JPS6341441A - Distillation of 2-hydroxyalkyl (meth)acrylate - Google Patents

Abstract

PURPOSE:To prevent the polymerization of product in the production of the titled compound from (meth)acrylic acid and an alkylene oxide, by introducing a liquid monomer from the top of a vertical double-pipe or multitubular heat- exchanger, countercurrently contacting the monomer with vapor introduced from the bottom of the exchanger and collecting the condensed vapor. CONSTITUTION:(Meth)acrylic acid is made to react with an alkylene oxide and the obtained reaction liquid is distilled to obtain the objective 2- hydroxyalkyl (meth)acrylate. In the above process, a cooling condenser 14 having a structure of vertical double-pipe or multitubular heat-exchanger is used as a vertical falling film cooling condenser. Condensed liquid is supplied to the condenser from the top, flowed down along the inner wall of a heat-transfer pipe and made to countercurrently contact with monomer vapor introduced from the bottom of the condenser to effect quick condensation of the vapor and cooling of the condensed liquid. The titled compound is obtained as the condensate. EFFECT:Superheated vapor sufficiently effective in preventing the polymerization can be condensed and collected to enable smooth continuous distillation operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to 2-hydroxyalkyl acrylate or 2-hydroxyalkyl methacrylate (hereinafter both are referred to as 2-hydroxyalkyl (meth)acrylate or monomer). ). More specifically, the present invention relates to a method for preventing polymerization during distillation purification of 2-hydroxyalkyl (meth)acrylate, in which the vapor of the monomer is condensed and collected.

Horaihuang Gishu 2-hydroxyalkyl (meth)acrylate is usually prepared by acrylic acid or methacrylic acid (hereinafter referred to as
Both are synthesized by reacting (generally referred to as (meth)acrylic acid) with alkylene oxide, and then purified by distillation to obtain a fraction.

This monomer is highly polymerizable, and the monomer can be prevented from polymerizing in the same manner as (meth)acrylic acid and (meth)acrylic acid esters obtained from this and alcohols such as methanol and ethanol. It is very difficult to purify the polymer by distillation.

Conventionally, various polymerization inhibitors have been proposed, but although these have a certain effect in distillers, they cannot prevent polymerization of cough monomers in vapor pipes or condensers.

Japanese Patent Publication No. 60-43056 discloses the following method as a method for preventing polymerization during retention.

■Cough! Li-mer vapor is a! However, since the condensate polymerizes when exposed to high temperatures, the steam conduit leading to the condenser maintains the monomer tea in a superheated state to prevent condensation.

■For condensation and collection of cough monomer stem air, the condenser uses a gas-liquid co-current direct heat exchange method, and the pre-cooled cough monomer liquid is sprayed onto the superheated steam introduced, causing condensation. In order to prevent polymerization, it is essential to quickly cool the condensate.

However, according to studies conducted by the present inventors, polymerization can be substantially prevented in the condenser by keeping the steam superheated in the conduit to prevent condensation. Superheated monomer vapor is much easier to polymerize than so-called saturated vapor. In addition, if the condenser type is a gas-liquid co-current direct heat exchange type that sprays pre-cooled condensate, the spray nozzle is exposed to high temperatures due to filtered steam, so the nozzle may polymerize. It was easy to get clogged with substances, making it difficult to run a smooth continuous distillation operation.

In order to solve the above-mentioned problem, the inventors of the present invention have conducted intensive studies to solve the above problems, and have used a double-tube heat exchanger or a multi-tube heat exchanger as the type of condenser. Exchanger design handbook 2nd
As a vertical falling liquid film type condensing cooler described in version (published by Kogakuzusho in 1981) P, 686-688, the condensate is supplied from the upper part and allowed to flow down along the inner wall surface of the heat transfer tube, and the jii
discovered that by bringing the monomer liquid into countercurrent contact with the monomer vapor introduced from the bottom, it is possible to condense and collect superheated stem gas without causing polymerization troubles,
This has led to the completion of the present invention.

That is, the method for distilling 2-hydroxyalkyl (meth)acrylate of the present invention involves reacting acrylic acid or methacrylic acid with alkylene oxide, and distilling the resulting reaction solution to obtain 2-hydroxyalkyl (meth)acrylate as a fraction.
When obtaining acrylate, a cooling condenser 14, which is a vertical double-tube or multi-tube heat exchanger, is used, and a single liquid is supplied from the upper part of the cooling condenser 14 into the heat exchanger tube. The cooling condenser 14 is made to flow down along the wall surface and maintained in a superheated state.
This is a T8 distillation method for 2-hydroquine alkyl (meth)acrylate, which is characterized in that the stem gas of the monomer introduced into the lower part and the liquid of the monomer are brought into countercurrent contact and condensed and collected.

An object of the present invention is to provide a means for condensing and collecting the vapor of the cough tetramer kept in an overheated state due to the necessity of preventing polymerization in the steam pipe without causing polymerization troubles. .

The method of the present invention will be explained below, including its embodiments.

The alkylene oxides used in the method of the present invention are alkylene oxides such as ethylene oxide and propylene oxide, and oquinrane compounds such as epichlorohydrin.

The reaction is usually carried out in the presence of a catalyst.

As catalysts, various amines (Japanese Patent Publication No. 44-2685), quaternary ammonium salts (Japanese Patent Publication No. 45-27083) are used.
, combinations of trivalent iron compounds and silver or mercury as co-catalysts (Japanese Patent Publication No. 18890/1989), chromium compounds (
JP-A No. 57-42657) is known, but any of them may be used. Generally, the amount of the catalyst is 0.01 to 10%, preferably 1% to 10%, based on the raw material (meth)acrylic acid. is a proportion of 0.03 to 3% by weight.

The synthesis reaction of 2-hydroxyalkyl (meth)acrylate is usually carried out batchwise as follows. A reactor equipped with heating and cooling functions and a stirring device is charged with (meth)acrylic acid, a catalyst, and a polymerization inhibitor, and the gas inside the reactor is filled with an inert gas such as nitrogen gas to avoid the risk of explosion. displacement, then the fi temperature is 50-110°C, preferably 60-9
Raise the temperature to 0°C.

Next, alkylene oxide is supplied to the reactor in gaseous or liquid form to start the reaction. The reaction begins with the supply of alkylene oxide, and the liquid temperature begins to rise.
The reaction operating pressure for maintaining the temperature at 50 to 110° C., preferably 70 to 90° C. by cooling is not particularly limited, and may be any one of increased pressure, normal pressure, and reduced pressure.

The molar ratio of alkylene oxide to (meth)acrylic acid is 1.0 to 1.2, preferably 1.03 to 1.10.
At the point when the supply of alkylene oxide is stopped,
The reaction is continued at the above reaction temperature until the (meth)acrylic acid concentration in the reaction solution becomes 1.0% by weight or less, preferably 0.5% by weight or less.

As the polymerization inhibitor, one or more of hydroquinone, hydroquinone monomethyl ether, catechol, phenothiazine, N,N'-di-2-naphthyl-p-phenylenediamine, nitric acid or nitrate, etc. is usually used.
It is used in an amount of 0.01 to 3% by weight, preferably 0.03 to 1% by weight based on (meth)acrylic acid.

A more detailed explanation will be given below based on the drawings.

The reaction solution obtained as described above is purified by distillation to obtain a product as a fraction.

The distillation apparatus is comprised of a distillation vessel 6, a gas-liquid separator 9 and/or a distillation column, a cooling condenser 14, an exhaust line 16, etc., which perform necessary heat transfer for evaporation.

Types of stills include jacketed containers and types that circulate the bottoms and heat them with a shell-and-tube heat exchanger, but the latter type, which is a flowing liquid model, is particularly suitable for heat transfer. This is preferable because the coefficient is large.

Distillation is carried out under reduced pressure.The operating pressure is preferably as low as possible from the viewpoint of preventing polymerization, but the operating pressure is 1 mmHgabs.
It is difficult in commercial production facilities to achieve pressures as low as 1 to 8 mmHgabs, preferably 3 to 6 mmHgabs.
mml1gabs. The liquid temperature in distillation can 6 is 70-10
0°C, preferably 80-90°C. The monomer vapor generated from the distillation vessel 6 is normally led to the cooling condenser 14 via a gas-liquid separator 9 and/or a distillation column. It is desirable to provide a demister 10 in the gas-liquid separator 9 and/or the distillation column to prevent droplet entrainment.

In the present invention, in order to prevent condensation of the monomer vapor within the conduit and, as a result, polymerization, the steam conduit 11 is heated, and the vapor is led to the cooling condenser 14 in a superheated state.

The temperature of the superheated steam does not need to be excessively high as long as it can prevent condensation, but it is usually 0.1 to 30°C, preferably 1 to 15°C higher than the boiling point at operating pressure.

The monomer vapor is introduced into a cooling condenser 14 . Since the monomer has high polymerizability and is in a superheated state, polymerization is extremely likely to occur, and special consideration is required in terms of the structure and operation of the cooling condenser.

The cooling condenser 14 used in the present invention is a vertical double-tube or multi-tube heat exchanger, and is used as a vertical falling film cooling condenser, and the condensate is poured from the top. It is possible to quickly condense and cool the condensed liquid by supplying the monomer and flowing it down along the inner wall surface of the heat transfer tube, and bringing the condensed liquid into countercurrent contact with the monomer vapor introduced from the lower part. can.

The condensate is supplied to the upper part of the cooling condenser 14. The amount of circulating liquid is usually 1 to 100 times by weight, preferably 3 to 30 times by weight, the amount of vapor of the monomer.

"The temperature of the condensate circulating fluid should be below 70'C, preferably 50'C.
It is best to keep it below ℃.

Ru.

Example 1 <Synthesis reaction> 66.1 kg of methacrylic acid was placed in a 5O3-3O4 reactor with an internal volume of 150 e, and chromic chloride (66.1 kg) was used as a catalyst.
10 g of chromium nitrate (9 hydrate), 66 g of phenothiazine as a polymerization inhibitor, 10 g of chromium nitrate (9 hydrate), and after replacing the internal gas with N8 gas, the temperature was raised to 80°C and the internal pressure was reduced to 2.
．． The pressure was 2 atm. 35.1 kg of ethylene oxide was supplied over 4 hours, and the reaction was carried out while maintaining the temperature at 80°C.

After the supply was completed, the temperature was raised to 90° C. and the reaction was continued for 3 hours. The methacrylic acid concentration in the reaction solution was 0.3% and the ethylene oxide concentration was 400 ppm. Thereafter, the reaction solution was cooled.

<Distillation> Double-pipe heat exchanger with a falling liquid film 2 using a 1-inch tube with a length of 1 m as a heat transfer tube! Distillation WiZ shown in Figure 1 with vessel A as a distillation can
The reaction solution obtained by the method described above was evaporated using the following method. The material of all the contact parts of the 2-hydroquinoethyl methacrylate of the Naru apparatus was 5O5-304. 200pp of methoxyhydroquinone was added to the reaction solution as a stabilizer.
m was added.

The liquid flow rate in the supply line of the distillation can 6 was set to 1001/llr, and heating in the distillation can 6 was performed using steam at 100°C. Also, 5Nj of air is pumped out from the top of distillation can 6! /Hr was supplied.

The pressure in the gas-liquid separator 9 is 4 mm 1 gat) s,
The liquid temperature at the outlet of the stem distiller 6 was 86°C. A mesoche-like demister IO made of Teflon was attached above the gas-liquid separator 9, and the steam conduit 11 beyond there was heated with a heater so that the wall temperature was 100°C. Similarly, the cooling condenser 14 is a double-tube heat exchanger using a 1-inch tube with a length of 1 m as a heat exchanger tube.
30~40j of condensate with a temperature of 40~50℃ on the tube side
! /lk was supplied from above so as to be in countercurrent contact with the steam. In this way, 5.5Kg of reaction liquid was supplied per hour, and 5.0Kg/Hr of distillate and 0.5Kg/Hr of distillate were supplied.
A bottoms liquid was constantly obtained, and this condition was maintained for XO days.

Thereafter, when the distillation apparatus was dismantled and inspected, it was found that the falling film cooling condenser 14, its surrounding areas, and the condensate circulation line 2
No formation or adhesion of polymer was observed on the 1st grade.

Comparative Example 1 As shown in Figure 2, diameter 150m...φ, height 2000m
A condenser made of +as 5tlS-304 was used. Distillation was carried out in substantially the same manner as in Example 1, except that the condenser was equipped with a cooling jacket 4 at a distance of 800 mm from the top, and a spray nozzle 7 was used to allow direct contact between gas and liquid in parallel flow.

The temperature of the spray liquid is 50℃, 2*l is 5001/ll
It was set as r. Further, cooling water having a water temperature of 30° C. was flowed through the cooling jacket 4.

3.5 days after the start of retention, the spray liquid flow rate was increased to 5001/f.
Since it could no longer be maintained in IR, distillation was stopped and a disassembly inspection was conducted to find that about half of the nozzles were blocked by polymers and the spray liquid could no longer flow. Also, condenser body work 3
Adhesion of polymers was observed in various places on the vessel wall.

In the case of 2-hydroxyalkyl (meth)acrylate, it is essential to superheat the vapor of the 3X polymer in the conduit in order to prevent polymerization. There was no satisfactory method for condensing and collecting superheated steam.

However, for the first time, the method of the present invention has made it possible to condense and collect superheated steam that can sufficiently prevent polymerization, making it possible to carry out smooth continuous distillation of 2-hydroxyalkyl acrylate.

[Brief explanation of the drawing]

FIG. 1 shows the flow route of the distillation apparatus shown in Example 1. In the figure, each code is as follows: l: reaction f night population 2; canned out 1 night exit 3;
City supply line 4. Air population 5: Liquid disperser 6
．． Distillation can 7 Steam population 8. Drain outlet 9: Gas-liquid separator 10: Demister 11: Steam conduit 12
; Heating section 13: Bottom fj, circulation pump 14: Cooling condenser 15: Liquid disperser 16: Exhaust line F: Cooling water inlet
18: Cooling water outlet 19: Condensate receiver 20; Condensate outlet 21: Gutter condensate circulation line 22: ei There is a condensate liquid circulation pump. FIG. 2 shows the flow route of the condenser section of the distillation apparatus shown in Comparative Example 1. In the figure, each symbol is as follows: 1: Superheated steam supply line 2: Superheated steam inlet 3: Heating section 4: Cooling jacket 5; Cooling water inlet 6: Cooling water outlet lower; Spray nozzle
8: Condensate circulation pump 9: Condensate outlet l
O: Condensation fl circulation line 11: Cooler 1
2: Exhaust line 13; This is the condenser body. Patent applicant Mitsui Toatsu Chemical Co., Ltd. Figure 1. Figure 2

Claims (1)

[Claims] (1) When reacting (meth)acrylic acid and alkylene oxide and then distilling the resulting reaction solution to obtain 2-hydroxyalkyl (meth)acrylate as a fraction, a vertical double tube type or Using the cooling condenser 14, which is a multi-tubular heat exchanger, a monomer liquid is supplied from the upper part of the cooling condenser 14 and flows down along the inner wall surface of the heat transfer tubes to maintain the superheated state and cool the liquid. 2-hydroxyalkyl (meth), characterized in that the vapor of the monomer introduced into the lower part of the condenser 14 and the liquid of the monomer are brought into countercurrent contact and condensed and collected.
Method of distilling acrylates.