How is Methyl MQ Resin Synthesized and Produced?
The synthesis of methyl MQ resin is primarily achieved through hydrolysis and polycondensation reactions, the core of which is the construction of a three-dimensional network structure of M units (monofunctional methylsiloxane) and Q units (tetrafunctional siloxane).
Common production processes include the water glass method, the orthosilicate ester method, emulsion polymerization, and bulk polymerization, with the water glass method and the orthosilicate ester method being the most widely used.
The water glass method uses sodium silicate (water glass) as the silicon source and hexamethyldisiloxane or trimethylchlorosilane as the methyl source. The raw materials are inexpensive and readily available, and the product has good temperature resistance and mechanical properties, but it produces many byproducts and has low purity.
The process includes:
Hydrolysis stage: Under stirring, the sodium silicate solution is mixed with an acid (such as hydrochloric acid), the temperature is controlled at 0–10℃, and the methyl source is slowly added to generate a silanol intermediate.
Polycondensation stage: The temperature is raised to 78–80℃ for reflux to promote the condensation reaction to form the resin, and the reaction endpoint is monitored by viscosity.
Post-treatment: Insoluble matter is removed by filtration, the solvent is removed by distillation, and ion exchange purification is performed if necessary.
The orthosilicate ester method uses ethyl orthosilicate or tetraethoxysilane as the silicon source, and similarly uses hexamethyldisiloxane as the methyl source. The product has fewer impurities, high transparency, and the reaction is controllable, but the cost is higher.
The process is similar to hydrolysis and polycondensation, usually using an acid catalyst (such as sulfuric acid), followed by heating and reflux after low-temperature hydrolysis. Post-treatment includes neutralization, drying, and solvent recovery.
Emulsion polymerization disperses the monomers in the aqueous phase using an emulsifier (such as sodium dodecyl sulfate), and an initiator (such as potassium persulfate) generates free radicals to initiate polymerization. It is suitable for preparing nanoscale resins, and post-treatment requires demulsification, washing, and drying.
Bulk polymerization involves the direct polymerization of pure monomers, requiring strict dehydration treatment. The reaction is initiated by heating, resulting in a high-purity product, but the process control is complex.
