JP3742166B2 - Polymer adhesion prevention method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for preventing polymer adhesion, and more specifically, when a monomer is polymerized using a stirred tank reactor, particularly when a methacrylic polymer or the like is produced by continuous bulk polymerization using a stirred tank reactor. The present invention relates to a method for preventing the polymer from adhering to the inner wall of the reactor in the gas phase and the stirring shaft.
[0002]
[Prior art]
Conventionally, when a monomer is polymerized in a polymerization tank using a stirred tank reactor, there has been a problem that the polymer adheres to the reactor inner wall and the stirring shaft in the gas phase, but as a method for solving this problem The following method has been proposed.
(1) As a method for preventing polymer adhesion at the gas-liquid interface, a rotating body is provided above the surface of the reactant liquid in the reaction vessel, and the monomer is attached to the wall of the reaction vessel by supplying cleaning monomer to the rotating body. A method of spraying and preventing polymer adhesion on the wall of the reaction vessel (Japanese Patent Publication No. 48-32431).
(2) A continuous bulk polymerization method in which a part of the monomer supplied into the reaction vessel is uniformly sprayed and supplied to the reaction liquid surface and the stirring shaft in contact with the reaction liquid surface (JP-A-7-149803). Issue gazette).
(3) A method for removing polymerization heat that promotes condensation in the gas phase by providing a cooling means and a stirring means in the gas phase in the reactor (Japanese Patent Publication No. 56-15641).
[0003]
[Problems to be solved by the invention]
However, in the gas-liquid interface polymer adhesion preventing method (1) or (2), it is preferable that the cleaning monomer does not contain a polymerization initiator, and two monomer supply paths for the raw material monomer and the cleaning monomer are required. In addition, the polymer adheres not only to the gas-liquid interface but also to the inner wall of the reactor in the gas phase and the stirring shaft. However, in the above method (1) or (2), the monomer is added to all the sites in the gas phase. There is a problem that it is difficult to spray like.
Further, in the method (3) for promoting the condensation in the gas phase part, since the condensation is performed by the internal cooling means, the amount of the condensate on the inner wall of the reactor is reduced, and the inner wall of the reactor is not sufficiently washed away. There is a problem that it causes adhesion and foreign matter mixing into the target object, and in order to provide a cooling means and a stirring means in the gas phase portion in the reactor, the equipment cost and the maintenance cost are considerably required.
Accordingly, an object of the present invention is to provide a method for preventing adhesion of a polymer to a reactor inner wall or a stirring shaft at a gas phase part or an interface between a gas phase part and a liquid phase part by a simple means.
[0004]
[Means for Solving the Problems]
As a result of diligent investigation focusing on the structure of the stirrer in the reactor, the present inventors have conducted a reaction so as not to boil the reaction liquid in the reactor or when the polymerizable monomer is polymerized in the stirred tank reactor. When continuous bulk polymerization is performed while maintaining the internal pressure of the reactor, the liquid phase part and the gas phase part are agitated by a stirring blade to increase the amount of monomer evaporation from the reaction solution, and the gas phase part is cooled by a cooling jacket. It has been found that by increasing the amount of condensate at the reactor inner wall and the stirring shaft of the phase part, and sufficiently washing away the wall surface of the gas phase part by the condensate, it is possible to prevent polymer adhesion to the gas phase part. completed.
[0005]
That is, the above-described object, upon continuous bulk polymerization while maintaining the reaction pressure as the reaction liquid in the reactor a polymerizable monomer in 撹拌槽reactor does not boil, the reaction liquid level and not only a liquid phase portion The gas phase portion is stirred by a lattice blade protruding from the liquid phase portion to the gas phase portion , and the gas phase portion is cooled by a cooling jacket so that the amount of the condensate is 1/10 or more of the amount of polymerizable monomer to be supplied. This can be achieved by a polymer adhesion prevention method.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
According to the method of the present invention, the effective evaporation area is increased by stirring the reaction liquid surface with the stirring blade, and the amount of evaporation of the monomer is increased. In addition, the vaporized monomer gas rapidly spreads to the gas phase portion by stirring the gas phase portion, and further the monomer gas is cooled on the reactor inner wall of the gas phase portion and the stirring shaft by cooling the gas phase portion with a cooling jacket. By condensing and constantly washing the reactor inner wall and the stirring shaft in the gas phase with the monomer condensate, it is possible to prevent the polymer from adhering to the reactor inner wall and the stirring shaft.
[0007]
The method of the present invention can be used without particular limitation when polymerizing a polymerizable monomer using a stirred tank reactor, but the reaction solution in the reactor boils from the viewpoint of productivity and the effect of preventing polymer adhesion. This is particularly effective in a continuous bulk polymerization method that is carried out while maintaining the internal pressure of the reaction so as not to occur. Also, the polymerizable monomer to be used is not particularly limited, but is suitable for a monomer mainly composed of, for example, methyl methacrylate (hereinafter sometimes abbreviated as MMA), styrene, etc. It is particularly preferably employed in the case of a monomer mixture comprising 20 to 0% by weight of another copolymerizable monomer.
[0008]
The stirring blade used in the method of the present invention, by having a blade protruding from the liquid surface, as well as the reaction solution, and a lattice blade that obtained was stirred well and the reaction liquid surface and the gas phase portion. MAX BLEND impeller is lattice blade in terms of stirring efficiency, especially is more preferably used.
[0009]
In order to obtain a sufficient polymer adhesion preventing effect in the method of the present invention, it is desirable to obtain a sufficient amount of condensate to wash away the reactor inner wall and the stirring shaft. Reaction conditions such as the number of revolutions, reaction liquid temperature, and polymerization rate are appropriately set.
[0010]
A preferred embodiment in the method of the present invention will be described with reference to FIG. A polymerizable monomer is supplied from the monomer supply pipe 4 of the reaction vessel 1 shown in FIG. 1, while an inert gas such as nitrogen is introduced from an inert gas supply pipe 17. When the amount of the reaction liquid in the reaction tank reaches a predetermined amount, continuous bulk polymerization is started. In that case, it is preferable to carry out by maintaining the internal pressure of the reaction so that the reaction liquid in the reactor does not boil. The stirring blade 3 is stirred in a state of protruding from the reaction liquid surface 10 while cooling is performed by flowing cooling water through the cooling jacket 13 in the gas phase portion.
[0011]
For the continuous bulk polymerization, in order to obtain a sufficient polymer adhesion preventing effect in the present invention, not less than 1/10 and Do that by Uni condensate quantity supplied polymerizable monomer amount, stirring speed reaction temperature The reaction conditions such as the polymerization rate are set. As the stirring rotation speed usually employed, the stirring consumption power is 0.5 to 20 KW per 1 m ^{3 of} the reaction solution, the reaction solution temperature is 130 to 160 ° C., and the polymerization rate is 45 to 70%. is there. Usually, the higher the stirring speed is, the higher the evaporation promoting effect is. However, since the required power increases, it is desirable to set the stirring speed to a level necessary for liquid phase stirring. The higher the reaction liquid temperature, the higher the monomer vapor pressure and the lower the reaction liquid viscosity, thereby increasing the amount of evaporation, but also increasing the amount of by-products generated. It is desirable. Furthermore, the lower the polymerization rate of the reaction solution, the more the amount of evaporation increases. However, in order to increase productivity, it is desirable to increase the polymerization rate within a range where a sufficient amount of condensate can be obtained.
[0012]
The heat transfer area of the cooling jacket in the gas phase is desirably as large as possible, but is preferably provided at a position higher than the reaction liquid surface so as not to directly cool the reaction liquid.
In addition, cooling water or refrigerant is allowed to flow through the cooling jacket in the gas phase portion. The appropriate cooling water or refrigerant temperature varies depending on the reaction temperature, but is usually in the range of −5 to 40 ° C.
[0013]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
[0014]
Example 1
MMA containing 80 ppm of azobisisobutylnitrile as an initiator and 0.3% by weight of octyl mercaptan as a chain transfer agent was continuously supplied from the monomer supply pipe 4 of the reaction vessel 1 shown in FIG. Nitrogen was introduced into the reaction vessel from the inert gas supply pipe 17 as an inert gas. The amount of the reaction liquid in the tank was 3,100 kg, the reaction liquid temperature was 140 ° C., the internal pressure was maintained at 3 kg / cm ² , and continuous bulk polymerization was performed with an average residence time of 2.5 hours. The gas phase portion was cooled by flowing cooling water at 20 ° C. through the cooling jacket 13 of the gas phase portion. When stirring blade 3 (manufactured by Sumitomo Heavy Industries, Max Blend (registered trademark) type) was protruded 400 mm from the liquid surface and stirred at a rotational speed of 60 rpm and continuously operated for 2 months, it was moved to the inner wall of the gas phase section and the stirring shaft. The polymer adhesion did not occur.
[0015]
Example 2
Although it was smaller than what was used in Example 1, the same reaction tank was used, the polymerizable monomer was supplied like Example 1, and nitrogen was supplied as an inert gas. The amount of the reaction liquid in the tank was 94 kg, the reaction liquid temperature was 150 ° C., the internal pressure was maintained at 7 kg / cm ² , and continuous bulk polymerization was performed with an average residence time of 3 hours. Also, the gas phase part was cooled in the same manner as in Example 1, and the stirring blade 3 (manufactured by Sumitomo Heavy Industries, Max Blend (registered trademark) type) was stirred at a rotational speed of 150 rpm with a protrusion of 40 mm from the liquid surface for 2 weeks. When continuously operated, polymer adhesion to the inner wall of the gas phase portion and the stirring shaft did not occur.
[0016]
Comparative Example 1
The same operation as in Example 1 was performed except that the stirring blade was submerged in the reaction solution. When continuously operated for two months, about 5 kg of polymer adhered to the reactor inner wall and the stirring shaft in the gas phase portion of the reactor, and an operator had to enter the reactor in order to remove the adhered polymer.
[0017]
【The invention's effect】
According to the present invention, it is possible to prevent the polymer from adhering to the inner wall of the reactor and the stirring shaft in the gas phase portion, so that the operation of removing the polymer in the reaction tank is not required, and not only continuous operation is possible, but also physical properties of the product due to the adhering polymer adhering Since no change occurs, stable quality is guaranteed.
Furthermore, since the polymer can be prevented from adhering in the gas phase without adding extra equipment in the reactor, the possibility of contamination is low and maintenance is facilitated.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a polymerization apparatus used in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Reaction container 2 ... Stirring shaft 3 ... Stirring blade 4 ... Monomer supply pipe 5 ... Reaction liquid extraction pipe 6 ... Heating medium supply pipe 7 ... Heating medium extraction pipe 8 ... Cooling water supply pipe 9 ... Cooling water extraction pipe 10 ... Reaction Liquid surface 11 ... Electric motor 12 ... Liquid phase part jacket 13 ... Gas phase part cooling jacket 14 ... Release gas condenser 15 ... Pressure control valve 16 ... Pressure gauge 17 ... Inert gas supply pipe

Claims (2)

In the reaction liquid in the reactor a polymerizable monomer in a stirred tank reactor is a continuous bulk polymerization while maintaining the reaction pressure to prevent boiling, liquid phase, the reaction liquid surface, and the liquid phase portion of the gas phase The mixture is stirred by a lattice blade protruding from the gas phase portion and cooled by the cooling jacket so that the amount of the condensate is 1/10 or more of the amount of the polymerizable monomer to be supplied. Adhesion prevention method. The method for preventing polymer adhesion according to claim 1 , wherein the polymerizable monomer is a monomer mainly composed of methyl methacrylate.

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