JPS608686B2 - Method for cleaning suspended polymer particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to the production of vinyl polymer particles synthesized by aqueous suspension polymerization using tricalcium phosphate as a main suspension stabilizer and an anionic surfactant as a suspension stabilizing aid. This invention relates to a method for removing surface-adhered tricalcium phosphate.

Suspension polymerization of vinyl monomers is generally carried out in the presence of a suspension stabilizer capable of keeping the monomers dispersed in droplets.

As this kind of suspension stabilizer, a hydrophobic polymer colloid such as gelatin, starch, polyvinyl alcohol or polyvinylpyrrolidone, or a hydrophobic metal salt powder such as tricalcium phosphate can be used. When using a hydrogen bombable polymer colloid as a suspension stabilizer, the following problems occur. '1} The water-soluble polymer colloid remains on the particle surface and cannot be removed by simple washing, and has a significant effect on the physical properties of the resulting polymer, such as solubility, transparency, and softening temperature.

[2' This is a major cause of resin tightening.

{3' Increase COD load in polymerization wastewater.

Therefore, in order to prevent such drawbacks, a suspension polymerization method using a water-repellent metal salt as the main suspension stabilizer is employed. However, lagoonal metal salts such as tricalcium phosphate have no affinity with monomer droplets by themselves and are difficult to use as suspension stabilizers. So U. S. As shown in P. 2594913, it is necessary to use it in combination with an anionic surfactant.
However, in this case as well, as in the case of using the water-lacquer polymer colloid as a suspension stabilizer, the inorganic suspension stabilizer ultimately remains on the surface of the polymer particles and is not removed by simple washing, resulting in the formation of a polymer. In addition, when a foamable synthetic resin is synthesized using tricalcium phosphate and an anionic surfactant in combination, the tricalcium phosphate attached to the surface of the polymer impairs foam moldability. In particular, the strength of the molded product is significantly reduced. Therefore, it is necessary to remove tricalcium phosphate from the surface of the polymer particles. As this method, washing with acid is generally considered. That is, it is known that tricalcium phosphate adhering to the surface of the polymer can be almost completely removed by washing the polymer particles to which tricalcium phosphate has adhered with a solution having a pH of 3 or less, preferably 2 or less. There is. However, the acid cleaning method has the disadvantage that when building actual production equipment, the cost of the equipment is high in order to solve problems such as acid corrosion and pH of wastewater. The present invention relates to tricalcium phosphate attached to the surface of styrenic vinyl polymer particles synthesized by suspension polymerization using the above tricalcium phosphate as a main suspension stabilizer and an anionic surfactant as a suspension stabilizing bedding agent. The present invention relates to a method for cleaning suspended particles, which is characterized by adding a cationic surfactant in an amount equal to or more than the anionic surfactant upon completion of polymerization.

The cationic surfactant used here is not particularly limited, but water-lacquer cationic surfactants are preferable, such as hexadecyltrimethylammonium chloride, alkyl(coconut)trimethylammonium chloride, dodecyltrimethylammonium chloride, alkyltrimethylammonium chloride, hexadecyldimethylbenzylammonium chloride, lauryldimethylbenzylammonium chloride, alkyldimethylbenzylammonium chloride, and the like.

The amount used is preferably at least equimolar to the anionic surfactant. If the amount is less than equimolar, tricalcium phosphate attached to the surface will not be removed much. Although the upper limit is not particularly limited, if too large a quantity is used, the cationic surfactant may cause severe foaming, making various subsequent operations difficult. The styrenic vinyl polymer refers to a styrene homopolymer and a copolymer mainly composed of styrene, and copolymerizable monomers include n-butyl acrylate, methyl methacrylate, acrylonitrile, butadiene, and the like.

The anionic surfactant that is the suspension stabilizer of the present invention is not particularly limited, but examples thereof include sodium dodecylbenzenesulfonate, sodium octylsulfate, sodium oleate, and sodium dodecyl-1ene-sulfonate.

When the resin washed by the above method is, for example, a foam, tricalcium phosphate, which is a factor that inhibits the adhesion (fusion) of the resin during molding, is removed, so the strength of the molded product is significantly improved.

In addition, the above-mentioned transparency and strength of materials other than foams are also very good. Next, specific examples will be shown.

Example 130 parts by weight of water was placed in an autoclave equipped with an Iso-Azusa machine, and then 0.6 parts by weight of tricalcium phosphate (manufactured by Ohira Kagaku Co., Ltd.) was added as a main dispersant, and an anionic surfactant (type and amount) was added as a dispersion aid. The details are shown in Table 1.

) was added and dispersed uniformly using a fly paste, and 0.0% of penzoyl peroxide was added thereto as a polymerization initiator. Tsuru weight part, t
-100 parts by weight of styrene monomer in which 0.2 parts by weight of butyl peroxybenzoate was dissolved was introduced, and after purging with nitrogen, polymerization was carried out at 9,000 for 7 hours, then at 10,500 for 3 hours, and then cooled to room temperature. I did it. After cooling, a cationic surfactant was added for the purpose of removing tricalcium phosphate attached to the surface of the polymer. The amount added and the type of cationic surfactant are shown in Table 1. After that, dehydrate and dry.
The amount of tricalcium phosphate attached to the surface of the produced resins having an average particle size of 0.3 to 0.5 m/m was measured. The determination of tricalcium phosphate is based on JIS-K-0102.
The phosphate ion concentration was measured according to the following. The results are shown in Table 1. Table 1

Claims (1)

[Claims] 1 Aqueous suspension polymerization is carried out using tricalcium phosphate as the main suspension stabilizer and an anionic surfactant as a suspension stabilizing agent. After the polymerization is completed, the polymer particles are washed with a cationic surfactant and the polymer particles are A method for cleaning styrene-based vinyl polymer suspension polymer particles, characterized by removing tricalcium phosphate adhering to the surface of the combined particles.