Compositions: coating or plastic – Coating or plastic compositions – Silicon containing other than solely as silicon dioxide or...
Reexamination Certificate
1999-04-16
2002-04-30
Nakarani, D. S. (Department: 1773)
Compositions: coating or plastic
Coating or plastic compositions
Silicon containing other than solely as silicon dioxide or...
C106S287130, C106S287140, C106S287160
Reexamination Certificate
active
06379448
ABSTRACT:
THE PRIOR ART
Many attempts have been made for improving the water-repellent property of glasses by applying onto said glasses a silicon layer, as well for improving the adhesion of the protective and water-repellent layer on the glasses.
For example, U.S. Pat. No. 5,415,927 teaches an inorganic or organic glass product, or tempered glass product excellent in weatherability, water resistance, moisture resistance and abrasion resistance, which is formed of a) a silicate glass substrate, b) a porous modified layer enriched with silicon oxide through removal of components other than silicon oxide in a surface layer of the silicate glass substrate, and c) a water-repellent layer formed of at least one compound of an organic silicon compound and an organic fluorine compound on a surface of the porous modified layer. The porous modified layer is prepared by etching the outer surface of the substrate, said etching being carried out by treating the substrate by means of HF (hydrofluoric acid).
Such an acid treatment attacks the glass and can be to aggressive for glasses having small defects.
It has also been proposed (U.S. Pat. No. 5,580,819) to provide a coating on a substrate, such as glass, ceramics, metals, and organic polymeric materials. The coating composition comprises, in combination, acid catalyzed hydrolysis and condensation products of water-silane monomer mixture and a film forming amount of a polymer having functional groups selected from amino, hydroxy and carboxy, hydroxy and amino, amino and carboxy, and amino, hydroxy and carboxy. The described process comprises applying the aforesaid coating composition (or an acid catalyzed sol-gel coating composition) substantially free of performed oxide sol and water soluble metal salt to the surface of a solid substrate, curing the applied coating, and treating the cured coating with an aqueous electrolyte solution for a time sufficient to produce a coating having graded porosity which is antireflective over a broad band of the visible spectrum.
The water-repellent property of a glass substrate provided with such a layer is not sufficient.
It has also been suggested to provide substrates with fluorinated coatings, for example by applying a fluoro aliphatic silicon layer on a glass. Even, if such coatings have some chemical resistance properties and some water-repellent properties, these coatings are not resistance against an attack by means of a sodium hydroxide solution.
The invention relates to siliceous substrate provided with a coating having excellent chemical resistance properties and excellent water-repellent properties.
BRIEF DESCRIPTION OF THE INVENTION
The invention relates to a siliceous substrate having a face which is at least partly 30 provided with a water-repellent layer having a thickness of no greater than 5000 Angstroms, said layer being a layer of at least one fluoro silane compound having at least one silicon atom chemically bound to the siliceous substrate and chemically bound to the silicon atom of another fluoro silane compound of the layer, said layer having such chemical bounds with the siliceous substrate and such chemical bounds between silicon atoms of the layer that it has a chemical resistance of at least 1 minute against the action of an aqueous solution containing 25% by weight of sodium hydroxide and having a temperature of 25° C. Preferably, said fluoro silane layer has a delta haze of less than 0.3% measured by the method ASTM D 1044-94, using a Taber abraser under the conditions where the abrading wheel was a CS- 10F wheel, the load was 500 g and the number of rotations was 1,000. In case said layer is substantially completely cured, said delta haze can be reduced to less than 0.1%.
According to a preferred embodiment, the fluoro silane layer has such chemical bounds with the siliceous substrate and such chemical bounds between silicon atoms of the layer that it has a chemical resistance of at least 24 hours against the action of concentrated phosphoric acid at a temperature of 25° C.
Preferably, the treated face of the siliceous substrate of the invention has also a chemical resistance of at least 1 minute against the action of at least the following agents: soap solution, alcohol, isopropanol, isoparaffinic hydrocarbon, acetone, diacetonalcohol, methylethyl ketone, concentrated HCl, concentrated formic acid, 25% KOH solution, and gazoline.
The treated face of the siliceous substrate of the invention(face provided with the fluoro silane layer) has preferably a very low surface energy, so as to ensure a high water-repellency.
It has been observed that it was not possible to mark the treated face of the siliceous substrate of the invention siliceous substrate with a solvent based ink or paint, whereby the fluoro silane layer of the siliceous substrate of the invention provides a good anti graffiti protection.
Advantageously, the layer is a layer of fluoro aliphatic silane, said aliphatic group of said silane being a fluoro linear alkyl group with 2 to 20, preferably 3 to 12 carbon atoms, said alkyl group being substantially fully substituted with fluorine atoms. Said aliphatic group contains advantageously 3 to 40 fluorine atoms, preferably 5 to 25 fluorine atoms, most preferably from 13 to 20 fluorine atoms.
The invention relates also to a process for the preparation of a siliceous substrate provided with a fluoro polysiloxane layer prepared by polymerizing at least a fluoro silane derivative,
in which at least a part of a face of the siliceous substrate is contacted with a composition containing 0.1 to 10% by weight fluoro polysiloxane compound, at least a polar solvent for said fluoro silane, less than 10% water (preferably less than 5% by weight water, most preferably less than 2% by weight water) and at least an acid system for lowering the pH of the composition to less than 4, preferably less than 2, most preferably less than 1, especially less than 0.5, said pH being measured at 25° C. by using a LiCl electrode with an open sleeve, and
in which said part of the face in contact with the said composition is dried at a temperature and during a period of time so as to obtain on said part, a fluoro polysiloxane layer having such chemical bounds with the siliceous substrate and such chemical bounds between silicon atoms of the layer that it has a chemical resistance of at least 1 minute against the action of an aqueous solution containing 25% by weight of sodium hydroxide and having a temperature of 25° C.
In the process according to the invention, the composition advantageously contains substantially no water.
Advantageously, prior to be contacted with the solution, the said part of the face is washed, for example decreased, while after to be contacted with the solution, the said part of the face is rinsed, for example with a solvent, a polar solvent, especially with the solvent used in the fluoro polysiloxane composition.
According to an embodiment of the process, the drying or curing of the composition is carried out at room temperature. A substantially complete drying of curing of the fluoro polysiloxane layer can be reached after about 24 hours.
Preferably, possibly after drying or removal of solvent or water, said face is subjected to a heat treatment at a temperature from 60° C. up to about 250° C., for example from 60° C. to about 200° C., in an oxidative atmosphere or up to about 350° C. in a non-oxidative atmosphere.
The siliceous substrate is advantageously selected from the group consisting of glass, glass containing substrates, ceramics and silicate surfaces.
The composition to be applied is preferably prepared by mixing a first composition substantially free of water containing a fluoro silane derivative and an organic polar solvent for said fluoro silane in an amount sufficient for dissolving substantially completely the fluoro silane derivative, with a second composition containing less than 20% by weight water, at least an organic polar solvent and an acid system sufficient for obtaining when mixing the first composition with the second composition a pH lower than 4 (advant
ICT Coatings N.V.
Nakarani D. S.
Ostrolenk Faber Gerb & Soffen, LLP
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