JP6961440B2 - Foamable polystyrene resin particles and manufacturing method - Google Patents

Description

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

Polystyrene-based resin foam is a well-balanced foam having light weight, heat insulating property, cushioning property, etc., and has been widely used as a heat insulating material for food containers, cold storage boxes, cushioning materials, and houses. ing.

Above all, in recent years, in relation to various problems such as global warming, energy saving by improving the heat insulating property of buildings such as houses is being aimed at, and polystyrene resin foam molded products obtained by using foamable polystyrene resin particles are being used. Demand is expected to grow. Therefore, various studies have been made on improving the foamability and heat insulating properties of the polystyrene-based resin foam.

For example, according to Patent Document 1, in foamable polystyrene resin particles, a foaming agent containing butane and pentane in a ratio of 20:80 to 80:20 is used, and the foaming ratio is 1.05-1. By forming a plurality of bubbles inside so as to be .25 times and making the bubbles function as bubble nuclei in pre-foaming, a foamed molded product having uniform foamability and excellent strength characteristics can be obtained. Is disclosed.

Further, in Patent Document 2, the effervescent polystyrene-based resin particles contain a radiant heat transfer inhibitor and a bromine-based flame retardant, and the content ratio of the hydrocarbon having 4 carbon atoms to the hydrocarbon having 5 carbon atoms is 2/98 to 2.98. It is disclosed that when the content is 20/80, high heat insulating properties and flame retardancy can be achieved at the same time, and foamable polystyrene-based resin particles that do not require an aging period can be obtained.

In Patent Document 3, in expandable polystyrene resin particles, is contained the following conductive carbon black volume resistivity 1.0 × 10 ⁴ Ω · cm, is made to function as a radiation heat transfer inhibitor, is excellent in thermal insulation performance It is disclosed that a foamed molded product can be obtained.

In Patent Document 4, the mass ratio of the styrene- (meth) acrylic acid copolymer to the polystyrene resin is 20:80 to 80:20, and the weight of graphite is 0.1 to 6 by weight based on 100 parts by weight of the base resin. It is disclosed that a styrene-based resin foamed polymer exhibiting excellent heat-resistant performance and heat-insulating performance can be obtained by containing it in a portion.

In Patent Document 5, a dispersion step of kneading polystyrene-based resin, graphite, and a bromine-based flame retardant to disperse polystyrene-based resin particles in an aqueous medium, and impregnating the polystyrene-based resin particles with a styrene-based monomer. Polystyrene exhibiting excellent heat insulating performance and flame retardant performance by a manufacturing method including a polymerization step of polymerizing and a foaming agent impregnation step of impregnating resin particles with a foaming agent during or after polymerization to obtain foamable polystyrene-based resin particles. It is disclosed that a polystyrene foam molded product can be obtained.

Japanese Unexamined Patent Publication No. 2013-136688 Japanese Unexamined Patent Publication No. 2014-118474 International release WO2016 / 017813 Japanese Unexamined Patent Publication No. 2014-148558 JP 2015-101702

The present invention is to provide foamable polystyrene-based resin particles containing a carbon-based radiant heat transfer inhibitor capable of high-magnification foaming.

In general, although heat insulation can be improved by using a radiant heat transfer inhibitor such as graphite for a polystyrene resin foam molded product, the foaming ratio tends to decrease, and pre-foaming when foamed at a high ratio tends to occur. There is a problem that the particles shrink.

Patent Document 1 is an invention for obtaining a polystyrene-based resin foam molded product having both long-term bead life and high strength by controlling air bubbles, but is a system containing a carbon-based radiant heat transfer inhibitor such as graphite. There is no point of view regarding both high foaming ratio and heat insulation.

Patent Document 2 stipulates that the content ratio of a hydrocarbon having 4 carbon atoms to a hydrocarbon having 5 carbon atoms is 2/98 to 20/80. In order to obtain a polystyrene-based resin foam molded product having a high foaming ratio, it is preferable that the amount of hydrocarbon having 4 carbon atoms is large. From this point, the foamable polystyrene-based resin particles of Patent Document 2 in which the content ratio of the hydrocarbon having 4 carbon atoms and the hydrocarbon having 5 carbon atoms is 2/98 to 20/80 can be increased to a higher foaming ratio. There is room for improvement.

Similarly, the invention of Patent Document 3 in which a polystyrene-based resin foam molded product contains conductive carbon black to achieve high heat insulating performance does not have a viewpoint regarding high-magnification foaming. If a large amount of an inorganic substance such as carbon black is contained, the foaming ratio decreases, and if foamed at a high ratio, the prefoamed particles may shrink. Considering the cost, it is preferable that the polystyrene-based resin foam molded product can have a high foaming ratio and can reduce the amount of resin. From this point, there is room for improvement in terms of increasing the foaming magnification.

Patent Documents 4 and 5 are inventions in which graphite is contained in a polystyrene resin to exhibit excellent heat insulating performance, but both are produced by a polymerization method and are radiated from the viewpoint of graphite dispersibility. There is a risk that the effect of the heat inhibitor cannot be fully exerted. Further, when inorganic substances such as graphite are agglomerated and present, it is considered that the cell film tends to break bubbles and the foamability tends to decrease. From this point, there is room for improvement in terms of high heat insulation performance and high foaming magnification.

Therefore, when the present inventors studied to solve the above-mentioned problems, a high foaming ratio was obtained by containing a specific amount of isobutane as a foaming agent and increasing the apparent density of the foamable polystyrene resin particles. At the same time, they have succeeded in producing a polystyrene-based resin foam molded product having a low thermal conductivity, and have completed the present invention.

That is, the present invention is an effervescent polystyrene-based resin particle composed of a polystyrene-based resin composition containing a carbon-based radiant heat transfer inhibitor and a foaming agent, wherein the foaming agent contains pentane and isobutane, and the total amount of pentane and isobutane. Isobutane is more than 20% by weight and 55% by weight or less with respect to 100% by weight, and the apparent density of the foamable polystyrene resin particles is ^{more than 1000 kg / m 3 and} more than 1060 ^{kg / m 3} or less.
The present invention relates to effervescent polystyrene-based resin particles (hereinafter, may be referred to as “expandable polystyrene-based resin particles of the present invention”).

In the effervescent polystyrene-based resin particles of the present invention, the average cell diameter of the pre-expanded polystyrene-based resin particles is 380 μm or less when the effervescent polystyrene-based resin particles are pre-foamed at a bulk magnification of 80 times and then cured at 30 ° C. for 24 hours. Is preferable.

In the foamable polystyrene-based resin particles of the present invention, the polystyrene-based resin composition preferably contains a flame retardant in an amount of 0.5 to 6% by weight based on 100% by weight of the polystyrene-based resin composition.

The foamable polystyrene-based resin particles of the present invention are pre-foamed particles of the foamable polystyrene-based resin particles described above, and have a bulk ratio of 75 times or more when cured at 30 ° C. for 24 hours after pre-foaming. Is preferable.

Further, in the present invention, a polystyrene-based resin composition containing a carbon-based radiant heat transfer inhibitor and a polystyrene-based resin melt composed of a foaming agent are extruded from a die having a plurality of small holes into pressurized circulating water and cut with a rotary cutter. It is a method for producing foamable polystyrene-based resin particles that are made into particles.
The foaming agent contains more than 20% by weight and 55% by weight or less of isobutane with respect to 100% by weight of the total amount of the foaming agent, and the apparent density of the foamable polystyrene resin particles is ^{more than 1000 kg / m 3 and} more than 1060 ^{kg / m 3} or less. The present invention relates to a method for producing foamable polystyrene-based resin particles (hereinafter, may be referred to as “the first production method of the present invention”).

In the present invention, a polystyrene-based resin composition containing a carbon-based radiant heat transfer inhibitor and a polystyrene-based resin melt composed of a foaming agent are extruded from a die having a plurality of small holes into pressurized circulating water and cut with a rotary cutter. A method for producing foamable polystyrene-based resin particles to be granulated, wherein the foaming agent contains pentane and isobutane, and isobutane is more than 20% by weight and 55% by weight or less based on 100% by weight of the total amount of pentane and isobutane. the apparent density of the expandable polystyrene resin particles is not more than 1000 kg / ^{m 3} super 1060kg / ^{m 3,} the production method of the expandable polystyrene resin particles (hereinafter, a second production method of the present invention) may be referred to as. ).

In the first production method of the present invention, the foaming agent preferably contains pentane and butane.

In the first and second production methods of the present invention, the average cell diameter of the prefoamed particles when the foamable polystyrene resin particles were prefoamed at a bulk magnification of 80 times and then cured at 30 ° C. for 24 hours was 380 μm or less. Is preferable.

In the first and second production methods of the present invention, the water pressure of the pressurized circulating water is preferably 0.9 MPa or more and 1.5 MPa or less.

According to the foamable polystyrene-based resin particles of the present invention, it is possible to obtain a polystyrene-based resin foam molded product having both a high foaming ratio and a high heat insulating property.

[Expandable polystyrene resin particles]
The foamable polystyrene-based resin particles of the present invention are foamable polystyrene-based resin particles containing a carbon-based radiant heat transfer inhibitor, and the polystyrene-based resin particles contain a carbon-based radiant heat transfer inhibitor and a foaming agent. It is a thing. In the foamable polystyrene-based resin particles of the present invention, the foaming agent contains pentane and isobutane, and isobutane is more than 20% by weight and 55% by weight or less based on 100% by weight of the total amount of pentane and isobutane. by the apparent density of the resin particles is not more than 1000 kg / ^{m 3} super 1060kg / ^{m 3,} it is possible to obtain a polystyrene resin foamed molded having both a high expansion ratio and high thermal insulation properties.

By using a radiant heat transfer inhibitor such as graphite for the polystyrene-based resin foam molded product, the heat insulating property can be improved. However, there is a problem that the foaming ratio decreases as the amount of the inorganic substance added such as graphite is increased, and the prefoamed particles shrink when foamed at a high ratio. Although it is not clear, it is presumed that this problem is mainly caused by inorganic substances, and holes are formed in the cell membrane in the pre-foamed particles during pre-foaming, and the foaming agent easily escapes from the resin during pre-foaming, making it impossible to maintain the internal pressure. Therefore, it is considered that shrinkage is likely to occur after foaming. When the pre-foamed particles are contracted, they can be recovered by curing the contracted pre-foamed particles, but it is foreseen that it will be difficult to control the magnification after curing. In addition, if the shrinkage generated is large, it is necessary to cure at a high temperature in order to restore the foaming ratio, a curing silo capable of curing at a high temperature is further required, and a large amount of heat energy is required for curing. Therefore, it costs money. In particular, if the generated shrinkage is further large, the prefoamed particles are crushed, the foaming ratio is difficult to recover even when cured at a high temperature, and the standard of the foaming ratio is not satisfied, so that the yield is lowered.

As a result of examining the above problems by the present inventors, when foaming polystyrene-based resin particles containing a carbon-based radiant heat transfer inhibitor using only pentane as a foaming agent are foamed at a high magnification, they shrink into pre-foamed particles immediately after pre-foaming. Was found to occur. Further, in the foamable polystyrene resin particles containing a carbon-based radiant heat transfer inhibitor, if the blending ratio of isobutane is 20% by weight or less with respect to the total amount of pentane and butane of 100% by weight, shrinkage is likely to occur immediately after foaming. It was found that the pre-foamed particles in which shrinkage occurred did not recover to a predetermined foaming ratio even after being cured at 30 ° C. for 24 hours.

In general, butane has a lower solubility in polystyrene resins than pentane, so that it tends to be supersaturated, and it is considered that butane tends to contribute to a high foaming ratio. In particular, isobutane has a higher molecular structure than normal butane, and the foaming agent is less likely to disperse from the effervescent polystyrene-based resin particles, so that a high expansion ratio can be achieved. On the other hand, in order to achieve a high foaming ratio with pentane, it is necessary to add a large amount of foaming agent, and especially in the melt extrusion method, the viscosity of the resin is significantly reduced, so that cutting during the production of polystyrene-based resin particles There is a concern that the properties will deteriorate and stable sampling will be difficult. Further, it is considered that when a large amount of foaming agent is added, the plasticizing effect on polystyrene becomes large, and the cell wall strength at the time of foaming decreases, resulting in shrinkage. Therefore, it has been found that a high foaming ratio can be achieved by increasing the blending ratio of isobutane to 100% by weight of pentane and butane, which is superior in foamability to pentane, to 20% by weight or more.

However, even if isobutane exceeds 20% by weight with respect to 100% by weight of the total amount of pentane and butane as the foaming agent, shrinkage may easily occur immediately after foaming.

The shrinkage of the foamed particles immediately after the pre-foaming is considered to be affected by the internal pressure of the foaming agent, the average cell diameter of the pre-foamed particles, and the closed cell ratio. If the foaming of polystyrene-based resin particles cannot be suppressed when the polystyrene-based resin melt composed of the polystyrene-based resin composition and the foaming agent is extruded from a die having a plurality of small holes into pressurized circulating water, the foamable polystyrene-based resin particles are foamed. The apparent density of resin particles is low. Further, in the high temperature state at the time of extrusion, the resin viscosity is lower than that at the time of pre-foaming with steam. It is considered that when foaming is performed in a state where the resin viscosity is low, the closed cell ratio tends to decrease because the bubbles are likely to break. In the present invention, by suppressing foaming during extrusion and setting the apparent density of the foamable polystyrene-based resin particles to ^{more than 1000 kg / m 3} , it is possible to suppress shrinkage immediately after pre-foaming, and the foaming ratio is high. It becomes possible to obtain prefoamed particles.

Furthermore, since a carbon-based radiant heat transfer inhibitor such as graphite also acts as a nucleating agent for bubbles, the foamable polystyrene-based resin particles containing the carbon-based radiant heat transfer inhibitor tend to have a smaller cell diameter and radiant heat. It is possible to develop more excellent heat insulating performance because it is easy to suppress.

(Polystyrene resin)
The polystyrene-based resin composition used for the foamable polystyrene-based resin particles of the present invention contains a polystyrene-based resin as a base resin. The polystyrene-based resin is not limited to a styrene homopolymer (polystyrene homopolymer), but is a copolymer of styrene with another monomer copolymerizable with styrene or a derivative thereof as long as the effects of the present invention are not impaired. It may be. These may be only one kind, or two or more kinds may be used in combination.

Other monomers copolymerizable with styrene or derivatives thereof include, for example, methylstyrene, dimethylstyrene, ethylstyrene, diethylstyrene, isopropylstyrene, bromostyrene, dibromostyrene, tribromostyrene, chlorostyrene, dichlorostyrene, etc. 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, 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 thereof 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, for example, diene-based rubber-reinforced polystyrene, acrylic-based rubber-reinforced polystyrene, polyphenylene ether-based resin, and the like can be blended from the viewpoint of impact resistance and heat resistance.

The polystyrene-based resin used in the present invention 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 insulating properties, flame retardancy, and cushioning properties. Therefore, styrene is used. It preferably contains a homopolymer.

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

(Carbon-based radiant heat transfer inhibitor)
In the present invention, by adding a carbon-based radiant heat transfer inhibitor to the foamable polystyrene-based resin particles, a polystyrene-based resin foam molded product having high heat insulating properties can be obtained. Here, the carbon-based radiant heat transfer inhibitor refers to a carbon material having a property of reflecting, scattering or absorbing light in the near infrared or infrared region (for example, a wavelength region of about 800 to 3000 nm). Examples of the carbon-based radiant heat transfer inhibitor include graphite (graphite), graphene, carbon black, expanded graphite, activated carbon, carbon nanotubes, carbon nanofibers, etc. Among them, dispersibility and cost in a polystyrene-based resin. Graphite is preferable from the above point of view.

Examples of graphite include scaly graphite, earthy graphite, spheroidal graphite, artificial graphite and the like. In addition, in this specification, the term "scaly" also includes scaly, flaky or plate-like ones. These graphites can be used alone or in combination of two or more. Among these, a graphite mixture containing scaly graphite as a main component is preferable, and scaly graphite is more preferable, because the effect of suppressing radiant heat transfer is high. From the viewpoint of high foaming magnification, heat insulating property, 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 manufacturing cost. Graphite having an average particle size of less than 1 μm is very expensive because of its high production cost including the cost of pulverization, and the cost of foamable polystyrene-based resin particles tends to be high. On the other hand, if the average particle size exceeds 9 μm, the cell film is easily torn when the pre-foamed particles and the polystyrene-based resin foam molded product are produced from the foamable polystyrene-based resin particles, which makes it difficult to increase the foaming magnification. The ease of molding tends to decrease, and the compressive strength of the polystyrene-based resin foam molded product tends to decrease. The average particle size of graphite referred to here refers to the D50 particle size calculated by a laser diffraction / scattering method based on the Mie theory based on JIS Z8825-1.

The content of the carbon-based radiant heat transfer inhibitor in the foamable polystyrene-based resin particles of the present invention is preferably 2 to 10% by weight based on 100% by weight of the polystyrene-based resin composition. It is more preferably 3 to 7% by weight, further preferably 3 to 6% by weight, from the viewpoint of easy control of the target foaming ratio and the balance of the effect of reducing thermal conductivity and the like. If the content of the carbon-based radiant heat transfer inhibitor is 2% by weight or more, the effect of reducing the thermal conductivity is sufficient, while if it is 10% by weight or less, the foamable polystyrene-based resin particles to the pre-foamed particles and the polystyrene Since the cell film is less likely to be torn when the based resin foam molded product is manufactured, it becomes easier to increase the foaming ratio and control the foaming ratio.

In the present invention, other radiant heat transfer inhibitors may be added in addition to the carbon-based radiant heat transfer inhibitor as long as the effects of the present invention are not impaired. It is not particularly limited as long as it is a known radiant heat transfer inhibitor, but for example, an aluminum compound, a zinc compound, a magnesium compound, a titanium compound, a heat ray reflecting agent, a metal sulfate, an antimony compound, a metal oxide, and a heat ray. Examples include absorbents and metal particles.

(Foaming agent)
In the foamable polystyrene-based resin particles of the present invention, pentane and butane are used in combination.

Isobutane is indispensable as butane, and isobutane is contained in an amount of more than 20% by weight and 55% by weight or less in a total amount of 100% by weight of pentane and isobutane. From the viewpoint of high foaming ratio and production stability by suppressing shrinkage immediately after pre-foaming, isobutane is preferably 25% by weight to 50% by weight, more preferably 25% by weight to 45% by weight, and 25% by weight to 40% by weight. Especially preferable. If the isobutane is more than 20% by weight, a high expansion ratio can be achieved, while if it is 55% by weight or less, foaming during production of foamable polystyrene-based resin particles is performed in the case of production by the melt extrusion method. It can be suppressed, cutting becomes possible, blockage of dies is suppressed, and sampling is stabilized.

As the foaming agent used in the present invention, other hydrocarbon foaming agents having 4 to 5 carbon atoms may be used as long as they contain pentane and butane as described above. For example, hydrocarbons such as normal pentane, isopentane, normal butane, neopentane, or cyclopentane can be mentioned. As the pentane, it is preferable to use normal pentane and isopentane in a mixed manner, and it is more preferable to use normal pentane and isopentane in a weight ratio (normal pentane / isopentane) of 100/0 to 60/40. 98 / 2-60/40 is more preferable from the viewpoint of recovery of the magnification of the prefoamed particles after curing at 30 ° C. for 24 hours and self-extinguishing property. From the viewpoint of solubility in polystyrene resin, the amount of normal butane added is preferably small, and the total amount of pentane and butane is 100% by weight, and normal butane is preferably used in an amount of 3% by weight or less.

The amount of the foaming agent added is preferably 4 to 10 parts by weight with respect to 100 parts by weight of the polystyrene resin composition. When the amount of the foaming agent added is 4 parts by weight or more, the foaming power is sufficient and the foaming ratio is easily increased, so that a polystyrene-based resin foam molded product having a high foaming ratio can be easily produced. Further, if the amount of the foaming agent is 10 parts by weight or less, the flame retardant performance is less likely to deteriorate, and the production time (molding cycle) when producing the polystyrene-based resin foam molded product is shortened, so that the production cost is suppressed. be able to. The amount of the foaming agent added is more preferably 4.5 to 9 parts by weight, still more preferably 5 to 8 parts by weight, based on 100 parts by weight of the polystyrene resin composition.

The effervescent polystyrene-based resin particles of the present invention contain a polystyrene-based resin, a carbon-based radiant heat transfer inhibitor, and a foaming agent, and if necessary, a flame retardant, a heat stabilizer, a radical generator, and other additives. It may contain at least one optional component selected from the group consisting of. The foamable polystyrene-based resin particles of the present invention preferably contain a polystyrene-based resin, a carbon-based radiant heat transfer inhibitor, a foaming agent and a flame retardant, and contain at least one of the above-mentioned optional components excluding the flame retardant. May be, more preferably, at least one of the above-mentioned optional components containing a polystyrene resin, a carbon-based radiant heat transfer inhibitor, a foaming agent, a flame retardant and a heat stabilizer, excluding the flame retardant and the heat stabilizer. It may be contained, and more preferably, it contains a polystyrene-based resin, a carbon-based radiant heat transfer inhibitor, a foaming agent, a flame retardant, a heat stabilizer and a nucleating agent, and contains a flame retardant, a heat stabilizer and a nucleating agent. It may contain at least one of the above-mentioned optional components excluding.

(Flame retardants)
The flame retardant that can be used in the present invention is not particularly limited, and any known flame retardant that has been conventionally used for polystyrene resin foam molded products can be used. Among them, bromine, which has a high flame retardant imparting effect, can be used. Flame retardants are preferred. 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 compound such as A-bis (2,3-dibromopropyl ether), brominated styrene / butadiene block copolymer, brominated random styrene / butadiene copolymer, brominated styrene / butadiene graft copolymer Such as brominated butadiene / vinyl aromatic hydrocarbon copolymer (for example, disclosed in Japanese Patent Application Laid-Open No. 2009-516019), tetrabromocyclooctane and the like. One of these brominated flame retardants may be used alone, or two or more thereof may be used in combination.

The flame retardant is 0.5 in 100% by weight of the polystyrene resin composition from the viewpoint of easy control of the target foaming ratio and the balance of flame retardancy when the carbon-based radiant heat transfer inhibitor is added. It is preferably ~ 6% by weight, more preferably 1-4% by weight. When the content is 0.5% by weight or more, the flame retardancy imparting effect is not reduced, and the strength of the obtained polystyrene resin foam molded product, which is 6% by weight or less, is unlikely to decrease.

(Heat stabilizer)
In the foamable polystyrene-based resin particles of the present invention, further, by using a heat stabilizer in combination, deterioration of flame retardancy due to decomposition of the flame retardant in the manufacturing process and deterioration of the foamable polystyrene-based resin particles can be suppressed. can.

The heat stabilizer in the present invention is appropriately used according to the type and content of the polystyrene resin used, the type and content of the foaming agent, the type and content of the carbon-based radiant heat transfer inhibitor, the type and content of the flame retardant, and the like. Can be used in combination.

As the heat stabilizer used in the present invention, a hindered amine compound, a phosphorus compound, and an epoxy compound are desirable from the viewpoint that the 1% weight loss temperature in the thermogravimetric analysis of the polystyrene resin composition can be arbitrarily controlled. The heat stabilizer may be used alone or in combination of two or more.

The heat stabilizer is easy to control to the target foaming ratio, and the heat stabilizer is 0 in 100% by weight of the polystyrene resin composition from the viewpoint of the balance of flame retardancy when the carbon-based radiant heat transfer inhibitor is added. It is preferably 5 to 3% by weight. If it is 0.5% by weight or more, decomposition of the flame retardant is unlikely to occur, the flame retardant imparting effect is not reduced, and if it is 3% by weight or less, the strength of the obtained polystyrene-based resin foam molded product is unlikely to decrease.

(Other additives)
The polystyrene-based resin composition of the foamable polystyrene-based resin particles of the present invention can be used as a radical generator, a processing aid, a light-resistant stabilizer, a nucleating agent, and foaming, if necessary, as long as the effects of the present invention are not impaired. It may contain one or more other additives selected from the group consisting of colorants such as auxiliaries, antistatic agents, and pigments. Examples of the radical generator include cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, poly-1,4-isopropylbenzene and the like. Be done. Examples of the processing aid include sodium stearate, magnesium stearate, calcium stearate, zinc stearate, barium stearate, liquid paraffin and the like. Examples of the light resistance stabilizer include the above-mentioned hindered amines, phosphorus-based stabilizers, epoxy compounds, phenol-based antioxidants, nitrogen-based stabilizers, sulfur-based stabilizers, benzotriazoles and the like. Examples of nucleating agents include silica, calcium silicate, wallastonite, kaolin, clay, mica, zinc oxide, calcium carbonate, sodium hydrogencarbonate, talc and other inorganic compounds, methyl methacrylate-based copolymers, ethylene-vinyl acetate. Examples thereof include polymer compounds such as copolymer resins, olefin waxes such as polyethylene wax, methylene bisstearyl amide, ethylene bisstearyl amide, hexamethylene bispalmitic acid amide, and fatty acid bisamide such as ethylene bisoleic acid amide. As the foaming aid, a solvent having a boiling point of 200 ° C. or lower under atmospheric pressure can be preferably used. For example, aromatic hydrocarbons such as styrene, toluene, ethylbenzene and xylene, and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane can be used. Examples thereof include acetate esters such as hydrogen, ethyl acetate and butyl acetate. As the antistatic agent and the colorant, those used in various resin compositions can be used without particular limitation. These other additives may be used alone or in combination of two or more.

The foamable polystyrene-based resin particles of the present invention have an apparent density of more than ^{1000 kg / m 3 and 1060 kg / m 3} or less. From the viewpoint of ^{foamability, it is preferably more than 1000 kg / m 3 and} more preferably 1010 kg / m ³ or more. On the other hand, from the viewpoint of heat insulating performance, is preferably 1055kg / ^{m 3} or less, more preferably 1050 kg / ^{m 3} or less, 1040 kg / ^{m 3} or less is particularly preferred. Further, since the density of a general polystyrene-based resin is 1050 kg / m ^{3 to} 1060 kg / m ³ , it should converge to the above density value when foaming can be suppressed. By apparent density of the foamed polystyrene resin particles is not more than 1000 kg / m ³ Super 1060kg / m ^3, the polystyrene resin melt consisting of polystyrene resin composition and foaming agent foaming during extrusion is suppressed Conceivable. By obtaining foamable polystyrene-based resin particles that suppress foaming during extrusion, the closed cell ratio in the prefoamed particles increases and the strength of the cell structure increases, so that shrinkage immediately after prefoaming can be suppressed. It is thought that it has become possible.

Further, if the apparent density of the foamable polystyrene resin particles is low, the pre-foamed particles are likely to shrink, and if the shrinkage immediately after the pre-foaming is large, the cells of the pre-foamed particles are crushed, and the magnification is high even if the pre-foamed particles are cured at a high temperature. Where the recovery does not occur, the effervescent polystyrene-based resin particles of the present invention suppress shrinkage, so that it is not necessary to cure the pre-expanded particles at a high temperature, and it becomes easy to control the magnification after curing. Further, by increasing the apparent density of the effervescent polystyrene-based resin particles, the bulk density of the effervescent polystyrene-based resin particles does not decrease, so that the filling is easy and the storage space can be reduced.

The foamable polystyrene-based resin particles of the present invention preferably have an average cell diameter of 380 μm or less after pre-foaming the foamable polystyrene-based resin particles at a bulk magnification of 80 times and then curing them at 30 ° C. for 24 hours. , 350 μm or less, more preferably 300 μm or less. On the other hand, the lower limit is more preferably 80 μm or more, further preferably 100 μm or more, and particularly preferably 130 μm or more, from the viewpoint of the closed cell ratio. When the average cell diameter is 380 μm or less, extreme cell enlargement can be suppressed, the number of cells in the foamed particles is not extremely reduced, and the strength of the foamed particles as a structure can be suppressed from being lowered. If the cell diameter becomes extremely large, the cell wall becomes thicker and the flexibility decreases. Therefore, if shrinkage occurs immediately after pre-foaming, the cell wall will be buckled and the strength of the foamed particles as a structure will decrease. Be done. Further, by setting the average cell diameter to 380 μm or less, the number of cells existing in the preliminary foamed particles is increased, the radiant heat is reduced, and the thermal conductivity is improved. On the other hand, when the average cell diameter is 80 μm or more, it is considered that the cell film is not extremely thin, bubble rupture due to an inorganic substance can be suppressed, and a decrease in the closed cell ratio can be suppressed.

In the foamable polystyrene-based resin particles of the present invention, the bulk ratio of the pre-foamed particles obtained by pre-foaming the foamable polystyrene-based resin particles is preferably 75 times or more after curing at 30 ° C. for 24 hours. 80 times or more is more preferable. When the bulk ratio of the pre-foamed particles is 75 times or more, the density of the polystyrene-based resin foam-molded product obtained by molding the pre-foamed particles is reduced, and a lighter polystyrene-based resin foam-molded product is produced. Is possible. In addition, the amount of resin used can be reduced by increasing the bulk ratio, which leads to cost reduction.

[Manufacturing method of foamable polystyrene resin particles]
The foamable polystyrene-based resin particles of the present invention can be obtained by a known melt-kneading method. Specifically, the polystyrene-based resin, carbon-based radiant heat transfer inhibitor, and foaming agent are melt-kneaded (melted) by an extruder. (Kneading process), the melt-kneaded product is extruded into a chamber filled with pressurized circulating water through a die with small holes attached to the tip of the extruder (extruded process), and the melt-kneaded product immediately after extrusion is cut by a rotary cutter. At the same time, it can be produced by cooling and solidifying with pressurized circulating water (cooling step). Preferably, it is obtained by the following method for producing foamable polystyrene-based resin particles of the present invention.

In the method for producing foamable polystyrene-based resin particles of the present invention, a polystyrene-based resin composition containing a carbon-based radiant heat transfer inhibitor and a polystyrene-based resin melt composed of a foaming agent are pressurized and circulated from a die having a plurality of small pores. A method for producing foamable polystyrene-based resin particles that are extruded into water and cut with a rotary cutter to form particles. It contains less than 20% by weight, or (B) more than 20% by weight and 55% by weight or less of isobutane with respect to 100% by weight of the total amount of pentane and isobutane, and
The apparent density of the effervescent polystyrene-based resin particles is more than ^{1000 kg / m 3 and 1060 kg / m 3} or less (hereinafter, may be referred to as "the production method of the present invention").

Among the configurations in the production method of the present invention, each configuration described in [Expandable polystyrene-based resin particles] can be similarly applied to the production method of the present invention.

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

As a preferred embodiment of the production method of the present invention, a polystyrene resin and a carbon-based radiant heat transfer inhibitor are kneaded by a kneading device equipped with a biaxial stirrer such as a Banbury mixer to prepare a master batch. The masterbatch, the new polystyrene resin, the foaming agent, and other components such as flame retardant, if necessary, were melt-kneaded with an extruder, and the obtained resin melt was melted and kneaded with a small hole attached to the tip of the extruder. It is extruded into a cutter chamber filled with pressurized circulating water through a die having a die, and immediately after extrusion, it is cut by a rotary cutter and cooled and solidified by pressurized circulating water. At this time, for melt-kneading in the extruder, a single extruder may be used, a plurality of extruders may be connected, or a second kneader such as a static mixer or a stirrer without a screw may be used in combination with the extruder. Yes, it can be selected as appropriate.

The polystyrene-based resin and the carbon-based radiant heat transfer inhibitor are kneaded by a kneading device equipped with a biaxial stirrer, for example, an intensive mixer, an internal mixer, or a Banbury mixer capable of kneading the resin under a load. It is preferable to prepare a master batch. 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% by weight to 80% by weight of the carbon-based radiant heat transfer inhibitor from the viewpoint of the balance between kneadability and cost. The prepared masterbatch, polystyrene resin, foaming agent, and if necessary, flame retardant, heat stabilizer, and other additives are added to the first extruder and, if necessary, the second kneader attached to the extruder. After melt-kneading and cooling the obtained resin melt to a predetermined temperature, it is extruded into a cutter chamber filled with pressurized circulating water through a die having small holes. Immediately after this extrusion, the pellets are cut with a rotary cutter to be pelletized, and the obtained pellets (resin particles) are cooled and solidified with pressurized circulating water to obtain foamable polystyrene-based resin particles. Similarly, for other additives such as flame retardants and heat stabilizers, a masterbatch of polystyrene resin and other additives may be prepared in advance and put into an extruder or the like. No. Further, the carbon-based radiant heat transfer inhibitor, flame retardant, heat stabilizer and other additives may be directly put into the extruder without masterbatch.

When pentane and butane are used in combination as a foaming agent, the method of addition thereof is not particularly limited as long as pentane and butane are added, and the addition may be performed at the same time, or one of them may be added first and then the other. You may do so.

The amount of isobutane added in the production method of the present invention is more than 20% by weight and 55% by weight or less based on 100% by weight of the total amount of foaming agent, or 20% by weight of isobutane based on 100% by weight of pentane and isobutane. It is more than% and 55% by weight or less. In the case of production by the melt extrusion method, if isobutane is more than 55% by weight, cutting becomes difficult and the die is clogged, which makes it difficult to collect a sample.

The set temperature of the melt-kneading portion of the extruder is preferably 100 ° C. to 250 ° C. Further, it is preferable that the residence time in the extruder from the supply of the polystyrene resin and various components to the extruder to the end of melt-kneading is 10 minutes or less. If the set temperature in the melt-kneading part 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 be decomposed when the flame retardant is added. Therefore, the desired flame retardancy can be obtained, and it is not necessary to add an excessive amount of the flame retardant in order to impart the desired flame retardancy. On the other hand, when the set temperature in the melt-kneading portion of the extruder is 100 ° C. or higher, the load on the extruder is not increased, the extrusion becomes stable, and the dispersibility of the added component becomes good.

Here, the melt-kneading portion of the extruder means from the feed portion to the tip of the final extruder on the downstream side when the extruder is composed of a single-screw or twin-screw screw. When a second kneader such as a static mixer or a stirrer without a screw is used in combination with the first extruder, it means from the feed portion of the first extruder to the tip of the second kneader.

The water pressure of the pressurized circulating water is preferably 0.9 MPa or more and 1.5 MPa or less, and more preferably 0.95 MPa or more and 1.4 MPa or less. When the water pressure is 0.9 MPa or more, foaming can be suppressed, the bulk density of the foamable polystyrene-based resin particles becomes high, and the foaming ratio and the transport efficiency are less likely to decrease. On the other hand, when the water pressure is 1.5 MPa or less, the rotary cutter is not pushed back by the water pressure, and the extruded molten resin does not wind around the rotary cutter, so that stable production can be achieved. Further, it is considered that the strain applied to the molten resin does not increase, the shape of the foamable polystyrene-based resin particles becomes good, and the foamability and moldability are excellent.

The die used in the present invention is not particularly limited, and examples thereof include those having a small hole having a diameter of 0.3 mm to 2.0 mm, preferably 0.4 mm to 1.0 mm.

The cutting device for cutting the molten resin extruded into the pressurized circulating water is not particularly limited. Equipment to be used, and the like.

[Polystyrene resin foam molded product]
The foamable polystyrene-based resin particles of the present invention are not particularly limited, but are formed by a pre-foaming method in which foamable polystyrene-based resin particles are foamed to a predetermined expansion ratio to obtain pre-expanded particles, and molding is performed using the pre-expanded particles. , Polystyrene-based resin foam molded products can be produced.

As the polystyrene-based resin foam molded product has a higher foaming ratio, the amount of foamable polystyrene-based resin particles used as a raw material decreases. Therefore, according to the present invention, the polystyrene-based resin foamed molded product having a high foaming ratio can be made cheaper. Can be manufactured. It should be noted that high-magnification foaming was difficult with the conventional foamable polystyrene-based resin particles containing graphite. However, according to the effervescent polystyrene-based resin particles of the present invention and the effervescent polystyrene-based resin particles obtained by the production method of the present invention, the content of isobutane contained in the effervescent polystyrene-based resin particles and the effervescent polystyrene-based particles. By controlling the apparent density of the resin particles, high-magnification foaming becomes possible, and it is possible to supply a heat insulating material that is lightweight, easy to handle, and cheaper.

The effervescent polystyrene-based resin particles of the present invention are foamed 10 to 110 times by a known pre-foaming step, for example, steam to obtain pre-foamed particles (pre-foaming step), and after being cured for a certain period of time if necessary, after Preliminary foamed particles are molded by steam using a known molding machine to produce a polystyrene-based resin foamed molded product. Depending on the shape of the mold used, it is possible to obtain a molded product having a complicated shape or a block-shaped molded product.

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

A known prefoaming machine can be used, for example, a can equipped with a stirrer and accommodating foamable polystyrene-based resin particles, and a steam chamber installed below the can and supplying steam to the can. , A pre-foaming machine equipped with a pre-foaming particle discharge port is used.

The pressure inside the can (cage pressure) at the time of adding steam is not particularly limited, but is preferably 0.001 to 0.15 MPa, more preferably 0.01 to 0.10 MPa, and further preferably 0.03 to 0.08 MPa. .. When the pressure inside the can is 0.01 MPa or more, the steam injection time in the preliminary foaming can be set to 500 seconds or less when a high foaming ratio is obtained. When the pressure inside the can is 0.15 MPa or less, it is not necessary to increase the pressure of water vapor, the number of blocking phenomena occurring decreases, and the preliminary foaming yield increases.

Further, the preliminary foaming step can be performed by either a continuous method or a batch method.

The continuous method is a method in which the foamable polystyrene-based resin particles are continuously supplied into the can and the pre-foamed particles are continuously discharged from the discharge port provided on the upper part of the can. The expansion ratio of the pre-expanded particles can be adjusted, for example, by appropriately selecting the amount (weight) of the effervescent polystyrene-based resin particles charged into the can per hour. In the case of the continuous method, the residence time in the pre-foaming machine can from the time when the foamable polystyrene resin particles are supplied into the can to the time when the pre-foaming particles are discharged is defined as the steam injection time.

In the batch method, a predetermined amount of foamable polystyrene resin particles are placed in a can, the particles are pre-foamed to a predetermined expansion ratio, the supply of water vapor is stopped, and then air is blown into the can as needed. This is a method of blowing in to cool and dry the prefoamed particles and then taking them out of the can. The expansion ratio of the pre-expanded particles can be adjusted by appropriately selecting the amount (weight) of the effervescent polystyrene-based resin particles charged into the can per batch. Since the batch method is a method of pre-foaming the charged polystyrene-based resin particles to a predetermined volume, the foaming ratio of the obtained pre-foamed particles increases as the input amount per batch is reduced.

In addition, it is better to cure the pre-foamed particles immediately after the pre-foaming. At the time of pre-foaming, water vapor is present in the foamed particles, but since the water vapor condenses in water in the cooling step after foaming, the inside of the pre-foamed particles immediately after the pre-foaming is in a reduced pressure state. If the cell wall strength of the prefoamed particles is low under reduced pressure, shrinkage may easily occur. Further, if the closed cell ratio of the pre-foamed particles is low, the strength of the cell structure is lowered and the pre-foamed particles are likely to shrink. Therefore, a curing step of replacing the inside of the prefoamed particles with air and returning the particles to atmospheric pressure is effective. Since the pre-foamed particles of the polystyrene-based resin foamable particles of the present invention are suppressed from shrinking immediately after the pre-foaming, they can be restored to a desired foaming ratio by the curing step.

The temperature at the time of curing is not particularly limited, but is preferably 20 to 80 ° C, more preferably 25 to 70 ° C, and even more preferably 30 to 60 ° C. When the curing temperature is 20 ° C. or higher, air is likely to be introduced into the pre-foamed particles that have been in a reduced pressure state, and the inside of the foamed particles is likely to return to atmospheric pressure. When the curing temperature is 80 ° C. or lower, the foaming agent present in the pre-foamed particles is less likely to disperse, the foaming power does not decrease, and the surface beauty of the molded product does not decrease.

The polystyrene-based resin foam molded product of the present invention is, for example, an agricultural and fishery product box such as a building heat insulating material used for floors, walls, roofs, etc., a box for transporting marine products such as fish, and a box for transporting agricultural products such as vegetables. It can be used for various purposes such as heat insulating materials for bathrooms and heat insulating materials for hot water storage tanks.

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

The measurement method and evaluation method in the following Examples and Comparative Examples are as follows.

(Method for measuring the apparent density of foamable polystyrene resin particles)
W (kg) of foamable polystyrene resin particles was collected as a measurement sample, and this measurement sample was naturally dropped into a measuring cylinder containing ethanol, and its mass (kg) and volume (m ³ ) were measured. The apparent density was measured based on the formula.

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

(Measuring method of bulk magnification of preliminary foamed particles)
W (g) of each of the prefoamed particles was collected as a measurement sample, and after the measurement sample was naturally dropped into the graduated cylinder, the graduated cylinder was struck to make the apparent volume V (cm ³ ) of the sample constant, and its mass (g). And the volume (cm ³ ) were measured, and the bulk magnification was measured based on the following formula.

Bulk magnification (cm ³ / g) = Volume of measurement sample (V) / Weight of measurement sample (W)
In the pre-foamed particles, the bulk ratio measured within 5 to 10 minutes after the pre-foamed particles are discharged from the pre-foaming machine is defined as the bulk ratio immediately after foaming in which shrinkage occurs after the pre-foaming.

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

(Method of measuring the average cell diameter of preliminary foamed particles)
(1) Observation condition device: DIGITAL MICROSCOPE VHX-900 manufactured by KEYENCE CORPORATION
Observation magnification: 100 times (2) Measurement conditions A bisector perpendicular to the major axis diameter in the preliminary foamed particles was cut with a razor, and the cross section was photographed with a DIGITAL MICROSCOPE manufactured by KEYENCE at an observation magnification of 100 times. To shoot. The number of cells existing in a range of 1000 μm × 1000 μm square within a radius of 1000 μm from the center point of the cross section is counted. Using the number of cells, the average cell diameter was calculated based on the following formula.
Average cell diameter (μm) = 2 x [1000 μm x 1000 μm / (number of cells x pi)] ^0.5
(Measuring method of thermal conductivity of polystyrene-based 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 it is necessary to determine the measured average temperature in order to compare the heat insulating properties. In this specification, 23 ° C. defined by JIS A9511: 2006R, which is a standard for foamed plastic heat insulating materials, is adopted as a reference.

The thermal conductivity is measured after cutting out a sample for measuring thermal conductivity from a polystyrene-based resin foam molded product, allowing the sample to stand at a temperature of 60 ° C. for 48 hours, and further allowing it to stand at a temperature of 23 ° C. for 24 hours. bottom.

More specifically, a sample having a length of 300 mm × a width of 300 mm × 25 mm was cut out from a polystyrene-based resin foam molded product. The sample was allowed to stand at a temperature of 60 ° C. for 48 hours, and further allowed to stand at a temperature of 23 ° C. for 24 hours, and then using a thermal conductivity measuring device (HC-074 manufactured by Eiko Seiki Co., Ltd.). The thermal conductivity was measured by a heat flow metering method in accordance with JIS A 1412-2: 1999 at an average temperature of 23 ° C. and a temperature difference of 20 ° C.

(Evaluation of production stability of effervescent polystyrene resin particles)
The effervescent polystyrene-based resin particles were produced under the conditions shown in Examples and Comparative Examples, and the production stability of the effervescent polystyrene-based resin particles was evaluated based on the following evaluation criteria.

◯: Stable sample collection possible △: Dice blockage is observed, but sample collection is possible ×: Sample collection is difficult.

The raw materials used in Examples and Comparative Examples are shown below.

(Styrene resin)
(A) Styrene homopolymer [manufactured by PS Japan Corporation, 680]
(Graphite)
(B) Graphite [Scale graphite SGP-40B, manufactured by Marutoyo Casting Co., Ltd.]
(Brominated flame retardant)
(C) 2,2-bis [4- (2,3-dibromo-2-methylpropoxy) -3,5-dibromophenyl] propane [manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., SR-130, bromine content = 66% 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].

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

(Manufacturing Example 1) (Graphite Masterbatch (G))
Raw materials are added to the Banbury mixer so that the total weight (A + B + F) of polystyrene resin (A) 49% by weight, graphite (B) 50% by weight, and ethylene bisstearic acid amide (F) 1% by weight is 100% by weight. Then, the mixture was kneaded for 20 minutes with a load of 5 kgf / cm ^{2 applied without heating and cooling.} At this time, the resin temperature was measured and found to be 180 ° C. A strand-shaped resin supplied to a ruder and extruded at a discharge rate of 250 kg / hr through a die having a small hole attached to the tip was cooled and solidified in a water tank at 30 ° C., and then cut to obtain a masterbatch (G). .. The graphite content in the masterbatch (G) was 50% by weight.

(Production Example 2) (Masterbatch (H) of a mixture of a brominated flame retardant and a heat stabilizer)
After supplying the polystyrene resin (A) to the twin-screw extruder and melt-kneading it, a mixture of the brominated flame retardant (C), the heat stabilizer (D1) and (D2) is supplied from the middle of the extruder. Further melt-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. A strand-shaped resin extruded at a discharge rate of 300 kg / hr is cooled and solidified in a water tank at 20 ° C. through a die having a small hole attached to the tip of the extruder, and then cut to form a brominated flame retardant and a heat stabilizer. A masterbatch (H) of the mixture was obtained. At this time, the set temperature of the extruder was 170 ° C.

(Example 1)
[Preparation of foamable polystyrene resin particles]
The polystyrene resin (A), the masterbatch (H), and the graphite masterbatch (G) were each put into 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 is supplied to a tandem type two-stage extruder in which a twin-screw extruder (first extruder) having a diameter of 40 mm and a single-screw extruder (second extruder) having a diameter of 90 mm are connected in series. The mixture was melt-kneaded at a set temperature of 190 ° C. and a rotation speed of 150 rpm of an extruder having a diameter of 40 mm. From the middle of the 40 mm diameter extruder (first extruder), 80% by weight of mixed pentane [normal pentane (E1) and 20 weight by isopentane (E2)) with respect to 100 parts by weight of the melt (resin composition) of the resin mixture. % Mixture] was press-fitted at a ratio of 4.3 parts by weight, and 2.2 parts of isobutane (E3) was press-fitted into 100 parts by weight of the resin composition, and a total of 6.5 parts of foaming agent was added. .. Then, it was supplied to a 90 mm diameter extruder (second extruder) through a continuous pipe set at 200 ° C.

After cooling the molten resin to a resin temperature of 160 ° C with a 90 mm diameter extruder (second extruder), the diameter is 0.65 mm and the land length is 3.0 mm attached to the tip of the second extruder set at 250 ° C. The die having 36 small holes was extruded into pressurized circulating water at a temperature of 65 ° C. and 1.3 MPa at a discharge rate of 50 kg / hour. The extruded molten resin was cut and atomized using a rotary cutter having six blades in contact with the die, and transferred to a centrifugal dehydrator to obtain foamable 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 preliminary foamed particles]
The obtained foamable polystyrene-based resin particles were stored at 15 ° C. for 1 week or longer, and then 0.04 part of zinc stearate was dry-blended into the foamable polystyrene-based resin particles. The additive expandable polystyrene resin particles 880g preliminary foaming machine including the large opening Kogyo Co., Ltd., BHP-300] was poured into the canister internal pressure setting and 0.05kg ^/ cm ² ~0.15kg ^/ cm 2 , 0.10 MPa of water vapor was introduced into a pre-foaming machine and foamed at a bulk ratio of 80 times to obtain pre-foamed particles.

[Preparation of polystyrene-based resin foam molded product]
After curing the obtained pre-foamed particles at 30 ° C. for 24 hours, an in-mold molding die (length 400 mm × width 400 mm ×) attached to a styrofoam molding machine [KR-57, manufactured by Daisen Kogyo Co., Ltd.] It was filled in (thickness 50 mm), and 0.06 MPa of steam was introduced to foam the inside of the mold, and then water was sprayed onto the mold to cool the mold. After holding the polystyrene resin foam molded product in the mold until the pressure at which the polystyrene resin foam molded product pushes the mold becomes 0.01 MPa (gauge pressure), the polystyrene resin foam molded product is taken out and the polystyrene resin foamed molded product is taken out. A foam molded product was obtained. As a result of measuring the thermal conductivity of the obtained polystyrene-based resin foamable molded product by the above-mentioned measuring method, it was 0.03094 W / m · K.

Various characteristics of the produced polystyrene-based resin particles and pre-expanded particles were measured and evaluated by the above-mentioned measuring method and evaluation method. Table 1 shows the measurement results and evaluation results for the foamable polystyrene resin particles and the pre-foamed particles.

(Example 2)
In [Preparation of foamable polystyrene-based resin particles], polystyrene-based resin foaming was carried out in the same manner as in Example 1 except that the molten resin was cooled to 170 ° C. with a 90 mm diameter extruder (second extruder). A molded body was produced. As a result of measuring the thermal conductivity of the obtained polystyrene-based resin foamable molded product by the above-mentioned measuring method, it was 0.03079 W / m · K.

Various characteristics of the obtained foamable polystyrene resin particles and pre-foamed 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 foamable polystyrene-based resin particles], polystyrene-based resin foaming was carried out in the same manner as in Example 1 except that the molten resin was cooled to 180 ° C. with a 90 mm diameter extruder (second extruder). A molded body was produced. As a result of measuring the thermal conductivity of the obtained polystyrene-based resin foamable molded product by the above-mentioned measuring method, it was 0.03082 W / m · K.

Various characteristics of the obtained foamable polystyrene resin particles and pre-foamed 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 4)
In [Preparation of foamable polystyrene resin particles], a polystyrene resin foam molded product was prepared by the same treatment as in Example 1 except that the mixed pentane was changed to 4.75 parts by weight and the isobutane was changed to 1.75 parts by weight. .. As a result of measuring the thermal conductivity of the obtained polystyrene-based resin foamable molded product by the above-mentioned measuring method, it was 0.03136 W / m · K.

Various characteristics of the obtained foamable polystyrene resin particles and pre-foamed 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 5)
In [Preparation of Expandable Polystyrene Resin Particles], a polystyrene resin foam molded product was produced by the same treatment as in Example 1 except that the mixed pentane was changed to 4.0 parts by weight and the isobutane was changed to 2.5 parts by weight. bottom. As a result of measuring the thermal conductivity of the obtained polystyrene-based resin foamable molded product by the above-mentioned measuring method, it was 0.03085 W / m · K.

Various characteristics of the obtained foamable polystyrene resin particles and pre-foamed 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 6)
In [Preparation of Expandable Polystyrene Resin Particles], a polystyrene resin foam molded product was produced by the same treatment as in Example 1 except that the mixed pentane was changed to 4.8 parts by weight and the isobutane was changed to 2.2 parts by weight. bottom. As a result of measuring the thermal conductivity of the obtained polystyrene-based resin foamable molded product by the above-mentioned measuring method, it was 0.03190 W / m · K.

Various characteristics of the obtained foamable polystyrene resin particles and pre-foamed 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 7)
In [Preparation of Expandable Polystyrene Resin Particles], a polystyrene resin foam molded product was produced by the same treatment as in Example 1 except that the mixed pentane was changed to 5.3 parts by weight and the isobutane was changed to 2.2 parts by weight. bottom. As a result of measuring the thermal conductivity of the obtained polystyrene-based resin foamable molded product by the above-mentioned measuring method, it was 0.03230 W / m · K.

Various characteristics of the obtained foamable polystyrene resin particles and pre-foamed 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 8)
In [Preparation of foamable polystyrene resin particles], a polystyrene resin foam molded product was produced by the same treatment as in Example 1 except that the mixed pentane was changed to 5.8 parts by weight and the isobutane was changed to 2.2 parts by weight. bottom. As a result of measuring the thermal conductivity of the obtained polystyrene-based resin foamable molded product by the above-mentioned measuring method, it was 0.03105 W / m · K.

Various characteristics of the obtained foamable polystyrene resin particles and pre-foamed 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], except that the mixed pentane was changed to 6.5 parts by weight, the isobutane was changed to 0 parts by weight, and the water pressure of the pressurized circulating water was changed to 0.8 MPa. A polystyrene-based resin foam molded product was produced by the same treatment. As a result of measuring the thermal conductivity of the obtained polystyrene-based resin foamable molded product by the above-mentioned measuring method, it was 0.03032 W / m · K.

Various characteristics of the obtained foamable polystyrene resin particles and pre-foamed 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 foamable polystyrene-based resin particles], foamable polystyrene-based resin particles and their pre-foamed particles were prepared by the same treatment as in Example 1 except that the water pressure of the pressurized circulating water was changed to 0.8 MPa. ..

Various characteristics of the obtained foamable polystyrene resin particles and pre-foamed 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 foamable polystyrene-based resin particles], except that the molten resin was cooled to 180 ° C. with a 90 mm diameter extruder (second extruder) and the water pressure of the pressurized circulating water was changed to 0.8 MPa. Prepared effervescent polystyrene-based resin particles and their pre-expanded particles by the same treatment as in Example 1.

Various characteristics of the obtained foamable polystyrene resin particles and pre-foamed 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 4)
In [Preparation of foamable polystyrene-based resin particles], foamable polystyrene was subjected to the same treatment as in Example 1 except that isobutane was changed to 1.75 parts by weight and the water pressure of the pressurized circulating water was changed to 0.8 MPa. System resin particles and their prefoamed particles were prepared.

Various characteristics of the obtained foamable polystyrene resin particles and pre-foamed 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 5)
Examples of [Preparation of Expandable Polystyrene Resin Particles], except that the mixed pentane was changed to 6.5 parts by weight, the isobutane was changed to 0.5 parts by weight, and the water pressure of the pressurized circulating water was changed to 0.8 MPa. Expandable polystyrene-based resin particles and their pre-expanded particles were prepared by the same treatment as in 1.

Various characteristics of the obtained foamable polystyrene resin particles and pre-foamed 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 6)
Examples of [Preparation of Expandable Polystyrene Resin Particles] except that the mixed pentane was changed to 6.0 parts by weight, the isobutane was changed to 1.0 part by weight, and the water pressure of the pressurized circulating water was changed to 0.8 MPa. Expandable polystyrene-based resin particles and their pre-expanded particles were prepared by the same treatment as in 1.

Various characteristics of the obtained foamable polystyrene resin particles and pre-foamed 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 7)
In [Preparation of foamable polystyrene-based resin particles], foamable polystyrene-based resin particles were prepared by the same treatment as in Example 1 except that the mixed pentane was changed to 3.0 parts by weight and the isobutane was changed to 4.0 parts by weight. Attempts were made, but cutting became difficult during the production of foamable polystyrene-based resin particles, and the dies were blocked, making it difficult to collect samples.

Claims (10)

Foamable polystyrene-based resin particles composed of a polystyrene-based resin composition containing a carbon-based radiant heat transfer inhibitor and a foaming agent.
The foaming agent contains pentane and isobutane, and isobutane is more than 20% by weight and 55% by weight or less based on 100% by weight of the total amount of pentane and isobutane.
Foamable polystyrene resin particles having an apparent density of more than ^{1000 kg / m 3 and 1060 kg / m 3} or less. The foamable polystyrene type according to claim 1, wherein the average cell diameter of the prefoamed polystyrene particles when the foamable polystyrene resin particles are prefoamed at a bulk magnification of 80 times and then cured at 30 ° C. for 24 hours is 380 μm or less. Resin particles. The foamable polystyrene-based resin particles according to claim 1 or 2, wherein the polystyrene-based resin composition contains a flame retardant in an amount of 0.5 to 6% by weight based on 100% by weight of the polystyrene-based resin composition. Preliminary foamed polystyrene-based resin particles according to any one of claims 1 to 3, wherein the bulk ratio is 75 times or more when the particles are pre-foamed and then cured at 30 ° C. for 24 hours. Foamed particles. A polystyrene-based resin composition containing a carbon-based radiant heat transfer inhibitor and a polystyrene-based resin melt composed of a foaming agent are extruded from a die having a plurality of small holes into pressurized circulating water and cut into particles by a rotary cutter. A method for producing polystyrene-based resin particles.
The foaming agent contains more than 20% by weight and 55% by weight or less of isobutane with respect to 100% by weight of the total amount of the foaming agent.
The apparent density of the expandable polystyrene resin particles Ri 1000 kg / ^{m 3} Super 1060Kgm ³ der below,
A method for producing effervescent polystyrene-based resin particles, wherein the average cell diameter of the pre-expanded polystyrene-based resin particles is 380 μm or less when the effervescent polystyrene-based resin particles are pre-foamed at a bulk magnification of 80 times and then cured at 30 ° C. for 24 hours. A polystyrene-based resin composition containing a carbon-based radiant heat transfer inhibitor and a polystyrene-based resin melt composed of a foaming agent are extruded from a die having a plurality of small holes into pressurized circulating water and cut into particles by a rotary cutter. A method for producing polystyrene-based resin particles.
The foaming agent contains more than 20% by weight and 55% by weight or less of isobutane with respect to 100% by weight of the total amount of the foaming agent.
The apparent density of the effervescent polystyrene resin particles is 1000 kg / m. ³ Super 1060kgm ³ Is below
A method for producing foamable polystyrene-based resin particles, wherein the water pressure of the pressurized circulating water is 0.9 MPa or more and 1.5 MPa or less. A polystyrene-based resin composition containing a carbon-based radiant heat transfer inhibitor and a polystyrene-based resin melt composed of a foaming agent are extruded from a die having a plurality of small holes into pressurized circulating water and cut into particles by a rotary cutter. A method for producing polystyrene-based resin particles.
The foaming agent contains pentane and isobutane, and isobutane is more than 20% by weight and 55% by weight or less based on 100% by weight of the total amount of pentane and isobutane.
A method for producing effervescent polystyrene resin particles, wherein the apparent density of ^{the effervescent polystyrene resin particles is more than 1000 kg / m 3 and} 1060 kg / m ^{3 or less.} The method for producing foamable polystyrene-based resin particles according to claim 5 or 6, wherein the foaming agent contains pentane and butane. The foamability according to claim 6 or 7 , wherein the average cell diameter of the pre-foamed particles is 380 μm or less when the foamable polystyrene-based resin particles are pre-foamed at a bulk magnification of 80 times and then cured at 30 ° C. for 24 hours. Method for producing polystyrene resin particles. The method for producing foamable polystyrene-based resin particles according to claim 5 or 7 , wherein the water pressure of the pressurized circulating water is 0.9 MPa or more and 1.5 MPa or less.