JPS5919126B2 - Suspension polymerization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for suspension polymerization of monomers mainly containing styrene.

More specifically, the present invention relates to a suspension polymerization method for obtaining styrene-based polymer particles with relatively uniform particle diameters. Conventional methods of suspension polymerizing monomers mainly composed of styrene include methods of polymerizing using organic surfactants such as polyvinyl alcohol and polyvinylpyrrolidone as dispersants, and methods of polymerizing monomers mainly composed of styrene, as well as methods of polymerizing with difficulty as shown in Japanese Patent Publication No. 29-1298. Known methods include polymerization using a water-soluble inorganic salt and an anionic surfactant as a combined dispersant.

However, when an organic surfactant is used as a dispersant, mixing of the dispersant into polymer particles may cause a decrease in thermal stability, deterioration of transparency, or a decrease in mechanical strength. It is known that this can have undesirable effects such as increasing the COD load of the polymerization effluent.

As a way to remove these effects,
A method as shown in No. 98 is known, but when a monomer mainly composed of styrene is subjected to suspension polymerization according to this method, the particle size distribution width of the obtained polymer particles is relatively wide.

Polymer particles mainly composed of styrene obtained by suspension polymerization are extruded or injection molded and used to make various products, but 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 of products increases.

J Also, 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. j(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) Foamed foam with a particle size of approximately 1300μ to approximately 3000μ
Styrene is used for building boards, etc.

These different uses require different properties of expanded styrene, so it is necessary to manufacture expanded styrene for each use, but if the polymer particles obtained by suspension polymerization have a wide particle size distribution, the purpose It is difficult to reach 5.

In order to solve this problem, the present inventors have conducted intensive research and found that the polymer particles obtained by suspension polymerization can be polymerized without impairing their thermal stability, transparency, and mechanical strength. We have invented a method that greatly narrows the particle size distribution width compared to known methods without increasing the COD load of the wastewater, and we hereby provide that method.

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 converted into a sodium salt of β-naphthalene sulfonic acid formalin condensate or After dispersing potassium salt, calcium chloride, and preferably a water-soluble metal salt that is neutral in an aqueous system in an aqueous medium, suspension polymerization is initiated, and the polymerization is carried out at a polymerization conversion rate of between 15% and 50%. Add trisodium phosphate to the system, react with the calcium chloride to synthesize tricalcium phosphate, and then polymerize to completion to obtain polymer particles with relatively uniform particle size. Regarding things.

The total uniformity coefficient UT of the polymer particles obtained by the present invention is about 3 or less, whereas in the known suspension polymerization method, the total uniformity coefficient UT is about 3 or less.
The present inventors have confirmed that the value is 3.5 or more.

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

Examples of copolymerizable monomers include chlorstyrene, and
- It refers to various substituted styrenes such as methylstyrene, or vinyl monomers such as acrylonitrile, methyl methacrylate, and butyl acrylate. Copolymerization with 10% or more of a copolymerizable monomer is not preferred because it significantly changes suspension stability.

Inorganic salts that are neutral in aqueous systems include potassium chloride, common salt, lithium chloride, magnesium chloride, calcium chloride, potassium sulfate, sodium sulfate, magnesium sulfate, and the like.

These inorganic salts are simple. Used in combination 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 t,
If an inorganic salt is not added, the suspension stability becomes unstable, and the polymer particles may not be spherical or the total uniformity coefficient may become large. The inorganic salt may be used in an amount of 0.01 part by weight or more per 100 parts by weight of the monomer. If the amount is less than this, the effect will be insufficient. There is no specific upper limit on the amount of inorganic salts used, but
Since a sufficient effect is exhibited at 2.0 parts by weight or less, there is no need to use more than that amount. 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 and potassium salt of β-naphthalene sulfonic acid formalin condensate act as a dispersant from the start of polymerization to a polymerization conversion rate of 15% to 50%, and may be used alone or in combination. .

The required amount may be between 0.001 part by weight and 0.1 part by weight per 100 parts by weight of the monomer. 0.001
If it is less than 0.1 part by weight, the suspension stability becomes unstable and polymerization becomes impossible, and if it is more than 0.1 part by weight, the COD load of the polymerization effluent becomes large. Since it is effective, there is no need to use it any more.

Calcium chloride may be used in the form of anhydrous salt, disaline water, hexahydrate salt, or the like.

Calcium chloride shows the same effect as the inorganic salt mentioned above before adding trisodium phosphate, and when trisodium phosphate is added, it reacts with trisodium phosphate to produce tricalcium phosphate according to the following formula. . The produced tricalcium phosphate exhibits efficacy as a dispersant together with the sodium salt or potassium salt of the β-naphthalene sulfonic acid formalin condensate. 10CaC12+6Na3
P04・12H20+2H20→3Ca3(PO4)2
-Ca(0H)+18NaC1+2HC1 When a stoichiometric excess of calcium chloride is used in the synthesis of tricalcium phosphate, the excess subsequently exhibits the effect of the inorganic salt.

The amount of trisodium phosphate used is such that the amount of tricalcium phosphate produced in the above reaction formula is 0.00 parts by weight per 100 parts by weight of the monomer.
The amount is limited to 1 part by weight to 1.0 parts by weight.

Calcium chloride should be used in an amount greater than the amount required for all trisodium phosphate to react stoichiometrically. The amount should be 1.0 parts by weight or less per 100 parts by weight. If trisodium phosphate is present in excess in the polymerization system after reacting with calcium chloride, the polymerization system will become alkaline and hinder the progress of polymerization. Further, even if an excess of 1.0 parts by weight or more of calcium chloride is present, no particularly great efficacy is observed, so there is no need to use any more. Trisodium phosphate has a polymerization conversion rate of 15% to 5.
Add between 0%.

When trisodium phosphate is added at a polymerization conversion rate of 15% or less, the particle size distribution width of the produced polymer particles becomes wider. Furthermore, even if 50% or more is added, the viscosity of the polymer is too high, so the tricalcium phosphate produced no longer exhibits sufficient dispersion ability, resulting in poor suspension stability and difficulty in obtaining desired particles and particle size distribution. I won't be able to do it. If trisodium phosphate is not added, suspension stability cannot be maintained only with the sodium salt or potassium salt of the β-naphthalene sulfonic acid formalin condensate. 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 diameters starting from particles with small platelet diameters. The particle size corresponding to 50% of the cumulative weight is referred to as 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 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 referred to as the total uniformity coefficient UT.

Therefore, the closer the uniformity coefficients U9O/40 and U6O/10 are to 1.0, and 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 width. It means that.

Examples are shown below.

Example-1 2164.59 (130 parts by weight) of water was placed in a 51-inch four-loaf flask equipped with a stirrer, cooling tube, thermometer, and nitrogen introduction tube.
, ethylene bisstearylamide 2.39 (0.14 parts by weight), common salt 16.659 (1 part by weight), calcium chloride dihydrate 8.49 (0.5 parts by weight), β-naphthalene sulfonic acid formalin condensation Sodium salt of 249η(
Add 0.015 tbg of Q and disperse it uniformly, then add 7.29 g of benzoyl peroxide (0.43 parts by weight) and 3.3 g of tert-butyl perbenozoate to styrene '16659 (100 parts by weight). (0.2 parts by weight) was added and heated to 90°C under a nitrogen stream while stirring thoroughly.
The temperature was raised to ℃ to start polymerization.

After polymerization for 1 hour and 30 minutes (polymerization conversion rate was 22%),
Trisodium phosphate dodecahydrate 11.29 (0.68 parts by weight) was dissolved in water 1309 (7.8 parts by weight) and added all at once to the polymerization system, followed by polymerization. However,
Solidified polystyrene polymer particles were obtained about 5 hours after the start of polymerization. After drying, the polymer particles were sieved into various particle sizes, and the average particle size DB was 940μ, with a uniformity coefficient of U9O/
401.35, U6O/101.44, total uniformity coefficient UT
was 2.79, and polymer particles were obtained whose particle size distribution width was much narrower than that obtained by conventionally known suspension polymerization methods.

Example-2 2164.5y (130 parts by weight) of water was placed in a 51-inch four-bottle flask equipped with a stirrer, cooling tube, thermometer, and nitrogen introduction tube.
, ethylene bisstearylamide 1.39 (0.08 parts by weight), calcium chloride dihydrate 16.659 (1.0
249Tf1f (0.015 parts by weight), a sodium salt of β-naphthalene sulfonic acid formaldehyde condensate, was added and thoroughly dispersed, and then styrene 1
665g (100 parts by weight) of benzoyl peroxide 7
．． 29 (0.43 parts by weight) and 3.3 g (0.2 parts by weight) of tert-butyl perbenzoate were added, and the temperature was raised to 9.0°C under a nitrogen stream with sufficient stirring to polymerize. started.

After 1 hour and 30 minutes (the polymerization conversion rate was 23.2%), 18.9 g (1.14
Parts by weight) were dissolved in 130 g (7.8 parts by weight) of water and added all at once to the polymerization system, followed by polymerization.
Solidified polystyrene polymer particles were obtained about 5 hours after the start of polymerization. After drying this polymer particle, it was sieved into various particle sizes, and the average particle size was DB9OOμ, and the uniformity coefficient was U9O.
/401.18, U6O/101.42, total uniformity coefficient U
'T was 2.60.

Example-3 According to the process of Example-2, only the addition time of the trisodium phosphate aqueous solution was changed, and the addition time was changed to 2.
When the time was 0 hours (the polymerization conversion rate was 30%),
The obtained polymer particles had an average particle diameter DBL of 28 Oμ, uniformity coefficients U9O/401.25, U6O/101.48, and total uniformity coefficient U〒2.73.

Example 4 According to the process of Example 2, only the amount of sodium salt of β-naphthalene sulfonic acid formalin condensate was reduced to 0.
When polymerization was carried out by changing the amount to 0075 parts by weight, the average particle size of the obtained polymer particles was DBl34Oμ, uniformity coefficient U9O/
401.411U60/101.59, total uniformity coefficient U〒
was 3.00.

Example-5 According to the process of Example-2, only the addition method of the trisodium phosphate aqueous solution was changed, and the trisodium phosphate aqueous solution was added dropwise for 100 minutes from 1.5 hours after the start of polymerization. A process of polymerization was used.

The conversion rate after 1.5 hours of polymerization was 22%, and the conversion rate immediately after the completion of dropping the trisodium phosphate aqueous solution was 45%. The average particle diameter DBllOOμ of the obtained polymer particles, uniformity coefficient U9O/401.43, U6O/101.46, and total uniformity coefficient UT were 2.89.

[Brief explanation of drawings]

The figure shows the particle size 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 Weight 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.

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 converted into a sodium salt or potassium salt of a β-naphthalene sulfonic acid formalin condensate. After dispersing calcium chloride and preferably a water-soluble metal salt that is neutral in an aqueous system in an aqueous medium, suspension polymerization is started, and the polymerization conversion rate is between 15% and 50%. 1. A method for suspension polymerization of monomers mainly composed of styrene, which comprises adding trisodium phosphate to the mixture, reacting with the calcium chloride to synthesize basic calcium phosphate, and then completing the polymerization.