KR19990012489A - Purification of Sucrose Fatty Acid Ester - Google Patents

Abstract

The present invention relates to a sucrose fatty acid ester prepared by a transparent emulsion method or a solvent-free method in which an unreacted substance and a side reaction substance are mixed when the sucrose fatty acid ester is prepared.

a) extracting the sucrose fatty acid ester by solid-liquid extraction using a mixed solvent and simultaneously precipitating the surfactant with a divalent metal salt;

b) filtering the solids; And

c) cooling the filtrate of step b) and filtering the sucrose fatty acid ester precipitate.

Description

Purification of Sucrose Fatty Acid Ester

The present invention relates to a method for purifying sucrose fatty acid esters. A sucrose fatty acid ester is a substance in which a fatty acid has an ester bond at one or more positions of six hydroxyl groups of sucrose.

Sucrose fatty acid ester is a tasteless and edible emulsifier and is widely used in food, cosmetics, and pharmaceutical industries. As a representative industrial manufacturing method, dimethylform described in Japanese Patent No. 35-13102. Solvent method for transesterification reaction of methyl ester of sucrose and higher fatty acid to organic solvents such as amide or dimethyl sulfoxide using a suitable basic catalyst and anionic surfactant instead of organic solvent as described in Belgian Patent No. 696700 Transparent emulsion method to obtain sucrose fatty acid ester through transesterification reaction in the state of transparent emulsion formed, and in the molten state using only anionic or nonionic surfactants without using a solvent as in US Pat. And a solvent-free method for causing an exchange reaction.

The reactants prepared by the above method commonly contain impurities such as sucrose fatty acid ester, unreacted sucrose, unreacted fatty acid methyl ester, catalyst, and a base and a soap made from fatty acids. Therefore, a process for purifying sucrose fatty acid ester is necessary. Do. In particular, the reaction product according to the transparent emulsion method and the solvent-free method contains about 10 to 40% of the anionic surfactant in the total amount depending on the conditions. Since it is emulsified, ordinary purification methods can be used and new purification methods are required. Done.

Currently used purification methods include a liquid-liquid extraction method in which anionic surfactant is precipitated and removed by adding a divalent or higher metal salt, and water-soluble impurities are removed by adding an organic solvent such as methyl ethyl ketone and water; Washing-filtration method to remove impurities using water and organic solvent sequentially, and recently, salting method to selectively precipitate sucrose fatty acid ester by adding appropriate salt in aqueous solution. There is this.

A representative example of a liquid-liquid extraction method is described in Japanese Patent Publication No. 51-14487. Although it is relatively easy to industrialize compared to other purification methods, it is cumbersome to repeat washing with water to remove water-soluble impurities. The loss of strong sucrose monoester is inevitable and it is difficult to completely remove water-soluble impurities from the organic layer even after washing. Representative examples of wash-filtration and salting-out methods are described in US Pat. No. 4,104,464 and Japanese Patent No. 63-162267, respectively. All of these methods involve filtering out sucrose fatty acid esters in water, because the sucrose fatty acid esters form fine particles in the water and prevent the passage of water by filtration, which impedes filtration. It takes a long time. At this time, the use of a filtration aid such as celite does not improve the filtration rate. In addition, the sucrose fatty acid ester obtained by the above washing-filtration method has a purity which is not suitable for food use.

The present inventors have improved the existing purification method of sucrose fatty acid ester, and while studying a purification method in which harmful substances are not added so as to be more economical and efficient while maintaining edible property, as in the liquid-liquid extraction method. Instead of separating anionic surfactants and separating water-soluble impurities such as sucrose and basic catalysts, only sucrose fatty acid esters can be selectively extracted from the solid product directly using a suitable mixed solvent. It turned out that it was. The mixed solvent used in this solid-liquid extraction method is methyl ethyl ketone containing 1 to 10% of water and is a single phase at room temperature. Therefore, as in the liquid-liquid extraction method, it is not necessary to acidify the solvent system for the separation of the layers and there is no need for the separation of the layers.

The anionic surfactant present in the reaction product prepared by the transparent emulsion method or the solventless method is a soap, that is, an alkali metal salt of a fatty acid. During the reaction, an esterification reaction occurs by emulsifying the sucrose and the methyl ester of a fatty acid and a basic catalyst. It plays a role.

Divalent or more metal salts may be added to convert the alkali metal salts of fatty acids into insoluble precipitates and to separate them by filtration (Japanese Patent No. 44-75652). This method is used before or after the solid-liquid extraction step because the fatty acid is combined with a divalent or higher metal salt to form a solid, which is difficult to dissolve in water or an ordinary organic solvent. It is possible to extract high purity sucrose fatty acid esters more efficiently, however, if performed simultaneously with the solid-liquid extraction step. That is, when the reaction product is dispersed in hydrous methyl ethyl ketone and the temperature is maintained at 40-70 ° C., a divalent or more metal salt or its aqueous solution is added, and all of the alkali metal salts of the fatty acid are immediately changed to the divalent or more metal salt form of the fatty acid. Form. Filtration while maintaining the above temperature, the metal salt of the fatty acid, unreacted sucrose, and other inorganic impurities remain in the form of a filter cake, the resulting sucrose fatty acid ester and unreacted fatty acid methyl ester is dissolved in the filtrate. When the filtrate is cooled, sucrose fatty acid ester having low solubility is precipitated, and when it is filtered again at low temperature, only sucrose fatty acid ester can be obtained with high purity.

The methyl ethyl ketone used in the solid-liquid extraction method contains water and preferably a single phase. That is, a water content of 1 to 10% by weight is suitable, preferably 2.5 to 5% by weight. When the methyl ethyl ketone single solvent system, that is, the water content of methyl ethyl ketone is less than 1% by weight, the divalent metal salt of the resulting fatty acid is finely dispersed and interferes with filtration, and thus, it takes much time for filtration and falls into lactation. If the water content exceeds 10%, sucrose or inorganic impurities are dissolved, and if more water enters this, it becomes troublesome to separate the layers.

The amount of the mixed solvent depends on the content of the sucrose fatty acid of the sucrose fatty acid-containing solids and the amount of the unreacted fatty acid methyl ester, but it is appropriate to use 5 to 8 times the solid content of the sucrose fatty acid. When the mixed solvent is used less than 5 times of the sucrose fatty acid-containing solids, it is not economical because it does not completely dissolve the sucrose fatty acids and fatty acid methyl esters in the sucrose fatty acid-containing solids, resulting in a large amount of product loss and raw material loss. In case of using more than 8 times, it is uneconomical to use excessive amount of solvent to obtain the same product because the facility investment should be excessive.

The temperature at which the metal salt of the fatty acid is produced, precipitated, and the sucrose fatty acid ester is extracted is preferably in the range of 40 to 70 ° C, more preferably 50 to 60 ° C. At low temperatures below 40 ° C, sucrose fatty acid esters do not dissolve completely. At high temperatures above 70 ° C, sucrose fatty acid esters are hydrolyzed by water contained in the solvent system to lower the yield. Maintenance is essential. In addition, to completely dissolve the sucrose fatty acid ester in the solid, it is preferable to stir the contents at a speed of several hundred rpm before or during the filtration.

It is preferable to use a filtration aid in order to improve the filtration rate when filtering. As the filtering aid, diatomaceous earth and acidic clay are preferably used, and about 10 to 20% of the weight of the sucrose fatty acid ester-containing solids is preferably used. In this case, when the filtration aid is used at less than 10%, the improvement of the filtration rate is insignificant, and when the filtration aid is used at 20% or more, there is a problem in that the productivity is reduced by increasing the load of the machine.

In solid-liquid filtration, the filtrate can be cooled to recover sucrose fatty acid esters, and the remaining filtrate can be circulated back to the first filter cake and recycled to extract residual sucrose fatty acid esters. By recycling the solvent as described above it is possible to reduce the cost of producing sucrose fatty acid ester, whereby most of the sucrose fatty acid ester can be extracted by two to four recycles.

For the understanding of the present invention will be described in more detail through the following examples.

EXAMPLE

23.3 g of stearic acid and 11.5 g of potassium carbonate were dehydrated at 130 ° C. and 100 mbar, saponified to form potassium stearate, and 50.0 g of stearic acid methyl ester was added thereto to completely melt. 60.2 g sucrose was added, the pressure was reduced to 100 mbar and the methanol was evaporated with vigorous stirring at 130 ° C. After 5 hours, when the contents were hardened and the stirring was no longer difficult, the pressure was raised to atmospheric pressure, the temperature was lowered to 70 ° C., and 483 g of methyl ethyl ketone was added, and the contents were evenly dispersed. When the temperature was further lowered to 55 ° C., 37 ml of 27% aqueous calcium chloride solution was added to precipitate calcium stearate and filtered while maintaining this temperature. The filtrate was left in a thermostat at -5 ° C to precipitate the sucrose fatty acid ester, which was then filtered again and the filter cake was dried to obtain a sucrose fatty acid ester. The filtrate was put back into the first filter cake containing calcium stearate and the solid-liquid extraction was repeated four times to further recover the sucrose fatty acid ester.

This gave 50.12 g (99% purity) of sucrose fatty acid ester in the form of a white powder. The composition of the obtained sucrose fatty acid ester was 40% monostearic acid sucrose, 44% distearic acid sucrose, and 16% tristearic acid sucrose.

Claims (9)

In the purification method of sucrose fatty acid ester prepared by a transparent emulsion method or a solventless method, a) extracting the sucrose fatty acid ester by solid-liquid extraction using a mixed solvent and simultaneously precipitating the surfactant with a divalent metal salt; b) filtering the solids; And c) cooling the filtrate of step b) and filtering the sucrose fatty acid ester precipitate. The process of claim 1 wherein the mixed solvent is methyl ethyl ketone containing 1 to 10 weight percent water. The process of claim 1 wherein the mixed solvent is methylethylketone containing 2.5-5% by weight of water. The process according to claim 1, wherein the mixed solvent is used at 5 to 8 times the weight of the sucrose fatty acid ester-containing solids. The process of claim 1 wherein the solid-liquid extraction temperature is between 40 and 70 ° C. 3. The process of claim 1 wherein the solid-liquid extraction temperature is between 50 and 60 ° C. 3. The process according to claim 1, wherein diatomaceous earth or acidic clay is used as the filter aid in the solid filtration. 8. The process according to claim 7, wherein the filtration aid is used at 10 to 20% by weight of the weight of the sucrose fatty acid ester-containing solids. The method of claim 1, wherein the filtrate of step c) is circulated to step a) and steps b) and c) are repeated 2 to 4 times.