WO2003042274A1

WO2003042274A1 - Method for the production of microcapsules

Info

Publication number: WO2003042274A1
Application number: PCT/EP2002/011736
Authority: WO
Inventors: Friedrich Georg Schmidt; Andreas Pawlik; Gerald Rafler; Jacqueline Lang; Reiner Friedrich
Original assignee: Creavis Gesellschaft Für Technologie Und Innovation Mbh; Fraunhofer Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2001-11-17
Filing date: 2002-10-19
Publication date: 2003-05-22
Also published as: DE10156672A1

Abstract

The invention relates to a dispersing method for the production of polyurea-based microcapsules with a liquid, suspension-containing or solid capsule core. An isocyanate/amine system which forms the microcapsule wall from the aqueous phase is used for encapsulation. Additional crosslinking components are used to morphologically modify the capsule wall.

Description

Process for the production of microcapsules

The invention relates to a dispersion process for the production of polyurea-based microcapsules with liquid, suspension-containing or solid capsule cores and to the microcapsules themselves. An isocyanate / amine system is used for encapsulation, which forms the microcapsule wall from the aqueous phase and additionally for the morphological modification of the capsule wall uses networking components.

The microencapsulation of organic and inorganic liquid, waxy and solid substances with polymers is well known. The various techniques of reactive or non-reactive microparticle formation and the geometric, morphological and chemical properties and fields of application of the matrix particles or microcapsules with a core-shell structure prepared in this way have been described many times (cf. for example "Microencapsulation, Processes and Applications", JE Vandegaer, Plenum Press, New York (1974); "Microencapsulation of Drugs", TL Whateley, Harwood Academic Publ., Chur (1992); K. Dietrich et al. "Amino Resin Microcapsules" Mitt. 1-3, Acta Polymerica 40 (1989) 243, 325, 683).

Non-reactive encapsulation processes, such as solvent evaporation, spray drying, coacervation, salting out or precipitation, use readily soluble synthetic or native polymers as the wall or matrix material of the microparticles. For the reactive encapsulation, reactive resin systems are used, preferably based on amino resin or polyurethane or polyurea and monomers which are readily polymerizable at phase boundaries.

For the reactive microencapsulation of hydrophobic liquid and solid phases, melamine-formaldehyde precondensates and isocyanate / amine systems are particularly suitable and have been state of the art for a long time. This type of reactive encapsulation is a polycondensation of the amino resin or polyaddition of a di- or oligoisocyanate onto a di- or higher-functional amine component at the interface of an emulsion or suspension. Reactive encapsulation processes with suitable isocyanate and amine components are used in a wide variety of ways with regard to component structure, component ratio, method of particle production and application of the isocyanate / amine-based microparticles. A two-phase technique is most frequently used in which the oil-soluble component is generally a relatively low molecular weight polyisocyanate adduct or an isocyanate prepolymer and the water-soluble component is a di- or higher-functional amine (DE 2242910, DE 2311712, US 3575822, US 3577515, US 3607776). The isocyanate component is emulsified or dissolved in the material to be encapsulated and then dispersed in the aqueous phase, often using emulsifiers. must be added to obtain a stable system. After addition of the amine, after a reaction time which is dependent on the reactivity of the components, microparticles with a polyurea as wall material are obtained, which can be cleaned and isolated by suitable methods.

This state-of-the-art microparticle process with distribution of the polyurea components in both phases has a number of disadvantages which limit its use. The capsules contain a relatively high residual amount of unreacted isocyanate, which can lead to undesirable side reactions within the microparticles and usually precludes the encapsulation of reactive substances. This residual isocyanate content is determined by the rate of mass transfer of the isocyanate within the oil phase and by the mass transfer from the isocyanate-containing oil to the aqueous, amine-containing phase. This results in a large number of chemical-physical and geometric factors influencing the residual isocyanate content in the microparticles, which limit the applicability of this procedure to the encapsulation of non-reactive substances or in which this residual content does not interfere with the later application of the microparticles.

Another limiting factor of the procedure corresponding to the prior art is the often necessary use of emulsifiers for dispersing the isocyanate-containing phase in the amine-containing, aqueous phase. The choice of emulsifiers that can be used is very limited, since on the one hand they affect the capsule wall-forming polyaddition reaction on the Do not disturb the interface and, on the other hand, must not adversely affect the stability of the microcapsules.

In order to overcome some of the disadvantages mentioned, it is known to use self-dispersing polyisocyanates as capsule wall materials. Isocyanates containing polyethylene oxide, such as are described in US Pat. No. 5,325,556, have proven particularly useful. The self-dispersing isocyanates are prepared by reacting a mixture consisting of bis (6-isocyanatohexyl) uretdione and tris (6-isocyanatohexyl) isocyanurate with monofunctional polyethylene oxides. The isocyanate prepolymer is then dispersed with the material to be encapsulated in a hydrophilic solvent, emulsified in water and reacted with this by adding a multifunctional amine (di- or triamine).

According to this known prior art (US 5342556) it is not possible to obtain stable capsules with the known isocyanate / amine process. In particular in the case of capsules with a liquid core and larger diameters (d> 50 μm), such as are inevitably formed, for example, when encapsulating suspensions because of the size of the suspended particles, sufficient mechanical wall stability is not achieved with the components polyisocyanate and polyfunctional amine alone.

Microcapsules with isocyanate / amine wall material produced according to the prior art are also limited in their usability with regard to the ingredients, since the capsule wall is often permeable to low-molecular organic core materials (i.e. the encapsulated materials), and the microcapsules are thus more liquid when encapsulated Ingredients such as organic solvents do not have sufficient storage stability.

The invention is therefore based on the object of providing a process for producing microcapsules based on water-dispersible polyisocyanates and modified polyamines, which is distinguished by the following properties: Wide variability with regard to the core material to be encapsulated: Enclosure for solids, liquids and water-insoluble as well as water-immiscible solids with high stability of the capsule wall, extremely low coefficient of pneeability of the capsule walls for organic solvents, inert behavior of the capsule wall towards the core materials

Surprisingly, it was found that this object can be achieved in that the capsule wall primarily formed from the water-dispersible polyisocyanates and polyamines is stabilized and compacted at the molecular level by an additional, chemically or physically initiated crosslinking step.

The present invention therefore relates to a method according to claim 1 for producing microcapsules with ingredients, in particular liquid and / or solid ingredients inside the capsules and capsule walls, which have polyurea-containing material, which is characterized in that the capsule walls made of polyurea-containing material, which has functional groups which are crosslinked by means of a crosslinker.

The present invention also relates to microcapsules produced by the process according to the invention.

The present invention also relates to microcapsules with a capsule wall that has a polyurea-containing material and ingredients, in particular liquid and / or solid ingredients inside the capsules, which are characterized in that the capsule wall, which has the polyurea-containing material, by a crosslinker is hardened.

In addition, the present invention relates to the use of microcapsules according to the invention as a container for ingredients, as a container for ingredients, the containers releasing the ingredients under pressure, as a micro memory, as a component in electronic displays or as microreactors.

In the context of the present invention, microcapsules are understood to mean microparticles which have a capsule wall or a particle matrix and one or more solid and / or liquid ingredients.

In the following, isocyanates or isocyanate components and amines or amine components in each case mean isocyanates or amines which have at least two isocyanate or amine groups, since only with such di- or polyamines or -Isocyanates the formation of polyurea-containing material is possible.

The microcapsules produced by the process according to the invention have the advantage that they can be used for a wide variability with regard to the core material to be encapsulated. For example, the microcapsules according to the invention can be used for coating both solids, liquids and also suspensions which are insoluble in water and immiscible with water. In particular, the microcapsules can also contain polyurea-containing material as an ingredient. The microcapsules have a significantly higher mechanical stability of the capsule wall compared to conventionally produced microcapsules. Due to the cross-linking of the capsule walls, they also have an extremely low permeability coefficient for organic solvents.

The method according to the invention is described below by way of example, without being restricted thereto. The method according to the invention for the production of microcapsules with ingredients, in particular liquid and / or solid ingredients inside the capsules and capsule walls, which have polyurea-containing material, is characterized in that the capsule walls are made of polyurea-containing material, which has functional groups, by means of a crosslinking agent be networked, manufactured.

The process according to the invention is based on the production of polyurea from isocyanates and amines according to the following formula: R-NCO + R'— NH ₂ ^■ R - NH - CO - NH - R ^*

Polyurea formation from isocyanate and amine

wherein R represents an alkyl radical with at least one isocyanate group and R 'represents an alkyl radical with at least one amine group.

The polyurea-containing material which has functional groups is preferably produced by a reaction of di- or polyamines and di- or polyisocyanates. It can be advantageous to use amines or isocyanates which have further functional groups in addition to the amine functions or the isocyanate functions to produce the polyurea-containing material. Amines with functional groups are preferably used.

In general, the method can be carried out in a two-phase system which has an aqueous and an organic phase. Preferred weight ratios between organic and aqueous phase are in the range from 1:99, preferably from 10:90 to 60:40, particularly preferably 20:80 to 50:50. Additives, such as stabilizers, protective colloids and / or dispersion auxiliaries, can be added to the aqueous phase be such. As gelatin, polyvinyl alcohol, carboxymethyl cellulose or polymethacrylic acid. However, the method can also preferably be carried out in a single-phase system, the capsule walls being formed from polyurea-containing material in the aqueous phase. When considering the one-phase or two-phase nature, the substance to be encapsulated should not be regarded as a separate phase, but the one-phase or two-phase nature only refers to the formation of the capsule walls, so that even when the process is carried out in the aqueous phase, organic ones , substances immiscible with water, such as. B. silicone oil can be encapsulated.

The proportions of the components used can be varied to a large extent. Based on 100 parts by weight of material to be encapsulated, preference is given to using 0.4 to 40, particularly preferably 1 to 25 parts by weight of polyisocyanate. The amine content results from the NCO content of the polyisocyanate used and is preferably from 0.5 to 3, particularly preferably from 0.75 to 2.5 and very particularly preferably from 1 to 2 equivalent masses of amine per equivalent mass of isocyanate.

To increase the solubility of the polymeric isocyanate component, water-miscible organic solvents as cosolvents can be added to the aqueous phase in proportions of 1 to 25% by volume, preferably 5 to 15% by volume. Suitable for this are, for example, tetraliydrofuran, dimethyl sulfoxide and dimethylformamide.

The materials to be encapsulated are water-immiscible liquids and solids and suspensions, which in turn can be provided with additional auxiliaries.

The known dispersion tools such as Ultra-Turrax, ultrasound or other intensively mixing stirrers are used to produce the water / core material dispersion in the case of a discontinuous process. Static mixers are preferably used under continuous encapsulation conditions.

Isocyanate, amine and crosslinker can be added to the encapsulation process in any order. In the case of a batchwise procedure, however, it has proven useful first to disperse the isocyanate in the aqueous phase, then to add the material to be encapsulated with stirring and then to add the melamine-containing amine or the amine and the crosslinking agent.

The capsule is formed preferably at room temperature by reacting the isocyanate groups with the aliphatic amines. After a reaction time of 10 minutes to 24 hours, preferably from 30 to 240 minutes and very particularly preferably from 45 to 90 minutes, this process is largely completed.

Water-dispersible polyisocyanates and polyamines are preferably used as amines and isocyanates, from which the polyurea-containing material of the capsule wall is produced. Through an additional, chemically or physically initiated crosslinking step the capsule wall is stabilized and compressed at the molecular level.

This crosslinking itself is achieved in that the amine component is functionalized in such a way that, in addition to the reaction with the isocyanate to give the polyurea-containing material, at least one further crosslinking reaction which is independent of it can take place. This crosslinking process can take place in parallel or after the polyurea formation. Preferred components for the modification of the polyamine component according to the invention are amino-s-triazines and α, β-unsaturated aldehydes or ketones.

The isocyanates or isocyanate components used according to the invention are preferably nonionically hydrophilized, water-dispersible polyisocyanate mixtures with aliphatic and / or cycloaliphatic bound isocyanate groups and polyether alcohols. The dispersibility or water solubility of the isocyanate component can be adjusted by means of the polyether alcohol component. The preparation of this class of substances is described in detail in various patents, e.g. B. EP 0 850 896, US 5,342,556, WO 98/14495. Water-dispersible polyisocyanate is e.g. B. commercially available under the trade name BAYHYDUR 3100 (Bayer AG).

Preferred amines are water-soluble primary and secondary diamines and polyamines such as. E.g .: hydrazine, bi-functional aliphatic amines H ₂ N- (CH ₂ ) _n -NH ₂ (n = 1-10), bis-amino-terminated polyethylene glycols H ₂ N- (CH ₂ -CH ₂ O) _n -NH ₂ (n = 1 - 100), bis-aminopropyl-terminated polyethylene glycols H ₂ N-CH (CH ₃ ) CH ₂ - (CH ₂ -CH ₂ O) _n -CH ₂ -CH (CH ₃ ) -NH ₂ (n = 1-100), tifunctional aliphatic amines H ₂ N- (CH ₂ ) _X -NH- (CH ₂ ) _Z -NH ₂ (x = 1 - 5 and z = 1 - 5), tris-alkylene amines as well polymeric polyfunctional amines, such as polyalkylene imines and polyvinylamine.

In a preferred embodiment of the process according to the invention, amines modified with amino-s-triazines, so-called melamine-containing amines or polyamines, are prepared from these amines. The amino-s-triazine-containing (melamine-containing) polyamines (I) for the capsule wall formation with the polyisocyanates can be easily obtained from the 2-halogeno-4,6-diamino-triazines and an amine or a substituted alcohol represent. Examples of suitable amines for the production of melamine-containing amines are the water-soluble primary and secondary diamines and polyamines such as, for. For example: hydrazine, bifunctional aliphatic amines, bis-amino-terminated polyethylene glycols, bis-aminopropyl-terminated polyethylene glycols, trifunctional aliphatic amines, tris-alkylene amines and also polymeric polyfu tional amines, such as polyalkyleneimines and polyvinylamine.

Formula I shows a general formula for melamine-containing amines, in which R = OR, OR "NHR" 'or NHR,

X = (CH ₂ ) _n , (CH ₂ CH ₂ O) _n or NHR '"with n = 1 to 10 and

R, R "and R" = branched or unbranched alkyl chain.

The melamine-containing amines can be prepared very easily from the corresponding triazine and an amine. Examples of suitable amines have already been mentioned in detail. To produce a melamine-containing amine, for example, 0.5-2.5 mol of amine in a suitable solvent such as water, 2-methoxyethanol or dioxane can be reacted with 1 mol of 2-chloro-4,6-diaminotriazine by adding the two reaction components in the solvent dissolved, mixed with 1 mol NaOH and heated to 80-130 ° C for 1-6 h. Finally, the solvent is distilled off and the residue, which has the melamine-containing amine, is freed from NaCl formed during the substitution by means of Soxthlette extraction.

Melamine-containing amines produced in this way or in a similar manner and melamine-containing polymeric polyfunctional amines are preferably used in this embodiment of the process according to the invention.

The advantage of melamine-containing amines over conventional amines for the poly The formation of urea consists in the fact that the amino groups of the modified melamine have different reactivities which are used for controllable crosslinking following the immediate wall formation process in the microencapsulation. In the first step, the aliphatic NH ₂ groups react preferentially with the aliphatic isocyanate groups because of their higher basicity; the capsule walls formed in this way have approximately the same stability as isocyanate / amine capsules produced according to the prior art.

The higher stability of the capsule walls according to the invention is achieved by crosslinking, with a mono- or dialdehyde of the formulas II or III preferably being used for the crosslinking when melamine-modified polyamines of free amino groups are used as crosslinkers in the polyurea-containing material. HRCHO II

OHC-R-CHO III with R in each case equal to (CH ₂ ) _n with n = 1 to 10, preferably from 1 to 5 and very particularly preferably from 2 to 4. It is also possible to crosslink free amino groups in the polyurea-containing material Use epoxides of the following formula IN.

CH2 - CH - R - R '

O _IV with R = (CH) _n and / or (CH ₂ O) _n with n = 1 to 10, preferably 2 to 6 and R '= Cl or

- CH2 - CH, such as B. epichlorohydrin and analogous compounds.

Sufficient crosslinking agent is preferably used that there is at least one aldehyde group for each free amino group. A 1.5 to 4-fold and very particularly preferably a 2 to 3-fold excess of aldehyde is used per melamine group.

The curing or crosslinking of the capsule wall formed by reaction of amines with isocyanates is preferably carried out at temperatures from 30 ° to 90 ° C., preferably from 40 ° to 60 ° C. When using the melamine-containing wall materials, one of the above is used mentioned compounds added as crosslinkers. It has been shown that to crosslink or harden the capsule wall, the pH of the reaction mixture by adding non-oxidizing acids, such as. B. HC1 or organic acids should be lowered. The reaction mixture preferably has a crosslinking pH of 5 to 1, very particularly preferably 4 to 2. The crosslinking or curing of the capsule wall is usually complete after 2 to 8 hours. The stable capsules can then be separated, cleaned and, if necessary, separated or sorted according to size by known methods.

As already described, the crosslinking can also be carried out during, ie parallel to, the wall formation process or only after the capsule wall has been formed. The subsequent hardening of the capsule wall by chemical crosslinking can be carried out without prior isolation of the uncured microcapsules. All that needs to be done is to lower the pH in the aqueous phase, add the aldehyde and complete the curing of the capsule wall at elevated temperature. The stable capsules can then be separated, cleaned and, if necessary, separated by known methods.

Through the additional crosslinking of the amino groups, in the case of melamine-containing amines on the Tiϊazinring, by means of simple mono- or dialdehydes, preferably formaldehyde, acrolein, crotonaldehyde and acetaldehyde or glyoxal or glutardialdehyde, these microcapsules or the capsule walls achieve a high final strength.

In a likewise preferred embodiment of the process according to the invention, amines modified with amino-s-triazines are not used, but polyamines modified with α, β-unsaturated aldehydes or ketones, which are obtained by hydroxyalkylation of the corresponding unsubstituted amines. Suitable amines for this reaction are the water-soluble primary and secondary diamines already listed and suitable for reaction with 2-halogeno-4,6-diamino-triazines, as well as higher-functional amino compounds and polymeric polyamines. For the modification of the amine components suitable α, β-unsaturated aldehydes or ketones are water-soluble or water-dispersible carbonyl compounds, such as. B. acrolein, 2-methyl-acrolein, crotonaldehyde or methyl vinyl ketone. This process variant is based on the aminoalkylation of polyurea according to the following reaction formula:

R - NH - CO - NH - + OHC - R "* ~

where R ', R "and R" represent an alkyl radical which may still have functional groups.

Alkenals and alkenones, in particular α, β-unsaturated aldehydes and ketones, very particularly 2-alkenals and 2-alkenones, with vinyl and carbonyl groups, have two groups with different reaction options. You can di-, oligo- or polymerize via hydroxyalkylation with amino group-containing components and initiated free-radical or ionically via the vinyl group in bulk or in solution, depending on the reactants, both homo- and copolymer structures can be formed. This variant of the process according to the invention makes use of this effect since the α, β-unsaturated aldehydes and / or ketones are coupled to the amine component via the hydroxyalkylation and thus a polyurea-containing material which has vinyl groups can be obtained by conversion with the isocyanate component that can be used for networking, the networking in different ways, e.g. B. can be started ionically or radically. It can be advantageous if the ratio of α, β-unsaturated aldehyde or ketone to amine group is from 1.5 to 10, particularly preferably from 3 to 7.

The modification with the α, β-unsaturated carbonyl compounds is preferably carried out via the amine component of the polyurea, the reaction with the polyfunctional amine being carried out before or during the encapsulation process, i.e. before the polyurea formation or in parallel with the polyurea formation from the polyfunctional components isocyanate and amine can.

The wall hardening of polyureas, which consists of α, ß-unsaturated

Carbonyl compounds modified amines were prepared, capsule walls is preferably carried out so that during or after the isocyanate / amine reaction, the initiator for the crosslinking of the vinylene groups is added, the approach within is heated to 50 to 80 ° C., preferably to 60 to 70 ° C. in a short time, preferably within less than 1 h, and is held at this temperature for 2-6 h. The hardened microcapsules can then be separated.

Suitable initiators for crosslinking via the vinyl groups are, in addition to radical polymerization initiators, such as inorganic and organic peroxides, azo compounds or redox initiators such as, for. B. hydrogen peroxide / iron (II) sulfate, also radiated energy and Jevra acids and Lewis Bas n, such as. B. tertiary amines (triethylamine). As the radiated energy z. B. UV radiation. Examples of inorganic or organic peroxides which can be used are ammonium peroxodisulfate, dibenzoyl peroxide, hydrogen peroxide or cumene hydroperoxide. The chemical polymerization initiators are preferably used in an amount of 0.001 to 0.1, preferably 0.005 to 0.05 mol / mol of added α, β-unsaturated aldehyde or vinylene group.

By modifying the polyurea chains by means of α, β-unsaturated aldehydes or ketones and subsequent crosslinking, the walls of microcapsules, which were produced according to this embodiment variant of the process according to the invention, also achieve a high final strength.

The method described in the present invention with its variants is suitable for all technical manufacturing processes of microcapsules which operate according to a dispersion method. It has the advantage that the capsule wall is formed exclusively from the aqueous phase in the procedure according to the invention.

Using the method according to the invention, microcapsules with reinforced capsule walls can be produced. The microcapsules with a capsule wall that has a polyurea-containing material and ingredients, in particular liquid and / or solid ingredients inside the capsules, are characterized in that the capsule wall, which has the polyurea-containing material, is hardened by a crosslinker. Liquids, dispersions, suspensions and powders or granules can be used as liquid and / or solid ingredients with the proviso that the ingredients do not match the hardened Capsule wall react. Particularly preferred ingredients are semiochemical, sensory, catalytic or indicator materials, such as flavors, perfume oils, dyes or substances whose effectiveness is based on the interaction with electrical or magnetic fields, such as magnets or dielectrics. The encapsulation of these ingredients makes it possible to use the capsules according to the invention in various fields, such as, for. B. the use as a container for a wide variety of materials, the containers on pressure can release these materials, especially perfume, ink or adhesive, as a micro memory in electronic components, such as. B. displays or as microreactors. By means of the microcapsules according to the invention, a separate fixable phase can also be created, active substances can be protected from the surrounding medium and the compatibility of the active substances with the matrices can be improved. Further possible uses of the microcapsules according to the invention can be found as process, process or processing aids.

The capsules can be made in a wide variety of sizes. The capsules according to the invention preferably have a diameter of 600 nm to 300 μm, preferably from 1 to 200 μm and very particularly preferably from 2 to 50 μm.

The method according to the invention and the microparticles according to the invention are explained in more detail with reference to the following examples, without the invention being restricted to these examples.

example 1

Synthesis of a melamine-containing amine To produce the melamine-containing amine, 2.5 mol of hexamethylenediamine are dissolved in 2-methoxyethanol and reacted with 1 mol of 2-chloro-4,6-diaminotriazine by adding 1 mol of aqueous NaOH at 80 ° C. within 5 hours. The solvent is then distilled off and the residue is purified by Soxhlet extraction with water. 300 g of 2- (6'-aminohexyl) amino-4,6-diamino-s-triazine are obtained.

Example 2 Synthesis of a melamine-containing polyamine

To prepare the melamine-containing polyamine, 250 ml of a 30% polyethyleneimine solution, prepared from anhydrous low-molecular weight polyethyleneimine (Aldrich) with 72.5 g of 2-chloro-4,6-diaminotriazine by adding 0.5 mol of aqueous NaOH 80 ° C implemented within 2 h. The aqueous reaction mixture is then concentrated. Without further workup, it can be used as a modified polyamine component for encapsulation as a reactant for the polyisocyanate.

Example 3 Encapsulation of paraffin oil

1.0 g of a hydrophilic, aliphatic polyisocyanate based on hexylene diisocyanate (BAYHYDUR 3100, Bayer AG) are stirred in a beaker in 150 ml of a 2.5% by weight solution of polyvinyl alcohol (M: 10 ⁵ g / mol) (Stirrer, 350 min ^" ). 20 ml of paraffin oil are added with continued stirring. 1.0 ml of a 30% aqueous solution of a melamine-modified polyethyleneimine obtained in accordance with Example 2 are added. The emulsion is left under stirring for 60 min at room temperature. Then 0.5 ml of glutardialdehyde are added, the pH of the solution is lowered to pH ~ 3 by adding semiconcentrated hydrochloric acid and the temperature of the mixture is raised to 60 ° C. in the course of 1 hour, after which the particle-containing reaction mixture is raised slowly cooled to room temperature, and the microparticles are separated off by filtration and washed several times with distilled water Particle size of 200 microns isolated. The particles are microcapsules that have a liquid phase of paraffin oil enclosed in capsule walls made of polyurea-containing material.

Example 4

Encapsulation of silicone oil

1.0 g of a hydrophilic, aliphatic polyisocyanate based on hexylene diisocyanate

BAYHYDUR 3100 are suspended in a beaker in 150 ml of a 2.5% by weight solution of polyvinyl alcohol (M: 10 ⁵ g / mol) (Ultraturrax, 15,000 rpm). 20 ml of silicone oil (DC 200, FLUKA) were added with continued stirring. 1.0 ml of the aqueous 30% polyethyleneimine solution from Example 2 and 1.0 ml crotonaldehyde are added. The emulsion is left under stirring for 30 minutes at room temperature. Subsequently, the pH of the solution is increased to pH -10 by adding concentrated sodium hydroxide solution and, with moderate mixing, the temperature of the mixture is raised to 60 ° C. in the course of 1.5 hours. After 2 hours at this temperature, the mixture is cooled and the microparticles are separated off by filtration. The filtrate is distilled. Washed water and then dried at 80 ° C. 18 g of particles with an average particle size of 5 μm are isolated. The particles are microcapsules that have a liquid phase of silicone oil that is enclosed in capsule walls made of polyurea-containing material.

Example 5

Encapsulation of silicone oil

Analogously to Example 3, 20 ml of silicone oil are microencapsulated with 1.0 g of BAYHYDUR 3100, 1.0 ml of the aqueous 30% polyethyleneimine solution from Example 2 and 1.0 ml of crotonaldehyde. After adding 10 mg of benzoyl peroxide, the procedure is continued as in Example 3. 18 g of particles with an average particle size of 3 μm are isolated. The particles are microcapsules that have a liquid phase of silicone oil that is enclosed in capsule walls made of polyurea-containing material.

Example 6

Encapsulation of molybdenum disulfide powder

1.0 g of BAYHYDUR 3100 are placed in a beaker in 150 ml of a 2.5% by weight solution of polyvinyl alcohol (M: 10 ⁵ g / mol) with stirring (paddle stirrer, 350 min ^"1 ), in which 20 g of molybdenum disulfide Powder are suspended, 3.0 ml of an 8% polyvinylamine solution and 1.0 ml of acrolein are added The suspension was left under stirring for 30 minutes at room temperature, after which the pH of the solution was determined by adding from concentrated sodium hydroxide solution to pH ~ 10 and the temperature while stirring the mixture further within 1.5 h to 60 ° C. After 2 h the particle-containing reaction mixture is slowly cooled to room temperature, and the microparticles are separated off by filtration and washed with distilled water Water is washed several times, 20 g of particles with an average particle size of 50 μm are isolated Have molybdenum sulfide in a shell made of polyurea-containing material.

Example 7

Encapsulation of molybdenum disulfide powder 50.0 g BAYHYDUR 3100 are in a reactor with dispersant and anchor stirrer in 7500 ml of a 2.5 wt .-% solution of polyvinyl alcohol (M: 10 ⁵ g / mol) with dispersing (3000 min ^"1 ) in which 1000 g of molybdenum disulfide powder are suspended, 150 ml of an 8% polyvinylamine solution and 50 ml of acrolein are added. After intensive dispersion, the suspension is stirred for 30 minutes with an anchor stirrer (30 min ^"1 ) leave at room temperature. Subsequently, the pH of the solution is increased to pH ~ 10 by adding concentrated sodium hydroxide solution and the temperature is raised to 60 ° C. in the course of 1.5 h with continued stirring of the mixture. After 2 h, the particle-containing reaction mixture is slowly cooled to room temperature, and the microparticles are separated off by filtration and washed with dist. Washed water several times. 1000 g of particles with an average particle size of 40 μm are isolated, which have molybdenum sulfide in a shell made of polyurea-containing material.

Example 8

Production of matrix particles 500.0 g BAYHYDUR 3100 are in a reactor with dispersant and anchor stirrer in 7500 ml of a 2.5% by weight solution of polyvinyl alcohol (M: 10 ⁵ g / mol) with intensive mixing with the dispersant (3000 min ^"1 ) finely divided. 1500 ml of an 8% polyvinylamine solution and 250 ml of acrolein are added. To initiate the crosslinking, 10 g of KOH are added and the mixture is intensively mixed for 10 minutes at room temperature. After the intensive mixing, the pH is adjusted - The value of the solution is adjusted to pH ~ 10 and the temperature is increased with continued stirring with the anchor stirrer within 1.5 h to 60 ° C. After 2 h, the reaction mixture containing particles is slowly cooled to room temperature and the microparticles are separated off by filtration and Washed several times with distilled water, 800 g of particles with an average particle size of 4 μm are isolated. These particles form microcapsules with solid contents The capsule and the walls are made of the same material.

Claims

claims:

1. Process for the production of microcapsules with liquid and / or solid ingredients inside the capsules and capsule walls which have polyurea-containing material, characterized in that the capsule walls are made of polyurea material which has functional groups which are crosslinked by means of a crosslinker.

2. The method according to claim 1, characterized in that the formation of the capsule walls takes place in the aqueous phase.

3. The method according to claim 1 or 2, characterized in that the cross-linking parallel to the formation of the capsule walls of polyurea

Material is stirred.

4. The method according spoke 1 or 2, characterized in that the crosslinking is carried out after the formation of the capsule wall.

5. The method according to any one of claims 1 to 4, characterized in that the polyurea-containing material which has functional groups is prepared by reaction of amines and isocyanates.

6. The method according to claim 5, characterized in that amines with functional groups are used.

7. The method according to claim 6, characterized in that melamine-containing amines are used.

8. The method according to any one of claims 1 to 7, characterized in that a mono- or dialdehyde is used as the crosslinking agent.

9. The method according to at least one of claims 1 to 6, characterized in that an amine is used which has been modified with an α, β-unsaturated aldehyde or ketone.

10. The method according to claim 9, characterized in that the crosslinking in the presence of free radical initiators or Lewis

Acids or bases or by irradiating energy.

11. Microcapsules with reinforced capsule walls, produced according to at least one of claims 1 to 10.

12. Microcapsules with a capsule wall, which has a polyurea-containing material, and liquid and / or solid ingredients inside the capsules, characterized in that the capsule wall, which has the polyurea-containing material, is hardened by a crosslinker.

13. Microcapsule according to claim 12, characterized in that the capsules have a diameter of 600 nm to 300 microns.

14. Microcapsule according to claim 12 or 13, characterized in that the capsules also contain a polyurea-containing material.

15. Use of microcapsules according to at least one of claims 11 to 14 as a container for ingredients, as a container for ingredients, the containers being

Pressure release the ingredients, as a micro memory, as a component in electronic displays or as microreactors.