JP3418926B2 - Method for producing vinyl chloride polymer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vinyl chloride polymer having improved prevention of scale adhesion to the inner wall surface of a polymerization vessel in the course of polymerization of a vinyl chloride monomer. It concerns the manufacturing method. [0002] In suspension polymerization and emulsion polymerization in which vinyl chloride is polymerized in an aqueous medium, a problem that a vinyl chloride polymer generally referred to as a scale adheres to the inner wall surface of a polymerization vessel or a stirring blade or the like. There is. This scale adhesion causes a decrease in the heat transfer efficiency of the polymerization vessel and the incorporation of the exfoliated scale into the product polymer, which causes a deterioration in the quality of the obtained product. Conventionally, when a scale is generated, a cleaning operation for removing the scale has been performed before the polymerization. However, it has been difficult to improve the operation rate of the polymerization vessel. [0003] In order to solve the above-mentioned problems, various studies have been made on a polymerization method which does not cause scale adhesion in the polymerization process of vinyl chloride. For example, a dye and / or a pigment is used as a scale adhesion preventing agent, and it is used as a polymerization reactor. A method in which a coating is applied in advance to a place where a vinyl chloride monomer contacts the inner wall surface or the like (Japanese Patent Publication No. 45-30835), or a method in which a reaction product of a phenolic compound and an aromatic aldehyde is used as a scale adhesion inhibitor ( JP-A-55-5
No. 4317) has been proposed. [0004] However, the above-mentioned method cannot effectively and surely prevent scale adhesion in all cases. For example, a reaction product of a phenolic compound and an aromatic aldehyde as a scale adhesion inhibitor is used. In the case where is used, there was a problem that the scale prevention performance was inferior when the number of polymerizations was increased. In addition, the effect of preventing the scale due to the application of the dye greatly depends on the amount of the coating, the effect is excellent as the coating amount is increased, but when the coating amount is increased,
There was a problem that suspension polymerization became unstable and the production ratio of coarse polymer particles increased. The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a sulphonic acid having a specific structure or a scale inhibitor comprising a salt thereof has been developed.
It has been found that an excellent effect of preventing scale can be obtained by applying the composition to a portion in contact with a vinyl chloride monomer or the like, that is, an inner wall of a polymerization vessel, and the present invention has been completed. That is, the present invention relates to a method for suspending or emulsifying a vinyl chloride monomer or a radical polymerizable monomer mixture containing the monomer as a main component in an aqueous medium. A vinyl chloride-based polymer, wherein a sulfonic acid having an amide group represented by the following formula (hereinafter referred to as amidosulfonic acid) or a salt thereof is applied in advance to a portion of the equipment where the monomer contacts. It is a manufacturing method of. [0006] Hereinafter, the present invention will be described in more detail. Examples of R in Chemical Formula 2 include an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, and a phenyl group. In the present invention, an amide having the above alkenyl group as R Sulfonic acid or a salt thereof (hereinafter collectively referred to as amidosulfonic acid, etc.)
Is preferred. Desirable R ^{1 to} R ⁴ are a hydrogen atom, a methyl group and an ethyl group. As a base ion forming a salt, a sodium ion, a potassium ion or an ammonium ion is preferable. Specific examples of the above R, ie, amidosulfonic acid having an alkyl group having 1 to 4 carbon atoms, include 2-acetamidopropanesulfonic acid, 2-acetamido-2-methylpropanesulfonic acid, and 2-propion. Amidopropanesulfonic acid and the like and salts thereof are mentioned. Specific examples of the above-mentioned R, ie, amidesulfonic acid having a phenyl group include 2-benzamide-
Examples include 2-methylpropanesulfonic acid and the like and salts thereof. As described above, preferred amidosulfonic acids and the like in the present invention are those having an alkenyl group having 2 to 4 carbon atoms as R in Chemical formula 2, and more preferably 2-acrylamido-2-methyl. Acrylic groups such as propanesulfonic acid, 2-methacrylamide-2-methylpropanesulfonic acid, 2-acrylamidopropanesulfonic acid, 2-acrylamidobutanesulfonic acid and 3-acrylamido-2,3-dimethylbutane-2-sulfonic acid; Amidosulfonic acid having a methacryl group or a salt thereof. Particularly preferred are 2-acrylamido-2-methylpropanesulfonic acid and its sodium or potassium salt. The reason why the amide sulfonic acid having an acryl group or a methacryl group has a better scale-inhibiting effect in the present invention is not clear, but the polymerization of vinyl chloride monomer or the like occurring on the wall of the polymerization vessel is a radical. It is presumed that the polymerization may be terminated by acrylamide or methacrylamide having a low copolymerization reaction ratio with a vinyl chloride monomer while having high polymerizability. The above-mentioned amide sulfonic acid and the like can be applied to the inner wall of the polymerization vessel and equipment attached to the polymerization vessel such as a baffle and a stirring propeller by the following method. That is, a solution in which the above amide sulfonic acid or the like is dissolved in a solvent such as water, methanol or ethanol at a concentration of about 0.1 to 5.0% by weight can be applied by brush coating or spray coating. After application, it is preferable to dry once with hot air of about 40 to 80 ° C. By drying, the scale prevention effect is maintained for a long time. As the solvent, lower alcohols such as methanol and ethanol are preferable, and as the alkali metal salt of amide sulfonic acid insoluble in lower alcohols, a mixed solvent of water and lower alcohol is preferable. The preferred coating amount of the amidosulfonic acid or the like is 0.001 to 10 g / m ² . In the present invention, a known fixing agent such as a natural polymer such as rosin or a nonionic fluorine-based surfactant can be used in combination in order to increase the adhesion of the amide sulfonic acid to the coated surface. . In addition, a condensate of pyrogallol and acetone, which is a kind of a scale inhibitor, together with the amide sulfonic acid and the like in the present invention (JP-A-5-1251)
No. 13) may be used in combination, and a condensate of pyrogallol and acetone is preferably used in combination under an acidic condition in an aqueous medium or an alcoholic medium using 0.75 to 1 mol of acetone per mol of pyrogallol. It is a condensate having a melting point of 100 to 300 ° C. obtained by condensing both. An aqueous medium is charged into a polymerization vessel coated with the above amide sulfonic acid and the like, and a vinyl chloride monomer or a radical polymerization monomer mixture containing the monomer as a main component is suspended under stirring in a conventional manner. By performing turbid polymerization or emulsion polymerization, a vinyl chloride polymer can be produced by repeating polymerization many times without causing scale adhesion.
As a dispersion stabilizer such as a vinyl chloride monomer, partially saponified vinyl alcohol and a cellulose derivative can be used, and as a polymerization initiator, isobutyryl peroxide, lauryl peroxide, diisopropyl peroxydicarbonate, 2-ethylhexyl Peroxydicarbonate and t-butyl peroxypivalate can be used. [0014] Examples of the radical polymerizable monomer which can be used together with the vinyl chloride monomer include vinyl acetate, propyl vinyl ether, butyl vinyl ether, methyl acrylate, vinylidene chloride, propylene, and alkylmaleimide. The present invention will be described more specifically below with reference to examples and comparative examples. <Example 1> 1 g of 2-acrylamido-2-methylpropanesulfonic acid was dissolved in 100 g of methanol to prepare a coating solution. This coating solution was thinly applied to the inner wall surface of a 5 L autoclave having a stirrer by brush coating, and the coated surface was heated to about 40 ° C. and dried for 10 minutes. Thereafter, the inner wall surface was cooled to room temperature, and the following raw materials were charged. That is, 2,700 g of pure water, 2 g of partially saponified polyvinyl alcohol and 1.2 g of 2-ethylhexyl peroxydicarbonate were charged into an autoclave, degassed to -600 mmHg by a vacuum pump, and 2,000 g of vinyl chloride monomer was further added. I charged. Then, the internal temperature was raised to 58 ° C., and after maintaining the temperature for 7 hours, the polymerization was stopped. The average particle size of the obtained polyvinyl chloride particles was 120 to 150 μm as intended. After polymerization, the inner wall surface of the polymerization vessel was washed with pure water, and the same polymerization as above was repeated 10 times using the same polymerization vessel. After each polymerization, the scale adhesion state on the inner wall surface was visually observed. As a result, no scale adhesion was observed even after the polymerization was performed 10 times. Example 2 Vinyl chloride was polymerized under the same conditions as in Example 1 except that 2-acetamido-2-methylpropanesulfonic acid was used as a scale inhibitor. In this case, no scale adhesion was observed up to seven times of polymerization. The obtained polyvinyl chloride was particles having an average particle size of 120 to 150 μm, and there was no problem in quality. Comparative Example 1 Polymerization of vinyl chloride was carried out in the same manner as in Example 1 except that a coating solution prepared by dissolving 2 g of nigrosine black in 500 g of methanol was used as a coating solution applied to the inner wall surface of the polymerization vessel. Was. In this case, no scale adhesion was observed up to 8 times of polymerization, but the polymerization itself was unstable, and the obtained polyvinyl chloride contained many coarse particles having a particle size of about 350 μm. Was. According to the present invention, the adhesion of the polymer scale can be effectively prevented even if the polymerization is repeated many times, and the polymerization proceeds stably. In addition, a high-quality vinyl chloride polymer having a target particle size can be efficiently produced.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor, Naonori Asada 1-1, Funami-cho, Minato-ku, Nagoya-shi, Aichi, Japan Toagosei Chemical Industry Co., Ltd. Nagoya Research Institute (56) References JP-A-4-31402 A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08F 2/00-2/60

Claims (1)

(57) [Claim 1] In suspension polymerization or emulsion polymerization of a vinyl chloride monomer or a radical polymerizable monomer mixture containing the monomer as a main component in an aqueous medium, At the part where the monomer of the polymerization reactor inner wall and the equipment attached to the polymerization reactor come into contact,
Wherein the sulfonic acid having an amide group represented by the formula (1) or a salt thereof is applied in advance. Embedded image