Claims:I claim:
1. A colouring composition for a coloured glass, comprising:
50-70% by weight of Lead Oxide (Pb3O4);
20-40% by weight of Silicon Dioxide (SiO2);
8-12% by weight of Sodium Tetraborate (Na2B4O7);
1-3% by weight of Antimony Trioxide (Sb2O3);
0.2-1.8% by weight of Zirconium Dioxide (ZrO2); and
3-7% by weight of Cadmium (II) Selenide and Zirconium Silicate (combined under reducing conditions) (CdSe, ZrSiO4).

2. The colouring composition as claimed in claim 1, wherein colouring composition comprises:
50% by weight of Lead Oxide (Pb3O4);
40% by weight of Silicon Dioxide (SiO2);
10% by weight of Sodium Tetraborate (Na2B4O7);
2% by weight of Antimony Trioxide (Sb2O3);
1% by weight of Zirconium Dioxide (ZrO2); and
5% by weight of Cadmium (II) Selenide and Zirconium Silicate (combined under reducing conditions) (CdSe, ZrSiO4).

3. The colouring composition as claimed in any one of the preceding claims, wherein one or more of Antimony Trioxide (Sb2O3), Zirconium Dioxide (ZrO2) and Cadmium (II) Selenide and Zirconium Silicate (combined under reducing conditions) (CdSe, ZrSiO4) act as colouring agents.

4. The colouring composition as claimed in any one of the preceding claims, wherein colouring composition is in powder form, or in the form of pellets, tablets or granules.

5. The colouring composition as claimed in any one of the preceding claims, wherein a granule of the colouring composition as claimed in any one of the preceding claims has a density which ranges from 4 to 8 g/cm3, preferably between 6 and 8 g/cm3, a size which ranges between 1 and 15 mm, preferably between 2 and 10 mm and a humidity of less than 5% w/w, preferably less than 3% w/w.

6. The colouring composition as claimed in any one of the preceding claims, wherein the colouring composition produces a coral red coloured glass.

7. The colouring composition as claimed in any one of the preceding claims, wherein the colouring composition includes at least one of Tin oxide, Calcium oxide, Arsenic oxide for varying the opaque characteristics of glass formed using the colouring composition.

8. The colouring composition as claimed in any one of the preceding claims, wherein said colouring composition comprises one or more by weight:

copper (II)oxide--0.001-0.003%
iron(III)oxide-0.020.030%, preferably 0.030%
arsenic oxide-0.010-0.020%, preferably 0.015%,
calcium oxide-0.03-0.07%, preferably 0.05%
aluminium oxide-0.03-0.07%, preferably 0.05%
potassium oxide-0.01-0.04%, preferably 0.02%
maganisium oxide-0.01-0.04%, preferably 0.02%.

9. A glazing pane comprising a coloured glass sheet, wherein the coloured glass sheet has a composition as claimed in in any of the preceding claims.

10. A process of manufacturing a glass having the composition as claimed in claims 1-8.
, Description:FIELD OF THE INVENTION
The present invention relates to a method for manufacturing coloured glass and coloured glass thereof. More particularly, the present invention relates to method for manufacturing coral red coloured lead based glass and coral red coloured lead based glass thereof.

BACKGROUND OF THE INVENTION

Essentially two methods for manufacturing glasses by means of a sintering process are known by those conversant with current state of the art technology: the sol-gel process and a method employing powder technology.

One method that can be employed to produce glass by means of a sol-gel process is described in U.S. Pat. No.4,432,956. However, this patent only describes the production of silica glass manufactured at temperatures of 1300-1500° C.

In order to include further components in glass synthesis one can avail oneself of methods such as those described in patents DE 4129409 A1, EP 0233732 A1 and U.S. Pat. No. 5,091,115. All these methods are based on silicon alkoxides such as tetraethyl ortho silicate (TEOS) and other soluble compounds that as a rule are processed using alcoholic solvents. A base material for SiO2 can be, for example tetraethyl ortho silicate and the base materials for adding further glass components, such as B2O3, Al2O3, Na2O or P2O5, can be boric acid trimethyl ester, aluminium triisopropylate, sodium methylate, zinc-2,4-pentanedionat, tributyl phosphate, or other alkoxides.

A disadvantage with such glasses based on SiO2 is that the glass has less density and shine. Accordingly, a need exist for providing a method for manufacturing a glass that has high density has more shine in comparison to the existing glasses. It is required to manufacture a glass that is typical coral red in colour.

SUMMARY OF THE INVENTION:

In an embodiment, a colouring composition for a coloured glass is provided. The colouring composition comprises:
50-70% by weight of Lead Oxide (Pb3O4);
20-40% by weight of Silicon Dioxide (SiO2);
8-12% by weight of Sodium Tetraborate (Na2B4O7);
1-3% by weight of Antimony Trioxide (Sb2O3);
0.2-1.8% by weight of Zirconium Dioxide (ZrO2); and
3-7% by weight of Cadmium (II) Selenide and Zirconium Silicate (combined under reducing conditions) (CdSe, ZrSiO4).

In the preferred embodiment, the colouring composition comprises:
50% by weight of Lead Oxide (Pb3O4);
40% by weight of Silicon Dioxide (SiO2);
10% by weight of Sodium Tetraborate (Na2B4O7);
2% by weight of Antimony Trioxide (Sb2O3);
1% by weight of Zirconium Dioxide (ZrO2); and
5% by weight of Cadmium (II) Selenide and Zirconium Silicate (combined under reducing conditions) (CdSe, ZrSiO4).

In another embodiment, a glazing pane comprising a coloured glass sheet, wherein the coloured glass sheet has a composition as stated above.

A process of manufacturing a glass having the composition as stated above.

An object of the present invention is to provide a glass composition that result in an coral red coloured glass.

Another object is to provide a composition those results in glass having high density in comparison to the existing glasses.

To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.

Detailed Description:

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.

Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises...a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

Embodiments of the present invention will be described below in detail.

In an embodiment, a colouring composition for a coloured glass is provided. The colouring composition comprises:
50-70% by weight of Lead Oxide (Pb3O4);
20-40% by weight of Silicon Dioxide (SiO2);
8-12% by weight of Sodium Tetraborate (Na2B4O7);
1-3% by weight of Antimony Trioxide (Sb2O3);
0.2-1.8% by weight of Zirconium Dioxide (ZrO2); and
3-7% by weight of Cadmium (II) Selenide and Zirconium Silicate (combined under reducing conditions) (CdSe, ZrSiO4).
In the preferred embodiment, the colouring composition comprises:

50% by weight of Lead Oxide (Pb3O4);
40% by weight of Silicon Dioxide (SiO2);
10% by weight of Sodium Tetraborate (Na2B4O7);
2% by weight of Antimony Trioxide (Sb2O3);
1% by weight of Zirconium Dioxide (ZrO2); and
5% by weight of Cadmium (II) Selenide and Zirconium Silicate (combined under reducing conditions) (CdSe, ZrSiO4).

In an embodiment, a process to manufacture glass in accordance with the invention is provided. Glass is produced in a two-step process, and then shaped to make it suitable for a variety of applications. The first step is batch mixing. In batch mixing the mixture of ingredients to make up the glass, together with small quantities of various other minor ingredients) are mixed in a rotary mixer to ensure an even mix of ingredients and fed into the furnace. In the present case, the mixture of ingredients to make up the glass are known as major primary mixtures and the others are referred to as secondary minor mixtures. In the present invention, the primary major ingredients are listed below along with their weight percentage:
50-70% by weight of Lead Oxide (Pb3O4);
20-40% by weight of Silicon Dioxide (SiO2);
8-12% by weight of Sodium Tetraborate (Na2B4O7).

The secondary minor ingredients are listed below along with their weight percentage:
1-3% by weight of Antimony Trioxide (Sb2O3);
0.2-1.8% by weight of Zirconium Dioxide (ZrO2); and
3-7% by weight of mixture of Cadmium (II) Selenide and Zirconium Silicate (combined under reducing conditions) (CdSe, ZrSiO4).

Glass is made of different ingredients in differing proportions depending on the desired end
product, but most glass (except for some specialist glass) consists of all the "majors" mixed
with small quantities of some of the minors. Thus the minors are weighed first in a special
weighing hopper, and added to the majors with a little water. Water is necessary as in a very
dry mix the fines can blow off the batch as it enters the furnace and clog up the furnace flues.
The two tonne batch is then mixed for between two and three minutes in a rotary mixer,
before being transported to a batch hopper, from which it is slowly fed into a furnace.

In the present case, the secondary minor ingredients act as colouring agents and their weight percentage determines the colour of the final product. Colour results from two factors: the oxidation state of the glass, and the specific colourant additives used. Glass oxidation is promoted by the addition of carbon, and the degree of oxidation is measured on an arbitrary scale known as the carbon number. Clear glass has a carbon number of zero, dark green glass is -28 and amber is -52. Other variations of colour are achieved through the action of coloured materials that act as dyes. In the present case, mixture of Antimony Trioxide (Sb2O3), Zirconium Dioxide (ZrO2); and Cadmium (II) Selenide and Zirconium Silicate (combined under reducing conditions) (CdSe, ZrSiO4) when mixed in appropriate weight percentage as stated previously result in a unique coral red colour. As glass is fed continuously into the furnaces, each furnace has to be dedicated to producing glass of a particular recipe, and it takes 12-48 hours and a number of steps to alter the mix to change to producing a different type of glass of an acceptable standard.

The next step after mixing the ingredients and putting the mixture in the furnace involves heating the mixture to 1100-1550 degrees C, where the ingredients melt and various chemical reactions take place and CO2 and SO3 are evolved. The ingredients mixture is fed continuously into a furnace fired by natural gas, boosted by electricity when necessary. The glass is initially heated to 1100 degrees C, then raised to 1550 degrees C, at which temperature the mixture melts. The glass is then held above 1400 degrees C while it is refined and CO2 and SO3 are evolved. When no more gases are evolved the liquid is ready to be formed into the desired end product. The furnaces are kept at these precise temperatures by a cross-fired system which reduces heat loss and promotes a more even heat distribution in the molten glass.

Thereafter, the molten glass is cooled and shaped into appropriate size and thickness.

The advantage of using lead oxide is that it produces more shine and increases the density of the resultant glass. The colouring composition as claimed in any one of the preceding claims, wherein one or more of Antimony Trioxide (Sb2O3), Zirconium Dioxide (ZrO2) and Cadmium (II) Selenide and Zirconium Silicate (combined under reducing conditions) (CdSe, ZrSiO4) act as colouring agents.

In an embodiment, the colouring composition may be in powder form, or in the form of pellets, tablets or granules. In an embodiment, the process of forming the granules include providing a composition in accordance with the invention and humidifying the same. Thereafter, the process involves reducing the composition into granules, humidifying the colorant granules; and drying the granules. the humidification step is carried out in an atmosphere comprising from 15 to 35% by weight of water, preferably from 20 to 30% by weight of water.

In an embodiment, the colouring composition may also include the following in their weight percentages:
copper (II)oxide--0.001-0.003%
iron(III)oxide-0.020.030%, preferably 0.030%
arsenic oxide-0.010-0.020%, preferably 0.015%,
calcium oxide-0.03-0.07%, preferably 0.05%
aluminium oxide-0.03-0.07%, preferably 0.05%
potassium oxide-0.01-0.04%, preferably 0.02%
maganisium oxide-0.01-0.04%, preferably 0.02%.

In an embodiment, a granule of the colouring composition in accordance with the invention has a density which ranges from 4 to 8 g/cm3, preferably between 6 and 8 g/cm3, a size which ranges between 1 and 15 mm, preferably between 2 and 10 mm and a humidity of less than 5% w/w, preferably less than 3% w/w.

In another embodiment, a glazing pane comprising a coloured glass sheet having the composition as stated above is provided.

In another embodiment, the colouring composition includes at least one of Tin oxide, Calcium oxide, Arsenic oxide for varying the opaque characteristics of glass formed using the colouring composition.
The glass prepared using the above composition is coral red in colour and it is opaque in character and generally used, but not limited to, for jewellery and decorative items. However, it is to be noted that the glass produced using the above composition may be used for other purposes as well. Further, slight colour variation and opacity resulting from varying the percentage of the ingredients are within the scope of the invention.

The forgoing description gives examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts necessarily need to be performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of embodiments is at least as broad as given by the following claims.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component of any or all the claims.