JP2023063388A - Styrenic resin composition, and method for producing foamable styrenic resin particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a styrenic resin composition that can give a styrenic resin foamed molding having a high expansion ratio and a low thermal conductivity, that is, a high heat insulation performance, and a method for producing a foamable styrenic resin particle.

SOLUTION: A method for producing a styrenic resin composition includes feeding styrenic resin and carbon to a twin screw extruder for melting and mixing. In the twin screw extruder, a specific energy is 0.13 kWh/kg or more.

SELECTED DRAWING: None

COPYRIGHT: (C)2023,JPO&INPIT

Description

TECHNICAL FIELD The present invention relates to a styrenic resin composition and a method for producing expandable styrenic resin particles.

Styrene-based resin foam molded products obtained using expandable styrene-based resin particles are foams with an excellent balance of lightness, heat insulation, shock-absorbing properties, etc., and have been used in food container boxes, cooler boxes, and shock-absorbing products. It is widely used as a heat insulating material for houses, etc. In particular, in recent years, in relation to various problems such as global warming, there is a growing desire to save energy by improving the heat insulating properties of buildings such as houses, and an increase in demand for styrene-based resin foam moldings is expected.

However, since styrene resin foam moldings are in a competitive market with other materials such as glass wool as heat insulating materials, thorough cost reduction is required in the production of styrene resin foam moldings. The thermal conductivity of the styrene-based resin foam-molded product increases as the expansion ratio increases, and the heat insulating property deteriorates. With a styrene resin foam molded product with a lower thermal conductivity, even if the expansion ratio is increased, it is possible to obtain the same heat insulation as a conventional styrene resin foam molded product with a low expansion ratio. The amount of certain expandable styrenic resin particles used can be reduced. Therefore, it is possible to inexpensively manufacture a heat insulating material comprising a styrene-based resin foam molded article.

In addition, a foaming agent such as butane or pentane contained in a styrene resin foam molded product has the effect of reducing thermal conductivity, but such a foaming agent escapes from the styrene resin foam molded product over time. It is known that the thermal conductivity of a styrene-based resin foam molded product increases with the lapse of time because the styrenic resin foam is dispersed and replaced with the atmosphere (air), and therefore the heat insulating property deteriorates with the lapse of time.

Therefore, it is required to keep the thermal conductivity of the styrene resin foam molding low even after the blowing agent such as butane or pentane contained in the styrene resin foam molding is replaced with air.

In view of the above circumstances, various studies have been made to lower the thermal conductivity of styrene resin foam moldings, and a method of using a radiation heat transfer inhibitor such as graphite in styrene resin foam moldings is known. there is A radiation heat transfer suppressor is a substance that can suppress radiation heat transfer among the heat transfer mechanisms that propagate in a foamed molded product. It has the effect of being able to lower the thermal conductivity as compared with foam molded articles.

For example, Patent Document 1 proposes expandable styrenic resin particles containing evenly distributed graphite powder, capable of yielding foams with densities of 35 g/L or less.

Patent Document 2 discloses that the graphite powder has a density of 10 to 100 kg/m3, a closed cell ratio of 60% or more, an average cell diameter of 20 to 1000 μm, and contains 0.05 to 9% by weight of graphite powder. The aspect ratio is 5 or more, the volume average particle diameter (50% particle diameter) is 0.1 to 100 μm, the specific surface area is 0.7 m2/cm3 or more, and the value obtained by dividing the 90% particle diameter by the 10% particle diameter is 1 to 20. A certain styrenic resin foam molded article is described.

In Patent Document 3, in the presence of an aromatic hydrocarbon having 6 to 10 carbon atoms, a styrene-based monomer is seed-polymerized in a styrene-based resin micropellet containing graphite particles, and at the same time, a foaming agent is added. A method for producing styrenic resin particles has been proposed.

In Patent Document 4, a resin composition containing a polystyrene resin, a flame retardant, graphite, and a volatile foaming agent is melt-kneaded in an extruder, and the resulting melt-kneaded product is extruded from a die into pressurized water, A method of producing expandable styrenic resin particles by cutting an extruded melt-kneaded product has been proposed.

Patent Document 5 proposes expandable styrene-based resin particles containing 0.1 to 25% by mass of graphite having an average particle size of more than 50 μm.

In Patent Document 6, styrene and optionally a monomer compound copolymerizable with styrene are polymerized in an aqueous suspension in the presence of graphite particles, and a foaming agent is added before, during, or after polymerization. A method for producing expandable styrene resin particles has been proposed.

In Patent Document 7, it is polymerized in an aqueous suspension in the presence of graphite and a nonionic surfactant, and has a thermal conductivity of less than 32 mW / m K measured at 10 ° C. according to DIN 52612 and a density of 25 g A method for producing expandable styrenic resin particles having a density of less than /L has been proposed.

Special Table No. 2001-525001 Japanese Patent Application Laid-Open No. 2005-2268 Special Table No. 2009-536687 JP 2013-75941 Special Table No. 2002-530450 Special Table No. 2001-522383 Special Table No. 2008-502750

As in Patent Documents 1 to 7, it is possible to obtain a styrene resin foam having a low thermal conductivity, that is, a high heat insulating performance, by using a radiation heat transfer inhibitor such as graphite in a styrene resin foam molded product. can.

Methods for incorporating a radiation heat transfer inhibitor such as graphite into a styrene resin are broadly classified into a method in which graphite is incorporated in the polymerization process of a styrene monomer, and a method in which graphite is incorporated in advance using a kneading facility such as an extruder. There is a method of melt-kneading styrene-based resin and graphite. Among these manufacturing methods, the melt-kneading method using extrusion kneading equipment is superior in terms of initial investment and manufacturing simplicity, but there is room for further improvement in terms of performance such as foamability and heat insulation. . In addition, in order to increase the competitiveness of styrene-based resin foams against other materials, further reductions in manufacturing costs are desired.

Accordingly, an object of the present invention is to provide a styrene resin composition and expandable styrene resin particles that can provide a styrene resin foam molded article having a high expansion ratio and low thermal conductivity, i.e., high heat insulation performance. It is to provide a manufacturing method.

The inventors of the present application conducted intensive studies to solve the above-mentioned problems, and found that the heat insulating property of the obtained melt-kneaded product was improved by controlling the kneading with carbon and styrene resin to specific melt-kneading conditions. I found that it could be improved. Among them, when used in a styrene-based resin foam molded product, it has a high expansion ratio, a high closed cell content, and a low thermal conductivity, without impairing the surface beauty despite containing graphite. The inventors have succeeded in obtaining a styrene-based resin foam molded article in which an increase in thermal conductivity over time is remarkably suppressed and which has high heat insulating properties over a long period of time, thereby completing the present invention.

That is, the present invention is a method for producing a styrenic resin composition, in which a styrenic resin and carbon are supplied to a twin-screw extruder and melt-kneaded, wherein the twin-screw extruder has a specific energy of 0.13 kWh/kg. The above-described method for producing a styrene-based resin composition (hereinafter sometimes referred to as "method for producing a styrene-based resin composition according to the present invention").

In the method for producing the styrene resin composition of the present invention, the carbon content is preferably 2 to 90% by weight with respect to 100% by weight of the styrene resin composition.

In the method for producing the styrenic resin composition of the present invention, the carbon is preferably at least one selected from the group consisting of graphite, graphene, carbon black, carbon nanotube, activated carbon graphite, and expanded graphite.

In the method for producing the styrenic resin composition of the present invention, the carbon preferably has an average particle size of 2.5 to 9.0 μm.

In the method for producing the styrene resin composition of the present invention, the laser scattering intensity per carbon unit solution concentration in the styrene resin composition is 4.0 {%/(mg/ml)}/wt% or more. preferable.

In the present invention, an expandable styrene resin composition can be produced by further adding a foaming agent to the styrene resin composition in the method for producing the styrene resin composition.

In addition, the first method for producing expandable styrene resin particles in the present invention comprises a step of supplying a styrene resin and carbon to a twin-screw extruder and melt-kneading them, a small hole attached after the twin-screw extruder Extruding a melt of a styrenic resin composition containing a foaming agent into a cutter chamber filled with circulating water through a die having a large number of In the method for producing styrenic resin particles, the twin-screw extruder has a specific energy of 0.13 kwh/kg or more and less than 0.41 kwh/kg.

The second method for producing expandable styrene-based resin particles in the present invention includes a step of supplying a styrene-based resin and carbon to a twin-screw extruder and melt-kneading them, and forming a large number of small holes attached after the twin-screw extruder. a step of extruding a melt of a styrene resin composition through a die having a styrene resin composition and cutting it with a cutter to obtain styrene resin particles; A method for producing styrene-based resin particles, wherein the twin-screw extruder has a specific energy of 0.13 kwh/kg or more (hereinafter referred to as the first method for producing expandable styrene-based resin particles and the second expandable styrene-based resin particles). The method for producing the styrene-based resin particles may be simply referred to as "the method for producing expandable styrene-based resin particles in the present invention").

In the method for producing expandable styrene-based resin particles in the present invention, the specific energy is preferably 0.16 kwh/kg or more and less than 0.41 kwh/kg.

In the method for producing expandable styrene resin particles according to the present invention, it is preferable that the resin temperature at the tip of the twin-screw extruder is 160°C or higher and lower than 210°C.

In the expandable styrene-based resin particles of the present invention, the carbon is preferably at least one selected from the group consisting of graphite, graphene, carbon black, carbon nanotube, activated carbon graphite, and expanded graphite.

In the method for producing expandable styrene-based resin particles according to the present invention, the carbon preferably has an average particle size of 2.5 to 9.0 μm.

In the method for producing the expandable styrene-based resin particles of the present invention, it is preferable that the carbon content is 2 to 8% by weight with respect to 100% by weight of the styrene-based resin composition.

In the method for producing the expandable styrene resin particles of the present invention, the laser scattering intensity per unit solution concentration of the expandable styrene resin particles is preferably 15.0%/(mg/ml) or more.

In the method for producing the expandable styrene resin particles of the present invention, the laser scattering intensity per carbon unit solution concentration in the expandable styrene resin particles is 4.0 {%/(mg/ml)}/% by weight or more. is preferred.

In the method for producing the expandable styrene resin particles of the present invention, when the expandable styrene resin particles are formed into an expanded molded article having an expansion ratio of 80 times, the expanded molded article having an expansion ratio of 80 times is allowed to stand at a temperature of 50° C. for 30 days. Further, after standing at a temperature of 23° C. for 24 hours, the thermal conductivity at 23° C. measured according to JIS A9511:2006R is preferably 0.0330 (W / mK) or less, and 0.0330 (W / mK) or less. 0320 (W/mK) or less is more preferable.

INDUSTRIAL APPLICABILITY According to the present invention, a styrene-based resin composition and an expandable styrene-based resin composition having good carbon dispersibility and excellent heat insulating properties can be produced. By using the styrene-based resin composition and the expandable styrene-based resin composition, a styrene-based resin foam-molded article having a high expansion ratio and a low thermal conductivity, i.e., a high heat insulating property, and the foam-molded article can be obtained. Expandable styrene resin particles can be obtained.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to produce expandable styrene-based resin particles capable of providing a styrene-based resin foam molded product having a high expansion ratio and a low thermal conductivity, that is, having a high heat insulating property.

(Styrene-Based Resin) The styrene-based resin used in the present invention is not limited to styrene homopolymers (styrene homopolymers). It may be copolymerized with a monomer or a derivative thereof. However, the brominated styrene/butadiene copolymer described later is excluded.

Other monomers copolymerizable with styrene or derivatives thereof include, for example, methylstyrene, dimethylstyrene, ethylstyrene, diethylstyrene, isopropylstyrene, bromostyrene, dibromostyrene, tribromostyrene, chlorostyrene, dichlorostyrene, and styrene derivatives such as trichlorostyrene; polyfunctional vinyl compounds such as divinylbenzene; (meth)acrylic acid esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and butyl methacrylate compounds; vinyl cyanide compounds such as (meth)acrylonitrile; diene compounds such as butadiene or derivatives thereof; unsaturated carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; N-methylmaleimide, N-butylmaleimide, and N-alkyl-substituted maleimide compounds such as N-cyclohexylmaleimide, N-phenylmaleimide, N-(2)-chlorophenylmaleimide, N-(4)-bromophenylmaleimide, and N-(1)-naphthylmaleimide. . These may be used alone or in combination of two or more.

The styrenic resin used in the present invention is not limited to the aforementioned styrene homopolymer and/or copolymers of styrene and other monomers copolymerizable with styrene or derivatives thereof. A homopolymer of the above-mentioned other monomers or derivatives, or a blend with a copolymer thereof may be used as long as the effect is not impaired.

The styrene resin used in the present invention may be blended with, for example, diene rubber-reinforced polystyrene, acrylic rubber-reinforced polystyrene, and/or polyphenylene ether resin.

Among the styrene resins used in the present invention, it is relatively inexpensive, can be foam-molded with low-pressure steam or the like without using a special method, and has an excellent balance of heat insulation, flame retardancy, and cushioning properties. Styrene homopolymers, styrene-acrylonitrile copolymers, or styrene-butyl acrylate copolymers are preferred.

The melt flow rate (hereinafter referred to as "MFR") of the styrene resin in the present invention is preferably 1 to 15 g/10 minutes. When the MFR is in this range, it becomes easier to obtain the specific energy necessary for dispersing carbon during melt-kneading of carbon and styrene resin in a twin-screw extruder, which will be described later, and as a result, excellent heat insulation performance is exhibited. It tends to be easy to obtain a styrenic resin composition that can give a styrenic resin foam molded article that has a high viscosity. In addition, there is a tendency to easily obtain expandable styrene resin particles, styrene resin pre-expanded particles, and styrene resin expansion moldings that are excellent in expandability (high expansion ratio, high air content) and surface beauty. The styrene-based resin foam molded article obtained has well-balanced properties such as mechanical strength such as compressive strength, bending strength or amount of bending deflection, and toughness. A more preferred range is 2 to 10 g/10 minutes. The MFR in the present invention is a value measured according to JIS K7210.

(Carbon) In the present invention, by adding carbon as a radiation heat transfer suppressor to the styrene resin, a styrene resin foam molded article having high heat insulating properties can be obtained. The term "radiation heat transfer inhibitor" as used herein refers to a substance having properties of reflecting, scattering or absorbing light in the near-infrared or infrared region.

Carbon used in the present invention includes graphite, graphene, carbon black, carbon nanotubes, activated carbon, expanded graphite, and the like. These carbons can be used individually by 1 type or in combination of 2 or more types. Among these, graphite is preferable because of its high effect of suppressing radiation heat transfer with respect to cost. Examples of graphite include flake graphite, earthy graphite, spherical graphite, and artificial graphite. Among these, flake graphite is preferable because it exhibits a high radiation suppressing effect. In the present specification, the term "scale-like" includes scale-like, flaky or plate-like ones.

The graphite of the present invention preferably has an average particle size of 2.5 to 9.0 μm, more preferably 3.0 to 6.0 μm, most preferably 4.0 to 6.0 μm. In this specification, the average particle size of graphite is measured and analyzed by a laser diffraction scattering method based on Mie theory in accordance with ISO13320:2009 and JIS Z8825-1, and the cumulative volume of all particles is 50%. The particle size (volume average particle size by laser diffraction scattering method) when it becomes is taken as the average particle size.

The larger the average particle size of graphite, the lower the manufacturing cost. In particular, graphite having an average particle size of 2.5 μm or more is very inexpensive and can be reduced in cost because the production cost including the cost of pulverization is low. Furthermore, when the average particle size of graphite is 2.5 μm or more, it is possible to produce a styrene-based resin foam molded article having good heat insulation properties. When the average particle diameter is 9.0 μm or less, the cell membrane is less likely to break when producing pre-expanded particles and a styrene resin foam molded article from the expandable styrene resin particles, and high expansion is facilitated. Also, there is a tendency that the easiness of molding is increased, and the compression strength of the styrene-based resin foam molded product is increased.

If the graphite has an average particle size of 3.0 μm or more, a lower thermal conductivity and therefore a higher heat insulating property can be obtained. Further, when the average particle size of graphite is 6.0 μm or less, the surface of the molded article is excellent, and lower thermal conductivity and thus higher heat insulation can be obtained.

In the present invention, the content of carbon is not particularly limited, but it is preferably 0.1 to 90% by weight, more preferably 2 to 90% by weight based on 100% by weight of the styrene resin composition.

When graphite is used as a preferred embodiment of the present invention, its content is 100% by weight of the styrene resin composition from the viewpoint of the balance between the effect of reducing thermal conductivity and the dispersibility of graphite in the styrene resin composition. is preferably 2% by weight or more and 90% by weight or less. When the graphite content is 2% by weight or more, the thermal conductivity reducing effect tends to be sufficient, while when it is 90% by weight or less, the carbon dispersibility in the styrene resin composition tends to be excellent. Excellent carbon dispersibility tends to result in excellent heat insulation performance.

Incidentally, the graphite content in the present invention is determined in the expandable styrene resin particles obtained in the present invention, and in the case of molding as expandable styrene resin particles, pre-expanded particles thereof, or expansion molded articles thereof, as well as in styrene. The graphite content in the expanded styrene resin particles and the expanded styrene resin product that can be provided from the styrene resin composition, the expandable styrene resin composition, and the expandable styrene resin particles is 100% by weight of the styrene resin composition. It is preferably 2% by weight or more and 8% by weight or less. When the graphite content is 2% by weight or more, the effect of reducing thermal conductivity tends to be sufficient. In addition, since the cell membrane is less likely to break, high foaming can be easily achieved, and the foaming ratio tends to be easily controlled.

Furthermore, the graphite content is more preferably 3% by weight or more and 7% by weight or less. When the graphite content is 3% by weight or more, the thermal conductivity is lowered, so that higher heat insulation can be obtained. Further, when the content of graphite is 7% by weight or less, the foamability and the surface beauty of the molded article are improved.

(Foaming Agent) In the present invention, the styrene resin composition may further contain a foaming agent to form an expandable styrene resin composition. The expandable styrene-based resin composition can be molded into expandable styrene-based resin particles or foam-molded articles, which will be described later, or extruded foams. The foaming agent used in the present invention is not particularly limited, but hydrocarbons having 3 to 6 carbon atoms are desirable, and more desirable, from the viewpoint of good balance between foamability and product life, and easy to achieve high magnification when actually used. is a hydrocarbon having 4 to 5 carbon atoms. If the number of carbon atoms in the foaming agent is 3 or more, the volatility of the foaming agent becomes low, and when the foaming agent is made into expandable styrene-based resin particles, it becomes difficult for the foaming agent to dissipate. It is preferable because it remains at a low level, it becomes possible to obtain sufficient foaming power, and it becomes easy to increase the magnification. Further, when the number of carbon atoms is 6 or less, the boiling point of the foaming agent is not too high, so that sufficient foaming power can be easily obtained by heating during preliminary foaming, and high foaming tends to be easily achieved. Examples of hydrocarbons having 3 to 6 carbon atoms include hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, neopentane, cyclopentane, normal hexane, and cyclohexane. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The amount of foaming agent added in the present invention is preferably 4 to 10 parts by weight with respect to 100 parts by weight of the styrene-based resin composition. When the expandable styrene resin particles are used, the expansion rate and expansion force are well balanced, and the expansion ratio can be stably increased. When the amount of the foaming agent added is 4 parts by weight or more, the foaming power required for foaming is sufficient, so high foaming is facilitated, and it is easy to produce a styrene-based resin foam molded article having a high expansion ratio of 50 times or more. Tend. In addition, when the amount of the foaming agent is 10 parts by weight or less, the flame retardancy is improved, and the production time (molding cycle) for producing the styrene-based resin foam molded article is shortened, resulting in a low production cost. tend to become The amount of foaming agent to be added is more preferably 4.5 to 9 parts by weight, more preferably 5 to 8.5 parts by weight, with respect to 100 parts by weight of the styrene-based resin composition.

(Flame Retardant) The styrenic resin composition of the present invention may contain a flame retardant. The flame retardant used in the present invention is not particularly limited, and any flame retardant conventionally used in foamed styrene resin articles can be used. desirable. Brominated flame retardants used in the present invention include, for example, 2,2-bis[4-(2,3-dibromo-2-methylpropoxy)-3,5-dibromophenyl]propane (also known as tetrabromobisphenol A -bis (2,3-dibromo-2-methylpropyl ether)), or 2,2-bis [4- (2,3-dibromopropoxy) -3,5-dibromophenyl] propane (also known as tetrabromobisphenol A - Brominated bisphenol compounds such as bis(2,3-dibromopropyl ether)), tetrabromocyclooctane, tris(2,3-dibromopropyl) isocyanurate, brominated styrene/butadiene block copolymer, brominated random Brominated butadiene/vinyl aromatic hydrocarbon copolymers such as styrene/butadiene copolymers or brominated styrene/butadiene graft copolymers (for example, disclosed in JP-T-2009-516019), and the like. be done. These brominated flame retardants may be used alone or in combination of two or more.

The brominated flame retardant is easy to control to the desired expansion ratio, and from the viewpoint of the balance of flame retardancy and the like when the radiation heat transfer inhibitor is added, the bromine content in 100% by weight of the styrene resin composition is preferably It is preferably 0.8% by weight or more, and more preferably 5.0% by weight or less. When the bromine content is 0.8% by weight or more, the effect of imparting flame retardancy tends to increase. . The styrenic resin composition and the expandable styrenic resin particles are blended such that the bromine content is more preferably 1.0 to 3.5% by weight.

(Thermal Stabilizer) In the present invention, by using a thermal stabilizer in combination, it is possible to suppress deterioration of flame retardancy and deterioration of the styrene resin due to decomposition of the brominated flame retardant in the manufacturing process. The heat stabilizers in the present invention can be used in appropriate combination according to the type of styrene resin used, the type and content of the foaming agent, the type and content of carbon, the type and content of the flame retardant, and the like. .

As the heat stabilizer used in the present invention, a hindered amine compound, a phosphorus compound, a phenolic stabilizer, or an epoxy compound is desirable because the weight loss temperature in the thermogravimetric analysis of the brominated flame retardant-containing mixture can be arbitrarily controlled. . A heat stabilizer can be used individually by 1 type or in combination of 2 or more types. These heat stabilizers can also be used as light stabilizers as described later. (Radical Generating Agent) In the present invention, by further containing a radical generating agent, it is possible to express high flame retardancy by using it in combination with a brominated flame retardant.

The radical generator used in the present invention is used in appropriate combination according to the type and content of the styrene resin used, the type and content of the foaming agent, the type and content of the radiation heat transfer inhibitor, and the type and content of the brominated flame retardant. be able to.

Examples of the radical generator used in the present invention include cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and poly-1,4- isopropylbenzene and the like. A radical generating agent can be used individually by 1 type or in combination of 2 or more types.

(Other Additives) The styrenic resin composition according to the present invention may optionally contain a processing aid, a light stabilizer, a nucleating agent, a foaming aid, and an electrifying agent within a range that does not impair the effects of the present invention. It may contain one or more other additives selected from the group consisting of inhibitors and colorants such as pigments.

Processing aids include sodium stearate, magnesium stearate, calcium stearate, zinc stearate, barium stearate, liquid paraffin, and the like.

Examples of light-resistant stabilizers include the aforementioned hindered amines, phosphorus stabilizers, epoxy compounds, phenolic antioxidants, nitrogen stabilizers, sulfur stabilizers, benzotriazoles, and the like.

Nucleating agents include inorganic compounds such as silica, calcium silicate, wollastonite, kaolin, clay, mica, zinc oxide, calcium carbonate, sodium hydrogen carbonate, or talc, methyl methacrylate copolymers, or ethylene- Polymer compounds such as vinyl acetate copolymer resins, olefin waxes such as polyethylene wax, or fatty acid bisamides such as methylenebisstearylamide, ethylenebisstearylamide, hexamethylenebispalmitamide, or ethylenebisoleic acid amide. mentioned.

As the foaming aid, a solvent having a boiling point of 200° C. or less under atmospheric pressure can be desirably used. hydrocarbons, or acetates such as ethyl acetate or butyl acetate.

As the antistatic agent and colorant, those used in various resin compositions can be used without particular limitation.

These other additives can be used individually by 1 type or in combination of 2 or more types. (Method for Producing Styrene-Based Resin Composition) Method for producing the styrene-based resin composition and the expandable styrene-based resin composition of the present invention (hereinafter sometimes simply referred to as "method for producing the styrene-based resin composition of the present invention") ) controls the specific energy in the twin-screw extruder to 0.13 kWh/kg or more in the melt-kneading step in which the styrene-based resin and carbon are supplied to the twin-screw extruder and melt-kneaded.

In the present invention, the form of supplying the styrene resin and carbon to the twin-screw extruder is not particularly limited, but from the viewpoint of the high effectiveness of the present invention, powdery carbon is supplied to the styrene resin and the twin-screw extruder. It is preferable to melt and knead the mixture. That is, the present invention does not require a prior kneading step of carbon and styrene resin, such as using a masterbatch prepared by kneading carbon and styrene resin in advance, and mixes carbon and styrene resin. A method for producing a styrenic resin composition that can provide a styrenic resin foam molded article that is excellent in production cost and excellent in heat insulation performance by directly supplying it to a twin-screw extruder and melt-kneading it to obtain a styrenic resin composition. can be provided. By ensuring the specific energy value in the twin-screw extruder within a specific range, the state of carbon dispersion in the styrene resin is improved, and a styrene resin foam molded product having high heat insulation performance is obtained at low cost. I found that it can be done.

The present invention does not exclude the use of a masterbatch prepared by kneading carbon and a styrenic resin in advance.

The twin-screw extruder used in the present invention may be a known twin-screw extruder, preferably a co-meshing twin-screw extruder. Single-screw extruders among kneading equipment capable of continuously obtaining a styrenic resin composition tend to have poorer carbon dispersibility than twin-screw extruders. In addition, batch-type kneaders such as mixers and kneaders tend to have better carbon dispersibility than continuous-type extruders, but tend to have poor productivity. As described above, a continuous twin-screw extruder is excellent as a method for producing a styrene-based resin composition that satisfies both performance and cost.

(Each condition in the melt-kneading process) Each condition of the melt-kneading process in the twin-screw extruder for the polystyrene-based resin and carbon in the manufacturing process of the styrene-based resin composition will be described.

(Specific Energy) The specific energy in the twin-screw extruder is 0.13 kWh/kg or more, preferably 0.16 kWh/kg or more, regardless of the presence or absence of a foaming agent. The higher the specific energy, the better the carbon dispersion state, and as a result, it is possible to obtain a polystyrene-based resin composition capable of providing a styrene-based resin foam molded article having high heat insulating performance. If it is less than 0.13 kWh/kg, the carbon will be insufficiently dispersed in the polystyrene resin, and the heat insulating performance will tend to deteriorate. On the other hand, it is preferably 0.50 kWh/kg or less from the viewpoint of preventing decomposition of the styrene resin.

The above specific energy refers to the value of the work performed by the twin-screw extruder per unit extrusion mass for all raw materials supplied to the twin-screw extruder, and the motor efficiency of the twin-screw extruder motor It can be obtained by dividing the power consumption by the extrusion mass, that is, the mass of all raw materials extruded per unit time.

Methods for controlling the specific energy include a method of adjusting the cylinder set temperature of the twin-screw extruder, a method of adjusting the screw length (L) with respect to the cylinder inner diameter (D) of the extruder, that is, L/D, and a screw configuration. A method of adjusting the extrusion rate (Q) with respect to the number of revolutions (N) of the screw, that is, a method of adjusting Q/N, a method of adjusting the MFR of the styrenic resin to be used, and the like.

The set temperature of the cylinder of the twin-screw extruder is preferably in the range of 100°C to 250°C, more preferably 100°C to 200°C, except for the raw material feeding portion. The lower the cylinder set temperature, the higher the viscosity of the polystyrene resin, so the specific energy tends to increase. In addition, when the set temperature in the melt kneading section of the extruder is 250 ° C. or less, the decomposition of the brominated flame retardant is unlikely to occur, it is possible to obtain the desired flame retardancy, and the desired flame retardancy is imparted. There is an effect that it is not necessary to add a flame retardant excessively. On the other hand, when the set temperature of the melt-kneading section of the extruder is 100° C. or higher, the load on the extruder is reduced and the extrusion becomes stable.

The L/D of the extruder is preferably 24 or more and 36 or less, more preferably 26 or more and 32 or less, and still more preferably 28 or more and 32 or less. When L/D is small, the stability of extrusion operation tends to be poor. If the L/D is too long, it tends to lead to an increase in facility costs.

Regarding the screw configuration, it is preferable to use a kneading element that distributes and disperses the carbon in the styrenic resin. The number, thickness, angle and other types of kneading elements to be used can be appropriately adjusted according to the specific energy. It is preferable that there are more than one. Without the kneading element, it becomes difficult to adjust the specific energy within the above range, and as a result, it may become difficult to disperse the carbon in the styrenic resin to a high degree.

The screw rotation speed is preferably 100 rpm or more from the viewpoint of dispersibility of carbon, other additives, and a foaming agent, and preferably 500 rpm or less from the viewpoint of extrusion stability.

Q/N is the discharge amount per screw rotation and represents the quantitative efficiency of the extruder. The smaller this value, the larger the specific energy.

<Method for Producing Expandable Styrene-Based Resin Particles> As a method for producing the expandable styrene-based resin particles of the present invention, the following two methods are exemplified.

As a first method for producing expandable styrene resin particles, a styrene resin, carbon, and, if necessary, additives such as a flame retardant, a radical generator, and a stabilizer are melted and kneaded by a twin-screw extruder to form small holes. After extruding the melt of the styrene resin composition through a die having a In this manufacturing method, expandable styrene-based resin particles are obtained by incorporating a foaming agent into styrene-based resin particles. Granulation by cutting with a cutter may be either a cold cut method or a hot cut method.

As a second method for producing expandable styrene resin particles, a styrene resin, carbon, and, if necessary, additives such as a flame retardant, a radical generator, and a stabilizer are supplied to a twin-screw extruder and melt-kneaded. , The blowing agent is dissolved and dispersed in the resin by the twin-screw extruder or the dispersing equipment after the twin-screw extruder, and through a die having many small holes attached after the extruder, a cutter filled with pressurized circulating water In this method, a melt of a foaming agent-containing styrene resin composition is extruded into a chamber, and immediately after extrusion, the melted resin is cut by a rotating cutter in contact with a die and cooled and solidified by pressurized circulating water.

In addition, due to the simplicity of the equipment, additives such as styrene resin, carbon, other flame retardants, radical generators, stabilizers are supplied, and the blowing agent is directly injected into the twin-screw extruder that melts and kneads. is dissolved and dispersed in the resin and extruded through a die with many small holes attached after the extruder into a cutter chamber filled with circulating water. A method for producing polystyrene-based resin particles is preferred.

In the method for producing expandable styrene-based resin particles of the present invention, the melt-kneading step for the above-described styrene-based resin composition is similarly performed as the melt-kneading step in the method for producing the first and second expandable styrene-based resin particles. Applicable. The styrene-based resin composition (styrene-based resin composition for expandable particles) in the method for producing the first and second expandable styrene-based resin particles includes the styrene-based resin composition used in the above-described styrene-based resin composition. Resins, carbons, other components (blowing agents, additives, etc.), etc. can be used in the same manner unless otherwise specified.

In addition, the second method for producing expandable styrene resin particles, that is, supplying a styrene resin, carbon, and, if necessary, additives such as a flame retardant, a radical generator, and a stabilizer to a twin-screw extruder, After melt-kneading, the foaming agent is dissolved and dispersed in the resin by the twin-screw extruder or the dispersing equipment after the twin-screw extruder, and filled with pressurized circulating water through a die having many small holes attached after the extruder. In the case of a method in which the molten resin is extruded into a cutter chamber where it is extruded, and immediately after extrusion, the molten resin is cut by a rotating cutter in contact with the die and cooled and solidified by pressurized circulating water, the specific energy is less than 0.41 kWh / kg. It is preferably 0.33 kWh/kg or less. As the specific energy increases, the resin temperature at the tip of the twin-screw extruder tends to increase. When the resin temperature exceeds 0.33 kWh/kg and the resin temperature rises, the shape of the expandable styrene resin particles may become distorted and the moldability may deteriorate. As a result, cutting becomes difficult, and although the carbon dispersibility is excellent, expandable styrene resin particles may not be obtained.

(Resin Temperature at Tip of Twin-screw Extruder) In the method for producing expandable styrene resin particles of the present invention, the resin temperature at the tip of the twin-screw extruder affects the decomposition of the flame retardant and the cutting of the expandable styrene resin particles. , the temperature at the tip of the twin-screw extruder is preferably 160°C or higher and lower than 210°C, more preferably 160°C or higher and lower than 190°C. If the resin temperature at the tip of the twin-screw extruder exceeds 210°C, the flame retardant may decompose, resulting in deterioration of the carbon-containing styrenic resin composition, which may lead to a decrease in flame retardancy.

Furthermore, in the case of the above-described second method for producing expandable styrene resin particles, if cooling equipment for the resin is not provided between the twin-screw extruder and the die, the resin temperature at the tip of the twin-screw extruder is It can have a large effect on the temperature of the molten resin. In this case, if the temperature of the resin at the tip of the twin-screw extruder exceeds 190°C, the temperature of the resin at the time of cutting the resin with a die increases, which may distort the shape of the expandable styrene resin particles. If the temperature exceeds °C, the resin tends to wrap around the cutter during cutting, which may make cutting very difficult.

(Each condition of the granulation step) The conditions of the styrenic resin particle granulation step in the first and second methods for producing expandable styrene resin particles will be described.

Although the die is not particularly limited, for example, it may have small holes with a diameter of 0.3 mm to 2.0 mm, preferably 0.4 mm to 1.0 mm.

In the second method for producing expandable styrene-based resin particles, the temperature of the molten resin immediately before it is extruded from the die is Tg+40° C. or higher, where Tg is the glass transition temperature of the resin in a state not containing a foaming agent. is preferred, Tg+40°C to Tg+110°C is more preferred, and Tg+60°C to Tg+90°C is even more preferred. In the case of styrene homopolymer, the Tg is about 100°C, so the preferred temperature range is 140°C to 210°C, and the more preferred range is 160°C to 190°C.

In the second method for producing expandable styrene resin particles, if the temperature of the molten resin immediately before being extruded from the die is Tg + 40°C or higher, the viscosity of the extruded molten resin becomes low and clogging of the small pores occurs. Since it is difficult to remove and does not cause a substantial decrease in small pore opening ratio, it is possible to avoid a situation in which the shape of the expandable styrene resin particles to be obtained is distorted or irregular. On the other hand, if the temperature of the molten resin immediately before it is extruded from the die is Tg+110° C. or less, the extruded molten resin is easily solidified, is less likely to wrap around the rotary cutter, and can be stably cut.

The cutting device for cutting the molten resin extruded into the circulating pressurized cooling water in the second method for producing expandable styrene resin particles is not particularly limited. A device that spheroidizes, transfers to a centrifugal dehydrator, dehydrates and aggregates without foaming in pressurized circulating cooling water, and the like.

The conditions of the pressurized circulating cooling water should be adjusted according to the type and content of the styrenic resin, additives, foaming agent, and carbon used. It is preferable to use a condition in which the blade is cut by a cutter immediately. Specifically, in the case of styrene homopolymer, the temperature condition of the pressurized circulating cooling water is preferably 45°C to 75°C, more preferably 50°C to 65°C. As for the pressure conditions, the pressure is adjusted so that the true density of the expandable styrene resin particles to be obtained is preferably 950 kg/m 3 to 1050 kg/m 3 , more preferably 1000 to 1050 kg/m 3 . Although it depends on the type of foaming agent used, when butane or pentane is used as the foaming agent, it is preferably 0.6 to 2.0 MPa, more preferably 0.7 to 1.7 MPa, and still more preferably 0.8 MPa. ~1.5 MPa.

In the method for producing expandable styrene-based resin particles of the present invention, conditions such as the impregnation conditions of the foaming agent in the first production method may be the same as those generally carried out, and may be appropriately set.

<Styrene-based resin composition, expandable styrene-based resin particles> In the present invention, the dispersion state of carbon in the styrene-based resin composition and the expandable styrene-based resin particles is determined by the specific energy value given by the twin-screw extruder. It has been found that the controllable state of carbon can be controlled, and high heat insulation performance can be achieved by improving the state of carbon dispersion.

(Laser Scattering Intensity) In the present invention, especially when carbon having an average particle size of 2.5 to 9.0 μm is used, the dispersed state of carbon is evaluated by the laser scattering intensity per unit solution concentration measured by a laser diffraction scattering method. I found that it is possible.

The laser scattering intensity of the present invention is determined as follows. First, the intensity Lb of transmitted light when a He—Ne laser beam with a wavelength of 632.8 nm is irradiated to a toluene solution that does not contain a styrene resin composition or expandable styrene resin particles, and the styrene resin composition of the present invention. Alternatively, from the intensity Ls of the transmitted light when a He—Ne laser beam with a wavelength of 632.8 nm is irradiated to a toluene solution containing a predetermined weight of expandable styrene resin particles, the laser scattering intensity Ob (%) is calculated by the formula Ob=( 1−Ls/Lb)×100. Next, from the determined laser scattering intensity Ob, the laser scattering intensity per unit solution concentration of the styrene resin composition or expandable styrene resin particles of the present invention is determined. Then, the laser scattering intensity calculated by dividing the obtained laser scattering intensity per unit solution concentration by the carbon content (% by weight) of the styrene resin composition or expandable styrene resin particles of a predetermined weight is expressed in units of carbon. Laser scattering intensity per solution concentration.

The styrene resin composition or expandable styrene resin particles according to the present invention has a laser scattering intensity of 15.0%/(mg/ml) or more per unit solution concentration of the styrene resin composition or expandable styrene resin particles. is preferably When the laser scattering intensity is 15.0%/(mg/ml) or more, a high thermal conductivity reduction effect can be obtained. Specifically, when the expandable styrene-based resin particles are formed into an expanded molded article having an expansion ratio of 80 times, the 80-fold expanded molded article is allowed to stand at a temperature of 50°C for 30 days, and then at a temperature of 23°C. After standing for 24 hours, the thermal conductivity at 23° C. measured according to JIS A9511:2006R tends to be 0.0330 (W/mK) or less. That is, it is possible to obtain a low thermal conductivity at a high expansion ratio, and thus a high heat insulating property. Furthermore, when the laser scattering intensity is 17.5%/(mg/ml) or more, it is possible to obtain a higher thermal conductivity reduction effect. Specifically, when the expandable styrene-based resin particles are formed into an expanded molded article having an expansion ratio of 80 times, the 80-fold expanded molded article is allowed to stand at a temperature of 50°C for 30 days, and then at a temperature of 23°C. After standing still for 24 hours, the thermal conductivity at 23° C. measured according to JIS A9511:2006R tends to be 0.0320 (W/mK) or less. That is, it is possible to obtain a low thermal conductivity at a high expansion ratio, and thus a high heat insulating property.

The styrenic resin composition or expandable styrenic resin particles according to the present invention preferably has a laser scattering intensity of 4.0 {%/(mg/ml)}/wt% or more per carbon unit solution concentration. When the laser scattering intensity is 4.0%/(mg/ml)/% by weight or more, a high thermal conductivity reduction effect can be obtained. Specifically, when the expandable styrene-based resin particles are formed into an expanded molded article having an expansion ratio of 80 times, the 80-fold expanded molded article is allowed to stand at a temperature of 50°C for 30 days, and then at a temperature of 23°C. After standing for 24 hours, the thermal conductivity at 23° C. measured according to JIS A9511:2006R tends to be 0.0330 (W/mK) or less. That is, it is possible to obtain a low thermal conductivity at a high expansion ratio, and thus a high heat insulating property. Furthermore, when the laser scattering intensity is 4.9 {%/(mg/ml)}/% by weight or more, a higher thermal conductivity reduction effect can be obtained. It is possible to obtain a high thermal conductivity reduction effect with respect to the carbon content. Specifically, when the expandable styrene-based resin particles are formed into an expanded molded article having an expansion ratio of 80 times, the 80-fold expanded molded article is allowed to stand at a temperature of 50°C for 30 days, and then at a temperature of 23°C. After standing still for 24 hours, the thermal conductivity at 23° C. measured according to JIS A9511:2006R tends to be 0.0320 (W/mK) or less. That is, it is possible to obtain a low thermal conductivity at a high expansion ratio, and thus a high heat insulating property.

(Pre-expanded resin particles and method for producing the same) The styrene resin composition obtained by the production method of the present invention may be used as a masterbatch as a raw material for expandable styrene resin particles, or may be used as an expandable resin containing a blowing agent. The styrene-based resin composition may be formed into expandable styrene-based resin particles or a styrene-based resin foam molded article. Also, the expandable styrene resin particles obtained by the production method of the present invention can be used for an in-mold expansion-molded product after being pre-expanded.

The expandable styrene-based resin particles obtained by the production method of the present invention are subjected to a conventionally known pre-expansion process, for example, by expanding to 10 to 110 times with heated steam to form pre-expanded resin particles, and if necessary, curing for a certain period of time. After that, it can be used for molding. The obtained pre-expanded resin particles are molded with steam (for example, in-mold molding) using a conventionally known molding machine to produce a styrene-based resin foam molded article. Depending on the shape of the mold used, it is possible to obtain molded articles of complicated shapes and block-shaped molded articles.

The expandable styrene resin particles obtained by the production method of the present invention can be molded into a styrene resin foam molded product having a high expansion ratio. Preferably, 80 times or more is particularly preferable. According to the styrene resin composition and expandable styrene resin particles obtained by the manufacturing method of the present invention, low thermal conductivity can be achieved even when a styrene resin foam molded article having a size of 80 times or more is formed. High-performance heat insulating performance can be exhibited even as a highly foamed styrene-based resin foam molded article. Since the heat insulating material is used for a long period of time, maintaining the heat insulating performance after a long period of time is an important issue. For the styrene resin foam molded article molded from the styrene resin composition and the expandable styrene resin particles obtained by the production method of the present invention, a thermal conductivity measurement sample is cut out from the styrene resin foam molded article, and the sample is measured. Even after annealing at 50°C for 30 days and then standing at 23°C for 24 hours, low thermal conductivity can be achieved. By annealing at 50° C. for 30 days, the content of hydrocarbon foaming agents such as butane and pentane contained in the styrene resin foam molding is 0.5% or less, which affects the thermal conductivity. The influence becomes slight, and the thermal conductivity can be evaluated when the styrene-based resin foam molded article is used at room temperature for a long period of time.

When the expandable styrene resin particles are formed into an expanded molded article having an expansion ratio of 80 times, the 80-fold expanded molded article is allowed to stand at 50° C. for 30 days, and then at 23° C. for 24 hours. After that, the thermal conductivity at 23° C. measured according to JIS A9511:2006R is preferably 0.0330 (W/mK) or less. That is, it can be said that, if it is 0.0330 (W/mK) or less, it is possible to maintain very low thermal conductivity and high heat insulating properties over a long period of time. More preferably, it is 0.0320 (W/mK) or less.

In this specification, the foaming ratio is indicated by the unit of "times" or "cm3/g", but these have the same meaning.

The styrene resin pre-expanded particles and the styrene resin expansion molding of the present invention preferably have an average cell diameter of 70 to 300 μm, more preferably 90 to 250 μm, still more preferably 100 to 200 μm. When the average cell diameter is within the above range, a styrene-based resin foam molded article with higher heat insulation can be obtained. When the average cell diameter is 70 μm or more, the foaming ratio tends to be increased easily, and when it is 300 μm or less, the thermal conductivity increases, ie, the deterioration of the heat insulation performance can be avoided.

(Use of foamed molded article) The foamed molded article molded using the styrene resin composition and the expandable styrene resin particles obtained by the production method of the present invention is excellent in surface beauty, and has a high expansion ratio and high independence. It has a low porosity, low thermal conductivity, remarkably suppresses an increase in thermal conductivity over time, and has high heat insulating properties over a long period of time. Therefore, it is suitable for various uses such as construction insulation, food container boxes, cold insulation boxes, cushioning materials, agricultural and fisheries boxes, bathroom insulation and hot water storage tank insulation.

One embodiment of the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims, and technical means disclosed in different embodiments are appropriately combined. The obtained embodiment is also included in the technical scope of one embodiment of the present invention.

An embodiment of the present invention will be specifically described below based on Examples and Comparative Examples, but the present invention is not limited to these.

The measurement methods and evaluation methods in the following examples and comparative examples are as follows.

(Measurement of thermal conductivity of styrene-based resin foam molding) It is generally known that the higher the average temperature measured for thermal conductivity, the higher the value of thermal conductivity. must define the measured average temperature. In this specification, 23° C. defined by JIS A9511:2006R, which is a standard for foamed plastic heat insulating materials, is adopted as a standard. In addition, in order to evaluate the thermal conductivity when the foaming agent is replaced with air after a long period of time, a thermal conductivity measurement sample was cut out from the styrene-based resin foam molded product, and the sample was allowed to stand at 50°C for 30 days. , and further left to stand at a temperature of 23°C for 24 hours, and then the thermal conductivity was measured.

By annealing at 50° C. for 30 days, the content of hydrocarbon foaming agents such as butane and pentane contained in the styrene resin foam molding is 0.5% or less, which affects the thermal conductivity. The effect is slight, and the thermal conductivity of the styrene-based resin foam molded article used at room temperature for a long period of time can be evaluated almost accurately.

More specifically, a sample having a length of 300 mm, a width of 300 mm, and a thickness of 25 mm was cut out from the foamed styrene-based resin. The sample was allowed to stand at 50°C for 30 days, and then at 23°C for 24 hours. Thermal conductivity was measured at an average temperature of 23°C and a temperature difference of 20°C by a heat flow meter method according to JIS A1412-2:1999.

(Measurement of carbon content) About 10 mg of each of the styrene resin composition, the expandable styrene resin particles, or the styrene resin foam molded product was used as a sample. This sample is subjected to the following I to III using a thermogravimetry device (TG/DTA 220U, manufactured by SII Nanotechnology Co., Ltd.) equipped with a thermal analysis system: EXSTAR6000, and weight loss in III The amount was taken as carbon weight and expressed as a percentage of the specimen weight. I. The temperature was raised from 40° C. to 600° C. at a rate of 20° C./min under a nitrogen stream of 200 mL/min, and then held at 600° C. for 10 minutes, II. The temperature was lowered from 600° C. to 400° C. at a rate of 10° C./min under a nitrogen stream of 200 mL/min, and then held at 400° C. for 5 minutes, III. The temperature was raised from 400° C. to 800° C. at a rate of 20° C./min under an air flow of 200 mL/min, and then held at 800° C. for 15 minutes.

(Measurement of carbon average particle diameter D50 (μm) and laser scattering intensity (%)) (1) Sample solution preparation conditions (a) Measurement target is styrene resin composition, expandable styrene resin particles or styrene resin In the case of foam molding, 500 mg each of the styrene resin composition, expandable styrene resin particles, or styrene resin foam molding was dissolved and dispersed in 20 mL of a 0.1% (w/w) span 80 toluene solution.

(b) When the object to be measured is carbon before kneading, that is, the raw material carbon itself 20 mg of carbon and 480 mg of a styrene resin (manufactured by PS Japan Co., Ltd., 680) in a 0.1% (w/w) span 80 toluene solution It was dissolved and dispersed in 20 mL.

The dissolution/dispersion described above refers to a state in which the resin is dissolved and the carbon is dispersed.

Next, the sample solution was irradiated with ultrasonic waves in an ultrasonic cleaner to relax the aggregation of carbon.

(2) Ultrasonic irradiation conditions Apparatus used: Ultrasonic cleaner model number USM manufactured by AS ONE Corporation Oscillation frequency: 42 kHz Irradiation time: 10 minutes Temperature: Room temperature.

(3) Particle size measurement conditions Measurement device: Mastersizer 3000 laser diffraction particle size distribution measurement device manufactured by Malvern Light source: 632.8 nm red He-Ne laser and 470 nm blue LED Dispersion unit: Wet dispersion unit Hydro MV Analysis with the following settings was carried out, and the volume distribution was determined by measurement and analysis by a laser diffraction/scattering method based on Mie theory in accordance with ISO13320:2009 and JIS Z8825-1, and the D50 particle size of carbon in the sample was calculated.

Particle type: Aspheric Carbon refractive index: 2.42
Carbon absorption rate: 1.0
Dispersion medium: 0.1% (w/w) span 80 toluene solution Refractive index of dispersion medium: 1.49 Stirring speed in dispersion unit: 2500 rpm
Analysis model: General purpose, single mode maintained Measurement temperature: Room temperature.

(4) Measurement Procedure 120 mL of 0.1% (w/w) Span 80 toluene solution was injected into the dispersing unit, stirred at 2500 rpm and stabilized. The intensity of light measured by the central detector when a 632.8 nm red He—Ne laser beam was irradiated in a state in which no sample solution sample was present in the measurement cell and only the dispersion medium was present was defined as the transmitted light intensity Lb. 2 mL of the sonicated sample solution was then taken and added to the dispersing unit. One minute after the addition of the sample solution, the light intensity measured by the central detector when a 632.8 nm red He—Ne laser beam was irradiated was defined as the transmitted light intensity Ls. At the same time, particle size (D50) was also measured. From the obtained Ls and Lb, the laser scattering intensity Ob of the sample solution was calculated by the following formula.

Ob = (1-Ls/Lb) x 100 (%)
The central detector is a detector located directly opposite the output of the laser light, where the detected light is a measure of the transmitted light that was not used for scattering. Laser scattering intensity is a measure of the amount of laser light that is lost when scattering a sample by the analyzer's laser.

(5) Calculation of laser scattering intensity per unit solution concentration of styrene resin composition, expandable styrene resin particles, or styrene resin foam molded product The laser scattering intensity per unit solution concentration of the resin particles or the foamed styrene-based resin was calculated.

Laser scattering intensity per unit solution concentration of styrene resin composition, expandable styrene resin particles, or styrene resin foam molded product (%/(mg/ml)) = laser scattering intensity (Ob)/{sample weight ( 500 mg)/toluene amount (20 mL)×sample injection amount (2 mL)/total toluene amount in dispersion unit (120 mL+2 mL)}
The laser scattering intensity per unit solution concentration is the measured laser scattering intensity divided by the sample concentration in toluene. Since this measuring device is a device that must be measured with a solution, the sample concentration in the toluene solution is kept constant, and the measured value is obtained at a constant sample amount.

(6) Calculation of laser scattering intensity per carbon unit solution concentration in styrene resin composition, expandable styrene resin particles, or styrene resin foam molded product The laser scattering intensity per carbon unit solution concentration contained in the styrene resin particles or the styrene resin foam molded article (hereinafter abbreviated as "measurement object") was calculated.

Laser scattering intensity per carbon unit solution concentration in measurement target {%/(mg/ml)}/% by weight = Laser scattering intensity per unit solution concentration of measurement target (%/(mg/ml))/measurement target Carbon content (wt%)
The essence of one embodiment of the present invention is that even with the same weight of carbon, the heat insulating property can be improved by the state of dispersion of the contained carbon. An embodiment of the present invention can be expressed by using the laser scattering intensity per carbon unit solution concentration.

In addition, since the graphite dispersion state in the expandable styrene resin particles is determined by the graphite dispersion state in the styrene resin composition, the laser scattering intensity per carbon unit solution concentration of the expandable styrene resin particles and the styrene resin composition It is substantially the same as the laser scattering intensity per carbon unit solution concentration of (expandable styrene resin composition).

(7) Calculation of laser scattering intensity per unit solution concentration of a mixture of carbon and styrene resin before kneading Laser scattering per unit solution concentration of a mixture of carbon and styrene resin before kneading is calculated using the following formula. Intensity was calculated.

Laser scattering intensity per unit solution concentration of a mixture of carbon and styrene resin before kneading {% / (mg / ml)} = laser scattering intensity (Ob) / [{weight of carbon (20 mg) + styrene resin (480 mg )}/volume of toluene (20 mL)×volume of sample injection (2 mL)/total volume of toluene in dispersion unit (120 mL+2 mL)].

(8) Laser scattering intensity per carbon unit solution concentration before kneading Carbon before kneading, that is, laser scattering intensity per raw material carbon unit solution concentration was calculated by the following formula.

Laser scattering intensity per unit solution concentration of carbon before kneading {%/(mg/ml)}/% by weight = Laser scattering intensity per unit solution concentration of a mixture of carbon and styrene resin before kneading (%/(mg /ml))/carbon content in the mixture of carbon and styrenic resin before kneading (20/500×100=4% by weight).

(Measurement of foaming ratio and evaluation of foaming performance and molding performance)
A sample having a length of 300 mm, a width of 300 mm, and a thickness of 25 mm was cut from a styrene-based resin foam molded body in the same manner as in the measurement of thermal conductivity. The weight (g) of the sample was measured, and the vertical dimension, horizontal dimension and thickness dimension were measured using vernier calipers. The volume (cm3) of the sample was calculated from each dimension measured, and the foaming ratio was calculated according to the following formula.

Foaming ratio (cm3/g) = sample volume (cm3)/sample weight (g)
Incidentally, as mentioned above, the expansion ratio "times" of a styrene-based resin foam molded article is customarily expressed in "cm3/g".

Further, the surface of the obtained molded product was observed at 80 times magnification, and the surface appearance was judged to be good when there were few voids between particles, and to be judged to be poor when the voids were conspicuous.

The expansion/molding performance of the styrene-based resin foam was evaluated based on the measured expansion ratio and the beauty of the surface of the molded article. Evaluation of foaming/molding performance was based on the following criteria.
⊚: 80-fold expansion is possible and a beautiful molded product is obtained.
○: 80-fold expansion is possible, but it is difficult to obtain a beautiful molded product.

(Evaluation of flame retardancy)
The foam molded article thus produced was allowed to stand at 60° C. for 48 hours and then at 23° C. for 24 hours, and then the oxygen index was measured according to JIS K7201.

(Method for measuring average cell diameter of styrene-based resin foam molded product)
A styrene-based resin foam molded product having an expansion ratio of 80 was cut with a razor, and the cross section was observed with an optical microscope. The number of cells existing within a 1000 μm×1000 μm square of the cross section was counted, and the value measured by the following formula (average area diameter) was taken as the average cell diameter. The average cell diameter of five samples was measured, and the average was taken as the average cell diameter of the standard.

Average cell diameter (μm)=2×[1000 μm×1000 μm/(number of cells×π)] 1/2 Raw materials used in Examples and Comparative Examples are shown below.

(styrene resin)
(A) Styrene homopolymer [manufactured by PS Japan Co., Ltd., 680]
(carbon)
(B) Graphite [Square graphite SGP-40B manufactured by Marutoyo Casting Co., Ltd.]
Average particle size D50 = 5.8 µm
Laser scattering intensity per carbon (graphite) unit solution concentration = 3.7%.

(Brominated flame retardant)
(C1) 2,2-bis[4-(2,3-dibromo-2-methylpropoxy)-3,5-dibromophenyl]propane [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., SR-130, bromine content = 66% by weight]
(C2) Bromination (Styrene-butadiene copolymer) [EMERALD INNOVATION 3000 manufactured by Chemtura, bromine content = 65% by weight]
(Heat stabilizer)
(D1) Tetrakis(2,2,6,6-tetramethylpiperidyloxycarbonyl)butane [LA-57 manufactured by ADEKA Corporation]
(D2) Bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite [PEP-36 manufactured by ADEKA Corporation]
(D3) 3,9-bis(2,4-di-tert-butylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane [Ultranox626 manufactured by ADDIVANT]
(D4) Pentaerythritol tetrakis [3-(3',5'-di-tert-butyl-4'-hydroxyphenyl) propionate] [ANOX20 manufactured by ADDIVANT] (D5) Cresol novolac type epoxy resin [Huntsman Japan Co., Ltd. manufactured by ECN-1280, epoxy equivalent 212-233 g/eq. ].

(mixture of brominated flame retardant and stabilizer)
(E1) Brominated flame retardant (C1), stabilizers (D1) and (D2) were mixed in a mixer to obtain a mixture (E1) of brominated flame retardant and stabilizer. However, the weight ratio of each material was (C1):(D1):(D2)=100:2.1:3.2 and (C1)+(D1)+(D2)=100% by weight.

(E2) Brominated flame retardant (C2), stabilizers (D3), (D4) and (D5) were mixed in a mixer to obtain a mixture (E2) of brominated flame retardant and stabilizer. However, the weight ratio of each material is (C2): (D3): (D4): (D5) = 100: 0.5: 10: 5, (C2) + (D3) + (D4) + (D5) = 100% by weight.

(radical generator)
(F) Poly-1,4-diisopropylbenzene [manufactured by UNITED INITIATORS, CCPIB]
(foaming agent)
(G1) normal pentane [manufactured by SK Sangyo Co., Ltd.]
(G2) Isopentane [manufactured by SK Sangyo Co., Ltd.]
(G3) Isobutane [manufactured by Mitsui Chemicals, Inc.] The twin-screw extruder, pre-foaming machine and molding machine used in Examples and Comparative Examples are shown below.

(1) Twin-screw extruder: co-meshing twin-screw extruder (manufactured by Technobel Co., Ltd., cylinder inner diameter D = 40 mm, L/D = 32, motor capacity 55 kW, motor efficiency: 0.95)
(2) Screw design: At least one forward kneading element and one or more reverse kneading element were set before the blowing agent was injected. In addition, in order to adjust the specific energy, screw design #3, screw design #1, and screw design #2 were designed in descending order of the number of kneading disc elements before injecting the blowing agent, and a total of three screw designs were evaluated. .

(3) Pre-foaming machine; BHP-300 manufactured by Daikai Kogyo Co., Ltd.
(4) Molding machine; KR-57 manufactured by Daisen Kogyo Co., Ltd.
(5) Molding mold: mold for in-mold molding (length 450 mm×width 310 mm×thickness 25 mm).

(Example 1)
[Production of expandable styrene resin particles]
Styrene-based resin (A), carbon (B), a mixture of brominated flame retardant and stabilizer (E1) are each supplied to the twin-screw extruder with a feeder, and the cylinder set temperature after the raw material feed section of the twin-screw extruder was set to 160° C., and melt-kneading was performed at a screw rotation speed of 129 rpm in the configuration of screw design #1. The weight ratio of (A):(B):(E1)=93.5:4.0:2.5 was used, and the total supply amount was 50 kg/hr.

From the middle of the twin-screw extruder, 4.3 parts by weight of mixed pentane [mixture of 80% by weight of normal pentane (G1) and 20% by weight of isopentane (G2)] with respect to 100 parts by weight of the resin composition, isobutane ( G3) was press-fitted at a rate of 2.2 parts by weight. After that, through a gear pump set to 170°C and a diverter valve connected to the tip of the twin-screw extruder, the temperature was set to 250°C with 36 small holes with a diameter of 0.65 mm and a land length of 3.0 mm attached downstream of the diverter valve. It was extruded from the die with a discharge rate of 53.25 kg/hr into pressurized circulating water at a temperature of 65° C. and 1.3 MPa. The extruded molten resin is cut and pulverized at 1800 rpm using a rotary cutter having ten blades in contact with the die, and transferred to a centrifugal dehydrator to obtain expandable styrene resin particles. rice field. The resin temperature at the tip of the extruder was 176° C. and the specific energy was 0.140 kWh/kg.

0.08 parts by weight of zinc stearate was dry-blended with 100 parts by weight of the expandable styrene-based resin particles obtained, and then stored at 15°C.

[Preparation of Pre-Expanded Particles] Expandable styrene resin particles were put into a pre-expanding machine, and 0.1 MPa of steam was introduced into the pre-expanding machine to expand them to obtain pre-expanded particles having an expansion ratio of 80 times. rice field.

[Preparation of styrene-based resin foam molded product]
The obtained pre-expanded particles with an expansion ratio of 80 times are filled in a mold for in-mold molding attached to a styrene foam molding machine, and after introducing steam of 0.06 MPa to expand in the mold, was cooled by spraying with water for 3 seconds. After holding the styrene resin foam molding in the mold until the pressure of the styrene resin foam molding against the mold reaches 0.015 MPa (gauge pressure), the styrene resin foam molding is taken out, and a rectangular parallelepiped styrene A system resin foam molded product was obtained. The expansion ratio was 80 times.

The expandable styrene resin particles obtained in Example 1 and the foamed styrene resin article were measured and evaluated according to the various measurement methods described above. Table 1 shows the measurement results and evaluation results.

(Example 2)
A styrene-based resin foam molded article was prepared in the same manner as in Example 1, except that in [Preparation of expandable styrene-based resin particles], the screw rotation speed was changed to 162 rpm. Evaluation was performed in the same manner as in Example 1, and the measurement results and evaluation results are shown in Table 1.

(Example 3)
A styrene-based resin foam molded article was prepared in the same manner as in Example 1, except that in [Preparation of expandable styrene-based resin particles], the screw rotation speed was changed to 195 rpm. Evaluation was performed in the same manner as in Example 1, and the measurement results and evaluation results are shown in Table 1.

(Example 4)
A styrene-based resin foam molded article was prepared in the same manner as in Example 1, except that in [Preparation of expandable styrene-based resin particles], the screw rotation speed was changed to 229 rpm. Evaluation was performed in the same manner as in Example 1, and the measurement results and evaluation results are shown in Table 1.

(Example 5)
A styrene-based resin expansion molding was prepared in the same manner as in Example 1, except that in [Preparation of expandable styrene-based resin particles], the screw rotation speed was changed to 292 rpm. Evaluation was performed in the same manner as in Example 1, and the measurement results and evaluation results are shown in Table 1.

(Example 6)
A styrenic resin foam molded product was produced in the same manner as in Example 1, except that in [Preparation of expandable styrene resin particles], the screw design was changed to #2 and the screw rotation speed was changed to 292 rpm. Evaluation was performed in the same manner as in Example 1, and the measurement results and evaluation results are shown in Table 1.

(Example 7)
Expandable styrene-based resin particles were prepared under the same conditions as in Example 1, except that in [Preparation of expandable styrene-based resin particles], the screw design was changed to #2 and the screw rotation speed was changed to 420 rpm. However, due to frequent occurrence of cutting defects in the die, it was not possible to obtain an amount of samples that could produce a styrene-based resin foam molded article. Table 1 shows the measurement results and evaluation results of the obtained expandable styrene resin particles.

(Example 8)
A styrene-based resin foam molded product was prepared in the same manner as in Example 1, except that in [Preparation of expandable styrene-based resin particles], the screw design was changed to #3 and the screw rotation speed was changed to 195 rpm. Evaluation was performed in the same manner as in Example 1, and the measurement results and evaluation results are shown in Table 1.

(Example 9)
A styrene-based resin foam molded product was prepared in the same manner as in Example 1, except that in [Preparation of expandable styrene-based resin particles], the screw design was changed to #3 and the screw rotation speed was changed to 292 rpm. Evaluation was performed in the same manner as in Example 1, and the measurement results and evaluation results are shown in Table 1.

(Example 10)
In [Production of expandable styrene resin particles], a styrene resin (A), carbon (B), a mixture of a brominated flame retardant and a stabilizer (E2), and a radical generator (F) are fed in a biaxial feeder. The mixture was supplied to an extruder, and melted and kneaded at a screw rotation speed of 195 rpm with a screw design #1 configuration and a set cylinder temperature of 160° C. after the raw material feed section of the twin-screw extruder. The weight ratio of (A):(B):(E2):(F)=93.05:4.0:2.75:0.2 and the total supply amount was 50 kg/hr. Subsequent operations were performed in the same manner as in Example 1 to produce a styrene-based resin foam molded article. Evaluation was performed in the same manner as in Example 1, and the measurement results and evaluation results are shown in Table 1.

(Comparative Example 1) A styrene-based resin foam molded article was prepared in the same manner as in Example 1, except that in [Preparation of expandable styrene-based resin particles], the screw rotation speed was changed to 97 rpm. Evaluation was performed in the same manner as in Example 1, and the measurement results and evaluation results are shown in Table 1.

From the results of Examples, it is possible to improve the dispersibility of carbon by controlling the specific energy, and it is possible to provide a styrene-based resin foam molded product having a high expansion ratio and a low thermal conductivity, that is, a high heat insulating performance. It can be seen that a styrenic resin composition and a method for producing expandable styrenic resin particles can be provided.

( Reference example 7)
Expandable styrene-based resin particles were prepared under the same conditions as in Example 1, except that in [Preparation of expandable styrene-based resin particles], the screw design was changed to #2 and the screw rotation speed was changed to 420 rpm. However, due to frequent occurrence of cutting defects in the die, it was not possible to obtain an amount of samples that could produce a styrene-based resin foam molded article. Table 1 shows the measurement results and evaluation results of the obtained expandable styrene resin particles.

Claims (17)

A method for producing a styrenic resin composition in which a styrenic resin and carbon are supplied to a twin-screw extruder and melt-kneaded, wherein the styrenic resin composition having a specific energy of 0.13 kWh/kg or more in the twin-screw extruder A method for producing a resin composition. The method for producing a styrenic resin composition according to claim 1, wherein the carbon content is 2 to 90% by weight with respect to 100% by weight of the styrenic resin composition. The styrenic resin composition according to any one of claims 1 and 2, wherein the carbon is at least one selected from the group consisting of graphite, graphene, carbon black, carbon nanotubes, activated carbon, and expanded graphite. manufacturing method. The method for producing a styrenic resin composition according to any one of claims 1 to 3, wherein the carbon has an average particle size of 2.5 to 9.0 µm. 5. The production method according to claim 4, wherein the laser scattering intensity per carbon unit solution concentration in the styrenic resin composition is 4.0 {%/(mg/ml)}/wt % or more. A method for producing an expandable styrene resin composition, wherein a foaming agent is further added to the styrene resin composition according to any one of claims 1 to 5. Styrene-based resin and carbon are supplied to a twin-screw extruder and melt-kneaded, and a blowing agent is contained in a cutter chamber filled with circulating water through a die with many small holes attached after the twin-screw extruder. A method for producing expandable styrene-based resin particles, comprising a step of extruding a melt of a styrene-based resin composition and cutting it with a rotating cutter in contact with a die immediately after extrusion, wherein the twin-screw extruder has a specific energy of 0. .13 kwh/kg or more and less than 0.41 kwh/kg, a method for producing expandable styrene-based resin particles. A step of supplying styrene resin and carbon to a twin-screw extruder and melt-kneading, extruding the melt of the styrene-based resin composition through a die having many small holes attached after the twin-screw extruder, and cutting with a cutter A method for producing expandable styrene resin particles, comprising a step of obtaining styrene resin particles by squeezing the styrene resin particles, and a step of suspending the styrene resin particles in water and impregnating them with a blowing agent. A method for producing expandable styrene resin particles having a specific energy of 0.13 kwh/kg or more. The method for producing expandable styrene resin particles according to claim 7 or 8, wherein the specific energy is 0.16 kwh/kg or more and less than 0.41 kwh/kg. The method for producing expandable styrene resin particles according to any one of claims 7 to 9, wherein the resin temperature at the tip of the twin-screw extruder is 160°C or higher and lower than 210°C. The foam according to any one of claims 7 to 10, wherein the carbon is at least one selected from the group consisting of graphite, graphene, carbon black, carbon nanotubes, activated carbon, and expanded graphite. A method for producing polystyrene-based resin particles. The method for producing expandable styrene resin particles according to any one of claims 7 to 11, wherein the carbon has an average particle size of 2.5 to 9.0 µm. 13. The method for producing expandable styrene resin particles according to any one of claims 7 to 12, wherein the carbon content is 2 to 8% by weight with respect to 100% by weight of the styrene resin composition. 14. The method for producing expandable styrene resin particles according to claim 12 or 13, wherein the laser scattering intensity per unit solution concentration of the expandable styrene resin particles is 15.0%/(mg/ml) or more. The laser scattering intensity per carbon unit solution concentration in the expandable styrene resin particles is 4.0 {%/(mg/ml)}/wt% or more, according to any one of claims 12 to 14. A method for producing expandable styrene resin particles. When the expandable styrene resin particles are formed into an expanded molded article having an expansion ratio of 80 times, the 80-fold expanded molded article is allowed to stand at 50° C. for 30 days, and then at 23° C. for 24 hours. After that, the thermal conductivity at 23 ° C. measured in accordance with JIS A9511: 2006R is 0.0330 (W / mK) or less, The expandable styrene resin according to any one of claims 7 to 15. Particle production method. 17. The method for producing expandable styrene resin particles according to claim 16, wherein the thermal conductivity is 0.0320 (W/mK) or less.