Encapsulated fragrance compounds based on natural amino acids
The present invention relates to a process for the production of multilayer microcapsules, in particular multilayer odiferous substance capsules or fragrance compound capsules, which have improved stability and odiferous substance release or fragrance compound release compared to prior art capsules. In addition, the present invention relates to multilayer microcapsules comprising at least one hydrophobic odiferous substance or fragrance compound obtainable by the process of the invention. In another aspect, the invention described herein relates to multilayer microcapsules comprising a core comprising at least one hydrophobic odiferous substance or fragrance compound, and a capsule shell. In addition, the present invention relates to the use of the multilayer microcapsules and suspensions of the multilayer microcapsules as an ingredient in detergents, fabric softeners, cleaning products, scent boosters in liquid or solid form, cosmetics, personal care products, agricultural products or pharmaceutical products.
1. A method for producing multilayer microcapsules comprising the following steps in this order:
a) forming a first crosslinking layer by:
a1) providing an internal non-aqueous phase comprising at least one isocyanate having two or more isocyanate groups and at least one active ingredient to be encapsulated;
a2) providing an external aqueous phase comprising at least one protective colloid;
a3) mixing the internal non-aqueous phase and the external aqueous phase to obtain an oil-in-water emulsion;
b) forming a second crosslinking layer by addition of an amine which reacts at an acidic pH;
c) forming a third crosslinking layer by addition of a hydroxyl group donor;
d) forming at least a fourth crosslinking layer by adding at least one amine which reacts at an alkaline pH, to obtain multilayer microcapsules;
e) curing the multilayer microcapsules obtained in step d);.
2. The method according to claim 1 , wherein the first crosslinking layer is formed from the protective colloid and the isocyanate in the presence of a catalyst.
3. The method according to claim 1 , comprising adding a catalyst in a step a4) after step a3).
4. The method according to claim 1 , wherein the at least one isocyanate having two or more isocyanate groups is selected from one or more isocyanates in the group consisting of aliphatic isocyanates and aromatic isocyanates.
5. The method according to claim 4 , wherein the at least one isocyanate having two or more isocyanate groups comprises at least two aliphatic isocyanates having two or more isocyanate groups, wherein the at least two isocyanates have different chain lengths.
6. The method according to claim 1 , comprising an additional optional step prior to curing in which a termination of microcapsule crosslinking is formed by addition of an amine having an amine functional group.
7. The method according to claim 1 , wherein the protective colloid comprises a polysaccharide.
8. The method according to claim 1 , wherein the catalyst comprises diazabicyclo [2.2.2] octane (DABCO).
9. The method according to claim 1 , wherein the acid-reacting amine is an acidic amino acid hydrochloride.
10. The method according to claim 1 , wherein the hydroxyl group donor comprises a polyol having two or more hydroxyl functional groups.
11. The method according to claim 1 , wherein the alkaline reacting amine comprises a guanidinium group donor.
12. The method according to claim 1 , wherein the amine used in an additional optional step prior to curing to terminate the microcapsule comprises an amino acid.
13. The method according to claim 1 , wherein the at least one active ingredient to be encapsulated is one or more selected from the group of fragrance compounds, odiferous substances, flavorings, biocides, insecticides, a substance from the group of repellents, food additives, cosmetic active ingredients, pharmaceutical ingredients, agrochemicals, colorants, luminous colors, optical brighteners, solvents, waxes, silicone oils, lubricants, and mixtures of the aforementioned active ingredients.
14. A multilayer microcapsule comprising at least one hydrophobic odiferous substance or hydrophobic fragrance compound prepared by a process according to claim 1 .
15. The method according to claim 1 , further comprising separating the microcapsules from the reaction solution.
16. The method according to claim 7 , wherein the protective colloid comprises a starch.
17. The method according to claim 9 , wherein the acid-reacting amine comprises lysine hydrochloride and/or ornithine hydrochloride.
18. The method according to claim 10 , wherein the hydroxyl group donor comprises one or more in the group of glycerol, propylene glycol, and 1,3,5-trihydroxybenzene.