JPS6013022B2 - Method for producing dialkylalkanolamine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing dialkyl alkanolamines.

More specifically, the present invention relates to a method for producing a dialkyl alkanolamine that is stable against coloring. Dialkylalkanolamines are usually produced by blowing alkylene oxide into an aqueous solution of dialkylamine at a relatively low temperature (40 to 80 qo), causing a reaction, and then distilling the reaction mixture. However, this method has the drawback that a large amount of impurities such as dialkylalkoxyalkanolamine are created in addition to dialkylalkanolamine, and the dialkylalkanolamine produced becomes colored over time. In addition, in order to suppress the creation of impurities, anhydrous dialkylamine is used, and this and alkylene oxide are heated at a relatively high temperature (
A method of reacting at a temperature of around 150°C has also been proposed. However, the dialkylalkanolamine produced by this method is extremely colored and difficult to sell as a commercial product. The applicant has discovered that by first adding nitric acid or its ammonium salt or nitrate of an amine to the reaction mixture after completion of the reaction between the dialkylamine and the alkylene oxide, and aging the reaction mixture, there is extremely little coloring over time. A method for industrially advantageous production of stable dialkyl alkanolamines has been disclosed (Japanese Patent Publication No. 49-10648).

As a result of further studies, the present inventors discovered that when ripening is carried out at a relatively high temperature, a product that is stable against coloring can be obtained without using the above-mentioned chemicals, and based on this knowledge, the present invention was developed. Achieved an invention. That is, in the present invention, when dialkylamiso and alkylene oxide are reacted to produce dialkyl alkanolamine, after the reaction is completed, the reaction mixture is aged at a high temperature of 180 to 280°C for 1 to 20 hours, and then the dialkyl alkanolamine is separated. This is a method for producing a dialkyl alkanolamine. In the method of the present invention, aging is performed at 180 to 2
It is carried out at 80° C. for 1 to 20 hours.

If the ripening temperature is less than 180 x 0, a long time will be required for ripening, and sufficient effects cannot be expected. If the temperature exceeds 280°C, by-products will occur due to thermal decomposition, reducing the yield of the desired dialkylalkanolamine, and at the same time new coloration caused by thermal decomposition products will be observed.

It is advantageous to shorten the ripening time if the ripening temperature is high, and to lengthen the ripening time if the ripening temperature is low because dialkylalkanolamines that are stable against coloring can be obtained.

For example, the conditions for obtaining dialkyl alkanolamines that are most stable against coloring are the ripening temperature of 230 to 280 oo
In this case, the aging time is 1 to 1%, and the aging temperature is 180℃.
At ~230°C, 6 to 2 feeding hours are required for ripening. The former high-temperature aging is more effective than the latter low-temperature aging.
A dialkylalkanolamine that is extremely stable against coloring can be obtained, and even when aged for a short time of about 2 hours, a dialkylalkanolamine that is extremely stable against coloring can be obtained compared to before ripening. However, if the high-temperature aging is performed for too long, the dialkyl alkanolamine becomes unstable against coloring. To explain the method of the present invention in more detail, the dialkylamine used as a raw material in the method of the present invention includes, for example, dimethylamine, diethylamine, di-n-propylamine, di-i-propylamine, di-n-butylamine to di-butylamine, A secondary amine containing a lower alkyl group in which the alkyl group has about 1 to 4 carbon atoms, such as sec-butylamine or di-butylamine, is advantageously used.As the alkylene oxide, for example, ethylene oxide or , propylene oxide, etc. are advantageously used.Although the ratio of the amounts of these raw materials used in the method of the present invention is appropriately selected, the smaller the amount of alkylene oxide relative to the amount of dialkylamine, the more stable it is against coloring. This is advantageous because dialkyl alkanolamine is obtained. However, it is disadvantageous that the amount of dialkyl amine recovered after the reaction is large and the amount of product output per batch is reduced. Considering both, the ratio of alkylene to dialkyl amine is The appropriate molar ratio of oxide is 0.3 to 1.1, preferably 0.5 to 1.0.To carry out the method of the present invention, for example, a dialkylamine is added to a reaction vessel according to a commonly used method. After charging and raising the temperature to a predetermined temperature, alkylene oxide is gradually added thereto in the form of a gas or liquid to cause a reaction, or dialkylamine and alkylene oxide are simultaneously charged into a reaction vessel and heated to a predetermined temperature to cause a reaction.

The reaction between the dialkylamine and the alkylene oxide is carried out according to a conventional method at a relatively low temperature, e.g.
It can be carried out at 100°C, or it can be carried out at a relatively high temperature, for example 100 to 200°C. When the molar ratio of alkylene oxide to dialkylamine is less than or equal to 1, excess dialkylamine is recovered either before or after ripening. Ripening at higher temperatures e.g.
Do this for several hours at 80 to 280 qo. After the ripening is completed, the dialkylalkanolamine produced may be separated from the reaction mixture by means such as distillation.
According to the method of the present invention, it is possible to prevent the produced dialkylalkanolamine from being discolored, and also to prevent discoloration due to changes over time as much as possible.

The reason for this is not clear, but there is a substance that causes coloration over time among the impurities created by the reaction between dialkyl amine and alkylene oxide, and its boiling point is similar to that of dialkyl alkanolamine, so distillation is required. It is thought that when the dialkyl alkanolamine is separated by this method, it comes out along with the dialkyl alkanolamine. However, according to the present invention, since the impurities that cause coloration over time are aged at a high temperature, the decomposition or polymerization reaction of the impurities is extremely accelerated, and the dialkyl alkali/
It is thought that it becomes a compound with a boiling point different from that of the amine, and is separated and removed. In addition, if ripening is carried out at high temperatures for too long, the stability against coloring of dialkylalkanolamines will deteriorate because ``during ripening, impurities increase due to the decomposition of dialkylalkanolamines, which may cause other coloring factors.'' In addition, since coloration can be prevented without additives compared to the prevention of coloration with additives, impurities caused by additives such as acids and alkalis are not mixed into the residue after separation of dialkyl alkanolamines. It is also advantageous for the treatment of residual materials without any problems.

Next, the method of the present invention will be explained in more detail with reference to Examples, but the method of the present invention is not limited to the following Examples unless the gist of the method is exceeded.

In addition, in the examples, the coloring test over time was carried out at room temperature (15 to 2
500) of dialkylalkanolamine at 50'
It was placed in a colorimetric tube and left to stand, and the change in color tone over time was examined using the APHA color tone standard. Example 1 Dimethylamine (
DMA) 547 liters was placed in an Azusa-style autoclave and heated to 150 ml.

At this time, the internal pressure of the autoclave was approximately 40k9/h. 561 tons of ethylene oxide (EO) was injected into the mixture at a rate of 8 tons per minute, and the internal pressure was raised to 18,000 degrees at an internal pressure of 50 k9/minute, followed by a constant temperature reaction. EO/DMA molar ratio is 1.05
It is. After the reaction was completed, the mixture was heated to 250 qo and aged for 6 hours. The reaction mixture aged 2 and 6 hours was distilled to obtain dimethylethanolamine. Yield is 95.3% for each
, 93.5%. The obtained dimethylethanolamine was colorless upon distillation, and the results of a color change test (20 days) showed that the color tone of the one aged for 2 hours was APH before the test.
A5, and APHA150 after 20 days. In addition, the color tone of dimethylethanolamine after 6 hours of aging was APHA5 before the test, and the color tone after 20 days was A.
PHA was 90. Example 2 443 ml of dimethylamine was charged into a flywheel autoclave and allowed to overflow to 15 ml.

433 ml of ethylene oxide was introduced into this at a rate of 9 ml per minute, and an isothermal reaction was carried out at 180°C. The EO/DMA molar ratio is 1.00. After the reaction was completed, aging was carried out at 25,030 ℃ for 6 hours. The yield was 95.6%. The dimethylethanolamine obtained by distillation was colorless, and the color tone was APHA40 as a result of a color change test (20 days). Comparative Example 1 451 ml of dimethylamine was placed in a Takahiro autoclave and heated to 15,000 ml.

Three volumes of ethylene oxide were injected into the solution at a rate of 5 parts per minute, and an isothermal reaction was carried out at 180°C. The EO/DMA molar ratio is 0.7. After the reaction was completed, unreacted dimethylamine and dimethylethanolamine were obtained by distillation. Yield is 9
It is 9.5%. The color tone of dimethylethanolamine during distillation was APHA20, but as a result of a coloring test over time (12 days), the color tone was APHA500 or higher. (Note that APHA of 500 or higher cannot be measured.) Example 3 451 ml of dimethylamine was charged into a Yoyo-style autoclave and heated to 150°C.

Ethylene oxide (308 mm) was injected into the flask at a rate of 8 mm/min, and an isothermal reaction was carried out at 18 mm/min. The EO/DMA molar ratio is 0.7. After the reaction was completed, unreacted dimethylamine was distilled off. Then, the reaction mixture after aging at 180 qo for 6 hours and 14 hours was distilled to obtain dimethylethanolamine, respectively. The yield for both is 99.4%. Aging 6
When dimethylethanolamine is distilled, the color tone is AP
The color tone was HA15, and the color tone was APHA300 as a result of a coloring test over time (12 days). Furthermore, dimethylethanolamine aged for 14 hours had a color lost during distillation, and the color tone was APHA170 as a result of a color change test (20 days). Example 4 448 quarts of dimethylamine was charged into a Western-style autoclave and allowed to rise to 150 qo.

306 mm of ethylene oxide was injected into this at a rate of 7 mm per minute, and an isothermal reaction was carried out at 180 mm. The EO/DMA molar ratio is 0.7. After the reaction was completed, unreacted dimethylamine was distilled off. Then, the reaction mixture after aging at 21°C for 6 hours and 1 hour was distilled to obtain dimethylethanolamine. The yields are 99.3% and 7%, respectively. Dimethylethanolamine aged for 6 hours is colorless when distilled, and as a result of a color change test (20 days), the color tone is APHA7.
It was 0. In addition, dimethylethanolamine that had been aged for 1 feeding time was colorless upon distillation, and the color tone was APHA35 as a result of a color change test (20 days) over time. Example 5 454 ml of dimethylamine was charged into a flywheel type autoclave and the temperature was raised to 150°C.

311 tons of ethylene oxide was injected into this at a rate of 6 tons per minute, and an isothermal reaction was carried out at 180 qo. The EO/DMA molar ratio is 0.7. After the reaction was completed, unreacted dimethylamine was distilled off. Then, it was aged at 250°C for 2 hours. After completion of aging, the reaction mixture was distilled to obtain dimethylethanolamine. Yield is 981%. The obtained dimethylethanolamine was colorless upon distillation, and a color change test (
After 20 days), the color tone was 70. Example 6 620 g of dimethylamine was charged into a rope frame autoclave and allowed to rise to 150°C.

Ethylene oxide 4242 was injected into this at a rate of 9 m/min, and an isothermal reaction was carried out at 18,000 m/min. The EO/DMA molar ratio is 0.7. After the reaction was completed, unreacted dimethylamine was removed. Then, it was aged at 250°C for 6 hours. After completion of aging, the reaction mixture was distilled to obtain dimethylethanolamine. Yield is 97.8%. The obtained dimethylethanolamine was colorless upon distillation, and the color tone was APHA15 as a result of a color change test (20 days). Comparative Example 2 Seven days of dimethylamine was placed in an Azusa type autoclave and the temperature was raised to 150°C.

Claims (1)

[Claims] 1. When producing a dialkyl alkanolamine by reacting a dialkyl amine and an alkylene oxide, the reaction mixture is heated at a high temperature of 180 to 280°C after the reaction is completed.
A method for producing a dialkyl alkanolamine, which comprises aging for ~20 hours and then separating the dialkyl alkanolamine.