JP6432410B2 - Foamed particle molded body and panel packing container - Google Patents

Description

  The present invention relates to a foamed particle molded body obtained by molding composite resin foamed particles in a mold and a panel packing container made of the foamed particle molded body.

  Conventionally, the packing of plate products such as liquid crystal panels and solar power generation panels does not cause wear, cracking or chipping due to pressing or rubbing, and it can be used multiple times, so that it can be used multiple times. A container made of a foamed particle molded body was used. In recent years, the packaging weight has increased with the expansion of the panel size. As a result, there has been a problem that the amount of deflection in the packaged state is increased in a container made of a foamed molded body of propylene-based resin. When the amount of deflection at the time of packing is large, there is a possibility that the liquid crystal panel may be damaged by bending or bending when the container is lifted by supporting both ends of the packed container with a transporter or the like.

  On the other hand, the foamed particle molded body of a composite resin of an ethylene resin and a styrene resin can improve the rigidity of the foamed particle molded body by increasing the amount of the styrene resin component (Patent Literature). 1-3). Therefore, in such a composite resin foamed particle molded body, the amount of deflection can be reduced to improve the deflection resistance, and the transportability can be improved. In addition, since the expansion ratio can be increased while maintaining the bending resistance, the composite resin foamed particle molded body has an advantage that the weight of the packaging material itself can be reduced.

JP 2014-196441 A JP 2014-196444 A Japanese Patent No. 5058866

  However, the composite resin foamed particle molded body has lower bending fracture energy than the propylene-based resin foam molded body. In particular, in order to increase rigidity, if the ratio of the styrene resin component in the composite resin is increased, even if the foamed particles are firmly fused together, the tenacity is insufficient, and they are stacked in a packed state or moved in a packed state. If a sudden load change occurs, cracking may occur.

  The present invention has been made in view of such a background, and is intended to provide a foamed particle molded body and a panel packing container that are difficult to sag, have excellent deflection resistance, and can prevent destruction due to deformation. .

One aspect of the present invention is a foamed particle molded body obtained by molding composite resin foamed particles in a mold,
The composite resin constituting the foamed particle molded body is formed by impregnating and polymerizing 400 to 900 parts by mass of a styrene monomer with respect to 100 parts by mass of an ethylene resin.
The ethylene resin is a linear low density polyethylene,
The degree of swelling in methyl ethyl ketone at a temperature of 23 ° C. is 23.degree. C. or higher when the composite resin is subjected to Soxhlet extraction with xylene and mixed with the acetone insoluble matter contained in the xylene solution after Soxhlet extraction. There exists in the expanded particle molded object characterized by there.

Another aspect of the present invention is a panel packing container comprising the above foamed particle molded body,
A panel packaging container having a housing portion that houses a plurality of panels stacked in a plate thickness direction.

  The foamed particle molded body is composed of a composite resin obtained by impregnating and polymerizing a predetermined ratio of a styrene monomer to an ethylene resin. Therefore, the foamed particle molded body has a high compressive strength and a high bending elastic modulus. Therefore, the foamed particle molded body is excellent in deflection resistance. Furthermore, the above-mentioned swelling degree of the composite resin is 1.25 or more. Therefore, the foamed particle molded body is not easily sagged while exhibiting excellent deflection resistance as described above, and further exhibits high bending elastic energy, so that it is possible to sufficiently prevent breakage due to deformation.

  The said panel packaging container consists of the above-mentioned foamed particle molded object, and has an accommodating part which accommodates in the state which laminated | stacked the several panel in the plate | board thickness direction. Therefore, even if a plurality of panels are accommodated in the accommodating portion, the panel packing container is not easily bent due to the panel weight, and is not easily broken due to deformation. Therefore, even if the panel packaging container is stacked in a packaged state or a sudden load change occurs during movement in the packaged state, cracks can be prevented from occurring. Moreover, the said panel packing container is hard to sag.

The perspective view of the panel packing container in Example 4. FIG. Sectional drawing of the panel packaging container in Example 4 (II-II arrow directional cross-sectional view). The expanded view of the panel packing container in Example 4. FIG. Explanatory drawing which shows a mode that the panel packing container in Example 4 was hold | gripped and lifted at the both ends of the longitudinal direction. Explanatory drawing which shows a mode that the panel packaging container in Example 4 was hold | gripped and lifted at the both ends of the transversal direction. Explanatory drawing which shows a mode that the panel packing container in the comparative example 5 was hold | gripped and lifted at the both ends of the longitudinal direction. Explanatory drawing which shows a mode that the panel packing container in the comparative example 5 was hold | gripped and lifted the both ends of the transversal direction.

Next, embodiments of the foamed particle molded body and the panel packing container will be described.
The foamed particle molded body is formed by molding composite resin foamed particles (hereinafter also referred to as “foamed particles” as appropriate), and the composite resin foamed particles are obtained by impregnating and polymerizing ethylene resin particles with styrene monomers. Is obtained. The compounding quantity of the styrene-type monomer with respect to 100 mass parts of ethylene-type resin is 400-900 mass parts. When the amount of the styrenic monomer is less than 400 parts by mass, the rigidity is lowered and the bending resistance may be insufficient. From the same viewpoint, the blending amount of the styrene monomer with respect to 100 parts by mass of ethylene fat is preferably more than 450 parts by mass, and more preferably 500 parts by mass or more. On the other hand, when the styrene monomer exceeds 900 parts by mass, the foamed particle molded body is easily broken and becomes brittle. From the same viewpoint, the blending amount of the styrene monomer with respect to 100 parts by mass of the ethylene fat is preferably 800 parts by mass or less, more preferably 700 parts by mass or less, and further preferably 600 parts by mass or less.

  Examples of the ethylene resin include linear low density polyethylene, branched low density polyethylene, high density polyethylene, ethylene-acrylic acid copolymer, ethylene-acrylic acid alkyl ester copolymer, and ethylene-methacrylic acid alkyl ester copolymer. A polymer or the like can be used. The ethylene resin may be one kind of polymer, but a mixture of two or more kinds of polymers can also be used.

  Preferably, the ethylene-based resin is mainly composed of linear low density polyethylene. The linear low-density polyethylene preferably has a branched structure having a linear polyethylene chain and a short-chain branched chain having 2 to 6 carbon atoms. Specific examples include an ethylene-butene copolymer, an ethylene-hexene copolymer, and an ethylene-octene copolymer. In particular, the ethylene resin is preferably a linear low-density polyethylene having a melting point of 105 ° C. or lower obtained by polymerization using a metallocene polymerization catalyst. In this case, the affinity between the ethylene resin and the styrene resin is further improved, and the toughness of the composite resin can be increased. Moreover, since the low molecular weight component can be reduced and the fusion strength between the foamed particles at the time of molding can be increased, the foamed particle molded body can be made difficult to break. Furthermore, it is possible to obtain a foamed particle molded body that combines the excellent rigidity of the styrene resin and the excellent tenacity of the ethylene resin at a higher level.

  Moreover, it is preferable that melting | fusing point Tm of ethylene-type resin is 95-105 degreeC. In this case, the ethylene resin can be sufficiently impregnated with the styrene monomer during the production of the composite resin foamed particles, and the suspension system can be prevented from becoming unstable during the polymerization. As a result, it is possible to obtain a foamed particle molded body that combines the excellent rigidity of the styrene resin and the excellent tenacity of the ethylene resin at a higher level. More preferably, the melting point Tm of the ethylene-based resin is 100 to 105 ° C. The melting point Tm can be measured by differential scanning calorimetry (DSC) based on JIS K7121 (1987).

  The ethylene-based resin is preferably made of linear low density polyethylene in which the melting point Tm (° C.) and the Vicat softening point Tv (° C.) satisfy the relationship Tm−Tv ≦ 20 (° C.). Such an ethylene resin exhibits a uniform molecular structure, and it is presumed that the network structure formed by crosslinking is more uniformly distributed in the ethylene resin. Therefore, in this case, the strength and tenacity of the foamed particle molded body can be further improved. From the same viewpoint, the linear low density polyethylene more preferably satisfies Tm−Tv ≦ 15 (° C.), and more preferably satisfies Tm−Tv ≦ 10 (° C.). The Vicat softening point Tv can be measured based on JIS K 7206 (1999).

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

  The styrenic resin means a resin having 50% by mass or more of styrene component units in the resin. The styrene component unit in the styrene resin is preferably 80% by mass or more, and more preferably 90% by mass or more. In the present specification, styrene constituting the styrene resin and a monomer copolymerizable with styrene added as necessary may be collectively referred to as a styrene monomer. Examples of the monomer copolymerizable with styrene include the following styrene derivatives and other vinyl monomers.

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

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

  As the styrene resin, polystyrene and a copolymer of styrene and an acrylic monomer are preferable from the viewpoint of enhancing foamability. Further, from the viewpoint of enhancing foamability, it is preferable to use styrene and butyl acrylate as monomers constituting the styrene resin, as shown in the examples described later. In this case, the content of the butyl acrylate component in the composite resin is preferably 0.5 to 10% by mass, more preferably 1 to 8% by mass, based on the entire composite resin. More preferably, it is -5 mass%.

  In the foamed particle molded body, the temperature 23 of the mixed insoluble part of the xylene insoluble content when the composite resin constituting the foamed particle molded body is Soxhlet extracted with xylene and the acetone insoluble content contained in the xylene solution after the Soxhlet extraction 23 If the degree of swelling in methyl ethyl ketone at 0 ° C. (hereinafter simply referred to as “swelling degree”) is too low, the bending rupture energy of the foamed resin molded article is small, and the tenacity may be insufficient. Therefore, the swelling degree of the composite resin is preferably 1.25 or more as described above, more preferably 1.5 or more, and further preferably 2 or more. Further, from the viewpoint of suppressing the shrinkage of the foamed particle molded body, the swelling degree of the composite resin is preferably 10 or less, and more preferably 5 or less.

  The reason why the rigidity and tenacity are excellent as described above when the degree of swelling is equal to or greater than the predetermined value is presumed as follows. The degree of swelling (degree of swelling) when a crosslinked ethylene resin is immersed in an organic solvent correlates with the crosslinked structure (three-dimensional network structure) of the resin, and the finer the network, the lower the amount of organic solvent absorbed. Therefore, the degree of swelling decreases. On the other hand, non-crosslinked ethylene-based resins hardly swell in methyl ethyl ketone at a temperature of 23 ° C. That is, as described above, the xylene-insoluble component (crosslinked ethylene resin component) of the composite resin and the acetone-insoluble component (crosslinked ethylene resin component that has passed through the mesh, non-crosslinked ethylene system) in the xylene soluble component When the swelling degree of the mixed insoluble matter with the resin component and the ethylene resin component graft polymerized with the styrene monomer is large, the ethylene resin constituting the composite resin has a higher degree of swelling than when the swelling degree is small. In other words, it means that a lot of the ethylene resin component having a coarse network of the crosslinked three-dimensional network structure is contained.

  For this reason, it is inferred that a foamed film having high strength is formed because the ethylene-based resin component having a coarse network having a cross-linked three-dimensional network structure is moderately easily stretched while foaming. Furthermore, when the composite resin foamed particles are compressed, the ethylene resin in the composite resin is flexible and sufficiently deformable, so even if the ratio of the styrene resin in the composite resin is high, the foamed foam bubbles It is assumed that the closed cell structure can be maintained without breaking the membrane. That is, when the degree of swelling is in a specific range, a foamed particle molded body having high rigidity and tenacity and high bending fracture energy can be obtained.

  In addition, production conditions that have been studied in the past (for example, a condition where the blending ratio of the ethylene resin core particles and the first monomer (styrene monomer) is large, and the ethylene monomer core particles are impregnated with the first monomer (styrene monomer). Under conditions of high temperature to be used and conditions for using a polymerization initiator with high hydrogen abstraction ability), the rate at which the styrene monomer is polymerized and precipitated as a styrene resin in the ethylene resin at the initial stage of polymerization is increased. It is inferred that the mesh of the crosslinked three-dimensional network structure of the resin becomes fine. On the other hand, by adjusting the type and addition amount of the polymerization initiator, the polymerization temperature, and the blending ratio of the ethylene resin core particles and the first monomer (styrene monomer), the rate at which the styrene resin component precipitates at the initial stage of polymerization is increased. Slowly, the amount of the ethylene resin component having a fine cross-linked three-dimensional network structure can be controlled to be small.

  Moreover, in the composite resin, it is preferable that the weight ratio of the xylene-insoluble matter by Soxhlet extraction is 40% or less (including 0). In this case, the foamability can be further improved. Further, the weight ratio of xylene insolubles is more preferably 5 to 35%, further preferably 10 to 30%. In this case, the rigidity and tenacity of the foamed particle molded body can be further improved.

The apparent density of the foamed particle molded body is preferably ³⁰ to 100 kg / m ³ . Within this range, high bending rigidity and sag resistance can be obtained while maintaining light weight and buffering performance. The apparent density of the foamed particle molded body is more preferably ³⁰ to 65 kg / m ³ .

The foamed particle molded body is obtained by in-mold molding of composite resin foam particles, and the composite resin foam particles are produced, for example, as follows.
First, core particles containing ethylene resin as a main component are suspended in an aqueous medium to prepare a suspension. A styrenic monomer is then added to the suspension. Then, the core particles are impregnated with a styrene monomer and polymerized. Subsequently, the composite resin foam particles can be produced by foaming the composite resin particles after polymerization.

  When the core particles are impregnated with the styrene monomer and polymerized, the entire amount of the styrene monomer used can be added all at once, but as in the dispersion step and the modification step described later, The amount used can be divided into, for example, a first monomer and a second monomer, and these monomers can be added at different timings. As in the latter case, by adding the styrenic monomer in a divided manner, condensation of the resin particles during polymerization can be suppressed.

  Specifically, the composite resin foamed particles can be produced, for example, by performing the following dispersion process, modification process, and foaming process. In the dispersion step, a first monomer (styrene monomer) and a polymerization initiator are added to a suspension obtained by suspending core particles mainly composed of an ethylene-based resin in an aqueous medium. The first monomer is dispersed in

In the reforming step, the second monomer (styrene monomer) is heated at a temperature of (Tm-10) to (Tm + 30) ° C., where Tm is the melting point of the ethylene resin in the core particles. Is continuously added to the suspension over a predetermined addition time, and the core particles are impregnated with a styrene monomer and polymerized.
If the seed ratio of the styrene monomer (first monomer) (weight ratio of the first monomer to the core particles) is too low, the composite resin particles may become flat and the filling property during molding may be deteriorated. . Therefore, the seed ratio of the first monomer is preferably 0.5 or more, more preferably 0.7 or more, and further preferably 0.8 or more. On the other hand, if the seed ratio is too high, polymerization may occur before the styrenic monomer is sufficiently impregnated with the core particles, which may result in a molded article with good rigidity and tenacity, and may be suspended and stabilized. It may be difficult to cause a resinous mass. Therefore, the seed ratio of the first monomer is preferably 1.5 or less, more preferably 1.3 or less, and further preferably 1.2 or less.

  In the foaming step, the composite resin foam particles are obtained by foaming the composite resin particles after polymerization.

Hereinafter, each step will be described in more detail.
In the dispersion step, the core particles can be suspended in an aqueous medium containing, for example, a suspending agent, a surfactant, a water-soluble polymerization inhibitor and the like to prepare a suspension. In the dispersion step, a polymerization initiator can be added to the suspension together with the first monomer.

  The core particle can contain additives such as a bubble regulator, a colorant, and a lubricant. The core particles can be produced by blending an additive that is added to the ethylene-based resin as necessary, melt-kneading the blend, and then refining. Melt kneading can be performed by an extruder. At this time, in order to perform uniform kneading, it is preferable to perform extrusion after mixing the resin components in advance. The mixing of the resin components can be performed using a mixer such as a Henschel mixer, a ribbon blender, a V blender, or a ladyge mixer. The melt-kneading is preferably performed using, for example, a high dispersion type screw such as a dalmage type, a Maddock type, or a unimelt type, or a twin screw extruder.

  The refining of the core particles is performed by cutting the compound melt-kneaded with an extruder or the like. The miniaturization can be performed by, for example, strand cutting, underwater cutting, or hot cutting.

The core particles are preferably dispersed in an aqueous medium together with a suspending agent.
Examples of the suspending agent include tricalcium phosphate, hydroxyapatite, magnesium pyrophosphate, magnesium phosphate, aluminum hydroxide, ferric hydroxide, titanium hydroxide, magnesium hydroxide, barium phosphate, calcium carbonate, magnesium carbonate. Fine particulate inorganic suspending agents such as barium carbonate, calcium sulfate, barium sulfate, talc, kaolin and bentonite can be used. In addition, organic suspending agents such as polyvinyl pyrrolidone, polyvinyl alcohol, ethyl cellulose, and hydroxypropyl methyl cellulose can also be used. Preferred are tricalcium phosphate, hydroxyapatite, and magnesium pyrophosphate. These suspending agents can be used alone or in combination of two or more.

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

  A surfactant can be added to the suspension. As the surfactant, for example, an anionic surfactant, a nonionic surfactant, a cationic surfactant, an amphoteric surfactant, and the like can be used.

As an anionic surfactant, for example, sodium alkyl sulfonate, sodium alkylbenzene sulfonate, sodium lauryl sulfate, sodium α-olefin sulfonate, sodium dodecylphenyl ether disulfonate, and the like can be used.
Examples of nonionic surfactants that can be used include polyoxyethylene dodecyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, and the like.
As the cationic surfactant, alkylamine salts such as coconut amine acetate and stearylamine acetate can be used. Further, quaternary ammonium such as lauryltrimethylammonium chloride and stearyltrimethylammonium chloride can also be used.
As the amphoteric surfactant, alkylbetaines such as lauryl betaine and stearyl betaine can be used. Moreover, alkylamine oxides, such as lauryl dimethylamine oxide, can also be used.
These surfactants can be used alone or in combination.

Preferably, an anionic surfactant is used as the surfactant. More preferably, it is an alkylsulfonic acid alkali metal salt (preferably a sodium salt) having 8 to 20 carbon atoms. Thereby, the suspension can be sufficiently stabilized.
In addition, an electrolyte made of an inorganic salt such as lithium chloride, potassium chloride, sodium chloride, sodium sulfate, sodium nitrate, sodium carbonate, sodium bicarbonate or the like can be added to the suspension as necessary.

Further, in order to obtain a foamed particle molded body having excellent toughness and mechanical strength, it is preferable to add a water-soluble polymerization inhibitor to the suspension.
As the water-soluble polymerization inhibitor, for example, sodium nitrite, potassium nitrite, ammonium nitrite, L-ascorbic acid, citric acid and the like can be used.
The water-soluble polymerization inhibitor is difficult to impregnate into the core particles and dissolves in an aqueous medium. Therefore, polymerization of the styrenic monomer impregnated in the core particles is performed, but styrene monomer near the surface of the core particles being absorbed by the core particles, and fine droplets of the styrenic monomer in the aqueous medium not impregnated in the core particles. Polymerization of the monomer can be suppressed. As a result, the amount of the styrene resin on the surface of the composite resin particles can be controlled to be small, and it is presumed that the toughness of the obtained foamed particle molded body is improved.
The addition amount of the water-soluble polymerization inhibitor is preferably 0.001 to 0.1 parts by mass with respect to 100 parts by mass of the aqueous medium (referring to all water in the system including water such as the reaction product-containing slurry). More preferably, 0.005-0.06 mass part is good.

  In order to uniformly polymerize the styrene monomer in the core particles, the core particles are impregnated with the styrene monomer and polymerized. In this case, the ethylene resin may be cross-linked with the polymerization of the styrene monomer. In the polymerization of the styrene monomer, a polymerization initiator is used, and a crosslinking agent can be used in combination as necessary. Moreover, when using a polymerization initiator and / or a crosslinking agent, it is preferable to previously dissolve the polymerization initiator and / or the crosslinking agent in a styrene monomer.

  As the polymerization initiator, those used in the suspension polymerization method of a styrene monomer, for example, a polymerization initiator that is soluble in a vinyl monomer and has a 10-hour half-life temperature of 50 to 120 ° C. can be used. Specifically, for example, cumene hydroxy peroxide, dicumyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxybenzoate, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t- Organic peroxides such as amyl peroxy-2-ethylhexyl carbonate, hexyl peroxy-2-ethylhexyl carbonate, and lauroyl peroxide can be used. As the polymerization initiator, an azo compound such as azobisisobutyronitrile can be used. These polymerization initiators can be used alone or in combination of two or more. Moreover, t-butylperoxy-2-ethylhexanoate is preferable as the polymerization initiator from the viewpoint that it is easy to adjust the swelling degree of the composite resin and to easily reduce the residual monomer.

The polymerization initiator may be added after being dissolved in a solvent and impregnated into the core particles.
As the solvent for dissolving the polymerization initiator, aromatic hydrocarbons, aliphatic hydrocarbons and the like can be used. Examples of the aromatic hydrocarbon include ethylbenzene and toluene. Examples of the aliphatic hydrocarbon include heptane and octane. The polymerization initiator is preferably used within a range of 0.01 to 3 parts by mass with respect to 100 parts by mass of the styrene monomer.

Further, as the crosslinking agent, it is preferable to use a crosslinking agent that does not decompose at the polymerization temperature but has a 10-hour half-life temperature that is 5 to 50 ° C. higher than the polymerization temperature. Specifically, for example, peroxides such as dicumyl peroxide, 2,5-t-butyl perbenzoate, and 1,1-bis-t-butyl peroxycyclohexane can be used. As a crosslinking agent, it can use individually or in combination of 2 or more types among these. It is preferable that the compounding quantity of a crosslinking agent is 0.1-5 mass parts with respect to 100 mass parts of styrene-type monomers.
In addition, the same compound can also be employ | adopted as a polymerization initiator and a crosslinking agent.

Moreover, a bubble regulator can be added to the styrene monomer. Further, when preparing the core particles, the bubble conditioner can be added to the core particles by kneading the bubble conditioner together with the ethylene-based resin. It is preferable to adjust the content of the cell regulator in the composite resin so as to be 0.01 to 2 parts by mass with respect to 100 parts by mass of the composite resin.
Examples of the air conditioner include fatty acid monoamide, fatty acid bisamide, talc, silica, polyethylene wax, methylene bis stearic acid, methyl methacrylate copolymer, silicone, talc, zinc borate, aluminum sulfate, alum, polytetrafluoroethylene, etc. Can be used. As the fatty acid monoamide, for example, oleic acid amide, stearic acid amide, lauric acid amide, erucic acid amide, behenic acid amide and the like can be used. As the fatty acid bisamide, for example, ethylene bis stearic acid amide can be used.

Moreover, a plasticizer, an oil-soluble polymerization inhibitor, a flame retardant, a dye, etc. can be added to a styrene-type monomer as needed.
As the plasticizer, for example, fatty acid esters, acetylated monoglycerides, fats and oils, hydrocarbon compounds and the like can be used. Examples of fatty acid esters that can be used include glycerin tristearate, glycerin trioctoate, glycerin trilaurate, sorbitan tristearate, sorbitan monostearate, and butyl stearate. Moreover, as an acetylated monoglyceride, glycerol diacetomonolaurate etc. can be used, for example. As fats and oils, hardened beef tallow, hardened castor oil, etc. can be used, for example. As a hydrocarbon compound, cyclohexane, a liquid paraffin, etc. can also be used, for example.
As the oil-soluble polymerization inhibitor, for example, para-t-butylcatechol, hydroquinone, benzoquinone and the like can be used.

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

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

A foamed particle molded body having a degree of swelling in the predetermined range can be obtained by adjusting the production conditions as follows. In particular,
(1) Impregnating the styrene-based monomer impregnated into the core particles containing the ethylene-based resin in a plurality of times, and relatively increasing the addition ratio of the styrene-based monomer (first monomer) impregnated first, Polymerizing the first monomer by relatively reducing the ratio of the polymerization initiator to one monomer;
(2) The use of t-butylperoxy-2-ethylhexyl monocarbonate or t-hexylperoxybenzoate as a polymerization initiator, which is lower in hydrogen abstraction than dicumyl peroxide,
(3) controlling the polymerization state of the styrenic monomer at the initial stage in the impregnation polymerization by dissolving the polymerization initiator only in the first monomer and polymerizing.
As a result, it is difficult to increase the crosslink density in the ethylene-based resin, and it becomes possible to produce a foamed particle molded body having a degree of swelling in the predetermined range. Under the production conditions that have been studied in the past, dicumyl peroxide having a small ratio of the styrene monomer (first monomer) impregnated into the core particles containing the ethylene resin and having a high hydrogen abstraction ability as a polymerization initiator is used. Since the polymerization initiator is dividedly added to the first monomer and the second monomer, it is considered that the crosslinking density in the ethylene-based resin becomes too high and the degree of swelling becomes low.

  For foaming of composite resin particles, pre-foaming method in which composite resin particles are impregnated with volatile foaming agent in advance and then heated with steam, hot water or hot air, or after heating with volatile foaming agent in a pressure vessel, low pressure It is possible to adopt a direct foaming method in which foaming is performed upon release. As the foaming agent to be used, organic foaming agents such as butane, pentane and propane can be used, and inorganic foaming agents such as carbon dioxide, air and nitrogen can also be used. An inorganic foaming agent is preferable. The organic foaming agent remains in the foamed particles even after the composite resin particles are foamed, and the internal pressure in the air bubbles is increased during molding, so that the cooling time tends to be long. In contrast, when an inorganic foaming agent is used, no gas remains in the foamed particles, so there is no increase in internal pressure during molding, and the molded product can be cooled in a short time and removed from the mold. It becomes.

  The foamed particle molded body can be manufactured by a known in-mold molding method using steam heating. That is, a foamed particle molded body can be obtained by filling a large number of composite resin foam particles in a mold such as a mold and introducing steam into the mold to fuse the composite resin foam particles together. it can.

  The flexural modulus of the foamed particle molded body is preferably 18 MPa or more, more preferably 19 MPa or more, and further preferably 20 MPa or more. From the viewpoint of the bending rigidity of the foamed particle molded body, the upper limit of the bending elastic modulus is not particularly limited, but the upper limit is about 30 MPa.

Bending fracture energy of the foamed bead molded article is preferably at 150 kJ / cm ² or more, more preferably 200 kJ / cm ² or more, and still more preferably 250 kJ / cm ² or more. From the viewpoint of toughness of the foamed particle molded body, the upper limit of the bending rupture energy is not particularly limited and is most preferably not ruptured, but the upper limit is about 400 kJ / cm ² .

  The bending elastic modulus is a value measured based on JIS K7221 (1999). The bending rupture energy is a value calculated from an area surrounded by a deflection amount-load curve and a horizontal axis (deflection amount) up to the rupture point obtained during the bending test.

  The 50% compressive stress of the foamed particle molded body is preferably 400 kPa or more, more preferably 450 kPa or more, and further preferably 500 kPa or more. From the viewpoint of the compression rigidity of the foamed particle molded body, the upper limit of the 50% compression stress is not particularly limited, but the upper limit is approximately 700 kPa.

  The 50% compressive stress means a compressive load at 50% strain measured based on JIS K 6767 (1999).

  The foamed particle molded body is suitable for a panel packing container. A panel packing container consists of a foamed particle molded object, and has an accommodating part comprised so that a some panel might be accommodated in the state laminated | stacked on the plate | board thickness direction. As the panel, there are a liquid crystal panel such as a television and a monitor, a photovoltaic power generation panel and the like in addition to a glass plate and the like, and the foamed particle molded body is suitable as a packaging container for these panels. Liquid crystal panels have become heavier with the recent increase in product size. Solar power panels are also heavy. For the packaging of such heavy panels, by adopting the panel packaging container made of the above-mentioned foamed particle molded body, the above-mentioned effect that it is difficult to sag, has excellent deflection resistance, and can be prevented from being damaged by deformation is sufficiently obtained. It will be used.

As such a packing container, specifically, it is a panel packing container having an accommodating part for accommodating a plurality of panels in a state of being laminated in the plate thickness direction in the horizontal direction,
The panel packing container is composed of a foamed particle molded body having an apparent density of 40 to 100 kg / m ³ formed by molding composite resin foamed particles in a mold,
The composite resin constituting the foamed particle molded body is formed by impregnating and polymerizing 400 to 900 parts by mass of a styrene monomer with respect to 100 parts by mass of an ethylene resin.
The degree of swelling in methyl ethyl ketone at a temperature of 23 ° C. is 23.degree. C. or higher when the composite resin is subjected to Soxhlet extraction with xylene and mixed with the acetone insoluble matter contained in the xylene solution after Soxhlet extraction. There is a panel packing container characterized by being.

  The panel packing container has a container main body having the housing part and a lid for closing the opening of the container main body, and the container main body and the lid are preferably made of the foamed particle molded body. In this case, since the inside of the accommodating portion can be sealed, it is possible to prevent foreign matters from being mixed. Moreover, the said accommodating part may be formed not only on the container main-body part side but on the cover body side.

In the panel packing container, it is preferable that an antistatic agent is present on at least the surface of the foamed particle molded body, and the surface resistivity of the foamed particle molded body is 1 × 10 ⁸ to 1 × 10 ¹³ Ω. In this case, the panel packing container exhibits sufficient antistatic performance, and is more suitable for a liquid crystal panel, a solar power generation panel, or the like. The surface resistivity of the foamed particle molded body is a value measured in an atmosphere of 23 ° C. and 50% relative humidity based on JIS C2170 (2004).

The antistatic agent can be contained in the foamed particle molded body by any of the following methods or a combination thereof. Specifically, a method in which an antistatic agent is kneaded into an ethylene-based resin during granulation of the core particles, a method in which an antistatic agent is added during polymerization, an antistatic agent is added during foaming of the composite resin particles, and the foamed particles are impregnated. And a method of applying an antistatic agent to the foamed particles, a method of applying an antistatic agent to the foamed particle molded body, and the like.
As the antistatic agent, at least one selected from a cationic surfactant, an anionic surfactant, an amphoteric surfactant, and a nonionic surfactant can be used. Preferably, a cationic surfactant and a nonionic surfactant are used in combination as an antistatic agent.

Example 1
Hereinafter, examples of the foamed particle molded body will be described. In this example, the composite resin foam particles are manufactured from the core particles as follows, and the foamed particle molded body is manufactured using the composite resin foam particles.

(1) Production of core particles As an ethylene-based resin, linear low-density polyethylene (“Nipolon Z HF210K” manufactured by Tosoh Corporation) obtained by polymerization using a metallocene polymerization catalyst was prepared. The ethylene resin of this example is hereinafter referred to as “PE-1” as appropriate. The MFR (190 ° C., load 2.16 kg; g / 10 min), density (kg / m ³ ), tensile elastic modulus (MPa), and melting point (° C.) of PE-1 are shown in Table 1 described later. The MFR (190 ° C., load 2.16 kg) of PE-1 is a value measured by the condition code D based on JIS K7210 (1999). In addition, as a measuring apparatus, a melt indexer (model L203 manufactured by Takara Kogyo Co., Ltd.) was used. Moreover, the tensile elasticity modulus of PE-1 is a value measured by JISK6922-2 (2010). The melting point of PE-1 was measured by heat flux differential scanning calorimetry (DSC) based on JIS K7121 (1987) using about 5 mg of PE-1 raw material pellets. In JIS K7121 (1987), “(2) When melting temperature is measured after performing a certain heat treatment” is used as the condition adjustment of the specimen, and both the heating rate and the cooling rate are used. The melting peak temperature measured as 10 ° C./min is the melting point.

  In addition, (CE-7335, manufactured by Polycol Co., Ltd.) was prepared as an air conditioner master batch. Incidentally, “CE-7335” manufactured by Polycol Co., Ltd. has a content of zinc borate (bubble regulator) of 10% by mass and a linear low density polyethylene (“Nipolon Z HF210K” manufactured by Tosoh Corporation). 90% by mass.

  8.65 kg of ethylene-based resin (PE-1) and 1.35 kg of an air conditioner master batch were charged into a Henschel mixer and mixed for 5 minutes to obtain a resin mixture. Next, using a 50 mmφ single-screw extruder, the resin mixture is melt-kneaded at an extruder maximum setting temperature of 250 ° C., and cut into an average of 0.5 mg / piece by an underwater cutting method to obtain core particles (ethylene-based resin core particles). )

(2) Production of Composite Resin Particles 1000 g of deionized water was added to an autoclave with an internal volume of 3 L equipped with a stirrer, and 6.0 g of sodium pyrophosphate was further added. Thereafter, 12.9 g of powdered magnesium nitrate hexahydrate was added and stirred at room temperature for 30 minutes. This produced the magnesium pyrophosphate slurry as a suspending agent. Next, 2.0 g of sodium lauryl sulfonate (10% by mass aqueous solution) as a surfactant, 0.2 g of sodium nitrite as a water-soluble polymerization inhibitor, and 75 g of core particles were added to this suspension (dispersion). Process).

  Next, 1.72 g of t-butylperoxy-2-ethylhexyl monocarbonate (“NO-butyl E” manufactured by NOF Corporation) as the polymerization initiator A and 0.86 g of t-butylperoxybenzoate as the polymerization initiator B ( NOFMER “Perhexyl Z”) and 0.63 g of α-methylstyrene dimer (“NOFMER MSD” manufactured by NOF Corporation) as a chain transfer agent were dissolved in the first monomer (styrene monomer). Then, the dissolved product was put into the suspension in the autoclave while stirring at a stirring speed of 500 rpm. As the first monomer, a mixed monomer of 70 g of styrene and 15 g of butyl acrylate was used.

  Next, after the air in the autoclave was replaced with nitrogen, the temperature increase was started, and the temperature was increased to 100 ° C. over 1 hour 30 minutes. After the temperature increase, the temperature was maintained at 100 ° C. for 1 hour. Thereafter, the stirring speed was lowered to 450 rpm and maintained at a temperature of 100 ° C. for 7.5 hours. (Modification process). When 1 hour had passed since the temperature reached 100 ° C., 350 g of styrene as the second monomer (styrene monomer) was added into the autoclave over 5 hours.

  Next, the temperature was raised to 125 ° C. over 2 hours, and the temperature was kept at 125 ° C. for 5 hours. Thereafter, the inside of the autoclave was cooled, and the contents (composite resin particles) were taken out. Nitric acid was added to dissolve the magnesium pyrophosphate adhering to the surface of the composite resin particles. Thereafter, dehydration and washing are performed with a centrifugal separator, and water adhering to the surface is removed with an air flow drying device, so that a styrene resin and an ethylene resin determined from a mass ratio of the styrene monomer and the ethylene resin are obtained. Composite resin particles having a ratio (mass ratio) of 85:15 were obtained.

(3) Production of Composite Resin Expanded Particles Next, 500 g of composite resin particles are charged into a 5 L sealed container (pressure vessel) equipped with a stirrer together with 3500 g of dispersion medium (water), and 5 g of kaolin as a dispersant in the dispersion medium. And 0.5 g of sodium alkylbenzene sulfonate as a surfactant were further added. Subsequently, it heated up to the foaming temperature of 165 degreeC, stirring the inside of a sealed container with the rotational speed of 300 rpm. Thereafter, carbon dioxide (CO ₂ ), which is an inorganic physical foaming agent, is pressed into the sealed container so that the pressure in the sealed container becomes 3.2 MPa (G: gauge pressure), and 15 ° C. at the same temperature (165 ° C.). By holding for a minute, carbon dioxide was impregnated into the composite resin particles to obtain expandable composite resin particles. Next, the foamable composite resin particles were discharged together with the dispersion medium from the sealed container under atmospheric pressure to obtain composite resin foam particles (primary foam particles) having a bulk density of 48 kg / m ³ .

  Next, 100 parts by mass of the composite resin foam particles obtained as described above, 2 parts by mass of an antistatic agent (cationic surfactant “Katiogen ES-O” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 1 part by mass of a nonionic antistatic agent (glycerin monostearate) was put in a plastic bag and shaken well, and then the composite resin foamed particles were dried in an oven at a temperature of 40 ° C. for 12 hours.

(5) Production of foamed particle molded body The composite resin foam particles obtained as described above were filled into a mold having a flat plate-shaped cavity having a length of 250 mm, a width of 200 mm, and a thickness of 50 mm. Next, by introducing water vapor into the mold, the composite resin foam particles were heated and fused to each other. Thereafter, the inside of the mold was cooled by water cooling, and then the foamed particle molded body was taken out from the mold. Furthermore, drying and curing were performed by placing the foamed particle compact in an oven adjusted to a temperature of 60 ° C. for 12 hours. The foamed particle molded body was manufactured as described above.

About the obtained expanded particle molded body, the mass ratio of styrene resin and ethylene resin in the composite resin calculated from the blend composition (styrene resin / ethylene resin), the content of butyl acrylate in the composite resin (Mass%) is shown in Table 2 described later. Further, as molding conditions, molding pressure (MPa) at the time of molding and water cooling time (seconds) are shown in Table 2 described later. Further, for the foamed particle molded body, the degree of swelling, the ratio (%) of insoluble matter in xylene, the weight average molecular weight Mw of the styrenic resin, the apparent density, the bending elastic modulus (MPa), the bending elastic energy (kJ / cm ² ), compression The strength (kPa) and surface resistivity (Ω) were measured as follows. The results are shown in Table 2 below.

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

"Ratio of xylene insoluble matter (XY gel amount)"
The proportion of xylene insoluble matter is based on the weight (W ₀ ) of the test piece measured at the above degree of swelling.
Ratio (W ₁ / W ₀ ; percentage (%) of weight (W ₁ ) of insoluble xylene obtained by measurement of the degree of swelling
%)).

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

"Apparent density"
The apparent density was calculated by dividing the mass of the foamed particle compact by its volume.

"Bending elastic modulus"
The flexural modulus was measured according to a three-point bending test method described in JIS K 7221 (1999). The flexural modulus was determined by cutting a test piece having a thickness of 20 mm, a width of 25 mm, and a length of 120 mm from the composite resin foamed particle molded body so that the entire surface was a cut surface, and keeping it in a constant temperature room at 23 ° C. and a humidity of 50% for 24 hours or more. Autograph AGS-10kNG (manufactured by Shimadzu Corporation) under conditions of 100 mm distance between fulcrums, radius of indenter R15.0 mm, radius of support R15.0 mm, test speed 20 mm / min, room temperature 23 ° C., humidity 50%. The average value of the values (5 points or more) calculated by measuring with a testing machine was adopted.

"Bending fracture energy"
A three-point bending test was performed in the same manner as the above-described measurement of the flexural modulus, and energy (kJ) up to the breaking point was determined from the relationship between the amount of deflection (mm) and the load (kN). The energy is calculated from the area surrounded by the deflection amount-load curve up to the breaking point and the horizontal axis (deflection amount). Then, by dividing the energy to break point (kJ) in the cross-sectional area of the specimen (cm ^2), it was calculated flexural fracture energy (kJ / cm ²⁾ per unit cross-sectional area.

"Compressive strength"
A rectangular parallelepiped test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm was cut out from the center portion of the foamed particle molded body. Next, the compression load at the time of 50% strain was calculated | required based on JISK6767 (1999) with respect to this test piece. The compressive stress (50% compressive stress) was calculated by dividing this compressive load by the pressure receiving area of the test piece. In the present specification, this compressive stress is also referred to as compressive strength.

"Surface resistivity"
The surface resistivity of the foamed particle molded body was measured as follows.
After the foamed particle molded body was cured for 1 day immediately after production under the conditions of 23 ° C. and 50% RH, the measurement was performed under the conditions of 23 ° C. and 50% RH by the following method in accordance with JIS C2170 (2004). went. First, a rectangular parallelepiped measurement test piece having a length of 100 mm, a width of 100 mm, and a thickness of the molded body (50 mm) was cut out from the vicinity of the center of the foamed particle molded body. Five measurement specimens were prepared. Using “HIRESTA MCP-HT450” manufactured by Mitsubishi Chemical Corporation as a measuring device, the surface resistivity (Ω) of the molded skin surface of each test piece was measured. A value obtained by geometrically averaging the surface resistivity values obtained from each of the five measurement test pieces was adopted.

(Example 2)
In this example, first, except that the amount of the ethylene resin (PE-1) was changed from 8.65 kg to 9 kg and the amount of the bubble regulator master batch was changed from 1.35 kg to 1 kg. In the same manner as in Example 1, core particles were prepared. Next, 100 g of the core particles were used, the same as in Example 1 except that a mixed monomer of 85 g of styrene and 15 g of butyl acrylate was used as the first monomer, and 300 g of styrene was used as the second monomer. Thus, composite resin particles were produced. And the foamed particle molded object was produced like Example 1 using this composite resin particle.

Example 3
In this example, first, except that the amount of the ethylene resin (PE-1) was changed from 8.65 kg to 8 kg and the amount of the bubble regulator master batch was changed from 1.35 kg to 2 kg. In the same manner as in Example 1, core particles were prepared. Next, 53 g of this core particle was used, the same as in Example 1 except that a mixed monomer of 38 g of styrene and 15 g of butyl acrylate was used as the first monomer, and 394 g of styrene was used as the second monomer. Thus, composite resin particles were produced. And the foamed particle molded object was produced like Example 1 using this composite resin particle.

(Comparative Example 1)
An ethylene-vinyl acetate copolymer (EVA) (“NUC-3221” manufactured by Nippon Unicar Co., Ltd.) was prepared as an ethylene-based resin. The ethylene resin of this example is hereinafter referred to as “PE-2” as appropriate. The MFR (190 ° C., load 2.16 kg; g / 10 min), density (kg / m ³ ), tensile elastic modulus (MPa), and melting point (° C.) of PE-2 are shown in Table 1 described later. These are values measured in the same manner as in Example 1 described above. In this example, 10 kg of PE-2 was used instead of 8.65 kg of PE-1 used as the ethylene-based resin in the preparation of the core particles in Example 1, and the amount of the bubble regulator master batch was 1.35 kg. A core particle was produced in the same manner as in Example 1 except that the amount was changed from 0 to 0 kg.

  Next, a suspension (magnesium pyrophosphate slurry) was prepared in the same manner as in Example 1, and then 2.0 g of sodium lauryl sulfonate (10 mass% aqueous solution) as a surfactant was added to the suspension. 0.2 g of sodium nitrite as an acidic polymerization inhibitor and 150 g of the above-mentioned core particles were added. Next, 1.29 g of benzoyl peroxide as a polymerization initiator A (“NIPER BW” manufactured by NOF Corporation, water-diluted powder product), and t-butylperoxy-2-ethylhexyl monocarbonate 2 as a polymerization initiator B .58 g (Nippon “Perbutyl E”) and 0.86 g of Dicumyl peroxide (Nippon “Park Mill D”) as polymerization initiator C were dissolved in the first monomer (styrene monomer). It was. Then, the dissolved product was put into the suspension in the autoclave while stirring at a stirring speed of 500 rpm. In addition, 150 g of styrene was used as the first monomer.

  Next, after the air in the autoclave was replaced with nitrogen, the temperature increase was started and the temperature was increased to 88 ° C. over 1 hour 30 minutes. After the temperature increase, the temperature was maintained at 88 ° C. for 30 minutes. Thereafter, the stirring speed was lowered to 450 rpm, and the temperature was cooled from 88 ° C. to 80 ° C. over 30 minutes. Subsequently, this polymerization temperature was kept at 80 ° C. for 8 hours. When the temperature reached 80 ° C., 200 g of styrene as the second monomer (styrene monomer) was added into the autoclave over 5 hours.

  Next, the temperature was raised to 125 ° C. over 4 hours, and the temperature was kept at 125 ° C. for 2 hours and 30 minutes. Thereafter, the mixture was cooled to a temperature of 90 ° C. over 1 hour, the stirring speed was lowered to 400 rpm, and the temperature was kept at 90 ° C. for 3 hours. When the temperature reached 90 ° C., 20 g of cyclohexane and 65 g of butane (a mixture of normal butane of about 20% by volume and isobutane of about 80% by volume) were added to the autoclave as the foaming agent over about 1 hour. Further, the temperature was raised to 105 ° C. over 2 hours, maintained at 105 ° C. for 5 hours, and then cooled to 30 ° C. over about 6 hours. After cooling, the contents were taken out, and nitric acid was added to dissolve the magnesium pyrophosphate adhering to the surface of the resin particles. Then, it dehydrated and washed with a centrifuge, and the water adhering to the surface was removed with an airflow drying device to obtain expandable composite resin particles. Next, an antistatic agent (N, N-bis (2-hydroxyethyl) alkylamine) is added to the foamable composite resin particles, and further coated with a mixture of zinc stearate, glycerol monostearate, and glycerol distearate. did. In this way, expandable composite resin particles were produced.

Next, the foamable composite resin particles obtained as described above were placed in a 30 L atmospheric pressure batch foaming machine, and steam was supplied into the foaming machine. As a result, foamed composite resin particles were produced as composite resin foamed particles (primary foamed particles) having a bulk density of 48 kg / m ³ . And the expanded particle molding was produced like Example 1 using this composite resin expanded particle.

(Comparative Example 2)
In an autoclave with an internal volume of 3 L equipped with a stirrer, 1100 g of deionized water was added, and 6.6 g of sodium pyrophosphate was further added. Thereafter, 14.2 g of powdered magnesium nitrate hexahydrate was added and stirred at room temperature for 30 minutes. This produced the magnesium pyrophosphate slurry as a suspending agent. Next, 2.2 g of sodium lauryl sulfonate (10% by mass aqueous solution) as a surfactant, 0.22 g of sodium nitrite as a water-soluble polymerization inhibitor, and the same core particles as in Example 1 were added to this suspension. 56 g was charged.

  Next, 1.29 g of benzoyl peroxide as a polymerization initiator A (“NIPER BW” manufactured by NOF Corporation, water-diluted powder product), and t-butylperoxy-2-ethylhexyl monocarbonate 2 as a polymerization initiator B .58 g (Nippon "Perbutyl E") and 0.86 g of dicumyl peroxide (Nippon "Parkmill D") as a crosslinking agent were dissolved in the first monomer (styrene monomer). . Then, the dissolved product was put into the suspension in the autoclave while stirring at a stirring speed of 500 rpm. Note that a mixed monomer of 100 g of styrene and 12 g of butyl acrylate was used as the first monomer.

  Next, after the air in the autoclave was replaced with nitrogen, the temperature increase was started and the temperature was increased to 88 ° C. over 1 hour 30 minutes. After the temperature increase, the temperature was maintained at 88 ° C. for 30 minutes. Thereafter, the stirring speed was lowered to 450 rpm, and the temperature was cooled from 88 ° C. to 80 ° C. over 30 minutes. Subsequently, this polymerization temperature was kept at 80 ° C. for 8 hours. When the temperature reached 80 ° C., 231 g of styrene as the second monomer (styrene monomer) was added into the autoclave over 5 hours.

  Next, the temperature was raised to 125 ° C. over 4 hours, and the temperature was kept at 125 ° C. for 2 hours and 30 minutes. Then, it cooled over 30 hours to the temperature of 30 degreeC, and produced the composite resin particle. And the foamed particle molded object was produced like Example 1 using this composite resin particle.

(Comparative Example 3)
In this example, first, except that the amount of ethylene resin (PE-1) was changed from 8.65 kg to 9.35 kg, and the amount of bubble regulator masterbatch was changed from 1.35 kg to 0.65 kg. Then, nuclear particles were produced in the same manner as in Example 1. Next, 150 g of the core particles were used, the same as in Example 1 except that a mixed monomer of 135 g of styrene and 15 g of butyl acrylate was used as the first monomer, and 200 g of styrene was used as the second monomer. Thus, composite resin particles were produced. And the foamed particle molded object was produced like Example 1 using this composite resin particle.

(Results of Examples and Comparative Examples)
Tables 1 and 2 show the same evaluation results as in Example 1 for the foamed particle molded bodies produced in Examples 2-3 and Comparative Examples 1-3.

  As known from Table 2, with respect to 100 parts by mass of an ethylene-based resin, 400 to 900 parts by mass of a styrene monomer is impregnated and polymerized, and the expanded particles are composed of a composite resin having a swelling degree of 1.25 or more. The molded bodies (Examples 1 to 3) have a high bending elastic modulus and a high bending fracture energy. Therefore, the foamed particle molded body has excellent deflection resistance and can prevent breakage due to deformation. Furthermore, since the expanded foam molded bodies of Examples 1 to 3 have high compressive strength, they are difficult to sag.

On the other hand, Comparative Example 1 uses, as the polymerization initiator, dicumyl peroxide having an ethylene-vinyl acetate copolymer and high hydrogen abstraction ability as the polymerization initiator. The crosslinking density tends to be high and the degree of swelling is too low. For this reason, there is a problem that bending fracture energy is insufficient and breakage due to deformation easily occurs. Furthermore, since the amount of the styrenic resin in the composite resin is too small, there is a problem that the compressive strength and the flexural modulus are low. Also, since an organic foaming agent such as butane is used as the foaming agent, the organic foaming agent remains in the composite resin foamed particles, and the molding water cooling time is longer than when carbon dioxide (CO ₂ ) is used as the foaming agent. become longer.

  Since Comparative Example 2 has a larger amount of styrene-based resin in the composite resin than Comparative Example 1, the compressive strength and the flexural modulus are high enough to be comparable to the Examples. However, in Comparative Example 2, when the composite resin particles are produced, dicumyl peroxide having a high addition ratio of the styrene monomer (first monomer) impregnated into the core particles first and having a high hydrogen abstraction ability is used as a polymerization initiator. As a result, the degree of swelling is too low. For this reason, there is a problem that bending fracture energy is insufficient and breakage due to deformation easily occurs.

  Comparative Example 3 is an example in which the amount of the styrene monomer impregnated and polymerized in the core particles is small, and the rigidity of the foamed particle molded body is low. Therefore, there exists a problem that compressive strength and a bending elastic modulus are low, and it is easy to deform | transform and to sag easily.

(Example 4)
This example is an example of a panel packing container made of a foamed particle molded body.
As shown in FIGS. 1 to 3, the panel packaging container 1 of the present example is made of a foamed particle molded body, and has a housing portion 10 that houses a plurality of panels 4 stacked in the thickness direction. The panel packaging container 1 has a container body 2 and a lid body 3 that closes the opening 21 of the container body 2, and both the container body 2 and the lid body 3 are formed of a foamed particle molded body. The panel packaging container 1 is used for accommodating a panel 4 such as a liquid crystal panel. As the foamed particle molded body, the same molded body as in Examples 1 to 3 described above is used.

Hereinafter, the panel packing container 1 will be described in further detail.
As shown in FIG. 3, the container main body 2 has a housing shape 20 that houses a plurality of panels 4 stacked in the thickness direction, and has a box shape having an opening 21 on the upper surface. Specifically, the container main body 2 includes a bottom plate portion 22 and side wall portions 23 that rise vertically from the periphery of the bottom plate portion 22. The lid 3 has a housing 30 that houses the stacked panels 4 from above, and has a box shape having an opening 31 on the lower surface. Specifically, the lid 3 includes an upper plate portion 32 and a side wall portion 33 that extends vertically from the periphery of the upper plate portion 32. On the side wall 23 of the container body 2 and the side wall 33 of the lid 3, a convex portion 231 and a concave portion 331 are formed at positions and shapes where both are fitted.

  As shown in FIG.2 and FIG.3, in the panel packing container 1 of this example, both the container main body 2 and the cover body 3 have the accommodating parts 20 and 30, respectively. And the accommodating part 10 in the panel packaging container 1 is formed by these accommodating parts 20 and the accommodating part 30, and the several panel 4 is accommodated in the accommodating part 10 in the lamination | stacking state.

  The panel packing container 1 of this example consists of the foamed particle molded body of Examples 1 to 3 described above. Therefore, even if a plurality of panels 4 having a large weight are accommodated in the accommodating portion 10, the panel packing container 1 is not easily bent due to the weight of the panel 4, and is not easily broken due to deformation. Therefore, even if the panel packaging container 1 is stacked in a packaged state or a sudden load change occurs during movement in the packaged state, cracks can be prevented from occurring. FIG. 4 shows a state in which the panel packing container 1 is lifted by holding both ends in the longitudinal direction of the panel packing container 1 of this example. As shown in the figure, the panel packing container 1 bends due to the weight of the panel 4 accommodated in the accommodating portion 10. The panel packing container 1 of this example is formed by impregnating and polymerizing 400 to 900 parts by mass of a styrene monomer with respect to 100 parts by mass of an ethylene resin as in Examples 1 to 3 described above, and the degree of swelling is Since it is composed of a foamed particle molded body made of a composite resin of 1.25 or more, the amount of deflection is small as shown in FIG. Further, FIG. 5 shows a state in which the panel packaging container 1 is lifted by holding both ends in the short direction of the panel packaging container 1 of this example, and the amount of deflection is also small in this case. In FIGS. 4 and 5 and FIGS. 6 and 7 to be described later, the illustration of the panel in the panel packing container 1 is omitted for the convenience of drawing. Is housed inside.

  In the above example, both the container main body 2 and the lid 3 have the accommodating portions 20 and 30 of the panel 4, but the container main body 2 has the accommodating portion, and the lid 3 is the accommodating portion 3. It is also possible to change to a configuration that does not have. In this case, the lid 3 has a plate shape (not shown).

(Comparative Example 5)
This example is an example of a panel packaging container having the same shape as that of the above-described Example 4 but made of the foamed particle molded body of Comparative Example 3 described above. The panel packing container 9 of this example has the same shape as that of the above-described Example 4 except that the panel packing container 9 is composed of the foamed particle molded body of Comparative Example 3, and a container body 91, a lid body 92, Consists of. The panel packing container 9 of this example is made of a foamed particle molded body (see Comparative Example 3) having an insufficient bending elastic modulus. Therefore, as shown in FIGS. 6 and 7, the panel packing container 9 is largely bent by the weight of the panel 4 accommodated in the accommodating portion 10. Therefore, when the panel packing container 9 is lifted, there is a risk of dropping or breakage of the panel. Note that. Although illustration is omitted, when the panel packing container 9 is formed of a foamed particle molded body having a small bending fracture energy as in Comparative Example 1 and Comparative Example 2 described above, the panel packing container 9 deformed by bending is broken. It becomes easy.

  As mentioned above, although the Example of this invention was described in detail, this invention is not limited to the said Example, A various change is possible within the range which does not impair the meaning of this invention.

DESCRIPTION OF SYMBOLS 1 Panel packing container 10 Storage part 2 Container main body 3 Cover body

Claims (6)

A foamed particle molded body obtained by molding composite resin foamed particles in a mold,
The composite resin constituting the foamed particle molded body is formed by impregnating and polymerizing 400 to 900 parts by mass of a styrene monomer with respect to 100 parts by mass of an ethylene resin.
The ethylene resin is a linear low density polyethylene,
The degree of swelling in methyl ethyl ketone at a temperature of 23 ° C. is 23.degree. C. or higher when the composite resin is subjected to Soxhlet extraction with xylene and mixed with the acetone insoluble matter contained in the xylene solution after Soxhlet extraction. There is a foamed particle molded article.   2. The foamed particle molded body according to claim 1, wherein the ethylene-based resin is a linear low-density polyethylene having a melting point of 105 ° C. or lower, which is obtained by polymerization using a metallocene-based polymerization catalyst. 3. The composite resin according to claim 1, wherein the composite resin is obtained by impregnating and polymerizing a styrene monomer that exceeds 500 parts by mass and is 900 parts by mass or less with respect to 100 parts by mass of the ethylene resin. Foamed particle molded body. The apparent density of the said foaming particle molded object is 30-100 kg / m < ³ >, The expanded particle molded object of any one of Claims 1-3 characterized by the above-mentioned. A panel packing container comprising the foamed particle molded body according to any one of claims 1 to 4,
A panel packaging container comprising a housing portion that houses a plurality of panels stacked in a plate thickness direction. The antistatic agent is present on at least the surface of the foamed particle molded body, and the surface resistivity of the foamed particle molded body is 1 × 10 ⁸ to 1 × 10 ¹³ Ω. Panel packing container.

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