POLYMER-BASED SUBSTRATE AND METHOD FOR ITS PREPARATION

Description

[0001] The invention relates to a polymer-based substrate which is particularly electrostatically coatable, and to a method for its production.

[0002] Electrostatic coating, especially powder coating of substrates, is of great importance in many applications, not only for decorative purposes but also particularly as corrosion protection.

[0003] Substrates are considered to be suitable for powder coating if, for example, the following points apply: a) good powder attraction and homogeneous powder coverage when spraying the electrostatically charged paint powder onto the grounded or electrically charged substrate; b) flawless fixing, e.g. by baking, melting, sintering, thermal curing of the paint - especially without blistering or pinhole formation within the paint layer or between the substrate and the paint layer; c) firm adhesion of the paint layer to the substrate to prevent delamination, flaking, or crumbling of the paint layer.

[0004] US patent application US 2016 / 0121361 A1 discloses a method for coating the surface of an electrically non-conductive substrate using powder coating. The uncoated substrate is heated to a temperature in the range of 40 °C to 140 °C to reduce the surface resistance of the uncoated substrate to a value in the range of 10 10< Ω to less than 10 12< Ω. The coating is then applied to the substrate in a single layer using powder coating and cured at a temperature of 170 °C or less.

[0005] International patent application WO 2005 / 097902 A1 describes a process for electrostatically coating substrates made of electrically conductive polyamide compositions. The compositions contain a polyamide, a novolac resin, a curing agent, and an electrically conductive filler.

[0006] WO 97 / 34709 A1 proposes a method for the electrostatic coating of substrates, in particular from the automotive sector, in which the substrate is produced from a composition which comprises a mixture of a thermosetting plastic, a filler and / or a reinforcing material in a proportion of at least 30% by weight and less than 3% by weight of carbon black with a primary particle size of less than 125 nm, the substrate having a conductivity of at least 10 -14< S / cm.

[0007] Powder-coatable substrates in the form of thermal insulation profiles or insulating bars for metal-plastic composite profiles are known from EP 0 638 368 A1. In this case, the outer surface of the insulating profiles, when installed, is coated with an electrically conductive coating. However, this coating maintains a certain distance from the metal profiles in the composite to minimize the thermal insulation of the metal profiles.

[0008] For the application of the electrically conductive coating, EP 0 638 368 A1 recommends flame spraying, electrodeless plasma spraying, arc spraying, and low-pressure spraying, as well as ion beam application, galvanic application, and finally, co-extrusion of the electrically conductive coating onto the thermally insulating strip. It also describes how the material of the insulating strip can be made electrically conductive by incorporating conductive carbon black, metal powders, or metal fibers, thus achieving improved adhesion of the powder coating.

[0009] According to EP 0 638 368 A1, the electrically conductive coating can be applied as a continuous coating or as a dot-like application to the surface of the insulating strip to be covered with the powder coating layer.

[0010] Polyamide materials electrostatically coated with a powder coating are described in EP 0 667 625 B1. In addition to the polyamide, the polyamide material contains up to 10 wt.% carbon fibers and 30 to 60 wt.% of a metallic powder, with the weight ratio of metallic powder to carbon fibers being 150:1 to 6:1. This results in plastic components that can also be powder coated together with metal parts.

[0011] EP 0 685 527 B1 recommends a special polyphenylene ether-polyamide-based polymer material with 1 to 7 parts by weight of conductive carbon black per 100 parts by weight of polymer, which allows for an Izod notched impact strength of more than 15 kJ / m 2 and a volume resistivity of less than 10 6 Ohm cm. The polymer material is designed for applications involving an electrostatic coating process.

[0012] EP 1 223 188 B1 recommends applying an electrically conductive primer layer to the surface of an insulating strip to be coated with a powder coating, said primer layer containing at least 45% by weight of an acrylic resin and optionally a proportion of a phosphoric acid-modified polymer.

[0013] EP 2 071 585 A1 proposes a thermoplastic composition with a polyamide-based continuous phase in which a polyphenylene ether is dispersed. The composition further contains a conductivity additive, which is present in the continuous phase at a level of at least 50%. The volume resistivity is less than 10 5< ohm cm. One area of ​​application for the material is automotive construction, where metallic and plastic-based components are often powder coated together.

[0014] Another process for coating substrates tailored to automotive engineering is known from WO 2005 / 097902 A1. For the production of the substrates, an electrically conductive polyamide composition is proposed, which, in addition to the polyamide as the main component, contains a portion of a novolac resin, a portion of a reinforcing material, and at least 0.1 wt.% of an electrically conductive particulate filler.

[0015] Electrically conductive polyamide molding compounds with reduced water absorption capacity are described in EP 2 427 518 B1. In addition to the polyamide, the molding compounds contain a propylene polymer, a compatibilizer in the form of graft copolymers of polypropylene, and a portion of carbon nanotubes (CNTs).

[0016] Problems with the state-of-the-art processes are the repeatedly observed insufficient powder coating coverage, insufficient coating adhesion and / or blistering of the coating layer after powder coating in the area of ​​the plastic components, e.g. the insulating webs of composite profiles.

[0017] Particularly in the case of substrates to be coated which are made from polyamide materials, very narrow, difficult or uncontrollable ranges for process parameters often arise, which must be observed in order to avoid, for example, blistering (residual moisture of the substrate is too high) and insufficient powder coating coverage or other coating defects, such as variations in coating thickness (generally insufficient electrostatic properties of the substrate and / or residual moisture of the substrate is too low).

[0018] In many known prior art processes, the polymer material is modified in volume, for example, by adding electrically conductive fillers, so that improved conductivity is achieved. These fillers can therefore negatively influence certain physical properties, such as mechanical strength or thermal conductivity, as well as material costs.

[0019] The present invention is therefore based on the object of providing substrates in which the electrostatic powder coating ability is improved in a reproducible and process-stable manner without their fundamental material or product properties, such as the thermal insulation properties, being significantly (adversely) reduced.

[0020] This object is achieved in a polymer-based substrate having the features of claim 1.

[0021] According to the invention, a coating is applied to a surface region of a substrate base body manufactured using a polymer material, which is essentially electrically non-conductive. The coating comprises a matrix polymer and an additive dispersed in the matrix polymer that reduces the surface resistance of the coating, in a proportion selected such that the specific surface resistance of the coating is approximately 10 10< ohms or less. The polymer material of the substrate base body comprises a first polymer that is compatible with the matrix polymer of the coating.

[0022] The substrates according to the invention provide reproducible results, particularly in electrostatic powder coating, and are process-stable, especially with substrates with low moisture contents.

[0023] Surprisingly, it was also found that the inventive method for coating the substrates barely alters the mechanical properties of the substrates, which represents a significant advantage for products such as insulating strips or add-on parts in the automotive sector. This is particularly surprising because the inventive method involves the use of solvents, which under certain circumstances can dissolve the substrate.

[0024] In many applications - especially in the case of thermal insulation profiles - the substrates according to the invention are used in conjunction with at least one metal profile, after which they are usually electrostatically powder coated or powder coated.

[0025] It is advantageous if the coating is applied to the substrate base body, which is connected to at least one metal profile, for example, an aluminum profile, in such a way that, after the substrate is connected to the metal profile, the coating with reduced surface resistance makes electrically conductive contact with the metal profile. This allows for good powder attraction and thus a good paint coverage rate during powder coating, primarily via a so-called grounded mechanism.

[0026] According to another variant, good powder attraction can be achieved via a so-called capacitive mechanism even without direct electrically conductive contact between the coating and the metal profile, with reduced surface resistance. Here, it is possible to apply the coating to the substrate body in such a way that the coating subsequently remains without any contact with the metal profile.

[0027] In the grounded mechanism according to the present invention, a charge applied via electrostatically charged powder particles is discharged from the substrate via a grounded electrical line. This prevents the formation or buildup of repulsive electrostatic forces during powder application, which would counteract a homogeneous, full-surface powder application.

[0028] In the capacitive mechanism, in the sense of the present invention, a local capacitance is provided on the substrate for absorbing electrical charge; this electrical charge is not initially dissipated but is only distributed over larger areas, thereby reducing the effective electrical field forces (in particular repulsive forces between powder particles charged with the same sign).

[0029] Preferably, the specific surface resistance of a coating according to the invention is approximately 10 9< Ohm or less, in particular 10 8< Ohm or less.

[0030] For comparison: the specific surface resistance of dry polyamide PA66 without the addition of conductive additives is approx. 10 12< Ohm to approx. 10 13< Ohm.

[0031] The specific surface resistance of the coating is measured in a dry state ("most unfavorable condition" for PA 66 ≤ 0.3% moisture content), or after storage at 23 °C + / - 2 °C and at 50 % + / -10 % relative humidity and in accordance with the specifications of DIN EN 61340-2-3.

[0032] Alternatively, a measurement can be performed using a rapid method in which surface resistance is determined using electrodes with point-shaped measuring tips. However, this method is limited to a measuring range of up to approximately 10 8< ohms. Depending on the model, commercially available digital multimeters that can be used with this rapid method typically have a measuring range of electrical resistance in the order of magnitude of up to approximately 10 7< ohms, possibly up to approximately 10 8< ohms. The electrodes are positioned, for example, at a distance of 1 cm from the surface to be measured.

[0033] Since the measurement of the surface resistance according to the above rapid method typically results in a higher value than the measurement of the specific surface resistance according to the standard test method described above, in which the measurement is carried out on a square surface, with the electrodes being arranged on two opposite sides of the square, the rapid method always allows an assessment of whether or not the specific surface resistance of a sample is below an upper limit of, for example, 10 10< Ohm, in particular also below 10 9< Ohm or below 10 8< Ohm.

[0034] If this quick method yields a surface resistance reading of, for example, 10 8< ohms or less, a statement can be made about the specific surface resistance, which in this case is considerably less than 10 9< ohms. On the other hand, if no value is displayed because the multimeter's measuring range has been exceeded, this does not necessarily mean that the specific surface resistance is above 10 9< ohms; in such a case, this must be retested using a device with a larger measuring range.

[0035] The specific surface resistance can be measured precisely using the standard test method described above. However, in individual cases, problems may arise when implementing the standard test method if the sample to be tested has a complex, fine-grained surface geometry. In these cases, the surface resistance can also be measured using the rapid method described above. For samples that have already been (powder-)coated, a preparatory exposure of the coating with reduced surface resistance can be performed to then measure the surface resistance.

[0036] In addition, the coating to be used according to the invention can of course be applied to a sufficiently dimensioned flat test specimen made of the polymer material of the substrate base body and then the specific surface resistance can be determined according to the standard method.

[0037] According to the invention, the polymer material of the substrate base body comprises a first polymer and the coating comprises a matrix polymer, the latter being selected to be compatible with the first polymer.

[0038] Two polymers are compatible within the meaning of the present invention if they can mix molecularly or microscopically (e.g., by interdiffusion). At the molecular level, this means that the polymer chains of the polymers can be mixed, entangled, and / or penetrate each other, thereby preferably forming a single-phase polymer mixture in one region (e.g., in a volume region of an interface or in a diffusion zone). Such a polymer mixture can then, for example, exhibit homogeneous properties that lie between the properties of the individual polymer components. This can, for example, be a homogeneous new melting point for semi-crystalline polymers or a homogeneous glass transition point, e.g., in compatible blends of PA6 and PA66. The determination of these parameters is described, for example, in Ehrenstein, Trawiel, Riedel: Praxis der Wärmen Analyse von Kunststoffen, 1998, Carl Hanser Verlag Munich, ISBN 3-446-21001-6, Chapter 1.2.3.7 .

[0039] A microscopic mixture exists when the two polymers have a tendency to demix due to incompatibilities (phase-segregated polymers), but such a two-phase system has a large interface and forms, for example, co-continuous structures or gyroidal structures or other polymeric mixed phases as structures in an intermediate region. These structures are perceived macroscopically as a mixture, whereas demixing can be detected microscopically, for example using electron microscopic imaging techniques or for example through X-ray diffraction experiments. Microscopically miscible within the meaning of the present invention are polymers in which, in a mixture, at best island structures or domains with an average diameter or domain size of approx. 5 µm or less remain. The average diameter or domain sizeThe average domain size can be determined by simple manual measurement based on the electron microscopic images.

[0040] In co-continuous phases, microscopic undercuts, for example, ensure the positive bonding of the two phases. However, macroscopically, no common properties such as a common melting point or glass transition temperature can be observed.

[0041] By forming a mixture, i.e., a homogeneous molecular or microscopic mixture of the first polymer and the matrix polymer of substrates according to the invention, a gradual transition from the material (first polymer) of the substrate base to the material (matrix polymer) of the coating is created in a defined transition phase. Forces are transmitted both physically and through chemical interactions and bonds. Thus, the adhesion of the coating to the substrate base is excellent, and unwanted detachment of the coating is avoided. The above-mentioned formation of the mixture of the first polymer and the matrix polymer is significantly influenced by the choice of a suitable solvent for the coating composition.

[0042] During the typical application of immiscible coating materials to a substrate, a one-step transition of the materials occurs; adhesion at the interface is then mainly ensured by chemical bonds and interactions.

[0043] The substrates according to the invention are readily electrostatically powder-coatable. In particular, powder coating can be carried out without the need for pretreatment of the surface areas of the substrates according to the invention to be coated, for example, by plasma or corona treatment or roughening. This enables particularly economical processing of the substrates according to the invention. Furthermore, the substrates according to the invention are also suitable for use as thermal insulation profiles.

[0044] Of course, substrates according to the invention can still be further processed using the aforementioned surface treatment methods in order to change or improve surface properties or to adapt them for a specific application.

[0045] Furthermore, the substrates according to the invention can be satisfactorily powder coated even with a complex geometric structure of the surface areas to be coated, in particular with undercut shapes, three-dimensional molded bodies (e.g., add-on parts for vehicles or machines), and even complicated profile geometries, such as hollow profiles. Insulating bars and thermal insulation profiles, such as those known, for example, from the insulbar ®< brand product ranges from Ensinger GmbH or from WO 01 / 48346 A1, are particularly suitable as substrate bases. Thermal insulation profiles can themselves also serve as load-bearing frame profiles or frame shells in window, door, roof, and facade applications.

[0046] Substrates according to the invention can be electrostatically coated, particularly powder coated, with high coating coverage. The coating coverage is approximately 90% or more, preferably approximately 95% or more, and particularly preferably approximately 98% or more. Ideally, a coating coverage of 100% is achieved in the area prepared for coating.

[0047] Paint coverage can be quantified by determining the proportion of uncoated areas within a representative reference area of ​​a painted surface – if any. True-to-scale, undistorted photographs or light microscope images at 50x magnification are particularly suitable for evaluation. A representative reference area in the form of a rectangular section of the surface is, for example, 25 mm long in both the longitudinal and transverse directions and is preferably located within direct line of sight. The proportion of the area not covered by paint (= paint-free area) is then determined within this reference area. This can be done by manual measurement or software-assisted calculation of the area integral. If necessary, this analysis can be repeated at different locations. The paint coverage rate is then calculated as follows: Lackabdeckung in % = 100 % × 1 − lackfreie F l ä che gesamte B e z u g s f l ä che

[0048] In addition to homogeneous coating coverage, flawless fixation, such as a powder coating layer, is also required through the powder coating baking process. This typically requires temperatures of 170 °C or more, preferably 180 °C or more, or even temperatures exceeding 200 °C.

[0049] During powder coating baking, the substrates are held at a high temperature for several minutes, e.g., 10 minutes or longer, especially 20 minutes or longer, to complete film formation and crosslinking of the powder coating. Drying steps can also be part of the coating process, in which the substrate is often pre-dried at moderate temperatures of 80°C to 150°C. Drying steps are preferably used, for example, to reduce or prevent outgassing of volatile substances and, in particular, the release of residual moisture during the subsequent coating baking process. The coating quality can be further improved by using optimized powder coating systems, e.g., powder coatings mixed with conventional degassing additives.

[0050] The advantage of substrates according to the invention compared to untreated substrate base bodies or even conventional substrates is that even with intensive pre-drying or the use of dry substrates (e.g. with 0.5 wt.% residual moisture or less, preferably with 0.3 wt.% residual moisture or less), a perfect paint coverage, ie a homogeneous, opaque powder application, is always possible.

[0051] Finally, the substrates according to the invention are also directly recyclable. This can include not only energy or thermal recovery, but also material and / or chemical recovery.

[0052] However, the use of conventional conductive inks, i.e., coatings designed to increase electrical conductivity, can lead to problems due to poor material compatibility. This often leads to adhesion problems between the conventional conductive ink and the substrates, e.g., UV-curing acrylate-based conductive inks applied to polyamide surfaces. Likewise, residues of a conventional conductive ink adhering to the substrates can also interfere with the recyclability of the substrates during subsequent material recycling.

[0053] The good recyclability of the substrates according to the invention results in particular from the fact that the materials of the substrate base and the coating are compatible, and the coating applied to the substrate base only needs to be very thin to ensure excellent paintability. The proportions of the additive in the coating relative to the total mass of the substrate according to the invention are thus generally essentially negligible in terms of their influence on thermal conduction, even after reuse to produce a substrate base. From this perspective, the additives and / or the matrix polymer can also be easily selected with regard to their compatibility (e.g., miscibility) with the substrate material.

[0054] Preferably, the matrix polymer is selected so that it is molecularly or microscopically miscible with the first polymer, wherein preferably the matrix polymer and the first polymer originate from the same polymer group, and wherein particularly preferably the matrix polymer and the first polymer are of the same polymer type.

[0055] A polymer group represents a category of different polymers which differ, for example, in molecular weight, in the arrangement or sequence of the repeating unit(s), but have the same categorization features, e.g. a linkage via amide or ester bonds in the polymer groups of polyamides or polyesters, respectively, or the structure of vinyl monomers as in the polymer group of vinyl polymers.

[0056] Polymer types are individual polymers within a polymer group with a chemically well-defined structure (monomer, sequence), such as polyamide 6, which is made from ε-caprolactam. These can also differ, for example, in molecular weight, arrangement, and / or sequence of the repeating unit(s).

[0057] According to the invention, the first polymer and the matrix polymer are selected from the polymer group polyamide, polyester, polyether, polyketone, polyvinyl, polyolefin, polycarbonate and copolymers and functionalized polymers thereof.

[0058] Among the polyvinyl polymers, syndiotactic polystyrene (sPS) or a styrene copolymer such as ABS (acrylonitrile butadiene styrene), ASA (acrylonitrile styrene acrylate) and / or SAN (styrene acrylonitrile) are particularly suitable as the first polymer and matrix polymer.

[0059] Cases in which the first polymer and the matrix polymer are identical are preferred; however, for certain applications, it may be desirable to select a matrix polymer as the coating that deliberately exhibits different properties. This can be a matrix polymer that differs from the first polymer in terms of, among other things, moisture absorption, cost, melting or softening point or range, crystallization temperature, crystallinity, vapor and / or gas permeability.

[0060] According to the present invention, the first polymer and / or the matrix polymer is particularly preferably selected from the polymer group of polyamides, with further preference a) the first polymer is a polyamide 66, a polyamide 6 or a partially aromatic polyamide, and / or b) the matrix polymer is a polyamide 6, a polyamide 66, a polyamide 610 or a polyamide 410.

[0061] Preferred pairings of first polymer and matrix polymer are: First polymer and matrix polymer: polyamide; solvent in the coating composition: cresol and / or formic acid; first polymer and matrix polymer: polyester; solvent in the coating composition: cresol; first polymer and matrix polymer: syndiotactic polystyrene; solvent in the coating composition: organic solvents, e.g., toluene, ethyl acetate. First polymer and matrix polymer: polycarbonate; solvent in the coating composition: organic solvents, e.g., dichloromethane.

[0062] Particularly preferred pairings are: First polymer: polyamide 66; matrix polymer: polyamide 6 or polyamide 66; solvent in the coating composition: methane or preparations based thereon.

[0063] A solvent is selected to match the matrix polymer and the first polymer of the substrate base, which is used as a processing aid in the coating composition. The solvent can be a liquid chemical pure substance, e.g., an organic liquid (a chemical, organic compound in liquid form), or a mixture of such pure substances. The solvent is used to adjust an applicable form of the coating composition containing the matrix polymer and the additive for reducing surface resistance. The solvent, optionally in the form of a solvent mixture, can also be used at elevated temperatures, in extreme cases even up to the boiling point or decomposition point.

[0064] The solvent should preferably be able to be removed from the coating without leaving residue, e.g., by evaporation, neutralization, decomposition, or leaching, and ideally be cost-effective, environmentally friendly, easy to handle, non-toxic, and not impair the processing processes or product properties. Organic solvents are preferred.

[0065] Preferably, the first polymer and the matrix polymer are soluble in the same solvent or in the solvent contained in the coating composition. If the first polymer has a very high molecular weight or is present in (partially) crosslinked form, the first polymer should preferably be swellable, at least by absorbing the selected solvent.

[0066] Preferred solvents are – depending on the polymer – organic liquids, in particular aromatic hydrocarbons and / or carboxylated hydrocarbons, inorganic acids, mineral acids as well as mixtures of the above-mentioned substances and aqueous solutions thereof. Halogenated liquid compounds can also be used, e.g. halogenated acetic acid (trichloroacetic acid, trifluoroacetic acid), hexafluoroisopropanol or dichloromethane as well as mixtures of these liquids that can be used as solvents. For the aromatic hydrocarbons, cresol, xylene and toluene are particularly preferred. For the carboxylated hydrocarbons, methanoic acid and ethanoic acid are particularly preferred. For the mineral acids, sulfuric acid and phosphoric acid are particularly preferred. Furthermore, organic esters, ethers, alcohols, aldehydes, ketones or carbonates can be used, such asEthyl acetate, butyl acetate, tetrahydrofuran, dioxane, ethanal, butanone and propylene carbonate, and mixtures thereof.

[0067] The coating preparations according to the invention can be easily formulated so that they can also be applied to complex contours of the substrate base bodies, in particular by spraying, printing, stamping, pouring, brushing, doctor blade coating, by means of transfer rollers, etc.

[0068] The solvent contributes in particular to the composition of the coating - in particular the matrix polymer - bonding firmly with the material of the substrate base - the first polymer - e.g. through interdiffusion of chain molecules.

[0069] For example, methane acid or a mixture containing for example, methane acid (e.g., with 50 wt.% for example or more) is a particularly preferred component or solvent for the coating composition, since for example, methane acid is sufficiently volatile, can be removed without residue, and is capable of dissolving, partially dissolving, or swelling a wide range of polymers (especially polyamides).

[0070] In certain embodiments of the invention, the first polymer in the polymer material is present as a blend with a second polymer. Blends with a continuous phase of polyamide and, for example, PPE or PS or PS-containing copolymers or polyacrylates or polyolefins as the dispersed, discontinuous phase are particularly preferred, since the aforementioned preferred pairings of first polymer and matrix polymer for polyamides can also be used here.

[0071] In preferred embodiments of the invention, the polymer material of the substrate base comprises reinforcing materials, in particular selected from particulate and fibrous reinforcing materials, more preferably selected from glass spheres, hollow glass spheres, glass fibers, carbon fibers, ceramic fibers, ceramic particles, or polymer fibers. Ground glass particles are also suitable as particulate reinforcing materials in substrate base bodies according to the invention.

[0072] The additive for reducing the surface resistance of the coating is preferably selected from electrically non-insulating materials and, in particular, from carbon-based components, in particular conductive carbon black (conductive carbon black), carbon nanotubes (CNT), carbon fibers, carbon layer materials, in particular graphite, graphene and graphene oxide, electrically conductive ceramics, in particular semiconductive tin oxides, electrically conductive organic compounds, conductive polymers, metal powders and metal fibers. It is important to select a concentration of the additive that provides sufficient electrical conductivity of the coating, e.g., by forming a percolation structure, and thus enables the reduction of the electrical resistance to the target range (i.e., a specific surface resistance of 10 10< Ohm or less). This concentration depends, among other things, onon the shape, orientation or intrinsic conductivity of the particles (particles, fibers, etc.) of the additive.

[0073] Conductive carbon black, CNT or carbon fiber is particularly preferred as a chemically inert electrically conductive additive for reducing surface resistance.

[0074] Among the semiconductive tin oxides, indium-doped and fluorine-doped tin oxide (ITO and FTO) are particularly preferred.

[0075] The specific surface resistance of the coating of the substrate base body according to the invention can be varied not only by selecting the additive, but also by varying its content in the coating.

[0076] The particle size of the additive to reduce surface resistance must be adapted to the coating composition used, the application process and the desired properties of the coating (layer thickness, homogeneity, dry basis weight, conductivity, etc.).

[0077] When applying the coating composition by spraying, for example, the diameter of the spray nozzle determines the maximum particle size.

[0078] Particles with a mean diameter (median value) of 50 µm or less are preferred, with particles with a mean diameter (median value) of 10 µm or less being particularly preferred. The median value can be determined by manually measuring electron micrographs. The length of the particles can reach several times the diameter of the particles, especially when fibrous additives such as carbon fiber or CNTs are used. Nanoparticles are further preferred.

[0079] The ratio of the particle length to its diameter represents the aspect ratio. A high aspect ratio is preferred because it increases the probability of forming a percolation path for the dissipation of electrical charge, thus potentially reducing the additive concentration.

[0080] The aspect ratio A is defined by the quotient of the length L in a spatial direction, e.g. x or y, and the thickness D (e.g. of platelet-shaped particles or of rod-shaped or fibrous particles) in a spatial direction z perpendicular to x or y. Thus, the relationship A = L / D .

[0081] For example, carbon fibers, e.g., ground or chopped carbon fibers with a thickness of approximately 5 µm to approximately 10 µm and lengths of several hundred µm to a few mm, can be used, resulting in aspect ratios of up to four digits. Conductive carbon black can also be used; this results in elongated, branched superstructures (aggregates and agglomerates) of primary particles, with the superstructures ranging from a few hundred nm to several µm in length, and the primary particles themselves being essentially spherical and having a diameter of approximately 100 nm or less.

[0082] The coating on the surface region of the substrate preferably has an average observable thickness of approximately 100 µm or less, in particular approximately 0.1 µm to approximately 50 µm, more preferably approximately 0.1 µm to approximately 25 µm. A certain fluctuation in the layer thickness can be tolerated, as this generally does not impair the function or the appearance.

[0083] The coating applied to the surface area of ​​the substrate according to the invention can be designed in a variety of ways, in particular as a continuous, full-surface, or large-area coating. The coating can be applied to one side, multiple sides, or all sides of the substrate base body.

[0084] However, it is also possible to equip a surface that is not visible in the final application with the coating according to the invention, in particular the back of a substrate base body or internal areas such as hollow chambers in hollow (chamber) profiles, since the electrostatic effects present can also act through the substrate body over short distances of a few millimeters and make the then uncoated visible side electrostatically paintable.

[0085] For certain applications, small-area coatings applied at specific points, lines, or regions may also be important. The coating can also be applied in the form of patterns, numbers, symbols, drawings, or letters; this is then used, for example, to enable specific decoration of the substrates. In this case, the coating is then selectively applied to one or more predetermined surface areas of the substrate base body which are / are intended for subsequent electrostatic coating, in particular powder coating, or which run / run essentially parallel to a surface area of ​​the substrate which is / are intended for electrostatic coating, in particular powder coating.

[0086] It can also be used to print specific structures, such as conductor tracks, onto substrates which can then be used, even after a painting process, to manufacture an electronic component from the substrate itself. For example, components (switches, LEDs, transmitter / receiver modules, actuators, Peltier elements, piezo elements, solar cells, power storage devices, sensors for humidity, temperature, vibration / sound, pressure / tension, or other electrical components) can be subsequently integrated onto an insulating profile equipped in this way with printed conductor tracks in order to produce so-called intelligent or electronically functionalized insulating profiles. In this case, electrical contact between the metal half-shells (e.g. the inner and outer aluminum half-shells of an aluminum window) for power or signal transmission is also advantageous.

[0087] The present invention is particularly important for substrates designed as thermal insulation profiles, particularly for the production of window, door, roof, or facade elements. The substrates can, in particular, also comprise a hollow profile or porous or semi-porous profiles as the substrate base. In the applications described above, these thermal insulation profiles are often firmly bonded to metal profiles (e.g., aluminum frame profiles).

[0088] In general, the present invention can also be implemented in a substrate which is designed as a molded part for outdoor use, in particular as a molded part with the function of a holding element, decorative element or covering element.

[0089] The matrix polymer used, the additive and the composition of the coating can also increase the weathering and / or UV stability, so that the products according to the invention have significantly improved stability in these application scenarios.

[0090] Of particular importance according to the invention as substrates are: molded parts with the function of a holding element or covering element in the field of plant engineering for renewable energies, e.g., wind power, solar energy, or hydropower plants, or also in the field of automotive engineering, transportation, gardening equipment, sports and leisure equipment, or housings for electrical or electronic systems and devices. Particular preference is given to add-on parts for means of transportation (cars, motorcycles, bicycles, scooters, etc.), such as bumpers, hubcaps, fenders, hoods, doors, hatches, and flaps.

[0091] According to the invention, matrix polymers that survive the coating processes described below without significant decomposition are preferred. In powder coating processes, substrates are typically exposed to temperatures of approximately 200°C for several minutes; for this reason, temperature stability of approximately 200°C or more, preferably approximately 250°C or more, is desired. The substrates must be sufficiently dimensionally stable at these temperatures to ensure the continued usability of the coated and coated substrates, as well as the functionality of the products manufactured from them.

[0092] In addition, there are also known coating processes that require higher temperatures; these are generally coating systems for high-end applications, such as PVDF powder coatings. It is obvious that the temperature stability and dimensional stability of the substrate must be adapted accordingly for these processes, as is familiar to those skilled in the art.

[0093] Temperature stability is not just understood as the melting or softening point or range of a polymer, but rather as the temperature up to which the polymer is sufficiently stable with regard to thermal decomposition (depolymerization, thermolysis, thermal oxidation, hydrolysis, outgassing, etc.). Measurable parameters for testing temperature stability include, for example, mass loss using thermogravimetry, the oxidation induction time, or the determination of mechanical parameters such as impact strength, flexural strength, tensile strength, or peel strength, where possible. The test scenarios should reasonably reflect the stresses involved in the painting process (baking temperatures, holding times, atmosphere, etc.). For example, for the above-mentioned thermal insulation bars (insulating profile made of a polymer material containing PA66 or with a matrix of PA66), this could be a thermogravimetric measurement (TGA) in air, which uses a temperature program with a holding time of approximately 20 minutes at 220 °C.The mass loss (without moisture release) should be less than approx. 5 wt.%, preferably less than approx. 2 wt.%.

[0094] The coating or matrix polymer should also be sufficiently thermally stable, but no high demands are placed on mechanical strength, since the substrate body is usually the load-bearing body.

[0095] According to the invention, coatings with reduced specific surface resistance are also preferred, which are UV-stable and / or weather-resistant. Test scenarios are described, for example, in DIN EN ISO 4892. Coatings are assessed as UV-stable or weather-resistant within the meaning of the present invention if they have properties relevant to an application (e.g. impact resistance, strength, degree of gloss, surface roughness, crack and fracture behavior) that deteriorate slightly or not at all after UV exposure or weathering. Slight deterioration is considered to be, in particular, deteriorations of up to 20% (relative to the initial properties), i.e. UV-stable or weather-resistant products retain 80% of their initial properties or more after (UV) weathering. The duration of UV exposure or weathering is chosen appropriately for the application; this can, for example,300 hours, 500 hours or 600 hours or longer.

[0096] For example, polyamide polymers with conductive carbon black as an additive to reduce surface resistance have proven to be particularly UV-stable, e.g. with approximately 5 wt.% carbon black content in the surface layer or more.

[0097] The invention further relates to substrates with a lacquer layer or a powder lacquer layer, which in particular has a layer thickness in the range from approximately 10 µm to approximately 300 µm, preferably from approximately 30 µm to approximately 200 µm.

[0098] A further aspect of the present invention relates to a process for producing electrostatically paintable polymer-based substrates having the features of claim 12.

[0099] The method according to the invention comprises: providing a substrate base body manufactured using a polymer material, wherein the polymer material comprises a first polymer, providing a coating composition comprising a solvent, a matrix polymer dissolved in the solvent and an additive that reduces electrical resistance, wherein the solvent is selected such that the first polymer is soluble or swellable in the solvent, wherein the matrix polymer is compatible with the first polymer, and wherein the additive is dispersed in the coating composition, applying the coating composition to a surface region of the substrate base body to form a surface layer and removing the solvent from the surface layer.

[0100] The coating composition used according to the invention can be applied evenly and thinly to any complex surface structures, for example by spraying, printing, stamping, pouring, brushing, doctor blade coating, dipping and also by means of transfer rollers.

[0101] The viscosity of the coating composition required for the respective processing can be easily adjusted by changing the proportion of dissolved polymer. Higher proportions of dissolved polymer or lower proportions of solvent increase the viscosity. Likewise, other additives can be added in a targeted manner. In addition to electrically conductive additives, these include rheological additives, dispersing additives (e.g., soaps, silicas, polyelectrolytes), or functional additives such as flame retardants (metal oxide hydroxides, organic and / or halogenated flame retardants) or formulation-reducing fillers (e.g., silicon oxide, glass powder, talc, gypsum, chalk, etc.). Dispersants are primarily used to keep finely dispersed electrically conductive additives in a stable dispersion in the solvent until the coating is applied.

[0102] Of particular importance are also coloring additives such as pigments, effect pigments, dyes or fluorescent dyes which can be used in a coating composition to, among other things, assume decorative functions or to serve to design copy protection features.

[0103] The solvent content of the coating composition used according to the invention contributes to the coating being firmly bonded to the surface of the substrate base. This occurs through the formation of a molecular or microscopic mixture of the matrix polymer and the first polymer of the substrate base. This mixture can occur spontaneously without any further intervention, e.g., through diffusion or interdiffusion of molecular chains of the dissolved polymers of the matrix polymer and the first polymer.

[0104] According to the invention, the coating creates a new surface on the substrate base body, which is, for example, lubricant-free, has a higher roughness, or contains adhesion-optimizing components (e.g., additional additives or functionalized polymers), thus resulting in improved adhesion of the powder coating to the surface. A separate post-treatment of the coating surface prior to powder coating is therefore unnecessary, which reduces costs for the entire downstream processing process.

[0105] Furthermore, it is usually sufficient to apply the coating composition in small layer thicknesses so that the geometry of the substrate base bodies, in particular their wall thickness, is only insignificantly changed and the thermal insulation properties of the substrate base bodies remain almost unchanged.

[0106] At the same time, by applying the coating composition according to the invention to a surface region of the substrate base body, the optical appearance of the latter can be improved. This makes it possible, in particular, to create a new surface that is visually perceived as homogeneous, which can, for example, be homogeneously matte black over a large area (i.e., with a low gloss level, preferably a gloss level of 30% or less, particularly preferably a gloss level of 10% or less).

[0107] For the purposes of the present invention, the solubility of the first polymer in the solvent is particularly present when the solvent can convert significant portions of the first polymer into a dissolved or dispersed state, e.g., approximately 10% by weight or more of the first polymer is soluble in a solvent, or approximately 50% by weight or more of the first polymer is soluble in a solvent. Particularly preferably, approximately 98% by weight or more of the first polymer is soluble in a solvent.

[0108] The solubility of polymers in a solvent is usually accompanied by an increase in the viscosity of the liquid phase, i.e. the resulting solution, and can also be tested in this way.

[0109] More preferably, the first polymer is swellable in contact with the solvent at least to an extent that the polymer absorbs approximately 50 g of solvent or more per 100 g of polymer upon swelling.

[0110] The removal of the solvent from the surface layer can be achieved using various methods, in particular by evaporation and / or vaporization and / or by conversion into volatile gaseous products (decomposition, conversion), whereby the volatility of the solvent or its decomposition rate is preferably increased. This can be achieved by lowering the ambient pressure and / or by increasing the temperature, in particular by using a vacuum chamber, radiant heaters, fan heaters, etc.

[0111] Alternatively, the solvent can be washed out: A washing process that removes the solvent from the solvent-containing substrate preferably uses an agent miscible with the solvent (a second solvent or a preparation, e.g., a neutralization solution), whereby this agent should be a non-solvent for the matrix polymer. Water or aqueous solutions are particularly preferred as agents. Such a water-based neutralization and / or washing process is particularly effective for removing inorganic acids from coated substrates, among other things, if these are used as solvents in coating compositions.

[0112] According to the invention, the solvent is preferably selected such that the solubility of the matrix polymer in the solvent is approximately 1 g / l or more, preferably approximately 5 g / l or more, particularly preferably approximately 50 g / l or more. This allows the use of sufficiently highly concentrated coating compositions and reduces the effort required to remove the solvent at the end of the coating process.

[0113] More preferably, the solvent is selected from volatile chemical liquid compounds which, in particular at 1 atm, have a boiling point or decomposition point of approximately 210 °C or less, particularly preferably a boiling point or decomposition point of approximately 120 °C or less.

[0114] In the process according to the invention, the first polymer is selected from polyamide, polyester, polyether, polyketone, polyolefin, polyvinyl and copolymers and functionalized polymers thereof.

[0115] The matrix polymer is preferably selected from polyamide, polyester, polyether, polyketone, polyolefin and polyvinyl.

[0116] As solvent, an organic liquid ("organic solvent") is preferred, more preferably an aromatic hydrocarbon, in particular cresol, xylene or toluene, and / or carboxylated hydrocarbons, preferably methane acid or ethanoic acid, or an inorganic acid, in particular sulfuric acid, phosphoric acid and mixtures thereof with other liquids, or a preparation thereof, e.g. a neutralization solution and / or aqueous solutions thereof, is used, wherein the additive reducing the electrical resistance is distributed, in particular homogeneously distributed, in the matrix polymer.

[0117] According to a further aspect of the present invention, the method according to the invention comprises, after the application of the coating to a surface region of the substrate base body, the electrostatic application of a lacquer, in particular a powder lacquer, wherein the powder lacquer is preferably baked at a temperature of approximately 170 °C or more, wherein a lacquer adhesion to the surface region of the substrate is achieved which preferably results in a cross-cut characteristic value of 0, 1 or 2, particularly preferably a cross-cut characteristic value of 0 or 1, according to a cross-cut test according to DIN EN ISO 2409.

[0118] The substrates according to the invention are preferably subjected to drying steps before electrostatic powder coating, for example to expel volatile substances in advance and thus to reduce or prevent outgassing of volatile substances and in particular the release of residual moisture during the subsequent paint baking process.

[0119] High paint coverage rates, e.g., when using standard powder coating systems, can be achieved in a reproducible and process-stable manner, especially when the substrates are dry, i.e., the residual moisture content in the substrate body is approximately 0.5 wt.% or less, in particular approximately 0.3 wt.% or less. This property is particularly important for the coating processes of hygroscopic polymer materials (e.g., polyamide-based materials), since dry polyamide materials without special treatment exhibit little or no blistering, but also only produce low paint coverage rates.

[0120] The coating according to the invention can often be permeable to diffusion; however, in exceptional cases, it is also possible and expedient to create a diffusion barrier, e.g., for water vapor, using additives in a coating composition. In this case, it is preferable to select platelet-shaped fillers with a high aspect ratio. These can be selected from, for example, graphite, delaminated / exfoliated graphite, graphene, graphene oxide, layered silicates (inorganic or organophilic), layered inorganic sulfides, or layered inorganic oxides (e.g., layered double hydroxides).

[0121] These and other advantages and advantageous embodiments of the present invention will become apparent from the following description of the figures and the examples.

[0122] They show in detail: Figures 1A to 1D show a schematic representation of the production of a substrate according to the invention with a surface coating; Figures 2A to 2D show two exemplary embodiments of a substrate according to the invention before and after powder coating; Figures 3A to 3F show several exemplary embodiments of substrates according to the invention; Figures 4A to 4D show further exemplary embodiments of substrates according to the invention; Figures 5A and 5B show test results of a powder-coated substrate according to the invention using cross-cut lines at different magnifications; Figures 6A and 6B show a powder-coated substrate with insufficient paint coverage; Figures 7A and 7B show a powder-coated substrate according to the invention with complete paint coverage; and Figure 8 shows paint coverage in a direct comparison of a substrate coated and an uncoated substrate according to the invention.

[0123] Figure 1 shows a substrate base body 10 in the form of a so-called bent insulating profile in cross section perpendicular to its longitudinal direction.

[0124] The cross-section has bent areas 14, 16 on both sides of a flat, central section 12, the free edges of which are designed as so-called curling projections 18, 20. The curling projections can be inserted into corresponding recesses in metal profiles and connected to the metal profile in a shear-resistant manner by a so-called "curling process."

[0125] The substrate base body 10 is typically made of a polymer material, for example based on polyamide as the first polymer.

[0126] Figure 1B shows schematically the process of applying a coating according to the present invention to produce a surface having a specific surface resistance of 10 10< ohms or less.

[0127] The process of applying the coating is realized here with a spraying technique, symbolized by a spray mist 24, which is directed in the direction of arrow a onto the Figure 1upper surface (visible side 28) of the insulating profile 10.

[0128] The surface layer can be applied, for example, as a dispersion of conductive carbon black in a solution of PA6 in methane acid.

[0129] In Figure 1C It can be seen that a surface layer 26 has formed on the substrate body (insulating profile) 10, extending over the central section 12 and into the bent regions 14, 16, which in the step C of the Figure 1 symbolized step of drying, during which solvent components of the sprayed coating mass (see arrows b) are removed.

[0130] In Figure 1D then the finished substrate 30 according to the invention is depicted, in which the substrate base body 10 is provided with a coating 32 which has a specific surface resistance of approximately 10 10< Ohm or less.

[0131] These in Figure 1The substrate shape shown is an example of a simple profile geometry without hollow chambers, undercuts or similar, but it is explicitly pointed out that the scheme of the Figure 1 can also be applied to many other, including highly complex profiles or molded parts with three-dimensional structures.

[0132] In Figure 2 are in the Figures 2A and 2C two polymer-based substrates according to the invention are shown, which are subsequently electrostatically coated with a powder coating layer (shown in the Figures 2B and 2D ). Here, too, the cross-section perpendicular to the longitudinal direction of the composite profiles is considered.

[0133] In Figure 2AShown is a section of a metal-plastic profile 40, which is formed from a polymer-based substrate 42 and metal profiles 44, 46 connected to its edges. The polymer-based substrate 42 is again designed as an insulating profile with bent-off roll-in projections 48, 50 formed on both sides, which are inserted into complementary roll-in grooves 52, 54 of the metal profiles 44, 46.

[0134] The substrate 42 (insulating profile) according to the invention has on its upper surface, which is accessible from the outside, a coating 56 according to the invention, which is analogous to Figure 1D about the one in the Figure 2A upper surface area of ​​the insulating profile 42, namely up to the rolling projections 48 and 50 of the insulating profile 42.

[0135] When the roll-in profiles 48, 50 are rolled into the roll-in grooves 52, 54 of the metal parts 44, 46, a conductive contact is established with the coating 56, so that an electrostatic powder coating of particularly high quality can be applied here.

[0136] The situation after powder coating of the dry substrates is in Figure 2B in which a powder coating layer 60 extends from the end face of the metal profile 44 over the surface of the coating 56 of the insulating profile 42 to the end face of the second metal profile 46.

[0137] The electrostatically applied lacquer layer 60 is particularly uniform and bubble-free and has a high lacquer coverage rate.

[0138] Figure 2Cshows a section of a composite profile 70 with a polymer-based insulating profile 72, which is held on both sides by metal profiles 74, 76 via a roll-in connection. Roll-in projections 78, 80 of the insulating profile (substrate) 72 are inserted into corresponding roll-in grooves 82, 84 of the metal profiles 74, 76, respectively.

[0139] In contrast to the illustration of Figure 2A In this embodiment, a coating 86 with a reduced specific surface resistance, applied according to the invention to the substrate base body 73, is not placed on the visible side, but on the back. The coating 86, in turn, is in electrically conductive contact with the metal profiles 74, 76, in that the coating 86 extends to the rolling projections and thus comes into contact with the metal profiles 74, 76 in the rolling grooves 82, 84.

[0140] A powder coating layer 90 is again applied to the visible side. It extends from the end face of the first metal profile 74 across the insulating profile 72 to the end face of the second metal profile 76. The coating 86 applied to the substrate base body according to the invention, with a reduced specific surface resistance of 10 10< ohms or less, again creates the prerequisite for a continuous, flawless coating layer 90 to be applied to the visible side of the composite profile 72, which coating layer 90 lies directly against the substrate base body 73 in the area between the metal profiles 74, 76.

[0141] Figure 3shows, with its examples in the partial figures 3A to 3F, different substrates according to the invention (each in a cross-section perpendicular to the longitudinal direction), which have different configurations of coatings applied according to the invention on the respective substrate base body 100, which has the shape of a bent insulating profile.

[0142] The substrate base body 100 has, in addition to a central, flat section 102, bent-off regions 104, 106 adjoining it at the sides, to which so-called curling projections 108 and 110 are then respectively connected.

[0143] The substrate base body 100 of the Figure 3A is provided with a coating 112 which runs completely around the circumference and extends not only on both sides of the central section 102, but also around the bent areas 104, 106 and the curling projections 108 and 110.

[0144] In the Figure 3BThe substrate base body 100 is again shown, in which the coating 114 to be applied according to the invention extends only on one side of the central section 102 and into the adjacent bent regions 104, 106 (each also only on one side). Figure 3B a coating of the substrate base body 100, similar to what is done in connection with the Figure 1D was described.

[0145] In Figure 3C A coating 116 is applied to one side of the base body 100 in the central section 102, which extends partially into the bent regions 104, 106 (also only on one side) on both sides of the flat central section 102. The other surface areas of the bent sections 104, 106 and the curling projections 108, 110 remain free of coating.

[0146] In another variant, 3D figurethe selective application of a coating is shown, wherein the coating has been divided into four parallel stripes or tracks 118a, 118b, 118c, 118d, all extending on the upper surface of the central portion 102 of the substrate base body 100.

[0147] Another variant of the selective coating of the substrate base body 100 is in Figure 3E shown, wherein here a coating 120 applied according to the invention extends approximately over half of one surface of the central section 102 as well as over the bent area 106 (on one side).

[0148] In the sixth example of Figure 3 is in Figure 3Fa substrate according to the invention is shown, in which the substrate base body 100 is provided with a coating 122 which extends both on a surface of the central section 102, over the entire bent regions 104, 106 (on one side) and into the regions of the curling projections 108, 110.

[0149] In the embodiments of the Figures 3A, 3B, 3E and 3F In each case, it is possible to bring the coating 102, 114, 120 or 122 applied according to the invention into contact with the metal profiles when rolling in the rolling projections 108, 110, so that these can have a dissipative effect during electrostatic powder coating.

[0150] In the other embodiments of the Figures 3C and 3D Such a conductive contact between the metal profiles is missing, so that a capacitive effect comes into play. 3D figure In addition, there may be an electrically conductive connection between the separate tracks (not shown).

[0151] In the Figure 4 Further embodiments are shown which are intended to illustrate the possibility of selectively applying a coating according to the invention to a substrate base body.

[0152] In Figure 4A A base body 150 is shown with a flat central section 152, bent regions 154, 156 adjoining it laterally, and curling projections 158, 160 formed thereon. On the upper surface of the central section 152, a coating according to the invention is selectively applied in the form of the letters ABC and the numbers 123, a circle, a dot, and the symbol ®<, which are referred to together with the reference numeral 162.

[0153] This lettering "ABC 123 ○ ● ®< " serves only as an example of any inscriptions that can be applied in this way to the surface of the central section 152, and optionally also to other surface areas of a substrate base body 150, using the coating according to the invention. Typically, suitable printing systems, stamps, or stencils are used for this purpose.

[0154] At the Figure 4B a coating with a plurality of strips 164a, 164b, 164c, 164d is applied to the base body 150, wherein the strip-shaped coatings 164a, 164b, 164c, 164d extend on the side lying at the top in the figure from the curling projection 158 over the bent region 154, the flat central region 152 into the bent region 156 and the curling projection 160.

[0155] Here, too, the possibility of electrical discharge via metal profiles (not shown) in the rolled-up state of the substrate base body 150 is provided during electrostatic powder coating.

[0156] In Figure 4C The coating is again limited to the upper region of the central section 152 of the substrate base body 150, with reference numeral 166 indicating randomly arranged round to oval, island-shaped surface areas, which can represent any other small-scale pattern. Within the island-shaped surface areas, the coating acts via a capacitive mechanism.

[0157] In Figure 4DFinally, the coating is again applied in web or strip form, with a first strip pattern 168a extending on the surface of the central section 152 in the longitudinal direction of the substrate base body 150, while a further element 168b extends perpendicular to the longitudinal stripes of the pattern 168a from the curl-in projection 158 via the bent region 154, the central section 152, the bent region 156 to the curl-in projection 160.

[0158] Because the coating area 168b extends transversely across all strip-shaped sections of the pattern 168a, a dissipative function can again be ensured if the base body 150 is provided with metal profiles in a rolled-up composite.

[0159] In the Figure 5 is shown a light microscopic image of a profile treated according to the invention, which was subsequently powder coated according to Example 6 described below.

[0160] The cross-cut test was carried out on this sample. Figures 5A and 5B show the result at different magnifications ( Figure 5A : 30x, Figure 5B A cross-cut characteristic value of "0" is evident, meaning clear cuts without flaking of the light powder coating from the dark surface of the substrate; the coating adhesion can therefore be classified as perfect.

[0161] In the illustrations of the Figure 6 light microscopic images of the painting result after powder coating a profile according to Example 3 described below are shown ( Figure 6A ). The image was taken at a magnification of 50x. The Figure 6B shows a black and white version of the Figure 6A , which was obtained by digital image conversion and serves as the basis for determining the paint coverage rate. Figure 6B a paint coverage rate of approximately 56% can be determined.

[0162] Figure 7 shows a light microscopic image of the painting result after powder coating a profile according to Example 6 ( Figure 7A ). The image was taken at a magnification of 50x. The Figure 7B shows a black and white version of the image of the Figure 7A , which was obtained by digital image conversion and serves as the basis for determining the paint coverage rate. For Figure 7B A paint coverage rate of approximately 100% is determined. The paint coverage is therefore perfect.

[0163] Figure 8 shows a photograph of a plastic-aluminum composite profile 200 with a first and a second metal profile 202, 204, which are connected to one another via a substrate 206, which is designed as an insulating profile, directly after the application of a white paint powder (electrostatic powder coating), but before the paint baking process.

[0164] In the left area 208 of the substrate 206, the substrate base body was provided with a coating according to Example 7 described below before the powder application, as is the case with the insulating profile of the Figure 3C is shown. In the right-hand region 210 of the substrate 206, the substrate base body was not provided with a coating according to the invention and thus corresponds to the reference sample from Example 7 described below.

[0165] The powder was applied to the present composite sample in a single step on the dried composite profile. Significant differences in the paint coverage are clearly visible, with paint deposits in the 208 area approaching 100% and in the 210 area barely visible to the naked eye. Examples:

[0166] In the following examples, the specific surface resistance was determined on substrate base bodies (Reference Examples 1 to 3) or on substrates according to the invention (Examples 4 to 6) after storage in standard climate and after additional drying.

[0167] Extruded insulating profiles were used as the substrate base body, and the measurement of the specific surface resistance was carried out on the so-called visible side 28 of the section 12 of the substrate base body 10 or on the surface of the coating 32. Example 1 (Reference):

[0168] In this example, a solid, extruded insulation profile 10 with a flat central section similar to that in Figure 1AThe insulating profile shown is made of a polymer material (a polymer blend of PA66 and PPE with similar weight proportions) and a glass fiber (GF) content of 10 wt.%. PA66 is used here as the first polymer and forms the continuous phase in the blend with PPE, while PPE is discontinuously dispersed in microscopically fine droplets.

[0169] A flat test specimen is then milled from the profile, which is suitable for measuring the specific surface resistance.

[0170] The measured values ​​for the specific surface resistance, measured under different conditions, are shown in Table 1. Example 2 (Reference):

[0171] In this example, a solid, extruded insulation profile 10 with a flat central section similar to that shown in Figure 1AThe insulating profile shown is made of the polymer material TECATHERM ®< LO from Ensinger GmbH. This is a polymer blend of PA66 and PPE (with similar weight proportions) with a glass fiber (GF) content of 20 wt.%. PA66 is used as the first polymer and forms the continuous phase in the blend with PPE, while PPE is discontinuously dispersed in µm-sized droplets.

[0172] A flat test specimen is then milled from the profile, which is suitable for measuring the specific surface resistance.

[0173] The measured values ​​for the specific surface resistance, measured under different conditions, are shown in Table 1. Due to the higher proportion of glass fibers, the specific surface resistance is slightly increased compared to the measured values ​​of Example 1. Example 3 (Reference):

[0174] In this example, a solid extruded insulation profile 10 with a flat central section similar to that in Figure 1A The insulating profile insulbar ®< REG is made of the polymer material TECATHERM ®< 66 GF from Ensinger GmbH. PA66 is the first polymer and is reinforced with a glass fiber (GF) content of 25 wt.%. A flat test specimen is then milled from the profile, which is suitable for measuring the specific surface resistance.

[0175] The measured values ​​for the specific surface resistance, measured under different conditions, are shown in Table 1. Due to the different composition (no PPE content) of the polymer material, in particular the resulting higher proportion of (moisture-absorbing) PA66, a further reduced specific surface resistance results compared to the measured values ​​of Examples 1 and 2.

[0176] The paint coverage of the dried and powder-coated profile is only approximately 56%, which is clearly insufficient. The painting tests were conducted using a white powder coating of type SA816G Interpon D1036 (manufacturer: Akzo Nobel Powder Coatings GmbH). The powder coating was applied to the pre-dried substrate using a standard electrostatic powder coating gun and baked in an oven at 200°C for 20 minutes. Example 4:

[0177] In this example, an insulating profile 10, as described in (reference) example 1, is also used as the substrate base body.

[0178] However, in contrast to Example 1, the insulating profile 10 was provided with a coating 32 according to the invention, as can be seen from Figure 1D is evident.

[0179] A coating composition containing conductive carbon black was prepared as the coating compound for producing coating 32. For this purpose, a commercially available conductive carbon black concentrate of the type Hubron NBB310 (manufacturer: Hubron International, Great Britain) with a solids content of 50 g / L was introduced into concentrated formic acid (concentration >98%, Carl Roth GmbH + Co. KG), dispersed, and sprayed onto the surface of the substrate. According to the manufacturer, the conductive carbon black concentrate Hubron NBB310 is conductive carbon black in a PA6 matrix polymer with small amounts of an unspecified ethylene terpolymer as a modifier.

[0180] The PA6 compound with conductive carbon black was dissolved during addition to the formic acid solution under vigorous stirring. Subsequently, the conductive carbon black was further dispersed in the PA6 formic acid solution using a rotor-stator mixer (Ultra-Turrax from IKA) to finely distribute the conductive carbon black. This coating composition is applied promptly to prevent degradation or sedimentation.

[0181] Alternatively, other dispersion techniques can also be used, such as grinding in ball mills, wet mills, colloid mills, or even using high-pressure homogenizers, roller mills, and ultrasonic homogenizers. This process can be supplemented by one or more passes through fine nozzles, decanting, filtration, or other fractionation methods to separate poorly dispersed coarse fractions of the conductive carbon black.

[0182] The coating composition is sprayed onto the substrate base body using a compressed air-operated paint spray gun with a flat jet nozzle (nozzle diameter 1.5 mm), whereby the substrate base body is continuously moved through the fine spray mist, so that a thin but deep black, opaque application is obtained without the accumulation of large quantities of the liquid coating composition.

[0183] Drying is achieved by evaporating the substrates at room temperature and with good ventilation. This is completed within a period of approximately 0.5 to 1 minute and the substrates are then touch-dry and matt black.

[0184] The average layer thickness of coating 32 was approximately 1 µm to approximately 5 µm.

[0185] The measured values ​​for the specific surface resistance of coating 32, measured under various conditions, are shown in Table 1. Compared to the measured values ​​of Examples 1 to 3, the specific surface resistance is significantly reduced due to the additive content (conductive carbon black). The influence of the drying process on the measured specific surface resistance is lower (in percentage terms) here than in Reference Examples 1 to 3. Example 5:

[0186] In this example, an insulating profile 10, described as in Example 2, is also used as the substrate base body.

[0187] However, in contrast to Example 2, the insulating profile 10 was provided with a coating 32 according to the invention, as can be seen from Figure 1D is evident.

[0188] The coating 32 was prepared from a composition according to Example 4.

[0189] The spraying of the coating composition onto the substrate and the drying process are carried out analogously to Example 4.

[0190] The average layer thickness of coating 32 was approximately 1 µm to approximately 5 µm.

[0191] The measured values ​​for the specific surface resistance of coating 32, measured under various conditions, are shown in Table 1. Compared to the measured values ​​of Examples 1 to 3, the specific surface resistance is significantly reduced due to the additive content (conductive carbon black). The influence of the drying process on the measured specific surface resistance is also lower (in percentage terms) here than in Reference Examples 1 to 3. Example 6:

[0192] In this example, an insulating profile 10, described as in Example 3, is also used as the substrate base body.

[0193] However, in contrast to Example 3, the insulating profile 10 was provided with a coating 32 according to the invention, as can be seen from Figure 1D is evident.

[0194] Coating 32 was obtained from a coating composition as described in Example 4.

[0195] The spraying of the coating composition onto the substrate and the drying also takes place analogously to Example 4.

[0196] The average layer thickness of coating 32 was approximately 1 µm to approximately 5 µm.

[0197] The measured values ​​for the specific surface resistance of coating 32, measured under various conditions, are shown in Table 1. The influence of the drying process on the measured specific surface resistance is (in percentage terms) lower here than in Reference Examples 1 to 3.

[0198] The paint coverage of the dried and powder-coated profile is approximately 100%, which is perfect. The painting tests were conducted analogously to Example 3, also using a white powder coating of type SA816G Interpon D1036 (manufacturer: Akzo Nobel Powder Coatings GmbH). The powder coating was applied to the pre-dried substrate using a standard electrostatic powder coating gun and baked in an oven at 200°C for 20 minutes.

[0199] Examples 1 to 6 clearly demonstrate that by applying even a thin coating according to the invention, the specific surface resistance can be significantly reduced, thus resulting in electrical conductivity of the surface. Any desired adjustment of the surface resistance can be easily achieved by adjusting the formulation, for example, by changing the proportion of the conductive additive. Example 7:

[0200] An insulating profile 30 produced according to the invention with the coating 32 was processed into a metal-plastic profile (analogous Figure 2A ) and subsequently electrostatically coated with a white powder coating together with an untreated insulating profile (without coating) as a reference example.

[0201] The basis for this was a bone-shaped insulating profile of the type insulbar ®< LO18 from Ensinger GmbH, which was coated according to the invention with a dispersion of Hubron NBB310 in formic acid (solids content 50 g / L).

[0202] The preparation of the coating composition and the spraying of the coating composition correspond to the description in Example 4. The average layer thickness of the coating 32 was approximately 1 µm to 5 µm.

[0203] In order to directly compare the positive effects on the substrate according to the invention with the untreated substrate base, rectangular areas of the substrate base were covered for test purposes, leaving segments uncoated. This yields test samples in the form of substrates (insulating profiles) that exhibit a direct sequence of areas or segments that are easy to coat and poorly coated (see Figure 8 ).

[0204] The coating tests were conducted using a white powder coating of type SA816G Interpon D1036 (manufacturer: Akzo Nobel Powder Coatings GmbH). The powder coating was applied to the pre-dried substrates (<0.1 wt.% residual moisture) using a standard electrostatic powder coating gun and baked in an oven at 200 °C for 20 minutes.

[0205] While on the reference example, i.e., the profile segment 210 without the coating according to the invention, no continuously covering paint layer could be formed (paint coverage not visible to the naked eye, therefore completely inadequate), the powder coating of the substrate 206 according to the invention in the area 208 resulted in a visually appealing, continuous, uniformly white paint layer with very good paint adhesion to the coating 32 according to the invention.

[0206] The paint adhesion to the substrate in the area 208 was tested using a cross-cut test (DIN EN ISO 2409), the result of which is shown in the Figures 5A and 5B The cross-cut characteristic value determined was "0," which represents the best possible result. The coating result using a substrate according to the invention can therefore be rated as excellent. Example 8:

[0207] In order to evaluate the possible change in the mechanical properties of the substrates 30 due to contact with a good solvent for the first polymer - in this case, formic acid - mechanical tests were carried out on uncoated substrate base bodies 10 of the insulbar ®< REG type according to Example 3 and on substrates coated according to the invention according to Example 6 - in each case without powder coating.

[0208] Mechanical tests were conducted in the form of tensile tests with a set of n=10 test specimens each; these were milled from the insulation profiles used. The arithmetic mean was calculated for the evaluation of the Young's modulus, transverse and longitudinal tensile strength (relative to the longitudinal direction of the profiles), and elongation at break.

[0209] For Example 8a, an untreated substrate base body 10 of the insulbar REG type as described in Example 7 is used as a reference. Example 8b corresponds to the substrate coated according to the invention (insulating profile 30 with the coating 32) in Example 6. The results are summarized in Table 2 and show that the application of a coating 32 does not significantly influence the observed mechanical parameters of the substrate base body. Table 1 The realized layer thicknesses of the coatings of examples 4 to 6 are on average approximately 1 µm to approximately 5 µm. Example first polymer Matrix polymer conductive additive Material substrate base body Coating specific surface resistance (storage in standard climate) [Ω] specific surface resistance after drying (160 °C / 6h) [Ω] 1 PA66 without without Blend PA66 with PPE and 10% GF uncoated - reference 5,69 E + 13 6,63 E + 14 2 PA66 without without Blend PA66 with PPE and 20% GF uncoated - reference 1,49 E + 14 7,20 E + 14 3 PA66 without without PA66 25% GF uncoated - reference 4,50 E + 13 2,73 E + 14 4 PA66 PA6 Conductive carbon black Blend PA66 with PPE and 10% GF Spray coating with dispersion of conductive carbon black PA6 compound in formic acid (solids content 50 g / L) 7,79 E + 05 1,13 E + 06 5 PA66 PA6 Conductive carbon black Blend PA66 with PPE and 20% GF Spray coating with dispersion of conductive carbon black PA6 compound in formic acid (solids content 50 g / L) 5,12 E + 05 7,73 E + 05 6 PA66 PA6 Conductive carbon black PA66 25% GF Spray coating with dispersion of conductive carbon black PA6 compound in formic acid (solids content 50 g / L) 1,74 E + 05 2,02 E + 05 Table 2 Changes in selected mechanical properties of substrate bodies after application of a coating according to the invention Example Substrate base body Coating Young's modulus [relative] Elongation at break [relative] Tensile strength, longitudinal [relative] Tensile strength, transverse [relative] Residual moisture [wt%] 8a - Ref. insulbar REG without 100,0% 100,0% 100,0% 100,0% 0,3 8b insulbar REG with 100,5% 102,4% 100,1% 99,3% 0,3

Claims

1. Polymer-based substrate, which in particular is electrostatically coatable, comprising a substrate base body made using a polymeric material and a coating applied to a surface region of the substrate base body, wherein the polymeric material comprises a first polymer, wherein the coating comprises a matrix polymer and an additive which is dispersed in the matrix polymer and reduces the surface resistance of the coating, said additive having a proportion that is selected such that the specific surface resistance of the coating is about 1010 Ohm or less, wherein the matrix polymer is selected such that it is compatible with the first polymer; and wherein the first polymer and the matrix polymer are selected from the polymer groups polyamide, polyester, polyether, polyketone, polyvinyl, polyolefin and copolymers and functionalized polymers thereof.

2. Substrate in accordance with Claim 1, wherein the specific surface resistance of the layer with a reduced specific surface resistance is about 109 Ohm or less, further preferably about 108 Ohm or less.

3. Substrate in accordance with Claim 1 or 2, wherein the matrix polymer is selected such that it is molecularly or microscopically mixable with the first polymer; and / or wherein the first polymer and the matrix polymer are soluble or swellable in the same solvent, wherein the solvent is preferably a pure substance or a mixture of a plurality of pure substances, wherein the pure substance or the pure substances are selected from organic liquids, in particular aromatic hydrocarbons, esters, ethers, ketones, carboxylated hydrocarbons or inorganic acids, in particular mineral acids.

4. Substrate in accordance with any one of Claims 1 to 3, wherein the first polymer and / or the matrix polymer is / are selected from the polymer group of polyamides, wherein preferably a) the first polymer is a polyamide 66, a polyamide 6, or a partially aromatic polyamide, and / or b) the matrix polymer is a polyamide 6, a polyamide 66, a polyamide 610, or a polyamide 410.

5. Substrate in accordance with any one of Claims 1 to 4, wherein the first polymer in the polymeric material is present as a blend with a second polymer.

6. Substrate in accordance with any one of Claims 1 to 5, wherein the polymeric material comprises reinforcing substances, in particular selected from particulate and fibrous reinforcing substances, further preferably selected from glass spheres, hollow glass spheres, glass fibers, ceramic fibers, carbon fibers, and / or ceramic particles and / or polymer fibers; and / or wherein the additive for reducing the surface resistance of the coating is selected from carbon-based components, in particular conductive soot, carbon nanotubes (CNT), carbon fibers, carbon layered materials, in particular graphite, graphene and graphene oxide, electrically conductive organic compounds, conductive polymers, electrically conductive ceramic, in particular semiconductive zinc oxides, metal powders and metal fibers.

7. Substrate in accordance with any one of Claims 1 to 6, wherein the coating has an average thickness of about 100 µm or less, in particular about 50 µm or less, further preferably about 0.1 µm to about 25 µm.

8. Substrate in accordance with any one of Claims 1 to 7, wherein the coating is configured as a continuous coating; or wherein the coating is selectively applied to one or a plurality of predetermined surface region(s) of the substrate body which is / are provided for a subsequent electrostatic coating, in particular a powder lacquering, or which extends / extend substantially in parallel to a surface region of the substrate which is provided for an electrostatic coating, in particular a powder lacquering.

9. Substrate in accordance with any one of Claims 1 to 8, wherein the substrate is configured as a heat-insulating profile, in particular for the production of window, door, roof, or facade elements; or wherein the substrate is designed as a moulded part for an application outdoors, in particular as a moulded part with the function of a holding element or a covering element.

10. Substrate in accordance with any one of Claims 1 to 9, wherein the matrix polymer has a temperature stability of about 200°C or more, preferably about 250°C or more; and / or wherein the coating is UV-stable.

11. Substrate in accordance with any one of Claims 1 to 10, wherein the substrate has a powder lacquer layer which in particular has a layer thickness in the range of about 10 µm to about 300 µm, preferably of about 50 µm to about 200 µm; wherein optionally the lacquer layer on the coating in the lacquered region has a lacquer coverage rate of about 90% or more, in particular about 98% or more, and wherein the lacquer layer is preferably a powder lacquer layer.

12. Method for producing an electrostatically lacquerable, in particular a powder lacquerable, polymer-based substrate, wherein the method comprises: - providing a substrate base body made using a polymeric material, wherein the polymeric material comprises a first polymer, - providing a coating composition, comprising a solvent, a matrix polymer dissolved in the solvent, and an additive reducing the electrical resistance, wherein the solvent is selected such that the first polymer is soluble or swellable in the solvent, wherein the matrix polymer is compatible with the first polymer, wherein the first polymer and the matrix polymer are selected from the polymer groups polyamide, polyester, polyether, polyketone, polyvinyl, polyolefin and copolymers and functionalized polymers thereof, and wherein the additive is dispersed in the coating composition, - applying the coating composition to a surface region of the substrate base body while forming a surface layer, and - removing the solvent from the surface layer.

13. Method in accordance with Claim 12, wherein the solvent is selected such that the first polymer has a solubility of about 10% by weight or more, preferably a solubility of about 50% by weight or more, further preferably a solubility of about 98% by weight or more; or wherein the solvent is selected such that the first polymer is swellable in the solvent, and in particular at a temperature of 23°C absorbs about 50g of solvent or more per 100g of polymer while swelling.

14. Method in accordance with Claim 12 or 13, wherein the solvent is selected from volatile solvents and preferably has a boiling point or decomposition point of about 210°C or less, particularly preferably a boiling point or decomposition point of about 120°C or less.

15. Method in accordance with any one of Claims 12 to 14, wherein the matrix polymer is selected from polyamide, polyester, polyether, polyketone, polyolefin, and polyvinyl; wherein the solvent comprises an organic liquid, preferably an aromatic hydrocarbon, in particular cresol, xylene, or toluene, and / or carboxylated hydrocarbons, preferably methane acid or acetic acid, or a mineral acid, in particular sulfuric acid, phosphoric acid and mixtures thereof and / or aqueous solutions thereof; and wherein the electrical resistance-reducing additive is substantially uniformly distributed in the matrix polymer and is preferably selected from soot and carbon fibers.

16. Method in accordance with any one of Claims 12 to 15, wherein a surface region of the substrate is electrostatically powder lacquered with a lacquer powder after the application of the coating, wherein the powder lacquer is baked at a temperature of about 170°C or more, wherein preferably a lacquer adhesion on the surface region of the substrate is achieved which after a cross-cut test according to DIN EN ISO 2409 preferably results in a cross-cut value of 0, 1, or 2, particularly preferably a cross-cut value of 0 or 1, and in particular a homogeneous lacquer coverage is achieved; wherein optionally the lacquer layer on the coating in the lacquered region has a lacquer coverage rate of about 90% or more, in particular about 98% or more, and wherein the lacquer layer is preferably applied as a powder lacquer layer.