Swellable polymer with anionic sites
The invention is directed to stable crosslinked water-soluble swellable polymers and methods for making same. More particularly, the invention relates to a composition comprising expandable polymeric particles having anionic sites and labile crosslinkers and stable crosslinkers, said particle mixed with a fluid and a cationic crosslinker that is capable of further crosslinking the particle on degradation of the labile crosslinker and exposure of the anionic sites so as to form a gel. A particularly important use is as an injection fluid in petroleum production, where the expandable polymeric particles are injected into target zone and when the heat and/or suitable pH of the target zone cause degradation of the labile crosslinker and the particle expands, the cationic crosslinker crosslinks the polymer to form a gel, thus diverting water to lower permeability regions and improving oil recovery.
1. A composition comprising expandable polymeric particles having charged monomers and being internally crosslinked with both labile crosslinkers and stable crosslinkers, said particle combined with a fluid and an external cationic crosslinker that is capable of further crosslinking the particle on degradation of the labile crosslinker so as to form a gel, wherein said charged monomers have predominantly anionic sites.
2. The composition of claim 1 , wherein the anionic site is selected from the group consisting of a carboxylate, a sulphate, a sulphonate, a nitrate, or a phosphate groups.
3. The composition of claim 1 , wherein the cationic crosslinker is at least one selected from the group consisting of Al 3+ , Fe 3+ , Cr 3+ , Ti 4+ , Sn 4+ , Zr 4+ or polyethylenimine (PEI).
4. The composition of claim 1 , wherein the expandable polymeric particles comprise a copolymer of acrylamide and sodium acrylate.
5. The composition of claim 1 , wherein the stable crosslinker is methylene bisacrylamide and the labile crosslinker is a diacrylate.
6. The composition of claim 1 , wherein the expandable polymeric particles comprise a copolymer of acrylamide and sodium acrylate, the stable crosslinker comprises methylene bisacrylamide, and the labile crosslinker comprises a polyethylene glycol diacrylate, and the cationic crosslinker is a polyvalent metal cation or a cationic polymer.
7. The composition of claim 1 , wherein the expandable polymeric particles comprise a copolymer of acrylamide and sodium acrylate, the stable crosslinker comprises methylene bisacrylamide, the labile crosslinker comprises a polyethylene glycol diacrylate, and the cationic crosslinker is at least one selected from the group consisting of a cationic polymer, Al + , Fe 3+ , Cr 3+ , Ti 4+ , Sn 4+ , Zr 4+ and complexes or nanoparticles containing same.
8. The composition of claim 1 , wherein the labile crosslinker is an acid labile ketal of the formula:
wherein Y is a lower alkyl, wherein n and m are independently an integer of between 1 and 10, and wherein R1 and R2 are independently a lower alkyl.
9. The composition of claim 1 , wherein the labile crosslinker is 2-bis[2,2′-di(N-vinylformamido)ethoxy]propane.
10. The composition of claim 1 , wherein the labile crosslinker is 2-bis[2,2′-di(N-vinylformamido)ethoxy]propane and the expandable polymeric particles comprise polymers of N-vinyl formamide, N-vinylacetamide, or N-vinylacetamine, or mixtures thereof.
11. A composition comprising highly crosslinked expandable hydrophilic polymeric particles having charged monomers and an unexpanded volume average particle size diameter of about 0.05 to about 10 microns and an internal crosslinking agent content of from about 1,000 to about 200,000 ppm of labile crosslinkers and from >0 to about 300 ppm of stable crosslinkers, combined with an external cationic crosslinker and a fluid comprising water, wherein said charged monomers have predominantly anionic sites.
12. The composition of claim 11 , wherein the cationic crosslinker is at least one selected from the group consisting of PEI, or Al 3+ , Fe 3+ , Cr 3+ , Ti 4+ , Sn 4+ , Zr 4+ and complexes thereof or nanoparticles containing same.
13. The composition of claim 11 , wherein the expandable hydrophilic polymeric particles comprise a copolymer of acrylamide and sodium acrylate.
14. The composition of claim 11 , wherein the stable crosslinker is methylene bisacrylamide and the labile crosslinker is polyethylene glycol diacrylate.
15. The composition of claim 11 , wherein the labile crosslinker is an acid labile ketal, or 2-bis[2,2′-di(N-vinylformamido)ethoxy]propane or the labile crosslinker comprises a diacrylate or polyethylene glycol diacrylate, and the expandable hydrophilic polymeric particles comprise polymers of N-vinyl formamide, N-vinylacetamide, N-vinylacetamine, acrylamide, sodium acrylate or mixtures thereof.