Patent GB-689648-A (GB)
Title: Improvements in or relating to organo-silicon resins and to the baking of bread
IPC: C08G77/00
Filed: 1950-08-09
Abstract: An organopolysilane-polysiloxane resin of the average formula [(CH3)a(C6H5)bSiOc(OH)d] in which c has a positive value, d has a value of 0.01 to 1 and a+b+2c+d has a value up to 3.5, may be made (1) by hydrolysing by reaction with water one or more organochloropolysilanes of the average formula (CH3)a(C6H5)bSiCl(4-a-b) (1-1/m) in which a+b is from 1.4 to 2, 30 to 75 per cent of the organic radicals are phenyl radicals and m is greater than 1 and less than 5, and partially condensing the hydroxyl radicals; (2) by reacting methylphenyldichlorosilane or a mixture of silanes of the average formula (CH3)a(C6H5)bSiCl4-a-b, in which a+b is from 1.4 to 2 and in which 30 to 75 per cent of the organic radicals are phenyl radicals, with an alkali metal in amount sufficient to cause condensation by removal of at least 20 per cent of the chlorine in the silane(s) but insufficient to cause complete condensation, hydrolysing by reaction with water the resulting chloropolysilane mixture which has the average formula given in (1), and partially condensing the hydroxyl radicals; or (3) by reacting methylphenyl dichlorosilane or a mixture of silanes of the average formula RnSiCl4-n, in which R represents methyl and phenyl radicals of which from 30 to 75 per cent are phenyl radicals and n has a value of from 1 to 2, with an alkali metal as in (2), and mixing the product with additional original silane or silane mixture to give a chlorosilane mixture of the average formula given in (1) prior to the hydrolysis step given in (2).  Organopolysilane-polysiloxanes of the general formula <FORM:0689648/IV (a)/1> , in which a, b, c and d have the values given above, may be made by similar methods, except that the chloropolysilane, used as the starting material or formed during the process, is reacted with an alcohol of the formula R1OH, wherein R1 is a primary or secondary alkyl radical, and the resulting alkoxypolysilane is partially hydrolysed and condensed. Alternatively, organoalkoxypolysilanes of the general formula (CH3)a(C6H5)bSi(OR1) (4-a-b) (1-1/m) may be partially hydrolysed and condensed, to give products containing both alkoxy and hydroxyl groups.  The disilane (Cl.C6H4.CH3.Si)2 alone or in mixture with other silanes such as methyl phenyl dichlorosilane may be used as a reactant or to prepare the chloropolysilane reactant by reaction with sodium.  Other silanes specified are methyltrichloro-, phenyltrichloro-, diphenyldichloro-, dimethyldichloro-, triphenylchloro-, diphenylmethylchloro-, phenyldimethylchloro-, and trimethylchloro-silanes.  Alkali metals specified are sodium, potassium, caesium, rubidium and lithium. The reaction with alkali metal is conducted in liquid phase and the hydrolysis is preferably effected in the presence of an organic solvent.  The resins per se or in solution in an organic solvent, e.g. benzene, toluene, xylene, naphtha and acrylic petroleum thinners, may be applied to surfaces to be coated. Solutions of the resins containing hydroxyl groups may be used to coat bread pans internally.  The resins, which are thermoplastic and are highly viscous liquids at room temperature, may be blended with one another, with organosiloxane resins, polysilane resins, siliconalkyd resins, natural resins such as wood rosin, copal and shellac, synthetic resins such as phenol-aldehyde resins, urea-aldehyde resins, alkyd resins, vinyl resins and esters of acrylic and methacrylic acid, cellulose esters such as cellulose-nitrate, -acetate and -p-toluene sulphonate, and with cellulose ethers such as methyl-, ethyl-, propyl-, butyl-, benzyl-, allyl- and hydroxyethyl-cellulose.  A solution of the resin may be used as a varnish, or be pigmented e.g. with aluminium powder, and used as a paint or enamel, curing after coating being effected by heating.  Such resin mixtures, pigmented with aluminium powder, and thinned with a volatile solvent, are suitable for coating ovens, smoke stacks and exhaust manifolds. Catalysts such as lead, zinc, cobalt and manganese salts accelerate the rate of setting.  The resins may also be used for electrical insulation, e.g. magnet wire enamels.  Examples are given.  Specifications 675,057 and 675,912 are referred to.ALSO:Disilanes of the formula <FORM:0689648/IV (b)/1> are made by reacting an alkali metal with an alkoxychlorosilane of the formula CH3.C6H5.SiOR11.Cl in which R11 is an alkyl radical.  In example (13), dimethyldiphenyldiethoxydisilane is made by refluxing a mixture of methylphenylethoxychlorosilane and sodium in dry toluene. Dimethyltetrachlorodisilane is made by reacting a methyl Grignard reagent (2 mols.) with hexachlorodisilane (1 mol.) in ether.ALSO:Organopolysilane - polysiloxanes (see Group IV (a)) are used in the baking of bread for coating bread pans.  The pans are coated with a solution (e.g. benzene, toluene, xylene or naphtha) of the organosilicon compound, and allowed to dry.  The resin may be cured by heating to 400-500 DEG  F. or during the baking of the bread.