DK142169B - Method and apparatus for applying a coating, especially of metal oxides, to a substrate, especially of glass. - Google Patents

Description

162169

The present invention relates to a method and apparatus for coating substrates, particularly glass substrates, with coatings composed primarily of metal oxides. The method and apparatus 5 of the invention are of the kind whereby the surface of the substrate is heated and contacted with vapors by reactants, thereby forming coatings thereon. Such treatments are known from e.g. US Patent Nos. 2,694,651 and 2,631,948 and Danish Patent Nos. 98,025.

It is also known that substrates can be coated with metal oxide coatings by contacting solutions formed of metal-3-diketonates and the like dissolved in suitable solvents, e.g. from U.S. Patent Nos. 3,202,054, 3,081,200, 3,660,061 and 3,652,246. These patents disclose a number of chemical compositions suitable for coating glass with metal oxide coatings. In general, this prior art is directed to directing a spray-atomized liquid coating material to the surface of the glass substrate to be coated. These patents describe as the best method for applying the coating materials to the process by which the substrate is brought into contact with the coating materials in liquid form. However, when applying both atomized and evaporated coating materials to heated substrates at atmospheric pressure, certain difficulties have been encountered, in particular having difficulties in obtaining coatings 30 which are sufficiently fine-grained and uniform in appearance. Only thick coatings have been produced by coating the substrate with a liquid spray (spray), and it has proved extremely difficult if not impossible to obtain films with a passage of visible light of less than approx. 50% when using the known vapor deposition technique.

Most commercial vapor-phase commercial embodiments are carried out under conditions of subatmospheric pressure. Several different types of technique have been developed to increase the film deposition rate. Thus, e.g. used electric fields, magnetic fields and magnetization by radio frequency or microwaves to increase the amount of motion of the particles in the evaporated coating materials during their application. Waveguides have also been used to direct the vapors of the coating materials to specially defined target areas, see United States Patent Nos. 3,144,652 and 15 3,561,940; but these methods are expensive, especially on an industrial scale.

It has now been found that one can increase the uniformity of films produced by chemical reaction after vapor phase deposition and the rate of this deposition and film formation, or significantly by simple measures in a single constructed apparatus, assuming a solution of at least one coating-producing reactant in a solvent therefor, and evaporating reactant (s) n (e) and, together with a gaseous carrier, targeting the hot substrate which is then coated upon contact with the (n) ) diluted gaseous reactant (s).

One (or more) vaporizable coating reactant (s) is injected into a gas-filled compartment and vaporized therein without significant degradation by intimate contact with a hot carrier gas, which then brings and dilutes the vaporized coating reactant to contact with the heat. substrates on which the reactant will react and be deposited as coatings.

The process is of the prior art, in which a gaseous mixture comprising at least one evaporative coating-producing reactant is maintained against the substrate which is kept heated to react therewith to provide a coating thereon, and is characterized in that dissolving at least one coating reactant in a volatile solvent thereof to form a coating solution, directing a stream of heated carrier gas into a closed chamber over and away from a heater mounted in the chamber, the carrier gas being heated to a temperature 1) 2) is sufficient to evaporate the solvent and 3) is below the decomposition temperature of the coating reactant to spray the solution in a stream directed towards the heating means and into the stream of carrier gas to mix the solution with the carrier gas so that the coating solution is evaporated and mix with the carrier gas under dannel view of a gaseous mixed stream passing through the heating means such that the temperature of the gaseous mixture is set to practically the same value as the temperature of the heating means and that the gaseous mixture so adjusted is directed to the substrate to be coated. It is peculiar to the invention that a heater disposed in a closed chamber is used to thermally stabilize the gaseous mixture of carrier gas, solvent and coating reactant, after which this gaseous mixture is sent to the substrate to be coated. As the mixture passes through the heater or heater, this will thermally stabilize the gaseous mixture, the heating capacity or heat of the heater being substantially greater than the gaseous mixture passing through it, thereby raising or lowering the temperature of the mixture in accordance with the heater's own temperature. The advantages of the present invention are particularly evident in the case of reactants with reactants which decompose autocatalytically at temperatures which are only slightly above their effective evaporation temperatures. By injecting, distributing and diluting such reactants upon introduction into a gas phase, this autocatalytic effect, otherwise obtained by some isolated local concentration superheat with consequent decomposition, can be practically eliminated and by evaporating the reactant from a mist. 10 or smoke mixed with hot gas, the evaporation efficiency can be sufficiently increased that the process is practically operable even at low temperatures immediately above the boiling point of the reactants, avoiding local overheating, yet 15 evaporates immediately at a large contact surface (droplet surface) as the reactant is diluted by dissolving in a suitable solvent, and the solution is sprayed into the chamber in countercurrent to the hot carrier gas, which then evaporates both the solvent and the reactant immediately by the vigorous mixing action when the two streams are mixed.

The reactive coating materials used especially in the process of the invention are pyrosolizable organometallic salts of metals of the Periodic Table Ib to IIb and Group VIII, in particular 3-diketonates, acetates, hexanoates, formates and the like. The acetylacetonates of iron, cobalt and chromium are particularly preferred; but also other kinds of reactants are used, e.g. hydrolytic reactants such as fluorinated 3-diketonates, especially acetylacetonates, and metal dicumens. Reactants may also be used which require the presence of significant amounts of other cooperating reactants such as oxygen, hydrogen and halogen.

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In particular, as a solvent, aliphatic and olefinic hydrocarbons and halogen-containing hydrocarbons serve, depending on the reactants. Single component solvent systems, especially a solvent system used for methylene chloride, are effectively used in the process of the invention. Solvent systems using two or more solvents have also proved particularly useful.

Some representative solvents which may be used are the following: methylene bromide, carbon tetrachloride, carbon tetrabromide, chloroform, bromoform, 1,1,1-trichloroethane, perchloroethylene, dichloriodo-methane, 1,1,2-tribromethane, trichloroethylene, Bromomethylene, trichloromonofluoroethane, hexachloroethane, 1,1,1,2-tetrachloro-2-fluoroethane, 1,1,2-trichloro-1,2-difluoroethane, tetrafluorobromoethane, hexachlorobutadiene and tetrachloroethane.

Other solvents may also be used, especially as mixtures of one or more organic polar solvents such as an alcohol containing 1-4 carbon atoms and a hydroxyl group and one or more aromatic nonpolar compounds such as benzene, toluene or xylene. The volatility of these materials makes their use somewhat more difficult than the above group of preferred fully or partially halogenated hydrocarbons, but they have particular economic utility.

The apparatus of the invention is characterized in that it comprises: a closed substantially horizontally positioned chamber, one or more heating means for controlling the temperature of gases passing therethrough, and mounted in the chamber such that it is divided into an upper and lower chamber. a lower compartment separated from each other by the heating means or heaters, 142169 6

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one or more means for delivering a spray stream comprising a solution of at least one coating reactant conducted into the upper space such that the axis of the spray stream intersects central portions 5 of the main plane of the heating means, one or more means for directing a flow of carrier gas into the the upper compartment in a direction transverse and away from the heater's marginal portions and opposite the spray stream to form a gaseous coating reactant-containing mixture flowing through the central portion of the heater and further down into the lower compartment, one or more means for distributing the gaseous coating mixture sent against the substrate 15 to be coated and one or more means for connecting the lower compartment to the distributing means to convey the mixture from the lower compartment and supplying it to the distributing means.

The solution of reactive organometallic salt in organic solvent is injected into an evaporation chamber designed to contain a heating element which heats the space surrounding it to a sufficiently high temperature to evaporate the coating solution in the room and not merely evaporating liquid which comes into contact with the heating element itself. A carrier gas is passed across and away from the heating means to meet and intercept the flow of the injected and preferably atomized coating solution and mixed for 30 minutes thereafter so that the solution droplets are immediately evaporated at high speed and the vapors are passed through the heater and evaporator to the substrate. that must be covered.

Vapors of the solvent and organometallic salt are sent from the evaporation chamber to an elongated manifold arranged to cover the heated

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substrates to be coated in almost its entire width. Connected to this manifold is an elongated nozzle by which the vapors are directed to the substrate. The smallest cross-section of the nozzle is preferably of uniformly continuous shape, providing practically continuous acceleration of the boundary layers of the vapors passing through the nozzle. The dimension of the largest cross-section of the nozzle is slightly smaller than the corresponding underlay width, so that a substrate placed next to the nozzle protrudes further at both ends than the main dimension of the nozzle. These conditions and this mode of application ensure that a practically uniform pressure drop along the main dimension of the nozzle is maintained and the 15 ensures that a disproportionate amount of vapor running through the nozzle avoids at each end of the nozzle and thus all vapors make good contact. with the substrate.

The front of the nozzle facing the substrate 20 is in such a position that the gap between the nozzle face and the nearest surface during the coating operation is at least 0.5 times the width of the nozzle at its exit. Preferably, the ratio of the distance to the nozzle width is at least 25 0.65 and most preferably between 0.9 and 5, but most preferably of 1.25 and 5.

Such a coating apparatus is described in the description for simultaneously filed Danish ans. No. 6807/73. Its evaporation chamber and manifold are operated at sufficient pressure to cause the vapor flow through the nozzle to run with a Reynolds number of at least 2500 and preferably at least about 20,000.

5000 to ensure quick, efficient and uniform coverage of the coating.

The apparatus and method of the present invention can be used to apply coatings to many different susceptible substrates. Fireproof solid substrates such as glass, glazed ceramics, ceramic / porcelain clad metals and the like are particularly suitable for coating by the process of the invention. Other substrates such as metals, plastics, paper and the like may also be coated according to the principles of the present invention. In particular, the method and apparatus of the invention are well suited to aid in the coating of flat glass with transparent metal oxide coatings. The resulting metal oxide-coated flat glass blanks have proved particularly useful for architectural purposes.

The drawing serves to further illustrate the method and in particular the apparatus according to the invention, with figs. 1 is a partial sectional view of a device according to the invention, showing the flow of vapors and liquids used in carrying out the process; FIG. 2 is a cross-sectional view of a portion of the evaporation means, manifold and nozzle used in combination with a supported float glass plate which is passed under the nozzle; FIG. 3 is a cross-sectional view of a portion of the apparatus of the invention taken along section line 3-3 of FIG. 2, FIG. 4 is a cross-sectional view of a portion of the apparatus of the invention taken along section line 4-4 of FIG. 3 and illustrating the particular placement of the heating element in the chamber relative to the inputs, outputs and arrangement of shield plates intended to promote the evaporation of reactant and solvent within the chamber more closely than by contact with the heating element itself; 5 is an enlarged cross-sectional view of the vaporization chamber having a suitable carrier gas distributor for directing a stream of carrier gas to the spray-atomized stream of reactant and solvent to be intimately mixed therewith and evaporated; and FIG. 6 is a partial view of the carrier gas distributor plate taken along section line 6-6 of FIG. 5th

In carrying out the process according to the invention, the carrier gas is preferably air. Air not only acts as a carrier, but also provides oxygen intimately mixed with the vaporized metal reactant such as metal acetylacetonate, whereby oxygen reacts with the metal reactant in contact with the hot glass surface thereby depositing a metal oxide film.

The evaporator is preferably provided with air of sufficient temperature to supply the heat required to evaporate both reactant and solvent which dilute and carry the metal reactant. In a preferred embodiment, the air / vapor mixture is delivered at a temperature of approx. 204 to 216 ° C at the outlet of the evaporator. Hot oil is fed to the heating element, which is thus kept at approx. 210 ° C. Carrier air is heated to approx. 260 ° C, but the air for atomizing metal reactant in solvent is provided at a temperature of approx. 21 ° C.

The spray atomization air flow is negligible compared to the carrier air flow and is provided at a pressure of approx. 0.14 to 0.7 and preferably about

0.35 ato.

The carrier air is provided at a pressure of approx.

30 to 3.5 to 7, and preferably of approx. 4.2 ato. The velocity of the carrier air sweeping across the heating element from the slots in the air distribution plates is approx. 1.5 to 3 m per minute. Preferably, the amount of carrier air supplied is above the required minimum required to keep all the reactant in the vapor phase. This means that the relative moisture in the carrier air with respect to metal reactant and solvent is kept saturated everywhere so as not to condense condensation in evaporators, manifolds, nozzles or vapor coating chambers, cf. Claim 2. In order to ensure good coating quality and reliable operation, it is particularly preferred in accordance with the invention that the mixture is from approx. 50% to approx.

95% saturated with coating reactant and solvent.

The minimum amount of air required to carry the reactants and solvent can be judged from conventionally known contexts for ideal gases on the basis of vapor pressure and molecular weight information for the particular reactants and solvents used.

The relative amounts of solvent and reactant to be evaporated are readily found from the solubility information and the total reactant flow desired in the vicinity of the substrate to obtain a desired coating thickness, taking into account the expected substrate temperature and therefore reaction temperature. temperature.

For a clearer understanding of the present invention, the following detailed description of the apparatus and method is provided with reference to the drawings.

25 FIG. 1 a substrate, e.g. a glass plate 11 to be provided with a coating. The glass plate 11 is generally supported, preferably in a horizontal plane, and the support is usually made with means movable in this plane or advancing the glass plate 11 along a path as indicated by the arrow at the bottom right of FIG. The coating apparatus according to the invention, comprising an evaporator assembly 12 and a steam distribution assembly 13, is positioned above and 35 directed to the glass plate 11. This arrangement is useful for continuous operation, especially in direct connection to the manufacture of sheet glass in infinite webs ( cf. claim 8).

Evaporator assembly 12 comprises an evaporation chamber 14, which is preferably a cylindrical chamber 5 containing elements for evaporation of the reactants, which elements will be described in more detail below. Evaporator assembly 12 further comprises means for supplying a reactant 15 and means for supplying a carrier gas 16.

A reactant is supplied in solution through a conduit 17 to a series of solution feed conduits 18, each of which is connected to a syringe tip 19, the discharge opening of which is provided inside the evaporator chamber 14. The solution conduit 17 is provided with a heating jacket 20 in which a heat medium such as water and which is divided by a partition 21 to provide both a forward flow and a backward flow of hot water. Spray gas (atomizing gas), preferably air, 20 is supplied to each spray tip 19 through a series of spray atomization feed lines 22, all of which are connected to an atomizing gas line 23.

The entire reactant supply means 15 is mounted on the evaporation chamber 14 by a series of 25 holders 24 surrounding the conduits and bolted or otherwise connected to a series of fittings 25 welded to the evaporation chamber 14.

The carrier gas supply means 16 comprises a carrier gas manifold 26 mounted on the evaporation chamber 14 30 with a bracket 27. Connected to the carrier gas manifold 26 are a plurality of carrier gas supply lines 28, each of which is connected to a carrier gas preheater 29, which in turn is connected to the evaporation chamber 14 in such a way that heated carrier gas can be fed into the chamber. The preheaters 29 are preferably electric resistance heaters, each having an electrical power connection 30 connected to a source of controlled electric power (not shown).

The above-described construction has proved suitable for imparting a sufficient gentle preheat to the solution, so that, when in contact with the appropriate hot carrier gas, it is supplied with the necessary evaporation mode without the risk of local overheating, and the evaporation occurs almost instantaneously when the two streams meet. in the upper room of the chamber. Thus, according to the invention it is convenient that the means for delivering the evaporative solution of the coating reactant further includes a heating means for heating the solution to a temperature below its evaporating temperature and the means for sending the carrier gas into the upper space includes means. to heat the carrier gas to a temperature above the evaporation temperature of the solution but below the decomposition reactant decomposition temperature.

The evaporation chamber 14 may be a single structure; but if its length is large, it is preferably a module constructiton with a series of relatively short evaporative chambers 14 connected end to end by couplings 31 which lock the 25 individual chambers together.

Inside the evaporation chamber 14 is a heat reservoir for stabilizing evaporated reactant and solvent. A heater 32 is mounted in the evaporation chamber 14 so that the chamber is divided 30 into two compartments, with all entering materials entering the upper and all outgoing materials leaving the lower. The heater 32 is designed so that vapors can pass through from the upper to the lower compartment. The heat reservoir has a large capacity and is in particular a pipe heat exchanger provided with fins, through which the temperature constant heat exchange fluid is circulated through the pipes.

142169 13

The heater 32 is mounted inside the chamber 14 on holders or hangers, which mounting brackets also serve as distributor plates 33 for introduced hot carrier gas and which are welded or otherwise connected to the interior walls of the chamber 14. The carrier gas distributor plates 33 are designed and connected to chamber 14 to form a confined manifold space by means of each plate 33 and the adjacent chamber wall. The carrier gas distributor plates 33 are provided with a series of openings which allow a free flow of gas into the upper compartment of the evaporator chamber 14 where this carrier gas stream is mixed with the spray-atomized reactant and the solvent and evaporates them momentarily.

The gaseous mixture containing evaporated reactant and solvent as well as carrier gas is displaced from the upper compartment and passes through the heater 32 which finely regulates the temperature of the mixture which enters the lower compartment of the evaporator chamber 14. The heater 32 preferably has a high heat capacity ratio. to the flowing gaseous mixture mass so as to ensure thermal stability. If the mixture is too hot, the heater cools it.

In the lower compartment of the evaporative chamber 14, a series of vapor outlet conduits 34 are found out through the wall of the evaporative chamber 14 and with several inlet apertures near the end facing into the chamber, each of each vapor outlet conduit 34 being preferably covered with an umbrella-shaped cap. or screen 35 which intercepts and prevents any random particulate material which may enter the chamber or form in the chamber, clogging the vapor outlet conduit and being entrained to the coating means where they will cause irregularities in the coating.

Around the steam outlet lines 34, there is a steam exhaust heating 36 having two cavities, a supply cavity and a return cavity connected to a recirculation heat exchanger fluid system (not shown). When the apparatus is in operation, hot fluid such as oil is circulated through the vapor outlet heater 36 to, if necessary, fine-tune the temperature of the gaseous mixture leaving the vaporization chamber 14.

Connected to each steam outlet line 10 34 is a preferably flexible coupling 37 which connects the evaporator assembly 12 to the steam distribution assembly 13 comprising a steam manifold or compressed air space 38 with two steam channels 39 separated by a partition 40 and lined with casing 15 on both sides, namely a inner and outer cavities 41 and 42 for circulating fluids for further heat regulation. In operation of the apparatus, hot fluid such as oil is circulated through the inner and outer cavities for temperature control of the gaseous mixture flowing through the vapor channels 39.

The vapor channels 39 in the air-filled chamber 38 terminate in nozzles 43, which are preferably inclined towards each other. The individual nozzle is formed of facing nozzle wall portions 44 connected to the pressure chamber 38. Preferably, each nozzle wall portion 44 is provided with a cavity 45 through which to heat heat fluid such as oil to accurately control the temperature of the gaseous coating mixture. which is directed through the nozzle 43 to the substrate 11.

The oil circulating through the cavities 45 usually removes heat and prevents the wall portions 44 from folding.

The above construction of the parts, which follow the evaporation chamber but come before the coating operation, serves to distribute the gaseous reactant completely uniformly and adhere strictly to the temperature requirements throughout the system and ensure that only gas contacts the substrate during the reaction. . Thus, according to the invention 5, the newly formed gaseous mixture is liberated from virtually all liquid and all entrained solids at the exit from the closed chamber, after which it is uniformly distributed over an elongated area and directed to the substrate.

The coating apparatus and method of the invention can be used in combination with a variety of other methods and substrates, e.g. in papermaking, rolling of sheet metal and the like. The process of the invention may be used to coat a continuous sheet or a variety of separate substrates, but in particular, a continuous glass sheet may be coated which may be made by any of the methods known herein (according to Colburn, Fourcault or Pitts-20 burgh). Pennvernon) or by the float glass manufacturing process. The method of the invention can be used effectively to apply a coating to a substrate in a vertical, horizontal or other joint oriented plane, and this particular feature is particularly valuable.

In a particularly preferred embodiment of the method, the apparatus is used to coat a ribbon freshly prepared glass plate in the process of glass-making. This glass band can easily be coated on one, the other, or both of its two main surfaces by the method of the invention, however, the following description relates only to coating the top surface of such band glass (for ease of understanding).

35 Referring now to FIGS. 2, 3 and 4, and still to FIG. 1, the apparatus of claim 16

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the finding can be observed in particularly preferred environments, namely, located between a float bath and a relaxation refrigerator.

A continuous glass strip 11 is shown on a molten metal 46 bath 5, such as molten tin contained in a bathtub 47 provided with refractory bottom, side walls and top walls 48 enclosed in a metal plate cover 49.

The band 11 is lifted from the molten metal 46 at the outlet end of the bath chamber 47 on lifting rollers 50 driven by conventional roller propulsion means connected to a drive motor (not shown).

Coal blocks 51, which are spring loaded and pressed against the bottom of the rotating rollers 50, remove any materials which may be deposited on the rollers.

The ball blocks 51 are supported and placed in a refractory extension of the bath chamber 52. Material removed from the rollers falling in this elongated portion 52 can be readily removed at intervals.

The glass band 11 is conveyed to a stress-free cooling furnace 53 for stress-free cooling and provided with several refrigeration rollers 54. Conventional drive means are provided for appropriate rotation of the rollers 54. Each cooling furnace roller 54 exerts a tensile force on the glass of sufficient size to transport the glass through the refrigerator. where its temperature is controlled so that permanent stresses in the glass are triggered. The rollers 54 form part of the means for transporting the glass formed by the float glass process 30 from the float bath chamber 47 through an evaporative coating chamber 55 and then through the annealing cooling furnace 53 to produce coated and permanently tension-free glass.

The atmosphere of the bath chamber 47 is a reducing atmosphere containing nitrogen and a small amount of hydrogen to ensure that oxidation of the molten metal 46 is inhibited. Generally, the atmosphere contains approx. 90-99.9% nitrogen, the remainder being hydrogen.

The atmosphere is kept at a pressure slightly above ambient pressure, e.g. of 2.5 to 12.7 mm water column to substantially prevent the ambient atmosphere from entering the bath chamber 47.

In order to maintain this atmosphere and allow the glass band to pass from the bath chamber 47, the outlet end of the bath chamber is provided with a series of curtains 10 56 which hang down and over the glass band and serve as means for blocking the low pressure atmosphere of the evaporative coating chamber 55 from the bathroom 47.

These curtains 56 are usually made of flexible asbestos or fiberglass material which does not discolour the glass and which withstands the ambient temperature, namely a temperature of approx. 540 to 650 ° C. In addition, further curtains 57 of similar material are found at the entrance of the cooling furnace 20 53, the latter curtains serving as means for blocking the cooling furnace 53 from the evaporative coating chamber 55.

The evaporative coating chamber 55 is provided with vacuum caps 58, the inlets of which are disposed both below and above and adjacent to the bath chamber and the refrigerator. The vacuum caps 58 extend vertically upwardly to a pair of suction tubes 59 and are spaced sufficiently apart to provide sufficient space for supporting I-beams 60 60 and for the vapor coating apparatus comprising for steamer assembly 12 and steam distribution assembly 13 and associated equipment. The vacuum caps 58 are movably supported on I-beams 60 by means of wheels 61 resting on the tops of I-beams 35 60. The I-beams 60 are disposed transversely along the path along which the glass band 11 moves from the bathtub 47 to the refrigerator. 53. Vacuum caps 142169 18 are spaced apart by means of a transverse strut 62. Extraction tubes 59 are mounted on brackets or clamps 63, which in turn are mounted on wheels 64 which rest on grooves 65 on a supporting top 5 beam 66. The entire vacuum hood assembly comprising the vacuum caps 68 and the suction tubes 59 can be moved across the feed path of the glass band 11 so that the assembly can be completely removed from the production line for maintenance and repair.

This removal is accomplished by allowing the assembly to move along beams 60 and 66 while rolling on support wheels 61 and 64.

The steam coating assembly is supported within the steam coating chamber 55 on the I-beams 60 by means of a steam coating support bracket 67.

Mounted on the support bracket 67 are steam coating support wheels 68. These steam coating support wheels 68 rest on the I-beams 60, one of which is fitted with a groove 69. The Fa-20 cone on the groove 69 and on the supporting wheel 68 which are engaged therewith are designed so that the aggregate is obstructed in transverse motion with respect to the groove and the I-beams.

The vapor coating assembly comprises, in addition to the vaporizing assembly 12 and the vapor distributing assembly 13, a mechanical structure to support these operative elements. This mechanical structure includes a motor 70 and a drive 71 for raising and lowering the assembly so that it can be positioned closer to or 30 farther from the substrate to be coated.

Hanging in the steam cover support brackets 67 are steam cover cross arms 72. Mounted on the cross arms 72 are a motor support 73 and drive supports 74. Mounted on the engine support 35 73, the engine 70 is preferably an even support.

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variable speed power motor. Connected to this engine 70 is a drive shaft 75 which is itself connected to the worm gears 71. Within each drive 71 there is a suitable gear wheel to turn the driving force of the first drive shaft 5 to the vertical direction.

Worm drive shafts 76 are connected to the drive shaft 75 through the drives 71 by means of the above gears.

By driving the drive shaft 75 by means of the motor 70, the worm gears 76 are moved vertically up or down to thereby raise or lower the vapor coating assembly. Mounted on the drive shafts 76 are yoke or fork joints 78 which are connected to transverse plates 79.

Mounted on the transverse plates 79 is a cradle support 80 for the evaporator bolted or otherwise attached to the pre-vent chamber 14.

As briefly described above, carrier gas, preferably air, is supplied to the evaporative chamber 20 14 and mixed with the spray atomized (atomized) coating material coming from the spray-spray nozzle tips 19 to increase the evaporation rate of coating material and then the gas mixture 32 is passed through additional heating to finally be delivered as a gas stream directed to the substrate to be coated. The carrier gas is supplied to the evaporator from manifolds 26, which are preferably pipes mounted to the assembly by means of shackles 27, Flexible 30 pipes 28 are connected to the carrier gas manifold 26 and pass through heating elements 29 to connecting means or connections which run through the wall of the evaporator chamber 14 and enter. and opens into the space bounded by the air distribution plates 35 33 and the adjacent wall of the evaporation chamber.

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The heating means 29 is powered by an electric cable 81 running through a supporting distribution line 82 mounted on the shackles 27 and 83.

The structural properties of the present preferred apparatus are clearly shown in FIG. 2, 3 and 4. Excess of reactant vapors and carrier gas discharged from the nozzles 43 toward the substrate 11 fills the vapor coating chamber 55. Unreacted vapors and gases are removed or withdrawn from the chamber by the vacuum cap 58. To minimize or avoid formation and accumulation of deposits on irregular structural surfaces, which could result in deposits that peel and fall onto the substrate 11 and thereby cause defects, the vapor coating aggregate is encapsulated in a vapor coating shield 84.

The vapor coating shield 84 may be provided with reinforcing plates 85. It is connected to or with the coating assembly by means of the transverse plates 79.

Thus, as indicated above, these transverse plates 79 are connected to the support member 78 and are further connected to the support cradle 80 of the evaporator. As already stated, the evaporation chamber 14 is connected to the cradle support 80 of the evaporator assembly. The transverse plates 79 are provided with access holes 86. The space between the vapor coating shield 84 and the steam manifold 38 is preferably filled with a heat insulation 87 such as mineral wool, asbestos or the like.

Thus, as shown in FIG. 3, the structure 30 of a vapor coating assembly to span the entire width of a conventionally produced glass strip may be constructed by means of modules. Module construction is preferred for ease of maintenance and repair of the equipment. Individual evaporation chambers 14 and associated equipment are joined together to form an assembly spanning the entire width of the belt.

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Although the evaporator means 14 may be constructed in modules, the steam distribution manifold 38 and the steam nozzles 43 are preferably single units. In this way, vapors are evenly distributed over the entire width of the substrate to be coated.

The reactant vapors are uniformly distributed along the substrate by means of the steam manifold or vapor pressure chamber 38. The length of this manifold or pressure chamber 38 across the path of the glass band, i.e. the span of the glass band to be coated is far greater than the width of the manifold.

The steam manifold 38 comprises many steam channels which are elongated and spaced apart at their exit ends, but which meet in a common channel at their entrance. The many couplings 37 which bring vapors from the evaporator 14 to the manifold 38 are connected to the manifold 38 along this common channel entrance.

Preferably, the individual vapor channel 39 may be constructed with two opposite curves, so that the path of movement of the vapors passing through the channel must change direction at least twice.

In this way, the uniform distribution of vapors is increased along the entire length of the channel. However, although baffle plates may be provided within the ducts to further interrupt the vapor flow and distribute the vapor throughout the length of the ducts, however, the simple construction without baffle plates but with altered flow direction is preferred.

Namely, in the preferred construction, there are no braking regions and no protruding bodies to produce substantial eddy currents.

Around the steam channels 39 are voids 41 and 42 which surround the channels and carry or convey a heating or cooling fluid as desired.

These chambers 41 and 42 extend into the steam manifold 38's 142169 22

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full-length and connected to a source of heat or cooling fluid (not shown). In the preferred embodiment, the chambers are supplied with hot oil.

Connected to the steam manifold 38 are provided nozzle wall portions 44 which form the nozzles 43 through which the evaporated coating material and carrier gas are sent to the substrate 11 to be coated. The nozzles 43 are elongated and slit-shaped, as seen in plan view. The preferred nozzles are narrowed significantly - * · 0 from their input to their output. Each single slit is such that steam passing through the slit is continuously accelerated along the length of the slit, ie. from entrance to exit. In this way, the boundary layer of the vapors against the gap wall 15 can be minimized and the entire circumference of the gap is moistened uniformly with the vapors, so that the outgoing vapors are directed uniformly to the substrate. The nozzles can be characterized by the narrowing ratio, which is the ratio of the cross-sectional area at the entrance of the nozzle and at its exit. The preferred flow conditions for achieving efficient and uniform coating should be set out below, the conditions being described and defined as the conditions applicable at the outlet end of the nozzles. The preferred nozzles are described in more detail in the specification of Danish patent application no.

6807/73.

Each steam channel 39 preferably has a volume of at least 6 times the volumetric flow rate of the channel per unit. minute. By having this capacity to accommodate vapors passing through it, the channel serves as a calming section for smoothing out any residual velocity variations resulting from the many separate currents or single currents entering the channel from the flexible couplings 37. As mentioned above, the steam channels 39 preferably reorient the steam flow with a tendency for uniform distribution of the steam over the entire length of the manifold 38. The configuration and size of the steam channels 39 have been found to cooperate with the shape of the nozzles 43. , especially for over approx. 5-6, the capacity or volume of the steam can-

C

clay 38 is lowered without detrimental effect.

The individual nozzle 43 is constituted by two parts 44, each of which has a curved surface connected to the manifold 38, these curved faces facing each other. The individual portion may be provided with a channel 10 45 which conducts a fluid such as a hot oil to regulate the temperature of the vapors and gas emitted through the nozzle. In a preferred embodiment, hot oil passes through the parallel channels 45 and then through channels 41 and 42. The temperature of the oil to and from the nozzles can be measured and the temperature calculated from such measurements is considered the nozzle temperature which is the temperature. ^ used to define the vapor flow conditions at each nozzle outlet.

20

The curved surfaces defining the flow area of the nozzles; are smoothly machined to avoid creating even the smallest obstructions or scratches that would cause local disturbances in the vapor and gas flow. In a preferred embodiment, the nozzle portions are made of machined steel or other base metal and the curved inner surfaces are plated with a lightly workable metal such as gold or another precious metal. A metal finish of at least approx. 16.5 µ and preferably about 38 µ 30 is satisfactory. When the constriction ratio is sufficiently large, this metal finish can be less slippery without this damaging effect.

The curvature of the inner nozzle surfaces is such that the radius of curvature is at least at the inlet and 35 greatest (as it approaches infinitely) at the outlet.

In the most preferred embodiment, the radius of curvature is increased monotonically (and preferably constant) as a function of the distance from the nozzle inlet to its outlet. To facilitate the construction of the apparatus, the nozzle portions 44 are machined to distinctly different radii in distinct areas along the nozzle feed length. Each area is machined for smooth transition in the next.

The outlet edges of the nozzle portions are preferably sharp well-defined corners so that the portions of the nozzle portions facing the substrate 10 will not be wetted with outgoing vapors and gas.

The details of the apparatus according to the invention will be understood even more clearly in the examination of the drawing of FIG. 5 and 6 together with FIG. 1. The evaporative chromium 14 is a cylinder in which the heating means 32 is mounted. This heater 32 roughly separates the chamber 14 into two enclosed spaces. The space above the heater 32 serves for introduction, mixing and evaporation, and the space below the heater serves for temperature and concentration stabilization and as a departure room.

The heater 32 is provided with holes so that vapors and gases can pass through it from the upper compartment to the lower compartment. In a preferred embodiment, the heating means is a pipe heat exchanger provided with fins of a similar construction as commonly used as a condenser for air conditioning.

In operation of the apparatus, heating fluid is supplied to the heat exchanger tube, which is heated and by line 30 heats the fins. Heat can then be transferred to the surrounding chamber and to vapors and gases passing through the heating element from the upper to the lower compartment.

Heat exchange fluid, preferably hot oil, 35 is supplied to heater 32 through a supply line 08. After the heat exchange fluid is passed through the heat exchanger 32, it is passed to the steam-discharge heater 36 through a transfer line 89, and from the steam outlet heater 86, this fluid is sent back 5 through a discharge line 90. Alternatively, the heat exchange fluid could flow in the opposite direction. As mentioned above, the heater 32 primarily serves the purpose of stabilizing the temperature of the mixture of air, evaporated reactant and solvent, but not so much the purpose of providing the heat of evaporation. Thus, the heating means preferably has a high heat capacity relative to the heat required for only a small influence on the temperature of the mixture. The temperature of the heater is maintained at the desired level of exhaust vapors, and therefore the heat transfer to the vapors is operated with as little temperature gradient as possible. The result is that the vapors of almost non-varying temperature are delivered from the chamber by means of the vapor outlet lines 20 34. However, if the gas mixture is too hot, it is cooled by the means 32.

In order to uniformly distribute the reactant, the solution is sprayed from many syringe tips 19 mounted along a line midway between the outer corners 25 or edges of the heater 32. The syringe tips 19 are mounted to face the heater 32 and so that each spray jet about it was allowed to proceed unchallenged, essentially would be captured by the heater. The central axis of each syringe 30 is preferably normal to the main plane of the heater and intersects the heater in its central portion. The dissolved reactants are further finely distributed preferably by spray atomization (atomization), which provides a very large phase interface.

The incoming carrier gas is directed in countercurrent to the spray-atomized stream of dissolved reactant and causes intimate mixing between droplets and carrier gas, resulting in increased evaporation. Each gas distribution plate 33 is provided with many angled bends 91 which send the heated carrier gas outwardly and upwardly away from the edges of the heater 32 and towards the syringe tips 19, so that the carrier gas intercepts and breaks the finely atomized spray atomization and causes both the reactant and dissolve. the solvent to evaporate immediately. Thus, it has been found advantageous in accordance with the invention that the solution of coating reactant and solvent be introduced into the stream of carrier gas by spraying in the direction of the heating means. The mixture of evaporated reactant, solvent and carrier gas then passes through the heater 32 in its central portion and flows out through the vapor outlet lines 34 and is continued to coat the substrate.

The following examples serve to further elucidate the method and apparatus of the invention and the advantages thereof.

Example 1

The apparatus shown and described above is positioned across a glass ribbon produced by the float glass process 25 between the float bath and a storage refrigerator.

A continuous strip of clear glass with a width of about 3 m and a thickness of approx. 6.35 mm is transported below the member at a linear speed of about 30 mm. 6.35 m per minute. The glass is a conventional baking soda-lime-sand glass with a visible light penetration of approx. 88%.

A coating solution is prepared. The solution has the following composition calculated at 3.785 liters.

35 142169 27

ISLAND

Iron acetylacetonate 510 grams

Chromium acetylacetonate 150 grams

Cobalt acetylacetonate 55 grams

Methylene chloride to 3.785 liters 5

The coating solution is delivered to the solution line 17 at a rate of approx. 0.75 liters per per minute at a pressure of approx. 0.7 ato and at a temperature of approx. 21 ° C. Atomizing air is supplied to the atomizing gas line 23 at a pressure of approx. 0.35 ato and a temperature of approx. 21 ° C.

Carrier air is delivered to the carrier gas manifold 26 at a pressure of approx. 2.67 ato and at a rate of approx. 4814 standard liters / min. The carrier air is heated to approx.

15 260 ° C in the preheaters 29 and delivered to the evaporation chamber 14 at an air velocity through the distributor plates 33 from approx. 1.5 to approx. 3 m per minute. The free heat in the air is sufficient to evaporate the coating solution and adjust the resulting air-20-vapor mixture temperature to a value in the range of approx. 204 ° C to about 216 ° C.

Hot oil is supplied to all heaters with a temperature of approx. 210 ° C. Thus, the coating mixture leaving the evaporator chamber 14 and passing through the manifold 38 and nozzles 43 has a stabilized temperature of approx. 210 ° C. The temperature in the glass under the nozzles is approx. 566 ° C.

The space between the nozzles and the support is b / a = 2. The conditions described here provide a Reynolds number of 5000 in the flow at the nozzle exit.

The apparatus is operated for a period of 20 minutes 2 to cover approx. 8 m glass. The resulting coating is uniform over the entire surface of the glass with an average throughput of visible 35 light in the coated glass of 40% and with variations in the light transmittance of less than 2%, except at the very outer edges of the glass which are outside nozzle span by main dimension of nozzles.

It is found that the coating is more uniform and here a more fine-grained appearance than coating 5 produced by known spraying methods using the same coating materials directly from solution.

Example 2

The procedure of Example 1 is repeated several times 10 except that in each case one process parameter is varied to determine its influence on the coatings produced.

First, the process is repeated with a discharge current having a Reynolds number of 2500. The resulting coatings have excellent quality as in Example 1, although the overall average light penetration is 50%, thus indicating a slightly less coating or deposition efficiency. than in the preferred embodiment of the invention.

20 Next, the procedure is repeated, with the outlet flow having a Reynolds number of 2000. The resulting coatings are even thinner and less uniform than in the previous example. The average light penetration is 60% and the variation interval 25 for light penetration is - 5%, which is unacceptable for architectural purposes.

Third, the process is repeated with a discharge stream having a Reynolds number of 7000. The resulting coating is of excellent quality 30 as in Example 1.

Finally, two tests are carried out where the discharge current has a Reynolds number of 5000. In one experiment the distance or gap between nozzle and substrate is 0.9 times the nozzle width and in the second experiment 35 the gap is 5 times the nozzle width. The coatings thus obtained are sufficient in each case to provide a total average light transmittance of less than 50%, but in each case the variations are approx. - 3%, indicating a quality, 5 which is on the limit of permissible for many architectural applications.

Claims (6)

Method for applying a coating, especially of metal oxides, to a substrate, particularly of glass, by which a gaseous mixture comprising at least one evaporative coating-producing reactant against the substrate is kept, heated to react, thereby providing a coating, characterized in that at least one coating reactant is dissolved in a volatile solvent 10 thereof to form a coating solution, directing a stream of heated carrier gas into a closed chamber over and away from a heater mounted in the chamber, the carrier gas is heated to a temperature which is 1) above the temperature of the heating means, 2) is sufficient to evaporate the solvent, and 3) is below the decomposition temperature of the coating reactant, to spray the solution in a stream directed towards the heating means and into the stream of carrier gas to mixing the solution with the carrier gas so that the coating solution is evaporated and, e.g. responds to the carrier gas to form a gaseous mixed stream passing through the heating means such that the temperature of the gaseous mixture is set to practically the same value as the temperature of the heating means and that the gaseous mixture so adjusted is directed towards the substrate to be coated. Process according to claim 1, characterized in that the carrier gas is provided in such an amount that the resulting mixture of evaporated coating reactant, evaporated solvent and carrier gas is unsaturated with coating reactant and solvent at the temperature at which the mixture is obtained after mixing. and adjustment. 3. A process according to claim 2, characterized in that the mixture is from ca. 50 to approx. 95% saturated with coating reactant and solvent. 142169 Method according to claim 1, characterized in that the newly formed gaseous mixture is liberated from practically all liquid and all entrained solids at the exit from the closed chamber, after which it is distributed uniformly over an elongated area and directed to the substrate. Process according to claim 4, characterized in that the solution of coating reactant and solvent is introduced into the flow of carrier gas by spray atomization towards the heating means. Apparatus for carrying out the method according to claims 1-5, characterized in that it comprises: a closed, substantially horizontally located 15 chamber, one or more heating means for controlling the temperature of gases passing therethrough and mounted in the chamber such that it is divided into an upper and a lower compartment separated from each other by the heating means or heating means, one or more means for delivering a spray stream comprising a solution of at least one coating reactant which is conducted into the upper compartment so that the axis of the syringe stream intersects central portions of the main plane of the heater, one or more means for directing a flow of carrier gas into the upper compartment in a direction transverse to and away from the marginal portions of the heater and opposite the syringe stream to form a gaseous coating 30 a reactant-containing mixture flowing through the central portion of the heating means and further into the lower space, one or more means for distributing the gaseous coating mixture duct which is sent against the substrate to be coated and one or more means for connecting the lower