JP2013071995A - Foamable polystyrene-based resin particle, method for producing the same, polystyrene-based resin pre-foamed particle and polystyrene-based resin foamed compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: foamable polystyrene-based resin particles that produce a foamed compact having excellent mechanical strength and a high expansion ratio; a method for producing the same; polystyrene-based resin pre-foamed particles; and a polystyrene-based resin foamed compact.SOLUTION: The foamable polystyrene-based resin particles are obtained by a melt extrusion method in which a foaming agent is pressed into a polystyrene-based resin which is melted in a resin feeder and kneaded, and the melted resin containing the foaming agent is extruded from small holes of a die mounted on the tip of the resin feeder and formed into a particle shape. The foamable polystyrene-based resin particles contain styrene oligomers (the amount of styrene oligomers is the total amount of a styrene dimer and styrene trimer) in a range of 600-30,000 ppm in the resin.

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 can be easily expanded at a high magnification by containing a specified amount of styrene oligomers (styrene dimer and styrene trimer). The present invention relates to an expandable polystyrene resin particle and a production method thereof, a polystyrene resin pre-expanded particle, and a polystyrene resin foam molded article.

  Regarding the content of the styrene oligomer contained in the expandable polystyrene resin particles, for example, in Patent Document 1, the content of styrene dimer and styrene trimer in the resin is 450 ppm or less. Expandable polystyrene resin particles are disclosed, and a polystyrene resin bead foam container for foods characterized in that the amount of styrene dimer and styrene trimer eluted into heptane is 5 ppb or less.

JP 2000-229617 A

  However, the expandable polystyrene resin particles for food containers disclosed in Patent Document 1 have pre-expanded particles by heating the expandable polystyrene resin particles because the content of styrene oligomer in the resin is 450 ppm or less. When producing a foamed molded article by molding the pre-foamed particles in-mold by foaming, it is difficult to obtain a good foaming property. There is a problem that the wearing is worse and the strength is lowered.

  On the contrary, if the content of styrene oligomer is too high, shrinkage during pre-foaming is likely to occur, blocking is likely to occur, moldability is deteriorated (toe), heat resistance and dimensional stability are deteriorated, and odor and elution are concerned. Is done.

  The present invention has been made in view of the above circumstances, and it is an object to provide expandable polystyrene-based resin particles that can obtain pre-expanded particles having a high expansion ratio and that can produce a foamed molded article that is lightweight and has sufficient mechanical strength. Yes.

  In order to achieve the above object, the present invention provides a small hole in a die in which a foaming agent is press-fitted and kneaded into a polystyrene resin melted in a resin supply device, and a foamed agent-containing molten resin is attached to the tip of the resin supply device. Expandable polystyrene resin particles obtained by a melt extrusion method in which particles are extruded to form styrene oligomers (where styrene oligomer is the sum of styrene dimer and styrene trimer). The expandable polystyrene resin particles contained within the range are provided.

  In addition, the present invention is a method in which a foaming agent is press-fitted and kneaded into a polystyrene resin melted in a resin supply apparatus, and the foaming agent-containing molten resin is directly contained in a cooling liquid from a small hole in a die attached to the tip of the resin supply apparatus. Expandable polystyrene resin obtained by the melt extrusion method that extrudates and extrudates are cut with a high-speed rotary blade at the same time as extrusion and the extrudates are cooled and solidified by contact with a liquid to obtain expandable polystyrene resin particles There is provided an expandable polystyrene-based resin particle, in which a styrene oligomer (wherein the styrene oligomer is the sum of styrene dimer and styrene trimer) is contained in the resin in the range of 600 to 30000 ppm.

  In the expandable polystyrene resin particles of the present invention, the styrene oligomer is preferably contained in the resin in the range of 1000 to 25000 ppm, more preferably in the range of 4500 to 20000 ppm.

  In the expandable polystyrene resin particles of the present invention, it is preferable that a styrene dimer is contained in the resin in a range of 50 to 3000 ppm among the styrene oligomers.

  In the expandable polystyrene resin particles of the present invention, it is preferable that styrene trimer is contained in the resin in a range of 300 to 20000 ppm among the styrene oligomers.

  In the present invention, a polystyrene resin containing a styrene oligomer (however, a styrene oligomer is the sum of styrene dimer and styrene trimer) is melted in a resin supply apparatus by press-fitting and kneading a foaming agent. A molten resin is extruded from a small hole of a die attached to the tip of a resin supply device to form particles, and expandable polystyrene resin particles containing styrene oligomers in a range of 600 to 30000 ppm in the resin are obtained. A method for producing expandable polystyrene resin particles is provided.

  In the present invention, a polystyrene resin containing a styrene oligomer (however, a styrene oligomer is the sum of styrene dimer and styrene trimer) is melted in a resin supply apparatus by press-fitting and kneading a foaming agent. Extrude the molten resin directly into the cooling liquid from the small hole of the die attached to the tip of the resin supply device, and simultaneously extrude and cut the extrudate with a high-speed rotary blade, and cool and solidify the extrudate by contact with the liquid. Provided is a method for producing expandable polystyrene resin particles, wherein expandable polystyrene resin particles containing a styrene oligomer in a range of 600 to 30,000 ppm in a resin are obtained.

  In the method for producing expandable polystyrene resin particles of the present invention, the content of the styrene oligomer is preferably in the range of 1000 to 25000 ppm in the resin, and more preferably in the range of 4500 to 20000 ppm.

  In the method for producing expandable polystyrene resin particles of the present invention, the content of styrene dimer in the styrene oligomer is preferably in the range of 50 to 3000 ppm in the resin.

  In the method for producing expandable polystyrene resin particles of the present invention, the content of styrene trimer in the styrene oligomer is preferably in the range of 300 to 20000 ppm in the resin.

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

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

  The expandable polystyrene resin particles of the present invention are those in which a styrene oligomer (however, a styrene oligomer is the sum of styrene dimer and styrene trimer) is contained within a range of 600 to 30000 ppm in the resin. Pre-expanded particles can be obtained, and a foamed molded article having a light weight and sufficient mechanical strength can be produced.

  In the production method of expandable polystyrene resin particles of the present invention, when producing expandable polystyrene resin particles by a melt extrusion method, styrene oligomer (however, styrene oligomer is the sum of styrene dimer and styrene trimer). Since the polystyrene-based resin is used to obtain expandable polystyrene-based resin particles in which the styrene oligomer is contained within the range of 600 to 30000 ppm in the resin, it is possible to obtain pre-expanded particles having a high expansion ratio, which is lightweight. It is possible to efficiently produce expandable polystyrene resin particles capable of producing a foamed molded article having sufficient mechanical strength.

It is a block diagram which shows an example of the manufacturing apparatus of the expandable polystyrene-type resin particle by a melt extrusion method.

(Expandable polystyrene resin particles)
The expandable polystyrene resin particles of the present invention are obtained by press-fitting and kneading a foaming agent into a polystyrene resin melted in a resin supply device, and a small hole in a die provided with a foaming agent-containing molten resin at the tip of the resin supply device. Expandable polystyrene resin particles obtained by a melt extrusion method in which particles are extruded to form styrene oligomers (where styrene oligomer is the sum of styrene dimer and styrene trimer). It is characterized by being contained within the range of.

  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.

  The polystyrene resin used as a raw material is a non-recycled polystyrene resin (virgin polystyrene) such as a commercially available ordinary polystyrene resin or a polystyrene resin newly produced by a method such as suspension polymerization. In addition, a regenerated polystyrene resin obtained by regenerating a used polystyrene resin foam molded article can be used. 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.

  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, preferable foaming agents include n-butane, isobutane, n-pentane, isopentane, and a foaming agent obtained by mixing two or more thereof. 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 amount of the styrene oligomer contained in the expandable polystyrene resin particles of the present invention is in the range of 600 to 30000 ppm in the resin, preferably in the range of 1000 to 25000 ppm, and in the range of 4500 to 20000 ppm. Is more preferable, and it is still more preferable that it is the range of 7000-20000 ppm. When the styrene oligomer content is less than 600 ppm, high foamability cannot be obtained when pre-expanded particles are produced by heating the expandable polystyrene resin particles, and the pre-expanded particles are subjected to in-mold foam molding. When producing a foamed molded article, a good appearance cannot be obtained at the time of molding, resulting in poor fusion between the foamed particles and a decrease in strength. On the other hand, when the styrene oligomer content exceeds 30000 ppm, there are problems such as shrinkage at the time of preliminary foaming, blocking easily, deterioration of moldability (toe), deterioration of heat resistance and dimensional stability, odor, elution and the like. May occur.

In the expandable polystyrene resin particles of the present invention, it is preferable that a styrene dimer in the styrene oligomer is contained in a range of 50 to 3000 ppm in the resin.
In the expandable polystyrene resin particles of the present invention, it is preferable that styrene trimer is contained in the resin in a range of 300 to 20000 ppm among the styrene oligomers.

  The method for preparing the polystyrene resin containing the styrene oligomer within the above content range is not particularly limited. For example, the amount of styrene oligomer (the amount of styrene dimer and the amount of styrene trimer) in the virgin polystyrene or recycled polystyrene resin is measured. In addition, a method of forming a polystyrene resin material having a desired styrene oligomer content by combining these polystyrene resin materials in an appropriate combination is preferable.

The expandable polystyrene resin particles of the present invention preferably contain an inorganic foam nucleating agent in addition to the foaming agent. Examples of the inorganic foam nucleating agent include talc, silica, and other inorganic powders. Among these, talc is preferable.
The amount of the inorganic foam nucleating agent is preferably in the range of 0.05 to 5 parts by mass, more preferably in the range of 0.1 to 2 parts by mass with respect to 100 parts by mass of the polystyrene resin.
The average particle diameter of the inorganic foam nucleating agent to be used is preferably in the range of 0.1 to 30 μm, and more preferably in the range of 0.5 to 10 μm.
By incorporating an expandable polystyrene resin particle with an inorganic foam nucleating agent such as talc together with a plasticizer, the effect of increasing the bulk expansion ratio of the pre-expanded particles and the effect of improving the mechanical strength of the foamed molded product can be enhanced.
The inorganic foam nucleating agent needs to be uniformly contained throughout the expandable polystyrene resin particles. If the inorganic foam nucleating agent is unevenly distributed in a local part of the resin particle, for example, a surface layer part of the resin particle, the mechanical strength of the obtained foamed molded product may be lowered.

  In the foamable polystyrene resin particles of the present invention, additives such as a crosslinking agent, a plasticizer, a filler, a flame retardant, a flame retardant aid, a lubricant, and a colorant may be added within a range that does not impair the physical properties. Well, if powder metal soaps such as zinc stearate are applied on the surface of the expandable styrene resin particles, the polystyrene resin pre-expanded particles are bonded together in the pre-expanding step of the expandable polystyrene resin particles. Is preferable.

  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 are those in which a styrene oligomer (however, a styrene oligomer is the sum of styrene dimer and styrene trimer) is contained within a range of 600 to 30000 ppm in the resin. Pre-expanded particles can be obtained, and a foamed molded article having a light weight and sufficient mechanical strength can be produced.

(Method for producing expandable polystyrene resin particles)
In the method for producing expandable polystyrene resin particles of the present invention, a polystyrene resin containing a styrene oligomer is melted in a resin supply apparatus, a foaming agent is press-fitted and kneaded, and the molten resin containing the foaming agent is attached to the tip of the resin supply apparatus. It is characterized by obtaining expandable polystyrene resin particles which are extruded from the small holes of the attached die and formed into particles, and the styrene oligomer is contained in the resin in the range of 600 to 30000 ppm.
In this production method, the foaming agent-containing molten resin extruded from the small holes of the die may be immediately guided into water and cut, and directly formed into particles, or may be extruded into strands. A strand cut method may be employed in which the particles are cooled and cut after cooling to form particles.

  In the method for producing expandable polystyrene resin particles of the present invention, a polystyrene resin containing a styrene oligomer (where styrene oligomer is the sum of styrene dimer and styrene trimer) is melted with a foaming agent in a resin feeder. Press-fitted and kneaded, the foaming agent-containing molten resin is extruded directly into the cooling liquid through a small hole in the die attached to the tip of the resin supply device, and at the same time, the extrudate is cut with a high-speed rotary blade. It is preferable to manufacture by a hot cut method in which solidification is achieved by contact with a liquid to obtain expandable polystyrene resin particles in which a styrene oligomer is contained within a range of 600 to 30000 ppm in the resin.

  FIG. 1 is a configuration diagram showing an example of a production apparatus used in the method for producing expandable polystyrene resin particles of the present invention. The production apparatus of this example includes an extruder 1 as a resin supply apparatus, and an extruder 1. A die 2 having a large number of small holes attached to the tip of the resin, a raw material supply hopper 3 for introducing a resin raw material or the like into the extruder 1, and a foaming agent through the foaming agent supply port 5 to the molten resin in the extruder 1. A high pressure pump 4 to be press-fitted, a cutting chamber 7 provided so that cooling water is brought into contact with a resin discharge surface in which a small hole of the die 2 is formed, and cooling water is circulated and supplied into the chamber, and a small hole of the die 2 The cutter 6 is rotatably provided in the cutting chamber 7 so as to cut the resin extruded from the resin, and the expandable polystyrene resin particles carried along with the flow of cooling water from the cutting chamber 7 are separated from the cooling water. And dehydration Dehydration dryer 10 with a solid-liquid separation function to obtain expandable polystyrene resin particles by drying, a water tank 8 for storing cooling water separated by the dehydration dryer 10 with a solid-liquid separation function, and cooling in the water tank 8 A high-pressure pump 9 for sending water to the cutting chamber 7 and a storage container 11 for storing expandable polystyrene resin particles dehydrated and dried by a dehydration dryer 10 with a solid-liquid separation function are configured.

  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.

  In order to produce expandable polystyrene resin particles using the production apparatus shown in FIG. 1, first, desired additions such as the above-mentioned polystyrene resin as a raw material, an inorganic foam nucleating agent, and a foaming nucleating agent added as necessary. The agent is weighed and charged 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.

  After supplying polystyrene resin, inorganic foam nucleating agent and other additives 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 melted resin. Through the screen for removing foreign matter provided in the extruder 1 as necessary, the melt is further kneaded and moved to the tip side, and the foaming agent is added. The melted product 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. Extruding the melt with the blowing agent added through a small hole in the die 2 attached to the tip of the extruder 1 causes the melt to be cut into granules, and at the same time, brought into contact with cooling water and rapidly cooled to solidify while suppressing foaming. Thus, expandable polystyrene resin particles are obtained.

  The formed expandable polystyrene resin particles are transferred from the cutting chamber 7 to the dewatering dryer 10 with a solid-liquid separation function along with the flow of the cooling water, 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.

  The method for producing a polystyrene-based resin foam molded article of the present invention is to produce a styrene oligomer (where styrene oligomer is the sum of styrene dimer and styrene trimer) when producing expandable polystyrene resin particles by melt extrusion. Since the polystyrene-based resin is used to obtain expandable polystyrene-based resin particles in which the styrene oligomer is contained within the range of 600 to 30000 ppm in the resin, it is possible to obtain pre-expanded particles having a high expansion ratio, which is lightweight. It is possible to efficiently produce expandable polystyrene resin particles capable of producing a foamed molded article having sufficient mechanical strength.

(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 specimen condition adjustment and measurement specimens were cut from a sample that had passed 72 hours or more after molding, and were subjected to atmospheric conditions of 23 ° C ± 2 ° C x 50% ± 5% or 27 ° C ± 2 ° C x 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 )

  The foamed molded product of the present invention is obtained by heating and foaming the expandable polystyrene resin particles according to the present invention, and the resulting pre-foamed particles are obtained by in-mold foam molding. You can get a body. In addition, a foamed molded article that is lightweight and excellent in mechanical strength such as bending strength can be obtained.

[Example 1]
(Preparation of styrene suspension polymerized 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. Styrene suspension polymerized particles having a diameter of 0.8 to 1.2 mm and a weight average molecular weight of 300,000 (hereinafter referred to as suspension polymerized particles) were obtained.

(Manufacture of expandable polystyrene resin particles)
Using the suspension polymerization particles and the recycle raw material (1) as a base resin at a mass ratio of 70/30%, adding 0.3 parts by mass of fine powder talc to 100 parts by mass of the base resin, time After feeding into a single-screw extruder with a diameter of 90 mm at a rate of 160 kg / hr and heating and melting the resin, 6 parts by mass of isopentane was injected from the middle of the extruder as a foaming agent to 100 parts by mass of the base resin. . 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 0.4 MPa circulated, and at the same time, 10 blades in the circumferential direction. A high-speed rotating cutter having the above-mentioned structure was brought into close contact with the 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.

(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, the expandable polystyrene resin particles 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 0.06 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 obtained foamable form had a density of 0.020 g / cm ³ (foaming factor: 50 times).

<Measurement of styrene dimer and styrene trimer>
The amount of styrene dimer and styrene trimer contained in the expandable polystyrene resin particles was measured as follows.
A sample (0.2 g) is dissolved in 10 mL of methyl ethyl ketone and dropped into 40 mL of methanol to cause reprecipitation. Next, 1 mL of an internal standard solution (a solution obtained by dissolving 0.2 g of eicosane in 100 ml of methyl ethyl ketone) was added to a 50 ml eggplant flask, and the reprecipitation solution was treated with NO. Filter with 5A filter paper and make up to the internal standard solution. This was measured by GC / MC (manufactured by Shimadzu Corp., trade name GC17A), and the chromatographic quantification was performed assuming that the peak areas of three dimer peaks and five trimer peaks and the relative sensitivity of the internal standard substance were the same. (The peak of dimer and trimer was confirmed using standard materials manufactured by Kanto Chemical.)
Device: Shimadzu Corporation, product name GC17A
Column: Product name DB-1 (manufactured by J & W, 0.25 mmφ × 30 m, membrane pressure 0.1 μm)
Inlet temperature: 240 ° C
Detector (FID) temperature: 260 ° C
Carrier gas (He): Pressure 80 psi
Column temperature: 40 ° C. (1 minute) to 50 ° C./minute to 150 ° C. (1 minute) to 5 ° C./minute to 250 ° C. (3 minutes) to 50 ° C./minute to 320 ° C. (8 minutes)
After the quantitative determination by GC / MC, the content (unit: ppm) of styrene dimer and styrene trimer in the polystyrene resin was calculated. The amount of oligomer was the sum of styrene dimer and styrene trimer.

<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 8 minutes to foam, and 2 g of this foamed particle was placed in a graduated cylinder, the volume was measured, and the apparent foaming factor (cm ³ / g) was divided by 2 g of mass. Asked.
The maximum value of the apparent expansion ratio of foaming by changing the heating time to 2 minutes, 5 minutes, and 8 minutes is as follows:
Excellent (◎): The maximum foaming factor is 65 times or more and all the foaming factors in each heating time are 50 times or more. Good (○): The maximum foaming factor is 50 times or more and less than 65 times, and each heating. Slightly poor (△): foaming times over time are all 50 times or more (△): those where the maximum foaming number is 50 times or more and less than 65 times, and the foaming times in each heating time include less than 50 times (× ): Evaluated based on the maximum foaming factor of less than 50 times.

<Measurement of blocking occurrence rate during preliminary 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:
Excellent (◎): Less than 1% Good (◯): 1% or more and less than 1.5% Defect (x): Evaluation was made based on 1.5% or more.

<Appearance evaluation of foam molded products>
The appearance of the foamed molded product was visually evaluated. The following evaluation criteria:
Excellent (◎): Good when the boundary part where the foamed particles on the surface of the molded product are joined is very smooth (Good): When the smoothness of the boundary part where the foamed particle on the surface of the molded product is joined is slightly inferior (X): The appearance was evaluated based on the case where the boundary between the foamed particles on the surface of the molded product was uneven and the smoothness was poor.

<Evaluation of fusion rate>
The resulting box-shaped foamed molded article was broken by impact, and the total number of particles (A) and the number of particles broken within the particles (in an arbitrary range including 100 to 150 expanded particles on the fracture surface ( B) was counted, and the fusion rate (%) was calculated by the following formula.
Fusing rate = (B) × 100 / (A)
The following evaluation criteria:
Excellent (◎): Fusion rate of 80% or more, less than 100% Good (◯): Fusion rate of 60% or more, less than 80% Defect (x): Fusion rate was evaluated based on a fusion rate of less than 60%. .

<Comprehensive evaluation>
The overall evaluation is based on the following four evaluation criteria: foamability, blocking, overall appearance, and fusion.
Excellent (◎): No x and Δ, both ◎ are good 3 or better (○): no x, ◎ is 2 or less defective (x): Evaluation is based on at least one x.

  For the expandable polystyrene resin particles, pre-expanded particles and foam-molded product produced in Example 1, <Measurement of styrene dimer and styrene trimer>, <Measurement of foamability>, <Measurement of blocking occurrence rate during pre-expansion >, <Evaluation of appearance of foam molded product>, <Evaluation of fusion rate> and <Comprehensive evaluation> were measured and evaluated. The results are shown in Tables 1 and 2.

[Example 2]
Except that 100% of the recycled raw material (2) was used as the base resin, expandable polystyrene resin particles and foamed molded articles were produced in the same manner as in Example 1, and the same measurements and evaluations were performed. The results are shown in Tables 1 and 2.

[Example 3]
Except that 100% of the recycled raw material (3) was used as the base resin, expandable polystyrene resin particles and foamed molded products were produced in the same manner as in Example 1, and the same measurements and evaluations were performed. The results are shown in Tables 1 and 2.

[Example 4]
Expandable polystyrene resin particles in the same manner as in Example 1, except that a base resin in which the suspension polymer particles and the recycle raw material (1) were in a ratio of 10/90% was used as the base resin. A foamed molded product was produced and subjected to the same measurement and evaluation. The results are shown in Tables 1 and 2.

[Example 5]
Expandable polystyrene resin particles in the same manner as in Example 1, except that the base resin was a suspension polymer particle and a recycled raw material (1) having a mass ratio of 25/75%. A foamed molded product was produced and subjected to the same measurement and evaluation. The results are shown in Tables 1 and 2.

[Example 6]
Expandable polystyrene resin particles in the same manner as in Example 1, except that a base resin in which the suspension polymer particles and the recycled raw material (1) are in a ratio of 50/50% is used as the base resin, A foamed molded product was produced and subjected to the same measurement and evaluation. The results are shown in Tables 1 and 2.

[Example 7]
Expandable polystyrene resin particles in the same manner as in Example 1, except that a base resin in which the suspension polymer particles and the recycled raw material (1) are in a ratio of 75/25% was used as the base resin. A foamed molded product was produced and subjected to the same measurement and evaluation. The results are shown in Tables 1 and 2.

[Example 8]
Expandable polystyrene resin particles in the same manner as in Example 1, except that a base resin in which the suspension polymer particles and the recycled raw material (1) are in a ratio of 90/10% was used as the base resin, A foamed molded product was produced and subjected to the same measurement and evaluation. The results are shown in Tables 1 and 2.

[Example 9]
Manufactured expandable polystyrene resin particles and foamed moldings in the same manner as in Example 1 except that the suspension polymer particles and the recycled material (1) were used as the base resin in a mass ratio of 95/5%. Then, the same measurement / evaluation was performed. The results are shown in Tables 1 and 2.

[Example 10]
Expandable polystyrene resin particles in the same manner as in Example 1 except that a base resin in which the ratio of recycled raw material (1) and recycled raw material (2) was 50/50% was used as the base resin. Then, a foam molded article was produced, and the same measurement / evaluation was performed. The results are shown in Tables 1 and 2.

[Example 11]
Except that a commercially available polystyrene resin (“G9305” manufactured by Toyo Styrene Co., Ltd.) was used at a rate of 100% as the base resin, expandable polystyrene resin particles and foamed molded articles were produced in the same manner as in Example 1. The same measurement / evaluation was performed. The results are shown in Tables 1 and 2.

[Comparative Example 1]
Except that recycled material (1) was used as a base resin at a rate of 100%, expandable polystyrene resin particles and foamed molded articles were produced in the same manner as in Example 1, and the same measurement and evaluation were performed. It was. The results are shown in Tables 1 and 2.

[Comparative Example 2]
(Production of expandable styrene resin particles)
In an autoclave with a stirrer having an internal volume of 50 liters, 22 kg of suspension polymerized particles, 21 kg of distilled water, 80 g of magnesium pyrophosphate, 5 g of sodium dodecylbezenesulfonate were pressed into 1900 g of foaming agent and held at 100 ° C. for 2 hours. Then, it cooled to 20 degreeC, took out, wash | cleaned, spin-dry | dehydrated, and dried (AC method). 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 5 days until the bubble diameter after foaming was completely stabilized.
After the surface coating of the expandable polystyrene resin particles, expandable polystyrene resin particles and a foamed molded product were produced in the same manner as in Example 1, and the same measurement and evaluation were performed. The results are shown in Tables 1 and 2.

[Comparative Example 3]
Except that the suspension polymer particles were used at a ratio of 100% as the base resin, expandable polystyrene resin particles and expanded molded articles were produced in the same manner as in Example 1, and the same measurements were performed. The results are shown in Tables 1 and 2.

[Comparative Example 4]
Except that recycled material (4) was used as a base resin at a rate of 100%, expandable polystyrene resin particles and foamed molded articles were produced in the same manner as in Example 1, and the same measurements and evaluations were performed. It was. The results are shown in Tables 1 and 2.

  From the results of Tables 1 and 2, the expandable polystyrene resin particles of Examples 1 to 11 had an oligomer content in the range of 600 to 30000 ppm, and the overall evaluation was good or better.

On the other hand, in Comparative Example 1, the oligomer content exceeded 30000 ppm, and the evaluation of blocking and appearance was poor.
In Comparative Example 2, Comparative Example 3 and Comparative Example 4, the oligomer contents were 252 ppm, 568 ppm, 581 ppm and less than 600 pm, respectively, and the evaluations of foamability, fusion, and appearance were 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.

  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 (14)

A melt extrusion method in which a foaming agent is press-fitted and kneaded into a polystyrene resin melted in a resin supply device, and the molten resin containing the foaming agent is extruded from a small hole in a die attached to the tip of the resin supply device to form particles. Expandable polystyrene resin particles obtained by
Expandable polystyrene resin particles in which a styrene oligomer (however, a styrene oligomer is a total of a styrene dimer and a styrene trimer) is contained within a range of 600 to 30000 ppm in the resin. When a foaming agent is press-fitted and kneaded into the polystyrene resin melted in the resin supply device, the molten resin containing the foaming agent 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 a liquid to obtain expandable polystyrene resin particles, which are expandable polystyrene resin particles obtained by a melt extrusion method,
Expandable polystyrene resin particles in which a styrene oligomer (however, a styrene oligomer is a total of a styrene dimer and a styrene trimer) is contained within a range of 600 to 30000 ppm in the resin.   The expandable polystyrene resin particle according to claim 1 or 2, wherein the styrene oligomer is contained in a range of 1000 to 25000 ppm in the resin.   The expandable polystyrene resin particle according to any one of claims 1 to 3, wherein the styrene oligomer is contained within a range of 4500 to 20000 ppm in the resin.   The expandable polystyrene resin particle according to any one of claims 1 to 4, wherein a styrene dimer is contained in the resin in a range of 50 to 3000 ppm in the styrene oligomer.   The expandable polystyrene resin particle according to any one of claims 1 to 5, wherein a styrene trimer is contained in the resin in a range of 300 to 20000 ppm in the styrene oligomer.   A polystyrene resin containing styrene oligomer (however, styrene oligomer is the total of styrene dimer and styrene trimer) is melted in a resin supply device by injecting and kneading a foaming agent, and a molten resin containing the foaming agent is supplied to the resin. Expandable polystyrene resin particles obtained by extruding from a small hole of a die attached to the tip of the apparatus to form particles, and obtaining expandable polystyrene resin particles containing a styrene oligomer in a range of 600 to 30000 ppm in the resin. For producing resin-based resin particles.   A polystyrene resin containing styrene oligomer (however, styrene oligomer is the total of styrene dimer and styrene trimer) is melted in a resin supply device by injecting and kneading a foaming agent, and a molten resin containing the foaming agent is supplied to the resin. Extrude directly into the cooling liquid from a small hole in the die attached to the tip of the device, and at the same time extrude is cut with a high-speed rotary blade, and the extrudate is cooled and solidified by contact with the liquid. A method for producing expandable polystyrene resin particles, comprising obtaining expandable polystyrene resin particles contained in a range of 600 to 30,000 ppm.   The method for producing expandable polystyrene resin particles according to claim 7 or 8, wherein the content of the styrene oligomer is in the range of 1000 to 25000 ppm in the resin.   The method for producing expandable polystyrene resin particles according to any one of claims 7 to 9, wherein the content of the styrene oligomer is in the range of 4500 to 20000 ppm in the resin.   The method for producing expandable polystyrene resin particles according to any one of claims 7 to 10, wherein the content of styrene dimer in the styrene oligomer is in the range of 50 to 3000 ppm in the resin.   The method for producing expandable polystyrene resin particles according to any one of claims 7 to 11, wherein the content of styrene trimer in the styrene oligomer is in the range of 300 to 20000 ppm in the resin.   Polystyrene resin pre-expanded particles obtained by heating and foaming the expandable polystyrene resin particles according to any one of claims 1 to 6.   A polystyrene-based resin foam molded article obtained by filling the polystyrene-based resin pre-expanded particles according to claim 13 into a cavity of a molding die and heating and molding in-mold foam molding.

Images