Preparation method of hydrophobic fumed silica for improving performance of sealant

Abstract

The invention provides a preparation method of hydrophobic fumed silica for improving the performance of a sealant. The method comprises steps as follows: hydrophilic fumed silica, silicone oil, a silane coupling agent, a solvent, a dispersing agent and the like are subjected to a mixed reaction, hydrophobic fumed silica with hydrophobic groups such as methyl and long-chain alkyl on the surface is prepared, the solvent is an alcohol solvent such as methanol, ethanol and isopropanol, the mass of the solvent is 20%-200% of that of the silicone oil, and the mass of the dispersing agent is 20%-30% of that of the hydrophobic fumed silica. The dispersing agent is a benzyl alcohol dispersing agent such as benzyl alcohol, phenethyl alcohol and phenyl isopropyl alcohol, and the mass of the dispersing agent is 10-50% of that of the silicone oil. According to the method disclosed by the invention, the technical parameters such as hydroxyl substitution degree, hydrophobic group coverage degree, particle size and particle hollowness on the surface of the fumed silica are regulated and controlled by changing factors such as the dosage, the variety, the reaction temperature and the reaction time of the solvent and the dispersing agent, and the obtained modified fumed silica has the characteristics of good hydrophobicity, high stability, high dispersity and the like. And the sealant has good compatibility with main components of the sealant such as epoxy resin and polyether polyol.

Description

Technical Field

[0001] The invention relates to a method for preparing hydrophobic fumed silica by utilizing hydrophilic fumed silica, and belongs to the technical field of micron and nanometer material preparation. Background Art

[0002] Hydrophilic fumed silica is a porous white fluffy powder material, non-toxic, tasteless, pollution-free and high temperature resistant. It has the characteristics of small particle size, large specific surface area and high purity. It is widely used in construction seam beautifier, wind power structural adhesive, lithium battery sealant, electronic packaging adhesive, building structural adhesive, catalyst carrier, decolorizer, matting agent, rubber reinforcing agent, plastic filler, ink thickener, metal soft polishing agent, insulation and thermal insulation filler, daily necessities filler and many other fields.

[0003] Sealing agent is mainly used for reserved gaps of ceramic tiles, mosaics, stones and other materials during decoration. As an important type of building material for filling gaps and decorating floors and walls, it is significantly better in decorativeness and practicality than cement-based seaming agent, solving the problems of unsightly, dirty and black ceramic tile gaps. Traditional seaming agent is applied on the surface of seaming agent, while new seaming agent does not require seaming agent as a base layer. It can be directly filled into the gap after ceramic tiles, mosaics, stones and other materials are pasted, and is suitable for filling various types of gaps. Due to its convenient construction, flexible and tough, heat and frost resistance, smooth and stain resistance, mildew and antibacterial, anti-slip and wear resistance, seaming agent is widely used in the field of building decoration and has gradually replaced cement-based seaming agent and become the main material in the seaming market.

[0004] The caulking agent is based on reactive resin, and various additives, pigments, fillers and / or aggregates are added to form a paste. Different colors of pigments and fillers such as glitter powder and pearl powder are added to the ingredients. The colors are colorful, so that every color of tile and stone can find the best caulking color to match it. The caulking agent products on the market currently have disadvantages such as low strength, poor pollution resistance, mold and blackening, and yellowing under light.

[0005] In view of the above problems of the current caulking agent products, hydrophilic fumed silica can be used as raw material, and a aging reaction can be carried out at a certain temperature under the protection of inert gas with silicone oil, silane coupling agent, etc. By changing the structural type and addition amount of silicone oil, the addition amount of silane coupling agent, the type and dosage of solvent, the type of inert gas, the spraying method, the stirring speed, the reaction temperature, the reaction time and other factors, the hydroxyl substitution degree on the surface of fumed silica, the coverage of hydrophobic groups, the particle size, the hollowness of particles and other technical parameters are comprehensively regulated, and the modified silica obtained has good hydrophobicity and high stability, and has good compatibility with the main components of caulking agents such as epoxy resins and polyether polyols, which can improve the strength, pollution resistance, mildew resistance, weather resistance and other properties of caulking agents.

[0006] At present, the surface treatment of hydrophilic fumed silica is mainly carried out with chlorosilane, fluorocarbon alkane, vinyl silicone oil, etc. Chinese Patent CN 106629742 A discloses a method for preparing hydrophobic fumed silica. This invention uses dimethyldichlorosilane or methyltrichlorosilane for modification to prepare hydrophobic fumed silica. This process has a strong hydrolysis reaction, exotherm, and generates a large amount of hydrogen chloride gas, posing serious potential production safety hazards, environmental protection pressure, and relatively serious corrosion to equipment. Chinese Patent CN 113185897 A uses fluoroalkylsilane, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, and heptadecafluorodecyltrimethoxysilane to modify silica to obtain hydrophobic silica. Due to the difficult availability of the raw materials of the modifier, this process is costly and has certain environmental protection risks. Chinese Patent CN 109592690 A discloses a method for preparing hydrophobic silica by modifying hydrophilic fumed silica with vinyl silicone oil. The reaction temperature of this process is as high as 300 - 400 °C, with large energy consumption and high production costs.

[0007] With the sharp increase in the application demand for caulking agents and the continuous increase in the demand for their characteristics, it is urgent to develop a production process of hydrophobic fumed silica with a suitable particle size, a hollow structure, good hydrophobic properties, good compatibility with the main components of caulking agents such as epoxy resin and polyether polyol, and the ability to improve the strength, stain resistance, mildew resistance, weather resistance, etc. of caulking agents. Therefore, it is of great significance to broaden the application field of fumed silica and meet the application requirements of the caulking agent market. Summary of the Invention

[0008] To meet the needs of the caulking agent market and address the deficiencies of existing hydrophobic fumed silica products, the present invention provides a method for preparing hydrophobic fumed silica using hydrophilic fumed silica. The method of the present invention enables the technical parameters such as the degree of hydroxyl substitution, coverage of hydrophobic groups, particle size, and particle hollowness of hydrophilic fumed silica to be adjusted according to needs. The obtained hydrophobic fumed silica has good hydrophobicity, high stability, good compatibility with the main components of caulking agents such as epoxy resin and polyether polyol, and can improve the strength, stain resistance, mildew resistance, weather resistance, etc. of caulking agents.

[0009] The technical solution of the present invention is as follows: A method for preparing hydrophobic fumed silica using hydrophilic fumed silica, comprising the steps: (1) Dissolve silicone oil and silane coupling agent with a solvent and a dispersant to form a homogeneous liquid, which is easy to pump and has small spray droplet particle size.

[0010] Preferably according to the present invention, the solvent used in step (1) is an alcohol solvent such as methanol, ethanol, isopropanol, etc.; preferably ethanol.

[0011] Preferably according to the present invention, the dispersant used in step (1) is a benzyl alcohol dispersant such as benzyl alcohol, phenethyl alcohol, phenyl isopropyl alcohol; preferably benzyl alcohol.

[0012] According to the present invention, the hydrophilic fumed silica used in step (1) can be purchased from the market.

[0013] According to the present invention, the silicone oil used in step (1) has the structure shown in the following formula I: (Formula I) In the formula: R1 is a saturated hydrocarbon group such as methyl, ethyl, long-chain alkyl; preferably methyl; R2 is an unsaturated hydrocarbon group such as methyl, vinyl, allyl; preferably methyl; R3 is a saturated hydrocarbon group such as methyl, ethyl, long-chain alkyl; preferably methyl; R4 is a saturated hydrocarbon group such as methyl, ethyl, long-chain alkyl; preferably methyl; R5 is a saturated hydrocarbon group such as methyl, ethyl, long-chain alkyl; preferably methyl; R6 is methyl or an unsaturated hydrocarbon group such as vinyl, allyl; preferably methyl; M is hydroxyl, methoxy, alkoxy, etc.; preferably hydroxyl; N is hydroxyl, methoxy, alkoxy, etc.; preferably hydroxyl; n is 5 ≤ n ≤ 100; preferably: 30 ≤ n ≤ 50.

[0014] According to the present invention, the mass of the silicone oil in step (1) is 2-25% of the mass of the hydrophilic fumed silica.

[0015] According to the present invention, the mass of the silane coupling agent in step (1) is 1-10% of the mass of the hydrophilic fumed silica.

[0016] According to the present invention, the mass of the solvent in step (1) is 20-200% of the mass of the silicone oil.

[0017] According to the present invention, the mass of the dispersant in step (1) is 10-50% of the mass of the silicone oil.

[0018] (2) Pump the mixed solution containing silicone oil and silane coupling agent obtained in step (1) into a mixing kettle and mix it thoroughly with the hydrophilic fumed silica.

[0019] According to the present invention, the hydrophilic fumed silica described in step (2) can be purchased from the market.

[0020] (3) Transfer the uniformly mixed fumed silica obtained in step (2) to a reaction kettle, and introduce an inert gas. The protective inert gas is nitrogen, argon or helium, preferably nitrogen.

[0021] (4) Heat up and stir the reactor described in step (3) so that the silicone oil, silane coupling agent and hydrophilic fumed silica undergo a modification reaction. The reaction temperature is 100°C to 300°C, preferably 150°C to 250°C.

[0022] Preferably according to the present invention, the reaction time in step (4) is 60 min to 480 min, preferably 120 min to 300 min.

[0023] Technical features and beneficial effects of the present invention: The present invention uses hydrophilic fumed silica as the raw material, and applies alcohol solvents and benzyl alcohol dispersants to enable the silicone oil and silane coupling agent to be fully mixed, which is beneficial for subsequent pumping and spray dispersion. After being mixed with hydrophilic fumed silica, at a higher temperature, the hydroxyl groups on the hydrophilic fumed silica are replaced, thereby introducing hydrophobic groups such as methyl groups on the surface of the silica, endowing it with hydrophobicity.

[0024] The present invention comprehensively regulates technical parameters such as the degree of hydroxyl group substitution, the coverage of hydrophobic groups, particle size, and particle hollowness on the surface of fumed silica by changing factors such as the type and addition amount of silicone oil, the addition amount of silane coupling agent, the type and amount of solvent, the type of inert gas, the spraying method, the stirring speed, the reaction temperature, and the reaction time.

[0025] The modified silica obtained by the present invention has good hydrophobicity and high stability, and has good compatibility with the main components of caulking agents such as epoxy resin and polyether polyol, and can improve the strength, stain resistance, mildew resistance, weather resistance and other properties of the caulking agent.

[0026] The preparation process of the present invention has a short process route, low equipment requirements, simple process, easy control of reaction conditions, less three-waste emissions, low cost, and high economic benefits. Specific embodiments

[0027] The following further illustrates the present invention with specific embodiments, but is not limited thereto.

[0028] Meanwhile, in the following embodiments, the experimental methods are all conventional methods unless otherwise specified; the reagents and materials are all commercially available unless otherwise specified.

[0029] In the embodiments, hydrophilic fumed silica, silicone oil, silane coupling agent, solvent, dispersant, etc. can all be purchased from the chemical market or Aladdin Reagent Company.

[0030] Example 1 A method for preparing hydrophobic fumed silica using hydrophilic fumed silica, comprising the steps: Dissolve 5 kg of silicone oil (Dow 0156) in 5 kg of ethanol, add 0.5 kg of dispersant benzyl alcohol, mix well and pump it into the mixing kettle for spray dispersion; add 50 kg of hydrophilic fumed silica to the mixing kettle and stir for 2 hours. Transfer the mixed material to the reaction kettle, introduce nitrogen for protection, stir at a speed of 63 revolutions per minute, gradually heat up to 190 °C, react for 4 hours, and obtain hydrophobic fumed silica after cooling.

[0031] Example 2 A method for preparing hydrophobic fumed silica from hydrophilic fumed silica, comprising the steps of: Dissolve 5 kg of silicone oil (Dow 0930) in 5 kg of methanol, add 0.5 kg of dispersant phenethyl alcohol, mix well and pump it into the mixing kettle for spray dispersion; add 50 kg of hydrophilic fumed silica to the mixing kettle and stir for 2 hours. Transfer the mixed material to the reaction kettle, introduce helium for protection, stir at a speed of 75 revolutions per minute, gradually heat up to 200 °C, react for 3 hours, and obtain hydrophobic fumed silica after cooling.

Claims

1. A method for preparing hydrophobic fumed silica using hydrophilic fumed silica, comprising the following steps: (1) Dissolve silicone oil and silane coupling agent in solvent and dispersant, and mix them with hydrophilic fumed silica by spray dispersion; (2) The mixed silica obtained in step (1) is heated to a certain temperature and reacted for a certain period of time under the protection of an inert gas to prepare hydrophobic fumed silica having hydrophobic groups such as methyl groups and long-chain alkyl groups on the surface.

2. The method for preparing hydrophobic fumed silica using hydrophilic fumed silica according to claim 1, characterized in that The silicone oil in step (1) has a structure as shown in the following formula I: (Formula I) Wherein: R1 is a saturated hydrocarbon group such as methyl, ethyl, and a long-chain alkyl group; R2 is an unsaturated hydrocarbon group such as methyl, vinyl, and an allyl group; R3 is a saturated hydrocarbon group such as methyl, ethyl, and a long-chain alkyl group; R4 is a saturated hydrocarbon group such as methyl, ethyl, and a long-chain alkyl group; R5 is a saturated hydrocarbon group such as methyl, ethyl, and a long-chain alkyl group; R6 is an unsaturated hydrocarbon group such as methyl, vinyl, and an allyl group; M is a hydroxyl group, a methoxy group, an alkoxy group, etc.; N is a hydroxyl group, a methoxy group, an alkoxy group, etc.; 5≤n≤100, preferably: 30≤n≤50.

3. The method for preparing hydrophobic fumed silica using hydrophilic fumed silica according to claim 1, characterized in that In step (1), the mass of the silicone oil is 2 to 25% of the mass of the hydrophilic fumed silica.

4. The method for preparing hydrophobic fumed silica using hydrophilic fumed silica according to claim 1, characterized in that In step (1), the mass of the silane coupling agent is 1 to 10% of the mass of the hydrophilic fumed silica.

5. The method for preparing hydrophobic fumed silica using hydrophilic fumed silica according to claim 1, characterized in that: The solvent is an alcohol solvent such as methanol, ethanol, isopropanol, etc., preferably ethanol; the dispersant is a benzyl alcohol dispersant such as benzyl alcohol, phenylethanol, phenyl isopropanol, etc., preferably benzyl alcohol.

6. The method for preparing hydrophobic fumed silica using hydrophilic fumed silica according to claim 1, characterized in that In step (1), the mass of the solvent is 20 to 200% of the mass of the silicone oil.

7. The method for preparing hydrophobic fumed silica using hydrophilic fumed silica according to claim 1, characterized in that In step (1), the mass of the dispersant is 10 to 50% of the mass of the silicone oil.

8. The method for preparing hydrophobic fumed silica using hydrophilic fumed silica according to claim 1, characterized in that In step (1), the protective inert gas is nitrogen, argon or helium.

9. The method for preparing hydrophobic fumed silica using hydrophilic fumed silica according to claim 1, characterized in that In step (1), the reaction temperature is 150°C to 250°C.

10. The method for preparing hydrophobic fumed silica using hydrophilic fumed silica according to claim 1, characterized in that In step (1), the reaction time is 60 min to 480 min.

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