A method of preparing polyorganosiloxane resins used as adhesion modifiers in hardenable silicone compositions for non-stick papers in which the silox products of the functionalization stage are recycled

摘要

A method of preparing a polyorganosiloxane resin (POS) comprising at least two types of different siloxy units (M, Q and optionally QOH) by preparing a POS comprising Q units for an alkaline silicate in an alkali medium, functionalizing with halogenosilanes in an apolar solvent, thereby generating volatile oligosiloxane (silox) products, recovering the silox products and rearranging the resin with a strong base to eliminate silanes with recycling of the silox products. The silox products are reused in the functionalization stage. In the first stage a reactor is charged, while stirring, with the following in order: an acid, preferably hydrochloric acid, an alkaline silicate, preferably sodium silicate and a stabilizer/initiator of hydrogen bonds which is preferably isopropyl alcohol. In the second, functionalization, stage the following products are added in order: the silox in solution in an apolar solvent, preferably xylene and optionally comprising isopropyl alcohol and water; optionally, an apolar solvent, preferably xylene; optionally oligoorganosiloxanes; halogenosilanes. The reaction mixture is heated to a temperature close to the reflux temperature of the stablilizer and preferably that of isopropyl alcohol. Apolar solvent is optionally added. The mixture is optionally cooled. The non-aqueous phase is separated from the aqueous phase, preferably by decantation and the latter is discarded. In the third, rearrangement, stage strong base, preferably KOH is added and heated to a temperature close to the reflux temperature of the reaction mixture, the condensation water, solvent and the siloxes in solution in it are removed, the reaction mixture is optionally cooled, an apolar solvent is added. The strong base is neutralized, preferably with acetic acid and the water produced is distilled out, optionally the neutralization product is removed by filtration and the non-aqueous solution of resin is recovered. Independent claims are included for (1) a polyorganosiloxane resin obtained by the claimed method; (2) a silicone composition comprising silox compounds recovered in the final stage of the claimed method in solution in an apolar solvent, preferably xylene; (3) the use of the claimed composition to functionalize a polyorganosiloxane resin comprising at least M and Q units.