Process for the surface treatment of an article containing silicone crosslinked by polyaddition
A process for increasing the surface tension (“wettability”) of a silicone element crosslinked by polyaddition from a liquid composition containing one or more α,ω-dimethylvinylpolydimethylsiloxanes (PDMS), one or more poly(dimethyl)(methylhydrogenosiloxy)-α,ω-dimethylhydrogenosiloxanes, and a platinum crosslinking catalyst. The silicone surface is treated with a homogeneous atmospheric plasma using a plasma spraying apparatus having a rotating head with one or more plasma nozzles that are offset relative to the axis of rotation, each one being capable of generating a plasma jet whose axis is parallel to said axis of rotation. The articles to which the invention relate include composites of flexible substrate (e.g. textile)/silicone coating. Application: adhesive bonding of silicone surfaces crosslinked by ≡Si—H/≡Si-vinyl polyaddition.
1. Process for the surface treatment of an article containing crosslinked silicone, selected from polyorganosiloxanes (POS) crosslinked by the polyaddition of ≡Si—H units onto ≡Si-alkenyl units, obtained from a silicone preparation comprising:
at least one polyorganosiloxane (POS) A with ≡Si-alkenyl units,
at least one polyorganosiloxane (POS) B with ≡Si—H units,
at least one metal catalyst C,
optionally at least one POS resin D carrying ≡Si-alkenyl units,
optionally at least one crosslinking inhibitor E,
optionally at least one adhesion promoter F,
optionally at least one mineral filler G,
optionally at least one functional additive H for imparting specific properties, wherein:
said process comprises spraying at least one plasma jet onto at least part of the silicone surface of said article,
the plasma used is a homogeneous atmospheric plasma,
and it is carried out continuously by means of a plasma spraying apparatus comprising a rotating head having one or more plasma nozzles that are offset relative to the axis of rotation, each one being capable of generating a plasma jet whose axis is parallel to said axis of rotation.
2. Process for the production of a crosslinked silicone article which has been treated by the process according to claim 1 , comprising:
(I) forming a silicone element with a liquid silicone preparation as defined in claim 1 ;
(II) crosslinking this liquid silicone preparation formed in step (I);
(III) treating at least part of the crosslinked silicone surface with a plasma;
(IV) repeating steps (I) and (II).
3. Process according to claim 1 , wherein the quantity of plasma received by the silicone surface is such that the energy of said surface is greater than 30 mN/m.
4. Process according to claim 1 , wherein the article containing silicone includes a substrate and one or more crosslinked silicone elements forming a monolayer or multilayer coating adhering to the substrate.
5. Process according to claim 1 , wherein the article containing silicone is a silicone mold or molded object.
6. Process for the assembly of articles containing crosslinked silicone selected from polyorganosiloxanes (POS) crosslinked by the polyaddition of ≡Si—H units onto ≡Si-alkenyl units, wherein at least one of the articles to be assembled is derived from the process according to claim 1 , and wherein said articles are assembled using liquid adhesive which is applied to at least part of the treated silicone surfaces.
7. Process according to claim 1 , wherein the chosen POS A have siloxy units of the formula:
W a Z b SiO (4−(a+b))/2 (1)
in which:
the symbols W, which are identical or different, are each an alkenyl group;
the symbols Z, which are identical or different, are each a non-hydrolyzable monovalent hydrocarbon group that is devoid of an unfavorable action on the activity of the catalyst, and is optionally halogenated;
a is 1 or 2, b is 0, 1 or 2 and a+b is between 1 and 3;
optionally at least some of the other units are units of the empirical formula
Z c SiO (4−c)/2 (2)
in which Z is as defined above and c has a value of between 0 and 3.
8. Process according to claim 1 , wherein the chosen POS B has siloxy units of the formula:
H d L e SiO (4−(d+e))/2 (3)
in which:
the symbols L, which are identical or different, are each a non-hydrolyzable monovalent hydrocarbon group that is devoid of an unfavorable action on the activity of the catalyst, and is optionally halogenated;
d is 1 or 2, e is 0, 1 or 2 and d+e has a value of between 1 and 3;
optionally at least some of the other units being units of the empirical formula
L g SiO (4−g)/2 (4)
in which L is as defined above and g has a value of between 0 and 3.
9. Process according to claim 1 , wherein the alkenyl groups W of the POS A and/or of the POS resins D are vinyl groups Vi carried by siloxy units D and optionally M and/or T.
10. Crosslinked silicone elastomer coating obtainable by the process according to claim 1 , wherein said coating has an adhesive strength, measured by a peel test T, greater than 2.7 N/cm.
11. The process of claim 1 , wherein said ≡Si-alkenyl units comprise ≡Si-vinyl units.
12. The process of claim 3 , wherein said energy is between 30 and 70 mN/m.
13. The process of claim 4 , wherein said substrate is flexible.
14. The process of claim 7 , wherein said alkenyl group comprises C 2 -C 6 alkenyl.
15. The process of claim 7 , wherein said non-hydrolyzable monovalent hydrocarbon group is selected from alkyl groups having from 1 to 8 carbon atoms inclusive and from aryl groups.
16. The process of claim 8 , wherein said non-hydrolyzable monovalent hydrocarbon group is selected from alkyl groups having from 1 to 8 carbon atoms inclusive and from aryl groups.
17. The process of claim 10 ,wherein said coating has an adhesive strength, measured by a peel test T, of between 3 and 10 N/cm.
18. Method for improving the adhesive performance characteristics of crosslinked silicone surface selected from polyorganosiloxanes (POS) crosslinked by the polyaddition of ≡Si—H units onto ≡Si-alkenyl units, obtained from a silicone preparation comprising:
at least one polyorganosiloxane (POS) A with ≡Si-alkenyl units,
at least one polyorganosiloxane (POS) B with ≡Si—H units, at least one metal catalyst C,
optionally at least one POS resin D carrying ≡Si-alkenyl units,
optionally at least one crosslinking inhibitor E,
optionally at least one adhesion promoter F,
optionally at least one mineral filler G,
optionally at least one functional additive H for imparting specific properties,
wherein said method comprises spraying at least one plasma jet onto at least part of the silicone surface of said article,
wherein the plasma used is a homogeneous atmospheric plasma, and
wherein said method is carried out continuously by means of a plasma spraying apparatus comprising a rotating head having one or more plasma nozzles that are offset relative to the axis of rotation, each one being capable of generating a plasma jet whose axis is parallel to said axis of rotation.