Abstract: A method for preparing a polyorganosiloxane which is sold at 25° C. and has R13SiO0.5 units wherein R1 is a hydrocarbon group having 1 to 10 carbon atoms and SiO2 units, said method comprising the steps of: [1] subjecting at least one selected from an organosilane and an organodisiloxane, and at least one selected from a tetralkoxysilane and a partial condensate of hydrolysates of the tetralkoxysilane to hydrolysis reaction and condensation reaction in the presence of an acidic catalyst; [2] adding a liquid aliphatic hydrocarbon; and subsequently [3] separating a liquid aliphatic hydrocarbon phase and an aqueous phase and then removing said aqueous phase; provided that the step [2] may be performed before, during, or after the step [1].

Abstract: A method for preparing a polyorganosiloxane which is sold at 25 ° C. and has R13SiO0.5 units wherein R1 is a hydrocarbon group having 1 to 10 carbon atoms and SiO2 units, said method comprising the steps of: [1] subjecting at least one selected from an organosilane and an organodisiloxane, and at least one selected from a tetralkoxysilane and a partial condensate of hydrolysates of the tetralkoxysilane to hydrolysis reaction and condensation reaction in the presence of an acidic catalyst; [2] adding a liquid aliphatic hydrocarbon; and subsequently [3] separating a liquid aliphatic hydrocarbon phase and an aqueous phase and then removing said aqueous phase; provided that the step [2] may be performed before, during, or after the step [1].

Abstract: For the preparation of organopolysiloxanes, water glass diluted with water to a concentration of 3 to 15 wt % is reacted with a triorganohalosilane in the presence of an acid and an oxygen-containing solvent such as isobutyl alcohol, methyl isobutyl ketone or 1-pentanol. The invention achieves a considerable reduction of the environmental load, an improved utilization of reactants, an improved yield, and a cost reduction, and enables production of low viscosity MQ resins.

Abstract: For the preparation of organopolysiloxanes, water glass diluted with water to a concentration of 3 to 15 wt % is reacted with a triorganohalosilane in the presence of an acid and an oxygen-containing solvent such as isobutyl alcohol, methyl isobutyl ketone or 1-pentanol. The invention achieves a considerable reduction of the environmental load, an improved utilization of reactants, an improved yield, and a cost reduction, and enables production of low viscosity MQ resins.

Abstract: A novel and efficient method is disclosed for decreasing the content of residual alkoxy groups in an organopolysiloxane such as so-called MQ resins, usually and unavoidably, having a considerable amount of residual alkoxy groups bonded to the silicon atoms to be very detrimental against practical application of the organopolysiloxane. The method comprises admixing the alkoxy-containing organopolysiloxane with a strongly alkaline compound such as alkali metal hydroxides as a catalyst, an aprotic polar solvent such as N,N-dimethyl formamide, dimethyl sulfoxide and the like and water each in a specified amount and heating the mixture, for example, under reflux so that the alkoxy groups are rapidly hydrolyzed and can be removed in the form of an alcohol.

Abstract: An efficient and economically advantageous method is proposed for the preparation of an organopolysiloxane comprising tetrafunctional siloxane units, i.e. Q units, and, typically, monofunctional siloxy units, i.e. M units, and useful as a reinforcing agent in silicone rubbers. The method comprises the steps of: mixing the reactants for providing the Q and M units, such as ethyl orthosilicate and trimethyl methoxy silane, in a desired molar ratio; and heating the mixture at a temperature higher by at least 10.degree. C. than the boiling point of the mixture under normal pressure in a closed vessel in the presence of water and a catalyst such as a sulfonic acid group-containing compound.

Abstract: An organopolysiloxane composed of tetrafuctional siloxane units SiO.sub.2 and monofunctional siloxane units R.sub.3 SiO.sub.0.5 can be prepared by reacting an alkyl orthosilicate, e.g., ethyl silicate, or a partial hydrolysis product thereof and an oligomeric organopolysiloxane containing the monofunctional siloxane units in the presence of a catalytic compound which is, different from conventional hydrogen chloride, selected from the group consisting of sulfonic acid group-containing compounds, e.g., sulfuric acid and p-toluene sulfonic acid, and phosphonitrile chloride. In particular, cation exchange resins of sulfonic acid type and fluorinated polysulfonic acid resins can be used as the catalyst in a continuous process in which the reaction mixture is passed through a bed of the catalyst continuously. The inventive method is advantageous over conventional methods because of the absence of the problems of heavy corrosion of the apparatuses and waste disposal due to the hydrogen chloride.