Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
  • C03C17/28—Surface treatment of glass, not in the form of fibres or filaments, by coating with organic material
  • C03C17/30—Surface treatment of glass, not in the form of fibres or filaments, by coating with organic material with silicon-containing compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
  • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking

Definitions

• the present invention relates to a method of strengthen ⁇ ing a brittle oxide substrate and also relates to aqueous solutions containing silane-based compositions and polymerized cross-linked siloxane coated brittle oxide substrates. More particularly, the present invention relates to a method of strengthening or restoring strength to a glass container and the resulting polymerized cross-linked siloxane coated glass container.
• Brittle materials such as glass substrates, generally exhibit some mechanical properties, such as, e.g., tensile strength, which are substantially lower than predicted. This manifestation can arise as the result of such factors as imperfections in the structure of a test specimen, or small amounts of impurities in either the body or the surface of an article made of that material. Progressive zone melting to reform the crystalline structure and floating impurities out of the melted brittle material have been used in the past for brittle metals in an attempt to improve the mechanical prop ⁇ erties of the brittle metals. Also, with regard to non-metal brittle materials, multi-layer structures made of the brittle material have been used to improve mechanical properties. In addition, surface treatments of the brittle material have been used to protect the surface " from abrasion and to provide a small measure of support to brittle articles.
• the surface flaws or defects can originate from many sources, ranging from unmelted batch materials to scratches produced by sliding across hard surfaces, including other glass articles.
• the glass articles can be heavily damaged by handling from the moment they are formed. Contact with par- ticulates and moisture in the air, other bottles, guiderails and other handling equipment, and the conveyor on which they are transported, can lead to large decreases in the strength of the container due to the flaws produced.
• 4,891,241 relates to treating the surface of the glass with a silane coupling agent followed by a polymer coating containing acryloyl and/or methacryloyl groups, followed by irradiation or thermal treatment to polymerize the molecules containing those groups.
• the '241 patent further shows that silanes alone do not strengthen substrates and that acrylates are necessary for any strengthening.
• the present invention relates to a method of strengthening a brittle oxide substrate which includes the following steps. First, the brittle oxide substrate is coated with an aqueous solution containing a silane-based composition.
• the aqueous solution containing the silane- based composition is substantially absent of any organic solvent.
• the silane-based composition upon being hydrolyzed in the aqueous solution has the following formula:
• R" is an organofunctional group.
• R" in the silane-based composition is selected so that (i) the strength of the brittle oxide substrate having the cured coating is substantially improved compared to the strength of the brittle oxide substrate prior to the coating step and (ii) the cured coating does not interfere with the labelability of the brittle oxide substrate.
• the present invention also relates to a method similar to the one described above, except R" is selected so that (i) the strength of the brittle oxide substrate having the cured coating is substantially improved compared to the strength of the brittle oxide substrate prior to the coating step and (ii) the substantially improved strength from the cured coating on the brittle oxide substrate has a maintained humidity resistance of at least about 50%.
• the present invention relates to a polymerized cross-linked siloxane coated brittle oxide container.
• the polymerized cross-linked siloxane coated brittle oxide container includes a brittle oxide container and a transparent layer of polymerized cross-linked siloxane preferably cured onto the outer surface of the brittle oxide container.
• the polymerized cross-linked siloxane is formed from a silane-based composition hydrolyzed in an aqueous solution and substantially lacks the presence of an organic solvent.
• the hydrolyzed silane-based composition can be selected from the group consisting of methacryloxypropyltrimethoxysilane (MPTMO), glycidoxy- propyltrimethoxysilane (GPTMO), vinyltrimethoxysilane (VTMO), 2-(3,4 epoxycyclohexyl)ethyltrimethoxysilane (CETMO) , methyltrimethoxysilane (MTMO) , 3,3-dimethoxypropyl- trimethoxysilane (DPTMO), 5,6-epoxyhexyltrimethoxysilane (EHTMO), N-(trimethoxysilylpropyl)-maleic acid amide, 3-ureidopropyltrimethoxysilane (UPTMO), l,2-bis(trimethoxy- silyl)ethane (BTMOE), 1,2-bis(3-trimethoxysilylpropoxy)ethane (BTMOPE), hydrolyzedo
• the present invention further relates to novel silane- based compositions including, but not limited to, a mixture of vinyltrimethoxysilane and 2-(3,4 epoxycyclohexyl)ethyl- trimethoxysilane; a mixture of methyltrimethoxysilane and 2-(3,4 epoxycyclohexyl)ethyltrimethoxysilane; a mixture of glycidoxypropyltrimethoxysilane, 2-(3,4 epoxycyclo ⁇ hexyl)ethyltrimethoxysilane, and methyltrimethoxysilane; and a mixture of glycidoxypropyltrimethoxysilane and 2-(3,4 epoxycyclohexyl)ethyltrimethoxysilane.
• the above generally described invention overcomes the difficulties encountered in working with brittle oxide sub ⁇ strates such as glass.
• the method of the present invention drastically and unexpectedly increases or restores the strength of brittle oxide substrates as compared to the strength of the substrate prior to receiving any coating.
• the coatings of the present invention are transparent and safe to use on brittle oxide substrates. Be ⁇ sides increasing or restoring the strength of the substrate, the coatings of the present invention preferably do not interfere with labelability which has been a problem in the past with coatings on substrates.
• the brittle oxide substrate used in the method of the present invention can be made of any brittle oxide material such as aluminum oxides or aluminates, silicon oxides or silicates, titanium oxides or titanates, germanates, or glass made from, for instance, the above materials. Further, the brittle oxide substrate can be of any form such as a glass bottle.
• silane-based compositions upon being hydrolyzed in the aqueous solution have the following formula:
• R" is an organofunctional group which may or may not hydrolyze in the aqueous solution. This organofuctional group may include residues of hydrolyzable silanes.
• the selection of R" is further based on the requirement that the resulting aqueous solution containing the hydrolyzed silane- based composition after being coated and cured on the brittle oxide substrate imparts a substantially improved strength to the brittle oxide substrate and does not interfere with the labelability of the brittle oxide substrate.
• Preferred examples of R" include glycidoxypropyl, 2-(3,4 epoxycyclohexyl)ethyl, 3,3-dimethoxypropyl, 3-ureidopropyl, and hydrolyzed forms thereof.
• hydrolyzed silane-based compositions include hydrolyzed glycidoxypropyl- trimethoxysilane, hydrolyzed 2-(3,4 epoxycyclohexyl)ethy1- trimethoxysilane, hydrolyzed 3-ureidopropyltrimethoxysilane, and hydrolyzed 3,3-dimethoxypropyltrimethoxysilane.
• the coating applied to the brittle oxide substrate can also be a mixture of one or more hydrolyzed silane-based com ⁇ positions.
• the mixture of two or more hydrolyzed silane- based compositions is especially advantageous when it is known that one hydrolyzed silane-based composition provides excellent labelability and another hydrolyzed silane-based composition provides excellent strength enhancing properties.
• a mixture would provide the desired balance of properties, that is, a coating which provides improved strength and which does not interfere with labelability.
• a mixture of hydrolyzed CETMO and methyltrimethoxy ⁇ silane (MTMO) can be used to obtain this balance of properties.
• hydrolyzed silane-based compositions which can be used in mixtures of one or more hydrolyzed silane-based compositions include hydrolyzed methacryloxy- propyltri ethoxysilane, hydrolyzed 3-ureidopropyltri- methoxysilane, hydrolyzed l-2-bis(trimethoxysilyl)ethane, hydrolyzed l,2-bis(3-trimethoxysilylpropoxy)ethane, hydrolyzed 5,6-epoxyhexyltrimethoxysilane, hydrolyzed N-(trimethoxysilylpropyl)-maleic acid amide, hydrolyzed dimethyltetramethoxydisiloxane, and hydrolyzed N-(3-triethoxysilylpropyl)4-hydroxybutyramide (HBTEO) .
• hydrolyzed methacryloxy- propyltri ethoxysilane hydrolyzed 3-ureido
• compositions for instance, can be used in a mixture with hydrolyzed CETMO and/or hydrolyzed GPTMO and/or hydrolyzed DPTMO.
• silane-based compositions used in a mixture can be added in equal proportions.
• a greater proportion of hydrolyzed CETMO, hydrolyzed GPTMO, or hydrolyzed DPTMO, for instance would be added.
• any of the compositions described herein can be used alone to substantially improve the strength of a brittle oxide substrate, if labelability is not a concern.
• silane-based compositions provided as specific examples are commercially available from one or more of the following sources. Union Carbide, Dow Corning, Huls America and PCR, Inc.
• coatings of the present invention can be mix ⁇ tures of one or more hydrolyzed silane-based compositions
• separate coatings of hydrolyzed silane-based compositions can be applied to a surface of a brittle oxide substrate.
• a coating of CETMO can be applied to a surface of a brittle oxide substrate and then while the CETMO coating is still wet or dry or after curing the first coating, a second coating, another CETMO coating or a different coating (e.g. MPTMO), can be applied. Any number of such consecutive separate coatings can be applied in this manner.
• a surfactant can be applied in this manner, namely, coating a brittle oxide surface with a surfactant before and/or after coating the surface with a hydrolyzed silane-based composition ⁇ ) .
• Even coatings like that of Hashimoto et al. (U.S. Patent No. 4,891,241) can be applied after applying the coatings of the present invention.
• this also includes applying the coating(s) of the present invention to any previous coating on the brittle ox ⁇ ide substrate.
• An example of a previous coating would include hot-end coatings, typically applied in the industry.
• silane-based compositions used in the method of the present invention can be present in the aqueous solution at an average concentration from about 1% to about 99% by weight in water or aqueous solution, preferably from about 1% to about 30% and most preferably from about 2% to about 10%.
• the amount of water added to the silane-based composition to prepare the aqueous solution of the present invention is based on the concentration of the resulting aqueous solution desired.
• a more dilute hydrolyzed silane-based composition would simply mean that more aqueous solution containing the hydrolyzed silane-based composition would need to be coated onto the brittle oxide substrate to achieve the substantially improved strength in the brittle oxide substrate.
• solution includes chemical solutions, suspensions, emulsions, and mixtures, any of which may exhibit complete or incomplete intermixing.
• the aqueous solution containing the hydrolyzed silane- based composition can be prepared all at once, meaning the silane-based composition is added to water at the manufactur ⁇ ing facility.
• the hydrolyzed silane-based composition can be prepared as a neat or concentrate and, at the user site, can be diluted with water in order to prepare the aqueous solution containing the hydrolyzed silane-based composition for actual coating onto the brittle oxide sub ⁇ strate.
• the aqueous solution containing the hydrolyzed silane-based composition of the present invention is substan ⁇ tially free of an organic solvent, meaning no organic solvent is intentionally added to the solution.
• organic compounds may be present as an impurity and/or by ⁇ product of the silane-based composition reacting with water or the aqueous solution reacting upon curing.
• some of the commercially available silane-based compounds may contain organic solvents which are diluted upon being introduced into the aqueous solution so that the percent solvent is approximately equal to or less than the silane concentration in the aqueous solution.
• One example is UPTMO.
• UPTMO UPTMO.
• UPTMO UPTMO
• reaction scheme sets forth the two reactions which are believed to occur in the preparation and application of the aqueous solution containing the hydrolyzed silane-based composition.
• the trialkoxy silane reacts in water to form the trisilanol in solution.
• the trisilanol in solution can contain oligomers.
• the trisilanol in solution condenses to form the polymerized cross-linked siloxane (Si-O-Si) coating upon curing.
• This siloxane (Si-O-Si) coating generally contains an organic substituent(s) such as the R" group(s).
• R'O can be any group that is hydrolyzable.
• the following R' groups best meet this
• the R group is an organofunctional group that may hydro- lyze during the hydrolysis reaction to form the R" group.
• This organofunctional group can be a residue of a hydrolyzable silane.
• the R" group contains at least one hydroxyl (OH) group. If the R group is not hydrolyzable, then R and R" would be the same, for instance, when R is vinyl or methyl.
• the R group in the above reaction scheme is preferably selected so that the silane-based compositions of the present invention provide the appropriate balance between improved or restored strength and labelability.
• R group examples include glycidoxypropyl, 2-(3,4 epoxycyclohexyl)ethyl, and 3,3-dimethoxypropyl. Further, preferred examples of the R" group would be hydrolyzed versions of these preferred R compounds.
• reaction scheme by no means is meant to limit the manner in which the aqueous solution containing the silane-based composition is prepared.
• start ⁇ ing with trialkoxy silanes one can just as easily begin with any hydrolyzable silane.
• halide silanes such as substituted trichlorosilanes.
• the R group can become hydroxyl (OH) containing as the R" group.
• OH hydroxyl
• CETMO and GPTMO which both have an epoxy ring in the R group, upon hydrolysis in the aqueous solution, will result in a dihydroxy group by the opening of the epoxide ring while the rest of the R" group remains hydrophobic.
• the R" group has a balance of hydrophilic (provided by the OH groups) and hydrophobic properties. The hydrophilic properties in the R" group particularly improve the strength and the labelability.
• a surfactant can be added to the aqueous solution containing the hydrolyzed silane-based composition to improve coverage of the aqueous solution containing the hydrolyzed silane-based composition around the brittle oxide substrate surface which results in a greater strengthening of the brittle oxide substrate and better appearance.
• Non-ionic surfactants have been especially useful in this regard.
• Triton X-102 obtained from Union Carbide which is octylphenoxy polyethoxy ethanol.
• a surfactant from about 0.001 wt.% to about 1.0 wt.% (based on total weight of solution) of a surfactant can be added.
• a surfactant Preferably, from about 0.01 wt.% to about 0.05 wt.% (based on total weight of solution) of a surfactant is added.
• the pH of the aqueous solution containing the silane- based compositions are generally adjusted to the range of about 1.5 to about 12 with the pH usually being adjusted in the preferred range of about 2 to about 4 because the aqueous solutions during testing have shown to be most stable at this pH range.
• the pH of the aqueous solutions con ⁇ taining the hydrolyzed silane-based compositions is adjusted based upon the R" group selected.
• the pH of the aqueous solutions can be adjusted to the desired pH by the addition of a basic or acidic compound.
• the aqueous solution containing the hydrolyzed silane- based composition can be affected by aging which can eventually result in a decrease in the amount of strengthening improvement of the brittle oxide substrate.
• slight aging can, in certain circumstances, be beneficial; for instance GPTMO.
• GPTMO GPTMO
• the shelf life of the aqueous solutions containing the hydrolyzed silane- based compositions is based on a composition by composition basis. For instance, with respect to an aqueous solution wherein the hydrolyzed silane-based composition is hydrolyzed CETMO, a shelf life of at least 100 days is possible without any effect on the ability to substantially improve the strength of the brittle oxide substrate.
• the aqueous solution containing the hydrolyzed silane- based composition is deposited or coated onto the substrate surface by spraying, dripping, dipping, painting, or any other techniques suited to the application of liquids, vapors, or aerosols.
• the aqueous solution containing the hydrolyzed silane-based composition is applied as a spray in an added or substituted spray step in the present commercial production and treatment of glass containers such as bottles, discussed below, using conventional spray equipment.
• the coating of the present invention can be applied directly onto any surface (e.g., internal, external, or portions thereof) of the brittle oxide substrate or can be applied to an exterior layer the composition of which is different from that of the brittle oxide substrate.
• the coating of the present invention can be applied to a tin-, titanium-, silicon-, or other metal-oxide layer or mixtures of such materials and still be effective in strengthening the brittle oxide substrate.
• the bottles which are on a conveyor line pass through 1) a hot end coating hood wherein a layer of an inorganic tin is applied, such as tin oxide; 2) an annealing lehr; and 3) a lubricant spray step.
• a hot end coating hood wherein a layer of an inorganic tin is applied, such as tin oxide
• an annealing lehr Typically, the application of the aqueous solution containing the silane-based solution preferably occurs after the glass bottles exit the annealing lehr and would be considered a cold-end coating.
• the aqueous solution containing the silane-based composition can be applied at any temperature below the boiling point of the aqueous solution, but generally is applied at or near room temperature.
• aqueous solution containing the silane-based composition can be applied at any brittle oxide (e.g. bottle) surface temperature above the freezing point of the aqueous solution, a brittle oxide surface temperature from about 20 to about 200°C is preferred, and a surface temperature from about 50 to about 60°C is most preferred.
• brittle oxide e.g. bottle
• the coated brittle oxide substrates enter a curing unit, such as a curing oven, wherein the surfaces of brittle oxide substrates usually obtain a temperature of at least about 230°C.
• a curing unit such as a curing oven
• the surfaces of brittle oxide substrates usually obtain a temperature of at least about 230°C.
• 230°C a temperature of at least about 230°C.
• BTMOE silane-based coatings
• the surface temperature can be held at the at least about 230°C for about 30 seconds.
• the temperatures used during curing need to be high enough to cure the coated brittle oxide substrates without browning the coating.
• the temperature range for effective curing is based, in part, on the R" group selected. For instance, for hydrolyzed CETMO, generally, temperatures below about 200 ⁇ C provide marginal results and temperatures above about 350°C result in the charring of the coating.
• the cure step in the method of the present invention can be effected by the application of energy of any source at a magnitude sufficient to remove, e.g., water or other non- coating reaction products from the surface of the treated brittle oxide substrate, provided that such application is not deleterious to either the brittle oxide substrate or the coating material.
• the curing step being a combined function of energy and time, can include a low magnitude of energy for a relatively long time, or the reverse, an application of a high magnitude of energy limited as noted hereinabove, for a relatively short period of time.
• energy sources include microwave, infrared, ultraviolet (UV), irradiation or exposure to ambient or elevated temperatures, such as in an electric or gas heating oven, at, above or below atmospheric pressure, or a combination of such conditions.
• a conventional lubricant spray step can be used to add a polymer coating such as polyethylene to the brittle oxide substrates for purposes of lubricity.
• the coatings of the present invention permit the adhesion of the lubricant to be at least as good as the adhesion of the lubricant to the hot end coating discussed above.
• Strength refers to the maximum load a specimen can withstand prior to catastrophic failure (and destruction of the article). There are numerous methods for measuring failure strength dependent upon sample geometry and article application. These include bending strength, vertical load, burst pressure, concentric ring strength, and impact testing. The method of the present invention actually strengthens the brittle oxide substrate. As stated in the background, theoretically, all brittle oxide substrates, especially glass, are damaged in some way by minute flaws or by the presence of small impurities.
• the present invention could characterize the present invention as a method of restoring strength to a brittle oxide substrate since the method of the present invention is providing a degree of strength to the brittle oxide substrate which is closer to its theoretical strength.
• a further way of measuring the strength is by an impact strength test as described in the instructions which are provided with the AGR Impact Tester. This test is industry recognized and is accomplished with the use of an AGR impact tester unit obtained from AGR, Int'l., Butler, PA. The strength test is commonly recognized by those skilled in the art as well.
• the application of the aqueous solution containing the hydrolyzed silane-based composition of the present invention substantially improves the strength of a brittle oxide substrate.
• the substantial strength improvement is demonstrated by the concentric ring strength, burst pressure strength, or impact strength improving at least about 10%. Preferably the strength improvement is at least 20%.
• a brittle oxide substrate or article e.g., glass
• a lesser amount of oxide substrate is needed to form an article of substantially equivalent strength and general mechanical performance.
• the bottle can be lighter in weight than its untreated counterpart.
• increasing the strength leads to less failures of the product (e.g., less breakage) during commercial use.
• the polymerized cross-linked siloxane linkage occurs within the coating, as well as between the coating and the brittle oxide substrate surface.
• the coating after bonding to the surface, can act to heal cracks in the surfaces by forming an Si-O-Si network across the flaw surfaces.
• the formation of the siloxane bonds in the region of the flaws acts to provide an increase in the breaking stress of the article.
• HEC hot-end coating
• this coating will be tin oxide, but can be titanium or other metal oxide, and can have other ingredients to enhance physical properties, e.g., electrical conductivity.
• This coating is typically about 50 to 125 Angstroms thick.
• the present invention restores or increases the strength of damaged glass, whether or not a previously deposited HEC exists on the surface.
• Labelability of the brittle oxide substrate it is to be understood that certain cured hydrolyzed silane-based coatings of the present invention do not interfere with this labelability as discussed previously. Labelability is measured by the following label peel test.
• a paper label with four corners and having an area of about 6 square inches is used.
• the label is weighed prior to the application of a casein type adhesive identified as 4242 available from National Starch. About 0.6 grams of the casein type adhesive is applied to the back of the label (opposite side) and spread on the label by rolling with a 5 mm glass rod or similarly shaped object to uniformly spread the adhesive on the label.
• the label is pressed on a surface of a brittle oxide substrate and allowed to dry for a minimum of two hours at room temperature.
• the label is peeled by hand at every corner until a portion of the label tears from every corner of the substrate.
• a coating is considered to have acceptable labelability for purposes of the present invention if greater than about 50% by weight of the label remains on the surface of the brittle oxide substrate.
• the labelability (based on the % by weight of the label remaining on the surface of the brittle oxide substrate) of the coated brittle oxide substrates of the present invention is greater than about 60%, most preferably greater than about 70% by weight.
• the substantially improved strength from the cured coating on the brittle oxide substrates can also exhibit a maintained resistance to the detrimental effects of humidity.
• a humidity resistance test provides an acceptable way of determining how well the coatings of the present invention allow a coated brittle oxide surface to retain the improved or restored strength.
• the excellent and maintained resistance to humidity which can be exhibited by the silane- based coatings of the present invention is generally dependent upon the R" group.
• One way to determine the effect of humidity on the coatings of the present invention is to compare the strength of coated brittle oxide substrate when the cured coating on the substrate is less than 3 hours old at relative humidity which generally is approximately 40%, with the strength of the same coated brittle oxide substrate subjected to a 90% humidity for a period of 30 days.
• the humidity resistance of the cured coatings of the present invention applied to the brittle oxide substrates has only about a 50%, preferably only about 20-30%, most preferably 0-10%, change in strength which is excellent, especially for purposes of glass bottles subjected to high humidity environments such as in the southern United States.
• the coating applied to the brittle oxide substrate can be a mixture of one or more hy ⁇ drolyzed silane-based compositions.
• a mixture of a hydrolyzed silane-based composition wherein R" is methyl and 2-(3,4 epoxycyclohexyl)ethyl is one excellent example. It is all the more remarkable that when such a mixture is made, none of the individual components in the mixture detract from any of the desired properties. For instance, the presence of MTMO does not detract from the labelability properties.
• aqueous solutions containing the hydrolyzed silane- based compositions of the present invention are non-flammable especially in view of the fact that there is a substantial absence of organic solvents in the aqueous solution.
• the hydrolyzed silane-based composition When coating brittle oxide substrates, especially glass containers, it is preferred that the hydrolyzed silane-based composition is not visible on the container.
• the silane coating should not discolor or become textured upon curing.
• the hydrolyzed silane-based compositions of the present invention meet this criteria. It is noted that in some commercial applications, a coating which is diffused (some haze or fresco) is desired.
• the coatings of the present invention are also capable of this diffused appearance by using an application temperature (e.g. brittle oxide substrate surface temperature) of from about 80°C to about 100°C.
• color dyes can be added to the aqueous solution in order to make colored coatings.
• suitable dyes include Celestine blue, Bismark brown, and Eriochrome black.
• dyes can be used in the aqueous solution for indicating the degree of cure and spray coverage.
• other components can be included in the aqueous solution, such as UV blockers and fluorescing agents. Including a fluorescing agent will permit the coated brittle oxide substrates to have a "glow-in-the-dark" property.
• the coatings of the present invention also advantageously have the ability to hide visible scuff damage to a substrate surface. This is particularly desirable in the refillable bottle industry wherein bottles eventually develop a whitened track around the bottle from numerous cycles through a filling line.
• soda-lime glass rods were indented with a Vickers diamond to produce approximately 50-micro-meter (u ) flaws in the surface. These rod samples were tested to failure in bending, and had average strengths of 56 MPa.
• Samples with identical flaws were spray-coated with a solution of 10 percent by weight (wt.%) of vinyl trimethoxysilane (VTMO) in water. The solution contained enough sulfuric acid to adjust the pH to between 3.0 and 3.4. The samples were thereafter heat-treated for 15 minutes (min.) at 200°C, and tested in bending. The average strength of these samples increased from 56 MPa to 90 MPa.
• VTMO vinyl trimethoxysilane
• Example 2 is a modification of Example 1.
• the samples were again indented rods, and the solution was 10 wt.% VTMO, acidified as set forth in Example 1.
• This solution also contained 0.75 wt.% of the nonionic surfactant Triton X-102. After curing, the indented samples increased in strength from 56 MPa to 93 MPa.
• Example 3 is identical to Example 1, with the exception that the silane used was methyltrimethoxysilane (MTMO) .
• the control samples had an average strength of 62 MPa. Upon coating and curing, the bend strength was increased to 96 MPa.
• MTMO methyltrimethoxysilane
• Example 4 is a duplication of Example 2, using MTMO.
• the average control strengths were again 62 MPa, but the strengthened samples averaged 103 MPa.
• Examples 5 and 6 are duplicates of Examples 1 and 2, respectively, with the exception that the silane used was methacryloxypropyltrimethoxysilane (MPTMO) .
• MPTMO methacryloxypropyltrimethoxysilane
• the average control strength was 60 MPa.
• This example illustrates the treatment of flat-glass samples which were indented with a Vickers diamond to form a controlled flaw. Samples were indented such that 90-um flaws were produced. These samples were coated with a silane solution consisting of three silanes in the same weight proportion. The overall silane concentration was 10 wt.% in water, while the amount of each silane was about 3.33 wt.%. The solution contained enough sulfuric acid to bring the pH to between 3.0 and 3.4. A nonionic surfactant, Triton X-102, was added in the amount of 0.75 wt.% in order to increase wetting. The 1:1:1 solution consisted of glycidoxypropyltrimethoxysilane (GPTMO), 2-(3,4 epoxycyclohexyl)ethyltrimethoxysilane (CETMO), and MTMO.
• GPTMO glycidoxypropyltrimethoxysilane
• CETMO 2-(3,4 epoxycyclohexy
• control strengths were 45 MPa, while the samples treated with the 1:1:1 solution were 160 MPa after a two-step cure consisting of a 15-minute cure at 125°C, followed by a cure at 225°C for 10 minutes, an increase in strength of about 3.5 times. Good labelability was also found for this mixture even though MTMO (generally exhibiting poor labelability by itself) was present in the formulation.
• Example 3 The same control samples as described in Example 3 were strengthened using a 1:1 solution of GPTMO and CETMO, also in a 10 wt.% total concentration.
• the solution contained enough sulfuric acid to bring the pH to between 3.0 and 3.4.
• These samples underwent the same heat treatment described in Example 3.
• the strength of the treated samples was increased to 118 MPa from the starting strength of 45 MPa, for an increase in strength of about 2.6 times.
• Example 3 The same flaws described in Example 3 were applied to the sidewalls of amber bottles. The average burst pressure of these flawed containers was 1.9 MPa. The flawed bottles were then silane-treated, using a 10 wt.% solution of CETMO and the same cure procedure described in Example 3. The average burst strength of the treated control-flawed samples was increased to 3.2 MPa, an increase of 68% over the flawed control samples.
• Lightweight 12-oz. bottles were indented as set forth above, and coated with the 10% CETMO solution described in Example 9.
• the average burst pressure for the indented controls was 1.5 MPa.
• the average burst pressure of the bottles was increased to 2.6 MPa.
• Lightweight 12-oz. bottles were coated in the as- received state with a 10 wt.% solution of CETMO.
• the burst strength of the control samples was 1.6 MPa.
• the coated and cured samples had an average burst strength of 3.0 MPa.
• soda-lime flat-glass specimens were indented with a Vickers diamond tip to produce the 50-um flaws on the surface as described in Example 1. These samples were tested with a concentric-ring fixture. The mean strength of these uncoated samples was 69 MPa.
• a suspension of MPTMO was prepared by adding the silane to water acidified to a pH of 2.5 with a suitable acid, e.g., H-SO., to give a 10 wt.% mixture.
• a suitable acid e.g., H-SO.
• Triton X-102 was added, and the composition aged for 24 hours at room temperature.
• the condensing oligomers phase-separated at room temperature after 24 hours, forming a suspension.
• This suspension was applied by drip-coating over the flaw region and heat-treating for 15 min. at 125°C, followed by an UV cure.
• the mean flat-glass strengths were 223 MPa.
• a 10 wt.% suspension of methacryloxypropylmethyldiethoxy-silane (MPMDEO) was prepared using the same procedure as described in Example 10, but using the surfactant at a 1 wt.% level.
• the suspension was drip-coated on flat glass and the coating was cured for 15 min. at 125°C followed by a cure at 225°C for 10 min.
• the treated flat-glass specimens had mean strengths of 143 MPa.
• a 10 wt.% suspension containing a 1:1 wt. mixture of dimethyltetramethoxydisiloxane and MPMDEO was prepared as described in Example 10, except that acetic acid was used to adjust the pH to 3.5, and no surfactant was added.
• the sample received a dual cure as described in Example 14.
• the treated flat-glass specimens had mean strengths of 193 MPa.
• Example 17 A 10 wt.% suspension containing a 1:1 wt. mixture of di-tert.-butoxydiacetoxysilane (DBDAS) and MPMDEO was prepared as described in Example 14, except that H-SO. was used to adjust the pH to 3.5, and 0.025 wt.% Triton X-102 was added. The sample received a dual cure as described in Example 12. The treated flat-glass specimens had mean strengths of 152 MPa.
• DDAS di-tert.-butoxydiacetoxysilane
• MPMDEO di-tert.-butoxydiacetoxysilane
• Soda-lime glass flat-glass specimens were indented with a Vickers diamond to produce approximately 50-um flaws. These samples were tested with a concentric-ring fixture, and had average strengths of 69 MPa.
• a solution of 10 wt.% N-(3-triethoxysilylpropyl)-4-hydroxybutyramide (HBTEO) was prepared in water and allowed to stand for 30 days; the pH was 9.5.
• the flawed slides were then drip-coated with the solution, and dual-cured at 125°C for 15 min., followed by 225°C for 10 min.
• the tested mean strength after treatment was 266 MPa.
• Soda-lime flat-glass specimens were indented with a Vickers diamond to produce approximately 50-um flaws. These samples were tested with a concentric-ring fixture, and had average strengths of 69 MPa.
• Soda-lime flat-glass specimens were indented as set forth in Example 21, and then coated with 150A of pyrolyti- cally deposited SnO,. The samples were then annealed to remove residual stresses. Tin-oxide-coated control samples had strengths of about 83 MPa. The Sn0 2 -coated specimens were then treated with a 10 wt.% solution of MTMO as described in Examples 3 and 4, producing specimens with strengths of 210 MPa.
• Soda-lime flat-glass specimens were indented with a Vickers diamond to produce approximately 50-um flaws. These samples were tested with a concentric-ring fixture, and had average strengths of 69 MPa.
• a solution of 10 wt.% of 3,3-dimethoxypropyltrimethoxysilane (DMPTMO) in water was prepared, and the pH adjusted to 3.5. After standing for two hours at room temperature, one portion of the solution was used to drip-coat the flawed slides. The slides were then cured at 125°C for 15 min. and then at 225°C for 10 min. The mean strength for the treated slides was 88 MPa.
• H nuclear- magnetic-resonance (NMR) analysis of the DMPTMO solution showed only the -CH(OCH 3 ) 2 group of the silane triol as a signal at 4.41 (triplet) ppm.
• the present invention was tested at a bottling manufacturing facility based on the following procedure: 120 16-ounce glass beverage containers were pressure tested prior to treatment using an AGR ramp pressure tester. The average burst pressure measured was 422 psi (2.9 MPa), and the percentage of the bottles failing below 300 psi (2.1 MPa) was 15%.
• the treatment process consisted of spraying a solution of the present invention (specifically, CETMO), thermally curing to achieve 230°C or better, followed by a standard cold-end-coating application.
• the samples were thereafter heat treated at 125°C for 15 minutes followed by 225°C for 10 minutes.
• the concentric ring strengths were uncoated 9588 psi (66.1 MPa) coated 25492 psi (176 MPa)
• Example 25 was repeated with the exception that the silane was l,2-bis(trimethoxysilyl)ethane.
• the control samples had an average concentric ring strength of 11566 psi (79.8 MPa). After coating and curing, the average concentric ring strength was 19728 psi (136 MPa).
• Example 26 was again repeated with the exception that the heat treatment consisted of only heating at 125°C for 15 minutes. The average strength went from 11566 psi (79.8 MPa) (uncoated) to 23799 psi (164 MPa) after coating and curing.
• Example 25 was repeated with the exception that the silane was l,2-bis(3-trimethoxysilylpropoxy)ethane.
• BTMOPE was made using the following procedure.
• Example 27 was repeated using the silane of Example 28.
• the strength of the coated and cured samples averaged 30153 psi (208.0 MPa) while the controls average 10139 psi (69.9 MPa) .
• Celestine Blue dye (CAS # 1562-90-9) was added to a 5% solution of CETMO that also contained 0.025% Triton X-102 surfactant. The solution was then spray applied onto 16-oz beverage containers using 2.0 g of solution/bottle. The samples were then heat treated for 33 seconds in an infrared oven set at 700°C. The coated bottles had a uniform blue coating.
• Rectangular alumina bars were tested in 3-point bending to evaluate the ability of the present invention to strengthen it.
• the other half of the samples were spray- coated with 10% by weight CETMO/0.025% by weight Triton X-102/0.025 % by weight RP-40 (obtained from T.H. Goldschmidt, Germany) formulation and thermally cured using the 2-step heat treatment protocol (15 minutes at 125°C followed by 10 minutes at 225°C).
• the control samples had an average failure strength of 23,300 psi, while the treated samples had an average strength of 28,200 psi. This represents an average increase of 21%.

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