Process for the preparation of acyloxyalkanesulfonic acids

Details Process for the preparation of acyloxyalkanesulfonic acids Process for the preparation of acyloxyalkanesulfonic acids

1999-06-09

2001-10-16

Carr, Deborah D. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Fatty compounds having an acid moiety which contains the...

C516S198000, C516S200000

Reexamination Certificate

active

06303802

ABSTRACT:

This application is a 371 of PCT/JP97/04467 filed on Dec. 5, 1997.
FIELD OF THE INVENTION
The present invention relates to a process for preparing an acyloxy alkanesulfonic acid and a salt thereof. More specifically, the invention relates to a process for preparing an acyloxy alkanesulfonic acid and a salt thereof wherein the acyloxy alkanesulfonic acid can be prepared under mild conditions.
DESCRIPTION OF THE RELATED ART
Sodium salts of fatty esters of hydroxy alkanesulfonic acids such as isethionic acid (2-hydroxy ethanesulfonic acid) have far stronger resistance to hard water than soap, are mild to the skin and provide lather with a rich body. They are also relatively thermoplastic when used as a material for molding synthesized soaps or composite soaps. Due to these characteristics, they have been used for a long time as materials for producing synthesized soaps or composite soaps, components of shampoos and body cleaning agents, fiber scouring agents or coloring aids and the like.
According to “HAPPI, 92, 1995”, PPG Industries, Inc. discovered that at room temperature the water solubility of a salt of a coconut oil fatty ester of isethionic acid was improved by 30% by changing the counter ion thereof from a sodium ion to an ammonium ion, and introduced the salt as an active agent which was mild, environmentally friendly and had good lathering qualities. Generally, ammonium salts are known to have a water solubility higher than that of sodium salts. However, there is a disclosure that the difference brought about by the ammonium salt of the coconut oil fatty ester of isethionic acid is unprecedentedly large, that this salt has low peroral toxicity and is considered to be almost innoxious, and that its biodegradability exceeds the OECD 301D guide lines, i.e. 65% in 15 days. Therefore, this substance is a surfactant with great promise.
These salts of acyloxy alkanesulfonic acids, such as salts of fatty esters of isethionic acid are typically prepared as follows, where isethionic acid is used as a representative example.
One such method is a process in which isethionic acid is allowed to directly react with a fatty acid (U.S. Pat. No. 3,151,136, Japanese Patent Laid-open No.2-1454). In another method, a salt of isethionic acid produced in any process, for example, from a hydrogen sulfite such as sodium hydrogen sulfite or ammonium hydrogen sulfite and ethylene oxide, is esterified with a fatty acid (hereinafter referred to as a direct esterification method).
In the above-mentioned U.S. Pat. No. 3,151,136, a fatty acid is heated to 100-120° C. under a reduced pressure, isethionic acid is then added thereto and the mixture is maintained at 110° C., and then at 135° C. to complete the esterification reaction. In the Japanese Patent Laid-open No.2-1454 discloses that isethionic acid and a fatty acid are reacted at 110-120° C., then after-stirring is carried out at 135° C.
In Japanese Patent Laid-open No.2-1454, sodium salt of a fatty ester of isethionic acid is produced from such materials as coconut oil fatty acid and isethionic acid. However, impurities are yielded as the reaction is carried out at a maximum temperature of up to 135° C., and the obtained salt of the fatty ester of isethionic acid has low purity and shows deteriorated water solubility. This does not present a problem for a salt such as a sodium salt which is not required to have high water solubility, but for a salt which is required to have high water solubility, this process is not practical.
Other examples employing the direct esterification method are given, for example, in WO 95/01331 and WO 95/11957 wherein a process in which ammonium isethionate is produced from ammonium hydrogen sulfite and ethylene oxide is described, and the obtained ammonium isethionate is used together with coconut oil fatty acid to produce an ammonium salt of coconut oil fatty ester of isethionic acid. In such a direct esterification process, although sodium chloride is not a by-product, the reaction requires a temperature as high as almost 200° C., which results in yielding by-products, deterioration of hue and generation of bad smell. Dehydration is carried out for the esterification reaction, however, as a lot of foaming occurs under a reduced pressure, the reaction takes a long time and a reaction vessel having a large capacity in relation to the amount of the product must be employed. There is no improvement on this point in the process shown in WO 95/01331 and WO 95/11957, since the main points thereof are to decrease the amount of impurities such as ethylene glycol during the production of salts of isethionic acid.
An alternative method is a process in which an obtained isethionate salt and a fatty acid chloride are allowed to react to produce a fatty ester of isethionic acid (hereinafter referred to as acid chloride method). In this acid chloride method, the product can be obtained at a relatively low temperature of not more than about 100° C., however, sodium chloride is disadvantageously by-produced.
Furthermore, there is still another method in which an obtained isethionate salt and a methyl ester of a fatty acid are subjected to an ester exchange reaction (hereinafter referred to as ester exchange method). In this ester exchange method, again, a temperature as high as about 200° C. is required for the reaction, therefore the problems of by-products, deteriorated hue and generation of smell exist. This process is less advantageous from the view point of cost and ease of operation, since the production of a methyl ester of a fatty acid is inevitable.
The sodium salt of coconut oil fatty ester of isethionic acid has limited uses due to its low water solubility, as an anionic surfactant, of up to several % at room temperature. Although the ammonium salt has relatively superior water solubility, it has a problem in that it smells at higher pH ranges. Therefore, a salt of a fatty ester of isethionic acid having the same or a higher level of water solubility and lathering properties has been desired. The industrially available hydrogen sulfite salts are more or less limited to sodium and ammonium salts, and since the counter ion is not displaced in the production of an isethionate from a hydrogen sulfite salt and ethylene oxide or in the direct esterification of an isethionate and a fatty acid, the types of counter ions of the fatty ester of isethionic acid are more or less limited to sodium and ammonium. In order to produce a salt of a desired type, a sodium salt or ammonium salt of a fatty ester of isethionic acid must be subjected to an ester exchange reaction and the like to be converted into the desired salt, thus it is not easy to industrially produce various salts. Once a fatty ester of isethionic acid is obtained, it can be neutralized with a desired counter base to industrially produce various kinds of salts easily, and there is no need for an ester exchange reaction. Therefore, development of a process for preparing the fatty ester of isethionic acid has been long desired.
The purpose of the present invention is to provide a process of preparing an acyloxy alkanesulfonic acid or a salt thereof having excellent solubility in polar solvents, and salts of various counter ions which can be easily produced therewith, wherein reaction is carried out under mild conditions. Accordingly, few by-products are yielded, the hue and smell are ameliorated, there is little foaming and dehydration of the reaction system under a reduced pressure can be easily carried out so that the reaction time can be shortened, to provide a polar solvent solution of the salt of the acyloxy alkanesulfonic acid.
SUMMARY OF THE INVENTION
In one aspect of the present invention, a process for preparing an acyloxy alkanesulfonic acid from a fatty acid and/or an alkyl ester of a fatty acid and a hydroxy alkylsulfonic acid is provided in which, an esterification reaction is carried out between the fatty acid and/or the alkyl ester of the fatty acid and the hydroxy alkylsulfonic acid at a maximum temperature of not more than 130° C.
In another aspect of the

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