Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2000-07-31
2002-02-05
Solola, T. A. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C549S315000
Reexamination Certificate
active
06344567
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for producing an alkaline earth metal salt of an ascorbic acid-2-phosphoric ester, which is an ascorbic acid derivative useful as a cosmetic, a medical product or a food additive and widely used in various industrial fields including these.
BACKGROUND OF THE INVENTION
In general, ascorbic acid (vitamin C) is known to have various physiological and pharmacological activities.
For example, ascorbic acid is used as a whitening cosmetic because of its effect of preventing melamine pigmentation, or as an artificial feed additive for preventing cultured fish from vitamin C deficiency. However, the ascorbic acid is unstable in oxygen or heat and readily undergoes coloration or degradation. Therefore, ascorbic acid generally used is stabilized against oxygen, heat or the like by forming the hydroxyl group at the 2-position of an ascorbic acid into a phosphoric ester. More specifically, ascorbic acid widely used is a vitamin C derivative easily soluble in water, in the form of a salt, particularly magnesium salt, of an ascorbic acid-2-phosphoric ester.
The process for producing an ascorbic acid-2-phosphoric ester magnesium salt (hereinafter sometimes referred to as “APM”) from an ascorbic acid-2-phosphoric ester (hereinafter sometimes referred to as “2-AP”) using magnesium oxide, magnesium hydroxide, magnesium carbonate or the like is described in a large number of publications and patents such as JP-B-52-18181 (the term “JP-B” as used herein means an “examined Japanese patent publication”), JP-A-59-51293 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-A-2-279690. However, specific conditions in the operation are not reported in detail.
JP-A-2-286693 describes a technique of adding magnesium oxide to an aqueous solution containing 2-AP obtained by phosphorylating 5,6-isopropylidene-L-ascorbic acid, while adjusting the pH using KOH to 8.5 to 9.0, separating the undissolved content by filtration, evaporation-concentrating the resulting solution, further crystallizing the solution with methanol, and filtering the solids obtained to produce APM.
However, in the case where APM is produced under the above-described conditions, excess phosphoric acid or a salt thereof is liable to intermingle in the product in a higher content or since the sedimentation of suspended matters is not completed within a short time, the filtration resistance increases and a washing operation is separately necessary. Thus, this technique is disadvantageous in the cumbersome process and also not satisfied in view of the cost.
In general, in the case of obtaining 2-AP by the phosphorylation reaction of an ascorbic acid, excess phosphoric acid, which is generated from the phosphorylating agent added and which cannot be completely removed in the purification step, remains in the solution obtained. This excess phosphoric acid reacts with a part of magnesium oxide added for the neutralization reaction of 2-AP and forms insoluble magnesium phosphate which is afterward separated by filtration and removed as an impurity. However, under conventional conditions, the magnesium phosphate cannot exhibit sufficiently high reactivity or precipitating property. Therefore, the excess phosphoric acid or magnesium phosphate intermingles in the solution of the step to adversely affect the product quality, and also a load is imposed on the filtering medium at the filtration of the residue, which is necessary in the next step.
SUMMARY OF THE INVENTION
The present invention has been made under these circumstances and provides a process for producing an ascorbic acid-2-phosphoric ester salt, where an ascorbic acid-2-phosphoric ester salt solution reduced in the content of excess phosphoric acid or a salt thereof mingled in the solution can be obtained from a solution containing an ascorbic acid-2-phosphoric ester or a salt thereof and a phosphoric acid or a salt thereof, with industrially high efficiency.
As a result of extensive investigations to solve the above-described problems, the present inventors have found that when an alkaline earth metal compound is added to a solution containing an ascorbic acid-2-phosphoric ester or a salt thereof and also containing phosphoric acid or a salt thereof, under a predetermined temperature condition to have a pH within a constant range, free phosphoric acid can be removed in the form of insoluble phosphoric acid alkaline earth metal having good precipitating property without imposing a load on the filtration medium. Thereby an ascorbic acid-2-phosphoric ester alkaline earth metal salt freed from any effect of the phosphoric acid contained on the quality can be produced efficiently.
More specifically, the present invention relates to the following embodiments:
(1) a process for producing an alkaline earth metal salt of an ascorbic acid-2-phosphoric ester, comprising adding an alkaline earth metal compound to a stock solution containing an ascorbic acid-2-phosphoric ester or a salt and a phosphoric acid or a salt thereof, at a liquid temperature of 0 to 30° C. to adjust the pH to 8.5 to 10.5;
(2) a process for producing an alkaline earth metal salt of an ascorbic acid-2-phosphoric ester as described in (1) above, which comprises a step of precipitating and separating the alkaline earth metal salt of phosphoric acid and recovering the supernatant;
(3) a process for producing an alkaline earth metal salt of an ascorbic acid-2-phosphoric ester as described in (2) above, which comprises precipitating and separating the alkaline earth metal salt of phosphoric acid and concentrating and crystallizing the supernatant recovered to obtain an alkaline earth metal salt of an ascorbic acid-2-phosphoric ester;
(4) a process for producing an alkaline earth metal salt of an ascorbic acid-2-phosphoric ester as described in any one of (1) to (3) above, wherein the molar ratio of the phosphoric acid or a salt thereof to the ascorbic acid-2-phosphoric ester or a salt thereof in the stock solution is from 0.02 to 0.5;
(5) a process for producing an alkaline earth metal salt of an ascorbic acid-2-phosphoric ester as described in any one of (1) to (4) above, wherein after the step of precipitating and separating the alkaline earth metal salt of phosphoric acid and recovering the supernatant, the molar ratio of the phosphoric acid or a salt thereof to the alkaline earth metal salt of an ascorbic acid-2-phosphoric ester in the supernatant is less than 0.02;
(6) a process for producing an alkaline earth metal salt of an ascorbic acid-2-phosphoric ester as described in any one of (1) to (5) above, wherein the alkaline earth metal is magnesium;
(7) a process for producing an alkaline earth metal salt of an ascorbic acid-2-phosphoric ester as described in any one of (1) to (6) above, wherein the alkaline earth metal compound is an oxide or hydroxide of an alkaline earth metal;
(8) a process for producing an alkaline earth metal salt of an ascorbic acid-2-phosphoric ester as described in any one of (1) to (7) above, wherein the stock solution has a pH of 3 or less.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is described in detail below.
The present invention relates to a process for producing an alkaline earth metal salt of an ascorbic acid-2-phosphoric ester, comprising adding an alkaline earth metal compound to a stock solution containing an ascorbic acid-2-phosphoric ester or a salt and also containing a phosphoric acid or a salt thereof, at a liquid temperature of 0 to 30° C. to adjust the pH to 8.5 to 10.5.
In the production process of an ascorbic acid-2-phosphoric ester alkaline earth metal salt of the present invention, the starting solution is not particularly limited as long as it is a solution containing 2-AP. Any of a 2-AP solution, a 2-AP alkali metal salt solution or a 2-AP alkaline earth metal salt solution may be used. For example, a 2-AP-containing solution obtained by directly phosphorylating ascorbic acid (see, JP-B-433-9219, JP-B-45-23746, JP-A-6-345786) and a 2-AP-containi
Fujiwara Yoshio
Kobayashi Yuji
Saito Makoto
Showa Denko Kabushiki Kaisha
Solola T. A.
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