Method of producing an amide product mixture, an amide product mixture and the use thereof
This application is 371 of PCT/SE92/00200 filed Apr. 29, 1992. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present application relates to a method of producing an amide product mixture having a low content of secondary amines. The amide product mixture obtained contains a minor amount of tertiary amines and exhibits advantageous properties when used for the formulation of cosmetic products, such as shampoos and creams; foam cleaning compositions, e.g., for textiles and cars; and functional fluids, such as lubricants, metal working fluids and hydraulic fluids. 
     2. Description of the Related Art 
     The use of amides manufactured by amidation of monocarboxylic acids or their alkylesters, such as methyl esters, with secondary amines, such as diethanolamine, in a variety of cosmetic products, foam cleaning compositions and industrial fluids, is well known. In order to avoid the formation of undesired by-products, such as monoesters, diesters, and different types of esteramides, the amidation reaction has normally been carried out in a surplus of the secondary amine, such as diethanolamine, which, after the reaction, is present unreacted in the reaction mixture. The content of the secondary amine in the reaction mixture may vary within wide limits, but will be above 1% by weight. Where the reactants are a monocarboxylic acid and diethanolamine, the content of secondary amine is normally between 10% and 30% by weight and with the metylester of a monocarboxylic acid and diethanolamine as reactants, the content of secondary amine will be about 5-10% by weight. 
     The fact that the amide product mixture contains a large amount of secondary amine, such as diethanolamine, has not been considered as any real drawback as the secondary amine has contributed to improved anticorrosion properties when used in functional fluids and to a desired alkalinity and foam stabilization when used in cosmetic products and foam cleaning compositions. 
     Recently, more attention has been paid to the fact that secondary amines, such as diethanolamine, are toxic and form nitrosamines, which are carcinogenic in animal tests. Therefore, a reduction of the content of secondary amines is desirable. The content should, according to recommendations, be less than 1% by weight. 
     Thus, one object of the present invention is to produce an amide product mixture which contains secondary amines containing less than 1% by weight. 
     Another object of the invention is that the method of producing the amide product mixture shall be simple to perform and that the amide product mixture shall be useable without any additional cleaning and/or working-up processes. 
     Another object of the invention is to keep the formation of esters, diesters and esteramides to a low level. 
     Still another object of the invention is that the amide product mixture shall at least have about the same corrosion inhibiting ability and/or defoaming properties in functional fluids and at least about the same foam stabilizing properties in cosmetics and foam cleaning products as the corresponding amide product mixture with high contents of secondary amines. 
     SUMMARY OF THE INVENTION 
     According to the invention it has been found that these objects can be met by producing an amide product mixture containing a major part of a monocarboxylic acid amide having the formula ##STR1## where R is an aliphatic hydrocarbon group having 7-23 carbon atoms, R 1  and R 2  are, independent of each other, an alkyl group having 2-8 carbon atoms, perferably 1-4 carbon atoms or hydroxylalkyl groups having 2-8 carbon atoms, preferably 2-4 carbon atoms; and less than 1% by weight of a secondary amine having the formula ##STR2## where R 1  and R 2  have the meaning mentioned above; from an amide product mixture containing a major part of a monocarboxylic acid amide having the formula (I) and more than 1% by weight of a secondary amine having the formula (II) characterised in that the amine product mixture containing more than 1% by weight of the secondary amine II is alkoxylated with an aliphatic alkylene oxide having 2-8 carbon atoms, preferably 2-4 carbon atoms in the absence of an essential amount of any alkoxylation catalyst, until the content of the secondary amine is less than 1% by weight. By the expression &#34;major part of a monocarboxylic acid amide&#34; is here understood that said amide constitutes at least 50% by weight of the amide product mixture. The secondary amine, which is one of the reactants in the process, has a catalytic effect and it seems to catalyse rather selectively its own alkoxylation. The presence of an effective amount of an alkoxylation catalyst other than the secondary amine must be avoided, as this will favour undesired side reactions. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     By the method of this invention, the contents of secondary amines are reduced to less than 1% by weight, while the undesired side reactions, such as alkoxylation of hydroxyl groups and esterification, are kept on a low level. Furthermore, the amide product mixture obtained is a clear, homogeneous fluid at room temperature, although the starting amide product mixture is normally solid or semi-solid. In order to further suppress the side reactions it has been found suitable to perform the reaction below 100° C., preferably below 80° C., and most perferably below 60° C. The amount of alkylene oxide added has to be adjusted according to the amount of secondary amines, so that the latter can be alkoxylated to the corresponding tertiary alkanol amine. Normally, the molar ratio of alkylene oxide to the secondary amine is 1.0 to 1.25, perferably 1.01-1.15. 
     Suitable monocarboxylic acid amides with the formula (I) are those, where the acyl group RCO is derived from fatty acid or aliphatic saturated or unsaturated, straight or branched synthetic acids. Specific examples of such monocarboxylic acids are 2-ethylhexanoic acid, n-octanoic acid, pelargonic acid, iso-nonanoic acid, n-decanoic acid, lauric acid, myristic acid, palmitic acid and oleic acid. 
     The choice of carboxylic acids regulates, among other things, the HLB-value of the monocarboxylic acid amides, but also the choice of the secondary amine is of importance. Normally, groups R 1  and R 2  designate groups containing few carbon atoms, but in case group R has a low number of carbon atoms and/or a rather hydrophobic amide is desired, it may be advantageous to elect secondary amines with alkyl or hydroxy-alkyl groups with more than 4 carbon atoms. The same is valid also for the choice of alkylene oxide. However, normally R 1  and R 2  designate lower alkyl groups, such as methyl, ethyl, propyl, isopropyl, butyl or isobutyl; or hydroxyalkyl, such as hydroxyethyl, hydroxypropyl and hydroxybutyl. Examples of suitable secondary amines with formula (II) are methylhydroxyethylamine, ethylhydroxyethylamine, methylhydroxypropylamine and ethylhydroxypropylamine. Especially diethanolamine and diisopropanolamine are preferred. 
     The choice of alkylene oxide affects the HLB-value of the tertiary alkanolamine formed during the reaction and a higher alkylene oxide may be preferred if a tertiary alkanolamine with a more hydrophobic and surface active character is desired. Normally, the alkylene oxide used has 2-4 carbon atoms. Although ethylene oxide reacts easily with the secondary amine, it has surprisingly been found that propylene oxide and higher alkylene oxides react with a high selectivity with respect to the hydrogen atom bound to the nitrogen atom in the secondary amine resulting in a low degree of side reactions like propoxylation of hydroxyl groups in the secondary or tertiary amine or in esterification. 
     The amide product mixture according to the invention which is obtainable by the above described process and contains a minor amount of a tertiary alkanolamine has very advantageous properties. Thus, application tests have clearly indicated that the amide product mixture according to the invention is very suitable to be used as a component in cosmetic formulations, such as shampoos and creams; foam cleaning compositions, e.g. for textiles and cars; and aqueous functional fluids, such as lubricants, metal working fluids and hydraulic fluids. The contents of tertiary amines in the amide product mixture contribute to improved corrosion inhibiting and foaming properties. When the amide product mixture is used in aqueous functional fluids, the monocarboxylic acid amide with Formula (I) is normally based on a monocarboxylic acid containing 14-22 carbon atoms, while when used in cosmetic formulations and foam cleaning compositions, monocarboxylic acid amides based on carboxylic acids having 8-13 carbon atoms are normally preferred. 
    
    
     The present invention is further illustrated by the following examples. 
     EXAMPLES 1-2 
     An amide product mixture containing about 92% by weight of the compound RCON(C 2  H 4  OH) 2 , where RCO is derived from coconut fatty acid, and 5.8% by weight of diethanolamine was used as a starting material. The amide product mixture was obtained by reacting the methyl ester of coconut fatty acid with diethanolamine. An amount of 950 g of the amide product mixture was added to a pressure reactor, whereupon 26.2 g of ethylene oxide or 33 g of propylene oxide was added gradually and an alkoxylation reaction took place at a controlled temperature of 55° C. in the absence of any alkoxylation catalyst. After complete reaction the reaction mixture was cooled and analysed. The content of the diethanolamine found in the reaction mixture was determined at less than 0.5% by weight (ethoxylation) and less than 0.3% by weight (propoxylation) respectively. The content of the carboxylic acid amide compound was in both cases about 89.5%, which indicates that undesired esterification reactions are kept on a low level. 
     EXAMPLES 3-4 
     The amide product mixtures obtained in Examples 1-2 were tested with respect to their effects on iron corrosion in accordance with Institute of Petroleum, IP 287, Corrosion Test. The product mixtures were dissolved in amounts of 1, 2, or 3% by weight in soft water (1,2° dH) and the pH value was adjusted with diluted acetic acid to 9.9. The following results were obtained. 
     
                       TABLE 1                                                     
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           Corrosion, % of area stained                                   
           Addition                                                       
Amide mixture                                                             
             0%      1%        2%    3%                                   
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Unalkoxylated                                                             
             100     45        45    25                                   
Ethoxylated  100     25        15    8                                    
Propoxylated 100     45        15    8                                    
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     From the results it is evident that the alkoxylated amide containing products according to the invention have superior corrosion inhibition properties in comparison with the unalkoxylated reference. 
     EXAMPLE 5 
     The ethoxylated amide product mixture according to Example 1 was dissolved in an amount of 25 mg together with 250 mg of sodium lauryl sulphate into 200 g of water having a total hardness of 10° dH or 20° dH. The pH value was adjusted to 7. The foaming ability of the formulations was then evaluated in accordance with Institute of Petroleum, IP 312, Foam Test. The following results were obtained. 
     
                       TABLE 2                                                     
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                      Foam height, cm                                     
Water hardness                                                            
           Temperature                                                    
                      Amide product                                       
°dH °C. Unalkoxylated                                       
                                  Ethoxylated                             
______________________________________                                    
20         30         400         430                                     
           40         435         460                                     
10         30         415         450                                     
           40         440         490                                     
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     From the results it is evident that the product according to the invention is able to advantageously replace the conventional unalkoxylated amide product mixtures in cosmetics and foam cleaning compositions. 
     EXAMPLES 6 TO 8 
     An amide product mixture containing about 71% by weight of the compound RCON(C 2  H 4  OH) 2 , where RCO is derived from a 1:1 mixture by weight of C 16  and C 18  fatty acids and about 25% by weight of diethanolamine was used as a starting material. The amide mixture was obtained by reacting the fatty acid mixture with diethanolamine. 
     An amount of 818 g of the amide product mixture was added to a pressure reactor followed by the gradual addition of 100 g ethylene oxide, 130 g propylene oxide or 159 g butylene oxide, whereupon alkoxylation was carried out in the absence of any alkoxylation catalyst at 60° C. After complete reaction, the product mixture was cooled and analysed. The content of diethanolamine was determined to less than 0.9% (ethoxylation), 0.6% (propoxylation), and 0.6% (butoxylation). 
     EXAMPLES 9-11 
     Semi-synthetic cutting fluid concentrates were formulated from the following ingredients. 
     
                       TABLE 3                                                     
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Material       Fluid A   Fluid B   Fluid C                                
______________________________________                                    
Monoethanolamine                                                          
               4.0       4.0       4.0                                    
Triethanolamine                                                           
               9.0       9.0       9.0                                    
Boric acid     6.0       6.0       6.0                                    
Water          16.0      16.0      16.0                                   
Alkylene glycol                                                           
               3.0       3.0       3.0                                    
Water soluble dispersant                                                  
               1.5       1.5       1.5                                    
Copper inhibitor                                                          
               0.2       0.2       0.2                                    
Paraffinic mineral oil                                                    
               37.5      37.5      37.5                                   
Tall oil fatty acid                                                       
               7.2       7.2       7.2                                    
(distilled)                                                               
Ethoxylated groundnut                                                     
               12.0      --        --                                     
fatty amide mixture                                                       
Propoxylated groundnut                                                    
               --        12.0      --                                     
fatty amide mixture                                                       
Butoxylated groundnut                                                     
               --        --        12.0                                   
fatty amide mixture                                                       
Alcohol type coupler                                                      
               3.6       3.6       3.6                                    
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     The concentrates were then diluted with water in accordance with Table 3 and then tested with respect to corrosion and foaming in the same manner as in Examples 3 and 5 respectively. The following results were obtained. 
     
                       TABLE 4                                                     
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Corrosion, % of area stained                                              
Dilution ratio                                                            
Fluid   1:20      1:30   1:40    1:50 1:60                                
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A       0         0      3       30   40                                  
B       0         0      5       20   40                                  
C       0         0      3       25   40                                  
______________________________________                                    
 
    
     
                       TABLE 5                                                     
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        Foam height, cm                                                   
        Seconds                                                           
Fluid     0     15       30  60     90  180                               
______________________________________                                    
A         90    40       20  10     5   0                                 
B         85    65       40  20     5   0                                 
C         85    65       30  15     5   0                                 
______________________________________                                    
 
    
     The results indicate that it is possible to formulate cutting fluids with good corrosion inhibiting effects and low initial foam heights which collapse quickly upon resting. 
     EXAMPLE 12 
     Example 1 was repeated, but 1.016 g of an amide product mixture containing 67% by weight of RCON(C 2  H 4  OH) 2 , where RCO was derived from groundnut fatty acid, and 29% by weight of diethanolamine was used as the starting material. The addition of ethylene oxide was 135 g. After ethoxylation, the diethanolamine content was less than 0.6% by weight. 
     EXAMPLE 13 
     Metal working fluids of the microemulsion type were prepared in accordance with the formulations below. 
     
                       TABLE 6                                                     
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                  % by weight                                             
Material            Fluid D  Fluid E                                      
______________________________________                                    
Paraffinic mineral oil                                                    
                    53.95    53.95                                        
Sodium petroleum sulphonates                                              
                    17.5     17.5                                         
Tall oil fatty acids (distilled)                                          
                    10.0     10.0                                         
Groundnut fatty diethanol                                                 
                    6.0      --                                           
amide mixture.sup.1/                                                      
Ethoxylated groundnut fatty                                               
                    --       6.0                                          
amide mixture.sup.2/                                                      
Potassium hydroxide (50%)                                                 
                    4.6      4.6                                          
Triethanolamine     1.0      1.0                                          
Calcium petroleum sulphonates                                             
                    0.45     0.45                                         
Biocide             0.65     0.65                                         
Glycol ether coupling agent                                               
                    3.85     3.85                                         
Copper inhibitor solution                                                 
                    2.0      2.0                                          
______________________________________                                    
 .sup.1/ Starting material in Example 12.                                 
 .sup.2/ According to Example 12.                                         
 
    
     The formulations were tested in 200 ppm (as CaCO 3 ) hard water with regard to their ability to prevent iron corrosion in the manner described in Example 3 and their foaming were determined in accordance with the VSI Foam Test procedure. The following results were obtained. 
     
                       TABLE 7                                                     
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           % Area of filter paper stained                                 
Dilution     Fluid D    Fluid E                                           
______________________________________                                    
40:1          1         1                                                 
50:1         10         5                                                 
60:1         13         8                                                 
80:1         30         12                                                
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                                           TABLE 8                                 
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         Foam developm. (secs)                                            
                          Foam decay (secs)                               
         Probe            Probe                                           
         1   2    3   Delay                                               
                          3    2   1                                      
Fluid                                                                     
     Conc.                                                                
         5 cms                                                            
             10 cms                                                       
                  15 cms                                                  
                      (secs)                                              
                          15 cms                                          
                               10 cms                                     
                                   5 cms                                  
__________________________________________________________________________
D    3%  2.4 24.0 127.2                                                   
                      40  2.3  9.3 68.0                                   
E    3%  2.8 27.2 136.5                                                   
                      40  1.9  8.2 64.6                                   
__________________________________________________________________________
 Note                                                                     
 Pressure 1.5 bar                                                         
 Probe heights 5, 10, 15 cms above fluid surface                          
 
    
     From the test results it is evident that the formulation containing the ethoxylated amide product mixture (fluid E) is superior in comparison with the formulation containing the unethoxylated amide product mixture.