Hydration of associative polymers
The present invention relates to a method which allows quick and effective hydration of associative polymers, in particular those intended for use in the field of oil drilling. This method uses a specific solid formulation, which can be easily hydrated, including, in a pre-mixture, said associative polymers and surfactants capable of improving the hydration of these polymers.
1. A process for hydration of associative polymers (P), resulting in the preparation of an aqueous composition comprising said associative polymers (P) in the form of a solution or of a gel, the process comprising a step (E) of adding water to a solid composition (C) comprising said associative polymers (P) and surfactants (S) suitable for improving the hydration of these polymers, the hydration being carried out in less than five hours,
wherein said solid composition (C) is as obtained by drying an aqueous composition comprising a mixture of the associative polymers (P) in the form of a gel in the hydrated state and of the surfactants (S) obtained by post-addition of the surfactants (S) to associative polymers (P) resulting from a micellar polymerization wherein the associative polymers (P) are synthesized according to a controlled micellar radical polymerization step in which the following are brought into contact, in an aqueous medium (M):hydrophilic monomers, dissolved or dispersed in said aqueous medium (M); hydrophobic monomers in the form of a micellar solution; at least one radical polymerization initiator; and at least one radical polymerization control agent.
2. The process as claimed in claim 1 , wherein the associative polymers (P) comprise a hydrophilic backbone and hydrophobic groups bonded to this backbone.
3. The process as claimed in claim 1 , wherein the associative polymers (P) have a weight-average molar mass Mw of at least 500 000 g/mol.
4. The process as claimed in claim 1 , wherein the surfactants (S) are deactivatable surfactants and wherein the process further comprises, following step (E), a step (E2) of deactivating all or part of the surfactants (S), wherein the surfactants are placed under physical and/or chemical conditions under which they lose their surfactant nature.
5. The process as claimed in claim 4 , wherein the surfactants (S) comprise labile surfactants, which are degraded under conditions under which the polymers are not degraded, and wherein, in step (E2), the surfactants are subjected to these conditions.
6. The process as claimed in claim 4 , wherein the surfactants comprise surfactants which have a cloud point, and wherein, in step (E2), the surfactants are subjected to a temperature above their cloud point.
7. The process as claimed in claim 1 , wherein the solid composition (C) used in step (E) is obtained according to the following steps, prior to step (E):
(E0) an aqueous composition comprising, in an intimate mixture, the associative polymers (P) in the form of a gel in the hydrated state and the surfactants (S) is prepared; then
(E1) the water, and where appropriate the other solvents, contained in the aqueous composition prepared in step (E0) is removed.
8. The process as claimed in claim 7 , wherein step (E0) is carried out by dissolving the associative polymer (P) in an aqueous medium containing the surfactants.
9. The process as claimed in claim 7 , wherein step (E0) is carried out by directly incorporating the surfactants (S) into the associative polymers (P) in the form of a gel without performing any dissolution of the polymer in the water.
10. The process as claimed in claim 2 , wherein the hydrophobic groups are concentrated in microblocks.
11. The process as claimed in claim 5 , wherein the surfactants (S) are degraded under temperature, pressure and/or pH conditions under which the polymers are not degraded.
12. The process as claimed in claim 1 , wherein the hydration is carried out in less than three hours.
13. The process as claimed in claim 12 , wherein the hydration is carried out in less than one hour.
14. The process of claim 1 , wherein the at least one radical polymerization control agent is a compound which comprises a thiocarbonylthio —S(C═S)— group.