Polyurea capsules prepared with aliphatic isocyanates and amines
Polyurea capsules that encapsulate active materials in polymeric walls resulting from the polymerization of an aliphatic polyisocyanate and a cross-linking agent such as a diamine, amphoteric amine or guanidine amine/salt are provided as are consumer products containing said polyurea capsules and for methods for producing such capsules.
1. A method for preparing a polyurea capsule composition comprising:
(a) preparing an oil phase comprising an active material and a polyisocyanate in which the active material is a fragrance oil;
(b) preparing a surfactant solution containing a capsule formation aid that is a mixture of polyvinyl alcohol and carboxymethyl cellulose;
(c) emulsifying the oil phase into the surfactant solution to form a fragrance emulsion;
(d) adding a cross-linking agent to the fragrance emulsion to form a capsule slurry; and
(e) curing the capsule slurry,
wherein the active material is present at a level of 5% to 80% of the polyurea capsule composition; the polyisocyanate is present at a level of 1% to 7.5% of the polyurea capsule composition; the capsule formation aid is present at a level of 0.25% to 2% of the polyurea capsule composition; the cross-linking agent, being a guanidine salt, is present at a level of 0.25% to 3% of the polyurea capsule composition; the polyurea capsule composition contains a microcapsule having an encapsulating polymer that encapsulates the active material; and the encapsulating polymer is the polymerization product between the polyisocyanate and the cross-linking agent in the presence of the capsule formation aid.
2. The method of claim 1 , wherein the polyisocyanate is an aromatic polyisocyanate or aliphatic polyisocyanate.
3. The method of claim 2 , wherein the aliphatic polyisocyanate is a dimer, biuret, symmetric trimer, or asymmetric trimer of hexamethylene diisocyanate.
4. The method of claim 1 , wherein the guanidine salt is 1,3-diaminoguanidine monohydrochloride, 1,1-dimethylbiguanide hydrochloride, guanidine carbonate or guanidine hydrochloride.
5. The method of claim 4 , further comprising addition of sodium carbonate to the fragrance emulsion.
6. The method of claim 1 , wherein the step of adding the cross-linking agent to the fragrance emulsion is at a temperature of 35° C.
7. The method of claim 1 , wherein the step of adding the cross-linking agent to the fragrance emulsion is at a temperature of 22° C.
8. The method of claim 1 , wherein the capsule slurry is cured at a temperature greater than 55° C., 65° C., 75° C., 85° C. or 95° C.
9. The method of claim 1 , wherein the step of curing the capsule slurry is carried out in the presence of a catalyst.
10. The method of claim 1 , further comprising the step of washing the cured capsule slurry with water.
11. The method of claim 10 , further comprising the step of adding a salt to the cured capsule slurry before washing the capsule slurry with water.