Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1999-12-21
2004-03-16
Wilson, James O. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S124000
Reexamination Certificate
active
06706877
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an improved process for the production of carbohydrate partial esters by transesterification of glycoses with fatty acid esters in the presence of emulsifiers and basic catalysts and to the use of the substances obtainable by the process for a number of applications.
Carbonhydrate esters, which are often also referred in short as “sugar esters”, are esters of mono- or oligosaccharides and—in the broader sense—of sugar alcohols with organic or inorganic acids. Carbohydrate esters have pronounced surface-active properties so that, today, they are regarded as an independent class of compounds (so-called sugar surfactants). By virtue of their favorable dermatological and toxicological compatibility, carbohydrate esters are mainly used as emulsifiers for the production of foods and cosmetics. Sucrose polyesters containing 6 to 8 fatty acid residues could be used as a fat substitute which is not utilized by the organism in the diet of overweight people and, in addition, are said to bind LDL cholesterol in the stomach. They are normally produced by subjecting glycoses to transesterification with fatty acid methyl esters in the presence of alkaline catalysts and optionally emulsifiers. One such process is described, for example, in German patent application DE-A14131505 (Henkel). Soaps are generally used as emulsifiers for the production of the carbohydrate esters, as disclosed for example in GB-A 2,256,869.
Unfortunately, known processes are attended by the disadvantage that long reaction times are required to achieve in particular relatively high degrees of esterification, which makes the products expensive on account of the considerable reactor possession times. In addition, the products are often discolored on account of their prolonged exposure to heat. Finally, solvents often have to be used which not only adds further to the cost of the products on account of the subsequent removal of the solvents used, but also is often undesirable if the products are to be used, for example, in the food sector.
Accordingly, the problem addressed by the present invention was to provide an improved process for the production of carbohydrate partial esters which would be free from the disadvantages mentioned above.
DESCRIPTION OF THE INVENTION
The present invention relates to a process for the production of carbohydrate partial esters with a degree of esterification of 1 to 6 by alkali-catalyzed transesterification in the presence of emulsifiers, characterized in that
(a) to form a catalytically active system, alkali metal carbonates are treated with fatty acid lower alkyl esters corresponding to formula (I):
R
1
CO—OR
2
(I)
in which R
1
CO is a linear or branched, saturated or unsaturated alkyl group containing 6 to 22 carbon atoms and R
2
is a linear or branched alkyl group containing 1 to 5 carbon atoms, and
(b) for transesterification, the resulting mixture is treated while stirring vigorously with a mixture of (b1) glycoses containing 5 to 12 carbon atoms and (b2) carbohydrate partial esters as emulsifiers, so that an emulsion/dispersion in which the particles have a mean diameter of 10 to 60 &mgr;m is obtained.
In the first step of the process according to the invention, a coating of fatty acid lower alkyl ester is formed on the alkali metal carbonate, so that the acyl group is activated. In the second step, the activated catalyst is contacted with a mixture of a glycose and a carbohydrate partial ester, the carbohydrate partial ester acting as an emulsifier. In the first step of the transesterification, acyl groups are transferred to the emulsifier which, in the further course of the reaction, itself functions as an acylating agent and transfers acyl groups to the glycose which is thus converted into a carbohydrate partial ester. The reaction takes place in the absence of solvents which is a considerable advantage not only from the economic point of view, but also with a view to the use of the end product in foods or cosmetics. Another unexpected advantage of the process is that, by virtue of the effective nature of the transesterification, the same degrees of esterification are obtained in very much shorter reaction times by comparison with the prior art.
Catalysts
Suitable catalysts are alkali metal carbonates, preferably sodium and/or potassium carbonate, which may be used in quantities of 5 to 50% by weight, preferably 10 to 20% by weight and more preferably 10 to 15% by weight, based on the fatty acid lower alkyl esters.
Fatty Acid Lower Alkyl Esters
Typical examples of suitable acylating agents are the esters of caproic acid, caprylic acid, 2-ethylhexanoic acid, capric acid, lauric acid, isotridecanoic acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, isostearic acid, oleic acid, elaidic acid, petroselic acid, linoleic acid, linolenic acid, elaeostearic acid, arachic acid, gadoleic acid, behenic acid and erucic acid and technical mixtures thereof with methanol, ethanol, propanol, isopropyl alcohol, n-butanol, i-butanol, tert.butanol, n-pentanol and isopentanol. Methyl and/or ethyl esters of C
12-18
fatty acids are preferably used, the molar ratio of ester to glycose being from 1:3 to 3:1 and preferably from 1:2 to 2:1, depending on the required degree of esterification.
Production of the Catalyst System
To produce the catalyst system, i.e. to activate the fatty acid alkyl ester as acylating agent, the ester and the alkali metal carbonate are mixed with intensive stirring. It has proved to be of advantage in this regard to carry out the activation at temperatures of 40 to 120° C. and preferably 80 to 100° C. The quantity of alkali metal carbonate used is preferably in the range from 5 to 50% by weight, based on the alkyl ester. The ester undergoes chemisorption onto the surface of the carbonate.
Glycoses
Glycoses in the context of the invention include the polyhydroxyaldehydes (aldoses) and polyhydroxyketones (ketoses) also referred to as carbohydrates and relatively high molecular weight compounds which can be converted into such substances by hydrolysis. According to the invention, both monomeric polyhydroxyaldehydes or polyhydroxyketones (monosaccharides) and their dimers to decamers (disaccharides, trisaccharides, oligosaccharides) may be used as glycoses. Suitable monosaccharides (also known as “simple sugars”) are, for example, bioses, trioses, tetraoses, pentoses, hexoses, heptoses, etc. Typical examples of aldopentoses are D-ribose, D-xylose and L-arabinose. The most important aldohexoses include D-glucose, D-mannose and D-galactose while the ketohexoses include D-fructose and sorbose. The 6-deoxysugars, L-fucose and L-rhamnose, are also widely used hexoses and are also suitable as starting materials. The simplest oligosaccharides suitable as starting materials are the disaccharides. Sucrose (cane sugar, beet sugar), lactose (milk sugar) and/or maltose (malt sugar) are preferably used. According to the invention it is preferred to mono- and/or disaccharides, sucrose or glucose being particularly preferred.
Emulsifiers
According to the invention, it has proved to be of particular advantage to use carbohydrate partial esters which are identical with the target products as emulsifiers. It is particularly preferred to use sucrose partial esters with a degree of etherification of 1 to 3. Other suitable co-emulsifiers are, for example, nonionic surfactants from at least one of the following groups:
(1) products of the addition of 2 to 30 mol of ethylene oxide and/or 0 to 5 mol of propylene oxide onto linear fatty alcohols containing 8 to 22 carbon atoms, onto fatty acids containing 12 to 22 carbon atoms and onto alkylphenols containing 8 to 15 carbon atoms in the alkyl group;
(2) C
12/18
fatty acid monoesters and diesters of products of the addition of 1 to 30 mol of ethylene oxide onto glycerol;
(3) glycerol monoesters and diesters and sorbitan monoesters and diesters of saturated and unsaturated fatty acids containing 6 to 22 carbon atoms and ethylene oxide adducts thereof;
(4) alkyl mono- and
Cecutti Christine
Claverie Valerie
Gaset Antoine
Le Hen Ferrenbach Catherine
Mouloungui Zephirin
Cognis Deutschland GmbH & Co. KG
Drach John E.
Maier Leigh C.
Trzaska Steven J.
Wilson James O.
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