The present invention relates to a process for preparing a fatty acid

monoalkanolamide, and particularly relates to a process for preparing a fatty acid monoalkanolamide having low odor and low color, which contains an extremely small amount or substantially no amount of impurities such as ester amines, amide esters, and cyclic amines.

Fatty acid monoalkanolamides are used in cleaning agents for kitchen, and cosmetic cleaning agents for skin or hair (body soaps, hair shampoos), or the like as chemicals which contribute to improvement in the thickening, foam stability and detergency of the cleaning agents.

When fatty acid monoalkanolamides are prepared from fatty acids and

monoalkanolamines, it is general to carry out a reaction by mixing and heating the fatty acids and monoalkanolamines and carry on the reaction under the removal of the water formed during the reaction from the system by distillation or the like. This is because the reaction is a dehydrating and condensation reaction. However, monoalkanolamines have two reaction sites capable of reacting with fatty acids in the single same molecule, that is, amine and alcohol moieties.

Therefore, it can be reasonably predicted that, in addition to the desired product fatty acid monoalkanolamides (hereinafter, referred to as amide (1)), fatty acid ester amines (hereinafter, referred to as ester amine (2)) and fatty acid

monoalkanolamide esters (hereinafter, referred to as amide ester (3)) may be formed as by-products.

For example, in a reaction between monoethanolamine and a fatty acid, the following substances form:

Desired reaction product: RCONHCH ₂ CH ₂ -OI-l (1)

By-product: H ₂ NCH ₂ CH ₂ OOCR (2)

By-product: RCONHCH ₂ CH ₂ OOCR (3) Moreover, when a product obtained from such a reaction was analyzed using gas chromatography, then the analysis has revealed that, in addition to the peaks for the aforementioned substances, other peaks appear at definitely different positions from those peaks. The GC mass spectrometry indicates that the by-products corresponding to said other peaks are mainly cyclic pyrrolidone and imidazole derivatives.

By-product: imidazoles

By product: pyrrolidones

JP4079470B is characterized in that 1.0 to 1.3 moles of a monoalkanolamine are added to a fatty acid in two stages; in particular, in the first stage, 0.8 to 0.95 moles of a monoalkanolamine is reacted to prepare a mixture composed mainly of an alkanolamide and an amide ester, and then in the second stage, the remaining monoalkanolamine is added to the reaction product from the first stage to convert the amide ester to an alkanolamide. In a system where the fatty acid exists in an excessive amount, the desired product amide and the by-product amide ester are formed by carrying out the reaction at a temperature of 150 to 160 °C under the removal of the resulting water from the system. However, in the case where the amide ester exists in a large amount, the addition of the alkanolamine in the second stage only offers a remarkably slow and impractical rate of the conversion of the amide ester to the alkanolamide, and therefore, as is carried out in

Examples, the conversion rate needs to be increased by using a sodiummethylate- methanol solution as a catalyst. However, the use of an organic solvent requires the removal of the organic solvent from the system after the completion of the reaction, in particular, in respect to methanol, the safety standard "must not be detected from products" is present in quality standards for household products and standards for cosmetics, and therefore, the use of such a substance poses a problem.

JP09157234A is characterized in that a fatty acid and an alkanolamine are added in two stages, wherein, in the first stage, 0.6 to 0.95 mole of an alkanolamine is added to a fatty acid and reacted for 1 to 8 hours, and then in the second stage, the remaining alkanolamine is reacted in the absence of a catalyst for 1 to 8 hours. The reaction temperature is 130 to 200 °C. Claim 4 recites that the reaction is carried out under a reduced pressure, or it is described in Examples that the reaction was carried out in a nitrogen stream; namely there is disclosed a process wherein the reaction is carried out under the removal of the water formed during through the reaction from the system.

However, the aforementioned processes have the following problems. That is, when the reaction temperature is 150 °C or less, the reaction proceeds slowly, thereby unreacted fatty acids remain in an amount of 2% or more even after

12 hours. When the reaction temperature is 150 °C or more, the formation rate of ester amines is promoted, further associated with the formation of by-products such as cyclic amines, thereby leading to a low purity of the desired product. It is possible to reduce the reaction temperature by using a basic catalyst such as sodium hydroxide and sodium methoxide and thereby prevent the formation of impurities such as cyclic amines; however, the treatment of the alkali formed from the alkali catalyst, and of the solvent, is problematic. Especially, though sodium methoxide only causes a less coloration problem and is useful, the methanol formed therefrom is classified as a substance which must not be detected, in quality standards for household products and standards for cosmetics and therefore, the use of sodium methoxide is hesitated. In addition, it has been proved during the studies of the present inventor that, in any of the aforementioned processes, the formation of a by-product, a cyclic amine, occurs when promoting the removal of water from the reaction system in such conditions that the amine is excessive relative to the fatty acid and the temperature is 130 °C or more. Therefore, in respect to the reaction between a fatty acid and a monoalkanolamine, there has been a demand for a process for effectively preparing a fatty acid monoalkanolamide in high-purity, which does not contain by-products such as amide esters, ester amines, and cyclic amine derivatives, without requiring the use of a catalyst, which causes coloration and forms alcohol by-products, and also of an organic solvent which needs to be removed out of the system after the reaction.

Furthermore, in addition to the aforementioned problem regarding by-products, there are other problems of undesirable coloration of the final product fatty acid monoalkanolamide, and an undesirable peculiar odor originating from the alkanolamine remaining in the final product.

An object of the present invention is to provide a process for effectively preparing a fatty acid monoalkanolamide comprising an extremely small amount or substantially no amount of impurities such as ester amines, amide esters, and cyclic amines without requiring the presence of a basic catalyst and an organic solvent.

A further object of the present invention is to provide a fatty acid

monoalkanolamide having low color and good color hue, and a process for preparing such a fatty acid monoalkanolamide.

A still further object of the present invention is to provide a fatty acid

monoalkanolamide having low odor and good smell, and a process for preparing such a fatty acid monoalkanolamide.

Other objects of the present invention will be understood from the following description. As a result of a diligent study aiming at solving the above problems, the present inventor has found the fact that, in the preparation of fatty acid

monoalkanolamides through a reaction between fatty acids and

monoalkanolamines, if the temperature is in the range of 140 to 170 °C, the reaction does not require the presence of a basic catalyst and an organic solvent and further, even if the water formed during the reaction is not removed, the formation rate of the desired product fatty acid monoalkanolamides does not alter compared to the reaction where the water is removed by means of a nitrogen stream or distillation, and the formation rate of the amides is higher at a higher temperature. Further preferably, the present inventor has found the fact that the removal of water by means of a nitrogen stream or under a reduced pressure at a high temperature exceeding 150 °C promotes the formation of ester amides or cyclic amides and gives an amide comprising by-products in a high amount; in contrast thereto, in the case of a reaction in a system where water is present, the formation of cyclic amine derivatives and the like is very low, further the contents of ester amines and amide esters formed are also extremely low, and therefore, the desired product is obtained in high purity. In addition, in respect to the amine odor of the product, it has also been found that, if water is added to a reaction mixture after the completion of the reaction, which comprises the final product, and the remaining monoalkanol amine is

azeotropically distilled off under a reduced pressure, and in this case, the temperature during the reduced-pressure distillation is set to 125 °C or less, then the remaining monoalkanol amine can be successfully removed, while

suppressing the formation of by-products; and moreover, in this case, by the addition of water, the by-product amide esters are hydrolyzed to the desired amides and, therefore, further improvement in purity of the final product can be achieved.

Furthermore, regarding the coloration problem of the final product, the present inventor assumed that the coloration of the final product would be due to the oxidation of the amine and has tried applying various types of reducing agents, and as a result has found that reducing agents of an inorganic salt type such as, for example, sodium sulphite, are not soluble in the final product amide, thus causing turbidity of the molted solution and, on the other hand, even in the case of reducing agents soluble in fats and oils components, no effect can be achieved with hypophosphorous acid; however, significant suppression of coloration can be first achieved using reducing organic acids, and products having a good color hue can be obtained.

Accordingly, the present invention relates to;

(1) A process for preparing a fatty acid monoalkanolamide by reacting a fatty acid with a monoalkanolamine, wherein, relative to the fatty acid, an equivalent amount or a molar excess amount of the monoalkanolamine is reacted at a temperature of 140 to 170 °C, and the reaction is carried out in the presence of water without substantially removing the resulting water from the reaction system as long as a reaction temperature in the range of

140 to 70 °C can be maintained;

A process for preparing a fatty acid monoalkanolamide by reacting a fatty acid with a monoalkanolamine, wherein, relative to the fatty acid, an equivalent amount or a molar excess amount of the monoalkanolamine is reacted at a reaction temperature of 140 to 170 °C, and the reaction is carried out in the presence of water under refluxing the water formed;

A process as set forth in (1) or (2), wherein, when a reaction temperature of 140 °C or more cannot be maintained, the water is partially removed by means of atmospheric distillation of the water;

A process as set forth in (1 ) to (3), wherein, per mol of the fatty acid, 1.0 to 1.5 moles of the monoalkanolamine is used;

A process as set forth in (1 ) to (4), wherein the reaction is carried out at a temperature of more than 150 °C; (6) A process as set forth in (1) to (5), wherein the reaction is carried out at a temperature of 160 to 170 °C;

(7) A process as set forth in (1) to (6), wherein the reaction is carried out in the absence of a basic catalyst;

(8) A process as set forth in (1) to (7), wherein the reaction is carried out in the absence of an organic solvent; (9) A process as set forth in of (1 ) to (8), wherein, after the completion of the reaction, the reaction mixture formed is distilled at a temperature of 125 °C or less under a reduced pressure;

(10) A process as set forth in (1) to (9), wherein, after the completion of the

reaction or after the distillation of the reaction mixture at a temperature of

125 °C or less under a reduced pressure after the completion of the reaction, water is added to the reaction mixture formed, and then the mixture is distilled at a temperature of 125 °C or less under a reduced pressure;

(11 ) A process as set forth in (1 ) to (10), wherein the reaction is carried out in the presence of a reducing organic acid.

Figure 1 is a gas chromatograph of a fatty acid monoalkanolamide obtained according to the present invention (Example 3).

Figure 2 is a gas chromatograph of a fatty acid monoalkanolamide obtained by carrying out a reaction with removal of water from the reaction system, according to the prior art (Comparative Example 1).

The fatty acid used according to the present invention is preferably represented by the following formula (1). R - COOH (1)

In the formula, R ¹ represents a linear or branched alkyl, alkenyl or hydroxyalkyl group having 5 to 21 carbon atoms. These compounds can be used alone or as a mixture thereof. Specifically, examples of the fatty acid include caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, nonadecanoic acid, behenic acid, erucic acid, and 12-hydroxystearic acid; and a vegetable or animal oil fatty acid such as coconut oil fatty acid, cotton seed oil fatty acid, corn oil fatty acid, tallow fatty acid, babassu fatty acid, palm kernel oil fatty acid, soybean oil fatty acid, linseed oil fatty acid, castor oil fatty acid, olive oil fatty acid, and whale oil fatty acid. Particular preference is given to caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, coconut oil fatty acid, and palm kernel oil fatty acid.

The monoalkanolamine, a further reactant used according to the present invention, is preferably represented by the following formula (2).

H— — R ³ — OH (2)

In the formula, R ² represents a hydrogen atom, or a linear or branched alkyl or hydroxyalkyl group having 1 to 8 carbon atoms, preferably 1 to 3 carbon atoms, or a linear or branched alkenyl group having 2 to 8 carbon atoms, preferably 2 to 3 carbon atoms. R ³ represents a linear or branched alkylene group having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms. Examples of R ² include a hydrogen atom, a hydroxyethyl group, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a hexyl group, and a 2-ethylhexyl group. In particular, R ² is a hydrogen atom.

Examples of R ³ include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, and a hexylene group. In particular, R ³ is an ethylene group. Examples of the monoalkanolamine represented by the formula (2) include monoethanolamine, diethanolamine, isopropanolamine, N-methylethanolamine, N-methylisopropanolamine, N- ethylethanolamine, and N-ethylbutanolamine, and preferably include

monoethanolamine, diethanolamine, isopropanolamine, N-methylethanolamine, and N-methylisopropanolamine.

The reaction between the fatty acid and the monoalkanolamine is carried out at a temperature of 140 to 170 °C, preferably of 150 to 170 °C. Even if the

temperature is less than 140 °C, for example at 130 °C, the desired amidation reaction occurs; however, the reaction rate is low and therefore not economical. On the other hand, when the temperature exceeds 170 °C, the formation rates of amide esters and cyclic amines are high, which may allow amide esters to remain in a large amount even if a subsequent hydrolyzing operation is performed by addition of water, and may further leads to a high content of cyclic amines, consequently reducing the purity. According to the present invention, the reaction is carried out in the presence of a certain appropriate amount of water unlike the prior art process where the reaction is carried out under the removal of the water formed. This can be attained by carrying out no substantial removal of the resulting reaction water from the reaction system, for example, by refluxing the resulting reaction water within the reaction system. However, if the temperature of the reaction mixture decreases due to the formation of reaction water and, due to this, a reaction temperature of 140 °C or more cannot be maintained, it is possible to suitably distill the water off under atmospheric pressure and thereby maintain a reaction temperature of 140 °C or more. That is, it is prerequisite that water is present in such an amount that the above reaction temperature can be

maintained, but sufficiently for preventing the formation of impurities as discussed below. In addition, in principle, the removal of water is not necessary as long as a temperature of 140 °C or more can be maintained, but, if an amount of water sufficient for suppressing the formation of by-products can be kept in the reaction system, the water may be removed continuously or discontinuously during the reaction. This is what the description "without substantially removing" means. In this manner, it is possible to suppress the formation of by-products such as ester amines, amide esters, and cyclic amines. Without wishing to be bound by the following theory, it is believed that, probably, in the present reaction, the desired amide, and the amide ester, ester amine and cyclic amine are presumed to form in respective formation rates in this order and, in this case, the presence of an appropriate amount of water inhibits the formation of the by-product ester or hydrolyzes the ester once formed, and also inhibits the occurrence of inter- molecular dehydrating condensation leading to the formation of the cyclic amine.

In this case, for the contents of the remaining fatty acid and the by-products in the final product, the following values can be aimed as standards for determining the reaction time or other reaction parameters;

Remaining fatty acid: 2.0 % by weight or less,

Ester amide: 1.0 % by weight or less,

Amide ester: 1.0 % by weight or less,

Other by-products (including cyclic amines): 1.0 % by weight.

However, the contents of the remaining fatty acid and the by-products required in a final product can naturally vary depending on conditions desirable in individual cases such as reaction time, intended use, and needs of users, and therefore, the aforementioned values are not intended to limit the scope of the present invention.

The reaction may be carried out in the presence of a basic catalyst such as sodium hydroxide and sodium methoxide. However, in the reaction according to the present invention, it is advantageously possible to dispense with basic catalysts without increasing the amounts of by-products formed even at a relatively high temperature of 140 to 170 °C by means of allowing a certain amount of water to exist during the reaction. This is followed by further advantages that the reaction can go without the use of additional chemicals and the removal operation of such additional chemicals, which provides an advantage in view of cost.

Moreover, as discussed in the prior art description, particularly, sodium methoxide is a substance which may form methanol classified as a substance which must not be detected in quality standards for household products and standards for cosmetics. The process according to the present invention does not require such a basic catalyst, and therefore, has a particular feature that there is no need to consider the possibility that methanol originating from the preparation remains in the final product.

Moreover, the reaction may be carried out in the presence of an organic solvent, while the presence of an organic solvent is not essential. However, organic solvents have a risk of, due to the fact that they usually have a boiling point lower than that of water, inhibiting the refluxing of water and preventing the reaction temperature from raising to a desired temperature; and also have the problem that, even in the case of organic solvents having a boiling point higher than that of water, the removal thereof is difficult. Furthermore, in general, handling of organic solvents is associated with fire or explosion hazards. Therefore, it is

advantageous to carry out the process according to the present invention in the absence of an organic solvent. Particularly advantageously, even if the reaction is carried out at a temperature of more than 150 °C, for example, at a temperature of 160 to 170 °C, the formation of by-products can be suppressed, and further the reaction time can be shortened to about 1/2 of that of the reaction at 150 °C and nevertheless, the desired amide can be obtained with a comparable or higher level of purity.

In the aforementioned reaction, the fatty acid and the monoalkanolamine are reacted with each other by using, relative to the fatty acid, an equivalent amount or a molar excess amount of the monoalkanolamine. In this case, the molar ratio of the monoalkanolamine per mole of the fatty acid is preferably 1.0 to 1.5 moles, and particularly preferably 1.0 to 1.3 moles. If the mole ratio is less than 1.0 mole, the amount of the fatty acid is excessive, and such an excessive unreacted fatty acid remains in the final product, which leads to a decrease in purity. In principle, the monoalkanolamine may be used in an amount more than 1.5 moles relative to the fatty acid, without influencing the purity, but it would require distilling off a higher amount of unreacted monoalkanol amines after the completion of the reaction and thus be not preferable from economical viewpoint. In one embodiment of the present invention, the reaction between the fatty acid and the monoalkanolamine is carried out in the presence of a reducing organic acid. In the reaction, the reaction product is sometimes colored due to an oxidized product derived from the amine. By adding a reducing organic acid, it is possible to inhibit the oxidation reaction and suppress the coloration. The amount of the reducing organic acid is generally 50 to 200 ppm by weight, preferably 50 to 100 ppm by weight relative to the total amount of the monoalkanolamine and the fatty acid. If the amount is less than 50 ppm, sufficient oxidation-suppressing effects cannot be expected. On the other hand, if the amount exceeds 200 ppm, the reducing organic acid may react with and consumes the amine which should have been available to the formation of the desired amide, and the product formed from such a reaction is a by-product, which leads to a decrease in purity of the final product. Examples of the reducing organic acid particularly include oxalic acid, formic acid, and ascorbic acid.

The unreacted monoalkanolamine remaining after the reaction can be removed by distillation under a reduced pressure, if necessary. In order to avoid explosive boiling of water, it is advantageous to carry out the distillation first under a slightly reduced pressure, followed by gradually reducing the pressure to a high degree. In this case, it is advantageous to carry out the distillation at a temperature of 125 °C or less, because a temperature exceeding 125 °C may promote intermolecular dehydrating cyclization, and lead to the formation of by-products.

In another embodiment of the present invention, after the reaction between the fatty acid and the monoalkanolamine has been completed or, preferably, the remaining monoalkanolamine has been distilled off under a reduced pressure as described above after the completion of the reaction, water may be added to the reaction mixture and then subjected to reduced-pressure distillation. In this way, the ester moiety in the by-product amide ester is hydrolyzed to form the desired amide, thereby further improvement in purity can be achieved. At the same time, the monoalkanolamine, which may still remain, is distilled off by azeotropic distillation with water, thereby yet further improvement in purity and further reduction of odor originating from the monoalkanolamine can be achieved. The conditions for this distillation are a temperature of 125 °C or less and a reduced pressure (for example, 100 to 3 Kpa/water pump at the beginning, and then, 1 Kpa or less/dry pump, for example, 0.1 to 0.3 Kpa/dry pump). Like the case mentioned above, a temperature exceeding 125 °C may promote intermolecular dehydrating cyclization and lead to the formation of by-products.

Furthermore, the reaction between the fatty acid and the monoalkanolamine can be carried out in the presence of a heavy metal amidation catalyst, for example, in the presence of at least one metal compound selected from compounds of chromium, manganese, iron, cobalt, nickel, hafnium, indium, copper, zinc, magnesium, calcium, aluminum, and lithium. Examples of such a heavy metal amidation catalyst include a halide such as chloride and bromide; a sulphate, a nitrate, a phosphate, a perchlorate; a carboxylate such as acetate, chloroacetate, trifluoroacetate, and acetylacetate; and an oxide of the aforementioned metals. By using such a catalyst, improvement in yield can be expected. However, there is sometimes an upper limit for the content of heavy metals depending on the use of fatty acid monoalkanolamides (for example, 10 ppm or less in cosmetics). In such use, the content of remaining heavy metal may exceed the limit, which offers a disadvantage.

Examples

The present invention is further described below in detail with reference to the following Examples and Comparative Examples, but it should be construed that the invention is in no way limited to those examples.

Example 1

64.05 g (1.05 moles) of monoethanolamine and 0.92 g of an aqueous 10 % oxalic acid-2H ₂ 0 solution were placed in a 500 ml four-necked flask, and the atmosphere was substituted by nitrogen under a reduced pressure of 5 to 7 Kpa at room temperature, and then, 204.8 g (1.0 mole) of molten coconut oil fatty acid (50 °C) was added under stirring and rising the temperature. A reflux device was installed and the heater temperature was set at 165 °C. However, since the temperature of the reaction mixture decreased due to the formation of reaction water, then the temperature was adjusted by the following procedure in order to prevent a decrease in the temperature of the reaction mixture. That is, if the temperature of the reaction mixture became 152 °C or less (30 minutes after the beginning of the reaction), the heater temperature was set at 160 °C, and then, the distillation line was opened and the reaction water was discharged by atmospheric distillation until the temperature of the reaction mixture rose to 158 °C. After that, the distillation line was closed to get back to refluxing. Further, at 1 hour, 2 hours, and 4 hours after the beginning of the reaction, analogously, the distillation line was opened and atmospheric distillation was carried out, and then refluxing was recovered again. At 12 hours after the beginning of the reaction, heating was stopped, and the reaction mixture was cooled to 90 °C and then subjected to distillation under a reduced pressure.

Thereafter, the following operation was repeated five times. That is, after the addition of 5 g of water and subsequent stirring, reduced-pressure distillation was carried out using a water pump instead, and subsequently reduced-pressure distillation was carried out using a dry pump then until the temperature was 120 °C. After the operation, the product thus obtained was poured onto an aluminum foil, and the cooled and solidified product was then subjected to GC analysis.

Example 2

70.15 g (1.15 moles) of monoethanolamine and 0.92 g of an aqueous 10 % oxalic acid-2H ₂ 0 solution were placed in a 500 ml four-necked flask, and the atmosphere was substituted by nitrogen under a reduced pressure of 5 to 7 Kpa at room temperature, and then 204.8 g (1.0 mole) of molten coconut oil fatty acid (50 °C) was added under stirring and rising the temperature.

Then, the subsequent operations were as in Example 1. Example 3

76.25 g (1.25 moles) of monoethanolamine and 0.92 g of an aqueous 10 % oxalic acid-2H ₂ 0 solution were placed in a 500 ml four-necked flask, and the atmosphere was substituted by nitrogen under a reduced pressure of 5 to 7 Kpa at room temperature, and then 204.8 g (1.0 mole) of molten coconut oil fatty acid (50 °C) was added under stirring and rising the temperature. Then, the subsequent operations were as in Example 1.

Example 4

76.25 g (1.25 moles) of monoethanolamine and 0.92 g of an aqueous 10 % oxalic acid 2H ₂ 0 solution were placed in a 500 ml four-necked flask, and the atmosphere was substituted by nitrogen under a reduced pressure of 5 to 7 Kpa at room temperature, and then 204.8 g (1.0 mole) of molten coconut oil fatty acid (50 °C) was added under stirring and rising the temperature. A reflux device was installed and the heater temperature was set at 170 °C. However, since the temperature of the reaction mixture decreased due to the formation of reaction water, then the temperature was adjusted by the following procedure in order to prevent a decrease in the temperature of the reaction mixture. That is, if the temperature of the reaction mixture became 160 °C or less (20 minutes after the beginning of the reaction), the distillation line was opened and the reaction water was discharged by atmospheric distillation until the temperature of the reaction mixture rose to 167 °C. After that, the distillation line was closed to get back to refluxing. Further, at 40 minutes, 1 hour, and 2 hours after the beginning of the reaction, analogously, the distillation line was opened and atmospheric distillation was carried out, and then refluxing was recovered again and the reaction was continued. At 7 hours after the beginning of the reaction, heating was stopped, and the reaction mixture was cooled to 90 °C and then subjected to distillation under a reduced pressure.

Thereafter, the following operation was repeated three times. That is, after the addition of 5 g of water and subsequent stirring, reduced-pressure distillation was carried out using a water pump instead, and subsequently reduced-pressure distillation was carried out using a dry pump then until the temperature was

120 °C. After the operation, the product thus obtained was poured onto an aluminum foil, and the cooled and solidified product was then subjected to GC analysis.

Example 5

76.25 g ( .25 moles) of monoethanolamine and 0.92 g of an aqueous 10 % oxalic acid-2H ₂ 0 solution were placed in a 500 ml four-necked flask, and the atmosphere was substituted by nitrogen under a reduced pressure of 5 to 7 Kpa at room temperature, and then 204.8 g (1.0 mole) of molten coconut oil fatty acid (50 °C) was added under stirring and rising the temperature. A reflux device was installed, and the heater temperature was set at 170 °C. However, since the temperature of the reaction mixture decreased due to the formation of reaction water, and then the temperature was adjusted by the following procedure in order to prevent a decrease in the temperature of the reaction mixture. That is, if the temperature of the reaction mixture became 160 °C or less (20 minutes after the beginning of the reaction), the distillation line was opened, and the reaction water was discharged by atmospheric distillation until the temperature of the reaction mixture rose to 167 °C. After that, the distillation line was closed to get back to refluxing. Further, at 40 minutes, 1 hour, and 2 hours after the beginning of the reaction, analogously, the distillation line was opened and atmospheric distillation was carried out, and then refluxing was recovered again and the reaction was continued. At 7 hours after the beginning of the reaction, heating was stopped, the reaction mixture was cooled to 90 °C and then subjected to distillation under a reduced pressure.

Thereafter, the product thus obtained was poured onto an aluminum foil, and the cooled and solidified product was then subjected to GC analysis.

Comparative Example 1

204.8 g (1.0 mole) of molten coconut oil fatty acid (50 °C) was placed in a 500 ml four-necked flask, and the atmosphere was substituted by nitrogen under a reduced pressure of 5 to 7 Kpa at 50 °C. 62.83 g (1.03 moles) of monoethanoiamine was added under stirring and rising the temperature. The heater temperature was set at 160 °C, and the reaction water was distilled off by atmospheric distillation with opening the distillation line and slowly introducing nitrogen gas. At 2 hours after the beginning of the reaction, reduced-pressure distillation (60 to 70 Kpa) was carried out using a water pump, and then the reduced-pressure state was maintained at 60 to 70 Kpa to promote the removal of the reaction water from the system. At 12 hours after the beginning of the reaction, reduced pressure distillation was carried out with maintaining the temperature at 160 °C. Thereafter, the product thus obtained was poured onto an aluminum foil, and the cooled and solidified product was then subjected to GC analysis.

Comparative Example 2

70.15 g (1.15 moles) of monoethanoiamine and 0.92 g of an aqueous 10 % oxalic acid-2H ₂ 0 solution were placed in a 500 ml four-necked flask, and the atmosphere was substituted by nitrogen under a reduced pressure of 5 to 7 Kpa at room temperature, and then 204.8 g (1.0 mole) of molten coconut oil fatty acid (50 °C) was added under stirring and rising the temperature. The heater temperature was set at 154 °C, and the reaction water was distilled off by atmospheric distillation with opening the distillation line and slowly introducing nitrogen gas. At 6 hours after the beginning of the reaction, reduced-pressure distillation (60 to 70 Kpa) was carried out using a water pump, and then the reduced -pressure state was maintained at 60 to 70 Kpa to promote the removal of the reaction water from the system.

At 12 hours after the beginning of the reaction, the temperature was set at 150 °C and reduced-pressure distillation was carried out. Thereafter, the following operation was repeated three times. That is, after the addition of 5 g of water and subsequent stirring, reduced-pressure distillation was carried out using a water pump instead, and then reduced-pressure distillation was carried out using a dry pump then until the temperature was 120 °C. After the operation, the product thus obtained was poured onto an aluminum foil, and the cooled and solidified product was subjected to GC analysis.

Comparative Example 3

70.15 g (1.15 moles) of monoethanolamine and 0.92 g of an aqueous 10 % oxalic acid 2H ₂ 0 solution were placed in a 500 ml four-necked flask, and the atmosphere was substituted by nitrogen under a reduced pressure of 5 to 7 Kpa at room temperature, and then 204.8 g (1.0 mole) of molten coconut oil fatty acid (50 °C) was added under stirring and rising the temperature. A reflux device was installed, and the heater temperature was set at 185 °C. However, since the temperature of the reaction mixture decreased due to the formation of reaction water, then the temperature was adjusted by the following procedure in order to prevent a decrease in the temperature of the reaction mixture. That is, if the temperature of the reaction mixture became 170 °C or less (20 minutes after the beginning of the reaction), the distillation line was opened and the reaction water was discharged by atmospheric distillation until the temperature of the reaction mixture rose to 178 °C. Thereafter, the distillation line was closed to get back to refluxing. Further, at 40 minutes, 1 hour, and 2 hours after the beginning of the reaction, analogously, the distillation line was opened and atmospheric distillation was carried out, and then refluxing was recovered again and the reaction was continued. At 5 hours after the beginning of the reaction, heating was stopped, and the reaction mixture was cooled to 90 °C and then reduced-pressure distillation was carried out.

Thereafter, the following operation was repeated three times. That is, after the addition of 5 g of water and subsequent stirring, reduced-pressure distillation was carried out using a water pump instead, and then reduced-pressure distillation was carried out using a dry pump then until the temperature was 120 °C. After the operation, the product thus obtained was poured onto an aluminum foil, and the cooled and solidified product was then subjected to GC analysis. Table : Result of purity measurement for Examples and Comparative Examples

n.d.: Not Detected

As is shown from Examples 1 to 3, according to the present invention, the residual content of the fatty acid was small (i.e., high reaction efficiency) and, further, it was possible to suppress the contents of the by-products to very low levels. In addition, the peculiar odor of the final product was slight.

The result of Example 4, which was carried out at higher temperature than

Examples 1 - 3, shows that, in this case, while suppressing the contents of the fatty acid and the by-products to low levels, it was possible to shorten the reaction time almost half of those in Examples 1 to 3. Again, the peculiar odor of the final product was slight.

In Example 5, which, compared to Examples 1 to 3, was carried out at a higher temperature and without azeotropic distillation by the addition water after the completion of the reaction, it was possible to reduce the content of the remaining fatty acid to a low level of .31 % already after 6.5 hours and, moreover, the amounts of the by-products formed were sufficiently satisfactory levels. In this example, however, a strong ammonium odor remained in the final product. This ammonia odor could be improved by adding water to the reaction mixture, followed by distillation.

In Comparative Example 1 , which was carried out a relatively high temperature (160 °C) while continuously discharging the water from the reaction system, a very large amount of the by-product amide ester formed 12 hours after the beginning of the reaction (the content of the remaining fatty acid: 1.1 %). In addition, the amounts of the other by-products formed were also higher than the examples according to the present invention. Furthermore, the final product emitted a strong ammonia odor.

In Comparative Example 2, which was carried out also while continuously discharging the water from the reaction system, but at a lower reaction

temperature (145 to 150 °C) compared to Comparative Example 1 , though, in this case, it was possible to suppress the amount of the amide ester formed to a lower level than that in Comparative Example 1 , a large amount of the fatty acid remained even after carrying out the reaction for 12 hours (4.1 %). Furthermore, the amide ester and the other by-products existed in relatively large amounts. Again, the final product also emitted a strong ammonia odor. Comparative Example 3 was carried out under refluxing the water analogously to the inventive examples, but at a higher reaction temperature of 170 to 180 °C. In this example, though the content of the remaining fatty acid decreased to 1.84 % after 5 hours, the amounts of the amide ester and the other by-products undesirably already reached high levels, 2.21 % and 1.61 %, respectively at this point of time. It is predicted that, if the reaction were further continued, part of the fatty acid would be consumed for the formation of amide esters, leading to a further increase in the amount of the amide esters, and the amides once formed would be converted to cyclic amides, and thus the purity would further worsen.