Nucleated titanium dioxide and preparation method thereof

Abstract

The invention relates to the technical field of titanium dioxide, and discloses a preparation process of oil paint core-coated titanium dioxide, which comprises the following steps: a core layer is rutile type titanium dioxide particles with the particle size range of 0.1-0.5 mu m and the specific surface area of 8-15m < 2 > / g, an inorganic coating layer is composed of silicon dioxide and aluminum oxide according to the mass ratio of 1: (0.2-1.5), the coating thickness is 5-15% of the diameter of the core layer, and the inorganic coating layer is composed of silicon dioxide and aluminum oxide according to the mass ratio of 1: (0.2-1.5). Wherein the silicon dioxide is coated by a hydrolytic deposition method, the aluminum oxide is coated by a sol-gel method, the organic coating layer comprises a copolymer containing a silane coupling agent and organic silicon resin, the organic silicon resin is methyl phenyl silicon resin, the organic coating layer accounts for 1-8% of the total mass of the titanium dioxide, and the surface contact angle of the organic coating layer is greater than or equal to 110 degrees. According to the preparation process of the oil paint core-coated titanium dioxide, an inorganic-organic gradient coating system is constructed, so that the core-coated titanium dioxide has a gloss retention rate of more than 95% (ASTM D523) and a delta E color difference of less than 1.5 (ISO 7724) after 1000 hours in a QUV accelerated aging test, and the weather resistance of the core-coated titanium dioxide is improved by more than 3 times compared with that of the traditional titanium dioxide.

Description

Technical Field

[0001] The invention relates to the technical field of titanium dioxide, in particular to a preparation process of oily paint-coated core titanium dioxide. Background Art

[0002] Titanium dioxide is an important inorganic chemical pigment, primarily composed of titanium dioxide. Titanium dioxide is produced via two processes: the sulfuric acid process and the chloride process. It is widely used in industries such as coatings, inks, papermaking, plastics and rubber, chemical fibers, and ceramics, and is particularly useful in oil-based paints.

[0003] Traditional titanium dioxide is used in oil-based coatings due to its surface photocatalytic activity (Ti 3 + site) is prone to resin degradation under the action of ultraviolet rays, resulting in accelerated powdering and yellowing of the coating. Therefore, we urgently need a preparation process for oil-based paint-coated core titanium dioxide. Summary of the Invention

[0004] To address the above-mentioned technical deficiencies, the present invention aims to provide a process for preparing oil-based paint-coated core titanium dioxide. By constructing an "inorganic-organic" gradient coating system, the core titanium dioxide achieves a gloss retention of >95% (ASTM D523) and a ΔE color difference of <1.5 (ISO 7724) after 1000 hours in a QUV accelerated aging test, demonstrating weather resistance more than three times that of conventional titanium dioxide.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A core-encapsulated titanium dioxide, comprising:

[0007] The core layer is rutile titanium dioxide particles with a particle size range of 0.1-0.5μm and a specific surface area of 8-15m 2 / g;

[0008] An inorganic coating layer, comprising silicon dioxide and aluminum oxide in a mass ratio of 1:0.2-1.5, with a coating thickness of 5-15% of the diameter of the core layer, wherein the silicon dioxide is coated by a hydrolysis deposition method, and the aluminum oxide is coated by a sol-gel method;

[0009] An organic coating layer comprising a copolymer of a silane coupling agent and an organic silicone resin, wherein the silane coupling agent is γ-methacryloxypropyltrimethoxysilane (KH570) or vinyltriethoxysilane (A151), and the organic silicone resin is a methylphenyl silicone resin. The organic coating layer accounts for 1-8% of the total mass of the titanium dioxide, and the surface contact angle of the organic coating layer is ≥110°.

[0010] The mass ratio of the inorganic coating layer to the organic coating layer is 1:0.05-0.5, and the oil absorption of the coated titanium dioxide is ≤18g / 100g, and the artificial accelerated aging test is ≥1000 hours without powdering.

[0011] Preferably, in the inorganic coating layer, the coating order of silicon dioxide and aluminum oxide is to deposit the silicon dioxide layer first and then coat the aluminum oxide layer, the thickness of the silicon dioxide layer is 10-50 nm, and the thickness of the aluminum oxide layer is 5-30 nm.

[0012] Preferably, in the preparation of the organic coating layer, the mass ratio of the silane coupling agent to the silicone resin is 1:0.3-2, the reaction temperature is 60-90° C., the pH value is controlled at 4-6, and the reaction time is 1-4 hours.

[0013] Preferably, the preparation of the inorganic coating layer comprises the following steps:

[0014] Disperse titanium dioxide in an ethanol-water mixture, add ethyl orthosilicate, and hydrolyze at pH = 8-10 and 50-70°C for 2-5 hours to form a silicon dioxide layer;

[0015] Aluminum isopropoxide was added, the pH was adjusted to 3-5, and the temperature was raised to 80-95° C. to react for 3-6 hours to form an aluminum oxide layer.

[0016] Preferably, the preparation of the organic coating layer comprises the following steps:

[0017] The inorganically coated titanium dioxide is dispersed in toluene, and a silane coupling agent and an organic silicone resin are added. The mixture is refluxed for 2-5 hours under nitrogen protection, and the finished product is obtained after centrifugation and drying.

[0018] A method for preparing core-coated titanium dioxide comprises:

[0019] Step 1: ultrasonically dispersing rutile titanium dioxide in a solvent, and sequentially performing inorganic coating and organic coating;

[0020] Step 2: In the inorganic coating stage, a step-by-step deposition method is used to control the coating thickness ratio of silicon dioxide and aluminum oxide;

[0021] Step three: In the organic coating stage, an in-situ polymerization process is used to form a cross-linked network between the silane coupling agent and the silicone resin on the surface of the titanium dioxide.

[0022] Preferably, in step 1, the solvent is a mixture of ethanol and deionized water in a volume ratio of 2:1-5:1, the ultrasonic power is 200-500 W, and the dispersion time is 30-60 minutes.

[0023] An oil-based paint, comprising:

[0024] 15-40 parts of the core-coated titanium dioxide according to any one of claims 1-7;

[0025] 50-70 parts of alkyd resin or acrylic polyurethane resin;

[0026] Dispersant (polycarboxylate) 0.5-2 parts;

[0027] Solvent (xylene / butyl acetate) 10-20 parts;

[0028] Additives (leveling agent, defoaming agent) 0.1-1 part.

[0029] Preferably, the coating has a Stormer viscosity of 70-90 KU at 25° C. and a storage stability of ≥12 months without hard precipitation.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] First, the present invention constructs an "inorganic-organic" gradient coating system, and deposits a nano-SiO2 porous layer (10-50nm) and an Al2O3 dense layer (5-30nm) on the surface of the rutile TiO2 core layer in sequence, wherein the SiO2 layer shields more than 80% of the TiO2. 3 The Al2O3 layer blocks 65%-85% of UV rays (280-400nm) through physical reflection, while the grafted methylphenyl silicone resin on the outer layer further absorbs residual UV rays (absorbance > 2.5@300nm), forming a dual-mechanism of "reflection-absorption" protection. This structure enables the core-encapsulated titanium dioxide to achieve a gloss retention rate of > 95% (ASTM D523) and a ΔE color difference of < 1.5 (ISO 7724) after 1000 hours in QUV accelerated aging tests, representing more than three times the weather resistance of traditional titanium dioxide.

[0032] Second, the present invention constructs a low-polarity interface (contact angle ≥110°) on the surface of titanium dioxide through the copolymerization reaction of KH570 silane coupling agent (surface energy 28mN / m) and methylphenyl silicone resin (surface energy 22mN / m), thereby reducing its surface energy from 45mN / m of bare powder to 25mN / m. This property significantly improves its compatibility with oily resins (such as alkyd resins with an HLB value of 10-12), reduces the amount of dispersant used by 30% (0.5-2% polycarboxylate can achieve a zeta potential of -45mV), stabilizes the Stormer viscosity at 70-90KU (GB / T 9269), and shows no hard precipitation after 12 months of storage. The leveling property during coating application is improved by 40%.

[0033] Third, the present invention uses an ethanol-water gradient solvent system (volume ratio 3:1) and staged pH control (SiO2 deposition pH 8-10, Al2O3 deposition pH 3-5) to achieve an inorganic layer thickness error of <±5nm (SEM statistics); the in-situ polymerization process uses toluene solvent reflux (110°C) and nitrogen protection to make the cross-linking density of the organic coating layer reach more than 85% (DSC gel rate measurement). This process can accurately control the total thickness of the coating layer to 5-15% of the core particle size, and the color difference ΔE between batches is <0.5 (CIE Lab). The single batch production capacity is increased to 500kg (traditional process ≤350kg), and the production cost is reduced by 20%. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart for the overall preparation of the core-coated titanium dioxide of the present invention;

[0035] Figure 2 This is a process flow chart of the step-by-step deposition of the inorganic coating layer of the present invention;

[0036] Figure 3 This is a flow chart of the in-situ polymerization process of the organic coating layer of the present invention;

[0037] Figure 4 A flow chart of the dispersion condition optimization process of the present invention;

[0038] Figure 5 This is a production quality control flow chart of the present invention;

[0039] Figure 6 is a UV transmittance flow chart of the present invention;

[0040] Figure 7 The present invention is a flow chart of the coating formulation application process. DETAILED DESCRIPTION

[0041] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. Specific implementation method 1

[0043] The following is a specific implementation of a core-coated titanium dioxide.

[0044] See also Figure 1-6 , a core-encapsulated titanium dioxide, comprising:

[0045] The core layer is rutile titanium dioxide particles with a particle size range of 0.1-0.5μm and a specific surface area of 8-15m 2 / g;

[0046] An inorganic coating layer, comprising silicon dioxide and aluminum oxide in a mass ratio of 1:0.2-1.5, with a coating thickness of 5-15% of the diameter of the core layer, wherein the silicon dioxide is coated by a hydrolysis deposition method, and the aluminum oxide is coated by a sol-gel method;

[0047] An organic coating layer comprising a copolymer of a silane coupling agent and an organic silicone resin, wherein the silane coupling agent is γ-methacryloxypropyltrimethoxysilane (KH570) or vinyltriethoxysilane (A151), and the organic silicone resin is a methylphenyl silicone resin. The organic coating layer accounts for 1-8% of the total mass of the titanium dioxide, and the surface contact angle of the organic coating layer is ≥110°.

[0048] The mass ratio of the inorganic coating layer to the organic coating layer is 1:0.05-0.5, and the oil absorption of the coated titanium dioxide is ≤18g / 100g, and the artificial accelerated aging test is ≥1000 hours without powdering.

[0049] Performance optimization is achieved through the synergistic effect of the three-layer structure. The core layer uses 0.1-0.5μm rutile TiO2, whose high refractive index (2.71) provides basic covering power, while the specific particle size range ensures maximum light scattering efficiency (0.2μm corresponds to 1 / 2 of the visible light wavelength of 400nm); the inorganic coating layer adopts a SiO2 / Al2O3 two-component structure, firstly, a porous SiO2 layer is generated by hydrolysis of ethyl orthosilicate (reaction formula: Si(OC2H5)4→SiO2) to cover the photocatalytic active sites, and then a dense Al2O3 is formed by hydrolysis of aluminum isopropoxide. The O3 layer (reaction formula: Al(OCH(CH3)2)3→Al2O3) improves corrosion resistance, and the two form a gradient coating at a mass ratio of 1:0.2-1.5; the organic coating layer is cross-linked with methylphenyl silicone resin through KH570 silane coupling agent (hydrolyzed to form Si-OH bonds) to form a low surface energy (25mN / m) hydrophobic layer (contact angle ≥110°). The synergistic effect of the three-layer structure reduces the oil absorption to below 18g / 100g, and after 1000 hours of QUV aging, ΔE is <1.5, which is 300% higher than the weather resistance of uncoated titanium dioxide.

[0050] Specifically, in the inorganic coating layer, the coating order of silicon dioxide and aluminum oxide is to deposit the silicon dioxide layer first and then coat the aluminum oxide layer. The thickness of the silicon dioxide layer is 10-50 nm, and the thickness of the aluminum oxide layer is 5-30 nm.

[0051] The integrity of the coating is directly affected by the control of the inorganic coating sequence and thickness. A 10-50 nm SiO2 layer is first deposited to form a porous substrate (porosity 30%). When the thickness is less than 10 nm, it cannot completely shield the Ti 3+ photocatalytic activity (photo-induced yellowing rate > 5%), exceeding 50nm will lead to a decrease in light scattering efficiency (hiding power reduced by 15%); the 5-30nm Al2O3 layer is then coated to fill the SiO2 pores through the sol (the porosity is reduced to <5%), forming a "brick-mud" composite structure. When the Al2O3 layer is too thin (<5nm), the acid and alkali resistance decreases (weight loss >2% after immersion in 5% H2SO4 for 24 hours); if it is too thick (>30nm), the surface roughness is increased (Ra>50nm), affecting the adhesion of the organic layer. This structure controls the total thickness of the coating layer to 5-15% of the core particle size, achieving a balance between 90GU high gloss (85GU for conventional products) and 95% UV blocking rate.

[0052] Specifically, the mass ratio of the silane coupling agent to the silicone resin is 1:0.3-2, the reaction temperature is 60-90° C., the pH value is controlled at 4-6, and the reaction time is 1-4 hours.

[0053] The surface properties are determined by regulating the organic coating parameters. The silane coupling agent and silicone resin are mixed in a mass ratio of 1:0.3-2. When the ratio is less than 0.3, the crosslinking density is insufficient (gel rate <60%), and when it is greater than 2, the silane self-polymerizes to form a loose structure (contact angle <100°). The reaction temperature is within the range of 60-90°C. Below 60°C, the conversion rate is less than 70% (FTIR detection shows unreacted C=C bonds), and above 90°C, the silicone resin decomposes (TGA shows 5% thermal weight loss). Acidic conditions of pH 4-6 promote silane hydrolysis (hydrolysis half-life <10 minutes at pH = 5) while inhibiting silicone resin gelation. A reaction time of 1-4 hours ensures coating uniformity (SEM shows coverage >95%). This process achieves a crosslinking density of the organic layer exceeding 85%, withstands 50 xylene wipes without shedding, and reduces the surface energy to 25mN / m (bare powder 35mN / m).

[0054] Specifically, the preparation of the inorganic coating layer includes the following steps:

[0055] Disperse titanium dioxide in an ethanol-water mixture, add ethyl orthosilicate, and hydrolyze at pH = 8-10 and 50-70°C for 2-5 hours to form a silicon dioxide layer;

[0056] Aluminum isopropoxide was added, the pH was adjusted to 3-5, and the temperature was raised to 80-95° C. to react for 3-6 hours to form an aluminum oxide layer.

[0057] The inorganic layer is precisely constructed by a step-by-step deposition process. Titanium dioxide is dispersed in an ethanol-water mixed solvent (volume ratio 3:1). Ethanol reduces the surface tension (from 72mN / m to 22mN / m) to prevent particle sedimentation. Ethyl orthosilicate is hydrolyzed under alkaline conditions (pH 8-10) to form a SiO2 layer. The reaction temperature is controlled at 50-70°C (hydrolysis rate 0.12min -1) to obtain a uniform coating of 10-50nm; then, aluminum isopropoxide was added under acidic conditions (pH 3-5) at 80-95°C to promote the condensation of AlO(OH) sol into a γ-Al2O3 layer (DLS showed that the particle size increased from 50nm to 200nm). This process increased the interface bonding strength of the SiO2 / Al2O3 layer by 40% (critical load of scratch test 15N), and the porosity of the coating layer was less than 5%.

[0058] Specifically, the preparation of the organic coating layer includes the following steps:

[0059] The inorganically coated titanium dioxide is dispersed in toluene, and a silane coupling agent and an organic silicone resin are added. The mixture is refluxed for 2-5 hours under nitrogen protection, and the finished product is obtained after centrifugation and drying.

[0060] The inorganic-coated titanium dioxide was dispersed in toluene (solubility parameter δ = 18.2 MPa) by in-situ polymerization to strengthen the organic-inorganic interface. 1 / 2 ), KH570 silane is added after the silicone resin is fully dissolved; the reaction is refluxed at 110°C under nitrogen protection for 2-5 hours to prevent silane oxidation (OIT is extended from 20 minutes to 120 minutes); the silane methoxy group is hydrolyzed to form Si-OH, which condenses with the hydroxyl groups on the inorganic layer surface (XPS detection of Ti-O-Si bond binding energy 532.5 eV). The methacryloyloxy group cross-links with the silicone resin to form a three-dimensional network. This process ensures that the organic layer thickness uniformity CV value is less than 5% (AFM test), the surface contact angle reaches 115°±2°, and the thermal stability of the coating is improved after centrifugal drying. Specific implementation method 2

[0062] The following is a specific implementation of a method for preparing core-coated titanium dioxide.

[0063] See also Figure 1-6 A method for preparing core-coated titanium dioxide comprises:

[0064] Step 1: ultrasonically dispersing rutile titanium dioxide in a solvent, and sequentially performing inorganic coating and organic coating;

[0065] Step 2: In the inorganic coating stage, a step-by-step deposition method is used to control the coating thickness ratio of silicon dioxide and aluminum oxide;

[0066] Step three: In the organic coating stage, an in-situ polymerization process is used to form a cross-linked network between the silane coupling agent and the silicone resin on the surface of the titanium dioxide.

[0067] Performance synergy is achieved through process optimization. A step-by-step deposition method is used to first construct a SiO2 buffer layer (10-50nm), followed by the deposition of an Al2O3 filling layer (5-30nm) to form an inorganic coating gradient structure. The in-situ polymerization process allows silane and silicone resin to react directly on the surface of titanium dioxide to form a chemically bonded organic layer (FTIR shows a characteristic peak of Si-O-Si at 1110cm -1 ), this method makes the total thickness deviation of the coating layer less than ±5nm, the performance difference between batches less than 3% (Lab value fluctuation ΔE <0.5), and the production capacity is increased to 500kg / batch.

[0068] Specifically, in step 1, the solvent is a mixture of ethanol and deionized water in a volume ratio of 2:1-5:1, the ultrasonic power is 200-500W, and the dispersion time is 30-60 minutes.

[0069] Dispersion conditions determine the basis of coating uniformity. An ethanol / water (2:1-5:1) mixed solvent is used to adjust the polarity, reducing the hydrolysis rate of ethyl orthosilicate by 60% (the half-life is extended from 5 min to 15 min); 200-500W ultrasonic treatment is used for 30-60 minutes, and the cavitation effect breaks up soft agglomerates (D50 decreases from 1.2μm to 0.4μm); the Zeta potential of the dispersion system is greater than +30mV to ensure stable suspension of particles (sedimentation rate <1% / 24h). This condition provides a monodisperse substrate for subsequent coating, making the SiO2 layer thickness deviation less than ±3nm. Specific implementation method three

[0071] The following is a specific implementation of an oil-based paint.

[0072] See also Figure 7 , an oil-based paint, comprising:

[0073] 15-40 parts of the core-coated titanium dioxide according to any one of claims 1-7;

[0074] 50-70 parts of alkyd resin or acrylic polyurethane resin;

[0075] Dispersant (polycarboxylate) 0.5-2 parts;

[0076] Solvent (xylene / butyl acetate) 10-20 parts;

[0077] Additives (leveling agent, defoaming agent) 0.1-1 part.

[0078] The structural advantages of the core-coated titanium dioxide are reflected through the coating formulation. When 15-40% core-coated titanium dioxide is added, the organic layer reduces the surface energy (25mN / m), improves the compatibility with alkyd resin (HLB=10), and reduces the amount of dispersant by 30% (0.5-2%). The TiO2 / resin interface bonding is enhanced (peel strength increases by 50%), and the coating Stormer viscosity is stabilized at 70-90KU. After 2000 hours of QUV aging, the gloss retention rate is greater than 80% (control sample <60%), and the DOI value reaches 92.

[0079] Specifically, the coating has a Stormer viscosity of 70-90 KU at 25° C. and a storage stability of ≥12 months without hard precipitation.

[0080] The SiO2 / Al2O3 inorganic layer reflects 85% of ultraviolet rays (280-400nm), and the organic layer phenyl silicone resin absorbs the remaining UV (absorbance > 2.5), achieving a composite shielding effect. The solvent system (xylene / butyl acetate) balances the volatilization rate (initial distillation point 120-140°C), and is combined with low surface energy titanium dioxide to achieve improved leveling (orange peel index ≤ 10μm). The storage stability test (50°C / 30 days) shows that the viscosity change is <10%, the distinctness of image index is ≥0.9 (national standard ≥0.8), and the salt spray resistance 1000 hours blistering level is ≤1.

[0081] Although specific embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A core-coated titanium dioxide, characterized in that: include: The core layer is rutile titanium dioxide particles with a particle size range of 0.1-0.5μm and a specific surface area of 8-15m 2 / g; An inorganic coating layer, comprising silicon dioxide and aluminum oxide in a mass ratio of 1:0.2-1.5, with a coating thickness of 5-15% of the diameter of the core layer, wherein the silicon dioxide is coated by a hydrolysis deposition method, and the aluminum oxide is coated by a sol-gel method; An organic coating layer comprising a copolymer of a silane coupling agent and an organic silicone resin, wherein the silane coupling agent is γ-methacryloxypropyltrimethoxysilane (KH570) or vinyltriethoxysilane (A151), and the organic silicone resin is a methylphenyl silicone resin. The organic coating layer accounts for 1-8% of the total mass of the titanium dioxide, and the surface contact angle of the organic coating layer is ≥110°. The mass ratio of the inorganic coating layer to the organic coating layer is 1:0.05-0.5, and the oil absorption of the titanium dioxide after coating is ≤18g / 100g, and the artificial accelerated aging test is ≥1000 hours without powdering.

2. The core-coated titanium dioxide according to claim 1, characterized in that: In the inorganic coating layer, the coating order of silicon dioxide and aluminum oxide is to deposit the silicon dioxide layer first and then coat the aluminum oxide layer. The thickness of the silicon dioxide layer is 10-50 nm, and the thickness of the aluminum oxide layer is 5-30 nm.

3. The core-coated titanium dioxide according to claim 1, characterized in that: In the preparation of the organic coating layer, the mass ratio of the silane coupling agent to the silicone resin is 1:0.3-2, the reaction temperature is 60-90° C., the pH value is controlled at 4-6, and the reaction time is 1-4 hours.

4. The core-coated titanium dioxide according to claim 1, characterized in that: The preparation of the inorganic coating layer comprises the following steps: Disperse titanium dioxide in an ethanol-water mixture, add ethyl orthosilicate, and hydrolyze at pH = 8-10 and 50-70°C for 2-5 hours to form a silicon dioxide layer; Aluminum isopropoxide was added, the pH was adjusted to 3-5, and the temperature was raised to 80-95° C. to react for 3-6 hours to form an aluminum oxide layer.

5. The core-coated titanium dioxide according to claim 1, characterized in that: The preparation of the organic coating layer comprises the following steps: The inorganically coated titanium dioxide is dispersed in toluene, and a silane coupling agent and an organic silicone resin are added. The mixture is refluxed for 2-5 hours under nitrogen protection, and the finished product is obtained after centrifugation and drying.

6. A method for preparing core-coated titanium dioxide, characterized in that: include: Step 1: ultrasonically dispersing rutile titanium dioxide in a solvent, and sequentially performing inorganic coating and organic coating; Step 2: In the inorganic coating stage, a step-by-step deposition method is used to control the coating thickness ratio of silicon dioxide and aluminum oxide; Step three: In the organic coating stage, an in-situ polymerization process is used to form a cross-linked network between the silane coupling agent and the silicone resin on the surface of the titanium dioxide.

7. The method for preparing a core-coated titanium dioxide according to claim 6, characterized in that: In step 1, the solvent is a mixture of ethanol and deionized water with a volume ratio of 2:1-5:1, the ultrasonic power is 200-500W, and the dispersion time is 30-60 minutes.

8. An oil-based paint, characterized in that: include: 15-40 parts of the core-coated titanium dioxide according to any one of claims 1-7; 50-70 parts of alkyd resin or acrylic polyurethane resin; Dispersant (polycarboxylate) 0.5-2 parts; Solvent (xylene / butyl acetate) 10-20 parts; Additives (leveling agent, defoaming agent) 0.1-1 part.

9. The oil-based paint according to claim 8, characterized in that: The coating has a Stormer viscosity of 70-90 KU at 25° C. and a storage stability of ≥12 months without hard precipitation.

Images