JPH10279628A - Method for producing vinyl chloride polymer - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce adhesion of polymer scale,
High quality polymer with few fish eyes under high productivity
Provided is a polymerization method which can be easily obtained under a wide range of conditions. SOLUTION: In a method for producing a vinyl chloride polymer by polymerizing a vinyl chloride monomer in an aqueous medium, a content liquid in a polymerization vessel is changed from the start of polymerization to a polymerization conversion of 0.1%. the net of agitation power per 1m ^3, 0.2kW / m ³
The polymerization is controlled at not less than 1.0 kW / m ³ and thereafter, at least until the polymerization conversion reaches 5.0%,
A method for producing a vinyl chloride polymer, wherein the stirring power is adjusted to 1.0 to 2.0 kW / m ³ to continue the polymerization and complete the polymerization within 6 hours.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a vinyl chloride polymer which prevents the generation of polymer scale. More specifically, a method for producing a vinyl chloride-based polymer capable of polymerizing a high-quality vinyl chloride-based resin with little adhesion of polymer scale and little fisheye in an aqueous medium under high-speed polymerization, that is, high productivity. It is about.

[0002]

2. Description of the Related Art A polymerization reaction of a vinyl chloride monomer is started.
In many polymerization reactions, adhesion of the polymer scale generated on the wall surface in the polymerization vessel causes a decrease in the yield of the polymer, a decrease in the heat removal capability of the polymerization vessel, and a deterioration in the quality due to the mixing of the exfoliated polymer scale, Further, it causes various problems such as a great effort and cost for removing the polymer scale. Heretofore, as a method for solving such a problem, a method of applying an appropriate substance to the inner wall of a polymerization reactor as a polymer scale adhesion inhibitor has been most widely used.

[0003]

However, the above-mentioned anti-adhesion agents include pigments and dyes, aromatic amine compounds,
There are many colored substances such as phenolic compounds, and when the reaction is carried out in a polymerization vessel coated with these as an anti-adhesion agent, there is a problem that the polymer is colored due to peeling and mixing of the anti-adhesion agent. Contains. In addition, under high-speed polymerization, which has recently become mainstream, satisfactory results have not yet been achieved only by using an antiadhesive agent.

[0004]

Means for Solving the Problems In view of such circumstances, the present inventors have made intensive studies and as a result, have found that when polymerizing a vinyl chloride-based monomer in an aqueous medium, the Pv value is controlled. As a result, they have found that this problem can be solved, and have completed the present invention. That is, the gist of the present invention is to provide a vinyl chloride monomer or a mixture of copolymerizable monomers mainly composed of a vinyl chloride monomer (hereinafter, referred to as “vinyl chloride monomer”) in an aqueous medium. In a method for producing a vinyl chloride polymer by polymerization in a polymerization vessel, a net stirring power per 1 m ³ of the content liquid in the polymerization vessel (hereinafter referred to as “Pv ").)
The present invention relates to a method for producing a vinyl chloride polymer, characterized in that polymerization is carried out at a control of 0.2 kW / m ³ or more and less than 1.0 kW / m ³ , and the polymerization is completed within 6 hours.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. As a method of controlling the stirring power of the polymerization vessel, for example, “Chemical Engineering Association, edited by Chemical Engineering Handbook, 3rd revised edition, 10
As described in detail in "Materials Co., Ltd., Showa 43, pp. 65-1115", an empirical diagram showing the relationship between the number of Rey nozzles Re and the number of powers Np of the stirring system for stirring devices of various shapes is used. Or by actually measuring the power value under a certain stirring condition, the Np as a device constant is obtained.
Can be arbitrarily adjusted by experimentally determining the rotation speed of the stirring blade and changing the rotation speed of the stirring blade.

That is, the density of the content liquid in the polymerization vessel is defined as ρ (kg
/ M ³ ), blade length d (m), viscosity coefficient μ (kg / m
s), the rotation speed of the stirring blade is n (1 / s), the power conversion coefficient is gc (kg · m / Kg · s ² ), and the net stirring power without loss in the reduction mechanism and shaft seal is P (Kg / m · s)
Then, Re and Np are respectively defined by Re = ρnd ² / μNp = Pgc / ρn ³ d ⁵ , and Np can be obtained from known literature or experiments. Here, assuming that the liquid volume in the polymerization vessel is V (m ³ ), the net stirring power P per 1 m ³ of the content liquid in the polymerization vessel is
v (kW / m ³ ) is represented by Pv = Nppn ³ d ² / 102Vgc. Therefore, when the Pv value is adjusted using a specific stirring device, the Pv value changes in proportion to the cube of the rotation speed of the stirring blade, so that a method of adjusting the Pv value by the rotation speed is easy. .

In general, in a method of producing a vinyl chloride polymer by polymerizing a vinyl chloride monomer in an aqueous medium, elementary particles having a polymerization conversion of less than 0.1% have a solid-liquid interface. It is said that a thin layer called a skin is not completed, and when the elementary particles collide with the wall of the polymerization vessel, it is in a state where adhesion is very likely to occur. Therefore, from the start of polymerization,
Pv value of 0.2 until polymerization conversion is at least 0.1%
be performed kW / m ³ or more 1.0 kW / m ³ under the control the polymerization is a need in preventing polymer scale deposition in a polymerization conversion rate of the Pv value up to about 1.0 percent, It is preferable to control within the above range.

[0008] Further, from the start of the polymerization, the Pv at which the polymerization conversion is at least 0.1%, preferably about 1.0%.
The polymerization is carried out while controlling the value to 0.2 kW / m ³ or more and less than 1.0 kW / m ³ , and the Pv value is adjusted to 1.0 to 2.0 kW / m ³ at least until the polymerization conversion reaches 5.0%. If readjusted to ³ , the particle size can change until the polymerization conversion reaches 5.0%, so that the adhesion of the polymer scale can be prevented while the FE with a small to medium particle size has a good weight. Coalescence can be obtained.

The shape of the stirrer used in the present invention and the stirrer such as a baffle used as desired are not particularly limited, and are conventionally employed generally in the polymerization of vinyl chloride monomers. Stirring device can be used, as the stirring blade, turbine blades, fan turbine blades, Faudler blades and blue margin blades are exemplified,
Examples of the baffle include a plate type, a cylindrical type, a D type, a loop type, and a finger type.

The vinyl chloride monomer used in the present invention includes a vinyl chloride monomer alone and a mixture of a copolymerizable monomer mainly composed of the vinyl chloride monomer. As the other monomer copolymerizable with the vinyl chloride monomer, those commonly used in the polymerization of vinyl chloride monomers can be used without any particular limitation. Examples of the other monomers include vinyl esters such as vinyl acetate, alkyl vinyl ethers such as cetyl vinyl ether, α-olefins such as ethylene and propylene, and (meth) such as methyl acrylate and methyl methacrylate. Examples thereof include alkyl acrylates and vinylidene compounds such as vinylidene chloride. These other monomers are usually used in a proportion of 20% by weight or less based on the vinyl chloride monomer.

The method of the present invention is applied to the polymerization of a vinyl chloride monomer in an aqueous medium. In general, polymerization of a vinyl chloride monomer in an aqueous medium uses a dispersion stabilizer such as partially saponified polyvinyl acetate (so-called polyvinyl alcohol) and uses a polymerization initiator soluble in the vinyl chloride monomer. Suspension polymerization method, a fine suspension polymerization method in which a surfactant such as sodium lauryl sulfate is used as an emulsifier, a polymerization initiator soluble in a vinyl chloride monomer is used, and polymerization is performed after homogenization treatment. And an emulsion polymerization method using a surfactant and a water-soluble polymerization initiator. In the polymerization to which the present invention is applied, specific polymerization recipes and methods may be those usually used in each polymerization method, and are not particularly limited.

The present invention uses an oil-soluble polymerization initiator,
The application to a suspension polymerization method using a dispersion stabilizer has a remarkable effect and is suitable. Examples of oil-soluble polymerization initiators include benzoyl peroxide, lauroyl peroxide, tert-butyl peroxypivalate, and di (2-ethylhexyl)
Organic peroxides such as peroxydicarbonate, diisopropylperoxydicarbonate, tert-butylperoxyneodecanoate, α-cumylperoxyneodecanoate, azobis (isobutyronitrile), and azobis (dimethylvaleronitrile) An azo compound can be exemplified. The amount of these polymerization initiators is usually 0.01 to 0.5% by weight based on the vinyl chloride monomer.

As the dispersion stabilizer, water-soluble partially saponified polyvinyl acetate (so-called polyvinyl alcohol) is used.
It is preferable to use a water-soluble cellulose derivative such as hydroxyisopropylmethylcellulose. In addition to the above-mentioned dispersion stabilizers, oil-soluble partially saponified polyvinyl acetate, gelatins, nonionic surfactants, anionic surfactants and the like may be used as dispersion stabilizing aids.

Further, in the present invention, various polymerization aids such as a chain transfer agent, an antioxidant, a cross-linking agent, a pH adjuster, and a scale adhesion inhibitor used for the polymerization of the vinyl chloride monomer, if necessary. Agents and the like can be appropriately used, and the amounts of these components to be charged and the like can be determined under general conditions. In carrying out the present invention, the vinyl chloride monomer, the aqueous medium, the dispersion stabilizer, the proportion of the polymerization initiator and various polymerization aids to be charged into the polymerization vessel, the charging method, or the type and application of the scale adhesion preventing agent The method is not particularly limited. Examples of the method for terminating the polymerization in the method of the present invention include a method of adding a so-called polymerization inhibitor or a polymerization terminator, and a method of recovering an unreacted monomer from a polymerization vessel. From the vinyl chloride polymer, a method for removing the residual vinyl chloride monomer, a method for separating the produced vinyl chloride polymer from the aqueous medium, a method for drying, and the like are also usually employed in each polymerization method. Method may be used.

[0015]

The present invention will be specifically described below with reference to examples. The evaluation method performed here is as follows. (1) Average degree of polymerization The measurement was carried out in accordance with the measurement method described in JIS K6721. (2) Bulk specific gravity The measurement was carried out in accordance with the measurement method described in JIS K6721. (3) Average particle size The median size (50% weight size) was determined from the particle size distribution measured using a low-tap vibrating sieve (using a JIS sieve) and defined as the average particle size. (4) Amount of Polymer Scale Attached After completion of each polymerization reaction, the state of scale attached to the polymerization vessel wall (liquid phase part, gas phase part) and baffle part was visualized. The evaluation criteria are as follows. ：: No adhesion at all. Δ: Lightly adhered partially. X: Adhesion exists over a wide range. (5) Fisheye test The vinyl chloride resin was mixed with each compounding agent at the ratio shown in Table 1,
Time shown in Table 1 at 155 ° C. in a mixing roll, to create a roll sheet by kneading, the rolled sheet 25 cm ²
The number of FEs observed therein was counted and defined as the number of FEs.

[0016]

[Table 1] Note 1) DOP: di-2-ethylhexyl phthalate Note 2) Polyester plasticizer: Adipic acid-based polyester plasticizer (trade name: Diasizer ^™ D643, manufactured by Mitsubishi Chemical Corporation) Note 3) The mixing ratio indicates parts by weight.

<Example 1, Comparative Examples 1-2> Content 400
After applying an anti-adhesion agent containing p-toluenesulfonic acid and solvent black as main components to a stainless steel polymerization vessel equipped with a 1-liter stirrer and an outer jacket, 150 kg of deionized water, 100 kg of vinyl chloride monomer, and average polymerization were used. 0.08% by weight of partially saponified polyvinyl acetate (based on vinyl chloride monomer) having a degree of hydrolysis of 2300 and a degree of saponification of 88.5 mol%, and tert-butyl peroxy neodecanoate as an oil-soluble polymerization initiator. After adding 0.05% by weight, the system was heated to 57 ° C. to initiate polymerization. After the start of the polymerization, the Pv value was adjusted as shown in Table 2 by using the polymerization conversion obtained by the blank test previously performed. When the polymerization conversion reached 80%, the unreacted vinyl chloride monomer was recovered out of the system to terminate the reaction, and the time from the start of polymerization to the point at which it reached here was defined as the reaction time. Further, the vinyl chloride monomer in the polymerization vessel was removed until the pressure reached atmospheric pressure, and then vacuum suction was applied and cooled. The obtained vinyl chloride polymer was taken out of the polymerization vessel, dehydrated and dried to obtain a vinyl chloride polymer.

Comparative Example 3 In Example 1, the amount of the oil-soluble polymerization initiator tert-butyl peroxy neodecanoate was set to 0.01% by weight, and further, 0.01% by weight of tert-butyl peroxypivalate was used. Was used in combination. The operation procedure other than the above was carried out in the same manner as in Example 1 to carry out the polymerization.

Example 2, Comparative Example 4 Polymerization was carried out in the same manner as in Example 1 and Comparative Example 1, except that the step of applying the antiadhesive agent was omitted.

[0020]

[Table 2]

[0021]

[Table 3]

[0022]

According to the present invention, it is possible to polymerize a high-quality vinyl chloride resin with little adhesion of polymer scale and little fisheye in an aqueous medium under high productivity. It becomes possible. In other words, when a vinyl chloride-based resin is produced by the method of the present invention, it is possible to reduce the labor, time, and cost for preventing the reduction in productivity and quality and removing the polymer scale based on the generation of the polymer scale. Becomes possible.

Claims (3)

[Claims] 1. A vinyl chloride monomer or a mixture of copolymerizable monomers mainly composed of a vinyl chloride monomer (hereinafter referred to as “vinyl chloride monomer”) is polymerized in an aqueous medium. In the method of producing a vinyl chloride-based polymer, a net stirring power per 1 m ³ of the content liquid in the polymerization vessel (hereinafter referred to as “Pv value”) from the start of polymerization to a polymerization conversion of 0.1% ) Is controlled to 0.2 kW / m ³ or more and less than 1.0 kW / m ³ , and the polymerization is completed within 6 hours. From wherein the polymerization initiator until the polymerization conversion rate of 1.0%, vinyl chloride polymer according to claim 1 for controlling the Pv value less than 0.2 kW / m ³ or more 1.0 kW / m ³ Manufacturing method. 3. The method according to claim 1, wherein the Pv value is readjusted to 1.0 to 2.0 kW / m ³ to continue the polymerization at least until the polymerization conversion reaches 5.0%. A method for producing a vinyl polymer.