Stable formaldehyde-free microcapsules

1. A process for the preparation of a core-shell microcapsule, said process comprising the steps of:

1) preparing an oligomeric composition comprising the reaction product of, or obtainable by reacting together:

a) a polyamine component in the form of melamine or of a mixture of melamine and at least one C 1-4 compound comprising two NH 2 functional groups;

b) an aldehyde component in the form of a mixture of glyoxal, a C 4-6 2,2-dialkoxy-ethanal and optionally a glyoxalate, said mixture having a molar ratio glyoxal/C 4-6 2,2-dialkoxy-ethanal comprised between 1/1 and 10/1; and

c) a protic acid catalyst;

2) preparing an oil-in-water dispersion, wherein the droplet size is comprised between 1 and 600 μm, and comprising:

i) an oil;

ii) a water medium;

iii) at least an oligomeric composition as obtained in step 1);

iv) at least a cross-linker selected amongst:

A) C 4 -C 12 aromatic or aliphatic di- or tri-isocyanates and their biurets, triurets, trimers and trimethylol propane-adduct; and/or

B) a di- or tri-oxiran compounds of formula

A-(oxiran-2-ylmethyl) n

wherein n stands for 2 or 3 and A represents a C 2 -C 6 group optionally comprising from 2 to 6 nitrogen and/or oxygen atoms;

v) optionally a C 1-4 compound comprising two NH 2 functional groups;

3) heating said dispersion;

4) cooling said dispersion; and

5) optionally adding to the dispersion of step 4) at least one cationic polymer and/or urea or ethylene urea; and

6) optionally drying the final dispersion to obtain the dried core-shell microcapsule.

2. A process according to claim 1 , wherein the dispersion comprises:

between 10% and 50% of oil;

between 1% and 20% of oligomeric composition;

between 0.5% and 15% of at least a cross-linker percentage being expressed on a w/w basis relative to the total weight of the dispersion.

3. A process according to claim 1 , wherein the water medium comprises between 0% and 5% of at least a stabilizer and between 0% and 10% of at least a polyol, percentage being expressed on a w/w basis relative to the total weight of the dispersion.

4. A process according to claim 3 , wherein said stabilizer is an ionic surfactant and said polyol is an aliphatic polymeric polyol.

5. A process according to claim 1 , wherein said polyamine component is a mixture of melamine and at least one compound selected amongst urea, 1H-1,2,4-triazole-3,5-diamine and mixtures thereof, and the molar ratio melamine/C 1-4 compound comprising two NH 2 functional groups comprised between 2/1 and 1/3.

6. A process according to claim 1 , wherein said aldehyde component is a mixture of glyoxal and at least one of a glyoxalate, 2,2-dimethoxy-ethanal, 2,2-diethoxy-ethanal and mixtures thereof, and has a molar ratio glyoxal/2,2-dialkoxy-ethanal comprised between 2.2/1 and 6.5/1 and the molar ratio glyoxal/glyoxalate is comprised between 4/1 and 1/1.

7. A process according to claim 1 , wherein there is added an amount of at least one cationic polymer comprised between 0% and 60% percentage being expressed on a w/w basis relative to the total weight of the resin.

8. A process according to claim 1 , wherein said di- or thi-isocyanate is selected amongst hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, toluene diisocyanate, a trimethylol propane-adduct of toluene diisocyanate, a trimethylol propane-adduct of xylylene diisocyanate, a trimer of hexamethylene diisocyanate, a trimer of isophorone diisocyanate, a trimethylol propane-adduct of hexamethylene diisocyanate or a biuret of hexamethylene diisocyanate.

9. A process according to claim 1 , wherein said di- or tri-oxiran compound is selected amongst 1,3,5-tris(oxiran-2-ylmethyl)-1,3,5-triazinane-2,4,6-trione, 4-(oxiran-2-ylmethoxy)-N,N-bis(oxiran-2-ylmethyl)aniline, 1,3-bis(oxiran-2-ylmethoxy)benzene, 1,2-bis(oxiran-2-ylmethoxy)ethane and 2,2′-(2-ethyl-2-((oxiran-2-ylmethoxy)methyl)propane-1,3-diyl)bis(oxy)bis(methylene)dioxirane.