Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-12-11
2002-06-04
Lambkin, Deborah C. (Department: 1626)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S127000, C558S162000, C558S092000
Reexamination Certificate
active
06399685
ABSTRACT:
BACKGROUND
Arylene polyphosphate esters such as bisphenol-A bis(diphenylphosphate) are useful as flame retardants for various polymeric materials. Reported methods for their preparation typically involve reacting a diphenolic compound such as bisphenol-A with a diarylphosphoryl halide such as diphenylphosphoryl chloride. In such synthesis operations the product as produced is associated with various impurities such as unreacted starting material, partially phosphorylated product, acidic impurities, color bodies, and/or catalyst residues. Washing procedures that have been used to remove such impurities are of ten plagued by the formation of emulsions. See for example, U.S. Pat. Nos. 3,254,973; 5,420,327; and 5,756,798; and WO 98/35970, published Aug. 20, 1998.
The purification of bisphenol-A bis(diphenylphosphate) is complicated by the fact that not only is there the possibility of emulsion formation but in addition, during washing procedures product losses due to hydrolytic degradation can occur. Emulsions, even if formed sporadically, can consume considerable time and effort in effectively dealing with them. Hydrolytic degradation, if experienced, cannot be undone; product loss is inevitable. Moreover, crude bisphenol-A bis(diphenylphosphate) as formed is a viscous liquid and thus the removal of impurities from impure or crude bisphenol-A bis(diphenylphosphate) reaction product is not an easy proposition. Thus the provision of an effective way of reducing or preventing the formation of emulsions and of suppressing hydrolysis during the purification of impure bisphenol-A bis(diphenylphosphate) would be of considerable advantage.
BRIEF SUMMARY OF THE INVENTION
This invention is deemed to provide an effective and efficient way of reducing or preventing the formation of emulsions and of suppressing hydrolysis during the purification of impure bisphenol-A bis(diphenylphosphate). The process technology of this invention is readily adaptable for use on an industrial scale, and is deemed independent of the particular process technology used in forming the impure product. Moreover, the process technology does not require large capital investments or involve excessive operating costs.
In one of its embodiments this invention is a process of minimizing or preventing emulsion formation and suppressing hydrolytic product degradation during the purification of an impure bisphenol-A bis(diphenylphosphate) product, which process comprises:
a) mixing such impure product with a liquid hydrocarbon solvent comprising at least one aromatic hydrocarbon and at least one paraffinic hydrocarbon in proportions of such impure product to such liquid hydrocarbon solvent in the range of about 25:75 to about 75:25 to form a hydrocarbon solution;
b) washing hydrocarbon solution from a) one or more times with an aqueous alkaline washing solution that has a specific gravity that differs from the specific gravity of the hydrocarbon solution by at least about 0.05 gram per cubic centimeter, after each such washing having the washed mixture settle into a purified organic phase and a separate aqueous phase, and separating these phases from each other, each such washing and separating being performed with the phases at a temperature in the range of about 25 to about 100° C.; and
c) after completing the one or more washings and separations in b), washing the resultant purified organic phase one or more times with water to remove alkaline components from the hydrocarbon solution, after each such washing having the washed mixture settle into a less alkaline purified organic phase and a separate aqueous phase, and separating these phases from each other, each such washing and separating being performed with the phases at a temperature in the range of about 25 to about 100° C.
The paraffinic hydrocarbon(s) used in forming the liquid hydrocarbon solvents employed in the practice of this invention can be (i) one or more cyclic paraffinic hydrocarbons (i.e., at least one cycloparaffinic hydrocarbon), (ii) one or more acyclic paraffinic hydrocarbons, or (iii) a mixture of (i) and (ii).
In preferred embodiments this invention is a process of minimizing or preventing emulsion formation and suppressing hydrolytic product degradation during the purification of an impure bisphenol-A bis(diphenylphosphate) product, which process comprises:
1) mixing (i) an aqueous buffer solution, or a dilute acid wash, or a water wash, the pH of any of which is less than about 5.5, with (ii) the impure product in the presence of a liquid hydrocarbon solvent comprising at least one aromatic hydrocarbon and at least one paraffinic hydrocarbon in proportions of impure product to such liquid hydrocarbon solvent in the range of about 25:75 to about 75:25, and then having the mixture settle into an organic phase and a separate aqueous phase, and separating these phases from each other;
2) washing organic phase from 1) one or more times with an aqueous alkaline washing solution that has a specific gravity that differs from the specific gravity of the organic phase by at least about 0.05 gram per cubic centimeter, after each such washing having the washed mixture settle into a purified organic phase and a separate aqueous phase, and separating these phases from each other, each such washing and separating in 2) being performed with the phases at a temperature in the range of about 25 to about 100° C.; and
3) after completing the one or more washings and separations in 2), washing the resultant purified organic phase one or more times with water to remove alkaline components from the hydrocarbon solution, after each such washing having the washed mixture settle into a less alkaline purified organic phase and a separate aqueous phase, and separating these phases from each other, each such washing and separating in 3) being performed with the phases at a temperature in the range of about 25 to about 100° C.
If in the above embodiments there are solids present in the solution formed either in a) or in 1), these can be separated as by filtration, decantation, or centrifugation. Although the number of times each of b) and c) above, or each of 2) and 3) above, is conducted depends on various factors such as the scale of operation and the relative quantities of aqueous washing liquids to organic phase, in a plant scale operation b) above or 2) above will typically be conducted twice, and c) above or 3) above will typically be conducted from two to three times as needed to suitably remove the alkaline residues from the purified product. When conducting b) above or 2) above at least twice, it is preferred that the concentration of the base such as sodium hydroxide in the first alkaline washing solution be higher than in the ensuing alkaline washing solution(s).
In the practice of the above embodiments, the times required in b) and c) above, or in 2) and 3) above, for the phases to separate and settle is typically quite short. For example, on a one-liter scale, each such separation and settling into separate liquid phases can occur in as little as about 1 to 2 minutes after agitation has been terminated.
If it is desired to isolate the purified bisphenol-A bis(diphenylphosphate) product, the final organic phase from c) above or 3) above is treated to remove the organic solvent. This can be readily accomplished either in vacuo and/or by removing the solvent(s) by azeotropic or steam distillation.
In particularly preferred embodiments, the organic solvent used is a mixture comprising in the range of about 10 to about 70 wt % of toluene, and in the range of about 10 to about 70 wt % of at least one liquid cycloparaffinic hydrocarbon, most preferably cyclohexane or methylcyclohexane, or both, with the total of these components being at least 90 wt %, with the balance, if any, to 100% being at least one other aromatic hydrocarbon. An especially preferred organic solvent is a liquid mixture consisting essentially of (i) toluene and (ii) cyclohexane or methylcyclohexane, or both, in a weight ratio of (i):(ii) in the range of about 30:70 to about 70:30. It is also parti
Broeker Jeffrey L.
Dadgar Billie B.
Harrod William B.
Heidebrecht Gary D.
Klobucar W. Dirk
Albemarle Corporation
Lambkin Deborah C.
Spielman, Jr. E. E.
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