Patent GB-804369-A (GB)
Title: Siloxane-oxyalkylene block copolymers
IPC: C07F7/08
Filed: 1955-03-02
Abstract: Polysiloxane-polyoxyalkylene block copolymers (see Group IV (a)) are in some cases water-soluble when they are useful as anti-foam agents or, in combination with water-soluble polyoxyethylene-polyoxypropylene diols, or their mono-or di-ethers or with ethylene or propylene glycol, as ingredients of hydrolubes. Certain of the block copolymers are also useful as metal-to-metal lubricants for moving surfaces.  The particular block copolymers of Examples III, V and VIII had good emulsifying properties, especially for toluene-water systems.ALSO:A polysiloxane-polyoxyalkylene block copolymer has the general formula <FORM:0804369/IV (a)/1> wherein R1 is a low molecular weight alkyl or alkylene radical with the valence of x, R, R11 and R111 are low molecular weight alkyl radicals, x is 1 or 2, y is an integer of at least 3, n is 2, 3 or 4, a is an integer of at least 1 and not more than 3x, and z is an integer of at least 5.  The polymers are formed by reacting an appropriate mono-alkyl ether of a polyalkylene glycol with a polysiloxane having 1 or 2 Si atoms bonded to carbon atoms of an alkyl or alkylene group, the remaining valencies of these Si atoms being satisfied by O linked either directly or via (-Si(R2)O-) units or chains of such units to alkyl radicals.  Typical copolymers have the formul  <FORM:0804369/IV (a)/2> in which p+q+r=y (above), <FORM:0804369/IV (a)/3> in which p+q=y, or <FORM:0804369/IV (a)/4> in which p+q+r+s+t+u=y, which in this case has a minimum value of 6.  The general reaction for the preparation of these polymers may be written <FORM:0804369/IV (a)/5> <FORM:0804369/IV (a)/6> The polysiloxanes used as staring materials may have mol. wts. of 300-10,000 and may be prepared by reacting a polysiloxane, e.g. a trimeric or tetrameric cyclic siloxane, with a trialkoxysilane or a bis-(trialkoxysilyl) ethane, e.g. as described in Specification 792,470.  Suitable polyoxyalkylene monoethers for the as starting materials are described in U.S.A. Specification 2,448,664 and in British Specification 616,256.  The reaction is preferably performed in presence of a mutual solvent, e.g. toluene, xylene. The alcohol removed in the reaction may pass off as an azeotrope with the solvent.  Suitable catalysts for the reaction are trifluoroacetic, perfluorobutyric, perfluoroglutaric, monochloroacetic or acetic acid, or alkali metal hydroxides.  The latter form silanolates with the siloxane.  Removal or neutralization of catalyst may be necessary for stability of the products.  In Example (1), monobutyl - poly - (oxyethylene - oxy - 1,2 - propylene) glycol, monobutyl-polypropylene glycol, or monomethyl-polyethylene glycol is condensed by refluxing in toluene and trifluoroacetic acid with a triethoxy-polydimethylsiloxane obtained by heating a cyclic dimethyl polysiloxane with ethyltriethoxysilane in presence of alkali.  The physical properties and solubilities of the products are tabulated.  Examples (2)-(9) are basically similar, illustrating variations of molecular weight and starting materials within the general field.  Example (10) describes the condensation of monobutyl-polypropylene glycol with a hexaethoxydimethylsiloxane obtained by equilibrating hexaethoxydisilylethane and dimethylsiloxane cyclic tetramer. Some of the products are water-soluble, and useful as antifoam agents, rubber lubricants especially for type moulds, or textile lubricants.  They are miscible with water-soluble polyoxyethylene-polyoxypropylene diols or their mono- or di-ethers, or with ethylene or propylene glycol to form useful lubricants or hydraulic fluids.  Certain products are good metal-to-metal lubricants for moving surfaces.  Their lubricating properties are compared in the Specification with those of conventional lubricants.ALSO:Polysilonare-polyonyathylen block copolymers (see Group IVa) when water soluble or useful as rubber lubricants especially for tyre moulds, when they may be applied from aqueous solutions and excess is readily removable by washing.  The particular product of Ex 1(a) was useful as a release-agent in rubber moulding.