TWI680999B - Expanded particle molded body and panel packaging container - Google Patents

Abstract

An object of the present invention is to provide a foamed particle molded body and a panel wrapping container which are excellent in compression rigidity and bending resistance and can prevent damage due to deformation.

The solution of the present invention is an expanded particle molded body formed by in-mold molding of composite resin expanded particles, and a panel wrapping container (1) composed of the expanded particle molded body. The composite resin constituting the expanded particle molded body is obtained by impregnating and polymerizing styrene-based monomers of 400 to 900 parts by mass with respect to 100 parts by mass of the ethylene-based resin, and the specific swelling degree is 1.25 or more.

Description

Expanded particle molded body and panel packaging container

The present invention relates to a foamed particle molded body formed by in-mold molding of composite resin foamed particles and a panel wrapping container formed of the foamed particle molded body.

In the past, in the packing of plate-like products such as liquid crystal panels, photovoltaic power generation panels, etc., foams made of acrylic resins have been used for reasons such as abrasion, cracks, and defects due to scratches or friction, which can be used multiple times, etc. A container made of shaped particles. In recent years, the weight of the bag has increased with the increase in the size of the panel. As a result, in a container formed of a foamed particle molded body of a propylene-based resin, there arises a problem that the amount of deflection in the packed state increases. If the amount of deflection during packing is large, there is a possibility that the container may be detached when lifted by both ends of the container in a packed state, or the liquid crystal panel may be damaged due to bending.

In contrast, the expanded particle molding system of a composite resin of a vinyl resin and a styrene resin can increase the rigidity of the expanded particle molded body by increasing the amount of the styrene resin component (for example, refer to Patent Documents 1 to 3 ). Therefore, in such a composite resin expanded particle molded body The system can reduce the amount of deflection and improve the deflection resistance, which can improve the transportability. In addition, since it is possible to increase the expansion ratio while maintaining the bending resistance, the composite resin expanded particle molded body has the advantages of reducing the weight of the wrapping material itself.

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Publication No. 2014-196441

[Patent Document 2] Japanese Laid-Open Patent Publication No. 2014-196444

[Patent Document 3] Japanese Patent No. 5058866

However, compared with the propylene resin foam molded body, the composite resin foamed particle molding system has a smaller bending breaking energy. In particular, if the ratio of the styrene-based resin component in the composite resin is increased in order to increase the rigidity, even if the foamed particles are strongly welded to each other, the adhesive strength is insufficient. If they are piled up in the wrapped state or moved in the wrapped state If there is a sudden load change in the middle, there is a fear of rupture.

The present invention has been completed in view of this background, and it provides an expanded particle molded body and a panel wrapping container which are excellent in compression rigidity and flex resistance, and can prevent damage due to deformation.

The same aspect of the present invention is an expanded particle molded body, which is an expanded particle molded body formed by in-mold molding of composite resin expanded particles, characterized in that the composite resin constituting the expanded particle molded body is For 100 parts by mass of ethylene-based resin, 400 to 900 parts by mass of styrene monomer is impregnated and polymerized. The xylene-insoluble matter and the above-mentioned Soxhlet extraction when the above composite resin is subjected to Soxhlet extraction by xylene The swelling degree of the mixed insoluble matter of the acetone insoluble matter contained in the xylene solution in methyl ethyl ketone at a temperature of 23°C is 1.25 or more.

Another aspect of the present invention is a panel packing container, which is a panel packing container composed of the above-mentioned expanded particle molded body, and is characterized by having a plurality of panels accommodated in a state of being stacked in the thickness direction unit.

The above-mentioned expanded particle molding system is composed of a composite resin formed by impregnating and polymerizing a certain proportion of styrene monomer in an ethylene resin. Therefore, the above-mentioned expanded particle molding system has high compressive strength and high bending elastic modulus. Therefore, the above-mentioned expanded particle molding system is excellent in bending resistance. In addition, the swelling degree of the composite resin is 1.25 or more. Therefore, the above-mentioned expanded particle molding system exhibits excellent flex resistance as described above, and exhibits high compression rigidity, and further exhibits high bending elastic energy. Prevent damage due to deformation.

The panel packing container is composed of the above-mentioned expanded particle molded body, and has an accommodating portion for accommodating a plurality of panels in a state of being stacked in the plate thickness direction. Therefore, even if a plurality of panels are accommodated in the accommodating portion, the panel packing container is less likely to deflect due to the weight of the panel, and thus is less likely to be damaged due to deformation. Therefore, even if the panel clad container is piled up in a clamshell state, or a sudden load change occurs during movement in the clamshell state, cracking can be prevented.

1‧‧‧Panel container

10‧‧‧ Containment Department

2‧‧‧Container body

3‧‧‧cover

[Figure 1] is a perspective view of a panel bag container of Example 4.

[Figure 2] is a cross-sectional view of a panel bag container of Example 4 (specifically, a cross-sectional view taken along line II-II).

[Figure 3] is a development view of a panel bag container of Example 4.

[FIG. 4] It is explanatory drawing which shows the state which lifted the panel bag container of Example 4 by holding both ends of the longitudinal direction.

[Fig. 5] It is an explanatory view showing a state in which the panel bag container of Example 4 is lifted by holding both ends in the short-side direction.

[Fig. 6] It is an explanatory view showing a state in which the panel bag container of Example 5 is lifted by holding both ends in the longitudinal direction.

[FIG. 7] It is explanatory drawing which shows the state which lifted up the panel bag container of Example 5 by holding both ends of the short side direction.

Next, an embodiment of the above-mentioned expanded particle molded body and panel wrapping container will be described.

Expanded particle forming system is formed by in-mold molding of composite resin expanded particles (hereinafter, also suitably referred to as "expanded particles"). The composite resin expanded particles are obtained by impregnating vinyl resin with styrene monomer The composite resin (specifically, composite resin particles) obtained by polymerizing the resin particles is expanded by foaming. The blending amount of the styrene monomer is 400 to 900 parts by mass relative to 100 parts by mass of the vinyl resin. When the styrene-based monomer is less than 400 parts by mass, the rigidity is reduced, and there is a fear that the flex resistance may be insufficient. From the same viewpoint, the blending amount of the styrene-based monomer is preferably more than 450 parts by mass, and more preferably 500 parts by mass or more with respect to 100 parts by mass of the vinyl resin. On the other hand, in the case where the styrene-based monomer exceeds 900 parts by mass, the expanded particle molded body is easily broken and becomes brittle. From the same viewpoint, the blending amount of the styrene-based monomer is preferably 800 parts by mass or less, more preferably 700 parts by mass or less, and even more preferably 600 parts by mass or less with respect to 100 parts by mass of the vinyl resin.

As the ethylene-based resin, for example, linear low-density polyethylene, branched low-density polyethylene, high-density polyethylene, ethylene-acrylic copolymer, ethylene-alkyl acrylate copolymer, ethylene-methacrylic acid can be used Alkyl ester copolymers, etc. Although the vinyl resin may be one kind of polymer, a mixture of two or more kinds of polymers may also be used.

Preferably, the vinyl-based resin system has linear low-density polyethylene as the main component. Straight-chain low-density polyethylene is preferably The branch structure is better. The branch structure is a linear polyethylene chain and a short-chain branch chain with a carbon number of 2-6. Specific examples include ethylene-butene copolymer, ethylene-hexene copolymer, and ethylene-octene copolymer. In particular, the ethylene-based resin is preferably a linear low-density polyethylene having a melting point of 105° C. or lower and polymerized by a metallocene-based polymerization catalyst. In this case, the affinity of the vinyl resin and the styrene resin will be more improved, and the toughness of the composite resin can be improved. In addition, since the low molecular weight component can be reduced and the fusion strength between the foamed particles during molding can be improved, the foamed particle molded body is less likely to break. Furthermore, it becomes a foamed particle molded body which can obtain both the excellent rigidity of the styrene resin and the excellent adhesive strength of the vinyl resin at a higher level.

In addition, the melting point Tm of the vinyl resin is preferably 95 to 105°C. In this case, the styrene-based monomer can be sufficiently impregnated with the vinyl-based resin during the production of the expanded composite resin particles, and the suspension system can be prevented from becoming unstable during polymerization. As a result, it is possible to obtain a foamed particle molded body having a higher level of excellent rigidity of styrene-based resin and excellent adhesive strength of ethylene-based resin. More preferably, the melting point Tm of the vinyl resin is preferably 100 to 105°C. In addition, the melting point Tm can be measured by differential scanning calorimetry (hereinafter, also suitably referred to as "DSC") according to JIS K7121-1987.

The vinyl resin is preferably composed of a linear low-density polyethylene having a melting point Tm (unit: °C) and a Vicat softening point Tv (unit: °C) satisfying the relationship of Tm-Tv≦20. Such a vinyl resin system shows a uniform molecular structure, and it can be speculated that the network structure due to cross-linking will be more uniform Distributed in vinyl resin. Therefore, in this case, the strength and viscosity strength of the expanded particle molded body can be further improved. Based on the same viewpoint, the linear low-density polyethylene preferably satisfies Tm-Tv≦15, and even more preferably satisfies Tm-Tv≦10. Generally, the melting point Tm is higher than the Vicat softening point Tv. In addition, Vicat softening point Tv system can be measured according to JIS K 7206-1999.

The melt flow rate of the ethylene-based resin at a temperature of 190°C and a load of 2.16 kg (hereinafter, also suitably referred to as "MFR") is preferably 0.5 to 4.0 g/ from the viewpoint of foamability. 10 points, preferably 1.0 to 3.0 g/10 points. The MFR of an ethylene-based resin at a temperature of 190°C and a load of 2.16 kg is a value measured under condition code D according to JIS K7210-1999. In addition, as the measuring device, MELT INDEXER (for example, Model L203 manufactured by Takara Industrial Co., Ltd.) can be used.

The styrene-based resin refers to a unit in which the styrene component in the resin is 50% by mass or more. The styrene component unit in the styrene-based resin is preferably 80% by mass or more, and more preferably 90% by mass or more. In addition, in this specification, the monomer which can copolymerize the styrene which comprises a styrene resin and the styrene added as needed is also called a styrene monomer. Examples of monomers copolymerizable with styrene include the following styrene derivatives and other vinyl monomers.

Examples of the styrene derivative system include: α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethyl Styrene, p-methoxystyrene, pn-butyl Styrene, pt-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4,6-tribromostyrene, divinylbenzene, styrenesulfonic acid, benzene Sodium ethylene sulfonate, etc. These systems can be used alone or in combination of two or more types.

In addition, examples of other vinyl monosystems include acrylates, methacrylates, acrylic acid, methacrylic acid, hydroxyl-containing vinyl compounds, nitrile-containing vinyl compounds, organic acid vinyl compounds, olefin compounds, and dienes. Compounds, halogenated vinyl compounds, halogenated vinylidene compounds, maleimide compounds, etc.

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

Examples of the methacrylate system include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate.

Examples of the hydroxy-containing vinyl compound include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate.

Examples of vinyl compounds containing nitrile groups include acrylonitrile and methacrylonitrile.

Examples of the organic acid vinyl compound system include vinyl acetate and vinyl propionate.

Examples of the olefin compound system include ethylene, propylene, 1-butene, and 2-butene.

Examples of the diene compound system include: butadiene, isoprene, and chloroprene Diene, etc.

Examples of vinyl halide compounds include vinyl chloride and vinyl bromide.

Examples of halogenated vinylidene compounds include vinylidene chloride.

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

These vinyl single systems can be used alone or in combination of two or more types.

As the styrene-based resin, from the viewpoint of improving foamability, polystyrene, a copolymer of styrene and an acrylic monomer is preferred. From the viewpoint of further improving foamability, as shown in the examples described later, it is preferable to use styrene and butyl acrylate as monomers constituting the styrene-based resin. In this case, the content of the butyl acrylate component in the composite resin is preferably 0.5 to 10% by mass for the entire composite resin, more preferably 1 to 8% by mass, and even more preferably 2 to 5% by mass.

In the expanded particle molded body, the xylene-insoluble substance when the composite resin constituting the expanded particle molded body is subjected to Soxhlet extraction by xylene is insoluble with the acetone contained in the xylene solution after the Soxhlet extraction. If the swelling degree of the insoluble substance in methyl ethyl ketone at a temperature of 23°C (hereinafter, abbreviated as "swelling degree") is too low, there is a fear that the foamed resin molded body has low bending breaking energy and stickiness. The sexual strength may become 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 even more preferably 2 or more. In addition, from the viewpoint of suppressing shrinkage of the expanded particle molded body, the swelling degree of the composite resin is preferably 10 or less, and more preferably 5 or less.

When the degree of swelling is equal to or greater than the above-mentioned specific value, as will be described later, the reason why the rigidity and the adhesive strength are excellent can be estimated as follows. The degree of swelling (that is, the degree of swelling) when the cross-linked vinyl resin is immersed in an organic solvent is related to the cross-linked structure such as the three-dimensional network structure of the resin, because the finer the network, the lower the absorption of the organic solvent , So the swelling will be reduced. On the other hand, non-crosslinked vinyl resins hardly swell in methyl ethyl ketone at a temperature of 23°C. In other words, it means that the xylene-insoluble matter in the composite resin (specifically, the cross-linked vinyl resin component) and the acetone-insoluble matter in the xylene soluble matter (specifically, through the mesh) The total swelling degree of the mixed insoluble matter of the cross-linked ethylene-based resin component and the uncross-linked ethylene-based resin component is greater than that of the case where the swelling degree is small. The resin contains many vinyl resin components with a cross-linked three-dimensional network structure.

Therefore, although the network of the cross-linked three-dimensional network structure is thick, the ethylene-based resin component system has strength when foamed, but it is also easy to extend moderately. Therefore, it is presumed that a bubble film with high strength can be formed. Furthermore, in the composite resin expanded particles, when compressed, the vinyl resin in the composite resin is soft and can be sufficiently deformed, so it can be speculated that even if the ratio of the styrene resin in the composite resin is high In addition, the bubble film of the expanded particles will not be broken and the independent bubble structure can be maintained. That is, when the degree of swelling is within a specific range, a high level of both rigidity and viscous strength can be obtained, and a foamed particle molded body having a large bending breaking energy can be obtained.

For example, the vinyl resin core particles and the first monomer (with Generally speaking, it is a condition that the blending ratio of the styrene monomer described later is large, the temperature at which the first monomer is impregnated with the vinyl resin core particles is high, and the hydrogen extraction reaction energy is high. In the previously discussed manufacturing conditions such as the conditions for the use of the agent, it is presumed that at the initial stage of polymerization, the styrene-based monomer is polymerized in the vinyl-based resin to precipitate as a styrene-based resin, and the vinyl-based resin The network of the cross-linked three-dimensional mesh structure will become thinner. On the other hand, by adjusting the type or amount of the polymerization initiator, the polymerization temperature, and the blending ratio of the vinyl resin core particles and the first monomer, it is possible to slow down the analysis rate of the styrene resin at the initial stage of polymerization However, the amount of the vinyl resin component whose cross-linked three-dimensional network structure is fine is controlled to be small.

In addition, in the composite resin, it is preferable that the weight ratio of the xylene-insoluble substance by Soxhlet extraction is 40% or less (however, 0 is included). In this case, the foamability can be further improved. In addition, the weight ratio of xylene-insoluble matter is more preferably 35% or less (including 0), and even more preferably 30% or less (including 0). Moreover, the weight ratio of xylene insoluble matter is more preferably 5% or more. In this case, the rigidity and viscous strength of the expanded particle molded body can be further improved.

The apparent density of the expanded particle molded body is preferably 30 to 100 kg/m ³ . Within this range, light weight and cushioning performance can be maintained, while high bending rigidity and compression recovery can be obtained. The apparent density of the expanded particle molded body is more preferably 30 to 65 kg/m ³ . In the case where the panel packing container is composed of the above-mentioned expanded particle molded body, the apparent density of the expanded particle molded body is more preferably 40 to 100 kg/m ³ .

The expanded particle molding system is obtained by in-mold molding of a composite resin expanded particle. The composite resin expanded particle is produced, for example, as follows.

First, suspension particles are prepared by suspending core particles containing ethylene-based resin as a main component in an aqueous medium. Next, styrene monomer is added to the suspension. Next, the styrene-based monomer is impregnated with the core particles and polymerized. Then, by expanding the polymerized composite resin particles, composite resin expanded particles can be produced.

In order to impregnate the styrene-based monomer with the core particles and perform polymerization, although the entire amount of the styrene-based monomer used can also be added together, the styrene can also be added as described later in the dispersion step and the modification step The usage amount of the monomer is divided into, for example, the first monomer and the second monomer, and these monomers are added at different timings. As in the latter case, by dividing and adding the styrene-based monomer, the aggregation of the resin particles during polymerization can be suppressed.

Specifically, the composite resin expanded particles can be produced by performing the following dispersion step, modification step, and expansion step, for example. In the dispersion step, the first monomer (that is, the styrene-based monomer) and the polymerization initiator are added to the suspension in which the core particles of the vinyl resin as the main component are suspended in the aqueous medium, so that the first The monomer is dispersed in the suspension.

In the modification step, the above suspension is heated, and when the melting point of the ethylene-based resin of the core particles is set to Tm, the second monomer ((Tm-10) to (Tm+30) °C That is, the styrene-based monomer) is continuously added to the above-mentioned suspension with a specific addition time, so that The styrene-based monomer is impregnated in the above-mentioned core particles and polymerized.

In addition, when the seed ratio with respect to the weight ratio of the first monomer of the core particles (that is, the styrene-based monomer) is too low, the composite resin particles may be flat. Therefore, the seed crystal of the first monomer is preferably 0.5 or more, more preferably 0.7 or more, and still more preferably 0.8 or more. On the other hand, if the seed ratio is too high, the styrene-based monomer may be polymerized before the core particles are sufficiently impregnated. As a result, there is a possibility that a molded product with good rigidity or viscous strength may not be obtained, or it may be difficult to suspend and stabilize, and agglomerates of resin may occur. Therefore, the seed crystal of the first monomer is preferably 1.5 or less, more preferably 1.3 or less, and even more preferably 1.2 or less.

In the foaming step, the composite resin foamed particles can be produced by foaming the composite resin particles after polymerization.

Hereinafter, each step will be described in further detail.

In the dispersion step, for example, the core particles can be suspended in an aqueous medium containing a suspending agent, a surfactant, a water-soluble polymerization inhibitor, etc. to prepare a suspension. In addition, in the dispersion step, the polymerization initiator may be added to the suspension together with the first monomer.

The core particle system may contain additives such as a bubble regulator, a coloring agent, and a sliding material. The core particles can be produced by blending the ethylene-based resin with additives that are added as needed, after the blend is melted and kneaded, and then refined. The melt-kneading system can be performed by an extruder. At this time, in order to perform uniform kneading, it is preferable to squeeze the resin components before mixing. Mixing of resin components, for example, Henschel mixer, screw It is carried out by mixers such as belt mixer, V-type mixer, Lodige mixer, etc. The melt-kneading is preferably carried out using a high-dispersion propeller such as Dulmage type, Maddock type, Unimelt type or a twin-shaft extruder.

Refinement of the core particles is performed by cutting the blend after melt-kneading with an extruder or the like. The miniaturization can be performed by, for example, strand cutting, underwater cutting, and thermal cutting.

The core particles are preferably dispersed in the aqueous medium together with the suspending agent.

As the suspending agent, for example, tricalcium phosphate, hydroxide apatite, magnesium pyrophosphate, magnesium phosphate, aluminum hydroxide, iron hydroxide, titanium hydroxide, magnesium hydroxide, barium phosphate, calcium carbonate, magnesium carbonate, Particulate inorganic suspending agent for barium carbonate, calcium sulfate, barium sulfate, talc, kaolin, bentonite, etc. In addition, for example, organic suspending agents such as polyvinylpyrrolidone, 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 is preferably based on the amount of solid content relative to 100 parts by mass of the aqueous medium of the suspension polymerization system (specifically, all water in the reaction system containing water such as slurry containing the reaction product) 0.05 to 10 parts by mass. More preferably, it is 0.3~5 parts by mass. When the amount of the suspending agent deviates from the above range and is too small, it may become difficult to suspend and stabilize the styrene-based monomer, and agglomeration of the resin may occur. On the other hand, when the amount of suspending agent deviates from the above range and is too large, it is not It only leads to an increase in manufacturing costs, and there is a fear that the particle size distribution may be enlarged.

In addition, a surfactant can be added to the suspension. As the surfactant system, for example, an anionic surfactant, a nonionic surfactant, a cationic surfactant, an amphoteric surfactant, or the like can be used.

As the anionic surfactant system, for example, sodium alkylsulfonate, sodium alkylbenzenesulfonate, sodium lauryl sulfate, sodium α-olefin sulfonate, sodium dodecyl diphenyl ether disulfonate, and the like can be used.

As the nonionic surfactant system, for example, polyoxyethylene lauryl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether and the like can be used.

As the cationic surfactant system, for example, alkylamine salts such as coconut oil alkylamine acetate and stearylamine acetate can be used. In addition, quaternary ammonium such as lauryl trimethyl ammonium chloride and stearyl trimethyl ammonium chloride can also be used.

As the amphoteric interface agent, alkyl betaines such as lauryl betaine and stearyl betaine can be used. In addition, 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 alkali metal salt of an alkylsulfonic acid having 8 to 20 carbon atoms, and even more preferably a sodium salt. This allows the suspension to be fully stabilized.

Furthermore, an electrolyte composed of inorganic salts such as lithium chloride, potassium chloride, sodium chloride, sodium sulfate, sodium nitrate, sodium carbonate, and sodium bicarbonate may be added to the suspension as needed.

In addition, in order to obtain an expanded particle molded body excellent in toughness and mechanical strength, it is preferable to add a water-soluble polymerization inhibitor to the suspension.

As the water-soluble polymerization inhibitor system, for example, sodium nitrite, potassium nitrite, ammonium nitrite, L-ascorbic acid, citric acid and the like can be used.

The water-soluble polymerization inhibitor system is difficult to impregnate into the core particles, but will dissolve in the aqueous medium. Therefore, although the polymerization of the styrene-based monomer impregnated with the core particles is carried out, the polymerization of the minute droplets of the styrene-based monomer that is not impregnated in the aqueous medium of the core particles can be suppressed and gradually absorbed by the core particles The polymerization of styrene monomer near the surface of the core particles. As a result, the amount of styrene resin on the surface of the composite resin particles can be suppressed to a small amount, and it is presumed that the toughness of the obtained expanded particle molded body is improved.

The addition amount of the water-soluble polymerization inhibitor is preferably 0.001 to 0.1 parts by mass relative to 100 parts by mass of the aqueous medium (specifically, all water in the reaction system containing water such as slurry containing the reaction product). More preferably, it is 0.005 to 0.06 parts by mass.

In addition, in order to uniformly polymerize the styrene-based monomer in the core particles, the styrene-based monomer is impregnated with the core particles and polymerized. In this case, the vinyl resin may be cross-linked together with the polymerization of the styrene-based monomer. Although a polymerization initiator is used in the polymerization of styrene-based monomers, a crosslinking agent can be used in combination as needed. In addition, when a polymerization initiator and/or crosslinking agent is used, it is preferable to dissolve the polymerization initiator and/or crosslinking agent in the styrene-based monomer in advance.

As the polymerization initiator, it can be used in the suspension polymerization method of styrene monomer, for example, it can be dissolved in vinyl monomer and 10 Polymerization initiator with hour half-life temperature of 50~120℃. Specifically, for example, cumene hydroperoxide, dicumyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxybenzone Ester, benzoyl peroxide, t-butyl peroxyisopropyl carbonate, t-pentyl peroxy-2-ethylhexyl carbonate, hexyl peroxy-2-ethylhexyl carbonate, laurel Organic peroxides such as acetyl peroxides. In addition, as the polymerization initiator, an azo compound such as azobisisobutyronitrile can also be used. These polymerization initiators can be used alone or in combination of two or more. In addition, from the viewpoint of easily adjusting the swelling degree of the composite resin described above and easily reducing residual monomers, t-butylperoxy-2-ethylhexanoate is preferably used as a polymerization initiator.

The polymerization initiator may also be dissolved, added to a solvent, and impregnated into the core particles.

As the solvent system for dissolving the polymerization initiator, aromatic hydrocarbons, aliphatic hydrocarbons and the like can be used. Examples of aromatic hydrocarbons include ethylbenzene and toluene. Examples of the aliphatic hydrocarbon system include heptane and octane. The polymerization initiator is preferably used in the range of 0.01 to 3 parts by mass relative to 100 parts by mass of the styrene-based monomer.

In addition, as the crosslinking agent, it is preferable to use one that does not decompose at the polymerization temperature, but the 10-hour half-life temperature decomposed at the crosslinking temperature is 5 to 50°C higher than the polymerization temperature. Specifically, peroxides such as dicumyl peroxide, 2,5-t-butyl peroxybenzoate, 1,1-bis-t-butyl peroxycyclohexane, etc. can be used Thing. As the crosslinking agent system, these can be used alone or in combination of two or more. Based on 100 parts by mass of styrene monomer, the The blending amount of the coupling agent is preferably 0.1 to 5 parts by mass.

In addition, the same compound can also be used as a polymerization initiator and a crosslinking agent.

In addition, a bubble regulator can be added to the styrene monomer. In addition, when the core particles are produced, the bubble regulator may be added to the core particles by kneading the bubble regulator with the vinyl resin. Preferably, the content of the bubble adjuster in the composite resin is adjusted to 0.01 to 2 parts by mass for 100 parts by mass of the composite resin.

As the bubble adjuster system, for example, fatty acid monoamide, fatty acid bisamide, talc, silica, polyethylene wax, methylene bisstearic acid, methyl methacrylate copolymer, silicone, talc can be used , Zinc borate, aluminum sulfate, alum, polytetrafluoroethylene, etc. As the fatty acid monoamide system, for example, amide oleate, amide stearate, amide laurate, amide erucate, and amide benzoate can be used. As the fatty acid bisamide system, for example, ethylenebisstearic acid amide can be used.

In addition, plasticizers, oil-soluble polymerization inhibitors, flame retardants, dyes and the like can be added to the styrene-based monomers as needed.

As the plasticizer system, for example, fatty acid esters, acetylated monoglycerides, oils, and hydrocarbon compounds can be used. As the fatty acid ester system, for example, glycerin tristearate, glycerin tricaprylate, glycerin trilaurate, sorbitan tristearate, sorbitan monostearate, butyl stearate can be used Ester and so on. In addition, as the acetylated monoglyceride system, for example, glycerol diethyl monolaurate and the like can be used. Examples of oils and fats that can be used include hardened tallow and hardened castor oil. As the hydrocarbon compound system, for example, cyclohexane, flow Paraffin, etc.

In addition, as the oil-soluble polymerization inhibitor system, for example, p-t-butylcatechol, hydroquinone, benzoquinone and the like can be used.

Next, in the above modification step, the heating of the suspension after the dispersion step is started. Furthermore, when the melting point of the vinyl resin of the core particles is set to Tm, the second monomer (that is, the styrene monomer) is preferably used at a temperature of (Tm-10) to (Tm+30)°C ) It takes a specific addition time to continuously add to the suspension. By this, the styrene-based monomer can be impregnated into the core particles and polymerized. When the temperature at which the second monomer is added deviates from (Tm-10) to (Tm+30)°C, there is a fear that the suspension system will become unstable and block the resin. The temperature at which the second monomer is added is more preferably (Tm-5)~(Tm+10)°C.

In addition, although the polymerization temperature in the modification step varies depending on the type of polymerization initiator used, it is preferably 60 to 105°C. Moreover, although the crosslinking temperature varies depending on the type of crosslinking agent used, it is preferably 100 to 150°C.

The expanded particle forming system whose swelling degree falls within the above-specified range is obtained by using the production conditions shown in (1) to (3) as follows.

(1) Divide the styrene monomer impregnated into the core particles containing the vinyl resin into plural times for impregnation, in which the addition ratio of the styrene monomer initially impregnated (ie, the first monomer) is set as In many cases, the production conditions for polymerizing the first monomer by setting the ratio of the polymerization initiator to the first monomer to be small.

(2) Using t-butylperoxy-2-ethylhexyl monocarbonate or t-hexylperoxybenzoate as the polymerization initiator is more efficient than dicumyl peroxide Low manufacturing conditions for the starter.

(3) Manufacturing conditions in which the polymerization state of the styrene-based monomer in the initial stage of impregnation polymerization is controlled by dissolving the polymerization initiator only in the first monomer to perform polymerization.

Under these production conditions, the cross-linking density in the ethylene-based resin is not easily improved, and it becomes possible to produce an expanded particle molded body having a swelling degree within the above-specified range. In the manufacturing conditions discussed in the past, the ratio of styrene-based monomers (specifically, the first monomer) impregnated with the core particles containing vinyl resin is small, and the use of diisopropyl with high hydrogen extraction reaction energy Benzene peroxide is used as a polymerization initiator, and the polymerization initiator is added in proportion to the first monomer and the second monomer. Therefore, it is presumed that the crosslink density in the vinyl resin is too high, and the degree of swelling decreases.

In the foaming of composite resin particles, a preliminary foaming method in which a volatile foaming agent is pre-impregnated in the composite resin particles and then heated with steam or warm water or warm air, or in a pressure vessel can be used After the foaming agent is heated together, a direct foaming method of releasing at low pressure to foam is performed. As the foaming agent used, organic foaming agents such as butane, pentane, and propane may be used, and inorganic foaming agents such as carbon dioxide, air, and nitrogen may also be used. It is preferably an inorganic foaming agent. The organic foaming agent system remains in the foamed particles after the foaming of the composite resin particles. Since the internal pressure in the bubbles is increased during molding, the cooling time tends to increase. In contrast, if an inorganic foaming agent is used, no gas remains in the foamed particles. During the shaping, the internal pressure of the particles does not rise, and the cooling of the molded body can be completed in a short time and taken out from the molding die.

The expanded particle forming system can be manufactured by a well-known in-mold forming method by steam heating. That is, by filling a plurality of composite resin expanded particles in a molding die such as a mold, and introducing steam into the molding die to fuse the composite resin expanded particles to each other, an expanded particle molded body can be obtained.

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

The PP bead molding is preferably curved rupture energy 150kJ / cm ² or more, more preferably 200kJ / cm ² or more, still more preferably 250kJ / cm ² or more. From the viewpoint of the toughness of the expanded particle molded body, although the upper limit of bending breaking energy is not particularly limited, it is preferably not broken, but the upper limit is about 400 kJ/cm ² .

The above-mentioned bending elastic modulus is a value measured according to JIS K7221-1999. The above-mentioned bending breaking energy is calculated based on the value of the deflection-load curve up to the breaking point obtained in the bending test and the area surrounded by the horizontal axis representing the deflection.

The 50% compressive stress of the expanded particle molded body is preferably 400 kPa or more, more preferably 450 kPa or more, and even more preferably 500 kPa or more. From the viewpoint of the compressive rigidity of the expanded particle molded body, although the upper limit of the 50% compressive stress is not particularly limited, the upper limit is about 700 kPa right.

The above 50% compression stress means the compressive load at 50% strain measured in accordance with JIS K 6767-1999.

The above-mentioned expanded particle forming system is suitable for a panel-wrapped container. The panel packing container is composed of a foamed particle molded body, and has an accommodating portion configured to accommodate a plurality of panels in a state of being stacked in the plate thickness direction. As the panel system, in addition to glass plates, etc., especially liquid crystal panels for televisions, monitors, etc., photovoltaic power generation panels, etc., the above-mentioned expanded particle molding system is suitable as a wrapping container for such panels. The liquid crystal panel has increased in weight with the increase in product size in recent years. The photovoltaic power generation panel is also heavy. By using a panel packing container composed of the above-mentioned expanded particle molded body as a packing for such a heavy panel, it is excellent in compression rigidity and bending resistance, and can fully exert the above-mentioned effect that can prevent damage due to deformation.

As such a wrap-around container, specifically, a panel wrap-around container having an accommodating portion for storing a plurality of panels stacked in a horizontal direction in the thickness direction, the panel wrap-around container is formed by foaming composite resin particles The expanded particle molded body having an apparent density of 40 to 100 kg/m ³ formed in the mold, and the composite resin constituting the expanded particle molded body will be 400 to 900 for 100 parts by mass of the vinyl resin Mass parts of styrene-based monomers are impregnated and polymerized. The xylene-insoluble matter in the Soxhlet extraction of the above composite resin with xylene and the acetone-insoluble matter contained in the xylene solution after the Soxhlet extraction The swelling degree of the mixed insoluble substance in methyl ethyl ketone at a temperature of 23°C is 1.25 or more.

The panel packing container includes a container body having the accommodating portion, and a lid body that closes the opening of the container body. The container body and the lid body are preferably formed of the expanded particle molded body. In this case, since it becomes possible to seal the inside of the accommodating portion, it is possible to prevent the mixing of foreign matter and the like. In addition, not only on the side of the container body, but also on the side of the lid, the above-mentioned housing portion can be formed.

In the panel packing container, it is preferable that an antistatic agent is present on at least the surface of the expanded particle molded body, and the surface resistivity of the expanded 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 liquid crystal panels or photovoltaic power generation panels. In addition, the surface resistivity of the expanded particle molded body is a value measured under an environment of 23° C. and a relative humidity of 50% in accordance with JIS C2170-2004.

The antistatic agent can be contained in the expanded particle molded body by any one of the following methods or a combination of these. Specifically, there are a method of mixing the antistatic agent into the vinyl resin during granulation of the core particles, a method of adding the antistatic agent during polymerization, and a method of adding the antistatic agent when foaming the composite resin particles The method of impregnating the expanded particles, the method of applying the antistatic agent to the expanded particles, the method of applying the antistatic agent to the expanded particle molded body, etc.

As an antistatic agent system, a cationic surfactant, anionic At least one selected from the group of surfactants, amphoteric surfactants, and nonionic surfactants. Preferably, a cationic surfactant and an anionic surfactant are used in combination as an antistatic agent.

[Example] (Example 1)

Hereinafter, examples of the expanded particle molded body will be described. In this example, the composite resin expanded particles are produced from the core particles as follows, and the expanded resin molded particles are produced using the composite resin expanded particles.

(1) Production of nuclear particles

As the ethylene-based resin system, there is prepared a linear low-density polyethylene polymerized using a metallocene polymerization catalyst (specifically, "Nipolon Z HF210K" manufactured by TOSOH Corporation). Hereinafter, the vinyl resin of this example is appropriately referred to as "PE-1". Under the conditions of PE-1 at a temperature of 190°C and a load of 2.16 kg, MFR (unit: g/10min), density (unit: kg/m ³ ), tensile modulus of elasticity (unit: MPa), melting point (unit: ℃) ) Is shown in Table 1 described later. The MFR under the condition of PE-1 at a temperature of 190°C and a load of 2.16 kg is a value measured under condition code D according to JIS K7210-1999. In addition, MELT INDEXER (specifically, Model L203 manufactured by Takara Industrial Co., Ltd., etc.) is used as the measuring device. In addition, the tensile elastic modulus of PE-1 is the value measured based on JIS K6922-2-2010. The melting point of PE-1 is about 5 mg of the raw material ingot of PE-1, which is measured by heat flux differential scanning calorimetry (ie, DSC) according to JIS K7121-1987. In addition, in the regulation of JIS K7121-1987, as the condition adjustment of the test piece, "(2) After a certain heat treatment, the melting temperature is measured", the heating rate and the cooling rate are both set to 10°C/ The melting peak temperature measured by the minute is the melting point.

In addition, it is prepared as a masterbatch system for the bubble adjuster (specifically, "CE-7335" manufactured by POLYCOL Co., Ltd.). In addition, the "CE-7335" made by POLYCOL Co., Ltd. is a linear low-density polyethylene containing 10% by mass of a bubble adjuster composed of zinc borate (specifically, "Nipolon Z HF210K" made by TOSOH) The content is 90% by mass.

8.65 kg of a vinyl resin (specifically, PE-1) and 1.35 kg of a masterbatch of a bubble adjuster were put into a Henschel mixer and mixed for 5 minutes to obtain a resin mixture. Next, using a 50 mm φ uniaxial extruder, the resin mixture was melted and kneaded at the maximum set temperature of the extruder at 250° C., and was cut into an average of 0.5 mg/piece by water cutting, thereby obtaining core particles (also That is, vinyl resin core particles).

(2) Fabrication of composite resin particles

Into an autoclave with an internal volume of 3 L equipped with a stirring device was charged with 1000 g of deionized water, and 6.0 g of sodium pyrophosphate was further added. Thereafter, 12.9 g of powdered magnesium nitrate‧6 hydrate was added, and the mixture was stirred at room temperature for 30 minutes. In this way, a magnesium pyrophosphate slurry as a suspending agent was produced. Next, lauryl sulfonic acid with a concentration of 10% by mass as a surfactant was put into this suspending agent 2.0 g of an aqueous sodium solution, 0.2 g of sodium nitrite as a water-soluble polymerization inhibitor, and 75 g of core particles. This is a dispersing step.

Next, 1.72 g of t-butylperoxy-2-ethylhexyl monocarbonate as a polymerization initiator A (specifically, "PERBUTYL E" manufactured by NOF Corporation) and t as a polymerization initiator B -0.86 g of butyl peroxybenzoate (specifically, "PERHEXYL Z" manufactured by NOF Corporation), and α-methylstyrene dimer as a chain transfer agent (specifically, "made by NOF Corporation" Nofmer MSD") 0.63 g was dissolved in the first monomer (specifically, styrenic monomer). Then, the dissolved substance was poured into the suspending agent in the autoclave while stirring at a stirring speed of 500 rpm. In addition, as the first monomer system, a mixed monomer of 70 g of styrene and 15 g of butyl acrylate was used.

Next, after replacing the air in the autoclave with nitrogen, the temperature was started, and the temperature was raised to a temperature of 100°C in 1 hour and 30 minutes. After raising the temperature, the temperature was kept at 100°C for 1 hour. Thereafter, the stirring speed was decreased to 450 rpm, and the temperature was maintained at 100°C for 7.5 hours. This is a modification step. In addition, when one hour passed after reaching the temperature of 100° C., 350 g of styrene as the second monomer (specifically, a styrene-based monomer) was added to the autoclave over 5 hours.

Next, it took 2 hours to raise the temperature to 125°C, and directly held at this temperature for 125 hours. Thereafter, the inside of the autoclave was cooled, and the contents (specifically, composite resin particles) were taken out. Nitric acid is added to dissolve the magnesium pyrophosphate attached to the surface of the composite resin particles. After that, dehydration and washing are carried out by a centrifugal separator, and the adhesion to the air dryer is removed. Moisture on the surface thereby obtained composite resin particles having a mass ratio of styrene-based resin to vinyl-based resin of 85:15 determined from the mass ratio of styrene-based monomer to vinyl-based resin.

(3) Production of composite resin expanded particles

Next, 500 g of composite resin particles were put into a 5 L pressure vessel equipped with a stirrer together with a dispersion medium (specifically, water), and 5 g of kaolin as a dispersant and alkane as a surfactant were further added to the dispersion medium Sodium benzene sulfonate 0.5g. Next, while stirring in a pressure vessel at a rotation speed of 300 rpm, the temperature was raised to a foaming temperature of 165°C. Then, carbon dioxide, which is an inorganic blowing agent, is pressed into the pressure vessel so that the gauge pressure in the pressure vessel becomes 3.2 MPa, and the carbon dioxide is kept at the same temperature (that is, 165°C) for 15 minutes. Impregnated with composite resin particles to obtain expandable composite resin particles. Next, by exposing the expandable composite resin particles together with the dispersion medium to the atmospheric pressure from the pressure vessel, composite resin expanded particles having a bulk density of 48 kg/m ³ (that is, primary expanded particles) were obtained.

Next, 100 parts by mass of the composite resin expanded particles obtained as described above and 2 parts by mass of an antistatic agent (specifically, the cationic surfactant "CATIOGEN ES-O" manufactured by First Industrial Pharmaceutical Co., Ltd.), And 1 part by mass of non-ionic antistatic agent (specifically, glycerol monostearate) is packed in a polyethylene bag, and after sufficient vibration mixing, the composite resin expanded particles are dried in an oven at a temperature of 40°C. 12 hour.

(5) Manufacture of shaped foam particles

The composite resin expanded particles obtained in the above manner were filled in a mold having a cavity having a flat plate shape 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 expanded particles are heated to be welded to each other. Thereafter, after cooling the inside of the mold by water cooling, the expanded particle molded body is taken out from the mold. Furthermore, by placing the expanded particle molded body in an oven adjusted to a temperature of 60° C. for 12 hours, drying and curing treatment was performed. The expanded particle shaped body is manufactured in the above manner.

For the obtained expanded particle molded body, the mass ratio of the styrene resin and the vinyl resin in the composite resin calculated from the blending composition (that is, styrene resin/vinyl resin), and the acrylic acid in the composite resin The content of butyl ester (unit: mass%) is shown in Table 2 described later. The molding pressure (unit: MPa) and water cooling time (unit: second) during molding are shown in Table 2 described later as molding conditions. Furthermore, for the expanded particle molded body, the swelling degree, the ratio of xylene-insoluble matter (unit: %), the weight average molecular weight Mw of the styrene-based resin, and the apparent density (unit: kg/m ^{2) were} measured as follows. ), bending elastic modulus (unit: MPa), bending elastic energy (unit: kJ/cm ² ), compressive strength (unit: kPa), surface resistivity (unit: Ω). The results are shown in Table 2 described later.

"Swelling"

First, a test piece of about 1 g was cut out of the expanded particle molded body, and its weight W _{0 was} measured to the fourth place in the summary. Next, the test piece was placed in a 150-mesh wire mesh bag. Next, about 200 ml of xylene was placed in a round flask with a capacity of 200 ml, and the sample placed in the wire mesh bag was set in a Soxhlet extraction tube. The flask was heated with a mantle heater for 8 hours, thereby performing Soxhlet extraction. After the extraction is completed, it is cooled by air cooling. After cooling, remove the wire mesh from the extraction tube and wash each wire mesh sample with about 600 ml of acetone. Next, after volatilizing acetone, it was dried at a temperature of 120°C. After drying here, the sample recovered from the barbed wire is "xylene insoluble material".

Furthermore, the xylene solution after the Soxhlet extraction was put into 600 ml of acetone. Next, the components insoluble in acetone were filtered using five types of A filter papers prescribed in JIS P3801, separated and recovered, and the recovered material was evaporated to dryness under reduced pressure. The obtained solid substance is "acetone-insoluble substance".

Mixing the insoluble matter obtained in the measurement by the sum of these "xylene-insoluble matter" and "acetone-insoluble" W _a weight to 4 decimal places. In addition, in other examples, when the weight of the mixed insoluble material is less than 0.2 g, in order to obtain a sufficient amount of mixed insoluble material, the above operation is repeated to obtain 0.2 g or more of mixed insoluble material. It is the same in other embodiments.

Next, the mixed insoluble material 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 the methyl ethyl ketone and wiped lightly with filter paper, and the weight W _{b of the} mixed insoluble matter was measured to the fourth decimal place. Next, based on the weights W _a and W _b of the mixed insoluble matter before and after the immersion of methyl ethyl ketone, the swelling degree S was determined by the following formula (1).

S=Wb/Wa. . . (1)

"Proportion of insoluble xylene"

The ratio of the xylene-insoluble substance is the ratio (specifically, percentage) of the weight W ₁ of the xylene-insoluble substance obtained by the measurement of the swelling degree to the weight W ₀ of the test piece measured at the swelling degree. That is, the ratio (unit: %) of xylene-insoluble substances is calculated from W ₁ /W ₀ ×100. In addition, the ratio of xylene-insoluble substances is shown as "XY gel amount" in the table.

"Weight average molecular weight of styrene resin (ie, Mw)"

First, Soxhlet extraction is performed in the same manner as the above method. Next, the extracted xylene solution was dropped into 600 ml of acetone, decanted, and evaporated to dryness under reduced pressure. As a result, styrene-based resin is obtained as an acetone-soluble substance. Next, the weight average molecular weight of the styrene-based resin was measured by gel permeation chromatography (that is, GPC method) using polystyrene as a standard substance. In the measurement, a mixed gel column for polymer measurement was used. Specifically, it uses the measurement device "HLC-8320GPC EcoSEC" made by TOSOH (share), in the eluent: tetrahydrofuran (that is, THF), flow rate: 0.6 ml/min, sample concentration: 0.1 wt%, column: TSKguardcolumn SuperH-H×1, TSK-GEL SuperHM-H×2 connected in series under measurement conditions. That is, the weight average molecular weight system is obtained by dissolving styrene resin in tetrahydrofuran, measuring by GPC method, and correcting with standard polystyrene.

"Apparent density"

The apparent density is calculated by dividing the mass of the expanded particle molded body by its volume.

"Bending Elasticity"

The bending elastic modulus is measured in accordance with the three-point bending test method described in JIS K 7221-1999. The bending modulus of elasticity is such that a test piece with a thickness of 20 mm×width 25 mm×length 120 mm is cut from the composite resin expanded particle molded body so that the entire surface becomes a cutting surface, and placed in a constant temperature and humidity room at a room temperature of 23° C. and a humidity of 50% After 24 hours or more, under the conditions of a distance of 100 mm between the fulcrums, a radius R15.0 mm of the indenter, a radius R15.0 mm of the support table, a test speed of 20 mm/min, a room temperature of 23° C., and a humidity of 50%, manufactured by Shimadzu Corporation The test machine "autograph AGS-10kNG" was used for measurement, and the calculated average value of 5 points was used.

"Bending Breaking Energy"

The 3-point bending test was carried out in the same manner as the above-mentioned measurement of the bending elastic modulus, and the energy (unit: kJ) to the breaking point was obtained from the relationship between the amount of deflection (unit: mm) and the load (unit: kN). The energy is calculated from the area surrounded by the deflection-load curve to the breaking point and the horizontal axis representing the deflection. Next, by dividing the energy (unit: kJ) to the breaking point by the cross-sectional area (unit: cm ² ) of the test piece, the bending breaking energy (unit: kJ/cm ² ) per unit cross-sectional area was calculated.

"Compression Strength"

A cuboid test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm was cut from the central portion of the expanded particle molded body. Next, for this test piece, in accordance with JIS K 6767-1999, the compression load at 50% strain was obtained. The compressive stress (specifically 50% compressive stress) was calculated by dividing this compressive load by the compression area of the test piece. In this specification, this compressive stress is also called compressive strength.

"Surface Resistivity"

The surface resistivity of the expanded particle molded body was measured in the following manner.

Immediately after manufacturing the expanded particle molded body under the conditions of 23°C and 50% RH and then curing it for 1 day, the method is performed under the conditions of 23°C and 50% RH by following the method of JIS C2170-2004 Determination. First, a cuboid measuring test piece in a state of longitudinal: 100 mm, lateral: 100 mm, thickness: thickness of the molded body (that is, 50 mm) was cut out from the vicinity of the center of the expanded particle molded body. Five measurement test pieces were prepared. Using "Hiresta MCP-HT450" manufactured by Mitsubishi Chemical Corporation as the measuring device, measuring The surface resistivity (unit: Ω) of the forming surface of each test piece. The value obtained by adding the geometric mean to the surface resistivity values obtained from each of the five measurement test pieces was used.

(Example 2)

In this example, first, the amount of vinyl resin (ie, PE-1) was changed from 8.65 kg to 9 kg, and the amount of the masterbatch of the bubble adjuster was changed from 1.35 kg to 1 kg. In the same manner as in Example 1, core particles were produced. Next, using 100 g of the core particles, using a mixed monomer of 85 g of styrene and 15 g of butyl acrylate as the first monomer, and using 300 g of styrene as the second monomer, it was produced in the same manner as in Example 1. Composite resin particles. Then, using this composite resin particle, an expanded particle molded body was produced in the same manner as in Example 1.

(Example 3)

In this example, first, the amount of the vinyl resin (ie, PE-1) was changed from 8.65 kg to 8 kg, and the amount of the masterbatch of the bubble adjuster was changed from 1.35 kg to 2 kg. In the same manner as in Example 1, core particles were produced. Next, using 53 g of the core particles, a mixed monomer of 38 g of styrene and 15 g of butyl acrylate as the first monomer, and 394 g of styrene as the second monomer, except that it was produced in the same manner as in Example 1. Composite resin particles. Then, using this composite resin particle, an expanded particle molded body was produced in the same manner as in Example 1.

(Comparative example 1)

An ethylene-vinyl acetate copolymer (that is, EVA) is prepared as an ethylene-based resin system. Specifically, "NUC-3221" manufactured by Japan Unicar Corporation was used as the EVA. The vinyl resin in this example is hereinafter referred to as "PE-2" as appropriate. The MFR (unit: g/10min), density (unit: kg/m ³ ), tensile modulus of elasticity (unit: MPa), melting point (unit: ℃) of PE-2 at a temperature of 190°C and a load of 2.16 kg ) Is shown in Table 1 described later. These are the values measured in the same manner as in Example 1 above. In this example, instead of 8.65 kg of PE-1 used as the ethylene-based resin in the production of the core particles in Example 1, 10 kg of PE-2 was used, and the amount of the masterbatch of the bubble regulator was from 1.35 kg Other than changing to 0 kg, the core particles were produced in the same manner as in Example 1.

Next, after preparing a suspending agent (specifically, magnesium pyrophosphate slurry) in the same manner as in Example 1, 2.0 g of an aqueous solution of sodium lauryl sulfonate having a concentration of 10% by mass as a surfactant was added to the suspending agent. , 0.2 g of sodium nitrite as a water-soluble polymerization inhibitor, and 150 g of the above-mentioned core particles. Next, 1.29 g of benzoyl peroxide as a polymerization initiator A (specifically, "NYPER BW" manufactured by NOF Corporation, water-diluted powder product) and t-butyl as a polymerization initiator B Oxy-2-ethylhexyl monocarbonate (specifically, "PERBUTYL E" manufactured by NOF Corporation) 2.58 g, and dicumyl peroxide as a polymerization initiator C (specifically, NOF Corporation) ("PERCUMYL D") 0.86 g was dissolved in the first monomer (specifically, a styrene-based monomer). Then, the dissolved substance was put into the suspension in the autoclave while stirring at a stirring speed of 500 rpm. In the agent. In addition, 150 g of styrene was used as the first system.

Next, after replacing the air in the autoclave with nitrogen, the temperature was started, and the temperature was raised to 88°C in 1 hour and 30 minutes. After raising the temperature, the temperature was kept at 88°C for 30 minutes. Thereafter, the stirring speed was reduced to 450 rpm, and it took 30 minutes to cool from 88°C to 80°C. Next, the polymerization temperature was kept at 80°C for 8 hours. In addition, when the temperature reached 80° C., 200 g of styrene as a second monomer (specifically, a styrene-based monomer) was added to the autoclave over 5 hours.

Next, it took 4 hours to increase the temperature to 125°C, and it was kept at this temperature for 125 hours for 2 hours and 30 minutes. After that, it took 1 hour to cool to 90°C, the stirring speed was reduced to 400 rpm, and the temperature was directly maintained at 90°C for 3 hours. On the other hand, when the temperature reached 90°C, 20 g of cyclohexane as a blowing agent and 65 g of butane were added to the autoclave in 1 hour. Butane is a mixture of about 20% by volume of normal butane and about 80% by volume of isobutane. Furthermore, it took 2 hours to raise the temperature to 105°C, and after maintaining the temperature at 105°C for 5 hours, it took about 6 hours to cool to a temperature of 30°C. After cooling, the contents were taken out, and nitric acid was added to dissolve the magnesium pyrophosphate adhered to the surface of the resin particles. After that, it was dehydrated and washed with a centrifugal separator, and the water attached to the surface was removed by an airflow drying device to obtain foamable composite resin particles. Next, an antistatic agent (specifically, N,N-bis(2-hydroxyethyl)alkylamine) is added to the expandable composite resin particles, and further, zinc stearate and glycerol monostearate , And a mixture of glyceryl distearate is coated. The expandable composite resin particles were produced in the above manner.

Next, the expandable composite resin particles obtained in the above manner were charged into an atmospheric pressure batch type foaming machine with a volume of 30 L, and steam was supplied into the foaming machine. In this way, expandable composite resin particles of composite resin expanded particles (that is, primary expanded particles) having a bulk density of 48 kg/m ^{3 were} produced. Then, using this composite resin expanded particle, an expanded particle molded body was produced in the same manner as in Example 1.

(Comparative example 2)

Into an autoclave with an internal volume of 3 L equipped with a stirring device was charged with 1100 g of deionized water, and 6.6 g of sodium pyrophosphate was further added. Thereafter, 14.2 g of powdered magnesium nitrate‧6 hydrate was added, and the mixture was stirred at room temperature for 30 minutes. In this way, a magnesium pyrophosphate slurry as a suspending agent was produced. Next, 2.2 g of a 10% by mass aqueous solution of sodium lauryl sulfonate as a surfactant, 0.22 g of sodium nitrite as a water-soluble polymerization inhibitor, and 56 g of the same core particles as in Example 1 were put into this suspending agent. .

Next, 1.29 g of benzoyl peroxide as a polymerization initiator A (specifically, "NYPER BW" manufactured by NOF Corporation, water-diluted powder product) and t-butyl as a polymerization initiator B Oxy-2-ethylhexyl monocarbonate (specifically, "PERBUTYL E" manufactured by NOF Corporation) 2.58 g, and dicumyl peroxide (specifically, manufactured by NOF Corporation) PERCUMYL D") 0.86 g was dissolved in the first monomer (specifically, a styrene monomer). Then, the dissolved substance was poured into the suspending agent in the autoclave while stirring at a stirring speed of 500 rpm. In addition, 100g of styrene and butyl acrylate were used as the first single system Mixed monomer of 12g of ester.

Next, after replacing the air in the autoclave with nitrogen, the temperature was started, and the temperature was raised to 88°C in 1 hour and 30 minutes. After raising the temperature, the temperature was kept at 88°C for 30 minutes. Thereafter, the stirring speed was reduced to 450 rpm, and it took 30 minutes to cool from 88°C to 80°C. Next, the polymerization temperature was kept at 80°C for 8 hours. In addition, when the temperature reached 80° C., 231 g of styrene as a second monomer (specifically, a styrene-based monomer) was added to the autoclave over 5 hours.

Next, it took 4 hours to increase the temperature to 125°C, and it was kept at this temperature for 125 hours for 2 hours and 30 minutes. Thereafter, it took about 6 hours to cool to a temperature of 30°C to produce composite resin particles. Then, using this composite resin particle, an expanded particle molded body was produced in the same manner as in Example 1.

(Comparative example 3)

In this example, first, the amount of vinyl resin (specifically, PE-1) was changed from 8.65 kg to 9.35 kg, and the amount of the masterbatch of the bubble regulator was changed from 1.35 kg to 0.65 kg. In the same manner as in Example 1, core particles were produced. Next, using 150 g of the core particles, using a mixed monomer of 135 g of styrene and 15 g of butyl acrylate as the first monomer, and using 200 g of styrene as the second monomer, it was produced in the same manner as in Example 1. Composite resin particles. Then, using this composite resin particle, an expanded particle molded body was produced in the same manner as in Example 1.

(Results of Examples and Comparative Examples)

For the expanded particle molded bodies produced in Examples 2 to 3 and Comparative Examples 1 to 3, the same evaluation results as in Example 1 are shown in Table 1 and Table 2.

As is known from Table 2, it is implemented by impregnating and polymerizing styrene-based monomers of 400 to 900 parts by mass for 100 parts by mass of vinyl resin, and having a swelling degree of 1.25 or more. The foamed particle forming systems of Examples 1 to 3 have a high bending elastic modulus, and further, the bending breaking energy is also high. Therefore, the above-mentioned expanded particle molding system is excellent in bending resistance, and can prevent damage due to deformation. Furthermore, the expanded particle forming system for the panel packing container of Examples 1 to 3 is excellent in compression recovery even if the compression strength is high.

On the other hand, in Comparative Example 1, since it has ethylene-vinyl acetate copolymer as the ethylene-based resin and the hydrogenation reaction energy used in the polymerization initiator is dicumyl peroxide, the cross-linkage in the ethylene-based resin The link density is easy to increase, while the swelling degree is too low. Therefore, the bending breaking energy is insufficient, and it is easy to cause damage due to deformation. Furthermore, since the amount of styrene-based resin in the composite resin is too small, there is a problem that the compressive strength or bending elastic modulus is low. In addition, since an organic foaming agent such as butane is used as the foaming agent, the organic foaming agent will remain in the composite resin foamed particles, and the forming water cooling time will be longer than that when carbon dioxide is used as the foaming agent. .

In Comparative Example 2, if compared with Comparative Example 1, the amount of styrene resin in the composite resin is large, so the compressive strength or bending elastic modulus is as high as comparable to the Examples. However, in Comparative Example 2, the production ratio of the styrene-based monomer (that is, the first monomer) initially impregnated into the core particles during the production of the composite resin particles was too large, and the reaction energy using hydrogen extraction was high No. 2 Cumene peroxide is used as a polymerization initiator Moisture is too low. Therefore, the bending breaking energy is insufficient, and it is easy to cause damage due to deformation.

Comparative Example 3 is an example in which the amount of styrene monomer impregnated and polymerized in the core particles is small, and the rigidity of the expanded particle molded body is low. Therefore, there is a problem that the compressive strength or bending elastic modulus is low, and it is easily deformed.

(Example 4)

This example is an example of a panel packing container composed of a molded product of expanded particles.

As shown in FIGS. 1 to 3, the panel packing container 1 of this example is composed of a foamed particle molded body, and has an accommodating portion for accommodating a plurality of panels 4 in a state of being stacked in the plate thickness direction 10. The panel packing container 1 includes a container body 2 and a lid body 3 that closes the opening 21 of the container body 2. Any one of the container body 2 and the lid body 3 is formed of a molded foamed body. The panel packing container 1 can be used to house a panel 4 such as a liquid crystal panel, for example. As the expanded particle molding system, the same molded bodies as in Examples 1 to 3 described above can be used.

Hereinafter, the panel bag container 1 will be described in further detail.

As shown in FIG. 3, the container body 2 has a storage portion 20 that stores a plurality of panels 4 in a stacked state in the plate thickness direction, and has a box shape with an opening 21 on the upper surface. Specifically, the container body 2 is composed of a bottom plate portion 22 and a side wall portion 23 standing perpendicular to the peripheral edge of the bottom plate portion 22 Posed. In addition, the lid body 3 has a box-like shape in which the stacked panel 4 is housed from above and has an opening 31 at the bottom. Specifically, the lid 3 is composed of the upper plate portion 32 and the side wall portion 33 extending perpendicularly to the peripheral edge of the upper plate portion 32. The side wall 23 of the container body 2 and the side wall 33 of the lid body 3 are formed with convex portions 231 and concave portions 331 at positions and shapes where the two fit.

As shown in FIGS. 2 and 3, in the panel bag container 1 of this example, both the container body 2 and the lid body 3 have the accommodating portions 20 and 30. Furthermore, the storage unit 10 in the panel packing container 1 is formed by the storage unit 20 and the storage unit 30, and a plurality of panels 4 are stored in the storage unit 10 in a stacked state.

The panel packing container 1 of this example is constituted by the expanded particle shaped bodies of the above examples 1 to 3. Therefore, even if a plurality of panels 4 with a large weight are accommodated in the accommodating portion 10, the panel packing container 1 is less likely to be flexed due to the weight of the panel 4, and thus not easily damaged due to deformation. Therefore, even if the panel pack container 1 is stacked in the pack state, or a sudden load change occurs during movement in the pack state, the occurrence of breakage can be prevented. FIG. 4 shows a state in which the panel bundling container 1 of this example is gripped at both ends in the longitudinal direction, and the panel bundling container 1 is lifted. As shown in the figure, the panel packing container 1 is bent by the weight of the panel 4 accommodated in the accommodating portion 10. The panel packing container 1 of this example is the same as the above Examples 1 to 3, because it is made by impregnating and polymerizing styrene-based monomers of 400 to 900 parts by mass for 100 parts by mass of the vinyl resin, and It is composed of a molded body of expanded particles made of a composite resin with a swelling degree of 1.25 or more, Therefore, as shown in Fig. 4, the amount of deflection is small. In addition, FIG. 5 shows a state in which the panel bundling container 1 of this example is gripped at both ends in the short-side direction and the panel bundling container 1 is lifted, and in this case, the amount of deflection is also small. In addition, in FIG. 4 and FIG. 5 described above, and FIG. 6 and FIG. 7 described later, although the illustration of the panel in the panel packing container 1 is omitted for the convenience of drawing, there are actually a plurality of panels Be contained inside.

In the above example, although either the container body 2 or the lid 3 has the storage portions 20, 30 of the panel 4, the container body 2 may be changed to have the storage portion, and the cover 3 does not have the storage portion 3. Construction. In this case, although the illustration is omitted, the lid 3 is formed into a plate shape.

(Comparative example 5)

This example is an example of a panel wrapping container formed in the same shape as in Example 4 described above, but composed of the expanded particle molded body of Comparative Example 3 described above. The panel packing container 9 of this example is composed of the expanded particle molded body of Comparative Example 3, and has the same shape as that of Example 4 described above, and is composed of the container body 91 and the lid 92. The panel packing container 9 of this example is composed of the expanded particle molded body of Comparative Example 3 in which the bending elastic modulus is insufficient. Therefore, as shown in FIG. 6 and FIG. 7, the panel packing container 9 is greatly 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 possibility that the panel may fall or the panel may be damaged. In addition, although the illustration is omitted, the panel packing container 9 is as shown in the above Comparative Example 1 and Comparative Example 2, and is deformed by bending when it is formed of a foamed particle molded body having a small bending breaking energy Panel The bag container 9 is easily damaged.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-mentioned embodiments, and various changes can be made within the scope not detracting from the interest of the present invention.

1‧‧‧Panel container

2‧‧‧Container body

3‧‧‧cover

23‧‧‧Wall part

32‧‧‧ Upper Board Department

33‧‧‧Side wall

231‧‧‧Convex

331‧‧‧recess

Claims (6)

An expanded particle molded body is an expanded particle molded body formed by in-mold molding of a composite resin expanded particle. The composite resin constituting the expanded particle molded body is 100 parts by mass of ethylene-based resin as 400~900 parts by mass of styrene monomer is impregnated and polymerized. The above-mentioned vinyl resin is linear low-density polyethylene. The xylene-insoluble substance and the above-mentioned resin when the composite resin is subjected to Soxhlet extraction by xylene The swelling degree of the mixed insoluble matter of the acetone insoluble matter contained in the xylene solution after the extraction in the methyl ethyl ketone at a temperature of 23°C is 1.25 or more. The expanded particle molded body according to claim 1, wherein the above-mentioned ethylene-based resin is a linear low-density polyethylene having a melting point of 105° C. or less, which is polymerized using a metallocene-based polymerization catalyst. The expanded particle molded body according to claim 1 or 2, wherein the above-mentioned composite resin is obtained by impregnating and polymerizing a styrene-based monomer that is more than 450 parts by mass and less than 900 parts by mass for 100 parts by mass of the ethylene-based resin. . The expanded particle molded body according to claim 1 or 2, wherein the apparent density of the expanded particle molded body is 30 to 100 kg/m ³ . A panel bundling container, which is a panel bundling container composed of the expanded particle shaped body according to any one of claims 1 to 4, which has a plurality of panels stacked in a state of being stacked in the thickness direction Containment Department. The panel packing container according to claim 5, wherein an antistatic agent is present on at least the surface of the expanded particle molded body, and the surface resistivity of the expanded particle molded body is 1×10 ⁸ to 1×10 ¹³ Ω.

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