JPH09208734A - Production of foamable styrene-based resin particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the above particle excellent in appearance and mechanical strength of a molding even in using a recovered and regenerated product, capable of treating a large amount of a recovered product, by melting and blending by an extruder, extruding the melt into a heated and pressurized solution and instantly cutting the extruded material. SOLUTION: A foamable styrene-based resin particle (preferably <=0.4mm or >=1.3mm average particle diameter, <=3.5wt.% of forming agent content) obtained by suspension polymerization is introduced into an extruder, melted and blended, extruded into a solution which is heated to a temperature and pressurized to pressure under which no blended melt is expanded, preferably under 2-20kg/cm<2> at 40-100 deg.C instantly cut to provide a particle, which is retained in the pressurized solution as it is and then cooled to a temperature not to foam under normal pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing expandable styrenic resin particles, and moreover, it is difficult to sell by a regular route generated during suspension polymerization which is a general production method.
Expandable styrenic resin particles that can be reused as small particles, particles in which the blowing agent has fallen below the specified amount at the time of inventory, or scraps generated during molding processing, nonstandard products and used molded products. The present invention relates to a method for producing expandable styrenic resin particles that are regenerated as described above.

[0002]

2. Description of the Related Art Conventionally, expandable styrenic resin particles are prepared by charging monomers, a dispersant, a surfactant, etc. into a pressure vessel equipped with a stirrer and polymerizing them by the action of heat and a catalyst. It is manufactured by a so-called suspension polymerization method in which a foaming agent is impregnated. However, with this method, 0.1-2.5 mm
While it is easy to obtain particles having a wide particle size distribution of 0.4, 0.4
Particles with large and small diameters of mm or less and 1.3 mm or more have no major use, and are difficult to sell on the regular route. In addition, the expandable styrenic resin particles contain a foaming agent that easily volatilizes and dissipates inside, so it cannot be stored for a long time, and the foaming agent vaporizes during storage, making it a product that cannot be sold. It often happens. Next, the foamed molded product made by foaming and molding the expandable styrenic resin particles with water vapor is defective products and scraps generated during the molding process, and used products are discarded.
It has become a major social issue in terms of environmental protection.

Various investigations have been made on the expandable resin particles which are troubled in these treatments and the method for reusing used products. For example, expandable resin particles having large and small particle sizes generated during suspension polymerization and the stock period. A method is known in which particles that have passed through or a crushed product of a used foam-molded product is dissolved in a monomer when a new polymerization is carried out and collected.

[0004]

However, when the expandable resin particles and the foamed molded product are recovered and polymerized again as described above, the reaction rate and the dispersion stability of the suspension phase are greatly adversely affected, and the resulting foamed product is obtained. There are problems that the bubble (cell) diameter of the molded product becomes non-uniform, the appearance and product strength become poor, and it is difficult to collect a large amount at one time.

The problem to be solved by the present invention relates to a method for producing expandable styrenic resin particles which has a good appearance of a molded product even when a recovered recycled product is used, and which can process a large amount of the recovered product.

[0006]

SUMMARY OF THE INVENTION The inventor of the present invention is involved in all processes from manufacturing to molding and consumption.
In order to find an effective treatment method for the styrene-based resin that needs to be recovered, as a result of extensive research, the recovered product was melt-kneaded in an extruder, and then extruded into a heated and pressurized liquid and immediately cut, The inventors have found that the problems can be solved and completed the present invention.

That is, according to the present invention, the expandable styrene resin particles obtained by suspension polymerization are introduced into an extruder, melt-kneaded, and then heated and pressurized to a temperature and pressure at which the melt-kneaded product does not foam. The present invention relates to a method for producing expandable styrenic resin particles, which is characterized in that the particles are extruded, cut immediately, and the obtained particles are held as they are in a pressurized liquid and then cooled to a temperature at which they do not foam under normal pressure.

In the present invention, the expandable styrene-based resin particles obtained by suspension polymerization and the resin forming the crushed product of the expanded styrene-based resin molded product are resins for regeneration treatment,
It is not particularly limited, and is a mixture of styrene or a copolymer resin containing styrene as a main component, or a mixture of styrene or a copolymer resin containing styrene as a main component, and another thermoplastic resin capable of being foamed by a foaming agent. If Specifically, polystyrene, styrene-butadiene copolymer (impact-resistant polystyrene), styrene- (meth) acrylic acid copolymer, styrene-maleic anhydride,
Copolymers of styrene and maleimides typified by N-phenylmaleimide, AS resins, ABS resins, copolymers of styrene and acrylic monomers typified by methyl (meth) acrylate, styrene- Methyl methacrylate-butadiene copolymer, copolymer of styrene and ethylene, an olefin compound represented by propylene, a mixture of these resins, and vinyl chloride resin, or polyphenylene ether, polycarbonate, nylon, poly Examples include a mixture with an engineering plastic such as butylene terephthalate.

Of the above-mentioned resins for regeneration treatment, the expandable styrene-based resin particles obtained by suspension polymerization are not particularly limited as long as they can be obtained by the same production method, but the present invention is as it is. It is extremely useful in practice when regenerating unusable so-called nonstandard foamable styrenic resin particles, and it is preferable to positively use such nonstandard products.

That is, in the expandable styrenic resin particles, particles having a diameter of more than 0.4 mm and less than 1.3 mm are usually used for agricultural seafood, food packaging containers such as drinking water, cushioning materials for home appliances, and civil engineering. It is widely used as a heat insulating material for construction materials and the like, but particles with a diameter of 0.4 mm or less, or 1.3 mm or more have no definite use, and the current situation is that there is a problem in its treatment. Particles within this range are the most suitable particles for the present invention.

Next, in the present invention, a crushed product of a foamed styrene resin molded product is a foamed molded product obtained by melt-mixing a foaming agent with the above-mentioned resin or various molten mixtures and extruded, or the above resin component. Molding used for food packaging containers, cushioning materials, heat insulating materials, etc., obtained by pre-expanding expandable resin particles obtained by suspension polymerization or the extrusion method of the present application with steam, and then foam-molding in a mold It is a product that is crushed to a size that can be supplied to a resin supply port (hopper) of an extruder, such as defective products and scraps generated during molding and wastes used for various purposes.

In the present invention, the term "other styrene resin" means, for example, when a styrene resin obtained by suspension polymerization is used, styrene obtained by ordinary emulsion polymerization, solution polymerization or bulk polymerization. On the other hand, when using a crushed product of a foamed styrene resin molded product, a styrene resin obtained by ordinary emulsion polymerization, suspension polymerization, solution polymerization or bulk polymerization, which has not been subjected to molding Say. In the present invention, by using the other styrene resin in combination, the appearance or mechanical strength of the finally obtained molded product can be further improved.

Such other styrene resins are not particularly limited, and polystyrene, styrene-butadiene copolymer (impact polystyrene), styrene- (meth) acrylic acid copolymer, styrene-anhydride Maleic acid, copolymers of styrene and maleimides represented by N-phenylmaleimide, AS resins, ABS resins,
Copolymer of styrene and acrylic monomers represented by methyl (meth) acrylate, styrene-methyl methacrylate-butadiene copolymer, copolymerization of styrene and ethylene, and olefin compounds represented by propylene Examples thereof include a combination, a mixture of these resins described above, and a mixture of these with a vinyl chloride resin or an engineering plastic such as polyphenylene ether, polycarbonate, nylon, or polybutylene terephthalate.

Further, when the other styrene-based resins mentioned above deviate from the standard for their original purpose and cannot be used as they are, they can be used alone for reprocessing.

In order to obtain a foamed styrene resin molded product obtained by using the regenerated expandable styrene resin particles according to the present invention, the molded product having a good appearance and excellent strength is introduced into an extruder. It is preferable that the weight average molecular weight of the whole styrene resin is 180,000 to 400,000. That is, when the weight average molecular weight is 180,000 or more, the cells (cells) of the foam become uniform, the appearance of the molded product is good, and the strength of the molded product is improved. On the other hand, when the weight average molecular weight is 400,000 or less, the foamability becomes good. Similarly, the weight average molecular weight of the resin phase forming the finally obtained molded article is 160,000 to 350,000.
The range of 00 is preferable from the viewpoint of the appearance of the molded product and the strength of the molded product.

When a crushed product of a foamed styrene resin molded product and another styrene resin are used in combination,
The use ratio of the both is that the expandable styrene resin molded product obtained by using the regenerated expandable styrene resin particles has good appearance and strength, and further, the production cost can be reduced, and thus the expandable styrene resin is used. It is preferable that the amount of the crushed product used is 10 to 70% by weight. Further, the introduction method into the extruder is not particularly limited,
For example, a crushed product of a foamed styrene-based resin molded product is finely crushed with a dedicated crusher, and expandable styrene-based resin particles obtained by suspension polymerization or a styrene-based resin obtained by a method other than suspension polymerization After mixing with, a method of supplying to the supply port (hopper) of the extruder can be mentioned.

In the present invention, the foaming agent is a foaming agent if the styrene resin to be used is already sufficiently impregnated with the foaming agent.
Although not particularly necessary, it is usually preferable to use a foaming agent.

Examples of such a foaming agent include an aliphatic hydrocarbon-based foaming agent, a halogenated hydrocarbon-based foaming agent and the like, and those having a boiling point of 95 ° C. or less under atmospheric pressure are preferable.

Examples of the aliphatic hydrocarbon-based foaming agent include ethane, propane, propylene, normal butane,
Examples of isobutane, isobutylene, normal pentane, isopentane, neopentane, cyclopentane, hexane, cyclohexane, petroleum ether, and the like, examples of the halogenated hydrocarbon-based blowing agent include methyl chloride,
Examples thereof include ethyl chloride, dichloroethane, chloroform, fluoromethane, difluoromethane, trifluoromethane, difluoroethane, trifluoroethane, fluorochloromethane, fluorochloroethane, dichlorodifluoromethane and the like, or a mixture thereof. Among them, aliphatic hydrocarbons having 3 to 6 carbon atoms, particularly normal butane,
Isobutane, normal pentane, and isopentane are preferable because they have an appropriate boiling point, are excellent in foamability, and are excellent in fine dispersibility in the inside of particles.

The amount of the foaming agent used is not particularly limited, but is usually 20 parts by weight or less with respect to 100 parts by weight of the resin, but uniform bubbles (cell diameter) are easily obtained. It is preferably from 2 to 10 parts by weight.

Generally, the expandable styrenic resin particles are pre-expanded 40 times or more by steam, and the amount of the foaming agent remaining in the resin before foaming is 3.5.
It suffices if it is at least weight percent. Therefore, in the present invention, when the crushed resin particles, the resin and the molded product having a content of 3.5% by weight or less are used, a foaming agent is injected in the extruder to foam at 3.5% by weight or more. It is preferable to properly select the amount to be used within the above range so that the styrene-based resin particles can be obtained.

When propane, normal butane, isobutane, normal pentane, isopentane, cyclohexane or the like among the above foaming agents is used alone or in combination, an organic solvent which dissolves the resin particles at the time of impregnating the foaming agent, a so-called foaming auxiliary agent. Is preferably used. Examples of such organic solvents include aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; halogenated hydrocarbons such as ethylene dichloride, trichloroethylene and tetrachloroethylene; well-known and commonly used esters such as ethyl acetate and butyl acetate. A solvent can be mentioned.

Of these, toluene and ethylbenzene are preferable because they have excellent compatibility with the styrene resin and the foaming agent and can efficiently incorporate the foaming agent into the resin particles. The amount of these foaming aids to be used is not particularly limited, but is usually preferably 0.1 to 2 weight percent.

In the production method of the present invention, a step of introducing the above-mentioned resin component, a foaming agent, and optionally a foaming auxiliary agent into an extruder and melt-kneading (step 1), melt-kneading, and then the melt-kneaded product. A step of extruding into a liquid heated and pressurized to a temperature and a pressure at which foaming does not occur and immediately cutting into particles (step 2),
The method comprises a step (step 3) of holding the obtained particles as they are in a pressurized liquid and then cooling them to a temperature at which they do not foam under normal pressure.

First, in step 1, as a method of melt-kneading the resin and the foaming agent, for example, a method of melt-kneading the resin and the foaming agent using a melt-kneader at a melting temperature of the resin or higher, Usually, an extruder such as a single-screw extruder, a twin-screw extruder, or a tandem extruder can be used. Above all, it is easy to supply and mix a crushed product of a foamed styrene resin molded product, It is preferable to use a twin-screw extruder or a tandem-type extruder in that the foaming agent is well dispersed.

The timing of introducing the foaming agent is not particularly limited, but it is preferable that the resin is semi-molten or melted, for example, press-fitted from the middle of the extruder. The temperature at the time of melt-kneading may be any temperature as long as the resin melts, and is not particularly limited, but a temperature range of 150 to 300 ° C. is preferable from the viewpoint of more uniform mixing of the foaming agent.

Next, in step 2, the melt-kneaded product of the resin and the foaming agent is extruded into the heated and pressurized liquid from the extrusion hole of the die head attached to the tip of the melt-kneader and then immediately cut into particles. It is said that Although the die head used here is not particularly limited, for example, a diameter of 0.3 to 3 mm,
Preferable ones have extrusion holes of 0.5 to 1 mm. In addition, the cutting device for cutting after extrusion is not particularly limited, but for example, a pressure-resistant container (hereinafter referred to as "cutting") that has a cutter inside and has an inlet and a drain through which the heated and pressurized liquid filled inside can be circulated. (Hereinafter referred to as a “box”), and is fixed to the die head so that the foaming agent-containing resin extruded from the die head can be immediately cut by a cutter.

The heating and pressurizing liquid is not particularly limited as long as it can pressurize above the pressure capable of preventing foaming of the particles, and examples thereof include water, ethylene glycol, and a mixture of water and ethylene glycol. To be Of these, water is preferable because it is easy to control the temperature of the heated and pressurized liquid and is more insoluble in the resin.

The temperature condition of the heating and pressurizing liquid used here is not particularly limited as long as it is heated to the extent that the molten resin can be extruded from the die and granulated by cutting. That is, below the temperature at which the particles obtained do not aggregate after cutting, the fluidity of the resin is improved and the distortion of the particles,
It is necessary to make the orientation easy to remove, to make the cell (cell) diameter in the case of pre-expanded particles more uniform, and to heat the die head at a temperature above the temperature at which the extrusion holes are less likely to be clogged. Specifically, the temperature for forming particles in the heated and pressurized liquid is preferably in the range of 40 to 100 ° C.

The pressure condition of the heated and pressurized liquid is not particularly limited, and the pressure at which the expandable styrenic resin particles do not foam at the liquid temperature in the cutting box, that is,
Usually, the pressure is equal to or higher than the saturated vapor pressure of the foaming agent at the temperature of the heated and pressurized liquid, but specifically, it is preferably ² to ²⁰ Kg / cm ² when the heated and pressurized liquid is filled in the cutting box. . More specifically, when the blowing agent is butane, it is usually 5 Kg / cm ² or more, preferably 7 to ²
0 kg / cm ² and ² when the blowing agent is pentane
Kg / cm ² or more and preferably is 3~10Kg / cm ^2.

Next, in step 3, the particles obtained in step 2 are held in a pressurized liquid as they are, then cooled to a temperature at which atmospheric pressure does not cause foaming, and then depressurized to take out expandable styrenic resin particles. .

Specifically, the expandable styrenic resin particles cut in the cutting box are cooled under pressure. In addition, the predetermined heating and pressurizing liquid filled in the cutting box can be used in the cooling process together with the resin particles, but by circulating it in the system and using it again, continuous production becomes possible and production efficiency jumps. Improve. Subsequently, the heated and pressurized liquid containing the expandable styrenic resin particles is separated from the system and cooled batchwise or continuously to a temperature at which no foaming occurs at atmospheric pressure. The "temperature at which foaming does not occur at normal pressure" is not particularly limited, but 3
One standard is 0 ° C. After the cooling is completed, the pressure in the system is returned to normal pressure, and the expandable styrene resin particles are taken out of the system to obtain the desired expandable styrene resin particles.

In the manufacturing method of the present invention detailed above,
An example of the series of manufacturing steps will be described based on the process diagram shown in FIG. Of the two tandem type extruders connected by the connecting pipe 5, the styrene resin component was supplied to the hopper 1 of the first extruder 2 and it was observed when the styrene resin component was melted by the screw from the lines 3 and 4. The foaming agent is pressed in by a pump and sufficiently melted and kneaded by a screw having a good kneading property (step 1). Then, the molten resin kneaded with the foaming agent passes through the connecting pipe 5 and is second extruded. It moves to the machine 6 and is cooled to an optimum temperature while continuing the kneading of the foaming agent and discharged from the die head 7 having a large number of pores.

The discharged resin is cut into spherical particles by a cutter blade 8 which rotates at a high speed in a cutting box 9 which is in close contact with the die head 7, and is then converted into an excessive slurry of heating and pressurizing liquid (resin particles). / Liquid = 1/50
˜300) It is transferred to the stirrer 17 (or 19) and the first pressure vessel 16 (or the second pressure vessel 18) equipped with a jacket for temperature control.

A filter 20 (or 21) is attached to the bottom of the first pressure vessel 16 (or the second pressure vessel 18), and the resin particles and the heated and pressurized liquid are separated here (step 2). The resin particles containing the foaming agent are pressure vessels 16
(Or 18), and the strain / stress in the resin particles generated by the residual stress is reduced by being retained under the set temperature and pressure.

On the other hand, the separated heated and pressurized liquid is supplied to the valve 22.
After passing through (or 23) and passing through the filter 20 (or 21) in the pressure container 16 (or 18), the fine resin particles are further removed by the filter 27, and then the normal pressure circulation container 28 is returned to normal pressure. . This normal pressure liquid is pump 32
Temperature is controlled by the heating liquid that has been sent by the heat exchanger 31 and has passed through the heat exchanger 31, and is pressurized by the pressurizing pump 29 and supplied again to the cutting box 9 for circulation and use. The pressure of the heated and pressurized liquid is finely adjusted not only by the pressurizing pump 29 but also by the pressure adjusting liquid return valve line 30.

The resin particles stored in the pressure vessel 16 (or 18) close the valve 10 and the valve 22 [at that time, the pressure adjusting valve 12 (or 14) is opened to hold the pressure. ] After being separated from the circulating heated and pressurized liquid, it is gradually cooled by hot water, cooling water, or chiller water passed through the jacket.

Next, when the resin particles containing the foaming agent are cooled to a temperature at which they do not foam under normal pressure, the pressure relief valve 1
3 (or 15) is opened [the valve 12 (or 14) is closed at this time] After returning the pressure in the pressure vessel to normal pressure,
The temperature is set to a predetermined temperature and the aging process is started.

After the aging treatment at a predetermined temperature and time under normal pressure is completed, the expandable resin particle discharge valve 24 (or 2).
5) is opened and the mixture of the resin particles and the liquid is discharged into the sample take-out container 26. [The emptied pressure vessel 16 (or 18) is filled with warm water, pressurized to a predetermined pressure, and enters a standby state. Next, the desired expandable styrenic resin particles are obtained by drying.

The regenerated expandable styrenic resin particles thus obtained have various known modifiers such as an antiblocking agent at the time of pre-expansion on the surface of the resin particles, a molding cycle improving agent at the time of molding, and an antistatic property. Various known modifiers such as agents may be applied.

To obtain a molded product from the regenerated expandable styrenic resin particles of the present invention, a conventional method may be used, and the method is not particularly limited.
Pre-expanded particles are formed by pre-expanding by heating to a bulk ratio of 5 to 100 times by applying water vapor of 5 to 110 ° C., exposing the pre-expanded particles to the atmosphere, allowing air to penetrate into the particles, and removing water adhering to the particles. Then, the pre-expanded particles that have been subjected to this aging step are filled in a mold of a closed mold having small holes and slits, and further heated and re-foamed with steam to fuse and integrate the individual particles. A method of forming a molded body can be mentioned. The foamed styrenic resin molded product thus obtained has a good molding appearance, is excellent in product strength, and has the effect of being able to economically advantageously manufacture the expandable styrenic resin particles that are the raw material. Play.

[0042]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples.

Example 1 Pure water 2 was placed in a pressure vessel equipped with a stirrer having an internal volume of 500 liters.
00 Kg, 8 Kg of calcium phosphate as a dispersant, 200 g of sodium dodecylbenzene sulfonate, 600 g of benzoyl peroxide as a polymerization initiator, and 200 Kg of styrene monomer were charged, the stirring speed was set to 140 rpm, and the temperature was started to 90 ° C. Was polymerized.

After 6 hours, the reactor was closed, 13 kg of butane as a foaming agent was pressure-injected, the temperature was raised to 120 ° C. and kept for 2 hours, then cooled to 30 ° C., taken out from the reactor, dehydrated and dried. 0.4mm or less with a sieve, 1.3mm
The above particles were classified separately to obtain expandable styrene resin particles for regeneration treatment.

The above particles have an average particle diameter of 1.5 mm.
The weight average molecular weight of the expandable styrenic resin particles (1.3 to 1.8 mm) was 300,000 as measured by GPC (gel permeation chromatography: HLC-8020 manufactured by Tosoh Corporation). It was The amount of residual butane was measured by gas chromatography and found to be 4.5 weight percent.

100 parts by weight of the expandable styrenic resin particles are supplied and extruded from a hopper of a tandem type extruder (50φ / 65φ) consisting of a first stage extruder and a second stage extruder, and then butane 0.5. Part by weight was supplied from the injection port in the latter half of the first stage extruder, and 1.2 parts by weight of toluene was supplied from another injection port located almost at the same place as the blowing agent injection port.
Polystyrene was melt-kneaded with butane and toluene in a single-stage extruder and a second-stage extruder.

The melt-kneaded resin was passed through a die head (extrusion hole: 0.6 mmφ × 70 pieces) of a second stage extruder to obtain 60
Extruded at a rate of 45 Kg / hr into a cutter box filled with heated and pressurized water at 15 ° C. and 15 Kg / cm ² , and immediately cut with a cutter to obtain particles of about 1 mm. The produced particles were transferred to a pressure vessel by heated and pressurized water (60 ° C., 15 Kg / cm ² ) which was circulated and used at a rate of 5 m ³ / hr, and stored and held while stirring under the same conditions.

Next, the particles were cooled to 60 ° C. to 30 ° C. in water under pressure of 15 Kg / cm ² and returned to normal pressure, then the particles were taken out of the system, dehydrated and dried by a centrifugal dehydrator, Regenerated foamable styrene resin particles were obtained.

The particles thus obtained have an average particle diameter of 1.0 mm, a weight average molecular weight of 280000, a butane content of 4.5 weight percent and a toluene content of 1.1.
Weight percent. After coating the resin particles with zinc stearate, heating with steam of 0.7 Kg / cm ^{2 to} give pre-expanded particles having a bulk ratio of 63 times. After aging for about one day and night, the pre-expanded particles are filled in a closed mold. , 0.
It is heated by steam of 7 kg / cm ² to melt and press it, and it is horizontal 2
A foamed molded body of 90 × length 490 × thickness 250 (mm) was obtained, and the surface appearance of this molded article, the degree of internal fusion of the expanded particles, and the compression strength of the molded article were measured. Table 1 shows the properties of the resin mixture composition, expandable styrene resin particles, pre-expanded particles, and molded products.

The properties were measured or evaluated by the following methods. O Average particle size of expandable particles: The particle size of 100 expandable particles was measured with a dial gauge, and the average value was obtained. Content of foaming agent and foaming aid of expandable particles and organic compound having polar group: Measured by gas chromatography. Expansion ratio: The expandable resin particles were heated with steam having a gauge pressure of 0.7 Kg / cm ² to obtain pre-expanded particles, and the bulk ratio at that time was measured. ○ Internal fusion degree: The foamed molded product (plate-shaped molded product) was broken at the center and ruptured, and the total number of particles on this fracture surface and the number of ruptures inside the particle were measured, and the following formula was used. Calculated value (number of fractures inside the particle) / (number of all particles on fracture surface) × 100 Compressive strength: Measured according to JIS A9511. ○ Appearance of molded product: The smoothness of the surface of the molded product was visually evaluated.

⊚: No unevenness or voids on the surface ◯: Some voids are recognized on the surface, but there is no problem in practical use Δ: Voids are conspicuous on the surface ×: Irregularities on the surface are remarkable

Example 2 Particles obtained by suspension polymerization in Example 1 having an average particle diameter of 0.3 mm (0.1 to 0.4 mm) and a weight average molecular weight of 300,000 were stored for a long period of time. In addition, 50 parts by weight of expandable styrene resin particles having a residual butane amount of 3.0% by weight, which is a foaming agent, and 50 parts by weight of a crushed product of a foamed styrene resin molded product having a weight average molecular weight of 200,000. Regenerated expandable styrenic resin particles were produced and evaluated in the same manner as in Example 1, except that 3.5 parts by weight of butane were melt-kneaded in the extruder. The results are shown in Table 1.

Example 3 Weight average molecular weight of 350,000 obtained by continuous bulk polymerization
60 parts by weight of polystyrene resin of 0 and weight average molecular weight of 1
40,000 crushed products of expanded styrene resin moldings
Regenerated and expandable styrenic resin particles were produced and evaluated in the same manner as in Example 1 except that 5.0 parts by weight of butane was melt-kneaded with 1 part by weight in an extruder. The results are shown in Table 1.

Example 4 An average particle diameter of 0.35 mm (0.1
~ 0.4 mm), 10 parts by weight of expandable styrene resin particles having a weight average molecular weight of 300,000 and a butane content of 2.5 weight percent, and a polystyrene resin 30 having a weight average molecular weight of 350,000 obtained by a continuous bulk polymerization method. Parts by weight and 60 parts by weight of a crushed product of a foamed styrene resin molded product having a weight average molecular weight of 200,000 are melt-kneaded in an extruder,
Except for injecting 4.8 parts by weight of butane, the same operation as in Example 1 was performed to produce regenerated expandable styrene resin particles and evaluated. The results are shown in Table 1.

Example 5 Average particle size 0.3 mm (0.1 to 0.1) obtained by suspension polymerization
0.4 mm), 30 parts by weight of expandable styrene resin particles having a weight average molecular weight of 330,000 and a content of butane of 2.0% by weight, and polystyrene 70 having a weight average molecular weight of 350,000 obtained by a continuous bulk polymerization method. Regenerated expandable styrenic resin particles were produced and evaluated in the same manner as in Example 1 except that 4.5 parts by weight of butane was melt-kneaded with 4 parts by weight in an extruder. The results are shown in Table 1.

Comparative Example 1 Average particle size 1.0 mm (0.9 to 0.9) obtained by suspension polymerization.
1.3 mm), a weight average molecular weight of 300,000, and a butane content of 4.5 weight percent of expandable styrenic resin particles were directly evaluated. The results are shown in Table 1.

The expandable styrenic resin particles were ordinary commercially available suspension-polymerized particles, and the evaluation results were good. It can be said that the regenerated expandable styrenic resin particles shown in the examples are comparable to the above.

Comparative Example 2 Only a crushed product of a foamable styrene resin molded product having a weight average molecular weight of 200,000 was melt-kneaded in an extruder to give butane 5.
The same operations as in Example 1 were carried out except that 0 part by weight was injected, to produce regenerated expandable styrene resin particles and evaluate them. The results are shown in Table 1.

Since heat and shear stress are applied in the extruder, not only the molecular weight is lowered and the strength of the molded article is lowered, but also bubbles (cells) at the time of foaming become non-uniform, resulting in poor fusion,
And a phenomenon of poor appearance occurred.

Comparative Example 3 140 kg of styrene monomer and 20 wt.
60 kg of styrene foamed styrene resin molded product
Suspension polymerization was carried out in the same manner as in Example 1 except that 200 kg of this solution was dissolved, and the dispersion stability of the suspension phase was impaired, and particles aggregated during the polymerization reaction, resulting in foaming. Styrene resin particles could not be obtained.

[0061]

[Table 1]

[0062]

EFFECTS OF THE INVENTION According to the present invention, large and small particles that are difficult to sell by a regular route generated during suspension polymerization which is a general production method, particles in which the blowing agent has been scattered below a specified amount at the time of inventory, Or, when manufacturing recycled products from scraps generated during molding, nonstandard products, used molded products, etc., productivity can be significantly improved, and foamed resin molded products manufactured from the expandable styrenic resin particles obtained are , Its appearance and product strength are excellent.

[Brief description of drawings]

FIG. 1 is a process chart showing a process for continuously producing expandable styrenic resin particles of the present invention. 1: Thermoplastic resin supply port (hopper) 2: Extruder (1st) 3: Foaming agent supply line 4: Foaming auxiliary agent supply line 5: Connection pipe 6: Extruder (2nd) 7: Die head 8: Cutter Blade 9: Cutter box 10 and 11: Valve (circulating fluid line) 12 and 14: Pressure adjusting valve 13 and 15: Pressure relief valve 16: Pressure vessel (first) 17 and 19: Stirrer 18: Pressure vessel (Second) 20 and 21: Filter 22 and 23: Valve (circulating fluid line) 24 and 25: Valve (expandable resin particle discharge line) 26: Expandable resin particle sample container 27: Filter 28: Normal pressure Circulating liquid container 29: Pressurizing pump 30: Valve line for returning liquid for pressure adjustment, 31: Heat exchanger 32: Pump for supplying heating liquid

Claims (10)

[Claims] 1. An expandable styrenic resin particle obtained by suspension polymerization is introduced into an extruder, melt-kneaded, and then extruded into a liquid heated and pressurized to a temperature and pressure at which the melt-kneaded product does not foam, A method for producing expandable styrenic resin particles, which comprises immediately cutting, holding the obtained particles as they are in a pressurized liquid, and then cooling them to a temperature at which they do not foam under normal pressure. 2. The expandable styrenic resin particles obtained by suspension polymerization have an average particle size of 0.4 mm or less, or
The manufacturing method according to claim 1, which is 1.3 mm or more. 3. The method according to claim 1, wherein the expandable styrene resin particles obtained by suspension polymerization have a content of a foaming agent of 3.5% by weight or less. 4. The production method according to claim 1, 2 or 3, wherein the expandable styrene resin particles obtained by suspension polymerization are used in combination with another styrene resin. 5. A crushed product of a foamed styrene resin molding,
Introducing a foamable styrenic resin component having other styrenic resin as an essential component into an extruder, and after melt kneading, extruding into a liquid heated and pressurized to a temperature and pressure at which the melt kneaded product does not foam, and immediately A method for producing expandable styrenic resin particles, which comprises cutting, holding the obtained particles as they are in a pressurized liquid, and then cooling them to a temperature at which they do not foam under normal pressure. 6. The manufacturing method according to claim 5, wherein the compounding ratio of the pulverized product of the expandable styrene resin molded product is 10 to 70% by weight. 7. The production method according to claim 1, wherein the weight average molecular weight of the entire styrene resin introduced into the extruder is 180,000 to 400,000. 8. The weight average molecular weight of the finally obtained expandable styrenic resin particles is 160,000 to 350,000.
It is 0, The manufacturing method as described in any one of Claims 1-7. 9. The manufacturing method according to claim 1, wherein the heated and pressurized liquid is pressurized to ² to 20 kg / cm ² . 10. The manufacturing method according to claim 1, wherein the heated and pressurized liquid is heated to 40 to 100 ° C.