Drug – bio-affecting and body treating compositions – Inorganic active ingredient containing – Elemental sulfur or compound thereof
Reexamination Certificate
1999-12-08
2002-12-17
Pryor, Alton (Department: 1616)
Drug, bio-affecting and body treating compositions
Inorganic active ingredient containing
Elemental sulfur or compound thereof
C424S663000, C424S722000, C424S723000
Reexamination Certificate
active
06495169
ABSTRACT:
BACKGROUND
Bromine-based biocides have proven biocidal advantages over chlorination-dechlorination for the microbiological control of cooling waters and disinfection of waste treatment systems. The water treatment industry recognizes these advantages to be cost-effective control at higher pH values, almost no loss in biocidal activity in the presence of ammonia, and effective control of bacteria, algae and mollusks.
A common way of introducing bromine based biocides into a water system is through the use of aqueous NaBr in conjunction with NaOCl bleach. The user feeds both materials to a common point whereupon the NaOCl oxidizes the bromide ion to HOBr/OBr
⊖
. This a activated solution is then introduced directly into the water system to be treated. The feeding of the two liquids in this fashion is necessary because the HOBr/OBr
⊖
mixture is unstable and has to be generated on-site just prior to its introduction to the water. Furthermore, the feeding, and metering of two liquids is cumbersome, especially as the system has to be designed to allow time for the activation of bromide ion to occur. Consequently many biocide users have expressed the need for a single-feed, bromine-based biocide. Elemental bromine and molecular bromine chloride have been considered to meet these demands. Both are liquids at room temperature and can be fed directly to the water system, where immediate hydrolysis occurs to yield HOBr.
Br
2
+H
2
O→HOBr+HBr (1)
BrCl+H
2
O→HOBr+HCl (2)
Properties of bromine and bromine chloride are compared in Table 1.
TABLE 1
Physical Properties of Bromine and Bromine Chloride
Property
Bromine (Br
2
)
Bromine Chloride (BrCl)
Appearance
Fuming, dark-red
Fuming, red liquid or gas
liquid
Boiling Point
59° C.
5° C.
Vapor Pressure (25° C.)
214 mm
1800 mm
Corrosivity
Corrodes most
Corrodes most metals in
metals in the
the presence of water
presence of water
It can be seen that certain characteristics of these materials—especially their corrosiveness, high vapor pressures and fuming tendencies—necessitate care and skill in their handling and use. Early efforts to overcome the deficiencies of these materials comprised complexing bromine with excess bromide ion in the presence of strong acid and stabilizing the resultant solutions with ethanolamine. The resultant solutions of ethanolammonium hydrogen perbromide contained up to 38% by weight elemental bromine. See in this connection, Favstritsky, U.S. Pat. No. 4,886,915; and Favstritsky, Hein, and Squires, U.S. Pat. No. 4,966,716.
These solutions permitted introduction of bromine to a water system using a single feed. As in the case of bromine and bromine chloride, the ethanolammonium hydrogen perbromide hydrolyzed in water to release HOBr. The vapor pressures of these solutions were lower than elemental bromine and bromine chloride. Nevertheless, the solutions still possessed measurable vapor pressures, and thus tended to produce undesirable reddish-colored vapors during storage and use.
An economically acceptable way of stabilizing high concentrations of aqueous solutions of bromine chloride is described in U.S. Pat. No. 5,141,652 to Moore, et al. The solution is prepared from bromine chloride, water and a halide salt or hydrohalic acid. These solutions were found to decompose at a rate of less than 30% per year and in cases of high halide salt concentration, less than 5% per year. Moreover, solutions containing the equivalent of 15% elemental bromine could be prepared. Unfortunately, the relatively high acidity of these solutions and their tendency to be corrosive and fuming impose limitations on their commercial acceptance.
Many solid bromine derivatives such as BCDMH (1,3-bromochloro-5,5-dimethylhydantoin) are limited in the amount of material that can be dissolved in water and fed as a liquid to the water treatment system. For example, the solubility of BCDMH in water is only around 0.15%. Another limitation of such derivatives is that at neutral pH, HOBr rapidly decomposes, eventually forming bromide ions. Thus, the ability to store and transport these aqueous solutions is greatly limited and of questionable commercial feasibility.
U.S. Pat. No. 3,558,503 to Goodenough et al. describes certain aqueous bromine solutions stabilized with various stabilizing agents and various uses to which such solutions can be put. The compositions described in the patent comprise an aqueous bromine solution having from about 0.01 to about 100,000 parts per million by weight of bromine values wherein the molar ratio of bromine to nitrogen present in the bromine stabilizer ranges from about 2.0 to 1 to about 0.5 to 1. The stabilizer used is biuret, succinimide, urea, a lower aliphatic mono- or disubstituted urea containing from about 2 to about 4 carbon atoms in each substituent group, sulfamic acid, or an alkyl sulfonamide of the formula RSO
3
NH
2
where R is a methyl or ethyl group. The solution also contains sufficient hydroxide additive to provide a pH in the solution ranging from about 8 to about 10, the hydroxide additive being an alkaline earth hydroxide or an alkali metal hydroxide.
U.S. Pat. No. 5,683,654 to Dallmier et al. discusses the preparation of aqueous alkali metal or alkaline earth metal hypobromite solutions by mixing an aqueous solution of alkali or alkaline earth metal hypochlorite with a water soluble bromide ion source to form a solution of unstabilized alkali or alkaline earth metal hypochlorite. To this solution is added an aqueous solution of an alkali metal sulfamate having a temperature of at least 50° C. and in an amount that provides a molar ratio of alkali metal sulfamate to alkali or alkaline earth metal hypobromite of from about 0.5 to about 6 whereby a stabilized aqueous alkali or alkaline earth metal hypobromite solution is formed. The Dallhmier et al. patent teaches that much higher levels of available halogen for disinfection were attained by this approach as compared to the Goodenough et al. approach. But the Dallmier et al. patent acknowledges that in their process, the stabilization must occur quickly after the unstable NaOBr is formed.
THE INVENTION
This invention involves a new process of forming concentrated aqueous solutions of biocidally active bromine and in so doing, provides novel and eminently useful concentrated aqueous biocidal solutions of bromine and bromine chloride.
In one of its embodiments this invention provides a process of producing a concentrated liquid biocide composition which comprises mixing (a) bromine chloride or bromine with (b) an aqueous solution of alkali metal salt of sulfamic acid (preferably the sodium salt), the solution having a pH of at least about 7, e.g., in the range of 7 to about 13.5, and preferably in the range of 7 to about 12. The amounts of (a) and (b) used are such that (i) the content of active bromine in the solution is at least 100,000 ppm (wt/wt) and (ii) the atom ratio of nitrogen to active bromine from (a) and (b) is greater than 1 when bromine is used, and greater than 0.93 when bromine chloride is used. It is preferred, however, to utilize an atom ratio of nitrogen to active bromine from (a) and (b) that is greater than 1 even when using bromine chloride in the process. In a preferred embodiment the aqueous solution of alkali metal salt of sulfamic acid used in the process is preformed by mixing together in water, (i) sulfamic acid and/or an alkali metal salt of sulfamic acid, and (ii) alkali metal base in proportions such that an aqueous solution of alkali metal salt of sulfamic acid is formed having a pH of at least 7. If sulfamic acid itself is used as the starting material, it is used initially as a slurry in water with which the alkali metal base is mixed.
When introducing the bromine chloride or bromine into the aqueous solution of alkali metal salt of sulfamic acid, it is desirable to maintain the desired pH of the resulting solution at 7 or above by also introducing into the solution (continuously or intermittently, as desired) additional alkali metal base, such as by a co-f
Moore, Jr. Robert M.
Nalepa Christopher J.
Albemarle Corporation
Pryor Alton
Spielman, Jr. Edgar E.
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