Method for stabilizing an engine coolant concentrate and preventing hard water salt formation upon dilution

Abstract

Disclosed is a stabilized concentrate comprising least one stabilizer selected from the group consisting of polyacrylate polymers of the formula: where R 1 is H; R 4 is a terminating group; X is and R 2 and R 3 are each independently hydrogen, an alkali metal or an alkaline earth metal, and the sum of m and n provide a number average equivalent weight of less than 6500, and a number average molecular weight of less than 6500. The concentrate comprises 90 or more wt % freezing point depressant. The stabilized coolant concentrate can be diluted with water to provide a final coolant composition.

1 . A coolant concentrate having improved storage stability, the concentrate consisting of:
 at least 90 wt % freezing point depressant, based on the total weight of the coolant concentrate;   at least one phosphate or the alkali metal or alkaline earth metal salt thereof, and one or more corrosion inhibitors selected from the group consisting of organic acids; azole type compounds; nitrites, nitrates; borates; and alkali metal or alkaline earth metal salts thereof;   at least one stabilizer selected from the group consisting of polyacrylate polymers of the formula:   
       
         
           
           
               
               
           
         
       
       where R 1  is H; R 4  is a terminating group; X is 
       
         
           
           
               
               
           
         
       
       and R 2  and R 3  are each independently hydrogen, an alkali metal or an alkaline earth metal, and the sum of m and n provide a number average equivalent weight of less than 6500, and
 optionally at least one additive selected from the group consisting of water, antifoam agents, lubricants, colorants, dispersants, anti-scaling agents, wetting agents, surfactants, pH adjusting and buffering agents. 
 
     
     
         2 . The concentrate of  claim 1  wherein R 4  is H or OH. 
     
     
         3 . The concentrate of  claim 2  wherein R 4  is H. 
     
     
         4 . The concentrate of  claim 1  wherein R 2  is an alkali metal or an alkaline earth metal. 
     
     
         5 . The concentrate of  claim 4  wherein R 2  is an alkali metal. 
     
     
         6 . The concentrate as in  claim 1  wherein the at least one stabilizer comprises 0.01 wt % to 1.00 wt % of the concentrate, based on the total weight of the concentrate. 
     
     
         7 . The concentrate of  claim 1  wherein an organic acid and a nitrite are present in the concentrate. 
     
     
         8 . The concentrate of  claim 1  wherein the one or more corrosion inhibitors comprise 0.10 wt % to 10 wt % of the concentrate, based on the total weight of the concentrate. 
     
     
         9 . The concentrate of  claim 1  wherein the freezing point depressant comprises propylene glycol. 
     
     
         10 . A coolant consisting of:
 a freezing point depressant   water;   at least one phosphate or the alkali metal or alkaline earth metal salt thereof, and one or more corrosion inhibitors selected from the group consisting of organic acids; azole type compounds; nitrites, nitrates; borates; and alkali metal or alkaline earth metal salts thereof;   at least one stabilizer selected from the group consisting of polyacrylate polymers of the formula:   
       
         
           
           
               
               
           
         
       
       where R 1  is H; R 4  is a terminating group; X is 
       
         
           
           
               
               
           
         
       
       and R 2  and R 3  are each independently hydrogen, an alkali metal or an alkaline earth metal, and the sum of m and n provide a number average equivalent weight of less than 6500, and
 optionally at least one additive selected from the group consisting of water, antifoam agents, lubricants, colorants, dispersants, anti-scaling agents, wetting agents, surfactants, pH adjusting and buffering agents. 
 
     
     
         11 . The concentrate of  claim 10  wherein R 4  is H or OH. 
     
     
         12 . The concentrate of  claim 11  wherein R 4  is H. 
     
     
         13 . The concentrate of  claim 10  wherein R 2  is an alkali metal or an alkaline earth metal. 
     
     
         14 . The concentrate of  claim 13  wherein R 2  is an alkali metal. 
     
     
         15 . The concentrate as in  claim 10  wherein the at least one stabilizer comprises 0.01 wt % to 1.00 wt % of the concentrate, based on the total weight of the concentrate. 
     
     
         16 . The concentrate of  claim 10  wherein an organic acid and a nitrite are present in the concentrate. 
     
     
         17 . The concentrate of  claim 10  wherein the one or more corrosion inhibitors comprise 0.10 wt % to 10 wt % of the concentrate, based on the total weight of the concentrate. 
     
     
         18 . The concentrate of  claim 10  wherein the freezing point depressant comprises propylene glycol. 
     
     
         19 . The concentrate of  claim 10  wherein the freezing point depressant comprises ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol or a combination comprising two or more of the foregoing freezing point depressants.