Encapsulated activator and its use to trigger a gelling system by physical means

1. An aqueous gelling system comprising:

i) water soluble or dispersable monomers comprising acrylated or methacrylated polyoxyethylene and/or polyoxypropylene monomers

ii) a polymerization initiator dispersed in said monomers i), and

iii) an encapsulated polymerization accelerator comprising drops of activator enclosed in shells of polyurethane dispersed in water, wherein the shells of polyurethane have an average diameter between 300 and 1500 μm, wherein the polymerisation accelerator is an alkylamine, polyalkylenamine, or polyalkylenimine.

2. The aqueous gelling system of claim 1 ,

wherein the encapsulated polymerization accelerator is obtained in a process comprising the steps of:

a) providing a reverse emulsion containing, in an oil phase, a water solution or dispersion (W1) containing said polymerisation accelerator, the oil phase including a heat curable mixture of an isocyanate and a hydroxylated polyalkyldiene or polyol,

b) pouring the reverse emulsion of step a) in a water phase (W2) to make a water/oil/water multiple emulsion, containing drops of the water solution or dispersion comprising the accelerator as the internal water phase and, then,

c) curing the mixture of isocyanate and hydroxylated polyalkyldiene or polyol in the multiple emulsion obtained in step b) to obtain polyurethane and enclose the drops of the water solution or dispersion comprising the accelerator in shells of the polyurethane dispersed in water, wherein the shells of polyurethane have an average diameter between 300 and 1500 μm.

3. The gelling system of claim 2 , wherein the hydroxylated polyalkyldiene or polyol is a hydroxylated polybutadiene.

4. The gelling system as claimed in claim 2 , wherein the isocyanate is a trimer form of alpha, omega aliphatic diisocyanate.

5. The gelling system of claim 2 , wherein the polymerisation accelerator is a polyethyleneimine (PEI).

6. The gelling system of claim 2 , wherein a further polymerization initiator is encapsulated with the polymerization accelerator, wherein the polymerization initiator is selected from the group consisting of water soluble persalts and/or peroxides.

7. The gelling system of claim 2 , wherein the water soluble or water dispersable acrylated or methacrylated polyoxyethylene and/or polyoxypropylene monomers have the general formula:

CH 2 ═CR 1 —CO—(O—CH 2 —CHR 2 )n-OR 3   (1)

wherein:

R 1 is a hydrogen atom or a methyl radical,

R 2 is a hydrogen atom or a methyl radical, and

R 3 is a hydrogen atom, a methyl radical, or a CH 2 ═CR 1 —CO— group, and

n is a whole or fractional number from 3 to 25.

8. The gelling system of claim 7 , wherein the water soluble or water dispersable acrylated or methacrylated polyoxyethylene and/or polyoxypropylene monomers is a mixture of methacrylate modified polyethylene oxide of the formulae:

wherein n is a number between 15 and 25, limits included, and/or

wherein n is a number between 10 and 20, limits included.

9. The gelling system of claim 7 , wherein the water soluble or water dispersable monomers is a mixture comprising at least two distinct kinds of monomers, obtained by reacting a mixture of two compounds (A1) and (A2) having the following formulae:

HO—(O—CH 2 —CHR 2 ) n —OMe  (A1)

HO—(O—CH 2 —CHR 2 ) n —OH  (A2)

wherein R 2 and n are as defined in claim 7 and Me is a methyl radical, with a (meth)acrylic acid, chloride or anhydride.

10. The gelling system of claim 9 , wherein the molar ratio (A2)/(A1) is from 10:90 to 50:50.

11. The gelling system of claim 9 , wherein the (meth)acrylic anhydride is a (meth)acrylic anhydride of formula (CH 2 ═CR 1 —C(O)) 2 O wherein R 1 is as defined in claim 7 .

12. The gelling system of claim 2 , wherein the polymerisation accelerator is an alkylamine, polyalkylenamine or polyalkylenimine comprising tertiary amino groups and whose alkyl or alkylen part comprises 2-4 carbon atoms.

13. The gelling system of claim 2 , wherein the isocyanate is alpha, omega aliphatic diisocyanate.

14. The gelling system of claim 2 , wherein the shells of polyurethane have an average diameter between 300 and 800 μm.

15. A process for sealing subterranean environments and consolidation of a soil or sealing of a subterranean structure, comprising underground railway tunnels, sewers, underground car parks, storage ponds, swimming pools, oil wells, mine shafts and dams, comprising the steps of:

e1) injecting into said environments soil or structure an aqueous gelling system of claim 1 ; and

e2) triggering the polymerisation of the resin by physical means, whereby the encapsulated polymerization accelerator is released from the polyurethane capsules.

16. The process of claim 15 , wherein said physical means is selected from the group consisting of high shear, high pressure, temperature, crushing, shearing, and any combination thereof.