JPH0150321B2 - - 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 particularly, to a suspension polymerization method for obtaining particles with a narrow particle size distribution synthesized by suspension polymerization. It is. Conventional methods for suspension polymerization of monomers mainly composed of styrene include polymerization using organic surfactants such as polyvinyl alcohol and polyvinylpyrrolidone, or tribasic calcium phosphate,
A method of polymerizing a poorly water-soluble inorganic salt such as hydroxyapatite or pyrophosphate, and an anionic surfactant such as sodium dodecylbenzenesulfonate, sodium α-olefin sulfonate, or sodium lauryl sulfate as a combined dispersant, etc. It has been known. However, when an organic surfactant is used as a dispersant, it may cause a decrease in thermal stability, deterioration of transparency, or decrease in mechanical strength due to the incorporation of the dispersant into polymer particles. Or,
In addition, the COD load of the polymerization effluent becomes high, and it is extremely difficult to remove it with wastewater treatment equipment, which is undesirable from the standpoint of environmental conservation. Furthermore, by using an anionic surfactant in combination with a poorly water-soluble inorganic salt, stable suspension polymerization ability can be obtained with a smaller amount of the poorly water-soluble inorganic salt. When polymers are subjected to suspension polymerization, the resulting polymer particles have a relatively wide particle size distribution. Polymer particles mainly composed of polystyrene obtained through suspension polymerization are extruded or injection molded and made into 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 can be used as blowing agents such as propane, butane, etc.
So-called expanded styrene is obtained by impregnating it with pentane or the like. 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 approximately 300μ to 700μ is used in cups for instant foods. 2 Particles with a particle size of approximately 700μ to 1800μ are used for various packaging purposes. 3 Styrene foam with a particle size of approximately 1300μ to approximately 3000μ is used as construction material for boats, etc. These differences in use require different properties of expanded styrene, so it is necessary to manufacture expanded styrene for each purpose. The goal is difficult to reach. 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, and that We have found a method that significantly narrows the particle size distribution compared to known methods without increasing the COD load of the liquid, and we hereby provide that method. According to the present invention, when carrying out suspension polymerization of a styrenic monomer, the monomer is prepared from a combination of a dodecyl phenyl oxide disulfonate, a poorly water-soluble inorganic salt, and a water-soluble metal salt that is neutral in an aqueous system. Polymer particles with a narrow particle size distribution can be obtained by dispersing the polymer particles in an aqueous medium in a dispersion system. The total uniformity coefficient U _T of the polymer particles obtained by the present invention is about 2.7, whereas in the known suspension polymerization method, U _T is 3.2 or more. The styrenic monomer in the present invention means styrene, but a monomer copolymerizable with styrene may be mixed in an amount of 10 parts by weight or less with respect to styrene and copolymerized. As the copolymerizable monomer, various substituted styrenes such as chlorstyrene and α-methylstyrene, or vinyl monomers such as acrylonitrile, methyl methacrylate, and stylacrylate are used. Copolymerization with more than 10 parts by weight of a copolymerizable monomer is not preferred because it significantly changes suspension stability. Inorganic salts that are neutral in aqueous systems include lithium chloride,
Potassium chloride, common salt, magnesium chloride, calcium chloride, potassium sulfate, sodium sulfate, magnesium sulfate, etc. are used. These inorganic salts may be used alone or in combination. Further, better suspension stability can be obtained for these inorganic salts by polymerizing a styrene monomer in the coexistence of methylene bis stearylamide or ethylene bis stearyl amide, which are known as nucleating agents for expanded styrene. The inorganic salt is particularly effective when used in an amount of 0.2 parts by weight or more, and the effect does not change much when it is used in an amount of 1.0 parts by weight or more, and there is no reason to use more than that from the viewpoint of economy. Moreover, as the inorganic salt, common salt is preferable because it is inexpensive and exhibits sufficient effects. The poorly water-soluble inorganic salt is an inorganic salt that is poorly soluble in water, such as calcium phosphate, magnesium phosphate, calcium carbonate, and magnesium carbonate, and acts as a dispersant when polymerizing styrene monomers. The amount used can be adjusted according to the target particle size of the polymer. For example, when using basic calcium phosphate,
It is practically sufficient to select an amount in the range of 0.05 parts by weight to 1.0 parts by weight, and those with a particle size of 2 μm or less are preferably used. Incidentally, the poorly water-soluble inorganic salt may be added in portions during the polymerization, and the polymerization may be carried out while maintaining a balance between suspension stability and particle size. In the present invention, in addition to the above-mentioned poorly water-soluble inorganic salts and inorganic salts that are neutral in water systems, dodecyl phenyl oxide disulfonate is used to produce a polystyrene polymer with a sharp particle size distribution. particles are obtained. For example, when sodium dodecyl phenyl oxide disulfonate is used together with basic calcium phosphate and common salt, it acts as a very effective dispersant for obtaining polystyrene polymer particles with a sharp particle size distribution. The amount used is preferably from 0.001 parts by weight to 0.01 parts by weight, more preferably from 0.001 parts by weight to 0.01 parts by weight, based on the monomer.
It is preferably 0.005 part by weight or more and 0.008 part by weight. If it exceeds 0.01 part by weight, the effect of narrowing the particle size distribution will be reduced, and if it is too large, the suspension stability may worsen. Furthermore, if the amount is less than 0.001 parts by weight, the effect of narrowing the particle size distribution will similarly decrease. As described above, the styrenic polymer is polymerized in a dispersion system, and a general polymerization initiator may be used as the polymerization initiator, such as benzoyl peroxide, t-butyl peroxybenzoate, etc. Ru. The amount used is usually 0.10 to 0.40 parts by weight based on the monomer. Hereinafter, this will be explained in more detail with reference to Examples. Example 1 1700 g (90 parts by weight) of water was placed in a 5-volume, 4-necked flask equipped with a stirrer, thermometer, etc., and then 2.20 g of basic calcium phosphate was added while stirring.
(0.120 parts by weight) (manufactured by Nippon Kagaku Kogyo Co., Ltd., trade name Supertite 10, solid content 10%), sodium dodecyl phenyl oxide disulfonate (Kao Soap Co., Ltd.)
Manufactured by Perex SSH, pure content 50%)
0.142g (0.0075 parts by weight), 6.38g (0.336 parts by weight) of common salt, 1.33g of ethylene bisstearylamide
(0.07 parts by weight), benzoyl peroxide 3.42g
(0.180 parts by weight), tertiary butyl perbenzoate
Add 2.85g (0.150 parts by weight) and disperse evenly.
Next, 1900g (100 parts by weight) of styrene was added,
While sufficiently stirring, the temperature was raised to 94°C to start polymerization.
True spherical polystyrene polymer particles solidified in about 5 hours after the start of polymerization were obtained. After drying these polymer particles, they were sieved to various particle sizes, and the average particle size was dB~
is 1.00 (mm), uniformity coefficient U90/40 = 1.30, U60/10
= 1.39, and the total uniformity coefficient U _T = 2.69, and the polymer particles had a particle size distribution width significantly narrower than that obtained by conventionally known suspension polymerization methods. Example 2 To demonstrate the effect of the concentration of sodium dodecyl phenyl oxide disulfonate on the total uniformity coefficient, the concentration of sodium dodecyl phenyl oxide disulfonate and basic calcium phosphate was varied according to the process of Example 1. Upon polymerization, polymer beads having particle sizes and uniformity coefficients as shown in Table 1 were obtained.

[Table] Comparative Example 1 According to the process of Example 1, instead of sodium dodecyl phenyl oxide disulfonate,
When polymerization was carried out using 0.0050 part of α-olefin sodium sulfonate, which is one of the conventionally known surfactants, the obtained polymer particles had an average particle size of dB~=1.06 (mm) and a uniformity coefficient of U90/40=1.65,
U60/10=1.55, and the total uniformity coefficient U _T =3.20.

[Brief explanation of drawings]

The figure shows the particle diameter (mm) on the horizontal axis and the cumulative weight percent of the polymer particles on the vertical axis. It is plotted against the particle size in order from particle size to particle size. The particle size C corresponding to 50% of the cumulative weight is called the average particle size dB~. Particle size E equivalent to 90% of cumulative weight
The value E/B divided by the particle diameter B equivalent to 40% is called the uniformity coefficient U90/40. The value D/A obtained by dividing the particle diameter D, which is equivalent to 60% of the cumulative weight, by the particle diameter A, which is equivalent to 10%, is called the uniformity coefficient U60/10. Uniform coefficient
U90/40+U60/10 is called the total uniformity coefficient _UT . Therefore, the closer the uniformity coefficients U90/40 and U60/10 are to 1.0, the
The closer the total uniformity coefficient U _T is to 2.0, the higher the uniformity of the obtained polymer particles, that is, the narrower the particle size distribution width. C: Average particle diameter dB ~ E/B: Uniformity coefficient U90/40 D/A: Uniformity coefficient U60/10 E/B+D/A: Total uniformity coefficient _UT .

Claims (1)

[Claims] 1. When carrying out suspension polymerization of styrenic monomers, the monomers are treated with dodecyl phenyl oxide disulfonate, poorly water-soluble inorganic salts, and water-soluble metal salts that are neutral in aqueous systems. A suspension polymerization method for styrenic monomers, which is characterized in that the styrenic monomers are polymerized after being dispersed in an aqueous medium containing a dispersant. 2. The amount of dodecyl phenyl oxide disulfonate used is 0.001 part by weight or more based on the monomer.
The polymerization method according to claim 1, wherein the amount is 0.01 part by weight or less. 3. The polymerization method according to claim 1, wherein the poorly water-soluble inorganic salt is basic calcium phosphate. 4. The polymerization method according to claim 3, wherein the amount of basic calcium phosphate used is 0.05 parts by weight or more and 1.0 parts by weight or less based on the monomer. 5. The polymerization method according to claim 1, wherein the water-soluble metal salt exhibiting neutrality in an aqueous system is common salt. 6. The polymerization method according to claim 5, wherein the amount of common salt used is in the range of 0.2 parts by weight or more and 1.0 parts by weight or less based on the monomer.