Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
1994-06-27
2001-07-10
Jones, Dwayne C. (Department: 1614)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S486000, C562S593000, C562S600000, C562S606000, C562S607000, C562S608000, C562S609000
Reexamination Certificate
active
06258980
ABSTRACT:
The present invention relates to the production of metal salts of organic acids. More particularly it relates to the production of such salts and their dissolution in a non-aqueous solvent.
BACKGROUND OF INVENTION
The production of metal salts of organic acids by the reaction of a basic compound of the metal with the appropriate acid is known. However, such a process usually produces water as a function of the acid-base neutralization reaction which occurs. This water is usually undesirable and has to be removed by physical means to yield the anhydrous salt which is normally required. Many techniques have been proposed for removing this water, for example, distillation. However, high temperatures or vacuum are needed to make this process efficient, which is often impractical because the salts formed are normally high melting solids, and unless special equipment is utilized do not lend themselves to easy or effective processing. Indeed, in some cases, conventional methods for removal of water by the use of heat, even with reduced pressure, lead to a material from which removal of further water (free or water of hydration) is difficult by conventional heating methods.
SUMMARY OF INVENTION
According to the present invention there is provided a process for the production of substantially anhydrous salts of organic acids which comprises reacting a basic compound of the metal with the appropriate organic acid, removing a substantial proportion of water present so as to produce the salt or its hydrate as a liquid phase; such liquid phase is then dissolved in a non aqueous solvent.
DETAILED EMBODIMENT OF THE INVENTION
The water present arises not only from water which may have been present as the solvent for an aqueous solution of the basic compound used in the reaction but may also be produced by the reaction. A substantial proportion of such water present may be removed e.g. to a level of about 0.05% to 5% based on the weight of the product, preferably about 0.5 to 1.5%, most preferably about 1% by conventional distillation, usually at atmospheric pressure, utilizing temperatures up to the order of 350° C. The water removal is preferably carried out in two stages, the first one removing part of the water e.g. to a level of about 5 to 20% followed by a second removal down to the final level required.
The present invention has particular applicability to the production of those metal salts which as such, or particularly in a hydrate form, have a melting point of less than 250° C. For such salts (or their hydrates), the distillation to remove a substantial proportion of the water can be conducted, not only in its earlier stages but also in its latter stages wherein effectively the liquid salt or liquid hydrate thereof is being treated, with stirring to assist removal of further water.
The metal salt resulting from the distillation may be cooled to some extent, but while still at elevated temperature and in a liquid phase, is then dissolved in the desired non aqueous solvent. The water content of the hot liquid metal salt being dissolved in the solvent is usually less than 5%. It can be substantially lower so that the water content of the solution of the metal salt in the non-aqueous solvent can be as low as of the order of 1% and can be considered as substantially anhydrous.
The metal is for example an alkali metal i.e. lithium, sodium, potassium, rubidium or cerium or an alkaline earth metal i.e. beryllium, magnesium, calcium, strontium or barium, and the basic compound of the metal may be, for example, a hydroxide or carbonate of an alkali metal or an alkaline earth metal and the organic acid may be, for example, one derived from an aliphatic hydrocarbon e.g. a carboxylic acid e.g. monocarboxylic acid, a dicarboxylic acid or a polycarboxilic acid, typically containing from about 2 to about 20 carbon atoms. If an alkali metal hydroxide is employed, it may be, for example, a commercially supplied material of 50% strength in water. Its use in such form would of course lead to the formation of a comparatively dilute solution of the metal salt in water.
The metal salt is preferably a sodium or potassium salt. The acid is preferably 2-ethyl hexanoic acid. The present invention is of particular applicability to the reaction of potassium hydroxide or carbonate with an organic acid such as, for example, 2-ethyl hexanoic acid leading to the formation of an aqueous solution or slurry of potassium 2-ethyl hexanoic.
The removal of water from the solution or slurry of the metal salt is undertaken firstly, as referred to above, by conventional distillation at atmospheric pressure, usually with agitation, at up to about 350° C. Preferably the temperature employed is in the range of 100° C. to 350° C., more preferably 100° C. to 250° C. In practice, the temperature rises as the amount of water present diminishes. In the region of the upper temperature of the range employed, the last traces of water which might remain can be substantially removed by applying a slight vacuum to the system. Also in that latter stage, it is preferred to maintain the upper limit of the temperature in the range of 200° C. to 250° C. in order to avoid charring or other detrimental thermal processes.
The molten metal salt, with the desired low water content, is dissolved while still hot but usually at a temperature lower than the upper limit of the temperature ranges referred to above, in a non-aqueous solvent in which the metal salt has reasonable solubility by slow addition. The addition is preferably conductional so that refluxing of the solvent cools the solution which forms. Classes of useful solvents include alcohols, for example isopropanol, esters, for example ethyl acetate, and ethers, for example tetrahydrofuran.
If the salt produced is potassium 2-ethylhexanoate, the concentration of it in the solution is usually in the range of 10 to 90%, with a water content of less than 5%, usually of the order of 1%.
The process of the present invention may be carried out using conventional equipment.
Once formulated one use of this product, either as a solution or as an anhydrous salt, is as a source of metal ions e.g. in the pharmaceutical industry, specifically in antibiotics production.
REFERENCES:
patent: 2895990 (1959-07-01), Larrison et al.
patent: 3719654 (1973-03-01), Stone
patent: 4374777 (1983-02-01), Henry
patent: 4558070 (1985-12-01), Bauer et al.
patent: 1173814 (1969-10-01), None
Contracts Chemicals Ltd.
Jones Dwayne C.
Smith Gambrell & Russell
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