COATING COMPOSITION FOR FLOORING

Description

[0001] The invention relates, in particular, to two-component coating compositions for coating floor surfaces in buildings, as well as coatings produced from the compositions.

[0002] It is known to provide floor surfaces, for example made of concrete or synthetic resin, with a covering in the form of a coating in order to achieve a variety of possible advantages relating, for example, to the performance characteristics, durability or appearance of the coated surface.

[0003] Known coatings include various designs, depending on the requirements to be met, from single layers to quite complex multi-layer coating systems. Such coatings are often based on synthetic resins containing reactive components. Typical examples are reactive resins and reactive resin compositions, which contain at least one polymerizable resin, at least one hardener, and optionally other components such as fillers, pigments, and conventional additives. Examples of resins that can be used include epoxy resins, polyurethane resins, poly(meth)acrylates, polyureas, and the like.

[0004] The properties of the coating can be influenced and often improved by adding functional or structural components. For example, it is already known to improve the mechanical properties and / or the insulating effect of the

[0005] To improve the coating by adding special fillers or fibers.

[0006] For example, the introduction of carbon, polymer, glass or mineral fibers is known from EP 164 30 46 B1 or DE 10 2011 105 673 A1.

[0007] More specifically, coatings are equipped with electrically conductive components to protect against unwanted electrical effects such as electrostatic charging and discharging.

[0008] The coating makes the floor covering electrically conductive. The coating can then be connected to a grounding system, which dissipates the unwanted electrical charge and renders it harmless. Such floor coverings are covered by several standards, e.g., DIN EN 61340-4-1, DIN EN 61340-4-5, and DIN VDE 0100-410. Examples of such floor coverings are known from EP 2829581, according to which conductive carbon black or graphite are incorporated into an epoxy coating. EP 2944162 discloses a multi-layer coating system with a thin conductive synthetic resin layer containing conductive fillers such as carbon fibers.

[0009] Coating agents containing carbon fibers and inorganic fillers and used for the production of antistatic floor coverings are also known from RU 2 654 759 C.

[0010] Such known coatings contain their components in as homogeneous a distribution as possible to achieve isotropic properties. The coating components are selected accordingly to achieve this homogeneous distribution.

[0011] This is where the invention comes in. It is based on the unexpected discovery that, in order to create a fully functional coating with improved properties, it can be advantageous to forego isotropic properties of the coating and instead deliberately induce anisotropic properties.

[0012] For example, when using fibers in the coating, for example, for mechanical reinforcement, it may be advisable to concentrate the fibers in an area close to the surface. Conversely, it may be advisable to concentrate color-disrupting functional components such as conductive carbon black or copper in the area of ​​the coating far from the surface, close to the substrate, where they are less visually noticeable.

[0013] Against this background, an important object of the invention is to provide novel coating compositions which enable the production of coatings on floor surfaces of buildings and the like, with anisotropic properties of the coating.

[0014] A further object of the invention is to achieve this by means of the components of the coating composition from which the coating is formed.

[0015] A more specific object of the invention is to provide a coating composition that can be used to form an electrically conductive coating with improved properties.

[0016] The feature combinations of the independent patent claims serve to solve these and other problems.

[0017] Advantageous embodiments of the invention are defined in the dependent patent claims.

[0018] According to the invention, the objects of the invention are achieved by utilizing the effect of gravity on the coating composition after the coating composition has been applied to the substrate and before it has cured. The coating composition is still liquid after application and before curing, so that heavier components such as fillers (FS) and pigments (PG) sink and accumulate in the lower region of the coating, closest to the substrate. Accordingly, the lighter components accumulate in the region of the coating farther from the substrate.

[0019] Because of the utilization of the effect of gravity, the invention is particularly suitable for surfaces arranged approximately perpendicular to the direction of gravity, especially floor surfaces in buildings.

[0020] The desired anisotropic distribution of the coating components in the coating is advantageously influenced by a suitable selection of the size and shape of the particles that comprise these components. For example, fillers (FS) or pigments (PG), which are intended to collect in the part of the coating closest to the substrate, should be chosen in a shape that facilitates settling.

[0021] The particle size (TG) distribution of the FS / PG (fillers or pigments) is preferably bimodal for the reasons stated below.

[0022] As a rule, particle sizes below 1 µm are referred to as pigments, and larger ones as fillers. We generally use the term "filler" here, with the understanding that a filler can also be a color carrier (i.e., a pigment). "Pigment" and "filler" are therefore generally interchangeable, unless the color is specifically relevant.

[0023] At least one filler in the bimodal TG distribution should have a mean particle size (d50) of 1 µm to 30 µm, preferably 1 µm to 20 µm, and even better 1 µm to 10 µm. The mean particle size (d50) is determined according to DIN ISO 9276-1:2004-09 (Presentation of particle size analysis results - Part 1: Graphic representation) and ISO 9276-2:2014-05 (Presentation of particle size analysis results - Part 2: Calculation of mean particle sizes, diameters, and moments from particle size distributions).

[0024] The at least second filler should then have a similarly determined average particle size (d50) of less than 1µm, better less than 0.8µm, even better 0.5µm, but not less than 0.1µm.

[0025] Due to the bimodal particle size distribution, the filler / pigment layer becomes particularly compact.

[0026] Although very fine-particle fillers and / or pigments are used, their sinking capacity is sufficient due to their compactness. Compactness depends primarily on the bulk density or bulk density as well as the shape and morphology of the fillers or pigments.

[0027] The shape of the particles can be defined by the oil number of the particles.

[0028] The oil absorption, or rather its determination, is defined in DIN EN ISO 787-5. Accordingly, the oil absorption corresponds to the amount of varnished linseed oil required to completely wet a filler sample under specified conditions. Filler particles with an unfavorable (non-compact) surface-to-volume ratio and / or a structured or porous surface have a correspondingly higher oil absorption.

[0029] The oil absorption depends particularly on the surface-to-volume ratio and the morphology of the filler particles. The shape and size of the particles play a role here. While compact, round shapes favor a low oil absorption, platelet- or rod-shaped filler particles lead to an increase in the oil absorption. For example, the particles of the comparatively inexpensive filler talc, which is a phyllosilicate, have a platelet shape. According to the invention, fine fillers with compact, round particle shapes are preferred, as they sink more quickly.

[0030] Furthermore, the surface quality of the filler particles influences the oil absorption. A structured and / or porous surface, for example, leads to an increase in the oil absorption. Depending on the production, processing, and / or origin of a filler, the oil absorption can therefore vary greatly. Conversely, if fillers with the lowest possible oil absorption are used, these particles have a good surface-to-volume ratio or are relatively "spherical" (as long as no porous fillers are used). If all filler particles are relatively spherical, they can be packed more densely. If relatively spherical filler particles of different sizes are used, the density of the sphere packing can be further increased. The smaller particles then sit in the gaps between the larger particles. The solids content is thus optimized.

[0031] It is also preferable to use fillers or pigments with the highest possible density, since heavier particles sink more quickly than lighter ones.

[0032] In a preferred embodiment of the invention, the coating composition is formulated so that it can be used to produce an electrically conductive coating suitable for dissipating static charges and discharges. The invention is explained in more detail below using this coating composition as an example (however, the generalized statements made therein also apply to other embodiments of the invention, for example, those in which electrical conductivity is not important).

[0033] In this embodiment, the coating composition is based on a two-component epoxy resin. It should be noted that single- or multi-component coating compositions can also be realized using the same principle.

[0034] As already explained in the introduction, synthetic resin-based coatings are known which contain particulate electrically conductive substances such as conductive carbon black or graphite in order to produce conductive floor coverings.

[0035] To achieve sufficient electrical conduction in flooring areas, the current state of the art relies on coating systems. A first, highly conductive layer of conductive paint or paste is applied to the substrate. This layer contains a high concentration of conductive substances such as carbon black or copper and is therefore highly colored. Tinting or coloring is not possible. Grounding is incorporated into this conductive primer. The electrical charges are dissipated horizontally in the coating plane down to the grounding point.

[0036] Additional layers are then applied to this primer, fulfilling other functions such as color and durability. However, these additional layers must possess sufficient "through-conductivity," i.e., sufficient conductivity perpendicular to the coating plane. Typically, the coatings do not have a preferred direction of conductivity; rather, the conductivity is isotropic. Conductivity is achieved by adding electrically conductive additives such as conductive carbon black or graphite, which are homogeneously distributed throughout the coating film.

[0037] A significant disadvantage of using conductive carbon black or graphite in conductive coatings is that significant amounts of these functional additives are required to achieve acceptable conductivity. Suitable conductive carbon blacks / graphites are also expensive. Often, they are synthetically produced pigments in which a conductive component is applied to a suitable carrier material. (For simplicity, we will refer to "conductive carbon black" below.)

[0038] The use of larger amounts of conductive carbon black results in a dark coating (often dark gray to black). The coloring and tinting of such a coating is limited or even impossible. The conductive carbon black is usually homogeneously dispersed in one component of the two-component coating composition and stabilized by suitable dispersing and wetting agents. Therefore, even in the applied dry coating film, the conductive carbon black is homogeneously distributed throughout the entire film thickness. This is generally not a disadvantage, but in comparison, the invention leads to a significant improvement in properties.

[0039] Significantly better conductivities can be achieved by using highly electrically conductive fibrous materials instead of these particulate substances (such as conductive carbon black). Commercially available carbon nanotubes (CNTs) are particularly suitable for this purpose. They advantageously combine particularly high electrical conductivity with a fibrous structure that contributes significantly to the mechanical strength of the coating.

[0040] The invention makes it possible to replace dark / black functional additives such as conductive carbon black / graphite with more powerful conductive additives (CNTs). The amount used is thereby reduced.

[0041] The advantages include increased performance, increased efficiency, cost reduction, improved tintability, and color design. The variety of combinations with other (functional) coatings (in a multi-layer coating system) is significantly increased.

[0042] Furthermore, other properties can be improved: anisotropic mechanical strength and elasticity (due to fiber enrichment, these mechanical properties can differ parallel and perpendicular to the coating plane). Added to this are material and time savings.

[0043] However, replacing conductive carbon black with the significantly more conductive and efficient carbon nanotubes (CNTs) according to the invention is not trivial. The (non-polar) CNTs are difficult to disperse and stabilize. In the presence of other (polar) fillers and pigments in one component of the 2-component coating composition, they cannot be dispersed and stabilized using conventional dispersants (used to disperse the polar fillers).

[0044] Due to the high prices for CNTs, only small amounts of CNTs should be used as efficiently as possible.

[0045] A very important aspect of the invention that helps overcome these problems is the aforementioned self-organization of a structure (layer, ply) within the coating film during the curing phase under the influence of gravity. In preferred embodiments, this is the enrichment of the functional fibers (e.g., CNTs) in a layer. Due to the compactness of the filler / pigment layer—promoted by the bimodal particle size distribution—the residual volume of the coating film in which the functional fibers are enriched is reduced. This increases the concentration of the functional fibers in the residual volume. The conductivity of the floor covering is therefore anisotropic and most pronounced within a "conducting plane" parallel to the coating plane. The self-organization is gravity-driven and therefore only functions on horizontal surfaces.

[0046] The ready-to-use coating composition contains functional, electrically conductive fibers (CNT), which are relatively light, as well as compact and heavy fillers and / or pigments.

[0047] A basic principle of the invention is that the heavy and compact fillers / pigments sink to the bottom and the lighter functional fibers arrange themselves above them.

[0048] The prerequisites for this are "Heaviness" of fillers / pigments: Bulk density greater than 4.2 kg / dm³. Compactness of fillers / pigments: Oil absorption (ISO 787 Part 5) less than or equal to 25 g / 100 g, preferably less than or equal to 20 g / 100 g, even more preferably less than or equal to 15 g / 100 g. "Lightness" of functional fibers: Bulk density between 1.0 kg / dm³ and 2.0 kg / dm³, better between 1.1 kg / dm³ and 1.9 kg / dm³, even better between 1.2 kg / dm³ and 1.8 kg / dm³. Fibers are not compact, but are considerably smaller (shorter) in at least one spatial direction than in others. Due to their geometric shape, the fibers do not sink as quickly as the FS / PG.

[0049] The dispersion and stabilization of fillers, pigments, and fibers is of crucial importance. In conventional coating compositions, the goal is to achieve the best possible dispersion in order to ensure the ingredients are distributed as evenly as possible throughout the coating film.

[0050] Since the invention avoids such a homogeneous distribution of the ingredients, the use of wetting and dispersing agents must be carried out in measured doses. Only enough dispersing agent should be used for stabilization to prevent agglomeration or conglomeration of the fillers / pigments. A sediment of the fillers / pigments can therefore form relatively quickly in the ready-to-use coating composition, but it must be easily resuspendable. The formation of such a sediment is an indication that the invention is working. However, the time for the sediment to form is not fixed or uniform, but must be adapted to the pot life and processing time. The measures required for this are known to the person skilled in the art.

[0051] Furthermore, it is virtually impossible to disperse and permanently stabilize polar fillers alongside non-polar functional fibers in a coating composition. At least two different dispersing and wetting agents would be required.

[0052] Therefore, it is advantageous to start with a two-component coating composition, with the FS / PG and the functional fibers incorporated into different components. The FS / PG are incorporated into component A (hardener component) and the fibers into component B (epoxy resin or isocyanate component).

[0053] Furthermore, it is advantageous that the fibers are incorporated into component B without dispersing agents in order to avoid later incompatibilities or unwanted interactions with components of component A.

[0054] The FS / PG must be heavy and compact. Therefore, oxidic, sulfidic, and / or sulfatic heavy metal compounds are particularly suitable. "Heavy metals" within the meaning of the invention are metallic elements with an atomic number greater than or equal to 21 (beginning of the transition group elements). The FS / PG are particularly preferably selected from the group comprising barium sulfate, zinc oxides or sulfides, tin oxides or sulfides, copper oxides or sulfides, iron oxides or sulfides, manganese oxides or sulfides, vanadates, titanium oxides, and zirconium oxides, particularly preferably in the rutile modification.

[0055] The bulk density, also called apparent or geometric density or volume weight, is the density of a porous solid based on the volume including the pore spaces.

[0056] The determination of bulk density, true density, and porosity is carried out according to DIN EN 1936, February 2007 (corresponds to the German version EN 1936:2006). Bulk and true densities are usually not determined by the user themselves, but are specified by the manufacturer or listed in tables in reference works.

[0057] With non-porous fillers / pigments, the bulk density approaches the true density. This is also the case with the preferred, compact fillers / pigments according to the invention.

[0058] The oil absorption of the FS / PG, which allows for statements about the morphology of the particles (particle shape, surface-to-volume ratio, surface texture, porosity, etc.), must be less than or equal to 25 g / 100 g, preferably less than or equal to 20 g / 100 g, and even more preferably less than or equal to 15 g / 100 g. The lower the oil absorption and the higher the density, the more compact and heavier the FS / PG are, and the more favorable their sinking behavior in the uncured coating film.

[0059] In other preferred embodiments, other fibers can be considered as functional fibers instead of or in addition to carbon nanotubes, e.g., carbon, polymer, glass, and / or mineral fibers, depending on the desired anisotropic function in the coating. To increase the electrical conductivity of the coating, electrically conductive fibers such as conventional carbon fibers or fibers made of conductive polymers should be used. Due to their outstanding properties, carbon nanotubes are preferred, most preferably single-wall carbon nanotubes (SWCNTs).

[0060] To be enriched above the heavy FS / PG (preferably in one layer), the functional fibers must be "light." They should have a bulk density between 1.0 kg / dm 3 and 2.0 kg / dm 3 , preferably between 1.1 kg / dm 3 and 1.9 kg / dm 3 , and even better between 1.2 kg / dm 3 and 1.8 kg / dm 3 . It is correct to speak of bulk density here, since the functional fibers may also include hollow fibers.

[0061] The fibers are on average between 0.1 µm and 1000 µm long, more preferably between 0.5 µm and 100 µm long, even more preferably between 1.0 µm and 50 µm long.

[0062] The fiber thickness (diameter of the fibers) is between 0.1 nm and 100 nm, more preferably between 0.5 nm and 50 nm, even more preferably between 0.6 nm and 20 nm.

[0063] According to the manufacturer's specifications, the CNTs preferred according to the invention have diameters of less than 2 nm and a length of > 1 micrometer.

[0064] The synthetic resin base preferably comprises known reactive binders based on epoxy resin or polyurethane. The reactive binders are preferably at least two-component. The curing process only begins when the reactive components are combined. The curing rate (and thus the pot life, processing time, and time until complete curing) can be controlled by the mixing ratio of the reactive components and is within the skill of the expert.

[0065] When selecting dispersants, the skilled person can rely on known methods. The amount used should be "sparing," but depends on the type of dispersant chosen, the fillers / pigments, and the other components of the coating composition. This selection is also within the skill of the skilled person.

[0066] The two-component coating composition according to the invention may be solvent-based, but is preferably aqueous. Water-based coating compositions are preferred from an ecological and toxicological perspective.

[0067] In the cured coating according to the invention, there are at least two distinct zones (layers or layers) due to gravity. The fillers and / or pigments are concentrated in a lower (near-substrate) zone. Above this zone lies a zone containing the functional fibers. These are arranged within this zone or layer in such a way that they form a two-dimensional network through which electrical charges can be dissipated. Thus, a particularly conductive zone (layer, layer) is created within the coating film.

[0068] Above the "fiber zone," there may be another zone (layer, layer) containing primarily the binder and possibly other ingredients such as dyes, etc. These additional ingredients can be substances that are, for example, even "lighter" than the fibers and have even more buoyancy, or substances that are dissolved in the binder.

[0069] The boundaries between the individual zones, layers, or strata are not sharp, but fluid. A sharp demarcation is also undesirable, because then the conductivity perpendicular to the "conducting plane" or coating plane would be very low or could potentially approach zero, which is not advantageous. Transporting electrical lines exclusively within the "conducting plane" would require that precisely this "conducting plane" (with the enrichment of CNTs) be connected to ground (thin grounded copper plates or contacts). In practice, this could lead to difficulties. It is easier to ground the entire coating film according to the invention or to embed the grounding in the coating film.

[0070] The specific resistance of the floor covering parallel to the coating is less than 1.0E+6 Ω*m, preferably less than 1.0E+5 Ω*m, even better less than 1.0E+4 Ω*m, and ideally less than 1.0E+3 Ω*m. The specific resistance perpendicular to the coating film is less than 1.0E+11 Ω*m, preferably less than 1.0E+9 Ω*m, even better less than 1.0E+7 Ω*m, but at least 10 times, preferably 100 times, or even better 1000 times higher than the specific resistance (parallel). Example

[0071] A 2K coating composition according to the invention comprises the following components: Component A : filled hardener component 35.0 wt.% Water 18.0 wt.% Amine hardener 41.0% by weight Fillers and / or pigments such as BaSO4 (d50 ~ 4µm) and TiO2 (d50 ~ 0.4µm) 1.0 wt.% Dispersing and wetting agents 5.0 wt.% Additives such as defoamers, surface and leveling additives, other colored pigments, etc. Component B : Epoxy resin mixture 65.0% by weight Epoxy resin A 23.0 wt.% Epoxy resin F 2.0 wt.% Carbon nanotubes 10 wt.% Epoxy reactive thinner

[0072] The mixing ratio of component A to component B is 100 to 22 parts by weight.

[0073] The coating is applied to the substrate with a wet film thickness of at least 40 µm to 500 µm, but at least five times the d50 value of the largest filler / pigment, and preferably ten times the d50 value. This ensures sufficient "fall height" and sufficient time for the particles and fibers to orient and separate as they sink within the still-liquid coating film.

[0074] The application can be carried out up to a dry layer thickness of 0.5 mm, but preferably a maximum of 0.3 mm, even better a maximum of 0.1 mm, but at least 40 µm.

[0075] The resistivity measurements were performed using a Metriso 2000 digital high-ohmmeter and were taken on free films of the coatings with a dry film thickness of 0.1 mm after one day and 28 days of drying under standard conditions. The geometric parameters of cross-section (area) and electrode spacing were taken into account when calculating the resistivity.

[0076] The resistivity of the soil coating within the "conductive plane" is 60 Ω*m (1 d) and 80 Ω*m (28 d), and perpendicular to the coating plane, 3.9E+5 Ω*m (1 d) and 6.4E+5 Ω*m (28 d). After 28 days, the resistivity values ​​hardly changed.

[0077] For comparison, an anisotropic specific resistance of 1.1E+5 Ω*m (1 d) and 4.3E+3 Ω*m (28 d) was determined for a corresponding commercially available conductive floor coating with conductive pigments.

Claims

1. A coating composition for coating floor areas which are orientated substantially perpendicular to the gravitational force direction, in particular surfaces such as flooring in buildings, comprising an organic binder, fillers and / or pigments and functional fibres, characterized in that the fillers and / or pigments have a bulk density in accordance with DIN EN 1936 of more than 4.2 kg / dm3 and an oil absorption value in accordance with DIN EN ISO 787-5 of less than or equal to 25 g / 100g and the bulk density of the functional fibres is between 1.0 kg / dm3 and 2.0 kg / dm3.

2. The coating composition as claimed in claim 1, characterized in that the binder is an at least two- component binder, wherein the fillers / pigments are situated in a first component and the functional fibres are situated in a second component.

3. The coating composition as claimed in claim 1 or claim 2, characterized in that the binder is a reactive binder selected from epoxy resins or polyurethane resins and is preferably an aqueous 2K epoxy resin, wherein the fillers and / or pigments are incorporated into the component A (curing component) and the fibres are incorporated into the component B (epoxy resin or isocyanate component).

4. The coating composition as claimed in one of the preceding claims, characterized in that the fillers and / or pigments have an oil absorption value of less than or equal to 20 g / 100g, preferably less than or equal to 15 g / 100g.

5. The coating composition as claimed in one of the preceding claims, characterized in that the fillers / pigments are oxide, sulphide and / or sulphate heavy metal compounds and are preferably selected from the group comprising barium sulphate, zinc oxides or sulphides, tin oxides or sulphides, copper oxides or sulphides, iron oxides or sulphides, manganese oxides or sulphides, vanadates, titanium oxides and zirconium oxides.

6. The coating composition as claimed in one of the preceding claims, characterized in that the fillers and / or pigments are present in a bimodal particle size distribution, wherein preferably, at least one first filler / pigment in the bimodal PS distribution has a mean particle size (d50) of 1 µm to 30 µm, preferably of 1 µm to 20 µm, more preferably of 1 µm to 10 µm and at least one second filler / pigment has a mean particle size (d50) of less than 1 µm, preferably less than 0.8 µm, more preferably 0.5 µm, but preferably not less than 0.1 µm.

7. The coating composition as claimed in one of the preceding claims, characterized in that the functional fibres have a bulk density between 1.1 kg / dm3 and 1.9 kg / dm3, more preferably between 1.2 kg / dm3 and 1.8 kg / dm3.

8. The coating composition as claimed in one of the preceding claims, characterized in that the functional fibres are selected from carbon nanotubes (CNT), carbon fibres, polymer fibres, glass fibres and / or mineral fibres, preferably from electrically conductive fibres such as carbon fibre, fibres produced from conductive polymers and preferably carbon nanotubes, most preferably single-walled carbon nanotubes (SWCNT).

9. The coating composition as claimed in claim 7, characterized in that the carbon nanotube (CNT) functional fibres have a diameter between 0.1 nm and 100 nm, more preferably between 0.5 nm and 50 nm, yet more preferably between 0.6 nm and 20 nm and particularly preferably less than 2 nm for a length of > 1 micrometre.

10. A coating for floor areas which are orientated substantially perpendicular to the gravitational force direction, in particular surfaces such as flooring in buildings, comprising an organic binder, fillers and / or pigments and functional fibres, which can be produced by means of the coating composition as claimed in at least one of the preceding claims.