Filler for wall coatings

Description

[0001] The present invention relates to a filler for wall coating compositions, a method for producing the filler for wall coating compositions, wall coating compositions comprising the filler and a method for producing a wall coating composition.

[0002] To increase the degree of whiteness and opacity or covering power, calcined kaolins are often used as fillers in wall coating compositions or wall paints.

[0003] EP 1 715 009 A2 discloses the use of calcined kaolin as a filler to increase the whiteness and opacity of white or colored surface coatings.

[0004] WO 2013 / 025444 A2 discloses a filler for wall coating compositions comprising a calcined kaolin clay and preferably fluxes. The fluxes are added to the kaolin clay to lower the calcination temperature. The resulting fillers have a positive effect on the wet abrasion resistance of wall coatings.

[0005] WO 2016 / 001303 A1 discloses particles that are calcined mixtures of clay minerals, crystalline silicas, feldspar and optionally other aggregates, and have a particle size (d50 grain size) in the range of 0.1 to 3 mm. These particles are used in roof coatings.

[0006] US 2013 / 045384 describes a kaolin-based filler. For this purpose, kaolin is calcined to achieve a mullite index of at least 25, preferably 25 to 62. The addition of fluxes is described.

[0007] One disadvantage of calcining kaolin is that the process takes place at approximately 1380 °C, requiring a significant amount of energy. Furthermore, calcined kaolin has a high oil content. The higher the oil content of a filler, the more binder a wall coating or paint must contain. A higher binder requirement increases costs and reduces the design flexibility when adding further additives to wall coatings. Additionally, a higher oil content in the filler can negatively impact the wet abrasion resistance of the wall coatings.

[0008] Therefore, there is a need for additional fillers for wall coating compositions.

[0009] It is therefore an object of the present invention to provide a filler for wall coating compositions, a method for its production, a wall coating composition comprising the filler, a method for producing such a wall coating composition, and uses of the filler for wall coating compositions which overcome at least some of the problems known from the prior art.

[0010] The problem according to the invention is solved by a filler for wall coating compositions, wherein the filler consists of particles, the particles being made from burnt mixtures of 40 to 70 wt.% clay minerals, 0 to 32 wt.%, preferably 5 to 32 wt.% crystalline silicas, 10 to 45 wt.% feldspar, 0 to 20 wt.% other additives are and wherein the particles have a d50 grain size between 1 µm and 40 µm.

[0011] The filler for wall coating compositions consists of particles with a defined d50 grain size between 1 µm and 40 µm. These particles are calcined mixtures. To produce the particles, mixtures of the described composition are created, sintered by calcination, and then ground to a defined grain size. The filler can be in powder form.

[0012] In a preferred embodiment, the filler consists of particles comprising burnt mixtures of 40 to 70 wt.% clay minerals, 5 to 30 wt.% crystalline silica, 10 to 30 wt.% feldspar, 0 to 20 wt.% other aggregates are and wherein the particles have a d50 grain size between 1 µm and 40 µm.

[0013] The addition of crystalline silica likely increases the proportion of the amorphous phase by forming a glass. It appears that the addition of crystalline silica particularly reduces the oil number of the particles compared to particles without crystalline silica.

[0014] Preferably, the particles have a d50 particle size between 3 µm and 40 µm, more preferably between 3 µm and 30 µm, and even more preferably between 3 µm and 25 µm.

[0015] In another embodiment according to the invention, the particles have a d50 grain size between 4 µm and 15 µm.

[0016] The d50 particle size distribution refers to the particle size distribution at which 50% by weight of the particles have a larger particle size and 50% by weight have a smaller particle size. Such particle size distributions can be easily determined according to ISO 13320:2020-01 "Particle size analysis - Particle measurement by laser diffraction." The d50 value can be measured, for example, with a laser granulometer from CILAS, model 1180, which complies with this standard.

[0017] Clay minerals are preferably selected from the group consisting of kaolin, dickite, nacrite, halloysite, vermicullite, and mixtures thereof. Other minerals from the phyllosilicate group are also suitable.

[0018] Preferably, the amount of clay minerals in the mixture to be fired is 45% by weight or more. More preferably, the amount of clay minerals is 65% by weight or less, and more preferably 60% by weight or less.

[0019] In a preferred embodiment, a clay mineral is used which has a low total lead content. Preferably, the clay mineral contains less than 300 ppmw, more preferably less than 200 ppmw, and even more preferably less than 150 ppmw of lead, in each case measured by X-ray fluorescence analysis according to DIN 51001:2003-08.

[0020] In a further preferred embodiment, a clay mineral is used which also contains a small amount of iron, in particular less than 1 wt% based on the clay minerals, more preferably less than 0.5 wt% based on the clay minerals. The iron content is measured by X-ray fluorescence analysis according to DIN 51001:2003-08 as Fe₂O₃.

[0021] The crystalline silicas are preferably selected from the group consisting of quartz, cristobalite, tridymite, and mixtures thereof. Other minerals of the quartz group, such as coesite or opal, are also suitable. The use of quartz is particularly preferred. Preferably, the proportion of quartz in the crystalline silicas is at least 50 wt.%.

[0022] Preferably, the amount of crystalline silica is 1 wt.% or more, 5 wt.% or more, or 9 wt.% or more. Preferably, the amount of crystalline silica is 30 wt.% or less, 25 wt.% or less, or 18 wt.% or less.

[0023] In a preferred embodiment, crystalline silica with a low total lead content is used. Preferably, the crystalline silica contains less than 300 ppmw of lead, measured by X-ray fluorescence analysis according to DIN 51001:2003-08.

[0024] Preferably, the amount of feldspar is 15 wt.% or more, 20 wt.% or more, or 25 wt.% or more. Preferably, the amount of feldspar is 40 wt.% or less, 30 wt.% or less, or 28 wt.% or less.

[0025] Preferably, the feldspar used has a low total lead content. Preferably, the feldspar contains less than 300 ppmw of lead, measured by X-ray fluorescence analysis according to DIN 51001:2003-08.

[0026] The other additives are preferably selected from the group consisting of alumina (Al 2 O 3 ), framework silicates that are not feldspars, phyllosilicates that are not clay minerals, silicates that are not framework or phyllosilicates, carbonates and mixtures thereof.

[0027] Preferably, the amount of other additives is at least 1% by weight. Preferably, the amount of other additives is 10% by weight or less.

[0028] Preferably, the other additives contain less than 300 ppmw lead, measured by X-ray fluorescence analysis according to DIN 51001:2003-08.

[0029] Preferably, the filler according to the invention for wall coating compositions has at least one of the following properties: i) a lead content of less than 300 ppmw, preferably less than 200 ppmw, in each case measured by X-ray fluorescence analysis according to DIN 51001:2003-08, ii) an amorphous content of more than 10%, preferably more than 12%, more preferably 15% or more, in each case measured by X-ray diffraction with subsequent Rietveld refinement, iii) an oil number of less than 80 g / 100 g, preferably 50 g / 100 g or less, more preferably 48 g / 100 g or less, in each case measured according to DIN EN ISO 787-5:1995-10, iv) a solar reflectance over the entire spectrum of at least 85% measured according to ASTM Standard C 1549-16, v) a solar reflectance in the UV range of at least 78%, preferably 79% or more, in each case measured according to ASTM Standard C 1549-16, vi) a softening temperature of less than 1720 °C, measured according to DIN 51730:2007-09, vii) a hemisphere temperature of less than 1740 °C, measured according to DIN 51730:2007-09.

[0030] The filler according to the invention can have one, two, three, four, five, six or seven of the aforementioned properties i) to vii) independently of one another.

[0031] A low lead content has the advantage that the use of fillers in wall coating compositions is harmless to health. Conventional calcined kaolin often has a lead content of significantly more than 300 ppmw.

[0032] The oil number was determined according to DIN EN ISO 787-5:1995-10. According to DIN EN ISO 787-5:1995-10, the oil number is the amount of linseed oil absorbed by a pigment or filler sample under specified conditions. The higher the oil number of the pigment or filler sample, the more binder a wall coating or paint must contain. A low oil number therefore has the advantage of reducing the binder requirement of a wall coating. This lowers the manufacturing costs of the wall coating and allows for the addition of further additives. Furthermore, a low oil number has a positive effect on the wet abrasion resistance of the wall coatings.

[0033] For a filler in wall coating compositions, high solar reflectivity across the entire spectrum can be advantageous. When used in facade paints, the filler reflects incoming solar radiation, thus preventing the surrounding area from overheating. This allows for the use of so-called... "Urban Heat Islands" This can be avoided. Furthermore, buildings are heated less by solar radiation, resulting in cost savings on air conditioning. It is particularly advantageous if the filler for wall coating compositions has a high solar reflectance in the UV range. Sunlight in the UV range can attack and destroy the binder in facade paint. Therefore, the use of fillers with high solar reflectance in the UV range can increase the UV stability of the wall coating composition.

[0034] Solar reflectance across the entire spectrum and solar reflectance in the UV range are determined according to ASTM Standard C 1549-16 ("standard test method for determination of solar reflection near ambient temperature using a portable solar reflectometer"). The "Solar Spectrum Reflectometer" Model SSR from Devices and Services, Dallas, Texas, USA, can be used as the measuring instrument.

[0035] The invention also relates to a method for producing a filler for wall coating compositions, wherein the filler consists of particles, comprising: a) Firing a mixture of 40 to 70 wt.% clay minerals, 0 to 32 wt.%, preferably 5 to 32 wt.% crystalline silicas, 10 to 45 wt.% feldspar, 0 to 20 wt.% other additives; b) crushing the fired mixture; c) grinding the crushed, fired mixture into particles, wherein the particles have a d50 grain size between 1 µm and 40 µm.

[0036] According to the invention, the mixture can be calcined at temperatures exceeding 1100 °C. The mixtures can be calcined at temperatures of approximately 1200 °C, while the calcination of kaolin takes place at approximately 1380 °C. This results in significant energy savings.

[0037] In the crushing step b) of the inventive method, the mixture, which has been pressed into a body and fired, is crushed using suitable crushers.

[0038] Subsequently, in step c) of the process according to the invention, the crushed, burnt mixture is ground into particles, wherein the particles have a d50 particle size between 1 µm and 40 µm. The grinding is carried out using suitable mills. Preferably these are ball mills, roller mills, pin mills, vibratory mills or air jet mills.

[0039] The invention further relates to a wall coating composition comprising the filler according to the invention.

[0040] The wall coating composition can consist of plaster or paint. Preferably, the paint is a dispersion, synthetic resin dispersion, acrylic, silicate, silicone, or dispersion acrylic paint, suitable for both interior and exterior / facade use. Preferably, the wall coating composition is an aqueous dispersion paint or an aqueous synthetic resin dispersion paint.

[0041] Preferably, the filler is contained in the wall coating composition in an amount between 2 and 25 wt.%, more preferably between 3 and 20 wt.%, even more preferably between 5 and 15 wt.%, and even more preferably between 8 and 12 wt.%.

[0042] Preferably, the wall coating composition additionally comprises at least one binder.

[0043] Preferably, the at least one binder is an organic binder, a silicate binder, or a mixture of organic and silicate binders. The organic binder is preferably selected from the group consisting of polyvinyl acetate, acrylate, vinyl acetate-ethylene copolymers, styrene-acrylate copolymers, and mixtures thereof. The silicate binder is preferably selected from the group consisting of sodium silicate, potassium silicate, lithium silicate, and mixtures thereof.

[0044] Preferably, at least one binder is included in the wall coating composition in an amount between 8 wt.% and 16 wt.%.

[0045] The wall coating composition according to the invention can also comprise further additives such as pigments, dispersants, thickeners, pigment stabilizers, or biocides. Suitable additives are known to those skilled in the art.

[0046] The invention further relates to a method for producing a wall coating composition comprising: Mixing the filler according to the invention with at least one binder.

[0047] The invention also relates to the use of particles that are fired mixtures of 40 to 70 wt.% clay minerals, 0 to 32 wt.%, preferably 5 to 32 wt.% crystalline silicas, 10 to 45 wt.% feldspar, 0 to 20 wt.% other additives are and have a d50 grain size between 1 µm and 40 µm, to increase the wet abrasion resistance of wall coatings.

[0048] The particles are the fillers according to the invention.

[0049] Wet abrasion resistance describes the wash and scrub resistance of cured or dried wall coatings. It is a measure of a wall coating's resistance to mechanical abrasion, such as that which can occur when cleaning a surface coated with the wall coating. Wet abrasion resistance is measured according to DIN EN ISO 11998:2006-10. Wet abrasion is defined as the mean loss of coating thickness. Wet abrasion resistance can be determined using a wash and scrub tester, such as the Model 494 MC, commercially available from Erichsen GmbH & Co. KG.

[0050] Surprisingly, it was found that wall coatings with very good wet abrasion resistance values ​​could be obtained using the fillers according to the invention. It is assumed that the low oil number of the fillers according to the invention leads to an increase in the wet abrasion resistance of the wall coatings containing the fillers.

[0051] The invention also relates to the use of particles that are fired mixtures of 40 to 70 wt.% clay minerals, 0 to 32 wt.%, preferably 5 to 32 wt.% crystalline silicas, 10 to 45 wt.% feldspar, 0 to 20 wt.% other additives are and have a d50 particle size between 1 µm and 40 µm, in wall coating compositions to reduce the amount of binder used in the wall coating compositions.

[0052] The particles are the fillers according to the invention.

[0053] Surprisingly, it was found that the use of the fillers according to the invention in wall coating compositions leads to a reduction in the amount of binder used in the wall coating composition. This is because the fillers have a low oil number.

[0054] The invention is further explained by the following examples: Example 1: Production of fillers

[0055] Articles of the following composition were produced by firing in an oxidizing atmosphere at 1200 °C: 60% by weight kaolin 21% by weight quartz 19% by weight feldspar

[0056] These items were subsequently crushed to a d50 grain size of approximately 1 mm.

[0057] The broken items were then ground. The following d50 particle sizes were obtained: Sample 1 Sample 2 Sample 3 3,3 µm 5,4 µm 11,8 µm

[0058] As a comparison sample, commercially available calcined kaolin (DORKAFILL® < H, Gebrüder Dorfner GmbH & Co. Kaolin- und Kristallquarzsandwerke KG, Hirschau) was used in Examples 2, 3, 4, 7, and 8. This had a d50 grain size, measured with a CILAS laser granulometer, of 11.6 µm. It has a mullite index of 45. Example 2: Oil level

[0059] The oil concentration of the samples was determined according to DIN EN ISO 787-5:1995-10. The following oil concentrations were measured: Sample 1 Sample 2 Sample 3 comparison sample 47 g / 100 g 41 g / 100 g 35 g / 100 g 80 g / 100 g

[0060] The samples 1 to 3 according to the invention exhibited significantly lower oil content than the reference sample. Wall coating compositions produced with samples 1 to 3 therefore required less binder than wall coating compositions using calcined kaolin A. Example 3: Lead content

[0061] The lead content of the samples was determined by X-ray fluorescence analysis according to DIN 51001:2003-08. The following lead contents were measured: Sample 1 Sample 2 Sample 3 comparison sample < 150 ppmw < 150 ppmw < 150 ppmw 1,200 ppmw

[0062] Due to their low lead content, the fillers according to the invention (samples 1 to 3) are harmless to health. In contrast to the comparison sample, the fillers according to the invention can be used without any problems in wall coatings. Example 4: Solar Reflection

[0063] Using a Model SSR solar spectrum reflectometer from Devices and Services, Dallas, Texas, USA, the total solar reflectance was measured at an angle of incidence of 20° to the vertical. A representative and sufficiently large subset of the sample was taken for this purpose. A sample dish with a diameter of 55 mm was filled with the sample to a height of 10 mm, and the surface was smoothed with a spatula. The solar reflectance value is given as the average of five measurements. The solar reflectance across the entire spectrum and the solar reflectance in the UV range (UV reflectance) were determined. The particles exhibited the following properties: Sample 1 Sample 2 Sample 3 comparison sample Solar reflection (total spectrum) 92,5% 91,4% 91,9% 92,5% UV reflection 83,1% 81,0% 79,5% 77,2%

[0064] The fillers according to the invention (samples 1 to 3) exhibited increased solar reflectance in the high-energy UV range compared to the control sample. Facade paints in which the fillers according to the invention are used can reflect incident solar radiation in the UV range very well. Example 5: Softening and hemisphere temperature

[0065] The melting behavior of the samples was investigated using a heating microscope. In accordance with DIN 51730:2007-09, a cube-shaped sample was heated, and its deformation was recorded using an imaging technique. Characteristic points (softening temperature, hemispherical temperature, flow temperature) could then be described. A Linseis heating microscope was used. The samples exhibited the following properties: Samples 1, 2 and 3 Comparative sample* softening temperature 1695 °C 1737 °C Hemisphere temperature 1720 °C > 1740 °C Flow temperature > 1740 °C > 1740 °C *calcined kaolin (AS 45 from Amberger Kaolinwerke Eduard Kick GmbH & Co.KG) Example 6: Amorphous component

[0066] The amorphous fraction of the samples was determined by X-ray diffraction followed by Rietveld refinement. For this purpose, the samples were finely ground and then imaged using an X-ray diffractometer (Malvern Panalytical EMPYREAN). The mineral composition was determined from these images. In a further step, 10 wt% rutile was added to each sample to determine the amorphous fraction of each sample, in addition to the crystalline components, using Rietveld analysis. The samples exhibited the following amorphous fractions: Samples 1, 2 and 3 Comparative sample* 16% 9% *calcined kaolin (AS 45 from Amberger Kaolinwerke Eduard Kick GmbH & Co.KG) Example 7: Wall coating composition

[0067] An aqueous dispersion paint with a pigment volume concentration of 80% was prepared. It had the following composition: ingredient % by weight Water 30,1 Calgon N 0,05 BYK 155 / 35 0,9 BYK 014 0,2 Acticide MBS 0,1 Walocell XM 6000 PV 0,5 Walocel XM 30,000 PV 0,1 Kronos 2300 10 CaCO3 Omyacarb 2 38 Sample 1, 2, 3 or comparison sample 10 Mowilith LDM 1871 10 BYK 014 0,2 Acrysol RM 8 W 0,1 sum 100,0 Example 8: Wet abrasion resistance

[0068] To determine the wet abrasion resistance of the wall coating, the deaerated, brushable paints from Example 7 (containing as a filler either one of samples 1, 2, or 3, or commercially available calcined kaolin (DORKAFILL®< H, Gebrüder Dorfner GmbH & Co. Kaolin- und Kristallquarzsandwerke KG, Hirschau)) were applied to a black and white paint card (Erichsen GmbH & Co. KG) using a film-pulling device (Zehntner, type ZAA 2300) and a doctor blade with a film thickness of 200 µm. After application, they were dried for two weeks according to DIN EN ISO 11998:2006-10. The wet abrasion resistance was measured according to DIN EN ISO 11998:2006-10, in which the surface to be tested is subjected to a defined number of strokes. Wet abrasion is defined as the mean loss of film thickness. The wet abrasion resistance was determined using a washing abrasion and scouring test device model 494 MC from Erichsen GmbH & Co.KG.The following values ​​were determined for wet abrasion: . Sample 1 Sample 2 Sample 3 comparison sample 45,3 µm 30,8 µm 14,9 µm 32,1 µm

[0069] The fillers according to the invention (samples 1 to 3) enabled the production of wall paints with very good wet abrasion resistance values. Excellent values ​​were achieved with particles from samples 2 and 3.

Claims

1. A filler for wall coating compositions, wherein said filler consists of particles, wherein said particles are fired mixtures of - 40 to 70% by weight of clay minerals - 5 to 32% by weight of crystalline silicic acids - 10 to 45% by weight of feldspar - 0 to 20% by weight of other aggregates, and wherein said particles have a d50 grain size of from 1 µm to 40 µm.

2. The filler according to claim 1, wherein said particles are fired mixtures of - 40 to 70% by weight of clay minerals - 5 to 30% by weight of crystalline silicic acids - 10 to 30% by weight of feldspar - 0 to 20% by weight of other aggregates.

3. The filler according to claim 1 or 2, wherein the particles have a d50 grain size of from 3 µm to 40 µm, preferably from 3 µm to 30 µm, more preferably from 3 µm to 25 µm.

4. The filler according to any of claims 1 to 3, wherein said clay minerals are selected from the group consisting of china clay, dickite, nacrite, halloysite, vermiculite, and mixtures thereof.

5. The filler according to any of claims 1 to 4, wherein the crystalline silicic acids are selected from the group consisting of quartz, cristobalite, tridymite, and mixtures thereof.

6. The filler according to any of claims 1 to 5, wherein the other aggregates are selected from the group consisting of alumina (Al2O3), tectosilicates that are not feldspars, phyllosilicates that are not clay minerals, silicates that are not tecto- or phyllosilicates, carbonates, and mixtures thereof.

7. The filler according to any of claims 1 to 6, wherein said filler has a lead content of less than 300 ppmw, preferably less than 200 ppmw, respectively measured by means of X-ray fluorescence analysis according to DIN 51001:2003-08, and / or an amorphous fraction of more than 10%, as measured by means of X-ray diffraction followed by Rietveld refinement.

8. The filler according to any of claims 1 to 7, wherein said filler has an oil number of less than 80 g / 100 g, preferably 50 g / 100 g or less, respectively measured according to DIN EN ISO 787-5:1995-10, and / or a solar reflection across the total spectrum of at least 85%, measured according to ASTM Standard C 1549-16.

9. The filler according to any of claims 1 to 8, wherein said filler has a softening temperature of less than 1720°C, measured according to DIN 51730:2007-09, and / or a hemisphere temperature of less than 1740°C, measured according to DIN 51730:2007-09.

10. A wall coating composition, comprising the filler according to any of claims 1 to 9, preferably further comprising at least one binder.

11. The wall coating composition according to claim 10, wherein said filler is contained therein in an amount of from 2 to 25% by weight.

12. A process for producing a filler for wall coating compositions, wherein said filler consists of particles, comprising: a) firing a mixture of - 40 to 70% by weight of clay minerals - 5 to 32% by weight of crystalline silicic acids - 10 to 45% by weight of feldspar - 0 to 20% by weight of other aggregates; b) crushing the fired mixture, c) grinding the crushed fired mixture to particles, wherein said particles have a d50 grain size of from 1 µm to 40 µm.

13. A process for producing a wall coating composition, comprising: - mixing the filler according to any of claims 1 to 8 with at least one binder.

14. Use of particles that are fired mixtures of - 40 to 70% by weight of clay minerals - 5 to 32% by weight of crystalline silicic acids - 10 to 45% by weight of feldspar - 0 to 20% by weight of other aggregates, and have a d50 grain size of from 1 µm to 40 µm, to increase the wet abrasion resistance of wall coatings.

15. Use of particles that are fired mixtures of - 40 to 70% by weight of clay minerals - 5 to 32% by weight of crystalline silicic acids - 10 to 45% by weight of feldspar - 0 to 20% by weight of other aggregates, and have a d50 grain size of from 1 µm to 40 µm, in wall coating compositions for reducing the amount of binder used in wall coating compositions.