Drug – bio-affecting and body treating compositions – Inorganic active ingredient containing – Elemental bromine or bromine compound containing
Reexamination Certificate
2001-06-28
2003-09-16
Pak, John (Department: 1616)
Drug, bio-affecting and body treating compositions
Inorganic active ingredient containing
Elemental bromine or bromine compound containing
C424S613000, C424S616000, C424S661000, C514S970000, C514S973000, C422S027000, C210S754000
Reexamination Certificate
active
06620441
ABSTRACT:
BACKGROUND
Background relating to, and one common way of producing, stabilized active bromine biocidal solutions are illustrated in U.S. Pat. Nos. 5,683,654; 5,795,487; and 5,942,126 to Dalimier et al, the entire disclosures of which are incorporated herein by reference. The method involves mixing an aqueous solution of alkali or alkaline earth metal hypochlorite with a water-soluble bromide ion source such as sodium bromide, allowing these materials to react to form an aqueous solution of unstabilized alkali or alkaline earth metal hypobromite, adding an alkali metal sulfamate either as a solid or as an aqueous solution to the hypobromite solution, and recovering a stabilized aqueous alkali or alkaline earth metal hypobromite solution.
While this method does improve the stability of the aqueous alkali or alkaline earth metal hypobromite solutions formed by use of the alkali metal sulfamate, it has been discovered that the “stabilized” hypobromite solution loses some of its active halogen content and consequent biocidal capabilities over the course of about 10 days after the concentrated product solution has been made. Also some loss of the alkali metal base typically present in the final finished product solution has been found to occur during this same period of time.
THE INVENTION
After considerable effort, during which many possible reasons for these problems were investigated, the cause of the above problems has finally been discovered and overcome. Surprisingly, the problem has been found to originate with the water-soluble bromide ion source used in the process, and more particularly with an impurity present therein, an impurity which, even if its presence had been taken into consideration, would not have been expected to survive the processing used in forming the “stabilized” hypobromite solution.
Pursuant to this invention it has been discovered that the loss of active halogen content and consequent biocidal capabilities over the course of several days after the concentrated product solution has been made is due to the presence of small amounts of alcohol, typically methanol, present as an impurity in the water-soluble bromide ion source used in the process. In commercial practice sodium bromide used in the manufacture of these “stabilized” hypobromite solutions has contained relatively small quantities of methanol. However, not until this invention have the existence of, cause of, or any solution to, the present problems been known or appreciated.
Accordingly, pursuant to one embodiment of this invention an aqueous solution of a water-soluble bromide ion source such as sodium bromide is oxidized in an aqueous medium in the absence of a detrimental amount of alcohol impurity to active bromine species. In other words, the water-soluble bromide ion source used is free of a detrimental amount of any alcohol, and the overall oxidation process is conducted in the absence of a detrimental amount of any alcohol. By “detrimental amount” of an alcohol with reference to the bromide ion source is meant that the water-soluble bromide ion source is either completely free of any detectible quantity of an alcohol or if any alcohol impurity is present therein, the amount of such alcohol is so small that it exerts no intolerable adverse effect upon the activity of final active halogen solution (expressed as wt % of chlorine, and as determinable by starch-iodine titration) during a 10-day period immediately following preparation of the product solution if stored at room temperature no higher than 30° C. in the absence of light. Likewise “detrimental amount” of an alcohol with reference to the aqueous reaction solution and the final product solution formed in the process means that at all times during the process and during foregoing the 10-day period of storage under the conditions just specified, the solutions are either completely free of any detectible quantity of an alcohol or if any alcohol impurity is present therein, the amount of such alcohol is so small that it exerts no intolerable adverse effect upon the activity of the final active halogen solution (expressed as wt % of chlorine, and as determinable by starch-iodine titration) during the 10-day period immediately following preparation of the product solution if stored at room temperature no higher than 30° C. in the absence of light.
As is customary in the art of water treatment chemicals for control of microbiocidal activity, analytical results are conventionally expressed in terms of chlorine, even when the analysis actually involves bromine species or a mixture of both chlorine and bromine species. Generally speaking, if the amount of alcohol present in the bromide ion source is at such a level that the alcohol would be in excess of about 0.11 wt % of the final stabilized active halogen solution, such amount of alcohol is a detrimental amount of alcohol as the loss of active halogen is intolerable and unacceptable. Amounts of alcohol of about 0.11 wt % and below are not deemed detrimental. If the amount of alcohol present in the bromide ion source is at such a level that the alcohol would constitute about 0.06 wt % or less of the final stabilized active halogen solution, the results are even better, and thus a maximum concentration of 0.06 wt % of alcohol, if any, based on the final product solution is preferred, and the lower the content of alcohol below this maximum, the better. Most preferred is the total absence of any detectable quantity of alcohol in the product solution.
Another embodiment of this invention is an aqueous microbiocidal solution having a pH of at least about 13 containing at least 4 wt %, and preferably at least 6 wt %, of stabilized active halogen species formed by oxidation of an alkali metal bromide, preferably sodium bromide, and incorporation of a stabilizer for the active bromine, preferably a source of sulfamate anion, such solution being characterized in that during the 10-day period immediately following its preparation, such product solution, if stored at room temperature no higher than 30° C. in the absence of light, undergoes no appreciable loss of active halogen content expressed in terms of wt % of active chlorine, and as determinable by starch-iodine titration.
The oxidation can be conducted in the absence of a stabilizer such as a sulfamate source, followed by mixing the stabilizer with the reaction solution containing the active halogen species to form a stabilized concentrated solution of active halogen. Alternatively, a small amount of the stabilizer can be present in the initial reaction solution and additional amounts of the stabilizer can be added during and after the oxidation. Irrespective of the pH of the reaction solution during the reaction, the pH of the final concentrated solution should be at least about 12 and preferably at least about 13, and thus if necessary, and preferably, a water-soluble inorganic base such as alkali metal hydroxide (most preferably sodium hydroxide) is added to the solution. As noted above, all stages of the process are conducted in the absence of a detrimental quantity of any alcohol such as methanol. Preferably the temperature is maintained below about 25° C. and more preferably below about 20° C. during the entire reaction.
In a preferred embodiment, this invention provides a process which comprises:
a) mixing an aqueous solution of alkali or alkaline earth metal hypochlorite with a water-soluble source of alkali metal bromide ion in the presence of a small amount of a water-soluble source of sulfamate ion;
b) allowing the solution formed in a) to undergo reaction to form a solution containing a mixture of stabilized and unstabilized active halogen species while mixing additional amounts of a water-soluble source of sulfamate ion to the reaction mixture; and
c) mixing a water-soluble source of alkali metal base, preferably a 20 to 50 wt % aqueous solution of NaOH, to solution formed in b) to form a stabilized solution of active halogen species having a pH of at least about 12, and preferably at least about 13;
the process being further chara
Dadgar Alireza M.
Kendall John K.
McKinnie Bonnie G.
Albemarle Corporation
Pak John
Spielman, Jr. Edgar E.
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