Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic halides
Reexamination Certificate
2000-06-07
2002-08-06
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic halides
C562S857000, C562S859000
Reexamination Certificate
active
06429334
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a process that can be used for producing an organic anhydride, an organic acid halide, or combinations thereof.
BACKGROUND OF THE INVENTION
Acid anhydrides and acid chlorides are important intermediates for the chemical industry.
Aliphatic and aromatic acid anhydrides have a variety of chemical uses, including the preparation of certain esters, such as cellulose esters and aspirin; the manufacture of alkyd resins; modification of the curing of certain epoxy resins and of polyester properties; as a retarder in rubber vulcanization; and in various syntheses, such as those of phenolphthalein, polypeptides, and peroxycarboxylic acids.
Acid chlorides, such as isophthaloyl and terephthaloyl chlorides are important polymer intermediates, for instance in the production of polymers for fibers and polycarbonates. Such applications require very low levels of impurities and by-products. Monofunctional contaminants can seriously reduce the molecular weight of a polyester and adversely affect the physical properties of fibers spun from the polymer. Traces of colored impurities can be unacceptable in polycarbonate products intended for optical uses.
Isophthaloyl chloride can be prepared from isophthalic acid by many routes. Commercially, the preferred chlorinating agent is phosgene, as described by Carnahan in U.S. Pat. No. 2,657,233. The uncatalyzed or “thermal” reaction is, however, slow. A problem is that, as the temperature is raised, the solubility of phosgene in the liquid phase decreases, limiting the acceleration of the reaction.
Consequently, numerous catalytic systems have been proposed for the reaction of acids with phosgene to produce the acid chlorides. A number of nitrogen containing compounds, e.g., amides and ureas are in use. An important example is dimethylformamide (hereinafter DMF) as described by Seagraves in U.S. Pat. No. 5,113,016. The active catalyst in the DMF process is the reaction product of DMF and phosgene. This material is thermally unstable, decomposing rapidly above 100° C., especially in the absence of excess acid.
Thus, the MF/phosgene complex is only marginally stable under the reaction conditions, and impurities such as formylbenzoyl chloride and dichlorotoluoyl chloride are formed. Seagraves, in U.S. Pat. No. 5,113,016, cited above, reduced the amount of these impurities by introducing an oxidizing air sparge into the process. Other nitrogen-containing catalysts also have the disadvantage of marginal stability under the reaction conditions. Essentially all the impurities in the product using the DMF catalyst result from decomposition of the DMF catalyst. Japanese Patent Kokai: Sho 56-103134, Nagata, et al discloses a purification procedure involving the addition of certain metals and their salts, including titanium and titanium chloride, to the reaction product formed by the reaction of organic carboxylic acids and phosgene using lower aliphatic amides as the catalyst.
Decomposition of the DMF catalyst results in emissions of methyl chloride. Methyl chloride is of environmental concern as a “greenhouse gas”. It also results in the formation of dimethylcarbamoyl chloride, a carcinogen, requiring responsible disposal, and careful control in the product. DMF decomposition further results in a tar purge stream requiring appropriate disposal and causing a yield loss. Finally, the DMF catalyst species is very corrosive, increasing the cost of materials of construction.
Other processes have been proposed using phosphorus compounds, nitrogen heterocyclic compounds, amines, and other catalysts. All possess some combination of disadvantages, high cost, higher reaction temperatures, lower yields, etc.
It would be desirable to develop a process for using organic acids to form the anhydride and, in the presence of phosgene, to form the acid chloride. The present invention provides such a process.
SUMMARY OF THE INVENTION
A process that can be used to produce an organic anhydride, an organic acid halide, or mixtures thereof is provided. The process comprises contacting a reaction medium with a catalyst in which the reaction medium comprises (1) at least one organic acid, (2) combination of the organic acid and phosgene, (3) combination of at least one organic anhydride and phosgene, or (4) combination of the organic acid, the organic anhydride, and phosgene; and the catalyst is a Group IVB transition metal halide.
DETAILED DESCRIPTION OF THE INVENTION
The contacting of a reaction medium with a catalyst can be carried out under any suitable conditions. Generally, the reaction medium comprising at least one organic acid, mixtures of at least one organic acid and phosgene, or mixtures of at least one organic anhydride and phosgene can be contacted with the catalyst at an elevated temperature under dry conditions and optionally with a solvent. The catalyst is a Group IVb transition metal halide.
The contacting of at least one organic acid with the catalyst produces an acid anhydride or acid anhydrides. The contacting of organic acid with phosgene produces an acid chloride or acid chlorides. An organic acid chloride or acid chlorides can also be produced by contacting at least one organic acid anhydride and phosgene. No aliphatic amide is used in the process of this invention, avoiding the multiple problems of decomposition and corrosivity characterizing the prior art.
The organic acid can be a branched, straight chain, or cyclic alkanoic, alkenoic, or alkynoic acid; or an aryl, alkyl aryl organic acid having one or more carboxylic acids groups; or a mixture of such acids. Examples of suitable organic acids include, but are not limited to, aliphatic carboxylic acids of 2 to about 20 carbon atoms, and aromatic and cycloaliphatic carboxylic acids of 7 to about 24 carbon atoms, per molecule. The suitable acids can contain 1 to 3 carboxyl groups. For example, suitable aliphatic acids include, but are not limited to, acetic acid, butyric acid, lauric acid, palmitic acid, neo-pentanoic acid, propanoic acid, chloroacetic acid, dichloroacetic acid, succinic acid, adipic acid, sebacic acid, acrylic acid, methacrylic acid, succinic acid, and mixtures of two or more thereof; suitable aromatic acids include, but are not limited to, benzoic acid, m-nitrobenzoic acid, isophthalic acid, phthalic, phenylacetic acid, p-chlorobenzoic acid, trans-cinnamic acid, m-toluic acid, terephthalic acid, and mixtures of two or more thereof; suitable cycloaliphatic acid includes, but is not limited to, cyclohexane carboxylic acid; and suitable mixtures of acids are benzoic and terephthalic acids, and isophthalic and terephthalic acids.
The suitable acid anhydrides for the purpose of this invention are anhydrides of the general formulae:
wherein each monovalent R or divalent R′ independently represents an organic radical such as a hydrocarbon group. Particularly suitable acid anhydrides are those having an aliphatic, cycloaliphatic, or aromatic group. Thus, R or R′ can be alkylene, alkenylene, cycloalkylene, arylene or like divalent, saturated and unsaturated radicals. Preferably, the number of carbon atoms in the R or R′ groups is from 1 to 24 and more preferably 1 to 12 per group.
The organic acid anhydride can be any anhydride of the above-listed organic acids. Illustrative acid anhydrides include, among others, acetic anhydride, butyric anhydride, hexanoic anhydride, benzoic anhydride, trimellitic anhydride, octanoic anhydride, chloroacetic anhydride, acrylic anhydride, phenylacetic anhydride, adipic anhydride, sebacic anhydride, nitrobenzoic anhydride, chlorobenzoic anhydride, toluic anhydride, isophthalic anhydride, terephthalic anhydride, succinic anhydride, and mixtures of two or more thereof.
For the purposes of describing this invention, but not to limit the scope of the invention, isophthalic acid and other specific acids and anhydrides are used as example starting materials.
The catalyst is a Group IVb transition metal halide, such as titanium or zirconium tetrachloride or tetrabromide. The term “halide” as used herein to de
Deemie Robert W.
E. I. du Pont de Nemours and Company
Killos Paul J.
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