Transport and storing container for liquids

IS 2 286 367 T3

DESCRIPTION

Transport and storage container for liquids.

The invention relates to transport and storage containers for liquids, with a lower frame in the form of a metal platform or an electrically conductive plastic, an inner plastic tank with four side walls that is vertical on the lower frame, a lower bottom and an upper one, at least one section of an electrically conductive synthetic material integrated into the body of the single or multi-layer inner tank, which forms an electrical connection between the inner surface and the upper surface of the inner tank, an upper filling sleeve that can be closed and a lower outlet sleeve with an intake armature or an upper drain sleeve that can be closed, as well as with an outer shell that surrounds the inner tank, which is made up of metal or sheet metal grid bars.

The plastic inner tank of transport and storage containers of the type indicated for liquids described in DE 100 42 297 A1 is provided with a contact pin guided through a wall of the inner tank or with an outlet of the tank for the establishment of an electrical connection between the liquid in the inner tank or outlet and the outer casing configured as a metal basket. The upper surface of the contact pin that is in contact with the liquid is formed of an electrically conductive, non-metallic or predominantly non-metallic material. Such a material retains its conductivity even in the face of aggressive liquids and thus the ability to divert the charges that are formed especially when the liquid exits the inner tank. The decisive drawback of this known transport and storage container must be seen in that by means of a single contact element configured as a pin, a complete electrical grounding of the internal plastic tank or of the liquid inside it is not guaranteed.

The plastic inner tank of transport and storage containers for liquids known from DE 196 05 890 A1 has a permanent antistatic outer layer, which together with the metallic lower frame serves as an electrical grounding, to prevent an electrostatic charge of the upper surface of the inner plastic tank by friction of the inner tank on the metallic outer casing during transport. In this way, electric shocks must be avoided with the formation of sparks between the inner plastic container and the metal mesh enclosure, which can lead to ignition of flammable filling materials in the transport and storage container as well as explosive gas and gas mixtures. vapors in closed spaces. Due to this external grounding by means of a permanent antistatic outer layer of the plastic container, the electrical charges produced by friction of the liquid on the inner surface of the container and on the liquid during filling and emptying of the container cannot be derived. inside and during stirring of liquids in the inner tank for example for mixing purposes.

DE 197 31518 A1 describes a transport and storage container for liquids, which is grounded by means of a mesh cover of fine metal wire mounted on the inner plastic tank or an electrically conductive mesh or fabric. By means of this external grounding, as in the case of the transport and storage container known from DE 196 05 890 A1, only the electrical charges that occur on the upper surface of the tank are derived. Furthermore, the electrical grounding of the container for liquids by means of a mesh cover, a net or a fabric is technically complicated and leads to a corresponding increase in manufacturing costs.

In a transport and storage container for liquids described in DE 198 15 082 A1, a grounding piece is arranged on the intake armature placed on the outlet sleeve of the inner tank, which is designed as a curved sheet or plate. made of metal, which extends over a partial area of ​​the inner bore of the intake frame and is connected to the lower frame of the container by means of a fixing screw and a grounding cable. By means of this internal grounding, only the electrical charges that are formed in the liquid due to the friction of the liquid are derived. Furthermore, in this container for liquids there is a danger that during the transport and storage of aggressive liquids the earthing piece may become damaged by the liquid in such a way that the electrical earthing is no longer functional.

The invention is based on the problem of improving the transport and storage container for liquids of the kind mentioned at the beginning with regard to a safe and complete earthing of the inner plastic tank and to an economical manufacture.

This problem is solved according to the invention by means of a transport and storage container for liquids with the particularities of claim 1, as well as by the manufacturing processes for the inner plastic tank of the transport and storage container according to claims 12 and 13.

The dependent claims contain advantageous and convenient developments of the invention.

The strips of an electrically conductive plastic material included in the non-conductive plastic material of the walls as well as the lower and upper bottom of the inner tank, the thickness of which corresponds to the wall thickness of the inner tank, form electrical connections between the surface. inner and upper surface of the inner multilayer tank, featuring a permanent antistatic outer layer, so that both the electrical charges that are produced in the liquid filling material and on the inner surface of the inner tank by friction of the liquid and the electric charges that can be formed by a reciprocal friction of the inner tank and the metallic outer casing, can be bypassed to the bottoms through the electrically conductive strips on the walls as well as the bottom and top bottom of the inner tank and the permanent antistatic outer layer of the inner tank, as well as through the electrically conductive bottom frame in the form of a platform . The electrically conductive strips of a plastic material, whose mechanical resistance is lower than that of the base plastic of the inner tank of the container

ES 2 286 367 T3 for transport and storage, in low-stress areas of the inner tank manufactured by extrusion blow molding can be arranged, for example, in the separation plane of the blow mold, so that the mechanical strength properties of the inner tank as a whole they are not depleted. The limited use of expensive antistatic plastic material, for example a high density polyethylene with a proportion of conductive carbon black for the formation of the electrically conductive strips and the permanent antistatic outer layer of the otherwise plastic inner container made of a Inexpensive plastic material such as high-density polyethylene leads to only a small increase in manufacturing costs. The electrical grounding of the upper surface of the tank and of the interior space of the internal plastic tank as well as the liquids to be transported or stored in it makes it possible to use the transport and storage container as a container for hazardous materials for liquids and flammable emulsions such as solvents, paints and varnishes with a flash point <35 ° C as well as the use of the container in workplaces where an explosive atmosphere can be formed by gases, vapors or mists.

The transport and storage container for liquids according to the invention is explained below with the aid of the figures of the drawing, which represent the following:

Figure 1 is a perspective representation of a transport and storage container, Figure 2 is a section through the wall of the inner plastic tank of the transport and storage container with a three-layer structure in an enlarged perspective representation, and Figure 3 a partial cross section of an inner tank with a six-layer structure in enlarged representation.

The transport and storage container 1 for liquids that can be used as a non-returnable and returnable container has as main construction elements a replaceable inner tank 2 in the form of a parallelepiped made of polyethylene with a front wall 3, a rear wall 4 and two side walls 5 , 6, a lower bottom 7 configured as outlet bottom, an upper bottom 8 with a filling sleeve 9 that can be closed by means of a screw cap 10 as well as an outlet sleeve 11 in the lower section of the front wall 3 with an outlet frame 12, an outer casing 13 of grid bars 14 , 15 metal that intersect vertical and horizontal, a lower frame 16 in the form of a platform with a bottom tray 17 made of sheet metal for housing the inner plastic tank 2 as well as two metal lid bars 18 for protecting the inner tank 2.

Figure 2 illustrates that the front wall 3, the rear wall 4, the side walls 5, 6 as well as the lower and upper bottoms 7, 8 of the inner plastic tank 2 made of a high-density polyethylene by extrusion blow molding are They consist of an inner layer 19, an intermediate layer 20 as well as a permanent antistatic outer layer 21 with a proportion of conductive carbon black, which guarantees a specific surface resistance <1θ⁵ohms and a specific step resistance <10³ ohms. The thickness of the intermediate layer 20 is 1 to 2, preferably 1.5 millimeters and the thickness of the inner and outer layer 19, 21 is 0.5 millimeters, preferably 0.2 millimeters.

For the production of the intermediate layer 20, a recycled granulate or ground material of pure polyethylene and / or polyethylene with a proportion of conductive carbon black is used, and as a starting material for the inner and outer layer 19, 21 a granulate of polyethylene like new.

Figure 3 shows a six-layer structure of the plastic inner tank 2 with an inner layer 19 of pure high-density polyethylene (HDPE), a barrier layer 32 of polyamide (PA) or of an ethylene-vinyl acetate copolymer. (EVA) against the infiltration of oxygen and hydrocarbons, which is included in two layers of adhering agent of a low-density polyethylene (LDPE), an intermediate layer 20 of recycled granulate or ground material of pure high-density polyethylene and / or high-density polyethylene with a proportion of conductive carbon black as well as a permanent antistatic outer layer 21 of high-density polyethylene with a proportion of black of conductive smoke.

Integrated into the body 22 of the inner tank 2 are electrically conductive sections 23 configured as strips 24, of a high-density polyethylene with a proportion of conductive carbon black, which form electrical connections between the inner surface 25 and the upper surface 26 of the tank interior 2 and whose thickness corresponds to the wall thickness 27 of the interior tank 2. The electrically conductive strips 24, which appear in light in Figure 1 for illustration, are developed vertically on the corner areas 28 between the side walls 3-6 and / or the walls and obliquely on the lower and upper bottoms 7, 8 of the inner tank 2.

The screw cap 10 for closing the filling sleeve 9 and the intake frame 12 of the inner tank 2 can be made of an electrically conductive plastic, preferably high-density polyethylene with a proportion of conductive carbon black.

The bottom bowl 17 of the lower frame 16 is with a certain depth freedom on corner and central supports 29, 30 and a support frame 31 or skids, so that the bottom bowl 17 for the transport of the container 1 can be transported from below from four sides by the gripping arms of a transport apparatus, for example a forklift truck. The supports 29, 30 and the support frame 31 or skids are made of metal or of an electrically conductive plastic or plastic, for example polyethylene with a proportion of conductive carbon black, so that the transport and storage container 1 it is electrically grounded through the electrically conductive strips 24 and the permanent antistatic outer layer 21 of the plastic inner tank 2, the outer casing 13 and the lower frame 16 and thus the electrical charges occurring on the inner surface of the inner tank and on the liquid filling material as well as on the upper surface of the tank are derived.

In the production of the plastic inner tank 2 for the transport and storage container 1, a multilayer flexible tube blank is first coextruded from a non-conductive base material, particularly high-density polyethylene, with strips of an electrically conductive material distributed over the perimeter,

ES 2 286 367 T3 particularly high density polyethylene with a proportion of conductive carbon black, and then the blank molded blank is blown into a blow mold to form an inner reservoir.

Another method for manufacturing the inner plastic tank for the above-described transport and storage container for liquids is characterized by the coextrusion of a multilayer flexible tube blank molded blank, the flexible tube being of material that exits continuously or discontinuously from an extruder head distributed split over the perimeter and being injected into the partition spaces an electrically conductive plastic to form strips, which are homogeneously welded with the blank molded blank in the form of flexible tube, as well as by blow molding the blank molded in a blow mold forming an inner reservoir.