JP2020050784A - Composite resin particle, expandable particle, expanded particle, and expanded molded body - Google Patents

Abstract

To provide a composite resin particle capable of manufacturing an expanded molded body of which mechanical strength and heat resistance are improved, at good molding processability.SOLUTION: There is provided a composite resin particle for expansion, containing a high density polyethylene resin, an ethylenic copolymer having a carbonyl group, and a polystyrene resin, in which the high density polyethylene resin, the ethylenic copolymer having the carbonyl group, and the polystyrene resin are contained at following mass ratios: (i) total amount of the high density polyethylene resin and an ethylenic copolymer having the carbonyl group/the polystyrene resin=5/95 to 40/60, (ii) the high density polyethylene resin/the ethylenic copolymer having the carbonyl group=5/95 to 50/50, the composite resin particle has a structure in which a surface absorbance ratio D1 (D698/D2850), which is a ratio of absorbance at 2850 cm(D2850) and absorbance at 698 cm(D698) calculated from an infrared absorption spectrum obtained by infrared spectroscopic analysis by an ATR method on a surface thereof, and a surface absorbance ratio D2 (D698/D2850), which is a ratio of absorbance at 2850 cm(D2850) and absorbance at 698 cm(D698) calculated from the infrared absorption spectrum obtained by infrared spectroscopic analysis by an ATR method on a surface of an expanded molded body constituted by a fusion body of an expanded particle derived from the composite resin particle, exhibit D1=0.5 to 2.5 and D2/D1=0.1 to 0.95, and the high density polyethylene resin has density of 935 to 960 kg/m.SELECTED DRAWING: None

Description

  The present invention relates to composite resin particles, expandable particles, expanded particles, and expanded molded articles. Specifically, the present invention relates to a composite resin particle capable of producing a foamed molded article having improved mechanical strength and heat resistance with good moldability, an expandable particle derived from the composite resin particle, a foamed particle, and a foamed molded article. About.

Conventionally, foamed molded articles containing a polystyrene-based resin as a resin component have excellent physical properties such as moldability, heat insulation properties, impact resistance, and cushioning properties. Widely used as such.
In applications of cushioning materials, foamed molded articles are particularly required to have higher impact resistance. Therefore, a foamed molded article containing a polystyrene-based resin and a polyethylene-based resin as a resin component has been proposed to satisfy such characteristics (Japanese Patent No. 6185873: Patent Document 1).
Patent Literature 1 discloses foaming derived from a composite resin particle containing a resin component consisting of 100 parts by mass of seed particles and 100 to 500 parts by mass of a styrene-based polymer obtained by impregnating and polymerizing a styrene-based monomer in the seed particles. Moldings are described. The seed particles include a mixed resin of 100 parts by mass of high-density polyethylene and 20 to 100 parts by mass of an ethylene copolymer,
The high density polyethylene has a density of 935 to 960 kg / m ³ and a softening temperature of 115 to 130 ° C.,
The ethylene copolymer is a copolymer of ethylene and an ester monomer selected from an alkyl acrylate and an aliphatic saturated vinyl monocarboxylate, and contains 1 to 20% by mass of a component derived from the ester monomer; Has a softening temperature of 110 ° C.,
The alkyl acrylate is selected from methyl acrylate and ethyl acrylate;
It is stated that the aliphatic saturated vinyl monocarboxylate is selected from vinyl acetate and vinyl propionate.

Japanese Patent No. 6185873

  In the example of Patent Document 1, an ethylene vinyl acetate copolymer is used as an ethylene copolymer. However, in Patent Document 1, since the amount of the ethylene copolymer is small relative to the amount of the high-density polyethylene resin, the mechanical strength and heat resistance of the foamed molded article derived from the composite resin particles, and the moldability in producing the foamed molded article. Had room for improvement.

  The present inventor has conducted extensive studies and found that by setting the position of the ethylene copolymer within a specific range, even when using a large amount of an ethylene copolymer having a carbonyl group such as an ethylene vinyl acetate copolymer, The present inventors have found that the mechanical strength and heat resistance of the foamed molded article and the moldability at the time of producing the foamed molded article can be improved, and the present invention has been accomplished.

Thus, according to the present invention, foamed composite resin particles comprising a high-density polyethylene resin and an ethylene copolymer having a carbonyl group and a polystyrene resin,
The mass ratio of the high-density polyethylene resin, the ethylene copolymer having a carbonyl group, and the polystyrene resin is as follows:
(I) the total amount of the high-density polyethylene-based resin and the ethylene-based copolymer having a carbonyl group / polystyrene-based resin = 5/95 to 40/60;
(Ii) The high-density polyethylene-based resin / ethylene-based copolymer having a carbonyl group = 5/95 to 50/50
Included in
The composite resin particles,
Part surface ATR method by infrared spectroscopy absorbance of 2850 cm ^-1, which is calculated from the infrared absorption spectrum obtained by (D2850) to the absorbance of 698cm ^-1 (D698) and the surface absorbance ratio is the ratio of D1 ( D698 / D2850),
An absorbance of 2850 cm ⁻¹ (D2850) calculated from an infrared absorption spectrum obtained by performing infrared spectroscopy analysis on the surface of a foamed molded product composed of a fusion body of foamed particles derived from the composite resin particles by the ATR method; ) And the absorbance at 698 cm ^-1 (D698), the surface absorbance ratio D2 (D698 / D2850), are the following values:
D1 = 0.5-2.5,
D2 / D1 = 0.1 to 0.95
Having a structure showing
Composite resin particles are provided, wherein the high-density polyethylene resin has a density of 935 to 960 kg / m ³ .

Further, according to the present invention, there is provided an expandable particle containing the composite resin particle and a blowing agent.
Further, according to the present invention, there is provided expanded particles obtained by expanding the expandable particles.
Further, according to the present invention, there is provided a foam molded article obtained by subjecting the above-mentioned foam particles to foam molding.

ADVANTAGE OF THE INVENTION According to this invention, the composite resin particle which can manufacture a foaming molded object with improved mechanical strength and heat resistance with good moldability can be provided.
In any of the following cases, it is possible to provide a composite resin particle capable of producing a foamed molded article having improved mechanical strength and heat resistance with good moldability.
(1) The ethylene-based copolymer having a carbonyl group is an ethylene-vinyl acetate copolymer, and the ethylene-vinyl acetate copolymer contains 1 to 20% by mass of a component derived from vinyl acetate.
(2) The high-density polyethylene has a melt tension at 160 ° C. of 40 mN or more.
(3) The composite resin particles include seed particles containing high-density polyethylene and an ethylene-vinyl acetate copolymer, and a polystyrene resin derived from a styrene-based monomer impregnated and polymerized in the seed particles.
(4) The difference between the melting point (T1) of the high-density polyethylene and the melting point (T2) of the ethylene-vinyl acetate copolymer is 10 to 40C, and the softening temperature (T3) of the seed particles is 110 to 125C.

(Composite resin particles)
The composite resin particles include a high-density polyethylene resin, an ethylene copolymer having a carbonyl group, and a polystyrene resin. Note that “composite” means that high-density polyethylene resin and polystyrene resin are present in the particles.

(1) high density polyethylene resin density polyethylene resin has a density of 935~960kg / ^{m 3.}
When the density of the high-density polyethylene resin is less than 935 kg / m ³ , the shock absorption of the foamed molded article may be reduced. When it is higher than 960 kg / m ³ , the resin component does not sufficiently soften during the polymerization step, and the expandable particles derived from the composite resin particles may not have sufficient expandability. Preferably the density is 935~950kg / ^{m 3,} more preferably 935~940kg / ^{m 3.}
The high-density polyethylene resin preferably has a melt tension at 160 ° C. of 40 mN or more and an MFR of 2.5 g / 10 minutes or less.
Further, the high-density polyethylene resin is preferably a copolymer of ethylene and an α-olefin having 3 to 8 carbon atoms. Commercial products can be used for the high-density polyethylene resin. Examples of commercially available products include TOSOH-HMS 10S65B (manufactured by Tosoh Corporation) and Novatec HD HY540 (manufactured by Nippon Polyethylene Corporation).
Note that linear low-density polyethylene resins having a density of 935 kg / m ³ or more such as Nipolon Z ZF260 (manufactured by Tosoh Corporation) and Nipolon LM50 (manufactured by Tosoh Corporation) are commercially available. Instead, even if this linear low-density polyethylene resin is used, it is not possible to obtain composite resin particles capable of producing a foamed molded article having sufficiently improved mechanical strength and heat resistance with good moldability.

(2) Ethylene-based copolymer having a carbonyl group An ethylene-based copolymer having a carbonyl group (hereinafter also referred to as an ethylene-based copolymer) does not include the above-mentioned polyethylene-based resin. Examples of the ethylene-based copolymer having a carbonyl group include ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid alkyl ester copolymer, ethylene-methacrylic acid copolymer, ethylene-alkyl methacrylate Ester copolymers and the like can be mentioned. The ethylene-based copolymer is preferably an ethylene-vinyl acetate copolymer. The ethylene-vinyl acetate copolymer preferably contains 1 to 20% by mass of a component derived from vinyl acetate. When the content of the component derived from vinyl acetate is less than 1% by mass, the foaming moldability deteriorates, and a sufficient effect of improving the moldability may not be expected. When the amount is more than 20% by mass, the strength of the foamed molded article is reduced, and sufficient impact absorption may not be provided. The content is preferably from 5 to 15% by mass, and more preferably from 8 to 12% by mass.

(3) Polystyrene-based resin Examples of the polystyrene-based resin include a styrene homopolymer or a copolymer of a styrene monomer as a main component and another monomer component copolymerizable with the styrene monomer. Can be Here, the main component means that the styrene monomer accounts for 50 parts by mass or more, preferably 60 parts by mass or more, more preferably 70 parts by mass or more based on 100 parts by mass of all the monomer components.
As the other monomer that gives the copolymer component contained in the polystyrene resin, a known monomer can be used as long as it does not affect desired physical properties. Specifically, cyclic olefin monomers, diene monomers, vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, ethyl acrylate, butyl acrylate, methyl methacrylate, Examples include vinyl monomers such as maleic anhydride and methylstyrene. These can be used alone or in combination of two or more.

(4) Content ratio of high-density polyethylene resin, ethylene copolymer having carbonyl group and polystyrene resin Composite resin particles are made of high-density polyethylene resin, ethylene copolymer having carbonyl group and polystyrene resin. Is contained in a mass ratio of the total amount of the high-density polyethylene resin and the ethylene copolymer having a carbonyl group / the polystyrene resin = 5/95 to 40/60. When the mass ratio of the total amount is less than 5, the mechanical strength of the obtained foam molded article may decrease. When it is more than 40, the foamable period of the obtained foamed particles may be short. The mass ratio is preferably from 10/90 to 40/60, and more preferably from 15/85 to 35/65.
The composite resin particles are obtained by mixing a high-density polyethylene resin and an ethylene copolymer having a carbonyl group with a mass ratio of 5/95 to 50/50 of the high-density polyethylene resin / ethylene copolymer having a carbonyl group. Including. When the mass ratio of the high-density polyethylene resin is less than 5, heat resistance may be reduced. If it is more than 50, the foam moldability may be reduced. The mass ratio is more preferably from 20/80 to 45/55, and even more preferably from 30/70 to 40/60.

(5) Absorbance ratio (D698 / D2850)
(A) Surface absorbance ratio D1 of composite resin particles (D698 / D2850)
The surface of the composite resin particles exhibits a surface absorbance ratio D1 (D698 / D2850) in the range of 0.5 to 2.5. D2850 and D698 are the absorbance at 2850 cm ^-1 (D2850) and the absorbance at 698 cm ^-1 (D698) calculated from the infrared absorption spectrum obtained by performing infrared spectroscopic analysis by the ATR method. D698 is an absorbance corresponding to an absorption spectrum derived from out-of-plane bending vibration of a benzene ring contained in the polystyrene resin. On the other hand, D2850 is an absorbance corresponding to an absorption spectrum derived from symmetric bending vibration of CH ₂ of —C—CH ₂ hydrocarbon contained in the high-density polyethylene resin and the ethylene copolymer. When the surface absorbance ratio is large, it means that the polystyrene resin component is large, and when it is small, it is small. When the surface absorbance ratio is less than 0.5, the mechanical strength of the obtained foamed molded article may decrease. When it is larger than 2.5, the foamable period of the obtained foamed particles may be short. The surface absorbance ratio is preferably from 0.5 to 2.2, more preferably from 0.5 to 2.0, and even more preferably from 1.0 to 2.0.

(B) The ratio of the surface absorbance ratio D2 (D698 / D2850) of the foam molded article to D1 (D2 / D1)
The ratio (D2 / D1) of the surface absorbance ratio D2 (D698 / D2850) and D1 of the foamed molded product is 0.1 to 0.95. This range of the ratio means that the polystyrene resin component on the surface of the foamed article obtained therefrom is smaller than the surface of the composite resin particle.
By the way, as described in Examples, in this specification, "surface" means a region of a sample in which an infrared absorption spectrum can be measured by the ATR method up to a depth of about several μm. Here, if the depth of the composite resin particle whose infrared absorption spectrum is measured is X1, and the depth of the composite resin particle corresponding to the measured depth of the foam molded product is X2, the relationship X1> X2 is satisfied. This is because the foamed molded article is composed of a fused body of foamed particles obtained by greatly foaming the composite resin particles. Therefore, the absorbance ratio of the surface of the foamed molded article is measured on the surface of the shallow region of the composite resin particle from the absorbance ratio of the surface of the composite resin particle. In the range of D1 and D2 / D1, the region of the depth X1 from the surface of the composite resin particle has more polystyrene resin component. In other words, the composite resin particles contain a little polystyrene resin component in the region closest to the surface. The inventor considers that it is surprising that such composite resin particles having the relationship of the abundance of the polystyrene resin component can produce a foamed molded article having improved mechanical strength and heat resistance with good moldability. ing.
Furthermore, the composite resin particles of the present invention contain a relatively large amount of an ethylene-based copolymer. Even with such composite resin particles, by satisfying the range of D1 and D2 / D1, a foamed molded article having improved mechanical strength and heat resistance can be manufactured with good moldability.
When D2 / D1 is less than 0.1, foamability may be reduced. When it is larger than 0.95, mechanical strength and heat resistance may not be obtained as expected. D2 / D1 is preferably 0.2 to 0.9, and more preferably 0.3 to 0.9.
D2 is preferably from 0.5 to 2.5, more preferably from 0.5 to 2.0, and even more preferably from 0.5 to 1.5.

(6) Other components Other components include resins other than polyethylene resins, ethylene copolymers and polystyrene resins (for example, polypropylene resins and acrylic resins), bubble regulators, coating agents, and light stability. Agents, ultraviolet absorbers, pigments, dyes, defoamers, heat stabilizers, flame retardants, lubricants and antistatic agents.
(7) Shape The shape of the composite resin particles is preferably spherical to approximately spherical. The average particle diameter is preferably from 0.71 to 2.5 mm, more preferably from 0.85 to 1.6 mm.

(Method for producing composite resin particles)
The method for producing the composite resin particles is not particularly limited as long as the composite resin particles described above can be obtained. As an example, composite resin particles can be obtained by the following production method.
That is, composite resin particles can be obtained by polymerizing a styrene-based monomer impregnated into seed particles containing a high-density polyethylene-based resin and an ethylene-based copolymer. This method is a so-called seed polymerization method. According to the seed polymerization method, it is possible to obtain composite resin particles in which a polyethylene resin and an ethylene copolymer are unevenly distributed on the particle surface.

An example of a more specific method for producing composite resin particles will be described below.
First, seed particles containing a high-density polyethylene-based resin and an ethylene-based copolymer, a styrene-based monomer, and a polymerization initiator are dispersed in an aqueous suspension. In addition, you may mix and use a styrene-type monomer and a polymerization initiator beforehand.
Seed particles can be obtained by a known method. For example, a strand was obtained by melt-kneading and extruding a high-density polyethylene-based resin and an ethylene-based copolymer together with an additive (for example, an inorganic nucleating agent) as necessary, in an extruder to obtain a strand. A method of granulating the strand by cutting the strand in the air, cutting in water, and cutting while heating may be used.
Preferably, the seed particles have a softening temperature of 110 to 130 ° C. When the softening temperature of the seed particles is lower than 110 ° C., sufficient heat dimensional stability may not be obtained. When the softening temperature of the seed particles is higher than 135 ° C., the foam moldability is poor, and the productivity may be deteriorated. The softening temperature of the seed particles is preferably from 114 to 130 ° C, more preferably from 116 to 128 ° C.

As the polymerization initiator, those generally used as an initiator for suspension polymerization of a styrene monomer can be used. For example, benzoyl peroxide, di-t-butyl peroxide, t-butylperoxybenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, t-butylperoxy Organic peroxides such as -3,5,5-trimethylhexanoate and t-butyl-peroxy-2-ethylhexyl carbonate. One or two or more of these polymerization initiators can be used.
Examples of the aqueous medium constituting the aqueous suspension include water and a mixed medium of water and a water-soluble solvent (for example, a lower alcohol).

The amount of the polymerization initiator to be used is preferably 0.1 to 0.9 part by mass, more preferably 0.2 to 0.5 part by mass, based on 100 parts by mass of the styrene monomer. If the amount of the polymerization initiator is less than 0.1 part by mass, the polymerization of the styrene monomer may take too long. If the amount of the polymerization initiator exceeds 0.9 parts by mass, the molecular weight of the polystyrene resin may be low.
A dispersant may be added to the aqueous suspension as needed. The dispersant is not particularly limited, and any known dispersant can be used. Specific examples include poorly soluble inorganic substances such as calcium phosphate, magnesium pyrophosphate, sodium pyrophosphate, and magnesium oxide. Further, a surfactant such as sodium dodecylbenzenesulfonate may be used.

Next, the resulting dispersion is heated to a temperature at which the styrene-based monomer is not substantially polymerized, so that the styrene-based monomer is impregnated into the seed particles. The time for impregnating the seed particles with the styrene monomer is preferably 30 minutes to 2 hours. If the polymerization proceeds before sufficient impregnation, a polymer powder of a polystyrene resin may be formed. The higher the temperature at which the monomer does not substantially polymerize is advantageous for increasing the impregnation rate, but it must be determined in consideration of the decomposition temperature of the polymerization initiator.
Next, the styrene monomer is polymerized. The polymerization is not particularly limited, but is preferably performed at 115 to 140 ° C. for 1.5 to 5 hours. The polymerization is usually performed in a pressurized closed container. In addition, impregnation and polymerization of the styrene-based monomer may be performed in plural times. By dividing into a plurality of times, the generation of the polymer powder of the styrene resin can be minimized. In addition, in consideration of the decomposition temperature of the polymerization initiator, the polymerization may be performed not while the seed particles are impregnated with the styrene monomer but while the styrene monomer is impregnated.
Composite resin particles can be obtained by the above method.

As a preferred method for producing composite resin particles, the impregnation and polymerization of the styrene-based monomer are divided into two times, and during the first impregnation, the styrene-based monomer is charged at a specific temperature before the polymerization and before the polymerization. A method including a step of absorbing the system monomer into the seed particles is exemplified. The seed particles used in this preferred production method preferably have at least two or more melting peak temperatures (T1 on the high temperature side and T2 on the low temperature side) in the DSC curve of the seed particles. The specific temperature range is within the temperature range of T1 and T2. The seed particles used in this preferred production method have at least two or more melting peak temperatures (T1 on the high temperature side and T2 on the low temperature side) in the DSC curve of the seed particles, and have a softening point defined by the TMA curve. Those having a temperature T3 are more preferred. The particular temperature range may be within the temperature range of T3 and T1. The step of causing the seed particles to absorb the styrene-based monomer at a specific temperature is more preferably a temperature equal to or higher than the softening temperature T3 defined by the TMA curve of the seed particles used, and 10 The half-life time is preferably performed within a temperature range of T10 ° C. to T10 + 5 ° C. In the step of absorbing the styrene-based monomer into the seed particles, the decomposition rate of the polymerization initiator used reaches 10 to 20%. It is preferable to carry out for a time. Furthermore, when the styrene-based monomer is absorbed by the seed particles at a specific temperature, the first polymerization temperature is preferably in the range of T2 to T1 + 10 ° C.
In addition, in the second polymerization step, it is preferable to perform the polymerization while introducing the styrene-based monomer at a rate of 1.5 parts by mass / minute or less based on 100 parts by weight of the seed particles.

(Expandable particles)
The expandable particles include the composite resin particles and a foaming agent.
As the foaming agent, a known foaming agent having volatility can be used. For example, propane, n-butane (normal butane), i-butane (isobutane), n-pentane (normal pentane), i-pentane (isopentane), n-hexane (normal hexane) and i-hexane (isohexane) alone Or a mixture thereof. Among these, any of n-butane, i-butane, n-pentane, and i-pentane, which can introduce greater foaming performance into the expandable particles, is preferable. The blowing agents may be used alone or in combination of two or more.

The content of the foaming agent is preferably 5 to 20 parts by mass, more preferably 8 to 17 parts by mass, based on 100 parts by mass of the composite resin particles. When the content of the blowing agent is lower than 5 parts by mass, the amount of the blowing agent is insufficient, and the expandable particles may not have sufficient expandability. On the other hand, when the content of the foaming agent is more than 20 parts by mass, the amount of the foaming agent becomes excessive, and also in this case, the expandable particles may not have sufficient expandability.
The shape of the expandable particles is preferably spherical to approximately spherical. The average particle diameter is preferably from 0.71 to 2.5 mm, more preferably from 0.85 to 1.6 mm.

  The expandable particles can be obtained by impregnating the composite resin particles during or after the polymerization with a blowing agent. The impregnation can be performed by a method known per se. For example, the impregnation during the polymerization can be performed by performing the polymerization reaction in a closed container and pressing a foaming agent into the container. Impregnation after the completion of the polymerization is performed by press-fitting a foaming agent in a closed vessel.

(Expanded particles)
The expanded particles are particles obtained by expanding (also referred to as pre-expanding) the expandable particles.
Foam particles, preferably 20 and 100 kg / ^{m 3,} more preferably having a bulk density of 25~100kg / ^{m 3.} If the bulk density is lower than 20 kg / m ³ , the mechanical properties of the obtained foamed molded article may be reduced. On the other hand, if the bulk density is higher than 100 kg / m ³ , the mass of the obtained foamed molded article may increase.
The shape of the expanded particles is preferably spherical to approximately spherical. The average particle size is preferably from 1.0 to 9.0 mm, and more preferably from 2.0 to 6.4 mm.

  The expanded particles can be obtained by expanding the expandable particles to a predetermined bulk density by a known method. Foaming can be obtained by foaming the expandable particles using heated steam of preferably 0.05 to 0.20 MPa (gauge pressure), more preferably 0.06 to 0.15 MPa.

(Foam molding)
The foam molded article is a foam obtained by subjecting the above-described foam particles to foam molding, and constituted by a fused body of the foam particles. Since the foamed molded article uses the composite resin particles as a raw material, it has excellent mechanical properties.
The density of the foamed molded article is preferably 20 and 100 kg / ^{m 3,} more preferably 25~100kg / ^{m 3.}
The foamed molded article can be obtained by filling the foamed particles into a mold of a foaming molding machine and heat-sealing the foamed particles while heating again to foam the foamed particles. Steam can be suitably used as the heating medium.
Other manufacturing conditions such as a process temperature, a process pressure, and a process time in each manufacturing process are appropriately set according to a used manufacturing facility, raw materials, and the like.
The foam molded article can be used for an automobile member, a component packaging material, and a cushioning material.

Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.
(Density of high density polyethylene resin)
The density of the high-density polyethylene resin was measured by a density gradient tube method in accordance with JIS K692-1: 1998.
(Melt flow rate (MFR) of high density polyethylene resin)
The MFR was measured at 190 ° C. under a load of 2.16 kg in accordance with JIS K6922-1: 1998.

(Melting point of high density polyethylene resin)
The melting point was measured by the method described in JIS K7122: 1987 “Method of measuring heat of transition of plastic”. That is, using a differential scanning calorimeter apparatus RDC220 type (manufactured by Seiko Denshi Kogyo), 7 mg of a sample is filled in a measuring container, and 10 ° C./L between room temperature and 220 ° C. under a nitrogen gas flow rate of 30 mL / min. The heating, cooling, and heating were repeated at the heating and cooling speeds, and the melting peak temperature of the DSC curve during the second heating was measured. This melting peak temperature was defined as the melting point. When there were two or more melting peaks, the lower peak temperature was defined as the melting point.

(Measurement of melt tension (160 ° C))
A heat-resistant stabilizer (Irganox 1010TM; 1500 ppm, Irgafos 168TM; 1500 ppm, manufactured by Ciba Specialty Chemicals) added to a polyolefin-based resin was used with an internal mixer (manufactured by Toyo Seiki Seisakusho Co., Ltd., trade name: Labo Plastomill). The mixture was kneaded under a nitrogen stream at 190 ° C. and a rotation speed of 30 rpm for 30 minutes to obtain a measurement sample.
A dice-like sample having a length of 8 mm and a diameter of 2.095 mm was attached to a capillary viscometer having a barrel diameter of 9.55 mm (manufactured by Toyo Seiki Seisakusho Co., Ltd., so that the inflow angle was 90 °). The melt tension was measured.
Regarding the melt tension at 160 ° C., the temperature was set to 160 ° C., the piston descending speed was set to 10 mm / min, the stretching ratio was set to 47, and the load (mN) required for take-up was set. When the maximum stretching ratio was less than 47, the load (mN) required for taking over at the highest stretching ratio that did not break was used.

(Melting peak temperature of seed particles)
The melting point was measured by the method described in JIS K7122: 1987 "Method for measuring heat of transition of plastic".
That is, using a differential scanning calorimeter apparatus DSC6220 type (manufactured by SII Nanotechnology Co., Ltd.), about 6 mg of the sample was filled in the bottom of the aluminum measuring container so that there was no gap. Next, under a nitrogen gas flow rate of 20 mL / min, the temperature was lowered from 30 ° C. to −40 ° C., held for 10 minutes, and then raised from −40 ° C. to 220 ° C. (1st Heating). A DSC curve was obtained when the temperature was lowered to (Cooling) for 10 minutes and then raised from -40 ° C to 220 ° C (2nd Heating) after holding for 10 minutes. In addition, all the temperature raising / lowering was performed at a rate of 10 ° C./min, and alumina was used as a reference substance.
The value obtained by reading the temperature at the top of the melting peak observed in the second heating process using analysis software attached to the apparatus was defined as the melting point. If there are two or more melting peaks, the deepest peak and the next deepest peak are selected, and the lower temperature side peak is the melting peak temperature T1 (° C) and the higher temperature side peak is the melting peak temperature T2 (° C). And

(Softening temperature of ethylene copolymer and seed particles)
The measurement was carried out according to the method described in JIS K7196: 1991 “Testing method for softening temperature of thermoplastic films and sheets by thermomechanical analysis”.
That is, the sample is hot-pressed at 180 ° C. for 5 minutes to produce a disk-shaped test piece having a thickness of 1 mm and a diameter of 10 mm. Using a heat / stress / strain measuring device (SII Nanotechnology Co., Ltd., trade name "EXSTRAR TMA / SS6100") under a nitrogen atmosphere in a penetration test mode (needle tip φ1 mm, quartz probe) at a load of 500 mN A needle was applied to the test piece, and the temperature was increased from 30 ° C. at a rate of temperature increase of 5 ° C./min to obtain a TMA curve. The obtained TMA curve is corrected by setting the quartz coefficient with the analysis software attached to the device, and the straight line portion of the TMA curve, which is recognized on the lower temperature side than the indenter (needle) starts to penetrate, is extended to the higher temperature side, and the penetration speed is reduced. The point of intersection of the tangent of the maximum portion with the extension to the lower temperature side was defined as the penetration temperature, and the penetration temperature was defined as the softening temperature of this sample.

(Absorbance ratio of composite resin particles (D698 / D2850))
(A) The surface absorbance ratio (D698 / D2850) was measured as follows.
In addition, each absorbance obtained from the infrared absorption spectrum was defined as a peak height derived from vibration of each resin component contained in the composite resin particles.
About 10 particles selected at random, the particle cross-section analysis was performed by the infrared spectroscopic analysis ATR measurement method, and the infrared absorption spectrum was obtained. In this analysis, an infrared absorption spectrum in a depth range from the sample surface to several μm (about 2 μm) was obtained.
An individual absorbance ratio (D698 / D2850) was calculated from each infrared absorption spectrum, and their arithmetic mean was defined as an absorbance ratio.
The absorbances D698 and D2850 are measured under the following conditions using a measuring device sold by Nicolet under the trade name “Fourier transform infrared spectrometer MAGNA560” and a “Thunderdome” manufactured by Spectra-Tech as an ATR accessory. did.

(1) Measurement conditions High refractive index crystal seed: Ge (germanium)
Incident angle: 45 ° ± 1 °
Measurement area: 4000 cm ^{-1 to} 675 cm ^-1
Fractional dependence of measurement depth: uncorrected Number of reflections: 1 Detector: DTGS KBr
Resolution: 4cm ^-1
Number of integration: 32 times Others: The infrared absorption spectrum was measured without contact with the sample under the following conditions, and the measured spectrum was used as the background. When measuring the sample, the measured data was processed so that the background did not contribute to the measured spectrum. In the ATR method, the intensity of the infrared absorption spectrum changed depending on the degree of adhesion between the sample and the high refractive index crystal. Therefore, the maximum load applied by the “Thunder Dome” of the ATR accessory was applied to make the degree of adhesion almost uniform, and the measurement was performed.

(2) Background measurement conditions Mode: Transmission Pixel size: 6.25 μm
Measurement area: 4000 cm ^{-1 to} 650 cm ^-1
Detector: MCT
Resolution: 8cm ^-1
Scan / pixel: 60 times Others: Processing not involving the measured spectrum was performed using the infrared absorption spectrum of the barium fluoride crystal in the vicinity of the sample where there was no sample as the background as the background.

The infrared absorption spectrum obtained under the above conditions was subjected to a peak treatment as follows, and the respective absorbances were obtained.
The absorbance D698 at 698 cm ⁻¹ obtained from the infrared absorption spectrum was an absorbance corresponding to the absorption spectrum derived from out-of-plane bending vibration of the benzene ring contained in the polystyrene resin. In the measurement of the absorbance, peak separation was not performed even when another absorption spectrum was overlapped at 698 cm ⁻¹ . Absorbance D698 is a straight line connecting the 2000 cm ^-1 and 870 cm ^-1 as a baseline, and the maximum absorbance between 710 cm ^-1 and 685cm ^-1.

Further, the absorbance D2850 at 2850 cm ⁻¹ obtained from the infrared absorption spectrum indicates the absorption derived from the symmetric bending vibration of CH ₂ of —C—CH ₂ hydrocarbon contained in the polyethylene resin and the ethylene copolymer. The absorbance corresponding to the spectrum was used. In the measurement of the absorbance, peak separation was not performed even when another absorption spectrum overlapped at 2850 cm ⁻¹ . Absorbance D2850 is a straight line connecting the 3125Cm ^-1 and 2720cm ^-1 as a baseline, and the maximum absorbance between 2875cm ^-1 and 2800 cm ^-1.
As a method of obtaining the composition ratio of the polystyrene resin, the polyethylene resin, and the ethylene copolymer from the absorbance ratio, the polystyrene resin, the polyethylene resin, and the ethylene copolymer are uniformly mixed to a predetermined composition ratio. A plurality of types of standard samples were prepared, and each standard sample was subjected to particle surface analysis by ATR infrared spectroscopy to obtain an infrared absorption spectrum. The absorbance ratio was calculated from each of the obtained infrared absorption spectra. A calibration curve was drawn by plotting the composition ratio (polystyrene resin ratio in the standard sample (% by mass)) on the vertical axis and the absorbance ratio (D698 / D2850) on the horizontal axis. Based on this calibration curve, the composition ratio of the polystyrene resin, the polyethylene resin, and the ethylene copolymer in the composite resin particles of the present invention was determined from the absorbance ratio of the composite resin particles of the present invention.

The calibration curve was approximated by the following equation.
When D698 / D2850 ≦ 1.42 Y = 21.112X ₂
· 1.42 <(D698 / D2850) < For _{8.24 Y = 28.415Ln (X 2)} +20.072
In the formula, X ₂ = (D698 / D2850), Y = amount of polystyrene resin (%)

(Absorbance ratio of foamed molded article (D698 / D2850))
The absorbance ratio of the foamed article was measured in the same manner as the composite resin particles after the foamed article was subjected to the following treatment.
By pouring the foamed molded article into an oven at 120 ° C. for 6 to 12 hours, the density of the foamed molded article is reduced to 500 kg / m ³ or more, thereby producing a porous molded article in which polymers are point-adhered to each other. did. The composite resin particles were peeled and collected from the obtained molded body to obtain a sample for measuring the absorbance ratio.

(Bulk density of expanded particles)
The bulk density of the expanded particles was measured in the following manner. First, the graduated cylinder was filled with the expanded particles to a scale of 500 cm ³ . However, the graduated cylinder was visually observed from the horizontal direction, and if even one foamed particle reached the scale of 500 cm ³ , the filling was completed. Next, the mass of the foamed particles filled in the measuring cylinder was weighed to two significant figures after the decimal point, and the mass was defined as W (g). The bulk density of the expanded particles was calculated by the following equation.
Bulk density (kg / m ³ ) = W / 500 × 1000

(Density of foamed molding)
The mass (a) and the volume (b) of a test piece (eg, 75 mm × 300 mm × 35 mm) cut out from a foamed molded product (formed and dried at 50 ° C. for 4 hours or more) each have three or more significant figures. The density (kg / m ³ ) of the foamed molded article was determined by the formulas (a) / (b).

(Falling ball impact value)
A sample obtained by cutting the foamed molded body into a size of 215 mm × 40 mm × 20 mm was prepared, and this sample was placed on a pair of holding members arranged at a span of 155 mm. At the center of the sample in the width direction, a steel ball having a weight of 321 g was dropped from a predetermined height to check whether the sample was broken.
This test was repeated while changing the height at which the steel balls were dropped, and the minimum value of the height at which the sample was broken was taken as the falling ball impact value, and the impact strength was evaluated. Therefore, the higher the falling ball impact value, the higher the impact strength.

(25% compressive strength of foam molding)
The compressive strength was measured by the method described in JIS K7220: 2006 “Hard foamed plastics—How to determine compression characteristics”. That is, using a Tensilon universal testing machine UCT-10T (manufactured by Orientec), the compression strength at the time of 25% compression (at the time of 10 mm displacement) at a compression speed of 10 mm / min for a test specimen having a size of 50 mm × 50 mm × 25 mm. It was measured.

(Heat shrinkage)
The heat-shrinkage rate of the foamed molded article was measured by the method B described in JIS K6767: 1999 “Expanded plastic-polyethylene-test method”. Specifically, a test piece having a length of 150 mm, a width of 150 mm and a height of 20 mm was cut out from the foamed molded article. On the surface of the test piece, three straight lines each having a length of 50 mm and extending in the vertical direction were written at intervals of 50 mm in parallel with each other, and three straight lines each having a length of 50 mm and extending in the horizontal direction and 50 mm each being parallel to each other. Completed at intervals. Thereafter, the test piece was left in a hot air circulating drier at 80 ° C. for 168 hours, then taken out, and taken out under a standard condition (20 ± 2 ° C., humidity 65 ± 5%) for 1 hour. I left it. Next, the lengths of the six straight lines drawn on the surface of the test piece were measured, and the arithmetic average L1 of the lengths of the six straight lines was calculated. The degree of change S was calculated based on the following equation, and the absolute value of the degree of change S was defined as the heat shrinkage (%).
S = 100 × (L1-50) / 50
About the heat shrinkage,
（(Good): 0 ≦ S <1.5; dimensional change rate was low and dimensional stability was good. X (impossible): S ≧ 1.5; dimensional change was remarkably observed.

(Combustion quality)
The flammability was evaluated by the burning rate measured by a method according to the United States automobile safety standard FMVSS302. However, only the sample to which the flame retardant was added was evaluated for flammability. The test piece had a size of 350 mm × 100 mm × 12 mm (thickness), and the skin was present on at least two sides of 350 mm × 100 mm.
The burning rate was evaluated according to the following criteria.
：: When the burning rate is 80 mm / min or less in the foam molded article having the predetermined bulk expansion multiple, or when the fire is extinguished before reaching the measurement start point in the foam molded article having the predetermined bulk expansion multiple. The burning rate in this case was AE (self-extinguishing).
×: When the burning rate is higher than 80 mm / min in a foam molded article having a predetermined bulk expansion multiple.

(Moldability)
The foamed particles were filled in a 300 mm × 400 mm × 30 mm mold of a foaming molding machine, and the foamed particles were heat-sealed while being heated by steam to foam the prefoamed particles.
At the time of heating with steam, the molding pressure was changed from 0.08 MPa to 0.25 MPa in increments of 0.01 MPa, and steam was introduced for 50 seconds to perform a molding test.
The fusion rate of the obtained foamed molded article was evaluated according to the above-described evaluation criteria. Based on the lowest steam pressure at which the fusion rate was 90% or more, the evaluation was performed according to the following criteria.
〇: A foam molded article having a fusion rate of 90% or more was obtained at a vapor pressure of 0.10 MPa or less. A foam molded article having good fusion at a low steam pressure was obtained, and had high productivity.
×: A vapor pressure exceeding 0.10 MPa was necessary to obtain a foam molded article having a fusion rate of 90% or more, and difficulty was observed in productivity.

Example 1
High-density polyethylene resin [A resin: Tosoh Corporation, product number 10S65B, density 940 kg / m ³ , MFR 2.0 g / 10 min, melting point 126 ° C, melt tension at 160 ° C 70 mN] and ethylene vinyl acetate copolymer [B resin : Made by Nippon Polyethylene, part number LV-115, MFR 0.3 g / 10 min, melting point 108 ° C, softening temperature 80 ° C, vinyl acetate content 4% by mass] into a tumbler mixer in a mass ratio of 20:80. And mixed for 10 minutes.
Next, this resin mixture is supplied to an extruder, melt-kneaded at a temperature of 230 to 250 ° C., granulated by an underwater cutting method, cut into elliptical spheres (eggs), and seeded from a modified high-density polyethylene resin. Particles were obtained. The average mass of the seed particles was 0.6 mg.
Next, in a 5-liter autoclave equipped with a stirrer, 40 g of magnesium pyrophosphate and 0.6 g of sodium dodecylbenzenesulfonate were dispersed in 2 kg of pure water to obtain a dispersion medium. 400 g of seed particles were dispersed in a dispersing medium at 30 ° C., maintained for 10 minutes, and then heated to 60 ° C. to obtain a suspension. Further, 200 g of styrene in which 0.4 g of dicumyl peroxide (10-hour half-life temperature T10 is 116.4 ° C.) was dissolved as a polymerization initiator was dropped into the suspension over 30 minutes. After the dropping, the temperature was raised to 120 ° C. over 60 minutes (1 ° C./min), and the temperature was maintained at 120 ° C. for 60 minutes to impregnate the seed particles with styrene. After the impregnation, the temperature was raised to 135 ° C. over 15 minutes (1 ° C./min), and polymerization (first polymerization) was performed at this temperature for 2 hours.
Next, 3 g of sodium dodecylbenzenesulfonate was dispersed in 20 g of pure water and added dropwise over 10 minutes to the suspension cooled to 115 ° C., and then t-butylperoxybenzoate (10-hour half-life temperature T10 was 104 (3.degree. C.) was added dropwise at a rate of 0.50 parts by mass / second (a rate with respect to 100 parts by mass of the seed particles). Thereafter, a dispersion medium prepared by dispersing 3 g of ethylenebisstearic acid amide as a bubble regulator in 100 g of pure water was added dropwise over 30 minutes. After the addition, the dispersion medium was maintained at 115 ° C. for 1 hour, so that styrene was contained in the seed particles. And a cell conditioner. After the impregnation, the temperature was raised to 140 ° C. and maintained at this temperature for 3 hours to perform polymerization (second polymerization). As a result of this polymerization, composite resin particles were obtained (mass ratio of seed particles to polystyrene of 20/80).
Next, the mixture was cooled to 30 ° C. or lower, and the composite resin particles were taken out of the autoclave. 2 kg of the composite resin particles, 2 liters of water, and 2.0 g of sodium dodecylbenzenesulfonate were placed in a 5-liter autoclave equipped with a stirrer. Further, 300 g (520 mL) of 15 parts by mass of butane (n-butane: i-butane = 7: 3) as a foaming agent was put in the autoclave. Thereafter, the temperature was raised to 70 ° C., and stirring was continued for 4 hours, whereby foamable particles could be obtained. Thereafter, the mixture was cooled to 30 ° C. or lower, and the expandable particles were taken out of the autoclave and dehydrated and dried.
Next, the obtained expandable particles were expanded to a bulk density of 29 kg / m ³ to obtain expanded particles. After leaving the obtained foamed particles at room temperature (23 ° C.) for one day, they were placed in a molding die having a size of 400 mm × 300 mm × 30 mm.
Thereafter, steam of 0.06 MPa was introduced for 50 seconds, heated, and then cooled until the maximum surface pressure of the foamed molded article was reduced to 0.01 MPa, thereby obtaining a foamed molded article having a density of 29 kg / m ³ . .
The appearance and fusion of the obtained foamed molded article were both good. The dimensional change rate, compressive strength, surface absorbance ratio, and falling ball impact value of the obtained foamed molded article under the conditions of 80 ° C. × 7 days were measured. The results are shown in the table.

Example 2
Seed particles having an average mass of 0.6 mg were obtained in the same manner as in Example 1.
Next, in a 5-liter autoclave equipped with a stirrer, 40 g of magnesium pyrophosphate and 0.6 g of sodium dodecylbenzenesulfonate were dispersed in 2 kg of pure water to obtain a dispersion medium. 800 g of seed particles were dispersed in a dispersing medium at 30 ° C., kept for 10 minutes, and then heated to 60 ° C. to obtain a suspension. Further, 400 g of styrene in which 0.8 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise to the suspension over 30 minutes. After the dropping, the temperature was raised to 120 ° C. over 60 minutes (1 ° C./min), and the temperature was maintained at 120 ° C. for 60 minutes to impregnate the seed particles with styrene. After the impregnation, the temperature was raised to 135 ° C. over 15 minutes (1 ° C./min), and polymerization (first polymerization) was performed at this temperature for 2 hours.
Next, 3 g of sodium dodecylbenzenesulfonate was dispersed in 20 g of pure water and added dropwise to the suspension at 115 ° C. over 10 minutes, and then 800 g of styrene in which 1.8 g of t-butylperoxybenzoate was dissolved. Was added dropwise at a rate of 0.50 parts by mass / second (a rate based on 100 parts by mass of the seed particles). Thereafter, a dispersion medium prepared by dispersing 3 g of ethylenebisstearic acid amide in 100 g of pure water as a bubble regulator was added dropwise over 30 minutes, and after dropping, the mixture was maintained at 115 ° C. for 1 hour, so that styrene was contained in the seed particles. And a cell conditioner. After the impregnation, the temperature was raised to 140 ° C. and maintained at this temperature for 3 hours to perform polymerization (second polymerization). As a result of this polymerization, composite resin particles could be obtained (mass ratio of seed particles to polystyrene of 40/60).
Thereafter, the temperature of the reaction system was raised to 60 ° C., and 50 g of tris (2,3-dibromopropyl) isocyanurate (TAIC6B, manufactured by Nippon Kasei Co., Ltd.) was added as a flame retardant, and diic was used as a flame retardant. 10 g of mill peroxide (DCP) was charged. After the introduction, the temperature of the reaction system was raised to 130 ° C., and stirring was continued for 2 hours to obtain composite resin particles containing a flame retardant.
Subsequently, in the same manner as in Example 1, expandable particles, expanded particles (bulk density: 29 kg / m ³ ), and expanded molded articles (density: 29 kg / m ³ ) were obtained.
The appearance and fusion of the obtained foamed molded article were both good. The dimensional change rate, compressive strength, surface absorbance ratio, and falling ball impact value of the obtained foamed molded article under the conditions of 80 ° C. × 7 days were measured. The results are shown in the table. In addition, in order to confirm the effect of the addition of the flame retardant, the flammability was measured.

Example 3
Seed particles were obtained in the same manner as in Example 1 except that the mass ratio of the high-density polyethylene resin and the ethylene-vinyl acetate copolymer was set to be 40:60.
In a 5-liter autoclave equipped with a stirrer, 40 g of magnesium pyrophosphate and 0.6 g of sodium dodecylbenzenesulfonate were dispersed in 2 kg of pure water to obtain a dispersion medium. 600 g of seed particles were dispersed in a dispersing medium at 30 ° C., kept for 10 minutes, and then heated to 60 ° C. to obtain a suspension. Further, 300 g of styrene in which 0.6 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise to the suspension over 30 minutes. After the dropping, the temperature was raised to 120 ° C. over 60 minutes (1 ° C./min), and the temperature was maintained at 120 ° C. for 60 minutes to impregnate the seed particles with styrene. After the impregnation, the temperature was raised to 135 ° C. over 15 minutes (1 ° C./min), and polymerization (first polymerization) was performed at this temperature for 2 hours.
Next, 3 g of sodium dodecylbenzenesulfonate was dispersed in 20 g of pure water and dropped over 10 minutes in the suspension cooled to 115 ° C., and then 1100 g of styrene in which 2.1 g of t-butylperoxybenzoate was dissolved Was added dropwise at a rate of 0.50 parts by mass / second (a rate based on 100 parts by mass of the seed particles). Thereafter, a dispersion medium prepared by dispersing 3 g of ethylenebisstearic acid amide as a bubble regulator in 100 g of pure water was added dropwise over 30 minutes. After the addition, the dispersion medium was maintained at 115 ° C. for 1 hour, so that styrene was contained in the seed particles. And a cell conditioner. After the impregnation, the temperature was raised to 140 ° C. and maintained at this temperature for 3 hours to perform polymerization (second polymerization). As a result of this polymerization, composite resin particles were obtained (mass ratio of seed particles to polystyrene of 30/70).
Thereafter, the temperature of the reaction system was raised to 60 ° C., and 50 g of tris (2,3-dibromopropyl) isocyanurate (TAIC6B, manufactured by Nippon Kasei) and biscumyl as a flame retardant were added to the suspension. 10 g were charged. After the introduction, the temperature of the reaction system was raised to 130 ° C., and stirring was continued for 2 hours to obtain composite resin particles containing a flame retardant.
Subsequently, in the same manner as in Example 1, expandable particles, expanded particles (bulk density: 29 kg / m ³ ), and expanded molded articles (density: 29 kg / m ³ ) were obtained.
The appearance and fusion of the obtained foamed molded article were both good. The dimensional change rate, compressive strength, surface absorbance ratio, and falling ball impact value of the obtained foamed molded article under the conditions of 80 ° C. × 7 days were measured. The results are shown in the table. In addition, in order to confirm the effect of the addition of the flame retardant, flammability was measured.

Example 4
High-density polyethylene was used as an ethylene-vinyl acetate copolymer [manufactured by Nippon Polyethylene, product number LV-430, MFR 1.0 g / 10 min, melting point 89 ° C., softening temperature 73 ° C., vinyl acetate-derived component content 15% by weight]. Seed particles were obtained in the same manner as in Example 1 except that the mass ratio of the system resin and the ethylene-vinyl acetate copolymer was adjusted to 30:70.
In a 5-liter autoclave equipped with a stirrer, 40 g of magnesium pyrophosphate and 0.6 g of sodium dodecylbenzenesulfonate were dispersed in 2 kg of pure water to obtain a dispersion medium. 300 g of seed particles were dispersed in a dispersing medium at 30 ° C., kept for 10 minutes, and then heated to 60 ° C. to obtain a suspension. Further, 150 g of styrene in which 0.3 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise to the suspension over 30 minutes. After the dropwise addition, the temperature was raised to 115 ° C. over 55 minutes (1 ° C./min), and the temperature was maintained at 115 ° C. for 60 minutes, thereby impregnating the seed particles with styrene. After the impregnation, the temperature was raised to 130 ° C. over 15 minutes (1 ° C./min), and polymerization (first polymerization) was performed at this temperature for 2 hours.
Next, 3 g of sodium dodecylbenzenesulfonate was dispersed in 20 g of pure water and dropped over 10 minutes in the suspension cooled to 115 ° C., and then 1550 g of styrene in which 2.8 g of t-butylperoxybenzoate was dissolved. Was dropped at a rate of 0.40 parts by mass / second (a rate based on 100 parts by mass of the seed particles). Thereafter, a dispersion medium prepared by dispersing 3 g of ethylenebisstearic acid amide in 100 g of pure water as a bubble regulator was added dropwise over 30 minutes, and after dropping, the mixture was maintained at 115 ° C. for 1 hour, so that styrene was contained in the seed particles. And a cell conditioner. After the impregnation, the temperature was raised to 140 ° C. and maintained at this temperature for 3 hours to perform polymerization (second polymerization). As a result of this polymerization, composite resin particles could be obtained (mass ratio of seed particles to polystyrene of 15/85).
Subsequently, in the same manner as in Example 1, expandable particles, expanded particles (bulk density: 29 kg / m ³ ), and expanded molded articles (density: 29 kg / m ³ ) were obtained.

Example 5
Using a high-density polyethylene resin [manufactured by Nippon Polyethylene Co., Ltd., product number HY350, density 951 kg / m ³ , MFR 2.5 g / 10 minutes, melting point 132 ° C.], a high-density polyethylene resin and an ethylene-vinyl acetate copolymer were used. Seed particles were obtained in the same manner as in Example 1 except that the mass ratio was 10:90.
In a 5-liter autoclave equipped with a stirrer, 40 g of magnesium pyrophosphate and 0.6 g of sodium dodecylbenzenesulfonate were dispersed in 2 kg of pure water to obtain a dispersion medium. 600 g of seed particles were dispersed in a dispersing medium at 30 ° C., kept for 10 minutes, and then heated to 60 ° C. to obtain a suspension. Further, 300 g of styrene in which 0.6 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise to the suspension over 30 minutes. After the dropping, the temperature was raised to 120 ° C. over 60 minutes (1 ° C./min), and the temperature was maintained at 120 ° C. for 60 minutes to impregnate the seed particles with styrene. After the impregnation, the temperature was raised to 135 ° C. over 15 minutes (1 ° C./min), and polymerization (first polymerization) was performed at this temperature for 2 hours.
Next, 3 g of sodium dodecylbenzenesulfonate was dispersed in 20 g of pure water and dropped over 10 minutes in the suspension cooled to 115 ° C., and then 1100 g of styrene in which 2.1 g of t-butylperoxybenzoate was dissolved Was added dropwise at a rate of 0.30 parts by mass / second (a rate relative to 100 parts by mass of the seed particles). Thereafter, a dispersion medium prepared by dispersing 3 g of ethylenebisstearic acid amide as a bubble regulator in 100 g of pure water was added dropwise over 30 minutes. After the addition, the dispersion medium was maintained at 115 ° C. for 1 hour, so that styrene was contained in the seed particles. And a cell conditioner. After the impregnation, the temperature was raised to 140 ° C. and maintained at this temperature for 3 hours to perform polymerization (second polymerization). As a result of this polymerization, composite resin particles were obtained (mass ratio of seed particles to polystyrene of 30/70).
Subsequently, in the same manner as in Example 1, expandable particles, expanded particles (bulk density: 29 kg / m ³ ), and expanded molded articles (density: 29 kg / m ³ ) were obtained.

Comparative Example 1
Seed particles were obtained in the same manner as in Example 1 except that the mass ratio of the high-density polyethylene resin to the ethylene-vinyl acetate copolymer was 70:30.
In a 5-liter autoclave equipped with a stirrer, 40 g of magnesium pyrophosphate and 0.6 g of sodium dodecylbenzenesulfonate were dispersed in 2 kg of pure water to obtain a dispersion medium. 600 g of seed particles were dispersed in a dispersing medium at 30 ° C., kept for 10 minutes, and then heated to 60 ° C. to obtain a suspension. Further, 300 g of styrene in which 0.6 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise to the suspension over 30 minutes. After the dropping, the temperature was raised to 120 ° C. over 60 minutes (1 ° C./min), and the temperature was maintained at 120 ° C. for 60 minutes to impregnate the seed particles with styrene. After the impregnation, the temperature was raised to 135 ° C. over 15 minutes (1 ° C./min), and polymerization (first polymerization) was performed at this temperature for 2 hours.
Next, 3 g of sodium dodecylbenzenesulfonate was dispersed in 20 g of pure water and dropped over 10 minutes in the suspension cooled to 115 ° C., and then 1100 g of styrene in which 2.1 g of t-butylperoxybenzoate was dissolved Was added dropwise at a rate of 0.50 parts by mass / second (a rate based on 100 parts by mass of the seed particles). Thereafter, a dispersion medium prepared by dispersing 3 g of ethylenebisstearic acid amide as a bubble regulator in 100 g of pure water was added dropwise over 30 minutes. After the addition, the dispersion medium was maintained at 115 ° C. for 1 hour, so that styrene was contained in the seed particles. And a cell conditioner. After the impregnation, the temperature was raised to 140 ° C. and maintained at this temperature for 3 hours to perform polymerization (second polymerization). As a result of this polymerization, composite resin particles were obtained (mass ratio of seed particles to polystyrene of 30/70).
Subsequently, in the same manner as in Example 1, expandable particles, expanded particles (bulk density: 29 kg / m ³ ), and expanded molded articles (density: 29 kg / m ³ ) were obtained.

Comparative Example 2
Seed particles were obtained in the same manner as in Example 1 except that the ethylene-vinyl acetate copolymer was not used.
In a 5-liter autoclave equipped with a stirrer, 40 g of magnesium pyrophosphate and 0.6 g of sodium dodecylbenzenesulfonate were dispersed in 2 kg of pure water to obtain a dispersion medium. 800 g of seed particles were dispersed in a dispersing medium at 30 ° C., kept for 10 minutes, and then heated to 60 ° C. to obtain a suspension. Further, 400 g of styrene in which 0.8 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise to the suspension over 30 minutes. After the dropping, the temperature was raised to 120 ° C. over 60 minutes (1 ° C./min), and the temperature was maintained at 120 ° C. for 60 minutes to impregnate the seed particles with styrene. After the impregnation, the temperature was raised to 135 ° C. over 15 minutes (1 ° C./min), and polymerization (first polymerization) was performed at this temperature for 2 hours.
Next, 3 g of sodium dodecylbenzenesulfonate was dispersed in 20 g of pure water and dropped over 10 minutes in the suspension cooled to 115 ° C., and then 800 g of styrene in which 1.8 g of t-butylperoxybenzoate was dissolved. Was added dropwise at a rate of 0.50 parts by mass / second (a rate based on 100 parts by mass of the seed particles). Thereafter, a dispersion medium prepared by dispersing 3 g of ethylenebisstearic acid amide as a bubble regulator in 100 g of pure water was added dropwise over 30 minutes. After the addition, the dispersion medium was maintained at 115 ° C. for 1 hour, so that styrene was contained in the seed particles. And a cell conditioner. After the impregnation, the temperature was raised to 140 ° C. and maintained at this temperature for 3 hours to perform polymerization (second polymerization). As a result of this polymerization, composite resin particles could be obtained (mass ratio of seed particles to polystyrene of 40/60).
Subsequently, in the same manner as in Example 1, expandable particles, expanded particles (bulk density: 29 kg / m ³ ), and expanded molded articles (density: 29 kg / m ³ ) were obtained.

Comparative Example 3
Example 1 was repeated except that a high-density polyethylene resin (manufactured by Tosoh Corporation, product number 09S53B, density 936 kg / m ³ , MFR 2.6 g / 10 min, melting point 123 ° C.) was not used, and no ethylene-vinyl acetate copolymer was used. Similarly, seed particles were obtained.
In a 5-liter autoclave equipped with a stirrer, 40 g of magnesium pyrophosphate and 0.6 g of sodium dodecylbenzenesulfonate were dispersed in 2 kg of pure water to obtain a dispersion medium. 600 g of seed particles were dispersed in a dispersing medium at 30 ° C., kept for 10 minutes, and then heated to 60 ° C. to obtain a suspension. Further, 300 g of styrene in which 0.6 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise to the suspension over 30 minutes. After the dropping, the seed particles were held for 30 minutes to impregnate the seed particles with styrene. After the impregnation, the temperature was raised to 140 ° C., and polymerization (first polymerization) was performed at this temperature for 2 hours.
Next, 3 g of sodium dodecylbenzenesulfonate was dispersed in 20 g of pure water and added dropwise over 10 minutes to the suspension cooled to 120 ° C., and 1100 g of styrene in which 2.5 g of dicumyl peroxide was dissolved was added to 0%. It was dropped at a rate of .50 parts by mass / second (a rate with respect to 100 parts by weight of the seed particles). After the dropping, a dispersion medium prepared by dispersing 3 g of ethylenebisstearic acid amide as a bubble regulator in 100 g of pure water was dropped over 30 minutes. Next, the temperature was raised to 140 ° C., and this temperature was maintained for 3 hours to carry out polymerization (second polymerization). As a result of this polymerization, composite resin particles were obtained (mass ratio of seed particles to polystyrene of 30/70).
Thereafter, the temperature of the reaction system was raised to 60 ° C., and 50 g of tris (2,3-dibromopropyl) isocyanurate (TAIC6B, manufactured by Nippon Kasei Co., Ltd.) was added as a flame retardant to the suspension. 10 g of mill peroxide (DCP) was charged. After the introduction, the temperature of the reaction system was raised to 130 ° C., and stirring was continued for 2 hours to obtain composite resin particles containing a flame retardant.
Subsequently, in the same manner as in Example 1, expandable particles, expanded particles (bulk density: 29 kg / m ³ ), and expanded molded articles (density: 29 kg / m ³ ) were obtained.

Comparative Example 4
In the same manner as in Example 1 except that a linear low-density polyethylene [manufactured by Nippon Polyethylene Co., Ltd., product number NF444A, density 912 kg / m ³ , MFR 2 g / 10 min, melting point 121 ° C.] is used instead of the high-density polyethylene resin. To obtain seed particles.
In a 5-liter autoclave equipped with a stirrer, 40 g of magnesium pyrophosphate and 0.6 g of sodium dodecylbenzenesulfonate were dispersed in 2 kg of pure water to obtain a dispersion medium. 800 g of seed particles were dispersed in a dispersing medium at 30 ° C., kept for 10 minutes, and then heated to 60 ° C. to obtain a suspension. Further, 400 g of styrene in which 0.8 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise to the suspension over 30 minutes. After the dropping, the temperature was raised to 120 ° C. over 60 minutes (1 ° C./min), and the temperature was maintained at 120 ° C. for 60 minutes to impregnate the seed particles with styrene. After the impregnation, the temperature was raised to 135 ° C. over 15 minutes (1 ° C./min), and polymerization (first polymerization) was performed at this temperature for 2 hours.
Next, 3 g of sodium dodecylbenzenesulfonate was dispersed in 20 g of pure water and dropped over 10 minutes in the suspension cooled to 115 ° C., and then 800 g of styrene in which 1.8 g of t-butylperoxybenzoate was dissolved. Was added dropwise at a rate of 0.50 parts by mass / second (a rate based on 100 parts by mass of the seed particles). Thereafter, a dispersion medium prepared by dispersing 3 g of ethylenebisstearic acid amide as a bubble regulator in 100 g of pure water was added dropwise over 30 minutes. After the addition, the dispersion medium was maintained at 115 ° C. for 1 hour, so that styrene was contained in the seed particles. And a cell conditioner. After the impregnation, the temperature was raised to 140 ° C. and maintained at this temperature for 3 hours to perform polymerization (second polymerization). As a result of this polymerization, composite resin particles could be obtained (mass ratio of seed particles to polystyrene of 40/60).
Thereafter, the temperature of the reaction system was raised to 60 ° C., and 50 g of tris (2,3-dibromopropyl) isocyanurate (TAIC6B, manufactured by Nippon Kasei Co., Ltd.) was added as a flame retardant to the suspension. 10 g of mill peroxide (DCP) was charged. After the introduction, the temperature of the reaction system was raised to 130 ° C., and stirring was continued for 2 hours to obtain composite resin particles containing a flame retardant.
Subsequently, in the same manner as in Example 1, expandable particles, expanded particles (bulk density: 29 kg / m ³ ), and expanded molded articles (density: 29 kg / m ³ ) were obtained.

Comparative Example 5
In a 5-liter autoclave equipped with a stirrer, 40 g of magnesium pyrophosphate and 0.6 g of sodium dodecylbenzenesulfonate were dispersed in 2 kg of pure water to obtain a dispersion medium. 400 g of the same seed particles as in Example 1 were dispersed in a dispersion medium at 30 ° C. and maintained for 10 minutes, and then heated to 60 ° C. to obtain a suspension. Further, 200 g of styrene in which 0.4 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise to the suspension over 30 minutes. After the dropping, the seed particles were held for 30 minutes to impregnate the seed particles with styrene. After the impregnation, the temperature was raised to 135 ° C., and polymerization (first polymerization) was performed at this temperature for 2 hours.
Next, 3 g of sodium dodecylbenzenesulfonate was dispersed in 20 g of pure water and added dropwise over 10 minutes to the suspension cooled to 120 ° C., and then 1400 g of styrene in which 2.1 g of t-butylperoxybenzoate was dissolved. Was added dropwise at a rate of 0.50 parts by mass / second (a rate based on 100 parts by mass of the seed particles). After the dropping, a dispersion medium prepared by dispersing 3 g of ethylenebisstearic acid amide as a bubble regulator in 100 g of pure water was dropped over 30 minutes. Next, the temperature was raised to 135 ° C., and the temperature was maintained for 3 hours to perform polymerization (second polymerization). As a result of this polymerization, composite resin particles were obtained (mass ratio of seed particles to polystyrene of 30/70).
Thereafter, the temperature of the reaction system was raised to 60 ° C., and 50 g of tris (2,3-dibromopropyl) isocyanurate (TAIC6B, manufactured by Nippon Kasei Co., Ltd.) was added as a flame retardant to the suspension. 10 g of mill peroxide (DCP) was charged. After the introduction, the temperature of the reaction system was raised to 130 ° C., and stirring was continued for 2 hours to obtain composite resin particles containing a flame retardant.
Subsequently, in the same manner as in Example 1, expandable particles, expanded particles (bulk density: 29 kg / m ³ ), and expanded molded articles (density: 29 kg / m ³ ) were obtained.
Table 1 shows the production conditions for the foamed molded articles of the examples and comparative examples. Table 2 shows the evaluation results of the examples and the comparative examples.

  From Table 2, it can be seen that in the examples, the mechanical strength and heat resistance of the foamed molded article and the moldability at the time of producing the foamed molded article could be improved.

Claims (9)

Composite resin particles for foaming comprising a high-density polyethylene resin and an ethylene copolymer having a carbonyl group and a polystyrene resin,
The mass ratio of the high-density polyethylene resin, the ethylene copolymer having a carbonyl group, and the polystyrene resin is as follows:
(I) the total amount of the high-density polyethylene-based resin and the ethylene-based copolymer having a carbonyl group / polystyrene-based resin = 5/95 to 40/60;
(Ii) The high-density polyethylene-based resin / ethylene-based copolymer having a carbonyl group = 5/95 to 50/50
Included in
The composite resin particles,
Part surface ATR method by infrared spectroscopy absorbance of 2850 cm ^-1, which is calculated from the infrared absorption spectrum obtained by (D2850) to the absorbance of 698cm ^-1 (D698) and the surface absorbance ratio is the ratio of D1 ( D698 / D2850),
An absorbance of 2850 cm ⁻¹ (D2850) calculated from an infrared absorption spectrum obtained by performing infrared spectroscopy analysis on the surface of a foamed molded product composed of a fusion body of foamed particles derived from the composite resin particles by the ATR method; ) And the absorbance at 698 cm ^-1 (D698), the surface absorbance ratio D2 (D698 / D2850), are the following values:
D1 = 0.5-2.5,
D2 / D1 = 0.1 to 0.95
Having a structure showing
The composite resin particles, wherein the high-density polyethylene resin has a density of 935 to 960 kg / m ³ .   The composite resin particles according to claim 1, wherein the ethylene-based copolymer having a carbonyl group is an ethylene-vinyl acetate copolymer, and the ethylene-vinyl acetate copolymer contains 1 to 20% by mass of a component derived from vinyl acetate.   The composite resin particle according to claim 1, wherein the high-density polyethylene has a melt tension at 160 ° C. of 40 mN or more.   The composite resin particle according to any one of claims 1 to 3, wherein the composite resin particle includes a seed particle containing a high-density polyethylene and an ethylene-vinyl acetate copolymer, and a polystyrene resin derived from a styrene monomer impregnated and polymerized in the seed particle. 5. The composite resin particles according to any one of the above.   The difference between the melting point (T1) of the high-density polyethylene and the melting point (T2) of the ethylene-vinyl acetate copolymer is 10 to 40C, and the softening temperature (T3) of the seed particles is 110 to 125C. Item 6. The composite resin particle according to Item 4,   An expandable particle comprising the composite resin particle according to any one of claims 1 to 5 and a blowing agent.   Expanded particles obtained by expanding the expandable particles according to claim 6.   A foam molded article obtained by subjecting the foamed particles according to claim 7 to foam molding.   The foamed molded article according to claim 8, wherein the foamed molded article is used for an automobile member, a component packaging material, or a cushioning material.