SODA LIME GLASS COMPOSITIONS AND PROCESS FOR MANUFACTURING CONTAINERS MADE FROM SAID COMPOSITIONS The present invention relates to soda lime glass compositions and process for manufacturing containers made from the compositions. In particular, the invention relates to soda lime glass compositions including rare earth elements to affect the light transmission properties of soda lime glass.
Glass packaged products which are light sensitive have traditionally been sold in amber glass containers. This was done so that ultraviolet (U.V.) light could not be absorbed through the glass and degradation of the product under the action of ultraviolet light was therefore avoided. Most beverages and many foodstuffs are prone to U.V. degradation resulting in greatly shortened shelf life. It is desirable to be able to produce clear flint glass containers which block U.V. light and prevent degradation of the product held in the container.
It has been discovered that rare earth elements when included in an appropriate amount in flint and green glass lead to production of glasses which blocks U.V. light. It has also been discovered that inclusion of certain rare earth element(s) in pre-determined amount(s) also cause a fluorescent effect in clear flint glass.
Selenium has traditionally been used in the production of flint glass to make the glass appear clear. However, Selenium has become very expensive and the discovery of the advantageous effects of including rare earth elements in the glass provides an alternative to Selenium by using appropriate amounts of suitable rare earth elements to produce a combined clarity, U.V. blocking and fluorescent effect in clear flint glass.
The present invention has applications not only in the production of flint glass containers, including bottles, but also in the production of "flat" glass, the term used in the industry to refer to window glass or anv glass produced in flat form, including spectacles.
OPEN TO PUBLIC INSPECTION UNDER SECTION 28 ANfl RULE 23 It 0503 1 3 The Rare Earth Elements (REE) are made up of two series of elements, namely, the Lanthanide and Actinide Series.
The Rare Earth Elements consist of the following elements: Lanthanide Series Actinide Series Lanthanum (La) Cerium (Ce) Praseodymium (Pr) Neodymium (Nd) Promethium (Pm) Samarium (Sm) Europium (Eu) Gadolinium (Gd) Terbium (Tb) Dysprosium (Dy) Holmium (Ho) Erbium (Er) Thulium (Tm) Ytterbium (Yb) Lutetium (Lu) Actinium (Ac) Thorium (Th) Protactinium (Pa) Uranium (U) Neptunium (Np) Plutonium (Pu) Americium (Am) Curium (Cm) Berkelium (Bk) Californium (Cf) Einsteinium (Es) Fermium (Fm) Mendelevium (Md) Nobelium (No) Lawrencium (Lw) Each individual rare earth element (REE) will produce a specific optical effects in the base glass. These effects can be exploited in certain applications. When used in combination, certain REE can be tailored to give the desired effect, such as the addition of Praseodymium (Pr) and Neodymium (Nd) to give the strong dichroic glass.
The present invention provides soda lime glass compositions having pre15 determined light transmission properties, the compositions including at least one IE 0503 1 3 rare earth element or a compound thereof in an appropriate amount to affect the light transmission properties of the glass.
The present invention also provides a process for manufacturing a soda lime glass having pre-determined light transmission properties, the process comprising the step of including in the composition at least one rare earth element, or a compound thereof.
The at least one rare earth element may be included in the form of the elemental oxide.
Advantageously, Cerium (Ce), Praseodymium (Pr), Neodymium (Nd) and Erbium (Er) are of particular use for influencing colour in producing flint glass.
In another aspect of the invention, there is provided soda lime glass compositions including rare earth elements or compounds thereof with other elements, preferably, Titanium. The combination of rare earth elements or compounds thereof, (especially oxides thereof) with Titanium provides an advantageous U.V. blocking effect.
Ideally, the glass can be in the form of a container or alternatively can be formed as "flat" glass.
The rare earth elements do not have to be pure and may include some contaminants that do not adversely affect the glass making process.
Preferably, the components are added within the following ranges with the total adding up to 100% by weight, including elemental oxides whose percentage lies under practical detection limit: S1O2 AI2O3 - 74% by weight 0.5 - 3.0% by weight IE 05 0 3 1 3 CaO 8.0 -12.0% by weight MgO 1.0 - 5.0% by weight Na2O 10.0-15.0% by weight K2O 0.0 - 3.0% by weight Fe2O3 0.0 - 0.5% by weight S03 0.01 - 0.6% by weight Advantageously, one or more of the following rare earth elements are also included within the range indicated below so as to produce the desired UV protective, dichroic and/or fluorescent glasses: Nd2O3 0.0-10.0% by weight CeO2 0.0 -10.0% by weight Pr2O3 0.0 -10.0% by weight Εγ2Ο3 0.0 -10.0% by weight Ideally, the glass having the ability to block UV light at specific wavelength contains the rare earth elements Erbium (Er) and Praseodymium (Pr). Glass containing these rare earth elements fluoresces a green/yellow colour under a UV light source.
Preferably, the compositions of the soda lime glass which is capable of blocking ultraviolet (U.V.) light and which fluoresces include the following components within the ranges indicated: Sio2 68 - 74% by weight AI2O3 0.5 - 3.0% by weight CaO 8.0 -12.0% by weight MgO 1.0- 5.0% by weight Na2O 10.0 -15.0% by weight K2O 0.0 - 3.0% by weight Fe2O3 0.0 - 0.5% by weight IE 0503 1 3 so3 0.01 - 0.6% by weight Pr2O3 0.0 -10.0% by weight Er2O3 0.0 -10.0% by weight In an alternative embodiment of the glass in accordance with the invention, the compositions of soda lime glass which demonstrates dichroic properties includes the following components within the ranges indicated: SiO2 68 - 74% by weight AI2O3 0.5 - 3.0% by weight CaO 8.0 -12.0% by weight MgO 1.0 - 5.0% by weight Na2O 10.0 -15.0% by weight K2O 0.0 - 3.0% by weight Fe2O3 0.0 - 0.5% by weight SO3 0.01 - 0.6% by weight Pr2O3 0.0 -10.0% by weight Nd2O3 0.0 -10.0% by weight The addition of Cerium (Ce) allied with Titanium (Ti) can produce a shift in the UV edge, reducing UV transmission to a minimum in the correct formulations. Specific identified wavelengths can be excluded from the glass by use of the other rare earth elements depending on the desired performance.
Advantageously, the following fluorescence’s are possible... (a) Inclusion of praseodymium (Pr) in the soda lime glass composition gives a number of results depending on the light source, white light will give yellow green fluorescence, and UV or green/yellow light is reported to give orange fluorescence, IE 0503 1 3 (b) Neodymium (Nd) fluoresces red yellow in soda lime glasses, (c) Europium (Eu) will fluoresce either a brilliant red or a weaker green depending on the chemistry of the glass, (d) Samarium (Sm) will also cause the glass to fluoresce giving pink/orange light but the total iron content of the glass needs to be low to prevent the effect being ‘quenched’. (e) Ceria will also fluoresce into the blue region, and this may be the one of most interest, but there are requirements to control the glass chemistry. (f) Uranium also gives excellent green/yellow fluorescence in soda lime silica glasses but has issues for commercial uses because of its radioactivity. However, a lot of the citron yellow glass from the 50’s and 60’s is based on adding uranium to the glass.
The present invention will now be described more particularly with reference to the accompanying drawings.
In the drawings; Figure 1 is a schematic diagram of the regenerative furnace included in the apparatus used for producing the soda lime glasses in accordance with the present invention; Figure 2 is a further schematic diagram of the furnace; Figure 3 is a schematic diagram of the forehearth of the apparatus; Figure 4 is a schematic diagram of the feeder of the apparatus; ΙΕ ο 3 0 3 1 3 Figure 5a, b, c are schematic diagrams showing formation of different shapes of containers using a container forming apparatus; Figure 6 is a graphical representation of the annealing process; Figure 7 is a light transmission curve for fluorescent glass of the composition described in Example 1 hereinbelow; Figure 8 is a light transmission curve for the glass with dichroic properties of the composition described in Example 2 hereinbelow; and Figure 9 is a light transmission curve for the glass with U.V. protective properties and having the composition of Example 3 hereinbelow.
The apparatus used for manufacturing the glass in accordance with the present invention will now be described: Referring now to Figure 1, the apparatus for manufacturing containers made of the compositions of the invention is indicated generally by the reference numeral 1. The apparatus 1 includes raw material silos 2 (for clarity, only one silo is shown in the drawing). The apparatus 1 also includes a regenerative furnace 3 having an entry port 4 and an exit port 5. Raw materials are fed into the furnace 3 through the entry port 4 and the raw materials are melted to produce molten glass within the furnace. The temperature of the molten glass is 1500°C in the lower half of the furnace. In the upper half of the furnace there is a combustion chamber which includes firing ports 6. The furnace includes a narrowed section 10, known as "the throat". Molten glass flows through the throat 10 to the working end 11 of the furnace and from there, the molten glass flows out the exit port 5 to one of three forehearths 12 (only one is showing in the drawings). The forehearth 12 delivers the molten glass to each of a number of feeders 13 (only one of which is shown in the drawings) each feeder then delivers the molten glass to a bottle making apparatus. In Figure 4, the feeder is indicated generally by reference numeral 13 and consists of a plunger 130 moveable within a chamber 131. The feeder 13 also includes an orifice ring 132 and a shearing mechanism consisting of two reciprocating blades 133,134 for breaking off a measured amount of molten glass. This measured amount is referred to as a "gob" of molten glass 15. The "gob" of molten glass 15 is then delivered to the glass making apparatus for forming into a container of predetermined shape, as shown in Figures 5a, 5b and 5c. After being formed in the glass making apparatus in the manner shown in Figures 5a, 5b or 5c the formed bottles are then annealed in an apparatus called a lehr indicated generally by reference numeral 20. The bottles are passed along a conveyor line from the hot end 21 to the cold end 22 of the lehr 20.
Having described the apparatus used, the composition of the soda lime glasses of the invention and the process for production of the soda lime glasses will now be described in the following Examples: EXAMPLE 1 A composition for the UV protective and Fluorescent glass is as follows: SiO2 70.76% by weight AI2O3 1.25% by weight CaO 11.70% by weight MgO 1.12% by weight Na2O 13.50% by weight K2O 0.35% by weight Fe2O3 0.08% by weight SO3 0.14% by weight Pr2O3 0.6% by weight CeO 0.1% by weight The light transmission curve for the glass of this composition compared with that of known flint glass is shown in Figure 7.
IE 0 5 0 3 1 3 The Glass Manufacturing Process The process for manufacturing flint glass containers having U.V. and fluorescent properties is as follows: When describing the glass manufacturing process for manufacturing containers it is useful to describe the process in four stages, namely, charging, melting, refining and homogenizing. 1. Charging: The charging operation consists of the feeding of mixed batch (Sand, Soda Ash, Limestone, and Cullet etc) into the rear of the furnace melting chamber. This furnace melting chamber comprises a rectangular refractory box, including the lower half which comprises the molten glass, glass bath and the upper half which comprises the combustion space.
The mixed batch is charged into the furnace 3 to match the rate that melted glass is being drawn off at the bottle forming apparatus. The charging system is controlled to ensure a uniform batch cover across the width of the furnace 3 and also at a consistent depth. 2. Melting: Once the mixed batch has been charged into the furnace, the melting operation begins. In the regenerative furnace, the melting operation takes place over the first two-thirds of the furnace 3, and the main source of heat comes from flames in the combustion space above the batch. The flame temperature is higher than that of the furnace structure, the batch piles and molten glass. Heat is therefore transferred by radiation and convection, from the flames to the furnace structure, batch piles and the molten glass. ΙΕ ο 5 0 3 1 3 The main mode of heat transfer is by radiation. Below glass level, heat is transferred to the underside of the batch by radiation, conduction and convection from the molten glass.
Temperature distribution inside a furnace is not uniform, and therefore differences in temperature give rise to temperature gradients, which in turn encourage convection currents to be established both laterally and longitudinally in the glass bath.
Along with the application of heat and the physical mixing of glass and batch by convection, there are also a number of chemical reactions taking place. As the batch temperature rises, the following reactions take place. > Evaporation of free water from the materials > Formulation and loss of gasses such as CO2, SO2 etc > Formulation of liquids from the melting and reactions of individual batch materials.
The melting phase of the process is said to be complete when the molten glass is free of any unmelted material. 3. Refining: The refining stage is concerned with the removal of bubbles from the melt. During the stages of charging and melting gases become entrained in the batch material and also evolve from reactions in the glass melt. These bubbles contain various percentages of CO2, SO2, etc although the highest percentage is usually CO2. By controlling the temperature gradients inside the furnace, influence can be exerted over the glass viscosity (decreases with increasing temperature) this encourages bubbles to rise to the surface collecting smaller bubbles enroute and also combining with others to increase buoyancy and rate of rise. This thermal refining process is also enhanced by the addition of sulphates to the batch. As these ΙΕ ο 5 Ο 3 1 3 decompose later in the melting process, again rising to the surface, collecting smaller bubbles making them grow and rise to the surface quicker, whilst some will be absorbed into the molten glass. 4. Homogenising: At this stage the glass is ready to be fed into the distribution channels via the furnace throat ready for temperature conditioning.
EXAMPLE 2 A composition for the dichroic glass is as follows: SiO2 68.00% by weight AI2O3 1.15% by weight CaO 10.80% by weight MgO 1.03% by weight Na2O 12.46% by weight K2O 0.32% by weight Fe2O3 0.07% by weight SO3 0.13% by weight Pr2O3 3.30% by weight Nd2O3 4.40% by weight The light transmission curve for the glass of this composition compared with that of known flint glass is shown in Figure 8.
The process for production of the dichroic glass is the same as that already described above in Example 1.
EXAMPLE 3 An alternative example of a glass composition which provides protection from U.V. light is as follows: IE 0503 1 3 S1O2 68 - 74% by weight AI2O3 0.5 - 3.0% by weight CaO 8.0 -12.0% by weight MgO 1.0- 5.0% by weight Na2O 10.0 - 15.0% by weight K20 0.0 - 3.0% by weight Fe2O3 0.0 - 0.5% by weight SO3 0.01 - 0.6% by weight CeO2 0.0 -10.0% by weight T1O2 0.0 -10.0% by weight The light transmission curve for the glass of the composition of Example 3 compared with that of known flint glass is shown in Figure 9.
The process for production of this glass composition is the same as that described in Example 1.
It will of course be understood that the present invention is not limited to the specific details herein described which are given by way of example only, and that various alterations and modifications may be made without departing from the scope of the invention.
MACLACHLAN & DONALDSON, Applicant’s Agents, 47 Merrion Square, DUBLIN 2. 1Z9 ΙΕ ο 5 Ο 3 1 3 CM FIGURE 1 2/9 IE ο 5 Ο 3 1 3 — — ~ί ι Ί Ί ΠΊ r FIGURE 2 3/9 ΙΕ ο 5 Ο 3 1 3 Making Apparatus ΙΕ ΰ 5 0 3 1 3 4Z9 130 Bottle Making Apparatus /9 IE 0 5 0 3 1 3 BLOW σ> ίΖ FIGURE 5 IE Ο 5 Ο 3 1 3 6/9 CJ Cl o Cl FIGURE 6 7/9 ΙΕ ο 5 Ο 3 1 3 Example 1 Known Flint Glass 100 ΙΕ ο 5 Ο 3 1 3 8/9 Ο Known Flint Glass-Example 2 ΙΕ ο 5 Ο 3 1 3 9/9 ’>* • I* *«.
The following replacement pages 12,13 & 14 were filed on 11 May 2006 IE ο 5 Ο 3 1 3 SiO2 68 - 74% by weight AI2O3 0.5 - 3.0% by weight CaO 8.0 -12.0% by weight MgO 1.0- 5.0% by weight Na2O 10.0 -15.0% by weight K20 0.0 - 3.0% by weight Fe2O3 0.0 - 0.5% by weight SO3 0.01 - 0.6% by weight CeO2 0.0 -10.0% by weight TiO2 0.0 -10.0% by weight The light transmission curve for the glass of the composition of Example 3 compared with that of known flint glass is shown in Figure 9.
The process for production of this glass composition is the same as that described in Example 1.
It will of course be understood that the present invention is not limited to the specific details herein described which are given by way of example only, and that various alterations and modifications may be made without departing from the scope of the invention as defined in the appended claims.