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Jan 21, 2021
Silicone resin has excellent thermal oxidation stability, weather resistance, electrical insulation, water repellency and corrosion resistance. It has been widely used in high and low temperature resistant insulating paint, special coatings, adhesives, film plastics, etc. However, the current high and low temperature resistant insulating varnishes and special coatings of silicone resins mainly use organics such as aromatic hydrocarbons and alcohols as solvents, which will generate a large amount of VOC (volatile organic compounds), which will cause great harm to the environment and human body. Water-based is the current research hotspot and development trend. This work researches and designs ammonia water as a salt-forming agent, and makes use of the characteristics of silanol in silicone resin that it is easy to form salt under alkaline conditions to make the salt self-emulsify, using water as the dispersion medium to form an aqueous emulsion. The resin uses water as the solvent, does not generate VOC, and is very convenient to use and store; when the ammonia and water are cured, they will be removed by themselves without affecting the structure and performance of the resin. The method is simple, reliable, low cost, low pollution, suitable for industrial production, and has good application prospects. Analysis by infrared and thermogravimetric test shows that the structure and performance of the resin will not be affected after water-based.
Detailed introduction: Silicone resin has excellent thermal oxidation stability, weather resistance, electrical insulation, water repellency and corrosion resistance. It has been widely used in high and low temperature resistant insulating paint, special coatings, adhesives, film plastics, etc. However, the current high and low temperature resistant insulating varnishes and special coatings of silicone resins mainly use organics such as aromatic hydrocarbons and alcohols as solvents, which will produce a large amount of VOC (volatile organic compounds), causing great harm to the environment and the human body. Water-based is the current research hotspot and development trend. In this research, ammonia water is designed as a salt-forming agent, and the silanol in the silicone resin is easily salt-formed under alkaline conditions to make the salt self-emulsify. Water is used as the dispersion medium to form an aqueous emulsion.
The resin uses water as the solvent, does not generate VOC, and is very convenient to use and store; when the ammonia and water are cured, they will be removed by themselves without affecting the structure and performance of the resin. The method is simple, reliable, low cost, low pollution, suitable for industrial production, and has good application prospects. The current emulsification methods of silicone resin mainly include direct emulsification, emulsion polymerization, and self-emulsification. The first two methods must introduce emulsifiers, which change the structure of the resin and affect the properties of the material. The self-emulsification method is usually by introducing hydrophilic groups, such as non-ionic -OH, -NH, -CO-NH-, -CO-, ionic -SO3, -NR2, -HX, these groups are all It can interact with water to form hydrogen bonds, or directly generate hydrated ions to dissolve in water.
This work adopts the self-emulsification method, the design uses ammonia water as the salt-forming agent, so that the silanol in the silicone resin becomes salt under alkaline conditions, and realizes self-emulsification and dispersion in water to form an aqueous emulsion. This method adopts the ammoniation method to react with the silanol in the resin to form a salt, thereby introducing a hydrophilic group, completing self-emulsification, using water as a dispersion medium to form an aqueous emulsion, and studying the structure and performance of the resin before and after modification Variety. Through modification, the hydrophilicity of the resin is improved, and water is used as the solvent, no VOC is generated, and no pollution, so that the use and storage of the resin are optimized, which is very innovative; and after the resin is cured, ammonia and water will change Take off by itself without affecting the structure and performance of the resin.
The method is simple, reliable, low cost, low pollution, suitable for industrial production, and has good application prospects. In the course of the experiment, in order to achieve the emulsification effect, we conducted conditional experiments to explore experimental conditions such as temperature, time, stirring intensity, and raw material ratio. Finally, the experimental method is simple and reliable, low cost, low pollution, suitable for industrial production, and has a good application prospect. According to the conditional experiment, at 30-40 ℃, put a certain mass ratio of industrial product silicone resin and 2%-4% (wt) ammonia water into the reactor, and use the disperser to stir vigorously at a speed of 1500r/ min～2000r/min, pre-emulsify for 1～2h, then add 20%～40%(wt) water, control the resin solid content in the solution to 40%～60%, continue to stir for 1～2h, you can make silicone Aqueous emulsion of resin.
Then place it at room temperature to observe whether it is stratified, and further centrifuge to achieve a stable state. The finished product is coated on tinplate to observe the film formation, and finally the film-forming stable emulsion is analyzed by infrared, thermogravimetric and other analytical methods. After the water-based silicone resin can be obtained: the structure and performance of the water-based resin are not affected and does not contain the environment Contaminated organic solvents.