1、 What are the chemical properties of hydroxyl silicone oil
Hydroxy silicone oil not only has properties similar to dimethyl silicone oil (such as methyl silicone oil), but also has special properties brought by active silanol based end capping. Under the action of acidic or alkaline media, organic alkoxysilane, organic acyloxysilane, and amino silane can undergo condensation reactions to form high molecular weight polymers; Reacting with boronic acid esters, titanium acid esters, silicate esters, silicon hydrogen bonds, etc. to generate cross-linked binding products.
Amino silicone oil can be synthesized by reacting hydroxyl silicone oil with amino alkyl silane (such as coupling agent KH-550 or coupling agent KH-602). The reaction product is an amino silicone oil grafted onto the side chain of the polysiloxane chain with an amino alkyl group, resulting in an increase in molecular weight. The ratio of raw materials for the reaction depends on the ammonia value of the prepared amino silicone oil. For example, when using KH-602, the product with an ammonia value of 0.3 uses 96.67% hydroxyl silicone oil and 3.33% KH-602.
2、 How is hydroxyl silicone oil made
1. Catalytic polymerization method
This method is a commonly used industrial production method, which uses octamethylcyclotetrasiloxane (D4) or dimethylcyclosiloxane (DMC) as the starting material, water as the end capping agent, and polymerizes under the catalysis of acid, base, ion exchange resin, and acidic clay. When using D4 as the raw material, the reaction process is described in the "Synthesis of Hydroxysilicone Oil by Catalytic Polymerization Method".
Method: Add octamethylcyclotetrasiloxane (D4) or dimethylcyclotetrasiloxane (DMC), catalyst (such as supported catalyst), and water into the reactor according to the proportion of ingredients. Then, the temperature is raised for the bulk polymerization reaction, and the conversion rate of the raw materials is sampled and tested. When it reaches 80% or above, the material is discharged to obtain the crude silicone oil product. Place the crude silicone oil in an evaporator above 100 ℃ and perform continuous distillation at 3kPa to remove low molecules and obtain the dimethyl hydroxy silicone oil product.
2. Hydrolysis method
Obtained by hydrolysis of dimethyl dichlorosilane and dimethyl dialkoxysilane, or by alcoholysis of dimethyl dichlorosilane with methanol.
Principle: Dimethyldichlorosilane is hydrolyzed first, with one chlorine atom being hydrolyzed first and the remaining chlorine atom being hydrolyzed slowly.
method:
(1) Add dimethyl dichlorosilane dropwise to 24% ammonia solution, stir and hydrolyze to quickly remove the generated oil phase from the reaction system. Separate the oil phase, dry it with anhydrous calcium chloride, decolorize it with activated carbon, and remove ammonia by gas extraction to obtain a colorless and transparent liquid, namely small molecule hydroxy silicone oil. It contains a mixture of approximately 50-80% linear structures and 20-50% cyclic structures.
(2) Add a measured amount of organic solvent, water, and alkaline neutralizing agent into the enamel hydrolysis kettle, start stirring, and slowly add dimethyl dichlorosilane directly into the kettle. Hydrolysis is carried out at a temperature below 10 ℃. After adding the material, continue stirring for 20 minutes, stop the reaction and let it settle for layering. Discharge the wastewater, dry the material, remove the solvent, and filter to obtain dimethyl hydroxysilicone oil product.
