JPH0772207B2 - Method for producing vinyl chloride polymer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing a vinyl chloride polymer which has improved prevention of scale adhesion to the inner wall surface of a polymerization vessel in the course of vinyl chloride monomer polymerization.

[0002]

2. Description of the Related Art In suspension polymerization and emulsion polymerization in which vinyl chloride is polymerized in an aqueous medium, there is a problem that a vinyl chloride polymer, which is generally called a scale, adheres to the inner wall surface of a polymerization vessel or a stirring blade. This scale deposition causes a decrease in heat transfer efficiency of the polymerization vessel and contamination of the exfoliation scale with the product polymer, which causes deterioration of the quality of the obtained product. Conventionally, when scale occurs, a cleaning operation for removing it is performed before the polymerization, but it is difficult to improve the operating rate of the polymerization vessel for that purpose. In order to solve the above-mentioned problems, various studies have been made on a polymerization method in which scale adhesion does not occur in the vinyl chloride polymerization process. For example, a dye and / or a pigment is used as a scale adhesion preventing agent, which is used as an inner wall surface of a polymerization vessel. Of the vinyl chloride monomer is applied in advance (Japanese Examined Patent Publication No. 45-30835), and a reaction product of a phenolic compound and an aromatic aldehyde is used as an anti-scale agent (Japanese Patent Application Laid-Open No. S60-12065). 55-54317) and the like have been proposed.

[0003]

However, the above method cannot effectively and surely prevent scale adhesion in all cases. For example, a reaction product of a phenolic compound and an aromatic aldehyde is used as a scale adhesion inhibitor. In this case, an excellent effect is exhibited when the number of polymerizations is small, but there is a problem that the scale prevention performance is deteriorated when the number of polymerizations is large. On the other hand, the scale prevention effect by the application of the dye largely depends on the application amount, and the larger the application amount is, the more excellent the effect is.However, as a result of the tests conducted by the inventors of the present invention, when the dye is applied in an amount suitable for scale prevention, It was found that there is a problem in suspension polymerization that polymer particles as designed cannot be obtained. That is, for example, even if the polymerization conditions for obtaining polymer particles having an average of 130 microns are adopted, the obtained particles have an average of 350 microns.

[0004]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, the present onset Ming, when a radical polymerizable monomer mixture mainly composed of vinyl chloride monomer or said monomer body suspension polymerization or emulsion polymerization in an aqueous medium,
The portion with which the monomer comes into contact of the polymerization vessel inner wall surfaces and the polymerization vessel ancillary equipment, our condensation reaction product of (i) pyrogallol and acetone
And (b) Ru manufacturing method der vinyl chloride polymer, characterized in that in advance coated dye.

The present invention will be described in more detail below. The condensation reaction product of pyrogallol and acetone (hereinafter referred to as pyrogallol-acetone condensate) used in the present invention is a compound represented by the following chemical formula 1.

[Chemical 1] (In the formula, n is an integer of 0 or more.) The above pyrogallol
The acetone condensate is used in an amount of 0.75 to 1 mol of acetone per mol of pyrogallol under acidic conditions in an aqueous medium or an alcoholic medium at a temperature of about 30 to 80 ° C.
It can be synthesized by maintaining for 10 hours. By the above synthesis method, a pyrogallol-acetone condensate having a melting point of about 100 to 300 ° C., which contains a compound in which n in Chemical formula 1 is 0 to 20 as a main component is usually obtained. According to the above synthetic method, a small amount of a compound other than the compound represented by Chemical formula 1 is by-produced, but in the present invention, the reaction product of the above synthetic method can be used without purification. The preferred purity of the pyrogallol-acetone condensate used is 70% by weight or more, more preferably 80% by weight or more.

The pyrogallol-acetone condensate can be applied to the inner wall surface of the polymerization and the equipment attached to the polymerization vessel such as a baffle and a stirring propeller by the following method. That is, by using the organic solvent solution of the condensate, can be applied by the brush coating or spray coating or the like. At that time, the concentration of the condensate in the organic solvent solution is preferably 0.1 to 1.0% by weight. As the organic solvent, polar organic solvents such as methanol, ethanol, n-butanol, acetone, methyl ethyl ketone, chloroform and tetrahydrofuran can be used, and lower alcohol is preferable from the viewpoint of enhancing the wettability of the inner wall surface of the stainless steel polymerization vessel. Preferred coating weight of pyrogallol-acetone condensate Ru 0.1-2 g / m ² der.

[0007] Next, Oite the pyrogallol to the onset Akira
Dyes used in combination with the acetone condensate include methylene blue, nigrosine black, spirit black, oil black, aniline black and fluorescein, as well as azo dyes, azoic dyes, anthraquinone dyes, brilliant indigo B and other indigoid dyes, sulfur blue FBB or sulfur. Sulfur dye such as black B, phthalocyanine dye such as copper phthalocyanine,
Carbonium dye such as crystal violet or rhodamine B and quinone imine dye, diphenylmethane or triphenylmethane dye, nitro dye, benzoquinone dye, naphthoquinone dye, methine dye, quinoline dye, naphthalimide dye, benoline dye, fluorescent dye and reactive dye To be Preferred are nigrosine black, spirit black and oil black.

By using the above dye in combination with the pyrogallol-acetone condensate, the scale adhesion preventive property is maintained for a longer period of time as compared with the case where the condensate is used alone. Preferred coating weight of the dye is 0.02~0.15g / m ^2, the scale preventing effect thereof coating amount is less than 0.02 g / m ² is not long-lasting, whereas 0.15 g / m ² If it exceeds, the polymerization stability of the polymerization system will be poor, and the particle size of the resulting polymer particles will significantly exceed the designed particle size. In relation to the amount of the pyrogallol-acetone condensate applied, the amount of the dye applied is preferably 1/5 to 1/20 of the condensate. As a method of applying the dye to the inner wall surface of the polymerization vessel, either one of the pyrogallol-acetone condensate or the dye is applied first, and the other is applied from the above, or the pyrogallol-acetone condensate. A method in which a dye is added to the dissolved organic solvent solution of and the two are simultaneously applied can be adopted. The preferred concentration of the dye in the organic solvent solution used for coating is 0.01 to 0.1% by weight.

In the present invention, in order to enhance the adhesion of the above-mentioned pyrogallol-acetone condensate and dye to the coated surface, known fixing agents such as natural polymers such as rosin or nonionic fluorosurfactants are used. You may use together an agent. Charged aqueous medium in a polymerization vessel coated with the pyrogallol-acetone condensate All and dyes, under stirring, by polymerizing a radical polymerizable monomer mixture mainly composed of vinyl chloride monomer or said monomer body It is possible to repeat the polymerization a number of times with no scale adhesion. The scale adhesion prevention according to the present invention is preferably applicable to suspension polymerization and emulsion polymerization, but it is speculated that it is also applicable to other bulk polymerization and gas phase polymerization.

Next, the outline of the polymerization method will be described by taking the case of employing the aqueous suspension polymerization as an example. Examples of the dispersion stabilizer used include partially saponified vinyl alcohol and cellulose derivatives, and as the polymerization initiator, isobutyryl peroxide, lauryl peroxide,
Examples include diisopropyl peroxydicarbonate, 2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, and the like. In addition, examples of radically polymerizable monomers that can be used together with vinyl chloride include vinyl acetate, propyl vinyl ether, butyl vinyl ether, methyl acrylate, vinylidene chloride, propylene and alkylmaleimide.

[0011]

EXAMPLES The present invention will be described more specifically below with reference to Examples and Comparative Examples. Example 11 In a 1 L flask, 500 g of methanol was added to 2 g of pyrogallol-acetone condensate (mp 210 ° C.) and Nigrosine Black 0.1 g .
Dissolve 2 g and prepare a coating solution. This coating solution is applied thinly on the inner wall surface of a 5 L autoclave having a stirrer by brush coating, and the coated surface is heated to 80 ° C. to 10
Dry for minutes. After that, the inner wall surface was cooled to room temperature, and then 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 further 2000 g of vinyl chloride monomer. I prepared it.
Then, the internal temperature was raised to 58 ° C., the temperature was maintained for 7 hours, and then the polymerization was stopped. After the polymerization, the inner wall surface of the polymerization vessel was washed with pure water, and the same polymerization as above was repeated using the same polymerization vessel, which was repeated 10 times. After each polymerization, the scale adhesion state on the inner wall surface was visually observed. As a result, no scale adhesion was observed up to the number of polymerizations of 9 .

Examples 2 to 3 Vinyl chloride was suspension-polymerized in the same manner as in Example 1 except that the following coating liquids were used as the coating liquids for coating the inner wall surface of the polymerization vessel. Polymerization was repeated 10 times, and in this case, Table 1 shows how many times from the first time the scale did not adhere. Example 2 : Pyrogallol-acetone condensate (m.p. 2)
(10 ° C.) 2 g, nigrosine black 0.2 g and rosin 2 g were dissolved in methanol 500 g to obtain a coating solution. Example 3 : Pyrogallol-acetone condensate (mp.2)
10g) 2g, Nigrosine black 0.2g and fluorosurfactant 2g dissolved in 500g of methanol and applied.
A liquid was obtained.

Comparative Examples 1 and 2 Comparative Example 1: 500 g of methanol and 0.1 g of Nigrosine Black.
Dissolve 2 g to prepare a coating solution. Then, vinyl chloride was suspension-polymerized in the same manner as in Example 1. Comparative Example 2: Nigrosine Black 2 in 500 g of methanol
g to prepare a coating solution. Hereinafter, the same operation as in each of the above examples was performed.

[0014]

[Table 1] Evaluation item A: The number of polymerizations in which the effect of preventing scale adhesion continued.
In the case of Examples 2 and 3 , it was shown that the scale did not adhere at least 10 times, and it was not confirmed how many times the scale did not adhere. Evaluation item B: Whether a polymer having a particle size as designed was obtained.

[0015]

According to the present invention, scale deposition does not occur even after repeated many times polymerization, since it is a small amount the coating amount of or dyeing agents, consisting of polymer particles having a particle size as designed chloride A vinyl polymer can be produced.

Claims (1)

[Claims] 1. An inner wall surface of a polymerization vessel and equipment attached to the polymerization vessel when suspension-polymerizing or emulsion-polymerizing a vinyl chloride monomer or a radical-polymerizable monomer mixture containing the monomer as a main component in an aqueous medium. A method for producing a vinyl chloride-based polymer, characterized in that (i) a condensation reaction product of pyrogallol and acetone and (b) a dye are applied in advance to a portion in contact with the monomer.