Silica for waterborne wood coatings and method for its preparation

Abstract

The present application belongs to the field of coating technology, and discloses a kind of silica for water-based wood coatings and a preparation method thereof.The preparation steps include: preparing a silica solution, adding sulfuric acid to form a silica gel, aging, heating and adjusting the pH to be alkaline, maintaining the condition and adding water glass and sulfuric acid solution, adding a silane coupling agent for surface modification after warming, adjusting the pH to be acidic after aging, re-aging to form a precipitate, washing with pure water, ammonium salt aqueous solution and pure water in sequence, adding a dispersant (HLB value ≥ 15) and an emulsifier, dispersing uniformly under a dispersing machine and an emulsifying machine, and spray drying and air jet pulverizing.The silica has a uniform structure, is easy to disperse, has a particle size of 4.0-6.0 μm, an oil absorption of 2.70-3.00 g / g, a porosity of 1.90-2.20 cm 3 / g, a conductivity of < 50 us / cm, and a loss on ignition of 12.0-16.0%.When used in water-based wood coatings, it has good transparency, weather resistance, scratch resistance and chemical resistance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water-based wood coatings, and particularly relates to a kind of silica for water-based wood coatings and a preparation method thereof. BACKGROUND

[0002] Water-based wood coatings are a kind of coatings with water as the dispersion medium. Water-based coatings have the characteristics of low VOC, environmental friendliness, less construction hazards, easy renovation, low odor, etc. After use, people can shorten the time of moving in and have less impact on normal life. The use of water-based coatings can meet the needs of energy saving and emission reduction and sustainable development required by environmental protection, and is an effective way to reduce indoor organic pollution. With the formulation and implementation of environmental protection laws in various countries, water-based coatings have become an important direction of the development of world coatings.

[0003] Water-based wood coatings can be divided into single-component and two-component water-based wood coatings, and each has its own characteristics. Two-component water-based wood coatings add a curing agent to help film formation, and the chemical reaction cross-linking film formation of two components significantly improves the comprehensive performance of the coating film, especially the water resistance, chemical resistance, anti-blocking, hardness, etc. But two-component wood coatings have the problems of inconvenient construction, poor activation period control, and high cost, etc. Single-component water-based coatings are convenient to use, have relatively low cost, and can meet the basic performance requirements, and are currently dominant in the market of water-based wood coatings. But it relies on the natural volatilization of water and film-forming additives, the accumulation and fusion of resin particles, and the diffusion of film formation, so it has certain requirements for construction temperature and humidity, and the formed coating film is not dense enough. Single-component water-based coatings have certain limitations in applications with high requirements for coating film hardness, scratch resistance, and chemical resistance.

[0004] At present, Chinese patent CN109704348A discloses a kind of water-based special matting powder and its preparation method, its scheme is to add water, silica powder into reaction kettle, adjust solution to be alkaline with water glass I, then add water glass II and sulfuric acid solution into reaction kettle, and flow, after completion of flow, again add modified additive into reaction kettle;Adjust the pH value of reaction to be alkaline state, aging 0.5-3h;Adjust the pH value of solution in reaction kettle to be 2.5-3.0, react for 30min, then the reaction product is obtained, then the reaction product is filtered, washed to conductivity <100 μS, then dried under the condition of 100-200 DEG C, after crushing, the water-based paint special matting powder is obtained.The pore volume of silica synthesized by the method is relatively low, the matting efficiency in water-based wood coating is relatively low, and the application aspect has no application comparison with the mainstream water-based wood product.Xiaobo Zheng, et al. published the literature "Research on Different Types of Matting Powder in Water-based Wood Coatings" in the journal China Coatings, mainly introduced the matting principle of water-based wood coatings, the characteristics of different types of matting powder in water-based wood coatings, the performance, difficulties and solution ideas related to matting powder in water-based matt wood coatings. The literature only discloses the application of different silicas in water-based wood systems, and does not carry out synthesis experiment of water-based silica.

[0005] In recent years, some wood furniture on the market has a strong demand for water-based matt coating, such as water-based matte wood door coating, and developing water-based matte wood coating formula meeting market demand is the trend of the times. It is more challenging to perform matting in water-based wood coatings than in solvent-based wood coatings. In addition to considering matting efficiency, film transparency, hand feeling and other properties, its water resistance, weather resistance and chemical resistance also need to be considered. SUMMARY

[0006] In view of the deficiencies in the prior art, the present application provides a kind of water-based wood coatings silica and its preparation method, the water-based wood coatings silica prepared by the present application has uniform particle size structure, is easy to disperse, has good transparency, weather resistance, scratch resistance and chemical resistance in single-component wood system, and has been successfully used in water-based wood coating system.

[0007] The primary purpose of the present application is to provide a preparation method of water-based wood coatings silica.

[0008] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0009] A preparation method of water-based wood coatings silica, comprising the following steps:

[0010] S1, under heating condition, mix water and water glass solution to form sodium oxide-containing silica solution, then add sulfuric acid to form silica gel;

[0011] S2, heating the reaction system, the silica gel obtained in step S1 is aged, stirred and dispersed, and then the pH is adjusted to be alkaline, the condition is maintained, and the remaining water glass and sulfuric acid solution are added, then the surface modification is carried out by adding silane coupling agent after heating, and then aging is carried out, after aging, the pH is adjusted to be acidic, and then aging is carried out to form silica precipitate;

[0012] S3, the silica precipitate obtained in step S2 is washed with pure water, ammonium salt aqueous solution and pure water in sequence, and then dispersing agent and emulsifying agent are added and uniformly dispersed under the condition of dispersing machine and emulsifying machine, and the HLB value of the dispersing agent is greater than or equal to 15;

[0013] S4, the slurry after dispersion in step S3 is spray dried, and then airflow crushing is carried out, and then the water-based wood paint silica is obtained.

[0014] The particle size of the water-based wood paint silica is 4.0-6.0 μm, the oil absorption is 2.70-3.00 g / g, the porosity is 1.90-2.20 cm 3 / g, the conductivity is less than 50 us / cm, and the ignition loss is 12.0%-16.0%.

[0015] Preferably, the water glass solution in step S1 has a water glass modulus of 3.30-3.50, a sodium oxide concentration of 0.05-0.1 mol / L, and a silica concentration of 10 wt%-20 wt%, and the sulfuric acid concentration is 5 wt%-10 wt%.

[0016] Preferably, the heating temperature in step S1 is 50°C-80°C.

[0017] Preferably, the silane coupling agent in step S2 is one of KH460 (γ-aminopropyl trimethoxysilane), KH792 (N-(β-aminoethyl)-γ-aminopropyl trimethoxy (ethyl) silane), and KH602 (N-β-(aminoethyl)-γ-aminopropyl methyl dimethoxysilane); and the addition amount of the silane coupling agent is 0.40 wt%-0.50 wt% of the silica content.

[0018] Preferably, the amount of concurrent water glass added in step S2 is 70% of the total amount of water glass.

[0019] Preferably, the heating condition in step S2 is 50°C-80°C, and the temperature after heating is 90°C-100°C.

[0020] Preferably, the pH is adjusted to be alkaline to 9.5-10.5, and the pH is adjusted to be acidic to 3.0-5.0 in step S2.

[0021] Preferably, the washing in step S3 is washing with pure water, an aqueous ammonium salt solution, and pure water in sequence with a time interval of 2:4:3, respectively, until the conductivity of the silica gel is below 50 us / cm; wherein the conductivity of the pure water is below 5 us / cm, and the temperature is 50-70℃, the ammonium salt is one of ammonium sulfate, ammonium bisulfate, ammonium carbonate, and ammonium bicarbonate, and the weight ratio of the ammonium salt to water in the aqueous ammonium salt solution is 0.05-0.10:1.

[0022] Preferably, the dispersant in step S3 is one of NP-15 (alkyl phenol polyoxyethylene (15) ether), NP-20 (alkyl phenol polyoxyethylene (20) ether), NP-21 (alkyl phenol polyoxyethylene (21) ether), NP-30 (alkyl phenol polyoxyethylene (30) ether), and NP-40 (alkyl phenol polyoxyethylene (40) ether), and the amount of the dispersant added is 0.10-0.50 wt% of the silica content.

[0023] Preferably, the emulsifier in step S3 is one of AEO-7 (fatty alcohol polyoxyethylene (7) ether), AEO-9 (fatty alcohol polyoxyethylene (9) ether), AEO-15 (fatty alcohol polyoxyethylene (15) ether), AEO-20 (fatty alcohol polyoxyethylene ether), A-20 (fatty alcohol polyethylene (20) ether), and SA-20 (fatty alcohol polyoxyethylene (20) ether), and the amount of the emulsifier added is 8.0-10.0 wt% of the silica content.

[0024] Preferably, the ratio of the emulsifier to the dispersant in step S3 is 20-100:1.

[0025] Preferably, the rotation speed of the disperser in step S3 is 1000-2000 rpm, the rotation speed of the emulsifier is 2000-3000 rpm, and the combined action time is 30-60 minutes.

[0026] The second object of the present application is to provide a water-based wood paint silica prepared by the above method.

[0027] The present application also provides the use of the above water-based wood paint silica in the preparation of a one-component water-based wood paint system.

[0028] Compared with the prior art, the present application has the following advantages:

[0029] (1) The present application uses a silica solution with a sodium oxide concentration of 0.05-0.10 mol / L as the initial reaction concentration, and the low concentration of the silica solution can ensure that the primary structure particles of the water-based wood paint silica sol are small and uniform in structure, thereby ensuring stable growth of the silica particles.

[0030] (2) The application uses a water-soluble silane coupling agent to treat silica, wherein the selected silane coupling agent can improve the formation of a silica particle network structure, improve the compatibility of silica with water-based wood resin and additives, form a silica structure with strong chemical bonds and chemical stability, make the hardness and strength of the paint film formed by the silica structure higher, and thus improve the water resistance, weather resistance, and other properties of the water-based paint film.

[0031] (3) The application adds an alkylphenol polyoxyethylene ether with an HLB value of 15 or more as a silica dispersant. The greater the HLB value, the greater the hydrophilicity, thereby improving the mixing and uniformity of the dispersant and the silica solution, uniformly dispersing the silica sol, inhibiting the formation of silica silanol after the silica particles grow and form, promoting the uniform emulsification of the silica particles, making the refractive index of the dispersant closer to the resin, and thus improving the transparency of the wood application. The use of an emulsifier to treat the silica solution ensures that the silica is dispersed in the form of microns in the continuous phase, reduces the interfacial tension of each component in the mixed system, forms a relatively strong film on the surface of the droplets to prevent the droplets from aggregating with each other, maintains the uniform emulsion of the silica, and thus forms uniform silica dispersion. The simultaneous addition of the dispersant and the emulsifier and the maintenance of a certain ratio can ensure the uniform emulsification of the dispersed silica primary particles, thereby improving the interfacial tension between the silica and the water-based resin, improving the wetting efficiency, improving the storage stability of the paint, enhancing the tinting strength, color development, weather resistance of the water-based paint, and imparting good weather resistance and gloss to the paint film.

[0032] (4) To ensure the comprehensive application performance of the silica for water-based wood coatings in a single-component water-based wood system, only the synergistic effect of the dispersant, silane coupling agent, emulsifier, and other various conditions in the entire technical solution can ensure good application performance when applied to the wood system. DETAILED DESCRIPTION

[0033] The technical solutions of the application will be described clearly and completely below in combination with the examples and comparative examples of the application. Obviously, the described examples are only some of the examples of the application, rather than all the examples. Based on the examples in the application, all other examples obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the application.

[0034] The test methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, and the like used are commercially available reagents and materials unless otherwise specified.

[0035] Example 1

[0036] At a temperature of 80°C, 5mL of 0.1% silane coupling agent was added to 5mL of 0.1% silica sol, and the mixture was stirred for 1 hour to obtain a silica solution. 3A silica solution with a sodium oxide concentration of 0.05 mol / L was prepared by adding 1000 L of pure water and 20 wt% water glass to a stirred reactor. Then, a 10 wt% sulfuric acid solution was added over 20 minutes until the pH reached 8.0. After reaching the pH, stirring was stopped. A silica gel formed after 10 minutes. The gel was then aged at 80°C for 30 minutes. After aging, the silica gel was dispersed by stirring at full speed for 30 minutes. Finally, a small amount of... The pH was adjusted to 9.5 with water glass. Then, 20 wt% water glass was added to the reactor at a flow rate of 800 L / h for a certain period of time, maintaining the total amount of water glass at 70% of the total amount. Simultaneously, a 10 wt% sulfuric acid solution was added to the reactor, maintaining the pH at 9.5. After the water glass was added, the temperature was raised to 100℃, and then 0.40 wt% silica-containing silane coupling agent KH792 (N-(β-aminoethyl)-γ-aminopropyltrimeth(ethoxysilane)) was added. The reaction was aged for 120 minutes under this pH condition. After aging, pure water was added to cool the temperature to 70°C. Then, sulfuric acid was added at this temperature to adjust the pH to 3.0 and the mixture was aged for 60 minutes. After aging, the mixture was pumped into a filter press frame for washing. The filter cake was washed in a sequence of 50°C pure water: 0.10wt% ammonium salt aqueous solution: 50°C pure water at time intervals of 2:4:3, for a total washing time of 6 hours, until the conductivity was below 50µs / cm. After washing, silica content of 0. 10 wt% of silica dispersant NP-15 (alkylphenol polyoxyethylene (15) ether) and 8.0 wt% of silica emulsifier AEO-9 (fatty alcohol polyoxyethylene (9) ether) were added. The ratio of emulsifier to dispersant was 80:1. The emulsion was then dispersed for 30 minutes using a disperser and an emulsifier. The speed of the disperser was 2000 rpm and the speed of the emulsifier was 2000 rpm. The resulting slurry was spray-dried and then air-jet pulverized to obtain silica products for water-based wood coatings.

[0037] Test methods and standards for the physicochemical properties of products:

[0038] (1) Porosity test: TriStar II 3020 fully automatic specific surface area and porosity analyzer;

[0039] (2) Average particle size: Laser particle size analyzer: Malvern 3000;

[0040] (3) Oil absorption value: Manual knife picking method: 1g of silica absorbs the amount of dibutyl phthalate; refer to industry standard HG / T3072-2019;

[0041] (4) Conductivity test: Leici DDS-11A;

[0042] (5) Loss on ignition: Chemical analysis method: The dry sample is ignited in a muffle furnace at 950±5℃, and the moisture content of the sample is determined by differential method; Refer to industry standard: HG / T3066-2008;

[0043] The physicochemical properties of the seven parallel products are shown in Table 1.

[0044] Table 1

[0045]

[0046] Example 2

[0047] At a temperature of 50℃, to a depth of 5m 3 A silica solution with a sodium oxide concentration of 0.10 mol / L was prepared by adding 2000 L of pure water and 10 wt% water glass to a stirred reactor. Then, a 5 wt% sulfuric acid solution was added over 10 minutes until the pH reached 9.0. Stirring was stopped after the pH was reached. Silica gel formed after 20 minutes. The solution was then aged at 50°C for 10 minutes. After aging, the silica gel was dispersed by full-speed stirring for 10 minutes. Finally, the solution was added... A small amount of water glass was used to adjust the pH to 10.5. Then, 10wt% water glass was added to the reactor at a flow rate of 600 L / h for a certain period of time, maintaining the total amount of water glass at 70% of the total volume. Simultaneously, a 5wt% sulfuric acid solution was added to the reactor, maintaining the pH at 10.5. After the water glass was added, the temperature was raised to 90℃, and then 0.50wt% of an aminosilane coupling agent KH460 (γ-aminopropyltrimethoxysilane) with a silica content was added. At this pH condition... The reaction was aged for 90 minutes. After aging, pure water was added to lower the temperature to 50°C. Then, sulfuric acid was added at this temperature to adjust the pH to 5.0, and the mixture was aged for another 30 minutes. After aging, the mixture was pumped into a filter press for washing. The filter cake was washed in a sequence of 70°C pure water: 0.05wt% ammonium salt aqueous solution: 70°C pure water, with time intervals of 2:4:3. The washing time was 6 hours, until the conductivity was below 50µs / cm. After washing, 0.50wt% silica was added. The emulsion was prepared by dispersing NP-20 (alkylphenol polyoxyethylene (20) ether) with t% silica content and emulsifier AEO-7 (fatty alcohol polyoxyethylene (7) ether) with 10.0wt% silica content. The ratio of emulsifier to dispersant was 20:1. The emulsion was dispersed for 60 minutes using a disperser and an emulsifier. The speed of the disperser was 1000 rpm and the speed of the emulsifier was 3000 rpm. The slurry obtained after dispersion was spray-dried and then pulverized by airflow to obtain silica products for water-based wood coatings.

[0048] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 2.

[0049] Table 2

[0050]

[0051] Example 3

[0052] At a temperature of 60℃, to a depth of 5m 3 A silica solution with a sodium oxide concentration of 0.08 mol / L was prepared by adding 1500 L of pure water and 15 wt% water glass to a stirred reactor. Then, a 7.5 wt% sulfuric acid solution was added over 15 minutes until the pH reached 8.5. Stirring was stopped after the pH was reached. After 15 minutes, a silica gel formed. The gel was then aged at 50°C for 20 minutes. After aging, the silica gel was dispersed by stirring at full speed for 20 minutes. A small amount of water glass was added to adjust the pH to 10.0. Then, 15wt% water glass was added to the reactor at a flow rate of 700 L / h for a certain period of time, maintaining the total amount of water glass at 70% of the total amount. Simultaneously, a 7.5wt% sulfuric acid solution was added to the reactor, maintaining the pH at 10.0. After the water glass was added, the temperature was raised to 95℃, and then 0.45wt% of an aminosilane coupling agent KH460 (γ-aminopropyltrimethoxysilane) with a silica content was added. The reaction was aged for 100 minutes under the specified pH conditions. After aging, pure water was added to lower the temperature to 60°C. Sulfuric acid was then added at this temperature to adjust the pH to 4.0, and the mixture was aged for 45 minutes. After aging, the mixture was pumped into a filter press for washing. The filter cake was washed using a sequence of 60°C pure water: 0.08wt% ammonium salt aqueous solution: 60°C pure water, with time intervals of 2:4:3, for a total washing time of 5 hours, until the conductivity was below 50 μS / cm. After washing, silica content was added... 0.30 wt% silica dispersant NP-21 (alkylphenol polyoxyethylene (21) ether) and 9.00 wt% silica content AEO-20 (fatty alcohol polyoxyethylene ether), with an emulsifier to dispersant ratio of 30:1, were used to disperse the emulsion liquid for 40 minutes using a disperser and an emulsifier. The disperser speed was 1500 rpm and the emulsifier speed was 2500 rpm. The resulting slurry was spray-dried and then air-jet pulverized to obtain a silica product for water-based wood coatings.

[0053] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 3.

[0054] Table 3

[0055]

[0056] Example 4

[0057] At a temperature of 70℃, to a depth of 5m 3 A silica solution with a sodium oxide concentration of 0.075 mol / L was prepared by adding 1800 L of pure water and 18 wt% water glass to a stirred reactor. Then, a 9 wt% sulfuric acid solution was added over 15 minutes until the pH reached 8.0. Stirring was stopped after the pH was reached. A silica gel formed after 20 minutes. The gel was then aged at 70°C for 25 minutes. After aging, the silica gel was dispersed by stirring at full speed for 25 minutes. Finally, a small amount of water was added. The pH was adjusted to 10.0 using glass. Then, 18wt% water glass was added to the reactor at a flow rate of 800 L / h for a certain period, maintaining the total amount of water glass at 70%. Simultaneously, a 9wt% sulfuric acid solution was added to the reactor, maintaining the pH at 10.0. After the water glass was added, the temperature was raised to 96℃, and then 0.49wt% of an aminosilane coupling agent KH792 (N-(β-aminoethyl)-γ-aminopropyltrimeth(ethoxysilane)) was added. The reaction was aged for 110 minutes under this pH condition. After aging, pure water was added to cool the mixture to 60°C, and then sulfuric acid was added at this temperature to adjust the pH to 4.5 for aging for another 60 minutes. After aging, the mixture was pumped into a filter press frame for washing. The filter cake was washed in a sequence of 65°C pure water: 0.10wt% ammonium salt aqueous solution: 65°C pure water, with time intervals of 2:4:3, for a total washing time of 5 hours, until the conductivity was below 50 μS / cm. After washing, 0.40% silica was added. The emulsion was prepared by mixing NP-30 (alkylphenol polyoxyethylene (30) ether) with wt% silica dispersant and AEO-15 (fatty alcohol polyoxyethylene (15) ether) with 9.80 wt% silica content, with a ratio of emulsifier to dispersant of 24.5:1. The emulsion was then dispersed for 50 minutes using a disperser and an emulsifier with a speed of 2000 rpm and a speed of 3000 rpm. The resulting slurry was spray-dried and then pulverized by airflow to obtain silica products for water-based wood coatings.

[0058] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 4.

[0059] Table 4

[0060]

[0061]

[0062] Example 5

[0063] At a temperature of 60℃, to a depth of 5m 3A silica solution with a sodium oxide concentration of 0.10 mol / L was prepared by adding 1700 L of pure water and 20 wt% water glass to a stirred reactor. Then, a 15 wt% sulfuric acid solution was added over 20 minutes until the pH reached 8.5. Stirring was stopped after the pH was reached. A silica gel formed after 15 minutes. The gel was then aged at 60°C for 20 minutes. After aging, the silica gel was dispersed by stirring at full speed for 30 minutes. Finally, a small amount of... The pH was adjusted to 9.5 with water glass. Then, 20 wt% water glass was added to the reactor at a flow rate of 700 L / h for a certain period, maintaining the total amount of water glass at 70% of the total volume. Simultaneously, a 15 wt% sulfuric acid solution was added to the reactor, maintaining the pH at 9.5. After the water glass addition was complete, the temperature was raised to 97°C, and then 0.50 wt% of an aminosilane coupling agent KH602 (N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane) was added. The reaction was aged for 120 minutes under the specified pH conditions. After aging, pure water was added to lower the temperature to 70°C. Sulfuric acid was then added at this temperature to adjust the pH to 5.0, and the mixture was aged for another 50 minutes. After aging, the mixture was transferred to a filter press for washing. The filter cake was washed using a sequence of 70°C pure water: 0.09wt% ammonium salt aqueous solution: 70°C pure water, with time intervals of 2:4:3, for a total washing time of 6 hours, until the conductivity was below 50 μS / cm. After washing, 0.30% silica was added. The emulsion was prepared by mixing 10.0 wt% silica dispersant NP-40 (alkylphenol polyoxyethylene (40) ether) and 10.0 wt% silica emulsifier SA-20 (fatty alcohol polyoxyethylene (20) ether), with a ratio of emulsifier to dispersant of 33.3:1. The emulsion was then dispersed for 60 minutes using a disperser and an emulsifier at a speed of 1500 rpm and 2500 rpm. The resulting slurry was spray-dried and then pulverized by airflow to obtain silica products for water-based wood coatings.

[0064] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 5.

[0065] Table 5

[0066]

[0067] Example 6

[0068] At a temperature of 70℃, to a depth of 5m 3A silica solution with a sodium oxide concentration of 0.06 mol / L was prepared by adding 1400 L of pure water and 10 wt% water glass to a stirred reactor. Then, an 8 wt% sulfuric acid solution was added over 15 minutes until the pH reached 8.5. Stirring was stopped after the pH was reached. Silica gel formed after 20 minutes. The gel was then aged at 70°C for 25 minutes. After aging, the silica gel was dispersed by stirring at full speed for 20 minutes. Finally, a small amount of water was added. The pH was adjusted to 10.0 using glass. Then, 10wt% water glass was added to the reactor at a flow rate of 750 L / h for a certain period, maintaining the total amount of water glass at 70%. Simultaneously, an 8wt% sulfuric acid solution was added to the reactor, maintaining the pH at 10.0. After the water glass was added, the temperature was raised to 95℃, and then 0.40wt% of an aminosilane coupling agent KH602 (N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane) was added. The reaction was aged for 100 minutes under this pH condition. After aging, pure water was added to cool the temperature to 60°C, and then sulfuric acid was added at this temperature to adjust the pH to 4.0 for aging for 45 minutes. After aging, the filter cake was drawn into a filter press frame for washing. The washing sequence was 60°C pure water: 0.10wt% ammonium salt aqueous solution: 60°C pure water, with time intervals of 2:4:3, and the washing time was 5 hours, until the conductivity was below 50 μS / cm. After washing, the initial silica content was added... 0.10 wt% silica dispersant NP-30 (alkylphenol polyoxyethylene (30) ether) and 10.0 wt% silica emulsifier A-20 (fatty alcohol polyethylene (20) ether), with a ratio of emulsifier to dispersant of 100:1, were used to disperse the emulsion liquid for 40 minutes using a disperser and an emulsifier. The disperser speed was 1000 rpm and the emulsifier speed was 3000 rpm. The resulting slurry was spray-dried and then air-jet pulverized to obtain silica products for water-based wood coatings.

[0069] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 6.

[0070] Table 6

[0071]

[0072] Comparative Example 1

[0073] The difference from Example 1 is that the sodium oxide concentration in the water glass solution is 0.15 mol / L, while the other conditions and operations are the same as in Example 1.

[0074] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 7.

[0075] Table 7

[0076]

[0077]

[0078] Comparative Example 2

[0079] The difference from Example 1 is that silane coupling agent KH550 with a silica content of 0.40 wt% is added instead of silane coupling agent KH792 with a silica content of 0.40 wt%, while other conditions and operations are the same as in Example 1.

[0080] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 8.

[0081] Table 8

[0082]

[0083] Comparative Example 3

[0084] The difference from Example 1 is that after the silica gel is aged, no silica dispersant is added to the reactor, and the other conditions and operations are the same as in Example 1.

[0085] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 9.

[0086] Table 9

[0087]

[0088]

[0089] Comparative Example 4

[0090] The difference from Example 1 is that after the silica gel is aged, NP-15 is not added to the reactor, but instead NP-7 (alkylphenol polyoxyethylene (7) ether) dispersant is added. Other conditions and operations are the same as in Example 1.

[0091] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 10.

[0092] Table 10

[0093]

[0094] Comparative Example 5

[0095] The difference from Example 1 is that the emulsifier AEO-9 (fatty alcohol polyoxyethylene (9) ether) with a silica content of 8.0 wt% was not added, while the other conditions and operations were the same as in Example 1.

[0096] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 11.

[0097] Table 11

[0098]

[0099] Comparative Example 6

[0100] The difference from Example 1 is that the emulsifier is different. OP-10 (polyoxyethylene octylphenol ether-10) with a silica content of 8.0 wt% is added instead of emulsifier AEO-9 (fatty alcohol polyoxyethylene (9) ether). Other conditions and operations are the same as in Example 1.

[0101] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 12.

[0102] Table 12

[0103]

[0104]

[0105] Comparative Example 7

[0106] The difference from Example 1 is that NP-15 (alkylphenol polyoxyethylene (15) ether), a silica dispersant with a silica content of 0.50 wt%, and AEO-9 (fatty alcohol polyoxyethylene (9) ether), an emulsifier with a silica content of 8.0 wt%, are added. The ratio of emulsifier to dispersant is 16:1. Other conditions and operations are the same as in Example 1.

[0107] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 13.

[0108] Table 13

[0109]

[0110] Comparative Example 8

[0111] The difference from Example 1 is that the dispersant and emulsifier are added separately. The dispersant is added after the silica gel is formed, and then aged at 80°C for 30 minutes. After aging, silica dispersant NP-15 (alkylphenol polyoxyethylene (15) ether) with an initial silica content of 0.10 wt% is added to the reactor, and the silica gel is dispersed by stirring at full speed for 30 minutes. Other conditions and operations are the same as in Example 1.

[0112] The testing methods and standards for the physical and chemical properties of the products are the same as in Example 1. The physical and chemical properties of the seven parallel products are shown in Table 14.

[0113] Table 14

[0114]

[0115] Results Analysis

[0116] The test data from the above six embodiments show that the physicochemical properties of the products produced according to the technical solution of the present invention are basically similar, indicating that the production of the technical solution is stable.

[0117] In Comparative Example 1, the sodium oxide concentration of the seed water glass solution was set to 0.15 mol / L, which is higher than the required range of 0.05–0.10 mol / L. Compared with the Example, the oil absorption, porosity, and loss on ignition of the Comparative Example were slightly lower, while the conductivity was increased. The silica particle size did not change much. The main reason is that the initial sodium oxide concentration was increased, and the concentration of seed silica also increased accordingly, making the primary silica particles larger. This affected the formation and growth of the silica particle pore structure, resulting in a decrease in silica porosity. Consequently, the oil absorption and loss on ignition decreased due to the reduced pore volume, and the conductivity after water washing increased due to the smaller porosity.

[0118] After replacing the coupling agent in Comparative Example 2, the product's oil absorption, porosity, and loss on ignition decreased, and the particle size after pulverization was unstable with relatively large fluctuations. The main reason is that the structures of other coupling agents are significantly different from those of K540, KH792, and K602 silane coupling agents. Secondly, K540, KH792, and K602 contain amino bond hydrolysis reactions that occur automatically in the presence of water, eliminating the need for acid additives. This can accelerate the stabilization of the chemical properties of silica and the formation of the silica network structure, thereby improving the porosity, oil absorption, and loss on ignition of silica.

[0119] Comparative Example 3 did not add NP-15 (alkylphenol polyoxyethylene (15) ether) silica dispersant. Compared with the example, the oil absorption, porosity, and loss on ignition of the comparative example were reduced, while the conductivity was increased. The decrease was greater than that of Comparative Example 1. The main reason is that the selected silica dispersant such as NP-15 (alkylphenol polyoxyethylene (15) ether) has an HLB value of greater than or equal to 15. The high HLB value makes it easier for silica to combine with silica particle solution. The dispersed silica particles can inhibit the formation of silica silanol groups, thereby making the silica particle structure more uniform. This can promote the growth of silica particle size and structure, thereby improving the porosity and oil absorption value of silica.

[0120] Comparative Example 4, which incorporates alkylphenol polyoxyethylene ether (NP-7) with an HLB value lower than 15, shows a lower oil absorption rate of silica compared to dispersants with an HLB value greater than or equal to 15. The main reason for this is that adding a dispersant with a lower HLB value is not conducive to the full and uniform dispersion of silica particles and the dispersant. The lower HLB value causes a large amount of dispersant to precipitate, resulting in the dispersant failing to meet the expected requirements and being unable to participate in dispersion. Consequently, Comparative Example 4 shows a reduction in oil absorption, porosity, and loss on ignition compared to the examples.

[0121] Comparative Example 5, which did not contain emulsifier, showed a significant reduction in loss on ignition, while other indicators were not affected. This is mainly because the emulsifier does not participate in the silica structure formation reaction, but rather enters the porosity of silica after the structure is formed, thus greatly reducing the loss on ignition of silica, while having little impact on other indicators.

[0122] In Comparative Example 6, the emulsifier was replaced by OP-10 (polyoxyethylene octylphenol ether-10) instead of AEO-9 (fatty alcohol polyoxyethylene (9) ether). The porosity, oil absorption, and loss on ignition of silica were significantly lower than those of the standard sample. Although OP-10 (polyoxyethylene octylphenol ether-10) is also an emulsifier, it reduced the interfacial tension of the dispersant in the mixed system, thus making it unable to achieve the emulsifying effect of AEO-9 (fatty alcohol polyoxyethylene (9) ether). This proves that the application effect can only be achieved when NP-15 (alkylphenol polyoxyethylene (15) ether) and AEO-9 (fatty alcohol polyoxyethylene (9) ether) are added simultaneously.

[0123] Comparative Example 7, with a silica emulsifier and dispersant ratio of 16:1, showed significantly higher porosity and oil absorption than the standard sample. This was because the smaller amount of emulsifier compared to the dispersant resulted in a relatively smaller amount of emulsifier coating the dispersed silica particles, thus increasing the silica porosity and oil absorption. The loss on ignition was significantly lower than in the previous example. Furthermore, this invention also found that if the emulsifier to dispersant ratio exceeds 100, it reduces the silica porosity and oil absorption because excessive emulsifier clogs the silica pores, thereby reducing the silica pore volume.

[0124] The dispersant was added at different stages in Comparative Example 8. The difference is that in Comparative Example 8, the dispersant was added during the formation of primary silica particles, while in the example, it was added after the silica particles had grown and formed. The purpose of adding the dispersant is to uniformly disperse the silica particles. The dispersed silica particles can inhibit the formation of silanol groups in silica, thereby promoting the growth of silica particles and surface emulsification. The purpose of adding the dispersant in the comparative example is to uniformly disperse the primary silica particles, thereby promoting the growth of the silica structure. Experimental data show that the effect of adding the dispersant after the secondary particles have formed and grown is better than that of adding it after the primary particles have grown, with higher oil absorption value, pore volume and loss on ignition.

[0125] Application performance testing

[0126] The three water-based silica products prepared according to this invention (Examples 1-2, 3-2, and 5-2) and comparative examples 2-2, 4-2, and 6-2) were compared with Grace W300 and Degussa OK607 in a single-component water-based wood system. The basic formulations for the tests are shown in Table 15 below:

[0127] Table 15. Test formulations for single-component wood products

[0128]

[0129] Preparation process:

[0130] Step 1: Add the single-component propionic acid emulsion Joncryl 7124 to BYK-163 and disperse for 10 minutes to form a mixed solution;

[0131] Step 2: Slowly add the matting powder sample to the mixture and disperse at high speed for 20 minutes. The fineness should be ≤30μm.

[0132] Step 3: Reduce the speed and slowly add the BYK-024 and BYK-019, which are diluted evenly with water, and disperse for 10 minutes; Step 4: Then add TEXANOL, Loxanol MI 6735, BYK-333, and U-W293A in sequence, dispersing for 5 minutes after each addition before adding the next one;

[0133] Step 5: Dilute BYK-420 and BYK-605 with water, then slowly add them to the already dispersed mixture, stir for 10 minutes, and test the filter using a 300-mesh filter.

[0134] Prepare single-component matte clear topcoat samples according to the above formula and process.

[0135] Performance testing methods:

[0136] 1. Surface Dry: Surface dry, also known as touch dry, refers to the stage where the wet coating film has reached surface dryness. The coating film changes from a flowable liquid state to a relatively non-flowable state where a film begins to form on the surface. At this point, the coating film no longer adheres to small particles. 2. Complete Dry: After the product reaches the time specified in the standard, check whether the paint film is actually dry within a range of at least 1 cm from the edge of the film surface. Use a safety blade to cut and scrape the paint film on a sample and observe that there is no adhesion to the underlying layer or inside the film (i.e., the paint film is considered to be actually dry).

[0137] 3. Gloss: Gloss is tested with a photometer; the standard is BGD516 / 3.

[0138] 4. Anti-settling properties are tested using industry-standard methods: after drying at 60℃ for one week, the height of the flocculent material in a 100cm measuring cylinder is observed. The higher the height, the more resistant it is to settling.

[0139] 5. Paint viscosity was tested using a rotational viscometer: NDJ-5S;

[0140] 6. Hardness test method: The test shall be conducted in accordance with GB / T 6739-2006 "Determination of Hardness of Paints and Varnishes by Pencil Method";

[0141] 7. Boiling water resistance: Immersed in boiling water at 100℃ for 15 minutes, and rated according to standard GB / T1766-2008;

[0142] 8. Weather resistance: Weather resistance is tested by exposing the board to sunlight and wind, and observing any changes in the board's condition.

[0143] 9. Alcohol resistance (95% alcohol): Rub the surface back and forth with a white cotton cloth soaked in 95% alcohol at a pressure of about 5N. Wipe the white cotton cloth dry and rub the paint film back and forth 200 times. Visually inspect the surface appearance. If the sample is qualified, leave it at room temperature for at least 2 hours. Rating shall be carried out in accordance with GB / T 9279-1988.

[0144] The physicochemical properties and application test results of the single-component matte clear topcoat are shown in Table 16.

[0145] Table 16

[0146]

[0147] Eight samples, including samples from Examples 1-2, 3-2, and 5-2, and comparative samples 2-2, 4-2, and 6-2, along with Grace W300 and Degussa OK607, were compared and tested in a single-component water-based wood product system.

[0148] Compared with Degussa OK607, the water-based silica for wood products synthesized in this invention has very similar performance indicators, except for slight differences in porosity and loss on ignition. The application performance of this invention is relatively similar to that of OK607, and its transparency is better than that of OK607.

[0149] Compared with Grace W300, the embodiment has lower porosity, oil absorption value and loss on ignition. Its application performance is poorer in anti-settling and lower in viscosity, but higher surface hardness after drying. Other properties are not much different from the embodiment. The overall performance of the embodiment is relatively close to that of Grace W300, and its anti-settling is better than that of Grace W300.

[0150] The porosity, oil absorption value, loss on ignition, anti-settling properties, application viscosity, water resistance, alcohol resistance, and matting properties of the comparative model cannot meet the requirements for single-component water-based wood products.

[0151] In summary, the performance of the water-based silica for wood products synthesized in this invention is close to that of commercially available Grace W300 and Degussa OK607, and some properties are even superior to those of Grace W300 and Degussa OK607.

[0152] Obviously, the above embodiments of the present invention are merely examples to clearly illustrate the technical solution of the present invention, and are not intended to limit the specific implementation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A method for the preparation of a silica for water-borne wood coatings, characterized in that It comprises the following steps: S1. Under heating, water and water glass solution are mixed to form a silica solution containing sodium oxide, and then sulfuric acid is added to form a silica gel; S2. The silica gel obtained in step S1 is aged and stirred to disperse, and then the pH is adjusted to be alkaline. The condition is maintained while the remaining water glass solution and sulfuric acid are added. After heating, a silane coupling agent is added for surface modification, and then aging is performed. After aging, the pH is adjusted to be acidic, and then aging is performed again to form a silica precipitate; S3. The silica precipitate obtained in step S2 is washed with pure water, an aqueous ammonium salt solution, and pure water in sequence. After washing, a dispersant and an emulsifier are added, and then they are uniformly dispersed using a dispersing machine and an emulsifying machine. The HLB value of the dispersant is greater than or equal to 15. S4, the slurry dispersed in step S3 is spray dried, and then airflow pulverized, to obtain the product; the particle size of the silica for water-based wood coatings is 4.0-6.0 μm, the oil absorption is 2.70-3.00 g / g, the porosity is 1.90-2.20 cm 3 / g, the conductivity is less than 50 μs / cm, and the loss on ignition is 12.0%-16.0%.

2. A method for preparing a silica for water-borne wood coatings according to claim 1, characterized in that, In step S1, the modulus of the water glass solution is 3.30-3.50, the concentration of sodium oxide in the silica solution is 0.05-0.1 mol / L, and the concentration of silica is 10wt%-20wt%.

3. The method for preparing silica for water-based wood coatings according to claim 1, characterized in that, In step S2, the heating temperature is 50℃-80℃, and the temperature after heating is 90℃-100℃.

4. The method of claim 1, wherein the silica for water-borne wood coatings is prepared by the steps of: In step S2, the silane coupling agent is one of γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxy (ethoxy) silane, and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane. The amount of the silane coupling agent added is 0.20wt%-0.50wt% of the silica content.

5. The method of claim 1, wherein the silica for water-borne wood coatings is prepared by the steps of: In step S3, the dispersant is one of alkylphenol polyoxyethylene (15) ether, alkylphenol polyoxyethylene (20) ether, alkylphenol polyoxyethylene (21) ether, alkylphenol polyoxyethylene (30) ether, and alkylphenol polyoxyethylene (40) ether. The amount of the dispersant added is 0.10wt%-0.50wt% of the silica content.

6. The method of claim 1, wherein the silica for water-borne wood coatings is prepared by the steps of: In step S3, the emulsifier is one of fatty alcohol polyoxyethylene (7) ether, fatty alcohol polyoxyethylene (9) ether, fatty alcohol polyoxyethylene (15) ether, fatty alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene (20) ether, and fatty alcohol polyoxyethylene (20) ether. The amount of the emulsifier added is 8.0wt%-10.0wt% of the silica content.

7. The method for preparing silica for water-based wood coatings according to claim 1, characterized in that, In step S3, the ratio of the emulsifier to the dispersant is 20-100:

1.

8. The method of claim 1, wherein the silica for water-borne wood coatings is prepared by the steps of: In step S3, the washing refers to washing with pure water, an aqueous ammonium salt solution, and pure water in sequence with a time interval of 2:4:3, respectively, until the conductivity of the silica gel is less than or equal to 50μs / cm. The conductivity of the pure water is less than 5μs / cm, and the temperature of the pure water is 50℃-70℃. The ammonium salt is one of ammonium sulfate, ammonium bisulfate, ammonium carbonate, and ammonium bicarbonate. The weight ratio of the ammonium salt to water in the aqueous ammonium salt solution is 0.05-0.10:

1.

9. A silica for water-based wood coatings prepared by the method of any one of claims 1-8.

10. The use of the silica of claim 9 in the preparation of a one-component water-based wood coating system.

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