OXIDIZING BIOCIDE

Cross-reference to Related Applications

This application claims the benefit of U.S. Provisional Application Ser. No.

5 61/246,713, filed September 29, 2009, which is incorporated herein by reference in its

entirety.

Field of the Invention

The invention relates to biocidal compositions and methods of their use for the control of microorganisms in aqueous and water-containing systems. The compositions 10 comprise 2,2-dibromomalonamide and an oxidizing biocide.

Background of the Invention

Water systems provide fertile breeding grounds for algae, bacteria, viruses, and fungi some of which can be pathogenic. Such microorganism contamination can create a variety of problems, including aesthetic unpleasantries such as slimy green water, serious health 15 risks such as fungal, bacterial, or viral infections, and mechanical problems including

plugging, corrosion of equipment, and reduction of heat transfer.

Biocides are commonly used to disinfect and control the growth of microorganisms in aqueous and water containing systems. However, not all biocides are effective against a wide range of microorganisms and/or temperatures, and some are incompatible with other 20 chemical treatment additives. In addition, some biocides do not provide microbial control over long enough time periods.

While some of these shortcomings can be overcome through use of larger amounts of the biocide, this option creates its own problems, including increased cost, increased waste, and increased likelihood that the biocide will interfere with the desirable properties of the treated medium. In addition, even with use of larger amounts of the biocide, many commercial biocidal compounds cannot provide effective control due to weak activity against certain types of microorganisms or resistance of the microorganisms to those compounds.

It would be a significant advance in the art to provide biocide compositions for treatment of water systems that provide one or more of the following advantages: increased efficacy at lower concentrations, compatibility with physical conditions and other additives in the treated medium, effectiveness against a broad spectrum of microorganisms, and/or ability to provide both short term and long term control of microorganisms.

BRIEF SUMMARY OF THE INVENTION

In one aspect, the invention provides a biocidal composition. The composition is useful for controlling microorganisms in aqueous or water containing systems. The composition comprises: 2,2-dibromomalonamide and an oxidizing biocide selected from monochloramine, bromochlorodimethylhydantoin, hypobromite ion or hypobromous acid, hydrogen peroxide, dichloroisocyanurate, trichloroisocyanurate, and chlorine dioxide.

In a second aspect, the invention provides a method for controlling microorganisms in aqueous or water containing systems. The method comprises treating the system with an effective amount of a biocidal composition as described herein.

DETAILED DESCRIPTION OF THE INVENTION

As noted above, the invention provides a biocidal composition and methods of using it in the control of microorganisms. The composition comprises: 2,2-dibromomalonamide and an oxidizing biocide selected from monochloramine, bromochlorodimethylhydantoin, hypobromite ion or hypobromous acid, and hydrogen peroxide. It has surprisingly been discovered that combinations of 2,2-dibromomalonamide and the oxidizing biocide as described herein, at certain weight ratios, are synergistic when used for microorganism control in aqueous or water containing media. That is, the combined materials result in improved biocidal properties than would otherwise be expected based on their individual performance. The synergy permits reduced amounts of the materials to be used to achieve the desired biocidal performance, thus reducing problems caused by growth of

microorganisms in industrial process waters while potentially reducing environmental impact and materials cost.

For the purposes of this specification, the meaning of "microorganism" includes, but is not limited to, bacteria, fungi, algae, and viruses. The words "control" and "controlling" should be broadly construed to include within their meaning, and without being limited thereto, inhibiting the growth or propagation of microorganisms, killing microorganisms, disinfection, and/or preservation. In some preferred embodiments, "control" and

"controlling" mean inhibiting the growth or propagation of microorganisms. In further embodiments, "control" and "controlling" mean the killing of microorganisms.

The term "2,2-dibromomalonamide" refers to a compound represented by the following chemical formula:

In some embodiments of the invention, the weight ratio of 2,2-dibromomalonamide to the oxidizing biocide is between about 100:1 and about 1:100, alternatively between about 40:1 and about 1:100, alternatively between about 32:1 and about 1:80.

In some embodiments, the composition of the invention comprises

2,2-dibromomalonamide and monochloramine. Monochloramine is readily prepared by those skilled in the art using well known techniques. For instance, it may be generated by mixing appropriate quantities of solutions of ammonium sulfate ([NH^SC ) and hypochlorite ion, such as sodium hypochlorite. Monochloramine may, for instance, also be prepared by mixing ammonium bromide and hypochlorite ion. Hypochlorite ion may be in the form of commercial bleach (e.g., Clorox ^® ). The product of mixing ammonium bromide and hypochlorite ion is sometimes considered to be "bromide-activated" monochloramine and other times simply monochloramine. All products of such mixing are encompassed by the term "monochloramine" as used in the invention, including bromide-activated monochloramine and simple monochloramine.

In some embodiments, the weight ratio of 2,2-dibromomalonamide to

monochloramine is between about 100:1 and about 1:20, alternatively between about 70:1 and about 1:10, alternatively about 40:1 and about 1:5, alternatively between about 32:1 and about 1:4, or alternatively between about 32:1 and about 1:2. In some embodiments, the weight ratio is between about 16: 1 and about 1:4.

In a still further embodiment, the composition of the invention comprises

2,2-dibromomalonamide and bromochlorodimethylhydantoin. Bromochloro- dimethylhydantoin is commercially available.

In some embodiments, the weight ratio of 2,2-dibromomalonamide to bromochlorodimethylhydantoin is between about 20:1 and about 1:100, alternatively between about 10:1 and about 1:70, alternatively between about 5:1 and about 1:20, or alternatively between about 4:1 and about 1:16.

In another embodiment, the composition of the invention comprises

2,2-dibromomalonamide and hypobromous acid or hypobromous ion. Hypobromous acid and hypobromite ion are commercially available or can be readily by those skilled in the art (e.g., hypobromous acid can be generated by dissolving bromine in excess of water).

In some embodiments, the weight ratio of 2,2-dibromomalonamide to hypobromous acid or hypobromite ion is between about 20:1 and about 1:100 , alternatively between about 10:1 and about 1:70 , alternatively between about 5: 1 and about 1:40, or alternatively between about 4:1 and about 1:32.

In a further embodiment, the composition of the invention comprises

2,2-dibromomalonamide and hydrogen peroxide. Solutions of hydrogen peroxide in water are commercially available.

In some embodiments, the weight ratio of 2,2-dibromomalonamide to hydrogen peroxide is between about 50:1 and about 1:100, alternatively between about 30:1 and about 1:80, alternatively between about 1:10 and about 1:80, or alternatively between about 1:20 and about 1:80.

In some embodiments, the oxidizing biocide is dichloroisocyanurate and the weight ratio of 2,2-dibromomalonamide to dichloroisocyanurate is between about 100:1 and about 1:20, alternatively between about 70: 1 and about 1:10, alternatively about 40:1 and about 1:5, alternatively between about 32:1 and about 1:1.

In some embodiments, the oxidizing biocide is trichloroisocyanurate and the weight ratio of 2,2-dibromomalonamide to trichloroisocyanurate is between about 100:1 and about 1 :20, alternatively between about 70: 1 and about 1:10, alternatively about 40: 1 and about 1:5, alternatively between about 16:1 and about 1:4.

In some embodiments, the oxidizing biocide is chlorine dioxide and the weight ratio of 2,2-dibromomalonamide to chlorine dioxide is between about 50:1 and about 1:50, alternatively between about 20:1 and about 1:20, alternatively about 16: 1 and about 1: 16. Various of the oxidizing biocides described herein may be electrolytically generated.

The composition of the invention is useful for controlling microorganisms in a variety of aqueous and water containing systems. Examples of such systems include, but are not limited to, paints and coatings, aqueous emulsions, latexes, adhesives, inks, pigment dispersions, household and industrial cleaners, detergents, dish detergents, mineral slurries polymer emulsions, caulks and adhesives, tape joint compounds, disinfectants, sanitizers, metalworking fluids, construction products, personal care products, textile fluids such as spin finishes, industrial process water (e.g. oilfield water, pulp and paper water, cooling water), oilfield functional fluids such as drilling muds and fracturing fluids, fuels, air washers, wastewater, ballast water, filtration systems, and swimming pool and spa water. Preferred aqueous systems are metal working fluids, personal care, household and industrial cleaners, industrial process water, and paints and coatings. Particularly preferred are industrial process water, paints and coatings, metal working fluids, and textile fluids such as spin finishes.

A person of ordinary skill in the art can readily determine, without undue experimentation, the effective amount of the composition that should be used in any particular application to provide microorganism control. By way of illustration, a suitable actives concentration (total for both 2,2-dibromomalonamide and an oxidizing biocide) is typically at least about 1 ppm, alternatively at least about 3 ppm, alternatively at least about 7 ppm, alternatively at least about 10 ppm, alternatively at least about 30 ppm, or alternatively at least about 100 ppm based on the total weight of the aqueous or water containing system. In some embodiments, a suitable upper limit for the actives

concentration is about 1000 ppm, alternatively about 500 ppm, alternatively about 100 ppm, alternatively about 50 ppm, alternatively about 30 ppm, alternatively about 15 ppm, alternatively about 10 ppm, or alternatively about 7 ppm, based on the total weight of the aqueous or water containing system.

The components of the composition can be added to the aqueous or water containing system separately, or preblended prior to addition. A person of ordinary skill in the art can easily determine the appropriate method of addition. The composition can be used in the system with other additives such as, but not limited to, surfactants, ionic/nonionic polymers and scale and corrosion inhibitors, oxygen scavengers, and/or additional biocides.

The following examples are illustrative of the invention but are not intended to limit its scope. Unless otherwise indicated, the ratios, percentages, parts, and the like used herein are by weight.

EXAMPLES

The results provided in the Examples are generated using a growth inhibition assay. Details of each assay are provided below.

Growth Inhibition Assay. The growth inhibition assay used in the Examples measures inhibition of growth (or lack thereof) of a microbial consortium. Inhibition of growth can be the result of killing of the cells (so no growth occurs), killing of a significant portion of the populations of cells so that regrowth requires a prolonged time, or inhibition of growth without killing (stasis). Regardless of the mechanism of action, the impact of a biocide (or combination of biocides) can be measured over time on the basis of an increase in the size of the community.

The assay measures the efficacy of one or more biocides at preventing growth of a consortium of bacteria in a dilute mineral salts medium. The medium contains (in mg/1) the following components: FeCl ₃ .6H ₂ 0 (1); CaCl ₂ .2H ₂ 0 (10); MgS0 ₄ .7H ₂ 0 (22.5); (NH ₄ ) ₂ S0 ₄ (40); KH ₂ P0 ₄ (10); K ₂ HP0 ₄ (25.5); Yeast Extract (10); and glucose (100). After all components are added to deionized water, the pH of the medium is adjusted to 7.5. Following filter sterilization, aliquots are dispensed in 100 ul quantities to sterile microtiter plate wells. Dilutions of 2,2-dibromomalonamide ("DBMAL") and/or "Biocide B" are then added to the microtiter plate. After preparing the combinations of actives as illustrated below, each well is inoculated with 100 μΐ of a cell suspension containing ca. 1 x 10 ⁶ cells per milliliter of a mixture of Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus, and Bacillus subtilis. The final total volume of medium in each well is 300 μΐ. Once prepared as described herein, the concentration of each active ranges from 25 ppm to 0.195 ppm as illustrated in Table 1. The resulting matrix allows testing of eight concentrations of each active and 64 combinations of actives in the ratios (of actives).

Table 1. Template for microtiter plate-based synergy assay showing concentrations of each active. Ratios are based on weight (ppm) of each active.

Controls (not shown) contain the medium with no biocide added. After preparing the combinations of actives as illustrated above, each well is inoculated with 100 μΐ of a cell suspension containing ca. 1 x 10 ⁶ cells per milliliter of a mixture of Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus, and Bacillus subtilis. The final total volume of medium in each well is 300 μΐ.

Immediately after the microtiter plates are prepared, the optical density (OD) readings for each well is measured at 580 nm and the plates are then incubated at 37 °C for

24 hr. After the incubation period, the plates are gently agitated before OD5 ₈₀ values are collected. The OD5 ₈₀ values at To are subtracted from T24 values to determine the total amount of growth (or lack thereof) that occurs. These values are used to calculate the percent inhibition of growth caused by the presence of each biocide and each of the 64 combinations. A 90% inhibition of growth is used as a threshold for calculating synergy index (SI) values with the following equation:

Synergy Index = M _DB MAL/C _D BMAL + M _B /C _B where

CDBMAL: Concentration of DBMAL required to inhibit -90% of bacterial growth when used alone

CB: Concentration of biocide (B) required to inhibit -90% of bacterial growth when used alone.

DBMAL: Concentration of DBMAL required to inhibit -90% of bacterial growth when used in combination with biocide (B).

MR: Concentration of biocide (B) required to inhibit -90% of bacterial growth when used in combination with DBMAL

The SI values are interpreted as follows:

SI <1 : Synergistic combination

SI = 1 : Additive combination

SI >1 : Antagonistic combination

In the Examples below, the amounts of biocides in the solution are measured in mg per liter of solution (mg/1). Since solution densities are approximately 1.00, the mg/1 measurement corresponds to weight ppm. Both units may therefore be used interchangeably in the Examples. Example 1

DBMAL and monochloramine prepared from Ammonium Sulfate and Bleach

Monochloramine (NH2CI) is generated by mixing appropriate quantities of solutions of ammonium sulfate ([NEL^SC^) and commercial bleach (Clorox ^® ). Table 2 shows inhibition growth assay results for DBMAL, monochloramine (NH2CI), and combinations thereof. The results demonstrate that the I90 values for NH2CI and DBMAL are 1.56 mg/1 and 12.5 mg/1, respectively (Table 2). Combinations of NH2CI and DBMAL are very effective at preventing growth as illustrated by the results obtained with the combination of 0.78 mg/1 NH ₂ C1 and 0.19 mg/1 DBMAL.

Table 2. Percent inhibition of growth in a species-defined microbial consortium by DBMAL and monochloramine (NH ₂ CI) and alone and combinations of these actives after a 24-hour incubation period. Numbers represent percent inhibition of growth as measured by optical density measurements (580 nm) at time = 24 hours compared with time = 0 values.

Table 3 shows ratios of DBMAL and N¾C1 found to be synergistic under the growth inhibition assay.

Example 3

DBMAL and Monochloramine prepared from Ammonium Bromide/Hypochlorite Monochloramine is prepared by mixing together appropriate quantities of ammonium bromide and hypochlorite.

Table 4 shows inhibition growth assay results for DBMAL, ammonium bromide/hypochlorite, and combinations thereof.

Table 4 percent inhibition of growth in a species-defined microbial consortium by DBMAL and/or ammonium bromide/hypochlorite after a 24-hour incubation period. Numbers represent percent inhibition of growth as measured by optical density measurements (580 nm) at time = 24 hours compared with time = 0 values.

Table 5 shows ratios of DBMAL and ammonium bromide/hypochlorite found to be synergistic under the growth inhibition assay.

Table 5

Example 4

DBMAL and BCDMH

Table 6 shows inhibition growth assay results for DBMAL, bromochloro- dimethylhydantoin ("BCDMH"), and combinations thereof.

Table 6. Percent inhibition of growth in a species -defined microbial consortium by DBMAL and/or BCDMH after a 24-hour incubation period. Numbers represent percent inhibition of growth as measured by optical density measurements (580 nm) at time = 24 hours compared with time = 0 values.

Table 7 shows concentrations of DBMAL and BCDMH that are found to be synergistic using the growth inhibition assay.

Table 7

Example 5

DBMAL and hypobromous acid

Table 8 shows inhibition growth assay results for DBMAL, hypobromous acid ("HOBr"), and combinations thereof. In this example, HOBr is generated immediately before use by mixing equimolar amounts of sodium hypochlorite (NaOCl) and sodium bromide (NaBr).

Table 8. Percent inhibition of growth in a species-defined microbial consortium by DBMAL and/or HOBr after a 24-hour incubation period. Numbers represent percent inhibition of growth as measured by optical density measurements (580 nm) at time = 24 hours compared with time = 0 values.

Table 9 shows concentrations of DBMAL and HOBr found to be synergistic using the growth inhibition assay.

able 9

Example 6

DBMAL and hydrogen peroxide

Table 10 shows inhibition growth assay results for DBMAL, hydrogen peroxide (¾(¾), and combinations thereof.

Table 10. Percent inhibition of growth in a species -defined microbial consortium by DBMAL and/or H2O2 after a 24-hour incubation period. Numbers represent percent inhibition of growth as measured by optical density measurements (580 nm) at time = 24 hours compared with time = 0 values.

Table 11 shows the one concentration of DBMAL and ¾(¾ found to be synergistic using the growth inhibition assay.

Example 7

DBMAL and dichloroisocyanurate

Table 12 shows inhibition growth assay results for DBMAL, dichloroisocyanurate, and combinations thereof.

Table 12. Percent inhibition of growth in a species -defined microbial consortium by DBMAL and/or DCI after a 24-hour incubation period. Numbers represent percent inhibition of growth as measured by optical density measurements (580 nm) at time = 24 hours compared with time = 0 values.

Table 13 shows the concentrations of DBMAL and DCI found to be synergistic using the growth inhibition assay.

Example 8

DBMAL and trichloroisocyanurate

Table 14 shows inhibition growth assay results for DBMAL, trichloroisocyanurate ("TCI"), and combinations thereof.

Table 14. Percent inhibition of growth in a species -defined microbial consortium by DBMAL and/or TCI after a 24-hour incubation period. Numbers represent percent inhibition of growth as measured by optical density measurements (580 nm) at time = 24 hours compared with time = 0 values

Table 15 shows the concentrations of DBMAL and TCI found to be synergistic using the growth inhibition assay.

Example 8

DBMAL and chlorine dioxide

Table 16 shows inhibition growth assay results for DBMAL, chlorine dioxide (CIO ₂ ), and combinations thereof.

Table 16. Percent inhibition of growth in a species -defined microbial consortium by DBMAL and/or chlorine dioxide (CIO ₂ ) after a 24-hour incubation period. Numbers represent percent inhibition of growth as measured by optical density measurements (580 nm) at time 24 hours compared with time = 0 values

Table 17 shows the concentrations of DBMAL and CIO ₂ found to be synergistic the growth inhibition assay.

While the invention has been described above according to its preferred

embodiments, it can be modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using the general principles disclosed herein. Further, the application is intended to cover such departures from the present disclosure as come within the known or customary practice in the art to which this invention pertains and which fall within the limits of the following claims.