MXPA97008862A - Container that absorb ultraviol radiation - Google Patents

Abstract

The invention relates to a container for food, based on glass of soda and lime, of green color, which absorbs ultraviolet radiation, which is permeable to visible light and has a dominant wavelength of 500 to 575 nm, whose glass , compared to the weight of the glass, contains at least 1.5% by weight of iron, calculated as Fe2O3, and at least 0.10% by weight of chromium, calculated as Cr2

Description

CONTAINER THAT ABSORBS ULTRAVIOLET RADIATION DESCRIPTION OF THE INVENTION The present invention relates to a package for foods that are sensitive to ultraviolet radiation. More particularly, the invention relates to a package made of green glass that absorbs ultraviolet light, for example, a bottle made of green glass that absorbs ultraviolet light, which is highly permeable to visible light and has a wavelength dominant from 500 to 575 nm, for packaging food and beverages. As is known, ultraviolet radiation, more particularly radiation having a wavelength of less than about 400 nm, has a negative effect on the smell and taste of food and beverages, such as beer. This negative effect is attributed to the chemical reaction of the components under the influence to ultraviolet radiation. It has been known for a long time that it is possible to reduce ultraviolet radiation by using glass containing a number of additives, mainly metal compounds. Only until recent dates, the green glass that absorbs radiation REF: 26215 ultraviolet, which is the objective of the present invention, was obtained mainly by the inclusion of chromium compounds in the glass. European Patent EP-A 261 725 describes the manufacture of green glass of soda and lime that absorbs ultraviolet radiation, which has a quantity of chromium compounds which can be partially replaced by nickel compounds. To obtain sufficient absorption of the ultraviolet radiation, it is necessary to include relatively large amounts of chromium in the glass, preferably as Cr (VI). According to the examples of the above European patent application, it is necessary to include at least 0.7% by weight of chromium in the glass to obtain a reasonable absorption of the ultraviolet radiation. From the literature, it is already known that green glass having absorptivity for infrared and ultraviolet radiation can be obtained by the inclusion of iron compounds in the glass. This one frequently refers to the manufacture of the glass used for windows, for example windows for cars resistant to heat and light. In general, this refers to a small reduction in radiation transmission, by including a smaller amount of iron, mainly in combination with some other additives. Such material is described in European patent EP-A 452 207. According to this publication, iron, chromium and cobalt are used to obtain a glass suitable for use in automobile sunroofs. The amount of iron compounds of such glass compositions is generally less than 2.5% by weight, if the chromium is also present, more in particular below 1% by weight of the glass composition. The transmission of ultraviolet radiation in such glass compositions is still high, because otherwise the transmission of visible light is too inhibited. For this reason, the transmission at 380 and 400 nm is still at a level which makes the glass composition unsuitable for use as a protective packaging glass, for foods and beverages that are sensitive to ultraviolet radiation. On the other hand, the problem occurs that the transmission to visible light must be at least partially maintained, because the consumer / user must be able to observe the contents of the container. In addition, the desire to obtain a specific color may be at least partially inconsistent with the objective of absorbing ultraviolet radiation. If the transmission for ultraviolet radiation must be high, this results in the color and / or absorption of ultraviolet radiation, which are negatively influenced. Glass Technology, Vol. 26, No. 1, 1985, pp. 60-62, states that the glass of soda and lime that contains iron and chromium, iron inhibits the formation of hexavalent chromium. This conclusion is also obtained in The Glass Industry, May 1996, pp 252-256 and 280-281. Hexavalent chromium is particularly responsible for the absorption of ultraviolet radiation, so that it will prevent those skilled in the art from using the combination of iron and chromium in the soda and lime glass. An object of the invention is to provide a package for food and / or beverages that are sensitive to ultraviolet radiation, whose package is based on the green glass of soda and lime. More particularly, an object of the invention is to provide a container from which the transmission of radiation having a wavelength <; 400 nm and more particularly also 380 nm, at a glass thickness of 2 mm, be zero or negligibly small, while retaining at least part of the transmission of visible light.

The invention is based on the surprising insight that such objectives can be achieved by the use of a relatively large amount of iron in combination with the small amounts of chromium, conventional for green glass, in the soda and lime glass. The invention therefore relates to a food container, based on green glass of soda and lime, which absorbs ultraviolet radiation, which is permeable to visible light and has a dominant wavelength of 500 to 575 nm, whose glass, in comparison with the weight of the glass, contains at least 1.5% by weight of iron, calculated as Fe203, and at least 0.10% by weight of chromium, calculated as Cr203,. Surprisingly, it has been found that such a container meets the requirements that are imposed on the absorption of ultraviolet light at wavelengths of 380 to 450 nm, and more particularly of 380 to 400 nm, while still obtaining a good green color on the which, in addition, can be adjusted by selecting the conditions in the melt, as well as by the selection of the other components of the glass batch. It can also be adjusted by these selections the degree of absorption above the wavelength, in which the ratio of the total amounts of iron and chromium in the final glass must be considered to be of great importance to obtain the fair properties. with respect to the color and absorption of ultraviolet light, or the transmission of visible light. Of importance to obtain the fair properties of glass, is the ratio between divalent and trivalent iron. This proportion is expressed as Fe (II) Fe (II) + Fe (III) for example, the amount of divalent iron in relation to total iron. Preferably, the amount of divalent iron is as small as possible, for example below 0.2. In practice, values below 0.05 are difficult to perform. The total amount of iron should not be less than about 1.5%, preferably, however, above 2.6% by weight, calculated as Fe203, because otherwise the effect thereof is not obtained to a sufficient degree. On the other hand, it needs to be used no more than 15%, more particularly not more than 10% by weight of iron, calculated as Fe203,. Larger amounts will lead to problems that occur with the transmission required for visible light.

The amounts of chromium, the ratio of trivalent to hexavalent chromium and the iron / chromium ratio also influence iron properties, more particularly the absorption of ultraviolet light radiation. It is assumed, but this is only a hypothesis, that by using a relatively large amount of Fe203, the proportion of chromium trivalent to hexavalent chromium moves a little towards hexavalent chromium, which could explain the synergistically increased absorption of radiation ultraviolet. The effect, however, does not occur when hexavalent chromium in aggregate only in the presence of conventional low amounts of iron in the glass. The package according to the invention, on the other hand, is characterized in that the transmission for the 380 nm radiation at a glass thickness of 2 mm is < of 5%, more in particular < of 1%, and at 400 nm < of 30%, more in particular < of 20% and more preferably < of 5%, or < of 1%, which in practice means that the package absorbs completely or almost completely the ultraviolet radiation, while, on the other hand, visible light is transmitted for the most part and the color of the glass is green. The latter means that the dominant wavelength of glass is between 500 and 575 nm, more particularly between 550 and 565 nm. Of course, it is also possible to define the color by means of the CIO-Lab system. Starting from a measurement in transparent colored glass that has a thickness of 2 mm, against a white background with L * = 98.89, a * = -0.06 and b * = 0.02, with light D65 at an observation angle of 2 °, with a BYK-Gardner spectrometer type Spectrogard Automaton Color System TCM 8800, under standard CIE-Lab conditions the color can be defined as follow: L * = 0 - 80, a * = 0 - -35, and b * = -10 - +55. The container according to the invention is based on the glass of soda and lime, which has the advantage that its cost remains low. This can be of special importance for glass for single or simple use, which is recycled again. The components of such glass soda and lime compositions are known to those skilled in the art. Although it is known that a large number of metal oxides influence the color and absorption of glass, it is preferred, according to the invention, not to use substantially vanadium, nickel and cobalt; As already indicated, this is important from the point of view of costs and environmental considerations. Certainly, if the container must be suitable for single use, the absence of such metals is of great importance. In addition, the glass should not contain arsenic and tin, since these substances are undesirable in the glass due to their environmental effects. Depending on the specific use and the desired color, it is possible to use a smaller proportion of nickel, if required. Amounts of nickel from 0.01 to 0.1% by weight have an effect of increasing the absorption, for the transmission of light at different wavelengths. To obtain similar effects, an amount (0.1 to 5% by weight) of titanium oxide, zirconium oxide or copper (II) oxide may also be used, if required. The maximum amount of chromium in the glass can also be maintained at low values, corresponding to the now conventional quantities for green glass that does not absorb ultraviolet radiation. An appropriate upper limit for the amount of chromium, calculated as Cr203, is 0.5% by weight, more particularly 0.35% by weight. In this context, it is noted that while with reference to the present invention reference is made to the use of metals, the final glass will contain these metals in the form of compounds thereof, substantially oxides. The glass used according to the invention for the package must have an emerald green color, which means that the dominant wavelength is in the range of between 500 and 575 nm, more in particular between 550 and 565 nm. This is also an absorber of ultraviolet radiation. An optimal combination of these two properties is achieved if 2.5 to 3.5% by weight of iron is combined with 0.10 to 0.35% by weight of chromium. In general, it is preferred that the glass comprises 1.5 to 10% by weight of iron, calculated as Fe203, 0.10 to 0.5% by weight, preferably 0.15 - 0.5% by weight of chromium, calculated as Cr203 50 - 85% by weight of Si02 5-25% by weight, preferably 5-12% by weight of alkali metal oxide 5-25% by weight of alkaline earth metal oxide 0-5% by weight, preferably 0-4% by weight of aluminum oxide 0- 5% by weight of traces. The amount of iron is preferably in the range between 2.6 and 8% by weight. As trace components, different additives can be used that influence the properties (color, Fe (II) / Fe (III) ratio, fusion properties, etc.). Examples of such components are manganese, titanium, zirconium or carbon compounds. However, coloring, heavy and toxic metals are excluded. The package is manufactured in the conventional manner for the manufacture of glass, by melting the components in an oven, under conditions such that the desired degree of oxidation of the iron is achieved. According to the present invention, the degree of air supply of the melt proves to be important. By controlling it, the proportion of di- and trivalent iron can also be influenced. In general, it is preferred that non-reducing conditions are used. Slightly oxidizing conditions are preferred. The raw materials or initial products for the glass are the conventional materials, of which in practice a (larger) portion is formed by recycling glass (waste glass). Thus, mixed green glass can be used in amounts up to 80% by weight of the initial products. The package is suitable for contact with food and beverages, such as soft drinks, alcoholic beverages and fruit juices. More in particular, the container is suitable as a beer bottle, since beer has the property to deteriorate strongly when exposed to ultraviolet radiation. The invention will be explained with reference to the following examples.

EXAMPLES Glass of soda and lime was prepared by melting the air at a temperature of 1450 ° C. The composition of the batch was in parts by weight: 74.5 parts sand 24.5 parts sodium carbonate 0.5 parts sodium sulfate 20.0 parts calcium carbonate 3.1 parts chromium aluminum hydroxide as Cr203 in an amount giving 0.24% by weight of chromium as Cr203 iron Fe203 in variable quantities This leads to the following basic glass composition: Si02 73% by weight Na20 14% by weight CaO 11% by weight A1203 2% by weight Cr203 0.24% by weight Fe203 in variable amounts The following table shows the transmission of (T) at 380, 400, 500 and 600 nm, as well as the color, given as a function of the amount of iron. or. ? Fe203"d T380 f> 400% Tseo% goo L * a * b * 0 71 71 56 60 73 -36 36 1 36 50 55 54 68 -37 40 3 12 30 47 48 61 -34 43 3 3 14 32 36 49 -28 41 4 0 5 25 30 38 -22 44 0 2 1 8 23 28 -15 37 It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it is applied. refers.

Having described the invention as above, property is claimed as contained in the following:

Claims (13)

1. A container for food, based on soda glass and green lime that absorbs ultraviolet radiation, characterized in that it is permeable to visible light and has a dominant wavelength of 500 to 575 n, preferably 550 to 565 nm, said glass, compared to the weight of the glass, contains at least 1.5% by weight of iron but not more than 15% by weight, calculated as Fe203, and at least 0.10% by weight of chromium, calculated as Cr203.

2. A container according to claim 1, characterized in that the amount of chromium, calculated as Cr203, is not greater than 0.5% by weight, more in particular not greater than 0.35% by weight.

3. A package according to claim 1 or 2, characterized in that the transmission of the glass for the 380 nm radiation to a thickness of 2 mm, is < of 5%, preferably < of 1 % .

4. A package according to claims 1 to 3, characterized in that the transmission for the radiation of 400 nm to a thickness of 2 mm is < of 20%, preferably < of 5%.

5. A package according to claims 1 to 4, characterized in that the iron content, calculated as Fe203, is not more than 8% by weight.

6. A package according to claims 1 to 5, characterized in that the content of iron, calculated as Fe203, is greater than 2.6% by weight, more particularly greater than 2.75% by weight.

7. A container according to claims 1 to 6, characterized in that the glass substantially does not contain nickel, cobalt, vanadium, arsenic and tin.

8. A container according to claims 1 to 7, characterized in that the glass also contains 0.1 to 5% by weight of titanium and / or zirconium, calculated as oxide.

9. - A package according to claims 1 to 7, characterized in that the glass also contains 0.1 to 5% by weight of copper, calculated as copper oxide (II).

10- A container according to claims 1 to 6, characterized in that the glass also contains 0.01 to 0.1% by weight of nickel, calculated as nickel (II) oxide.

11. - A package according to claims 1 to 10, characterized in that the glass consists of: 1.5-10% by weight of iron, calculated as Fe2O3; 0.10-0.5% by weight of chromium, calculated as Cr2O3; 50-85% by weight of SiO2; 5-25% by weight of alkali metal oxide; 5-25% by weight alkaline earth metal oxide; 0-5% by weight of aluminum oxide; and 0-5% by weight of remains. 12. A container according to claim 11, characterized in that the glass consists of: 2.5-3.5% by weight of iron, calculated as Fe2O3; 0. 10-0.35% by weight of chromium, calculated as Cr2O3; 50-85% by weight of

SiO2; 5-12% by weight of alkali metal oxide; 5-25% by weight alkaline earth metal oxide; 0-4% by weight of aluminum oxide; 0.1-5% by weight of titanium dioxide or copper (II) oxide or 0.01-0.1% by weight of nickel (II) oxide, and 0-5% by weight of residues.

13. - The use of at least 1.5% by weight of iron, calculated as Fe2O3, and at least 0.10% by weight of chromium, calculated as Cr2O3, compared to the weight of the glass, in soda and lime glass, to inhibit the transmission of light having a wavelength of Z_ 450 nm, more in particular from 380 to 450 nm, in a glass thickness of 2 mm.