Tint base and tinted coating composition

Description

[0001] The invention relates to a tinting base for a tinted coating composition, in particular for forming a tinted coating on a sheet material. Furthermore, the invention relates to a tinted coating composition produced from a tinting base according to the invention. State of the art

[0002] Tinted coatings are used in the construction industry for the color design of surfaces, such as sheet materials. These sheet materials can be, in particular, facade panels, for example, fiber cement panels, which are attached to the exterior wall of a building using a substructure to create a ventilated facade. The sheet materials or facade panels used here are pre-coated with a tinted coating at the factory, so that after the panels are attached to the exterior wall, no further coating, especially a final coat of paint, is necessary.

[0003] To create a tinted coating, a tinted coating composition is generally used, containing a tinting base and color pigments, especially a color pigment mixture, often in the form of a pigment paste, to adjust the color. The more intense the color achieved through the color pigments, the higher the requirements regarding color stability and gloss retention of the tinted coating applied to the panel material.

[0004] Especially with sheet materials used in curtain wall facades, undesirable color changes can often occur due to sunlight.

[0005] Exposure to electromagnetic radiation in the range of 350 nm to 2500 nm, i.e., in the UV to IR range, can permanently damage individual components of a tinted coating. For example, it can lead to the destruction of color pigments, resulting in pigment failure and / or damage to the binder matrix. Furthermore, electromagnetic radiation can cause certain components, such as additives, to degrade photolytically.

[0006] If the color changes occur primarily over a large area, this is usually due to the UV component of sunlight. If the color changes occur primarily in the area of ​​the substructure, this creates thermal bridges. Here, the thermal influence of electromagnetic radiation in the NIR range, i.e., the near-infrared range, becomes noticeable. In both cases, the electromagnetic radiation leads to permanent damage to the tinted coating.

[0007] To prevent damage from UV radiation, UV protectants can be added. However, these are very expensive and lose their protective effect over time. To prevent damage from NIR radiation, NIR-reflecting color pigments can be added. However, these are also very expensive, and the color selection is limited.

[0008] Another approach involves reducing the pigment volume concentration (PVC). Achieving a low PVC requires a high proportion of binder, particularly dispersion binders. This is neither economically nor fire safety-wise justifiable. Furthermore, a single coat of paint is usually insufficient to form the tinted coating, necessitating the application of multiple layers.

[0009] WO 2023 / 215254 A1 provides an example of a coating composition that can be used as a paint and contains an organic polymer binder with a glass transition temperature > 45°C as well as other components.

[0010] The present invention addresses the problem of eliminating or at least reducing the disadvantages of the prior art. To achieve this problem, the tinting base with the features of claim 1 is specified. Advantageous embodiments of the invention are described in the dependent claims. Furthermore, a tinted coating composition containing a tinting base according to the invention is specified. Disclosure of the invention

[0011] The proposed tinting base for a tinted coating composition, in particular for forming a tinted coating on a sheet material, contains: at least one organic polymer binder with a glass transition temperature (TG) according to EN ISO 16805 > 45°C, preferably > 50°C, further preferably > 55°C, comprising at least one filler of barium sulfate and / or calcium carbonate, comprising (i) a mean particle size D50 according to DIN ISO 9276-1:2004-09 and ISO 9276-2:2014-05 of 1-20 µm, preferably of 1-15 µm, further preferably of 2-10 µm, and (ii) an oil number according to DIN EN ISO 787-5 of 1-22 g / 100 g, preferably of 2-18 g / 100 g, further preferably of 3-15 g / 100 g, wax, conventional additives and water.

[0012] A key feature of the invention is the at least one filler, consisting of barium sulfate and / or calcium carbonate, contained in the proposed tinting base. Due to their chemical composition, both fillers exhibit high reflective properties, which, particularly in the range of 350 nm to 2500 nm, result in minimal absorption of electromagnetic radiation, with almost all of it being reflected. The reflective properties of barium sulfate, especially in the visible light range, even exceed those of known white pigments such as titanium dioxide or zinc oxide. Calcium carbonate behaves similarly, although its reflective properties in the UV and short-wave range are somewhat inferior to those of barium sulfate. Calcium carbonate also has a slight yellow tint, which can influence the color quality depending on the specific hue. In this case, barium sulfate is the preferred filler.

[0013] When selecting the filler (at least one) contained in the tinting base, not only its chemical composition is important, but also its average particle size and oil content. These factors determine the color depth and quality of the resulting tinted coating. Average particle size and oil content are mutually dependent.

[0014] The mean particle size D50, also called the D50 value or median value, indicates the average particle size of a filler such that the proportion of particles larger than the D50 value is equal to the proportion of particles smaller than the D50 value. These values ​​are preferably determined according to DIN ISO 9276-1:2004-09 (Presentation of results of particle size analyses - Part 1: Graphical representation) and ISO 9276-2:2014-05 (Presentation of results of particle size analyses - Part 2: Calculations of mean particle sizes / diameters and moments from particle size distributions). The Mastersizer 3000 from Malvern Instruments Limited can be used as an instrument for size determination. However, these values ​​can usually also be easily obtained from a technical data sheet.

[0015] The filler contained in the proposed tinting base, at least one of which has a comparatively low D50 value of 1-20 µm, and thus an improved (diffuse) reflectivity.

[0016] The oil number according to DIN EN ISO 787-5 correlates with the specific surface area of ​​the individual filler particles, which in turn is determined by the size and morphology of the filler particles. Fillers consisting of very small particles with lamellar particle shapes and / or porous surfaces have a larger specific surface area and thus a higher oil number than fillers consisting of larger particles with a nodular, i.e., rounded-compact, particle shape. In the paint and coatings industry, the oil number is a frequently used characteristic value for pigments and / or fillers. It represents a measure of the binder requirement of the respective pigment and / or filler. The higher the oil number, the greater the binder requirement.

[0017] The at least one filler contained in the proposed tinting base has a comparatively low oil content of 1-22 g / 100 g (preferably 2-18 g / 100 g, and even more preferably 3-15 g / 100 g). A high oil content, on the other hand, would significantly increase the binder requirement and thus impair the color depth of the subsequent tinted coating.

[0018] A filler that is intended to have a low oil number combined with a low D50 value must have a nodular, compact particle shape, as is the case, for example, with barium sulfate. Furthermore, it exhibits a very high pure or crude density, which is less than 4.3 g / cm³. Therefore, even with a low D50 value, barium sulfate can still maintain a very low oil number. Calcium carbonate achieves an oil number of 10–22 g / 100 g at a D50 value of 2–10 µm. Other fillers, such as calcined kaolin, in contrast, already exhibit an oil number of over 55 g / 100 g at a D50 value of 5 µm.

[0019] The high density of barium sulfate offers a further significant advantage: it leads to a reduced pigment volume concentration (PVC) for the same weight fraction of filler.

[0020] The PVK (pigment binder content) denotes the ratio of the volume of the contained pigments and fillers to the total volume of non-volatile components, typically pigments, fillers, and binders. It is therefore a crucial parameter for characterizing the volume ratio of pigment and filler to binder. The lower the PVK, the higher the binder content generally is. DIN EN ISO 4618-1 can be used to determine the PVK. The following formula can be used to calculate the PVK: PVK % = ∑ V Pigmente + ∑ V Füllstoffe / ∑ V Pigmente + ∑ V Füllstoffe + ∑ V Bindemittel × 100

[0021] The pigment volume concentration according to DIN EN ISO 4618-1 is preferably 5-40%, preferably 10-30%, and further preferably 15-25% for the proposed tinting base. By using a filler with a high pure or bulk density, a correspondingly low pigment volume concentration can be achieved even without increasing the binder content. This is because a heavier filler occupies less volume, thus increasing the volume-related binder content.

[0022] In addition to barium sulfate and / or calcium carbonate, at least one other filler may be included. In this case, however, the proportion of the at least one other filler is less than 15% by weight, preferably less than 10% by weight, and further preferably less than 5% by weight, based on the total weight of the fillers contained.

[0023] Preferably, the proportion of fillers is 10-40 wt.%, preferably 15-35 wt.%, and more preferably 20-30 wt.%, based on the total weight of the starting materials.

[0024] Furthermore, the at least one organic polymer binder contained in the tinting base contributes to solving the aforementioned problem. This binder exhibits high UV resistance and high color stability at a glass transition temperature (TG) > 45°C. Moreover, the at least one organic polymer binder is characterized by good blocking resistance, despite low PVK (polycyclic aromatic hydrocarbon) or a high volumetric binder content.

[0025] The at least one organic polymer binder contained in the tint base is preferably a polymer binder based on vinyl acetate / ethylene copolymers, copolymers based on vinyl aromatics, in particular styrene, and acrylates, and / or homo- or copolymers based on pure acrylates, in particular styrene acrylate copolymers, and / or pure acrylates comprising homo- or copolymers of acrylates and / or methacrylates, optionally with acrylic and / or methacrylic acid as a comonomer. Self-crosslinking core-shell polymer binders based on acrylates, in particular pure acrylates, are especially suitable. Homo- or copolymers based on pure acrylates and / or styrene acrylate copolymers are particularly preferred as the organic polymer binder.

[0026] Preferably the proportion of organic polymer binder is 10-40 wt.%, preferably 15-35 wt.%, and more preferably 20-30 wt.%, based on the total weight of the starting materials.

[0027] The wax contained in the tinting base also plays an important role. It acts as an anti-settling agent, which is particularly advantageous when using "heavy" fillers. Furthermore, the wax in the tinting base increases the mechanical strength of the resulting coating.

[0028] Preferably, the at least one wax is of fossil origin, a semi-synthetic wax, and / or a synthetic wax. Suitable examples include paraffin wax, amide wax, modified montan wax, polypropylene wax, and / or polyethylene wax, particularly high-density polyethylene wax (HDPE wax). The use of a non-polar wax, such as paraffin wax or HDPE wax, increases the water resistance of the subsequent coating. Furthermore, the at least one wax contained in the tinting base preferably has a melting range between 110°C and 150°C, preferably between 120°C and 145°C, and even more preferably between 125°C and 140°C. The relatively high melting range of the wax increases the blocking resistance ("anti-blocking"), with paraffin wax and / or HDPE wax again being preferred for this purpose.

[0029] Furthermore, the at least one wax contained in the tinting base can serve as a matting agent. The mean particle size D50 of the wax contained as a solid is crucial for this. Therefore, the mean particle size D50 of the at least one wax is preferably 50-1000 nm, more preferably 50-600 nm, and even more preferably 50-400 nm.

[0030] Furthermore, the proportion of wax is preferably 0.5-3.0 wt.%, preferably 0.6-2.5 wt.%, and more preferably 0.8-2.0 wt.%, based on the total weight of the starting materials.

[0031] Furthermore, an amorphous silicate, in particular amorphous silica, is preferably included as a matting agent. Since amorphous silica is a solid that is difficult to stabilize, its use in combination with the at least one wax proves advantageous, as the wax acts as an anti-settling agent. The mean particle size D50 of the amorphous silicate is 1–30 µm, preferably 4–25 µm, and more preferably 6–20 µm.

[0032] Furthermore, the tinting base may contain rheological additives, thickeners, wetting and dispersing agents, in-can and film preservatives, film-forming aids, biocides, defoamers, deaerators, light stabilizers, radical scavengers, pH adjusters, water repellents, and / or fibers as conventional additives. The processing properties of the composition can be adjusted using these conventional additives. Preferred rheological additives are thickeners based on polyacrylate and / or polyurea, preferably a combination thereof. These additives have significantly improved the flow and runnability of the tinting base or of a tinted coating composition produced from it. A silicone oil-based defoamer or deaerator is preferably included in the tinting base.

[0033] Preferably, the proportion of additives contained in the tinting base is 1-10 wt.%, more preferably 2-8 wt.%, and further preferably 3-6 wt.%, based on the total weight of the starting materials. This also includes matting agents, such as amorphous silicate, if present. However, the wax content is excluded, as it is specified separately.

[0034] Furthermore, the proportion of water is preferably 20-70 wt.%, preferably 30-60 wt.%, and more preferably 35-55 wt.%, based on the total weight of the starting materials.

[0035] To obtain a tinted coating composition, a color pigment or a mixture of color pigments, for example in the form of a pigment paste, simply needs to be added to the tinting base. The hue and color intensity can then be adjusted by the addition, and especially the quantity, of at least one color pigment.

[0036] In a further development of the invention, a tinted coating composition is therefore additionally proposed, which is particularly suitable for forming a tinted coating on a sheet material. The tinted coating composition contains a tinting base according to the invention as well as at least one color pigment, preferably a color pigment mixture, for example in the form of a pigment paste. Any desired color shade can be achieved via the at least one color pigment. The incorporation into the tinting base can be carried out, in particular, using known mixing methods.

[0037] Preferably, the proportion of color pigments is a maximum of 12% by weight, or better, a maximum of 10% by weight, based on the total weight of the starting materials of the coating composition. In this way, a tinted coating composition with PVK values ​​between 20 and 30% is obtained, even for intense colors.

[0038] Furthermore, a coating composition made from a tinting base according to the invention and at least one color pigment must be applied in only one layer to produce a tinted coating with high color depth and color quality.

[0039] A specific embodiment of a tinting base according to the invention for a tinted coating composition is given below. Example of implementation (tonal base)

[0040] 25,0 % by weight organic polymer binder based on pure acrylate (solid) 25,0 % by weight Barium sulfate filler (D50 value: 6 µm, oil number: 10 g / 100 g) 1,5 % by weight Wax (solid) 5,0 % by weight common additives, in particular alkalizing agents, wetting and dispersing agents, defoamers, matting agents, film-forming aids, preservatives, thickeners, leveling agents, etc.) 43,5 % by weight Water 100 % by weight

[0041] To produce the tinting base, all raw materials are mixed homogeneously. The tinting base produced in this way has the following technical properties: PVK: approximately 22% Solid fraction: approximately 53% Organic content: approximately 50%

[0042] To create a tinted coating composition, only one or more color pigments need to be added to the tinting base.

[0043] The following is an exemplary embodiment of a tinted coating composition produced from the tinting base specified above, in the form of a dispersion paint in the color anthracite (RAL 7016). For this purpose, 10.5 parts by weight of a pigment preparation in paste form, containing titanium dioxide, iron oxides, and organic pigments (total pigment content 70% by weight based on the total weight of the pigment preparation), were added to 100.0 parts by weight of the tinting base and homogenized. The PVK (polycyclic aromatic hydrocarbon) of the tinted coating composition, or dispersion paint, was approximately 35%.

[0044] For outdoor weathering tests, the tinted coating composition or dispersion paint was applied to several panels, specifically the following panels: a fiber cement panel, a composite panel consisting of two aluminum cover sheets and a mineral-filled polymer core ("Alucobond") and a panel made of pressed, high-density rock wool ("Rockpanel").

[0045] These plates were chosen because they differ in thermal conductivity and heat storage capacity. Whether these differences have an effect in the experiment should also be investigated.

[0046] Subsequently, in March 2022, the coated panels were exposed to outdoor weathering in southern Germany, i.e., in a cool temperate climate zone. The coated panels were oriented to the south and installed at a 45° angle to the ground level.

[0047] As a reference example, another tinted coating composition was produced, in whose tinting base an aluminum hydroxide (D50 ~5 µm, OE 30 g / 100 g) was used as a filler in equal proportions by weight. The PVK of this tinted coating composition was approximately 45%. The coating composition serving as a reference example was also applied to several panels, using the same panel types. These were then exposed to outdoor weathering in southern Germany in the same orientation and arrangement.

[0048] For all coated panels, color variations (ΔE) and gloss development (at 85°C) were recorded after 18 months of outdoor weathering and compared with the respective initial values. The following results were obtained: Color deviation (ΔE) according to EN ISO 11664-4

[0049] 18 months Example of implementation Fiber cement 0,9 Reference example 3,8 Example of implementation Alucobond 0,8 Reference example 3,2 Example of implementation Rockpanel 0,8 Reference example 2,8 Gloss development (at 85°C) according to DIN EN ISO 2813 (compared to initial value)

[0050] Initial value 18 months Example of implementation Fiber cement 11,1 13,5 Reference example 11,2 9,3 Example of implementation Alucobond 7,2 11,6 Reference example 11,0 5,5 Example of implementation Rockpanel 9,8 13,4 Reference example 13,2 10,3

[0051] A ΔE value below 1.0 corresponds to a very small color deviation. For example, with a ΔE value below 0.5, the color deviation is no longer perceptible to the naked eye. This means that in the embodiments according to the invention, the color deviation was minimal. In contrast, in the reference examples with ΔE values ​​around 3.0 and above, clear to strong color deviations occurred.

[0052] With regard to gloss development, the panels coated with a tinted coating composition according to the exemplary embodiment also showed better results. In particular, improved tolerance to dulling or loss of gloss was observed, regardless of the type of underlying panel.

Claims

1. A tint base for a tinted coating composition, in particular for forming a tinted coating on a panel material, containing - at least one organic polymer binder with a glass transition temperature (TG) according to EN ISO 16805 of > 45 °C, preferably > 50 °C, more preferably > 55 °C, - at least one filler produced from barium sulphate and / or calcium carbonate, having (i) a mean particle size D50 according to DIN ISO 9276-1:2004-09 and ISO 9276-2:2014-05 of 1-20 µm, preferably of 1-15 µm, more preferably of 2-10 µm, and (ii) an oil absorption value according to DIN EN ISO 787-5 of 1-22 g / 100g, preferably of 2-18 g / 100g, more preferably of 3-15 g / 100g, - at least one wax, - conventional additives, and - water.

2. The tint base as claimed in claim 1, characterized in that the pigment volume concentration according to DIN EN ISO 4618-1 is 5-40%, preferably 10-30%, more preferably 15-25%.

3. The tint base as claimed in claim 1 or claim 2, characterized in that it contains at least one further filler, wherein the proportion of the at least one further filler is less than 15% by weight, preferably less than 10% by weight, more preferably less than 5% by weight, with respect to the total weight of the fillers contained in the filler combination.

4. The tint base as claimed in one of the preceding claims, characterized in that the proportion of fillers is a total of 10-40% by weight, preferably 15-35% by weight, more preferably 20-30% by weight, with respect to the total weight of the starting materials.

5. The tint base as claimed in one of the preceding claims, characterized in that the at least one organic polymer binder is a polymer binder on the basis of vinyl acetate / ethylene copolymers, copolymers on the basis of vinyl aromatics, in particular styrene, and acrylates, and / or homopolymers or copolymers on the basis of pure acrylates, in particular on the basis of styrene acrylate copolymers, and / or pure acrylates, comprising homopolymers or copolymers of acrylates and / or methacrylates, optionally with acrylic acid and / or methacrylic acid as the comonomeric unit.

6. The tint base as claimed in one of the preceding claims, characterized in that the proportion of organic polymer binder is 10-40% by weight, preferably 15-35% by weight, more preferably 20-30% by weight, with respect to the total weight of the starting materials.

7. The tint base as claimed in one of the preceding claims, characterized in that the at least one wax is a wax of fossil origin, a semi-synthetic wax and / or a synthetic wax, for example a paraffin wax, an amide wax, a modified montan wax, a polypropylene wax and / or a polyethylene wax, in particular a high density polyethylene wax, and has a melting range between 110°C and 150°C, preferably between 120°C and 145°C, more preferably between 125°C and 140°C.

8. The tint base as claimed in one of the preceding claims, characterized in that the mean particle size D50 of the at least one wax is 50-1000 nm, preferably 50-600 nm, more preferably 50-400 nm.

9. The tint base as claimed in one of the preceding claims, characterized in that the proportion of wax is 0.5-3.0% by weight, preferably 0.6-2.5% by weight, more preferably 0.8-2.0% by weight, with respect to the total weight of the starting materials.

10. The tint base as claimed in one of the preceding claims, characterized in that it contains an amorphous silicate, in particular amorphous silica, as a matting agent, wherein the mean particle size D50 of the amorphous silicate is 1-30 µm, preferably 4-25 µm, more preferably 6-20 µm.

11. The tint base as claimed in one of the preceding claims, characterized in that it contains rheological additives, thickening agents, wetting agents and dispersion agents, in-can preservatives and film preservatives, film-forming agents, biocides, defoaming agents, deaerators, light stabilizers, radical scavengers, pH adjusters, water-repellent agents and / or fibres as the conventional additives.

12. The tint base as claimed in one of the preceding claims, characterized in that the proportion of additives is 1-10% by weight, preferably 2-8% by weight, more preferably 3-6% by weight, with respect to the total weight of the starting materials.

13. The tint base as claimed in one of the preceding claims, characterized in that the proportion of water is 20-70% by weight, preferably 30-60% by weight, more preferably 35-55% by weight, with respect to the total weight of the starting materials.

14. A tinted coating composition for forming a tinted coating on a panel material containing a tint base as claimed in one of the preceding claims as well as at least one coloured pigment, preferably a coloured pigment mixture, for example in the form of a pigment paste, wherein more preferably, the proportion of coloured pigments is a maximum of 12% by weight, particularly preferably a maximum of 10% by weight, with respect to the total weight of the starting materials of the coating composition.