Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1994-07-06
2001-10-16
Geist, Gary (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S115000, C536S116000, C536S124000, C536S127000
Reexamination Certificate
active
06303777
ABSTRACT:
TECHNICAL FIELD
This application relates to the synthesis of highly esterified polyol fatty acid polyesters, especially highly esterified sucrose polyesters. This application particularly relates to an improved, solvent-free, two-stage trans-esterification process for preparing such polyesters having reduced levels of difatty ketones and &bgr;-ketoesters.
A number of different processes have been disclosed in the art for preparing highly esterified polyol fatty acid polyesters, in particular sucrose polyesters useful as reduced calorie fat substitutes. One such process for preparing these polyesters involves a solvent-free, essentially two-step transesterification of the polyol (e.g., sucrose) with the fatty acid esters of an easily removable alcohol (e.g., fatty acid methyl esters). In the first step, a mixture of sucrose, methyl esters, alkali metal fatty acid soap and a basic esterification catalyst are heated to form a melt. The amount of methyl esters is such that the melt forms primarily partial fatty acid esters of sucrose, e.g., sucrose mono-, di- and/or triesters. In the second step, an excess of methyl esters are added to this melt which is then heated to convert the partial sucrose esters to more highly esterified sucrose polyesters, e.g., sucrose hexa-, hepta-, and particularly octaesters. See, for example, U.S. Pat. No. 3,963,699 (Rizzi et al), issued Jun. 15, 1976; U.S. Pat. No. 4,517,360 (Volpenhein), issued May 14, 1985; and U.S. Pat. No. 4,518,772 (Volpenhein), issued May 21, 1985, which disclose solvent-free, two-step trans-esterification processes for preparing highly esterified polyol fatty acid polyesters, in particular highly esterified sucrose polyesters.
In some processes for preparing highly esterified polyol fatty acid polyesters, all of the fatty acid methyl esters are added to the polyol (e.g., sucrose) at the beginning of the reaction, i.e. a one-step addition process. See, for example, U.S. Pat. No. 4,611,055 (Yamamoto et al), issued Sep. 9, 1986. Like the previously described two-step processes, such one-step processes first form primarily partial fatty acid esters of sucrose that are then converted to more highly esterified sucrose polyesters. Accordingly, these single-step and two-step processes are collectively referred to hereafter as “two-stage” transesterifications, wherein the “first stage” involves the formation of the partial esters and wherein the “second stage” involves the conversion of the partial esters to more highly esterified polyesters.
In addition to highly esterified sucrose polyesters, this two-stage transesterification reaction typically forms by-products. One such by-product formed is difatty ketones. It is believed these difatty ketones result from &bgr;-ketoesters formed primarily during the second stage of the transesterification reaction; &bgr;-ketoesters can also form, to a more limited extent, during the first stage of the transesterification reaction.
These &bgr;-ketoesters are formed as a result of a Claisen condensation. In this Claisen condensation, two equivalents of the fatty acid methyl esters are condensed in the presence of one equivalent of a base. (A similar Claisen condensation can occur involving one or more sucrose esters.) In the first step of this condensation, a proton from the &agr;-carbon atom on the methyl ester is removed by the base to give the resulting methyl ester anion and methanol. In the second step of this condensation, there is a nucleophilic attack by this methyl ester anion on the carbonyl of another fatty acid methyl ester with the concomitant loss of methoxide to give the &bgr;-ketoester. This &bgr;-ketoester may then lose carbon dioxide (decarboxylation) by either a hydrolytic or thermalytic pathway to yield the difatty ketones.
From the standpoint of sucrose polyester purity, it would be desirable to reduce the level of difatty ketones and/or &bgr;-ketoesters that are formed. However, this reduction in difatty ketone/&bgr;-ketoester formation needs to be carried out in a manner such that the yield of highly esterified sucrose polyesters, particularly sucrose octaesters, is not decreased significantly.
BACKGROUND ART
U.S. Pat. No. 3,963,699 (Rizzi et al), issued Jun. 15, 1976, discloses the preparation of polyol polyesters (in particular sucrose polyesters), by a solvent-free, two-stage transesterification of the polyol (e.g., sucrose) with fatty acid lower alkyl esters (e.g., fatty acid methyl esters) by: (1) heating (preferably to from about 130° to 145° C. under a pressure of from about 0.5 mm to about 25 mm Hg.) a mixture of sucrose, methyl esters, alkali metal fatty acid soap and a basic catalyst to form a melt; and (2) adding to this melt excess methyl esters to provide the sucrose polyesters.
U.S. Pat. No. 4,517,360 (Volpenhein), issued May 14, 1985, discloses the preparation of polyol polyesters, in particular sucrose polyesters, by a solvent-free, two-stage trans-esterification of the polyol (e.g., sucrose) with fatty acid lower alkyl esters (e.g., fatty acid methyl esters) by: (1) heating (preferably to from about 130° to 145° C. under a pressure of from about 0.5 mm to about 25 mm Hg.) a mixture of sucrose, methyl esters, alkali metal fatty acid soap, and a potassium, sodium or barium carbonate catalyst to form a melt; and (2) adding to this melt excess methyl esters to provide the sucrose polyesters.
U.S. Pat. No. 4,518,772 (VolDenhein), issued May 21, 1985, discloses the preparation of polyol polyesters, in particular sucrose polyesters, by a solvent-free, two-stage transesterification of the polyol (e.g., sucrose) with fatty acid lower alkyl esters (e.g., fatty acid methyl esters) by: (1) heating (preferably to from about 130° to 145° C. under a pressure of from about 0.5 mm to about 25 mm Hg.) a mixture of sucrose, methyl esters, alkali metal fatty acid soap, and basic catalyst where the soap:sucrose molar ratio is from about 0.6:1 to about 1:1 to form a melt; and (2) adding to this melt excess methyl esters to provide the sucrose polyesters.
European patent application 256,585 (van der Plank et al), published Feb. 24, 1988, alleges that the catalysts used in the process of U.S. Pat. No. 3,963,699, and the way in which these catalysts are used, increases the risk of forming by-products, e.g., by ester condensation, leading to the formation of &bgr;-ketoesters, e.g., by the reducing effect of sodium hydride, the recommended catalyst in the process of this U.S. patent. See page 2, lines 37-39. By-product formation is allegedly minimized by using a different process, e.g., forming an alkaline solution of sucrose which is then added to a mixture of soap and fatty acid methyl esters, followed by removal of the water and then heating to 110°-140° C. to form the sucrose polyesters.
European patent application 322,971 (Willemse), published Jul. 5, 1989, discloses a two-stage process for the transesterification of a polyol (e.g., sucrose) with fatty acid lower alkyl esters (e.g., fatty acid methyl esters) to provide polyol polyesters (e.g., sucrose polyesters). Pressure control is used during the first stage trans-esterification so that the sucrose is converted primarily to the corresponding monoesters and/or oligoesters, leading to higher yields of sucrose polyesters during the second stage transesterification. See page 2, right-hand column, lines 33-37. Pressure conditions used are from 60 to 180 millibars, preferably from 90 to 150 millibars. See page 3, left-hand column, lines 53-58. Pressure control during the first stage is also alleged to reduce foam formation. See page 2, right-hand column, lines 40-43. During the second stage, the pressure is reduced to less than 25 millibars, most preferably less than 5 millibars. See page 3, right-hand column, lines 15-23.
European patent application 349,059 (Willemse), published Jan. 3, 1990, discloses a process for making polyol polyesters (e.g., sucrose polyesters) in which a polyol and/or fatty acid oligoester thereof, is esterified by reaction with fatty acid lower alkyl esters (e.g., fatty acid methyl esters) in the presence o
Bruno, Jr. David Joseph
Corrigan Patrick Joseph
Flynn Katherine Eleanor
Holzschuh Nelson James
Howie John Keeney
Geist Gary
Hemm Erich D.
Roof Carl J.
The Procter & Gamble Co.
White Everett
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