TW201800457A - Composite resin foamed particles, composite resin foamed granules, and composite resin foamed particles - Google Patents

Abstract

The invention provides a composite resin foamed particle capable of obtaining a fixability of an antistatic agent and a molded article excellent in filling property in a mold, and excellent in fusion property, and a molded body using the composite resin foamed particles, and a method for producing a composite resin foamed particle. The present invention relates to a composite resin foamed particle (1) in which a composite resin obtained by impregnating a polymerized styrene monomer with a vinyl resin as a base resin is used as a base resin, and the composite resin foamed particles (1) A molded body, and a method for producing the composite resin foamed particles (1). The composite resin foamed particles (1) contain a predetermined proportion of the fatty acid (2). Preferably, the number of carbon atoms of the fatty acid is 12 to 22, preferably the fatty acid is a saturated fatty acid.

Description

Composite resin expanded particle, composite resin expanded particle formed body, and method for producing composite resin expanded particle

The present invention relates to composite resin foamed particles obtained by using a composite resin obtained by impregnating a polymerized styrene monomer with a styrene resin as a base resin, and a molded body obtained by fusing the composite resin foamed particles to each other, and composite resin foamed particles. Of manufacturing method.

The in-mold molded body (ie, the foamed particle molded body) of composite resin foamed particles formed from an olefin-based resin component and a styrene-based resin component is widely used as a component packaging and cushioning packaging material for electronic equipment or precision equipment. In order to prevent dust from adhering to dust and electrical damage caused by overcurrent caused by electrical discharge, molded articles of this type are generally provided with antistatic properties.

As a method for imparting antistatic performance, as disclosed in Patent Document 1, a method of impregnating a resin particle with a volatile foaming agent or impregnating it with an antistatic agent. As disclosed in Patent Document 2, a method of applying an antistatic agent to foamed composite resin particles obtained by foaming with an inorganic foaming agent.

Prior art literature Patent literature

Patent Document 1: Japanese Patent Application Laid-Open No. 2009-242634

Patent Document 2: Japanese Unexamined Patent Publication No. 2015-81274

However, as shown in Patent Document 1, when the resin particles are impregnated with the volatile foaming agent and then the antistatic agent is impregnated, the resin particles may be plasticized due to the excess of the antistatic agent, so that the fusion properties of the foamed particles may be reduced. In contrast, as shown in Patent Document 2, in a method of applying an antistatic agent to foamed particles, a foamed particle molded body having good antistatic performance can be obtained. However, further improvement of antistatic performance is required due to the use of the formed body.

When a large amount of antistatic agent is applied to the foamed particles in order to further improve the antistatic performance, the fluidity of the foamed particles when they are filled in the molding die is reduced, and the filling properties relative to the molding die may be deteriorated. In addition, even if the application amount of the antistatic agent is increased, the antistatic agent partially attached to the foamed particles may be detached due to steam or the like during molding in the mold. As a result, variations in the surface resistivity easily occur due to the location of the foamed particle molded body. Therefore, in order to obtain a molded article having excellent antistatic properties, further improvement of the expanded particles is expected.

In view of this problem, the present invention is to provide composite resin foamed particles having excellent fixability of an antistatic agent and filling properties in a molding die to obtain a molded body having excellent fusion properties, and use of the composite resin to develop hair A molded article of foam particles and a method for producing composite resin expanded particles.

One aspect of the present invention is composite resin expanded particles, which are 100 parts by mass of the composite resin in the composite resin expanded particles obtained by using a composite resin obtained by impregnating a polymerized styrene monomer with a vinyl resin as a base resin. Contains 0.05 to 0.7 parts by mass of fatty acids.

Another aspect of the present invention is a composite resin foamed particle molded body, which is a molded body obtained by melting the composite resin foamed particles with each other, and the surface resistivity of the molded body is less than 1 × 10 ¹² Ω .

Another aspect of the present invention is a method for producing composite resin expanded particles, which comprises a dispersion step of dispersing core particles containing a vinyl resin in an aqueous medium, and impregnating the core particles with a styrene-based monomer in the aqueous medium. Body, a modification step of polymerized composite resin particles, a step of foaming the composite resin particles impregnated with a foaming agent, and a step of foaming the composite resin particles containing the foaming agent, and a step of foaming The composite resin particles are impregnated fatty acids.

Since the composite resin foamed particles contain the above-mentioned amount of fatty acids, they can have excellent fixation properties of an antistatic agent, and can prevent a decrease in fluidity, and have sufficient fusing properties. Therefore, when the antistatic agent is coated on the composite resin foam particles and molded in the mold, it can stably obtain excellent antistatic performance with a surface resistivity of less than 1 × 10 ¹² Ω, and reduce the antistatic by the part of the molded body Composite resin foamed particle shaped body with uneven performance.

The composite resin foamed particles may be obtained by foaming with an organic physical foaming agent, but may be obtained by foaming with an inorganic foaming agent such as carbon dioxide. Even if the said composite resin foamed particle is foamed with an inorganic foaming agent, it can have the fixing property of an excellent antistatic agent as mentioned above. Therefore, the composite resin expanded particles (hereinafter referred to as “molded bodies”) obtained by in-mold molding of the composite resin expanded particles and fused with the composite resin expanded particles can exhibit excellent antistatic properties.

The above-mentioned manufacturing method is performed by performing a dispersion step, a modification step, and a foaming step to obtain composite resin foamed particles. In the foaming step, the composite resin particles are impregnated fatty acids. Therefore, by using the obtained composite resin foamed particles, it is possible to obtain a molded body having excellent fixability with respect to the fixability of an antistatic agent and the filling property in a molding die.

1‧‧‧ composite resin foam particles

2‧‧‧ fatty acids

3‧‧‧Antistatic agent

11‧‧‧ surface

FIG. 1 is a cross-sectional view of foamed particles in Example 1. FIG.

FIG. 2 is an explanatory view showing an enlarged cross section near the surface of the foamed particles in Example 1. FIG.

FIG. 3 is an explanatory view showing an enlarged cross section near the surface of the foamed particles to which an antistatic agent is attached in Example 1. FIG.

FIG. 4 is an explanatory view (a) showing a cylindrical tube filled with foamed particles provided at a certain height from the stage in Example 1, and showing that the cylindrical tube falls from the cylindrical tube to Illustration (b) of the expanded particle group on the stage.

Embodiment of the invention

Next, embodiments of the composite resin expanded particles will be described. The composite resin foamed particles in the present specification are suitably referred to as "foamed particles", and the foamed particles are used, for example, for applications in which an antistatic agent is coated on the surface. The foam particles used in this kind of application have an antistatic agent contact surface for attaching an antistatic agent on the surface. In addition, the concept of the foamed particles in the present invention includes any one of particles having an antistatic agent attached to the surface or particles having no antistatic agent attached to the surface.

The expanded particles are used to obtain a molded body by molding in a mold. That is, a plurality of foamed particles are filled in a molding die, and the composite resin particles are fused to each other in the molding die to obtain a molded body having a desired shape.

The expanded particles are based on a composite resin obtained by impregnating a polymerized styrene monomer with an ethylene resin as a base resin. The composite resin in this specification, as described above, is a resin obtained by impregnating a styrene-based single system of an ethylene-based resin, and a resin containing a styrene-based resin component obtained by polymerizing a vinyl-based resin component and a polymerized styrene-based monomer. A mixed resin formed by mixing a polymerized ethylene resin and a polymerized styrene resin. When styrenic monomers are polymerized, not only styrenic monomers polymerize with each other, but also graft polymerization of styrenic monomers on the polymer chain constituting the vinyl resin. Therefore, the composite resin contains not only vinyl resin components formed from vinyl resins, but also styrene ethyl ester obtained by polymerizing styrene monomers. The olefin-based resin component may further contain an ethylene-based resin component (ie, a PE-g-PS component) obtained by graft polymerization of a styrene-based monomer.

The content of the styrene monomer impregnated and polymerized in the vinyl resin can be appropriately adjusted according to the desired physical properties. Specifically, when the proportion of the vinyl resin in the composite resin is increased, toughness and resilience can be improved, but rigidity tends to be reduced. In addition, when the proportion of the structural unit of the styrene-based monomer is increased, the rigidity can be improved, but the toughness and the resilience tend to be reduced. For example, the composite resin may be a structural unit derived from a styrene-based monomer in an amount of 100 parts by mass or more and 1,900 parts by mass or less with respect to 100 parts by mass of the vinyl resin. However, in order to obtain a molded body having a good balance of toughness, resilience, and rigidity, the composite resin preferably has a structure derived from a styrene-based monomer in an amount of more than 400 parts by mass and less than 1,900 parts by mass based on 100 parts by mass of the vinyl resin. unit. From the viewpoint of further improving the rigidity of the formed body, the content of the structural unit derived from the styrene monomer relative to 100 parts by mass of the vinyl resin is preferably 450 parts by mass or more, more preferably 500 parts by mass or more. In order to further improve the toughness and resilience of the formed body, the content of the structural unit derived from the styrene monomer relative to 100 parts by mass of the vinyl resin is preferably 1,000 parts by mass or less, and more preferably 900 parts by mass or less. The preferred range, the better range, and the better range of the upper and lower limits of the numerical range in this specification can be determined by all combinations of the upper and lower limits.

Examples of the vinyl resin include linear low-density polyethylene, branched low-density polyethylene, high-density polyethylene, ethylene-acrylic copolymer, ethylene-acrylic acid alkyl ester copolymer, and ethylene-methacrylic acid alkyl ester. Copolymers, ethylene-vinyl acetate copolymers, and the like. Ethylene used The resin may be one polymer or a mixture of two or more polymers.

The ethylene-based resin preferably contains a linear low-density polyethylene as a main component. Specifically, the content of the linear low-density polyethylene in the ethylene-based resin is preferably 50% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably only by the linear low-density Formed from polyethylene. Other ethylene-based resins include ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and ethylene-methacrylic acid copolymer. The content of the ethylene-vinyl acetate copolymer is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less. The vinyl acetate content in the ethylene-vinyl acetate copolymer is preferably 5% by mass or less, and more preferably 3% by mass or less. The linear low-density polyethylene preferably has a structure including a linear polyethylene chain and a short-chain branched chain having 2 to 6 carbon atoms. Specific examples include ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer, and the like. Ethylene resin is particularly preferably a linear low-density polyethylene obtained by polymerization using a metallocene-based polymerization catalyst and having a melting point of 105 ° C or lower. In this case, the ethylene-based resin component in the composite resin can be further improved, and the affinity of the styrene-based resin component obtained by polymerizing the styrene-based monomer can also improve the toughness of the composite resin. In addition, since the low-molecular-weight component can be reduced, and the fusion strength between the foamed particles can be improved at the same time, a molded body having a low VOC and hardly cracking can be obtained. In addition, a molded body having excellent rigidity of a higher level of styrene resin and excellent adhesive strength of vinyl resin can be obtained.

The melting point Tm of the vinyl resin is preferably 95 to 105 ° C. In this case, since the vinyl resin can be sufficiently impregnated with the styrene monomer, it is possible to prevent the suspension system from being unstable during polymerization. The result is a higher level of phenethyl A molded body having excellent rigidity of olefin resin and excellent adhesive strength of styrene resin. From the same viewpoint, the melting point Tm of the vinyl resin is more preferably 100 to 105 ° C. The melting point Tm can be measured from the melting peak temperature using differential scanning calorimetry (DSC) based on JIS K7121 (1987).

The composite resin contains a styrene-based resin component obtained by polymerizing a styrene-based monomer. In this specification, styrene constituting a styrene-based resin component, and a monomer copolymerizable with styrene as necessary, is referred to as a styrene-based monomer. The proportion 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. Monomers copolymerizable with styrene, such as styrene derivatives and other vinyl monomers.

The styrene-based resin component is preferably a copolymer of polystyrene, styrene, and an acrylic-based monomer from the viewpoint of improving foamability. From the viewpoint of further improving the foamability, it is preferable to use styrene and butyl acrylate as the styrene-based monomer constituting the styrene-based resin component. At this time, the content of the structural unit derived from butyl acrylate in the composite resin is preferably 0.5 to 10% by mass relative to the entire composite resin, more preferably 1 to 8% by mass, and even more preferably 2 to 5% by mass.

The expanded particles contain 0.05 to 0.7 parts by mass of fatty acid based on 100 parts by mass of the composite resin. When the content of the fatty acid exceeds 0.7 parts by mass, the fusion properties of the foamed particles may be insufficient. Therefore, the bonding strength of the formed body may be reduced, and cracking may occur easily. In addition, when the content of fatty acid exceeds 0.7 parts by mass, the recoverability during molding is insufficient, and it is difficult to obtain a molded body having a desired shape and a desired size, which may deteriorate the appearance of the molded body. on From the viewpoint of further improving the fusion properties of the foamed particles and further improving the recoverability during molding, the fatty acid content is preferably 0.5 parts by mass or less, more preferably 0.3 parts by mass or less, relative to 100 parts by mass of the composite resin. In addition, when the content of the fatty acid is less than 0.05 parts by mass, the fluidity of the foamed particles and the fixability of the antistatic agent may be insufficient. From the viewpoint of further improving the fluidity and fixability, the content of the fatty acid relative to 100 parts by mass of the composite resin is preferably 0.07 parts by mass or more, and more preferably 0.1 parts by mass or more.

The fatty acid is preferably located on the surface of the foamed particles or the surface layer portion including the surface. The bias to the surface or the surface layer portion including the surface can be achieved by adjusting the time for adding fatty acids in the manufacturing steps of the foamed particles described later. Specifically, fatty acid can be added when impregnating the polymerized styrene monomer, or the fatty acid can be added into the pressure vessel together with the composite resin particles before foaming, or the fatty acid can be coated on the foamed particles after foaming, so that Fatty acids are on the surface. More preferably, the entire surface of the foamed particles is coated with a fatty acid. In this case, the effect of adding the fatty acid can be fully exerted.

The fatty acid is localized on the surface of the foamed particles or the surface layer portion including the surface can be confirmed by, for example, an infrared absorption spectrum. Such as absorption by the total reflection (ATR method) of infrared absorption spectrum is obtained when, based on a central portion of each of the foamed particles contained in the surface layer portion of the expanded particles, is obtained with respect to the absorbance D at around 698cm ^-1 ₆₉₈ of the after ratio 1550cm ^-1 (D ₁₅₅₀ / D ₆₉₈₎ in the vicinity of the absorbance D _1550, the surface layer portion by the absorbance ratio D ₁₅₅₀ / D ₆₉₈ value is greater than the central portion of the absorbance ratio of D ₁₅₅₀ / D ₆₉₈ value in fatty acid partial confirmation. Also, in the absorbance ratio D ₁₅₅₀ / D ₆₉₈ , the absorbance D ₆₉₈ refers to an absorption value derived from out-of-plane angle vibration of a benzene ring mainly contained in a polystyrene resin, and the absorbance D ₁₅₅₀ refers to absorption from a carboxyl group contained in a fatty acid value.

The fatty acid is a monovalent carboxylic acid, preferably a long-chain fatty acid (ie, a higher fatty acid) having a carbon number of 12 or more. The carbon number of the fatty acid is preferably 12-22, the carbon number is more preferably 16-20, and the carbon number is particularly preferably 18. . In this case, the affinity between the resin component (that is, the vinyl resin component and the styrene resin component) and the fatty acid in the foamed particles can be further improved. Therefore, the effect of adding fatty acids is easily found on the entire surface of the expanded particles. As a result, for example, the antistatic agent can easily adhere to the entire surface of the foamed particles and improve the fixing property of the antistatic agent, thereby further reducing the deviation of the antistatic performance. The fatty acid may be a single type or a mixture of two or more types. Since fatty acids are acids, they do not contain fatty acid salts such as zinc stearate. When a fatty acid salt is used, characteristics such as fusion properties may be insufficient. In addition, the fatty acid is preferably a fatty acid derivative that does not contain a functional group in a hydroxyl portion of a fatty acid such as hydroxystearic acid.

From the viewpoint of mechanical strength, the main component of the vinyl-based resin is preferably the linear low-density polyethylene as described above, but the linear low-density polyethylene does not contain a polar group. Therefore, it is presumed that when the content of the linear low-density polyethylene in the vinyl resin is increased, it is generally difficult to fix the antistatic agent to the vinyl resin. However, since the composite resin foamed particles contain fatty acids as described above, even if the content ratio of the linear low-density polyethylene is increased, the antistatic agent has excellent fixability. That is, with the composite resin foamed particles, excellent mechanical strength and antistatic performance can be established at the same time.

The fatty acid may be a saturated fatty acid or an unsaturated fatty acid. But saturated fatty acids are preferred. At this time, the The fluidity improves the filling with respect to the mold. In addition, the fixing property of the antistatic agent can be further improved, and the antistatic agent can be further prevented from flowing out due to steam or the like during molding, so it has the effect of making the surface resistivity more stable.

The apparent density of the fatty acid-containing foamed particles is preferably 10 to 300 kg / m ³ , more preferably 20 to 150 kg / cm ³ , and more preferably 30 to 100 kg / m ³ .

An antistatic agent may be attached to the surface of the foamed particles. The adhesion amount of the antistatic agent in the foamed particles coated with the antistatic agent is preferably 0.4 to 3.5 parts by mass relative to 100 parts by mass of the expanded particles. In this case, sufficient antistatic performance can be obtained, and further reduction in fusion properties can be prevented. From the viewpoint of obtaining more sufficient antistatic performance, the adhesion amount of the antistatic agent to 100 parts by mass of the foamed particles is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more. From the viewpoint of further preventing a decrease in fusion properties, 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.

Examples of the antistatic agent include cationic surfactants, nonionic surfactants, and amphoteric surfactants. These surfactants may be used alone or in combination. As the antistatic agent, for example, various commercially available products can be used.

The antistatic agent preferably contains at least a cationic surfactant. At this time, the antistatic agent can be more easily attached to the foamed particles, and the antistatic performance is further improved. This is because, as described above, the foamed particles contain a fatty acid, so that the surface has a negative electrostatic charge derived from the carboxyl group of the fatty acid. Therefore, it is easier to fix the antistatic agent formed by the cationic surfactant. So even if less A large amount of antistatic agent can also obtain excellent antistatic performance, and further prevent a decrease in fusion properties and a decrease in filling properties with respect to a forming mold.

The antistatic agent is preferably a combination of a cationic surfactant and a nonionic surfactant. In this case, the surface resistivity variation of the surface of the molded body obtained by molding the foamed particles coated with the antistatic agent in the mold can be reduced. That is, variations in the antistatic performance of the molded body can be reduced. From the above point of view, the amount of the cationic surfactant and the nonionic surfactant used is preferably when the content of the cationic surfactant is 1, so that the content of the nonionic surfactant is 0.1 to 1.0 mass. The ratio is more preferably such that the content of the non-ionic surfactant is a mass ratio of 0.2 to 0.8, and particularly preferred is that the content of the non-ionic surfactant is a mass ratio of 0.4 to 0.6.

The formed body obtained by fusing the antistatic agent-containing foamed particles to each other can further reduce the deviation of the antistatic performance (specifically the surface resistivity) from the measurement part, so it can be stably obtained to meet the surface resistivity of less than 1 × 10 ¹² Ω excellent antistatic performance.

The coefficient of variation Cv of the surface resistivity of the formed body is preferably 3 or less, more preferably 2 or less, and even more preferably 1 or less. The coefficient of variation Cv of the surface resistivity is expressed by a value obtained by dividing the standard deviation V of the surface resistivity by the average value Tav of the surface resistivity, and is an index indicating the degree of deviation from the average value. The standard deviation V of the surface resistivity is obtained from the following formula (1).

V = (Σ (Ti-Tav) ² / (n-1)} ^1/2 ‧‧‧ (1)

In the formula (1), Ti represents each measured value of the surface resistivity, Tav represents the average value of the surface resistivity, n represents the number of measurements, and Σ represents the total of (Ti-Tav) ² described in the respective measured values. The coefficient of variation Cv is obtained by the following formula (2).

Cv = V / Tav‧‧‧ (2)

Next, an embodiment of a method for producing expanded particles will be described. The expanded particles are obtained by foaming composite resin particles containing an ethylene-based resin component and a styrene-based resin component. The composite resin particles can be produced, for example, by performing the following dispersing step and modification step. The dispersion step is to disperse core particles whose main component is an ethylene-based resin in an aqueous medium. In the modification step, the core particles are impregnated with a styrene-based monomer in the presence of a polymerization initiator in an aqueous medium to polymerize. In addition, after the composite resin particles are impregnated with a foaming agent to obtain foamable composite resin particles, the foaming particles are obtained by performing a foaming step of foaming the foamable composite resin particles. Each step will be described in detail below.

In the dispersing step, core particles containing a vinyl-based resin component as a main component are used. The core particles may contain additives such as a bubble adjusting agent, a colorant, a slipper, and a dispersion diameter expanding agent. The core particles can be prepared by adding the above-mentioned additives, if necessary, to the vinyl resin component, melt-kneading the additives, and granulating. Melt kneading can be performed by an extruder. For uniform kneading, it is preferred to mix the resin components in advance and then extrude. The resin components can be mixed using, for example, a mixer such as a Han's mixer, a ribbon blender, a V blender, a Loedige mixer, and the like. Melt kneading is better, for example, using High-dispersion screw or biaxial extruder with scraper type, Maddock type, Yunimeruto type, etc.

The granulation of the core particles can be performed, for example, by a method in which the additives obtained by melt-kneading are extruded using an extruder or the like and cut at the same time. Granulation can be performed by, for example, a monofilament cutting method, a water immersion cutting method, or a hot cutting method.

In the dispersing step, the core particles are dispersed in an aqueous medium to obtain a dispersion. As the aqueous medium, for example, deionized water can be used. The core particles are preferably dispersed in a suspending agent and an aqueous medium. In this case, the styrene-based monomer can be uniformly suspended in the aqueous medium. The suspending agent is preferably tricalcium phosphate, hydroxyapatite, or magnesium pyrophosphate. These suspending agents can be used alone or in combination of two or more.

The amount of the suspending agent is preferably 100 parts by mass with respect to the aqueous medium of the suspension polymerization system (specifically, all water in the system including water containing reaction products such as mud and the like). The solid content is 0.05 to 10 parts by mass, more preferably It is preferably 0.3 to 5 parts by mass. When the amount of the suspending agent is too small, it is difficult to stabilize the styrene-based monomer during the modification step, so that a resinous block may occur. In addition, when the suspending agent is too much, in addition to increasing the manufacturing cost, the particle size distribution of the composite resin particles obtained after the upgrading step may be widened.

In order to stabilize the suspension, dispersing aids such as sodium dodecylbenzenesulfonate and sodium alkanesulfonate can be added to the aqueous medium. Alkyl sulfonic acid alkali metal salts (preferably sodium salts) having 8 to 20 carbon atoms are preferred. This makes the suspension sufficiently stable.

If necessary, the aqueous medium may be an electrolyte formed by inorganic salts such as lithium chloride, potassium chloride, sodium chloride, sodium sulfate, sodium nitrate, sodium carbonate, and sodium bicarbonate. In addition, in order to obtain more excellent toughness It is preferable that a water-soluble polymerization inhibitor is added to the water-based medium for a molded article having good properties and mechanical strength. Examples of the water-soluble polymerization inhibiting agent include sodium nitrite, potassium nitrite, ammonium nitrite, L-ascorbic acid, and citric acid.

The water-soluble polymerization inhibiting agent is not easily impregnated in the core particles, but can be dissolved in an aqueous medium. Therefore, when polymerizing styrene-based monomers impregnated with core particles, it is possible to suppress minute droplets of styrene-based monomers that are not impregnated in the aqueous medium of core particles, and those particles that are absorbed by the core particles and located near the surface of the core particles. The styrene-based monomer is polymerized. As a result, the amount of the styrene-based resin in the surface layer of the composite resin particles can be reduced, and it is estimated that the toughness of the obtained molded body can be further improved. The addition amount of the water-soluble polymerization inhibiting agent is preferably 0.001 to 0.1 parts by mass, and more preferably 0.005 to 100 parts by mass of the aqueous medium (specifically, all water in the system including water containing a reaction product such as mud). 0.06 parts by mass.

In the modification step, the core particles are impregnated with a styrene-based monomer in an aqueous medium to be polymerized. The styrene-based monomer can be polymerized in the presence of a polymerization initiator. In this case, the styrene-based monomer can be polymerized and the ethylene-based resin can be crosslinked at the same time. When polymerizing a styrene-based monomer, a polymerization initiator is used, but a cross-linking agent may be used in combination when necessary. Moreover, when using a polymerization initiator and a crosslinking agent, it is preferable to dissolve a polymerization initiator and a crosslinking agent in a styrene-based monomer in advance.

When the core particles are impregnated with styrene-based monomers for polymerization, the whole amount of the styrene-based monomers to be added may be added to the aqueous medium after the core particles are dispersed, or the whole amount of the styrene-based monomers to be added may be batched into For example, two or more times, add at different time points. Specifically, the schedule can be added to A part of the entire amount of the styrene-based monomer is added to the aqueous medium after dispersing the core particles, and then the remaining predetermined styrene-based monomer is added to the aqueous medium in one or two or more batches. By adding the styrene-based monomer in batches like the latter, it is possible to further suppress the resin particles from coagulating with each other during polymerization.

The polymerization initiator may be added to the aqueous medium in a state of being dissolved in the styrene-based monomer. For example, when the styrenic monomers scheduled to be added at different time points are added in two or more batches, each styrenic monomer added at any time point can dissolve the polymerization initiator, and the polymerization initiator can be added to different In each styrene monomer added at the time point. When the styrene-based monomer is added in portions, it is preferable to add a polymerization initiator to at least the styrene-based monomer (hereinafter referred to as the "first monomer") added first. In the first monomer, more than 75% of the total amount of the polymerization initiator to be added is preferably dissolved, more preferably 80% or more. In this case, the ethylene-based resin can be sufficiently impregnated with the styrene-based monomer when the composite resin particles are produced, and the suspension system can be prevented from being unstable during polymerization. As a result, a molded body having both the superior rigidity of a higher-level styrene resin and the superior adhesive strength of a vinyl resin can be obtained. In addition, when the styrene-based monomer that is scheduled to be added as the first monomer is added as described above, the second monomer may be added after the first monomer is added at a different time from the first monomer. The remainder of the total amount of styrene monomer added. The second monomer may be added in batches.

The permeability ratio of the styrene-based monomer added with the first monomer (that is, the mass ratio of the first monomer to the core particles) is preferably 0.5 or more. At this time, the shape of the composite resin particles is easier to approximate a spherical shape. Under the same viewpoint, the permeability ratio is preferably 0.7 or more, and more preferably 0.8 or more. Again, penetration comparison It is preferably 1.5 or less. In this case, the polymerization can be further prevented before the core particles are sufficiently impregnated with the styrene-based monomer, and the occurrence of resin lumps can be further prevented. Under the same viewpoint, the permeability ratio of the first monomer is preferably 1.3 or less, and more preferably 1.2 or less.

The melting point Tm (° C) of the ethylene-based resin in the core particles and the polymerization temperature Tp (° C) in the modification step are preferably in accordance with the relationship of Tm-10 ≦ Tp ≦ Tm + 30. In producing the composite resin particles at this time, the vinyl resin can be sufficiently impregnated with the styrene monomer, and the suspension system can be prevented from being unstable during polymerization. As a result, a foamed particle molded body having excellent rigidity of a higher level of styrene resin and excellent adhesive strength of vinyl resin can be obtained. In addition, the impregnation temperature and the polymerization temperature in the modification step vary depending on the type of the polymerization initiator used, but it is preferably 60 to 105 ° C, and more preferably 70 to 105 ° C. The crosslinking temperature varies depending on the type of the crosslinking agent used, but it is preferably 100 to 150 ° C.

Moreover, a plasticizer, an oil-soluble polymerization inhibitor, a flame retardant, a colorant, a chain transfer agent, etc. may be added to the styrene-based monomer as necessary. Examples of the plasticizer include fatty acid esters, ethylated monoglycerides, oils and fats, and hydrocarbon compounds.

Additives such as the aforementioned plasticizer, oil-soluble polymerization inhibitor, flame retardant, colorant, and chain transfer agent can also be dissolved in the core particles of the solvent. Examples of the solvent include aromatic hydrocarbons such as ethylbenzene and toluene, and aliphatic hydrocarbons such as heptane and octane.

The method for foaming the composite resin particles may be a preliminary foaming method in which the composite resin particles are impregnated with a foaming agent and then heated with steam or warm water or warm air, or after the foaming agent is heated in a pressure vessel at the same time, the pressure is lowered and lowered. Direct foaming method for foaming. The foaming agent used may be an organic foaming agent such as butane, pentane, propane, etc., or an inorganic foaming agent such as carbon dioxide, air, nitrogen, or the like. An inorganic foaming agent is preferred, and carbon dioxide is particularly preferred. At this time, the foaming agent can be dispersed from the foamed particles after foaming, so the foaming agent does not remain in the foamed particles. Therefore, it is difficult for the internal pressure of the particles to rise during forming, and the formed body can be cooled in a short time and taken out from the forming mold.

The fatty acid contained in the foamed particles may be added to the core particles, for example. The fatty acid is soluble in the styrene-based monomer added in the upgrading step. In addition, the composite resin particles and the fatty acid may be added into the pressure vessel at the same time in the foaming step, or the fatty acid may be coated on the obtained foamed particles after the foaming step. The fatty acid is preferably added by dissolving the fatty acid in a styrene-based monomer, or added during or after the foaming step. At this time, the fatty acid is biased on the surface of the foamed particles, and the effect of adding the fatty acid is more remarkable.

In addition, fatty acids are dissolved in styrene-based monomers, and the total amount of styrene-based monomers added in advance is divided into two or more batches. When these monomers are added at different times, it is preferable to dissolve fatty acids in Among the styrene-based monomers added after the second time, it is more preferable that the fatty acid is dissolved in the styrene-based monomer added last. In this case, the fatty acid may be unevenly distributed on the surface of the expanded particles. In addition, the point of time of adding the fatty acid does not increase the manufacturing step, and a viewpoint of the effect of adding a fatty acid significantly can be obtained. Particularly preferred is the foaming step.

The formed body can be produced by a known in-mold forming method using steam heating. That is, after a large number of expanded particles are put into a forming mold such as a metal mold, steam is introduced into the forming mold to melt the expanded particles with each other. Together, a shaped body can be obtained.

Examples

(Example 1)

The expanded particles related to the examples will be described below.

The expanded particles according to the examples are composite resins obtained by impregnating a polymerized styrene monomer with an ethylene-based resin as a base resin. That is, the composite resin contains a styrene-based resin component obtained by polymerizing a vinyl-based resin component and a styrene-based monomer. The foamed particles contain 0.2 parts by mass of fatty acid (specifically stearic acid) with respect to 100 parts by mass of the composite resin. The method for producing the expanded particles of this example will be described below. In this example, a molded body was produced by forming the obtained foamed particles in a mold.

(1) making nuclear particles

A linear low-density polyethylene obtained by polymerization of a metallocene polymerization catalyst (for example, "Nipolon Z HF 210K" manufactured by Tosoh Corporation) is intended to be used as an ethylene-based resin. The melting point Tm of this vinyl resin was 103 ° C. Prepare a 10% masterbatch of zinc borate (for example, "CE-7335" manufactured by Polyco) for use as a foaming nucleating agent. Prepare 10% master batch of antioxidants (for example, "TMB 113" manufactured by Toho Corporation, 6.5% of phosphorus-based stabilizers and 3.5% of hindered phenol-based antioxidants) as antioxidants. Next, put 8.58 kg of vinyl resin, 1.33 kg of zinc borate master batch, and 0.9 kg of antioxidant master batch into Han's mixer (such as the model FM-75E made by Mitsui Miike Chemical Machinery Co., Ltd.) and mix 5 Minutes to get a resin mixture.

單軸擠壓機，moddock型之螺桿)，以溫度230~250℃熔融混練樹脂混合物，再藉由水中切斷方式切成平均0.5mg/個，得核粒子。 Secondly, use an extruder (such as the MS50-28, 50mm made by Aikenji)

Single-screw extruder, moddock type screw), melt-knead the resin mixture at a temperature of 230-250 ° C, and cut into 0.5 mg / piece by cutting in water to obtain core particles.

(2) making composite resin particles

Put 1000 g of deionized water into a 3L autoclave with a stirring device, and then add 6.0 g of sodium pyrophosphate. Then, 12.9 g of powdery magnesium nitrate-hexahydrate was added, and it stirred at room temperature for 30 minutes. Thus, a magnesium pyrophosphate slurry was prepared as a suspending agent. Next, 2.0 g of sodium lauryl sulfonate (specifically, a 10% by mass aqueous solution) used as a dispersing aid, 0.2 g of sodium nitrite used as a water-soluble polymerization inhibiting agent, and 75 g of core particles were put into the suspension.

Next, t-butylperoxy-2-ethylhexyl monocarbonate (specifically, such as "perbutyl ester E" manufactured by Nippon Oil Co., Ltd.) and t-hexyl peroxybenzoate (specifically, described by "Nippon Oil Co., Ltd." Hexyl ester Z ") is used as a polymerization initiator. In addition, an α-methylstyrene dimer (for example, "Norman MSD" manufactured by Nippon Oil Co., Ltd.) was prepared as a chain transfer agent. Next, 1.72 g of t-butylperoxy-2-ethylhexyl monocarbonate, 0.86 g of t-hexyl peroxybenzoate, and 0.63 g of α-methylstyrene dimer were dissolved in the first monomer (styrene Department of monomers). After that, the dissolved substance was stirred into the suspending agent in the autoclave at a stirring speed of 500 rpm. In the first single system, a mixed monomer of 70 g of styrene and 15 g of butyl acrylate was used.

Secondly, the temperature in the autoclave was replaced by nitrogen, and the temperature increased. The temperature in the autoclave was raised to 100 ° C over 1 hour and 30 minutes. After the temperature increase, the temperature was maintained at 100 ° C for 1 hour. Thereafter, the stirring speed was reduced to 450 rpm, and the temperature was maintained at 100 ° C for 7.5 hours. The temperature at this time (specifically, 100 ° C) is the polymerization temperature. After the temperature reached 100 ° C, 350 g of styrene used as a second monomer (specifically, a styrene-based monomer) was added to the autoclave over 1 hour and 5 hours.

Next, the temperature in the autoclave was raised to 125 ° C over 2 hours, and the temperature was maintained at 125 ° C for 5 hours. Thereafter, the inside of the autoclave was cooled, and the contents (specifically, composite resin particles) were taken out. Next, nitric acid was added to dissolve magnesium pyrophosphate adhering to the surface of the composite resin particles. Thereafter, dehydration and washing were performed by a centrifugal separator, and then moisture attached to the surface was removed by an air-flow drying device, so that the ratio of the structural unit derived from the styrene monomer to the vinyl resin (specifically, the mass ratio) was 85: The composite resin of 15 was used as a composite resin particle of the base resin. The ratio of the structural unit derived from the styrene-based monomer to the styrene-based resin is determined from the addition ratio (mass ratio) of the styrene-based monomer to the styrene-based resin used in the production.

(3) Foaming step

500 g of composite resin particles and 3500 g of water used as a dispersion medium were placed in a 5 L pressure vessel equipped with a stirrer. Next, 3 g of kaolin as a dispersant, 0.2 g of sodium alkylbenzene sulfonate as a dispersing aid, and 1 g of stearic acid as a fatty acid (specifically, "stearic acid" deer grade 1 "manufactured by Kanto Chemical) Add to the dispersion medium in the container. The fatty acid used in this example is hereinafter referred to as fatty acid A. Next, stir the inside of the container at a rotation speed of 300 rpm. At the same time, the foaming temperature in the container was raised to 165 ° C. Thereafter, the carbon dioxide acid of the inorganic physical blowing agent was pressed into the inside of the container so that the pressure in the container was 3.5 Mpa (G: gauge pressure), and kept at the same temperature (ie, 165 ° C) for 15 minutes. As a result, foamable composite resin particles in which the composite resin particles are impregnated with carbon dioxide are obtained. Next, the foamable composite resin particles and the dispersion medium are released from the container under the atmospheric pressure to obtain foamed particles.

As shown in FIG. 1 and FIG. 2, the foamed particles 1 thus obtained contain fatty acid 2 and the surface 11 has a negative electrostatic charge derived from the carboxyl group of the fatty acid 2. In this example, the fatty acid 2 is added to the foam, so the fatty acid 2 may be biased on the surface 11 of the foamed particles 1. FIG. 2 is a sectional image view near the surface of the foamed particles.

(4) Coating step of antistatic agent

"Carggio ES-O" (active ingredient amount: 50% by mass) manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd. whose active ingredient is a cationic surfactant is used as an antistatic agent. Hereinafter, the antistatic agent used in this example is referred to as "antistatic agent A". Secondly, the foamed particles and the antistatic agent are put into a plastic tape to be fully vibrated and mixed, and then the bag is placed in a tumbler and mixed for 30 minutes, so that the antistatic agent is coated on the foamed particles. The added amount of the antistatic agent is 2 parts by mass with respect to 100 parts by mass of the foamed particles (the amount of the active ingredient is 1 part by mass). Thereafter, the foamed particles were dried in an oven at a temperature of 40 ° C for 12 hours to obtain foamed particles with an antistatic agent adhered to the surface.

As shown in FIG. 3, the foamed particles 1 have the antistatic agent 3 attached to the negatively-charged surface 11 by the presence of the fatty acid 2. Inferred anti-static The electric agent 3 can be strongly adhered by the surface 11 of the foamed particles 1. FIG. 3 is a sectional image view of the vicinity of the surface of the foamed particles to which the antistatic agent is attached.

The production conditions of the foamed particles obtained as described above are shown in Table 3 described later. The specific fatty acid addition period, the type of fatty acid, the amount of fatty acid added to 100 parts by mass of composite resin, the type of antistatic agent, and the amount of antistatic agent applied to 100 parts by mass of foamed particles are shown in Table 3. Show. In addition, the apparent density of the foamed particles and the adhesion amount of the antistatic agent were measured, and the filling property with respect to the molded film was evaluated. The results are shown in Table 3. The measurement methods and evaluation methods are shown below.

[Apparent density of foamed particles]

Use a metal net to weigh the foamed particles with a weight of 50 (W) in advance and apply antistatic agent to the foamed particles before sinking into a 200ml graduated cylinder with 100ml of water. Read the volume V (ml) ). After obtaining W / V, the unit conversion is performed to calculate the apparent density (kg / m ³ ) of the expanded particles.

"Amount of Antistatic Agent"

A Sox extraction device (for example, B-811 manufactured by BUCHI) was used to measure the amount of antistatic agent adhered. First, weigh 1.0g of foamed particles correctly. Next, 1.0 g of foamed particles were placed in a wire diameter of 0.06 mm. The 150mesh stainless steel metal basket is placed above the Sox extraction device. 170 mL of ethanol was added to a BUCHI-made solvent container under the Sox extraction device. The upper temperature and the lower temperature were set to 80 ° C. and 320 ° C., respectively, and then heated by a heater to perform Sox extraction for 2 hours. After that, the residue dissolved in the metal mesh basket was taken out, and then filtered and separated by a 100 mesh metal mesh, and dried with a reduced-pressure dryer at a temperature of 80 ° C for more than 8 hours. After drying the weight of the resultant dried product was measured W _2, and then take the weight of the expanded particles weighing 1.0g and the difference between the amount of extracted W ₂ (g) was calculated. Using the amount of the extract as the adhesion amount of the antistatic agent, the adhesion amount of the antistatic agent to 100 parts by mass of the foamed particles was calculated.

[Filling property with respect to forming mold]

The evaluation of the filling property is performed by evaluating the fluidity of the expanded particles. Specifically, as shown in FIG. 4 (a), first, a cylindrical tube 9 having an opening portion 92 having a diameter of 35 mm is prepared. In a state where the vertical direction of the cylindrical tube 9 is downward, the cylindrical tube 9 is set at a height H = 70 mm from the table 90. In a state where the opening portion 92 of the cylindrical tube 9 is sealed by a sealing plate or the like, the foamed particles 1 having a volume of 600 ml are filled in the cylindrical tube 9. Next, the sealing plate is removed and the opening portion 92 is opened. As a result, the foamed particles 1 are dropped by their own weight, and as shown in FIG. 4 (b), a mountain formed by the foamed particle group 100 is formed. Measure the height H ₁ of the mountain. After the above operation was repeated three times, the arithmetic mean value H _AVE of the height of the mountain was calculated. When the average height of the mountain was 60 mm or less, it was evaluated as "good", and when it exceeded 60 mm, it was evaluated as "bad".

(5) In-mold forming

Next, the foamed particles coated with the antistatic agent are filled into a metal mold having a flat plate-shaped mold groove with a length of 250 mm, a width of 200 mm, and a thickness of 50 mm. By Water vapor is introduced into a metal mold, and the foamed particles are heated to fuse each other. Thereafter, the inside of the metal mold is cooled by water cooling, and the formed body is taken out from the metal mold. The formed body was placed in an oven adjusted to 60 ° C. for 12 hours to dry and maintain the formed body. Thus, a formed body in which a large number of foamed particles are fused with each other.

Table 3 shows the forming pressures of the formed bodies produced as described above at the time of forming. In addition, the bulk density and surface resistivity of the molded body were measured, and the fusion properties and recoverability of the molded body were evaluated. The results are shown in Table 3. The measurement method and evaluation method are as follows.

[Bulk density]

、相對濕度50%之環境下24小時後之成形體的外形尺寸求取體積。又，測定成形體之重量。其次重量除外形尺寸，再藉由單位換算再算出體積密度(kg/m³)。 Placed at temperature 23

Calculate the volume of the shaped body after 24 hours at 50% relative humidity. The weight of the formed body was measured. Next, the weight is excluded from the dimensions, and the bulk density (kg / m ³ ) is calculated by unit conversion.

"Fusion"

The formed body was bent to rupture slightly. The fracture surface was observed, and the number of foamed particles that were internally cracked and the number of foamed particles that were peeled from the surface were measured. Next, the ratio of the internally broken foamed particles to the total number of internally broken foamed particles and the total number of foamed particles peeled from the surface was calculated, and the value expressed as a percentage was taken as the fusion rate (%). Those with a fusion rate of 80% or more were evaluated as "good", and those with a fusion rate of less than 80% were evaluated as "bad".

"Resilience"

The evaluation of the recoverability was performed by measuring the dimensions of the thickness of the formed body. Specifically, first, the thickness T _{1 of the} molded body 10 mm from the inside of the end portion and the thickness T ₂ of the center portion of the molded body bisected in the longitudinal direction and the width direction are measured. Next, the thickness ratio T ₂ / T _{1 of the} formed body is calculated. When the thickness ratio T ₂ / T ₁ is 0.95 or more, it is evaluated as "good", and when it is less than 0.95, it is evaluated as "bad".

"Surface resistivity"

The antistatic performance of the formed body was evaluated by measuring the surface resistivity of the formed body. Surface resistivity was measured according to the method of JIS K 6271-1: 2015. At the time of measurement, a cube-shaped test piece having a length of 100 mm × width 100 mm × thickness 25 mm was cut out from the vicinity of the center of the molded body after being maintained at a temperature of 23 ° C and 50% RH for one day. At this time, a test piece was cut out as if the surface (ie, the skin surface) of the foamed particle molded body was formed on either side of a cube having a length of 100 mm × width of 100 mm. Next, the surface resistivity of the skin surface of the test piece was measured using "Herez MCP-HT450" manufactured by Mitsubishi Chemical Corporation. The probe used was "UR 100" manufactured by Mitsubishi Chemical Corporation, and the measurement was performed under conditions of 23 ° C, 50% RH, and applied voltage of 500 V for 30 seconds. The measurement was performed at four different points, and the average value and the coefficient of variation were obtained. The skin surface refers to the surface of a foamed particle molded body obtained by molding in a mold.

In addition, by changing the manufacturing conditions of Example 1, the foamed particles and molded bodies of Examples 1 to 9 and Comparative Examples 1 to 4 were produced. Confirm example Medium fatty acids are on the surface. Table 1 shows the types of fatty acids and their derivatives (specifically, fatty acid salts) used in Examples and Comparative Examples. Table 2 shows the types of antistatic agents used in the examples and comparative examples. Tables 3 and 4 show manufacturing conditions, evaluation results, and the like of each of the examples and comparative examples.

It is known from Table 3 that the foamed particles in the example contain a certain amount of fatty acids, so the foamed particles have excellent fixation properties of the antistatic agent. The molded body obtained by molding the foamed particles with the antistatic agent in the mold is , Has excellent antistatic performance less than 1 × 10 ¹² Ω. In addition, variations in antistatic performance can be reduced. In addition, the foamed particles with antistatic performance can exhibit the excellent antistatic performance mentioned above and not reduce the fluidity, and also have excellent filling properties relative to the forming mold. In addition, since the foamed particles also have excellent fusion properties, a molded body having excellent fusion properties between the foamed particles can be obtained by molding. That is, the formed article of the example has excellent mechanical strength. Therefore, the molded article obtained by using the expanded particles of the examples is suitable for electronic components such as automobile components, liquid crystal panels, solar power generation panels, and packaging containers for precision equipment.

The above is described with reference to the examples, but the present invention is not limited to the above examples, and various changes can be made without departing from the gist thereof.

1‧‧‧ composite resin foam particles

2‧‧‧ fatty acids

3‧‧‧Antistatic agent

11‧‧‧ surface

Claims (10)

A composite resin expanded particle, which is a composite resin expanded particle obtained by using a composite resin obtained by impregnating a polymerized styrene monomer with a vinyl resin as a base resin, and containing 0.05 to 0.7 parts by mass relative to 100 parts by mass of the composite resin. Of fatty acids. For example, the composite resin expanded particle of claim 1, wherein the carbon number of the above fatty acid is 12-22. The composite resin expanded particles according to claim 1 or 2, wherein the fatty acid is a saturated fatty acid. The composite resin expanded particles according to any one of claims 1 to 3, wherein the composite resin has a structure derived from a styrene-based monomer in an amount of more than 400 parts by mass and less than 1,900 parts by mass based on 100 parts by mass of the vinyl resin. unit. The composite resin expanded particles according to any one of claims 1 to 4, wherein the main component of the above-mentioned vinyl resin is a linear low-density polyethylene. For example, the composite resin expanded particles according to any one of claims 1 to 5, wherein the surface of the composite resin expanded particles is coated with an antistatic agent, and the adhesion amount of the antistatic agent is 100 parts by mass of the composite resin expanded particles. 0.4 to 3.5 parts by mass. The composite resin expanded particle according to claim 6, wherein the antistatic agent contains at least a cationic surfactant. The composite resin expanded particle according to claim 6, wherein the antistatic agent contains a cationic surfactant and a nonionic surfactant. A composite resin foamed particle molded body is a molded body obtained by fusing the composite resin foamed particles according to any one of claims 6 to 8, and the surface resistivity of the molded body does not reach 1 × 10 ¹² Ω. A method for producing foamed composite resin particles, comprising a dispersion step of dispersing core particles containing a vinyl-based resin in an aqueous medium, and impregnating and polymerizing the core particles with the styrene-based monomer in the aqueous medium. The modified step of obtaining the composite resin particles and the foaming step of impregnating the composite resin particles with a foaming agent and foaming the composite resin particles containing the foaming agent, and the compounding in the foaming step. The resin particles are impregnated with fatty acids.