Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2000-02-02
2001-11-13
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S472000
Reexamination Certificate
active
06316666
ABSTRACT:
The present invention relates to a method for producing purified phenylenedioxydiacetic acids.
Phenylonedioxydiacetic acids represented by the following general formula (I):
wherein, R represents a halogen, carboxyl group or hydrocarbon group having 1 to 4 carbon atoms, and n represents an integer from 0 to 3,
are used as raw materials of polyesters, polyamides and the like and industrially useful compounds
For producing purified phenylenedioxydiacetic acids, a method is known in which phenylenedioxydiacetic acids is precipitated from an alkaline aqueous solution of crude phenylenedioxydiacetic acids, which mainly contain phenylenedioxydiacetic acids, by the action of an acid. In an example of such methods, a mineral acid is used and the precipitation is conducted at a temperature of 80° C. or higher, followed by keeping the temperature of the system at 80° C. or higher (JP-A-4-173764).
However, in this method, the purity and the like of the resultant purified phenylenedioxydiacetic acids are not fully satisfactory, and improvements in these points hive been desired.
Under these circumstances, the present inventors have intensively studied the method for the precipitation of phenylenedioxydiacatic acids from an alkaline aqueous solution of crude phenylenedioxydiacetic acids by the action of an acid to obtain highly purified phenylenedioxydiacetic acids at high yield As a result, the present inventors have found that highly purified phenylenedioxydiacetic acids can be obtained at high yield by conducting the precipitation of phenylenedioxydiacetic acids from an alkaline aqueous solution of crude phenylenedioxydiacetic acids by mixing the solution with an acid at 0 to 50° C., followed by raising and keeping the temperature of the mixture at 80 to 110° C. The present inventor further found that at least 10% by weight or more of the phenylenedioxydiacetic acids needs to be precipitated at 0 to 50° C. in order to obtain intended highly purified products. The present invention was thus completed.
The present invention provides a method for producing purified phenylenedioxydiacetic acids in which an alkaline aqueous solution of crude phenylenedioxydiecetic acids which mainly contains phenylenedioxydiacetic acids represented by the following general formula (I):
wherein, R represents a halogen, carboxyl group or hydrocarbon group having 1-4 carbon atoms, and n represents an integer from 0 to 3, is mixed with a mineral acid to precipitate the phenylenedioxydiacetic acids,
wherein at least 10% by weight of the alkaline aqueous Solution is mixed with a mineral acid at 0 to 50° C.; and, after completion of the mixing, the temperature of the mixture is kept at 80 to 110° C.
The phenylenedioxydiacetic acids in the present invention is represented by the above-described general formula (I).
Examples of the substituent R in the f formula (I) include halogen atoms such as fluorine, chlorine and bromine, carboxyl group or salts thereof, and hydrocarbon groups having about 1 to 4 carbon atoms such as methyl, ethyl, t-butyl groups. in the formula (I), “n” is an integer of 0 to 3, and preferably 0.
Crude phenylenedioxydiacetic acids which are raw materials in the present invention mainly contain the above-described phenylenedioxydiacetic acids of formula (I).
The content of the phenylenedioxydiacetic acids of formula (I) in crude phenylenedioxydiacetic acids is preferably about 80% by weight or More, particularly preferably about 90% by weight or more in terms of solid components.
The alkaline aqueous solution of crude phenylenedioxydiacetic acids used in the present invention is an alkaline aqueous solution dissolving phenylenedioxydiacetic acids of the formula (I) ar well as impurities. It may further contain impurities as well as phenylenedioxydiacetic acids of the formula (I) which are not dissolved and are dispersed in the form of solid. That is, the alkaline aqueous solution of crude phenylenedioxydiacetic acids used in the present invention may be in the form of slurry.
The production method thereof is not particularly restricted and the following methods (1) and (2) can be exemplified.
(1) Dihydroxybenzenes represented by the following general formula (II)
wherein, R and n are as defined above, are reacted with ethylene oxide in the presence of alkali, and the resulting phenylenedioxy diethanols are oxidized in an alkaline aqueous solution to obtain an alkaline aqueous solution of crude phenylenedioxydiacetic acids (JP-B62-28940, JP-A-3-500653 and JP-A-3-38544).
(2) Dihydroxybenzenes of the formula (II) and halogenated acetic acid are etherified in an alkaline aqueous solution to obtain an alkaline aqueous solution of crude phenylenedioxydiacetic acids (JP-A-4-173764).
Among the above, the method (2) is preferable since the content of phenylenedioxydiacetic acids in crude phenylenedioxydiacetic acids is higher.
Examples of the dihydroxybenzenes of the formula (II) include resorcinol and hydroquinone. Among them, resorcinol is preferred.
Examples of the halogenated acetic acid include monochloro acetic acid and monobromo acetic acid. Among them, monochloro acetic acid is preferred.
The amount of the halogenated acetic acid used in the method (2) is usually from about 2.0 to 4.0 mol, preferably from about 2.2 to 3.0 d mol per 1 mol of the dihydroxybenzenes.
Examples of the alkali used in the above-described method (2) include hydroxides, carbonates and the like of alkali metals such as sodium and potassium. Among them, sodium hydroxide and potassium hydroxide are preferable.
The amount of the alkali is usually from about 1.8 to 2.5 equivalent, preferably from about 1.9 to 2.1 equivalent per 1 mol of halogenated acetic acid.
The preferable concentration of an alkali in the aqueous solution varies depending on the kind of an alkali. In the case of sodium hydroxide, it is preferably from about 20 to 50% by weight.
The etherification reaction can be conducted, for example, by the following methods (1)-(3) as well as other methods.
(1) A halogenated acetic acid and an aqueous solution of alkali are poured together into an aqueous solution of dihydroxybenzenes.
(2) A halogenated acetic acid and an aqueous solution of alkali are poured together into a solution prepared by dissolving dihydroxybenzenes with a small amount of an aqueous solution of alkali, and then mixed.
(3) An alkaline aqueous solution containing dihydroxybenzenes dissolved and halogenated acetic acid are poured together in a reaction vessel and mixed.
The etherification reaction is conducted preferably at a pH of the reaction solution of about 7.5 to 12, more preferably of about 7.5 to 8.5. A pH of the reaction solution of less than 7.5 is not preferable since hydroxyphenyleneoxyacetic acid tend to increase. A pH over 12 is not preferable since then halogenated acetic acid tends to be hydrolyzed.
The etherification reaction is conducted at a temperature of usually from about 80 to 110° C., preferably from about 90 to 110° C.
The etherification reaction is preferably conducted until halogenated acetic acid in the reaction mass disappears. The reaction time is usually from about 1 to 10 hours.
In the present invention, an alkaline aqueous solution of crude phenylenedioxydiacetic acid; is mixed with a mineral acid to precipitate phenylenedioxydiacetic acids, and at least 10% by weight of the alkaline aqueous solution is mixed with a mineral acid at 0 to 50° C. Thereafter, the temperature of the mixture is raised and, after completion of the mixing, the temperature is kept at 80 to 110° C.
When leas than 10% by weight of an alkaline aqueous solution of crude phenylenedioxydiacetic acids is mixed with a mineral acid at 50° C. or lower, impurities in the resulting purified phenylenedioxydiacetic acids increase, and highly purified phenylenedioxydiacetic acids cannot be obtained. Although a temperature of leet than 0° C. is possible for mixing the alkaline aqueous solution with a mineral acid, such a temperature is economically undesirable since a cooling apparatus and the like are required.
Examples of the method for mixing the alkal
Kamikawa Takashi
Morimoto Junji
Ueda Hiroshi
Fitch Even Tabin & Flannery
Killos Paul J.
Sumitomo Chemical Company Ltd.
LandOfFree
Method for producing purified phenylenedioxydiacetic acids does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for producing purified phenylenedioxydiacetic acids, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for producing purified phenylenedioxydiacetic acids will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2604114