JP2000198750A - Reaction for preventing polymerization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reaction method capable of preventing the production and accumulation of a polymerization product by carrying out the reaction in a reaction system containing a polymerizable substance, while the upper inner wall of a reaction vessel above the surface of a liquid is always covered and wet with the reaction liquid and the mists and splashes of the reaction liquid. SOLUTION: This reaction method comprises reacting in a reaction system containing a polymerizable substance as a raw material or its product, while the upper inner wall of the reaction vessel above the surface of a liquid is always covered and wet with the reaction liquid and the mists and splashes of the reaction liquid. When the reaction is e.g. a Diels Alder reaction, the reaction is carried out by reacting a dienophile such as maleic anhydride with a diene such as butadiene. The reaction method includes a method for stirring the reaction liquid with a stirring blade. The effect for preventing the production and accumulation of a polymerization product can be enhanced, for example, by attaching a device for upward jetting out a reaction liquid to a place above the surface of the liquid, jetting the reaction liquid, and further attaching a diffusion device 1 and a diffusion plate for enhancing the diffusion of the reaction liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a reaction containing a polymerizable substance and not intended for a polymerization reaction, such as a Diels-Alder reaction, esterification of acrylic acid or methacrylic acid, or epoxidation of an unsaturated substance. The present invention relates to a method for preventing polymerization of a toxic substance.

[0002]

2. Description of the Related Art In a reaction using a polymerizable substance which is not intended for polymerization, since it is often the same as a normal chemical reaction, a normal reaction vessel is often used, and a special apparatus for preventing polymerization is required. Used without installation. In the reaction step, generally, the raw materials are charged into a reaction vessel, and the reaction is carried out under a predetermined condition while stirring the reaction solution by means of a stirring blade or liquid circulation. The liquid phase portion in the reaction vessel is usually provided with some stirring device, but the gas phase portion is not currently equipped with any special device.

[0003]

In the case where a polymerizable substance is used in such a reactor, polymerization can be suppressed in the liquid phase even if a polymerization inhibitor is added. Polymerization inhibition was almost impossible.

[0004] In the conventional reaction method and apparatus, a polymer is produced in the reaction vessel, and as a result, the polymer is mixed in the product or adheres to and accumulates on the wall of the reaction vessel by repeating the above-mentioned steps, and the quality of the product is reduced. Has been adversely affected. Generally 100
If the operation is continued for a long time, the polymer adheres and accumulates on the can wall, and its thickness reaches 10 mm. When a condenser is installed, the line to the condenser may be blocked, and furthermore, it may also accumulate and accumulate in the nozzle above the reaction vessel, so that the pressure gauge diaphragm cannot be detected. For this reason, removal has to be performed, which has been a great hindrance to improvement in productivity at present.

[0005] In view of such circumstances, the present invention has intensively studied a reaction method for suppressing the production of a polymer while using a polymerizable substance as a raw material or a product, and as a result, completed the present invention. .

[0006]

Means for Solving the Problems The present inventors have found that the polymer is mainly formed on the gas wall of the gas phase, and from this fact, it is possible to completely cover the can wall with the reaction solution at all times, It has been found that the formation and accumulation of a polymer can be prevented by wetting, and the present invention has been completed.

That is, in the present invention, in a reaction system containing a polymerizable substance as a raw material or a product, the can wall above the liquid level of the reaction vessel is always covered and wet with the reaction liquid or the mist of the reaction liquid or droplets. It is characterized by.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The reason why a polymer is formed in the gas phase in the upper part of the reaction vessel is not always clear, but the vapor pressures of the raw materials involved in the reaction are different, and the concentration of some of the components in the gas phase is different. As a result, it is presumed that the intended reaction does not proceed, and the can wall exhibits the same action as the catalyst. As a result, polymerization is promoted and the polymer adheres and accumulates on the can wall. For example, in the Diels-Alder reaction in which maleic anhydride and butadiene are used as raw materials, it is presumed that the polymerization containing butadiene as a main component proceeds as a result of a very high concentration of butadiene as compared with maleic anhydride in the gas phase. You. A reaction containing a polymerizable substance in a raw material or a product and not for the purpose of polymerization is a Diels-Alder reaction,
Polymerizable acids such as acrylic acid or methacrylic acid, allyl alcohol, esterification or transesterification of alcohol, amidation of polymerizable acids such as acrylic acid and methacrylic acid, ethylene, propylene, styrene, and other olefins Epoxidation, ene reaction of maleic anhydride olefin and the like, but are not limited thereto. In addition, any one or more of these raw materials used in the reaction may be polymerizable, and not all substances need to be polymerizable.

The starting materials used in the reaction are, for example, Diels-
In the case of the alder reaction, the diene and dienophile used in the reaction may be those which are generally known, and are performed by reacting a dienophile such as maleic anhydride with a diene. As the diene used in the reaction, butadiene, isoprene, piperylene, cyclopentadiene, dicyclopentadiene, cyclohexadiene, 1,3-hexadiene, 2,4-hexadiene, styrene, 3-vinylcyclohexene, sorbic acid, conjugated linoleic acid, conjugated It is selected from linoleic acid and the like.

[0010] The reaction method may be a conventionally used method, and may be replaced with a method of stirring the reaction solution by a stirring blade or a method of stirring the solution by liquid circulation or the like.

The method used in the practice of the present invention is preferably any method as long as the reaction solution is sprayed and wetted on the wall of the can. Attach a device that ejects the liquid and spray the liquid (Fig. 1), or attach a device that has the same function as a sprinkler (hereinafter referred to as a sprinkler) to the can wall above the reaction vessel and spray the liquid. The purpose can be achieved by wetting the can wall of the reaction can.

In the former method, the effect can be enhanced by installing a diffusion device or a diffusion plate effective for enhancing the liquid dispersion. Also in the latter method, the effect can be enhanced by wetting the reaction vessel can wall by attaching an effective diffusion device or diffusion plate for enhancing the liquid dispersion and ejecting the liquid so as to flow along the can wall. I can do it. Further, by simultaneously circulating the ejected liquid with a circulation pump, the reaction speed can be increased. Circulation is performed by cycling the reaction solution with a circulation pump. The cycle liquid can be wetted on the can wall of the reaction vessel by the above-described jetting device or sprinkler installed in the reaction vessel.

According to the above method, the can wall of the reaction vessel is constantly wet with the liquid, and the formation and accumulation of the polymer are suppressed. The cycle amount of the reaction solution is preferably large, and the gas-liquid contact effect is improved by this method, and the reaction rate is also improved.

In the former method, when the size of the reaction vessel is large, one nozzle may not sufficiently disperse the liquid. It is also possible to use a spray nozzle at the nozzle tip. However, in this case, it is necessary to devise so that the tip of the nozzle is also covered with the liquid film. The diameter of the nozzle and the diameter of the hole of the diffuser to be attached must be set so as to maintain a jetting speed sufficient to wet the can wall of the reactor. Since the sprinkler allows the liquid to flow in all directions from the upper part of the reactor, only one sprinkler is sufficient. However, if there is no appropriate flow rate and flow rate, the cycle liquid does not flow along the can wall and cannot wet the can wall, so that a constant flow rate and flow rate are required.

If there is a condenser above the reactor,
In the part of the condenser tube, a part of the cycle liquid is pruned and allowed to flow down from the upper part of the condenser with a thin film, so that the reaction liquid can cover the wall surface in the tube. Alternatively, a liquid ejected from a nozzle or the like can be directly introduced into the inside of the condenser tube. In the case of a sprinkler, a method of removing the cycle liquid is preferable. If there is a diaphragm pressure gauge,
Blowing the liquid directly toward the diaphragm surface is not preferable because it causes an error in pressure indication, and can be solved by improving the nozzle to blow toward the side wall.

[0016]

EXAMPLES The effects of the present invention will be described below with reference to examples.

EXAMPLE 1 After replacing the reactor shown in FIG. 1 equipped with a diffusion device with nitrogen gas, 1.5 tons of molten maleic anhydride was charged, and butadiene gas was added to the lower portion of the reactor at 100 ° C. while circulating the reaction solution. Introduced from. The reaction was terminated when the amount of butadiene gas introduced reached 1.05 equivalents of maleic anhydride. The reaction time during this period was 4 hours. At this time, no production of a polymer was recognized on the reaction product or on the can wall of the reaction vessel.

Example 2 A reaction was carried out in the same manner as in Example 1 except that piperylene was used instead of butadiene, and that piperylene was dropped from the top of the reactor. As in Example 1, no formation of a polymer was found on the reaction product or on the can wall of the reaction vessel.

Example 3 Using a reaction vessel without a special device for wetting the can wall, ordinary liquid agitation is used (there is sufficient agitation effect and the reaction vessel is always covered with a liquid film on the inner wall of the reaction vessel). The reaction was carried out in the same manner as in Example 1 except that the reaction was carried out. As a result, Example 1
Similarly to the above, no formation of a polymer was observed on the reaction product or on the wall of the reaction vessel.

Example 4 After replacing the reactor equipped with the diffusion apparatus shown in FIG. 1 with nitrogen gas, 0.6 t of methyl methacrylate, 0.77 t of octanol, 3 kg of sodium methylate as a transesterification catalyst, and hydroquinone as a polymerization inhibitor were used. 0.8 kg of monomethyl ether was charged, and transesterification was carried out in a usual manner while circulating the reaction solution at 100 ° C. The reaction time was 6 hours. At this time, no production of a polymer was recognized on the reaction product or on the can wall of the reaction vessel.

Example 5 A reaction was carried out in the same manner as in Example 1 except that a reactor in which a diffusion plate was attached to a sprinkler was used. As in Example 1,
No formation of a polymer was found on the reaction product or on the can wall of the reaction vessel.

Comparative Example The same procedure as in Example 1 was carried out except that a reactor without a nozzle and a sprinkler was used. As a result, the formation of a polymer was observed in the upper part of the reaction vessel. When the reaction was repeated five more times, the polymer adhered to the reaction vessel had a thickness of 1-2.
mm.

[0023]

According to the conventional reactor, when the reactor is operated for about 240 hours, it is necessary to remove the polymer. However, the reactor according to the present invention is provided with a device for wetting the can wall of the gas phase. No reaction product was observed at all even after the reaction was repeated 100 times. Patent applicant Shin Nippon Rika Co., Ltd.

[Brief description of the drawings]

FIG. 1 is a plan view of a reaction can. DESCRIPTION OF SYMBOLS 1 ... Diffusion apparatus 2 ... Nozzle 3 ... Liquid distributor

Claims (1)

[Claims] In a reaction system containing a polymerizable substance as a raw material or a product, a can wall above a liquid surface of a reaction vessel is always covered and wet with a reaction solution or a mist or a droplet of the reaction solution. Reaction method.