FR3009290A1 - BULK STORAGE DEVICE FOR PULVERULENT MATERIALS - Google Patents

Abstract

Bulk storage device (1) for powdery materials, said device comprising a flexible bulk container (2) and an insulating inner liner (3) with a surface resistivity greater than 1.0 x 1012 Ω, devoid of conductive layer of static electricity and without a dissipative layer of static electricity, said inner lining (3) covering the inner walls of the container, said inner liner (3) comprising micro-perforations, through, distributed over the entire surface of said inner liner (3) and such that the breakdown voltage of said inner liner (3) is less than 4 kV and in that the breakdown voltage of the container wall is less than 6 kV.

Description

The invention relates to a flexible storage device comprising a flexible container and an inner liner. The field of the invention is that of flexible intermediate bulk containers (abbreviated to GRVS), and or FIBC (of the English "Flexible Intermediate Bulk Container") still 5 commonly called "Big Bag". Such flexible bulk packages are commonly used for storage and transport of powdery or granular materials. The container is generally of parallelepipedal shape, usually ranging from 0.5 to 3 m3. This container is a flexible structure whose mechanical strength makes it possible to take up the load of the stored materials. The container is conventionally obtained from fabric of polymer fibers (PP, PE, PET, etc.), which is often permeable to products of small particle sizes. In order to avoid the passage of pulverulent materials through the fabric, it is known to use an internal lining, also called "internal protective coating" in the standard IEC 15 61340 4-4 Edition 2.0. When filling or emptying such packages, the friction between the material and the packaging generates an electrostatic charge on the packaging and / or on the material. In the presence of an explosive atmosphere, particularly when fine particles are suspended in the air, the electrostatic discharges that may result therefrom represent a risk of explosion and / or flame, by the ignition of these powders. In order to avoid these risks, it is known from IEC 61340 4-4 Edition 2.0 to classify packaging according to their construction, the nature of their operation, and their performance requirements with respect to these risks. FIBCs are classified into one of the following four types: Type A, Type B, Type C, and Type D. In particular, Type B FIBCs are made of plastic to prevent certain landfills and landfills from spreading. require grounding. Such FIBCs are suitable for explosive atmospheres formed of fine particle clouds in suspension, but are not suitable for gaseous explosive atmospheres. Type C FIBCs are designed with conductive, cloth or plastic foil or interwoven with conducting wires or filaments, and are designed to prevent the occurrence of incendiary sparks, discharge and the propagation of certain discharges. In such a type C FVC, superior protection is obtained against the risk of explosion compared to a type B FVC. Type C FIBCs are suitable for explosive atmospheres consisting of fine particle clouds in suspension, and also, for explosive atmospheres of gaseous nature. On the other hand, this protection is only ensured if the conductive sheet or equivalent is connected to the ground, at least during filling and emptying operations. However and according to the findings of the inventor, in practice, it is not uncommon for operators to forget to ground the storage device during filling or emptying operations, which can be particularly dangerous. Finally, D-type FIBCs are made of a static-protected fabric designed to prevent the occurrence of sparks and certain discharges, without the need to connect the FIBC to the earth. Conventionally, type B, C or D FIBCs use L2 type internal protective coatings according to the aforementioned standard, with materials having a surface resistivity of between 1.0 x 109 S 2 and 1.0. Such dissipative dissipative materials include antistatic additives whose effect is, however, of limited duration. The life of such an interior liner does not exceed 2 years. In addition, these additives are likely to migrate and come into contact with the stored product, and thus contaminate it. This is a problem often considered unacceptable in the case of use of the storage device for food applications, and especially pharmaceutical. Therefore, to the knowledge of the inventor, to the knowledge of the inventor, those skilled in the art, for these sensitive applications, almost always use a Type C FVC, without an L2 type liner, which is preferably coated. The purpose of the present invention is to propose a device intended for the storage of powdery products, offering effective protection against the risks of explosion, in particular during emptying operations and / or filling the bag. More particularly, the object of the present invention is to provide such a device which does not require grounding during the emptying and / or filling operations to comply with the safety conditions.

Another object of the present invention is to provide such packaging which does not expose the stored product to the risk of contamination by migration of the container to the contents. Other objects and advantages of the present invention will become apparent during the description which is given for information only and which is not intended to limit it. Also, the invention relates to a package comprising a flexible bulk container, as well as an insulating inner lining, of surface resistivity greater than 1.0 × 10 12 S 2, covering the internal walls of the container, without a conductive layer of static electricity and no dissipative layer of static electricity.

According to the invention, the inner lining comprises micro-perforations, passing through, distributed over the entire surface of the inner lining and in such a way that the breakdown voltage of the inner lining is less than 4 kV and that the voltage of breakdown of the container wall is less than 6 kV. According to features of the invention, taken alone or in combination: the inner lining is constituted by a single film of material, having said micro-perforations; - the flexible bulk container is formed from canvas; - the canvas is a coated canvas; - the canvas is a laminated canvas; the density of the micro-perforations over the entire surface of the coating is such that two neighboring micro-perforations are separated by a distance less than or equal to 2 cm, preferably between 0.5 cm and 2 cm; the diameter of the micro-perforations is between 5 microns and 130 microns, the maximum surface having no micro-perforations must not exceed the surface of a disk 2 cm in diameter, the thickness A, of the inner liner is between 20 microns and 700 microns. According to an advantageous embodiment, the fabric of the flexible bulk container is an air-permeable fabric, preferably non-laminated and uncoated, in such a way as to allow the deaeration of the package by means of micro-perforations. the inner liner and the web of said container.

The storage device finds particular application as a large flexible bulk container type B, according to IEC 61340-4-4 Edition 2.0 2012-01. The invention will be better understood on reading the following description accompanied by the appended drawings, in which: FIG. 1 is a schematic view of a storage device according to the invention according to one embodiment; - Figure 2 is a sectional view of the container wall and the wall of the inner protective coating. Also the invention relates to a device 1 for storage for bulk, for the transport and storage of powdery materials. Said device comprises a container 2, for flexible bulk, and an inner liner 3. The container 2 forms a flexible structure whose mechanical strength allows to resume the charge of the stored material. The container 2 may be of a substantially parallelepipedal shape, with a capacity of between 0.5 m 3 and 3 m 3, by way of non-limiting example. Optionally, and conventionally, this structure can be provided with handling straps 5 at the corners of the structure. This structure may consist essentially of canvas, synthetic, especially based on polypropylene.

The inner liner is an insulator, that is to say with a surface resistivity greater than 1.0 x 10 12 52, on its inside and on its outside, according to the IEC 613404-4 Edition 2.0 2012-01 standard. The inner liner is a type L3 inner protective coating according to the aforementioned standard. This inner liner 3 is devoid of electrically conductive layer. Electrically conductive layer means any element, for example in the form of a sheet or filament, having a surface resistivity of less than 1.0 × 10 7 Q Thus, and in accordance with the IEC 61340-4-4 Edition 2.0 standard 2012-01, such an inner liner 3, and more generally the storage device 1 as a whole, does not require grounding, especially during the filling or emptying operations of the device with the powdery materials. In addition, and according to the invention, the inner liner 3 is devoid of dissipative layer of static electricity. Dissipative layer is understood to mean a material whose surface resistivity is between 1.0 × 10 9 S 2 and 1.0 × 10 12 S 2, and which comprises for this purpose, in a conventional manner, antistatic additives capable of contaminating the material stored. Also, and according to the invention, such contamination risks are avoided in that the inner liner is devoid of such additives, for example an untreated plastic material. By way of nonlimiting example, the inner liner 3 is constituted by a single film of material having said micro-perforations 4, untreated plastic material, such as for example polypropylene. According to another embodiment, the inner liner may comprise several layers of different insulating materials, for example several plastics. For example, the internal double 3 is a multilayer (ie double layer, triple layer, see more) of the same plastic, PE for example, to increase the mechanical performance of the inner liner 3. Alternatively, the inner liner can be a multilayer (ie double layer, triple layer, see more) of several different insulators, such as several different plastics. This multilayer is obtained by extrusion, in particular coextrusion. The thickness A of the inner liner 3 may be between 20 microns and 700 microns, and for example between 90 microns and 500 microns. According to the invention, the inner liner 3 covers the inner walls of the container 2, said inner liner 3 comprising micro-perforations 4, preferably through-holes.

These micro-perforations 4 are distributed over the entire surface of the inner liner 3 and such that the breakdown voltage of the inner liner 3 is less than 4 kV. In addition and according to the invention, the breakdown voltage of the container wall is less than 6 kV. Such a storage device 1 can be considered as a large container for flexible bulk classified type B according to IEC 61340-4-4 Edition 2.0 2012-01. According to one embodiment, the breakdown voltage of the entire container 2 / inner liner 3 is less than or equal to 6 kV, and preferably less than or equal to 4 kV. According to the invention, the micro-perforations 4 are distributed over the entire surface of the inner liner 3, and not on a part of its surface only, and in such a way as to avoid strong accumulations of electrostatic charges on the inner liner 3. Preferably, the density of the micro-perforations 4 on the surface of the inner liner 3 is such that two neighboring micro-perforations are separated by a distance δ less than or equal to 2 cm, preferably between 0.5 cm and 1.5 cm. cm. Preferably, the maximum surface having no micro-perforations should not exceed a disc of 2 cm in diameter. The diameter d of micro-perforations 4 may be between 5 microns and 130 microns. The diameter of the micro-perforations 4 will be chosen according to the particle size of the material to be stored and in order to prevent the material from passing through the inner lining 3. For this purpose, the micro-perforations 4 are preferably of diameter less than the particle size of the material to be stored. These micro-perforations of the inner liner 3 may be obtained mechanically, for example by means of a matrix provided with needles for perforating the liner, or by means of a roller provided on its circumference with such needles, provided to roll on the lining by perforating it. The material of the container 2, in particular the web 20 of the container, is an insulator within the meaning of the aforementioned standard, for example based on polypropylene, without antistatic additive, nor electrically conductive layer. According to one embodiment, the fabric 20 is a coated fabric, or a laminated fabric. According to an advantageous embodiment, the fabric 20 of the flexible bulk container is an air permeable fabric, preferably unlaminated and uncoated, so as to allow the deaeration of the device 1 by means of micro-perforations. 4 of the inner liner 3 and, through the web 20, said container 2, in particular during the filling operations of the device with the materials. Such a phenomenon is illustrated by the arrows in FIG. 2. Such a deaeration makes it possible to minimize the quantity of fine particles suspended in the air during the filling operations, and thus to limit the risks of creating an explosive atmosphere. . Such an arrangement contributes, with the minimization of breakdown voltages of the inner liner 3 and the container, to a better safety vis-à-vis the risk of explosion during filling operations of the device with powdery materials. It should be noted that the values mentioned above, in particular surface resistances, breakdown voltage, are measured in accordance with the IEC 61340-4-4 Edition 2.0 2012-01 standard. Naturally other embodiments could have been envisaged without departing from the scope of the invention as defined below.

NOMENCLATURE 1. Storage device, 2. Container, 3. Inner liner (inner protective coating), 4. Micro-perforations, 5. Handling straps, 20. Canvas.

Claims (11)

REVENDICATIONS1. A bulk storage device (1) for powdery materials, said device comprising a flexible bulk container (2) and an insulating inner liner (3) having a surface resistivity greater than 1.0 x 10 12 52, without a conductive layer of static electricity and without a dissipative layer of static electricity, said inner lining (3) covering the internal walls of the container, said inner lining (3) comprising micro-perforations (4), through, distributed over the entire surface of said inner liner (3) and in such a way that the breakdown voltage of said inner liner (3) is less than 4 kV and in that the breakdown voltage of the container wall is less than 6 kV. 2. Device according to claim 1, wherein the inner liner (3) is constituted by a single film of material having said micro-perforations (4). 3. Device according to claim 1 or 2, wherein the container (2) for flexible bulk is formed from canvas (20). 4. Device according to claim 3, wherein the fabric (20) is a coated fabric. 5. Device according to claim 3, wherein the fabric (20) is a laminated fabric. 6. Device according to claim 3, wherein the fabric (20) of the flexible bulk container is an air-permeable, preferably non-laminated and uncoated fabric, so as to permit the de-aeration of the device (1). through the micro-perforations (4) of the inner liner (3) and through the web (20) of said container (2). 7. Device according to one of claims 1 to 6, wherein the density of micro-perforations (4) over the entire surface of the inner liner (3) is such that two neighboring micro-perforations are spaced a dimension O less than or equal to 2 cm, preferably between 0.5 cm and 1.5 cm. 20 8. Device according to one of claims 1 to 7, wherein the diameter of the micro-perforations (4) is between 5 microns and 130 microns. 9. Device according to one of claims 1 to 8, wherein the breakdown voltage of the entire container (2) / inner liner (3) is less than or equal to 6 kV. 10. Device according to one of claims 1 to 9, wherein the thickness A of the inner liner (3) is between 20 microns and 700 microns. 11. Use of the storage device (1) according to one of claims 1 to 10 as a large container for flexible bulk classified type B according to the standard 61340-4-4 Edition 2.0 2012-01.10