WO2012043439A1

WO2012043439A1 - Expandable polystyrene resin particles and process for producing same, pre-expanded polystyrene resin beads, molded polystyrene resin foam and process for producing same, heat insulator, and cushioning medium

Info

Publication number: WO2012043439A1
Application number: PCT/JP2011/071811
Authority: WO
Inventors: 賢治平井; 樽本　裕之; 翔太遠藤; 和人佐藤
Original assignee: 積水化成品工業株式会社
Priority date: 2010-09-30
Filing date: 2011-09-26
Publication date: 2012-04-05
Also published as: TW201219468A; CN103140545B; TWI464203B; CN103140545A

Abstract

These expandable polystyrene resin particles are resin particles comprising polystyrene resin particles and a blowing agent contained therein. When heated and expanded 50 times in terms of bulk expansion ratio, the resin particles give expanded beads that have a cell structure in which the inner part has an average cell diameter of 35-140 µm, the ratio of the surface-layer-part average cell diameter to the inner-part average cell diameter is 0.80-1.20, and the proportion of open cells is 10% or less.

Description

Expandable polystyrene resin particles and production method thereof, polystyrene resin pre-expanded particles, polystyrene resin foam molding and production method thereof, heat insulating material, and buffer material

The present invention relates to a polystyrene-based resin foam molded article excellent in mechanical strength such as bending strength, compressive strength, impact resistance, heat insulating properties, and buffering properties, and expandable polystyrene-based resin particles used in the production thereof.
The present application includes Japanese Patent Application No. 2010-222101, filed in Japan on September 30, 2010, Japanese Patent Application No. 2010-222102, filed in Japan on September 30, 2010, and Japan, on September 30, 2010. Priority is claimed based on Japanese Patent Application No. 2010-2221063 filed in Japan, the contents of which are incorporated herein by reference.

A polystyrene resin foam molded article obtained by foam molding of expandable polystyrene resin particles is excellent in compression resistance, light weight, heat insulation, buffering properties, economy, and the like. This polystyrene-based resin foam molded product is widely used as a heat insulating material such as a cold storage container for food, a heat insulating material for a house, a cooler box, or a cushioning material such as a packing material for transportation or a shock absorbing material between contacting members. Yes.

As one method for producing expandable polystyrene resin particles, a so-called melt extrusion method is known. In the melt extrusion method, a foaming agent is added to a polystyrene resin melted in an extruder and kneaded, and the foaming agent-containing molten resin is directly put into a cooling liquid from a small hole of a die provided at the tip of the extruder. The extrudate is cut with a high-speed rotary blade at the same time as extrusion, and the extrudate is cooled and solidified by contact with a cooling liquid to produce expandable polystyrene resin particles.
Conventionally, for example, techniques disclosed in Patent Documents 1 to 3 have been proposed regarding a method for producing expandable polystyrene resin particles by a melt extrusion method.

Patent Document 1 includes (a) a step of extruding a foaming agent-containing polymer through a die head portion in a water bath or a fluid bath that is maintained at a temperature higher than the glass transition temperature (hereinafter abbreviated as Tg) of the foamable polymer. (B) a step of immediately cutting the polymer at the outlet of the die head to form granules in a water bath or fluid bath maintained at a temperature higher than the Tg value of the foamable polymer; and (c) foaming the granules into the foam. And a step of cooling to a temperature equal to or lower than the Tg value of the expandable polymer, an extrusion-type production method of expandable granules made of a non-oriented and stress-free thermoplastic styrene polymer is disclosed. In this extrusion-type production method, in the continuous process, the granules are gradually cooled from Tg + 5 ° C. to Tg−5 ° C. at a cooling rate slower than 3 ° C. per minute, and the polymer is cut into granules and the granules Is cooled under a pressure of 2 bar or more.

In Patent Document 2, a thermoplastic resin and a foaming agent are melt-kneaded, and then extruded from the extrusion hole of the die head into a heated and pressurized liquid of Tg + 5 ° C. or higher of the foamable thermoplastic resin particles, and obtained by immediate cutting. A method for producing expandable thermoplastic resin particles is disclosed in which the particles are kept at the same temperature or higher in a heated and pressurized liquid to relieve residual stress in the particles, and then cooled.

Patent Document 3 discloses a step of melt-kneading the thermoplastic resin (A) and the foaming agent (B) (step 1), and the obtained melt-kneaded product from the extrusion hole of the die head to the thermoplastic resin (A). And a step of immediately cutting (Step 2) and the resulting particles (foaming) after extrusion into a heated and pressurized liquid heated and pressurized to a temperature and pressure at which the melt-kneaded product of the foaming agent (B) does not foam When the temperature of the foamable thermoplastic resin is measured with a differential thermal analyzer (DSC) (step 3) and the temperature is cooled to a temperature at which the thermoplastic resin is not foamed at normal pressure (step 3). Of the two endothermic peaks, the step of aging the particles in a liquid at normal pressure heated to a temperature range of 30 to (T1 + 15) ° C., where T1 is the peak temperature on the low temperature side (step 4) , A method for producing expandable thermoplastic resin particles is disclosed

Japanese Patent Publication No. 5-59138 JP-A-6-32932 JP-A-7-314438

However, in the production method of Patent Document 1, when the resin extruded from the die head part is cut into granules, the extrusion and cutting are performed in a heated and pressurized liquid maintained at a high temperature equal to or higher than the Tg value of the foamable polymer. Therefore, the particles obtained by cutting are easily fused together, and the incidence of defective products in which a large number of particles are bonded together to form a lump is high.

In the production method of Patent Document 2, particles obtained by immediate cutting are maintained in a heated and pressurized liquid at Tg + 5 ° C. or higher to relieve residual stress in the particles, and then cooled to obtain expandable thermoplastic resin particles. Manufacture. However, when foamable thermoplastic resin particles are produced under the production conditions described in the examples of Patent Document 2, the particles obtained by cutting are easily fused, and a large number of particles are bonded together. The incidence of defective products that have become clumped is high. Further, when the expandable polystyrene resin particles obtained by this production method are heated and pre-expanded, the average cell diameter of the obtained pre-expanded resin particles tends to be large. When the average cell diameter is increased, there is a possibility that the mechanical strength of the foam molded product obtained by in-mold foam molding of the pre-expanded particles may be reduced, or the heat conductivity may be increased to deteriorate the heat insulation performance.

The production method of Patent Document 3 is a method for obtaining pre-expanded particles having a large cell diameter (bubble diameter). However, when the cell diameter in the cell structure of the pre-expanded particles is increased, the mechanical strength of the foam molded product obtained by in-mold foam molding of the pre-expanded particles is decreased, or the heat conductivity is increased to increase the heat insulation performance. It may get worse.

The present invention has been made in view of the above circumstances, and has a polystyrene resin foam molded article excellent in mechanical strength, heat insulation, and buffering property, and a method for producing the same, and a foamable polystyrene resin particle used in the production and a method for producing the same. The purpose is to provide.

According to the first aspect of the present invention, the expandable polystyrene resin particles are resin particles containing a foaming agent in the polystyrene resin particles, and the resin particles are heated and expanded to a bulk expansion ratio of 50 times. In the state of the expanded particles, the internal average bubble diameter is in the range of 35 to 140 μm, the surface layer average bubble diameter / internal average bubble diameter is in the range of 0.80 to 1.20, and the open cells It has a bubble structure with a rate of 10% or less.

In this case, the internal average cell diameter D ₁ ′ of the expanded particles when expanded to the bulk expansion ratio X times is expressed by the following formula (1) (where D ₁ is the inside of the expanded particles converted to the bulk expansion ratio 50 times). Expanded particle which represents an average cell diameter (μm), and D ₁ ′ is converted to a bulk foaming factor of 50 times using an internal average cell diameter (μm) of the foamed particle when foamed to a bulk foaming factor X times. It is preferable that the internal average bubble diameter D ₁ satisfies the relationship of 35 μm ≦ D ₁ ≦ 140 μm.

Further, the internal average bubble diameter is preferably within a range of 40 to 120 μm.

Further, the open cell ratio is preferably 8% or less.

Further, it is preferable that the value of the surface layer average bubble diameter / internal average bubble diameter is in the range of 0.90 to 1.10.

Moreover, it is preferable that the inorganic cell nucleating agent is contained in an amount of 5.0 parts by mass or less with respect to 100 parts by mass of the polystyrene resin.

Moreover, it is preferable that the inorganic cell nucleating agent is talc.

According to the second aspect of the present invention, in the method for producing expandable polystyrene resin particles, a foaming agent is added to and kneaded with polystyrene resin in a resin supply device, and the foaming agent-containing molten resin is added to the resin supply device. Extrude into the cooling liquid having a temperature lower than the glass transition temperature Tg of the expandable polystyrene resin particles from the small hole of the die provided at the tip, and at the same time, extrudate is cut, and the extrudate is brought into contact with the cooling liquid. By cooling and solidifying to obtain expandable polystyrene resin particles, and heating the obtained expandable polystyrene resin particles at a temperature of (glass transition temperature Tg-5 of expandable polystyrene resin particles) ° C. or higher. And obtaining the expandable polystyrene resin particles.

In this case, the temperature of the cooling liquid when cutting the extrudate is preferably in the range of 20 to 60 ° C.

Moreover, it is preferable to add 5.0 parts by mass or less of the inorganic cell nucleating agent with respect to 100 parts by mass of the polystyrene-based resin.

Moreover, it is preferable that the inorganic cell nucleating agent is talc.

The present invention also includes polystyrene resin pre-expanded particles obtained by heating and pre-expanding the expandable polystyrene resin particles.

The present invention also includes a polystyrene resin foam molded article obtained by filling the polystyrene resin pre-foamed particles in a cavity of a molding die and heating and foam molding in the mold.

According to the third aspect of the present invention, the polystyrene-based resin foam molded article is molded from polystyrene-based resin pre-expanded particles obtained by heating expandable polystyrene-based resin particles containing a foaming agent in the polystyrene-based resin particles. Filled into the mold cavity and heated, foamed in-mold, and obtained by pre-expanded particles obtained by heating the expandable polystyrene resin particles to be expanded to a bulk expansion ratio of 50 times. A cell structure in which the diameter is in the range of 35 to 140 μm, the value of the surface layer part average bubble diameter / internal average bubble diameter is in the range of 0.80 to 1.20, and the open cell ratio is 10% or less. Have.

In this case, the internal average cell diameter D ₂ ′ of the pre-expanded particles when expanded to the bulk expansion ratio X times is expressed by the following formula (2) (where D ₂ is the expansion ratio of the expanded particles converted to the bulk expansion ratio 50 times). The inside average cell diameter (μm) is represented, and D ₂ ′ is a preliminary value converted into a bulk foaming factor of 50 times using an internal average cell diameter (μm) of foamed particles when foamed to a bulk foaming factor X times. It is preferable that the internal average cell diameter D _{2 of the} expanded particles satisfies the relationship of 35 μm ≦ D ₂ ≦ 140 μm.

Further, the open cell ratio is preferably 8% or less.

Moreover, it is preferable that the inorganic cell nucleating agent is talc.

According to the fourth aspect of the present invention, a polystyrene resin foam molded article is obtained by filling polystyrene resin pre-expanded particles in a cavity of a mold, steam-heating the mold, and in-mold foam molding. The internal average cell diameter D ₃ ′ of the foam particles fused together in this foam molded product in the state when foam-molded at the expansion factor X times is expressed by the following formula (3) (where D ₃ is Represents the internal average cell diameter (μm) of the foamed particles in the foamed molded product converted to a foaming multiple of 50 times, and D ₃ ′ is the internal average cell size of the foamed particles in the foamed molded product when foamed to a foamed multiple of X times. diameter ([mu] m) using a representative) of the foamed molded body in terms of expansion ratio 50 times foamed average internal cell diameter D ₃ of the particles satisfy the relationship of 35μm ≦ D ₃ ≦ 140μm, a surface layer portion of the expanded particles Within the range of average bubble diameter / internal average bubble diameter of 0.80 to 1.20 Ri, and continuous cell ratio of the foamed molded product has a cellular structure is 10% or less.

According to the fifth aspect of the present invention, the heat insulating material is made of the polystyrene-based resin foam molding.

According to the sixth aspect of the present invention, the buffer material is made of the polystyrene resin foam molded article.

According to the seventh aspect of the present invention, in the method for producing a polystyrene resin foam molded article, a foaming agent is added to and kneaded with polystyrene resin in a resin supply device, and the foaming agent-containing molten resin is added to the resin supply device. Extrude into the cooling liquid having a temperature lower than the glass transition temperature Tg of the expandable polystyrene resin particles from the small hole of the die provided at the tip, and at the same time, extrudate is cut, and the extrudate is brought into contact with the cooling liquid. The first step of obtaining the expandable polystyrene resin particles by cooling and solidifying by the above, and the obtained expandable polystyrene resin particles at a temperature of (glass transition temperature Tg-5 of expandable polystyrene resin particles) ° C. or higher The second step of obtaining expandable polystyrene resin particles by heating, and then heating the obtained expandable polystyrene resin particles, and converting to a bulk expansion ratio of 50 times using the formula (2) Internal average cell diameter _{D 2} of the pre-expanded particles is in the range of 35 ~ 140 .mu.m, values of the surface layer portion average cell diameter / average internal cell diameter is in the range of 0.80 to 1.20, and continuous A third step of producing polystyrene resin pre-expanded particles having a cell structure with a cell ratio of 10% or less, and then filling the polystyrene resin pre-expanded particles in a cavity of a mold and heating the mold, A fourth step of inner foam molding.

Moreover, it is preferable that the inorganic cell nucleating agent is talc.

In the fourth step, the polystyrene resin pre-expanded particles may be filled in a cavity of a molding die and heated, and in-mold foam molding may be performed to obtain a heat insulating material.

Further, in the fourth step, the polystyrene resin pre-expanded particles may be filled in a cavity of a mold and heated, and foamed in-mold to obtain a buffer material.

According to the present invention, the expandable polystyrene resin particles are in the form of expanded particles expanded to a bulk expansion ratio of 50 times, and the internal average cell diameter is in the range of 35 to 140 μm, and the surface layer portion average cell diameter / internal It has a cell structure in which the average cell diameter is in the range of 0.80 to 1.20, and the open cell rate is 10% or less. Therefore, relatively small, uniform, and independent bubbles are formed throughout the foam particles, and the foam molded product obtained by in-mold foam molding of the foam particles has mechanical strength such as bending strength, compression strength, and impact resistance, and heat insulation. Excellent in buffering properties.

According to the present invention, the method for producing expandable polystyrene resin particles is obtained by converting expandable polystyrene resin particles obtained by a melt extrusion method to (glass transition temperature Tg-5 of expandable polystyrene resin particles) of not less than This is a method of obtaining expandable polystyrene resin particles by heating at a temperature. Therefore, when the obtained expandable polystyrene resin particles are heated and foamed, relatively small, uniform and independent bubbles are formed over the entire expanded particles. Efficient foamable polystyrene resin particles to produce foamed products with excellent mechanical strength such as bending strength, compressive strength, impact resistance, heat insulation, and buffering by foaming these foamed particles in-mold Can be manufactured well.

According to the present invention, the polystyrene-based resin foam molded article has the internal average cell diameter D ₃ ′ of the fused foam particles in the foam molded article in a state where the foam-molded article is foam-molded to X times the expansion ratio. formula (3) is the average internal cell diameter D ₃ of the expanded beads of foamed molded body in terms of expansion ratio 50-fold with, satisfy the relationship of 35 [mu] m ≦ D ₃ ≦ 140 .mu.m, the surface layer portion average cell of the foamed particles It has a cell structure in which the value of the diameter / internal average cell size is in the range of 0.80 to 1.20, and the open cell ratio of the foamed molded product is 10% or less. Therefore, relatively small, uniform and independent bubbles are formed over the entire foamed molded product, and this foamed molded product is excellent in bending strength, compressive strength, mechanical strength such as impact resistance, heat insulation, and buffering properties.

It is a block diagram which shows an example of the manufacturing apparatus used for manufacture of the expandable polystyrene-type resin particle of this invention.

(Expandable polystyrene resin particles)
The expandable polystyrene resin particles of the present invention are expandable polystyrene resin particles containing a foaming agent in polystyrene resin particles, and in the state of expanded particles that are heated and expanded to a bulk expansion ratio of 50 times, an internal average A cell structure in which the cell diameter is in the range of 35 to 140 μm, the surface layer part average bubble diameter / internal average cell diameter is in the range of 0.80 to 1.20, and the open cell ratio is 10% or less. Have In addition, the bulk foaming factor of the said foamed particle refers to the bulk foaming factor measured by the measuring method of the bulk foaming multiple of the polystyrene-type resin pre-expanded particle mentioned later.

In the expandable polystyrene-based resin particles of the present invention, when the expanded foamed foam particles heated and expanded are other than 50 times, the internal average cell diameter D ₁ ′ of the expanded particles is expressed by the above formula (1). It is converted into a bulk expansion ratio of 50 times, and the internal average bubble diameter D ₁ satisfies the relationship of 35 μm ≦ D ₁ ≦ 140 μm. The same applies to the cell structure of the polystyrene resin pre-expanded particles and the polystyrene resin foam molded article according to the present invention.

The expandable polystyrene resin particles of the present invention are in the form of expanded particles that are heated and expanded to a bulk expansion ratio of 50 times, and the internal average cell diameter is in the range of 35 to 140 μm, and further in the range of 40 to 120 μm. It is preferable that When the internal average cell diameter is less than 35 μm, the polystyrene-based resin foam molded article obtained by in-mold foam molding increases the open cell ratio and decreases closed cells, so that bending strength, compressive strength, impact resistance are increased. Such as mechanical strength will be reduced. When the internal average bubble diameter exceeds 140 μm, mechanical strength such as bending strength, compressive strength, and impact resistance is lowered.

The expandable polystyrene resin particles of the present invention are in the form of expanded particles heated to be expanded to a bulk expansion ratio of 50 times, and the value of the surface layer part average cell diameter / internal average cell diameter is 0.80 to 1.20. It is preferably within the range, and more preferably within the range of 0.90 to 1.10. When the value of the surface layer part average cell diameter / internal average cell diameter is out of the above range, the mechanical strength such as bending strength, compressive strength, impact resistance, etc. of the polystyrene-based resin foam molded product obtained by in-mold foam molding decreases. Resulting in. In the present invention, the “surface layer part average cell diameter” is a cross-section obtained by cutting the foamed particles so as to pass through the center in the state of foamed particles obtained by foaming expandable polystyrene resin particles to a bulk foaming factor of 50 times. , The region where the depth from the surface of the expanded particles is up to ¼ of the diameter of the expanded particles is defined as “surface layer portion”, which means the average cell diameter of the bubbles in the surface layer portion. The “internal average bubble diameter” is defined as “inside” a region deeper than the surface layer portion of the same foamed particle (region on the center side), and refers to the average bubble diameter of the bubbles in the inside. Yes.

The expandable polystyrene resin particles of the present invention are in the form of expanded particles that are heated and expanded to a bulk expansion ratio of 50 times, and the open cell ratio is preferably 10% or less, and more preferably 8% or less. If the open cell ratio exceeds 10%, the mechanical strength such as bending strength, compressive strength, impact resistance and the like of the polystyrene-based resin foam molded product obtained by in-mold foam molding will decrease.

In the expandable polystyrene resin particles of the present invention, the polystyrene resin is not particularly limited. For example, styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, bromostyrene. Homopolymers of styrene monomers such as these, or copolymers thereof. A polystyrene resin containing 50% by mass or more of styrene is preferable, and polystyrene is more preferable.

Also, the polystyrene resin may be a copolymer of the styrene monomer and a vinyl monomer copolymerizable with the styrene monomer, the main component of which is the styrene monomer. Examples of such vinyl monomers include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, alkyl (meth) acrylates such as cetyl (meth) acrylate, (meth) acrylonitrile, dimethyl maleate, In addition to dimethyl fumarate, diethyl fumarate, and ethyl fumarate, bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate are exemplified.

If the polystyrene resin is the main component, other resins may be added. Examples of the resin to be added include diene rubbery heavy polymers such as polybutadiene, styrene-butadiene copolymer, and ethylene-propylene-nonconjugated diene three-dimensional copolymer in order to improve the impact resistance of the foamed molded product. Examples thereof include rubber-modified polystyrene resins to which coalescing has been added, so-called high impact polystyrene. Alternatively, a polyethylene resin, a polypropylene resin, an acrylic resin, an acrylonitrile-styrene copolymer, an acrylonitrile-butadiene-styrene copolymer, and the like can be given.

As a polystyrene resin used as a raw material, a polystyrene resin (virgin polystyrene) that is not a recycled material, such as a commercially available ordinary polystyrene resin, a polystyrene resin newly produced by a method such as suspension polymerization, can be used. In addition, a recycled raw material obtained by regenerating a used polystyrene resin foam molded article can also be used. As this recycled material, used polystyrene-based resin foam moldings such as fish boxes, household appliance cushioning materials, food packaging trays, etc. are collected and recycled from the recycled materials recovered by the limonene dissolution method or heating volume reduction method. A raw material having a mass average molecular weight Mw in the range of 120,000 to 400,000 can be appropriately selected, or a plurality of recycled raw materials having different mass average molecular weights Mw can be appropriately used in combination.

The foaming agent used for the expandable polystyrene resin particles of the present invention is not particularly limited. Examples include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, neopentane, and cyclopentane, ethers such as dimethyl ether and diethyl ether, various alcohols such as methanol and ethanol, carbon dioxide, nitrogen, water, etc. It can be used. Of these, aliphatic hydrocarbons are preferred, and normal butane, isobutane, normal pentane, isopentane alone or a mixture thereof is more preferred. Further, normal pentane, isopentane, neopentane, cyclopentane, cyclopentadiene alone or a mixture thereof, which is a hydrocarbon having 5 carbon atoms, is particularly suitable. Of these, a mixture of one or both of isopentane and normal pentane is preferable. Further, it mainly comprises the hydrocarbon having 5 carbon atoms and has a boiling point of 20 ° C. or higher, and may contain a blowing agent other than the hydrocarbon having 5 carbon atoms (for example, normal butane, isobutane, propane, carbon dioxide gas, etc.). .
The amount of the foaming agent added is preferably in the range of 2 to 15 parts by mass, more preferably in the range of 3 to 8 parts by mass, and particularly preferably in the range of 4 to 7 parts by mass with respect to 100 parts by mass of the polystyrene resin.

In the foamable polystyrene resin particles, an inorganic fine powder (inorganic bubble nucleating agent) such as talc, calcium silicate, synthetically produced or naturally produced silicon dioxide as a cell nucleating agent with respect to 100 parts by mass of polystyrene resin. It is preferable to add a chemical foaming agent. As the bubble nucleating agent, talc is particularly preferable. The amount of the cell nucleating agent added is preferably 5 parts by mass or less, more preferably 0.05 to 2.0 parts by mass with respect to 100 parts by mass of the thermoplastic resin. Examples of the chemical foaming agent include azodicarbonamide, N, N′-dinitrosopentamethylenetetramine, 4,4′-oxybis (benzenesulfonylhydrazide), sodium hydrogen carbonate, and the like.

Further, as the cell nucleating agent, it is preferable to use a master batch type cell nucleating agent in which an inorganic powder such as talc or a chemical foaming agent is uniformly dispersed in a base resin, preferably a polystyrene resin. By using this master batch type cell nucleating agent, when mixing polystyrene resin and cell nucleating agent in the resin feeder, inorganic powder or chemical foaming agent is dispersed in polystyrene resin in a very uniform state. Can be made.

In the expandable polystyrene resin particles of the present invention, in addition to the foaming agent and the cell nucleating agent, within the range that does not impair the physical properties of the resulting expandable polystyrene resin particles and the foamed molded product, a binding inhibitor and a cell adjustment You may add additives, such as an agent, a crosslinking agent, a filler, a flame retardant, a flame retardant adjuvant, a lubricant, and a coloring agent.

The expandable polystyrene resin particles of the present invention are in the form of expanded particles expanded to a bulk expansion ratio of 50 times, and the internal average cell diameter is in the range of 35 to 140 μm, and the surface layer part average cell diameter / internal average cell diameter In the range of 0.80 to 1.20 and the open cell ratio is 10% or less. Therefore, relatively small, uniform, and independent bubbles are formed throughout the foam particles, and the foam molded product obtained by in-mold foam molding of the foam particles has mechanical strength such as bending strength, compression strength, and impact resistance, and heat insulation. Excellent in buffering properties.

(Method for producing expandable polystyrene resin particles)
Next, a method for producing expandable polystyrene resin particles according to the present invention will be described with reference to the drawings.
In the method for producing expandable polystyrene resin particles according to the present invention, a foaming agent is added to and kneaded with a polystyrene resin in a resin supply device, and a foaming agent-containing molten resin is provided on the tip of the resin supply device. The foamed polystyrene resin particles are extruded from the pores into a cooling liquid having a temperature lower than the glass transition temperature Tg. At the same time, the extrudate is cut, and the extrudate is cooled and solidified by contact with the cooling liquid. A granulating step for obtaining resin-based resin particles, and the obtained expandable polystyrene-based resin particles are heated at a temperature equal to or higher than (glass transition temperature Tg-5 of expandable polystyrene-based resin particles) ° C. And a reheating step for obtaining expandable polystyrene resin particles.

(Granulation process)
FIG. 1 is a configuration diagram showing an example of a production apparatus used for producing expandable polystyrene resin particles in the granulation step.
The manufacturing apparatus of this example includes an extruder 1 as a resin supply apparatus, a die 2 having a large number of small holes attached to the tip of the extruder 1, and a raw material supply hopper that inputs resin raw materials into the extruder 1. 3, a high-pressure pump 4 for press-fitting the foaming agent into the molten resin in the extruder 1 through the foaming agent supply port 5, and a resin discharge surface provided with a small hole in the die 2 so as to contact the cooling water. Cooling from the cutting chamber 7 into which the cooling water is circulated and supplied to the room, the cutter 6 rotatably provided in the cutting chamber 7 so as to cut the resin extruded from the small hole of the die 2, and the cutting chamber 7 A dehydrating dryer 10 with a solid-liquid separation function and a dehydrating dryer 10 with a solid-liquid separation function are obtained by separating foamable resin particles carried along with the flow of water from cooling water and dehydrating and drying to obtain expandable resin particles. The cooling water separated in A water tank 8, a high-pressure pump 9 for sending cooling water in the water tank 8 to the cutting chamber 7, and a storage container 11 for storing foamable resin particles dehydrated and dried by a dehydration dryer 10 with a solid-liquid separation function; , And is configured.

In addition, as the extruder 1, both an extruder using a screw or an extruder not using a screw can be used. Examples of the extruder using a screw include a single-screw extruder, a multi-screw extruder, a vent-type extruder, and a tandem extruder. Examples of the extruder that does not use a screw include a plunger type extruder and a gear pump type extruder. Moreover, any extruder can use a static mixer. Among these extruders, an extruder using a screw is preferable from the viewpoint of productivity. Moreover, the conventionally well-known thing used in the granulation method by melt extrusion of resin can also be used for the cutting chamber 7 which accommodated the cutter 6. FIG.

In order to produce expandable polystyrene resin particles using the production apparatus shown in FIG. 1, first, a desired additive such as a polystyrene resin as a raw material, a cell nucleating agent, or a flame retardant added as necessary is added. Weigh and put into the extruder 1 from the raw material supply hopper 3. The raw polystyrene resin may be pelletized or granulated and mixed well in advance and then fed from one raw material supply hopper. For example, when multiple lots are used, the supply amount is adjusted for each lot. The raw materials may be fed from a plurality of raw material supply hoppers and mixed in an extruder. Also, when using a combination of recycled materials from multiple lots, mix the raw materials from multiple lots in advance and remove foreign matter using appropriate sorting methods such as magnetic sorting, sieving, specific gravity sorting, and air blowing sorting. It is preferable to keep it.

After supplying polystyrene-based resin, bubble nucleating agent, and other optional additives into the extruder 1, the resin is heated and melted, and the molten resin is transferred to the die 2 side, and the high-pressure pump 4 is supplied from the blowing agent supply port 5. The foaming agent is pressed in to mix the foaming agent with the molten resin. A die provided at the front end of the extruder 1 by moving the melt to the front end side while further kneading through a foreign matter removing screen provided in the extruder 1 as necessary. Extrude through 2 small holes.

The resin discharge surface in which the small holes of the die 2 are drilled is disposed in the cutting chamber 7 into which cooling water is circulated and supplied. A cutter 6 is rotatably provided in the cutting chamber 7 so that the resin extruded from the small hole of the die 2 can be cut. When the melted product added with the foaming agent is extruded from the small hole of the die 2 provided at the tip of the extruder 1, the melted product is cut into granules by the cutter 6 and simultaneously cooled in contact with cooling water to expand the expanded polystyrene. System resin particles are obtained.

The obtained expandable polystyrene resin particles are transferred from the cutting chamber 7 to the flow of cooling water and carried to the dehydrating dryer 10 with a solid-liquid separation function. The expandable polystyrene resin particles are separated from the cooling water by the dehydration dryer 10 with a solid-liquid separation function and dehydrated and dried. The dried expandable polystyrene resin particles are stored in the storage container 11.

In the method for producing expandable polystyrene resin particles of the present invention, the temperature of the cooling water is lower than the glass transition temperature Tg of the expandable polystyrene resin particles, and is preferably in the range of 20 to 60 ° C. . When the temperature of the cooling water exceeds the glass transition temperature Tg of the expandable polystyrene resin particles, the expandable polystyrene resin particles are easily fused together, and a defective product in which a large number of particles are bonded to form a lump. Incidence increases.
If the temperature of the cooling water is less than 20 ° C., the resulting expandable polystyrene resin particles may not be spheroidized and cracks may occur.

The cooling water is preferably pressurized to 0.5 MPa or more. In order to pressurize the cooling water, a portion of the circulation path of the cooling water passing through the cutting chamber 7 from the discharge side of the high-pressure pump 9 to the inlet side of the dehydrating dryer 10 with a solid-liquid separation function is added. It can be executed by increasing the discharge pressure of the high-pressure pump 9 in the pressure region. The cooling water pressure is preferably in the range of 0.6 to 2.0 MPa, and more preferably in the range of 0.8 to 1.5 MPa.

(Reheating process)
The expandable polystyrene resin particles obtained in the granulation step are then heated at a temperature equal to or higher than (glass transition temperature Tg-5 of expandable polystyrene resin particles) ° C., whereby the expanded foam according to the present invention. Polystyrene resin particles.
This reheating step may be carried out continuously immediately after producing the expandable polystyrene resin particles in the granulation step, or stored after producing the expandable polystyrene resin particles in the granulation step. In addition, it may be taken out after an arbitrary storage period and the reheating step may be performed.

In this reheating step, for example, a heat medium such as water is placed in a pressure-resistant container having a temperature control function, and heated and kept at a temperature within the temperature range. By introducing the obtained expandable polystyrene resin particles, it can be carried out efficiently.

The heating temperature in the reheating step may be a temperature of (glass transition temperature Tg-5 of expandable polystyrene resin particles) ° C. or higher. Specifically, in the case of expandable polystyrene resin particles having a Tg of 61 ° C. used in Examples described later, the heating temperature is 56 ° C. or higher. Although heating temperature is good also as 150 degreeC or more, it is preferable to make about 150 degreeC into an upper limit from a viewpoint of reducing fusion | melting of resin particles. In this case, the heating temperature is more preferably in the range of 60 to 90 ° C. When this heating temperature is less than (glass transition temperature Tg-5 of expandable polystyrene resin particles) ° C., the bubbles in the expanded particles obtained by heating and foaming the obtained expandable polystyrene resin particles do not become fine. There is a possibility that the mechanical strength of the foamed molded product obtained by foam-molding the foamed particles in the mold is lowered.

The pressure in the reheating step is 1.5 MPa or less, preferably 0.1 to 1.0 MPa, more preferably 0.1 to 0.5 MPa. When this pressure exceeds 1.5 MPa, the mechanical strength of the obtained foamed molded article may be lowered. Furthermore, it is necessary to make the container thicker in order to increase the pressure resistance of the pressure vessel used in the reheating process, which is not preferable because the mass of the pressure vessel becomes heavy.

The heat treatment time in the reheating step is not particularly limited, but is preferably about 1 to 10 minutes, more preferably about 1 to 5 minutes. If this heat treatment time is short, the effect of improving the cellular structure of the expandable polystyrene resin particles obtained in the granulation step and improving the mechanical strength of the foamed molded article cannot be sufficiently obtained. On the other hand, if the heat treatment time is lengthened, the production efficiency of expandable polystyrene resin particles is lowered, leading to an increase in cost, which is not preferable.

The expandable polystyrene resin particles that have undergone this reheating step are used for the production of pre-expanded polystyrene resin particles after necessary post-treatments such as addition of additives such as surface modifiers and drying treatments.
In the method for producing expandable polystyrene resin particles of the present invention, expandable polystyrene resin particles obtained by melt extrusion are heated at a temperature of (glass transition temperature Tg-5 of expandable polystyrene resin particles) ° C. or higher. Thus, it is a method of obtaining expandable polystyrene resin particles. Therefore, when the obtained expandable polystyrene resin particles are heated and foamed, relatively small, uniform and independent bubbles are formed over the entire expanded particles. Efficient foamable polystyrene resin particles to produce foamed products with excellent mechanical strength such as bending strength, compressive strength, impact resistance, heat insulation, and buffering by foaming these foamed particles in-mold Can be manufactured well.

(Polystyrene resin pre-expanded particles and polystyrene resin foam molding)
The expandable polystyrene resin particles of the present invention are pre-foamed by heating with steam or the like using a well-known apparatus and technique in the field of producing foamed resin moldings, and the polystyrene-based resin pre-expanded particles of the present invention (hereinafter, (Referred to as pre-expanded particles). The pre-expanded particles are pre-expanded so as to have a bulk density equivalent to the density of a polystyrene-based resin foam-molded product to be manufactured (hereinafter referred to as a foam-molded product). In the present invention, the bulk density and the bulk foaming factor are not limited, but are usually in the range of 0.010 to 0.100 g / cm ³ (in the range of 10 to 100 times as the bulk foaming factor), and 0.015 to It is preferable to be in the range of 0.050 g / cm ³ .

In the present invention, the bulk density and the bulk expansion ratio of the pre-expanded particles refer to those measured in accordance with JIS K6911: 1995 “General Test Method for Thermosetting Plastics”.
<Bulk density of pre-expanded particles>
Fill the graduated cylinder with pre-expanded particles to a scale of 500 cm ³ . However, the graduated cylinder is visually observed from the horizontal direction, and if at least one pre-expanded particle reaches the scale of 500 cm ³ , the filling is finished. Next, the mass of the pre-expanded particles filled in the graduated cylinder is weighed with two significant figures after the decimal point, and the mass is defined as W (g). The bulk density of the pre-expanded particles is calculated by the following formula.
Bulk density (g / cm ³ ) = W / 500

<Bulk expansion ratio of pre-expanded particles>
Moreover, the bulk expansion ratio of the pre-expanded particles is a numerical value calculated by the following equation.
Bulk foaming factor = 1 / bulk density (g / cm ³ )

The pre-expanded particles are filled in a cavity of a molding die by using a well-known apparatus and method in the field of manufacturing a foamed resin molded body, heated by steam heating or the like, and subjected to in-mold foam molding, foaming A molded body is manufactured.

The polystyrene-based resin foam molded article of the present invention is in the state when foam-molded at a foam multiple X times, and the internal average cell diameter D ₃ ′ of the foam particles fused together in this foam molded article is expressed by the above formula. (3) is used to convert the expansion ratio to 50 times, and the internal average cell diameter D ₃ of the expanded particles in the expanded molded product satisfies the relationship of 35 μm ≦ D ₃ ≦ 140 μm. It has a cell structure in which the value of the diameter / internal average cell size is in the range of 0.80 to 1.20, and the open cell ratio of the foamed molded product is 10% or less.

The polystyrene-based resin foam molded article of the present invention is in the state when foam-molded at a foam multiple X times, and the internal average cell diameter D ₃ ′ of the foam particles fused together in this foam molded article is expressed by the above formula. Using (3), the expansion ratio is converted to 50 times, and the internal average cell diameter D ₃ of the expanded particles in the expanded molded product satisfies the relationship of 35 μm ≦ D ₃ ≦ 140 μm. When the internal average cell diameter D ₃ is less than 35 [mu] m, a polystyrene type resin foamed molded product obtained by mold foaming closed cell decreases with increasing open cell ratio, bending strength, compression strength, impact The mechanical strength such as property will decrease. When the internal average cell diameter D ₃ greater than 140 .mu.m, flexural strength, compressive strength, mechanical strength such as impact resistance is lowered. A preferable range of D ₃ is 40 μm ≦ D ₃ ≦ 120 μm, and a more preferable range is 45 μm ≦ D ₃ ≦ 115 μm.

In the styrenic resin foam molded article of the present invention, the value of the surface layer part average cell diameter / internal average cell diameter of the expanded particles is in the range of 0.80 to 1.20. When the value of the surface layer part average cell diameter / internal average cell diameter is out of the above range, the mechanical strength such as bending strength, compressive strength, impact resistance, etc. of the polystyrene-based resin foam molded product obtained by in-mold foam molding decreases. Resulting in. A preferred range is 0.90 to 1.10, and a more preferred range is 0.93 to 1.06.

In the styrene resin foam molded article of the present invention, the open cell ratio of the foam molded article is 10% or less, preferably 8% or less. If the open cell ratio exceeds 10%, the mechanical strength such as bending strength, compressive strength, impact resistance and the like of the polystyrene-based resin foam molded product obtained by in-mold foam molding will decrease.

The density of the foamed molded product of the present invention is not particularly limited, but is usually in the range of 0.010 to 0.100 g / cm ³ (10 to 100 times as the bulk foaming factor), and 0.015 to 0.050 g / cm 3. ^It is preferable to be within the range of ³ .

In the present invention, the density of the foamed molded article refers to the density of the foamed molded article measured by the method described in JIS K7122: 1999 “Foamed Plastics and Rubber—Measurement of Apparent Density”.
<Density of foam molding>
A specimen of 50 cm ³ or more (100 cm ³ or more in the case of semi-rigid and soft materials) was cut so as not to change the original cell structure of the material, its mass was measured, and the density was calculated by the following formula.
Density (g / cm ³ ) = Test piece mass (g) / Test piece volume (cm ³ )
Test specimens are cut from a sample that has passed 72 hours or more after molding, and atmospheric conditions (temperature and humidity conditions) of 23 ° C. ± 2 ° C. × 50% ± 5% or 27 ° C. ± 2 ° C. × 65% ± 5% The test piece was allowed to stand for 16 hours or longer.

<Folding multiple of foamed molded product>
Further, the expansion factor of the foamed molded product is a numerical value calculated by the following equation.
Foaming factor = 1 / density (g / cm ³ )

Since the foamed molded article of the present invention is manufactured using the expandable polystyrene resin particles, compared to the conventional product not subjected to the reheating step, mechanical strength such as bending strength, compressive strength, impact resistance, Excellent heat insulation and buffering properties.
In addition, you may manufacture a heat insulating material or a buffering material using the foaming molding of this invention. By using the foamed molded article of the present invention, a heat insulating material having excellent heat insulating properties or a buffer material having excellent buffer properties can be produced.

(Polystyrene resin foam molding, heat insulating material, and cushioning material)
The polystyrene resin foam molded article of the present invention is obtained by filling polystyrene resin pre-expanded particles obtained by heating expandable polystyrene resin particles containing a foaming agent in polystyrene resin particles into the mold cavity. It is obtained by heating and in-mold foam molding. The polystyrene-based resin foam molded article of the present invention is a pre-expanded particle state in which the expandable polystyrene-based resin particles are heated and expanded to a bulk expansion ratio of 50 times, and the internal average cell diameter is in the range of 35 to 140 μm. And the surface layer part average bubble diameter / internal average bubble diameter is in the range of 0.80 to 1.20, and the open cell ratio is 10% or less. The bulk expansion ratio of the pre-expanded particles refers to a bulk expansion ratio measured by a method for measuring the bulk expansion ratio of polystyrene resin pre-expanded particles described later.

In the expandable polystyrene resin particles, when the bulk expansion ratio of the pre-expanded particles heated and expanded is other than 50 times, the internal average cell diameter D ₂ ′ of the pre-expanded particles is expressed by the above formula (2). It is preferably converted to a bulk foaming ratio of 50 times, and the internal average bubble diameter D ₂ preferably satisfies the relationship of 35 μm ≦ D ₂ ≦ 140 μm. The same applies to the cell structure of a heat insulating material or a buffer material made of a polystyrene resin foam molded product obtained by in-mold foam molding of the pre-expanded particles.

The expandable polystyrene resin particles are in the form of expanded particles that are heated and expanded to a bulk expansion ratio of 50 times, and the internal average cell diameter is in the range of 35 to 140 μm, and further in the range of 40 to 120 μm. It is preferable. When the internal average cell diameter is less than 35 μm, the polystyrene-based resin foam molded article obtained by in-mold foam molding increases the open cell ratio and decreases closed cells, so that bending strength, compressive strength, impact resistance are increased. Such as mechanical strength will be reduced. When the internal average bubble diameter exceeds 140 μm, mechanical strength such as bending strength, compressive strength, and impact resistance is lowered.

The expandable polystyrene resin particles are in the form of expanded particles that are heated and expanded to a bulk expansion ratio of 50 times, and the surface layer part average cell diameter / internal average cell diameter value is within the range of 0.80 to 1.20. In addition, it is preferably in the range of 0.90 to 1.10. When the value of the surface layer part average cell diameter / internal average cell diameter is out of the above range, the mechanical strength such as bending strength, compressive strength, impact resistance, etc. of the polystyrene-based resin foam molded product obtained by in-mold foam molding decreases. Resulting in. In the present invention, the “surface layer average cell diameter” means a state of pre-expanded particles obtained by expanding expandable polystyrene resin particles to a bulk expansion ratio of 50 times, and cutting the pre-expanded particles so as to pass through the center thereof. In the cross section, the region where the depth from the surface of the pre-expanded particles is up to 1/4 of the diameter of the expanded particles is defined as “surface layer portion”, which means the average cell diameter of the bubbles in the surface layer portion. . In addition, the “inner average bubble diameter” is defined as “inner” as a region deeper than the surface layer portion of the same pre-expanded particle (region on the center side), and refers to the average bubble diameter of the bubbles inside. Yes.

The expandable polystyrene resin particles are in the form of expanded particles heated to be expanded to a bulk expansion ratio of 50 times, and the open cell ratio is preferably 10% or less, and more preferably 8% or less.
If the open cell ratio exceeds 10%, the mechanical strength such as bending strength, compressive strength, impact resistance and the like of the polystyrene-based resin foam molded product obtained by in-mold foam molding will decrease.

In the expandable polystyrene resin particles, the polystyrene resin is not particularly limited, and examples thereof include styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, bromostyrene, and the like. Examples include homopolymers of styrene monomers or copolymers thereof. A polystyrene resin containing 50% by mass or more of styrene is preferable, and polystyrene is more preferable.

As a polystyrene resin used as a raw material, a polystyrene resin (virgin polystyrene) that is not a recycled material, such as a commercially available ordinary polystyrene resin, a polystyrene resin newly produced by a method such as suspension polymerization, can be used. In addition, a recycled raw material obtained by regenerating a used polystyrene resin foam molded article can also be used. As this recycled material, used polystyrene-based resin foam moldings such as fish boxes, heat insulating materials for household appliances, trays for food packaging, etc. are collected and recycled from the recycled materials recovered by the limonene dissolution method or heating volume reduction method. A raw material having a mass average molecular weight Mw in the range of 120,000 to 400,000 can be appropriately selected, or a plurality of recycled raw materials having different mass average molecular weights Mw can be appropriately used in combination.

The foaming agent used for the expandable polystyrene resin particles is not particularly limited. Examples include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, neopentane, and cyclopentane, ethers such as dimethyl ether and diethyl ether, various alcohols such as methanol and ethanol, carbon dioxide, nitrogen, water, etc. It can be used. Of these, aliphatic hydrocarbons are preferred, and normal butane, isobutane, normal pentane, isopentane alone or a mixture thereof is more preferred. Further, normal pentane, isopentane, neopentane, cyclopentane, cyclopentadiene alone or a mixture thereof, which is a hydrocarbon having 5 carbon atoms, is particularly suitable. Of these, a mixture of one or both of isopentane and normal pentane is preferable. Further, it mainly comprises the hydrocarbon having 5 carbon atoms and has a boiling point of 20 ° C. or higher, and may contain a blowing agent other than the hydrocarbon having 5 carbon atoms (for example, normal butane, isobutane, propane, carbon dioxide gas, etc.). .
The amount of the foaming agent added is preferably in the range of 2 to 15 parts by mass, more preferably in the range of 3 to 8 parts by mass, and particularly preferably in the range of 4 to 7 parts by mass with respect to 100 parts by mass of the polystyrene resin.

In the foamable polystyrene resin particles, an inorganic fine powder (inorganic bubble nucleating agent) such as talc, calcium silicate, synthetically or naturally produced silicon dioxide as a cell nucleating agent with respect to 100 parts by mass of polystyrene resin. It is preferable to add a chemical foaming agent. As the bubble nucleating agent, talc is particularly preferable. The amount of the cell nucleating agent added is preferably 5 parts by mass or less, more preferably 0.05 to 2.0 parts by mass with respect to 100 parts by mass of the thermoplastic resin. Examples of the chemical foaming agent include azodicarbonamide, N, N′-dinitrosopentamethylenetetramine, 4,4′-oxybis (benzenesulfonylhydrazide), sodium hydrogen carbonate, and the like.

In the expandable polystyrene resin particles, in addition to the foaming agent and the cell nucleating agent, in the range that does not impair the properties of the resulting expandable polystyrene resin particles and the foamed molded article, a binding inhibitor, a cell regulator, You may add additives, such as a crosslinking agent, a filler, a flame retardant, a flame retardant adjuvant, a lubricant, and a coloring agent.

The polystyrene-based resin foam molded article of the present invention is a state of pre-expanded particles in which expandable polystyrene-based resin particles are heated and expanded to a bulk expansion ratio of 50 times, and the internal average cell diameter is in the range of 35 to 140 μm. In-mold foam molding of pre-expanded particles having a cell structure in which the surface layer average cell diameter / internal average cell diameter is in the range of 0.80 to 1.20 and the open cell ratio is 10% or less. Is obtained. Therefore, relatively small, uniform, and independent bubbles are formed throughout the pre-expanded particles, and the foam-molded product obtained by in-mold foam molding of the pre-expanded particles has mechanical strength such as bending strength, compressive strength, and impact resistance. , Excellent heat insulating properties and buffer properties.
In addition, you may manufacture a heat insulating material or a buffering material using the polystyrene-type resin foaming molding of this invention. By using the polystyrene resin foam molded article of the present invention, a heat insulating material having excellent heat insulating properties or a buffer material having excellent buffering properties can be produced.

(Production method of polystyrene resin foam molding)
Next, a method for producing a polystyrene resin foam molded article according to the present invention will be described with reference to the drawings.
The method for producing a polystyrene-based resin foam molded article according to the present invention includes adding a foaming agent to a polystyrene-based resin in a resin supply apparatus and kneading, and a foam-containing molten resin at the tip of the resin supply apparatus. The foamed polystyrene resin particles are extruded from the pores into a cooling liquid having a temperature lower than the glass transition temperature Tg. At the same time, the extrudate is cut, and the extrudate is cooled and solidified by contact with the cooling liquid. A granulation step (first step) for obtaining resin-based resin particles, and the obtained expandable polystyrene-based resin particles are heated at a temperature of (glass transition temperature Tg-5 of expandable polystyrene-based resin particles) ° C. or higher. Reheating step (second step) for obtaining expandable polystyrene resin particles, and then heating the obtained expandable polystyrene resin particles, and using the above formula (2), the bulk expansion ratio is 50 times Convert to average internal cell diameter _{D 2} of the pre-expanded particles, in the range of 35 ~ 140 .mu.m, values of the surface layer portion average cell diameter / average internal cell diameter is in the range of 0.80 to 1.20, and A pre-foaming step (third step) for producing polystyrene-based resin pre-foamed particles having a cell structure with an open cell ratio of 10% or less, and then filling the polystyrene-based pre-foamed particles in the mold cavity And a molding process (fourth process) for heating and in-mold foam molding.

(Granulation process)
FIG. 1 is a configuration diagram showing an example of a production apparatus used for producing expandable polystyrene resin particles in the granulation step.
The manufacturing apparatus in this embodiment includes an extruder 1 as a resin supply device, a die 2 having a large number of small holes attached to the tip of the extruder 1, and a raw material supply for charging a resin raw material or the like into the extruder 1. A hopper 3, a high-pressure pump 4 for press-fitting the foaming agent into the molten resin in the extruder 1 through the foaming agent supply port 5, and a resin discharge surface in which a small hole of the die 2 is drilled are provided in contact with the cooling water. From the cutting chamber 7 into which the cooling water is circulated and supplied to the room, the cutter 6 rotatably provided in the cutting chamber 7 so as to cut the resin extruded from the small hole of the die 2, and the cutting chamber 7 A dehydrating dryer 10 with a solid-liquid separation function that separates foamable resin particles carried along with the flow of cooling water from cooling water and dehydrating and drying to obtain expandable resin particles, and a dehydrating dryer with a solid-liquid separation function 10 separated A water tank 8 for storing the cooling water, a high-pressure pump 9 for sending the cooling water in the water tank 8 to the cutting chamber 7, and a storage for storing the expandable resin particles dehydrated and dried by the dehydrating dryer 10 with a solid-liquid separation function. And a container 11.

The resin discharge surface in which the small holes of the die 2 are drilled is disposed in the cutting chamber 7 into which cooling water is circulated and supplied. A cutter 6 is rotatably provided in the cutting chamber 7 so that the resin extruded from the small hole of the die 2 can be cut. When the melt added with the foaming agent is extruded from the small hole of the die 2 provided at the tip of the extruder 1, the melt is cut into particles by the carter 6, and at the same time, brought into contact with cooling water and rapidly cooled, and expandable polystyrene. System resin particles are obtained.

In the granulation step, the temperature of the cooling water is lower than the glass transition temperature Tg of the expandable polystyrene resin particles, and is preferably in the range of 20 to 60 ° C. When the temperature of the cooling water exceeds the glass transition temperature Tg of the expandable polystyrene resin particles, the expandable polystyrene resin particles are easily fused together, and a defective product in which a large number of particles are bonded to form a lump. Incidence increases. If the temperature of the cooling water is less than 20 ° C., the resulting expandable polystyrene resin particles may not be spheroidized and cracks may occur.

Expandable polystyrene resin particles that have undergone this reheating step are subjected to the necessary post-treatments such as addition of additives such as surface modifiers and drying treatment, and then through polystyrene resin pre-expanded particles, polystyrene resin foam molding Used for the production of the body.

(Pre-foaming process)
The expandable polystyrene resin particles obtained by the reheating treatment are pre-expanded by heating with water vapor heating or the like using a well-known apparatus and method in the field of manufacturing a foamed resin molded article. Hereinafter referred to as pre-expanded particles). The pre-expanded particles are pre-expanded so as to have a bulk density equivalent to the density of the polystyrene-based resin foam molding to be manufactured. In the present invention, the bulk density and the bulk foaming factor are not limited, but are usually in the range of 0.010 to 0.100 g / cm ³ (in the range of 10 to 100 times as the bulk foaming factor), and 0.015 to It is preferable to be in the range of 0.050 g / cm ³ .

Using a well-known apparatus and method in the field of manufacturing a foamed resin molded body, the pre-expanded particles are filled into a cavity of a molding die, heated by steam heating or the like, and subjected to in-mold foam molding, and a polystyrene-based resin foam molded body is obtained. To manufacture. For example, the pre-expanded particles are filled in a cavity of a molding die, heated, and subjected to in-mold foam molding to obtain a heat insulating material or a buffer material as a polystyrene-based resin foam molding.

The polystyrene-based resin foam molded article of the present invention is in a state where it is foam-molded to a multiple of X times, and the internal average cell diameter D ₃ ′ of the fused particles in the foam molded article is expressed by the above formula ( 3), the internal average cell diameter D ₃ of the expanded particles in the expanded molded product satisfies the relationship of 35 μm ≦ D ₃ ≦ 140 μm, and the surface layer portion average cell diameter of the expanded particles / The cell has a cell structure in which the value of the internal average cell diameter is in the range of 0.80 to 1.20, and the open cell ratio of the foamed molded product is 10% or less.

The polystyrene-based resin foam molded article of the present invention is in a state where it is foam-molded to a multiple of X times, and the internal average cell diameter D ₃ ′ of the fused particles in the foam molded article is expressed by the above formula ( 3) is used to convert the expansion ratio to 50 times, and the internal average cell diameter D ₃ of the expanded particles in the expanded molded product satisfies the relationship of 35 μm ≦ D ₃ ≦ 140 μm. When the internal average cell diameter D ₃ is less than 35 [mu] m, a polystyrene type resin foamed molded product obtained by mold foaming closed cell decreases with increasing open cell ratio, bending strength, compression strength, impact The mechanical strength such as property will decrease. When the internal average cell diameter D ₃ greater than 140 .mu.m, flexural strength, compressive strength, mechanical strength such as impact resistance is lowered. A preferable range of D ₃ is 40 μm ≦ D ₃ ≦ 120 μm, and a more preferable range is 45 μm ≦ D ₃ ≦ 115 μm.

In the polystyrene resin foam molded article of the present invention, the value of the surface layer part average cell diameter / internal average cell diameter of the expanded particles is in the range of 0.80 to 1.20. When the value of the surface layer part average cell diameter / internal average cell diameter is out of the above range, the mechanical strength such as bending strength, compressive strength, impact resistance, etc. of the polystyrene-based resin foam molded product obtained by in-mold foam molding decreases. Resulting in.
A preferred range is 0.90 to 1.10, and a more preferred range is 0.93 to 1.06.

In the polystyrene resin foam molded article of the present invention, the open cell ratio of the foam molded article is 10% or less, and preferably 8% or less. If the open cell ratio exceeds 10%, the mechanical strength such as bending strength, compressive strength, impact resistance and the like of the polystyrene-based resin foam molded product obtained by in-mold foam molding will decrease.

The density of the polystyrene resin foam molded article of the present invention is not particularly limited, but is usually within the range of 0.010 to 0.100 g / cm ³ (10 to 100 times as the bulk foaming factor), and 0.015 to 0.00. It is preferable to be within the range of 050 g / cm ³ .

In the present invention, the density of the polystyrene resin foam molded article refers to the density of the foam molded article measured by the method described in JIS K7122: 1999 “Measurement of Foamed Plastics and Rubber—Apparent Density”.
<Density of foam molding>
A specimen of 50 cm ³ or more (100 cm ³ or more in the case of semi-rigid and soft materials) was cut so as not to change the original cell structure of the material, its mass was measured, and the density was calculated by the following formula.
Density (g / cm ³ ) = Test piece mass (g) / Test piece volume (cm ³ )
Test specimens are cut from a sample that has passed 72 hours or more after molding, and atmospheric conditions (temperature and humidity conditions) of 23 ° C. ± 2 ° C. × 50% ± 5% or 27 ° C. ± 2 ° C. × 65% ± 5% The test piece was allowed to stand for 16 hours or longer.

In the method for producing a polystyrene resin foam molded article of the present invention, expandable polystyrene resin particles obtained by melt extrusion are used at a temperature of (glass transition temperature Tg-5 of expandable polystyrene resin particles) ° C. or higher. This is a method of obtaining expandable polystyrene resin particles by performing heat treatment at a pressure of 0.5 MPa or less. Therefore, when heated and foamed, relatively small, uniform, and independent bubbles are formed throughout the foamed particles, and the foamed particles are subjected to in-mold foam molding to provide mechanical strength such as bending strength, compressive strength, impact resistance, and heat insulation. A polystyrene-based resin foam molded article, a heat insulating material, or a buffer material excellent in properties and buffering properties can be obtained.

[Example 1]
(Manufacture of expandable polystyrene resin particles)
As a base resin, 0.5 part by mass of talc master batch (polystyrene resin 40% by mass, talc 60% by mass) is premixed with 100 parts by mass of polystyrene resin (trade name “HRM-10N” manufactured by Toyo Styrene Co., Ltd.). Was supplied into a single-screw extruder with a diameter of 90 mm at a rate of 160 kg / hr per hour, and the resin was heated and melted. Then, 6 parts by mass of isopentane as a foaming agent was added to 100 parts by mass of the resin from the middle of the extruder. Press-fitted. While kneading the resin and the foaming agent in the extruder and cooling so that the resin temperature at the front end of the extruder is 170 ° C., the diameter of 0.6 mm is maintained at 290 ° C. by a heater installed in the extruder. Then, through a granulation die having 200 nozzles with a land length of 3.0 mm, it was extruded into an underwater cutting chamber in which cooling water with a temperature of 50 ° C. and a water pressure of 1.5 MPa circulated, and at the same time, 10 blades in the circumferential direction. The resin was cut by bringing a high-speed rotary cutter having close contact with the die and rotating at 3000 rpm, and dehydrated and dried to obtain spherical expandable polystyrene resin particles. The obtained expandable polystyrene resin particles had an average particle size of 1.1 mm without the occurrence of deformation or beard.
Next, in order to perform the reheating treatment, 2000 g of the above expandable polystyrene resin particles, 2500 g of distilled water, and 0.5 g of sodium dodecylbenzenesulfonate were placed in an autoclave with a stirrer having an internal volume of 5.7 liters, and stirred and dispersed. . This dispersion was pressurized to 0.2 MPa with nitrogen, heated to 80 ° C., held for 3 minutes, then cooled, taken out, washed, dehydrated, and dried.
Polyethylene glycol 0.03 parts by mass, zinc stearate 0.05 parts by mass, stearic acid monoglyceride 0.05 parts by mass, hydroxystearic acid triglyceride 0.05 parts by mass with respect to 100 parts by mass of the obtained expandable polystyrene resin particles. The entire surface of the expandable polystyrene resin particles was uniformly coated with the part.

(Manufacture of foam molded products)
The expandable polystyrene resin particles (hereinafter may be referred to as beads) obtained as described above are supplied to a cylindrical batch type pre-foaming machine, heated by steam with a blowing pressure of 0.05 MPa, and foamed. Expanded particles were obtained. The obtained pre-expanded particles had a bulk density of 0.020 g / cm ³ (bulk expansion ratio: 50 times).
Subsequently, the pre-expanded particles obtained were allowed to stand at room temperature for 24 hours, and then the pre-expanded particles were filled into a mold having a rectangular cavity of length 400 mm × width 300 mm × height 25 mm. , Molding steam pressure 0.08 MPa (gauge pressure), mold heating 3 seconds, one heating 10 seconds, reverse one heating 3 seconds, double side heating 10 seconds, water cooling 5 seconds, set extraction surface pressure 0.02 MPa went.

For the beads, pre-expanded particles, and foamed molded article, the gas content, Tg of expandable polystyrene resin particles, internal average cell diameter, surface layer average cell diameter, open cell ratio, flexural strength, compression according to the following measurement method It measured about each test item of an intensity | strength, heat insulation (thermal conductivity), and a drop test. The results are shown in Table 1.

<Contained gas amount>
With respect to the beads, the heating loss was measured at a heating temperature of 145 ° C. for 2 hours, and the amount of gas contained was calculated.

<Measurement of Tg of Expandable Polystyrene Resin Particle>
Tg was measured according to the test method of JIS K7121. Specifically, using a differential scanning calorimeter DSC6220 type (manufactured by SII NanoTechnology Co., Ltd.), 6.5 mg of a sample bead is filled in a measurement container, and a nitrogen gas flow rate of 25 ml / min is 20 ° C./min. The temperature was raised from 30 ° C. to 200 ° C. at a rate of temperature rise, and the midpoint glass transition temperature was taken as the glass transition temperature.

<Measurement of internal average cell diameter of pre-expanded particles>
The internal average cell diameter of the pre-expanded particles is measured in accordance with the test method of ASTM D2842-69. Specifically, first, a razor tooth is used to cut a plane passing through the vicinity of the center of the pre-foamed particles, and the cut surface is enlarged 15 times using a scanning electron microscope (JOEL product name “JSM-6360LV”). To shoot.
Next, the photographed image is printed on A4 paper, and a first circle (inscribed circle) inscribed in the surface layer of the pre-expanded particles is drawn. A second concentric circle having a diameter of ½ (a radius of ¼) is drawn with respect to the diameter of the first circle, and a straight line having a length of 60 mm is placed at an arbitrary position inside the second circle. This drawing is performed, and the average chord length (t) of the bubbles is calculated from the number of bubbles existing on this straight line by the following formula.
Average string length t = 60 / (number of bubbles × photo magnification)
When drawing a straight line, the straight line should be penetrated as much as possible without making point contact with the bubbles. Also, if some of the bubbles come into point contact with a straight line, this bubble is included in the number of bubbles, and if both ends of the straight line are located in the bubble without penetrating the bubbles Includes the bubbles in which both ends of the straight line are located in the number of bubbles.
Based on the calculated average chord length t, the average bubble diameter can be calculated by the following equation.
Average bubble diameter (mm) D = t / 0.616
Furthermore, the average bubble diameter is calculated in the same manner as described above at any five locations in the photographed image, and the arithmetic average value of these average bubble diameters is used as the internal average bubble diameter of the pre-expanded particles.

<Surface layer average cell diameter of pre-expanded particles>
A razor tooth is used to cut a plane passing through the vicinity of the center of the pre-foamed particles, and the cut surface is photographed at a magnification of 15 times using a scanning electron microscope (trade name “JSM-6360LV” manufactured by JOEL).
Next, the photographed image is printed on A4 paper, and a first circle (inscribed circle) inscribed in the surface layer of the pre-expanded particles is drawn. A second concentric circle having a diameter of ½ (a radius of ¼) is drawn with respect to the diameter of the first circle, and a length of 60 mm is provided at an arbitrary position between the second circle from the surface layer. A straight line is drawn, and the average chord length (t) of the bubbles is calculated in the same manner as the internal average bubble diameter from the number of bubbles existing on the straight line, and is used as the surface layer average bubble diameter.

<Measurement of internal average cell diameter of foam molded article>
The foamed molded product is cut with a razor tooth, and the cut surface is photographed with a scanning electron microscope (trade name “JSM-6360LV” manufactured by JOEL) at a magnification of 15 times.
Next, the photographed image is printed on A4 paper, and a first circle (inscribed circle) inscribed in the grain boundary portion of the fused foam particles existing on the cut surface is drawn. Draw a second concentric circle having a diameter of 1/2 (1/4 radius) with respect to the diameter of the first circle, and form a straight line with a length of 60 mm at any location inside the second circle. One bubble was drawn, and the average chord length (t) of the bubbles was calculated from the number of bubbles present on this straight line in the same manner as the internal average cell diameter of the pre-expanded particles, and the internal average cell size of the foam molded product was obtained.

<Measurement of average cell diameter of surface layer of foam molded article>
The foamed molded product is cut with a razor tooth, and the cut surface is photographed with a scanning electron microscope (trade name “JSM-6360LV” manufactured by JOEL) at a magnification of 15 times.
Next, the photographed image is printed on A4 paper, and a first circle (inscribed circle) inscribed in the grain boundary portion of the fused foam particles existing on the cut surface is drawn. A second concentric circle having a diameter of ½ (a radius of ¼) is drawn with respect to the diameter of the first circle, and the length is set at an arbitrary position between the second circle from the grain boundary portion. A straight line of 60 mm is drawn, and the average chord length (t) of the bubbles is calculated from the number of bubbles existing on the straight line in the same manner as the internal average bubble size of the pre-expanded particles. Asked.

<Measurement of open cell ratio of pre-expanded particles>
The following tests (1) to (3) were performed to determine the open cell ratio (%) of the pre-expanded particles.
(1) Mass and volume measurement of pre-expanded particles The mass of the pre-expanded particles that are about 80% into the sample cup of an air-comparing hydrometer (1000 type, manufactured by Tokyo Science) was measured in advance [pre-expanded particle mass A (g )]].
Next, the pre-expanded particles were put in a cup, and the cup was set in the above-described specific gravity meter, and the volume was measured by the 1-1 / 2-1 atmospheric pressure method [volume B (cm ³ ) of the pre-expanded particles].
(2) Apparent volume measurement of pre-expanded particles Remove the weighing pan from the electronic balance (HB3000, manufactured by Daiwa Seikan Co., Ltd.) and immerse the container in water with the wire mesh container suspended from the mounting bracket. The mass of the container in water was measured [the container mass C (g) in water].
Next, the total amount of the pre-expanded particles measured in the above (1) was put in the same container, and the total mass of the container and the pre-expanded particles was measured in the same manner as described above [total mass D in water D ( g)].
The apparent volume E (cm ³ ) of the pre-expanded particles was determined by the following formula. In addition, 1 g of water was converted as a volume of 1 cm ³ .
E = A + (CD)
(3) Open cell ratio From the results of (1) and (2) above, the open cell ratio [%] was determined by the following equation.
Open cell ratio (%) = (EB) / E × 100

<Measurement of open cell ratio of foam molded article>
For the foamed molded article, the open cell ratio was measured according to the measurement method described in ASTM D2856-87. That is, five specimens (25 mm cubes) composed of a cut surface having no skin such as a six-side co-molded surface were cut out, the apparent volume was measured using a caliper, and then the air comparison specific gravity system The volume was measured by the 1-1 / 2-1 atmospheric pressure method using (1000 type manufactured by Tokyo Science).
Open cell ratio (%) = (apparent volume−volume measured with a comparative hydrometer) / apparent volume × 100

<Bending strength>
A test piece having a length of 300 mm, a width of 75 mm, and a thickness of 25 mm was cut out from the foamed molded article, and a bending test was performed on the test piece in accordance with JIS-A9511 to calculate a bending strength.

<Compressive strength>
A test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm was cut out from the foamed molded product, and a bending test of the test piece was performed in accordance with JIS-A9511 to obtain a bending strength.

<Insulation (thermal conductivity)>
A rectangular parallelepiped test piece having a length of 200 mm, a width of 200 mm, and a thickness of 25 mm was cut out from the polystyrene-based resin foam molding. The thermal conductivity of the test piece was measured at a measurement temperature of 23 ° C. using a thermal conductivity meter (AUTO-Λ HC-072) manufactured by Eihiro Seiki Co., Ltd. according to JIS A1412.

<Drop test>
A plane rectangular test piece having a length of 215 mm, a width of 40 mm, and a thickness of 20 mm is cut out from the polystyrene-based resin foam molded body, and tested between a pair of fulcrums arranged at intervals of 150 mm in accordance with JIS K7211. The piece was installed and a 198 g steel ball was dropped, and the falling ball impact value, that is, the 50% breaking height was calculated based on the following formula.
Falling ball impact value = H50 = Hi−ΔH × (S / 100−1 / 2)
However,
H50: 50% fracture height (cm),
Hi: Minimum height (cm) at which 100% destruction occurs,
ΔH: Height interval (cm) when raising and lowering the height of the test piece,
S: Total of% destroyed at each height (%),
And

[Example 2]
A foamed molded article was produced in the same manner as in Example 1 except that the heating temperature during the reheating treatment was 150 ° C. and the pressure was 0.5 MPa, and the same measurement was performed. The results are shown in Table 1.

[Example 3]
A foamed molded article was produced in the same manner as in Example 1 except that the heating temperature during the reheating treatment was 60 ° C., and the same measurement was performed. The results are shown in Table 1.

[Example 4]
A foamed molded article was produced in the same manner as in Example 1 except that the heating temperature during the reheating treatment was 57 ° C., and the same measurement was performed. The results are shown in Table 1.

[Example 5]
A foamed molded article was produced in the same manner as in Example 1 except that the same amount of butane was used as the foaming agent and the pressure during the reheating treatment was 0.5 MPa, and the same measurement was performed. The results are shown in Table 1.

[Comparative Example 1]
A foamed molded article was produced in the same manner as in Example 1 except that the heating temperature during the reheating treatment was 100 ° C., and the same measurement was performed. The results are shown in Table 1.

[Comparative Example 2]
The foamed molded article was produced in the same manner as in Example 1 except that the cooling water temperature in the underwater cut chamber was 70 ° C., the pressure during the reheating treatment was 1.5 MPa, and the reheating treatment time was 5 minutes after heating. The same measurement was performed. The results are shown in Table 1.

[Comparative Example 3]
A foamed molded article was produced in the same manner as in Example 1 except that the reheating treatment was not performed, and the same measurement was performed. The results are shown in Table 1.

[Comparative Example 4]
A foamed molded article was produced in the same manner as in Example 1 except that the heating temperature during the reheating treatment was 40 ° C., and the same measurement was performed. The results are shown in Table 1.

[Comparative Example 5]
A foamed molded article was produced in the same manner as in Example 1 except that the heating time after the temperature increase during the reheating treatment was 1 minute, and the same measurement was performed. The results are shown in Table 1.

From the results shown in Table 1, the foamed molded products obtained in Examples 1 to 5 according to the present invention are in the form of expanded particles expanded to a bulk expansion ratio of 50 times and have an internal average cell diameter of 35 to 140 μm. Within the range, the surface layer portion average bubble diameter / internal average bubble diameter is in the range of 0.80 to 1.20, and the cell has a bubble structure in which the open cell ratio is 10% or less. Further, a foamed molded product obtained by in-mold foam molding of pre-foamed particles foamed to a bulk foaming factor of 50 times has a low open cell ratio, a large number of closed cells, and is not subjected to reheating treatment. The bending strength and compressive strength of the foamed molded product were higher than those of the foamed molded product.

On the other hand, the foamed molded product of Comparative Example 1 had a high open cell ratio and a small number of closed cells, and therefore the bending strength and compressive strength of the foamed molded product were low.
Moreover, since the internal average bubble diameter of the foaming molding of the comparative example 2 exceeded the range of this invention, the bending strength and compressive strength of the foaming molding were low.
Moreover, since the internal average bubble diameter exceeded the range of this invention as a result of the foaming molding of the comparative example 3 not performing a reheating process, the bending strength and compressive strength of the foaming molding were low.
Moreover, since the internal average bubble diameter exceeded the range of this invention as a result of performing the reheating process at low temperature, the foaming molding of the comparative example 4 had low bending strength and compressive strength.
Moreover, since the value of surface layer part average cell diameter / internal average cell diameter was outside the scope of the present invention, the foamed molded product of Comparative Example 5 had low bending strength and compressive strength.

The expandable polystyrene resin particles of the present invention can be widely applied to the production of polystyrene resin foam molded articles having excellent mechanical strength such as bending strength, compressive strength, impact resistance, heat insulation, and buffering properties.
Moreover, the polystyrene resin foam molded article of the present invention can be widely applied to various uses such as a heat insulating material and a buffer material.

1 ... Extruder (resin feeder)
2 ... Die 3 ... Raw material supply hopper 4 ... High pressure pump 5 ... Foaming agent supply port 6 ... Cutter 7 ... Cutting chamber 8 ... Water tank 9 ... High pressure pump 10 ... Dehydration dryer 11 with solid-liquid separation function ... Storage container

Claims

Expandable polystyrene resin particles containing a foaming agent in polystyrene resin particles,
In the state of expanded particles obtained by heating the expandable polystyrene resin particles to expand to a bulk expansion ratio of 50 times, the internal average cell diameter is in the range of 35 to 140 μm, and the surface layer part average cell diameter / internal average cell diameter Expandable polystyrene resin particles having a cell structure in which the value of is in the range of 0.80 to 1.20 and the open cell rate is 10% or less.
The internal average cell diameter D 1 ′ of the expanded particles when expanded to a bulk expansion ratio X times is expressed by the following formula (1)

2. The expandable polystyrene resin particles according to claim 1, wherein an internal average cell diameter D 1 of the expanded particles converted to a bulk expansion ratio of 50 times using the above satisfies a relationship of 35 μm ≦ D 1 ≦ 140 μm.
The expandable polystyrene resin particles according to claim 1, wherein the internal average cell diameter is in the range of 40 to 120 µm.
The expandable polystyrene resin particles according to claim 1, wherein the open cell ratio is 8% or less.
2. The expandable polystyrene resin particles according to claim 1, wherein the value of the surface layer average cell diameter / internal average cell diameter is in the range of 0.90 to 1.10.
The expandable polystyrene resin particle according to claim 1, comprising 5.0 parts by mass or less of an inorganic cell nucleating agent with respect to 100 parts by mass of the polystyrene resin.
The expandable polystyrene resin particles according to claim 6, wherein the inorganic cell nucleating agent is talc.
A foaming agent is added to and kneaded with a polystyrene resin in a resin supply device, and the foaming agent-containing molten resin is less than the glass transition temperature Tg of the expandable polystyrene resin particles from the small holes of the die provided at the tip of the resin supply device. Extruding into a cooling liquid at the temperature of, and simultaneously extruding and cutting the extrudate, cooling and solidifying the extrudate by contact with the cooling liquid to obtain expandable polystyrene resin particles,
The expandable polystyrene resin particles according to any one of claims 1 to 5, wherein the expandable polystyrene resin particles obtained are heated at a glass transition temperature Tg of -5 ° C or higher of the expandable polystyrene resin particles. A step of obtaining resin particles, and a method for producing expandable polystyrene resin particles.
The method for producing expandable polystyrene resin particles according to claim 8, wherein the temperature of the cooling liquid when cutting the extrudate is in the range of 20 to 60 ° C.
The method for producing expandable polystyrene resin particles according to claim 8, wherein an inorganic cell nucleating agent of 5.0 parts by mass or less is added to 100 parts by mass of the polystyrene resin.
The method for producing expandable polystyrene resin particles according to claim 10, wherein the inorganic cell nucleating agent is talc.
Polystyrene resin pre-expanded particles obtained by heating and pre-expanding the expandable polystyrene resin particles according to any one of claims 1 to 7.
A polystyrene-based resin foam molded article obtained by filling the polystyrene-based resin pre-expanded particles according to claim 12 into a cavity of a mold, heating the mold with steam, and performing in-mold foam molding.
Obtained by filling polystyrene resin pre-expanded particles obtained by heating expandable polystyrene resin particles containing a foaming agent in polystyrene resin particles into a mold cavity, heating, and in-mold foam molding. A polystyrene resin foam molded article,
In the state of pre-expanded particles in which the expandable polystyrene resin particles are heated and expanded to a bulk expansion ratio of 50 times, the internal average cell diameter is in the range of 35 to 140 μm, and the surface layer part average cell diameter / internal average cell A polystyrene-based resin foam molded article having a cell structure having a diameter value in the range of 0.80 to 1.20 and an open cell ratio of 10% or less.
The internal average cell diameter D 2 ′ of the pre-expanded particles when expanded to a bulk expansion ratio X times is expressed by the following formula (2)

The polystyrene-based resin foam-molded article according to claim 14, wherein the internal average cell diameter D 2 of the pre-expanded particles converted to a bulk expansion ratio of 50 times using the above satisfies a relationship of 35 μm ≦ D 2 ≦ 140 μm.
The polystyrene-based resin foam molded article according to claim 14, wherein the internal average cell diameter is in the range of 40 to 120 µm.
The polystyrene-based resin foam molded article according to claim 14, wherein the open cell ratio is 8% or less.
15. The polystyrene-based resin foam molded article according to claim 14, wherein the value of the surface layer part average cell diameter / internal average cell diameter is in the range of 0.90 to 1.10.
The polystyrene-based resin foam-molded article according to claim 14, comprising 5.0 parts by mass or less of an inorganic cell nucleating agent with respect to 100 parts by mass of the polystyrene-based resin.
The polystyrene-based resin foam molded article according to claim 19, wherein the inorganic cell nucleating agent is talc.
The heat insulating material which consists of a polystyrene-type resin foaming molding of Claim 14.
A cushioning material comprising the polystyrene-based resin foam molded article according to claim 14.
A polystyrene-based resin foam molded article obtained by filling polystyrene-based resin pre-expanded particles into a cavity of a mold, heating the mold with steam, and foam-molding in the mold,
In the state when foaming is performed at the expansion ratio X times, the internal average cell diameter D 3 ′ of the foam particles fused together in the foamed molded product is expressed by the following formula (3):

Internal average cell diameter D 3 of the foamed particles in the foamed molded product in terms of expansion ratio 50-fold with, satisfy the relationship of 35μm ≦ D 3 ≦ 140μm, a surface layer portion average cell diameter / average internal of the foamed particles A polystyrene-based resin foam molded article having a cell structure in which the value of the cell diameter is in the range of 0.80 to 1.20 and the open cell ratio of the foam molded article is 10% or less.
A heat insulating material comprising the polystyrene-based resin foam molded article according to claim 23.
A cushioning material comprising the polystyrene-based resin foam molded article according to claim 23.
A foaming agent is added to and kneaded with a polystyrene resin in a resin supply device, and the foaming agent-containing molten resin is less than the glass transition temperature Tg of the expandable polystyrene resin particles from the small holes of the die provided at the tip of the resin supply device. A first step of extruding into a cooling liquid at a temperature of 5 ° C, cutting the extrudate at the same time as extruding, and cooling and solidifying the extrudate by contact with a cooling liquid to obtain expandable polystyrene resin particles;
A second step of obtaining the expandable polystyrene resin particles by heating the expandable polystyrene resin particles obtained at a glass transition temperature Tg of -5 ° C or higher of the expandable polystyrene resin particles;
Then heated resulting expandable polystyrene resin particles, the average internal cell diameter D 2 of the pre-expanded particles in terms of 50-fold volume expansion ratio by using the formula of claim 15 (2), 35 ~ 140μm A polystyrene-based resin reserve having a cell structure in which the value of the surface layer part average bubble diameter / internal average bubble diameter is in the range of 0.80 to 1.20 and the open cell ratio is 10% or less A third step of producing expanded particles;
Next, a method for producing a polystyrene-based resin foam molded article, comprising: a fourth step of filling the polystyrene-based resin pre-expanded particles in a cavity of a molding die and heating the foamed resin in-mold foam molding.
The method for producing a polystyrene resin foam molded article according to claim 26, wherein the temperature of the cooling liquid when cutting the extrudate is in the range of 20 to 60 ° C.
The manufacturing method of the polystyrene-type resin foam molding of Claim 26 which adds 5.0 mass parts or less inorganic cell nucleating agent with respect to 100 mass parts of polystyrene-type resins.
The method for producing a polystyrene resin foam molded article according to claim 28, wherein the inorganic cell nucleating agent is talc.
27. In the fourth step, the polystyrene resin pre-expanded particles are filled in a cavity of a mold and heated, and foam-molded in the mold to obtain a heat insulating material. Production method.
27. In the fourth step, the polystyrene resin pre-foamed particles are filled in a cavity of a mold and heated, and foam-molded in the mold to obtain a buffer material. Production method.