New Solid Catalyst Preparation Of Low Molecular Weight Polysiloxane Technology

In this paper, two types of reactive polysiloxanes, hydrogen-silicone oil and low molecular weight hydroxyl-silicone oil, were prepared by using solid-phase catalysts to replace concentrated sulfuric acid and corresponding new process.To obtain the linear reactive polyhydrogensiloxane, methyldichlorosilane and trimethylchlorosilane were co-hydrolyzed in the present of hydrochloric acid and solvent (such as petroleum ether). The reaction was preferably carried out at low temperature below 25°C. The crude hydrolysate was washed with water. After drying, rearrangement reaction took place under the catalyst, in which most of the cyclic siloxane was conversed into linear polysiloxane. Then the residual catalyst was easily removed by filtration and the pure linear hydrogen-silicone oil was obtained after removing solvent. Various factors that influence the hydrolysis and rearrangement reactions were discussed. It is found that the new solid catalyst was more effective than concentrated sulfuric acid. The product was characterized by IR, ~1H-NMR and GPC etc. The products produced by the new catalysts and by the new process have desired structure and have better quality than those yielded from traditional process. The hydrogen content can reach up to 1.61%.Low molecular weight hydroxyl-silicone oil was prepared using new solid catalyst as well. Octamethyl cyclosiloxane (DMC) and acetic anhydride were mixed and cationic ring-open reaction was conducted in the present of solid catalyst at high temperature. The catalyst was removed by filtration and the product of ring-open reaction was hydrolyzed under basic condition. Various factors that influence the ring-open reaction and hydrolysis were discussed. The products were characterized by IR and ~1H-NMR etc. The results indicated the products have the desired structure and qualified properties. The hydroxyl content is more than 9%.