DE20300592U1 - Pallet for transport and storage of a container with flowing, easily inflammable contents is made of a plastic material with an electrical conduction capability - Google Patents

Abstract

The pallet for transport and storage of a container with flowing, easily inflammable contents is made of a plastic material with an electrical conduction capability.

Description

Designation: Transport pallet for a container arrangement

for the transport and storage of easily flammable, flowable substances

Description

Container arrangements for transporting and storing flowable materials, particularly liquids, generally consist of a transport pallet and a plastic container placed on top of it and surrounded by a protective grid. With such plastic containers there is a risk that the container surfaces will become electrostatically charged due to friction with the contents. When using such container arrangements for liquids whose vapors are highly flammable, or when using such container arrangements in areas that are classified as potentially explosive for other reasons, there is a risk that an explosion can be triggered by a discharge of the electrostatic charge on the container surface, causing sparks.

To avoid this risk, a container arrangement of the type described above is known from DE 202 06 436 U, in which the plastic container is provided with a permanently antistatic outer layer made of a plastic with a conductive carbon black component. This prevents electrical discharges with spark formation between the container and the electrically conductive metal base frame and/or the protective grille.

Transport pallets made of plastic are generally known. Due to the electrically non-conductive properties of transport pallets made of plastic, the use of transport pallets made of metal is necessary for the container arrangements described above with electrically conductive containers made of plastic. If such container arrangements are to be used for the transport of corrosive substances or in areas

If they are used in areas with a corrosive atmosphere, the service life of such metal pallets is limited.

It is basically possible to manufacture such transport pallets from a plastic material that is made electrically conductive by adding conductive carbon black. The disadvantage, however, is that by adding conductive carbon black in an appropriate amount to the base plastic, usually high-density polyethylene (HDPE), the original high strength of the base plastic is significantly reduced, so that to compensate for this, correspondingly thicker walls and thus a correspondingly higher material expenditure are necessary to manufacture transport pallets from such a conductive plastic in order to achieve comparable strength properties with transport pallets made of metal. This practically eliminates the cost advantage of a plastic pallet compared to a metal pallet.

The invention is based on the object of creating a transport pallet made of plastic that is protected against electrostatic charges for such a container arrangement, which avoids the above disadvantages.

This object is achieved according to the invention by a transport pallet for a container arrangement for transporting and storing flowable materials, which consists of a plastic material with electrically conductive (intrinsic) properties. The advantage here is that a plastic material is used which has electrically conductive (intrinsic) properties of its own, so that the addition of conductive materials, such as conductive carbon black, is avoided.

It has now been found that in order to protect against electrostatic charges, even a small intrinsic property of the plastic material used is necessary, so that in one embodiment of the invention the plastic material

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Material with intrinsic properties consists of a mixture of an electrically non-conductive plastic as a base plastic with an intrinsic plastic. This means that the intrinsic plastic with its high electrical conductivity is "diluted" accordingly by mixing it with the electrically non-conductive plastic. This means that proven plastic with high inherent mechanical strength can be used for the base material, so that the somewhat lower strength of the intrinsic plastics is more than compensated for. Since intrinsic plastics are very expensive in comparison to conventional plastics, another advantage is a considerable reduction in costs, since only enough intrinsic plastic needs to be mixed into the mixture with the base plastic to ensure that the required charge density on the container surface of max. 40 nano-coulombs per square centimeter can be maintained.

For the purposes of the present invention, the term "plastic" is used for the genuine plastic, while the term "plastic material" is used for a mixture of several plastics. Accordingly, the term "plastic material with intrinsic properties" means a mixture of an electrically non-conductive plastic with a plastic that has electrically conductive, i.e. intrinsic, properties due to its molecular structure.

In an embodiment of the invention, it is provided that a polyethylene, in particular a high-density polyethylene (HDPE), is used as the base plastic.

In an embodiment of the invention, it is provided that the proportion of intrinsic plastic in the plastic material with intrinsic properties consisting of the base plastic and the intrinsic plastic is max. 50% by volume. Further proportions are specified in the subclaims.

The invention further relates to a method for producing a transport pallet for a container arrangement according to the invention using a plastic material with electrically conductive (intrinsic) properties, which is characterized in that a part of an intrinsic plastic is mixed as a master batch with a portion of an electrically non-conductive base plastic in a predeterminable volume ratio in an extruder to form a plastic material with intrinsic properties and that the plastic material with intrinsic properties formed by the mixture is fed from the extruder nozzle to the mold. This procedure makes it possible to use the intrinsic plastic as a concentrate and to create a homogeneous mixture with the base plastic in the extruder with a small volume proportion, which can then be introduced into the mold.

In an advantageous embodiment of the method, it is further provided that the proportion of plastic with intrinsic properties is at least partially formed by reprocessed plastic material that accrues during the cleaning of the finished transport pallet. Since, according to the invention, the transport pallet consists of a mixture of an electrically non-conductive plastic with an intrinsic plastic, whereby the intrinsic plastic is contained in this plastic material with only a relatively small volume proportion, the waste generated during the cleaning can be granulated in the usual way and, based on experience, if necessary by further mixing in a small proportion of the intrinsic plastic present as a master batch, can be "improved" in relation to the requirements for intrinsic conductivity and used again to manufacture transport pallets. This results in further cost savings. Since the amount of waste is smaller in relation to the total amount of plastic required, the advantage is that

This is because a genuine, preferably freshly manufactured, non-conductive plastic, such as HDPE, can be used to manufacture the transport pallet, to which the intrinsic plastic material, which has been processed using waste and adjusted to the desired electrical conductivity, is then mixed in appropriate proportions before molding. Accordingly, a reliable guarantee is given for the strength and load-bearing capacity of such a transport pallet.

Further features of the invention can be found in the following description of embodiments and the claims.
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The invention is explained in more detail using schematic drawings. They show:

Fig. 1 a container arrangement with a plastic container on a transport pallet with protection

grid,

Fig. 2 the manufacturing process in the form of a schematic flow diagram.

The container arrangement shown in Fig. 1 consists essentially of a closable cubic container 1 made of a plastic with electrically conductive properties, which stands on a transport pallet 2 made of an electrically conductive plastic. To protect the container 1 against mechanical impact, a protective grid 3 made of metal is connected to the transport pallet 2, which essentially consists of a series of vertical bars 4, each of which is firmly and electrically connected to a frame 5 at the lower end and to a frame 6 at the upper end.

Instead of such a bar grid, protective grids with intersecting bars can also be used. The container 1 is

at the level of its bottom with a drain valve 7. The container top is provided with a filler neck which can be closed by means of a screw cap 8.

As can be seen from the flow diagram shown schematically in Fig. 2, the transport pallet 2 is manufactured using the extrusion process.

The plastic material with intrinsic properties required to manufacture the transport plate is produced in an extruder 9, to which a base material B, for example high-density polyethylene (HDPE), is fed and, in addition, an intrinsic plastic A is fed as a master batch with an appropriate volumetric dosage. Both plastics A and B are mixed homogeneously in the extruder 9, with the extruder 9 being set in terms of pressure and temperature so that the structure of the intrinsic plastic is not damaged. The homogeneous mixing of both plastics in the extruder 9 produces a plastic material with intrinsic properties, which is introduced into the mold 10 by the extruder 9. In the case of a transport pallet made up of two or more parts, several parts must be produced from the intrinsic plastic material, which are then joined together.

The volumetric addition of plastic A with intrinsic properties to the base plastic B can be up to 50 vol.%. However, significantly lower proportions of plastic A in the mixture are appropriate and sufficient.

When using waste from final processing, the content of intrinsic plastics is determined during processing by appropriate testing of samples, for example by conductivity measurements. The supply of "pure" plastic A (master batch) and "pure" plastic B can then be adjusted accordingly. It is useful if the amounts of

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collected in larger batches and homogenized, for example, in the form of granules. It may be useful to process the plastic material generated from waste into
a separate processing step, for example a second extruder upstream of the extruder 9, to adjust it to the desired proportion of intrinsic material.

Claims (11)

1. Transport pallet protected against electrostatic charging for a container arrangement for the transport and storage of flowable substances, which consists of a plastic material with electrically conductive (intrinsic) properties. 2. Transport pallet according to claim 1, characterized in that the plastic material with intrinsic properties consists of a mixture of an electrically non-conductive plastic as a base plastic with an intrinsic plastic. 3. Transport pallet according to claim 1 and 2, characterized in that polyethylene is used as the base plastic. 4. Transport pallet according to claim 3, characterized in that a high-density polyethylene is used as the base plastic. 5. Transport pallet according to one of claims 1 to 4, characterized in that the proportion of the intrinsic plastic in the plastic material consisting of the base plastic and the intrinsic plastic is up to 50 vol.%. 6. Transport pallet according to one of claims 1 to 4, characterized in that the proportion of the intrinsic plastic in the plastic material consisting of the base plastic and the intrinsic plastic is up to 40 vol.%. 7. Transport pallet according to one of claims 1 to 4, characterized in that the proportion of the intrinsic plastic in the plastic material consisting of the base plastic and the intrinsic plastic is up to 30 vol.%. 8. Transport pallet according to one of claims 1 to 4, characterized in that the proportion of the intrinsic plastic in the plastic material consisting of the base plastic and the intrinsic plastic is up to 20 vol.%. 9. Transport pallet according to one of claims 1 to 4, characterized in that the proportion of the intrinsic plastic in the plastic material consisting of the base plastic and the intrinsic plastic is up to 15 vol.%. 10. Transport pallet according to one of claims 1 to 4, characterized in that the proportion of the intrinsic plastic in the plastic material consisting of the base plastic and the intrinsic plastic is up to 10 vol.%. 11. Transport pallet according to one of claims 1 to 4, characterized in that the proportion of the intrinsic plastic in the plastic material consisting of the base plastic and the intrinsic plastic is up to 5 vol.%.