Process for producing an overbased metal detergent

Abstract

A high TBN overbased metal sulfonate detergent is prepared by reacting a hydrocarbyl-substituted organic sulfonic acid or metal salt thereof with a basic alkali metal or alkaline earth metal compound in the presence of a mono-alcohol and a carboxylic acid and reacting this mixture with carbon dioxide to form a carbonated overbased metal sulfonate. The resulting overbased metal detergent has a metal equivalent to sulfonic acid substrate ratio of 5:1 to 27:1. The product thus prepared has improved viscometrics, filterability, and TBN:ash ratio. Lubricating compositions comprising said overbased detergent display reduced friction and wear performance. The invention further relates to methods of lubricating an internal combustion engine with a lubricant containing an overbased detergent prepared as described.

What is claimed is: 
     
         1 - 21 . (canceled) 
     
     
         22 . A process for preparing an overbased metal detergent in an oil medium comprising the steps of:
 (1) providing an organic acid selected from a group consisting of:
 a hydrocarbyl-substituted organic sulfonic acid, 
 a mixture of a hydrocarbyl-substituted organic sulfonic acids, 
 a metal salt of said organic acid, and 
 mixtures thereof, 
   (2) further providing at least one mono-alcohol;   (3) further providing a basic metal compound;   (4) further providing a carboxylic acid having 12 to 20 carbon atoms (5) reacting the mixture of step (4) with carbon dioxide to form a carbonated overbased metal sulfonate;   
       wherein the resultant overbased metal detergent has a metal equivalent to sulfonic acid substrate ratio of 5:1 to 27:1. 
     
     
         23 . A process as claimed in  claim 22 , wherein the resultant overbased metal detergent has a metal equivalent to sulfonic acid substrate ratio of 7:1 to 20:1. 
     
     
         24 . A process as claimed in  claim 22  comprising an additional step (6) wherein steps (3), (4) and (5) are performed at least two additional times. 
     
     
         25 . A process as claimed in  claim 24 , wherein the product of either step (5) or step (6) is heated to at least 150° C. in an additional step (7). 
     
     
         26 . A process as claimed in  claim 25 , wherein the product of step (7) may be cooled in a further step (8). 
     
     
         27 . A process as claimed in  claim 22 , wherein the carboxylic acid has 16 to 18 carbon atoms. 
     
     
         28 . A process as claimed in  claim 27 , wherein the carboxylic acid is stearic acid. 
     
     
         29 . A process as claimed in  claim 22 , wherein the carboxylic acid is provided as 2 to 20 wt %, or 4 to 8 wt % of reactants. 
     
     
         30 . A process as claimed in  claim 22 , wherein the at least one mono-alcohol comprises 2 to 10 carbon atoms. 
     
     
         31 . A process as claimed in  claim 22 , wherein between 10 and 20 wt % of the total amount of the basic metal compound may be added at each occurrence of step (3). 
     
     
         32 . A process as claimed in  claim 22 , wherein an oil medium is present. 
     
     
         33 . A process as claimed in  claim 22 , wherein the metal salt of step (1) is a metal salt of a hydrocarbyl-substituted sulfonic acid and is represented by the formula:
   (R 1 ) k -A-SO 3 M   
       wherein each R 1  is independently a hydrocarbyl group having between 6 and 40 carbon atoms; A is a cyclic or acyclic hydrocarbon group; M is a valence of at least one metal ion; and k is 1 to 5. 
     
     
         34 . A process as claimed in  claim 33 , wherein M is a valence of calcium, sodium, or magnesium. 
     
     
         35 . An overbased metal detergent prepared by the process of  claim 22 . 
     
     
         36 . A lubricating composition comprising an oil of lubricating viscosity and an overbased detergent prepared according to  claim 35 . 
     
     
         37 . A method for lubricating an internal combustion engine, comprising supplying thereto a lubricant composition of  claim 36 .