Estolide derivatives useful as biolubricants

Abstract

A composition comprising a mixture of esters prepared by a three-step process comprising the steps of a oligomerization, a transesterification, and a capping. The composition is useful in a variety of applications, including as a biolubricant having a high level of renewable carbons, and may exhibit particularly desirable properties relating to pour point, thermo-oxidative stability, and viscometric behavior due to reduced or eliminated levels of unsaturation in the final double esters.

What is claimed is: 
     
         1 . A process for preparing a composition comprising a mixture of esters, the process comprising 
       the ordered steps of:
 (1-a) at least partially oligomerizing a mixture of at least two hydroxylated fatty acids or fatty esters to form a mixture of hydroxylated fatty acid or fatty ester oligomers; 
 (1-b) capping the mixture of hydroxylated fatty acid or fatty ester oligomers with an acid, acid anhydride or ester to form a mixture of capped fatty acid or fatty ester oligomers; and 
 (1-c) transesterifying the capped fatty acid or fatty ester oligomers with an alcohol to form the mixture of esters; 
 
       or 
       the ordered steps of
 (2-a) transesterifying a mixture of at least two hydroxylated fatty acids or fatty esters with an alcohol to form a mixture of hydroxylated fatty esters; 
 (2-b) oligomerizing the hydroxylated fatty esters to form a mixture of hydroxylated fatty ester oligomers; and 
 (2-c) capping the hydroxylated fatty ester oligomers with an acid, acid anhydride or ester to form the mixture of esters. 
 
     
     
         2 . The process of  claim 1  wherein
 step (1-a) further includes using a tin-containing, titanium-containing, or nitrogen-containing catalyst, and forming as a second product an alcohol, and removing the formed alcohol; 
 step (1-b) further includes using, an acid that contains from 2 to 12 carbon atoms, an ester that contains from 3 to 13 carbon atoms, or an acid anhydride that contains from 4 to 24 carbon atoms, and also using a tin-containing, titanium-containing, or nitrogen-containing catalyst, and optionally recovering the mixture of capped fatty acid or fatty ester oligomers from an excess of the acid, the acid anhydride or the ester added in step (1-b); 
 step (1-c) further includes using a tin-containing, titanium-containing, or nitrogen-containing catalyst; 
 step (2-a) further includes using a tin-containing, titanium-containing, or nitrogen-containing catalyst and optionally recovering the mixture of hydroxylated fatty esters from residual or formed alcohol; 
 step (2-b) further includes using a tin-containing, titanium-containing or nitrogen-containing catalyst and removing the formed alcohol, optionally by using one or more of an entrainer, reduced pressure and nitrogen sparging; and 
 step (2-c) further optionally includes recovering the mixture of esters from an excess of the acid, acid anhydride or ester added as a reactant in step (2-b) and alcohol added as a reactant in step (2-c). 
 
     
     
         3 . A process for preparing a composition comprising a mixture of esters, the process comprising either the ordered steps of (1-a) through (1-c), or of (2-a) through (2-c), the ordered steps being:
 (1-a) oligomerizing a mixture of at least two hydroxylated fatty acids or fatty esters, using a tin-containing, titanium-containing or nitrogen-containing catalyst and removing formed alcohol, optionally by using one or more of an entrainer, reduced pressure and nitrogen sparging, to yield a product 1-X with distribution of compounds represented by Formula 1:   
       
         
           
           
               
               
           
         
         wherein R is an alkyl group that contains from 1 to 12 carbon atoms, R 1  is hydrogen or a methyl radical, x is a rational number from 0 to 12 and n is a rational number from 1 to 20, and the formed alcohol having the formula R 1 OH;
 (1-a1) optionally recovering product 1-X from residual R 1 OH and, when used, the entrainer; 
 
         (1-b) reacting product 1-X with an acid that contains from 2 to 12 carbon atoms, an ester that contains from 3 to 13 carbon atoms, or an acid anhydride that contains from 4 to 24 carbon atoms, optionally using an additional amount of a tin-containing, titanium-containing or nitrogen-containing catalyst, and removing formed alcohol to yield a product 1-Y with a distribution of compounds represented by Formula 2: 
       
       
         
           
           
               
               
           
         
         wherein R, R 1 , x and n are as defined above and R 3  is an alkyl group that contains from 1 to 11 carbon atoms;
 (1-b1) optionally recovering product 1-Y from excess acid, acid anhydride or ester added as a reactant in step (1-b); and 
 
         (1-c) reacting product 1-Y with an alcohol to form product 1-Z with a distribution of compounds represented by Formula 3: 
       
       
         
           
           
               
               
           
         
         wherein R, R 3 , x and n are as defined above, R 2  is an alkyl group that contains from 1 to 20 carbon atoms;
 (1-c2) optionally recovering product 1-Z from alcohol and residual R 1 OH added during (1-c) and acid formed during reaction of 1-Y with the acid, acid anhydride or ester added in (1-b); 
 
       
       or the ordered steps of:
 (2-a) reacting a mixture of at least two hydroxylated fatty acids or fatty esters with an alcohol to form product 2-X with a distribution of compounds represented by Formula 4: 
 
       
         
           
           
               
               
           
         
         wherein R is an alkyl group that contains from 1 to 12 carbon atoms; R 2  is an alkyl group that contains from 1 to 20 carbon atoms, x is a rational number from 0 to 12;
 (2-a1) optionally recovering product 2-X from residual or formed R 2 OH; 
 
         (2-b) oligomerizing product 2-X, using a tin-containing, titanium-containing or nitrogen-containing catalyst and removing the formed R 2 OH, optionally by using one or more of an entrainer, reduced pressure and nitrogen sparging, to yield a product 2-Y with distribution of compounds represented by Formula 5: 
       
       
         
           
           
               
               
           
         
         wherein R, R 2 , and x are as defined above and n is a rational number from 1 to 20;
 (2-b1) optionally recovering product 2-Y from residual R 2 OH and, when used, the entrainer; and 
 
         (2-c) reacting product 2-Y with an acid that contains from 2 to 12 carbon atoms, an ester that contains from 3 to 13 carbon atoms, or an acid anhydride that contains from 4 to 24 carbon atoms, optionally using an additional amount of a tin-containing, titanium-containing or nitrogen-containing catalyst, to yield a product 2-Z with distribution of compounds represented by Formula 6: 
       
       
         
           
           
               
               
           
         
         wherein R, R 2 , R 3 , x and n are as defined above; and
 (2-c1) optionally recovering product 2-Y from excess acid, acid anhydride or ester added as a reactant in (2-b) and alcohol added as a reactant in (2-c). 
 
       
     
     
         4 . A composition comprising a mixture of esters, prepared by the process of  claim 1  or  claim 3 . 
     
     
         5 . The composition of  claim 4  that exhibits properties including at least one of a pour point that is less than or equal to −10° C. (measured according to ASTM D97); a viscosity index that is greater than or equal to 150; a kinematic viscosity at 40° C. that is more than 15 centistokes (cSt) (measured according to ASTM D445); a total acid number that is less than 1 milligram of potassium hydroxide per gram (mg KOH/g); a hydroxyl number that is less than or equal to 10; an iodine number that is less than 3 weight percent; and a renewable carbon level that is at least 50 percent by weight (measured according to ASTM 6866-08). 
     
     
         6 . The composition of  claim 5  wherein the pour point is less than −15° C.; the kinematic viscosity at 40° C. is greater than 20 cSt; the total acid number is less than 0.5 mg KOH/g; and the hydroxyl number is less than 5. 
     
     
         7 . A composition comprising a distribution of compounds represented by Formula 3: 
       
         
           
           
               
               
           
         
         wherein R is an alkyl group that contains from 1 to 12 carbon atoms; R 2  is an alkyl group that contains from 1 to 20 carbon atoms; R 3  is an alkyl group that contains from 1 to 11 carbon atoms; x is a rational number from 0 to 12 and n is rational number from 1 to 20, wherein at least two compounds in the distribution of compounds have different values of x.