JP5809508B2 - Expandable polystyrene resin particles and method for producing the same, polystyrene resin pre-expanded particles, and polystyrene resin foam molded article - Google Patents

Description

  TECHNICAL FIELD The present invention relates to an expandable polystyrene resin particle comprising a polystyrene resin particle containing a foaming agent and a method for producing the same, and an expandable polystyrene resin particle capable of being easily expanded at a high magnification by adding a plasticizer and the method for producing the same. Further, the present invention relates to a polystyrene resin pre-expanded particle and a polystyrene resin foam molded article.

As one of the methods for producing expandable polystyrene resin particles, a polystyrene resin particle is obtained by polymerizing a styrene monomer in an aqueous medium by suspension polymerization or seed polymerization, and further, the polystyrene series in an autoclave. There is known an impregnation method in which resin particles are impregnated with a foaming agent to obtain expandable polystyrene resin particles.
In addition, in a conventional impregnation method, a technique has been proposed in which polystyrene resin particles contain a plasticizer such as cyclohexane or diisobutyl adipate (see, for example, Patent Documents 1 and 2).
By containing the plasticizer in the polystyrene resin particles, the resin is easily softened, and it is possible to produce a foam with a high expansion ratio at the time of foaming, that is, to increase the magnification.

  In Patent Document 1, an aliphatic hydrocarbon or a cyclic aliphatic hydrocarbon having a boiling point lower than the softening point of the resin is contained in a resin particle made of polystyrene, a styrene copolymer or a styrene graft polymer. Expandable thermoplastic resin particles characterized by containing 1 to 15% by weight of the resin and 0.2 to 3.0% by mass of diisobutyl adipate are disclosed.

  In Patent Document 2, the residual styrene monomer is 0.1% by weight or less, the total amount of aromatic solvents is 0.2% by weight or less, and paraffins that are liquid at room temperature or esters whose boiling point is not less than 200 ° C. Styrenic expandable resin particles characterized by containing 0.1 to 5% by weight of at least one plasticizer selected from the above and a foaming agent are disclosed.

Japanese Patent No. 3292634 JP 2002-356575 A

However, the prior art has the following problems.
When a plasticizer such as diisobutyl adipate is contained in the polystyrene-based resin particles, an excellent appearance of the molded product can be obtained, but the magnification cannot be sufficiently increased. When the blending amount of the plasticizer is increased in order to increase the magnification, there is a problem that blocking at the time of pre-foaming increases, and further, surface slipping occurs at the time of foam molding.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide expandable polystyrene resin particles that can produce a foamed molded article having an excellent appearance, can be enlarged at the time of preliminary foaming, and have little blocking.

In order to achieve the above object, the present invention is an expandable polystyrene resin particle obtained by impregnating a polystyrene resin particle with a foaming agent,
A plasticizer having a boiling point of 150 ° C. or higher is contained within a range of 0.2 to 3.0 parts by mass with respect to 100 parts by mass of the resin content, and an aromatic hydrocarbon having a boiling point of 50 ° C. or higher is contained in 100 parts by mass of the resin. On the other hand, the expandable polystyrene resin particle contained in the range exceeding 0.3 mass part and 1.5 mass part is provided.

  In the expandable polystyrene resin particles of the present invention, the plasticizer is preferably an adipate ester plasticizer.

  In the expandable polystyrene resin particles of the present invention, the plasticizer is preferably diisobutyl adipate.

  In the expandable polystyrene resin particles of the present invention, the aromatic hydrocarbon is preferably one or more selected from the group consisting of toluene, xylene, benzene, ethylbenzene, and styrene.

  The expandable polystyrene resin particles of the present invention preferably further contain an aliphatic hydrocarbon having a boiling point of 50 ° C. or higher.

  In the expandable polystyrene resin particles of the present invention, the aliphatic hydrocarbon is preferably contained within a range of 0.2 to 2.0 parts by mass with respect to 100 parts by mass of the resin.

  In the expandable polystyrene resin particles of the present invention, the aliphatic hydrocarbon is preferably cyclohexane.

Further, the present invention is a production method for obtaining expandable polystyrene resin particles by impregnating polystyrene resin particles with a foaming agent,
A polystyrene resin particle is impregnated with a foaming agent together with a plasticizer having a boiling point of 150 ° C. or higher and an aromatic hydrocarbon having a boiling point of 50 ° C. or higher. Expandable polystyrene contained in the range of ~ 3.0 parts by mass and the aromatic hydrocarbon contained in the range of more than 0.3 parts by mass and up to 1.5 parts by mass with respect to 100 parts by mass of the resin Provided is a method for producing expandable polystyrene resin particles to obtain resin particles.

  In the method for producing expandable polystyrene resin particles of the present invention, the plasticizer is preferably an adipate ester plasticizer.

  In the method for producing expandable polystyrene resin particles of the present invention, the plasticizer is preferably diisobutyl adipate.

  In the method for producing expandable polystyrene resin particles of the present invention, the aromatic hydrocarbon is preferably one or more selected from the group consisting of toluene, xylene, benzene, ethylbenzene, and styrene.

  In the method for producing expandable polystyrene resin particles of the present invention, it is preferable to further include an aliphatic hydrocarbon having a boiling point of 50 ° C. or higher.

  In the method for producing expandable polystyrene resin particles of the present invention, the aliphatic hydrocarbon is preferably contained within a range of 0.2 to 2.0 parts by mass with respect to 100 parts by mass of the resin.

  In the method for producing expandable polystyrene resin particles of the present invention, the aliphatic hydrocarbon is preferably cyclohexane.

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

  The polystyrene-based resin pre-expanded particles preferably have an average cell diameter in a range of 50 to 300 μm when pre-expanded to a bulk expansion ratio of 50 times. .

  The present invention also provides a polystyrene-based resin foam molded article obtained by filling the polystyrene-based resin pre-expanded particles according to claim 24 or 25 into a cavity of a molding die and heating and molding in-mold.

  In the polystyrene-based resin foam molded article of the present invention, it is preferable that the average cell diameter in the state of being expanded to 50 times the expansion ratio is in the range of 50 to 300 μm.

The expandable polystyrene resin particles of the present invention contain a plasticizer having a boiling point of 150 ° C. or higher within a range of 0.2 to 3.0 parts by mass with respect to 100 parts by mass of the resin, and have a boiling point of 50 ° C. or higher. The amount of the pre-expanded particles obtained by heating and pre-expanding is therefore included in the range of more than 0.3 parts by weight and up to 1.5 parts by weight with respect to 100 parts by weight of the resin. The expansion ratio can be increased, and a foamed molded article having a high expansion ratio can be obtained.
In addition, it is possible to produce a foamed molded article having an excellent appearance and sufficient mechanical strength.
Furthermore, blocking during foaming is reduced.

  The method for producing expandable polystyrene resin particles of the present invention can obtain a foamed molded product having a high expansion ratio, can produce a foamed molded product having excellent appearance and sufficient mechanical strength. Expandable polystyrene resin particles with little blocking can be produced efficiently.

(Expandable polystyrene resin particles)
The expandable polystyrene resin particles of the present invention are expandable polystyrene resin particles obtained by impregnating polystyrene resin particles with a foaming agent, and a plasticizer having a boiling point of 150 ° C. or more is 100 parts by mass of the resin content. The range of the aromatic hydrocarbon contained within the range of 0.2 to 3.0 parts by mass and having a boiling point of 50 ° C. or higher exceeds 0.3 parts by mass with respect to 100 parts by mass of the resin. It is characterized by being included within.
In the present invention, the “boiling point” of a plasticizer, an aromatic hydrocarbon, or an aliphatic hydrocarbon means a boiling point under 1 atm.

  The polystyrene resin used for the expandable polystyrene resin particles of the present invention is not particularly limited. For example, styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, bromo Examples thereof include homopolymers of styrene monomers such as styrene or copolymers thereof, and polystyrene resins containing 50% by mass or more of styrene are preferable, and polystyrene is more preferable.

  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.

  Examples of the foaming agent contained in the expandable polystyrene resin particles of the present invention include aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, and neopentane, 1,1-dichloro-1-fluoroethane ( HCFC-141b), 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123), chlorodifluoromethane (HCFC-22), 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124) and other chlorofluorocarbons, 1,1-difluoroethane (HFC-152a), 1,1,1-trifluoroethane (HFC-143a), 1,1,1,2-tetrafluoroethane (HFC- 134a), fluorocarbons such as difluoromethane (HFC-32), various alcohols, carbon dioxide, water And physical blowing agents can be mentioned such as nitrogen, can be used in combination one or more of these. Among these, particularly preferable blowing agents include n-butane, isobutane, n-pentane, and isopentane. The addition amount of a foaming agent shall be the range of 1-15 mass parts with respect to 100 mass parts of polystyrene-type resins, More preferably, it shall be the range of 3-12 mass parts.

  The plasticizer having a boiling point of 150 ° C. or higher contained in the expandable polystyrene resin particles of the present invention is preferably an ester plasticizer, and among them, adipine such as diisobutyl adipate, isononyl adipate, dioctyl adipate, etc. Acid esters are more preferable, and diisobutyl adipate (DIBA) is particularly preferable. The said plasticizer may be used individually by 1 type, and may use 2 or more types together.

  Content of the said plasticizer is the range of 0.2-3 mass parts with respect to 100 mass parts of resin, and it is more preferable that it is the range of 0.3-2 mass parts. When the content of the plasticizer is less than the above range, the plasticizing effect by the plasticizer cannot be sufficiently obtained, it is difficult to obtain pre-expanded particles having a high expansion ratio, and it is lightweight and has a sufficient mechanical strength. Making it difficult to manufacture. When the content of the plasticizer is larger than the above range, the mechanical strength of the obtained foamed molded product is lowered, and the appearance of the foamed molded product may be deteriorated.

  The aromatic hydrocarbon having a boiling point of 50 ° C. or higher contained in the expandable polystyrene resin particles of the present invention is one or more selected from the group consisting of toluene, xylene, benzene, ethylbenzene, and styrene. Is preferred.

  The content of the aromatic hydrocarbon is in the range of more than 0.3 parts by mass and up to 1.5 parts by mass with respect to 100 parts by mass of the resin, and in the range of 0.35 to 1.0 parts by mass. It is preferable. When the content of the aromatic hydrocarbon is less than the above range, the appearance of the obtained foamed molded article may be deteriorated. When the content of the aromatic hydrocarbon is larger than the above range, there is a possibility that the foamed molded article may be damaged and the appearance of the foamed molded article may be deteriorated.

The expandable polystyrene resin particles of the present invention preferably further contain an aliphatic hydrocarbon having a boiling point of 50 ° C. or higher in addition to the plasticizer and the aromatic hydrocarbon. Examples of the aliphatic hydrocarbon having a boiling point of 50 ° C. or higher include linear or branched aliphatic hydrocarbons and alicyclic hydrocarbons having 6 to 12 carbon atoms, and cyclohexane is particularly preferable.
The content of the aliphatic hydrocarbon is preferably 3 parts by mass or less with respect to 100 parts by mass of the resin.

  In the foamable polystyrene resin particles of the present invention, additives such as a foam nucleating agent, a crosslinking agent, a filler, a flame retardant, a flame retardant aid, a lubricant, and a colorant are added within a range that does not impair the physical properties. In addition, if powder metal soaps such as zinc stearate are coated on the surface of the expandable styrene resin particles, the polystyrene resin pre-expanded particles may be bonded together in the pre-expanding step of the expandable polystyrene resin particles. This is preferable because the binding can be reduced.

  The particle size of the expandable polystyrene resin particles of the present invention is not particularly limited, but is usually preferably in the range of 0.5 to 3.0 mm, more preferably in the range of 0.7 to 2.0 mm. The shape of the particles is not particularly limited, but is preferably spherical or substantially spherical.

The expandable polystyrene resin particles of the present invention contain a plasticizer having a boiling point of 150 ° C. or higher within a range of 0.2 to 3.0 parts by mass with respect to 100 parts by mass of the resin, and have a boiling point of 50 ° C. or higher. The amount of the pre-expanded particles obtained by heating and pre-expanding is therefore included in the range of more than 0.3 parts by weight and up to 1.5 parts by weight with respect to 100 parts by weight of the resin. The expansion ratio can be increased, and a foamed molded article having a high expansion ratio can be obtained.
In addition, it is possible to produce a foamed molded article having an excellent appearance and sufficient mechanical strength.
Furthermore, blocking during foaming is reduced.

(Method for producing expandable polystyrene resin particles)
As the polystyrene resin particles used in the method for producing expandable polystyrene colored resin particles of the present invention, for example, polystyrene resin particles obtained by the following production methods (1) to (3) can be used.
(1) A so-called suspension polymerization method in which a polymerizable monomer having a styrene monomer as a main component is dispersed in an aqueous suspension to perform polymerization to obtain polystyrene resin particles.
(2) After the polystyrene resin seed particles are dispersed in the aqueous suspension, the polymerizable monomer mainly containing a styrene monomer is absorbed into the seed particles to perform polymerization, and the polystyrene resin So-called seed polymerization method to obtain particles,
(3) A polystyrene resin is put into an extruder and melted by heating. The foaming agent mixed resin is extruded from the small holes of a die having a large number of small holes attached to the discharge side of the extruder, and immediately after that, cut in water. A so-called melt-extrusion method (also referred to as an underwater cutting method) that obtains polystyrene-based resin particles by rapid cooling.

Examples of the styrene monomer used in the above (1) suspension polymerization method and (2) seed polymerization method include styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, bromo. The main component is a styrene monomer such as styrene, and the styrene monomer is usually contained in an amount of 50% by mass or more, preferably 80% by mass or more. Of these styrene monomers, styrene is particularly preferable.
Further, the polymerizable monomer that can be used in combination with the styrene monomer is not particularly limited as long as it is copolymerizable with the styrene monomer, and divinylbenzene, alkylene glycol dimethacrylate, acrylonitrile, methyl methacrylate, and the like. Is mentioned.

(2) When producing expandable polystyrene resin particles by the seed polymerization method, the polystyrene resin particles obtained by the suspension polymerization method are used as seed particles, or the polystyrene resin is obtained in advance by an extruder. After adjusting to the diameter, it may be used as seed particles.
(2) When seed particles are produced using an extruder in the seed polymerization method, or (3) polystyrene resins used in the melt extrusion method are commercially available ordinary polystyrene resins, suspension polymerization methods, etc. In addition to using polystyrene resins that are not recycled materials (virgin polystyrene), such as newly produced polystyrene resins by the method, use recycled materials obtained by reprocessing used polystyrene resin foam moldings. Can do. As this recycled polystyrene-based resin, used polystyrene-based resin foam molded products, for example, fish boxes, household appliance cushioning materials, food packaging trays, etc. are recovered and recycled by the limonene dissolution method or heating volume reduction method. Can be used. In addition, recycled polystyrene resins that can be used are not only those obtained by reprocessing used polystyrene resin foam moldings, but also household electrical appliances (for example, televisions, refrigerators, washing machines, air conditioners, etc.) In addition, a recycled polystyrene resin obtained by pulverizing, melt-kneading, and re-pelletizing a non-foamed polystyrene resin molded product separated and collected from office equipment (for example, a copying machine, a facsimile machine, a printer, etc.) can be used.

  In the present invention, the molecular weight of the polystyrene-based resin used is preferably 170,000 to 700,000 in terms of mass average molecular weight (Mw) by GPC method. If the molecular weight of the polystyrene-based resin is less than 170,000, the strength of the foamed molded product finally obtained is lowered, and if it exceeds 700,000, it is difficult to obtain sufficient foamability, which is not preferable.

  The polymerization initiator used in the above (1) suspension polymerization method and (2) seed polymerization method is not particularly limited as long as it is usually used in suspension polymerization of styrene. For example, a radical generating polymerization initiator is used. Can be used. Specifically, benzoyl peroxide, lauryl peroxide, t-butyl peroxide, t-butyl peroxypivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, 2,2-t-butylperoxide Organic peroxides such as oxybutane, t-butylperoxy-3,3,5-trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate, azobisisobutyronitrile, azobisdimethylvaleronitrile, etc. Of the azo compound. These polymerization initiators can be used alone or in combination of two or more.

In carrying out the (1) suspension polymerization or (2) seed polymerization, a suspending agent may be used to disperse styrene monomer droplets or seed particles in an aqueous medium. Examples of the suspending agent include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone, and poorly water-soluble inorganic compounds such as tricalcium phosphate and magnesium pyrophosphate. In addition, when using a slightly water-soluble inorganic compound, it is preferable to use an anionic surfactant together.
Examples of the anionic surfactant include fatty acid soaps, N-acyl amino acids or salts thereof, carboxylates such as alkyl ether carboxylates, alkylbenzenesulfonates, alkylnaphthalenesulfonates, dialkylsulfosuccinates, alkylsulfates. Sulfates such as acetates and α-olefin sulfonates; sulfates such as higher alcohol sulfates, secondary higher alcohol sulfates, alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates; alkyls And phosphoric acid ester salts such as ether phosphoric acid ester salts and alkyl phosphoric acid ester salts.

The polystyrene-based resin particles obtained as described above are expanded polystyrene by impregnating a foaming agent, a plasticizer, an aromatic hydrocarbon, and an aliphatic hydrocarbon or other additives added as necessary. Resin particles can be produced.
A method for impregnating a foaming agent, a plasticizer, an aromatic hydrocarbon, or the like is not particularly limited, but a method of first impregnating a polystyrene resin particle with a plasticizer and an aromatic hydrocarbon and then impregnating the foaming agent is preferable. Further, these impregnations are preferably performed in a pressure-resistant vessel such as an autoclave in the presence of an aqueous medium.

  The method for producing expandable polystyrene resin particles of the present invention can obtain a foamed molded product having a high expansion ratio, can produce a foamed molded product having excellent appearance and sufficient mechanical strength. Expandable polystyrene resin particles with little blocking can be produced efficiently.

(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 the foamed molded product to be manufactured. In the present invention, its bulk density is not limited, usually in the range of 0.010~0.10g / cm ^3, preferably in the range of 0.015~0.050g / cm ^3.

In the present invention, the bulk density of the pre-expanded particles refers to those measured in accordance with JIS K6911: 1995 “General Test Method for Thermosetting Plastics”.
<Bulk density of pre-expanded particles>
First, Wg was sampled from pre-expanded particles as a measurement sample, this measurement sample was naturally dropped into a graduated cylinder, and the volume Vcm ³ of the measurement sample dropped into the graduated cylinder was measured using an apparent density measuring instrument based on JIS K6911. The bulk density of the pre-expanded particles is measured based on the following formula.
Bulk density (g / cm ³ ) = mass of measurement sample (W) / volume of measurement sample (V)

<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 mold using a well-known apparatus and method in the field of manufacturing a foamed resin molded article, heated by steam heating or the like, and subjected to in-mold foam molding. -Based resin foam molded body (hereinafter referred to as foam molded body) is produced.
Although the density of the foamed molded article of the present invention is not particularly limited, usually in the range of 0.010~0.10g / cm ^3, preferably in the range of 0.015~0.050g / cm ^3.

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 left 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 )

[Example 1]
(Preparation of styrene polymer seed particles)
An autoclave with a stirrer having an internal volume of 100 liters (hereinafter also referred to as a reactor) 120 g of tricalcium phosphate (manufactured by Ohira Chemical Co., Ltd.), 4 g of sodium dodecylbenzenesulfonate, 140 g of benzoyl peroxide (purity 75%), t-butyl per After charging 30 g of oxy-2-ethylhexyl monocarbonate, 40 kg of ion exchange water and 40 kg of styrene monomer, the mixture was dissolved and dispersed under stirring at 100 rpm to form a suspension.
Subsequently, the temperature in the autoclave was raised to 90 ° C. while stirring the stirring blade at 100 rpm, and then held at 90 ° C. for 6 hours.
After that, the temperature inside the autoclave is further raised to 120 ° C. and held at 120 ° C. for 2 hours, then the temperature inside the autoclave is cooled to 25 ° C., the contents are taken out from the autoclave, dehydrated, dried and classified. Styrenic polymer seed particles having a diameter of 0.5 to 0.7 mm and a weight average molecular weight of 300,000 were obtained.

(Production of expandable styrene resin particles)
Next, 5.2 kg of the above styrene polymer seed particles, 19.5 kg of distilled water, 161 g of magnesium pyrophosphate, and 1.8 g of sodium dodecylbenzenesulfonate are placed in an autoclave equipped with a stirrer with an internal volume of 50 liters, stirred and suspended. It was.
Next, 2000 g of distilled water prepared in advance, 36 g of magnesium pyrophosphate, 3.6 g of sodium dodecylbenzenesulfonate and 1350 g of styrene were stirred with a homomixer to prepare a suspension, and the reactor was maintained at 72 ° C. The polystyrene particles were allowed to absorb styrene for 15 minutes.
Subsequently, 61 g of benzoyl peroxide (purity 75%) as a polymerization initiator and 26.5 g of t-butylperoxy-2-ethylhexyl monocarbonate were dissolved in 1000 g of styrene, 0.8 g of sodium dodecylbenzenesulfonate, and 2000 g of distilled water. A suspension prepared by stirring with a homomixer was added to a reactor maintained at 72 ° C.
The reactor internal temperature is maintained at 72 ° C. for 60 minutes from the start of adding the suspension containing the polymerization initiator to the reactor, and the styrene resin seed particles absorb styrene and the polymerization initiator. While continuously supplying into the reactor in 3 hours, the temperature in the reactor was continuously increased so as to reach 109 ° C. at the end of the styrene supply.
Subsequently, the temperature was raised to 120 ° C. and maintained for 60 minutes, and then distilled pyrogen 700 g of distilled water 22 g magnesium pyrophosphate, sodium dodecylbezene sulfonate 0.4 g effervescent auxiliary diester butyl adipate (boiling point: 293 ° C.) ) Add 180 g of toluene (boiling point: 110.6 ° C.) as an aromatic hydrocarbon with a boiling point of 50 ° C. or higher and 105 g of cyclohexane (boiling point: 80.7 ° C.) as an aliphatic hydrocarbon with a boiling point of 50 ° C. or higher with a homomixer. A suspension was prepared by stirring and the suspension was pressed into the reactor. Then, after cooling to 100 ° C., 2100 g of butane (isobutane: normal butane = 30: 70 (mass ratio)) as a foaming agent was injected and held at 100 ° C. for 2 hours, then cooled to 20 ° C. and taken out, Washed, dehydrated and dried. When the expandable polystyrene particles were washed, the coalesced particles that did not pass through the JIS 1000 μm sieve and the fine powdery polymer that passed through the JIS 500 μm sieve were removed, and their weights were measured. Further, the foamed styrene polymer particles having a median diameter of 0.85 mm were obtained by aging at 15 ° C. for 3 days until the bubble diameter after foaming was completely stabilized.

(Coating of expandable styrene resin particles)
5 kg of this expandable styrene polymer particle was put into a radige mixer M20 type (with an internal volume of 20 liters) manufactured by Matsuzaka Trading Co., Ltd. Subsequently, 4.5 g of zinc stearate, 3 g of 12-hydroxystearic acid triglyceride, and 2.5 g of stearic acid monoglyceride were sequentially added and stirred at 230 rpm for 3 minutes. Next, 1.5 g of polyethylene glycol having a weight average molecular weight of 300 and 1.0 g of dimethylpolysiloxane having a weight of 100 cs were added and stirred at 230 rpm for 5 minutes to coat the resin particle surfaces.

(Manufacture of pre-expanded particles)
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 0.017 g / cm ³ (bulk expansion ratio: 60 times).

(Manufacture of foam molded products)
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 0.06 to 0.10 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 Molding was performed under conditions. The foamable shape obtained had a density of 0.017 g / cm ³ (expansion factor 60 times).
The following measurements / evaluations were performed on the expandable polystyrene resin particles, the pre-expanded particles, and the foamed molded product thus produced. The results are shown in Table 1.

<Measurement of foamability>
<Measurement of foamability>
In order to examine the foamability of the obtained expandable polystyrene-based resin particles, foaming was performed in a foaming tank with steam having a foaming steam pressure of 0.01 MPa (gauge pressure). The heating time at that time was changed to 2 minutes, 5 minutes, and 10 minutes to foam, and 2 g of this foamed particle was placed in a graduated cylinder, the volume was measured, and divided by 2 g of mass to obtain the apparent expansion ratio (cm3 / g). It was.
The maximum value of the apparent expansion ratio of foaming by changing the heating time to 2 minutes, 5 minutes and 10 minutes is as follows:
Especially good when the maximum expansion ratio is 80 times or more (◎)
Excellent foaming ratio of 65 times or more and less than 80 times (○)
If the maximum expansion ratio is less than 65 times, it is defective (×)
Based on the evaluation.

<Measurement and evaluation of blocking rate during pre-foaming>
During the production of the pre-foamed particles, the resin particles are agglomerated, so-called so-called blocking particles are separated using a sieve having an opening of 10 mm, the weight is measured, and divided by the total weight of the charged, Determined as the incidence of blocking, the following criteria:
Less than 1% is particularly good (◎)
1% or more and less than 1.5% is good (○)
1.5% or more defective (×)
Based on the evaluation.

<Appearance evaluation of foam molded products>
The appearance of the foamed molded product was visually evaluated. Molding pressure 0.6k. The following evaluation criteria at 0.8k and 1.0k respectively:
Especially good when the boundary part where the foam particles on the surface of the molded product are joined is very smooth (◎)
Good when the smoothness of the boundary part where the foam particles on the surface of the molded product are joined is slightly inferior (○)
If the boundary of the foam particles on the surface of the molded product is uneven and the smoothness is inferior, or if a part of the surface of the molded product has melted, it is defective (×)
Based on this, the appearance was evaluated.
Moreover, what melt | dissolved a part of molded article surface was described in Table 1 as (token).

<Comprehensive evaluation>
The overall evaluation is a total of five evaluation criteria: foaming, appearance (three), and blocking:
There is no x and ◎ is particularly good when 3 or more (◎)
There is no x and ◎ is less than 3 good (○)
Defects with at least one × (×)
Based on the evaluation.

[Example 2]
A foamed molded article was produced in the same manner as in Example 1 except that 79 g of diisobutyl adipate, 92 g of toluene, and 79 g of cyclohexane were used in the production of the expandable styrene resin particles of Example 1, and the same measurement and evaluation were performed. Went. 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 510 g of diisobutyl adipate, 130 g of toluene, and 630 g of cyclohexane were used in the production of the expandable styrene resin particles of Example 1, and the same measurement and evaluation were performed. Went. The results are shown in Table 1. However, Example 3 is a reference example.

[Example 4]
A foamed molded article was produced in the same manner as in Example 1 except that 255 g of toluene was used and no cyclohexane was used during the production of the expandable styrenic resin particles of Example 1, and the same measurement and evaluation were performed. It was. The results are shown in Table 1. However, Example 4 is a reference example.

[Example 5]
Except that ethylbenzene (boiling point: 136 ° C.) was used instead of toluene when producing the expandable styrene resin particles of Example 1, a foamed molded article was produced in the same manner as in Example 1, and the same measurement / Evaluation was performed. The results are shown in Table 1.

[Example 6]
Except that styrene (boiling point: 145 ° C.) was used in place of toluene when producing the expandable styrene resin particles of Example 1, a foamed molded article was produced in the same manner as in Example 1, and the same measurement / Evaluation was performed. The results are shown in Table 1.

[Example 7]
Glycerin diacetomonolaurate (boiling point: 401.6 ° C., manufactured by Riken Vitamin Co., Ltd., trade name “Riquemar PL-102”) was used instead of diisobutyl adipate when producing the expandable styrene resin particles of Example 1. Except for the above, a foamed molded article was produced in the same manner as in Example 1, and the same measurement and evaluation were 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 27 g of diisobutyl adipate was used when producing the expandable styrene resin particles of Example 1, and the same measurements and evaluations were performed. The results are shown in Table 1.

[Comparative Example 2]
Except that 880 g of diisobutyl adipate was used during the production of the expandable styrene resin particles of Example 1, a foamed molded article was produced in the same manner as in Example 1, and the same measurement and evaluation were 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 55 g of toluene was used during the production of the expandable styrene-based resin particles of Example 1, and the same measurement and evaluation were 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 550 g of toluene was used when producing the expandable styrene-based resin particles of Example 1, and the same measurement and evaluation were performed. The results are shown in Table 1.

  From the results of Table 1, Examples 1 to 7 according to the present invention can increase the bulk foaming factor of the prefoamed particles obtained by heating and prefoaming, and obtain a foamed molded product having a high foaming factor. it can. In addition, it is possible to produce a foamed molded article having an excellent appearance and sufficient mechanical strength. Furthermore, blocking during foaming is reduced.

On the other hand, Comparative Example 1 in which the content of the plasticizer (diisobutyl adipate) is 0.1 parts by mass with respect to 100 parts by mass of the resin is poor in appearance when molded at a low pressure when producing a foamed molded article. It was.
Moreover, the comparative example 2 which made content of a plasticizer 3.5 mass parts with respect to 100 mass parts of resin was easy to produce blocking. In addition, when the foamed molded article was produced, a toe was generated and the appearance was poor.
In Comparative Example 3 in which the aromatic hydrocarbon content was 0.2 parts by mass with respect to 100 parts by mass of the resin, the appearance was poor when the foamed molded article was molded at a low pressure.
In Comparative Example 4 in which the aromatic hydrocarbon content was 2.0 parts by mass with respect to 100 parts by mass of the resin, the foamability was poor. In addition, when the foamed molded article was produced, a toe was generated and the appearance was poor.

  The present invention relates to a method for producing expandable polystyrene resin particles by melt extrusion, and relates to a foamable polystyrene resin particle capable of obtaining a foamed molded article having a high expansion ratio and excellent mechanical strength, a method for producing the same, and a polystyrene type The present invention relates to resin pre-expanded particles and polystyrene-based resin foam moldings.

Claims (10)

Expandable polystyrene resin particles obtained by impregnating a polystyrene resin particle with a foaming agent,
A plasticizer having a boiling point of 150 ° C. or more is contained within a range of 0.2 to 3.0 parts by mass with respect to 100 parts by mass of the resin component,
Boiling point is contained in the range up to 1.5 parts by weight of more than 0.3 parts by mass with respect to aromatic hydrocarbons over 50 ° C. 100 parts by weight resin,
In addition, expandable polystyrene resin particles containing an aliphatic hydrocarbon having a boiling point of 50 ° C. or more in a range of 0.2 to 2.0 parts by mass with respect to 100 parts by mass of the resin.   The expandable polystyrene resin particles according to claim 1, wherein the plasticizer is an adipate ester plasticizer.   The expandable polystyrene resin particles according to claim 2, wherein the plasticizer is diisobutyl adipate.   The expandable polystyrene resin particles according to any one of claims 1 to 3, wherein the aromatic hydrocarbon is one or more selected from the group consisting of toluene, xylene, benzene, ethylbenzene, and styrene. . The expandable polystyrene resin particles according to any one of claims 1 to 4, wherein the aliphatic hydrocarbon is cyclohexane. A method for producing expandable polystyrene resin particles according to any one of claims 1 to 5 , wherein polystyrene resin particles are impregnated with a foaming agent.
A plasticizer having a boiling point of 150 ° C. or higher, an aromatic hydrocarbon having a boiling point of 50 ° C. or higher, and an aliphatic hydrocarbon having a boiling point of 50 ° C. or higher is impregnated into the polystyrene resin particles together with the foaming agent, and the plasticizer 1.5 mass exceeding 0.3 parts by mass with respect but included within the scope of 0.2 to 3.0 parts by weight with respect to the resin component 100 parts by weight of 100 parts by weight before Symbol aromatic hydrocarbon resins Expandable polystyrene resin particles containing an aliphatic hydrocarbon having a boiling point of 50 ° C. or more in a range of 0.2 to 2.0 parts by mass with respect to 100 parts by mass of the resin. A method for producing expandable polystyrene resin particles.   Polystyrene resin pre-expanded particles obtained by heating and foaming the expandable polystyrene resin particles according to any one of claims 1 to 5. The polystyrene-based resin pre-expanded particles according to claim 7 , wherein an average cell diameter in a state of being pre-expanded to a bulk expansion ratio of 50 times is in a range of 50 to 300 µm. A polystyrene-based resin foam molded article obtained by filling the polystyrene-based resin pre-expanded particles according to claim 7 or 8 into a cavity of a molding die and heating and molding in-mold foam molding. 10. The polystyrene-based resin foam molded article according to claim 9 , wherein an average cell diameter in a state in which the foaming ratio is 50 times is within a range of 50 to 300 μm.