Claims:We Claim:

1. A method for producing a coating layer on a glass surface, said method comprising the steps of:
sensitizing the surface to be coated by applying solution of a sensitizing agent selected from stannous chloride dihydrate, palladium chloride, and the like;
depositing on the surface to be coated a coating mixture comprising a first metal solution including at least one precious metal salt in a concentration in the range of 0.002 to 1.00 % by weight, sodium hydroxide in a concentration in the range of 0.0005 to 0.9 % by weight, and an amine in a concentration in the range of 0.001 to 0.9 % by weight, and a second reducing solution including a monosaccharide in a concentration in the range of 0.0005 to 0.9 % by weight; and
protecting the coated surface by applying a protective solution including a copper salt in a concentration in the range of 0.0005 to 0.8 % by weight, an amine in a concentration in the range of 0.001 to 0.8 % by weight, a strong acid in a concentration in the range of 0.0005 to 1.0 % by weight, and a zinc salt in a concentration in the range of 0.0005 to 0.9 % by weight; and
drying the coated surface at a temperature in the range of 20 to 180 °C for a duration in the range of 10 seconds to 10 minutes.

2. The method as claimed in claim 1, which comprises the step of rinsing the surface to be coated with a cleaning agent selected from an acid or a solvent before sensitizing the surface.

3. The method as claimed in claim 1, which comprises the step of allowing the coating mixture to contact the surface to be coated with continuous stirring for a duration in the range of 30 seconds to 9 minutes.

4. The method as claimed in claim 1, which comprises the step of allowing the protective solution to contact the coated surface for a duration in the range of 1 second to 10 minutes.

5. The method as claimed in claim 1, wherein the steps of sensitizing, depositing and protecting are carried out at a temperature in the range of 4 to 50 °C.

6. The method as claimed in claim 1, which comprises an additional step of spraying on the coated surface a layer of lacquer, silane, plastic, polyurethane, and the like.

7. The method as claimed in claim 1, which comprises an additional step of forming a protective layer on the coated surface by sol gel process.

8. The method as claimed in claim 1, wherein said precious metal is selected from silver, gold, nickel, copper, platinum, zinc, palladium, rhodium, ruthenium and the like.

9. The method as claimed in claim 1, wherein said monosaccharide is selected from glucose, fructose, sucrose and dextrose.

10. The method as claimed in claim 1, wherein said amine is selected from diethanol amine, triethanol amine, ammonia, diethylene triamine, triethylene tetra amine and ammonium nitrate.

11. The method as claimed in claim 1, wherein said copper salt is selected from copper sulfate and copper nitrate.

12. The method as claimed in claim 1, wherein said strong acid is selected from sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid, and the like.

13. The method as claimed in claim 1, wherein said zinc salt is selected from zin oxide, zinc sulfate, zinc acetate, and the like.

14. The method as claimed in claim 1, which comprises forming the coating layer on the glass surface by spraying solution to be coated directly on the glass surface for a period in the range of 10 seconds to 20 minutes.

15. The method as claimed in claim 1, which comprises forming the coating layer on the glass surface by depositing solution to be coated on the glass surface with rotation for a period in the range of 10 seconds to 20 minutes at a rotation speed in the range of 30 rpm to 300 rpm.
, Description:FIELD OF THE INVENTION
The present invention relates to a method for coating a transparent or translucent material. More particularly, the present invention relates to a method for coating a glass bottle by partially or completely coating the inside of the bottle.

BACKGROUND
Today, the aesthetics of a bottle play as much an important role in the buyer’s decision to purchase a particular product as the product or the brand itself. The aesthetics are more likely to make a first impression on the consumer, and thereby cause an impulsive reflux of purchasing by the consumers. Thus, in the industry, especially in the cosmetics, alcohol and perfumery industry, the manufacturers seek to give the best possible aesthetics and packaging to their products by way of original shapes and decorations to appeal the consumers.

In past several methods have been developed for coating the inside of a bottle. A traditional method for decorating an inside of a transparent bottle comprises using a color lacquer which is sprayed inside the bottle. European Patent No. 1599295 teaches one such method for decorating a glass flask from the inside. In the method a layer of lacquer is created on the inner surface of the flask by spraying a mist of liquid or powder from a nozzle introduced into the flask to create reduced pressure. By using this method, it is possible to make an inner decoration, that is, a single decorating coating layer or multiple coating layers.

Typically, the lacquers used are liquid epoxy or polyurethane lacquers or lacquers made by using a solvent-free powder of the epoxy, polyurethane, polyester or polyethylene, and derivatives thereof. A drawback of such coating is that the chemical nature of the decorating layers can be incompatible with the perfumes or cosmetics which are likely to fill the decorated bottles, causing the perfumes or cosmetics to be polluted or degraded.

To prevent this contamination, in a final step, a layer capable of acting as a barrier can be deposited on the lacquer layer. The French patent 2889485 teaches a method for decorating a glass bottle which involves forming a lacquer coat on an inner surface of a bottle by spraying a fog of an enamel in the form of powder or liquid inside the container and by application of an electro-magnetic field around the container. The method, however, includes a baking step which involves heating at temperatures as high as 800 °C, which step makes the method costly and unfeasible on all glass surfaces.

There is therefore need for a novel method for decorating a glass bottle from the inside, which overcomes the afore-noted drawbacks in conventional methods and provides not only an elegant decoration but also protects the product filled in the bottle from any contamination by creating a barrier layer and isolating the product.

SUMMARY OF THE INVENTION
Accordingly, a primary object of the present invention is to provide a method for decorating an inner surface of a glass bottle by forming a partial or complete inner coating, which coating though permanently contacting the content of the bottle, that is a perfume, alcohol, creams, lotions, cosmetics and the like, is chemically inert and thereby does not cause any possible migration detrimental to the quality of the said contents, as for example detrimental to the fragrance, color, usability, efficacy or preservation of the contents thereof.

Another object of the present invention is to provide a method for coating an inner surface of a glass bottle in which a colored pattern is formed on said inner surface of composition including one or more metallic oxides of silver, gold, nickel, copper, platinum, zinc, palladium, rhodium, ruthenium and the like.

An additional object of the present invention is to provide a method for coating an inner surface of a glass bottle which is simple and economical.

Other objects, aspects and advantages of the present invention will be more apparent from the following description.

According to the present invention the method for producing a coating layer on a glass surface comprising the steps of:
sensitizing the surface to be coated by applying solution of a sensitizing agent selected from stannous chloride dihydrate, palladium chloride, and the like;
depositing on the surface to be coated a coating mixture comprising a first metal solution including at least one precious metal salt in a concentration in the range of 0.002 to 1.00 % by weight, sodium hydroxide in a concentration in the range of 0.0005 to 0.9 % by weight, and an amine in a concentration in the range of 0.001 to 0.9 % by weight, and a second reducing solution including a monosaccharide in a concentration in the range of 0.0005 to 0.9 % by weight; and
protecting the coated surface by applying a protective solution including a copper salt in a concentration in the range of 0.0005 to 0.8 % by weight, an amine in a concentration in the range of 0.001 to 0.8 % by weight, a strong acid in a concentration in the range of 0.0005 to 1.0 % by weight, and a zinc salt in a concentration in the range of 0.0005 to 0.9 % by weight; and
drying the coated surface at a temperature in the range of 20 to 180 °C for a duration in the range of 10 seconds to 10 minutes.

The method may comprise the step of rinsing the surface to be coated with a cleaning agent selected from an acid or a solvent before sensitizing the surface.

Preferably, the method of present invention includes allowing the coating mixture to contact the surface to be coated with continuous stirring for a duration in the range of 10 seconds to 9 minutes. Additionally, the method includes allowing the protective solution to contact the coated surface for a duration in the range of 1 second to 10 minutes. More preferably, the steps of sensitizing, depositing and protecting are carried out at a temperature in the range of 4 to 50 °C.

According to the present invention, the method may further comprise the additional step of spraying on the coated surface a layer of lacquer, silane, plastic, polyurethane, and the like. Alternatively, the method may comprise an additional step of forming a protective layer on the coated surface by sol gel process.

According to the present invention, the precious metal can be selected from silver, gold, nickel, copper, platinum, zinc, palladium, rhodium, ruthenium and the like. The monosaccharide can be selected from glucose, fructose, sucrose and dextrose. The amine can be selected from diethanol amine, triethanol amine, ammonia, diethylene triamine, triethylene tetra amine and ammonium nitrate. The copper salt is preferably selected from copper sulfate and copper nitrate. The strong acid is selected from sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid, and the like. The zinc salt can be selected from zin oxide, zinc sulfate, zinc acetate, and the like.

Preferably, the method for forming the coating layer on the glass surface involves depositing the solution to be coated on the glass surface with rotation for a period in the range of 10 seconds to 20 minutes at a rotation speed in the range of 30 rpm to 300 rpm. Alternatively, the method for forming the coating layer on the glass surface involves spraying the solution to be coated directly on the glass surface for a period in the range of 10 seconds to 20 minutes.

DETAILED DESCRIPTION OF THE INVENTION
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting examples in the following description. The examples used herein are intended merely to facilitate an understanding of the ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The description herein after, of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

The present invention provides a method for coating a transparent or translucent surface, particularly glass surface, and more particularly an inner surface of a glass bottle, jar, pot, vase, container, tube, etc. The method of the present invention can be used to partially or completely coat the inner surface of the glass bottle, jar, pot, vase, container or tube. The coating according to the present invention is chemically inert and is compatible with alcohol, perfumes, cosmetics, creams, lotions, and the like, that is, the coating does not contaminate the contents of the bottle or container to affect its color, efficacy or quality.

According to the method of the present invention, the coating layer is formed on the inner surface of the bottle, jar, pot, vase or tube (hereafter termed as a container). This inner coating is made to contact the product of the container. According to the method, at least one decorating layer is formed on the inner surface of the container, knowing that, several coating layers may be formed. The layer contacting the product will be an inert layer, having properties close to those of glass.

Depending upon type of the container, particularly, the dimension of the container neck, the following methods may be used for forming the coating layer.

The method of coating may involve securing the container movably to a clamping device. The material to be coated is then fed to the container, manually or automatically, in defined quantities. During the coating process, the container is sealed by a head made of rubber, resin, glass or polymer. To deposit the material uniformly on the inner surface of the container, the container is rotated vertically and horizontally, in clockwise or anticlockwise direction. The material to be coated preferably has a low viscosity to allow uniform spreading on the surface. The rotation may be continued for a period between 10 seconds to 20 minutes at a speed between 30 rpm to 300 rpm to obtain the desired coating layer.

Alternatively, the method of coating may involve spraying on the inner surface of the container, directly onto the glass, by using a low pressure air gun having an extension which can be introduced in the container, with a spraying nozzle. During the spraying, the nozzle and the bottle can be moved relatively to each other in order to deposit a homogeneous layer. The nozzle can also be moved vertically with rotation. Additionally, the nozzle can be moved vertically and the bottle can be evenly rotated about an axis.

The method for producing the coating layer on the glass surface in accordance to the present invention comprises a preliminary step of sensitizing the surface to be coated by applying solution of a sensitizing agent. The surface to be coated is first cleaned by rinsing with a cleaning agent to remove any dirt, oil or impurity. The cleaning agent can be an acid or a solvent. The surface to be coated is then washed with demineralized water to remove any residue of the cleaning agent. Post-washing the surface to be coated is sensitized. The sensitizing agent is selected from stannous chloride dihydrate or palladium chloride. A solution of the sensitizing agent in a concentration in the range of 0.001 to 0.8 % by wt. with demineralized water is applied to the surface to be coated. The sensitizing of the glass surface assists in adhering the metal salt to the surface.

A coating mixture is then deposited on the sensitized surface. The coating mixture comprises a first metal solution and a second reducing solution. The first metal solution includes at least one precious metal salt in a concentration in the range of 0.002 to 1.0 % by weight, sodium hydroxide in a concentration in the range of 0.0005 to 0.9 % by weight, and an amine in a concentration in the range of 0.001 to 0.9 % by weight. The second reducing solution includes a monosaccharide in a concentration in the range of 0.0005 to 0.9 % by weight. The precious metal salt can be a salt of any of the precious metals selected from silver, gold, nickel, copper, platinum, zinc, palladium, rhodium, ruthenium and the like. The amines can be selected from diethanol amine, triethanol amine, ammonia, diethylene triamine, triethylene tetra amine and ammonium nitrate. The monosaccharide in the second reducing solution can be selected from glucose, sucrose, fructose or dextrose. The coating mixture is contacted with the sensitized surface for a duration between 30 seconds to 9 minutes with continuous stirring. The stirring can be manual or automatic. Any excess coating mixture can be removed from the surface.

The coated surface is then protected by applying a protective solution. The protective solution comprises a copper salt in a concentration in the range of 0.0005 to 0.8 % by weight, an amine in a concentration in the range of 0.001 to 0.8 % by weight, a strong acid in a concentration in the range of 0.0005 to 1.0 % by weight, and a zinc salt in a concentration in the range of 0.0005 to 0.9 % by weight. The copper salt is preferably selected from copper sulfate and copper nitrate. The amines can be selected from diethanol amine, triethanol amine, ammonia, diethylene triamine, triethylene tetra amine and ammonium nitrate. The strong acid can be an acid selected from sulfuric acid, nitric acid, hydrochloric acid or hydrofluoric acid. The zinc salt can be selected from zin oxide, zinc sulfate or zinc acetate. The protective solution is made in two parts, viz., a first part containing the copper salt, amine and strong acid; and a second part containing the zinc salt. The ratio of the first part to the second part in the protective solution is in the range of 5:1 to 10:1. The protective solution is contacted with the coated surface for a duration between 1 second to 10 minutes. Any excess protective solution can be removed from the surface.

The temperature during the process is maintained in the range of 4 to 50 °C. Further to the application of the protective solution to the coated surface, the coated surface is dried in an oven at a temperature in the range of 20 to 180 °C for a duration between 10 seconds to 10 minutes.

The method may comprise an additional step of spraying on the coated surface a layer of lacquer, silanes, plastic, polyurethane, and the like. Furthermore, the coated surface may be protected by forming a protective layer on the coated surface by sol gel process.

EXAMPLE:
The invention will now be explained by way of a non-limiting example which in no way limits the scope and ambit of the present invention.

Process for metalizing inner surface of a glass bottle by using silver nitrate:
The inner surface of the glass bottle was rinsed with a cleaning agent. The cleaning agent was removed and the glass bottle was rinsed with demineralized water. The inner surface was then sensitized with a sensitizing solution of 5 gms stannous chloride dihydrate in 1 litre of demineralized water.

Preparing a metal solution by combining a first solution of 2 gms silver nitrate in 0.5 litre of demineralized water and a second solution of 0.5 gms sodium hydroxide and 5 ml diethanol amine in 0.5 litre of demineralized water. Adding 5 ml of diethanol amine to make the metal solution clear.

Preparing a reducing solution of 10 gms of fructose in 1 litre of demineralized water.

Obtaining the coating mixture by combining the metal solution and the reducing solution in a ratio of 5:1. Applying the coating mixture to the inner surface of the bottle for 2 minutes at a temperature of about 20 – 37 °C with continuous stirring. Removing the excess coating mixture from the bottle.

Preparing a protective solution by combining a first solution containing 3 gms copper sulfate, 5 ml diethylene triamine and 5 ml nitric acid in 2 litre of demineralized water, and a second solution containing 3 gms zinc sulfate in 1 litre of demineralized water. The first solution and the second solution were combined in the ratio 5:1 in the protective solution. The protective solution was applied to the inner surface of the glass bottle for 2 minutes at a temperature of about 10 – 40 °C. The excess protective solution was removed from the bottle.

The coated inner surface was then dried in an oven at a temperature of about 40 – 120 °C for 2 minutes. The dried coated surface was additionally protected by forming a secondary protective layer on the coated surface by sol gel process.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the invention as it existed anywhere before the priority date of this application.

Embodiment of the present invention is applicable over a wide number of uses and other embodiments may be developed beyond the embodiment discussed heretofore. Only the most preferred embodiments and their uses have been described herein for purpose of example, illustrating the advantages over the prior art obtained through the present invention; the invention is not limited to these specific embodiments or their specified uses. Thus, the forms of the invention described herein are to be taken as illustrative only and other embodiments may be selected without departing from the scope of the present invention. It should also be understood that additional changes and modifications, within the scope of the invention, will be apparent to one skilled in the art and that various modifications to the composition described herein may fall within the scope of the invention.