JPS59176308A - Suspension polymerization - Google Patents

Abstract

PURPOSE:To produce a polymer of a narrow particle diameter distribution width, by dispersing a styrene monomer in an aqueous medium containing a specified dispersant system and suspension-polymerizing the dispersion in the presence of a specified polymerization initiator. CONSTITUTION:A styrene monomer (e.g., styrene) is dispersed in an aqueous system containing a dispersant system comporising a combination of an anionic surfactant, a sparingly water-soluble inorganic salt (e.g., calcium phosphate) and a water-soluble metal salt which reacts alkaline in an aqueous system (e.g., NaCl), and the dispersion is suspension-polymerized in the presence of tert- butyl peroxy(2-ethylhexanoate) as a polymerization initiator. It is thus possible to obtain polymer particles having a particle diameter distribution which is markedly narrower than that of particles obtained by a well-known process without to heat resistance, transparency, and mechanical strength and without any increase in the COD load of the waste polymerization solution.

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 relates to suspension polymerization.

Conventionally, in the suspension polymerization of monomers mainly composed of styrene, benzoyl peroxide is used as a polymerization initiator, and organic surfactants such as polyvinyl alcohol and polyvinylpyrrolidone, or poorly water-soluble inorganic surfactants are used as polymerization dispersants. Combinations of salts and anionic surfactants have been used, but in either case 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, but if the particle size distribution is wide, there will be variations in the supply of raw materials to the molding machine, resulting in product defects. The problem arises that the rate increases.

In addition, polymer particles mainly composed of styrene obtained through suspension polymerization are used for purposes such as expanded styrene, and the uses of expanded styrene can be roughly divided into the following three fields depending on the size of the particles. .

■) Styrene foam with a particle size of approximately 03 to 0.7 mm is used in cups for instant foods.

2) Styrene foam with a particle size of approximately 07 to 1.8 πm is used for various packaging materials.

3) Styrene foam with a particle size of approximately 1.3 to 30 yttm is a board for building materials.

The properties of expanded styrene required by these different uses differ, so it may be necessary to manufacture expanded styrene for each use.) If the particle size distribution of the polymer particles obtained by turbidity polymerization is wide, the purpose It's a fly.

In order to solve this problem, the present inventors have conducted extensive research and have found that the polymer particles obtained by suspension polymerization can be produced without impairing their thermal stability, transparency, and mechanical strength, and that the polymerization effluent can be We have found a method that allows the particle size distribution to be much narrower than known methods without increasing the COD load, and we hereby provide that method.

According to the present invention, when suspension polymerizing a styrenic monomer, the monomer is made of a combination of an anionic surfactant, a poorly water-soluble inorganic salt, and a water-soluble metal salt that is neutral in an aqueous system. After being dispersed in an aqueous dispersion medium, polymer particles having a narrow particle size distribution width can be obtained by polymerizing using tert-butyl peroxy (2-ethylhexanoate) as a polymerization initiator. The total uniformity coefficient UT of the polymer particles obtained by the present invention is about 27, whereas in the known suspension polymerization method, UT is usually a value of 3.2 or more.

The styrene monomer in the present invention means styrene, but a monomer copolymerizable with styrene may be mixed with 10 parts by weight or less of styrene for copolymerization. Copolymerizable monomers include various substituted styrenes such as chlorostyrene and a-methylstyrene.

Aluminum or vinyl monomers such as acrylonitrile, methyl methacrylate, and methyl acrylate are used.

Copolymerization with more than 10 parts by weight of a copolymerizable monomer is not preferred because it significantly changes suspension stability.

In the present invention, it is essential to use tertiary-butyl peroxy (2-ethylhexanoate) as a polymerization initiator in order to achieve the object of the present invention.

The amount of the polymerization initiator to be used may be determined depending on the degree of polymerization of the target polymer particles, but it is usually 0.000% relative to the monomer.
10 to 040 parts by weight is sufficient, practically 0.15 to 0.32
Polymer particles with a sufficient degree of polymerization can be obtained in parts by weight. In addition to the polymerization initiator, general catalysts such as benzoyl peroxide and t-butrubroxybenzoate may be used in combination. When used in combination, the amount of other polymerization initiators used is preferably 20% by weight or less of tert-butyl peroxy (2-ethylhexanoate). Furthermore, for the purpose of reducing the residual monomer, the effect of the present invention can also be obtained by using a high temperature polymerization initiator such as tertiary butyl perbenzoate in an amount of, for example, 0.01 to 0.30 parts by weight based on the monomer. It does not change.

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. Its usage is
It may be adjusted according to the target particle size of the polymer. For example, when using basic calcium phosphate, select an amount in the range of 0.05 parts by weight or more and 1.0 parts by weight or less based on the monomer. This is sufficient for practical use. Also, those having 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 taking a balance between suspension stability and particle size.

The anionic surfactant acts as a dispersant together with a poorly water-soluble inorganic salt, and common sodium alkylbenzenesulfonate, sodium a-olefinsulfonate, etc. can be used.

Examples of inorganic salts that are neutral in aqueous systems include lithium chloride, potassium chloride, common salt, magnesium chloride, calcium chloride, and the like. These inorganic salts may be used alone or in combination, but they are particularly effective when used in an amount of 0.2 parts by weight or more based on the monomer, and the effects do not change much when used in amounts of 1.0 parts by weight or more. There is no reason to use it any more from an economic point of view. Among these inorganic salts, common salt is particularly preferred because it is inexpensive and exhibits sufficient effects.

Hereinafter, a more specific explanation will be given with reference to Examples.

Example 1 170 ON (90 parts by weight) of water was placed in a 51-volume 40 flask equipped with a stirrer, a thermometer, etc., and then 238 g (0,125 parts by weight) of basic calcium phosphate (Nihon Kagaku Kogyo Co., Ltd.) was added while stirring. Plain made, product name: Super Tight 1o
, solid content 10%), sodium α-olefin sulfonate 0.076y (0,004.0 parts by weight) di-salt 6.8
89 (0,336 parts by weight), 1.33 g (0, (17 parts) by weight) of ethylene bisstearylamide, 342 g (2 ethylhexanoate) of tert-butyl peroxy
0,180 parts by weight) (manufactured by Nippon Oil & Fats Co., Ltd., trade name Perbutyl O, Tertiary Butylpa-Benzony) 2.85y (0,
Then, 1.900 fl (100 parts by weight) of styrene was added, and the temperature was raised to 94°C with sufficient stirring to initiate 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 into various particle sizes, and the average particle size was 1.20π7i, with a uniformity coefficient of U 90/40 = L34°U 60/10 =
1.89. The total uniformity coefficient UT was 2.74, and the polymer particles had a particle size distribution width significantly narrower than that obtained by conventionally known suspension polymerization methods.

Example 2 According to the process of Example 1, sodium dodecyl phenyl oxide disulfonate (manufactured by Kao Seiko ■, trade name: Perex 5SF (purity content 50%), pure content 0.076 f) was used instead of sodium α-olefin sulfonate. (0,00
When using 40 heavy image part 9, the average particle size of the obtained polymer particles was 1.1977? .

Uniformity coefficient U90/40 = 1.81. U60/10=1
．． The polymer particles had a 38° total uniformity coefficient of 2.69, and the particle size distribution width was much narrower than that obtained by conventionally known suspension polymerization methods.

Comparative Example 1 According to the process of Example 1, the same amount of common benzoyl peroxide was used instead of tert-butyl peroxy (2-ethylhexanoate). The average particle size of the obtained polymer particles was 1.061ff, and the uniformity coefficient was 09.
0/40 = 1.66. U60/10=1.55. The total uniformity coefficient UT was 3.20, indicating a typical particle size distribution.

[Brief explanation of the drawing]

In the figure, the horizontal axis shows the particle size (嬬), the vertical axis shows the cumulative 1ift percent of polymer particles, and the weight of all particles of each particle size obtained by sieving the particles obtained by polymerization into each particle size is calculated. Particles of small particle size are plotted against particle size in order. The particle size C corresponding to 50% of the cumulative weight is called the average particle size dB. The uniformity coefficient U90/B is the value E/B obtained by dividing the particle diameter E, which is equivalent to 90% of the cumulative weight, by the particle diameter B, which is equivalent to 40%.
It is called 40. The particle size equivalent to 60% of the cumulative weight is 1
The uniformity coefficient U6 is the value D/A divided by the particle diameter A equivalent to 0%.
It is called 0/10. Uniform coefficient U90/40+U60/10
is called the total uniformity coefficient UT. Therefore, uniformity coefficient U90/4
0. The closer U60/10 is 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. C: Average particle diameter i E/B: Uniformity coefficient U90/40 D/A: Uniformity coefficient U60/10 EZB+D/A: Total uniformity coefficient UT Patent applicant Kanebuchi Chemical Co., Ltd. agent Patent attorney Makoto Asano -

Claims (5)

[Claims] (1) When suspension polymerizing styrenic monomers, the monomers are treated with a dispersant system consisting of a combination of an anionic surfactant, a poorly water-soluble inorganic salt, and a water-soluble metal salt that is neutral in an aqueous system. After being dispersed in an aqueous medium, a tertiary compound is used as a polymerization initiator.
A method for layer temperature polymerization of styrenic monomers, characterized by polymerization using butyl peroxy (2-ethylhexanoate). (2) The polymerization method according to claim 1, wherein the poorly water-soluble inorganic salt is basic phosphoric acid. (3) The polymerization method according to claim 2, 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. (4) The polymerization method according to claim 1, wherein the water-soluble metal salt or common salt is neutral in an aqueous system. (5) The polymerization method according to claim 4, wherein the amount of common salt used is 0.2 parts by weight or more and 1.0 parts by weight or less based on the monomer.