JPH10176005A - Production of styrene-based resin particle and foamable styrene-based resin particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain both a styrene-based resin particle having fixed particle diameters in high recovery ratio and a foamable styrene based resin particle without any trouble in productivity, by subjecting specific plural dispersions to suspension polymerization. SOLUTION: (B) A dispersion obtained by finely dispersing (iv) a styrene- based monomer to an aqueous medium is added to (A) a dispersion obtained by finely dispersing (iii) a styrene-based monomer having very small particle diameters to an aqueous medium containing (i) a slightly water-soluble inorganic salt and (ii) a surfactant, and the mixture is subjected to suspension polymerization. Preferably, the amounts of the components (i) and (ii) are 0.2-3.0 pts.wt. and 0.003-0.05 pt.wt. based on 100 pts.wt. of the component (iii), respectively, the particle diameters of the component (iii) are smaller than those of finally prepared styrene-based resin particles and are <=0.8mm and the particle diameters of oil drops of the component (iv) dispersed in the component B is <= the particle diameters of the component (iii).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing styrene resin particles and expandable styrene resin particles.
More specifically, the present invention relates to a method capable of producing styrene-based resin particles and expandable styrene-based resin particles having a desired particle diameter at a high recovery rate.

[0002]

2. Description of the Related Art As a method for producing styrene resin particles, a method has conventionally been employed in which a styrene monomer is subjected to suspension polymerization in an aqueous medium containing an organic or inorganic dispersant.

[0003] The desired particle size of the styrene-based resin particles differs depending on the application, but in the above-mentioned suspension polymerization method, the type and amount of the dispersant added to the aqueous medium and the stirring conditions are appropriately selected to produce the styrene-based resin particles. By adjusting the particle size of the resin particles used, the ratio of the particle size of the product is increased. However, since the resin particles to be produced have a distribution in particle size, large and small unnecessary particles that deviate from the product particle size are generated.
Product recovery was necessarily reduced. These unnecessary particles are rarely used as a product, and the product value is significantly reduced. Therefore, a method has been adopted in which unnecessary small resin particles are reused as raw materials when manufacturing new resin particles. ing. This method is described in JP-B-46-29.
As disclosed in JP-A-87-87, after unnecessary styrene resin particles having an unnecessary small particle size are dispersed in an aqueous medium, a styrene monomer is impregnated, and the particle size is increased to a desired particle size. It is intended to be commercialized as resin particles by polymerization. According to this method, unnecessary resin particles can be reused, and if the particle size distribution of the resin particles used as a raw material is kept within a certain range, the particle size distribution after synthesis is theoretically extremely sharp, and Therefore, the recovery rate of the resin having the particle diameter becomes high, which should be very effective. However, in actual polymerization, a plurality of resin particles that have absorbed the styrene monomer at the time of the addition of the styrene monomer stick, plasticize, and coalesce. There is a problem that excessive particles are generated and a recovery rate of a resin having a particle diameter as a product is impaired, and a technology for preventing generation of excessive particles is required.

As a technique for preventing the generation of excessive particles, as disclosed in JP-B-49-19109, styrene-based resin particles 1 among styrene-based monomers used are disclosed.
An amount equivalent to at least 3 parts by weight with respect to 00 parts by weight is made into a fine suspension with water and an emulsifier, and this suspension is added in advance to an aqueous medium in which styrene resin particles are dispersed.
Further, there is a method in which the remaining styrene monomer and a polymerization initiator are added to cause polymerization. In this method, at least 3 parts by weight of a styrene-based monomer to be added first is finely dispersed in a dispersion liquid containing an emulsifier, and the dispersion is added. A method of uniformly dispersing a water-insoluble inorganic salt suspending agent attached to the body onto the resin particle surface to prevent multiple resin particles from sticking, plasticizing, and coalescing. This is effective when relatively large resin particles exceeding the above are used.

However, in recent years, in the field of expandable polystyrene in which styrene-based resin particles are mainly used, the filling property of a mold is high in order to improve the appearance of a molded product or to produce a thin molded product. There is an increasing demand for resin particles having a small particle size of about 0.6 to 0.8 mm or less. However, according to the method disclosed in Japanese Patent Publication No. 49-19109, when the resin particles used as the raw material have a particle diameter of 0.8 mm or less, a large amount of excessive particles generated by sticking, plasticizing, and coalescing of a plurality of resin particles are generated. In addition, there is a disadvantage that the recovery rate of resin particles as a product is significantly reduced. In order to remedy these drawbacks, Japanese Patent Application Laid-Open No. Hei 3-275739 discloses that a styrene-based monomer dispersed below the styrene-based resin particle size is dispersed in an aqueous medium in which styrene-based resin particles having a small particle size are dispersed. The suspension polymerization is carried out by addition. According to this method, even when the diameter of the resin particles as the raw material is relatively small, desired resin particles can be obtained at a higher recovery rate than the above-mentioned method. However, in this method, the dispersion stability is not sufficient depending on the polymerization temperature, and the recovery rate of the resin particles is reduced. In addition, since the dispersion stability is not sufficient, the adhesion of the polymer to the inner wall of the polymerization vessel and the stirring blade is not achieved. This was not a good method of resin recovery.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and provides a styrene-based resin particle and an expandable styrene-based resin particle having a desired particle size at a high recovery rate without any hindrance to productivity. It is intended to provide a method of manufacturing.

[0007]

[Means for Solving the Problems]

[0008] The present invention relates to a method for preparing a styrene-based monomer in a dispersion (I) in which styrene-based resin particles (a) having a small particle diameter are dispersed in an aqueous medium containing a poorly water-soluble inorganic salt and a surfactant. Dispersion (II) in which (b) is finely dispersed in an aqueous medium
And a method for producing styrene-based resin particles, wherein suspension polymerization is performed by adding styrene-based resin particles.

In the present invention, the use amount of the poorly water-soluble inorganic salt is 0.2 to 3.0 parts by weight based on 100 parts by weight of the styrene resin particles (a). The present invention relates to a method for producing styrene resin particles.

Further, the present invention provides a method for producing styrene resin particles wherein the amount of the surfactant used is 0.003 to 0.05 parts by weight based on 100 parts by weight of the styrene resin particles (a). About.

Further, the present invention relates to a method for producing styrene resin particles wherein the particle diameter of the styrene resin particles (a) is 0.8 mm or less.

In the present invention, the particle diameter of the oil droplets of the styrene monomer (b) finely dispersed in the dispersion (II) is not more than the particle diameter of the styrene resin particles (a). The present invention relates to a method for producing styrene resin particles.

Further, the present invention provides any one of the above methods for producing styrene resin particles, wherein a foaming agent is added during or after the suspension polymerization. About.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below. The present invention is characterized in that a predetermined dispersion (II) is added to a predetermined dispersion (I) to carry out suspension polymerization. 1. Dispersion (I) In the present invention, the dispersion (I) is obtained by dispersing styrene resin particles (a) having a small particle diameter in an aqueous medium containing a poorly water-soluble inorganic salt and a surfactant.

(1) Styrene resin particles (a) The styrene resin particles (a) used in the present invention are homopolymers of styrene or styrene derivatives or copolymer particles with other monomers. means. Examples of the styrene derivative include α-methylstyrene and vinyltoluene. Other monomers include methyl methacrylate,
Methacrylates such as ethyl methacrylate and butyl methacrylate, acrylates such as methyl acrylate, ethyl acrylate and butyl acrylate;
Acrylonitrile, methacrylonitrile and the like are used. The particle diameter of the styrene resin particles (a) is preferably smaller than the particle diameter of the desired finally obtained styrene resin particles and has a particle diameter of 0.8 mm or less. This method can be adopted even when resin particles (a) having a particle diameter of more than 0.8 mm are used, but in this case, if the type and amount of the dispersant and the stirring conditions are appropriately selected, the monomer can be used There is no generation of excessive particles even when suspension polymerization is carried out by directly adding the compound to an aqueous medium. If the method of the present invention is adopted, a method of finely dispersing the monomer in the aqueous medium is introduced, and the production capacity is rather increased. Tends to lower. Therefore, during the production process of the present invention, the particle diameter of the styrenic resin particles was 0.8 mm.
If it exceeds, then the monomer may be added directly to polymerize. If the particle size distribution of the resin particles (a) to be used is too wide, unnecessary resin particles having a size deviating from the desired particle size are generated, and the recovery rate of the resin particles as a product is reduced. The particle size distribution of the resin particles to be formed must be appropriately selected based on the particle size distribution of the target product.

As the styrene-based resin particles (a) used in the present invention, unnecessary particles having a small particle size, which cannot be produced as described above, can be used. Not something.

(2) Aqueous medium containing poorly water-soluble inorganic salt and surfactant Aqueous medium As the aqueous medium used in the present invention, deionized water is usually used. Poorly water-soluble inorganic salt Examples of the poorly water-soluble inorganic salt used in the present invention include magnesium phosphate, magnesium pyrophosphate, tricalcium phosphate, sodium silicate, magnesium carbonate and the like. The amount of the hardly water-soluble inorganic salt to be used is appropriately selected depending on the diameter of the styrene resin particles (a) and the ratio of a styrene monomer (b) described later with respect to the styrene resin particles (a). Particle (a) 1
The range of 0.2 to 3.0 parts by weight relative to 00 parts by weight is preferred. If it is less than 0.2 parts by weight, the dispersion stability is not sufficient, and particles larger than the desired particle size tend to increase. If it exceeds 3.0 parts by weight, conversely, the particle size is smaller than the desired particle size. The amount of generated particles tends to increase. Surfactant As the surfactant, an anionic surfactant or a nonionic surfactant is used. In general, an anionic surfactant is used. Examples of the anionic surfactant include sodium oleate, sodium alkylbenzene sulfonate, sodium α-olefin sulfonate and the like. The amount of the surfactant added is 0.003 to 100 parts by weight of the styrene resin particles (a).
Preferably, it is used in the range of 0.05 to 0.05 parts by weight. 0.
If the amount is less than 003 parts by weight, the dispersion stability is not sufficient,
Particles larger than the desired particle size tend to increase,
If it exceeds 0.05 parts by weight, the dispersion stability tends to be impaired.

2. Dispersion (II) In the present invention, the dispersion (II) is obtained by finely dispersing a styrene monomer (b), a polymerization initiator, a dispersant, and the like in an aqueous medium. (1) Styrene-based monomer (b) The styrene-based monomer (b) used in the present invention is styrene or one or more styrene derivatives such as α-methylstyrene and vinyltoluene, or a combination thereof. And methacrylates such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate; and similar polymerizable monomers such as acrylates, vinyl cyanide such as acrylonitrile and methacrylonitrile, and vinyl chloride. Further, a crosslinking agent such as divinylbenzene or diallyl phthalate may be used.

(2) Polymerization initiator The polymerization initiator used in the polymerization is not particularly limited as long as it is used in the suspension polymerization method. Examples thereof include benzoyl peroxide, t-butyl perbenzoate, and lauroyl par Benzoate, t-butylperoxyacetate, t-butylperoxyisopropyl carbonate, t-butylperoxy-2-ethylhexanoate,
One or more organic peroxides such as 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexanone and azo compounds such as azobisisobutyronitrile can be used. . The amount of the polymerization initiator varies depending on the type of the polymerization initiator, but is generally preferably in the range of 0.1 to 0.5 part by weight based on 100 parts by weight of the total amount of the monomer (b). The polymerization initiator is added by dissolving in a part or the whole amount of the solvent using the styrene monomer (b) or the solvent. Examples of the solvent include aromatic hydrocarbons such as ethylbenzene and toluene, and aliphatic hydrocarbons such as heptane and octane.
It is used in an amount of 3 parts by weight or less based on 100 parts by weight of the styrene monomer. Further, in the method of the present invention, oleamide,
Fatty acid monoamides such as palmitic acid amide and stearic acid amide, and fatty acid bisamides such as methylenebisstearic acid amide and ethylenebisstearic acid amide are used as foam control agents for expandable thermoplastic resin particles. You may dissolve in the said solvent and use it.

(3) Dispersant As the dispersant used for the styrene monomer (b), either an organic dispersant or an inorganic dispersant may be used. Examples of the organic dispersant include polyvinyl alcohol, polyvinyl pyrrolidone, methyl cellulose, and the like. Examples of the inorganic dispersant include magnesium phosphate, magnesium pyrophosphate, and tricalcium phosphate. Further, a surfactant can also be used. Examples of the surfactant include sodium oleate, sodium α-olefin sulfonate, sodium dodecylbenzene sulfonate, and other anionic surfactants and nonionic surfactants generally used in suspension polymerization. it can. The surfactant is particularly preferably used in combination with an inorganic dispersant from the viewpoint of improving the dispersion stability of the styrene resin particles. Among these dispersants, it is preferable to use an organic dispersant in view of the stability of the oil droplets of the styrene monomer (b). The amount of organic dispersant used is
0.05 to 100 parts by weight of the monomer (b)
A range of 0.2 parts by weight is preferred. If the amount is less than 0.05 part by weight, the stability of the styrene-based monomer oil droplets is insufficient, and if it exceeds 0.2 part by weight, the fluidity of the obtained styrene-based resin particles tends to be inhibited. .

(4) Aqueous Medium As the aqueous medium in which the styrenic polymer (b), polymerization initiator, dispersant and the like are dispersed, deionized water is usually used.

(5) Dispersion method The method of adding the styrene monomer (b), the polymerization initiator, the dispersant and the like to the aqueous medium and finely dispersing them is not particularly limited as long as the apparatus has a stirring blade. Although it is not a thing, it is preferable to use a homomixer as a method of making the finer. At this time, the dispersion (II) in which the monomer (b) is dispersed
Is preferably dispersed until the particle diameter becomes equal to or less than the particle diameter of the styrene resin particles (a). When the oil droplet diameter of the dispersion (II) in which the monomer (b) is dispersed is larger than the particle diameter of the resin particles (a), the monomer (b)
A plurality of resin particles (a) are added to oil droplets of a dispersion (II) in which
Is taken in, and adhesion, plasticization, and coalescence of the resin particles (a) occur, and excessive particles are easily generated. The ratio of the aqueous medium to the monomer in the dispersion (II) in which the monomer (b) is dispersed is the former /
In the latter case, the ratio is preferably 1/1 to 1.2 / 1 (weight ratio).

3. Suspension polymerization Dispersion (II) in which monomer (b) thus obtained is dispersed
Is a dispersion (I) in which the styrene resin particles (a) are dispersed.
And suspension polymerized. Addition of dispersion liquid (II)
It may be performed in a divided manner or continuously. The addition rate varies depending on the capacity, shape, polymerization temperature and the like of the polymerization apparatus and is appropriately selected. The polymerization temperature is preferably in the range of 75 to 93 ° C.

4. Addition of foaming agent When producing foamable styrenic resin particles, the foaming agent is pressed into the container during or after suspension polymerization, and the temperature is usually raised to a temperature higher than the softening point of the styrenic resin particles. Impregnated into particles. As the foaming agent, those which do not dissolve or slightly swell the resin particles (a) are preferable, and specific examples thereof include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane and normal hexane; Alicyclic hydrocarbons such as cyclopentane and cyclohexane are used. These blowing agents are usually used in an amount of 3 to 20 parts by weight based on 100 parts by weight of the resin particles.

[0025]

The present invention will be described in detail with reference to the following examples. Example 1 Styrene resin particles (styrene is tricalcium phosphate and sodium dodecylbenzenesulfonate) having a diameter of 0.21 to 0.35 mm (weight average diameter of 0.28 mm) are placed in a pressure-resistant stirring vessel with 600 g of deionized water. , 600 g of tricalcium phosphate (1 part), 0.06 g of sodium dodecylbenzenesulfonate (0.1 part).
01 parts) and heated to 85 ° C. while stirring. Next, 1400 g of deionized water and 1.4 g of polyvinyl alcohol were put into a monomer dispersion container and mixed, and 1400 g of a styrene monomer in which 4.2 g of benzoyl peroxide and 1.12 g of t-butyl perbenzoate were dissolved was added. 585 using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.)
The mixture was stirred at 0 rpm for 60 seconds to disperse the styrene monomer finely (average diameter of monomer oil droplets: 10 to 100 μm). The styrene monomer dispersion was added to the container at an equal rate (addition rate: 14.4 g / min) over 3 hours. After cooling for 2 hours, dehydration and drying were performed to obtain spherical styrene resin particles having a particle diameter of 0.30 to 0.50 mm.

The weight of the obtained resin particles was measured. The ratio obtained by dividing the weight by the weight (total charge) of the styrene resin particles added to the container and the added styrene monomer was measured as the recovery rate. In addition, 30 mesh openings (JIS
The mixture was sieved with a sieve (mesh opening), and the weight of the resin particles remaining on the 30 mesh was measured as excessive particles. In addition, sift through 50 mesh (JIS mesh), and
The weight of the resin particles that passed through the mesh was measured as fine particles. Table 1 shows the results.

Example 2 In the same pressure vessel as in Example 1, 600 g of deionized water and styrene resin particles 600 having a diameter of 0.21 to 0.30 mm (weight average diameter of 0.28 mm) were used.
g, 6.0 g (1 part) of tricalcium phosphate and 0.06 g (0.01 part) of sodium dodecylbenzenesulfonate, and the temperature was raised to 85 ° C. while stirring. Next, 1400 g of deionized water and 1.4 g of polyvinyl alcohol were put into a monomer dispersion vessel and mixed, and 4.2 g of benzoyl peroxide and 1.12 g of t-butyl perbenzoate were added thereto.
1400 g of a styrene monomer in which styrene was dissolved was added, and a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) was used.
Stir for 2 seconds to make the styrene monomer fine (average
0-100 μm). This styrene dispersion was added to the container at an equal rate over 3 hours. Two hours later, 70 g of butane was injected. After another hour, the temperature was raised to 120 ° C., left standing for 3 hours, cooled, dehydrated and dried to obtain spherical expandable styrene resin particles. In the same manner as in Example 1, the recovery rate of the resin particles and the generation amount of excessive particles and fine particles were measured.
Table 1 shows the results.

Example 3 600 g of deionized water and styrene resin particles 600 having a diameter of 0.21 to 0.30 mm (weight average diameter of 0.28 mm) were placed in the same pressure vessel as in Example 1.
g, 6.0 g (1 part) of tricalcium phosphate and 0.06 g (0.01 part) of sodium dodecylbenzenesulfonate, and the temperature was raised to 85 ° C. while stirring. Next, 700 g of deionized water and 0.7 g of polyvinyl alcohol were put and mixed in a monomer dispersion container, and 700 g of a styrene monomer in which 4.2 g of benzoyl peroxide and 1.12 g of t-butyl perbenzoate were dissolved. The mixture was stirred at 5850 rpm for 60 seconds using a homomixer to disperse styrene finely (average diameter of monomer oil droplets: 10 to 100 μm). This styrene dispersion was added to the container at a constant rate over 1.5 hours. 30 minutes later, the remaining styrene monomer 70
0 g of polyvinyl alcohol 0.7 g in 700 g of deionized water
g was added to the dissolved solution, finely dispersed by a homomixer in the same manner as described above, and added at a constant rate over 1.5 hours. After cooling for 2 hours, dehydration and drying were performed to obtain spherical styrene resin particles. The resin particle recovery rate and the amount of excessive particles and fine particles generated were measured. Table 1 shows the results.

Example 4 The polymerization temperature was from 85 ° C. to 93 ° C.
Resin particles were obtained with the same materials and method as in Example 1 except that the resin particles were changed to. The recovery rate of the resin particles after dehydration and drying and the generation amount of excessive particles and fine particles were measured. Table 1 shows the results.

Example 5 900 g of deionized water and styrene resin particles 900 having a diameter of 0.25 to 0.36 mm (weight average diameter of 0.33 mm) were placed in the same pressure vessel as in Example 1.
g, 7.2 g (0.8 parts) of tricalcium phosphate, 0.072 g (0.00 parts) of sodium dodecylbenzenesulfonate
8 parts) and heated to 75 ° C. while stirring. Next, 1100 g of deionized water and 1.1 g of polyvinyl alcohol were put and mixed in a monomer dispersion container, and 3.3 g of benzoyl peroxide and 0.1 g of t-butyl perbenzoate were added thereto.
550 g of a styrene monomer in which 88 g are dissolved and 550 g of methyl methacrylate are added, and the mixture is stirred at 5850 rpm for 60 seconds using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) for 60 seconds to produce fine particles (average diameter of monomer oil droplets: 30 to 120 μm). Was dispersed. This dispersion was added to the container at a constant rate (addition rate: 14.4 g / min) over 2.5 hours. After cooling for 2 hours, true spherical styrene resin particles were obtained. The recovery rate of the resin particles after dehydration and drying and the generation amount of excessive particles and fine particles were measured. Table 1 shows the results.

Example 6 900 g of deionized water and styrene resin particles 900 having a diameter of 0.25 to 0.36 mm (weight average diameter 0.33 mm) were placed in the same pressure vessel as in Example 1.
g, 8.4 g of tricalcium phosphate (1.4 parts), 0.06 g of sodium dodecylbenzenesulfonate (0.01 g)
And heated to 85 ° C. while stirring. Next, 1100 g of deionized water and polyoxyethylene monostearate (nonionic surfactant, HLB
13.6) 0.11 g was added and mixed, and 3.3 g of benzoyl peroxide and 1100 g of a styrene monomer having 0.88 g of t-butyl perbenzoate dissolved therein were added.
5850 rp using a homomixer (manufactured by Tokushu Kika Kogyo KK)
Stir for 60 seconds at m.
μm). This dispersion was added at a constant rate to the container over 3 hours. After cooling for 2 hours, true spherical styrene resin particles were obtained. The recovery rate of the resin particles after dehydration and drying and the generation amount of excessive particles and fine particles were measured. Table 1 shows the results.

Comparative Example 1 1960 g of deionized water and styrene resin particles 60 having a diameter of 0.21 to 0.30 mm (weight average diameter 0.28 mm) were placed in the same pressure vessel as in Example 1.
0 g, tricalcium phosphate 6.0 g (1 part), sodium dodecylbenzenesulfonate 0.06 g (0.01 part)
And heated to 85 ° C. while stirring. Next, 40 g of deionized water and 0.04 g of polyvinyl alcohol were put and mixed in a monomer dispersion container, and 40 g of a styrene monomer in which 0.12 g of benzoyl peroxide was dissolved was added thereto.
5850 rp using a homomixer (manufactured by Tokushu Kika Kogyo KK)
and then stirred for 60 seconds to obtain fine particles (average diameter of monomer oil droplets: 10 to 10).
0 μm). This dispersion was added to the vessel for 0.1 hour (addition rate 114.4 g / min). Subsequently, styrene monomer 13 in which 4.08 g of benzoyl peroxide and 1.09 g of t-butyl perbenzoate were dissolved.
60 g at a constant rate over 2.9 hours (addition rate 14.4 g /
Min). After cooling for 2 hours, styrene resin particles were obtained. After the obtained resin particles were dehydrated and dried, the resin recovery rate and the amount of excessive particles and fine particles generated were measured in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 2 600 g of deionized water and styrene resin particles 600 having a diameter of 0.21 to 0.30 mm (weight average diameter of 0.28 mm) were placed in the same pressure vessel as in Example 1.
g and 1.8 g of polyvinyl alcohol, and heated to 85 ° C. while stirring. Next, 1400 g of deionized water and 4.2 g of polyvinyl alcohol were added to the monomer dispersion and mixed, and 1400 g of a styrene monomer in which 4.2 g of benzoyl peroxide and 1.12 g of t-butyl perbenzoate were dissolved was added. 5850r using a homomixer
Stir at 60 pm for 60 seconds to fine (average diameter of monomer oil droplets 10 to 10
0 μm). The dispersion was added to the container at an equal rate (addition rate: 14.4 g / min) over 3 hours.
After cooling for 2 hours, dehydration and drying were performed to obtain spherical styrene resin particles. The resin particle recovery rate and the amount of excessive particles and fine particles generated were measured. Table 1 shows the results.

[Comparative Example 3] The polymerization temperature was from 85 ° C to 93 ° C.
Resin particles were obtained using the same materials and method as in Comparative Example 2 except that the above-described method was used. The resin particle recovery rate and the amount of excessive particles and fine particles generated were measured. Table 1 shows the results.

[0035]

[Table 1]

[0036]

As described above, according to the present invention,
Styrene-based resin particles and expandable styrene-based resin particles having a desired particle size at a high recovery rate can be produced without any hindrance to productivity.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B01F 17/52 B01F 17/52

Claims (6)

[Claims] 1. A styrene-based monomer (b) is added to a dispersion (I) in which styrene-based resin particles (a) having a small particle size are dispersed in an aqueous medium containing a poorly water-soluble inorganic salt and a surfactant. A method for producing styrene-based resin particles, comprising adding a dispersion (II) obtained by finely dispersing styrene in an aqueous medium to carry out suspension polymerization. 2. The amount of the hardly water-soluble inorganic salt to be used is from 0.2 to 3 based on 100 parts by weight of the styrene resin particles (a).
The method for producing styrene resin particles according to claim 1, wherein the amount is 0 parts by weight. 3. The amount of the surfactant to be used ranges from 0.003 to 0.5% based on 100 parts by weight of the styrene resin particles (a).
3. The method for producing styrene resin particles according to claim 1, wherein the amount is 05 parts by weight. 4. The particle size of the styrene resin particles (a) is as follows:
The particle diameter of the styrene resin particles finally obtained is smaller than 0.8 mm and is not more than 0.8 mm.
The method for producing styrene resin particles according to the above item. 5. The styrene-based monomer (b) finely dispersed in the dispersion liquid (II) has an oil droplet having a particle diameter of not more than the particle diameter of the styrene-based resin particles (a). 5. The method for producing styrenic resin particles according to any one of items 4 to 4. 6. The expandable styrene resin according to claim 1, wherein a foaming agent is added during or after the suspension polymerization. Method for producing particles.