Patent Publication Number: US-5424324-A

Title: Use of carbonyl stabilizers for 3-isothiazolones

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a continuation-in-part of Ser. No. 07/438,816, filed Nov. 17, 1989, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention concerns the stabilization of 3-isothiazolone compounds by the incorporation with those compounds of certain carbonyl compounds. 
     2. Description of the Prior Art 
     Isothiazolones have generated high commercial interest as microbicides to prevent spoilage of certain aqueous and non-aqueous products caused by microorganisms. Isothiazolones are highly effective microbicides (as used herein, &#34;microbicides&#34; includes bactericides, fungicides and algicides and microbicidal activity is intended to include both the elimination of and the inhibition or prevention of growth of microbial organisms such as bacteria, fungi and algae); by suitable choice of functional groups, they are useful in a broad range of applications. However, it has been long recognized that either in storage prior to addition to the substrate to be treated or after addition, their efficacy may be decreased because they are not stable under practical conditions of long-term storage. Means have thus been sought for some time to improve the stability of isothiazolones. 
     U.S. Pat. Nos. 3,870,795 and 4,067,878 teach the stabilization of isothiazolones against chemical decomposition by addition of a metal nitrite or metal nitrate, but teach that other common metal salts, including carbonates, sulfates, chlorates, perchlorates, and chlorides are ineffective in stabilizing solutions of isothiazolones, such solutions usually being in water or in an hydroxylic solvent. 
     U.S. Pat. Nos. 4,150,026 and 4,241,214 teach that metal salt complexes of isothiazolones are useful because they have enhanced thermal stability, while retaining biological activity. 
     It is known to use certain organic stabilizers for isothiazolones, generally for use situations where metal salts may create problems, such as corrosion, coagulation of latices, insolubility in non-aqueous media, interaction with the substrate to be stabilized, and the like. Formaldehyde or formaldehyde-releasing chemicals are known as stabilizers, (see U.S. Pat. Nos. 4,165,318 and 4,129,448), as are certain organic chemicals such as orthoesters (U.S. application Ser. No. 118,366) and epoxides (U.S. application Ser. No. 194,234). 
     Grove, U.S. Pat. No. 4,783,221 teaches blends of isothiazolones with at least one metal salt of an organic carboxylic acid having at least six carbon atoms, wherein the metal is a transition metal, zinc, mercury, antimony, or lead; and also with a solvent diluent. 
     In certain applications, however, it is desirable to avoid addition of organic stabilizers by virtue of their volatility, decomposition under high heat, higher cost, difficulty in handling, potential toxicity, and the like. Formaldehyde is a suspected carcinogen, and it is desirable not to use formaldehyde in applications where contact with human skin or lungs may occur. 
     In actual use, copper salts, such as copper sulfate, have proved efficacious in the stabilization of isothiazolones. However, copper salts may be undesirable in effluent streams in such operations as in the manufacture of stabilized isothiazolones or in their blending into a product or the use of that product. Copper salts, especially the chlorides, may contribute to possible corrosion, or in the presence of polymers in aqueous dispersion may lead to coagulation of the dispersion. 
     German patent application No. 3144137A discloses the use of isothiazolone derivatives to provide bacteriostatic activity in disinfectant compositions containing aldehydes. The minimum ratio of aldehyde to isothiazolone disclosed is 10:1, and there is nothing in the disclosure relating to the stability or otherwise of the isothiazolone. 
     U.S. Pat. No. 4,539,071 discloses a combination of an isothiazolone and glutaraldehyde as a biocide, but there is no discussion in this disclosure relating to the stability of the composition. Commercial formulations of isothiazolones and N,N-methylolchloroacetamide are also known, being sold under the trademark Parmetol, but the carbonyl compound is not being employed as a stabilizer. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a stabilization system for isothiazolones which overcomes some or all of the disadvantages of prior art systems. It is also an object to provide an isothiazolone stabilized by only low levels of stabilizer so as to avoid interference with other components in systems in which isothiazolones are used as microbicides. 
     These objects, and others which will become apparent from the following disclosure, are achieved by the present invention. It has been surprisingly found that isothiazolones may be stabilized against decomposition by the addition of a carbonyl compound to the composition containing the isothiazolone. Accordingly the invention provides in one aspect a composition comprising: 
     a) at least one 3-isothiazolone of the formula (I) ##STR4## wherein Y is an unsubstituted or substituted (C 1  -C 18 ) alkyl, an unsubstituted or substituted (C 3  -C 12 ) cycloalkyl, an unsubstituted or halogen-substituted (C 2  -C 8 ) alkenyl or alkynyl, an unsubstituted or substituted (C 7  -C 10 ) aralkyl, or an unsubstituted or substituted aryl; and 
     R and R 1  is each independently H, halogen or (C 1  -C 4 ) alkyl; and 
     b) a carbonyl compound selected from the group consisting of (C 2  -C 6 ) aldehydes, (C 7  -C 10 ) aromatic aldehydes and acids, (C 2  -C 4 ) dialdehydes, (C 1  -C 12 ) acids, (C 2  -C 8 ) diacids, triacids and tetracids, (C 3  -C 10 )α,β unsaturated carbonyls, otherwise unsubstituted (C 1  -C 6 ) haloamides of the formula ##STR5## where R 1  =phenyl or (C 1  -C 4 )alkyl-substituted phenyl, 
     R 2  =(C 1  -C 7 )alkyl, (C 1  -C 7 )alkoxylalkyl, or (C 1  -C 7 )carbalkoxyalkyl; 
     X 1 ,X 2 ,X 3  =H or halogen wherein at least one X is halogen; furfural, dibutylene furfural and maleimides of the formula ##STR6##  where R&#34; is H, (C 1  -C 4 ) alkyl or aryl; provided that when (b) is selected from the group consisting of aldehydes and dialdehydes the ratio (b):(a) is less than 10:1. 
     In another aspect, the invention comprises a method for inhibiting or preventing the growth of bacteria, fungi, yeast or algae in a locus subject or susceptible to contamination by bacteria, fungi, yeast or algae, which comprises incorporating onto or into the locus, in an amount which is effective to adversely affect the growth of bacteria, fungi, yeast, or algae, the aforementioned composition. 
     DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS 
     The isothiazolones which are stabilized include those disclosed in U.S. Pat. Nos. 3,523,121 and 3,761,488 and represented by the formula ##STR7## as defined above. In particular, Y may be a (C 1  -C 18 )alkyl or (C 3  -C 12 )cycloalkyl each optionally substituted with one or more of hydroxy, halo, cyano, alkylamino, dialkylamine, arylamino, carboxy, carbalkoxy, alkoxy, aryloxy, alkylthio, arylthio, haloalkoxy, cycloalkylamino, carbamoxy, or isothiazolonyl; and unsubstituted or halo-substituted (C 2  -C 8 ) alkenyl or alkynyl; a (C 7  -C 10 )aralkyl optionally substituted with one or more of halogen, (C 1  -C 4 )alkyl or (C 1  -C 4 )alkoxy; and an aryl optionally substituted with one or more of halogen, nitro, (C 1  -C 4 )alkyl, (C 1  -C 4 )alkyl-acylamino, carb(C 1  -C 4 )alkoxy or sulfamyl. 
     Preferred substituents for Y are substituted or unsubstituted (C 1  -C 18 ) alkyl or (C 3  -C 12 ) cycloalkyl; R is preferred to be H, Me or Cl; and R 1  is preferred to be H or Cl. Representative of such preferred Y substituents are methyl, ethyl, propyl, isopropyl, butyl, hexyl, octyl, cyclohexyl, benzyl, 3,4-dichlorobenzyl, 4-methoxybenzyl, 4-chlorobenzyl, 3,4-dichlorophenyl, 4-methoxyphenyl, hydroxymethyl, chloromethyl, chloropropyl, hydrogen, and the like. 
     Particularly preferred isothiazolones are 5-chloro-2-methyl-3-isothiazolone, 2-methyl-3-isothiazolone, 2-n-octyl-3-isothiazolone, 4,5-dichloro-2-cyclohexyl-3-isothiazolone and 4,5-dichloro-2-octyl-3-isothiazolone. 
     Most preferred is 5-chloro-2-methyl-3-isothiazolone, either as a sole compound or in admixture with 2-methyl-3-isothiazolone. When in admixture, the preferred ratio of monochlorinated/unchlorinated isothiazolone is from about 70:30 to about 85:15, and an especially preferred ratio is from about 70:30 to about 80:20. A second especially preferred isothiazolone is 2-methyl-3-isothiazolone in combination with low levels of 5-chloro-2-methyl-3-isothiazolone, a preferred ratio being from about 98:2 to about 96:4, and an especially preferred ratio being about 97:3. 
     The carbonyl compounds may possess other functionality such as a halogen substituent in addition to the carbonyl group: in particular, aromatic aldehydes may have other substituents on the aromatic ring. It will also be appreciated that carbonyl compounds may exist in the form of salts which can be equally active as stabilizers, and accordingly the present invention is intended to cover the claimed compounds when they exist as salts. Preferred carbonyl compounds are (C 2  -C 4 ) aldehydes, (C 4  -C 6 ) acids, (C 3  -C 5 ) α,β-unsaturated carbonyls, (C 2  -C 4 ) dialdehydes, (C 2  -C 4 ) diacids, and maleimides. Particularly preferred specific compounds include crotonaldehyde, glyoxal, maleic acid, succinic acid, fumaric acid, maleimide, (methyl-1-naphthyl) maleimide, N-ethyl maleimide, N-phenylmaleimide, malonic acid, glutaric acid and cinnamaldehyde. Additional preferred compounds include acetaldehyde, benzaldehyde, citral, and vanillin. 
     Some carbonyl compounds are known to have microbicidal activity, although their efficacy as stabilizers of isothiazolones has not previously been appreciated. Such compounds will be particularly desirable to use as stabilizers; examples are acrolein, benzoic acid, sorbic acid, dehydroacetic acid, glycolic acid and citric acid. 
     The composition may contain from about 0.01 to about 99.9999 parts of the one or more isothiazolones, and from about 0.0001 to about 99.9 parts of the carbonyl compound. 
     Generally, the composition of the invention will be in the form of a solution. Typical formulation ranges are illustrated in the following Table (all percentages are parts by weight) for both a concentrated solution of the isothiazolone and a dilute solution. For certain uses, such as shipping of large quantities, more concentrated solutions may also be utilized. 
     
         ______________________________________                                    
FORMULATIONS TABLE                                                        
Isothiazolone                                                             
             Carbonyl Compound                                            
                            Solvent                                       
______________________________________                                    
(I, Supra)   0.0001-99.9%   0-99.9899%                                    
0.01-99.9999%                                                             
Preferred     0.01-20%      30-99.89%                                     
0.1-50%                                                                   
______________________________________                                    
 
    
     Solvents may be used to dissolve the isothiazolones and may be any organic solvent which dissolves the isothiazolones, is compatible with the proposed end use, does not destabilize the isothiazolone, and does not react with the carbonyl compound to eliminate its stabilizing action. 
     Hydroxylic solvents, for example, polyols, such as glycols, alcohols and the like, may be used. Under conditions of high dilution and high ratios of stabilizer to isothiazolone, glycols may be successfully used. In certain formulations, hydrocarbons, either aliphatic or aromatic, are useful solvents. 
     Preferred solvents are capped polyols, wherein the free hydroxyl group is replaced with an ether or ester function. Especially preferred are 2,5,8,11-tetraoxadodecane, commonly known as triethylene glycol dimethyl ether, and 4,7-dioxaundecanol-1 acetate, commonly known as diethylene glycol butyl ether acetate. 
     Water is a solvent for certain of the preferred isothiazolones and the carbonyl compound may be employed in aqueous formulations. 
     The amounts of carbonyl compound employed will vary depending on use conditions and concentrations of the isothiazolone in the mixture: effective amounts of carbonyl compounds based on isothiazolone may be ratios in the range of from about 1:100 to about 1000:1 stabilizer to isothiazolone. In concentrated solutions, ratios are generally from about 1:50 to about 50:1. Obviously higher amounts may be used, but at additional cost. At high levels of dilution of the isothiazolone (such as from 1 to 10,000 ppm isothiazolone in the solvent), the ratio of stabilizer to isothiazolone can range from about 1:10 to about 20:1. The preferred range is from 1:1 to 20:1. 
     The stabilization advantages of the carbonyl compounds of the present invention are noted even when the isothiazolone contains other salt stabilizers recorded in U.S. Pat. Nos. 3,870,795, 4,067,878, 4,150,026 and 4,241,214. 
     Uses of these new organically stabilized microbicides are typically at any locus subject to contamination by bacteria, fungi, yeast or algae. Typically loci are in aqueous systems such as water cooling, laundry wash water, oil systems such as cutting oils, oil fields and the like where microorganisms need to be killed or where their growth needs to be controlled. However these stabilized microbicides may also be used in all applications for which known microbicidal compositions are useful; preferred utilities of the compositions are to protect wood paint, adhesive, glue, paper, textile, leather, plastics, cardboard, lubricants, cosmetics, food, caulking, feed and industrial cooling water from microorganisms. 
     The following lists typical industries and applications of compositions: 
     
         ______________________________________                                    
Industry       Application                                                
______________________________________                                    
Adhesives, Sealants                                                       
               adhesives                                                  
               caulks                                                     
               sealants                                                   
Agriculture/food chain                                                    
               adjuvant preservation                                      
               agricultural active ingredient                             
               agricultural chemical preservative                         
               agricultural formulations preservation                     
               animal feed preservation                                   
               dairy chemicals                                            
               fertilizer preservation                                    
               food preservation                                          
               food processing chemicals                                  
               grain preservation                                         
               post-harvest produce protection                            
               sugar processing                                           
               tobacco                                                    
Construction products                                                     
               asphalt/concrete                                           
               cement modifiers                                           
               construction products                                      
               roof mastics                                               
               synthetic stucco                                           
               wall mastics                                               
               joint cement                                               
Cosmetics and toiletries                                                  
               cosmetics                                                  
               raw materials for cosmetics, toiletries                    
               toiletries                                                 
Disinfectants, antiseptics                                                
               antiseptic                                                 
               disinfectant                                               
Emulsions, dispersions                                                    
               aqueous dispersions                                        
               dispersed pigments                                         
               latex                                                      
               photographic emulsions                                     
               pigment slurries                                           
               polymer latices                                            
Formulated household                                                      
               fabric softeners                                           
products       polishes                                                   
               waxes                                                      
               hand dish detergents                                       
               raw materials                                              
               liquid detergents                                          
               hand soaps                                                 
Industrial processing, misc                                               
               electrodeposition paint, baths, rinses.                    
               electrodeposition pretreatment, post                       
               rinses                                                     
               industrial fluids preservation                             
               pasteurization baths                                       
               process aid preservation                                   
Industrial water treatment                                                
               air washers                                                
               cooling towers                                             
               cooling water                                              
               water cooling                                              
               preservation/treatment of wooden                           
               cooling tower slats and structural                         
               members                                                    
               can warmers                                                
               brewery pasteurization                                     
               closed loop water cooling systems                          
Laundry        household laundry products                                 
               laundered goods                                            
               laundry wash water                                         
               sanitizers-laundry                                         
Leather, leather products                                                 
               leather and hide                                           
               leather and hide products                                  
Lubricants, hydraulic aids                                                
               automotive lubricants and fluids                           
               conveyor lubricants                                        
               greases                                                    
               hydraulic fluids                                           
               lubricants                                                 
Medical devices                                                           
               diagnostic enzymes                                         
               diagnostic kits                                            
               medical devices                                            
Metalworking &amp; related                                                    
               cutting fluids                                             
app&#39;s          metal cleaning                                             
               metalworking fluids                                        
Odor control   air conditioning                                           
(active ingredient)                                                       
               animal bedding                                             
               cat litter                                                 
               chemical toilet prep&#39;ns                                    
               deodorizers                                                
               humidifiers                                                
               industrial deodorants                                      
               sanitary formulations                                      
               toilet bowls                                               
Paints and coatings                                                       
               emulsions                                                  
               paints                                                     
Paper and wood pulp,                                                      
               absorbant materials of paper and                           
their products wood pulp                                                  
               packaging materials of paper and                           
               wood pulp                                                  
               paper                                                      
               paper products                                             
               paper treatment                                            
               soap wrap                                                  
               wood pulp                                                  
               wood pulp products                                         
Paper mill     paper mill slimicides                                      
               pulp and paper slurries                                    
Petroleum refining, fuels                                                 
               aviation fuels (jet fuel, aviation gas)                    
               crude oils                                                 
               burner, diesel and turbine fuel oils                       
               coal slurries                                              
               diesel fuel additives                                      
               diesel fuels                                               
               fuels                                                      
               gasoline                                                   
               heating oils                                               
               hydrocarbons                                               
               kerosene                                                   
               liquefied petroleum gas                                    
               petrochemical feedstocks                                   
               petroleum products, storage,                               
               transportation and production                              
               recycled petroleum products                                
               residual fuel oils                                         
               turbine oils                                               
Photographic Chemicals                                                    
               photographic processing - wash                             
and process    water, rinses                                              
               photoprocessing                                            
               photoplate processing chemicals                            
               (developers, stabilizers etc)                              
Printing       fountain solutions (printing)                              
               ink components (pigments, resins,                          
               solvents, etc)                                             
               inks                                                       
Sanitizers (active)                                                       
               sanitizers                                                 
               sanitizers-dairy                                           
               sanitizers-dental                                          
               sanitizers-fermentation                                    
               sanitizers-food preparation                                
               sanitizers-food processing                                 
               sanitizers-medical                                         
               sanitizers-rendering                                       
               sanitizers-veterinary                                      
Soaps, detergents, cleaners                                               
               cleaners                                                   
               detergents                                                 
               household cleaners                                         
               industrial cleaners                                        
               liquid soaps                                               
               oil and grease remover                                     
               powdered soaps                                             
               raw materials for cleaning products                        
               soaps                                                      
               surfactants                                                
Textiles, textile products                                                
               bonded fabrics                                             
               burlap                                                     
               canvas                                                     
               canvas goods                                               
               carpet backing                                             
               carpets                                                    
               clothing                                                   
               coated fabrics                                             
               curtains                                                   
               draperies                                                  
               engineering textiles                                       
               fibers                                                     
               geotextiles                                                
               goods made of textiles                                     
               knitted fabrics                                            
               nets                                                       
               nonwoven fabrics                                           
               rope                                                       
               rugs                                                       
               textile accessories                                        
               textile products                                           
               textiles                                                   
               upholstery                                                 
               woven fabrics                                              
               yarn                                                       
Textile processing                                                        
               dye fixatives                                              
               dyes                                                       
               fiber lubricants                                           
               hand modifiers                                             
               sizes                                                      
               textile processing fluids                                  
Therapeutic (active or                                                    
               animal health/veterinary                                   
preservative)  aquaculture                                                
               dental                                                     
               human health                                               
               pharmaceutical/therapeutic                                 
Water purification                                                        
               charcoal beds                                              
               deionization resins                                        
               filters                                                    
               membranes                                                  
               reverse osmosis membranes                                  
               ultrafilters                                               
               water purification                                         
               water purification pipes, tubing                           
Wood applications                                                         
               lazures (wood stains)                                      
               wood                                                       
               wood products                                              
Miscellaneous  alcohols                                                   
               bedding incorporating water or gels                        
               ceramic                                                    
               contact lens cases-leaching                                
               electronic circuitry                                       
               electronics chemicals                                      
               enzymes-food production                                    
               enzymes                                                    
               enzymes-industrial                                         
               gel cushions                                               
               marine antifoulants                                        
               mildewcides                                                
               wood                                                       
               plastics                                                   
               laundry                                                    
               mining                                                     
               natural rubber latex                                       
               oil field injection waters including                       
               enhanced recover injection fluids,                         
               drilling, fracturing and completion                        
               fluids                                                     
               pipes                                                      
               plastics                                                   
               polymer systems                                            
               polymers and resins (synthetic and                         
               natural)                                                   
               reagent preservation                                       
               rubber                                                     
               rubber products                                            
               skin remover                                               
               solid protective/decorative films                          
               stains                                                     
               swimming pools                                             
               waste treatment                                            
               water beds                                                 
______________________________________                                    
 
    
     Because isothiazolones are so active as microbicides and only low levels of carbonyl compounds are required to achieve stabilization, the amount of carbonyl compound in systems being treated will be very small, and therefore it is not likely to interfere with other components in systems requiring protection or with systems to which the protected systems will be applied. Potential areas of general application include metal-working fluids, cooling water, and air washers. 
     One significant area of application for the compositions of the invention is as microbicides in metal working fluids. Metal working fluids are proprietary combinations of chemicals, which may contain, inter alia, ingredients such as alkanolamines, petroleum sulfonate surfactants, oils (naphthenic, paraffinic, etc.), chlorinated paraffins and fatty esters, sulfurized fatty compounds, phosphate esters, fatty acids and their amine salts, glycols, polyglycols, boric acid esters and amides. They are utilized in the milling, machining, drilling, and other processing technologies for fabricating metal for the purposes of lubricating, cooling, preventing surface corrosion, and the like. They are sold in the form of active metal working fluid (MWF) concentrates, and are diluted in use to 1-10% active ingredients in water. 
     Because metal working fluids are recycled and stored, the growth of microorganisms is favored. Isothiazolones have been found effective in preventing the growth of such organisms. Certain of the components in the metal working fluids will tend to destroy the isothiazolone and so remove its microbicidal protective activity, so that stabilizers for the isothiazolone against such degradation are desirable. 
     It is known in the art that the performance of microbicides may be enhanced by combination with one or more other microbicides. Thus, other known microbicides may be combined advantageously with the composition of this invention. 
    
    
     The following examples are intended to illustrate the present invention and not to limit it except as it is limited by the claims. All percentages are by weight unless otherwise specified, and all reagents are of good commercial quality unless otherwise specified. Methods for quantitative determination of the isothiazolones in the following examples in metal-working fluids are described in detail in &#34;Kathon® 886 MW Microbicide and Kathon® 893 MW Fungicide: Analysis in Metalworking Fluids by High-Performance Liquid Chromatography&#34;, 1988, Rohm and Haas Company. 
     EXAMPLES 
     EXAMPLES 1 TO 4 
     These examples demonstrate the stabilizing effect of carbonyl compounds for isothiazolones added to several different metal working fluids (MWF). MWF concentrates A and B were &#34;semisynthetic&#34; types having about 10 to 15 percent naphthenic/paraffinic oil, about 50 percent water, emulsifying agents, pH adjusting amines, anticorrosive agents, and EP (extreme pressure) agents. 
     Into a glass vial in the following order were placed: a) 5 parts by weight of the MWF concentrate solution, b) 5 parts of the stabilizer in solution or dispersion, c) 5 parts water, d) 5 parts of an aqueous solution containing 80 ppm active ingredient (AI), prepared by dilution of a 14.4% aqueous solution of an approximately 75/25 mixture of 5-chloro-2-methyl-3-isothiazolone and 2-methyl-3-isothiazolone, the former being considered the active ingredient for these purposes; also present was 9.2% magnesium chloride and 15.7% magnesium nitrate. Thus the final mixture contained 3-5% of the MWF concentrate, 15 ppm active ingredient of the isothiazolone, and 0 (control) to 1,000 ppm of the stabilizer. 
     The vials were then capped, stored at ambient room temperature in a closed cabinet for a designated time, filtered through a 0.45 micron filter into another vial and analyzed the same day. The relative concentration of the active ingredient was determined by reverse phase high pressure liquid chromatography, utilizing a Varian model 5500 chromatograph and an ultraviolet detector. 
     
                       TABLE 1                                                     
______________________________________                                    
STABILIZATION OF 5-CHLORO-2-METHYL-3-                                     
ISOTHIAZOLONE IN MWF CONCENTRATE A                                        
AFTER FIVE DAYS                                                           
Original system contained 15 ppm 5-chloro-2-                              
methyl-3-(AI) with 3% MWF Concentrate A in water.                         
All stabilizers were added at 1000 ppm                                    
Stabilizer           % AI remaining                                       
______________________________________                                    
None, (comparative)   3                                                   
crotonic acid        87                                                   
trans-cinnamic acid  56                                                   
fumaric acid         100                                                  
maleic acid          100                                                  
N-phenylmaleimide    35                                                   
4-acetylbutyric acid 73                                                   
2-oxoadipic acid     65                                                   
3-oxoadipic acid     38                                                   
3-oxoglutaric acid   37                                                   
4-ketopimelic acid   66                                                   
succinic acid        100                                                  
3-bromopropionic acid                                                     
                     91                                                   
4-hydrazinobenzoic acid                                                   
                     34                                                   
Comparative                                                               
benzalacetophenone   11                                                   
2-oxooctanenitrile    0                                                   
pyruvonitrile         0                                                   
2,4-hexanedione       0                                                   
acetoacetanilide      0                                                   
4-chlorocinnamonitrile                                                    
                      5                                                   
2-acetoxy-3-butene nitrile                                                
                      0                                                   
N-(2-hydroxyethyl)acetoacetamide                                          
                      1                                                   
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     EXAMPLE 2 
     This example demonstrates the stabilizing effect of several carbonyl compounds on a commercial MWF after 4 days at room temperature. Testing was as in Example 1. In the absence of the MWF, the relative concentration of the AI remained at 100%. 
     
                       TABLE 2                                                     
______________________________________                                    
MWF A STABILIZED WITH CARBONYL COMPOUNDS                                  
AGED 4 DAYS                                                               
Original system contained 15 ppm 5-chloro-2-methyl-3-                     
isothiazolone (AI) with 3% MWF concentrate A in water.                    
All stabilizers were added at 1000 ppm.                                   
Stabilizer       % AI remaining                                           
______________________________________                                    
None              3                                                       
acrylic acid     79                                                       
propiolic acid   88                                                       
crotonic acid    70                                                       
trans-2-pentenoic acid                                                    
                 65                                                       
trans-2-hexenoic acid                                                     
                 39                                                       
butyric acid     72                                                       
vinyl acetic acid                                                         
                 59                                                       
crotonaldehyde   63                                                       
succinic acid    78                                                       
phthalic acid    22                                                       
maleic acid      91                                                       
fumaric acid     68                                                       
maleimide        67                                                       
isophthalic acid 67                                                       
malonic acid     91                                                       
succinic acid    79                                                       
glutaric acid    73                                                       
3-oxoglutaric acid                                                        
                 28                                                       
Comparative                                                               
methyl crotonate  9                                                       
crotononitrile    6                                                       
3-penten-2-one    4                                                       
succinamide       6                                                       
succinonitrile    4                                                       
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     EXAMPLE 3 
     This example demonstrates the stabilizing effect of further carbonyl compounds on a commercial MWF after 3 days at room temperature. 
     The original system contained 15 ppm of 5-chloro-2-methyl-3-isothiazone (AI) with 3% MWF concentrate A in water. All stabilizers were added at 1000 ppm. 
     
                       TABLE 3                                                     
______________________________________                                    
Stabilizer       % AI remaining                                           
______________________________________                                    
None             19                                                       
adipic acid      55                                                       
citric acid      79                                                       
tactic acid      43                                                       
(D)(L) malic acid                                                         
                 69                                                       
(D)(L) mandelic acid                                                      
                 37                                                       
oxalic acid      76                                                       
propionic acid   63                                                       
sorbic acid      52                                                       
tartaric acid    65                                                       
______________________________________                                    
 
    
     EXAMPLE 4 
     In this experiment, further results are shown for a variety of carbonyl compounds in two different MWFs. The carbonyl compounds tested were readily soluble in the test system; there was no color development with the systems on mixing. 
     
                       TABLE 4                                                     
______________________________________                                    
COMPARISON OF SEVERAL CARBONYL COMPOUNDS                                  
IN TWO MWF SYSTEMS AFTER 11 DAYS                                          
Original system contained 15 ppm 5-chloro-2-methyl-3-                     
isothiazolone (AI) with 3% MWF concentrate A in water.                    
All stabilizers were added at 1000 ppm.                                   
            Stabilizer                                                    
                     MWF Conc. A MWF Conc. B                              
            level    % AI        % AI                                     
Stabilizer  (ppm)    Remaining   Remaining                                
______________________________________                                    
None,         0      43           3                                       
(comparative)                                                             
N-ethylmaleimide                                                          
            1000     77           3                                       
N-phenylmaleimide                                                         
            1000     72          19                                       
t-cinnamaldehyde                                                          
            1000     61          50                                       
iodoacetamide                                                             
            1000     83          31                                       
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     EXAMPLE 5 
     This example illustrates the ability of carbonyl compounds to stabilize isothiazolone in the presence of typical formulations used for water treatment in cooling towers. 
     A synthetic cooling tower water was prepared by adding 466.4 mg sodium carbonate into a liter of deionized water. The pH was adjusted to 9.0 using concentrated hydrochloric acid. Into the solution was added 10.7 ml scale/corrosion inhibitor stock solution (Acrysol QR 1086, Bahibit AM, and Cobratec TT-50-S), then 160 mg CaCl 2 .2H 2  O and 122 mg MgCl 2 .6H 2  O. The final solution was adjusted to pH 9.0 with hydrochloric acid. 
     The synthetic water contained 170 ppm hardness as CaCO 3 , 440 ppm alkalinity as CaCO 3 , 5 ppm Acrysol® QR 1086, 5 ppm Bahibit™ AM (Phosphonate), and 2 ppm Cobratec® TT-50-S (Tolyltriazole). The hardness was 160 ppm CaCl 2 .2H 2  O and 122 ppm MgCl 2 .6H 2  O. 
     Isothiazolone was added at 5 ppm AI and incubated for 10 days at room temperature. AI analysis was done as described in Example 1. Results are given in Table 5. 
     
                       TABLE 5                                                     
______________________________________                                    
COMPARISON OF CARBONYL STABILIZERS IN                                     
COOLING TOWER WATER AFTER 10 DAYS                                         
AT ROOM TEMPERATURE                                                       
Stabilizer  Stabilizer Level (ppm)                                        
                           % AI Remaining                                 
______________________________________                                    
None         0             40                                             
crotonaldehyde                                                            
            50             40                                             
crotonaldehyde                                                            
            25             40                                             
glyoxal     50             74                                             
glyoxal     25             60                                             
maleimide   50             71                                             
maleimide   25             57                                             
t-cinnamaldehyde                                                          
            50             43                                             
t-cinnamaldehyde                                                          
            25             40                                             
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     EXAMPLES 6-9 
     These examples illustrate the stabilizing effect of carbonyl compounds for isothiazolones in metalworking fluids. Tests were run as described for Examples 1-4. Results are given in Tables 6-10. 
     
                       TABLE 6                                                     
______________________________________                                    
11.25 ppm AI, 300 ppm stabilizer, 2 days at room temperature,             
a synthetic metalworking fluid (MWF-A)                                    
Stabilizer     % AI remaining                                             
______________________________________                                    
None           50                                                         
Benzaldehyde   56                                                         
Salicylaldehyde                                                           
               66                                                         
Acetaldehyde   67                                                         
Methacrolein   69                                                         
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                       TABLE 7                                                     
______________________________________                                    
15 ppm AI, 1000 ppm stabilizer, 3 days at room temperature,               
MWF-A                                                                     
Stabilizer        % AI remaining                                          
______________________________________                                    
None              23                                                      
Furfuraldehyde    55                                                      
4-Methoxysalicylaldehyde                                                  
                  66                                                      
Methyl glyoxal    77                                                      
Glycollic acid    77                                                      
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                       TABLE 8                                                     
______________________________________                                    
15 ppm AI, 2000 ppm stabilizer, 3 days at room temperature,               
MWF-A                                                                     
Stabilizer   % AI remaining                                               
______________________________________                                    
None         14                                                           
Acrolein     67                                                           
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                       TABLE 9                                                     
______________________________________                                    
11.25 ppm AI, 300 ppm stabilizer, 2 days at room temperature,             
a synthetic metalworking fluid (MWF-A).                                   
Stabilizer     % AI remaining                                             
______________________________________                                    
None           32                                                         
Metolachlor    44                                                         
Diethatyl Ethyl                                                           
               72                                                         
Alachlor       46                                                         
Butachlor      42                                                         
______________________________________                                    
 
    
     The four stabilizers were added as the commercially available emulsifable concentrates (stabilizer in an aromatic or aliphatic solvent plus a mixture of nonionic and anionic emulsifiers). The products and suppliers were metolachlor (Dual EC-Ciba-Geigy); diethatyl ethyl (Antor EC-BFC Chemicals); alachlor (Lasso EC-Monsanto); and butachlor (Machete EC-Monsanto). 
     While the invention has been described with reference to specific examples and applications, other modifications and uses for the invention will be apparent to those skilled in the art without departing from the spirit and scope of the invention defined in the appended claims.