Process for producing a water-repellent and release coating on a support

A process for producing a water-repellent and release coating on a support S, optionally on a flexible support S comprising paper or of synthetic polymer film, the process comprising:

• 1) Preparing an aqueous silicone emulsion E1 which can be crosslinked into a silicone elastomer by a polyaddition reaction, comprising:
• at least one organopolysiloxane A having, per molecule, at least two unsaturated functional groups of C2-C6 alkenyl type, bonded to the silicon,
• at least one organopolysiloxane B having, per molecule, at least three hydrogen atoms bonded to the silicon,
• at least one polyaddition catalyst C,
• at least one emulsifying agent D,
• water,
• optionally at least one crosslinking inhibitor F,
• optionally at least one pH-fixing agent G chosen so as to maintain the pH of the emulsion E1 between 5 and 9
• optionally at least one formulation additive H, and
• at least one additive X which is a linear organopolysiloxane comprising siloxyl units (I.1) to (I.3) having the formulae below:
• Y
• a
• ⁢
• Z
• b
• 1
• ⁢
• SiO
• 4
• -
• (
• a
• +
• b
• )
• 2
• (
• I
• ⁢
• .1
• )
• Z
• 3
• 2
• ⁢
• SiO
• 1
• 2
• (
• I
• ⁢
• .2
• )
• H
• d
• ⁢
• Z
• e
• 3
• ⁢
• SiO
• 4
• -
• (
• d
• +
• e
• )
• 2
• (
• I
• ⁢
• .3
• )
• and not comprising units of formula (I.4):
• Z
• 2
• 2
• ⁢
• SiO
• 2
• 2
• (
• I
• ⁢
• .4
• )
• in which:
• a=1 and b=1 or 2;
• d=1 and e=1 or 2;
• the symbol Y represents a radical comprising a hydrocarbon-based group having from 2 to 20 carbon atoms and an epoxy function, with optionally one or more heteroatoms such as an oxygen atom, and
• the symbols Z1, Z2 and Z3, which may be identical or different, represent a monovalent hydrocarbon-based group having from 1 to 30 carbon atoms, with the following conditions:
• the additive X comprises, per molecule, at least two siloxyl units (I.1) bearing epoxyfunctional hydrocarbon-based groups, at least three siloxyl units (I.3) bearing hydrosiloxyl groups and a total number N of siloxyl units of between 7 and 30, and
• the additive X has a content of siloxyl units (I.1) of greater than or equal to 200 mmol per 100 g of additive X;
• 2) applying on at least one face of said flexible support S the aqueous silicone emulsion E1, and
• 3) removing the water and carrying out the crosslinking, optionally by heating to a temperature of between 80° C. and 220° C.