TWI704175B - Composite resin particle and expandable particle thereof, expanded particle and expanded molded article - Google Patents

Abstract

The present invention provides a composite resin particle which contains polyethylene type resin and polystyrene type resin respectively in the range of 50 to 20 mass% and 50 to 80 mass% to the sum of these resins. The polyethylene type resin contains a low density polyethylene type resin of 910 to 930 kg/m³ and an ethylene- vinyl acetate copolymer with a content rate of ethylene-vinyl acetate of 10 to 30 mass% respectively in the range of 45 to 85 mass% and 15 to 55 mass% to the sum of these resins, and substantially free of brominated flame retardant.

Description

Composite resin particles and their expandable particles, expanded particles and foamed moldings

The present invention relates to polystyrene-based composite resin particles, expandable particles, expanded particles, and expanded molded articles. According to the present invention, it is possible to provide polystyrene-based composite resin particles and their expandable particles, expanded particles, and hair foams capable of imparting foamed molded articles with excellent impact resistance and delayed flame resistance without adding flame retardants. Bubble shaped body.

The foamed molded body composed of polystyrene resin has excellent cushioning and heat insulating properties and is easily molded, so it is widely used as a packaging material and a heat insulating material. However, due to insufficient impact resistance or flexibility, cracks or defects are likely to occur, and there is a problem that it is not suitable for packaging of precision machine products.

On the other hand, although a foamed molded article composed of a polyolefin-based resin is excellent in impact resistance and flexibility, it requires huge equipment for its molding. In addition, in terms of the nature of the resin, it must be transported from the raw material manufacturer to the molding manufacturer in the form of expanded particles. As a result, there is a problem of conveying fluffy expanded particles, and there is a problem of increased manufacturing costs.

Therefore, a variety of polystyrene-based composite resin particles having the advantages of the above-mentioned two different resins and foamed molded products using these have been proposed.

For example, in Japanese Patent Application Laid-Open No. 2014-77078 (Patent Document 1), a composite resin foamed particle is disclosed, which is composed of 20-50% by mass of olefin resin (A) and 50-80% by mass. The composite resin of styrene resin (B) (except that the total of olefin resin (A) and styrene resin (B) is 100% by mass) is used as the base resin and the composite resin containing brominated flame retardant Among the foam particles, the styrene resin (B) contains one or more selected from the group consisting of alkyl ester components having 1 to 10 carbon atoms of methacrylic acid and alkyl ester components having 1 to 10 carbon atoms of acrylic acid (former The content of the (meth)acrylate component (b1) in 100% by mass of the styrene-based resin (B) is 2-12% by mass, and the styrene-based resin ( The glass transition temperature (Tg) of B) is 100~104℃, and the 50% decomposition temperature of brominated flame retardants is 260~340℃.

According to Patent Document 1, although this composite resin foamed particle uses a composite resin that is not easily flame-retardant as the base resin, it does not hinder the original heat resistance of the composite resin, but has excellent mechanical properties and exhibits high flame retardancy. Sex.

In addition, in Japanese Patent Application Laid-Open No. 2014-237747 (Patent Document 2), a composite resin foamed particle is disclosed, which is made of linear low-density polyethylene resin (A) and impregnated with a styrene monomer The composite resin of the polystyrene resin (B) which is polymerized with the resin (A) is used as the composite resin foamed particles of the base resin. The composite resin contains 20-50% by mass of the resin (A) and the resin (B) ) 50~80% by mass (However, the total of resin (A) and resin (B) is 100% by mass), and resin (A) forms a dispersed phase, and resin (B) forms a continuous phase. The bulk density is 5~15kg/m ³ , the independent bubble rate is above 90%.

(Prior technical literature)

Patent literature

Patent Document 1: Japanese Patent Application Publication No. 2014-77078

Patent Document 2: Japanese Patent Application Publication No. 2014-237747

However, as described in the above-mentioned prior art, the combination of linear low-density polyethylene resin (LLDPE) and ethylene-vinyl acetate copolymer (EVA), from the viewpoint of obtaining good impact resistance of the foamed molded product It is advantageous, but a foamed molded product using a linear low-density polyethylene resin as a base resin tends to be flammable, and it is difficult to satisfy the delayed flammability. Therefore, in the prior art, it is necessary to add a bromine-based flame retardant in order to satisfy the delayed flame property. Therefore, it is difficult for the foamed molded article to achieve a high expansion ratio exceeding 20.4 times (density 49 kg/m ³ ).

In addition, Patent Document 1 describes that the apparent density of the expanded composite resin particles is preferably 10 to 500 kg/m ³ , but in fact, only the case where the expansion ratio is about 20 times has been verified.

Furthermore, Patent Document 1 describes that the base resin of the composite resin contains 20-50% by mass of olefin resin (A) and 50-80% by mass of styrene resin (B), but in fact it is only Verify the quality of resin (A)/resin (B) The ratio is 30/70.

On the other hand, the foamed molded product of polyethylene resin particles modified with low density polyethylene resin (LDPE) by styrene has excellent light weight but insufficient impact resistance and delayed flame resistance, which is particularly desirable Improvement of delayed burning.

Therefore, the subject of the present invention is to provide polystyrene composite resin particles, expandable particles, and expanded particles capable of imparting foamed molded articles with excellent impact resistance and flame retardancy without adding flame retardants. And foam molding.

The inventors of the present invention conducted careful studies in order to achieve the above-mentioned problem, and found that styrene will contain low-density polyethylene resin (LDPE) with a density of 910~930kg/m ³ and vinyl acetate in a specific ratio. Composite resin particles modified by polyethylene resin of ethylene-vinyl acetate copolymer (EVA) with ester content of 10-30% by mass, and composite resin modified by low-density polyethylene resin by styrene Compared with particles, the impact resistance and delayed flame resistance are excellent, and the present invention has been completed.

Thus, according to the present invention, there is provided a composite resin particle which contains a polyethylene resin and a polyethylene resin in a range of 50 to 20% by mass and 50 to 80% by mass relative to the total of the polyethylene resin and polystyrene resin. Polystyrene resins, the aforementioned polyethylene resins are relative to low-density polyethylene resins with a density of 910 to 930 kg/m ³ and ethylene-vinyl acetate copolymers with a vinyl acetate content of 10 to 30% by mass In total, low-density polyethylene resin with a density of 910-930 kg/m ³ and ethylene-vinyl acetate with a vinyl acetate content of 10-30% by mass are contained in the ranges of 45~85 mass% and 15~55 mass% respectively. Ester copolymer and substantially no brominated flame retardant.

In addition, according to the present invention, there is provided expandable particles containing the above-mentioned composite resin particles and a volatile foaming agent.

Furthermore, according to the present invention, there is provided an expanded particle obtained by pre-expanding the above-mentioned expandable particle.

Furthermore, according to the present invention, there is provided a foamed molded article obtained by foaming and molding the above-mentioned expanded particles.

According to the present invention, it is possible to provide polystyrene-based composite resin particles and their expandable particles, expanded particles, and hair foams capable of imparting foamed molded articles with excellent impact resistance and delayed flame resistance without adding flame retardants. Bubble shaped body.

The composite resin particles in which the low density polyethylene resin is modified by styrene are compared with the composite resin particles in which the linear low density polyethylene resin is modified by styrene. It has a tendency to be inflammable. The composite resin particles of the present invention can meet the delayed flammability without adding bromine-based flame retardants, and in the foamed molded body, the density can reach 49kg/m ³ and the expansion ratio exceeds 20.4 times higher magnification.

In addition, the composite resin particles of the present invention can exhibit the above-mentioned excellent effects when at least one of the following conditions is satisfied: (1) the polyethylene resin contains 3-10% by mass of vinyl acetate, (2) when the temperature is When 100ml of toluene at 130°C treats about 1g of composite resin particles, the colloidal fraction of composite resin particles insoluble in toluene is 15~35 mass %, (3) The composite resin particles have an average particle diameter of 1.0 to 2.0 mm.

Furthermore, when the foamed molded article of the present invention has a density of less than 49 kg/m ³ , the above-mentioned excellent effects can be more exerted.

Figure 1 is a TEM image of (a) the surface layer of the particle and (b) the inside of the particle of the conventional composite resin particle.

Figure 2 is a TEM image of (a) the surface layer of the particle and (b) the inside of the particle of the composite resin particle of the present invention (Example 1).

Figure 3 is a TEM image of (a) the surface layer of the particle and (b) the inside of the particle of the composite resin particle of the present invention (Example 3).

(1) Composite resin particles

The composite resin particles of the present invention are characterized by containing polyethylene resin and polystyrene resin in the range of 50 to 20% by mass and 50 to 80% by mass, respectively, relative to the total of polyethylene resin and polystyrene resin , The aforementioned polyethylene resin is a low-density polyethylene resin with a density of 910~930kg/m ³ and an ethylene-vinyl acetate copolymer with a vinyl acetate content of 10~30% by mass in total respectively 45~ The range of 85% by mass and 15~55% by mass contains a low-density polyethylene resin with a density of 910~930kg/m ³ and an ethylene-vinyl acetate copolymer with a vinyl acetate content of 10~30% by mass, and the substance It does not contain brominated flame retardants.

In the present invention, the term "substantially free of brominated flame retardants" means that a flame retardant, especially a brominated flame retardant, is not actively added in the production process of the composite resin particles. However, flame-retardant ingredients derived from resin raw materials are excluded.

According to the analysis and evaluation of TEM images etc. of the present inventors, in the conventional composite resin particles, there is a co-continuous structure region in which amorphous polystyrene resin is dispersed in polyethylene resin (refer to Figure 1) However, in the composite resin particles of the present invention, the particles mixed with polystyrene resin are dispersed in the sea-island structure region of the polyethylene resin, and the non-shaped polystyrene resin is dispersed in the polyethylene resin. Continuous structure area (refer to Figure 2 and Figure 3).

(Polystyrene resin: PS)

The polystyrene resin constituting the composite resin particles of the present invention is not particularly limited as long as it is a resin containing a styrene monomer as the main component. Examples thereof include homopolymers of styrene or styrene derivatives or Copolymer.

Examples of the styrene derivative system include α-methylstyrene, vinyl toluene, chlorostyrene, ethylstyrene, isopropylstyrene, dimethylstyrene, bromostyrene, and the like. These styrene-based monomers can be used alone or in combination.

The polystyrene resin may also be a vinyl monomer that can be copolymerized with a styrene monomer in combination.

Examples of vinyl monomers include divinylbenzene such as o-divinylbenzene, m-divinylbenzene, p-divinylbenzene, ethylene glycol di(meth)acrylate, and poly(meth)acrylic acid. Multifunctional monomers such as glycol di(meth)acrylate, etc.; (meth)acrylonitrile, methyl (meth)acrylate, (Meth) butyl acrylate and the like. Among these, polyfunctional monomers are preferred, and ethylene glycol di(meth)acrylate is particularly preferred, polyethylene glycol di(meth)acrylate with 4 to 16 ethylene units, Divinylbenzene, particularly preferably divinylbenzene and ethylene glycol di(meth)acrylate. A single system can be used alone or in combination of two or more.

In addition, when monomers are used in combination, the content is preferably set to an amount that makes the styrene-based monomer the main component (for example, 50% by mass or more).

In the present invention, "(meth)acrylic acid" means "acrylic acid" or "methacrylic acid".

(Low density polyethylene resin: LDPE)

The low-density polyethylene resin constituting the composite resin particles 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 specific examples include the commercially available ones used in the examples. Product.

The LDPE used in the present invention is defined by high pressure low density polyethylene, branched low density polyethylene, long chain branched low density polyethylene, free radical polymerization polyethylene, and vinyl low density polymer Polyethylene resin. On the other hand, the linear low-density polyethylene resin (LLDPE) not used in the present invention refers to low-density polyethylene, linear low-density polyethylene, short-chain branched low-density polyethylene, Polyethylene resin defined by ionic polymerization method polyethylene and ethylene-α-olefin copolymer.

(Ethylene-vinyl acetate copolymer: EVA)

Copolymerization of ethylene-vinyl acetate constituting the composite resin particles of the present invention The substance is not particularly limited as long as it is a copolymer of ethylene and vinyl acetate with a vinyl acetate content rate of 10 to 30% by mass, and specific examples include the commercially available products 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 set to a certain amount, ethylene-vinyl acetate copolymer kneaded with low-density polyethylene resin The ratio has increased. Since the melting point of the ethylene-vinyl acetate copolymer tends to be lower than that of the low-density polyethylene resin, the heat resistance of the resulting foamed molded product may sometimes decrease. 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 set to a certain amount, ethylene-vinyl acetate kneaded with the low-density polyethylene resin The ratio of the ester copolymer decreases. Therefore, the dispersibility of vinyl acetate in the polyethylene resin (seed particles) is reduced, and the retardation may be reduced.

The vinyl acetate content rate (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.

The preferable vinyl acetate content rate in the ethylene-vinyl acetate copolymer is 15-25% by mass.

(Mass ratio of resin components)

The composite resin particles of the present invention contain a polyethylene resin and a polystyrene resin in the ranges of 50 to 20% by mass and 50 to 80% by mass, respectively, with respect to the total of the polyethylene resin and the polystyrene resin.

In the mass ratio of polyethylene resin to polystyrene resin, polystyrene When the olefin resin is less than 50% by mass, foamability and moldability may be insufficient. On the other hand, when the polystyrene resin exceeds 80% by mass, impact resistance or flexibility may be insufficient.

The mass ratio (mass %) of the polystyrene resin is 50, 55, 60, 62.5, 65, 67.5, 70, 72.5, 75, and 80, for example.

The preferred mass ratio of the polyethylene resin to the polystyrene resin is in the range of 40-25% by mass and 60-75% by mass.

The polyethylene resin of the composite resin particles of the present invention contains low-density polyethylene resins in the range of 45 to 85% by mass and 15 to 55% by mass relative to the total of the low-density polyethylene resin and ethylene-vinyl acetate copolymer. Ethylene resin and ethylene-vinyl acetate copolymer.

In the mass ratio of low-density polyethylene resin and 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) Decrease, and sometimes the flame retardancy decreases. On the other hand, when the ethylene-vinyl acetate copolymer exceeds 55% by mass, the melting point of the ethylene-vinyl acetate copolymer tends to be lower than that of the low-density polyethylene resin, so the resulting foamed molded product has a heat resistance Time will decrease.

The mass ratio (mass%) of the ethylene-vinyl acetate copolymer is 15, 20, 22.5, 25, 27.5, 30, 32.5, 35, 37.5, 40, 42.5, 45, 47.5, 50, 55, for example.

The preferred mass ratio of the low-density polyethylene resin to the ethylene-vinyl acetate copolymer is in the range of 50 to 80 mass% and 20 to 50 mass%.

In addition, the polyethylene resin preferably has 3-10% by mass The content of vinyl acetate.

When the vinyl acetate content is less than 3% by mass, the resulting foamed molded article may have insufficient impact resistance and flame retardancy. On the other hand, when the vinyl acetate content exceeds 10% by mass, the heat resistance of the resulting foamed molded article may be insufficient.

The vinyl acetate content rate (mass %) is 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, for example.

The preferable vinyl acetate content in the polyethylene resin is 4 to 8% by mass.

(Colloid fraction)

The composite resin particle of the present invention has a colloidal fraction of 15 to 35% by mass that is insoluble in toluene boiling at 130°C. Specifically, when about 1 g of the composite resin particle is treated with 100 ml of toluene at 130°C, it is insoluble in toluene. The colloid fraction is preferably 15 to 35% by mass.

Thereby, the impact resistance of the foamed molded body formed by using the composite resin particles can be improved.

When the colloid fraction is less than 15% by mass, the impact resistance of the foamed molded product may decrease, and the impact resistance as a cushioning material may become insufficient. On the other hand, when the colloid fraction exceeds 35% by mass, processability such as foamability and moldability may decrease, and a molded body with high foaming or a good appearance may not be obtained.

The colloid fraction (mass%) is, for example, 15, 16, 17, 18, 19, 20, 20.5, 21, 21.5, 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.

The colloid fraction is particularly preferably in the range of 20-30% by mass, more preferably in the range of 25-30% by mass.

The method for measuring the colloidal fraction is detailed in the examples.

(The average particle size)

The composite resin particles of the present invention preferably have an average particle diameter of 1.0 to 2.0 mm.

When 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 properties of the expanded particles during the molding process may become insufficient.

The average particle size (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.

The average particle size of the composite resin particles is preferably 1.2~1.6mm.

(Z average molecular weight: Mz and weight average molecular weight: Mw)

The Z average molecular weight of the composite resin particles of the present invention: Mz is 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, or 1,000.

In addition, the weight average molecular weight of the composite resin particles of the present invention: Mw, is about 250,000-450,000.

The weight average molecular weight (×10 ³ ) of the composite resin particles is 250, 300, 350, 400, 450, for example.

These measurement methods are as detailed in the examples.

(2) Manufacturing of composite resin particles

The composite resin particles of the present invention are not particularly limited, and can be produced by, for example, a seed polymerization method.

(Seed aggregation)

The seed polymerization method generally involves seed particles absorbing monomers, and polymerizing the monomers after or while absorbing them, thereby obtaining composite resin particles. In addition, it is also possible to impregnate the composite resin particles with a foaming agent after polymerization or while polymerizing, to obtain expandable particles.

Specifically, first, in an aqueous medium, the styrene-based monomer is absorbed in the seed particles composed of the above-mentioned polyethylene-based resin, and the styrene-based monomer is polymerized after being absorbed or while being absorbed, thereby Composite resin particles are obtained.

The styrene-based monomer does not need to supply all the monomers constituting it to the aqueous medium at the same time, and all or part of the monomers may be supplied to the aqueous medium at different times. When the additive is contained in the composite resin particles, the additive may be added to the styrene monomer or aqueous medium, or contained in the seed particles.

The amount of monomer and resin is almost the same.

The polymerization of the styrene monomer can be performed by heating at 60 to 150°C for 2 to 40 hours, for example.

In the polymerization step, it is preferable to keep the polymerization temperature for a long time, that is, to perform annealing.

In the steps up to the annealing step, the styrene-based monomer and the polymerization initiator absorbed in the seed particles have not completely reacted, and there are many unreacted substances in the composite resin particles. Therefore, when the resulting composite resin particles are used without annealing to obtain a foamed molded body, due to the influence of low molecular weight unreacted substances such as styrene-based monomers, there are mechanical properties or heat resistance of the foamed molded body The reduction of odor, or the problem of odor caused by volatile unreacted substances. Therefore, by introducing the annealing step, it is possible to ensure the time for the unreacted substances to cause the polymerization reaction, and to remove the remaining unreacted substances without affecting the physical properties of the foamed molded product.

Examples of the styrene-based monomer include those exemplified in the item of composite resin particles, and the usage amount is within the range described in the item of composite resin particles.

(Seed particle)

The seed particles (also referred to as "medium core resin particles") are the above-mentioned polyethylene resins and include a low-density polyethylene resin and an ethylene-vinyl acetate copolymer in a specific mass ratio.

The seed particle system can be obtained by, for example, mixing these resins, melting and kneading, extruding into a bundle, and cutting into a desired particle size.

The particle diameter of the core resin particles can be appropriately adjusted in accordance with the average particle diameter of the composite resin particles, etc. The preferred particle diameter is in the range of 0.2 to 1.5 mm, and the average mass is 10 to 100 mg/100 particles. In addition, examples of the shape include a true spherical shape, an elliptical spherical shape (egg shape), a cylindrical shape, and a square column shape.

(Aqueous medium)

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

(Dispersant)

In an aqueous medium, in order to stabilize the dispersibility of the styrene-based monomer droplets and seed particles, a dispersant may be used. Examples of this dispersant include organic dispersants such as partially saponified polyvinyl alcohol, polyacrylate, polyvinylpyrrolidone, carboxymethyl cellulose, and methyl cellulose; magnesium pyrophosphate, calcium pyrophosphate, phosphoric acid, etc. Inorganic dispersant for calcium, calcium carbonate, magnesium phosphate, magnesium carbonate, magnesium oxide, etc. Among these, since a more stable dispersion state can be maintained, an inorganic dispersant is preferable.

When an inorganic dispersant is used, it is preferable to use a surfactant in combination. Examples of the surfactant include sodium dodecylbenzene sulfonate and sodium α-olefin sulfonate.

(Polymerization initiator)

Styrenic 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-based monomer.

The polymerization initiator is not particularly limited as long as it is used in the polymerization of conventional styrene-based monomers. For example, benzoyl peroxide, tertiary butyl peroxybenzoate, tertiary butyl peroxy pivalate, tertiary butyl peroxide-2-ethylhexyl monocarbonate, tertiary butyl peroxy Isopropyl peroxide Carbonate, tertiary butyl peroxyacetate, 2,2-tertiary butyl peroxy butane, tertiary butyl peroxy-3,3,5-trimethylhexanoate, di-tertiary Organic peroxides such as butylperoxyhexahydroterephthalate, 2,5-dimethyl-2,5-bis(benzylperoxy)hexane, and dicumyl peroxide. These polymerization initiators can be used alone or in combination of two or more kinds. The amount of the polymerization initiator is, for example, in the range of 0.1 to 5 parts by mass relative to 100 parts by mass of the styrene-based monomer.

In order to uniformly absorb the polymerization initiator in the seed particles or the particles in the middle of the growth from the seed particles, when the polymerization initiator is added to the aqueous medium, it is preferable to pre-suspend or emulsify the polymerization initiator in the aqueous medium. It is added to the dispersion liquid after being in the medium, or the polymerization initiator is dissolved in the styrene-based monomer beforehand and then added to the aqueous medium.

The preferable addition amount of the polymerization initiator is 0.1 to 0.9 parts by mass per 100 parts by mass of the styrene-based monomer.

When the addition amount of the polymerization initiator is less than 0.1 parts by mass, the molecular weight becomes too high, and the foamability may decrease. On the other hand, when the addition amount of the polymerization initiator exceeds 0.9 parts by mass, the polymerization rate becomes too fast, and sometimes it is impossible to control the dispersion of the polystyrene-based resin particles in the polyolefin-based resin. The preferred addition amount of the polymerization initiator is 0.2 to 0.5 parts by mass.

(Other ingredients)

In the composite resin particles, plasticizers, anti-binding agents, air bubble regulators, crosslinking agents, fillers, lubricants, colorants, fusion accelerators, antistatic agents, and extensions can be added to the composite resin particles within the range of not impairing physical properties. Additives such as agents.

In addition, the composite resin particles may contain Flame retardants other than brominated flame retardants and flame retardant additives.

In the composite resin particles, even if the pressure of water vapor used during heating and foaming is low, in order to maintain good foaming moldability, it is preferable to contain a plasticizer having a boiling point of more than 200°C at 1 atmosphere.

Examples of plasticizers include glycerol fatty acid esters such as phthalate, glycerol diacetyl monolaurate, glycerol tristearate, glycerol diacetate monostearate, and diisobutyl hexyl esters. Plasticizers such as adipates and coconut oil.

The content of the plasticizer in the composite resin particles is preferably 0.1 to 3.0% by mass.

Examples of the anti-binding agent include calcium carbonate, silicon dioxide, zinc stearate, aluminum hydroxide, ethylene distearate, tricalcium phosphate, and dimethyl silicon.

Examples of the air bubble regulator system include ethylene distearate, polyethylene wax, and the like.

The cross-linking agent system can include 2,2-di-tertiary butyl peroxide, 2,2-bis(tertiary butyl peroxide) butane, dicumyl peroxide, 2,5-di Organic peroxides such as methyl-2,5-di-tertiary butyl hexane peroxide, etc.

The filler series may include synthetic or naturally-produced silica.

Examples of the lubricant system include paraffin wax and zinc stearate.

Colorants include furnace black, Ketjen Black, channel black, thermal black, acetylene black, graphite, carbon fiber and other carbon black; lead yellow, zinc yellow, barium yellow and other chromates; indigo, etc. Ferrocyanide; sulfides such as cadmium yellow and cadmium red; oxides such as iron black and iron oxide; ultramarine-like Silicate; Inorganic pigments such as titanium oxide; Azo pigments such as monoazo pigments, disazo pigments, azo lake pigments, condensed azo pigments, chelate azo pigments, etc.; phthalocyanine series, Anthraquinone series, Perylene series, Perinone series, Thioindigo series, Quinacridone series, Dioxazine series, Isoindolinone ( Isoindolinone series, quinophthalone series and other polycyclic pigments are organic pigments.

Examples of the fusion accelerator system include stearic acid, stearic acid triglyceride, hydroxystearic acid triglyceride, sorbitan stearate, and polyethylene wax.

Examples of antistatic agents include polyoxyethylene alkanol ether, stearic acid monoglycerin, polyethylene glycol, and the like.

Examples of the extender system include polybutene, polyethylene glycol, and silicone oil.

(3) Expandable particles

The expandable particle system contains composite resin particles and a volatile foaming agent, and can be produced by impregnating the composite resin particles with the volatile foaming agent by a generally known method.

The temperature at which the volatile foaming agent is impregnated into the composite resin particles. If it is too low, the impregnation time will be consumed and the production efficiency of the expandable particles will decrease. On the other hand, if the temperature is too high, the adhesion of the expandable particles to each other will be large. Occurs, so it is preferably 50~130°C, particularly preferably 60~100°C.

(Foaming agent)

As long as the volatile foaming agent is the foaming of conventional polystyrene resin All users are required and there is no particular limitation. For example, volatile foaming agents such as aliphatic hydrocarbons with carbon number 5 or less such as isobutane, n-butane, isopentane, n-pentane, neopentane, etc. , Particularly preferred are butane-based foaming agents and pentane-based foaming agents. The role of pentane as a plasticizer is also expected.

The content of the volatile blowing agent in the expandable particles is usually in the range of 5-13% by mass, preferably in the range of 8-12% by mass, and particularly preferably in the range of 9-11% by mass.

When the content of the volatile blowing agent is small, for example, less than 5% by mass, it may not be possible to obtain a low-density foamed molded product from the expandable particles, and it may not be possible to improve the secondary growth during foam molding in the mold. Because of the effect of foaming power, the appearance of the foamed molded product may sometimes decrease. On the other hand, when the content of the volatile foaming agent is large, for example, when it exceeds 13% by mass, the time required for the cooling step in the manufacturing step of the foamed molded article using the expandable particles increases, and the productivity sometimes decreases. .

(Foaming aid)

The expandable particles may contain a foaming aid together with the foaming agent.

The foaming aid system is not particularly limited as long as it is used for the foaming of polystyrene resins in the past, and examples include aromatic organic compounds such as styrene, toluene, ethylbenzene, and xylene; Cycloaliphatic hydrocarbons such as alkanes and methylcyclohexane; solvents with boiling points below 200°C at 1 atmosphere, such as ethyl acetate and butyl acetate.

The content of the foaming aid in the expandable 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 expressed. On the other hand, when the content of the foaming aid is large, for example, when it exceeds 2.5% by mass, the foamed product obtained by foaming the expandable particles may shrink or melt to reduce the appearance, or it may be used for hair The time required for the cooling step in the manufacturing step of the foamed molded article of foamable particles increases.

(4) Expanded particles (also called "pre-expanded particles")

Expanded particles can be obtained by pre-expanding expandable particles to a predetermined bulk density by a generally known method. Examples include batch or continuous expansion with steam introduction, and pressure-reducing Release foam.

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 is likely 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 molded foam 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 .

The bulk density of the expandable particles is preferably in the range of 20 to 48 kg/m ³ .

In pre-foaming, air can be introduced together with steam during foaming if necessary.

(5) Foam molding

The foamed molded product can be obtained by a generally known method, for example, by filling the foamed particles in a mold of an foaming molding machine, heating again, and foaming the foamed particles while thermally fusing the foamed particles to each other.

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 flame retardancy and impact resistance may be insufficient. On the other hand, when the density of the foamed molded product exceeds 200 kg/m ³ , the weight of the foamed molded product will increase and the transportation cost will increase, which is sometimes undesirable.

Molded foam density (kg / m ^3), 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 foamed molded body is preferably in the range of 20 to 48 kg/m ³ .

Example

The following examples and comparative examples illustrate the present invention in detail. However, the following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples.

In the Examples and Comparative Examples, the obtained composite resin particles, expanded particles, and molded foams were evaluated in the following manner.

<Vinyl acetate content of polystyrene resin particles (seed particles)>

The finely weighed sample is 0.1~0.5mg, and is pressed with a strong magnetic metal body (Pyrofoil: Japan Analytical Industry Co., Ltd.) whose Curie Point is 445℃. Co., Ltd.), using gas chromatograph GC7820 (manufactured by Agilent Technology Co., Ltd.) (detector: FID), and using Curie Point Pyrolyzer JPS-700 (manufactured by Japan Analytical Industry Co., Ltd.) The acetic acid produced by decomposition is measured, and the peak area is used to calculate it from the absolute calibration curve prepared in advance.

[Thermal decomposition conditions]

‧Heating (445℃-5sec)

‧Oven temperature (300℃)

‧Needle temperature (300℃)

[GC measurement conditions]

‧Pipe column (EC-5 (φ 0.25mm×30m (film thickness 0.25μm)): manufactured by GRACE)

‧ GC oven heating conditions: initial temperature 50℃ (hold for 0.5min)

1st stage heating rate 10℃/min (up to 200℃)

The second stage heating rate 20℃/min (up to 290℃)

The final temperature is 320℃ (hold for 0.5min)

‧Carrier gas (He)

‧He flow rate (25mL/min)

‧Injection pressure (100kPa)

‧Injection temperature (300℃)

‧Detector temperature (300℃)

‧Split ratio (1/30)

The standard sample for making the calibration line uses the EVA resin Novatec made by Japan Polyethylene Co., Ltd. with a vinyl acetate content = 4% LV-115.

<Colloid fraction of composite resin particles>

The measurement of the colloid fraction (mass %) was performed in the following manner.

In a 200 mL pear-shaped flask, 1.0 g of composite resin particles were precisely weighed, 100 mL of toluene and 0.03 g of zeolite were added, and a cooling tube was installed. After being immersed in an oil bath maintained at 130°C and refluxing for 24 hours, the mixture When the dissolved liquid inside has not been cooled, it is filtered with 80 mesh (wire diameter φ 0.12mm) metal mesh. In a vacuum oven, dry the metal mesh with resin insoluble matter for 1 hour, and then dry it at a gauge pressure of -0.06MPa for 2 hours to remove toluene. After cooling to room temperature, the quality of the insoluble resin on the metal mesh is carefully weighed. The colloid fraction (mass %) is calculated by the following formula.

Colloid fraction (mass%) = mass of insoluble resin on metal mesh (g)/mass of sample (g)×100

<Average particle size of composite resin particles>

Specifically, an upper strike screen vibrator (manufactured by Iida Manufacturing Co., Ltd.) is used, with mesh openings of 4.00mm, 3.35mm, 2.80mm, 2.36mm, 2.00mm, 1.70mm, 1.40mm, 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 standard sieves (JIS Z8801-1: 2006), about 25g of the sample is classified into 10 Minutes, and determine the mass of the sample on the screen. From the results obtained, a cumulative mass distribution zone line is produced, and the particle size (median diameter) at which the cumulative mass becomes 50% is set as the average particle size.

<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 weight average molecular weight (Mw) of the polystyrene-based resin mean the average molecular weight in terms of polystyrene as measured by gel permeation chromatography (GPC: Gel Permeation Chromatography). The following is a description of the methods for measuring various average molecular weights of polystyrene resins in foamed molded products. However, foamed molded products are aggregates of composite resin particles, and various average molecular weights will not be affected by the production of foamed molded products from composite resin particles. The previous steps vary, so the various average molecular weights of composite resin particles, expandable particles, and pre-expanded particles are set to be the same as the foamed molded article.

First, the molded foam was sliced into a thickness of 0.3 mm, a length of 100 mm, and a width of 80 mm with a slicer (FK-4N manufactured by Fujishima Koki Co., Ltd.), and this was used as a sample for molecular weight measurement. Specifically, 3 mg of the sample was placed in 10 mL of tetrahydrofuran (THF) for 24 hours to completely dissolve it, and the resulting solution was filtered with a non-aqueous 0.45 μm chromatography disc (13N) manufactured by GL, and then measured as follows Under the conditions, use a chromatograph for measurement, and obtain the average molecular weight of the sample from the calibration curve of the standard polystyrene prepared in advance. In addition, when it is not completely dissolved at this point, it is further confirmed whether it is completely dissolved after standing for 24 hours (72 hours in total). When it cannot be completely dissolved after 72 hours, it is determined that the sample contains crosslinking components. And determine the molecular weight of the dissolved components.

(Measurement conditions)

Device used: Tosoh HLC-8320GPC EcoSEC System (built-in RI detector)

Guard column: TSKguardcolumn Super HZ-H (4.6mm I.D.×2cm) x 1 made by Tosoh

Column: TSKgel Super HZM-H (4.6mm I.D.×15cm) × 2 manufactured by Tosoh

Column temperature: 40℃

System temperature: 40℃

Mobile phase: THF

Mobile phase flow rate: sample side pump=0.175mL/min

Reference side pump=0.175mL/min

Detector: RI detector

Sample concentration: 0.3g/L

Injection volume: 50μL

Measurement time: 0-25min

Execution time: 25min

Sampling distance: 200msec

(Making of calibration line)

The standard polystyrene sample for the calibration line uses: Tosoh Corporation, brand name "TSK standard POLYSTRYENE" with a weight average molecular weight of 5,480,000, 3,840,000, 355,000, 102,000, 37,900, 9,100, 2,630, 500, and Showa Denko Corporation System, product name "Shodex "STANDARD" has a weight average molecular weight of 1,030,000.

After dividing the standard polystyrene sample for the calibration curve into 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), weigh After 5 mg of group A was dissolved in 20 mL of THF, group B was also weighed 5-10 mg and dissolved in 50 mL of THF, and group C was also weighed 1 mg to 5 mg and dissolved in 40 mL of THF. The standard polystyrene calibration curve is obtained by injecting 50μL of the prepared A, B and C solutions and measuring the retention time. The calibration curve is created by the HLC-8320GPC special data analysis program GPC workstation (EcoSEC-WS) ( Cubic formula) is obtained, and the average molecular weight is calculated using this calibration curve.

<Bulk density and volume multiple of expanded particles>

The bulk density of the pre-expanded particles is measured by the following method.

First, the pre-expanded particles are filled in a graduated cylinder to a mark of 500 cm ³ . However, when the measuring cylinder is visually viewed from the horizontal direction, the filling is finished when the pre-expanded particles reach the mark of 500 cm ³ even for one particle. Next, weigh the mass of the pre-expanded particles filled in the measuring cylinder with 2 significant figures below the decimal point, and set the mass as W(g). The bulk density of the pre-expanded particles was calculated by the following formula.

Bulk density (kg/m ³ )=W÷500×1000

1000 times the reciprocal of the bulk density is the volume multiple.

<Density and expansion ratio of molded foam>

The density of the foam molding is measured by the method described in JIS A9511: 1995 "Foam Plastic Insulation Board".

A test piece of 10 cm×10 cm×3 cm (300 cm ³ ) was cut out from the obtained foamed molded product, and the mass W (g) was weighed to two decimal places.

From the mass W of the obtained foamed molded body and the volume of the foamed molded body, the expansion ratio (fold) was calculated by the following formula.

Density of foam molding (kg/m ³ )=W÷300×1000

1000 times the reciprocal of the density is a multiple.

<Compressive strength of molded foam>

It is measured by the method described in JIS K6767: 1999 "Foam Plastic-Polyethylene-Test Method". That is, using Tensilon universal testing machine UCT-10T (manufactured by Orientec) and universal testing machine data processing UTPS-237 (manufactured by Soft Brain), the size of the test body is 50×50×thickness 25mm (only on the pressure surface side (Skin surface), and set the compression speed to 10.0mm/min (the moving speed per minute is as close as possible to the speed of 50% of the thickness of the test piece). And measure the compressive stress (MPa) when the thickness is compressed by 10%. The number of test strips is set to 3, in JIS K7100: 1999 "Plastic-Standard Gas Environment for Condition Control and Testing", the symbol "23/50" (temperature 23℃, relative humidity 50%), Class 2 standard gas Adjust the state under the environment for 16 hours, and measure under the same standard gas environment.

The compressive stress is calculated by the following formula.

σ ₁₀ =F ₁₀ /A ₀

σ ₁₀ : Compressive stress (MPa)

F ₁₀ : Load when deformed 10% (N)

A ₀ ：The initial cross-sectional area of the test piece (mm ² )

<Bending strength and bending fracture point displacement of foamed molded products>

The bending strength and the displacement of the bending fracture point are measured by the method described in JIS K7221-1: 2006 "Rigid Foam Plastics-Bend Test-Part 1: Determination of Flexural Characteristics". That is, the Tensilon universal testing machine UCT-10T (manufactured by Orientec) and the universal testing machine data processing UTPS-237 (manufactured by Soft Brain) are used. The size of the test body is 25 x 130 x 20 mm (only on the pressure surface). The side has a skin surface), the test speed is set to 10mm/min, the pressure wedge 5R is used as the support seat 5R, the distance between the fulcrums is 100mm, and the test piece does not have a surface of the skin. Determination. The number of test strips is set to 5, which is marked "23/50" (temperature 23°C, relative humidity 50%), Class 2 standard gas in JIS K7100: 1999 "Plastic-Standard Gas Environment for Condition Control and Testing" Adjust the state under the environment for 16 hours, and measure under the same standard gas environment.

The bending strength (MPa) is calculated by the following formula.

R=(1.5F _R ×L/bd ² )×10 ³

R: Flexural strength (MPa)

F _R ：Maximum load (N)

L: Distance between fulcrums (mm)

b: width of test piece (mm)

d: thickness of test piece (mm)

In this test, the fracture detection sensitivity is set to 0.5%, and the When the reduction exceeds 0.5% of the set value (deflection: 30mm) compared to the load sampling point, the sampling point not long ago is measured as the bending fracture point displacement (mm), and the number of tests is 5 average.

Use the following criteria to evaluate the resulting displacement of the bending fracture point. The greater the displacement of the bending fracture point, the greater the flexibility of the foamed molded product.

○(Good): The displacement of the bending fracture point is more than 15mm

△(possible): The displacement of the bending fracture point is more than 12mm and less than 15mm

× (not possible): The displacement of the bending fracture point is less than 12mm

<Falling ball impact value of foam molding>

Measure the falling ball impact strength according to the method described in JIS K7211: 1976 "General Rules of Falling Weight Impact Test Method for Rigid Plastics".

After drying the obtained foamed molded body at a temperature of 50°C for 1 day, a test piece of 40 mm × 215 mm × 20 mm (thickness) (with no skin on all 6 sides) was cut out from the foamed molded body.

Next, the two ends of the test piece were clamped with clamps so that the interval between the fulcrums was 150 mm, and a hard ball weighing 321 g was dropped from a predetermined height to the center of the test piece, and the test piece was observed for damage.

From the lowest height where all the five test specimens are damaged to the highest height where no damage occurs, the drop height of the hard ball (test height) is changed at 5 cm intervals and the test is performed. The falling ball impact is calculated by the following formula Value (cm), that is, 50% damage height.

H50=Hi+d[Σ(i‧ni)/N±0.5]

The symbols in the formula mean as follows.

H50: 50% damage height (cm)

Hi: Test height (cm) when the height level (i) is 0, which is the height that predicts the damage of the test piece

d: The height interval when the test height is moved up and down (cm)

i: Set to 0 when Hi, and increase or decrease one height level at a time (i=‧‧‧-3,-2,-1,0,1,2,3‧‧‧)

ni: the number of damaged (or undamaged) test pieces in each level, and use the data of the larger one (when the same number, any one can be used)

N: The total number of damaged (or undamaged) test pieces (N=Σ ni), the data of the larger one is used (when the same number, any one can be used)

±0.5: Use a negative number when using damaged data, and use a positive number when using undamaged data

Use the following criteria to evaluate the resulting impact value of the ball. The larger the ball impact value, the greater the impact resistance of the foamed molded product.

○(Good): The impact value of the ball is more than 30cm

△(Yes): The impact value of the falling ball is above 20cm and less than 30cm

× (not possible): the impact value of the ball is less than 20cm

<The heating dimensional change rate of the foamed molded article: Heat resistance evaluation>

The heating dimensional change rate was measured by the B method described in JIS K6767: 1999 "Foam Plastic-Polyethylene-Test Method".

After drying the obtained foamed molded body at a temperature of 50°C for 1 day, cut out 150×150×30mm (thickness) from the foamed molded body, and set it in the vertical direction at the center part with 50mm intervals. Draw 3 lines parallel to each other in the horizontal and horizontal directions. Place them in a hot-air circulation dryer at 80°C for 168 hours and then take them out. After leaving them in a standard state for 1 hour, measure the vertical lines and The size of the horizontal line.

S=(L0-L1)/L0×100

In the formula, S is the heating dimensional change rate (%), L1 is the average size after heating (mm), and L0 is the initial average size (mm).

The heating dimensional change rate S is evaluated based on the following criteria.

○: 0≦S<1.5 (low dimensional change rate, good dimensional stability)

△: 1.5≦S<3 (Although dimensional changes are observed, it can be used practically)

×: S≧3 (significant change in size is observed, but it cannot be used practically)

<The burning rate of the foamed molded product: Evaluation of the delayed flame property>

The burning speed is measured according to the method of American automobile safety standard FMVSS302.

A test piece of 350mm×100mm×12mm (thickness) is cut out from a molded product of 300×400×30mm (thickness), and there is a skin on both sides of at least 350mm×100mm.

Use the following benchmarks to evaluate the resulting burning rate.

○: Below 80mm/min

△: Below 100mm/min

×: more than 100mm/min

(Example 1)

(Production of composite resin particles)

(Production of seed particles)

100 parts by mass of low-density polyethylene resin (LDPE(1): density 923 kg/m ³ , melting point 112°C, MFR 0.3 g/10 min, manufactured by Japan Polyethylene Co., Ltd., product name: Novatec LD LF122) and ethylene-acetic acid Vinyl ester copolymer (EVA(1): Vinyl acetate content rate 15% by mass, melting point 89°C, MFR1.0g/10min, manufactured by Japan Polyethylene Co., Ltd., product name: Novatec EVA LV430) 67 parts by mass, put into the drum Mixer and mix for 10 minutes.

Next, the obtained resin mixture was supplied to a uniaxial extruder (manufactured by Hoshi Plastic Co., Ltd., model: CER40Y 3.7MB-SX, diameter 40mm φ, template: diameter 1.5mm), and melted and kneaded at a temperature of 230 to 250°C. And cut into a cylindrical shape 0.40~0.60mg/piece (average 0.5mg/piece) with a fan blade cutter (manufactured by Hoshi Plastic Co., Ltd., model: FCW-110B/SE1-N) in a beam cutting method, 4000 g of seed particles composed of polyethylene resin were obtained. The vinyl acetate content rate of the seed particles was measured and shown in Table 1.

(Production of composite resin particles)

Next, in a 5 liter autoclave with a stirrer, 20 g of magnesium pyrophosphate and 0.15 g of sodium dodecylbenzene sulfonate were dispersed in 1900 g of pure water to obtain a fraction. Bulk media.

600 g of seed particles obtained at a temperature of 30°C were dispersed in a dispersion medium and kept for 10 minutes, and then the temperature was raised to a temperature of 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 dropped into the obtained suspension within 30 minutes. After the dropping, keep for 30 minutes to impregnate the styrene monomer in the seed particles. After the impregnation, the temperature was raised to a temperature of 130°C, and polymerization (first polymerization) was performed at this temperature for 1 hour and 40 minutes.

Next, dissolve 0.65 g of sodium dodecylbenzene sulfonate in 100 g of pure water and put it in a suspension whose temperature is lowered to 90°C, and then dissolve 3.03 g of benzyl peroxide and tertiary 0.28g of peroxybenzoic acid ester, 5.34g of dicumyl peroxide, and 2,2-methylenebis(4-methyl-6-tributylphenol) 0.06g of benzene as an oil-soluble polymerization inhibitor 400 g of ethylene monomer was dropped in 2 hours. Then, 740 g of styrene monomer was dropped in 2 hours. The total amount of styrene monomer was set to 233 parts by mass relative to 100 parts by mass of seed particles. After the dropping, 8.0 g of ethylene-bisstearate amide as a bubble regulator was added, and the temperature was maintained at 90°C for 1 hour and 30 minutes to impregnate the seed particles with styrene monomer. After the impregnation, the temperature was raised to a temperature of 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 can be produced.

(Production of expandable particles)

Next, it was cooled to a temperature of 30°C or lower, and the composite resin particles were taken out from the autoclave. Combine 2 kg of composite resin particles with 2 liters of water and dodecyl benzene sulfonate 0.50 g of sodium is charged into a 5 liter autoclave with a mixer. Furthermore, 520 milliliters (300 g) of butane (n-butane:isobutane=7:3 (mass ratio)) as a foaming agent was charged into the autoclave. Then, the temperature was raised to 70°C, and stirring was continued for 3 hours to obtain 2,200 g of expandable particles.

Then, it was cooled to a temperature of 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. These results are shown in Table 1.

(Production of expanded particles and foamed molded products)

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. These results are shown in Table 1.

After the obtained expanded particles were left at room temperature (23°C) for 1 day, they were placed in a molding mold with a size of 400 mm × 300 mm × 30 mm.

Then, water vapor of 0.075 MPa was introduced for 40 seconds for heating, and then, cooling was performed until the surface pressure of the foamed molded body was reduced to 0.01 MPa, thereby obtaining a density of 25.0 kg/m ³ (40 times the expansion ratio) Foam molding. The appearance and fusion of the obtained foamed molded product were good.

The physical properties of the obtained foamed molded article were measured and evaluated. These results are shown in Table 1.

(Example 2)

Seed particles, composite resin particles, expandable particles, and expanded particles were obtained in the same manner as in Example 1, and their physical properties were measured and evaluated.

In the production of the foamed molded body, heating was carried out by introducing 0.07 MPa of water vapor for 35 seconds, and then cooling until the surface pressure of the foamed molded body was reduced to 0.01 MPa, except that the others were the same as in Example 1. A foamed molded product having a density of 20.0 kg/m ³ (50 times the expansion ratio) was obtained, and the physical properties were measured and evaluated.

The results obtained are shown in Table 1.

(Comparative example 1)

In the production of seed particles, except that EVA (1) was not used, the same as in Example 1 was used to obtain seed particles, composite resin particles, expandable particles, expanded particles, and expanded molded products, and then measured and evaluated These physical properties.

The results obtained are shown in Table 1.

(Comparative example 2)

In the preparation of the seed particles, the 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 then these physical properties were measured and evaluated.

In the production of the foamed molded body, 0.09 MPa of water vapor was introduced for 35 seconds for heating, and then cooled until the surface pressure of the foamed molded body was reduced to 0.01 MPa. Other than that, the same as Example 1 A foamed molded body with a density of 20.0 kg/m ³ (expansion ratio 50 times) was obtained, and then the physical properties were measured and evaluated.

The results obtained are shown in Table 1.

(Comparative example 3)

In the production of seed particles, a linear low-density polyethylene resin (LLDPE: density 924kg/m ³ , melting point 121°C, MFR 0.5g/10 min, manufactured by Tosoh Co., Ltd., product name: Nipolon-L T140A) is used To replace LDPE (1) and use ethylene-vinyl acetate copolymer (EVA (4): vinyl acetate content rate 15%, density 936kg/m ³ , melting point 88°C, MFR3.0g/10 minutes, Tosoh Co., Ltd. Produced by the company, product name: Ultrasen 626) instead of EVA (1), except that the others are the same as in Example 1 to obtain seed particles, composite resin particles, expandable particles, expanded particles, and expanded molded products. Measure and evaluate these physical properties.

The results obtained are shown in Table 1.

(Example 3)

For the production of seed particles, ethylene-vinyl acetate copolymer (EVA(2): vinyl acetate content rate 19%, density 939kg/m ³ , melting point 86°C, MFR2.5g/10min, manufactured by Hanwha Chemicals , Product name: EVA2319) instead of EVA (1), and set as polyethylene resin/ethylene-vinyl acetate copolymer=79/21 and seed particles/polystyrene resin=40/60, and in composite resin particles During the production of 1900g of pure water, 0.1g of sodium nitrite as a water-soluble polymerization inhibitor was added. Other than that, the same as in Example 1 to obtain seed particles, composite resin particles, expandable particles and expanded particles , And then measure and evaluate these physical properties.

In the production of the foamed molded body, water vapor of 0.075 MPa was introduced for 40 seconds to heat, and then cooled until the surface pressure of the foamed molded body was reduced to 0.01 MPa. Other than that, the same as Example 1 A foamed molded body with a density of 33.3 kg/m ³ (expansion ratio 30 times) was obtained, and then the physical properties were measured and evaluated.

The results obtained are shown in Table 2.

(Example 4)

In the production of seed particles, except that the polyethylene resin/ethylene-vinyl acetate copolymer = 68/32 was set, the same as in Example 3 was used to obtain seed particles, composite resin particles, expandable particles, and hair. Bubble particles, and then measure and evaluate these physical properties.

In the production of the foamed molded body, heating was performed by introducing 0.070 MPa of water vapor for 35 seconds, and then cooling until the surface pressure of the foamed molded body was reduced to 0.01 MPa. Other than that, the same as Example 1 A foamed molded body with a density of 33.3 kg/m ³ (expansion ratio 30 times) was obtained, and then the physical properties were measured and evaluated.

The results obtained are shown in Table 2.

(Example 5)

In the production of the seed particles, except that the polyethylene resin/ethylene-vinyl acetate copolymer was set to 58/42, the other was the same as in Example 3 to obtain seed particles, composite resin particles, expandable particles, and hair. Bubble particles, and then measure and evaluate these physical properties.

In the production of the foamed molded body, heating was performed by introducing 0.070 MPa of water vapor for 35 seconds, and then cooling until the surface pressure of the foamed molded body was reduced to 0.01 MPa. Other than that, the same as Example 1 A foamed molded body with a density of 33.3 kg/m ³ (expansion ratio 30 times) was obtained, and then the physical properties were measured and evaluated.

The results obtained are shown in Table 2.

(Comparative Example 4)

In the production of seed particles, EVA (2) was not used, but seed particles/polystyrene resin=40/60. Other than that, the same as in Example 3 to obtain seed particles, composite resin particles, Expandable particles and expanded particles, and then measure and evaluate these physical properties.

In the production of the foamed molded body, 0.09 MPa of water vapor was introduced for 35 seconds to heat, and then cooled until the surface pressure of the foamed molded body was reduced to 0.01 MPa. Other than that, it was the same as in Example 1. A foamed molded body having a density of 33.3 kg/m ³ (expansion ratio 30 times) was obtained, and then the physical properties were measured and evaluated.

The results obtained are shown in Table 2.

(Comparative Example 5)

In the production of seed particles, LLDPE is used instead of LDPE (1), and EVA (4) is used instead of EVA (2), and set as polyethylene resin/ethylene-vinyl acetate copolymer = 73/27 and seed particles /Polystyrene resin=40/60, other than that are the same as in Example 3 to obtain seed particles and composite resin particles , Expandable particles and expanded particles, and then measure and evaluate these physical properties.

In the production of the foamed molded body, 0.09 MPa of water vapor was introduced for 35 seconds for heating, and then cooled until the surface pressure of the foamed molded body was reduced to 0.01 MPa. Other than that, the same as Example 1 A foamed molded body with a density of 33.3 kg/m ³ (expansion ratio 30 times) was obtained, and then the physical properties were measured and evaluated.

The results obtained are shown in Table 2.

(Example 6)

In the production of seed particles, low-density polyethylene resin (LDPE(2): density 928kg/m ³ , melting point 115°C, MFR0.7g/10 minutes, manufactured by Japan Polyethylene Co., Ltd., product name: Novatec LD LF280H) To replace LDPE (1), and use ethylene-vinyl acetate copolymer (EVA (3): vinyl acetate content rate 28%, density 950kg/m ³ , melting point 69 ℃, MFR 20.0g/10 minutes, NUC shares limited Company system, product name: DQDJ-3269) instead of EVA (1), and set polyethylene resin/ethylene-vinyl acetate copolymer = 71/29 and seed particles/polystyrene resin = 22/78, except Otherwise, the same as in Example 3 was carried out to obtain seed particles, composite resin particles, expandable particles, expanded particles, and expanded molded articles, and then these physical properties were measured and evaluated.

The results obtained are shown in Table 3.

(Example 7)

In the production of seed particles, except for polyethylene resin/ethylene-ethyl Except for the vinyl acid ester copolymer = 66/34, the same as in Example 6 was used to obtain seed particles, composite resin particles, expandable particles, and expanded particles, and these physical properties were measured and evaluated.

In the production of the foamed molded body, water vapor of 0.070 MPa was introduced for 35 seconds for heating, and then cooled until the surface pressure of the foamed molded body was reduced to 0.01 MPa. Other than that, it was the same as in Example 1. A foamed molded body having a density of 25.0 kg/m ³ (expansion ratio 40 times) was obtained, and then the physical properties were measured and evaluated.

The results obtained are shown in Table 3.

(Comparative Example 6)

In the production of seed particles, LDPE(2) is used instead of LDPE(1), ethylene-vinyl acetate copolymer (EVA(4)) is not used, and seed particles/polystyrene resin=22/78 Other than that, the same as in Example 4 was carried out to obtain seed particles, composite resin particles, expandable particles, expanded particles, and expanded molded articles, and then these physical properties were measured and evaluated.

The results obtained are shown in Table 3.

From the results of Table 1 to Table 3, it can be seen that the composite resin particles of Examples 1 to 7 can provide foamed molded articles with excellent impact resistance and delayed flame without adding a flame retardant.

On the other hand, the composite resin particles of Comparative Examples 1 to 6 are inferior to the composite resin particles of Examples 1 to 7.

(Example 8)

In the preparation of the seed particles, except that the polyethylene resin/ethylene-vinyl acetate copolymer = 83/17 was set, the seed particles were obtained in the same manner as in Example 1 (vinyl acetate content rate 2.6% by mass), Composite resin particles, expandable particles, expanded particles, and expanded molded articles are then measured and evaluated for their physical properties.

The results obtained are shown in Table 4.

(Example 9)

For the production of seed particles, ethylene-vinyl acetate copolymer (EVA(2): vinyl acetate content rate 19%, density 939kg/m ³ , melting point 86°C, MFR2.5g/10min, manufactured by Hanwha Chemicals , Product name: EVA2319) instead of EVA (1), and set to polyethylene resin/ethylene-vinyl acetate copolymer = 45/55, except for the same as in Example 1 to obtain seed particles (vinyl acetate Ester content of 10.5% by mass), composite resin particles, expandable particles, expanded particles, and expanded molded articles, and then measured and evaluated these physical properties.

The results obtained are shown in Table 4.

(Example 10)

In the production of composite resin particles, the addition amount of dicumyl peroxide was reduced from 5.34 g to 3.76 g. Other than that, the same as in Example 4 was used to obtain seed particles and composite resin particles (colloid fraction 14.2 Mass %), expandable particles, expanded particles, and expanded molded articles, and then measure and evaluate these physical properties.

The results obtained are shown in Table 4.

(Example 11)

In the production of composite resin particles, the addition amount of dicumyl peroxide was increased from 5.34 g to 6.32 g. Other than that, the same as in Example 5 to obtain seed particles and composite resin particles (colloid fraction 36.8 Mass %), expandable particles, expanded particles, and expanded molded articles, and then measure and evaluate these physical properties.

The results obtained are shown in Table 4.

From the results in Table 4, it can be seen that when the vinyl acetate content of the polyethylene resin is outside the range of 3-10% by mass (Examples 8 and 9) and the colloidal fraction in the composite resin particles is 15-35 When the mass% is out of the range (Examples 10 and 11), at least one of the impact resistance and the post-flammability of the foamed molded article is inferior to the other Examples.

Claims (8)

A composite resin particle containing polyethylene resin and polystyrene resin in the range of 50-20% by mass and 50-80% by mass, respectively, relative to the total of polyethylene resin and polystyrene resin, wherein The total of the polyethylene resin series relative to the low density polyethylene resin with a density of 910~930kg/m ³ and the ethylene-vinyl acetate copolymer with a vinyl acetate content of 10~30% by mass is 45~85 mass. % And the range of 15 to 55% by mass contains the aforementioned low-density polyethylene resin with a density of 910 to 930 kg/m ³ and the aforementioned ethylene-vinyl acetate copolymer with a vinyl acetate content of 10 to 30% by mass, and, The composite resin particles do not substantially contain a bromine-based flame retardant, and the low-density polyethylene-based resin system does not use a linear low-density polyethylene-based resin. The composite resin particle described in the first item of the scope of patent application, wherein the polyethylene resin has a vinyl acetate content of 3-10% by mass. The composite resin particle described in the first item of the patent application, wherein when about 1 g of the composite resin particle is treated with 100 ml of toluene at a temperature of 130° C., the colloidal fraction of the composite resin particle insoluble in toluene is 15 to 35% by mass. The composite resin particles described in the first item of the scope of patent application, wherein the aforementioned composite resin particles have an average particle diameter of 1.0 to 2.0 mm. An expandable particle containing the composite resin particle described in item 1 of the patent application and a volatile blowing agent. A kind of foamed particles, which makes the foaming property described in item 5 of the scope of patent application The particles are pre-expanded. A foamed molded product obtained by foaming and molding the expanded particles described in item 6 of the scope of patent application. The foamed molded article as described in item 7 of the scope of patent application, wherein the aforementioned foamed molded article has a density of less than 49 kg/m ³ .

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