Polyorganosiloxane-based composition intended for tyre moulding/stripping

A process of lubricating an expandable rubber bladder during a vulcanization of a green tire within a metal press, the process comprising providing the bladder so that an outer surface of the bladder, intended to be in contact with an inner face of the green tire, is coated with a mold release agent composition (I) in the form of an oil-in-water emulsion, wherein the mold release agent composition comprises:

• (a) at least one reactive polyorganosiloxane (A) comprising at least two silanol groups ≡SiOH per molecule;
• (b) at least one crosslinking agent (B) having at least three ≡SiH units per molecule;
• (c) at least one non-reactive linear polyorganosiloxane oil (C) which is a linear homopolymer or copolymer which has, per molecule, monovalent organic substituents, which are identical to or different from one another, bonded to the silicon atoms, and which are selected from the group consisting of C1-C6 alkyl radicals, C3-C8 cycloalkyl radicals, C6-C10 aryl radicals and C7-C15 alkylaryl radicals;
• (d) glass beads (D) as spherical amorphous filler, the composition of which is as follows:
• the content of silicon expressed as SiO2 is less than 63% by weight,
• the content of calcium expressed as CaO is greater than 20% by weight,
• the content of sodium expressed as Na2O is less than 2.9% by weight,
• the content of aluminum expressed as Al2O3 is from 0.5% to 15% by weight,
• the content of boron expressed as B2O3 is from 0.2% to 2.5% by weight,
• the content of potassium expressed as K2O is from 0.35% to 1% by weight, and
• the content of magnesium expressed as MgO is from 1% to 4% by weight,
• relative to the total weight of SiO2, CaO, Na2O, Al2O3, B2O3, K2O and MgO;
• (e) at least one surfactant (E);
• (f) optionally at least one additive (F) selected from the group consisting of:
• a film-forming polymer, a complementary lubricant, an antifriction agent, a coalescence agent, a wetting or dispersing agent, a mineral filler, an antifoam agent, a thickener, a stabilizer, an acidifying agent, a biocide and an antifungal agent;
• (g) optionally at least one dehydrogenation-condensation catalyst (G);
• and
• (h) water (H);
• the amounts of surfactant(s) and water being sufficient to obtain an oil-in-water emulsion;
• the process thus making it possible to directly obtain an expandable rubber bladder lubricated on the outer surface thereof and leading to several cycles of green tire molding and of vulcanized tire demolding.

A process of lubricating an expandable rubber bladder during a vulcanization of a green tire within a metal press, the process comprising in a first step outside the press, coating an inner surface of the green tire with a mold release agent composition (I) in the form of an oil-in-water emulsion that comprises:

• (a) at least one reactive polyorganosiloxane (A) comprising at least two ≡SiOH groups per molecule;
• (b) at least one crosslinking agent (B) having at least three ≡SiH units per molecule;
• (c) at least one non-reactive linear polyorganosiloxane oil (C) which is a linear homopolymer or copolymer which has, per molecule, monovalent organic substituents, which are identical to or different from one another, bonded to the silicon atoms, and which are selected from the group consisting of C1-C6 alkyls, C3-C8 cycloalkyls, C6-C10 aryls and C7-C15 alkylaryls;
• (d) glass beads (D) as spherical amorphous filler, the composition of which is as follows:
• the content of silicon expressed as SiO2 is less than 63% by weight,
• the content of calcium expressed as CaO is greater than 20% by weight,
• the content of sodium expressed as Na2O is less than 2.9% by weight,
• the content of aluminum expressed as Al2O3 is from 0.5% to 15% by weight,
• the content of boron expressed as B2O3 is from 0.2% to 2.5% by weight,
• the content of potassium expressed as K2O is from 0.35% to 1% by weight, and
• the content of magnesium expressed as MgO is from 1% to 4% by weight,
• relative to the total weight of SiO2, CaO, Na2O, Al2O3, B2O3, K2O and MgO;
• (e) at least one surfactant (E);
• (f) optionally at least one additive (F) selected from the group consisting of:
• a film-forming polymer, a complementary lubricant, an antifriction agent, a coalescence agent, a wetting or dispersing agent, a mineral filler, an antifoam agent, a thickener, a stabilizer, an acidifying agent, a biocide and an antifungal agent;
• (g) optionally at least one dehydrogenation-condensation catalyst (G);
• and
• (h) water (H);
• the amounts of surfactant(s) and water being sufficient to obtain an oil-in-water emulsion;
• the first step thus making it possible to obtain a green tire, the inner surface of which is coated with the composition (I) and
• during a subsequent step within the metal press, bringing the coated inner surface of the green tire into contact with an expandable rubber bladder;
• the process thus making it possible to obtain, by transfer, an expandable rubber bladder lubricated on the outer face thereof and leading to several cycles of green tire molding and of vulcanized tire demolding.