JP2014237747A - Composite resin expanded particle and composite resin expanded particle molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite resin expanded particle and a composite resin expanded particle molded body having excellent rigidity and restoration property even when bulk density is made low.SOLUTION: There are provided a composite resin expanded particle 1 containing a composite resin 2 of a straight-chain low-density polyethylene resin (A) and a polystyrene-based resin (B) obtained by impregnating a styrenic monomer into the resin (A) and polymerizing the styrenic monomer, as a base resin, and a composite resin expanded particle molded body manufactured by molding the composite resin expanded particle 1 in a mold. The composite resin 2 contains resin (A) of 20 to 50 mass% and the resin (B) of 50 to 80 wt.%, and shows morphology such that the resin (A) forms a dispersion phase, and the resin (B) forms a continuous phase. The composite resin expanded particle 1 has a bulk density of 5 to 15 kg/mand a closed cell ratio of 90% or more.

Description

  The present invention relates to a composite resin foam particle using a composite resin of a polyethylene resin and a polystyrene resin as a base resin, and a composite resin foam particle molded body using the composite resin foam particle.

  Conventionally, foamed resin particles have been used as fillers such as cushions and mattresses. For these applications, it is common to use expanded polystyrene particles among the expanded resin particles. For example, a cushion body is known in which a stretchable bag body is filled with foamed resin particles made of styrene resin and having an average particle diameter of 0.4 to 1.4 mm (see Patent Document 1). Further, a mat filled with expanded polystyrene particles is known (see Patent Document 2).

JP 2004-223002 A JP-A-63-79760

Since the expanded polystyrene particles have high foaming agent retainability and excellent foamability, they can be reduced in weight by increasing the expansion ratio, and further have excellent rigidity. On the other hand, since the expanded polystyrene particles are inferior in restoring properties, there is a problem that the particles are crushed when used for a long time as a filler such as a cushion or a mattress. In order to suppress the collapse of the expanded polystyrene particles, it is necessary to lower the expansion ratio and increase the bulk density of the expanded polystyrene particles. Actually, expanded polystyrene particles are generally used in an apparent density range of 33 to 25 kg / m ³ . However, even at this bulk density, the effect of suppressing the collapse of the expanded polystyrene particles is insufficient, and further improvement is desired.

  On the other hand, foamed olefin resin particles such as foamed polyethylene particles and foamed polypropylene particles, which are excellent in resilience compared to expanded polystyrene particles, are also known, but olefinic resins have a low foaming agent retention and significantly poor foamability. It is difficult to increase the expansion ratio. Therefore, it is not suitable for uses such as the above-described fillers that require weight reduction. In addition, since the foamed olefin resin particles are inferior in rigidity to the foamed polystyrene particles, it is necessary to increase the bulk density (lower the expansion ratio) in order to obtain sufficient rigidity.

  The present invention has been made in view of such a background, and intends to provide a composite resin foamed particle having excellent rigidity and restorability, and a composite resin foam particle molded body even when the bulk density is lowered. is there.

  In order to solve the above-mentioned problems, the present inventors have prepared a composite resin of a linear low density polyethylene resin and a polystyrene resin obtained by impregnating and polymerizing the linear low density polyethylene resin with a styrene monomer. We have intensively studied the morphology of the composite resin foam particles used as the base resin. As a result, the ethylene resin and styrene resin in the composite resin foam particles exhibit a predetermined morphology, so that the composite resin foam particles maintain a closed cell structure even when the foam density is increased and the bulk density is extremely low. It has been found that it exhibits excellent rigidity and resilience, and the present invention has been completed.

That is, in one embodiment of the present invention, a base resin is a composite resin of a linear low density polyethylene resin (A) and a polystyrene resin (B) obtained by impregnating and polymerizing the resin (A) with a styrene monomer. A composite resin foam particle,
The composite resin contains 20-50% by mass of the resin (A) and 50-80% by weight of the resin (B) (however, the total of the resin (A) and the resin (B) is 100% by mass). And the resin (A) forms a dispersed phase and the resin (B) forms a continuous phase,
The composite resin foamed particle has a bulk density of 5 to 15 kg / m ³ and a closed cell ratio of 90% or more (Claim 1).

Another aspect of the present invention resides in a composite resin foam particle molded body having an apparent density of 5 to 15 kg / m ³ formed by molding the composite resin foam particles in a mold.

The composite resin foamed particles are obtained by impregnating and polymerizing a linear low density polyethylene resin (A) (referred to as “resin (A)” as appropriate) and a linear low density polyethylene resin (A) with a styrene monomer. A composite resin with a polystyrene resin (B) (referred to as “resin (B)” as appropriate) is used as a base resin. The composite resin contains the resin (A) and the resin (B) at a specific blending ratio, the resin (A) forms a dispersed phase, and the resin (B) forms a continuous phase. The composite resin foam particles exhibit a specific morphology. Furthermore, the composite resin foam particles have a low bulk density of 5 to 15 kg / m ³ by increasing the foaming ratio as compared with conventional foam particles having the same resin composition ratio. The closed cell structure can be maintained even at such a high expansion ratio, and the closed cell rate can be 90% or more. Such composite resin foamed particles have excellent rigidity, which is a characteristic of a styrene resin, and excellent restorability, which is a characteristic of a polyethylene resin, at a low bulk density.

  Further, the composite resin foamed particle molded body having the predetermined apparent density formed by molding the composite resin foamed particles in a mold maintains the high rigidity and excellent resilience of the composite resin foamed particles while being lightweight. be able to.

Explanatory drawing which shows typically the cross section of the composite resin foam particle in an Example. The drawing substitute photograph which shows the transmission electron micrograph (magnification 10,000 times) of the center cross section of the expandable composite resin particle in Example 1. The drawing substitute photograph which shows the transmission electron micrograph (magnification 10,000 times) of the center cross section of the composite resin expanded particle in Example 1. FIG. The drawing substitute photograph which shows the transmission electron micrograph (50,000 times magnification) of the resin reservoir part of the center cross section of the composite resin expanded particle in Example 1. FIG. The drawing substitute photograph which shows the transmission electron microscope photograph (magnification 50,000 times) of the cell membrane part in the center cross section of the composite resin foam particle in Example 1. FIG.

Next, a preferred embodiment of the composite resin expanded particle will be described.
The composite resin foamed particle of the present invention comprises a composite resin having a specific ratio of a linear low density polyethylene resin (A) and a polystyrene resin (B) obtained by impregnating and polymerizing the resin (A) with a styrene monomer. By using the composite resin as a base resin and exhibiting a specific morphology and having a specific bulk density and a closed cell ratio, foamed particles having high rigidity and excellent resilience are obtained.

  The composite resin foamed particles are composed of a composite resin having a linear low density polyethylene resin (A) and a polystyrene resin (B) as essential components. In the composite resin, when the resin (B) is too much and the resin (A) is too little, the properties of the linear low density polyethylene resin that is an olefin resin may be impaired. That is, there is a possibility that the restoration property and the like of the composite resin foam particles may be lowered. On the other hand, when the amount of the resin (A) is too much and the amount of the resin (B) is too small, the characteristics of the styrenic resin are impaired, and the rigidity of the composite resin foamed particles may be lowered. Therefore, when the total amount of the resin (A) and the resin (B) is 100% by mass, the composite resin may contain 20-50% by mass of the resin (A) and 50-80% by mass of the resin (B). Preferably, the resin (A) is contained in an amount of 20 to 30% by weight and the resin (B) is contained in an amount of 70 to 80% by weight.

  In the composite resin foamed particles, the composite resin forms a morphology in which the resin (A) forms a dispersed phase and the resin (B) forms a continuous phase. That is, the composite resin has an island sea structure in which the resin (A) has an island structure and the resin (B) has an sea structure. When the composite resin constituting the expanded particles exhibits the island-sea structure, the expanded particles exhibit excellent restoration properties. In addition, the morphology of the resin (A) and the resin (B) in the composite resin can be confirmed in a transmission electron micrograph (for example, a magnification of 10,000 to 50,000 times) of the cross section of the central portion of the composite resin expanded particle.

Moreover, in the said composite resin expanded particle, when a bulk density is too small, there exists a possibility that rigidity may become inadequate. On the other hand, when the bulk density is too large, the weight reduction is insufficient. Therefore, it is preferable that the bulk density of the composite resin foamed particles is ^{5~15kg / m 3, 7kg / m} 3 or more, and more preferably less than 12 kg / m ^3.

  Further, in the composite resin foamed particles, when the closed cell ratio is too small, there is a possibility that rigidity and restorability are insufficient. Therefore, the closed cell ratio of the composite resin expanded particles is preferably 90% or more, and more preferably 93% or more. Such composite resin particles having a high closed cell ratio can be obtained by foaming expandable composite resin particles obtained by performing a dispersion step, a modification step, and an impregnation step described later. In addition, the measuring method of a closed cell rate is demonstrated in the below-mentioned Example.

Further, by polymerizing a styrene monomer in the resin (A), the styrene monomer is graft polymerized to the resin (A), and the resin (A) and the styrene monomer in the composite resin are polymerized. Interfacial tension with (B) decreases. Therefore, it is considered that when such a composite resin is foamed at a high foaming ratio, foamed particles having a high closed cell ratio are obtained.
Further, by foaming particles having such a composite resin as a base resin to an extremely low bulk density, the resin (A) which is a dispersed phase is expanded along the cell membrane (cell membrane). It is considered that the film can be stretched and oriented (in a direction perpendicular to the thickness direction), and as a result, a high closed cell ratio can be maintained even when the foamed particles are compressed.

The composite resin foam particles can be produced by foaming expandable composite resin particles. The expandable composite resin particles are composed of composite resin particles containing the resin (A) and the resin (B) in the predetermined blending ratio, and the particles are impregnated with a foaming agent.
The morphology of the composite resin in the foamable composite resin particles is such that even if the resin (A) and the resin (B) are in a co-continuous phase (sea-sea structure), the resin (A) is in a dispersed phase (island structure) ( Even if B) has an island-sea structure in which the continuous phase (sea structure) is formed, or if the resin (A) has a continuous phase (sea structure) and the resin (B) has a dispersed phase (island structure), Good. Preferably, the morphology of the composite resin in the expandable composite resin particles is such that the resin (A) and the resin (B) are in a co-continuous phase (sea-sea structure). If the morphology of the composite resin in the foamable composite resin particles forms a sea-sea structure, it is possible to effectively suppress the destruction of the bubble film during foaming, so that it is possible to obtain foamed particles having a high closed cell ratio It is considered possible.
The morphology of the composite resin in the expandable composite resin particles can be confirmed in a transmission electron micrograph (for example, 10,000 times magnification) of the cross section of the center of the expandable composite resin particles.

In the transmission electron micrograph of the center cross section of the expandable composite resin particle, the total length of the interface (μm) between the resin (A) and the resin (B) is the area of the region where the interface is observed. The interface ratio obtained by dividing by (μm ² ) is preferably 6 μm / μm ² or less. In this case, the foamability in the foamable composite resin particles is improved.

The interface ratio μm / μm ² can be determined by the following method.
Specifically, from a transmission electron micrograph (preferably at a magnification of 10,000 times) of the cross section of the center of the expandable composite resin particles (the center of the cross section that divides the expandable composite resin particles into two equal parts) The interface ratio is measured for the phase of the resin (A) and the resin (B) present in the region. The interface ratio is the phase of the resin (A) and the resin (B) observed in the transmission electron micrograph of the central cross section of the expandable composite resin particles (the central portion of the cross section that bisects the expandable composite resin particles). The total length of the interface (μm) with the other phase is divided by the area (μm ² ) of the entire region where the interface is observed.
The above operation is performed on five randomly selected expandable composite resin particles, and the average can be defined as the interface ratio (μm / μm ² ).

  The xylene-insoluble matter in the composite resin is preferably 30% by mass or less (claim 2). In this case, the expansion ratio is increased to facilitate the production of the composite resin foam particles having a low bulk density as described above, and the composite resin foam particles are excellent in resilience and rigidity. The xylene-insoluble content (gel amount) is more preferably 25% by mass or less, and further preferably 20% by mass or less.

  When the average particle diameter of the composite resin foamed particles is too small, the foamed particles are easily charged. For example, when used for cushioning, there is a possibility that workability when putting into a bag is deteriorated. On the other hand, when the average particle diameter is too large, the foamed particles may be deteriorated in the touch when used for cushioning, for example, and when used for in-mold molding, There is a possibility that the filling property is lowered. Therefore, the average particle diameter of the composite resin foamed particles is preferably 4 to 8 mm (Claim 3), and more preferably 4 to 7 mm.

The density of the linear low-density polyethylene resin (A) is usually 0.88 to 0.945 g / cm ³ , preferably 0.88 to 0.94 g / cm ³ , more preferably 0. It is good that it is .88-0.93 g / cm < ³ >. The melt mass flow rate (MFR: 190 ° C., 2.16 kgf) of the resin (A) is 0.5 to 4.0 g / 10 from the viewpoint of foamability of the foamable composite resin particles used for producing the composite resin foam particles. Minute is preferable, and 1.0 to 3.0 g / 10 minutes is more preferable. More preferably, from the viewpoint of foamability, the resin (A) is preferably a linear low density polyethylene polymerized with a metallocene catalyst.

  The polystyrene resin (B) is a resin mainly composed of a styrene monomer, and is a polymer of a styrene monomer, or a copolymer of a styrene monomer and a monomer copolymerizable with the styrene monomer. Coalescence is mentioned. The content of the styrene monomer component in 100% by mass of the polystyrene resin (B) is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 80% by mass.

  Styrene monomers include styrene, α-methyl styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-ethyl styrene, 2,4-dimethyl styrene, p-methoxy styrene, pn-butyl. Examples thereof include styrene, pt-butylstyrene, 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.

  Monomers that can be copolymerized with styrenic monomers include acrylic acid esters, methacrylic acid esters, vinyl compounds containing hydroxyl groups, vinyl compounds containing nitrile groups, vinyl acid organic compounds, olefin compounds, diene compounds, and halogenated compounds. Examples of the vinyl monomer include vinyl compounds, vinylidene halide compounds, and maleimide compounds.

Specific examples of the acrylate ester include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate.
Specific examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate.
Specific examples of the vinyl compound containing a hydroxyl group include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.
Specific examples of the vinyl compound containing a nitrile group include acrylonitrile and methacrylonitrile.

Specific examples of the organic acid vinyl compound include vinyl acetate and vinyl propionate.
Specific examples of the olefin compound include ethylene, propylene, 1-butene, and 2-butene.
Specific examples of the diene compound include butadiene, isoprene, chloroprene and the like.
Specific examples of the vinyl halide compound include vinyl chloride and vinyl bromide.
Specific examples of the vinylidene halide compound include vinylidene chloride.
Examples of maleimide compounds include N-phenylmaleimide and N-methylmaleimide.

  Specific examples of the polystyrene resin (B) include polystyrene, rubber-modified polystyrene, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, acrylonitrile-ethylenepropylene rubber-styrene copolymer, and the like. In the composite resin, the polystyrene resin (B) may be present alone or in two or more kinds.

In addition, from the viewpoint that the foamability of the foamable composite resin particles used for the production of the composite resin foam particles can be improved, the resin (B) includes a copolymer of a styrene monomer and an acrylic monomer. preferable. More preferred is a copolymer of styrene and butyl acrylate.
Further, when using a copolymer of styrene and butyl acrylate, the content of the butyl acrylate component in the composite resin is preferably 0.5 to 10% by mass with respect to the entire composite resin, It is more preferably 1 to 8% by mass, and further preferably 2 to 5% by mass.

Moreover, it is preferable that the weight average molecular weights of the said resin (B) are 100,000-300,000.
In this case, the foamed particles are excellent in resilience and rigidity. More preferably, the weight average molecular weight of the resin (B) is 150,000 to 250,000.
The glass transition temperature (Tg) of the resin (B) is preferably 75 ° C. to 105 ° C., and more preferably the glass transition temperature (Tg) of the resin (B) is 80 ° C. to 95 ° C.

In addition to the resin (A) and the resin (B), the composite resin can contain an ethylene-vinyl acetate copolymer (C) (hereinafter referred to as “resin (C)” as appropriate). The content of the resin (C) in the composite resin is preferably 5% by mass or less (however, the total amount of the resin (A), the resin (B), and the resin (C) is 100% by mass). The content of C) may be 0% by mass, and if the content of the resin (C) exceeds 5% by mass, the excellent restorability cannot be expressed. In view of this, the foamability of the composite resin particles may be reduced, making it impossible to obtain composite resin foam particles having a desired bulk density of 5 to 15 kg / m ³ and a high closed cell ratio. The content of the resin (C) in is preferably 2% by mass or less Preferably, the polyolefin resin in the composite resin is more preferably composed of only the resin (A).

Moreover, in order to set it as the said interface ratio, the said composite resin is an acrylonitrile styrene copolymer and / or (meth) acrylic acid with respect to 100 mass parts of total mass of resin (A) and resin (B). It is preferable to contain 1-10 mass parts resin (D) which consists of an alkylester styrene copolymer.
In the foamable composite resin particles used for the production of the composite resin foam particles, the resin (D) (hereinafter referred to as “dispersion diameter expanding agent (D)” as appropriate) is dispersed in the phase of the resin (B). Preferably it is.
The content of the dispersion diameter-enlarging agent (D) with respect to 100 parts by mass of the total amount of the resin (A) and the resin (B) is more preferably 1 to 7 parts by mass, and further preferably 5 parts by mass or less. preferable.

  The dispersion diameter expanding agent (D) is composed of an acrylonitrile-styrene copolymer and / or a (meth) acrylic acid alkyl ester-styrene copolymer. Preferably, it consists of an acrylonitrile-styrene copolymer. The amount of acrylonitrile component in the acrylonitrile-styrene copolymer is preferably 20 to 40% by mass.

  The melt mass flow rate (MFR (200 ° C., 5 kgf)) of the dispersion diameter expanding agent (D) is preferably 1 g / 10 min to 20 g / 10 min, more preferably 2.5 g / 10 min to 15 g / 10 min. preferable.

The MFR (200 ° C., 5 kgf) of the dispersion diameter expanding agent (D) can be measured as follows.
First, using a melt indexer (for example, model L203 manufactured by Takara Kogyo Co., Ltd.), a 5000 g load was applied to the dispersion diameter expanding agent at a temperature of 200 ° C., and the die (inner diameter 2.09 mm, length 8.00 mm) was used. Extrude the dispersion diameter expanding agent. And the weight of the said dispersion diameter expansion agent which flowed out from die | dye in 10 minutes is measured, and let this be MFR (200 degreeC, 5 kgf).

  Further, the weight average molecular weight of the dispersion diameter expanding agent (D) is preferably 50,000 to 150,000, and more preferably 60,000 to 120,000.

  In the foamable composite resin particles, the dispersed phase composed of the dispersion diameter expanding agent (D) dispersed in the phase of the resin (B) is, for example, shown in FIG. 2 in the internal cross-sectional observation of the foamable composite resin particles by a transmission microscope. As shown, it can be confirmed as a phase dispersed in the form of salami in the continuous phase of the styrene resin (B).

The foamable composite resin particles contain a physical foaming agent. As the physical foaming agent, a volatile organic compound having a boiling point of 80 ° C. or less is preferable.
Examples of such volatile organic compounds include saturated hydrocarbon compounds, lower alcohols, ether compounds, and the like.

As the saturated hydrocarbon compound, for example, methane, ethane, propane, n-butane, isobutane, cyclobutane, n-pentane, isopentane, neopentane, cyclopentane, n-hexane, cyclohexane and the like can be used.
As the lower alcohol, for example, methanol, ethanol and the like can be used.
As the ether compound, for example, dimethyl ether, diethyl ether or the like can be used.
These physical foaming agents can be used alone or in a mixture of two or more.

Moreover, it is preferable that a physical foaming agent consists of 30-100 mass% of isobutanes, and 0-70 mass% of other C4-C6 hydrocarbons. However, the total amount of isobutane and other hydrocarbons having 4 to 6 carbon atoms is 100% by mass. In this case, the foamable composite resin particles can be sufficiently impregnated and held with a physical foaming agent.
Examples of the other hydrocarbons having 4 to 6 carbon atoms include normal butane, normal pentane, isopentane, neopentane, normal hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, and 2,3-dimethyl. Examples include butane, cyclobutane, cyclopentane, and cyclohexane.

By using a hydrocarbon compound having 4 to 6 carbon atoms as the foaming agent, the foaming agent retention of the foamable composite resin particles can be improved and the foamability can be improved.
Moreover, when the ratio which isobutane accounts in a physical foaming agent is 30 mass% or more, the foaming agent holding | maintenance property of an expandable composite resin particle can be improved more. More preferably, the proportion of isobutane in the physical foaming agent is 50% by mass or more.

  Moreover, it is preferable that content of the physical 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. More preferably, the content of the physical foaming agent is 4 to 9% by mass.

Next, a preferred embodiment of the method for producing expandable composite resin particles will be described.
The expandable composite resin particles are obtained by suspending an olefin-based resin core particle (hereinafter referred to as “core particle” as appropriate) containing the linear low-density polyethylene resin (A) in an aqueous medium. It can be produced by adding a styrene monomer, impregnating the core particles with the styrene monomer, and polymerizing the styrene monomer. The addition amount of the styrene monomer can be 100 to 400 parts by mass with respect to 100 parts by mass of the core particles. When the core particles are impregnated with a styrene monomer and polymerized, the styrene monomer can be added all at once. From the viewpoint of making the base resin of the expanded particles into a specific morphology, the amount of styrenic monomer used is divided into, for example, a first monomer and a second monomer, as in the dispersion step and the modification step described below, and these It is preferable to add the monomers at different timings.

The expandable composite resin particles are preferably 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 obtained by suspending the core particles containing the resin (A) in an aqueous medium, and the suspension is mixed with the above-described suspension. The first monomer is dispersed. The first monomer is composed of a styrene monomer or a mixed monomer of a styrene monomer and a monomer copolymerizable therewith.
In the reforming step, the second monomer is continuously added to the suspension heated to a predetermined temperature over a predetermined addition time, and the core particles are impregnated with the styrene monomer and polymerized. The second monomer is composed of a styrene monomer or a mixed monomer of a styrene monomer and a monomer copolymerizable therewith.
In the impregnation step, expandable composite resin particles are obtained by impregnating the resin particles with a physical foaming agent during and / or after polymerization of the styrene monomer.

  Expandable composite resin particles can be obtained by performing the dispersion step, the modification step, and the impregnation step. And the said composite resin foaming particle can be obtained by making a foamable composite resin particle foam.

Hereinafter, a preferred embodiment in each of the above steps will be described.
In the dispersion step, a suspension is prepared by suspending the core particles containing the resin (A) in an aqueous medium containing, for example, a suspending agent, a surfactant, a water-soluble polymerization inhibitor and the like. be able to. In the dispersion step, the first monomer and the polymerization initiator are added to the suspension. The first monomer is composed of a styrene monomer or a mixed monomer of a styrene monomer and a monomer copolymerizable with the styrene monomer.

The core particles contain the resin (A) as an olefin resin.
Moreover, it is preferable that melting | fusing point (Tm) of the olefin resin in a core particle is 95 to 115 degreeC. In this case, the olefin 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. More preferably, the melting point (Tm) of the olefin resin is 100 to 110 ° C. The melting point can be measured by differential scanning calorimetry (DSC).

Moreover, it is preferable that the crystallinity degree of the olefin resin (A) in a core particle is 20 to 35%, and it is more preferable that it is 20 to 30%.
In this case, the foamability of the foamable composite resin particles can be further improved. The reason is considered as follows. That is, when the crystallinity of the resin (A) is high, the gas molecules (foaming agent) are difficult to spread the polymer chain of the resin (A), and the permeability of the foaming agent is lowered. It can be inferred that the retention will be high. The crystallinity can be measured by differential scanning calorimetry (DSC).

Moreover, when using the said dispersion diameter expansion agent (D), the resin particle containing resin (A) and a dispersion diameter expansion agent (D) can be used as a core particle. In this case, after performing the dispersion step, the modification step, and the impregnation step, it is possible to obtain expandable composite resin particles in which the dispersed phase composed of the dispersion diameter expanding agent (D) is dispersed in the phase of the resin (B). it can.
Further, the core particles can contain additives such as a bubble adjusting agent, a pigment, a slip agent, an antistatic agent, and a flame retardant, as long as the effects of the present invention are not impaired.

  The core particles can be produced by blending the resin (A) and a dispersion diameter expanding agent (D) 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.

Further, in order to improve the foaming property and to obtain more reliably composite resin foamed particles exhibiting the excellent resilience characteristic of the olefin resin (resin (A)), the dispersion diameter expanding agent (D) is used as a core. It is preferable to uniformly disperse the particles in the resin (A). 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.
10-1000 nm is preferable and, as for the dispersion diameter of the dispersion diameter expansion agent currently disperse | distributed to resin (A) in a core particle, 10-500 nm is more preferable.

Moreover, in order to adjust the bubble size of the composite resin foam 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.
When an organic substance is used as the bubble regulator, it is preferable that the blending amount of the organic substance (bubble regulator) is 0.01 to 2 parts by mass with respect to 100 parts by mass of the resin for the core particles.
Moreover, when using an inorganic substance as a bubble regulator, it is preferable that the compounding quantity of an inorganic substance (bubble regulator) shall be 0.1-5 mass parts with respect to 100 mass parts of resin for nucleus particles.
When the amount of the bubble regulator added is too small, there is a possibility that a sufficient effect of reducing the bubble size cannot be obtained. On the other hand, when the addition amount is too large, the bubble size becomes extremely small, the bubbles of the expanded particles are destroyed and contracted at the time of foaming, and it may be difficult to obtain a high expansion ratio.

  The core particles can be refined by melt-kneading with an extruder, and then 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. In the case of using an extruder, the particle diameter is adjusted by, for example, extruding a resin from a hole having a diameter substantially the same as the desired particle diameter, and changing the cut speed to a length within the desired particle diameter range. This can be done by cutting it.

The particle diameter of the core particles is preferably 0.1 to 3.0 mm, more preferably 0.3 to 1.5 mm. If the particle size is too small, the retention of the foaming agent may be reduced. On the other hand, when the particle size is too large, the particle size of the expanded foamed particles is also increased, and the average particle size of the composite resin expanded particles satisfying a predetermined bulk density of 5 to 15 kg / m ³ is set to 4 to 4 above. There is a possibility that the preferable range of 8 mm cannot be obtained.

The particle diameter of the core particle can be measured, for example, 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. In addition, 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.

  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. Therefore, the amount of the suspending agent used is 0.05 to 10 in terms of 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). Part by mass is preferred. More preferably, 0.3-5 mass parts is good.

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

As the anionic surfactant, for example, sodium alkyl sulfonate, sodium alkylbenzene sulfonate, sodium lauryl sulfate, sodium α-olefin sulfonate, sodium dodecylphenyl ether disulfonate, and the like can be used.
Examples of nonionic surfactants that can be used include polyoxyethylene dodecyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, and the like.

As the cationic surfactant, alkylamine salts such as coconut amine acetate and stearylamine acetate can be used. Further, 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.
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, a water-soluble polymerization inhibitor can be added 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 styrene monomer near the surface of the core particles being absorbed by the core particles, and fine droplets of the styrenic monomer in the aqueous medium not impregnated in the core particles. Polymerization of the 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 is 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). More preferably, 0.005-0.06 mass part is good.

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, crosslinking may occur together 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.
In the polymerization process of the styrenic monomer, the olefin contained in the core particle may be cross-linked. Therefore, in this specification, “polymerization” may include “cross-linking”.

  As the polymerization initiator, those used in the suspension polymerization method of a styrene monomer, for example, a polymerization initiator that is soluble in a vinyl 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-butylperoxyisopropyl carbonate, t- Organic peroxides such as amylperoxy-2-ethylhexyl carbonate, hexylperoxy-2-ethylhexyl carbonate, and lauroyl peroxide, and azo compounds such as azobisisobutyronitrile can be used. These polymerization initiators can be used alone or in combination of two or more.

The polymerization initiator may be added after being dissolved in a solvent and impregnated into the core particles.
Examples of the solvent that dissolves 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 crosslinking agent 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 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.
The bubble regulator is preferably used in an amount of 0.01 to 2 parts by weight with respect to 100 parts by weight 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.
Examples of the plasticizer include fatty acid esters such as glycerin tristearate, glycerin trioctate, glycerin trilaurate, sorbitan tristearate, sorbitan monostearate, and butyl stearate. Further, acetylated monoglycerides such as glycerin diacetomonolaurate, fats and oils such as hardened beef tallow and hardened castor oil, and organic compounds such as cyclohexane and liquid paraffin can be used.
As the oil-soluble polymerization inhibitor, for example, para-t-butylcatechol, hydroquinone, benzoquinone and the like can be used.

  The blending of the core particles and the styrene monomer is preferably adjusted so that the blending ratio of the styrene resin to 100 parts by weight of the olefin resin contained in the core particles is 100 to 400 parts by weight. It is more preferable to adjust the styrene resin to 230 to 400 parts by mass with respect to 100 parts by mass of the olefin resin.

  Next, in the reforming step, heating of the suspension after the dispersing step is started, and the second monomer is continuously added to the suspension that has reached a predetermined temperature over a predetermined addition time. . As a result, the core particles can be impregnated with the styrene monomer and polymerized. The second monomer is composed of a styrene monomer or a mixed monomer of a styrene monomer and a monomer copolymerizable therewith. When the melting point of the olefin resin in the core particle is Tm, the addition temperature of the second monomer into the suspension is preferably (Tm-30) to (Tm + 20) ° C. When the addition temperature of the second monomer deviates from the above temperature range of (Tm-30) to (Tm + 20) ° C., there is a possibility that the suspension system becomes unstable and a lump of resin is generated. The addition temperature of the second monomer is more preferably Tm-25 to Tm + 10 (° C.), and further preferably Tm-25 to Tm (° C.).

Further, the addition amount of the core particles in the dispersion step is D (parts by mass), the addition amount of the first monomer with respect to 100 parts by mass (D = 100) of the core particles in the dispersion step is E (parts by mass), and the addition amount in the reforming step. When the addition amount of 2 monomers is F (parts by mass) and the addition time of the second monomer in the reforming step is G (h), the above formulas (1) and (2) are satisfied. It is preferable to perform a dispersion | distribution process and the said modification | reformation process.
1 ≦ E / F ≦ 8 Formula (1)
F / (D × G) ≦ 1 Formula (2)

If E / F, which is the blending ratio (mass ratio) of the first monomer added in the dispersion step and the second monomer added in the modification step, is less than 1, the shape of the resin particles may become flat after polymerization. is there.
On the other hand, if E / F exceeds 8, the styrene monomer cannot be sufficiently impregnated into the core particles, and the suspension system may become unstable and a resin mass may be generated. In this case, when the dispersion diameter expanding agent (D) is included, the dispersion diameter of the dispersion phase of the dispersion diameter expanding agent (D) dispersed in the phase of the resin (B) may be reduced. Therefore, there is a possibility that the effect of improving the retention of the above-mentioned foaming agent by adding the dispersion diameter expanding agent cannot be sufficiently obtained. More preferably, 1 ≦ E / F ≦ 4, and even more preferably 1.5 ≦ E / F ≦ 3.

  When F / (D × G) exceeds 1, the core particles cannot be sufficiently impregnated with the styrenic monomer, and the suspension system may be destabilized to generate a lump of resin. is there. More preferably, F / (D × G) ≦ 0.5 is preferable, and F / (D × G) ≦ 0.3 is even more preferable.

  Moreover, although the polymerization temperature in a modification process 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.

Further, the melting point (Tm) of the olefin resin in the core particles and the glass transition temperature (Tg) of the polystyrene resin (B) produced by the polymerization in the modification step satisfy −5 ≦ Tm−Tg ≦ 20 (° C.). It is preferable to satisfy the relationship.
In this case, the olefin resin and the polystyrene resin (B) can be easily impregnated with the foaming agent evenly during the production of the expandable composite resin particles, and the expandability of the expandable composite resin particles can be further improved. . More preferably, −5 ≦ Tm−Tg ≦ 15 (° C.), and further preferably −5 ≦ Tm-Tg ≦ 10 (° C.).

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

When the glass transition temperature of the polystyrene resin is Tg (° C.), the impregnation temperature of the physical foaming agent is preferably in the range of Tg−10 to Tg + 40 ° C., and Tg−5 (° C.) to Tg + 25 (° C.). More preferably within the range.
When the impregnation temperature of the physical foaming agent is less than Tg-10 ° C, the initial foaming agent content increases, and the foamable composite resin particles are foamed after being stored or transported in an atmosphere at room temperature (25 ° C) or higher. In such a case, the retention of the foaming agent may be reduced and the foamability may be reduced. Further, in this case, plasticization becomes insufficient, and a load is applied when the foamable composite resin particles are foamed, and there is a possibility that the closed cell ratio and the restorability are lowered in the composite resin foam particles obtained after foaming. This is because the olefin resin phase that is easily impregnated with the physical foaming agent is impregnated with the physical foaming agent, but the styrene resin phase is not sufficiently impregnated with the physical foaming agent, and the physical foaming agent is easily dissipated. It is presumed that the physical foaming agent escapes from the resin 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.

In addition, after the impregnation with the physical foaming agent, the foamable composite resin particles can be dehydrated and dried, and the surface of the foamable composite resin particles can be coated on the surface 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 morphology of the composite resin in the foamable composite resin particles adjusts the amount of styrene monomer added to the amount of olefin resin in the core particles, the polymerization temperature, the amount of polymerization initiator, the addition rate of styrene monomer added in the modification process, etc. Can be controlled.

  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.

Foaming of the expandable composite resin particles can be performed in one stage until a composite resin foam particle having a target bulk density of, for example, 5 to 15 kg / m ³ is obtained, but can also be performed in multiple stages. In the case of foaming in multiple stages, foamable composite resin particles are foamed to produce foam particles (primary foam particles) having a bulk density larger than the target bulk density, and the foam particles are further foamed one or more times. As a result, it is possible to obtain composite resin foamed particles having a desired bulk density.

Preferably, the composite resin foamed particles are produced by foaming the foamable composite resin particles to produce primary foamed particles having a bulk density of 20 to 50 kg / m ³ , and the primary foamed particles are further foamed one or more times. (Claim 4).
In this case, the foamed particles are particularly excellent in resilience. The primary foamed particles can be obtained by foaming the foamable composite resin particles (primary foaming). By setting the bulk density of the primary foamed particles to 20 to 50 kg / m ³ as described above, it is easy to obtain foamed particles having a high closed cell ratio, and by further foaming the foamed particles, Thus, the resin (A) can be more easily stretched and oriented. From this viewpoint, it is more preferably 20 to ³⁰ kg / m ³ . Further foaming of the primary foamed particles can be performed once (secondary foaming) or two or more times (third foaming or more). When the foamed particles are further foamed, it is preferable to increase the air partial pressure in the bubbles by aging the foamed particles after foaming for one day or more or pressurizing the foamed particles.

It is preferable that the composite resin foam particles are used as a cushion or a mattress by filling the composite resin foam particles into a bag.
In this case, the above-described characteristics of the composite resin foamed particles that are lightweight and have both rigidity and resilience can be sufficiently utilized. The composite resin foamed particles can be used not only for cushioning but also for in-mold molding. In this case as well, high rigidity and excellent resilience can be maintained while being lightweight.

The composite resin foamed particle molded body is filled with the composite resin foam particles in a mold in which a cavity having a desired shape is formed, a heating medium such as steam is introduced into the mold, and the composite resin foam particles are bonded together. It can be manufactured by fusing. From the viewpoint of combining excellent lightweight properties, rigidity, and restoring properties, the apparent density of the composite resin foamed particle molded body is preferably 5 to 15 kg / m ³ . The apparent density of the composite resin foam particle molded body can be calculated by obtaining the volume from the outer dimensions of the molded body, then measuring the mass of the molded body, and dividing the mass by the volume.

Next, examples and comparative examples of the composite resin foam particles will be described.
Example 1
As shown in FIG. 1, the composite resin foamed particle 1 of this example includes a linear low-density polyethylene resin (A), a polystyrene resin (B) formed by impregnating and polymerizing the resin (A) with a styrene monomer. The composite resin 2 is used as a base resin and has a large number of bubbles 3 inside. The composite resin 2 contains the resin (A) and the resin (B) at a predetermined blending ratio. In the composite resin foamed particle 1, the composite resin 2 shows a morphology in which the resin (A) forms the dispersed phase 21 and the resin (B) forms a continuous phase (see FIGS. 3 to 5). Moreover, the composite resin foamed particle 1 of this example has a low bulk density of 11 kg / m ^{3 and} a high closed cell ratio of 96%.

Hereinafter, the manufacturing method of the composite resin expanded particle of this example is demonstrated.
In the production of the composite resin foam particles, first, core particles are manufactured, and expandable composite resin particles are manufactured using the core particles. Next, the foamable composite resin particles are foamed to produce the desired composite resin foam particles. Details will be described below.

(1) Production of core particles First, 20 kg of linear low density polyethylene polymerized by a metallocene catalyst (“Nipolon Z 9P51A” manufactured by Tosoh Corporation) and an acrylonitrile-styrene copolymer (electrochemical industry as a dispersion diameter expanding agent) "AS-XGS,""AS-XGS, weight average molecular weight: 109000, acrylonitrile component amount: 28 mass%, MFR (200 ° C, 5 kgf): 2.8 g / 10 min) 1 kg of Henschel mixer (Mitsui Miike Chemical Co., Ltd.) Made in Model FM-75E) and mixed for 5 minutes.The resin mixture of the composition used here is Resin a, and MFR (190 ° C., 2.16 kgf) of Resin a is shown in Table 1 below.
Next, this resin mixture was melt-kneaded at a temperature of 230 to 250 ° C. with an extruder (manufactured by Icage Co., Ltd .; model MS50-28; 50 mmφ single screw extruder, Maddock type screw), and 0.4 by an underwater cutting method. It cut | disconnected to -0.6 mg / piece (average 0.5 mg / piece), and obtained the core particle (olefin resin particle) which consists of olefin resin.

(2) Production of expandable composite resin particles 1000 g of deionized water was added to an autoclave with a stirrer and a volume of 3 L, and 6.0 g of sodium pyrophosphate was added, followed by powdered magnesium nitrate and 6 water. 12.9 g of the Japanese product was added, and the mixture was stirred at room temperature for 30 minutes. This produced the magnesium pyrophosphate slurry as a suspending agent.
Next, 1.5 g of sodium lauryl sulfonate (10% by mass aqueous solution) as a surfactant, 0.5 g of sodium nitrite as a water-soluble polymerization inhibitor, and 125 g of core particles were added to this suspension.

Next, 1.29 g of benzoyl peroxide (“Nyper BW” manufactured by NOF Corporation, water-diluted powder product) as a polymerization initiator and 2.58 g of t-butylperoxy-2-ethylhexyl monocarbonate (NOF Corporation) “Perbutyl E”) and 0.86 g of dicumyl peroxide (“Park Mill D” manufactured by NOF Corporation) as a cross-linking agent are dissolved in 245 g of styrene and 15 g of butyl acrylate as monomers, and the solution is stirred. While stirring at 500 rpm, it was put into the suspension in the autoclave.
Next, after the inside of the autoclave was purged with nitrogen, the temperature increase was started and the temperature was raised to 88 ° C. over 1 hour 30 minutes. After the temperature increase, this temperature was maintained at 88 ° C. for 30 minutes, and then the stirring speed was lowered to 450 rpm. The temperature was cooled from 88 ° C. to 80 ° C. over 30 minutes, and the polymerization temperature was maintained at 80 ° C. for 8 hours. When the temperature reached 80 ° C., 115 g of styrene as a monomer was added into the autoclave over 5 hours.

Next, the temperature was raised to 125 ° C. over 4 hours, and the temperature was maintained at 125 ° C. for 2 hours and 30 minutes.
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 reached 90 ° C., 20 g of cyclohexane and 65 g of butane (a mixture of normal butane of about 20% by volume and isobutane of about 80% by volume) were added to the autoclave over about 1 hour as a blowing agent. 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. Thereafter, dehydration and washing were performed with a centrifugal separator, and water adhering to the surface was removed with an airflow drying device, thereby obtaining expandable composite resin particles having an average particle diameter (d ₆₃ ) of about 1.4 mm.
The expandable composite resin particles obtained in this example are a composite resin of a linear low density polyethylene resin (A) and a polystyrene resin (B) obtained by impregnating and polymerizing the resin (A) with a styrene monomer. Is a base resin and contains a foaming agent. FIG. 2 shows a transmission electron micrograph (magnification of 10,000 times) of the cross section of the center portion of the expandable composite resin particles. As the transmission electron microscope, JEM1010 manufactured by JEOL Ltd. was used. In FIG. 2, the dark black part is the phase of the linear low-density polyethylene resin (A), and the light gray part is the phase of the polystyrene resin (B). As can be seen from the figure, in the expandable composite resin particles of this example, the composite resin has a sea-sea structure in which the resin (A) and the resin (B) are in a co-continuous phase.

  The obtained foamable composite resin particles are sieved to take out particles having a diameter of 0.7 to 2.0 mm, and N, N-bis (2- Hydroxyethyl) alkylamine (0.008 parts by mass) was added, and the mixture was further coated with a mixture of 0.12 parts by mass of zinc stearate, 0.04 parts by mass of glycerol monostearate, and 0.04 parts by mass of glycerol distearate. About the obtained foamable composite resin particles, the mass ratio (PE of linear low density polyethylene resin (PE), polystyrene resin (PS) and other ethylene resin (ethylene-vinyl acetate copolymer (EVA)) (PE / PS / EVA) is shown in Table 2 below.

  Next, for the foamable composite resin particles obtained as described above, the content of the physical foaming agent, the retention rate of the physical foaming agent, the foamability, the morphology, the interface ratio between PE and PS, the gel amount, the polystyrene series The glass transition temperature (Tg) of the resin, the weight average molecular weight (Mw) of the polystyrene resin, the melting point (Tm) of the olefin resin particles, the crystallinity of the olefin resin, and the average particle diameter of the expandable composite resin particles are as follows: I investigated as follows. The results are shown in Table 2 below.

"Physical foaming agent content"
1 g of the foamable composite resin particles was weighed and heated at 195 ° C. with a “compact halogen moisture meter HB-43S” manufactured by METTLER TOLEDO. And the content of the physical foaming agent was calculated | required by measuring the amount of weight changes before and behind a heating. Specifically, the content (mass%) of the physical foaming agent in the foamed composite resin particles was calculated based on the following formula.
Content of physical foaming agent = (weight before heating−weight after heating) / weight before heating × 100

"Retention rate of physical foaming agent"
First, the content (mass%) of the foaming agent was measured from the weight change before and after heating as described above. This is S ₀ .
The foamable composite resin particles were allowed to stand for 24 hours in an open state at a temperature of 23 ° C., and then the content (mass%) of the physical foaming agent was measured by the method described above. This is referred to as S _1.
Next, the physical foaming agent content (S ₁ ) after being allowed to stand at a temperature of 23 ° C. for 24 hours was divided by the initial physical foaming agent content (S ₀ ), and expressed as a percentage. This is the retention rate (%) of the physical foaming agent. That is, the retention rate of the physical foaming agent was calculated from the formula: retention rate = S ₁ / S ₀ × 100.

"Foaming"
The foamable composite resin particles were left in an open state at a temperature of 23 ° C. for 24 hours to dissipate the physical foaming agent. Next, the foamable composite resin particles from which the physical foaming agent was dissipated were heated at a heating steam temperature of 107 ° C. for 270 seconds and dried at a temperature of 23 ° C. for 24 hours. And the bulk density (kg / m < ³ >) of the foamed particle after drying was measured, and this was made foamable. In addition, the bulk density (kg / m ³ ) of the expanded particles is prepared by preparing a 1 L graduated cylinder, filling the composite resin expanded particles up to the 1 L mark in an empty graduated cylinder, and adding the composite resin expanded particles per 1 L. It calculated | required by measuring a weight (g).

“Morphology and the interface ratio between PE and PS”
A sample for observation was cut out from the center of the expandable composite resin particles. The observation sample was embedded in an epoxy resin and stained with ruthenium tetroxide, and then an ultrathin section was prepared with an ultramicrotome. This ultrathin slice was placed on a grid, and the morphology of the cross section at the center of the foamable composite resin particle was observed with a transmission electron microscope (JEM1010 manufactured by JEOL Ltd.) at a magnification of 10,000 times, and a cross-sectional photograph (TEM photograph) was taken. . The result is shown in FIG.
From the cross-sectional photograph, the morphology of the phase of the linear low density polyethylene resin and the phase of the polystyrene resin in the expandable composite resin particles was visually observed.
Next, a cross-sectional photograph was captured with a scanner (600 dpi / color photograph). The captured image is analyzed by image processing software (NanoHunter NS2K-Pro of Nano System Co., Ltd.), and the central cross section of the expandable composite resin particle (the central portion of the cross section that divides the expandable composite resin particle into two equal parts) From the transmission electron micrograph (magnification of 10,000 times is preferable), the interface ratio was measured for all phases of the linear low-density polyethylene resin (PE) and polystyrene-based resin (PS) on the photo. The interfacial ratio is a linear low density polyethylene resin (PE) observed in a transmission electron micrograph of the central cross section of the expandable composite resin particles (the central portion of the cross section that bisects the expandable composite resin particles). ) And the polystyrene-based resin (PS).
The above operation was performed on five randomly selected foamable composite resin particles, and the total length of the interface (μm) between PE and PS existing in five or more micrographs was observed. The value obtained by dividing by the area (μm ² ) is defined as the interface ratio (μm / μm ² ) between PE and PS.
In addition, when calculating | requiring the interface ratio of PE and PS with image processing software, it carried out on the processing conditions of following (1)-(8).
(1) Monochrome conversion → (2) Smoothing filter (3 × 3, 8 neighborhoods, processing count = 1) → (3) Binarization with NS method (brighter than background, sharpness = 100, sensitivity = 5, noise removal) , Density range = 0 to 255) → (4) filling in hole → (5) shrinkage (near 8; number of processing = 3) → (6) selecting only image based on feature quantity (area) (0.01 to ∞ μm ² , 8 (Near) → (7) Expansion that is not adjacent to the neighbor (8 vicinity, number of treatments = 3) → (8) Circumference (interface length) measurement

"Xylene insoluble matter (gel amount)"
First, 1.0 g of expandable composite resin particles were placed in a 150 mesh wire mesh bag. Next, about 200 ml of xylene was placed in a 200 ml round flask, and a sample of expandable composite resin particles 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, and cooling was performed by air cooling after the extraction was completed.
Next, about 600 ml of acetone was put into a 1000 ml beaker, and the sample in the wire mesh taken out from the extraction tube after the completion of extraction was washed with this acetone. Next, after acetone was volatilized, the sample was dried in a drier at a temperature of 120 ° C. for 4 hours. The residual content was defined as the gel content, and the ratio of the gel content (mass) to the initial foamable composite resin particle content (mass) was expressed as a percentage, and this was defined as the gel content (mass%) insoluble in xylene.

"Glass transition temperature (Tg) of polystyrene resin"
First, 1.0 g of expandable composite resin particles were placed in a 150 mesh wire mesh bag. Next, about 200 ml of xylene was placed in a 200 ml round flask, and a sample of expandable composite resin particles 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. The xylene solution extracted here was dropped into 600 ml of acetone, followed by decantation and evaporation under reduced pressure to obtain a styrene resin as an acetone-soluble component.
About 2 to 4 mg of the obtained polystyrene resin, heat flux differential scanning calorimetry was performed. The heat flux differential scanning calorific value was measured according to JIS K7121 (1987) using a 2010 DSC measuring instrument manufactured by TI Instruments. And the midpoint glass transition temperature of the DSC curve obtained on the conditions of a heating rate of 10 degree-C / min was calculated | required, and this was made into the glass transition temperature (Tg) of a polystyrene-type resin.

"Weight average molecular weight (Mw) of polystyrene resin"
First, in the same manner as described above, a polystyrene resin was obtained as an acetone-soluble component from the foamable composite resin particles. The weight average molecular weight of the obtained 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 (GPC-8020Model II) manufactured by Tosoh Corporation, measurement of eluent: tetrahydrofuran (THF), flow rate: 2 ml / min, column: TSK-GEL GMH manufactured by Tosoh Corporation Measurement can be performed under conditions. The weight average molecular weight was obtained by dissolving a polystyrene resin in tetrahydrofuran, measuring with gel permeation chromatography (GPC), and calibrating with standard polystyrene.

"Melting point and crystallinity of olefin resin"
First, 1.0 g of expandable composite resin particles were placed in a 150 mesh wire mesh bag. Next, about 200 ml of xylene was placed in a 200 ml round flask, and a sample of expandable composite resin particles 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. Here, the extracted xylene solution was dropped into 600 ml of acetone, followed by decantation and evaporation under reduced pressure to obtain an olefin resin as an acetone insoluble matter.
About the obtained olefin resin, heat flux differential scanning calorimetry was performed. The heat flux differential scanning calorific value was measured according to JIS K7121 (1987) using a 2010 DSC measuring instrument manufactured by TI Instruments.
Specifically, after weighing a sample of 2 to 4 mg of an olefin resin in a sample pan, the sample was heated to a temperature of 190 ° C. in a nitrogen atmosphere. Thereafter, the temperature was decreased to −50 ° C. at a temperature decrease rate of 10 ° C./min, and the heat of fusion was determined from the endothermic peak area of the DSC curve obtained when the temperature was increased to 190 ° C. at a temperature increase rate of 10 ° C./min. Then, the degree of crystallinity (%) was calculated from the ratio between the value of heat of fusion and the heat of fusion of polyethylene crystals. In addition, the value of 286.7 J / g was used for the heat of fusion of complete polyethylene crystals.
The temperature at the top of the endothermic peak on the DSC curve was defined as the melting point (Tm) of the olefin resin.

"Average particle size"
The average particle diameter of the expandable resin particles can be measured as follows.
That is, first, a graduated cylinder containing water at a temperature of 23 ° C. was prepared, and an arbitrary amount of expandable resin particles (expandable resin particles) left for 2 days under conditions of 50% relative humidity, 23 ° C. and 1 atm. The mass W ₁ ) of the group is submerged in water in the graduated cylinder using a tool such as a wire mesh. The volume V ₁ [L] of the expandable resin particle group read from the rise in the water level is measured in consideration of the volume of the tool such as a wire mesh, and the volume V ₁ of the expandable resin particle placed in the measuring cylinder is measured. By dividing (V ₁ / N) by the number (N), the average volume per one expandable resin particle is calculated. And let the diameter of the virtual sphere which has the same volume as the obtained average volume be the average particle diameter [mm] of the expandable resin particles.

(3) Preparation of Composite Resin Expanded Particles Next, primary expanded particles having a bulk density of 25.1 kg / m ³ were prepared using the expandable composite resin particles obtained as described above.
Specifically, first, the expandable composite resin particles obtained as described above were placed in a 30 L atmospheric pressure batch foaming machine, and steam was supplied into the foaming machine. Thereby, the expandable composite resin particles were expanded to a bulk density of 25.1 kg / m ³ to obtain primary expanded particles having an expansion ratio of 40 times.
After aging the primary foamed particles obtained above at room temperature for 1 day, the primary foamed particles were placed in a 30 L atmospheric pressure batch foaming machine, and steam was supplied into the foaming machine. Thereby, the primary expanded particles were further expanded to a bulk density of 11.0 kg / m ³ to obtain secondary expanded particles having an expansion ratio of 91 times. This is the composite resin foamed particle of this example.

For the bulk density (kg / m ³ ) of the composite resin foam particles, prepare a 1L graduated cylinder, put the composite resin foam particles up to the 1L mark in an empty graduated cylinder, and put the composite resin foam in the graduated cylinder. It was determined by measuring the weight of the particles. The bulk density (kg / m ³ ) of the composite resin foam particles was calculated by converting the weight of the composite resin foam particles per liter of the bulk volume obtained by this operation into a unit. Moreover, the expansion ratio of the composite resin expanded particles was calculated by the formula: expansion ratio = 1000 / bulk density (kg / m ³ ).

  Next, the morphology, average particle diameter, closed cell ratio, maximum compressive stress, and compressive strain of the composite resin foam particles of this example were examined as follows. The results are shown in Table 2. In addition, the values of the mass ratio of PE / PS / EVA in the composite resin foam particles, the content of the dispersion diameter expanding agent, the xylene insoluble matter (gel amount), and the like are the same as the values related to the foamable composite resin particles described above ( (See Table 2).

"Morphology"
A transmission electron micrograph of the cross section was taken in the same manner as the foamable composite resin particles described above, and the morphology of the linear low density polyethylene resin phase and the polystyrene resin phase in the composite resin foam particles was taken from the cross section photograph. Was visually observed. With respect to the composite resin foam particles of this example, transmission electron micrographs were taken at magnifications of 10,000 and 50,000 times. A transmission electron micrograph at a magnification of 10,000 times is shown in FIG. Regarding the transmission electron micrograph at a magnification of 50000 times, a photograph of a region where the adjacent bubbles 3 of the composite resin foamed particles 1 are not close to each other and a resin reservoir exists (region A surrounded by a dotted line in FIG. 1). 4 shows a photograph of a region (region B surrounded by a dotted line in FIG. 1) in which the adjacent bubbles 3 are close to each other to form a bubble film (cell film).

"Average particle size"
The average particle diameter of the composite resin foam particles was measured by the same method as that for the expandable composite particles described above.

"Closed cell ratio"
The composite resin foamed particles were allowed to stand for 10 days in a constant temperature room under conditions of atmospheric pressure, relative humidity 50%, and 23 ° C. Next, the composite resin foamed particles having a bulk volume of about 20 cm ³ was allowed to stand for 10 days was used as a sample for measurement was measured volume V _a of the apparent accurate. Next, after the measurement sample is sufficiently dried, the true volume of the measurement sample is measured by an air comparison type hydrometer 930 manufactured by Toshiba Beckman Co., Ltd. according to Procedure C described in ASTM-D2856-70. to measure the value V _x. Then, based on these volume values V _a and V _x , the closed cell ratio was calculated by the following formula (3), and the average value of N = 5 was obtained.
Closed cell ratio (%) = (V _x −W / ρ) × 100 / (V _a −W / ρ) (3)
(Where V _x : the true volume of the composite resin foamed particles measured by the above method, that is, the volume of the resin constituting the composite resin foamed particles and the total cell volume of the closed cell portion in the composite resin foamed particles) Sum (cm ³ ), V _a : Submerged foam particles in a graduated cylinder containing water, apparent volume (cm ³ ) of composite resin foam particles measured from the rise in water level, W: Weight of composite resin foam particles (G), ρ: Density of resin constituting the composite resin foamed particles (g / cm ³ ))
In this way, the closed cell ratio of the composite resin foamed particles before compression, at 25% compression, and at 50% compression was determined.

"Compressive stress"
First, 330 ml of composite resin foam particles weighed in advance with a graduated cylinder were put into a cylindrical container with a lid having a diameter of 78 mm, and the lid was capped. Next, a load was applied to the composite resin foam particles from the lid portion at a compression rate of 100 mm / min, and the load was released immediately after reaching a predetermined load. This operation was repeated 100 times. The load was performed under the following conditions of being compressed by 25% and 50% with respect to the original volume of the composite resin foam particles in the container.
(25% compression)
Based on the following formulas (4) and (5), a load was applied until the volume of the composite resin foamed particles in the cylindrical container reached 247.5 ml.
Original volume (330 ml) × 0.25 = 82.5 ml (4)
Original volume (330 ml) −82.5 ml = 247.5 ml (5)
(50% compression)
Based on the following formulas (6) and (7), a load was applied until the volume of the composite resin foamed particles in the cylindrical container reached 165 ml.
Original volume (330 ml) × 0.5 = 165 ml (6)
Original volume (330 ml) -165 ml = 165 ml (7)
The compressive stress in the above measurement is indicated by the first compressive stress value.

"Repetitive compression distortion"
In the above compressive stress measurement, a load was applied 100 times and then left for 24 hours with the load released to measure the volume. From this volume value, the compression strain was repeatedly calculated using the following equation (8). It means that the smaller the value of the compressive strain, the better the restoring property.
Compression strain (%) = (original volume (330 ml) −volume after compression test) / original volume (330 ml) × 100 (8)

(Example 2)
In this example, the polyethylene resin constituting the core particle is changed from that of Example 1, and in Example 1, the foaming composite resin particles are prepared by changing the polymerization conditions of the styrene monomer and the like. This is an example of producing composite resin foamed particles using resin particles.
Specifically, Example 1 was used except that “Kernel KF270” manufactured by Nippon Polyethylene Co., Ltd., which is a linear low density polyethylene polymerized with a metallocene catalyst, was used as the linear low density polyethylene resin. Nuclear particles were prepared in the same manner as described above. The resin mixture having the composition used here is resin b, and the MFR (190 ° C., 2.16 kgf) of resin b is shown in Table 1 described later.

  Next, to the suspension prepared in the same manner as in Example 1, 1.5 g of sodium lauryl sulfonate (10% by mass aqueous solution) as a surfactant, 0.15 g of sodium nitrite as a water-soluble polymerization inhibitor, and 150 g of core particles were charged.

Next, 1.72 g of benzoyl peroxide as a polymerization initiator (“NIPPER BW” manufactured by NOF Corporation, water-diluted powder product) and 1.29 g of t-butylperoxy-2-ethylhexyl monocarbonate (NOF Corporation) “Perbutyl E”) and 0.43 g of dicumyl peroxide (“Park Mill D” manufactured by NOF Corporation) as a cross-linking agent are dissolved in 335 g of styrene and 15 g of butyl acrylate as monomers, and the solution is stirred. While stirring at 500 rpm, it was put into the suspension in the autoclave.
Next, after the inside of the autoclave was purged with nitrogen, the temperature increase was started and the temperature was increased to 87 ° C. over 1 hour 30 minutes. After the temperature increase, this temperature was maintained at 87 ° C. for 30 minutes, and then the stirring speed was lowered to 450 rpm. This polymerization temperature was maintained at 87 ° C. for 6 hours.

Next, the temperature was raised to 125 ° C. over 4 hours, and the temperature was maintained at 125 ° C. for 2 hours and 30 minutes.
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 reached 90 ° C., 20 g of cyclohexane and 65 g of butane (a mixture of normal butane of about 20% by volume and isobutane of about 80% by volume) were added to the autoclave over about 1 hour as a blowing agent. 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. Thereafter, dehydration and washing were performed with a centrifugal separator, and water adhering to the surface was removed with an airflow drying device, whereby expandable composite resin particles having an average particle diameter (d ₆₃ ) of about 1.3 mm were obtained.
Next, as in Example 1, the obtained foamable composite resin particles were sieved, and N, N-bis (2-hydroxyethyl) alkylamine, zinc stearate, glycerol monostearate, and glycerol distearate were added. The surface of the expanded particles was coated. Thus, the expandable composite resin particle of this example was obtained.

Next, the foamable composite resin particles of this example were foamed to produce composite resin foam particles.
In this example, the expandable composite resin particles were expanded to a bulk density of 24.6 kg / m ³ to produce primary expanded particles, and the primary expanded particles were further expanded to a bulk density of 11.3 kg / m ^3. Except for, composite resin expanded particles (secondary expanded particles) were produced in the same manner as in Example 1.

Example 3
In this example, expandable composite resin particles were prepared by changing the type of dispersion diameter expanding agent and the polymerization conditions of the styrene monomer, etc. from Example 1, and using these expandable composite resin particles, composite resin expanded particles were prepared. This is an example.
Specifically, in this example, except that 1 kg of “MS200” manufactured by Nippon Steel Chemical Co., Ltd., which is a methyl methacrylate-styrene copolymer (MS), was used as a dispersion diameter expanding agent. Core particles were prepared in the same manner as in Example 1. The resin mixture of the blend used here is Resin c, and the MFR (190 ° C., 2.16 kgf) of Resin c is shown in Table 1 described later.
Next, expandable composite resin particles (average particle diameter: 1.4 mm) were produced in the same manner as in Example 2 except that the core particles were used.

Next, the foamable composite resin particles of this example were foamed to produce composite resin foam particles.
In this example, the foamable composite resin particles were foamed to a bulk density of 24.1 kg / m ³ to produce primary foamed particles, and the primary foamed particles were further foamed to a bulk density of 11.6 kg / m ^3. Except for, composite resin expanded particles (secondary expanded particles) were produced in the same manner as in Example 1.

(Examples 4 and 5)
In this example, foamable composite resin particles are foamed in three stages to produce composite resin foam particles.
Specifically, first, nuclear particles were produced in the same manner as in Example 1. Next, expandable composite resin particles (average particle diameter: 1.4 mm) were produced in the same manner as in Example 2 except that the core particles were used.

Next, the foamable composite resin particles were foamed to produce composite resin foam particles.
Specifically, the foamable composite resin particles produced in this example were foamed to a bulk density of 25.1 kg / m ^{3 in the same} manner as in Example 1 to produce primary foamed particles. The primary foamed particles were further increased in bulk density. Secondary expanded particles were produced by further foaming to 11.0 kg / m ³ . Next, the obtained secondary foamed particles were aged at room temperature for 1 day, and then placed in a 30 L normal pressure batch foaming machine, and steam was supplied into the foaming machine to further foam the secondary foamed particles.
In Example 4, secondary expanded particles were further expanded to a bulk density of 8.3 kg / m ³ to obtain tertiary expanded particles having an expansion ratio of 120 times. The tertiary expanded particles were used as the composite resin expanded particles of Example 4.
In Example 5, the secondary expanded particles were further expanded to a bulk density of 6.1 kg / m ³ to obtain tertiary expanded particles having an expansion ratio of 164 times. This was designated as composite resin foamed particles of Example 5.

(Comparative Example 1)
This example is an example in which composite resin foamed particles are produced by changing the core particles from the above-described example.
Specifically, first, as an ethylene-based resin, 5 kg of “Ultrasen 626” manufactured by Tosoh Corporation, which is an ethylene-vinyl acetate copolymer, and 15 kg of “Nipolon Z 9P51A” manufactured by Tosoh Corporation, which is a linear low density polyethylene, are used. The core particles were prepared in the same manner as in Example 1 except that “SANH” manufactured by Techno Polymer Co., Ltd., which is an acrylonitrile-styrene copolymer, was used as the dispersion diameter expanding agent. The resin mixture having the composition used here is Resin d, and MFR (190 ° C., 2.16 kgf) of Resin d is shown in Table 1 described later.

Next, expandable composite resin particles (average particle diameter: 1.6 mm) were produced in the same manner as in Example 2 except that the core particles were used.
Next, the foamable composite resin particles of this example were foamed to produce composite resin foam particles. In this example, expandable composite resin particles were expanded to a bulk density of 27.1 kg / m ³ to produce primary expanded particles. Next, the primary expanded particles were further expanded to a bulk density of 21.1 kg / m ³ to produce secondary expanded particles.

(Comparative Example 2)
In this example, expandable composite resin particles were produced in the same manner as in Comparative Example 1 except that the average particle diameter was changed, and the expandable composite resin particles were expanded at a different expansion ratio from Comparative Example 1. Composite resin foam particles were prepared.
In this example, expandable composite resin particles were expanded to a bulk density of 21.1 kg / m ³ to produce primary expanded particles. Next, the primary expanded particles were further expanded to a bulk density of 14.1 kg / m ³ to produce secondary expanded particles.

(Comparative Examples 3 and 4)
This example is an example of producing expanded polystyrene particles (expanded PS particles) for comparison with the composite resin expanded particles of the above-described Examples.
In an autoclave with an internal volume of 3 L with a stirrer, 760 g of deionized water, 0.6 g of tribasic calcium phosphate (manufactured by Taihei Chemical Sangyo Co., Ltd.) as a suspending agent, sodium tetradecene sulfonate (Lipolan, manufactured by Lion) LB440) 1% aqueous solution 2.7 g, disodium dodecyl diphenyl ether sulfonate (Perox SSH manufactured by Kao Corporation) 0.9% aqueous solution, 3.8 g potassium persulfate 0.01% aqueous solution as a suspension aid, As the electrolyte, 1.2 g of sodium acetate was added.

  Next, 2.4 g of benzoyl peroxide (NIPPER BW manufactured by NOF Corporation, water-diluted powder product), 0.8 g of t-butylperoxy-2-ethylhexyl monocarbonate (Perbutyl E manufactured by NOF Corporation) as polymerization initiators, And 0.8 g of dicumyl peroxide (Nippon Yushi Co., Ltd., Park Mill D), 0.12 g of alpha-methylstyrene dimer as a chain transfer agent, 6 g of liquid paraffin as a plasticizer, and 760 g of styrene as a monomer were stirred at 400 rpm. However, it was put into the autoclave. After the atmosphere in the autoclave was replaced with nitrogen, the temperature was raised and the temperature was raised to 90 ° C. over 1 hour and a half.

  After reaching 90 ° C., the temperature was raised to 100 ° C. over 5 hours, further raised to 112 ° C. over 1 hour 30 minutes, held at 112 ° C. for 3 hours, and then cooled to 30 ° C. over about 6 hours. . 4 hours after reaching 90 ° C., 25 g of pentane and 45 g of butane (a mixture of about 20% by volume of normal butane and about 80% by volume of isobutane) were added to the autoclave over about 30 minutes. After adding the blowing agent, the stirring speed was lowered to 350 rpm.

After cooling, the contents are taken out, nitric acid is added to dissolve the tertiary calcium phosphate adhering to the surface of the expandable styrene resin particles, then dewatering and washing with a centrifuge, and moisture adhering to the surface with an airflow dryer Was removed to obtain expandable styrene resin particles having an average particle diameter of about 1.2 mm.
The obtained expandable styrenic resin particles are sieved to extract particles having a diameter of 0.8 to 1.6 mm, and N, N-bis (2) which is an antistatic agent is added to 100 parts by mass of the expandable composite resin particles. -Hydroxyethyl) alkylamine 0.008 parts by mass was added, and further coated with a mixture of zinc stearate 0.12 parts by mass, glycerol monostearate 0.04 parts by mass, and glycerol distearate 0.04 parts by mass.

Next, the expandable PS particles obtained as described above were placed in a 30 L normal pressure batch foaming machine, and steam was supplied into the foaming machine. Thereby, expandable PS particles were expanded to produce expanded polystyrene particles (primary expanded particles). Comparative Example 3 is foamed PS particles obtained by foaming expandable PS particles to a bulk density of 20.3 kg / m ^3. Comparative Example 4 is foamed PS particles up to a bulk density of 10.5 kg / m ^3. Foamed PS particles obtained by foaming.

For Examples 2 to 5 and Comparative Examples 1 and 2 described above, the MFR of the resins (resins a to g) used for the production of the core particles is shown in Table 1 as in Example 1. Further, for the expandable composite resin particles in Examples 2 to 5 and Comparative Examples 1 and 2, as in Example 1, the content of the physical foaming agent, the retention rate of the physical foaming agent, the foamability, the morphology, PE and Interfacial ratio with PS, gel amount, glass transition temperature (Tg) of styrene resin, weight average molecular weight (Mw) of styrene resin, melting point (Tm) of olefin resin, crystallinity of olefin resin, and average The particle diameter was examined, and the results are shown in Tables 2 to 3. In addition, "mass part" in Tables 2-3 is a value with respect to 100 mass parts of total mass of PE and PS.
In addition, the composite resin foamed particles in Examples 2 to 5, Comparative Examples 1 and 2, and the expanded polystyrene particles in Comparative Examples 3 and 4, as in Example 1, morphology, bulk density, average particle diameter, closed cell ratio , Compression stress, and repeated compression strain were examined, and the results are shown in Tables 2 to 4.

(Results of Examples and Comparative Examples)
As is known from Tables 2-3, as in Examples 1-5, polystyrene, which is a linear low density polyethylene resin (A) and a polymer of a styrene monomer or a mixed monomer containing a styrene monomer. The composite resin foam particles having a high expansion ratio and a high closed cell ratio, in which the morphology of the composite resin including the resin (B) is adjusted, were excellent in rigidity and restorability.

On the other hand, as known from Table 3, the composite resin foamed particles of Comparative Examples 1 and 2 were inferior in resilience compared to Examples 1-5.
Moreover, although foamable polystyrene particle | grains (Comparative Examples 3 and 4) are excellent in foamability as known from Table 4, the expandable polystyrene particle obtained was inferior in resilience compared with Examples 1-5 ( Table 2 and Table 4).

1 Composite resin foamed particles 2 Composite resin 3 Bubbles

Claims (6)

A composite resin foamed particle using a composite resin of a linear low density polyethylene resin (A) and a polystyrene resin (B) obtained by impregnating and polymerizing the resin (A) with a styrene monomer. ,
The composite resin contains 20-50% by mass of the resin (A) and 50-80% by weight of the resin (B) (however, the total of the resin (A) and the resin (B) is 100% by mass). And the resin (A) forms a dispersed phase and the resin (B) forms a continuous phase,
A composite resin foamed particle having a bulk density of 5 to 15 kg / m ³ and a closed cell ratio of 90% or more.   2. The composite resin foamed particles according to claim 1, wherein the xylene-insoluble matter in the composite resin is 30% by mass or less.   The composite resin foamed particles according to claim 1 or 2, wherein the composite resin foamed particles have an average particle diameter of 4 to 8 mm. The composite resin foamed particles, the composite resin foamed particles according to any one of claims 1 to 3, characterized by being foamed further one or more times expanded beads having a bulk density of 20 to 50 kg / m ^3.   The composite resin foam particles according to any one of claims 1 to 4, wherein the composite resin foam particles are used as a cushion or a mattress by filling the composite resin foam particles into a bag. Composite resin foamed bead molded article of the apparent density 5~15kg / m ³ obtained by in-mold molding of the composite resin foamed particles according to any one of claims 1 to 4.