Patent GB-758640-A (GB)
Title: Production of stable aqueous silanol dispersions
Filed: 1953-03-16
Abstract: Stable aqueous dispersions of silanols are prepared by adding one or more hydrolysable silanes having an R/Si ratio of 0.05 to 3 to an aqueous solution of a buffer, the amount of water used being such that the final solution is at least 80 per cent water and the amount of buffer being such that the final pH is between 3 and 8. The silane and buffer solution may be added simultaneously to a vessel.  The Specification lists a large number of suitable silanes, organic radicals R, (which may be divalent, unsaturated and halogen-substituted), and hydrolysable radicals.  Specified buffers are borates, carbonates, alcoholates, bicarbonates, citrates, phosphates and acetates, particularly of alkali metals. The pH is preferably maintained at about 6.8 to 7.5 during the hydrolysis.  The resulting solutions are useful for waterproofing various materials (see Groups III, IV (c), V, VI, VIII and XVII). The silanols condense on drying to form polysiloxanes.  The Specification gives a large number of examples of the hydrolysis of various silanes, using various buffer solutions to give stable aqueous silanol dispersions.ALSO:Stable aqueous dispersions of silanols are prepared by adding one or more hydrolysable silanes having an R/Si ratio of 0.05 to 3 to an aqueous solution of a buffer, the amount of water used being such that the final solution is at least 80 per cent water and the amount of buffer being such that the final pH is between 3 and 8. The silane and buffer solution may be added simultaneously to a vessel.  The Specification lists a large number of suitable silanes, organic radicals R (which may be divalent, unsaturated and halogen-substituted), and hydrolysable radicals.  Specified buffers are borates, carbonates, alcoholates, bicarbonates, citrates, phosphates, and acetates, particularly of alkali metals.  The pH is preferably maintained between 6.8 and 7.5 during the hydrolysis.  The resulting solutions are useful for waterproofing various materials (see Groups III, IV (c), V, VI, VIII and XVII).  The silanols condense on drying to form polysiloxanes.  The Specification gives a large number of examples of the hydrolysis of various silanes using various buffer solutions to give stable aqueous silanol dispersions. Organochlorosilanes are obtained by reacting a mixture of silico-chloroform and commercial di-isobutylene (80 per cent 2.4.4-trimethylpentene-1 and 20 per cent 2.4.4-trimethylpentene-2) in a tube heated to 320 DEG  to 340 DEG  C. for 4 hours at a pressure of 1000-1200 p.s.i.  The product is distilled and yields in addition to hydrocarbons and starting materials, methallyltrichlorosilane, pentyl, hexyl and heptyltrichlorosilanes, octyltrichlorosilanes (identified), and 1.3-bis-(trichlorosilyl) isobutane.ALSO:The Specification refers to the waterproofing of silicates, particularly magnesium silicate, sand, clay, talc, mica and asbestos by treatment with aqueous dispersions of silanols obtained by hydrolysing hydrolysable silanes with aqueous solutions of buffers at a pH of 3-8; (see Group IV(a)).  The treated materials are subsequently dried whereupon the silanols condense to form polysiloxanes.  The treated materials may be used as fillers in moulding compositions.ALSO:The specification refers to the waterproofing of ores for flotation by treatment with an aqueous dispersion of a silanol obtained by hydrolysing a hydrolysable silane with an aqueous solution of a buffer at a pH of 3-8 (see Group IV(a)).  The treated ore is subsequently dried whereupon the silanol condenses to form a polysiloxane.ALSO:The Specification refers to making asbestos and mica water-repellent by treatment with aqueous solutions of silanols obtained by hydrolysing hydrolysable silanes with aqueous solutions of buffers at a pH of 3-8; (see Group IV(a)).  The treated materials are subsequently dried whereupon the silanols condense to form polysiloxanes.  The treated materials may be used as fillers in moulding compositions.