Water swellable rubber composition having stable swelling property at high temperatures

Abstract

A water swellable rubber composition comprising (a) a non-water swellable base rubber, (b) an ethylene oxide based hydrophilic elastomer having from zero up to and including 20 mole % of a crosslinkable curable functional group, and (c) a water swellable non-elastomeric material. The composition has excellent water swell characteristics under prolonged exposure to high temperature and various electrolyte solutions (strongly saline as well as acid conditions) and is particularly suitable for oil field applications. When the ethylene oxide based hydrophilic elastomer (b) has from zero to less than 5 mole % of crosslinkable functional group, the amount of (b) is between about 30 parts and 300 parts by weight based on 100 parts by weight of the base rubber (a) and the amount of (c) is between about 20 parts and 200 parts by weight based on 100 parts by weight of the base rubber (a), the composition is characterized by good shape retention after undergoing constrained swell, as well as a high degree of constrained swell at elevated temperatures in different saline concentrations.

What is claimed is: 
     
         1 . A water swellable rubber composition comprising:
 (a) 100 phr of a non-water swellable base rubber which is at least one selected from the group consisting of hydrogenated acrylonitrile-butadiene rubber (HNBR) and epichlorohydrin rubber,   (b) 10-200 phr of a crosslinkable ethylene oxide based hydrophilic elastomer having an ethylene oxide content of least 65 mole %, and having at least one crosslinkable curable functional group, wherein one of said functional group is vinyl, and   (c) 50-200 phr of a water swellable non-elastomeric material which is at least one selected from the group consisting of a partially neutralized/crosslinked polyacrylic acid salt and an organic acid salt.   
     
     
         2 . A water swellable rubber composition according to  claim 1 , which comprises 20-180 phr of the crosslinkable ethylene oxide based hydrophilic elastomer (b). 
     
     
         3 . A water swellable rubber composition according to  claim 1 , which comprises 70-180 phr of the water swellable non-elastomeric material (c). 
     
     
         4 . A water swellable rubber composition according to  claim 1 , wherein the ethylene oxide based hydrophilic elastomer (b) has from 0.1 mole % up to and including 20 mole % of the crosslinkable curable functional group. 
     
     
         5 . A water swellable rubber composition according to  claim 1 , wherein the ethylene oxide based hydrophilic elastomer (b) is an ethylene oxide-propylene oxide-allyl glycidyl ether terpolymer having at least 75% mole ratio of ethylene oxide and 0.1-20% mole ratio of allyl glycidyl ether. 
     
     
         6 . A water swellable rubber composition according to  claim 1 , wherein the organic acid salt is at least one selected from the group consisting of sodium acetate, sodium formate, and sodium acrylate. 
     
     
         7 . A water swellable rubber composition according to  claim 1 , further comprising:
 (d) up to 40 phr of a compatibilizing agent.   
     
     
         8 . A water swellable rubber composition according to  claim 7 , wherein the compatibilizing agent is at least one selected from the group consisting of trioctyl trimellitate, ditridecyl adipate, and dialkyl diether glutarate. 
     
     
         9 . A water swellable rubber composition according to  claim 1 , comprising a peroxide cure system or a sulfur cure system. 
     
     
         10 . A water swellable rubber composition according to  claim 9 , comprising at least one accelerator for the cure system. 
     
     
         11 . An article comprising the composition of  claim 1 . 
     
     
         12 . An article according to  claim 11 , wherein the composition is cured. 
     
     
         13 . An article according to  claim 11 , wherein the composition is uncured. 
     
     
         14 . An article according to  claim 11 , which is a seal, a gasket, a component of a well packer, a component of a device for controlling fluid flow, a component of a device for detecting water, a component of a device for detecting depletion of water, a component for an activating mechanism in a control device, a toy, or a game element.