BR112022010957B1 - ENCAPSULATED ODOR COMPOUNDS BASED ON NATURAL AMINO ACIDS - Google Patents

Abstract

ODORANT COMPOUNDS ENCAPSULATED BASED ON NATURAL AMINO ACIDS. The present invention relates to a method for producing multilayer microcapsules, in particular multilayer fragrance capsules or odor capsules, which have improved stability and fragrance or odor release compared to prior art capsules. The present invention further relates to multilayer microcapsules which comprise at least one hydrophobic fragrance or odor and can be obtained by the method according to the invention. In a further aspect, the invention described herein relates to multilayer microcapsules comprising a core, comprising at least one hydrophobic fragrance or odor, and a capsule shell. Furthermore, the present invention relates to the use of multilayer microcapsules and suspensions of multilayer microcapsules as a component of detergents, softeners, cleaning agents, aroma enhancers (fragrance enhancers) in liquid or solid form, cosmetics, products for the body, agricultural products or pharmaceutical products.

Description

Description

[001] The present invention relates to a method for preparing multilayer microcapsules, preferably multilayer odorous substance capsules or fragrance compound capsules, which have improved stability and release of odorous substance or compound of fragrance compared to prior art capsules. Furthermore, the present invention relates to multilayer microcapsules comprising at least one hydrophobic odorous substance or fragrance compound obtainable by the method of the invention. In another aspect, the invention described herein relates to multilayer microcapsules comprising a core comprising at least one hydrophobic odorous substance or fragrance compound and a capsule shell. Furthermore, 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, perfume enhancers in liquid or solid form, cosmetics, care products personal items, agricultural products or pharmaceutical products.

[002] The purpose of encapsulation is, among other things, to ensure the targeted release of active ingredients, the conversion of liquids into a manageable powder form, the delay of losses of volatile components (e.g. in the case of flavorings), the prevention of premature chemical reactions with other components of the mixture or better handling before or during processing. Encapsulated active ingredients, such as odorous substances or fragrance compounds, can be incorporated into various application formulations in encapsulated form for this purpose.

[003] The contents of the microcapsules can be subsequently released in various ways and are based in particular on one of the mechanisms described below: mechanical destruction of the capsule by crushing or shearing; destruction of the capsule by melting of the wall material, destruction of the capsules by dissolution of the wall material or diffusion of the active ingredients through the capsule wall.

[004] Nowadays, many articles of daily use, such as cleaning agents, waxes, shampoos, etc., are scented with fragrance compounds or mixtures of fragrance compounds. In order to avoid possible interactions of the fragrance compounds with the other ingredients of the product or, for example, to avoid volatilization of the fragrance compounds and thus not falsify or reduce the desired odor impression, the fragrance compounds can be added to the formulation in encapsulated form. In this way, the desired odor impression can be guaranteed.

[005] For example, document EP 2111214 B1 describes microcapsules with an odoriferous core and an aminoplastic polymer encapsulation. In addition to the high impermeability of the descriptive capsule shell, it is also highly resistant to reactive chemicals. The polycondensation of the amine-formaldehyde precondensate and the water-insoluble hydrophobic active ingredient, such as a perfume oil, is initiated by a change in pH.

[006] Document DE 2303866 A1 describes microcapsules prepared from (a) an epoxypropyltrialkylammonium salt and additionally an alkylsulfosuccinate having alkyl groups with 6 to 16 carbon atoms or an alkylsulfosuccinamate whose carboxylic acid amide group is replaced by an alkyl group with 8 to 20 carbon atoms and a water-miscible solvent as component (b).

[007] Document EP 3238816 A1 describes a method for preparing microcapsules, in particular aminoplast microcapsules, from a first aqueous preparation containing at least one prepolymer and a second non-aqueous preparation containing the active ingredient to be encapsulated , so that the average diameter of the capsules is reduced and standardized. Furthermore, the method described herein leads to a significant reduction of the microcapsule particle size and therefore a stabilization of the emulsion.

[008] Document WO 2017/148504 A1 describes a method for preparing capsules of fragrance compounds exhibiting improved storage stability in an aqueous surfactant environment, wherein the fragrance composition, which has an acid number not exceeding 5 mg KOH/g immediately before encapsulation, is encapsulated with natural coating materials or synthetic, anionic or cationic polymers or mixtures thereof.

[009] Microcapsules can also be made from other polymerizable materials, such as acrylate monomers, polyureas or even biopolymers. Isocyanate-based microcapsules are generally produced from polyisocyanates and guanidinium carbonate in an alkaline environment.

[0010] However, the prior art microcapsules described above have the disadvantage that the polymeric capsule wall or capsule shell materials require a large polymer content to ensure sufficient stability and avoid excessive loss of active ingredients. Furthermore, such microcapsules often do not have biodegradable properties. Furthermore, the release of the active ingredient in the order is generally insufficient.

[0011] In particular, the demand for biodegradable and bio-based solutions is increasing due to increasing social pressure with regard to environmental aspects.

[0012] In this context, the present invention was based on the complex task of providing a method for producing microcapsules that makes it possible to provide highly stable microcapsules with a low polymer content, which at the same time exhibit excellent release behavior of the encapsulated active ingredients and have properties that are as biodegradable as possible.

[0013] Surprisingly, it was found that this task can be solved in that targeted layered cross-linking at defined temperatures and targeted catalyzed mechanisms lead to stable multi-layered microcapsules, thus ensuring efficient encapsulation of active ingredients with subsequent targeted release of these ingredients active, for example, by mechanical friction or pressure.

Summary of the Invention

[0014] The present problem is resolved by the objects of the independent patent claims. Preferred embodiments result from the wording of the dependent patent claims and the following description.

[0015] Thus, a first object of the present invention relates to a method for producing multilayer microcapsules, preferably multilayer odorous substance capsules or fragrance compound capsules, 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 with two or more isocyanate groups and at least one active ingredient to be encapsulated; a2) provide 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) form a second crosslinking layer by adding an amine that reacts at an acidic pH; c) forming a third cross-linking layer by adding a hydroxyl group donor; d) forming at least a fourth crosslinking layer by adding at least one amine that reacts at an alkaline pH to obtain multilayer microcapsules; e) curing the multilayer microcapsules obtained in step d); and, optionally: f) separating the microcapsules from the reaction solution and drying the microcapsules, if necessary.

[0016] Furthermore, it is an object of the invention described herein to provide multilayer microcapsules comprising at least one hydrophobic odorous substance or fragrance compound prepared by the method of the invention.

[0017] Another aspect of the present invention are multilayer microcapsules comprising a core comprising at least one hydrophobic odoriferous substance or fragrance compound and a capsule shell, wherein the capsule shell comprises or consists of, from the inside out: a first layer comprising or consisting of polyurethane; a second layer comprising or consisting of polyurea; a third layer comprising or consisting of polyurethane; and at least a fourth layer comprising or consisting of polyurea.

[0018] Finally, in a further aspect, the present invention relates to the use of the multilayer microcapsule or suspension of the multilayer microcapsules according to the invention, for the manufacture of detergents, fabric softeners, cleaning agents, enhancers of perfume in liquid or solid form, cosmetics, personal care products, agricultural products or pharmaceutical products.

[0019] Surprisingly, it has been found in the context of the present invention that the combination of targeted, defined and layered deposition of cross-linked capsule wall materials at defined temperatures and targeted catalyzed mechanisms leads to stable multilayer microcapsules, thus ensuring encapsulation efficient release of active ingredients with subsequent targeted release of these active ingredients, for example by mechanical friction or pressure.

[0020] Furthermore, the multilayer microcapsules described here exhibit good biocompatibility due to their bio-based and biodegradable building blocks, such as amino acids and starch.

[0021] Furthermore, significant savings in capsule wall material can be achieved by the method described in this document.

[0022] These and other aspects, features and advantages of the present invention will be evident to those skilled in the art from a study of the following detailed description and claims. In this regard, any feature of one aspect of the invention may be used or substituted in another aspect of the invention. The examples in this document illustrate the invention without limiting it.

[0023] The terms “at least one” or “at least one” or “one or more”, as used herein, refer to 1 or more, e.g., 2, 3, 4, 5, 6, 7 , 8, 9 or more.

[0024] Numerical examples given in the form “from x to y” include the named values. If multiple preferred numeric ranges are specified in this format, all ranges created by combining the different endpoints are also included.

Figures

[0025] Figure 1 is a light microscope image of multilayer microcapsules produced from 100% longer chain diisocyanate according to the invention. An Olympus BX51 was used for light microscope imaging. The bar shown corresponds to 50 μm.

[0026] Figure 2 is a light microscope image of multilayer microcapsules produced from 100% shorter chain diisocyanate according to the invention. An Olympus BX51 was used for light microscope imaging. The bar shown corresponds to 50 μm.

[0027] Figure 3 is a light microscope image of multilayer microcapsules produced from 50% longer chain diisocyanate and 50% shorter chain diisocyanate according to the invention. An Olympus BX51 was used for light microscopic imaging. The bar shown corresponds to 50 μm.

[0028] Figure 4 is a light microscope image of multilayer microcapsules produced from 80% longer chain diisocyanate and 20% aromatic diisocyanate according to the invention. An Olympus BX51 was used for light microscopic imaging. The bar shown corresponds to 50 μm.

[0029] Figure 5 is a diagram showing the results of an IR spectroscopic analysis of prior art microcapsules, that is, microcapsules based on a pure network of polyurea structures and microcapsules according to the invention. Analysis was performed using ATR (Attenuated Total Reflection) infrared spectroscopy.

[0030] Figure 6 shows a diagram of the particle size distribution (d value (0.5)) of multilayer microcapsules according to the invention and prior art microcapsules based on a pure polyurea network. A MALVERN Mastersizer 3000 was used to determine particle size distribution. The corresponding calculation is based on Mie theory.

[0031] Figure 7 is a diagram showing the results of a sensory evaluation of prior art microcapsules, that is, microcapsules based on a pure network of polyurea structures and microcapsules according to the invention.

Detailed Description of the Invention

[0032] In a first aspect, the present invention relates to a method for producing multi-layer microcapsules, preferably a method for producing multi-layer odorous substance capsules or fragrance compound capsules comprising or consisting of the following steps in this order: g) forming a first crosslinking layer by: a1) providing an internal non-aqueous phase comprising at least one isocyanate with 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, preferably the protective colloid is a polysaccharide, particularly preferably starch; a3) mixing the internal non-aqueous phase and the external aqueous phase to obtain an oil-in-water emulsion; h) forming a second crosslinking layer by adding an amine that reacts at an acidic pH; i) forming a third cross-linking layer by adding a hydroxyl group donor; j) forming at least a fourth crosslinking layer by adding at least one amine that reacts at an alkaline pH to obtain multilayer microcapsules; k) curing the multilayer microcapsules obtained in step d); and, optionally: l) separating the microcapsules from the reaction solution and drying the microcapsules, if necessary.

[0033] In the context of the present invention, multilayer microcapsules are understood as microparticles that have a capsule shell or capsule wall and one or more active ingredients as the core material inside the capsule. Preferably, these are hydrophobic active ingredients. The terms “microcapsule” and “capsule” are used synonymously for the purposes of the present invention.

[0034] In the context of the present invention, the capsule shell or capsule wall is preferably composed of several layers, which preferably have different compositions. Thus, a particularly preferred embodiment of the capsule shell comprises at least one polyurethane-based layer and at least one polyurea-based (crosslinking) layer. In particular, alternating layers comprising polyurethane and polyurea structures are preferred.

[0035] In a first step of the method according to the invention, a first crosslinking layer is formed. For this purpose, an internal non-aqueous phase is provided, which comprises at least one isocyanate with two or more isocyanate groups and at least one active ingredient to be encapsulated.

[0036] The at least one isocyanate used in the production method described in this document has at least two isocyanate groups for the formation of polymeric networks and, therefore, for the formation of the capsule shell or capsule wall by polymerization. The corresponding polymerizable isothiocyanates, alone or in combination with isocyanates, are also applicable for use in the method according to the invention. Aliphatic, cycloaliphatic, hydroaromatic, aromatic or heterocyclic polyisocyanates or polyisothiocyanates, their substitute products and mixtures of the monomeric or oligomeric compounds mentioned above are particularly preferred, aliphatic and/or aromatic compounds preferably being used. Among the polyisocyanates, diisocyanates are particularly preferred and are therefore mainly used in implementing the present invention.

[0037] Therefore, in a preferred embodiment, the present invention relates to a method for preparing multilayer microcapsules, in which the at least one isocyanate having two or more isocyanate groups is selected from the group consisting of aliphatic isocyanates and /or aromatic isocyanates and the corresponding isothiocyanates. Preferably, the aliphatic isocyanates used have five or more carbon atoms.

[0038] In a particularly preferred embodiment, the internal non-aqueous phase comprises mixtures of different polymerizable isocyanates and/or isothiocyanates that can form copolymers.

[0039] Examples of monomeric isocyanates and/or isothiocyanates that can be used according to the invention and that contain at least two isocyanate groups or isothiocyanate groups are: ethylene diisocyanate, trimethylene diisocyanate, 1 ,4-tetramethylene, 1,6-hexamethyldiisocyanate, ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3-di -isocyanate, cyclohexane- 1,4-diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, mixtures of 1,3-phenylene diisocyanate and diisocyanate 1,4-phenylene, p-phenylene diisocyanate, xylene-1,4-diisocyanate, xylylene-1,4-diisocyanate, 2,4-toluylene diisocyanate, di -2,6-toluylene isocyanate, mixtures of 2,4-toluylene diisocyanate and 2,6-toluylene diisocyanate, xylylene diisocyanate-1,4-diisocyanate, xylene diisocyanate - 1,3-diisocyanate and mixtures of xylene diisocyanate-1,4-xylene diisocyanate, 2,4-hexane diisocyanate, 2,6-hexane diisocyanate, diisocyanate 2,4-hexane and 2,6-hexylutylene diisocyanate, 2,4-isocyanate diisocyanate, xylene diisocyanate, xylylene diisocyanate, 1 1,3-diisocyanene diisocyanate, 1,3-diisocyanene diisocyanate, 1,3-diisocyanene diisocyanate, 1,3-diisocyanene diisocyanate 1,3,4-diisocyanene, naphenylene, naphenylene-2,4,4,4-diisocyanate, 1,3-diisocyanate, naphenylene, 1,3-diisocyanate-1 ,3-diisocyanene, naphenylene, 1,3-diisocyanene diisocyanate, 1,3-diisocyanene diisocyanate, 1,3-didiisocyanate - isocyanene, 1,3-diisocyanate diisocyanate, naphenylene and xylylene mixtures.

[0040] As polymerizable compounds containing at least two isocyanate or isothiocyanate groups, preference is given to di- and polyisocyanates produced on an industrial scale, for example TDI: toluylene diisocyanate (mixture of 2,4 diisocyanate isomers and 2,6-toluylene in a ratio of 80:20), HDI: hexamethylene-diisocyanate-(1,6), IPDI: isophorone diisocyanate or DMDI: diphenylmethane-4,4'-diisocyanate.

[0041] Other particularly preferred monomeric isocyanate compounds are: diisocyanates such as 1,4-diisocyanatobutane, 1,6-diisocyanatohexane, 1,5-diisocyanate-2,2-dimethylpentane, 2,2 ,4- and 2,4,4-trimethyl-1,6-diisocyanatohexane, 1,10-diisocyanatodecane, 1,3- and 1,4-diisocyanatocyclohexane, 1-isocyanate-3,3,5 -trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate), 4,4'-diisocyanatodicyclohexylmethane, 2,4- and 2,6-diisocyanatomethylcyclohexane and mixtures thereof. In principle, aromatic isocyanates, for example toluylene diisocyanates or 4,4'-diisocyanatodiphenylmetha can also be used.

[0042] Polyisocyanates that can be prepared by modifying the above-mentioned diisocyanates or mixtures thereof by known methods and that contain, for example, uretdione, urethane, isocyanurate, biuret and/or allophanate groups can also be used proportionately.

[0043] Surprisingly, it has been demonstrated that the use of longer chain aliphatic diisocyanates with six or more carbon atoms in particular leads to the formation of more stable capsule shells or capsule walls.

[0044] Even more preferred is the combination of at least two different diisocyanates (preferably aliphatic and/or aromatic). In a further preferred embodiment of the invention, the different diisocyanates (preferably aliphatic) also have different chain lengths. Primary embodiments comprise, in particular, mixtures of longer chain and shorter chain diisocyanates in any desired mixing ratios. Preferably, the mixing ratio of longer chain diisocyanates to shorter chain diisocyanates is in a range of 4:1 to 1:4 and particularly preferably 2:1 to 1: 2. The longer chain diisocyanates in this context preferably have six or more carbon atoms, but even more preferably have six to twelve carbon atoms and particularly preferably six to eight carbon atoms . By shorter chain diisocyanates we mean diisocyanates with one to five carbon atoms and preferably diisocyanates with three to five carbon atoms.

[0045] It has been demonstrated that particularly stable and better, i.e. more densely branched, crosslinks are produced within the capsule shell if fundamentally different diisocyanates were used in a mixed form and, in particular, if a mixture of aliphatic isocyanates of longer chain and shorter chain was selected, or else a mixture of aliphatic and aromatic isocyanates (and/or isothiocyanates) was used.

[0046] Thus, the method described in this document could be used to produce good-performance microcapsules provided from a mixture of linear and aromatic isocyanates, as well as from a mixture of two different linear isocyanates. Such microcapsules exhibit excellent perfume storage properties and excellent associated fragrance compound release, particularly when used as fragrance compound capsules, as illustrated by the following embodiments.

[0047] The combination of different polymerizable isocyanates therefore leads to particularly stable capsule shells or capsule walls, which in turn is reflected in better performance (fragrance compound release) of the capsules, e.g. area of encapsulation of an odorous substance or fragrance compound. Therefore, in principle, the combination of at least two different polymerizable isocyanates (preferably aliphatic and/or aromatic) is preferred in the present invention.

[0048] Such microencapsulation of fragrance compounds or mixtures of fragrance compounds also offers the possibility of reducing or completely preventing interactions in the perfumed product or evaporation of highly volatile odorous components.

[0049] Figures 1 to 4 show the influence of the length of the isocyanate chain on the resulting microcapsules. Figure 1 shows the light microscope image of microcapsules according to the invention produced exclusively from longer chain diisocyanates, in this case hexamethylene isocyanate diisocyanate, while Figure 2 shows microcapsules based on shorter chain diisocyanates, such as pentamethylene isocyanate diisocyanate. The microcapsules shown in Figure 2 have a more homogeneous morphology but are less stable.

[0050] Figures 3 and 4 show microcapsules based on mixed isocyanates according to the invention: Figure 3 shows the morphology of the microcapsules based on a mixture of 50% shorter chain and 50% longer chain aliphatic isocyanates (mixture of hexamethylene diisocyanate and pentamethylene diisocyanate in the ratio 50 : 50), while Figure 4 shows a corresponding mixture of 80% longer chain diisocyanates and 20% of an aromatic diisocyanate ( hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate in the ratio 80 : 20).

[0051] In general, microcapsules prepared from mixed aliphatic and/or aromatic isocyanates exhibit better stabilities and are, therefore, primarily suitable for the method described in this document and, therefore, for the preparation of multilayer microcapsules according to the invention, which exhibit excellent stabilities and active ingredient release properties, as illustrated in the following embodiments.

[0052] Particularly preferred in this context is the use of aliphatic isocyanates and/or isothiocyanates with chain lengths of one to twelve carbon atoms in the chain, preferably three to eight carbon atoms and particularly preferably four to seven carbon atoms for producing multilayer microcapsules according to the present invention.

[0053] Polymerizable aliphatic isocyanates are particularly preferable in this context due to their chemical relationship with bio-based systems. For example, both lysine and 1,5-diisocyanatopentane show the same degradation product, 1,5-diaminopentane, and are therefore particularly suitable for use in the production of bio-based and biodegradable microcapsules, taking into account environmental aspects.

[0054] Therefore, in a particularly preferred embodiment, the present invention further relates to a method for preparing multilayer microcapsules comprising at least two aliphatic isocyanates with two or more isocyanate groups, wherein the at least two isocyanates have chain lengths many different.

[0055] A method comprising at least two aliphatic isocyanates and/or isothiocyanates with two or more isocyanate/isothiocyanate groups is further preferred, wherein the at least two isocyanates/isothiocyanates have different chain lengths.

[0056] Preferably, at least one of the isocyanates and/or aliphatic isothiocyanates has a chain length of five or more carbon atoms.

[0057] In another embodiment, mixtures of isocyanate and isothiocyanate compounds in the internal non-aqueous phase are therefore also conceivable in principle, which exhibit the above-mentioned properties.

[0058] It was observed that the choice of at least two aliphatic isocyanates of different chain lengths or the choice of mixtures of aliphatic and aromatic isocyanates leads to a significant gain in stability and performance (release of fragrance compounds in the case of capsules odoriferous substances or capsules of fragrance compounds) due to different reaction times, dissociations and cross-linking structures.

[0059] Furthermore, the microcapsules described here can be prepared from aromatic isocyanates with two or more isocyanate groups.

[0060] Therefore, in another embodiment, the present invention relates to a method for preparing multilayer microcapsules, in which isocyanate(s) having two or more isocyanate groups is(are) selected of the group consisting of aromatic isocyanates.

[0061] Also in this case, a mixture of several aromatic isocyanates (or isothiocyanates) can be used.

[0062] The proportion of the isocyanate component to the internal non-aqueous phase is preferably between 1: 50 and 1: 20, even more preferably between 1: 40 and 1: 30.

[0063] The internal non-aqueous phase may therefore contain, for example, 0.1 to 10.0% by weight and preferably 0.5 to 3.0% by weight of isocyanate based on the total weight of the internal non-aqueous phase.

[0064] Due to the low proportion of the isocyanate component, it is possible, based on the present invention, to produce multilayer microcapsules in which the absolute isocyanate content is only 1/50 of the total capsule comprising the ingredient(s). ) active). Thus, multilayer microcapsules having, for example, an isocyanate content of only 0.6% by weight could be produced by the method described herein. Preferably, however, the isocyanate content is about 1.1% by weight of the capsule wall.

[0065] In the method according to the invention for producing multilayer microcapsules, the at least one polymerizable isocyanate and/or isothiocyanate is first dissolved in a mixture of inert, non-aqueous solvent or solvent together with the ingredient(s) asset(s) to be encapsulated. Therefore, in the context of the present description, the active ingredient to be encapsulated is preferably a hydrophobic active ingredient. By choosing such an active ingredient, it can be ensured that the material to be encapsulated is in the internal non-aqueous phase and does not mix with the external aqueous phase. This results in the hydrophobic active ingredient being effectively trapped within the multilayer microcapsule as the core material. The internal non-aqueous phase thus formed is further characterized by its organic hydrophobic oily character.

[0066] Inert solvents suitable for the internal non-aqueous phase are: chlorinated diphenyl, chlorinated kerosene, vegetable oils such as cottonseed oil, peanut oil, palm oil, tricresyl phosphate, silicone oil, dialkyl phthalates , dialkyl adipates, partially hydrogenated terphenyl, alkylated biphenyl, alkylated naphthalene, diaryl ether, aryl alkyl ether and higher alkylated benzene, benzyl benzoate, isopropyl myristate, as well as any mixtures of these hydrophobic solvents and mixtures of one or more of these hydrophobic solvents with kerosene, kerosenes and/or isoparaffins. Preferably, vegetable oils such as sunflower oil, triglycerides, benzyl benzoate or isopropyl myristate are used as solvents to provide the internal non-aqueous phase.

[0067] The ratio of the active ingredient component to the internal non-aqueous phase is preferably about 1 : 14. The internal non-aqueous phase may therefore comprise, for example, 88 to 99% by weight and of preferably 92 to 96% by weight of the active ingredient (or active ingredient mixture) to be encapsulated, based on the total active ingredient capsule. The capsule as a whole, in this context, comprises both the oil core, i.e. the active ingredient (or active ingredient mixture) and the capsule wall components formed from the isocyanate component and the respective capsule cross-linking agents. external aqueous phase.

[0068] Thus, it is possible to encapsulate a significantly greater amount of active ingredient using the method described in this document, in contrast to prior art microcapsules.

[0069] Furthermore, the first step of the method described in this document comprises providing an external aqueous phase comprising at least one protective colloid.

[0070] For this purpose, the protective colloid is dissolved in the aqueous solvent (preferably water). Preferably, the protective colloid is a polysaccharide and starch is particularly preferred.

[0071] Thus, a particularly preferred embodiment of the present invention relates to a method for producing multilayer microcapsules, in which the protective colloid is a polysaccharide, in particular starch.

[0072] A protective colloid is a compound that prevents primary particles from agglomerating (agglomeration, aggregation, flocculation, coagulation) in precipitation reactions, that is, in reactions in which a solid phase is deposited from a homogeneous liquid phase . In the production of oil-in-water emulsions, the protective colloid binds to the primary particles with its hydrophobic part and turns its polar molecular part, that is, hydrophilic, towards the aqueous phase. By this connection to the interface, it reduces interfacial tension and prevents the agglomeration of primary particles. It also stabilizes the emulsion and promotes the formation of comparatively smaller droplets and therefore also corresponding microcapsules.

[0073] The protective colloid used in the method according to the invention is preferably a polysaccharide, in particular starch, especially wheat, potato, corn, rice, tapioca or oat starch, or chemically, mechanically and/or enzymatically starch modified (succinates, acetates, formates), as well as mixtures of the compounds mentioned above. Other suitable protective colloids include carboxymethylcelluloses, gum arabic, proteins, gelatin, polyols, polyphenols or polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl alcohol derivatives, such as ammonium derivatives and mixtures of the above compounds.

[0074] More preferably, however, starches are used as a protective colloid. Particularly preferred, therefore, is the use of (modified) starch as a protective colloid for the production of multilayer microcapsules.

[0075] The protective colloids used here have a dual function in that, on the one hand, they react with the polymerizing isocyanate(s) to form a first or more cross-linking layers and, thus, accumulate on the wall of the capsule or capsule shell and are an integral part thereof and, on the other hand, act as a protective colloid and thus prevent the agglomeration of solid particles, stabilize the subsequently formed emulsion and thus promote the formation of small droplets.

[0076] Therefore, it is particularly preferred that the selected protective colloid has polymerizable properties, as in the case of starch due to the presence of at least one hydroxyl group.

[0077] Starches are naturally occurring polysaccharides that are biodegradable. In combination with the isocyanates described herein, the present method can thus provide bio-based and biodegradable capsule shells. In the method described here, starch therefore functions mainly as a so-called biocrosslinker.

[0078] According to the present invention, the ratio of the amount of protective colloid or colloids used in relation to the aqueous phase is preferably in a range of 1: 50 to 1: 10, more preferably in a range from 1 : 40 to 1 : 30.

[0079] The amount of protective colloid used, or the amount of a combination of protective colloids used, is therefore in a range of 1 to 8% by weight, preferably in a range of 2 to 4% by weight , even more preferably in a range of 3 to 4% by weight, based on the total weight of the external aqueous phase.

[0080] The oil-in-water emulsion is formed by mixing the internal non-aqueous phase and the external aqueous phase. The weight ratio of the internal non-aqueous phase to the external aqueous phase is preferably in a range of 2: 1 to 1: 10, more preferably in a range of 1: 2 to 1: 4.

[0081] The ratio of protective colloid in the external aqueous phase to isocyanate or isothiocyanate in the internal non-aqueous phase is in a range of 1: 5 to 1: 2, preferably in a range of 1: 2 to 1: 1.

[0082] Emulsion formation in the case of liquid active ingredients or suspension formation in the case of solid active ingredients, that is, emulsification or suspension of the internal non-aqueous or oily phase with the external aqueous or hydrophilic phase, occurs under high turbulence or strong shear, whereby the resistance of turbulence or shear determines the diameter of the microcapsules obtained. The production of microcapsules can be continuous or discontinuous. As the viscosity of the water phase increases or the viscosity of the oil phase decreases, the size of the resulting capsules generally decreases.

[0083] The method according to the invention for producing multilayer microcapsules can be carried out, for example, by means of a forced metering pump using the “in-line” technique, or also in a conventional dispersion apparatus or emulsification with stirring.

[0084] The emulsification of the external aqueous phase and the internal non-aqueous phase was carried out to produce multilayer microcapsules according to the invention by means of an emulsifying turbine (IKA Eurostar 20 high-speed stirrer). The emulsification method in the first step of the method according to the invention is advantageously carried out for a time of 30 seconds to 20 minutes, preferably 1 to 4 minutes, at an agitation speed of 2000 rpm to 5000 rpm, of preferably at 3250 rpm to 4500 rpm.

[0085] Optionally, it is possible to dissolve or disperse so-called stabilizers or emulsifying auxiliaries in the external aqueous phase to stabilize the emulsion formed and prevent segregation of the internal non-aqueous phase (oily/organic/hydrophobic) and the external aqueous phase (hydrophilic).

[0086] It has surprisingly been shown that the further addition of a catalyst to the emulsion or suspension leads to the formation of a first inner core shell of protective colloid and isocyanate at the interfaces of the emulsified or suspended hydrophobic particles or droplets (active ingredient) to be encapsulated. Interfacial polymerization can result in the formation of a capsule shell or capsule wall, which surrounds the active ingredient(s) within as a capsule core.

[0087] The formation of this first capsule layer is based on the polyaddition reaction of the isocyanate or isocyanates (and/or the corresponding isothiocyanates) with the protective (preferably polymerizable) colloid, preferably starch, to form a shell of capsule or capsule wall based on a polyurethane structure.

[0088] Therefore, a preferred embodiment of the present invention relates to a method for preparing multilayer microcapsules, in which the first crosslinking layer is formed from protective colloid and isocyanate in the presence of a catalyst.

[0089] The catalyst added in the method according to the invention is preferably diazabicyclo[2.2.2]octane (DABCO). DABCO, also known as triethylenediamine (teda), a bicyclic tertiary amine. DABCO is generally used as a catalyst for producing polyurethane plastics. The tertiary amine with free electron pairs promotes the reaction between the at least one polymerizable isocyanate in the internal non-aqueous phase and the hydroxyl groups (alcohol groups) of the protective colloid in the external aqueous phase.

[0090] The amount in which the catalyst is added to the emulsion or suspension is in a range of 0.01 to 1% by weight and preferably in a range of 0.05 to 0.2% by weight, based in the total weight of the emulsion or suspension. In the case of slow polymerization reactions, the amount of catalyst required can be adjusted accordingly.

[0091] Thus, the ratio of catalyst in the emulsion or suspension to the at least one isocyanate or isothiocyanate in the internal non-aqueous phase is preferably in a range of 1: 20 to 1: 50.

[0092] It has been shown to be advantageous for the catalyst to be first dispersed in water and then added to the emulsion or suspension with stirring.

[0093] The catalyst is preferably added at a stirring speed of 500 rpm to 2000 rpm, particularly preferably at 1000 rpm to 1500 rpm and at temperatures of 20°C to 35°C, preferably at temperatures of 22°C to 26°C.

[0094] It was also surprising that the addition of the catalyst after the emulsification or suspension step led to a significant increase in capsule stability. Capsules prepared in this way exhibit significantly greater stability, even after 10 days at 50°C, and a marked reduction in free perfume oil compared to reference capsules in which the catalyst is added to the aqueous phase prior to emulsification or suspension.

[0095] Particularly stable capsules can be prepared with the catalyst diazabicyclo[2.2.2]octane (DABCO). In the examples described here, an increase in stability by at least a factor of 3 was observed.

[0096] According to a particularly preferred embodiment, the catalyst is therefore diazabicyclo[2.2.2]octane (DABCO).

[0097] Therefore, the present invention additionally relates, in a particularly preferred embodiment, also to a method for the preparation of multilayer microcapsules comprising the addition of a catalyst in a step a 4) after step a3).

[0098] After addition of the catalyst to the emulsion or suspension, a first cross-linking layer forms at the interfaces of the emulsified or suspended active ingredient particles or droplets to be encapsulated by interfacial polymerization, which represents the first inner capsule shell, while the particles or droplets of hydrophobic active ingredient to be encapsulated represent the core of the microcapsules according to the invention. Interfacial polymerization, in this case, corresponds to a polyaddition reaction of the polyisocyanate(s) or isothiocyanate(s) (or mixtures thereof) with the protective colloid, that is, preferably with starch, to form a capsule shell based on cross-linked polyurethane in the presence of a catalyst. Therefore, the addition of a catalyst causes efficient formation of the first innermost polyurethane-based shell layer.

[0099] The polyaddition reaction described in this document is generally characterized by the reaction of individual polymers or oligomers with two or more functional groups with binding bond and rearrangement of a hydrogen atom, such as by reaction of polyisocyanates or polyisothiocyanates and polyols (e.g. polysaccharides such as starch).

[00100] The polyaddition reaction of at least one polyisocyanate, preferably a diisocyanate, with the protective colloid, preferably starch (a polyol), leads to the formation of so-called urethane bridges (-NH -CO-C-) by adding the hydroxyl groups of the polyol (-OH) to the carbon atom of the carbon-nitrogen bond of the isocyanate groups (-N=C=O) according to the following reaction scheme: Reaction Scheme 1

[00101] In this way, a hydrophilic boundary layer, i.e. capsule shell, can be formed, which prevents the diffusion of the hydrophobic active ingredient (or active ingredient mixture) enclosed in the capsule. In the case of fragrance compounds and odoriferous substances, for example, this leads to the effective shell of the sensory active ingredient (fragrance compound/perfume oil mixture, single fragrance compound), which is only effectively released by mechanical activation.

[00102] In the case of the reaction of diisocyanates with diols, linear polyurethane chains are thus generally formed, which can be spatially cross-linked in a directed manner by means of an excess of isocyanate over the amino groups of the untreated polyurethane chains. reticulated.

[00103] The greater the number of cross-linking functional groups, the greater the spatial cross-linking and the more stable the capsule shell or capsule wall resulting from the microcapsule. In addition to the number of functional groups, i.e. the number of branches, the chain length of the individual building blocks significantly influences the mechanical properties, i.e. the stability of the capsules. In this context, the large number of hydroxyl groups of the protective colloidal starch should be noted, which allows the formation of particularly pronounced spatial cross-links.

[00104] Other protective colloids or mixtures thereof, as well as additional emulsifying auxiliaries or stabilizers, are generally not necessary to ensure efficient cross-linking, but can be added, if necessary, on the one hand, to improve the emulsification method or the method of suspension in case of insufficient crosslinking and, on the other hand, to increase the density and crosslinking rate.

[00105] This reaction with formation of a first innermost polyurethane-based crosslinking layer (first layer of the capsule shell or capsule wall) occurs in the presence of the catalyst already at room temperature and especially preferably at temperatures between 25 and 40°C.

[00106] Isocyanate-based capsule shells can typically only be used to encapsulate selected active ingredients. Encapsulation with isocyanates is therefore not suitable for encapsulating active ingredients with aldehyde, carboxylic acid or ester functionalities, since such active ingredients are deprotonated, oxidized or saponified at an alkaline pH, making the resulting emulsion unstable. Consequently, the relatively neutral pH at which polyurethane-based encapsulation is performed allows for effective encapsulation of such active ingredients. The present method thus allows particularly mild conditions due to the selected pH ranges, so that no pH extremes are present and thus, theoretically, there are no longer any limitations regarding the active ingredients to be encapsulated.

[00107] In a second subsequent step of the method according to the invention, a second crosslinking layer is formed by adding an amine that reacts at an acidic pH. Furthermore, with stirring at a stirring speed of 500 rpm to 2000 rpm, particularly preferably at 1000 rpm to 1500 rpm, an amine that reacts at an acidic pH is added to the mixture for this purpose.

[00108] Particularly stable crosslinking is achieved if the second crosslinking with the amine reacting at an acidic pH occurs at an acidic pH of 2 to 7, preferably at a pH of 2 to 6 and more preferably at a pH 3 to 5. For this purpose, an acid, for example formic acid or acetic acid, is added to the external aqueous phase of the mixture in order to set an appropriate pH and avoid potential saponification of the hydrophobic active ingredients. This ensures that the pH does not drift too quickly and therefore penetrates the first thin and still quite unstable layer of protective colloid and isocyanate.

[00109] This second cross-linking layer forms additional cross-links of the capsule shell that surrounds the core material, i.e. the active ingredients, and surrounds it on the outside, stabilizing it further.

[00110] Furthermore, this layer preferably has a hydrophobic character and surrounds the first internal hydrophilic cross-linking layer, thus acting as an additional barrier layer that prevents the diffusion of the closed active ingredient.

[00111] Even more preferably, the second crosslinking step is carried out at a temperature of 35°C to 50°C. Preferred temperatures are 40°C to 45°C.

[00112] The amine that reacts at an acidic pH, that is, the second crosslinking agent, is selected from the group consisting of basic amino acids and their hydrochlorides, in particular lysine hydrochloride and/or ornithine hydrochloride, with lysine hydrochloride being particularly preferred as the crosslinking agent.

[00113] From an environmental point of view in terms of biodegradability and biocompatibility, such amino acid-based amines are particularly preferred.

[00114] Performing this crosslinking in an acidic pH range has the advantage over crosslinking in a basic environment that hydrophobic active ingredients with aldehyde, carboxylic acid or ester functionalities do not saponify during crosslinking with the at least one isocyanate or isothiocyanate, since the first innermost shell layer is still quite labile towards diffusion and similar methods. This prevents, for example, the active ingredient(s) to be encapsulated, for example a perfume oil, from being chemically altered and thus on the one hand, there is a loss of active ingredients and, on the other hand, the emulsion becomes unstable. Thus, encapsulation of hydrophobic active ingredients, in particular hydrophobic active ingredients that have an aldehyde, carboxylic acid or ester functionality, is possible.

[00115] Therefore, a preferred embodiment of the present invention relates to a method for preparing multilayer microcapsules comprising a second/another crosslinking step, wherein the acidic reaction amine used for crosslinking is an acidic amino acid hydrochloride, in particular lysine hydrochloride and/or ornithine hydrochloride.

[00116] In principle, however, all such basic amino acids and their hydrochlorides that have two or more amino groups are suitable for forming a second cross-linking layer, that is, a second shell layer, in this second cross-linking step.

[00117] The amine, which reacts at an acidic pH, is added to the suspension or emulsion directly in the form of a solid or in the form of an aqueous solution.

[00118] The amino acid hydrochloride is preferably added in the form of a 5 to 40% solution, more preferably a 10 to 20% solution.

[00119] Preferably, the second crosslinking of the method according to the invention is carried out for a period between 5 minutes and 30 minutes with stirring and preferably for a period between 10 and 20 minutes.

[00120] It has been demonstrated that after the addition of the amine reacting at an acidic pH to the emulsion or suspension, a second cross-linking layer forms around the particles or droplets of active ingredient already encapsulated in the first step by interfacial polymerization, which involves the first inner capsule shell and the hydrophobic active ingredient particles or droplets contained therein. Interfacial polymerization corresponds to a polyaddition reaction of at least one polyisocyanate or isothiocyanate (or mixtures thereof) with the amine reacting at an acidic pH, i.e. preferably with amino acid hydrochlorides, in particular lysine hydrochloride and ornithine hydrochloride, to form a cross-linked polyurea-based capsule shell.

[00121] The formation of the polyurea bond is carried out in a manner analogous to the formation of the polyurethane bond by polyaddition of the amine group of amines (-NH) to the corresponding isocyanate according to the reaction scheme below: Reaction scheme 2

[00122] Any starch still present can be incorporated into this layer as a secondary component, which further increases the stability of the second crosslinking layer. Basically, however, this second crosslinking layer is mainly based on a polyurea-type crosslinking as the main component that defines this layer.

[00123] Subsequently, a third cross-linking layer is formed around the existing capsule shell or capsule wall material by adding a hydroxyl group donor to form a spatially extended cross-link, mainly based on polyurethane.

[00124] By reacting the at least one isocyanate and/or isothiocyanate with the hydroxyl groups of the hydroxyl group donor, a third spatially cross-linked shell layer is formed, the structure of which can be derived in principle analogously to the first innermost cross-linked layer of polyurethane .

[00125] To obtain particularly efficient, dense and stable crosslinks, additional crosslinking with the hydroxyl group donor is carried out at temperatures between 40°C and 60°C, and preferably at temperatures between 45°C and 55°C even more preferably at temperatures between 45°C and 50°C.

[00126] Furthermore, it is preferred that the additional cross-linking step is carried out by adding the hydroxyl group donor at stirring speeds of 900 rpm to 1700 rpm, preferably 1000 rpm to 1300 rpm, and at a pH of 5 to 9, and preferably at a pH of 6 to 8.

[00127] The pH value required for crosslinking is adjusted using an organic acid, such as formic acid or acetic acid. This step is optional, however, as the pH is often already shifted into the correct range due to the previous polymerization reaction.

[00128] In this context, it has been found that the addition of the hydroxyl group donor in aqueous form leads to particularly stable crosslinks and therefore particularly stable capsule shells or capsule walls. The concentration of the hydroxyl group donor in the aqueous solution is preferably 10% to 70% and even more preferably the concentration of the hydroxyl group donor in the aqueous solution is 40% to 60%.

[00129] Thus, the crosslinking described in this document preferably results in a third crosslinking layer defined around the core comprising the at least one active ingredient to be encapsulated.

[00130] The hydroxyl group donor is preferably at least one polyol comprising two or more hydroxyl functional groups, with good to very good water solubility at temperatures above 40°C, in particular the hydroxyl group donor is selected from the group consisting of glycerol, propylene glycol and/or 1,3,5-trihydroxybenzene.

[00131] Surprisingly, it was observed that capsules according to the invention, which have such an additional layer based mainly on polyurethane, exhibit significantly more stable properties than microcapsules without such an additional stabilizing layer. Furthermore, such multilayer microcapsules (according to the invention) show significantly more efficient entrapment of the active ingredients.

[00132] The hydroxyl group donor is added while stirring according to the agitation speeds mentioned above for the formation of the above polyurethane and polyurea-based crosslinking layers.

[00133] Thus, in a preferred embodiment, the present invention relates to a method for preparing multilayer microcapsules, in which the hydroxyl group donor is a polyol with two or more hydroxyl functional groups, in particular glycerol, propylene glycol and /or 1,3,5-trihydroxybenzene.

[00134] Protective colloid crosslinking structures can also be found in this layer as a minor component.

[00135] Optionally, the present method for preparing multilayer microcapsules comprises an additional cross-linking step by adding an amino acid, in particular an aromatic amino acid, more preferably by adding the amino acid histidine and/or tryptophan with stirring. .

[00136] Surprisingly, it has been shown that a cross-linking layer based on an aromatic amino acid influences the diffusion of the active ingredient in such a way that it no longer diffuses through the capsule wall, which in turn leads to an increase additional stability of the capsule.

[00137] Particularly advantageous results for capsule shell formation are obtained if this additional (optional) cross-linking with the amino acid, i.e. an amine, is carried out at a pH of 5 to 9 and preferably at a pH of 6 to 8.

[00138] Optionally, the pH value required for crosslinking is adjusted by adding a sodium hydroxide solution.

[00139] Even more preferably, this optional additional crosslinking step is carried out at a temperature of 50°C to 70°C, preferably 55°C to 65°C.

[00140] The corresponding amino acid, and in particular the aromatic amino acid, preferably has aromatic rings of five to six carbon atoms and at least one nitrogen atom in the aromatic system, as well as two or more amino groups or imine groups and is, in particular, histidine and/or tryptophan.

[00141] It has been demonstrated that the addition of the corresponding amino acid in aqueous form leads to a particularly pronounced and strong polyurea-based crosslinking and therefore contributes decisively to the stability of the resulting capsules. The concentration of the (aromatic) amino acid in the aqueous solution is preferably 10% to 70% and even more preferably 40% to 60%.

[00142] Additional optional cross-linking in the method according to the invention occurs over a period of about 5 minutes to 30 minutes and preferably within 10 minutes to 20 minutes at a stirring speed of 500 rpm to 2000 rpm, preferably 1000 rpm and 1500 rpm.

[00143] Alternatively, it is possible for this additional optional cross-linking step to be carried out after the cross-linking step described below by adding at least one amine that reacts at an alkaline pH.

[00144] Thus, the invention described in this document comprising a method for preparing multilayer microcapsules further comprises at least a fourth crosslinking layer adding at least one reactive amine at an alkaline pH to obtain multilayer microcapsules with formation of a layer of polyurea-based crosslinking defined around the previously described crosslinking layers. The layers can be partially interlaced. Furthermore, all layers may thus contain portions of cross-linked protective colloid.

[00145] Particularly stable capsules were obtained when this crosslinking with the amine reacting at an alkaline pH occurs at an alkaline pH of 7 to 11 and, preferably, at an alkaline pH of 8 to 9.

[00146] Even more preferably, the at least fourth crosslinking step is carried out at a temperature of 60°C to 80°C, and preferably 65°C to 75°C, and particularly in a preferred at temperatures of 60°C to 70°C and with stirring.

[00147] The amine that reacts at an alkaline pH is preferably a guanidinium group donor and is selected from the group consisting of di-, tri- and polyamines, arginine, guanidinium hydrochloride and/or guanidinium carbonate. However, guanidinium carbonate is more preferred as a crosslinking agent to form the at least fourth crosslinking layer.

[00148] The addition of the guanidinium group donor in aqueous form with stirring leads to the formation of particularly stable capsule shells or capsule walls. The concentration of the guanidinium group donor in the aqueous solution is preferably 1% to 50% and more preferably 10% to 25%. The stirring speed used in this method is advantageously between 500 rpm and 2000 rpm and preferably between 1000 rpm and 1500 rpm for 5 minutes to 30 minutes and preferably for 10 minutes to 20 minutes.

[00149] Preferably, the suspension or emulsion then has a pH of 7 to 8. Optionally, the pH value required for further cross-linking is adjusted, for example, by means of formic acid or acetic acid or by means of a sodium hydroxide solution.

[00150] In this sense, a preferred embodiment of the present invention refers to a method for preparing multilayer microcapsules comprising the formation of at least a fourth crosslinking layer, in which the alkaline reaction amine is a guanidinium group donor. , in particular arginine, guanidinium carbonate and/or guanidinium hydrochloride.

[00151] Furthermore, in a preferred embodiment, the present invention relates to a method comprising an additional optional step before curing in which a termination of the microcapsule crosslink is formed by the addition of an amine with an amine functional group.

[00152] The amine with a functional amine group described here is preferably a corresponding amino acid, in particular alanine, glycine, aspartic acid, cysteine and/or proline, and serves to close the last cross-linking layer and does not exhibit any cross-linking spatially, but closes the network locally by incorporating the corresponding building blocks in the last outermost crosslinking layer.

[00153] Termination of the outermost cross-linking layer or microcapsule in an additional optional step before curing is thus carried out at a pH of 6 to 11 and, preferably, at a pH of 7 to 9 and, optionally, at a temperature above 75°C, preferably at a temperature of 75°C to 85°C to shorten the reaction time.

[00154] In this case, the final amines are preferably added in aqueous form in concentrations of preferably 1% to 50%, and preferably in concentrations of 10% to 25%, with stirring. Analogous to the previous additions of the corresponding cross-linking agents, stirring is thus carried out at 500 rpm to 2000 rpm, preferably at 1000 rpm to 1500 rpm, for between 1 and 10 minutes, or preferably for 2 to 5 minutes.

[00155] In this context, therefore, an additional preferred embodiment of the present invention refers to a method according to the invention in which the amine used in an additional optional step before curing to finish the microcapsule is an amino acid, in particular an amino acid comprising an amino group, more preferably alanine, glycine, aspartic acid, cysteine and/or proline.

[00156] This additional step, which completes the capsule wall or shell, surprisingly leads to even more stable and efficiently confining microcapsules, while at the same time reducing the total shell material required.

[00157] After complete cross-linking, the coated microcapsules are present as a raw microcapsule in the form of an aqueous dispersion with shells or capsule walls still soft and flexible.

[00158] It is then necessary to subject the resulting multilayer microcapsules to an additional curing method in order to harden the still soft, flexible and unstable multilayer microcapsule shells or walls and thus give them stability. Curing after the last crosslinking or final step of the multilayer capsules formed in this method is carried out at a temperature of about 80°C and generally for 60 to 240 minutes. Furthermore, it is advantageous to add substances to the external aqueous phase for curing. These substances are, for example, natural vegetable tanning agents.

[00159] Furthermore, it was surprisingly shown that direct curing of microcapsules at 80°C compared to gradual heating leads to more stable cassettes.

[00160] The present invention and the method described here for producing multilayer microcapsules comprising layers based on polyurethane and polyurea are characterized, in particular, by the choice of different pH ranges to carry out the individual crosslinking steps. In combination with the gradually increasing temperature ranges, it is thus possible to produce individual, defined layers. The compositional transition between layers can be steep, that is, the layers are materially delimited and defined to the greatest extent possible. In principle, however, the cross-linking methods described here can also be carried out at room temperature, but result in broad gradients, lower stabilities, and long reaction times.

[00161] Consequently, with the method described herein, it is possible to alternately layered polyurethane and polyurea-based crosslinking layers around the core comprising at least one hydrophobic active ingredient, thus creating a stable multilayer capsule wall or shell. of capsule. In principle, polyurea or polyurethane bonds form the main component of the respective layers. Furthermore, the protective colloid (e.g. starch) can also be present in the individual layers through polyurethane bonds. Partial cross-linking between individual alternating layers cannot be excluded to a certain extent. However, by means of the present method, the following layers are basically formed: a first layer comprising or consisting of polyurethane structures, a second layer comprising or consisting of polyurea structures, a third layer comprising or consisting of polyurethane structures, and at least at least a fourth layer comprising or consisting of polyurea structures.

[00162] In this context, the first innermost capsule layer is essentially constructed from a polyurethane-based crosslinking matrix (step a), followed by a second polyurea-based crosslinking layer (step b). The third layer is again preferably polyurethane-based crosslinked (step c), while the at least fourth outermost layer preferably comprises essentially a polyurea-based crosslinking system (step d). Optionally, other additional or final cross-linking layers, for example, based on polyurea by cross-linking other amines such as amino acids, are conceivable, which provide a further gain in stability due to further additional cross-linking.

[00163] Subsequently, the multilayered and cured microcapsules formed in this way are separated from the reaction solution and dried, if necessary.

[00164] After curing, the microcapsules produced by the method according to the invention are present as a dispersion in water, which is also referred to as a microcapsule dispersion. In this form, the microcapsules are basically ready for sale; however, for preservation purposes, it is advisable to dry them. Suitable drying methods include freeze drying or spray drying.

[00165] Furthermore, the present invention is characterized by the fact that, preferably, amino acids as the main component are cross-linked with starch and isocyanates through specifically catalyzed mechanisms, thus allowing the production of bio-based and biodegradable microcapsules based on biocompatible polymers.

[00166] Overall, the method described in this document allows the production of microcapsules which, due to the multiple and more efficient cross-linking layers, allow significant savings in shell material and thus make it possible to further reduce the required isocyanate content in comparison with prior art capsules without adversely affecting the stability of the capsules. This can be justified, on the one hand, by the more efficient and defined cross-linking of the individual layers and, on the other hand, by the generally alternating/different composition of the individual capsule shell layers.

[00167] Due to efficient spatial crosslinking, the multilayer microcapsules according to the invention thus have a significantly lower overall isocyanate content compared to prior art capsules. The absolute isocyanate content of the microcapsules described here corresponds to only 1/50 of the total capsules comprising the active ingredient(s). In this sense, isocyanates do not directly form a component of the capsule wall or capsule shell, but only act as a cross-linking agent between, for example, significantly larger starch molecules. Assuming that the raw materials react quantitatively, it can be assumed that in the case of 100% wall material, exactly 1/5 of the wall material consists of isocyanates and that, due to the small quantity in which they are represented, these can only be considered crosslinkers.

[00168] Compared to prior art capsules based on pure polyurethane compounds, it is possible with the method described in this document, comprising directed depositions at defined temperatures and times, to produce microcapsules in which the ratio of the capsule shell to the Total capsule volume could be reduced from 1 to 14 to 1 to 21 and thus the total shell material required could be significantly reduced without sacrificing stability, as illustrated in the following embodiment examples. Although the proportion of capsule wall material in the prior art (pure polyurea capsule) is 6.8% by weight compared to the total capsule (capsule consisting of active ingredient and capsule wall material), in multiple microcapsules layers described in this document a reduction of capsule wall material to 4.4% by weight is possible, despite additional stability gains. This corresponds to a 36% reduction in wall material. Thus, the method described herein allows the production of stable microcapsules in which the amount of capsule wall material required can be significantly reduced compared to prior art capsules and, in particular, the amount of isocyanate required, whilst at the same time the amount of active ingredient to be encapsulated (active ingredient mixture) does not need to be reduced.

[00169] Furthermore, despite the externally decreasing isocyanate content and therefore the externally decreasing degree of cross-linking, it was surprisingly possible to produce stable microcapsules that showed a significant improvement in sensory performance (fragrance compound release) compared to the state of the art capsules.

[00170] The protective colloid, preferably starch, can also be preferably included in each of the other defined cross-linking layers as a secondary component and incorporated into the respective polyurethane or polyurea-based network. Due to the structure of starch, it is thus possible to generate even branched, spatially extended and even stabilized networks that intertwine the layers and thus form a stable cross-linking matrix in the form of a capsule shell or capsule wall. This secondary component in the respective layers leads to better spatial crosslinking.

[00171] The protective colloid, for example starch, forms an essential component of the first polyurethane-like crosslinking, which is achieved by reaction with the catalyst already at a temperature of 25°C to 40°C. The reaction of the polyol with the catalyst leads to greater stability of the emulsion. Surprisingly, it has been shown that the further development of a polyol to a polysaccharide leads to greater stabilities, while at the same time the dual function of the protective colloid as an emulsion stabilizing factor and as a reaction partner, e.g. polyvinyl, is improved.

[00172] As mentioned previously, the microcapsules according to the invention comprise in their core at least one active ingredient to be encapsulated as a core material which preferably has hydrophobic properties.

[00173] In principle, any material suitable for inclusion in microcapsules can be used as a core material for producing multilayer microcapsules according to the invention. Preferably, hydrophobic, water-insoluble or water-immiscible liquids or solids, as well as suspensions, can be considered as materials to be encapsulated. In the context of the present description, the term “hydrophobic active ingredient” means that the material to be encapsulated is in the internal non-aqueous phase and does not mix with the external aqueous phase.

[00174] In a particularly preferred additional embodiment of the present invention, the microcapsules according to the invention are configured in such a way that they comprise a core material of at least one hydrophobic active ingredient, in particular a hydrophobic odorous fragrance substance or compound or a hydrophobic scented perfume oil or oil (odoriferous substance mixture or fragrance compound mixture), a pesticide, a biocide, an insecticide, a substance from the group of repellents, food additives, cosmetic active ingredients, pharmaceutical active ingredients, dyes, agrochemicals, dyes, luminous paints, optical brighteners, solvents, waxes, silicone oils, lubricants, as well as mixtures of the active ingredients mentioned above, i.e., as long as it is sufficiently water resistant, the microcapsules according to the invention can be used in the form of a microcapsule, i.e. as long as it is sufficiently insoluble in water or does not mix with the aqueous phase, otherwise no emulsion can form and no deposition of the polymer on the surface of the droplet can occur.

[00175] In a preferred variant of the present invention, hydrophobic odoriferous substances or perfume oils or fragrance compounds or mixtures of fragrance compounds (perfume oils), aromas or also biogenic principles are particularly suitable as active ingredients.

[00176] In a preferred embodiment of the present invention, the microcapsules according to the invention have a core material in the form of a single hydrophobic odorous substance or single fragrance compound, wherein the core material comprises at least a single odoriferous substance or single fragrance compound, or mixtures thereof, selected from one or more of the following groups: hydrocarbons, such as 3-carene; a-pinene; beta-pinene; alpha-terpinene; gamma-terpinene; p-cymene; bisabolene; camphene; caryophyllene; cedreno; farnesene; limonene; longifolene; myrcene; ocimeno; valencene; (E,Z)-1,3,5-undecatiene; aliphatic alcohols such as hexanol; octanol; 3-octanol; 2,6-dimethylheptanol; 2-methylheptanol, 2-methyloctanol; (E) -2-hexenol; (E)- and (Z)-3-hexenol; 1-octen-3-ol; mixture of 3,4,5,6,6-pentamethyl-3,4-hepten-2-ol and 3,5,6,6-tetramethyl-4-methylene-heptan-2-ol; (E,Z)-2,6-nonadienol; 3,7-dimethyl-7-methoxyoctan-2-ol; 9-decenol; 10-undecenol; 4-methyl-3-decen-5-ol; aliphatic aldehydes and their acetals, such as hexanal; heptanal; octanal; nonanal; decanal; undecanal; dodecanal; tridecanal; 2-methyloctanal; 2-methylnonanal; (E) -2-hexenal; (Z)-4-heptenal; 2,6-dimethyl-5-heptenal; 10- undecennial; (E) -4-decenal; 2-dodecenal; 2,6,10-trimethyl-5,9-undecadienal; heptanaldiethyl acetal; 1,1-dimethoxy-2,2,5-trimethyl-4-hexene; citronelliloxy acetaldehyde; aliphatic ketones and their oximes, such as 2-heptanone; 2- octanone; 3-octanone; 2-nonanone; 5-methyl-3-heptanone; 5-methyl-3-heptanone oxime; 2,4,4,7-tetramethyl-6-octen-3-one; aliphatic sulfur-containing compounds such as 3-methylthiohexanol; 3-methylthiohexyl acetate; 3-mercaptohexanol; 3-mercaptohexyl acetate; 3-mercaptohexyl butyrate; 3-acetylthiohexyl acetate; 1-menten-8-thiol; aliphatic nitriles, such as 2-nonenoic acid nitrile; 2-tridecenoic acid nitrile; 2,12-tridecenoic acid nitrile; 3,7-dimethyl-2,6-octadienoic acid nitrile; 3,7-dimethyl-6-octenoic acid nitrile; aliphatic carboxylic acids and their esters, such as (E)- and (Z)-3-hexenyl formate; ethyl acetoacetate; isoamyl acetate; hexyl acetate; 3,5,5-trimethylhexyl acetate; 3-methyl-2-butenyl acetate; (E)-2-hexenyl acetate; (E)- and (Z)-3-hexenyl acetate; octyl acetate; 3-octyl acetate; 1-octen-3-yl acetate; ethyl butyrate; butyl butyrate; isoamyl butyrate; hexyl butyrate; (E)- and (Z)-3-hexenyl isobutyrate; hexyl crotonate; ethyl isovalerate; ethyl 2-methyl pentanoate; ethyl hexanoate; allyl hexanoate; ethyl heptanoate; allyl heptanoate; ethyl octanoate; (E,Z) ethyl-2,4-decadienoate; methyl 2-octinate; methyl 2-nonate; allyl 2-isoamyloxyacetate; methyl 3,7-dimethyl 2,6-octadienoate; acyclic terpene alcohols, such as citronellol; geraniol; nerol; linalool; lavadulol; nerolidol; farnesol; tetrahydrolinalool; tetrahydrogeraniol; 2,6-dimethyl-7-octen-2-ol; 2,6-dimethyloctan-2-ol; 2-methyl-6-methylene-7-octen-2-ol; 2,6-dimethyl-5,7-octadien-2-ol; 2,6-dimethyl-3,5-octadien-2-ol; 3,7-dimethyl-4,6-octadien-3-ol; 3,7-dimethyl-1,5,7-octatrien-3-ol; 2,6-dimethyl-2,5,7-octatrien-I-ol; and their formats, acetates, propionates, isobutyrates, butyrates, isovalerianates, pentanoates, hexanoates, crotonates, tiglinates, 3-methyl-2-butenoates; acyclic terpene aldehydes and ketones, such as geranial; neral; citronellal; 7-hydroxy-3,7-dimethyloctanal; 7-methoxy-3,7-dimethyloctanal; 2,6,10-trimethyl-9-undecenal; geranylacetone; and the dimethyl and diethylacetals of geranial, neral, 7-hydroxy-3,7-dimethyloctanal; cyclic terpene alcohols, such as menthol; isopulegol; a- terpineol; terpinenol-4; mentan-8-ol; mentan-1-ol; mentan-7-ol; borneol; isoborneol; linalool oxide; nopol; cedrol; ambrinol; vetiverol; guaiaol; and their formats, acetates, propionates, isobutyrates, butyrates, isovalerianates, pentanoates, hexanoates, crotonates, tiglinates, 3-methyl-2-butenoates; cyclic terpene aldehydes and ketones, such as menthone; isomenthone; 8-mercaptomenthan-3-one; carvone; camphor; fenchona; α- ionone; beta-ionone; α-n-methylionone; beta-n-methylionone; α-isomethylionone; beta-isomethylionone; α-iron; β-iron; α-damascenone; beta-damascenone; gamma-damascenone; d-damascenone; 1-(2,4,4-trimethyl-2-cyclohexen-1-yl)-2-buten-1-one; 1,3,4,6,7,8a-hexahydro-1,1,5,5-tetramethyl-2H-2,4a-methanonaphthalen-8(5H)-one; nootkatone; dihydronootkatone; α-sinene salt; beta-sinene salt; acetylated cedarwood oil (methylcedryl ketone); cyclic alcohols such as 4-tert-butylcyclohexanol; 3,3,5-trimethylcyclohexanol; 3-isocamphilcyclohexanol; 2,6,9-trimethyl-(Z2,Z5,E9) cyclododecatrien-1-ol; 2-isobutyl-4-methyltetrahydro-2H-pyran-4-ol; from the group of cycloaliphatic alcohols, such as 3,3,3-trimethylcyclohexylmethanol; 2-methyl-4-(2,2,3-trimethyl-3-cyclopent-1-yl)butanol; 2-methyl-4-(2,2,3-trimethyl-3-cyclopent-1-yl)-2-buten-1-ol; 2-ethyl-4-(2,2,3-trimethyl-3-cyclopent-1-yl)-2-buten-1-ol; 3-methyl-5-(2,2,3-trimethyl-3-cyclopent-1-yl)-pentan-2-ol; 3-methyl-5-(2,2,3-trimethyl-3-cyclopent-1-yl)-4-penten-2-ol; 3,3-dimethyl-5-(2,2,3-trimethyl-3-cyclopent-1-yl)-4-penten-2-ol; 1-(2,2,6-trimethylcyclohexyl)pentan-3-ol; 1-(2,2,6-trimethylhexyl)hexan-3-ol; cyclic and cycloaliphatic ethers, such as cineole; cedril methyl ether; cyclododecyl methyl ether; (ethoxymethoxy) cyclododecane; a-cedrene epoxide; 3a,6,6,9a-tetramethyldodecahydronaphtho[2,1-b]furan; 3a-ethyl-6,6,9a-trimethyl-dodecahydronaphtho[2,1-b]furan; 1,5,9-trimethyl-13-oxabicyclo[10.1.0]trideca-4,8-diene; rose oxide; 2-(2,4-dimethyl-3-cyclohexen-1-yl)-5-methyl-5-(1-methylpropyl)-1,3-dioxane; cyclic ketones, such as 4-tert-butylcyclohexanone; 2,2,5-trimethyl-5-pentylcyclopentanone; 2-heptylcyclopentanone; 2- pentylcyclopentanone; 2-hydroxy-3-methyl-2-cyclopenten-1-one; 3-methyl-cis-2-penten-1-yl-2-cyclopenten-1-one; 3-methyl-2-pentyl-2-cyclopenten-1-one; 3-methyl-4-cyclopentadecenone; 3-methyl-5-cyclopentadecenone; 3- methylcyclopentadecanone; 4-(1-ethoxyvinyl)-3,3,5,5-tetramethylcyclohexanone; 4- tert-pentylcyclohexanone; 5-cyclohexadecen-1-one; 6,7-dihydro-1,1,2,3,3-pentamethyl-4(5H)-indanone; 9-cycloheptadecen-1-one; cyclopentadecanone; cyclohexadecanone; cycloaliphatic aldehydes such as 2,4-dimethyl-3-cyclohexenecarbaldehyde; 2-methyl-4-(2,2,6-trimethyl-cyclohexen-1-yl)-2-butal; 4-(4-hydroxy-4-methylpentyl)-3-cyclohexenecarbaldehyde; 4-(4-methyl-3-penten-1-yl)-3-cyclohexenecarbaldehyde; cycloaliphatic ketones, such as 1-(3,3-dimethylcyclohexyl)-4-penten-1-one; 1-(5,5-dimethyl-2-cyclohexen-1-yl)-4-penten-1-one; 2,3,8,8-tetramethyl-1,2,3,4,5,6,7,8-octahydro-2-naphthalenyl methyl ketone; methyl-2,6,10-trimethyl-2,5,9-cyclododecatrienyl ketone; tert-butyl-(2,4-dimethyl-3-cyclohexen-1-yl)ketone; esters of cyclic alcohols, such as 2-tert-butylcyclohexyl acetate; 4-tert-butylcyclohexyl acetate; 2-tert-pentylcyclohexyl acetate; 4-tert-pentylcyclohexyl acetate; decahydro-2-naphthyl acetate; 3-pentyltetrahydro-2H-pyran-4-yl acetate; decahydro-2,5,5,8a-tetramethyl-2-naphthyl acetate; 4,7-methane-3a,4,5,6,7a-hexahydro-5- or -6-indenyl acetate; 4,7-methane-3a,4,5,6,7,7a-hexahydro-5- or -6-indenyl propionate; 4,7-methane-3a,4,5,6,7a-hexahydro-5- or -6-indenyl isobutyrate; 4,7-methaneoctahydro-5- or -6-indenyl acetate; esters of cycloaliphatic carboxylic acids, such as allyl 3-cyclohexyl propionate; allyl cyclohexyloxyacetate; methyl dihydrojasmonate; methyl jasmonate; methyl 2-hexyl-3-oxocyclopentanecarboxylate; ethyl 2-ethyl-6,6-dimethyl-2-cyclohexenecarboxylate; ethyl 2,3,6,6-tetramethyl-2-cyclohexenecarboxylate; ethyl 2-methyl-1,3-dioxolane-2-acetate; aromatic hydrocarbons such as styrene and diphenylmethane; araliphatic alcohols, such as benzyl alcohol; 1-phenylethyl alcohol; 2-phenylethyl alcohol; 3-phenylpropanol; 2-phenylpropanol; 2- phenoxyethanol; 2,2-dimethyl-3-phenylpropanol; 2,2-dimethyl-3-(3-methylphenyl)propanol; 1,1-dimethyl-2-phenyl-ethyl alcohol; 1,1-dimethyl-3-phenylpropanol; 1-ethyl-1-methyl-3-phenylpropanol; 2-methyl-5-phenylpentanol; 3-methyl-5-phenylpentanol; 3-phenyl-2-propen-1-ol; 4-methoxybenzyl alcohol; 1-(4-isopropylphenyl)ethanol; esters of araliphatic alcohols and aliphatic carboxylic acids, such as benzyl acetate; benzyl propionate; benzyl isobutyrate; benzyl isovalerate; 2-phenylethyl acetate; 2-phenylethyl propionate; 2-phenylethyl isobutyrate; 2-phenylethyl isovalerate; 1-phenylethyl acetate; α-trichloromethyl benzyl acetate; a, α-dimethylphenylethyl acetate; a, a-dimethylphenylethyl butyrate; cinnamyl acetate; 2-phenoxyethyl isobutyrate; 4-methoxybenzyl acetate; araliphatic ethers, such as 2-phenylethyl methyl ether; 2-phenylethyl isoamyl ether; 2-phenylethyl-1-ethoxyethyl ether; phenylacetaldehyde dimethylacetal; phenylacetaldehyde diethylacetal; dimethylacetal hydratropaaldehyde; phenylacetaldehyde glycerol acetal; 2,4,6-trimethyl-4-phenyl-1,3-dioxanes; 4,4a,5,9b-tetrahydroindene[1,2-d]-m-dioxin; 4,4a,5,9b-tetrahydro-2,4-dimethylindene[1,2-d]-m-dioxin; aromatic and araliphatic aldehydes, such as benzaldehyde; phenylacetaldehyde; 3-phenylpropanal; hydratropaaldehyde; 4-methylbenzaldehyde; 4- methylphenylacetaldehyde; 3-(4-ethylphenyl)-2,2-dimethylpropanal; 2-methyl-3-(4-isopropylphenyl)-propanal; 2-methyl-3-(4-tert-butylphenyl)propanal; 3-(4-tert-butylphenyl)propanal; cinnamaldehyde; a-butylcinnamaldehyde; a-amylcinnamaldehyde; a-hexylcinnamaldehyde; 3-methyl-5-phenylpentanal; 4-methoxybenzaldehyde; 4-hydroxy-3-methoxybenzaldehyde; 4-hydroxy-3-ethoxybenzaldehyde; 3,4- methylenedioxybenzaldehyde; 3,4-dimethoxybenzaldehyde; 2-methyl-3-(4-methoxyphenyl)propanal; 2-methyl-3-(4-methylenedioxyphenyl)propanal; aromatic and araliphatic ketones, such as acetophenone; 4- methylacetophenone; 4-methoxyacetophenone; 4-tert-butyl-2,6-dimethylacetophenone; 4-phenyl-2-butanone; 4-(4-hydroxyphenyl)-2-butanone; 1-(2-naphthalenyl)ethanone; benzophenone; 1,1,2,3,6-hexamethyl-5-indanyl methyl ketone; 6-tert-butyl-1,1-dimethyl-4-indanyl methyl ketone; 1-[2,3-dihydro-1,1,2,6-tetramethyl-3-(1-methylethyl)-1H-5-indenyl]ethanone; 5',6',7',8'-tetrahydro-3',5',5',6',8',8'-hexamethyl-2-acetonaphtone; aromatic and araliphatic carboxylic acids and their esters, such as benzoic acid; phenylacetic acid; methyl benzoate; ethyl benzoate; hexyl benzoate; benzyl benzoate; methyl phenyl acetate; ethyl phenyl acetate; geranyl phenyl acetate; phenyl phenyl phenyl acetate; methyl cinnamate; ethyl cinnamate; benzyl cinnamate; ethyl phenyl cinnamate; cinnamyl cinnamate; allyl phenoxy acetate; methyl salicylate; isoamyl salicylate; hexyl salicylate; cyclohexyl salicylate; cis-3-hexenyl salicylate; benzyl salicylate; phenyl ethyl salicylate; methyl 2,4-dihydroxy-3,6-dimethylbenzoate; ethyl 3-phenyl glycidate; ethyl 3-methyl-3-phenyl glycidate; nitrogen-containing aromatic compounds such as 2,4,6-trinitro-1,3-dimethyl-5-tert-butylbenzene; 3,5-dinitro-2,6-dimethyl-4-tert-butylacetophenone; cinnamic acid nitrile; 5-phenyl-3-methyl-2-pentenoic acid nitrile; 5-phenyl-3-methylpentanoic acid nitrile; methyl anthranilate; N-methyl anthranilate; methylanthranilate Schiff bases with 7-hydroxy-3,7-dimethyloctanal, 2-methyl-3-(4-tert-butylphenyl)propanal or 2,4-dimethyl-3-cyclohexenecarbaldehyde; 6-isopropylquinoline; 6-isobutylquinoline; 6-sec-butylquinoline; indole; skatole; 2-methoxy-3-isopropylpyrazine; 2-isobutyl-3-methoxypyrazine; 4-(4,8-dimethyl-3,7-nonadienyl)-pyridine; phenols, phenyl ethers and phenyl esters, such as tarragol; anethole; eugenol; eugenic methyl ether; isoeugenol; isoeugenyl methyl ether; thymol; carvacrol; diphenyl ether; beta-naphthyl methyl ether; beta-naphthyl ethyl ether; beta-naphthyl isobutyl ether; 1,4-dimethoxybenzene; eugenyl acetate; 2-methoxy-4-methylphenol; 2-ethoxy-5-(1-propenyl)phenol; p-cresylphenyl acetate; from the group of heterocyclic compounds such as 2,5-dimethyl-4-hydroxy-2H-furan-3-on; 2-ethyl-4-hydroxy-5-methyl-2H-furan-3-on; 3-hydroxy-2-methyl-4H-pyran-4-on; 2-ethyl-3-hydroxy-4H-pyran-4-on; lactones such as 1,4-octanolide; 3-methyl-1,4-octanolide; 1,4- nonanolide; 1,4-decanolide; 8-decene-1,4-olide; 1,4-undecanolide; 1,4- dodecanolide; 1,5-decanolide; 1,5-dodecanolide; 1,15-pentadecanolide; cis and trans-11-pentadecene-1,15-olide; cis and trans-12-pentadecene-1,15-olide; 1,16- hexadecanolide; 9-hexadecene-1,16-olide; 10-oxa-1,16-hexadecanolide; 11- oxa-1,16-hexadecanolide; 12-oxa-1,16-hexadecanolide; ethylene-1,12-dodecanedioate; ethylene-1,13-tridecanedioate; coumarin; 2,3-dihydrocoumarin; octahydrocoumarin; as well as stereoisomers, enantiomers, positional isomers, diastereomers, cis/trans isomers and epimers, respectively, of the substances mentioned above.

[00177] In an alternative embodiment, scented oils or scented oils are used as core material or active ingredients. These are compositions containing at least one fragrance compound. Such compositions, in particular perfume oils or scented oils, preferably comprise two, three, four, five, six, seven, eight, nine, ten or more fragrance compounds. Perfumed oils or perfume oils are preferably selected from the group of extracts of natural raw materials, such as essential oils, concretes, absolutes, resins, resinoids, balms, tinctures, such as Ambergris oil; Amyris oil; angelica seed oil; angelica root oil; Anise oil; Valerian oil; basil oil; tree moss absolute; Bay oil; Mugwort oil; Benzoeresin; Bergamot oil; beeswax absolute; birch tar oil; bitter almond oil; savory oil; Bucco leaf oil; Cabreuva oil; Cade oil; Calmus oil; Camphor oil; cananga oil; Cardamom oil; Cascarilla oil; Cassia oil; Cassie absolute; Castoreum absolute; cedar leaf oil; cedar oil; cedar oil; Cistrum oil; Citronella oil; Citron oil; Copaiva balm; Copaiva balm oil; Coriander oil; Costus root oil; cumin oil; Cypress oil; Davana Oil; Dill herb oil; Dill seed oil; Kale absolute; Oakmoss absolute; Elemi Oil; Tarragon oil; z\l 1 • J • 1 1 1 • J z\l 1 1 z\l 1 11 1 1 J Eucalyptus lemongrass oil; Fennel oil; Fir needle oil; Galbanum oil; Galbanum resin; Geranium oil; Grapefruit oil; Guaiac wood oil; Gurjun balm; Gurjun Balm Oil, Helichrysum Absolute; Helichrysum Oil; Ginger oil; Iris root absolute; Jasmine absolute; calamus oil; Blue chamomile oil; z\l 1 ’1 z\l 1 J 1 z\l 1 *11 Roman chamomile oil; Carrot seed oil; Cascarilla oil; Pine needle oil; Curly mint oil; Caraway oil; Labdanium oil; Labdanum; Labdanum absolute; Resin; Lavender absolute; Lavender oil; Lavender absolute; Lavender oil; lemongrass oil; Lovage Oil; Distilled Lemon Oil; pressed lemon oil; Linal Oil; Litsea cubeba oil; bay leaf oil; Mace oil; Marjoram oil; Mandarin oil; Pasta shell oil; Mimosa absolute; Musk grain oil; Musk tincture; Muscat oil; Myrrh absolute; Myrtle oil; Clove oil; Clove flower oil; Clove oil; Neroli oil; Frankincense absolute; Frankincense oil; opopanax oil; Orange flower absolute; Orange oil; Origanum oil; Palmarosa oil; patchouli oil; Perilla oil; Peruvian balsam oil; parsley leaf oil; parsley seed oil; J • J • z\l 11 J 1 ~ • J z\l 1 • J z\l 1 • J z\l petitgrain oil; Peppermint oil; chili oil; chili oil; Pine oil; polley oil; Rose absolute oil; rose oil; Rosemary oil; Dalmatian sage oil; Spanish sage oil; Sandalwood oil; z\l 1 J 1 z\l 11 1 z\l 1 • j 1 1 z\l 1 Celery seed oil; Lavender oil; Star anise oil; styrax oil; tagetes oil; Fir needle oil; Tea tree oil; Turpentine oil; Thyme oil; Tolu Balm; Tonka absolute; Tuberosis absolute; Vanilla extract; Violet leaf absolute; Verbena oil; vetiver oil; Juniper berry oil; wine yeast oil; Wormwood oil; Wintergreen Oil; Ylang Oil; Hyssop oil; Civet absolute; Cinnamon leaf oil; cinnamon bark oil; and fractions thereof or isolated ingredients thereof.

[00178] In a further variant of the method according to the invention, the flavorings can also be encapsulated as core material in the form of a single flavoring, the core material comprising at least a single flavoring agent or mixtures thereof as an active ingredient.

[00179] Typical examples of aromas that can be encapsulated according to the invention are selected from the group consisting of: acetophenone; allyl capronate; alpha-ionone; beta-ionone; nisaldehyde; anisyl acetate; anisyl format; benzaldehyde; benzothiazole; benzyl acetate; Benzilic alcohol; benzyl benzoate; beta-ionone; butyl butyrate; butyl capronate; butylidene phthalide; carvone; camphene; caryophyllene; cineole; cinnamyl acetate; citral; citronellol; citronellal; citronellyl acetate; cyclohexyl acetate; cymene; apricot; decalactone; dihydrocoumarin; dimethylanthranilate; dimethyl anthranilate; dodecalactone; ethoxyethyl acetate; ethylbutyric acid; ethyl butyrate; ethyl caprinate; ethyl capronate; ethyl crotonate; ethyl furanol; ethyl guaiacol; ethyl isobutyrate; ethyl isovalerate; ethyl lactate; ethylmethyl butyrate; ethyl propionate; eucalyptol; eugenol; ethyl heptlate; 4-(p-hydroxyphenyl)-2-butanone; gamma-decalactone; geraniol; geranyl acetate; geranyl acetate; grapefruit aldehyde; methyl dihydrojasmonate (e.g. Hedion®); heliotropin; 2- heptanone; 3-heptanone; 4-heptanone; trans-2-heptenal; cis-4-heptenal; trans-2-hexenal; cis-3-hexenol; trans-2-hexenoic acid; trans-3-hexenoic acid; cis-2-hexenyl acetate; cis-3-hexenyl acetate; cis-3-hexenyl capronate; trans-2-hexenyl capronate; cis-3-hexenyl formate; cis-2-hexyl acetate; cis-3-hexyl acetate; trans-2-hexyl acetate; cis-3-hexyl format; parahydroxybenzyl acetone; isoamyl alcohol; isoamyl isovalerate; isobutyl butyrate; isobutyraldehyde; isoeugenol methyl ether; isopropylmethylthiazole; Lauric acid; leavulinic acid; linalool; linalool oxide; linalyl acetate; menthol; menthofuran; methyl anthranilate; methylbutanol; methylbutyric acid; 2-methylbutyl acetate; methyl capronate; methyl cinnamate; 5-methylfurfural; 3,2,2-methylcyclopentenolone; 6,5,2-methylheptenone; methyl dihydrojasmonate; methyl jasmonate; 2-methylmethyl butyrate; 2-methyl-2-pentenolic acid; methyl thiobutyrate; 3,1-methylthiohexanol; 3-methylthiohexyl acetate; nerol; neryl acetate; trans,trans-2,4-nonadienal; 2,4-nonadienol; 2,6-nonadienol; 2,4-nonadienol; nootkatone; delta-octalactone; gamma-octalactone; 2-octanol; 3-octanol; 1,3- octenol; 1-octyl acetate; 3-octyl acetate; Palmitic acid; paraldehyde; phellandrene; pentanedione; phenylethyl acetate; phenylethyl alcohol; phenylethyl alcohol; phenylethyl isovalerate; piperonal; propionaldehyde; propyl butyrate; pulegona; pulegol; sinensal; sulfurol; terpinene; terpineol; terpinolene; 8,3-thiomentanone; 4,4,2-thiomethylpentanone; thymol; delta-undecalactone; gamma-undecalactone; valence; valeric acid; vanillin; acetoin; ethyl vanillin; ethylvanillin isobutyrate (3-ethoxy-4-isobutyryloxybenzaldehyde); 2,5-dimethyl-4-hydroxy-3(2H)-furanone and its derivatives (preferably homofuranol (2-ethyl-4-hydroxy-5-methyl-3(2H)-furanone), homofuronol (2-ethyl- 5-methyl-4-hydroxy-3(2H)-furanone and 5-ethyl-2-methyl-4-hydroxy-3(2H)-furanone); maltol and maltol derivatives (preferably ethylmaltol and coumarin derivatives); coumarin; gamma-lactones (preferably gamma-undecalactone, gamma-nonalactone, gamma-decalactone); or 5)-ethyl-5 (or 2)-methyl-3(2H)furanone; acetic acid isoamyl ester; butyric acid ethyl ester; n-hexanoic acid n-butyl ethyl ester; ethyl 2-trans-4-cis-decadienoate; 4-(p-hydroxyphenyl)-2-butanone; 1,1-dimethoxy-2,2,5-trimethyl-4-hexane; 2,6-dimethyl-5-heptene-1-al; phenylacetaldehyde; 2-methyl-3-(methylthio)furan; 2-methyl-3-furantiol; bis(2-methyl-3-furyl)disulfide; furfuryl mercaptan; metal; 2-acetyl-2-thiazoline; 3-mercapto-2-pentanone; 2,5-dimethyl-3-furantiol; 2,4,5-trimethylthiazole; 2- acetylthiazole; 2,4-dimethyl-5-ethylthiazole; 2-acetyl-1-pyrroline; 2-methyl-3-ethylpyrazine; 2-ethyl-3,5-dimethylpyrazine; 2-ethyl-3,6-dimethylpyrazine; 2,3-diethyl-5-methylpyrazine; 3-isopropyl-2-methoxypyrazine; 3-isobutyl-2-methoxypyrazine; 2- acetylpyrazine; 2-pentylpyridine; (E,E)-2,4-decadienal; (E,E)-2,4-nonadienal; (E)-2-octenal; (E)-2-nonenal; 2-undecennial; 12-methyltridecanal; 1-penten-3-one; 4-hydroxy-2,5-dimethyl-3(2H)-furanone; guaiacol; 3-hydroxy-4,5-dimethyl-2(5H)-furanone; 3-hydroxy-4-methyl-5-ethyl-2(5H)-furanone; cinnamaldehyde; cinnamalcohol; methyl salicylate; isopulegol and the stereoisomers, enantiomers, positional isomers, diastereomers, cis/trans isomers and epimers, respectively, of these substances not explicitly mentioned in this document.

[00180] More preferably, odoriferous substances or fragrance or flavoring compounds are used in the preparation of the multilayer microcapsules, which are selected from the group consisting of: AGRUMEX LC; AGRUNITRIL; UNDECYLENE C11 ALDEHYDE; ALDEHYDE C12 LAURINE; ALDEHYDE C12 MNA; ALDEHYDE C14 SOG; ALDEHYDE C16 SOG.; ALLYLAMYGLICOLATE; ALLYLCAPRONATE; ALLYLCOHEXYLPROPIONATE; ALYLHEPTYLATE; AMBROCENIDE® 10 TEC; AMBROCENIDE® Krist. 10% IPM; AMBROXIDE; ANETOL NAT. EX ESTERNANIS; PURE ANISALDEHYDE; APRIFLOREN®; BENZYL ACETONE; BENZYL SALICYLATE; BORNEOL L/ISOBORNEOL 65/35; BUCCOBLAETTEROEL; CITRONELLOL 950; CLONE; CYCLOEXYL SALICYLATE; CYMOL FOR SUPRA; DELTA DAMASCONE; DIHYDROMYRCENOL; DIMETHYLBENZYLCARBINYL BUTYRATE; DYNASCONE; ETHYLENE BRASSYLATE; ETHYL METHYL BUTYRATE-2; ETHYL SAFFRONATE; EUCALYPTOL NAT.; EUCALYPTUS GLOBULUS OIL 80/85%; EUGENOL NAT.; FARENAL®; FENNEL OIL AROMA NAT SWEET TYPE; FILBERTONE 10% IPM; FILBERTON; FLOROPAL; GALBASCONE; GERANIOL 60; GLOBANONE®; HEDIONE; HERBAFLORATE; HERBANATE; HERBIL PROPIONATE; HEXENYL ACETATE CIS-3; HEXENYL SALICYLATE CIS-3; HEXYLACETATE; HEXYLACETATE S; HEXYLYSOBUTYRATE; HEXYL SALICYLATE; ISOAMYL BUTYRATE; ISOBORNYL ACETATE; ISOPROPYL METHYL BUTYRATE-2; ISORALDEINE 70; JAVANOL; CAMPHORA DL; CRESOL METHYLETHER P(CR< 10 PPM); LEMONILLA; LIGUSTRAL; LILIAL; LINALOOL; MANZANATO; MELONAL; METHYLHEPTIN CARBONATE; METHYLOCTIN CARBONATE; MUSCENONE; NEOCYCLOCITRAL; NEROLIN BROMELIA; NEROLIN YARA YARA CRYST.; NEROLIONE; NORLIMBANOL; ORANGENOEL; ORIVONE; OZONIL; PATCHOULIOEL ENTF.; TRIGLYCERIDE VEGETABLE OIL; PHELLANDRENE FRACTION EX EUCALYPTUS OIL; FENIRAT®; PHENYLETHYL ACETATE; PINK OXIDE HIGH CIS; SANDRANOL®; STYRENE ACETATE; SULTANENE®; TERPINE RANGE; TETRAHYDROLINALOL; TIMBERSILK; TRIETHYLCITTRATE; UNDECAVERTOL; VERTOCITRAL; VERTOFIX; YSAMBER® K and mixtures of the above active ingredients.

[00181] In a further variant of the method according to the invention, the biogenic principles can also be encapsulated as core material, wherein the core material comprises at least one biogenic principle or mixtures thereof.

[00182] Biogenic principles are active ingredients with biological activity, for example, tocopherol, tocopheryl acetate, tocopheryl palmitate, ascorbic acid, carnotine, carnosine, caffeine, (deoxy)ribonucleic acid and its fragmentation products, β-glucans, retinol , bisabolol, allantoin, phytantriol, panthenol, AHA acids, amino acids, ceramides, pseudoceramides, essential oils, plant extracts and vitamin complexes.

[00183] In a particularly preferred embodiment, the present invention therefore relates to a method for producing multilayer microcapsules, in which the at least one active ingredient, preferably hydrophobic, to be encapsulated is selected from the group which consists of fragrance compounds, odoriferous substances, flavoring substances, biocides, insecticides, a substance from the group of repellents, food additives, cosmetic active ingredients, pharmaceutical active ingredients, agrochemicals, dyes, luminous colors, optical brighteners, solvents, waxes, oils silicone, lubricants, as well as mixtures of the above-mentioned active ingredients, particularly preferably the active ingredient is a fragrance compound or a fragrance compound mixture and is therefore preferably a hydrophobic odorous substance or fragrance compound or a hydrophobic odorous substance or fragrance compound mixture.

[00184] Such microcapsules are characterized by excellent stability and release capacity. In the case of fragrance compounds as active ingredient (core material), the multilayer microcapsules produced in this way also exhibit excellent sensory properties, which can be attributed to the stable active ingredient encapsulation and the associated low active ingredient losses. A particularly defined and good sequence of method steps leads to these defined, dense and very thin capsule shells or capsule walls, which as a quartet synergistically explain the very good sensory performance of the capsules. Furthermore, due to the different chemical properties of the selected cross-linking agents, particularly thin capsule walls or capsule shells can be produced, which, however, leads to analytical stability being maintained (active ingredient in the capsule) and the sensory performance being even improved.

[00185] Surprisingly, it has been found that capsules of corresponding fragrance compounds produced by the method of the invention exhibit greater stability and a reduction of unintentionally escaping perfume oil, which can be attributed, in particular, to a more efficient encapsulation of the fragrance compounds. Capsules produced in this way therefore exhibit a significantly greater odor intensity when the perfume is released from opening the capsules through mechanical friction or pressure.

[00186] Thus, another object of the present invention relates to multilayer microcapsules comprising at least one hydrophobic odorous substance or fragrance compound prepared by a method described herein.

[00187] As explained previously, such microcapsules comprising multi-layer capsule shells or capsule walls have particularly good active ingredient release properties, while at the same time having a significantly lower polymer content (capsule wall components). At the same time, there are no restrictions against individual fragrance compounds. This means that a universal capsule is available that according to the current status, can encapsulate many or even all tested odorous substances or fragrance compounds.

[00188] Another aspect of the present invention are multilayer microcapsules comprising a core comprising at least one hydrophobic odoriferous substance or fragrance compound and a capsule shell, wherein the capsule shell comprises or consists of, from the inside out: a first layer comprising or consisting of polyurethane; a second layer comprising or consisting of polyurea; a third layer comprising or consisting of polyurethane; and at least a fourth layer comprising or consisting of polyurea.

[00189] Alternating cross-linking of isocyanate units with amines or hydroxyl groups results in a stable capsule wall of defined and dense and therefore stable alternating layers mainly based on polyurethane and polyurea.

[00190] Surprisingly, it has been found that the microcapsules produced by the method of the invention have a multi-layer capsule shell which basically comprises an innermost polyurethane-based first layer, a polyurethane-based second layer, a third polyurethane-based layer of polyurethane and at least a fourth outermost polyurea-based layer.

[00191] As previously indicated, the first innermost barrier layer is formed mainly by cross-linking the at least one isocyanate and the protective colloid, for example, a polysaccharide. The second cross-linking step mainly results from the polyaddition of isocyanates and the acidic reaction amine, for example, an amino acid, while the third cross-linking layer mainly results from a reaction of isocyanates and the hydroxyl group donor. Finally, the capsule is surrounded by at least a fourth cross-linking layer formed mainly by the reaction of isocyanates and at least one basic reaction amine. Thus, the multilayer microcapsule according to the invention generally has an alternating shell system based on polyurethane and polyurea bonds, which gives the capsules particularly high stability.

[00192] By constructing the capsule wall based on several defined and alternating individual layers, which are formed by directed deposition at defined temperatures and times and which support and surround each other, it is possible, based on the present invention, to produce particularly stable microcapsules with excellent sensory performance while significantly reducing shell components.

[00193] In another preferred embodiment, the present invention therefore relates to multilayer microcapsules, wherein: the first layer comprises cross-linked units of at least one isocyanate having two or more isocyanate groups and a protective colloid; the second layer comprises cross-linked units of at least one isocyanate having two or more isocyanate groups and an amine that reacts at an acidic pH; the third layer comprises cross-linked units of at least one isocyanate having two or more isocyanate groups and a hydroxyl group donor; and the at least fourth layer comprises cross-linked units of at least one isocyanate having two or more isocyanate groups and at least one amine that reacts at an alkaline pH.

[00194] Surprisingly, the microcapsules described here were shown to have greater stabilities and exhibit excellent sensory properties (excellent microcapsule release capacity), while overall less shell material was required compared to comparatively stable prior art capsules, as illustrated in the following modalities. Thus, the present invention allows, for example, the provision of efficient fragrance system and flavoring systems through the efficient encapsulation of hydrophobic odorous substances and fragrance compounds.

[00195] Furthermore, it is possible to encapsulate a broad spectrum of hydrophobic active ingredients with the microcapsules described here. This means there are no longer restrictions on individual active ingredients such as fragrance compounds. This means that a universal capsule is available which according to the current state of the art, can encapsulate the majority of tested fragrance compounds.

[00196] It is particularly advantageous in the context of the present invention to use biodegradable fragrance compounds or odoriferous substances or mixtures of fragrance compounds or mixtures of odoriferous substances to achieve a fully biodegradable product.

[00197] In a particularly preferred embodiment of the present invention, multilayer microcapsules are therefore described, wherein the multilayer microcapsule comprises at least one bio-based and biodegradable odorous substance or fragrance compound or a mixture of odoriferous substance or fragrance compound mixture.

[00198] The choice of defined temperature ranges for the addition of the individual reactants also leads to a completely new separation mechanism compared to the prior art. This has several advantages, such as increasing the stability of the emulsion. By selectively adding the reagents at defined temperatures, no pH peaks in the direction of alkaline or acidic pH values are generated. In the present method, the pH values used or resulting after the individual cross-linking steps are generally in a range between 3 and 9, while the final product is almost neutral with a pH between 7 and 8. This is reflected in the exceptionally good stabilities - despite the significantly reduced capsule wall material (polymer content) - and the excellent releases of active ingredients from the produced microcapsules.

[00199] The microcapsules produced by the method of the invention can be characterized by the value d(0.5) of their size distribution, that is, 50% of the capsules produced are larger, 50% of the capsules are smaller than this value.

[00200] To determine particle size, the microcapsules of the invention are dispersed in water as part of a dynamic method and the particle size is then determined by laser diffraction. Depending on the size of the capsule, the laser beam is refracted differently and can therefore be converted to a size. Mie theory was used for this purpose. A MALVERN Mastersizer 3000 was used for particle measurement.

[00201] The microcapsules according to the invention are characterized by having a particle size distribution at a d(0.5) value of 10 μm to 100 μm, preferably a d(0.5) value of 20 μm to 65 μm. The corresponding particle size distributions of microcapsules according to the invention and prior art microcapsules, i.e. microcapsules based on a pure polyurea network, are illustrated in Figure 6. Direct comparison of the microcapsules shows that, due to With an improved emulsification method as described herein, a more homogeneous particle size distribution of the microcapsules can be achieved compared to prior art microcapsules.

[00202] Figure 5 shows the IR images of the microcapsules according to the invention and the prior art microcapsules. State-of-the-art capsules correspond to microcapsules produced using known encapsulation technology and based on a pure polyurea-based network. No catalyst was used to produce such microcapsules and polyvinyl alcohol was chosen as the protective colloid. Production was also carried out at a pH of 9. Based on the graph, clear differences in the bands can be seen, particularly in the digital printing area. Due to the significantly more intense band at 626 cm-1 of the multilayer microcapsules compared to the prior art, it can be concluded that there is an asymmetric stretching vibration of an OH group, which can be attributed to the modified starch used, e.g. example. Another example is the band at 510 cm-1, which can be attributed to an N-H vibration of a polyurethane. Comparison of the IR spectra shows that, compared to prior art capsules (pure polyurea-based capsules), an additional new polymer has been formed to which improved stabilities and sensory properties can be attributed (polyurethane crosslinks).

[00203] Due to their stability and the targeted release of the active ingredients, the microcapsules according to the invention are suitable for a wide range of applications and, in particular, for use in detergents, fabric softeners, cleaning agents, moisture enhancers. perfume in liquid or solid form, cosmetics, personal care products, agricultural products or pharmaceutical products and the like.

[00204] In another aspect of the invention, the use of the multilayer microcapsule or a suspension of multilayer microcapsules for the manufacture of detergents, fabric softeners, cleaning agents, perfume enhancers or fragrance enhancers in liquid or solid form , cosmetics, personal care products, agricultural products or pharmaceutical products is also described.

Project Examples

[00205] The multilayer microcapsules according to the invention and their advantageous properties are described in more detail with reference to the following examples.

[00206] The stability tests listed below were carried out at 50°C.

[00207] The prior art capsules chosen were generally capsules whose capsule walls were exclusively due to a polyurea network. No catalyst was generally used in the production of these capsules and the synthesis was carried out at a pH of 9. Polyvinyl alcohol was chosen as the protective colloid.

Example 1: Stability data of multilayer microcapsules produced by the method of the invention with comparative capsules; gain in general stability.

[00208] In a first example, the stability data of multilayer microcapsules prepared according to the invention are compared with the stability data of corresponding microcapsules prepared without the addition of a catalyst. For the preparation of the latter, a mixture of two different isocyanates of hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate in a ratio of 80 : 20, modified starch as a protective colloid and the crosslinking agents sodium hydrochloride lysine (amine reacting at an acidic pH), glycerol (hydroxyl group donor) and guanidinium carbonate (amine reacting at an alkaline pH) were used. No catalyst was used in the preparation of these capsules.

[00209] The multilayer microcapsules of the invention were prepared from a mixture of two different isocyanates of hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate in a ratio of 80 : 20, modified starch as colloid protector, the DABCO catalyst and the crosslinking agents lysine hydrochloride (amine reacting at an acidic pH), glycerol (hydroxyl group donor) and guanidinium carbonate (amine reacting at an alkaline pH) according to the following scheme: Table 1 : Fabrication of the multilayer microcapsules using the method described in this document.

[00210] Both capsules included Tom Cap perfume oil.

[00211] The starch used in the examples herein as a protective colloid and cross-linking agent is generally in the form of a succinate. For this purpose, starch is derivatized with succinic acid.

[00212] The stability test was carried out using a representative softener (fabric softener) in which the corresponding microcapsules were incorporated in an amount of 1% by weight. The softener was then stored at a temperature of 50°C for the periods indicated below (see Table 1). Table 2: Stability data of multilayer microcapsules according to the invention compared to stability data of reference capsules prepared without the use of a catalyst.

[00213] The stability of the microcapsules is determined by the residual oil content (the perfume oil remaining in the microcapsule). From a residual oil content of more than 40% after 10 days, the microcapsules produced are considered stable.

[00214] The contents of the capsule after several days were analyzed by GC/MS (gas chromatography with mass spectrometry coupling). The perfume oil content in the capsules was determined by comparison measurement with a standard. A result of 46%, for example, means that 64% of the amount of perfume oil originally used is no longer included in the capsule.

[00215] The determination of free oil immediately after its production, that is, of oil that escaped from the capsules, was carried out by placing the microcapsules in isopropanol and was determined after 30 seconds by means of solid phase microextraction (SPME) and then by GC/MS and is considered as a measure of the quality of the capsules, i.e. the escaped free perfume oil is determined through gas chromatographic measurements with a standard. The proportion of perfume oil still contained can be calculated in reverse. The tested capsules were found to be stable up to a level of less than 1% leaked free oil. It has been demonstrated that fresh microcapsules produced by the method according to the invention leak significantly less perfume oil than comparative capsules and therefore exhibit a higher level of quality.

[00216] This example clearly shows that the use of a catalyst significantly influences the stability of the capsule and that significantly more stable multilayer microcapsules can be produced using a catalyst. In comparative capsules, produced without the use of a catalyst, no polyurethane-based first innermost capsule shell can form (see reaction scheme 1), resulting in a lower overall stability of the capsule wall due to the smaller number of layers. crosslinking. Furthermore, it should be noted in this context that the catalyst was added at room temperature and that this first innermost polyurethane-based crosslinking layer already forms efficiently at room temperature.

Example 2: Stability data of multilayer microcapsules prepared by the method of the invention, with and without a hydroxyl group donor.

[00217] In a second example, the stability data of multilayer microcapsules prepared according to the invention are compared with the stability data of corresponding microcapsules prepared without the addition of a hydroxyl group donor, that is, microcapsules without the additional third layer of polyurethane-based capsule shell.

[00218] For the preparation of the latter, a mixture of two different isocyanates of hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate in a ratio of 80 : 20, polyvinyl alcohol (PVOH) as protective colloid, the DABCO catalyst and the crosslinking agents lysine hydrochloride (amine reacting at an acidic pH) and guanidinium carbonate (amine reacting at an alkaline pH) were used. No hydroxyl group donors were used in the manufacture of these capsules.

[00219] The multilayer microcapsules of the invention were prepared from a mixture of two different isocyanates of hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate in a ratio of 80 : 20, starch as protective colloid , the DABCO catalyst and the crosslinking agents lysine hydrochloride (amine reacting at an acidic pH), glycerol (hydroxyl group donor) and guanidinium carbonate (amine reacting at an alkaline pH) [see Example 1]. Table 3: Data of stability of multilayer microcapsules according to the invention with and without additional polyurethane-based crosslinking layer by addition of a hydroxyl group donor (with/without addition of a hydroxyl group donor).

[00220] Stability was determined as described in Example 1.

[00221] In general, all microcapsules have good stability. With the additional use of a hydroxyl group donor, better stabilities could be achieved, which can be attributed to the formation of an additional third layer of polyurethane-based shell. Surprisingly, this further development of the method and the more targeted deposition of the individual shells leads to a high gain in stability.

Example 3: Stability data of multilayer microcapsules prepared by the method according to the invention as a function of catalyst addition time.

[00222] In another example, the stability data of the multilayer microcapsules prepared according to the invention are compared with the stability data of the corresponding microcapsules to which the catalyst has already been added in the aqueous phase (i.e. in step a2) .

[00223] The multilayer microcapsules of the invention were prepared from a mixture of two different isocyanates of hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate in a ratio of 80 : 20, starch as protective colloid , the catalyst DABCO and the crosslinking agents lysine hydrochloride (amine reacting at an acidic pH), glycerol (hydroxyl group donor) and guanidinium carbonate (amine reacting at an alkaline pH) according to the scheme in Example 1. In comparative capsules, catalyst addition occurred before emulsification, while in multilayer microcapsules according to the method described here, catalyst addition occurred after emulsification of the internal aqueous and non-aqueous phases.

[00224] Both capsules, the multilayer microcapsule according to the invention produced by the method described herein and the reference capsule have an average particle size distribution of d(0.5) > 60 μm. Table 4: Stability data of multilayer microcapsules according to the invention as a function of catalyst addition time.

[00225] Stability was determined as described in Example 1.

[00226] Compared to the reference capsules, the microcapsules according to the invention, in which the catalyst was added after emulsification and not yet in the aqueous phase, show significantly greater stability, even after 10 days at 50°C, and a significant reduction in free perfume oil. This corresponds to an increase in stability by a factor of 3.

[00227] In the case of the multilayer microcapsules prepared by the method described here, the resulting shell material was 40% of the shell material of the hydroxyl group donor microcapsules of Example 2. Despite the reduced amount of shell material required, By means of the method of the invention, multilayer microcapsules can be obtained which exhibit excellent stabilities.

Example 4: Sensory evaluation of microcapsules according to the invention.

[00228] The sensory evaluation of the microcapsules was carried out as follows: The microcapsules, as listed in Figure 7, were embedded in a fabric softener and then washed. Rinsing was carried out on mixed cotton and polyester fiber cloths.

[00229] Both the prior art capsules (capsules based on pure polyurea) and the microcapsules according to the invention contain TomCap perfume oil. The prior art capsules were manufactured exclusively by polyurea crosslinking. No catalyst was used for production and polyvinyl alcohol was chosen as the protective colloid. Production was carried out at a pH of 9. Such capsules thus exhibit a pure polyurea-based shell network. The multilayer microcapsules according to the invention were prepared as described in Example 1.

[00230] 12 test subjects rated the odor intensity of the mixed fiber wipes after washing on a scale of 1 (no odor) to 9 (very strong odor).

[00231] The microcapsules according to the invention effectively have the same odor profile as the prior art microcapsules. However, test subjects were able to perceive significantly greater odor intensity on average for the untreated, crumpled, and rubbed mixed-fiber wipes. In this case, the perfume is released by the mechanical destruction of the microcapsules of the invention. The advantage is due to the stability of the microcapsules according to the invention.

[00232] Another great advantage of isocyanate-based encapsulations is the fact that these capsules are formaldehyde-free. Furthermore, compared to the prior art, a gain in stability and sensory performance can be observed despite significantly lower amounts of polymer. This can be explained based on the thin multilayer capsules. At the same time, there are no restrictions against individual fragrance compounds. This means that an almost universal capsule is available which, according to the current state of the art, can encapsulate almost any tested fragrance compound.

[00233] State of the art microcapsules lose oil more quickly over time and, therefore, have a less intense odor than the microcapsules of the invention.

Example 5: Influence of selected isocyanates on the stability of multilayer microcapsules according to the invention.

[00234] The multilayer microcapsules of the invention were prepared according to Example 1, with arginine being used instead of guanidinium carbonate. Thus, the microcapsules were prepared from a mixture of two different isocyanates or from one isocyanate according to the following table, starch as protective colloid, the DABCO catalyst and the crosslinking agents lysine hydrochloride (amine reacting to an acidic pH), glycerol (hydroxyl group donor) and arginine (amine reacting to an alkaline pH).

[00235] The following table shows the direct comparison of the influence of the isocyanates selected for the production of multilayer microcapsules according to the invention on the stability of said microcapsules. Light microscope images of the corresponding microcapsules according to the invention are given in Figures 1 to 4. Table 5: Comparison of the influence of selected isocyanates on the stability of the multilayer microcapsules according to the invention

[00236] Stability was determined as described in Example 1.

[00237] In the example described here, hexamethylene diisocyanate was selected as the longest chain diisocyanate; pentamethylene diisocyanate was selected as the shortest chain diisocyanate; and 4,4'-methyldiphenylene diisocyanate was selected as the aromatic diisocyanate.

[00238] It has been demonstrated that the use of longer chain aliphatic diisocyanates is generally preferable, since less free oil escapes. Even more preferable, however, is the choice of two different diisocyanates and, in particular, mixed longer chain and short chain aliphatic diisocyanates or mixed aliphatic and aromatic isocyanates. This leads to particularly stable and better, i.e. more densely branched, cross-links within the capsule shell, which has a positive effect on the stability of the capsules. Furthermore, due to the different diffusive properties of isocyanates, the high reaction rates underlying isocyanates are exploited here during synthesis. However, it is surprising in this case that already one more or less carbon atom causes a decisive difference in the reaction rate. A clear difference can therefore be observed when OCN-(C5 chain)-NCO or OCN-(C6 chain)-NCO is used.

Example 6: Influence of the hydroxyl group donor and catalyst on the stability of the microcapsule.

[00239] In another example, the stabilities of multilayer microcapsules prepared according to the invention are compared with microcapsules prepared without a hydroxyl group donor and/or a catalyst.

[00240] The multilayer microcapsules of the invention were prepared from a mixture of two different diisocyanates/diisothiocyanates (mixture of hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate in a ratio of 80 : 20) with the same functionalities. In the present example, emulsion formation occurs at 25°C. Modified starch was chosen as the protective colloid and the crosslinking agents were lysine hydrochloride (amine reacting at an acidic pH), glycerol (hydroxyl group donor) and guanidinium carbonate (amine reacting at an alkaline pH). The microcapsules were prepared as in the manufacturing method described here according to Example 1. Table 6: Stability data of multilayer microcapsules according to the invention, depending on the influence of the hydroxyl group donor and the catalyst.

[00241] Stability was determined as described in Example 1.

[00242] It can be seen from the table above that the use of a catalyst leads to significantly more stable capsules. After addition of the catalyst to the emulsion or suspension, a cross-linked polyurethane-based capsule shell is formed at the interfaces of the emulsified or suspended active ingredient particles or droplets to be encapsulated as a result of polyaddition reactions of the diisocyanate/ di-isothiocyanate with the modified starch. In the absence of the catalyst, such a cross-linked layer cannot form and the starch acts only as a protective colloid and not additionally as a cross-linking agent. Therefore, the addition of a catalyst effectively causes the formation of the (additional) polyurethane-based shell layer, which contributes decisively to the stability of the resulting microcapsules.

[00243] Furthermore, it can be inferred from this experiment that cross-linking by the addition of an additional hydroxyl group donor, in this case glycerol, also contributes decisively to the overall stability of the microcapsules thus produced. The polyaddition reaction of the diisocyanate/diisothiocyanate mixture with the hydroxyl group donor forms an additional polyurea-based crosslinking layer, which gives the microcapsules additional stability.

[00244] In this sense, microcapsules according to the invention with an additional polyurethane-based capsule shell and an additional polyurea-based capsule shell show the best stability properties. The microcapsules thus produced have a multilayer capsule wall of generally cross-linked layers of polyurethane and polyurea in the following order: first innermost layer comprising polyurethane structures, second layer comprising polyurea structures, third layer comprising polyurethane structures and fourth outermost layer external comprising polyurea structures.

Example 7: Influence of selected temperature ranges.

[00245] In the following experiment, the influence of temperature staging of individual steps a) to d) is shown based on microcapsules according to the invention and prior art capsules (capsules based on pure polyurea produced without catalyst at a pH of 9 using polyvinyl alcohol as protective colloid). The addition of all reagents was carried out at room temperature in the prior art example.

[00246] For the preparation of microcapsules according to the invention, the following temperature ranges were selected for the addition of the individual components (the reagents were added as described in the present invention): - addition of DABCO catalyst: 22 to 26°C (step a4); - addition of the amine (lysine hydrochloride) reacting at an acidic pH: 40 to 45°C (step b); - addition of the hydroxyl group donor (glycerol): at 45 to 50°C (step c); - addition of the amine (guanidinium carbonate) reacting at an alkaline pH: 60 to 70°C (step d). Table 7: Stability data and polymer proportions of prior art microcapsules and multilayer capsules according to the invention.

[00247] Stability was determined as described in Example 1.

[00248] The composition of the capsule wall components can ideally be described as follows: Table 8: Composition of the multi-layer capsule shell or capsule wall.

[00249] Despite the lower polymer content, the microcapsules according to the invention show comparatively good, if not even better, stability data. On the one hand, the improved stability can be attributed to the four-layer shell system. On the other hand, specifically selected temperatures result in more efficient cross-linking of the cross-linking building blocks and thus allow a reduction in the total polymer content required.

Example 8: Stability data of microcapsules according to the invention with reduced shell content.

[00250] The multilayer microcapsules of the invention were prepared from a mixture of two different isocyanates (mixture of hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate in a ratio of 80: 20), starch as a protective colloid, the catalyst DABCO (added at 22°C to 26°C) and the cross-linking agents lysine hydrochloride (amine reacting at an acidic pH; added at 40°C to 45°C), glycerol (the donor of hydroxyl group; added at 45°C to 50°C) and guanidinium carbonate (amine reacting at an alkaline pH; added at 60°C to 70°C). The microcapsules thus produced according to the invention thus have a capsule wall comprising basically four different cross-linking layers based on polyurethane and polyurea in an alternating sequence.

[00251] The capsules of the prior art are common capsules with single-layer capsule walls based on pure polyurea of a mixture of hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate in the ratio 80: 20 and guanidinium carbonate. These capsules were produced without the use of a catalyst at a pH of 9 using polyvinyl alcohol as a protective colloid. Table 9: Polymer proportions and stability data of multilayer microcapsules according to the invention and prior art capsules.

[00252] Stability was determined as described in Example 1.

[00253] Increasing the number of individual layers results in a stable capsule with a reduced amount of polymer, which is more stable despite 36% less polymer (comparison of prior art with Invention 1) and even with a fraction of the amount of polymer of 16% of the initial amount (Invention 3) still stably envelops almost 50% of the oil in the capsule after 10 days at 50°C inside.

Example 9: Stability data of microcapsules according to the invention as a function of the pH value used in relation to the formation of the first innermost crosslink of the capsule shell or isocyanate capsule wall and protective colloid.

[00254] The microcapsules studied were prepared according to the method described here. The isocyanate component was composed of a mixture of hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate in a ratio of 80 : 20. DABCO acted as a catalyst, while starch was used as a protective colloid (see Example 1). . Table 10: Stability data of multilayer microcapsules as a function of the pH of the first polymerization with starch.

[00255] Stability was determined as described in Example 1.

[00256] The experience described here shows that capsules having an inner polyurethane-based capsule shell of starch and isocyanates exhibit particularly stable properties when this first polymerization, that is, the formation of the innermost capsule shell, occurs at a pH from 7 to 9. Furthermore, it was surprisingly shown that the modified starch used could be used in a dual function simultaneously as a protective colloid and as a reagent (capsule wall component/cross-linking agent).

Example 10: Optional step before curing in which a termination of the microcapsule crosslink is formed by the addition of an amine with an amine functional group.

[00257] The studied microcapsules were prepared according to the procedure described here. The following reagents were used for this purpose: Two linear isocyanates of hexamethylene diisocyanate and pentamethylene diisocyanate in a ratio of 90 : 10, DABCO as catalyst (addition at 25°C), lysine hydrochloride (addition at 40 °C, glycerol (addition at 50°C) and arginine (addition at 60°C) and the amines histidine or alanine (addition at 80°C). The latter amines are amino acids comprising an amino group. of multilayer microcapsules comprising final additional cross-linking.

[00258] Stability was determined as described in Example 1.

[00259] The example described here clearly demonstrates that the additional optional step of crosslinking with an amine, preferably an amino acid with a functional group leads to additional stabilization of the capsule.

Example 11: Stability data of multilayer microcapsules and the influence of colloid group donor and protective hydroxyl on the stability of multilayer microcapsules.

[00260] In another example, the stabilities of multilayer microcapsules produced according to the invention are shown as a function of the protective colloid (with/without PVOH or modified starch) and the hydroxyl group donor (with/without glycerol or phloroglucin) .

[00261] The synthesis of microcapsules according to the invention was basically as described in Example 1, with variations according to the following tables. The state of the art microcapsules are microcapsules based on pure polyurea. Here, the individual components were added to the reaction mixture or suspension or emulsion within defined temperature ranges. The prior art capsule is a microcapsule based on a pure polyurea network. In the production of these capsules, no catalyst was generally used and the synthesis was carried out at a pH of 9. Polyvinyl alcohol was selected as the protective colloid. Table 12: Stability data of multilayer microcapsules according to the invention depending on the influence of the hydroxyl group donor and the protective colloid.

[00262] Stability was determined as described in Example 1.

[00263] The choice of different temperature ranges for the addition of the individual reactants also leads to a completely new separation mechanism compared to the prior art, due to which greater stability of the emulsion can be achieved, since no peaks in the pH value in the direction of alkaline or acidic pH values is generated by selective addition of the reactants at defined temperatures. In the present method, the pH values used or resulting after the individual cross-linking steps are generally in a range between 3 and 9, while the final product is almost neutral with a pH value between 7 and 8.

[00264] It can be seen from the table above that an increase in hydroxyl groups both in the protective colloid and by the addition of a hydroxyl group donor, in this case glycerol, leads to a significant increase in the stability of the capsules. This leads to the fact that the capsules according to the invention, produced with modified starch and glycerol, show the best stabilities. Table 13: Stability data of multilayer microcapsules according to the invention depending on the influence of the hydroxyl group donor and the protective colloid.

[00265] Stability was determined as described in Example 1.

[00266] The table shows that, in contrast to a combination of modified starch and glycerol, a comparable system with phloroglucin (1,3,5-trihydroxybenzene) gives worse results. Surprisingly, not every polyol appears to allow these high stability gains, so the expected reactive triphenol, such as phloroglucin as hydroxyl group donor, with modified starch does not lead to microcapsule formation. Preferably, therefore, the hydroxyl group donor is a polyol with two or more functional hydroxyl groups, in particular glycerol and/or propylene glycol.

Claims (16)

1. Method for producing multilayer microcapsules, characterized by the fact that it comprises the following steps in this order: a) forming a first cross-linking layer by: a1) providing an internal non-aqueous phase comprising at least one isocyanate with two or more isocyanate groups and at least one active ingredient to be encapsulated; a2) provide 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 cross-linking layer by adding an amine that reacts at an acidic pH; c) forming a third cross-linking layer by adding a hydroxyl group donor; d) forming at least a fourth crosslinking layer by adding at least one amine that reacts at an alkaline pH, to obtain multilayer microcapsules; e) curing the multilayer microcapsules obtained in step d); and, optionally: f) separating the microcapsules from the reaction solution and optionally drying the microcapsules. 2. Method according to claim 1, characterized in that the first crosslinking layer is formed from the protective colloid and the isocyanate in the presence of a catalyst. 3. Method according to claim 1 or 2, characterized by the fact that it comprises adding a catalyst in a step a4) after step a3). 4. Method according to any one of claims 1 to 3, characterized in that the at least one isocyanate having two or more isocyanate groups is selected from the group consisting of aliphatic isocyanates and/or aromatic isocyanates. 5. Method according to any one of claims 1 to 4, characterized in that it comprises at least two aliphatic isocyanates having two or more isocyanate groups, wherein the at least two isocyanates have different chain lengths. 6. Method according to any one of claims 1 to 5, characterized by the fact that it comprises an additional optional step before curing in which a microcapsule cross-linking termination is formed by the addition of an amine with an amine functional group. 7. Method according to any one of claims 1 to 6, characterized in that the protective colloid is a polysaccharide, in particular starch. 8. Method according to any one of claims 1 to 7, characterized in that the catalyst is diazabicyclo[2.2.2]octane (DABCO). 9. Method according to any one of claims 1 to 8, characterized in that the acidic reaction amine is an acidic amino acid hydrochloride, in particular lysine hydrochloride and/or ornithine hydrochloride. 10. Method according to any one of claims 1 to 9, characterized in that the hydroxyl group donor is a polyol with two or more hydroxyl functional groups, in particular glycerol, propylene glycol and/or 1,3,5-tri -hydroxybenzene. 11. Method according to any one of claims 1 to 10, characterized in that the alkaline reaction amine is a guanidinium group donor, in particular arginine, guanidinium carbonate and/or guanidinium hydrochloride. 12. Method according to any one of claims 1 to 11, characterized in that the amine used in an optional additional step before curing to finish the microcapsule is an amino acid, in particular an amino acid comprising an amino group, more than one preferably alanine, glycine, aspartic acid, cysteine and/or proline. 13. Method according to any one of claims 1 to 12, characterized in that the at least one active ingredient to be encapsulated is selected from the group consisting of fragrance compounds, odoriferous substances, flavorings, biocides, insecticides, a substance from the group of repellents, food additives, cosmetic active ingredients, pharmaceutical ingredients, agrochemicals, dyes, luminous colors, optical brighteners, solvents, waxes, silicone oils, lubricants and mixtures of the above-mentioned active ingredients, particularly preferably the active ingredient is an odoriferous substance or a fragrance compound or a mixture of an odoriferous substance or a mixture of a fragrance compound. 14. Multilayer microcapsule, characterized in that it comprises a core comprising at least one hydrophobic odorous substance or hydrophobic fragrance compound and a capsule shell, wherein the capsule shell comprises from the inside out: (i) a first layer comprising or consisting of polyurethane; (ii) a second layer comprising or consisting of polyurea; (iii) a third layer comprising or consisting of polyurethane; and (iv) at least a fourth layer comprising or consisting of polyurea. 15. Multilayer microcapsule according to claim 14, characterized by the fact that: (i) the first layer comprises cross-linked units of at least one isocyanate having two or more isocyanate groups and a protective colloid; (ii) the second layer comprises cross-linked units of at least one isocyanate having two or more isocyanate groups and an amine that reacts at an acidic pH; (iii) the third layer comprises cross-linked units of at least one isocyanate having two or more isocyanate groups and a hydroxyl group donor; and (iv) the at least fourth layer comprises cross-linked units of at least one isocyanate having two or more isocyanate groups and at least one amine that reacts at an alkaline pH. 16. Use of a multilayer microcapsule as defined in any one of claims 14 to 15, or a suspension of multilayer microcapsules as defined in any one of claims 14 to 15, characterized by the fact that it is for the manufacture of detergents, fabric softeners, cleaning agents, perfume enhancers or fragrance enhancers in liquid or solid form, cosmetics, personal care products, agricultural products or pharmaceutical products.