Encapsulation of hydrophilic additives
The instant invention relates to a process for the encapsulation of a non-amine hydrophilic compound C, comprising the steps of: (E1) providing a reverse emulsion containing: an oil phase (O), comprising a curable mixture of isocyanate and polyalkyldiene hydroxylated or polyol dispersed in said oil phase, drops of an aqueous phase W 1 , containing: said non-amine hydrophilic compound C; and at least 5% by weight of a compound C carrying more than 2 amine groups; (E2) pouring the reverse emulsion of step (E1) in a second water phase W 2 to make a multiple emulsion water/oil/water; and, then, (E3) curing into polyurethane all or part of the curable mixture contained in the oil phase.
1. A process for the encapsulation of a non-amine hydrophilic compound C, wherein the non-amine hydrophilic compound C does not contain any amine groups and is boric acid, or a zirconate, titanate or aluminate complex, the process comprising the steps of:
(E1) providing a reverse emulsion containing:
an oil phase (O), comprising a curable mixture of
isocyanate; and
hydroxylated polyalkyldiene or polyol
dispersed in said oil phase, drops of a water solution or dispersion (aqueous phase W 1 ), containing:
said non-amine hydrophilic compound dissolved therein; and
at least 5% by weight, based on the total weight of the phase W 1 , of a compound C′ carrying more than 2 amine groups, wherein the compound C′ includes at least one polyethyleneimine;
(E2) pouring the reverse emulsion of step (E1) in a second water phase W 2 to make a multiple emulsion water/oil/water, containing, as the internal water phase, drops including the non-amine hydrophilic compound C; and, then,
(E3) curing into polyurethane all or part of the curable mixture contained in the oil phase, whereby a formulation is obtained, containing, dispersed in the phase W 2 particles of polyurethane encapsulating an aqueous internal phase including the non-amine hydrophilic compound C.
2. The process of claim 1 , wherein the oil phase (O) has a viscosity lower than the viscosity of phase (W 1 ) in the conditions of steps (E1) and (E2).
3. The process of claim 1 , wherein the water phase (W 1 ) includes fatty acid esters.
4. The process of claim 3 , wherein the fatty acid esters are esters of rapeseed oil.
5. The process of claim 1 , wherein the water phase (W 2 ) contains a mineral salt.
6. The process of claim 5 , wherein the mineral salt is NaCl.
7. The process of claim 1 , wherein the water phase (W 2 ) contains a protective colloid and rheological agent.
8. The process of claim 7 , wherein the protective colloid and rheological agent is xanthan gum.
9. A formulation obtained according to the process of claim 1 , comprising drops of a water phase including non-amine hydrophilic compound encapsulated in particles of polyurethane, said particles being dispersed in a water phase.
10. A method for allowing a targeted release of a compound C just at the drill bit by drilling with the formulation of claim 9 .
11. A method for allowing a targeted release of a compound C, wherein capsules comprising the formulation of claim 9 are sheared entering the fractures and as fractures are closing at the end of a fracturing operation.