JPS5920683B2 - Suspension polymerization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a suspension polymerization method for monomers mainly composed of styrene, and more specifically to a method for obtaining particles with a narrow particle size distribution synthesized by suspension polymerization. It concerns the turbidity polymerization method.

Conventional methods for suspension polymerization of styrene-based monomers involve dispersing styrene-based monomers in which a catalyst has been dissolved into an aqueous system with the aid of stirring and a suspension stabilizer, and then heating the system. By this process, polymerization is initiated and polymer particles are produced.

In this case, a suspension stabilizer is indispensable to prevent coalescence and agglomeration of monomer droplets as the polymerization progresses, and such suspension stabilizers generally include polyvinyl alcohol,
Polyvinylpyrrolidone, polymeric colloids such as gelatin, and U.S. Pat. No. 2,673,194 by Grim.
A combination of a poorly water-soluble inorganic salt such as tricalcium phosphate and a surface extender is known. However, when these polymer colloids are used as suspension stabilizers, they may cause a decrease in thermal stability, deterioration of transparency, or decrease in mechanical strength due to their incorporation into polymer particles, or may cause a decrease in polymerization wastewater. This causes various unfavorable effects such as increasing COD load. Also U
In the method described in SP2673194, the particles produced span a wide range of particle sizes. Generally, styrenic polymer particles obtained by suspension polymerization are extruded or injection molded and used to make various products. However, if the particle size distribution is wide, there will be variations in the supply of raw materials to the molding machine, resulting in A problem arises in that the defective rate increases. In addition, polymer particles mainly composed of styrene obtained by suspension polymerization are impregnated with a blowing agent (e.g. propane, butane, pentane, etc.).
So-called expanded styrene is obtained. The uses of expanded styrene can be roughly divided into the following three fields depending on the particle size. (1) Styrene foam with a particle size of about 300μ to about 700μ is used in cups for instant foods.

(2) Particles with a particle size of approximately 700μ to approximately 1800μ are used for various packaging purposes. (3) Particle size from about 1300μ to about 3000μ
Styrene foam is used as building material boards, etc. Due to these differences in use, the required properties of expanded styrene also differ, so it is necessary to manufacture expanded styrene for each purpose, but the wide particle size distribution of the polymer particles obtained by suspension polymerization makes it possible to is difficult to reach.

In order to solve this problem, the present inventors have conducted intensive research and have found that the present inventors can improve the thermal stability, transparency, and mechanical strength of polymer particles obtained by suspension polymerization, and also improve the polymerization effluent. COI) We have discovered a method that makes the particle size distribution much narrower than known methods without increasing the load.

In the present invention, when suspension polymerizing styrene or a mixture of styrene and a monomer copolymerizable with styrene in an amount of 10% or less, the monomer is converted into a sodium or potassium β-naphthalene sulfonic acid formalin condensate. After starting polymerization by dispersing salt, tricalcium phosphate, and preferably a water-soluble metal salt that is neutral in an aqueous system in water, a cationic surfactant is added at a polymerization conversion rate of 20 to 50%. This is a suspension polymerization method for monomers mainly containing styrene, which is characterized by adding and polymerizing monomers.

In the present invention, a monomer copolymerizable with styrene may be copolymerized in an amount of 10% or less based on styrene.

Copolymerizable monomers include various substituted styrenes such as α-methylstyrene and chlorostyrene, and vinyl monomers such as acrylonitrile, methyl methacrylate, and butyl acrylate. In that case, copolymerization of 10% or more is not preferred because it significantly changes suspension stability. Examples of inorganic salts that are neutral in aqueous systems include potassium chloride, sodium chloride, lithium chloride, magnesium chloride, calcium chloride, potassium sulfate, magnesium sulfate, and sodium sulfate.

These inorganic salts may be used alone or in combination. The inorganic salt has the effect of providing good suspension stability when a monomer mainly composed of styrene is polymerized in the coexistence of methylene bis stearylamide or ethylene bis stearyl amide, which are known as nucleating agents for expanded styrene. If no inorganic salt is added, the suspension stability deteriorates, the polymer particles do not become spherical, and the total uniformity coefficient increases. The amount of inorganic salt used is 0.6 parts per 100 parts by weight of monomer.
01 parts by weight or more may be used. If it is less than this, the effect will be insufficient. The upper limit of the amount of inorganic salt to be used is not particularly stipulated, but sufficient effects are exhibited at 2.0 parts by weight or less, so there is no need to use more than that. Further, in the case of polymerization in which a nucleating agent for expanded styrene such as ethylene bis stearylamide or methylene bis stearyl amide is not present, the inorganic salt may be particularly omitted. β
- Even if the sodium salt and potassium salt of the naphthalene sulfonic acid formalin condensate are used alone at the start of polymerization,
It may be used in combination with tricalcium phosphate, and its method of use is not particularly limited.

However, when used alone, it is necessary to add tricalcium phosphate during the course of polymerization to prevent collapsing due to increased viscosity as the polymerization progresses.

The amount of the sodium salt and potassium salt of the β-naphthalene sulfonic acid formalin condensate may be between 0.001 part by weight and 0.1 part by weight per 100 parts by weight of the monomer. If the amount is less than 0.001 part by weight, suspension stability will be impaired and polymerization will be impossible.

Moreover, if the amount is more than 0.1 part by weight, the COD load of the polymerization waste water will become large, and since a sufficient effect is exhibited by less than 0.1 part by weight, there is no need to use any more. Tricalcium phosphate is described, for example, in US Pat. No. 2,673,194 by Grimm, and is a finely divided phosphate salt that is sparingly water-soluble and contains at least 3 equivalents of calcium in each phosphate group.

The amount used is 0.05 to 1.0% per 100 parts by weight of the monomer.
It is 0 parts by weight. If the amount is less than 0.05 parts by weight, the addition of the cationic surfactant shown later will cause a collapsing phenomenon, and 1
It is not necessary to use more than 0 parts since it is sufficiently effective.

Cationic surfactants generally refer to alkylammonium chlorides, such as octadecyltrimethylammonium chloride, alkyl(an)trimethylammonium chloride, hexadecyldimethylbenzylammonium chloride, octadecyldimethylbenzylammonium chloride, and dodecyltrimethylammonium chloride. etc.

As for how to use it, it is preferable to add it to the system at a polymerization conversion rate of between 20% and 50%, and if it is less than 20% and more than 50%, its effect will not be noticeable. The amount used is less than the equimolar amount of the sodium salt or potassium salt of the β-naphthalene sulfonic acid formalin condensate. If the amount exceeds the equivalent amount, the suspension system will be significantly destabilized. In the figure, the horizontal axis shows the particle size,
The cumulative weight percentage of the polymer particles is plotted on the vertical axis, the particles obtained by polymerization are sieved into each particle size, and the weight of all the sieved particles of each particle size is calculated sequentially from the small particle size particles. It is plotted against particle diameter.

The particle diameter corresponding to 50% of the cumulative weight is referred to as the average particle diameter DB.

The value obtained by dividing the particle size corresponding to 90% of the cumulative weight by the particle size corresponding to 40% is called the uniformity coefficient U9O/10.

The value obtained by dividing the particle size corresponding to 60% of the cumulative weight by the particle size corresponding to 10% is called the uniformity coefficient U6O/10.

U6O/10+U9O/40 is called the total uniformity coefficient UT.

Therefore, the uniformity coefficient U9O/40, . U60/10 is 1.0
The closer the total uniformity coefficient UT is to 2.0, the higher the uniformity of the obtained polymer particles, that is, the narrower the particle size distribution.

Specific examples will be shown below.

Example 1 2164.57 (130 parts by weight) of water,
Ethylene bisstearylamide 2.3V (0.14 parts by weight), sodium chloride 16.657 (1 part by weight), β
- Add 249 ~ (0.015 parts by weight) of the sodium salt of naphthalene sulfonic acid formalin condensate (hereinafter abbreviated as DM-N) and disperse it uniformly, and then, while stirring, benzoyl peroxide 5.337 (0.0 Styrene monomer 1665y (10 parts by weight) in which 3.37 (0.2 parts by weight) of t-butyl perbenzoate was dissolved.
0 parts by weight) was added thereto, and polymerization was started at a temperature of 90° C. in a nitrogen stream.

After polymerization for 1 hour and 30 minutes (polymerization conversion rate was 22%), 8.33y (0
．． 5 parts by weight) was dispersed in water 1307 (7.8 parts by weight) and added all at once to the polymerization system, followed by polymerization, and 2 hours and 30 minutes after the start of polymerization (polymerization conversion rate was 38%). Atsuta)
0.057 (1.003 parts by weight) of hexadecyldimethylbenzyl ammonium chloride was uniformly dissolved in 507 (3 parts by weight) of water and added all at once to the polymerization system, followed by polymerization. It solidified about 5 hours after the start of polymerization to obtain polystyrene polymer particles. After drying, the polymer particles were sieved into various particle sizes, and the average particle size was 1300.
μ, uniformity coefficient U9O/401.18, U6O/101.
58, the total uniformity coefficient UT was 2.76, and polymer particles were obtained whose particle size distribution was much narrower than that obtained by conventionally known suspension polymerization methods.

Example 2 According to the process of Example 1, only the amount of hexadecyldimethylbenzylammonium chloride was changed to 0.083
7 (0.005 parts by weight), the average particle size height of the obtained polymer particles was 970μ, U9O/401.13, U6
O/101.61, and the total uniformity coefficient UT was 2.74.

Example 3 According to the process of Example 1, tricalcium phosphate manufactured by Nihon Kagaku Co., Ltd. was used, and the amount was 33.37 (0.2
(parts by weight), the average particle size center of the obtained particles was 113
0μ, U9O/401.17, U6O/101.48,
The total uniformity coefficient UT was 2.65.

Example 4 2164.57 (130 parts by weight) of water,
Ethylene bisstearylamide 2.37 (0.14 parts by weight), calcium chloride dihydrate 16.657 (1 part by weight), and DM-N2497n9 (0.015 parts by weight) were added and dispersed uniformly and thoroughly. While stirring, add benzoyl peroxide 5.33y (0.32 parts by weight), t-
Styrene monomer 16657 (100 parts by weight) in which 3.37 (0.2 parts by weight) of butyl perbenzoate was dissolved was added, and polymerization was started at 90° C. in a nitrogen stream.

Next, 1 hour and 30 minutes after the start of polymerization (the polymerization rate was 22%), 18.9 y of trisodium phosphate dodecahydrate (1
．． 14 parts by weight) was dissolved in 130 y (18 parts by weight) of water and added all at once to the polymerization system, followed by polymerization, and 2 hours and 30 minutes after the start of polymerization (the polymerization conversion rate was 38%). Hexadecyldimethylbenzyl ammonium chloride 0.08337 (0.005 parts by weight) was uniformly dissolved in water 507 (3 parts by weight) and added to the polymerization system all at once, followed by polymerization, and the polymerization started. After solidification for 5 hours, polystyrene polymer particles were obtained.

After drying, these polymer particles were sieved into various particle sizes.
6O/101.57, and the total uniformity coefficient UT was 2.83. Example 5 According to the process of Example 4, the addition time of trisodium phosphate was changed and addition was made in three equal portions at 1 hour and 30 minutes, 2 hours, and 2 hours and 30 minutes after the start of polymerization. Furthermore, the amount of hexadecyldimethylbenzylammonium chloride was reduced to 0.
05t (0.03 parts by weight), the average particle size 4 of the obtained polymer particles was 1100μ, and the uniformity coefficient was U9O/401.
．． 25, U6O/101.47, total uniformity coefficient UT is 2.
It was 72.

Example 6 According to the process of Example 3, the amount of DM-N was 0.0833.
7 (0.005 parts by weight), the amount of trisodium phosphate was 11
．． 4f1 (0.68 parts by weight) for 1 hour 3 after the start of polymerization.
When the polymer particles were added in two equal portions at 0 minutes and 2 hours, the average particle size of the obtained polymer particles was 740μ, U9O/401.
28, U6O/101.67, total uniformity coefficient UT is 2.9
It was 5.

Example 7 2,164.5 f of water (130
parts by weight), 2.3 t of ethylene bisstearylamide (
0.14 parts by weight), tricalcium phosphate (Supertite 10 manufactured by Nihon Kagaku Co., Ltd.) 16.65V (0.1 parts by weight),
DM-NO. Add l33f7 (0.080 parts by weight) and disperse it uniformly, then add 5.33 t (0.32 parts by weight) of benzoyl peroxide and 3.3 t (0.2 parts by weight) of t-butyl perbenzoate while stirring. Styrene monomer 1665y (100 parts by weight) in which was dissolved was added, and polymerization was started at 90° C. in a nitrogen stream.

Next, 2 hours after the start of polymerization (the polymerization conversion rate was 30%), 16,657 (0.1 parts by weight) of tricalcium phosphate (Supertite 10 manufactured by Nihon Kagaku Co., Ltd.) was added to the polymerization system at once. Then, 2 hours and 30 minutes after the start of polymerization (the polymerization conversion rate was 38%), 0.05y (0.003 parts by weight) of hexadecyldimethylbenzylammonium chloride was added at 50V (3 parts by weight). The mixture was uniformly dissolved in water and added all at once to the polymerization system, followed by polymerization, which solidified approximately 5 hours after the start of polymerization to obtain polystyrene polymer particles.
After drying, these polymer particles were sieved into various particle sizes, and the average particle size core was 980μ, the uniformity coefficient was U9O/401.17, and U
6O/101.72, and the total uniformity coefficient UT was 2.89.

Example 8 According to the process of Example 7, the initial tricalcium phosphate was made by Taihei Kagaku Co., Ltd., the amount was 2.51 (0.15 parts by weight), and the phosphorus added 2 hours after the start of polymerization was added. Tricalcium acid was also made by Taihei Kagaku Co., Ltd., and the amount was 3.3y (0.
2 parts by weight), the average particle size height of the obtained polymer particles was 2100μ, uniformity coefficient U9O/401.22, U
6O/101.21, and the total uniformity coefficient UT was 2.43.

[Brief explanation of the drawing]

The figure shows the particle size μ on the horizontal axis and the cumulative weight percent of the polymer particles on the vertical axis.The particles obtained by polymerization are sieved into each particle size, and the total particles of each sieved particle size are The weight is plotted against successive particle sizes starting from small particles. A: Particle diameter equivalent to 10% of cumulative weight, B: Particle diameter equivalent to 40% of cumulative weight, C: Average particle diameter DB. D: Particle diameter corresponding to 60% of the cumulative weight; E: Particle diameter corresponding to 90% of the cumulative weight.

Claims (1)

[Claims] 1 When carrying out suspension polymerization of styrene or a mixture of styrene and a monomer copolymerizable with styrene in an amount of 10% or less, the monomer is mixed with sodium or potassium salt of β-naphthalene sulfonic acid formalin condensate, phosphorus Tricalcium acid and preferably a water-soluble metal salt that is neutral in an aqueous system are dispersed in water to initiate polymerization, and then a cationic surfactant is added at a polymerization conversion rate of 20 to 50% to polymerize. A method for suspension polymerization of styrene-based monomers, which is characterized by the following: