Stabilized enzymatic liquid detergent composition
TECHNICAL FIELD 
     This invention concerns stabilized enzymatic liquid detergent compositions for cleaning a wide range of items including hard surfaces and soft goods such as textiles both for commercial and home use. 
     BACKGROUND ART 
     Aqueous liquid enzymatic detergents are well-known in the prior art. The enzymes incorporated in liquid detergents have mostly been Bacillus protease, but the prior art also suggests that incorporation of enzymes other than Bacillus proteases may be useful, e.g., other enzyme types (such as amylases, lipases and cellulase) as well as enzymes of non-Bacillus origin (e.g., fungal enzymes). A major problem which is encountered with such compositions is that of ensuring a sufficient storage stability of the enzymes in such compositions. 
     The prior art deals extensively with stabilization of enzymes in liquid detergents. It is known that a number of commonly used detergent ingredients may reduce their storage stability, e.g., aniomic surfactants and detergent builders. The prior art also suggest that various materials that are not detergent-active can be incorporated as enzyme stabilizers. 
     It can also be mentioned that JP-A 58-194,806 and JP-A 58-069,808 suggest the incorporation of imidazoline amphoteric surfactant in tooth paste to improve the storage stability of amylase; this teaching has apparently not been utilized in detergents. 
     It is now the object of the invention to provide a liquid detergent composition comprising a detergent enzyme with improved storage stability. 
     STATEMENT OF THE INVENTION 
     The object of the invention is achieved by providing a stabilized enzymatic liquid detergent composition comprising 
     (a) an effective amount of a microbial enzyme 
     (b) from about 0.1 to 10% by weight of an amphoteric compounds having the general formula (I) ##STR2## R is zero, or C 1-12  alkyl, or C 11-17  alkyl --CONH --(CH 2 ) 3  n is 1-3 
     In preferred compounds of formula (I) R is zero or CH 3 , n is 1, i.e., dimethylglycine, and betaine. 
     In the propyl amido compounds of formula (I), the alkanoyl moiety is a saturated, unbranched and unsubstituted C 12-18  Preferred examples of the group R are those derived from coco acids (mainly C 12  -C 14 ) and from tallow acids (mainly C 16  -C 18 ), e.g., lauryl, stearyl, palmityl. 
     Preferred proportions for the stabilizer compound are in the range of 0.25-10%, more preferably, 0.5-5% by wt of the liquid detergent composition. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Microbial Enzyme 
     Microbial enzymes suitable for the present compositions include proteases, lipases, amylases and cellulases. The enzymes are derived from microbial sources, such as Bacillus and fungi. Some specific examples of detergent enzymes follow, each identified by enzyme type, microbial source and reference to a commercial product and/or a patent publication: 
     Protease of Bacillus, especially from B. licheniformis (e.g. Alcalase™) and from alkalophilic Bacillus strains according to U.S. Pat. No. 3,723,250 (e.g. Savinase™) (all available from Novo-Nordisk A/S) 
     Alpha-amylase of Bacillus, especially B. licheniformis. Termamyl™(Novo Industri A/S) 
     Protease of Fusarium, especially f. oxysporum, U.S. Pat. No. 3,652,399 (Takeda) 
     Protease according to DK 6376/87 (Novo) 
     Cellulase of Humicola, especially H. insolens. Celluzyme™ (Novo Industry A/S), U.S. Pat. No. 4,435,307 (Novo) 
     Lipase of Humicols, especially H. lanuginosa. Lipolase™ (Novo), EP 177,183 (Novo). 
     The detergent of the invention may contain two or more detergent enzymes. Examples are combinations of any two of the above enzymes, especially combinations of a Bacillus protease and any one of the above enzymes. 
     Amphoteric Compound of Formula (I) 
     Commercially available example of amphoteric compounds having the general formula (I) includes betaine. A related compound is dimethyl glycine; both are preferred compounds. The respective formulae of the two are as follows: 
     
         --(CH.sub.3).sub.3 --N.sup.+ --CH.sub.2 --COO-and -(CH.sub.3).sub.2 --N--CH.sub.2 --COO- 
    
     Surfactants 
     The detergent composition of the invention will usually also contain a nonionic surfactant, e.g., about 3-20% by weight. Further, the composition may optionally contain anionic surfactant and/or a second amphoteric surfactant, e.g., about 3-15% by weight. 
     Examples of suitable surfactants are: 
     Nonionics: Nonyl phenol ethoxylate, alcohol ethoxylate. 
     Anionics: linear alkylbenzene sulfonate, secondary alkane sulfonate, alcohol ethoxylate sulfate, alpha olefin sulfonate. 
     Other Ingredients 
     The liquid detergent of the invention may be aqueous, e.g., containing 20-70% of water and 0-20% of solvent, e.g., ethanol, propyleneglycol, or containing 1-20% of water and 5-25% of solvent. Satisfactory enzyme stability may be obtained even at water contents above 50%. Alternatively, it may be essentially free of water (e.g., water content below 1%), and will then typically contain 10-30% of solvent. 
     Typical solvents are mono- and dihydroxy lower alcohols and glycol ethers. 
     The detergent composition of the invention may be built (i.e., comprising a detergent builder) or unbuilt (i.e., essentially free of a detergent builder). 
     A soluble calcium salt may be included suitably in the range of about 1-20 millimole/l since calcium ion stabilizes many detergent enzymes. 
     pH will typically be neutral or alkaline, particularly preferred between 8-10. 
     The compositions may also contain, depending on the intended use, one or more of the usual known in the art detergent additives such as fabric conditioner (e.g., quaternary ammonium salts, typically 1-5%), foam boosters (e.g., 1-5%), bactericides (e.g., 1-5%), optical brighteners (e.g., 0.1-1%), dyes (e.g., 0.1-1%) and perfumes (e.g., 0.1-1%). Such additives are commonly present in detergent formulations. 
    
    
     In the following Examples the samples were stored at 37° C., the enzyme activity was measured before and after storage, and the results were expressed as residual activity in % of initial activity. 
     
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Example 1                                                                 
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Detergent base I composition, w/w                                         
Nonionic (Neodol 25-7) AE                                                 
                 25%                                                      
Anionic (Neodol 25-35) AES                                                
                 5%                                                       
Triethanolamine  5%                                                       
Ethanol          10%                                                      
Stabilizer (see table below)                                              
                       5% (control - no stabilizer)                       
protease         1%                                                       
amylase          0.3%                                                     
water            up to 100%                                               
Final pH = 9.0                                                            
Stability at 37° C. with various stabilizer                        
                        % Amylase Activity                                
         % Protease Activity                                              
                        Left After Six Weeks                              
         Left After 8 Weeks                                               
                        Termamyl                                          
Stabilizer                                                                
         Alcalase                                                         
              Esperase                                                    
                   Savinase                                               
                        + Alcalase                                        
                              + Esperase                                  
                                    + Savinase                            
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none     48   58   48   86    98    94                                    
Bentaine 65   78   70   86    86    84                                    
Dimethyl glycine                                                          
         74   79   66   110   72    91                                    
Alkyl amino Propyl betaine                                                
Cocoyl   67   74   61   95    77    91                                    
Isostearyl                                                                
         65   76   60   62    74    118                                   
Myristoyl                                                                 
         68   65   59   41 (?)                                            
                              97    93                                    
Palmytoyl                                                                 
         57   65   61   62    84    107                                   
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Example II                                                                
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Detergent base II                                                         
Nonionic (Neodol 25-7) AE                                                 
                   25%                                                    
Anionic (Vista C-550) LAS                                                 
                   5%                                                     
Triethanolamine    5%                                                     
Ethanol            10%                                                    
Stabilizer         0 (control), 0.5, 2.5, 5%                              
protease           1%                                                     
amylase            0.3%                                                   
water              up to 100%                                             
adjust to pH = 90                                                         
Stability at 37° C. with various stabilizer                        
              % Activity left after 8 weeks                               
Stabilizer        Alcalase   Savinase                                     
                                    Termamyl                              
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none              43         38     69                                    
Bentaine,   0.5   56         52     74                                    
            2.5   59         53     74                                    
            5.0   66         53     74                                    
Dimethylglycine,                                                          
            0.5   63         53     76                                    
            2.5   65         53     76                                    
            5.0   66         56     74                                    
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