Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2001-02-20
2002-12-10
Moore, Margaret G. (Department: 1712)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C528S031000, C528S042000
Reexamination Certificate
active
06491981
ABSTRACT:
FIELD OF THE INVENTION
The field of the invention is that of formulations for the treatment of substrates for the purpose of conferring on them resistance to aqueous and fatty substances. More particularly, the invention relates to silicone compositions comprising perhalogenated, preferably perfluorinated, radicals which can be used in particular for the preparation of hydrophobic and/or oleophobic coatings and/or for carrying out hydrophobic and/or oleophobic impregnations of various substrates.
More particularly still, the invention relates to silicone compositions which can be employed as fluorinated finishing preparations in the textile field for rendering the treated fabrics impermeable and for contributing stain-resistant and/or soil-resistant properties, combined with ease of washing. Such properties are also advantageous for other fields of application than the textile field. Mention may be made, for example, of the construction field, in which coatings, paints, coats or other glazings of a water- and oil-repellent nature are employed which render resistant surfaces which are non-adhesive with respect to ice, biological fouling of the type of that which becomes attached to boat hulls, or graffiti, or with respect to other undesirable contaminants.
DESCRIPTION OF RELATED ART
Silicone oils grafted with fluorinated units can also be used as lubricant, as specific antiadhesive agent with respect to certain adhesives (silicones with a high adhesive power), as grease-resistant agent or alternatively as antifoaming agent. They can also be formulated with various thickeners in order to form mastics or any other leakproofing and/or pointing material.
The present invention is targeted at the use of functionalized silicone compositions comprising linear or cyclic perhalogenated, preferably perfluorinated, polyorganosiloxanes exhibiting at least one silicon atom substituted by at least one perfluorinated radical Rf for the preparation of hydrophobic and/or oleophobic coatings and/or for carrying out hydrophobic and/or oleophobic impregnations with a low surface energy (for example, soil-resistant coating on textile substrates).
The invention also comprises a selection of silicone compositions with given perfluorinated functional groups and with other specific functional groups, in particular for attachment.
The present invention also relates to a process for the preparation of a hydrophobic and/or oleophobic coating and/or for carrying out a hydrophobic and/or oleophobic impregnation employing said composition.
Finally, the invention is targeted at precursors of coatings, coats, paints or other glazings comprising this composition.
The role of halogens and in particular of fluorine and of the carbon/fluorine bond in contributing specific properties to organic polymer systems is a notion which is well known in polymer chemistry. In particular, it is known that fluorination and more specifically the introduction of perfluorinated units into polymers leads to a decrease in the surface energies, an improvement in the thermal and chemical stability and an improvement in the hydrophobicity, organophobicity and oleophobicity properties. It is thus known that, in order to resist aqueous and fatty substances, a coating must comprise a high density of perfluorinated end groups Rf at the surface. Since the 1970s, this type of functionalization by perfluorination has been applied to silicone polymers, in particular of the linear or cyclic, preferably linear, polyorganosiloxane (POS) type.
For more details on these fluorosilicones, reference may be made to the article by Ogden R. Pierce entitled “Fluorosilicons”, 1970, John Wiley & Sons Inc., pages 1 to 15.
A first known strategy for the industrial synthesis of silicones comprising perfluorinated units consists essentially in “hydrosilylating” a dihalohydroorganosilane, such as MeHSiCl
2
(Me=methyl), with an unsaturated compound carrying a perfluorinated unit with the general formula: CH
2
═CH—Rf (Rf=perfluorinated unit). The addition of the silane to this olefin results in a perfluorinated dihalo-organosilane, which can be hydrolyzed so as to produce a functionalized silicone, which may, for example, be a cyclic tetramer. It is possible to subject the latter to a redistribution in order to obtain a perfluorinated linear polyorganosiloxane (POS). The hydrosilylation reactions which are involved in this type of synthesis and which employ various combinations of silicone hybrids and of perfluorinated olefins are known to be catalyzed by selected metal compounds and in particular certain metals from Group VIII, such as platinum. Pt/Sn complexes have thus been employed as hydrosilylation catalyst—cf. U.S. Pat. No. 4,089,882 (Shinetsu). This synthetic strategy appears to be relatively complex and therefore expensive.
For the sake of industrial simplification, a second synthetic strategy has been proposed based on the direct hydrosilylation of a silicone comprising an SiH unit using &agr;-fluorinated olefin, e.g. of the CH
2
═CH—Rf type, this perfluorinated unit Rf being directly attached to the olefinic CH via a carbon atom carrying at least one fluorine atom. Here again, various metal catalysts from Group VIII, in particular based on platinum, are used in the context of this hydrosilylation reaction. However, it turned out that these catalysts did not make it possible to achieve very high yields. In particular, conventional platinum-based industrial hydrosilylation catalysts (for example of the Karstedt type) are not very efficient. In addition, it could be observed that large amounts of by-product are generated, this very clearly being at the expense of the perfluorination of the silicones.
In U.S. Pat. No. 5,233,071, it is these linking units which are employed. They originate from the hydrosilylation of &agr;-olefins. However, in order to overcome the shortcomings of the hydrosilylation catalysts used previously, the process disclosed in this patent resorts to cobalt-based organometallic complexes [(Co
2
CO
8
.Co
2
CO
6
) (PR
3
)
3
with R=alkyl, aryl]. It is apparent that such a technical proposal is unsatisfactory, as the reaction times obtained are of the order of a few days and it is essential to use a large amount of catalyst (1-2%), which is particularly penalizing to the economics of the process.
A not insignificant disadvantage of these cobalt-based complexes is that they catalyze other reactions than the hydrosilylation. In particular, they can participate in polymerization processes by cleavage of epoxy rings. This lack of specificity is a particular hindrance. In addition, these catalysts are not industrially usable.
U.S. Pat. No. 5,348,769 discloses linear or cyclic polyorganosiloxanes comprising D siloxyl units substituted by a first perfluorinated functional unit of formula —R
3
ZRf and other D siloxyl units carrying a second type of functional unit of the etherhydroxyl or alkylhydroxyl type. The linking unit or the bridge connecting Si to Rf of the first perfluorinated functional unit is composed in particular of: (CH
2
)
x
Z, with x=2, 3 or 4 and Z=NHCO, NHSO
2
, O
2
C, O
3
S, OCH
2
CH
3
, NHCH
2
CH
2
or CH
2
CHOHCH
2
. The catalyst employed is preferably chloroplatinic acid.
Apart from these linking units, the precursors of which are perfluoroalkylated &agr;-olefins of formula CH
2
═CH—Rf, the prior technical literature also discloses bridges for which the olefinic precursors are of the CH
2
═CH—L—Rf type; the chemical bond between L and Rf being an ester bond. The latter results from the reaction of a carboxyl functional group with a perhalogenated alcohol, preferably a perfluorinated alcohol. And generally, said carboxyl functional group is the product of the hydrolysis of an acid anhydride.
Thus it is that PCT Patent Application WO 94/12561 discloses POSs grafted with fluorinated units solely at the &agr;- and &ohgr;-positions at the ends of the silicone chains. These &agr;,&ohgr;-(alkyl ester perfluorinated) POSs do not exhibit optimum properties as regards
Guichard Gérald
Mignani Gerard
Olier Philippe
Dennison, Schultz & Dougherty
Moore Margaret G.
Rhodia Chimie
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