Coating processes – With post-treatment of coating or coating material – Chemical agent applied to treat coating
Reexamination Certificate
2001-01-29
2003-04-15
Cameron, Erma (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Chemical agent applied to treat coating
C427S387000
Reexamination Certificate
active
06548116
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method for manufacturing a chemically adsorbed film on the surface of a substrate comprising active hydrogens via siloxane bonding and a chemically adsorbent solution for using therefor. More particularly, this invention relates to a method for manufacturing a chemically adsorbed film using an alkoxysilane surface active agent, a nonaqueous solvent and a silanol condensing catalyst and a chemical adsorbent solution using therefor.
BACKGROUND OF THE INVENTION
The surface of the substrate such as plastic, metal, ceramics, fiber, woods, concrete, paint or the like have been treated for improved use in a variety of fields. For example, a method for treating a surface containing macromolecules includes; coating with a fluorosilane coupling agent to provide water and oil repellency; coating with a wax to provide lubrication; coating with a polyvinyl alcohol to provide hydrophilicity; and coating with a suspension of a fluorocarbon-based polymer in order not to catch dirt on the surface of a substrate. The above-mentioned methods are recognized in the field.
However, coating films of the prior art have a relatively weak binding strength to the substrates containing macromolecules. Consequently, if the substrates are wiped by a cloth or washed repeatedly, coating films are peeled off from the substrate and lose the finishing effect. Moreover, coating films of the prior art have a large number of pin-holes on their surfaces because molecules arrange in various directions therein, thus deteriorating the property. Moreover, fluorocarbon-based polymer coating films are deficient in transparency so that they cannot be used for the treatment of optical materials that require transparency.
Methods for manufacturing chemically adsorbed monomolecular films are suggested by the inventor of this invention. See, for example, Japanese Laid-Open Patent No.(Tokkai-Hei) 4-132637, Japanese Laid-Open Patent No.(Tokkai-Hei) 4-221636, Japanese Laid-Open Patent No.(Tokkai-Hei) 4-367721 which are incorporated by reference. Such films are free from peeling off from the substrates, being pin-hole free, having thickness on the order of nanometers, and having a high transparency, in other words, transparency and lustering properties.
However, according to the conventional method for manufacturing chemically adsorbed films, the films were formed by a dehydrochloric reaction between a chlorosilane-based surface active agent and the surface of a substrate. Consequently, harmful hydrochloric acid gas can generate during the formation of such films. Also certain methods have attempted to form films by a dealcohol reaction by way of an alkoxysilane surface active agents. However, since this reaction proceeds slowly, films are not easily formed. The method of using a dealcohol catalyst is also possible, but the surface active agent cross-links with the moisture content in the air and loses the activity if only the dealcohol catalyst is added. In other words, if the finishing agent includes moisture, the surface active agent cross-links before reacting to the surface of the substrate so that the reaction at the interface of solid and liquid is prevented, thus making chemically adsorption difficult.
SUMMARY OF THE INVENTION
To solve the above-noted problems, the invention aims to provide a method of forming a chemically adsorbed film which allows practical reaction rates and does not generate hydrochloric acid gas in forming the films.
To attain the above aim, the invention provides a first method of forming a chemically adsorbed film on a substrate having an active hydrogen, comprising the step of contacting the substrate with a solution mixture containing an alkoxysilane surface active agent, an active hydrogen-free nonaqueous solvent and silanol condensing catalyst to form a chemically adsorbed film covalently bonded to a surface of the substrate via siloxane bonding. The term “active hydrogen-free nonaqueous solvent” relates to a nonaqueous solvent containing substantially no active hydrogen. Preferably, it is free of all active hydrogen. The nonaqueous solvents can include any solvents other than water.
The first method can comprise contacting the substrate with the solution mixture containing the alkoxysilane surface active agent, the active hydrogen-free nonaqueous solvent and the silanol condensing catalyst, covalently bonding the alkoxysilane surface active agent to the surface of the substrate via a siloxane bond, and washing the substrate with a nonaqueous solvent to form a monomolecular coating film covalently bonded to the surface of the substrate via a siloxane bond. This method efficiently forms a monomolecular film made from the surface active agent, and the film is covalently bonded to the surface of the substrate via siloxane bonds.
The first method can also comprise contacting the substrate with a solution mixture containing the alkoxysilane surface active agent, the active hydrogen-free non aqueous solvent and the silanol condensing catalyst, covalently bonding the alkoxysilane surface active agent to the surface of the substrate via siloxane bonds, evaporating the nonaqueous solvent, and subjecting the substrate and the alkoxysilane surface active agent to a reaction with water to form a coating of a polymer film covalently bonded to the surface of the substrate via siloxane bonds. This method efficiently forms a polymer coating film made from the surface active agent, and the film is covalently bonded to the surface of the substrate via siloxane bonds.
The invention further provides a second method comprising the steps of contacting the substrate with a solution mixture containing a first alkoxysilane surface active agent, an active hydrogen-free nonaqueous solvent and a silanol condensing catalyst to form an inner layer which is a siloxane chemically adsorbed film covalently bonded to a surface of the substrate via a siloxane bond, and contacting the inner layer with a solution mixture containing at least a second alkoxysilane surface active agent, an active hydrogen-free nonaqueous solvent and a silanol condensing catalyst to form an outer layer made from a second alkoxysilane surface active agent and covalently bonded to a surface of the inner layer via a siloxane bond. In this embodiment, the first alkoxysilane surface active agent is preferably at least one selected from the group consisting of hexaalkoxy disiloxane, octaalkoxy trisiloxane, dialkoxysilane, trialkoxysilane and tetraalkoxysilane. This method efficiently forms a bi-layer chemically adsorbed film having an inner layer which is a chemically adsorbed monomolecular film of siloxane and an outer layer which is a chemically adsorbed monomolecular film from the second alkoxysilane surface active agent.
The second method can comprise contacting the substrate with the solution mixture containing the first alkoxysilane surface active agent, the active hydrogen-free nonaqueous solvent and the silanol condensing catalyst, covalently bonding the first alkoxysilane surface active agent to the surface of the substrate via a siloxane bond, washing the substrate with a nonaqueous solvent to form the inner layer which comprises a siloxane and is a chemically adsorbed monomolecular film covalently bonded to a surface of the substrate via a siloxane bond and then contacting the substrate covered with the inner layer with a solution mixture containing the second alkoxysilane surface active agent, the active hydrogen-free nonaqueous solvent and the silanol condensing catalyst, covalently bonding the second alkoxysilane surface active agent to the surface of the inner layer via a siloxane bond, and washing the substrate with a nonaqueous solvent to form an outer layer made from the second alkoxysilane surface active agent and covalently bonded to a surface of the inner layer via a siloxane bond. The first alkoxysilane surface active agent is preferably at least one selected from the group consisting of hexaalkoxy disiloxane, octaalkoxy trisiloxane, dialkoxysilane, trialkoxysilane and tetraalkoxysilan
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