JPH0539308A - Polymerization - Google Patents

Abstract

PURPOSE:To suppress markedly the deposition of scale on the inside wall of a reactor during polymerization. CONSTITUTION:Emulsion or suspension polymerization is performed by using the inside wall of a polymerizer 1 as one electrode, placing another electrode 4 in a liquid medium in the polymerizer, coating at least either of the electrodes with an electrical insulator 2, and impressing a direct voltage which does not cause dielectric breakdown between the electrodes to form a capacitor circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymerization method which makes it possible to prevent scales and the like from adhering to the inner wall of a polymerization reactor.

[0002]

2. Description of the Related Art High molecular polymers are industrially produced by various polymerization methods such as emulsion polymerization and suspension polymerization. One of the problems of the emulsion polymerization method and the suspension polymerization method is the formation of deposits of the produced polymer on the inner wall of the polymerization reactor. The formation of such deposits is not only disadvantageous in that the polymer yield and the ability to remove the heat of polymerization are reduced, but also the peeled deposits (scale) are mixed into the product polymer to cause various problems such as fish eyes. This may cause product defects. In addition, it takes an excessive amount of labor and time to remove the deposits, which not only causes a decrease in productivity, but in recent years, the deposit removal work is regarded as one of the 3K works, and the production using these polymerization methods is not performed. The existence of the method itself is in jeopardy.

Therefore, in the production of high molecular weight polymers by the emulsion polymerization method and the suspension polymerization method, researches for reducing or preventing the deposits in the polymerization reactor have been continuously conducted. As a conventional prevention method, a polar compound is applied to the inner wall of the polymerization reactor or added to an aqueous medium (Japanese Patent Publication No.
No. 5-30343), a method of applying a dye and / or a pigment (Japanese Patent Publication No. 45-30835), and a method of adding magnesium hydroxide to a reaction dispersion (Dutch Patent 6).
914059), or a method of adding an inorganic oxidizing agent such as permanganic acid, chromic acid or dichromic acid (Japanese Patent Publication No. 46-46-
No. 20821) has been proposed. However, these methods are unsatisfactory in the scale prevention effect, and the method of applying the drug and the method of drying the product are extremely complicated and require a long time,
It is difficult to carry out industrially, or the additives are mixed in the product, resulting in coloration, deterioration of physical properties, etc. It had various drawbacks such as occurrence.
On the other hand, in emulsion polymerization and suspension polymerization, a method of carrying out the polymerization in a state where an electric circuit is formed between the inner wall of the metallic polymerization reactor and the insoluble electrode in the polymerization liquid medium by an external power source (JP-A-48-69886). However, this method was extremely dangerous because hydrogen and oxygen formed an explosive mixture by electrolysis of an aqueous medium. Therefore, the inventors of the present invention have conducted extensive studies as to a method for preventing scale adhesion to the inside of the polymerization reactor, particularly the inner wall surface of the polymerization machine, a stirrer, a baffle plate, etc. Reached

[0004]

[Means for Solving the Problems] That is, in the polymerization method of the present invention, when emulsion-polymerizing or suspension-polymerizing a polymerizable monomer in a polymerization reactor, a reactor such as an inner wall of the polymerization reactor and a stirring blade is used. The metal part of the internal arrangement serves as one electrode, at least one insoluble conductor arranged in the liquid medium in the polymerization reactor serves as the other electrode, and one or both of these electrodes are made of an electrically insulating material. Use the coated one, and use the liquid medium in the polymerization reactor and the coated electrical insulator as a composite dielectric, and apply a DC voltage less than the dielectric breakdown voltage between both electrodes to carry out the polymerization in a state where a capacitor circuit is generated. It is characterized by carrying out.

[0005]

In the polymerization method of the present invention, an electrode is arranged in the liquid medium of the polymerization reactor, and a DC voltage is applied between this electrode and the other electrode composed of the inner wall of the polymerization reactor, In the state where the capacitor circuit is generated, that is, the electric polarization phenomenon is caused at each interface of the liquid medium and the coating electric insulating material of one or both electrodes in the polymerization reactor which is a composite dielectric placed in an electric field. It is a method of carrying out polymerization in a closed state.

In the method of the present invention, one electrode composed of the inner wall of the polymerization reactor and the internal arrangement of the polymerization reactor such as a stirring blade or the other electrode arranged in the liquid medium in the polymerization reactor is used. One or both electrodes coated with an electrical insulating material are used. For example, if the inner wall of the polymerization reaction vessel is glass-lined, use a metal polymerization reaction vessel such as a stirrer or a baffle plate that is also coated with an electrically insulating material in a liquid medium. For the placement electrode, use one that is not covered with an electrical insulating material. On the contrary, when the placement electrode in the liquid medium is coated with an electrical insulating material, the inner wall of the polymerization reactor is not coated with the electrical insulating material.

The insoluble electrode used in the present invention means an electrode which does not elute metal ions when it is used as an anode in electrolyzing a salt solution and does not itself significantly change in anodized state. Examples of such an insoluble electrode include known so-called insoluble electrodes such as carbon, titanium, platinum, gold, or a metal such as iron, chromium, or zinc plated with titanium, platinum, gold, or the like. The shape, size of these insoluble electrodes,
The number and the position to be placed in the polymerization apparatus can be arbitrarily selected depending on the stirring effect of the polymerization system, the strength of the electric field, the size of the main body of the polymerization reactor, the polymerization method, and the like. The shape of the insoluble electrode may be a cylinder, a prism, a flat plate, a square plate, a lattice, or a spiral shape.

As the electric insulating material used in the present invention, not only inorganic materials such as glass and ceramics but also organic polymer materials such as polytetrafluoroethylene, polypropylene and polyethylene terephthalate can be used.

The thickness of the electrically insulating material covering the electrodes is
It suffices that the thickness is such that dielectric breakdown does not occur due to the imperfections of the coating, and is usually 0.01 mm or more.
On the other hand, if the thickness of the coating layer is too thick, the voltage required to generate the electric polarization phenomenon increases, so the thickness is preferably 5 mm or less, although it is affected by the dielectric constant of the electric insulating material. ..

The polymerization method to which the method of the present invention is applied is a method of polymerizing a polymerizable monomer in an aqueous medium, such as emulsion polymerization and suspension polymerization.

Suitable polymerizable monomers include ethylene,
Olefins such as propylene, butadiene and chloroprene; vinyl halides such as vinyl chloride; vinylidene halides such as vinylidene chloride; vinyl esters such as vinyl acetate; aromatic vinyls such as styrene; nitriles such as acrylonitrile; (meth) acrylic acid And esters thereof; unsaturated carboxylic acids such as maleic acid and crotonic acid. Further, as the dispersant used in these polymerizations, polyvinyl alcohol, water-soluble cellulose derivative, polyacrylic acid, polyvinylpyrrolidone, vinyl acetate-maleic anhydride copolymer, vinylpyrrolidone-vinyl acetate copolymer, gelatin, Starch or various anionic, nonionic or cationic surfactants such as sodium alkylbenzenesulfonate, sodium alkylsulfate and sodium dialkylsulfosuccinate; talc, bentonite, calcium sulfate, magnesium carbonate and the like are used. As the polymerization catalyst, an acyl peroxide such as lauroyl peroxide, a peroxy ester of an organic acid such as t-butyl peroxypiperate, an azo compound such as azobisisobutyronitrile, a diisopropyl peroxy diester, and the like. An oil-soluble catalyst such as peroxydicarbonate such as carbonate, a water-soluble catalyst such as potassium persulfate, or a redox catalyst composed of persulfuric acid as an oxidizing component and sulfurous acid as a reducing component is used.

The DC voltage applied in the present invention depends on the shape, size and type of the insoluble electrode, the size of the main body of the polymerization apparatus, the dielectric constant of the liquid medium and the coated electrical insulator, and cannot be uniformly defined. Is a voltage within a range in which at least dielectric breakdown does not occur between both electrodes,
A voltage of about 0 to 5000 V is applied.

[0013]

EFFECTS OF THE INVENTION The polymerization method of the present invention makes it possible to almost eliminate the adhesion of scale or the like to the inner wall of a polymerization reactor or a stirrer.

[0014]

【Example】

Example 1 The following components were added to a 50 l iron autoclave having an inner wall and a stirrer lined with a 2 mm thick polyester resin.

[0015]

[Table 1] A platinum electrode was provided as a cathode in the polymerization reaction vessel, and an anode was connected to the metal portion of the vessel wall. During the polymerization reaction, while applying a voltage of 300 V, the polymerization was carried out at a bending pressure of 5 kg / cm ² G and a temperature of 58 ° C. for 7 hours. After completion of the polymerization, the autoclave was cooled, the pressure in the autoclave was released, the polymer was discharged, and the upper lid of the autoclave was opened. No polymer deposit was found on the inner wall surface of the polymerization reactor or on the stirrer. In addition, the same polymerization operation was performed 10
After repeating the cycle, there were no deposits in the autoclave. Comparative Example Except that the voltage from the external power supply was not applied,
Polymerization was carried out in exactly the same manner as in Example 1.

After the first polymerization reaction, a slight white opaque deposit was formed on the inner surface of the autoclave. When the above polymerization reaction was repeated 10 times without cleaning the inside, 1
White deposits with a thickness of mm or more were formed, and the attached amount was particularly large at the gas-liquid interface of the inner wall and the center part of the stirring blade attachment.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a polymerization method of the present invention.

FIG. 2 is a schematic view showing another embodiment example of the polymerization method of the present invention.

[Explanation of symbols]

 1 Polymerization reactor body 2 Coated electrical insulator 3 External electrode 4 Insoluble electrode

Claims (1)

[Claims] 1. When emulsion-polymerizing or suspension-polymerizing a polymerizable monomer in a polymerization reactor, a metal portion of an inner wall of the polymerization reactor and a reactor internal arrangement such as a stirring blade is used as one electrode,
At least one insoluble conductor disposed in a liquid medium in the polymerization reactor is used as the other electrode, and one or both of these electrodes coated with an electric insulating material is used. A polymerization method, wherein the medium and the coated electric insulator are composite dielectrics, and a polymerization is carried out in a state where a DC voltage lower than the dielectric breakdown voltage is applied between both electrodes to form a capacitor circuit.