Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Using disinfecting or sterilizing substance
Reexamination Certificate
2000-03-02
2002-07-23
Thornton, Krisanne (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Using disinfecting or sterilizing substance
C210S754000, C210S758000, C210S764000, C252S186100, C252S186440, C422S028000, C422S040000, C422S041000, C423S462000
Reexamination Certificate
active
06423267
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to formulations used in biofouling control in industrial water systems. More specifically, the present invention relates to methods of preparing stable oxidizing bromine formulations and their use in biofouling control in industrial water systems.
BACKGROUND OF THE INVENTION
While elemental liquid bromine is an effective biocide, its low solubility (<4 g/100 g water), low boiling point (54.3° C.), high vapor pressure (214 mm Hg at 25° C.) and extreme corrosivity limit its use as a biocide in industrial applications. Another oxidizing bromine compound, bromate, has very little antimicrobial activity. Bromate is also very toxic to mammals and is a suspected carcinogen. Nonoxidizing inorganic bromine compounds, such as bromide, have little or no antimicrobial activity.
A mixture of an aqueous bromine solution and a bromine stabilizer has been used to generate stable oxidizing bromine compounds for use as a biocide. An unstabilized aqueous bromine solution is very acidic, unstable and emits very pungent bromine fumes. The concentration of stabilized hypobromite solution that can be made from liquid bromine, however, has been limited due to the low solubility of bromine in water.
It has also been suggested that, in addition to a bromine stabilizer, an oxidizer, such as hypochlorite, be added to activate the bromide to hypobromite. After the completion of the conversion of bromide to hypobromite, the hypobromite is stabilized by the addition of a halogen stabilizer, such as sulfamate. While this is an improved process with a higher level of oxidizing halogen content (around 14% as Br
2
), this process still requires the separate step of synthesizing sodium hypobromite (NaOBr) as a bromine source. NaOBr is known to be very unstable and will rapidly disproportionate to bromide and bromate, both of which have little or no antimicrobial activity. In addition, because sodium hypochlorite (NaOCl) is used as an activation agent, the concentration of stabilized product is limited by the available concentration of NaOCl.
Also known are methods of generating bromine for on-site use. Such processes involve electrolytically converting bromate into active bromine compounds such as bromine, hypobromous acid, hypobromite ion and hydrogen tribromide under acidic conditions. However, because the above process generates bromine for on-site use, methods or measures for optimizing bromine stabilization are not addressed.
Therefore, methods of generating higher concentrations of stable oxidizing bromine formulations in a safer manner are needed.
SUMMARY OF THE INVENTION
The present invention satisfies the aforementioned needs by providing a method of generating a stable oxidizing bromine compound which includes the steps of mixing an alkali or alkaline earth metal bromide and an alkali or alkaline earth metal bromate in water to provide an aqueous solution, cooling the solution to a temperature of less than 25° C., preferably less than 20° C. and more preferably less than 10° C., and thereafter adding a halogen stabilizer to the solution, the halogen stabilizer being selected from the group consisting of R—NH
2
, R—NH—R
1
, R—SO
2
—NH
2
, R—SO
2
—NHR
1
, R—CO—NH
2
, R—CO—NH—R
1
and R—CO—NH—CO—R
1
wherein R is a hydroxy group, an alkyl group or an aromatic group and R
1
is an alkyl group or an aromatic group. Preferred halogen stabilizers include urea, thiourea, creatinine, cyanuric acids, alkyl hydantoins, mono or diethanolamine, organic sulfonamides, biuret, sulfamic acid, organic sulfamates and melamine. Sulfamic acid is the most preferred halogen stabilizer.
In an embodiment, the halogen stabilizer is added to the solution in a molar amount approximately equal to the combined molar amount of alkali or alkaline earth metal bromide and alkali or alkaline earth metal bromate.
In an embodiment, the step of adding the halogen stabilizer results in the solution having a pH of less than 2.
In an embodiment, the method comprises agitating the solution for a time period of greater than 5 minutes after the step of adding the halogen stabilizer.
In an embodiment, the method comprises adjusting the solution to a pH of greater than 13 through the addition of alkali or alkaline earth metal hydroxide after the step of adding the halogen stabilizer.
In an embodiment, the step of mixing the alkali or alkaline earth metal bromide and alkali or alkaline earth metal bromate further comprises mixing the alkali or alkaline earth metal bromide and alkali or alkaline earth metal bromate in a molar ratio of alkali or alkaline earth metal bromide:bromate of about 2:1.
In an embodiment, the method of the present invention provides a stable oxidizing bromine compound which includes the steps of mixing about 2 moles of alkali or alkaline earth metal bromide and about 1 mole of alkali or alkaline earth metal bromate in water to provide an aqueous solution, followed by the step of cooling the solution to a temperature of less than 10° C., followed by the step of adding an acidic halogen stabilizer to the solution to lower the pH of the solution to less than 2, the acidic halogen stabilizer being selected from the group consisting of R—NH
2
, R—NH—R
1
, R—SO
2
—NH
2
, R—SO
2
—NHR
1
, R—CO—NH
2
, R—CO—NH—R
1
and R—CO—NH—CO—R
1
wherein R is a hydroxy group, an alkyl group or an aromatic group and R
1
is an alkyl group or an aromatic group. Preferred halogen stabilizers include urea, thiourea, creatinine, cyanuric acids, alkyl hydantoins, mono or di ethanolamine, organic sulfonamides, biuret, sulfamic acid, organic sulfamates and melamine. The acidic halogen stabilizer is added to the solution in a molar amount approximately equal to a combined molar amount of alkali or alkaline earth metal bromide and alkali or alkaline earth metal bromate, followed by the step of agitating the solution for a time period of greater than 5 minutes, followed by the step of adding an alkali or alkaline earth metal hydroxide to the solution to increase the pH of the solution to a level greater than 13.
In an embodiment, the method of the present invention provides a method of preparing a stable oxidizing bromine compound which includes the steps of preparing a caustic solution comprising a halogen stabilizer, water and an alkali or alkaline earth metal hydroxide, adding bromine to the solution while agitating the solution and cooling the solution.
In an embodiment, the halogen stabilizer is selected from the group consisting of R—NH
2
, R—NH—R
1
, R—SO
2
—NH
2
, R—SO
2
—NHR
1
, R—CO—NH
2
, R—CO—NH—R
1
and R—CO—NH—CO—R
1
wherein R is a hydroxy group, an alkyl group or an aromatic group and R
1
is an alkyl group or an aromatic group. Preferred halogen stabilizers include urea, thiourea, creatinine, cyanuric acids, alkyl hydantoins, mono or di ethanolamine, organic sulfonamides, biuret, sulfamic acid, organic sulfamates and melamine.
In an embodiment, the caustic solution has a pH greater than 13 after the addition of bromine.
In an embodiment, the step of adding bromine is further characterized as adding bromine in a molar amount approximately equal to the molar amount of halogen stabilizer and approximately equal to one-half of the molar amount of alkali or alkaline earth metal hydroxide.
In an embodiment, the solution is cooled to a temperature of less than 25° C.
In an embodiment, the step of adding bromine is performed without exposing the bromine to air.
In an embodiment, an alkali or alkaline earth metal hydroxide is added to the solution after the addition of bromine to increase the pH of the solution above 13.
In an embodiment, the method of the present invention provides a method of preparing a stable oxidizing bromine compound in an aqueous solution which includes the steps of dissolving an alkali or alkaline earth metal bromate salt in water to form a solution, followed by the step of adding a halogen stabilizer to the solution, the halogen stabilizer being selected from the group consisting of R—NH
2
, R—NH—R
1
, R—SO
2
—NH
2
, R—SO
2
—NHR
1
, R—CO—NH
2
, R—CO—NH—R
1
and R—CO—NH
Dallmier Anthony W.
McCoy William F.
Yang Shunong
Breininger Thomas M.
Cummings Kelly L.
Nalco Chemical Company
Thornton Krisanne
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