JPH09221562A - Production of expandable thermoplastic resin particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain exactly spherical expandable resin particles which can give moldings having excellent quality by melt-kneading a thermoplastic resin and a blowing agent, extruding the melt into a heated pressurized liquid, cutting the extrudate and heating the cut extrudate in the presence of a dispersant. SOLUTION: These resin particles are produced by (1) melt-kneading a thermoplastic resin and a blowing agent at 130-300 deg.C, (2) extruding the melt from the extrusion holes of the die head into a liquid heated and pressurized to a temperature (40-100 deg.C) and a pressure (2-20kg/cm<2> ) at which the melt does not foam, instantaneously cutting the extrudate, (3) heating the obtained resin particles to 90-130 deg.C and (4) cooling the particles to a temperature not causing their foaming at ordinary temperature under a pressure of 2-30kg/cm<2> in the presence of a dispersant and/or a surfactant which function to inhibit the particles from agglomerating, decreasing the pressure to normal pressure and withdrawing the expandable resin particles.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to various packaging containers,
The present invention relates to a method for producing expandable thermoplastic resin particles which is useful in applications such as cushioning materials and heat insulating materials.

[0002]

2. Description of the Related Art Conventionally, as a method for obtaining a foamed molded article of a thermoplastic resin, for example, thermoplastic resin particles obtained by suspension polymerization are impregnated with 1 to 20% by weight of an easily volatile foaming agent to obtain foamability. A closed type in which thermoplastic resin particles are used, and after the expandable thermoplastic resin particles are heated to a softening point or higher with steam or the like to form pre-expanded particles, the interior of the pre-expanded particles can be heated with steam or the like through small holes or slits. Filling in a mold and heating with steam or the like to melt and fuse the pre-expanded particles to each other, and a multi-foamed thermoplastic molded article (hereinafter referred to as a foamed molded article) as in the closed mold. The method of doing is generally done. However, the suspension polymerization method for producing the expandable resin particles to be used for in-mold foam molding cannot obtain a uniform particle size, and it is essential to adjust the particle size by sieving, and it also hinders dispersion stability in water. In addition to the problem that production of products using additives that are subject to restrictions is extremely difficult, this method also makes it possible to recycle recovered products such as foamed molded products and expandable thermoplastic resin particles that do not reach quality standards into products. Some challenges were not possible.

Therefore, as an alternative to the thermoplastic resin particles obtained by the suspension polymerization, for example, a thermoplastic resin and a foaming agent are melt-kneaded in an extruder and pressurized to prevent foaming,
A so-called melt extrusion cutting method has been proposed in which the material is discharged into a heated liquid and cut in the liquid.

[0004]

According to this method, not only the expandable resin particles can be produced all at once from the raw material resin, but continuous production is also possible and the productivity is remarkably excellent. There is a problem in that particles are not formed into a true spherical shape due to residual marks of cutting due to mechanical cutting with a blade, uneven discharge, and swelling due to die swell. When such particles are foamed, the degree of deformation is further expanded, and finally the surface of the foamed molded product using the particles not only loses its smoothness and deteriorates in appearance, but it is also difficult to draw surface gaps. Due to the occurrence of water, there is a problem that water leakage occurs in the case of a container for fresh fish which is transported while being soaked in ice water while being weakened.

The problem to be solved by the present invention is to obtain a spherical spherical foaming heat which can provide a foamed molded article having excellent quality characteristics such as surface smoothness and fusion bondability in the melt extrusion cutting method with good productivity. It is to provide a method for producing plastic resin particles.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, after melt-kneading a foaming agent with a thermoplastic resin, a heating and pressurizing liquid under a temperature and pressure at which foaming does not occur. Discharge into, immediately cut, after further heating the obtained resin particles under pressure, and further in a heating and pressure liquid containing a dispersant and / or a surfactant that prevents aggregation of the resin particles,
The present invention has been completed by finding that a uniform pre-expanded particle and a foamed molded article excellent in quality characteristics such as surface smoothness and fusion property can be obtained by cooling and depressurizing and taking out.

That is, the present invention provides a thermoplastic resin (A) comprising:
The foaming agent (B) is melt-kneaded (step 1), and this is extruded from the die head through the thermoplastic resin (A) and the foaming agent (B).
And melt-kneaded product is discharged into a heating / pressurizing liquid heated and pressed to a temperature and pressure at which it does not foam, and immediately cut (step 2), and the obtained resin particles are under pressure and a dispersant and / or Alternatively, the present invention relates to a method for producing expandable thermoplastic resin particles, which comprises further heating in the presence of a surfactant (step 3), cooling, depressurizing and taking out (step 4).

The thermoplastic resin (A) used in the present invention is not particularly limited as long as it can be foamed with a foaming agent, and examples thereof include polystyrene and styrene-butadiene copolymer (impact-resistant polystyrene). Aromatic vinyl resins such as styrene- (meth) acrylic acid copolymers, styrene-maleic anhydride copolymers, AS resins, ABS resins, vinyl chloride resins, vinylidene chloride resins, vinyl chloride-vinyl acetate copolymers, etc. Vinyl chloride resin, olefin resin such as polyethylene and polypropylene, acrylic resin such as poly (meth) acrylate, ethyl poly (meth) acrylate, methyl methacrylate-styrene copolymer, polyethylene terephthalate, polybutylene Polyester resins such as terephthalate, polycaprolactam, hexamethylene Amide resins such as adipamide resin, polyurethane, polycarbonate, polyetherimide, alone or a mixture of polyphenylene ether and the like, among which an aromatic vinyl-based resin, preferably an olefin resin, particularly an aromatic vinyl resin is preferable.

Examples of the foaming agent (B) used in the present invention include aliphatic hydrocarbon-based foaming agents and halogenated hydrocarbon-based foaming agents, which usually have a boiling point of 95 ° C. or less under atmospheric pressure. preferable.

Examples of the above-mentioned aliphatic hydrocarbon-based foaming agents include ethane, propane, propylene, normal butane,
Isobutane, isobutylene, normal pentane, isopentane, neopentane, cyclopentane, hexane, cyclohexane, petroleum ether, and the like, and examples of the halogenated hydrocarbon-based foaming agent include methyl chloride, ethyl chloride, dichloroethane, chloroform, fluoromethane, Examples thereof include difluoromethane, trifluoromethane, difluoroethane, trifluoroethane, fluorochloromethane, fluorochloroethane, dichlorodifluoromethane and the like, alone or in a mixture. 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 foaming property, and are also excellent in fine dispersibility.

The amount of the foaming agent (B) used is not particularly limited, but is usually 20 parts by weight or less with respect to 100 parts by weight of the thermoplastic resin, and among them, there is no agglomeration of the particles and it is uniform. It is preferably from 2 to 10 parts by weight from the viewpoint that it is easy to obtain a large cell diameter.

Among the above foaming agents (B), propane,
When normal butane, isobutane, normal pentane, isopentane, cyclohexane, or the like is used alone or in combination, it is preferable to use an organic solvent that dissolves the thermoplastic resin particles at the time of impregnating the foaming agent, that is, a so-called foaming auxiliary. Examples of such foaming aids are aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; halogenated hydrocarbons such as ethylene dichloride, trichloroethylene and tetrachloroethylene; esters such as ethyl acetate and butyl acetate, which are commonly used The solvent can be mentioned.

Of these, toluene and ethylbenzene are preferable because they have excellent compatibility with the thermoplastic resin particles (A) and the foaming agent (B) and can efficiently incorporate the foaming agent into the thermoplastic resin particles.

The amount of such a foaming aid used is usually in the range of 0.1 to 2% by weight based on 100 parts by weight of the thermoplastic resin.

The production method of the present invention is to produce the target expandable thermoplastic resin particles by using the above-mentioned components as raw material components and through the following steps. That is, 1. Melt and knead the thermoplastic resin (A) and the foaming agent (B),
(Step 1) 2. 2. Extrude into a heated and pressurized liquid from an extrusion hole of a die head attached to the tip of the melt-kneading, and then cut into particles (Step 2). 3. The heating and pressurizing liquid containing the particles cut in step 2 and a dispersant and / or a surfactant is further heated under pressure to make the resin particles spherical (step 3). After cooling and depressurization, the expandable resin particles are taken out (step 4) By the above steps 1 to 4, the desired expandable thermoplastic resin particles are obtained.

More specifically, it has an extruder and a cutter arranged so as to cut the resin discharged from the die head of the extruder into particles, and has a pressure resistance sufficient to fill the heating and pressurizing liquid. A container and a storage container to which a heating / cooling jacket is attached, and using a device in which piping is installed so that the heating and pressurizing liquid can circulate between the pressure resistant container and the storage container, 1. 1. The thermoplastic resin (A) and the foaming agent (B) are introduced into an extruder and melt-kneaded (Step 1). Next, this is discharged from the extrusion hole of the die head into a pressure-resistant container filled with a heating and pressurizing liquid, and cut into resin particles in the container (step 2). While circulating the heating and pressurizing liquid between the pressure-resistant container and the storage container via a pipe, the resin particles are transferred to a storage container provided with a heating and cooling jacket, and then, in the storage container, a dispersant. And / or further heating the obtained particles in the presence of a surfactant, (step 3) 4. Next, the pressure is returned to a temperature at which foaming does not occur at normal pressure, the pressure is returned to normal pressure, and then the particles are taken out (step 4). It is preferable because continuous production is possible and productivity is remarkably improved.

Each step will be described in detail below. Step 1
In order to melt-knead the thermoplastic resin (A) and the foaming agent (B), for example, the thermoplastic resin (A) and the foaming agent (B) are melted and kneaded at a temperature not lower than the melting temperature of (A) by using an extruder. The method of melt-kneading may be mentioned. As the extruder, an extruder such as a single-screw extruder, a twin-screw extruder or a tandem type extruder is usually used. A static mixer can also be used as another extruder. For example, as an example of using a static mixer, a melted thermoplastic resin obtained by a continuous bulk or solution polymerization method is used to remove unreacted monomers and solvents in a devolatilization tank after completion of polymerization. A method in which a foaming agent is mixed with various additives in a static mixer attached via a gear pump and melt-kneaded.

The time of introduction of the foaming agent is not particularly limited, but when the thermoplastic resin is semi-molten or melted, for example, from the middle of the extruder, or when using a static mixer, press-fit from the inlet. It is preferable. The temperature of melt kneading is not particularly limited as long as it is a temperature at which the thermoplastic resin (A) is melted,
130 to 30 from the point that the foaming agent (B) is more uniformly mixed
A temperature range of 0 ° C. is preferred.

Next, in step 2, the thermoplastic resin (A)
The melt-kneaded product of the foaming agent (B) and the foaming agent (B) is discharged into the heating and pressurizing liquid from the extrusion hole of the die head attached to the tip of the melt-kneading machine, and then cut into particles. The die head used here is not particularly limited, but for example, a die head having an extrusion hole with a diameter of 0.3 to 3 mm, preferably 0.5 to 1.5 mm can be mentioned. The cutting device for cutting after extrusion is not particularly limited, but has, for example, a cutter inside, and an inlet port and a drain port through which the heated and pressurized liquid filled inside can be circulated with the storage container through the pipe. Pressure resistant container (hereinafter referred to as "cutting box")
And is fixed to the die head so that the foaming agent-containing thermoplastic resin extruded from the die head can be immediately cut with a cutter.

The heating and pressurizing liquid is not particularly limited as long as it can pressurize at a pressure higher than that capable of preventing foaming of the particles, and examples thereof include water, glycol, ethylene glycol, and a mixture of water and ethylene glycol. Can be mentioned. Of these, water heated and pressurized 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 such an extent that the molten resin can be extruded from the die and can be granulated by cutting. The range of 40-100 degreeC is preferable. More specifically, for example, the thermoplastic resin (A)
Is a styrene-based resin and the foaming agent (B) is butane (including various isomers of normal butane) or pentane (including various isomers of normal pentane), particles are formed in a heated and pressurized liquid. The temperature is preferably in the range of 50 to 85 ° C.

The pressure condition of the heated and pressurized liquid is not particularly limited, and the pressure at which the expandable thermoplastic resin particles do not foam at the liquid temperature in the cutting box, that is, the foaming at the temperature of the normally heated and pressurized liquid. It may be a pressure equal to or higher than the saturated vapor pressure of the agent, but specifically, it is 2 to 20 Kg / cm when the cutting box is filled with the heated and pressurized liquid.
It is preferably 2.

The step 3 is a step for making the thermoplastic resin particles obtained in the step 2 into a spherical shape, in which the resin particles obtained by cutting are in a pipe or in a storage container. Although heating is carried out while stirring inside, it is preferable to carry out heat treatment after transferring to a storage container from the viewpoint of shape uniformity. Further, in the heat treatment of the heated and pressurized liquid in step 3,
As described above, a dispersant and / or a surfactant is used to prevent the particles from aggregating, which may be pre-existed in the cutting box in step 2,
From the viewpoint of easiness of post-treatment and productivity, it is preferable to transfer the resin particles obtained in step 2 to a storage container, add a dispersant and / or a surfactant under pressure, and then heat.

The dispersant is not particularly limited, and examples of the organic compound include partially saponified polyvinyl alcohol, polyacrylic acid salts, polyvinylpyrrolidone, carboxymethylcellulose, and methylcellulose. As the compound, calcium,
Examples thereof include phosphates such as magnesium and barium, carbonates, sulfates, magnesium oxide, and bentonite. The following surfactants are generally used in combination with these, but they may not be added unless aggregation occurs.

The surfactant used herein is not particularly limited, and examples thereof include sodium alkylbenzene sulfonate, sodium C6 to C12 α-olefin sulfonate, sodium oleate and sodium laurate. .

In order to prevent the resin particles in the heated and pressurized liquid from aggregating and stabilizing the dispersion in the step 3, a pH adjusting agent, an electrolyte compound or the like can be used. For example, caustic soda, sodium chloride, sodium sulfate and the like can be used. Can be mentioned.
These can be used in combination with the above-mentioned dispersants.

In step 3, the heated and pressurized liquid containing the resin particles is further heated with the dispersant and / or the surfactant added, but the temperature condition is such that the resin containing the foaming agent and various additives is softened. The optimum value may be appropriately determined depending on the temperature and the melt viscosity. Higher temperatures are desirable in order to complete spheroidization and shorten the treatment time, but treatment at higher than appropriate temperatures tends to lead to particle agglomeration. In consideration of such various effects and restrictions, 90 to 130
C. is preferred. Further, the liquid pressure condition of the heated and pressurized liquid may be a pressure at which the expandable thermoplastic resin particles do not foam during the spheroidizing treatment, but it is preferably, for example, 2 to 30 kg / cm 2. The time required to maintain the post-heating temperature required for the spheroidizing treatment under such conditions varies depending on the softening temperature of the expandable resin particles, the temperature of the heating / pressurizing liquid, and the effect of stirring, but after the heating, it is 5 to 300. It is preferably for minutes.

The abundance ratio of the resin particles and the heating / pressurizing liquid in the above steps 2 and 3 is not particularly limited, but in the step 2, the heating / pressurizing liquid is excessive with respect to the expandable resin particles. Amount, specifically, the range of expandable resin particles / heating and pressurizing liquid (weight ratio) = 1/50 to 1/300 is preferable from the viewpoint of preventing aggregation of particles and stability during transfer in a pipe. On the other hand, in step 3, the resin particles and the liquid are separated before the transfer to the storage container, and, for example, the expandable resin particles /
Increasing the concentration of resin particles in the range of heating and pressurizing liquid = 1/1 to 1/3 (weight ratio) is effective for treating waste liquid containing a dispersant and for slurry (a mixture of resin particles and heating and pressurizing liquid). It is preferable in terms of temperature rising and cooling rate. Then, it is preferable in terms of production efficiency to return the separated heated and pressurized liquid to the cutting box and circulate it for continuous production.

Subsequently, in step 4, the heating and pressurizing liquid containing the expandable thermoplastic resin particles, which has been treated in step 3, is separated from the system and batchwise or continuously until the temperature at which no foaming occurs at atmospheric pressure. , Cooled under pressure. The "temperature at which foaming does not occur at normal pressure" is not particularly limited, but is 30 ° C.
Is one guide. After the cooling is completed, the pressure in the system is returned to normal pressure, the expandable thermoplastic resin particles are taken out of the system, and a series of manufacturing operations are completed. Also in this case, it is preferable that the liquid separated from the expandable resin particles is recycled to the cutting box and reused.

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 thermoplastic resin component is supplied to the hopper 1 of the first extruder 2, and when the screw melts, it is possible to check the melting time 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 that 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 first storage container 16 (or second storage container 18) equipped with a stirrer 17 (or 19) and a jacket for temperature control.

A filter 20 (or 21) is attached to the bottom of the first storage container 16 (or the second storage container 18), and the resin particles and the heated and pressurized liquid are separated here (step 2). The resin particles containing the foaming agent are stored in the storage container 16
(Or 18).

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 storage 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 storage container 16 (or 18) close the valve 10 and the valve 22 [at that time, the pressure adjusting valve 12 (or 14) is opened to maintain the pressure). ] After being separated from the circulating heating and pressurizing liquid, a dispersant or a surfactant is press-fitted and the temperature is raised to a set temperature, which is then held for a predetermined time and subjected to a spheroidizing treatment. After the treatment, it is gradually cooled with warm 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 target expandable thermoplastic resin particles are obtained by drying.

The spherical spherical expandable thermoplastic resin particles thus obtained are various known modifiers such as an antiblocking agent at the time of prefoaming 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.

The process from the spherical spherical expandable thermoplastic resin particles obtained in the present invention to obtaining a molded product may be a conventional method and is not particularly limited. Apply steam at 110 ° C to obtain a bulk ratio of 5
Heat-expanded 100 times to form pre-expanded particles, exposing the pre-expanded particles to the atmosphere, allowing air to penetrate into the particles, and removing moisture adhering to the particles, and then subjecting the pre-expanded particles to a small hole. A method can be mentioned in which a molded body in which individual particles are fused and integrated is filled by filling the inside of a closed mold having slits or slits and then re-foaming by heating with steam. The expandable thermoplastic resin molded body thus obtained has a good molding appearance and is excellent in product strength, and moreover, the expandable thermoplastic resin particles as a raw material are efficiently and economically advantageous. The effect of being able to manufacture is produced.

[0039]

The present invention will be specifically described below with reference to examples and comparative examples.

Example 1 First, 100 parts of polystyrene (weight average molecular weight 280,000)
Tandem type extruder consisting of single-stage extruder and second-stage extruder (first-stage extruder: 50 mm diameter screw, L / D = 28, second
Stage extruder: 65 mm screw, L / D = 28) supplied from the hopper to extrude, and then 5.0 parts by weight of butane is the first
It was supplied from the injection port in the latter half of the single-stage extruder, and 1.6 parts by weight of cyclohexane was supplied from another injection port located almost at the same place as the foaming agent injection port, and polystyrene was mixed in the first-stage extruder and the second-stage extruder. Butane and cyclohexane were melt-kneaded. At this time, the set temperature of the extruder was 240 ° C. in the first half of the extruder and 150 ° C. just before the die part.

The melt-kneaded resin was passed through a die head (extrusion hole: 0.5 mmφ × 100 pieces) of a second stage extruder to obtain 6
Filled with heated and pressurized water at 0 ° C., 10 Kg / cm 2 with 0.25% by weight of tricalcium phosphate as a dispersant and 8 ppm of sodium dialkyldiphenylsulfonate as a surfactant (both relative to water + resin amount). Ratio of 50 kg / Hr in the cutter box (resin particles /
The mixture was extruded with a heating / pressurizing liquid ratio = 1/500 weight ratio) and immediately cut in water with a cutter to obtain 1.0 mm expandable resin particles.

The produced particles are transferred to a storage vessel equipped with a stirrer with heated and pressurized water (60 ° C., 10 Kg / cm 2) at a rate of 5 m 3 / Hr. The heated and pressurized liquid is separated from the resin particles by a filter provided at the bottom of the container, and is circulated and used. At a time when a certain amount of resin particles were stored in the pressure vessel (resin particle / heating / pressurizing liquid ratio = 1/1 weight ratio), the system was separated from the system and this slurry (mixture of resin particles and heating / pressurizing liquid) was removed. After raising the pressure to 15 Kg / cm 2, the mixture was heated to 120 ° C. and stirred for 0.5 hour. The particles cut in the cutting box during the spheroidizing process are transferred and stored in another pressure vessel.

After the spheroidizing treatment was completed, the slurry was cooled to 40 ° C. under pressure (15 Kg / cm 2) to return the pressure inside the container to normal pressure, then the particles were taken out, dehydrated and dried by a centrifuge. , Expandable polystyrene resin particles were obtained.

The particles thus obtained were perfectly spherical, the butane content was 4.5% by weight, and cyclohexane was 1.5% by weight. Further, no aggregation of the resin particles occurred during the spheroidizing treatment. After coating these resin particles with zinc stearate, heat with steam to make pre-expanded particles with a bulk ratio of 60 times, and after aging for about one day and night, fill the pre-expanded particles in a closed mold and heat with steam to melt and press-bond. Then, a foamed molded product having a width of 290 × a length of 490 × a thickness of 25 (mm) was obtained, and the surface smoothness of this molded product, the fusion rate of the foamed particles, and the like were measured. The properties of expandable polystyrene resin particles, pre-expanded particles, and molded products are shown in the table.

The properties were measured or evaluated by the following methods. 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 in expandable particles: Measured by gas chromatography. Expansion ratio of pre-expanded particles: Heated with steam having a gauge pressure of 1 Kg / cm @ 2 to obtain pre-expanded particles having a bulk ratio of about 60 times. Appearance of molded product: The smoothness of the surface of the molded product was visually evaluated.

⊚: No irregularities or voids on the surface. ◯: There are some voids on the surface, but there is no problem in practical use.

Δ: Voids are conspicuous on the surface. X: The surface has remarkable irregularities. Fusing rate: The foamed molded product (plate-shaped molded product) was broken at the center and fractured, and the total number of particles on this fracture surface and the number of fractures inside the particle were measured and calculated by the following formula .

(Number of fractures inside the particles) / (Number of all particles on the fracture surface) × 100 Water leakage: Water was applied to the box-shaped molded product (290 × 490 × 25 mm), and after 1 week, water was added. The presence or absence of leakage was visually determined. Spheroidization: The shape of the expandable resin particles was visually determined.

◯: Spherical ×: Flat rectangular parallelepiped Presence / absence of particle aggregation: The shape of the expandable resin particles was visually determined.

Example 2 In order to prevent agglomeration of resin particles, a dispersant and a surfactant were added to the storage container for spheroidizing treatment (step 3) separated from the system (melt-kneaded resin). Except that it is not added to the heated and pressurized liquid used in the step 2 of cutting
By performing the same operation as in Example 1, spherical expandable styrene resin particles were produced and evaluated. The results are shown in Table 1.

Example 3 Addition amount of butane was 3.5% by weight, a dispersant and a surfactant were added to a pressure vessel for spheroidization treatment, and the spheroidization treatment temperature
Except that the time was 120 ° C. and 1 hour, the same operation as in Example 1 was performed to produce and evaluate the true spherical expandable styrene resin particles. The results are shown in Table 1.

Example 4 Styrene-methacrylic acid copolymer resin (methacrylic acid content of 10% by weight), which is a transparent and heat-resistant resin, is used as the thermoplastic resin.
And the same operation as in Example 2 except that the temperature of the heated and pressurized liquid for cutting the resin particles is 80 ° C. (step 2) and the spheroidizing treatment (step 3) is 120 ° C. for 2 hours. hand,
The spherical heat-resistant expandable styrene resin particles were manufactured and evaluated. The results are shown in Table 1.

Comparative Example 1 Expandable styrene resin particles were produced and evaluated in the same manner as in Example 1 except that the temperature rising in the storage container and the spheroidizing treatment (step 3) were not performed. . The results are shown in the table.

Comparative Example 2 A foamable styrene resin was prepared in the same manner as in Example 1 except that the spheroidizing treatment (step 3) was carried out at 120 ° C. for 2 hours without adding a dispersant and a surfactant. An attempt was made to make particles, but the particles clumped together and no product was obtained.

[0055]

[Table 1] (In Table 1, the surfactant is sodium dedecyl diphenyl ether disulfonate and the SMAA resin is a styrene-methacrylic acid copolymer resin.)

[0056]

According to the present invention, the spherical expandable thermoplastic resin particles can be obtained while using the melt extrusion cutting method which is excellent in productivity.

Therefore, the foamed molded product obtained by using the expandable thermoplastic resin particles obtained in the present invention has excellent quality characteristics such as surface smoothness and fusion property.

[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 release valve 16: Storage container (first) 17 and 19: Stirrer 18: Storage container (Second) 20 and 21: Filter 22 and 23: Valve (circulating fluid line) 24 and 25: Valve (expandable resin particle discharge line) 26: Expandable thermoplastic resin particle sample extraction container 27: Filter 28: Normal pressure circulating liquid container 29: Pressurizing pump 30: Pressure adjusting liquid return valve line, 31: Heat exchanger 32: Heating liquid supply pump

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Claims (10)

[Claims] 1. A thermoplastic resin (A) and a foaming agent (B) are melted and kneaded (step 1), and the thermoplastic resin (A) and the foaming agent (B) are extruded through an extrusion hole of a die head. The melted and kneaded product is discharged into a heated and pressurized liquid which is heated and pressurized to a temperature and pressure at which the resin is not cut (step 2), and the obtained resin particles are under pressure, and the dispersant and / or the interface are added. A method for producing expandable thermoplastic resin particles, which comprises heating (step 3) in the presence of an activator, cooling, depressurizing and taking out (step 4). 2. A pressure-resistant container having an extruder, a cutter arranged so as to cut the resin discharged from the die head of the extruder into particles, and a pressure vessel filled with a heating and pressurizing liquid, and heating. A storage container having a cooling jacket attached thereto, and a device in which a pipe is installed so that the heated and pressurized liquid can circulate between the pressure resistant container and the storage container, and a thermoplastic resin ( A) and the foaming agent (B) are introduced into the extruder and melt-kneaded (step 1), and then the mixture is discharged from the extrusion hole of the die head into the pressure vessel filled with the heating and pressurizing liquid, The resin particles are cut into resin particles (step 2) in the container, and then the resin particles are fitted with a heating / cooling jacket while circulating the heating / pressurizing liquid between the pressure resistant container and the storage container through a pipe. To the storage container, and then in the storage container In, the obtained particles are further heated in the presence of a dispersant and / or a surfactant (step 3), and then cooled to a temperature at which atmospheric pressure does not cause foaming, the pressure is returned to atmospheric pressure, and then the particles are taken out. (Step 4) The manufacturing method according to claim 1. 3. The production method according to claim 2, wherein in step 3, after the resin particles are transferred to the storage container, a dispersant or a surfactant is introduced into the storage container and then heating is performed. 4. The heating and pressurizing liquid in the step 2 is 2 to 20.
The production method according to claim 1, 2 or 3, wherein the pressure is Kg / cm ² . 5. The heating and pressurizing liquid in the step 2 is 40 to 1
It is what was heated at 00 degreeC, 1, 2, 3 or 4.
The manufacturing method as described. 6. The manufacturing method according to claim 1, wherein in step 3, the temperature is raised to 90 to 130 ° C., the temperature is maintained as it is, and the spheroidizing treatment is performed. 7. The heating and holding in step 3 is 2 to
The production method according to claim 6, which is carried out under a pressure condition of 30 kg / cm ² . 8. A thermoplastic resin (A) in step 1,
The manufacturing method according to any one of claims 1 to 7, wherein the melt-kneading with the foaming agent (B) is performed in a temperature range of 130 to 300 ° C. 9. The cooling in step 4 is carried out from the temperature of the heating and pressurizing liquid in the storage container in step 3 to a temperature at which the expandable thermoplastic resin particles do not foam at atmospheric pressure and a temperature of 40 ° C. or less. Item 9. The manufacturing method according to any one of items 1 to 8. 10. The production method according to claim 1, wherein the thermoplastic resin (A) is an aromatic vinyl resin.