Another mainstream production method of silicone oil is catalytic equilibrium method, which is especially suitable for the preparation of hydrogen-containing silicone oil and modified silicone oil. Its core lies in the use of end-capping agents to regulate the molecular chain structure.


Catalytic equilibrium reaction
Hexamethyldisiloxane (MM) is used as an end-capping agent and is subjected to equilibrium reaction with methylhydrogendichlorosilane under the catalysis of concentrated sulfuric acid. The addition of MM can effectively terminate the growth of siloxane chains, control the viscosity of the product, and reduce side reactions (such as ring formation). After the reaction, the stratification is allowed to stand, and the upper layer product is washed with water and distilled under reduced pressure to obtain the target silicone oil.


Production of modified silicone oil


Amino-modified silicone oil: amino groups are introduced into the siloxane chain, and amino-containing monomers need to be added in the polycondensation stage. This type of silicone oil is widely used in fabric softeners due to its excellent adsorption.


Polyether-modified silicone oil: polyether segments are connected to the siloxane main chain through copolymerization to enhance hydrophilicity. This process requires strict control of the ratio of polyether to silane to balance water solubility and surface activity.


Innovation in solvent-free method
The traditional process relies on solvent dilution to prevent gelation, but solvent residue affects product quality. The solvent-free method directly generates low-volatile, linear silicone oil through controlled hydrolysis at low temperature (-5~45℃). The product has no odor and is suitable for high-end fields.


Environmental protection and high efficiency trend
Modern processes focus on resource recycling, such as recycling the hydrogen chloride gas produced by hydrolysis to make hydrochloric acid, or using high-boiling organic silicon products (by-products) to regenerate silicone oil and reduce waste emissions.


Technical challenges and prospects
Although the catalytic equilibrium method can improve product quality, it has strict requirements on catalyst activity and reaction conditions. Future development directions include the development of green catalysts, continuous production lines and large-scale production of high-end modified silicone oils to replace imported products.