MXPA06007481A - Reinforced fluoropolymer plates, production methods thereof, corrosion-resistant reactors containing said plates, production methods of same and fluorination methods performed in said reactors - Google Patents

Abstract

The invention relates to a reinforced fluoropolymer plate comprising a fluoropolymer layer on one of the faces thereof and a carbon fibre sheet on the other face of same, whereby at least part of the carbon fibre sheet is impregnated with flouropolymer. The invention also relates to an acid-corrosion-resistant chemical reactor comprising said plates, the production methods thereof and the uses of same in processes in superacid media.

Description

REINFORCED FLUORITE POLYMER PLATES, MANUFACTURING PROCEDURES, REACTORS THAT CONTAIN THESE PLATES RESISTANT TO CORROSION, YOUR MANUFACTURING PROCEDURES AND FLUORATION PROCEDURES PLACED IN PRACTICE IN THESE REACTORS FIELD OF THE INVENTION The present invention relates to fluoropolymer plates reinforced on one of their faces by carbon fibers, to a chemical reactor resistant to acid corrosion comprising said plates, their manufacturing processes and their uses in procedures in the medium super acid.

PREVIOUS TECHNIQUE AND TECHNICAL PROBLEM Reactions in superacid medium, in particular liquid phase fluorination reactions, need, in order to be effective, to use a reaction medium rich in HF and in SbCI5 (or SbClxFy) and elevated temperatures (from 80 to 120 ° C). The anhydrous HF in the form of a liquid phase forms a very corrosive superacid medium with SbCI5. The usual anticorrosive metals and alloys such as stainless steels, inconel, nickel, hastelloy, etc. , do not have enough resistance to make an industrial reactor. One solution (JP 07-233102) consists in applying a coating of fluorinated polymer inside the stainless steel reactor. Another solution (US 4166536, US 3824115) consists in using a fluorinated polymer containing particles of inorganic substances such as silica, graphite or carbon. However, the application of this type of coatings to the interior of the reactor presents numerous technical problems as highlighted in the patent WO 99/00344: The deposits of polymers obtained by spraying and melting polymer powder are porous, the metal is attacked by the HF and the coating comes off. - The deposits obtained by fusion and rotation molding are thicker and waterproof, but this technique is limited to small reactors (<3,785 liters) and, in addition, these coatings, although thick, are still slightly permeable and the acids they eventually penetrate between the polymer layer and the metal wall of the reactor and overpressures are created and cause significant bumps and deformations of the fluoropolymer coating. The patent WO 99/00344 proposes to evacuate these overpressures by drilling small holes in the walls of the reactor (from 0.31 cm to 1.27 cm in diameter). Nowadays, the use of a fluorinated polymer coating in an industrial reactor is only possible at a low temperature (from 20 to 40 ° C) since the coefficient of expansion of the fluorinated polymers is much higher than that of steel. At the temperatures necessary for the liquid phase fluorination of chloroalkanes (from 80 to 120 ° C), the dilation of the shell (inner jacket) is very important and causes structural disorders (folds, tension, deformation, tears, rips) aggravated due to the weak mechanical strength of the hot polymer. Furthermore, the problems of differential expansion between the polymer and the metal in the reactors are known, which involve detachments and stripping of the coating. There are solutions that use multi-layer coatings of fluorinated polymers, and of resin (US Pat. No. 3779854) and of glass fibers, but are totally unsuitable for the implementation of reactions in superacid medium such as HF. Therefore, up to now, no satisfactory solution has been found to make reactors resistant in the chemical and mechanical plane to superacid corrosive media.

BRIEF DESCRIPTION OF THE INVENTION The invention aims to propose plates of fluorinated polymers reinforced on one side with carbon fibers and a new type of reactor comprising these plates resistant both at the mechanical and chemical level to acid corrosive media . These plates can constitute a floating internal coating in the reactor, or can form an integral part of the reactor wall. Therefore, the invention relates to: Reinforced fluorinated polymer plate comprising on one side a layer of fluorinated polymer and on the other side a carbon fiber sheet, at least a part of the carbon fiber sheet being impregnated with fluoropolymer. Plate according to item 1, wherein the impregnated polymer thickness represents at least 10% of the thickness of the carbon fiber sheet, preferably 10% to 90%, advantageously 30 to 70%. Plate according to item 1 or 2, wherein the fluorinated polymer is selected from the group consisting of polychlorotrifluoroethylene (PCTFE), poly (vinylidene fluoride) (PVDF), tetrafluoroethylene and perfluoropropene (FEP) copolymers, tetrafluoroethylene copolymers and perfluoropropylvinylether (PFA), copolymers of tetrafluoroethylene and ethylene (ETFE), polymers of trifluorochloroethylene and ethylene (E-CTFE) and their mixtures. Plate according to one of items 1 to 3, in which the fluorinated polymer is the copolymer of tetrafluoroethylene and hexafluoropropylene (FEP). Plate according to one of points 1 to 4, whose total thickness is between 1 and 20 mm, preferably 2 to 5 mm. Plate according to one of items 1 to 5, wherein the sheet of carbon fibers is in the form of a woven or non-woven sheet, preferably in the form of a sheet of crosslinked carbon fibers. Plate according to one of points 1 to 6, wherein the carbon fiber sheet has a thickness comprised between 0.1 and 1.0 mm, preferably 0.5 to 3 mm. Plate according to one of items 1 to 7 comprising: a fluoropolymer layer on one side of the plate, a fluoropolymer-free carbon fiber layer on the other side of the plate, and a layer central consisting of carbon fibers impregnated with fluorinated polymer. Use of a plate according to one of points 1 to 8 for the manufacture of floating coatings for reactors, tanks, elements of pipes intended to be in contact with corrosive acids and / or superacids. Floating coating comprising a plurality of plates according to one of points 1 to 8, said plates being welded together edge to edge. Reactor comprising: - a metallic inner wall, and - a floating coating according to point 10, located on all or part of the internal wall of the reactor, the face of the coating being comprised of free carbon fibers of fluorinated polymer positioned against the metallic inner wall of the reactor. Reactor according to item 1 1, further comprising: - a plurality of holes in the internal wall, joined to a piping network; - a pressure regulation device connected to the piping network that maintains the pressure in the space between the fluoropolymer layer and the inner wall below the pressure that prevails inside the reactor. Reactor comprising an internal wall, comprising one or more plates according to one of points 1 to 8, reinforced by a layer of composite material and carbon fibers. Reactor according to point 13, which comprises, around the inner wall, a supplementary external metal casing which is not connected. Process for manufacturing plates according to one of points 1 to 8, comprising: contacting the carbon fiber sheet with the fluorinated polymer; - the melting of one face of the fluoropolymer plate; Y - pressure pressing until the polymer is cooled. Manufacturing process according to item 1 5, wherein: - contacting and melting a face of the fluoropolymer plate is obtained by extruding said fluorinated polymer onto the fiber sheet. Process for manufacturing a floating coating according to item 10, which comprises: provision of at least one plate according to one of points 1 to 8; - the trimming and shaping of this plate into a metal reactor, the face being covered with carbon fiber fabric in contact with the metal wall of the reactor; - optionally welding edge to edge of the cut-outs of said at least one plate. Process for manufacturing a reactor according to item 13, comprising: - the provision of at least one plate according to one of points 1 to 8; - the trimming and shaping of this plate on a shape, the face of the fluorinated polymer being in contact with the shape; - optionally, edge-to-edge welding of the cut-outs of said at least one plate; - the application of at least one layer of composite material and one sheet of carbon fibers on said free face, and then the polymerization of the composite material. Fluoridation process in liquid phase in which said reaction is carried out in a reactor according to one of points 1 to 14. Fluoridation process according to point 20, wherein the temperature is between 60 and 150 ° C .

DETAILED DESCRIPTION OF THE INVENTION The thickness of the endplate of reinforced fluorinated polymer can be from 1 to 20 mm and preferably from 2 to 5 mm. The fluorinated polymers (PF) used in the invention are thermoplastic polymers resistant to the acid media especially chosen from the group consisting of polychlorotrifluoroethylene (PCTFE), poly (vinylidene fluoride) (PVDF), copolymers of tetrafluoroethylene and perfluoropropene (FEP), copolymers of tetrafluoroethylene and perfluoropropyl vinyl ether (PFA), copolymers of tetrafluoroethylene and ethylene (ETFE), polymers of trifluorochloroethylene and ethylene (E-CTFE) and mixtures thereof. Preferably, the fluorinated polymer used is the copolymer of tetrafluoroethylene and hexafluoropropylene (FEP) for its non-diffusion properties of antimony (Sb) in the polymer. The used FEP has from 1 0 to 1 5% and preferably 12% by weight of hexafluoropropylene. The PF layer guarantees the chemical resistance of the plate once formed and allows to protect the metal of the reactor from corrosion thanks to its impermeability through its barrier action. The carbon fibers are used in the form of sheets of fibers (or fabric), in particular woven or nonwoven identical to those commonly used in the composite materials industry in carbon fibers (automobile, ski, ship). The carbon fibers are used in the form of weaving or winding according to the classical techniques for manufacturing composite materials in carbon fibers.

Preferably, sheets of crosslinked carbon fibers are used. The thickness of the carbon fiber sheet can be between 0.1 and 1.0 mm, preferably 0.5 to 3 mm. The chosen thickness depends on the type of subsequent application of the reinforced plate. The carbon fiber sheet increases the mechanical strength of the PF layer and in particular its resistance to hot creep. It allows the subsequent coupling of composite material on the PF-free carbon fiber layer, in particular in the case of a composite reactor as described below. The manufacturing process of the reinforced plates can comprise the contacting of the carbon fibers with the fluorinated polymer, the melting of one face of the fluoropolymer plate, the application of the carbon fibers on the face of the molten polymer, pressure pressing until the polymer is cooled. The carbon fiber sheet is attached to one face of the PF plate by melting the PF in contact with the sheet and penetrating the melted PF through at least a part of the thickness of the sheet. According to a preferred embodiment, the reinforced fluoropolymer plate comprises: a fluoropolymer layer on one side of the plate; - a layer of carbon fibers free of fluorinated polymer on the other side of the plate; - a central layer constituted by carbon fibers impregnated with fluorinated polymer. The implementation can be carried out by heating one face of the PF plate until the melting of a surface layer of PF, and then the application of the sheet and pressing under high pressure until cooling of the PF. The techniques of coextrusion of the PF and the sheet during the manufacture of the PF plate can also be advantageously employed. The impregnation of the carbon fiber sheet by the molten PF can be carried out at least partially. The impregnation thickness (impregnation rate) is at least 10%, preferably from 10 to 90% of the thickness of the sheet or fabric of carbon fibers and advantageously from 30 to 70%. Due to the partial impregnation, the part of the non-impregnated carbon fiber sheet can, thanks to its porosity, serve as free space (for gases) between the metallic inner wall of the reactor and the impermeable layer of FP, in particular in the case of a reactor lined with an inner jacket as described below. A) Yes, the impregnation rate as defined above is sufficient to guarantee the strength of the coupling of the sheet on the PF, to guarantee the mechanical reinforcement of the PF plate whose hot mechanical characteristics are too weak and finally to guarantee the dimensional stability of the PF plate during the expansion of the polymer under the action of temperature. Once formed, the reinforced plates can be used for the manufacture of a floating coating (called inner jacket) of the reactor. This inner jacket is made with one or more PF plates reinforced with carbon fibers on one side. When the inner sleeve is made with several plates, these are welded edge to edge. Using the FEP, a particularly impermeable coating is obtained which acts as an obstacle in particular to the diffusion of antimony. The FEP also has the advantage of being easy to weld at low temperature. In the inner jacket according to the invention, the carbon fiber sheet is very solidly bonded to the PF plate (extrusion of the PF through one face of the carbon fiber sheet). This carbon fiber framework guarantees the dimensional stability of the PF plate constituting the inner jacket, the expansion of the PF is carried out only on the thickness of the plate. This prevents creep and crease formation during heating of the reaction medium in the reactor. The inner jacket (or floating coating) is applied to the interior of the reactor or on only the part of the reactor in contact with the corrosive medium (liquid phase), advantageously the inner jacket is only applied on the reactor tank. The porous layer of carbon fiber fabric on the outer face of the PF plate creates a gas permeable space. This porous layer improves the distribution of pressure between the metal wall of the reactor and the inner jacket and thus avoids the formation of gas pockets resulting from the diffusion of reagents through the barrier layer of fluorinated polymer. This space makes it possible to collect the gaseous HF which can diffuse very lightly through the PF under the action of the high pressures of the fluorination reaction (from 10 to 15 bar). This space created by the porous layer also allows the gas to circulate to the holes drilled in the metal wall of the reactor, when said holes are present. These orifices are connected to a network of ducts that allows to control the pressure that prevails in this space and to keep it always lower than the one that prevails in the reactor.

Thus, the inner jacket is always strongly pressed against the wall of the reactor under the effect of pressure without the use of glues which do not resist the diffusion of HF; In addition, it is more easily removable. For this, the reactor can include a device that allows to maintain a pressure lower than the pressure of the reactor in the space between the internal metal wall of the reactor and the external wall equipped with carbon fibers of the PF of the inner jacket. The pipes lead to a reservoir whose pressure is maintained at a value always lower than that of the reactor by means of a vacuum pump (reactor at atmospheric pressure) or injecting an inert gas. This pressure difference can be from 0.1 to 15 bar and preferably 0.5 to 2 bar. The diameter of the holes can be from 1 to 20 mm and a grid can be placed on the side of the hole in contact with the inner sleeve. The diameter of this grid is advantageously greater than that of the hole. The number of holes drilled in the wall of the reactor depends on the diameter of these holes and the thickness of the carbon fiber sheet not impregnated by the PF. It can be from 1 to 20 per m2 of wall and preferably from 2 to 5 per m2. The presence of this porous layer also makes it possible to reduce the number of holes necessary for the evacuation of the gases without reducing the efficiency of the engagement of the inner jacket on the metal wall of the reactor under the action of the internal pressure of the reactor. The reactors coated with an inner jacket as described above can withstand reaction conditions in superacid medium, in particular the liquid phase fluorination reactions, such as temperatures ranging from 0 to 1 50 ° C and preferably from 60 to 1 20 ° C and a pressure of 1 to 1 5 absolute bars.

According to another aspect, the invention relates to a reactor (called composite reactor) whose wall comprises an inner layer of fluorinated polymer, a central layer consisting of carbon fibers impregnated with fluorinated polymer and a layer of carbon fibers free of fluorinated polymer and impregnated with a composite material (called a composite layer of carbon fibers). The composite material used is preferably a resin chosen from resins compatible with (super) acid media and in particular HF. In particular, poly (phenylene sulfide) (PPS) and polyetheretherketone (PEEK) can be used. The carbon fibers are in the form of sheets or fabrics or yarns. This layer composed of carbon fibers particularly guarantees the mechanical strength of the reactor, the tank or the pipe elements. Its thickness is calculated as a function of the voltages and in particular of the pressure of use of the reactor. Its thickness can go from a few millimeters to several centimeters. In this embodiment, the joints of the layers present are the following: the composite layer is bonded to the carbon fiber sheet (central layer) by the resin at the level of the FP-free face of the sheet; the central layer of the carbon fiber sheet is joined to the PF layer by melting the PF in contact with this sheet and penetration of the molten PF through a part of the carbon fiber sheet. The coating of the carbon fiber sheet by the PF is only partial so that the surface of the carbon fiber sheet in contact with the composite layer is not coated with PF and the engagement of the composite material on the sheet can be effected by the resin. These composite reactors can be manufactured according to the process in which: - in a first step, PF plates reinforced by a carbon fiber sheet are made with one face of the PF-free sheet; - the central layer of the carbon fiber sheet is joined to the PF layer by melting the PF in contact with this sheet and penetration of the molten PF through a part of the carbon fiber sheet. The thickness of this PF plate is preferably 2 to 5 mm and that of the carbon fiber sheet of 0.5 to 3 mm; - as above, the sheet of carbon fibers is fixed on the PF at the moment of extrusion of the plate and the sheet is covered by the molten PF over a part of its thickness; - then, in a second stage, one or more of these plates are cut out and the face of the PF against the shape is applied to a shape having the inner dimensions of the reactor, and then optionally welded between them edge to edge by a jet hot gas; - then, in a third step, the composite layer is placed by successive applications of composite material and carbon fibers around the coated form of reinforced PF plates; - then, after drying and polymerization, the inner shape is disassembled to release the inner wall of the composite reactor. The composite material reactor according to the invention makes it possible to limit, even eliminate, the problems of differential expansion between the polymer and the metal, thus preventing detachment and tearing of the coating. According to a particular embodiment, when the reactors, tanks or pipe elements are used at high pressures, an additional metal jacket, for example steel, can be added around the composite reactor. This casing is not joined, a space of a few centimeters is provided to allow the expansion of the composite reactor. The steel casing is dimensioned to withstand the pressure of the reactor in case of escape / exit or breakage of the composite reactor. A leak detection device may be added to detect the presence of chemicals in the free space between the composite reactor and the metal enclosure. When FEP is used as a fluorinated polymer in the manufacture of the reinforced plates, their main defects are overcome, that is to say a softening and an expansion too important in hot. Thus, the use of FEP makes it possible to carry out an effective reactor (or reservoir or piping element) coating, particularly for the implementation of chloroalkane fluorination reactions in liquid, pressurized and hot phases. The reactors thus manufactured with the reinforced plates according to the invention can withstand reaction conditions in superacid medium, in particular the liquid phase fluorination reactions, such as temperatures ranging from 0 to 1 50 ° C and preferably from 60 to 120 ° C and a pressure of 1 to 15 absolute bars. The plates according to the invention can be used to manufacture floating coatings (inner jacket) of metal reactors or to manufacture reactors, tanks or elements of pipes of composite materials used for the reaction, storage or transport of corrosive acid products, in in particular mixtures of hydrofluoric acid and antimony halide. The conditions of use of reactors, tanks or pipe elements include temperatures from 0 to 150 ° C and pressures from 0 to 1 5 bars. EXAMPLES The following examples illustrate the present invention without limiting it.

Example 1 Preparation of reinforced fluorinated polymer plates FEP plates coated on one face with carbon fiber fabric (woven carbon fiber sheet) are made. The thickness of the FEP plate is 3 mm and that of the carbon fabric is 1 mm. The carbon fabric is fixed on the FEP plate at the time of extrusion of the FEP and the tissue is covered by the fused FEP about half its thickness. The total thickness of the plate is 3.3 mm. EXAMPLE 2 Preparation of a floating coating (inner jacket) The plates prepared in Example 1 of about 3 m2 in size are cut out and applied inside the reactor tank, the face coated with carbon fiber fabric against the wall metallic The plates cut between them edge to edge are welded by a jet of hot gas to form a continuous impermeable coating over the entire inner surface of the reactor vessel included on the part of the tub in contact with the gasket of the reactor shell. The cutting of the plates is carried out in such a way that the welds of the plates are preferably placed on the surfaces with a large radius of curvature. Example 3 Preparation of the composite reactor The plates prepared in Example 1 of about 3 m2 in size are cut out and applied to a shape having the internal dimensions of the reactor., the face of FEP against the shape, then they are welded together edge to edge by a jet of hot gas. The composite layer is then placed by successive applications of resin and carbon fiber fabric around the shape. After drying and polymerization, the inner shape is dismantled. EXAMPLE 4 Strength tests in superacid medium of a plate prepared according to example 1 A sample of FEP plate coated with carbon fiber fabric of 2 cm x 2 cm x 3.3 mm in size was placed for 400 h in a reactor. used for liquid phase fluorination reactions according to the following conditions: Temperature: from 80 to 1 1 0 ° C Pressure: from 1 0 to 13 bar Fluoridation medium: mixture of anhydrous HF and SbCI5 Reagents subjected to fluorination: trichlorethylene, dichloromethane and trichloroethane. At the end of these tests, no alteration was observed in the sample, no detachment of the carbon fiber layer, or any weight loss.

Claims (20)

1. REIVI NDICATIONS 1. Reinforced fluorinated polymer plate comprising on one side a layer of fluorinated polymer and on the other side a carbon fiber sheet, at least a part of the carbon fiber sheet being impregnated with fluoropolymer. A plate according to claim 1, wherein the impregnated polymer thickness represents at least 10% of the thickness of the carbon fiber sheet, preferably from 10% to 90%, advantageously from 30 to 70%. The plate according to claim 1 or 2, wherein the fluorinated polymer is selected from the group consisting of polychlorotrifluoroethylene (PCTFE), poly (vinylidene fluoride) (PVDF), tetrafluoroethylene and perfluoropropene (FEP) copolymers, tetrafluoroethylene copolymers and perfluoropropyl vinyl ether (PFA), copolymers of tetrafluoroethylene and ethylene (ETFE), polymers of trifluorochloroethylene and ethylene (E-CTFE) and mixtures thereof. Plate according to one of claims 1 to 3, in which the fluorinated polymer is the copolymer of tetrafluoroethylene and hexafluoropropylene (FEP). Plate according to one of claims 1 to 4, the total thickness of which is between 1 and 20 mm, preferably 2 to 5 mm. Plate according to one of claims 1 to 5, in which the carbon fiber sheet is in the form of a woven or non-woven sheet, preferably in the form of a sheet of crosslinked carbon fibers. Plate according to one of claims 1 to 6, in which the carbon fiber sheet has a thickness comprised between 0.1 and 1.0 mm, preferably 0.5 to 3 mm. Plate according to one of claims 1 to 7, comprising: a fluoropolymer layer on one side of the plate, a fluoropolymer-free carbon fiber layer on the other side of the plate, and a central layer constituted by carbon fibers impregnated with fluorinated polymer. 9. Use of a plate according to one of claims 1 to 8 for the manufacture of floating coatings for reactors, tanks, pipe elements intended to be in contact with acidic and / or superacid corrosive media. 1 0. Floating coating comprising a plurality of plates according to one of claims 1 to 8, said plates being welded together edge to edge. eleven . Reactor comprising: - a metallic inner wall, and - a floating coating according to claim 10, located on all or part of the internal wall of the reactor, the face of the coating comprising the free carbon fibers of fluorinated polymer positioned against the metallic inner wall of the reactor. Reactor according to claim 1 1, further comprising: - a plurality of holes in the inner wall, joined to a piping network; - a pressure regulation device connected to the piping network that maintains the pressure in the space between the fluoropolymer layer and the inner wall below the pressure that prevails inside the reactor. 13. Reactor comprising an internal wall, comprising one or more plates according to one of claims 1 to 8, reinforced by a layer of composite material of resin and carbon fibers. 14. Reactor according to claim 13, comprising a non-bonded supplementary outer metal envelope around the inner wall. 5. Process for manufacturing the plates according to one of claims 1 to 8, comprising: contacting the carbon fiber sheet with the fluorinated polymer; - the melting of one face of the fluoropolymer plate; Y - pressure pressing until the polymer is cooled. The manufacturing process according to claim 15, wherein: - contacting and melting a face of the fluoropolymer plate is obtained by extruding said fluorinated polymer onto the fiber sheet. Process for manufacturing a reactor according to one of claims 1 to 12, provided with a floating coating according to claim 10, comprising: - the provision of at least one plate according to one of claims 1 to 8; - the trimming and shaping of this plate into a metal reactor, the face being covered with carbon fiber fabric in contact with the metal wall of the reactor; - optionally welding edge to edge of the cut-outs of said at least one plate. 8. The method of manufacturing a reactor according to claim 13, comprising: providing the at least one plate according to one of claims 1 to 8; - the trimming and shaping of this plate on a shape, the face of the fluorinated polymer being in contact with the shape; - optionally, edge-to-edge welding of the cut-outs of said at least one plate; - the application of at least one layer of composite material and carbon fibers on said free face, and then the polymerization of the composite material. 9. Fluoridation process in liquid phase in which said reaction is carried out in a reactor according to one of claims 1 to 14. 20. Method of fluorination according to claim 19 and wherein the temperature is between 60 and 150. ° C.