EP1517956A1 - Composite material containing a core-covering-particle - Google Patents

Abstract

The invention relates to composite materials having an optical effect, containing at least one moulded body which is essentially made of core-covering particles. The covering thereof forms a matrix and the core thereof is essentially solid and has an essentially monodisperse size distribution. There is a difference between the refractive indices of the core material and the covering material and at least one further material which determines the mechanical properties of the composite. The invention also relates to a method for producing composite materials. The inventive materials have a colouring effect, according to the observation angle, and freely adjustable mechanical properties.

Description

 Composite material containing core-shell particles

The invention relates to composite materials with an optical effect and methods for producing the composite materials.

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, elasticity, hardness, deformability, differ from one another, 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 to graft the sheathing polymer onto the reinforcing polymer in order also to prevent the shell from detaching from the reinforcing particles by means of covalent bonds. (W.-M. Billig-Peters, "Core-shell polymers using 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 acting as “seed particles” the surface of which the shell polymers preferentially separate. 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 planes 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 sedimented from an aqueous suspension. The mass obtained is then dried in air and then calcined at 800 ° C. The calcined material is introduced into the solution of a zirconium alkoxide in a second step, 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.

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.Sci. 33 (1995) 1849-1857 (monodisperse particles with core-shell structure), EP-A-0 292 261 (production with the addition of seed particles).

EP-A-0441 559 describes core-shell polymers with different refractive indices of core and shell and their use 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 the production of effect colorants are also described. The process for producing an effect colorant comprises the following steps: application of the core / shell particles to a substrate with low adhesion, if necessary allowing the solvent or diluent contained in the applied layer to evaporate or being driven off, transferring the shell material of the core / shell Particles in 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 cured film from the substrate and if a pigment or a powder is to be produced, comminution 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.

Moldings with an optical effect are known from the older German patent application DE 10145450.3, which essentially consist of core-shell particles, the shell of which forms a matrix and whose core is essentially solid and has an essentially monodisperse size distribution, the shell preferably is firmly connected to the core via an intermediate layer. The refractive indices of the core material and the differ Sheath material, whereby said optical effect, preferably an opalescence. According to the older German patent application DE 10204338.8, contrast materials such as pigments are additionally introduced into moldings of such core-shell particles. The embedded contrast materials result in an increase in the brilliance, contrast and depth of the observed color effects in these moldings.

The mechanical properties of these moldings are essentially determined by the shell polymers. Preferred shell polymers are elastomers. The moldings of such preferred embodiments thus necessarily show material properties of elastomers. For many applications, however, material properties such as can only be offered by thermoplastics are required.

The object of the present invention was to achieve the above-mentioned. To avoid disadvantages and to provide moldings which at the same time have a color effect which is dependent on the viewing angle and mechanical properties which can be set as desired.

It has now surprisingly been found that this problem can be solved by using composite materials. The composite is formed by at least one molded body, which essentially consists of core-shell particles and determines the optical properties of the composite, and at least one further material that determines the mechanical properties of the composite.

A first object of the present invention is therefore a composite material with an optical effect containing at least one shaped body, which essentially consists of core-shell particles, the shell of which forms a matrix and whose core is essentially solid and has an essentially monodisperse size distribution, where on There is a difference between the refractive indices of the core material and the cladding material and at least one other material that determines the mechanical properties of the composite.

Another object of the present invention is a method for producing composite materials with an optical effect, characterized in that at least one shaped body, which consists essentially of core-shell particles, the shell of which forms a matrix and whose core is essentially solid and a essentially has a monodisperse size distribution, there being a difference between the refractive indices of the core material and the cladding material, is firmly bonded to at least one further material which determines the mechanical properties of the composite.

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, and in a preferred embodiment the effect is an opalescence in the visible range, i.e. by a change in the observed color impression depending on the viewing angle. 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 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 polymeric materials with a correspondingly high glass transition temperature (T _g ), preferably crosslinked polymers, or by using inorganic core materials. The suitable materials are described in detail below.

The moldings contained in the composite material according to the invention preferably correspond to the moldings described in the older German patent application DE 10145450.3, the production and composition of which are described again below.

The shaped body is preferably a film or a layer which is preferably firmly bonded to at least one further layer of another material which determines the mechanical properties of the composite. In the following, the designation "layer" is chosen for this embodiment, since a film in the composite material can also be referred to as a layer. In a preferred embodiment, such composite materials are in the form of two or multi-layer laminates.

Due to the numerous established processing options, the material which determines the mechanical properties of the composite is usually selected from the materials metal, glass, ceramic, wood or polymers (plastics), with polymers preferably being selected. Among the polymers, the thermoplastic plastics and the rubber polymers are preferred due to their material properties. Examples of thermoplastic polymers are given below; among the rubber-like polymers are again 1,4-polyisoprene, polychloroprene, polybutadiene, styrene-butadiene Rubber, nitrile rubber, butyl rubber, ethylene-propylene rubber with an ethylidene norbomene content and polyoctenamer are particularly preferred, and the choice of other thermoplastics or rubber polymers does not pose any difficulties for the person skilled in the art.

In addition to the mechanical properties, the thermal, acoustic and electronic properties of the composite material can also be controlled in the composite by selecting suitable materials.

If the molded articles form the outer material from core-shell particles in the composite, the hapticity of the surface is also an advantage according to the invention. The hapticity can be described as a "soft grip".

The composite materials according to the invention combine the advantages of the shaped bodies, consisting essentially of core-shell particles with the easy processability and the superior mechanical properties of the material connected to the shaped body. If the bonded material is rubber polymers, the composite shows the high elasticity and tear resistance of the rubber in connection with the color effect of the molded article, which is dependent on the viewing angle. Such composite materials with rubber-like properties are suitable for the production of sensors for the detection of mechanical force as well as sensors with an optical effect. The observable color effect also depends on the elongation state of the rubber-like carrier material.

If thermoplastics or thermoplastic elastomers are used in the composite material, the composite material shows the mechanical hardness and scratch resistance of these polymers in addition to the color effect mentioned above. At the same time, the material can be processed using processing techniques developed for such thermoplastics. are processed. It is particularly advantageous with this combination that the composite materials can be processed by hot forming into corresponding molded parts, which then show the color effect according to the invention.

In addition to controlling the mechanical properties, the composites also make it possible to change the optical properties of the moldings via the additional changes in the refractive index at the interfaces. In particular, a surface structuring can additionally, as explained above, further reduce the diffuse scattering and thus increase the brilliance of the color.

In a preferred embodiment of the present invention, at least one contrast material is embedded in the at least one shaped body, which essentially consists of core-shell particles, the at least one contrast material usually being a pigment, preferably an absorption pigment, and in one variant of the invention is particularly preferably a black pigment.

The embedded contrast materials bring about an increase in the brilliance, contrast and depth of the color effects observed in the shaped articles according to the invention. Contrast materials are understood according to the invention to mean all materials which bring about such an enhancement of the optical effect. These contrast materials are usually pigments or organic dyes.

In the context of the present invention, pigments are understood to mean any solid substance which has an optical effect in the visible wavelength range of light. According to the invention, in particular those substances are referred to as pigments which correspond to the definition of pigments according to DIN 55943 or DIN 55945. According to this By definition, a pigment is an inorganic or organic, colored or achromatic colorant that is practically insoluble in the application medium. According to the invention, both inorganic and organic, natural or synthetic pigments can be used.

Inorganic pigments found in nature are obtained by mechanical treatment such as grinding, slurrying, drying, etc. Examples include chalk, ocher, umber, green earth, terra di sienna (baked) and graphite. Synthetic inorganic pigments are in particular white, black, colored u. Luster pigments that are made from inorganic raw materials by former u./od. physikal. Conversion like unlocking, falling, glowing, etc. can win. Examples are white pigments such as titanium white (titanium dioxide), lead white, zinc white, lithopone, antimony white, black pigments such as carbon black, iron oxide black, manganese black and cobalt black and antimony black, colored pigments such as lead chromate, red lead, zinc yellow, zinc green, cadmium red, cobalt blue, manganese blue, Berlin blue Cadmium yellow, Schweinfurter Grün, Molybdatorange u. Molybdate red, chrome orange and red, iron oxide red, chrome oxide green, strontium yellow and many others. Also to be mentioned are glossy pigments with a metallic effect and pearlescent pigments,

Evaporation layers, luminescent pigments with fluorescent and phosphorescent pigments as well as the fillers or extenders. A distinction can therefore be made between groups in the case of inorganic pigments: metal oxides, hydroxides and the like. hydrates;

Mixed phase pigments; Sulfur-containing silicates; Metal sulfides and the like selenides; complex metal cyanides; Metal sulfates, chromates and. molybdates; Mixed pigments (inorganic-organic) as well as the metals themselves (bronze pigments).

Organic pigments found in nature are, for example, umber, gum, bone charcoal, Kasseler brown, indigo, chlorophyll and other vegetable dyes. Synthetic organic pigments are, for example, azo dyes, indigoids, dioxazine (for example PV real violet RL; Clariant), quinacridone, phthalocyanine (for example PV real blue A2R; Clariant), isoindolinone, perylene and. Perinone, metal complex, alkali blue u. recently the diketopyrrolopyrrole (DPP) pigments, the extreme light u. They have weather fastness and are used a lot in paints as clear, pure orange to red tones. The variety of organic pigments will not be discussed in more detail here, but it is not difficult for the person skilled in the art to select suitable pigments as contrast material from the commercially available pigments.

According to their physical functionality, pigments can be divided into absorption pigments and gloss pigments. at

Absorption pigments are pigments that absorb at least part of the visible light and therefore produce a color impression and, in extreme cases, appear black. According to DIN 55943 or DIN 55944, luster pigments are pigments in which luster effects are created by specular reflection on predominantly flat and aligned metallic or highly refractive pigment particles. According to these standards, interference pigments are glossy pigments whose coloring effect is based entirely or predominantly on the phenomenon of interference. These are, in particular, so-called mother-of-pearl pigments or fire-colored metal bronzes. Of particular importance among the interference pigments are the pearlescent pigments, which consist of colorless, transparent and highly refractive platelets. After orientation in a matrix, they produced a soft gloss effect, which is referred to as pearlescent. Examples of Peilglanz pigments are guanine-containing fish silver, pigments based on lead carbonates, bismuth oxychloride or titanium dioxide mica. In particular, the titanium dioxide mica that stands out mechanical, chemical and thermal stability are often used for decorative purposes.

According to the invention, both absorption and gloss pigments can be used, and interference pigments in particular can also be used. It has been shown that the use of absorption pigments is preferred in particular to increase the intensity of the optical effects. Both white and color or black pigments can be used, the term color pigments meaning all pigments which give a different color impression than white or black, such as, for example, Heliogen ™ Blue K 6850 (from BASF, Cu phthalocyanine pigment) , Heliogen ™ Green K 8730 (from BASF, Cu phthalocyanine pigment), Bayferrox ™ 105 M (from Bayer, iron oxide-based red pigment) or chromium oxide green GN-M (from Bayer, chromium oxide-based green pigment). Again, the black pigments are preferred among the absorption pigments due to the color effects achieved. For example, pigmentary carbon black (e.g. the carbon black product line from Degussa (in particular Purex ™ LS 35 or Corax ™ N 115)) as well as iron oxide black, manganese black as well as cobalt black and antimony black can be mentioned. Black mica qualities can also advantageously be used as black pigment (eg Iriodin ™ 600, Merck; iron oxide-coated mica).

It has been shown that it is advantageous if the particle size of the at least one contrast material is at least twice as large as the particle size of the core material. If the particles of the contrast material are smaller, only inadequate optical effects are achieved. It is believed that smaller particles interfere with the arrangement of the nuclei in the matrix and cause a change in the lattices that form. The particles of at least preferably used according to the invention Double the size of the nuclei interact only locally with the lattice formed from the nuclei. Electron micrographs (see also Example 3) show that the embedded particles do not or only slightly interfere with the core particle lattice. The particle size of the contrast materials, which are often also platelet-shaped as pigments, means the greatest extent of the particles in each case. If platelet-shaped pigments have a thickness in the region of the particle size of the nuclei and or even below it, this does not interfere with the lattice orders according to the available studies. It has also been shown that the shape of the embedded contrast material particles has little or no influence on the optical effect. According to the invention, both spherical and platelet-shaped and needle-shaped contrast materials can be incorporated. Only the absolute particle size in relation to the particle size of the nuclei seems to be of importance. It is therefore preferred according to the invention if the particle size of the at least one contrast material is at least twice as large as the particle size of the core material, the particle size of the at least one contrast material preferably being at least four times as large as the particle size of the core material, since then the observable interactions are even smaller are.

A reasonable upper limit for the particle size of the contrast materials results from the limit at which the individual particles themselves become visible or, owing to their particle size, impair the mechanical properties of the shaped body. The determination of this upper limit poses no difficulties for the person skilled in the art.

The amount of contrast material that is used is also important for the desired effect. It has been shown that effects are usually observed when at least 0.05% by weight of contrast material, based on the weight of the shaped body, is used become. It is particularly preferred if the shaped body contains at least 0.2% by weight and particularly preferably at least 1% by weight of contrast material, since, according to the invention, these increased contents of contrast material generally also lead to more intensive effects.

Conversely, larger amounts of contrast material may impair the processing properties of the core / shell particles and thus make it more difficult to produce moldings according to the invention. In addition, it is expected that above a certain proportion of contrast material, which depends on the respective material, the formation of the lattice from core particles will be disturbed and oriented contrast material layers will be formed. It is therefore preferred according to the invention if the shaped body contains a maximum of 20% by weight of contrast material, based on the weight of the shaped body, it being particularly preferred if the shaped body contains a maximum of 12% by weight and particularly preferably a maximum of 5% by weight. Contains contrast material.

In a particular embodiment of the present invention, however, it can also be preferred if the shaped bodies contain as large amounts of contrast material as possible. This is particularly the case if the contrast material is to increase the mechanical strength of the molded body at the same time.

Shaped articles which contain a contrast material preferably correspond to the shaped articles described in the earlier German patent application DE 10204338.8.

Regardless of whether the moldings contain a contrast material, they are preferably produced by a process for producing moldings with an optical effect, which is characterized in that a) core-shell particles, the shell of which forms a matrix and the core of which essentially is solid and essentially monodisperse Size distribution, with a difference between the refractive indices of the core material and the cladding material, are heated to a temperature at which the cladding is flowable, and b) the flowable core-cladding particles are exposed to a) mechanical force.

If the shaped bodies are to contain the contrast material described above, the core-shell particles are mixed with the contrast material before being exposed to the mechanical force from a).

In a preferred variant of the production, the temperature in step a) is 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 suitable shaped bodies, 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.

The mechanical action of force can be such an action 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 or layers. Films or layers according to the invention can preferably also be produced by rolling, 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-Verlag; 1996 are taken.

The extrusion is suitable for the production of pipes, wires, profiles, hoses, etc. The extrusion takes place in extruders, which are usually designed as screw, less often as piston extruders. They are loaded with core-shell particles in the form of powders or granules through filling funnels. The material is heated or cooled, homogenized, plasticized, transported by the (often step-shaped) screw and pressed through the shaping nozzle in the spray head.

Extruders exist in different variants; one differentiates z. B. depending on the number of screw conveyors single and multi-screw extruders, devices with electronic control or guidance by ultrasound. Extruders can also be used to advantage when plasticizing materials that are difficult to process. All extruders described here are suitable for processing corresponding core-shell particles.

During extrusion (extrusion), preheated material is conveyed out of the extruder by a screw or twin screw through a perforated screen and allowed to cool in air or in a cooling bath. In this way, tubes, profiles, plates, foils, cables or filaments can be made from core-shell particles; Many spinning processes are also extrusion processes. The required dimensional stability can be achieved by using polymers with high molecular weights, ie those with entanglement of chain molecules. Alternatively, polymers can also be easily crosslinked.

A special case is the extrusion with wide slot dies to z. B. Flat films of 20-1000 mm thickness. The film can then be quenched by chill rolls or water baths (melt casting or chill roll process). However, the film can also be produced by extrusion blow molding with ring dies. Wide slot nozzles are also used in the so-called extrusion coating of paper or cardboard. The papers treated in this way can then be heat-sealed. Extrusion also sheaths cables and fibers.

When extruding core-shell particles with a shell of polyethylene acrylate or copolymers thereof, it has proven to be optimal if the piston or screw temperature and the mold temperature are not significantly above 220 ° C. For optimal results, however, these temperatures should not be significantly below 120 ° C.

In a preferred variant of the method, a structured surface is generated at the same time as the mechanical force is applied. This is achieved in that the tools used already have such a surface structure. For example, appropriate shapes can be used in injection molding, the surface of which specifies this structuring, or pressing tools can also be used in uniaxial pressing, in which at least one of the pressing tools has a surface structuring. For example, these methods can be used to produce imitations of leather that have a leather-like surface structure and at the same time show the color effects discussed above. If technically advantageous, the moldings can 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 agents and agents for viscosity modification, for. B. thickeners or flow improvers.

Additions of film-forming aids and film-modifying agents based on compounds of the general formula H0-C _n H _2rr 0- (C _n H _2n -O) mH, in which 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 different 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 copolymers with molecular weights up to approx. 15000 and statistical or block-like distribution of the ethylene oxide and propylene oxide assemblies.

If appropriate, organic or inorganic solvents, dispersants or diluents are also possible, for example the open time of the formulation, i. H. extend the time available for their application on substrates, waxes or hot melt adhesives as additives possible.

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. When processing by injection molding, it can be particularly preferred if chalk or other finely particulate release agents, such as, for example, silica or waxes, are added to the core-shell particles as auxiliaries to reduce the stickiness.

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 desired optical or photonic effect, it is desirable for the core-shell particles to 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 in the case of 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 particular 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 so 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 shaped bodies, 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 III-V semiconductors or of materials which 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 of the core-shell particles in the moldings suitable according to the invention has hitherto been unknown. However, it has been shown that the application of force is essential for the formation of the far-reaching order. It is believed that the elasticity of the jacket material among the Processing conditions is crucial for the ordering process. 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 coil 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 is generated by the interplay of these forces.

Core-shell particles, the shell of which is connected to the core via an intermediate layer, have proven particularly suitable for the production of the shaped bodies.

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 problem 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 be suitably modified, for example, 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 organyles, each of which contains organic side chains with corresponding functions. In the case of polymer 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 uncross-linked organic polymers which are preferably grafted onto the core via an at least partially cross-linked intermediate layer. The jacket can either consist of thermoplastic or of 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. Accordingly, the wavelengths of the interacting light and the effects to be observed change.

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 are preferably monodisperse cores made of silicon dioxide, which can be obtained, for example, by the process described in US 4,911,903. The cores are produced by hydrolytic polycondensation of tetraalkoxysilanes in an aqueous-ammoniacal medium, in which case a sol of primary particles is first produced and then the Si0 ₂ particles obtained are brought to the desired particle size by continuous, controlled metering in of tetraalkoxysilane. This process can be used to produce monodisperse Si0 ₂ cores with average particle diameters between 0.05 and 10 μm with a standard deviation of 5%.

Also preferred as the starting material are SiO ₂ cores which are coated with (semi-) metals or metal oxides which are non-absorbent in the visible range, such as, for example, TiO ₂ , ZrO ₂ , ZnO ₂ , SnO ₂ or Al ₂ O ₃ . The production of SiO ₂ cores coated with metal oxides is 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 ₂ , Zr0 ₂ , Zn0 ₂ , Sn0 ₂ or Al ₂ 0 ₃ or metal oxide mixtures can also be used as the starting material. 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 Si0 ₂ cores can be transferred to other oxides easily and with the same result. Tetraethoxysilane, tetrabutoxytitanium, tetrapropoxyzirconium or their mixtures are added in one pour with intensive mixing to a mixture of alcohol, water and ammonia, the temperature of which is adjusted with a thermostat to from 30 to 40 ° C., and the mixture obtained for further Vigorously stirred for 20 seconds, a suspension of monodisperse nuclei in the nanometer range being formed. 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 included as the starting material for the production of the core-shell particles according to the invention. Such materials are offered, for example, by 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 / shell 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 sheath can be chosen so that it is essentially dimensionally stable and tack-free 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. their composition, the particle size, the mechanical data, the refractive index, the glass transition temperature, the melting point and the weight ratio of core: shell and thus also the application properties of the core / shell particles to determine, which ultimately also affect the properties of the molded body made from it.

Polymers and / or copolymers which can be contained in the core material or of which it consists, are high-molecular compounds which 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. B. melamine / formaldehyde, urea / formaldehyde and phenol / formaldehyde condensates.

For the 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, are 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 have been postcrosslinked in a separate process step after the actual (co) polymerization or (co) polycondensation has been completed.

A detailed description of the chemical composition of suitable polymers follows below. For the shell material, as for the core material, in principle polymers of the classes already mentioned above are suitable, provided that they are selected or constructed in such a way that they correspond to the specification given above for the shell polymers.

Favorable for certain applications, e.g. 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 molded 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. the 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 in principle suitable 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, polyester are suitable, for example, Polyamides, polyepoxides, polyurethane, rubber, polyacrylonitrile and polyisoprene.

If the jacket 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 cross-linked polystyrene and the shell of a polyacrylate, preferably polyethyl acrylate and / or polymethyl methacrylate.

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 specific 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 crosslinked 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. 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 Controlled / 'iving "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 above-mentioned literature references.

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

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 H ₂ O ₂ , salts of peroxosulfuric acid and peroxodisulfuric acid, such as ammonium, sodium or potassium peroxodisulfate , Azo compounds, boralkyl compounds and homolytically decomposing hydrocarbons. The initiators and / or photoinitiators, which, depending on the requirements of the polymerized material, are used in amounts of between 0.01 and 15% by weight, based on the polymerizable components, can be used individually or in combination 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, especially ammonium, sodium or potassium peroxodisulfate in combination with dithionite or bisulfite, the sodium salts being preferably used. Another suitable redox system consists of the combination

Hydrogen peroxide / ascorbic acid with iron (II) salts.

Appropriate 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.

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 give 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 polyester, polyurethane, polyamide, polyurea, polyepoxide 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 weight 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, starch copolymers, modulated, are preferably used as dispersants. low molecular weight, carbon and / or sulfonic acid group-containing polymers or mixtures of these substances.

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-Λ / inylpropionate 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 dialkylsulfosuccinates or alkyldiphenyloxide 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 producing 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 producing the cores all that is required is to ensure that the polymers are as uniform as possible, in particular 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 preparation - 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 adjusted, 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, d. H. via 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 Ulimann'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, isopropyl penylbiphenyl, vinyl pyridine, isopropenyl pyridine, vinyl carbazole, vinyl anthracene, N-benzyl methacrylamide, p-hydroxymethacrylic acid anilide.

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:

In the formulas above and in the form below, for the sake of clarity and simplification of the spelling, 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.

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

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 to optimize the properties of the molded articles according to the invention that are relevant in terms of application technology.

Suitable substituents are in particular halogen, NO ₂ , 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. The alkyl chains of these radicals can in turn optionally be substituted, or by double-bonded heteroatoms or assemblies, such as. B. -0-, -S-, -NH-, -COO-, -OCO- or -OCOO- be interrupted 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.

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 that 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-radical polymers.

In the following, examples of suitable crosslinkers are presented, which 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 methylene-bisacrylamide, triallyl cyanurate, divinylethylene urea, trimethylolpropane tri- (meth) acrylate, Trimethylolpropane tricinyl ether, pentaerythritol tetra (meth) acrylate, pentaerythritol tetra vinyl ether, and also crosslinkers with two or more different reactive ends, such as, for. B. (Meth) allyl (meth) acrylates of the formulas:

(where R is hydrogen or methyl).

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

Examples include: N-methylol- (meth) acrylamide, acrylamidoglycolic acid, and their ethers and / or esters with C ₁ to C ₆ alcohols, diacetone acrylamide (DAAM), glycidyl methacrylate (GMA), methacryloyloxypropyltrimethoxysilane (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 like polyvalent metal ions. Acrylic acid, methacrylic acid, maleic anhydride, itaconic acid and fumaric acid are preferably used as unsaturated carboxylic acids for this purpose. 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, post-crosslinkers with reactive groups, such as, for. 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 given above can be combined with one another in a targeted manner and (co-) polymerized, 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 can 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 are, 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 of modifying particle surfaces are well known to those skilled in the art and are described, for example, in various textbooks such as Unger, K.K., Porous Silica, Elsevier Scientific Publishing Company (1979).

The production in the composite materials according to the invention is preferably carried out by connecting at least one molded body, which essentially consists of core-shell particles, to at least one further material that determines the mechanical properties of the composite. In a preferred embodiment of this method, the connection is brought about by the action of mechanical force, preferably uniaxial pressing, and / or heating. For example, the connection of two or more layers can be achieved by uniaxial pressing at an elevated temperature.

In a preferred embodiment, such composite materials are in the form of laminates, i.e. the molded body is a film or a layer which is firmly bonded to at least one further layer of another material which determines the mechanical properties of the composite.

It is also preferred if the molded body, which dominates the optical properties of the material, is embedded in the other material and is therefore surrounded by it.

Laminates are preferred in which the molded body, which dominates the optical properties of the material, is embedded between two different materials. For example, a material that determines the mechanical properties of the composite material and a transparent film that only changes the surface structure and feel of the composite material can be attached to one side of the molded body, for example structured PMMA films can be used to further increase the brilliance of the color effects. By means of a suitable structuring of such foils, the diffuse reflection on the shaped bodies which dominate the optical properties of the material can be reduced or prevented.

In another preferred embodiment of the method according to the invention, the composites are produced by coextrusion. By coextrusion e.g. Sheets or sheets made from two or more layers for packaging and as semi-finished products.

There are various common coextrusion processes: In one process variant, the materials to be extruded are mixed in the nozzle. This process requires similar flow properties of the different materials. It is advantageous that only one nozzle is required and the coextrudate is obtained directly.

In another process variant, a separate nozzle is required for each component. The individual extrudate strands are only brought together to form the coextrudate after they have emerged from the nozzles via rollers or rollers. This process is more complex in terms of equipment, but enables the coextrusion of materials with different flow characteristics.

Extrusions are also used to produce nets made of thermoplastic materials, in which, in contrast to knotted fabrics, the contact points of warp and weft are firmly connected. With this method, two counter-rotating tools, each with a set of circularly arranged nozzle openings, are attached to the extruder head. If the openings of the two tools are on top of each other, only one strand is created. By rotating the openings, the strand is divided into two individual strands and then reunited during further rotation, etc. With the same speed of rotation of the two tools, a tube with a diamond-like network structure is created, which, after being cut open, gives a flat network. By varying the slots, speeds, etc., very different networks can be created.

When extruding, chemical reactions can also be carried out at the same time, namely polyreactions of monomers or prepolymers to thermoplastics and thermosets, crosslinking or grafting reactions on the shell of the core-shell particles. In order to avoid different hardenings, piston extrusion presses are used here and not screw or

Twin-screw extruder. When rubber is extruded however, vulcanization to elastomers in a separate process step after extrusion.

In a manufacturing method preferred according to the invention, such composites are produced by pouring or back injection. In both cases, the shaped body, consisting essentially of core-shell particles, is placed in the mold and the at least one other material is either cast in in the form of a melt or precursor or injected by means of an injection molding apparatus; in other preferred variants, the composite materials are laminated or lamination of individual layers. The connection of the materials can be produced by an adhesive process and / or a pressing process.

As has been shown, it is also possible and preferably also according to the invention to process the core-shell particles simultaneously with the other material in an injection molding apparatus. It can be particularly preferred if chalk or other finely particulate release agents, such as silica, are added to the core-shell particles as auxiliaries to reduce the stickiness.

Laminate-shaped composites, in a particularly preferred embodiment of the present invention, can preferably be processed further by hot forming.

If the composite materials according to the invention are to be processed by hot forming, then it is necessary that the material which determines the mechanical properties of the composite material is a thermoplastic which is suitable for hot forming. Suitable plastics are typically those that can be processed in the flexible state. Preferred thermoplastics can be processed at temperatures below 200 ° C. For example, thermoplastic polyolefins such as Various polystyrene grades, such as standard polystyrene, impact-resistant polystyrene, polystyrene foams or copolymers of styrene with other monomers, such as acrylonitrile or acrylonitrile-butadiene or acrylonitrile-styrene-acrylic esters are mentioned. Furthermore, customary polymers such as polyvinyl chloride, polyethylene, polypropylene, polymethyl methacrylate, polyoxymethylene, polycarbonate, polyester carbonate, polyphenylene ether, polyamides, acrylonitrile-methacrylate-butadiene copolymers, cellulose (di) acetate and generally also thermoplastic elastomers, such as Styrene-butadiene-styrene block copolymers, thermoplastic olefin elastomers made of ethylene and propylene; Thermoplastic polyurethane elastomers; Thermoplastic elastomers based on polyester or polyether and polyamides can be used.

During hot forming, the laminate-shaped composite material (semi-finished product) is heated until the material that determines the mechanical properties of the composite is flexible and deformed under low force. Thereafter, if the deformation force persists, it cools down below the freezing area. Typical heat sources for such processes are infrared radiators, heating cabinets, hot air flow, gas flames or heated liquids, the hot forming can be carried out as punching, embossing or by applying a vacuum, so-called deep drawing, or overpressure ("blowing into free space"). Bending, bending, stretching or shrinking of the composite material can also be used for hot forming the material. Such techniques are well known to those skilled in polymer processing and can be found, for example, in A. Franck "Kunstoff-Kompendium", Vogel-Verlag, 1996, Chapter 4 "Kunststoffverarbeitung". A particularly preferred hot forming according to the invention is deep drawing.

The composite materials according to the invention can also be comminuted into pigments of a suitable size by cutting or breaking and possibly subsequent grinding. This process can, for example, in one continuous belt process. Such pigments can then be used to pigment lacquers, powder coatings, paints, printing inks, plastics and cosmetic formulations, such as 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, e.g. for paints 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 Ti0 ₂ , have become particularly popular , Carbon black, chromium oxide, iron oxide, and organic “color pigments” have been found 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 The present invention also relates to pigments which are obtainable from the composite materials according to the invention and formulations which contain the pigment according to the invention , The composite materials can be installed as security features in surfaces such as chip cards, banknotes, OEM products etc. In these cases, the security feature represents the reflection or transmission color that is dependent on the viewing angle, ie the angle and wavelength-resolved spectrum of the composite materials.

For this purpose, the core-shell particles can be applied as thin films in the product in question (lamination), or applied in the form of pigments in a formulation to the product in question. The formulations can consist, for example, of steel engraving colors (pigment size: 20-25 μm) or screen printing inks (pigment size: 70-80 μm).

It is also possible to further refine these composite materials by painting or using various printing techniques, such as pad printing, screen printing or spraying techniques. The finishing can take place both on the surface made of core-shell particles and on the surface of the material that influences the mechanical properties.

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

Examples

Used abbreviations:

BDDA Butanl, 4, -dioldiacrylatt

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 reflux condenser, a template tempered to 4 ° C. consisting of 217 g of water, 0.4 g of butanediol diacrylate, 3.6 g of styrene (from BASF, destabilized) and 80 mg of sodium dodecyl sulfate (SDS ; Merck) and dispersed with vigorous stirring. Immediately after filling, the reaction is started by directly adding 50 mg sodium dithionite (Merck), 250 mg ammonium peroxodisulfate (Merck) and again 50 mg sodium dithionite (Merck), each dissolved in 5 g water. After 10 minutes, a monomer emulsion of 6.6 g of butanediol diacrylate, 59.4 g of styrene (from BASF, destabilized), 0.3 g of SDS, 0.1 g of KOH and 90 g of water is metered in continuously over a period of 210 minutes. The reactor contents are stirred for 30 minutes without further addition. A second monomer emulsion of 3 g allyl methacrylate, 27 g methyl methacrylate (from BASF, destabilized), 0.15 g SDS (from Merck) and 40 g water is then metered in continuously over a period of 90 minutes. The reactor contents are then stirred for 30 minutes without further addition. It is then a monomer emulsion of 130 g of ethyl acrylate (from BASF, destabilized), 139 g of water and 0.33 g of SDS (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 11 methanol, with 11 dest. 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.

When carrying out the experiment analogously, 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:

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

3 kg of the core-shell particles from Example 1 are comminuted in a granulator mill (Rapid, type: 1528) with ice cooling and then with 2% by weight black pigment (Iriodin®600 or Black Mica®; Fa. Merck) or with 0.2% by weight of a colored absorption pigment (e.g. PV real blue A2R; Clariant) and suitable processing aids (0.1% by weight antioxidants, 0.2% by weight UV stabilizers, 0.2 wt .-% mold release agent and 0.2 wt .-% flow improver) mixed. After 15 minutes in the tumble mixer (Engelmann; type: ELTE 650), the mixture is in a single-screw extruder (Plasti-Corder; Brabender; Screw diameter 19 mm compounded with 1-hole nozzle (3mm)). After a cooling section, granulation is carried out in an A 90-5 granulator (from Automatic). The pellets are then mixed with 0.2% by weight of release agent in the tumble mixer over 10 minutes.

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

2 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.

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

25 g of the granules from Example 2 are heated in a press with a cassette cooling system (Dr. Collin GmbH; type: 300E) between two sheets of polyethylene terephthalate at a pressure of 1 bar for 3 min to a temperature of 150 ° C., then at a pressure of 250 bar and a temperature of 150 ° for 3 minutes, and cooled to room temperature under a pressure of 200 bar for 8 minutes. The protective films made of polyethylene terephthalate are then removed.

Example 4a: Production of a laminate by pressing

A film from Example 3b is heated with a polycarbonate plate (d = 1 mm) in a press with a cassette cooling system (from Dr. Collin GmbH; type: 300E) without pressure to a temperature of 150 ° C. and at a pressure pressed from 250 bar to a laminate. After cooling to room temperature, the pressure is reduced again after 8 minutes.

Example 4b: Production of a laminate by pressing

25 g of granules from Example 2 are heated with a polycarbonate plate (d = 1 mm) between two polyethylene terephthalate films in a press with a cassette cooling system (from Dr. Collin GmbH; type: 300E) to a temperature of 150 ° C. without pressure and at a pressure of 250 bar for 3 min to a laminate. The mixture is then cooled to room temperature within 8 minutes without opening the press at a pressure of 200 bar. The protective films made of polyethylene terephthalate are then removed.

Example 5: Production of a composite material by back injection

A film from Example 3b is placed in an injection molding plate tool (diameter: 140 mm; thickness 4 mm; central gating) and fixed. Polystyrene (Polystyrol® 143E; BASF) is then injected using a screw injection molding machine (Battenfeld, type: BA 1000/315 CDC Unilog B4; locking force 1000 kN; screw diameter 45 mm). (Cylinder temperature: 175 ° C, tool temperature: 40 ° C; dosing pressure: 90 bar; peripheral screw speed when dosing: 100 mm / s; injection speed: 50 cm ³ / s over 1.7 s; injection pressure: 830 bar). After reaching a pressure of 830 bar, the pressure is set to 600 bar and held for 15 seconds. There is a remaining cooling time of 40s before the tool is removed from the mold. Example 6: Production of a half-shell by hot forming a laminate

A laminate from Example 4b is heated on one side with an infrared emitter in a thermoforming machine (Illing; type: U-60; frame size 600mmx500mm) and then blown into a half-shell into the open via a frame opening of 150mmx150mm. The heating time was 100s, the deformation temperature was approx. 180 ° C.

Example 7: Production of a molded part by hot forming a laminate

A laminate from Example 4b is processed in a deep-drawing machine (Illing, type U-60; frame size 600mmx500mm) using a corresponding tool insert to form a molded part (cup). For this purpose, the laminate is clamped into the frame, heated to a deformation temperature of approx. 180 ° C. in a time of 100 s with the aid of an IR radiator and inflated to a half-shell. Then a tool insert in the form of a yogurt cup is driven into the half-shell from below. The volume between the half-shell and the tool is evacuated via small openings in the tool insert, causing the half-shell to fit onto the mold.

Example 8: Production of core-shell particles with a silicon dioxide core (150 nm)

66 g Monospher® 150 suspension (from Merck; 38% by weight solids content, corresponding to 25 g SiO ₂ monospheres; average particle size 150 nm; standard deviation of the average particle size <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 stirred vigorously. 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 in 5 g of water are added in succession. Immediately after the addition, the reactor is heated to 75 ° C. and 25 g of ethyl acrylate are metered in continuously over a period of 120 minutes. 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 filtered off and dried and processed further in accordance with Examples 2 to 7.

Example 9: Production of core-shell particles with a silicon dioxide core (250 nm)

60 g of Monospher® 250 (Merck; average particle size 250 nm; standard deviation of the average particle size <5%) are suspended. At 40 ° C, 3.2 g of AICI ₃ and 1.9 g of Na ₂ S0 _{4 are added} to the suspension. 5.9 g of 3-methacryloxypropyltrimethoxysilane is added dropwise at pH = 2.6 and 75 ° C. A pH = 8.5 is set at 75 ° C. by adding sodium hydroxide solution. After hydrolysis, 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. Then the suspension is in a homogenizer (Niro Soavi, NS1001L) dispersed. 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 an 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 in 5 g of water are added in succession. 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 7.

Example 10: Production of core-shell particles with a silicon dioxide core (100 nm)

66 g of Monospher® 100 suspension (Merck; 38% by weight solids content, corresponding to 25 g of SiO ₂ monospheres; average particle size 150 nm; standard deviation of the average particle size <5%) are mixed with 354 g of water in 25 C. temperature-controlled stirred tank double-wall reactor with argon protective gas supply, reflux condenser and propeller stirrer and mixed with a solution of 450 mg aluminum trichloride hexahydrate (Acros) in 50 ml and stirred vigorously for 30 min. 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.

Thereafter, 50 mg of sodium dithionite, 150 mg of ammonium peroxodisulfate and again 50 mg of sodium dithionite are each successively in 5 g of water added. 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 continuously metered. 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 7.

Example 11: Production of core-shell particles, the core being composed of silicon dioxide with an outer shell of titanium dioxide

80 g of Monospher® 100 (monodisperse silicon dioxide balls with an average size of 100 nm with a standard deviation <5%) from Merck KGaA are dispersed at 40 ° C. in 800 ml of ethanol. A freshly prepared solution consisting of 50 g of tetraethyl orthotitanate (Merck KGaA) and 810 ml of ethanol is metered into the monosphers / ethanol dispersion with vigorous stirring together with demineralized water. 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 2 g of methacryloxypropyltrimethoxysilane (ABCR), dissolved in 10 ml of ethanol, are added over a period of 15 minutes. After heating at reflux 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 passed through a homogenizer (Niro Soavi, NS1001 L) dispersed. 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 an 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 in 5 g of water are added in succession. 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 7.

Example 12: 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 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 BDDA, 510.3 g styrene, 2.625 g SDS, 0.7 g KOH and 770 g water is used over a period of. 120 minutes continuously metered in via the wobble piston pump. The reactor contents are stirred for 30 minutes without further addition. Then a second monomer emulsion of 10.5 g ALMA, 94.50 g methyl methacrylate, 0.525 g SDS and 140 g Water is continuously metered in over a period of 30 min 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 7. Shaped bodies or composite materials with a color effect (color flop) in the red-green area result.

Example 13: 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 started by directly adding 50 mg sodium dithionite (Merck), 250 mg ammonium peroxodisulfate (Merck) and again 50 mg sodium dithionite (Merck), each dissolved in 5 g water. After 10 minutes, a monomer emulsion composed of 6.6 g of butanediol diacrylate (from Merck, destabilized), 59.4 g of styrene (from BASF, destabilized), 0.3 g of SDS, 0.1 g of KOH and 90 g of water is passed through one Period of 210 min continuously metered. The reactor contents are 30 minutes without further Addition stirred. A second monomer emulsion of 3 g allyl methacrylate (Merck, destabilized), 27 g methyl methacrylate (BASF, destabilized), 0.15 g SDS (Merck) and 40 g water is then metered in continuously over a period of 90 min , 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) is then metered in continuously over a period of 180 minutes. 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 7.

Example 14: 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 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 60 mg of sodium dodecyl sulfate (SDS; Merck) and dispersed with vigorous stirring. Immediately after filling, the reaction is started by directly adding 50 mg sodium dithionite (Merck), 300 mg ammonium peroxodisulfate (Merck) and again 50 mg sodium dithionite (Merck), each dissolved in 5 g 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. A second monomer emulsion of 1, 5 is then g of allyl methacrylate (from Merck, destabilized), 13.5 g of methyl methacrylate (from BASF, destabilized), 0.075 g of SDS (from Merck) and 20 g of water were metered in continuously over a period of 45 minutes. 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 (from 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) is then used continuously over a period of 240 min added. 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 and dried and processed further in accordance with Examples 2 to 7.

Claims

claims

1. Composite material with an optical effect containing at least one shaped body which consists 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, with a difference between the refractive indices of the core material and the cladding material and at least one other material that determines the mechanical properties of the composite.

2. Composite material according to claim 1, characterized in that in the core-shell particles, the shell is connected to the core via an intermediate layer.

3. Composite material according to at least one of the preceding claims, characterized in that in the at least one shaped body, which consists essentially of core-shell particles, at least one contrast material is embedded, the at least one contrast material being a pigment, preferably an absorption pigment and particularly preferably a black pigment.

4. Composite material according to at least one of the preceding claims, characterized in that the core-shell particles have an average particle diameter in the range from about 5 nm to about 2000 nm, preferably in the range from about 5 to 20 nm or in the range from 50-500 nm.

5. Composite material according to at least one of the preceding claims, characterized in that the difference between the refractive indices of the core material and the cladding material is at least 0.001, preferably at least 0.01 and particularly preferably at least 0.1.

6. Composite material according to at least one of the preceding claims, characterized in that the at least one molded body, which consists essentially of core-shell particles, is in the form of a layer.

7. Composite material according to at least one of the preceding claims, characterized in that the at least one further material which determines the mechanical properties of the composite consists essentially of polymers, preferably thermoplastic polymers.

8. Composite material according to at least one of the preceding claims, characterized in that it is a laminate arrangement and the at least one further material, which determines the mechanical properties of the composite, can be processed at temperatures below 200 ° C.

9. Composite material according to at least one of claims 1 to 6 or 8, characterized in that the at least one further material which determines the mechanical properties of the composite consists essentially of rubber polymers.

10. A process for the production of composite materials with an optical effect, characterized in that at least one shaped body, which essentially consists of core-shell particles, the shell of which forms a matrix and whose core is essentially solid and has an essentially monodisperse size distribution, with a difference between the refractive indices of the core material and the cladding material, fixed with at least one other Material that determines the mechanical properties of the composite is connected.

11. A method for producing composite materials according to claim 10, characterized in that the fixed connection is brought about by mechanical force and / or heating.

12. A method for producing composite materials according to at least one of the preceding claims, characterized in that the fixed connection is effected by uniaxial pressing.

13. A method for producing composite materials according to at least one of the preceding claims, characterized in that the fixed connection is effected by pouring or injection molding.

14. A method for producing composite materials according to at least one of the preceding claims, characterized in that the fixed connection is further processed by hot forming, in particular deep drawing.

15. A method for producing composite materials according to at least one of the preceding claims, characterized in that the solid connection is effected by coextrusion.