JP2907068B2 - Method for producing expandable styrene polymer particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing expandable styrene polymer particles, and more particularly, to a method of suspending a styrene monomer (ie, a monomer mainly composed of styrene) in an aqueous medium. The present invention relates to a method of producing expandable styrene-based polymer particles by impregnating a foaming agent (butane, pentane, etc.) into the polymerized and formed styrene-based polymer particles, and then performing a certain aging treatment.

[0002] Expandable styrenic polymer particles are then
The foamed molded article (styrene foam product) is processed through foaming treatment including prefoaming, and the produced foamed molded article is used for packing materials for home electric appliances, building boards and heat insulating blocks, heat insulating containers such as fish boxes and the like. And instant food cups.

[0003]

2. Description of the Related Art Generally, styrene-based polymer particles are synthesized by suspension polymerization of a styrene-based monomer in an aqueous medium.
A dispersant system comprising a combination of a poorly water-soluble inorganic salt (particularly, basic calcium phosphate) and a water-soluble neutral inorganic salt (particularly, sodium chloride) is used. Compared with organic dispersants such as polyvinyl alcohol and polyvinylpyrrolidone, this dispersant system does not cause a decrease in thermal stability, transparency and mechanical strength and does not cause an increase in the COD load of the waste liquid. This is advantageous. In addition, in order to obtain high suspension stability, an anionic surfactant such as sodium dodecylbenzenesulfonate and sodium α-olefin sulfonate is usually used in combination with the above dispersant system. Japanese Patent Publication No. 1-50321 and Japanese Patent Laid-Open Publication No. 3-64308 are conventional publications which disclose a suspension polymerization method of a styrene monomer using such a dispersant system.

[0004]

In the production of expandable styrene polymer particles, it is required to suppress the generation of fine particles and to minimize the amount of fine particles. For example, applications of expandable polystyrene are divided into the following three fields according to the size of the particle diameter. (1) Particle size: about 0.4 to about 0.7 mm At present, it is limitedly used for instant food cups. (2) Particle size: about 0.7 to about 1.8 mm Used in a wide range of fields such as various packing materials for home electric appliances and the like. (3) Particle size: about 1.8 to about 3.0 mm Used for building boards, heat insulation blocks, and the like. As described above, the use of expandable polystyrene having fine particles (particle diameter of less than about 0.7 mm) is limited, that is, all the excess portion of the expandable polystyrene fine particles produced is unnecessary, so that expandable polystyrene is used. In the production of
It is required to minimize the generation amount of fine particles (particularly, particles having a particle diameter of less than 0.5 mm) to improve the yield.
In addition, the two patent publications mentioned above raise the same problem as the above problem in the description.

Further, expandable styrene-based polymer particles (expandable polystyrene particles) have a cut surface in the range of 50 μm to 150 μm when pre-expanded using steam in view of the quality characteristics of the expanded molded article. It is required that pre-expanded particles having a cell structure (cell size) be obtained. Cell dimensions of the cut surface in the pre-expanded particles,
That is, the cell size is an important factor that determines various qualities and characteristics of the foam molded article, such as heat resistance, heat insulation, hardness, surface gloss, and appearance of the cut surface. If the cell size is less than 50 μm, especially when the pre-expanded particles are molded in a mold, shrinkage is likely to occur in the molded product, and the accuracy of the shape (dimension) of the molded product is extremely poor. Quality problems such as a decrease in the surface strength of the steel. On the other hand, when the cell size of the pre-expanded particles is about 100 μm, the finally obtained expanded molded article has high shape (dimensional) accuracy, excellent surface strength, etc., and excellent quality and moldability. Become something. Conventionally, as a method of adjusting the size of the cell size in the pre-expanded particles, suspension polymerization of a styrene monomer with a bisamide such as ethylene bisstearyl amide or methylene bis stearyl amide or a polymer such as an ethylene vinyl acetate copolymer. At this time, a method of adding to the polymerization medium is used. However, this method
This technique aims to suppress the cell size to a certain size or less, and when the cell size of the pre-expanded particles becomes smaller than a desired level (50 μm) due to other causes, the effect of the method is used. Cannot be exerted on the expandable styrenic polymer.

In short, in the production of expandable styrenic polymer particles, the amount of fine particles to be produced is kept as small as possible, and the cell size (in the range of 50 μm to 150 μm) of the pre-expanded particles to be subsequently produced is appropriate.
Is required. Such demands should be naturally satisfied regardless of the size of the production scale.

Nevertheless, in the past, satisfactory quality characteristics were obtained for expandable polystyrene particles on a laboratory scale (scale of polymerization vessel of 1 to 10 liters). Intermediate test plant scale (room of polymerization vessel 100-1000)
Liter scale) and mass production scale (polymerization vessel volume 1
(A scale of 10,000 liters or more), the amount of generated fine particles (particle size: less than 0.5 mm) per unit volume (1 liter) increases, and the polymerization stability of the suspension polymerization solution deteriorates. There was also a phenomenon that the cell size of the pre-expanded particles further decreased and did not reach the desired level. This phenomenon is a process that has been regarded as the most preferable mode in the prior art, that is, as disclosed in, for example, Japanese Patent Publication No. 1-50321.
It has also been occasionally observed in processes for the suspension polymerization of styrenic monomers using a dispersant system consisting of tricalcium phosphate, sodium chloride and dodecylphenyl oxide disulfonate. In general, as the production scale is expanded, the size of the dispersion stirrer becomes larger, and the shear stress around the stirring blade increases, so that it is estimated that more fine particles are generated. Such a simple scale-up rule cannot provide a sufficient explanation. Therefore, the two requirements of reducing the generation amount of fine particles and adjusting the cell size appropriately for the pre-expanded particles are irrespective of the production scale of the expandable styrene-based polymer particles, that is, from the laboratory scale to the mass production scale. Even so, it was necessary to satisfy them sufficiently.

Accordingly, the present invention relates to a technique for producing expandable styrene-based polymer particles, wherein the fine particles (particle size: 0.5 mm
) Is as low as possible,
In order to improve the yield, the cell size of the pre-expanded particles to be produced is adjusted to an appropriate range (50 to 150 μm).
m) to improve the quality characteristics of the foamed molded product, and to maintain their performance satisfactorily from the laboratory scale to the mass production scale without depending on the size of the production scale. It is an issue.

[0009]

In a suspension polymerization process of a styrene-based monomer described in Example 1 of Japanese Patent Publication No. 1-50321 as a conventional known technique, 100 parts by weight of styrene is used. As a dispersant system, basic calcium phosphate (0.120 parts by weight), salt (0.336 parts by weight) and sodium dodecylphenyl oxide disulfonate (0.0075 parts by weight) were used.
(Parts by weight) are used, and as these drugs, commercially available drugs are used. That is,
In the prior art, suspension polymerization of a styrene monomer was advanced at a stage where a predetermined amount of a commercially available dispersant was added to an aqueous medium for polymerization and dispersed by stirring. However, in such a method, if the amount of the dispersant used is reduced, the polymerization becomes unstable, and aggregation and coalescence of particles are likely to occur. Tends to be incorporated into the aqueous medium.

As a result of intensive studies, the present inventor has found that the generation amount of fine particles of the expandable styrenic polymer and the value of the cell size in the pre-expanded particles are particularly large as the production scale (capacity of the polymerization vessel) increases. It was found that the increase in the amount and the decrease in the cell size were closely related to the internal calcium amount of the expandable styrenic polymer particles. The larger the amount of calcium contained in the expandable styrene polymer particles, the more the amount of fine particles generated and the smaller the cell size tends to be, which tends to be smaller.
It becomes more noticeable as the production scale increases. This tendency is presumed to be due to the following causes. When the amount of calcium contained in the styrene-based polymer particles increases, that is, when the amount of tricalcium phosphate in the polymer particles increases, this acts as a nucleating agent for the cells, so that the cell structure is smaller. become. As production scales up,
As the agitation power of the polymerization equipment is significantly increased, the styrenic polymer particles are more strongly agitated in the aqueous polymerization medium, and the fragmentation and coalescence of the polymer particles become more active, and thus more and more. Amount of tricalcium phosphate is incorporated into the polymer particles, resulting in the production of more pre-expanded particles having a smaller cell size.

However, in the conventional polymerization method using a commercially available dispersant, in order to secure the suspension stability, it is necessary to reduce the calcium content in the expandable styrene-based polymer particles produced. There are certain limitations. Therefore, the method for producing expandable styrene-based polymer particles according to the present invention comprises preparing a calcium compound dispersant (tricalcium phosphate) in an aqueous medium prior to suspension polymerization, so that calcium in the polymerization medium is reduced. It allows the concentration of the compound to be reduced to a low concentration at which aggregation coalescence has occurred in the prior art, and thus, the calcium content in the expandable styrenic polymer particles produced. This makes it possible to significantly reduce the content as compared with the conventional case.

Accordingly, the present invention is specifically directed to a foamable styrenic polymer by suspension polymerizing a styrenic monomer in an aqueous medium and impregnating the resulting polymer particles with a blowing agent. In the method for producing particles, first, trisodium phosphate and calcium chloride are added in an aqueous medium so that 0.03 per 100 parts by weight of the styrene monomer is obtained.
Tricalcium phosphate is synthesized in an amount of 1 to 0.1 part by weight, and then the styrene monomer is added to the aqueous medium together with a dispersing agent, dodecylphenyl oxide disulfonate, to carry out suspension polymerization. And a method for producing expandable styrene-based polymer particles.

[0013] The production method according to the present invention is a method for preparing a dispersing agent, triphosphate, from trisodium phosphate and calcium chloride in an aqueous medium (eg, ion-exchanged water) according to the following reaction formula before the start of suspension polymerization. It is a method of synthesizing calcium. 10 CaCl ₂・ 2 H ₂ O ＋ 6 Na ₃ PO ₄・ 12 H ₂ O ＋ 2 H ₂ O
→ [Ca ₃ (PO ₄ ) ₂ ] ₃ · Ca (OH) ₂ +18 NaCl + 2 HCl The amount of tricalcium phosphate synthesized by this method is
0.01 to 0.5 parts by weight per 100 parts by weight of the styrene monomer.
1 part by weight, more preferably 0.03 to 0.0
7 parts by weight. When the synthesis amount of tricalcium phosphate is within this range, the amount of internal calcium in the generated styrene-based polymer particles can be suppressed to a sufficiently low level. The amount can be reduced and the cell size of the pre-expanded particles can be appropriately adjusted. The amount of the synthesized tricalcium phosphate is 0.01 to 0.1 per 100 parts by weight of the styrene monomer, depending on the size of the target expandable styrene polymer particles. It is adjusted appropriately within the range of parts by weight. When producing expandable styrene-based polymer particles having a smaller average particle size, increase the synthesis amount of tricalcium phosphate and, on the contrary, produce larger expandable styrene-based polymer particles having an average particle size. In some cases, the synthesis amount of tricalcium phosphate is reduced.

As prior art related to the method of the present invention,
A suspension polymerization method using a dispersant consisting of a combination of tricalcium phosphate and an anionic surfactant, wherein a dispersant tricalcium phosphate is synthesized from trisodium phosphate and calcium chloride in the polymerization system. Are already described, for example, in Japanese Patent Publication No. 62-51962. However, the technology described in this publication is directed to polymer beads (in the examples, a copolymer of styrene and acrylonitrile) produced by suspension polymerization of a vinyl monomer in the presence of a diene rubber polymer. ) Is not intended for synthesis of expandable polymer particles such as expandable polystyrene. In addition, this publication does not disclose any expandable polymer particles, and is not a publication that gives any suggestion on suppression of the amount of fine particles produced and adjustment of cell size in the pre-expanded particles. In fact, when expandable styrene polymer particles are produced by suspension polymerization using the dispersant system described in the above-mentioned publication, the amount of fine particles having a particle size of 0.5 mm or less is significantly increased, and the yield is extremely high. It will be bad. The technology described in the above publication is
Trisodium phosphate and calcium chloride 1: 1.25
This is a technique in which a polymerization reaction is carried out by adding and using a molar ratio of 66, that is, under conditions in which excess calcium chloride is present together with the generated tricalcium phosphate. In other words,
This technique is not aimed at utilizing substantially equimolar amounts of trisodium phosphate and calcium chloride. Furthermore, the technique described in the above-mentioned publication discloses that, as an anionic surfactant of a dispersing aid, one selected from alkali salts of alkyl sulfates, alkali salts of alkyl benzene sulfonic acids and alkali salts of fatty acids (in the examples, sodium lauryl sulfate). This is a technique to be used, and does not use dodecylphenyl oxide disulfonate. Therefore, Japanese Patent Publication No. 62-51962 does not include those which can be caused or triggered by the method for producing expandable styrene-based polymer particles according to the present invention.

The production method of the present invention differs from the technique described in the above-mentioned publication in that the tricalcium phosphate is prepared in an aqueous medium, that is, in a polymerization system according to the above chemical reaction formula before the start of suspension polymerization. Is synthesized. Trisodium phosphate and calcium chloride, which are raw materials for the synthesis, are more preferably used in a substantially equimolar ratio. That is, in the production method of a more preferred embodiment of the present invention, trisodium phosphate and calcium chloride used for the synthesis of tricalcium phosphate are added in an equivalent molar ratio in the range of 1: 0.8 to 1: 1.2. Is done. When the equivalent molar ratio of calcium chloride to trisodium phosphate is less than 0.8, the amount of fine particles produced relative to the expandable styrene-based polymer particles to be produced is relatively larger. On the other hand, when the equivalent molar ratio exceeds 1.2, suspension stability deteriorates. Therefore, it is more desirable to use these two kinds of raw materials in an equivalent molar ratio in the range of 0.8 to 1.2.

In the production method of the present invention, dodecylphenyl oxide disulfonate is added as a dispersing aid in order to further stabilize the dispersion of the suspended particles in the polymerization system. Is preferably 0.001 to 0.01 parts by weight, more preferably 0.003 parts by weight, based on 100 parts by weight of the styrene monomer.
Parts by weight to 0.006 parts by weight. If the addition amount of dodecylphenyl oxide disulfonate exceeds 0.01 part by weight based on 100 parts by weight of the styrene monomer, the suspension stability tends to deteriorate, while 0.00
When the amount is less than 1 part by weight, the amount of fine particles generated with respect to the expandable styrene-based polymer particles further increases, particularly when the production scale is expanded. Therefore, it is more desirable to add and use the above dispersing aid in the range of 0.001 part by weight to 0.01 part by weight.

In the present invention, the styrene monomer includes substituted styrene such as α-methylstyrene and p-chlorostyrene in addition to styrene alone, and further includes styrene and a monomer copolymerizable with styrene. It also means a combination.
Examples of monomers copolymerizable with styrene include, for example, α-
Examples include various substituted styrenes such as methylstyrene and p-chlorostyrene, and vinyl monomers such as acrylonitrile, methyl methacrylate, methyl acrylate, butyl methacrylate, and butyl acrylate. Accordingly, the styrene-based polymer particles produced according to the method of the present invention include polystyrene and polysubstituted styrene such as poly-α-methylstyrene and poly-p-chlorostyrene, as well as styrene and substituted styrene (for example, α-methylstyrene). And the like, or a copolymer of styrene and a vinyl monomer (eg, acrylonitrile).

In the production method of the present invention, as a polymerization initiator in suspension polymerization, for example, a radical initiator such as benzoyl peroxide, butyl perbenzoate, t-butylperoxybenzoate, azobisisobutyronitrile, etc. A radical polymerization initiator generally used for polymerization is used. In the production method of the present invention, for example, hexane, n-pentane, isopentane, butane, propane, etc. are used as the foaming agent. These foaming agents may be used alone or in combination of two or more.

Further, in the production method of the present invention, in order to obtain expandable styrene polymer particles, a foaming agent is pressed into the suspension system during the suspension polymerization of the styrene monomer. The resulting styrene polymer particles may be impregnated, or after the suspension polymerization of the styrene monomer is completed, a blowing agent is pressed into the suspension system to impregnate the styrene polymer particles. You may do it at least. The expandable styrene-based polymer particles thus produced according to the method of the present invention are pre-expanded to any apparent specific gravity as necessary, and then, according to a conventional method, the pre-expanded particles are filled in a mold such as a mold. By heating and foaming using steam, the pre-expanded particles can be fused to each other to produce a foam molded article having a desired shape (dimension).

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below, including the best mode (example).

-Production of expandable styrene particles- First, trisodium phosphate was placed in a polymerization vessel (autoclave) having a propeller type stirrer and containing 100 parts by weight of ion-exchanged water as an aqueous medium in the capacity shown in Table 1. And calcium chloride were added at the equivalent molar ratios shown in Table 1, and these were dissolved by stirring to synthesize tricalcium phosphate in the amount shown in Table 1 in ion-exchanged water. Next, dodecylphenyl oxide disulfonate in an amount shown in Table 1 as a dispersing aid was added to the ion-exchanged water and stirred for 5 minutes. Subsequently, 100 parts by weight of a styrene monomer and a polymerization initiator were added. 0.3 parts by weight of benzoyl peroxide and 0.1 parts of t-butyl perbenzoate
Each combination of parts by weight was added and dispersed sufficiently by stirring. Then, the temperature of the suspension was raised to 90 ° C., and polymerization was allowed to proceed at that temperature for 5 hours to produce polystyrene particles. After completion of the polymerization, n-pentane (7.0 parts by weight) as a foaming agent was pressed into the polymerization vessel, and then the temperature of the reaction system was increased to 120 ° C., and the state was maintained for 3 hours to form a foam. The agent was impregnated into polystyrene particles.
After this treatment, the polymerization reaction system was cooled to room temperature, and the produced expandable polystyrene particles were taken out of the polymerization vessel.

-Measurement of the amount of generated fine particles- A predetermined amount of the expandable polystyrene particles are sieved to remove the particles having a particle size of less than 0.5 mm, and the weight thereof is measured. The generation ratio (%) of the fine particles having a particle size of less than 0.5 mm in the whole was determined.

-Average particle size- The resulting expandable polystyrene particles are sieved into several particle size ranges, and the weight of the expandable polystyrene particles in the smallest size range is reduced to The weight of the expandable polystyrene particles was sequentially accumulated, and the particle size at which the cumulative weight corresponds to 50% of the total weight of the expandable polystyrene particles was determined as the average particle size of the expandable polystyrene particles.

-Quantification of the amount of internal calcium in polystyrene particles- From the generated expandable polystyrene particles, particles having a particle size of 1.0 to 1.2 mm were selected by sieving, and the amount of internal calcium in the particles was determined according to the following procedure. did. The expandable polystyrene particles having such a particle size are washed with 10-fold diluted hydrochloric acid, dissolved in tetrahydrofuran (THF), and then extracted with 10-fold diluted hydrochloric acid, and the calcium ion concentration in the extract is determined. Quantification is performed according to ICP emission spectrometry.

-Measurement of cell size in pre-expanded particles- Expandable polystyrene particles having a particle size of 1.0 to 1.2 mm are selected by sieving, and then zinc stearate as an anti-blocking agent is added to the expandable polystyrene particles. Particle 10
0.2 parts by weight per 0 parts by weight was added and blended by stirring, and then this was aged at room temperature for 5 days. Thereafter, the aged expandable polystyrene particles were foamed with steam to a bulk magnification of 50 times to obtain pre-expanded particles. Then, the cell size was determined by observing the cut surface of the obtained pre-expanded particles using an electron microscope and photographing the cut surface.

[0026]

【Example】

Examples 1 to 7 In each of the examples, a 5 liter autoclave was used as a polymerization vessel, and 1800 gr of ion-exchanged water was charged into the autoclave. , An initiator, a foaming agent and the like were added to the polymerization reaction system, and the suspension polymerization and the impregnation of the foaming agent were allowed to proceed. As a synthesis system of the dispersant tricalcium phosphate, a combination of trisodium phosphate decahydrate and calcium chloride dihydrate was used in a molar ratio shown in Table 1. For example, in Example 1, 0.136 parts by weight of trisodium phosphate dodecahydrate and calcium chloride dihydrate
A combination of 0.088 parts by weight was used.

Example 8 A polymerization vessel for a test plant having a capacity of 1000 liters was used as a polymerization vessel, and 440 kgr of ion-exchanged water was added to the polymerization vessel. A body, an initiator, a foaming agent and the like were added to the polymerization reaction system, and the suspension polymerization and the impregnation of the foaming agent were allowed to proceed. Others are the same as the first to seventh embodiments.

Example 9 A polymerization vessel for a test plant having a capacity of 10,000 liters was used as a polymerization vessel.
gr, and the amount is set to 100 parts by weight, a predetermined part by weight of a monomer, an initiator, a foaming agent and the like are added to the polymerization reaction system, and the suspension polymerization and the impregnation of the foaming agent are allowed to proceed. Was.
Others are the same as the first to seventh embodiments.

Comparative Examples 1 and 2 In each Comparative Example, a 5 liter autoclave was used as a polymerization vessel, and 1800 gr of ion-exchanged water was charged into the autoclave. A monomer, an initiator, a foaming agent and the like were added to the polymerization reaction system, and the suspension polymerization and the impregnation of the foaming agent were allowed to proceed. As a synthesis system of the dispersant tricalcium phosphate, a combination of trisodium phosphate decahydrate and calcium chloride dihydrate was used in a molar ratio shown in Table 1. Comparative Example 1 used a combination of 0.136 parts by weight of trisodium phosphate dodecahydrate and 0.114 parts by weight of calcium chloride dihydrate, and Comparative Example 1 used 0.136 parts by weight of trisodium phosphate dodecahydrate 0.136 parts by weight and calcium chloride dihydrate.
A combination of 0.061 parts by weight was used. Others are described in Example 1.
Is the same as

Comparative Example 3 An autoclave having a capacity of 5 liters was used as a polymerization vessel, and 1800 gr of ion-exchanged water was charged into the autoclave.
An initiator, a foaming agent and the like were added to the polymerization reaction system, and the suspension polymerization and the impregnation of the foaming agent were allowed to proceed. However, instead of dodecylphenyl oxide disulfonate as a dispersing aid,
The amounts of sodium alkylbenzenesulfonate shown in Table 1 were used. Others are the same as the first embodiment.

Comparative Example 4 An autoclave having a capacity of 5 liters was used as a polymerization vessel, and 1800 gr of ion-exchanged water was charged into the autoclave.
An initiator, a foaming agent and the like were added to the polymerization reaction system, and the suspension polymerization and the impregnation of the foaming agent were allowed to proceed. However, instead of dodecylphenyl oxide disulfonate as a dispersing aid,
The amount of sodium lauryl sulfate shown in Table 1 was used. Others are the same as the first embodiment.

Comparative Examples 5 and 6 A 5 liter autoclave was used as a polymerization vessel, and 1800 gr of ion-exchanged water was charged into the autoclave.
An initiator, a foaming agent and the like were added to the polymerization reaction system, and the suspension polymerization and the impregnation of the foaming agent were allowed to proceed. However, as a method of preparing the dispersant system, instead of the method of synthesizing tricalcium phosphate or the like by adding trisodium phosphate and calcium chloride, commercially available tricalcium phosphate in the amount shown in Table 1 was used. A method was employed in which the product was added directly to the polymerization reaction system with sodium chloride. Others are the same as the first embodiment.

Comparative Example 7 A polymerization vessel for a test plant having a capacity of 1000 liters was used as a polymerization vessel, 440 kgr of ion-exchanged water was charged into the polymerization vessel, and the amount was defined as 100 parts by weight. A body, an initiator, a commercially available dispersant system, a foaming agent, and the like were added to the polymerization reaction system to allow suspension polymerization and foaming agent impregnation to proceed. Others are the same as Comparative Example 6.

Comparative Example 8 A polymerization vessel for a test plant having a capacity of 10,000 liters was used as a polymerization vessel.
gr, and the amount is taken as 100 parts by weight. A predetermined amount by weight of a monomer, an initiator, a commercially available dispersant system and a foaming agent are added to the polymerization reaction system, and the suspension polymerization and the foaming agent are added. Impregnation was allowed to proceed. Others are the same as Comparative Example 6.

The results of each of the above examples are summarized in Table 1 below.

According to the table, according to the examples, during the suspension polymerization of the expandable polystyrene particles, the tricalcium phosphate (0.01 to 0) was added by adding approximately equivalent molar amounts of trisodium phosphate and calcium chloride before the start of the polymerization. .1 part by weight) in an aqueous medium, and employing dodecylphenyl oxide disulfonate as a dispersing agent, so that the calcium content of the produced expandable polystyrene particles is lower than that of the conventional foamable polystyrene particles. The amount of fine particles having a particle size of less than 0.5 mm can be remarkably reduced, and the cell size of the pre-expanded particles can be adjusted to about 100 μm.
It can be seen that even when the scale of production is increased from 5 liters to 10,000 liters, the reduction in the amount of generated fine particles and the optimal adjustment of the cell size are maintained.

On the other hand, from Comparative Examples 1 and 2, the molar ratio of trisodium phosphate to calcium chloride was 1: 0.
When the ratio exceeds 8 to 1.2, the generation amount of fine particles in the expandable polystyrene particles is remarkably increased, and when calcium chloride is excessive, the amount of internal calcium in the particles is also increased. Further, from Comparative Examples 3 and 4, it can be seen that the use of a dispersing agent other than dodecylphenyl oxide disulfonate greatly increases the amount of fine particles generated for the expandable polystyrene particles. Further, from Comparative Examples 5 to 8, when commercially available tricalcium phosphate and sodium chloride are used as the dispersant system, the amount of internal calcium in the expandable polystyrene particles increases, and the cell size of the pre-expanded particles is less than 50 μm. It can be seen that the production amount of the expandable polystyrene particles is significantly increased, and the cell size of the pre-expanded particles is further reduced with the expansion of the production scale.

[0038]

As described above, according to the present invention,
For example, the following effects can be obtained. With respect to the expandable styrene-based polymer particles to be produced, the amount of fine particles (particle diameter of less than 0.5 mm) can be significantly reduced as compared with the conventional method, and therefore, the yield in the production of the polymer particles can be improved. Can be achieved. For the pre-expanded particles, adjust the cell size to an appropriate range (50
１５０150 μm), so that it is possible to provide a foam molded article having extremely excellent quality characteristics such as heat resistance, heat insulation, hardness (dimensional accuracy), and surface gloss. The two good performances of reducing the amount of fine particles generated for expandable styrenic polymer particles and adjusting the appropriate cell size for pre-expanded particles can be achieved from a laboratory scale to a mass production scale regardless of the scale of production. Can be held satisfactorily. Furthermore, at the laboratory scale, test plant scale, and mass production scale, the same blending ratio is used for raw materials, dispersant systems, polymerization initiators, and the like to produce foamable styrene-based polymer particles having the desired quality characteristics. Therefore, it is possible to accurately predict the productivity of the expandable styrenic polymer and the quality characteristics of the foam molded article on a mass production scale based on the results on a laboratory scale.

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Claims (2)

(57) [Claims] 1. A method for producing expandable styrene-based polymer particles by suspension-polymerizing a styrene-based monomer in an aqueous medium and impregnating the polymer particles with a foaming agent into the polymer particles. By adding trisodium phosphate and calcium chloride, tricalcium phosphate in an amount of 0.01 to 0.1 part by weight per 100 parts by weight of the styrene monomer in an aqueous medium is synthesized, and A method for producing expandable styrene-based polymer particles, comprising adding a styrene-based monomer together with a dispersing agent, dodecylphenyl oxide disulfonate, to perform suspension polymerization. 2. The method according to claim 1, wherein the trisodium phosphate and calcium chloride used for the synthesis of tricalcium phosphate are added in an equivalent molar ratio in the range of 1: 0.8 to 1: 1.2. 2. The production method according to 1.