WO2016136460A1 - Composite resin particle, and foamable particle, foamed particle and foamed molding thereof - Google Patents

Abstract

Composite resin particles, wherein: the particles comprise polyethylene resin and polystyrene resin in ranges of 50-20 mass% and 50-80 mass%, respectively, with respect to the total thereof; the polyethylene resin comprises a low density polyethylene resin of 910-930 kg/m³ density and an ethylene-vinyl acetate copolymer in which the vinyl acetate content is 10-30 mass% in ranges of 45-85 mass% and 15-55 mass%, respectively, with respect to the total thereof; and the particles comprise essentially no bromine flame retardant.

Description

Composite resin particles and their expandable particles, expanded particles and expanded molded articles

The present invention relates to a polystyrene-based composite resin particle and its expandable particle, expanded particle, and expanded molded article. According to the present invention, there is provided a polystyrene-based composite resin particle capable of giving a foamed molded article excellent in impact resistance and slow flame retardancy without adding a flame retardant, and its foamable particles, foamed particles and foamed molded article. can do.

Foamed molded articles made of polystyrene resin are widely used as packaging materials and heat insulating materials because they have excellent buffering properties and heat insulating properties and are easy to mold. However, since the impact resistance and flexibility are insufficient, there is a problem that cracks and chips are likely to occur, and it is not suitable, for example, for packaging precision instrument products.
On the other hand, a foam-molded article made of polyolefin resin is excellent in impact resistance and flexibility, but requires a large facility for molding. Also, due to the nature of the resin, it must be transported from the raw material manufacturer to the molding processing manufacturer in the form of expanded particles. Therefore, bulky expanded particles are transported, and there is a problem that the manufacturing cost increases.

Therefore, various polystyrene-based composite resin particles having the characteristics of the above two different resins and foamed moldings using them have been proposed.

For example, Japanese Patent Application Laid-Open No. 2014-77078 (Patent Document 1) discloses a composite resin containing 20 to 50% by mass of an olefin resin (A) and 50 to 80% by mass of a styrene resin (B) (however, In the composite resin foamed particles including the olefin resin (A) and the styrene resin (B) as a base resin and containing a brominated flame retardant, the styrene resin (B) The copolymer component includes one or more (meth) acrylic acid ester components (b1) selected from methacrylic acid alkyl ester components having 1 to 10 carbon atoms and acrylic acid alkyl esters components having 1 to 10 carbon atoms. The content of the (meth) acrylic acid ester component (b1) in 100% by mass of the styrene resin (B) is 2 to 12% by mass, and the glass transition of the styrene resin (B). Temperature (Tg) of a is 100 ~ 104 ° C., the composite resin foamed particles is disclosed a 50% decomposition temperature of the brominated flame retardant is a 260 ~ 340 ° C..
According to Patent Document 1, the composite resin foamed particles have excellent mechanical properties without inhibiting the inherent heat resistance of the composite resin, while using the composite resin that is difficult to be flame retardant as the base resin. However, it is said that it can exhibit high flame retardancy.

JP-A-2014-237747 (Patent Document 2) discloses a linear low-density polyethylene resin (A) and a polystyrene resin (B) obtained by impregnating and polymerizing the resin (A) with a styrene monomer. The composite resin foam particles having a composite resin as a base resin, the composite resin contains 20 to 50% by mass of the resin (A) and 50 to 80% by mass of the resin (B) (provided that the resin (A) ) And the resin (B) are 100% by mass), the resin (A) forms a dispersed phase, and the resin (B) forms a continuous phase, the bulk density is 5 to 15 kg / m ³ , Composite resin foam particles having a closed cell ratio of 90% or more are disclosed.

JP 2014-77078 A JP 2014-237747 A

However, the combination of a linear low density polyethylene resin (LLDPE) and an ethylene-vinyl acetate copolymer (EVA) as described in the prior art described above has good impact resistance of the foamed molded article. However, it is difficult to satisfy the slow flammability because the foamed molded article using a linear low density polyethylene resin as a base resin tends to burn easily. Therefore, in the prior art, it is essential to add a brominated flame retardant in order to satisfy the slow flame retardancy. However, as a foamed molded article, a high multiplication factor exceeding 20.4 times the expansion ratio (density 49 kg / m ³ ) is not possible. It becomes difficult.
Patent Document 1 describes that the composite resin foam particles preferably have an apparent density of 10 to 500 kg / m ³ , but in actuality, only the case where the expansion ratio is about 20 times is verified. It has only been done.
Further, Patent Document 1 describes that the base resin of the composite resin contains 20 to 50% by mass of the olefin resin (A) and 50 to 80% by mass of the styrene resin (B). Actually, only when the mass ratio of resin (A) / resin (B) is 30/70 has been verified.

On the other hand, a foamed molded product of polyethylene resin particles obtained by modifying low density polyethylene resin (LDPE) with styrene is excellent in light weight, but has insufficient impact resistance and retarded flame retardancy, particularly retarded flame retardancy. Improvement of the property is desired.
Therefore, the present invention provides a polystyrene-based composite resin particle capable of giving a foamed molded article excellent in impact resistance and retarding flame resistance without adding a flame retardant, and its foamable particles, foamed particles and foamed molded article. The task is to do.

The inventors of the present invention have intensively studied to achieve the above-mentioned problems. As a result, a low-density polyethylene resin (LDPE) having a density of 910 to 930 kg / m ³ and a vinyl acetate content of 10 to 30% by mass. Composite resin particles modified with styrene of a polyethylene resin containing ethylene-vinyl acetate copolymer (EVA) in a specific ratio are more resistant to impact than composite resin particles modified with styrene of a low-density polyethylene resin. The present invention has been completed by finding that it has excellent properties and slow flame retardancy.

Thus, according to the present invention, the polyethylene resin and the polystyrene resin are contained in a range of 50 to 20% by mass and 50 to 80% by mass, respectively, based on the total of these, and the polyethylene resin has a density of 910 to 930 kg. / M ³ low density polyethylene resin and ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 30% by mass in the range of 45 to 85% by mass and 15 to 55% by mass, respectively. Provided is a composite resin particle that contains and is substantially free of brominated flame retardants.

Moreover, according to this invention, the expandable particle | grains containing said composite resin particle and a volatile foaming agent are provided.
Furthermore, according to the present invention, there are provided expanded particles obtained by pre-expanding the expandable particles.
Moreover, according to this invention, the foaming molding obtained by carrying out foam molding of said foaming particle is provided.

According to the present invention, there is provided a polystyrene-based composite resin particle capable of giving a foamed molded article excellent in impact resistance and slow flame retardancy without adding a flame retardant, and its foamable particles, foamed particles and foamed molded article. can do.
Composite resin particles obtained by modifying low density polyethylene resin with styrene tend to be less combustible due to the molecular structure of polyethylene than composite resin particles obtained by modifying linear low density polyethylene resin with styrene. The composite resin particles can satisfy the slow flame retardancy without adding a brominated flame retardant, and moreover, the foamed molded article has a foaming ratio of less than 49 kg / m ^{3 and} a foaming ratio exceeding 20.4 times. Is also possible.

The composite resin particles of the present invention are
(1) The polyethylene resin contains 3 to 10% by mass of vinyl acetate.
(2) When about 1 g of the composite resin particles is treated with 100 ml of toluene at a temperature of 130 ° C., the gel fraction insoluble in toluene is 15 to 35% by mass.
(3) The composite resin particles have an average particle diameter of 1.0 to 2.0 mm.
The above excellent effect is further exhibited when at least one of the above conditions is satisfied.
Furthermore, when the foamed molded product of the present invention has a density of less than 49 kg / m ³ , the above excellent effect is further exhibited.

It is a TEM image in (a) particle | grain surface layer part and (b) particle | grain inside in the conventional composite resin particle. It is a TEM image of (a) particle | grain surface layer part and (b) particle | grain inside in the composite resin particle (Example 1) of this invention. It is a TEM image of (a) particle | grain surface-layer part and (b) particle | grain inside in the composite resin particle (Example 3) of this invention.

(1) Composite resin particles The composite resin particles of the present invention comprise a polyethylene resin and a polystyrene resin in the range of 50 to 20% by mass and 50 to 80% by mass, respectively, based on the total of these, However, a low-density polyethylene resin having a density of 910 to 930 kg / m ³ and an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 30% by mass with respect to the total of 45 to 85% by mass and 15 to It is characterized by being contained in the range of 55% by mass and substantially not containing a brominated flame retardant.
In the present invention, “substantially free of a brominated flame retardant” means that no flame retardant, particularly a brominated flame retardant, is actively added in the production process of composite resin particles. However, flame retardant components derived from resin raw materials are excluded.

According to the analysis and evaluation of the present inventors such as a TEM image, the conventional composite resin particles have a co-continuous structure region in which an amorphous polystyrene resin is dispersed in a polyethylene resin ( 1), the composite resin particles of the present invention include a sea-island structure region in which polystyrene resin particles are dispersed in a polyethylene resin, and a co-continuous structure region in which amorphous polystyrene resin is dispersed in a polyethylene resin. Are mixed (see FIGS. 2 and 3).

(Polystyrene resin: PS)
The polystyrene resin constituting the composite resin particle of the present invention is not particularly limited as long as it is a resin mainly composed of a styrene monomer, and examples thereof include styrene or a styrene derivative alone or a copolymer.
Examples of the styrene derivative include α-methylstyrene, vinyl toluene, chlorostyrene, ethyl styrene, isopropyl styrene, dimethyl styrene, bromostyrene, and the like. These styrenic monomers may be used alone or in combination.

The polystyrene resin may be a combination of a vinyl monomer copolymerizable with a styrene monomer.
Examples of the vinyl monomer include divinylbenzene such as o-divinylbenzene, m-divinylbenzene and p-divinylbenzene, alkylene glycol di (meth) acrylate such as ethylene glycol di (meth) acrylate and polyethylene glycol di (meth) acrylate. And polyfunctional monomers such as (meth) acrylate; (meth) acrylonitrile, methyl (meth) acrylate, butyl (meth) acrylate and the like. Among these, polyfunctional monomers are preferable, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate having 4 to 16 ethylene units, and divinylbenzene are more preferable, and divinylbenzene, ethylene glycol di ( Particularly preferred is (meth) acrylate. In addition, you may use a monomer individually or in combination of 2 or more types.
Moreover, when using a monomer together, it is preferable that the content is set so that it may become the quantity (for example, 50 mass% or more) which a styrene-type monomer becomes a main component.
In the present invention, “(meth) acryl” means “acryl” or “methacryl”.

(Low density polyethylene resin: LDPE)
The low density polyethylene resin constituting the composite resin particle of the present invention is not particularly limited as long as it is a polyethylene resin having a density of 910 to 930 kg / m ³ , and specifically, a commercial product as used in the examples. Is mentioned.
The LDPE used in the present invention refers to a polyethylene-based resin defined by a high pressure method low density polyethylene, a branched low density polyethylene, a long chain branched low density polyethylene, a radical polymerization polyethylene, and an ethylene low density polymer. On the other hand, the linear low density polyethylene (LLDPE) not used in the present invention is a medium-low pressure method low density polyethylene, a linear low density polyethylene, a short chain branched low density polyethylene, an ion polymerization method polyethylene, an ethylene / α-olefin copolymer. It refers to a polyethylene-based resin defined as a polymer.

(Ethylene-vinyl acetate copolymer: EVA)
The ethylene-vinyl acetate copolymer constituting the composite resin particle of the present invention is not particularly limited as long as it is a copolymer of ethylene and vinyl acetate having a vinyl acetate content of 10 to 30% by mass. Is a commercially available product as used in the examples.
When the vinyl acetate content is less than 10% by mass, when the vinyl acetate content of the final polyethylene resin (seed particles) is constant, the proportion of the ethylene-vinyl acetate copolymer kneaded with the low density polyethylene resin is large. turn into. Since the ethylene-vinyl acetate copolymer tends to have a lower melting point than low density polyethylene, the heat resistance of the obtained foamed molded product may be lowered. On the other hand, when the vinyl acetate content exceeds 30% by mass, when the vinyl acetate content of the final polyethylene resin (seed particles) is constant, the ethylene-vinyl acetate copolymer kneaded with the low density polyethylene resin The ratio will decrease. For this reason, the dispersibility of vinyl acetate in the final polyethylene resin (seed particles) is low, and the slow flame retardancy may be lowered.
The vinyl acetate content (% by mass) is, for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30.
A preferable vinyl acetate content in the ethylene-vinyl acetate copolymer is 15 to 25% by mass.

(Mass ratio of resin component)
The composite resin particles of the present invention contain a polyethylene resin and a polystyrene resin in the range of 50 to 20% by mass and 50 to 80% by mass, respectively, based on the total of these.
If the polystyrene resin is less than 50% by mass in the mass ratio of the polyethylene resin and the polystyrene resin, foamability and moldability may be insufficient. On the other hand, if the polystyrene resin exceeds 80% by mass, the impact resistance and flexibility may be insufficient.
The mass ratio (mass%) of the polystyrene resin is, for example, 50, 55, 60, 62.5, 65, 67.5, 70, 72.5, 75, 80.
Preferred mass ratios of polyethylene resin and polystyrene resin are in the range of 40 to 25 mass% and 60 to 75 mass%.

The polyethylene resin of the composite resin particle of the present invention contains a low density polyethylene resin and an ethylene-vinyl acetate copolymer in a range of 45 to 85% by mass and 15 to 55% by mass, respectively, based on the total of these.
Of the mass ratio of the low density polyethylene resin and the ethylene-vinyl acetate copolymer, when the ethylene-vinyl acetate copolymer is less than 15% by mass, the dispersibility of vinyl acetate in the final polyethylene resin (seed particles) is low, Delayed flammability may be reduced. On the other hand, if the ethylene-vinyl acetate copolymer exceeds 55% by mass, the ethylene-vinyl acetate copolymer tends to have a lower melting point than low-density polyethylene, so the heat resistance of the resulting foamed molded product is reduced. There are things to do.
The mass ratio (% by mass) of the ethylene-vinyl acetate copolymer is, for example, 15, 20, 22.5, 25, 27.5, 30, 32.5, 35, 37.5, 40, 42.5, 45, 47.5, 50, and 55.
Preferred mass ratios of the low density polyethylene resin and the ethylene-vinyl acetate copolymer are in the range of 50 to 80% by mass and 20 to 50% by mass.

The polyethylene resin preferably has a vinyl acetate content of 3 to 10% by mass.
When the vinyl acetate content is less than 3% by mass, the obtained foamed molded article may have insufficient impact resistance and slow flame retardancy. On the other hand, if the vinyl acetate content exceeds 10% by mass, the obtained foamed molded article may have insufficient heat resistance.
The vinyl acetate content (% by mass) is, for example, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 and 10.
The preferable vinyl acetate content in the polyethylene resin is 4 to 8% by mass.

(Gel fraction)
The composite resin particle of the present invention has a gel fraction insoluble in toluene boiling at 130 ° C. of 15 to 35% by mass. More specifically, about 1 g of the composite resin particle is added with 100 ml of 130 ° C. toluene. When treated, the gel fraction insoluble in toluene is preferably 15-35% by weight.
Thereby, the impact resistance of the foaming molding shape | molded using the composite resin particle improves.
When the gel fraction is less than 15% by mass, the impact resistance of the foamed molded product is lowered, and the impact resistance as a buffer material may not be sufficient. On the other hand, when the gel fraction exceeds 35% by mass, processability such as foamability and moldability is deteriorated, and a highly foamed molded article or a molded article having a good appearance may not be obtained.
The gel fraction (mass%) is, for example, 15, 16, 17, 18, 19, 20, 20.5, 21, 2, 1.5, 22, 22.5, 23, 23.5, 24, 24.5. 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5, 30, 31, 32, 33, 34, 35.
A more preferable gel fraction is in the range of 20 to 30% by mass, and further preferably in the range of 25 to 30% by mass.
The method for measuring the gel fraction will be described in detail in Examples.

(Average particle size)
The composite resin particles of the present invention preferably have an average particle size of 1.0 to 2.0 mm.
If the average particle diameter of the composite resin particles is less than 1.0 mm, high foamability may not be obtained. On the other hand, when the average particle diameter of the composite resin particles exceeds 2.0 mm, the filling property of the foamed particles during molding may be insufficient.
The average particle diameter (mm) of the composite resin particles is, for example, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0.
More preferably, the average particle diameter of the composite resin particles is 1.2 to 1.6 mm.

(Z average molecular weight: Mz and weight average molecular weight: Mw)
The composite resin particles of the present invention have a Z average molecular weight: Mz of about 600,000 to 1,000,000.
The Z average molecular weight (× 10 ³ ) of the composite resin particles is, for example, 600, 650, 700, 750, 800, 850, 900, 950, 1000.
The composite resin particles of the present invention have a weight average molecular weight: Mw of about 250,000 to 450,000.
The weight average molecular weight (× 10 ³ ) of the composite resin particles is, for example, 250, 300, 350, 400, 450.
These measurement methods will be described in detail in Examples.

(2) Production of composite resin particles The composite resin particles of the present invention are not particularly limited, but can be produced, for example, by a seed polymerization method (seed polymerization).
In the seed polymerization method, the composite resin particles can be generally obtained by allowing the seed particles to absorb the monomer and polymerizing the monomer after or while absorbing the monomer. Alternatively, the foamed particles can be obtained by impregnating the composite resin particles with a foaming agent after polymerization or while polymerizing.

Specifically, first, in the aqueous medium, seed particles composed of the above-mentioned polyethylene-based resin are allowed to absorb the styrene-based monomer, and after the absorption or absorption, the styrene-based monomer is polymerized. To obtain composite resin particles.
The styrenic monomer does not need to be supplied to the aqueous medium at the same time, and all or part of the monomer may be supplied to the aqueous medium at different timings. When the additive is included in the composite resin particles, the additive may be added to the styrene monomer or the aqueous medium, or may be included in the seed particles.
The amount of monomer and resin is almost the same.

The polymerization of the styrene monomer can be carried out, for example, by heating at 60 to 150 ° C. for 2 to 40 hours.
In the polymerization step, it is preferable to hold at the polymerization temperature for a long time, that is, to anneal.
In the previous steps up to the annealing step, the styrene monomer and polymerization initiator absorbed in the seed particles have not completely completed the reaction, and there are not a few unreacted substances in the composite resin particles. is doing. Therefore, when a foamed molded product is obtained using composite resin particles obtained without annealing, the mechanical properties and heat resistance of the foamed molded product are degraded due to the influence of low molecular weight unreacted materials such as styrene monomers. And odor caused by volatile unreacted materials becomes a problem. Therefore, by introducing an annealing step, it is possible to secure a time for the unreacted material to undergo a polymerization reaction, and to remove the remaining unreacted material so as not to affect the physical properties of the foam molded article.
Examples of the styrenic monomer include those exemplified in the section of composite resin particles, and the amount used is in the range described in the section of composite resin particles.

(Seed particles)
The seed particles (also referred to as “nuclear resin particles”) are the above-described polyethylene-based resins, and include a low-density polyethylene-based resin and an ethylene-vinyl acetate copolymer having a specific mass ratio.
Seed particles can be obtained, for example, by a method of mixing and melting and kneading these resins, extruding them into strands, and cutting them with a desired particle diameter.
The particle diameter of the core resin particles can be appropriately adjusted according to the average particle diameter of the composite resin particles, and the preferable particle diameter is in the range of 0.2 to 1.5 mm, and the average mass is 10 to 100 mg / 100 particles. It is. In addition, examples of the shape include a true spherical shape, an elliptical spherical shape (egg shape), a cylindrical shape, and a prismatic shape.

(Aqueous medium)
Examples of the aqueous medium include water and a mixed medium of water and a water-soluble solvent (for example, a lower alcohol such as methyl alcohol or ethyl alcohol).

(Dispersant)
In the aqueous medium, a dispersant may be used in order to stabilize the dispersibility of the styrene monomer droplets and seed particles. Examples of such a dispersant include organic dispersants such as partially saponified polyvinyl alcohol, polyacrylate, polyvinyl pyrrolidone, carboxymethyl cellulose, and methyl cellulose; magnesium pyrophosphate, calcium pyrophosphate, calcium phosphate, calcium carbonate, magnesium phosphate, Examples thereof include inorganic dispersants such as magnesium carbonate and magnesium oxide. Among these, an inorganic dispersant is preferable because a more stable dispersion state may be maintained.
When an inorganic dispersant is used, it is preferable to use a surfactant in combination. Examples of such surfactants include sodium dodecylbenzene sulfonate and sodium α-olefin sulfonate.

(Polymerization initiator)
Styrene monomers are usually polymerized in the presence of a polymerization initiator. The polymerization initiator is usually impregnated into the seed particles simultaneously with the styrene monomer.
The polymerization initiator is not particularly limited as long as it is conventionally used for the polymerization of styrene monomers. For example, benzoyl peroxide, t-butyl peroxybenzoate, t-butyl peroxypivalate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, 2, 2-t-butylperoxybutane, t-butylperoxy-3,3,5-trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate, 2,5-dimethyl-2,5-bis (benzoyl) Organic peroxides such as peroxy) hexane and dicumyl peroxide. These polymerization initiators may be used alone or in combination of two or more. The amount of the polymerization initiator used is, for example, in the range of 0.1 to 5 parts by mass with respect to 100 parts by mass of the styrene monomer.

In order to uniformly absorb the polymerization initiator from the seed particles or the seed particles to the growing particles, the polymerization initiator is suspended or emulsified and dispersed in advance in the aqueous medium when the polymerization initiator is added to the aqueous medium. It is preferable to add to the dispersion liquid above, or to add the polymerization initiator to the aqueous medium after previously dissolving it in the styrene monomer.

A preferable addition amount of the polymerization initiator is 0.1 to 0.9 parts by mass per 100 parts by mass of the styrene monomer.
When the addition amount of the polymerization initiator is less than 0.1 part by mass, the molecular weight becomes too high and foamability may be lowered. On the other hand, when the addition amount of the polymerization initiator exceeds 0.9 parts by mass, the polymerization rate may become too fast, and the dispersion state of the polystyrene resin particles in the polyolefin resin may not be controlled. A preferable addition amount of the polymerization initiator is 0.2 to 0.5 parts by mass.

(Other ingredients)
The composite resin particles have a plasticizer, a binding inhibitor, a bubble regulator, a crosslinking agent, a filler, a lubricant, a colorant, a fusion accelerator, an antistatic agent, and a spreading agent as long as the physical properties are not impaired. Additives such as may be added.
In addition, the composite resin particles may contain a flame retardant other than bromine flame retardant and a flame retardant aid within a range where physical properties are not impaired.

The composite resin particles can contain a plasticizer having a boiling point exceeding 200 ° C. under 1 atm in order to maintain good foam moldability even when the pressure of water vapor used at the time of heat foaming is low.
Examples of the plasticizer include glycerin fatty acid esters such as phthalic acid ester, glycerin diacetomonolaurate, glycerin tristearate and glycerin diacetomonostearate, adipic acid esters such as diisobutyl adipate, and plasticizers such as coconut oil. .
The content of the plasticizer in the composite resin particles is preferably 0.1 to 3.0% by mass.

Examples of the binding inhibitor include calcium carbonate, silica, zinc stearate, aluminum hydroxide, ethylene bis stearamide, tricalcium phosphate, and dimethyl silicon.
Examples of the air conditioner include ethylene bis stearamide and polyethylene wax.
Examples of the crosslinking agent include 2,2-di-t-butylperoxybutane, 2,2-bis (t-butylperoxy) butane, dicumyl peroxide, 2,5-dimethyl-2,5-di-t. -Organic peroxides such as butylperoxyhexane.
Examples of the filler include synthetic or naturally produced silicon dioxide.
Examples of the lubricant include paraffin wax and zinc stearate.

Colorants include furnace black, ketjen black, channel black, thermal black, acetylene black, carbon black such as graphite and carbon fiber, chromate such as yellow lead, zinc yellow and barium yellow, and ferrocyanides such as bitumen Sulfides such as cadmium yellow and cadmium red, oxides such as iron black and red husk, silicates such as ultramarine blue, inorganic pigments such as titanium oxide, monoazo pigments, disazo pigments, azo lakes, condensed azo pigments, chelate azos Organic pigments such as azo pigments such as pigments, polycyclic pigments such as phthalocyanine, anthraquinone, perylene, perinone, thioindigo, quinacridone, dioxazine, isoindolinone, quinophthalone, and the like can be mentioned.

Examples of the fusion accelerator include stearic acid, stearic acid triglyceride, hydroxystearic acid triglyceride, sorbitan stearate, and polyethylene wax.
Examples of the antistatic agent include polyoxyethylene alkylphenol ether, stearic acid monoglyceride, polyethylene glycol and the like.
Examples of the spreading agent include polybutene, polyethylene glycol, and silicone oil.

(3) Expandable particles Expandable particles include composite resin particles and a volatile foaming agent, and can be produced by impregnating composite resin particles with a volatile foaming agent by a known method.
When the temperature at which the composite resin particles are impregnated with the volatile foaming agent is low, it takes time for the impregnation, and the production efficiency of the expandable particles may be reduced. Since it may occur in a large amount, it is preferably 50 to 130 ° C, more preferably 60 to 100 ° C.

(Foaming agent)
The volatile foaming agent is not particularly limited as long as it is conventionally used for foaming polystyrene-based resins. For example, isobutane, n-butane, isopentane, n-pentane, neopentane and the like having 5 or less carbon atoms are used. Examples include volatile foaming agents such as aliphatic hydrocarbons, and butane-based foaming agents and pentane-based foaming agents are particularly preferable. Pentane can also be expected to act as a plasticizer.

The content of the volatile blowing agent in the expandable particles is usually in the range of 5 to 13% by mass, preferably in the range of 8 to 12% by mass, and particularly preferably in the range of 9 to 11% by mass.
When the content of the volatile foaming agent is small, for example, less than 5% by mass, it may not be possible to obtain a low-density foam molded article from the foamable particles, and the effect of increasing the secondary foaming power during in-mold foam molding Cannot be obtained, the appearance of the foamed molded product may deteriorate. On the other hand, if the content of the volatile foaming agent is large and exceeds 13% by mass, for example, the time required for the cooling step in the production process of the foamed molded article using the foamable particles becomes long and the productivity may be lowered.

(Foaming aid)
The foamable particles can contain a foaming aid together with the foaming agent.
The foaming aid is not particularly limited as long as it is conventionally used for foaming polystyrene resins. For example, aromatic organic compounds such as styrene, toluene, ethylbenzene, xylene, cyclohexane, methylcyclohexane, etc. Examples thereof include solvents having a boiling point of 200 ° C. or less under 1 atm, such as cycloaliphatic hydrocarbons, ethyl acetate, and butyl acetate.

The content of the foaming aid in the foamable particles is usually in the range of 0.3 to 2.5% by mass, and preferably in the range of 0.5 to 2% by mass.
When the content of the foaming aid is small, for example, less than 0.3% by mass, the plasticizing effect of the polystyrene resin may not be exhibited. On the other hand, if the content of the foaming aid is large and exceeds 2.5% by mass, the foamed molded product obtained by foaming the foamable particles may be shrunk or melted to deteriorate the appearance, or foamable. The time required for the cooling step in the production process of the foamed molded article using the particles may be long.

(4) Expanded particles (also referred to as “pre-expanded particles”)
The foamed particles are obtained by pre-foaming the foamable particles to a predetermined bulk density by a known method, and examples thereof include batch-type foaming in which steam is introduced, continuous foaming, and release foaming under pressure.
The expandable particles of the present invention preferably have a bulk density in the range of 20 to 200 kg / m ³ .
When the bulk density of the expandable particles is less than 20 kg / m ³ , the foamed molded product tends to shrink and the appearance may be impaired. On the other hand, when the bulk density of the expandable particles exceeds 200 kg / m ³ , the advantage of weight reduction as a foamed molded product may be impaired.
The density (kg / m ³ ) of the expanded particles is, for example, 20, 22.5, 25, 27.5, 30, 32.5, 35, 37.5, 40, 42.5, 45, 48, 50, 75, 100, 125, 150, 175, 200.
A preferred bulk density of the expandable particles is in the range of 20 to 48 kg / m ³ .
In the pre-foaming, air may be introduced simultaneously with steam when foaming as necessary.

(5) Foam molded body The foam molded body is a known method, for example, the foam particles are filled in a mold of a foam molding machine and heated again to foam the foam particles, and the foam particles are thermally fused. Can be obtained.
The foamed molded article of the present invention preferably has a density in the range of 20 to 200 kg / m ³ .
When the density of the foamed molded product is less than 20 kg / m ³ , the retarded flame resistance and impact resistance may not be sufficient. On the other hand, if the density of the foamed molded product exceeds 200 kg / m ³ , the weight mass of the foamed molded product increases and the transportation cost increases, which may not be preferable.
The density (kg / m ³ ) of the foamed molded product is, for example, 20, 22.5, 25, 27.5, 30, 32.5, 35, 37.5, 40, 42.5, 45, 48, 50. 75, 100, 125, 150, 175, 200.
The density of the preferred foamed molded product is in the range of 20 to 48 kg / m ³ .

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, the following examples are only illustrations of this invention and this invention is not limited only to the following examples.
In Examples and Comparative Examples, the obtained composite resin particles, expanded particles and expanded molded articles were evaluated as follows.

<Vinyl acetate content of polyethylene resin particles (seed particles)>
A 0.1-0.5 mg sample is precisely weighed and wrapped so as to be crimped to a ferromagnetic metal body (Pyrofoil: manufactured by Nippon Analytical Industrial Co., Ltd.) having a Curie point of 445 ° C., and Curie Point Pyrolyzer JPS-700 type (Japan) Acetic acid produced by decomposition in an analytical industry apparatus was measured using a gas chromatograph GC7820 (manufactured by Agilent Technologies) (detector: FID), and an absolute calibration curve prepared in advance using the peak area. calculate.
[Pyrolysis conditions]
・ Heating (445 ℃ -5sec)
・ Oven temperature (300 ℃)
・ Needle temperature (300 ℃)
[GC measurement conditions]
Column (EC-5 (φ0.25 mm × 30 m (film thickness 0.25 μm)): manufactured by GRACE)
-GC oven temperature rising condition: initial temperature 50 ° C (holding 0.5 min)
First stage heating rate 10 ° C / min (up to 200 ° C)
Second stage heating rate 20 ° C / min (up to 290 ° C)
Final temperature 320 ° C (0.5 min hold)
・ Carrier gas (He)
・ He flow rate (25mL / min)
・ Inlet pressure (100 kPa)
・ Inlet temperature (300 ℃)
・ Detector temperature (300 ℃)
・ Split ratio (1/30)
As a standard sample for preparing a calibration curve, EVA resin Novatec LV-115 manufactured by Nippon Polyethylene Co., Ltd. having a vinyl acetate content of 4% is used.

<Gel fraction of composite resin particles>
The gel fraction (mass%) is measured as follows.
In a 200 mL eggplant flask, 1.0 g of composite resin particles are precisely weighed, 100 mL of toluene and 0.03 g of boiling stone are added, a cooling tube is attached, immersed in an oil bath maintained at 130 ° C. and refluxed for 24 hours. The solution is filtered through an 80 mesh (wire diameter φ0.12 mm) wire net before the solution is cooled. After drying the wire mesh with resin insolubles in a vacuum oven for 1 hour, it was dried at −0.06 MPa at gauge pressure for 2 hours to remove toluene, cooled to room temperature, and precisely weighed the insoluble resin mass on the wire mesh To do. The gel fraction (mass%) is determined by the following calculation formula.
Gel fraction (mass%) = mass of insoluble resin on wire mesh (g) / sample mass (g) × 100

<Average particle diameter of composite resin particles>
The average particle diameter is a value expressed by D50.
Specifically, using a low-tap type sieve shaker (manufactured by Iida Seisakusho), sieve openings are 4.00 mm, 3.35 mm, 2.80 mm, 2.36 mm, 2.00 mm, 1.70 mm, 1.40 mm. 1.18mm, 1.00mm, 0.85mm, 0.71mm, 0.60mm, 0.50mm, 0.425mm, 0.355mm, 0.300mm, 0.250mm, 0.212mm and 0.180mm JIS About 25 g of the sample is classified for 10 minutes with a standard sieve (JIS Z8801-1: 2006), and the sample mass on the sieve mesh is measured. A cumulative mass distribution curve is created from the obtained results, and the particle diameter (median diameter) at which the cumulative mass is 50% is defined as the average particle diameter.

<Z average molecular weight (Mz) and weight average molecular weight (Mw) of polystyrene resin of composite resin particles>
The Z-average molecular weight (Mz) and the weight-average molecular weight (Mw) of the polystyrene-based resin mean the average molecular weight in terms of polystyrene measured using gel permeation chromatography (GPC). In the following, a method for measuring various average molecular weights of polystyrene-based resin in a foamed molded product is described. However, the foamed molded product is an aggregate of composite resin particles until the foamed molded product is produced from the composite resin particles. Since the various average molecular weights do not change depending on the process, the various average molecular weights of the composite resin particles, the expandable particles and the pre-expanded particles are the same as those of the foamed molded product.
First, the foamed molded product is sliced into 0.3 mm in thickness, 100 mm in length, and 80 mm in width with a slicer (FK-4N manufactured by Fujishima Koki Co., Ltd.), and this is handled as a sample for molecular weight measurement. Specifically, 3 mg of the sample was allowed to stand for 24 hours in 10 mL of tetrahydrofuran (THF) for complete dissolution, and the resulting solution was filtered through a nonaqueous 0.45 μm chromatodisc (13N) manufactured by GL. Measurement is performed using a chromatograph under the following measurement conditions, and the average molecular weight of the sample is determined from a standard polystyrene calibration curve prepared in advance. If it is not completely dissolved at that time, check whether it is completely dissolved every 24 hours (up to 72 hours in total). Is determined, and the molecular weight of the dissolved component is measured.

(Measurement condition)
Equipment used: Tosoh HLC-8320GPC EcoSEC system (with built-in RI detector)
Guard column: Tosoh TSKguardcolumn SuperHZ-H (4.6 mm ID × 2 cm) × 1 Column: Tosoh TSKgel SuperHZM-H (4.6 mm ID × 15 cm) × 2 Column temperature: 40 ° C.
System temperature: 40 ° C
Mobile phase: THF
Mobile phase flow rate: sample-side pump = 0.175 mL / min
Reference side pump = 0.175mL / min
Detector: RI detector Sample concentration: 0.3 g / L
Injection volume: 50 μL
Measurement time: 0-25min
Runtime: 25min
Sampling pitch: 200 msec

(Create a calibration curve)
The standard polystyrene samples for the calibration curve have a weight average molecular weight of 5,480,000, 3,840,000, 355,000, 102,000, 37,900, 9 manufactured by Tosoh Corporation and trade name “TSK standard POLYSTYRENE”. , 100, 2,630, 500, and those having a weight average molecular weight of 1,030,000, manufactured by Showa Denko KK and trade name “Shodex STANDARD” are used.
The standard polystyrene samples for the calibration curve were group A (1,030,000), group B (3,840,000, 102,000, 9,100, 500) and group C (5,480,000, 355,000). , 37,900, 2,630), Group A was weighed 5 mg and then dissolved in 20 mL of THF, Group B was also weighed 5 to 10 mg and then dissolved in 50 mL of THF, and Group C was also weighed 1 mg to 5 mg and then THF 40 mL. Dissolved in. The standard polystyrene calibration curve was prepared by injecting 50 μL each of the prepared A, B, and C solutions, and using the retention time obtained after measurement, a calibration curve (cubic equation) was obtained from the GPC workstation (EcoSEC-WS), a data analysis program dedicated to HLC-8320GPC. The average molecular weight is calculated using the calibration curve.

<Bulk density and multiple of foamed particles>
The bulk density of the pre-expanded particles is measured as follows.
First, pre-expanded particles are filled in a measuring cylinder to a scale of 500 cm ³ . However, the graduated cylinder is visually observed from the horizontal direction, and if at least one pre-expanded particle reaches the scale of 500 cm ³ , the filling is finished. Next, the mass of the pre-expanded particles filled in the graduated cylinder is weighed with two significant figures after the decimal point, and the mass is defined as W (g). The bulk density of the pre-expanded particles is calculated by the following formula.
Bulk density (kg / m ³ ) = W ÷ 500 × 1000
1000 times the reciprocal of the bulk density is the bulk multiple.

<Density and expansion ratio of foamed molded product>
The density of the foamed molded product is measured by the method described in JIS A9511: 1995 “Foamed Plastic Insulating Plate”.
A test piece of 10 cm × 10 cm × 3 cm (300 cm ³ ) is cut out from the obtained foamed molded article, and its mass W (g) is weighed at the second decimal place.
From the mass W of the obtained foamed molded product and the volume of the foamed molded product, the expansion factor (times) is calculated by the following formula.
Density of foamed molded product (kg / m ³ ) = W ÷ 300 × 1000
1000 times the reciprocal of the density is a multiple.

<Compressive strength of foam molding>
Measured according to the method described in JIS K6767: 1999 “Foamed Plastics—Polyethylene—Test Method”. That is, using Tensilon universal testing machine UCT-10T (Orientec Co., Ltd.) and universal testing machine data processing UTPS-237 (Soft Brain Co., Ltd.), the test specimen size is 50 × 50 × thickness 25 mm (only on the pressure surface side) The compression speed is 10.0 mm / min (with a skin surface) (the moving speed per minute is as close to 50% of the specimen thickness as possible). The compressive stress (MPa) at 10% compression of the thickness is measured. The number of test pieces is 3, and the symbol “23/50” (temperature 23 ° C., relative humidity 50%) of JIS K7100: 1999 “Plastics-Standard atmosphere for conditioning and testing”, under a standard atmosphere of grade 2 After adjusting the state for 16 hours, the measurement is performed under the same standard atmosphere.
The compressive stress is calculated by the following formula.
σ ₁₀ = F ₁₀ / A ₀
σ ₁₀ : Compression stress (MPa)
F ₁₀ : Load at 10% deformation (N)
A ₀ : Initial cross-sectional area of the test piece (mm ² )

<Bending strength and bending breaking point displacement of foam molded article>
The bending strength and the amount of displacement at the bending break point are measured by the method described in JIS K7221-1: 2006 “Hard foam plastic—Bending test—Part 1: Determination of flexural properties”. That is, using Tensilon universal testing machine UCT-10T (Orientec) and universal testing machine data processing software UTPS-237 (Softbrain), the test piece size is 25 x 130 x 20 mm in thickness. The test surface is 10 mm / min, the pressure wedge is 5R, and the support base is 5R, the distance between the fulcrums is 100 mm, and the surface of the test piece without skin is stretched and measured. The number of specimens shall be five, and the symbol “23/50” (temperature 23 ° C., relative humidity 50%) of JIS K7100: 1999 “Plastic – Standard atmosphere for conditioning and testing”, under a second grade standard atmosphere After adjusting the state for 16 hours, the measurement is performed under the same standard atmosphere.
The bending strength (MPa) is calculated by the following formula.
R = (1.5F _R × L / bd ² ) × 10 ³
R: Bending strength (MPa)
F _R : Maximum load (kN)
L: Distance between supporting points (mm)
b: Width of test piece (mm)
d: Test piece thickness (mm)
In this test, the fracture detection sensitivity was set to 0.5%, and when the decrease exceeded the set value of 0.5% (deflection: 30 mm) compared to the previous load sampling point, the previous sampling point was Measured as the displacement at the bending break point (mm), and the average of 5 tests is obtained.

The obtained bending fracture point displacement is evaluated according to the following criteria. It shows that the flexibility of a foaming molding is so large that a bending fracture point displacement amount is large.
○ (good): Bending rupture point displacement is 15 mm or more △ (possible): Bending rupture point displacement is in the range of 12 mm or more and less than 15 mm × (not possible): Bending rupture point displacement is less than 12 mm

<Falling ball impact value of foam molding>
The falling ball impact strength is measured in accordance with the method described in JIS K7211: 1976 “General Rules for Hard Plastic Drop Weight Impact Test Method”.
The obtained foamed molded article is dried at a temperature of 50 ° C. for 1 day, and then a 40 mm × 215 mm × 20 mm (thickness) test piece (six surfaces are not covered) is cut out from the foamed molded article.
Next, both ends of the test piece are fixed with clamps so that the distance between the fulcrums is 150 mm, and a hard ball having a weight of 321 g is dropped from a predetermined height onto the center of the test piece to check whether the test piece is broken or not. Observe.
The test piece was tested by changing the falling height (test height) of the hard sphere at 5 cm intervals from the lowest height at which all five specimens were destroyed to the highest height at which all were not destroyed, and the falling ball impact value (cm), ie 50% The fracture height is calculated by the following formula.

H50 = Hi + d [Σ (i · ni) /N±0.5]
The symbols in the formula mean the following:
H50: 50% fracture height (cm)
Hi: Test height (cm) when the height level (i) is 0, and the height at which the test piece is expected to break d: Height interval (cm) when the test height is raised or lowered
i: Height level when Hi is 0, and increases or decreases by 1 (i = ...- 3, -2, -1, 0, 1, 2, 3 ...)
ni: Number of test pieces destroyed (or not destroyed) at each level, whichever data is used (in the case of the same number, either may be used)
N: The total number of specimens that were destroyed (or not destroyed) (N = Σni), whichever data is used (in the case of the same number, either may be used)
± 0.5: Use a negative number when using destroyed data, and a positive number when using data that was not destroyed

The obtained falling ball impact value is evaluated according to the following criteria. The larger the falling ball impact value, the greater the impact resistance of the foamed molded product.
○ (Good): Falling ball impact value is 30 cm or more. △ (possible): Falling ball impact value is a range of 20 cm or more and less than 30 cm. X (Not possible): Falling ball impact value is less than 20 cm.

<Change in heating dimension of foamed molded article: heat resistance evaluation>
The heating dimensional change rate is measured by the method B described in JIS K6767: 1999 “Foamed Plastics—Polyethylene—Test Method”.
The obtained foamed molded product was dried at a temperature of 50 ° C. for 1 day, and then a test piece 150 × 150 × 30 mm (thickness) was cut out from the foamed molded product, and 3 and 3 in the longitudinal and lateral directions were parallel to each other at the center. Write a straight line of books at intervals of 50 mm, leave it in a hot air circulating dryer at 80 ° C. for 168 hours, take it out, leave it for 1 hour in a standard location, and then measure the vertical and horizontal line dimensions according to the following formula To do.
S = (L0-L1) / L0 × 100
In the formula, S represents a heating dimensional change rate (%), L1 represents an average dimension (mm) after heating, and L0 represents an initial average dimension (mm).

The obtained heating dimensional change rate S is evaluated according to the following criteria.
○: 0 ≦ S <1.5 (Dimensional change rate is low and dimensional stability is good)
Δ: 1.5 ≦ S <3 (although a change in dimensions is observed, it can be used practically)
×: S ≧ 3 (dimensional change is noticeable and cannot be used practically)

<Burning rate of foamed molded article: Evaluation of slow flammability>
The combustion rate is measured by a method in accordance with US automobile safety standard FMVSS302.
A 350 mm × 100 mm × 12 mm (thickness) test piece is cut out from a molded product of 300 × 400 × 30 mm (thickness), and skins are present on at least two sides of 350 mm × 100 mm.
The burning rate obtained is evaluated according to the following criteria.
○: 80 mm / min or less Δ: 100 mm / min or less ×: exceeding 100 mm / min

(Example 1)
(Production of composite resin particles)
(Preparation of seed particles)
Low-density polyethylene resin (LDPE (1): density 923 kg / m ³ , melting point 112 ° C., MFR 0.3 g / 10 min, manufactured by Nippon Polyethylene Co., Ltd., product name: Novatec LD LF122) 100 parts by mass and ethylene-vinyl acetate copolymer 67 parts by mass (EVA (1): vinyl acetate content 15%, melting point 89 ° C., MFR 1.0 g / 10 min, manufactured by Nippon Polyethylene Co., Ltd., product name: Novatec EVA LV430) was put into a tumbler mixer for 10 minutes. Mixed.

Next, the obtained resin mixture was supplied to a single screw extruder (made by Hoshi Plastic Co., Ltd., model: CER40Y, 3.7 MB-SX, diameter 40 mmφ, die plate: diameter 1.5 mm) at a temperature of 230 to 250 ° C. Melt-kneaded and cut into a cylindrical shape 0.40 to 0.60 mg / piece (average 0.5 mg / piece) with a fan cutter (made by Hoshi Plastic Co., Ltd., model: FCW-110B / SE1-N) by strand cutting Thus, 4000 g of seed particles made of a polyethylene resin were obtained. The vinyl acetate content of the seed particles was measured and shown in Table 1.

(Production of composite resin particles)
Next, 20 g of magnesium pyrophosphate and 0.15 g of sodium dodecylbenzenesulfonate were dispersed in 1900 g of pure water in a 5 liter autoclave equipped with a stirrer to obtain a dispersion medium.
600 g of seed particles obtained at a temperature of 30 ° C. were dispersed in a dispersion medium and held for 10 minutes, and then the temperature was raised to 60 ° C. to obtain a suspension.
Furthermore, 260 g of styrene monomer in which 0.31 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise to the obtained suspension over 30 minutes. After dropping, the seed particles were impregnated with styrene monomer by holding for 30 minutes. After impregnation, the temperature was raised to 130 ° C., and polymerization was carried out at this temperature for 1 hour and 40 minutes (first polymerization).

Next, an aqueous solution in which 0.65 g of sodium dodecylbenzenesulfonate was dissolved in 100 g of pure water was added to the suspension lowered to a temperature of 90 ° C., and then 3.03 g of benzoyl peroxide, t-butylperoxybenzoate. 0.28 g of dicumyl peroxide, 5.34 g of dicumyl peroxide, and 400 g of styrene monomer in which 0.06 g of 2,2-methylenebis (4-methyl-6-tert-butylphenol) was dissolved as an oil-soluble polymerization inhibitor. It was dripped over 2 hours. Thereafter, 740 g of styrene monomer was added dropwise over 2 hours. The total amount of styrene monomer was 233 parts by mass with respect to 100 parts by mass of seed particles. After the dropwise addition, 8.0 g of ethylene / bisstearic acid amide was added as a bubble adjusting agent, and the seed particles were impregnated with styrene monomer by maintaining at a temperature of 90 ° C. for 1 hour and 30 minutes. After impregnation, the temperature was raised to 143 ° C., and the temperature was maintained at this temperature for 2 hours for polymerization (second polymerization). As a result of this polymerization, 2000 g of composite resin particles could be obtained.

(Production of expandable particles)
Subsequently, it cooled to the temperature of 30 degrees C or less, and took out the composite resin particle from the autoclave. 2 kg of composite resin particles, 2 liters of water, and 0.50 g of sodium dodecylbenzenesulfonate were placed in a 5 liter autoclave equipped with a stirrer. Further, 520 ml (300 g) of butane (n-butane: isobutane = 7: 3 (mass ratio)) as a foaming agent was placed in an autoclave. Thereafter, the temperature was raised to 70 ° C. and stirring was continued for 3 hours to obtain 2200 g of expandable particles.
Thereafter, the mixture was cooled to 30 ° C. or lower, and the expandable particles were taken out from the autoclave and dehydrated and dried.
The physical properties of the obtained expandable particles were measured and evaluated. The results are shown in Table 1.

(Preparation of expanded particles and expanded molded body)
Next, the obtained expandable particles were pre-expanded with water vapor to a bulk density of 25.0 kg / m ³ to obtain expanded particles.
The physical properties of the obtained expanded particles were measured and evaluated. The results are shown in Table 1.
The obtained expanded particles were allowed to stand at room temperature (23 ° C.) for 1 day, and then placed in a molding die having a size of 400 mm × 300 mm × 30 mm.
Thereafter, 0.075 MPa of water vapor is introduced for 40 seconds and heated, and then cooled until the surface pressure of the foamed molded article is reduced to 0.01 MPa, whereby a density of 25.0 kg / m ³ (expansion factor: 40 times). The foamed molded product was obtained. Both the appearance and fusion of the obtained foamed molded article were good.
About the obtained foaming molding, the physical property was measured and evaluated. The results are shown in Table 1.

(Example 2)
In the same manner as in Example 1, seed particles, composite resin particles, expandable particles, and expanded particles were obtained, and their physical properties were measured and evaluated.
In the production of the foam molded article, 0.07 MPa water vapor was introduced for 35 seconds and heated, and then cooled until the surface pressure of the foam molded article decreased to 0.01 MPa, as in Example 1. A foam molded article having a density of 20.0 kg / m ³ (50 times the expansion ratio) was obtained, and its physical properties were measured and evaluated.
The obtained results are shown in Table 1.

(Comparative Example 1)
In preparation of seed particles, seed particles, composite resin particles, expandable particles, expanded particles, and expanded molded articles were obtained in the same manner as in Example 1 except that EVA (1) was not used, and their physical properties were measured. ·evaluated.
The obtained results are shown in Table 1.

(Comparative Example 2)
In preparation of seed particles, seed particles, composite resin particles, expandable particles, and expanded particles were obtained in the same manner as in Example 1 except that EVA (1) was not used, and their physical properties were measured and evaluated.
In the production of the foam molded article, 0.09 MPa of water vapor was introduced for 35 seconds and heated, and then cooled until the surface pressure of the foam molded article decreased to 0.01 MPa, as in Example 1. A foam molded article having a density of 20.0 kg / m ³ (50 times the expansion ratio) was obtained, and its physical properties were measured and evaluated.
The obtained results are shown in Table 1.

(Comparative Example 3)
In the preparation of seed particles, instead of LDPE (1), a linear low density polyethylene resin (LLDPE: density 924 kg / m ³ , melting point 121 ° C., MFR 0.5 g / 10 min, manufactured by Tosoh Corporation, product name: Nipolon- LT 140A), instead of EVA (1), ethylene-vinyl acetate copolymer (EVA (4): vinyl acetate content 15%, density 936 kg / m ³ , melting point 88 ° C., MFR 3.0 g / 10 min. Except for using Tosoh Corp., product name: Ultrasen 626), seed particles, composite resin particles, expandable particles, expanded particles and expanded molded articles were obtained in the same manner as in Example 1, and their physical properties were measured. ·evaluated.
The obtained results are shown in Table 1.

(Example 3)
In preparation of seed particles, instead of EVA (1), an ethylene-vinyl acetate copolymer (EVA (2): vinyl acetate content 19%, density 939 kg / m ³ , melting point 86 ° C., MFR 2.5 g / 10 minutes, Hanwha Chemical Co., Ltd., product name: EVA2319), polyethylene resin / ethylene-vinyl acetate copolymer = 79/21 and seed particles / polystyrene resin = 40/60, and at the time of preparing composite resin particles, Seed particles, composite resin particles, expandable particles and expanded particles were obtained in the same manner as in Example 1 except that 0.1 g of sodium nitrite was added as a water-soluble polymerization inhibitor to 1900 g of pure water, and their physical properties were obtained. Was measured and evaluated.
In the production of the foam molded body, 0.075 MPa water vapor was introduced for 40 seconds and heated, and then cooled until the surface pressure of the foam molded body decreased to 0.01 MPa, as in Example 1. A foamed molded article having a density of 33.3 kg / m ³ (foaming ratio 30 times) was obtained, and the physical properties thereof were measured and evaluated.
The obtained results are shown in Table 2.

Example 4
Seed particles, composite resin particles, expandable particles, and expanded particles were obtained in the same manner as in Example 3 except that polyethylene resin / ethylene-vinyl acetate copolymer = 68/32 in the preparation of seed particles. The physical properties were measured and evaluated.
In the production of the foamed molded product, 0.070 MPa water vapor was introduced for 35 seconds and heated, and then cooled until the surface pressure of the foamed molded product decreased to 0.01 MPa, as in Example 1. A foamed molded article having a density of 33.3 kg / m ³ (foaming ratio 30 times) was obtained, and the physical properties thereof were measured and evaluated.
The obtained results are shown in Table 2.

(Example 5)
Seed particles, composite resin particles, expandable particles and expanded particles were obtained in the same manner as in Example 3 except that polyethylene resin / ethylene-vinyl acetate copolymer = 58/42 was used in the preparation of seed particles. The physical properties were measured and evaluated.
In the production of the foamed molded product, 0.070 MPa water vapor was introduced for 35 seconds and heated, and then cooled until the surface pressure of the foamed molded product decreased to 0.01 MPa, as in Example 1. A foamed molded article having a density of 33.3 kg / m ³ (foaming ratio 30 times) was obtained, and the physical properties thereof were measured and evaluated.
The obtained results are shown in Table 2.

(Comparative Example 4)
In preparation of seed particles, seed particles, composite resin particles, expandable particles, and foam are the same as in Example 3 except that EVA (2) is not used and seed particles / polystyrene resin = 40/60. Particles were obtained and their physical properties were measured and evaluated.
In the production of the foam molded article, 0.09 MPa of water vapor was introduced for 35 seconds and heated, and then cooled until the surface pressure of the foam molded article decreased to 0.01 MPa, as in Example 1. A foamed molded article having a density of 33.3 kg / m ³ (foaming ratio 30 times) was obtained, and the physical properties thereof were measured and evaluated.
The obtained results are shown in Table 2.

(Comparative Example 5)
In the preparation of seed particles, LLDPE was used instead of LDPE (1), EVA (4) was used instead of EVA (2), polyethylene resin / ethylene-vinyl acetate copolymer = 73/27 and seed particles / Seed particles, composite resin particles, expandable particles and expanded particles were obtained in the same manner as in Example 3 except that polystyrene resin = 40/60, and their physical properties were measured and evaluated.
In the production of the foam molded article, 0.09 MPa of water vapor was introduced for 35 seconds and heated, and then cooled until the surface pressure of the foam molded article decreased to 0.01 MPa, as in Example 1. A foamed molded article having a density of 33.3 kg / m ³ (foaming ratio 30 times) was obtained, and the physical properties thereof were measured and evaluated.
The obtained results are shown in Table 2.

(Example 6)
In preparation of seed particles, instead of LDPE (1), a low density polyethylene resin (LDPE (2): density 928 kg / m ³ , melting point 115 ° C., MFR 0.7 g / 10 min, manufactured by Nippon Polyethylene Co., Ltd., product name: Novatec LD LF280H), instead of EVA (1), an ethylene-vinyl acetate copolymer (EVA (3): vinyl acetate content 28%, density 950 kg / m ³ , melting point 69 ° C., MFR 20.0 g / 10 minutes, Example 3 except that NUC Co., Ltd., product name: DQDJ-3269) was used, and polyethylene resin / ethylene-vinyl acetate copolymer = 71/29 and seed particles / polystyrene resin = 22/78. In the same manner, seed particles, composite resin particles, expandable particles, expanded particles, and expanded molded articles were obtained, and their physical properties were measured and evaluated.
The obtained results are shown in Table 3.

(Example 7)
Seed particles, composite resin particles, expandable particles, and expanded particles were obtained in the same manner as in Example 6 except that polyethylene resin / ethylene-vinyl acetate copolymer = 66/34 in preparation of seed particles. The physical properties were measured and evaluated.
In the production of the foamed molded product, 0.070 MPa water vapor was introduced for 35 seconds and heated, and then cooled until the surface pressure of the foamed molded product decreased to 0.01 MPa, as in Example 1. A foamed molded article having a density of 25.0 kg / m ³ (foaming factor 40 times) was obtained, and its physical properties were measured and evaluated.
The obtained results are shown in Table 3.

(Comparative Example 6)
In preparation of seed particles, LDPE (2) is used instead of LDPE (1), ethylene-vinyl acetate copolymer (EVA (3)) is not used, and seed particles / polystyrene resin = 22/78. Except for the above, seed particles, composite resin particles, expandable particles, expanded particles, and expanded molded articles were obtained in the same manner as in Example 4, and their physical properties were measured and evaluated.
The obtained results are shown in Table 3.

From the results in Tables 1 to 3, it can be seen that the composite resin particles of Examples 1 to 7 can give a foamed molded article having excellent impact resistance and retarded flame retardancy without adding a flame retardant.
On the other hand, it can be seen that the composite resin particles of Comparative Examples 1 to 6 are inferior to the composite resin particles of Examples 1 to 7.

(Example 8)
Seed particles (vinyl acetate content 2.6 mass%), composites were prepared in the same manner as in Example 1 except that polyethylene resin / ethylene-vinyl acetate copolymer = 83/17 in the preparation of seed particles. Resin particles, expandable particles, expanded particles, and expanded molded articles were obtained, and their physical properties were measured and evaluated.
Table 4 shows the obtained results.

Example 9
In preparation of seed particles, instead of EVA (1), an ethylene-vinyl acetate copolymer (EVA (2): vinyl acetate content 19%, density 939 kg / m ³ , melting point 86 ° C., MFR 2.5 g / 10 minutes, Hanwa Chemical Co., Ltd., product name: EVA2319), except that polyethylene resin / ethylene-vinyl acetate copolymer = 45/55 was used, and seed particles (vinyl acetate content 10. 5% by mass), composite resin particles, foamable particles, foamed particles and foamed molded products were obtained, and their physical properties were measured and evaluated.
Table 4 shows the obtained results.

(Example 10)
In preparation of composite resin particles, seed particles and composite resin particles (gel fraction 14.2 mass) were obtained in the same manner as in Example 4 except that the amount of dicumyl peroxide added was reduced from 5.34 g to 3.76 g. ), Expandable particles, expanded particles, and foamed molded articles were obtained, and their physical properties were measured and evaluated.
Table 4 shows the obtained results.

(Example 11)
In preparation of composite resin particles, seed particles and composite resin particles (gel fraction 36.8 mass) were obtained in the same manner as in Example 5 except that the amount of dicumyl peroxide added was increased from 5.34 g to 6.32 g. ), Expandable particles, expanded particles, and foamed molded articles were obtained, and their physical properties were measured and evaluated.
Table 4 shows the obtained results.

From the results in Table 4, when the vinyl acetate content of the polyethylene resin is outside the range of 3 to 10% by mass (Examples 8 and 9), the gel fraction in the composite resin particles is outside the range of 15 to 35% by mass. In the case of (Examples 10 and 11), it can be seen that at least one of the impact resistance and the retarded flame resistance of the foam molded article is inferior to those of the other examples.

Claims (8)

1. A low-density polyethylene-based resin having a density of 910 to 930 kg / m ³ , comprising a polyethylene-based resin and a polystyrene-based resin in the range of 50 to 20% by mass and 50 to 80% by mass, respectively, based on the total of these. A resin and an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 30% by mass in a range of 45 to 85% by mass and 15 to 55% by mass, respectively, and a brominated flame retardant Composite resin particles not substantially contained.
2. The composite resin particle according to claim 1, wherein the polyethylene resin has a vinyl acetate content of 3 to 10% by mass.
3. The composite resin particle according to claim 1, wherein when about 1 g of the composite resin particle is treated with 100 ml of toluene at a temperature of 130 ° C., the gel fraction insoluble in toluene is 15 to 35% by mass.
4. The composite resin particles according to claim 1, wherein the composite resin particles have an average particle diameter of 1.0 to 2.0 mm.
5. Expandable particles comprising the composite resin particles according to claim 1 and a volatile foaming agent.
6. Expanded particles obtained by pre-expanding the expandable particles according to claim 5.
7. A foam-molded product obtained by foam-molding the foamed particles according to claim 6.
8. The foamed molded product according to claim 7, wherein the foamed molded product has a density of less than 49 kg / m ³ .

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