WO2017016971A1

WO2017016971A1 - Process for producing a microcapsule composition

Info

Publication number: WO2017016971A1
Application number: PCT/EP2016/067389
Authority: WO
Inventors: Roland Hinrich STAFF; Marco Schmidt; Kresimir Cule; Britta Katz; Achim PIESCH; Jutta BRUST
Original assignee: Basf Se
Priority date: 2015-07-30
Filing date: 2016-07-21
Publication date: 2017-02-02

Abstract

The present invention relates to a process for producing a microcapsule composition comprising microcapsules with an average particle diameter of D4,3 of from 0.5 to 5 µm, comprising the steps of a) preparation of an oil-in-water emulsion comprising a monomer composition, hydrophobic core material, water, radical starter, inorganic protective colloid and polyalkylene glycol ether, where the monomer composition comprises 40 to 90% by weight of one or more monomers (monomers I) selected from C₁-C₂₄-alkyl esters of acrylic acid and/or methacrylic acid, acrylic acid and methacrylic acid, 10 to 60% by weight of one or more ethylenically unsaturated monomers which has two, three, four or more ethylenically unsaturated radicals (monomers II) and 0 to 40% by weight of one or more other monomers (monomers III), in each case based on the total weight of the monomers, b) formation of the microcapsules by means of polymerization of the monomers in the oil-in-water emulsion obtained in step a) and c) optionally dewatering of the microcapsule dispersion obtained from b), the microcapsule composition obtainable according to this process, and also its use for producing thermoplastic moldings.

Description

Process for the preparation of a microcapsule composition

The present invention relates to a process for the preparation of a microcapsule composition comprising microcapsules having an average particle diameter of D [4,3] of 0.5 to 5 μηη comprising the steps

Preparation of an OI-in-water emulsion comprising a monomer composition, hydrophobic core material, water, radical initiator, inorganic protective colloid and polyalkylene glycol ether,

wherein the monomer composition

From 40 to 90% by weight of one or more monomers (monomers I) selected from C 1 -C 24 -alkyl esters of acrylic and / or methacrylic acid, acrylic acid and methacrylic acid,

10 to 60 wt .-% of one or more ethylenically unsaturated monomers having two, three, four or more ethylenically unsaturated radicals (monomers II) and

0 to 40 wt .-% of one or more other monomers (monomers III), each based on the total weight of the monomers comprises

forming the microcapsules by means of polymerizing the monomers in the oil-in-water emulsion obtained in step a) and

optionally dewatering the microcapsule dispersion obtained from b). Furthermore, the present invention relates to the microcapsule composition obtainable by this process and its use for the production of thermoplastic moldings.

In recent years, there have been many developments in the field of microencapsulated PCMs (phase change materials). The functioning of the PCMs is based on the conversion enthalpy occurring during the solid / liquid phase transition, which means an energy absorption or energy release to the environment, so that they are used for the storage of heat as so-called latent heat storage. Another effect is described in WO2009 / 080232. The difference of

Refractive index between solid and liquefied core material, as observed in PCMs, can be exploited in conjunction with the polymeric support materials such as thermoplastic polymers for optical effects. This change of radiation transmission can also be used for heat regulation. The effect used here is called a thermotropic effect. The thereafter obtained thermotropic plastics are suitable for sun protection.

Muehling, Seeboth, Haeusler, Ruhmann, Potechius, cousin; Solar Energy Materials & Solar Cells "93 (2009) 1510-1517, describes microcapsules based on crosslinked Methyl methacrylate, which are obtained by means of miniemulsion polymerization with polyvinyl alcohol as a nonionic surfactant. The microcapsules described herein have a thermotropic effect embedded in a polymeric matrix. Hereafter produced

However, microcapsules have a broad particle distribution.

WO 2012/069976 teaches the preparation of a thermoplastic molding composition containing microencapsulated latent heat storage materials. According to this doctrine, the

Microcapsules, in order to minimize the thermal load, fed late in the plasticizing zone of the extruder. The polymer blends obtainable in this way can be used to produce fibers, films and shaped articles.

If one wants to process a microcapsule powder together with a thermoplastic polymer, an important requirement is the uniform distribution of the microcapsules in thermoplastics. Thus, WO 2014/127951 teaches that the use of emulsion polymers as spray aids leads to aggregates of microcapsules which can then be separated in the melt of the thermoplastic polymer. The microcapsules used for this purpose have an average particle size of 5 μηη.

Microcapsules with average particle diameters <2 μm are generally known and are described, for example, in WO 01/54809. According to this teaching, they are prepared by means of polyvinyl alcohol as a protective colloid. When the microcapsules obtained according to this teaching are tried to be spray-dried and extruded with a thermoplastic polymer, it is found that the extrudates obtained thereafter hardly receive isolated microcapsules. Therefore, the object of the present invention to provide a method which makes it possible to produce microcapsules of average particle size D [4,3] from 0.7 to 5 μηη whose dispersion can be spray-dried and the aggregates obtained thereafter process well in with a thermoplastic polymer and let it separate uniformly in the thermoplastic polymer.

It was a further object to provide a process which makes it possible to produce microcapsules having an average particle diameter of D [4,3] of 0.7 to 2 μm, which can then be separated well in a thermoplastic polymer. The moldings produced in this way should show a good thermotropic effect.

Moreover, it has been desired for the embodiment of the use of a powder that it can be processed non-dustingly and, on the other hand, can be advantageously incorporated into thermoplastic polymer. Furthermore, it was an object of the present invention to provide thermoplastic moldings containing microcapsules which have a temperature-dependent change in the radiation permeability. Accordingly, the process defined at the beginning, as well as the microcapsule composition obtainable hereinafter, has been found, its use for the production of thermoplastic moldings and the resulting thermoplastic moldings. The microcapsule composition prepared according to the invention comprises microcapsules (primary particles) having an average particle diameter D [4,3] of 0.5 to 5 μm, preferably of 0.7 to 2 μm (volume-weighted average, determined by means of light scattering).

The microcapsules are composed of a capsule core of hydrophobic core material and a capsule wall polymer. The capsule core consists predominantly, to more than 90 wt .-%, of hydrophobic core material. The capsule core can be both solid and liquid, depending on the temperature. 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 93: 7. Since the microcapsules are prepared by free-radical polymerization in an oil-in-water emulsion, an aqueous microcapsule dispersion is obtained. If this microcapsule dispersion is dehydrated, for example by means of spray drying, then aggregates (secondary particles) of the microcapsules are obtained. Such secondary particles are often referred to as granules or agglomerate. The shape of the aggregates can be uneven or spherical or egg-shaped.

According to the invention, an inorganic protective colloid is used. It has been observed that this protective colloid is also part of the capsule wall. In general, the surface of the capsule wall polymer in particular has the protective colloid. Thus, up to 20% by weight protective colloid, based on the total weight of the microcapsules, may be part of the microcapsule.

Hydrophobic core materials are, for example, aliphatic hydrocarbon compounds such as saturated or unsaturated C 10 -C 40 -hydrocarbons which are branched or preferably linear, aromatic hydrocarbon compounds, saturated or unsaturated C 6 -C 30 -fatty acids, fatty alcohols and the so-called oxo alcohols which are obtained by hydroformylation of α- Olefins and further reactions are obtained, ethers of fatty alcohols, C6-C3o-fatty amines, esters such as Ci-Cio-alkyl esters of fatty acids such as propyl palmitate, methyl stearate or methyl palmitate and preferably their eutectic mixtures or methyl cinnamate, natural and synthetic see waxes and halogenated hydrocarbons , as listed in WO 2009/077525, the disclosure of which is expressly incorporated by reference.

Suitable substances may be mentioned by way of example:

aliphatic hydrocarbon compounds such as saturated or unsaturated

Cio-C4o hydrocarbons which are branched or preferably linear, 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-hexacosane, n-heptacosane, n-octacosane and cyclic hydrocarbons, for example cyclohexane, cyclooctane, cyclodecane;

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

saturated or unsaturated C6-C30 fatty acids such as lauric, stearic, oleic or behenic acid, preferably eutectic mixtures of decanoic acid with e.g. Myristic, palmitic or lauric acid;

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;

C6-C3o fatty amines, such as decylamine, dodecylamine, tetradecylamine or hexadecylamine; 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;

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 hard waxes;

halogenated hydrocarbons such as chlorinated paraffin, bromoctadecane, bromopentadecane, bromononadecane, bromeicosane, bromodocosane.

It is advantageous, for example, the use of pure n-alkanes, n-alkanes having a purity of greater than 90% or of alkane mixtures, as obtained as a technical distillate and are commercially available as such. Preferred hydrophobic core materials are aliphatic hydrocarbons, particularly preferably those enumerated above by way of example. In particular, aliphatic hydrocarbons having 14 to 20 carbon atoms and mixtures thereof are preferred.

Furthermore, it may be advantageous to add soluble compounds to the hydrophobic core material so as to prevent the crystallization retardation which sometimes occurs with the nonpolar core materials. It is advantageous to use, as described in US Pat. No. 5,456,852, compounds having a melting point 20 to 120 K higher than the actual core material. Suitable compounds are the fatty acids mentioned above as hydrophobic core materials, fatty alcohols, fatty amides and aliphatic hydrocarbon compounds and chlorinated paraffin. They are added in amounts of from 0.1 to 10% by weight, based on the capsule core. As hydrocarbon compounds having a melting point of 20 to 120 K, suitable compounds include Sasolwax 6805, British Wax 1357 and, as fatty acid, stearic acid by way of example.

The polymers of the capsule wall generally contain at least 40% by weight, preferably at least 50% by weight, in particular at least 55% by weight, very preferably at least 70% by weight and in general up to 90% by weight. %, preferably at most 85 Wt .-%, in particular at most 85 wt .-% and most preferably at most 80 wt .-%, based on the total weight of the monomers, of at least one monomer selected from Ci-C24-alkyl esters of acrylic and / or methacrylic acid, acrylic acid and Methacrylic acid (monomers I), copolymerized.

Furthermore, the polymers of the capsule wall contain at least 10 wt .-%, preferably at least 15 wt .-%, preferably at least 20 wt .-% and generally at most 60 wt .-% and in a preferred form at most 50 wt .-%, in particular at most

45 wt .-% of one or more ethylenically unsaturated monomers having two, three, four or more ethylenically unsaturated groups, (monomers II) copolymerized, based on the total weight of the monomers. The polymers of the capsule wall preferably comprise, as monomers II, monomers having three, four or more ethylenically unsaturated radicals in copolymerized form.

In addition, the polymers may contain up to 40% by weight, preferably up to 30% by weight, in particular up to 20% by weight, of other monomers III in copolymerized form. Preferably, the capsule wall is composed only of monomers of groups I and II.

Suitable monomers I are C 1 -C 24 -alkyl esters of acrylic and / or methacrylic acid and the unsaturated C ₃ - and C ₄ -carboxylic acids, such as acrylic acid and methacrylic acid. Suitable monomers I are isopropyl, isobutyl, sec-butyl and tert-butyl acrylate and the corresponding methacrylates, and particularly preferred methyl, ethyl, n-propyl and n-butyl acrylate and the corresponding methacrylates. Generally, the methacrylates and methacrylic acid are preferred. Suitable monomers II are ethylenically unsaturated monomers having two, three, four or more ethylenically unsaturated radicals. Ethylenically unsaturated monomers having two, three, four or more ethylenically unsaturated radicals are understood as meaning those which have non-conjugated ethylenic double bonds. They cause a crosslinking of the capsule wall during the polymerization. One or more monomers having two non-conjugated ethylenic double bonds (divinyl monomers) and / or one or more monomers having three, four or more non-conjugated ethylenic double bonds may be copolymerized. Preference is given to using monomers having vinyl, allyl, acrylic and / or methacrylic groups. Preferred are monomers which are insoluble or sparingly soluble in water but have good to limited solubility in the hydrophobic core material. Low solubility is to be understood as meaning a solubility of less than 60 g / l at 20 ° C.

Suitable divinyl monomers are divinylbenzene and divinylcyclohexane. Preferred divinyl monomers are the diesters of diols with acrylic acid or methacrylic acid, furthermore the diallyl and divinyl ethers of these diols. Examples which may be mentioned are ethanediol diacrylate, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, methallyl methacrylamide, allyl acrylate and allyl methacrylate. Particular preference is given to propanediol, butanediol, pentanediol and hexanediol diacrylate and the corresponding methacrylates. Preferred monomers having three, four or more nonconjugated ethylenic double bonds are the esters of polyhydric alcohols with acrylic acid and / or methacrylic acid, furthermore the allyl and vinyl ethers of these polyhydric alcohols, trivinylbenzene and trivinylcyclohexane. In particular, trimethylol and pentaerythritol are mentioned as polyhydric alcohols. Particularly preferred are trimethylolpropane triacrylate and methacrylate, pentaerythritol triallyl ether, pentaerythritol tetraallyl ether, pentaerythritol triacrylate and pentaerythritol tetraacrylate and their technical mixtures. Thus, pentaerythritol tetraacrylate is generally present in industrial blends mixed with pentaerythritol triacrylate and minor amounts of oligomerization products. Preference is given to the combinations of divinyl monomers and monomers having three, four or more nonconjugated ethylenic double bonds, such as butanediol diacrylate and pentaerythritol tetraacrylate, hexanediol diacrylate and pentaerythritol tetraacrylate, butanediol diacrylate and trimethylolpropane triacrylate, and hexanediol diacrylate and trimethylolpropane triacrylate. In particular, those combinations are preferred in which at least 80 wt .-% based on the monomer II, one or more monomers having three, four or more ethylenically unsaturated radicals.

Suitable monomers III are other monomers which are different from the monomers I and II, such as vinyl acetate, vinyl propionate, vinylpyridine and styrene or .alpha.-methylstyrene and particularly preferred monomers itaconic acid, vinylphosphonic acid, maleic anhydride, 2-hydroxyethyl acrylate and methacrylate , Acrylamido-2-methylpropanesulfonic acid, methacrylonitrile, acrylonitrile, methacrylamide, N-vinylpyrrolidone, N-methylolacrylamide, N-methylol-methacrylamide, dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate. Preferably, microcapsules are selected whose capsule wall is built up

From 40 to 90% by weight of one or more C 1 -C 24 -alkyl esters of acrylic and / or methacrylic acid (monomers I),

10 to 60 wt .-% of one or more ethylenically unsaturated monomers having two, three, four or more ethylenically unsaturated radicals (monomers II), wherein at least 40 wt .-%, in particular at least 60% by weight, based on monomer II, one or more monomers having three, four or more ethylenically unsaturated radicals, and

0 to 30% by weight of one or more monoethylenically unsaturated monomers (monomer III) other than the monomers I,

in each case based on the total weight of the monomers.

Preferably, microcapsules are selected whose capsule wall is built up

50 to 70 wt .-% of one or more Ci-C24-alkyl esters of acrylic and / or methacrylic acid (monomers 30 to 50 wt .-% of one or more ethylenically unsaturated monomers having three, four or more ethylenically unsaturated radicals (monomers II), and

0 to 20% by weight of one or more monoethylenically unsaturated monomers (monomer III) other than the monomers I,

in each case based on the total weight of the monomers.

The microcapsules used according to the invention can be prepared by a so-called in situ polymerization. The principle of microcapsule formation is based on preparing from the monomers, radical initiator, inorganic protective colloid, polyalkylene glycol ethers and the hydrophobic core material to be encapsulated an oil-in-water emulsion in which the monomers and the hydrophobic core material are in the form of a disperse phase. According to one embodiment, it is possible to add the radical initiator only after the dispersion. Subsequently, the polymerization of the monomers is initiated by heating and optionally controlled by further increase in temperature, wherein the resulting polymers form the capsule wall, which encloses the hydrophobic core material. This general principle is described, for example, in DE-A-10 139 171, to the contents of which reference is expressly made. As free-radical initiators for the free-radical polymerization reaction, the usual oil-soluble peroxo and azo compounds, preferably in amounts of from 0.2 to

5 wt .-%, based on the weight of the monomers used. Under oil-soluble is to be understood that the radical starter is part of the oil phase of the oil-in-water emulsion and there triggers the polymerization.

Preferred free-radical initiators are tert-butyl peroxoneodecanoate, tert-amyl peroxypivalate, dilauroyl peroxide, tert-amyl peroxy-2-ethylhexanoate, 2,2'-azobis (2,4-dimethyl) valeronitrile, 2,2'-azobis (2 methyl butyronitrile), dibenzoyl peroxide, tert-butyl per-2-ethylhexanoate, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di- (tert-butylperoxy) hexane and cumene hydroperoxide.

Particularly preferred radical initiators are di (3,5,5-trimethylhexanoyl) peroxide, 4,4'-azobisisobutyronitrile, tert-butyl perpivalate, dilauroyl peroxide, tert-butyl peroxoneodecanoate and dimethyl 2,2-azobisisobutyrate. These have a half-life of 10 hours in a temperature range of 30 to 100 ° C.

According to the invention, the microcapsules are prepared in the presence of at least one inorganic protective colloid. Inorganic protective colloids are inorganic solid particles, so-called Pickering systems. Such a Pickering system can consist of the solid particles alone or in addition of auxiliaries. The auxiliaries improve the dispersibility of the inorganic solid particles or the wetting of the inorganic solid particles by the oil phase. The mode of action and its use is described in EP-A-1 029 018 and EP-A-1 321 182, to the contents of which reference is expressly made.

The inorganic solid particles may be metal salts, such as salts, oxides and hydroxides of calcium, magnesium, iron, zinc, nickel, titanium, aluminum, silicon, barium and manganese. These include magnesium hydroxide, magnesium carbonate, magnesium oxide, calcium oxalate, calcium carbonate, barium carbonate, barium sulfate, titanium dioxide, aluminum oxide, aluminum hydroxide and zinc sulfide. Silicates, bentonite, hydroxyapatite and hydrotalcites are also mentioned. Particular preference is given to SiO 2 -based silicas, magnesium pyrophosphate and tricalcium phosphate.

Suitable SiO 2 -based protective colloids are finely divided silicas. They can be dispersed as fine, solid particles in water. But it is also possible to use so-called colloidal dispersions of silica in water. Such colloidal dispersions are alkaline, aqueous mixtures of silica. In the alkaline pH range, the particles are swollen and stable in water. For use of these dispersions as protective colloid, it is advantageous if the pH of the oil-in-water emulsion is adjusted to pH 2 to 7 with an acid. Preferred colloidal dispersions of silica at pH 9.3 have a specific surface area in the range of 70 to 90 m ² / g.

As SiO 2 -based protective colloids, preference is given to highly disperse silicas whose mean particle diameters are in the range from 40 to 150 nm at pH values in the range from 8 to 11. Examples include Levasil® ^® 50/50 (HC Starck), Köstrosol ^® 3550 (CWK Bad Köstritz), and Bindzil ^® mentioned 50/80 (Akzo Nobel Chemicals).

Likewise preferred as SiO 2 -based protective colloids are highly disperse silicas whose average particle diameters are in the range from 5 to 40 nm at pH values in the range from 8 to 11. One example is Ludox ^® mentioned HS-40 (Grace Davison). The inorganic protective colloid is preferably present in an amount of 10 to 30,

preferably 15 to 25 wt .-% based on the sum of hydrophobic core materials and monomers used.

Furthermore, a polyalkylene glycol ether is added according to the invention.

Polyalkylene glycol ethers are nonionic surfactants of a C6 to C3o fatty alcohol and a polyethylene glycol or polypropylene glycol. Preferred aliphatic, primary alcohols, so-called fatty alcohols, are 1-hexanol, 1-heptanol, 1-octanol, 1-decanol, 1-dodecanol (lauryl alcohol), 1-tetradecanol (myristyl alcohol), 1-hexadecanol (cetyl alcohol), 1-heptade- canol (margaryl alcohol), 1-octadecanol (stearyl alcohol), 1-eicosanol (arachidyl alcohol), 1-doscosanol (behenyl alcohol), 1-tetracosanol (lignoceryl alcohol), 1-hexacosanol (ceryl alcohol), 1-octacosanol (montanyl alcohol), 1 Triacontanol (melissyl alcohol), cis-9-hexadecene-1-ol (palmitic acid) mitoleyl alcohol), cis-9-octadecene-1-ol (oleyl alcohol), trans-9-octadecene-1-ol (elaidyl alcohol), cis-1 1-octadecene-1-ol, 6,9,12-octadecatriene-1 - ol (γ-linolenyl alcohol)

The number of ethoxylation or propoxylation units is generally from 1 to 100. Particular preference is given to ethoxylated hexadecanols having an average of from 10 to 80 ethylene oxide units, very particularly preferably ethoxylated hexane-cananols having on average from 18 to 80 ethylene oxide units. By way of example, Lutensol® AT25 (BASF SE) may be mentioned. Preference is given to polyalkylene glycol ethers having an HLB value (hydrophilic-lipophilic-balance) between 12 and 20, particularly preferably between 15 and 20. The HLB values refer to Griffin's HLB scale whose maximum value is 20. Examples which may be mentioned are polyoxyethylene (10) cetyl ether, polyoxyethylene (10) stearyl ether, polyoxyethylene (10) oleyl ether, polyoxyethylene (23) lauryl ether, polyoxyethylene (20) cetyl ether, polyoxyethylene (25) cetyl stearyl ether,

Polyoxyethylene (20) stearyl ether and polyoxyethylene (20) called oleyl ether.

The polyalkylene glycol ether is preferably used in an amount of 0.01 to 1 wt .-%, preferably 0.1 to 0.5 wt .-%, based on the sum of hydrophobic core materials and monomers.

The polyalkylene glycol ether can be added together with the inorganic protective colloid or individually to the mixture. It is preferably added to the water phase.

The polymerization of the monomers (step b) in the oil-in-water emulsion obtained in step a) is generally known and described, for example, in DE-A-10 139 171 and application WO 201 1/004006 and WO 2012/1 10443 to which reference is expressly made.

In this way it is possible to produce the microcapsules (primary particles) according to the invention having an average particle diameter of D [4,3] of from 0.5 to 5 μm, it being possible to adjust the particle diameter in a manner known per se via the shearing force and the stirring speed. Preference is given to microcapsules having an average particle diameter in the range from 0.7 to 2 μm, (volume-weighted average D [4,3], determined by means of light scattering)).

The present invention relates to the microcapsule compositions thus obtainable. Furthermore, it relates to microcapsule compositions containing microcapsules and water, such as are obtainable, for example, according to the above-described method as an aqueous dispersion. Furthermore, the present invention relates to microcapsule compositions which are present as powders. This powdery microcapsule composition is obtainable by dehydrating the microcapsule dispersion obtained from b). By dewatering, it is to be understood below that the microcapsule composition has a water content of <5% by weight, preferably <3% by weight, based on the weight of the microcapsule composition (determined by means of Karl Fischer titration).

The dehydration can be carried out by methods known to the person skilled in the art, for example by means of spray drying, freeze drying or drying in an oven. Preference is given to a process for preparing the microcapsule composition in which the dehydration of the microcapsule dispersion obtained from b) takes place by means of spray-drying.

The spray drying of the microcapsule dispersion can be carried out in the usual way. In general, the procedure is that the inlet temperature of the drying gas, usually nitrogen or air, in the range of 100 to 200 ° C, preferably 120 to 160 ° C, and the starting temperature of the drying gas in the range of 30 to 90 ° C, preferably 60 to 80 ° C is located. The spraying of the aqueous microcapsule dispersion in the drying gas stream can take place, for example, by means of single-component or multi-component nozzles or via a rotating disk. The droplet size on exit is chosen so as to produce a microcapsule powder having the desired particle diameter.

Depending on the viscosity of the microcapsule dispersion, the person skilled in the art will choose the diameter of the nozzle and the precursor pressure of the material stream. The higher the form, the smaller the droplets are produced. Usually, the microcapsule dispersion is fed in the range of 2-200 bar. Advantageously, a single-fluid nozzle with swirl generator is used. By selecting the swirl generator, droplet size and spray angle can be additionally influenced.

For example, it is possible to use single-substance nozzles from Delavan, which have a typical structure consisting of swirl chamber, which influences the spray angle, and perforated plate, which influences the throughput.

The deposition of the powdered microcapsule composition is usually carried out using cyclones or filter separators. The sprayed aqueous microcapsule dispersion and the drying gas stream are preferably conducted in parallel. Preferably, the drying gas stream is blown in cocurrent with the microcapsule dispersion from above into the tower.

According to a variant of the method, it is possible, downstream of the dryer, to switch a fluidized bed to possibly discharge residual moisture. Process in which the

Spray-drying fluidized-bed drying is preferred because it results in a micro-capsule composition having a lower fines content. As a spray tower, for example, dryers Anhydro, Miro or Nubilosa can be used, the tower heights of 12-30 meters and widths of 3 to 8 meters have. The throughput of drying gas is typically in the range of 20-30 t h for such spray towers. The throughput of microcapsule dispersion is then usually at 1 to 1, 5 t / h.

Optionally, spraying aids are added for spray-drying in order to facilitate spray-drying or to adjust certain powder properties.

According to a preferred variant, it works without the addition of spraying aids.

According to a further preferred variant, an emulsion polymer in the form of an aqueous dispersion is used as spraying assistant, the emulsion polymer

50 to 99.9 wt .-% esters of acrylic and / or methacrylic acid with 1 to 12 carbon atoms aufwei send alkanols and / or styrene, or

From 50 to 99.9% by weight of styrene and / or butadiene, or

From 50 to 99.9% by weight of vinyl chloride and / or vinylidene chloride, or

Contains 50 to 99.9 wt .-% vinyl acetate, vinyl propionate, vinyl ester of Versatiesäure, vinyl esters of long-chain fatty acids and / or ethylene in copolymerized form.

The total amount of emulsion polymer (calculated as solids), which is added to the aqueous microcapsule dispersion before or during, but especially before spray drying, for example, 1 to 40 parts by weight, often 1 to 25 parts by weight and often 5 to 25 wt ., Each based on 100 parts by weight of microcapsules.

Emulsion polymers are familiar to the person skilled in the art and are prepared, for example, in the form of an aqueous polymer dispersion by free-radically initiated aqueous emulsion polymerization of ethylenically unsaturated monomers. This method has been described many times and is therefore well known to the person skilled in the art. Aqueous polymer dispersions are also commercially available, eg under the brands ACRONAL® ^®, STYRONAL® ^®, Butofan ^®, Styrofan ^® and Kollicoat ^® of BASF SE, Ludwigshafen, Germany, VINNOFIL ^® and VINNAPAS ^® from. Wacker Chemie GmbH, Burghausen, and RHODIMAX ^® from. Rhodia SA

The preparation of such emulsion polymers to be used as spraying aids and also preferred emulsion polymers are described in WO 2014/127951 and DE 2214410, to which reference is expressly made. Preference is given in particular to those emulsion polymers present in aqueous dispersion which contain from 50 to 99.9% by weight of vinyl acetate and / or ethylene in a polymerized form.

Very particular preference is given to those emulsion polymers present in aqueous dispersion which

0.1 to 5% by weight of at least one α, β-monoethylenically unsaturated mono- and / or dicarboxylic acid having 3 to 6 C atoms and / or its amide and

50 to 99.9 wt .-% vinyl acetate, and / or ethylene in polymerized form. The preferred aqueous vinyl acetate-ethylene dispersions have an ethylene content of from 5 to 40% by weight, based on the polymer. If other monomers are used in addition to vinyl acetate and ethylene, the polymer advantageously has a vinyl acetate content of more than 45% by weight. Other suitable monomers are olefinically unsaturated monomers, such as vinyl ethers of straight-chain or branched carboxylic acids having 3-18 C atoms, acrylic, methacrylic, maleic or fumaric acid esters of aliphatic alcohols having 1-18 C atoms, vinyl chloride, furthermore isobutylene or higher α-olefins with 4 to 12 C atoms. In addition to the combination of vinyl acetate and ethylene are suitable monomer combinations z. As vinyl acetate / vinyl pivalate / E-thy-len, vinyl acetate 2-ethylhexanoic acid vinyl ester / ethylene, vinyl acetate / methyl methacrylate ethylene and vinyl acetate / vinyl chloride / ethylene, from the group of so-called terpolymers. Advantageous are monomer combinations with a minimum film-forming temperature of the corresponding dispersions of> 16 ° C. In addition to the monomers mentioned, it is also possible for other stabilizing monomers, such as the sodium salt of vinylsulfonic acid, monomers containing carboxyl groups, such as acrylic, methacrylic, crotonic or itaconic acid or monoesters of maleic acid, whose alcohol component has 1 to 18 carbon atoms, to be incorporated in copolymerized form, in a concentration of up to 5% by weight, based on the emulsion polymer.

The aqueous emulsion polymer dispersion can be used directly as a spray aid in the form of its aqueous dispersion resulting from the synthesis. Advantageously, they are used as 45 to 65 wt .-% dispersions.

If an emulsion polymer described above is used in the form of an aqueous dispersion as a spray aid, this is preferably done with the addition of a release agent. Suitable release agents are those which are usually used in the isolation of these emulsion polymers as a solid, such as kaolin or silica.

The powdery microcapsule compositions obtained by spray-drying are particles which usually consist of 2 to several thousand individual capsules which are together are connected. The powder particles (secondary particles) are aggregates of microcapsules (primary particles). Preference is given to average particle diameter of the microcapsule powder whose particle diameter is at least twice the primary particle. Particle diameters D [4,3] of the powder particles up to 200 μm, in particular up to 150 μm, are preferred. Particular preference is given to mean particle diameters of the powder particles with D [4,3] of 1 to 50 μm, in particular of 5 to 20 μm. Larger mean particle diameters are possible, but can be singularly worse when extruded in moldings usually. Similarly, smaller average particle diameters are possible, but these tend to dust more.

The microcapsule compositions of the invention are non-dusting powders. They are further distinguished by the fact that they can be incorporated advantageously into thermoplastic polymers and thereby isolated.

The microcapsule compositions of the invention can be incorporated advantageously into thermoplastic polymers. The microcapsule compositions according to the invention are particularly preferably incorporated into thermoplastic polymers in an extruder or in an injection molding machine for the production of thermoplastic moldings. If the melt-processable molding material is not to be obtained as granules, but is to be used further directly, also the further processing in the hot state or the direct extrusion of plates, films, pipes and profiles or the direct production of plastic components is advantageous. The term film is often used by a person skilled in the art synonymous with film.

Under the processing conditions of the thermoplastic polymers, which is usually done at temperatures above 105 ° C, the particulate microcapsule compositions can be processed advantageously. It is a good, uniform distribution of the individual microcapsules in the thermoplastic polymer to observe, since the preferably used emulsion polymer of the composition in the thermoplastic polymer evenly distributed and thus the microcapsules are isolated.

Exemplary thermoplastic materials in which the microcapsule compositions according to the invention can be incorporated are:

Polyolefins such as polyethylene (PE) and polypropylene (PP),

- polyoxymethylene (POM),

- polyvinyl chloride (PVC),

Styrene polymers such as polystyrene (impact-resistant or not impact-modified),

Impact modified vinyl aromatic copolymers such as ABS (acrylonitrile-butadiene-styrene), ASA (acrylonitrile-styrene-acrylate) and MABS (transparent ABS containing methacrylate units),

Styrene-butadiene block copolymers ("SBS"), in particular thermoplastic elastomers based on styrene ("S-TPE"),

- polyamides, Polyesters such as polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG) and polybutylene terephthalate (PBT),

- polycarbonate,

Polymethylmethacrylate (PMMA),

- poly (ether) sulfones,

- polyphenylene oxide (PPO)

- thermoplastic polyurethanes (TPU)

Ethylene-butyl acrylate (E / BA) and ethylene-ethyl acrylate (E / EA)

Ethylene-vinyl acetate copolymers (EA / A)

- polyvinyl acetate (PVAc)

Polyvinyl butyral (PVB),

Polyvinylformal (PVF) and

- Polyisobutylene (PIB). In particular, a particularly good distribution of the microcapsules can be found when the emulsion polymer and the thermoplastic material into which the microcapsules are to be incorporated have the same main monomers.

Particularly preferably, the thermoplastic polymer is a polyolefin, polymethyl methacrylate, polyvinyl butyral or polyolefin copolymer such as ethylene-vinyl acetate copolymers. In particular, ethylene-vinyl acetate copolymers are preferred.

With the microcapsules obtained according to the invention, the properties of a thermoplastic polymer can be modified. Utilized is the solid-liquid phase transition of the hydrophobic core material associated with a change in refractive index. The hydrophobic core material is, depending on the desired temperature at which the radiation transmission is to be changed, chosen so that it has its phase transition at this temperature. In order to achieve a thermotropic effect in a shaped body, for example a foil, one of the two phases of the hydrophobic core material must have a refractive index similar to the thermoplastic polymer of the shaped body. If, for example, shading is desired when the temperature is raised, then the solid phase and the thermoplastic polymer have a similar refractive index. A film made from this is translucent as long as the core material is solid. As the ambient temperature increases, the hydrophobic core material melts and its refractive index changes. Due to the now different refractive index of thermoplastic polymer and hydrophobic core material, the film becomes cloudier or cloudier than before. This change of radiation transmission can cause heat regulation.

By analogy with this, irradiation can also be intensified if the liquid phase and the thermoplastic polymer of the shaped body have a similar refractive index. Based on the refractive index of the thermoplastic polymer, a hydrophobic core material is selected such that the refractive indices have a maximum difference of 0 at a temperature of 25 ° C and the wavelength 589 nm (sodium D-line) of the solid phase of the hydrophobic core material and the thermoplastic polymer , 05 preferably has 0.03, in particular 0.01.

The refractive indices of the hydrophobic core materials or of the polymers are usually to be taken from tables or determined by a simple experiment.

Furthermore, the microcapsule compositions according to the invention are suitable as additives in polymeric moldings or polymeric coating compositions. These are thermoplastic materials. The films according to the invention can be obtained by extrusion through a flat die or preferably as blown films.

The films have a good temperature-dependent change in the radiation transmission. The films according to the invention can be used as sunscreen films,

for example in building applications for shading windows, transparent roofs and skylights and walls made of glass or plastic, transparent thermal insulation,

Solar panels and shading of motor vehicles.

Examples

The following examples are intended to explain the invention in more detail. The percentages in the examples are by weight unless otherwise specified.

The particle diameter of the microcapsule dispersion is determined with a Malvern Mastersizer 2000, Sample Dispersing Unit Hydro 2000S according to a standard measuring method documented in the literature. The value D [4,3] stands for the volume-weighted average.

Determination of the water content of the microcapsule composition

Titration according to Karl Fischer: For this, approx. 2 g of powder are weighed exactly and titrated with a 799 GPT Titrino according to Karl Fischer.

A Preparation of the microcapsule dispersion

Example 1 (according to the invention)

water phase

475 g demineralised water (VE = demineralized) 175 g of a 40 wt .-% dispersion of a colloidal silica having a particle diameter of 12 nm

7 g of a 5 wt .-% aqueous solution of methyl hydroxypropyl cellulose having an average molecular weight of 26000 g / mol

1.4 g of a 2.5% strength by weight aqueous sodium nitrite solution

8.75 g of a 10% aqueous solution of an alkylpolyethylene glycol ether having the general formula RO (CH 2 CH 2 O) 50H where R is a linear, saturated fatty alcohol (Lutensol AT 50) 6 g of a 20% strength by weight aqueous nitric acid

Inlet 1

226.63 g of n-octadecane

18.38 g paraffin mixture with a melting point of 57-58 ° C

Inlet 2

26.25 g of 1,4-butanediol diacrylate

52.5 g of methyl methacrylate

26.25 g of pentaerythritol methacrylate

Feed 3:

0.93 g of a 75 wt .-% solution of tert-butyl perpivalate in aliphatic hydrocarbons

Inlet 4:

35 g of a 2 wt .-% aqueous solution of sodium peroxodisulfate

The water phase was initially introduced at 25.degree. C. and heated to 45.degree. Feeds 1 and 2 were added and the mixture was dispersed for 40 minutes at 45 ° C and 6000 revolutions per minute. After addition of feed 3, the emulsion was heated to a temperature of 67 ° C. over a period of 60 minutes and then heated to a temperature of 90 ° C. over a period of 60 minutes. The mixture was then held at this temperature for 150 minutes, and fed to feed 4. Following was cooled to room temperature. A dispersion having a solids content of 40.1% by weight and a mean particle diameter D [4.3] of 1.10 μm, determined by means of light scattering, was obtained.

Subsequently, the dispersion was spray-dried. A white powder was obtained. Example 2 (according to the invention)

The microcapsule dispersion was prepared as in Example 1. The resulting microcapsule dispersion was further added after cooling to room temperature:

29.75 g of a 26% strength by weight aqueous solution of Densodrin BA (spraying assistant, maleic acid / C 2 O-α-olefin copolymer)

154.7 g of a 5 wt .-% aqueous solution of methyl hydroxypropyl cellulose having an average molecular weight of 26 kg / mol

220 g of deionised water

A dispersion having a solids content of 32.2% by weight and a mean particle diameter D [4.3] of 1.75 μm was obtained, determined by means of light scattering.

After connection, the dispersion was spray-dried. A white powder was obtained.

Example 3 (not according to the invention) water phase

800 g of deionised water

1200 g of a 10% strength by weight aqueous solution of polyvinyl alcohol powder (Mowiol 18/88 from Kuraray Europe GmbH, viscosity of a 4% strength by weight aqueous solution at 20 ° C.: 18 mPas in accordance with DIN 53015, degree of hydrolysis of 88%)

4.8 g of a 2.5% aqueous sodium nitrite solution

Inlet 1

777 g of n-octadecane

63 g paraffin mixture with a melting point of 57-58 ° C.

Inlet 2

18 g of 1,4-butanediol diacrylate

234 g of methyl methacrylate

72 g of pentaerythritol methacrylate

36 g of methacrylic acid

Feed 3:

3.2 g of a 75% strength by weight solution of tert-butyl perpivalate in aliphatic hydrocarbons

Inlet 4:

24 g of a 10 wt .-% aqueous solution of tert-butyl hydroperoxide Feed 5:

101, 44 g of a 1, 42 wt .-% aqueous solution of ascorbic acid The water phase was initially charged at 25 ° C and heated to 70 ° C. Feeds 1 and 2 were added and the mixture was dispersed for 40 minutes at 70 ° C and 3500 revolutions per minute. After addition of feed 3, the emulsion was held at a temperature of 70 ° C. over a period of 60 minutes and then heated to a temperature of 85 ° C. over a period of 60 minutes. Subsequently, the mixture was kept at 85 ° C for 60 minutes. Subsequently, feed 4 was added. Then feed 5 was metered in over a period of 30 minutes and cooled to 20 ° C. during this period. Feed 6 was then added at this temperature.

A dispersion having a solids content of 39.5% by weight and an average particle diameter D [4.3] of 1.880 μm, determined by means of light scattering, was obtained.

The dispersion was then spray-dried to remove the water. A white powder was obtained.

Examples 4 to 9

The microcapsule dispersion was prepared as in Example 1. However, different monomer compositions were used, which are shown in Table 1.

Table 1: Monomer composition of the microcapsule wall

Ex. MMA PETIA BDA ₂ MAS n-butyl-MAA AS D [4, FG

[% By weight [% by weight] [wt. [Wt. acrylate [wt.%] [wt.%] 3]

] -%]%] [% by weight] [μπΊ]

1 50 25 25 0 0 0 0 1, 10 40.1

4 75 25 0 0 0 0 0 0.91 38.9

5 75 0 25 0 0 0 0 2,10 35,7

6 50 20 20 10 0 0 0 1, 17 39,9

7 50 20 20 0 10 0 0 1, 36 39.1

8 50 20 20 0 0 10 0 1, 23 39.6

9 50 20 20 0 0 0 10 1, 07 39.6 PETIA pentaerythritol methacrylate

MMA methylmethacrylate

MAS methacrylic acid

MAA methacrylic anhydride

AS: acrylic acid

FG: solids content

B) Preparation of the particulate microcapsule composition

Example B1

At obtained from Example 1 aqueous microcapsule dispersion (685.28 g) was 643.27 g Vi- acetate-ethylene dispersion (Vinnapas ^® (Fa. Wacker polymer) and eluted with 671, filled 45 g of demineralized water.

The dispersion thus obtained was dried to obtain a powder with a laboratory spray dryer (cylinder diameter 250 mm, cylinder length 500 mm). For this purpose, the dispersion was atomized with a two-fluid nozzle (nozzle 1, 4 mm, nozzle pressure 3 bar). The drying gas (nitrogen) was passed in cocurrent with the sprayed microcapsule dispersion from above into the spray cylinder. The drying gas had an inlet temperature of 150 ° C and an outlet temperature of 80 ° C. A particulate microcapsule composition (cyclone discharge) was obtained.

Particle diameter: 1 1, 65 μηη;

Water content: less than 2%

Example B2

The aqueous microcapsule dispersion obtained from Example 2 was spray-dried directly without further addition. The spray drying was otherwise as described above.

A particulate microcapsule composition was obtained. The particles were not agglomerated. The particle diameter was unchanged.

Water content: less than 2%

Example B3

The aqueous microcapsule dispersion obtained from Example 3 was spray-dried directly without further addition. The spray drying was otherwise as described above.

Aggregates of microcapsules were obtained, the particle diameter D [4,3] was 181, 27 m.

Water content: less than 2%

Application Example Example Film 1

10 parts by weight of the particulate microcapsule composition of Example B1 was added to 90 parts by weight of an ethylene vinyl acetate copolymer (Exxon Mobil - Escorene Ultra UL00014). mixed and refluxed in a mini extruder (DSM Micro 15) at 180 ° C for 3 minutes. Subsequently, the melt is extruded through a 200 μm nozzle and drawn up manually as a film. Example of foil 2

In a further example, 5 parts by weight of the particulate microcapsule composition of Example B1 were mixed with 95 parts by weight of an ethylene vinyl acetate copolymer (Exxon Mobil - Escorene Ultra UL00014) and refluxed in a mini extruder (DSM Micro 15) at 180 ° C. for 3 minutes. Subsequently, the melt is extruded through a 200 μm nozzle and drawn up manually as a film.

Example slide 3:

10 parts by weight of the particulate microcapsule composition of Example B3 was blended with 90 parts by weight of an ethylene vinyl acetate copolymer (Exxon Mobil - Escorene Ultra UL00014) and refluxed in a mini extruder (DSM Micro 15) at 180 ° C for 3 minutes. Subsequently, the melt is extruded through a 200 μm nozzle and drawn up manually as a film.

To analyze whether the capsules are present individually, the resulting film is broken up in liquid nitrogen and the fracture edge is examined with the aid of a scanning electron microscope. The degree of singulation and distribution of the capsules in the polymer film is detected optically. Both film 1 and film 2 showed isolated microcapsules. By contrast, only aggregates of the capsules were present in film 3. Film 1 and film 2 had at a temperature of 40 ° C a significantly higher compared to 20 ° C turbidity. There was no difference in film 3, which is due to the lack of separation of the capsules.

Claims

claims

A process for preparing a microcapsule composition comprising microcapsules having an average particle diameter of D [4,3] of 0.5 to 5 μm comprising the steps of a) preparing an oil-in-water emulsion comprising a monomer composition, hydrophobic core material, water, radical initiator, inorganic protective colloid and polyalkylene glycol ether,

wherein the monomer composition

40 to 90 wt .-% of one or more monomers (monomers I) selected from

C 1 -C 24 -alkyl esters of acrylic and / or methacrylic acid, acrylic acid and methacrylic acid,

b) forming the microcapsules by means of polymerizing the monomers in the oil-in-water emulsion obtained in step a) and

c) optionally dewatering the microcapsule dispersion obtained from b).

A process for producing a microcapsule composition according to claim 1, characterized in that a microcapsule composition having microcapsules having an average particle diameter of D [4,3] of 0.7 to 2 μm is prepared.

A process for preparing a microcapsule composition according to claim 1 or 2, characterized in that the hydrophobic core material is selected from aliphatic hydrocarbon compounds, aromatic hydrocarbon compounds, saturated or unsaturated C6-C30 fatty acids, fatty alcohols, oxoalcohols obtained by hydroformylating α-olefins and others Reactions obtained, ethers of fatty alcohols, C6-C3o-fatty amines, Ci-Cio-alkyl esters of fatty acids, natural and synthetic waxes and halogenated hydrocarbons.

A process for preparing a microcapsule composition according to any one of claims 1 to 3, characterized in that the inorganic protective colloid is selected from SiO 2 -based silicas, magnesium pyrophosphate and tricalcium phosphate.

A process for preparing a microcapsule composition according to any one of claims 1 to 4, characterized in that the polyalkylene glycol ether is an ethoxylated or propoxylated C6 to C30 fatty alcohol.

6. A process for preparing a microcapsule composition according to any one of claims 1 to 5, characterized in that the microcapsule dispersion obtained from b) is dehydrated by spray drying.

7. A process for the preparation of a microcapsule composition according to any one of claims 1 to 5, characterized in that the dewatering of the microcapsule dispersion obtained from b) is carried out by spray drying and spray additive is an aqueous dispersion of an emulsion polymer is used, which 50 bis

99.9 wt .-% vinyl acetate and / or ethylene in polymerized form.

8. A microcapsule composition obtainable according to any one of claims 1 to 7.

9. Microcapsule composition according to claim 8, characterized in that it comprises microcapsules and water.

10. Use of the microcapsule composition according to any one of claims 8 or 9 for incorporation together with a thermoplastic polymer in the extruder or in an injection molding machine for producing a thermoplastic molding. 1 1. Use according to claim 10 wherein the thermoplastic polymer is selected from polyolefin, polymethyl methacrylate, polyvinyl butyral or polyolefin copolymer.

12. Use according to claim 10 or 1 1 wherein it is the thermoplastic moldings are granules, sheets, films, tubes, profiles or plastic components.

13. Thermoplastic molded bodies containing microcapsules having an average particle diameter of D [4,3] of 0.7 to 2 μηη wherein the microcapsules are obtainable by a process according to claims 1 to 7.