Painted multi-layer composite system

Abstract

The invention relates to a multilayer composite comprising at least one substrate, a functional layer based on a synthetic polymer, and an uppermost coating layer, wherein the coating layer comprises at least one elastomeric and / or thermosetting film-forming polymer and a matting agent containing microparticles, wherein the microparticles comprise at least polymer-based particles, characterized in that the particle size of the microparticles is at most 1.5 times the thickness of the coating layer and that the microparticles have at least two different particle sizes, wherein the particle size distributions, characterized by the D90 value and measured according to ISO 13320-1, of two differently sized microparticles differ from each other by at least 2 µm. In this way, particularly matte and tactilely appealing surfaces can be produced.

Description

[0001] The invention relates to a multilayer composite comprising at least one substrate, a functional layer based on a synthetic polymer and an uppermost coating layer, wherein the coating layer comprises at least one elastomeric and / or thermosetting film-forming polymer and a matting agent containing microparticles, wherein the microparticles comprise at least polymer-based particles.

[0002] Various surfaces, for example in the automotive sector or in the interior and exterior of buildings, are subject to high demands regarding their mechanical properties, as well as their haptic and visual effects, depending on the application. It is known from the prior art that elastic, embossable plastics are predominantly coated with water-based or solvent-based lacquers. External plastic-based or mineral lacquers are generally used to adjust the gloss level of the lacquered surfaces. These lacquers typically contain water or organic solvents and are thermally cured. Lacquers that cure under the influence of UV radiation are also referred to as UV lacquers.

[0003] With the increasing importance of sustainability, ever more environmentally friendly and energy-efficient coating formulations and processes are being developed. For example, UV coatings that are solvent-free (including water) are being used more frequently. Combined with so-called "excimer technology," very deep matte, tactilely pleasing, and elegant-looking surfaces can be produced. Furthermore, the "barrier properties" of the coating layer improve mechanical and chemical resistance (e.g., anti-fingerprint properties, "soft-touch" surfaces). The change in feel and the associated reduction in sliding friction make the process particularly interesting for many applications.

[0004] In a first step, the surface layer of an applied coating material is cured / polymerized to form a skin-like layer. Due to reaction shrinkage, this surface layer contracts during curing, resulting in a wrinkled structure at the micrometer level. In a second step, the applied coating fluid is polymerized / cured across the entire layer thickness, ensuring that the wrinkled surface structure is preserved. This wrinkled structure determines the surface's gloss level.

[0005] The microfolding process itself and the resulting microfold pattern on the surface can, according to current technology, be controlled within certain limits by adjusting the system parameters (system speed, pre-gelling, radiation power, radiation dose, oxygen concentration). However, this technology frequently reaches its limits. For example, the coating application method and the associated coating thickness and its thickness variation influence the homogeneity of the microfold pattern. Under certain lighting conditions, these inhomogeneities are visually disruptive and can also lead to deviations in important surface properties of the product, such as gloss level, chemical resistance, and scratch resistance.

[0006] The gloss level can be adjusted to a certain extent by adding commercially available matting agents. However, the amount and type of matting agent are limited due to its significant influence on the material's mechanical properties, making a defined folding pattern and the resulting surface structure currently impossible. Therefore, the surface structure is based more on random principles depending on the formulation of the foldable reactive mass, the airflow, the irradiation duration, etc.

[0007] Matting surfaces can be achieved through various chemical and physical processes. One possibility is the addition of fine particles, such as silicate or aluminum oxide powders, which scatter light and thus make the surface appear matte. Another method involves altering the surface through etching or sandblasting to create a rough texture that diffuses light.

[0008] The selection of a suitable matting agent depends on various factors, such as the desired surface texture, the type of material, and the processing conditions. Calculation formulas can be used to evaluate the effectiveness of a matting agent. One possible formula for calculating matting efficiency is based on determining the diffusion coefficient. This coefficient indicates how strongly light is scattered and depends on various physical properties of the matting agent. The most common commercially available matting agents are silica, waxes, and silicones.

[0009] Therefore, the object of the invention was to provide a multi-layered composite system with a surface of adjustable properties. The resulting measurable parameters of greater importance were gloss level, roughness, scratch resistance, chemical resistance, surface energy, anti-fingerprint properties, elongation, and frictional resistance.

[0010] This problem was solved according to independent claim 1. Advantageous embodiments are defined according to dependent claims.

[0011] According to the invention, the multilayer composite comprises at least one substrate, a functional layer based on a synthetic polymer, and an uppermost coating layer. The coating layer comprises at least one elastomeric and / or thermosetting film-forming polymer and a matting agent containing microparticles. The microparticles comprise at least polymer-based particles. The particle size of the microparticles is at most 1.5 times the thickness of the coating layer. Simultaneously, the microparticles exhibit at least two different particle sizes. The particle size distributions of these differently sized microparticles differ from each other by at least 2 µm, with the particle size distributions being characterized by the D90 value and measured according to ISO 13320-1.

[0012] Surprisingly, it was found that the coating wrinkling can be adjusted by using particles of different sizes that do not contribute to the coating's curing reaction. In this way, the dried surface of the entire multilayer composite can be individually adjusted and optimized with regard to gloss development and roughness measurement. In particular, the gloss level, haptics (e.g., softness, roughness and / or frictional resistance), scratch and chemical resistance, anti-fingerprint properties, and elongation can be optimized.

[0013] The particle size of the microparticles is at most 1.5 times larger than the thickness of the coating layer. Within the scope of the invention, the particle size distribution of microparticles is characterized by the D90 value and measured according to ISO 13320-1. Here, particle size distribution refers to the cumulative distribution, indicated by the percentiles that show the particle size above which 10% (based on the total number of particles) of the largest particles lie.

[0014] Within the scope of the present invention, "microparticles" are understood to mean particles of various shapes (e.g., spherical, plate-shaped, rod-shaped, etc.). Microparticles are defined as stable solids between D90 = 1 µm and 1000 µm, which are insoluble in common solvents but can only be dispersed into primary particles. The particle size distribution specified according to ISO 13320-1 therefore does not refer to primary particles, but to mixtures of primary particles, aggregates, and agglomerates measured by laser diffraction, which are assumed to be spherical to a first approximation. In the evaluation according to the aforementioned standard, all signals are treated as if they were generated by ideally spherical particles. Irregular particle shapes lead to broader size distributions, since both the width and length of the particles contribute to the overall signal and are included in the result.

[0015] Preferably, the particle size distribution of all microparticles has a maximum D90 of 45 µm, more preferably a maximum D90 of 25 µm, and more preferably a maximum D90 of 15 µm, with a coating layer thickness of a maximum of 30 µm, more preferably a maximum of 25 µm, and more preferably a maximum of 15 µm. According to the invention, the coating layer thickness is at least 1 µm, more preferably at least 3 µm, and most preferably at least 5 µm. The smaller the D90 value, the more haptically interesting the surface can be designed, which is manifested, for example, as a so-called "soft-touch" surface.

[0016] According to the invention, the microparticles have at least two, preferably at least three, different particle sizes. The microparticles of different sizes can be based on the same chemical composition and differ only in their particle size distribution, represented by the D90 value. Alternatively or additionally, the microparticles can have chemically different compositions and also differ in their particle size distribution, represented by the D90 value.

[0017] The particle size distributions of these differently sized microparticles differ from each other by at least D90 = 2 µm, preferably D90 = 3 µm, and more preferably D90 = 4 µm, as measured according to ISO 13320-1. This means that a multimodal distribution results from the graphical evaluation of the particle size distribution of all the microparticles.

[0018] According to the invention, the microparticles comprise at least polymer-based particles. In addition, the microparticles can, in principle, comprise all other microparticles known to those skilled in the art that are used as matting agents, i.e., agents that serve as matting agents in paints and coatings according to DIN EN ISO 8780-4:2014-05, provided that they have the particle sizes according to the invention. In preferred embodiments, the polymer-based particles are micronized modified polyolefin waxes, preferably polyethylene waxes, with a melting point of more than 100°C, preferably more than 120°C. Such suitable microparticles are commercially available and generally known to those skilled in the art. For example, microparticles from the Biomer product line of Deurex, Ceraflour of Byk, Wax PE and Wax PP of Deuteron, Lanco of Lubrizol, or Ceretan of Münzing are suitable.In preferred embodiments, the polymer-based microparticles are PTFE-free.

[0019] Alternatively or additionally, the polymer-based microparticles can be based on polymethylureas and / or polyamides. Polymethylureas are thermosetting urea-methanal polycondensates. These products are available as finely micronized powders in various size distributions and shapes. Such matting agents exhibit particularly high mechanical resistance to polishing and scratching and are especially temperature-resistant.

[0020] In preferred embodiments, the microparticles additionally comprise inorganic particles. Such inorganic microparticles can be based, for example, on silicon dioxide, corundum, titanium dioxide, zirconium dioxide, zinc oxide, magnesium silicate, barium sulfate, and mixtures thereof. Preferably, the inorganic microparticles are based on silicon dioxide (silica-based), in particular silica particles with more than 95 wt% SiO₂, based on the weight of the silica particles and determined according to ISO 3262-19, and a specific surface area of ​​50 to 600 m² / g, determined according to ISO 9277. Such silica-based microparticles exhibit high matting efficiency and transparency and provide a fine surface texture.

[0021] The concentration of microparticles in the coating composition is limited insofar as the coating dispersion required for producing the coating layer must have a minimum viscosity and must not exceed a certain viscosity for processing reasons. The microparticles can serve to adjust the static and dynamic viscosity or rheology of the polymerizable mass applied as a coating layer to the composite system. Therefore, the microparticles are present in the coating composition at a concentration of at least 0.5 wt.%, preferably at least 2 wt.%, based on the total weight of the coating dispersion to be applied. The maximum concentration depends on the type of microparticles used. For example, the coating composition may contain a maximum of 10 wt.% microparticles, preferably 6 wt.%, based on the total weight of the coating dispersion to be applied.

[0022] The coating layer according to the invention further comprises at least one film-forming polymer. The polymer can be an elastomeric polymer, a thermosetting polymer, or a mixture thereof, depending on the selected degree of cross-linking of the polymer. Preferably, the elastomeric and / or thermosetting film-forming polymer is a cross-linked poly(meth)acrylate. Particularly preferred are epoxy(meth)acrylate, urethane(meth)acrylate, polyether(meth)acrylate, polyester(meth)acrylate, silicone(meth)acrylate, silicone urethane(meth)acrylate, or mixtures thereof. The coating formulation used to produce the coating layer does not include any solvent (e.g., water, butyl acetate). The coating dispersion used to produce the coating layer comprises conventional photoinitiators which, upon irradiation with UV light, trigger polymerization of the dispersion components, leading to hardening of the coating dispersion and thus to the formation of the coating layer.Such procedures are known to the expert and require no further explanation.

[0023] The multilayer composite according to the invention comprises at least one substrate. In principle, all surfaces known to a person skilled in the art and suitable for the purpose, both indoors and outdoors, of buildings or vehicles are suitable as substrates. In particular, the substrate is a textile surface. Alternatively, the substrate can be a natural substrate, especially wood. Furthermore, the substrate can be a laminate, a plastic component, or a metal component. The multilayer composite can, for example, be artificial leather, a film for furniture surfaces (e.g., tables, kitchen units, cabinets, shelves for indoor and / or outdoor use), a window profile, a building facade (element), a garage element, a floor, or interior trim elements of an automobile. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] DIN EN ISO 8780-4:2014-05

[0018]