DE3202759A1 - Process for improving the alkali resistance of pyrolytically produced metal oxide coatings - Google Patents

Description

The invention is directed to a method for depositing metal oxide layers on glass, in particular to a method for coating glass with metal oxides by bringing a hot glass surface into contact with an oxidizing one Atmosphere with a coating composition that pyrolyzes upon contact with the hot glass surface and wherein a Metal oxide is formed.

US Pat. No. 3,660 oB1 describes a process for depositing metal oxide films by applying a solution, containing a composition forming the metal oxide film in an oxidizing atmosphere onto the surface of freshly made ribbon glass, the temperature of the surface being high enough to allow the coating composition to pyrolyze and form a metal oxide film · The durability and durability of one so formed Metal oxide film is tested by spraying with saline solution. It is believed that the good durability of a film so produced is due to the presence of tin vapor over the Bad is conditioned, which is reflected on the surface of the glass ribbon and at least partially immediately after Entry into the oxidizing atmosphere of the coating station is oxidized. It is stated that in general the Films produced at a lower glass transition temperature are less stable.

The object of the invention is to provide a method with which the durability of such pyrolytically produced coatings can be increased.
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This object is achieved by the method according to claim and the device according to claim 6.

In the subclaims are preferred embodiments of Invention described

The method of the present invention improves alkali resistance of metal oxide films produced by the well-known pyrolysis technique, in which a solution of thermally decomposable organometallic Compounds is sprayed onto the hot glass surface improves This improvement is due to a low temperature of the sprayed solution. The alkali resistance can be improved range from complete film detachment to the resistance of the coated carrier material to 5n solution won sodium hydroxide at 93 Celsius for 30 minutes by lowering it the solution temperature to about 10 ° - 18 ° Celsius A further increase can be achieved by further lowering the temperature of the solution, whereby the lower temperature limit is given by the fact that at this temperature the coating reagents begin to precipitate out of the solution This occurs at around - 1 ° Celsius. In the same way, durability can be improved by lowering the Temperature of the air used to atomize the solution. A certain improvement is also possible by that the temperature in the vicinity of the coating station is lowered

A continuous ribbon of glass is used in a standard float glass system over the surface of a bath of molten metal where the molten metal bath is generally tin or a tin alloy and in a reducing atmosphere which consists predominantly of nitrogen and hydrogen, is arranged. Once the glass has cooled and solidified sufficiently is to be dimensionally stable, but while the temperature is still sufficiently high to be thermal To pyrolyze decomposable organometallic compounds, the glass surface is treated with a solution of a thermally decomposable Metal connection brought into contact · This is known and the coating technique is in US patent specification .3 66ο o61 described in detail.

Various known metal compounds can be used for the invention Process are used. Such metal salts are acetates, 2-ethylhexoate and acetylacetonate one large number of different metals such as copper, chromium, manganese, Nickel, cobalt, iron, tin, titanium, vanadium, and mixtures thereof. The coating reagents are used in appropriate Solvents dissolved to form liquid coating compositions

Preferred solvents are aliphatic and olefinic halocarbons and halogenated hydrocarbons ωie Methyl bromide, carbon tetrachloride, chloroform, bromoform, Trichloroethane, perchlorethylene, hexachloroethane, tetrachloroethane and preferably methylene chloride · The coating compositions are preferably applied under pressure in one connected system and fed through lines cer spray gun, which is isolated from the hot environment are. The solution is applied to the glass ribbon at a relatively high speed by means of the spray gun and passed through only a relatively short distance to contact with the glass surface. Nevertheless, the solution temperature increases significantly and considerable evaporation occurs before the solution reaches surface.

In the method according to the invention, the solution is preferably cooled to temperatures below about 21 ° Celsius, very particularly preferably to about 4 ° Celsius, and then fed to the spray gun through a double-walled pipe. In a preferred embodiment, a double tube made of nylon tubing is used, the diameter of the inner tube being 9.5 mm and the diameter of the outer tube being 22.2 mm. The coating solution flows through the inner tube and cooling water is passed through the annular gap between the inner tube and the outer tube in order to keep the coating solution at a low temperature while it is being fed to the spray gun

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The air used for spraying and spraying onto the surface of the glass is cooled to a temperature below room temperature of about 22 ° C. The cooling is preferably carried out to a temperature of around 4 -1 o Celsius.
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In the most preferred embodiment of the invention the coating solution and the air used for spraying are cooled to a temperature of about 4 Celsius and the supply lines to the spray guns are insulated, to keep the temperature below about 27 ° Celsius until the solution and air reach the spray guns * Before inventive cooling of the coating reagents and In the air, the temperatures of the coating reagents often reach more than 41 ° Celsius. In addition, you can also the room temperature can be lowered by supplying a stream of fresh air to the vicinity of the coating station, to dissipate the heat radiated from the hot carrier substrate.

The invention will now be explained in more detail by means of an example explained.

A coating composition is prepared from 12.55 parts by weight of cobalt acetylacetonate, iron acetylacetonate, and 3.14 parts 4.21 parts by weight of chromium acetyl acetonate and comprising a total metal content of 2 wt.% In a solution containing equal volumes of methylene chloride and trichloroethane. The solution is kept under pressure in a tank that allows pressure regulation and a flow meter aufU) B · If necessary, the Beschichtungszuaammen-reduction, supplied through insulated pipes with a coolant, preferably made of stainless steel and have double the coating head. Cold water is used as the cooling medium, so that the coating solution is cooled to a temperature of around 18 ° Celsius. The solution is then fed through double-walled tubes to the actual spray gun, whereby

the solution flows in the inner tube and the cooling medium, i.e. water, passes through the annular space between the outer tube and the inner tube to bring about a further cooling of the solution to about 15 ° Celsius. This double pipe connects the spray guns with the storage container. Air can also be used as an insulating medium for the double-walled pipes.

The spray guns are filled with air to spray the spray * Stratification solution supplied. The air required for this is also sent through a cooler to cool it down to around 7 ° Celsius. The line for the spray air is surrounded by a copper pipe, using cold water as the cooling medium keep the air supplied to the spray gun cool. The temperature of the ambient air in the coating station is reduced by the fact that fresh air is introduced into the coating station by means of fans.

The sprayed coating solution is then applied to the hot Glass surface applied, wherein the coating reagents decompose to form a metal oxide film on the Glass.

Claims (8)

Dr. Michael Hann Dr. H.-G. Sternail Patent attorneys January 15, 1982 Marburger Str. 38 (1434) St / I 63oo pouring PPG Industries Inc. "Pittsburgh Pa. UNITED STATES. V / experienced for improving the alkali resistance of pyrolytically produced metal oxide layers Priority USA. Serial No. 232.o55 of February 5, 1981 Claims Process for coating glass with metal oxides by bringing a hot glass surface into contact with a solution a thermally decomposable metal compound at a temperature sufficient to pyrolyze the compound and to form a metal oxide, pyrolyze the mixture and form a metal oxide layer, characterized by UaQ man a) preparing a solution of the thermally decomposable metal compound at a first temperature and b) the solution to a second temperature prior to application the hot glass surface cools down. 2.) Method according to claim 1, characterized in that that the solution to a temperature of - 1 ° to + 1 o ° Celsius cools. 35 3.) The method according to claim 1, characterized in that the solution is decoratively dusted by means of air and sprayed onto the hot glass surface.
5 4.) Method according to claim 3, characterized in that » that one uses cooled air for atomization » 5.) The method according to claim 4, characterized in that one air with a:
Atomizing used. that air with a temperature of 4 ° to 22 ° Celsius for 6.) Device for coating hot glass surfaces with metal oxides, characterized by a) a storage vessel for the coating solution at the first temperature
b) devices for cooling the coating solution to a second temperature, c) Devices for conveying the cooled coating solution onto the surface to be coated. 7.) Device according to claim 6, characterized in that that it further comprises means for preventing the temperature of the coating solution from rising until it becomes hot Glass surface is fed. 8.) Device according to claims 6 or 7, characterized in _t that said means comprise for cooling and preventing the temperature rise as the coolant cold water.