1.The effect of stirring speed
In the silicone resin synthesis, the stirring speed has a great influence on the reaction. It was found in the experiment that in the process of sulfuric acid and sodium silicate reflection, if the sodium silicate was not added dropwise to the sulfuric acid without stirring, it was found that the mixed solution had a gel phenomenon; otherwise, if it was rapidly stirred during the dropwise addition, there was no gel phenomenon. appear. The gel will cause the loss of raw materials, reduce the number of effective silanol groups, seriously affect the formation of the resin, and affect the performance of the silicone pressure-sensitive adhesive.
2. Influence of raw material ratio
Synthetic hydroxy silicone resin is an important part of the preparation of silicone pressure-sensitive adhesives. During the synthesis process, the ratio of the raw materials has a great influence on the properties of the silicone resin. Depending on the ratio of raw materials, the properties of the prepared silicone resin and silicone pressure-sensitive adhesive are different. Within a certain range, as the amount of the silicone resin continues to increase, the holding force of the pressure-sensitive adhesive will decrease. This is because the main role of silicone rubber in the adhesive is to give the necessary cohesive force to the pressure-sensitive adhesive. Therefore, the smaller the relative amount of silicone rubber in the formula, the worse the cohesive force of the pressure-sensitive adhesive, but if the relative amount of silicone rubber is too large, it will make the year of the pressure-sensitive adhesive too large and difficult to apply. viscosity.
The industrial production of silicone resins usually uses methyltrichlorosilane and phenyltrichlorosilane as the main raw materials. In order to reduce the brittleness and hardness of the resin and improve the adhesion of the resin, difunctional monomers such as dimethyldichlorosilane and methylphenyldichlorosilane can be added. The above monomers are hydrolyzed and polycondensed in a solvent, and the by-produced hydrogen chloride is washed away to obtain a resin liquid which still contains a small amount of silyl hydroxyl groups. When used, a small amount of catalyst such as cobalt naphthenate is added to complete the polycondensation of the resin to obtain a cross-linked three-dimensional network-shaped cured resin. The feed rate, reaction temperature, and stirring intensity during the hydrolysis process all have an effect on the resin performance.
Silicone resin can be used to make 180 ° C resistant motor insulation materials, such as glass varnished cloth, glass cloth laminate, mica tape, dipping varnish, magnetic lacquer, etc. After adding aluminum powder to the latter two, it can be formulated into high-temperature coatings that can withstand 500 ° C for a long time and 1000 ° C for instantaneous use, and are used for coating jet nozzles, metal chimneys, etc. The molding compound reinforced with glass fiber or asbestos can be used as a material for making high-current and high-voltage resistant arc switches. Silicone resin (commonly known as silicone glass resin) made from methyltrialkoxysilane can be used to treat paper, Plastic, and metal surfaces to make them have good brightness and abrasion resistance. The silicone resin can be used as an outdoor coating with good weather resistance after being modified (such as with alkyd resin).