JPS6263544A - Production of acrylic acid or methacrylic acid tertiary butyl ester - Google Patents

Abstract

PURPOSE:To produce the titled compound in high yield and purity suppressing the production of by-product, by reacting (meth)acrylic acid with isobutylene in the presence of a strongly acidic ion exchange resin catalyst under a specific temperature condition at a low molar ratio of isobutylene. CONSTITUTION:(Meth)acrylic acid is made to react with isobutylene at 0-20 deg.C (preferably starting the reaction at 15-20 deg.C and decreasing the temperature stepwise to 0-5 deg.C) for 3-15hr in the presence of a strongly acidic ion exchange resin catalyst (e.g. sulfonic acid type resin of styrene-divinylbenzene polymer) at a molar ratio of isobutylene to (meth)acrylic acid of 0.5-2.0, the unreacted isobutylene is separated from the reaction product, the low-boiling compounds are separated and the mixture is supplied to a fractionation column to obtain the objective high-purity compound from the column top. At least a part of the bottom residue of the fractionation column is treated with a thin-film evaporator to remove high-boiling compounds and the recovered unreacted (meth) acrylic acid is recycled to the reaction system.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides highly pure tert-butyl acrylate or tert-butyl methacrylate produced from acrylic acid or methacrylic acid and isobutylene using a strongly acidic ion exchange resin as a catalyst. The present invention relates to a method for producing butyl in high yield.

Specifically, the molar ratio of isobutylene to acrylic acid or methacrylic acid is 0.5 to 2.0, and the amount of strongly acidic ion exchange resin present to acrylic acid or methacrylic acid is 5.
~20% concavity, reaction temperature 0-20°C, reaction pressure normal pressure ~2. OKl/t: i G, reaction time 3-15
tertiary-butyl acrylate or tertiary-butyl methacrylate, which is reacted under the conditions of 100-300 mL and then distilled under reduced pressure to separate and recover unreacted acrylic acid or methacrylic acid, yielding high-yield and high-purity products. Regarding the manufacturing method.

Tert-butyl acrylate or tert-butyl methacrylate (hereinafter referred to as ATB or MATB)
When made into paints or molding materials by copolymerizing with other monomers, they are used as modifiers to improve heat resistance and electret properties.

(Prior Art) Various methods have been used to produce esters by reacting carboxylic acids and olefins together in a liquid phase in the presence of an acidic catalyst such as sulfuric acid or a strongly acidic ion exchange resin. proposed, but the process is complicated or
Alternatively, the yield is low, and an advantageous industrial method is not yet known.

A method for producing ATS or MATS from acrylic acid or methacrylic acid and isobutylene using sulfuric acid as a catalyst is described, for example, in JP-A-53-65815. According to this description, the molar ratio of isobutylene to acrylic acid or methacrylic acid is 3 to 6, and the concentration of sulfuric acid to acrylic acid or methacrylic acid (98% by weight).
(converted) 8 to 16% by weight, reaction temperature 18 to 50°C, reaction pressure 1.5 to 7.0 Kg/ci, reaction time 2 to 6 hours, and the obtained product was dissolved in an alkaline aqueous solution or After neutralization with an alkaline aqueous solution containing inorganic salts, the oil reservoir valve is distilled under reduced pressure to obtain the product. This method is
Due to the high molar ratio, it has economic disadvantages such as high pressure, recovery of unreacted isobutylene, and loss of product into the aqueous layer during neutralization.

In addition, since the reactivity is generally low in the sulfuric acid method, the reactivity can be increased by raising the reaction temperature, but side reactions also occur at the same time, lowering the yield of isobutylene, and at the same time increasing the burden on the purification process, making it uneconomical. It is disadvantageous. Also,
When neutralizing a sulfuric acid catalyst, a large amount of waste water such as aqueous solution or the loss of the product into the aqueous layer occurs, and the product ATB or MATB and unreacted acrylic acid or methacrylic acid are removed from the neutralization solution. The process is complicated because acrylic acid or methacrylic acid is recovered from the alkali salts of . Furthermore, the use of sulfuric acid limits the equipment in terms of materials.

A method for producing MATB using a strongly acidic ion exchange resin as a catalyst is described, for example, in US Pat. No. 3,037,052. According to this description, methacrylic acid has a temperature of -5°C.
Then, add isobutylene for 10 minutes and then reduce the temperature to 0~1℃.
The MATB is obtained by making the reaction occur. In this case, the reaction between methacrylic acid and isobutylene is an exothermic reaction, and industrially adding isobutylene under the above conditions is economically disadvantageous in terms of cooling, and the melting point of methacrylic acid is 14 to 16
℃, so difficulties in reaction operation are expected. Moreover,
The treatment of unreacted methacrylic acid and the industrial purification method of produced MATB are unknown.

(Problems to be Solved by the Invention) Generally, the above-mentioned conventional techniques have the following problems.

■ When a strongly acidic ion exchange resin is used as a catalyst, unreacted acrylic acid or methacrylic acid has a small difference in boiling point from the main product ATB or MATB, and when recovered, it contains ATB or MATB and is recycled to the reaction system. Here, the catalyst tends to generate decomposition products, resulting in lower yields and losses.
Easy to listen to.

■ When reacting with a strongly acidic ion exchange resin, the activity of the strongly acidic ion exchange resin tends to decrease due to high boiling point compounds and polymerization inhibitors produced as by-products during the reaction.

◎ The molar ratio of isobutylene to acrylic acid or methacrylic acid is large, and equipment for separating and recovering unreacted or excess isobutylene is required, which further increases utility costs, which is economically disadvantageous.

■ Strongly acidic ion exchange resins have stronger catalytic activity than sulfuric acid, and side reactions of isobutylene tend to increase.

■ When lowering the reaction temperature, the reaction solution solidifies, making it impossible to react.

(Means for solving problems) The present invention aims to reduce the above problems.

That is, the present invention is specified as follows.

(1) In a method for producing tert-butyl acrylate or tert-butyl methacrylate from acrylic acid or methacrylic acid and isobutylene using a strongly acidic ion exchange resin as a catalyst, the molar ratio of isobutylene to acrylic acid or methacrylic acid is 0.5-2
．． 01 Strongly acidic ion exchange resin amount 5-20% by weight relative to acrylic acid or methacrylic acid, reaction temperature 0-20%
℃ for a reaction time of 3 to 15 hours, unreacted isobutylene is separated from the reaction product, and light boiling compounds as impurities are separated in a light boiling compound separation column.
Furthermore, tert-butyl acrylate is supplied to a rectification column, and at the same time, acrylic acid or methacrylic acid is separated and recovered from the bottom of the column. Or a method for producing tert-butyl methacrylate.

(2) The method described in (1) above, characterized in that the reaction temperature is lowered stepwise from 15 to 20°C to 0 to 5°C.

(3) The method described in (1) or (2) above, characterized in that a thin film evaporator is used during separation and recovery of acrylic acid or methacrylic acid.

(4) Hydroquinone, hydroquinone monomethyl ether and 2,4-
The method described in (1), (2) or (3) above, characterized in that at least one selected from the group consisting of dimethyl-6-tert-butylphenol is used.

The present invention will be explained in detail below.

In the present invention, the reaction method is not particularly limited. The isobutylene supplied may be in either liquid or gaseous form, and even if it is supplied into the reaction solution where acrylic acid or methacrylic acid and the catalyst are being stirred, a multi-tube type is used to sufficiently remove the reaction heat. The reaction solution may be supplied into the reaction solution by circulating the reaction solution in a heat exchanger type device filled with the catalyst.

The strongly acidic ion exchange resin of the catalyst used in the present invention is generally a styrene-divinylbenzene-based sulfonic acid type.
There is no particular limitation as long as it is a macroporous type. For example, the product names are DOWEX 88 and Amberlyst 1.
5. Diaion PK, Revachit 5PC118, etc. are effective.

In the present invention, it is known that lowering the reaction temperature improves the selectivity of the isobutylene reaction. However, if the temperature is as low as 0° C. from the start of the reaction, the reaction system will coagulate below the melting point of 13° C. for acrylic acid or 16° C. for methacrylic acid, causing problems in reactivity and equipment.

As a result of intensive research by the present inventors, the composition of the reaction solution changes as the reaction progresses, so by lowering the reaction temperature accordingly, we aim to improve selectivity and further reduce the decomposition of ATB or MATB in the reaction product. It was found that this can be prevented.

That is, it has been found that the reaction can be started at 15 to 20°C and finally adjusted to 0 to 5°C in order to prevent coagulation of acrylic acid or methacrylic acid.

Specifically, as the reaction progresses, the composition changes, acrylic acid or methacrylic acid decreases, and ATS or M
ATB is generated and lowers the freezing point. That is, it has been found that as 5 mol% of acrylic acid or methacrylic acid reacts, the melting point of the reaction system decreases by 3 to 6°C. Therefore, it is only necessary to lower the reaction temperature while maintaining the reaction temperature above the freezing point. Preferably, by adjusting the reaction temperature to always 1°C or higher, especially 2 to 5°C higher than the freezing point, the reaction rate will be sufficient. It was discovered that the reaction could be carried out quickly and with excellent selectivity.

The present invention provides an economical advantage of substantially eliminating the need to recover unreacted isobutylene by lowering the molar ratio of isobutylene to acrylic acid or methacrylic acid when reacting isobutylene with acrylic acid or methacrylic acid. However, the reaction rate of acrylic acid or methacrylic acid naturally decreases. However, since recovery of acrylic acid or methacrylic acid is easier than recovery of isobutylene, the molar ratio of isobutylene was set in a lower range than in the conventional method, that is, in the range of 0.5 to 2.0.

When the molar ratio is less than 0.05, the reaction rate is slow, the reaction rate of acrylic acid or methacrylic acid is low, the production amount per reaction is small, and acid recovery is burdensome; 2.
If it exceeds 0, the reaction rate will be faster, but the concentration of isobutylene in the reaction solution will exceed the saturated solubility, and the reactor will be under high pressure due to the vapor pressure of isobutylene, requiring equipment that can handle high pressure. You will be at a disadvantage. Moreover, recovery of isobutylene is economically disadvantageous.

In the present invention, the time required to supply isobutylene during the reaction can be adjusted by adjusting the reaction temperature, taking into account the balance between the heat generated by the reaction and the heat removal ability of the equipment, as described above.
Although it is not limited, it usually takes about 2 to 12 hours.

By maintaining the temperature within the range of 0 to 5°C after the supply of isobutylene is stopped, unreacted acrylic acid or methacrylic acid and isobutylene can further react, and the yield can be increased. The appropriate time from the start of the reaction is 3 to 15 hours; if it is less than 3 hours, there will be little effect, and if it exceeds 15 hours, not only will the utility cost increase, but the AT produced
S or MATB decomposes into isobutylene 2m and 3
mer and acrylic acid or methacrylic acid, and the reaction appears to be in an equilibrium state, but the
It is preferable to maintain the above range since this may cause an increase in Eobata and 3'' bodies. Further, the reaction pressure according to the present invention is usually from normal pressure to 2 K9/t:i G.

In the present invention, when the reaction method is carried out using a stirring method, the amount of the catalyst used is 5 to 5 to 50% relative to acrylic acid or methacrylic acid.
20% by weight is preferable; if it is less than 5Iffi%, the reaction rate will be slow and it will take time; if the amount exceeds 20% by weight, the ratio of the catalyst to the volume of the reactor will be high, resulting in poor productivity. At the same time, the slurry becomes highly viscous and difficult to stir, even if a stirring method is used.

On the other hand, when carrying out the present invention in a shell-and-tube heat exchanger type, the catalyst used only needs to be 5% by weight or more based on acrylic acid or methacrylic acid, and the reaction time and reaction temperature can be easily controlled. . The product after the reaction contains unreacted isobutylene, and isobutylene is preferably separated in the next step to prevent operational failures due to vaporization of isobutylene.

In other words, after the reaction is completed, the product remains as it is when the reaction is carried out using a shell-and-tube heat exchanger type, and when the reaction is carried out using a stirring type, the product is separated from the catalyst by a filter built into the reactor. Introduced into a heating device with a stirrer,
Isobutylene is separated by blowing an inert gas or air containing an oxygen concentration of 1.0% by volume or more into the liquid while raising the internal temperature to 30 to 60°C and entraining it with the supplied gas.

In the present invention, separation of isobutylene after the reaction can be carried out easily and safely by dissipation using an inert gas or recovery to minimize loss of isobutylene.

The isobutylene contained in the inert gas can be easily liquefied by compressing and cooling the gas, and it can be separated from the inert gas and reused in the reaction 5. The differential isobutylene that cannot be recovered can be absorbed and liquefied with water. It can be made safe by oxidation, or it can be treated by combustion.

In the present invention, if the distillation method using a rectification column is used as a means of recovering unreacted acrylic acid or methacrylic acid, impurities etc. produced by the reaction can be separated in parallel, so the resulting product will also have high purity. Become something.

Most of the impurities produced as by-products during the reaction are isobutylene 2-isobutylene or 3-m-isobutylene, which are diisobutylene and triisobutylene, respectively. Among them, diisobutylene is AT
It is necessary to separate it because it has a lower boiling point than S or MATB and has a significant impact on the purity of the product.

During separation, the operating pressure is increased from 50 to 100 seconds as mentioned above.
H (in order to efficiently separate it into J, distillation is carried out using a rectification column, and common substances such as the same polymerization inhibitor used during the reaction, 1-nothiazine, silver dibutyldithiocarbamate, etc. are introduced from the top of the column, A small amount of air or oxygen is supplied from the bottom to distill and remove light boiling point compounds from the top of the column.

Furthermore, since unreacted acrylic acid or methacrylic acid, the aforementioned triisobutylene and other high-boiling point compounds, and excess polymerization inhibitor are included as substances with a higher boiling point than ATB or MATB, the same equipment and conditions as above are used. This time, high-purity ATB or MATB is produced from the top of the column.
All you have to do is get it.

In order to satisfy the conditions for long-term use of the catalyst used in the present invention, it is clear that the presence of impurities that behave in the same way as acrylic acid or methacrylic acid and high-boiling point compounds in the column bottom residue is a detrimental factor. Became. but,
If it is removed from the system as it is, acrylic acid or methacrylic acid will be lost, so evaporation is an effective means of recovering acrylic acid or methacrylic acid from its components, but since these have high boiling points, There arises a need to operate under reduced pressure and to handle substances that are easily polymerized by heat, such as acrylic acid or methacrylic acid, under economically reasonable conditions. As a means for this purpose, it is preferable to use a thin film evaporator to process a liquid containing a high boiling point compound in a short time.

Furthermore, in that case, it is not necessary to process the entire liquid, but it is only necessary to extract a portion of the liquid to prevent high concentrations of high-boiling compounds in the composition of each part.

In order to maintain polymerization prevention, 30 to 80 #Hg
By operating under reduced pressure, the operating temperature is low and can be carried out industrially.

In addition to the above-mentioned means for extending the life of the catalyst of the present invention, there is also the selection of a polymerization inhibitor.

For example, select a polymerization inhibitor that is inactive against strongly acidic ion exchange resins, preferably hydroquinone, hydroquinone monomethyl ether, 2,4-dimethyl-6-
It is best to use phenolic compounds such as tert-butylphenol in an amount of about 0.01 to 1.5% by weight for each composition solution, and basic or ionic compounds such as amines and metal salts are generally used. At such a concentration, it is not preferable because it reacts with the strongly acidic ion exchange resin, lowering the acidity and deteriorating the activity. Further, in order to effectively prevent polymerization, the coexistence of molecular oxygen is preferred.

The use of molecular oxygen is also effective in various distillation operations used as a means of purification, and allows stable operation over a long period of time without causing polymerization.

(Actions and Effects of the Invention) In the present invention, by adjusting the reaction temperature according to the above findings, the adverse effect on the equipment due to coagulation of acrylic acid or methacrylic acid can be eliminated, and the generation of byproducts due to side reactions of isobutylene can be suppressed to a low level. In addition, the generated A
Decomposition of TB or MATB is also minimized, the burden on the purification process is reduced, the yield of ATS or MATB is increased, and furthermore, it becomes possible to easily obtain highly purified ATS or MATB.

By using a thin-film evaporator for all or part of the bottom liquid during the purification process, it is possible to condense and remove high-boiling compounds, minimizing the loss of acrylic acid or methacrylic acid, which behaves together with high-boiling compounds. At the same time, substances that are adsorbed or bonded to the surface of the strongly acidic ion exchange resin, which is the catalyst, and are considered to impair its function as a catalyst are efficiently removed, avoiding a decrease in the activity of the catalyst, and making it possible to use it repeatedly over a long period of time. This made the process both industrially and economically advantageous.

Furthermore, by using a polymerization inhibitor that is inert to the catalyst, the action of the strongly acidic ion exchange resin as a catalyst and its effectiveness as a polymerization inhibitor can be maintained at a high level, and polymerization troubles can be sufficiently prevented. .

(Brief Description of Apparatus) Next, the present invention will be explained using a flow sheet showing one embodiment of the present invention shown in FIG.

Fresh acrylic acid or methacrylic acid from line 1 to the reactor 101 and acrylic acid or methacrylic acid recovered from line 2 are mixed and charged in line 3, and then isobutylene is supplied from line 4. The product after the reaction is introduced into the isobutylene separator 102 through line 5, and inert gas or air is blown through line 6.
Line 7 exhausts isobutylene and inert gas out of the system. The crude product from which isobutylene has been separated is continuously supplied to line 8 to a sieve tray type light boiling point compound separation column 103, and light boiling point compounds are distilled out from line 9. The crude product from which the light-boiling point compounds have been separated is continuously supplied to a sieve tray type rectification column 104 through line 70, and the product ATB or MATB is distilled out through line 11. The acrylic acid or methacrylic acid containing high-boiling compounds from which ATS or MATB has been removed is extracted from the inlet 12 and a portion thereof is passed through line 13 to a high-boiling compound concentrator 10 of the thin film evaporator type.
5, the concentrated high-boiling compounds are extracted from line 15, and acrylic acid or methacrylic acid containing few high-boiling compounds is distilled from line 14, and the concentrated high-boiling compounds are extracted from line 14.
Return to step 2 and collect and use.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 It was manufactured according to the flow shown in FIG.

250 kg of strongly acidic ion exchange resin (Amberlyst 15 manufactured by Rohm and Haas) was charged into a reactor 101 made of stainless steel with a jacket and equipped with a stirrer, and 11,256 kg of recovered methacrylate (MATB 137K) was charged.
g, high boiling point compound 280! g and 5 Kg of hydroquinone monomethyl ether. ) from line 2,
Next, 1,666 g/g of methacrylic acid was charged into each line from line 1.The internal temperature was adjusted to 20°C, and the line 4
1629Nff of isobutylene was set to be supplied into the liquid over 12 hours, and methacrylic acid reacted sequentially, and MAT
As B is produced, the melting point decreases, so the temperature is lowered to a temperature that does not solidify according to the composition of the reaction solution, and the temperature is adjusted to 2 to 5 degrees Celsius higher than the freezing point shown in Table 1. After 5 hours, the melting point is lowered.
℃.

In fact, since the melting point falls below 0°C in about 4 hours, the reaction can be sustained without solidifying even if the temperature is set at 0°C. After the supply of inbutylene was completed, the product was further aged for 10 hours at the same temperature, and MATB was 2862 K in the product 4551 K9.
g was included.

In this case, the production rate of M A T B was 66 mol %.

A filter for separating the catalyst from the reaction product containing about 5% by weight of unreacted isobutylene (JGC Universal Johnson strainer line 5 at the residual pressure of the reactor from the nozzle to the right, 8 with a heating coil) Nitrogen gas containing 7% oxygen by volume was introduced into the isobutylene separator 102 equipped with a stirrer for the first 4 hours, and then at 55 m'/Hrr for 4 hours each. When the temperature reached 35°C, the concentration of isobutylene in the liquid became 0.1%.

Under a pressure of 75 stHg at the top of a light-boiling compound separation column 103 having a multi-tubular heat exchanger boiler with 35 stages of sieve trays having an inner diameter of 300 #l, the crude product is continuously passed through line 8 from the 15th stage from the top of the column. 205. J/)lr, and at a reflux ratio of 12, the light-boiling compounds are discharged as a distillate from line 9 at 121/Hr, and the crude product from which the light-boiling compounds have been removed is 194j! from the bottom of the column via line 10. /Hr and sent to the next process.

1 from the top of the column under a pressure of 60a*) - IQ of the light boiling point compound separation column 104, which has 23 stages of sieve trays with an internal diameter of 400 am and a multi-tubular heat exchanger type glue boiler.
The crude product is fed to the eighth stage through line 10 at the above flow rate, and the product MATB is fed from line 11 to 1 at a reflux ratio of 4.
27J! /Hr, and the liquid containing methacrylic acid and high boiling point compounds was distilled from the bottom of the column through line 12 at 65J/Hr.
It was extracted at 1-1r. Part 221/Hr from line 12
The methacrylic acid is extracted through the line 13 to the rotary vane type thin film evaporator 105, where it is evaporated at a pressure of 45 aaHg, the methacrylic acid is recovered, distilled from the line 14 at 154/Hr, and returned to the line 12, and the evaporated residue is It was extracted from line 15, and the components were mainly high boiling point compounds.
It was a polymerization inhibitor. The liquid in line 12 was again provided for reaction through line 2.

In operating the distillation columns 103 and 104, hydroquinone monomethyl ether was used as a polymerization inhibitor to prevent polymerization within the columns, and air was blown into the bottom of the column as molecular oxygen.

MATB obtained through this series of steps has a purity of 99
% or more, and the yield was 96.5% based on the methacrylic acid used.

The strongly acidic ion exchange resin used as a catalyst was used for 35 reactions, but no decrease in activity was observed, and there were no problems with polymerization at any part of the process, making it possible to continue the process further. Met.

Example 2 Using the same equipment as in Example 1, two strongly acidic ion exchange resins (Amberlyst 15 manufactured by Rohm and Haas) were placed in the reactor 101.
40 kg was input, and 788 kg of recovered acrylic acid (A
T 8178 Ky, containing 203 Kg of high-boiling compounds and 6 Kg of hydroquinone monomethyl ether. )
from line 2, then acrylic lit from line 1
200 Kg was charged in each case.

The internal temperature was adjusted to 15°C, and settings were made to feed 1870 kg of isobutylene into the liquid from line 4 over 10 hours.Methacrylic acid reacts sequentially, and as ATS is produced, the melting point decreases, so the reaction liquid The temperature was lowered to a temperature that would not cause solidification according to the composition, and the temperature was adjusted to 2 to 5°C higher than the freezing point so as not to fall below the temperature shown in Table 2, and the temperature was lowered to 0°C after 4 hours.

In fact, since the melting point drops below 0°C in about 2 hours, the reaction can be sustained without solidification even when set at 0°C. After the supply of inbutylene was finished, the product was further aged for 7 hours at the same temperature, and the ATS was 3720 kg in 4658 kg of the product.
It was included. In this case, the production rate of ATS is 83 mol%
Met.

The reaction product containing about 2% by weight of unreacted isobutylene was separated from the catalyst in the same manner as in Example 1, introduced into the isobutylene separator 102 via line 5, and nitrogen containing 7% by volume of oxygen was introduced into the isobutylene separator 102 while gradually increasing the temperature. 20 Go/Hr for the first 2 hours of gas
Then, the mixture was further blown into the liquid at 55 g/hr for 5 hours. When the temperature was raised to 30°C, the concentration of isobutylene in the liquid became 0.1% by weight.

Under a pressure of 80 MiHg at the top of the light-boiling compound group 103, the crude product is continuously fed through line 8 to the 15th stage from the top of the column at a flow rate of 2201/1-1r, and at a reflux ratio of 12, the light-boiling compound is The distillate was discharged from line 9 at a rate of 10 Jl/Hr, and the crude product from which light boiling point compounds had been removed was extracted from the bottom of the column through line 10 at a flow rate of 2104/Hr and sent to the next step.

Under the pressure of the top pressure of the high boiling point compound separation column 104 of 70IllIHq, the crude product is supplied at the above flow rate through line 10 from the top of the column to the 18th stage, and at a reflux ratio of 4, the ATS of the product is 165j! from line 11! /Hr, and the liquid containing acrylic acid and high-boiling compounds is passed through line 12 from the bottom of the column to 41j! /Hr. line 1
Part 2 to 14j! /Hr, and led to the thin film evaporator 105 through the line 13 and evaporated at a pressure of 50 Hg.
Acrylic acid is recovered, distilled from line 14 at 9 J/Hr, and returned to line 12, and the evaporated residue is passed through line 15.
The main components were high-boiling compounds and polymerization inhibitors.

The liquid in line 12 was again provided for reaction via line 2.

In order to prevent polymerization in the columns when operating the distillation columns 103 and 104, hydroquinone monomethyl ether was used as a polymerization inhibitor, and air was blown into the bottom of the column as molecular oxygen.

The ATS obtained through this series of steps has a purity of 99%.
The yield is 97% based on the acrylic acid used.
%Met.

The strongly acidic ion exchange resin used as a catalyst was used in the reaction 30 times, but no decrease in activity was observed, and there were no problems with polymerization at any part of the process, indicating that the process was sufficient to continue. Ta.

Table 1

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing an example of a process of the method of the present invention. Patent applicant Nippon Shokubai Kagaku Kogyo Co., Ltd. Procedural amendment (voluntary) October 8, 1985 Director of the Patent Office Michibe Uga 1, Indication of the case 1985 Patent Application No. 183879 2, Name of the invention Acrylic acid Or ILAi method 3 of tert-butyl ester of methacrylic acid, relationship with the case of the person making the amendment Patent applicant Taka WItI, Higashi-ku, Osaka City, Osaka Prefecture! 5-chome 1 (462)
Nippon Shokubai Chemical Co., Ltd. Representative Director Ishikawa Mibe 4, Agent Address: 1-2-2 Uchisaiwai-cho, Chiyoda-ku, Tokyo 1-100 Nippon Shokubai Chemical Co., Ltd. Tokyo Branch Telephone: 03-5
02-1651 5. Detailed explanation of the invention in the specification subject to amendment 111 6. Contents of amendment (1) In line 3 of page 6 of the specification, [...] methacrylic acid at -5°C... ] is written as ``...a mixture of methacrylic acid and a catalyst at -5℃...
” is corrected. (2) On page 17, line 17 of the same document, the phrase ``Just doing it is fine.'' should be corrected to ``Just doing it is fine.'' (3) On page 21, line 11, "from line 14" is deleted. (4) On page 26, line 5, [acrylic M2O0N9J] was replaced with "acrylic R2
Corrected to 000K9 J.

Claims (4)

[Claims] (1) In a method for producing tert-butyl acrylate or tert-butyl methacrylate from acrylic acid or methacrylic acid and isobutylene using a strongly acidic ion exchange resin as a catalyst, the molar ratio of isobutylene to acrylic acid or methacrylic acid is 0.5-2
．． 0, strongly acidic ion exchange resin amount 5-20% by weight relative to acrylic acid or methacrylic acid, reaction temperature 0-20%
℃ for a reaction time of 3 to 15 hours, unreacted isobutylene is separated from the reaction product, and light boiling compounds as impurities are separated in a light boiling compound separation column.
Furthermore, tert-butyl acrylate is supplied to a rectification column, and at the same time, high-purity tert-butyl acrylate or tert-butyl methacrylate is obtained from the top of the column, and acrylic acid or methacrylic acid is separated and recovered from the bottom of the column. Or a method for producing tert-butyl methacrylate. (2) The method according to claim (1), characterized in that the reaction humidity is lowered stepwise from 15 to 20°C to 0 to 5°C. (3) The method according to claim (1) or (2), characterized in that a thin film evaporator is used during separation and recovery of acrylic acid or methacrylic acid. (4) Hydroquinone, hydroquinone monomethyl ether and 2,4-
The method according to claim (1), (2) or (3), characterized in that at least one selected from the group consisting of dimethyl-6-tert-butylphenol is used.