JP2023145171A - Foamable polystyrenic resin particle and production method - Google Patents

Abstract

To provide a foamable polystyrenic resin particle that achieves a high foaming rate and yields a polystyrenic foamed resin molding with high thermal insulation performance.SOLUTION: A foamable polystyrenic resin particle contains a radiation heat transfer inhibitor. The foamable polystyrenic resin particle has a sphericity of 0.985 or less. The foamer contains isobutane. Assuming the total amount of the polystyrenic resin composition and the foamer to be 100 wt.%, the isobutane is more than 2.7 wt.% and 6.0 wt.% or less.SELECTED DRAWING: None

Description

The present invention relates to expandable polystyrene resin particles and a method for producing the same.

Polystyrene resin foam is a well-balanced foam that has lightness, heat insulation, and cushioning performance, and has been widely used as food container boxes, cold storage boxes, cushioning materials, and insulation materials for houses, etc. ing.

In particular, in recent years, in connection with various problems such as global warming, there has been a trend towards energy saving by improving the insulation performance of buildings such as houses, and the use of polystyrene resin foam molded products obtained using expandable polystyrene resin particles has been increasing. Demand is expected to increase. Therefore, various studies have been made to improve the foaming performance and heat insulation performance of the polystyrene resin foam.

For example, in Patent Documents 1 and 2, a polystyrene resin foam molded product exhibits excellent foaming performance and heat insulation performance by containing a radiation heat transfer inhibitor and containing a specific amount of isobutane with respect to the total amount of pentane and butane. is disclosed.

In Patent Document 3, high expansion ratio and high heat insulation performance are achieved by setting the aspect ratio of expandable polystyrene resin particles containing a radiation heat transfer inhibitor to 0.95 or less and the sphericity to 0.97 or more. It is disclosed that a polystyrene-based resin foam molded article compatible with the above can be obtained.

In Patent Document 4, a polystyrene resin composition obtained by kneading a polystyrene resin and a radiant heat transfer inhibitor is impregnated with a flame retardant and a foaming agent in an aqueous medium, and the flame retardant content in the surface layer of the foamable resin particles is determined. (wt%) is 1.05 times or more the flame retardant content (wt%) of the whole particle, and the foaming property is impregnated with a pentane content of 15 vol% or more in order to exhibit stable self-extinguishing property. A polystyrene resin foam molded article of polystyrene resin particles is disclosed.

JP2018-145212 JP2019-65073 JP2020-33481 JP2004-346281

The expandable polystyrene resin particles described in Patent Documents 1 to 4 have room for improvement, particularly in terms of increasing the expansion ratio.

An object of the present invention is to provide expandable polystyrene resin particles from which a polystyrene resin foam molded article having both a high expansion ratio and high heat insulation performance can be obtained.

In general, the use of radiation heat transfer inhibitors such as graphite in polystyrene resin foam moldings improves the heat insulation performance, but the foaming performance of expandable polystyrene resin particles tends to decrease, especially However, there is a problem in that the pre-expanded particles shrink when foamed at a high magnification.

In the above Patent Documents 1 and 2, isobutane is specified to be more than 20% by weight, 50% by weight, or less than 55% by weight with respect to 100% by weight of the total amount of pentane and butane. In order to obtain a polystyrene resin foam molded product with a high expansion ratio of 90 times or more, it is preferable to use a large amount of isobutane. From this point of view, the expandable polystyrene resin particles of Patent Documents 1 and 2, which contain isobutane in an amount of more than 20% by weight but not more than 50% by weight or not more than 55% by weight based on 100% by weight of the total amount of pentane and butane, have a higher Since the foaming ratio can be increased, there is room for improvement.

Patent Document 3 specifies that the aspect ratio of the expandable polystyrene resin particles is 0.95 or less and the sphericity is 0.97 or more, but there is no consideration regarding the blowing agent. The inventors of the present invention have investigated that when the amount of isobutane is small, the expansion ratio of the expandable polystyrene resin particles decreases, and in particular, when foamed to a high ratio, shrinkage may occur in the pre-expanded particles. From this point of view, there is room for improvement since it is possible to achieve a higher expansion ratio.

Patent Document 4 is an invention that exhibits excellent flame retardant performance by impregnating the surface layer of polystyrene resin particles with a flame retardant. There is a concern that the foaming performance may decrease locally, promoting the dissipation of the foaming agent, and deteriorating the foaming performance. From this point of view, there is room for improvement in increasing the expansion ratio.

Therefore, the present inventors conducted studies to solve the above-mentioned problems and found that by containing a specific amount of isobutane as a blowing agent and controlling the shape of the expandable polystyrene resin particles, a high expansion ratio and a low heat We succeeded in producing a polystyrene resin foam molded product with high conductivity, and completed the present invention.

That is, the present invention provides expandable polystyrene resin particles comprising a polystyrene resin composition containing a radiation heat transfer inhibitor and a blowing agent, wherein the expandable polystyrene resin particles have a sphericity of 0.985 or less. Expandable polystyrene resin particles, wherein the blowing agent contains isobutane, and the amount of isobutane is more than 2.7% by weight and 6.0% by weight or less based on 100% by weight of the total amount of the polystyrene resin composition and the blowing agent. (hereinafter sometimes referred to as "expandable polystyrene resin particles of the present invention"). In the expandable polystyrene resin particles of the present invention, the flame retardant content is preferably more than 1.0% by weight and 6.0% by weight or less based on 100% by weight of the polystyrene resin composition.
The expandable polystyrene resin particles of the present invention preferably contain pentane.
In the expandable polystyrene resin particles of the present invention, it is preferable that the expanded particles satisfy (Formula 1) after being pre-foamed to a bulk ratio of 90 times.
(Formula 1) (A)/(B)×100≦25.0
(A) Bulk ratio immediately after foaming of expanded particles pre-expanded to a bulk ratio of 90 times (B) Bulk ratio after curing of the pre-expanded particles after curing at 30°C for 24 hours Expandable polystyrene resin particles of the present invention In this case, the apparent density of the expandable polystyrene resin particles is preferably more than 950 kg/m ³ and less than 1200 kg/m ³ .
In the expandable polystyrene resin particles of the present invention, when the expandable polystyrene resin particles are pre-expanded to a bulk ratio of 90 times and then cured at 30°C for 24 hours, the amount of blowing agent in the pre-expanded particles is 5.0% to 5.0%. Preferably it is 6.0%.
In the expandable polystyrene resin particles of the present invention, heat conduction of the foam molded product when the expandable polystyrene resin particles are pre-foamed to a bulk ratio of 90 times and then cured at 30°C for 24 hours. It is preferable that the rate is 0.034 W/m·K or less.
The pre-expanded particles of the present invention are pre-expanded particles of the expandable polystyrene resin particles of the present invention, and have a bulk ratio of 90 times or more.

Furthermore, the present invention involves extruding a polystyrene resin melt consisting of a polystyrene resin composition containing a radiation heat transfer inhibitor and a blowing agent into pressurized circulating water through a die having a plurality of small holes, and cutting the polystyrene resin composition with a rotating cutter. 6. A method for producing expandable polystyrene resin particles, wherein the blowing agent contains isobutane, and the amount of isobutane is more than 2.7% by weight based on 100% by weight of the total amount of the polystyrene resin composition and the blowing agent. 0% by weight or less (hereinafter sometimes referred to as "the first manufacturing method of the present invention").

In the first manufacturing method of the present invention, the radiation heat transfer inhibitor preferably contains a carbon-based radiation heat transfer inhibitor.
In the first manufacturing method of the present invention, the blowing agent preferably contains pentane.

According to the expandable polystyrene-based resin particles of the present invention, it is possible to obtain a polystyrene-based resin foam molded product that has both a high expansion ratio and high heat insulation performance.

[Expansible polystyrene resin particles]
The expandable polystyrene resin particles of the present invention are expandable polystyrene resin particles containing a radiation heat transfer inhibitor, that is, the radiation heat transfer inhibitor and the foaming agent are contained in the polystyrene resin particles. Although the expandable polystyrene resin particles of the present invention have a sphericity of 0.985 or less, isobutane is 2% based on 100% by weight of the total amount of the polystyrene resin composition and blowing agent. By containing more than .7% by weight and not more than 6.0% by weight, it is possible to obtain a polystyrene resin foam molded product that has both a high expansion ratio and high heat insulation performance.

Generally, heat insulation properties can be improved by using a radiation heat transfer inhibitor such as graphite in a polystyrene resin foam molded product. However, as the amount of inorganic substances such as graphite added increases, the foaming performance of the expandable polystyrene resin particles decreases, and there is a problem that the expanded pre-expanded particles shrink. Although it is not certain, it is assumed that this problem is mainly caused by inorganic substances, and holes are formed in the cell membranes in the pre-expanded particles during pre-foaming, and the blowing agent easily escapes from the resin during foaming, making it impossible to maintain internal pressure. It is thought that this makes shrinkage more likely to occur after foaming. If the pre-expanded particles are shrunk, it can be recovered by curing the shrunken pre-expanded particles, but it is foreseen that it will be difficult to manage the magnification after curing. In addition, if the shrinkage that occurs is large, it will be necessary to cure at a high temperature in order to recover the expansion ratio, which will require additional curing silos that can be cured at high temperatures, and a large amount of thermal energy will be required during curing. This is costly. In particular, if the shrinkage that occurs is even greater, the pre-expanded particles will buckle and the expansion ratio will be difficult to recover even after curing at high temperatures, and the expansion ratio standard will no longer be met, resulting in a decrease in yield.

In addition, as the expandable polystyrene resin particles containing a radiation heat transfer inhibitor are expanded to a higher magnification, the shrinkage of the pre-expanded particles immediately after pre-expanding becomes more pronounced, making it difficult to achieve a high magnification of 90 times or more. becomes.

Since butane has a low solubility in polystyrene resin, it tends to become supersaturated, and it is thought that it tends to contribute to increasing the expansion ratio. Furthermore, since butane has a smaller molecular weight than pentane, even a small amount added tends to contribute to high foaming. In particular, isobutane has a bulkier molecular structure than normal butane, making it difficult for the blowing agent to escape from the expandable polystyrene resin particles, making it possible to achieve a high expansion ratio. However, even if the mixing ratio of pentane and isobutane is controlled as described in Patent Documents 1 and 2, shrinkage may occur immediately after foaming at a high magnification of 90 times or more.

Additionally, in general, the higher the sphericity of the expandable polystyrene resin particles, the more the expandable polystyrene resin particles approach a true spherical shape, and the lower the sphericity of the expandable polystyrene resin particles, the more the expandable polystyrene resin particles approach the true spherical shape. becomes elliptical. Since the elliptical shape has a larger specific surface area than the true spherical shape, external additives (anti-blocking agent during pre-foaming and fusion promoter during molding) coated on the surface of the expandable polystyrene resin particles are effective. It is presumed that this improves moldability. Furthermore, the amount of external additives used can be reduced, which is thought to lead to cost reductions. On the other hand, when foaming the expandable polystyrene resin particles to a high magnification of 90 times or more, if the sphericity of the expandable polystyrene resin particles is too low, shrinkage immediately after foaming tends to be significant.

Therefore, the sphericity of the expandable polystyrene resin particles containing the radiation heat transfer inhibitor was set to 0.985 or less, and 2.7 weight % of isobutane was added to 100% by weight of the total amount of the polystyrene resin composition and the blowing agent. %, it is possible to obtain a polystyrene resin foam molded article that has both a high expansion ratio and high heat insulation performance.

Furthermore, since the inorganic radiant heat transfer inhibitor also acts as a nucleating agent for bubbles, expandable polystyrene resin particles containing the radiant heat transfer inhibitor tend to have smaller cell diameters, making it easier to suppress radiant heat. Therefore, it is possible to achieve better heat insulation performance.

(Polystyrene resin)
The polystyrene resin composition used for the expandable polystyrene resin particles of the present invention contains a polystyrene resin as a base resin. The polystyrene resin includes not only styrene homopolymer (polystyrene homopolymer), but also copolymers of styrene and other monomers copolymerizable with styrene or derivatives thereof to the extent that the effects of the present invention are not impaired. It may be. These may be used alone or in combination of two or more.

Other monomers copolymerizable with styrene or derivatives thereof include, for example, methylstyrene, dimethylstyrene, ethylstyrene, diethylstyrene, isopropylstyrene, bromostyrene, dibromostyrene, tribromostyrene, chlorostyrene, dichlorostyrene, Styrene derivatives such as trichlorostyrene; polyfunctional vinyl compounds such as divinylbenzene; (meth)acrylic acid ester compounds such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and butyl methacrylate; 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, N-cyclohexyl Examples include N-alkyl-substituted maleimide compounds such as maleimide, N-phenylmaleimide, N-(2)-chlorophenylmaleimide, N-(4)-bromophenylmaleimide, and N-(1)-naphthylmaleimide. These may be used alone or in combination of two or more.

In the present invention, from the viewpoint of impact absorption resistance and heat resistance, for example, diene rubber reinforced polystyrene, acrylic rubber reinforced polystyrene, polyphenylene ether resin, etc. can be blended.

The polystyrene resin used in the present invention is relatively inexpensive, can be foam-molded using low-pressure steam, etc. without using special methods, and has an excellent balance of heat insulation performance, flame retardancy performance, and cushioning performance. Preferably, it contains a homopolymer.

In the present invention, while the polystyrene resin is the main component, other resins may be used in combination as long as the effects of the present invention are not impaired. Examples of other resins include homopolymers of other monomers or derivatives thereof that can be copolymerized with the above-mentioned styrene, such as polyolefin resins, polyester resins, polycarbonate resins, and acrylic resins, and copolymers thereof. can be mentioned.

(Radiation heat transfer inhibitor)
In the present invention, a polystyrene resin foam molded article having high heat insulation performance can be obtained by incorporating a radiation heat transfer inhibitor into expandable polystyrene resin particles. Here, the radiation heat transfer inhibitor refers to a material that has the property of reflecting, scattering, or absorbing light in the near-infrared or infrared region (eg, wavelength range of about 800 to 3000 nm). The radiation heat transfer inhibitor is not particularly limited, but examples include carbon materials, metal particles, metal compounds, metal oxides, and the like. Since metal particles, metal compounds, and metal oxides have low affinity for resins and tend to deteriorate foaming performance, it is preferable that carbon materials, that is, carbon-based radiation heat transfer inhibitors, be included.

Examples of the carbon material include graphite, graphene, carbon black, expanded graphite, activated carbon, carbon nanotubes, carbon nanofibers, etc. Among them, graphite is preferable from the viewpoint of dispersibility in polystyrene resin and cost. .

Examples of graphite include flaky graphite, earthy graphite, spherical graphite, and artificial graphite. In addition, in this specification, the term "scaly" also includes scale-like, flake-like, or plate-like. These graphites can be used alone or in combination of two or more. Among these, a graphite mixture containing flaky graphite as a main component is preferable, and flaky graphite is more preferable, since it has a high radiation heat transfer suppressing effect. From the viewpoints of high expansion ratio, heat insulation, and moldability, the average particle size of graphite is preferably 1 to 9 μm, more preferably 2 to 6 μm. The smaller the average particle size of graphite, the higher the production cost. Graphite with an average particle diameter of less than 1 μm is very expensive because of its high manufacturing cost including the cost of pulverization, and the cost of expandable polystyrene resin particles tends to be high. On the other hand, if the average particle size exceeds 9 μm, the cell membrane becomes easy to tear when producing pre-expanded particles and polystyrene resin foam molded articles from expandable polystyrene resin particles, making it difficult to achieve a high expansion ratio. There is a tendency that the ease of molding is reduced and the compressive strength of the polystyrene resin foam molded product is reduced. The average particle size of graphite here refers to the D50 particle size calculated by laser diffraction/scattering method based on Mie theory according to JIS Z8825-1.

Examples of the metal particles include gold, silver, copper, platinum, palladium, zinc, aluminum, and tin.

Examples of the metal compound include aluminum compounds, zinc compounds, magnesium compounds, titanium compounds, antimony compounds, calcium compounds, and tin compounds.

Examples of metal oxides include aluminum oxide, magnesium oxide, titanium oxide, calcium oxide, copper oxide, zinc oxide, iron oxide, and the like.

The content of the radiation heat transfer inhibitor in the expandable polystyrene resin particles of the present invention is preferably 2 to 40% by weight based on 100% by weight of the polystyrene resin composition. From the viewpoint of easy control of the expansion ratio to a desired level and balance of thermal conductivity reduction effect, etc., the amount is preferably 3 to 30% by weight, and even more preferably 3 to 20% by weight. If the content of the radiant heat transfer inhibitor is 2% by weight or more, the effect of reducing thermal conductivity is sufficient, while if it is 40% by weight or less, the content is reduced from the expandable polystyrene resin particles to the pre-expanded particles and the polystyrene resin. Since the cell membrane is less likely to be torn during the production of a foamed molded article, it becomes easier to increase the expansion ratio and control the expansion ratio. Here, the "polystyrene resin composition" in this specification is a component composition that constitutes expandable polystyrene resin particles, and does not contain a blowing agent.

In the present invention, a combination of two or more types of radiant heat transfer inhibitors may be added as long as the effects of the present invention are not impaired.

(foaming agent)
The expandable polystyrene resin particles of the present invention contain butane as a blowing agent. As butane, isobutane is essential, and from the viewpoint of high expansion ratio by suppressing shrinkage immediately after pre-foaming and production stability, isobutane is 2.7% based on 100% by weight of the total amount of polystyrene resin composition and blowing agent. Contains more than 6.0% by weight or less. The content of isobutane based on 100% by weight of the total amount of the polystyrene resin composition and blowing agent is preferably 2.75% by weight or more, more preferably 2.8% by weight or more, and particularly preferably 2.9% by weight or more. On the other hand, the content of isobutane based on 100% by weight of the total amount of the polystyrene resin composition and blowing agent is preferably 5.0% by weight or less, more preferably 4.5% by weight or less, particularly preferably 4.2% by weight or less. . If isobutane is more than 2.7% by weight, a high expansion ratio can be achieved, while if it is less than 6.0% by weight, when producing expandable polystyrene resin particles by melt extrusion method. The foaming of the polystyrene resin particles can be suppressed, cutting becomes possible, clogging of the die is suppressed, and collection of expandable polystyrene resin particles is stabilized.

As the blowing agent used in the present invention, in addition to the above-mentioned isobutane, other hydrocarbon blowing agents having 4 to 5 carbon atoms may be used. Examples include hydrocarbons such as normal pentane, isopentane, normal butane, neopentane, and cyclopentane. When isobutane and other hydrocarbon blowing agents having 4 to 5 carbon atoms are used together, the amount of the other hydrocarbon blowing agents having 4 to 5 carbon atoms is as follows: It is preferably 1 to 8 parts by weight. From the viewpoint of improving productivity by shortening the heating time during pre-foaming and flame retardant performance, the amount is more preferably 2 to 6 parts by weight. Moreover, since pentane has a higher effect of plasticizing polystyrene resin than isobutane, it is preferable to use isobutane and pentane in combination, since the heating time during pre-foaming can be shortened. Therefore, when isobutane and pentane are used together, the amount of pentane added is preferably 1 to 8 parts by weight based on 100 parts by weight of the polystyrene resin composition. From the viewpoint of improving productivity by shortening the heating time during pre-foaming and flame retardant performance, the amount is more preferably 2 to 6 parts by weight. As the pentane, normal pentane and isopentane are preferably used as a mixture, and it is more preferable to use normal pentane and isopentane in a weight ratio (normal pentane/isopentane) of 100/0 to 60/40. From the viewpoint of recovery of the magnification of the pre-expanded particles after curing at 30° C. for 24 hours and self-extinguishing properties, 98/2 to 60/40 is more preferable.

The amount of the blowing agent added is preferably 2.8 to 15 parts by weight based on 100 parts by weight of the polystyrene resin composition. When the amount of the blowing agent added is 2.8 parts by weight or more, the foaming power is sufficient and it becomes easy to achieve a high expansion ratio, making it easy to produce a polystyrene resin foam molded product with a high expansion ratio. In addition, if the amount of the blowing agent is 15 parts by weight or less, the flame retardant performance is less likely to deteriorate, and the manufacturing time (molding cycle) when manufacturing polystyrene resin foam moldings is shortened, which reduces manufacturing costs. be able to. The amount of the blowing agent added is preferably 3 to 12 parts by weight, and even more preferably 4 to 10 parts by weight, based on 100 parts by weight of the polystyrene resin composition.

The expandable polystyrene resin particles of the present invention contain a polystyrene resin, a radiant heat transfer inhibitor, and a foaming agent, and optionally include a flame retardant, a heat stabilizer, a radical generator, an external additive, and other additives. It may contain at least one optional component selected from the group consisting of agents. The expandable polystyrene resin particles of the present invention preferably contain a polystyrene resin, a radiant heat transfer inhibitor, a blowing agent, an external additive, and a flame retardant, and at least one of the above-mentioned optional components other than the flame retardant. It may contain, more preferably, a polystyrene resin, a radiant heat transfer inhibitor, a foaming agent, an external additive, a flame retardant, and a heat stabilizer, and any of the above-mentioned optional components excluding the flame retardant and heat stabilizer. It may contain at least one kind, and more preferably contains a polystyrene resin, a radiant heat transfer inhibitor, a foaming agent, an external additive, a flame retardant, a heat stabilizer, and a nucleating agent. It may contain at least one of the above-mentioned optional components except for the agent and the nucleating agent.

(Flame retardants)
The flame retardant that can be used in the present invention is not particularly limited, and any known flame retardant conventionally used in polystyrene resin foam moldings can be used, but among them, bromine, which has a high flame retardant effect, Preferred are flame retardants. Examples of the brominated flame retardant that can be used in the present invention include 2,2-bis[4-(2,3-dibromo-2-methylpropoxy)-3,5-dibromophenyl]propane (also known as tetrabromo Bisphenol A-bis(2,3-dibromo-2-methylpropyl ether)), 2,2-bis[4-(2,3-dibromopropoxy)-3,5-dibromophenyl]propane (also known as tetrabromobisphenol) Brominated bisphenol compounds such as A-bis(2,3-dibromopropyl ether), brominated styrene/butadiene block copolymers, brominated random styrene/butadiene copolymers, brominated styrene/butadiene graft copolymers Examples include brominated butadiene/vinyl aromatic hydrocarbon copolymers such as (for example, disclosed in Japanese Patent Application Publication No. 2009-516019), tetrabromocyclooctane, and the like. These brominated flame retardants may be used alone or in combination of two or more.

The flame retardant should be used in an amount of 1.0% by weight based on 100% by weight of the polystyrene resin composition, in order to easily control the expansion ratio to the desired expansion ratio and to balance flame retardancy when adding a radiation heat transfer inhibitor. It is preferably more than 6.0% by weight, and more preferably more than 1.0% by weight and not more than 4.0% by weight. If the content exceeds 1.0% by weight, the effect of imparting flame retardancy will not be reduced, and if the content is 6.0% by weight or less, the strength of the obtained polystyrene resin foam molded product will not easily decrease.

(thermal stabilizer)
In the expandable polystyrene resin particles of the present invention, further, by using a heat stabilizer in combination, deterioration of flame retardant performance and deterioration of the expandable polystyrene resin particles due to decomposition of the flame retardant during the manufacturing process can be suppressed. can.

The heat stabilizer in the present invention can be combined as appropriate depending on the type and content of the polystyrene resin used, the type and content of the blowing agent, the type and content of the radiant heat transfer inhibitor, the type and content of the flame retardant, etc. Can be used.

The thermal stabilizer used in the present invention is preferably a hindered amine compound, a phosphorus compound, or an epoxy compound, since the 1% weight loss temperature in thermogravimetric analysis of the polystyrene resin composition can be controlled arbitrarily. The heat stabilizer can be used alone or in combination of two or more.

The heat stabilizer should be used in a proportion of 0.5% by weight in 100% by weight of the polystyrene resin composition, from the viewpoint of easy control of the desired expansion ratio and balance of flame retardancy when adding the radiation heat transfer inhibitor. It is preferably 3% by weight. When it is 0.5% by weight or more, the flame retardant is difficult to decompose and the effect of imparting flame retardation is not reduced, and when it is 3% by weight or less, the strength of the obtained polystyrene resin foam molded product is not easily reduced.

(external additive)
The external additives that can be used in the present invention are not particularly limited, and any known external additives conventionally used for expandable polystyrene resin particles can be used. By coating the expandable polystyrene resin particles with an external additive, it is possible to suppress blocking (adhesion of expanded particles to each other) during pre-foaming and to promote fusion during molding.
Examples of external additives include fatty acid triglycerides such as lauric acid triglyceride, stearic acid triglyceride, and linoleic acid triglyceride, fatty acid diglycerides such as lauric acid diglyceride, stearic acid diglyceride, and linoleic acid diglyceride, lauric acid monoglyceride, stearic acid monoglyceride, and linoleic acid. Fatty acid monoglycerides such as monoglyceride, fatty acid metal salts such as zinc stearate, calcium stearate, magnesium stearate, aluminum stearate, zinc laurate, calcium laurate, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxyethylene stearyl Examples include nonionic surfactants such as ether, polyoxyethylene laurate, polyoxyethylene palmitate, polyoxyethylene stearate, and polyoxyethylene oleate. These external additives may be used alone or in combination of two or more. A preferred method for coating with these external additives is to apply them after drying and to coat by mixing. As a preferable external additive, a method of combining zinc stearate and hydroxystearic acid triglyceride is preferable in that it is easy to suppress blocking during pre-foaming and promote fusion during molding.

(Other additives)
The polystyrene resin composition of the expandable polystyrene resin particles of the present invention may contain a radical generator, a processing aid, a light resistance stabilizer, a nucleating agent, a foaming agent, a foaming agent, etc., as necessary, to the extent that the effects of the present invention are not impaired. It may contain one or more other additives selected from the group consisting of auxiliary agents, antistatic agents, and colorants such as pigments. Examples of the radical generator include cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and poly-1,4-isopropylbenzene. It will be done. Examples of processing aids include sodium stearate, magnesium stearate, calcium stearate, zinc stearate, barium stearate, liquid paraffin, and the like. Examples of the light resistance stabilizer include the aforementioned hindered amines, phosphorus stabilizers, and epoxy compounds, as well as 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, and talc, methyl methacrylate copolymers, and ethylene-vinyl acetate. Examples include polymeric compounds such as copolymer resins, olefin waxes such as polyethylene wax, fatty acid bisamides such as methylene bis stearyl amide, ethylene bis stearyl amide, hexamethylene bis palmitic acid amide, and ethylene bis oleic acid amide. As the foaming aid, a solvent whose boiling point under atmospheric pressure is 200°C or lower can be preferably used, such as aromatic hydrocarbons such as styrene, toluene, ethylbenzene, and xylene, alicyclic carbonized solvents such as cyclohexane, methylcyclohexane, etc. Examples include hydrogen, acetate esters such as ethyl acetate, and butyl acetate. Note that as the antistatic agent and coloring agent, those used in various resin compositions can be used without particular limitation. These other additives can be used alone or in combination of two or more.

The sphericity of the expandable polystyrene resin particles of the present invention is 0.985 or less. In order for the external additive to act effectively, the sphericity is preferably 0.983 or less, more preferably 0.980 or less. When the sphericity of the expandable polystyrene resin particles is 0.985 or less, the external additive acts effectively and moldability is improved, making it possible to obtain a foamed molded product with a high expansion ratio. It is assumed that On the other hand, the sphericity of the expandable polystyrene resin particles is preferably 0.900 or more, more preferably 0.920 or more, and particularly preferably 0.940 or more. If the sphericity of the expandable polystyrene resin particles is 0.900 or more, the particles will not have an extremely distorted shape, and significant shrinkage that occurs during high-magnification foaming can be alleviated.

In the expandable polystyrene resin particles of the present invention, the shrinkage rate of the expanded particles pre-expanded to a bulk ratio of 90 times is preferably 25.0 or less, more preferably 22.0 or less, and 20.0 or less. It is particularly preferable that The shrinkage rate of the pre-expanded particles is calculated by the following formula.
(Formula) Shrinkage rate (%) of pre-expanded particles = (A)/(B) x 100
(A) Bulk magnification immediately after foaming of foamed particles pre-expanded to a bulk magnification of 90 times (B) Bulk magnification after curing after curing the pre-expanded particles at 30°C for 24 hours Reserve calculated from the above (formula) When the shrinkage ratio of the foamed particles is 25.0 or less, the foaming ratio after curing at 30° C. for 24 hours becomes high, and the foaming ratio recovers easily. If the shrinkage rate of the pre-expanded particles is greater than 25.0, the cells of the pre-expanded particles will buckle, making it difficult to recover the magnification even after curing at high temperatures. This eliminates the need to cure the pre-expanded particles at high temperatures, making it easier to manage the magnification after curing.

The apparent density of the expandable polystyrene resin particles of the present invention is preferably more than 950 kg/m ³ and less than 1200 kg/m ³ . From the viewpoint of foamability, it is preferably more than 980 kg/m ³ , more preferably 1000 kg/m ³ or more. On the other hand, from the viewpoint of heat insulation performance, it is preferably 1150 kg/m ³ or less, more preferably 1100 kg/m ³ or less, and particularly preferably 1080 kg/m ³ or less.
Here, the density of general polystyrene-based resin is 1050 kg/m ³ to 1060 kg/m ³ , but since the polystyrene-based resin composition contains a high-density inorganic substance as a radiation heat transfer inhibitor, foaming is possible. If foaming during extrusion during the production of polystyrene resin particles can be suppressed, the density of the expandable polystyrene resin particles should be higher than the above density of 1050 kg/m ³ to 1060 kg/m ³ . Since the apparent density of the expandable polystyrene resin particles is more than 950 kg/m ³ and less than 1200 kg/m ³ , foaming of the polystyrene resin melt consisting of the polystyrene resin composition and the blowing agent is suppressed during extrusion. it is conceivable that. By obtaining expandable polystyrene resin particles that suppress foaming during extrusion, the closed cell ratio in the pre-expanded particles increases and the strength of the cell structure increases, so shrinkage immediately after pre-expanding can be suppressed and high It becomes possible to increase the foaming ratio.

In the expandable polystyrene resin particles of the present invention, after the pre-expanded particles obtained by pre-expanding the expandable polystyrene resin particles are cured at 30°C for 24 hours, the amount of blowing agent remaining in the pre-expanded particles is 5.0 weight. % to 6.0% by weight, more preferably 5.2% to 5.8% by weight. When the amount of blowing agent in the pre-expanded particles is 5.0% by weight or more, molding becomes easy, and when it is 6.0% by weight or less, the cycle during molding is shortened, and the productivity of the foamed molded product is excellent. .

In the expandable polystyrene resin particles of the present invention, the bulk ratio of the pre-expanded particles obtained by pre-expanding the expandable polystyrene resin particles after curing at 30° C. for 24 hours is preferably 90 times or more. Since the bulk ratio of the pre-expanded particles is 90 times or more, the density of the polystyrene resin foam molded product formed by molding the pre-expanded particles is reduced, and a lighter polystyrene resin foam molded product can be produced. becomes possible. Furthermore, by increasing the bulk factor, the amount of resin used can be reduced, leading to cost reductions.

[Method for manufacturing expandable polystyrene resin particles]
The expandable polystyrene-based resin particles of the present invention can be obtained by a known melt-kneading method. Specifically, the polystyrene-based resin, a radiant heat transfer inhibitor, and a foaming agent are melt-kneaded using an extruder (melt-kneading step). ), the melt-kneaded product is extruded through a die with small holes attached to the tip of the extruder into a chamber filled with pressurized circulating water (extrusion step), and the melt-kneaded product immediately after extrusion is cut by a rotating cutter, It can be produced by cooling and solidifying with pressurized circulating water (cooling step). According to this manufacturing method, expandable polystyrene resin particles having a sphericity of 0.985 or less are easily obtained. Preferably, they are obtained by the following method for producing expandable polystyrene resin particles of the present invention.

The method for producing expandable polystyrene resin particles of the present invention involves introducing a polystyrene resin melt consisting of a polystyrene resin composition containing a radiation heat transfer inhibitor and a blowing agent into pressurized circulating water from a die having a plurality of small holes. A method for producing expandable polystyrene resin particles by extruding and cutting with a rotary cutter to form particles, the blowing agent containing isobutane, based on 100% by weight of the total amount of the polystyrene resin composition and the blowing agent. The content of isobutane is more than 2.7% by weight and not more than 6.0% by weight (hereinafter sometimes referred to as "the production method of the present invention").

Among the configurations in the manufacturing method of the present invention, each of the configurations described in the above [expandable polystyrene resin particles] can be similarly applied to the manufacturing method of the present invention.

In the manufacturing method of the present invention, from the viewpoint of dispersibility of the polystyrene resin and various components, the polystyrene resin and various components are mixed in advance using a kneading device equipped with a twin-shaft stirrer (for example, a Banbury mixer). It is preferable to prepare a kneaded product by kneading the mixture by applying the following steps, and to put the obtained kneaded product and polystyrene-based resin into an extruder, melt-knead them, and then cut into particles.

In a preferred form of the production method of the present invention, a masterbatch as a kneaded product is prepared by kneading a polystyrene resin and a radiant heat transfer inhibitor using a kneading device equipped with a two-shaft stirrer, such as a Banbury mixer. The prepared masterbatch, new polystyrene resin, blowing agent, and other components such as flame retardants as needed are melt-kneaded in an extruder, and the resulting resin melt is attached to the tip of the extruder. It is extruded through a die with small holes into a cutter chamber filled with pressurized circulating water, and immediately after extrusion, it is cut by a rotating cutter and is cooled and solidified by the pressurized circulating water. At this time, the melt kneading in the extruder may be performed by using a single extruder, by connecting multiple extruders, or by using the extruder together with a second kneading device such as a static mixer or an agitator without a screw. Yes, you can select as appropriate.

The polystyrene resin and the radiation heat transfer inhibitor are kneaded using a kneading device equipped with a twin-shaft stirrer, such as an intensive mixer, an internal mixer, or a Banbury mixer that can knead the resin under a load. Preferably, a masterbatch is made. In this case, the concentration of the masterbatch is not particularly limited, but it is preferable to prepare the masterbatch at a concentration of 20% to 80% by weight of the radiant heat transfer inhibitor in view of the balance between kneading performance and cost. The prepared masterbatch, polystyrene resin, blowing agent, flame retardant, heat stabilizer, and other additives are mixed in a first extruder and, if necessary, in a second kneading device attached to the extruder. After melt-kneading and cooling the resulting resin melt to a predetermined temperature, it is extruded through a die with small holes into a cutter chamber filled with pressurized circulating water. Immediately after this extrusion, it is cut into pellets by a rotary cutter, and the obtained pellets (resin particles) are cooled and solidified with pressurized circulating water to obtain expandable polystyrene resin particles. Note that for other additives such as flame retardants and heat stabilizers, it is also possible to prepare a master batch of polystyrene resin and other additives in advance and feed it into an extruder, etc. do not have. Furthermore, the radiation heat transfer inhibitor, flame retardant, heat stabilizer, and other additives may be added directly to the extruder without being masterbatched.

When pentane and butane are used together as blowing agents, the method of addition is not particularly important as long as pentane and butane are added; they may be added at the same time, or one of them may be added first and then the other. You can do it like this.

The amount of isobutane used in the production method of the present invention is more than 2.7% by weight and not more than 6.0% by weight based on 100% by weight of the total amount of the polystyrene resin composition and blowing agent. When producing by melt extrusion, if isobutane exceeds 6.0% by weight, it will be difficult to suppress foaming during the production of expandable polystyrene resin particles, and the die will become clogged, resulting in stable foaming. It becomes difficult to collect polystyrene resin particles.

In the production method of the present invention, isobutane and pentane may be used in combination. When isobutane and pentane are used in combination, the amount of pentane added should be 1 to 8 parts by weight per 100 parts by weight of the polystyrene resin composition. is preferred. From the viewpoint of improving productivity by shortening the heating time during pre-foaming and flame retardant performance, the amount is more preferably 2 to 6 parts by weight.

The temperature set in the melt-kneading section of the extruder is preferably 100°C to 250°C. Further, it is preferable that the residence time in the extruder from the time when the polystyrene resin and various components are supplied to the extruder until the end of melt-kneading is 10 minutes or less. If the set temperature in the melt-kneading section of the extruder is 250°C or less and/or the residence time in the extruder until the end of melt-kneading is 10 minutes or less, the flame retardant may decompose when added. Therefore, the desired flame retardance can be obtained, and there is no need to add an excessive amount of flame retardant to impart the desired flame retardance. On the other hand, if the set temperature in the melt-kneading section of the extruder is 100° C. or higher, the load on the extruder will not increase, resulting in stable extrusion and good dispersibility of the added components.

Here, the melt-kneading section of the extruder means the area from the feed section to the downstream end of the final extruder when the extruder is configured with a single screw or twin screws. When a second kneading device, such as a static mixer or an agitator without a screw, is used in conjunction with the first extruder, this means from the feed section of the first extruder to the tip of the second kneading device.

The pressure of the pressurized circulating water is preferably 1.0 MPa or more and 2.0 MPa or less, more preferably 1.1 MPa or more and 1.8 MPa or less. If the water pressure is 1.0 MPa or more, foaming can be suppressed, the bulk density of the expandable polystyrene resin particles will increase, and a decrease in expansion ratio and transport efficiency will hardly occur. On the other hand, since the water pressure is 2.0 MPa or less, the rotary cutter is not pushed back by the water pressure, and the extruded molten resin does not wrap around the rotary cutter, allowing stable production.

The temperature of the pressurized circulating water is preferably 45°C or more and 80°C or less, more preferably 50°C or more and 70°C or less. If the water temperature is 45° C. or higher, clogging of the dice due to cooling can be suppressed. On the other hand, when the water temperature is 80° C. or lower, foaming in the pressurized circulating water can be suppressed, the bulk density of the expandable polystyrene resin particles increases, and transport efficiency is less likely to decrease.

The die used in the present invention is not particularly limited, but includes, for example, those having small holes with a diameter of 0.3 mm to 2.0 mm, preferably 0.4 mm to 1.5 mm.

The cutting device for cutting the molten resin extruded into pressurized circulating water is not particularly limited, but for example, a rotary cutter in contact with a die lip is used to cut the molten resin into spherules, which are then transferred to a centrifugal dehydrator to be dehydrated and aggregated. For example, devices that can be used

The method of coating the external additive used in the present invention is not particularly limited, but a preferred coating method includes, for example, a method of applying the external additive after drying and then coating by mixing.

[Polystyrene resin foam molded product]
The expandable polystyrene resin particles of the present invention are produced by a pre-expanding method in which expandable polystyrene resin particles are foamed to a predetermined expansion ratio to obtain pre-expanded particles, and then molded using the pre-expanded particles. , a polystyrene resin foam molded article can be produced.

The higher the expansion ratio of a polystyrene resin foam molded product, the lower the amount of expandable polystyrene resin particles used as a raw material. can be manufactured. It should be noted that it is difficult to foam at a high magnification with conventional expandable polystyrene resin particles containing graphite. However, according to the expandable polystyrene resin particles of the present invention and the expandable polystyrene resin particles obtained by the production method of the present invention, by controlling the content of isobutane contained in the expandable polystyrene resin particles, high It is possible to perform multiplier foaming, and it is possible to supply a heat insulating material that is lightweight, easy to handle, and inexpensive.

The expandable polystyrene resin particles of the present invention are produced by a known pre-foaming process, for example, by foaming them 10 to 120 times with water vapor to form pre-foamed particles (pre-foaming process), and if necessary, curing for a certain period of time. A polystyrene resin foam molded article is produced by molding the pre-expanded particles with water vapor using a known molding machine. Depending on the shape of the mold used, it is possible to obtain complex-shaped molded products or block-shaped molded products.

(Pre-foaming process)
The pre-foaming step can be carried out using a pre-foaming machine in the same manner as the conventional pre-foaming of expandable polystyrene resin particles.

A known pre-foaming machine can be used, such as a can equipped with a stirring device and containing expandable polystyrene resin particles, and a steam chamber installed below the can to supply water vapor to the can. A pre-foaming machine is used which is equipped with a pre-foamed particle outlet and a pre-foamed particle outlet.

The pressure inside the can (cage pressure) when steam is introduced is not particularly limited, but is preferably 0.001 to 0.15 MPa, more preferably 0.01 to 0.10 MPa, and even more preferably 0.03 to 0.08 MPa. . When the pressure inside the can is 0.01 MPa or more, when obtaining a high expansion ratio, the water vapor injection time in preliminary foaming can be 500 seconds or less. When the pressure inside the can is 0.15 MPa or less, it is not necessary to increase the pressure of steam, the number of occurrences of blocking phenomenon decreases, and the pre-foaming yield increases.

Further, the pre-foaming step can be carried out by either a continuous method or a batch method.

The continuous method is a method in which expandable polystyrene resin particles are continuously supplied into the can and pre-expanded particles are discharged from an outlet provided at the top of the can. The expansion ratio of the pre-expanded particles can be adjusted, for example, by appropriately selecting the amount (weight) of the expandable polystyrene resin particles charged into the can per hour. In the case of a continuous method, the residence time in the prefoamer can from the time the expandable polystyrene resin particles are supplied into the can until the prefoamed particles are discharged is defined as the steam input time.

In addition, in the batch method, a predetermined amount of expandable polystyrene resin particles are placed in a can, and after the particles are pre-foamed to a predetermined expansion ratio, the supply of steam is stopped, and then air is introduced into the can as needed. In this method, the pre-expanded particles are cooled and dried by blowing, and then taken out from the can. The expansion ratio of the pre-expanded particles can be adjusted by appropriately selecting the amount (weight) of expandable polystyrene resin particles to be charged into the can per batch. Since the batch method is a method in which the input expandable polystyrene resin particles are pre-foamed to a predetermined volume, the smaller the input amount per batch, the higher the expansion ratio of the resulting pre-expanded particles.

Further, it is better to cure the pre-foamed particles immediately after pre-foaming. During pre-foaming, water vapor exists within the foamed particles, but in the cooling step after foaming, the water vapor condenses into water, so the pressure inside the pre-foamed particles becomes reduced immediately after pre-foaming. If the cell wall strength of the pre-expanded particles is low during reduced pressure, shrinkage may easily occur. Furthermore, if the closed cell ratio of the pre-expanded particles is low, the strength of the cell structure will decrease and it will tend to shrink. Therefore, a curing process in which the inside of the pre-expanded particles is replaced with air and returned to atmospheric pressure is effective. Since the pre-expanded polystyrene resin expandable particles of the present invention are suppressed from shrinking immediately after pre-expanding, the expansion ratio can be restored to a desired expansion ratio through a curing step.

The temperature during curing is not particularly limited, but is preferably 20 to 80°C, more preferably 25 to 70°C, and still more preferably 30 to 60°C. When the curing temperature is 20° C. or higher, air is likely to be introduced into the pre-expanded particles, which have been in a reduced pressure state, and the inside of the expanded particles is likely to return to atmospheric pressure. When the curing temperature is 80°C or less, the blowing agent present in the pre-expanded particles becomes difficult to escape, the foaming power does not decrease, and the surface beauty of the molded product does not decrease.

The polystyrene resin foam molded product of the present invention can be used, for example, as a building insulation material used for floors, walls, roofs, etc., agricultural and fishery boxes such as boxes for transporting fish and other marine products, and boxes for transporting agricultural products such as vegetables, etc. It can be used for various purposes such as bathroom insulation and hot water tank insulation.

The present invention will be specifically described below based on Reference Examples, Examples, and Comparative Examples, but the present invention is not limited thereto.

Note that the measurement methods and evaluation methods in the following Reference Examples, Examples, and Comparative Examples are as follows.

(Method for measuring sphericity of expandable polystyrene resin particles)
(1) Measuring device: CAMSIZER P4 manufactured by Retsch Technology
(2) Setting conditions: The feeder and funnel parameters were set to the following conditions.
・Control level when moving forward at high speed: 55
・Maximum time when moving forward at high speed [seconds]: 60
・Level at start of measurement: 50
・Maximum control level: 75
・Target coverage area [%]: 0.5
・Feeder width [mm]: 60
- Guidance sheet was used. Also, the following conditions were used as measurement data.
・Basic camera coverage area [%] < 3
・Zoom camera coverage area [%] < 5
However, particles satisfying the following conditions from the photographed projection diagram were excluded from the measurement data.
・Convexity ≧ 0.99
If the particles overlap each other and fall onto the projection map measurement location, the shape of each particle cannot be accurately evaluated, so the feeder and funnel parameters were set to the above conditions. Furthermore, if a large number of particles fall at the same time, it may not be possible to accurately evaluate the shape of each particle. For this reason, when more particles fell than the set coverage area, that projection map and data were excluded.

Furthermore, in order to exclude the influence of minute foreign matter such as dust, data with Convexity (surface unevenness) of 0.99 or more was excluded from the analysis.
(3) Measuring method: A projected image of approximately 50 g of expandable polystyrene resin particles was photographed using CAMSIZER P4 set as above, and the perimeter and area of the obtained projected image of each expandable polystyrene resin particle were measured. It was measured. The average value of sphericity was calculated based on the following formula from the perimeter and area of the projected view of each of the obtained expandable polystyrene resin particles.

However, in the above formula, S _i is the area (mm ² ) of the i-th particle, and R _i is the circumferential length (mm) of the i-th particle.

(Method for measuring apparent density of expandable polystyrene resin particles)
Collect W (kg) of expandable polystyrene resin particles as a measurement sample, drop this measurement sample naturally into a measuring cylinder containing ethanol, measure its mass (kg) and volume (m ³ ), and calculate the following. The apparent density was measured based on the formula.

Apparent density (kg/m ³ )=weight of measurement sample (W)/volume of measurement sample (V).

(Method for measuring bulk ratio of pre-expanded particles)
Collect W (g) of each pre-expanded particle as a measurement sample, let the measurement sample fall naturally into a measuring cylinder, and then tap the measuring cylinder to keep the sample's apparent volume V (cm ³ ) constant and calculate its mass (g). ) and volume (cm ³ ) were measured, and the bulk magnification was determined based on the following formula.

Bulk magnification (cm ³ /g) = Volume of measurement sample (V) / Weight of measurement sample (W)
The bulk ratio of the pre-expanded particles measured within 5 to 10 minutes after the pre-expanded particles are discharged from the pre-expander is defined as the bulk ratio immediately after foaming at which shrinkage has occurred after pre-expanding.

In the pre-expanded particles, the bulk ratio measured after curing at 30° C. for 24 hours after shrinkage is defined as the bulk ratio after curing.

(Method for calculating shrinkage rate of pre-expanded particles)
The value calculated by the following formula is defined as the shrinkage rate of the pre-expanded particles.

Formula: (A)/(B)×100
(A) Bulk ratio immediately after foaming of foamed particles pre-expanded to a bulk ratio of 90 times (B) Bulk ratio after curing of the pre-expanded particles after curing at 30°C for 24 hours (Measurement of the amount of blowing agent in pre-expanded particles) Method)
After pre-foaming the expandable polystyrene resin particles and curing them at 30°C for 24 hours, the weight W ₁ (g) of the expanded particles was measured, heated in an oven at 150°C for 30 minutes, and then cooled to room temperature in a desiccator. After cooling for 30 minutes, the weight W ₂ (g) was measured again. The value calculated using the following formula was taken as the amount of blowing agent in the pre-expanded particles.

Amount of blowing agent in pre-expanded particles (wt%) = (W ₁ - W ₂ )/W ₁ ×100
(Foaming ratio of polystyrene resin foam molded product)
After drying the polystyrene resin foam molded product taken out from the molding mold at 30°C for 24 hours, the weight (g) of the foam molded product was measured, and the vertical dimension, horizontal dimension, and thickness dimension were measured using calipers. was measured. The volume (cm ³ ) of the polystyrene resin foam molded article was calculated from each measured dimension, and the expansion ratio was calculated according to the following calculation formula.
Expansion ratio (cm ³ /g) = test piece volume (cm ³ ) / test piece weight (g)
Note that the expansion ratio "times" of a polystyrene resin foam molded product is also conventionally expressed as "cm ³ /g".

(Method for measuring thermal conductivity of polystyrene resin foam molded product)
It is generally known that the larger the measured average temperature of thermal conductivity, the larger the value of thermal conductivity, and in order to compare the thermal insulation properties, it is necessary to determine the measured average temperature. In this specification, 23° C., which is defined by JIS A9511:2006R, which is a standard for foamed plastic heat insulating materials, is used as a standard.

Thermal conductivity was measured after the polystyrene resin foam molding was allowed to stand at a temperature of 70°C for 96 hours, a sample for thermal conductivity measurement was cut out, and the sample was further left at a temperature of 23°C for 24 hours. .

More specifically, after the polystyrene resin foam molding was allowed to stand at 70° C. for 96 hours, a sample measuring 300 mm in length x 300 mm in width x 50 mm was cut out. Furthermore, after allowing the sample to stand at 23°C for 24 hours, a heat flow meter was measured using a thermal conductivity measuring device (manufactured by Hideko Seiki Co., Ltd., HC-074) in accordance with JIS A1412-2:1999. Thermal conductivity was measured using a method with an average temperature of 23°C and a temperature difference of 20°C.

(Evaluation of flame retardant performance of polystyrene resin foam moldings)
Flame retardant performance was measured after the polystyrene resin foam molding was allowed to stand at a temperature of 70°C for 96 hours, a sample for flame retardant performance evaluation was cut out, and further left at a temperature of 23°C for 24 hours. . Flame retardant performance was evaluated in accordance with JISA9511:2006R (measurement method A was adopted). The flame-out time was the average value of the measurement results of five test pieces, and the flame retardant performance of the polystyrene resin foam molded product was evaluated based on the following criteria.

〇: Extinguished within 3 seconds ×: Burning continues for 3 seconds or more (Evaluation of fusion of polystyrene resin foam moldings)
The obtained polystyrene resin foam molded product is ruptured, the fractured surface is visually observed, and the area of the entire fractured surface where the particles themselves are fractured, rather than the particle interface, is determined, and the area of the entire fractured surface is determined. Then, the ratio (%) of the area where the particles themselves were broken was determined. The fusion of the polystyrene resin foam molded product was evaluated based on the following criteria.

〇: Over 80% fusion bond △: Over 60% fusion bond no more than 80% ×: No more than 60% fusion bond Below, raw materials used in reference examples, examples, and comparative examples are shown.

(Styrene resin)
(A) Styrene homopolymer [manufactured by PS Japan Co., Ltd., 680]
(graphite)
(B) Graphite [Scaly graphite SGP-40B, manufactured by Marutoyo Casting Materials Co., Ltd.]
(brominated flame retardant)
(C) 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].

(thermal stabilizer)
(D1) Tetrakis(2,2,6,6-tetramethylpiperidyloxycarbonyl)butane [LA-57 manufactured by ADEKA Co., Ltd.]
(D2) Bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite [PEP-36 manufactured by ADEKA Corporation].

(foaming agent)
(E1) Normal pentane [manufactured by Wako Pure Chemical Industries, Ltd., reagent]
(E2) Isopentane [manufactured by Wako Pure Chemical Industries, Ltd., reagent]
(E3) Isobutane [manufactured by Mitsui Chemicals, Inc.]
(Other additives)
(F) Ethylene bisstearic acid amide [Alflo H-50S, manufactured by NOF Corporation].

(Production example 1) (Graphite masterbatch (G))
Raw materials were added to a Banbury mixer so that the total weight (A + B + F) of 49% by weight of polystyrene resin (A), 50% by weight of graphite (B), and 1% by weight of ethylene bisstearamide (F) was 100% by weight. The mixture was kneaded for 20 minutes under a load of 5 kgf/cm ² without heating or cooling. At this time, the resin temperature was measured and found to be 180°C. A strand-shaped resin was supplied to a ruler and extruded through a die with a small hole attached to the tip at a discharge rate of 250 kg/hr. After cooling and solidifying in a 30°C water bath, the resin was cut to obtain a masterbatch (G). . The graphite content in the masterbatch (G) was 50% by weight.

(Production Example 2) (Masterbatch (H) of mixture of brominated flame retardant and heat stabilizer)
After supplying the polystyrene resin (A) to a twin-screw extruder and melt-kneading it, a mixture of a brominated flame retardant (C), heat stabilizers (D1) and (D2) is supplied from the middle of the extruder, The mixture was further melted and kneaded. However, the weight ratio of each material is (A): (C): (D1): (D2) = 70:28.5:0.6:0.9, (A) + (C) + (D1) +(D2)=100% by weight. The strand-shaped resin is extruded through a die with a small hole attached to the tip of the extruder at a discharge rate of 300 kg/hr, and is cooled and solidified in a 20°C water bath, then cut to separate the brominated flame retardant and heat stabilizer. A masterbatch (H) of the mixture was obtained. At this time, the temperature of the extruder was set at 170°C.

(Production Example 3) (Mixture of brominated flame retardant and heat stabilizer (I)) Brominated flame retardant (C), heat stabilizers (D1) and (D2) are mixed in a mixer, and the brominated flame retardant and A mixture of heat stabilizers (I) was obtained. However, the weight ratio of each material was (C):(D1):(D2)=100:2.1:3.2, (C)+(D1)+(D2)=100% by weight.

(Reference example 1)
[Preparation of polystyrene resin particles]
Polystyrene resin (A), masterbatch (H), and graphite masterbatch (G) were each placed in a blender and blended for 10 minutes to obtain a resin mixture.

The weight ratio of each material was (A):(H):(G)=83.65:8.35:8.00, (A)+(H)+(G)=100% by weight. The obtained resin mixture was supplied to a co-directional twin-screw extruder with a diameter of 40 mm, and melted and kneaded at a set temperature of 190°C and a screw rotation speed of 230 rpm, and 30 small holes with a diameter of 1.4 mm were installed at the tip of the extruder. The resin in the form of a strand was extruded through the molded die at a discharge rate of 70 kg/hour, was cooled and solidified in a 20° C. water tank, and then cut with a strand cutter to obtain styrene resin particles. At this time, the resin temperature at the tip of the extruder was 220°C.

[Preparation of expandable polystyrene resin particles]
Next, 200 parts by weight of deionized water, 1 part by weight of tricalcium phosphate, and 0.03 parts by weight of sodium dodecylbenzenesulfonate were added to 100 parts by weight of the obtained styrene resin particles in an autoclave having a volume of 6 L and equipped with a stirring device. Then, 1 part by weight of sodium chloride was added and the pressure vessel was sealed. The temperature was then heated to 105°C over 1 hour, and 7 parts by weight of mixed pentane (a mixture of 80% normal pentane and 20% isopentane) and 1.5 parts by weight of isobutane were added as blowing agents into the pressure vessel over 30 minutes. , the temperature was raised to 115° C. over 10 minutes, and maintained at that temperature for 4 hours. After holding, cool to room temperature, take out the resin particles impregnated with the foaming agent from the autoclave, pickle with hydrochloric acid, wash with water, dehydrate with a centrifuge, and remove water adhering to the surface of the resin particles with a flash dryer. Dry. The resulting expandable polystyrene resin particles had a sphericity of 0.988 and an apparent density of 1030 kg/m ³ .

(Example 1)
[Preparation of expandable polystyrene resin particles]
Polystyrene resin (A), graphite (B), and a mixture of brominated flame retardant and heat stabilizer (I) were fed into feeders using a co-directional twin-screw extruder (first extruder) with a diameter of 40 mm and a co-directional twin-screw extruder with a diameter of 90 mm (first extruder). The mixture was supplied to a tandem two-stage extruder connected in series with a single-screw extruder (second extruder), and melt-kneaded at a set temperature of 190° C. and a rotation speed of 167 rpm of the extruder having a diameter of 40 mm. Note that the weight ratio of (A):(B):(I)=93:4.5:2.5 was used, and the total supply amount was 55.7 kg/h. From the middle of an extruder with a diameter of 40 mm (first extruder), mixed pentane [80% by weight of normal pentane (E1) and 20% by weight of isopentane (E2) was added to 100 parts by weight of the melt of the resin mixture (resin composition). % mixture] was injected at a ratio of 5.2 parts by weight, and 3.0 parts by weight of isobutane (E3) was injected into 100 parts by weight of the resin composition, and a total of 8.2 parts by weight of the blowing agent was injected. Added. Thereafter, it was supplied to a 90 mm diameter extruder (second extruder) through a continuation tube set at 200°C.

After cooling the molten resin to a resin temperature of 160°C in an extruder with a diameter of 90mm (second extruder), a molten resin with a diameter of 0.65mm and a land length of 5.0mm was attached to the tip of the second extruder set at 250°C. The sample was extruded from a die having 60 small holes into pressurized circulating water at a temperature of 62° C. and 1.3 MPa. The extruded molten resin was cut into small particles using a rotary cutter having six blades in contact with a die, and transferred to a centrifugal dehydrator to obtain expandable polystyrene resin particles. At this time, the residence time in the first extruder was 2 minutes, and the residence time in the second extruder was 5 minutes.

[Preparation of pre-expanded particles]
After storing the obtained expandable polystyrene resin particles at 15° C. for one week or more, 0.04 parts by weight of zinc stearate and 0.1 part of hydroxystearate triglyceride as external additives were added to the expandable polystyrene resin particles. Parts by weight were dry blended. 220 g of expandable polystyrene resin particles containing the external additive were put into a pre-foaming machine [batch-type pre-foaming machine manufactured by Daikai Kogyo Co., Ltd.], and the pressure inside the can was set at 0.05 kg/cm ² to 0.15 kg/cm. ² , and 0.10 MPa of water vapor was introduced into the pre-expanding machine to foam to a bulk ratio of 90 times to obtain pre-expanded particles.

[Production of polystyrene resin foam molded product]
After curing the obtained pre-expanded particles at 30°C for 24 hours, an in-mold mold (length 400 mm x width 400 mm x After filling the mold into a mold with a thickness of 50 mm and introducing water vapor at 0.06 MPa to cause foaming in the mold, the mold was cooled by spraying water. After holding the polystyrene resin foam molded product in the mold until the pressure of the polystyrene resin foam molding against the mold reaches 0.01 MPa (gauge pressure), the polystyrene resin foam molded product is taken out and the polystyrene resin foam molded product is pressed against the mold. A foam molded article was obtained. The expansion ratio of the obtained polystyrene resin foam molded product was 90.5 times, and the thermal conductivity of the polystyrene resin foam molded product was measured by the above-mentioned measuring method, and it was found to be 0.03084 W/m・K. there were.

Various properties of the produced expandable polystyrene resin particles and pre-expanded particles were measured and evaluated using the above-mentioned measuring method and evaluation method. Table 1 shows the measurement results and evaluation results for the expandable polystyrene resin particles and pre-expanded particles.

(Example 2)
In [Preparation of expandable polystyrene resin particles], polystyrene resin foaming was performed in the same manner as in Example 1, except that isobutane (E3) was changed to 3.2 parts by weight with respect to 100 parts by weight of the resin composition. A molded body was produced. The foaming ratio of the obtained polystyrene resin foam molded product was 92.6 times, and the thermal conductivity was measured by the above-mentioned method and was 0.03078 W/m·K.

Various properties of the obtained expandable polystyrene resin particles and pre-expanded particles were measured and evaluated in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 1.

(Example 3)
In [Preparation of expandable polystyrene resin particles], isobutane (E3) was changed to 3.7 parts by weight with respect to 100 parts by weight of the resin composition, and except that it was extruded into pressurized circulating water at 1.38 MPa, A polystyrene resin foam molded body was produced by the same treatment as in Example 1. The foaming ratio of the obtained polystyrene resin foam molded product was 92.6 times, and the thermal conductivity was measured using the above-mentioned method and was 0.03088 W/m·K.

Various properties of the obtained expandable polystyrene resin particles and pre-expanded particles were measured and evaluated in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 1.

(Comparative example 1)
In [Preparation of expandable polystyrene resin particles], isobutane (E3) was changed to 2.5 parts by weight with respect to 100 parts by weight of the resin composition, and except that it was extruded into pressurized circulating water at 1.25 MPa, A polystyrene resin foam molded body was produced by the same treatment as in Example 1. The foaming ratio of the obtained polystyrene-based resin foam molded article was 92.1 times, and the thermal conductivity was measured using the above-mentioned method and was found to be 0.03130 W/m·K.

Various properties of the obtained expandable polystyrene resin particles and pre-expanded particles were measured and evaluated in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 1.

(Comparative example 2)
In [Preparation of expandable polystyrene resin particles], isobutane (E3) was changed to 2.8 parts by weight with respect to 100 parts by weight of the resin composition, and except that it was extruded into pressurized circulating water at 1.25 MPa, A polystyrene resin foam molded body was produced by the same treatment as in Example 1. The foaming ratio of the obtained polystyrene resin foam molded product was 92.2 times, and the thermal conductivity was measured using the above-mentioned method and was found to be 0.03101 W/m·K.

Various properties of the obtained expandable polystyrene resin particles and pre-expanded particles were measured and evaluated in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 1.

(Comparative example 3)
In [Preparation of expandable polystyrene resin particles], the weight ratio of polystyrene resin (A): graphite (B): mixture of brominated flame retardant and heat stabilizer (I) = 95:4.5:0.5. The same process as in Example 1 was carried out, except that the amount of isobutane (E3) was changed to 2.5 parts by weight based on 100 parts by weight of the resin composition, and the mixture was extruded into pressurized circulating water at 1.25 MPa. A polystyrene resin foam molded article was produced. The foaming ratio of the obtained polystyrene-based resin foam molded article was 90.6 times, and the thermal conductivity was measured by the above-mentioned measuring method, and as a result, it was 0.03255 W/m·K.

Various properties of the obtained expandable polystyrene resin particles and pre-expanded particles were measured and evaluated in the same manner as in Example 1. The measurement results and evaluation results are shown in Table 1.

Claims (11)

Expandable polystyrene resin particles comprising a polystyrene resin composition containing a radiation heat transfer inhibitor and a foaming agent,
The sphericity of the expandable polystyrene resin particles is 0.985 or less,
the blowing agent includes isobutane,
Expandable polystyrene resin particles containing isobutane in an amount of more than 2.7% by weight and not more than 6.0% by weight based on 100% by weight of the total amount of the polystyrene resin composition and the blowing agent. The polystyrene resin composition contains a flame retardant,
The expandable polystyrene resin particles according to claim 1, wherein the flame retardant is present in an amount of more than 1.0% by weight and 6.0% by weight or less based on 100% by weight of the polystyrene resin composition. The expandable polystyrene resin particles according to claim 1 or 2, wherein the blowing agent contains pentane. Expandable polystyrene-based resin particles, wherein the expanded polystyrene-based resin particles are pre-foamed to a bulk ratio of 90 times and satisfy the following (Formula 1).
(Formula 1) (A)/(B)×100≦25.0
(A) Bulk ratio immediately after foaming of foamed particles pre-expanded to a bulk ratio of 90 times (B) Bulk ratio after curing of the pre-expanded particles after curing at 30°C for 24 hours The expandable polystyrene resin particles according to any one of claims 1 to 4, wherein the expandable polystyrene resin particles have an apparent density of more than 950 kg/m ³ and 1200 kg/m ³ or less. When the expandable polystyrene resin particles are pre-foamed to a bulk ratio of 90 times and then cured at 30° C. for 24 hours, the amount of blowing agent in the pre-expanded particles is 5.0% by weight to 6.0% by weight. The expandable polystyrene resin particles according to any one of claims 1 to 5. When the expandable polystyrene resin particles are pre-foamed to a bulk ratio of 90 times and then cured at 30°C for 24 hours, the thermal conductivity of the foam molded product is 0.034 W/m K or less. The expandable polystyrene resin particles according to any one of claims 1 to 6. Pre-expanded particles of the expandable polystyrene resin particles according to any one of claims 1 to 6, which have a bulk ratio of 90 times or more. Expandable polystyrene is made by extruding a polystyrene resin melt consisting of a polystyrene resin composition containing a radiation heat transfer inhibitor and a foaming agent into pressurized circulating water through a die with multiple small holes, and cutting it with a rotary cutter to form particles. A method for producing resin particles, the method comprising:
the blowing agent includes isobutane,
A method for producing expandable polystyrene resin particles, wherein isobutane is contained in an amount of more than 2.7% by weight and not more than 6.0% by weight based on 100% by weight of the total amount of the polystyrene resin composition and the blowing agent. The method for producing expandable polystyrene resin particles according to claim 9, wherein the radiation heat transfer inhibitor includes a carbon-based radiation heat transfer inhibitor. The method for producing expandable polystyrene resin particles according to claim 9 or 10, wherein the blowing agent contains pentane.