Strengthening oxide substrates with crosslinking silanes

This application is a partial continuation of U.S. Patent Application No. 08/043980, filed April 7, 1993, which is a partial continuation of U.S. Patent Application No. 07 / 873,315, filed April 24, 1992, now discontinued, which is a partial continuation of U.S. Patent Application No. 07 / 576,052 of August 30, 1990, now discontinued. The present application is also a partial continuation of U.S. Patent Application No. 07 / 986,894, filed December 8, 1992, which is a continuation of U.S. Patent Application No. 07 / 738,030, filed Jul 30, 1991, now discontinued, which forms part of U.S. Patent Application No. 07 / 575,052 of August 30, 1990, now discontinued.

The invention relates to methods of strengthening a brittle oxide substrate and to aqueous solutions containing silane-based compositions and brittle oxide substrates coated with polymerized, cross-linked siloxane. In particular, the invention relates to a method of strengthening or restoring the strength of a glass package and the resulting polymerized cross-linked siloxane coated glass package.

Brittle materials such as glass substrates typically exhibit certain mechanical properties, such as tensile strength, well below expectations. Such symptoms may result from factors such as structural defects of the tested samples or small amounts of contamination inside or on the surface of the product made of this material. In the past, gradual zone melting has been used with brittle metals to form a crystalline structure and cause contaminants to float to the surface, which will improve the mechanical properties of brittle metals. Also for non-metallic brittle materials, multi-layer structures made of brittle material have been used to improve the mechanical properties. Additionally, a surface treatment of the brittle material was applied to protect the surface against abrasion and to provide a slight reinforcement of the brittle products.

Glass is inherently one of the most durable materials known to man. In theory, ordinary silicate glass should be able to withstand stresses as high as 14-20 GPa. In practice, however, strengths of the order of 70 MPa are usually achieved.

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The differences between the predicted and measured values ​​are explained by the presence of surface flaws or cracks. These flaws essentially crack the siloxane (Si-O-Si) lattice that forms the backbone of the glass. These failures in the glass cause any applied forces to concentrate pointwise, resulting in catastrophic failure of the glass product, usually at loads much lower than expected. The theory described for glass can also be applied to any brittle material that does not exhibit any significant plastic deformation prior to failure.

For example, in the case of glass packaging, surface blemishes or defects can come from a variety of sources, ranging from unmelted raw materials to scratches caused by sliding on hard surfaces, including other glassware. For example, in a typical glass factory, the glassware can be severely damaged by handling from the moment it is formed. Contact with particles and moisture from the air, with other bottles, with guide rails and other handling devices, and with the conveyor on which the packages are transported, can lead to significant deterioration of strength due to the resulting blemishes.

Researchers have long searched for measures to overcome the problems associated with glass strength. Many modifications to the molding and handling process did not lead to a satisfactory increase in strength as such modified handling still left blemishes on the surface. Therefore, the aim of the research was to reduce the impact of inevitably formed blemishes on the product.

Among the solutions for improving the strength of glass, mention should be made of US Patent No. 4,859,636 to Aratani et al., According to which metal ions in the glass are replaced with ions of a larger radius to create compressive surface stresses. U.S. Patent No. 3,743,491 to Poole et al also deals with compressive surface stress, but with the use of a polymer top coat to protect the surface from further abrasion. U.S. Patent No. 4,891,241 to Hashimoto et al. Relates to the treatment of a glass surface with a silane coupling agent followed by a polymeric coating material containing acryloyl and / or methacryloyl groups, followed by irradiation or heat treatment to polymerize molecules containing these groups. The '241 patent also states that silanes alone do not strengthen substrates and that acrylates are required to achieve reinforcement.

Although each of the above-mentioned patents provides some degree of improvement in the strength of the glass as a result of the applied treatment, they are not without drawbacks. Some of these methods require longer processing times than those achievable during the manufacturing process, necessitating off-line processing. There are also problems related to the safety and health of workers. In particular, the use and handling of organic solvents, as well as acrylates and methacrylates, pose health and safety problems for the manufacturer.

Accordingly, there is an unmet need for a method of strengthening a brittle tissue substrate that eliminates the above problems and provides an acceptable increase in strength to the brittle oxide substrate. There is also a need for a brittle oxide substrate with substantially increased strength compared to a brittle oxide substrate without any coating.

There is also a need for a method of strengthening an oxide brittle substrate that also provides labelability and / or moisture resistance.

There is also a need for a brittle oxide substrate coated with a polymerized cross-linked siloxane for which the cured coating is transparent.

Additional objects and advantages of the invention will be set forth in part in the description below, and in part will be apparent from the description, and will be apparent from the practice of the invention. The objects and advantages of the invention will be realized and attained by the elements and combinations thereof specifically recited in the appended claims.

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The invention which achieves the above objects, generally described in the description, relates to a method for strengthening a brittle oxide substrate comprising the following steps. First, the brittle oxide substrate is coated with an aqueous solution containing the silane-based composition. The aqueous solution containing the silane-based composition is substantially free of any organic solvent. In addition, the silane-based composition after hydrolyzing in an aqueous solution is given by the formula (OH)₃SiR^ff wherein R is an organic functional group. After the aqueous solution containing the hydrolyzed silane-based composition is applied to the brittle oxide substrate, the coating is cured to form a transparent layer on the brittle oxide substrate. In addition, R in the silane-based composition is selected such that (i) the strength of the brittle oxide substrate with the cured film is substantially higher than that of the brittle oxide substrate prior to the coating step, and (ii) the cured coating does not deteriorate the labelability of the brittle oxide substrate.

The invention also relates to a process similar to that described above, but such that R is selected such that (i) the strength of the brittle oxide substrate with the cured coating is substantially greater than that of the brittle oxide substrate prior to the coating step, and (ii) the substantial increase in strength provided by the cured brittle coating on the brittle surface. the oxide substrate retains at least 50% resistance to moisture.

The invention also relates to a brittle oxide package coated with a polymerized, cross-linked siloxane. In particular, a brittle oxide package coated with a polymerized cross-linked siloxane is a brittle oxide package with a transparent layer of polymerized, cross-linked siloxane, preferably cured on the outer surface of the friable oxide package. Polymerized, cross-linked siloxane is formed from a silane-based composition hydrolyzed in an aqueous solution, substantially free of an organic solvent. The hydrolyzed silane based composition may be selected from the group consisting of methacryloxypropyltrimethoxysilane (MPTMO), glycidoxypropyltrimethoxysilane (GPTMO), vinyl trimethoxysilane (VTMO), 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-Mimethoxysilane, 3-Mimethoxyspropyl) methyl (CETMimethoxysilane). (DPTMO), 5,6-epoxyhexyltrimethoxysilane (EHTMO), maleic acid N- (trimethoxysilylpropyl) amide, 3-ureidopropyltrimethoxysilane (UPTMO), 1,2-bis (trimethoxysilyl) ethane (BTMOE), 1,2-bis (3-trimethoxysilylpropoxy) ethane (BTMOPE), their hydrolysed forms, and mixtures thereof.

The invention further relates to novel silane-based compositions comprising, but not limited to, a mixture of vinyltrimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; a mixture of methyltrimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; a mixture of glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane and methyltrimethoxysilane; and a mixture of glycidoxypropyltrimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane.

The above generally described invention overcomes the difficulties of treating brittle oxide substrates such as glass. The process of the invention dramatically and unexpectedly increases or restores the strength of brittle oxide substrates compared to the strength of the substrate prior to application of any coating. Moreover, the coatings of the invention are transparent and safe to use on brittle oxide substrates. By increasing or restoring the strength of the substrate, the coatings of the invention preferably do not interfere with labelability, which has been a problem with known coatings on substrates.

It should be understood that the foregoing general description and the following detailed description are given by way of example and explanation only and are not intended to limit the invention as defined by the claims.

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The brittle oxide substrate used in the process of the invention can be made of any brittle oxide material such as aluminum and aluminates, silicon oxides and silicates, titanium oxides and titanates, germanates, and glass made from, for example, the above materials. In addition, the brittle oxide substrate may be in any form, e.g., in the form of a glass bottle.

Silane-based compositions after hydrolysis in aqueous solution are represented by the formula (OH5SiR wherein R is an organic functional group which may or may not be hydrolyzed in aqueous solution. Such organic functional group may include residues of hydrolysable silanes. The selection of the R group is also done taking into account the requirement that the resulting aqueous solution containing the hydrolyzed silane based composition when applied and cured on the brittle oxide substrate will impart substantially increased strength to the brittle oxide substrate and not interfere with the labeling ability of the brittle oxide substrate.

Examples of R groups are preferably glycidoxypropyl, 2- (3,4-epoxycyclohexyloyethyl, 3,3-dimethoxypropyl, 3-ureidopropyl, and their hydrolysed forms).

Accordingly, preferred examples of silane-based compositions are hydrolyzed glycidoxypropyl trimethoxysilane, hydrolyzed 2- (3,4-epoxycyclohexyl yethyl trimethoxysilane, hydrolyzed 3-ureidopropyl trimethoxysilane, and hydrolyzed 3,3-dimethoxyspropyl).

The coating applied to the brittle oxide substrate may also be a mixture of one or more hydrolyzed silane based compositions. A mixture of two or more hydrolyzed silane-based compositions is particularly useful when one of the hydrolyzed silane-based compositions is known to provide excellent labelability and the other hydrolyzed silane-based composition provides excellent strength properties. Accordingly, the mixture should provide the required set of properties, that is, a coating providing increased strength and one that does not interfere with the labelability. For example, a mixture of hydrolyzed CETMO and methyltrimethoxysilane (MTMO) may be used to obtain such a set of properties.

Other examples of hydrolyzed silane-based compositions that can be used in mixtures of one or more hydrolyzed silane-based compositions include hydrolyzed methacryloxypropyltrimethoxysilane, hydrolyzed, 3-ureidopropyl trimethoxysilane, hydrolyzed, 1,2-bis (trimethoxysilyl). (3-trimethoxysilylpropoxy) ethane, hydrolyzed 5,6-epoxyhexyltrimethoxysilane, hydrolyzed N- (trimethoxysilylpropyl) maleic acid amide, hydrolyzed dimethyl tetramethoxydisiloxane and hydrolyzed N- (3-triethoxysilylpropyl) -4-hydroxybutyramide (HBTEO). Such compositions can be used, for example, in admixture with hydrolyzed CETMO and / or hydrolyzed GPTMI and / or hydrolyzed DPTMO. Typically, the silane-based compositions used in the mixture can be added in equal amounts. However, if increased labeling ability is required, larger amounts may be added, e.g., hydrolyzed CETMO, hydrolyzed GPTMO or hydrolyzed DPTMO. In addition, any one of the compositions described above may be used to substantially improve the strength of the brittle oxide substrate when labelability is not a concern.

Unless otherwise stated, silane-based compositions given as specific examples are commercially available from one or more of the following sources: Union Carbide, Dow Corning, Huls America, and PCR Inc.

Although the coatings of the invention may be mixtures of one or more hydrolyzed silane based compositions on the surface of the brittle oxide substrate

178 796, separate coatings can be applied from the hydrolyzed silane based compositions. For example, a CETMO coating can be applied to the surface of the brittle oxide substrate, then, while the CETMO coating is still wet or dry, or after the first coating is fixed, a second coating can be applied, e.g. another CETMO coating or another coating (e.g. MPTMO ).

Any number of such consecutive separate coatings may thus be applied. Moreover, a surfactant may be applied in this manner by coating the brittle oxide surface with the surfactant before and / or after the surface is coated with one or more hydrolyzed silane based compositions. Even coatings such as those disclosed in US Patent No. 4,891,241 (Hashimoto et al.) Can be applied after the coatings of the invention have been applied.

It will be appreciated that applying the coatings (i) of the invention to the surface of a brittle oxide substrate also includes applying the coatings (i) of the invention to any of the previous coatings on the brittle oxide substrate. Examples of previous coatings may be the hot-end coatings normally used in the art.

The average concentration of the silane-based compositions used in the process of the invention in the aqueous solution may be from about 1 to about 99 weight percent. in water or aqueous solution, preferably from about 1 to about 30%, and most preferably from about 2 to about 10%.

Regarding the aqueous solution containing the hydrolyzed silane-based composition, the amount of water added to the silane-based composition in preparing the aqueous solution according to the invention depends on the required concentration of the resulting aqueous solution. The use of a more dilute hydrolyzed silane based composition simply means that more of the aqueous solution containing the hydrolyzed silane based composition will need to be applied to the brittle oxide substrate to achieve a substantial improvement in the strength of the brittle oxide substrate.

As used herein, the term "solution" includes chemical solutions, suspensions, emulsions, and mixtures, any of which systems may exhibit complete or incomplete mixing.

The aqueous solution containing the hydrolyzed silane-based composition can be prepared immediately, which means that the silane-based composition is added to the water at the manufacturer's premises. Alternatively, the hydrolyzed silane-based composition may be prepared in undiluted or concentrated form and then diluted with water at the point of use to prepare an aqueous solution containing the hydrolyzed silane-based composition ready for application to a brittle oxide substrate.

The aqueous solution containing the hydrolyzed silane-based composition of the invention is essentially free of organic solvent, meaning that no organic solvent is intentionally added to the solution. Certain organic compounds, however, may exist as impurities and / or by-products of the reaction of the silane-based composition with water or of the reaction in an aqueous solution during curing. In addition, some commercially available silane compounds may contain organic solvents which dilute upon addition to the aqueous solution such that the concentration of the solvent is about the same as or less than the concentration of the silane in the aqueous solution. One example is UPTMO.

Of course, it is known that the addition of a solvent can increase the stability of the solution.

The following reaction scheme shows two reactions which are believed to occur in the preparation and use of an aqueous solution containing the hydrolyzed silane-based composition.

(RO) jSiR + 3H₂O θ (OH)₃SiR + 3R'OH -> Si-O-Si shell

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In this reaction, the trialkoxysilane reacts with water to form trisilanol in solution. The trisilanol in solution may contain oligomers. The trisilanol in solution then condenses to form a polymerized cross-linked siloxane (Si-O-Si) coating during curing. The siloxane (Si-O-Si) coating typically carries an organic substituent (s) such as the R group (s).

In the reaction scheme, the R'O group may be any hydrolyzable group. To O

Group II that best meets this requirement are: -CH3, -C2H5 and -CCH3. However, those skilled in the art are aware of other groups that satisfy this criterion.

The R group is an organic functional group that can hydrolyze during the hydrolysis reaction to form the R group. Such an organic functional group can be the rest of the hydrolyzing silane. After the hydrolysis reaction and when the R group is hydrolyzed, the R group contains at least one hydroxyl (OH) group. When the R group is not hydrolyzed, R and R may be the same, e.g. when R is a vinyl or methyl group. In principle, the R group in the above reaction scheme is preferably selected such that the silane-based compositions of the invention provide the appropriate balance between increased or restored strength! labeling ability. In this connection, preferred R groups include, for example, glycidoxypropyl, 2- (3,4-epoxycyclohexyl) ethyl and 3,3-dimethoxypropyl. In addition, preferred R groups include hydrolyzed versions of compounds containing such preferred R groups.

The above reaction scheme does not in any way limit the manner in which an aqueous solution of the silane-based composition is prepared. Instead of starting with a trialkoxysilane, any hydrolysable silane may be used with success, e.g., halosilanes such as substituted trichlorosilanes.

As noted above, an R group can transform into an R containing a hydroxyl (OH) group. For example, CETMO and GPTMO containing epoxy rings in the R group by hydrolysis in aqueous solution will form a dihydroxy moiety upon epoxy ring opening, while the remainder of the R group will remain hydrophobic. Thus, the R group exhibits some balance between hydrophilic (OH groups) and hydrophobic properties. The water-repellent properties of the R group contribute in particular to improving the strength and labeling properties.

A surfactant can be added to the aqueous solution containing the hydrolyzed silane-based composition to increase the coverability of the aqueous solution containing the silane-hydrolyzed composition to the brittle oxide substrate surface, resulting in a stronger reinforcement and appearance of the brittle oxide substrate. Typically, only a small amount of surfactant is added to ensure better flow of the silane coating on the brittle oxide substrate. Especially useful in this regard are non-ionic surfactants. One example of this type of surfactant is the commercially available Triton Χ-102 (from Union Carbide), which is octylphenoxy polyethoxyethanol. Typically, from about 0.001 to about 1.0 wt.% May be added. (based on the total weight of the solution) of the surfactant. Preferably from about 0.01 to about 0.05 wt.% Is added. (based on the total weight of the solution) of the surfactant.

It will be understood by those skilled in the art that other compounds may be added to the aqueous solution containing the silane-based composition to improve wetting or to provide other characteristics such as UV resistance or rheological control.

The pH of the aqueous solution containing the silane-based composition is typically adjusted in the range of from about 1.5 to about 12, with the preferred pH range being from about 2 to about 4, as the aqueous solutions proved to be most stable over this pH range during testing. Typically, the pH of aqueous solutions containing compositions based on hydrolyzed si

178 Depending on the selected R group, the 796 fields are adjusted. The pH of the aqueous solutions can be adjusted to the required range by adding a basic or acidic compound.

The aqueous solution containing the hydrolyzed silane-based composition may age, which may result in a reduction in the degree of strengthening of the brittle oxide substrate. It should be noted, however, that a slight aging may be beneficial in some cases, e.g. when using GPTMO. However, with further aging, the properties eventually deteriorate. The pot life of aqueous solutions containing compositions based on hydrolyzed silanes is dependent on the composition of the composition. For example, in the case of an aqueous solution in which the hydrolyzed silane-based composition is hydrolyzed CETMO, the pot life may be at least 100 days without any effect on the ability to substantially increase the strength of the brittle oxide substrate.

The aqueous solution containing the hydrolyzed silane-based composition is deposited or applied to the surface of the substrate by spraying, dripping, dipping, painting or any other method suitable for the application of liquids, vapors or aerosols. Preferably, the aqueous solution containing the hydrolyzed silane-based composition is spray applied in an additional or altered spraying step of a known industrial process for the manufacture and treatment of glass containers such as bottles described below using known spray equipment.

The coating of the invention can be applied directly to any surface (inner, outer, or part of the surface) of the brittle oxide substrate, or it can be applied to an outer layer that is different in composition from the brittle oxide substrate. For example, a coating of the invention may be applied to a layer of tin, titanium, silicon or other metal oxide, or a mixture of such materials, with the coating still being effective in strengthening the brittle oxide substrate.

Typically, in the production of glass packages, such as bottles, pass on a conveyor through 1) a hot end coating station where a layer of an inorganic tin compound such as tin oxide is applied, 2) a lehr, and 3) a lubricant spraying step. Using the method of the invention, the silane-based aqueous solution is preferably applied after the bottles have exited the lehr, so that this step can be considered 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 is typically applied at or around room temperature.

In addition, while the aqueous solution containing the silane-based composition may be applied at any surface temperature of the brittle oxide (e.g., bottle) above the freezing point of the aqueous solution, preferably the surface temperature of the friable oxide is from about 20 to about 200 ° C, with the most preferred temperature being from about 50 to about 60 ° C.

After the brittle oxide substrates (e.g., glass bottles) are coated with an aqueous solution containing the silane-based composition, the coated brittle oxide substrates are introduced into a curing apparatus such as a curing oven in which the surfaces of the brittle oxide substrates are heated to a temperature of at least about 230 ° C. It is certainly possible to cure effectively at surface temperatures below 230 ° C with certain silane based coatings such as BTMOE. When this surface temperature is reached, effective curing takes place. For example, the surface may be kept at a temperature of at least about 230 ° C for about 30 seconds. The temperatures during curing should be high enough that the coated brittle oxide substrates cure without turning the coating brown. The range of effective curing temperatures depends in part on the R group selected. with hydrolyzed CETMO at temperatures below about 200 ° C, minor results are obtained, and at temperatures above about 350 ° C, carbonization of the coating occurs.

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The curing step of the process of the invention may be carried out by applying energy from any source at a rate sufficient to remove e.g. water or other non-coating reaction products from the surface of the treated brittle oxide substrate, provided that the brittle oxide substrate or the coating material is not adversely affected by the energy. . The energy and time dependent curing step can be performed at low energy for a relatively long period of time or at high energy, within the constraints outlined above, for a relatively short period of time. Examples of energy sources include microwave, infrared or ultraviolet (UV) radiation or the effects of ambient or elevated temperatures, e.g. in an electrically or gas fired oven at a pressure equal to, above or below atmospheric pressure, or a combination thereof.

Following the curing step, the conventional lubricant spraying step mentioned above may be used to apply a polymer coating, e.g. polyethylene, to the brittle oxide substrates for lubricity. The inventive coatings provide adhesion of the lubricant at least as good as that of the lubricant to the hot end coating mentioned above.

The coatings of the invention can provide sufficient lubricity to the brittle oxide substrate that any lubricant spraying step, especially in the manufacture of bottles, can be eliminated.

Strength in the sense above is the maximum load that the specimen can withstand before final failure (and destruction of the product). There are numerous methods of measuring the resistance to failure, depending on the geometry of the sample and the intended use of the product. These include the determination of flexural strength, vertical loading, determination of burst pressure, determination of symmetrical ring strength and impact measurement.

The method according to the invention does indeed make it possible to strengthen the brittle oxide substrate. As noted in the prior art, theoretically, all brittle oxide substrates, and glass in particular, suffer to some degree from minor flaws or the presence of small amounts of impurities. Since the brittle oxide substrates theoretically should exhibit much higher strength, the method of the invention can be defined as a method of restoring the strength of a brittle oxide substrate as the process of the invention achieves a degree of strength of the brittle oxide substrate closer to its theoretical strength.

One method of measuring the actual strength of a brittle oxide substrate with or without an aqueous solution coating containing a hydrolyzed silane-based composition is the symmetric ring strength test described in Journal of Strain Analysis, Vol. 19, No. 3 (1984) and in the Journal of Non-Crystalline Solids. , 38 and 39, pp. 419-424 (1980), which is a test well known to those skilled in the art.

Another method of measuring the strength is the Burst Pressure Resistance Test as described in ASTM Test C-147 performed with a uniform pressure change apparatus (available from AGR, Intl. Literature), also a test well known to those skilled in the art.

Another method of measuring strength is the impact test described in the instructions supplied with the AGR Impact Tester. This is an industry known test performed with an AGR impact tester available from AGR Intl., Butler, PA. The immunity test is well known to those skilled in the art.

As noted, the use of an aqueous solution containing the hydrolyzed silane-based composition of the present invention substantially improves the strength of the brittle oxide substrate. The substantial improvement in strength in the symmetrical ring strength measurements, the burst pressure resistance measurement or the impact strength measurement is an increase of at least 10%. Preferably, the increase in strength is at least 20%.

It will be understood by those skilled in the art that while increasing the strength of the brittle oxide substrate or article, e.g., glass, less oxide substrate is needed to produce an article of substantially equivalent strength and overall mechanical properties.

178 796. Thus, in the particular case of a glass package, such as a bottle, it may be lighter in weight than the corresponding untreated product. In addition, the increase in strength leads to a reduction in the amount of damage to the product (less number of cracks) during use.

It is assumed that the polymerized, cross-linked siloxane bonds are present in the coating and between the coating and the surface of the brittle oxide substrate. The coating, after bonding to the substrate, can close the cracks in the surface by creating a network of Si-O-Si bonds around surface blemishes. The formation of siloxane bonds in the area of ​​the blemishes increases the resistance of the product to breaking stress.

In order for the coating to actually restore or increase the strength of a sample that has previously been damaged, the effect of stress-concentrating flaws on the tensile load bearing surface must be minimized. This requires the partial or complete sealing of the flaws in the tensile load bearing surface. In the case of a pressure-tested glass package, the surface on which the tensile forces act is primarily the outer surface of the bottle, since the walls actually flex outward as the pressure increases. As a rule, it is on the outer surface that convex curves appear during loading.

However, the impact load on the specimen can be increased without restoring the strength of the substrate. This technique covers the surface that is exposed to impact, not the sides with tensile loads. (Impacts typically create tensile stresses on the inside of the package.) In this case, the mechanism is based on the ability of the coating to absorb impact energy, so that energy is not transferred to the substrate in the form of tensile stresses. The measured impact load causing failure is increased, but the flexural strength of the product does not change.

Commercially produced glass containers are typically coated with a metal oxide film just after fabrication using chemical vapor deposition; this is referred to as hot end coating (HEC). Typically, it is a tin oxide coating, although it may also be titanium oxide or an oxide of another metal, and may contain other components to improve the physical properties, e.g., electrical conductivity. The thickness of such a coating is usually around 50 - 125 -. The method according to the invention makes it possible to restore or increase the strength of damaged glass, whether or not the previously deposited HEC coating is present on the surface.

With respect to labeling ability, it will be appreciated that certain cured silane hydrolyzed coatings do not deteriorate labelability as previously described. The labeling ability is determined by the label peel test below.

A four-corner paper sticker is used, approximately 6 inches in size². The label is weighed before applying the casein glue designated 4242, available from National Starch. About 0.6 g of casein glue is applied to the underside (reverse side) of the label and spread over the label with a 5 mm rolling glass rod or other similar shape to evenly distribute the glue on the label. The label is pressed against the surface of a brittle oxide substrate and allowed to dry for at least 2 hours at room temperature. The sticker is torn by hand at each corner until a portion of the sticker is torn from the backing at each corner. The coating is considered to exhibit satisfactory labelability for the purposes of the invention when greater than about 50 wt. the sticker will remain on the surface of the brittle oxide substrate.

Preferably, the labelability (determined as the percentage by weight of a label remaining on the brittle oxide substrate surface) of the coated brittle oxide substrates of this invention is greater than about 60% by weight, and most preferably greater than about 70% by weight.

The maintenance of resistance to the adverse effects of moisture also demonstrates the substantial increase in strength provided by the hardened coating on brittle oxide substrates. In fact, the moisture resistance test provides a convenient way to do things

178 The coatings of the invention ensure that the coated surface of the brittle oxide retains increased or restored strength. The excellent and retained moisture resistance that the silane-based coatings of the invention can exhibit is usually dependent on the R group. One way to determine the effect of moisture on the coatings of the invention is to compare the strength of a coated brittle oxide substrate when the cured coating on the substrate has been for less than 3 hours at a relative humidity of typically about 40%, from the strength of the coated brittle oxide substrate itself after 30 days at humidity of 90%. In such moisture resistance tests, the cured coatings of the invention applied to brittle oxide substrates exhibit only about 50%, preferably about 20-30%, and most preferably 0-10% strength variation, which is excellent, especially for glass bottles subjected to high exposure to high temperatures. humidity in environments such as the southern United States.

It should be noted that not all hydrolyzed silane based coatings provide excellent moisture resistance when applied to a brittle oxide substrate. For example, for comparison, it can be stated that if a hydrolyzed silane-based composition in which R is a vinyl or methyl group is applied to a brittle oxide support and then cured, there will be a substantial increase in the strength of the support (e.g. an increase of 110% (symmetric ring test) when R is a vinyl group and by 200% (symmetric ring test) when R is a methyl group) and excellent resistance to moisture is obtained (e.g. 0% loss (100% strength retained) in the case of R is a vinyl group and 0% loss (100% strength retained in the case of R is methyl); however, if a hydrolyzed silane based composition in which R is 2- (3,4-epoxycyclohexyl) ethyl or glycidoxypropyl is applied to a brittle oxide substrate and then cured, there will be a substantial increase in the strength of the substrate (e.g. an increase of 200% (symmetric ring test) when R is 2- (3,4-epoxycyclohexyl) ethyl and by 200% (symmetric ring test) when R is glycidoxypropyl), but only moderate resistance to moisture will be obtained (e.g. loss 40-50% (retention of 50-60% strength) in the case when R is a 2- (3,4-epoxycyclohexyl) ethyl group and a loss of 90-100% (retention of 0-10% strength) in the case when R is a glycidoxypropyl group) .

It is even more interesting to compare the labeling ability of such coatings:

<td>R</td><td>Labeling ability</td>

<td>methyl</td><td> 0%</td>

<td>vinyl</td><td> 0-10%</td>

<td>2- (3,4-epoxycyclohexyl) ethyl</td><td> &gt;60%</td>

<td>glycidoxypropyl</td><td> &gt;60%</td>

However, as previously noted, the coatings applied to the brittle oxide substrate may be mixtures of one or more hydrolyzed silane based compositions.

Thus, a mixture was found to provide substantially increased strength combined with excellent labelability and moisture resistance. One excellent example is a mixture of a hydrolyzed silane based composition in which R is methyl and 2- (3,4-epoxycyclohexyl) ethyl. It is even more emphasized that in preparing such a mixture, none of the ingredients in the mixture deteriorate any of the required properties. For example the presence of MTMO does not deteriorate labeling ability.

Aqueous solutions containing compositions based on hydrolysed silanes according to the invention are non-flammable, especially as they contain essentially no organic solvents in the aqueous solution.

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When coating brittle oxide substrates, especially glass containers, the hydrolyzed silane-based composition preferably should not be visible on the packaging. The silane coating should not discolor or form texture during curing. Compositions based on hydrolyzed silanes according to the invention fulfill these criteria. It should be noted that fuzzy (slightly cloudy or fresco-like) coatings are desirable for some commercial applications. Coatings of the invention having such blurred appearance can be obtained by application at a suitable temperature (e.g., surface temperature of the brittle oxide substrate) of about 80 to about 100 ° C.

In addition, dyes can be added to the aqueous solution to obtain colored coatings. Examples of suitable dyes include Celestine blue, Bismark brown, and Eriochrome black.

In addition, dyes can be used in an aqueous solution as indicators of the degree of cure and surface coverage for spray application. Other ingredients such as UV blockers and fluorescent agents can also be incorporated into the aqueous solution. The use of a fluorescent agent makes it possible to obtain brittle "glow in the dark" oxide substrates.

The coatings according to the invention also show the ability to hide visible pitting defects in the surface of the substrate. This is particularly desirable in the case of multiple bottle refilling where whitish marks appear on the bottles as a result of repeated exposure to the filling lines.

The invention will now be illustrated in more detail by means of examples, the sole purpose of which is to illustrate the invention.

Example 1 In this example, soda-lime glass rods were incised with a Vickers diamond to give a surface spot of approximately 50 µm. From the bend-to-failure tests, the average strength of the samples was found to be 56 MPa. Samples with identical blemishes were sprayed with 10 wt.%. a solution of vinyltrimethoxysilane (VTMO) in water. The solution contained enough sulfuric acid to bring the pH to 3.0-3.4. The samples were then heat treated for 15 minutes at 200 ° C and bend tests were performed. The average strength of the samples increased from 56 to 90 MPa.

Example2. Example 2 is a modification of Example 1. In this example, the samples were also notched bars and 10 wt% was used as the solution. VTMO acidified as in Example 1. This solution further contained 0.75 wt. Triton Χ-102 non-ionic surfactant. After curing, the strength of the notched samples increased from 56 to 93 MPa.

Example 3. Example 3 is similar to Example 1 except that m-methyltrimctoxysilane (MTMO) was used as the silane. The average strength of the control samples was 62 MPa. After coating and hardening, the flexural strength increased to 96 MPa.

Example 4. Example 4 repeats Example 2 using MTMO. The mean strength of the controls was also 62 MPa, but for the reinforced samples the mean size was 103 MPa.

Examples 5 and 6. Examples 5 and 6 are a repetition of Examples 1 and 2, respectively, except that methacryloxypropyltrimethoxysilane (MPTMO) was used as the silane. In this case, the average strength of the control samples was 60 MPa.

After coating, the specimens were thermally cured as described above and additionally UV irradiated to increase the degree of cure. The reinforced specimens of Example 5 had an average strength of 126 MPa, and of Example 6-124 MPa.

Example 7. This example illustrates the processing of flat glass samples that were scored with a Vickcrs diamond to obtain controlled blemishes. The samples were cut to obtain a 90 µm blemish. These samples were coated with a silane solution containing three silanes in the same weight proportions. The total silane concentration in water was 10 wt%, such that the concentration of each silane was about 3.33 wt%. The solution contained enough sulfuric acid to bring the pH to 3.0-3.4. A non-ionic surfactant, Triton, was also added

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Χ-102 in an amount of 0.75 wt.% To improve wetting. The 1: 1: 1 solution contained glycidoxypropyl trimethoxysilane (GPTMO), 2- (3,4-epoxycyclohexyl) ethyl trimethoxysilane (CETMO) and MTMO.

The strength of the control samples was 45 MPa, and the samples after treatment with a 1: 1: 1 MPa solution, after two-stage curing consisting of curing at 125 ° C for 15 minutes, and then curing at 225 ° C for 10 minutes, which is about 3.5 times increase in endurance. This blend also found good labelability, even though it contained MTMO (usually poorly labeling).

Example 8. The same controls as described in Example 3 were fortified with a 1: 1 solution of GPTMO and CETMO, also at a total concentration of 10 wt.%. The solution contained enough sulfuric acid to bring the pH to 3.0-3.4. These samples were subjected to the same heat treatment as in Example 3. The strength of the samples increased from 45 MPa to 118 MPa as a result of the treatment, which means that the strength increased about 2.6 times.

Example 9. The same blemishes as described in Example 3 were made on the sidewalls of amber bottles. The average burst pressure of these scratched packages was 1.9 MPa. Scratched bottles were silane treated using 10 wt.%. CETMO solution and the same method of curing as in example 3. The average breaking strength of the treated scratched controls increased to 3.2 MPa, which means that the strength was increased by 68% over the scratched controls.

Example 10. Standard 12 oz beer bottles were scratched as described in Examples 3 and 9. The average burst pressure of these scratched packages was 1.9MPa. The samples were coated and cured using the 1: 1: 1 solution described in Example 7. The average tear strength increased from 1.9 MPa for the controls to 3.5 MPa for the treated samples.

Example 11. Lightweight 12 oz. Bottles were scratched as described above and coated with the 10% CETMO solution described in Example 9. The average burst pressure of the scratched controls was 1.5MPa. By spray coating followed by curing as in Example 3, the average burst pressure of the bottles was increased to 2.6MPa.

Example 12. 12 oz. Light bottles as supplied were coated with 10 wt. CETMO solution. The tear strength of the control samples was 1.6 MPa. In the case of the coated and cured samples, the average tear strength was 3.0 MPa.

Example 13-16 In these examples, flat soda-lime glass specimens were scratched with a Vickers diamond tip giving a 50 [mu] m spot as described in Example 1. These specimens were tested in a symmetrical ring arrangement. The average strength of the uncoated samples was 69 MPa.

Example 13. MPTMO suspension was prepared by adding silane to water acidified to pH 2.5 with a suitable acid, e.g. H₂SO₄% so as to obtain 10 wt. mixture. 0.5 wt.% Was added. Triton®-102 and the composition was allowed to stand for 24 hours at room temperature. After 24 hours, the condensed oligomer phase had separated so that a suspension was obtained. This slurry was dripped onto a flat area which was heat treated for 15 minutes at 125 ° C and then UV cured. The average strength of the flat glass was 223 MPa.

Example 14. 10 wt.% a suspension of methacryloxypropylmethyldiethoxysilane (MPMDEO) was prepared as described in Example 10 but with a surfactant concentration of 1% by weight. The slurry was dripped onto flat glass and the coating was then cured for 15 minutes at 125 ° C then 225 ° C for 10 minutes. The average strength of the treated flat glass samples was 143 MPa.

Example 15.10 wt. a slurry containing a 1: 1 mixture of dimethyl tetramethoxydisiloxane 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.

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The sample was cured in two steps as described in Example 14. The average strength of the treated flat glass samples was 193 MPa.

Example 16. 10 wt.% a slurry containing a 1: 1 wt. ditert-butoxydiacetoxysilane (DBDAS) and MPMDEO were prepared as outlined in Example 14 except that H₂SO₄ to adjust the pH to 3.5 and added 0.025 wt. Triton Χ-102 agent. The sample was cured in two steps as described in Example 12. The average strength of the treated flat glass samples was 152 MPa.

Example 17 In this example, flat samples of soda-lime glass were scored with a Vickers diamond to give a blemish of about 50 µm. These samples were tested in a symmetrical ring arrangement. The average strength of the uncoated samples was 69 MPa. 10 wt.% the solution of DBDAS in water was adjusted to pH 3.5 with acetic acid. The solution was used for drip coating on a flat glass sample, after which the product was thermally cured for 15 minutes at 125 ° C. The average strength of the cured samples was 133 MPa.

Example 18 Flat glass samples were prepared as described in Example 17. pH 10 wt.%. of the GPTMO solution in water was adjusted to 3.5 with sulfuric acid. The solution was stored for 2 weeks at room temperature after which the flat plates were dripped with the solution and cured first at 125 ° C for 15 minutes and then at 225 ° C for 10 minutes. The average strength was 219 MPa.

Example 19. Flat soda-lime glass specimens were scratched with a rounded diamond tip giving clearly visible blemishes. The average strength of the samples by the symmetrical ring method was 43 MPa.

pH 10 wt.% of the CETMO solution in water was adjusted to 3.5 with sulfuric acid. The scratched panels were dripped with the solution and cured first at 125 ° C for 15 minutes and then at 225 ° C for 10 minutes. The average strength was 61 MPa.

Example 20. Flat samples of soda-lime glass were scored with a Vickers diamond to give a blemish of about 50 µm. These samples were tested in a symmetrical ring arrangement. The average strength of the uncoated samples was 69 MPa. 10 wt.% Was prepared. a solution of N- (3-triethoxysilylpropyl) -4-hydroxybutyramide (HBTEO) in water and allowed to stand for 30 days. The pH of the solution was 9.5. The scratched tiles were coated with a drip solution and cured in two steps, first at 125 ° C for 15 minutes and then at 225 ° C for 10 minutes. The average strength after treatment was 266 MPa.

Example 21. Flat samples of soda-lime glass were incised with a Vickers diamond to give an approximately 50 µm spot. These samples were tested in a symmetrical ring arrangement. The average strength of the uncoated samples was 69 MPa.

Flat glass samples were dip coated with undiluted MPTOM and then cured by passing through a UV curing apparatus three times with an irradiation degree of 5.3 J / cm.² on the transition. The average strength after such treatment was 104 MPa.

Example 22 Flat soda-lime glass specimens were scratched as in Example 21, e.g. a 150 A thick coating of pyrolytically deposited SnO was produced₂. The samples were then relaxed to remove residual stresses. The strength of the tin oxide coated control samples was about 83 MPa.

Samples with SnO coating₂ then treated with 10 wt.%. MTMO solution in the manner described in examples 3 and 4, obtaining samples of strength 210 MPa.

Example 23. Flat samples of soda-lime glass were incised with a Vickers diamond to give a blemish of approximately 50 µm. These samples were tested in a symmetrical ring arrangement. The average strength of the uncoated samples was 69 MPa. 10 wt.% Was prepared. a solution of 3,3-dimethoxypropyltrimethoxysilane (DMPTMO) in water, and its pH was adjusted to 3.5. After standing for 2 hours at room temperature, one aliquot of the solution was used to drip the scratched plates. The tiles were cured at 125 ° C for 15 minutes and then at 225 ° C for 10 minutes. The average strength of the tiles after treatment was 88 MPa. Nuclear magnetic resonance * H (NMR) analysis of the DMPTMO solution showed only the -CH (OCH₃)₂ in silanotriol, signal at 4.41 ppm (triplct).

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Another aliquot of the solution after standing for 192 hours at room temperature was used to coat the other scratched plaques by drip coating and then cured as described above. The average strength of these plates was 256 MPa. NMR analysis of this solution showed the presence of -CH (OH) (CH₃), -CH (OH)₂ and -CHO in the silanotriol of approximate composition at 4: 4: 2 equilibrium, signals 4.55 (triplet), 490 (triplet) and 9.63 ppm (singlet), respectively.

Example 24. The invention was tested in a bottle production plant as follows: 120 16 oz glass beverage containers were tested for pressure resistance in an AGR apparatus providing a uniform pressure variation. The mean burst pressure was measured to be 2.9MPa with 15% of the bottles failing at pressures below 2.1MPa. The treatment process consisted of spraying a solution of the invention (specifically CETMO), heat curing at 230 ° C or above, and then applying a conventional cold end coating. 120 packages were tested for pressure resistance in the same manner as above; an average burst pressure of 490 3.5 Mpa (increase by 16%) was obtained with 6% damage at the pressure below 2.1 MPa (decrease by 57%).

Example 25 Cast glass, scratched with a Vickers apparatus, was drip coated with a 10% aqueous solution of 3-ureidopropyltrimethoxysilane (UPTMO), pH 3.4, containing 0.05% Triton®-102 surfactant. The samples were heat treated at 125 ° C for 15 minutes and then at 225 ° C for 10 minutes. The following strengths of symmetrical rings were obtained:

<td>no coating</td><td>66.1 MPa</td>

<td>with coating</td><td>176 MPa</td>

Example 26. Example 25 was repeated using 1,2-bis (trimethoxysilyl) ethane as the silane. The strength of the symmetric ring method of the control samples was 79.8 MPa. After coating and curing, the average strength by the symmetrical ring method was 136 MPa.

Example 27. Example 26 was repeated again but the heat treatment was only heating at 125 ° C for 15 minutes. The average strength after coating and curing increased from 79.8 MPa to 164 MPa.

Example 28. Example 25 was repeated except 1,2-bis (3-trimethoxysilylpropoxy) ethane was used as the silane. BTMOPE was obtained as follows.

Allyl bromide, 0.7 mol, was added dropwise over 1.5 hours to a stirred mixture of 0.33 mol of ethylene glycol, 1.25 mol of 50% aqueous sodium hydroxide and 0.025 mol of tributylmethyl ammonium chloride. The mixture was heated at 80-90 ° C for 12 hours. The mixture was cooled to 25 ° C and the aqueous phase separated and discarded. The organic phase was diluted with 5 volumes of diethyl ether, washed with a saturated aqueous sodium chloride solution and dried over sodium sulfate. 1,2-bis (allyloxy) ethane, BAOE, isolated by distillation under reduced pressure, bp 89-90 ° C at about 50 Torr.

A mixture of 0.075 mole BAOE and 50 µL of platinum divinyl complex in xylene (Huls America, cat # PC072) was heated to 85 ° C. To the resulting stirred mixture, trimethoxysilane, 0.160 mol (Aldrich Chem. Co.) was added dropwise over 2 hours under an inert atmosphere. The reaction mixture was stirred at 85 ° C for 2 hours then distilled under reduced pressure. BTMOPE was isolated as a fraction with a boiling point of 135-136 ° C at 0.25 Torr. After coating and curing, the average strength by the symmetrical ring method increased from 69.9 MPa to 201 MPa. ,

Example 29. Example 27 was repeated using the silane of example 28. The average strength of the coated and cured samples was 208.0MPa, while the average size of the controls was 69.9MPa.

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Example 30.0.5% Celestine Blue dye (CAS # 1562-90-9) was added to a 5% CETMO solution also containing 0.025% Triton Χ-102 surfactant. This solution was spray applied to 16 ounce beverage packages using 2.0 g of solution / bottle. The samples were then heat treated for 33 seconds in an infrared oven set at 700 ° C. Bottles with an even blue coating were obtained.

Example 31. To a 10% CETMO solution containing 0.05% Triton Χ-102 surfactant, 1 wt.% Of each was added. of Uvinul MS-40 (from BASF Corp.) and Tinopal CBS-X (from Ciba-Geigy Corp.). The solution was sprayed onto flat glass. The samples were heat treated as described in Example 25. The final coating thickness was 0.9 μιη. Ultraviolet light transmittance was measured before and after coating and curing. The following results were obtained:

<td rowspan="2">A sample</td><td colspan="2">% transmittance at λ</td>

<td>340 nm</td><td>380 nm</td>

<td>uncoated</td><td> 89</td><td> 90</td>

<td>coated</td><td> 5</td><td> 27</td>

Example 32. A silane mixture was prepared as follows:

g of Nafion perfluorinated acid resin, 2 g (0.0085 mol) of GPTMO and 2 g (0.11 mol) of deionized water were added to a plastic bottle at room temperature. After 15 minutes, a further 91.9 g of water was added, followed by 3 g (0.017 mol) of MTEO (methyltrimethoxysilane) and 0.1 g of Triton®-102 to make a total of 100 g of solution.

This formulation (after aging for 1 hour and 20 days) was sprayed onto 16-ounce beverage bottles in a bra simulating a 1-minute time on the production line with a surface temperature of 55 ° C (using an AGR line simulator). The bottles were cured at an average surface temperature of 225 ° C for 30 seconds. The burst pressure of the bottles was found to increase compared to the untreated control bottles by 51 and 71%, respectively.

0.6 g stickers (4 corners) were then affixed to the bottles and 0.6 g of adhesive was applied to the surfaces. The adhesive was allowed to cure for 16 hours (overnight) at room temperature. The bottles showed the ability to retain 75-80% of the label (cohesive fracture) after 4 attempts to peel the label (the label was torn off by hand at each corner until peeled off). In the case of the comparative formulation of 5 g MTEO and 0.1 g of Triton Χ-102, which was allowed to stand for 1 hour, applied in the same way to the same type of bottles, the labels did not stick (adhesive break).

Example 33. Rectangular alumina bars were tested in a three point bending test to test the suitability of the inventive method for strengthening them. Half of the alumina samples (n = 6) as controls were tested on the Instron set to three point bending. The other half of the samples were sprayed with the formulation containing 10 wt. CETMO / 0.025 wt.% % Triton X-102 / 0.025 wt. RP-40 agent (obtained from TH Goldschmidt, Germany) and then thermally cured using a two-stage heat treatment (15 minutes at 125 ° C, then 10 minutes at 225 ° C) achieving a strength increase of 21%.

In view of the results reported by Hashimoto et al in U.S. Patent No. 4,891,241, especially Comparative Examples 1, 2 and 3 at column 25, lines 27-29, which found no increase in strength when the coating was applied containing only silanes, the degree of strength increase obtained by the treatment described in the examples of the invention is surprising. As noted herein, no additional treatment such as that described by Hashimoto et al. Was applied, yet achieved a two-fold or greater increase in the strength of the treated glass compared to untreated controls, with the scattering of the observed reinforcement being relatively small. The growth achieved by the invention is particularly surprising in view of the statement by Hashimoto et al in column 5, lines 36 et seq.

178 796 19 where it is stated that treating the substrate with siloxane alone is not sufficient to achieve reinforcement, and that application of the polymer top coat is critical to achieve the stated reinforcement.

Other embodiments of the invention will become apparent to those skilled in the art from reading the description and practicing the invention disclosed therein. It should be considered that the description and examples merely illustrate the invention, the true scope and essence of which are merely indicated by the following claims.