Lubricating composition based on siloxane, not releasing hydrogen, preparation method and use thereof

A lubricating composition, in the form of an oil-in-water emulsion, based on siloxane and not emitting hydrogen, comprising:

• a) a polydiorganosiloxane oil which is nonreactive to the lubricating properties, having a dynamic viscosity of the order of 5×10−2 to 30×10−2 Pa.s at 25° C.
• b) a polyorganosiloxane resin carrying, before emulsification, condensable hydroxyl substituents and comprising, before emulsification, at least two different siloxyl units selected from the group consisting of formula (RO)3SiO1/2(M);
• (RO)2SiO3/2(D);
• ROSiO3/4(T) and SiO4/2(Q), at least one of these units being a T or Q unit, in which formulae RO represents a monovalent organic substituent, the average number per molecule of organic radicals RO for a silicon atom being between 1 and 2;
• and said resin having a weight content of hydroxyl substituents of between 0.1 and 10% by weight;
• c) a crosslinking agent which is soluble in the silicone phase, comprising at least two functional groups capable of reacting with the polyorganosiloxane resin (b);
• d) a condensation catalyst capable of catalyzing the reaction of constituent (b) with constituent (c);
• e) a surfactant;
• and
• f) water,
• said composition comprising
• from 5 to 95 parts by weight of constituent (a);
• from 0.5 to 50 parts by weight of constituent (b);
• from 0.1 to 20 parts by weight of constituent (c);
• from 0.05 to 10 parts by weight of constituent (d);
• per 100 parts by weight of the sum of constituents (a)+(b)+(c)+(d);
• the quantities of surfactants and water being sufficient to obtain an oil-in-water emulsion.