Estolide derivatives useful as biolubricants

A process for preparing a double ester of a secondary hydroxy fatty acid or fatty ester, 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) partially homopolymerizing a hydroxylated fatty acid compound, 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 in individual compounds R is an alkyl group that contains from 6 to 12 carbon atoms, R1 is hydrogen or a methyl radical, x is an integer within a range of from 8 to 12 and n is an integer between 1 and 20, and the formed alcohol having the formula R1OH;
• (1-a1) optionally recovering product 1-X from residual R1OH 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, R1, x and n are as defined above and R3 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, R3, x and n are as defined above, R2 an alkyl group that contains from 1 to 20 carbon atoms;
• (1-c2) optionally recovering product 1-Z from alcohol and residual R1OH 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 secondary hydroxyl fatty acid or fatty ester 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 6 to 12 carbon atoms;
• R2 is an alkyl group that contains from 1 to 20 carbon atoms, x is an integer within a range of from 8 to 12;
• (2-a1) optionally recovering product 2-X from residual or formed R2OH;
• (2-b) partially homopolymerizing product 2-X, using a tin-containing, titanium-containing or nitrogen-containing catalyst and removing the formed R2OH, 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 in individual compounds R, R2, and x are as defined above and n is an integer between 1 and 20;
• (2-b1) optionally recovering product 2-Y from residual R2OH 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, R2, R3, 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).