JP2016014104A - Compressed composite resin foam-molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compressed composite resin foam-molded article, which has excellent flexibility and little permanent set, and weight of which can be reduced.SOLUTION: Provided is a compressed foam-molded article formed by subjecting an in-mold molded article of foamed particles to a compression treatment. The compressed composite resin foam-molded article is composed of a composite resin comprising 5 to 25 wt% of a polyethylene-based resin and 75 to 95 wt% of a polystyrene-based resin (where a total of the two resins is 100 wt%). An insoluble matter mixture of a xylene insoluble matter when the composite resin is subjected to Soxhlet extraction with xylene and an acetone insoluble matter contained in the xylene solution after the Soxhlet extraction shows a degree of swelling of 1.25 or more in methyl ethyl ketone at 23°C. A value obtained by dividing 10% compression stress [kPa] by an apparent density [kg/m] and a compression permanent set are adjusted to 3 or more and 10% or less, respectively, by the compression treatment.

Description

  The present invention relates to a compression composite resin foam molded article having excellent rigidity and impact resilience, which is suitably used as a packaging material, bedding, playground equipment, and the like.

  Foamed particle compacts that are formed by in-mold molding of foamed particles and are fused to each other, such as packaging materials, building materials, impact absorbing materials, etc., taking advantage of their excellent buffering properties, light weight, heat insulation, etc. It is used for a wide range of purposes. As the foamed particle molded body, a base resin made of a polyolefin resin such as polypropylene or polyethylene, or a base resin made of a polystyrene resin such as polystyrene is used.

Compared to polystyrene resin foamed particle molded products, polyolefin resin foamed particle molded products are superior in impact resistance, toughness, and resilience, so they can be used as packing materials and packaging materials for precision parts and heavy products. It's being used. In addition, since the polyolefin-based resin expanded particle molded article is excellent in heat resistance and oil resistance, it is also used as an automobile member such as an impact absorbing material, a bumper, and a floor spacer. As described above, the polyolefin resin expanded particle molded body is widely used in various applications.
However, although the polyolefin resin foamed particle molded article has the excellent characteristics as described above, it is difficult to increase the expansion ratio and it is difficult to reduce the weight as compared with the polystyrene resin foamed particle molded article. In addition, since the rigidity is low and the steam temperature at the time of in-mold molding is high, there are also disadvantages that a special mold or the like is required.

On the other hand, the polystyrene-based resin expanded particle molded body is superior in rigidity as compared to the polyolefin-based resin expanded particle molded body. In addition, since the molding vapor pressure at the time of in-mold molding is low and the processability is good, it is widely used in the market. In addition, the polystyrene-based resin expanded particle molded body has a feature that the expansion ratio can be increased and the weight can be reduced.
However, the polystyrene-based resin expanded particle molded body also has the disadvantages of being inferior in resilience, toughness, and restorability compared to the polyolefin resin expanded particle molded body.

In order to solve the above-mentioned disadvantages, methods have been proposed in which a polystyrene-based resin expanded particle molded body is mechanically compressed to give resilience, flexibility, and restorability (Patent Documents 1 and 2). reference).
In addition, a method has been developed in which a foamed molded body composed of a thermoplastic resin and a rubber polymer is mechanically compressed to impart flexibility (see Patent Document 3).

JP 56-51337 A JP-A-4-345638 JP 2000-37784 A

  However, the compression-foamed molded article obtained by the methods of Patent Documents 1 to 3 still does not have sufficient rebound resilience, flexibility, and resilience of the foamed molded article, and further, a reduction in rigidity and deformation of the molded article after the compression treatment are performed. There was a problem that the amount was large, the density increased, and the weight increased.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a foamed molded article obtained by compression treatment, which is excellent in flexibility and has a small permanent set and can be reduced in weight. .

According to the present invention, the following novel compressed composite resin foam molded article is provided.
<1> A compression-foamed molded body obtained by compressing an in-mold molded body of expanded particles,
The compression foamed molded body is formed from a composite resin of 5 to 25% by weight of a polyethylene resin and 75 to 95% by weight of a polystyrene resin (however, the total of both is 100% by weight). The degree of swelling in methyl ethyl ketone at a temperature of 23 ° C. is a mixed insoluble matter of xylene insoluble matter when the composite resin is subjected to Soxhlet extraction with xylene and acetone insoluble matter contained in the xylene solution after Soxhlet extraction is 1.25 or more. ,
A compression composite resin foam molded article in which the value obtained by dividing the apparent density [kg / m ³ ] by 10% compression stress [kPa] is 3 or less and the compression set is 10% or less by the compression treatment.
<2> The compressed composite resin foam molded article according to <1>, wherein the cell membrane has a bent deformation part.
<3> The compressed composite resin foam molded article according to <1> or <2>, wherein the closed cell ratio is 60% or more.
<4> The compression composite resin foam molded article according to any one of <1> to <3>, wherein an apparent density is in a range of 5 to 50 kg / m ³ .
<5> The compressed composite resin foam molded article according to any one of <1> to <4>, wherein the molded article in the mold is compressed in a range of a compression rate of 25 to 95%.

The compression foamed molded product obtained by compressing the in-mold molded product of the composite resin foamed particles of the present invention is composed of 5 to 25% by weight of a polyethylene resin and 75% of the composite resin forming the compression foamed molded product. -95 wt% polystyrene resin (however, the total of both is 100 wt%), and the xylene insoluble matter when the composite resin is subjected to Soxhlet extraction with xylene and the xylene solution after Soxhlet extraction The swelling degree in methyl ethyl ketone at a temperature of 23 ° C. of the mixed insoluble component with the acetone insoluble component contained is 1.25 or more, and the compression foamed molded article has an apparent density [kg] of 10% compression stress [kPa] by the compression treatment. / m ^3] a value obtained by dividing the 3 or less, and since the compression set is adjusted to 10% or less, excellent from the characteristics of the polystyrene resin stiffness While having the amount of deformation of the molded body after the compression process is small, and excellent resilience, exhibits resiliency. Therefore, the compression-foamed molded article of the present invention is suitably used as a packaging material, bedding, play equipment, etc. that require characteristics such as rigidity, impact resilience, and resilience.

The drawing substitute photograph which shows the result of having observed the bubble film part in the center part cross section of the compression foaming molding which concerns on this invention with the scanning electron micrograph. The drawing substitute photograph which shows the result of having observed the center part cross section of the expandable composite resin particle in Example 1 with the transmission electron micrograph. The drawing substitute photograph which shows the result of having observed the center part cross section of the expandable composite resin particle in Example 11 with the transmission electron micrograph. The drawing substitute photograph which shows the result of having observed the center part cross section of the expandable composite resin particle in the comparative example 11 with the transmission electron micrograph.

(Compressed foam molding)
The compression foamed molded product (hereinafter also referred to as a compressed composite resin foamed molded product) obtained by compressing an in-mold molded product of composite resin foamed particles according to the present invention is a composite that forms the compressed composite resin foamed molded product. The first feature is that the resin is composed of a composite resin of 5 to 25% by weight of a polyethylene resin and 75 to 95% by weight of a polystyrene resin (however, the total of both is 100% by weight).

  The compressed composite resin foam molded article of the present invention can be obtained by compressing an in-mold molded article of composite resin foam particles. The composite resin foam particles can be obtained by foaming expandable composite resin foam particles (hereinafter also referred to as expandable composite resin particles) containing a foaming agent.

(Composition of composite resin)
The composite resin forming the compressed composite resin foamed molded article of the present invention is 5 to 25% by weight of a polyethylene resin and 75 to 95% by weight of a polystyrene resin (however, the total of both is 100% by weight). It is a composite resin.

In the composite resin, when the ratio of the polyethylene resin to the total amount of the polyethylene resin and the polystyrene resin is less than 5% by weight, the bubbles of the foamed particle molded body are easily broken during the compression treatment. There is a possibility that the resin foam molded article does not show sufficient resilience and resilience.
On the other hand, when the ratio of the polyethylene resin in the composite resin is more than 25% by weight, the composite resin itself becomes too flexible, so that the compressed composite resin foam molded article may not exhibit sufficient rigidity.
From this point of view, the composite resin is preferably composed of 10 to 20% by weight of a polyethylene resin and 80 to 90% by weight of a polystyrene resin (however, the total of both is 100% by weight). More preferably, it is made of a polyethylene resin of wt% and 83 to 88 wt% of polystyrene resin (however, the total of both is 100 wt%).
In addition, the ratio of the polyethylene-type resin and the polystyrene-type resin in the said composite resin can be calculated | required from the compounding composition of the raw material at the time of manufacture of a composite resin.

By the way, in general, in a foamed particle molded body made of a composite resin of a polyethylene resin and a polystyrene resin, when the ratio of the polystyrene resin is increased, the rigidity is improved, but the resilience, compression set and toughness are decreased. .
Also in the present invention, as described above, a composite resin having a high proportion of polystyrene resin of 75 to 95% by weight is used, but the swelling degree of the composite resin is 1.25 or more, which is different from the conventional one. It is extremely expensive. Therefore, the compression composite resin foamed molded article of the present invention can greatly improve the resilience and resilience by the compression treatment even if the proportion of polystyrene resin is high.

(Swelling degree of composite resin)
That is, in the compression composite resin foam molded body obtained by compressing the in-mold molded body of the composite resin foam particles of the present invention, the swelling degree of the composite resin forming the compression composite resin foam molding is 1.25 or more. It is a second feature.
Here, the degree of swelling of the composite resin means that the xylene insoluble content when the composite resin is soxhlet extracted with xylene and the mixed insoluble content of the acetone insoluble content contained in the xylene solution after the soxhlet extraction is 23 ° C. The degree of swelling in methyl ethyl ketone (hereinafter simply referred to as “swelling degree”) is meant.
When the swelling degree of the composite resin is lower than 1.25, the bubbles of the foamed particle molded body are easily destroyed during the compression treatment, and the compressed composite resin foam molded body does not exhibit sufficient rebound resilience, flexibility, and restorability. There is a fear. From this viewpoint, the swelling degree of the composite resin is more preferably 1.5 or more, and further preferably 2 or more.

The degree of swelling of the composite resin is determined by the following method.
About 1 g of a sample for measurement was collected from the compressed composite resin foam molded article, and its weight (W ₀ ) was weighed to the fourth decimal place and placed in a 150 mesh wire mesh bag. Next, about 200 ml of xylene was placed in a round flask having a capacity of 200 ml, and the sample placed in the wire mesh bag was set in a Soxhlet extraction tube. Soxhlet extraction was performed by heating the flask for 8 hours with a mantle heater. After the extraction, it was cooled by air cooling. After cooling, the wire mesh was taken out from the extraction tube, and the sample together with the wire mesh was washed with about 600 ml of acetone. Next, acetone was volatilized and dried at a temperature of 120 ° C. The sample collected from the wire net after this drying is “xylene-insoluble matter”.
The xylene solution after the Soxhlet extraction was put into 600 ml of acetone. And the component which is not melt | dissolved in acetone was filtered and separated and collected using the filter paper of 5 types A prescribed | regulated to JISP3801, and the recovered material was evaporated to dryness under reduced pressure. The obtained solid is “acetone-insoluble matter”.
The mixed insoluble weight (W _a ) of “xylene insoluble” and “acetone insoluble” obtained by these operations is measured to the fourth decimal place. Next, the mixed insoluble matter is immersed in 50 ml of methyl ethyl ketone and left at a temperature of 23 ° C. for 24 hours. Thereafter, the mixed insoluble matter is taken out from methyl ethyl ketone, lightly wiped with filter paper, and the weight (W _b ) of the mixed insoluble matter is measured to the fourth decimal place. Then, based on the weight (W _a , W _b ) of the mixed insoluble matter before and after immersion in methyl ethyl ketone, the degree of swelling S can be obtained by the following formula.
S = W _b / W _a

The reason why the rigidity and the restorability are excellent as described above when the swelling degree of the composite resin is equal to or greater than the predetermined value is presumed as follows.
The degree of swelling (degree of swelling) when a crosslinked polyethylene resin is immersed in an organic solvent has a correlation with the crosslinked structure (three-dimensional network structure) of the resin, and the finer the network, the lower the amount of organic solvent absorbed. Therefore, the degree of swelling decreases. On the other hand, non-crosslinked polyethylene resins hardly swell in methyl ethyl ketone at a temperature of 23 ° C.

  That is, as described above, the xylene-insoluble component (crosslinked polyethylene resin component) of the composite resin, and the acetone-insoluble component (crosslinked polyethylene resin component that has passed through the mesh, non-crosslinked polyethylene system) in the xylene soluble component In the case where the swelling degree of the mixed insoluble matter with the resin component and the polyethylene resin component in which the styrene monomer is graft-polymerized is large, in the polyethylene resin constituting the composite resin, compared with the case where the swelling degree is small. In other words, it means that a polyethylene resin component having a coarse crosslinked three-dimensional network structure is contained.

  Therefore, the crosslinked polyethylene resin component with a coarse three-dimensional network structure is easy to stretch moderately while foaming, so it has excellent foaming properties and forms a foam film with high strength. It is guessed. Furthermore, since the polyethylene resin in the composite resin is flexible and sufficiently deformable when the composite resin foam particle molded body is compressed, the foamed particles can be produced even when the ratio of the polystyrene resin in the composite resin is high. It is presumed that the cell structure can be maintained without breaking the cell membrane. That is, when the degree of swelling of the composite resin forming the foamed particle molded body is within a specific range, a compressed composite resin foam molded body having high levels of rigidity, impact resilience, and resilience can be obtained.

  Further, as described above, the cell membrane of the compression composite resin foam molded article of the present invention is composed of a polyethylene-based resin component having a high strength and appropriate stretchability, and having a crosslinked three-dimensional network structure with a coarse mesh. ing. Therefore, when deformed and bent by the compression process, as shown in FIG. 1, at least a part of the bubble film 1 is formed with a bent deformation portion 2. Since this bending deformation part 2 is bowl-shaped and is flexible and rich in elasticity, the compression composite resin foam molded article of the present invention is flexible and sufficiently deformable, and further has excellent resilience and resilience. It will be a thing.

  As will be described later, the composite resin forming the foamed particle molded body is obtained by impregnating a polyethylene resin core particle with a styrene monomer together with a polymerization initiator and polymerizing the styrene monomer in the core particle. be able to. At this time, the degree of swelling of the composite resin can be adjusted by adjusting the ratio of the styrene monomer impregnated in the initial stage and the amount of the polymerization initiator present in the initial stage of polymerization of the styrene monomer. Specifically, by increasing the ratio of the styrene monomer to be impregnated in the initial stage with respect to the core particles, and further reducing the concentration of the polymerization initiator with respect to the polyethylene resin, a crosslinked polyethylene system having a rough three-dimensional network structure by crosslinking. Resin components are easily formed.

  Moreover, in the composite resin, it is preferable that the weight ratio of the xylene-insoluble matter by Soxhlet extraction is 40% or less (including 0). In this case, foamability is particularly excellent, and the rigidity and resilience of the compressed composite resin foamed molded product can be further improved. As for the weight ratio of the xylene insoluble part of an expandable composite resin particle, it is more preferable that it is 5-35%, and it is further more preferable that it is 10-30%.

  A composite resin of a polyethylene resin and a polystyrene resin can be obtained by impregnating polyethylene resin core particles with a styrene monomer and polymerizing the styrene monomer in the core particles. Moreover, a part of polystyrene resin may be previously contained in the polyethylene resin core particles as a dispersion diameter expanding agent or the like as described later. In the polymerization process of the styrene monomer, the polyethylene resin contained in the core particles is cross-linked. Therefore, in this specification, “polymerization” may include “cross-linking”.

(Polyethylene resin constituting composite resin)
Examples of the polyethylene resin include branched low density polyethylene, linear low density polyethylene, high density polyethylene, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, and ethylene-acrylic acid alkyl ester copolymer. , Ethylene-methacrylic acid alkyl ester copolymers, and the like can be used. Moreover, as a polyethylene-type resin, 1 type of polymer may be sufficient, but the mixture of 2 or more types of polymers can also be used.

  Preferably, the polyethylene resin is mainly composed of linear low density polyethylene. The linear low-density polyethylene preferably has a branched structure having a linear polyethylene chain and a short-chain branched chain having 2 to 6 carbon atoms. Specific examples include an ethylene-butene copolymer, an ethylene-hexene copolymer, and an ethylene-octene copolymer. In particular, the polyethylene resin is preferably a linear low-density polyethylene polymerized using a metallocene polymerization catalyst.

  Moreover, it is preferable that melting | fusing point Tm of a polyethylene-type resin is 95-115 degreeC. In this case, when obtaining the composite resin, the polyethylene resin can be sufficiently impregnated with the styrene monomer, and the suspension system can be prevented from becoming unstable during the polymerization. As a result, it is possible to obtain a foamed resin molded article having both the excellent rigidity of the polystyrene-based resin and the excellent restorability of the polyethylene-based resin at a higher level. More preferably, the melting point Tm of the polyethylene resin is 100 to 110 ° C. The melting point Tm of the polyethylene resin can be measured by differential scanning calorimetry (DSC) based on JIS K7121 (1987).

  Further, the polyethylene resin is preferably made of linear low density polyethylene in which the melting point Tm (° C.) and the Vicat softening point Tv (° C.) satisfy the relationship of Tm−Tv ≦ 20 (° C.). Since such a polyethylene-based resin exhibits a uniform molecular structure, it is presumed that the network structure due to crosslinking is more uniformly distributed in the polyethylene-based resin. From this viewpoint, the linear low-density polyethylene preferably satisfies Tm−Tv ≦ 15 (° C.), and more preferably satisfies Tm−Tv ≦ 10 (° C.). The Vicat softening point Tv of the polyethylene resin can be measured based on JIS K 7206 (1999).

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

(Polystyrene resin constituting composite resin)
Moreover, the said polystyrene-type resin means what a styrene component unit is 75 mass% or more. The styrene component unit in the polystyrene resin is preferably 80% by mass or more, and more preferably 90% by mass or more. In the present specification, styrene constituting the polystyrene resin and a monomer copolymerizable with styrene added as necessary may be collectively referred to as a styrene monomer.
Examples of the monomer copolymerizable with styrene include the following styrene derivatives and other vinyl monomers.

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

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

  As the polystyrene resin, polystyrene or a copolymer of styrene and an acrylic monomer is preferable because of particularly excellent foamability, and a copolymer of styrene and butyl acrylate is preferable. In this case, the content of the butyl acrylate component in the composite resin is preferably 0.5 to 10% by mass, more preferably 1 to 8% by mass, based on the entire composite resin. More preferably, it is -5 mass%.

The weight average molecular weight of the polystyrene resin is preferably 100,000 to 600,000.
In this case, when the foamable composite resin particles are foamed, shrinkage of the foamed particles can be prevented, and further, the fusibility between the foamed particles can be improved when the foamed particles are molded in the mold. As a result, the dimensional stability of the foamed resin molded body can be improved. From the same viewpoint, the weight average molecular weight of the polystyrene-based resin is more preferably 300,000 or more, further preferably 350,000 or more, and further preferably 400,000 or more. The weight average molecular weight of the polystyrene resin is more preferably 550,000 or less.

The glass transition temperature (Tg) of the polystyrene resin is preferably 85 to 100 ° C. In this case, the foamability of the foamable composite resin particles can be improved, the shrinkage at the time of foaming can be prevented. Therefore, the dimensional stability of the foamed resin molded product can be improved.
The glass transition temperature (Tg) of the polystyrene resin can be measured, for example, as follows.
First, 1.0 g of expandable composite resin particles are placed in a 150 mesh wire net bag. Next, about 200 ml of xylene is placed in a 200 ml round flask, and the sample placed in the wire mesh bag is set in a Soxhlet extraction tube. Heat with a mantle heater for 8 hours to extract Soxhlet. The extracted xylene solution is dropped into 600 ml of acetone, decanted, and the supernatant is evaporated to dryness under reduced pressure to obtain a polystyrene resin as an acetone-soluble component. About 2-4 mg of obtained polystyrene resin, a heat flux differential scanning calorimetry is performed based on JIS K7121 (1987) using the DSC measuring device (Q1000) by a TI instrument company. And glass transition temperature Tg can be calculated | required as a midpoint glass transition temperature of the DSC curve obtained on the conditions of a heating rate of 10 degree-C / min.

(Morphology of composite resin in expandable composite resin particles)
The morphology of the composite resin in the foamable composite resin particles includes a morphology in which a polyethylene resin and a polystyrene resin form a co-continuous phase (sea-sea structure), a polyethylene resin in a dispersed phase (island phase), and a polystyrene resin. There is a morphology (island structure) forming a continuous phase (sea phase), or a morphology (sea island structure) in which a polyethylene resin forms a continuous phase and a polystyrene resin forms a dispersed phase. Among these morphologies, polyethylene resin forms a continuous phase and polystyrene resin forms a dispersed phase (sea-island structure), or polyethylene resin and polystyrene resin form a co-continuous phase (sea-sea structure). It is preferable to show. In this case, more excellent resilience can be obtained as compared with the morphology (the island sea structure) in which the polystyrene-based resin forms a continuous phase and the polyethylene-based resin forms a dispersed phase.

The morphology of the expandable composite resin particles can be observed by the following method.
Specifically, first, a sample for observation is cut out from the center of the expandable composite resin particles. Next, the observation sample is embedded in an epoxy resin and stained with ruthenium tetroxide, and then an ultrathin section is prepared from the sample using an ultramicrotome. This ultrathin slice is placed on a grid, and the morphology of the cross section at the center of the foamable composite resin particle is observed with a transmission electron microscope (JEM1010 manufactured by JEOL Ltd.) at a magnification of 10,000 to take a cross-sectional photograph (TEM photograph). . From the cross-sectional photograph, the morphology of the polyethylene resin phase and the polystyrene resin phase in the expandable composite resin particles is visually observed.
In addition, when the composite resin exhibits the morphology of the above form at the center of the foamable composite resin particle, it has been confirmed that a foamed resin molded body having more excellent resilience can be obtained. In this case, it is considered that the same morphology is exhibited not only in the central portion of the expandable composite resin particles but also in the substantially entire portion excluding the surface portion.

(Compressive stress and apparent density of the compressed composite resin foam molding)
The third feature of the compressed composite resin foam molded article obtained by compressing the in-mold molded article of the composite resin foam particles of the present invention is that 10% compression stress of the compressed composite resin foam molded article obtained by the compression treatment [ kPa] is divided by apparent density [kg / m ³ ] (hereinafter also referred to as compression stress ratio) is 3 or less, preferably 2.8 or less, more preferably 2.5 or less.

  In general, in foamed resin moldings made of the same base resin, there is a correlation between the apparent density and the compressive stress, and the higher the apparent density, the higher the compressive stress and the relatively higher the compressive stress ratio. It has been. On the other hand, the compression stress ratio of the compression composite resin foam molded article of the present invention is as small as 3 or less, and it can be said that the foam is more flexible than the conventional composite resin foam molded article.

The 10% compression stress [kPa] of the compression composite resin foam molded article is obtained by cutting a plate-shaped test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm from the compression composite resin foam molded article, in accordance with JIS K 7220 (2006). The compression stress [kPa] when the compression test is conducted and the compression strain is 10%.
Further, the apparent density [kg / m ³ ] of the compressed composite resin foamed molded product is calculated by dividing the mass of the compressed composite resin foamed molded product by its volume.

(Compression set of compression composite resin foam molding)
The fourth feature of the compression composite resin foam molded article obtained by compressing the in-mold molded article of the composite resin foam particles of the present invention is that the compression set is 10% or less, preferably 9% or less, more preferably 8% or less. By this, the compression composite resin foaming molding of this invention can exhibit the outstanding recoverability reliably.

  The compression set is JIS K 6767 (1999) except that a plate-like test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm is cut out from the compressed composite resin foamed molded article and the thickness is measured after 10 days from the end of compression. ). Usually, the speed of recovery of the foamed molded product after compression is determined not only by the characteristics of the base resin and the state of destruction of the bubbles, but also by the pressure in the bubbles due to the foaming agent and air remaining in the bubbles. In the polyolefin resin foam molded article, since the polyolefin resin is flexible, the thickness is sufficiently recovered from compression in about 24 hours. On the other hand, in the polystyrene resin foam molded article, since the bubbles are destroyed, the thickness cannot be recovered even after being left for 24 hours or longer. On the other hand, the compression composite resin foam molded article of the present invention has a high rigidity of the base resin, and since the bubbles are not destroyed, the thickness gradually recovers with the recovery of the bubble internal pressure. For this reason, in the present invention, the compression set was obtained by adopting the thickness after 10 days from the time when the thickness recovery degree is stabilized.

(Closed cell ratio of compressed composite resin foam molding)
The compressed composite resin foam molded article of the present invention preferably has a closed cell ratio of 60% or more. In this case, a high closed cell ratio is maintained even after the compression treatment, and excellent rebound resilience and resilience can be more reliably exhibited. The method for measuring the closed cell ratio will be described in the examples described later.

(Apparent density of compressed composite resin foam molding)
In addition, from the viewpoint that the restoring property can be stably expressed, the bulk density of the compressed composite resin foam molded article is preferably 5 kg / m ³ or more, and more preferably 8 kg / m ³ or more. On the other hand, the bulk density of the composite resin expanded particles is preferably 50 kg / m ³ or less, more preferably 33 kg / m ³ , and further preferably 25 kg / m ³ or less.

(Compression rate of compressed composite resin foam molding)
In the compressed composite resin foam molded article of the present invention, the composite resin foam molded article has a compression ratio in the range of 25 to 95%, more preferably 50% or more, and more preferably 70% or more so that sufficient resilience is exhibited. It is preferably compressed.

(Method for producing compressed composite resin foam molding)
Below, the manufacturing method of the compression composite resin foaming molding of this invention is demonstrated.
The compressed composite resin foam molded article of the present invention can be easily produced, for example, by the following method.
(1) Production of expandable composite resin particles (2) Production of composite resin foam particles (3) Production of composite resin foam molding (4) Production of compression composite resin foam molding

(1) Expandable composite resin particles The expandable composite resin particles are prepared by first suspending the core particles mainly composed of the above-mentioned polyethylene resin in an aqueous medium, and then preparing a styrene monomer. It is added to the suspension, and the core particles are impregnated with a styrene monomer, polymerized, and the particles are further impregnated with a foaming agent.
When the core particles are impregnated with a styrene monomer and polymerized, the entire amount of styrene monomer can be added in one batch, but the use of a styrene monomer as in the dispersion step and the modification step described later. It is preferable to divide the amount into, for example, a first monomer and a second monomer and add these monomers at different times.

More specifically, the expandable composite resin particles can be produced by performing the following dispersion step, modification step, and impregnation step.
In the dispersion step, a first monomer (styrene monomer) and a polymerization initiator are added to a suspension obtained by suspending core particles mainly composed of a polyethylene resin in an aqueous medium, The first monomer is dispersed in

  Next, in the reforming step, when the suspension is heated and the melting point of the polyethylene resin in the core particles is Tm, the second monomer (styrene) is used at a temperature of (Tm-10) to (Tm + 30) ° C. System monomer) is continuously added to the suspension over a predetermined addition time, and the core particles are impregnated with styrene monomer and polymerized.

  In the impregnation step, the resin particles are physically treated during and / or after polymerization at a temperature within the range of Tg-10 to Tg + 40 (° C.) (where Tg is the glass transition temperature (° C.) of the resulting polystyrene resin). By impregnating the foaming agent, expandable composite resin particles are obtained.

  As the organic physical foaming agent, for example, a saturated hydrocarbon compound having 3 to 6 carbon atoms, a lower alcohol having 5 or less carbon atoms, an ether compound, or the like can be used. Specifically, as the saturated hydrocarbon compound, for example, propane, n-butane, isobutane, cyclobutane, n-pentane, isopentane, neopentane, cyclopentane, n-hexane, cyclohexane and the like can be used. As the lower alcohol, methanol, ethanol or the like can be used. Moreover, as an ether compound, dimethyl ether, diethyl ether, etc. can be used. These foaming agents can be used alone or in a mixture of two or more. In addition, as an ether compound, a C6 or less thing can be used, for example.

  Preferably, the organic physical foaming agent is a saturated hydrocarbon compound having 3 to 6 carbon atoms, more preferably 30 to 80% by mass of isobutane and other hydrocarbons having 4 to 6 carbon atoms. It is preferable to use a mixture with 70% by mass. However, the total amount of isobutane and other hydrocarbons having 4 to 6 carbon atoms is 100% by mass.

  Moreover, it is preferable that content of the foaming agent in an expandable composite resin particle is 3-10 mass%. In this case, the foamability of the foamable composite resin particles can be further improved, and shrinkage during foaming can be prevented. Furthermore, when the composite resin foam particles obtained after foaming are molded in the mold, the fusion property between the composite resin foam particles can be further improved. As a result, the dimensional stability of the obtained foamed resin molded product can be improved. More preferably, the content of the foaming agent is 4% by mass or more and 9% by mass or less.

Hereinafter, each process in the manufacturing method of an expandable composite resin particle is demonstrated in detail.
In the dispersion step, for example, the core particles can be suspended in an aqueous medium containing a suspending agent, a surfactant, a water-soluble polymerization inhibitor, and the like to prepare a suspension. In the dispersion step, the first monomer and the polymerization initiator are added to the suspension.

  The core particle can contain additives such as a bubble regulator, a pigment, a slip agent, an antistatic agent, a flame retardant and the like. The core particles can be produced by blending a polyethylene-based resin and a dispersion diameter expanding agent (thermoplastic resin) added as necessary, and melt-kneading the blend, and then pulverizing it. 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. By using a dispersion diameter expanding agent, the size of the polystyrene resin phase can be adjusted, and the morphology of the polyethylene resin and the polystyrene resin can be controlled. As a result, it is possible to improve the retention of the foaming agent and the foam moldability, and it is possible to realize a foamed resin molded article excellent in strength while maintaining the tenacity characteristic of the polyethylene resin. In order to uniformly disperse the dispersion diameter expanding agent, it is preferable to perform melt kneading using a high dispersion type screw or twin screw extruder such as a dalmage type, a Maddock type, and a unimelt type.

  As the dispersion diameter expanding agent, for example, at least one selected from polystyrene, acrylonitrile-styrene copolymer, rubber-modified polystyrene, ABS resin, and AES resin can be used. An acrylonitrile-styrene copolymer is preferable. The amount of acrylonitrile component in the acrylonitrile-styrene copolymer is preferably 20 to 40% by mass.

When a dispersion diameter expanding agent is used, the dispersion diameter expanding agent is dispersed in the polyethylene resin of the core particles. At this time, the average diameter (dispersion diameter) of the phase composed of the dispersion diameter expanding agent dispersed in the polyethylene resin is preferably 10 to 1000 nm, and more preferably 10 to 500 nm. This dispersion diameter is an average value of the equivalent circle diameters of the phase composed of the dispersion diameter expanding agent in the cross section of the core particle.
The melt mass flow rate (MFR (200 ° C., 5 kgf)) of the dispersion diameter expanding agent is preferably 1 g / 10 min to 20 g / 10 min, and more preferably 2.5 g / 10 min to 15 g / 10 min. The MFR (200 ° C., 5 kgf) of the dispersion diameter expanding agent is a value measured by the condition code H based on JIS K7210 (1999). As a measuring device, a melt indexer (for example, model L203 manufactured by Takara Kogyo Co., Ltd.) can be used.

  The content of the dispersion diameter-enlarging agent in the core particles is preferably 1 to 10 parts by mass, and more preferably 3 to 7 parts by mass with respect to 100 parts by mass of the polyethylene resin constituting the core particles. If content of a dispersion diameter expansion agent is in the said range, it will become easy to form the morphology in which a polyethylene-type resin and a polystyrene-type resin show a co-continuous phase (sea-sea structure). Moreover, if it is in the said range, it will become easy to enlarge the dispersion diameter of a polystyrene-type resin (dispersed phase) in the morphology (sea island structure) in which a polyethylene-type resin makes a continuous phase and a polystyrene-type resin makes a dispersed phase. As a result, the foaming agent holding performance of the expandable composite resin particles can be sufficiently improved. Further, from the viewpoint of maintaining good restoration property of the foamed resin molded product obtained by foaming the foamable composite resin particles and molding in-mold, it is preferable to set the content of the dispersion diameter expanding agent in the above range. .

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

The refinement of the core particles can be performed by cutting the compound melt-kneaded with an extruder 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.
Considering the balance between the holding power of the foaming agent and the filling property into the mold at the time of in-mold molding, the particle diameter of the core particles is preferably 0.1 to 3.0 mm, more preferably 0.3 to 1.5 mm. .
When an extruder is used, for example, the resin is extruded from a hole having a diameter within a desired particle diameter range, and the particle diameter is adjusted to a desired range by cutting the resin by changing the cut speed. be able to.

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. Fine particulate inorganic suspending agents such as barium carbonate, calcium sulfate, barium sulfate, talc, kaolin and bentonite can be used. In addition, organic suspending agents such as polyvinyl pyrrolidone, polyvinyl alcohol, ethyl cellulose, and hydroxypropyl methyl cellulose can also be used. Preferred are tricalcium phosphate, hydroxyapatite, and magnesium pyrophosphate. These suspending agents can be used alone or in combination of two or more.

  The amount of the suspending agent used is 0.05 to 10 parts by mass in solid content with respect to 100 parts by mass of the suspension polymerization aqueous medium (all water in the system including water such as the reaction product-containing slurry). Is preferred. More preferably, 0.3-5 mass parts is good. If the suspending agent is out of the above range and is too small, it becomes difficult to suspend and stabilize the styrene-based monomer, and a lump of resin may be generated. On the other hand, when the suspending agent is too much out of the above range, not only the manufacturing cost increases but also the particle size distribution may be widened.

  A surfactant can be added to the suspension. As the surfactant, conventionally known ones such as an anionic surfactant, a nonionic surfactant, a cationic surfactant, and an amphoteric surfactant can be used.

In order to obtain a foamed resin molded article having excellent toughness and mechanical strength, it is preferable to add a water-soluble polymerization inhibitor to the suspension.
As the water-soluble polymerization inhibitor, for example, sodium nitrite, potassium nitrite, ammonium nitrite, L-ascorbic acid, citric acid and the like can be used.
The water-soluble polymerization inhibitor is difficult to impregnate into the core particles and dissolves in an aqueous medium. Therefore, polymerization of the styrenic monomer impregnated in the core particles is performed, but 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 polystyrene-based 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.

  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 styrene 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 amyl peroxy-2-ethylhexyl carbonate, hexyl peroxy-2-ethylhexyl carbonate, and lauroyl peroxide can be used. As the polymerization initiator, an azo compound such as azobisisobutyronitrile can be used. These polymerization initiators can be used alone or in combination of two or more. Moreover, t-butylperoxy-2-ethylhexanoate is preferable as the polymerization initiator from the viewpoint that it is easy to adjust the swelling degree of the composite resin and to easily reduce the residual monomer.

  The polymerization initiator can be dissolved in a solvent such as toluene and added to impregnate the core particles, but it is preferably dissolved in advance in a styrene monomer. The polymerization initiator is preferably used within a range of 0.01 to 3 parts by mass with respect to 100 parts by mass of the styrene monomer.

  In order to efficiently crosslink the polyethylene resin, it is preferable to use an organic peroxide or the like having a 10-hour half-life temperature of 5 to 50 ° C. higher than the polymerization temperature of the styrene monomer. Specifically, for example, peroxides such as dicumyl peroxide, 2,5-t-butyl perbenzoate, and 1,1-bis-t-butyl peroxycyclohexane can be used. Among these, it can use individually or in combination of 2 or more types, and it is preferable that the compounding quantity is 0.1-5 mass parts with respect to 100 mass parts of styrene-type monomers.

  In order to make the swelling degree of the composite resin within the above range, the ratio of the mass of the styrene monomer added as the first monomer to the mass of the core particles is preferably 1 or more. The upper limit is about 3 in general. Furthermore, the concentration of the polymerization initiator with respect to the core particles is preferably 4% by mass or less. The lower limit is about 2% by mass.

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. The bubble regulator is preferably used in an amount of 0.01 to 2 parts by mass with respect to 100 parts by mass of the styrene monomer.

Moreover, a plasticizer, an oil-soluble polymerization inhibitor, a flame retardant, a dye, etc. can be added to a styrene-type monomer as needed.
As the plasticizer, for example, fatty acid esters, acetylated monoglycerides, fats and oils, hydrocarbon compounds and the like can be used. As the oil-soluble polymerization inhibitor, for example, para-t-butylcatechol, hydroquinone, benzoquinone and the like can be used.

  Next, in the reforming step, heating of the suspension after the dispersing step is started. When the melting point of the polyethylene resin in the core particle is Tm, the second monomer (styrene monomer) is added to the suspension at a temperature of (Tm-10) to (Tm + 30) ° C. over a predetermined addition time. It is preferable to add continuously. As a result, the core particles can be impregnated with the styrene monomer and polymerized. When the temperature at which the second monomer is added deviates from the temperature of (Tm-10) to (Tm + 30) ° C., the suspension system may become unstable and a resin mass may be generated. The temperature at which the second monomer is added is more preferably (Tm−5) to (Tm + 10) ° C.

  The blend of the core particles and the styrene monomer is adjusted so that the mass ratio of the polyethylene resin and the polystyrene resin is 5:95 to 25:75 (polyethylene resin: polystyrene resin, the total of both being 100). It is preferable to do. Furthermore, the mass ratio (polyethylene resin: polystyrene resin) is more preferably adjusted to be 10:90 to 19:81, and further preferably adjusted to be 12:88 to 17:83.

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

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

Moreover, after impregnation with the foaming agent, the foamable composite resin particles can be dehydrated and dried, and the surface coating agent can be coated on the surface of the foamable composite resin particles 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. It is preferable that the addition amount of a surface coating agent is 0.01-2 mass parts with respect to 100 mass parts of expandable composite resin particles.

(2) Composite resin foam particles Composite foam foam particles can be obtained by foaming the foamable composite resin particles obtained above by heating with a heating medium. 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. The foamable composite resin particles can also be foamed by releasing the foamable composite resin particles dispersed in the aqueous medium in the sealed container from the sealed container together with the dispersion medium.
For the pre-foaming of the expandable composite resin particles, it is desirable to use a batch-type foaming facility used for pre-foaming of ordinary expandable polystyrene. At that time, if the bulk density of the pre-expanded particles is less than 5 kg / m ³ , molding with a mold becomes difficult, and if it is 50 kg / m ³ or more, the pressure required for the compression treatment of the foamed molded product becomes excessive.

(3) Composite resin foam molded body The composite resin foam particle molded body is filled with the above composite resin foam particles in a mold in which a cavity having a desired shape is formed, and a heating medium such as steam is introduced into the mold. It can be produced by fusing the composite resin foamed particles together. The apparent density of the composite resin foamed particle molded body is preferably ⁵ to 50 kg / m ³ from the viewpoint of combining excellent lightweight properties, rigidity, and restoring properties. 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.

(4) Compressed composite resin foam molded body The compressed composite resin foam molded body is manufactured by compressing the composite resin foam molded body.
The compression ratio of the composite resin foam molding is preferably in the range of 25 to 95%, more preferably 50% or more, and more preferably 70% or more. If the compression rate is less than 25%, sufficient rebound resilience cannot be obtained. If the compression rate exceeds 95%, the pressure becomes excessive in the compression treatment.
The compression direction of the composite resin foam molded body is one axis or more, preferably two axes or more. More preferably, there are three axes. Furthermore, the compression directions are preferably orthogonal to each other.
The number of compressions of the composite resin foam molded article is one or more times, preferably two or more times, more preferably three or more times. The compression speed of the composite resin foam molded article is preferably 100 mm / min or less, more preferably 50 mm / min or less, more preferably, in order to suppress the reduction in the resilience and resilience of the resulting compressed composite resin foam molded article. 30 mm / min or less.

  The compression composite resin foam molded article according to the present invention has a small deformation amount after the compression treatment and exhibits excellent resilience and resilience. Therefore, the compression composite resin foam molded article of the present invention is suitably used as packaging materials, cushions, mattress bedding, playground equipment, etc. that require characteristics such as rigidity, impact resilience, and resilience.

  Below, the Example and comparative example of a compression composite resin foaming molding are demonstrated.

(Example 1)
In this example, first, (1) core particles (polyethylene resin core particles) are prepared, and (2) expandable composite resin particles are prepared from the core particles. Next, (3) composite resin foam particles and (4) composite resin foam molded article are produced from the expandable composite resin particles. Next, a target (5) compression composite resin foam molded article is produced from the composite resin foam molded article.
Hereinafter, the manufacturing method of the compression composite resin foaming molding of this example is explained.

(1) Production of Core Particles As a polyethylene resin, linear low density polyethylene (“Nipolon Z 9P51A” manufactured by Tosoh Corporation) obtained by polymerization using a metallocene polymerization catalyst was prepared. The melting point Tm (° C.), Vicat softening point Tv (° C.) of resin A, and the difference between these (Tm−Tv: ° C.) are shown in Table 1 below. A polymer (“AS-XGS, manufactured by Denki Kagaku Kogyo Co., Ltd., weight average molecular weight: 109000, acrylonitrile component amount: 28 mass%, MFR (200 ° C., load 5 kg): 2.8 g / 10 min) was prepared. Then, 20 kg of a polyethylene resin and 1 kg of a dispersion diameter expanding agent are put into a Henschel mixer (Mitsui Miike Kako Co., Ltd .; Model FM-75E) and mixed for 5 minutes. To obtain a resin mixture Te.
Next, the resin mixture was melt-kneaded at a temperature of 230 to 250 ° C. using an extruder (Icage Co., Ltd .; model MS50-28; 50 mmφ single-screw extruder, Maddock type screw), and 0. Core particles (polyethylene resin core particles) were obtained by cutting into 4 to 0.6 mg / unit (average of 0.5 mg / unit).

(2) Production of Expandable Composite Resin Particles 1000 g of deionized water was added to an autoclave with an internal volume of 3 L equipped with a stirrer, and 6.0 g of sodium pyrophosphate was further added. Thereafter, 12.9 g of powdered magnesium nitrate hexahydrate was added and stirred at room temperature for 30 minutes. This produced the magnesium pyrophosphate slurry as a suspending agent.

  Next, 1.5 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, as polymerization initiators, 1.29 g of benzoyl peroxide (“NIPER BW” manufactured by NOF Corporation, water-diluted powder product) and 2.58 g of t-butylperoxy-2-ethylhexyl monocarbonate (manufactured by NOF Corporation “ Perbutyl E "), dicumyl peroxide (" PARK Mill D "manufactured by NOF Corporation) 0.86 g was dissolved in the first monomer (styrene monomer). Then, the dissolved product was put into the suspension in the autoclave while stirring at a stirring speed of 500 rpm. As the first monomer, a mixed monomer of 250 g of styrene and 15 g of butyl acrylate was used.

  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, the temperature was maintained at 88 ° C. for 30 minutes. Thereafter, the stirring speed was lowered to 450 rpm, and the temperature was cooled from 88 ° C. to 80 ° C. over 30 minutes. Subsequently, this polymerization temperature was kept at 80 ° C. for 8 hours. When the temperature reached 80 ° C., 110 g of styrene as the second monomer (styrene monomer) was added into the autoclave over 5 hours.

  Next, the temperature was raised to 125 ° C. over 4 hours, and the temperature was kept 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., 16 g of cyclohexane and 52 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 as the blowing agent over about 1 hour. 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. FIG. 2 shows a transmission electron micrograph (magnification of 10,000 times) of the cross section of the center part of the expandable composite resin particles obtained in this example. As the transmission electron microscope, JEM1010 manufactured by JEOL Ltd. was used. In the figure, the dark gray portion is a polyethylene resin, and the light gray portion is a polystyrene resin. In the figure, the dark gray portion is a polyethylene resin, and the light gray portion is a polystyrene resin. As shown in the figure, the foamable composite resin particles of this example showed a morphology (sea-sea structure) in which the polyethylene resin and polystyrene resin of the composite resin become a co-continuous phase (sea-sea structure). Further, an antistatic agent (N, N-bis (2-hydroxyethyl) alkylamine) is added to the foamable composite resin particles obtained, and a mixture of zinc stearate, glycerol monostearate, and glycerol distearate. Coated with. In this way, expandable composite resin particles were produced.

  About the foamable composite resin particles obtained as described above, polymerization conditions (mixing ratio of polyethylene resin and polystyrene resin, type of polyethylene resin, mixing ratio of the first monomer with respect to the amount of polyethylene resin (core particles)) (First monomer / polyethylene resin; mass ratio)), polymerization initiator amount (mixing ratio of polymerization initiator to composite resin (mass%)), transition of temperature control during polymerization) are shown in Table 2 below. In addition, with respect to the expandable composite resin particles, the degree of swelling, the ratio of xylene insolubles, the weight average molecular weight (Mw) of the polystyrene resin, the morphology of the composite resin composed of the polyethylene resin (PE) and the polystyrene resin (PS), PE The interfacial ratio between PS and PS was examined as follows. The results are shown in Table 2.

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

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

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

"Morphology of composite resin and interfacial ratio of PE and PS"
An observation sample 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 (center) of the foamable composite resin particles was observed with a transmission electron microscope (JEM1010 manufactured by JEOL Ltd.) at a magnification of 10,000 times. ). From the cross-sectional photograph, the morphology of the phase of the polyethylene resin (PE) and the phase of the polystyrene resin (PS) in the expandable composite resin particles was visually observed.

(3) Preparation of Composite Resin Expanded Particles Next, composite resin expanded particles having a bulk density of about 12.5 kg / m ³ were prepared using the expandable composite resin particles obtained as described above.
Specifically, first, the foamable composite resin particles were placed in a 30 L atmospheric pressure batch foaming machine, and steam was supplied into the foaming machine. Thereby, the foamable composite resin particles were foamed to a bulk density of about 25 kg / m ³ to obtain composite resin foam particles having a bulk foaming magnification of 40 times. The obtained composite resin expanded particles were aged at room temperature for 1 day.
Subsequently, the composite resin foam particles having a bulk foaming ratio of 40 times were placed in a 30 L atmospheric pressure batch foaming machine, and steam was supplied into the foaming machine. Thereby, the composite resin foamed particles were foamed to a bulk density of about 12.5 kg / m ³ to obtain composite resin foamed particles having a bulk foaming magnification of 80 times. The obtained composite resin expanded particles were aged at room temperature for 1 day.

(4) Production of Composite Resin Foam Molded Article Next, the composite resin foamed particles were molded into a 1000 mm × 600 mm × 150 mm rectangular compact using a mold molding machine (DAISEN Co., Ltd., VS1300). The obtained molded body was dried at a temperature of 40 ° C. for 1 day, and further cured at room temperature for 1 day or more.
In this way, composite resin foam particles having a bulk density of about 12.5 kg / m ³ were molded to obtain a composite resin foam molded article having an expansion ratio of 80 times. The expansion ratio of the composite resin foamed molded product can be calculated from the following equation by calculating the apparent density (kg / m ³ ) by dividing the mass of the molded product by its volume.
Foaming magnification (times) = 1000 / apparent density (kg / m ³ )

Next, the composite resin foam molded article was measured for 10% compression stress (kPa), compression set (%), coefficient of restitution (%), and closed cell ratio (%) as follows.
The results are shown in Table 2. Table 2 also shows the apparent density (value divided by the composite resin foam molded product before compression) of the composite resin foam molded product.

"10% compressive stress"
A plate-shaped test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm was cut out from the foamed resin molded article, and a compression test was performed in accordance with JIS K 7220 (2006). The compressive stress when the compressive strain is 10% is 10% compressive stress (kPa).

"Compression set"
A compression set (%) according to JIS K 6767 (1999) except that a plate-like test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm was cut out from the foamed resin molded article and the thickness was measured after 10 days had elapsed after completion of compression. )

"Restitution coefficient"
A plate-shaped test piece having a length of 75 mm, a width of 75 mm, and a thickness of 25 mm was cut out from the foamed resin molded article, and the coefficient of restitution was measured according to JIS K 6400-3 (2011).

"Closed cell ratio"
A cube-shaped test piece having a length of 25 mm, a width of 25 mm, and a thickness of 25 mm was cut out from the foamed resin molded body, and then the test piece was left in a temperature-controlled room at atmospheric pressure, relative humidity of 50%, and temperature of 23 ° C. for one day. . It was then measured volume V _a of the exact appearance of the test piece. Next, after sufficiently drying the test piece, according to the procedure C described in ASTM-D2856-70, the true volume V _x of the test piece was measured by an air comparative hydrometer 930 manufactured by Toshiba Beckman Co., Ltd. Was measured. Based on these volume values V _a and V _x , the closed cell ratio was calculated from the following formula (6). In addition, measurement and calculation were performed about five different test pieces, and the average value was calculated | required. This average value was defined as the closed cell ratio.
Closed cell ratio (%) = (V _x −W / ρ) × 100 / (V _a −W / ρ) (6)
(However, V _x : the true volume of the foamed resin molded body measured by the above method, that is, the volume of the resin constituting the foamed resin molded body and the total volume of bubbles in the closed cell portion in the foamed resin molded body. Sum (cm ³ ), V _a : Foamed resin molded body is submerged in a graduated cylinder containing water, and apparent volume (cm ³ ) of the foamed resin molded body measured from the rise in water level, W: Foamed resin molded body Weight (g), ρ: density of the composite resin constituting the foamed resin molding (g / cm ³ ))

(5) Production of compression composite resin foam molded body A plate-shaped test piece having a length of 100 mm, a width of 100 mm, and a thickness of 100 mm was cut out from the composite resin foam molded body, and the compression rate was 30 mm / min in the thickness direction from the upper surface using a press machine. Compressed 75% and immediately unloaded.

  Next, with respect to the obtained compressed composite resin foamed molded article, the apparent density, 10% compressive stress (kPa), compression set (%), coefficient of restitution (%), closed cells, in the same manner as the composite resin foam molded article The rate (%) was measured. The results are shown in Table 2. Table 2 also shows the value obtained by dividing the 10% compression stress of the compressed composite resin foam molded article by the apparent density (apparent density after compression). Table 1 shows the polyethylene resin used.

(Example 2)
In this example, a compressed composite resin foam molded article was produced in the same manner as in Example 1 except that the compression rate of the composite resin foam molded article was 50%.

(Example 3)
In this example, a compressed composite resin foam molded article was produced in the same manner as in Example 1 except that the compression rate of the composite resin foam molded article was 90%.

Example 4
In this example, a compressed composite resin foam molded article was produced in the same manner as in Example 1 except that in the compression treatment of the composite resin foam molded article, the compression directions were two axes perpendicular to each other.

(Example 5)
In this example, a compressed composite resin foam molded article was produced in the same manner as in Example 1 except that in the compression treatment of the composite resin foam molded article, the compression directions were three axes orthogonal to each other.

(Example 6)
In this example, a compressed composite resin foamed molded article was produced in the same manner as in Example 1 except that the number of compressions was three in the compression treatment of the composite resin foamed molded article.

(Example 7)
In this example, a compressed composite resin foam molded article was produced in the same manner as in Example 1 except that the compression speed of the composite resin foam molded article was 10 mm / min.

(Example 8)
In this example, a compressed composite resin foam molded article was produced in the same manner as in Example 1 except that the compression speed of the composite resin foam molded article was 80 mm / min.

Example 9
The foamable composite resin particles of Example 1 were placed in a 30 L atmospheric pressure batch foaming machine, steam was supplied into the foaming machine, and the foamable composite resin particles were foamed to a bulk density of about 20 kg / m ^3. 50-fold composite resin expanded particles were obtained. The obtained composite resin expanded particles were aged at room temperature for 1 day.
Subsequently, the composite resin foamed particles having a bulk foaming ratio of 50 times 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 about 9.1 kg / m ³ to obtain composite resin expanded particles having a bulk expansion ratio of 110 times. The obtained composite resin expanded particles were aged at room temperature for 1 day.
Subsequently, it shape | molded and compressed by the method similar to Example 1, and obtained the compression composite resin foaming molding.

(Example 10)
The foamable composite resin particles of Example 1 were placed in a 30 L atmospheric pressure batch foaming machine, steam was supplied into the foaming machine, and the foamable composite resin particles were foamed to a bulk density of about 20 kg / m ^3. 50-fold composite resin expanded particles were obtained. The obtained composite resin expanded particles were aged at room temperature for 1 day.
The obtained composite resin foam particles were aged at room temperature for 1 day, and then molded and compressed in the same manner as in Example 1 to obtain a compressed composite resin foam molded article.

(Example 11)
(1) Production of expandable composite resin particles To an autoclave with an internal volume of 3 L equipped with a stirrer was added 1000 g of deionized water, and 6.0 g of sodium pyrophosphate was further added. Thereafter, 12.9 g of powdered magnesium nitrate hexahydrate was added and stirred at room temperature for 30 minutes. This produced the magnesium pyrophosphate slurry as a suspending agent.

Next, 1.25 g of sodium lauryl sulfonate (10 mass% aqueous solution) as a surfactant, 0.15 g of sodium nitrite as a water-soluble polymerization inhibitor, and the same method as in Example 1 were prepared for this suspension. 75 g of the core particles were charged.
Next, 1.715 g of t-butyl peroxy-2-ethylhexyl monocarbonate (“Perbutyl E” manufactured by NOF Corporation) as a polymerization initiator was dissolved in the first monomer (styrene monomer). Then, the dissolved material was added to the suspension in the autoclave while stirring at a stirring speed of 500 rpm (dispersing step). As the first monomer, a mixed monomer of 60 g of styrene and 15 g of butyl acrylate was used.

  Next, after the inside of the autoclave was purged with nitrogen, the heating was started and the temperature was raised to 100 ° C. over 1 hour and 30 minutes. After the temperature increase, this temperature was maintained at 100 ° C. for 60 minutes. Thereafter, the stirring speed was lowered to 450 rpm and held at a polymerization temperature of 100 ° C. for 7 hours and 30 minutes (reforming step). When 60 minutes had passed since the temperature reached 100 ° C., 350 g of styrene as the second monomer (styrene monomer) was added into the autoclave over 5 hours.

  Next, the temperature was raised to 125 ° C. over 2 hours, and the temperature was kept at 125 ° C. for 5 hours. Thereafter, the mixture was cooled to a temperature of 90 ° C. over 1 hour, the stirring speed was lowered to 400 rpm, and the temperature was kept at 90 ° C. for 3 hours. When the temperature reaches 90 ° C., 20 g of cyclohexane, 15 g of pentane (a mixture of about 80% by mass of normal pentane and about 20% by mass of isopentane) and butane (about 20% by mass of normal butane, about 80% of isobutane) are used as the organic physical foaming agent. 50 g of (mass% mixture) was added into the autoclave over about 1 hour (impregnation step). Further, the temperature was raised to 105 ° C. over 2 hours, kept at 105 ° C. for 5 hours, and then cooled to 30 ° C. over about 6 hours.

After cooling, the contents were taken out, and nitric acid was added to dissolve the magnesium pyrophosphate adhering to the surface of the resin particles. Thereafter, dehydration and washing were performed with a centrifugal separator, and water adhering to the surface was removed with an airflow drying device to obtain expandable composite resin particles having an average particle diameter (d ₆₃ ) of about 1.7 mm.
FIG. 3 shows a transmission electron micrograph (magnification of 10,000 times) of the cross section of the center part of the expandable composite resin particles obtained in this example. As the transmission electron microscope, JEM1010 manufactured by JEOL Ltd. was used. As shown in the figure, the foamable composite resin particles of this example show a morphology (sea-island structure) in which the polyethylene resin of the composite resin forms a continuous phase and the polystyrene resin of the composite resin forms a dispersed phase. It was. In the figure, the salami-like portion present in the polystyrene resin phase (light gray phase) is a dispersion diameter expanding agent.

  0.008 parts by mass of N, N-bis (2-hydroxyethyl) alkylamine as an antistatic agent is added to 100 parts by mass of the resulting expandable composite resin particles, and further 0.12 parts by mass of zinc stearate. Part, 0.04 parts by mass of glycerin monostearate and 0.04 parts by mass of glycerin distearate were added to coat the foamable composite resin particles.

  About the foamable composite resin particles obtained as described above, polymerization conditions (mixing ratio of polyethylene resin and polystyrene resin, type of polyethylene resin, mixing ratio of the first monomer with respect to the amount of polyethylene resin (core particles)) (First monomer / polyethylene resin; mass ratio)), the concentration (% by mass) of the polymerization initiator with respect to the polyethylene resin core particles, and the transition of temperature control during polymerization are shown in Table 2 below. In addition, for the expandable composite resin particles, the degree of swelling, the ratio of xylene insolubles, the weight average molecular weight (Mw) of the polystyrene resin, and the morphology of the composite resin composed of the polyethylene resin (PE) and the polystyrene resin (PS) are shown. It is shown in 2.

(2) Preparation of Composite Resin Expanded Particles Next, composite resin expanded particles having a bulk density of about 20 kg / m ³ were prepared using the expandable composite resin particles obtained as described above.
Specifically, first, the foamable composite resin particles were placed in a 30 L atmospheric pressure batch foaming machine, and steam was supplied into the foaming machine. As a result, the expandable composite resin particles were expanded to a bulk density of about 20 kg / m ³ to obtain composite resin expanded particles having a bulk expansion ratio of 50 times.

(3) Production of compressed foamed resin molded body The obtained composite resin foamed particles were aged at room temperature for 1 day, and then molded and compressed in the same manner as in Example 1 to obtain a compressed foamed resin molded body. It was.

(Example 12)
In this example, expandable composite resin particles were produced in the same manner as in Example 11 except that linear low-density polyethylene (“Kernel KF270” manufactured by Nippon Polyethylene Co., Ltd.) was used as the polyethylene resin. The polyethylene resin used in this example is referred to as “resin B.” Melting point Tm (° C.), Vicat softening point Tv (° C.) of resin B, and the difference between these (Tm−Tv: ° C.) are shown in Table 1 described later. .

(Comparative Example 1)
(1) Preparation of expanded polystyrene particles Expanded polystyrene particles having a bulk density of about 12.5 kg / m ³ were prepared using expandable polystyrene particles (Styrodia PA200).
Specifically, first, expandable polystyrene particles 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 about 12.5 kg / m ³ to obtain expanded polystyrene particles having a bulk expansion ratio of 80 times. The obtained expanded polystyrene particles were aged at room temperature for 1 day.

(2) Production of compression-expanded polystyrene molded body Next, the expanded polystyrene particles were molded into a 1000 mm × 600 mm × 50 mm rectangular body using a mold molding machine (VS1300 manufactured by Daisen Corporation). The obtained molded body was dried at a temperature of 40 ° C. for 1 day, and further cured at room temperature for 1 day or more.
In this manner, expanded polystyrene particles having a bulk density of about 12.5 kg / m ³ were molded to obtain an expanded polystyrene molded body having an expansion ratio of 80 times.
Subsequently, the compression process was performed by the same method as Example 1, and the compression-expanded polystyrene molding with a compression rate of 75% was obtained.

(Comparative Example 2)
In this example, a compression-expanded polystyrene molded body was produced in the same manner as in Comparative Example 1 except that the compression ratio of the expanded polystyrene molded body was 50%.

(Comparative Example 3)
In this example, a compressed foamed resin molded body was produced in the same manner as in Comparative Example 1 except that the compression ratio of the expanded polystyrene molded body was 90%.

(Comparative Example 4)
In this example, a compression-foamed resin molded body was produced in the same manner as in Comparative Example 1 except that the compression direction of the expanded polystyrene molded body was biaxial.

(Comparative Example 5)
In this example, in the compression treatment of the expanded polystyrene molded body, a compressed expanded polystyrene molded body was produced in the same manner as in Comparative Example 1 except that the compression direction was triaxial.

(Comparative Example 6)
In this example, a compressed polystyrene molded body was produced in the same manner as in Comparative Example 1 except that the number of compressions was 3 in the compression treatment of the expanded polystyrene molded body.

(Comparative Example 7)
In this example, a compression-expanded polystyrene molded body was produced in the same manner as in Comparative Example 1 except that the compression rate of the expanded polystyrene molded body was 10 mm / min.

(Comparative Example 8)
In this example, a compressed expanded polystyrene molded article was produced in the same manner as in Comparative Example 1 except that the compression rate of the expanded polystyrene molded article was 80 mm / min.

(Comparative Example 9)
The expandable polystyrene particles of Comparative Example 1 were placed in a 30 L atmospheric pressure batch foaming machine, steam was supplied into the foaming machine, the expandable polystyrene particles were expanded to a bulk density of about 20 kg / m ³ , and the bulk foaming ratio was 50 times. Expanded polystyrene particles were obtained. The obtained expanded polystyrene particles were aged at room temperature for 1 day.
The obtained expanded polystyrene particles were aged at room temperature for 1 day, and then molded and compressed in the same manner as in Comparative Example 1 to obtain a compressed expanded polystyrene molded body.

(Comparative Example 10)
First, in the same manner as in Example 11, core particles and a suspending agent (magnesium pyrophosphate slurry) were prepared. 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 100 g of core particles were added to the suspension.

  Next, 1.29 g of benzoyl peroxide as a polymerization initiator (“NIPER BW” manufactured by NOF Corporation, water diluted powder product) and 2.58 g of t-butylperoxy-2-ethylhexyl monocarbonate (manufactured by NOF Corporation “ Perbutyl E ") and 0.86 g of dicumyl peroxide (" PARK Mill D "manufactured by NOF Corporation) as a crosslinking agent were dissolved in the first monomer (styrene monomer). Then, the dissolved product was put into the suspension in the autoclave while stirring at a stirring speed of 500 rpm. As the first monomer, a mixed monomer of 185 g of styrene and 15 g of butyl acrylate was used.

  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, the temperature was maintained at 88 ° C. for 30 minutes. Thereafter, the stirring speed was lowered to 450 rpm, and the temperature was cooled from 88 ° C. to 80 ° C. over 30 minutes. Subsequently, this polymerization temperature was kept at 80 ° C. for 8 hours. When the temperature reached 80 ° C., 200 g of styrene as the second monomer (styrene monomer) was added into the autoclave over 5 hours.

  Next, the temperature was raised to 125 ° C. over 4 hours, and the temperature was kept 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 as the foaming agent over about 1 hour. 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. FIG. 4 shows a transmission electron micrograph (magnification of 10,000 times) of the cross section of the central portion of the expandable composite resin particles obtained in this example. As the transmission electron microscope, JEM1010 manufactured by JEOL Ltd. was used. In the figure, the dark gray portion is a polyethylene resin, and the light gray portion is a polystyrene resin. As shown in the figure, the expandable composite resin particles of this example showed a morphology (sea-sea structure) in which the polyethylene resin and the polystyrene-based resin of the composite resin became a co-continuous phase (sea-sea structure).
Further, in the same manner as in Example 1, an antistatic agent (N, N-bis (2-hydroxyethyl) alkylamine) was added to the obtained foamable composite resin particles, and zinc stearate and glycerin monostearate were further added. And a mixture of glycerin distearate. In this way, expandable composite resin particles were produced.

  Moreover, foaming, shaping | molding, and compression of the foaming molding were performed like Example 1 using the foamable composite resin particle obtained by this example, and the compression composite resin foaming molding was obtained.

(Comparative Example 11)
In this example, an expandable composite resin was used in the same manner as in Comparative Example 1 except that ethylene-vinyl acetate copolymer (“Ultrasen 626” manufactured by Tosoh Corporation (hereinafter referred to as “resin C”) was used as the polyethylene resin. Particles were made.

  Moreover, foaming, shaping | molding, and compression of the foaming molding were performed like Example 1 using the foamable composite resin particle obtained by this example, and the compression composite resin foaming molding was obtained.

(Results of Examples and Comparative Examples)
About the composite resin foaming molding and compression composite resin foaming molding produced in Examples 2-12 and Comparative Examples 1-11, similarly to Example 1, those 10% compression stress (kPa), compression set (%) The coefficient of restitution (%) and the closed cell ratio (%) were measured. The results are shown in Tables 2-4. Tables 2 to 4 also show values obtained by dividing the 10% compression stress of the composite resin foam molding by the apparent density before compression and the values obtained by dividing the 10% compression stress of the compression composite resin molding by the apparent density before compression. did.
Moreover, about the expandable composite resin particle used in Examples 2-12 and Comparative Examples 10-11, polymerization conditions (mixing ratio of polyethylene resin and polystyrene resin, type of polyethylene resin, polyethylene resin (nuclear particles) Table 2 shows the blending ratio of the first monomer to the amount (first monomer / polyethylene resin; mass ratio), the concentration of the polymerization initiator with respect to the polyethylene resin core particles (mass%), and the temperature control during polymerization). 4 shows. For the foamable composite resin particles, the degree of swelling, the proportion of xylene insolubles, the weight average molecular weight (Mw) of the polystyrene resin, and the morphology of the composite resin composed of the polyethylene resin (PE) and the polystyrene resin (PS) The examination was performed in the same manner as in Example 1. The results are shown in Tables 2 and 4. The polyethylene resins used in Examples 1 to 12 and Comparative Examples 10 to 11 are shown in Table 1.

From Tables 2 to 4, the foamed particle molded body obtained by compressing the in-mold molded body of the composite resin foamed particles of Examples 1 to 12 is excellent in rigidity but has a small compression set, a coefficient of restitution and a restoration. It turns out that it is a compression foaming resin molding excellent in property.

On the other hand, it can be seen that the conventional expanded polystyrene moldings of Comparative Examples 1 to 9 are 50 to 90%, and the compression expanded polystyrene molding has a large compression set and is inferior in the coefficient of restitution and resilience.
Furthermore, it turns out that the compression foaming resin molding of Comparative Examples 10-11 has a large compression set, and a resilience coefficient and a resilience are also inferior.

Claims (5)

A compression-foamed molded product obtained by compressing an in-mold molded product of expanded particles,
The compression foamed molded body is formed from a composite resin of 5 to 25% by weight of a polyethylene resin and 75 to 95% by weight of a polystyrene resin (however, the total of both is 100% by weight). The degree of swelling in methyl ethyl ketone at a temperature of 23 ° C. is a mixed insoluble matter of xylene insoluble matter when the composite resin is subjected to Soxhlet extraction with xylene and acetone insoluble matter contained in the xylene solution after Soxhlet extraction is 1.25 or more. ,
A compression composite resin foam molded article in which a value obtained by dividing a 10% compression stress [kPa] by an apparent density [kg / m ³ ] by a compression treatment is adjusted to 3 or less and a compression set is adjusted to 10% or less.   The compressed composite resin foamed molded article according to claim 1, wherein the foamed film has a bent deformation portion.   3. The compressed composite resin foam molded article according to claim 1, wherein the closed cell ratio is 60% or more. The compressed composite resin foam molded article according to any one of claims 1 to 3, wherein an apparent density is in a range of 5 to 50 kg / m ³ .   The compressed composite resin foamed molded product according to any one of claims 1 to 4, wherein the molded product in the mold is compressed within a range of a compression rate of 25 to 95%.