Hydroxyalkyl bis(dialkylaminoalkyl)amine manufacture
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains to the field of catalyst manufacture. 
     2. Description of the Prior Art 
     Hydroxyalkyl bis(dialkylaminoalkyl)amine is disclosed as a useful urethane catalyst in U.S. Pat. No. 4,101,470. The patent discloses that these compositions may be prepared by first making bis(dialkylaminopropyl)amine which may be readily reacted with various olefin oxides. However, it has been found that in the manufacture of the bis(dialkylaminopropyl)amines by the reaction of a dialkylamine with acrylonitrile followed by hydrogenation that a significant quantity of dimethylaminoalkylaminoalkylnitrile is also produced. This is difficult to separate from the bis(dialkylaminopropyl)amine. 
     The invention disclosed herein provides a method whereby very pure hydroxyalkyl bis(dialkylaminoalkyl)amine is made. 
     SUMMARY OF THE INVENTION 
     The invention is a process for preparing relatively pure hydroxyalkyl bis(dialkylaminoalkyl)amine by adding to a mixture of dialkylaminoalkylaminoalkylnitrile and bis(dialkylaminoalkyl)amine under alkoxylation conditions sufficient alkylene oxide to react with substantially all of the bis(dialkylaminoalkyl)amine and then separating the reacted materials by distillation. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In one embodiment of the invention, bis(dialkylaminopropyl)amine, represented by the structure ##STR1## and dialkylaminopropylaminopropionitrile, represented by the structure ##STR2## where R is lower alkyl in both structures, are reacted with an alkylene oxide which preferentially reacts with the bis(dialkylaminopropyl)amine. The products are then separated by distillation. 
     A preferred embodiment is the following reaction sequence which produces a mixture of dimethylaminopropylamine (A), bis(dimethylaminopropyl)amine (B) and dimethylaminopropylaminopropionitrile (C) ##STR3## (A) can be separated readily from B and C by distillation; however, it is very difficult to separate B from C by distillation. 
     In this invention an alkylene oxide such as ethylene oxide, propylene oxide, butylene oxide or the like (preferably propylene oxide) is reacted with the mixture of bis(dialkylaminoalkyl)amine and the dimethylaminoalkylaminoalkylnitrile under conventional alkoxylation conditions and the alkylene oxide reacts with substantially all of the bis(dialkylaminoalkyl)amine in preference to the nitrile compound. The resulting hydroxyalkyl bis(dialkylaminoalkyl)amine has the following structure if propylene oxide, for example, is used ##STR4## 
     This compound may then be separated from the nitrile compound by simple distillation techniques resulting in a relatively pure hydroxyalkyl derivative of the bis(dialkylaminoalkyl)amine. 
     The following examples this separation technique. 
    
    
     EXAMPLE 1 
     The amines were charged to a kettle and then heated to 130° C. The propylene oxide was then added while maintaining the reaction temperature between 130° C. and 140° C. After all of the propylene oxide had been added, the reaction was digested to a constant pressure and then cooled and discharged. 
     
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               A    B      C      D    E                                  
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Reactants                                                                 
bis(dimethylaminopropyl)amine                                             
                 200    200    200  200  200                              
Dimethylaminopropylamino-                                                 
                 20     20     20   20   20                               
propionitrile                                                             
Water            --     4.0    4.0  4.0  --                               
Propylene oxide  37.2   37.2   62   49.6 62.1                             
Gas Chromatogram, area %                                                  
bis(dimethylaminopropyl)amine                                             
                 43     56     33   44   21                               
Dimethylaminopropylamino-                                                 
                 9      9      8    9    7                                
propionitrile                                                             
Hydroxypropyl bis(di-                                                     
                 46     33     56   45   63                               
methylaminopropyl)amine                                                   
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     Example B was distilled using a 9&#34; Vigreaux column. The first distillation cut was 90°-110° C. at 2.1 mm Hg vacuum. It contained 86% bis(dimethylaminopropyl)amine and 11% dimethylaminopropylaminopropionitrile. The product hydroxypropyl bis(dimethylaminopropyl)amine was obtained at 131° C. and 2.5 mm Hg vacuum. It was 99% pure by gas chromatograph.