Encapsulated flavors based on natural amino acids

Abstract

The present invention relates to a method for preparing multilayer microcapsules, in particular multilayer fragrance capsules or fragrance agent capsules, which have improved stability and fragrance agent or fragrance agent release capacity compared to capsules of the prior art. In addition, the present invention relates to multilayer microcapsules comprising at least one hydrophobic fragrance substance or fragrance agent that can be obtained according to the method of the present invention. In another aspect, the invention described herein also relates to multilayer microcapsules, which comprise a core and a capsule shell, wherein the core comprises at least one hydrophobic fragrance substance or fragrance agent. In addition, the present invention relates to the use of the multilayer microcapsules and the suspension formed by the multilayer microcapsules as a component of a detergent, a softener, a cleaning agent, an odor enhancer in liquid or solid form, a cosmetic product, a body cleaning product, an agricultural product or a pharmaceutical product.

Description

[0001] manual

[0002] The present invention relates to a method for preparing multilayer microcapsules, preferably multilayer fragrance capsules or fragrance agent capsules, which have improved stability and fragrance or fragrance agent release capacity compared to capsules of the prior art. In addition, the present invention relates to multilayer microcapsules comprising at least one hydrophobic fragrance substance or fragrance agent that can be obtained according to the method of the present invention. In another aspect, the invention described herein also relates to multilayer microcapsules, which comprise a core and a capsule shell, wherein the core comprises at least one hydrophobic fragrance substance or fragrance agent. In addition, the present invention relates to the use of the multilayer microcapsules and the suspensions formed by the multilayer microcapsules as components of detergents, softeners, cleaning agents, odor enhancers in liquid or solid form, cosmetics, body cleaning products, agricultural products or pharmaceutical products.

[0003] The purpose of encapsulation is, among other things, to ensure targeted release of active ingredients, to convert liquids into a processable powder form, to delay the loss of volatile components (e.g. aroma substances), to prevent premature chemical reactions with other mixture components or to achieve better processability before or during processing. Encapsulated active ingredients, such as aroma substances or fragrances, can be processed in an encapsulated manner to give different application formulations.

[0004] The contents of the microcapsules can subsequently be released in different ways and in particular involve one of the mechanisms described below: mechanical destruction of the capsule by crushing or shearing; destruction of the capsule by melting the wall material, destruction of the capsule by dissolving the wall material, or diffusion of the active ingredient through the capsule wall.

[0005] Nowadays, many products for daily use, such as cleaning agents, detergents, shampoos, etc., are scented with fragrances or fragrance mixtures. In order to prevent any interaction of the fragrance with other ingredients of the product or, for example, to prevent the fragrance from evaporating and thus not distorting or weakening the desired odor impression, the fragrance can be added to the preparation in encapsulated form. The desired odor impression can then be ensured.

[0006] Thus, for example, document EP 2111214 B1 describes a microcapsule having a fragrance substance core and an aminoplast polymer encapsulation. In addition to the high tightness of the capsule shell, the described capsule shell also has a very high resistance to reactive chemicals. The polycondensation of amine-formaldehyde precondensation products and water-insoluble hydrophobic active ingredients (such as perfume oils) is initiated here by changing the pH value.

[0007] DE 2303866 A1 describes microcapsules prepared from (a) glycidyltrialkylammonium salts and additionally alkyl sulfosuccinates or alkyl sulfosuccinamates having an alkyl group having 6 to 16 carbon atoms, and as component (b) a water-miscible solvent. The alkyl sulfosuccinates have an alkyl group having 6 to 16 carbon atoms, the carboxylic acid amide groups of the alkyl sulfosuccinamates being substituted by alkyl groups having 8 to 20 carbon atoms.

[0008] Document EP 3238816 A1 discloses a method for producing microcapsules, in particular aminoplast microcapsules, from an aqueous first preparation comprising at least one prepolymer and a non-aqueous second preparation comprising the active ingredient to be encapsulated, so that the average diameter of the capsules is reduced and uniform. In addition, the method described therein leads to a significant reduction in the particle size of the microcapsules and thus achieves stabilization of the emulsion.

[0009] WO 2017 / 148504 A1 describes a method for producing fragrance capsules having improved storage stability in an aqueous-surface-active environment, wherein a fragrance composition having an acidity value of a maximum of 5 mg KOH / g immediately before encapsulation is encapsulated with a natural covering material or a synthetic anionic or cationic polymer or a mixture thereof.

[0010] In addition, microcapsules can be prepared from other polymerizable materials, such as acrylate monomers, polyureas or also biopolymers. Microcapsules based on isocyanates are generally prepared from polyisocyanates and guanidine carbonate in an alkaline environment.

[0011] However, the above-mentioned prior art microcapsules have the following disadvantages: the polymeric capsule wall material or capsule shell material requires a large polymer ratio to ensure sufficient stability and not suffer too much loss of active ingredients. In addition, such microcapsules are usually not biodegradable. This results in insufficient active ingredient release capacity in most cases in application.

[0012] Due to the constantly increasing societal pressure from an environmental technology perspective, the demand for bio-based and biodegradable solutions in particular is increasing.

[0013] Against this background, the present invention is based on the complex object of providing a method for producing microcapsules which allows the provision of extremely stable microcapsules with relatively low polymer proportions, which simultaneously exhibit an excellent release behavior of the encapsulated active ingredient and are as biodegradable as possible.

[0014] Surprisingly, it has been found that this object can be achieved in that targeted layer crosslinking at defined temperatures and targeted catalytic mechanisms produces stable multilayer microcapsules and can thus ensure efficient encapsulation of the active ingredients and subsequent targeted release of these active ingredients, for example by mechanical friction or by pressure. Summary of the invention

[0015] This problem is solved by the subject matter of the independent claims. Preferred embodiments emerge from the statements of the dependent claims and the following description.

[0016] The first subject matter of the present invention therefore relates to a method for producing multilayer microcapsules, preferably multilayer fragrance substance capsules or fragrance agent capsules, which method comprises the following steps in sequence:

[0017] a) forming a first cross-linked layer by:

[0018] a1) providing an inner non-aqueous phase, said non-aqueous phase comprising at least one isocyanate having two or more isocyanate groups and at least one active ingredient to be encapsulated;

[0019] a2) providing an external aqueous phase, said aqueous phase comprising at least one protective colloid;

[0020] a3) mixing the inner non-aqueous phase and the outer aqueous phase to obtain an oil-in-water emulsion;

[0021] b) forming a second crosslinked layer by adding an amine that reacts at acidic pH;

[0022] c) forming a third crosslinked layer by adding a hydroxyl donor;

[0023] d) forming a fourth crosslinking layer by adding at least one amine that reacts at alkaline pH to obtain a multilayer microcapsule;

[0024] e) hardening the multilayer microcapsules obtained in step d);

[0025] and optionally:

[0026] f) separating the microcapsules from the reaction solution and optionally drying the microcapsules.

[0027] Furthermore, a subject of the invention described herein are multilayer microcapsules produced according to the process of the invention which comprise at least one hydrophobic aroma substance or aroma agent.

[0028] Another aspect of the present invention is a multilayer microcapsule, comprising a core and a capsule shell, wherein the core comprises at least one hydrophobic fragrance substance or fragrance agent, wherein the capsule shell comprises or consists of the following items from the inside to the outside:

[0029] (i) a first layer comprising or consisting of polyurethane;

[0030] (ii) a second layer comprising or consisting of polyurea;

[0031] (iii) a third layer comprising or consisting of polyurethane; and

[0032] (iv) at least a fourth layer comprising or consisting of polyurea.

[0033] Finally, in another aspect, the present invention relates to the use of multilayer microcapsules or suspensions formed from the multilayer microcapsules of the present invention for preparing detergents, softeners, cleaning agents, odor enhancers in liquid or solid form, cosmetics, body cleaning products, agricultural products or pharmaceutical products.

[0034] It has surprisingly been found within the scope of the present invention that the combination of targeted, defined and layered deposition of crosslinked capsule wall materials at defined temperatures and targeted catalytic mechanisms produces stable multilayer microcapsules and can thus ensure efficient encapsulation of active ingredients and subsequent targeted release of these active ingredients, for example by mechanical friction or by pressure.

[0035] Additionally, the multilayer microcapsules described herein exhibit good biocompatibility due to their bio-based and biodegradable building blocks (eg, amino acids and starch).

[0036] Additionally, significant savings in capsule wall material may be achieved by the methods described herein.

[0037] For those skilled in the art, these and other aspects, features and advantages of the present invention can be derived from the study of the following detailed description and claims. Here, any feature from one aspect of the present invention can be used in another aspect of the present invention or exchanged. The embodiments included in this article illustrate the present invention, but do not limit the present invention.

[0038] As used herein, the term "at least one" or "at least one" or "one or more" refers to 1 or more, for example 2, 3, 4, 5, 6, 7, 8, 9 or more.

[0039] Examples of numerical values ​​given in the format "from x to y" include the values ​​recited. When multiple preferred numerical ranges are given in this format, all ranges resulting from combinations of the different endpoints are also described. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1is an optical microscope photograph of a multilayer microcapsule according to the invention prepared from 100% long-chain diisocyanate. The optical microscope photograph was carried out using an Olympus BX51. The bars shown here correspond to 50 μm.

[0041] Figure 2 is an optical microscope photograph of a multilayer microcapsule according to the invention prepared from 100% short-chain diisocyanate. The optical microscope photograph was carried out using an Olympus BX51. The bars shown here correspond to 50 μm.

[0042] Figure 3 is an optical microscope photograph of a multilayer microcapsule according to the invention prepared from 50% long-chain diisocyanate and 50% short-chain isocyanate. The optical microscope photograph was carried out using an Olympus BX51. The bars shown here correspond to 50 μm.

[0043] Figure 4 is an optical microscope photograph of a multilayer microcapsule according to the invention prepared from 80% long-chain diisocyanate and 20% aromatic diisocyanate. The optical microscope photograph was carried out using an Olympus BX51. The bars shown here correspond to 50 μm.

[0044] Figure 5 The following is a diagram showing the results of IR spectroscopy analysis of microcapsules from the prior art (that is to say microcapsules based on a pure polyurea structural network) and microcapsules according to the invention. The analysis was carried out with the aid of ATR infrared spectroscopy (English: Attenuated total reflection).

[0045] Figure 6 Graph showing the particle size distribution (d(0.5) value) of multilayer microcapsules according to the invention and microcapsules from the prior art based on pure polyurea networks. To determine the particle size distribution, a Malvern Mastersizer 3000 was used. The corresponding calculations were based on the Mie theory.

[0046] Figure 7 is a graph showing the results of the sensory evaluation of microcapsules from the prior art, that is to say microcapsules based on a pure polyurea structural network, and microcapsules according to the invention. DETAILED DESCRIPTION

[0047] In a first aspect, the present invention relates to a method for producing multilayer microcapsules, preferably a method for producing multilayer fragrance substance capsules or fragrance agent capsules, the method comprising or consisting of the following steps in sequence:

[0048] a) forming a first cross-linked layer by:

[0049] a1) providing an inner non-aqueous phase, said non-aqueous phase comprising at least one isocyanate having two or more isocyanate groups and at least one active ingredient to be encapsulated;

[0050] a2) providing an external aqueous phase, which comprises at least one protective colloid, preferably a polysaccharide, particularly preferably starch;

[0051] a3) mixing the inner non-aqueous phase and the outer aqueous phase to obtain an oil-in-water emulsion;

[0052] b) forming a second crosslinked layer by adding an amine that reacts at acidic pH;

[0053] c) forming a third crosslinked layer by adding a hydroxyl donor;

[0054] d) forming a fourth crosslinking layer by adding at least one amine that reacts at alkaline pH to obtain a multilayer microcapsule;

[0055] e) hardening the multilayer microcapsules obtained in step d);

[0056] and optionally:

[0057] f) separating the microcapsules from the reaction solution and optionally drying the microcapsules.

[0058] In the context of the present invention, multilayer microcapsules are understood to be microparticles having a capsule shell or capsule wall and one or more active ingredients as core material in the capsule interior. Hydrophobic active ingredients are preferred. The terms "microcapsules" or "capsules" are used as synonyms in the sense of the present invention.

[0059] In the context of the present invention, the capsule shell or capsule wall preferably consists of a plurality of layers, which preferably have different compositions. Thus, a particularly preferred embodiment of the capsule shell comprises at least one (crosslinked) layer based on polyurethane and at least one (crosslinked) layer based on polyurea. Particularly preferred are layers which alternately comprise polyurethane structures and polyurea structures.

[0060] In the first step of the process according to the invention, a first crosslinked layer is formed. For this purpose, an inner 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.

[0061] The at least one isocyanate used in the preparation method described herein has at least two isocyanate groups in order to form a polymer network and thus form a capsule shell or capsule wall by polymerization. Corresponding polymerizable isothiocyanates (alone or in combination with isocyanates) can also be used in the method of the present invention. Particularly preferred are aliphatic, cycloaliphatic, hydrogenated aromatic, aromatic or heterocyclic polyisocyanates or polyisothiocyanates, their substitution products and the above-mentioned monomeric or oligomeric compounds, wherein aliphatic and / or aromatic compounds are preferably used. Diisocyanates are particularly preferred among polyisocyanates and are therefore preferably used to perform the present invention.

[0062] Therefore, in a preferred embodiment, the present invention relates to a method for preparing multilayer microcapsules, wherein the at least one isocyanate with two or more isocyanate groups is selected from the group of aliphatic isocyanates and / or aromatic isocyanates and the corresponding isothiocyanates. The aliphatic isocyanates used preferably have five or more carbon atoms.

[0063] In a particularly preferred embodiment, the inner non-aqueous phase comprises a mixture of various polymerizable isocyanates and / or isothiocyanates that can form mixed polymer products.

[0064] Examples of monomeric isocyanates and / or isothiocyanates which can be used according to the invention and which contain at least two isocyanate or at least two isothiocyanate groups are:

[0065] Ethylene diisocyanate, trimethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethyl diisocyanate, ethylene diisothiocyanate, tetramethylene diisothiocyanate, hexamethylene diisothiocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 1,3-phenylene diisocyanate and 1,4-phenylene diisocyanate mixture of esters, p-phenylene diisocyanate, xylylene-1,4-diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, and a mixture of xylylene-1,4-diisocyanate and xylylene-1,3-diisocyanate, 2,4-hexahydroisocyanate Tolyl diisocyanate, 2,6-hexahydrotolyl diisocyanate, a mixture of 2,4-hexahydrotolyl diisocyanate and 2,6-hexahydrotolyl diisocyanate, hexahydro-1,3-phenylene diisocyanate, hexahydro-1,4-phenylene diisocyanate, a mixture of hexahydro-1,4-phenylene diisocyanate and hexahydro-1,4-phenylene diisocyanate, 1,3-diisocyanatobenzene, 1,3,5-trimethylbenzene-2,4-diisocyanate, 1,3,5-triisocyanatobenzene 2,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, triphenylmethane-4,4',4"-triisocyanate, tolylene-2,4,6-triisocyanate, dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate or a mixture of the above compounds.

[0066] Preferred polymerizable compounds having at least two isocyanate groups or isothiocyanate groups are diisocyanates and polyisocyanates prepared on a large scale, for example TDI tolylene diisocyanate (an isomer mixture of 2,4- and 2,6-tolylene diisocyanate in a ratio of 80:20), HDI hexamethylene diisocyanate-(1,6), IPDI isophorone diisocyanate or DMDI diphenylmethane-4,4′-diisocyanate.

[0067] Other particularly preferred monomeric isocyanate compounds are diisocyanates such as 1,4-diisocyanatobutane, 1,6-diisocyanatohexane, 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- and 2,4,4-trimethyl-1,6-diisocyanatohexane, 1,10-diisocyanatodecane, 1,3- and 1,4-diisocyanatocyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate), 4,4'-diisocyanatodicyclohexylmethane, 2,4- and 2,6-diisocyanato-methylcyclohexane and mixtures thereof. In principle, aromatic isocyanates such as tolylene diisocyanate or 4,4'-diisocyanato-diphenylmethane can also be used.

[0068] In part it is also possible to concomitantly use polyisocyanates which can be formed by modifying the abovementioned diisocyanates or mixtures thereof according to known methods and which comprise, for example, uretdione, urethane, isocyanate, biuret and / or allophanate groups.

[0069] It has surprisingly been found that in particular the use of long-chain aliphatic diisocyanates having six or more carbon atoms leads to the formation of more stable capsule shells or capsule walls.

[0070] Still further preferred is a combination of at least two different (preferably aliphatic and / or aromatic) diisocyanates. In a preferred improvement of the present invention, the different (preferably aliphatic) diisocyanates also have different chain lengths. The main embodiment especially includes a mixture of long-chain and short-chain diisocyanates in any mixing ratio. The mixing ratio of long-chain diisocyanates to short-chain diisocyanates is preferably in the range of 4:1 to 1:4 and particularly preferably 2:1 to 1:2. In this context, long-chain diisocyanates preferably have six or more carbon atoms, but more preferably have six to twelve carbon atoms and particularly preferably have six to eight carbon atoms. Short-chain diisocyanates are understood to be diisocyanates with one to five carbon atoms and preferably diisocyanates with three to five carbon atoms.

[0071] It has been shown that particularly stable and better, ie more dense, branched crosslinking is achieved within the capsule shell when essentially different diisocyanates are used in mixture and in particular when a mixture of long-chain and short-chain aliphatic isocyanates is selected or a mixture of aliphatic and aromatic isocyanates (and / or isothiocyanates) is used.

[0072] Thus, the process described here makes it possible to prepare microcapsules with good properties, which are provided not only from mixtures of linear and aromatic isocyanates but also from mixtures of two different linear isocyanates. Such microcapsules, in particular when used as fragrance capsules, exhibit outstanding fragrance storage properties and, associated therewith, excellent fragrance release capabilities, as will be demonstrated by the examples below.

[0073] The combination of different polymerizable isocyanates thus results in a particularly stable capsule shell or capsule wall, which in turn is reflected in a better performance of the capsule (fragrance release capacity), for example in the field of fragrance encapsulation or fragrance encapsulation. Accordingly, in the present invention, a combination of at least two different polymerizable (preferably aliphatic and / or aromatic) isocyanates is essentially preferred.

[0074] Such microencapsulation of a fragrance or fragrance mixture also offers the possibility of reducing or completely preventing the evaporation of interacting or volatile fragrance components in the fragranced product.

[0075] exist Figures 1 to 4 The effect of the chain length of the isocyanate on the obtained microcapsules is shown in FIG. Figure 1 The optical microscope photograph of the microcapsules of the present invention prepared only from long-chain diisocyanates (here hexamethylene diisocyanate) is shown. Figure 2 Microcapsules based on short-chain diisocyanates, such as pentamethylene diisocyanate, are shown in Figure 2 Although the microcapsules have uniform morphology, they have low stability.

[0076] exist Figure 3 and Figure 4 The microcapsules of the invention starting from mixed isocyanates are shown in: Figure 3 shows the morphology of microcapsules based on a mixture of 50% short-chain and 50% long-chain aliphatic isocyanates (hexamethylene diisocyanate and pentamethylene diisocyanate in a 50:50 ratio), while Figure 4 A corresponding mixture of 80% long-chain diisocyanate and 20% aromatic diisocyanate (hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate in a ratio of 80:20) is shown.

[0077] Microcapsules prepared from mixed aliphatic and / or aromatic isocyanates generally have better stability and are therefore preferably suitable for the process described herein and therefore for the preparation of multilayer microcapsules according to the invention, which, as demonstrated in the examples hereinafter, have outstanding stability and active ingredient release properties.

[0078] In this context, it is particularly preferred to use aliphatic isocyanates and / or isothiocyanates having a chain length of one to twelve carbon atoms, preferably three to eight carbon atoms and particularly preferably four to seven carbon atoms in the chain for the preparation of the multilayer microcapsules according to the invention.

[0079] In this context, polymerizable aliphatic isocyanates are particularly preferred due to their chemical affinity with bio-based systems. Thus, for example, lysine and 1,5-diisocyanatopentane both exhibit the same decomposition product, namely 1,5-diaminopentane, and are therefore particularly suitable for the production of bio-based and biodegradable microcapsules from an environmental perspective.

[0080] Therefore, in a particularly preferred embodiment, the present invention further relates to a method for producing multilayer microcapsules, which comprise at least two aliphatic isocyanates having two or more isocyanate groups, wherein the at least two isocyanates have different chain lengths.

[0081] Additionally preferred is a process comprising at least two aliphatic isocyanates and / or isothiocyanates carrying two or more isocyanate / isothiocyanate groups, wherein the at least two isocyanates / isothiocyanates have different chain lengths.

[0082] At least one of the aliphatic isocyanates and / or isothiocyanates here has a chain length of five or more carbon atoms.

[0083] In a further embodiment, therefore, a mixture of isocyanate and isothiocyanate compounds having the above-described properties in the inner non-aqueous phase is also conceivable in principle.

[0084] It can be observed that the selection of at least two aliphatic isocyanates of different chain lengths or a mixture of aliphatic and aromatic isocyanates leads to significant gains in stability and performance (in the case of fragrance capsules or fragrance capsules, fragrance release capacity) due to different reaction times, dissociation and crosslinking structures.

[0085] Additionally, the microcapsules described herein can be prepared from aromatic isocyanates bearing two or more isocyanate groups.

[0086] Therefore, in another variant, the invention relates to a process for preparing multilayer microcapsules, wherein the isocyanate carrying two or more isocyanate groups is selected from the group of aromatic isocyanates.

[0087] In this case, it is also possible to use a mixture of a plurality of aromatic isocyanates (or isothiocyanates).

[0088] The ratio of isocyanate component to inner, nonaqueous phase is preferably between 1:50 and 1:20, still more preferably between 1:40 and 1:30.

[0089] Thus, the inner non-aqueous phase may, for example, comprise from 0.1 to 10.0% by weight and preferably from 0.5 to 3.0% by weight of isocyanate, relative to the total weight of the inner non-aqueous phase.

[0090] Due to the low proportion of the isocyanate component, multilayer microcapsules can be produced according to the invention, in which the absolute isocyanate proportion is only 1 / 50 of the total capsule including the active ingredient. Thus, for example, multilayer microcapsules with an isocyanate proportion of only 0.6% by weight can be produced using the process described herein. However, the isocyanate proportion is preferably about 1.1% by weight of the capsule wall.

[0091] In the method for preparing multilayer microcapsules of the present invention, at least one isocyanate and / or isothiocyanate having polymerization ability is first dissolved in an inert non-aqueous solvent or a solvent mixture together with the active ingredient to be encapsulated. Here, the active ingredient to be encapsulated in the context of this specification is preferably a hydrophobic active ingredient. By selecting such an active ingredient, it can be ensured that the material to be encapsulated is located in the internal non-aqueous phase and does not mix with the external aqueous phase. This causes the hydrophobic active ingredient to be effectively enclosed in the interior of the multilayer microcapsule as a core material. The uniqueness of the internal non-aqueous phase thus formed is also its organic hydrophobic, oily nature.

[0092] Suitable inert solvents for the inner non-aqueous phase are: chlorinated biphenyls, chlorinated paraffins, vegetable oils such as cottonseed oil, peanut oil, palm oil, tritolyl phosphates, silicone oils, dialkyl phthalates, dialkyl adipates, partially hydrogenated terphenyls, alkylated biphenyls, alkylated naphthalenes, diaryl ethers, aryl alkyl ethers and higher alkylated benzenes, benzyl benzoate, isopropyl myristate and any mixtures of these hydrophobic solvents and mixtures of one or more of these hydrophobic solvents with kerosene, paraffin and / or isoparaffin. Preferably, vegetable oils such as sunflower seed oil, triglycerides, benzyl benzoate or isopropyl myristate are used as solvents for providing the inner non-aqueous phase.

[0093] The ratio of active ingredient component to inner non-aqueous phase is preferably about 1:14. Thus, the inner non-aqueous phase can contain, for example, 88 to 99% by weight and preferably 92 to 96% by weight of the (hydrophobic) active ingredient (or active ingredient mixture) to be enclosed, relative to the total active ingredient capsule. In this context, the capsule as a whole comprises not only the oil core, that is to say the active ingredient (or active ingredient mixture), but also the capsule wall components formed by the isocyanate component and the corresponding crosslinking agent from the outer aqueous phase.

[0094] Thus, in contrast to the microcapsules of the prior art, significantly larger amounts of active ingredients can be encapsulated with the method described here.

[0095] Additionally, the first step of the methods described herein includes providing an external aqueous phase comprising at least one protective colloid.

[0096] For this purpose, the protective colloid is dissolved in an aqueous solvent, preferably water. The protective colloid is preferably a polysaccharide, particularly preferably starch.

[0097] Therefore, a particularly preferred embodiment of the present invention relates to a method for producing multilayer microcapsules, wherein the protective colloid is a polysaccharide, in particular starch.

[0098] Protective colloids are compounds which, in the precipitation reaction, that is to say when a solid phase is precipitated from a homogeneous liquid phase, prevent agglomeration (coagulation, aggregation, flocculation, flocculation) of the primary particles. In the preparation of oil-in-water emulsions, the protective colloids are supported with their hydrophobic parts on the primary particles and point their polarity (that is to say the hydrophilic molecular part) towards the aqueous phase. By supporting on the surface, the interfacial tension is reduced and agglomeration of the primary particles is prevented. In addition, this stabilizes the emulsion and at the same time facilitates the formation of relatively small droplets and thus also the formation of corresponding microcapsules.

[0099] The protective colloid used in the process according to the invention is preferably a polysaccharide, particularly preferably starch, in particular starch from wheat, potato, corn, cassava or oats, or chemically, mechanically and / or enzymatically modified starch (succinates, acetates, formates), and mixtures of the above compounds. Other suitable protective colloids are carboxymethylcellulose, gum arabic, proteins, gelatin, polyols, polyphenols or polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl alcohol derivatives such as ammonium derivatives, and mixtures of the above compounds.

[0100] However, it is most preferred to use starch as protective colloid. It is therefore particularly preferred to use (modified) starch as protective colloid for the preparation of multilayer microcapsules.

[0101] The protective colloid used in this context has a dual function in that, on the one hand, it reacts with the isocyanate during polymerization to form a first or further crosslinked layer and thereby forms the capsule wall or capsule shell and is a solid component of the capsule wall or capsule shell, and on the other hand, it acts as a protective colloid and thereby prevents agglomeration of solid particles, stabilizes the emulsion that is subsequently formed and thereby contributes to the formation of small droplets.

[0102] It is therefore particularly preferred if the protective colloid selected has polymerizing properties, for example in the case of starch due to the presence of at least one hydroxyl group.

[0103] Starch is a biodegradable, naturally occurring polysaccharide. In combination with the isocyanates described herein, bio-based and biodegradable capsule shells can thus be provided using the present method. In the method described herein, starch is therefore primarily used as a so-called biocrosslinker.

[0104] According to the present invention, the amount of the protective colloid used is preferably in the range of 1:50 to 1:10, more preferably in the range of 1:40 to 1:30, relative to the aqueous phase.

[0105] The amount of protective colloid used or the amount of protective colloid combination used is thus in the range from 1 to 8% by weight, preferably in the range from 2 to 4% by weight, still more preferably in the range from 3 to 4% by weight, relative to the total weight of the external aqueous phase.

[0106] The formation of the oil-in-water emulsion is carried out by mixing an inner non-aqueous phase and an outer aqueous phase. The weight ratio of the inner non-aqueous phase to the outer aqueous phase is preferably in the range of 2:1 to 1:10, still more preferably in the range of 1:2 to 1:4.

[0107] The ratio of protective colloid in the outer aqueous phase to isocyanate or isothiocyanate in the inner non-aqueous phase is in the range from 1:5 to 1:2, preferably in the range from 1:2 to 1:1.

[0108] The emulsion formation in the case of liquid active ingredients or the suspension formation in the case of solid active ingredients, that is to say the emulsification or suspension of the inner non-aqueous or oily phase with the outer aqueous or hydrophilic phase, takes place under high turbulence or strong shearing, wherein the intensity of the turbulence or shearing determines the diameter of the microcapsules obtained. The preparation of the microcapsules can be carried out continuously or discontinuously. The size of the capsules obtained generally decreases with increasing viscosity of the aqueous phase or with decreasing viscosity of the oily phase.

[0109] The process according to the invention for producing multilayer microcapsules can be carried out, for example, according to the “inline” technology via a forced metering pump or else also with stirring in customary dispersing or emulsifying apparatuses.

[0110] To prepare the multilayer microcapsules according to the invention, the emulsification of the external aqueous phase and the internal non-aqueous phase is carried out with the aid of an emulsifying turbine (IKA Eurostar 20 high-speed stirrer). The emulsification process in the first step of the method according to the invention is advantageously carried out at a stirring speed of 2000 to 5000 rpm, preferably 3250 to 4500 rpm, for 30 seconds to 20 minutes, preferably 1 to 4 minutes.

[0111] So-called stabilizers or emulsification assistants may optionally be dissolved or dispersed in the outer aqueous phase in order to stabilize the emulsion formed and prevent the inner nonaqueous (oily / organic / hydrophobic) phase from separating from the outer aqueous (hydrophilic) phase.

[0112] It has surprisingly been shown that the additional addition of a catalyst to the emulsion or dispersion enables the formation of a first inner core shell from protective colloid and isocyanate at the interface of the emulsified or suspended hydrophobic (active ingredient) particles or droplets to be encapsulated. The capsule shell or capsule wall can be formed by interfacial polymerization, which encloses the active ingredient as capsule core in its interior.

[0113] The formation of this first capsule layer is based on a polyaddition reaction of isocyanates (and / or the corresponding isothiocyanates) with a (preferably polymerizable) protective colloid, preferably starch, to form a capsule shell or capsule wall based on a polyurethane structure.

[0114] Therefore, a preferred embodiment of the present invention relates to a method for producing multilayer microcapsules, wherein the first crosslinking layer is formed from a protective colloid and an isocyanate in the presence of a catalyst.

[0115] The catalyst added in the method of the present invention is preferably diazabicyclo[2.2.2]octane (DABCO). DABCO, also known as triethyldiamine (TEDA), is a bicyclic tertiary amine. DABCO is generally used as a catalyst for preparing polyurethane plastics. The tertiary amine with a free electron pair facilitates the reaction between at least one polymerizable isocyanate in the internal non-aqueous phase and the hydroxyl (alcohol) group of the protective colloid in the external aqueous phase.

[0116] The amount of catalyst added to the emulsion or suspension is in the range of 0.01 to 1% by weight and preferably in the range of 0.05 to 0.2% by weight relative to the total weight of the emulsion or suspension. In the case of slow polymerization, the required amount of catalyst can be adapted accordingly.

[0117] Therefore, the ratio of catalyst in the emulsion or suspension to isocyanate or isothiocyanate in the inner non-aqueous phase is preferably in the range from 1:20 to 1:50.

[0118] It has been shown to be advantageous to first disperse the catalyst in water and subsequently add it to the emulsion or suspension with stirring.

[0119] The catalyst is preferably added at a stirring speed of 500 to 2000 rpm, particularly preferably at 1000 to 1500 rpm, and at a temperature of 20 to 35° C., preferably at a temperature of 22 to 26° C.

[0120] It was also surprising that the addition of the catalyst after the emulsification step or dispersion step resulted in a significant improvement in the stability of the capsules. The capsules prepared in this way had a significantly higher stability, even after 10 days at 50° C., and had a significant reduction in free perfume oils relative to the control capsules in which the catalyst had been added to the aqueous phase before emulsification or dispersion.

[0121] Particularly stable capsules can be prepared using the catalyst diazabicyclo[2.2.2]octane (DABCO). Thus, in the examples described herein, an at least 3-fold increase in stability was observed.

[0122] Therefore, according to a particularly preferred embodiment, the catalyst is diazabicyclo[2.2.2]octane (DABCO).

[0123] Therefore, in a particularly preferred embodiment, the present invention also relates to a method for producing multilayer microcapsules, which method comprises adding a catalyst in a step a4) after step a3).

[0124] After the catalyst is added to the emulsion or suspension, a first crosslinked layer is formed by interfacial polymerization at the interface of the emulsified or dispersed active ingredient particles or active ingredient droplets to be encapsulated, which first crosslinked layer forms the inner first capsule shell, while the hydrophobic active ingredient particles or active ingredient droplets to be encapsulated form the core of the microcapsule of the present invention. Here, the interfacial polymerization corresponds to the polyaddition reaction of polyisocyanates or isothiocyanates (or mixtures thereof) with protective colloids (that is, preferably with starch) in the presence of a catalyst, thereby forming a polyurethane-based crosslinked capsule shell. Therefore, the addition of the catalyst enables the efficient formation of the innermost first polyurethane-based shell layer.

[0125] The uniqueness of the polyaddition reactions described herein generally resides in the reaction of individual polymers or oligomers with two or more functional groups with bond attachment and rearrangement of hydrogen atoms, such as by reaction of a polyisocyanate or polyisothiocyanate with a polyol (eg, a polysaccharide such as starch).

[0126] The polyaddition reaction of the at least one polyisocyanate, preferably a diisocyanate, with the protective colloid, preferably starch (polyol), results in the formation of so-called urethane bridges (—NH—CO—C—) by addition of the hydroxyl groups (—OH) of the polyol to the carbon atoms of the carbon-nitrogen bonds (—N═C═O) of the isocyanate groups according to the following reaction scheme.

[0127]

[0128] Thus, a hydrophilic interface layer, that is to say a capsule shell, can be formed which prevents the diffusion of the hydrophobic active ingredient (active ingredient mixture) enclosed in the capsule. In the case of fragrances and fragrance substances, this enables, for example, effective encapsulation of sensory perceptible active ingredients (fragrance mixtures / perfume oils, individual fragrances) which can only be effectively released by mechanical activation.

[0129] Thus, in the case of the reaction of diisocyanates with diols, generally straight polyurethane chains are formed which can be crosslinked spatially in a targeted manner by the excess of isocyanate over the amino groups of the uncrosslinked polyurethane chains.

[0130] The greater the number of crosslinking functional groups, the higher the degree of spatial crosslinking and the more stable the capsule shell or capsule wall of the resulting microcapsules. In addition to the number of functional groups, that is to say the number of branches, the chain length of the individual building blocks also has a significant influence on the mechanical properties, that is to say the stability of the capsule. In this context, the large number of hydroxyl groups of the protective colloid starch should be mentioned, which allows the formation of particularly spatially specific crosslinks.

[0131] Further protective colloids or mixtures thereof and additional emulsifying aids or stabilizers are not theoretically necessary to ensure efficient crosslinking, but can be added in certain cases in order to improve the emulsification or suspension process in the case of insufficient crosslinking and to increase the crosslinking density and crosslinking rate.

[0132] The reaction in the formation of the innermost first crosslinked polyurethane-based layer (first layer of the capsule shell or capsule wall) is carried out in the presence of a catalyst already at room temperature and particularly preferably at a temperature between 25 and 40° C.

[0133] With isocyanate-based capsule shells, only selected active ingredients can be encapsulated under normal circumstances. Encapsulation with isocyanates is therefore not suitable for encapsulation of active ingredients with aldehyde, carboxylic acid or ester functional groups, because such active ingredients are deprotonated, oxidized or saponified at alkaline pH values, making the obtained emulsion unstable. The relatively neutral pH values ​​for polyurethane-based encapsulation therefore allow effective encapsulation of such active ingredients. Due to the selected pH range, the present method can thus achieve particularly mild conditions, so that there are no pH extremes and thus theoretically no longer limitations on the active ingredients to be encapsulated.

[0134] In the subsequent second step of the invention, the second crosslinking layer is formed by adding an amine which reacts at acidic pH values. For this purpose, the amine which reacts at acidic pH values ​​is added to the mixture, likewise while stirring at a stirring speed of 500 to 2000 rpm, particularly preferably at 1000 to 1500 rpm.

[0135] Particularly stable crosslinking is achieved when the second crosslinking is carried out with an amine that reacts at acidic pH values ​​at an acidic pH value of 2 to 7, preferably at an acidic pH value of 2 to 6 and most preferably at a pH value of 3 to 5. For this purpose, an acid, for example formic acid or acetic acid, is added to the mixture in the outer aqueous phase in order to set the corresponding pH value and avoid potential saponification of the hydrophobic active ingredients. This ensures that the pH value does not drift rapidly and thus penetrate the still relatively unstable first shell formed by protective colloid and isocyanate.

[0136] The core material, ie the capsule shell of the active ingredient, is further crosslinked, surrounded from the outside and thus further stabilized by the second crosslinked layer formed.

[0137] Furthermore, this layer preferably has hydrophobic properties and surrounds the inner, hydrophilic first crosslinked layer and thus acts as an additional barrier layer which makes the diffusion of the surrounded active ingredient more difficult.

[0138] Still more preferably the second crosslinking step is carried out at a temperature of 35° C. to 50° C. A temperature of 40° C. to 45° C. is preferred.

[0139] The amine that reacts at acidic pH values, ie the second crosslinker, is selected from the group consisting of basic amino acids and their hydrochlorides, in particular lysine hydrochloride and / or ornithine hydrochloride, lysine hydrochloride being particularly preferred as crosslinker.

[0140] Such amino acid-based amines are particularly preferred from the environmental technology perspective with regard to biodegradability and biocompatibility.

[0141] The advantage of carrying out such crosslinking in the acidic pH range over crosslinking in an alkaline environment is that hydrophobic active ingredients with aldehyde, carboxylic acid or ester functions are not saponified during crosslinking with at least one isocyanate or isothiocyanate, since the innermost first shell is still relatively unstable to diffusion and similar processes. This prevents, for example, the active ingredient or ingredients to be encapsulated (e.g. perfume oils) from being chemically altered and thus causing losses of active ingredient on the one hand and destabilizing the emulsion on the other hand. This makes it possible to encapsulate hydrophobic active ingredients, in particular hydrophobic active ingredients with aldehyde, carboxylic acid or ester functions.

[0142] Therefore, a preferred embodiment of the present invention relates to a method for preparing multilayer microcapsules, which comprises a second / additional crosslinking step, wherein the acid-reactive amine used for crosslinking is an acidic amino acid hydrochloride, in particular lysine hydrochloride and / or ornithine hydrochloride.

[0143] In this second crosslinking step, however, theoretically all basic amino acids having two or more amino groups and their hydrochlorides are suitable for forming the second crosslinked layer, ie, the second shell layer.

[0144] The amine which reacts at acidic pH is added here directly in solid form or in the form of an aqueous solution to the suspension or emulsion.

[0145] The addition of the amino acid hydrochloride is preferably carried out here in the form of a 5 to 40% solution, still more preferably a 10 to 20% solution.

[0146] The second crosslinking of the process according to the invention is preferably carried out under stirring for a period of between 5 and 30 minutes and preferably for a period of between 10 and 20 minutes.

[0147] It has been shown that after the addition of an amine that reacts at acidic pH values ​​to the emulsion or suspension, a second crosslinked layer is formed by interfacial polymerization around the active ingredient particles or active ingredient droplets that have been encapsulated in the first step, which second crosslinked layer surrounds the inner first capsule shell and the hydrophobic active ingredient particles or active ingredient droplets contained therein. The interfacial polymerization corresponds to the polyaddition reaction of the at least one polyisocyanate or isothiocyanate (or a mixture thereof) with an amine that reacts at acidic pH values, that is to say preferably with amino acid hydrochlorides, in particular lysine hydrochloride and ornithine hydrochloride, to form a crosslinked capsule shell based on polyurea.

[0148] The formation of polyurea linkages takes place in a similar manner to the formation of polyurethane linkages by polyaddition of the amine group (—NH) of the amine to the corresponding isocyanate according to the following reaction scheme:

[0149]

[0150] Starch still present can be incorporated into this layer as an auxiliary component at the same time, thereby further increasing the stability of the second crosslinked layer.In theory, however, this second crosslinked layer is mainly based on polyurea-type crosslinks as the main component, which define this layer.

[0151] Subsequently, a third crosslinking layer is formed by adding hydroxyl donor material around the resulting capsule shell or capsule wall, so that a spatially extended, predominantly polyurethane-based crosslink is formed.

[0152] By reacting the at least one isocyanate and / or isothiocyanate with the hydroxyl groups of the hydroxyl donor, a spatially crosslinked third shell layer is formed, the structure of which can theoretically be similar to the innermost first polyurethane crosslinked layer.

[0153] In order to obtain particularly efficient, dense and stable crosslinking, the further crosslinking with the hydroxyl donor is carried out at a temperature between 40°C and 60°C, and preferably at a temperature between 45°C and 55°C, still more preferably at a temperature between 45°C and 50°C.

[0154] It is further preferred that the step of further crosslinking by addition of a hydroxyl donor is carried out at a stirring speed of 900 to 1700 rpm, preferably 1000 to 1300 rpm, and a pH value of 5 to 9 and preferably at a pH value of 6 to 8.

[0155] The pH value required for crosslinking is set with the aid of an organic acid, such as formic acid or acetic acid. However, this step is optional, since the pH value is usually already shifted into the correct range due to the preceding polymerization reaction.

[0156] In this context, it has been shown that the addition of the hydroxyl donor in aqueous form leads to particularly stable crosslinking and thus particularly stable capsule shells and capsule walls. The concentration of the hydroxyl donor in the aqueous solution is preferably 10% to 70% and the concentration of the hydroxyl donor in the aqueous solution is still more preferably 40% to 60%.

[0157] The crosslinking described herein then preferably results in a defined third crosslinked layer surrounding the core comprising at least one active principle to be encapsulated.

[0158] The hydroxyl donor is preferably at least one polyol comprising two or more functional hydroxyl groups having good to very good water solubility at temperatures above 40° C., in particular selected from the group consisting of glycerol, propylene glycol and / or 1,3,5-trihydroxybenzene.

[0159] Surprisingly, it can be observed that the capsules according to the invention having such additional layers, mainly based on polyurethane, have significantly more stable properties than microcapsules without such additional stabilizing layers. In addition, such multilayer microcapsules (according to the invention) show significantly higher encapsulation efficiency of the active ingredients.

[0160] The addition of the hydroxyl donor takes place here with stirring at a stirring speed corresponding to the aforementioned stirring speed, in order to form the aforementioned crosslinked layer based on polyurethane and polyurea.

[0161] Thus, in a preferred embodiment, the present invention relates to a process for producing multilayer microcapsules, wherein the hydroxyl donor is a polyol with two or more functional hydroxyl groups, in particular glycerol, propylene glycol and / or 1,3,5-trihydroxybenzene.

[0162] In this layer, crosslinked structures of protective colloids may also be present as auxiliary components.

[0163] Optionally, the process according to the invention for preparing multilayer microcapsules comprises a further crosslinking step by adding amino acids, especially aromatic amino acids, still more preferably by adding the amino acids histidine and / or tryptophan, under stirring.

[0164] It has surprisingly been found that a crosslinking layer based on aromatic amino acids influences the diffusion of the active ingredient in such a way that the active ingredient no longer diffuses through the capsule wall, which in turn leads to an additional increase in the stability of the capsule.

[0165] Particularly advantageous results with regard to capsule shell formation are achieved when the further (optional) crosslinking is carried out with amino acids, ie amines, at a pH value of from 5 to 9 and preferably at a pH value of from 6 to 8.

[0166] Optionally, the pH value required for crosslinking is set, for example via addition of sodium hydroxide solution.

[0167] This step of further optional crosslinking is still more preferably carried out at a temperature of 50 to 70°C, preferably 55 to 65°C.

[0168] The corresponding amino acids, and in particular the aromatic amino acids, preferably have an aromatic ring formed from five to six carbon atoms and at least one nitrogen atom and two or more amino or imine groups in the aromatic system, and are in particular histidine and / or tryptophan.

[0169] It has been shown that the addition of the corresponding amino acids in aqueous form results in particularly excellent and high-strength polyurea-based crosslinking and thus correspondingly contributes to the stability of the obtained capsules. The concentration of the (aromatic) amino acid in the aqueous solution is preferably 10% to 70% and still more preferably 40% to 60%.

[0170] The further / additional optional crosslinking in the process of the invention is carried out over a period of about 5 to 30 minutes and preferably within 10 to 20 minutes at a stirring speed of 500 to 2000 rpm, preferably 1000 to 1500 rpm.

[0171] Alternatively, this additional, optional cross-linking step can be carried out after the cross-linking step described below by addition of at least one amine which reacts at alkaline pH values.

[0172] By adding at least one amine that reacts at alkaline pH values, the invention described herein, which includes a method for producing multilayer microcapsules, therefore also includes at least one fourth crosslinking layer, so that multilayer microcapsules are obtained with a defined crosslinking layer based on polyurea formed around the previously described crosslinking layer. These layers can be partially interwoven with one another. Thus, in addition, all layers can have a certain proportion of crosslinked protective colloid.

[0173] Particularly stable capsules are achieved when this crosslinking is carried out at an alkaline pH of 7 to 11 and preferably at an alkaline pH of 8 to 9 using amines that react at alkaline pH values.

[0174] Still more preferably, the at least fourth crosslinking step is carried out at a temperature of 60 to 80°C, and preferably at a temperature of 65 to 75°C and particularly preferably at a temperature of 60 to 70°C and under stirring.

[0175] The amine reacting at alkaline pH is preferably a guanidine cationic group donor and is selected from the group consisting of diamines, triamines and polyamines, arginine, guanidine hydrochloride and / or guanidine carbonate. However most preferred is guanidine carbonate as crosslinking agent to form the at least fourth crosslinked layer.

[0176] The addition of the guanidine cationic group donor in aqueous form under stirring enables the formation of a particularly stable capsule shell or capsule wall. The concentration of the guanidine cationic group donor in the aqueous solution is preferably 1% to 50% and still more preferably 10% to 25%. The stirring speed used here is advantageously between 500 rpm and 2000 rpm and preferably between 1000 rpm and 1500 rpm for 5 to 30 minutes and preferably for 10 to 20 minutes.

[0177] The suspension or emulsion then preferably has a pH of 7 to 8. Optionally, the pH required for further crosslinking is set, for example with the aid of formic acid or acetic acid or with the aid of sodium hydroxide solution.

[0178] In this sense, a preferred embodiment of the present invention relates to a method for preparing multilayer microcapsules, which comprises forming at least a fourth crosslinked layer, wherein the alkaline-reactive amine is a guanidine cationic group donor, in particular arginine, guanidine carbonate and / or guanidine hydrochloride.

[0179] Furthermore, in a preferred embodiment, the present invention relates to a method which, before curing, comprises an additional optional step in which the crosslinking of the microcapsules is terminated by adding an amine having functional amine groups.

[0180] The amines with functional amine groups described herein are preferably the corresponding amino acids, in particular alanine, glycine, aspartic acid, cysteine ​​and / or proline, and are used to terminate the last crosslinking layer and at the same time do not have spatial crosslinking, but rather terminate the network locally by inserting the corresponding building blocks into the last, outermost crosslinking layer.

[0181] Here, the outermost crosslinked layer or the microcapsules are terminated in an additional optional step before hardening at a pH value of 6 to 11 and preferably at a pH value of 7 to 9 and optionally at a temperature of more than 75° C., preferably at a temperature of 75° C. to 85° C., in order to shorten the reaction time.

[0182] The addition of the terminating amine is preferably carried out in aqueous form at a concentration of preferably 1% to 50% and preferably at a concentration of 10% to 25% with stirring. Analogously to the above-described addition of the corresponding crosslinker, stirring is carried out here at 500 to 2000 rpm, preferably at 1000 to 1500 rpm, for a period of between 1 and 10 minutes or preferably 2 to 5 minutes.

[0183] Against this background, a further preferred embodiment of the present invention therefore relates to a method according to the invention, wherein the amine used to seal the microcapsules in an additional optional step before hardening is an amino acid, in particular an amino acid comprising an amino group, more preferably alanine, glycine, aspartic acid, cysteine ​​and / or proline.

[0184] This additional step of terminating the capsule wall or capsule shell surprisingly enables still more stable and more efficiently encapsulated microcapsules, while at the same time the required shell material can be reduced overall.

[0185] After complete crosslinking, the encapsulated microcapsules are present as coarse microcapsules in the form of an aqueous dispersion having a still relatively soft and flexible capsule shell or capsule wall.

[0186] That is, the multilayer microcapsules obtained subsequently need to be subjected to an additional hardening process in order to harden the still relatively soft, flexible and unstable multilayer microcapsule shell or microcapsule wall and thereby impart stability thereto. The hardening of the multilayer capsules formed at this point after the last crosslinking or termination step is carried out at a temperature of about 80° C. and generally lasts for 60 to 240 minutes. It is also advantageous to add substances for hardening to the external aqueous phase. These substances are, for example, natural vegetable tanning agents.

[0187] Furthermore, it has been surprisingly shown that direct hardening of the microcapsules at 80° C. results in more stable capsules relative to gradual heating.

[0188] The method for producing multilayer microcapsules comprising a polyurethane layer and a polyurea layer according to the invention and described herein is particularly unique in the choice of different pH ranges in which the individual crosslinking steps are carried out. In combination with a gradually increasing temperature range, individual and defined layers can thus be produced. The composition transitions between the layers are relatively steep here, that is to say the layers are delimited and defined in a materially very different manner. In theory, however, the crosslinking described herein can also be carried out at room temperature, but this results in wider gradients, lower stability and longer reaction times.

[0189] Therefore, the method described in this article can be used to alternately coat defined polyurethane-based and polyurea-based crosslinked layers around a core comprising at least one hydrophobic active ingredient and thereby produce a stable multilayer capsule wall or capsule shell. The main components of the corresponding layers essentially form polyurea or polyurethane connections. In addition, protective colloids (such as starch) can also be present in the individual layers through polyurethane connections. Partial crosslinking of the alternating individual layers with each other is not excluded to a certain extent. Nevertheless, the following layers can be formed in theory with the help of this method: a first layer comprising a polyurethane structure or consisting of a polyurethane structure, a second layer comprising a polyurea structure or consisting of a polyurea structure, a third layer comprising a polyurethane structure or consisting of a polyurethane structure, and at least a fourth layer comprising a polyurea structure or consisting of a polyurea structure.

[0190] In this context, the innermost first capsule layer consists essentially of a crosslinked matrix based on polyurethane (step a), followed by a second crosslinked layer essentially based on polyurea (step b). The third layer is again preferably based on polyurethane crosslinks (step c), while the outermost at least fourth layer preferably has a crosslinking system essentially based on polyurea (step d). Optionally, further additional or terminating crosslinking layers are conceivable, for example based on polyurea, by means of crosslinking with other amines (e.g. amino acids), which bring additional stability gains by means of additional additional crosslinking.

[0191] The multilayered and hardened microcapsules thus formed are subsequently separated from the reaction solution and optionally dried.

[0192] After hardening, the microcapsules prepared according to the process of the invention are present as a dispersion in water, which is also referred to as microcapsule dispersion. The microcapsules are essentially already marketable in this form; however, for preservation purposes, it is recommended to dry them. Suitable drying methods are, for example, freeze drying or spray drying.

[0193] Furthermore, the present invention is unique in that amino acids as main components are cross-linked with starch and isocyanate, preferably by a targeted catalytic mechanism, and thereby achieving the preparation of bio-based and biodegradable biocompatible polymer-based microcapsules.

[0194] The process described herein generally allows the production of microcapsules which, due to more efficient multiply crosslinked layers, allow a significant saving in shell material and can achieve a reduction in the required isocyanate proportions compared to capsules of the prior art without adversely affecting the stability of the capsules. This can be attributed on the one hand to the more efficient and defined crosslinking by the individual layers and on the other hand to the generally alternating / different composition of the individual capsule shell layers.

[0195] Due to the efficient spatial crosslinking, the multilayer microcapsules according to the invention thus have a significantly lower isocyanate proportion overall compared to capsules according to the prior art. The absolute isocyanate proportion of the microcapsules described here corresponds to only 1 / 50 of the total capsule including the active ingredient. Isocyanates in this sense do not directly form a constituent of the capsule wall or capsule shell, but only serve as crosslinkers between, for example, significantly larger starch molecules. Assuming a quantitative reaction of the starting materials, 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 relatively small amount they represent, isocyanates can only be regarded as crosslinkers.

[0196] Compared to capsules of the prior art based on pure polyurethane bonding, the method described herein, which includes targeted deposition at defined temperatures and times, can produce microcapsules in which the ratio of the capsule shell to the total capsule volume can be reduced from 1 to 14 to 1 to 21, and the overall required shell material can be significantly reduced without causing a loss of stability, as shown in the examples below. The ratio of capsule wall material to the total capsule (capsule consisting of active ingredient and capsule wall material) in the prior art (pure polyurea capsules) is 6.8% by weight, while in the multilayer microcapsules described herein, the capsule wall material can be reduced to 4.4% by weight, but still obtain an additional stability gain. This corresponds to a reduction of 36% in wall material. Thus, the method described herein can produce stable microcapsules, in which the amount of capsule wall material required and in particular the amount of isocyanate required can be significantly reduced relative to the capsules of the prior art, while at the same time the amount of active ingredient (active ingredient mixture) to be encapsulated does not need to be reduced.

[0197] Furthermore, despite a decreasing isocyanate proportion and thus a decreasing degree of crosslinking, it is surprisingly still possible to produce stable microcapsules which have a clear improvement in sensory properties (fragrance release capacity) compared to capsules of the prior art.

[0198] Preferably, protective colloids, in particular starch, can also be included as auxiliary components in any of the other defined crosslinked layers and embedded in the corresponding network based on polyurethane or polyurea. Due to the structure of starch, a further branched, spatially extended and further stabilized network can be generated, which interweaves the layers and thus forms a stable crosslinked matrix in the form of a capsule shell or capsule wall. These auxiliary components in the corresponding layers produce improved spatial crosslinking.

[0199] Protective colloids, such as starch, form an important constituent of the first crosslinking of polyurethanes, which is already achieved by reaction with a catalyst at temperatures of 25° C. to 40° C. It has surprisingly been found that the modification of polyols to polysaccharides leads to higher stability, while at the same time the dual function of the protective colloid as a stabilizing factor for the emulsion and as a reaction partner (for example compared to polyvinyl alcohol) is further improved.

[0200] As already mentioned above, the microcapsules according to the invention comprise in their core at least one active ingredient to be encapsulated which has preferably hydrophobic properties as core material.

[0201] As core material for the preparation of the multilayer microcapsules according to the invention, any material suitable for encapsulation in microcapsules can be considered in principle. As materials to be encapsulated, hydrophobic, water-insoluble or water-immiscible liquids or solids and suspensions are preferably considered. In the context of this specification, the term "hydrophobic active ingredient" means that the material to be encapsulated is located in the inner non-aqueous phase and does not mix with the outer aqueous phase.

[0202] In a particularly preferred embodiment of the present invention, the microcapsules according to the present invention are designed to have a core material formed by at least one hydrophobic active ingredient, in particular hydrophobic fragrance substances or fragrance agents or hydrophobic fragrance oils or perfume oils (fragrance substance mixtures or fragrance agent mixtures), pesticides, biocides, insecticides, substances selected from the group of repellents, food additives, cosmetic active ingredients, pharmaceutical active ingredients, dyes, agricultural chemicals, dyes, luminescent pigments, optical brighteners, solvents, waxes, silicone oils, lubricants, and mixtures of the above-mentioned active ingredients, that is, as long as they are sufficiently insoluble in water or immiscible with the aqueous phase, because otherwise no emulsion can be formed and polymer deposition on the surface of the droplets cannot be carried out.

[0203] In a preferred variant of the invention, hydrophobic fragrance substances or fragrance oils or fragrances or fragrance mixtures (perfume oils), aromas or ingredients of biogenic origin come into consideration as active ingredients.

[0204] In a preferred development of the present invention, the microcapsules according to the invention have a core material in the form of a hydrophobic individual fragrance substance or individual fragrance agent, wherein the core material comprises at least one individual fragrance substance or individual fragrance agent or a mixture thereof selected from one or more of the following groups:

[0205] - hydrocarbons, for example 3-carene; α-pinene; β-pinene; α-terpene; γ-terpene; p-cymene; bisabolol; camphene; caryophyllene; cedrene; afarnesene; limonene; longifolene; myrcene; ocimene; valenciarene; (E,Z)-1,3,5-undecatriene;

[0206] - fatty 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; a mixture of 3,4,5,6,6-pentamethyl-3,4-hepten-2-ol and 3,5,6,6-tetramethyl-4-methyleneheptan-2-ol (E,Z)-2,6-nonadienol; 3,7-dimethyl-7-methoxyoctan-2-ol; 9-decenol; 10-undecenol; 4-methyl-3-decen-5-ol;

[0207] - fatty aldehydes and their acetals, for example hexanal; heptanal; octanal; nonanal; decanal; undecanal; dodecanal; tridecanal; 2-methyloctanal; 2-methylnonanal; (E)-2-hexenal; (Z)-4-heptenal; 2,6-dimethyl-5-heptenal; 10-undecenal; (E)-4-decenal; 2-dodecenal; 2,6,10-trimethyl-5,9-undecadienal; heptaldehyde diethyl acetal; 1,1-dimethoxy-2,2,5-trimethyl-4-hexene; citronellyl oxoacetaldehyde;

[0208] - aliphatic ketones and their ketoximes, for example 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;

[0209] - aliphatic sulfur compounds, such as 3-methylthiohexanol; 3-methylthiohexyl acetate; 3-mercaptohexanol; 3-mercaptohexyl acetate; 3-mercaptohexyl butyrate; 3-acetylthiohexyl acetate; 1-menthene-8-thiol;

[0210] - aliphatic nitriles, for example 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;

[0211] - aliphatic carboxylic acids and their esters, for example (E)- and (Z)-3-hexenol 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; butyl isopentyl ester; hexyl butyrate; (E)- and (Z)-3-hexenol isobutyrate; hexyl crotonate; ethyl isovalerate; ethyl 2-methylpentanoate; ethyl hexanoate; allyl hexanoate; ethyl heptanoate; allyl heptanoate; ethyl octanoate; ethyl-(E,Z)-2,4-decadienoate; methyl 2-octynoate; methyl 2-nonynoate; allyl 2-isopentyloxyacetate; methyl-3,7-dimethyl-2,6-octadienoate;

[0212] - acyclic terpene alcohols, for example citronellol; geraniol; nerol; linalool; lavandulol; 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-1-ol; and their formates, acetates, propionates, isobutyrates, butyrates, isovalerates, valerates, hexanoates, crotonates, tiglic acid esters, 3-methyl-2-butenoate esters;

[0213] - acyclic terpene aldehydes and terpene ketones, for example geranial; neral; citronellal; 7-hydroxy-3,7-dimethyloctanal; 7-methoxy-3,7-dimethyloctanal; 2,6,10-trimethyl-9-undecenal; geranylacetone; and the dimethyl acetal and diethyl acetal of geranial, neral and 7-hydroxy-3,7-dimethyloctanal;

[0214] - cyclic terpene alcohols, for example menthol; isopulegol; α-terpineol; terpineol-4; menthan-8-ol; menthan-1-ol; menthan-7-ol; bornyl alcohol; isobornyl alcohol; linalool oxide; knopol; cedrol; ambroxanol; vetiverol; guaiacol; and their formates, acetates, propionates, isobutyrates, butyrates, isovalerates, valerates, hexanoates, crotonates, tiglic acid esters, 3-methyl-2-butenoates;

[0215] - cyclic terpene aldehydes and terpene ketones, for example menthone; isomenthone; 8-mercaptomenthan-3-one; carvone; camphor; fenchone; α-ionone; β-ionone; α-n-methylionone; β-n-methylionone; α-isomethylionone; β-isomethylionone; α-iron; β-iron; α-damascenone; β-damascenone; γ-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-methylnaphthalene-8(5H)-one; nootkatone; dihydronootkatone; α-sweet orange aldehyde; β-sweet orange aldehyde; acylated cedarwood oil (methyl cedarwood ketone);

[0216] - cyclic alcohols, for example 4-tert-butylcyclohexanol; 3,3,5-trimethylcyclohexanol; 3-isocamphorylcyclohexanol; 2,6,9-trimethyl-(Z2,Z5,E9)cyclododecatrien-1-ol; 2-isobutyl-4-methyltetrahydro-2H-pyran-4-ol; from the group of cycloaliphatic alcohols, for example 3,3,3-trimethylcyclohexylmethanol; 2-methyl-4-(2,2,3-trimethyl-3-cyclopenten-1-yl)butanol; 2-methyl-4-(2,2,3-trimethyl-3-cyclopenten-1-yl)-2-buten-1-ol; 2-ethyl 3-Methyl-5-(2,2,3-trimethyl-3-cyclopenten-1-yl)-pentan-2-ol; 3-methyl-5-(2,2,3-trimethyl-3-cyclopenten-1-yl)-4-penten-2-ol; 3,3-dimethyl-5-(2,2,3-trimethyl-3-cyclopenten-1-yl)-4-penten-2-ol; 1-(2,2,6-trimethylcyclohexyl)pentan-3-ol; 1-(2,2,6-trimethylcyclohexyl)hexan-3-ol;

[0217] - cyclic and cycloaliphatic ethers, for example eucalyptol; cedryl methyl ether; cyclododecyl methyl ether; (ethoxymethoxy)cyclododecane; α-cedryl oxide; 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;

[0218] - cyclic ketones, for example 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-methylcyclopentadecenone; 4-(1-ethoxyvinyl)-3,3,5,5-tetramethylcyclohexanone; 4-tert-pentylcyclohexanone; 5-cyclohexadecene-1-one; 6,7-dihydro-1,1,2,3,3-pentamethyl-4(5H)-indanone; 9-cycloheptadecene-1-one; cyclopentadecenone; cyclohexadecenone;

[0219] - cycloaliphatic aldehydes, for example 2,4-dimethyl-3-cyclohexenecarboxaldehyde; 2-methyl-4-(2,2,6-trimethyl-cyclohexen-1-yl)-2-butenal; 4-(4-hydroxy-4-methylpentyl)-3-cyclohexenecarboxaldehyde; 4-(4-methyl-3-penten-1-yl)-3-cyclohexenecarboxaldehyde;

[0220] - cycloaliphatic ketones, for example 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-naphthyl methyl ketone; methyl-2,6,10-trimethyl-2,5,9-cyclododecatrienyl ketone; tert-butyl-(2,4-dimethyl-3-cyclohexen-1-yl) ketone;

[0221] - esters of cyclic alcohols, for example 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-methano-3a,4,5,6,7,7a-hexahydro-5- or -6-indenyl acetate; 4,7-methano-3a,4,5,6,7,7a-hexahydro-5- or -6-indenyl propionate; 4,7-methano-3a,4,5,6,7,7a-hexahydro-5- or -6-indenyl isobutyrate; 4,7-methanooctahydro-5- or -6-indenyl acetate;

[0222] - esters of cycloaliphatic carboxylic acids, for example allyl-3-cyclohexylpropionate; allylcyclohexyloxyacetate; 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;

[0223] - aromatic hydrocarbons, such as styrene and diphenylmethane;

[0224] - aromatic aliphatic 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-ethanol; 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;

[0225] - Esters of aromatic aliphatic alcohols with aliphatic carboxylic acids, for example benzyl acetate; benzyl propionate; benzyl isobutyrate; benzyl isovalerate; 2-phenylethyl acetate; 2-phenylethyl propionate; 2-phenylethyl isobutyrate; 2-phenylethyl isovalerate; 1-phenylethyl acetate; α-trichloromethylbenzyl acetate; α,α-dimethylphenylethyl acetate; α,α-dimethylphenylethyl butyrate; cinnamyl acetate; 2-phenoxyethyl isobutyrate; 4-methoxybenzyl acetate;

[0226] - aromatic aliphatic ethers, for example 2-phenylethyl methyl ether; 2-phenylethyl isopentyl ether; 2-phenylethyl-1-ethoxyethyl ether; phenylacetaldehyde dimethyl acetal; phenylacetaldehyde-diethyl acetal; solanum nigrum-dimethyl acetal; phenylacetaldehyde-glycerol acetal; 2,4,6-trimethyl-4-phenyl-1,3-dioxane; 4,4a,5,9b-tetrahydroindeno[1,2-d]-m-dioxin; 4,4a,5,9b-tetrahydro-2,4-dimethylindeno[1,2-d]-m-dioxin;

[0227] - aromatic and aromatic aliphatic aldehydes, for example benzaldehyde; phenylacetaldehyde; 3-phenylpropanal; hydroataldehyde; 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; α-butylcinnamaldehyde; α-amylcinnamaldehyde; α-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;

[0228] - aromatic and aromatic aliphatic ketones, for example acetophenone; 4-methylacetophenone; 4-methoxyacetophenone; 4-tert-butyl-2,6-dimethylacetophenone; 4-phenyl-2-butanone; 4-(4-hydroxyphenyl)-2-butanone; 1-(2-naphthyl)ethanone; benzophenone; 1,1,2,3,3,6-hexamethyl-5-indanylmethyl ketone; 6-tert-butyl-1,1-dimethyl-4-indanylmethyl 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-naphthylacetophenone;

[0229] - aromatic and aromatic aliphatic carboxylic acids and their esters, for example benzoic acid; phenylacetic acid; methyl benzoate; ethyl benzoate; hexyl benzoate; benzyl benzoate; methyl phenyl acetate; ethyl phenyl acetate; geranyl phenyl acetate; phenylethyl-phenyl acetate; methyl cinnamate; ethyl cinnamate; benzyl cinnamate; phenylethyl cinnamate; cinnamyl cinnamate; allylphenoxyacetate; methyl salicylate; isopentyl salicylate; hexyl salicylate; cyclohexyl salicylate; cis-3-hexenyl salicylate; benzyl salicylate; phenylethyl salicylate; methyl-2,4-dihydroxy-3,6-dimethylbenzoate; ethyl-3-phenylglycerate; ethyl-3-methyl-3-phenylglycerate;

[0230] - nitrogen-containing aromatic compounds, for example 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-methylpentenoic acid nitrile; methyl aminobenzoate; methyl-N-methylaminobenzoate; Schiff bases of methyl aminobenzoate with 7-hydroxy-3,7-dimethyloctanal, 2-methyl-3-(4-tert-butylphenyl)propanal or 2,4-dimethyl-3-cyclohexenecarboxaldehyde; 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;

[0231] -phenols, phenyl ethers and phenyl esters, for example estragole; anethole; eugenol; eugenol methyl ether; isoeugenol; isoeugenol methyl ether; thymol; carvacrol; diphenyl ether; β-naphthyl methyl ether; β-naphthyl ethyl ether; β-naphthyl isobutyl ether; 1,4-dimethoxybenzene; eugenol acetate; 2-methoxy-4-methylphenol; 2-ethoxy-5-(1-propenyl)phenol; p-tolylphenyl acetate; from the group of the heterocyclic compounds, for example 2,5-dimethyl-4-hydroxy-2H-furan-3-one; 2-ethyl-4-hydroxy-5-methyl-2H-furan-3-one; 3-hydroxy-2-methyl-4H-pyran-4-one; 2-ethyl-3-hydroxy-4H-pyran-4-one;

[0232] -lactones, such as 1,4-octanolactone; 3-methyl-1,4-octanolactone; 1,4-nonanolactone; 1,4-decanolactone; 8-decene-1,4-lactone; 1,4-undecanolactone; 1,4-dodecanolactone; 1,5-decanolactone; 1,5-dodecanolactone; 1,15-pentadecanolactone; cis- and trans-11-pentadecanolactone; cis- and trans-12-decene-1,15-lactone Pentadecene-1,15-lactone; 1,16-hexadecene-lactone; 9-hexadecene-1,16-lactone; 10-oxa-1,16-hexadecene-lactone; 11-oxa-1,16-hexadecene-lactone; 12-oxa-1,16-hexadecene-lactone; 1,12-dodecanoic acid vinyl ester; 1,13-tridecanedioic acid vinyl ester; coumarin; 2,3-dihydrocoumarin; octahydrocoumarin;

[0233] and stereoisomers, enantiomers, positional isomers, diastereomers, cis / trans isomers or epimers of the above substances.

[0234] In an alternative embodiment, a fragrance oil or perfume oil is used as the core material or as the active ingredient used. This involves a composition comprising at least one fragrance. Such a composition, in particular a fragrance oil or perfume oil, preferably comprises two, three, four, five, six, seven, eight, nine, ten or more fragrances. The flavor or perfume oil is preferably selected from the group of extracts from natural raw materials, such as essential oils, condensed esters, absolutes, resins, resinoids, balsam gums, tinctures, for example ambergris tincture; balsam oil; angelica seed oil; angelica root oil; anise oil; valerian oil; basil oil; tree moss absolute; bay leaf oil; mugwort oil; benzoin resin; bergamot oil; beeswax absolute; birch tar; bitter almond oil; savory oil; buchu leaf oil; balsam oil; juniper oil; calamus oil; camphor oil; ylang ylang oil; cardamom oil; balsam bark oil; black currant oil; black currant absolute; castoreum absolute; cypress leaf oil; cypress oil; labdanum oil; citronella oil; lemon oil; copaiba balsam; copaiba balsam oil; coriander oil; zingiber officinale root oil; cumin oil; cypress oil; indigo oil; dill weed oil; Dill Seed Oil; Orange Leaf Water Absolute; Oakmoss Absolute; Elemi Resin Oil; Tarragon Oil; Lemon Eucalyptus Oil; Eucalyptus Oil; Cumin Oil; Spruce Needle Oil; Galbanum Oil; Galbanum Resin; Geranium Oil; Grapefruit Oil; Guaiac Wood Oil; Guyun Balm; Guyun Balm Oil, Helichrysum Absolute; Helichrysum Oil; Ginger Oil; Iris Root Absolute; Iris Root Oil; Jasmine Absolute; Calamus Oil; Chamomile Oil, Blue; Chamomile Oil, Roman; Carrot Seed Oil; Balsam Bark Oil; Pine Needle Oil; Spearmint Oil; Caraway Oil; Lavandula Oil; Lavandula Absolute; Lavandula Resin; Lavender Absolute; Lavender Oil; Lavender Absolute; Lavender Oil; Lemongrass Oil; Lovage Oil; Lime Oil Distilled; Lime Oil Pressed; Linalool; Litsea Cubeba Oil; Bay Leaf Oil; Nutmeg Oil Marjoram oil; Mandarin oil; Masson pine oil; Mimosa absolute; Musk granules; Musk tincture; Clary sage oil; Nutmeg oil Myrrh Absolute; Myrrh Oil; Myrtle Oil; Carnation Leaf Oil; Carnation Flower Oil; Neroli Oil; Frankincense Absolute; Frankincense Oil; Acacia Oil; Neroli Absolute; Orange Oil; Oregano Oil; Palmarosa Oil; Patchouli Oil; Perilla Oil; Peruvian Balm Oil; Parsley Leaf Oil; Parsley Seed Oil; Petitgrain Oil; Peppermint Oil; Peppermint Oil; Pine Oil; Porridge Oil Rose absolute; rosewood oil; rose oil; rosemary oil; sage oil, Dalmatian; sage oil, Spanish; sandalwood oil; celery seed oil; lavender oil; anise oil; benzoin oil; marigold oil; fir needle oil; tea tree oil; rosin oil; thyme oil; tolu balsam; tonka absolute; tuberose absolute; vanilla extract; violet leaf absolute; verbena oil; vetiver oil; juniper berry oil; wine yeast oil; wormwood oil; wintergreen oil; ylang-ylang oil; hyssop flower oil; civet absolute; cinnamon leaf oil; cinnamon bark oil; and fractions thereof, or components isolated therefrom.

[0235] In another variant of the method according to the invention, the aromatic substances can also be encapsulated as core material in the form of individual aromatics, wherein the core material comprises at least one individual aromatic substance or a mixture thereof as active ingredient.

[0236] Typical examples of aromatic substances which can be encapsulated in the sense of the present invention are selected from the group consisting of: acetophenone; allyl hexanoate; α-ionone; β-ionone; anisaldehyde; anisyl acetate; anisyl formate; benzaldehyde; benzothiazole; benzyl acetate; benzyl alcohol; benzyl benzoate; β-ionone; butyl butyrate; butyl hexanoate; butenylphthalide; carvone; camphene; caryophyllene; eucalyptol; cinnamyl acetate; citral; citronellol; citronellal; citronellyl acetate; cyclohexyl acetate; cymene; damascenone; Decanolide; dihydrocoumarin; dimethyl anthranilate; dimethyl anthranilate; dodecanolactone; ethoxyethyl acetate; ethyl butyrate; ethyl butyrate; ethyl decanoate; ethyl caproate; ethyl crotonate; ethyl furanone; ethyl guaiacol; ethyl isobutyrate; ethyl isovalerate; ethyl lactate; ethyl methylbutyrate; ethyl propionate; eucalyptol; eugenol; ethyl heptanoate; 4-(p-hydroxyphenyl)-2-butanone; gamma-decanolide; geraniol; geranyl acetate; geranyl acetate; viniferal; methyl dihydrojasmonate (e.g. ); jasminaldehyde; 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 hexanoate; trans-2-hexenyl hexanoate; cis-3-hexenyl formate; cis-2-hexyl acetate; cis-3-hexyl acetate; trans-2-hexyl hexanoate; cis-3-hexyl formate; p-hydroxybenzyl acetone; isopentanol; isopentanyl isovalerate; isobutyl butyrate; isobutyraldehyde; isoeugenol methyl ether; isopropyl methylthiazole; lauric acid; levulinic acid; linalool; linalool oxide ; linalyl acetate; menthol; menthofuran; methyl aminobenzoate; methyl butanol; methyl butyric acid; 2-methylbutyl acetate; methyl caproate; methyl cinnamate; 5-methylfurfural; 3,2,2-methylcyclopentenolone; 6,5,2-methylheptenone; methyl dihydrojasmonate; methyl jasmonate; 2-methyl methyl butyrate; 2-methyl-2-pentenol 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; δ-octalactone; γ-octalactone; 2-octanol; 3-octanol; 1,3-octanol; 1-octylethyl esters; 3-octyl acetate; palmitic acid; paraaldehyde; phellandrene; pentanedione; phenylethyl acetate; phenylethyl alcohol; phenylethyl alcohol; phenylethyl isovalerate; piperonal; propionaldehyde; propyl butyrate; pulegone; pulegol; sweet orange aldehyde; thiothiazole; terpenes; terpineol; terpinolene; 8,3-thiomenthone; 4,4,2-thiomethylpentyl ketone; thymol; δ-undeca lactone; γ-undeca lactone; valencia orangene; valeric acid; vanillin; acetoin; ethyl vanillin; ethyl vanillin isobutyrate (3-ethoxy-4-isobutyryloxybenzaldehyde); 2,5-dimethyl-4-hydroxy-3(2H)-furanone and its derivatives (preferably soy sauce ketone (2-ethyl-4-hydroxy-5-methyl-3( 2H)-furanone), homofuranone 2-ethyl-5-methyl-4-hydroxy-3(2H)-furanone and 5-ethyl-2-methyl-4-hydroxy-3(2H)-furanone); maltol and maltol derivatives (preferably ethyl maltol); coumarin and coumarin derivatives; γ-lactones (preferably γ-undecanolactone, γ-nonalactone, γ-decanolactone); δ-lactones (preferably 4-methyl δ-decanolactone, dihydropentylpyran, δ-decanolactone, tuberolactone); methyl sorbate; divanillin; 4-hydroxy-2(or 5)-ethyl-5(or 2)-methyl-3(2H)furanone; 2-hydroxy-3-methyl-2-cyclopentenone;3-Hydroxy-4,5-dimethyl-2(5H)-furanone; isopentyl acetate; ethyl butyrate; n-butyl acetate; isopentyl butyrate; 3-methyl-ethyl butyrate; ethyl hexanoate; allyl hexanoate; n-butyl hexanoate; ethyl octanoate; ethyl-3-methyl-3-phenylglycerate; 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-aldehyde; phenylacetaldehyde; 2-methyl-3-(methylthio)furan; 2-methyl-3-furanthiol; bis(2-methyl-3-furfuryl) disulfide; furfurylthiol; methylthiopropanal; 2-acetyl-2-thiazoline; 3-mercapto-2-pentanone; 2,5-dimethyl-3-furanthiol; 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-undecenal; 12-methyltridecal Carbonaldehyde; 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; cinnamyl alcohol; methyl salicylate; isopulegol and stereoisomers, enantiomers, positional isomers, diastereomers, cis / trans isomers or epimers of these substances not explicitly mentioned in this text. ;

[0237] Most preferably, in the preparation of the multilayer microcapsules, a fragrance or aroma substance selected from the group consisting of: AGRUMEX LC; citronellal nitrile; aldehyde C11 undecyl aldehyde; aldehyde C12 lauryl aldehyde; aldehyde C12 MNA; aldehyde C14 SOG; aldehyde C16 SOG; allyl isopentyl acetate; allyl hexanoate; allyl cyclohexyl propionate; allyl heptanoate; wood ambergris 10TEC; Woody Ambergris Crystals 10% IPM; Ambrox; Natural anethole from anise; Pure anisaldehyde; Benzyl lactone; benzyl salicylate; borneol L / isoborneol 65 / 35; Buchu leaf oil; citronellol 950; clonal; cyclohexyl salicylate; supra-paracymene; damascenone delta; dihydromyrcenol; dimethyl benzyl butyrate; dynasty ketone; cycloethylene tridecane ester; ethyl methyl butyrate-2; ethyl crocetin; natural eucalyptol; eucalyptus globulus leaf oil 80 / 85%; natural eugenol; Sweet natural aromatic anise oil; hazelnut ketone 10% IPM; hazelnut ketone; flopa; geranyl ketone; geraniol 60; Methyl dihydrojasmonate; tricyclodecenyl acetate; cymene; tricyclodecenyl propionate; hexenyl acetate, cis-3; hexenyl salicylate, cis-3; hexyl acetate; hexyl acetate S; hexyl isobutyrate; hexyl salicylate; isoamyl butyrate; isobornyl acetate; isopropyl methyl butyrate-2; isomethyl ionone 70; Java sandalwood; camphor (KAMPFER) DL; cresol methyl ether P (CR<10PPM); limonitrile; privet aldehyde; lily aldehyde; linalool; matricarbaldehyde; melon aldehyde; methyl heptane carbonate; methyl octyne carbonate; muscene; neocyclic citral; nerol; naphthyl methyl ether crystals; nerol; sabdariffa; orange oil; cyclohexanone; tridecene nitrile (OZONIL); patchouli oil ENTF.; vegetable oil triglycerides; phellandrene fraction from eucalyptus oil; Phenylethyl acetate; Homocis-rose oxide; Styryl acetate; Terpene γ; Tetrahydrolinalool; TIMBERSILK; Triethyl citrate; Methyl decenyl alcohol; Ligustrum aldehyde; Methyl cedryl ketone; K and a mixture of the above active ingredients.

[0238] In another variant of the method according to the invention, it is also possible to encapsulate biogenic components as core material, wherein the core material comprises at least one biogenic component or a mixture thereof.

[0239] Biologically derived ingredients are understood to be biologically active ingredients, such as tocopherol, tocopherol acetate, tocopherol palmitate, ascorbic acid, primrose yellow, carnosine, caffeine, (deoxy)ribonucleic acid and its fragmentation products, β-glucan, retinol, bisabolol, allantoin, phytantriol, panthenol, AHA acid, amino acids, ceramides, pseudoceramides, essential oils, plant extracts, and multivitamins.

[0240] In a particularly preferred embodiment, the present invention therefore relates to a method for preparing multilayer microcapsules, wherein the at least one, preferably hydrophobic, active ingredient to be encapsulated is selected from the group consisting of: fragrances, fragrance substances, aromatic substances, biocides, insecticides, substances selected from the group of repellents, food additives, cosmetic active ingredients, pharmaceutical active ingredients, agricultural chemicals, dyes, luminescent pigments, optical brighteners, solvents, waxes, silicone oils, lubricants, and mixtures of the above-mentioned active ingredients, the active ingredient being particularly preferably a fragrance or a fragrance mixture, and therefore preferably a hydrophobic fragrance substance or fragrance or a hydrophobic fragrance substance mixture or a fragrance mixture.

[0241] The uniqueness of this type of microcapsules lies in excellent stability and excellent release capacity. In the case of flavoring agents as active ingredients (core materials), the multilayer microcapsules prepared in this way also show outstanding sensory properties, which can be attributed to the stable active ingredient encapsulation and the less active ingredient loss associated with it. The particularly defined and good sequence of method steps produces such a defined, dense and very thin capsule shell or capsule wall, which achieves very good sensory performance of the capsule in a synergistic manner as a quartet. In addition, due to the different chemical properties of the selected crosslinking agents, particularly thin capsule walls or capsule shells can be prepared, which still maintain the analytical stability (of the active ingredient in the capsule) and further improve the sensory performance.

[0242] As has been surprisingly found, the corresponding fragrance capsules produced according to the method of the invention have a higher stability and reduced undesired leaching of perfume oil, which can be attributed in particular to a more efficient encapsulation of the fragrance. The capsules produced in this way therefore exhibit a significantly higher odor intensity when the fragrance is released by opening the capsule by means of mechanical friction or by pressure.

[0243] A further subject matter of the present invention is therefore multilayer microcapsules produced according to the process described herein, which comprise at least one hydrophobic aroma substance or aroma agent.

[0244] As already explained above, such microcapsules, which comprise a multilayer capsule shell or capsule wall, have particularly good active ingredient release properties, while at the same time also having a significantly lower polymer content (capsule wall component). At the same time, there is no restriction to a single fragrance. In other words, there are universal capsules which, depending on the current situation, can encapsulate many or even any tested fragrance substances or fragrances.

[0245] An additional aspect of the present invention relates to a multilayer microcapsule comprising a core and a capsule shell, wherein the core comprises at least one hydrophobic fragrance substance or fragrance agent, wherein the capsule shell comprises or consists of the following items from the inside to the outside:

[0246] (v) a first layer comprising or consisting of polyurethane;

[0247] (vi) a second layer comprising or consisting of polyurea;

[0248] (vii) a third layer comprising or consisting of polyurethane; and

[0249] (viii) at least a fourth layer comprising or consisting of polyurea.

[0250] The alternating crosslinking of isocyanate units with amine or hydroxyl groups results in a stable capsule wall formed from alternating defined and dense and therefore stable layers based predominantly on polyurethane and polyurea.

[0251] Surprisingly, it has been found that microcapsules produced by the process of the invention have a multilayer capsule shell which essentially comprises a first innermost layer based on polyurethane, a second layer based on polyurea, a third layer based on polyurethane and at least one fourth outermost layer based on polyurea.

[0252] As already indicated previously, the innermost first barrier layer is formed predominantly by the crosslinking of the at least one isocyanate and a protective colloid (e.g. a polysaccharide). The second crosslinked layer is produced predominantly by the polyaddition of isocyanates and acidic-reactive amines (e.g. amino acids), while the third crosslinked layer is caused predominantly by the reaction of isocyanates with hydroxyl donors. Finally, the capsules are surrounded by at least one fourth crosslinked layer, which is formed predominantly by the reaction of isocyanates with at least one alkaline-reactive amine. Thus, the multilayer microcapsules of the invention generally have an alternating shell system based on polyurethane and polyurea linkages, which imparts a particularly high stability to the capsules.

[0253] By constructing a capsule wall based on a plurality of individual defined and alternating layers, which are formed by targeted deposition at defined temperatures and times and support and surround one another, the invention makes it possible to produce particularly stable microcapsules with outstanding sensory properties, while at the same time significantly reducing the shell components.

[0254] Therefore, in another preferred embodiment, the present invention relates to multilayer microcapsules, wherein:

[0255] (i) the first layer comprises the following crosslinking units: at least one isocyanate having two or more isocyanate groups and a protective colloid;

[0256] (ii) the second layer comprises the following crosslinking units: at least one isocyanate having two or more isocyanate groups and an amine that reacts at an acidic pH;

[0257] (iii) the third layer comprises the following crosslinking units: at least one isocyanate having two or more isocyanate groups and a hydroxyl donor; and

[0258] (iv) the at least fourth layer comprises the following crosslinking units: at least one isocyanate having two or more isocyanate groups and at least one amine that reacts at alkaline pH.

[0259] Surprisingly, it has been shown that the microcapsules described herein have a higher stability and have outstanding sensory properties (outstanding release capacity of the microcapsules), while requiring less shell material overall compared to prior art capsules of similar stability, as demonstrated in the examples below. Thus, the present invention can provide an efficient aromatization or fragrance system, for example, by efficiently encapsulating hydrophobic aroma substances or fragrance agents.

[0260] In addition, a wide range of hydrophobic active ingredients can be encapsulated with the microcapsules described herein. This makes it possible to no longer have restrictions with respect to individual active ingredients such as fragrances. In other words, there are universal capsules that can encapsulate most of the tested fragrances according to current conditions.

[0261] It is particularly advantageous within the scope of the invention to use biodegradable aroma substances or aroma agents or aroma substance mixtures or aroma agent mixtures in order to achieve completely biodegradable products.

[0262] In a particularly preferred embodiment of the invention, multilayer microcapsules are therefore described, wherein the multilayer microcapsules comprise at least one bio-based and biodegradable fragrance substance or fragrance agent or fragrance substance mixture or fragrance agent mixture.

[0263] The temperature range defined for the addition of the reactants also produces a completely new deposition mechanism compared to the prior art. It has many advantages, such as improved emulsion stability. By adding the reactants in a targeted manner at a defined temperature, no pH peaks are generated in the direction of alkaline or acidic pH values. In the present method, the pH values ​​used or obtained after the individual crosslinking steps are generally in the range between 3 and 9, while the final product is almost neutral, with a pH value between 7 and 8. This is reflected in the exceptionally good stability of the prepared microcapsules - despite the significantly reduced capsule wall material (polymer ratio) - and the outstanding active ingredient release capacity.

[0264] The microcapsules prepared according to the method of the invention can be characterized by the d(0.5) value of their size distribution, that is to say that 50% of the prepared capsules are larger than this value and 50% of the capsules are smaller than this value.

[0265] To determine the particle size, the microcapsules according to the invention were dispersed in water within the scope of a dynamic process and then determined by means of laser diffraction. Depending on the size of the capsule, the laser beam is refracted in different ways and can be converted into size. The Mie theory is used for this purpose. For particle measurement, a Malvern Mastersizer 3000 was used.

[0266] The microcapsules of the invention are characterized in that they have a particle size distribution with a d(0.5) value of 10 μm to 100 μm, preferably with a d(0.5) value of 20 μm to 65 μm. The corresponding particle size distribution of the microcapsules of the invention and the prior art microcapsules (that is to say microcapsules based on a pure polyurea network) is Figure 6 A direct comparison of the microcapsules shows that due to the improved emulsification process as described herein, a uniform distribution of microcapsule particle size can be achieved relative to prior art microcapsules.

[0267] Figure 5 IR images of the microcapsules according to the invention and the microcapsules of the prior art are shown in FIG. The microcapsules according to the prior art correspond to microcapsules prepared according to known encapsulation techniques and based on a pure polyurea network. For the preparation of such microcapsules, no catalyst was used and polyvinyl alcohol was selected as the protective colloid. Furthermore, the preparation was carried out at a pH value of 9. Clear differences can be identified from the images, especially in the fingerprint region. Due to the fact that the multilayer microcapsules have a higher IR value at 626 cm-1 compared to the prior art, the IR value of the multilayer microcapsules is 0.17 W / cm-1. -1 A significantly stronger band at 510 cm-1 allows conclusions to be drawn about asymmetric stretching vibrations of the OH groups, which can be attributed, for example, to the modified starch used. Another example is the band at 510 cm-1. -1 The IR spectra show that a new additional polymer has been formed relative to the capsules of the prior art (purely polyurea-based capsules), to which the improved stability and sensory properties can be attributed (polyurethane crosslinking).

[0268] Due to their stability and targeted release of active ingredients, the microcapsules of the present invention are suitable for a wide range of applications and are particularly suitable for use in detergents, softeners, cleaners, odor enhancers in liquid or solid form, cosmetics, body cleansing products, agricultural products or pharmaceutical products, etc.

[0269] In another aspect of the present invention, the use of multilayer microcapsules or suspensions formed by multilayer microcapsules for preparing detergents, softeners, cleaning agents, odor enhancers in liquid or solid form, cosmetics, body cleaning products, agricultural products or pharmaceutical products is also described.

[0270] Example

[0271] The multilayer microcapsules according to the invention and their advantageous properties are explained in detail with the aid of the following examples.

[0272] The stability tests detailed below were conducted at 50°C.

[0273] As capsules of the prior art, capsules whose capsule wall is exclusively composed of a polyurea network are generally selected. When preparing these capsules, generally no catalyst is used and the synthesis is carried out at a pH value of 9. Polyvinyl alcohol is selected as the protective colloid.

[0274] Embodiment 1: Stability data of multilayer microcapsules prepared according to the process of the present invention and comparative capsules; general stability gain.

[0275] 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, hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate, in a ratio of 80:20, a modified starch as protective colloid, and the crosslinking agents lysine hydrochloride (amine that reacts at acidic pH), glycerol (hydroxyl donor) and guanidine carbonate (amine that reacts at alkaline pH) were used. No catalyst was used in the preparation of these capsules.

[0276] The preparation of the multilayer microcapsules of the invention is carried out according to the following scheme from a mixture of two different isocyanates, hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate, in a ratio of 80:20, modified starch as protective colloid, catalyst DABCO, and crosslinking agents lysine hydrochloride (amine reacting at acidic pH), glycerol (hydroxyl donor) and guanidine carbonate (amine reacting at alkaline pH):

[0277] Table 1: Multilayer microcapsules were prepared according to the method described herein.

[0278] step 1 Dissolve the isocyanate in the hydrophobic phase 2 Dissolve starch in water 3 Forming emulsion 4 Add DABCO at 25°C 5 Add lysine hydrochloride at 40°C 6 Add glycerol at 50°C 7 Add guanidine carbonate solution at 60°C

[0279] Both capsules include TomCap perfume oil.

[0280] The starch used as protective colloid and crosslinking agent in the examples detailed herein is generally present in the form of a succinate. To this end, the starch is derivatized with succinic acid.

[0281] The stability test was carried out with the aid of a representative softener (softener), into which the corresponding microcapsules were processed in an amount of 1% by weight. The softener was subsequently stored at a temperature of 50° C. for the time period mentioned below (see Table 1).

[0282] Table 2: Comparison of stability data of multilayer microcapsules of the invention with stability data of comparative capsules prepared without using a catalyst.

[0283]

[0284] The stability of the microcapsules was determined via the residual oil content (perfume oil remaining in the microcapsules). From a residual oil content of more than 40% after 10 days, the prepared microcapsules were considered stable.

[0285] After several days, the capsule contents were analyzed by GS / MS (gas chromatography coupled to mass spectrometry). The perfume oil content in the capsules was determined by comparative measurement with standards. For example, a result of 46% means that 64% of the perfume oil initially added is no longer encapsulated in the capsules.

[0286] The free oil is determined by introducing the microcapsules into isopropanol and after 30 seconds by means of solid phase microextraction (SPME) and subsequently by means of GC / MS and is considered a measure of the capsule quality. That is, the free perfume oil that has leached out is determined by gas chromatography measurement with standards. The proportion of perfume oil still contained can be calculated back. A proportion of free oil that has leached out of less than 1% allows the tested capsule to be considered stable. It has been shown that the freshly produced microcapsules according to the process according to the invention leached out less perfume oil than the control capsules and therefore have a better quality measure.

[0287] This example clearly shows that the use of a catalyst significantly influences the capsule stability and that significantly more stable multilayer microcapsules can be produced by using a catalyst. In the case of comparative capsules prepared without the use of a catalyst, the first innermost capsule shell based on polyurethane cannot be formed (see reaction scheme 1), so that the capsule wall has a lower stability overall due to the smaller number of crosslinked layers. Furthermore, it should be noted in this context that the addition of the catalyst is carried out at room temperature and this first innermost crosslinked layer based on polyurethane is already effectively formed at room temperature.

[0288] Embodiment 2:Stability data for multilayer microcapsules prepared according to the process of the invention with and without hydroxyl donors.

[0289] In a second example, the stability data of multilayer microcapsules produced according to the invention were compared with the stability data of corresponding microcapsules produced without added hydroxyl donors, that is to say without an additional third capsule shell layer based on polyurethane.

[0290] To prepare the latter, a mixture of two different isocyanates, hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate, in a ratio of 80:20, polyvinyl alcohol (PVOH) as protective colloid, catalyst DABCO and crosslinkers lysine hydrochloride (amine reacting at acidic pH) and guanidine carbonate (amine reacting at alkaline pH) were used. No hydroxyl donor was used in the preparation of this capsule.

[0291] The preparation of the multilayer microcapsules of the present invention is carried out from a mixture of two different isocyanates, hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate, in a ratio of 80:20, starch as a protective colloid, a catalyst DABCO, and crosslinking agents lysine hydrochloride (amine reacting at acidic pH), glycerol (hydroxyl donor) and guanidine carbonate (amine reacting at alkaline pH) [see Example 1].

[0292] Table 3: Stability data of multilayer microcapsules according to the invention with and without an additional polyurethane-based crosslinked layer formed by adding a hydroxyl donor (with / without added hydroxyl donor).

[0293]

[0294] Stability was achieved as described in Example 1.

[0295] In general, all microcapsules showed good stability. When a hydroxyl donor is additionally used, even better stability can be achieved, which is attributed to the formation of an additional third shell layer based on polyurethane. This refinement of the method and the targeted deposition of the individual shells surprisingly leads to a high stability gain.

[0296] Embodiment 3: Stability data of the multilayer microcapsules produced according to the process of the invention as a function of the time point of catalyst addition.

[0297] In another example, the stability data of multilayer microcapsules prepared according to the invention were compared with the stability data of corresponding microcapsules prepared with the catalyst having been added in the aqueous phase, that is to say in step a2.

[0298] The preparation of the multilayer microcapsules according to the invention was carried out according to the protocol of Example 1 from a mixture of two different isocyanates, hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate, in a ratio of 80:20, starch as protective colloid, catalyst DABCO, and crosslinking agents lysine hydrochloride (amine that reacts at acidic pH values), glycerol (hydroxyl donor) and guanidine carbonate (amine that reacts at alkaline pH values). In the comparative capsules, the addition of the catalyst was already carried out before emulsification, while in the multilayer microcapsules according to the method described herein, the addition of the catalyst was carried out after the emulsification of the aqueous phase and the internal non-aqueous phase.

[0299] Both capsules, the inventive multilayer microcapsules prepared according to the process described herein and the comparative capsules, had an average particle size distribution with d(0.5)>60 μm.

[0300] Table 4: Stability data of the multilayer microcapsules according to the invention in dependence on the time point of catalyst addition.

[0301]

[0302]

[0303] Stability was achieved as described in Example 1.

[0304] Compared to the control capsules, the microcapsules according to the invention, to which the catalyst addition had been carried out after emulsification instead of in the aqueous phase, showed significantly higher stability and a significant reduction in free perfume oil even after 10 days at 50° C. This corresponds to a 3-fold increase in stability.

[0305] In the case of multilayer microcapsules prepared according to the process described here, the shell material obtained was 40% of the shell material of the microcapsules with hydroxyl donors from Example 2. Although the amount of shell material required is reduced, multilayer microcapsules with excellent stability can be obtained with the help of the process according to the invention.

[0306] Embodiment 4: Sensory evaluation of the microcapsules of the present invention.

[0307] The sensory evaluation of the microcapsules was carried out as follows: Figure 7 As shown in , the microcapsules were processed into softener and then washed. A blend of cotton and polyester towels was sniffed.

[0308] The capsules of the prior art (purely polyurea-based capsules) and the microcapsules of the invention both contain the perfume oil TomCap. The preparation of the capsules of the prior art is carried out exclusively by polyurea crosslinking. For the preparation, no catalyst is used and polyvinyl alcohol is selected as the protective colloid. The preparation is carried out at a pH value of 9. Such capsules thus have a shell network purely based on polyurea. The multilayer microcapsules of the invention are prepared as described in Example 1.

[0309] Twelve testers have evaluated the fragrance intensity of the washed mixed-fiber towels on a scale from 1 (no odor) to 9 (very strong odor).

[0310] The microcapsules according to the invention have virtually the same odor characteristics as the microcapsules from the prior art. However, the testers perceived a significantly higher odor intensity in the untreated, kneaded and rubbed mixed fiber towels. The fragrance release takes place here by mechanically destroying the microcapsules according to the invention. The reason for this advantage is the stability of the microcapsules according to the invention.

[0311] Another great advantage of isocyanate-based encapsulation is that these capsules are formaldehyde-free. In addition, despite the significantly lower polymer content compared to the prior art, a gain in stability and sensory properties can be observed. This can be explained by the thin multilayer capsule shell. At the same time, there is no restriction to individual fragrances. In other words, there are almost universal capsules that can encapsulate almost any tested fragrance according to current conditions.

[0312] Microcapsules from the prior art lose oil faster over time than the microcapsules of the present invention and therefore smell less intense.

[0313] Embodiment 5: Effect of the selected isocyanate on the stability of the multilayer microcapsules of the present invention.

[0314] The preparation of multilayer microcapsules according to the invention was carried out according to Example 1, with the aid of arginine instead of guanidine carbonate. The capsules were then prepared from a mixture of two different isocyanates or an isocyanate according to the table below, starch as protective colloid, catalyst DABCO, and the crosslinking agents lysine hydrochloride (amine that reacts at acidic pH), glycerol (hydroxyl donor) and arginine (amine that reacts at alkaline pH).

[0315] The following table shows a direct comparison of the effect of the selected isocyanates used to prepare the multilayer microcapsules of the present invention on the stability of the microcapsules. Figures 1 to 4 The corresponding optical microscope photos of the microcapsules of the present invention are given in .

[0316] Table 5: Comparison of the effects of selected isocyanates on the stability of the multilayer microcapsules of the present invention.

[0317] Selected isocyanate Free perfume oil 100% long chain diisocyanate 0.57％ 100% short chain diisocyanate 0.94％ 50% long chain and 50% short chain diisocyanates (50:50 mixture) 0.32％ 80% long chain diisocyanate and 20% aromatic diisocyanate 0.46％

[0318] Stability was achieved as described in Example 1.

[0319] In the examples described herein, hexamethylene diisocyanate was selected as the long-chain diisocyanate. Pentamethylene diisocyanate was selected as the short-chain diisocyanate; and 4,4'-methyldiphenylene diisocyanate was selected as the aromatic diisocyanate.

[0320] It has been shown that the use of long-chain aliphatic diisocyanates is theoretically preferred because less free oil is exuded here. However, it is still further preferred to select two different diisocyanates and especially select mixed long-chain and short-chain aliphatic diisocyanates or mixed aliphatic and aromatic isocyanates. This produces a particularly stable and better, that is to say more densely branched crosslinking within the capsule shell, which positively affects the stability of the capsule. In addition, due to the different diffusion characteristics of isocyanates, the basic high reaction speed for isocyanates is fully utilized during synthesis. In this case, it is still surprising that one carbon atom has more or less caused a decisive difference in the reaction speed. Therefore, when using OCN-(C5 chain)-NCO or OCN-(C6 chain)-NCO, obvious differences can be observed.

[0321] Embodiment 6: Effects of hydroxyl donors and catalysts on the stability of microcapsules.

[0322] In a further example the stability of multilayer microcapsules prepared according to the invention was compared with microcapsules prepared in the absence of hydroxyl donors and / or catalysts.

[0323] The preparation of the multilayer microcapsules of the invention is carried out from a mixture of two different diisocyanates / diisothiocyanates with the same functionality (a mixture of hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate in a ratio of 80:20). In this example, the emulsion is formed at 25°C. Modified starch is selected as protective colloid and the crosslinking agents are lysine hydrochloride (amine reacting at acidic pH values), glycerol (hydroxyl donor) and guanidine carbonate (amine reacting at alkaline pH values). The preparation of the microcapsules is carried out as described herein according to the preparation method of Example 1.

[0324] Table 6: Stability data of the multilayer microcapsules according to the invention in dependence on the influence of the hydroxyl donor and the catalyst.

[0325] Features 3 days, 50°C 10 days, 50℃ Glycerin-free and catalyst-free 64％ 57％ Glycerin-free and with catalyst 70％ 61％ With glycerol and without catalyst 46％ 40％ With glycerol and catalyst 88％ 85％

[0326] Stability was achieved as described in Example 1.

[0327] As can be seen from the table above, the use of a catalyst produces significantly more stable capsules. After the addition of a catalyst to an emulsion or suspension, a polyurethane-based crosslinked capsule shell is formed at the interface of the emulsified or suspended active ingredient particles or droplets to be encapsulated by a polyaddition reaction of a diisocyanate / diisothiocyanate mixture with modified starch. In the absence of a catalyst, such a crosslinked layer cannot form and the starch serves only as a protective colloid and not additionally as a crosslinking agent. Therefore, the addition of a catalyst effectively promotes the formation of an (additional) polyurethane-based shell layer, which contributes decisively to the stability of the obtained microcapsules.

[0328] Furthermore, it can be seen from this experiment that the crosslinking caused by the addition of an additional hydroxyl donor (here glycerol) also makes a decisive contribution to the overall stability of the microcapsules prepared in this way. An additional crosslinking layer based on polyurea is formed by the polyaddition reaction of the diisocyanate / diisothiocyanate mixture with the hydroxyl donor, which imparts additional stability to the microcapsules.

[0329] In this sense, the microcapsules of the present invention with an additional polyurethane-based capsule shell and an additional polyurea-based capsule shell show the best stability characteristics. The microcapsules prepared in this way have a multilayer capsule wall formed by generally alternating crosslinked polyurethane-based and polyurea-based layers in the following order: an innermost first layer comprising a polyurethane structure, a second layer comprising a polyurea structure, a third layer comprising a polyurethane structure, and an outermost fourth layer comprising a polyurea structure.

[0330] Embodiment 7: The influence of the selected temperature range.

[0331] In the following experiments, the influence of the temperature profile of the individual steps a) to d) is demonstrated with the aid of microcapsules according to the invention and capsules according to the prior art (purely polyurea-based capsules produced without catalyst at a pH of 9 using polyvinyl alcohol as protective colloid). In the prior art examples, the addition of all reaction partners was carried out at room temperature.

[0332] For the preparation of the microcapsules according to the invention, the following temperature range is selected for the addition of the individual components (addition of the reactants as described in the present invention):

[0333] - Addition of catalyst DABCO: 22 to 26°C (step a4);

[0334] - Addition of an amine (lysine hydrochloride) that reacts at acidic pH: 40 to 45°C (step b);

[0335] - Addition of hydroxyl donor (glycerol): 45 to 50°C (step c);

[0336] - Addition of an amine (guanidine carbonate) that reacts at basic pH: 60 to 70°C (step d).

[0337] Table 7: Stability data and polymer ratios of multilayer microcapsules of the present invention and prior art capsules.

[0338] capsule Polymer ratio of capsule 3 days, 50°C 10 days, 50℃ Prior art 6.8 wt% 81％ 75％ The present invention 4.4 wt% 84％ 77％

[0339] Stability was achieved as described in Example 1.

[0340] In an ideal situation, the composition of the capsule wall components can be described as follows:

[0341] Table 8: Composition of multilayer capsule shell or capsule wall.

[0342]

[0343] Despite the lower polymer proportion, the microcapsules of the invention show comparable good (if not even better) stability data. The improved stability can be attributed on the one hand to the four-sublayer shell system. On the other hand, the targeted selection of the temperature leads to a more efficient crosslinking of the crosslinked building blocks and thus allows the required reduction in the total polymer proportion to be achieved.

[0344] Embodiment 8: Stability data for microcapsules according to the invention with reduced shell ratio.

[0345] The multilayer microcapsules of the invention are prepared from a mixture of two different isocyanates (a mixture of hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate in a ratio of 80:20), starch as protective colloid, a catalyst DABCO (added at 22 to 26° C.), and the crosslinking agents lysine hydrochloride (amine reacting at acidic pH values; added at 40 to 45° C.), glycerol (hydroxyl donor; added at 45 to 50° C.) and guanidine carbonate (amine reacting at alkaline pH values; added at 60 to 70° C.). The microcapsules of the invention thus prepared thus have a capsule wall comprising essentially four different crosslinked layers based on polyurethane and polyurea in alternating order.

[0346] The prior art capsules are conventional capsules with a capsule wall based on pure polyurea formed from a mixture of hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate and guanidine carbonate in a ratio of 80:20. These capsules were prepared without the use of a catalyst at a pH of 9 using polyvinyl alcohol as protective colloid.

[0347] Table 9: Polymer ratios and stability data of multilayer microcapsules of the present invention and prior art capsules.

[0348] capsule Polymer ratio of capsule 3 days, 50°C 10 days, 50℃ Prior art 6.8 wt% 81％ 75％ The present invention 1 4.4 wt% 84％ 77％ The present invention 2 2.2 wt% 58％ 50％ Present invention 3 1.1 wt% 59％ 47％ The present invention 4 0.6 wt% 32％ 24％

[0349] Stability was achieved as described in Example 1.

[0350] Due to the increased number of individual layers, stable capsules with a reduced amount of polymer are produced, which are more stable despite a 36% reduction in polymer (prior art compared to invention 1) and even with a polymer amount fraction of 16% (invention 3) of the initial amount, almost 50% of the oil in the capsule is always stably enclosed in its interior after 10 days at 50°C.

[0351] Embodiment 9: The stability data of the microcapsules according to the invention depend on the pH value used in forming the innermost first crosslink of the capsule shell or capsule wall from isocyanate and protective colloid.

[0352] The microcapsules investigated were prepared according to the method described herein. The isocyanate component consisted of a mixture of hexamethylene diisocyanate and 4,4'-methyldiphenylene diisocyanate in a ratio of 80:20. DABCO was used as catalyst, while starch was used as protective colloid (see Example 1).

[0353] Table 10: Stability data of multilayer microcapsules in dependence on the pH value of the first polymerization with starch.

[0354]

[0355]

[0356] Stability was achieved as described in Example 1.

[0357] The experiments described here show that capsules having an inner polyurethane-based capsule shell formed from starch and isocyanate have particularly stable properties when this first polymerization, that is to say the formation of the innermost capsule shell, is carried out at a pH value of 7 to 9. In addition, it was surprisingly found that the modified starch used can be used in a dual function as protective colloid and reactant (capsule wall component / crosslinker) at the same time.

[0358] Embodiment 10: An optional step prior to hardening in which the crosslinking of the microcapsules is terminated by adding an amine with functional amine groups.

[0359] The microcapsules investigated were prepared in accordance with the method described herein. The following reactants were used for this purpose: the two linear isocyanates hexamethylene diisocyanate and pentamethylene diisocyanate in a ratio of 90:10. DABCO as catalyst (added at 25° C.), lysine hydrochloride (added at 40° C.), glycerol (added at 50° C.) and arginine (added at 60° C.) and the amines histidine or alanine (added at 80° C.). The last-mentioned amines are amino acids comprising an amino group.

[0360] Table 11: Stability data of multilayer microcapsules including additional final crosslinking.

[0361] The capsule of the present invention contains arginine Free oil No optional steps before hardening 0.87％ Additional cross-linking with histidine 0.45％ Additional cross-linking with alanine 0.63％

[0362] Stability was achieved as described in Example 1.

[0363] The examples described herein clearly show that an additional optional cross-linking step with amines, preferably amino acids carrying functional groups, results in an additional stabilization of the capsules.

[0364] Embodiment 11: Stability data of multilayer microcapsules and the influence of protective colloid and hydroxyl donor on the stability of multilayer microcapsules.

[0365] In another example, the stability of the multilayer microcapsules prepared according to the invention in dependence on the protective colloid (with / without PVOH or modified starch) and the hydroxyl donor (with / without glycerol or phloroglucinol) is demonstrated.

[0366] The synthesis of the microcapsules according to the invention was carried out essentially as described in Example 1, with changes being made according to the table below. The microcapsules of the prior art are microcapsules based purely on polyurea. Here, the individual components are added to the reaction mixture or suspension or emulsion within a defined temperature range. The capsules of the prior art are microcapsules based purely on a polyurea network. When preparing these capsules, generally no catalyst is used and the synthesis is carried out at a pH of 9. Polyvinyl alcohol was selected as the protective colloid.

[0367] Table 12: Stability data of multilayer microcapsules according to the invention in dependence on the influence of hydroxyl donor and protective colloid.

[0368] capsule 3 days, 50°C 10 days, 50℃ Prior art capsules [with PVOH and without glycerin] 77％ 70％ The capsule of the present invention contains PVOH and does not contain glycerin 70％ 61％ Capsules of the present invention, having ammonium derivatives of PVOH and no glycerol 41％ 33％ The capsule of the present invention comprises an ammonium derivative of PVOH and glycerol 55％ 49％ The capsule of the present invention has modified starch and no glycerin 76％ 67％ The capsule of the present invention contains modified starch and glycerol 88％ 85％

[0369] Stability was achieved as described in Example 1.

[0370] The selection of different temperature ranges for adding the individual reactants also results in a completely new deposition mechanism compared to the prior art, due to which an increased emulsion stability can be achieved, since no pH peaks in the direction of alkaline or acidic pH values ​​are produced by the targeted addition of the reactants at defined temperatures. In the present method, the pH values ​​used or obtained after the individual crosslinking steps are generally in the range between 3 and 9, while the end product is almost neutral with a pH value of between 7 and 8.

[0371] As can be seen from the table above, increasing the hydroxyl groups in the protective colloid and by adding a hydroxyl donor (here glycerol) leads to a significant improvement in the stability of the capsules. This results in the capsules of the invention prepared with modified starch and glycerol having the best stability.

[0372] Table 13: Stability data of multilayer microcapsules according to the invention in dependence on the influence of hydroxyl donor and protective colloid.

[0373]

[0374] Stability was achieved as described in Example 1.

[0375] This table shows that, in contrast to the combination of modified starch and glycerol, a similar system with phloroglucinol (1,3,5-trihydroxybenzene) provides inferior results. Surprisingly, not every polyol appears to be able to achieve such a high stability gain, so that the expected reactive triphenols, such as phloroglucinol, as hydroxyl donor with modified starch are completely unable to form microcapsules. The hydroxyl donor is therefore preferably a polyol with two or more functional hydroxyl groups, in particular glycerol and / or propylene glycol.

Claims

1. A method for preparing multilayer microcapsules, the method comprising the following steps in order: a) forming a first cross-linked layer by: a1) providing an inner non-aqueous phase, said non-aqueous phase comprising at least one isocyanate having two or more isocyanate groups and at least one active ingredient to be encapsulated; a2) providing an external aqueous phase, said aqueous phase comprising at least one protective colloid; a3) mixing the inner non-aqueous phase and the outer aqueous phase to obtain an oil-in-water emulsion; b) forming a second crosslinked layer by adding an amine that reacts at acidic pH; c) forming a third crosslinked layer by adding a hydroxyl donor; d) forming a fourth crosslinking layer by adding at least one amine that reacts at alkaline pH to obtain a multilayer microcapsule; e) hardening the multilayer microcapsules obtained in step d); and optionally: f) separating the microcapsules from the reaction solution and optionally drying the microcapsules. 2 . The method according to claim 1 , wherein the first crosslinked layer is formed from a protective colloid and an isocyanate in the presence of a catalyst.

3. The method according to claim 1 or 2, comprising adding a catalyst in step a4) after step a3).

4. The process according to claim 1 or 2, wherein the at least one isocyanate carrying two or more isocyanate groups is selected from the group of aliphatic isocyanates and / or aromatic isocyanates.

5. The method according to claim 1 or 2, comprising at least two aliphatic isocyanates carrying two or more isocyanate groups, wherein the at least two isocyanates have different chain lengths.

6. The method according to claim 1 or 2, comprising an additional optional step before hardening in which the crosslinking of the microcapsules is terminated by adding an amine with functional amine groups.

7. The method according to claim 1 or 2, wherein the protective colloid is a polysaccharide.

8. The method according to claim 7, wherein the protective colloid is starch.

9. The method of claim 2, wherein the catalyst is 1,4-diazabicyclo[2.2.2]octane.

10. The method according to claim 1 or 2, wherein the amine reacted at an acidic pH value is an acidic amino acid hydrochloride.

11. The method according to claim 10, wherein the amine reacting at acidic pH is lysine hydrochloride and / or ornithine hydrochloride.

12. The method according to claim 1 or 2, wherein the hydroxyl donor is a polyol having two or more functional hydroxyl groups.

13. The method according to claim 12, wherein the hydroxyl donor is glycerol, propylene glycol and / or 1,3,5-trihydroxybenzene.

14. The method of claim 1 or 2, wherein the amine that reacts at alkaline pH is a guanidine cationic group donor.

15. The method according to claim 14, wherein the amine that reacts at alkaline pH is arginine, guanidine carbonate and / or guanidine hydrochloride.

16. The method of claim 6, wherein the amine used to terminate the cross-linking of the microcapsules in an additional optional step prior to hardening is an amino acid.

17. The method according to claim 16, wherein the amine used to terminate the cross-linking of the microcapsules in an additional optional step before hardening is alanine, glycine, aspartic acid, cysteine ​​and / or proline.

18. The method according to claim 1 or 2, wherein the at least one active ingredient to be encapsulated is selected from the group consisting of: flavoring agents, food additives, cosmetic active ingredients, pharmaceutical active ingredients, agricultural chemicals, optical brighteners, solvents, and mixtures of the above active ingredients to be encapsulated.

19. The method according to claim 18, wherein the active ingredient to be encapsulated is a fragrance or a mixture of fragrances.

20. The method according to claim 1 or 2, wherein the at least one active ingredient to be encapsulated is selected from the group consisting of: flavor substances, food additives, cosmetic active ingredients, pharmaceutical active ingredients, agricultural chemicals, optical brighteners, solvents, and mixtures of the above active ingredients to be encapsulated.

21. The method according to claim 1 or 2, wherein the at least one active ingredient to be encapsulated is selected from the group consisting of aromatic substances, food additives, cosmetic active ingredients, pharmaceutical active ingredients, agricultural chemicals, optical brighteners, solvents, and mixtures of the above active ingredients to be encapsulated.

22. The method according to claim 1 or 2, wherein the at least one active ingredient to be encapsulated is selected from the group consisting of: biocides, substances selected from the group of repellents, dyes, silicone oils, lubricants, and mixtures of the above active ingredients to be encapsulated.

23. The method according to claim 1 or 2, wherein the at least one active ingredient to be encapsulated is selected from the group consisting of insecticides, luminescent pigments, waxes, and mixtures thereof.

24. A multilayer microcapsule comprising at least one hydrophobic aroma substance, said microcapsule being prepared according to a method corresponding to any one of the preceding claims 1 to 23.

25. Use of the multilayer microcapsules according to claim 24 or a suspension formed from the multilayer microcapsules according to claim 24 for preparing softeners, cleaning agents, odor enhancers in liquid or solid form, cosmetics, body cleaning products, agricultural products or pharmaceutical products.

26. A multilayer microcapsule comprising at least one hydrophobic fragrance agent, said microcapsule being prepared according to a method corresponding to any one of the preceding claims 1 to 23.

27. Use of the multilayer microcapsules according to claim 26 or a suspension formed from the multilayer microcapsules according to claim 26 for preparing softeners, cleaning agents, odor enhancers in liquid or solid form, cosmetics, body cleaning products, agricultural products or pharmaceutical products.

28. A multi-layer microcapsule comprising a core and a capsule shell, wherein the core comprises at least one hydrophobic flavoring substance, wherein the capsule shell comprises or consists of the following items from the inside to the outside: (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.

29. The multilayer microcapsule according to claim 28, wherein (i) the first layer comprises the following crosslinking units: at least one isocyanate having two or more isocyanate groups and a protective colloid; (ii) the second layer comprises the following crosslinking units: at least one isocyanate having two or more isocyanate groups and an amine that reacts at an acidic pH; (iii) the third layer comprises the following crosslinking units: at least one isocyanate having two or more isocyanate groups and a hydroxyl donor; and (iv) the at least fourth layer comprises the following crosslinking units: at least one isocyanate having two or more isocyanate groups and at least one amine that reacts at alkaline pH.

30. A multilayer microcapsule comprising a core and a capsule shell, wherein the core comprises at least one hydrophobic flavoring agent, wherein the capsule shell comprises or consists of the following 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.

31. The multilayer microcapsule according to claim 30, wherein (i) the first layer comprises the following crosslinking units: at least one isocyanate having two or more isocyanate groups and a protective colloid; (ii) the second layer comprises the following crosslinking units: at least one isocyanate having two or more isocyanate groups and an amine reactive at acidic pH; (iii) the third layer comprises the following crosslinking units: at least one isocyanate having two or more isocyanate groups and a hydroxyl donor; and (iv) the at least fourth layer comprises the following crosslinking units: at least one isocyanate having two or more isocyanate groups and at least one amine that reacts at alkaline pH.

32. Use of the multilayer microcapsules according to any one of claims 28 to 31 or a suspension formed from the multilayer microcapsules according to any one of claims 28 to 31 for preparing softeners, cleaning agents, odor enhancers in liquid or solid form, cosmetics, body cleaning products, agricultural products or pharmaceutical products.

33. Use of the multilayer microcapsules according to any one of claims 28 to 31 or a suspension formed from the multilayer microcapsules according to any one of claims 28 to 31 for preparing a detergent.

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