Patent ID: 7592490

Claim:
A method for producing a solution of zinc dialkyldithiophosphate, said method comprising the steps of: initiating a reaction by introducing a mixture of P 2 O 5 and P 2 S 5 to a solution comprising methyl isobutyl carbinol and isopropyl alcohol; maintaining said reaction in a temperature range of from about 58° C. to about 68° C.; adding said mixture of P 2 O 5 and P 2 S 5 to said solution comprising methyl isobutyl carbinol and isopropyl alcohol so as to form a slurry; diluting said slurry by adding an additional quantity of said solution comprising methyl isobutyl carbinol and isopropyl alcohol so as to form a dilute slurry while maintaining said dilute slurry in said temperature range; maintaining said dilute slurry in said temperature range so as to form a thioacid; sparging said thioacid with nitrogen until said thioscid tests negative for H 2 S with lead acetate paper; neutralizing said thioacid by dosing said thioacid into a zinc oxide slurry so as to form a reaction mixture; maintaining said reaction mixture in a second temperature range while adding said thioacid; holding said reaction mixture in said second temperature range for at least 45 minutes after adding said thioacid; optionally vacuum stripping said reaction mixture; optionally filtering said reaction so as to remove any solid particles; and optionally diluting said reaction mixture with process oil thereby producing said zinc dialkyldithiophosphate solution.