Hydraulic oil formulation and method to improve seal swell

Abstract

In one embodiment, a hydraulic oil with favorable seal swell is disclosed. The hydraulic oil comprises, a major amount of base stock, an antiwear additive, a phosphorous containing additive wherein the phosphorous comprises at least 10 ppm and less than 2500 ppm of the hydraulic oil, the hydraulic oil contains less than 200 ppm zinc and less than 100 ppm sulfur, wherein the ratio of phosphorous to metal ratio is chosen to obtain a favorable seal swell performance with at least a ratio of 0.5 and less than 20. In a second embodiment, a method to improve seal swell is disclosed. In a third embodiment, a method of formulating an oil to improve seal swell performance is disclosed. In a fourth embodiment, a method of improving seal swell is disclosed. The method uses a system cleaner for hydraulic systems comprising CaSo 4 .

1 . A hydraulic oil with favorable seal swell, comprising
 a) a major amount of base stock;   b) an antiwear additive;   c) a phosphorous containing additive wherein the phosphorous comprises at least 50 ppm and less than 2500 ppm of the hydraulic oil;   d) the hydraulic oil contains less than 200 ppm zinc and less than 100 ppm sulfur; and   e) wherein the ratio of phosphorous to metal ratio is chosen to obtain a favorable seal swell performance with at least a ratio of 0.5 and less than 20.   
   
   
       2 . The hydraulic oil of  claim 1  further comprising a rust inhibitor wherein the rust inhibitor is less than 1.8 weight percent of the hydraulic oil. 
   
   
       3 . The hydraulic oil of  claim 1  wherein the phosphorous to metal ratio is at least 1.5 and less than 5. 
   
   
       4 . The hydraulic oil of  claim 1  wherein the phosphorous to metal ratio is at least 2 and no more than 4. 
   
   
       5 . The hydraulic oil of  claim 1  wherein at least one base stock is chosen form the group consisting of PAOs, Group III, GTL, aromatic esters, polyol esters, alkylated aromatics, phosphate esters, and any combinations thereof 
   
   
       6 . The hydraulic oil of  claim 1  wherein the hydraulic oil has a phosphorous level of at least 25 and less than 600 ppm. 
   
   
       7 . The hydraulic oil of  claim 2  wherein the rust inhibitor is a calcium sulfonate. 
   
   
       8 . The hydraulic oil of  claim 1  further comprising a system cleaner. 
   
   
       9 . The hydraulic oil of  claim 1  wherein the system cleaner comprises at least 5 percent and less than 10 percent of the hydraulic oil. 
   
   
       10 . A method of improving the seal swell performance of a hydraulic oil comprising:
 a) obtaining a hydraulic lubricating oil, comprising a major amount of base stock, an antiwear additive; a phosphorous containing additive wherein the phosphorous comprises at least 50 ppm and less than 2500 ppm of the hydraulic oil and wherein the hydraulic oil contains less than 200ppm zinc and less than 100 ppm sulfur; and   b) formulating the additives to achieve a ratio of phosphorous to zinc or sulfur is chosen to obtain a favorable seal swell performance.   
   
   
       11 . The method of  claim 10  further comprising a rust inhibitor wherein the rust inhibitor is less than 1.8 weight percent of the hydraulic oil. 
   
   
       12 . The method of  claim 10  wherein the phosphorous to metal ratio is at least 1.5 and less than 5. 
   
   
       13 . The method of  claim 10  wherein the phosphorous to metal ratio is at least 2 and no more than 4. 
   
   
       14 . A method of blending a oil to provide improved seal swell performance comprising:
 obtaining at least one base stock and obtaining at least one additive, and   blending at least one base stock and at least one additive to achieve a ratio of phosphorous to zinc or sulfur is chosen to obtain a favorable seal swell performance.   
   
   
       15 . The method of  claim 14  further comprising a rust inhibitor wherein the rust inhibitor is less than 1.8 weight percent of the hydraulic oil. 
   
   
       16 . The method of  claim 14  wherein the phosphorous to metal ratio is at least 1.5 and less than 5. 
   
   
       17 . The method of  claim 14  wherein the phosphorous to metal ratio is at least 2 and no more than 4. 
   
   
       18 . A method of improving seal swell comprising:
 obtaining a system cleaner for hydraulic systems, the system cleaner comprising CaSo 4 ;   using the system cleaner as a field conditioner;   lubricating with a hydraulic oil with favorable seal swell properties.