Coated container and process of preparation

Abstract

A coated glass container comprising: a glass container coated with a protective layer based on titanium dioxide doped with tin.

Description

[0001] Coated Container And Process Of Preparation

[0002] This invention relates to a coated glass container and a process for preparing a coated glass container.

[0003] In a number of applications, glass containers are required to be reusable. Bottles for milk, soda, and beer have been part of closed-loop use-return-clean-refill-reuse cycles for many years. The bottles must be able to withstand the demands of these cycles while remaining aesthetically acceptable to consumers. In particular, the bottles are susceptible to scuffing and other surface damage which can occur when the bottles travel on conveyers and during transit.

[0004] In order to alleviate such scuffing, after the container has been annealed, “cold end” coatings have routinely been deposited at temperatures of around 21 to 80 °C. Examples are stearate, oleic acid, polyethylene coatings. Such coatings are suitable for single use bottles but are prone to be washed off during the cleaning and refilling process for reusable bottles. Hence any contact points become scuffed.

[0005] To reduce the scuffing of reusable bottles, “hot end” coatings such as such as titanium oxide have been utilised. Such coatings are applied at around 450 to 600 °C after the formation of the bottles but before a cooling annealing step.

[0006] However, titanium oxide coatings have been found to still exhibit issues with scuffing as a result of container cleaning cycles. Therefore, it would be beneficial to provide a coated glass container that alleviates these problems.

[0007] According to a first aspect of the present invention there is provided a coated glass container comprising: a glass container coated with a protective layer based on titanium dioxide doped with tin.

[0008] The inventors have surprisingly found that the composition of the protective layer affords the coated glass container with improved durability in abrasion and caustic wash cycle tests.

[0009] In the context of the present invention, where a layer is said to be “based on” a particular material or materials, this means that the layer predominantly consists of the corresponding said material or materials, which means typically that it comprises at least 50 at.% of said material or materials.

[0010] In the following discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parameter, lying between the more preferred and the less preferred of said alternatives, is itself preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value.

[0011] Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of other components. The term “consisting essentially of” or “consists essentially of” means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention. Typically, when referring to compositions, a composition consisting essentially of a set of components will comprise less than 5% by weight, typically less than 3% by weight, more typically less than 1% by weight of non-specified components.

[0012] The term “consisting of” or “consists of” means including the components specified but excluding other components.

[0013] Whenever appropriate, depending upon the context, the use of the term “comprises” or “comprising” may also be taken to include the meaning “consists essentially of” or “consisting essentially of”, and also may also be taken to include the meaning “consists of” or “consisting of”.

[0014] References herein such as “in the range x to y” are meant to include the interpretation “from x to y” and so include the values x and y.

[0015] In the context of the present invention a transparent material or a transparent container is a material or a container that is capable of transmitting visible light so that objects or images situated beyond or behind said material can be distinctly seen through said material or container. In the context of the present invention the “thickness” of a layer is, for any given location at a surface of the layer, represented by the distance through the layer, in the direction of the smallest dimension of the layer, from said location at a surface of the layer to a location at an opposing surface of said layer.

[0016] In the context of the present invention a “derivative” is a chemical substance related structurally to another chemical substance and theoretically derivable from it.

[0017] In the context of the present invention a “container” is a device suitable for containing, amongst other things, liquids, powders and gels.

[0018] When a container is completely filled with e.g. a liquid, only part of its surface is in contact with said liquid. In the context of the present invention, the “inner surface” of the container denotes the part of the surface of the container that is in contact with the liquid when the container is completely filled. By contrast, the remainder of the surface of the container, which is not in contact with the liquid when the container is filled completely, is referred to as the “external surface”.

[0019] Preferably the glass container is a bottle, vial, tube, canister or jar.

[0020] Preferably the protective layer is located on the external surface of the container. In some embodiments the protective layer may coat the entire external surface of the container. In alternative embodiments the protective layer may coat part of the external surface of the container. Preferably the protective layer coats at least 70%, more preferably at least 80%, even more preferably at least 90%, most preferably at least 95% of the external surface of the container.

[0021] The glass container preferably comprises a closed base located at a first end of the glass container. Preferably the glass container further comprises a body extending from the closed base and being circumferentially closed. Preferably the glass container further comprises an open mouth (commonly called “the finish”). Preferably the open mouth is located at a second end of the glass container. Said second end of the glass container is preferably an end that is opposite (i.e. farthest from) said first end of the glass container. Preferably the body extends axially from the base. Preferably the glass container further comprises a neck that extends from the body and terminates at the open mouth. Preferably the neck extends axially from the body. Preferably the neck is generally conical in shape.

[0022] Preferably the protective layer does not coat the open mouth. This arrangement reduces the likelihood of issues arising from filling the glass container with a substance which then contacts the protective layer. Preferably the protective layer coats the entire external surface of the container apart from a region at least 0.5 cm from the open mouth, more preferably at least 1 cm from the open mouth, even more preferably at least 1.5 cm from the open mouth, most preferably at least 2 cm from the open mouth, but preferably at most 4 cm from the open mouth, more preferably at most 3.5 cm from the open mouth, even more preferably at most 3 cm from the open mouth.

[0023] Preferably the protective layer consists essentially of titanium dioxide doped with tin. More preferably the protective layer consists of titanium dioxide doped with tin.

[0024] Preferably the protective layer has a bulk tin concentration of 0.01 to 8 at%, more preferably 0.1 to 6 at%, even more preferably 0.1 to 5 at%, most preferably 0.2 to 4.5 at%. In the context of the present invention the term “bulk” means the part of the protective layer that is at least 2 nm, in the direction of the smallest dimension of the protective layer, from the surface of the protective layer.

[0025] Preferably the protective layer has a bulk tin dioxide concentration of less than 1 at%, more preferably less than 0.5 at%, even more preferably less than 0.1 at%, even more preferably less than 0.01 at%. Most preferably the bulk of the protective layer contains no tin dioxide. Preferably the entire protective layer has a tin dioxide concentration of less than 1 at%, more preferably less than 0.5 at%, even more preferably less than 0.1 at%, even more preferably less than 0.01 at%. Most preferably the entire protective layer contains no tin dioxide.

[0026] Preferably the surface of the protective layer exhibits a water droplet contact angle of at least 55°, more preferably at least 65°, even more preferably at least 70°, but preferably at most 90°, more preferably at most 80°, even more preferably at most 75°, where the contact angle is measured using a 5 microlitre droplet of water.

[0027] Preferably the protective layer is based on titanium dioxide doped with tin wherein the tin is in the 4+ oxidation state. Preferably the protective layer has a physical thickness of at least 5 nm, more preferably at least 15 nm, even more preferably at least 20 nm, most preferably at least 25 nm, but preferably at most 200 nm, more preferably at most 150 nm, even more preferably at most 100 nm, most preferably at most 70 nm.

[0028] Preferably the protective layer is pyrolytic. As used herein, the term “pyrolytic” refers to a coating or a layer thereof that is chemically bonded to a glass container.

[0029] Preferably the protective layer consists essentially of titanium dioxide doped with tin, and has a bulk tin concentration 0.1 to 5 at%, and the surface of the protective layer exhibits a water droplet contact angle of at least 60°, but at most 90°, where the contact angle is measured using a 5 microlitre droplet of water.

[0030] Preferably the glass container is transparent. The glass container may be clear or tinted. The glass container may be a metal oxide-based glass container. The glass container may be a clear or tinted glass container. A typical soda-lime-silicate glass composition is (by weight), SiC>269 - 74 %; AI2O3 0 - 3 %; Na2<D 10 - 16 %; K2O 0 - 5 %; MgO 0 - 6 %; CaO 5 - 14 %; SO30 - 2 % and Fe2O30.005 - 2 %. The glass composition may also contain other additives, for example, refining aids, which would normally be present in an amount of up to 2 %. By clear float glass, it is meant a glass having a composition as defined in BS EN 572-1 and BS EN 572-2 (2004). For clear float glass, the Fe2<D3 level by weight is typically 0.11 %. Float glass with an Fe2<D3 content less than about 0.05% by weight is typically referred to as low iron float glass. Such glass usually has the same basic composition of the other component oxides i.e. low iron float glass is also a soda-lime-silicate glass, as is clear float glass. Typically, tinted float glass has at least 0.5% by weight Fe2Os, e.g. 1.0% by weight Fe2Os. Alternatively, the glass container is a borosilicate-based glass container, an alkali- aluminosilicate-based glass container, or an aluminium oxide-based crystal glass container.

[0031] The protective layer may be in direct contact with the surface of the glass container. Alternatively, said protective layer may be in indirect contact with the surface of the glass container, i.e. said protective layer may be deposited over one or more previously deposited layers. According to a second aspect of the present invention there is provided a process for preparing a coated glass container in accordance with the first aspect of the present invention, said process comprising the following steps in sequence: a) providing a glass container, b) delivering a titanium-containing precursor and a tin-containing precursor to a surface of the glass container or adjacent to a surface of the glass container, and c) reacting said titanium-containing precursor and said tin-containing precursor to deposit a protective layer based on titanium dioxide doped with tin on a surface of the glass container.

[0032] Preferably the protective layer is deposited by chemical vapour deposition (CVD). Alternatively, the coating may be deposited by a physical vapour deposition process, such as sputtering or pulsed laser deposition, or a sol-gel process or other solutionbased process.

[0033] When the protective layer is deposited by CVD, preferably the container is at a temperature of between 400°C and 700°C, more preferably between 450°C and 650°C, even more preferably between 500°C and 650°C. This temperature is conveniently provided by residual heat from casting of a glass container when the process is incorporated in a continuous process for manufacturing glass containers. Thus, preferably the process is incorporated in a continuous process for manufacturing glass containers, and more preferably wherein the temperature of the glass container is provided by residual heat from casting of the glass container.

[0034] Preferably the titanium-containing precursor comprises one or more of a titanium alkoxide, titanium acetylacetonate, titanium acetate such as titanium tetraacetate, and a titanium alkyl. Preferably the titanium-containing precursor comprises a titanium alkoxide. The titanium alkoxide may be selected from one or more of titanium tetraisopropoxide (TTIP), titanium ethoxide (TET), titanium n-butoxide, titanium t- butoxide, di(i-propoxide)bis(2,2,6,6-tetramethyl-3,5-heptanedionato)titanium(IV), pentamethylcyclopentadienyltitanium trimethoxide, titanium (di-i- propoxide)bis(acetylacetonate) and derivatives. Preferably the titanium alkoxide is titanium tetraisopropoxide (TTIP). TTIP is beneficial in terms of its volatility and stability at relatively high temperatures. It also has the advantages of being readily available and low cost. Preferably the tin-containing precursor comprises one or more of a tin alkoxide such as tin isopropoxide; tin acetylacetonate; a tin acetate such as tin diacetate, tin tetraacetate, methyl tin diacetate or dibutyltin diacetate (DBTA); a tin alkyl such as tetramethyl tin, tetraethyl tin, tetraisobutyl tin and derivatives. The tin alkoxide may be selected from one or more of tin methoxide, tin ethoxide, tin n-butoxide, tin t-butoxide, tin n-propoxide, tin isopropoxide and derivatives. Preferably the tin alkoxide is tin isopropoxide. Preferably the tin-containing precursor comprises DBTA.

[0035] Preferably, step b) includes the formation of one or more gas and / or gaseous mixture, more preferably by heating the titanium-containing precursor and the tin-containing precursor. Precursor compounds may at some point be a liquid or a solid but may be volatile such that they can be vaporised or sublimed for use in a gaseous mixture. Once in a gaseous state, precursor compounds can be included in a gaseous stream and utilized in a CVD process. Preferably the formation of the gas and / or gaseous mixture comprises heating the titanium-containing precursor, the tin-containing precursor and / or any further precursor compound using a bubbler system or a thin film evaporator system. Thin film evaporator systems are particularly suited to production scale processes.

[0036] The gaseous mixture(s) may further comprise an oxygen-containing precursor that is different to the titanium-containing precursor and the tin-containing precursor. Preferably the oxygen-containing precursor is selected from one or more of organic oxygen-containing compounds or inorganic oxygen-containing compounds. Preferably the one or more oxygen-containing precursor is one or more organic oxygen-containing compound.

[0037] The organic oxygen-containing compound may be one or more carbonyl compound. Preferably, the carbonyl compound is an ester. More preferably, the carbonyl compound is an ester having an alkyl group with a p-hydrogen. Alkyl groups with a p- hydrogen containing two to ten carbon atoms are preferred. Preferably, the ester is selected from one or more of ethyl acetate (EtoAc), ethyl formate, ethyl propionate, isopropyl formate, isopropyl acetate, n-butyl acetate and t-butyl acetate. Most preferably the one or more oxygen-containing compound is a mixture of both t-butyl acetate and ethyl acetate.

[0038] In another embodiment, the oxygen-containing precursor may be provided as a part of a gaseous composition such as air. Alternatively, oxygen is provided in a substantially purified form. In either of these two embodiments, oxygen is provided in the form of molecular oxygen. The inorganic oxygen-containing compound may be selected from one or more of water (H2O), carbon dioxide (CO2), nitric oxide (NO), nitrogen dioxide (NO2), and nitrous oxide (N2O).

[0039] The gaseous mixture(s) may further comprise one or more carrier gas or diluents, for example, nitrogen, air and / or helium, preferably nitrogen. Thus, the process may further comprise providing a source of the one or more carrier gas or diluents from which separate supply lines may extend.

[0040] Preferably, the gaseous mixture is delivered to a coating apparatus. In certain embodiments, the gaseous mixture is fed through a coating apparatus and discharged from the coating apparatus utilizing one or more gas distributor beams prior to deposition of the protective layer. In certain embodiments, the gaseous mixture is formed prior to being fed through the coating apparatus. For example, the titanium- containing precursor, the tin-containing precursor, and preferably a carrier gas or diluent such as nitrogen, may be mixed in a feed line connected to an inlet of the coating apparatus. In other embodiments, the gaseous mixture may be formed within the coating apparatus. In a preferred embodiment the titanium-containing precursor and the tin-containing precursor are kept separate until they are delivered to a surface of the glass container or adjacent to a surface of the glass container.

[0041] The process is preferably a dynamic process in which the glass container is moving during steps b) and c). Preferably, the container moves at a predetermined rate of, for example, greater than 3m / min, more preferably between 3m / min and 20 m / min.

[0042] Preferably the CVD is carried out during a continuous process for manufacturing glass containers, preferably at substantially atmospheric pressure (APCVD). Alternatively the CVD may be carried out using low-pressure CVD or ultrahigh vacuum CVD. The CVD may be carried out using aerosol assisted CVD or direct liquid injection CVD. Furthermore, the CVD may be carried out using microwave plasma-assisted CVD, plasma-enhanced CVD, remote plasma-enhanced CVD, atomic layer CVD, combustion CVD (flame pyrolysis), hot wire CVD, metalorganic CVD, rapid thermal CVD, vapour phase epitaxy, or photo-initiated CVD.

[0043] Preferably, the process further comprises: providing a tunnel on a conveyor belt prior to step a) such that the conveyor belt transports the glass container from an upstream end, at which the glass container enters the tunnel, to a downstream end, at which the glass container exits the tunnel, the tunnel having: a top and first and second sidewalls; one or more nozzles, arranged on at least one side wall to deliver jets of gas, which jets traverse a path of the glass container conveyed through the tunnel; wherein the titanium-containing precursor and the tin-containing precursor are delivered to the surface of the glass container or adjacent to the surface of the glass container in the form of the jets of gas.

[0044] Preferably a linear array of nozzles is arranged on at least one side wall of the tunnel. Preferably at least one exhaust aperture is arranged on a sidewall, more preferably wherein the exhaust aperture is located closer to the downstream end than the nozzles. Preferably the tunnel further comprises means for applying a negative pressure to the exhaust aperture, e.g. an extractor fan. Preferably the tunnel further comprises an evaporator, preferably wherein the evaporator comprises a heatable tube. Preferably a carrier gas stream is directed through the evaporator to one or more of the nozzles. Preferably the titanium-containing precursor and the tin-containing precursor are introduced to the carrier gas stream in the evaporator. Preferably a diluent gas is introduced to the carrier gas stream, preferably after it passes from the evaporator and before it reaches the one or more nozzles.

[0045] According to a third aspect of the present invention there is provided the use of a protective layer based on titanium dioxide doped with tin to improve the durability of a glass container.

[0046] Any feature set out above in relation to the first and second aspects of the present invention may also be utilised in relation to any other aspect of the present invention. Any invention described herein may be combined with any feature of any other invention described herein mutatis mutandis. It will be appreciated that optional features applicable to one aspect of the invention can be used in any combination, and in any number. Moreover, they can also be used with any of the other aspects of the invention in any combination and in any number. This includes, but is not limited to, the dependent claims from any claim being used as dependent claims for any other claim in the claims of this application. The reader’s attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0047] All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive.

[0048] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0049] The invention will now be further described by way of the following specific embodiments, which are given by way of illustration and not of limitation, with reference to the accompanying drawings in which:

[0050] Fig. 1 is a schematic diagram of an APCVD system used to prepare samples according to the invention and

[0051] Fig. 2 shows images demonstrating water contact angle for samples according to the invention and for comparative samples before and after caustic wash treatments.

[0052] Examples

[0053] A custom-made APCVD system 1 as shown in Figure 1 was used to prepare comparative samples (“B” samples). The two precursors detailed below were contained in separate stainless steel bubblers 2,3 and subsequently heated in order to generate the vapour pressure needed to be transported through the system 1 and into a mixing chamber 4. The flow of gas through the system 1 was directed by stainless steel pipes 5 connected to the mixing chamber 4 and through stainless steel valves (6 = two-way valve, 7 = three-way valve) fitted to the bubblers 2, 3 and segments of the pipes 5. All the components of the CVD system 1 (e.g. pipes 5, mixing chamber 4, bubblers 2, 3) were connected to RS type-k thermocouples that measured the temperature of the individual parts of the system 1 and were further connected to Eurotherm™ temperature controllers. The vapour generated from the precursors was carried through the system by oxygen-free N2 gas (BOCTM99.99%) 8 over a range of flow rates. Flow meters were fitted to each pipe 5 to control the flow of carrier gas 8 before it reached the system 1 . The gases were transported from the mixing chamber 4 to a quartz tube reactor 9 through a double baffle manifold. The substrates 10 were contained in the reactor 9 and heated on a graphite block (320-mm in length) 11 containing three Whatman™ heater cartridges. An exhaust pipe 12 was fitted to the reactor 9 to carry the by-products generated during depositions. Further exhaust pipes 13 were indirectly connected to the bubblers 2, 3 and the mixing chamber 4. For preparing samples according to the invention (“A” samples) the same method was used except the two precursors were transported into two separate mixing chambers before being combined in the reactor.

[0054] Using the APCVD system described above, a range of Sn-doped TiC>2 films according to the invention (“A” samples) and comparative mixed titania : tin oxide films (“B” samples) were deposited on uncoated standard soda-lime-silicate glass (80 x 225 x 3.2 mm3) used to effectively mimic sections of container glass. The glass substrates were washed with acetone (99%), isopropanol (99.9%) and distilled water prior to coating in order to avoid contamination from the environment or from handling and were subsequently dried in a furnace. Titanium (IV) isopropoxide (TTIP, 97%, Sigma- Aldrich™) was used as a single-source precursor of titanium and oxygen. Dibutyltin diacetate (DBTDA, 99.5%, Sigma-Aldrich™) was used as a source of tin in the deposition alongside TTIP. The choice of precursors was primarily governed by industrial relevance. Non-chlorinated titanium precursors are preferred in the glass bottle industry in order to reduce the effects of Na+migration from the glass substrate, and of the chemical washing process that is part of the recycling cycle.

[0055] The bubbler temperature was set to 110 °C for the TTI P in order to achieve the desired vapour pressure while the bubbler containing DBTDA was set to 130 °C. The temperature of the mixing chambers was set to 200 °C while the TTIP and DBTDA lines were heated to 180 °C. All the samples were prepared for a deposition time of 60-180 s and with a total gas flow of 18.5 L min-1at a substrate temperature of 550 °C. In a typical deposition, all parts of the system were heated to the appropriate temperatures and it was allowed to stabilize, in the presence of a constant flow of carrier gas. The carbon block containing the glass substrate was heated to the target deposition temperature. The precursors, carried by the appropriate flow of N2, were then released from the bubblers with enough vapour pressure as to reach the mixing chamber and reactor. The flow of precursors was redirected to an exhaust route after the deposition time elapsed which was subsequently closed. The samples were then removed from the reactor upon cooling under a flow of N2 carrier gas to room temperature and were further handled and stored in air. Subsequent to coating, the samples were cut into 30 x 30 mm pieces in order to perform characterisation. The samples used for analysis were selected from similar regions of the reactor, hence ensuring the gas flow and temperature at the characterization sites is constant throughout.

[0056] Sample Characterisation

[0057] Raman Spectroscopy measurements

[0058] The optical properties of the samples were investigated through the use of a double beam, double chromated Perkin Elmer Lambda 950 UV / Vis / NIR Spectrophotometer. Transmission spectra were recorded for all samples of interest over a wavelength range of 0-2500 nm. All measurements were performed over a number of 10 scans, with 60 s per scan.

[0059] X-Ray Photoelectron Spectroscopy (XPS) measurements

[0060] Selected samples of pristine and Sn-doped TiC>2 (20 x 20 mm2) thin films were analysed with a Thermo Scientific K-a spectrometer using monochromated Al Ka radiation and a dual beam charge compensation system. The spectra were recorded under a constant pass energy of 50 eV and a spot size of 400 pm. The acquisition time was of 25 s over a combination of 100 scans in order to ensure an optimum peak definition and to reduce errors arising from the background. The instrument yields binding energy values with an error of less than ± 0.2 eV. Both surface and depth profiles were obtained for the samples. For the later, etching time was of 500 s for all samples. All survey spectra were recorded over the range of 0-1200 eV. High definition profiles were obtained for Ti 2p (449-475 eV), Sn 3d (480-500 eV), O 1s (526-545 eV), and C 1s (280-299 eV) orbitals for both surface and depth profile scans. Upon recording, all spectra were calibrated with respect to the C 1s orbital, using a standard value of 284.8 eV. The peaks were further modelled using XPSCasa software to account for different environments as well as to calculate film composition. This was achieved by dividing the under-peak areas by their respective Relative Sensitivity Factor (RSF) value (NIST database) as this relates to the relative concentrations of elements in the material.

[0061] Water Contact Angle (WCA) Measurements

[0062] The hydrophilicity of the samples was investigated by WCA measurements across several regions of each sample. This was achieved by using an FTA (First Ten Angstroms Inc.) 1000 B surface analyser set-up. The droplet size across all measurements was of 5 pL. Images of the water droplet in contact with the sample surface were recorded for all samples, over accumulations of 40 images per sample.

[0063] Raman Spectroscopy Analysis

[0064] Raman spectra were recorded for four samples according to the invention (“A” samples) comprising tin doped titania films with bulk tin concentrations in the range of 0.1-5 at% Sn. All four samples show well defined vibration bands at approximately 143 cm ’1, 199 cm ’1, 398 cm ’1, 518 cm ~1and 640 cm ’1, which are consistent with the spatial group of TiC>2 in the anatase phase and suggests the deposited films are found primarily in the anatase phase. Further less intense vibration modes were observable in samples with relatively higher tin bulk concentration (at.% Sn > 3) at 250 cm ’1, 325 cm ~1and 366 cm-1and are consistent with small traces of the brookite phase which is in accordance with previous studies of Sn-doped TiC>2 films prepared via a sol-gel method. No SnC>2 was identified via Raman spectroscopy suggesting the incorporation of Sn4+ions was achieved substitutionally. A shift in Raman frequency of the main anatase Raman peak at approximately 143 cm ~1and full width at half maximum (FWHM) values seem to confirm this as a trend was identified as a result of increasing tin bulk concentrations, which is consistent with previous work on similar materials and acts as a general trend in the case of doped thin films.

[0065] Raman spectra were also recorded for five comparative samples (“B” samples) comprising mixed titania : tin oxide films with bulk tin concentrations between 8 and 17% at.% Sn. All spectra showed the characteristic anatase peak at a frequency of approximately 143 cm-1while the peaks consistent with the other five fundamental vibrations of anatase were significantly less intense. No other phases of titanium dioxide were observed, suggesting no phase transition occurred as bulk tin concentration increased. Peaks characteristic to vibrational modes of SnC>2 were identified at 636 cm’1. These results suggest that the incorporation of Sn4+into the films was in the form of SnC>2. The overall weak spectral features further suggest the presence of SnC>2 rather than tin doped titania, since SnC>2 is known to be a poor Raman scatterer. A lack of a shift in Raman frequency of the main anatase Raman peak with increasing tin bulk concentrations further supports the incorporation of Sn4+into the material in the form of SnC>2, forming a composite film of anatase and tin oxide, and not as a dopant. Furthermore, increasing tin bulk concentrations did not induce any significant change in the calculated FWHM values. This finding further suggests that the anatase structure in the B samples was not perturbed by the presence of tin. In turn, the characteristic anatase Raman features are weak in comparison with A samples which is consistent with the presence of a mixed-phase material.

[0066] X-Ray Photoelectron Spectroscopy (XPS) Analysis

[0067] Surface scans of the Tin 3d orbitals

[0068] A samples

[0069] The binding energies corresponding to the Sn 3d doublet are shown in Table 1. The error associated with these values is of ±0.2 eV. All values within their error ranges are consistent with Sn in the oxidation state 4+ only.

[0070] Table 1. Binding energies of the Sn 3d orbital doublet of selected A. samples with Sn surface concentration decreasing from left to right across the table.

[0071] A trend of decreasing binding energy with increasing Sn surface concentration for both components of the 3d doublet can be identified in Table 1. This further confirms the environmental change in the film upon tin incorporation.

[0072] B samples

[0073] The binding energies corresponding to the Sn 3d doublet are shown in Table 2. The error associated with these values is of ±0.2 eV. All values within their error ranges are consistent with Sn in the oxidation state 4+ only. There is no change in binding energy across the table, showing no changes induced by a range of tin concentrations. This further suggests that tin oxide is the form of the tin incorporation into the samples and not as a dopant.

[0074] Table 2. Binding energies of the Sn 3d orbital doublet of selected B samples with Sn surface concentration decreasing from left to right across the table.

[0075] Concentration calculations from XPS profiles The relative concentration of Sn to Ti was calculated for both surface and bulk XPS profiles for a range of A samples. This was achieved by converting the raw area of the peaks of interest to effective areas using the Relative Sensitivity Factor (RSF). The RSF values used for the Ti 2p orbitals and Sn 3d orbitals are 7.81 and 25.1 , respectively. The relative concentrations of Sn and Ti were obtained and therefore different values for x were determined for the proposed ternary oxide formula SnxTii.xO2. At the surface, x ranges from 0.35 to 0.50 while in the bulk this decreases considerably, becoming as low as 0.03.

[0076] Abrasion and caustic wash cycle tests

[0077] Film integrity of the samples was tested by simulating the industrial process of washing reusable glass bottles. All samples tested had film thicknesses of between 30 and 150 nm. The samples were introduced to a 2% NaOH solution at 80°C for 15-minute cycles. Between any two cycles, the surface of the films was abraded with sandpaper of grit grade 150. The “A” samples passed 10 cycles of caustic washing with no scuff marks and maintaining film integrity throughout.

[0078] In contrast, the “B” samples presented scuff marks where abraded after 5 cycles, with the effect becoming more pronounced after 7 cycles. The integrity of films in places where the material did not show scratches was not visibly affected.

[0079] Thus the A samples comprising tin doped titania films performed far better in these tests than the comparative B samples comprising mixed titania : tin oxide films.

[0080] Water contact angles (WCAs) were measured before and after the caustic wash tests. The A samples showed an average contact angle of 70-75° as measured before caustic treatment whereas the comparative B samples showed lower average WCA of approximately 50-55°. This further illustrates that the two sets of films have distinct compositions. WCA measurements were taken after 5 caustic wash cycles for all samples. The films of the A samples exhibited minimal to no change in WCA (see Figure 2a), where the upper row shows an image of a water droplet on the sample before the 5 cycles and the lower row shows an analogous image after the five cycles). In contrast, the B samples showed a trend of decreasing WCA after caustic treatment (see Figure 2b), where the upper and lower rows again depict the before and after images). The invention is not restricted to the details of the foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS1 . A coated glass container comprising: a glass container coated with a protective layer based on titanium dioxide doped with tin.

2. The coated glass container according to claim 1 , wherein the protective layer consists essentially of titanium dioxide doped with tin, preferably wherein the protective layer consists of titanium dioxide doped with tin.

3. The coated glass container according to claim 1 or claim 2, wherein the protective layer has a bulk tin concentration of 0.01 to 8 at%, preferably 0.1 to 6 at%, more preferably 0.1 to 5 at%, most preferably 0.2 to 4.5 at%.

4. The coated glass container according to any preceding claim, wherein the protective layer has a bulk tin dioxide concentration of less than 1 at%, preferably less than 0.5 at%, more preferably less than 0.1 at%, even more preferably less than 0.01 at%.

5. The coated glass container according to any preceding claim, wherein the entire protective layer has a tin dioxide concentration of less than 1 at%, preferably less than 0.5 at%, more preferably less than 0.1 at%, even more preferably less than 0.01 at%.

6. The coated glass container according to any preceding claim, wherein the entire protective layer contains no tin dioxide.

7. The coated glass container according to any preceding claim, wherein the surface of the protective layer exhibits a water droplet contact angle of at least 55°, preferably at least 65°, more preferably at least 70°, but at most 90°, preferably at most 80°, more preferably at most 75°, where the contact angle is measured using a 5 microlitre droplet of water.

8. The coated glass container according to any preceding claim, wherein the protective layer has a physical thickness of at least 5 nm, preferably at least 15 nm, more preferably at least 20 nm, most preferably at least 25 nm, but at most 200 nm, preferably at most 150 nm, more preferably at most 100 nm, most preferably at most9. The coated glass container according to any preceding claim, wherein the protective layer is pyrolytic.

10. The coated glass container according to any preceding claim, wherein the protective layer consists essentially of titanium dioxide doped with tin, and has a bulk tin concentration 0.1 to 5 at%, and the surface of the protective layer exhibits a water droplet contact angle of at least 60°, but at most 90°, where the contact angle is measured using a 5 microlitre droplet of water.

11. A process for preparing a coated glass container in accordance with any preceding claim, said process comprising the following steps in sequence: a) providing a glass container, b) delivering a titanium-containing precursor and a tin-containing precursor to a surface of the glass container or adjacent to a surface of the glass container, and c) reacting said titanium-containing precursor and said tin-containing precursor to deposit a protective layer based on titanium dioxide doped with tin on the surface of the glass container.

12. The process according to claim 11 , wherein the protective layer is deposited by chemical vapour deposition (CVD) and wherein the titanium-containing precursor and the tin-containing precursor are kept separate until they are delivered to the surface of the glass container or adjacent to the surface of the glass container.

13. The process according to claim 12, wherein the container is at a temperature of between 400°C and 700°C, preferably between 450°C and 650°C, more preferably between 500°C and 650°C.

14. The process according to any of claims 11 to 13, wherein the titanium-containing precursor comprises one or more of a titanium alkoxide, titanium acetylacetonate, titanium acetate such as titanium tetraacetate, and a titanium alkyl, preferably the titanium-containing precursor comprises a titanium alkoxide, more preferably the titanium alkoxide is titanium tetraisopropoxide (TTIP).

15. The process according to any of claims 11 to 14, wherein the tin-containing precursor comprises one or more of a tin alkoxide such as tin isopropoxide; tinacetylacetonate; a tin acetate such as tin diacetate, tin tetraacetate, methyl tin diacetate or dibutyltin diacetate (DBTA); a tin alkyl such as tetramethyl tin, tetraethyl tin, tetraisobutyl tin and derivatives, preferably the tin-containing precursor comprises a tin alkoxide, more preferably the tin-containing precursor is DBTA.

16. Use of a protective layer based on titanium dioxide doped with tin to improve the durability of a glass container.

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