Method for recovering cyclosiloxane monomers by catalytic cracking of waste silicone rubber

Abstract

The invention discloses a method for recovering cyclosiloxane monomers by catalytic cracking of waste silicone rubber, which comprises the following steps: 1, cleaning, drying and pulverizing waste silicone rubber to obtain waste silicon old rubber powder; 2, putting the waste silicon old rubber powder obtained in the step 1 into a reactor, adding solid acid and concentrated sulfuric acid, and mixing and stirring the mixture to obtain pretreated waste silicon rubber powder; and 3, heating the pretreated waste silicone rubber powder obtained in the step 2 until the material is liquefied, stirring and mixing the mixture for 5-10 minutes, carrying out a reaction for 3-5 hours under a vacuum condition, and collecting the reaction product to obtain the cyclosiloxane monomer. According to the method, equipment corrosion can be reduced; wherein the calcium sulfate and residual sulfuric acid generated in the cracking slag are greatly reduced, so that subsequent treatment and further recyclingof the cracking slag are facilitated, and the catalytic cracking efficiency is equivalent to that of a concentrated sulfuric acid method; therefore, the cyclosiloxane monomer with the mass being 45-65% of that of the waste silicone rubber can be recycled, and the method has extremely high industrial application prospects.

Description

technical field [0001] The invention relates to the field of three waste treatment methods, in particular to a method for recovering cyclosiloxane monomer by catalytic cracking of waste silicone rubber. Background technique [0002] Silicone rubber is a special synthetic rubber that can maintain rubber elasticity for a long time in the range of -100 to 300°C. It is non-toxic, odorless, has good air permeability, and has outstanding characteristics of aging resistance, physiological inertia, and does not cause blood coagulation. It is widely used It is used in various industries such as electronics, building materials, textiles, light industry, medical treatment, machinery, transportation, plastics and rubber. With the increase in the demand for silicone rubber materials in production and life, the resulting recycling of waste silicone rubber is also particularly important. [0003] At present, the common methods for recycling cyclosiloxane monomers from waste silicone rubbe...

AI Technical Summary

Problems solved by technology

Among them, the alkali-catalyzed cracking method has a small application range, difficult product utilization, and poor safety, and local reactions are prone to excessive local reactions in the reactor, causing combustion and explosion accidents; the thermal cracking method has a small reaction volume, consumes more energy, and has a low recovery rate. , low safety; and the acid-catalyzed cracking method is widely used in industry due to its relatively high reaction safety and high recovery rate.

[0004] At present, the widely used method of acid-catalyzed cracking of waste silicone rubber to recover cyclosiloxane monomer is the concentrated sulfuric acid cracking method, which has high cracking efficiency, but has problems such as strong corrosion, high equipment replacement rate, difficult disposal of cracking residues, and serious pollution.

The acid-catalyzed cracking of waste silicone rubber can also use the solid acid cracking method, which is less corrosive, but due to the insufficient reaction contact surface, the recovery rate and recovery cycle of the entire cyclosiloxane monomer are greatly prolonged compared with concentrated sulfuric acid cracking.