JP5986410B2 - Expandable polystyrene resin particles and production method thereof, polystyrene resin pre-expanded particles, polystyrene resin foam molding - Google Patents

Description

  The present invention relates to an expandable polystyrene resin particle from which a polystyrene resin foam molded article excellent in mechanical strength such as bending strength and compressive strength and heat insulation can be obtained.

  Polystyrene resin foam molded products obtained by foam molding of expandable polystyrene resin particles are excellent in compression resistance, light weight, heat insulation, economy, etc., and are widely used as heat insulation materials, buffer materials, etc. Yes. The mechanical strength (bending strength and compressive strength) of the polystyrene-based resin foam molded product is uniform when compared with a foam molded product having the same foam multiple, for example, a foam multiple of about 50 times, and It is known that if the average cell diameter is within a predetermined range, a foamed molded article having particularly excellent mechanical strength can be obtained.

As one of the methods for producing expandable polystyrene resin particles, a foaming agent is press-fitted and kneaded into polystyrene resin melted in an extruder, and a small hole in a die provided with a foaming agent-containing molten resin at the tip of the extruder A so-called melt extrusion method in which extrudates are extruded directly into a cooling liquid from the same time, and at the same time the extrudate is cut with a high-speed rotary blade and the extrudate is cooled and solidified by contact with the liquid to obtain expandable polystyrene resin particles Are known. In general, expandable polystyrene resin particles produced by a melt extrusion method tend to have coarse bubbles in the expanded particles obtained by heating and foaming, and the bubble diameter tends to be non-uniform. Various studies have been conducted for the refinement and uniformization of bubbles.
Conventionally, with respect to the melt extrusion method, for example, a technique disclosed in Patent Document 1 has been proposed as a production method for providing an expandable polystyrene resin particle in which the average cell diameter of the foamed molded product has an appropriate size. ing.

In Patent Document 1, (a) a step of extruding a foaming agent-containing polymer through a die head part into a water bath or a fluid bath maintained at a high temperature equal to or higher than the Tg value of the foamable polymer (b) In a water bath or fluid bath maintained at a high temperature equal to or higher than the Tg value, the polymer is immediately cut at the outlet of the die head to form granules. (C) The granules are cooled to a temperature not higher than the Tg value of the foamable polymer. In a continuous process, the cooling of the granules is slow cooling at a rate of less than 3 ° C. per minute from at least (Tg + 5) ° C. to (Tg−5) ° C., and the cutting of the polymer into granules and the cooling of the granules is 2 bar. An extrusion-type production method of foamable granules of a non-oriented and stress-free thermoplastic styrene polymer, which is performed under the above pressure, is disclosed.
According to the production method of Patent Document 1, it is described that expandable polystyrene resin particles having an average cell diameter of about 80 to 200 μm of foamed particles after being heated and foamed are described. However, since the manufacturing method of Patent Document 1 requires a large pressure vessel to relieve the residual stress of the expandable polystyrene resin particles obtained by the melt extrusion method, and requires large-scale equipment, the equipment cost However, there is a problem that a large installation area is required.

For example, a technique disclosed in Patent Document 2 has been proposed as an expandable polystyrene resin particle capable of shortening the molding cycle while the average cell diameter after foaming is within a predetermined range.
Patent Document 2 discloses a foaming property that is made of a styrene resin containing a foaming agent, and that the average cell diameter D of the foamed particle surface layer when foamed to a bulk foaming ratio of 60 times satisfies the relationship of 40 μm ≦ D ≦ 150 μm. 0.01 to 0.2 parts by mass of a methylphenyl silicone oil having a refractive index of 1.45 or more at 25 ° C. and a metal salt of a higher fatty acid 0.05 to 0 with respect to 100 parts by mass of the styrene resin particle body Disclosed is an expandable styrenic resin particle characterized in that 2 parts by mass is coated on the particle surface and the coating amount of the higher fatty acid triglyceride having no hydroxyl group in the molecule is less than 0.05 parts by mass. ing.
However, the expandable polystyrene resin particles described in the examples of Patent Document 2 are not melt extrusion methods, but are produced by conventional well-known suspension polymerization methods or seed polymerization methods. It is intended for expandable polystyrene resin particles produced by the so-called polymerization impregnation method to be impregnated, and the same effect can be obtained when the surface of the expandable polystyrene resin particles produced by the melt extrusion method is coated. This has not been proven. As a result of verification by the present inventors, when the coating is applied to the surface of the expandable polystyrene resin particles produced by the melt extrusion method, the effect of miniaturizing and uniformizing the bubbles of the expanded particles cannot be obtained. The result was obtained.

  Unlike the melt-extrusion method, the expandable polystyrene resin particles produced by the above-described polymerization impregnation method are refined if the foamed polystyrene resin particles are stored for a predetermined time after being produced. The phenomenon called “aging” occurs, and thereby expandable polystyrene resin particles capable of producing expanded particles with fine bubbles can be obtained. Regarding “ripening” that occurs in expandable polystyrene resin particles produced by a polymerization impregnation method, for example, paragraph [0007] of Patent Document 3 states that “in general, expandable particles contain a foaming agent and expandable particles. After that, it was determined that it could only be used for foaming after being stored at low temperature for several days to several days, because the polystyrene particles immediately after containing the foaming agent were heated to be preliminarily heated. When foamed, the resulting foamable particles foamed non-uniformly, bubbles became coarse, or could not be foamed at a high magnification. This is because pre-foaming after storage leads to uniform and good foaming with fine bubbles.The above-mentioned storage after producing expandable particles is generally called aging and is used in the production of expandable particles. Is Came is that it is Ku Bekara forced process. Has been described as ".

Further, for example, Patent Document 4 discloses a technique for improving the production efficiency of the expandable resin particles by promoting the completion of the ripening in the expandable polystyrene resin particles manufactured by the polymerization impregnation method.
In Patent Document 4, an average particle size obtained by suspension polymerization of a styrene-based monomer is 0.05 to 2.0 mm, and the foaming contains 3 to 10% by weight of a volatile foaming agent. An expandable styrene resin particle composition in which a polyether-modified silicone compound is impregnated in the styrene resin particle is disclosed.
However, in Patent Document 4, resin particles are produced by suspension polymerization, and expandable polystyrene resin particles obtained by a polymerization impregnation method in which the resin particles are impregnated with a foaming agent, that is, resin particles that undergo aging, It is intended to promote the completion of ripening, and there is no description and no suggestion about expandable polystyrene resin particles produced by a melt extrusion method, which is a different production method. In paragraph [0024] of Patent Document 4, after resin particles are produced by suspension polymerization, polyether-modified silicone dissolved in cyclohexane and a blowing agent (butane) are added to impregnate the resin particles. The production of expandable resin particles is described, and the added polyether-modified silicone is impregnated only on the surface of the expandable resin particles and is uniformly contained throughout the interior of the expandable resin particles. It is not recognized as a thing.

JP-A-6-32932 JP 2007-246705 A Japanese Patent No. 2737721 JP-A-11-172035

Expandable polystyrene resin particles produced by the melt extrusion method tend to have coarse bubbles in the expanded particles obtained by heating and foaming, and the bubble diameter tends to be non-uniform. Even when stored for a long period of time, the “ripening” phenomenon hardly occurs, and there is a feature that bubbles are not refined.
In order to make the foamed polystyrene resin particles produced by the melt extrusion method finer and uniform, the extruded molten resin is cut and cooled under pressure as disclosed in Patent Document 1 described above. Although a method has been proposed, this method requires a large pressure vessel and requires a large-scale facility, so that there is a problem that the equipment cost increases and the installation area is greatly required. In this technical field, there has been a demand for miniaturization and uniformization of the bubbles of the expanded particles by a simple method without requiring large-scale equipment. However, this has not been achieved until now.

  The present invention has been made in view of the above circumstances, and expandable polystyrene resin particles capable of producing a polystyrene resin foam molded article having fine and uniform air bubbles and excellent mechanical strength without using a large facility and its It is an object to provide a manufacturing method.

In order to achieve the above object, the present invention provides an expandable polystyrene resin particle containing a foaming agent composed of a hydrocarbon having 6 or less carbon atoms in the polystyrene resin particle. The organic compound having 7 or more carbon atoms is uniformly contained in the organic compound, and the solubility parameter (A) of the organic compound is the following formula (a) with respect to the solubility parameter (B) of the blowing agent:
((B) −0.5) ≦ (A) ≦ ((B) +1.5) (a)
Expandable polystyrene resin particles characterized by satisfying the above relationship are provided.

Further, the present invention provides a die in which a foaming agent comprising a hydrocarbon having 6 or less carbon atoms is press-fitted and kneaded into a polystyrene resin melted in a resin supply device, and the foaming agent-containing molten resin is attached to the tip of the resin supply device. By extruding directly into the cooling liquid from the small holes of the glass, and simultaneously extruding the extrudate with a high-speed rotary blade, and cooling and solidifying the extrudate by contact with the liquid to obtain expandable polystyrene resin particles In the obtained expandable polystyrene resin particles, the entire expandable polystyrene resin particles (excluding internal bubbles) uniformly contain an organic compound having 7 or more carbon atoms, and the solubility parameter (A ) For the solubility parameter (B) of the blowing agent, the following formula (a)
((B) −0.5) ≦ (A) ≦ ((B) +1.5) (a)
Expandable polystyrene resin particles characterized by satisfying the above relationship are provided.

In the expandable polystyrene resin particles of the present invention, the solubility parameter (A) of the organic compound is the following formula (b) with respect to the solubility parameter (B) of the foaming agent.
(B) ≦ (A) ≦ ((B) +1.5) (b)
It is preferable that the relationship is satisfied.

  In the expandable polystyrene resin particles of the present invention, the foaming agent is preferably one or a mixture of two or more selected from the group consisting of propane, normal butane, isobutane, normal pentane, and isopentane.

  In the expandable polystyrene resin particles of the present invention, the organic compound is preferably contained in the range of 0.01 to 3 parts by mass in the resin component.

The expandable polystyrene-based resin particles of the present invention have an average cell diameter D ₁ ′ of the expanded particles when heated to be expanded to a bulk expansion ratio X times after completion of aging, by the following formula (1):

(In the formula, D ₁ represents an average cell diameter (μm) of the expanded particles converted to a bulk expansion ratio of 50 times, and D ₁ ′ represents an average cell diameter (μm) of the expanded particles when expanded to a bulk expansion ratio X times ) average cell diameter D ₁ of the expanded beads in terms of 50-fold volume expansion ratio using the representative), it is preferable to satisfy the relation of 50μm ≦ D ₁ ≦ 250μm.

  In the expandable polystyrene resin particles of the present invention, the entire expandable polystyrene resin particles (excluding internal bubbles), from higher fatty acid metal salts, higher fatty acid esters, higher fatty acid amides, higher fatty acid bisamides, and inorganic cell nucleating agents. It is preferable that the 1 type (s) or 2 or more types selected were contained uniformly.

Further, the present invention provides a die in which a foaming agent comprising a hydrocarbon having 6 or less carbon atoms is press-fitted and kneaded into a polystyrene resin melted in a resin supply device, and the foaming agent-containing molten resin is attached to the tip of the resin supply device. By extruding directly into the cooling liquid from the small holes of the glass, and simultaneously extruding the extrudate with a high-speed rotary blade, and cooling and solidifying the extrudate by contact with the liquid to obtain expandable polystyrene resin particles In the method for producing expandable polystyrene resin particles, the polystyrene resin is an organic compound having 7 or more carbon atoms [wherein the solubility parameter (A) of the organic compound is the following with respect to the solubility parameter (B) of the foaming agent). Formula (a)
((B) −0.5) ≦ (A) ≦ ((B) +1.5) (a)
To obtain expandable polystyrene resin particles in which the organic compound is uniformly contained in the entire expandable polystyrene resin particles (excluding internal bubbles). A method for producing resin particles is provided.

In the method for producing expandable polystyrene-based resin particles of the present invention, the organic compound has a solubility parameter (A) with respect to the solubility parameter (B) of the foaming agent.
(B) ≦ (A) ≦ ((B) +1.5) (b)
It is preferable that the relationship is satisfied.

  In the method for producing expandable polystyrene resin particles of the present invention, the foaming agent is preferably one or a mixture of two or more selected from the group consisting of propane, normal butane, isobutane, normal pentane, and isopentane.

  In the method for producing expandable polystyrene resin particles of the present invention, it is preferable to add the organic compound in a resin content in the range of 0.01 to 3 parts by mass.

  In the method for producing expandable polystyrene resin particles of the present invention, the expandable polystyrene resin particles obtained by the melt extrusion method are subjected to an aging step in which the expandable polystyrene resin particles are stored in an atmosphere of 40 ° C. or less for 1 hour or more. It is preferable to obtain resin particles.

  In the expandable polystyrene resin particles of the present invention, the entire expandable polystyrene resin particles (excluding internal bubbles), from higher fatty acid metal salts, higher fatty acid esters, higher fatty acid amides, higher fatty acid bisamides, and inorganic cell nucleating agents. It is preferable that the 1 type (s) or 2 or more types selected were contained uniformly.

  The present invention also provides polystyrene resin pre-expanded particles obtained by aging the expandable polystyrene resin particles, followed by heating and pre-expanding.

  The present invention also provides a polystyrene resin foam molded article obtained by filling the polystyrene resin pre-expanded particles in a cavity of a mold, steam-heating the mold, and performing in-mold foam molding.

In the polystyrene-based resin foam molded article of the present invention, the average cell diameter D ₂ ′ of the foamed particles fused together in the foam molded article in the state when foam-molded to a multiple of X times is expressed by the following formula ( 2)

(Wherein, D ₂ represents the average cell diameter of the expanded beads of foamed molded body in terms of 50-fold expansion ratio ([mu] m), D 2 _'is foamed molded product when foamed in expansion ratio X times average cell diameter D ₂ of the average cell diameter expanded beads of the foamed molded body in terms of expansion ratio 50 times using a representative of the ([mu] m)) of the expanded particles, it is preferable to satisfy the relation of 50 [mu] m ≦ D ₂ ≦ 250 [mu] m .

The expandable polystyrene resin particle of the present invention is an expandable polystyrene resin particle containing a foaming agent composed of a hydrocarbon having 6 or less carbon atoms in the polystyrene resin particle. The organic compound having 7 or more carbon atoms is uniformly contained in the organic compound, and the solubility parameter (A) of the organic compound is the following formula (a) with respect to the solubility parameter (B) of the blowing agent:
((B) −0.5) ≦ (A) ≦ ((B) +1.5) (a)
When the resin particles are produced by a melt extrusion method, the foaming obtained by heating and foaming the resin particles by storing the resin particles after production. The particles undergo a ripening phenomenon in which the bubbles become finer than foamed particles that are foamed immediately after production. Therefore, even when the expandable polystyrene resin particles of the present invention are produced by a melt extrusion method without using a large facility, the foamed polystyrene resin particles are fine and uniform, and have excellent mechanical strength. Expandable polystyrene resin particles that can be produced can be provided.

In the method for producing expandable polystyrene resin particles of the present invention, a foaming agent comprising a hydrocarbon having 6 or less carbon atoms is press-fitted and kneaded into a polystyrene resin melted in a resin supply device, and a foaming agent-containing molten resin is obtained. Extruded directly from the small hole of the die attached to the tip of the resin supply device into the cooling liquid, and at the same time, the extrudate is cut with a high-speed rotary blade, and the extrudate is cooled and solidified by contact with the liquid. In the method for producing expandable polystyrene resin particles by melt extrusion method for obtaining resin particles, an organic compound having 7 or more carbon atoms in the polystyrene resin [wherein the solubility parameter (A) of the organic compound is the solubility of the foaming agent] For parameter (B), the following equation (a)
((B) −0.5) ≦ (A) ≦ ((B) +1.5) (a)
Is satisfied, and after the production, the foamable polystyrene resin particles in which the organic compound is uniformly contained in the entire expandable polystyrene resin particles (excluding internal bubbles) are obtained. By storing the resin particles, foamed particles obtained by heating and foaming the resin particles can be obtained such that a ripening phenomenon occurs in which bubbles become finer than foamed particles that are foamed immediately after production. Therefore, the method for producing expandable polystyrene resin particles of the present invention is a polystyrene resin foam molded article having fine and uniform air bubbles and excellent mechanical strength by aging after production without using a large facility. Can be easily produced.

  The polystyrene resin foam molded article of the present invention is prepared by filling the polystyrene resin pre-expanded particles obtained by heating and foaming the expandable polystyrene resin particles in a cavity of the mold, and heating the mold with steam. However, since it is obtained by in-mold foam molding, the bubbles are fine and uniform, and the mechanical strength is excellent.

It is a block diagram which shows an example of the manufacturing apparatus used for the manufacturing method of the expandable polystyrene-type resin particle of this invention. It is an enlarged image of the cross section of the pre-expanded particle produced in Example 1, (a) is the pre-expanded particle which pre-expanded the expandable polystyrene resin particle immediately after extrusion, (b) is the expandable polystyrene-based resin after aging. Pre-expanded particles obtained by pre-expanding particles, and (c) are pre-expanded particles obtained by pre-expanding expandable polystyrene resin particles during aging. It is an enlarged image of the cross section of the pre-expanded particle produced in Example 2, (a) is the pre-expanded particle which pre-expanded the expandable polystyrene resin particle immediately after extrusion, (b) is the expandable polystyrene resin after aging. Pre-expanded particles obtained by pre-expanding the particles. It is an enlarged image of the cross section of the pre-expanded particle produced in Example 6, (a) is the pre-expanded particle which pre-expanded the expandable polystyrene resin particle immediately after extrusion, (b) is the expandable polystyrene resin after aging. Pre-expanded particles obtained by pre-expanding particles, and (c) are pre-expanded particles obtained by pre-expanding expandable polystyrene resin particles during aging.

(Expandable polystyrene resin particles)
The expandable polystyrene resin particle of the present invention is an expandable polystyrene resin particle containing a foaming agent composed of a hydrocarbon having 6 or less carbon atoms in the polystyrene resin particle. The same applies to the phrase “whole resin particles” hereinafter.) The organic compound having 7 or more carbon atoms is uniformly contained, and the solubility parameter (A) of the organic compound is the solubility parameter of the blowing agent. For (B), the following equation (a)
((B) −0.5) ≦ (A) ≦ ((B) +1.5) (a)
It is characterized by satisfying the relationship.

In the present invention, the solubility parameter (also referred to as SP value) refers to a value calculated by the following equation (c).
Solubility parameter (SP value) = dΣG / M (c)
(In the formula, M represents molecular weight, d represents specific gravity, and G represents an attractive constant of an atom or substituent in the molecule. This attractive constant is small [PASmall, J. Appl. Chem. 3, 71. (1953)] is shown.)

In a preferred embodiment of the present invention, the expandable polystyrene resin particles are obtained by press-fitting and kneading a foaming agent composed of a hydrocarbon having 6 or less carbon atoms into a polystyrene resin melted in a resin supply apparatus, and containing a foaming agent-containing melt. Resin is extruded directly into the cooling liquid through a small hole in the die attached to the tip of the resin supply device. At the same time, the extrudate is cut with a high-speed rotary blade, and the extrudate is cooled and solidified by contact with the liquid to foam. In the expandable polystyrene resin particles obtained by the melt extrusion method for obtaining the expandable polystyrene resin particles, the entire expandable polystyrene resin particles uniformly contain an organic compound having 7 or more carbon atoms, and the solubility of the organic compound When the parameter (A) is the solubility parameter (B) of the foaming agent, the following formula (a)
((B) −0.5) ≦ (A) ≦ ((B) +1.5) (a)
It is preferable that the relationship is satisfied. According to this melt extrusion method, the expandable polystyrene resin particles of the present invention in which the organic compound is uniformly contained in the entire expandable polystyrene resin particles can be easily obtained.

When normal pentane having a solubility parameter (hereinafter referred to as SP value) of 7.0 is used as the foaming agent, the organic compound satisfying the relationship of the above formula (a) has an SP value of 6.5 to 8.5. An organic compound having 7 or more carbon atoms in the range is used.
Examples of the organic compound that satisfies the above conditions include polymethylphenylsiloxane (SP value: 7.6), polydimethylsiloxane (SP value: 7.1), polyether-modified silicone (SP value: 7.9), and polyethylene. Wax (SP value: 8.1), decamethylcyclopentasiloxane (SP value: 7.1), squalane (SP value: 7.7), olive oil (SP value: 8.2), jojoba oil (SP value: 8.3).
Further, when isopentane having an SP value of 6.6 is used as the foaming agent, the organic compound satisfying the relationship of the formula (a) has 7 or more carbon atoms having an SP value in the range of 6.1 to 8.1. These organic compounds are used.
Examples of the organic compound that satisfies the above conditions include polytetrafluoroethylene (SP value: 6.2), polymethylphenylsiloxane (SP value: 7.6), polydimethylsiloxane (SP value: 7.1), poly Examples include ether-modified silicone (SP value: 7.9), polyethylene wax (SP value: 8.1), decamethylcyclopentasiloxane (SP value: 7.1), squalane (SP value: 7.7), and the like. .
When normal butane having an SP value of 6.8 is used as the foaming agent, the organic compound satisfying the relationship of the formula (a) has a carbon number of 7 having an SP value in the range of 6.3 to 8.3. The above organic compounds are used.
Examples of the organic compound that satisfies the above conditions include polymethylphenylsiloxane (SP value: 7.6), polydimethylsiloxane (SP value: 7.1), polyether-modified silicone (SP value: 7.9), and polyethylene. Wax (SP value: 8.1), decamethylcyclopentasiloxane (SP value: 7.1), squalane (SP value: 7.7), olive oil (SP value: 8.2), jojoba oil (SP value: 8.3).
In addition, when isobutane having an SP value of 6.6 is used as the foaming agent, the organic compound satisfying the relationship of the formula (a) has 7 or more carbon atoms having an SP value in the range of 6.1 to 8.1. These organic compounds are used.
Examples of the organic compound that satisfies the above conditions include polytetrafluoroethylene (SP value: 6.2), polymethylphenylsiloxane (SP value: 7.6), polydimethylsiloxane (SP value: 7.1), poly Examples include ether-modified silicone (SP value: 7.9), polyethylene wax (SP value: 8.1), decamethylcyclopentasiloxane (SP value: 7.1), squalane (SP value: 7.7), and the like. .

In a preferred embodiment of the present invention, the organic compound has an SP value (A) of the following formula (b) with respect to the SP value (B) of the foaming agent.
(B) ≦ (A) ≦ ((B) +1.5) (b)
It is preferable that the relationship is satisfied.

  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, copolymers thereof, and the like, and polystyrene resins containing 50% by mass or more of styrene are preferable, and polystyrene is more preferable. The mass average molecular weight of polystyrene is preferably in the range of 12 to 400,000, and more preferably in the range of 15 to 400,000.

  Further, 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. As, for example, alkyl (meth) acrylate such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cetyl (meth) acrylate, (meth) acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl In addition to fumarate and ethyl fumarate, bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate are exemplified.

  If a polystyrene resin is the main component, other resins may be added. Examples of the resin to be added include polybutadiene, styrene-butadiene copolymer to improve the impact resistance of the foam molded article. Examples thereof include rubber-modified polystyrene resins to which a diene rubbery polymer such as a polymer, ethylene-propylene-nonconjugated diene three-dimensional copolymer is 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-based resin foam molded article can 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 used in appropriate combination.

The foaming agent used for the expandable polystyrene resin particles of the present invention is preferably a hydrocarbon having 6 or less carbon atoms, for example, an aliphatic hydrocarbon such as propane, normal butane, isobutane, normal pentane, isopentane, neopentane, cyclopentane and the like. Further, normal butane, isobutane, normal pentane, isopentane alone or a mixture thereof is more preferable.
The amount of the foaming agent added is preferably in the range of 2 to 10 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.

  The amount of the organic compound added to the expandable polystyrene resin particles of the present invention is preferably in the range of 0.01 to 3% by mass in the resin content, more preferably in the range of 0.05 to 2.5% by mass. The range of 0.1 to 2.0% by mass is more preferable. When the addition amount of the organic compound is less than the above range, an aging phenomenon is caused by storing the expandable polystyrene resin particles produced by the melt extrusion method, and the bubbles are fine and uniform by performing this aging. Thus, the effect of the present invention that a foamed molded article having excellent mechanical strength can be obtained cannot be obtained sufficiently. When the addition amount of the organic compound exceeds the above range, the effect of the present invention reaches its peak, and on the contrary, the cost increases, and the mechanical strength of the resulting foamed molded product decreases.

  As a method for adding the organic compound to the polystyrene-based resin, there are a method of directly feeding into an extruder, a method of preparing a master batch in advance and then feeding it into the extruder. Among these, a master batch made of a polystyrene resin containing the organic compound at a high concentration is prepared in advance, and the organic compound-containing master batch and the polystyrene resin are put into the resin supply device, and expandable polystyrene resin particles. It is preferable to manufacture. By using such an organic compound-containing masterbatch, expandable polystyrene resin particles in which an organic compound is uniformly contained over the entire expandable polystyrene resin particles can be produced.

In addition to the foaming agent and the organic compound, the expandable polystyrene resin particles may be one or two selected from higher fatty acid metal salts, higher fatty acid esters, higher fatty acid amides, higher fatty acid bisamides, and inorganic cell nucleating agents. You may contain the above. Examples of the higher fatty acid metal salt include zinc stearate, calcium stearate, magnesium stearate and the like. Examples of the higher fatty acid ester include 12-hydroxystearic acid triglyceride and stearic acid glyceride. Examples of the higher fatty acid amide include stearic acid amide and 12-hydroxystearic acid amide. Examples of the higher fatty acid bisamide include ethylene bis stearic acid amide and methylene bis stearic acid amide. Examples of the inorganic cell nucleating agent include talc, calcium silicate, synthetically or naturally produced silicon dioxide, and the like. These addition amounts are preferably in the range of 0.01 to 3% by mass in the polystyrene-based resin.
When one or two or more kinds selected from a higher fatty acid metal salt, a higher fatty acid ester, a higher fatty acid amide, a higher fatty acid bisamide, and an inorganic cell nucleating agent are used in combination with the organic compound as polystyrene nucleating agent, The average cell diameter of the expanded particles obtained by heating and foaming can provide finer bubbles than when the organic compound is used alone.

  When a cell nucleating agent such as a higher fatty acid metal salt, a higher fatty acid ester, a higher fatty acid amide, a higher fatty acid bisamide or an inorganic cell nucleating agent is added, the cell nucleating agent is uniformly dispersed in a base resin, preferably a polystyrene resin. It is preferable to use a masterbatch type cell nucleating agent. By using this master batch type cell nucleating agent, when mixing the polystyrene resin and the cell nucleating agent in the resin supply device, the cell nucleating agent can be uniformly contained throughout the polystyrene resin.

  In addition to the expandable polystyrene resin particles and the foamed molded article, the expandable polystyrene resin particles of the present invention are within the range that does not impair the physical properties of the expandable polystyrene resin particles and the foamed molded article. Additives such as flame retardant aids, lubricants, and colorants may be added.

The expandable polystyrene resin particles of the present invention are obtained by using the above formula (1) to calculate the average cell diameter D ₁ ′ of the expanded particles when heated and foamed to a bulk expansion ratio X times after completion of aging. The average cell diameter D ₁ of the expanded particles converted to 50 times preferably satisfies the relationship of 35 μm ≦ D ₁ ≦ 300 μm, and more preferably satisfies the relationship of 50 μm ≦ D ₁ ≦ 250 μm. When the average cell diameter D ₁ is less than the above range, closed cell ratio decreases the open cell ratio is increased, the bending strength, compressive strength, decrease and moldability of the mechanical strength such as impact resistance deteriorates End up. When the average cell diameter D ₁ exceeds the above range, the mechanical strength of the foamed molded product obtained (bending strength and compression strength) decreases.

The expandable polystyrene resin particle of the present invention is an expandable polystyrene resin particle containing a foaming agent composed of a hydrocarbon having 6 or less carbon atoms in the polystyrene resin particle, and the entire expandable polystyrene resin particle has 7 or more carbon atoms. The organic compound is uniformly contained, and the solubility parameter (A) of the organic compound is the following formula (a) with respect to the solubility parameter (B) of the blowing agent:
((B) −0.5) ≦ (A) ≦ ((B) +1.5) (a)
When the resin particles are produced by a melt extrusion method, the foaming obtained by heating and foaming the resin particles by storing the resin particles after production. The particles undergo a ripening phenomenon in which the bubbles become finer than foamed particles that are foamed immediately after production. Therefore, even when the expandable polystyrene resin particles of the present invention are produced by a melt extrusion method without using a large facility, the foamed polystyrene resin particles are fine and uniform, and have excellent mechanical strength. Expandable polystyrene resin particles that can be produced can be provided.

(Method for producing expandable polystyrene resin particles)
Next, an embodiment of a method for producing expandable polystyrene resin particles according to the present invention will be described with reference to the drawings.
The method for producing expandable polystyrene resin particles according to the present invention includes the steps of press-fitting and kneading a foaming agent comprising a hydrocarbon having 6 or less carbon atoms into a polystyrene resin melted in a resin supply apparatus, and a foaming agent-containing molten resin. Is extruded directly from the small hole of the die attached to the tip of the resin supply device into the cooling liquid, and at the same time the extrudate is cut with a high-speed rotary blade, and the extrudate is cooled and solidified by contact with the liquid to foam. In the method for producing expandable polystyrene resin particles by melt extrusion to obtain polystyrene resin particles, the polystyrene resin is an organic compound having 7 or more carbon atoms [wherein the solubility parameter (A) of the organic compound is that of the foaming agent. For the solubility parameter (B), the following equation (a)
((B) −0.5) ≦ (A) ≦ ((B) +1.5) (a)
The above-mentioned relationship is satisfied] to obtain expandable polystyrene resin particles in which the organic compound is uniformly contained throughout the expandable polystyrene resin particles.

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; It is configured with.

  As the extruder 1, either 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.

(Granulation process)
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, the organic compound, or a cell nucleating agent 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 for each lot may be reduced. A plurality of adjusted raw material supply hoppers may be charged 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. Furthermore, it is preferable to add the masterbatch previously added to the polystyrene resin at a high concentration as an additive component such as the organic compound.

  After the polystyrene resin, the organic compound, and other optional additives are supplied into the extruder 1, the resin is heated and melted, and the molten resin is transferred to the die 2 side. The foaming agent is pressed into the melted resin, and the foaming agent is mixed with the molten resin. Through the foreign matter removing screen provided in the extruder 1 as necessary, the melt is further kneaded and moved to the tip side, The added melt is extruded through a small hole in the die 2 attached to the tip of the extruder 1.

  The resin discharge surface in which the small holes of the die 2 are drilled is disposed in the cutting chamber 7 in which cooling water is circulated and supplied into the chamber, and the resin extruded from the small holes of the die 2 is placed in the cutting chamber 7. A cutter 6 is provided so as to be rotatable. When the melt with the blowing agent added is extruded through a small hole in the die 2 attached to the tip of the extruder 1, the melt is cut into granules and simultaneously cooled in contact with cooling water. can get.

  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, where the expandable polystyrene resin particles are separated from the cooling water. 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 preferably in the range of 20 to 60 ° C. If the temperature of the cooling water is too high, the expandable polystyrene resin particles are likely to be fused together, and the incidence of defective products in which a large number of particles are combined to form a lump is increased. When the temperature of the cooling water is too low, the resulting expandable polystyrene resin particles may not be spheroidized and cracks may occur.

  The cooling water may be pressurized to 0.5 MPa or more. In order to pressurize the cooling water, the portion of the cooling water circulation passage that passes from the discharge side of the high-pressure pump 9 through the cutting chamber 7 to the inlet side of the dehydrating dryer 10 with a solid-liquid separation function is pressurized. This can be performed by increasing the discharge pressure of the high-pressure pump 9. When pressurizing the cooling water, the 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. If it is the pressure of the upper limit of the said pressure range, it can implement, without using facilities, such as a large sized pressure vessel and a dedicated pressurization apparatus.

(Aging process)
The expandable polystyrene resin particles obtained in the granulation step can be made fine and uniform by performing the aging step.
Aging means that after adding foaming agent to the resin to make expandable resin particles, it is stored under low temperature for several days or several days, and by aging, the bubbles become finer from the surface, It refers to obtaining expandable polystyrene resin particles that foam fine bubbles uniformly and well by completing aging. This aging is common for expandable polystyrene resin particles produced by a polymerization impregnation method. However, this phenomenon could not be observed for the expandable polystyrene resin particles produced by the melt extrusion method. In the present invention, when the expandable polystyrene resin particles are produced by the melt extrusion method, the organic compound is uniformly contained in the resin to obtain the expandable polystyrene resin particles. Similarly, an aging phenomenon can be caused.

This aging step is preferably performed in an atmosphere at a temperature of 40 ° C. or less, and more preferably in the range of 10 to 40 ° C.
The storage time in this aging step is preferably 1 hour or longer, more preferably 6 hours or longer, further preferably about 12 hours to 60 days, and most preferably about 12 hours to 7 days.

  In addition, before or after the aging step, as usual with respect to conventional expanded styrene resin particles, the surface of the expandable polystyrene resin particles, such as fatty acid metal salts, fatty acid esters, antistatic agents, etc. A surface treatment agent can be coated. By coating the surface treatment agent, the flowability and pre-foaming characteristics of the expandable polystyrene resin particles can be improved. The total amount of the surface treatment agent is preferably about 0.01 to 2.0 parts by mass with respect to 100 parts by mass of the expandable polystyrene resin particles.

In the method for producing expandable polystyrene resin particles of the present invention, a foaming agent comprising a hydrocarbon having 6 or less carbon atoms is press-fitted and kneaded into a polystyrene resin melted in a resin supply device, and a foaming agent-containing molten resin is obtained. Extruded directly from the small hole of the die attached to the tip of the resin supply device into the cooling liquid, and at the same time, the extrudate is cut with a high-speed rotary blade, and the extrudate is cooled and solidified by contact with the liquid. In the method for producing expandable polystyrene resin particles by melt extrusion method for obtaining resin particles, an organic compound having 7 or more carbon atoms in the polystyrene resin [wherein the solubility parameter (A) of the organic compound is the solubility of the foaming agent] For parameter (B), the following equation (a)
((B) −0.5) ≦ (A) ≦ ((B) +1.5) (a)
Is satisfied, and the resin particles are stored after the production by obtaining the expandable polystyrene resin particles in which the organic compound is uniformly contained in the entire expandable polystyrene resin particles. As a result, the foamed particles obtained by heating and foaming the resin particles are those in which a ripening phenomenon occurs in which the bubbles become finer than the foamed particles foamed immediately after production. Therefore, the method for producing expandable polystyrene resin particles of the present invention is a polystyrene resin foam molded article having fine and uniform air bubbles and excellent mechanical strength by aging after production without using a large facility. Can be easily produced.

(Polystyrene resin pre-expanded particles and polystyrene resin foam molding)
The expandable polystyrene resin particles of the present invention are pre-expanded by heating with water vapor heating or the like using a well-known apparatus and method in the field of manufacturing foamed resin molded articles, and then polystyrene-based resin pre-expanded particles (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 0.10 g / cm ³ (in the range of 10 to 100 times as the bulk foaming factor), 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 are 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 the cavity of the mold 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. In the present invention, the density and expansion ratio of the foamed molded product are not limited, but are usually within the range of 0.010 to 0.10 g / cm ³ (within the range of 10 to 100 times as the expansion ratio). It is preferable to be in the range of 0.050 g / cm ³ .

The foamed molded product of the present invention is in the state when foamed and molded at a multiple of X times, and the average cell diameter D ₂ ′ of the fused foam particles in the foamed molded product is expressed by the above formula (2). in terms of expansion ratio 50-fold with its foamed molding average cell diameter _{D 2} of the expanded beads in the can, preferably satisfies 35 [mu] m ≦ _{D 2} ≦ 300 [mu] m relationship, satisfying the relation of 50 [mu] m ≦ _{D 2} ≦ 250 [mu] m It is more preferable. When the average cell diameter D ₂ is less than the above range, the foamed molded product obtained by mold foaming closed cell decreases with increasing open cell ratio, bending strength, compression strength, such as impact resistance The mechanical strength is lowered or the moldability is deteriorated. When the average cell diameter D ₂ exceeds the above range, bending strength, compression strength, mechanical strength such as impact resistance is lowered.

In the present invention, the density of the foamed molded product refers to the density of the foamed molded product measured by the method described in JIS K7122: 1999 “Measurement of foamed plastic and rubber-apparent density”.
<Density of foam molding>
A test piece 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 calculated by the following formula.
Density (g / cm ³ ) = Test piece mass (g) / Test piece volume (cm ³ )
Test piece condition adjustment and measurement test pieces were cut out from samples that had passed 72 hours or more after molding, and were subjected to atmospheric conditions of 23 ° C. ± 2 ° C. × 50% ± 5% or 27 ° C. ± 2 ° C. × 65% ± 5%. It has been stored for more than an hour.

<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 )

  The foamed molded article of the present invention is prepared by filling pre-expanded particles obtained by heating and pre-foaming the expandable polystyrene resin particles in the mold cavity, heating the mold with steam, Since it is obtained by foam molding, the bubbles are fine and uniform, and have excellent mechanical strength.

[Example 1]
(Manufacture of master batch)
Polystyrene resin (trade name “G9305” manufactured by PS Japan Co., Ltd.) is used as the base resin, and polymethylphenylsiloxane (trade name “TSF4300” manufactured by GE Toshiba Silicone Co., SP value: 7.6) is used as the organic compound. A master batch was prepared by adding the amount to 5% by mass.

(Manufacture of expandable polystyrene resin particles)
160 kg per hour of polystyrene resin (made by PS Japan Co., Ltd., trade name “G9305”) with the above master batch mixed in advance so that polymethylphenylsiloxane is 0.5 mass% in the resin component as the base resin. After feeding into a single screw extruder with a diameter of 90 mm at a rate of / hr and heating and melting the resin, 7 parts by weight of normal pentane (SP value: 7.0) is extruded as a foaming agent with respect to 100 parts by weight of the resin. Press-fitted from the middle of the machine. Then, while kneading the resin and the foaming agent in the extruder, while cooling so that the resin temperature at the tip of the extruder is 170 ° C., the diameter is 0.6 mm, connected to the extruder and held at 290 ° C. by the heater. 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. A high-speed rotating cutter having the above structure was brought into close contact with a die, cut at 3000 rpm, 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.

(Maturation of expandable polystyrene resin particles)
The obtained expandable polystyrene resin particles were immediately placed in an atmosphere at 15 ° C. for aging.

(Surface coating of expandable polystyrene resin particles)
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 with respect to 100 parts by mass of the expandable polystyrene resin particles obtained as described above. 0.05 part by mass was uniformly coated on the entire surface of the expandable polystyrene resin particles.

(Manufacture of foam molded products)
Subsequently, expandable polystyrene resin particles (hereinafter may be referred to as beads) were supplied to a cylindrical batch type pre-foaming machine and heated with steam having a blowing pressure of 0.05 MPa to obtain pre-foamed particles. 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.
Further, for the beads, pre-expanded particles, and foamed molded article, according to the following measurement methods, each test of average cell diameter, surface layer average cell diameter / center average cell diameter, aging period, bending strength, compressive strength, and strength evaluation Items were measured. The results are shown in Table 1.

<Measurement of average cell diameter of pre-expanded particles>
The average cell diameter of pre-expanded particles refers to that measured according to the test method of ASTM D3576-77. Specifically, it is cut with a razor tooth on a plane passing through the vicinity of the center of the pre-expanded particles, and the cut surface is enlarged 30 times using a scanning electron microscope (trade name “JSM-6360LV” manufactured by JOEL). To do.
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 straight line having a length of 60 mm is drawn at an arbitrary position inside the first circle, and the average chord length (t) of the bubbles is calculated from the number of bubbles existing on the 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 taken as the average bubble diameter of the pre-expanded particles.

<Measurement of the average cell diameter of the foam particles fused together in the foamed molded product>
The average cell diameter of the fused foam particles in the foamed molded product refers to those measured in accordance with the method for measuring the average cell diameter of the pre-expanded particles.
However, in the measurement of the pre-foamed particles, the first circle (inscribed circle) inscribed in the surface layer of the pre-foamed particles was drawn, but in the measurement of the fused foam particles in the foam molded article, The first circle (inscribed circle) inscribed in the fusion layer was drawn.

<Aging period>
Foamed particles obtained by foaming expandable polystyrene resin particles during aging are finer from the surface layer, and as the aging progresses, the finer bubbles reach the center, and the entire expanded particles become fine uniform bubbles. Become. Aging is completed when the ratio of the average cell diameter in the surface layer to the average cell diameter in the center (surface layer average cell diameter / center average cell diameter) is 0.80 or more, and the period required at that time is aged The period. Moreover, even if 60 days have passed since the start of aging, those that did not start to refine the bubbles from the surface layer portion were not aged.
Further, the surface layer portion average bubble diameter and the internal average bubble diameter are obtained by printing a photographed image on A4 paper and drawing a first circle (inscribed circle) inscribed in the surface layer of the pre-foamed particles. A second concentric circle having a radius of ¼ of the diameter of the circle is drawn, the surface layer portion is between the surface layer and the second circle, the inside of the second circle is the center portion, and the average cell diameter of the pre-expanded particles is The one measured according to the measuring method.
In this example, the pre-expanded particles (FIG. 2A) obtained by pre-expanding the expandable polystyrene resin particles immediately after production had a large cell diameter of 550 μm. The pre-expanded particles (FIG. 2 (c)) obtained by pre-expanding the expandable particles after aging for 3 hours had fine bubbles in the surface layer but not in the center, and average cell diameter / center in the surface layer. The part average bubble diameter was 0.66, and it was in the state of aging. The pre-expanded particles (FIG. 2 (b)) obtained by pre-expanding the expandable particles after one day of aging are such that the bubbles are miniaturized to the center, the average cell diameter is 150 μm, and the surface layer average cell diameter / center average cell bubble diameter is The aging was completed. The aging period was 1 day.

<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 product, and a bending test of the test piece was performed according to JIS-A9511 to calculate a bending strength [MPa].

<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 article, and a compression test of the test piece was performed in accordance with JIS-A9511 to calculate the compressive strength [MPa].

<Strength evaluation>
From the results of the bending strength and compressive strength, the strength was evaluated according to the following criteria.
Very good (（): satisfying bending strength of 0.31 MPa or more and compressive strength of 0.12 MPa or more.
Good (O): A bending strength of 0.28 MPa or more and less than 0.31 MPa and a compressive strength of 0.11 MPa or more and less than 0.12 MPa.
Defect (x): At least one of bending strength and compressive strength is lower than the above standard.

[Example 2]
A foam molded article was produced in the same manner as in Example 1 except that the master batch described in Example 1 was used so that polymethylphenylsiloxane was 0.2% by mass in the resin component. Measurements were made. The results are shown in Table 1. The aging period of this example was 1 day.

[Example 3]
Polyether-modified silicone (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “KF945A”) (SP value: 7.8) was used instead of polymethylphenylsiloxane during the production of the masterbatch of Example 1, and expandable polystyrene resin particles. A foamed molded article was produced in the same manner as in Example 1 except that the master batch was used so that the amount of the polyether-modified silicone in the resin component was 0.2% by mass, and the same measurement was performed. . The results are shown in Table 1. The aging period of this example was 30 days.

[Example 4]
Polytetrafluoroethylene (Mitsui / DuPont Fluoro Chemical) “MP-1100” (SP value: 6.2) was used instead of polymethylphenylsiloxane during the production of the masterbatch of Example 1, and an expandable polystyrene system. Other than using the master batch at the time of production of the resin particles so that the polytetrafluoroethylene in the resin content is 0.2% by mass, and using isopentane (SP value: 6.6) instead of normal pentane as the foaming agent. Produced a foamed molded product by the same method as in Example 1, and performed the same measurement. The results are shown in Table 1. The aging period of this example was 1 day.

[Example 5]
In the production of the masterbatch of Example 1, polyethylene wax (trade name “Sunwax 131-P”, manufactured by Sanyo Chemical Co., Ltd.) (SP value: 8.1) is substituted for polymethylphenylsiloxane, and an expandable polystyrene type A foamed molded article was produced in the same manner as in Example 1 except that the master batch was used so that the polyethylene wax was 0.2% by mass in the resin during production of the resin particles, and the same measurement was performed. . The results are shown in Table 1. The aging period of this example was 3 days.
However, Example 5 is a reference example.

[Example 6]
A master batch of polymethylphenylsiloxane and magnesium stearate was prepared at the time of manufacturing the masterbatch of Example 1, and the content of polymethylphenylsiloxane in the resin content was 0.2% by mass, and magnesium stearate was 0.05% by mass. A foamed molded article was produced in the same manner as in Example 1 except that it was used so that the same measurement was performed. The results are shown in Table 1. The aging period of this example was 1 day. In addition, FIG. 4C shows the bubble state after 3 hours of aging (during aging).

[Example 7]
Except for using 6 parts by weight of butane (isobutane: normal butane = 30: 70 (mass ratio)) (SP value: 6.7) with respect to 100 parts by weight of the resin as the foaming agent, the same as in Example 2 A foam molded article was produced by the method, and the same measurement was performed. The results are shown in Table 1. The aging period of this example was 1 day.

[Example 8]
(Manufacture of master batch)
Polystyrene resin (trade name “G9305” manufactured by PS Japan Co., Ltd.) is used as the base resin, and diisobutyl adipate (boiling point: 293 ° C., product name “DI4A” manufactured by Taoka Chemical Industries, Ltd.) is 10% by mass as the plasticizer. A master batch was prepared.
As a foaming agent, 6 parts by mass of butane (isobutane: normal butane = 30: 70 (mass ratio)) (SP value: 6.7) is added to 100 parts by mass of the resin, and the master batch is added to 100 parts by mass of the resin. On the other hand, a foamed molded article was produced in the same manner as in Example 2 except that diisobutyl adipate was used at 2.5 parts by mass, and the same measurement was performed. The results are shown in Table 1. The aging period of this example was 1 day.

[Comparative Example 1]
A foamed molded article was produced in the same manner as in Example 1 except that polymethylphenylsiloxane and its masterbatch were not used in Example 1, and the same measurement was performed. The results are shown in Table 1. This comparative example did not age.

[Comparative Example 2]
In the production of the master batch of Example 1 and the production of expandable polystyrene resin particles, polymethylphenylsiloxane and its master batch are not used, and the polymethylphenylsiloxane is coated with 100 masses of resin particles when the expandable polystyrene resin particles are coated. A foamed molded article was produced in the same manner as in Example 1 except that 0.1 part by mass was coated on the part, and the same measurement was performed. The results are shown in Table 1. This comparative example did not age.

[Comparative Example 3]
Instead of polymethylphenylsiloxane, diisobutyl adipate (SP value: 8.7) was used in the production of the masterbatch of Example 1, and when the expandable polystyrene resin particles were produced, the masterbatch had 0 diisobutyladipate in the resin content. A foamed molded article was produced in the same manner as in Example 1 except that it was used so as to be 5% by mass, and the same measurement was performed. The results are shown in Table 1. This comparative example did not age.

[Comparative Example 4]
Xylene (SP value: 8.8) was used in place of polymethylphenylsiloxane in the production of the masterbatch of Example 1, and the masterbatch was produced in the resin component with a xylene content of 0.00 in the production of expandable polystyrene resin particles. A foamed molded article was produced in the same manner as in Example 1 except that it was used so as to be 5% by mass, and the same measurement was performed. The results are shown in Table 1. This comparative example did not age.

[Comparative Example 5]
The same as Example 1 except that instead of polymethylphenylsiloxane and its masterbatch in Example 1, a magnesium stearate masterbatch was used and the magnesium content was 0.05% by mass in the resin content. A foamed molded article was produced by the method described above, and the same measurement was performed. The results are shown in Table 1. This comparative example did not age.

From the results shown in Table 1, the expandable polystyrene resin particles produced in Examples 1 to 8 according to the present invention were prefoamed in the state (before ripening start) in which the expandable polystyrene resin particles immediately after production were prefoamed. Although the average cell diameter in the particles was 400 μm or more, by aging the resin particles, the average cell diameter of the pre-expanded particles prepared after aging was reduced to half or less than that before aging. Thus, it was proved that the expandable polystyrene resin particles produced in Examples 1 to 8 according to the present invention can refine the bubbles of the foamed particles by aging treatment even when produced by the melt extrusion method.
Moreover, the bending strength and the compressive strength of the foam molded articles obtained in Examples 1 to 8 were good, and among them, Examples 1, 3, 4, 5, 6, 7 and 8 were extremely good.
On the other hand, in Comparative Examples 1 and 5 in which the organic compound in the present invention was not added, the average cell diameter of the pre-expanded particles prepared before and after the aging did not change at all, and the effect of refining the bubbles by aging was obtained. There wasn't.
In addition, Comparative Example 2 in which the organic compound was coated on the surface of the expandable polystyrene resin particles after granulation by the melt extrusion method without adding the organic compound at the time of granulation was also prepared before and after aging. The average cell diameter of the expanded particles did not change at all, and the effect of refining the cells by aging was not obtained.
Further, in Comparative Examples 3 and 4 in which an organic compound having an SP value outside the scope of the present invention was added in place of the organic compound of the present invention, the average cell diameter of the pre-expanded particles prepared before and after aging was also high. There was no change at all, and the effect of refining bubbles by aging was not obtained.

FIG. 2 is an enlarged image of the cross section of the pre-expanded particles produced in Example 1, (a) is pre-expanded particles obtained by pre-expanding expandable polystyrene resin particles immediately after extrusion, and (b) is expanded foam after aging. (C) is pre-expanded particles obtained by pre-expanding expandable polystyrene-based resin particles during aging.
FIG. 3 is an enlarged image of a cross section of the pre-expanded particles produced in Example 2. (a) is pre-expanded particles obtained by pre-expanding expandable polystyrene resin particles immediately after extrusion, and (b) is expanded after aging. It is a pre-foamed particle obtained by pre-foaming a functional polystyrene resin particle.
FIG. 4 is an enlarged image of a cross section of the pre-expanded particles produced in Example 6, (a) is pre-expanded particles obtained by pre-expanding expandable polystyrene resin particles immediately after extrusion, and (b) is an expanded foam after aging. (C) is pre-expanded particles obtained by pre-expanding expandable polystyrene-based resin particles during aging.
From FIG. 2 to FIG. 4, the foamable polystyrene resin particles produced in Examples 1 to 8 according to the present invention are refined by subjecting them to aging treatment even when they are produced by melt extrusion. I understand that I can do it.

  The present invention relates to an expandable polystyrene resin particle from which a polystyrene resin foam molded article excellent in mechanical strength such as bending strength and compressive strength can be obtained. The polystyrene resin foam molded article of the present invention can be used for various applications such as a heat insulating material and a buffer material.

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

Claims (15)

An expandable polystyrene resin particle containing a foaming agent composed of a hydrocarbon having 6 or less carbon atoms in the polystyrene resin particle, the organic compound having 7 or more carbon atoms in the entire expandable polystyrene resin particle (excluding internal bubbles). (Excluding polyethylene wax), and the solubility parameter (A) of the organic compound is the following formula (a) with respect to the solubility parameter (B) of the foaming agent.
((B) −0.5) ≦ (A) ≦ ((B) +1.5) (a)
Expandable polystyrene resin particles characterized by satisfying the above relationship. The organic compound has a solubility parameter (A) in which the solubility parameter (B) of the blowing agent is
(B) ≦ (A) ≦ ((B) +1.5) (b)
The expandable polystyrene resin particles according to claim 1 , which satisfy the relationship: The expandable polystyrene resin according to claim 1 or 2 , wherein the blowing agent is one or a mixture of two or more selected from the group consisting of propane, normal butane, isobutane, normal pentane, and isopentane. particle. The expandable polystyrene resin particles according to any one of claims 1 to 3 , wherein the organic compound is contained in a resin content in a range of 0.01 to 3% by mass. The average cell diameter D ₁ ′ of the expanded particles when heated to be expanded to a bulk expansion ratio X times after completion of aging is expressed by the following formula (1)
(In the formula, D ₁ represents an average cell diameter (μm) of the expanded particles converted to a bulk expansion ratio of 50 times, and D ₁ ′ represents an average cell diameter (μm) of the expanded particles when expanded to a bulk expansion ratio X times ) using a representative) an average cell diameter D ₁ of the terms the expanded beads 50 times volume expansion ratio is, any one of claims 1 to 4, characterized by satisfying the relation of 50 [mu] m ≦ D ₁ ≦ 250 [mu] m Expandable polystyrene resin particles as described in 1. 1 type or 2 types or more selected from higher fatty acid metal salts, higher fatty acid esters, higher fatty acid amides, higher fatty acid bisamides, and inorganic cell nucleating agents are uniform on the entire expandable polystyrene resin particles (excluding internal bubbles) The expandable polystyrene resin particles according to claim 1 , wherein the expandable polystyrene resin particles are contained in A foaming agent composed of a hydrocarbon having 6 or less carbon atoms is press-fitted and kneaded into a polystyrene resin melted in the resin supply device, and the foaming agent-containing molten resin is directly from a small hole of a die attached to the tip of the resin supply device. Expandable polystyrene resin by melt extrusion method that extrudes into cooling liquid and simultaneously extrudes and cuts the extrudate with a high-speed rotary blade and cools and solidifies the extrudate by contact with the liquid to obtain expandable polystyrene resin particles In the method for producing particles, the polystyrene resin has an organic compound having 7 or more carbon atoms (excluding polyethylene wax) [wherein the solubility parameter (A) of the organic compound is smaller than the solubility parameter (B) of the blowing agent) The following formula (a)
((B) −0.5) ≦ (A) ≦ ((B) +1.5) (a)
To obtain expandable polystyrene resin particles in which the organic compound is uniformly contained in the entire expandable polystyrene resin particles (excluding internal bubbles). For producing resin-based resin particles. The organic compound has a solubility parameter (A) in which the solubility parameter (B) of the blowing agent is
(B) ≦ (A) ≦ ((B) +1.5) (b)
The method for producing expandable polystyrene resin particles according to claim 7 , wherein the relationship is satisfied. The expandable polystyrene resin according to claim 7 or 8 , wherein the blowing agent is one or a mixture of two or more selected from the group consisting of propane, normal butane, isobutane, normal pentane, and isopentane. Particle manufacturing method. The method for producing expandable polystyrene resin particles according to any one of claims 7 to 9 , wherein the organic compound is added to the resin component in an amount of 0.01 to 3 parts by mass. Claim 7-10, characterized in that the expandable polystyrene resin particles obtained by melt extrusion method to obtain expandable polystyrene resin particles by performing an aging step of storing in an atmosphere of 40 ° C. or less 2. A method for producing an expandable polystyrene resin particle according to item 1. One or more kinds selected from higher fatty acid metal salts, higher fatty acid esters, higher fatty acid amides, higher fatty acid bisamides, and inorganic cell nucleating agents are added to the polystyrene resin, and the resin particles as a whole (however, the internal bubbles are The method for producing expandable polystyrene resin particles according to any one of claims 7 to 11 , characterized in that it is uniformly contained. Polystyrene resin pre-expanded particles obtained by aging the expandable polystyrene resin particles according to any one of claims 1 to 6 and then heating and pre-expanding. A polystyrene-based resin foam molded article obtained by filling the polystyrene-based resin pre-expanded particles according to claim 13 in a cavity of a mold, heating the mold with steam, and performing in-mold foam molding. The average cell diameter D ₂ ′ of the foam particles fused together in this foam molded product in the state of foam molding at the expansion factor X times is expressed by the following formula (2)
(Wherein, D ₂ represents the average cell diameter of the expanded beads of foamed molded body in terms of 50-fold expansion ratio ([mu] m), D 2 _'is foamed molded product when foamed in expansion ratio X times average cell diameter D ₂ of the average cell diameter expanded beads of the foamed molded body in terms of expansion ratio 50 times using a representative of the ([mu] m)) of the expanded particles, characterized by satisfying the relation of 50 [mu] m ≦ D ₂ ≦ 250 [mu] m The polystyrene-based resin foam molded article according to claim 14 .