Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
2001-07-26
2002-09-17
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C106S002000, C106S287130, C106S287140, C106S287160, C106S287270, C427S162000, C427S163300, C427S165000, C427S419800, C428S447000, C428S448000, C428S912200
Reexamination Certificate
active
06451432
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the hydrophobic/oleophobic treatment of a substrate, especially made of a glass material, a ceramic, a glass ceramic or a plastic.
This type of treatment is intended, in a known manner, to impart non-wettability on the substrate.
The term “wettability” should be understood to mean the property whereby polar or non-polar liquids adhere to the substrate and form an undesirable film, as well as the tendency of a substrate to retain dust or dirt particles of any type, fingermarks, insects, etc.
BACKGROUND OF THE INVENTION
The presence of water and/or dirt particles is undesirable, in particular for a transparent substrate of the glazing type, especially used in the transport field.
A substrate exhibits the property of non-wettability, more commonly referred to as hydrophobicity/oleophobicity, when the contact angles between a liquid and this substrate are high, for example at least 90° in the case of water. The liquid therefore has a tendency to run off easily, in the form of drops, on the substrate simply by gravity, if the substrate is inclined, or under the effect of aerodynamic forces in the case of a moving vehicle. Known agents for imparting this hydrophobicity/oleophobicity property are, for example, fluoroalkyl-silanes, such as those described in Patent Applications EP 0,492,417, EP 0,492,545 and EP 0,672,779. According to these documents, this layer is obtained by applying a solution containing fluoroorganosilanes in a non-aqueous organic solvent to the surface of a substrate. As non-aqueous organic solvent, document EP 0,492,545 mentions, in particular, n-hexadecane, toluene, xylene, etc. These solvents are particularly suitable for a fluorochlorosilane. It is also possible, according to that document, to use a methyl or ethyl alcohol as the solvent when the fluorosilane is a fluoroalkoxysilane.
Common hydrophobic/oleophobic agents are, in particular, alkyltrihalosilanes or trialkoxysilanes, the alkyl group of which has at least one perfluorinated end, that is to say consisting of an F
3
C—(CF
2
)—
n
group in which n is a positive or zero integer. For these hydrophobic/oleophobic agents, Patent Application EP 0,719,743 mentions perfluorinated carbides as suitable solvents.
It is also known, from the aforementioned Application EP 0,492,545 A2, to increase the adhesion of the hydrophobic/oleophobic coating by subjecting the substrate to a priming treatment before applying the coating. This treatment consists in forming a thin interlayer using agents called priming agents or primers which are silicon compounds having at least two hydrolysable functional groups. One of the two hydrolysable functional groups provides the chemical bond to the substrate via an oxygen atom linked to the silicon atom; the second hydrolysable functional group reacts into a hydroxyl group linked to the silicon atom, which, by reacting subsequently with a hydrolysable functional group of the hydrophobic/oleophobic agent, will form a point of attachment to the latter. Application EP 0,492,545 A2 mentions, as priming agents, compounds SiCl
4
, SiHCl
3
, SiH
2
Cl
2
and Cl—(SiCl
2
O)
n
SiCl
3
, n being an integer between 1 and 4.
According to another technique, indicated by document EP 0,548,775 A1, the compounds mentioned above as priming agents are mixed with the hydrophobic/oleophobic agent in solution. Although in this case there is no longer any priming, the terms “integrated primer” or “integrated priming agent” are frequently used for these compounds. Document EP 0,548,775 A1 thus describes aqueous solutions of hydrophobic/oleophobic agents, including Si(OCH
3
)
4
, Si(OC
2
H
5
)
4
, H
3
CSi(OCH
3
)
3
or Si(OC
3
H
7
)
4
. In this type of approach, the hydrolysis and condensation reactions described above already partly occur between the integrated priming agent and the hydrophobic/oleophobic agent before the application of the treatment solution to the substrate. During this application, still-available hydrolysable functional groups belonging to one or other of the two compounds participate in the adhesion to the substrate, and others to the linking of two such compounds together, whether they be of different or even identical nature.
SUMMARY OF THE INVENTION
The invention makes available a family of novel integrated priming agents which are modifiable and compatible with the hydrophobic/oleophobic agents, such as those mentioned above.
The subject of the invention is therefore a composition for a hydrophobic/oleophobic coating, consisting of an aqueous solution of a hydrophobic/oleophobic agent containing a priming agent of formula:
in which:
R
3
represents a carbon chain;
R
1
and R
2
each represent an alkyl group or a hydrogen atom;
X
1
and X
2
are identical or different hydrolysable functional groups such as a halogen or an alkoxy, and
q and q′ are equal to 0, 1 or 2.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS THEREOF
Under hydrolysis conditions, the carbon chain R
3
is not viable to scission and its entire backbone is preserved. The molecule of formula (I) therefore has at least two hydrolysable functional groups carried by two different silicon atoms linked to each other by a sequence of stable, particularly hydrolytically stable, atoms. A judicious choice of carbon chain R
3
mainly involves the length of the backbone, that is to say the number of atoms participating in the linkage between the two silicon atoms, and possibly the steric hindrance created in the region of the silicon atoms, which influences the reactivity of the hydrolysable functional groups carried by these Si atoms.
Moreover, the carbon chain R
3
increases the hydrophobicity of the priming agent, and therefore improves its compatibility with the hydrophobic/oleophobic agent.
Preferably:
the hydrolysable functional groups X
1
and X
2
of the priming agent are alkoxy functional groups which, used in aqueous treatment solutions, guarantee the best optical quality on transparent substrates, by preventing the formation of any haze likely to appear in certain operating conditions, with other hydrolysable functional groups;
q and q′ are both equal to 0 or 1, or in other words each of the two silicon atoms of the priming agent carries two or three hydrolysable functional groups, which favours the chemical bonding of each of these two atoms, by means of oxygen atoms, both to the substrate and to the hydrophobic/oleophobic agent, hence an improvement in the cohesion of the coating and in its adhesion to the substrate.
The hydrophobic/oleophobic agent to which the priming agent of the invention is particularly suitable is of the perfluoroalkylalkylsilane type of formula:
in which:
m=0 to 15;
n=1 to 5;
p=0, 1 or 2;
R is an alkyl group or a hydrogen atom; and
X is a hydrolysable functional group such as a halogen or an alkoxy, the latter being advantageous for the reasons already mentioned.
Proportions by weight of hydrophobic/oleophobic agent and of priming agent in the composition of the invention from 0.2 to 10% and from 0.05 to 10%, respectively, guarantee the best performance with regard to hydrophobicity/oleophobicity, to the adhesion of the coating to the substrate and to its durability, that is to say its erosion and abrasion resistance. In particular, superior performance is not achieved using higher proportions by weight.
With regard to the other characteristics of the solution of hydrophobic/oleophobic agent of the invention, such as the proportion of water, the use of alcohol as auxiliary solvent, and in what proportions, pH conditions, etc., Application EP 0,799,873 A1 is entirely applicable and is, in this regard, incorporated by way of reference.
The subject of the invention is also a process for forming a hydrophobic/oleophobic coating on a substrate using a composition described above, this process comprising a step consisting in bringing the substrate into contact with a priming agent in solution, in the absence of any hydrophobic/oleophobic agent, prior to bringing it into contact with the said
Azzopardi Marie-Jose
Codazzi Nathalie
DeLattre Laurent
Nakarani D. S.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Saint-Gobain Glass France
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