MXPA97003426A - Packaging that absorbes ultraviol radiation - Google Patents

Abstract

The present invention relates to a food packaging based on a glass of soda and lime of green color, absorber of UV radiation and transmitter of visible light, characterized in that the glass consists of: 2.5-10% by weight of iron , calculated as Fe2O3, 50-82.55 by weight of SiO2, 12-25% by weight of alkali metal oxide, 3-25% by weight of alkaline earth metal oxide, 0-4% by weight of alkaline earth metal oxide, 0-45% by weight weight of aluminum oxide, 0-5% by weight of traces, whereby the glass contains at least 125 by weight of sodium, calculated as Na2O and has a Fe (II) ratio of at least 0.05, but does not exceed Fe (II) ) + Fe (III) of 0.

Description

PACKAGING THAT ABSORBES ULTRAVIOLET RADIATION The invention relates to a package for foods sensitive to UV radiation. More specifically, the invention relates to a package made of green glass absorbing UV radiation, e.g. a bottle for the packaging of food and drinks made of green glass that absorbs UV radiation and largely a transmitter of visible light. This means that the efforts are aimed at obtaining a type of glass in a large part of a visible light transmitter and having a green color. The latter means that the dominant wavelength of the glass is in the vicinity of 500 to 565 nm. As is known, UV radiation, more specifically 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 compounds under the influence of UV radiation. It has long since it is known that it is possible to reduce UV radiation by using a glass provided with a number of additions, mainly metal compounds. Until recently, the green glass absorbing UV radiation, to which the present invention refers, was obtained mainly by the incorporation of chromium compounds in the glass. EP-A 261 725 describes the manufacture of a glass of soda and lime ABS with a quantity of chromium compounds which are partially replaced by nickel compounds, if required. The use of chromium compounds especially, similar to nickel compounds, is considered to be increasingly less appropriate, both from the cost point of view and from the environmental effects point of view of the metal compounds. Japanese patent application JP-A 1/65044 discloses the use of iron-containing lava as an addition to the soda and lime glass to obtain a glass having a green-dark color. However, by adding the lava the composition of the glass batch is changed in such a way that the processability deteriorates while the color tends towards a very dark green has almost black. From the literature it is already known that green-colored glass having absorption capacity for IR and UV radiation can be obtained by the incorporation of iron compounds in glass. This is often related to the manufacture of glass used for windows, e. g. car glasses resistant to light and heat. In general, this involves an insignificant reduction in the transmission of radiation by incorporating a smaller amount of iron, mainly in combination with a number of other additions. The amount of iron compounds in such glass compositions in general is less than 2, more in particular less than 1% by weight of the glass composition. The transmission of UV radiation in such compositions - the glass is still high, because otherwise the transmission - of visible light is also largely inhibited. For this reason the transmission at 380 and 400 nm is at a level that makes the composition of the glass inadequate for use as packaging glass for food and drinks sensitive to UV radiation. On the other hand, the problem arises in that the trans mission for visible light must be maintained at least partially, because the consumer / user can be ready to see the contents of the package. Also, the desire to obtain a specific color can at least partially be contrary to the objective of the absorption of UV radiation. It is an object of the invention to provide a package for food and / or beverages sensitive to UV radiation, which, the package is based on a glass of soda and lime, green, chrome-free and preferably also nickel-free . More specifically, it is an object of the invention to provide a package in which the transmission of radiation having a wavelength of less than 400 nm and more particularly also of 380 nm, to a glass thickness of 2mm. , it is insignificant or nothing, while at least part of the transmission of visible light is retained. The invention is based on the surprising idea that such an objective is carried out using a relatively large amount of iron in the soda and lime glass. The invention relates to a packaging for food on the basis of green soda and lime glass, absorber of UV radiation and transmitter of visible light, in which the glass consists of: at least 2.5% by weight of iron, calculated as Fe ^ O ,,, at least 12% by weight of sodium, calculated as Na2 ?, and at most 4% by weight of aluminum, calculated as Surprisingly, it was found that such packaging meets the requirements imposed in the absorption of -UV. at 380 and 400 nm. , while still a good green color is obtained which, in addition, is adjusted by selecting the conditions during the fusion, as well as selecting the other compounds -of the glass lot. Also, the degree of absorption at the established on-da lengths is adjustable by these selections, in relation to which "it should be considered that the total amount of iron and the proportion of Fe (II) to Fe (III) in The final glass is of great importance to obtain the correct properties with respect to color and UV absorption, or transmission of visible light, preferably the Fe (II) Fe (II) + Fe (III) ratio. in the glass does not exceed 0.25. To obtain the correct properties in glass, this ratio between divalent iron and trivalent iron is of great importance. This ratio is expressed as Fe (II) for example the amount of iron diva- Fe (II) + Fe (III) lens in relation to total iron. Preferably, the amount of the divalent is as small as possible, for example, less than 0.15. In practice, lower values of 0.05 are -hard to perform. The total amount of iron should not be less than almost 2.5% by weight, calculated as Fe2? ? because otherwise this effect is not reached to a sufficient degree. On the other hand, it is not necessary to use more than almost 12% in pso, calculated as Fe20 ~. At this concentration the glass, at a thickness of 2 mm, does not or practically does not transmit the visible light. In the following table the transmission (T) at 380 and 400 nm is shown as a function of the iron content, measured in a glass of soda and lime having a thickness of 2 mm.

% Fe by weight% of T 380% of T 400 2 25 54 3.5 5 22 5 or 5 6.5 0 2 8 0 0 It is noted that in J. of the Society of glass Technology, 22, (1938), pages 372 - 389, a theoretical consideration is given for the equilibrium between Fe (II) and Fe (III). In this article the amounts of .0.002 to 12.50% by weight of iron, calculated as Fe2? ~, In the soda and lime glass are examined. This publication does not give an indication of the properties of glass with respect to UV abscission or with respect to the use of such glass for packaging purposes. The color adjustment of the glass can also be effected by selecting the redox value of the starting materials. This redox value partly determines the Fe (11) / Fe (III) equilibrium, so the value can be adjusted by adding compounds. that affect this value. Suitable additions are known to those skilled in the art. In this connection it is observed that the waste of optical glasses, provided that they are substantially free of undesirable heavy metals, can be used as raw material, However, the presence of -paper and other organic impurities affect the proportion of Fe ( 11) / Fe (III) and therefore the movement of color in an undesirable direction. The packaging according to the invention is, on the one hand, characterized by the transmission of radiation of 380 nm to a glass thickness of 2 mm being less than 5%, more in particular less than 1%, and at 400 nm less that 20%, more specifically - less than 5% and more preferably less than 1% which, in practice, whenever the package absorbs UV radiation completely or almost completely, while, on the other hand, visible light is largely transmitted and the color of the glass is green. The latter means that the dominant wavelength - of the glass is easily in the vicinity of 500 to 565 nm, Of course, it is also possible to define the color on the basis of the CIÉ-lab system. Initiating a measurement on the glass -coloured transparent 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 degrees, with a BYK-Gardner spectrometer, type Spectrogard Automative Color System TCM 8800, under standard CIE-lab conditions the color is defined as follows: L * = 0 - 80, a * = 0 35 in b * = -10 - +55. The packaging according to the invention is based on soda and lime glass, which has the advantage that its costs are kept low. This can be particularly important for glass that is used only once and is then recycled - again. The compounds of such lime and lime glass compositions are known to those skilled in the art. According to the invention, chrome, vanadium, nickel and cobalt are substantially not used; As already indicated, this is important in both cost and environmental considerations. Certainly when the packaging is suitable for a single use, the absence of such metals is of great importance. - Also, the glass should not contain arsenic and tin, since these substances are undesirable in the glass because of their environmental effects. In this regard, it is noted that even in connection with the present invention, reference is made to the use of metals, even these metals will be contained in the final glass in the form of compounds thereof, in particular oxides. In general, it is preferred that the glass consist of 2.5-10% by weight of iron, calculated as Fß2? 50 - 82.5% by weight of SiO 12 - 25% by weight of alkali metal oxide 2.5 - 25% by weight of alkaline earth metal oxide. 0 - 4% by weight of aluminum oxide 0 - 5% by weight of traces. The amount of iron is preferably in the range from 2.75 to 8% by weight. As components in traces, different additions can be used that affect the properties (color, Fe (II) / Fe (III) ratio, fusion properties and the like). Examples of such compounds are manganese and titanium. The sodium content should be at least 12% in -weight, because at decreasing contents the processability is increasingly unsatisfactory due to the increase in viscosity. The aluminum content should not exceed 4% by weight. Above this value a marked increase in viscosity exists, which has the result that under conventional conditions the glass can not be made in an acceptable product. It is observed that the addition of a quantity of lava, as described in JP-A 1/65044, leading to an iron content of at least 2.5 by weight, gives an alumina content of almost 4.5% in weight and a sodium content of almost -10% by weight. The package according to the invention is manufactured in the conventional manner for the manufacture of glass, by melting the compounds in a furnace under such conditions that the desired degree of oxidation of iron is reached. According to the present invention, the degree of air supply during melting becomes important. Controlling this the di- and trivalent propoj- tion can be partially influenced. The packaging is suitable for contact with food and beverages such as non-alcoholic beverages, aleo holic drinks and fruit juices. More specifically, the packaging is suitable as a beer bottle, since beer has the property to seriously deteriorate when exposed to UV radiation. The invention will be explained by means of the following examples: EXAMPLES The glass of soda and lime was made by melting in the air at a temperature of 1450 ° C. The composition of the lot was in parts of weight: 74. 5 parts sand 24.5 parts sodium carbonate 0.5 parts sodium sulfate 20.0 parts calcium carbonate 3.1 parts aluminum hydroxide iron as Fe2? ~ In varying quantities.

This leads to the composition of the following base glass: SiO, 73% by weight Na20 14% by weight CaO 11% by weight Al2 ° 3 2% by weight Fe203 in varying amounts.

In the following table the transmission (T) at 380, - 400, 500 and 600 nm, as well as the color, is given as a function of the amount of iron.

Fe203% T 380% T 400% T 500% T 600 L * b * 2 25 54 73 72 79 -13 13 3. 5 5 22 81 52 59 -15 25 0 5 30 35 39 -11 31 6. 5 0 2 14 20 20 -4.5 25 8 0 0 5 10 6.3 -0.2 8.3

Claims (9)

REVINDICACIOMES

1. A food packaging based on a glass of soda and lime of green color, absorbing of UV radiation and transmitter of visible light, characterized in that the glass consists of: at least 2.5% by weight of iron, calculated as Fe20, at least 12% by weight of sodium, calculated as Na ^ O, and at most 4% by weight of aluminum, calculated as Al20

2. A package according to claim 1, characterized in that the proportion of Fe (II) in Fe (II) + Fe (III) Glass does not exceed 0.25, preferably does not exceed 0.15.

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

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

5. In packaging according to claims 1-4, characterized in that the content of iron, calculated as - Fe 0o, exceeds 2.75% by weight, but does not exceed 8% by weight.

6. A package according to claims 1-5, characterized in that the glass substantially does not contain chromium, nickel, cobalt, vanadium, arsenic, and tin.

7. A package according to claims 1-6 characterized in that the glass consists of 2.5-10 wt.% Of iron, calculated as Fe20 50-82.5 wt% of Si02 12-25 wt.% Alkali metal oxide 3 - 25% by weight of alkaline earth metal oxide 0 - 4% by weight of aluminum oxide 0 - 5% by weight of traces.

8. A process for the manufacture of green glass according to claims 1-7, characterized in that the amount of Fe (III) is adjusted by modifying the conditions of the furnace or by adding changing ions of equilibrium.

9. The use of at least 2.5% by weight of iron, calculated as Fe20_ with respect to the weight of the glass, in the soda and lime glass having a proportion of Fe (II) Fe (II) + Fe (III) in the glass that does not exceed 0.25, for the inhibition of the transmission of UV radiation having a wavelength -of 308 and / or 400 nm, to a glass thickness of 2 mm.