Lime-based inorganic coating and preparation method thereof

Abstract

The invention relates to the technical field of building materials, and particularly discloses a lime-based inorganic coating and a preparation method thereof. The lime-based inorganic coating is prepared from the following raw materials: cellulose, an ammonium salt dispersing agent, a wetting dispersing agent, a mineral oil defoaming agent, dispersible rubber powder, titanium dioxide, nano silicon dioxide dispersion liquid, quick lime, calcium carbonate, 2, 2, 4-trimethyl-1, 3-pentanediol monoisobutyrate, a bio-based thickening agent, initially added water and secondarily added water. Meanwhile, a three-stage sanding mode is adopted, the first-stage low-speed mixing ensures that the material is fully wetted, the second-stage high-speed shearing realizes primary dispersion, and the three-stage heat-preservation stirring promotes interface bonding and structure stabilization. Therefore, the lime-based inorganic coating and the preparation method thereof have the effects of being good in product stability, capable of reducing sagging and dripping, and high in wear resistance and corrosion resistance.

Description

Technical Field

[0001] The present application relates to the technical field of building materials, and in particular to a lime-based inorganic coating and a preparation method thereof. Background Art

[0002] Inorganic architectural coatings offer protective and decorative properties, as well as specialized features. These coatings are primarily based on inorganic alkali metal silicates or silica sols, with pigments, fillers, and modifying agents added. These coatings are readily available and cost-effective, making them suitable for applications in architecture, painting, textiles, aviation, aerospace, marine, and automotive fields. Depending on the application, inorganic coatings offer stable physical and chemical properties, easy storage, aging resistance, and a long service life. Furthermore, the use of water as a dispersion medium reduces environmental pollution.

[0003] Conventional lime-based inorganic coatings are typically dry powders that require on-site mixing with water and cannot be used immediately after opening. Their viscosity and workability also change with the amount of water added. Improper handling can lead to slow film strength development and cracking. They also have low adhesion to the substrate, prone to powder shedding, and reduced wear and corrosion resistance. Conventional lime-based inorganic coatings take a long time to dry and form films. Replacing traditional inorganic coatings with new inorganic coatings requires not only overcoming the limited performance of traditional inorganic coatings but also adapting to the demands of interior and exterior building decoration, such as improving film quality, facilitating construction, conserving resources, and adapting to the environment. Furthermore, the active development of water-based, high-solids, high-performance, and environmentally friendly coatings has gradually become a major theme in the development of the coatings industry.

[0004] Therefore, this field urgently needs to develop a lime-based inorganic coating that can simultaneously meet the requirements of being ready for use as soon as the lid is opened, having good product stability, quickly recovering high viscosity after construction, reducing sagging and dripping, having strong wear resistance and corrosion resistance, and being a high-performance environmentally friendly inorganic coating product with good biodegradability. Summary of the Invention

[0005] In order to solve the technical problems that lime-based inorganic coatings have low hardness and corrosion resistance, are prone to sagging and dripping, and consume energy during the production process, the present application provides a lime-based inorganic coating and a preparation method thereof, which is ready for use after opening the lid, has good product stability, quickly recovers high viscosity after construction, reduces sagging and dripping, has strong wear resistance and corrosion resistance, and has good biodegradability, thereby reducing production energy consumption.

[0006] In a first aspect, the present application provides a lime-based inorganic coating, which adopts the following technical solution: A lime-based inorganic coating is prepared from the following raw materials in parts by weight: 0.6-0.9 parts of cellulose, 0.6-1.2 parts of an ammonium salt dispersant, 0.4-0.55 parts of a wetting dispersant, 0.1-0.25 parts of a mineral oil defoamer, 2-4 parts of a dispersible rubber powder, 0.5-2.75 parts of titanium dioxide, 2-4 parts of a nano-silicon dioxide dispersion, 18-22 parts of quicklime, 28-34 parts of calcium carbonate, 0.5-1.25 parts of dodecyl alcohol ester, 0.3-0.6 parts of a bio-based thickener, 12-19 parts of water are initially added, and 20-24 parts of water are added secondary.

[0007] By adopting the above technical solution, the nano-silica dispersion is used to react with the Ca(OH)2 generated by the hydration of quicklime through the surface hydroxyl groups to form a CSH gel network, while filling the pores of the coating, realizing the dual action of "chemical bonding + physical reinforcement", which is beneficial to improving the mechanical properties of the coating, and making the hardness and corrosion resistance stronger; at the same time, the use of bio-based thickeners obtains efficient thickening ability, which can significantly increase the viscosity of the lime-based inorganic coating, so that it can quickly restore high viscosity after construction, improve its rheological properties, reduce sagging and dripping, and has good biodegradability, reducing pollution to the environment.

[0008] Preferably, the lime-based inorganic coating is made from the following raw materials in parts by weight: 0.7-0.9 parts of cellulose, 0.8-1 parts of ammonium salt dispersant, 0.45-0.55 parts of wetting dispersant, 0.15-0.25 parts of mineral oil defoamer, 2.5-3.5 parts of dispersible rubber powder, 1.25-2.75 parts of titanium dioxide, 2-3 parts of nano-silica dispersion, 19-21 parts of quicklime, 30-32 parts of calcium carbonate, 0.75-1 parts of dodecyl alcohol, 0.4-0.6 parts of bio-based thickener, 13-17 parts of water added initially, and 21-22 parts of water added secondary.

[0009] Preferably, the lime-based inorganic coating is made from the following raw materials in parts by weight: 0.8 parts of cellulose, 1 part of ammonium salt dispersant, 0.5 parts of wetting dispersant, 0.2 parts of mineral oil defoamer, 3 parts of dispersible rubber powder, 2 parts of titanium dioxide, 3 parts of nano-silica dispersion, 20 parts of quicklime, 32 parts of calcium carbonate, 1 part of dodecyl alcohol, 0.5 parts of bio-based thickener, 15 parts of water added initially, and 21 parts of water added secondary.

[0010] Preferably, the cellulose is cellulose with a viscosity of 200,000 units.

[0011] Preferably, the ammonium salt dispersant is any one or more of polyacrylate ammonium salt, polyacrylate sodium salt, nonionic block copolymer, and sodium hexametaphosphate. Although ammonium salt dispersants account for a small proportion of the raw materials, they play a key role in the physical and chemical properties of the coating.

[0012] Preferably, the wetting and dispersing agent is any one or more of an amphiphilic wetting agent, an acetylene glycol wetting agent, an octylphenol ethoxylate, and an isomeric fatty alcohol ether wetting agent.

[0013] Preferably, the mineral oil defoamer is any one or more of paraffin oil, alkane oil, cycloalkane oil, aromatic oil, and silicone-modified polyether.

[0014] Preferably, the nano-silica dispersion is prepared by dissolving a silane coupling agent in an ethanol-water solution, slowly adding the solution to the nano-silica and stirring until the solution is initially wetted. Ultrasonic treatment is then performed at 30-50 kHz for 30 minutes, with the temperature controlled below 30-50°C to prevent solvent volatilization during the ultrasonic treatment. Ultrasonic treatment more effectively disperses the nanoparticles and reduces poor performance caused by agglomeration of the nanoparticles.

[0015] Preferably, the nano-silica dispersion is prepared by dissolving a silane coupling agent in an ethanol-water solution, slowly adding the solution to the nano-silica, and stirring until the solution is initially wetted. Ultrasonic treatment is then performed at 40 kHz for 30 minutes, with the temperature controlled below 40°C to prevent solvent volatilization during the ultrasonic treatment. Nanoparticle agglomeration results in poor performance, and ultrasonic treatment more effectively disperses the nanoparticles.

[0016] Preferably, the silane coupling agent is KH-550. The use of KH-550 coupling agent can enhance the bonding between the nanoparticles and the matrix, reduce interface defects, and lower water absorption.

[0017] Preferably, the ethanol-water solution is composed of ethanol and water in a mass ratio of 1:3. The ratio of the ethanol-water solution affects the dispersion effect, and the 1:3 ratio strikes a balance between dispersion and volatility to ensure that the treated solution is stable.

[0018] Preferably, the mass ratio of the nano-silica dispersion to the silane coupling agent: nano-silica: ethanol aqueous solution is (1-2): (40-60): (900-1000).

[0019] Preferably, the mass ratio of the nano-silica dispersion to the silane coupling agent: nano-silica: ethanol aqueous solution is 1:50:950.

[0020] Preferably, the bio-based thickener is a compound of xanthan gum and modified cellulose nanocrystals.

[0021] By adopting this approach, the surface properties of cellulose nanocrystals are improved by introducing quaternary ammonium groups. The modified cellulose nanocrystals have a positive surface charge, enhancing their dispersibility in water and reducing agglomeration. The combination of xanthan gum and modified cellulose nanocrystals can create a synergistic effect, further enhancing the thickening effect and improving the stability and uniformity of lime-based inorganic coatings. This makes the coating easier to apply during application and maintains a high viscosity at rest, preventing sagging.

[0022] Preferably, the bio-based thickener is xanthan gum and modified cellulose nanocrystals in a mass ratio of 1:2-4.

[0023] Preferably, the bio-based thickener is xanthan gum and modified cellulose nanocrystals in a mass ratio of 1:3.

[0024] Preferably, the preparation method of the modified cellulose nanocrystals is as follows: cellulose nanocrystals are dispersed in dimethyl sulfoxide, ultrasonically treated for 10 minutes, dodecyl succinic anhydride is added, and the reaction is carried out under the conditions of controlling the temperature below 100°C and stirring speed below 300 r / min. The mixture is poured into ice ethanol to terminate the reaction, and the precipitate is collected by centrifugation at 8000 r / min for 10 minutes, washed three times with acetone, and dried for later use.

[0025] By adopting this scheme, the dodecyl chains of dodecyl succinic anhydride are grafted onto the hydroxyl groups on the surface of CNCs through an esterification reaction, imparting hydrophobic properties to the material. This modification significantly improves the dispersibility of cellulose nanocrystals in the non-polar polymer matrix and reduces the agglomeration problem caused by the hydrophilic surface.

[0026] Preferably, in the preparation method of the modified cellulose nanocrystals, the mass ratio of cellulose nanocrystals to dimethyl sulfoxide to dodecylsuccinic anhydride is 1:(15-25):(0.3-0.7).

[0027] Preferably, in the preparation method of the modified cellulose nanocrystals, the mass ratio of cellulose nanocrystals to dimethyl sulfoxide to dodecylsuccinic anhydride is 1:20:0.5.

[0028] Preferably, the preparation method of the modified cellulose nanocrystals comprises reacting for 1.5-2.5 hours at a stirring speed of less than 300 r / min.

[0029] Preferably, the preparation method of the modified cellulose nanocrystals comprises reacting for 2 hours at a stirring speed of less than 300 r / min.

[0030] Preferably, the dispersible rubber powder is any one or more of ethylene / vinyl acetate copolymer, vinyl acetate / versatate copolymer, and acrylic copolymer. By adding the film-forming agent, the composite material is made to have stable properties such as uniform coating, fast film formation, and resistance to peeling off the substrate.

[0031] In a second aspect, the present application provides a method for preparing a lime-based inorganic coating, which adopts the following technical solution: A method for preparing a lime-based inorganic coating comprises the following steps: The first stage: add the initial water to the dispersion tank, move the dispersion tank to the sand mill disperser, add ammonium salt dispersant, cellulose, wetting dispersant, mineral oil defoamer in sequence, and mix at a low speed of 500-800 rpm for 4-10 minutes; The second stage: add dispersible rubber powder, titanium dioxide, nano-silica dispersion, and quicklime in sequence, increase the speed to 1500-2100 rpm, and high-speed shear for 10-16 minutes to disperse the nano-agglomerates. Check that the fineness is less than 80 μm and the fineness fluctuation is less than 5 μm. The third stage: Pour the beaten slurry into a horizontal mixer, add calcium carbonate, stir for 5 minutes, add dodecyl alcohol and bio-based thickener in turn, stir evenly and then add water for the second time, reduce the speed to 900-1200rpm, keep warm at 40-60℃, stir for 8-14 minutes to promote interfacial reaction.

[0032] By adopting the above technical solution, due to the three-stage sand milling method, low-speed mixing in the first stage ensures that the material is fully wetted, avoiding secondary agglomeration of nanoparticles caused by instantaneous high shear force; at the same time, it ensures that the filler is in full contact with the liquid phase, reducing the energy consumption of subsequent dispersion; in the second stage, high-speed shear force breaks through the van der Waals force and electrostatic attraction of the nanoparticles, achieving primary dispersion and improving dispersion uniformity; in the third stage, heat preservation stirring promotes interfacial bonding and structural stabilization, and medium-speed stirring promotes Ca bonding between the nanoparticles and quicklime. 2+ Ionic bonding and heated stirring accelerate the hydrolysis and condensation of the silane coupling agent, forming a stable interface layer and enhancing the mechanical properties of the coating. As a result, the dispersion efficiency is improved, the coating performance is enhanced, and the production process is stable and energy-saving.

[0033] Preferably, the method for preparing the lime-based inorganic coating comprises the following steps: Stage 1: Add the initial water to the dispersion tank, move the dispersion tank to the sand mill disperser, add ammonium salt dispersant, cellulose, wetting dispersant, mineral oil defoamer in sequence, and mix at a low speed of 700 rpm for 6 minutes; The second stage: add dispersible rubber powder, titanium dioxide, nano-silica dispersion, and quicklime in sequence, increase the speed to 1900 rpm, and high-speed shear for 12 minutes to disperse the nano-agglomerates. Check that the fineness is less than 80 μm and the fineness fluctuation is less than 5 μm. The third stage: Pour the beaten slurry into a horizontal mixer, add calcium carbonate, stir for 5 minutes, add dodecyl alcohol and bio-based thickener in turn, stir evenly and then add water for the second time, reduce the speed to 1000 rpm, keep warm at 50°C, stir for 12 minutes to promote interfacial reaction.

[0034] In summary, this application has the following beneficial effects: 1. The present application provides a lime-based inorganic coating that can be used immediately after opening the cover, has good product stability, quickly recovers high viscosity after construction, reduces sagging and dripping, has good wear resistance and corrosion resistance, has good biodegradability, and reduces the pollution to the environment.

[0035] 2. The present application discloses a lime-based inorganic coating, which preferably uses a nano-silica dispersion to react surface hydroxyl groups with Ca(OH)2 generated by quicklime hydration to form a CSH gel network, while filling the coating pores to achieve the dual action of "chemical bonding + physical reinforcement", which is beneficial to improving the mechanical properties of the coating, and making it harder and more corrosion-resistant.

[0036] 3. The present application discloses a lime-based inorganic coating, which preferably adopts a bio-based thickener to obtain a highly efficient thickening ability, which can significantly increase the viscosity of the lime-based inorganic coating, so that it can quickly restore high viscosity after construction, improve its rheological properties, reduce sagging and dripping, and at the same time, has good biodegradability, reducing pollution to the environment.

[0037] 4. The method of the present application adopts a three-stage sand milling method. The first stage is low-speed mixing to ensure sufficient wetting of the material, the second stage is high-speed shearing to achieve primary dispersion, and the three-stage heat preservation and stirring promotes interface bonding and structural stabilization. Therefore, the dispersion efficiency is improved, the coating performance is enhanced, and the production process is stable and energy-saving. DETAILED DESCRIPTION

[0038] The technical solution of the present application is further illustrated below through specific embodiments. The specific embodiments do not limit the scope of protection of the present application; some non-essential modifications and adjustments made by others based on the concept of the present application still fall within the scope of protection of the present application.

[0039] Unless otherwise specified, the experimental methods described in the following examples are conventional methods. The reagents and materials used are all commercially available. Dispersible rubber powder: Aksu Yilaitai Model: FX2350.

[0040] The present application is further described in detail below with reference to the following examples and comparative examples.

[0041] Unless otherwise specified, percentages in the following preparation examples and embodiments are all by mass.

[0042] Preparation Example of Nano-Silica Dispersion Preparation Examples 1-7 According to the ratio and preparation conditions shown in Table 1, the silane coupling agent KH-550 was dissolved in an ethanol aqueous solution, the ethanol aqueous solution was prepared at a mass ratio of 1:3, and then slowly added to the nano-silica, stirred until initial wetting, and ultrasonically treated for 30 minutes. The temperature was controlled to avoid solvent volatilization during the ultrasonic process to prepare a nano-silica dispersion.

[0043] Table 1 Ratio of raw materials and ultrasonic conditions of nano-silicon dioxide dispersions in Preparation Examples 1-7 The performance test determines the dispersion according to the settling velocity of the particles under the action of gravity. The nano-silica dispersion is poured into a 500 mL graduated cylinder and allowed to stand. The initial height is recorded. The settling height is then recorded after standing for 7 days.

[0044] Calculation formula: Sedimentation rate = (initial height - height after sedimentation) / time The test results are shown in Table 2: Table 2 Performance test results of nano-silicon dioxide dispersions of Preparation Examples 1-9 Combined with the experimental results of Preparation Examples 1-9, it can be seen that the nano-silica dispersions prepared with different ratios and ultrasonic conditions were observed to see whether there was stratification or precipitation and the sedimentation rate. If the dispersion remained uniform without obvious sedimentation or stratification, the stability was qualified. The lower the sedimentation rate, the better the dispersion stability.

[0045] Compared with other preparation examples, the sedimentation rate of Preparation Example 5 is 0, and the stability is better. The nano-silica dispersion is prepared according to the mass ratio of silane coupling agent: nano-silica: ethanol aqueous solution of 1:50:950. The sedimentation rate of the prepared nano-silica dispersion is 0 after standing for 7 days, and no stratification or precipitation occurs; 40kHz ultrasonic treatment is performed for 30 minutes, and the temperature is controlled at <40°C. The solvent volatilization during the ultrasonic process is avoided to obtain a nano-silica dispersion. Nanoparticle agglomeration leads to poor performance. Ultrasonic treatment is more effective in dispersing nanoparticles. The nano-silica dispersion remains uniform and has qualified stability.

[0046] Preparation example of bio-based thickener The bio-based thickener is prepared by mixing xanthan gum and modified cellulose nanocrystals according to a mass ratio to obtain the bio-based thickener.

[0047] The preparation method of modified cellulose nanocrystals is as follows: cellulose nanocrystals are dispersed in dimethyl sulfoxide, ultrasonically treated for 10 minutes, dodecyl succinic anhydride is added, and the reaction is carried out under the conditions of controlling the temperature below 100°C and stirring speed below 300 r / min. The mixture is poured into ice ethanol to terminate the reaction, and the precipitate is collected by centrifugation at 8000 r / min for 10 minutes, washed three times with acetone, and dried for use.

[0048] Preparation Examples 10-18 During the preparation of modified cellulose nanocrystals, they were obtained according to the ratios and preparation conditions shown in Table 3 .

[0049] Table 3 Different components and reaction schedule of modified cellulose nanocrystals in Preparation Examples 10-18 The grafting rate determination steps of the performance test are as follows: accurately weigh 0.5 g of the modified cellulose nanocrystal product, add 80 ml of xylene, heat and reflux until dissolved, cool to 90°C, add 1 drop of distilled water, 1 drop of pyridine and 1.5 ml of KOH-ethanol standard solution, and continue to reflux for 30 minutes; add 6 ml of isopropanol and phenolphthalein indicator, back-titrate the excess KOH with HCl-isopropanol solution, and calculate the grafting rate based on the consumption.

[0050] Contact angle method: Press the modified material into a sheet or coat it on a glass slide, ensuring the surface is flat. Use a microsyringe to drop 5 μL of deionized water onto the sample surface, and use a contact angle meter to record the droplet morphology. Hydrophobic materials generally require a contact angle greater than 90°.

[0051] The performance test results are shown in Table 4: Table 4 Test results of modified cellulose nanocrystals of Preparation Examples 10-18 Combined with the test results of Preparation Examples 10-18, it can be seen that among the modified cellulose nanocrystals prepared by Preparation Examples 10-18 with different components and stirring reaction times, Preparation Example 14 has the best comprehensive performance, with a grafting rate of 92.1% and a hydrophobic angle of 133°. When the volume of dimethyl sulfoxide solution added is too small (<15ml), the cellulose nanocrystals are unevenly dispersed, and the local concentration is too high, resulting in side reactions. The volume is too large (>25ml), resulting in a decrease in the concentration of reactants and a decrease in the reaction rate. When 0.3g of dodecyl succinic anhydride is added, the CNC hydroxyl group: acyl chloride is ≈1:0.8, and the molar ratio is insufficient, resulting in a limited grafting rate. When 0.8g of dodecyl succinic anhydride is added, the excess reagent is prone to self-polymerization, which increases the difficulty of purification. When 0.5g of dodecyl succinic anhydride is added, the reaction is carried out under the condition of a stirring speed of less than 300r / min for 2h, and the acyl chloride is fully reacted to penetrate into the hydroxyl groups inside the cellulose nanocrystals.

[0052] Based on the experiments in Preparation Examples 10-18, modified cellulose nanocrystals were prepared according to the method of Preparation Example 14 as follows: 1 g of cellulose nanocrystals was dispersed in 20 ml of dimethyl sulfoxide, ultrasonically treated for 10 minutes, and 0.5 g of dodecylsuccinic anhydride was added. After reacting for 2 hours at a temperature below 100°C and a stirring speed below 300 rpm, the mixture was poured into 200 ml of icy ethanol to terminate the reaction. The precipitate was collected by centrifugation at 8000 rpm for 10 minutes, washed three times with acetone, and dried for later use.

[0053] Preparation Example 19 Preparation of bio-based thickener: xanthan gum and modified cellulose nanocrystals are mixed in a mass ratio of 1:2 to obtain a bio-based thickener; the modified cellulose nanocrystals are prepared according to the ratio in Preparation Example 14.

[0054] Preparation Example 20 Preparation of bio-based thickener: xanthan gum and modified cellulose nanocrystals are mixed in a mass ratio of 1:3 to obtain a bio-based thickener; the modified cellulose nanocrystals are prepared according to the ratio in Preparation Example 14.

[0055] Preparation Example 21 Preparation of bio-based thickener: xanthan gum and modified cellulose nanocrystals are mixed in a mass ratio of 1:4 to obtain a bio-based thickener; the modified cellulose nanocrystals are prepared according to the ratio in Preparation Example 14. Example

[0056] Examples 1-8 Examples 1-8 disclose a lime-based inorganic coating comprising the following raw materials: 20W cellulose, ammonium salt dispersant, wetting dispersant, mineral oil defoamer, dispersible rubber powder, titanium dioxide, nano-silica dispersion, quicklime, calcium carbonate, dodecyl alcohol ester, bio-based thickener, initial water addition, and secondary water addition.

[0057] The nano-silicon dioxide dispersion was prepared according to the method in Preparation Example 5.

[0058] The preparation method of lime-based inorganic coating comprises the following steps: The first stage: add the initial water into the dispersion tank, move the dispersion tank to the sand mill disperser, add ammonium salt dispersant, 20W cellulose, wetting dispersant, mineral oil defoamer in sequence, and mix at low speed; The second stage: add dispersible rubber powder, titanium dioxide, nano-silica dispersion, quicklime in sequence, increase the speed, high-speed shear, disperse the nano-agglomerates, check the fineness is less than 80um, and the fineness fluctuation is less than 5μm; The third stage: Pour the beaten slurry into a horizontal mixer, add calcium carbonate, stir evenly, then add dodecyl alcohol and bio-based thickener in sequence, stir evenly, add water a second time, reduce the speed, keep warm and stir to promote interfacial reaction.

[0059] Examples 1-8 all provide a raw material for a lime-based inorganic coating, wherein the bio-based thickener is prepared in a mass ratio of 1:3 between xanthan gum and modified cellulose nanocrystals according to Preparation Example 20; the lime-based inorganic coating preparation method is prepared according to the conditions in Example 9; the weight of the lime-based inorganic coating including the raw materials is shown in Table 5.

[0060] Table 5 Addition amount of each component in the lime-based inorganic coating of Examples 1-8 (weight / kg) Examples 9-12 all disclose parameters of each step in a method for preparing a lime-based inorganic coating, as shown in Table 6.

[0061] Table 6 Step parameters in the preparation method of lime-based inorganic coatings of Examples 9-12 Comparative Example Comparative Examples 1-8 respectively provide a raw material of a lime-based inorganic coating and the raw material addition amount as shown in Table 7. The preparation method of the lime-based inorganic coating is prepared according to the conditions in Example 9.

[0062] Compared with Example 4, in Comparative Example 1, the nano-silicon dioxide dispersion was replaced with water.

[0063] Comparative Example 2: The bio-based thickener was replaced with xanthan gum.

[0064] Comparative Example 3: The bio-based thickener is replaced by cellulose nanocrystals.

[0065] Comparative Example 4: The bio-based thickener was replaced with a polyurethane thickener.

[0066] Comparative Example 5: The bio-based thickener was prepared according to Preparation Example 19, with the mass ratio of xanthan gum to modified cellulose nanocrystals being 1:2.

[0067] Comparative Example 6: The bio-based thickener was prepared according to Preparation Example 20, with the mass ratio of xanthan gum to modified cellulose nanocrystals being 1:3.

[0068] Comparative Example 7: The bio-based thickener was prepared according to Preparation Example 21, with the mass ratio of xanthan gum to modified cellulose nanocrystals being 1:4.

[0069] Table 7 Addition amount of each component in the lime-based inorganic coating of Comparative Examples 1-7 (weight / kg) Note: “ / ” means that the component is not added.

[0070] Performance testing The lime-based inorganic coatings were prepared according to the addition amounts of the components in Table 5 according to Examples 1-8 and the parameters of each step in the preparation method of the lime-based inorganic coating in Example 9. The coating was applied and dried. The state in the container, workability, coating appearance, low-temperature stability, low-temperature film-forming type, surface drying time, mildew resistance, mildew resistance durability, adhesion, impact resistance, and artificial weathering resistance were measured according to the methods in "GB / T 51732-2020 Determination of impact resistance of paint films", "GB / T 5210-2006 Adhesion test of paints and varnishes by pull-off method", "GB / T 9269-2009 Determination of viscosity of coatings", "GB / T 17669-2008 Aging resistance", "GB / T 1741-2020 Test method for mildew resistance of paint films", and "JG / T 26-2002 Exterior wall inorganic architectural coatings". The test items and requirements are shown in Table 8, and the results are shown in Table 9.

[0071] Table 8 Testing items and requirements for lime-based inorganic coatings The lime-based inorganic coatings prepared according to Examples 1-8 had the raw material ratios shown in Table 5, and the bio-based thickener was prepared according to Preparation Example 20; the lime-based inorganic coating preparation method was prepared according to the conditions in Example 9. The test results of Examples 1-8 are shown in Table 9 Table 9 Results of various test items of lime-based inorganic coatings in Examples 1-8 As shown in the test data in Table 9, Examples 1-8 exhibited good performance in all test indicators, including container state, workability, coating appearance, open-air time, mildew resistance, mildew resistance durability, adhesion, impact resistance, acid resistance, water resistance, and artificial weathering resistance. The lime-based inorganic coatings obtained in Examples 1-8 exhibited good viscosity and mechanical properties, enhanced hardness and corrosion resistance, allowing them to quickly recover high viscosity after application, improving their rheological properties and reducing sagging and dripping.

[0072] Table 10 Results of various test items of comparative examples 1-7 lime-based inorganic coatings As can be seen from the test data in Table 10, Comparative Example 1 has a longer dry time of 35 minutes and a lower adhesion of 2.69 MPa than Examples 1-8. In addition, blistering and softening occurred in the 500-hour artificial weathering resistance test. This indicates that the lime-based inorganic coating of Comparative Example 1, in the absence of a nano-silica dispersion, exhibits varying degrees of degradation in performance, such as dry time, adhesion, and artificial weathering resistance. Compared to Examples 1-8, due to the use of a nano-silica dispersion, surface hydroxyl groups react with Ca(OH)2 generated by quicklime hydration to form a CSH gel network, which simultaneously fills the coating pores and achieves a dual effect of "chemical bonding + physical reinforcement," which is beneficial for improving the mechanical properties of the coating, with enhanced hardness and corrosion resistance.

[0073] Compared with Examples 1-8, Comparative Examples 2-4 have different types of thickeners in the raw materials. The surface drying time of Comparative Example 2 is longer at 45 minutes, the adhesion is 2.49 MPa, and peeling and powdering phenomena occur in the 500-hour artificial weathering aging resistance test. The surface drying time of Comparative Example 3 is longer at 40 minutes, the adhesion is 2.77 MPa, and peeling phenomena occur in the impact resistance test, and peeling and powdering phenomena occur in the 500-hour artificial weathering aging resistance test. The surface drying time of Comparative Example 4 is longer at 40 minutes, and there is an obstacle in the second coat of brush application, the adhesion is 2.53 MPa, and peeling, powdering, and softening phenomena occur in the 500-hour artificial weathering aging resistance test. This shows that the types of different thickeners in Comparative Examples 2-4 have a significant impact on the performance of lime-based inorganic coatings, and on the adjustment of the rheological properties, construction performance, and film quality of the coatings. Compared with Examples 1-8, the performance of various test indicators such as coating appearance, surface drying time, adhesion, impact resistance, acid resistance, water resistance, and resistance to artificial weathering is better.

[0074] Comparative Examples 5, 6, and 7 all use bio-based thickeners. Compared with Comparative Examples 1, 2, 3, and 4, they have achieved efficient thickening capabilities, can significantly increase the viscosity of lime-based inorganic coatings, enable them to quickly restore high viscosity after construction, improve their rheological properties, reduce sagging and dripping, and at the same time, have good biodegradability, reducing pollution to the environment.

[0075] Furthermore, the addition amount of each component of the lime-based inorganic coating in Example 4 and the parameters of each step in the preparation method of the lime-based inorganic coating in Examples 9-12 were used for testing. The test items and requirements are shown in Table 8, and the results are shown in Table 11.

[0076] Table 11 Results of various test items of lime-based inorganic coatings in Examples 9-12 As can be seen from the test results in Table 11, the lime-based inorganic coatings obtained in Examples 9-11 have better adhesion and resistance to artificial weathering after film formation, fast surface drying time, good dispersibility during the preparation process, and a smooth, non-rough coating surface after drying, with stable performance. By adopting the above technical solution, due to the three-stage sand milling method, the first stage low-speed mixing ensures that the material is fully wetted, avoiding the secondary agglomeration of nanoparticles due to the instantaneous high shear force; at the same time, it is ensured that the filler is in full contact with the liquid phase, reducing the subsequent dispersion energy consumption; the second stage high-speed shear force breaks through the nanoparticle van der Waals force and electrostatic attraction, achieves primary dispersion, and improves dispersion uniformity; the third stage heat preservation stirring promotes interfacial bonding and structural stabilization, and medium-speed stirring promotes Ca2+ ion bonding of nanoparticles and quicklime, and heating stirring accelerates the hydrolysis and condensation of the silane coupling agent to form a stable interface layer, thereby enhancing the mechanical properties of the coating. Therefore, the dispersion efficiency is improved, the coating performance is enhanced, and the production process is stable and energy-saving.

[0077] The present application provides a lime-based inorganic coating and a preparation method thereof, which has the characteristics of being ready for use upon opening the lid, having good product stability, quickly recovering high viscosity after construction, reducing sagging and dripping, having strong wear resistance and corrosion resistance, and having good biodegradability, thereby reducing production energy consumption and creating a high-performance, environmentally friendly lime-based inorganic coating product.

[0078] The above description is only a preferred embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

Claims

1. A lime-based inorganic coating, characterized in that: The invention comprises the following raw materials in parts by weight: 0.6-0.9 parts of cellulose, 0.6-1.2 parts of ammonium salt dispersant, 0.4-0.55 parts of wetting dispersant, 0.1-0.25 parts of mineral oil defoamer, 2-4 parts of dispersible rubber powder, 0.5-2.75 parts of titanium dioxide, 2-4 parts of nano-silicon dioxide dispersion, 18-22 parts of quicklime, 28-34 parts of calcium carbonate, 0.5-1.25 parts of dodecyl alcohol ester, 0.3-0.6 parts of bio-based thickener, 12-19 parts of water are initially added, and 20-24 parts of water are added for the second time.

2. A lime-based inorganic coating according to claim 1, characterized in that, The preparation method of the nano-silica dispersion is as follows: dissolving a silane coupling agent in an ethanol aqueous solution, slowly adding the silane coupling agent to the nano-silica and stirring until the nano-silica is initially wetted, ultrasonically treating the nano-silica dispersion at 30-50 kHz for 30 minutes, and controlling the temperature to be less than 30-50° C. to obtain the nano-silica dispersion.

3. A lime-based inorganic coating according to claim 1, characterized in that, The preparation method of the nano-silicon dioxide dispersion comprises 40 kHz ultrasonic treatment for 30 minutes and controlling the temperature to be less than 40°C.

4. A lime-based inorganic coating according to claim 1, characterized in that, The mass ratio of the nano-silica dispersion liquid to the silane coupling agent: nano-silica: ethanol aqueous solution is (1-2): (40-60): (900-1000).

5. A lime-based inorganic coating according to claim 1, characterized in that, The bio-based thickener is xanthan gum and modified cellulose nanocrystals in a mass ratio of 1:(2-4).

6. A lime-based inorganic coating according to claim 1, characterized in that, The bio-based thickener also includes a preparation method of modified cellulose nanocrystals as follows: dispersing the cellulose nanocrystals in dimethyl sulfoxide, ultrasonically treating for 10 minutes, adding dodecyl succinic anhydride, and reacting under the conditions of controlling the temperature below 100°C and stirring speed below 300 r / min. After that, the mixture is poured into ice ethanol to terminate the reaction, centrifuged at 8000 r / min for 10 minutes, collecting the precipitate, washing it with acetone three times, and drying it for later use.

7. A lime-based inorganic coating according to claim 6, characterized in that, The mass ratio of the bio-based thickener, cellulose nanocrystals, dimethyl sulfoxide and dodecyl succinic anhydride is 1: (15-25): (0.3-0.7).

8. A lime-based inorganic coating according to claim 6, characterized in that, The bio-based thickener and the preparation method of modified cellulose nanocrystals are characterized by reacting for 1.5-2.5 hours at a stirring speed of less than 300 r / min.

9. A lime-based inorganic coating, characterized in that: The lime-based inorganic coating is prepared by using the lime-based inorganic coating according to any one of claims 1 to 8.

10. A method for preparing a lime-based inorganic coating according to any one of claims 1 to 8, characterized in that: It includes the following steps: The first stage: add the initial water to the dispersion tank, move the dispersion tank to the sand mill disperser, add ammonium salt dispersant, cellulose, wetting dispersant, mineral oil defoamer in sequence, and mix at a low speed of 500-800 rpm for 6 minutes; The second stage: add dispersible rubber powder, titanium dioxide, nano-silica dispersion, and quicklime in sequence, increase the speed to 1500-2000rpm, and high-speed shear for 10-15 minutes to disperse the nano-agglomerates. Check that the fineness is less than 80um and the fineness fluctuation is less than 5μm. The third stage: Pour the beaten slurry into a horizontal mixer, add calcium carbonate, stir for 5 minutes, add dodecyl alcohol and bio-based thickener in sequence, stir evenly and then add water for the second time, reduce the speed to 1000-1500rpm, keep warm at 40-60℃, stir for 10-15 minutes to promote interfacial reaction.

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