The silane coupling agent is difficult to hydrolyze in water without additives, and the hydrolysis cycle is very long. The hydrolysis of the silane coupling agent will be accompanied by the side reaction of polycondensation, and the polycondensation product will precipitate at the bottom of the aqueous solution, affecting the use effect of the product. In order to ensure the normal progress of the hydrolysis reaction, we usually use the following methods:
First of all, both weakly acidic and weakly alkaline aqueous solutions can promote the hydrolysis of silane coupling agents. Some silane coupling agents with acidic groups (IOTA 560) or basic groups (IOTA 550) are relatively easy to hydrolyze, because Their own Y groups will affect the pH value of the aqueous solution, making the silane coupling agent easier to hydrolyze. The silane (such as A151) whose own group has a weak influence on the pH value of the aqueous solution can adjust the pH value of the aqueous solution by adding acetic acid, ammonia water and other substances to make the silane coupling agent easier to hydrolyze. For example, after adding acetic acid to adjust the pH value to be weakly acidic Then carry out the hydrolysis of silane coupling agent A151, and its hydrolysis speed has obvious promotion.
Secondly, when the silane coupling agent is hydrolyzed, a certain amount of methanol, ethanol and other solvents that can be freely miscible with water will be produced, which is determined by the X group in the silane structure. If the silane coupling agent is added in advance to hydrolyze The solvent that will be generated when used will make the silane coupling agent more fully dispersed in the aqueous solution and make the hydrolyzed solution more stable. If a small amount of ethanol is added to the aqueous solution before hydrolysis of vinylsilane A151, the oil bead-like silane coupling agent is more miscible with the aqueous solution, and it is not easy to polycondensate and precipitate. In addition, when the silane coupling agent is hydrolyzed, it needs to be fully stirred, so that the silane coupling agent can fully contact with water, and reduce the polycondensation reaction between the silane coupling agent molecules due to contact. Once the silane coupling agent is polycondensed, it will be difficult. Then hydrolyzed.