JP5942763B2 - Composite resin foam particles - Google Patents

Description

  The present invention relates to a composite resin foamed particle containing a composite resin of a styrene resin and an olefin resin as a base resin and containing a brominated 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, light weight, vibration proofing properties, soundproofing properties, heat insulation properties and the like. The foamed particle molded body is obtained by, for example, producing foamable resin particles by impregnating resin particles with a physical foaming agent such as propane, butane, pentane, etc., and heating the foamable resin particles to obtain foamed particles. After that, the foamed particles are produced by fusing each other in a mold.
As the base resin of the foamed particle molded body, those made of styrene resin such as polystyrene resin and those made of olefin resin such as polypropylene resin and polyethylene resin are mainly used. Recently, olefin resin and styrene resin are used. A composite resin with a resin (hereinafter also simply referred to as “composite resin”) has attracted attention.

The foamed particle molded body using the composite resin as a base resin is superior in toughness, oil resistance, etc., compared with, for example, a foamed particle molded body using a styrene resin as the base resin. Used as a material. Moreover, since it has sufficient compressive strength and buffering property, it is widely used as automobile members such as bumpers and floor spacers.
However, the foamed particle molded body using the composite resin as a base resin has a drawback that it is easily burnt.

Therefore, a technique for imparting flame retardancy to a foamed particle molded body using the composite resin as a base resin has been developed. Specifically, for example, when the expansion ratio of the styrene-modified polyethylene 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 for obtaining foamed particles using styrene-modified polyolefin resin as a base resin, using tetrabromocyclooctane or tris (2,3-dibromopropyl) isocyanurate as a flame retardant (Patent Literature). 2-4).

JP-A-6-57027 Japanese Patent Laid-Open No. 7-179646 Japanese Patent Laid-Open No. 7-179647 JP 2006-257150 A

  However, in the method of impregnating a resin particle with a flame retardant with an aliphatic hydrocarbon or a cycloaliphatic hydrocarbon as in Patent Documents 1 to 4 described above, foaming is performed by pre-foaming the foamable resin particles and aging in a short time. Problems arise when forming the particles. That is, there is a problem that the residual amount of aliphatic hydrocarbon or cycloaliphatic hydrocarbon in the obtained expanded particle molded body (foamed resin molded body) increases. As a result, there exists a problem that the flame retardance and heat resistance of a foamed resin molding become inadequate.

  Furthermore, when the composite resin foamed particle molded body is used as a vehicle interior material such as an impact absorbing member, the composite resin foamed particle molded body is required to have higher flame resistance and heat resistance. Here, even if the amount of the flame retardant is simply increased so as to further improve the flame retardancy, the flame retardancy corresponding to the amount of blending is not obtained, and mechanical properties such as the compression strength of the foamed particle molded body, There was a tendency to reduce heat resistance.

  This invention is made | formed in view of this background, Comprising: While it is excellent in mechanical physical property, it intends to provide the composite resin expanded particle which can exhibit the outstanding flame retardance and heat resistance.

One embodiment of the present invention is a composite resin (provided that the olefin resin (A) and the styrene resin) containing 20 to 50% by mass of the olefin resin (A) and 50 to 80% by mass of the styrene resin (B). In the composite resin foamed particles including the resin (B) as a base resin and a brominated flame retardant, the total amount of the resin (B) is 100% by mass.
In the styrene resin (B), as a copolymerization component, one or more (meth) selected from a C 1-10 alkyl ester component of methacrylic acid and a C 1-10 alkyl ester component of acrylic acid. An acrylic ester component (b1) is included,
The content of the (meth) acrylic acid ester component (b1) in 100% by mass of the styrene resin (B) is 2 to 12% by mass,
The glass transition temperature (Tg) of the styrenic resin (B) is 100 to 104 ° C.,
The composite resin foamed particles are characterized in that the brominated flame retardant has a 50% decomposition temperature of 260 to 340 ° C. (Claim 1).

  The composite resin foamed particles are composed of a composite resin of the specific ratio olefin resin (A) and styrene resin (B), and the styrene resin (B) has the (meth) acrylic as a copolymerization component. A brominated flame retardant containing the specific amount of the acid ester component (b1), the glass transition temperature (Tg) of the styrene-based resin (B) being 100 to 104 ° C., and exhibiting a 50% decomposition temperature within a specific range. Including. Therefore, the composite resin foamed particles have the above-mentioned composite resin, which is difficult to be flame retardant, as a base resin, but do not hinder the heat resistance inherent in the composite resin and have excellent mechanical properties. However, high flame retardancy can be exhibited.

In the composite resin foamed particles in which the base resin is a composite resin composed of the olefin resin (A) and the styrene resin (B), the inventors of the present invention combine a brominated flame retardant with a styrene resin ( When B) contains a specific amount of the (meth) acrylic acid ester component (b1) as a copolymer component, the composite resin foam particles have excellent flame resistance while maintaining good heat resistance and mechanical strength. We found the knowledge to show.
Specifically, first, in the composite resin foamed particles composed of the olefin resin (A) and the styrene resin (B), if the addition amount of the brominated flame retardant is increased, it becomes difficult accordingly. The inventor found that flammability does not always improve. As a result of further investigation on such knowledge, when the styrene resin (B) in the composite resin contains an appropriate amount of the (meth) acrylic acid ester component (b1) as a copolymerization component, the styrene resin (B) becomes (meta ) It has been found that the flame retardant effect of the brominated flame retardant is improved as compared with the case where the acrylate component (b1) is not contained. This finding is that, in the composite resin foamed particles composed of the olefin resin (A) and the styrene resin (B), the so-called (meth) acrylic acid ester component (b1) acts as a flame retardant improvement aid. It has been found that it can.

  Therefore, the composite resin foamed particles can exhibit excellent flame retardancy while maintaining good heat resistance and mechanical strength. Therefore, by molding the composite resin expanded particles in a mold, it is possible to obtain a composite resin expanded particle molded body having excellent mechanical properties and excellent flame retardancy and heat resistance.

Next, a preferred embodiment of the composite resin expanded particle will be described.
The composite resin foamed particles contain a composite resin containing 20 to 50% by mass of an olefin resin (A) and 50 to 80% by mass of a styrene resin (B) as a base resin. However, the total of the olefin resin (A) and the styrene resin (B) is 100% by mass. Composite resin foam particles obtained by molding the composite resin foam particles in a mold in order to use a composite resin in which the olefin resin (A) and the styrene resin (B) are blended in the above-mentioned blending ratio. In the molded product, the foamed particles constituting the molded product itself can exhibit excellent tenacity unique to the olefin resin. Furthermore, the composite resin foamed particle molded body can exhibit excellent rigidity peculiar to the styrene resin.

If the styrene resin (B) exceeds 80% by mass, the properties of the olefin resin may be impaired. That is, the toughness, heat resistance, chemical resistance, etc. of the composite resin foamed particles may be reduced. As a result, there is a possibility that the toughness, heat resistance, chemical resistance, etc. of the composite resin foam particle molded body obtained by in-mold molding of the composite resin foam particles may be lowered. From the same viewpoint, the upper limit of the content of the styrene resin (B) is more preferably 78% by mass, and further preferably 75% by mass.
On the other hand, when the styrene resin (B) is less than 50% by mass, it may be difficult to obtain spherical composite resin foamed particles. Moreover, the characteristic of a styrene resin may be impaired and the mechanical strength of the said composite resin expanded particle may fall. As a result, the mechanical strength of a composite resin foamed particle molded body obtained by molding the composite resin foamed particles in a mold may be lowered. From the same viewpoint, the lower limit of the content of the styrene resin (B) is more preferably 55% by mass, and further preferably 60% by mass.

  The composite resin foamed particles are formed by impregnating a physical foaming agent into foamed composite resin particles containing an olefin resin (A), a styrene resin (B), and a bromine-based flame retardant. The blending ratio of the olefin resin (A) and the styrene resin (B) in the composite resin particles is the same as the blending ratio in the composite resin foam particles described above.

  Examples of the olefin resin (A) include linear low density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid alkyl ester copolymer, ethylene- Ethylene resins such as methacrylic acid alkyl ester copolymers can be used. Examples of the olefin resin (A) include a propylene homopolymer, a propylene-ethylene copolymer, a propylene-butene-1 copolymer, a propylene-ethylene-butene-1 copolymer, and propylene-4-methyl. A propylene-based resin such as a pentene-1 copolymer can also be used. The olefin resin (A) may be a single polymer, but a mixture of two or more polymers can also be used.

From the viewpoint of excellent in-mold moldability of the composite resin foamed particles and the improvement of mechanical properties such as compression strength of the resulting composite resin foam particle molded body, the olefin resin (A) is a linear low It is preferable that the main component is density polyethylene. Specifically, the content of the linear low density polyethylene in 100% by mass of the olefin resin (A) is preferably 50% by mass or more. The linear low-density polyethylene preferably has a branched structure having a linear polyethylene chain and a short-chain branched chain having 2 to 6 carbon atoms. For example, an ethylene-α-olefin copolymer can be mentioned.
In this case, the strength of the composite resin expanded particles can be further improved. As a result, the strength of the composite resin foamed particle molded body obtained by molding the composite resin foamed particles in a mold can be further improved.

The density of the linear low density polyethylene is usually 0.88 to 0.945 g / cm ³ , but the mechanical strength such as the compression strength of the composite resin foam particles formed by molding the composite resin foam particles in a mold. terms such that the physical properties can be further improved, is preferably 0.90~0.94g / cm ^3, more preferably 0.91~0.93g / cm ^3.
The melt mass flow rate of linear low density polyethylene (MFR 190 ° C., 2.16 kgf) is preferably 0.5 to 4.0 g / 10 min from the viewpoint of foaming properties, more preferably 1.0 to 3.0 g / 10 min. preferable. More preferably, linear low density polyethylene polymerized with a metallocene catalyst is used.
The MFR (190 ° C., 2.16 kgf) 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.
Further, the Vicat softening temperature of the linear low density polyethylene is preferably 80 to 120 ° C., more preferably 90 to 100 ° C., from the viewpoint of stabilizing the particle size of the core particles described later used in the production of the composite resin foam particles. .

The olefin resin (A) preferably contains an ethylene-vinyl acetate copolymer.
Ethylene - Density vinyl acetate copolymer is generally a 0.90~0.96g / cm ³ or so, foaming and molding of the viewpoint, in particular moldability viewpoint, it is 0.95 g / cm ³ or less Preferably, 0.94 g / cm ³ or less is more preferable.
The ethylene-vinyl acetate copolymer generally has a long-chain polyethylene chain branch and a short-chain branch structure derived from vinyl acetate. The content of vinyl acetate (structure ratio derived from vinyl acetate monomer in the copolymer) is usually 1 to 45% by mass, from the viewpoint of impregnation of styrene monomer and graft polymerizability, etc. The thing of 3-20 mass% is preferable, and the thing of 5-15 mass% is more preferable.
The melt mass flow rate (190 ° C., 2.16 kgf) of the ethylene-vinyl acetate copolymer is as follows: 1. From the viewpoint of extrusion suitability at the time of granulation extrusion of the below-described core particles used for the production of the composite resin foam particles. It is preferably 5 to 4.0 g / 10 min, and more preferably 2.0 to 3.5 g / 10 min. Further, the Vicat softening temperature of the ethylene-vinyl acetate copolymer is preferably 60 to 110 ° C., more preferably 60 to 90 ° C., from the viewpoint of stabilizing the particle size of the core particles.
The ethylene-vinyl acetate copolymer as described above can be obtained as a commercial product.

Moreover, it is preferable that melting | fusing point (Tm) of the said olefin resin (A) is 95 to 115 degreeC.
In this case, during the production of the composite resin particles, the olefin resin (A) can be sufficiently impregnated with a polymerizable monomer including a styrene monomer, which will be described later, and the suspension system becomes unstable during the polymerization. Can be prevented. As a result, it is possible to obtain composite resin foamed particles that combine the excellent mechanical properties of the styrene resin (B) and the excellent tenacity of the olefin resin (A) at a higher level. More preferably, the melting point (Tm) of the olefin resin (A) is 100 to 110 ° C. The melting point (Tm) of the olefin resin (A) can be measured by differential scanning calorimetry (DSC) based on JIS K7121 (1987), and the melting peak temperature in the obtained DSC curve. Is the melting point (Tm). When the olefin resin (A) is a mixture of two or more olefin resins, the melting point of the mixture is measured, and when there are a plurality of melting peaks, the highest peak height is obtained. Let the melting peak temperature of the melting peak be the melting point (Tm).

  The styrene resin (B) is a resin mainly composed of a styrene monomer component (b0). The content of the styrenic monomer component (b0) in 100% by mass of the styrenic resin (B) is preferably 50% by mass or more, and more preferably 60% by mass or more.

Examples of the styrenic monomer include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-methoxystyrene, and pn-. Examples include butyl styrene, pt-butyl styrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4,6-tribromostyrene, styrene sulfonic acid, sodium styrene sulfonate, and the like. Although the said styrenic monomer can also be polymerized independently, two or more types can also be polymerized.
Of these styrenic monomers, styrene is preferable from the viewpoint that the mechanical strength of the composite resin expanded particles and the composite resin expanded particle molded body is further improved.

  Furthermore, the styrene-based resin (B) includes, as a copolymerization component, one or more (1 or more) selected from an alkyl ester component having 1 to 10 carbon atoms of methacrylic acid and an alkyl ester component having 1 to 10 carbon atoms of acrylic acid. A (meth) acrylic acid ester component (b1) is used. Hereinafter, in the specification, “one or more (meth) acrylic acid ester components (b1 selected from alkyl ester components having 1 to 10 carbon atoms of methacrylic acid and alkyl ester components having 1 to 10 carbon atoms of acrylic acid) ) "Is appropriately referred to as" (meth) acrylic acid ester component (b1) ".

The content of the (meth) acrylic acid ester component (b1) in 100% by mass of the styrene resin (B) is 2 to 12% by mass, and the glass transition temperature (Tg) of the styrene resin (B) is 100-104 ° C.
In the range where the glass transition temperature (Tg) of the styrene resin (B) is 100 to 104 ° C., the (meth) acrylic acid ester component (b1) is contained in the styrene resin (B) with the above specific content. Therefore, the foamability and moldability of the composite resin foam particles are improved. Furthermore, it becomes possible to sufficiently exhibit the flame retardant effect of the brominated flame retardant without greatly reducing the heat resistance of the composite resin expanded particles.

  When the glass transition temperature (Tg) of the styrene resin (B) is less than 100 ° C., the heat resistance may be insufficient. Moreover, when it exceeds 104 degreeC, there exists a possibility that foamability may fall. Preferably, the temperature is 101 ° C to 103 ° C.

The glass transition temperature (Tg) of the styrenic resin (B) can be determined by the following method.
Specifically, 1.0 g of the composite resin foam particles is put into 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.
Next, the extracted xylene solution is dropped into 600 ml of acetone, followed by decantation and evaporation under reduced pressure to obtain a styrene resin as an acetone-soluble component. The obtained styrene resin 2 to 4 mg is subjected to heat flux differential scanning calorimetry based on JIS K7121 (1987). And the midpoint glass transition temperature of the DSC curve obtained on the conditions of a heating rate of 10 degree-C / min can be made into the glass transition temperature (Tg) of the said styrene resin (B). As a measuring apparatus, a 2010 DSC measuring instrument manufactured by T.A. Instruments Inc. can be used.

  When the content of the (meth) acrylic acid ester component (b1) is less than 2% by mass, or when the carbon number of the alkyl group in the (meth) acrylic acid ester component (b1) is out of the range of 1 to 10, There is a possibility that sufficient flame retardancy may not be obtained. On the other hand, when the content of the (meth) acrylic acid ester component (b1) exceeds 12% by mass, condensation occurs during the polymerization of the styrene resin (B) or the moldability of the composite resin foam particles is increased. There is a risk of deterioration. Moreover, there exists a possibility that the mechanical physical property of a composite resin expanded particle and the composite resin expanded particle molded object formed by in-mold molding this may fall. The content of the (meth) acrylic acid ester component (b1) in 100% by mass of the styrene resin (B) is more preferably 2 to 10% by mass, and further preferably 3 to 8% by mass. .

Specifically, as the (meth) acrylic acid ester component (b1), for example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, acrylic acid Octyl, 2-ethylhexyl acrylate, nonyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate and the like can be used.
Preferably, the (meth) acrylic acid ester component (b1) comprises a methyl methacrylate component and a butyl acrylate component, and the content of the methyl methacrylate component in 100% by mass of the styrene resin (B) is 2 to 2. It is good that it is 9 mass% and content of the said butyl acrylate component is 1-2.5 mass% (Claim 2).
In this case, flame retardance can be improved with a small amount of the (meth) acrylic acid ester component (b1) while maintaining the glass transition temperature of the styrene resin (B) in the desired range. In this case, the suspension stability during polymerization can be enhanced, and the deterioration of mechanical properties can be further suppressed.

Moreover, the composite resin foamed particles are blended with a brominated flame retardant having a 50% decomposition temperature of 260 to 340 ° C.
Since the brominated flame retardant having a 50% decomposition temperature of 260 to 340 ° C. is contained, the composite resin foam particles exhibit a sufficient flame retardant effect by the brominated flame retardant in a temperature range in which the thermal decomposition of the composite resin proceeds. it can. From the same viewpoint, the brominated flame retardant has a 50% decomposition temperature of preferably 270 to 320 ° C, and more preferably 285 to 305 ° C.
When the 50% decomposition temperature of the brominated flame retardant deviates from the range of 260 to 340 ° C, there is a possibility that sufficient flame retardancy cannot be obtained.

  The 50% decomposition temperature of a brominated flame retardant can be measured by a differential thermothermal gravimetric simultaneous measurement device (TG / DTA). Specifically, a differential heat loss curve is obtained under the measurement conditions of a temperature increase rate: 10 ° C./min, a measurement temperature range: 40 ° C. to 500 ° C., a nitrogen atmosphere, a sample pan material: Pt, and a sample mass: 50 mg. The temperature at which the weight is reduced by 50% in the differential heat loss curve can be determined as the 50% decomposition temperature.

  Examples of the brominated flame retardant include bis [3,5-dibromo-4- (2,3-dibromopropoxy) phenyl] sulfone and 2,2-bis (4- (2,3-dibromopropoxy) -3. , 5-Dibromophenyl) propane, triallyl isocyanurate hexabromide, brominated styrene-butadiene block copolymer, tris (tribromoneopentyl) phosphate, 2,2-bis (4- (2,3-dibromo-2) -Methylpropoxy) -3,5-dibromophenyl) propane and the like. 2,2-bis (4- (2,3-dibromo-2methylpropoxy) -3,5-dibromophenyl) propane is preferred. The brominated flame retardant may be used alone or in combination of two or more.

In addition to the above brominated flame retardants, flame retardant aids, non-halogen phosphorous flame retardants, and halogen-containing phosphorous flame retardants containing halogens other than bromine can be used in appropriate amounts.
Examples of the flame retardant aid include antimony trioxide and 2,3-dimethyl-2,3-diphenylbutane. Non-halogen phosphorus flame retardants include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tributoxyethyl phosphate, triphenyl phosphate, tricresyl phosphate and the like. Examples of the halogen-containing phosphorus-based flame retardant containing halogen other than bromine include tris (chloroethyl) phosphate, tris (dichloropropyl) phosphate, and tris (chloropropyl) phosphate. The flame retardant aid and the phosphorus flame retardant can be used alone and in combination with the bromine flame retardant, but two or more types can be mixed and used together.

Composite resin expanded particles containing a styrene resin (B) containing the specific amount of (meth) acrylic acid ester component (b1) as a copolymer component and further containing a brominated flame retardant showing the specific 50% decomposition temperature, The reason for exhibiting excellent flame retardancy as described above is presumed as follows.
That is, in this case, since the thermal decomposition timing of the base resin of the composite resin foamed particles and the thermal decomposition of the brominated flame retardant can be optimized, the composite resin foamed particles are more excellent in flame retardancy. It is assumed that can be expressed.
Therefore, by selecting the type of the halogen-based flame retardant according to the composition of the base resin of the composite resin expanded particles, an optimal combination for exhibiting excellent flame retardancy can be realized.

In the composite resin foamed particles, the blending amount of the brominated flame retardant is determined according to the desired flame retardancy.
When the amount of the brominated flame retardant is too small, there is a possibility that sufficient flame retardancy cannot be obtained. On the other hand, as the blending amount increases, the in-mold moldability of the composite resin foam particles tends to decrease, and the mechanical properties of the resulting composite resin foam particle molded body tend to decrease. Therefore, when there are too many compounding quantities, there exists a possibility that desired in-mold moldability and mechanical physical properties may not be obtained. In this case, the polymerization of the styrene monomer is inhibited, and the content of VOC components such as the styrene monomer in the composite resin foam particles and composite resin foam particle molded body may increase. From this viewpoint, in the composite resin foamed particles, the amount of the brominated flame retardant is preferably 0.3 to 2 parts by mass with respect to 100 parts by mass of the composite resin (Claim 3). It is more preferable that it is 5-1.5 mass%.

In the composite resin foamed particles, the morphology of the composite resin includes a morphology in which the olefin resin (A) and the styrene resin (B) form a co-continuous phase (sea-sea structure), and the olefin resin (A) is dispersed. Morphology (island structure) in which the styrene resin (B) forms the continuous phase (sea phase) or the olefin resin (A) forms the continuous phase and the styrene resin (B) is the dispersed phase. There is a morphology (sea-island structure).
Preferably, the composite resin has a morphology in which the olefin resin (A) forms a continuous phase and the styrene resin (B) forms a dispersed phase.
In this case, high rigidity derived from the styrene resin (B) and high toughness derived from the olefin resin (A) are combined at a higher level.

As described above, the composite resin foamed particles are formed by impregnating a physical foaming agent into foamed composite resin particles containing an olefin resin (A), a styrene resin (B), and a bromine-based flame retardant.
As said physical foaming agent, inorganic physical foaming agents, such as a carbon dioxide, nitrogen, air, can be used. In addition, it is preferable to use an inorganic physical foaming agent as a physical foaming agent in the range of 50-100 mass% with respect to the physical foaming agent whole quantity. More preferably, carbon dioxide is used in a range of 50 to 100% by mass with respect to the total amount of the physical blowing agent.

  In the composite resin expanded particles, the content of the aliphatic hydrocarbon having 3 to 6 carbon atoms is preferably adjusted to less than 0.1% by mass (including 0). In order to make the content of the aliphatic hydrocarbon less than 0.1% by mass, it is preferable to use the inorganic physical foaming agent as a physical foaming agent in a range of 50 to 100% by mass with respect to the total physical foaming agent. It is. In this case, even when the composite resin foamed particles are molded by aging for a short time, the content of flammable aliphatic hydrocarbons remaining in the molded body can be extremely reduced, and stable flame retardancy can be exhibited. Further, by foaming the composite resin particles impregnated with the inorganic physical foaming agent, the styrene monomer, toluene, xylene, and ethylbenzene present in the base resin of the composite resin particles are extracted and removed. As a result, it is possible to obtain composite resin foamed particles having a total content of volatile organic compounds (VOC) such as styrene monomer, toluene, xylene, and ethylbenzene of 200 ppm or less (including 0). Thereby, a flame retardance improves further and it becomes possible to obtain the composite resin expanded particle which shows nonflammability. Further, by molding the composite resin foam particles in a mold, a composite resin foam particle molded body suitable as a low VOC vehicle member or a building member can be obtained.

The composite resin foamed particles are used to obtain a composite resin foamed resin particle molded body (hereinafter, appropriately referred to as “foamed particle molded body”) by filling the mold into a mold and molding in the mold.
The foamed particle molded body is suitable for building members, civil engineering members, vehicle members, aviation members, transportation members, and the like that require flame retardancy.

Next, the manufacturing method of the said composite resin expanded particle is demonstrated.
First, core particles containing the olefin resin (A) as a main component are suspended in an aqueous medium to prepare a suspension. Next, one or more (meth) acrylic acid esters (hereinafter referred to as these two) selected from styrene monomers, alkyl esters of 1 to 10 carbon atoms of methacrylic acid and alkyl esters of 1 to 10 carbon atoms of acrylic acid. (Also referred to as a polymerizable monomer) is added to the suspension. Then, the core particles are impregnated with a polymerizable monomer and polymerized to obtain composite resin particles. Further, the composite resin foamed particles can be produced by impregnating the resin particles with a physical foaming agent during and / or after the polymerization to foam the composite resin particles.

The composite resin foamed particles can be produced, for example, by performing the following reforming step, impregnation step, and foaming step.
In the reforming step, a polymerizable monomer in which the brominated flame retardant is dissolved is added to a suspension in which core particles mainly composed of the olefin resin (A) are suspended in an aqueous medium. The core particles are impregnated with the polymerizable monomer, and suspension polymerization is performed in the presence of a polymerization initiator. Thereby, the composite resin particle comprised from an olefin resin (A) and a styrene resin (B) containing a brominated flame retardant is obtained. In addition, from the viewpoint of preventing performance degradation due to the thermal history of the flame retardant, a modification step for obtaining composite resin particles employing the above method is preferable. However, the brominated flame retardant and the olefin resin (A) are preliminarily used. It is also possible to employ a modification process in which a composite monomer particle is obtained by impregnating a polymerizable monomer into a core particle blended with a brominated flame retardant produced by kneading.

  Next, in the impregnation step, the resin particles are impregnated with a physical foaming agent during and / or after the polymerization of the composite resin particles, and the composite resin particles impregnated with the physical foaming agent are heated in the foaming step. Foamed composite resin particles can be obtained. Alternatively, in the impregnation step and the foaming step, the composite resin particles are dispersed together with a physical foaming agent in a dispersion medium in a pressure resistant container, impregnated with the physical foaming agent, and the composite resin particles are heated and softened in the pressure-resistant state. The composite resin foam particles can also be obtained by discharging from a container and foaming.

  As a preferable impregnation step and foaming step, the composite resin particles and the physical foaming agent are dispersed in a dispersion medium such as water in a sealed container, and heated under stirring to soften the composite resin particles and to make the composite resin particles physically There is a method in which after the impregnation with the foaming agent, the composite resin particles in the softened state impregnated with the physical foaming agent are released from the inside of the closed container under a low pressure (usually atmospheric pressure) and foamed.

The olefin resin (A) described above can be used as the olefin resin in the core particles.
The olefin resin (A) constituting the core particle preferably contains linear low density polyethylene as a main component and further contains an ethylene-vinyl acetate copolymer. A suitable blending ratio of the resin in the olefin resin (A) is 50 to 80 mass of linear low density polyethylene with respect to 100 mass% of the total of linear low density polyethylene and ethylene-vinyl acetate copolymer. %, And ethylene-vinyl acetate copolymer is 20 to 50% by mass.

  The said core particle can be manufactured by mix | blending the above-mentioned olefin resin (A) suitably, melt-kneading with an extruder etc., and then making it fine particle. At this time, in order to uniformly knead the resin, it is preferable that the resin components are mixed in advance using a mixer such as a Henschel mixer, a ribbon blender, a V blender, or a ladyge mixer and then supplied to the extruder.

Moreover, it is preferable to add a bubble regulator to the core particles in order to make the bubble diameter of the composite resin expanded particles uniform and fine and to improve the expansion ratio.
As the bubble regulator, an inorganic bubble regulator and / or an organic bubble regulator can be used. Examples of the inorganic cell regulator include talc, calcium carbonate, silica, titanium oxide, gypsum, zeolite, zinc borate, aluminum hydroxide, and carbon. Examples of the organic bubble adjusting agent include a phosphoric acid nucleating agent, a phenol nucleating agent, and an amine nucleating agent. In addition, these bubble regulators can be added individually or in combination of 2 or more types.
The addition amount of the bubble regulator is preferably 3 parts by mass or less with respect to 100 parts by mass of the olefin resin (A) in the core particles. More preferably, it is 1.5 parts by mass or less, more preferably 1 part by mass or less, and still more preferably 0.5 parts by mass or less.
In addition to the bubble adjusting agent, a pigment, a slip agent, an antistatic agent, and the like can be added to the core particles as necessary.

Fine-grained core particles are obtained from a porous die attached to the tip of the extruder after melt-kneading the olefin resin (A) constituting the core particles in the extruder and various additives blended as necessary. It can be obtained by extrusion and pelletizing into small particles by a strand cut method, a hot cut method, an underwater cut method or the like. Other methods may be employed as long as the desired particle diameter and particle mass are obtained.
From the viewpoint of adjusting the composite resin particles obtained using the core particles to an appropriate size, the average particle diameter of the core particles is preferably 0.1 to 3.0 mm, and 0.3 to 1 More preferably, it is 5 mm. From the same viewpoint, the average mass of the core particles is preferably 0.000625 to 20 mg / piece, more preferably 0.02 to 2.5 mg / piece.
In addition, adjustment of a particle diameter and particle | grain mass can be adjusted with an extruder. Specifically, for example, when extruding a resin from a die provided with a hole having a diameter within a range of a desired particle diameter, the ejection amount, the cutter speed, etc. are adjusted to obtain core particles having a desired particle diameter. The particle diameter and particle mass can be adjusted by cutting into lengths.

In the modification step, the core particles are suspended in a dispersion medium such as water to obtain a suspension. Dispersion in the dispersion medium is usually carried out using a polymerization apparatus comprising a pressure vessel equipped with a stirrer. As the dispersion medium, for example, ethylene glycol, glycerin, methanol, ethanol or the like can be used, but water is preferably used.
In addition, when the core particles are suspended in the dispersion medium, a suspending agent, a surfactant, a water-soluble polymerization inhibitor, or the like can be added to the dispersion medium.

  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, carbonate Fine particulate inorganic suspending agents such as magnesium, barium carbonate, calcium sulfate, barium sulfate, talc, kaolin and bentonite can be used. In addition, organic suspending 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 as a solid content with respect to 100 parts by mass of a suspension polymerization aqueous medium (referring to all water in the system including water such as a reaction product-containing slurry). 10 parts by mass is preferred. More preferably, 0.3-5 mass parts is good. When the amount is less than 0.05 parts by mass, it is difficult to suspend and stabilize the polymerizable monomer, and there is a possibility that a lump of resin is generated. On the other hand, when the amount exceeds 10 parts by mass, not only the production cost increases, but also the particle size distribution may spread.

Moreover, as said surfactant, an anionic surfactant, a nonionic surfactant, a cationic surfactant, an amphoteric surfactant etc. can be used, for example.
Examples of the anionic surfactant include sodium alkyl sulfonate, sodium alkylbenzene sulfonate, sodium lauryl sulfate, sodium α-olefin sulfonate, sodium dodecyl phenyl oxide disulfonate, and the like.

Examples of the nonionic surfactant include polyoxyethylene dodecyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene lauryl ether, and the like.
As the cationic surfactant, alkylamine salts such as coconutamine acetate and stearylamine cetate can be used. Further, as the cationic surfactant, quaternary ammonium such as lauryltrimethylammonium chloride and stearyltrimethylammonium chloride can also be used.
As the amphoteric surfactant, alkylbetaines such as lauryl betaine and stearyl betaine can be used. Moreover, alkylamine oxides, such as lauryl dimethylamine oxide, can also be used.
Preferably, the surfactant is an anionic surfactant. More preferably, it is an alkylsulfonic acid alkali metal salt (more preferably a sodium salt) having 8 to 20 carbon atoms. Thereby, the effect of the outstanding suspension stabilization is acquired.
The mass ratio of the suspending agent and the surfactant (the mass of the suspending agent / the mass of the surfactant) can be 0.01 to 500. Preferably 1-50 is good.

In addition, as the water-soluble polymerization inhibitor, it is possible to employ a water-soluble polymerization inhibitor that does not easily impregnate into the core particles and dissolves in an aqueous medium. In this case, the polymerizable monomer impregnated in the core particles is polymerized, but is being absorbed into the microdroplets of the polymerizable monomer in the aqueous medium not impregnated in the core particles and the core particles. Polymerization of the polymerizable monomer near the surface of the core particle can be suppressed. As a result, it is presumed that the amount of the styrene resin in the surface portion is smaller than that in the central portion of the composite resin particle.
Specific examples of the water-soluble polymerization inhibitor include sodium nitrite, potassium nitrite, ammonium nitrite, L-ascorbic acid, and citric acid.
By using the water-soluble polymerization inhibitor, it is possible to further improve the tenacity, bending strength, compressive strength and the like of the foamed particle molded body obtained by molding the composite resin foamed particles in a mold.

  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). 0.002-0.02 mass part is more preferable. If it exceeds 0.1 parts by mass, the remaining amount of the polymerizable monomer may increase, and good composite resin foam particles and foamed particle molded articles may not be obtained.

In addition, an electrolyte composed of an inorganic salt or the like can be added to the suspension polymerization aqueous medium as necessary. In this case, the number of voids in the composite resin particle can be adjusted.
As the electrolyte, for example, sodium acetate, lithium chloride, potassium chloride, sodium chloride, sodium sulfate, sodium nitrate, sodium carbonate, sodium bicarbonate and the like can be used.
The added amount of the electrolyte is 0.01 to 0.5 as a solid content with respect to 100 parts by mass of the suspension polymerization aqueous medium (referring to all water in the system including water such as the reaction product-containing slurry). It is preferable that it is a mass part, and it is more preferable that it is 0.05-0.2 mass part.

Moreover, as a polymerizable monomer, as above-mentioned, 1 or more (meth) selected from a styrene-type monomer, a C1-C10 alkylester of methacrylic acid, and a C1-C10 alkylester of acrylic acid. Acrylic acid esters can be used.
The ratio of the styrenic monomer in the polymerizable monomer is preferably 50% by mass or more, more preferably 80% by mass or more, and still more preferably 88% by mass or more, based on all monomers. It is particularly preferably 90% by mass or more.
Moreover, as a polymerizable monomer, it is preferable to use styrene, methyl methacrylate, and butyl acrylate.

In order to uniformly polymerize the polymerizable monomer in the core particle, it is preferable to polymerize the core particle by impregnating the polymerizable monomer. In this case, crosslinking may occur together with polymerization of the polymerizable monomer. In the polymerization of the polymerizable monomer, a polymerization initiator is used, and a crosslinking agent can be used in combination as necessary. 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 the polymerizable monomer.
In the polymerization process of the polymerizable monomer, the olefin resin (A) contained in the core particles may be cross-linked. Therefore, in this specification, “polymerization” may include “cross-linking”. .

As said polymerization initiator, what is used for the suspension polymerization method of the said polymerizable monomer can be used. For example, a polymerization initiator that is soluble in a polymerizable monomer and has a 10-hour half-life temperature of 50 to 120 ° C. can be used. Specifically, for example, cumene hydroxy peroxide, dicumyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxybenzoate, benzoyl peroxide, t-butylperoxy-2-ethylhexyl mono Organic peroxides such as carbonate, t-butylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexyl carbonate, hexylperoxy-2-ethylhexyl carbonate, and lauroyl peroxide can be used. An azo compound such as azobisisobutyronitrile can also be used. These polymerization initiators can be used alone or in combination of two or more.
The amount of the polymerization initiator used is preferably 0.01 to 3 parts by mass with respect to 100 parts by mass of the polymerizable monomer.

The crosslinking agent is preferably one that does not decompose at the polymerization temperature but decomposes at the crosslinking temperature. Specific examples include peroxides such as dicumyl peroxide, 2,5-t-butyl perbenzoate, and 1,1-bis-t-butyl peroxycyclohexane. These may be used alone or in combination of two or more. It is preferable that the compounding quantity of a crosslinking agent is 0.1-5 mass parts with respect to 100 mass parts of polymerizable monomers.
In addition, the same compound can also be employ | adopted as the said polymerization initiator and the said crosslinking agent.

The above-mentioned brominated flame retardant can be dissolved in the polymerizable monomer. In addition to the brominated flame retardant, if necessary, a plasticizer, an oil-soluble polymerization inhibitor, a bubble regulator and the like can be added to the polymerizable monomer.
Examples of the plasticizer include fatty acid esters such as glycerin tristearate, glycerin trioctate, glycerin trilaurate, sorbitan tristearate, sorbitan monostearate, and butyl stearate. Moreover, acetylated monoglycerides such as glycerin diacetomonolaurate can also be used. Moreover, fats and oils, such as hardened beef tallow and hardened castor oil, can also be used. Moreover, hydrocarbon compounds, such as a cyclohexane and a liquid paraffin, can also be used.
In addition, as the oil-soluble polymerization inhibitor, para-t-butylcatechol, hydroquinone, benzoquinone, or the like can be used.

Examples of the bubble regulator include fatty acid monoamide, fatty acid bisamide, talc, silica, polyethylene wax, methylene bis stearic acid, methyl methacrylate copolymer, and silicone.
Examples of fatty acid monoamides that can be used include oleic acid amide and stearic acid amide.
As the fatty acid bisamide, for example, ethylene bis stearic acid amide can be used.
When using a bubble regulator, it is preferable that the addition amount of the bubble regulator is 2 parts by mass or less with respect to 100 parts by mass of the polymerizable monomer.

When the above core particles are impregnated with a polymerizable monomer and polymerized, the entire amount of the polymerizable monomer used can be added all at once, but the amount of the polymerizable monomer used may be, for example, the first monomer and the second monomer. These monomers can be added at different timings. As in the latter case, it is possible to prevent the resin particles from condensing during polymerization by adding the polymerizable monomer in portions. When adding in divided portions, for example, the first monomer can be added before the start of polymerization (before heating), and the second monomer can be further added after the start of polymerization (after heating).
Moreover, 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.

For the method of producing the composite resin foamed particles, refer to the known foaming methods described in, for example, Japanese Patent Publication No. 49-2183, Japanese Patent Publication No. 56-1344, Japanese Patent Publication No. 62-61227, etc. Can do.
In the foaming step for obtaining composite resin foam particles preferably exemplified, when the contents in the sealed container are released from the sealed container to the low pressure region, the contents are sealed with the used physical foaming agent or an inorganic gas such as nitrogen or air. It is preferable to discharge the contents in such a manner that back pressure is applied to the container so that the pressure in the container does not drop rapidly. In this case, the apparent density of the resulting composite resin foamed particles can be made more uniform.

  As the physical foaming agent, an inorganic physical foaming agent is preferably used. The inorganic physical foaming agent has a heat insulation coefficient of 1.1 to 1.7, which is a ratio of the constant pressure molar specific heat (Cp) to the constant volume molar specific heat (Cv), and a gas body that can be commonly used as a gas can be used. . Specific examples include nitrogen, carbon dioxide, argon, air, helium, water vapor, and the like, and a mixture of two or more of these may be used. Among the inorganic physical foaming agents, carbon dioxide is preferable. When obtaining the composite resin foam particles, when water is used as a dispersion medium and water-absorbing resin or the like is used as the composite resin particles, water can be used as a foaming agent. .

  The amount of the physical foaming agent used can be determined in consideration of the apparent density of the desired composite resin foamed particles, the composition of the base resin, the type of the physical foaming agent, and the like. In general, it is preferable to use 0.5 to 30 parts by mass of a physical foaming agent with respect to 100 parts by mass of the composite resin particles. The composite resin foam particles obtained by the above method can be subjected to a normal curing step under atmospheric pressure.

  Next, after adjusting the pressure in the composite resin foamed particles to 0.01 to 0.6 MPa (G) by pressurizing with a pressurized gas such as air filled in a pressurized airtight container as necessary, The composite resin foam particles are taken out from the container and heated using saturated water vapor, hot air, a mixture of saturated water vapor and air, hot water, or the like. Thereby, it can be set as the composite resin foaming particle whose apparent density is lower (this process may be called two-stage foaming hereafter).

The apparent density of the composite resin expanded particles is preferably 10 to 500 kg / m ³ . The apparent density can be controlled by adjusting, for example, the composition of the base resin, foaming conditions (temperature, pressure), the amount of foaming agent, and the like.

The average cell diameter of the composite resin foamed particles is preferably 50 to 500 μm, more preferably 80 to 300 μm, and further preferably 100 to 250 μm.
When the average cell diameter is too small, although depending on the apparent density of the composite resin foam particles, the thickness of the cell membrane constituting the cells tends to be small, and the styrene resin (B) is formed on the surface of the cell membrane. Is likely to be exposed. And when the said styrene-type resin (B) is exposed, it will become easy to produce a bubble breakage by the heating at the time of the shaping | molding of the composite resin foam particle. This tendency becomes more prominent as the composite resin expanded particles have a higher expansion ratio. If the composite resin foamed particles have a low expansion ratio, molding may be possible even if the average cell diameter is small, but in order to stabilize the mold transfer performance, the average cell diameter is also low. Is preferably 50 μm or more.
On the other hand, when the average cell diameter is too large, the strength of the foamed particle molded body formed by molding the composite resin foamed particles in the mold may be lowered, or the flame retardancy may be lowered.

  The average cell diameter of the composite resin foam particles is adjusted comprehensively with the foaming temperature, the amount of impregnation of the physical foaming agent, the number of voids in the composite resin particles, and the type and amount of the air conditioner dispersed in the core particles. Can be controlled. For example, setting the foaming temperature high basically acts in the direction of increasing the bubble diameter, and increasing the amount of impregnation of the physical foaming agent acts in the direction of decreasing the bubble diameter. Further, the smaller the number of voids in the composite resin particles, the larger the bubbles tend to be, but the foaming ratio tends to be smaller. On the other hand, when the number of voids increases, it becomes easy to obtain composite resin foam particles having a high expansion ratio, but the bubbles tend to be fine. With respect to the bubble regulator added to the core particles, the bubbles tend to become finer when the amount added is increased.

The average cell diameter of the composite resin foamed particles can be measured as follows.
Specifically, first, the composite resin foam particles are roughly divided into two, and the cut surface is photographed with a scanning electron microscope. In the obtained cross-sectional photograph, a straight line is drawn at equal intervals in the eight directions from the vicinity of the center of the cut surface of the composite resin foamed particle, the number of bubbles intersecting the straight line is counted, and the total length of the straight line is counted. The value obtained by dividing by the number can be used as the cell diameter of the composite resin foamed particles. This operation is performed on a large number (at least 30 or more) of the composite resin foam particles, and the arithmetic average value of the cell diameters of the composite resin foam particles is defined as the average cell diameter. In the measurement of the bubble diameter of each composite resin expanded particle, the bubbles that intersect even part of the straight line are counted. In the above measurement, the reason why straight lines are drawn at equal intervals in the eight directions from the vicinity of the center of the composite resin foam particle cut surface is that the straight lines are drawn at equal intervals in the eight directions from the center of the composite resin foam particle cut surface. This is because, even if the shape of the bubble to be measured is different depending on the direction on the cut surface of the composite resin foam particle, a stable value of the bubble diameter can be obtained.

Below, the Example and comparative example of a composite resin expanded particle are demonstrated.
In this example, unless otherwise specified, the following reforming step, impregnation step, and foaming step are performed to produce composite resin foam particles, which are then molded in-mold to form composite resin foam particles. obtain.
In the reforming step, a polymerizable monomer containing a styrene monomer and a (meth) acrylate ester in a suspension obtained by suspending olefin resin particles (core particles) in an aqueous medium, a brominated flame retardant And a polymerization initiator are added, the core particles are impregnated with the polymerizable monomer and the like, and a polymerization reaction of the polymerizable monomer is caused to obtain composite resin particles. Next, an impregnation step is performed in which the composite resin particles are dispersed together with carbon dioxide, which is an inorganic physical foaming agent, in a dispersion medium in a pressure resistant container, and carbon dioxide is impregnated into the composite resin particles. Subsequently, the foamed composite resin particles impregnated with carbon dioxide are discharged together with the dispersion medium from the pressure-resistant container in a heat-softened state and foamed to produce composite resin foamed particles. The composite resin foam particles are molded in-mold to produce a composite resin foam particle molded body.
Below, each Example and a comparative example are demonstrated in detail.

Example 1
In this example, the composite resin foamed particles according to the example are produced, and the composite resin foamed particle molded body is produced using the composite resin foamed particles.
(1) Production of core particles 5 kg of an ethylene-vinyl acetate copolymer (trade name: Ultracene 626, manufactured by Tosoh Corporation) having a vinyl acetate component content of 15% by mass, and directly polymerized using a metallocene polymerization catalyst. Henschel mixer containing 15 kg of chain low density polyethylene resin (product of Tosoh Corporation, trade name: Nipolon 9P51A) and 0.144 kg of zinc borate (Tonda Pharmaceutical Co., Ltd., zinc borate 2335, average particle size: 6 μm) (Mitsui Miike Kako Co., Ltd .; model: FM-75E) was added and mixed for 5 minutes.
Next, this resin mixture was melt-kneaded at a temperature of 230 to 250 ° C. in an extruder (model MS50-28, 50 mmφ single-screw extruder, Maddock type screw manufactured by Icage Co., Ltd.), and 0.4 by an underwater cutting method. It cut | disconnected to -0.6 mg / piece (average 0.5 mg / piece), and the core particle was obtained.

(2) Preparation of composite resin particles (modification process)
1000 g of deionized water was added to an autoclave with a 3 L internal volume equipped with a stirrer, and 6 g of sodium pyrophosphate was added and dissolved. 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 g of sodium lauryl sulfonate (10% by mass aqueous solution) as a surfactant, 0.2 g of sodium nitrite as a water-soluble polymerization inhibitor, and 150 g of core particles were added to the magnesium pyrophosphate slurry.
Next, 1.29 g of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, trade name: “Perbutyl O”) as a polymerization initiator and t-butylperoxy-2-ethylhexyl monocarbonate (day) 0.17 g (trade name: “Perbutyl E” manufactured by Oil Co., Ltd.), 0.95 g of dicumyl peroxide (manufactured by NOF Corporation, product name: “Park Mill D”) as a crosslinking agent, and as brominated flame retardant 2.45 g of 2,2-bis (4- (2,3-dibromo-2-methylpropoxy) -3,5-dibromophenyl) propane (Daiichi Kogyo Seiyaku “SR130”, 50% decomposition temperature 294 ° C.) Were dissolved in the first monomer. Then, the dissolved material was charged into the slurry in the autoclave while stirring at a stirring speed of 500 rpm. As the first monomer, a mixed monomer of 280 g of styrene, 15 g of methyl methacrylate, and 5 g of butyl acrylate was used.

  Next, after the inside of the autoclave was purged with nitrogen, the temperature was raised and the temperature was raised to 90 ° C. over 1 hour and a half. After the temperature increase, this temperature was maintained at 90 ° C. for 30 minutes, and then the stirring speed was lowered to 450 rpm. The mixture was cooled from 90 ° C. to 80 ° C. over 30 minutes and held at this polymerization temperature of 80 ° C. for 6 hours. When 80 ° C. was reached, 50 g of styrene as the second monomer was added into the autoclave over 130 minutes.

Next, the temperature was raised to 125 ° C. over 4 hours, and the temperature was kept at 125 ° C. for 5 hours. Then, it cooled over about 6 hours to the temperature of 30 degreeC.
After cooling, the contents were taken out and nitric acid was added to dissolve the magnesium pyrophosphate adhering to the surface of the composite resin particles. Subsequently, it was dehydrated and washed with a centrifuge, and water adhering to the surface was removed with an airflow drying device. Thus, composite resin particles having an average particle diameter (d63) of 1.52 mm and an aspect ratio of 1.05 were obtained. The glass transition temperature Tg of the styrene resin (B) contained in the composite resin particles was 103 ° C.
In addition, the flame retardant used for the production of the composite resin particles, 50% decomposition temperature (° C.), blending of the brominated flame retardant with 100 parts by mass of the composite resin of the olefin resin (A) and the styrene resin (B) The amount (parts by mass) is shown in Table 1 described later. Moreover, the kind and compounding ratio of the (meth) acrylic acid ester component (b1) which are copolymerization components in the styrene resin (B) are shown in Table 1 described later.
The average particle diameter (d63), aspect ratio, and glass transition temperature Tg of the composite resin particles were measured as follows.

"Average particle size (d63)"
The average particle size (d63) of the composite resin particles is determined by using a dry particle size distribution measuring device (Millitrack JPA manufactured by Nikkiso Co., Ltd.), when the weight cumulative particle size value from the minimum particle size reaches 63% ( d63) was calculated. The results are shown in Table 1 below.

"aspect ratio"
The aspect ratio of the composite resin particles is determined by measuring the major and minor diameters of the composite resin particles using a dry particle size distribution measuring apparatus (Miltrack JPA manufactured by Nikkiso Co., Ltd.), and calculating the arithmetic average of the measured values of 1000 composite resin particles each. Was determined by The results are shown in Table 1 below.

"Glass transition temperature Tg of styrene resin (B)"
First, 1.0 g of composite resin particles was put in a 150 mesh wire net bag. Next, about 200 ml of xylene was placed in a round flask having a volume of 200 ml, and a sample placed in a wire mesh bag was set in a Soxhlet extraction tube. The soxhlet extraction was performed by heating with a mantle heater for 8 hours. The extracted xylene solution was dropped into 600 ml of acetone, followed by decantation and evaporation under reduced pressure to obtain a styrene resin (B) as an acetone-soluble component.
For 2 to 4 mg of the obtained styrenic resin, differential scanning calorimetry is performed to determine the midpoint glass transition temperature of the DSC curve obtained at a heating rate of 10 ° C./min, and this is the glass of the styrene resin (B). The transition temperature (Tg) was used. The differential scanning calorimetry was performed according to JIS K7121 (1987) using a Q1000 DSC measuring instrument manufactured by TI Instruments. The results are shown in Table 1 below.

(3) Preparation of composite resin foamed particles (impregnation process, foaming process)
1 kg of the composite resin particles prepared as described above was charged into a 5 L pressure vessel equipped with a stirrer together with 3.5 liters of water as a dispersion medium, and further 5 g of kaolin as a dispersant and an interface in the dispersion medium. 0.6 g sodium alkylbenzene sulfonate as activator was added. Subsequently, it heated up to foaming temperature (163 degreeC), stirring with stirring speed 300rpm. Thereafter, carbon dioxide as an inorganic physical foaming agent was injected into the pressure vessel at a pressure of 4.0 MPa, and held for 20 minutes under stirring. Thereafter, the contents were released under atmospheric pressure to obtain composite resin expanded particles having an apparent density of about 49 kg / m ³ . Table 1 shows the foaming temperature of the composite resin foamed particles.
The apparent density of the composite resin foamed particles was measured as follows.

"Apparent density"
A graduated cylinder containing water at a temperature of 23 ° C. was prepared, and about 500 ml of the composite resin foam particles (mass W1 of the composite resin foam particles) was submerged using a tool such as a wire mesh. The volume V1 (cm ³ ) of the composite resin foam particles read from the rise in water level was measured in consideration of the volume of a tool such as a wire mesh. Next, the apparent density (kg / m ³ ) of the composite resin foam particles was determined by dividing the mass W1 (g) of the composite resin foam particles placed in the graduated cylinder by the volume V1 (W1 / V1). In Example 1, Examples 2 to 14 and Comparative Examples 1 to 8 described later, the apparent density of the composite resin foam particles was designed to 49 kg / m ³ . And when the apparent density was measured about the obtained composite resin expanded particle, it confirmed that the apparent density as designed was 49 kg / m < ³ >.

(4) Production of molded composite resin foam particles (molding process)
The composite resin foam particles obtained as described above were filled at a filling rate of 110% into a cavity (length 700 mm × width 200 mm × thickness 50 mm) of a flat plate mold. Next, steam having a molding vapor pressure (original pressure) of 0.07 MPa was introduced into the molding cavity for 15 seconds, and the composite resin foamed particles were heated to foam and fused together to perform in-mold molding. After the heating, water cooling was performed. When the surface pressure decreased to 0.01 MPa (gauge pressure), the mold was opened, and the composite resin foamed particle molded product was released to obtain a molded product with an apparent density of 33 kg / m ³ . . The apparent density of the foamed particle molded body was calculated by obtaining the volume from the outer dimensions, then measuring the mass, and dividing the mass by the volume. In Example 1, Examples 2 to 14 described later, and Comparative Examples 1 to 8, the apparent density of the composite resin foamed particle molded body was 33 kg / m ³ .
The above-mentioned molding vapor pressure is the minimum steam pressure necessary to obtain a foamed particle molded body having a surface smoothness that can be judged visually and having an internal fusion rate of 80% or more. The value of the forming vapor pressure in this example is shown in Table 1 described later.
Subsequently, the composite foamed particle molded body obtained as described above was cured for 12 hours in an atmosphere at a temperature of 60 ° C., and then allowed to stand for 24 hours in an atmosphere at a temperature of 23 ° C. and a relative humidity of 50%. Thereafter, the VOC component amount and the burning rate were measured for the composite resin expanded particle molded body as follows, and the heat resistance and 50% compressive stress were evaluated as follows.

"VOC component amount"
About 1 g of a test piece was cut out from the foamed particle compact, and the test piece was precisely weighed. Subsequently, the test piece was dissolved in 25 ml of dimethylformamide, and the content (mass ppm) of styrene monomer, toluene, xylene, and ethylbenzene was measured by gas chromatography as the total amount (VOC component amount).
The gas chromatography was performed using equipment: gas chromatography GC-9A manufactured by Shimadzu Corporation, column filler: <liquid phase name> PEG-20M, <liquid phase impregnation ratio> 25% by weight, <carrier particle size> 60. / 80 mesh, column material: 3 mm inner diameter, 3000 mm long glass column, carry gas: N2, detector: FID (hydrogen flame ionization detector), quantification: internal standard method.

"Burning rate"
A 340 mm × 102 mm × 12.7 mm rectangular parallelepiped test piece was cut out from the foamed particle molded body. Using this test piece, FMVSS (Federal Motor Vehicle Safety Standards) No. 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.

"Heat-resistant"
A 150 mm × 150 mm × 25 mm rectangular parallelepiped test piece was cut out from the foamed particle molded body. The test piece was further placed at a temperature of 23 ° C. for one day or more, and then the vertical and horizontal dimensions were measured with a caliper. Subsequently, the test piece after the dimension measurement was heated in an oven at a temperature of 80 ° C. for 240 hours, and then allowed to stand at a temperature of 23 ° C. for one day. Subsequently, the dimension of the same location as before heating was measured, and the vertical and horizontal heating dimensional change rates were calculated from the following equations.
Heating dimensional change rate (%) = (molded body dimension before heating at 80 ° C.−dimension of molded body after heating at 80 ° C.) × 100 / (molded body dimension before heating at 80 ° C.)
This measurement was performed on three test pieces to obtain the arithmetic average value of the heating dimensional change rate, and the arithmetic average value was defined as the heating dimensional change rate.
The case where the heating dimensional change rate was within ± 1.0% was evaluated as good heat resistance (◯), and the case where deformation was exceeded was evaluated as poor heat resistance (×). The results are shown in Table 1 below. In the table, the value (%) of the heating dimensional change rate and the evaluation result of the heat resistance are shown.

"50% compressive stress evaluation"
A 50 mm × 50 mm × 25 mm rectangular parallelepiped test piece was cut out from the foamed particle molded body. Using the test piece, a compression test was performed in accordance with JIS K7220 (2006). The compressive stress when the compressive strain was 50% was taken as 50% compressive stress (kPa). And the case where 50% compressive stress was 240 kPa or more was evaluated as favorable ((circle)), and 50% compressive stress evaluated less than 240 kPa as defect (x). The results are shown in Table 1 below. In the table, the value of 50% compressive stress (kPa) and the evaluation result are shown together.

(Examples 2 to 14 and Comparative Examples 1 to 8)
As shown in Tables 1 to 3 below, the type of brominated flame retardant, 50% decomposition temperature (° C.) of brominated flame retardant, 100 mass of composite resin of olefin resin (A) and styrene resin (B) Blending amount (part by mass) of brominated flame retardant with respect to part, kind of (meth) acrylic acid ester component (b1), blending of (meth) acrylic acid ester component (b1) in 100% by mass of styrene resin (B) Amount (mass%), average particle diameter of composite resin particles (d63, mm), aspect ratio of composite resin particles, glass transition temperature Tg (° C.) of styrene-based resin (B), and composite resin foam particles Except that the foaming temperature (° C.) and the molding vapor pressure (MPa, gauge pressure) at the time of in-mold molding were changed, the composite resin foamed particles and the foamed particle molded body were formed by the same method and conditions as in Example 1. Manufactured. About the obtained expanded particle molded object, the amount of VOC components (mass ppm) and a combustion rate (mm / min) were measured similarly to Example 1 above, and further heat resistance (%) and 50% compression stress (kPa) ) Was evaluated. The results are shown in Tables 1-3.

  In Tables 1 to 3, “emerald 3000 (brominated styrene-butadiene block copolymer)” used as a flame retardant is manufactured by Chemtura Corporation, and “CR900 (tris (tribromoneopentyl) phosphate)”. "Is manufactured by Daihachi Chemical Industry Co., Ltd. “FCP-680G (2,2-bis (4- (2,3-dibromopropoxy) -3,5-dibromophenyl) propane)” is manufactured by Suzuhiro Chemical Co., Ltd., and “FCP-65CN” (Bis [3,5-dibromo-4- (2,3-dibromopropoxy) phenyl] sulfone) "is manufactured by Suzuhiro Chemical Co., Ltd. “FR200 (1,2,5,6-tetrabromocyclooctane)” is manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and “SR245 (2,4,6-tris (2,4,6-tris) Bromophenoxy) -1,3,5-triazine) ”is manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

As known from Table 1 and Table 2, it was confirmed that Examples 1 to 14 were all excellent in flame retardancy, heat resistance, and compressive strength.
On the other hand, as is known from Table 3, Comparative Examples 1 to 8 showed insufficient evaluation in at least one of flame retardancy, heat resistance and compressive strength.
In addition, paying attention to the content of the (meth) acrylic acid ester component (b1) in the styrene-based resin (B), Examples 1, 6, 7 and Comparative Example 7, or Example 5 and Comparative Examples 2, 3 When each was compared, even if the compounding quantity of the flame retardant was the same, it was confirmed that the flame retardance improves by containing a suitable amount of (meth) acrylic acid ester.

Claims (3)

Composite resin containing 20 to 50% by mass of olefin resin (A) and 50 to 80% by mass of styrene resin (B) (however, the sum of olefin resin (A) and styrene resin (B)) In the composite resin foamed particles containing a bromine-based flame retardant,
In the styrene resin (B), as a copolymerization component, one or more (meth) selected from a C 1-10 alkyl ester component of methacrylic acid and a C 1-10 alkyl ester component of acrylic acid. An acrylic ester component (b1) is included,
The content of the (meth) acrylic acid ester component (b1) in 100% by mass of the styrene resin (B) is 2 to 12% by mass,
The glass transition temperature (Tg) of the styrenic resin (B) is 100 to 104 ° C.,
Composite resin foamed particles, wherein the brominated flame retardant has a 50% decomposition temperature of 260 to 340 ° C.   2. The composite resin foamed particle according to claim 1, wherein the (meth) acrylic acid ester component (b1) is composed of a methyl methacrylate component and a butyl acrylate component, and the methacrylic acid in the styrene-based resin (B) 100 mass%. A composite resin foamed particle having a methyl acid component content of 2 to 9% by mass and a butyl acrylate component content of 1 to 2.5% by mass.   The composite resin foamed particles according to claim 1 or 2, wherein the compounding amount of the brominated flame retardant is 0.3 to 2 parts by mass with respect to 100 parts by mass of the composite resin. .