PROCESS FOR MAKING AN ANTI-SOILING COATING COMPOSITION AND A COATING MADE THEREFROM

Abstract

The disclosure relates to a process to provide a substrate having improved anti-soiling properties. The disclosure also relates to an anti-soiling coating composition, and to a process of making an anti-soiling coating composition. Use of the coating composition to improve anti-soiling properties of a substrate.

Claims

1. A process to provide a substrate having improved anti-soiling properties comprising the steps a) Providing a substrate having a surface; b) Providing a coating composition comprising: i. organic-inorganic core shell nanoparticles having a core comprising an emulsion stabilizer C and a shell comprising inorganic oxide; and ii. at least one water soluble solvent; iii. at least 5 wt % water based on the total weight of the coating composition; and iv. an organic compound A; c) Applying a layer of the composition to the surface to obtain a coated substrate; and d) Drying the applied layer to obtain a coated substrate.

2. The process according to claim 1, wherein in step d) the applied layer is exposed to a temperature of at least 5 degrees Celsius, for the duration of at least at least one hour.

3. The process according to claim 1, wherein the composition comprises a binder, preferably the binder comprises an inorganic oxide binder, preferably the inorganic oxide binder comprises inorganic oxide precursor is selected from metal alkoxides, metal chelates, metal salts, and mixtures thereof, preferably the inorganic oxide binder comprises an alkoxy silane.

4. The process according to claim 1, wherein the composition comprises between 0 to 30 wt-%, preferably between 0.1 to 30 wt-%, pref between 1 and 15 aluminium oxide equivalents of aluminium containing compound, preferably the coating formulation comprises between 0.5 to 30 wt-% aluminium oxide equivalents of aluminium containing compound.

5. Process according to claim 1, wherein the organic-inorganic core shell nanoparticles have particle size is in a range of from 20 to 300 nm as measured using DLS.

6. The process according to claim 1, wherein compound A is a non-polymeric compound.

7. The process according to claim 1, wherein compound A has a boiling point of at least 10 C. and at most 300 C., preferably compound A has a boiling point of at least 30 C. and at most 200 C.

8. The process according to claim 1, wherein compound A has solubility in water at room temperature of at most 3 kg/m.sup.3.

9. Process according to claim 1, wherein copolymer C is obtained form 1-25 mole % of at least one cationic or basic monomer M1, like vinyl monomers with a tertiary amine group; 50-99 mole % of at least one non-ionic apolar monomer M2; and 0-25 mole % of at least one polar, anionic or acidic monomer M3; with the sum of M1, M2, and M3 adding up to 100%.

10. Process according to claim 1 wherein mass ratio C/A is 0.15-1.0.

11. Process according to claim 1 wherein metals include at least one element selected from Si, Al, Be, Bi, B, Fe, Mg, Na, K, In, Ge, Hf, La and lanthanoids, Sb, Sn, Ti, Ta, Nb, Y, Zn and Zr.

12. A coated substrate obtained with the process according to claim 1.

13. Use of the coating composition as defined in claim 1 to improve anti-soiling properties of a substrate

14. An anti-soiling coating composition comprising i. organic-inorganic core shell nanoparticles having a core comprising and an emulsion stabilizer C and a shell comprising inorganic oxide; ii. at least 5 wt % water based on the total weight of the coating composition; iii. at least one water soluble solvent; and iv. an organic compound A.

15. Process of making an anti-soiling coating composition comprising the steps of 1) Preparing an oil-in-water emulsion by mixing an apolar organic compound A; a cationic addition copolymer C as emulsion stabilizer; and aqueous medium of pH 2-6; at a mass ratio C/A of 0.1 to 2, to result in 1-50 mass % (based on emulsion) of emulsified droplets of particle size 30-300 nm; 2) Providing an inorganic oxide shell layer to the emulsified droplets by adding to the emulsion obtained in step 1) at least one inorganic oxide precursor, to result in organic/inorganic core-shell nano-particles with mass ratio core/shell of from 0.2 to 25; 3) Optionally combining the core-shell nanoparticles thus obtained with water and/or water soluble solvent; 4) Optionally adjusting pH; and 5) Optionally adding an organic or inorganic polymeric or polymerizable binder.

Description

EXPERIMENTS

Organic Compounds

[0308] Table 1 provides relevant data on compounds A that are applied in experiments as organic core or template.

TABLE-US-00001 TABLE 1 Melting Boiling Solubility point point in water Reference Compound ( C.) ( C.) (kg/m.sup.3) A1 Cyclohexane 6.5 81 0.04 A2 Toluene 93 110 0.5 A3 Isoamyl 78 142 1.1 acetate

Cationic Copolymers

[0309] Table 2 presents monomer composition for a number of cationic copolymers C, which are obtained following the procedure described in the experimental part of EP2178927, which is incorporated herein by reference. Copolymers were used as aqueous dispersion with a concentration of about 20 mass %, with pH of about 4 (acidified with formic acid). The copolymers had Mw in the range 25-40 kDa (GPC).

TABLE-US-00002 TABLE 2 C1 C2 C3 C4 C5 monomer Comonomer content (mole %) DMAEMA 10.1 38.3 17.5 10.3 8.3 MMA 89.9 61.7 82.5 91.7 IBOA 89.7

DLS Measurements

[0310] A Malvern Nano ZS dynamic light scattering instrument was used to measure particle size of dispersed particles on 1 drop of dispersion in 10 ml aqueous KCl solution (1 mmol/L) at 25 C. and in back-scattering mode. Particle size herein refers to average particle size measured as Z-averaged hydrodynamic diameter.

[0311] For formulations (example 10) made in isopropanol the DLS measurements were performed in isopropanol as the diluting solvent. For these measurements 10 drops of formulation was added to 10 ml of isopropanol.

Felt Test

[0312] Scratch resistance of applied coating layers is evaluated by the felt test according to EN1096-2.

Optical Properties

[0313] Reflection and transmission of coated transparent substrates is evaluated with a Shimadzu UV-2450 spectrophotometer. Relative specular reflectance is measured at an incident angle of 5 with a reflectance attachment. For measuring transmission the integrating sphere attachment is installed in the sample compartment, and incidence angle was 0 (normal to the sample surface). Average reflection values are calculated for the wavelength range 425-675 nm. Measurements are performed on two-sided coated plates. Transmission measurements in example 10 were performed on a Schimadzu 2600 or Perkin Elmer 1050 spectrophotometer. Average transmission values are calculated for the wavelength range 400-1200 nm.

Example 1

[0314] 20 grams of cyclohexane (p.a.) containing 1 mass % of heptadecane was dispersed using a Ultra-turrax unit T25 into a mixture of 14 grams Milli-Q water, 1 gram of 2-propanol and 15 grams of a dispersion containing 21.5 mass % of cationic copolymer C1 (Mw about 30 kDa). The resulting coarse emulsion was further dispersed using a high-pressure homogenizer (DeBee, operated at a pressure 30 kPsi, using diamond orifice and applying water cooling) in 9 cycles of about 15 strokes each and allowing the temperature to decrease after each cycle to 40 C. This resulted in a stable emulsion with emulsion droplets of particle size (DLS Z-averaged hydrodynamic diameter) of 265 nm (Polydispersity Index, PDI 0.28). To this emulsion 2 grams of copolymer C1 were added, rendering a clear positive charge of the droplets, indicated by the zeta potential >+11 mV (pH 4). Silication was then performed by gradually adding (90 minutes) by perfusor pump 41.5 g of tetramethoxy silane (TMOS) to a mixture of 35 g of the resulting emulsion and 80 g Milli-Q water, under firmly stirring with magnetic stirring bar. After the addition was completed stirring was continued for another 90 minutes. 100 g of the mixture was diluted with 100 g of Milli-Q water and acidified with 6 drops of concentrated HNO.sub.3. The DLS size of the final product was 255 nm (PDI 0.20) and TEM analysis revealed spherical silica particles with particle size in the range 60-120 nm. (see FIG. 1).

[0315] Cyclohexane could be removed by rota-evaporation treatment, while gradually increasing the water temperature of the water bath from 30 to 40 C., and reducing the pressure from 300 to 100 mbar. The final dispersion contained 6.4 mass % of hollow silica particles with DLS size of 219 nm (PDI 0.35) and zeta potential of 12 mV (pH=4); and was found to be stable in time.

Example 2

[0316] Example 1 was repeated, but now 20.7 g of TMOS was used. After evaporation of cyclohexane TEM analysis showed hollow silica spheres of similar size as in Example 1, but the particles appeared to be partly collapsed; likely due to limited strength of the silica shell during sample preparation for the TEM analysis.

Comparative Experiment 3

[0317] Example 1 was repeated, but now copolymer C2 was used. It appeared not possible to obtain a stable emulsion of cyclohexane; polymer C2 apparently being too hydrophilic to function as emulsion stabilizer.

Example 4

[0318] Example 1 was repeated, but now copolymer C3 was used. After evaporation of cyclohexane TEM analysis showed hollow silica particles of similar size as in Example 1, but the particles appeared to be less regularly shaped.

Example 5

[0319] 21 g of cyclohexane containing 1 mass % of heptadecane was dispersed using a Ultra-turrax unit T25 into 51.3 g of a dispersion containing 17.4 mass % of cationic copolymer C4 (Mw about 31 kDa). This resulted in a stable emulsion (>1 week) with emulsion droplets of DLS size of 202 nm (PDI 0.02). Silication was performed by gradually adding (90 min) 41.5 g of TMOS to a mixture of 35 g of the resulting emulsion and 80 g Milli-Q water, while firmly stirring with magnetic stirring bar. After the addition was completed the dispersion was stirred for another 90 minutes. 135 g of the mixture was diluted in 750 g Milli-Q water and acidified with 15 drops of concentrated HNO.sub.3. The final dispersion of 2.2 mass % displayed a DLS size of 200 nm (PDI 0.06), a zeta potential of +19 mV at pH 4.0 and was stable for more than one week. A TEM micrograph on the resulting dispersion after sample preparation showed spherical hollow silica particles of about 100-150 nm and a shell thickness of about 10 nm; also showing some collapsed particles.

[0320] Cyclohexane was removed from the dispersion by spray-drying (Bchi Mini Spray drying B-191) at an evaporation temperature of 130-150 C., flow rate at 270 mL/h in combination with an air flow of 640 normal L/h. TEM performed on the obtained white powder showed aggregated particles having multi-hollow structure. The product showed opacifier (whitening) power, when applied as a simple paint formulation on black photo paper.

Example 6

[0321] 23.3 g of toluene was mixed with 52.6 g of a dispersion of copolymer C5 (19 mass % in water, pH 3.9, particle size 44 nm (PDI 0.06) by DLS) using a Dispermat mixing unit, and then diluted with 180 grams of water; resulting in about 13 mass % emulsified droplets in water. To 100 g of this emulsion 52 g of TMOS was added drop-wise over 2 hours at ambient temperature under stirring. Particle size of resulting particles was about 82 nm (according to DLS). The obtained dispersion was acidified with 50% nitric acid to a pH of 1.8; and showed stability over time. A TEM micrograph revealed spherical particles showing a core-shell structure, and particle size in the range 30-80 nm (see FIG. 3).

Example 7

[0322] 50 g of isoamyl acetate was mixed with 113 g of a dispersion of copolymer C5 (19 mass % in water, pH 3.9, particle size 44 nm (PDI 0.06) by DLS) using a Dispermat mixing unit, and then diluted with 385 grams of water; resulting in about 13 mass % emulsified droplets in water. To 180 g of this emulsion 70 g of TMOS was added drop-wise over 2 hours at ambient temperature under stirring. Particle size of resulting particles was about 100 nm (according to DLS). The obtained dispersion was acidified with 50% nitric acid to a pH of 1.9; and showed stability over time. Moreover, the dispersion could be diluted with water, ethanol, or isopropanol and remain stable (no visual flocculation or sedimentation).

[0323] A Cryo-TEM micrograph revealed spherical particles showing a core-shell structure, and particle size in the range 30-70 nm (see FIG. 4).

[0324] Several coatings were prepared from the dispersion obtained, by diluting with isopropanol and adding different amounts of a sol made from tetraethoxy silane (TEOS) as binder.

[0325] The sol of TEOS was prepared by adding to a solution of TEOS in iso-propanol a molar excess of water while stirring, to pre-hydrolyse the silane compound. After cooling back to room temperature glacial acetic acid was added, and after 24 hrs stirring at ambient conditions more iso-propanal and nitric acid (65%) were added. The resulting dispersion contained about 4 mass % of silica particles of about 3-5 nm size.

[0326] Composition 7-1 was made by diluting the core-shell particles dispersion with 5-fold amount of acidified isopropanol, followed by adjusting pH of the final dispersion to 1.5 by adding nitric acid (50%).

[0327] Compositions 7-2, 7-3, 7-4 and 7-5 were prepared by mixing an amount of above prepared core-shell particles dispersion with different amounts of the TEOS sol as binder and iso-propanol, after which the pH was adjusted to about 1.5 by adding nitric acid (50%). The amount of binder was calculated as mass of SiO.sub.2 resulting from TEOS relative to the sum of binder and core-shell particles.

[0328] The obtained coating compositions were used to provide coating layers to glass plates by dip-coating in a dust-free room. Pilkington Optiwhite S glass plates of 2 mm thickness were cleaned with water and household cleaner, then rinsed with water and demi-water, and then dip-coated by immersing in a container with coating composition; the coating bath being kept at room temperature (at about 21 C.) and 50% relative humidity. The plate was then vertically pulled up from the bath at a rate of about 2.5 mm/s. The coated plate was subsequently dried at ambient conditions for at least 5 minutes.

[0329] After application the coated glass was dried at 125 C. during 15 minutes in an air circulation oven, or dried at 650 C. during 2.5 minutes. All samples passed the felt test. Minimum reflection of the samples dried at 650 C. was between 0.5 and 1%. As an example the reflection curve measured for sample 7-1 is shown in FIG. 2. In case the coated plates were dried at 125 C. the average reflection was between 1.7 and 3.2%. This difference in reflection can be attributed to different porosity levels, resulting from the copolymer (emulsion stabiliser C) present in the core-shell particles being pyrolyzed (or depolymerized) and evaporated at 650 C.; but not at the low drying temperature, whereas drying at 125 C. will result in evaporation of the organic compound contained in the core-shell particles dispersion, and thus in some porosity. Reflection data are summarized in Table 3.

Comparative Experiment 8

[0330] 52.6 g of dispersion of copolymer C5 (19 mass % in water, pH 3.9, particle size 44 nm (PDI 0.06) by DLS) was mixed with 173.3 g of water (5% emulsion stabilizer in water), and subsequently 20 g of TMOS was drop-wise added over 2 hours at ambient temperature. Increase of particle size to about 84 nm (according to DLS) was observed. The obtained dispersion was acidified with 50% nitric acid to a pH of 1.8; and showed stability over time. A cryo-TEM micrograph shows spherical, but somewhat aggregated particles having core-shell structure, with particle size in the range 25-90 nm (see FIG. 5).

[0331] Analogously to Example 7, coating compositions were made by combining the obtained dispersion with different amounts of TEOS sol and iso-propanol; and used for preparing coated glass samples. For the products obtained average reflection is about 1% when dried at 650 C., but is above about 5.8% when dried at 125 C. This difference indicates that at low temperature hardly any porosity is obtained, whereas at high temperature porosity may result from calcination of organic copolymer in the coating; demonstrating the advantage of the coating composition according to the invention as prepared in e.g. Example 7 particularly when prepared at dried at low temperature where the emulsion stabilizer is not pyrolysed or evaporated. Results are summarized in Table 3.

TABLE-US-00003 TABLE 3 Amount of Average reflection Average reflection binder (%) (%) Sample (mass %) (dried at 125 C.) (dried at 650 C.) Example 7-1 0 1.7 0.8 Example 7-2 9 2.3 0.8 Example 7-3 16 2.4 0.8 Example 7-4 23 2.7 1.1 Example 7-5 28 3.2 1.8 Comp. exp. 8-1 0 5.8 0.8 Comp. exp. 8-2 21 7.1 0.9 Comp. exp. 8-3 36 5.9 0.8 Comp. exp. 8-4 45 6.0 1.2 Comp. exp. 8-5 52 6.1 1.1

[0332] Humidity sensitivity: For the comparative coating compositions, where only the emulsion stabilizer and no component A is present, the minimum reflection is below 1% when dried at 650 C., but increases to above 3% at 90% relative humidity. It could be theorized (without being limited thereto) that this may be due the mesoporosity of the coating. When coating compositions wherein component A is present in the nano particles are dried at 650 C. the minimum reflections stay below 1.5% even at 90% relative humidity.

[0333] Outdoor durability: After accelerated outdoor durability tests (1000 hours @ 85% relative humidity and 85 C.) the coatings are off white possibly due to sodium and calcium salts having diffused out of the glass plates, but after washing with water and ethanol the AR properties are retained.

[0334] Mechanical properties: The scratch resistance of the coating compositions 13.1-13.4 as well as on the comparative coating composition pass the felt test according to EN 1096-2 with a change in transmission of less than 0.5%.

Example 9

[0335] Several coating formulations were prepared by mixing core-shell particle dispersions of Example 6 (with toluene as component A) with isopropanol and varying amounts of binder in the form of the sol of TEOS prepared as described in Example 7.

[0336] Coating formulation 9.1: (No binder): To 500 grams of isopropanol 6.5 grams of 1:1 65% nitiric acid/water was added after which 90 grams of the core-shell particle dispersion of Example 6. Final pH of the formulation is 1.6 and particle size of 87 nm according to DLS. After 6 weeks at room temperature the DLS value was increase less than 10 nm indication good storage stability of the particles. The formulation contains an equivalent SiO.sub.2 content of 1.27%.

[0337] Comparative coating formulation 9.2: (100% binder): Binder in the form of the sol of TEOS prepared as described in Example 7 containing an equivalent amount of silica of 4% was diluted with isopropanol to a relative amount of 1.27% SiO.sub.2.

[0338] Coating formulation 9.3: (35% binder): To 200 grams of the core-shell particle dispersion of Example 6, 107.8 grams of binder in the form of the sol of TEOS prepared as described in Example 7 was added so a SiO.sub.2 equivalence ratio of 35/65 was obtained.

[0339] Coating formulation 9.4: (65% binder): To 100 grams of the core-shell particle dispersion of Example 6, 185.9 grams of binder in the form of the sol of TEOS prepared as described in Example 7 was added so a SiO.sub.2 equivalence ratio of 65/35 was obtained.

[0340] Coating formulation 9.5: (90% binder): To 100 grams of the core-shell particle dispersion of Example 6, 900.7 grams of binder in the form of the sol of TEOS prepared as described in Example 7 was added so a SiO.sub.2 equivalence ratio of 90/10 was obtained.

[0341] The pH of the formulations was maintained at 1.5+/0.2 and adjusted with nitric acid if needed.

[0342] Coating formulations 9.1-9.5 were dip coated and assessed on the optical properties via optical transmission measurements relative to glass (type Pilkington Optiwhite S; average transmission between 350 and 850 nm of 91.4%). Morphology of the coatings (only dried at room temperature) was determined via cross-section SEM analysis. To achieve complete drying and hardness, the transmission was measured after 1 week.

TABLE-US-00004 TABLE 4 Average Cross transmission Sample section gain Observations coating FIG. 6 6.02% Many core-shell particles formulation with rather rough coating 9.1 surface Comparative FIG. 7 2.27% No pores observed. Nano coating pores between binder particles formulation may be present but are too small to be observed with this technique. Very smooth surface coating FIG. 8 5.5% Core-shell particles formulation observedand some surface 9.3 roughness coating FIG. 9 5.05% Core-shell particles formulation observedand some surface 9.4 roughness coating FIG. 10 4.05% Only limited number of formulation core-shell particles observed. 9.5 Smooth surface

[0343] In FIG. 11, the average transmission gain is plotted as a function of the origin of the silica. Each sample composition is indicated with number. Surprisingly, a highly un-linear behavior is observed in that the transmission gain remains high even at very binder contents and that the transmission gain only is reduced substantially when more than 90% of the silica originates from the binder.

[0344] Mechanical performance was evaluated using abrasion test performed according to NEN-EN 1096-2). For all formulation above >50% POT only minor changes (<0.5%) in transmission gain were observed after the test. Hence, even after the abrasion test, good optical properties are obtained that are of interest for commercial application in for example the solar cell cover glass market.

Example 10

[0345] Several coating formulations were prepared by mixing core-shell particle dispersions of Example 6 (with toluene as component A) [referred to below as CSP-EX6] with isopropanol and varying amounts of binder in the form of the sol of TEOS prepared as described in Example 7.

[0346] Several coating formulations were prepared by mixing core-shell particle dispersions of Example 7 (with isoamyl acetate as component A) [referred to below as CSP-EX7] and varying amounts of binder in the form of the sol of TEOS prepared as described in Example 7.) [referred to below as binder-EX7]

10-1: Coating Formulation 100% CSP: 100% Core-Shell Particle Dispersion CSP EX6

[0347] 41.6 g of CSP-EX6 was diluted with 280.0 g of IPA and acidified with 65% nitric acid to pH<2. The [SiO.sub.2] is 1.7 wt %.

10-2: Coating Formulation 50% CSP: 50 wt % Core-Shell Particle Dispersion and 50 wt % Binder

[0348] 25.0 g of CSP-EX6 was diluted with 143.3 g of IPA to a [SiO.sub.2] of 2.0 wt %. Then, 168.3 g of binder was added (this is binder EX7 diluted in isopropanol (1:1) to [SiO.sub.2] of 2.0 wt %). The formulation was stirred to obtain good mixing. pH=1.6

10-3: Coating Formulation 30% CSP: 30 wt % Core-Shell Particle Dispersion 70 wt % Binder

[0349] 13.4 g of CSP-EX6 was diluted with 76.7 g of IPA to a [SiO.sub.2] of 2.0 wt %. Then, 210.0 g of binder (of EX7 diluted 1:1 in isopropanol to [SiO.sub.2] of 2.0 wt %) was added, and the formulation was stirred. pH=1.5

10-4: Coating Formulation 70% CSP: 70 wt % Core-Shell Particle Dispersion and 30 wt % Binder

[0350] 31.3 g of CSP-EX6 was diluted with 178.9 g of IPA to a [SiO.sub.2] of 2.0 wt %. Then, it was mixed with 89.9 g of binder (of Ex7 diluted 1:1 in isopropanol to [SiO.sub.2] of 2.0 wt %). The pH=1.7

10-5: Coating Formulation 100% CSP: 100% Core-Shell Particle Dispersion CSP EX7

[0351] 54.5 g of CSP-EX7 was diluted with 245.5 g of IPA to a [SiO.sub.2] of 2.0 wt %. pH was adjusted with nitric acid to <2.0. DLS=93 nm

10-6: 50% Coating Formulation 50% CSP: 50 wt % Core-Shell Particle Dispersion and 50 wt % Binder

[0352] 27.3 g of CSP-EX7 was diluted with 122.8 g of IPA to a [SiO.sub.2] of 2.0 wt %. This was mixed with 150.0 g of binder (of Ex7 diluted 1:1 in isopropanol to [SiO.sub.2] of 2.0 wt %). pH=1.8

[0353] DLS=95 nm

10-7: Coating Formulation 100% Binder

[0354] Binder-EX7 was diluted 1:1 with IPA to a [SiO.sub.2] of 2.0 wt %.

[0355] Dipcoating experiments were performed on Pilkington Optiwhite S float glass with, 3.2 mm thickness and size of 1010 cm with coating formulations 10-1 to 10-7 as described above.

[0356] Dip-coating was done in a dust-free room. Pilkington Optiwhite S glass plates of 3.2 mm thickness were cleaned with water and household cleaner, then rinsed with water and demi-water, and then dip-coated by immersing in a container with coating composition; the coating bath being kept at room temperature (at about 21 C.) and 40% relative humidity. The plate was then vertically pulled up from the bath at a rate (as indicated in tables 5-7 below). The coated plate was subsequently dried at ambient conditions for at least 5 minutes. After drying as indicated in the tables below the soiling measurement as described below was performed.

Method of Soiling Measurement

[0357] Soiling procedure: The anti-soiling properties of the coatings were tested with a Taber Oscillating Abrasion Tester (model 6160) using commercially available Arizona test dust from quartz A4 coarse (size varying from 1 to 200 m) as soiling medium, commercially available from KSL Staubtechnik GMBH. The 1010 cm glass plate to be tested was first cleaned with deionized water and a soft cloth, rinsed with laboratory grade ethanol and left to dry overnight. The coated sample was then placed in the tray of the Taber Oscillating table so that the top surface of the glass plate is at the same height as the sample holder inside the tray. Next, 20 g of Arizona test dust is gently dispersed over the whole glass plate using a brush. The soiling procedure (300 cycles at a speed of 100 cycles per minute; one cycle was defined as a full revolution of the circular drive disk: one completed back-and-forth movement of the tray) was performed. The test sample was then removed from the tray and gently tapped to remove the excess of sand on its surface. The relative humidity in the testing environment was at 40% RH and the temperature was 20 C.

Soiling Evaluation: Soiling ScoreVisual Assessment (Table 5-8):

[0358] The degree of soiling of the coatings was determined by visually assessing the soiled substrate using the following soiling scale:

3: high soiling
2: acceptable soiling
1: low soiling
0: zero to minor soiling

Soiling EvaluationTransmission Measurement to Determine AS Loss/ARE/ASR (Table 9)

[0359] The degree of soiling of the coatings was determined by relative loss in transmittance after soiling, measured with an Optosol Transpec VIS-NIR spectrophotometer. To that end, transmittance spectra were recorded prior and post artificial soiling via the Taber Oscillating Abrasion Tester. Subsequently, the average of transmittance over 400-1200 nm was established from the spectra. Based on the resulting differences between the before and after values of the average transmittance over 400-1200 nm recorded in the spectra, conclusions regarding the level of soiling and hence the effectiveness of the anti-soiling coatings could be drawn.

TABLE-US-00005 TABLE 5 Code Dip Drying (coating CSP- speed time Soiling formulation) EX6 Binder (mm/sec) (20 C.) score 10-1 100 0 3.5 1 day 0-1 100 0 3.5 5 days 0-1 10-4 70 30 3.5 1 day 0-1 10-2 50 50 3.5 1 day 1-2 50 50 3.5 5 days 1-2 10-3 30 70 3.5 1 day 2 10-7 0 100 3.0 1 day 3 (Binder EX7)

TABLE-US-00006 TABLE 6 Code Dip Drying (coating CSP speed time Soiling formulation) EX7 Binder (mm/sec) (20 C.) score 10-5 100 0 2.5 1 day 0 10-6 50 50 2.5 1 day 2

TABLE-US-00007 TABLE 7 Code Dip (coating Drying speed Drying Soiling formulation) temperature (mm/sec) time scale 10-4 20 C. 2.5 1 day 0-1 10-4 650 C. 3.2 1 minute 1 10-4 650 C. 3.4 2 minutes 1 10-4 650 C. 3.6 3 minutes 1-2 10-4 650 C. 3.8 4 minutes 1-2 10-4 650 C. 4.0 5 minutes 2

TABLE-US-00008 TABLE 8 Average T % Average after Max AS T % Max T % soil T % loss* Sample 400- ( at 400- after (%- Float glass 1200 nm Max) 1200 nm soil points) ASR ARE 0 92.7 87.6 5.1 10-1 96.8 98.3 96.6 98.1 0.2 96.1 4.1 (689) 10-4 96.1 97.3 95.9 97.1 0.2 96.1 3.4 (703) 97.4 10-2 95.9 (610) 95.1 96.5 0.8 84.3 3.2 10-3 95.4 96.9 94.2 95.5 1.2 76.5 2.7 (586) *AS loss is transmission loss after soiling on the same plate, Tprior soil minus Tafter soil based on Average T % 400-1200 nm

[0360] FIG. 12 shows a photograph of a glass plate coated with coating formulation 10-1 as described above: 100% CSP EX6 (soiling score 0-1) with an uncoated edge at the top (soiling score 3).