JPH07149803A - Continuous bulk polymerization method - Google Patents

Abstract

PURPOSE:To produce an uniform polymer with preventing the adhesion of the polymer on gas-liquid interfaces and without requiring the cleaning of a reactor by spraying and feeding a monomer consisting mainly of methyl methacrylate on the surface of the reaction solution, on a container wall contacting with the solution surface and on a stirring shaft. CONSTITUTION:In a method for continuously bulk-polymerizing a monomer consisting mainly of methyl methacrylate, the monomer is fed, while a part 5 of the monomer to be fed into a reactor is sprayed 6 on the surface of the reaction solution, on a container wall contacting the reaction solution surface and on a stirring shaft 2. A flat spray nozzle, an elliptic blow nozzle, etc., is used for the spraying, and 30-70% of the whole monomer to be fed into the reaction container is preferably used for the spraying. The monomer contains the methyl methacrylate in an amount of >=80wt.%, and is polymerized at a polymerization temperature of 125-135 deg.C. The monomer not containing a polymerization initiator is preferably used for the spraying.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous bulk polymerization method, and more particularly to a continuous bulk polymerization of a monomer containing methyl methacrylate as a main component capable of preventing the polymer from sticking to the gas-liquid interface in a reaction vessel. Regarding the method.

[0002]

2. Description of the Related Art Syrup (monomer-polymer mixture) containing methyl methacrylate as a main component is used for casting polymerization, but it has extremely strong adhesion. Therefore, in the conventional method for producing syrup containing methyl methacrylate as a main component using a stirred tank reactor, when the polymerization is carried out for a long time, the polymer adheres to the inner wall of the reaction vessel and the gas-liquid interface of the stirring shaft. However, continuous operation for a long time was impossible.

As a continuous bulk polymerization method for preventing the sticking of the polymer at the gas-liquid interface, a rotator is provided above the liquid surface of the reactant in the reaction vessel, and the monomer is supplied onto the rotator. Japanese Patent Publication No. 48-32431 discloses a method of spraying a monomer on the wall surface of a reaction vessel to prevent the polymer from sticking to the vessel wall of the reaction vessel.

[0004]

However, this method has a disadvantage that the monomer cannot be sprinkled in the lower part of the rotating body. Especially, when the rotating body is installed on the stirring shaft of the reaction vessel, the gas of the stirring shaft is not generated. It has a drawback that the polymer cannot be supplied to the liquid surface and the polymer is fixed.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and provides a continuous bulk polymerization method in which the polymer does not stick to the inside of the reaction vessel even during long-term operation. .

[0006]

Means for Solving the Problems That is, in the present invention, in continuous bulk polymerization of a monomer containing methyl methacrylate as a main component, a part of the monomer supplied to the reaction vessel is
A continuous bulk polymerization method characterized in that the reaction liquid surface, the reaction vessel wall surface in contact with the reaction liquid surface, and the stirring shaft in contact with the reaction liquid surface are uniformly sprayed and supplied in a spray state. is there.

The method of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a polymerization apparatus used to carry out the method of the present invention. The reaction container 1 is provided with a stirring shaft 2 equipped with a stirring blade 3 for stirring the reaction liquid 10 at a substantially central portion of the reaction container 1 . Further, in the upper area of the reaction container 1 , a raw material monomer supply pipe 4 for supplying a monomer containing a polymerization initiator and a monomer for spraying and supplying the monomer into the reaction container. A supply pipe 5 is provided. Further, in the lower area of the reaction vessel 1 , a reaction liquid take-out pipe 7 is provided. Further, a jacket 12 for controlling the polymerization reaction is provided outside the reaction vessel 1 .

In the method of the present invention, when a monomer containing methyl methacrylate as a main component is polymerized using a stirred tank type reaction vessel as shown in FIG. 1, the monomer supplied into the reaction vessel is used. Part of is supplied from the monomer supply pipe 5, and in a spray state,
The reaction liquid surface, the inner wall of the reaction container in contact with the reaction liquid surface, and the stirring shaft are uniformly sprayed to prevent the adhesion of the polymer at the gas-liquid interface.

In the present invention, the method of spraying and supplying the monomer is not particularly limited, but it is preferable to use the nozzle 6 as shown in FIG. As the nozzle 6, any of a flat spray nozzle, an elliptical spray nozzle, an elliptical spray nozzle, a square spray nozzle, a hollow cone nozzle, a full cone nozzle, a side spray nozzle, a porous nozzle, etc. may be used. Depending on the size, one or two or more may be used in combination. The material is not particularly limited as long as it has corrosion resistance, and stainless steel is usually used.

In the method of the present invention, the amount of the monomer supplied from the monomer supply pipe 5 cannot be unconditionally determined depending on the polymerization conditions and the like, but is 30% of the total weight of the monomers supplied to the reaction vessel.
The range of ˜70% is preferable. Further, the monomer supplied from the monomer supply pipe 5 may have the same composition as the monomer supplied from the raw material monomer supply pipe 4 or may have a different composition, but contains a polymerization initiator. It is preferable to use the one that is not present.

The monomer containing methyl methacrylate as the main component used in the method of the present invention is methyl methacrylate alone or a monomer mixture containing the main component of methyl methacrylate. In the case of a monomer mixture, methyl methacrylate preferably contains 80% by weight or more. Examples of the monomer used as a mixture with methyl methacrylate include ethyl methacrylate, propyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid esters such as benzyl methacrylate, and acrylic acid. Methyl acid, butyl acrylate, cyclohexyl acrylate, acrylic acid-2-
Examples thereof include acrylic acid esters such as ethylhexyl and benzyl acrylate, styrene, and α-methylstyrene.

In the method of the present invention, examples of the polymerization initiator used for polymerizing the above-mentioned monomer include di-isopropyl peroxydicarbonate and tert.
-Butyl neodecanoate, tert. -Butyl peroxypivalate, lauroyl peroxyside, benzoyl peroxide, tert. Butyl peroxyisopropyl carbonate, tert. -Butyl peroxybenzoate, dichromyl peroxide, di-ter
t. -Organic oxides such as butyl peroxide; 2,2 '
-Azobis (2,4-dimethylvaleronitrile), 2,
Radical polymerization initiator selected from azo compounds such as 2′-azobisisobutyl nitrile, 1-1 ′ azobis (1-cyclohexanecarbonitrile), 2,2′-azobis (2,2,4-trimethylpentane): Is mentioned. The amount of the polymerization initiator used is not particularly limited and is appropriately determined depending on the polymerization temperature and the intended polymer conversion rate, but is usually in the range of 0.01 to 0.5% by weight relative to the monomer. .

In the method of the present invention, a molecular weight modifier can be used if necessary. Specifically, primary, secondary, and tertiary having an alkyl group or a substituted alkyl group.
Grade mercaptans such as n-butyl mercaptan, is
o. -Butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, sec. -Butyl mercaptan, sec. -Dodecyl mercaptan, ter
t. -Butyl mercaptan.

The polymerization temperature in the method of the present invention is 100.
The temperature is in the range of to 140 ° C, preferably 125 to 135 ° C.

The solid content in the polymerization reaction product obtained according to the present invention is in the range of 15 to 40% as the polymer conversion rate, although it cannot be unconditionally determined depending on the polymerization degree of the polymer.

[0016]

EXAMPLES The present invention will be described in more detail below with reference to examples. The polymerization in the examples was carried out using the polymerization apparatus shown in FIG. % In the examples represents% by weight.

EXAMPLE 1 Methyl methacrylate containing 0.06% 2,2'-azobis (2,4-dimethylvaleronitrile) and 0.1% n-octyl mercaptan was placed in a polymerization vessel 1 (volume 5).
Liter) at a rate of 5 kg / hour from the raw material monomer supply pipe 4. On the other hand, the methyl methacrylate containing no polymerization initiator was passed through the nozzle 6 (using a full cone nozzle) from the monomer supply pipe 4 at a flow rate of 5 kg / hour to generate the reaction liquid surface in the reaction vessel and the reaction liquid surface. It was uniformly supplied to the wall surface of the reaction vessel and the stirring shaft in contact with each other in a spray state. While sufficiently stirring the reaction solution in the reaction vessel, the polymerization temperature was maintained at 130 ° C. and the internal pressure was maintained at 3 kg / cm ² · G, and the average residence time was 8.5.
Continuous polymerization was carried out in minutes. After reaching the steady state, the polymer conversion rate of the reaction product taken out from the reaction vessel was 25%. After continuous operation for 10 hours, no sticking of polymer was observed in the reaction vessel.

Example 2 5 kg of methyl methacrylate containing 0.06% of 2,2'-azobis (2,4-dimethylvaleronitrile) and 0.3% of n-octyl mercaptan in a reaction vessel 1 .
It was supplied from the raw material monomer supply pipe 4 at a rate of / hour. on the other hand,
Methyl methacrylate containing no polymerization initiator is reacted from the monomer supply pipe 5 through the nozzle 6 (using a full cone nozzle) at a flow rate of 4 kg / hour to the reaction liquid surface in the reaction vessel and the reaction in contact with the reaction liquid surface. It was uniformly sprayed onto the wall surface of the container and the stirring shaft. While sufficiently stirring the reaction liquid in the reaction vessel, the polymerization temperature is 130 ° C and the internal pressure is 3 kg / cm ² ·.
Maintaining G, continuous polymerization was carried out with an average residence time of 8.5 minutes. After reaching the steady state, the polymer conversion rate of the reaction product taken out from the reaction vessel was 35%. After continuous operation for 10 hours, no sticking of polymer was observed in the reaction vessel.

[0019]

EFFECTS OF THE INVENTION According to the present invention, the polymer is prevented from sticking at the gas-liquid interface of the inner wall of the reactor and the stirring shaft, and at the same time, abnormal polymerization due to the stuck polymer is prevented, so that a uniform polymer is produced. You can do it. Further, the number of times of disassembly and cleaning of the reactor for removing the adhered polymer is reduced, so that the productivity is improved. The method of the present invention is extremely useful in the production of methacrylic resin molding materials, including the production of cast polymerization syrup.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a polymerization apparatus used in the present invention.

[Explanation of Codes] 1 Reaction vessel 2 Stirring shaft 3 Stirring blade 4 Raw material monomer supply pipe 5 Monomer supply pipe 6 Nozzle 7 Reaction liquid take-out pipe 8 Steam supply pipe 9 Steam drain take-out pipe 10 Reaction liquid 11 Electric motor 12 Jacket

Claims (1)

[Claims] 1. During continuous bulk polymerization of a monomer containing methyl methacrylate as a main component, a part of the monomer supplied into the reaction vessel is in contact with the reaction liquid surface and the reaction liquid surface. A continuous bulk polymerization method, characterized in that the reaction is uniformly sprayed and supplied to the wall surface of the reaction vessel and the stirring shaft in contact with the reaction liquid surface.