Thiophosphoric acid products for antiwear additives

1. A thiophosphoric acid product comprising at least a compound having the structure of Formula I

wherein

R 1 is sulfur or oxygen;

R 2 and R 3 are, independently, one of —OR 4 or —OH, and each R 4 if included is, independently, a C3 to C18 linear or branched alkyl group, a C5 to C6 cycloalkyl group, a phenyl group, or a C6 to C18 alkylphenol group; and

wherein the thiophosphoric acid product has about 0.1 mmoles/gram or less of active sulfur as measured via titration with triphenyl phosphine.

2. The thiophosphoric acid product of claim 1 , wherein R 1 is sulfur, R 2 and R 3 are, independently, the —OR 4 group with each R 4 , independently, a C3 to C18 linear or branched alkyl group.

3. The thiophosphoric acid product of claim 1 , wherein the thiophosphoric acid product is substantially free of phosphorus polysulfide compounds.

4. The thiophosphoric acid product of claim 3 , wherein the thiophosphoric acid product includes phosphorus polysulfide compounds, but no more than about 1 weight percent of the phosphorus polysulfide compounds.

5. The thiophosphoric acid product of claim 1 , wherein the compound of Formula I includes the reaction product of an organic hydroxy compound and phosphorus pentasulfide.

6. The thiophosphoric acid product of claim 5 , wherein the organic hydroxy compound is provided in a molar ratio relative to the phosphorus pentasulfide of about 4:1 to about 10:1.

7. The thiophosphoric acid product of claim 5 , wherein the organic hydroxy compound is one or more of methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, tert-butyl alcohol, sec-butyl alcohol, phenol, naphthol, an amyl alcohol, hexyl alcohol, iso-hexyl alcohol, octyl alcohol, decyl alcohol, dodecyl alcohol, octadecyl alcohol, 2-ethylhexyl alcohol, 4-methyl-2-pentyl alcohol, phenyl alcohol, butylphenyl alcohol, cyclohexyl alcohol, methylcyclopentyl alcohol, propenyl alcohol, butenyl alcohol, or combinations thereof.

8. The thiophosphoric acid product of claim 1 , wherein the thiophosphoric acid product is distilled and recovered as a condensate of the distillation.

9. The thiophosphoric acid product of claim 8 , wherein the distillation occurs at a temperature of at least about 80° C. and/or a pressure of at least about 0.4 torr.

10. The thiophosphoric acid product of claim 9 , wherein the condensate is recovered at a temperature of about 10° C. or less.

11. The thiophosphoric acid product of claim 8 , wherein the distillation occurs in a falling-film evaporator, a wiped-film evaporator, a thin-film evaporator, a short-path evaporator, or combinations thereof.

12. The thiophosphoric acid product of claim 1 , wherein the compound of Formula I is selected from a dipropyl dithiophosphoric acid, a diisopropyl dithiophosphoric acid, a dibutyl dithiophosphoric acid, a diisobutyl dithiophosphoric acid, a di-ethylhexyl dithiophosphoric acid, or combinations thereof.

13. An antiwear additive for lubricating compositions comprising the reaction product of the thiophosphoric acid product of claim 1 and a reactant selected from (i) an unsaturated carboxylic acid, (ii) a basic or neutral metal compound including one or more of a metal oxide, a metal hydroxide, or a metal carbonate; or (iii) an unsaturated ester of a carboxylic acid.

14. The antiwear additive of claim 13 , wherein the reactant is (i) the unsaturated ester of a carboxylic acid and wherein the unsaturated ester of a carboxylic acid is an C1 to C20 alkyl (meth)acrylate.

15. The antiwear additive of claim 14 , wherein the unsaturated ester of a carboxylic acid is methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, or combinations thereof.

16. The antiwear additive of claim 13 , wherein the reactant is (ii) the basic or neutral metal compound and includes a metal oxide, a metal hydroxide, or a metal carbonate of aluminum, lead, tin, molybdenum, manganese, nickel, copper, titanium, zirconium, zinc, or combinations thereof.

17. The antiwear additive of claim 16 , wherein the basic or neutral metal compound is a molar excess of zinc oxide.

18. The antiwear additive of claim 13 , wherein the reactant is (iii) the unsaturated carboxylic acid and wherein the unsaturated carboxylic acid is a C3 to C20 unsaturated fatty acid.

19. The antiwear additive of claim 18 , wherein the unsaturated carboxylic acid is acrylic acid, methacrylic acid, 2-ethyl acrylic acid, or combinations thereof.

20. A lubricating composition including the antiwear additive of claim 13 .