JPS6396161A - Production of fatty acid alkanolamide - Google Patents

Abstract

PURPOSE:To suppress side reaction and obtain the titled compound having excellent low-temperature stability, by reacting a fatty acid ester with an alkanolamide using an alkali hydroxide dissolved in a mixed solvent of a lower alcohol and polyhydric alcohol as a catalyst. CONSTITUTION:A fatty acid ester, e.g. coconut fatty acid methyl ester, etc., is reacted with an alkanolamine, e.g. diethanolamine, etc., using an alkali hydroxide, particularly preferably KOH dissolved in a mixed solvent (preferably 1:10-1:1 weight ratio) of a lower alcohol, e.g. methanol, ethanol, etc., and a polyhydric alcohol, e.g. glycerol, ethylene glycol, etc., to afford a fatty acid alkanolamide, e.g. coconut fatty acid diethanolamide, etc. The amount of soap formed as a by-product in the fatty acid alkanolamide can be reduced. The resultant product is used as a surfactant ingredient in kitchen detergents, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing a fatty acid alkanolamide that has a low soap content and excellent low temperature stability by preventing side reactions as much as possible.

Fatty acid jetanolamide has traditionally been widely used as a surfactant component in shampoos, kitchen detergents, etc. However, since fatty acid jetanolamide generally has a high freezing point, it is not suitable for winter use. There are problems such as solidification, separation of two layers, or cloudiness at low temperatures, which makes handling difficult and causes a decrease in commercial value.

Conventionally, such a phenomenon was considered to be an inherent physical property that depended on the carbon chain length of the fatty acid ester used as a raw material, but according to the results of studies conducted by the present inventors, the relationship between fatty acid ester and jetanolamine It was found that the content of soap produced by the side reaction between the fatty acid ester and the alkali hydroxide catalyst during the amidation reaction is also a major factor in raising the freezing point of fatty acid jetanolamide.

That is, conventionally, as a method for producing fatty acid jetanolamide, a fatty acid ester and jetanolamine are mixed with an alkaline catalyst, such as KOH.

Na0I4. A method of reacting using a methanol solution such as Na0CH as a catalyst is known, but in this method, in addition to the main reaction of formula (1) below, fatty acid ester and hydroxylation are performed as shown in formula (2). A side reaction with alkali occurs and soap is produced.

Main reaction Side reaction 1111□011 RC0CHz+ KOH-+RCONa + CH,O
H-(2) This side reaction proceeds very rapidly, especially in the presence of moisture, and in this case, the routes for moisture to be introduced include the fatty acid ester and jetanolamine as raw materials. That is, when producing a fatty acid ester,
Generally, fats and oils such as coconut oil are transesterified, washed with water, and then dehydrated, but they still contain about 0.05% water. Further, jetanolamine is expressed by the following formula (3) under heating conditions.

As shown in (4), water is produced as a by-product by condensation within a molecule or two molecules.

...(4) Therefore, as mentioned above, when producing fatty acid jetanolamide, it is unavoidable that water from the raw materials is mixed into the reaction system, and for this reason, in the conventional method for producing fatty acid jetanolamide. In this case, the side reaction described in (2) occurs and a considerable amount of soap is produced, but this soap increases the freezing point of the fatty acid jetanolamide from which the soap is produced and impairs its low-temperature stability. Since this reduces the quality, it is desirable to reduce the amount of by-product soap as much as possible to improve low-temperature stability.

In this regard, the present applicant has previously proposed a method for producing fatty acid jetanolamide with a low cloud point by carrying out an amidation reaction in the presence of triethanolamine when reacting fatty acid ester with jetanolamine. (Japanese Unexamined Patent Publication No. 59-80643), however, this method is subject to practical limitations due to the presence of triethanolamine in the component composition, and for this reason, it is not necessary to coexist with triethanolamine. What is needed is a method for producing fatty acid jetanolamide with a low melting point.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a method for simply and reliably producing fatty acid alkanolamide such as fatty acid ethanolamide, which has a small content of by-product soap and excellent low-temperature stability.

Measures and Actions to Solve the Problems In order to achieve the above object, the inventors of the present invention have carried out an amidation reaction between a fatty acid ester and an alkanolamine in the presence of an alkali hydroxide catalyst. height,
When producing fatty acid alkanolamide, when a mixed solvent of lower alcohol and polyhydric alcohol is used as a solvent for alkali hydroxide, the side reaction of formula (2) above is surprisingly suppressed and the amount of by-product soap can be minimized. I found out that it can be done. In other words, in the past, alkali hydroxide catalysts were dissolved in lower alcohols such as methanol and added to the reaction system, but in this way, alkali hydroxide catalysts were simply dissolved in lower alcohols. Even if added to the system, the side reaction of formula (2) cannot be suppressed as described above. and the latter in a mixed solvent in a ratio of 1:10 to 1:1.

When added to the reaction system, a fatty acid alkanolamide with low soap content, high purity, low freezing point, and excellent low temperature stability can be obtained by suppressing the side reaction of formula (2). In this case, for example, fatty acid gel When producing tanolamide, even if only jetanolamine is used as the alkanolamine component without coexisting triethanolamine as shown in JP-A-59-80643,
The present invention was based on the discovery that fatty acid jetanolamide with excellent low-temperature stability can be obtained.

Therefore, the present invention provides a method for producing a fatty acid alkanolamide by reacting a fatty acid ester and an alkanolamine as a catalyst in the presence of an alkali hydroxide, in which the alkali hydroxide is dissolved in a mixed solvent of a lower alcohol and a polyhydric alcohol. The present invention provides a method for producing a fatty acid alkanolamide, which is characterized in that a fatty acid alkanolamide is added to the fatty acid alkanolamide.

The present invention will be explained in more detail below.

The method for producing fatty acid alkanolamide according to the present invention includes:
A fatty acid ester and an alkanolamine are subjected to an amidation reaction, and these raw fatty acid esters and alkanolamines are appropriately selected depending on the type of target fatty acid alkanolamide. In general, fatty acid esters include fatty acids having 8 to 22 carbon atoms, higher fatty acids such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, and linoleic acid, methanol, and ethanol. and mixtures thereof with lower alcohols are used. In this case, the fatty acid may be a mixed fatty acid such as coconut oil, pearl kernel oil, palm oil, beef tallow, etc. Further, as the alkanolamine, monoethanolamine, jetanolamine, triethanolamine, monopropylamine, etc. are used.

In this case, the molar ratio of the fatty acid ester and the alkanolamine is selected as appropriate, but is preferably 1 to 1.2 moles of the latter to 1 mole of the former.

The present invention uses an alkali hydroxide dissolved in a mixed solvent of a lower alcohol and a polyhydric alcohol as a catalyst when carrying out an amidation reaction between the above-mentioned fatty acid ester and an alkanolamine. The side reaction between fatty acid ester and alkali hydroxide is suppressed, and the amount of impurity soap in fatty acid alkanolamide is minimized.

Examples of the alkali hydroxide include potassium hydroxide, sodium hydroxide, etc., but potassium hydroxide is more preferable from the viewpoint of obtaining a fatty acid alkanolamide with better low-temperature stability. In addition, methanol, ethanol, etc. are used as lower alcohols, and glycerin is used as polyhydric alcohol.

Ethylene glycol, diethylene glycol, triethylene glycol, etc. are used. The mixing ratio of lower alcohol and polyhydric alcohol is 1:10 to 1 by weight.
:1. In particular, the ratio is preferably 1:5 to 1:2. If the amount of polyhydric alcohol is more than 10 parts per 1 part of lower alcohol, the polyhydric alcohol remaining in the reaction mixture may reduce the purity and cause restrictions on blending into the final product. When the amount of polyhydric alcohol is less than 1 part, the content of by-product soap increases and low temperature stability may be impaired.

The alkali hydroxide concentration in the mixed solvent is not particularly limited, but it is preferably 1 to 10% (by weight, same hereinafter), more preferably 4 to 8%, and the alkali hydroxide concentration is If it is less than 1%, the amount of mixed solvent brought into the reaction system will increase, which may lead to an increase in the load on the distillation system condenser, so it is not a good idea. If it is more than 10%, dispersion and dissolution in the reaction liquid will be insufficient. , which may further lead to an increase in the content of by-product soap. Further, the amount of the alkali hydroxide catalyst added to the reaction mixture is not limited, but the alkali hydroxide should be present in the reaction mixture at a ratio of 0.1% or less, more preferably 0.03 to 0.07%. If the amount of alkali hydroxide increases too much, the content of by-product soap tends to increase.

In the present invention, the reaction conditions for reacting fatty acid ester and alkanolamine are variously selected depending on the type of raw materials, amount of catalyst, etc., but the reaction temperature is 100 to 150°C.
The reaction pressure is preferably 10 to 40 Torr. If the reaction temperature is lower than 100°C, the reaction rate will be slow and the reaction mixture may deteriorate over time and discolor.
If the temperature is higher than 50°C, the deactivation of the catalyst may increase.

Furthermore, if the reaction pressure is lower than 10 Torr, the reaction solution may reach a bumping state due to distillation of alkanolamine and bubbles of by-product alcohol vapor, and if it is higher than 400 Torr, by-product alcohol may remain dissolved in the reaction mixture. This results in an equilibrium reaction, and a large amount of unreacted fatty acid ester may remain. Note that the reaction time is usually 3 to 5 hours. Further, it is preferable to stir during one reaction.

As a reaction method for reacting a fatty acid ester with an alkanolamine, a semi-batch method, a continuous method, or a batch method can be adopted, and among these, the semi-batch method can be most advantageously adopted. That is, since the reaction between fatty acid ester and alkanolamine proceeds quickly in the presence of a catalyst, if fatty acid ester is continuously supplied after alkanolamine is charged, the production of by-product methanol 4 is rate-limiting to the supply of fatty acid ester. This is industrially advantageous, and therefore, it is preferable to adopt a semi-batch method in which the fatty acid ester is continuously added to the alkanolamine. In this case, it is preferable that the alkali hydroxide catalyst is also added intermittently or continuously to the reaction system in which fatty acid ester is continuously added to the alkanolamine.By adopting such a semi-batch method, the amount of soap produced can be reduced. The semi-batch method is advantageous from this point of view as well, since it is possible to produce a fatty acid alkanolamide with better low-temperature stability. In this case, the reaction proceeds almost completely.

After the above-described amidation reaction is completed, the reaction mixture can be treated according to a conventional method, for example, aged at 40 to 60°C for about 1 to 2 days.

Effects of the Invention According to the method for producing fatty acid alkanolamide of the present invention, by using a mixed solvent of a lower alcohol and a polyhydric alcohol as the solvent for the alkali hydroxide catalyst solution,
The amount of by-product soap in the fatty acid alkanol can be reduced, and a fatty acid alkanolamide with excellent low temperature stability can be obtained. Therefore, the fatty acid alkanolamide produced according to the present invention is suitably used as a surfactant component in shampoos, kitchen detergents, and the like.

EXAMPLES Hereinafter, the present invention will be specifically explained by showing examples and comparative examples, but the present invention is not limited to the following examples.

[Example 1] Jetanolamine (amine value 534) was placed in a separable flask with an inner diameter of 100mm and a height of 150mm equipped with a stirrer.
After adding 59g and raising the temperature to 100℃, the inside of the reactor was heated to 1
The temperature was maintained at 0.00 Torr. Next.

A mixed solvent of methanol and glycerin (1:
Potassium hydroxide was uniformly dissolved in 1) at a concentration of 5.94%, and the potassium hydroxide concentration in the reaction solution was 0.05%.
After adding 667.8 g of coconut fatty acid methyl ester (degree of saponification 256, average molecular weight 219) under conditions of temperature 110°C, pressure 100 Torr, and sufficient stirring over 4 hours (4 hours). The reaction molar ratio of jetanolamine and fatty acid ester is 1.12:1
). During this reaction, the catalyst solution was continuously added so that the amount of free potassium hydroxide in the reaction solution was 0.05±0.02% (the amount of catalyst solution added at the end of the reaction). was 31.4 g). Note that methanol produced as a by-product in the above reaction was distilled off using a cold trap provided in the distillation system.

Next, after the completion of the above reaction, the reaction solution was cooled to 40°C, the inside of the reactor was returned to normal pressure, and transferred to a glass bottle with a capacity of IQ, sealed tightly and aged in a 40°C constant temperature bath for 2 days. A transparent and viscous liquid coconut fatty acid jetanolamide was obtained.

[Example 2] A 1:3 mixed solvent of methanol and glycerin was used as the catalyst solution, and the total amount of the catalyst solution added was 30.5
Coconut fatty acid jetanolamide was obtained in the same manner as in Example 1, except that g was used.

[Example 3] A 1:10 mixed solvent of methanol and glycerin was used as the catalyst solution, and the total amount of the catalyst solution added was 30.
Coconut fatty acid jetanolamide was obtained in the same manner as in Example 1 except that the amount was 2 g.

[Example 4] Coconut fatty acid jetanolamide was prepared in the same manner as in Example 1, except that a 1:3 mixed solvent of ethanol and diethylene glycol was used as the catalyst solution, and the total amount of the catalyst solution added was 32.3 g. I got it.

[Example 5] Coconut fatty acid gel was prepared in the same manner as in Example 1, except that a 1:3 mixed solvent of ethanol and triethylene glycol was used as the catalyst solution, and the total amount of the catalyst solution added was 32.5 g. Tanolamide was obtained.

[Comparative Example 1] Methanol was used alone as a solvent as a catalyst solution,
Coconut fatty acid jetanolamide was obtained in the same manner as in Example 1, except that the entire amount of 32 g of this catalyst solution was added to jetanolamine before adding the coconut fatty acid methyl ester.

[Comparative Example 2] Glycerin was used alone as a solvent as a catalyst solution,
Coconut fatty acid jetanolamide was obtained in the same manner as in Example 1, except that the entire amount of 32 g of this catalyst solution was added to jetanolamine before adding the coconut fatty acid methyl ester.

[Comparative Example 3] 2% (based on the reactant) of glycerin was added to the aged coconut fatty acid jetanolamide reaction product obtained by the method of Comparative Example 1.

The amine value, fatty acid potassium content, and low temperature stability of the coconut fatty acid jetanolamide obtained by the above method were measured by the following methods. The results are shown in Table 1.

5 g of the amine value sample was taken into an Erlenmeyer flask, dissolved in 99% neutral ethanol 20%, titrated with a standard N/5 HCQ isopropanol solution using methylene blue as an indicator, and the amine value was determined using the following formula.

Amine value = 2.244X titration - × Normal solution factor Fatty acid potassium amount Sample Log was taken in a platinum crucible, roasted in a matzuru, the ash was diluted with water, and the total potassium amount in the sample was N/1.
Quantitate with O-HCQ standard solution (8-), similarly sample Lo
Take g into an Erlenmeyer flask.

Add 20 d of 99% neutral ethanol to dissolve, titrate with a standard solution of N/1O-HCQ/isopropanol using phenolphthalein as an indicator, and calculate the fatty acid potassium amount using the following formula.

However, after heating the sample at 30℃ for 1 hour and confirming that it is transparent, place sample 10 in a test tube with an inner diameter of 15 mφ and a height of 100 m.
0 mQ was taken and sealed tightly. After storage in a constant temperature bath at 0° C. for 48 hours, the appearance of the sample (transparent, cloudy, precipitate) and amount of precipitate (volume percentage of precipitate in 100 ml of sample) were evaluated.

Claims (1)

[Claims] 1. In a method for producing a fatty acid alkanolamide by reacting a fatty acid ester and an alkanolamine in the presence of an alkali hydroxide as a catalyst, the alkali hydroxide is used as a mixed solvent of a lower alcohol and a polyhydric alcohol. A method for producing a fatty acid alkanolamide, characterized in that a fatty acid alkanolamide is added to the fatty acid alkanolamide dissolved in the alcohol. 2. The manufacturing method according to claim 1, wherein the mixing ratio of lower alcohol and polyhydric alcohol in the mixed solvent is 1:10 to 1:1 by weight. 3. The manufacturing method according to claim 1 or 2, wherein the concentration of potassium hydroxide in the mixed solvent of lower alcohol and polyhydric alcohol is 1 to 10% by weight. 4. Claims 1 to 3 in which the fatty acid ester and the alkanolamine are reacted by adding alkali hydroxide to the reaction mixture at a concentration of 0.1% by weight or less. Any of the manufacturing methods described. 5. The fatty acid ester and the alkanolamine are reacted at a reaction temperature of 100 to 150°C, a reaction pressure of 10 to 400 Torr, and a molar ratio of the fatty acid ester to the alkanolamine of 1:1 to 1.
The manufacturing method according to any one of claims 1 to 4, wherein the reaction is carried out under the conditions of 1.2. 6. A patent claim in which a fatty acid ester is continuously added to an alkanolamine, and a reaction is carried out while a mixed solvent solution of an alkali hydroxide with a lower alcohol and a polyhydric alcohol is added intermittently or continuously. The manufacturing method according to any one of the ranges 1 to 5. 7. The production method according to any one of claims 1 to 6, wherein the alkanolamine is diethanolamine or a mixture of diethanolamine and triethanolamine. 8. The manufacturing method according to any one of claims 1 to 7, wherein the alkali hydroxide is potassium hydroxide.