TWI749014B - Composite resin foamed particles, antistatic composite resin foamed particles, and composite resin foamed particle molded body - Google Patents

Abstract

The present invention provides a composite resin foamed particle, a charge-preventable composite resin foamed particle, and a molded body using the same. The composite resin has a high proportion of the styrene resin component, and the internal fusion is good, stable and stable. A molded body with excellent anti-static properties.

A composite resin foamed particle in which a composite resin impregnated with a polymerized styrene-based monomer in a vinyl resin is used as a base resin, a charge-preventing composite resin foamed particle in which the foamed particle has been coated with a charge preventive agent, and the molded body . The composite resin contains a component derived from a vinyl resin and a component derived from a styrene monomer in a specific ratio. A mixture of ethylene-based resin-based linear low-density polyethylene and an ethylene-based copolymer with a polar group, and the content of the ethylene-based copolymer with a polar group in the ethylene-based resin is adjusted to a specific range. The water vapor adsorption capacity of the composite resin expanded particles is 0.50 cm ³ /g or more.

Description

Composite resin foamed particles, antistatic composite resin foamed particles, and composite resin foamed particle moldings

The present invention relates to composite resin foamed particles, charge-preventable composite resin foamed particles, and charge-preventable composite resin foamed particles in which a composite resin in which a styrene-based monomer is impregnated and polymerized in a vinyl resin is used as the base resin. Fusion shaped body.

In-mold moldings of composite resin foamed particles containing ethylene resin components and styrene resin components (ie, composite resin foamed particle moldings) are widely used as packaging containers for parts of electronic equipment or precision equipment Or cushioning packaging materials. In order to prevent the adhesion of dust or electrical damage caused by overcurrent such as discharge, the molding system for such applications is generally provided with anti-static properties.

As a method of obtaining composite resin expanded particles, the following methods are known, for example. Specifically, first, by impregnating and polymerizing a styrene-based monomer in a core particle containing a vinyl-based resin component, a composite resin containing a vinyl-based resin component and a styrene-based resin component as a base resin is obtained. Resin particles. Next, the composite resin particles are impregnated with a foaming agent, and the composite resin particles are foamed to obtain composite resin foam particles (see Patent Documents 1 to 3). As the above-mentioned ethylene-based resin system, an ethylene-based copolymer having a polar group such as linear low-density polyethylene or an ethylene-vinyl acetate copolymer, a mixture of these, and the like can be used.

In addition, as a method of imparting antistatic performance to the expanded particle molded article, generally, a antistatic agent composed of a surfactant or the like can be added. Specifically, a method of impregnating composite resin particles with a volatile blowing agent or impregnating an anti-static agent after impregnation is known. In addition, a method of applying an antistatic agent to composite resin expanded particles is also known.

The method of impregnating the anti-static agent during the impregnation of the volatile foaming agent is that the resin particles are excessively plasticized due to the anti-static agent. There is a concern that the heat resistance of the expanded particles decreases during molding and the molded body is deformed or foaming Doubts about reduced fusion of particles. Therefore, as in Patent Document 4, a method of applying a cationic antistatic agent to composite resin expanded particles in a specific amount has been developed.

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] International Publication No. 2007/138916

[Patent Document 2] JP 2015-189911 A

[Patent Document 3] JP 2005-97555 A

[Patent Document 4] JP 2015-81274 A

On the other hand, in order to maintain the toughness or resilience of the composite resin expanded particle molded body while increasing the rigidity, a technology has been developed to increase the ratio of the styrene resin component in the composite resin. However, as the composite resin foamed particles disclosed in Patent Documents 1 to 3, when an ethylene resin containing an ethylene copolymer having a polar group such as an ethylene-vinyl acetate copolymer is used as a core particle, if it is improved The ratio of the styrene-based resin component in the composite resin is suspected of lowering the fusion property of the expanded particles. Also, in this case, in the case where the content of the ethylene copolymer having a polar group has been reduced, although the fusion property of the expanded particles is in a tendency to be improved, there is still room for further improvement. In addition, when the content of the ethylene-based copolymer having a polar group is further reduced, there is a concern that the fixability of the anti-static agent may be reduced. Therefore, it is difficult to obtain expanded particles that have a high ratio of the styrene-based resin component in the composite resin and are excellent in fusibility and fixability of the anti-charge agent.

In addition, as described in Patent Document 4, the method of applying the antistatic agent to the composite resin expanded particles may have insufficient fixability of the antistatic agent. Depending on the heating conditions during the in-mold molding, for example, it may be caused by steam. There is a concern that the anti-static agent adhered to the expanded particles may partially flow out due to the heating medium. Depending on the position of the molded body, the adhesion amount of the anti-static agent decreases, etc., and it is difficult to stably obtain the molding with the desired anti-static performance. body.

The present invention was made in view of such a background, and it is intended to provide a composite resin foamed particle, a charge-preventable composite resin foamed particle, and a molded body using the charge-preventable composite resin foamed particle, which can be obtained in a composite resin The styrene-based resin component has a high proportion, and the internal fusion is good, and it is stable and has excellent anti-static properties.

One aspect of the present invention is a composite resin foamed particle in which a composite resin in which a styrene-based monomer is impregnated and polymerized in a vinyl resin is used as a base resin. The mass% of the component derived from the above-mentioned ethylene-based resin, and the component derived from the above-mentioned styrene-based monomer exceeding 80% by mass and 95% by mass or less (however, the total of the two is 100% by mass.), the above-mentioned ethylene-based resin A mixture of linear low-density polyethylene and an ethylene copolymer having a polar group, the content of the ethylene copolymer having the polar group in the ethylene resin is 1 to 45% by mass, the composite resin foamed particles Composite resin foam particles with a water vapor adsorption capacity of 0.50 cm ^{3 /g or more.}

Another aspect of the present invention is an anti-static composite resin foamed particle, the surface of the composite resin foamed particle is coated with an anti-static agent containing a cationic surfactant.

In another aspect of the present invention, the anti-static composite resin foam particles are formed bodies fused with each other, and the composite resin foam particles formed bodies having a surface resistivity of less than 1×10 ¹² Ω.

The above-mentioned composite resin expanded particles (hereinafter, appropriately referred to as "expanded particles") are based on the ethylene resin containing linear low-density polyethylene and an ethylene copolymer having a polar group at a high blending ratio. The composite resin impregnated with polymerized styrene monomer is used as the base resin, and the above specific ethylene copolymer contains the above specific amount, and the amount of water vapor that the expanded particles can absorb, that is, the amount of water vapor adsorbed is adjusted to the above specific amount. Value above. Therefore, even if the antistatic agent is applied to the expanded particles, the expanded particles can sufficiently adsorb and retain the antistatic agent. Since the outflow of the antistatic agent during molding can be suppressed, a stable compound with good antistatic properties can be obtained. A molded body of expanded resin particles (hereinafter, appropriately referred to as a "molded body"). In addition, in the case of using an ethylene resin containing a high proportion of the styrene resin component in the composite resin and an ethylene copolymer having a polar group at the same time, the internal fusion of the molded body, that is, the fusion of the expanded particles Excellent performance. Therefore, the molding system can exhibit strength characteristics such as the inherently excellent compression rigidity and flexural resistance of the composite resin based on the composition of the ethylene resin or styrene resin. In addition, the aforementioned antistatic composite resin expanded particles can also exhibit the same effects as the aforementioned expanded particles.

In addition, the anti-static composite resin foamed particles are fused with each other, and ^{the molding system with a surface resistivity of less than 1×10 12} Ω is not only excellent in anti-static performance, because the foamed particles constituting the molded body are fully fused with each other, Therefore, the strength characteristics such as compression rigidity and flexural resistance are excellent as described above. Therefore, the molding system using antistatic composite resin foamed particles is suitable for applications such as packaging containers or cushion packaging materials for electronic equipment such as liquid crystal panels and solar power generation panels or parts of precision equipment.

Next, a description will be given of a preferred embodiment of the above-mentioned expanded particles. The expanded particle system is used, for example, in the application of applying an antistatic agent to the surface. The expanded particles for such applications can be said to have a charge preventive agent contact surface on which the charge preventive agent adheres on the surface.

Expanded particles can be used because a molded body is obtained by in-mold molding. That is, by filling a large number of expanded particles in a molding die, and fusing the composite resin particles with each other in the molding die, a molded body of a desired shape can be obtained.

The expanded particle system is a composite resin in which ethylene resin is impregnated and polymerized with a styrene monomer to form a base resin. In this specification, the composite resin is a resin in which a vinyl resin is impregnated and polymerized with a styrene monomer as described above, and it is a resin containing a component derived from the vinyl resin and a component derived from the styrene monomer. The component system derived from the styrene-based monomer is, for example, a styrene-based resin. Generally, the main component of the component derived from the styrene-based monomer is a styrene-based resin obtained by polymerizing a styrene-based monomer. In addition, during the polymerization of styrene-based monomers, etc., not only the styrene-based monomers are mutually, but also the graft copolymerization of the styrene-based monomers is produced in the polymer chains constituting the vinyl-based resin. In this case, the composite resin system contains not only a vinyl resin component and a styrene resin component polymerized with a styrene monomer, but also a vinyl resin component in which the styrene monomer has been graft-copolymerized ( That is, PE-g-PS component). In addition, when the styrene monomer is polymerized, the crosslinking of the ethylene resin may occur. In this case, the composite resin contains uncrosslinked ethylene resin and crosslinked ethylene as the ethylene resin component. Department resin. Therefore, a composite resin is a different concept from a mixed resin formed by melting and mixing a polymerized ethylene resin and a polymerized styrene resin.

The amount of the styrene monomer impregnated and polymerized in the ethylene resin can be appropriately adjusted according to the desired physical properties. Specifically, if the ratio of the component derived from the ethylene-based resin in the composite resin is increased, the toughness and restorability of the molded body are improved, but the rigidity tends to decrease. On the other hand, when the component derived from the styrene monomer is increased, that is, when the ratio of the component derived from the styrene monomer in the polymer chain constituting the composite resin is increased, the rigidity of the molded body is increased , But the toughness and resilience tend to decrease.

The above-mentioned expanded particles are because the composite resin contains 5% by mass or more and less than 20% by mass of components derived from ethylene-based resins, and more than 80% by mass and 95% by mass or less of components derived from styrene-based monomers (but, The total of the two is 100% by mass.), so a molded body that maintains toughness and restorability, and is particularly excellent in rigidity, can be obtained. From the viewpoint of improving the rigidity of the molded body, the composite resin contains 19% by mass or less of the component derived from the ethylene resin and 81% by mass or more of the component derived from the styrene monomer (however, the total of the two is 100% by mass.) is more desirable, containing 18% by mass or less of components derived from vinyl resins and 82% by mass or more of components derived from styrene monomers (however, the total of the two is 100% by mass.) More ideal. In addition, in order to improve the toughness and restorability of the molded body, the composite resin contains 10% by mass or more of the component derived from the ethylene resin and 90% by mass or less of the component derived from the styrene-based monomer (however, between the two The total is 100% by mass.) Ideally, it contains 11% by mass or more of components derived from ethylene-based resins and 89% by mass or less of components derived from styrene-based monomers (however, the total of the two is 100% by mass. ) Is more ideal. In this specification, the ideal range, the more ideal range, and the more ideal range of the upper limit and lower limit of the numerical range can be determined by all combinations of the upper limit and the lower limit.

The ethylene resin system contains linear low-density polyethylene and an ethylene copolymer having a polar group. In this specification, the linear low-density polyethylene is appropriately referred to as "LLDPE" hereinafter, and the ethylene-based copolymer having a polar group is appropriately referred to as "polar copolymer" hereinafter. Ethylene resins are preferably linear low-density polyethylene as the main component. Specifically, the content of linear low-density polyethylene in the ethylene resin is preferably 50% by mass or more, and more preferably 55 mass. % Or more, more preferably 60% by mass or more. Furthermore, as an ethylene resin other than linear low-density polyethylene or polar copolymer, branched low-density polyethylene or high-density polyethylene can be exemplified.

It is ideal for linear low-density polyethylene to have a linear polyethylene chain and a short-chain branched chain with 2-6 carbon atoms. Specifically, for example, ethylene-butene copolymers, ethylene-hexene copolymers, ethylene-octene copolymers, etc. can be mentioned, especially linear low-density polymers formed by polymerization using metallocene-based polymerization catalysts. Ethylene is ideal. In this case, the affinity between the vinyl resin component in the composite resin and the styrene resin component formed by polymerization of the styrene monomer is improved, and the toughness of the molded body can be improved. However, it is desirable that the linear low-density polyethylene has a density of approximately 0.910 to 0.925 g/cm ^3.

The melt mass flow rate (ie, MFR) of LLDPE at a temperature of 190°C and a load of 2.16kg is considered from the viewpoint of improving foamability, 0.5~4.0g/10 divided into ideal, 1.0~3.0g/ A score of 10 is ideal. However, the MFR of ethylene resins such as LLDPE or polar copolymers such as ethylene-vinyl acetate copolymers is measured in accordance with JIS K7210-1 (2014) at a temperature of 190°C and a load of 2.16 kg. In addition, a melt index measuring machine (for example, model L203 manufactured by Takara Kogyo Co., Ltd., etc.) can be used as a measuring device.

In addition, it is ideal that the melting point Tm of LLDPE is 80°C to 115°C. In this case, since the styrene-based monomer can be sufficiently impregnated in the ethylene-based resin, the suspension system can be prevented from becoming unstable during polymerization. As a result, it is possible to obtain a molded body having both the excellent rigidity of the styrene-based resin and the excellent toughness and strength of the ethylene-based resin in a higher grade. From the same point of view, it is ideal that the melting point (Tm) of LLDPE is 85~110℃. However, the melting point Tm can be measured by differential scanning calorimetry (DSC) as the melting peak temperature in accordance with JIS K7121 (1987).

In addition, the ethylene-based resin system contains a polar copolymer. As the polar copolymer system, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-alkyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-alkyl methacrylate copolymer, etc. can be used More than one kind. Examples of the polar group system in the polar copolymer include functional groups such as a carboxyl group, a hydroxyl group, a carbonyl group, a nitro group, an amino group, and a sulfonic acid group. Since the composite resin contains a polar copolymer, the hydrophilicity of the expanded particles can be increased, and it is considered that the amount of water vapor adsorbed by the expanded particles described later can be increased. As a result, it is considered that the fixability of the antistatic agent is improved, and the outflow of the antistatic agent during molding can be suppressed. It is desirable to have a carbonyl group as a polar group.

The content of the polar copolymer in the ethylene resin is 1 to 45% by mass. When it exceeds 45% by mass, crosslinking of the ethylene-based resin is likely to occur during immersion polymerization, and there is a concern that the fusion between the expanded particles may decrease. Furthermore, in this case, because the content of LLDPE in the ethylene resin is inevitably reduced, there is a concern that the bending fracture energy of the molded body becomes insufficient. From the viewpoint of the improvement of the fusion property and the improvement of the bending fracture energy, the content of the polar copolymer in the ethylene resin is preferably 35% by mass or less, and more preferably 30% by mass or less. On the other hand, when the content of the polar copolymer is less than 1% by mass, the hydrophilicity of the surface of the expanded particles cannot be improved, and the retention of the anti-charge agent may become insufficient. From the viewpoint of improving the retention of the antistatic agent, the content of the polar copolymer in the ethylene-based resin is preferably 2% by mass or more, and more preferably 5% by mass or more.

The content of the polar copolymer in the composite resin is preferably 0.1-7 mass%. In this case, the toughness and strength of the molded body can be improved, and the fracture of the molded body can be suppressed. At the same time, the retention of the antistatic agent of the expanded particles can be improved. From the viewpoint of suppressing the cracking of the molded body more, the content of the polar copolymer in the composite resin is preferably 5% by mass or less, and more preferably 4.5% by mass or less. On the other hand, from the viewpoint of further improving the retention of the antistatic agent of the expanded particles, the content of the polar copolymer in the composite resin is preferably 0.5% by mass or more, and more preferably 1% by mass or more.

The content of the structural unit derived from the monomer of the polar group contained in the polar copolymer is preferably 10-50% by mass. In this case, it is possible to increase the hydrophilicity of the expanded particles without impairing the mechanical properties of the molded body, and to further improve the fixability of the anti-charge agent. From the viewpoint of suppressing the outflow of the anti-charge agent more, it is desirable that the content of the structural unit derived from the monomer of the polar group contained in the polar copolymer is 15-50% by mass. Furthermore, the component (that is, the structural unit) derived from the monomer having the polar group in the polar copolymer is, for example, a component derived from vinyl acetate when the polar copolymer is an ethylene-vinyl acetate copolymer.

The polar copolymer is preferably an ethylene-vinyl acetate copolymer. In this case, it is possible to obtain a molded body having both the excellent rigidity of the styrene resin and the excellent toughness and strength of the ethylene resin in a higher grade. The ethylene-vinyl acetate copolymer is a polymer obtained by copolymerizing ethylene and vinyl acetate, for example, by high-pressure radical polymerization. The ethylene-vinyl acetate copolymer system generally has a long chain composed of a polyethylene chain and a short chain of vinyl acetate derived from the long chain branch.

The MFR of ethylene-vinyl acetate copolymer is preferably 1~120g/10 minutes (190℃, 2.16kg load). In this case, the fusion rate of the composite resin foamed particle molded body formed by in-mold molding of the composite resin foamed particle can be further improved, and the toughness of the composite resin foamed particle molded body can be further improved. From the same point of view, the MFR (190°C, load 2.16kg) of the ethylene-vinyl acetate copolymer is preferably 2~30g/10 minutes, and 2~10g/10min is more ideal.

The amount of water vapor adsorption per 1 g of the expanded particles is 0.50 cm ³ /g or more. When the amount of water vapor adsorption is less than 0.50 cm ³ /g, the fixability of the antistatic agent of the expanded particles becomes insufficient. As a result, for example, the antistatic agent becomes easy to flow out during molding, and the antistatic performance of the molded body may become insufficient. The expanded particles of the charged agent to prevent the ascension of a given viewpoint, the amount of steam adsorption of expanded particles based 0.60cm ³ / g or more is over, 0.70cm ³ / g or more is more desirable, 0.80cm ³ / g The above is more ideal. In addition, it is desirable that the amount of water vapor adsorption of the expanded particles is about 4.0 cm ³ /g or less.

The previous foamed particles, which are composite resins impregnated with ethylene-based resins and polymerized styrene-based monomers, are used as base resins because they are basically hydrophobic, so for example, it is determined when a hydrophilic antistatic agent is attached. The effect is low. Therefore, according to the previous heating conditions for in-mold molding of expanded particles, the anti-static agent attached to the expanded particles may be partially detached due to the steam of the heating medium, etc., depending on the part of the molded body, it is due to electrification. It is difficult to stably obtain a molded body having the desired antistatic performance, such as the decrease in the adhesion amount of the preventive agent. In addition, since the amount of water vapor adsorption of the expanded particles is increased, in the case of using an ethylene resin with a large content of a polar copolymer as the core particles as shown in the above-mentioned Patent Documents 1 to 3, the ethylene resin The toughness itself is reduced, or cross-linking of the ethylene-based resin becomes easy to occur, the fusion of the expanded particles is reduced, and the physical properties such as compression rigidity or flexural resistance of the molded body are suspected to be reduced. Furthermore, when the methods shown in Patent Documents 1 to 3 increase the blending ratio of styrene-based monomers, the amount of styrene-based monomers impregnated and polymerized in the core particles increases, making it difficult to make the styrene-based monomers. The body is uniformly impregnated, and because the styrene-based resin component of the surface layer of the resin particles increases, there is a concern that the fusion property of the expanded particles or the fixation property (water vapor adsorption amount) of the anti-charge agent is reduced.

On the other hand, for example, the expanded particles disclosed in this specification, which are obtained by the production method described later, are not only high in the proportion of the styrene monomer-derived component in the composite resin, but also have a high polarity relative to the total amount of the composite resin. The content of the copolymer is small, and because the foamed particles have a high water vapor adsorption capacity, the fixedness of the anti-charge agent can be improved while maintaining the fusion of the foamed particles. Therefore, with the above-mentioned expanded particles, a molded body can be obtained that can have both excellent mechanical properties and anti-static properties.

Furthermore, the above-mentioned expanded particles are produced by the production method described later, and it can be considered that the amount of the polar copolymer on the surface is increased compared to the previous expanded particles. Therefore, it can be considered that there is no need to excessively increase the blending ratio of the polar copolymer or the content of the polar group component relative to the total amount of the composite resin. Hydrophilization.

In this specification, the amount of water vapor adsorbed by the expanded particles refers to the amount of water vapor that the expanded particles can adsorb. That is, the adsorption isotherm of the expanded particles at a temperature of 25°C measured using the vapor adsorption amount measuring device, and the water vapor adsorption amount at the maximum relative pressure is the water vapor adsorption amount of the expanded particles. The specific measurement method is described later in the examples.

The composite resin system contains a styrene-based resin component obtained by polymerizing styrene-based monomers. In this specification, styrene constituting the styrene-based resin component, and monomers copolymerizable with styrene added as necessary are collectively referred to as styrene-based monomers. The ratio of styrene in the styrene-based monomer is preferably 50% by mass or more, more preferably 80% by mass or more, and more preferably 90% by mass or more. As a single system copolymerizable with styrene, there are, for example, the following styrene derivatives, other vinyl monomers, and the like.

Examples of styrene derivatives include α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, and 2,4-dimethylstyrene. Styrene, p-methoxystyrene, pn-butylstyrene, p-tertiary butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4, 6-Tribromostyrene, divinylbenzene, styrene sulfonic acid, sodium styrene sulfonate, etc. These systems can be used individually or in mixture of 2 or more types.

In addition, examples of other vinyl monomer systems include acrylates, methacrylates, vinyl compounds containing acrylic acid, methacrylic acid, and hydroxyl groups, vinyl compounds containing nitrile groups, organic acid vinyl compounds, olefin compounds, Diene compounds, halogenated vinyl compounds, halogenated vinylidene compounds, maleimide compounds, etc. These vinyl single systems may be used alone or in a mixture of two or more types.

Examples of acrylic acid esters include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and the like. Examples of the methacrylate system include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and the like. These systems may be used singly or as a mixture of two or more types.

Examples of the hydroxyl-containing vinyl compound system include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate. Examples of the nitrile group-containing vinyl compound system include acrylonitrile and methacrylonitrile. Examples of the organic acid vinyl compound system include vinyl acetate and vinyl propionate. These systems can be used individually or in mixture of 2 or more types.

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. Examples of the halogenated vinyl compound system include vinyl chloride and vinyl bromide. Examples of the halogenated vinylidene compound system include vinylidene chloride and the like. Examples of the maleimide compound system include N-phenylmaleimide, N-methylmaleimide, and the like. These systems can be used individually or in mixture of 2 or more types.

From the viewpoint of improving foamability, it is desirable to use styrene and acrylic monomers as a styrene-based single-system styrene or a combination of styrene and acrylic monomers. Furthermore, it is desirable to use styrene and butyl acrylate in combination from the viewpoint of improving foamability. In this case, the content of the structural unit derived from butyl acrylate in the composite resin is 0.5-10% by mass relative to the total composite resin, preferably 1-8% by mass, and more preferably 2-5% by mass. ideal.

In addition, the composite resin system may contain other resin components other than the above-mentioned ethylene-based resin component or styrene-based resin component, as long as the effect of the present invention is not hindered. Examples of other resin component systems include polymethyl methacrylate, polycarbonate, and polyvinyl alcohol. In this case, the content of other resin components relative to 100% by mass of the composite resin (including other resin components) is preferably about 10% by mass or less, more preferably 5% by mass or less, and more preferably 3% by mass or less.

The antistatic agent can be attached to the surface of the expanded particles. The adhesion amount of the antistatic agent also depends on the type of antistatic agent used, but 0.4 to 3.5 parts by mass relative to 100 parts by mass of the expanded particles is ideal. In this case, the anti-charge performance can be sufficiently obtained, and at the same time, the reduction of the fusion property can be more prevented. From the viewpoint of sufficiently obtaining the antistatic performance, it is preferable that the adhesion amount of the antistatic agent relative to 100 parts by mass of the expanded particles is 0.5 parts by mass or more, and more preferably 0.6 parts by mass or more. In addition, from the viewpoint of preventing deterioration of the fusion property, the adhesion amount of the antistatic agent is preferably 2.7 parts by mass or less, and more preferably 2.5 parts by mass or less.

As the anti-charge agent system, for example, a cationic surfactant, a nonionic surfactant, an amphoteric surfactant, etc. can be used. These surfactants can be used alone or in combination. As the antistatic agent system, for example, various commercially available products can be used.

As the cationic surfactant system, for example, octyl dimethyl ethyl ammonium ethyl sulfate, lauryl dimethyl ethyl ammonium ethyl sulfate, didecyl dimethyl ammonium chloride, and tetraalkyl ammonium can be used. Salt, trialkylbenzylammonium salt, etc. As the nonionic surfactant system, for example, hydroxyalkylamine, hydroxyalkylmonoetheramine, polyoxyalkylene alkylamine, glycerin fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkyl ether can be used Wait. As an anionic surfactant system, for example, alkyl sulfonate, alkylbenzene sulfonate, alkyl phosphate, etc. can be used.

The antistatic agent system preferably contains at least a cationic surfactant. In this case, the anti-static agent becomes easier to fix to the expanded particles, and the anti-static performance can be improved. It is considered that since the surface of the expanded particles has a negative electrostatic charge, the anti-charge agent containing the cationic surfactant becomes easy to fix. Then, even a small amount of the anti-static agent can show excellent anti-static performance, and can further prevent the decrease of the fusion property or the decrease of the filling property into the mold.

In addition, the infrared absorption spectrum of the surface of the expanded particle measured by the infrared total reflection absorption measurement method (that is, ATR method) using Ge (that is, germanium) has a wave number of 1740 cm ^-1 and a wave number of 2850 cm ^It is desirable that the absorbance ratio D _1740/2850-Ge of -1 is 0.2 or more. In other words, in the infrared absorption spectrum of the surface of the composite resin foamed particles measured by the ATR method using Ge 稜鏡, the absorbance D _1740-Ge ^{at the wave number 1740 cm -1 and} the absorbance at the wave number 2850 cm ^-1 It _{is ideal that D 2850-Ge} and absorbance ratio D _1740/2850-Ge satisfy the relationship of the following formula I.

D _1740/2850-Ge =D _1740-Ge /D _2850-Ge ≧0.2‧‧‧‧(Formula I)

It is considered that when a carbonyl group is included as a polar group in a polar copolymer, the amount of carbonyl group on the surface of the expanded particle is sufficiently large because the above formula is satisfied, so the hydrophilicity of the surface of the expanded particle is relatively reliable Becomes high. As a result, it is considered that the fixability of the antistatic agent can be improved more reliably, and the outflow of the antistatic agent during molding can be suppressed more reliably. From the viewpoint of increasing the hydrophilicity of the surface of the expanded particle, the absorbance on the surface of the expanded particle _{is preferably 0.23 or more than D 1740/2850-Ge} , and more preferably 0.25 or more. In addition, the absorbance ratio of D _1740/2850-Ge system is preferably about 0.5 or less. Moreover, the absorbance D ₂₈₅₀ at the wave number 2850 cm ^-1 is derived from the peak height of the CH stretching vibration of the methylene group contained in both the vinyl resin and the styrene resin, and the absorbance D ₁₇₄₀ ^{at the wave number 1740 cm -1} It is mainly derived from the peak height of the C=O stretching vibration of the carbonyl group contained in the polar copolymer such as the component of vinyl acetate in the ethylene-vinyl acetate copolymer.

The absorbance ratio D _1740/2850-Ge is the method for producing expanded particles described later, by impregnating the styrene-based monomer at the immersion temperature or the styrene-based monomer (that is, the first monomer) at the initial stage of polymerization The ratio to the core particles is adjusted to an appropriate range so that the styrene-based monomer is sufficiently impregnated in the ethylene-based resin core particles, and can be adjusted to the above-mentioned specific value or more. As a result, not only the content of the polar copolymer in the total amount of the composite resin is small, but the amount of the polar copolymer in the surface layer of the expanded particles can be increased.

The absorbance ratio D ₁₇₄₀ of the infrared absorption spectrum of the surface of the composite resin foamed particles measured by the ATR method using ZnSe (that is, zinc selenide) is 1740 cm ^-1 and 2850 cm ^-1 It is desirable that the ratio of _/2850-ZnSe to the aforementioned absorbance ratio D _{1740/2850-Ge D 1740/2850-Ge} /D _{1740/2850-ZnSe exceeds 1.} In other words, in the infrared absorption spectrum of the surface of the composite resin expanded particles measured by the ATR method using ZnSe 稜鏡, the absorbance D _1740-ZnSe ^{at the wave number 1740 cm -1 and} the absorbance at the wave number 2850 cm ^-1 D _2850-ZnSe and absorbance ratio D _{1740/2850-ZnSe} satisfy the following formula II, the above absorbance ratio D _1740/2850-Ge and the above absorbance ratio D _{1740/2850-ZnSe} satisfy the following formula III The relationship is ideal.

D _{1740/2850-ZnSe} =D _1740-ZnSe /D _2850-ZnSe ‧‧‧(Formula II)

D _1740/2850-Ge /D _{1740/2850-ZnSe} >1‧‧‧(Formula III)

It can be considered that when a carbonyl group is included as a polar group in a polar copolymer, the amount of carbonyl groups near the surface of the expanded particles becomes large because the above formula is satisfied, so the hydrophilicity of the surface of the expanded particles is more certain The ground becomes higher. As a result, it is considered that the fixability of the antistatic agent can be improved more reliably, and the outflow of the antistatic agent during molding can be suppressed more reliably. From the viewpoint of improving the hydrophilicity of the expanded particle surface, the absorbance ratio D _{1740/2850-ZnSe is} the absorbance ratio D _1740/2850-Ge ratio D _1740/2850-Ge /D _{1740/2850-ZnSe} series 1.1 or more Ideally, 1.2 or more is more ideal. In addition, the absorbance ratio D _{1740/2850-ZnSe and} the absorbance ratio D _1740/2850-Ge ratio D _1740/2850-Ge /D _{1740/2850-ZnSe} system are preferably about 5 or less.

In the ATR system, the different refractive index is used depending on the material of the 稜頡, and the penetration depth of the infrared rays to the sample can be changed and measured. Specifically, in the case of using Ge as the material of the enamel, since the penetration depth of infrared rays becomes shallower than that in the case of using ZnSe, it is possible to measure the infrared absorption spectrum of the expanded particles compared to the surface layer. However, in the case of using Ge, the infrared absorption spectrum can be obtained roughly from the outermost surface to the depth of 0.2~0.5μm, but in the case of using ZnSe, the infrared absorption spectrum can be obtained roughly from the outermost surface to the depth of 0.6~1.5μm. Absorption spectrum.

The absorbance ratio D _1740/2850-Ge and the ratio D _1740/2850-Ge /D _{1740/2850-ZnSe} are described later in the method for producing expanded particles. By impregnating the styrene-based monomer at the immersion temperature (that is, immersion The polymerization temperature) or the ratio of the styrene monomer (that is, the first monomer) to the core particles fed into the initial stage of polymerization is adjusted to an appropriate range so that the styrene monomer is fully impregnated in the ethylene resin core particles, which can be adjusted Above the specified value.

The content of xylene insoluble matter in the expanded particles is preferably 20% or less. In this case, the content of the crosslinked ethylene resin in the composite resin is small, and the foamability at the time of the production of the expanded particles described later or the moldability at the time of the production of the molded body can be improved. In addition, the content ratio of the xylene insoluble matter is appropriately referred to as the "XY gel amount" hereinafter. From the viewpoint of improving foamability or moldability, the XY gel content of the expanded particles is preferably 18% or less. The method for measuring the XY gel amount of the expanded particles is described later in the examples.

It is desirable that the amount of XY gel on the surface of the expanded beads is 25% or less. In this case, it is considered that because the content of the crosslinked ethylene resin component in the surface layer of the expanded particles is small, the fusion property between the expanded particles can be improved. That is, it can be considered that the above-mentioned expanded particle system not only has a small content of the polar copolymer in the total amount of the composite resin, but also contains a polar copolymer that can improve the hydrophilicity on the surface layer, and at the same time, the amount of XY gel in the surface layer (specifically, The content of the cross-linked ethylene resin component) is less. Therefore, the expanded particles can have both the excellent fixability of the anti-static agent and the excellent fusion property with the expanded particles at a high level. The method for measuring the amount of XY gel on the surface of the expanded particles is described later in the examples, but the surface part of the molded body formed by fusion of a large number of expanded particles is cut out to make a surface part sample, and this surface part is measured The XY gel amount of the sample is calculated, and the XY gel amount on the surface of the expanded particle is calculated. From the viewpoint of further improving the fusion property, the XY gel amount on the surface layer of the expanded beads is preferably 23% or less, more preferably 21% or less, and more preferably 20% or less.

From the viewpoint of moldability, or light weight when used as a molded body, and mechanical physical properties, the bulk density of the expanded particles ^{is preferably about 5 kg/m 3} or more, and more preferably 10 kg/m ³ or more. On the other hand, the bulk density of the expanded particles ^{is preferably about 200 kg/m 3} or less, and preferably 100 kg/m ³ or less.

From the viewpoint of formability, or light weight when used as a molded body, and mechanical physical properties, the density of the molded body after the foamed particles are fused with each other ^{is preferably about 5kg/m 3} or more, and 10kg/m ³ or more. For more ideal. On the other hand, the apparent density of the molded body ^{is preferably about 200 kg/m 3} or less, and preferably 100 kg/m ³ or less.

It is desirable that the surface resistivity of the foamed particles fused with each other is less than 1×10 ^{12 Ω.} If the surface resistivity is in the above range, the antistatic performance required for packaging containers and cushion packaging materials such as liquid crystal panels and solar power generation panels can be fully exhibited. The surface resistivity of the molded body ^{is preferably 7×10 11} Ω or less, and more preferably 5×10 ¹¹ Ω or less.

Next, a description will be given of an embodiment of a method for producing expanded beads. Expanded particles can be obtained through a dispersion step, a modification step, and a foaming step. Hereinafter, each step will be described in detail.

In the dispersion step system, an ethylene resin containing LLDPE and a polar copolymer can be used as the core particles. The core particle system may further contain additives such as other resins or foaming core agents, bubble regulators, colorants, lubricants, and dispersion size expanders. The core particles can be produced by blending the above-mentioned additives and the like added as necessary to an ethylene-based resin, melting and kneading the blend, and then making it into fine particles. The melting and kneading system can be performed by an extruder. In order to perform uniform kneading, it is desirable to mix the resin beforehand and then to extrude it. For the resin mixing system, for example, a Henschel mixer, a belt blender, a V-blender, a Roddy mixer, etc. can be used. The melting and kneading system is desirably performed using, for example, a high-dispersion type single-screw extruder or a two-screw extruder equipped with a screw, such as a Durmeck type, a Maddock type, and a unified melt type.

The granulation of the core particles is performed, for example, by extruding the melted and kneaded formulation with an extruder or the like while cutting it. The granulation system can be performed by, for example, a strand cutting method, a water immersion cutting method, a thermal cutting method, and the like.

In the dispersion step system, a dispersion liquid in which the core particles are dispersed in an aqueous medium can be obtained. As the aqueous medium system, for example, deionized water can be used. The core particle system is preferably dispersed in an aqueous medium together with a suspending agent. In this case, the styrene-based monomer can be uniformly suspended in the aqueous medium. As the suspending agent system, for example, tricalcium phosphate, hydroxyapatite, magnesium pyrophosphate, magnesium phosphate, aluminum hydroxide, iron hydroxide, titanium hydroxide, magnesium hydroxide, barium phosphate, calcium carbonate, magnesium carbonate, and barium carbonate can be used. , Calcium sulfate, barium sulfate, talc, kaolin, bentonite and other particulate inorganic suspending agents. In addition, for example, organic suspending agents such as polyvinylpyrrolidone, polyvinyl alcohol, ethyl cellulose, and hydroxypropyl methyl cellulose can also be used. Ideally tricalcium phosphate, hydroxyapatite, magnesium pyrophosphate. These suspending agents can be used alone or in combination of two or more kinds.

The amount of suspending agent used is relative to 100 parts by mass of an aqueous medium of suspension polymerization (specifically, all water in the system including slurry containing the reaction product, etc.), and the solid content is 0.05-10 Parts by mass are ideal. More preferably, it is 0.3 to 5 parts by mass. When the suspending agent is in the above range, the styrene-based monomer can be stabilized and suspended in the reforming step, and at the same time, the increase in the particle size distribution of the composite resin particles that can be obtained after the reforming step can be suppressed.

Dispersants such as surfactants can be added to aqueous media. As the surfactant system, for example, it is desirable to use an anionic surfactant or a nonionic surfactant. These surfactants can be used alone or in combination.

As an anionic surfactant system, for example, sodium alkyl sulfonate, sodium alkylbenzene sulfonate, sodium lauryl sulfate, sodium α-olefin sulfonate, sodium dodecyl diphenyl ether disulfonate, etc. can be used.

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

Furthermore, as necessary, an electrolyte composed of inorganic salts such as lithium chloride, potassium chloride, sodium chloride, sodium sulfate, sodium nitrate, sodium carbonate, and sodium bicarbonate can be added to the aqueous medium. In addition, it is ideal to add a water-soluble polymerization inhibitor to an aqueous medium because an excellent molding system is obtained due to toughness and mechanical strength. As the water-soluble polymerization inhibitor system, for example, sodium nitrite, potassium nitrite, ammonium nitrite, L-ascorbic acid, citric acid, etc. can be used. From the viewpoint of reducing the amount of styrene resin near the outermost surface of the composite resin particles, the amount of water-soluble polymerization inhibitor added is relative to the amount of water-based For 100 parts by mass, 0.001 to 0.1 parts by mass is ideal, and 0.005 to 0.06 parts by mass is more desirable.

In the modification step, a styrene-based monomer is impregnated and polymerized in the core particles in an aqueous medium. Furthermore, the polymerization of styrene-based monomers and the like can be carried out in the presence of a polymerization initiator. In this case, the cross-linking of the vinyl resin occurs with the polymerization of the styrene-based monomer and the like. In addition, a crosslinking agent may be used in combination as necessary. When using a polymerization initiator and a crosslinking agent, it is desirable to dissolve the polymerization initiator and the crosslinking agent in the styrene-based monomer in advance.

As the polymerization initiator, those used in suspension polymerization of styrene-based monomers can be used. For example, for styrene-based monomers, a polymerization initiator that is soluble and has a 10-hour half-life temperature of 50 to 120°C can be used. As the polymerization initiator system, for example, cumene hydroxyperoxide, dicumyl peroxide, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxybenzoic acid can be used. Ester, benzyl peroxide, tertiary butyl peroxy isopropyl carbonate, tertiary butyl peroxy-2-ethylhexyl carbonate, tertiary pentyl peroxy-2-ethyl Organic peroxides such as hexyl carbonate, hexyl peroxy-2-ethylhexyl carbonate, and lauryl peroxide. In addition, azo compounds such as azobisisobutyronitrile and the like can be used as the polymerization initiator. These polymerization initiators can be used singly or in combination of two or more kinds. In addition, from the viewpoint of easy reduction of residual styrene-based monomers, tert-butylperoxy-2-ethylhexanoate is preferable. The polymerization initiator is preferably 0.01 to 3 parts by mass with respect to 100 parts by mass of the styrene-based monomer.

In addition, as a crosslinking agent, it is preferable to use a substance that does not decompose at the polymerization temperature, and the 10-hour half-life temperature of decomposition at the crosslinking temperature is 5°C to 50°C higher than the polymerization temperature. Specifically, peroxides such as dicumyl peroxide, 2,5-tert-butylperbenzoate, and 1,1-bis-tert-butylperoxycyclohexane can be used. The crosslinking agent can be used alone or in combination of two or more kinds. The blending amount of the crosslinking agent is preferably 0.1 to 5 parts by mass relative to 100 parts by mass of the styrene-based monomer. Still, as the polymerization initiator and crosslinking agent, the same compound can also be used.

When the styrene-based monomer is immersed in the core particles and polymerized, the total amount of the predetermined styrene-based monomer is divided into, for example, two or more in an aqueous medium in which the core particles are dispersed. Timing is ideal. Specifically, a part of the total amount of the predetermined styrene-based monomer can be added to the aqueous medium in which the core particles have been dispersed, while the styrene-based monomer is impregnated and polymerized, and then the predetermined benzene can be prepared. The remaining part of the vinyl monomer is divided into 1 time or 2 times or more and added to the aqueous medium. In the latter method, by dividing the styrene-based monomer and adding it, the coagulation of the resin particles during polymerization can be suppressed, or the content of the polar copolymer on the surface of the expanded composite resin particles can be increased.

In addition, the polymerization initiator can be added to an aqueous medium in a state of being dissolved in a styrene-based monomer. As described above, when the styrene-based monomer to be formulated is divided into two or more times and added at different timings, the styrene-based monomer can be added at any timing to dissolve the polymerization initiator It is also possible to add a polymerization initiator to each styrene-based monomer added at different timings. In the case of dividing and adding the styrene-based monomer, it is desirable to dissolve the polymerization initiator first at least the styrene-based monomer (hereinafter, referred to as the "first monomer") added initially. It is ideal to dissolve more than 75% of the total amount of the predetermined polymerization initiator in the first single system, and it is ideal to dissolve more than 80% first. In this case, the suspension system can be prevented from becoming unstable during polymerization. As a result, it is possible to obtain a molded body that has both the excellent rigidity of the styrene-based resin and the excellent toughness and strength of the ethylene-based resin in a higher grade. In addition, as in the above-mentioned manner, when a part of the predetermined styrene-based monomer is added as the first monomer, the remaining part of the total amount of the predetermined styrene-based monomer can be used as the second monomer. , After the first monomer is added, it is added at a different timing from the first single system. Still, the second monomer may be further divided and added, or the second monomer may be continuously added for a specific time.

Furthermore, it is preferable that the permeation ratio of the styrene-based monomer added as the first monomer (that is, the mass ratio of the first monomer to the core particles) is 0.5 or more. In this case, even when the proportion of the styrene-based resin component in the composite resin is high, the addition of the second monomer can be prevented from increasing excessively, so that the styrene-based monomer can be impregnated uniformly and the particles can be reduced. The styrene resin composition on the surface. In addition, it becomes easy to make the shape of the composite resin particles close to a spherical shape. From the same point of view, the penetration ratio of 0.7 or more is more desirable, and 0.8 or more is more desirable. In addition, it is desirable that the penetration ratio is 1.5 or less. In this case, even when the ratio of the styrene-based resin component in the composite resin is high, the styrene-based monomer can be sufficiently impregnated in the core particles. In addition, the styrene monomer can be prevented from being polymerized before the core particles are sufficiently impregnated, and the generation of resin lumps can be prevented. From the same viewpoint, the penetration ratio of the first monomer is preferably 1.3 or less, and more preferably 1.2 or less. If the permeation ratio of the first monomer is set in the above range, even if the ratio of the styrene resin component in the composite resin is high, the amount of polar copolymer on the surface of the expanded particles can be increased, and the The hydrophilicity of the surface of the expanded particles is improved.

It is ideal that the melting point Tm (°C) of the ethylene resin in the core particles and the immersion polymerization temperature Tp (°C) in the modification step satisfy the relationship Tm-10≦Tp≦Tm +30. In this case, even if the ratio of the styrene resin component in the composite resin is high, the styrene monomer can be sufficiently impregnated in the ethylene resin, so the suspension system can be prevented from becoming unstable during polymerization. . In particular, by combining the range of the above-mentioned polymerization temperature and the range of the penetration ratio of the aforementioned first monomer, even if the proportion of the styrene-based resin component in the composite resin is high, it becomes possible to increase the surface of the expanded particles. Even if the content of the polar copolymer is small relative to the total amount of the composite resin, the hydrophilicity of the surface of the expanded particles can be improved. As a result, it is possible to obtain a foamed particle molded body having a higher grade, having both the excellent rigidity of the styrene resin and the excellent toughness and strength of the ethylene resin, and the excellent fixability of the antistatic agent. The immersion polymerization temperature in the modification step varies depending on the type of polymerization initiator used, but 60~105°C is ideal, and 70~105°C is more ideal. In addition, the crosslinking temperature varies depending on the type of crosslinking agent used, but 100 to 150°C is ideal.

In addition, a plasticizer, an oil-soluble polymerization inhibitor, a flame retardant, a coloring agent, a chain transfer agent, etc. may be added to the styrene-based single system as necessary. As the plasticizer system, for example, fatty acid esters, acetylated monoglycerides, oils and fats, hydrocarbon compounds, etc. can be used. As the fatty acid ester system, for example, glyceryl tristearate, glyceryl tricaprylate, glyceryl trilaurate, sorbitan tristearate, sorbitan monostearate, and butyl stearate can be used. Wait. In addition, as the acetylated monoglyceride system, for example, glycerol diacetyl monolauryl ester and the like can be used. As the fats and oils, for example, hardened tallow, hardened castor oil, etc. can be used. As the hydrocarbon compound system, for example, cyclohexane, fluidized paraffin, etc. can also be used. Further, as the oil-soluble polymerization inhibitor system, for example, p-tert-butylcatechol, hydroquinone, benzoquinone, etc. can be used. As the flame retardant system, for example, hexabromocyclododecane, tetrabromobisphenol A-based compound, trimethyl phosphate, brominated butadiene-styrene block copolymer, aluminum hydroxide, etc. can be used. As the colorant system, furnace black, channel black, thermal black, acetylene black, Ketjen black, graphite, carbon fiber, etc. can be used. As the chain transfer agent system, for example, n-dodecyl mercaptan, α-methylstyrene dimer, and the like can be used. The above-mentioned additives can be added singly or in combination of two or more kinds.

The aforementioned plasticizers, oil-soluble polymerization inhibitors, flame retardants, colorants, chain transfer agents, and other additives may also be dissolved in a solvent and impregnated in the core particles. As the solvent system, for example, aromatic hydrocarbons such as ethylbenzene and toluene, and aliphatic hydrocarbons such as heptane and octane can be used.

In the foaming step, the composite resin particles are foamed. The foaming method is not particularly limited, and examples thereof include a gas immersion preliminary foaming method, a dispersion medium releasing foaming method, or other foaming methods based on these methods and principles.

In the gas impregnation preliminary foaming method, a foaming agent such as a physical foaming agent is immersed in polymerized and/or polymerized composite resin particles to prepare foamable composite resin particles. After that, the expandable composite resin particles are put into a preliminary foaming machine, and heated with a heating medium such as water vapor, hot air, or a mixture thereof, to expand the expandable composite resin particles to obtain expanded particles. In addition, the prepared composite resin particles are filled in a pressure vessel, and the foaming agent is impregnated in the composite resin particles by pressing the foaming agent to prepare expandable composite resin particles.

On the other hand, in the dispersing medium release foaming method, first, composite resin particles dispersed in an aqueous medium in a pressure vessel are impregnated with a foaming agent under heating and pressure to produce expandable composite resin particles. Next, under the condition of suitable temperature for foaming, the foamable composite resin particles can be released from the pressure vessel at a lower pressure than the inside of the pressure vessel together with the water-based medium to make the foamable composite resin particles Expanded to obtain expanded particles.

For the impregnation system of the blowing agent, a liquid phase impregnation method or a gas phase impregnation method can be appropriately selected. Examples of physical blowing agents include inorganic gases such as nitrogen, carbon dioxide, argon, air, helium, and water; methane, ethane, propane, n-butane, isobutane, cyclobutane, n-pentane, Isopentane, neopentane, cyclopentane, n-hexane, cyclohexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethyl Organic volatile gases such as butane. Ideally, it is an inorganic foaming agent. In this case, the foaming agent diffuses from the foamed particles after foaming, and no foaming agent remains in the foamed particles. Therefore, it is difficult for the internal pressure of the expanded particles to rise excessively during molding, so that the cooling of the molded body can be completed in a short time and the molded body can be taken out from the molding die.

As a method of applying the anti-charge agent to the expanded particles, spray coating, airless coating, dip coating, blending method, or other coating methods based on these methods and principles can be cited. The spray coating is a method of spraying the antistatic agent solution as a mist on the expanded particles together with high-pressure air. Airless coating is a method of applying a high-pressure anti-static agent solution and spraying the foamed particles from a spray nozzle using the pressure. Still, it is desirable that the expanded particles are set in a fluid state during spraying, or they are stirred after spraying so that the anti-static agent solution adheres to the entire surface of the expanded particles. Dip coating is a method in which expanded particles are immersed in a solution of an anti-static agent and then pulled up. The blending method is a method of coating by stirring expanded particles and a small amount of anti-static agent solution.

The concentration of the anti-static agent used for coating is not limited, and it can also be a diluted solution of stock solution, powder, water, or alcohol. Furthermore, the container system when the antistatic agent is applied to the expanded particles may be a closed system or an open system, and the temperature at the time of application may be equal to or lower than the heat-resistant temperature of the expanded particles. It is ideal to agitate the expanded particles well during or after application, so that the anti-charge agent adheres to the entire surface of the composite expanded particles. The coating method may also be any one or a combination of the above.

The anti-charge agent is not particularly limited, and examples include non-ionic hydroxyalkylamines, hydroxyalkylmonoetheramines, polyoxyalkylene alkylamines, glycerin fatty acid esters, and polyoxyethylene alkyl ethers. Surfactant; anionic surfactants such as alkyl sulfonate, alkyl benzene sulfonate, alkyl phosphate, etc.; octyl dimethyl ethyl ammonium ethyl sulfate, lauryl dimethyl ethyl Cationic surfactants such as ammonium ethyl sulfate, didecyldimethylammonium chloride, tetraalkylammonium salt, trialkylbenzylammonium salt, etc. In addition, these antistatic agents may be used alone or in combination.

From the viewpoint of exhibiting excellent anti-static performance, it is desirable to use at least a cationic surfactant for the anti-static agent, and it is more desirable to use at least octyl dimethyl ethyl ammonium ethyl sulfate.

The application step of the anti-static agent is such that the adhesion amount of the anti-static agent falls within the aforementioned range, and 0.4 to 4 parts by mass of the anti-static agent is preferably applied relative to 100 parts by mass of the composite resin expanded particles. In this case, sufficiently excellent anti-static properties can be imparted to the expanded particles, and at the same time, the fluidity of the expanded particles can be prevented from decreasing, and poor filling during molding can be prevented. It is preferable that the coating amount of the anti-static agent is 0.5 to 3.5 parts by mass relative to 100 parts by mass of the composite resin expanded particles, and more preferably, 0.6 to 3 parts by mass. However, if the adhesion (coating) of the anti-static agent is to obtain the desired anti-static performance, it is not necessary to completely cover the surface of the expanded particles, and it may be provided on the surface of the expanded particles without the use of an anti-static agent. And the covered part.

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

[Example] (Example 1)

Hereinafter, the expanded beads related to the examples will be described.

In the expanded particle system of the example, a composite resin in which a vinyl resin is impregnated and polymerized with a styrene monomer is used as a base resin. That is, the composite resin system contains a styrene-based resin component in which a vinyl-based resin component and a styrene-based monomer are polymerized. Hereinafter, the manufacturing method of the expanded particles of this example will be described. In this example, the obtained expanded particles were further subjected to in-mold molding to produce a molded body.

(1) Production of nuclear particles

As the ethylene resin, LLDPE (manufactured by Tosoh Corporation, trade name: Nipolon-Z HF210K) and ethylene-vinyl acetate copolymer (manufactured by Asahi Kasei Chemicals, trade name: EF1531, the content of the vinyl acetate component (that is, the structural unit) in the ethylene-vinyl acetate copolymer is 15% by mass). The ethylene-vinyl acetate copolymer contains a carbonyl group as a polar group and corresponds to the above-mentioned polar copolymer. The ethylene-vinyl acetate copolymer is appropriately referred to as "EVA" below. In addition, as a foaming nucleating agent, zinc borate (manufactured by Tomita Pharmaceutical Co., Ltd., zinc borate 2335) was prepared.

之2軸擠出機(具體而言係東芝機械公司製之型式TEM-26SS)，將樹脂混合物以溫度230~250℃溶融混練。擠出溶融混練物，藉由水中切割方式而切斷為平均0.5mg/個，得到包含乙烯系樹脂的核粒子。 LLDPE 7.5 kg, EVA 2.5 kg, and zinc borate 0.144 kg were put into Henschel mixer (manufactured by Mitsui Miike Chemical Industry Co., Ltd.; model: FM-75E) and mixed for 5 minutes to obtain a resin mixture. Next, use 26mm

The 2-axis extruder (specifically, TEM-26SS manufactured by Toshiba Machine Co., Ltd.) melts and kneads the resin mixture at a temperature of 230 to 250°C. The melted kneaded product was extruded and cut into an average of 0.5 mg/piece by the underwater cutting method to obtain core particles containing a vinyl resin.

(2) Production of composite resin particles

In a 3L autoclave with a stirring device, 1000 g of deionized water was placed, and 6.0 g of sodium pyrophosphate was added. After that, 12.9 g of powdered magnesium nitrate ‧ hexahydrate was added, and stirred at room temperature for 30 minutes. Thus, a magnesium pyrophosphate slurry as a suspending agent was prepared. Then, in an aqueous medium containing the suspending agent, 2.0 g of sodium lauryl sulfonate (specifically, a 10% by mass aqueous solution) as a surfactant, 0.21 g of sodium nitrite as a water-soluble polymerization inhibitor, and core particles were added 75g.

Next, as a polymerization initiator, t-butylperoxy-2-ethylhexyl monocarbonate (specifically, "PERBUTYL E" manufactured by NOF Corporation) and t-hexylperoxybenzoate (specifically For example, it is "PERHEXYL Z" manufactured by NOF Corporation. Also, as a chain transfer agent, α-methylstyrene dimer (specifically, "NOFMER MSD" manufactured by NOFMER) is prepared. Then, the peroxide is thirdly oxidized 1.67g of butyl-2-ethylhexyl monocarbonate, 0.835g of t-hexylperoxybenzoate and 0.665g of α-methylstyrene dimer, dissolved in the first monomer (that is, styrene-based Monomer). Then, the dissolved substance was stirred at a rotation speed of 500 rpm, and at the same time it was poured into the above-mentioned autoclave into which the core particles etc. had been put. Also, as the first single system, a mixed monomer of 60 g of styrene and 15 g of butyl acrylate was used .

Next, after replacing the air in the autoclave with nitrogen, the temperature began to rise, and it took 1 hour and 30 minutes to raise the temperature in the autoclave to 100°C. After the temperature was raised, the temperature was kept at 100°C for 1 hour. After that, the stirring speed was lowered to 450 rpm, and the temperature was maintained at 100°C for 7.5 hours. Still, after 1 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, the inside of the autoclave was heated to 125°C over 2 hours, and maintained at 125°C for 5 hours as it is. After that, the inside of the autoclave was cooled and the contents (specifically, composite resin particles) were taken out. Next, nitric acid is added to dissolve the magnesium pyrophosphate adhering to the surface of the composite resin particle. After that, dehydration and washing are performed by a centrifugal separator, and moisture adhering to the surface is removed by an airflow drying device to obtain composite resin particles. Furthermore, from the blending ratio (mass ratio) of the styrene-based monomer and the ethylene-based resin used in the production, the mass ratio of the component derived from the styrene-based monomer to the component derived from the ethylene-based resin in the composite resin was determined.

Regarding the composite resin particles obtained as described above, the compounding or polymerization conditions are shown in Table 1 described later. Also, regarding the obtained composite resin particles, the mass ratio of the component derived from the ethylene resin (that is, PE) to the component derived from the styrene monomer (that is, PS), the content of EVA, and the vinyl acetate component The content is shown in Table 2. Regarding the composite resin particles, the XY gel amount, the glass transition temperature Tg of the acetone-soluble substance, and the weight average molecular weight Mw of the acetone-soluble substance were measured in the following manner. The results are shown in Table 2.

"The amount of xylene insoluble matter (XY gel amount) W _XY "

First, take about 1 g of composite resin particles, _{measure the weight W 0} to the fourth decimal place, and put it into a 150-mesh metal mesh bag. Next, put about 200 ml of xylene in a round bottom flask with a capacity of 200 ml, and set the sample that has been placed in the metal mesh bag in the Soesler extraction tube. Soxler extraction was performed by heating with a heating mantle for 8 hours. After the extraction, it is cooled by air cooling. After cooling, remove the metal mesh from the extraction tube, and wash each metal mesh sample with about 600 ml of acetone. Next, after volatilizing the acetone, it was dried at a temperature of 120°C. The sample recovered from the metal mesh after drying here is "xylene insoluble matter". _{Measure the weight W 1} of the xylene insoluble matter obtained by such operations to the fourth decimal place. The content ratio of the xylene insoluble matter, that is, the XY gel amount W _XY is the ratio of the weight W ₁ of the xylene insoluble matter relative to the weight W ₀ of the composite resin particle (ie 100×W ₁ /W ₀ , unit:%). Furthermore, the XY gel amount of the composite resin particles, the XY gel amount of the expanded particles that can be obtained by using the composite resin particles, and the XY gel amount of the molded body are substantially the same, so the XY gel amount of the composite resin particles can be changed. The value of the gel amount is regarded as the XY gel amount of the expanded particles and the XY gel amount of the molded body. In addition, instead of composite resin particles, by performing the same operations as described above by using an expanded particle molded body or a molded body, it is also possible to directly measure the XY gel amount of the expanded particle molded body and the XY gel amount of the molded body.

"Glass transition temperature Tg of acetone-soluble substance"

First, put 1.0 g of composite resin particles in a 150-mesh metal mesh bag. Next, put about 200 ml of xylene in a round bottom flask with a volume of 200 ml, and set the sample (ie, composite resin particles) that has been placed in the metal mesh bag in the Soxler extraction tube. It was heated with a heating mantle for 8 hours to perform Soesler extraction. The extracted xylene solution was poured into 600 ml of acetone, decanted, and the supernatant liquid was evaporated and dried under reduced pressure to obtain an acetone-soluble substance. Regarding 2 to 4 mg of the obtained acetone-soluble substance, the heat flux differential scanning calorimetry measurement was performed in accordance with JIS K7121-1987 using a DSC measuring device Q1000 manufactured by TA Instruments. Then, as the glass transition temperature at the middle point of the DSC curve obtained under the condition of a heating rate of 10°C/min, the glass transition temperature Tg of the acetone-soluble substance can be calculated. Furthermore, the acetone-soluble substance obtained by dissolving the xylene-soluble substance in the composite resin in acetone is mainly a styrene-based resin.

"Mw of acetone-soluble substance"

First, the soxler extraction is performed in the same manner as the measurement of the glass transition temperature described above. Then, the extracted xylene solution was poured into 600 ml of acetone, and after decantation, it was evaporated and dried under reduced pressure to obtain an acetone-soluble substance. The Mw of the acetone-soluble substance is determined by the gel permeation chromatography (ie, GPC) method using polystyrene as a standard substance. In the measurement system, a hybrid gel column for polymer measurement is used. Specifically, a measuring device manufactured by Tosoh Corporation (specifically, HLC-8320GPC EcoSEC) was used, with eluent: tetrahydrofuran (ie, THF), flow rate: 0.6 ml/min, sample concentration: 0.1 wt% The measurement conditions are measured. As the column system, a column in which TSKguardcolumn SuperH-H×1 and TSK-GEL SuperHM-H×2 are connected in series is used. That is, Mw is determined by measuring the molecular weight of the acetone-soluble substance dissolved in tetrahydrofuran by the GPC method and calibrating it with standard polystyrene.

(3) Production of foamed particles

500 g of composite resin particles and 3500 g of water as a dispersion medium were placed in a 5L pressure vessel equipped with a stirrer. Next, 5 g of kaolin as a dispersant and 0.5 g of sodium alkylbenzene sulfonate as a surfactant are added to the dispersion medium in the container. Next, while stirring the inside of the container at a rotation speed of 300 rpm, the inside of the container was heated to a foaming temperature of 165°C. After that, the carbon dioxide of the inorganic physical foaming agent was pressed into the container so that the pressure in the container became 3.6 MPa (but a gauge pressure), and kept at the same temperature (that is, 165° C.) for 15 minutes. In this way, the composite resin particles are impregnated with carbon dioxide to obtain expandable composite resin particles. Next, by discharging the expandable composite resin particles together with the dispersion medium from the container under atmospheric pressure, expanded particles ^{having a bulk density of 50 kg/m 3 were obtained.} Since the expanded particles are foams of composite resin particles, they can also be referred to as composite resin expanded particles. The foaming conditions are shown in Table 2 described later.

Still, the bulk density of the dried expanded particles (kg/m ³ ) is filled with the expanded particles dried at a temperature of 23°C for 24 hours into an empty 1L measuring cylinder to the marking line of 1L, and measured per 1L of expanded particles The mass (g) is calculated by unit conversion.

Regarding the expanded particles obtained by the above method, the following method is used. The absorbance measured by the ATR method using Ge 稜鏡 is higher than that of D _1740/2850-Ge and the ATR method using ZnSe 稜鏡. The measured absorbance ratio D _{1740/2850-ZnSe} , these ratios D _1740/2850-Ge /D _{1740/2850-ZnSe} , the amount of water vapor adsorption, and the amount of surface layer XY gel were measured in the following manner. The results are shown in Table 2 described later.

"Water vapor adsorption capacity of expanded particles"

The water vapor adsorption capacity of the expanded particles means the adsorption capacity of water vapor at the maximum relative pressure (specifically 0.9) at the adsorption isotherm (but set relative pressure: 0.005~0.9) at a temperature of 25°C. In addition, the term "relative pressure system" means the pressure ratio of the measurement environment to the saturated vapor pressure. In addition, the saturated water vapor pressure at a temperature of 25°C is 3.169 kPa. The measurement was performed using a vapor adsorption amount measuring device BELSORP-max manufactured by BEL Corporation of Japan. First, a group of expanded particles having an average particle diameter of 4 mm per expanded particle was dried under atmospheric pressure at a temperature of 60°C for 24 hours, and then 100 expanded particles were collected from the group of expanded particles and measured. The total weight of the expanded particle group determined from the measurement result was 0.20 g. Next, put all the measured expanded particles into the sample tank of the device, set the relative pressure to 0.005 to 0.9, and measure the adsorption isotherm of water vapor at a temperature of 25°C for the expanded particles in the tank. Next, from the adsorption amount of water vapor of the expanded particle group at the maximum relative pressure of the adsorption isotherm (that is, 0.9), the amount of water vapor adsorption per 1 g of the expanded particles (cm ³ /g) is calculated. Let the adsorption amount of the maximum relative pressure here be the water vapor adsorption amount of the expanded particles. In the measurement system, it is assumed that a group of expanded particles having an average weight of 1 to 3 mg and an average particle diameter of 3 to 5 mm per one expanded particle is used. In addition, the average particle diameter per one expanded particle is measured as follows.

First, prepare a measuring cylinder into which water with a temperature of 23°C is placed, and place any amount of expanded particles (mass Wα of the expanded particles) for 2 days under the conditions of a relative humidity of 50%, a temperature of 23°C, and 1 atm, using metal Nets and other props sink into the water in the above-mentioned measuring cylinder. Then, by considering the volume of the metal mesh and other items, the volume Vα(L) of the expanded particle group read according to the amount of water level rise is measured, and the volume Vα is used as the number of expanded particles put into the measuring cylinder (N ) Divide (Vα/N) to calculate the average volume per one expanded particle. Then, the diameter of a virtual real sphere having the same volume as the obtained average volume is set as the average particle diameter per expanded particle.

"Absorbance ratio D _1740/2850-Ge , absorbance ratio D _{1740/2850-ZnSe} , ratio D _1740/2850-Ge /D _{1740/2850-ZnSe} ”

_{The absorbance ratio D 1740/2850-Ge} and the absorbance ratio D _{1740/2850-ZnSe} system on the surface of the expanded particles can be obtained from the infrared absorption spectrum measured by the ATR method. As the measuring device, the infrared spectrophotometer "FT/IR-460plus" manufactured by JASCO Corporation and the total reflection absorption measuring device "ATR PRO 450-S" manufactured by JASCO Corporation were used. The absorbance ratio D _1740/2850-Ge system was measured using Ge 稜樜, and the absorbance ratio D _{1740/2850-ZnSe} system was measured using ZnSe 稜樜. The specific measurement conditions are: Ge or ZnSe, incident angle: 45°, the expanded particles are ^{pressed at a pressure of 170 kg/cm 2} and adhered to the surface of the total reflection absorption measuring device to obtain the surface of the expanded particles. Infrared absorption spectrum (However, no ATR correction).

With the above-mentioned measuring device and measuring conditions, firstly, the infrared absorption spectrum measured by the ATR method using Ge 稜鏡 (but without ATR correction) is measured, and the infrared absorption spectrum is measured at a wavenumber around ^{1740 cm -1.} Absorbance D _1740-Ge , absorbance D _2850-Ge near wave number 2850cm ^-1 . Then, the ratio of the absorbance D _1740-Ge to the absorbance D _2850-Ge , that is, the absorbance ratio D _{1740/2850-Ge was} calculated. Further, by using the infrared ZnSe ATR method Prism the measured absorption spectrum (however, without ATR correction), this wave number was measured infrared absorption spectrum of the absorbance near 1740cm ^-1 D _1740-ZnSe, wavenumber 2850cm ^- The absorbance near ^{1 is} _{D 2850-ZnSe} . Then, the ratio of the absorbance D _1740-ZnSe to the absorbance D _2850-ZnSe , that is, the absorbance ratio D _{1740/2850-ZnSe was} calculated. Furthermore, the absorbance ratio D _1740/2850-Ge ratio D _1740/2850-Ge /D _{1740/2850-ZnSe} relative to the absorbance ratio D _{1740/2850-ZnSe was} calculated. The results are shown in Table 2 described later. In the calculation of each absorbance ratio, the same measurement was performed on 5 expanded particles, and the average value of these was calculated.

"The amount of xylene insoluble matter in the surface layer (surface layer XY gel)"

First, using the expanded particles produced in the above-mentioned manner, a molded body is produced by the method described later. Next, super deluxe slicer WSD-2P & 3P manufactured by Watanabe Foodmach was used as a slicer to cut out the surface layer from the outermost surface of the molded body to the area with a depth of 0.1 mm. Then, take a sample of the surface layer of about 1 g, and measure the weight W ₀₀ to the fourth decimal place. Put the measured surface layer sample into a 150-mesh metal mesh bag. Next, put about 200 ml of xylene in a round bottom flask with a capacity of 200 ml, and set the surface layer sample that has been placed in the metal mesh bag in the Soesler extraction tube. Soesler extraction was performed by heating with a heating mantle for 8 hours. After the extraction, it is cooled by air cooling. After cooling, remove the metal mesh from the extraction tube, and wash each metal mesh surface sample with about 600 ml of acetone. Next, after volatilizing the acetone, it was dried at a temperature of 120°C. The sample recovered from the metal mesh after drying is the "surface-layer xylene insoluble matter". _{Measure the weight W 01 of the} xylene insoluble substance in the surface layer obtained by such operations to the fourth decimal place. The content ratio of the xylene insoluble matter in the surface layer, that is, the amount of surface layer XY gel W _{XY-S is the ratio of the weight W 01} of the surface layer xylene insoluble matter relative to the weight W ₀₀ of the surface layer sample (that is, 100×W ₀₁ /W ₀₀ , unit: %). In this case, the amount of XY gel on the surface of the molded body is measured. However, since the foamed particles and the amount of gel on the surface of the molded body are the same, the amount of XY gel on the surface of the molded body can be measured as described above. Set the amount of XY gel on the surface layer of the expanded bead.

"Adhesion amount of antistatic agent"

Approximately 5 g of the expanded particles to which the antistatic agent has adhered and approximately 5 g of the expanded particles to which the antistatic agent has not adhered were weighed. _{Let W 000} (W ₀₀₀ ≒ 5) be the weight% of the expanded particles to which the anti-static agent is not attached. ^{The weighed expanded particles were washed 3 times with 100 cm 3} (ml) of washing liquid (specifically, ethanol). ^{About 300 cm 3} of the washing liquid after washing was recovered, and the washing liquid was evaporated by keeping it at a temperature of 40°C for 24 hours. Then, the weight of the residue after evaporation of the cleaning solution of the expanded particles to which the anti-static agent has adhered, W _A , and the weight of the residue after evaporation of the cleaning solution of the expanded particles to which the anti-static agent has not adhered, W _{B are} measured. Based on the weight of these residues W _A , W _B and the weight of the expanded particles W ₀₀₀ , calculate the adhesion amount A (mass share). The results are shown in Table 2.

A=(W _A -W _B )/W ₀₀₀ ×100‧‧‧(Formula IV)

(4) Application of anti-static agent

As an anti-charge agent, octyl dimethyl ethyl ammonium ethyl sulfate (specifically, "CATIOGEN ES-O" manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.; active ingredient: 50%) was prepared. Put the foamed particles and the anti-static agent into a plastic bag with a volume of 50L, and close the mouth of the plastic bag. Then, after the expanded particles and the anti-charge agent are well shaken in the plastic bag, each bag is put into a drum mixer and mixed for 30 minutes, and the anti-charge agent is applied to the expanded particles. The coated composite resin foamed particles were dried in an oven at 40°C for 12 hours. In this manner, expanded particles (expanded anti-static particles) with the anti-static agent attached to the surface are obtained. In addition, the addition amount of the antistatic agent was set to 2 parts by mass with respect to 100 parts by mass of the expanded particles. The effective ingredient amount is 1 part by mass with respect to 100 parts by mass of the expanded particles.

(5) In-mold forming

Next, the expanded particles covered with the anti-static agent were filled in a mold having a flat plate-shaped cavity with 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 expanded particles are heated to fuse them together. After that, after cooling the inside of the mold by water cooling, the molded body was taken out from the mold. Furthermore, by placing the molded body in an oven adjusted to a temperature of 60°C for 12 hours, the molded body was dried and matured. In this way, a molded body in which a large number of expanded particles are fused with each other is obtained.

Regarding the molded body produced as described above, the apparent density, fusion rate, surface resistivity, flexural modulus, fracture energy, and compressive strength were measured. The results are shown in Table 2. The measurement method is as described below.

"Apparent density"

The apparent density is calculated by dividing the mass of the formed body by the volume.

"Fusion rate"

The formed body is bent and broken into approximately equal parts. The fractured surface was observed, and the number of foamed particles that fractured internally, that is, the number of foamed particles that had broken the material, and the number of foamed particles that peeled off at the interface were counted. Next, the ratio of the expanded particles broken inside relative to the total count of the expanded particles broken inside and the expanded particles peeled off at the interface was calculated, and the value expressed as a percentage was taken as the fusion rate (%).

"Surface resistivity"

By measuring the surface resistivity of the molded body, the anti-static performance of the molded body was evaluated. The surface resistivity is measured by the method according to JIS K 6271-1-2015. When measuring, cut out a rectangular parallelepiped test piece with a length of 100 mm × a width of 100 mm × a thickness of 25 mm from the vicinity of the center of the molded body that was cured for one day at a temperature of 23° C. and 50% RH. At this time, one of the two surfaces of the rectangular parallelepiped that is 100 mm in length x 100 mm in width is cut out so as to be the surface of the expanded particle molded body (that is, the skin surface). Then, using "Hiresta MCP-HT450" manufactured by Mitsubishi Chemical Corporation, the surface resistivity on the outer surface of the test piece was measured. As the probe system, "UR100" manufactured by Mitsubishi Chemical Corporation was used, and the measurement was performed under the conditions of 23°C, 50% RH, and an applied voltage of 500V for 30 seconds. The measurement is performed on any 4 locations on the same test piece, and the maximum value, minimum value, and arithmetic mean value are obtained. The so-called outer skin surface refers to the surface of an expanded particle molded body obtained by in-mold molding.

"Bending modulus"

The bending modulus is measured in accordance with the 3-point bending test method described in JIS K7221-1-2006. Specifically, first, five test pieces measuring 20 mm in thickness × 25 mm in width × 120 mm in length were cut out from any part of the molded body so that the entire surface becomes a cut surface. After placing the test piece in a constant room with a room temperature of 23°C and a humidity of 50% for more than 24 hours, the distance between the fulcrums is 100mm, the radius of the indenter is R15.0mm, the radius of the support table is R15.0mm, and the test speed is 20mm/min. Under the conditions of a temperature of 23°C and a humidity of 50%, the bending modulus was measured with an AUtograph AGS-10kNG test machine manufactured by Shimadzu Corporation. The arithmetic average of the measured values of 5 points is adopted as the measurement result of the bending modulus.

"Bending Break Energy"

Perform a 3-point bending test in the same way as the above-mentioned bending modulus measurement. From the relationship between strain (unit: m/m) and stress (unit: MPa), the arithmetic average of the measured values at 5 points is calculated to the breaking point The energy (unit: MJ/m ³ ). Furthermore, the bending fracture energy is calculated from the strain-stress curve to the fracture point and the area enclosed by the horizontal axis (that is, strain).

"Compressive strength"

Cut out a rectangular parallelepiped test piece with a length of 50 mm, a width of 50 mm, and a thickness of 25 mm from the central part of the foamed particle molded body. Next, with respect to this test piece, the compressive load at 50% strain is based on JIS K6767-1999. By dividing the compressive area of the test piece by this compressive load, the compressive strength (ie, 50% compressive stress) is calculated.

(Example 2)

In this example, in addition to changing the amount of LLDPE used in the production of core particles to 6kg and the amount of EVA to 4kg, the foaming conditions during foaming (specifically, the CO _{2 in the container during foaming)} Compression) Except for the changes in the method shown in Table 2 described later, the same procedure as in Example 1 was carried out to produce expanded beads and molded articles.

(Example 3)

In this example, in addition to changing the amount of LLDPE used in the production of core particles to 9.8 kg and the amount of EVA to 0.2 kg, the foaming conditions during foaming (specifically, the foaming conditions in the container during foaming are changed). CO ₂ pressure) Except for the change of the method shown in Table 2 described later, the same procedure as in Example 1 was carried out to produce expanded beads and molded articles.

(Example 4)

In this example, except that the amount of core particles used in the production of composite resin particles is changed to 100g, as the first monomer, 85g of styrene and 15g of butyl acrylate are used, and 300g of styrene is used as the second monomer. Other than that, the same procedure as in Example 1 was carried out to produce composite resin particles. Next, using this composite resin particle, the foaming conditions during foaming (specifically, the CO ₂ pressure in the container during foaming) were changed as shown in Table 2 below, with the exception of Example 1 was carried out in the same manner to produce expanded beads and molded articles.

(Example 5)

In this example, except that the amount of core particles used in the production of composite resin particles is changed to 50g, 35g of styrene and 15g of butyl acrylate are used as the first monomer, and 400g of styrene is used as the second monomer. Other than that, the same procedure as in Example 1 was carried out to produce composite resin particles. Next, using this composite resin particle, the foaming conditions during foaming (specifically, the CO ₂ pressure in the container during foaming) were changed as shown in Table 2 below, with the exception of Example 1 was carried out in the same manner to produce expanded beads and molded articles.

(Example 6)

In this example, it was first used as a foaming nucleating agent for the production of core particles, except that 14 g of polytetrafluoroethylene (manufactured by Seishin Co., Ltd., TFW1000, average particle size: 10μm) was used, and the same as in Example 1. In the same way, nuclear particles are produced. Next, except for using this core particle, as the first monomer, 52.5 g of styrene and 22.5 g of butyl acrylate were used in the same manner as in Example 1 to produce composite resin particles. Also, in addition to adding 5 g of kaolin and 0.5 g of sodium alkylbenzene sulfonate in the container where the composite resin particles were placed during foaming, stearic acid ("Deer Stearic Acid Grade 1" manufactured by Kanto Chemical Co., Ltd.) was added. ) 1g, except that the foaming conditions during foaming (specifically, the CO ₂ pressure in the container during foaming) were changed as shown in Table 2 described later, it was carried out in the same manner as in Example 1 Produce expanded particles and molded bodies.

(Example 7)

In this example, in addition to changing the amount of LLDPE used in the production of nuclear particles to 9kg, as EVA, EVAFLEX EV-45LX made by DUPONT-MITSUI POLYCHEMICALS with a vinyl acetate content of 46% by mass was used, and the EVA Except for changing the amount to 1 kg, the same procedure as in Example 1 was carried out to produce core particles. Next, using this core particle, at the same time, the foaming conditions during foaming (specifically, the CO ₂ pressure in the container during foaming) were changed as shown in Table 2 below. Example 1 was carried out in the same manner to produce expanded beads and molded articles.

(Comparative example 1)

In this example, in addition to changing the amount of LLDPE used in the production of core particles to 10kg and not using EVA, the foaming conditions during foaming (specifically, the CO ₂ pressure in the container during foaming) Except for the change of the method shown in Table 4 described later, the same procedure as in Example 1 was carried out to produce expanded beads and molded articles.

(Comparative example 2)

In this example, in addition to changing the amount of LLDPE used in the production of core particles to 5kg and the amount of EVA to 5kg, the foaming conditions during foaming (specifically, the CO _{2 in the container during foaming)} Compression) Except for the changes shown in Table 4, which will be described later, in the same manner as in Example 1, expanded beads and molded articles were produced.

(Comparative example 3)

In this example, except that the amount of core particles used in the production of composite resin particles is changed to 150g, 135g of styrene and 15g of butyl acrylate are used as the first monomer, and 200g of styrene is used as the second monomer. Other than that, the same procedure as in Example 1 was carried out to produce composite resin particles. Next, using this composite resin particle, the foaming conditions during foaming (specifically, the CO ₂ pressure in the container during foaming) were changed as shown in Table 4 below, with the exception of Example 1 was carried out in the same manner to produce expanded beads and molded articles.

(Comparative example 4)

In this example, except that the amount of core particles used in the production of composite resin particles was changed to 24g, 9g of styrene and 15g of butyl acrylate were used as the first monomer, and 452g of styrene was used as the second monomer. Other than that, the same procedure as in Example 1 was carried out to produce composite resin particles. Next, using this composite resin particle, the foaming conditions during foaming (specifically, the CO ₂ pressure in the container during foaming) were changed as shown in Table 4 below, with the exception of Example 1 was carried out in the same manner to produce expanded beads and molded articles.

(Comparative Example 5)

In this example, the following methods were used to produce expanded beads and molded articles. Specifically, first, nuclear particles were produced in the same manner as in Example 1. Next, in a 3L autoclave with a stirring device, the same procedure as in Example 1 was carried out to prepare a magnesium pyrophosphate slurry as a suspending agent. Next, 2.0 g of sodium lauryl sulfonate (specifically, a 10% by mass aqueous solution) as a surfactant, and 75 g of core particles were put into this suspending agent.

Next, as a polymerization initiator, benzyl peroxide (specifically, "NYPER BW" manufactured by NOF Corporation), tert-butyl peroxide-2-ethylhexyl monocarbonate (specifically, It refers to "PERBUTYL E" manufactured by NOF Corporation), and 1,1-bis-tert-butylperoxycyclohexane (specifically, "LUPEROX 331M70" manufactured by Arkema Jifu Co., Ltd.). Then, 1.5 g of benzyl peroxide, 0.25 g of tert-butylperoxy-2-ethylhexyl monocarbonate, and 5.36 g of 1,1-bis-tert-butylperoxycyclohexane were dissolved. For the first monomer (ie, styrene-based monomer). Then, while stirring the dissolved substance at a rotation speed of 500 rpm, it was poured into the above-mentioned autoclave into which the nuclear particles and the like had been charged. Still, a mixed monomer of 410 g of styrene and 15 g of butyl acrylate was used as the first single system.

Next, after replacing the air in the autoclave with nitrogen, the temperature began to rise, and it took 1 hour and 30 minutes to raise the temperature in the autoclave to 88°C. After the temperature was raised, the temperature was kept at 88°C for 1 hour. After that, the stirring speed was lowered to 450 rpm, and the temperature was maintained at 88°C for 5 hours. Next, the inside of the autoclave was heated to 130°C over 2 hours, and maintained at 130°C for 10 hours as it is. After that, the inside of the autoclave was cooled and the contents (specifically, composite resin particles) were taken out. Next, nitric acid is added to dissolve the magnesium pyrophosphate adhering to the surface of the composite resin particle. After that, dehydration and washing are performed by a centrifugal separator, and moisture adhering to the surface is removed by an airflow drying device to obtain composite resin particles. Except for the use of composite resin particles obtained in this way, the same procedure was performed as in Example 1 to produce expanded particles and molded articles.

(Comparative Example 6)

In this example, it was performed in the same manner as in Example 1, except that 10 g of styrene and 15 g of butyl acrylate were used as the first monomer, and 400 g of styrene was used as the second monomer. Produce composite resin particles. Next, using this composite resin particle, the foaming conditions during foaming (specifically, the CO ₂ pressure in the container during foaming) were changed as shown in Table 4 below, with the exception of Example 1 was carried out in the same manner to produce expanded beads and molded articles.

(Comparative Example 7)

In this example, instead of using linear low-density polyethylene as the ethylene resin, EVA (manufactured by Tosoh Corporation, trade name: Ultrathene 515EVA, whose content of vinyl acetate is 6 mass%) is 10 kg. Other than that, nuclear particles were produced in the same manner as in Example 1. Next, using this core particle, the foaming conditions during foaming (specifically, the CO ₂ pressure in the container during foaming) were changed as shown in Table 4 below. Example 1 was carried out in the same manner to produce expanded beads and molded articles.

Regarding Examples 2 to 7 and Comparative Examples 1 to 7, the evaluation results and the like are also shown in Tables 1 to 4 in the same manner as in Example 1.

As can be seen from Tables 1 and 2, the molding system to which the antistatic agent has been adhered using the expanded particles of the examples exhibited excellent antistatic properties with a ^{surface resistivity of less than 1×10 12 Ω.} In addition, the expanded particles to which the anti-static agent has been attached exert the above-mentioned excellent anti-static performance and also have excellent fusion properties. Therefore, it is possible to produce a molded body that has good internal fusion, is excellent in compression strength and flexural resistance, and can prevent damage due to deformation. Therefore, the molding system obtained by using the expanded particles of the examples is suitable for electronic equipment such as automobile parts, liquid crystal panels, solar power generation panels, etc., packaging containers for precision equipment, and the like.

Regarding this, as can be understood from Tables 3 and 4, Comparative Example 1 in which the content of the polar copolymer is 0 is insufficient in the anti-static performance. This system is considered to be due to the low fixation of the cationic antistatic agent, and the effect of suppressing the outflow of the antistatic agent due to the polar copolymer cannot be obtained.

In addition, the fusion rate of the molded body of Comparative Example 2 or Comparative Example 7 in which the amount of the polar copolymer was excessive was insufficient. It is considered that the main reason for this system is that cross-linking of the ethylene resin becomes easy to occur and the amount of XY gel in the surface layer of the expanded particles increases. As a result, the bending fracture energy of the molded body is insufficient, and damage due to deformation is likely to occur.

The molded body of Comparative Example 3 with a small amount of styrene-based monomer has insufficient rigidity, low compressive strength, and low bending modulus. Therefore, the molding system of Comparative Example 3 was easily deformed due to flexure, and the flexural resistance was insufficient. On the other hand, the compression strength or flexural modulus of the molded body of Comparative Example 4 with a large amount of styrene-based monomers is increased, but the bending fracture energy is insufficient, and damage due to deformation is likely to occur.

In Comparative Example 5 where the permeation ratio was too high, lumps of resin were generated during polymerization. In addition, the fusion rate of the formed body is insufficient. It can be considered that the main reason for this system is that the styrene monomer is added in a large amount, and the suspension system during polymerization becomes unstable. At the same time, the styrene monomer cannot be sufficiently impregnated in the vinyl resin, so the expanded particles The styrene resin composition on the surface increases. As a result, the bending fracture energy of the forming system of Comparative Example 5 was insufficient, and fracture due to deformation was likely to occur. In addition, in Comparative Example 5, the absorbance of the system was smaller than D _1740/2850-Ge or D _1740/2850-Ge /D _{1740/2850-ZnSe} , the amount of water vapor adsorption was small, and the anti-charge performance was insufficient.

On the other hand, in Comparative Example 6 in which the penetration ratio was too low, flat composite resin particles were produced. If the particles are flattened, poor filling of the expanded particles tends to occur during molding. In addition, the fusion rate of the formed body is insufficient. It is considered that the main reason for this system is that the addition amount of the second monomer becomes too large, making it difficult to uniformly impregnate the styrene-based monomer, and the styrene-based resin component on the surface of the expanded particles increases. As a result, the bending fracture energy of the molded body is insufficient, and damage due to deformation is likely to occur. In addition, in Comparative Example 7, the absorbance of the system was smaller than D _1740/2850-Ge or D _1740/2850-Ge /D _{1740/2850-ZnSe} , the amount of water vapor adsorption was small, and the anti-charge performance was insufficient.

The embodiments are described in the above manner, but the present invention is not limited by the above-mentioned embodiments, and various changes can be made within the scope that does not deviate from the gist.

Claims (12)

A composite resin foamed particle, which is a composite resin foamed particle in which a composite resin impregnated and polymerized with a styrene-based monomer in a vinyl resin is used as a base resin, and is characterized in that the composite resin system contains 5 mass% or more, and Up to 20% by mass of the above-mentioned ethylene-based resin component, and more than 80% by mass and 95% by mass or less of the above-mentioned styrene-based monomer component (however, the total of the two is 100% by mass), the above-mentioned ethylene resin A mixture of linear low-density polyethylene and an ethylene copolymer with a polar group, the content of the ethylene copolymer with the polar group in the ethylene resin is 1 to 45% by mass, and the composite resin foamed particles The water vapor adsorption capacity is above 0.50cm ³ /g. The composite resin expanded particle of claim 1, wherein the content of the structural unit derived from the monomer containing the polar group in the ethylene-based copolymer is 10-50% by mass. The composite resin expanded particles of claim 1 or 2, wherein the content of the ethylene-based copolymer having the polar group in the composite resin is 0.1 to 7 mass%. The expanded composite resin particle of claim 1 or 2, wherein the ethylene-based copolymer having the above-mentioned polar group contains a carbonyl group as the above-mentioned polar group. The composite resin expanded particle of claim 1 or 2, wherein the ethylene-based copolymer having the above-mentioned polar group is an ethylene-vinyl acetate copolymer. The composite resin expanded particle of claim 4, wherein the wavenumber in the infrared absorption spectrum of the surface of the composite resin expanded particle measured by the infrared total reflection absorption measurement method using Ge 稜鏡 is 1740 cm ^-1 and The absorbance ratio D _{1740/2850-Ge with} a wavenumber of 2850 cm ^-1 is 0.2 or more. The composite resin expanded particle of claim 6, wherein the wavenumber in the infrared absorption spectrum of the surface of the composite resin expanded particle measured by the infrared total reflection absorption measurement method using ZnSe 稜鏡 is 1740 cm ^-1 and The absorbance ratio D _{1740/2850-ZnSe} with a wavenumber of 2850 cm ^-1 and the above absorbance ratio D _1740/2850-Ge ratio D _1740/2850-Ge /D _{1740/2850-ZnSe} are more than 1. The composite resin expanded particle of claim 1 or 2, wherein the content of xylene insoluble matter in the surface layer of the composite resin expanded particle is 25% or less. The composite resin foamed particles of claim 1 or 2, wherein the composite resin system contains 10-18% by mass of components derived from ethylene-based resins and 82-90% by mass of components derived from styrene-based monomers (but , Of the two The total is 100% by mass). An antistatic composite resin foamed particle characterized in that the surface of the composite resin foamed particle according to any one of claims 1 to 9 is coated with an antistatic agent containing a cationic surfactant. The antistatic composite resin expanded particles of claim 10, wherein the adhesion amount of the antistatic agent is 0.4 to 3.5 parts by mass relative to 100 parts by mass of the expanded composite resin particles. A composite resin foamed particle formed body, which is a formed body formed by fusion of the antistatic composite resin foamed particles of claim 10 or 11, characterized in that the surface resistivity of the formed body is less than 1× 10 ¹² Ω.