Resource Use Of Byproducts In The Production Process Of Methylchlorosilane Monomer

The paper is mainly concerned with the resource use of the huge amount of the byproducts of high boiling and low boiling fractions, which are produced in the production process of dimethyldichlorosilane. Besides, an ionic liquids (ILs) based new hydrolysis process of dimethyldichlorosilane is studied aimed to get anhydrous hydrochloride in the hydrolyzing process. In order to use the chlorine and silicon elements efficiently, the high and low boiling components were first subject to alcoholysis giving out hydrogen chloride gas and silicon ester, which is further hydrolyzed to reclaim methanol and silicone resin. After a certain treatment, the silicone resine can be mixed with polymers to prepare organic/inorganic composites so as to achive an efficient and cost effective use of the byproducts. The main experimental study includes two parts as follows.The first part is the successive alcoholysis and hydrolysis of the byproducts. In the alcoholysis process of the low and high boiling byproducts, anhydrous hydrochloride can be obtained along with the silicon ester, the latter is further hydrolyzed to reclaim methanol and produce organic silicone resin. The morphology, structure and composition of the resins were characterized by means of FT-IR, SEM and TGA. The optimal condition of the alcoholysis-hydrolysis reaction was found as follows:mass ratio of byproducts and methanol 1:0.5, reaction temperature 65℃and the reaction time 2 hours. Under these conditions, the yield of HCl gas was 35.3%, the yield of the silicon resin was 43.2%, and the recovery ratio of methanol was 81.5%.The second part focuses on the pretreatment of silicone resine, preparation of silicone resin/polymer composites and test of the mechanical properties (tensile strength and impact strength) of the composites thus obtained, which were further compared with control composite made of silica SiO2 and polymer. The results show that the tensile strength of the compsite made by the pretreated organic silicone resin and PVC is almost the same as that of SiO2/PVC composite. In the aspects of elongation at break and impact strength, the composites made of low-boiling silicone resin and PVC were close to SiO2/PVC, reaching to 84% and 96% of the control values respectively, in contrast, the silicone resin made from high boiling byproduct was less appropriate as inorganic fillers. For the composites prepared by combining organic silicone resin and low density polyethylene (LDPE), the tensile strength only decreased slightly, but the elongation at break and impact. strength were poorer than the control composite of SiO2/LDPE.In addition, we also studied a new method for hydrolyzing dimethyldichlorosilane, in which the dimethyldichlorosilane is hydrolyzed by concentrated aqueous solution of ionic liquids giving out anhydrous hydrochloride and cyclosiloxane. After reaction, the products and ionic liquid can be separeted with ease and low energy, further the ionic liquid can be reused. Although the new process is greener, the hydrolyzate is quite complex, suggesting that the activity and selectivity of the catalyst need to be improved further.