Compositions: coating or plastic – Coating or plastic compositions – Silicon containing other than solely as silicon dioxide or...
Reexamination Certificate
1999-09-29
2001-07-10
Brunsman, David (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Silicon containing other than solely as silicon dioxide or...
Reexamination Certificate
active
06258156
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a composition for a non-wettable coating and its application on a substrate. It also relates to the various products prepared from the composition. More specifically, it relates to the manufacturing process for glass provided with a non-wettable coating.
2. Description of the Background
The wettable nature of a substrate referred to the fact that polar or non-polar liquids adhere to the substrate and form a bothersome film. Wettability means the tendency of the substrates to retain frost, as well as dust and stains of all types, fingerprints, dirt, insects, etc.
The presence of water, frost and/or stains is detrimental to the appearance of the substrate, a possible reduction in transparency of the substrate, as well as an impairment of vision through the substrate. The latter are particularly bothersome when the substrate is glass used in vehicles.
Different types of non-wettable coatings are known, including a non-wettable layer obtained from fluorous organosilanes. This layer can be obtained by applying on the surface of a substrate a solution containing fluorous organosilanes in a non-aqueous organic solvent. As a non-aqueous organic solvent, document 492,545 cites, in particular, n-hexadecane, toluene, xylene, etc. These solvents are particularly appropriate for a fluorochlorosilane. It is also possible, according to this document, to use a methyl or ethyl alcohol as a solvent when the fluorous silane is a fluoroalkoxysilane. However, it is necessary to deposit the layer in the absence of moisture, which is difficult to implement.
SUMMARY OF THE INVENTION
An object of the invention is a composition for coating a substrate, where the wettability properties of the coating are satisfactory and for which the deposition process is simple and practical.
Another object of the invention is a composition deposited on the surface of a substrate in the presence of moisture, particularly in the ambient atmosphere with no moisture restrictions.
These objects are provided by a hydrophobic and oleophobic composition comprising at least one fluoroalkoxysilane, the alkoxy moieties of which are directly bonded to a silicon atom, an aqueous solvent system and at least one catalyst selected from an acid and/or a Bronsted base.
In addition to the hydrophobic, oleophobic, anti-rain, anti-frost, anti-stain, anti-dirt, etc. effects obtained by this composition, other advantages are gained when underlying functional layers are included, or with stacks. This case refers in particular to application A1-0 682,463 describing a glass comprising a glass substrate, an anti-reflection, low-emission and/or conducting functional stack, overlaid with a hydrophobic and oleophobic layer.
In such a configuration, the composition of the invention protects the functional stack from climatic conditions, or a possible chemical or hydrolytic assault. In the latter case, there is an improvement in holding quality in warm, moist atmospheres and by superior results in neutral saline fog tests. An increase in durability is obtained, or even a guaranteed quasi-permanence of the underlying anti-reflection or low-emission function.
The anti-adherent property of the hydrophobic and oleophobic coating according to the invention is particularly important when it overlays an anti-reflection layer or stack, since anti-reflection layers and stacks are typically plagued by the presence of undesirable markings on their surfaces.
Aqueous solvent system for use in the present invention are any type of solvent capable of both solubilizing and hydrolyzing the fluoroalkoxysilane. Preferably, it is a mixture of two components: a solvent capable of solubilizing the fluoroalkoxysilane and optionally a catalyst, and an aqueous compound capable of hydrolyzing the silane in the presence of a catalyst. An alkanol, for example an alkanol of low molecular weight, such as methanol, ethanol, butanol or isopropanol, is preferred as a solvent. An aqueous compound is a compound capable of releasing H
+
(protons), preferably water.
The fluorous silanes used according to the invention comprise a hydrolyzable moiety, capable of forming silanols with the formula Si—OH. The nature of this moiety affects the speed of hydrolysis of the silane. It is selected so as to allow the deposition of the compound on the substrate in an ambient atmosphere, preferably an alkoxy moiety.
The fluorine groups of the alkoxysilane impart to the layer obtained a particularly marked hydrophobia and oleophobia. The fluorine groups further impart a good resistance to ultraviolet light. The fluoroalkoxysilanes used according to the invention are preferably perfluoroalkoxysilanes having the formula:
with:
m=0 to 15
n=1 to 5
p=0, 1, 2
R is an alkyl
R′ is an alkyl or H
The alkyl of R or R′ may be C
1-100
or C
1-30
. Each R and R′ may be selected independently.
The organosilane carbon chain is preferably relatively long. Preferably, the number of —CF
2
— moieties is larger than the number of —CH
2
— moieties in order to impart a greater fluorine density on the outside: m is preferably at least 2×n.
The fluoroalkoxysilane are preferably selected from the following alone or in combination:
A perfluorotrialkoxysilane, having the formulas:
CF
3
—(CF
2
)
5
—(CH
2
)
2
Si(OR)
3
; CF
3
—(CF
2
)
7
—(CH
2
)
2
Si(OR)
3
; CF
3
—(CF
2
)
9
—(CH
2
)
2
Si(OR)
3
Where R is an alkyl, preferably methyl or ethyl; a perfluorodialkoxysilanes having the formulas:
CF
3
—(CF
2
)
5
—(CH
2
)
2
SiH(OR)
2
; CF
3
—(CF
2
)
7
—(CH
2
)
2
SiH(OR)
2
; CF
3
—(CF
2
)
9
—(CH
2
)
2
SiH(OR)
2
where R is an alkyl, preferably methyl or ethyl.
The proportion of fluoroalkoxysilane in the composition may range from 0.05 to 5%, by weight with respect to the composition, preferably, 1 to 3% by weight.
The proportions of the various components of the composition affect the wettability of the coating. The proportion of the aqueous compound, for example water, with respect to the solvent itself, for example an alcohol, ranges from 3 to 20% by volume, and preferably is on the order of 10% by volume. Thus, it is possible that the alkoxysilanes present in an aqueous solvent system may begin to hydrolyze, forming silanols capable of reacting with the reactive groups on the surface of the substrate. An excessively large proportion of hydrolyzed silanes may lead to homopolymerization. The number of alkanols capable of reacting with the surface of the substrate is then reduced. Likewise, an excessively small proportion of hydrolyzed silanes may lead to an excessively small number of silanes affixed to the surface of the substrate.
A catalyst catalyzes the hydrolysis reaction. The catalyst may be a Bronsted acid and/or base; it is capable of releasing an H
+
or an OH
−
ion, for example, hydrochloric or acetic acid. The proportion of catalyst in the composition also affects the wettability nature of the coating, and preferably is present in from 0.005 and 20% by weight with respect to the composition, and more preferably, on the order of 10% by weight with respect to the composition.
The coating is obtained through reaction of the hydrolyzed alkoxysilanes with reactive groups on the surface of the substrate, forming a covalent bond. The overall structure of the layer is, for an organosilane, covalent bonding at the point of fixation on the surface of the substrate, and one or two covalent bonds with neighboring organosilane molecules, through other hydrolyzable moieties.
The thickness of the layer obtained ranges from 10 to 150 angstroms, preferably 10 to 100 angstroms. The layer preferably does not impair the transparency of, or vision through, the substrate.
The composition according to the invention is applied on at least one portion of a surface of a substrate, comprising, in particular OH groups capable of reacting with the hydrolyzed silane of the compound. The substrate may be made of a mineral glass, a plastic material, such as polycarbonate for example, or a base coated with at least one
Azzopardi Marie-Jose′
Gauthier Fabienne
Talpaert Xavier
Brunsman David
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Saint-Gobain Vitrage
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