JPH0212939B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention involves transesterifying an unsaturated lower carboxylic acid ester and a higher alcohol using an acid catalyst to produce a higher alcohol ester of an unsaturated carboxylic acid. Regarding the method.

(Prior art) An unsaturated lower carboxylic acid ester (e.g., methyl (meth)acrylate, ethyl (meth)acrylate, etc.) in the presence of an acid catalyst (e.g., sulfuric acid, phosphoric acid, p-toluenesulfonic acid, etc.) , higher alcohols [e.g., butanol (norman, iso, tertiary), octanol, lauryl alcohol,
It is known to produce higher esters by transesterification with stearyl alcohol, etc.).

However, in such a production method, it is especially necessary to effectively remove the catalytic acid at the end of the reaction from the viewpoint of the material used in the subsequent process and the prevention of side reactions. Even if
Problems remain, such as the occurrence of polymerization of higher esters and the indistinct boundary between the ester phase and aqueous phase after neutralization, making separation difficult. Depending on the neutralization operation and the temperature of the liquid during neutralization and separation, insoluble solids are generated, causing great inconvenience to the process.

Conventionally, for example, (1) aryl sulfonic acid anhydride was used as a catalyst to suppress the by-product of methacrylic acid and avoid emulsification problems presumed to be caused by the presence of polymethacrylic acid (Tokuko Sho et al.
49-20295), (2) for the reaction solution in the presence of an acid catalyst,
Add alkaline earth metal carbonate and introduce water vapor under total reflux to clearly separate the organic phase and aqueous phase to prevent emulsification (Special Publication No. 1972-21929), (3) (Meta) When producing tertiary butyl (meth)acrylate from acrylic acid and isobutylene using a sulfuric acid catalyst, the reaction solution is neutralized with an alkaline aqueous solution or an alkaline aqueous solution containing an inorganic salt to prevent the produced ester from being lost to the aqueous phase. (Japanese Unexamined Patent Publication No. 53-65815) etc. are shown.

(Problems to be Solved by the Invention) The following problems remain in the above conventional method.

In method (1), by using anhydrous acid,
There is a concern about etherification of alcohol. Also, when refining while leaving the acid, decomposition of the ester,
There is a risk of causing corrosion of the equipment.

In method (2), the reactor in which the alkaline earth metal carbonate is present may cause problems such as scale adhesion inside the reactor due to the slightly soluble inorganic salt and clogging due to solid matter during extraction. There is a high risk of being exposed.

In method (3), a simple comparison cannot be made because the reaction format is different, but the purpose is to suppress the decomposition of the produced ester and prevent its loss to the aqueous phase.
The objective of the present invention, which is to eliminate impurity acids (catalytic acid and by-product (meth)acrylic acid) by neutralization and avoid problems with emulsification of esters, is a different technical field.

(Means for Solving the Problems) As a result of extensive research in order to solve these problems, the present inventors have found that the catalyst acid remaining in the reaction-completed liquid and the by-product (meth)alkaline acid, etc. Impurities are eliminated by neutralization with alkali, making it easier to select materials for the next process, and by using a water-soluble alkali in an aqueous solution, the generated neutralized salt is dissolved as an aqueous solution, eliminating clogging of the process. In addition, we discovered that there is a difference in alkalinity between the oil phase and the aqueous phase, and in order to maintain the PH in the aqueous phase at an alkaline level (preferably keep the PH at 10 or higher), and during neutralization and two-phase separation, Do not lower the liquid temperature below 50℃ (the upper limit is the boiling point of water).
In addition to the above conditions, in addition to the above conditions, the most preferred polymerization inhibitor is A substance represented by the following general formula P-NH-P-NH-P (in the formula, P represents a phenyl group or a naphthyl group) is added at a weight ratio of 0.002 or less to the total amount charged, and in this way, When transesterification is performed, it is no longer difficult to select materials due to impurity acids.
It is now possible to prevent quality deterioration, eliminate deterioration of separation due to ester emulsification, eliminate ester loss, etc., and prevent clogging of the purification process and fouling of the reactor, solving various difficult issues all at once. I was able to solve the problem.

According to the method of the present invention, methyl (meth)allylate or ethyl (meth)acrylate is used as an unsaturated carboxylic ester, sulfuric acid, phosphoric acid para-toluenesulfonic acid, etc. are used as an acid catalyst, and ( The reaction is carried out using normal, iso, tertiary) butanol, octanol, lauryl alcohol, stearyl alcohol, etc. At that time, put a higher alcohol with a high boiling point into the reactor,
Then, as a polymerization inhibitor, the general formula P-NH-P
Compounds represented by -NH-P (wherein P is the same as above), such as Nonflex F (trade name,
Manufactured by Seiko Kagaku Co., Ltd., chemical composition N, N′-Di-2-
The total amount of Naphtyl-p-Phenylene Diamine
Add an amount equal to or less than 0.002 weight ratio.

When the higher alcohol is heated to a temperature at which the unsaturated carboxylic acid ester sufficiently reacts and the liberated azeotrope of lower alcohol and lower ester vaporizes to proceed with the reaction efficiently, lower Add ester. Alternatively, mix the higher alcohol and lower ester with the catalyst and heat it from the beginning.
Any method of reacting and removing the lower alcohol alone or as an azeotrope with the lower ester may be used. In order to increase the conversion rate of higher alcohols, lower esters are usually added in excess (2 to 6 times the mole).
Additions are made to

Next, from the fully reacted higher ester, most of the lower alcohol and lower ester contained as coexisting impurities are removed by evaporation as necessary.
Next, the catalytic acid and the acid of the lower ester produced as a by-product are neutralized. For neutralization, caustic soda,
A water-soluble alkali such as caustic potash or ammonia is added in an aqueous solution. At this time, if the alkali concentration is too high, neutralized salts will precipitate and it will be difficult to sufficiently dissolve and remove other water-soluble impurities, so it is preferable to use an aqueous solution with approximately the same volume as the reaction solution volume. Also, when neutralizing, keep the liquid temperature above 50℃.
By keeping the temperature below 100°C, emulsification of the ester can be prevented and the amount of insoluble solids can be kept to a minimum.

In addition, during neutralization, the PH of the oil phase is different from the PH of the water phase and is generally inaccurate.
By keeping the pH alkaline, excess acid can be almost completely neutralized, and an emulsified state that occurs at the boundary between the ester and the aqueous phase or at the ester itself can be avoided. More preferably, the pH of the aqueous phase is 10 or higher.

When the reaction solution is neutralized in this manner, insoluble solids gradually precipitate into the solution. Therefore, it is important not to separate the aqueous phase and oil phase until sufficient precipitation occurs, preferably for 30 minutes or more. The amount and properties of such solids vary depending on the type of polymerization inhibitor, and the amount of precipitation varies depending on the amount.

According to the research conducted by the present inventors, the most preferable type of polymerization inhibitor is the general formula P-NH-P-NH-P.
(wherein P is the same as above).
In addition, the amount is 0.002 weight ratio (0.2
%), precipitation of insoluble solids during the above neutralization increases rapidly.

By doing this, the desired reaction product is clearly transferred to the oil phase, and emulsification problems are no longer caused.
There are no impurity acids, and purification in subsequent steps is extremely easy.

(Effects of the Invention) According to the present invention, when producing a higher alcohol ester of an unsaturated carboxylic acid from an unsaturated lower carboxylic acid ester and a higher alcohol by a transesterification method in the presence of an acid catalyst, It has excellent effects such as preventing difficulties in material selection and deterioration of quality, eliminating deterioration of separation properties due to emulsification of esters, loss of esters, etc., and preventing clogging of purification processes and fouling of reactors. It will be done.

(Example) Examples of the present invention are shown below.

Example 1 148 g of n-butanol, 8 g of concentrated sulfuric acid, and 0.8 g of Nonflex F (manufactured by Seiko Kagaku Co., Ltd.) were charged into a glass reactor equipped with a stirring device, and after raising the temperature to 105°C, 400 g of methyl methacrylate was added to 150 g of methyl methacrylate. Added in portions. Keep the liquid temperature at 105-110℃ during addition.
After the addition was completed, the temperature was gradually raised to 125℃, and the distillate was led to a condensation tube and liquefied, yielding 93.8g.
obtained. 455g remained in the reactor.

The composition of the liquid remaining in the reactor is shown below.

n-Butyl methacrylate 58.8% by weight Methyl methacrylate 37.5 〃 n-butanol 1.1 〃 Methanol 0.5 〃 Methacrylic acid 0.3 〃 Other 1.8 〃 Next, while keeping this reaction-completed liquid at 60°C,
After adding 490 ml of wt% caustic soda aqueous solution and leaving it to stand, 415 g of organic components mainly containing n-butyl methacrylate were obtained from the oil phase showing a transparent interface, and 450 g of transparent components containing weakly alkaline sodium sulfate were obtained from the aqueous phase. did. The pH of this aqueous phase was 13.
The organic content was 97.3% n-butyl methacrylate, 1.2% methyl methacrylate, 0.9% n-butanol, and 0.6% others.

No turbidity or suspended matter was observed in either the aqueous phase or the organic phase.

Example 2 Using the same reactor as in Example 1, 148 g of iso-butanol, 400 g of methyl methacrylate, 8 g of concentrated sulfuric acid and 0.8 g of Nonflex F were charged, and 100 g of non-flex F was charged.
The temperature was raised to 123°C, and after distillation started, the temperature was gradually increased, and heating was discontinued when the temperature reached 123°C after 6.5 hours. Next, pump the reaction system with a vacuum pump.
Reduce pressure to 120Torr and heat at 68-70℃ for 120 minutes.
302 g of a liquid having the following composition was obtained in the reactor.

Iso-butyl methacrylate 87.7% by weight Methyl methacrylate 10.0 〃 Iso-butanol 0.6 〃 Methanol 0.1 〃 Methacrylic acid 0.4 〃 Others 1.2 〃 Next, 427 ml of 3% caustic potash aqueous solution was added to this liquid, and then heated and heated at 100℃. After holding for 30 minutes, the oil and water phases were separated showing a transparent interface. The oil phase thus obtained weighed 286 g, was transparent and free of suspended matter. The aqueous phase weighed 443 g and had a pH of 12.
The composition of the oil phase is: 2.3% isobutyl methacrylate;
MMA6.6%, Isobutanol 0.5%, Others 0.6%
It was hot.

Comparative Example 1 455g of reaction solution obtained by carrying out the same reaction as in Example 1
After cooling to room temperature, it was divided into two parts, and 250 ml of water was added to one of the reaction liquids (220 g) at room temperature, stirred, and allowed to stand, followed by two-phase separation. The boundary surface was unclear due to the milky white suspended matter, the oil phase was cloudy, and the milky white suspended matter was suspended in the aqueous phase, making it substantially difficult to separate the two phases.

Further, 160 ml of 2% caustic soda was added to 220 g of the other reaction solution at room temperature to adjust the pH of the aqueous phase to 9. The interface has a layer of milky white floating matter;
Separation was difficult, and although the liquid containing the suspended matter was sucked through a suction type glass filter, it quickly became clogged and separation was virtually impossible.

Example 3 Two processing solutions that were difficult to separate in Comparative Example 1 were
Add 2% caustic soda solution to PH12 and heat to 70
When the temperature was lowered to ℃, the milky white floating substances disappeared, the interface became transparent, and separation was possible without any problems.

Comparative Example 2 When 1 g of hydroquinone was charged in place of Nonflex F to the same apparatus as in Example 2 and the same reaction was carried out, the reaction completed liquid turned blackish brown and contained tar-like components. When 430 ml of 2% caustic soda solution was added to 400 g of this liquid and heated to 70°C, 1.8 g of black granular solids, 346 g of a dark brown oil phase and 482 g of a yellowish white aqueous phase were obtained at the interface. The oil and aqueous phases thus obtained require further purification methods.

Claims (1)

[Claims] 1. From an unsaturated lower carboxylic acid ester and a higher alcohol, in the presence of an acid catalyst, the following general formula can be obtained by transesterification. (In the formula, R ₁ is H or CH ₃ , and R ₂ represents an alkyl group having 4 or more carbon atoms.) In producing a higher alcohol ester of an unsaturated carboxylic acid represented by the formula, as a polymerization inhibitor,
The reaction is carried out by adding a compound represented by the following general formula P-NH-P-NH-P (in the formula, P represents a phenyl group or a naphthyl group) at a weight ratio of 0.002 or less to the total amount charged. Add an aqueous solution of a water-soluble alkali to the finished liquid so that the alkalinity of the aqueous phase is PH10 or higher, and at this time, maintain the temperature of the aqueous phase and oil phase at 50°C or higher and lower than 100°C to separate them into two phases. A transesterification reaction method characterized in that the higher alcohol ester is obtained from the oil phase after the reaction. 2. The method according to claim 1, wherein the water-soluble alkali is caustic soda, caustic potash, or ammonia.