The production of silicone oil is mainly based on the hydrolysis and polycondensation of organosilicon monomers, and its core raw materials are chlorosilanes (such as methylhydrodichlorosilane, trimethylchlorosilane, etc.) and alcohol solvents. The following are the key steps of the process:


Raw material preparation
The production of silicone oil requires the use of high-purity chlorosilane as a silicon source, supplemented by solvents (such as toluene, heptane) and acidic or alkaline catalysts (such as concentrated sulfuric acid or strongly acidic ion exchange resins). The purity of chlorosilane directly affects the molecular weight distribution and final performance of the product.


Hydrolysis reaction
The mixed solution of chlorosilane and water is hydrolyzed in a reactor to generate silanols and hydrochloric acid. The traditional process uses the "positive hydrolysis method", that is, adding chlorosilane to water, but this method is prone to produce a large amount of acid water and is difficult to recover. The improved "reverse hydrolysis method" significantly reduces the acid residue by slowly dripping water into the chlorosilane solution, which is convenient for subsequent treatment.


Polycondensation reaction
Silanols undergo polycondensation under the action of catalysts to form siloxane chains. By adjusting the type of catalyst (such as sulfuric acid or quaternary ammonium salt) and reaction conditions (temperature, pressure), the viscosity and molecular weight of the product can be controlled. For example, low molecular weight silicone oil is easily generated under acidic conditions, while high molecular weight products are preferred under alkaline conditions.


Post-treatment and refining
After the reaction, the acid catalyst needs to be neutralized, and the residual hydrochloric acid is removed by stratification and water washing. Subsequently, distillation or thin film evaporation is performed to remove low boiling substances (such as unreacted chlorosilane and solvent), and then further purified by activated carbon adsorption or acid washing to finally obtain a colorless and transparent silicone oil product.


Process advantages and disadvantages
The traditional hydrolysis and polycondensation process is mature, but there are problems of acid water pollution and high energy consumption. Improved continuous production (such as automatic control of reactors and acid water recycling) has improved efficiency and environmental protection, and has been adopted by some domestic companies.