Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Biocides; animal or insect repellents or attractants
Reexamination Certificate
2001-02-02
2003-11-04
Levy, Neil S. (Department: 1616)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Biocides; animal or insect repellents or attractants
C424S408000, C424S420000, C424S417000, C514S389000
Reexamination Certificate
active
06641828
ABSTRACT:
BACKGROUND
As is known in the art of water treatment for microbiological control, a deficiency of chlorine, of hypochlorites, and of certain halogenated organic water-treating agents is the formation, during usage, of undesirable disinfection by-products. These by-products are undesirable both from the standpoint of environmental concerns and also from the standpoint of toxicological considerations.
Certain 1,3-dihalo-5,5-dialkylhydantoins have been found to be effective as biocides for aqueous systems such as industrial cooling water, recreational water, and wastewater.
Persons using biocidal agents in the biocidal treatment of water customarily, if not universally, refer to “free chlorine” level as a measure of biocidal control. To achieve “free chlorine” levels in water treatment, solid materials are often preferred because of their high weight percent activity. N,N′-bromochloro-5,5-dimethylhydantion (BCDMH) has been one of the most widely-used solid sources of “free chlorine” for water treatment. One of the features emphasized for BCDMH by suppliers of BCDMH is that in use, the combined chlorine from the biocide regenerates “free chlorine” by reaction with inactive bromide species formed during the water treatment operation. In other words, the chlorine atom in the initial N,N′-bromochloro-5,5-dialkylhydantoin is said to be a precursor for additional “free chlorine” for sanitation purposes.
In use, BCDMH hydrolyzes into HOBr and HOCl both of which register as “free chlorine” species in commonly-used standard test procedures. These methods for determining “free chlorine” levels in treated water, involve use of a reagent known as DPD (i.e., N,N′-diethyldiphenylenediamine) and a buffer, and the results of such analyses are commonly used, if not universally used, as the basis for determining the quantity of a halogen-containing microbiocidal agent to be used for water treatment. Heretofore, consumers of BCDMH have only been concerned with the level of “free chlorine” provided by a given quantity of that biocidal material. What has not been realized by such consumers is the amount of “total chlorine” being utilized in order to achieve the requisite “free chlorine” level. As a consequence, the consumer has not had available a yardstick by which to determine the true economic efficiency of using BCDMH as a biocidal agent in the treatment of water. To achieve optimum economic efficiency, the consumer should have available for use a biocidal agent in which the amount of “free chlorine” released into the water corresponds closely to the “total chlorine” content of the biocidal agent.
In the event a biocidal agent provides a relatively small amount of “free chlorine” in relation to its “total chlorine” content, it has been deemed necessary to utilize a relatively large amount of such agent in order to achieve microbiological control. This in turn means high levels of halogenated materials are released into the environment. If on the other hand, a biocidal agent could provide to the water an amount of “free chlorine” that closely corresponds to the “total chlorine” content of the biocidal agent, effective microbiological control could be realized by use of much smaller dosages and with consequent minimal adverse impact upon the environment.
BRIEF SUMMARY OF THE INVENTION
This invention involves, inter alia, the discovery that there is a substantial disparity between the “free chlorine” level and the “total chlorine” level delivered to the water when using BCDMH as a biocidal agent. Thus the consumer of BCDMH as a water treating agent unknowingly has been paying for a relatively ineffective microbiocidal agent. Moreover, such consumer has been contributing unknowingly to the release of undesirable quantities of halogenated materials to the environment.
This invention further involves, inter alia, the discovery that the level of “free chlorine” available from 1,3-dibromo-5,5-dimethylhydantoin (DBDMH), especially when used in water having a pH of at least about 8.0, closely approximates its “total chlorine” content. Consequently the use of one or more water-soluble dialkyldibromohydantoins such as DBDMH as a water treating agent, especially when used in the treatment of industrial cooling water, is highly effective from an economic standpoint and highly desirable from an environmental standpoint. That is to say, the dosage levels of water-soluble dialkyldibromohydantoins such as DBDMH needed to provide effective microbiological control with respect to such undesirable organisms and pathogens as bacteria, algae, and biofilms, are relatively low compared to dosage levels of BCDMH required for the same degree of control, especially in industrial cooling water. Moreover, the levels of halogenated materials released to the environment are much smaller when using a water-soluble dialkyldibromohydantoin such as DBDMH as compared to BCDMH.
Accordingly, this invention provides in one of its embodiments a method of providing microbiological control in an aqueous medium such as recreational water, industrial cooling water, process water, or wastewater, and preferably in water having a pH of at least about 8.0 such as cooling water and/or eradication or reduction of biofilm on a surface in contact with such aqueous medium, which method comprises introducing into the aqueous medium a microbiocidally effective amount of at least one 1,3-dibromo-5,5-dialkylhydantoin in which one of the alkyl groups in the 5-position is a methyl group and the other alkyl group in the 5-position contains in the range of 1 to 4 carbon atoms (DBDAH), (i) the molar quantity of the DBDAH introduced being less than the molar quantity of N,N′-bromochloro-5,5-dimethylhydantoin (BCDMH) that would be required to effect the same degree of microbiological control in such medium, (ii) the quantity of DBDAH introduced into such aqueous medium releasing an amount of “free chlorine” that is greater than the amount of “free chlorine” that would be released in such medium by an equimolar quantity of BCDMH, and (iii) the amount of “free chlorine” released by the quantity of such at least one DBDAH introduced into such aqueous medium being greater than the amount of “free chlorine” that could be predicted to be released by that quantity of DBDAH on the basis of the amount of “free chlorine” that would be released in such medium by an equimolar quantity of BCDMH. The most preferred DBDAH used in this embodiment is 1,3-dibromo-5,5-dimethylhydantoin (DBDMH).
In another of its embodiments this invention provides a method of effecting microbiocidal activity in water preferably but not necessarily having a pH of at least about 8.0, which method comprises providing in such water using a 1,3-dibromo-5,5-dialkylhydantoin (DBDAH) microbiocidal agent in which one of the alkyl groups of the DBDAH in the 5-position is a methyl group and the other alkyl group in the 5-position contains in the range of 1 to 4 carbon atoms, a microbiocidally effective amount of “free chlorine” that is greater than could be predicted from the amount of “free chlorine” that would be released by an equimolar quantity of N,N′-bromochloro-5,5-dimethylhydantoin (BCDMH) in such water, while using a smaller molar quantity of the DBDAH than the molar quantity of BCDMH required to release such microbiocidally effective amount of “free chlorine”. 1,3-Dibromo-5,5-dimethylhydantoin (DBDMH) is also the most preferred microbiocidal agent employed in this embodiment.
A further embodiment of this invention is a composition having microbiocidal activity, which composition comprises water preferably but not necessarily having a pH of at least about 8.0 to which has been added a microbiocidally effective quantity of a 1,3-dibromo-5,5-dialkylhydantoin (DBDAH) in which one of the alkyl groups is a methyl group and the other alkyl group contains in the range of 1 to 4 carbon atoms, (i) the molar quantity of the DBDAH added being less than the molar quantity of N,N′-bromochloro-5,5-dimethylhydantoin (BCDMH) that would be required to effect the same degree of
Howarth Jonathan N.
Nalepa Christopher J.
Sanders Michael J.
Albemarle Corporation
Levy Neil S.
Spielman, Jr. Edgar E.
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