There are numerous examples of surfactants which are able to inhibit the colonization of surfaces by inhibiting the overall growth of the organisms in the target environment. Many surfactants, regardless of class, show some inhibition of bacterial growth when used at concentrations high enough to impede surface colonization. In the water treatment industry, the most well known class of surfactants which impart a measure of colonization resistance to submerged surfaces are the cationic quaternary amine surfactants, which also function as biocides. However, even relatively mild nonionic and anionic surfactants can function in an analogous fashion. The concentration of nonionic or anionic surfactants necessary to mediate toxicity is substantially higher than for cationic surfactants, however.

Surfactants have historically been added to biocide packages because they (1) help to maintain some actives in aqueous solution which may otherwise separate (formulation aids) and (2) help relatively hydrophobic biocides to be more miscible in an aqueous environment. Surfactants have also been considered as enhancers of the efficacy of biocides against biofilm-associated organisms by increasing the accessibility of the biocide to its cellular target.

As previously noted, bacteria attach to surfaces, metabolize and grow, resulting in biofilms or microbial slime. This can result in problems in cooling water systems, such as reduced heat exchanger efficiency, blockage of pipes, corrosion of equipment, and harboring of potentially harmful bacteria. Control of slime, including the prevention of formation of slime and/or removal of slime, is important in alleviating these problems.

The present invention refers to a method for enhancing the activity of biocides to control the growth of microbes in an aqueous system. The materials of the present invention have been previously used in areas such as spray, soak tank, in-place pipeline cleaners, and floor scrubbing formulations.

SUMMARY OF THE INVENTION The present invention relates to methods for enhancing a treatment containing biocidal component to control growth of microbes in an aqueous system. the method comprising adding low foaming, ethoxylated anionic surfactant to the aqueous system, the low foaming, ethoxylated anionic surfactant comprising (a) at least one of alkyl substituted carboxylated acid and alkyl substituted carboxylated acid salt, and (b) polyoxyethylene-polyoxypropylene block copolymer.

The (a) at least one of alkyl substituted carboxylated acid and alkyl substituted carboxylated acid salt, and (b) polyoxyethylene-polyoxypropylene block copolymer can be added in amounts effective to control growth of microbes in the aqueous system at lower levels of biocidal component in the aqueous system than in the absence of the (a) at least one of alkyl substituted carboxylated acid and alkyl substituted carboxylated acid salt, and (b) polyoxyethylene-polyoxypropylene block copolymer.

The (a) at least one of alkyl substituted carboxylated acid and alkyl substituted carboxylated acid salt, and (b) polyoxyethylene-polyoxypropylene block copolymer can be added in amounts effective to obtain at least the same, if not better, control of growth of microbes in the aqueous system as compared to same and/or higher concentrations of biocidal component in the aqueous system in the absence of the (a) at least one of alkyl substituted carboxylated acid and alkyl substituted carboxylated acid salt, and (b) polyoxyethylene-polyoxypropylene block copolymer.

The (a) at least one of alkyl substituted carboxylated acid and alkyl substituted carboxylated acid salt, and (b) polyoxyethylene-polyoxypropylene block copolymer can be added in amounts effective to obtain greater control of growth of microbes in the aqueous system as compared to higher concentrations of biocidal component in the aqueous system in the absence of the (a) at least one of alkyl substituted carboxylated acid and alkyl substituted carboxylated acid salt, and (b) polyoxyethylene-polyoxypropylene block copolymer.

The alkyl substituted carboxylated acid or salt can contain from 6 to 18 carbon atoms, preferably 6 to 12 carbon atoms, and even more preferably 6 to 9 carbon atoms.

The alkyl groups can contain from 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, and even more preferably 1 carbon atom. Preferably, the alkyl substitution is on 3 and 5 carbon atoms of the carboxylic acid. Preferably, the alkyl substituted carboxylated acid or salt comprises at least one of 3, 5, 5 trimethyl hexanoic acid and salts thereof, 3, 5, 5 trimethyl octanoic acid and salts thereof, 3, 7, 7 trimethyl octanoic acid and salts thereof, 3, 5, 5 trimethyl decanoic acid and salts thereof, and 3, 9, 9 trimethyl decanoic acid and salts thereof.

Preferably, the alkyl substituted carboxylated acid or salt comprises alkyl substituted carboxylated acid salt, preferably a potassium or sodium salt.

The polyoxyethylene-polyoxypropylene block copolymer preferably has a mole ratio of about 1 to 1. 6 moles of polyoxyethylene to 1 mole of polyoxypropylene, more preferably about 1. 3 moles of polyoxyethylene to 1 mole of polyoxypropylene.

The polyoxyethylene-polyoxypropylene block copolymer preferably has a molecular weight of about 3, 000 to 6, 600, more preferably about 4, 000 to 5, 000, and even more preferably about 4, 500.

The low foaming, ethoxylated anionic surfactant preferably comprises about 35 to 60 wt% water, based upon total weight of the surfactant, preferably about 25 to 45 wt% of the at least one of alkyl substituted carboxylated acid and alkyl substituted carboxylated acid salt, and more preferably about 28 to 32 wt% of the at least one of alkyl substituted carboxylated acid and alkyl substituted carboxylated acid salt, and about 5 to 25 wt% of the polyoxyethylene-polyoxypropylene block copolymer, more preferably about 11 to 18 wt% of the polyoxyethylene-polyoxypropylene block copolymer.

The biocidal component can comprise at least one of non-oxidizing and oxidizing biocidal compounds. The at least one non-oxidizing biocidal compound can comprise at least of at least one isothiazolone compound and at least one bromonitropropanediol compound. The at least one isothiazolone compound can comprise at least one of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4- isothiazolin-3-one, as well as a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one, 2- methyl-4-isothiazolin-3-one, and 2-bromo-2-nitropropane-1, 3-diol. The at least one oxidizing biocidal compound can comprise at least one of hypochlorites, sodium bromide ; hydantoins ; peracetic acid ; chlorine dioxide ; ozone ; hydrogen peroxide ; and halogenated isocyanurates, preferably sodium hypochlorite.

The surfactant can include additional components such as at least one sequestrant, which preferably comprises at least one of polyepoxysuccinic acid and hydroxyethylidene diphosphonic acid.

At least about 5 ppm of the surfactant, more preferably at least about 10 ppm of the surfactant, can be added to the aqueous system, with preferred ranges being about 5 to 200 ppm, more preferably 10 to 50 ppm of the surfactant added to the aqueous system.

The microbes can comprise bacteria, fungi, algae and/or protozoa, including protozoan cysts.

The aqueous system can comprise at least one of cooling water systems (preferably recirculating and/or closed water systems), reverse osmosis systems, pulping and papermaking systems, air washer systems, pasteurizer systems, fire water safety systems, shower water systems, metalworking fluid systems, hydrocarbon storage systems, and aqueous mineral processing systems.

Preferably, the at least one of alkyl substituted carboxylated acid and alkyl substituted carboxylated acid salt comprises potassium or sodium salt of an alkyl substituted carboxylated acid having 6 to 12 carbon atoms and alkyl groups of 1 carbon atom, and the polyoxypropylene-polyoxyethylene block copolymer has a molecular weight of about 4, 000 to 5, 000 and a mole ratio of about 1 to 1. 6 moles of polyoxyethylene to 1 mole of polyoxypropylene. More preferably, the potassium or sodium salt of an alkyl substituted carboxylated acid comprises a potassium or sodium salt of 3, 5, 5 trimethyl hexanoic acid.

DETAILED DESCRIPTION OF THE INVENTION The particulars shown herein are by way of example and for purposes of illustrative discussion of embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description making apparent to those skilled in the art how varying forms of the present invention may be embodied in practice.

Unless otherwise stated, all percentages, parts, ratios, etc., are by weight.

Also, all percent measurements in this application, unless otherwise stated, are measured by weight based upon 100% of a given sample weight. Thus, for example, 30% represents 30 weight parts out of every 100 weight parts of the sample.

Unless otherwise stated, a reference to a compound or component includes the compound or component by itself, as well as in combination with other compounds or components, such as mixtures of compounds.

Further, when an amount, concentration, or other value or parameter, is given as a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of an upper preferred value and a lower preferred value, regardless whether ranges are separately disclosed.

The dispersant of the present invention enhances biocidal activity as compared to the use of biocides alone. The dispersant according to the present invention includes a combination of an alkyl substituted carboxylated acid salt and a block copolymer that when agitated, such as in cooling towers, will not form excessive amounts of foam, which would be unacceptable for use in various aqueous systems.

The method of the present invention allows for a decrease in the amount of biocidal compound added to the system, while maintaining the efficacy of the treatment. Thus, a more environmentally acceptable outcome is achieved, in that less biocidal material may be used while still preferably achieving at least the same level of biofilm kill efficacy. Thus, the dispersant of the present invention is particularly useful in combination with biocides to kill organisms. In addition, it is very effective at removing pre-existing biofilms in aqueous systems. Thus, the dispersant of the present invention is particularly useful in the control of microbes, including the prevention of formation and/or the removal of slime in aqueous systems.

The present invention relates to methods and compositions for enhancing activity of a treatment including a biocidal compound to control growth of microbes, including the prevention of formation and/or the removal of slime, in aqueous systems, which comprises adding to the aqueous system an effective amount of dispersant comprising low foaming, ethoxylated anionic surfactant which is composed of alkyl substituted carboxylated acid and/or salt thereof and ethylene oxide/propylene oxide block copolymer.

The alkyl substituted carboxylated acid or salt thereof can include, but is not limited to, acids and/or salts containing from about 6 to 18 carbon atoms, more preferably from about 6 to 12 carbon atoms, and most preferably from about 6 to 9 carbon atoms. Moreover, the alkyl groups can comprise alkyl groups having from about 1 to 6 carbon atoms, more preferably from about 1 to 3 carbon atoms, and most preferably 1 carbon atom. Preferably, the alkyl substituted carboxylated acid or salt comprises up to about 7 alkyl groups, and preferably contains 3 alkyl groups.

Preferably, the acid comprises hexanoic, octanoic and/or decanoic acid, with from 1 to 3 alkyl groups on the various carbons of the acid, which are preferably methyl groups.

Moreover, preferably the alkyl substitution is on the 3 and 5 carbons, preferably of hexanoic acid. Particularly preferred alkyl substituted carboxylated acid or salt thereof comprises hexanoic acid, with the alkyl substitution being on the 3 and 5 carbons, preferably one alkyl group on the 3 carbon and two alkyl groups of the 5 carbon, and preferably each of the three alkyl groups are methyl. Thus, a particularly preferred alkyl substituted carboxylated acid or salt thereof comprises 3, 5, 5 hexanoic acid or salt thereof.

Preferably, the alkyl substituted carboxylated acid and/or salt thereof comprises the salt. The salt form can include any cation that helps dissolve the carboxylic acid into solution, and preferably comprises potassium or sodium as the cation. For example, the acid can be formed into the salt by reaction with potassium hydroxide or sodium hydroxide.

Examples of alkyl substituted carboxylated acid and salts according to the present invention include, but are not limited to, 3, 5, 5 trimethyl hexanoic acid and salts thereof, preferably sodium or potassium salts thereof, 3, 5, 5 trimethyl octanoic acid and salts thereof, 3, 7, 7 trimethyl octanoic acid and salts thereof, 3, 5, 5 trimethyl decanoic acid and salts thereof, and 3, 9, 9 trimethyl decanoic acid and salts thereof.

The block copolymer comprises polyoxyethylene (EO)-polyoxypropylene (PO), which for the sake of convenience will also be referred to herein as EO/PO block coplymer. The EO/PO block copolymer can comprise any EO/PO block coploymer that maintains low foaming and/or reduces foaming of the alkyl substituted carboxylated acid or salt. The EO/PO mole ratio preferably ranges from about 1 to 1. 6 moles EO to 1 mole PO, with a particularly preferred mole ratio being about 1. 3 moles EO to 1 mole PO.

The molecular weight range of the EO/PO block copolymer is preferably about 3, 000 to 6, 600, most preferably about 4, 000 to 5, 000, with a particularly preferred value being about 4, 500. Thus, a particularly preferred EO/PO block copolymer comprises EO/PO having 1. 3 moles EO to 1 mole PO, and a molecular weight of about 4, 500.

Examples of EO/PO block copolymers according to the present invention include, but are not limited to, the Plutonic P series available from BASF (Mount Olive, New Jersey), and examples thereof include P65, P68, P84, P85, P104 and P105.

An especially useful material for forming the dispersant of the present invention is Mona NF 10, available from Uniqema, Paterson, NJ (formerly Mona Industries, Inc.), which includes therein alkyl substituted carboxylated acid salt and EO/PO block copolymer according to the present invention.

Still further, a particularly preferred low foaming, ethoxylated anionic surfactant according to the present invention is composed of the potassium salt of 3, 5, 5 trimethyl hexanoic acid and EO/PO block copolymer having a molecular weight of about 4, 500, such as P85 available from BASF.

The dispersant preferably comprises about 35 to 70 wt% water, based on the total weight of the dispersant. The amount of the alkyl substituted carboxylated acid or salt in the dispersant is preferably from about 25 to 45 wt%, more preferably from about 28 to 32 wt%, based on the total weight of the dispersant. Moreover, the amount of the EO/PO block copolymer in the dispersant is preferably from about 5 to 25 wt%, more preferably from about 11 to 18 wt%, based on the total weight of the dispersant.

The dispersant according to the present invention can include one or more biocides therein, or biocides can be separately added to the aqueous system. In this regard, the biocide can be added to the aqueous system at the same time as the dispersant, prior to the addition of the dispersant, and/or after the addition of the dispersant. It is preferred that the dispersant be added to the aqueous system prior to addition of the biocide.

As noted above, the present invention allows a decrease in the amount of biocide fed to a system, without decreasing the efficacy of a particular treatment protocol.

Biocides utilizable with the present invention are not limited to any particular biocide or mixture of biocides. Therefore, the following discussion of biocides is not intended to limit the present invention, but is provided to indicate preferred biocides according to the present invention.

Preferably, the biocides according to the present invention include"non- oxidizing"biocides and/or"oxidizing"biocides, and mixtures thereof. For example, non-oxidizing biocides include, but are not limited to, isothiazolones including 5- chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, and a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one sold as Kathon 886F, available from Rohm and Haas Co. ; and 2-bromo-2-nitropropane-1, 3- diol (BNPD), available from Angus Chemical Co.

A particularly preferred non-oxidizing biocide comprises a mixture of 5- chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one and 2-bromo-2- nitropropane-1, 3-diol, such as disclosed in U. S. Patent No. 4, 732, 905, which is incorporated by reference herein in its entirety. Preferably, the weight ratio of a combination of the 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4- isothiazolin-3-one to the 2-bromo-2-nitropropane-1, 3-diol is about 1 : 2.

Oxidizing biocides include, but are not limited to hypochlorites, such as sodium hypochlorite (bleach), potassium hypochlorite and calcium hypochlorite ; sodium bromide ; hydantoins ; peracetic acid ; chlorine dioxide ; ozone ; hydrogen peroxide ; and halogenated isocyanurates, preferably sodium hypochlorite.

The organism that is treatable with the dispersant of the present invention can include diverse organisms, including bacteria, fungi, algae and protozoa, including protozoan cysts. In the examples herein Pseudomonas aeruginosa, a bacterial species, was utilized in studying the present invention. However, with the guidelines herein, the invention can be utilized to treat various organisms, and is not limited to the specifically disclosed examples.

Materials in addition to the alkyl substituted carboxylated acid salt, the EO/PO block copolymer, and optionally one or more biocides can be included in the dispersant according to the present invention. For example, additives such as sequestrants such as polyepoxysuccinic acid, hydroxyethylidene diphosphonic acid, citric acid and/or ethylenediamine tetraacetic acid (EDTA) can be included in the dispersant according to the present invention.

The dispersant, by itself, or including sequestrants such as polyepoxysuccinic acid or hydroxyethylidene diphosphonic acid, is able to control microbial slime on surfaces. The means of control is by increasing the effectiveness of biocides to kill cells within the slime.

The dispersant according to the present invention is preferably included in the aqueous system at a concentration of at least about 5 parts per million (ppm), more preferably about 10 ppm, with preferred ranges being about 5 to 200 ppm, more preferably about 5 to 50 ppm, more preferably about 10 to 50 ppm.

The concentration of biocide in an aqueous system can be reduced by about 25%, and even more preferably by about 50%, and still maintain at least the same level of effectiveness of biocidal activity by incorporating the effective amounts of dispersion of the present invention in the aqueous system.

The dispersant according to the present invention can be utilized in a variety of aqueous systems, e. g., open recirculating cooling water systems, closed cooling systems, reverse osmosis systems, pulping or papermaking systems, air washer systems, pasteurizer systems, once-through cooling reverse osmosis systems, fire water safety systems, shower water systems, metalworking fluid systems, hydrocarbon storage systems, and aqueous mineral processing systems.

The invention will now be described with respect to certain examples which are merely representative of the invention and should not be construed as limiting thereof.

EXAMPLES The invention is illustrated in the following non-limiting examples, which are provided for the purpose of representation, and are not to be construed as limiting the scope of the invention. All parts and percentages in the examples are by weight unless indicated otherwise.

Examples 1-8 Bacteria in slime (biofilm) was simulated by incorporating bacteria (P. aeruginosa) into alginate, which was then layered onto metal coupons. Layers were exposed to biocide with surfactant and with and without sequestrants. At the end of the treatment (about 24 hours), the alginate was dissolved, releasing bacteria that were monitored by determining viable numbers of bacteria and microbial ATP.

As noted in Table I below, the alkyl carboxylic acid/block copolymer dispersants, examples are the commercial product, Mona NF-10 (available from Uniqema, formerly Mona Industries, Inc.) with and without sequestrant (polyepoxysuccinic acid, available from BetzDearborn Inc., Trevose, PA) enhanced biocide performance. This was detected by plate counting and ATP measurement. Biocide NX1100 (isothiazolinone/bronopol, available from BetzDearborn Inc., Trevose, PA) with 10 or 50 ppm Mona NF-10 killed 0. 4 and 0. 6 log more bacteria, respectively, than biocide (NX1100) alone. In other experiments, biocide (NX1100) with 20 ppm Mona NF-10 and sequestrant killed 0. 9 log more bacteria and decreased ATP levels 81% greater than with biocide alone. At 100 ppm Mona-NF-10 with sequestrant, biocide efficacy measured as CFU/ml increased 1. 2 logs, and as ATP decreased 96% (Table 1). Still further, Dispersant A is prepared by mixing 38 wt% 3, 5, 5 trimethyl hexanoic acid (obtained from BetzDearborn Inc., Trevose, PA) and 12 wt% P85 (obtained from BASF (Mount Olive, New Jersey) with sufficient KOH to get the 3, 5, 5 trimethyl hexanoic acid into solution. Increased performance is most likely due to these types of dispersants increasing biocide penetration into the biofilm.

Table 1 Example Treatment: product CFU/ml # log, Decrease mATP Decrease No. (ppm) (log) decrease from (%) (RLU) biocide 1 Biocide (25 ppm) 6. 5E (3. 8) 2 Mona NF-10/Biocide 2. 5E3 (3. 4) 0. 4 62 (10 ppm/25 ppm) 3 Mona NF-10/biocide 1. 5E3 (3. 2) 0. 6 77 (50 ppm/25 ppm) 4 Biocide (25 ppm) IE5 (5) ----- ----- 2238 ----- 5 MonaNF10/Sequestrant/ 1.3E4 (4. 1) 0. 9 85 427 81 Biocide (20 ppm/40 ppm/25 ppm) 6 Mona NF10 5. 8E3 (3. 8) 1. 2 94 93 96 /Sequestrant/Biocide (100 ppm/40 ppm/25 ppm) 7 Biocide (25 ppm) 9. 5E4-------- (4. 98) 8 Dispersant A/biocide 1. 8E4 0. 72 81---------- (50 ppm/25 ppm) (4.26) Examples 9-18 Bacteria were suspended in phosphate/saline water to which was added NX1100, obtained from BetzDearborn Inc., Trevose, PA, (representative of non- oxidizer biocide) or sodium hypochlorite, obtained from BetzDearborn Inc., Trevose, PA (representative of oxidizer biocide), and Mona NF-10, obtained from Uniqema.

Paterson, NJ (representative of alkyl carboxylic acid/block copolymer dispersant material), with and without sequestrant (polyepoxysuccinic acid, obtained from BetzDearborn Inc., Trevose, PA). Initial concentration of bacteria was about 107-108 CFU/ml. Treatment was for 3 hours at 24 2°C. Samples were removed and plated, with results shown in Table 2, below. The dispersant increases the efficacy of the non- oxidizer and oxidizer biocide above the biocide alone. As found in Table 2, the biocide efficacy increase for the non-oxidizer was 98%, and for the oxidizer was 78%.

Table 2 Example Treatment : % Decrease % Decrease No. product (ppm) From Biocide From Control 9 A (10)----51 10 A/B (10/10) 98. 1 99. 1 11 A/B (10/20) 98. 6 99. 3 12 A/B (10/50) 99. 3 99. 7 13 A/B/C (10/10/40) 98. 3 99. 1 14 A/B/C (10/50/40) 99. 5 99. 8 15 D (0. 75) 34. 5 16 D/B/C (0. 75/10/40) 78 85. 5 17 D/B/C (0. 75/50/40) 90 93. 3 18 D/B/C (0. 75/100/40) 99 99. 1 A = NX1100 (Isothiazolinone/Bronopol) B = Mona NF-10 (alkyl carboxylic acid/block copolymer) C = Polyepoxysuccinic Acid D = Hypochlorite While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention.