JP7078849B2 - Effervescent composite resin particles - Google Patents

Description

The present invention relates to effervescent composite resin particles containing butane, pentane, and cyclohexane as a foaming agent.

Foamed particle molded products are used in a wide range of applications such as packaging materials, building materials, and shock absorbing materials by taking advantage of their excellent cushioning properties, light weight, and heat insulating properties. As the base resin of the foamed particle molded product, those made of polystyrene-based resin such as polystyrene and those made of polyolefin-based resin such as polypropylene and polyethylene are mainly used. However, in recent years, a foamed particle molded product using a composite resin containing a polyolefin-based resin component and a polystyrene-based resin component as a base resin has attracted attention.

For example, as disclosed in Patent Documents 1 to 5, a foamed particle molded body using a composite resin as a base resin is, for example, a foamable composite resin particle obtained by impregnating composite resin particles with a physical foaming agent such as butane or pentane. The foamed composite resin particles were heated and foamed to obtain foamed particles, and then the foamed particles were fused to each other in a mold. The foamed particle molded product using such a composite resin as a base resin has the characteristics of a foamed particle molded product using a polyolefin resin as a base resin and a foamed particle molded product using a polystyrene resin as a base resin. It has high toughness, high resilience, and high rigidity.

International Publication No. 2016/047526 Japanese Unexamined Patent Publication No. 2014-062171 Japanese Unexamined Patent Publication No. 2015-07478 Japanese Unexamined Patent Publication No. 2016-180038 JP-A-2017-105882

Since the foamed particles have a large volume per weight, they are disadvantageous in terms of transportation cost. Therefore, in recent years, transportation and storage of the foamable composite resin particles before foaming have been required. Therefore, foamable composite resin particles having excellent retention of a foaming agent are desired.

As a method for increasing the retention of the foaming agent of the foamable composite resin particles, for example, there is a method for increasing the ratio of the polystyrene-based resin component in the composite resin. However, if the ratio of the polystyrene resin component is increased, the cooling time after heating tends to be long when the foamed particles formed by foaming the foamable composite resin particles are molded in the mold, which leads to an increase in the molding cycle.

The present invention has been made in view of this background, and an object of the present invention is to provide foamable composite resin particles which are excellent in foamability and can suppress an increase in molding cycle while maintaining excellent in-mold moldability. Is.

In one aspect of the present invention, a composite resin of a polyolefin-based resin and a polystyrene-based resin, which is obtained by impregnating and polymerizing a polyolefin-based resin with a styrene-based monomer, is used as a base resin, and the base resin is impregnated with a foaming agent. Effervescent composite resin particles made of
The content of the foaming agent is 0.80 to 1.35 mol per 1 kg of the composite resin.
The foaming agent is composed of a chain-type aliphatic hydrocarbon and a cyclic-type aliphatic hydrocarbon.
The molar ratio of the chain aliphatic hydrocarbon to the cyclic aliphatic hydrocarbon is 60:40 to 80:20.
The above chain aliphatic hydrocarbons are butane and pentane.
The molar ratio of the butane to the pentane is 30:70 to 75:25.
The cyclic aliphatic hydrocarbon is in the effervescent composite resin particles of cyclohexane.

The foamable composite resin particles use a composite resin of a polyolefin resin and a polystyrene resin as a base resin, and have both the characteristics of the polyolefin resin and the characteristics of the polystyrene resin. Thereby, the foamable composite resin particles enable the production of a foamed composite resin molded product having both toughness and rigidity at a high level.

The effervescent composite resin particles contain butane, pentane, and cyclohexane as a foaming agent in the above-mentioned predetermined ratios. Therefore, a foamed particle molded product having excellent foamability, excellent in-mold moldability, and shortening of the molding cycle, as well as excellent fusion property, light weight, and good appearance, while improving the foamability of the foamable composite resin particles. Will be able to be manufactured.

In the present specification, when a numerical value or a physical property value is inserted before and after using "-", it is used as including the values before and after that.

[Effervescent composite resin particles]
Next, a preferred embodiment of the effervescent composite resin particles will be described. The foamable composite resin particles use the composite resin as a base resin and contain a foaming agent. The foamable composite resin particles are used for producing composite resin foamed particles by foaming them. That is, the composite resin foamed particles are particulate foams obtained by pre-foaming the foamable composite resin particles and using the composite resin as the base resin. Further, the composite resin foamed particles are used to obtain a foamed particle molded product by, for example, in-mold molding. That is, a molded body having a desired shape can be obtained by filling a large number of foamed particles in a molding die and fusing the composite resin foamed particles to each other in the molding die. In the following description, the "foamable composite resin particles" may be appropriately referred to as "foamable particles", and the "composite resin foamed particles" may be appropriately referred to as "foamed particles".

The effervescent particles are made of a composite resin obtained by impregnating and polymerizing a polyolefin-based resin with a styrene-based monomer as a base resin. In the present specification, the composite resin is a resin obtained by impregnating a polyolefin resin with a styrene monomer or the like and polymerizing the resin as described above, and comprises a component derived from the polyolefin resin and a component derived from the styrene monomer. Is a resin containing. Usually, the main component of the component derived from the styrene-based monomer is a polystyrene-based resin obtained by polymerizing the styrene-based monomer. Further, during the polymerization of the styrene-based monomer, not only the polymerization of the styrene-based monomers but also the graft polymerization of the styrene-based monomer on the polymer chain of the polyolefin-based resin occurs. In this case, the composite resin not only contains a polyolefin-based resin component and a polystyrene-based resin component obtained by polymerizing a styrene-based monomer, but also a polyolefin-based resin component obtained by graft-polymerizing a styrene-based monomer (a polyolefin-based resin component). That is, it contains PO-g-PS component). Further, when the styrene-based monomer is polymerized, cross-linking of the polyolefin-based resin may occur. In this case, the composite resin is a polyolefin-based resin that is cross-linked with the non-cross-linked polyolefin-based resin as a polyolefin-based resin component. including. Therefore, the composite resin is a concept different from the mixed resin obtained by melt-kneading a polymerized polyolefin resin and a polymerized polystyrene resin.

The content ratio of the component derived from the polyolefin-based resin and the component derived from the styrene-based monomer in the composite resin can be appropriately adjusted. By increasing the proportion of the polyolefin-based resin, the impact resistance and toughness of the foamed particle molded product are improved. On the other hand, by increasing the proportion of the component derived from the styrene-based monomer, the retention of the foaming agent and the rigidity of the foamed particle molded product are improved. For example, the blending amount of the styrene-based monomer can be in the range of 100 to 2000 parts by mass with respect to 100 parts by mass of the polyolefin-based resin.

The blending amount of the styrene-based monomer is preferably more than 400 parts by mass and 2000 parts by mass or less with respect to 100 parts by mass of the polyolefin-based resin. In this case, not only the balance between the toughness and the rigidity of the foamed particle molded product is improved, but also the effect of improving the foaming agent retention is more remarkable. From the viewpoint of further enhancing this effect, the blending amount of the styrene-based monomer with respect to 100 parts by mass of the polyolefin-based resin is more preferably 450 parts by mass or more and 1500 parts by mass or less, and further preferably 500 parts by mass or more and 1000 parts by mass or less.

(Polyolefin resin)
Examples of the polyolefin resin include branched low-density polyethylene, linear low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and ethylene-acrylic acid alkyl ester copolymer. Polyethylene-based resins such as an ethylene-methacrylic acid copolymer and an ethylene-methacrylic acid alkyl ester copolymer can be used. Examples of the polyolefin resin include a propylene homopolymer, a propylene-ethylene copolymer, a propylene-1-butene copolymer, a propylene-ethylene-1-butene copolymer, and a propylene-4-methyl-1-pentene. A polypropylene-based resin such as a copolymer can also be used. Further, as the polyolefin-based resin, one kind of polymer can be used, but a mixture of two or more kinds of polymers can also be used.

The polyolefin-based resin preferably contains linear low-density polyethylene as a main component. The linear low-density polyethylene is a copolymer of ethylene and an α-olefin such as 1-butene or 1-hexene, and has a density of 910 kg / m ³ or more and less than 930 kg / m ³ . The linear low-density polyethylene preferably has a branched structure having a linear polyethylene chain and a short-chain branched chain having 2 to 6 carbon atoms. Specific examples thereof include ethylene-butene copolymers, ethylene-hexene copolymers, ethylene-4-methylpentene copolymers, ethylene-octene copolymers and the like. The polyolefin-based resin is more preferably linear low-density polyethylene polymerized using a metallocene-based polymerization catalyst. In this case, it is possible to obtain a foamed particle molded product having particularly excellent resilience after compression. From the viewpoint of further enhancing this effect, the content of the linear low-density polyethylene in the polyolefin resin is preferably 50% by mass or more, more preferably 60% by mass or more, and 70% by mass or more. Is more preferable.

The melting point Tm of the polyolefin resin is preferably 80 ° C to 115 ° C. In this case, the polyolefin-based resin can be sufficiently impregnated with the styrene-based monomer during the production of the effervescent particles, and the suspension system can be prevented from becoming unstable during the polymerization. As a result, it becomes possible to obtain a foamed particle molded product having both the excellent rigidity of the polystyrene-based resin and the toughness of the polyolefin-based resin at a higher level. From the same viewpoint, the melting point Tm of the polyolefin resin is more preferably 85 to 110 ° C. The melting point Tm of the polyolefin resin is measured as the melting peak temperature by differential scanning calorimetry (DSC) based on JIS K7121-1987. As the state adjustment of the test piece, "(2) When the melting temperature is adopted after performing a certain heat treatment" is adopted, and both the heating temperature and the cooling temperature are set to 10 ° C./min. When two or more melting peaks are present on the DSC curve, the melting peak on the lowest temperature side is set to the melting point Tm of the polyolefin resin.

Further, the polyolefin resin has a melting point Tm (° C) and a Vicat softening point Tv (° C).
It is preferably made of linear low density polyethylene that satisfies the relationship of Tm—Tv ≦ 20 (° C.). It is presumed that such a polyolefin-based resin has a uniform molecular structure, and that the network structure due to cross-linking is more uniformly distributed in the polyolefin-based resin at the time of cross-linking. Therefore, in this case, the strength and resilience of the foamed particle molded product can be further improved. From the same viewpoint, the linear low-density polyethylene more preferably satisfies Tm-Tv ≦ 15 (° C.), and further preferably satisfies Tm-Tv ≦ 10 (° C.). The Vicat softening point Tv of the polyolefin resin is measured based on the A50 method of JIS K 7206: 1999.

The melt mass flow rate (MFR) of the polyolefin resin is preferably 0.5 to 4.0 g / 10 minutes, more preferably 1.0 to 3.0 g / 10 minutes from the viewpoint of foamability. The MFR of the polyolefin resin is measured based on JIS K7210-1: 2014 under the conditions of a temperature of 190 ° C. and a load of 2.16 kg. Further, as the measuring device, a melt indexer (for example, model L203 manufactured by Takara Kogyo Co., Ltd.) can be used.

The crystallinity of the polyolefin resin is preferably 20 to 35%. In this case, the retention and foamability of the foaming agent can be further improved. From the same viewpoint, the crystallinity of the polyolefin resin is more preferably 20 to 30%. The crystallinity of the polyolefin resin is determined from the amount of heat of melting measured by differential scanning calorimetry (DSC) based on JIS K7122: 1987. As the state adjustment of the test piece, "(2) When the heat of fusion is adopted after performing a certain heat treatment" is adopted, and both the heating temperature and the cooling temperature are set to 10 ° C./min.

The content of the xylene insoluble content of the composite resin particles is preferably 0.1 to 10% by mass. In this case, it is possible to improve the foamability at the time of foaming and the moldability at the time of in-mold molding. From the viewpoint of further improving foamability and moldability, the content of the xylene insoluble content of the composite resin particles is more preferably 0.1 to 6.0% by mass. The xylene insoluble component is mainly a crosslinked polyolefin resin component in the composite resin.

(Polystyrene resin)
The composite resin contains a polystyrene-based resin component obtained by polymerizing a styrene-based monomer. In the present specification, styrene constituting the polystyrene-based resin component and a monomer copolymerizable with styrene added as needed may be collectively referred to as a styrene-based monomer. The polystyrene-based resin means a resin having a styrene-derived constituent unit of 50% by mass or more. The ratio of styrene in the styrene-based monomer is preferably 80% by mass or more, and more preferably 90% by mass or more. Examples of the monomer copolymerizable with styrene include the styrene derivative described later and other vinyl monomers.

Examples of the styrene derivative include α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-methoxystyrene, pn-butylstyrene, and p. -T-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4,6-tribromostyrene, divinylbenzene, styrenesulfonic acid, sodium styrenesulfonate and the like can be mentioned. These may be used alone or in admixture of two or more.

Examples of other vinyl monomers include acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, a vinyl compound containing a hydroxyl group, a vinyl compound containing a nitrile group, an organic acid vinyl compound, an olefin compound, a diene compound, and a halogen. Examples thereof include vinyl halide compounds, vinylidene halide compounds, and maleimide compounds. These vinyl monomers may be used alone or in combination of two or more.

Examples of the acrylate ester include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and the like.

Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate and the like.

Examples of the vinyl compound containing a hydroxyl group include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate and the like.

Examples of the vinyl compound containing a nitrile group include acrylonitrile and methacrylonitrile.

Examples of the organic vinyl acid compound include vinyl acetate and vinyl propionate. Examples of the olefin compound include ethylene, propylene, 1-butene and 2-butene.

Examples of the diene compound include butadiene, isoprene, chloroprene and the like.

Examples of the vinyl halide compound include vinyl chloride and vinyl bromide.

Examples of the halogenated vinylidene compound include vinylidene chloride and the like.

Examples of the maleimide compound include N-phenylmaleimide and N-methylmaleimide.

From the viewpoint of enhancing the foamability of the effervescent particles, the polystyrene-based resin is preferably polystyrene or a copolymer of styrene and an acrylic monomer. From the viewpoint of further enhancing foamability, it is preferable to use styrene and butyl acrylate as the monomers constituting the polystyrene-based resin. In this case, the content of the butyl acrylate component in the composite resin is preferably 0.5 to 10% by mass, more preferably 1 to 8% by mass, based on the entire composite resin. It is more preferably to 5% by mass.

The weight average molecular weight of the polystyrene-based resin is preferably 200,000 to 300,000, more preferably 220,000 to 260,000. In this case, when the effervescent particles are effervescent, more excellent effervescence can be exhibited. In addition, the shrinkage of the foamed particles can be prevented more effectively. Further, it is possible to improve the fusion property between the foamed particles at the time of in-mold molding of the foamed particles. As a result, the dimensional stability of the foamed particle molded product can be improved. The range of the weight average molecular weight of the polystyrene-based resin can be determined from the above range. In Examples, a method for measuring the weight average molecular weight of a polystyrene-based resin will be described.

The glass transition temperature Tg of the polystyrene-based resin is preferably 85 to 120 ° C, more preferably 85 to 100 ° C. In this case, the foamability of the foamable particles can be improved, and shrinkage during foaming can be prevented more effectively. Further, it is possible to improve the fusion property between the foamed particles at the time of in-mold molding of the foamed particles, and it is possible to improve the dimensional stability of the foamed particle molded body.

The glass transition temperature Tg of the polystyrene-based resin is measured, for example, as follows. Specifically, first, 1.0 g of effervescent particles is placed in a 150 mesh wire mesh bag. Next, about 200 ml of xylene is placed in a 200 ml round-bottom flask, and the sample placed in the wire mesh bag is set in a Soxhlet extractor. Heat with a mantle heater for 8 hours to extract Soxhlet. The extracted xylene solution is dropped into 600 ml of acetone, decanted, and the supernatant is evaporated to dryness under reduced pressure to obtain a polystyrene-based resin as an acetone-soluble component. About 10 mg of the obtained polystyrene resin is measured by heat flux differential scanning calorimetry using a DSC measuring instrument (Q1000) manufactured by TA Instruments Co., Ltd. in accordance with JIS K7121-1987. Then, the glass transition temperature Tg can be obtained as the intermediate point glass transition temperature of the DSC curve obtained under the condition of a heating rate of 10 ° C./min.

(Effervescent agent)
The effervescent particles contain a foaming agent. The content of the foaming agent is 0.80 to 1.35 mol per 1 kg of the composite resin. If the content of the foaming agent per 1 kg of the composite resin is less than 0.80 mol, the foamability of the foamable particles may be insufficient. From the viewpoint of further enhancing the foamability, the content of the foaming agent per 1 kg of the composite resin is preferably 0.90 mol or more, and more preferably 1.00 mol or more. On the other hand, when the content of the foaming agent exceeds 1.35 mol, the foaming rate is too fast, and the bubbles of the foamed particles may become coarse and spoil the appearance of the foamed particle molded body, or the foamed particle molded body may be molded. The forming cycle of the time may be long. From the viewpoint of further preventing this, the content of the foaming agent per 1 kg of the composite resin is preferably 1.30 mol or less, and more preferably 1.25 mol or less.

The effervescent particles contain a chain aliphatic hydrocarbon and a cyclic aliphatic hydrocarbon as a foaming agent. The molar ratio of chain aliphatic hydrocarbons to cyclic aliphatic hydrocarbons (however, chain aliphatic hydrocarbons: cyclic aliphatic hydrocarbons) is 60:40 to 80:20. If the amount of chain aliphatic hydrocarbons increases and the amount of cyclic aliphatic hydrocarbons decreases outside this range, the effect of plasticizing the composite resin during in-mold molding is insufficient, and the foamed particles are melted during molding. There is a risk that the wearability will decrease. On the other hand, when the amount of chain-type aliphatic hydrocarbons decreases and the amount of cyclic aliphatic hydrocarbons increases outside the above range, the foamed particles obtained when the foamable particles are foamed shrink, and the target foaming magnification is achieved. May not be obtained. From the viewpoint of further enhancing the fusion property of the foamed particles and further suppressing the shrinkage of the foamed particles, the molar ratio of the chain-type aliphatic hydrocarbon to the cyclic-type aliphatic hydrocarbon may be 65:35 to 80:20. It is preferably 70:30 to 80:20, more preferably 70:30 to 80:20.

In effervescent particles, the cyclic aliphatic hydrocarbons are at least cyclohexane and the chain aliphatic hydrocarbons are at least butane and pentane. The effervescent particles can contain a foaming agent other than butane, pentane, and cyclohexane as long as the effects of the present invention are not impaired.

The molar ratio of butane to pentane (however, butane: pentane) contained in the effervescent particles is 30:70 to 75:25. If the amount of butane increases and the amount of pentane decreases outside this range, the cooling time during the production of the foamed particle molded product becomes long, and as a result, the molding cycle may become long. On the other hand, if the amount of butane is reduced and the amount of pentane is increased outside the above range, the bubbles in the foamed particles and the foamed particle molded product may be coarsened and the appearance may be impaired. The molar ratio of butane to pentane is preferably 40:60 to 65:35, preferably 50:50 to 60:40, from the viewpoint of further enhancing the effect of shortening the molding cycle and the effect of suppressing the coarsening of bubbles. Is more preferable.

Butane contains at least one of normal butane and isobutane. The pentane contains at least one selected from normal pentane, isopentane, and neopentane.

It is preferable that at least isobutane is contained as butane, and the content ratio of isobutane to the butane contained in the effervescent particles is 50 to 100% by mass. In this case, the effect that the effervescent particles are particularly excellent in the retention of the effervescent agent can be obtained. From the viewpoint of further enhancing this effect, the content ratio of isobutane in the butane contained in the effervescent particles is more preferably 70 to 100% by mass, further preferably 90 to 100% by mass. Further, the pentane preferably contains at least one of normal pentane and isopentane.

(Other additives)
The effervescent particles can further contain, as an additive, a bubble modifier, a colorant, a flame retardant, a lubricant, an antioxidant, a weather resistant agent, a dispersion diameter expanding agent, and the like.

As the bubble adjusting agent, fatty acid monoamide, fatty acid bisamide, talc, silica, polyethylene wax, methylene bisstearic acid, zinc borate, citrus, polytetrafluoroethylene and the like can be used. Preferably, the effervescent particles may contain ethylene bisstearate amide. In this case, the combination of ethylene bisstearic acid amide and the above-mentioned three types of foaming agents facilitates bubble adjustment and further prevents bubble coarsening.

The blending amount of ethylene bisstearic acid amide in the effervescent particles is preferably 0.05 to 0.2 parts by mass with respect to 100 parts by mass of the composite resin. In this case, the above-mentioned effect of preventing the coarsening of bubbles can be more sufficiently obtained. From the viewpoint of further enhancing this effect, the blending amount of ethylene bisstearic acid amide in the effervescent particles is more preferably 0.08 to 0.12 parts by mass with respect to 100 parts by mass of the composite resin.

As the colorant, either pigments or dyes can be used, and carbon blacks such as furnace black, channel black, thermal black, acetylene black and ketjen black, and carbon pigments such as graphite and carbon fibers can be used. preferable.

As the flame retardant, for example, hexabromocyclododecane, tetrabromobisphenol A-based compound, trimethyl phosphate, brominated butadiene-styrene block copolymer, aluminum hydroxide and the like can be used.

<Manufacturing method of effervescent particles>
The effervescent particles are made by impregnating the composite resin particles with a foaming agent. The composite resin particles are obtained by impregnating nuclear particles containing a polyolefin resin with a styrene-based monomer and polymerizing the composite resin particles. Nuclear particles are also commonly referred to as seed particles.

(Granulation method of nuclear particles)
Nuclear particles can be produced by melt-kneading a polyolefin-based resin and an additive added as needed and then granulating. Examples of the additive include a bubble adjusting agent, a coloring agent, a flame retardant, a lubricant, an antioxidant, a weather resistant agent, a dispersion diameter expanding agent and the like. Melt kneading can be performed by an extruder. In order to perform uniform kneading, it is preferable to mix the resin in advance and then extrude. The melt-kneading is preferably performed using a single-screw extruder or a twin-screw extruder equipped with a screw of a high dispersion type such as a dalmage type, a madock type, and a unimelt type.

Granulation of nuclear particles is performed by, for example, a strand cut method, an underwater cut method, a hot cut method, or the like.

(Dispersion process and reforming process)
Effervescent particles can be obtained, for example, by performing a dispersion step and a modification step as follows. In the dispersion step, first, nuclear particles containing a polyolefin resin as a main component are dispersed in an aqueous medium to prepare a dispersion liquid.

As the aqueous medium, for example, deionized water or the like can be used. The nuclear particles are preferably dispersed in an aqueous medium together with the suspending agent. In this case, the styrene-based monomer can be uniformly suspended in the aqueous medium. Examples of the suspending agent include tricalcium phosphate, hydroxyapatite, magnesium pyrophosphate, magnesium phosphate, aluminum hydroxide, ferric hydroxide, titanium hydroxide, magnesium hydroxide, barium phosphate, calcium carbonate, and magnesium carbonate. , Calcium carbonate, calcium sulfate, barium sulfate, talc, kaolin, bentonite and the like can be used as fine particle inorganic suspending agents. Further, for example, an organic suspending agent such as polyvinylpyrrolidone, polyvinyl alcohol, ethyl cellulose, hydroxypropylmethyl cellulose and the like can also be used. Preferred are tricalcium phosphate, hydroxyapatite, and magnesium pyrophosphate. These suspending agents may be used alone or in combination of two or more.

The amount of the suspending agent used is preferably a solid content with respect to 100 parts by mass of an aqueous medium of the suspension polymerization system (specifically, all water in the system including water such as a reaction product-containing slurry). Is 0.05 to 10 parts by mass, more preferably 0.3 to 5 parts by mass. By setting the suspending agent in the above range, the styrene-based monomer can be stably suspended in the reforming step, and the particle size distribution of the composite resin particles obtained after the reforming step is widened. It can be suppressed.

A dispersant consisting of a surfactant can be added to the aqueous medium. As the surfactant, for example, an anionic surfactant or a nonionic surfactant is preferably used. These surfactants may be used alone or in combination of two or more.

As the anionic surfactant, for example, sodium alkylsulfonate, sodium alkylbenzenesulfonate, sodium laurylsulfate, sodium α-olefin sulfonate, sodium dodecyldiphenyl ether disulfonate and the like can be used. As the nonionic surfactant, for example, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether and the like can be used.

Further, if necessary, an electrolyte composed of inorganic salts such as lithium chloride, potassium chloride, sodium chloride, sodium sulfate, sodium nitrate, sodium carbonate and sodium bicarbonate can be added to the aqueous medium. Further, in order to obtain a molded product having better toughness and mechanical strength, it is preferable to add a water-soluble polymerization inhibitor to the aqueous medium. As the water-soluble polymerization inhibitor, for example, sodium nitrite, potassium nitrite, ammonium nitrite, L-ascorbic acid, citric acid and the like can be used. From the viewpoint of reducing the amount of polystyrene-based resin component near the outermost surface of the composite resin particles, the amount of the water-soluble polymerization inhibitor added is in an aqueous medium (specifically, in a system containing water such as a reaction product-containing slurry). All water) is preferably 0.001 to 0.1 parts by mass, more preferably 0.005 to 0.06 parts by mass with respect to 100 parts by mass.

In the reforming step, the styrene-based monomer is impregnated into the nuclei and polymerized in the aqueous medium. The polymerization of the styrene-based monomer can be carried out in the presence of a polymerization initiator. In this case, cross-linking of the polyolefin-based resin such as the polyethylene-based resin may occur along with the polymerization of the styrene-based monomer or the like. In addition, a cross-linking agent can be used in combination if necessary. When using the polymerization initiator and the cross-linking agent, it is preferable to dissolve the polymerization initiator and the cross-linking agent in the styrene-based monomer in advance.

As the polymerization initiator, those used in the suspension polymerization method for styrene-based monomers can be used. For example, a polymerization initiator that is soluble in a styrene-based monomer and has a 1-hour half-life temperature of 70 to 140 ° C. can be used. Examples of the polymerization initiator include lauroyl peroxide, t-butylperoxy-2-ethylhexanoate, benzoyl peroxide, hexylperoxyisopropyl carbonate, 1,1-bis-t-butylperoxycyclohexane, and t-amyl. Peroxy-2-ethylhexyl carbonate, t-butylperoxyisopropylcarbonate, hexylperoxybenzoate, t-butylperoxy-2-ethylhexylcarbonate, t-butylperoxybenzoate, t-hexylperoxybenzoate, dicumyl peroxide And other organic peroxides can be used. Further, as the polymerization initiator, an azo compound such as azobisisobutyronitrile or 1,1'-azobis (cyclohexane-1-carbonitrile) can be used. These polymerization initiators may be used alone or in combination of two or more. Further, a polymerization initiator having a 1-hour half-life temperature of 100 to 140 ° C. is preferable from the viewpoint that the styrene-based monomer can be easily impregnated into the core particles. The amount of the polymerization initiator added is preferably 0.01 to 3 parts by mass with respect to 100 parts by mass of the styrene-based monomer.

Further, as the cross-linking agent, it is preferable to use a cross-linking agent having a 1-hour half-life temperature of 110 to 160 ° C. Specifically, for example, t-butylperoxy-2-ethylhexyl carbonate, t-butylperoxybenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, di. Peroxides such as -t-butyl peroxide can be used. The cross-linking agent may be used alone or in combination of two or more. The blending amount of the cross-linking agent is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the styrene-based monomer. The same compound may be used as the polymerization initiator and the cross-linking agent.

When the nuclei particles are impregnated with the styrene-based monomers and polymerized, the total amount of the styrene-based monomers to be blended is divided into, for example, two or more in an aqueous medium in which the nuclei particles are dispersed, and these monomers are different. It is preferable to add at the timing. Specifically, a part of the total amount of the styrene-based monomer to be blended is added to the aqueous medium in which the nuclear particles are dispersed to impregnate and polymerize the styrene-based monomer, and then the styrene-based monomer is then impregnated. Further, the remainder of the styrene-based monomer to be blended can be added to the aqueous medium once or twice or more. By adding the styrene-based monomer in a divided manner in this way, it becomes possible to suppress the condensation of the resin particles during the polymerization.

Further, the polymerization initiator can be added to the aqueous medium in a state of being dissolved in the styrene-based monomer. As described above, when the styrene-based monomer to be blended is divided into two or more times and added at different timings, the polymerization initiator is dissolved in the styrene-based monomer added at any timing. Alternatively, the polymerization initiator may be dissolved in each styrene-based monomer added at different timings. When the styrene-based monomer is added in a divided manner, it is preferable to dissolve the polymerization initiator in at least the styrene-based monomer added first (hereinafter referred to as "first monomer"). It is preferable that 75% or more of the total amount of the polymerization initiator to be blended is dissolved in the first monomer, and it is more preferable that 80% or more is dissolved in the first monomer. In this case, it is possible to prevent the suspension system from becoming unstable during polymerization. As a result, it becomes possible to obtain a molded product having both the excellent rigidity of the polystyrene-based resin and the excellent toughness of the polyolefin-based resin at a higher level. Further, as described above, when a part of the styrene-based monomer to be blended is added as the first monomer, the balance of the total amount of the styrene-based monomer to be blended is used as the second monomer. After the addition of one monomer, it can be added at a timing different from that of the first monomer. The second monomer may be further divided and added, or the second monomer may be continuously added over a predetermined time.

The seed ratio of the styrene-based monomer added as the first monomer (that is, the mass ratio of the first monomer to the nuclei particles) is preferably 0.5 or more. In this case, even when the proportion of the polystyrene-based resin component in the composite resin is high, the impregnation property of the styrene-based monomer can be enhanced, so that the polystyrene-based resin component on the particle surface can be reduced. can. In addition, it becomes easy to make the shape of the composite resin particles closer to a spherical shape. From the same viewpoint, the seed ratio is more preferably 0.7 or more, and further preferably 0.8 or more. The seed ratio is preferably 1.5 or less. In this case, even when the proportion of the component derived from the styrene-based monomer in the composite resin is high, the impregnation property of the styrene-based monomer can be enhanced, and the styrene-based monomer is used as the core particles. It can be sufficiently impregnated. In addition, it is possible to further prevent the styrene-based monomer from polymerizing before the nuclear particles are sufficiently impregnated, and it is possible to further prevent the generation of lumps of resin. From the same viewpoint, the seed ratio of the first monomer is more preferably 1.3 or less, and further preferably 1.2 or less.

It is preferable that the melting point Tm (° C.) of the polyolefin resin in the nuclear particles and the impregnation polymerization temperature Tp (° C.) in the reforming step satisfy the relationship of Tm-10 ≦ Tp ≦ Tm + 30. In this case, even when the proportion of the polystyrene-based resin component in the composite resin is high, the polyolefin-based resin can be sufficiently impregnated with the styrene-based monomer, and the suspension system becomes unstable during polymerization. Can be prevented from doing so. Further, it is preferable that the impregnation polymerization temperature Tp (° C.) and the crosslinking temperature Tx (° C.) in the reforming step satisfy the relationship of Tp + 10 ≦ Tx ≦ Tp + 30. In this case, the polyolefin-based resin in the composite resin can be appropriately crosslinked, the internal fusion of the foamed particles is good, and a molded product having excellent toughness can be obtained.

Further, a plasticizer, an oil-soluble polymerization inhibitor, a flame retardant, a colorant, a bubble adjusting agent, a chain transfer agent and the like can be added to the styrene-based monomer, if necessary. As the plasticizer, for example, fatty acid ester, acetylated monoglyceride, oils and fats, liquid paraffin and the like can be used. As the fatty acid ester, for example, glycerin tristearate, glycerin trioctate, glycerin trilaurate, sorbitan tristearate, sorbitan monostearate, butyl stearate and the like can be used. Further, as the acetylated monoglyceride, for example, glycerin diacet monolaurate or the like can be used. As the fats and oils, for example, hardened beef tallow, hardened castor oil and the like can be used. Further, as the oil-soluble polymerization inhibitor, for example, para-t-butylcatechol, hydroquinone, benzoquinone and the like can be used. As the flame retardant, the colorant, and the bubble adjusting agent, the same ones as described above can be used. As the chain transfer agent, for example, n-dodecyl mercaptan, α-methylstyrene dimer and the like can be used. The above additives can be added alone or in combination of two or more.

Additives such as the above-mentioned plasticizers, oil-soluble polymerization inhibitors, flame retardants, colorants, and chain transfer agents can also be dissolved in a solvent and impregnated into nuclear particles.

(Impregnated with foaming agent)
At a temperature in the range of Tg-10 to Tg + 40 (° C.) (where Tg is the glass transition temperature (° C.) of the obtained polystyrene-based resin), the styrene-based monomer becomes resin particles during and / or after polymerization. By impregnating with a foaming agent, foamable particles can be obtained.

[Effervescent particles]
Foamed particles can be obtained by using the composite resin as a base resin and foaming the above-mentioned effervescent particles containing a foaming agent. The method for foaming the foamable particles is not particularly limited, but there is, for example, a method for heating the foamable particles with a heating medium. Specifically, by introducing a heating medium such as steam into a prefoaming machine to which the effervescent particles are supplied, the effervescent particles can be heated and foamed to obtain effervescent particles.

The foamed particles are particulate foams having a composite resin of a polyolefin-based resin and a polystyrene-based resin as a base resin, which is obtained by impregnating and polymerizing a polyolefin-based resin with a styrene-based monomer. The bulk density of the foamed particles is preferably 10 to 50 kg / m ³ , more preferably 15 to 30 kg / m ³ .

(Measuring method of bulk density of foamed particles)
A 1 L graduated cylinder is filled with dried foamed particles up to a 1 L marked line. By measuring the mass of the foamed particles, the mass (g) of the foamed particles per 1 L is obtained, and the value converted into units of kg / m ³ is taken as the bulk density of the foamed particles.

The average bubble diameter of the foamed particles is preferably 200 μm or less. In this case, a foamed particle molded product having a better appearance can be obtained. From the viewpoint of further improving the appearance, the average bubble diameter is more preferably 150 μm or less, and further preferably 120 μm or less. Further, from the viewpoint of further improving the moldability of the foamed particles, the average cell diameter is preferably 50 μm or more.

(Measuring method of average bubble diameter of foamed particles)
The foamed particles are cut in two so as to pass through the center thereof, and a cross section of the foamed particles is photographed by, for example, a scanning electron microscope. In the obtained enlarged photograph, a straight line is drawn from the surface of the foamed particles to the surface on the counter plate side so as to pass through the center of the foamed particles, and the number of bubbles intersecting the straight line is measured. The bubble diameter is the value obtained by dividing the actual length of the straight line by the number of bubbles intersecting the straight line. The bubble diameter is measured in the same manner for 10 or more foamed particles, and the value obtained by arithmetically averaging the bubble diameters is taken as the average bubble diameter of the foamed particles.

[Effervescent particle molded product]
A foamed particle molded product is obtained by filling a molding mold with a large number of foamed particles and heating them to fuse them to each other. The apparent density of the foamed particle molded product is preferably 10 to 50 kg / m ³ , and more preferably 15 to 30 kg / m ³ . The apparent density of the foamed particle molded body is obtained by dividing the mass of the foamed particle molded body by the volume of the foamed particle molded body obtained from the external dimensions of the foamed particle molded body.

Hereinafter, the effervescent particles, the effervescent particles, and the effervescent particle molded product according to the examples will be described. The present invention is not limited to the following examples, and various modifications can be made without departing from the gist thereof.

(Example 1)
(1) Preparation of Nuclear Particles As a polyolefin resin, linear low-density polyethylene (specifically, "Niporon Z HF210K" manufactured by Tosoh Corporation) polymerized using a metallocene polymerization catalyst was prepared. The linear low-density polyethylene is appropriately referred to as "LL" below. The melting point Tm of this LL is 103 ° C. Further, as a dispersion diameter expanding agent, acrylonitrile-styrene copolymer (AS-XGS manufactured by Denki Kagaku Kogyo Co., Ltd., weight average molecular weight: 109,000, acrylonitrile component amount: 28% by mass, MFR (200 ° C., load). 5 kg): 2.8 g / 10 min) was prepared.

In addition, a masterbatch of antioxidant (specifically, "TMB113" manufactured by Toho Co., Ltd., linear low-density polyethylene: 90% by mass, phosphorus-based stabilizer: 6.5% by mass, hindered phenol-based antioxidant. : 3.5% by mass) was prepared. Furthermore, ethylene bis (stearate amide) as a bubble regulator (“Kaowax EB-FF” manufactured by Kao Co., Ltd.) and zinc 12-hydroxystearate (Nitto Kasei Kogyo Co., Ltd. “ZS-” manufactured by Nitto Kasei Kogyo Co., Ltd.) as a lubricant. 6 ”) mixed masterbatch (specifically,“ Kaowax EB-FF ”manufactured by Kao Co., Ltd .: 10% by mass,“ ZS-6 ”manufactured by Nitto Kasei Kogyo Co., Ltd .: 3% by mass, linear Low density polyethylene: 87% by mass) was prepared.

Then, 87.7 kg of the polyolefin resin, 4.7 kg of the dispersion diameter expanding agent, 0.9 kg of the masterbatch of the antioxidant, and 6.7 kg of the mixed masterbatch of the bubble adjusting agent and the lubricant are mixed with a Henshell mixer (specifically, , Mitsui Miike Machinery Co., Ltd .; Model FM-75E) and mixed for 5 minutes (specifically, dry blend) to obtain a resin mixture.

Next, using a twin-screw extruder with a barrel inner diameter of 26 mm (specifically, manufactured by Toshiba Machinery Co., Ltd .; model TEM-26SS), the resin mixture was melt-kneaded at the extruder set temperature of 210 ° C., and the average was 0 by the underwater cutting method. Nuclear particles were obtained by cutting to .19 mg / piece.

(2) Preparation of effervescent particles 1400 g of deionized water was placed in an autoclave having an internal volume of 3 L equipped with a stirrer, and 8.4 g of sodium pyrophosphate was further added. Then, 18.1 g of powdered magnesium nitrate hexahydrate was further added, and the mixture was stirred at room temperature for 30 minutes. As a result, a magnesium pyrophosphate slurry as a suspending agent was prepared. Next, 2 g of sodium lauryl sulfonate (specifically, a 10% by mass aqueous solution) as a surfactant, 0.28 g of sodium nitrite as a water-soluble polymerization inhibitor, and 105 g of nuclear particles were put into the autoclave.

Next, 1.17 g of t-hexyl peroxybenzoate as a polymerization initiator (NOF "Perhexyl Z") and 2.33 g of t-butylperoxy-2-ethylhexyl monocarbonate (NOF "Perbutyl E"). ), 0.93 g of α-methylstyrene dimer (“Nofmer MSD” manufactured by NOF CORPORATION) as a chain transfer agent was dissolved in the first monomer (styrene-based monomer). Then, this solution was put into the autoclave while stirring at a stirring speed of 500 rpm. As the first monomer, 84 g of styrene and 21 g of butyl acrylate were used.

Then, after replacing the air in the autoclave with nitrogen, the temperature rise was started, and the temperature in the autoclave (the temperature of the contents) was raised to 100 ° C. over 1.5 hours. After raising the temperature, this temperature was maintained at 100 ° C. for 1 hour. After that, the stirring speed was lowered to 450 rpm and maintained at 100 ° C. for 7.5 hours. One hour after reaching 100 ° C., 490 g of styrene was added into the autoclave as a second monomer (specifically, a styrene-based monomer) over 5 hours.

Then, the temperature in the autoclave was raised to 125 ° C. over 2 hours and kept at 125 ° C. for 5 hours. Then, the inside of the autoclave was cooled to 90 ° C. over 2 hours, the stirring speed was lowered to 400 rpm, and then the mixture was held at 90 ° C. for 3 hours. When the temperature reached 90 ° C., 21 g of cyclohexane, 24.5 g of pentane (a mixture of about 80% by mass of normal pentane and about 20% by mass of isopentane), and 26.3 g of isobutane were added as a foaming agent in the autoclave for about 0.5 hours. Was added to. Then, the temperature was raised to 105 ° C. over 1 hour, kept as it was at 105 ° C. for 5 hours, and then cooled to a temperature of 30 ° C. over about 2.5 hours.

Then, the composite resin particles containing the foaming agent were taken out. Then, nitric acid was added to dissolve magnesium pyrophosphate adhering to the surface of the composite resin particles. Then, dehydration and washing were performed with a centrifuge, and moisture adhering to the surface was removed with an air flow drying device to obtain effervescent particles. In order to prevent the foaming agent from escaping from the effervescent particles, the effervescent particles were immediately housed in a closed container after the water was removed, and the whole closed container was stored in a low temperature storage (6 ° C. or lower).

Table 1 shows the polymerization conditions of the effervescent particles obtained as described above. Specifically, Table 1 shows the types of the polyolefin-based resin of the nuclear particles used at the time of production, the amount of the nuclear particles, and the types and blending amounts of the styrene-based monomers. Regarding effervescent particles, the average particle size d63, the amount of xylene insoluble content (that is, the amount of Xy gel), the weight average molecular weight Mw of the acetone-soluble component (polystyrene resin), the total content of the foaming agent, the content of isopentane, and the normal butane. The content, isopentane content, normal pentane content, cyclohexane content, and foamability were measured as follows. The results are shown in Table 1.

"Average particle diameter d63"
The particle size distribution of the effervescent particles was measured using a particle size distribution measuring device "Millitrack JPA" manufactured by Nikkiso Co., Ltd. Specifically, first, 40 g of effervescent particles were freely dropped from the sample supply feeder of the measuring device, and the projected image was imaged with a CCD camera. Next, calculation and combination processing were sequentially performed on the captured image information, and measurement was performed under the conditions of an image analysis method that outputs the particle size distribution and shape index results. As a result, the particle size (d63) mm at a volume integration value of 63% in the rosin-ramler distribution was determined. This particle size (d63) was taken as the average particle size.

"Content of xylene insoluble matter (Xy gel amount)"
First, 1.0 g of effervescent particles was placed in a 150 mesh wire mesh bag. Next, about 200 ml of xylene was placed in a round bottom flask having a capacity of 200 ml, and the sample placed in the wire mesh bag was set in the Soxhlet extraction tube. Soxhlet extraction was performed by heating with a mantle heater for 8 hours. After the extraction was completed, it was cooled by air cooling. After cooling, the wire mesh was taken out from the extraction tube, and the sample was washed together with the wire mesh with about 600 ml of acetone. The acetone was then volatilized and then the sample was dried in a desiccator at a temperature of 120 ° C. for 4 hours. The sample recovered from the wire mesh after this drying is "xylene insoluble matter". The ratio of the gel amount (mass) to the initial amount of composite resin particles was expressed as a percentage, and this was defined as the content of xylene insoluble content, that is, the Xy gel amount (mass%). The xylene insoluble component is mainly a crosslinked polyolefin resin component in the composite resin.

"Weight average molecular weight Mw of acetone-soluble component (polystyrene resin)"
First, 1.0 g of effervescent particles was placed in a 150 mesh wire mesh bag. Next, about 200 ml of xylene was placed in a round-bottomed flask having a volume of 200 ml, and the sample (that is, effervescent particles) placed in the wire mesh bag was set in the Soxhlet extraction tube. Soxhlet extraction was performed by heating with a mantle heater for 8 hours. The extracted xylene solution was dropped into 600 ml of acetone, decanted, and then evaporated to dryness under reduced pressure to obtain an acetone-soluble component. The acetone-soluble Mw was measured by gel permeation chromatography (that is, GPC) using linear polystyrene as a standard material. A mixed gel column for polymer measurement was used for the measurement. Specifically, using a measuring device manufactured by Tosoh Corporation (specifically, HLC-8320GPC EcoSEC), eluent: tetrahydrofuran (that is, THF), flow rate: 0.6 ml / min, sample concentration: 0. The measurement was performed under the measurement condition of 1 wt%. As the column, a column in which TSKguardcolum SuperH-H x 1 and TSK-GEL SuperHM-H x 2 were connected in series was used. The acetone-soluble component obtained by further dissolving the xylene-soluble component in the composite resin in acetone is mainly a polystyrene-based resin.

"Contents of foaming agent, isobutane, normal butane, isopentane, normal pentane, cyclohexane"
The effervescent particles were dissolved in dimethylformamide (DMF), and the contents of the foaming agent, isobutane, normal butane, isopentane, normal pentane, and cyclohexane were measured by gas chromatography. Specifically, the procedure was as follows.

First, about 5 g of cyclopentanol was precisely weighed to the third decimal place in a 100 mL volumetric flask (the weight at this time is Wi), and DMF was added to make the whole volume 100 mL. This DMF solution was further diluted 100-fold with DMF to obtain an internal standard solution. Next, after taking out the effervescent particles to be measured from the closed container, about 1 g of the effervescent particles was precisely weighed to the third decimal place, and the weight at this time was defined as Ws (g). The weighed effervescent particles were dissolved in about 18 mL of DMF, and exactly 2 mL of the internal standard solution was added with a whole pipette. 1 μL of this solution was collected with a microsyringe and introduced into gas chromatography to obtain a chromatogram. The foaming agent component and the peak area of the internal standard were determined from the obtained chromatogram, and the concentration of each component was determined by the following formula (1). The foaming agent content was the total content of isobutane, normal butane, isopentane, normal pentane, and cyclohexane.

Component concentration (% by weight) = (Wi / 10000) ² × (An / Ai) × Fn ÷ Ws × 100 ... (1)
here,
Wi: Cyclopentanol weight (g) when preparing an internal standard solution
Ws: Sample weight (g) dissolved in DMF
An: Peak area of each component at the time of gas chromatograph measurement Ai: Peak area of internal standard substance at the time of gas chromatograph measurement Fn: Correction coefficient of each component obtained from a calibration curve prepared in advance The conditions for the above gas chromatograph analysis are as follows. It was a street.
Equipment used: Gas chromatograph GC-6AM manufactured by Shimadzu Corporation
Detector: FID (hydrogen flame ionization detector)
Column material: Glass column with an inner diameter of 3 mm and a length of 5000 mm Column packing material: [Liquid phase name] FFAP (free fatty acid), [Liquid phase impregnation rate] 10% by mass, [Carrier name] Gas chromatograph diatomaceous soil Chomasorb W, [Carrier] Particle size] 60/80 mesh, [Carrier treatment method] AW-DMCS (washing with water, baking, acid treatment, silane treatment), [Filling amount] 90 mL
Injection port temperature: 250 ° C
Column temperature: 120 ° C
Detection unit temperature: 250 ° C
Carrier gas: N ₂ , flow rate 40 ml / min

"Effervescent"
The effervescent particles taken out of the closed container are immediately placed in a shelf-type foaming machine and foamed by heating at a heating steam temperature of 100 ° C. for 270 seconds to obtain foamed particles, and then the foamed particles are dried at a temperature of 23 ° C. for 24 hours. rice field. Then, the bulk density (kg / m ³ ) of the foamed particles after drying was measured, and the result was used as the evaluation result of the foamability. A 1L graduated cylinder is prepared, an empty graduated cylinder is filled with foamed particles up to the 1L marked line, the mass (g) of the foamed particles per 1L is measured ^, and the unit is converted into kg / m3. From this, the bulk density (kg / m ³ ) of the foamed particles was determined. When the bulk density of the foamed particles is 16.6 kg / m ³ or more and less than 25 kg / m ³ , it is regarded as "good", when it is less than 16.6 kg / m ³ , it is regarded as "excellent", and when it is 25 kg / m ³ or more, or. The case where significant shrinkage was observed immediately after foaming was evaluated as "impossible".

(3) Foaming The foamable particles taken out from the closed container were immediately placed in a normal pressure batch foaming machine having a volume of 30 L, and steam was supplied into the foaming machine. As a result, the effervescent particles were foamed to the bulk density shown in Table 1 and then dried at a temperature of 23 ° C. for 24 hours to obtain effervescent particles.

"The bulk density"
Prepare a 1L graduated cylinder, fill an empty graduated cylinder with foamed particles up to the 1L marked line, measure the mass (g) of the foamed particles per 1L, and convert the unit into bulk density (kg / m). ³ ) was requested.

"Average bubble diameter"
First, 10 foam particles were randomly selected. Next, the foamed particles were cut into two pieces using a razor blade so as to pass through the center thereof, and then a cross section of the foamed particles was photographed with a scanning electron microscope (“TM3030Plus” manufactured by Hitachi, Ltd.) (observation magnification 100). Double). Then, in the obtained electron micrograph, a straight line is drawn from the surface of the foamed particles to the opposite surface so as to pass through the center of the foamed particles, and the actual length of the straight line is divided by the number of bubbles intersecting the straight line. The bubble diameter (μm) of the foamed particles was obtained. The bubble diameters of the 10 foamed particles were measured in the same manner, and the average bubble diameter of the foamed particles was obtained by arithmetically averaging.

(4) In-mold molding Using a mold molding machine (DSM-0705VS manufactured by DABO Co., Ltd.), a mold having a rectangular parallelepiped molding cavity of 300 mm × 75 mm × 25 mm is used as a molding mold, and foamed particles are molded in the mold. It was molded to obtain a rectangular parallelepiped molded body. The obtained molded product was dried at a temperature of 40 ° C. for 1 day and then cured at room temperature for 1 day or longer to obtain a foamed particle molded product having the densities shown in Table 1.

Next, for the foamed particle molded body obtained as described above, the fusion coefficient, 50% compressive stress (kPa), toughness (breaking point strain), average cell diameter, and molding cycle were measured as follows. .. The results are shown in Table 1.

"Fusion rate"
The molded body was broken, the fracture surface was observed, and the number of foamed particles in which the material was broken and the number of foamed particles peeled off at the interface were measured. Next, the ratio of the material-destroyed foamed particles to the total number of the material-destroyed foamed particles and the foamed particles peeled off at the interface was calculated, and the value expressed as a percentage was taken as the fusion rate (%). When the fusion rate was 80% or more, it was regarded as "possible", and when it was less than 80%, it was regarded as "impossible".

"50% compressive stress"
A plate-shaped test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm was cut out from the foamed particle molded body, and a compression test was performed according to JIS K 7220 (2006). When the compressive strain is 50%, the compressive stress is 50% compressive stress (MPa).

"Toughness (breaking point strain)"
The foamed particle molded body is used as it is as a test piece, and in accordance with JIS K 7221-2: 2006, the conditions are that the distance between fulcrums is 200 mm, the pressure wedge 10R and the support base 10R, and the pressure wedge descent speed is 10 mm / min. A three-point bending test was performed to measure the bending strength of the foamed particle molded body. The case where the foamed particle molded product did not break was evaluated as "possible", and the case where it broke was evaluated as "impossible".

"Average bubble diameter"
A plate-shaped test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm was cut out from the foamed particle molded body, and the molded skin of the test piece was further removed using a slicer. Next, the slice cross section of the test piece was colored with carbon spray, and the cross-sectional area (opening area) of 100 randomly selected bubbles was measured using a cell size measuring device (PORE! SCAN manufactured by Goldlucke). did. Then, the diameter of a virtual perfect circle having the same area was taken as the bubble diameter of each bubble, and the average cell diameter of the foamed particle molded body was obtained by arithmetically averaging them. When the average bubble diameter of the molded product is more than 150 μm and 200 μm or less, it is “OK”, when it is more than 120 μm and 150 μm or less, it is “Good”, when it is 120 μm or less, it is “Excellent”, and when it is larger than 200 μm, it is “Not possible”. It was evaluated as.

"Molding cycle"
Foamed particles are molded in a mold using a mold molding machine (PEONY manufactured by Kasahara Kogyo Co., Ltd., model number AD / 0907) using a mold having a rectangular parallelepiped molding cavity of 300 mm × 300 mm × 50 mm as a molding die. And the molding cycle was evaluated. Specifically, the molding conditions are set to a heating steam pressure of 0.06 MPa (gauge pressure), a water cooling time of 20 seconds, and a mold release surface pressure of 0.02 MPa (gauge pressure). The molding cycle was evaluated by the time taken for the internal pressure to reach the mold release surface pressure of 0.02 MPa (gauge pressure).
When the time to reach the mold release surface pressure exceeded 150 seconds and was 200 seconds or less, it was evaluated as "possible", when it was 150 seconds or less, it was evaluated as "good", and when it was longer than 200 seconds, it was evaluated as "impossible".

(Example 2)
In this example, the blending amount of ethylene bisstearic acid amide as a bubble adjusting agent is 0.2 parts by mass with respect to 100 parts by mass of the composite resin, and 19.6 g of cyclohexane and pentane (about 80% by mass of normal pentane) are used as a foaming agent. , 42.7 g of isopentane (a mixture of about 20% by mass) and 14.0 g of isopentane were added into the autoclave over about 0.5 hours, and the same procedure as in Example 1 was carried out.

(Example 3)
In this example, as a foaming agent, 21.0 g of cyclohexane, 13.3 g of pentane (a mixture of about 80% by mass of normal pentane and about 20% by mass of isopentane), and 34.3 g of isobutane are added into the autoclave over about 0.5 hours. Except for the above, the procedure was the same as in Example 1.

(Example 4)
In this example, 21 g of cyclohexane, 40.6 g of pentane (a mixture of about 80% by mass of normal pentane and about 20% by mass of isopentane), and 29.4 g of isobutane were added as foaming agents into the autoclave over about 0.5 hours. Was performed in the same manner as in Example 1.

(Example 5)
In this example, ethylene bisstearic acid amide as a bubble adjusting agent is not used, and as a foaming agent, 21 g of cyclohexane, 15.4 g of pentane (a mixture of about 80% by mass of normal pentane and about 20% by mass of isopentane), and 21. The procedure was the same as in Example 1 except that 0 g was added into the autoclave over about 0.5 hours (impregnation step).

(Example 6)
This example does not use ethylene bisstearic acid amide as a bubble regulator, but as a foaming agent, 21 g of cyclohexane, 21.7 g of pentane (a mixture of about 80% by mass of normal pentane and about 20% by mass of isopentane), and 28. The procedure was the same as in Example 1 except that 7 g was added into the autoclave over about 0.5 hours (impregnation step).

(Example 7)
In this example, ethylene bisstearic acid amide as a bubble adjusting agent is not used, and as a foaming agent, 21 g of cyclohexane, 32.2 g of pentane (a mixture of about 80% by mass of normal pentane and about 20% by mass of isopentane), and 30. The procedure was the same as in Example 1 except that 1 g was added into the autoclave over about 0.5 hours (impregnation step).

(Example 8)
This example does not use ethylene bisstearic acid amide as a bubble regulator, but as a foaming agent, 21 g of cyclohexane, 29.4 g of pentane (a mixture of about 80% by mass of normal pentane and about 20% by mass of isopentane), and 26. The procedure was the same as in Example 1 except that 6 g was added into the autoclave over about 0.5 hours (impregnation step).

(Example 9)
In this example, the blending amount of ethylene bisstearic acid amide as a bubble adjusting agent is 0.05 parts by mass with respect to 100 parts by mass of the composite resin (total of nuclear particles and styrene-based monomer), and the foaming agent is used as a foaming agent. Example 1 except that 21 g of cyclohexane, 19.6 g of pentane (a mixture of about 80% by mass of normal pentane and about 20% by mass of isopentane), and 25.9 g of isopentane were added into the autoclave over about 0.5 hours (impregnation step). I went in the same way.

(Comparative Example 1)
In this example, ethylene bisstearate amide as a bubble adjusting agent was not used, pentane was not used as a foaming agent, and 21.0 g of cyclohexane and 60.2 g of isobutane were added into the autoclave over about 0.5 hours. Was performed in the same manner as in Example 1.

(Comparative Example 2)
In this example, 19.6 g of cyclohexane and 52.5 g of pentane (a mixture of normal pentane of about 80% by mass and isopentane of about 20% by mass) are autoclaved over about 0.5 hours without using isobutane as a foaming agent. It was carried out in the same manner as in Example 1 except that it was added therein.

(Comparative Example 3)
In this example, as a foaming agent, 21.0 g of cyclohexane, 52.5 g of pentane (a mixture of about 80% by mass of normal pentane and about 20% by mass of isopentane), and 25.9 g of isobutane are added into the autoclave over about 0.5 hours. Except for the above, the procedure was the same as in Example 1.

(Comparative Example 4)
This example does not use ethylene bisstearic acid amide as a bubble regulator, but as a foaming agent, 12.6 g of cyclohexane, 10.5 g of pentane (a mixture of about 80% by mass of normal pentane and about 20% by mass of isopentane), and isobutane. The procedure was the same as in Example 1 except that 27.3 g was added into the autoclave over about 0.5 hours.

(Comparative Example 5)
In this example, as a foaming agent, 30.1 g of cyclohexane, 18.2 g of pentane (a mixture of about 80% by mass of normal pentane and about 20% by mass of isopentane), and 21.7 g of isobutane are added into the autoclave over about 0.5 hours. Except for the above, the procedure was the same as in Example 1.

(Comparative Example 6)
In this example, as a foaming agent, 7.7 g of cyclohexane, 35.0 g of pentane (a mixture of about 80% by mass of normal pentane and about 20% by mass of isopentane), and 34.3 g of isobutane are added into the autoclave over about 0.5 hours. Except for the above, the procedure was the same as in Example 1.

As is known from Table 1, by using the effervescent particles of Examples 1 to 9, the vacuum cooling time at the time of in-mold molding is shortened, and the molding cycle of the foamed particle molded body is shortened. In Examples 1 to 9, even if the molding cycle is shortened, a foamed particle molded product having a small average bubble diameter, excellent appearance, and excellent rigidity and toughness can be obtained. Further, the effervescent particles of Examples 1 to 9 are excellent in effervescence.

On the other hand, as is known from Table 2, in Comparative Example 1, the proportion of butane was too large, so that the molding cycle became long. In Comparative Example 2, since the ratio of butane was too small, the foamed particles contracted during the shelf-type foaming, and the foamability was inferior. In addition, the average cell diameter of the foamed particle molded product was large and the appearance was poor.

In Comparative Example 3, since the content of the foaming agent was too large, the average cell diameter of the foamed particle molded product was large and the appearance was poor. In Comparative Example 4, since the content of the foaming agent was too small, only foamed particles having poor foamability and a low foaming ratio could be obtained.

In Comparative Example 5, since the ratio of cyclohexane was too large, the foamed particles shrank during the shelf-type foaming, and the foamability was inferior. In Comparative Example 6, since the ratio of cyclohexane was too small, the fusion property of the foamed particles was poor, and the fusion rate of the foamed particle molded product was low.

As described above, by comparing Examples and Comparative Examples, the effervescent particles containing butane, pentane, and cyclohexane as a foaming agent in a predetermined ratio are excellent in effervescence, and the forming cycle is increased and the average bubble diameter is increased. It is possible to suppress coarsening and to produce a foamed particle molded product having high toughness and rigidity. This effect becomes particularly remarkable when the amount of the component derived from the styrene-based monomer in the composite resin contained in the effervescent particles is large. Therefore, the blending amount of the styrene-based monomer is preferably more than 400 parts by mass and 2000 parts by mass or less with respect to 100 parts by mass of the polyolefin-based resin.

Claims (6)

A foamable composite resin obtained by impregnating a polyolefin resin with a styrene monomer and polymerizing a composite resin of a polyolefin resin and a polystyrene resin as a base resin and impregnating the base resin with a foaming agent. It ’s a particle,
The content of the foaming agent is 0.80 to 1.35 mol per 1 kg of the composite resin.
The foaming agent is composed of a chain-type aliphatic hydrocarbon and a cyclic-type aliphatic hydrocarbon.
The molar ratio of the chain aliphatic hydrocarbon to the cyclic aliphatic hydrocarbon is 60:40 to 80:20.
The above chain aliphatic hydrocarbons are butane and pentane.
The molar ratio of the butane to the pentane is 30:70 to 75:25.
Effervescent composite resin particles in which the cyclic aliphatic hydrocarbon is cyclohexane. The foamable composite resin particles according to claim 1, wherein the polystyrene-based resin has a weight average molecular weight of 200,000 to 300,000, and the content of xylene insoluble content in the composite resin is 0.1 to 10% by mass. .. The foamable composite resin particles according to claim 1 or 2, wherein the blending amount of the styrene-based monomer is more than 400 parts by mass and 2000 parts by mass or less with respect to 100 parts by mass of the polyolefin-based resin. The invention according to any one of claims 1 to 3, wherein the butane contains at least isobutane, and the content ratio of the isobutane to the butane contained in the foamable composite resin particles is 90 to 100% by mass. Effervescent composite resin particles. The foamable composite resin particles further contain ethylene bisstearic acid amide, and the blending amount of the ethylene bisstearic acid amide in the foamable composite resin particles is 0.05 to 0. The foamable composite resin particles according to any one of claims 1 to 4, which are 2 parts by mass. The foamable composite resin particles according to any one of claims 1 to 5, wherein the polyolefin-based resin contains 50% by mass or more of linear low-density polyethylene.