Methods and compositions for potentiating the activity of antimicrobal agents in industrial water based fluids
BACKGROUND OF THE INVENTION 
     Antimicrobial compositions are generally added to various kinds of industrial water based fluids to reduce or inhibit the growth of microorganisms. In particular, a wide variety of industrial water based fluids such as metal-working fluids, latex paints, water based hydraulic fluids, require antimicrobial compositions to control the growth microorganisms which eventually render the fluids rancid. 
     One of the problems often associated with water based fluids is the susceptibility of the fluid to the infestation and growth of various microorganisms such as bacteria and fungi (which particularly feed on the organic components thereof). The presence and buildup of such microorganisms can often lead to interference of mechanical operations as a result of the clogging of filters, buildup of slime and sludge, development of odors, rust, emulsion instability, reduced tool life and poor finish. Furthermore, where the workers&#39; hands necessarily come in contact with these deteriorated fluids, usually containing finely divided sharp metal cuttings, serious problems of dermatitis may arise. These and other such similar problems have resulted in the continuing need for better antimicrobial additives for industrial water based fluids. Much effort has been devoted in recent years to controlling this problem; however, it continues to be a major annoyance which costs industry many millions of dollars each year. 
     Antimicrobial agents constitute an important ingredient of industrial fluids which are commonly depleted faster than the other components of the fluids. Quite often, additional antimicrobial agents must be added to the industrial water based fluid at periodic intervals in order to compensate for their loss from the fluid after continuous use. 
     Preservatives are removed from the fluid after interacting with the microbes to bring about their inhibition or death. The greater the microbial population, the more quickly they are lost from the system. Thus, the concentration of any preservative declines with time and may be reduced to subinhibitory levels in only a few days. 
     A number of suggestions have been made for inhibiting the growth of bacteria in aqueous fluids such as those described in U.S. Pat. Nos. 4,172,140, 3,951,830, 3,799,876, 3,515,671, and 2,976,244. The use of various formaldehyde preservatives for metalworking fluids including monomethylol dimethyl hydantoin and dimethylol dimethyl hydantoin has also been proposed (see Bennett, E. O., Int. Biodetn. Bull. 9: 95-100 (1973) and Maeda et al, Agr. Biol. Chem., 40: 1111-2222 (1976)). 
     Gray and Wilkinson in J. Gen. Microbiol., 39: 385-399 (1965) and J. App. Bact., 28: 153-164 (1965) describe the action of the ethylenediaminetetraacetic acid (EDTA) on some bacteria. The effectiveness of such chelating agents as EDTA along for bacterial control in aqueous systems is disputed as evidenced by U.S. Pat. Nos. 3,240,701, 3,408,843, and 3,591,679. 
     The antimicrobial compositions used in industrial water based fluids seem to suffer from one or more disadvantages including high cost, unacceptable toxicity or low degree of effectiveness at the present state of the art. 
     The present invention provides agents which when combined with antimicrobial agents are effective to potentiate the activity of the antimicrobial agent in controlling the growth of microorganisms in industrial water based fluids. Hence, less antimicrobial agent is required to produce the same antimicrobial effect as compared to using the antimicrobial agent alone. 
     SUMMARY OF THE INVENTION 
     The present invention provides antimicrobial potentiating agents. The antimicrobial potentiating agents of the invention are alkanolamines and alkyl alkanolamines of the formula: 
     
         RNHR.sup.1 OH 
    
     wherein 
     R is hydrogen or normal C 1-6  alkyl; and R 1  is a normal or branched chain C 2-4  alkyl or hydoxymethyl C 2-4  alkyl. 
     Representative examples of alkanolamines which potentiate the activity of antimicrobial agents include n-hexyl ethanolamine, 2-methyl ethanolamine, 2-hydroxymethyl ethanolamine, n-amyl ethanolamine, 2-amine-1-butanol, 3-amino-1-propanol, and isopropanolamine. 
     The alkanolamines of this invention when combined with antimicrobial agents are effective to potentiate the activity of and extend the useful life the antimicrobial agents in preventing and controlling the fouling of industrial water based fluids. In particular, the use of the antimicrobial potentiating agents of the invention reduces the amount of antimicrobial agent needed to effect a desired control of microbial (including bacterial and fungal) growth in industrial water based fluids. Alternatively, the use of the antimicrobial potentiating agents of this invention can extend the useful life of the antimicrobial agent used to control microbial growth in industrial water based fluids. For example, 500-1500 ppm of the antimicrobial potentiating agents can reduce the needed amount of anitmicrobial agent by about 20-50%. Alternatively, 500-1500 ppm of the antimicrobial potentiating agent admixed with an antimicrobial agent will extend the normal useful life of the antimicrobial agent by about 20-100% or more. 
     In the context of this invention, the amount of potentiating agent added to the industrial water fluid does not by itself exhibit sufficient activity to control microbial growth in the fluid. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides compositions of antimicrobial potentiating agents together with antimicrobial agents. The compositions of the present invention when added to industrial water based fluids are useful to control the growth of microorganisms, including for example bacteria, algae and fungi, which tend to foul the industrial waters. 
     In the context of this invention, the term &#34;industrial water based fluid&#34; is meant to encompass water, oil in water, water in oil emulsions and like compositions which are susceptible to the infestation and growth of microorganisms. Thus, for example, soaps and detergent fluids, cosmetics, latex paints, paper pulping fluids, drilling muds, water based hydraulic fluids, water for coolant towers, metalworking fluids or cutting fluids, are included. 
     As used herein, the term &#34;antimicrobial effective amount&#34; means that amount of the antimicrobial agent which when added to the industrial water based fluid will adequately inhibit the growth of microorganisms in that fluid. The term &#34;antimicrobial potentiating effective amount&#34; or words to that effect, mean the amount of the antimicrobial potentiating agent which when combined with the antimicrobial agent is effective to enhance the activity of or prolong the useful life of the antimicrobial agent in controlling the growth of microorganisms in the industrial water based fluids. 
     Generally, from about 500 to 1500 parts of the alkanolamine, antimicrobial potentiating agent are admixed with the recommended effective amount of the antimicrobial agent per million parts of the industrial water based fluid. 
     In general, the antimicrobial agents which are potentiated by the alkanolamines of this invention include triazines, phenols, morpholines, &#34;formaldehyde releasers (compounds which will hydrolyze into formaldehyde and other non-persistent fragments in aqueous solution including, e.g., tris(hydroxymethyl)nitromethane, hexahydro-1,3,5-tris(2-hydroxyethyl)-S-triazine, hexahydro-1,3,5-triethyl-S-triazine, hexahydro-1,3,5-tris(2-hydroxyethyl)-S-triazine iodine complex, and 1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride),&#34; azoniatricylodecanes, omadines and oxazolidines. Commericial products of such agents are currently marketed under the tradenames: Triadine 10, Grotan, Vancide TH, Dowicil, Dowicide A, Bioban P-1487, Tris Nitro, Busan 1024, Cosan 101, Nuosept 95. 
     The following examples are offered to more fully illustrate the invention, but are not intended to limit the scope thereof. 
     Experimental Procedures 
     The test units consisted of quart jars placed in rows. Above each row, a metal framework was constructed to support the aeration system which consisted of aquarium valves connected together with plastic tubing. The amount of aeration of each unit was controlled by adjusting the valves. Capillary pipettes were employed as aerators to produce a fine steam of bubbles in the diluted coolants. 
     Five hundred ml of tap water (120 ppm hardness) was added to each jar. The n-hexyl ethanolamine and selected antimicrobial agent were added to each jar along with 15.0 ml of cutting fluid concentrate to produce the desired coolant concentration. Each unit was then made up to a total volume of 600.0 ml by adding additional tap water. 
     Each test unit was inoculated with a mixture of bacteria and fungi which were obtained and maintained as described in Bennett, &#34;The Deterioration of Metal Cutting Fluids&#34;, Prog. Indust. Microbiol. 13: 121-249 (1974), the entire contents of which are incorporated herein by reference. Each unit was inoculated once each week with 1.0 ml of a 50-50 mixture of both inocula. 
     Each unit was examined once each week for its microbial content for as long as the count remained below 100,000 organisms/ml. Two consecutive counts in excess of this figure at weekly intervals was considered to constitute a failure and the test was discontinued at that time. 
     Two different types of control experiments were included. Each shipment of fresh coolant was tested upon arrival to determine if the product exhibited any inhibitory properties, as defined in the previous paragraph. All of the coolants used in the investigation were especially prepared by coolant manufacturers for this work and they did not contain a preservative. None of the products employed in this investation exhibited any inhibitory properties and failed in the first week of testing. The second set of controls consisted of a particular cutting fluid preserved with a commonly used antimicrobial agent. Normally, these control units failed within 21 days due to mold growth. The controls functioned normally during the test period. A third control consisted of representative cutting fluids with added n-hexyl ethanolamine. Normally, such controls failed within less than 7 days. 
     Since the test units were under constant aeration, there was considerable evaporation from each unit. The units were calibrated at the 600.0 ml mark and, once or twice each week, depending upon environmental conditions, distilled water was added to each unit to bring the liquid level back to this mark. Distilled water was used in order to avoid a buildup of inorganic salts in the test units. 
     Results 
     A series of sample jars were prepared according to the procedure outlined above to ascertain the antimicrobial potentiating effects of n-hexyl ethanolamine (HEA) when admixed with a selected antimicrobial agent. The sample coolants were mixed with water in a ratio of 1:40 (coolant to water). The results are set forth below, wherein the time in days is recorded when the microbial count in such test reached the level of 100,000 or the test discontinued. 
     The n-hexyl ethanolamine used in these examples was prepared according to the alternate synthesis scheme described in U.S. Pat. No. 4,749,503, issued Jun. 7, 1988. 
     As used in the following tables, the underlined numbers indicate that the test failed due to slime at the time noted, and the * means the test continued to show inhibitory action at the time the test was discontinued. 
     
                       TABLE 1                                                     
______________________________________                                    
EFFECTIVENESS OF DIFFERENT COMBINATIONS                                   
OF HEA AND GROTAN IN CUTTING FLUIDS                                       
______________________________________                                    
Compound    Concentration in ppm                                          
Grotan      500    1000   1500                                            
HEA                            500  1000 1500                             
Coolant     Days of control                                               
IRMCO emulsion                                                            
            7      21     14   0    7    7                                
Monroe Primecut                                                           
            7      21     21   0    0    0                                
Stuart emulsion                                                           
            7      21     14   0    0    0                                
Sanson coolant                                                            
            7      21     14   0    7    14                               
Buckeye emulsion                                                          
            7      21     14   0    7    7                                
Compound    Concentration in ppm                                          
Grotan       500    500   1000 1000 1500 1500 1500                        
HEA         1000   1500    500 1000  500 1000 1500                        
Coolant     Days of control                                               
IRMCO emulsion                                                            
            28     49     21   35   42   35   70                          
Monroe Primecut                                                           
            48     42     28   21   35   21   84                          
Stuart emulsion                                                           
            14     42     21   21   28   21   91                          
Sanson coolant                                                            
            21     84     21   28   28   35   98                          
Buckeye emulsion                                                          
            63     91     84   98   77   91   105*                        
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                       TABLE 2                                                     
______________________________________                                    
EFFECTIVENESS OF DIFFERENT                                                
COMBINATIONS OF HEA AND                                                   
BIOBAN P-1487 IN CUTTING FLUIDS                                           
______________________________________                                    
Compound    Concentration in ppm                                          
Bioban P-1487                                                             
            250    500    1000 500   250  500 1000                        
HEA                            500  1500 1500 1500                        
Coolants    Days of stability                                             
IRMCO emulsion                                                            
            0      14     35   21   28   42   84                          
Monroe Primecut                                                           
            28     56     84   14   35   56   63                          
Stuart emulsion                                                           
            7      42     49   21   21   42   56                          
Sanson coolant                                                            
            7      35     42   21   21   112  140*                        
Buckeye emulsion                                                          
            35     42     49   35   119  112  140*                        
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                                           TABLE 3                                 
__________________________________________________________________________
EFFECTIVENESS OF DIFFERENT COMBINATIONS OF HEA AND                        
NA OMADINE IN CUTTING FLUIDS                                              
__________________________________________________________________________
Compound                                                                  
       Concentration in ppm                                               
Na Omadine                                                                
       100 250 500 100  100                                               
                           250                                            
                              250                                         
                                 500  500                                 
HEA                1500 2000                                              
                           1500                                           
                              2000                                        
                                 1000 1500                                
Coolants                                                                  
       Days of stability                                                  
IRMCO  0   0   0   14   105                                               
                            28                                            
                              119                                         
                                 7    112                                 
Monroe 0   0   21  28    196*                                             
                            28                                            
                              119                                         
                                 7     28                                 
Stuart 0   21  35  42   147                                               
                            49                                            
                              119                                         
                                 49   112                                 
Sanson 0   7   21  21    77                                               
                            28                                            
                              112                                         
                                 7     140*                               
Buckeye                                                                   
       0   21  21  42    196*                                             
                            140*                                          
                               140*                                       
                                 77    140*                               
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                       TABLE 4                                                     
______________________________________                                    
EFFECTIVENESS OF DIFFERENT                                                
COMBINATIONS OF HEA AND                                                   
TRIADINE 10 IN CUTTING FLUIDS                                             
______________________________________                                    
Compound Concentration in ppm                                             
Triadine 10                                                               
         250    500    1000  250  250  500  500 1000                      
HEA                         1500 2000 1000 1500 1500                      
Coolant  Days of stability                                                
IRMCO    21     28     35   28   77   63   56   175                       
emulsion                                                                  
Monroe   49     49     77   42   84   49   42   112                       
Primecut                                                                  
Stuart   35     77     98   42   91   70   98   161                       
emulsion                                                                  
Sanson   28     42     56   77   63   42   140* 182*                      
coolant                                                                   
Buckeye  35     49     42   140* 105* 105* 140* 182*                      
coolant                                                                   
______________________________________                                    
 *Still inhibitory when taken off test                                    
 
    
     
                       TABLE 5                                                     
______________________________________                                    
EFFECTIVENESS OF DIFFERENT                                                
COMBINATIONS OF HEA AND                                                   
AMINE CS 1135 IN CUTTING FLUIDS                                           
______________________________________                                    
Compound    Concentration in ppm                                          
Amine CS 1135                                                             
            500    1000             1000  500 1000                        
HEA                       1000 1500 1000 1500 1500                        
Coolants    Days of stability                                             
IRMCO emulsion                                                            
            28     28     7    7    49   35   84                          
Monroe Primecut                                                           
            28     28     0    0    35   35   77                          
Stuart emulsion                                                           
            28     21     0    0    49   35   84                          
Sanson coolant                                                            
            28     14     7    14   35   35   91                          
Buckeye emulsion                                                          
            28     14     7    7    84   48   126                         
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                       TABLE 6                                                     
______________________________________                                    
EFFECTIVENESS OF HEA AND                                                  
COSAN 101 IN CUTTING FLUIDS                                               
           1000 ppm    1500 ppm Combination                               
Coolants   Cosan 101   HEA      of both                                   
______________________________________                                    
IRMCO emulsion                                                            
           14          7        84                                        
Monroe emulsion                                                           
           21          0        91                                        
Stuart emulsion                                                           
           21          0        70                                        
Sanson coolant                                                            
           21          14       98                                        
Buckeye emulsion                                                          
           21          7        140*                                      
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                       TABLE 7                                                     
______________________________________                                    
EFFECTIVENESS OF HEA IN COMBINATION                                       
WITH BUSAN 85 IN CUTTING FLUIDS                                           
           1000 ppm    1500 ppm Combination                               
Coolants   Busan 85    HEA      of both                                   
______________________________________                                    
IRMCO emulsion                                                            
           7           7        63                                        
Monroe Primecut                                                           
           7           0         7                                        
Stuart emulsion                                                           
           14          0        91                                        
Sanson coolant                                                            
           7           14       49                                        
Buckeye emulsion                                                          
           7           7        140*                                      
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                       TABLE 8                                                     
______________________________________                                    
EFFECTIVENESS OF HEA IN COMBINATION                                       
WITH BUSAN 1024 IN CUTTING FLUIDS                                         
           1000 ppm    1500 ppm Combination                               
Coolants   Busan 1024  HEA      of both                                   
______________________________________                                    
IRMCO emulsion                                                            
           0           7        14                                        
Monroe Primecut                                                           
           0           0        7                                         
Stuart emulsion                                                           
           7           0        7                                         
Sanson coolant                                                            
           0           14       7                                         
Buckeye emulsion                                                          
           0           7        49                                        
______________________________________                                    
 
    
     
                       TABLE 9                                                     
______________________________________                                    
EFFECTIVENESS OF HEA IN COMBINATION                                       
WITH TRIS NITRO IN CUTTING FLUIDS                                         
           1000 ppm    1500 ppm Combination                               
Coolants   Tris Nitro  HEA      of both                                   
______________________________________                                    
IRMCO emulsion                                                            
           7           7         0                                        
Monroe Primecut                                                           
           49          0        35                                        
Stuart emulsion                                                           
           0           0        28                                        
Sanson coolant                                                            
           14          14       42                                        
Buckeye emulsion                                                          
           7           7        56                                        
______________________________________                                    
 
    
     
                       TABLE 10                                                    
______________________________________                                    
EFFECTIVENESS OF HEA IN COMBINATION                                       
WITH AMINE CS-1246 IN CUTTING FLUIDS                                      
           1000 ppm    1500 ppm Combination                               
Coolants   CS-1246     HEA      of both                                   
______________________________________                                    
IRMCO emulsion                                                            
           7           7        21                                        
Monroe Primecut                                                           
           7           0        42                                        
Stuart emulsion                                                           
           7           0        21                                        
Sanson coolant                                                            
           7           14       21                                        
Buckeye emulsion                                                          
           7           7        105*                                      
______________________________________                                    
 
    
     
                       TABLE 11                                                    
______________________________________                                    
EFFECTIVENESS OF HEA IN COMBINATION                                       
WITH NUOSEPT 95 IN CUTTING FLUIDS                                         
           1000 ppm    1500 ppm Combination                               
Coolants   Nuosept 95  HEA      of both                                   
______________________________________                                    
IRMCO emulsion                                                            
           7           7        28                                        
Monroe Primecut                                                           
           7           0        28                                        
Stuart emulsion                                                           
           0           0        21                                        
Sanson coolant                                                            
           7           14       21                                        
Buckeye emulsion                                                          
           7           7        105*                                      
______________________________________                                    
 
    
     
                       TABLE 12                                                    
______________________________________                                    
EFFECTIVENESS OF HEA IN COMBINATION                                       
WITH TROYSAN 174 IN CUTTING FLUIDS                                        
            1000 ppm   1500 ppm   Combination                             
Coolants    Troysan 174                                                   
                       HEA        of both                                 
______________________________________                                    
IRMCO emulsion                                                            
            28         0          98                                      
Monroe Primecut                                                           
            42         14         98                                      
Stuart emulsion                                                           
            28         0          84                                      
Sanson coolant                                                            
            28         14         91                                      
Buckeye emulsion                                                          
            28         21         136                                     
______________________________________                                    
 
    
     Grotan is 78.5% active solution of hexahydro-1,3,5-tris (2-hydroxyethyl)-S-triazine. 
     Bioban P-1487 is a mixture of 70% 4-(2-nitrobutyl) morpholine and 20% 4,4-(2-ethyl-2-nitromethylene) dimorpholine. 
     Triadine 10 is a mixture of sodium 2-pyridinethiol-1-oxide 6.4% and hexahydro-1,3,5-tris-(2-hydroxyethyl)-S-triazine 63.6%. 
     Amine CS 1246 is 4,4-dimethyloxazolidine p-toluenesulfonic acid. 
     Cosan 101 is 74.9% 4,4 dimethyloxazolidine and 2.8% 3, 4, 6 trimethyloxazolidine. 
     Busan 85 is 90% by weight of barium metaborate. 
     Busan 1024 is a 40% aqueous solution of sodium salt of 1-carboxymethyl-3,5,7-triaza-1-azoniatricyclodecane chloride. 
     Tris Nitro is a 50% active solution of tris(hydroxymethyl)-nitromethane. 
     Nuosept 95 is a mixture of bicylicpolyoxymethylene oxazolidines. 
     Troysan 174 is 2-hydroxymethyl ethanolamine. 
     While the invention has been explained in relation to certain illustrative embodiments of it, it is understood that many modifications and substitutions may be made in any of the specific embodiments within the scope of the appended claims which are intended also to cover equivalents of them.