Method for modifying expandable curing membranes for manufacturing tyres
A process for modifying an expandable curing bladder for a tire, which bladder has a surface intended to come into contact with a tire casing is provided. The process comprises a step of applying to the surface a layer of a silicone rubber composition comprising a first liquid organopolysiloxane bearing chain-end alkenyl groups, a second liquid organohydropolysiloxane and a photoactivatable hydrosilylation catalyst, and a step of exposing the silicone rubber composition covering the surface to irradiation with ultraviolet-visible light.
1 . A process for modifying an expandable curing bladder for a tire, which bladder has a surface intended to come into contact with a tire casing, which process comprises the following steps:
a) applying to said surface a layer of a silicone rubber composition, the silicone rubber composition comprising a first liquid organopolysiloxane having repeating units R 2 SiO 2/2 and having two chain ends each bearing an alkenyl group, the first organopolysiloxane being a polydialkylsiloxane, a second liquid organopolysiloxane having repeating units R′HSiO 2/2 and having two chain ends each bearing a group SiR′ 3 O 1/2 , the second organopolysiloxane being a polyhydromethylsiloxane, a photoactivatable hydrosilylation catalyst, and polyamide microparticles with a melting point of greater than 100° C., the symbols R, which may be identical or different, representing an alkyl, aryl or aralkyl group, the symbols R′, which may be identical or different, representing an alkyl group, the ratio between the number of the repeating units R′HSiO 2/2 and the number of alkenyl groups being greater than 1, and
b) exposing the silicone rubber composition covering said surface to irradiation with ultraviolet-visible light.
2 . The process as claimed in claim 1 , in which the photoactivatable hydrosilylation catalyst is a platinum, Pt, catalyst.
3 . The process as claimed in claim 1 , in which the photoactivatable hydrosilylation catalyst is an organometallic complex containing at least one metal-carbon sigma bond.
4 . The process as claimed in claim 1 , in which the photoactivatable hydrosilylation catalyst is a complex of the formula Pt(η 5 -Cp 1 )L 3 , Cp 1 denoting a cyclopentadienyl group, a cyclopentadienyl group substituted with alkyl or trialkylsilyl groups, and the symbols L, which may be identical or different, denoting alkyl.
5 . The process as claimed in claim 1 , in which the rubber composition also comprises a photosensitizer.
6 . The process according to claim 1 , in which the alkenyl groups are vinyl groups.
7 . The process as claimed in claim 1 , in which the ratio of the number of (R′HSiO 2/2 ) units to the number of alkenyl groups is greater than 5.
8 . The process as claimed in claim 1 , in which the ratio of the number of (RHSiO 2/2 ) units to the number of alkenyl groups is less than 100.
9 . The process as claimed in claim 1 , in which the groups represented by the symbols R and R′ contain from 1 to 8 carbon atoms.
10 . The process as claimed in claim 1 , in which the silicone rubber composition contains a hydrophobic silica.
11 . The process as claimed in claim 1 , in which the silicone rubber composition contains a micrometre-sized silicone powder.
12 . The process as claimed in claim 1 , in which the silicone rubber composition contains a silicone solvent.
13 . The process as claimed in claim 1 , in which the total mass amount of the first and second organopolysiloxanes represents more than 50% by mass of the silicone rubber composition.
14 . The process as claimed in claim 3 , in which the photoactivatable hydrosilylation catalyst is a platinum complex with one or more sigma ligands, the ligand being alkyl.
15 . The process as claimed in claim 4 , in which the complex is a trimethyl(pentamethylcyclopentadienyl) platinum complex.
16 . The process as claimed in claim 10 , in which the hydrophobic silica is in a mass content greater than or equal to 5% of the weight of the silicone rubber composition and less than or equal to 40% of the weight of the silicone rubber composition.
17 . The process as claimed in claim 1 , in which the polyamide microparticles are in a mass content greater than or equal to 5% of the weight of the silicone rubber composition and less than or equal to 15% of the weight of the silicone rubber composition.
18 . The process as claimed in claim 11 , in which the micrometre-sized silicone powder is in a mass content of from 5% to 35% of the weight of the silicone rubber composition, the micrometre-sized silicone powder consists of crosslinked silicone rubber microparticles covered with a silicone resin, and the silicone resin is a polyorganosilsesquioxane.