnated and polymerized with respect to 100 parts by mass of the ethylene resin is too large, the content of the ethylene resin in the composite resin is low, and vinyl acetate The content of components is also low. Therefore, in spite of containing a sufficient amount of flame retardant as compared with the above-mentioned examples, the flame retardancy was insufficient. Further, the amount of the residual styrene monomer was high, and the foamed composite resin molded article had a low fusion rate and an insufficient restorability. On the other hand, the expandable composite resin particles of Comparative Example 4 have a low content of styrene resin in the composite resin because the amount of the styrene monomer impregnated and polymerized with respect to 100 parts by mass of the ethylene resin is too small. Therefore, the retainability of the foaming agent in the expandable composite resin particles was insufficient. Further, the rigidity of the foamed composite resin molded article was insufficient.

  The expandable composite resin particles of Comparative Example 5 are examples in which the vinyl acetate component content in the composite resin constituting the particles is too small. Therefore, the foamed composite resin molded article obtained by foam-molding the foamable composite resin particles of Comparative Example 5 has insufficient flame retardancy. In the expandable composite resin particles of Comparative Example 6, the ethylene resin constituting the composite resin does not contain linear low density polyethylene, and the content of the vinyl acetate component is too high. Therefore, the retainability of the foaming agent of the foamable composite resin particles is insufficient, and the foamability is also insufficient. As a result, the foamable composite resin particles could not be foamed to a desired foaming ratio, and a foamed composite resin molded article could not be obtained.

1 Expandable composite resin particles 2 Composite resin

Claims (6)

Expandable composite resin particles containing a composite resin of an ethylene-based resin and a styrene-based resin, a physical foaming agent, and a brominated flame retardant,
The composite resin is formed by impregnating and polymerizing 400 to 1900 parts by mass of a styrene monomer with respect to 100 parts by mass of the ethylene resin.
The ethylene-based resin is composed of an ethylene-vinyl acetate copolymer and / or a mixture of polyvinyl acetate and linear low density polyethylene, and the linear low density polyethylene as a main component,
Expandable composite resin particles, wherein the content of the vinyl acetate component derived from the ethylene-vinyl acetate copolymer and / or polyvinyl acetate in the composite resin is 0.2 to 5% by mass.   A mixture of a linear low density polyethylene of 75 to 95% by mass of the above-mentioned ethylene resin and an ethylene / vinyl acetate copolymer of 5 to 25% by mass (provided that the linear low density polyethylene and the ethylene / vinyl acetate copolymer) The foamable composite resin particle according to claim 1, comprising a total amount of 100% by mass with the polymer.   The expandable composite resin particle according to claim 1 or 2, wherein the content of the vinyl acetate component in the ethylene-vinyl acetate copolymer is 25 to 50% by mass.   The brominated flame retardant is a brominated product of a butadiene-styrene copolymer, and the amount of the brominated product is 0.5 to 4.5 parts by mass with respect to 100 parts by mass of the composite resin. The expandable composite resin particle according to any one of claims 1 to 3.   The composite resin has a continuous phase composed of the ethylene resin and a dispersed phase composed of the styrene resin dispersed in the continuous phase. The expandable composite resin particle as described.   The degree of swelling in methyl ethyl ketone at a temperature of 23 ° C. is a mixed insoluble matter of xylene insolubles when the foamable composite resin particles are subjected to Soxhlet extraction with xylene and acetone insolubles in the xylene solution after Soxhlet extraction. The expandable composite resin particle according to any one of claims 1 to 5, wherein the expandable composite resin particle is 25 or more.