WO2009071499A1 - Microcapsules having radiation-induced release - Google Patents

Abstract

The present invention relates to a novel microcapsule comprising a capsule wall made of polyurea and a capsule core comprising a polyacrylate copolymer and at least one compound absorbing electromagnetic radiation of the wavelength range from 700 nm to 1 m, a method for the production thereof, the use thereof for radiation-induced release of polyacrylate copolymer, and microcapsule dispersions comprising said microcapsules, and a method for gluing at least two substrates.

Description

 Microcapsules with radiation-induced release

description

The present invention relates to microcapsules comprising a capsule wall of polyurea and a capsule core containing a polyacrylate copolymer and at least one compound which absorbs electromagnetic radiation from the wavelength range of 700 nm to 1 m, a process for their preparation and their use for the radiation-induced release of polyacrylate copolymer.

Microcapsules are known in various embodiments and are used depending on the tightness of the capsule wall for very different purposes. For example, they serve to protect core materials that are to be released only by targeted mechanical destruction of the capsule wall, such as dyes for carbonless paper or encapsulated fragrances. In such fields of application, capsule wall materials based on gelatin, polyurethane, and on polyurea and on polyacrylates and methacrylates are known. Other requirements are placed on wall materials for herbal or pharmaceutical active substances as core materials, in which it depends on a permeability of the capsule wall, which allows a controlled release and the targeted transport of the active ingredients.

US 5,596,051 describes microcapsules with a poly-n-butyl acrylate as the core material and a copolymer of methyl methacrylate and methacrylic anhydride as a wall material. The wall opening is carried out by addition of bases which chemically solve the crosslinking or swell the anhydride groups and thus allow the escape of the adhesive resin.

DE 3918141 teaches microcapsules with capsule walls of difunctional acids or acid derivatives and hexamethylenetetramine or acetaldehyde ammonia derivatives as crosslinkers. The incorporated hexamethylenetetramine or the Acetaldehydammoniak- derivative is thermolabile and thus represents a predetermined breaking point in the capsule wall, which thermally induced causes the release of the active substance.

WO 91/12883 and WO 91/12884 teach photo- and thermolabile microcapsules with polyurea capsule walls. In the wall polymer azo or peroxide groups are included as predetermined breaking points that triggered photochemically or thermally, lead to the opening of the capsule wall. The installation of such predetermined breaking points requires special monomers that do not allow any process control, especially at higher temperatures.

WO 02/20683 teaches a microencapsulated acrylate adhesive wherein the adhesive is formed during encapsulation. As wall materials, ren polyurea resins and alkyl acrylate / acrylic acid copolymers called. The release takes place by pressure or heat, with the disadvantage that the parts to be bonded must be heated as a whole.

From the earlier European applications 06126997.3 and 06126994.0 thermally destructible microcapsules for a Kaschierklebstoffdispersion are known. The microcapsule walls described therein based on polymethyl methacrylate become permeable as a rule at temperatures above 60 ⁰ C for the information contained in the core carbodiimides and so cause the post-crosslinking of the laminating adhesives.

WO 03/054102 describes adhesives which contain at least one mixed metal oxide in the form of superparamagnetic, nanoscale particles, and also processes for heating such preparations with the purpose of producing or dissolving adhesive compounds based on these preparations. Thus, according to one embodiment variant, the curing-triggering component, such as a monomer or catalyst, in the form of microcapsules containing superparamagnetic nanoscale particles as capsule core, are dispersed in an adhesive composition and released by irradiation.

A similar approach is taken by WO 02/48278, which describes a 1 K dosage form of a two-component adhesive in which one component A is microencapsulated and the microcapsules are distributed in a matrix of the second component B. By irradiation with light of the wavelength 200-700 nm, the component A is released and the adhesive is formed.

WO 2004/076578 teaches hot melt adhesives containing near infrared absorbing dyes or pigments. Tackiness can be reactivated by near-infrared irradiation by applying energy at the irradiated sites until the hotmelt adhesive has melted.

A particular problem can be found in pressure-sensitive adhesives, as they are known from label adhesives, as they are permanently sticky. When you process them, you need to protect the adhesive surface specially coated papers, which are only when the adhesive effect is desired to be deducted. The protective papers fall as waste.

An object of the present invention was a new dosage form of pressure-sensitive adhesives, which should make it possible to control the adhesive effect both temporally and spatially targeted.

Accordingly, microcapsules have been found comprising a capsule wall of polyurea and a capsule core containing a polyacrylate copolymer and at least at least one compound that absorbs electromagnetic radiation from the wavelength range of 700 nm to 1 m, hereinafter also referred to as absorber. Furthermore, a process for their preparation and microcapsule dispersions containing these microcapsules was found. Furthermore, it has been found that polyacrylate copolymer encapsulated in this way can be released in a radiation-induced manner. Furthermore, the application relates to a method for bonding at least two substrates.

The microcapsules according to the invention comprise a capsule core and a polymer capsule wall. The mean particle size of the capsules weight average (by means of light scattering) is 0.5 to 50 μm, preferably 0.5 to 30 μm. The weight ratio of capsule core to capsule wall is generally from 50:50 to 95: 5. Preferred is a core / wall ratio of 70:30 to 95: 5.

The term polyurea includes both the reaction products of isocyanate with di- and / or polyamines, the reaction products of isocyanate with di- and / or polyamidines and the reaction products of isocyanate with mixtures of di- and / or polyamines and di- and / or polyamidines.

The basic principle of microencapsulation is based on so-called interfacial polymerization or addition. In the interfacial polyaddition, a lipophilic mixture of the substances to be encapsulated, one or more isocyanates and optionally a lipophilic solvent is prepared in a first process step and then mixed with a hydrophilic solvent and processed into an emulsion. The continuous phase of the emulsion usually contains surface-active substances to prevent the droplets from flowing together. In this emulsion, the lipophilic mixture is the discontinuous later disperse phase and the hydrophilic solvent is the continuous phase. If the hydrophilic solvent is water, the term oil-in-water emulsion is also illustrative. The emulsified droplets have a size which corresponds approximately to the size of the later microcapsules. To form the capsule wall, the emulsion is mixed in a second process step with the diamine or polyamine capable of forming a wall and / or di- and / or polyamidine. The isocyanate is capable of reacting at the interface between the discontinuous and the continuous phase with the dissolved in the continuous phase di- or polyamine and / or di- and / or polyamidine to form the polymeric film.

The third process step comprises the so-called post-treatment of the freshly prepared capsule dispersion. In this case, the reaction between isocyanate and / or polyamine and / or di- and / or polyamidine is brought to an end under the control of temperature and residence time and optionally with the use of further auxiliaries. A process for the production of microcapsules with polyurea walls is described for example in EP 227 562. A hydrophilic solvent is understood as meaning both water and aqueous mixtures which, apart from water, comprise up to 20% by weight of a water-miscible organic solvent, such as C 1 - to C 4 -alkanols, in particular methanol, ethanol, isopropanol or a cyclic Contain ethers such as tetrahydrofuran. Preferred hydrophilic solvent is water.

Suitable hydrophilic solvents are also ethylene glycol, glycerol, polyethylene glycols and butylene glycol, their mixtures and their mixtures with water or the above-mentioned aqueous mixtures. Preferred as hydrophilic solvents are mixtures of these solvents with water.

The substances to be encapsulated are polyacrylate copolymer, absorber and optionally further auxiliaries such as plasticizers, tackifying resins, solvents, UV stabilizers and radical scavengers. Depending on its solubility, the absorber is dispersed in the lipophilic phase or in solution.

A polyacrylate copolymer is a polymer which is obtainable by free-radical polymerization of acrylic monomers, which are also understood to mean methylacrylic monomers, and other copolymerizable monomers. The polyacrylate copolymer is preferably composed of at least 40% by weight, more preferably at least 60% by weight, very preferably at least 80% by weight, of C 1 -C 10 -alkyl (meth) acrylates. Particular mention may be made of C 1 -C 8 -alkyl (meth) acrylates, e.g. Methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (methacrylate).

Other monomers from which the polyacrylate copolymer can be constructed are e.g. Vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinylaromatics having up to 20 carbon atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers of alcohols having 1 to 10 carbon atoms, aliphatic hydrocarbons having 2 to 8 carbon atoms and 1 or 2 Double bonds or mixtures of these monomers.

As vinyl aromatic compounds are e.g. Vinyltoluene, o- and p-methylstyrene, o-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene into consideration. Examples of nitriles are acrylonitrile and methacrylonitrile.

The vinyl halides are chloro, fluoro or bromo substituted ethylenically unsaturated compounds, preferably vinyl chloride and vinylidene chloride.

To name as vinyl ethers are, for. As vinyl methyl ether or vinyl isobutyl ether. Vinyl ether is preferably from 1 to 4 C-containing alcohols. As hydrocarbons having 2 to 8 carbon atoms and two olefinic double bonds may be mentioned butadiene, isoprene and chloroprene.

In particular, monomers having carboxylic acid, sulfonic acid or phosphonic acid groups are also suitable as further monomers. Preferred are carboxylic acid groups. Called z. For example, acrylic acid, methacrylic acid, itaconic acid, maleic acid or fumaric acid.

Other monomers are z. B. also hydroxyl-containing monomers, in particular Ci-Cio-hydroxyalkyl (meth) acrylates, (meth) acrylamide.

In addition, phenyloxyethyl glycol mono- (meth) acrylate, glycidyl acrylate, glycidyl methacrylate, amino (meth) acrylates such as 2-aminoethyl (meth) acrylate may be mentioned. Monomers which, in addition to the double bond, carry further functional groups, eg. As isocyanate, amino, hydroxy, amide or glycidyl, z. B. improve adhesion to substrates.

UV crosslinkable polyacrylate copolymers are preferred. The photoinitiator is bound to the polyacrylate copolymer in this preferred variant. By irradiation with high-energy light, in particular UV light, the photoinitiator effects a crosslinking of the polymer, preferably by a chemical grafting reaction of the photoinitiator with a spatially adjacent polymer chain. In particular, crosslinking may be accomplished by insertion of a carbonyl group of the photoinitiator into an adjacent C-H bond to form a -C-C-O-H moiety.

The polyacrylate copolymer preferably contains from 0.0001 to 1 mol, particularly preferably from 0.0002 to 0.1, very particularly preferably from 0.0003 to 0.01 mol, of the photoinitiator, or of the photoinitiator-effective polymer group, per 100 g polyacrylate copolymer.

The photoinitiator is preferably incorporated into the polymer chain by free-radical copolymerization. Preferably, the photoinitiator contains an acrylic or (meth) acrylic group.

Suitable copolymerizable photoinitiators are acetophenone or benzophenone derivatives which contain at least one, preferably one ethylenically unsaturated group. The ethylenically unsaturated group is preferably an acrylic or methacrylic group.

The ethylenically unsaturated group may be bonded directly to the phenyl ring of the acetophenone or benzophenone derivative. In general, there is a spacer group (spacer) between the phenyl ring and the ethylenically unsaturated group. The spacer group may have, for example, a molecular weight of up to 500, in particular up to 300 or 200 g / mol.

Suitable acetophenone or benzophenone derivatives are e.g. in EP-A-346 734, EP-A-377199 (claim 1), DE-A-4 037 079 (claim 1) and DE-A-3 844 444 (claim 1) and are by this reference also disclosed in the present application. Preferred acetophenone and benzophenone derivatives are those in which the attachment of the spacer group to the phenyl ring takes place via a carbonate group. Preference is given to compounds of the formula I:

wherein R ^{1 is} an organic radical having up to 30 C atoms, R ^{2 is} an H atom or a methyl group and R ^{3 is} an optionally substituted phenyl group or a Ci-C4-alkyl group.

R ¹ particularly preferably represents an alkylene group, in particular a C ₂ -C 5 -alkylene group.

R ³ particularly preferably represents a methyl group or a phenyl group, very particularly preferably a phenyl group.

Also preferred are acetophenone and benzophenone derivatives of the formula II

wherein R ³ and R ^{2 have} the above meaning and R ⁴ can stand for:

a single bond for a radical R ¹ with the above meaning, for (-CH ₂ -CH ₂ -O) _n ,

NH

~ C _n H _2V -o-

⁰ or , NH

^ C _n H-NH-O

where n is an integer from 1 to 12.

Particular preference is given to compounds of the formula I.

The polyacrylate copolymer preferably has a K-value of 10 to 100, particularly preferably from 40 to 60, as measured in tetrahydrofuran (1% solution, 21 ⁰ C). The K value according to Fikentscher is a measure of the molecular weight and viscosity of the polymer.

The glass transition temperature (T ₉ ) of the polyacrylate copolymer is preferably - 60 to +10 ⁰ C, more preferably -55 to 0 ⁰ C, most preferably -55 to - 10 ⁰ C. The glass transition temperature can be determined by conventional methods such as differential thermal analysis or Differential scanning calorimetry (see eg ASTM 3418/82, so-called "midpoint temperature").

The polyacrylate copolymers can be prepared by copolymerization of the monomeric components using the customary polymerization initiators and, if appropriate, regulators, polymerization being carried out at the customary temperatures in bulk, in emulsion, for example in water or liquid hydrocarbons, or in solution. The polyacrylate copolymers are preferably prepared by polymerization of the monomers in solvents, in particular in solvents having a boiling range from 50 to 150 ^° C., preferably from 60 to 120 ^° C., using the usual amounts of polymerization initiators, generally from 0.01 to 10, in particular 0.1 to 4 wt .-%, based on the total weight of the monomers is prepared.

Preferred solvents for the polymerization include ketones, alkyl alcohols or alkylene LaCetate having a boiling point below 150 ⁰ C (at 1 bar), such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), ethanol, i-butanol, i-propanol, methyl acetate, Ethyl acetate and aromatic hydrocarbons such as benzene, toluene or xylene.

Suitable polymerization initiators in the solution polymerization are, for example, azo compounds, ketone peroxides and alkyl peroxides.

The polyacrylate copolymer used according to the invention can be used in bulk or in solution. Suitable are lipophilic solvents which form a phase boundary with water. Examples of suitable solvents for polyacrylate copolymers include:

a) aliphatic hydrocarbon compounds such as saturated or unsaturated Cio-C4o-hydrocarbons which are branched or preferably linear, e.g. such as n-tetradecane, n-pentadecane, n-hexadecane, n-heptadecane, n-octadecane, n-nonadecane, n-eicosane, n-heneicosane, n -docosan, n-tricosane, n-tetracosane, n-pentacosane, n Hexacosan, n-heptacosane, n-octacosane and cyclic hydrocarbons, eg Cyclohexane, cyclooctane, cyclodecane;

b) aromatic hydrocarbon compounds such as benzene, naphthalene, biphenyl, o- or m-terphenyl, C 1 -C 4 -alkyl-substituted aromatic hydrocarbons such as toluene, xylene, dodecylbenzene, tetradecylbenzene, hexadecylbenzene, hexylnaphthalene or decylnaphthalene;

c) saturated or unsaturated Cβ-Cso fatty acids such as lauric, stearic, oleic or behenic acid, preferably eutectic mixtures of decanoic acid with e.g. Myristic, palmitic or lauric acid;

d) fatty alcohols such as lauryl, stearyl, oleyl, myristyl, cetyl alcohol, mixtures such as coconut fatty alcohol and the so-called oxo alcohols, which are obtained by hydroformylation of α-olefins and further reactions;

e) C 6 -C 30 fatty amines, such as decylamine, dodecylamine, tetradecylamine or hexadecylamine;

f) esters, such as C 1 -C 10 -alkyl esters of fatty acids, such as propyl palmitate, methyl stearate or methyl palmitate, and preferably their eutectic mixtures or methyl cinnamate;

g) natural and synthetic waxes such as montanic acid waxes, montan ester waxes, carnauba wax, polyethylene wax, oxidized waxes, polyvinyl ether wax, ethylene vinyl acetate wax or Fischer-Tropsch wax waxes;

h) halogenated hydrocarbons such as chloroparaffin, bromoctadecane, bromopentadecane, bromononadecane, bromeicosane or bromodocosane and

i) natural oils such as peanut oil, soybean oil. Also suitable are solvents whose solutions of the polyacrylate copolymer in mixture with water form a phase boundary. The presence of these solvents usually results in an advantageous viscosity reduction. By way of example, the solvents of group k) are mentioned:

k) ketones or alkyl acetates having a boiling point below 150 ⁰ C (at 1 bar) such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), methyl acetate or ethyl acetate.

According to a preferred embodiment, a solvent is chosen which is also suitable for the preparation of the polyacrylate copolymers, i. in the polymerization of the monomers as a solvent. Particular preference is given to the solvents mentioned under a), b) and k) and mixtures of these solvents.

Of course, it is also possible to carry out the polymerization of the polyacrylate copolymer in another solvent and then to exchange the solvent.

The polyacrylate copolymers can be used as 20-99% by weight solutions, preferably 50-90% strength by weight solutions in the solvents listed in groups a) to k).

According to a preferred embodiment, the lipophilic mixture is solvent-free and contains only the polyacrylate copolymer, the compound which absorbs electromagnetic radiation from the wavelength range from 700 nm to 1 m, particularly preferably from> 700 nm to 1 m (absorber), and optionally excipients. According to another embodiment, the lipophilic mixture contains the polyacrylate copolymer, the absorber, the solvent, preferably lipophilic solvent, and optionally excipients.

Preferably, the absorbers are s.o. blended in the polyacrylate copolymer.

Suitable plasticizers are, for example, diesters of phthalic acid, cyclohexanedicarboxylic acid or adipic acid or tackifying resins. Such resins are, as described in EP 1329492, e.g. Natural resins such as rosins or hydrocarbon resins.

Due to the affinity of the absorber for the core material, the absorber is predominantly mixed with the core material and / or incorporated into the capsule wall.

There are different types of absorbers: - Organic IR absorbers - Organic microwave absorber

- Inorganic IR absorbers

- Inorganic microwave absorber

For the purposes of this application, the term "IR absorber" is to be understood as meaning a compound which has an absorption of> 90% applied in a layer thickness of 50 μm at at least one wavelength of radiation in the wavelength range from 700 nm to 1 mm. Preferably, the wavelength range of> 700 nm to 2000 nm, and the wavelengths 9.6 microns and 10.6 microns.

In the context of this application, microwave absorber is to be understood as meaning a compound which absorbs microwaves of the wavelength range of> 1 mm to 1 m. Particularly preferred are the technically relevant frequencies of 2.45 GHz, 433-444 MHz and 902-928 MHz.

Organic IR absorbers are widely described in the literature. Such compounds include cyanines, metal complexes, quinones, azo dyes, multiphenylmethanes, perylenes, quaterrylenes, aromatic annulenes and especially metallophthalocyanines, metal naphthalocyanines, metalloporphyrins, terrylimides and quaterrylimides. Depending on the substituents, compounds having such backbones are soluble in solvents, ie dyes, or insoluble, and thus pigments. By way of example, mention may be made of IR absorbers, as described in WO 02076988. Particular preference -Lumogen ^® IR 765 and 788 of BASF Aktiengesellschaft.

Organic microwave absorbers are described for example in the earlier European application 07 106 445.5, to which reference is expressly made.

Inorganic microwave absorbers are metal oxides that have a magnetic moment as well as soot and graphite. As a rule, the compounds also absorb IR radiation, so that the enumeration applies to both types of excitation.

Suitable inorganic absorbers are particles having an average particle size in the range from 0.1 to 5 μm, which are electrically conductive, magnetic, ferrimagnetic, ferromagnetic, antiferromagnetic or superparamagnetic. The application of an additional static magnetic field leads to a better absorption of these particles (typical field strengths are 10 - 60 mTesla). Examples include metals and transition metals such as Al, Fe, Zn, Ti or Cu, their salts such as their oxides such as ZnO, iron oxides, especially ferrites, and TiÜ2, carbonates or sulfides, carbon such as graphite, carbon black, nanoparticulate carbon or nanotubes , Silicon carbides, silicon, alkali and alkaline earth metal salts, etc. Furthermore, the metal mixed oxides mentioned in WO 03/054102 are suitable, to which reference is expressly made. Preference is given to carbon black, FesCU and graphite.

According to one embodiment, microcapsules having a capsule core containing a polyacrylate copolymer, more preferably a UV-crosslinkable polyacrylate copolymer, and at least one organic IR absorber are preferred.

According to a further embodiment, microcapsules having a capsule core comprising a polyacrylate copolymer, particularly preferably a UV-crosslinkable polyacrylate copolymer, and at least one inorganic microwave absorber are preferred.

The absorber particles are, if they are inorganic particles such as carbon black or Fe3Ü4, dispersed in the lipophilic solvent of the capsule core. If the absorber particles are dispersed, they should have a particle size <5 microns, preferably <2 microns.

The microcapsules according to the invention contain, depending on the type of absorber and the activation form, at most 10% by weight of absorber, preferably 0.1 to 10% by weight, in particular 1 to 7% by weight, very particularly preferably 2 to 5% by weight % Absorber, based on the total amount of polyacrylate copolymer and polyurea capsule wall.

The capsule wall according to the invention consists essentially of polyurea.

For the purposes of this application, isocyanate is to be understood as meaning a compound which carries two or more isocyanate groups and reacts with the amine component, namely a diamine, polyamine, di- and / or polyamidine.

Suitable polyisocyanates are aliphatic, cycloaliphatic, araliphatic and aromatic isocyanates.

Suitable aromatic diisocyanates are, for example, 2,2'-, 2,4'- and / or 4,4'-diphenylmethane diisocyanate (MDI), 1, 5-naphthylene diisocyanate (NDI), 2,4- and / or 2,6-toluene diisocyanate (TDI), diphenylmethane diisocyanate, 3,3'-dimethyldiphenyl diisocyanate, 1, 2-diphenylethane diisocyanate, phenylene diisocyanate and / or tetramethylxylylendiisocyat.

Aliphatic and cycloaliphatic diisocyanates include, for example, tri-, tetra-, penta-, hexa-, hepta- and / or octamethylene diisocyanate, 2-methyl-pentamethylene-1,5-diisocyanate, 2-ethylbutylene-1,4-diisocyanate, 1-isocyanato 3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 1, 4- and / or 1, 3-bis (isocyanatomethyl) cyclohexane (HXDI), cyclohexane-1, 4-diisocyanate, 1-methyl 2,4- and / or 2,6-cyclohexanediisocyanato and / or 4,4'-, 2,4'- and / or 2,2'-dicyclohexylmethane diisocyanate.

Examples of higher functionality isocyanates are triisocyanates, e.g. B. Triphenylmethane-4,4 ', 4 "-triisocyanate, furthermore the cyanurates of the aforementioned diisocyanates, as well as the oligomers obtainable by partial reaction of diisocyanates with water, eg the biurets of the abovementioned diisocyanates, furthermore oligomers obtained by specific reaction of semiblocked diisocyanates with polyols having on average more than 2 and preferably 3 or more hydroxy groups.

It is also possible to use the distillation residues having isocyanate groups obtained in the industrial preparation of isocyanate, if appropriate dissolved in one or more of the abovementioned polyisocyanates. Furthermore, it is possible to use any mixtures of the aforementioned polyisocyanates.

Suitable modified aliphatic isocyanates are, for. For example, those based on hexamethylene-1, 6-diisocyanate, m-xylylene diisocyanate, 4, 4'-diisocyanatodicyclohexylmethane and isophorone diisocyanate, which have at least two isocyanate groups per molecule.

Furthermore suitable are z. B. polyisocyanates based on derivatives of hexamethylene-1, 6-diisocyanate with biuret structure as described in DE-AS 1 101 394, DE-AS 1 453 543, DE-OS 1 568 017 and DE-OS 1 931 055 ,

It is also possible to use polyisocyanate polyuretonimines, such as those obtained by carbodiimidization of biuret-group-containing hexamethylene-1,6-diisocyanate with organophosphorus catalysts, primary carbodiimide groups reacting with further isocyanate groups to give uretonimine groups.

It is also possible to use isocyanurate-modified polyisocyanates having more than two terminal isocyanate groups, eg. B. those whose preparation is described based on hexamethylene diisocyanate in DE-OS 2,839,133. Other isocyanurate-modified polyisocyanates can be obtained analogously.

It is also possible to use mixtures of said isocyanates, eg. As mixtures of aliphatic isocyanates, mixtures of aromatic isocyanates, mixtures of aliphatic and aromatic isocyanates, in particular mixtures containing optionally modified diphenylmethane diisocyanates.

The di- and / or polyisocyanates described herein may also be used as mixtures with di- and polycarboxylic acid chlorides, such as sebacoyl chloride, terephthaloyl chloride, adipic acid dichloride, oxalic acid dichloride, tricarballyl trichloride, and 1,2,5,4- Benzolcarbonsäuretetrachlorid, with di- and polysulfonyl chlorides wiel, 3-benzenesulfonic acid dichloride and 1, 3, 5-benzenesulfonic acid trichloride, phosgene and with dichloro and polychloroformate, such as 1, 3, 5-benzenesulfonyl benzoate and Ethylbischloroformiat apply.

It is also possible to use, for example, oligoisocyanates or polyisocyanates which are prepared from the abovementioned diisocyanates or polyisocyanates or mixtures thereof by linking by means of urethane, allophanate, urea, biuret, uretdione, amide, isocyanate, carbodiimide, uretonimine , Oxadiazinetrione or iminooxadiazinedione structures.

Preferred isocyanates are biuretically or isocyanuretically linked oligomers of hexamethylene diisocyanate, and isophorone diisocyanate, m-

Tetramethylxylylene diisocyanate or oligomers of Methylendiphenyldiisocyanat, and mixtures of these and the above-mentioned isocyanates. Particularly preferred are isophorone diisocyanate and isocyanuretically linked oligomers of hexamethylene diisocyanate.

Di- and polyamines according to the invention may be substituted by hydroxyl groups. Likewise suitable are di- and / or polyamidines, in particular those which have an intramolecular azo or peroxy group. These compounds can be used in pure form or as mixtures with one another. The incorporation of additional azo or peroxo groups-bearing di- and / or polyamidines leads to microcapsules which release their ingredients well with an increase in temperature.

Suitable amines are generally di- and polyamines of the molecular weight range from 32 to 500 g / mol, which contain at least two amino groups selected from the group of primary or secondary amino groups. Examples of these are diamines, such as diaminoethane, diaminopropanes, diaminobutanes, diaminohexanes, amino-3-aminomethyl-3,5,5-trimethyl-cyclohexane (isophoronediamine, IPDA), 4, 4'-

Diaminodicyclohexylmethane, 1, 4-diaminocyclohexane, aminoethylethanolamine, hydrazine, hydrazine hydrate or triamines such as diethylenetriamine, 1, 8-diamino-4-aminomethyloctane, hexahydro-2,4,6-trimethyl-1, 3,5-triazines or polyamines such Tetraethylenetriamine, pentaethylenetetramine or polyimines or polyetheramines. As amidine is exemplified 2,2'-azobis (2-methylpropionamidine) called dihydrochloride, which is sold as a basic solution by WAKO Inc. Azo or peroxo-containing amines are described in EP-AO 516 742. Furthermore, it is possible the amines also in blocked form, for. In the form of the corresponding ketimines (see, for example, CA-A-1 129 128), ketazines (cf., for example, US Pat. No. 4,269,748) or amine salts (see US Pat. No. 4,292,226). use. Preferred di- or polyamines are C2-C6 aliphatic diamines such as ethylenediamine, C2-C6 aliphatic triamines such as diethylenetriamine and hexahydro-2,4,6-trimethyl-1,3,5-triazine. Also preferred is the amidine 2,2'-azobis (2-methylpropionamidine) dihydrochloride in basic solution.

The amount of the isocyanate to be used according to the invention and of the amine components, namely the diamine, polyamine, di- and / or polyamidine, is in the range customary for interfacial polyaddition processes.

The theoretical amount of the amine component necessary for wall formation is calculated from the content of reactive isocyanate groups of the isocyanate used and the total mass of desired polymer shell around the microcapsule core.

For the reaction of all NCO groups in the oil phase at least theoretically the same number of amino groups are required. It is therefore advantageous to use the isocyanate and the amine component in relation to their equivalent weights. However, it is also possible to deviate either downwards from the stoichiometrically calculated amount of amine since, in the case of interfacial polyaddition processes, a side reaction of the isocyanate with the excess water can not be ruled out or an excess of the amine component can be used, because such is not critical.

In particular, therefore, one uses the amine component in an amount which is between 50 and 150 wt .-% of theoretical calculated. Preferably, this amount is between 100 and 130 wt .-%, based on the theoretically calculated amount.

The present invention further relates to a process for the preparation of microcapsules comprising the steps

a) preparing a lipophilic mixture comprising a polyacrylate copolymer and at least one compound which absorbs electromagnetic radiation from the wavelength range from 700 nm to 1 m, one or more isocyanates and optionally solvents, b) emulsifying the mixture obtained from a) in a hydrophilic solvent and c) Formation of the capsule wall by addition of the emulsion obtained from b) with a di- and / or polyamine and / or a di- and / or polyamidine.

and the microcapsule dispersion obtained according to this method. The present invention further relates to a second alternative process for the preparation of microcapsules comprising the steps

a) preparing a lipophilic mixture comprising a polyacrylate copolymer and at least one compound which absorbs electromagnetic radiation from the wavelength range from 700 nm to 1 m and optionally solvent, b) emulsifying the mixture obtained from a) in a hydrophilic solvent, c) adding one d) emulsifying the mixture obtained from c) and e) forming the capsule wall by adding the emulsion obtained from d) with a di- and / or polyamine and / or a di- and / or polyamidine ,

and the microcapsule dispersion obtained according to this method.

The optional solvent is a non-hydrophilic solvent. It is preferably one of the above-described lipophilic solvents which is optionally present.

In order to obtain a stable emulsion, surfactants such as polymeric protective colloids are generally required. As a rule, surfactants are used which mix with the hydrophilic phase.

In general, the microcapsules are prepared in the presence of at least one organic protective colloid. These protective colloids may be ionic or neutral. Protective colloids can be used both individually and in mixtures of several identically or differently charged protective colloids.

Preference is given to using organically neutral protective colloids. Organic protective colloids are preferably water-soluble polymers which ensure the formation of closed capsule walls and form microcapsules with preferred particle sizes in the range from 0.5 to 50 μm, preferably 0.5 to 30 μm, in particular 0.5 to 10 μm.

Organic neutral protective colloids are, for example, cellulose derivatives such as hydroxyethylcellulose, methylhydroxyethylcellulose, methylcellulose and carboxymethylcellulose, polyvinylpyrrolidone, copolymers of vinylpyrrolidone, gelatin, gum arabic, xanthan, casein, polyethylene glycols, polyvinyl alcohol and partially hydrolyzed polyvinyl acetates and also methylhydroxypropylcellulose. Preferred organic neutral protective colloids are polyvinyl alcohol and partially hydrolyzed polyvinyl acetates and methylhydroxypropyl cellulose, preferably in combination. Polyvinyl alcohol is obtainable by polymerizing vinyl acetate, optionally in the presence of comonomers, and hydrolysis of the polyvinyl acetate with elimination of the acetyl groups to form hydroxyl groups. The degree of hydrolysis of the polymers can be, for example, from 1 to 100% and is preferably in the range from 50 to 100%, in particular from 65 to 95%. For the purposes of this application, partially hydrolyzed polyvinyl acetates are to be understood as meaning a degree of hydrolysis of <50% and polyvinyl alcohol of> 50 to 100%. The preparation of homo- and copolymers of vinyl acetate and the hydrolysis of these polymers to form polymers containing vinyl alcohol units are well known. Vinyl alcohol units-containing polymers are sold, for example as Mowiol ^® brands from Kuraray Specialties Europe (KSE).

Preferred are polyvinyl alcohols or partially hydrolyzed polyvinyl acetates whose Vis viscosity by a 4 wt .-% aqueous solution at 20 ⁰ C has a value in the range from 3 to 56 mPa * s DIN 53015, preferably a value of 14 to 45 mPa * s , in particular from 22 to 41 mPa ^* s. Preference is given to polyvinyl alcohols having a degree of hydrolysis of> 65%, preferably> 70%, in particular> 75%.

Also advantageous are hydroxypropyl as sold as Culminal.RTM ^® brands from Hercules GmbH, Dusseldorf. Hydroxypropyl celluloses are preferred having a viscosity of 2 wt .-% solution at 20 ⁰ C 25-16000 mPas, preferably 40-600, particularly preferably 90-125 mPas (Brookfield viscosity RVT).

In general, polyvinyl alcohol or teilhydrolysiert.es polyvinyl acetate or mixtures of these with Hydroxylpropylcellulosen in a total amount of at least 3 wt .-%, preferably from 3.5 to 8 wt .-% used, based on the micro- rocapsules (without protective colloid). It is possible to add further abovementioned protective colloids in addition to the preferred amounts of polyvinyl alcohol or partially hydrolyzed polyvinyl acetate or hydroxylpropyl cellulose. The microcapsules are preferably prepared only with polyvinyl alcohol and / or partially hydrolyzed polyvinyl acetate and / or hydroxylpropyl cellulose without the addition of further protective colloids.

Furthermore, it is possible for costabilization to add surfactants, preferably nonionic surfactants. Suitable surfactants can be found in the "Handbook of Industrial Surfactants", the contents of which are expressly referred to The surfactants can be used in an amount of from 0.01 to 10% by weight, based on the water phase of the emulsion.

With the help of the surfactant, a stable emulsion is prepared with stirring. According to a preferred variant, the amine component is first added to the stable emulsion of the solution of polyacrylate copolymer, absorber and isocyanate or during its emulsification step. As a rule, this starts the interfacial polyaddition or condensation and thus the wall formation.

According to a likewise preferred variant, the isocyanate is first added to the stable emulsion of the solution of polyacrylate copolymer and absorber in water or even during its emulsification step. The stable emulsion thus prepared or during its emulsifying step, the amine component is added first. As a rule, this starts the interfacial polyaddition or condensation and thus the wall formation.

The interface reaction can proceed, for example, at temperatures in the range from -3 to +98 ⁰ C, preferably carried out at 10 to 80 ⁰ C.

The dispersion of the core material is carried out in a known manner, depending on the size of the capsules to be prepared. For the preparation of large capsules, the dispersion is sufficient using effective stirrers, in particular propeller or impeller stirrers. Small capsules, especially if the size is to be below 50 microns, require homogenizing or dispersing machines, these devices may be provided with or without Zwangsdurchlaufvorrichtung.

Homogenization can also be achieved by the use of ultrasound (eg Branson Sonifier Il 450). For homogenization by means of ultrasound, for example, the devices described in GB 2250930 and US Pat. No. 5,108,654 are suitable.

The capsule size can be about the number of revolutions of the dispersing / homogenizing and / or with the help of the concentration of the protective colloid or on its molecular weight, d. H. controlled by the viscosity of the aqueous continuous phase within certain limits. The size of the dispersed particles decreases as the number of turns increases up to a limit of the number of tails.

It is important that the dispersing equipment be used at the beginning of capsule formation. In continuous positive displacement machines it is advantageous to pass the emulsion through the shear field several times.

For the dispersion of highly viscous temperature-stable media, the preparation of the emulsion in a temperature range of 30 to 130 ⁰ C, preferably 40 to 100 ⁰ C.

Microcapsule dispersions containing from 5 to 50% by weight of microcapsules can be prepared by the process according to the invention. The microcapsules are single capsules. By suitable conditions for the dispersion, capsules having an average particle size in the range of 0.5 to 80 μm and larger can be prepared. Preference is given to capsules having an average particle size of from 0.5 to 50 μm, in particular up to 30 μm.

The mean particle diameter is the weight-average particle diameter, determined by quasi-elastic, dynamic light scattering. Particularly advantageous is the very narrow size distribution of the capsules.

The microcapsules according to the invention can preferably be processed directly as an aqueous dispersion. Spray drying to a microcapsule powder is generally possible, but has to be done gently.

The microcapsules of the invention can be processed well and have good tightness. With temperature increase usually to temperatures in the range of 100 to 180 ⁰ C, they become permeable to their ingredients. This allows a targeted release of the ingredients, which can thus be formulated directly in the form of the microcapsules and do not need to be dosed cumbersome shortly before use.

The microcapsules according to the invention are suitable as pressure-sensitive adhesives, e.g. for the construction of block-resistant coatings on paper, cardboard, wood, etc., whereby the capsule contents can be released from these radiation-induced. In particular, they are suitable for the production of coatings, e.g. on labels, adhesive tapes and foils. The labels may e.g. be made of paper or plastics such as polyester, polyolefins or PVC. The adhesive tapes or films may also be made of the above plastics.

The application of the microcapsules takes place as a dispersion in a hydrophilic solvent, preferably as an aqueous dispersion. This may optionally further effect substances, such as. As slip additives, adhesion promoters, leveling agents, film-forming aids, flame retardants, corrosion inhibitors, waxes, siccatives, matting agents, deaerating agents, thickeners and biocides are added.

According to a preferred embodiment, it is possible to add to the microcapsule dispersion further above-mentioned IR or microwave absorbers in order to increase the absorption. This can be both the absorber used concretely in the encapsulation and a different one. In contrast to the encapsulated absorbers, these absorbers are freely dispersed in the continuous phase. The present invention therefore also provides a process for bonding at least two substrates, in which on the surface of at least one substrate microcapsules comprising a capsule wall of polyurea and a capsule core containing a polyacrylate copolymer and at least one compound, the electromagnetic radiation from the wavelength range of> 700 nm to 1 m absorbed, and before, during or after joining the substrates is irradiated with radiation in the wavelength range of absorption of the absorber, wherein in the case of irradiation after assembly of the substrates at least one of the substrates for the radiation is at least partially transmissive have to be.

To prepare the coatings, the microcapsule dispersions can be applied to the substrates to be coated, i. the solvent is then removed by suitable methods. It is possible in accordance with the invention to apply a non-sticky microcapsule dispersion in a planar or pointwise manner and to release the adhesive only at these points by targeted irradiation of individual regions.

For energy input and thus release of the adhesives are electromagnetic alternating fields. These can be generated, for example, with lamps which emit a high proportion of infrared radiation, infrared lasers, or microwave generators such as klystrons or magnetrons.

Suitable lasers are listed by way of example:

Gas lasers such as CO 2 lasers (wavelength 9.6 μm or 10.6 μm), helium-neon

Laser (HeNe laser, wavelength 632.8 nm) and krypton ion laser, (647.1 nm strongest line; 676.4 nm; 752.5 nm; 799.3 nm); Dye lasers Solid state lasers such as Nd: YAG laser (1064 nm), Nd: glass laser (1061 nm), titanium: sapphire laser (tunable 670-1 100 nm) and fiber laser (erbium, ytterbium or neodymium doped, 0.7 μm up to 3 μm) as well as semiconductor lasers (700 nm to 4 μm).

The wavelengths of the IR radiation used are preferably in a range> 700 nm to 2000 nm. Well suited wavelengths are 9.6 microns and 10.6 microns. For the NIR / IR irradiation, a line density of 1-100 W / cm ^{2 is} preferred, preferably 1-40 W / cm ² , with an irradiation time of 0.01-20 s.

The frequency of the microwave radiation used is preferably in a range of 500 MHz to 25 GHz. Thus, for example, electromagnetic radiation of the so-called ISM areas (Industrial Scientific and Medical Application) can be used, in which the frequencies are between 100 MHz and 200 GHz. Further details on electromagnetic alternating fields in the microwave range are described in Kirk Othmer, "Encyclopedia of Chemical Technology", 2nd edition, Volume 15, chapter "Micro-wave technology", which is incorporated herein by reference.

Preferred layer thicknesses for both IR and microwave irradiation are e.g. 1 to 500 microns, more preferably 5 to 300, most preferably 10 to 100 microns. Thicker layers are possible in principle, but usually decrease in their depth of radiation transmission.

If the polyacrylate copolymer is a polyacrylate copolymer which can be crosslinked with UV light, the coating can additionally be irradiated with high-energy radiation, preferably UV light, so that crosslinking takes place. This may be done before, at the same time or, preferably, subsequent to the release of the polyacrylate copolymer from the capsules. In general, the coated substrates are placed on a conveyor belt for this purpose and the conveyor belt is guided past a radiation source, for example a UV lamp. The degree of crosslinking of the polymers depends on the duration and intensity of the irradiation. Preferably, the UV radiation dose is a total of 2 to 1500 mJ / cm ² irradiated area.

The resulting coated substrates may preferably be used as self-adhesive articles, such as labels, adhesive tapes or protective films.

The resulting hot melt adhesive coatings have good performance properties, e.g. a good adhesion and high internal strength, even with long storage times of the inventive microcapsule dispersions.

Examples

Example 1 (model system with dye to demonstrate the capsule wall opening by means of IR radiation)

In a 2 l kettle with a dispenser stirrer (diameter 5 cm) the following mixture of water phase was added

467.8 g demineralised water (VE = demineralized water)

35 g of a 10 wt .-% aqueous polyvinyl alcohol (Mowiol ^® 15 /

79 of Kuraray Europe GmbH, viscosity of the 4% strength by weight solution at 20 ^° C., of 15 mPa s according to DIN 53015 and a saponification degree of 79%) 140 g of a 5% strength by weight aqueous methylhydroxypropylcellulose solution

(Culminal.RTM ^® MHPC 100, Hercules GmbH)

and from oil phase

17.85 g Isocyanuratisiertes hexamethylene diisocyanate (Basonat HI 100 ^®, the

BASF Aktiengesellschaft)

314.13 g of diisopropylnaphthalene

0.94 g Pergascript Red I 6 B ^® (Ciba Specialty Chemicals) 0.03 g Lumogen ^® IR 788 (BASF Aktiengesellschaft)

prepares.

The mixture was dispersed at room temperature for 15 minutes at a speed of 5000 rpm, and then transferred to a 2-liter kettle equipped with an anchor stirrer. Within 30 minutes, 17.08 g of a 20% by weight aqueous solution of hexahydro-2,4,6-trimethyl-1,3,5-triazines were added. The reaction mixture was then subjected to the following temperature program: heating to 60 ^° C. in 30 minutes, keeping the temperature for 60 minutes, then cooling to room temperature.

The solids content of this dispersion was 27.6%, with an average particle size of 12.02 microns (determined by light scattering).

Example 2 (without IR absorber - not according to the invention)

In a 2 l kettle with a dispenser stirrer (diameter 5 cm) the following mixture of water phase was added

467.8 g of deionised water

35 g of a 10% strength by weight aqueous polyvinyl alcohol solution (Mowiol

15/79)

140 g of a 5% strength by weight aqueous methylhydroxypropylcellulose solution

(Culminal MHPC 100,)

and from oil phase

17.85 g isocyanurated hexamethylene diisocyanate (Basonat HI 100)

314.13 g of diisopropylnaththalene

0.94 g Pergascript Red I 6 B

prepares. The mixture was dispersed at room temperature for 15 minutes at a speed of 5000 rpm, and then transferred to a 2-liter kettle equipped with an anchor stirrer. Within 30 minutes, 17.08 g of a 20% by weight aqueous solution of hexahydro-2,4,6-trimethyl-1,3,5-triazines were added. The reaction mixture was then subjected to the following temperature program: heating to 60 ^° C. in 30 minutes, keeping the temperature for 60 minutes, then cooling to room temperature.

The solids content of this dispersion was 25.5%, with an average particle size of 7.19 μm (determined by light scattering).

Example 3 The procedure was analogous to Example 1 with the difference that, instead of the 20% strength by weight aqueous hexahydro-2,4,6-trimethyl-1,3,5-triazines, 73.3 g of a 7.5% strength aqueous solution Solution of diethylenetriamine was added.

The solids content of the resulting dispersion was 33.5%, with an average particle size of 8.89 μm (determined by light scattering).

Application Examples 1 - 3

The microcapsule dispersions obtained according to Examples 1-3 were each applied by means of a doctor blade to a glass plate coated with silica gel, homogeneous films being obtained after drying. To destroy the capsule wall, these were then irradiated with a titanium / sapphire laser (wavelength: 773 nm, power density: 20 W / cm ² ).

The release of the capsule contents, which is evidence for the destruction of the capsule wall, is indicated by the leuco base Pergascript Red I 6B, which is protonated by the acidic silica gel and thereby assumes a red color.

The results of this irradiation test are summarized in Table 1. The color of the silica gel plate was visually evaluated

0: no coloration 1: slight red coloration

2: Strong red color.

The intensity of the staining is indicated by the irradiation Io and after n seconds of irradiation I _n .

Table 1

Example A: Preparation of the polyacrylate copolymer

In a polymerization apparatus consisting of glass reactor, feed vessels, reflux condenser, stirrer and nitrogen inlet 283 g of methyl ethyl ketone (MEK) were placed in a gentle stream of nitrogen and heated to 80 ⁰ C. There were added 61.1 l of a monomer mixture consisting of 90% by weight of 2-ethylhexyl acrylate, 9% by weight of methyl methacrylate and 1% by weight of 4- (4-benzoylphenoxycarbonyloxy) acrylate butyl ester (photoinitiator). After again reaching 80 ⁰ C. 3.23 g of an initiator solution of 8 g of tert-butyl perpivalate and 56.7 g MEK were added and 10 min merized anpoly-. Then 1 161, 2 g of monomer mixture in 3 h and 61, 45 g starter solution in 3 h 15 min. fed in. Subsequently, a solution of 3.20 g of tert-butyl perpivalate in 37.25 g of MEK was added in 5 minutes, and the temperature was increased to 85 ° C. and polymerized for 45 minutes. Then, 0.36 g of 2,6-di-tert. Butyl p-cresol added. Then the solvent was distilled off in vacuo, while the temperature slowly lifted to 135 ° C and degassed in vacuo for 1 h at 135 ° C.

Solid content: 99.9% K-value: 46 zero-shear viscosity at 110 ⁰ C: 25 Pas.

The polymer can be redissolved in other solvents.

Example 4

In a 2 l kettle with a dispenser stirrer (diameter 5 cm) the following mixture of water phase was added

440.65 g of deionized water 70 g of a 10% strength by weight aqueous polyvinyl alcohol solution (Mowiol

15/79)

140 g of a 5% strength by weight aqueous methylhydroxypropylcellulose solution

(Culminal MHPC 100)

and from oil phase

95.27 g of heptane 218.75 g of an 80 wt .-% solution of a polyacrylate of Example A in

isooctane

0.04 g lumogen IR 788 18.1 g isocyanurated hexamethylene diisocyanate (Basonat HI 100) 10.54 g isophorone diisocyanate

prepares.

The mixture was dispersed at room temperature for 15 minutes at a speed of 6000 rpm, and then transferred to a 2 liter kettle equipped with an anchor stirrer. Within 30 minutes, 76.37 g of a 9% by weight aqueous solution of hexahydro-2,4,6-trimethyl-1,3,5-triazine was added. The reaction mixture was then subjected to the following temperature program: heating to 60 ^° C. in 30 minutes, keeping the temperature for 2 hours, then cooling to room temperature.

The solids content of the resulting dispersion was 25%, with an average particle size of 14.19 μm (determined by light scattering).

Example 5 Water phase 440.65 g of deionized water 70 g of a 10% strength by weight aqueous polyvinyl alcohol solution (Mowiol 15/79)

140 g of a 5 wt .-% aqueous Methylhydroxypropylcelluloselösung (Culminal MHPC 100) 1, 0 g Defoamer based on an organic silicone-free, silica-containing polymer (TEGO ^® Foamex 830)

oil phase

95.31 g of heptane

201, 25 g of an 80 wt .-% solution of the polyacrylate of Example A in o

Xylene, 0.55 g of carbon black (Printex ^® 300, Degussa)

Addition 1

17.68 g of isocyanurated hexamethylene diisocyanate (Basonat HI 100)

10.29 g of isophorone diisocyanate

The mixture of water and oil phase was heated to 60 ⁰ C, dispersed for 40 minutes at a speed of 6000 rpm in a laboratory dissolver, then on cooled to a temperature below 20 ⁰ C, addition 1 fed, dispersed for a further 10 minutes at a speed of 600 rpm and then transferred to a equipped with an anchor stirrer 2 I vessel.

77.07 g of a 1% strength by weight aqueous solution of diethylenetriamine were added over 30 minutes, after which the reaction mixture was subjected to the following temperature program: heating to 60 ^° C. in 30 minutes, keeping the temperature for 2 hours, then cooling to room temperature.

The solids content of this dispersion was 28.8%, with an average particle size of 10.74 microns (determined by light scattering).

Example 6

Water phase 447.61 g of deionized water 70 g of a 10% strength by weight aqueous polyvinyl alcohol solution (Mowiol 15/79)

140 g of a 5% strength by weight aqueous methylhydroxypropylcellulose solution (Culminal MHPC 100)

1.0 g antifoam concentrate based on an organic, silicone-free, siliceous polymer (TEGO Foamex 830)

Oil phase 301.14 g of an 80 wt .-% solution of a polyacrylate of Example A in o-

xylene

0.84 g of carbon black (Degussa Printex 40)

Addition 1. 17.68 g isocyanurated. Hexamethylene diisocyanate (Basonat HI 100) 10.29 g isophorone diisocyanate

The mixture of water and oil phase was heated to 60 ⁰ C, dispersed for 40 minutes at a speed of 6000 rpm in a laboratory dissolver, then cooled to a temperature below 20 ⁰ C, fed addition 1, another 10 minutes at a speed of 600 rpm dispersed and then transferred to a equipped with an anchor stirrer 2 I-kettle. Within 30 minutes, 77.07 g of a 9% by weight aqueous solution of diethylenetriamine were added. The reaction mixture was then subjected to the following temperature program: heating to 60 ^° C. in 30 minutes, keeping the temperature for 2 hours, then cooling to room temperature. The solids content of this dispersion was 34.7%, with an average particle size of 31, 55 microns (determined by light scattering).

Example 7 Water phase 380 g of deionized water 70 g of a 10% strength by weight aqueous polyvinyl alcohol solution (Mowiol 15/79)

140 g of a 5% strength by weight aqueous methylhydroxypropylcellulose solution (Culminal MHPC 100)

1, 0 g antifoam concentrate based on an organic, silicone-free, siliceous polymer (TEGO Foamex 830)

oil phase

218.7 g of an 80% strength solution of a polyacrylate from Example A in o-xylene 104 g of heptane 0.04 g of Lumogen IR 788

Addition 1 9 g of isocyanurated hexamethylene diisocyanate (Basonat HI 100)

5.25 g of isophorone diisocyanate

Addition 2 9.6 g of 2,2'-azobis (2-methylpropionamidine) dihydrochloride (WAKO V 50)

5 g of a 50% solution of sodium hydroxide in water 70 g of deionised water

The mixture of water and oil phase was heated to 75 ⁰ C, dispersed for 40 minutes at a speed of 6000 rpm in a laboratory dissolver stirrer, then cooled to a temperature below 20 ⁰ C, addition 1 fed, another 10 minutes at a speed of 600 rpm dispersed and then transferred to a equipped with an anchor stirrer 2 I-kettle.

Within 30 minutes, the addition of 2 and then within 30 minutes 72.4 g of a 3.3 wt .-% aqueous solution of diethylenetriamine was supplied. The reaction mixture was then subjected to the following temperature program: heating to 60 ^° C. in 30 minutes, keeping the temperature for 2 hours, then cooling to room temperature.

The solids content of this dispersion was 20.7%, with an average particle size of 4 microns (determined by light scattering). Examples 8-1 1

To improve the radiation absorption, an aqueous dispersion of carbon blacks ( ^Lepton® Black, BASF AG) was additionally added to the microcapsule dispersions of Examples 4 and 6.

Application Examples 4 - 11 a) and b) (activation by NIR laser and microwave) The microcapsule dispersions obtained according to Examples 4-11 were each applied to a glass slide by means of a doctor blade. After drying, homogeneous films were obtained. The homogeneous films were block-resistant, so not sticky.

a) Release by Irradiation To destroy the capsule wall, these were then irradiated with a titanium / sapphire laser (wavelength: 773 nm, power density: 20 W / cm ² ). In a series experiment, 5 points were irradiated on the plate for different lengths of time. It was then assessed visually and haptically, from which soft exposure time the adhesive was released. The irradiated point shone slightly and felt sticky. The following table shows the respective minimum irradiation times.

The results of this irradiation test are summarized in Table 2:

Table 2 .: Minimum exposure time until the adhesive has been released

b) release by microwave irradiation

To release the contents by means of microwave radiation, 10 cm ² pieces of the coated glass were irradiated in a microwave (power 300 watts, 7 l volume).

The results are summarized in Table 3.

Table 3: Minimum exposure time until the adhesive is released.

Claims

claims

1. microcapsules comprising a capsule wall made of polyurea and a capsule core containing a polyacrylate copolymer and at least one compound, the electromagnetic radiation from the wavelength range of 700 nm to

Absorbed 1 m.

2. Microcapsules according to claim 1, characterized in that the polyacrylate copolymer is a copolymer which is composed of at least 40 wt .-% of Ci - C10 alkyl acrylates and / or methacrylates.

3. microcapsules according to claim 1 or 2, characterized in that the polyacrylate copolymer 0.0001 to 1 mol of a photoinitiator, or effective as a photoinitiator, bound to the polymer molecule group, per 100 g of polyacrylate latcopolymer contains.

4. microcapsules according to one of claims 1 to 3, characterized in that the glass transition temperature (T ₉ ) of the polyacrylate copolymer is -60 to +10 ⁰ C.

5. microcapsules according to one of claims 1 to 4, characterized in that the compound which absorbs electromagnetic radiation from the wavelength range of 700 nm to 1 m, an organic IR absorber.

6. microcapsules according to one of claims 1 to 4, characterized in that the compound which absorbs electromagnetic radiation from the wavelength range of 700 nm to 1 m, an inorganic absorber.

7. Microcapsules according to one of claims 1 to 6, characterized in that the capsule wall of a di- and / or polyamine and / or a di- and / or

Polyamidine and an isocyanate selected from biuretically or isocyanuretically linked oligomers of hexamethylene diisocyanate, isophorone diisocyanate, m-Tetramethylxylylenediisocyanat or oligomers of Methylendiphenyldiisocy- anat or isocyanate mixtures of these isocyanates with other isocyanates built up.

8. microcapsules according to one of claims 1 to 7, characterized in that the capsule wall of an isocyanate and a di- or polyamine selected from aliphatic C2-C6-diamines, aliphatic C2-C6-triamines and hexa-hydro-2,4, 6-trimethyl-1,3,5-triazine.

9. A process for the preparation of microcapsules according to claims 1 to 8, comprising the steps

a) preparing a lipophilic mixture comprising a polyacrylate copolymer and at least one compound which absorbs electromagnetic radiation from the wavelength range of 700 nm to 1 m, one or more isocyanates and optionally solvents b) emulsifying the mixture obtained from a) in a hydrophilic solvent and c ) Formation of the capsule wall by addition of the emulsion obtained from b) with a di- and / or polyamine and / or a di- and / or polyamidine.

10. A process for the preparation of microcapsules according to claims 1 to 8, comprising the steps

a) preparing a lipophilic mixture comprising a polyacrylate copolymer and at least one compound which absorbs electromagnetic radiation from the wavelength range from 700 nm to 1 m and optionally solvent, b) emulsifying the mixture obtained from a) in a hydrophilic solvent, c) adding one d) emulsifying the mixture obtained from c) and e) forming the capsule wall by adding the emulsion obtained from d) with a di- and / or polyamine and / or a di- and / or polyamidine ,

1 1. microcapsule dispersion obtainable according to the method of claim 8 or 9.

12. microcapsule dispersion containing the microcapsules according to claim 1 dispersed in a hydrophilic solvent.

13. The microcapsule dispersion according to claim 12 additionally containing a compound which absorbs electromagnetic radiation from the wavelength range 700 nm to 1 m dispersed in the continuous phase.

14. Use of microcapsules comprising a capsule wall of polyurea and a capsule core containing a polyacrylate copolymer and at least one compound which absorbs electromagnetic radiation from the wavelength range 700 nm to 1 m as pressure-sensitive adhesives.

15. Method for bonding at least two substrates, in which microcapsules comprising a capsule on the surface of at least one substrate wall of polyurea and a capsule core containing a Polyacrylatcopo- lymer and at least one compound which absorbs electromagnetic radiation from the wavelength range 700 nm to 1 m applied and before, during or after joining the substrates with radiation in the wavelength range of absorption of the absorber is irradiated, wherein in the case of irradiation after assembly of the substrates at least one of the substrates for the radiation must be at least partially permeable.

16. Use of microcapsules comprising a polyurea capsule wall and a capsule core containing a polyacrylate copolymer and at least one compound which absorbs electromagnetic radiation from the wavelength range 700 nm to 1 m for the radiation-induced release of adhesives.