WO2006097173A1 - Elongation and compression sensor - Google Patents

Abstract

The invention relates to the use of shaped bodies for detecting mechanical forces. These bodies are essentially composed of core-shell particles comprising a shell which forms a matrix and which is connected to the core via an intermediate layer, and a core which is essentially solid and has an essentially monodisperse size distribution, the refractive index of the core material being different from that of the shell material and the shell matrix being an elastomer. The invention also relates to corresponding sensors and to methods for producing them.

Description

 Strain and compression sensor

The invention relates to the use of core-shell particles for the production of sensors for the detection of mechanical force, as well as corresponding sensors for the detection of mechanical force and a method for producing such sensors.

Numerous methods for detecting mechanical forces are known from the prior art. In particular, the measurement of strain or compression processes, as well as the determination of pressure are requirements that are frequently made in practice. Conventional detection systems of these mechanical influences are mostly based on MEMS (microelectromechanical systems) and represent RC resonant circuits. In addition to variable resonance frequencies for detection, sensors can use the changes of resistances to make mechanical force effects visible. For example, European patent application EP-A-0 469 336 describes a resistive pressure sensor. Two or four ohmic resistors are mounted on a membrane in such a way that the resistances closest to the edge lie outside the membrane area in which maximum elongation or stagnation is to be expected. A sensor of conductive polymer particles is described in US Pat. No. 6,276,214. The composite material from which the sensor is constructed consists of polymers and individual conductive particles dispersed in these polymers. The pressure effect changes the distance between these conductive particles and, correspondingly, the electrical resistance of the sensor changes. From the change in resistance, the strength of the pressure can be calculated.

International Patent Application WO 03/064988 discloses the use of core-shell particles whose shell forms a matrix and whose core is substantially solid and has a substantially monodisperse size distribution, with a difference between the refractive indices of the core material and the cladding material . for the production of sensors for the detection of mechanical force described.

In the case of the films according to WO 03/064988, the matrix which is formed from the shell polymers is mechanically fixed only by entanglement. If a stretching force acts for a longer time, it can happen that these entanglements are dissolved and the material suffers a white fracture and then flows apart. The elastic deformation takes place only in a small strain area, so that the sensors described in WO 03/064988 are only partially suitable for repetitive applications.

It has now been found that sensors with improved properties can be obtained when the shell matrix is an elastomer.

Consequently, a first subject of the present application is the use of moldings consisting essentially of core-shell particles whose shell forms a matrix and whose shell is connected to the core via an intermediate layer and the core is substantially solid and a substantially monodisperse Having size distribution and in which there is a difference between the refractive indices of the core material and the cladding material, wherein the cladding matrix is an elastomer, for the detection of mechanical force.

For the purposes of the present invention, the shell matrix is then an elastomer if the expansion is proportional to an elongation of at least 50%, preferably at least 100% and particularly preferably at least 200%, in each case based on the original length to the acting force. These elastomeric properties can be achieved, for example, when the cladding matrix is crosslinked. The cross-linking forms stable, chemical fixation points between the polymer chains of different core-shell particles, whereby the shell matrix becomes an elastomer. Thus, in a preferred embodiment of the present invention, the shell matrix is chemically crosslinked.

In a preferred embodiment according to the invention, the core-shell particles are processed prior to their use according to the invention to form sensors, in particular films or injection-molded articles.

The use of films consisting essentially of Kem-Mantei particles whose shell forms a matrix and whose jacket is connected to the core via an intermediate layer and the core is substantially solid and has a substantially monodisperse size distribution and a difference between the refractive indices of the core material and the cladding material, wherein the cladding matrix is an elastomer, for detection of mechanical force is therefore a further object of the present invention. The films are used in a preferred variant of the invention as a surface coating for the detection of mechanical force acting on components.

Another object of the present invention is a sensor or a shaped body suitable for the detection of mechanical force substantially consisting of core-shell particles whose shell forms a matrix and whose jacket is connected to the core via an intermediate layer and the core substantially is fixed and has a substantially monodisperse size distribution, wherein there is a difference between the refractive indices of the core material and the cladding material, which is characterized in that the cladding matrix is an elastomer. In the following, the term "sensor" means both the sensors, which are expressly the subject of the invention, as well as those which result when shaped bodies or core-shell particles are used according to the above definition according to the invention.

Core-shell particles which can be used according to the invention are known per se.

From the German patent application DE-A-10145450 moldings are known with optical effect, consisting essentially of core-shell particles whose shell forms a matrix and the core is substantially solid and have a substantially monodisperse size distribution. In this case, the refractive indices of the core material and the cladding material differ, as a result of which said optical effect, preferably an opalescence, is produced. Preferably, in these moldings, the core is connected to the jacket via an intermediate layer.

The effect exploited here according to the invention is the change in the color of the sensor during elongation or compression of the sensor material. As known from WO 03/064988, the core-shell particles in the use according to the invention or in the sensors according to the invention form a so-called colloidal-crystalline lattice. It is a dense or densest packing of the core-shell particles or cores in the shell matrix. The observed color of the sensors is determined by the lattice spacings of this colloidal crystal. During stretching or compression processes, these distances and thus the observed color change.

According to the invention, it is further preferred if at least one contrast material is incorporated into the jacket matrix of the molded bodies or sensors. This contrast material reinforces the optical effect of the core-Mantθl particles under force and thus facilitates the optical detection.

The preferably stored contrast materials cause an increase in brilliance, contrast and depth of the observed color effects in the sensors according to the invention. Under contrast materials are understood according to the invention, all materials that cause such a gain of the optical effect. Usually these contrast materials are coloring agents, such as pigments and / or dyes.

For the purposes of the present invention, pigments are understood to mean any solid substance which exhibits an optical effect in the visible wavelength range of the 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 definition, a pigment is a virtually insoluble, inorganic or organic, colored or achromatic colorant in the application medium. In this case, both inorganic and organic pigments can be used according to the invention.

According to their physical mode of operation, pigments can be classified into absorption pigments and luster pigments. Absorption pigments are those pigments which absorb at least part of the visible light and therefore cause a color impression and in extreme cases appear black. Luster pigments according to DIN 55943 or DIN 55944 are those pigments in which gloss effects are produced by directional reflection on predominantly flat-shaped and aligned metallic or strongly refractive pigment particles. As interference pigments according to these standards, such luster pigments are called, whose coloring effect entirely or predominantly based on the phenomenon of interference. These are in particular so-called nacreous pigments or fire-colored metal bronzes. Of particular economic 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 called pearlescent. Examples of reflective pigments are guanine-containing fish silver, pigments based on lead carbonates, bismuth oxychloride or titanium dioxide mica. In particular, the titanium dioxide mica, which are characterized by mechanical, chemical and thermal stability, are often used for decorative purposes.

Both absorption and gloss pigments can be used according to the invention, it also being possible to use interference pigments in particular. It has been shown that the use of absorption pigments is particularly preferred for increasing 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, for example Heliogen ™ Blue K 6850 (from BASF, Cu phthalocyanine pigment) , Heliogen ™ Green K 8730 (BASF, Cu phthalocyanine pigment), Bayferrox ™ 105 M (Bayer, iron oxide-based red pigment) or chrome oxide green GN-M (Bayer, chromium oxide-based green pigment). Due. The color effects achieved are again preferred among the absorption pigments, the black pigments. For example, pigmentary carbon black (for example the Degussa carbon black product line (in particular Purex ™ LS 35 or Corax ™ N 115)) is flame black, as well as iron oxide black, manganese black, cobalt black and antimony black. Black mica qualities can also be used advantageously as black Pigment (eg Iriodin ™ 600, Merck, iron oxide coated mica).

It has been found that it is advantageous 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. If the particles of the contrast material are smaller, only insufficient optical effects are achieved. It is believed that smaller particles interfere with the alignment of the nuclei in the matrix and cause a change in the forming lattices. The particles of at least twice the size of the cores which are preferably used according to the invention interact only locally with the grating formed from the cores. Electron micrographs (see also Example 3) show that the embedded particles do not disturb the lattice of Kemteilchen, or only slightly. In this case, the particle size of the contrast materials, which are often also platelet-shaped pigments, means the respectively greatest extent of the particles. If platelet-shaped pigments have a thickness in the range of the particle size of the cores and / or even below it, this does not disturb the lattice orders according to available investigations. It has also been shown that the shape of the incorporated contrast material particles has no or only little influence on the optical effect. According to the invention, both spherical and platelet-shaped and needle-shaped contrast materials can be incorporated. Of importance only seems to be the absolute particle size in relation to the particle size of the cores. Therefore, it is inventively preferred 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, wherein the particle size of the at least one contrast material is preferably at least four times as large as the particle size of the core material, since then the observable interactions even lower. A reasonable upper limit of the particle size of the contrast materials results from the limit at which the individual particles themselves become visible or impair the mechanical properties of the sensor due to their particle size. The determination of this upper limit presents no difficulty for the skilled person.

Of importance for the present invention desired effect is also the amount of contrast material that is used. It has been found that effects are usually observed when at least 0.02% by weight of contrast material, based on the weight of the sensor, is used. It is particularly preferred if the sensor contains at least 0.05% by weight and more preferably at least 0.2% by weight of contrast material, since these increased contents of contrast material according to the invention as a rule also lead to more intensive effects.

Conversely, larger amounts of contrast material may affect the processing properties of the core / shell particles and thus complicate the production of sensors according to the invention. Moreover, it is expected that above some level of contrast material that depends on the particular material, the formation of the lattice of core particles will be disturbed, forming oriented contrast material layers. Therefore, it is preferred according to the invention if the sensor contains a maximum of 20% by weight of contrast material, based on the weight of the sensor, and it is particularly preferred if the sensor has a maximum of 12% by weight and particularly preferably not more than 5% by weight. Contains contrast material.

In a particular embodiment of the present invention, however, it may also be preferred for the sensors to contain as large amounts of contrast material as possible or for the core-shell particles as much as possible large quantities of contrast material are added. This is especially the case when the contrast material is to simultaneously increase the mechanical strength of the sensor.

The sensors according to the invention or moldings to be used according to the invention can be obtained essentially analogously to the method described in German Patent Application DE-A-10145450, whereby it must be ensured by suitable measures that the jacket matrix is an elastomer.

In a preferred variant of the invention, this takes place - as described above - by crosslinking of the cladding matrix.

Another object of the present invention is therefore a process for the production of moldings consisting essentially of core-shell particles with elastomeric jacket or for the production of sensors for the detection of mechanical force, which is characterized in that in a step a) core Clad particles whose cladding forms a matrix and whose core is substantially solid and has a substantially monodisperse size distribution with a difference between the indices of refraction of the core material and the cladding material, mixed with a crosslinking aid, and the mixture in one step b) at a temperature at which the shell is flowable is subjected to a mechanical force, and in a step c) a chemical crosslinking of the shell takes place.

In this case, the crosslinking can be carried out by methods known per se, for example by thermally-induced or light-induced.

In a preferred variant of the invention, the crosslinking takes place thermally induced. It is again preferred if the shell of the core-shell particles contains free cyanate, isothiocyanate, amino, epoxide, isocyanate or Hydroxy-Gruppθn and is used as a crosslinking aid, a (poly) isocyanate, (poly) amine or (poly) epoxide. The crosslinking agent is selected so that it reacts with the reactive, complementary free functional groups

Can crosslink polyaddition mechanisms. The combination of free hydroxyl groups in the shell with (poly) isocyanates as crosslinking assistant is therefore particularly preferred according to the invention. In this case, it is particularly preferred if the jacket is formed by a copolymer which contains hydroxyalkyl (meth) acrylate units, such as hydroxyethyl acrylate (HEA), hydroxyethyl methacrylate (HEMA) or hydroxybutyl methacrylate (HBMA). As crosslinking agents are in particular protected (poly) suitable isocyanates which are also referred to in the trade as polyisocyanate curing agent, and are sold for example by Bayer under the trade name Crelan ^®.

Aliphatic or cycloaliphatic and aromatic isocyanates can be used as polyisocyanates. As aliphatic and cycloaliphatic isocyanates in particular hexamethylene diisocyanate, isophorone diisocyanate and 1, 4-cyclohexyl diisocyanate are used. The aromatic polyisocyanates have a higher reactivity towards hydroxyl groups due to the aromatic radical and are therefore used with particular preference. The most important representatives are toluene diisocyanate, 4,4 ^I -Methylendiphenyldiisocyanat and 1, 5-naphthalene.

According to the invention, it is preferred if the isocyanate function is present in the isocyanates in protected or blocked form. A suitable protective group is in particular ε-caprolactam. The isocyanate functions may also be blocked by the presence of di- or oligomers of the isocyanate compounds. For example, isophorone diisocyanate may be blocked as a dimer. In another variant of the present invention, the induction of the crosslinking takes place by means of light quanta, preferably with energies in the range of UV and / or VIS radiation. As a crosslinking agent is preferably at least one photoinitiator, preferably of the type Il used.

In the case of bond cleavage by light energy, more stable bonds can also be split by dissociation in comparison with thermally induced crosslinking. For example, UV photons having a wavelength of 300 nm have an energy of 400 kJ / mol.

Depending on the requirements of the crosslinked shaped bodies, the photoinitiators are used in amounts of between 0.01 and 15% by weight, based on the core / shell particles, and can be used individually or, in combination, to exploit advantageous synergistic effects.

Suitable photoinitiators should combine a high reactivity, synonymous with a low and therefore economical use concentration, optimal and defined light absorption, high storage stability, low toxicity, good compatibility and incorporation. It is a variety of compounds in commerce, which combine the conditions mentioned in a suitable manner, so that it does not give the expert any difficulty to select corresponding compounds.

A distinction is made here essentially according to so-called alpha splitters, such as hydroxyalkylphenone, benzil ketal, acylphosphine oxide and aminoalkylphenone derivatives,

Hydroxyalkylphenone aminoalkylphenol

Acylphosphoric oxide benzil ketal

and bimolecular type II photoinitiators, such as benzophenone, thioxanthone and camphorquinone derivatives.

Campherchinonbenzophenone

camphorquinone

According to the invention, the use of photoinitiators of the type II and in particular of the benzophenone derivatives or of the parent substance benzophenone is preferred. It is suggested that benzophenone as a radical can abstract an H atom from the mantle polymer chain, creating a reactive point of attachment to crosslink.

In a preferred variant of the invention sensitizers are additionally used which absorb the photon energy and pass it on to the initiator. These substances do not participate in the reaction, but only absorb the light energy and transfer it to the initiator. In particular, compounds known to those skilled in the art, such as various ketones and dyes, can be used for this purpose. The preferred sensitizers include acetophenone, benzophenone, quinones such as anthraquinone and duroquinone, fused aromatics such as pyrene and anthracene, dyes such as eosin, erythrosine, rose bengal, porphyrins, chlorophyll and zinc tetraphenylporphine.

The crosslinking with the aid of photoinitiators allows great freedom in the selection of the shell polymers and the processing temperatures, while the thermal crosslinking here has a limiting effect in the form that the shell polymers must contain thermally crosslinkable groups and processing temperatures of the core-shell particles must be chosen so that the networking only starts after the arrangement of the nuclei has taken place; ie the processing temperatures should remain below 150 ⁰ C, preferably below 100 ⁰ C.

Thus, the photo-induced crosslinking is particularly preferred especially when the processing is to be carried out by film extrusion.

To produce preferred contrast material-containing sensors or moldings, the core-shell particles are mixed with at least one contrast material. The further processing of the mixture then depends on the intended spatial configuration of the sensor or molding. Preferably, the mixture of core-shell particles and crosslinking aid is exposed to a mechanical force at a temperature at which the shell is flowable.

In a preferred variant of the preparation according to the invention sensors, the temperature at which the mixture is subjected to the mechanical force, at least 4O ⁰ C, preferably at least 60 ° C above the glass temperature of the shell of the core-shell particles. It has been empirically shown that the flowability of the jacket in this temperature range meets the requirements for economical production of the sensors in particular.

In a likewise preferred process variant, which leads to sensors according to the invention, the flowable mixtures are cooled under the action of the mechanical force to a temperature at which the jacket is no longer flowable.

According to the invention, the mechanical action of force may be such a force effect which occurs in conventional processing steps of polymers. In preferred variants of the present invention, the mechanical force is either:

- by uniaxial pressing or

- Force during an injection molding process or

during a transfer molding process,

during a (co) extrusion or

- during a calendering process or

- during a blowing process.

If the force is applied by uniaxial pressing, the moldings according to the invention are preferably films. Films according to the invention can preferably also be characterized by Calendering, film blowing or flat film extrusion are produced. The various possibilities of processing polymers under the action 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, "Kunststoff-Kompendium";Vogel-Verlag; 1996 be removed.

If sensors or molded bodies are produced by injection molding, then it is particularly preferred if the demolding takes place only after cooling of the mold with the molded part contained therein. In the technical implementation, it is advantageous if molds with a large cooling channel cross section are used, since the cooling can then take place in a shorter time. It has been shown that the color effects of the invention become significantly more intense due to the cooling in the mold. It is believed that this uniform cooling process leads to a better arrangement of the core-shell particles to the grid. It is particularly advantageous if the mold has been heated prior to the injection process.

In a preferred variant of the method according to the invention, a structured surface is simultaneously produced during the mechanical force action. This is achieved in that the tools used already have such a surface structuring. For example, corresponding shapes can be used in the injection molding, the surface of which specifies this structuring or it can also press tools are 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 which have a leather-like surface structure and at the same time show the color effects discussed above and are thus suitable as decorative sensors. Furthermore, mirror reflections can be reduced by the surface structuring or be eliminated, which complicate the optical detection - in particular by the human eye.

The sensors according to the invention may, if it is technically advantageous, contain auxiliaries and additives. They can serve the optimum setting of the application-technical data or properties required or required for the application and processing. Examples of such auxiliaries and / or additives are plasticizers, film-forming aids, leveling agents, fillers, melt aids, adhesives, release agents, application aids, viscosity modifiers, e.g. B. thickener.

Especially recommended are additives of film-forming agents and film modifiers based on compounds of the general formula HO-C _n H _2n -O- (C _n H _2n -O ^ H, wherein n is a number from 2 to 4, preferably 2 or 3, and m is a number from 0 to 500. The number n can vary within the chain and the different chain links can be incorporated in random or in 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 having molecular weights up to about 15,000 and random or block-like distribution of the ethylene oxide and propylene oxide assemblies.

Optionally, organic or inorganic solvents, dispersants or diluents, for example, the open time of the formulation, d. H. the time available for their order on substrates, extend waxes or melt adhesive as additives possible.

If desired, the sensors also stabilizers against UV radiation and weathering can be added. 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 ester, o-hydroxyphenyl-s triazines or sterically hindered amines. These substances can also be used individually or as mixtures. When using UV stabilizers, however, when the cladding matrix is to be crosslinked, it should be noted that the UV stabilizers are not absorbent in the wavelength range in which the induction of a light-induced crosslinking should possibly take place.

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 sensors. Accordingly, the sensors consist of at least 60% by weight, preferably at least 80% by weight and more preferably at least 95% by weight, of core / shell particles.

For use according to the invention and for use in sensors according to the invention, 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 may be particularly preferred if the core-shell particles have an average particle diameter in the range of about 5 to 20 nm, preferably 5 to 10 nm. In this case, the cores can be called "quantum dots"; they show the corresponding effects known from the literature. In order to achieve color effects in the visible light range, it is particularly advantageous if the core-shell particles have an average particle diameter in the range of about 40-500 nm. Particular preference is given to using particles in the range from 80 to 500 nm, since the reflections of different wavelengths of visible light occur in the case of particles in this order of magnitude range clearly different from each other and so the color shift occurs particularly pronounced.

Effects which can be used according to the invention for detecting the forces can be effects in the visible wavelength range of the light, as well as, for example, effects in the UV or infrared range. Recently, it has become common to call such effects generally photonic effects. All of these effects are optical effects in the sense of the present invention, wherein in a preferred embodiment the effect is an opalescence in the visible range. For the purposes of a common definition of the term, the sensors according to the invention are photonic crystals (cf Chemistry, 49 (9) September 2001, pp. 1018-1025).

According to the invention it is particularly preferred if the core of the core-shell particles consists of a material which either does not flow or becomes fluid at a temperature above the flow temperature of the jacket material. This can be achieved by the use of polymeric materials having a correspondingly high glass transition temperature (T ₉ ), preferably crosslinked polymers or by using inorganic core materials. The suitable materials in detail will be described below.

Decisive for the intensity of the observed effects is the difference between the refractive indices of the core and the cladding. Sensors 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 more preferably at least 0.1. If the sensors according to the invention are to show detectable photonic effects with the naked eye, then refractive index differences of at least 0.05 are preferred. In a particular embodiment of the invention, further nanoparticles are incorporated into the matrix phase of the sensors in addition to the cores of the core-shell particles. These particles are selected with regard to their particle size so that they do not disturb the regular arrangement of the cores or only slightly. By selective selection of appropriate materials and / or the particle size, it is on the one hand possible to change the optical effects of the sensors, for example, to increase the intensity. On the other hand, the matrix can be appropriately functionalized by incorporating suitable "quantum dots". Preferred materials are inorganic nanoparticles, in particular nanoparticles of metals or of H-Vl or III-V semiconductors or of materials which influence the mechanical, thermal, magnetic, electrical, optical and / or acoustic properties of the materials. Examples of preferred nanoparticles are gold, zinc sulfide, hematite, gallium nitride, cadmium selenide, cadmium telluride or gallium arsenide.

In one embodiment of the present invention, it is preferred if the sensor is a pressure indicator which displays the pressure, for example in a line, qualitatively or semi-quantitatively via the visible color. At the same time, the sensor is at the same time an overpressure valve which indicates the increase in pressure due to discoloration even before bursting.

In a further embodiment of the present invention it is preferred if the sensor is designed in the form of a film suitable for coating surfaces. With such a film surfaces, such as metallic components can be coated. The film-shaped surface coating then detects mechanical stresses on the component. In an additional embodiment of the present invention, it is preferred if the sensor is integrated in a component in the form of a shaped body. With such an integrated sensor, it is also possible, fatigue behavior of components, such as the elongation of steel cables, which secure structures such. As suspension bridges, or the elongation or compression of safety-related parts of means of transport, such as aircraft parts, ship hulls, supporting parts of automobiles, among other things to observe. This can preferably be done by optical measurements. So it is also possible to reveal concealed or hidden accident damage that has led to deformations.

In another, likewise preferred embodiment of the present invention, the sensor is designed as a measuring strip which can be clamped between two components in order to detect movements between these components. For example, the sensor according to the invention can advantageously be used in load-bearing parts of bridges or structures. The possible applications of the sensors according to the invention are not limited to these preferred embodiments.

In principle, the sensors according to the invention can be used for the qualitative or semi-quantitative or even quantitative determination of mechanical forces or of elongation or compression without further detection system. For detection, the human eye is sufficient here. In particular, such sensors are suitable here, which, as described above, contain a contrast material.

In a further likewise preferred variant of the present invention, the sensor according to the invention serves to detect acceleration. In a preferred construction, the sensor is connected to an inert mass, the vibrations or Speed changes deform the sensor. Corresponding arrangements are disclosed, for example, in EP-A-1 329 758, the disclosure of which is expressly included in the subject matter of the present disclosure. Such detectors can be used, for example, with a suitable arrangement, for example, for the detection of earthquake or seaquake, as well as storm-induced fluctuations of bridges or structures. Other applications include acceleration sensors in vehicle airbag deployment systems or automatic braking systems or stability systems.

In another preferred variant of the present invention, piezoelectric crystals, such as polyvinylidene chlorides, quartz, tourmaline, BaTiO ₃ , U ₂ SO ₄ , KDaPO ₄ , potassium sodium tartrate, ethylenediamine tartrate, perovskite-type ferroelectrics, in particular PZT (obtainable by continuous exchange of the Ti from lead titanate by zirconium in a continuous series up to the lead zirconate) and PLZT (lanthanum-containing PZT) and electrets, applied to the sensors or integrated into the sensors, whereby a strain can be detected by strain / compression.

Furthermore, in other preferred embodiments of the invention, the sensor film may be joined to another material, preferably laminated to a stretchable material. This is advantageous, for example, if the composite material remains stable in direct contact with an aggressive medium against which the sensor film would not be resistant or in which it would swell. Furthermore, such a composite can also be advantageous in terms of pressure-tightness, and the mechanical characteristics, such as the modulus of elasticity, of the sensor film can be finely adjusted by selecting the composite material and thus influence the sensor characteristics. Preferably, the bonded materials are rubbery polymers such that the composite exhibits the high resilience and tear strength of the rubber in conjunction with the rubber From the viewing angle dependent color effect of the molding. The production of corresponding composites can be carried out according to the methods described in International Patent Application WO 2003/106557. The relevant disclosure expressly also belongs to the content of the present application.

For the quantitative determination of the mechanical forces or the elongation or compression, it is advantageous if, instead of the human eye, an automated detection system is used, which may be, for example, a commercially available UV-VIS spectrometer, the detection taking place both in reflection and in transmission can.

The core-shell particles which are used according to the invention are known per se. In a preferred embodiment, the shell of these core-shell particles, prior to processing, consists of essentially unvarnished organic polymers, which are preferably grafted onto the core via an at least partially crosslinked intermediate layer.

In this case, the jacket can consist of either thermoplastic or elastomeric or thermoelastic polymers. Since the jacket substantially determines the material properties and processing conditions of the core-shell particles, those skilled in the art will select the jacket material according to common considerations in polymer technology. In particular, when movements or stresses in a material are to lead to optical effects, the use of elastomers as a shell material is preferred. In sensors according to the invention, the distances between the core-shell particles are changed by such movements. Accordingly, the wavelengths of the interacting light and the effects to be observed change. The core can be made of a variety of materials. It is essential according to the invention, as already stated, that there is a refractive index difference to the cladding and that the core remains firm 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; pnictides are 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 occur as an electropositive partner in comparison to the counterions, such as the classical metals of the subgroups or the main group metals of the first and second main group, as well as all elements of the third main group and 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, and silicon and phosphorus nitride.

As starting material for the preparation of the core-shell particles according to the invention are in a variant of the present invention Preference is given to using monodisperse silicon dioxide cores which can be obtained, for example, by the process described in US Pat. No. 4,911,903. The cores are produced by hydrolytic polycondensation of tetraalkoxysilanes in an aqueous ammoniacal medium, wherein first of all a sol of primary particles is produced, and then the resulting SiO 2 particles are brought to the desired particle size by a continuous, controlled metered addition of tetraalkoxysilane. With this method, monodisperse SiO ₂ cores having mean particle diameters between 0.05 and 10 μm can be produced with a standard deviation of 5%.

Further preferred starting materials are SiO ₂ nuclei coated with (semi) metals or nonabsorbing metal oxides such as TiO ₂ , ZrO ₂ , ZnO ₂ , SnO ₂ or Al ₂ O ₃ . The production of SiO ₂ -KeHIe coated with metal oxides is described in more detail, for example, in US Pat. No. 5,846,310, DE 19842 134 and DE 199 29 109.

Also suitable as starting material are monodisperse cores of non-absorbing metal oxides, such as TiO ₂ , ZrO ₂ , ZnO ₂ , SnO ₂ or Al ₂ O ₃ or metal oxide mixtures. Their preparation is described for example in EP 0 644 914. Furthermore, the process according to EP 0 216 278 for the production of monodisperse SiO ₂ cores is readily transferable to other oxides with the same result. To a mixture of alcohol, water and ammonia, whose temperature is adjusted with a thermostat to 30 to 40 ⁰ C, are added with intensive mixing tetraethoxysilane, tetrabutoxytitanium, tetrapro- poxyzircon or mixtures thereof in one pour and the mixture obtained for a further 20 Stirred vigorously for seconds, forming a suspension of monodisperse nuclei in the nanometer range. After a post-reaction time of 1 to 2 hours, the cores are separated in the usual manner, for example by centrifuging, washed and dried. Furthermore, suitable starting materials for the production of the core-shell particles according to the invention are also monodisperse cores of polymers which contain particles, for example metal oxides. Such materials are offered, for example, by the company micro caps Entwicklungs- und Vertriebs GmbH in Rostock. According to customer requirements, microencapsulations based on polyesters, polyamides and natural and modified carbohydrates are manufactured.

It is also possible to use monodisperse cores of metal oxides which are coated with organic materials, for example silanes. 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.

In addition, the cores of the core-shell particles according to the invention may also contain dyes or phosphors. For example, so-called nanocolorants, as described, for example, in WO 99/40123, can be used. The disclosure of WO 99/40123 is hereby expressly incorporated in the disclosure of the present application.

For the intended use of the core / shell particles according to the invention for the production of sensors, it is important that the shell material is filmable, ie that it softens by simple measures, visco-elastic plasticized or liquefied, that the cores of the core / Sheath particles can form at least domains of regular arrangement. The cores regularly arranged in the matrix formed by filming the cladding of the core / shell particles form a diffraction grating which causes interference phenomena and thereby leads to very interesting color effects. The materials of the core and the cladding, provided that they satisfy the conditions given above, may have an inorganic, organic or even metallic character or may be hybrid materials.

In view of the ability to vary the invention relevant properties of the cores of the core / shell particles according to the invention as needed, it is expedient, however, that the cores contain one or more polymers and / or copolymers (core polymers) or that they consist of such polymers consist.

Preferably, the cores 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, if appropriate, auxiliaries and additives Composition of the jacket can be chosen so that it is in non-swelling environment at room temperature substantially dimensionally stable and tack-free.

it the use of polymeric substances as sheath material and possibly Kemmaterial wins the skilled artisan freedom whose relevant properties, such. B. its composition, the particle size, the mechanical data, the refractive index, the glass transition temperature, the melting point and the weight ratio of Kem: coat and thus determine the performance characteristics of the core / shell particles, which ultimately also on the properties of it affected sensors.

Polymers and / or copolymers which may or may not be included in the core material are high molecular compounds which conform to the specification given above for the core material. Both polymers and copolymers are suitable for polymerization unsaturated monomers as well as polycondensates and copolycondensates of monomers having at least two reactive groups, such as. As high molecular weight aliphatic, aliphatic / aromatic or wholly aromatic polyester, polyamides, polycarbonates, polyureas and polyurethanes, but also aminoplast and phenolic resins, such as. As melamine / formaldehyde, urea / formaldehyde and phenol / Formaldehy condensates.

For the preparation of epoxy resins which are also suitable as core material, usually epoxide prepolymers, for example by reaction of bisphenol A or other bisphenols, resorin, hydroquinone, hexanediol or other aromatic or aliphatic diol or polyols phenol-formaldehyde condensates or mixtures thereof with each other be obtained with epichlorohydrin or other di- or polyepoxides, mixed with other compounds capable of condensation directly or in solution and allowed to cure.

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

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 to correspond to the specification given above for the sheath polymers.

Polymers which meet the specifications for a jacket material can also be found in the groups of polymers and copolymers of polymerizable unsaturated monomers and the polycondensates and copolycondensates of monomers having at least two reactive groups, such as. As the high molecular weight aliphatic, aliphatic / aromatic or wholly aromatic polyester and polyamides.

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

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

If the sheath is to be comparatively low-breaking, polymers such as polyethylene, polypropylene, polyethylene oxide, polyacrylates, polymethacrylates, polybutadiene, polymethyl methacrylate, polytetrafluoroethylene, polyoxymethylene, polyesters, polyamides, polyepoxides, polyurethane, rubber, polyacrylonitrile and polyisoprene are suitable.

If the jacket is to be comparatively high-refractive, for example, polymers with preferably aromatic basic structure such as polystyrene, polystyrene copolymers such as, for example, are suitable for the jacket. As SAN, aromatic-aliphatic polyesters and polyamides, aromatic polysulfones and polyketones, polyvinyl chloride, polyvinylidene chloride and, with a suitable choice of a high-refractive core material and polyacrylonitrile or polyurethane. In a particularly preferred embodiment according to the invention of core-shell particles, the core consists of crosslinked polystyrene and the shell consists of a polyacrylate, preferably polyethyl acrylate and / or polymethyl methacrylate.

As regards particle size, particle size distribution and refractive index differences, the same applies to the core-shell particles according to the invention as those already mentioned above for the sensors.

In view of the processability of the core-shell particles to sensors, it is advantageous if the weight ratio of core to shell in the range of 2: 1 to 1: 5, preferably in the range of 3: 2 to 1: 3, and particularly preferred in the range of 1: 1 to 2: 3. Generally, it applies here that it is advantageous to increase the proportion of sheath as the particle diameter of the cores increases.

The core-shell particles to be used according to the invention can be prepared by various processes. A preferred way to obtain the particles is a process for producing core-shell particles, by a) surface treatment of monodisperse cores, and b) applying the shell of organic polymers to the treated cores.

In a variant of the process, the monodisperse cores are obtained in a step a1) 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 shell can be covalently bonded. ATR polymerization here stands for Atomic Transfer Radicalic polymerization, as described, for example, in K. Matyjaszewski, Practical Atom Transfer Radical Polymerization, Polym. Mater. Be. Closely. 2001, 84 is described. The encapsulation of inorganic materials by ATRP is described, for example, in T. Werne, TE Patten, Atomic Transfer Radical Polymerization from Nanoparticles: A Tool for the Preparation of Well-Defined Hybrid Nanostructures and for Understanding the Chemistry of Controlled Living "Radical Polymerization from Surfaces, J. Am Chem. Soc., 2001, 123, 7497-7505 and WO 00/11043 The carrying out of both this method and the performance of emulsion polymerizations are familiar to the person skilled in the art of polymer preparation and are described, for example, in the abovementioned references.

The liquid reaction medium in which the polymerizations or copolymerizations can be carried out consists of the solvents, dispersants or diluents customarily employed in polymerizations, in particular in emulsion polymerization processes. In this case, the selection is made so that the emulsifiers used for homogenization of the core particles and shell precursors can develop sufficient activity. A favorable liquid reaction medium for carrying out the process according to the invention are aqueous media, in particular water.

Polymerization initiators, for example, which decompose either thermally or photochemically, form free radicals and thus initiate the polymerization, are suitable for initiating 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 Azovθrbindungen, boroalkyl and homolytically decomposing hydrocarbons. The initiators and / or photoinitiators, which are used depending on the requirements of the polymerized material in amounts between 0.01 and 15 wt .-%, based on the polymerizable components, can individually or, to exploit advantageous synergistic effects, in combination with each other be applied. In addition, redox systems are used, for example salts of peroxodisulfuric acid and peroxodisulfuric acid in combination with low-valency sulfur compounds, in particular ammonium peroxodisulfate in combination with sodium dithionite.

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

Polyaddition products are obtained analogously by reaction by compounds containing at least two, preferably three reactive groups such. Example, epoxy, cyanate, isocyanate, or isothiocyanate groups, with compounds that carry complementary reactive groups. For example, isocyanates react with alcohols to give urethanes, with amines to urea derivatives, while epoxides react with these complements to form hydroxy ethers or hydroxyamines. Like the polycondensations, polyaddition reactions can advantageously be carried out in an inert solvent or dispersant.

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

To prepare the stable dispersions required for these polymerization-polycondensation or polyaddition processes, dispersants are generally used.

As dispersing agents are preferably water-soluble high molecular weight organic compounds having polar groups, such as polyvinylpyrrolidone, copolymers of vinyl propionate or acetate and vinylpyrrolidone, partially saponified Copolymeriste of an acrylic ester and acrylonitrile, polyvinyl alcohols with different residual acetate content, cellulose ethers, gelatin, block copolymers, modified starch, low molecular weight, carbon-containing and / or sulfonic acid-containing polymers or mixtures of these substances used.

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

It is possible to use nonionic or else ionic emulsifiers, if appropriate also as a mixture. Preferred emulsifiers are optionally ethoxylated or propoxylated, long-chain alkanols or alkylphenols having different degrees of ethoxylation or propoxylation (for example adducts with 0 to 50 mol of alkylene oxide) or their neutralized, sulfated, sulfonated or phosphated derivatives. Also neutralized Dialkylsulfobemsteinsäureester or Alkyldiphenyloxid disulfonates are particularly well suited. Combinations of these emulsifiers with the abovementioned protective colloids are particularly advantageous because they give particularly finely divided dispersions.

Special processes for the preparation of monodisperse polymer particles have also been described in the literature (for example BRC Backus, RC Williams, J. Appl. Phys. 19, p. 1186, (1948) and can be used with advantage in particular for the production of the cores. It is only necessary to ensure that the above-mentioned particle sizes are kept in. The greatest possible uniformity of the polymers is to be achieved, in particular the particle size can be adjusted by selecting suitable emulsifiers and / or protective colloids or corresponding amounts of these compounds.

By adjusting the reaction conditions such as temperature, pressure, reaction time, use of suitable catalyst systems which influence the degree of polymerization in a known manner and the choice of the monomers used for their preparation by type and amount can be set specifically the desired property combinations of the required polymers.

Monomers which lead to polymers of high refractive index are usually those which have either aromatic substructures, or those which have heteroatoms with a high atomic number, such as. As halogen atoms, in particular bromine or iodine atoms, sulfur or metal ions, have, d. H. via atoms or atomic groups, which increase the polarizability of the polymers.

Accordingly, polymers with a low refractive index are obtained from monomers or monomer mixtures which do not or only to a small extent contain the abovementioned substructures and / or atoms of high atomic number. An overview of the refractive indices of various common homopolymers can be found for. In Ullmanns Encyklopadie der technischen Chemie, 5th ed., Volume A21, page 169. Examples of radically polymerizable monomers which lead to polymers with a high refractive index are:

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

Group b): acrylates having aromatic side chains, such as. As phenyl (meth) acrylate (= abbreviated notation for the two compounds phenyl acrylate and phenyl methacrylate), phenyl vinyl ether, benzyl (meth) acrylate, benzyl vinyl ethers, and compounds of the formulas

In the above and below formulas, for the sake of clarity and simplicity of writing, carbon chains are represented only by the bonds between the carbon atoms. This notation corresponds to the representation of aromatic Cylischer compounds, wherein z. B. the benzene is represented by a hexagon with alternating simple and double bonds. Furthermore, those compounds are suitable which contain sulfur bridges instead of oxygen bridges such. B.

In the above formula, R is 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 specifically to optimize in particular the application-relevant properties of the sensors according to the invention.

Suitable substituents are, in particular, halogen, NO ₂ , alkyl having one to twenty C atoms, preferably methyl, alkoxy having one to twenty C atoms, carboxyalkyl having one to twenty C atoms, carbonylalkyl having one to twenty C atoms, or OCOO-alkyl having one to twenty carbon atoms. The alkyl chains of these radicals may in turn be optionally substituted or by divalent hetero atoms or groups such as. B. -O-, -S-, -NH-, -COO-, -OCO- or -OCOO- be interrupted in non-adjacent positions.

Group c): monomers which have heteroatoms, such as. For example, vinyl chloride, acyl nitrile, methacrylonitrile, acrylic acid, methacrylic acid, acrylamide and methacrylamide or organometallic compound such. B.

Group d): An increase in the refractive index of polymers can also be achieved by copolymerizing monomers containing carboxylic acid groups and conversion of the thus obtained "acidic" polymers into the corresponding salts with metals of higher atomic weight, such. B. preferably with K, Ca, Sr, Ba, Zn, Pb, Fe, Ni, Co, Cr, Cu, Mn, Sn or Cd.

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

In addition, any bi- or polyfunctional compounds which are copolymerizable with the abovementioned monomers or which can subsequently react with the polymers with crosslinking can also be used as crosslinking agents for producing crosslinked polymer cores from radically produced polymers.

The following are 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 polydydroxy compounds in particular 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- hydroxymethylbenzene, bisphenol A or mti ethylene oxide spacers, Propylenoxidspacern or mixed Ethlenoxid- Propylenoxidspacern.

Further crosslinkers of this group are z. B. di- or polyvinyl compounds such as divinylbenzene or methylene-bisacrylamide, triallyl cyanurate, divinylethyleneurea, trimethylolpropane tri- (meth) acrylate, trimethylol propane tricinyl ether, pentaerythritol tetra (meth) acrylate, pentaerythritol tetra- vinyl ether, and crosslinkers with two or several different reactive ends such. B. (meth) allyl (meth) acrylates of the formulas

where R is hydrogen or methyl.

Group 2: Reactive crosslinkers which are crosslinking, but largely postcrosslinking, z. As in heating or drying, and which are copolymerized in 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),

Methacryloxypropyltrimethoxysilane (MEMO), vinyltrimethoxysilane, m-isopropenylbenzyl isocyanate (TMI). Group 3: Carboxylic acid groups which have been incorporated into the polymer by copolymerization of unsaturated carboxylic acids are cross-linked via polyvalent metal ions. Acrylic acid, methacrylic acid, maleic anhydride, itaconic acid and fumaric acid are preferably used as the unsaturated carboxylic acids. Suitable metal ions are Mg, Ca, Sr, Ba, Zn, Pb, Fe, Ni, Co, Cr, Cu, Mn, Sn, Cd. Particularly preferred are Ca, Mg and Zn, Ti and Zr.

Group 4: post-crosslinked additives. This is understood to mean bis- or higher-functionalized additives 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: epoxide, aziridine, isocyanate-acid chloride, carbodiimide or carbonyl groups, furthermore z. B. 3,4-dihydroxy-imidazolinone and its derivatives (®Fixapret @ brands of BASF).

As already stated above, post crosslinkers with reactive groups such. B. epoxy and isocyanate groups complementary reactive groups in the polymer to be crosslinked. For example, isocyanates react with alcohols to give urethanes, with amines to form urea derivatives, while epoxides react with these complementary groups to form hydroxyethem or hydroxyamines.

Postcrosslinking is also understood to mean photochemical curing, oxidative or air or moisture induced curing of the systems.

The abovementioned monomers and crosslinkers can be combined with one another in any desired manner and (co) polymerized in such a way that an optionally crosslinked (co) polymerisate can be polymerized with the desired refractive index and the required stability criteria and mechanical properties is obtained.

It is also possible to use other common monomers, eg. As acrylates, methacrylates, vinyl esters, butadiene, ethylene or styrene, in addition to copolymerize, for example, to adjust the glass transition temperature or the mechanical properties of the core and / or sheath polymers as needed.

It is likewise preferred according to the invention for the coat to be applied from organic polymers by grafting, preferably by emulsion polymerization or ATR polymerization. In this case, the methods and monomers described above can be used accordingly.

In particular, when using inorganic cores, it may also be preferred that the core is subjected to a pre-treatment prior to the polymerization of the shell, which allows a tethering of the shell. This can usually consist in a chemical functionalization of the particle surface, as is known for a wide variety of inorganic materials from the literature. In particular, it may be preferable to provide such chemical functions on the surface, which enable grafting of the shell polymers as an active chain end. Here are as examples in particular terminal double bonds, epoxy functions as well

To name polycondensable 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 described, for example, in various textbooks, such as Unger, KK, Porous Silica, Elsevier Scientific Publishing Company (1979). The sensors according to the invention can themselves be plastic sensors which are commercially available as end products. In another preferred embodiment of the present invention, the sensors are films suitable for coating surfaces. A field of application of the sensor materials according to the invention are also decorative applications. Thus, the sensor materials in textiles, such as clothing, in particular sports clothing can be integrated. For example, parts of sports shoes can be made from these materials. If the materials are applied in areas that deform during movement, then in addition to the angle-dependent color effect, a further color effect is observed, which is correlated with the elongation and compression of the material. In a further preferred embodiment of this invention, the sensors are processed into pigments. The pigments thus obtainable are particularly suitable for use in paints, lacquers, printing inks, plastics, ceramic materials, glasses and cosmetic formulations. These pigments show the above-discussed color effect under mechanical stress and can thus develop additional decorative effect. For this purpose, they can also be used mixed with commercially available pigments, for example inorganic and organic absorption pigments, metallic effect pigments and LCP pigments. Furthermore, the particles of the invention are also suitable for the preparation of pigment preparations and for the production of dry preparations, such as granules. Such pigment particles preferably have a platelet-shaped structure with an average particle size of 5 μm-5 mm.

In this case, the preparation of the pigments can be carried out, for example, by first producing a film from the core-shell particles which can optionally be cured. Subsequently, the film can be suitably cut or broken and possibly followed by grinding Be crushed pigments of suitable size. This process can be done for example in a continuous belt process.

The pigment according to the invention can then be used for pigmenting paints, powder coatings, paints, printing inks, plastics and cosmetic formulations, such as e.g. of lipsticks, nail polishes, cosmetic sticks, molding powders, make-ups, shampoos and loose powders and gels.

The concentration of the pigment in the application system to be pigmented is currently in progress! between 0.1 and 70 wt .-%, preferably between 0.1 and 50 wt .-% and in particular between 1, 0 and 20 wt .-%, based on the total solids content of the system. It is usually dependent on the specific application. Plastics usually contain the pigment of the invention in amounts of 0.01 to 50 wt .-%, preferably from 0.01 to 25 wt .-%, in particular from 0.1 to 7 wt .-%, based on the plastic composition. In the paint sector, the pigment mixture is used in amounts of from 0.1 to 30% by weight, preferably from 1 to 10% by weight, based on the paint dispersion. In the pigmentation of binder systems, for example, for inks and printing inks for gravure printing, offset printing or screen printing, or as a precursor for printing inks, for example in the form of highly pigmented pastes, granules, pellets, etc., pigment mixtures with spherical colorants, such as T1O ₂ Carbon black, chromium oxide, iron oxide and organic "color pigments." The pigment is generally incorporated into the printing ink in amounts of from 2 to 35% by weight, preferably from 5 to 25% by weight, and in particular from 8 to 20% by weight. Offset printing inks may contain up to 40% by weight or more of the pigment The precursors for the printing inks, for example in granular form, as pellets, briquettes, etc., contain, in addition to the binder and additives, up to 95% by weight % of the pigment according to the invention Invention are therefore also formulations containing the pigment according to the invention.

The following examples are intended to illustrate the invention without limiting it.

Examples

Used abbreviations:

BDDA butane, 4, -dιoldιacrylat

SBS sodium bisulfite

SDS dodecyl sulfate sodium salt

SDTH sodium dithionite

SPS sodium peroxodisulfate

APS ammonium peroxodisulfate

KOH potassium hydroxide

ALMA allyl methacrylate

MMA methyl methacrylate

EA ethyl acrylate

HEMA hydroxyethyl methacrylate

Example 1: Production of thermally crosslinked sensor films

A temperature-controlled at 30 ⁰ C emulsion consisting of 217 g water, 3.6 g of styrene, 0.4 g BDDA (butane-1, 4-diol diacrylate), 0.05 g of SBS (sodium bisulfite) and 200 mg SDS (sodium dodecyl sulfate), is transferred to the preheated reactor. Immediately afterwards, the reaction is started by adding 375 mg of SPS (sodium peroxodisulfate) and 50 mg of SBS, each dissolved in 10 g of water. After 10 min. is a monomer emulsion of 72.9 g of styrene, 8.1 g of BDDA, 0.375 g of SDS, 0.1 g of KOH and 110 g of water over a period of 130 min. continuously added. After completion of dosing is 10 min. maintained and added another 0.1 g of SPS dissolved in 10 g of water. After another 10 min. with the addition of an emulsion of 13.5 g MMA, 1, 5 g ALMA (allyl methacrylate), 0.075 g SDS and 20 g of water over a period of 25 min. began. After completion of dosing is 10 min. with the addition of an emulsion of 136 g EA (ethyl acrylate), 2.7 g HEMA (hydroxyethyl methacrylate) solution, 0.375 g SDS and 136 g of water over a period of 180 min. began. After the addition is 60 min. stirred for a long time. 250 ml of emulsion are quickly poured into 1 l of methanol with constant stirring. The flocculation is accelerated as needed with up to 400 ml of saturated sodium chloride solution. After stirring for one hour, the precipitated polymer is filtered off and pre-dried at 40 ⁰ C in a vacuum of a diaphragm pump for about 2-3 days and then finally dried at 40 ⁰ C in an oil pump vacuum again 1-2 days.

The polymers (weight 9,703 g) are mixed with 0.297 g of Crelan ™ Ul (Bayer AG), 0.3% by weight (30 mg) of Licolub FA1 (demolding force reducer, Clariant GmbH) and 0.1% (10 mg ) carbon black N990 (Fa. Freudenberg) at 120 ⁰ C and 80 rev / min, is extruded.

The extruded polymers are added in portions of about 4 g between

PET release film protected polished panels spent. The polished

Plates are then placed in a Collin laboratory press and the appropriate temperature-pressure program is set.

With plates preheated to 130 ^° C., the following steps are carried out:

1.) 130 ⁰ C, 1 bar hydraulic pressure, 1 min.

2.) 130 ⁰ C, 50 bar hydraulic pressure, 1 min.

3.) Open the press without cooling

4.) remove polished plates from the press

5.) Allow the PET / film / PET pellets to cool to room temperature

6) Peel one of both PET release film from the film.

Films prepared in this way and yet uncrosslinked are then depressurized down to the PET film down on the pre-heated to 190 ⁰ C plate of the Collin- laboratory press and for 5 or 10 min. leave there. The thus crosslinked films are removed from the release film after cooling to room temperature. Analogously, the production of corresponding films, for example, using Crelan ™ VP LS 2007 and Crelan ™ VP LS 2147 (Bayer AG) done.

Tensile stress-strain diagrams are shown below (Figure 1) to contrast the comparison between an uncrosslinked film and films of the same composition but with different Crelan types and cure times of 5 minutes and 10 minutes, respectively, at a crosslinking temperature of 190 ^° C ,

In FIG. 1 a, it can be seen that the post-crosslinking of films gives them elastic properties up to an elongation of more than 300%. In comparison, the elastic range of uncrosslinked films is only pronounced to strains below 20% (Figure 1 b). At expansions above 20%, the uncrosslinked film reaches the so-called plastic area and does not return to its original position when the stretching force is removed. Furthermore, in contrast to the uncrosslinked film, the crosslinked film does not flow when the stretching force is applied for a longer time.

Example 2: Production of UV-crosslinked sensor films

A crude polymer (core-shell particles of polystyrene core, on which an intermediate layer of p (MMA-co-ALMA) is grafted a random copolymer coat of ethyl acrylate with 10 wt% methyl methacrylate), with 2 wt .-% benzophenone and 0.2 wt .-% Licolub FA-1 (Entformungskrafterniedriger, Fa. Clariant GmbH) in the extruder at 12O ⁰ C compounded. The compound is in a Collin laboratory press at a hydraulic pressure of 50 bar between two to 13O ⁰ C. preheated press plates pressed into a film over 4 minutes. The press plates are depressurized to room temperature before the film is removed. Subsequently, the film is irradiated at a distance of 10 cm over a period of 20 minutes with an incandescent lamp Osram Ultra Vitalux 300 Watt.

Transmission spectra were recorded from the crosslinked film in the unstretched state and at 10%, 20% and 30% elongation (FIG. 2).

FIGS. 3 to 5 show diagrams of tensile-strain measurements of various films produced analogously to Example 2. Before the measurement, specimens were punched out of the films and then uniaxially measured in the longitudinal direction using a tensile tester Zwick Z020 at a constant tensile speed of 20 mm / min.

The slope of the curves increases with increasing exposure time and thus increase in cross-linking. Consequently, the benzophenone concentration and the exposure time have an influence on the mechanical properties of the crosslinked films. Further possibilities for the adaptation of the mechanical properties lie in the selection of the shell polymers and interlayer polymers: the higher their glass transition temperature, the "harder" the resulting film is, thus adapting the mechanical properties of films for sensor applications to the area of the applied tensile forces to be detected the manufacturing conditions of the films take place. characters

Figure 1: Tensile stress-strain diagrams of films according to Example 1. The crosslinked film (Figure 1a) has a much larger elastic range (up to about 300% elongation). The elastic region of the unvarnished film (Figure 1 b) is very narrow; from about 20% elongation, there is a non-linear behavior here, which turns into a tile instead. In Fig. 1A, Ul stands for a sample prepared using Crelan ™ Ul, VP LS 2007 for a sample prepared using Crelan ™ VP LS 2007 and VP LS 2147 for a sample made using Crelan ™ VP LS 2147 (all Fa. Bayer AG) was produced. 5 min or 10 min refers to the time during the crosslinking took place.

FIG. 2: Transmission spectrum of a photochemically crosslinked film mixed with 2% by weight of benzophenone (according to Example 2) at different elongation states (ε indicates the percentage elongation in relation to the original film length). The spectrum was recorded with a UV / VIS spectrometer Perkin Elmer Lambda 900.

3 shows a diagram of tensile-strain measurements of various films produced analogously to Example 2 (1% by weight of benzophenone, irradiation duration: 5, 10, 15 or 20 minutes). Measured from the films test specimens were uniaxial on a Zwick Z020 tensile tester with a constant tensile speed of 20 mm / min in the longitudinal direction.

4: Diagram of tensile-strain measurements of various films produced analogously to Example 2 (2% by weight of benzophenone, irradiation duration: 5, 10, 15 or 20 minutes). Measured were The test pieces punched out on the films were uniaxially stretched on a tensile tester Zwick Z020 at a constant tensile speed of 20 mm / min in the longitudinal direction.

5 shows a diagram of tensile-strain measurements of various films prepared analogously to Example 2 (5% by weight of benzophenone, irradiation duration: 5, 10, 15 or 20 minutes). Measured from the films test specimens were uniaxial on a Zwick Z020 tensile tester with a constant tensile speed of 20 mm / min in the longitudinal direction.

Claims

claims 1. Use of moldings consisting essentially of core-shell particles whose shell forms a matrix and whose jacket is connected to the core via an intermediate layer and the core is substantially solid and has a substantially monodisperse size distribution and a difference between the Refractive indices of the core material and the cladding material, wherein the cladding matrix is an elastomer, for the detection of mechanical force. 2. Use of moldings according to claim 1, characterized in that the jacket matrix is chemically crosslinked. 3. Use of moldings according to at least one of claims 1 or 2, characterized in that it is the moldings are films. 4. Sensors for detecting mechanical force consisting essentially of core-shell particles whose shell forms a matrix and whose jacket is connected to the core via an intermediate layer and the core is substantially fixed and has a substantially monodisperse size distribution, wherein There is a difference between the refractive indices of the core material and the cladding material, characterized in that the cladding matrix is an elastomer. 5. Sensors according to claim 4, characterized in that the jacket matrix is chemically crosslinked. 6. Sensors according to at least one of claims 4 or 5, characterized in that the core-shell particles have an average particle diameter in the range of about 5 nm to about 2000 nm, preferably in the range of about 5 to 20 nm or in the range of 40 - 500 nm. 7. Sensors 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 more preferably at least 0.1. 8. Sensors according to at least one of the preceding claims, characterized in that it is the sensor is a pressure sensor, which is preferably at the same time a pressure relief valve. 9. Sensors according to at least one of the preceding claims, characterized in that the sensor is designed in the form of a film suitable for coating surfaces. 10. Sensors according to at least one of the preceding claims, characterized in that the sensor is designed as a measuring strip. 11. A molded body consisting essentially of core-shell particles whose shell forms a matrix and whose jacket is connected to the core via an intermediate layer and whose core is substantially solid and has a substantially monodisperse size distribution, wherein a difference between the refractive indices the core material and the cladding material, characterized in that the cladding matrix is an elastomer. 12. Shaped body according to claim 11, characterized in that the sheath matrix is chemically crosslinked. 13. Shaped body according to at least one of claims 11 or 12, characterized in that it is in the moldings are films. 14. A process for the production of moldings consisting essentially of core-shell particles with elastomeric shell or for the production of sensors for the detection of mechanical force, characterized in that o in a step a) Kem-shell particles whose shell a Matrix and whose core is substantially solid and has a substantially monodisperse size distribution, with a difference between the refractive indices of the core material and the cladding material, mixed with a crosslinking aid, or the mixture in a step b) at a temperature at which Sheath flowable is subjected to a mechanical force, o in a step c) chemical cross-linking of the sheath takes place. 15. A method for the production of sensors according to claim 14, characterized in that the crosslinking is thermally induced and the jacket of the core-shell particles free cyanate, isothiocyanate, amino, epoxy, isocyanate or hydroxy groups, and as a crosslinking aid, a (poly) isocyanate, (poly) amine or (poly) epoxide is used. 16. A method for producing sensors according to claim 15, characterized in that the jacket has free hydroxyl groups, wherein the sheath is preferably formed from a copolymer containing hydroxyalkyl (meth) acrylate units, and the cross-linking aid is preferably an isocyanate, more preferably a protected isocyanate. 17. A method for producing sensors according to claim 14, characterized in that the crosslinking is induced by means of light quanta, preferably with energies in the range of UV and / or VIS radiation, and it is in the crosslinking aid is preferably at least one photoinitiator of the type Il and thereby particularly preferably is at least one benzophenone derivative or benzophenone.