Moulded bodies consisting of core-shell particles

Shaped body made of core-shell particles

The invention relates to moldings with an optical effect, which essentially consist of core-shell particles, and the core-shell particles and methods for producing the moldings or core-shell particles.

Polymeric core / shell particles have been recommended for the production of adhesives, binder systems, in particular also as reinforcing materials in the production of certain groups of composite materials. Such composites consist of a plastic matrix and reinforcing elements embedded therein. A problem in the production of such materials is the production of a positive connection between the matrix and reinforcement material. Only when there is such a connection can forces be transferred from the matrix to the reinforcing elements. The more the mechanical properties of matrix and reinforcement material differ from one another, particularly with regard to elasticity, hardness and deformability, the greater the risk of the matrix becoming detached from the reinforcement elements. This risk is to be countered by encasing the polymeric reinforcement particles with a second polymer material which is more similar to the matrix material and can therefore form a stronger bond to the matrix. (Young-Sam Kim, "Synthesis and Characterization of Multiphase Polymeric Latices with Kern / Shell Morphology", Diss. Univ. Karlsruhe (TH), Verlag Shaker Aachen, (1993), pages 2-22.). In addition, it has also been recommended that the sheathing polymer be grafted onto the reinforcing polymer in order also to avoid detachment of the shell from the reinforcing particles by means of covalent bonds. (W.-M. Billig-Peters, "Core-shell polymers with the aid of polymeric azo initiators", Diss. Univ. Bayreuth, (1991).

The targeted production of core / shell polymers is generally carried out by stepwise emulsion polymerization, with a latex first being produced from core particles in the first step and the shell polymer being produced in the second step. The core particles act as "seed particles", on the surface of which the shell polymers preferentially separate.

The deposition can lead to a more or less symmetrical shell around core particles, but irregular depositions can also take place, so that structures with a blackberry-like appearance are formed. A good overview of the production of two-phase polymer particles and the phenomena that occur, in particular the formation of core / shell particles, can be found in the dissertation by Katharina Landfester, "Synthesis and characterization of core-shell latices with electron microscopy and solid-state NMR ", University of Mainz, (1995).

Natural precious opals are made up of domains, consisting of monodisperse, densely packed and therefore regularly arranged silica gel spheres with diameters of 150-400 nm. The play of colors of these opals comes about through Bragg-like scattering of the incident light on the grating levels of the crystal-like domains.

There has been no shortage of attempts to synthesize white and black opals for jewelry purposes, using water glass or silicone esters as the starting product.

US 4 703 020 describes a method for producing a decorative material which consists of amorphous silica spheres which are arranged three-dimensionally, zirconium oxide or zirconium hydroxide being located in the spaces between the spheres. The beads have a diameter of 150-400 nm. The production takes place in two stages. In a first stage, silica spheres are allowed to sediment from an aqueous suspension. The mass obtained is then air-dried and then calcined at 800 ° C. In a second step, the calcined material is introduced into the solution of a zirconium alkoxide, the alkoxide penetrating into the spaces between the cores and zirconium oxide being precipitated by hydrolysis. This material is then calcined at 1000-1300 ° C.

From US-A-4 434 010 pigments are known based on inorganic, which have pronounced color flops. These pigments are characterized by an extremely homogeneous structure consisting of layers with different refractive indices. This structure leads to pronounced interference effects, which are used for color generation. However, the production of these pigments is difficult and only possible using complex and costly production processes.

Organic effect pigments based on cholesteric liquids are known from US Pat. No. 5,364,557. In these, an interference effect results from a helical superstructure. Here, too, the materials required for the production are complicated to manufacture and therefore very expensive. The pigments are produced from the cholesteric liquid crystals (LCs) in such a way that the cholesteric mass is applied in a thin layer to a carrier film, photochemical polymerization is carried out in the LC phase, and the film thus obtained is detached from the film and ground . In addition to the expensive production of the starting materials, it is a very serious disadvantage of this method that during the production process the greatest attention must be paid to the orientation of the LCs, since even the smallest impurities can negatively influence them.

A method for coating and printing substrates, in which cholesteric liquid crystals are used, is known from WO 96/02597. In this process, one or more liquid-crystalline compounds, at least one of which is chiral and which have one or two polymerizable groups, are applied to a substrate together with suitable co-monomers - if this is done by a printing process, dispersants are added to the mixture - and copolymerized. The layers thus obtained, if they are brittle, can be detached from the substrate, crushed and used as pigments.

Aqueous, monodisperse polymer dispersions are also known, e.g. B. from T. Okubu, Prague. Polym. Be. 18 (1993) 481-517, which tend to crystallize latex in liquid form, possibly after cleaning, and thereby lead to color effects.

A large number of publications are known for producing monodisperse particles, e.g. B. EP-A-0 639 590 (preparation by precipitation polymerization), A. Rudin, J. Polym. Sci., A. Polym. Be. 33 (1995) 1849-1857 (monodisperse particles with core-shell structure), EP-A-0 292 261 (production with the addition of seed particles).

EP-A-0 441 559 describes core-shell polymers with different refractive indices of core and shell and the use of these materials as additives for paper coating compositions.

EP-A-0 955 323 describes core / shell particles whose core and shell materials can form a two-phase system and which are characterized in that the shell material is filmable and the cores are essentially dimensionally stable under the conditions of filming the shell , through which the shell material is not swellable or only to a very small extent and has a monodisperse size distribution, with a difference between the refractive indices of the core material and the shell material of at least 0.001. The production of the core / shell particles and their use for producing effect colorants are also described. The process for producing an effect colorant comprises the following steps: Apply the core / shell particles to a substrate with low adhesion, if necessary allow the solvent or diluent contained in the applied layer to evaporate or expel, transfer the shell material of the core / shell particles into a liquid, soft or visco-elastic matrix Phase, orientation of the cores of the core / shell particles at least to domains of regular structure, hardening of the shell material to fix the regular core structure, Detachment of the hardened film from the substrate and, if a pigment or powder is to be produced, shredding of the detached film to the desired particle size. In these core-shell particles disclosed in EP-A-0 955 323, the core "floats" in the shell matrix; a long-range order of the nuclei does not form in the melt, but only a short-range order of the nuclei in domains. As a result, these particles are only of limited suitability for processing using methods customary for polymers.

For technical applications, however, it would be desirable to be able to produce large-area structures or three-dimensional moldings directly with a long-range order of the cores, which show the optical effect homogeneously over the entire area and with great brilliance.

The object of the present invention was to avoid the disadvantages mentioned above and to provide moldings which can be obtained using customary processing methods.

A first object of the present invention are therefore shaped articles with an optical effect, consisting essentially of core-shell particles, the shell of which forms a matrix and whose core is essentially solid and has an essentially monodisperse size distribution, a difference between the refractive indices of the Core material and the jacket material, characterized in that the molded body is obtainable by a process at which a) the core-shell particles are heated to a temperature at which the shell is flowable, and b) the flowable core-shell particles are exposed to a mechanical force.

Another object of the present invention is a process for the production of moldings with an optical effect, which is characterized in that a) core-shell particles, the shell of which forms a matrix and whose core is essentially solid and an essentially monodisperse size distribution with a difference between the refractive indices of the core material and the cladding material, heated to a temperature at which the cladding is flowable, and b) the flowable core-shell particles are exposed to a) a mechanical force.

According to the invention, an optical effect is understood to mean both effects in the visible wavelength range of light and, for example, effects in the UV or infrared range. Recently, it has become common to generally refer to such effects as photonic effects. All of these effects are optical effects in the sense of the present invention, wherein in a preferred embodiment the effect is an opalescence in the visible range. In the sense of a customary definition of the term, the shaped bodies according to the invention are photonic crystals (cf. Chemistry News; 49 (9) September 2001; pp. 1018-1025).

According to the invention, it is particularly preferred if in the core-shell particles the shell is connected to the core via an intermediate layer.

It is further preferred according to the invention if the core of the core-shell particles consists of a material which either does not flow or becomes flowable at a temperature above the flow temperature of the shell material. This can be achieved by using polymer materials with a correspondingly high glass transition temperature (T_G), preferably cross-linked polymers or by using inorganic core materials. The suitable materials are described in detail below.

In a preferred variant of the production of molded articles according to the invention. the temperature in step a) at least 40 ° C, preferably at least 60 ° C above the glass point of the shell of the core-shell particles. It has been shown empirically that the flowability of the jacket in this temperature range particularly meets the requirements for economical production of the shaped bodies.

In a likewise preferred process variant, which leads to moldings according to the invention, the flowable core-shell particles are cooled under the action of the mechanical force from b) to a temperature at which the shell is no longer flowable.

According to the invention, the mechanical action of force can be such an action of force that occurs in the usual processing steps of polymers. In preferred variants of the present invention, the mechanical force is applied either:

- by uniaxial pressing or

- Force during an injection molding process or

- during a transfer press process,

- during a (co-) extrusion or

- during a calendering process or

- during a blowing process.

If the force is exerted by uniaxial pressing, the shaped bodies according to the invention are preferably films. Films according to the invention can preferably also be produced by calendering, film blowing or flat film extrusion. The various possibilities of processing polymers under the influence of mechanical forces are well known to the person skilled in the art and can be found, for example, in the standard textbook Adolf Franck, "Plastic Compendium"; Vogel publishing house; 1996 are taken. If moldings are produced by injection molding, it is particularly preferred if the demolding takes place only after the mold with the molding contained therein has cooled. In terms of technical implementation, it is advantageous if molds with a large cooling channel cross section are used, since the cooling can then take place in a shorter time. It has been shown that the color effects according to the invention become significantly more intense as a result of the cooling in the mold. It is assumed that this uniform cooling process leads to a better arrangement of the core-shell particles with the lattice. It is particularly advantageous if the mold was heated before the injection process.

The moldings according to the invention can, if it is technically advantageous, contain auxiliaries and additives. They can be used to optimally set the application data or properties desired or required for application and processing. Examples of such auxiliaries and / or additives are antioxidants, UV stabilizers, biocides, plasticizers, film-forming aids, leveling agents, fillers, melting aids, adhesives, release agents, application aids, mold release aids, agents for viscosity modification, for. B. thickener.

Additions of film-forming aids and film-modifying agents based on compounds of the general formula are particularly recommended <img file="WO03025035A2_D0001.tif" /> wherein n is a number from 2 to 4, preferably 2 or 3, and m is a number from 0 to 500. The number n can vary within the chain and the various chain links can be built in in a statistical or block-wise distribution. Examples of such auxiliaries are ethylene glycol, propylene glycol, di-, tri- and tetraethylene glycol, di-, tri- and tetrapropylene glycol, polyethylene oxides, polypropylene oxide and ethylene oxide / propylene oxide mixed polymers with molecular weights of up to approx. 15,000 and statistical or block distribution of the ethylene oxide and propylene oxide assemblies. If appropriate, organic or inorganic solvents, dispersants or diluents which, for example, extend the open time of the formulation, ie the time available for its application to substrates, are also possible, waxes or hot-melt adhesives as additives.

If desired, stabilizers against UV radiation and weather influences can also be added to the moldings. For this purpose, z. B. Derivatives of 2,4-dihydroxybenzophenone, derivatives of 2-cyano-3,3'-dephenyl acrylate, derivatives of 2,2 ', 4₎4'-tetrahydroxybenzophenone, derivatives of o-hydroxyphenyl-benzotriazole, salicylic acid esters, o-hydroxyphenyl-s-triazines or sterically hindered amines. These substances can also be used individually or as mixtures.

The total amount of auxiliaries and / or additives is up to 40% by weight, preferably up to 20% by weight, particularly preferably up to 5% by weight, of the weight of the moldings. Accordingly, the moldings consist of at least 60% by weight, preferably at least 80% by weight and particularly preferably at least 95% by weight, of core-shell particles.

In order to achieve the optical or photonic effect according to the invention, it is desirable that the core-shell particles have an average particle diameter in the range from about 5 nm to about 2000 nm. It can be particularly preferred if the core-shell particles have an average particle diameter in the range from about 5 to 20 nm, preferably 5 to 10 nm. In this case, the nuclei can be called "quantum dots"; they show the corresponding effects known from the literature. To achieve color effects in the range of visible light, it is particularly advantageous if the core-shell particles have an average particle diameter in the range of approximately 50-500 nm. Particles in the range from 100 to 500 nm are particularly preferably used, since with particles in this order of magnitude (depending on the refractive index contrast which can be achieved in the photonic structure) the reflections of different wavelengths of visible light differ significantly from one another and thus those for optical effects in the visible range particularly important opalescence occurs particularly pronounced in various colors. In a variant of the present invention, however, it is also preferred to use multiples of this preferred particle size, which then lead to reflections corresponding to the higher orders and thus to a broad play of colors.

The difference in the refractive indices of the core and the cladding is also decisive for the intensity of the observed effects. Shaped bodies according to the invention preferably have a difference between the refractive indices of the core material and the cladding material of at least 0.001, preferably at least 0.01 and particularly preferably at least 0.1.

In a special embodiment of the invention, further nanoparticles are embedded in the matrix phase of the shaped bodies in addition to the cores of the core-shell particles. These particles are selected with regard to their particle size in such a way that they fit into the cavities of the spherical packing from the cores and so change the arrangement of the cores only slightly. Through the targeted selection of appropriate materials and / or the particle size, it is possible, on the one hand, to change the optical effects of the moldings, for example to increase their intensity. On the other hand, the matrix can be functionalized accordingly by incorporating suitable “quantum dots”. Preferred materials are inorganic nanoparticles, in particular nanoparticles of metals or of II-VI or Ill-V semiconductors or of materials that influence the magnetic / electrical (electronic) properties of the materials. Examples of preferred nanoparticles are noble metals, such as silver, gold and platinum, semiconductors or insulators, such as zinc and cadmium chalcogenides, oxides, such as hematite, magnetite or perovskite, or metal pnictides, e.g. B. gallium nitride or mixed phases of these materials.

The exact mechanism which leads to the uniform orientation (FIGS. 1 and 2) of the core-shell particles in the shaped bodies according to the invention is hitherto unknown. However, it has been shown that the application of force is essential for the formation of the far-reaching order. As shown in FIG. 3, it is assumed that the elasticity of the jacket material is decisive for the ordering process under the processing conditions. The chain ends of the shell polymers generally endeavor to assume a coil shape. If two particles come too close, the balls are compressed according to the model and repulsive forces arise. Since the shell polymer chains of different particles also interact with each other, the polymer chains are stretched according to the model if two particles move away from each other. The effort of the sheath polymer chains to resume a ball shape creates a force that pulls the particles closer together again. According to the model, the extensive order of the particles in the molded body (Figures 1 and 2) is generated by the interplay of these forces.

Core-shell particles whose shell is connected to the core via an intermediate layer have proven to be particularly well suited for the production of molded articles according to the invention.

Core-clad particles, the core of which is substantially solid and has a substantially monodisperse size distribution, with a difference between the refractive index of the core material and that of the cladding material, and the core of which consists of a material that either does not or at a temperature above the flow temperature of the casing material becomes flowable and the casing is connected to the core via an intermediate layer, and the use of such particles for the production of moldings are therefore further objects of the present invention.

In a preferred embodiment of the invention, the intermediate layer is a layer of crosslinked or at least partially crosslinked polymers. The interlayer can be crosslinked via free radicals, for example induced by UV radiation, or preferably via di- or oligofunctional monomers. Preferred intermediate layers of this embodiment contain 0.01 to 100% by weight, particularly preferably 0.25 to 10% by weight, di- or oligofunctional monomers. Preferred di- or oligo-functional monomers are in particular isoprene and allyl methacrylate (ALMA). Such an intermediate layer of crosslinked or at least partially crosslinked polymers preferably has a thickness in the range from 10 to 20 nm. If the intermediate layer is thicker, the refractive index of the layer is selected such that it corresponds either to the refractive index of the core or to the refractive index of the cladding.

If copolymers are used as the intermediate layer which, as described above, contain a crosslinkable monomer, the person skilled in the art will have no problems in selecting suitable copolymerizable monomers in a suitable manner. For example, corresponding copolymerizable monomers can be selected from a so-called Qe scheme (cf. textbooks of macromolecular chemistry). Monomers such as methyl methacrylate and methyl acrylate can preferably be polymerized with ALMA.

In another, likewise preferred embodiment of the present invention, the shell polymers are grafted directly onto the core via a corresponding functionalization of the core. The surface functionalization of the core forms the intermediate layer according to the invention. The type of surface functionalization mainly depends on the material of the core. Silicon dioxide surfaces can, for example, be suitably modified with silanes which have correspondingly reactive end groups, such as epoxy functions or free double bonds. Other surface functionalizations, for example for metal oxides, can be titanates or aluminum organyls, each of which contains organic side chains with corresponding functions. In the case of polymeric cores, a styrene functionalized on the aromatic, such as bromostyrene, can be used for surface modification, for example. The growth of the shell polymers can then be achieved via this functionalization. In particular, the intermediate layer can also cause the cladding to adhere to the core via ionic interactions or complex bonds.

In a preferred embodiment, the shell of these core-shell particles consists of essentially uncrosslinked organic polymers which are preferably grafted onto the core via an at least partially crosslinked intermediate layer.

The jacket can either consist of thermoplastic or elastomeric polymers. Since the shell essentially determines the material properties and processing conditions of the core-shell particles, the person skilled in the art will select the shell material in accordance with customary considerations in polymer technology. In particular, if movements or tensions in a material are to lead to optical effects, the use of elastomers as the jacket material is preferred. In moldings according to the invention, the distances between the cores are changed by such movements. The wavelengths of the interacting light and the effects to be observed change accordingly. The core can consist of various materials. It is essential according to the invention, as already stated, that there is a refractive index difference from the cladding and that the core remains solid under the processing conditions.

Furthermore, in a variant of the invention, it is particularly preferred if the core consists of an organic polymer, which is preferably crosslinked.

In another likewise preferred variant of the invention, the core consists of an inorganic material, preferably a metal or semimetal or a metal chalcogenide or metal pnictide. For the purposes of the present invention, chalcogenides are compounds in which an element of the 16th group of the periodic table is the electronegative binding partner; as pnictide those in which an element of the 15th Group of the periodic table is the electronegative binding partner.

Preferred cores consist of metal chalcogenides, preferably metal oxides, or metal pnictides, preferably nitrides or phosphides. Metal in the sense of these terms are all elements that can appear as electropositive partners in comparison to the counterions, such as the classic metals of the subgroups or the main group metals of the first and second main group, but also all elements of the third main group, as well as silicon, Germanium, tin, lead, phosphorus, arsenic, antimony and bismuth. The preferred metal chalcogenides and metal pnictides include in particular silicon dioxide, aluminum oxide, gallium nitride, boron and aluminum nitride as well as silicon and phosphorus nitride.

In one variant of the present invention, the starting material for the production of the core-shell particles according to the invention is preferably monodisperse silicon dioxide cores, which can be obtained, for example, by the process described in US Pat. The cores are produced by hydrolytic polycondensation of tetraalkoxysilanes in an aqueous-ammoniacal medium, whereby firstly a sol of primary particles is produced and then the Si0 obtained by continuous, controlled metering in of tetraalkoxysilane₂-Particles to the desired particle size. With this process are monodisperse SiO₂Cores with average particle diameters between 0.05 and 10 μm can be produced with a standard deviation of 5%.

Furthermore, SiO is the starting material₂Cores preferred, those with (semi) metals or in the visible range non-absorbent metal oxides, such as Ti0₂, Zrθ₂, Zn0₂, Sn0₂ or AI₂O₃, are coated. The production of Si0 coated with metal oxides₂Cores are described in more detail, for example, in US Pat. No. 5,846,310, DE 198 42 134 and DE 199 29 109.

Monodisperse cores made of non-absorbent metal oxides such as Ti0 are also used as the starting material₂, ZrO₂, Zn0₂, Sn0₂ or Al₂0₃ or metal oxide mixtures can be used. Their manufacture is described, for example, in EP 0 644 914. Furthermore, the process according to EP 0 216 278 for the production of monodisperse Si0₂-Keme easily transferable to other oxides with the same result. Tetraethoxysilane, tetrabutoxytitanium, tetrapropoxyzirconium or their mixtures are added in one pour with vigorous mixing to a mixture of alcohol, water and ammonia, the temperature of which is adjusted with a thermostat to between 30 and 40 ° C. Vigorously stirred for seconds, forming a suspension of monodisperse nuclei in the nanometer range. After a reaction time of 1 to 2 hours, the cores are separated off, washed and dried in the customary manner, for example by centrifugation.

Furthermore, monodisperse cores made of polymers which contain particles, for example metal oxides, are also suitable as the starting material for the production of the core-shell particles according to the invention. Such materials are offered for example by the company micro caps Entwicklungs- und Vertriebs GmbH in Rostock. Microencapsulations based on polyester, polyamides and natural and modified carbohydrates are manufactured according to customer-specific requirements.

Monodisperse cores made of metal oxides which are coated with organic materials, for example silanes, can also be used. The monodisperse cores are dispersed in alcohols and modified with common organoalkoxysilanes. The silanization of spherical oxide particles is also described in DE 43 16 814. The silanes preferably form the above-mentioned intermediate layer.

For the intended use of the core / shell particles according to the invention for the production of moldings, it is important that the shell material can be film-coated, ie that it can be softened, plasticized or liquefied visco-elastically to the extent that the cores of the core / Sheath particles can form at least domains of a regular arrangement. The nuclei which are regularly arranged in the matrix formed by filming the cladding of the core / cladding particles form a diffraction grating which causes interference phenomena and thus leads to very interesting color effects.

The materials of the core and shell can, provided they meet the above conditions, have an inorganic, organic or metallic character or they can be hybrid materials. With regard to the possibility of varying the properties of the cores of the core / shell particles according to the invention as required, however, it is often expedient if the cores contain one or more polymers and / or copolymers (core polymers) or they consist of such polymers consist.

The cores preferably contain a single polymer or copolymer. For the same reason, it is expedient that the shell of the core / coating particles according to the invention also contains one or more polymers and / or copolymers (shell polymers; matrix polymers) or polymer precursors and optionally auxiliaries and additives, the The composition of the jacket can be selected so that it is essentially dimensionally stable and non-tacky in a non-swelling environment at room temperature.

With the use of polymer substances as a sheath material and possibly core material, the expert gains the freedom of their relevant properties, such as. B. to determine their composition, the particle size, the mechanical data, the refractive index, the glass transition temperature, the melting point and the weight ratio of core: cladding and thus also the application properties of the core / cladding particles, which ultimately also depend on the properties of the moldings produced from them impact.

Polymers and / or copolymers that can be contained in the core material or that consist of high-molecular compounds that correspond to the specification given above for the core material. Both polymers and copolymers of polymerizable unsaturated monomers are suitable, as are polycondensates and copolycondensates of monomers with at least two reactive groups, such as, for. B. high molecular weight aliphatic, aliphatic / aromatic or fully aromatic polyesters, polyamides, polycarbonates, polyureas and polyurethanes, but also aminoplast and phenoplast resins, such as, for. B. melamine / formaldehyde, urea / formaldehyde and phenol / formaldehyde condensates. To the man production of epoxy resins, which are also suitable as core material, epoxy prepolymers are usually used, for example by reaction of bisphenol A or other bisphenols, resorcinol, hydroquinone, hexanediol, or other aromatic or aliphatic di or polyols, or phenol-formaldehyde condensates , or their mixtures with one another with epichlorohydrin, or other di- or polyepoxides, mixed with other compounds capable of condensation directly or in solution and allowed to harden.

In a preferred variant of the invention, the polymers of the core material are expediently crosslinked (co) polymers, since these usually only show their glass transition at high temperatures. These crosslinked polymers can either have already been crosslinked in the course of the polymerization or polycondensation or copolymerization or copolycondensation, or they can be after the actual (co) polymerization or (Co-) polycondensation have been post-crosslinked in a separate process step.

A detailed description of the chemical composition of suitable polymers follows below.

As in the case of the core material, in principle polymers of the classes already mentioned are suitable for the jacket material, provided that they are selected or constructed in such a way that they correspond to the specification given above for the jacket polymers.

Convenient for certain applications, such as B. for the production of coatings or color foils, it is, as already said above, if the polymer material of the shell forming the matrix phase of the core-shell particles according to the invention is an elastically deformable polymer, for. B. a polymer with a low glass transition temperature. In this case it can be achieved that the color of the shaped body according to the invention varies with stretching and compression. Also of interest for the application are core / shell particles according to the invention which lead to moldings during filming which show a dichroism. Polymers that meet the specifications for a sheath material can also be found in the groups of polymers and copolymers of polymerizable unsaturated monomers, as well as the polycondensates and copolycondensates of monomers with at least two reactive groups, such as, for. B. high molecular weight aliphatic, aliphatic / aromatic or fully aromatic polyesters and polyamides.

Taking into account the above conditions for the properties of the shell polymers (= matrix polymers), selected building blocks from all groups of organic film formers are suitable in principle for their production.

Some other examples may illustrate the wide range of polymers suitable for making the sheath.

If the sheath is to have a comparatively low refractive index, polymers such as polyethylene, polypropylene, polyethylene oxide, polyacrylates, polymethacrylates, polybutadiene, polymethyl methacrylate, polytetrafluoroethylene, polyoxymethylene, polyesters, polyamides, polyepoxides, polyurethane, rubber, polyacrylonitrile and polyisoprene are suitable, for example.

If the sheath is to be comparatively high-index, then, for example, polymers with a preferably aromatic basic structure such as polystyrene, polystyrene copolymers such as. B. SAN, aromatic-aliphatic polyesters and polyamides, aromatic polysulfones and polyketones, polyvinyl chloride, polyvinylidene chloride, and with suitable selection of a high-index core material also polyacrylonitrile or polyurethane.

In a particularly preferred embodiment of core-shell particles according to the invention, the core consists of crosslinked polystyrene and the shell consists of a polyacrylate, preferably polyethyl acrylate, polybutyl acrylate, polymethyl methacrylate and / or a copolymer thereof. With regard to particle size, particle size distribution and refractive index differences, what has already been said above regarding the shaped bodies applies analogously to the core-shell particles according to the invention.

With regard to the processability of the core-shell particles into shaped bodies, it is advantageous if the weight ratio of core to shell is in the range from 2: 1 to 1: 5, preferably in the range from 3: 2 to 1: 3 and particularly preferably is in the range of less than 1.2: 1. In particular embodiments of the present invention, it is even preferred if the weight ratio of core to jacket is less than 1: 1, a typical upper limit of the jacket proportion being a weight ratio of core to jacket of 2: 3.

The core-shell particles according to the invention can be produced by various processes. Another preferred object of the present invention is to obtain the particles. It is a process for the production of core-shell particles by a) surface treatment of monodisperse cores, and b) application of the shell from organic polymers to the treated cores.

In one process variant, the monodisperse cores are obtained in a step a) by emulsion polymerization.

In a preferred variant of the invention, a cross-linked polymeric intermediate layer is applied to the cores in step a), preferably by emulsion polymerization or by ATR polymerization, which preferably has reactive centers to which the jacket can be covalently attached. ATR-Polymerization stands here for Atomic Transfer Radicalic Polymerization, as for example in K. Matyjaszewski, Practical Atom Transfer Radical Polymerization, Polym. Mater. Be. Closely. 2001 , 84 is described. Encapsulation of inorganic materials using ATRP is described, for example, in T. Werne, TE Patten, Atom Transfer Radical Polymerization from Nanoparticles: A Tool for the Preparation of Well-Defined Hybrid Nanostructures and for Understanding the Chemistry of Controlledf Living "Radical Polymerization from Surfaces, J. Am Chem. Soc. 2001, 123, 7497-7505 and WO 00/11043. The implementation of both this method and the implementation of emulsion polymerizations are familiar to the person skilled in the art of polymer production and are described, for example, in the abovementioned references.

The liquid reaction medium in which the polymerizations or copolymerizations can be carried out consists of the solvents, dispersants or diluents customarily used in polymerizations, in particular in processes of emulsion polymerization. The selection is made in such a way that the emulsifiers used to homogenize the core particles and shell precursors can have sufficient effectiveness. Aqueous media, in particular water, are favorable as a liquid reaction medium for carrying out the process according to the invention.

For initiating the polymerization, for example, polymerization initiators are suitable which either decompose thermally or photochemically, form free radicals and thus initiate the polymerization. Among the thermally activatable polymerization initiators, preference is given to those which decompose between 20 and 180 ° C., in particular between 20 and 80 ° C. Particularly preferred polymerization initiators are peroxides, such as dibenzoyl peroxide, di-tert-butyl peroxide, peresters, percarbonates, perketals, hydroperoxides, but also inorganic peroxides, such as H2O2, salts of peroxosulfuric acid and peroxodisulfuric acid, azo compounds, boralkyl compounds and homolytically decomposing hydrocarbons. The initiators and / or photoinitiators, which, depending on the requirements for the polymerized material, are used in amounts between 0.01 and 15% by weight, based on the polymerizable components, can be used individually or in combination with one another to take advantage of advantageous synergistic effects be applied. In addition, redox systems are used, such as Salts of peroxodisulfuric acid and peroxosulfuric acid in combination with low-valent sulfur compounds, in particular ammonium peroxodisulfate in combination with sodium dithionite.

Corresponding processes have also been described for the production of polycondensation products. Thus, it is possible to disperse the starting materials for the production of polycondensation products in inert liquids and, preferably with low molecular weight reaction products such as water or - e.g. B. when using dicarboxylic acid di-lower alkyl esters for the production of polyesters or polyamides - lower alkanols to condense.

Polyaddition products are obtained analogously by reaction with compounds which have at least two, preferably three reactive groups such as, for. B. epoxy, cyanate, isocyanate, or isothiocyanate groups, with compounds that carry complementary reactive groups. For example, isocyanates react with alcohols to form urethanes, with amines to form urea derivatives, while epoxides react with these complementaries to form hydroxyethers or hydroxyamines. Like the polycondensation reactions, polyaddition reactions can also advantageously be carried out in an inert solvent or dispersant.

It is also possible to use aromatic, aliphatic or mixed aromatic-aliphatic polymers, e.g. As polyesters, polyurethanes, polyamides, polyureas, polyepoxides or solution polymers, in a dispersant, such as. B. in water, alcohols, tetrahydrofuran, hydrocarbons to disperse or emulsify (secondary dispersion) and post-condense in this fine distribution, crosslink and harden.

Dispersing aids are generally used to produce the stable dispersions required for these polymerization-polycondensation or polyaddition processes.

Water-soluble, high-molecular organic compounds with polar groups, such as polyvinylpyrrolidone, copolymers of vinyl propionate or acetate and vinypyrrolidone, partially saponified copolymer list of an acrylic ester and acrylonitrile, polyvinyl alcohols with different residual acetate content, cellulose ethers, gelatin, starchy, low-molecular-weight, block copolymers, are preferably used as dispersants. polymers containing carbon and / or sulfonic acid groups or mixtures of these substances are used.

Particularly preferred protective colloids are polyvinyl alcohols with a residual acetate content of less than 35, in particular 5 to 39 mol% and / or vinylpyrrolidone-oleylpropionate copolymers with a vinyl ester content of less than 35, in particular 5 to 30% by weight.

Nonionic or ionic emulsifiers, optionally also as a mixture, can be used. Preferred emulsifiers are optionally ethoxylated or propoxylated, longer-chain alkanols or alkylphenols with different degrees of ethoxylation or propoxylation (e.g. adducts with 0 to 50 mol of alkylene oxide) or their neutralized, sulfated, sulfonated or phosphated derivatives. Neutralized dialkyl sulfosuccinic acid esters or alkyl diphenyl oxide disulfonates are also particularly suitable. Combinations of these emulsifiers with the protective colloids mentioned above are particularly advantageous since they give particularly finely divided dispersions.

Special processes for the production of monodisperse polymer particles have also already been described in the literature (for example BRC Backus, RC Williams, J. Appl, Physics 19, p. 1186, (1948) and can advantageously be used in particular for the production of the cores all that is required is to ensure that the particle sizes given above are adhered to, and that the polymers should be as uniform as possible. In particular, the particle size can be adjusted by selecting suitable emulsifiers and / or protective colloids or corresponding amounts of these compounds.

By setting the reaction conditions, such as temperature, pressure, reaction time and the use of suitable catalyst systems, which influence the degree of polymerization in a known manner, and the selection of the monomers used for their production - by type and proportion - the desired combinations of properties of the required polymers can be set in a targeted manner . The particle size can be set, for example, via the selection and amount of the initiators and other parameters, such as the reaction temperature. The appropriate setting of these parameters does not pose any difficulties for the person skilled in the field of polymerization.

Monomers which lead to polymers with a high refractive index are generally those which either have aromatic partial structures or those which have heteroatoms with a high atomic number, such as, for example, B. halogen atoms, especially bromine or iodine atoms, sulfur or metal ions, ie, atoms or groupings of atoms which increase the polarizability of the polymers. Polymers with a low refractive index are accordingly obtained from monomers or monomer mixtures which do not contain the mentioned partial structures and / or atoms with a high atomic number or only in a small proportion.

An overview of the refractive indices of various common homopolymers can be found e.g. B. in Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, volume A21, page 169. Examples of radical-polymerizable monomers which lead to polymers with a high refractive index are:

Group a): styrene, alkyl-substituted styrenes in the phenyl nucleus, α-methylstyrene, mono- and dichlorostyrene, vinylnaphthalene, isopropenylnaphthalene, isopropenylbiphenyl, vinylpyridine, isopropenylpyridine, vinylcarbazole, vinylanthracene, N-benzyl-methacrylamide, p-hydroxymethyl acrylate.

Group b): Acrylates which have aromatic side chains, such as. B. phenyl (meth) acrylate (= abbreviation for the two compounds phenyl acrylate and phenyl methacrylate), phenyl vinyl ether, benzyl (meth) acrylate, benzyl vinyl ether, and compounds of the formulas:

<img file="WO03025035A2_D0002.tif" />

In the formulas above and in the form below, for the sake of clarity and simplification of the writing, carbon chains are only represented by the bonds between the carbon atoms. This notation corresponds to the representation of aromatic cyclic compounds, z. B. the benzene is represented by a hexagon with alternating single and double bonds.

Also suitable are those compounds which contain sulfur bridges instead of oxygen bridges, such as. B .:

<img file="WO03025035A2_D0003.tif" />

In the above formulas, R represents hydrogen or methyl. The phenyl rings of these monomers can carry further substituents. Such substituents are suitable for modifying the properties of the polymers produced from these monomers within certain limits. They can therefore be used in a targeted manner, in particular in order to optimize the properties of the moldings according to the invention which are relevant to the application technology.

Suitable substituents are especially halogen, N0_2l Alkyls with one to twenty carbon atoms, preferably methyl, alkoxides with one to twenty carbon atoms, carboxyalkyls with one to twenty carbon atoms, carbonylalkyls with one to twenty carbon atoms, or -OCOO-alkyls with one to twenty carbon atoms Atoms. The alkyl chains of these radicals can in turn be optionally substituted, or by double-bonded heteroatoms or structural groups, such as. B. -O-, -S-, -NH-, -COO-, -OCO- or -OCOO- in non-adjacent positions. Group c): monomers which have heteroatoms, such as, for. B. vinyl chloride, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, acrylamide and methacrylamide or organometallic compound, such as. B.

<img file="WO03025035A2_D0004.tif" />

Group d): The refractive index of polymers can also be increased by polymerizing in monomers containing carboxylic acid groups and converting the “acidic” polymers thus obtained into the corresponding salts with metals of higher atomic weight, such as, for example, B. preferably with K, Ca, Sr, Ba, Zn, Pb, Fe, Ni, Co, Cr, Cu, Mn, Sn or Cd.

The monomers mentioned above, which make a high contribution to the refractive index of the polymers produced therefrom, can be homopolymerized or copolymerized with one another. They can also be copolymerized with a certain proportion of monomers which make a lower contribution to the refractive index. Such copolymerizable monomers with a lower refractive index contribution are, for example, acrylates, methacrylates, vinyl ethers or vinyl esters with purely aliphatic radicals.

In addition, all bifunctional or polyfunctional compounds which can be copolymerized with the above-mentioned monomers or which can subsequently react with the polymers with crosslinking can also be used as crosslinking agents for producing crosslinked polymer cores from free-radically produced polymers. The following are examples of suitable crosslinkers that are divided into groups for systematization:

Group 1: bisacrylates, bismethacrylates and bisvinyl ethers of aromatic or aliphatic di- or polyhydroxy compounds, in particular of butanediol (butanediol-di (meth) acrylate, butanediol-bis-vinyl ether), hexanediol (hexanediol-di (meth) acrylate, hexanediol-bis- vinyl ether), pentaerythritol, hydroquinone, bis-hydroxyphenylmethane, bis-hydroxyphenyl ether, bis-hydroxymethyl-benzene, bisphenol A or with ethylene oxide spacers, propylene oxide spacers, or mixed ethylene oxide-propylene oxide spacers.

Other crosslinkers in this group are e.g. B. di- or polyvinyl compounds, such as divinybenzene, or also methylene bisacrylamide, triallyl cyanurate, divinylethylene urea, trimethylolpropane tri- (meth) acrylate, trimethylolpropane tricinyl ether, pentaerythritol tetra (meth) acrylate, pentaerythritol tetra vinyl ethers, and crosslinkers with two or more different reactive ends, such as. B. (Meth) allyl (meth) acrylates of the formulas:

<img file="WO03025035A2_D0005.tif" />

(where R is hydrogen or methyl).

Group 2: reactive crosslinkers that have a crosslinking effect, but mostly have a postcrosslinking effect, e.g. B. with heating or drying, and which are copolymerized into the core or shell polymers as copolymers.

Examples are: N-methylol- (meth) acrylamide, acrylamidoglycolic acid, and their ethers and / or esters with Ci to C₆-Alcohols, diacetone-acrylamide (DAAM), glycidyl methacrylate (GMA), methacryloyloxypropyl-trimethoxysilane (MEMO), vinyl-trimethoxysilane, m-isopropenyl-benzyl-isocyanate (TMI).

Group 3: Carboxylic acid groups which have been incorporated into the polymer by copolymerization of unsaturated carboxylic acids are crosslinked in a bridging manner via polyvalent metal ions. Acrylic acid, methacrylic acid, maleic anhydride, itaconic acid and fumaric acid are preferably used as unsaturated carboxylic acids. Mg, Ca, Sr, Ba, Zn, Pb, Fe, Ni, Co, Cr, Cu, Mn, Sn, Cd are suitable as metal ions. Ca, Mg and Zn, Ti and Zr are particularly preferred. Monovalent metal ions, such as Na or K, are also suitable.

Group 4: Post-crosslinked additives. This is understood to mean additives which are functionalized to a greater or greater extent and which react irreversibly with the polymer (by addition or preferably condensation reactions) to form a network. Examples of these are compounds which have at least two of the following reactive groups per molecule: epoxy, aziridine, isocyanate acid chloride, carbodiimide or carbonyl groups, furthermore, for. B. 3,4-Dihydroxy-imidazolinone and its derivatives (®Fixapret @ brands from BASF).

As already explained above, postcrosslinkers with reactive groups, such as. B. epoxy and isocyanate groups, complementary, reactive groups in the polymer to be crosslinked. For example, isocyanates react with alcohols to form urethanes, with amines to form urea derivatives, while epoxides react with these complementary groups to form hydroxyethers or hydroxyamines.

Post-crosslinking is also understood to mean photochemical curing, an oxidative, or an air- or moisture-induced curing of the systems. The monomers and crosslinking agents specified above can be combined with one another and (co-) polymerized in any desired and targeted manner, so that an optionally crosslinked (co-) polymer is obtained with the desired refractive index and the required stability criteria and mechanical properties.

It is also possible to use other common monomers, e.g. As acrylates, methacrylates, vinyl esters, butadiene, ethylene or styrene, additionally copolymerize, for example to adjust the glass transition temperature or the mechanical properties of the core and / or shell polymers as required.

It is also preferred according to the invention if the coating of organic polymers is carried out by grafting, preferably by emulsion polymerization or ATR polymerization. The methods and monomers described above can be used accordingly.

In particular when using inorganic cores, it may also be preferred that the core is subjected to a pretreatment before the shell is polymerized on, which enables the shell to be bonded. This can usually consist in a chemical functionalization of the particle surface, as is known from the literature for a wide variety of inorganic materials. It may be particularly preferred to apply chemical functions to the surface which, as a reactive chain end, enable the jacket polymers to be grafted on. Examples here include, in particular, terminal double bonds, epoxy functions and polycondensation groups. The functionalization of hydroxyl-bearing surfaces with polymers is known, for example, from EP-A-337 144. Other methods for modifying particle surfaces are well known to the person skilled in the art and are described, for example, in various textbooks, such as Unger, KK, Porous Silica, Elsevier Scientific Publishing Company (1979).

The invention furthermore relates to the use of moldings according to the invention or of core-shell particles according to the invention for the production of pigments. The pigments thus obtainable are particularly suitable for use in paints, lacquers, printing inks, plastics, ceramic materials, glasses and cosmetic formulations. For this purpose, they can also be mixed with commercially available pigments, for example inorganic and organic absorption pigments, metallic effect pigments and LC pigments. Furthermore, the particles according to the invention are also suitable for the production of pigment preparations and for the production of dry preparations, such as, for example, granules. Such pigment particles preferably have a platelet-like structure with an average particle size of 5 μm - 5 mm.

The pigments can be produced, for example, by first producing a film from the core-shell particles, which can optionally be hardened. The film can then be comminuted in a suitable manner by cutting or breaking and possibly subsequent grinding to give pigments of a suitable size. This process can take place, for example, in a continuous belt process.

The pigment according to the invention can then be used for pigmenting lacquers, powder coatings, paints, printing inks, plastics and cosmetic formulations, such as, for example, lipsticks, nail varnishes, cosmetic sticks, press powder, make-ups, shampoos, and loose powders and gels. The concentration of the pigment in the application system to be pigmented is generally between 0.1 and 70% by weight, preferably between 0.1 and 50% by weight and in particular between 1.0 and 20% by weight, based on the Total solid content of the system. It is usually dependent on the specific application. Plastics usually contain the pigment according to the invention in amounts of from 0.01 to 50% by weight, preferably from 0.01 to 25% by weight, in particular from 0.1 to 7% by weight, based on the plastic composition. In the paint sector, the pigment mixture is used in amounts of 0.1 to 30% by weight, preferably 1 to 10% by weight, based on the paint dispersion. When pigmenting binder systems, for example For inks and printing inks for gravure printing, offset printing or screen printing, or as a preliminary product for printing inks, e.g. in the form of highly pigmented pastes, granules, pellets, etc., pigment mixtures with spherical colorants such as Ti0₂, Carbon black, chromium oxide, iron oxide, and organic “color pigments” have proven to be particularly suitable. The pigment is generally used in the printing ink in amounts of 2-35% by weight, preferably 5-25% by weight, and in particular 8 -20% by weight. Offset printing inks can contain the pigment up to 40% by weight and more. The precursors for the printing inks, for example in granular form, as pellets, briquettes, etc., contain up to 95 in addition to the binder and additives % By weight of the pigment according to the invention. The invention thus also relates to formulations which contain the pigment according to the invention.

The following examples are intended to explain the invention in more detail without limiting it. Examples

Used abbreviations:

BDDA butane 1,4-diol diacrylate

SDS dodecyl sulfate sodium salt

SDTH sodium dithionite

APS ammonium peroxodisulfate

KOH potassium hydroxide

ALMA allyl methacrylate

MMA methyl methacrylate

EA ethyl acrylate

Example 1: Production of core-shell particles

In a stirred tank reactor preheated to 75 ° C. with a propeller stirrer, argon protective gas inlet and a reflux condenser, a receiver tempered to 4 ° C., consisting of 217 g water, 0.4 g butanediol diacrylate (Merck, destabilized), 3.6 g styrene ( BASF, destabilized) and 80 mg of sodium dodecyl sulfate (SDS; Merck) and dispersed with vigorous stirring. Immediately after filling, the reaction is carried out by adding 50 mg sodium dithionite (Fa. Merck), 250 mg of ammonium peroxodisulfate (from Merck) and again 50 mg of sodium dithionite (from Merck), each dissolved in 5 g of water. After 10 min, a monomer emulsion composed of 6.6 g of butanediol diacrylate (Merck, destabilized), 59.4 g styrene (BASF, destabilized), 0.3 g SDS, 0.1 g KOH and 90 g water Period of 210 min continuously metered. The reactor contents are stirred for 30 minutes without further addition. A second monomer emulsion comprising 3 g of allyl methacrylate (from Merck, destabilized), 27 g of methyl methacrylate (from BASF, destabilized), 0.15 g of SDS (from Merck) and 40 g of water is then metered in continuously over a period of 90 minutes . The reactor contents are then stirred for 30 minutes without further addition. A monomer emulsion of 130 g of ethyl acrylate (from BASF, destabilized), 139 g of water and 0.33 g of SDS (from. Merck) metered in continuously over a period of 180 min. For almost complete reaction of the monomers, the mixture is then stirred for a further 60 min. The core-shell particles are then precipitated in 1 liter of methanol, with 1 liter of dist. Water added, suction filtered and dried.

Scanning or transmission electron micrographs of the core-shell particles show that the particles have a particle size of 220 nm.

In an analogous test procedure, the particle size of the particles can be varied via the surfactant concentration in the template. The following particle sizes are obtained by selecting appropriate amounts of surfactant:

<img file="WO03025035A2_D0006.tif" />

Example 2: Production of granules of the core-shell particles

3rd kg of the core-shell particles from Example 1 are comminuted in a cutting mill (Rapid, type: 1528) with ice cooling and then in a single-screw extruder (Plasti-Corder; Brabender; screw diameter 19 mm with 1-hole nozzle ( 3mm)) compounded. After a cooling section, granulation is carried out in an A 90-5 granulator (from Automatic). Example 3a: Production of a film from core-shell particles

2nd g of the granules from Example 2 are heated in a Collin 300P press without pressure to a temperature of 120 ° C. and pressed into a film at a pressure of 30 bar. After cooling to room temperature, the pressure is reduced again. Transmission electron micrographs (Fig. 1 and 2 show particles with a particle size of 180 nm) confirm the alignment of the nuclei in the cladding matrix to an extensive crystal lattice. FIG. 2 shows the orientation of three superimposed layers of the core-shell particles to form an fcc lattice.

The results of optical absorption spectroscopy (UV / VIS) are shown in FIGS. 4 and 5.

Example 3b: Production of a film from core-shell particles

25th g of the granules from Example 2 are heated in a press with a cassette cooling system (Dr. Collin GmbH; type: 300E) without pressure to a temperature of 150 ° C. and pressed into a film at a pressure of 250 bar. After cooling to room temperature, the pressure is reduced again after 8 minutes.

Example 4: Production of molded articles by injection molding

The granules from Example 2 are 0.2% by weight release agent (Ceridust^® 3615; Clariant) added. The mixture is processed with a Klöckner Ferromatik 75 FX 75-2F injection molding machine. The granulate is injected into the mold at 80 ° C at a cylinder temperature of 190 ° C at 900 bar, then cooled in the mold and demolded at a mold temperature of 30 ° C. Shaped articles with an optical effect depending on the viewing angle result.

Example 5: Production of a flat film (tape)

Granules from Example 2 are made on a flat film line consisting of a single-screw extruder (from Göttfert; type: extrusiometer; screw diameter 20 mm; L / D 25), a thickness-adjustable film tool (width 135 mm) and a temperature-controlled smoothing unit (from Leistritz; roll diameter 15 mm; roller width 350 mm) processed. A film strip 125 mm wide and 1 mm thick is obtained.

Example 6: Production of core-shell particles with a silicon dioxide core (150 nm)

66 g Monospher® 150 suspension (Merck; 38% by weight solids content, corresponding to 25 g SiO₂-Monospheres; average particle size 150 nm; Standard deviation of mean. Particle size &lt;5%) are initially charged with 354 g of water in a stirred tank double-wall reactor heated to 25 ° C. with an argon protective gas feed, reflux condenser and propeller stirrer and mixed with a solution of 450 mg of aluminum trichloride hexahydrate (Acros) in 50 ml and 30 min vigorously stirred. A solution of 40 mg of sodium dodecyl sulfate in 50 g of water is then added and the mixture is stirred vigorously for another 30 minutes.

Then 50 mg of sodium dithionite, 150 mg of ammonium peroxodisulfate and again 50 mg of sodium dithionite are each added in succession in 5 g of water. Immediately after the addition, the reactor is heated to 75 ° C. and 25 g of ethyl acrylate are added over a period of

120 min metered continuously. For complete reaction of the

Monomers, the reactor contents are then stirred at 75 ° C. for a further 60 min.

The hybrid material obtained is filtered off and dried and processed further in accordance with Examples 2 to 5.

Example 6a. Analogously, core-shell particles with other silicon dioxide core diameters (for example 100 nm) can be produced.

Example 7: Production of core-shell particles with a silicon dioxide core (250 nm)

60 g Monospher® 250 (Merck; average particle size 250 nm; standard deviation of the average particle size &lt;5%) are suspended in ethanol. 6 g of 3-methacryloxypropyltrimethoxysilane are added dropwise at 75 ° C. in the course of 15 min with vigorous stirring. After 12 h at 75 ° C., the resulting powder is separated off and dried. 10 g of the functionalized Monospher® 250 are mixed with 90 g of water and 50 mg of sodium dodecyl sulfate and stirred vigorously for 1 day to disperse. The suspension is then dispersed in a homogenizer (Niro Soavi, NS1001 L). 70 g of water are added to the dispersion and the mixture is cooled to 4 ° C.

The dispersion is then placed in a stirred tank double-wall reactor with argon protective gas feed, reflux condenser and propeller stirrer. Then 50 mg of sodium dithionite, 150 mg of ammonium peroxodisulfate and again 50 mg of sodium dithionite are each added in succession in 5 g of water. Immediately after the addition, the reactor is heated to 75 ° C. and an emulsion of 10 g of ethyl acrylate and 20 g of water is metered in continuously over a period of 120 min. To complete the reaction of the monomer, the reactor contents are then stirred at 75 ° C. for a further 60 min. The hybrid material obtained is precipitated in a solution of 10 g of calcium chloride and 500 g of water, filtered off and dried and processed further in accordance with Examples 2 to 5.

Example 8: Production of core-shell particles, the core being composed of silicon dioxide with an outer shell of titanium dioxide

80 g Monospher®100 (monodisperse silicon dioxide balls with an average size of 100 nm with a standard deviation &lt;5%) from Merck KGaA are dispersed at 40 ° C in 800 ml ethanol. A freshly prepared solution consisting of 50 g of tetraethyl orthotitanate (from Merck KGaA) and 810 ml of ethanol is metered into the monosphers / ethanol dispersion together with deionized water with vigorous stirring. The dosing is initially carried out over a period of 5 minutes at a dropping rate of 0.03 ml / min (titanate solution) or 0.72 ml / min. The titanate solution is then added at 0.7 ml / min and the water at 0.03 ml / min until the corresponding containers have been completely emptied. For further processing, the ethanolic dispersion is stirred at 70 ° C. with cooling under reflux and with 2 g of methacryloxypropyltrimethoxysilane (Fa. ABCR), dissolved in 10 ml of ethanol. After refluxing overnight, the resulting powder is separated off and dried. 10 g of the functionalized silicon dioxide-titanium dioxide hybrid particles are mixed with 90 g of water and 50 mg of sodium dodecyl sulfate and stirred vigorously for dispersing for 1 day. The suspension is then dispersed in a homogenizer (Niro Soavi, NS1001 L). 70 g of water are added to the dispersion and the mixture is cooled to 4 ° C. The dispersion is then placed in a stirred tank double-wall reactor with argon protective gas feed, reflux condenser and propeller stirrer. Then 50 mg of sodium dithionite, 150 mg of ammonium peroxodisulfate and again 50 mg of sodium dithionite are each added in succession in 5 g of water. Immediately after the addition, the reactor is heated to 75 ° C. and an emulsion of 10 g of ethyl acrylate and 20 g of water is metered in continuously over a period of 120 min. To complete the reaction of the monomer, the reactor contents are then stirred at 75 ° C. for a further 60 min. The hybrid material obtained is precipitated in a solution of 10 g of calcium chloride and 500 g of water, filtered off and dried and processed further in accordance with Examples 2 to 5.

Example 9: Production of core-shell particles in a 5 l reactor

In a 5 l double jacket reactor tempered to 75 ° C. with a double propeller stirrer, argon protective gas inlet and a reflux condenser, a template tempered to 4 ° C. is composed of 1519 g demineralized water, 2.8 g BDDA, 25.2 g styrene and 1030 mg SDS filled and dispersed with vigorous stirring. Immediately afterwards, the reaction is started by successively injecting 350 mg SDTH, 1.75 g APS and again 350 mg SDTH, each dissolved in approx. 20 ml water. The injection takes place by means of disposable syringes. After 20 minutes, a monomer emulsion of 56.7 g of BDDA, 510.3 g of styrene, 2.625 g of SDS, 0.7 g of KOH and 770 g of water is metered in continuously over a period of 120 minutes via the wobble piston pump. The reactor contents are stirred for 30 minutes without further addition. A second monomer emulsion consisting of 10.5 g ALMA, 94.50 g methyl methacrylate, 0.525 g SDS and 140 g water is then metered in continuously over a period of 30 minutes via the wobble piston pump. After about 15 minutes, 350 mg of APS are added and then stirred for a further 15 minutes. A third monomer emulsion consisting of 900 g EA, 2.475 g SDS and 900 g water is then metered in continuously over a period of 240 min via the wobble piston pump. The mixture is then stirred for 120 minutes. Argon is introduced for about half a minute before and after each template change. The next day, the reactor is heated to 95 ° C. and steam distillation is carried out. The core-shell particles are then precipitated in 4 l of ethanol, precipitated with 5% calcium chloride solution, filtered off and dried and processed further in accordance with Examples 2 to 5. Shaped bodies result with a color effect (color flop) in the red-green area.

Example 10: Production of core-shell particles with a butyl acrylate shell

In a stirred tank reactor preheated to 75 ° C. with a propeller stirrer, argon protective gas inlet and a reflux condenser, a receiver tempered to 4 ° C., consisting of 217 g water, 0.4 g butanediol diacrylate (Merck, destabilized), 3.6 g styrene ( BASF, destabilized) and 80 mg of sodium dodecyl sulfate (SDS; Merck) and dispersed with vigorous stirring. Immediately after filling, the reaction is carried out by adding 50 mg sodium dithionite (Fa. Merck), 250 mg of ammonium peroxodisulfate (from Merck) and again 50 mg of sodium dithionite (from Merck), each dissolved in 5 g of water. After 10 min, a monomer emulsion composed of 6.6 g of butanediol diacrylate (Merck, destabilized), 59.4 g styrene (BASF, destabilized), 0.3 g SDS, 0.1 g KOH and 90 g water Period of 210 min continuously metered. The reactor contents are stirred for 30 minutes without further addition. A second monomer emulsion comprising 3 g of allyl methacrylate (from Merck, destabilized), 27 g of methyl methacrylate (from BASF, destabilized), 0.15 g of SDS (from Merck) and 40 g of water is then metered in continuously over a period of 90 minutes . The reactor contents are then stirred for 30 minutes without further addition. A monomer emulsion of 130 g of butyl acrylate (from Merck, destabilized), 139 g of water and 0.33 g of SDS (from. Merck) metered in continuously over a period of 180 min. For almost complete reaction of the monomers, the mixture is then stirred for a further 60 min. The core-shell particles are then precipitated in 1 liter of methanol, with 1 liter of dist. Water was added, filtered off with suction, dried and further processed in accordance with Examples 2 to 5.

Example 11: Production of core-shell particles with an ethyl acrylate-butyl acrylate shell

In a stirred tank reactor preheated to 75 ° C. with a propeller stirrer, argon protective gas inlet and reflux condenser, an initial temperature set to 4 ° C., consisting of 217 g water, 0.4 g butanediol diacrylate (Merck, destabilized), 3.6 g styrene ( BASF, destabilized) and 60 mg sodium dodecyl sulfate (SDS; Merck) and dispersed with vigorous stirring. Immediately after filling, the reaction is carried out by adding 50 mg sodium dithionite (Fa. Merck), 300 mg ammonium peroxodisulfate (from Merck) and again 50 mg sodium dithionite (from Merck), each dissolved in 5 g of water. After 10 minutes, a monomer emulsion of 8.1 g of butanediol diacrylate (from Merck, destabilized), 72.9 g of styrene (from BASF, destabilized), 0.375 g of SDS, 0.1 g of KOH and 110 g of water over a period of 150 minutes continuously metered. The reactor contents are stirred for 30 minutes without further addition. Subsequently, a second monomer emulsion of 1.5 g allyl methacrylate (Merck, destabilized), 13.5 g methyl methacrylate (BASF, destabilized), 0.075 g SDS (Merck) and 20 g water over a period of 45 min metered in continuously. The reactor contents are then stirred for 30 minutes without further addition. Then 50 mg of APS dissolved in 5 g of water are added. A monomer emulsion of 59.4 g of ethyl acrylate (Fa. MERCK, destabilized), 59.4 g of butyl acrylate, 1.2 g of acrylic acid, 120 g of water and 0.33 g of SDS (from Merck) were metered in continuously over a period of 240 min. For almost complete reaction of the monomers, the mixture is then stirred for a further 60 min. The core-shell particles are then precipitated in 1 liter of methanol, with 1 liter of dist. Water added, suction filtered and dried and further processed according to Examples 2 to 5 ..

Illustrations

Figure 1: Transmission electron micrograph of a section through a film of 1 mm thickness, which was prepared according to Example 3a (particle size 180 nm).

Figure 2: Transmission electron micrograph of the top view of a film that was produced according to Example 3a (particle size 180 nm). Three superimposed layers of the core-shell particles can be seen.

Figure 3: Model of the crystallization mechanism; Rubber elasticity of the jacket.

FIG. 4: absorption spectra of different films made of core-shell particles (according to example 3a); a: average particle distance [nm]

Figure 5: absorption spectra of a film made of core-shell particles (according to Example 3a; average particle spacing = 200 nm) as a function of the angle θ between the film surface and the incident light beam;