EP0061638A1 - Utilization of a vacuum foil package for packing alumino-thermic mixtures - Google Patents

Abstract

This type of packaging prevents demixing of the aluminothermic mixture which consists of powders having a different specific weight and different grain size and particle shape. The aluminothermic mixture solidifies to form a rigid block which can be transported without demixing even on long routes. After opening of the vacuum film packaging, the aluminothermic mixture is again immediately pourable.

Description

Aluminothermic mixtures consist of finely divided aluminum and Schwenoetalloxid, the mixture to dampen the reaction and / or to form an alloy during the reaction further finely divided metals, metal oxides or other alloy elements, such as Iron filings, copper, copper oxides, chromium, manganese, carbon or the like can be added.

In order to achieve a uniform reaction and to control it in a controlled manner, it is necessary for the reactants contained in the aluminothermic mixture to be present within a predetermined particle size range and with a desired particle size distribution.

The different specific weights of the reactants in the aluminothermal mixture as well as their specific particle shape cause changes in the optimally adjusted mixing ratio of the reactants within a packaging unit during transport and storage, especially with shaking stress, which cannot be excluded during loading and transport , e.g. a cloth bag containing 7 to 15 kg of aluminothermic mixture as the usual packaging form for aluminothermic welding compounds for performing aluminothermic rail welds.

This separation can lead to an uneven course of the aluminothenuic reaction. If, for example, in the case of aluminothermic rail welding, the reaction is too violent or uneven due to the segregation in the reaction crucible open at the top, for example, part of the melt can whereby the Bedienungsper- is _personnel at risk and may also chweißgutes to faulty welds due to lack of _S or the formation of undesirable alloys Zusamnensetzung be ejected from the crucible. Demixed aluminothermic mixtures can also react too slowly, which can lead to heat loss and thus also to faulty welds. Since the majority of the aluminothermic mixtures are used for rail connection welding, such sources of error must be excluded for traffic safety reasons alone.

Attempts have been made to counteract the segregation of aluminothermic mixtures by pelletizing the reactants. However, this requires inorganic or organic binders. A possible inorganic binder is water glass, with which the aluminothermic mixtures could rise and solidify with CO ₂ . In this way, however, end elements are introduced into the reaction mixture which can interfere in the molten metal. If organic binders are used, the organic constituents can lead to gas evolution during the reaction and thus to porous reaction products. Another disadvantage of pelletized mixtures is the increase in the bulk volume. Due to the sudden heat development during the aluminothermic reaction, the air contained in the bed expands strongly and causes violent splashing of the reaction mass at the start of the reaction.

The invention is based on the object of finding a simple solution to the problem of preventing segregation of the aluminothermic mixtures which are optimally mixed during production, without the need to add substances to the mixture which remain in the aluminothermic reaction or which interfere in the event of remaining. In particular, the bulk density of the reaction mixture should not be reduced. All application properties of the aluminothermic mixture should remain unchanged.

According to the invention, this object can be achieved in a surprising manner by using the vacuum film packaging of aluminothermic mixtures.

• a) Durch die Entfernung der Luft aus der Verpackungseinheit, z.B. dem aus Kunststoff-Folie gebildeten Beutel, wird das Volumen der gefüllten Verpackungseinheit auf einem Minimum gehalten, so daß die größtmögliche Anzahl von Verpackungseinheiten in einem vorgegebenen Volumen transportiert und/oder gelagert werden kann.
• b) Durch die Entfernung der Luft aus der Verpackungseinheit werden durch Sauerstoff verursachte Abbauvorgänge verringert oder vermieden. Man hat deshalb dieses Verfahren z.B. zum Abpacken von gemahlenem, frisch geröstetem Kaffee eingesetzt und erreicht, daß das Gebinde das kleinstmögliche Volumen aufweist und andererseits die Aromastoffe des Kaffees erhalten bleiben. Dem Verbraucher sind auch andere, in gleicher Weise verpackte Lebensmittel, wie z.B. vakuumverpackte Erdnüsse, geläufig.

The packaging of powdery or granular goods in packaging containers, which are essentially formed by thermoplastic films and the air is removed from the packaging unit by applying a vacuum after filling, has long been known. Vacuum film packaging of this type has become particularly important in the packaging of food. This type of packaging essentially solves two tasks:

• a) By removing the air from the packaging unit, for example the bag formed from plastic film, the volume of the filled packaging unit is kept to a minimum, so that the largest possible number of packaging units can be transported and / or stored in a predetermined volume.
• b) By removing the air from the packaging unit, degradation processes caused by oxygen are reduced or avoided. This process has therefore been used, for example, for packaging ground, freshly roasted coffee and the container has the smallest possible volume and, on the other hand, the aroma substances of the coffee are retained. The consumer is also familiar with other foods packaged in the same way, such as vacuum-packed peanuts.

Industrial granular or powdered goods have also been packaged using vacuum film packaging, the primary aim being to ensure that the contents have the highest possible bulk density. For this reason, the bulk material was mostly compacted during or after packaging by additional shaking. A suitable device for this is e.g. described in DE-AS 11 43 434.

The application of this vacuum packaging, which is known per se, to aluminothermic mixtures is given its inventive character in that a completely different and unforeseeable effect can be achieved with this type of packaging. By packaging the aluminothermic mixture in a flexible container, in particular a bag or sack made of plastic film, which, after evacuation, wraps tightly around and encloses the aluminothermic mixture, the aluminothermic mixture is pressed together and solidified in such a way that by shaking during transportation and storage _e nt mix optimally mixed in the production aluminothermic mixture no longer takes place.

The particular advantage is to be seen in the fact that no. Solidifying foreign substance has to be added to the aluminothermic mixture, which could interfere with the subsequent aluminothermic reaction by influencing the metal melt or the slag formed. When the container is torn open, the previously compact aluminothermic mixture immediately becomes pourable again and can be filled into the reaction crucible.

Vacuum film packaging is therefore particularly suitable for aluminothermic mixtures if they have to be transported over long distances using different means of transport. Such long transport routes are quite common when sending aluminothermic mixtures, since these mixtures are produced in specialized companies, whereby the place of manufacture and the place of use can be quite far apart. These mixtures are transported by motor vehicle, rail, ship and occasionally by plane. The majority of the aluminothermic mixtures are used for rail connection welding in railway tracks. The aluminothermic mixtures must therefore be transported to the track to be welded on construction site vehicles immediately before they are used. It is understandable that with these transport stresses, segregation of aluminothermic mixtures in a packaging of a conventional type, e.g. in linen bags, could not be avoided. This segregation is favored by the fact that the components of the mixture have very different specific weights and different particle sizes and shapes.

. By using the vacuum film packaging according to the invention, it is possible to practically completely prevent these segregation processes.

Packaging films known from the prior art, in particular thermoplastic films, can be used to produce the packaging units. You just have to meet the condition that they enable essentially vacuum-tight packaging. Suitable films are, in particular, films made of polyethylene, film thicknesses of 0.1 to 0.3 mm being preferred. Thermoplastic films have the advantage that they can be sealed in a vacuum-tight manner by welding.

To achieve higher mechanical stability, the films can be wrapped with additional packaging material, e.g. Paper, such as sodium kraft paper, may be laminated. However, even after lamination, the packaging material must be flexible so that when the vacuum is applied it lies tightly around the aluminothermic mixture and clings to it.

It is also possible to use foils that shrink due to heat treatment. In this case, the aluminothermic mixture is first filled into a bag formed from the film and the bag is sealed airtight after the vacuum has been applied. The packaging unit thus obtained can then be additionally shrunk by heating with warm air or by placing it in a heated liquid such as water.

The aluminothermic mixture packaged according to the invention is solidified into a hard, rigid block, from which the aluminothermic mixture can be obtained in a poured shape after the vacuum packaging has been opened.

Claims (1)

Use of vacuum film packaging for packaging aluminothermic mixtures.