JPH0834758A - Production of long-chain carboxylic acid lactic acid ester - Google Patents

Abstract

PURPOSE:To industrially produce a long-chain carboxylic acid lactic acid ester having good purity. CONSTITUTION:A long-chain carboxylic acid or its reactive mixture is reacted with lactic acid or its salt to give a reaction mixture containing a long-chain carboxylic acid lactic acid ester. Then, an acid aqueous solution is added to the reaction mixture. Thereby, a polylactic acid which coexists therewith is decomposed and the long-chain carboxylic acid lactic acid ester forming a salt is isolated. When the long-chain carboxylic acid lactic acid ester is deposited as an oily material from water phase, the compound is collected and when the compound is not deposited, the aqueous solution is extracted with organic solvent to collect the long-chain carboxylic acid lactic acid ester. The long-chain carboxylic acid lactic acid ester thus collected is fractionated and crystallized from the organic solvent. Thereby, the long-chain carboxylic acid which coexists with the lactic acid ester is removed to provide the objective high-purity long- chain carboxylic acid lactic acid ester. By the method, a high-purity long-chain carboxylic acid lactic acid ester is extremely readily obtained. A salt derivatized from the ester is extremely excellent as a surfactant.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a long-chain carboxylic acid lactic acid ester. More specifically, the present invention relates to a method for industrially producing a high-purity long-chain carboxylic acid lactic acid ester.

[0002]

2. Description of the Related Art Long-chain carboxylic acid lactic acid ester salts are anionic surfactants and are known to be useful in applications such as foods, cosmetics and detergents (JP-A-64-62).
37, see JP-A-4-23900). The long-chain carboxylic acid lactic acid ester can be produced by reacting a long-chain carboxylic acid and lactic acid at 100 to 250 ° C. in the presence of an alkali catalyst (US Pat. No. 2,733,252), lactic acid or a salt thereof. A method of reacting a long-chain carboxylic acid with an acid chloride (US Pat. No. 2,789,992), and a method of reacting lactic acid with a long-chain carboxylic acid chloride in a basic solvent (J. Sci. Food Agric. , 32, 12
5 (1981)) and the like are known.

[0003]

In the reaction mixture produced by the above method, unreacted long-chain carboxylic acid and lactic acid derived from the raw materials are present in addition to the long-chain carboxylic acid lactic acid ester. . In addition, lactic acid and a long-chain carboxylic acid (in the present specification, lactic acid is lactic acid or a salt thereof, and long-chain carboxylic acid is a long Chain carboxylic acid or a reactive derivative thereof) is carried out under anhydrous conditions, but under these conditions lactic acid readily polymerizes to form polylactic acid, so that the reaction mixture contains no polycarboxylic acid. Lactic acid and its long-chain carboxylic acid esters are also present. Conventionally, a reaction mixture containing these various components has been used as it is as a long-chain carboxylic acid lactic acid ester salt, if necessary, simply by neutralizing with an alkali. This is because no industrially applicable purification method was known. It is also because the influence of these coexisting substances on the properties of the long-chain carboxylic acid lactate salt has not been clarified, and the motivation to use the purified product was poor.

However, according to the studies by the present inventors, the purified long-chain carboxylic acid lactic acid ester salt has a p-value in the neutral region.
Since H has a remarkably excellent surfactant activity and has a low Kraft point, it is far preferable to use a purified product rather than using the reaction mixture as it is as in the past. it is obvious. Therefore, the present invention is intended to provide a method for producing a purified long-chain carboxylic acid lactic acid ester.

[0005]

According to the present invention, an aqueous acid solution is first added to a reaction mixture of a long-chain carboxylic acid and lactic acid to decompose polylactic acid and form a long-chain carboxylic acid. Release the lactate ester. Although it depends on the composition of the reaction mixture, in general, when the pH of the reaction mixture is set to 3.0 or less, the long-chain carboxylic acid lactic acid ester precipitates as an oily substance, which is collected. PH of reaction mixture is 3.0
If it is larger than the above value and if an oily substance does not precipitate even at 3.0 or less, the reaction mixture is extracted with an organic solvent to extract the long-chain carboxylic acid lactic acid ester into the organic solvent phase.

The oily substance or the organic solvent solution containing the long-chain carboxylic acid lactate thus obtained contains a considerable amount of long-chain carboxylic acid. In the present invention, the both are then separated by fractional crystallization using an organic solvent to obtain highly purified long-chain carboxylic acid lactic acid ester as crystals. To explain the present invention in detail, in the present invention, first, a long-chain carboxylic acid and lactic acid are reacted with each other to produce a target long-chain carboxylic acid lactic acid ester. The reaction can be performed by a conventional method. As the long-chain carboxylic acid, one having 8 to 24 carbon atoms, preferably 10 to 22 carbon atoms is usually used. The long chain carboxylic acid may be saturated or unsaturated,
Further, it may be linear or branched. In the case of a branched chain, the longest chain preferably has 8 or more carbon atoms.
In some cases, it may be a hydroxycarboxylic acid having a hydroxyl group. These long-chain carboxylic acids include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, oleic acid, erucic acid, elaidic acid, ricinoleic acid, 2
-Butyloctanoic acid, 2-hexyldecanoic acid, 2-hexylundecanoic acid, 2-octyldecanoic acid, 2-decyltetradecanoic acid, 10-hydroxyoctadecanoic acid, 2
-Hydroxydecanoic acid and the like. Of these, lauric acid, stearic acid, capric acid, myristic acid, palmitic acid, oleic acid and the like are preferable. These long chain carboxylic acids can also be used as a mixture. However, in general, a long-chain carboxylic acid having a purity of 70% or more is used in order to smoothly proceed the crystallization operation of the long-chain carboxylic acid lactic acid ester described later (in this specification, the term “purity of a long-chain carboxylic acid means a long-chain carboxylic acid”). Means the weight percentage of one type of fatty acid in the chain carboxylic acid). The higher the purity of the long-chain carboxylic acid used in the reaction, the better the crystallization. Therefore, it is preferable to use a long-chain carboxylic acid having a purity of 80% or more, particularly 95% or more. The long-chain carboxylic acid may be subjected to the reaction as it is, or may be subjected to the reaction as a reactive derivative such as an acid chloride.

Lactic acid may be produced by either a fermentation method or a synthetic method, but is produced by a highly pure synthetic method (D
L-form) is preferred. As is well known, when an aqueous lactic acid solution is concentrated, lactic acid polymerizes to produce polylactic acid. However, using a dilute aqueous solution of lactic acid containing no polylactic acid is not preferable because a large amount of water is brought into the reaction system which should be in an anhydrous state. Therefore, the concentration is usually 85 with some polylactic acid.
It is preferable to use about% lactic acid.

The charge ratio of lactic acid to long-chain carboxylic acid may be 1: 1 (molar ratio), but in order to increase the reaction rate of long-chain carboxylic acid, excess lactic acid, for example, 1: 1.2-3.
It is preferable to charge it to 0 (molar ratio). The reaction can be carried out in the presence or absence of a solvent. When using a solvent, it is preferable to use a basic solvent such as pyridine which is soluble in both the reaction raw material and the product. In a typical embodiment thereof, lactic acid is dissolved in pyridine and kept at room temperature, and an acid chloride of a long-chain carboxylic acid is added dropwise to the reaction to cause reaction, and when the addition is completed, the temperature is raised to 50 to 90 ° C. Hold for ~ 3 hours to complete reaction. The content of long-chain carboxylic acid lactic acid ester in the reaction mixture varies depending on the ratio of the long-chain carboxylic acid and lactic acid used in the reaction, but the total of long-chain carboxylic acid lactic acid ester, unreacted lactic acid and long-chain carboxylic acid 30-70 mol% based on amount
It is a degree.

When no solvent is used, lactic acid and long-chain carboxylic acid are reacted in the molten state of long-chain carboxylic acid using an alkali metal hydroxide or carbonate as a catalyst. In a typical embodiment thereof, a reactor is charged with raw materials and a catalyst, and while removing by-produced water under reduced pressure, the mixture is stirred to maintain a uniform suspension state at 100 to 250 ° C. for 2 to 10 ° C. React for about an hour. In this case, the content of the long-chain carboxylic acid lactic acid ester in the reaction mixture is usually about 5 to 50 mol%.

In the present invention, an aqueous acid solution is added to the reaction mixture obtained as described above. As the acid, hydrochloric acid or sulfuric acid is usually used. This causes the polylactic acid in the reaction mixture to decompose into lactic acid. When a solvent is used in the reaction, the solvent may be distilled off beforehand. The amount of acid aqueous solution added is
The total amount of long-chain carboxylic acid lactic acid ester, long-chain carboxylic acid and lactic acid in the reaction mixture after addition of the aqueous acid solution is 3 to
It is preferable to set it to 40 (weight)%.

The behavior of long-chain carboxylic acid lactic acid ester in the reaction mixture when the aqueous acid solution is added to the reaction mixture is pH.
Depends on Generally, p depends on the composition of the reaction mixture.
When H is lower than 3.0, the long-chain carboxylic acid lactic acid ester is precipitated as an oily substance together with a part of the long-chain carboxylic acid or lactic acid, and this is collected. Therefore, when it is desired to precipitate the long-chain carboxylic acid lactic acid ester as an oily substance, the pH of the reaction mixture is lowered to 1.5 to 3.0.
If the pH is lowered too much, the long-chain carboxylic acid lactic acid ester will be decomposed, so it is necessary to avoid lowering the pH more than necessary.

When the long-chain carboxylic acid lactic acid ester in the reaction mixture is not collected as an oily substance, the pH is lowered to 5.0 or less, preferably 2.0 to 4.0. At this time, even if an oily substance is deposited, the deposition of the oily substance does not hinder the subsequent liquid-liquid extraction. Insufficient pH reduction may result in poor separation of the aqueous and organic phases in the liquid-liquid extraction of the reaction mixture. The reaction mixture obtained by adding an aqueous acid solution to a predetermined pH is then extracted with an organic solvent to partition lactic acid into the aqueous phase and long-chain carboxylic acid lactic acid ester into the organic solvent phase. Here, the long-chain carboxylic acids in the reaction mixture generally partition into the organic solvent phase. As the organic solvent used for extraction, any solvent can be used as long as it is sparingly soluble or insoluble in water and has a large dissolving power for long-chain carboxylic acid lactic acid ester. Examples thereof include hydrocarbons such as hexane and heptane, halogenated hydrocarbons such as methylene chloride and chloroform, alcohols such as isobutyl alcohol, ketones such as methyl ethyl ketone, and esters such as ethyl acetate. Among these, hexane, heptane, isobutyl alcohol, chloroform and the like, which have a boiling point of 50 ° C. or higher and are easy to handle, are preferable. Particularly preferred is hexane or chloroform.

The liquid-liquid extraction is usually carried out using 0.2 to 5 times by volume, preferably 0.3 to 2 times by volume, of the organic solvent with respect to the aqueous phase containing the reaction mixture. The extraction temperature is usually room temperature to 6
The temperature is 0 ° C, preferably 40 to 60 ° C. The extraction operation can be performed according to a conventional method by using various batch-type or continuous-type liquid-liquid extractors. From the organic solvent phase obtained by liquid-liquid extraction, long-chain carboxylic acid lactic acid ester is recovered by fractional crystallization. When the long-chain carboxylic acid lactic acid ester is obtained by precipitating it as an oily substance, it is dissolved in an organic solvent, and the long-chain carboxylic acid lactic acid ester is recovered from this solution by fractional crystallization. Since lactic acid is contained in the oily substance, it is preferable to remove lactic acid by washing with water before dissolving it in an organic solvent.

The organic solvent used for the fractional crystallization can be the same as the organic solvent used for the above extraction operation. Therefore, when recovering the long-chain carboxylic acid lactic acid ester from the organic solvent phase obtained by extraction, the long-chain carboxylic acid lactic acid ester may be crystallized directly from this organic solvent phase, or the organic solvent phase may be used as an organic solvent. May be distilled off, the residue may be dissolved in a new organic solvent, and the long-chain carboxylic acid lactic acid ester may be crystallized from this solution. The concentration of the long-chain carboxylic acid lactic acid ester in the organic solvent solution used for the crystallization operation is usually 5 to 40 (wt)%. If the concentration of the long-chain carboxylic acid lactic acid ester is too high, the crystallization operation becomes difficult and the purity of the obtained crystal decreases. The preferred concentration of the long-chain carboxylic acid lactate ester in the organic solvent solution is 5-35.
(Wt)%, especially 5 to 15 (wt)%. The crystallization operation is usually performed at -20 to 40 ° C. Generally, it is preferable to carry out at a relatively high temperature when the melting point of the long-chain carboxylic acid is high, and at a relatively low temperature when the melting point is low.

The purity of the long-chain carboxylic acid lactic acid ester obtained by this crystallization operation is usually about 80 to 95 mol%, and about 20 to 5 mol% of long-chain carboxylic acid is contained as an impurity. When this long-chain carboxylic acid lactic acid ester is again dissolved in an organic solvent to form a solution and subjected to crystallization operation again, a high-purity long-chain carboxylic acid lactic acid ester with a purity of 99% or higher can be obtained.

The long-chain carboxylic acid lactic acid ester obtained by the method of the present invention includes alkali metal and alkaline earth metal hydroxides and carbonates, as well as ammonia, alkanolamines such as ethanolamine, and lower alkyls such as tributylamine. It is used for various purposes as a salt by reacting with an amine. Generally, when the purity of the long-chain carboxylic acid lactic acid ester is 75 to 80 mol% or more, the long-chain carboxylic acid lactic acid ester salt obtained by reacting this with a basic substance is remarkably excellent in a neutral pH range. It has a high surface activity.

[0017]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. The analysis of long-chain carboxylic acid lactic acid ester and carboxylic acid was carried out as follows. Preparation of sample: Tetrahydrofuran / water = 20
Dissolve in a 1/1 (volume) solution. After adjusting the pH to 3.0 with dilute sulfuric acid, 9-Anthryl diazometh
A solution of an (ADAM) (product of Funakoshi Co., Ltd.) in methanol / acetone = 1/1 (volume) is added. Store in the dark for 1 hour at room temperature to react.

Quantitative analysis: Measured by high performance liquid chromatography under the following conditions Equipment: Shimadzu LC-6A Column: Nomura Chemical Develosil ODS-5
(4.6 mmφ × 250 mm) Column temperature: 35 ° C. Mobile phase: Acetonitrile Flow rate: 2.0 ml / min Detector: Fluorescence detector (Shimadzu RF535) Ex.
365 mm, Em. 412 mm. When analyzed under the above conditions, the ADAM esterified product flows out in the order of long-chain carboxylic acid lactate and long-chain carboxylic acid. Further, the measurement of the craft point is performed by K. Tsujii
et al. , J. et al. Phys. Chem. 1980, 8
4, pp2287, 1 wt% aqueous solution at about 0.3 ℃
It was determined by the point that the aqueous solution became completely transparent when the temperature was raised at a rate of / min.

Example 1 150 ml of pyridine and lactic acid (purity 90%) were placed in a reaction vessel.
Charge 50 g, and stearoyl chloride 50 g
Was added dropwise under water cooling for 1.5 hours, then at 50 ° C. for 1 hour,
The reaction was carried out with stirring. 400m of 4N hydrochloric acid in the reaction mixture
1 was added and neutralized to pH 3.0. Chloroform (525 ml) was added to the reaction mixture (640 g) containing water, and the mixture was shaken well and then separated into a chloroform phase and an aqueous phase. Chloroform was removed from the chloroform phase by evaporation to obtain 63 g of a solid consisting of 90 mol% stearoyl lactic acid ester and 10 mol% stearic acid.

This was added to 250 ml of hexane and heated at 50 ° C.
After being heated to dissolve it, the solution was left at room temperature for one day to precipitate crystals. After filtration, 45 g of crystals were obtained. The composition of the crystals was 96 mol% stearoyl lactic acid ester and 4 mol% stearic acid. This crystal is hexane 180
Recrystallization from ml gave 39 g of white plate-like stearoyl lactic acid ester crystals. The content of stearic acid in this product was 1 mol% or less. The stearoyl lactic acid ester was dispersed in water, and equimolar potassium hydroxide was allowed to act on the stearoyl lactic acid ester to obtain potassium stearoyl lactic acid ester.
The craft point of this product was 49 ° C.

Example 2 A reaction vessel was charged with 163 g of an 80% aqueous solution of potassium lactate and 284 g of stearic acid and reacted at 200 ° C. for 2 hours under a reduced pressure of 50 to 100 mmHg to give a reaction mixture 370.
g was obtained. 50 g of 1N hydrochloric acid was added to 20 g of this reaction mixture.
Was added to neutralize the pH to 3.0 or less. Chloroform (45 ml) was added thereto, and the mixture was shaken well at 50 ° C., and then, the layers were separated into a chloroform phase and an aqueous phase. Chloroform was removed from the chloroform phase by evaporation to give a solid 1 consisting of 39 mol% stearoyl lactic acid and 60 mol% stearic acid.
4 g was obtained. This was added to 67 g of hexane, heated and dissolved, and then allowed to stand at room temperature for 24 hours to precipitate crystals.
Filtration gave 5 g of crystals. The composition of this product was stearoyl lactic acid 84 mol% and stearic acid 16%. The crystals were recrystallized from hexane to obtain white plate-like stearoyl lactic acid crystals. The content of stearic acid in this product was 1 mol% or less. This stearoyl lactic acid ester was dispersed in water, and equimolar sodium hydroxide was allowed to act thereon to obtain sodium stearoyl lactic acid ester.
The craft point of this product was 53 ° C. The Kraft point of commercially available sodium stearoyl lactylate (unpurified product) is 90 ° C or higher.

Example 3 Pyridine (300 ml) and lactic acid (purity 90%) were placed in a reaction vessel.
Charge 100 g, and add palmitoyl chloride 10 to it.
0 g dropwise, under water cooling for 1.5 hours, then 50-60
The reaction was carried out at 0 ° C for 1 hour. When 8N hydrochloric acid was added to the reaction mixture until the pH reached 2.0, a white oily substance was precipitated, so it was separated from the reaction mixture. The amount acquired was 138 g. Dissolve this in 550 ml of hexane and add 400 m of water.
After adding 1 and shaking well, it was stratified into an aqueous phase and a hexane phase. Hexane was removed from the hexane phase by evaporation to obtain 88 g of a solid of palmitoyl lactic acid ester 88 mol% and palmitic acid 12 mol%. Hexane 4
After dissolving in 00 ml, it was kept at 18 ° C. to precipitate crystals. The obtained crystals were recrystallized from hexane to obtain white plate-shaped palmitoyl lactic acid ester. The yield is 56g,
The content rate of palmitic acid was 1 mol% or less. This palmitoyl lactic acid ester was dispersed in water, and equimolar potassium hydroxide was allowed to act on it to obtain potassium palmitoyl lactic acid ester.

Example 4 300 ml of pyridine and lactic acid (purity 90%) were placed in a reaction vessel.
Charge 100 g and add 93 g of lauroyl chloride.
Was added dropwise, and the mixture was reacted under water cooling for 1.5 hours and then at 50 ° C. for 1 hour. The reaction product solution was neutralized by adding 900 ml of 4N hydrochloric acid to pH 2.0. Precipitated oil 145
g and 430 ml of water and hexane were added and shaken well, and then the water phase and the hexane phase were stratified. The hexane phase was kept at 0 ° C. to obtain 70 g of white plate crystals. This crystal was recrystallized from hexane under the same conditions,
63 g of white plate-like lauroyl lactic acid ester crystals were obtained.
The content of lauric acid in this product was 1 mol% or less. The crystals were dispersed in a water-ethanol mixed solvent, and equimolar potassium hydroxide was allowed to act to give lauroyl lactate potassium. The craft point of this product was 0 ° C or lower.

Reference Example 1 40 g of a mixture of 1 part by weight of potassium stearoyl lactylate obtained in Example 1, 30 parts by weight of rapeseed oil and 69 parts by weight of demineralized water was placed in a 50 ml test tube, and 20
An oil-in-water emulsion was prepared by shaking up and down at 0 times / minute for 5 minutes. This was left at room temperature for 1 month, but no syneresis was observed. For comparison, the oil-in-water emulsion prepared in the same manner by using potassium stearate instead of potassium stearoyl lactylate was observed to start water separation in 4 hours. In addition, 284 g of stearic acid, lactic acid (purity 9
0%) 120 g, potassium carbonate 41 g under nitrogen stream 20
In the oil-in-water emulsion prepared by using the reaction mixture obtained by reacting at 0 ° C. for 4 hours as it was as an emulsifier, the onset of water separation was observed in 30 minutes.

Reference Example 2 Regarding potassium lauroyl lactate obtained in Example 4 or potassium laurate added thereto, lactic acid was added to adjust pH to 6.3 or 7.0.
The foaming power was measured. The measurement was carried out by placing 10 ml of a 0.25 (wt)% aqueous solution of a surfactant in a 50 ml graduated test tube, shaking up and down at 200 times / minute for 1 minute, and then measuring the foam volume after standing for 30 seconds. I did. The results are shown in Table-1 and Table-2. The mol% is a value with the total of potassium lauroyl lactate, potassium laurate and lactic acid taken as 100%.

[0026]

[Table 1]

[0027]

[Table 2]

As is clear from Tables 1 and 2, when the ratio of potassium laurate to potassium lauroyl lactate increases, the foaming power decreases and the Kraft point increases.

[0029]

According to the present invention, a high-purity long-chain carboxylic acid lactic acid ester can be easily obtained. The ester salt derived from this ester exhibits remarkably excellent surface-active ability as compared with the one using the conventional reaction mixture as it is.

Claims (10)

[Claims] 1. A long-chain carboxylic acid or its reactive derivative is reacted with lactic acid or its salt, and the reaction mixture is adjusted to pH 5.0.
Liquid-liquid extraction with an aqueous solvent and an organic solvent is performed below to form an organic solvent phase rich in long-chain carboxylic acid lactic acid ester and an aqueous solvent phase rich in lactic acid to separate both phases, and then this organic solvent phase A method for producing a long-chain carboxylic acid lactate ester, which comprises separating the long-chain carboxylic acid lactate ester from coexisting long-chain carboxylic acid ester by crystallization. 2. The method according to claim 1, wherein the long-chain carboxylic acid lactic acid ester is crystallized from the organic solvent phase containing the long-chain carboxylic acid lactic acid ester obtained by extraction. 3. A long-chain carboxylic acid lactate ester is obtained by removing the organic solvent from the organic solvent phase containing the long-chain carboxylic acid lactate ester obtained by extraction and dissolving the residue in a new organic solvent to prepare a solution. 2. The method according to claim 1, wherein the crystallization is performed. 4. A long-chain carboxylic acid or its reactive derivative is reacted with lactic acid or its salt, and the reaction mixture is adjusted to pH 3.
A long-chain carboxylic acid lactic acid ester is precipitated by adding an aqueous acid solution until it becomes lower than 0, and the oily material is separated and dissolved in an organic solvent to give a solution. A method for producing a long-chain carboxylic acid lactic acid ester, which comprises crystallizing 5. The method according to claim 4, wherein the separated oily substance is washed with water and then dissolved in an organic solvent. 6. The method according to claim 1, wherein crystallization from an organic solvent is repeated. 7. The method according to claim 1, wherein the long-chain carboxylic acid is a saturated or unsaturated carboxylic acid having 10 to 22 carbon atoms. 8. The production method according to claim 1, wherein the long-chain carboxylic acid has a purity of 70% or more. 9. The concentration of long-chain carboxylic acid lactate is 4
The method according to any one of claims 1 to 8, wherein the long-chain carboxylic acid lactic acid ester is crystallized from an organic solvent solution of 0 (wt)% or less. 10. The long-chain carboxylic acid lactic acid ester obtained by the method according to claim 1, is added with an alkali metal hydroxide, an alkali metal carbonate, an alkaline earth metal hydroxide, ammonia, or an alkanolamine. And a method for producing a long-chain carboxylic acid lactic acid ester salt, which comprises reacting at least one basic compound selected from the group consisting of :, and a lower alkylamine.