The silicate method and the water glass method are two different raw material routes for producing MQ resin (a silicone resin composed of monofunctional siloxane units (M, R₃SiO₁/₂) and tetrafunctional siloxane units (Q, SiO₄/₂)). They have significant differences in raw material sources, process conditions, product performance, etc. The following are the main differences between the two:
1. Different raw materials
Silicate method
Raw materials: Use tetraethyl orthosilicate (TEOS, Si(OC₂H₅)₄) or other silicate compounds as silicon source.
Features: Organic silicate has high purity, few impurities, strong reaction controllability, but high cost.
Water glass method
Raw materials: Use water glass (sodium silicate, Na₂O·nSiO₂) as silicon source, and need to be neutralized by acid (such as hydrochloric acid) to release active silicic acid (H₂SiO₃).
Features: The raw materials are cheap and easy to obtain, but contain a large amount of inorganic salts (such as NaCl) and impurities, and the subsequent purification steps are complicated.
2. Reaction mechanism and process
Silicate method
Hydrolysis condensation: Silicate esters are hydrolyzed under acidic or alkaline conditions to generate silanol (Si-OH), which is then condensed with compounds containing M units (such as hexamethyldisiloxane, MM) to form MQ resin.
Process characteristics: The reaction conditions are mild (normal temperature or heating), the solvent (such as ethanol) is easy to recover, the by-product is alcohol (such as ethanol), and it is environmentally friendly.
Water glass method
Neutralization reaction: Water glass must first react with acid to generate silica gel, and then condense with M units.
Process difficulties: pH and temperature must be strictly controlled to avoid too fast gel formation; the residual inorganic salts in the product must be removed by washing, filtration and other steps, and the energy consumption is high.
3. Product performance differences
Purity
The silicate method has higher product purity, less impurities (such as Na⁺, Cl⁻), and is suitable for high-end applications (such as electronic packaging, optical coatings).
The water glass method may have residual inorganic salts in the product, affecting the transparency, heat resistance and electrical insulation of the resin.
Structural control
The silicate method can accurately control the M/Q ratio by adjusting the ratio of TEOS to M units, and the molecular weight distribution is more uniform.
The water glass method is difficult to accurately control the degree of polymerization of silicate, the M/Q ratio fluctuates greatly, and the product structure uniformity is poor.
4. Economic and environmental protection**
Cost
The raw material cost of the water glass method is extremely low, which is suitable for large-scale, low value-added products (such as coatings, fillers).
The raw material cost of the silicate method is high, but the process is simplified (the salt separation step is omitted), and the comprehensive cost may be close.
Environmental protection
Silicate method