CA1172918A

CA1172918A - Process for making glass surfaces abrasion-resistant and article produced thereby

Info

Publication number: CA1172918A
Application number: CA000370543A
Authority: CA
Inventors: William E. Hofmann; Louis C. Konst
Original assignee: Owens Illinois Inc
Current assignee: OI Glass Inc
Priority date: 1980-02-15
Filing date: 1981-02-10
Publication date: 1984-08-21
Also published as: AU520227B2; ES509628A0; GB2069475B; JPS6035301B2; GB2069475A; DE3105566A1; FR2476065A1; ES499397A0; ES8302611A1; IT1170726B; AU6724881A; IT8147813A0; ES8207492A1; JPS56129644A; ES8302610A1; ES509629A0

Abstract

ABSTRACT OF THE DISCLOSURE

The present invention relates to improving the scratch and abrasion resistance of glass surfaces, and especially the exterior surfaces of glass containers such as bottles, jars, tumblers, stemware, and the like. Hollow glass-ware for container use is subject to abrasive contact with similar articles as well as handling equipment in the normal processes of manufacturing, packaging, filling and shipping.
This invention further relates to providing improved abrasion resistance to glass articles and particularly hollow glass containers which are treated by the present hot-end process while retaining considerable heat of formation. The articles are then able to be overcoated at a lower temperature such as by organic materials to further improve their lubricity and durability. The subject process of providing a primary coating is markedly more economical than presently known processes.

Description

i ~ 729 ~~ ~

It is generally known that glass derives its considerable strength from a pristine or unblemished surface condition and any scratches or flaws which occur or are developed on its surface decrease its strength many fold. Normally, glass containers exhibit a maximum strength immediately upon formation, and their strength decreases as the containers come into contact with one another, and with other surfaces, such as during auto-matic handling.
It is well understood that if the exterior glass surfaces are coated with a composition having good wet and dry scratch resist:ance, as well as abrasion resistance, which characteristically decrease the likeli-hood of breakage, a greater number of containers can be hand]ed by filling and packaging equipment in the same amount of time by spacing the containers closer together and by increasing the speed of the handling conveyors, even though the glass surfaces are subjected to greater contact with l:Lke and unlike surfaces. Also, since many products such aLS carbonated beverages are packaged under pressure, Lt is highly desirable that the exterior surfaces of he glass containers have a minimal number or no scratches to minimize the possi-bility of breakage.
Various types oE single and dual surface coating compositions have been employed previously to provide abrasion and scra~ch resistance, as well as desired lubricity and durability to withstand handling

- 2 -r''`~ ~R

i ~ 7 2 9 1 ~

use.
U.S. Patent No. 3,323,889 to Carl et al relates to a method for increasing the scratch resistance of a glass surface with a pyrolyzing treatment and a coating of an olefin polymer thereover. U.S. Patent No.

3,368,915 to Carl et al relates to an abrasion-resistant glass article having dual protective coatings thereon made by the aforesaid method. Also, U.S. Patents 3,403,015, 3,577,257, 3,598,632, 3,645,778, 2,813,045, 2,8~31,566, 2,982,672, 3,258,444, 3,407,085, 3,414,429, 3,4]8,153, 3,418,154, 3,425,859, 3,432,331, 3,438,801, 3,441,399, 3,441,432 and 3,445,269, all relate to rendering glass surfaces abrasion-resistant and glass articles produced thereby.
In none of the foregoing processes are two metal oxide forming compounds applied simultaneously with a stream of hot, dry air to form a combined metallic oxide primary coating on glass surfaces in an economical manner, where one compound is highly reactive with atmospheric moisture and 1he other compound is much less reactive and serves a dessicating function to shield the application of the former.
It is a problem in the art to provide an abrasion resistant dual primary coating on glass sur-faces which is highly resistant to abrasion and scratches, and which is economical to apply, thereby maintaining the inherent ,trength characteristics of the glass.

~,~, ,. "~j, il7291 8 It is another problem to provide a thin ; substantially uniform coating on glass surfaces which coating is transparent and highly resistant to scratches and abrasiue action in order to prevent weakening of the glass surfaces.
Accordingly the invention provides a method of forming a protective coating on selected exterior surface portions of a glass article comprising the steps of forming an atmosphere of dry air and a pyrolytically-decomposable treatment gas containing at least twoconstituents of different hygroscopicity, introducing the treatment gas into a treatment chamber through at least one inlet port and exhausting the treatment gas from the treatment chambe.r through exhaust means thereby creating a positive flow pattern from the at least one inlet port to exhaust means, the said flow pattern being confined substantially to the selected exterior surface portions of the glass container, a highly moisture-reacti.ve first constituer.t confined to the center of the flow pattern and a less moisture-reactive second constituent enveloping the first constituent of the flow pattern to act as a shie].d therearound, passing a glass article at a temperature above the decomposition point temperature of the treatment gas constituents through the treatment chamber wit:h an unselected portion of the glass article protruded outside the treat~ent chamber, . forming a substantially-lmiform coating of both con-stituents on the selectecl exterior surface portions of ~.~

; l7291 a the article within the treatment chamber from the decomposition products of the treatment gas constitu-ents, and removing the sa:d article from the treatment chamber whereby the protruding unselected portion of the article is uncoated and the selected exterior surface portions of the container are protectively coated.
In one aspect the invention provides a method of applying an abrasion reisistant coating to hot glass articles comprising the sleps of transporting the glass articles upon the surface of a conveyor, directing a dry gaseous stream, compr:ising, dry air and, as viewed in cross section, a pyrolvtically decomposable, highly moisture-reactive titanium-compound-containing vapor shieldably enveloped by a pyrolytically decomposable, less moisture-reactive tin-compound-containing vapor to isolate the moisture-reactive titanium-compound-containing vapor from atmospheric moisture and prevent hydrolysis thereof, to desired selec~ed exterior surfaces of the glass articles while main.aining the selected exterior surfaces contacted by the vapors above the pyrolytic decomposition point temperatures of the decomposable compounds whereby a substantially uniform protective scratch-resistant combined coating of tin and titanium oxides is formed upon the said exterior surfaces of the glass articles.
According to another features of the invention there is provided a vapor treatment apparatus for coating selected exterior surface portions of glass ~, ~1~291~

containers wherein the con.tainers are moved serially in spaced-apart, upright relation through an enclosed treatment hood which is open at its juxtaposed ends, the hood comprising a pair of vertical, spaced-apart walls extending along both sides of the line of travel of the glass containers ar,d forming side ducts, a pair of inlet ports and exhaust means for gaseous treatment vapors mounted transversely of the line of travel of the containers at the ends of the side ducts, the inlet ports and exhaust means being diametrically disposed to form a closed treatment gas loop through the side ducts, means for introducing a highly moisture-reactive first gaseous constituent into the center of the flow pattern at the inlet ports, means for combining dry heated air with the first gaseous constituent prior to its delivery to the center. of the inlet ports, means for introducing a less mo:sture-reactive constituent around the centrally-disposed first gaseous constituent at the inlet ports, and means for introducing additional air at an upper region of the inlet ports facing the exhaust means for protecting the upper finish portion of the containers from the first and second gaseous coating constituents while uniformly coating the selected exterior surface areas of the body portions of the containers.
One important feature resides in treating the glass surfaces simultaneously with at least two pyrolytically-decomposable metal-containing constituents, . ~

; t 7 2 9 1 8 i.e. materials which are c:hemically decomposed by the action of heat to form ox:.des of the metals on the glass surfaces which are at a temperature above the pyrolyzing temperature of the constil:uents. The dual metal oxide-treated surfaces may then be coated, such as in an annealing lehr, thereby providing strengthened glass articles. The treatment process is performed by pro-tecting the more moisture--reactive constituent by a less moisture-reactive constituent during their combined application to the glass ,urfaces.
The pyrolytical:Ly decomposable materials may be tin-containing and titanium-containing compounds which are both pyrolyzable, i.e. chemically decomposable by the action of heat to -orm dual oxides on the glass surfaces while the glass surfaces are at a temperature above the pyrolyzable temperature of the several com-pounds, and then cooling lhe tin-titanium treated glass articles, such as in an annealing lehr. The metal oxide treatment may then be fol:Lowed by the application of an organic overcoat of wi~ely-varying types.
Embodiments of 1he invention will now be described by way of exampLe with reference to the drawings in which:
Fig. 1 is a schematic flow diagram of the gas flow in the subject coating apparatus showing the trans-ported bottle and conveyor belt.
Fig. 2 is a schematic plan view of the coating apparatus of Fig. 1 showing the gas flow, bottle and i17291~

conveyor.
Fig. 3 is a fragmentary side elevational view taken along the line 3-3 of Fig. 2 showing the tubular delivery device for the first gaseous constituent, and the several ducts of the coating apparatus.
Fig. 4 is an enlarged fragmentary perspective view showing the tubular delivery device for the delivering of the first gaseous constituent to the bottle.
Fig. 5 is a schematic block diagram of the gas flow to the coating apparatus.
In practicing the present invention, the glass articles are treated soon after the articles leave the glass-forming machine and where they are being conveyed on a flight conveyor to the annealing lehr. This is immediately after their forming and while they still possess considerable heat from the molten state which is carried through the forming process. Two separate solutions of pyrolyzable compounds are sprayed onto the selected exterior surfaces of the glass articles in vaporized form and in a prescribed pattern flow at a temperature above the pyrolyzing temperature of the two individual compounds. The pyrolyzing temperatures for many common types of tin and titanium compounds which may be ;

~ .~g I~7291 8 1 employed herein are between about 700~F to 1300F, with the more preferred being from about 900~F to 1200F for their halide compounds.

As shown in Figure 1, the conveyor lO is employed to transfer the newly-formed glass bottles 11 from a forming machine to an annealing lehr in regularly spaced-apart align-ment. The bottles are conveyed in upright relation on the upper reach of the conveyor surface through a treatment ap-paratus or hood 12. The bottles are not rotated or revolved during such generally horizontal conveyance, and full~ ade~uate, uniform surface treatment is attained without rotation.

The treatment hood 12 is comprised of two side ducts 13 and 14, each of which have inlet ports 15 and 16 at one ena and exhaust ports 17 and 18 at the other end. The inlet ports and exhaust ports of the hood 12 are located in trans-verse relation on opposite sides of the conveyor in diametri-cally opposing arrangement.

The juxtaposed inlet ports and exhaust ports with their parallel side ducts are thus able to form a treatment gas recycling loop for the selected gases employed to treat the containers. The relative locations of the inlets, outlets and interconnecting side ducts ~xeshown in Figures 1 and 2 over a limited horizontal reach of the conveyor, the hood enclosing the containers during a short time interval of their horizontal conveyance.

A first gas is introduced into one side duct 13 at one point, preferably at side inlet port 20. This gas serves to essentially fill the side duct 13 and surround a second ~ Ub/

1 gas introduced into the center of the gas stream at the con-veyor inlet port 15. The first gas serves a dessicating function for the second gas which is introduced into the gas stream closely adjacent the conve~ed containers 11.

5Another duct 21 is mounted over side duct 13 to deliver clean auxiliary air across the conveyor adjacent and between an upper region of the inlet and outlet ports 15 and 18, respectively. A separate primary exhaust duct 22 for the clean air is located across from duct 21 to remove the air and excess gases after their sweep across the conveyor. The clean air sweeps around the upper extremity or mouth portions of the containers 11 to prevent deposition of the metal oxides thereat. A separate loop or secondary exhaust duct 23 extends from a central region of the hood parallel with the conveyor 10 and then to primary exhaust duct 22 to ensure that excess treatment gases and clean air are collec~ed and directed into the primary exhaust duct 22.

Si~ilarly, another auxiliary clean air duct 24 is mounted adjacent inlet and outlet ports 16 and 19, respectively, to deliver clean air over the mouth portions of the containers 11 to an~ther primary exhaust port 25. Another secondary ex-haust duct 26 extends from a region adjacent inlet and outlet ports 16 and 19 over a central downstream side of the conveyor to collect treatment gases and excess clean air and deliver the same into primary exhaust duct 25.

Figure 2 shows, in schematic outline, the juxtaposed inlet and outlet ports at each of the two adjacent coating . I o - i l7~918 locations along the conveyor, the respective ports being in diametric, nearly closea-loop arrangement. Figure 3 shows one inlet port 15 with the first gas delivered from its side inlet 20 and then through side duct 13 to the inlet port.
The clean air is directed over the neck and mouth portion of the containers fLom upper duct 21.

A second gas is introduced into the center of this stream by a perforated pipe or wand 30 having a series of apertures 30a at the inlet area below auxiliary clean air duct 21. The apertures face the containers to direct the second gas into the center of the flow pattern to flow toward the closely adjacent containers 11.

As stated, two separate solutions of pyrolyzable compounds are delivered onto the body portions of the glass containers. The vaporized solutions are directed at the containers in the prescribed flow pattern to impinge upon the con~airers at a temperature above the pyrolyzing temperatures of the two individual coating compounds, preferably tin and titanium containing.

Figure 5 illustratesin block diagram how the tin containing compound, preferably tin chloride, is vaporized with air at point A, prior to its delivery into side duct 20 and then into the two side ducts 13 and 14 for delivery to inlet ports 15 and 16. The second titanium containing compound, preferably titanium tetrachloride, is delivered at point B
from which it is introduced into a mixing tee E where it is intermixed with hot, dry, pressurized air from points C and D.

~n i t7291 8 1 The titanium compound vaporized with air is then delivered into the two pipes or wands 30 each having a lineal array of apertures 30a.

The two gases are preferably mixed having a volume ratio of the first constituent to the second constituent ranging from about 2:1 to 8:1 when both constituents in vapor form are generated at the same pressure and temperature.

The titanium compounds are more highly reactive with moisture than the tin compounds, thus having a great tendency to react with such moisture in hydrolysis reactions prior to ~ their impingement onto the glass surfaces. The titanium com-; pounds which have reacted with the available moisture are then not able to form as durable or uniform metallic oxide films on the glass surfaces. This is often the case where titanium tetrachloride alone is sprayed onto hot glass surfaces as a first coating. The titanium compounds upon reaction with water and water vapor tend to plug vaporizing nozzles with hydration products, thus inter~upting the spray patterns and producing erratic results. A prescribed flow pattern with the titanium compound being centered in the stream surro~nded by the tin compound in acGord with this invention is preferred in order to deposit uniformly both metal oxides on the glass surface in a combined, very adherent and uniform coating.

The titanium compound employed in this invention is one which, upon contact with the heated surface, will react to form titanium oxide. Among the suitable titanium containing compounds are the titanium tetrahalides; and especially titanium ~ ~ l~UO /

i ~7 29 ' ~
1 tetrachloride. The ammonium salts of titanium lactate are also suitable. In addition, the volatile metallo-organic compounds such as alkyl titanates preferably where the alkyl group contains from 1 to 8 carbon atoms are also suitable.
Among the alkyl titanates which may be used are tetrabutyl titanate, tetraisopropyl titanate, tetramethyl titanate, tetraethyl titanate, tetranonyl titanate, and the like.

The tin compounds that may be used for the purpose of the present invention include both stannous and stannic compounds. Among the suitable stannic compounds are the stannic halides and the alkyl stannic carboxylates. The stannic halides may be exemplified by stannic chloride, stannic bromide and stannic iodide. The alkyl stannic carboxylates have the general formula (Rl)xSn(OOCR2)y wherein Rl and R2 are alkyl groups and wherein x and y are whole numbers from 1 to 3, the sum of which is equal to four. The alkyl groups may be branched or straight chain. ~he R2 alkyl group preferably contains from 1 to 18 carbon atoms, such as stearate, palmitate, laurate, and the like. The Rl alkyl group preferably contzins 1 to g carbon atoms such as methyl, propyl, butyl, isopropyl, isobutyl, hexyl, octyl, and the like. Included among the compounds coming within the scope of the foregoing are dibutyl tin di-chloride, butyl tin acetate, dipropyl tin diacetate, diioctyl tin diacetate, dibutyl tin distearate, dibutyl tin dipalmitate, dibutylin dilaurate, dibutyl tin maleate, and the like.

Among the stannous tin compounds suitable for the purpose of this invention are the stannous dihalides such as stannous chloride, stannous bromide, stannous iodide and the i i 7 2 9 1 8 carboxylic acid salts of stannous tin. The latter include compounds having the formula Sn(OOCR)2 wherein R is an ali-phatic or aromatic grou~. Included among the aliphatic groups are the alkyls, both su~stituted and unsubstituted having up to 18 c~rbon atoms. The aroma~ic groups include the cyclic carboxylic acids wherein the aryl is ben~yl, phenyl,naphthyl, or the like. The carboxylic acid salts suitable for the pur-pose of this invention include stannous oleate, stannous palm-itate, stannous stearate, stannous caproate, stannous ~urate, stannous maphthenate, stannous tartrate, stannous gluconate, stannous acetate, and the like. It is understood that any titanium or tin compound may be used, provided it is càpable of forming an oxide on the glass surface at the reaction tem-peratures indicated.

The titanium and tin compounds which are preferably employed in the present invention are ones which upon contact with the heated glass surface react to form a substantially colorless, trans~arent, layer or coating of combined metallic oxide~, both TiO2 and SnO2, on the glass surfaces. The combined oxide coating is firmly adherent to the glass surface and is of the order of a few microns in thickness. Such dual coating serves as a primary coating for an overlying second layer or coating preferably of orgarlic mhterial applied at a lower temperature.

The glass articles, when coated with the thin, dual oxide primary coating, are then transferred to an annealing lehr, where they are progressively cooled and stress annealed over a period of time. I~h~n cooled to a temperature of about 400F and lower, during a latter phase of the annealing cycle, i l72g-l ~
1 they are normally sprayed with a second coating of poly-ethylene emulsion, for example, to provide a protective lubricant coating. Such second coating or layer can be varied widely depending upon the end use requirements and does not comprise a part of the present invention. One such second coating or layer comprised polyethylene constitutes a typical overcoat, such polyethylene emulsion distributed by Owens-Illinois, Inc., Toledo, Ohio, under the trade name "Duracote".
U. S. Patent No. 2,995,533 to Parmer and Schaefer, issued 10 August 8, 1961, entitled, "Lu4ricant Coating for Glassware", discloses the preparation and use of a polyethylene emulsion as a lubricant coating for glass containers, this patent being assigned to the same assignee as the present application.
The organic coating composition can be applied by any suitable - 15 apparatus such as a traversing spray nozzle delivering a uniform amount of coating material per unit area of lehr belt.
The amount is frequently established at between about 1/2 to 1 quart o~ organic coating per 100 sguare feet of lehr belt.
It is preferred that organic overcoat be applied by spraying near the cool end of the lehr such as when the glass articles are in the temperature range of from about 100F to 400F.

Returning to discussion of the first primary coating, with which this invention is primarily concerned, the second constituent of the gas treatment is normally a high moisture-reactive gas such as titanium tetrachloride which normallycannot be satisfactorily applied alone to the glass surface.
At least, such reactive vaporized constituent frequently en-counters stoppage problems when employed singly to coat glassware over long-term campaigns. In accordance with this invention, _y~_ ;:~729~8 this compound in gaseous form is combined in regulated amount with a heated, dry stream of pressurized air for delivery to a central region at the inlet ports of the treatment hood. The ratio of treatment gas to dry hot air is carefully controlled, the latter usually bein~ in excess to guard against hydrolysis of the former.

The secondgas is preferably titanium tetrachloride due to its economical cost and ready availability. It is combined with the heated, dry air in a mixing tee immediately prior to use. The dry, hot air is heated to about 300F and having a dew point of less than about -80F. The mixed TiC14 and hot, dry air are delivered together to a perforated pipe or wand which is mounted vertically in the center of the inlet port. Two such inlet ports are used in the treatment chamber, on diametrically opposite sides of the containex conveyor belt.
Each perforated pipe or wand has a series of apertures facing the conveyed containers and in close proximity thereto, the apertures preferably being about 1/16 inch diameter. Each wand is located in the center of the inlet duct which carries the less moisture-reactive, first gas such as stannic chloride to the inlet port area. The SnCl~ is normally carried by dry, pressurized air in the inlet duct and serves to surround the more moisture-reactive secondgas such as TiC14. Thus, the TiC14 is protected from reaction with atmospheric moisture prior to its delivery onto the adjacent hot glass surfaces. The two metal-containing gases are directed against the hot glass sur-faces of the container and are deposited thereon in the form of metal oxides~ The body portion of the container normally com-prises the selected surface areas of the container ~or such ,P.~

i 172~1 8 1 coating, the mouth or finish portion of th~ container beingprotected by the delivery of auxiliary hot dry air to prevent metal oxide deposition thereon.

The first and second gas constituents which flow under pressure within the treatment chamber and across the conveyor surround and uniformly coat the exterior surfaces o the container body portion. Excess treatment gas is trans-ported through the exhaust port across from the inlet port and through the side duct extending parallel to the conveyor to the second inlet port.

The secondary perforated pipe or wand is located in vertical alignment in the second inlet port facing across the conveyor. An amount of second treatment gas, i.e., TiC14, equivalent to that introduced at the initial inlet port is then 1~ introduced at the secondary inlet port. The two metal-containing gases, i.e., TiC14 and SnC14, are then forcefully directed across the conveyor belt from the opposite direction to impinge upon the other side of the container body surfaces. At both inlet ports of the treatment chamber, the second gas, i.e., TiC14, is surrounded by the first gas, i.e., SnC14, so that little or no adverse reaction with moisture or water vapor by the susceptible second gas can occur. The container exterior surfaces are then essentially uniformly coated around their circumference and from top to bottom of their body portions, the mouth or finish portion of the container being uncoated.
The exterior surfaces, from inlet facing sides to conveyor axis sides, of the non-rotated container, show some variation in thickness within the desired range of uniformity for improved durability.

~ l7291 a 1 The excess treatment gas from the second inlet port is transported through the side duct parallel to the conveyor axis back to the initial inlet port, where the gas treatment loop is completed. Except for the container open-ings which exist at the opposite ends of the treatment hood and through which the conveyor belt is mounted, and upon which the glass containers are moved, the hood is totally enclosed for maximum efficiency of container treatment.

The titanium tetrachloride compound is a much less expensive constituent than the stannic chloride compound, thereby permitting much more economical coating of glass arti-cles. The ratio of amount of second constituent to first constituent can be varied through wide limits so that very appreciable amounts of the cheaper constituent can be used, thus significantly decreasing coating costs. The volume ratio of æcondconstituent to first constituent can suitably range from about 2:1 to 8:1 when both constituents are generated at the same pressure and temperature. Thus, substantially more TiC14 can be combined with the SnC14 for their joined deposi-tion on a combined unitary coating on the glass surfaces. Bothmetals being of the same Periodic Group permit their joinder as a thin coating having physical and chemical properties some-what similar to the individual oxides when deposited alone in the form of thin films. Treatment results using mixtures of tin and titanium oxides in combination are very comparable to results obtained with tin oxide only. Material costs can be significantly reduced using mixtures of tin and titanium com-pounds as opposed to a tin compound only.

~17291.8 1 The size openings in the perforated pipes or wands for delivery of the TiC14 into ~e gas stream is not critical, but it is important that such constituent be combined with super-dry, hot air and be introduced into the center of such combining stream closely adjacent the point of deposition.
The quantity of dry air is important, and usually from 50 to 100 cubic feet per hour of heated, super-dry propellant air is used to convey the TiC14 into the delivery wands. Total flow rates of from 30 to 100 cubic feet per hour of the mixed working TiC14 containing vapor is delivered into the gas stream for container coating.

By keeping the metal oxide coating off the finish area of the containers, such especially lessened tin oxide thereat, steel cap corrosion is prevented or significantly lessened when the containers are filled and capped with such closures.

The dual coating of tin and titanium oxides permits the attainment of a uniformly-di~tributed, chemically-reactive, metallic oxide coating on glass containers prior to their annealing which will combine with organic surfactants applied at a lower temperature to achieve a scratch-resistant, strength-retentive lubricious exterior coating for glass containers.
The dual coating of tin and titanium utilizes the best features of both materials, i.e., the uniformity of the SnC14 appli-cation and low cost of the TiC14 material, to pro~uce an accept-able coating distribution comparable with that achieved with tin containing materials used alone but at a greatly reduced cost per container.

: ~ ;17291~
1 The present process can be used with many existing types of treatment hoods or chambers designed for SnC14 treatment alone. Only the perforated pipes and hot air mixing equipment for transporting the TiC14 need be used for the surrounded æcond gas. Thus, both materials can be applied in the same apparatus and, if desired, with only slight modifi-cation of standard types of hoods. The recirculating SnCl~
vapors tend to shield the TiC14 vapors, making the resulting coating more uniform and considerably less expensive.

Stannic chloride (SnC14) is usually generated at a given temperature (normally ambient) by bubbling dry air (-4QF or lower dew point), or dry nitrogen, or by passing this dry air over the liquid material to form a vapor. Titanium tetrachloride (TiC143 vapor is generated in the same manner using hot, dry air (-60F or lower dew point~, or dry nitrogen over the liquid TiC14 to form a vapor. Both vapors are in-troduced into the treatment chamber with the tin vapor being introduced from a single source into a recirculating vapor/air stream. The titanium vapor is mixed with dry air (as stated) preferably heated above about 300F, and introduced into the treatment chamber at two points in close proximity to the glass articles being treated.

Generally, where 3Q cubic feet per hour of bubbling gas is required to achieve tin oxide coatings on glass con-tainer surfaces, between the minimum required to achieve goodscratch protection (when overcoated with a suitable organic lubricant) and an upper limit defined by the coating visibility limit, it is possible to attain a dual tin-titanium coating :'~17~918 1 with 80 cubic feet per hour of dry air bubbled through the TiC14 with only 10 to 15 cubic feet per hour of SnC14 bubbling gas required. At any given ambient temperature, tin to titanium flow ratios of 1:6 to 1:8 will produce the desired combination coating on the glass surfaces.

The following table indicates typical process com-parisons between the tin only and titanium only known coating processes and the dual coating process results using both metals, with the material consumptions. Comparative coating thicknesses are listed as well as the vaporizing flow rates.

Max/Min Coating Average Wt of Vaporizing Thickness Coating Wt of ~n Titanium Material Flow Rate Ratio Thickness Consumed Consumed 1. SnCl Alone 30 CFH2.8:1 33.5 CTU 1.22Xlhr 2. TiC14 Alone 80 CFH72:1 22.0 CTU -- 0.4~lhr 3. Dual Coating SnC14 10 CFH
TiC14 80 CFH4.8:1 41.2 CTU 0.4~1hr 0.4~1hr

4. Dual Coating SnCl 15 CFH
TiC14 80 CFH3.05:1 41.0 CT0.6~1hr 0.4~1hr ~/ .

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The method of forming a protective coating on selected exterior surface portions of a glass article compris-ing the steps of forming an atmosphere of dry air and a pyro-lytically-decomposable treatment gas containing at least two constituents of different hygroscopicity, introducing the treat-ment gas into a treatment chamber through at least one inlet port and exhausting the treatment gas from said treatment chamber through exhaust means thereby creating a positive flow pattern from the at least one inlet port to exhaust means, the said flow pattern being confined substantially to the selected exterior surface portions of the glass container, a highly moisture-reactive first constituent confined to the center of said flow pattern and a less moisture-reactive second constituent enveloping said first constituent of said flow pattern to act as a shield therearound, passing a glass article at a tempera-ture above the decomposition point temperature of the treatment gas constituents through the treatment chamber with an un-selected portion of said glass article protruded outside the treatment chamber, forming a substantially-uniform coating of both constituents on the selected exterior surface portions of said article within the treatment chamber from the decom-position products of the treatment gas constituents, and re-moving the said article from the treatment chamber whereby the protruding unselected portion of the article is uncoated and the selected exterior surface portions of the container are protectively coated.

2. The method in accordance with claim 1, in which the article is a container and the unselected portion is a mouth portion of the container.

3. The method in accordance with claim 1, wherein the highly-moisture-reactive first constituent of the treatment gas is a titanium compound and the less-moisture resistant second constituent is a tin compound.

4. The method in accordance with claim 3, wherein the titanium compound is titanium tetrachloride and the tin compound is stannic chloride.

5. The method in accordance with claim 4, in which the dry air has a dew point temperature of less than about -80°F
and which has been heated to at least about 300°F.

6. The method in accordance with claim 4, including the steps of injecting the highly moisture-reactive first con-stituent of titanium tetrachloride into the center of the flow pattern of said treatment gas at said at least one inlet port and injecting the less moisture-reactive second constituent of stannic chloride around the center of the flow pattern of said treatment gas at said at least one inlet port.

7. The method in accordance with claim 4, including the step of injecting the treatment gas having a volume ratio of the first constituent to the second constituent ranging from about 2:1 to 8:1 when both constituents in vapor form are generated at the same pressure and temperature.

8. The method in accordance with claim 2, wherein said glass container is retained in non-rotational upright align-ment between said at least one inlet port and said exhaust means during its passage through said treatment chamber.

9. The method in accordance with claim 1, including the step of creating a recirculating stream of said treatment gas to constitute a continuous flow pattern of said treatment gas between inlet ports to exhaust means and from said exhaust means to said inlet ports.

10. The method in accordance with claim 5, inclu-ding the step of providing at least two treatment zones within said treatment chamber, the said two zones being adjacent and having their inlet ports and exhaust means diametrically op-posed transversely to the path of said container and inter-connected into a treatment gas recycling loop.

11. The method of applying an abrasion resistant coating to hot glass articles comprising the steps of trans-porting the glass articles upon the surface of a conveyor, directing a dry gaseous stream, comprising, dry air and, as viewed in cross-section, a pyrolytically decomposable, highly moisture-reactive titanium-compound-containing vapor shieldably enveloped by a pyrolytically decomposable, less moisture-reactive tin-compound-containing vapor to isolate said moisture-reactive titanium-compound-containing vapor from atmsopheric moisture and prevent hydrolysis thereof, to desired selected exterior surfaces of said glass articles while maintaining said selected exterior surfaces contacted by said vapors above the pyrolytic decomposition point temperatures of the decomposable compounds whereby a substantially uniform protective scratch-resistant combined coating of tin and titanium oxides is formed upon the said exterior surfaces of the glass articles.

12. The method in accordance with claim 11, wherein said decomposable, highly moisture-reactive titanium-compound-containing vapor is titanium tetrachloride and said decompos-able, less moisture-reactive tin-compound-containing vapor is stannic chloride, said titanium tetrachloride being injected into the center of the gaseous stream of the treatment gas vapors as viewed in cross-section and said stannic chloride being in-jected around the center of the gaseous stream of the treatment gas vapors as viewed in cross-section.

13. In a vapor treatment apparatus for coating selected exterior surface portions of glass containers wherein the containers are moved serially in spaced-apart, upright rela-tion through an enclosed treatment hood which is open at its juxtaposed ends, the hood comprising a pair of vertical, spaced-apart walls extending along both sides of the line of travel of said glass containers and forming side ducts, a pair of inlet ports and exhaust means for gaseous treatment vapors mounted transversely of the line of travel of said containers at the ends of said side ducts, the inlet ports and exhaust means being diametrically disposed to form a closed treatment gas loop through said side ducts, means for introducing a highly moisture-reactive first gaseous constituent into the center of the flow pattern at said inlet ports, means for combining dry heated air with said first gaseous constituent prior to its delivery to the center of said inlet ports, means for intro-ducing a less moisture-reactive constituent around said centrally-disposed first gaseous constituent at said inlet ports, and means for introducing additional air at an upper region of said inlet ports facing said exhaust means for protecting the upper finish portion of said containers from said first and second gaseous coating constituents while uniformly coating the selected exterior surface areas of the body portions of said containers.

14. The vapor treatment apparatus including the hood in accordance with claim 13, wherein said means for introducing the highly moisture-reactive first constituent comprises a vertically-disposed perforated pipe mounted substantially within the center of each of said inlet ports.

15. The vapor treatment apparatus including the hood in accordance with claim 14, wherein said highly moisture-reactive first constituent comprises titanium tetrachloride.

16. The vapor treatment apparatus including the hood in accordance with claim 14, wherein said less moisture-reactive second constituent comprises stannic chloride.

17. The vapor treatment apparatus including the hood in accordance with claim 14, including a pair of side ducts extending parallel to the direction of travel of said containers through said hood, two inlet ports located on diametrically opposite sides of said hood, two exhaust ports with each facing one of said inlet ports, the said side ducts, inlet ports and exhaust ports forming a closed treatment gas recycling loop for the combined first and second gaseous constituents for their transport as a continuous gas stream twice impinging upon the conveyed containers from opposite sides.