JP2023147764A - Method for producing expandable styrenic resin particle, expandable styrenic resin particle, pre-expanded styrenic resin particle, expanded styrenic resin molding, and method for washing expandable particle - Google Patents

Abstract

To provide a method for efficiently producing expandable styrenic resin particles which have a sufficiently reduced surface adhesion amount of a dispersion agent and polymerized powder; expandable styrenic resin particles which are obtained by the production method and have a sufficiently reduced surface adhesion amount of a dispersion agent and polymerized powder; pre-expanded styrenic resin particles obtained by pre-expanding the expandable styrenic resin particles; an expanded styrenic resin molding molded from the expandable styrenic resin particles and the pre-expanded styrenic resin particles; and a method for washing expandable particles which can efficiently and sufficiently wash a dispersion agent and polymerized powder attached to the expandable particles.SOLUTION: A method for producing expandable styrenic resin particles includes a step of washing expandable particles containing a styrenic resin and an expanding agent with water, wherein the temperature of the water in the step is adjusted to 1-37°C, and the amount of the water with respect to 100 pts.mass of the expandable particles is adjusted to 31-390 pts.mass.SELECTED DRAWING: None

Description

The present invention relates to a method for producing expandable styrenic resin particles, expandable styrenic resin particles, pre-expanded styrenic resin particles, a styrenic resin foam molded article, and a method for cleaning expandable particles.

Foam molded products are lightweight and have excellent heat insulating properties and mechanical strength, so they are used as heat insulating materials used in houses and automobiles, heat insulating materials used in construction materials, etc., embankment materials used in styrofoam civil engineering methods, fish boxes, and food products. It is widely used in transportation packaging materials such as containers, cushioning materials, and cushion fillers. Among these, in-mold foam molded products manufactured using expandable particles (typically expandable styrenic resin particles or pre-expanded styrenic resin particles obtained by pre-expanding them) as raw materials are easy to obtain the desired shape. It is widely used due to its advantages. Such a foamed molded article is composed of a plurality of expandable particles fused together.

Conventionally, in producing expandable styrenic resin particles, a dispersant attached to the surface of expandable particles obtained by polymerizing monomer components containing styrenic monomers and adding a blowing agent is used. Since the expandable particles are washed with a large amount of water in order to remove the polymer powder and polymer powder, there is a problem in that a large amount of waste liquid generated needs to be treated.

A method for cleaning foamable resin particles obtained by separating a slightly water-soluble inorganic salt present as a suspension stabilizer in a foaming agent impregnation step from the suspension after decomposing the foaming agent, the foamable resin particles being separated from the suspension. Washing water is supplied into the washing tank containing the resin particles without stirring the inside of the washing tank to wash the foamable resin particles, while draining the waste water generated by washing the foamable resin particles outside the washing tank. The foamable resin particles are washed by supplying washing water into the washing tank until the concentration of chlorine ions in the wastewater discharged to the outside of the washing tank becomes 10 ppm or less. A method of cleaning foamable resin particles has been reported that can effectively remove chlorine ions caused by hydrochloric acid and prevent corrosion of equipment (Patent Document 1). However, with this cleaning method, the foamed resin particles at the top of the cleaning tank are easily cleaned by supplying pure cleaning water, but in order to completely clean the center and bottom of the cleaning tank, a large amount of water is required. There are problems in that washing water is required and the washing time is long.

The foamable resin particles obtained by impregnating resin particles with a foaming agent in an aqueous medium containing magnesium oxide as a dispersion stabilizer are treated with a water-soluble salt that can collect magnesium oxide to form the foamed resin particles. A cleaning method for cleaning and removing magnesium oxide adhering to resin particles has been reported (Patent Document 2). However, this cleaning method is a method that can remove the dispersant attached to the foamable resin particles when magnesium oxide is used as a dispersant, and the removal of polymer powder attached to the foamable resin particles has not been studied. do not have.

In addition, as a method for suppressing the generation of fine powder during the production of expandable styrene resin particles, 21 parts by mass or more and 30 A first step of adding and absorbing a styrenic monomer in a range of less than parts by mass, and a second step of adding a polymerization initiator and a monomer into an aqueous medium to initiate a polymerization reaction of the monomers. and a third step of continuously or intermittently supplying and polymerizing the remaining monomers when the polymerization conversion rate of the monomers in the polymerization reaction reaches 75 to 95%, The monomer added in the first step and the second step is calculated by the formula (M1+M2)÷(QP+M1+M2)×100 (where M1 is the amount of monomer added in the first step, and M2 is the amount of monomer added in the second step. A method for producing expandable polystyrene resin particles has been reported in which the percentage calculated from the amount of polystyrene added (QP is the mass of the seed particles) is in the range of 26% or more and less than 35% (Patent Document 3) . However, this method is aimed at suppressing the generation of fine powder during production, and cannot be applied to the dispersant or polymer powder that has finally adhered to the expandable resin particles.

Japanese Patent Application Publication No. 2005-263912 Japanese Patent Application Publication No. 1999-240977 Japanese Patent Application Publication No. 2011-195769

The present invention has been made in order to solve the above-mentioned conventional problems, and its main purpose is to provide foaming properties in which the amount of surface adhesion of dispersant and polymer powder is sufficiently reduced while maintaining fusion properties during molding. An object of the present invention is to provide a method for efficiently producing styrenic resin particles. Another object of the present invention is to provide expandable styrenic resin particles in which the amount of dispersant and polymerized powder adhering to the surface is sufficiently reduced, which is obtained by such a manufacturing method. Another object of the present invention is to provide pre-expanded styrenic resin particles obtained by pre-expanding such expandable styrenic resin particles. Another object of the present invention is to provide a styrenic resin foam molded article formed from such expandable styrenic resin particles or pre-expanded styrenic resin particles. Another object of the present invention is to provide a method for cleaning expandable particles that can efficiently and thoroughly clean the dispersant and polymer powder adhering to the expandable particles.

A method for producing expandable styrenic resin particles according to an embodiment of the present invention includes:
A method for producing expandable styrenic resin particles, the method comprising the step of washing expandable particles containing a styrenic resin and a blowing agent with water,
In this step, the temperature of the water is adjusted to a range of 1° C. to 37° C., and the amount of water is adjusted to a range of 31 parts by mass to 390 parts by mass based on 100 parts by mass of the expandable particles.

According to one embodiment, the expandable particles are formed by any one of a one-stage method, a two-stage method, and a seed polymerization method.

Expandable styrenic resin particles according to an embodiment of the present invention are obtained by the above manufacturing method.

Pre-expanded styrenic resin particles according to embodiments of the present invention include:
Pre-expanded styrenic resin particles obtained by pre-foaming the expandable styrenic resin particles,
The bulk expansion ratio of the preliminary foaming is 2 times to 150 times.

The styrenic resin foam molded article according to the embodiment of the present invention is molded from the above-mentioned expandable styrenic resin particles.

The styrenic resin foam molded article according to the embodiment of the present invention is molded from the pre-expanded styrenic resin particles.

A method of cleaning expandable particles according to an embodiment of the present invention includes:
A cleaning method for cleaning foamable particles containing a styrenic resin and a foaming agent with water, the method comprising:
Adjusting the temperature of the water to a range of 1°C to 37°C,
The amount of water based on 100 parts by mass of the expandable styrenic resin particles is adjusted to a range of 31 parts by mass to 395 parts by mass.

According to the present invention, it is possible to provide a method for efficiently producing expandable styrenic resin particles in which the amount of surface adhesion of a dispersant and polymer powder is sufficiently reduced while maintaining fusion properties during molding. Further, it is possible to provide expandable styrenic resin particles obtained by such a production method, in which the amount of dispersant and polymerized powder adhering to the surface is sufficiently reduced. Furthermore, pre-expanded styrenic resin particles can be provided by pre-expanding such expandable styrenic resin particles. Furthermore, a styrenic resin foam molded article formed from such expandable styrenic resin particles or pre-expanded styrenic resin particles can be provided. Furthermore, it is possible to provide a method for cleaning expandable particles that can efficiently and thoroughly clean the dispersant and polymer powder adhering to the expandable particles.

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

In this specification, "(meth)acrylic" means acrylic and/or methacrylic, and "(meth)acrylate" means acrylate and/or methacrylate. "Mass" in this specification may be read as "weight."

≪≪A. Method for manufacturing expandable styrenic resin particles≫≫
A method for producing expandable styrenic resin particles according to an embodiment of the present invention includes a step of washing expandable particles containing a styrenic resin and a blowing agent with water. That is, in this specification, when manufacturing expandable styrenic resin particles, the particles before being washed with water are referred to as "expandable particles," and the particles after being washed with water are referred to as "expandable styrenic resin particles." ”.

≪A-1. Expandable particles≫
The expandable particles contain a styrenic resin and a foaming agent.

<A-1-1. Styrenic resin>
The styrenic resin contains a styrene monomer as a monomer component constituting the styrenic resin. That is, styrenic resins are obtained by polymerizing monomer components containing styrene monomers.

Styrenic monomers include styrene or styrene derivatives. Examples of styrene derivatives include α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, and bromostyrene. The number of styrenic monomers may be one, or two or more. The styrenic monomer preferably contains at least styrene. The content ratio of styrene to the total amount of styrenic monomers is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. It is.

The monomer component may contain other monomers as long as it contains a styrene monomer as a main component. In this specification, the term "main component" means that the content of the component in all components is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more. , particularly preferably 95% by mass or more.

Other monomers typically include vinyl monomers.

Examples of the vinyl monomer include polyfunctional monomers, (meth)acrylic acid ester monomers, maleic acid ester monomers, and fumaric acid ester monomers. The number of vinyl monomers may be one, or two or more.

Specific examples of polyfunctional monomers include divinylbenzenes such as o-divinylbenzene, m-divinylbenzene, and p-divinylbenzene; alkylenes such as ethylene glycol di(meth)acrylate and polyethylene glycol di(meth)acrylate; Glycol di(meth)acrylate; By using a polyfunctional monomer, a branched structure can be imparted to the styrenic resin. The content of the polyfunctional monomer in the monomer components constituting the styrene resin is preferably 0% by mass to 0.1% by mass, more preferably 0.005% by mass to 0.05% by mass. It is.

Specific examples of (meth)acrylate monomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and (meth)acrylate. Examples include pentyl, 2-ethylhexyl (meth)acrylate, and hexyl (meth)acrylate. Among these (meth)acrylic acid ester monomers, butyl acrylate, 2-ethylhexyl acrylate, and ethyl acrylate are preferred, and butyl acrylate is more preferred. By using the (meth)acrylic acid ester monomer, the glass transition temperature (Tg) of the styrenic resin can be lowered. The content of acrylic acid ester monomer in the monomer components constituting the styrene resin is preferably 0% by mass to 4.0% by mass, more preferably 0.1% by mass to 3.0% by mass. %.

Examples of maleic acid ester monomers include dimethyl maleate.

Examples of the fumarate monomer include dimethyl fumarate, diethyl fumarate, and ethyl fumarate.

The styrenic resin may be a styrenic resin that is not a recycled raw material, such as a general-purpose styrene resin (GPPS), a commercially available styrenic resin, or a styrenic resin newly prepared by a method such as suspension polymerization. , styrene-based resin that is a recycled raw material may be used. The recycled raw material may typically be a used styrenic resin foam molded product. The recycled raw materials may be those recovered from food packaging trays, fish boxes, home appliance cushioning materials, etc., and recycled using a limonene dissolution method or a heating volume reduction method. Recycled raw materials are made by pulverizing non-foamed styrene resin moldings that are separated and collected from home appliances (e.g., televisions, refrigerators, washing machines, air conditioners, etc.) and office equipment (e.g., copiers, facsimile machines, printers, etc.). , or may be melt-kneaded and re-pelletized.

In one embodiment, the styrenic resin may be a composite resin of a styrene resin and an olefin resin. The content ratio of styrene resin and olefin resin in the composite resin (styrene resin/olefin resin: mass ratio) is preferably 50/50 to 90/10, more preferably 60/40 to 85/15. It is. If the content of the styrene resin is too low, foamability and/or moldability may become insufficient. If the content of styrenic resin is too high, impact resistance and/or flexibility may become insufficient.

As the olefin resin, any suitable olefin resin can be used as long as the effects of the present invention are not impaired. The number of olefin resins may be one, or two or more. Specific examples include branched low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and crosslinked products of these polymers. Polypropylene resins such as propylene homopolymer, propylene-vinyl acetate copolymer, ethylene-propylene random copolymer, propylene-1-butene copolymer, ethylene-propylene-butene random copolymer, etc. ; can be mentioned. Among these olefin resins, ethylene-vinyl acetate copolymers, high-density polyethylene, linear low-density polyethylene, and mixtures thereof are preferred. Note that the low density is preferably 0.91g/cm ³ to 0.94g/cm ³ , more preferably 0.91g/cm ³ to 0.93g/cm ³ . The high density is preferably between 0.95g/cm ³ and 0.97g/cm ³ , more preferably between 0.95g/cm ³ and 0.96g/cm ³ . Medium density is a density between low density and high density.

<A-1-2. Foaming agent>
The number of foaming agents may be one, or two or more.

As the foaming agent, any appropriate foaming agent can be used as long as it does not impair the effects of the present invention. The blowing agent is preferably an organic compound whose boiling point is lower than the softening point of the styrene resin and which is gaseous or liquid at normal pressure. Specific examples include aliphatic hydrocarbons such as propane, n-butane, isobutane, pentane (n-pentane, isopentane or neopentane), n-hexane; alicyclic hydrocarbons such as cyclopentane and cyclopentadiene; acetone , Ketones such as methyl ethyl ketone; Alcohols such as methanol, ethanol, and isopropyl alcohol; Low boiling point ether compounds such as dimethyl ether, diethyl ether, dipropyl ether, and methyl ethyl ether; Halogen-containing such as trichloromonofluoromethane and dichlorodifluoromethane Hydrocarbons; As the blowing agent, an inorganic gas such as carbon dioxide, nitrogen, or ammonia may be used. Among these, aliphatic hydrocarbons are preferred as the blowing agent. This is because deterioration of the ozone layer can be prevented, and since air is replaced quickly, deterioration of the foamed molded product over time can be suppressed. More preferred blowing agents are propane, n-butane, isobutane, n-pentane, isopentane, and combinations thereof.

The content of the foaming agent in the expandable particles can be appropriately set depending on the purpose as long as it is sufficient to form pre-expanded styrenic resin particles and a styrenic resin foam molded article. The content of the blowing agent is preferably 2 parts by mass to 16 parts by mass, more preferably 3 parts by mass to 8 parts by mass, based on 100 parts by mass of the expandable particles.

<A-1-3. Method for manufacturing expandable particles>
The expandable particles can be produced by any suitable method as long as the effects of the present invention are not impaired. Such a production method typically includes a step of polymerizing a monomer component containing a styrene monomer, and adding a blowing agent during and/or after the polymerization to obtain expandable particles. process.

A typical example of a method for polymerizing the monomer components is a suspension polymerization method.

A method of adding and impregnating a blowing agent during and/or after the polymerization is called a one-stage method.

The particles obtained by polymerization without adding a blowing agent are sieved to obtain only particles within the required particle size range, and the temperature of the reaction vessel containing the particles, water, and dispersant is raised to form a dispersion liquid. A method in which a blowing agent is added to this dispersion to impregnate the particles with the blowing agent is called a two-step method (post-impregnation method).

A dispersion liquid is prepared by raising the temperature of a reaction vessel containing small styrene resin particles (seed particles), water, and a dispersant, and a monomer component with a polymerization initiator dissolved therein is continuously fed. However, a method in which a monomer component is further continuously supplied as necessary to perform polymerization and grow the particles to a desired particle size is called a seed polymerization method. In the seed polymerization method, a blowing agent is added during and/or after the polymerization is impregnated.

Expandable particles can also be formed by any one of a one-stage method, a two-stage method, and a seed polymerization method.

As the polymerization initiator for the polymerization of styrenic monomers, any suitable radical-generating polymerization initiator can be used as long as the effects of the present invention are not impaired. Examples of such polymerization initiators include benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxybenzoate, t-butylperoxy-2-ethylhexyl monocarbonate, dicumyl Peroxide, t-butylperoxypivalate, t-butylperoxyisopropyl carbonate, 2,2-t-butylperoxybutane, t-butylperoxy-3,3,5-trimethylhexanoate, di-t - Organic peroxides such as butylperoxyhexahydroterephthalate; azo compounds such as azobisdimethylvaleronitrile; The number of these polymerization initiators may be one, or two or more.

As a polymerization initiator, in order to adjust the molecular weight and reduce the amount of residual monomer, a polymerization initiator whose decomposition temperature is in the range of 50°C to 80°C to obtain a half-life of 10 hours, and a polymerization initiator for 10 hours are used. It may be used in combination with a polymerization initiator whose decomposition temperature is in the range of 80°C to 120°C to obtain a half-life of . Since the polymerization initiator needs to be uniformly absorbed into the seed particles, it is preferable to add it as a liquid. If the polymerization initiator is added directly to the dispersion, it will be difficult to absorb it uniformly into the seed particles. Therefore, the polymerization initiator should be added suspended or emulsified in an aqueous medium, or a small amount of styrene monomer may be added to the dispersion. It is preferable to dissolve it in the body and add it as an aqueous suspension with the addition of a dispersing agent.

Any appropriate amount of the polymerization initiator may be adopted as long as the effects of the present invention are not impaired. The amount used is preferably 0.1% by mass to 1.0% by mass, more preferably 0.1% by mass to 0.8% by mass, based on the styrene monomer.

As the dispersant, any suitable dispersant may be used as long as it does not impair the effects of the present invention. Examples of such dispersants include suspension stabilizers and anionic surfactants. There may be only one type of these, or two or more types may be used.

Examples of suspension stabilizers include water-soluble polymers such as polyvinyl alcohol, methylcellulose, polyacrylamide, and polyvinylpyrrolidone; sparingly soluble inorganic metal salts such as tricalcium phosphate, magnesium pyrophosphate, and magnesium oxide. When using a sparingly soluble inorganic metal salt, an anionic surfactant is usually used in combination.

Examples of anionic surfactants include alkyl sulfates such as sodium lauryl sulfate; alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate; higher fatty acid salts such as sodium oleate; and β-tetrahydroxynaphthalenesulfonates. It will be done.

The polymerization initiator is preferably added dissolved in a monomer component containing a styrene monomer or a solvent. Examples of the solvent include aromatic hydrocarbons such as ethylbenzene and toluene; aliphatic hydrocarbons such as heptane and octane. When a solvent is used, it is usually used in an amount of 10% by mass or less based on the styrenic monomer.

The reaction solution (typically a suspension) containing the styrenic monomer may further contain an additive. Examples of additives include radiation heat transfer suppressing components, resins other than styrene resins, crosslinking agents, plasticizers, fillers, coloring agents, bubble control agents, weathering agents, anti-aging agents, antifogging agents, fragrances, etc. Can be mentioned. The type, number, combination, content, etc. of additives can be appropriately set depending on the purpose. The number of additives may be one, or two or more.

When manufacturing expandable particles, a foaming aid may be included together with a foaming agent. Examples of the foaming aid include diisobutyl adipate, toluene, cyclohexane, ethylbenzene, liquid paraffin, and coconut oil. The number of foaming aids may be one, or two or more.

When manufacturing expandable particles, a flame retardant or a flame retardant aid may be included together with a foaming agent. Examples of flame retardants include tetrabromocyclooctane, hexabromocyclododecane, hexabromocyclohexane, trisdibromopropyl phosphate, tetrabromobisphenol A, tetrabromobisphenol F, and tetrabromobisphenol A-bis(2,3-dibromo-2 -methylpropyl ether), tetrabromobisphenol A-bis(2,3-dibromopropyl ether), tetrabromobisphenol A-diglycidyl ether, 2,2-bis[4'(2'',3''-dibromoalkoxy) )-3',5'-dibromophenyl]-propane. Examples of flame retardant aids include cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and 3,4-dimethyl-3,4-diphenyl. Examples include hexane.

Expandable particles may be manufactured by melt extrusion. In the melt extrusion method, styrenic resin pellets are fed to a resin supply device, a blowing agent is press-fitted and kneaded into the molten styrene resin in the resin feed device, and the molten resin containing the blowing agent is transferred to the tip of the resin feed device. This is a method in which expandable styrenic resin particles are obtained by extruding through small holes in an attached die and then cooling. A method of extruding particles directly into a cooling liquid through small holes in a die, cutting the extrudate with a rotating blade immediately after extrusion, and cooling the cut particles in the cooling liquid is called a hot-cut method. Strand cutting is a method in which the strands are extruded into the air through a small hole in a die, introduced into a cooling water tank before foaming, and then cut into cylindrical particles after being cooled in the cooling water tank. method (cold cut method). Expandable particles can be produced by either a hot cut method or a strand cut method (cold cut method).

≪A-2. Process of washing expandable particles with water≫
A method for producing expandable styrenic resin particles according to an embodiment of the present invention includes a step of washing expandable particles containing a styrenic resin and a blowing agent with water. This step may be hereinafter referred to as a cleaning step.

In the cleaning process, the temperature of the water is adjusted to a specific temperature range. The temperature range is preferably 1°C to 37°C, more preferably 3°C to 35°C, even more preferably 5°C to 30°C, particularly preferably 8°C to 25°C. ℃ range, most preferably 10°C to 20°C. By washing the expandable particles with water in this temperature range, expandable styrene-based particles can be produced with a more sufficiently reduced surface adhesion amount of dispersant and polymer powder while maintaining the fusion properties of the molded product. Resin particles can be produced.

In the washing step, the amount of water per 100 parts by mass of expandable particles is adjusted to a specific amount range. The amount range is preferably 31 parts by mass to 390 parts by mass, more preferably 35 parts by mass to 350 parts by mass, even more preferably 40 parts by mass to 300 parts by mass, Particularly preferably, the amount is in the range of 45 parts by weight to 200 parts by weight, and most preferably in the range of 45 parts by weight to 180 parts by weight. By washing the expandable particles with water in such an amount range, it is possible to produce expandable styrenic resin particles in which the amount of the dispersant and polymer powder attached to the surface is more sufficiently reduced.

The cleaning time in the cleaning step can be set to any appropriate time within a range that does not impair the effects of the present invention. In consideration of manufacturing costs and the like, the cleaning time is preferably 90 minutes or less, more preferably 60 minutes or less.

≪A-3. Other processes≫
The method for producing expandable styrenic resin particles according to the embodiment of the present invention preferably includes a drying step of drying the particles obtained through the above-mentioned washing step, since the effects of the present invention can be further expressed. As the drying conditions, any suitable drying conditions may be set within a range that does not impair the effects of the present invention.

A method for producing expandable styrenic resin particles according to an embodiment of the present invention includes a step of adding (typically coating) a surface additive to the surface of expandable styrenic resin particles obtained through the above-mentioned washing step. May contain.

By applying the surface additive to the surface of the expandable styrenic resin particles, the surface properties of the resulting expandable styrenic resin particles can be appropriately modified depending on the purpose. The number of surface additives may be one, or two or more.

Any suitable amount of the surface additive may be adopted as long as the effect of the present invention is not impaired. Typically, the amount added is preferably 0.05 parts by mass to 3.0 parts by mass, more preferably 0.05 parts by mass, per 100 parts by mass of expandable styrene resin particles. 2.0 parts by weight, more preferably 0.1 parts by weight to 1.6 parts by weight.

Examples of surface additives include spreading agents, antistatic agents, anti-bonding agents, adhesion promoters, and lubricants.

Examples of surface additives include polyethylene glycol (typically functions as a spreading agent and antistatic agent), medium-chain fatty acid triglycerides (glycerides of linear or branched fatty acids having 5 to 12 carbon atoms), etc. Aliphatic compounds that are liquid at 5°C (typically function as fusion promoters); metal salts of higher fatty acids such as zinc stearate, magnesium stearate (typically function as binding inhibitors) ; stearic acid triglyceride (typically functions as a fusion promoter), stearic acid monostearate (typically functions as an antistatic agent); silicone oil (typically functions as a lubricant); Can be mentioned.

≪≪B. Expandable styrenic resin particles≫≫
Expandable styrenic resin particles according to an embodiment of the present invention are obtained by a method for producing expandable styrenic resin particles according to an embodiment of the present invention.

The expandable styrenic resin particles according to the embodiments of the present invention have a particle shape as a whole. As the specific shape of the expandable styrenic resin particles according to the embodiment of the present invention, any suitable shape can be adopted as long as the effects of the present invention are not impaired. Examples of such a shape include a spherical shape, a substantially spherical shape, an ellipsoidal shape (ovoid shape), a cylindrical shape, and a substantially cylindrical shape.

The expandable styrenic resin particles according to the embodiment of the present invention preferably have an average particle diameter of 0.3 mm to 3.0 mm, more preferably 0.3 mm to 1.7 mm.

The expandable styrenic resin particles may further contain any other suitable additives. Other additives include, for example, radiation heat transfer suppressing components, resins other than styrene resins, crosslinking agents, plasticizers, fillers, coloring agents, bubble control agents, weathering agents, anti-aging agents, antifogging agents, and fragrances. can be mentioned. The type, number, combination, content, etc. of other additives can be appropriately set depending on the purpose. The number of additives may be one, or two or more.

≪≪C. Pre-expanded styrene resin particles≫≫
The pre-expanded styrenic resin particles are obtained by pre-foaming expandable styrenic resin particles.

That is, the pre-expanded styrenic resin particles according to the embodiment of the present invention are obtained by pre-foaming the expandable styrenic resin particles according to the embodiment of the present invention. Pre-foaming includes foaming the expandable styrenic resin particles to a desired bulk expansion ratio (bulk density) using water vapor or the like. The bulk expansion ratio of the pre-expanded styrenic resin particles is preferably 2 times to 150 times, more preferably 5 times to 100 times. Bulk density is the reciprocal of bulk expansion ratio. The bulk foaming ratio and bulk density are determined, for example, as follows. By having the bulk expansion ratio of the pre-expanded styrenic resin particles within the above range, blocking during foaming and molding can be better prevented, and furthermore, charging properties during foaming and molding can be suppressed and better melting can be achieved. It is possible to provide pre-expanded styrenic resin particles that exhibit adhesion and surface properties and can be molded into a styrenic resin foam molded product with less static electricity.

W (g) of expandable styrene resin particles is collected as a measurement sample. This measurement sample is allowed to fall naturally into a graduated cylinder, and the volume V (cm ³ ) of the measurement sample dropped into the graduated cylinder is measured using an apparent density measuring device based on JIS K 6911. From the mass and volume of the measurement material, the bulk foaming ratio and bulk density can be determined based on the following formula.
Bulk foaming ratio (times = cm ³ /g) = Volume of measurement sample (V) / Mass of measurement sample (W)
Bulk density (g/cm ³ )=mass of measurement sample (W)/volume of measurement sample (V)

In one representative embodiment, the pre-expanded styrenic resin particles can be used to form a styrenic resin foam molded article. In another embodiment, the pre-expanded styrenic resin particles can be used as is as a buffer, a heat insulator, etc. When the pre-expanded styrenic resin particles are used as they are, the pre-expanded styrenic resin particles can preferably be used as a filler in which a bag is filled with a large number of pre-expanded styrenic resin particles.

≪≪D. Styrenic resin foam molded product≫≫
A styrenic resin foam molded article according to one embodiment of the present invention is a styrenic resin foam molded article molded from expandable styrenic resin particles according to an embodiment of the present invention. A styrenic resin foam molded article according to another embodiment of the present invention is a styrenic resin foam molded article molded from pre-expanded styrenic resin particles according to the embodiment of the present invention.

The styrenic resin foam molded article typically includes expanded styrenic resin particles (hereinafter sometimes simply referred to as "expanded particles") obtained by further foaming pre-expanded styrenic resin particles.

A styrenic resin foam molded article is typically composed of a plurality of foamed particles fused together.

A styrenic resin foam molded article can typically be produced by placing pre-expanded styrenic resin particles into a mold having a predetermined shape depending on the purpose and performing in-mold foam molding. More specifically, in-mold foam molding involves (i) filling pre-expanded styrenic resin particles into a closed mold having a large number of small holes; (iii) heating and foaming foamed styrene resin particles to obtain foamed particles; (iii) filling voids between foamed particles through the heating and foaming, and integrating the foamed particles by fusing them to each other; . The density of the styrenic resin foam molded product can be appropriately set depending on the purpose. The density of the styrenic resin foam molded product can be determined, for example, by adjusting in advance the bulk expansion ratio of the pre-expanded styrene resin particles filled into the mold, or by adjusting the amount of pre-expanded styrenic resin particles filled into the mold. It can be adjusted by adjusting.

The temperature of heating and foaming (substantially the temperature of the heating medium) is preferably 90°C to 150°C, more preferably 110°C to 130°C. The heating and foaming time is preferably 5 seconds to 50 seconds, more preferably 10 seconds to 50 seconds. The molding vapor pressure (blow gauge pressure of heating medium) for heating and foaming is preferably 0.04 MPa to 0.1 MPa, more preferably 0.06 MPa to 0.08 MPa. If heating and foaming are carried out under such conditions, the foamed particles can be well fused to each other.

If necessary, the pre-expanded styrenic resin particles may be aged before forming the styrenic resin foam molded article. The aging temperature of the pre-expanded styrenic resin particles is preferably 20°C to 60°C. If the aging temperature is too low, excessively long aging times may be required. If the aging temperature is too high, the blowing agent in the pre-expanded styrenic resin particles may dissipate and the moldability may deteriorate.

The bulk expansion ratio of the foamed particles in the styrenic resin foam molded product is preferably 2 to 150 times, more preferably 5 to 100 times.

≪≪E. Method of cleaning foamable particles≫≫
As described above, in the method for manufacturing expandable styrenic resin particles according to the embodiment of the present invention, the cleaning step of washing expandable particles containing a styrenic resin and a blowing agent with water is performed by adjusting the temperature of the water to a specific temperature. By adjusting the amount of water per 100 parts by mass of the expandable particles within a specific range, expandable styrenic resin particles can be produced in which the amount of surface adhesion of the dispersant and polymerized powder is more sufficiently reduced. can do. That is, the method for cleaning expandable particles according to an embodiment of the present invention is a cleaning method in which expandable particles containing a styrene resin and a blowing agent are washed with water, and the temperature of the water is set at 1°C to 37°C. The amount of water is adjusted to a range of 31 parts by mass to 395 parts by mass based on 100 parts by mass of the expandable styrenic resin particles.

The temperature range of water in the expandable particle cleaning method according to the embodiment of the present invention is preferably in the range of 1°C to 37°C, more preferably in the range of 3°C to 35°C, even more preferably in the range of 5°C to 30°C. ℃ range, particularly preferably from 8°C to 25°C, most preferably from 10°C to 20°C. By washing the expandable particles with water in this temperature range, expandable styrene-based particles can be produced with a more sufficiently reduced surface adhesion amount of dispersant and polymer powder while maintaining the fusion properties of the molded product. Resin particles can be provided.

The amount of water in the method for cleaning expandable particles according to the embodiment of the present invention is preferably in the range of 31 parts by mass to 390 parts by mass, more preferably in the range of 35 parts by mass to 350 parts by mass, and even more preferably is in the range of 40 parts by weight to 300 parts by weight, particularly preferably in the range of 45 parts by weight to 200 parts by weight, and most preferably in the range of 45 parts by weight to 180 parts by weight. By washing the expandable particles with water in such an amount range, it is possible to provide expandable styrenic resin particles in which the amount of the dispersant and polymer powder attached to the surface is more sufficiently reduced.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples. In addition, the measurement method and evaluation method of each characteristic are as follows.

<Measurement and evaluation of the residual adhesion rate of the dispersant and polymer powder adhering to the surface of the expandable styrene resin particles after washing>
Collect 600 g of wet expandable styrene resin particles that have been washed and dehydrated, put them into a poly beaker from which the supernatant liquid will flow down, and stir while pouring in an aqueous solution of 50 ppm of sodium dodecylbenzenesulfonate at a flow rate of 400 ml/min. The machine was washed by stirring at 270 rpm, and a total of 6 L of supernatant liquid was collected while being careful not to mix in the foamable styrene resin particles.
6L of the recovered liquid was suction filtered using a glass fiber filter paper (GA-200) whose mass had been measured in advance, and the obtained filter paper was dried in an oven at 45 degrees overnight, and the mass was measured the next day.
Separately, 1 g of wet expandable styrenic resin particles after washing and dehydration was dried in an oven at 45°C overnight, and the mass of the expanded expandable styrenic resin particles after drying was measured the next day. The mass of the actual expandable styrene resin particles was determined using a mathematical formula.
Actual mass of expandable styrenic resin particles = 600 x (mass of expandable styrenic resin particles after drying/1)
The percentage of remaining adhesion of the dispersant and polymer powder adhering to the surface of the expandable styrenic resin particles after washing was calculated using the following formula.
Remaining adhesion rate (%) = (mass of dispersant and polymer powder on filter paper/mass of actual expandable styrenic resin particles)
)×100
The residual adhesion rate was evaluated as follows.
◎: Less than 0.1%〇: 0.1% or more and less than 0.15% △: 0.15% or more and less than 0.2% ×: 0.2% or more

<Evaluation of fusion of foam molded product>
After making a cut line about 2 mm deep with a cutter knife along a straight line connecting the centers of a pair of long sides on the surface of a flat plate-shaped styrene resin foam molded product with a width of 300 mm, a length of 400 mm, and a thickness of 30 mm. The styrenic resin foam molded product is manually divided into two parts along this score line, and the number of broken particles ( Count a) and the number of particles broken at the interface between particles (b), and then substitute the value into the formula [(a)/((a) ten (b))] x 100 and fuse the obtained value. It was expressed as the arrival rate (%).
Furthermore, the evaluation criteria for fusion adhesion were as follows.
◎: Fusion rate is 90% or more ○: Fusion rate is 85% or more and less than 90% △: Fusion rate is 80% or more and less than 85% ×: Fusion rate is less than 80%

[Example 1]
<Production of expandable styrenic resin particles>
40,000 parts by mass of water, 100 parts by mass of tricalcium phosphate as a suspension stabilizer, and 3.2 parts by mass of sodium dodecylbenzenesulfonate as an anionic surfactant were supplied to a polymerization vessel with a content of 100 liters equipped with a stirrer. While stirring, 40,000 parts by mass of styrene, 102 parts by mass of benzoyl peroxide as a polymerization initiator, and 24 parts by mass of t-butylperoxy-2-ethylhexyl monocarbonate were added, and the temperature was raised to 90°C for polymerization. did. This temperature was maintained for 6 hours, and then the temperature was raised to 125°C, and 2 hours later, the mixture was cooled to obtain styrene resin particles. The obtained styrene resin particles were sieved to obtain styrene resin particles having a particle size of 0.5 mm to 0.71 mm as seed particles. Note that the stirring rotation speed was adjusted so that the above particle size could be obtained.
Next, 2150 parts by mass of seed particles, 7520 parts by mass of water, 30 parts by mass of magnesium pyrophosphate, and 1.0 parts by mass of sodium dodecylbenzenesulfonate were fed into a polymerization container with an internal volume of 25 liters equipped with a stirrer. A dispersion was prepared by heating to 72° C. while stirring. Subsequently, 31 parts by mass of benzoyl peroxide, 8 parts by mass of t-butylperoxy-2-ethylhexyl monocarbonate, 0.7 parts by mass of didodecyl 3,3'-thiodipropionate as a bubble regulator, and styrene: A solution was prepared in which 786 parts by mass of butyl acrylate was dissolved in a monomer mixture of 137 parts by mass, and the entire solution was supplied to the above dispersion while stirring. After the above solution was supplied into the dispersion, the temperature was maintained at 72° C. for 60 minutes.
Next, 2346 parts by mass of styrene was constantly supplied while raising the temperature to 87°C over 1 hour, and then 2.7 parts by mass of divinylbenzene was added to 3744 parts by mass of styrene while being held at 87°C for 1 hour and 30 minutes. A monomer mixture in which was dissolved was constantly fed and held for an additional 30 minutes.
Next, the temperature was raised to 125° C. and held for 30 minutes to cause unreacted monomers to react. Next, it was cooled to 100°C, and 92 parts by mass of cyclohexane, 82 parts by mass of diisobutyl adipate, 45 parts by mass of styrene, and 640 parts by mass of mixed butane were press-fitted into the polymerization container, and after holding for 2 hours, polymerization was carried out. The inside of the container was cooled to 25°C.
After that, the reaction liquid and the expandable styrene resin particles were separated, only the reaction liquid was removed, and 96 parts by mass of washing water whose temperature had been adjusted in advance to 12°C was added to 100 parts by mass of the expandable styrene resin particles. It was washed for 10 minutes and dehydrated.
After the dehydration was completed, a portion of the particles was sampled to measure the residual adhesion rate of the dispersant and polymer powder on the surface of the expandable styrene resin particles after washing.
After dehydration and drying, 0.1 part by mass of zinc stearate as an anti-blocking agent and 0.08 part by mass of 12-hydroxystearic acid triglyceride as an adhesion promoter were added to the resulting expandable styrenic resin particles. coated.
After coating, the expandable styrene resin particles were left in a constant temperature room at 13° C. for 5 days. It was confirmed that the aging was completed, and expandable styrenic resin particles (1) were obtained.
<Preparation of pre-expanded styrene resin particles>
The obtained expandable styrenic resin particles (1) were heated and pre-foamed to a bulk density of 0.0166 g/cm ³ to obtain pre-expanded styrenic resin particles (1). The obtained pre-expanded styrenic resin particles (1) were aged at 20° C. for 24 hours.
<Production of styrene resin foam molded product>
The aged pre-expanded styrene resin particles (1) were left for 24 hours at room temperature and then foam-molded in a mold to obtain a plate-shaped styrenic resin foam molded product (1) with a size of 400 mm x 300 mm x 30 mm. Ta. In-mold foam molding was performed using an ACE-3SP molding machine manufactured by Sekisui Koki Co., Ltd. The heating time was 8 seconds on one side, 2 seconds on the other side, and 5 seconds on both sides, and the molding pressure (steam blowing gauge pressure) was 0.06 MPa.
The results are shown in Table 1.

[Example 2]
The same procedure as in Example 1 was carried out except that the amount of washing water was changed to 50 parts by mass, and expandable styrenic resin particles (2), pre-expanded styrenic resin particles (2), and styrenic resin foam molded articles (2) were prepared. ) was obtained.
The results are shown in Table 1.

[Example 3]
The same procedure as in Example 1 was carried out except that the amount of washing water was changed to 40 parts by mass, and expandable styrenic resin particles (3), pre-expanded styrenic resin particles (3), and styrenic resin foam molded articles (3) were prepared. ) was obtained.
The results are shown in Table 1.

[Example 4]
The same procedure as in Example 1 was carried out except that the amount of washing water was changed to 150 parts by mass, and expandable styrenic resin particles (4), pre-expanded styrenic resin particles (4), and styrenic resin foam molded articles (4) were prepared. ) was obtained.
The results are shown in Table 1.

[Example 5]
The same procedure as in Example 1 was carried out except that the amount of washing water was changed to 200 parts by mass, and expandable styrenic resin particles (5), pre-expanded styrenic resin particles (5), and styrenic resin foam molded product (5 ) was obtained.
The results are shown in Table 1.

[Example 6]
The same procedure as in Example 1 was carried out except that the amount of washing water was changed to 300 parts by mass, and expandable styrenic resin particles (6), pre-expanded styrenic resin particles (6), and styrenic resin foam molded articles (6) were prepared. ) was obtained.
The results are shown in Table 1.

[Example 7]
The same procedure as in Example 1 was carried out except that the temperature of the washing water was changed to 1° C., and expandable styrenic resin particles (7), pre-expanded styrenic resin particles (7), and styrenic resin foam molded product (7) were prepared. I got it.
The results are shown in Table 1.

[Example 8]
The same procedure as in Example 1 was carried out except that the temperature of the washing water was changed to 20°C, and expandable styrenic resin particles (8), pre-expanded styrenic resin particles (8), and styrenic resin foam molded product (8) were prepared. I got it.
The results are shown in Table 1.

[Example 9]
The same procedure as in Example 1 was carried out except that the temperature of the washing water was changed to 35°C, and expandable styrenic resin particles (9), pre-expanded styrenic resin particles (9), and styrenic resin foam molded product (9) were prepared. I got it.
The results are shown in Table 1.

[Comparative example 1]
The same procedure as in Example 1 was carried out except that the amount of washing water was changed to 30 parts by mass, and expandable styrenic resin particles (C1), pre-expanded styrenic resin particles (C1), and styrenic resin foam molded articles (C1 ) was obtained.
The results are shown in Table 1.

[Comparative example 2]
The same procedure as in Example 1 was carried out except that the amount of washing water was changed to 400 parts by mass, and expandable styrenic resin particles (C2), pre-expanded styrenic resin particles (C2), and styrenic resin foam molded articles (C2) were prepared. ) was obtained.
The results are shown in Table 1.

[Comparative example 3]
The procedure was carried out in the same manner as in Example 1, except that the temperature of the washing water was changed to 38° C., and foamable styrenic resin particles (C3), pre-expanded styrene resin particles (C3), and styrenic resin foam molded articles (C3) were prepared. I got it.
The results are shown in Table 1.

Expandable styrenic resin particles, pre-expanded styrenic resin particles, styrenic resin foam molded articles obtained by the manufacturing method according to the embodiment of the present invention, and expandable particles obtained using the cleaning method according to the embodiment of the present invention It is suitably used for heat insulating materials used in houses and automobiles, heat retaining materials used in building materials, packaging materials for transportation such as fish boxes and food containers, cushioning materials, and the like. More specifically, the expandable styrenic resin particles, pre-expanded styrenic resin particles, and styrenic resin foam molded articles according to the embodiments of the present invention include wall insulation materials, floor insulation materials, roof insulation materials, Insulating materials for automobiles, insulating materials for hot water tanks, insulating materials for piping, insulating materials for solar systems, insulating materials for water heaters, containers for food and industrial products (e.g. food containers such as fish boxes, returnable boxes), cushioning materials , floats, blocks, packaging materials for fish and agricultural products, embankment materials (formed bodies for embankments, embankment blocks, etc.), core materials for tatami mats, core materials for cushions, aggregates for concrete, etc.

Claims (7)

A method for producing expandable styrenic resin particles, the method comprising the step of washing expandable particles containing a styrenic resin and a blowing agent with water,
In this step, the temperature of the water is adjusted to a range of 1 ° C. to 37 ° C., and the amount of the water is adjusted to a range of 31 parts by mass to 390 parts by mass based on 100 parts by mass of the expandable particles.
A method for producing expandable styrenic resin particles. The method for producing expandable styrenic resin particles according to claim 1, wherein the expandable particles are formed by any one of a one-stage method, a two-stage method, and a seed polymerization method. Expandable styrenic resin particles obtained by the manufacturing method according to claim 1 or 2. Pre-expanded styrenic resin particles obtained by pre-foaming the expandable styrenic resin particles according to claim 3,
The pre-foaming has a bulk expansion ratio of 2 to 150 times.
Pre-expanded styrene resin particles. A styrenic resin foam molded article molded from the expandable styrenic resin particles according to claim 3. A styrenic resin foam molded article formed from the pre-expanded styrenic resin particles according to claim 4. A cleaning method for cleaning foamable particles containing a styrenic resin and a foaming agent with water, the method comprising:
Adjusting the temperature of the water to a range of 1°C to 37°C,
Adjusting the amount of water to 100 parts by mass of the expandable particles in a range of 31 parts by mass to 395 parts by mass;
Method of cleaning foamable particles.