JPS5810406B2 - Kendakuji Yugohou - 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 essential to prevent coalescence and collapse of monomer droplets as the polymerization progresses, and such suspension stabilizers generally include polyvinyl alcohol, Polyvinylpyrrolidone, polymeric colloids such as gelatin, and U.S. Patent No. 2.673 to Grim,
No. 194, a poorly water-soluble inorganic salt, such as one consisting of a combination of 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, in the method described in US Pat. No. 2,673,194, 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.

Furthermore, the polymer particles mainly composed of styrene obtained by suspension polymerization are impregnated with a blowing agent (eg, propane, butane, pentane, etc.) to obtain so-called expanded styrene.

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) Styrene foam with a particle size of approximately 1,300μ to approximately 3,000μ 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 extensive research and found that the COD load of the polymerization effluent can be reduced without impairing the thermal stability, transparency, and mechanical strength of polymer particles obtained by suspension polymerization. We have found a method that allows the particle size distribution to be much narrower than known methods without increasing the particle size.

In the present invention, 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 β-naphthalene sulfonic acid formalin condensate. After dispersing a potassium salt and preferably a water-soluble metal salt that is neutral in an aqueous system in water and initiating polymerization, the polymerization conversion rate is 15 to 50%.
This is a suspension polymerization method of styrene-based monomers, which is characterized by adding tricalcium phosphate to the bonded fibers to complete the polymerization.

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 preferable 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. It shows
If an inorganic salt is not added, the suspension stability deteriorates, and the polymer particles do not become spherical or the total uniformity coefficient increases.

The amount of inorganic salt used is 0.01 parts by weight per 100 parts by weight of monomer.
It is sufficient to use more than part by weight.

If the amount 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.

The sodium salt or potassium salt of the β-naphthalene sulfonic acid formalin condensate is initially added to the system in order to uniformly disperse the styrene-based monomer.

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 o or ooi parts 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, for example, Grimm's USP 2,6
No. 73,194, it is a finely divided phosphate salt that is poorly water-soluble and contains at least 3 equivalents of calcium in each phosphate group.

The amount used is 1.0 to 0.0 per 100 parts by weight of monomer.
5 parts by weight or more is required.

If the amount is less than 0.05 part by weight, suspension stability will be impaired and pearl-like particles will not be obtained.

Further, since sufficient effects are exhibited at 1.0 parts by weight or less, there is no need to use more than that amount.

The figure shows the particle size on the horizontal axis and the cumulative weight percentage of polymer particles on the vertical axis.The particles obtained by polymerization are sieved into each particle size, and the weight of all particles of each sieved particle size is shown. is plotted against successive particle sizes starting from small particles.

The particle size corresponding to 50% of the cumulative weight is referred to as the average particle size 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 U90/40.

The value obtained by dividing the particle size corresponding to 60% of the cumulative weight by the particle size corresponding to 10070 is called the uniformity coefficient U60/10.

U60/10+U90/40 is referred to as total uniformity coefficient UT.

Therefore, the closer the uniformity coefficients U90/40 and U60/10 are to 1.0, the closer the total uniformity coefficient '[JT is to 2.0, the higher the uniformity of the obtained polymer particles. means narrow.

Specific examples will be shown below.

Example 1 51 equipped with a stirrer, cooling pipe, thermometer and nitrogen introduction pipe
2164.5g (130 parts by weight) of water in the fourth flask
, sodium salt of β-naphthalene sulfonic acid formalin condensate (hereinafter abbreviated as DM-N).

249m9 (0,015 parts by weight) of benzoyl peroxide was added and dissolved uniformly, followed by benzoyl peroxide 5.
Added 1,665 g (100 parts by weight) of styrene monomer in which 33 g (0.32 parts by weight) and 3.3 g (0.2 parts by weight) of t-butyl perbenzoate were dissolved, and polymerized at a temperature of 90°C in a nitrogen stream. started.

Next, after 1 hour and 30 minutes (the polymerization conversion rate was 22%), 13.3 g (0.8
Parts by weight) were dispersed in 130 g (7.8 parts by weight) of 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 true spherical polystyrene particles. Ta.

After drying this polymer particle, it was sieved into various particle sizes, and the average particle size dB was 800μ, and the uniformity coefficient was U90/401.24.
, U60/101.32, and the total uniformity coefficient UT is 2.56.
When manufactured by the method of Example 4 of No. 1298, the average particle size dB was 800μ, the uniformity coefficient U90/401.61,
U60/101.85 and total uniformity coefficient TJT were 3.46, indicating that the polymer particles obtained by this method had a much narrower particle size distribution.

Example 2 Polymerization was carried out according to the process of Example 1, with only the amount of DM-N changed from 166.5 to (0.01 parts by weight), and the average particle size of the obtained polymer particles was 1B is 850μ,
Uniformity coefficient U90/401.27, U60/101.43
, the total uniformity coefficient UT was 2.70.

Example 3 Polymerization was carried out according to the process of Example 1, with only the amount of DM-N changed to 33.3■ (0.02 parts by weight), and the average particle size of the obtained polymer particles was IB is 800μ, uniformity coefficient U90/401.17, U60/101.38,
The total uniformity coefficient UT was 2.55.

Example 4 According to the process of Example 1, the amount of DM-N was changed to 16
6.5 to (0.01 parts by weight) and the addition time of tricalcium phosphate was changed to 2.0 hours (polymerization conversion rate was 30%), and the average of the obtained polymer particles was Particle size dB is 850μ, uniformity coefficient U90/401.21, U
60/101.38, and the total uniformity coefficient UT was 2,59.

Example 5 According to the process of Example 1, the amount of DM-N was changed and 83
．． 3 mg (0,005 parts by weight), and changed the addition time of tricalcium phosphate for 2.0 hours (polymerization conversion rate was 30
When polymerized as
3. U60/101.39, total uniformity coefficient UT is 2.62
Met.

Example 6 51 equipped with a stirrer, cooling pipe, thermometer and nitrogen introduction pipe
2164.5 g (130 parts by weight) of water in a four-loaf flask
, 16.65 g (1.0 parts by weight) of sodium chloride, 3.33 g (0.20 parts by weight) of ethylene bisstearylamide, and 249 mg (0,015 parts by weight) of DM-N were uniformly dispersed and dissolved. While stirring, 5.33 g (0.32 parts by weight) of benzoyl peroxide,
1665 g (100 g) of styrene monomer in which 3.33 g (0.2 parts by weight) of t-butyl perbenzoate was dissolved
(parts by weight) was added, and the temperature was raised to 90° C. in a nitrogen stream to start polymerization.

Next, after 1 hour and 30 minutes (the polymerization conversion rate was 22%), 8.33 g (0,5
parts by weight) in 130 g of water (5 parts by weight),
When it was added all at once to the polymerization system and then polymerized, it solidified in about 5 hours after the start of polymerization to obtain true spherical polystyrene particles.

After drying the polymer particles, they were sieved into various particle sizes, and the average particle size dB was 1200μ, and the uniformity coefficient was U990/401.
36, U60/101.50, total uniformity coefficient UT is 2.8
It was 6.

Example 7 According to the process of Example 6, the amount of DM-N was changed to 50
0 mg (0.03 parts by weight) and polymerization was carried out for 2.0 hours by changing the addition time of tricalcium phosphate (polymerization conversion rate was 30%), and the average particle size of the obtained polymer particles was Diameter 1B is 1700μ, uniformity coefficient U90/401.29
, U60/101.54, total uniformity coefficient' [JT is 2.8
It was 3.

Example 8 Following the process of Example 6, the amount of tricalcium phosphate added was changed to 10 g (0.6 parts by weight), and the addition time was changed to -2.0 hours (polymerization conversion rate was 30 g). %)
When polymerized as
is 1500μ, uniformity coefficient U90/401.32, U60
/101.60, and the total uniformity coefficient UT was 2.92.

[Brief explanation of drawings]

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

Claims (1)

[Claims] 1. 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 mixed with a sodium or potassium salt of β-naphthalene sulfonic acid formalin condensate and Preferably, after starting polymerization by dispersing a water-soluble metal salt that is neutral in an aqueous system in water, tricalcium phosphate is added to the system at a polymerization conversion rate of 15 to 50% to complete the polymerization. A suspension polymerization method for monomers mainly composed of styrene, which is characterized by