GB999600A - Organosilicon co-polymers - Google Patents

Abstract

A block co-polymer comprising (A) polymer blocks of the average general formula <FORM:0999600/C3/1> wherein the sum of x+y+z has a value of from 6 to 50 of which y and z each have a value of up to 10%, and (B) polymer blocks of the average formula <FORM:0999600/C3/2> wherein q has a value of from 1 to 1.1, and w has a value of up to 0.1, the siloxane units in (A) being from 10 to 75 mol per cent and those in (B) being from 25 to 90 mol per cent of the total siloxane units in the copolymer, can be made by (1) reacting (C) (C6H5)SiX3, wherein X is halogen, with (D) a polymer of the formula (A) but containing at least 2 Si-bonded-OH radicals per molecule in amount such that there is at least 1 mol of (C) per mol of -OH radicals in (D), and under such conditions that by-produced hydrogen halide is removed as it is formed, and (2) and co-hydrolysing the product with (E) a halosilane of the formula <FORM:0999600/C3/3> wherein q has a value such that in the total of components (C) and (E) there are from 1 to 1.1 C6H5-radicals per Si atom and w likewise has a value to give a total of up to 0.1 CH3-radicals per Si atom, and the proportions of the reactants are such as to give the required molar proportions of the specified siloxane units. Reaction (1), viz. <FORM:0999600/C3/4> can be effected at room or elevated temperature, and usually in solution in an organic solvent which is immiscible with water. The hydrohalide can be removed by trapping, e.g. as an amine hydrohalide, or be allowed to escape as a gas. In other embodiments (i) additional silane prior to hydrolysis is omitted, (ii) alkoxy silanes are used instead of halosilanes, and (iii) hydroxy-terminated siloxanes are replaced by siloxanes having terminal hydrolysable radicals. Numerous examples of catalysts are given for the reactions involving alkoxy silanes. In a typical Example (2) a toluene solution of an OH-terminated dimethylpolysiloxane was added to a toluene solution of phenyltrichlorosilane and pyridine, and the resulting mixture was then added to water with stirring; after washing free of acids &c. the product was bodied by refluxing with toluene sulphonic acid. The copolymers can be mixed with phthalocyanins, oxides of Sb, Ti, Al, Fe or Zr, SiO2 (natural, fume or xerogel), sand, silicates of Al, Mg, Zr, Mg-Al, or Ca-Al, graphite, C black, or powdered Al, Fe, Cu or Zn, and heat cured, e.g. with tributylamine, iron octoate or cobalt naphthenate. Uses.-In coating, encapsulating, laminating and moulding applications.