MXPA99000565A - Fluoropolymer tubes and methods for elaborating - Google Patents

Abstract

The present invention relates to a flexible expanded PTFE membrane tube in layers, comprising: a first layer of expanded PTFE membrane exhibiting a structure of nodes and fibrils, comprising an internal surface and an external surface, at least one Subsequent layer of expanded PTFE membrane exhibiting a node and fibril structure comprising an inner surface and an outer surface, wherein each subsequent layer surrounds at least a portion of the outer surface of the immediately preceding layer, and wherein the diameter inner tube is greater than 25.4

Description

FLUOROPOLYMER TUBES AND METHODS FOR ELABORATING THEM RELATED APPLICATIONS The present application is a continuation in part of the copending United States of America Patent Application Serial No. 05 / 682,037 filed on July 16, 1996.

FIELD OF THE INVENTION The present invention relates to flexible fluoropolymer tubes that exhibit excellent properties, such as mechanical strength, wear resistance and dimensional stability when subjected to repeated flexing due to vibration, bending or the like.

BACKGROUND OF THE INVENTION Polytetrafluoroethylene (PTFE) has proven useful in many areas. As industrial material, such as for packaging or flexible pipe material, PTFE exhibited an excellent utility in extreme chemical environments that normally degrade many metals and conventional polymeric materials. The non-reactive nature of PTFE, maintains its purity during use in the articles manufactured from it, because these B1058 / 99MX PTFE articles, normally do not contain plasticizers, fillers, stabilizers or antioxidants that could be leached and react with the fluids or powders of the process or with the manufactured components coming from high value industries including manufacturing processes. semiconductors and pharmaceutical production. PTFE can also be used in a wide range of temperatures, from as high as approximately 280 ° C or higher to as low as approximately -273 ° C. PTFE tubes have been manufactured by a variety of methods. Normally, PTFE tubes are manufactured by extruding pulp in the presence of an organic lubricant, followed by removal of the lubricant, immobilization in amorphous form at temperatures above the crystalline melting point of the PTFE and further processing. U.S. Patent No. 4,267,863 to Burelle and U.S. Patent No. 3,225,129 to Taylor et al., Treat the manufacture of rigid non-porous PTFE tubes by winding thin calendered PTFE tapes over a metallic mandrel, followed by heating the ribbon tube in layers to a temperature above the crystal melt of the PTFE for a sufficient time to reach or achieve the intralayer adhesion. Further, P1058 / 99MX can be molded directly from large diameter tubes or machined from molded rods produced from granular PTFE resins. PTFE tubes, manufactured using the aforementioned techniques have shown utility as expansion joint coatings, as described in, for example, U.S. Patent No. 4,536,018 to Patarcity. These conventional non-porous PTFE tubes manufactured through extrusion, tape winding or compression molding exhibit poor mechanical properties, such as poor flexibility, low tensile strength and low flexural strength. In accordance with this, despite several and very desirable performance characteristics, the use of non-porous PTFE tubes is generally limited to applications that require only limited flexibility. The bending stresses applied to the tubular components, particularly those stresses experienced with repeated bending or rapid compression and axial recovery resulting in a cyclic movement or vibration of the apparatus on which the tube is mounted, are a particular problem for non-porous PTFE tubes and PTFE composite tubes. Specifically, these materials are normally weakened as a result of bending stresses and / or P1058 / 99MX abrasion associated with bending or continuous bending with axial orientation, which leads to the development of cracks and flaws in the tube and which eventually results in catastrophic failure of the tube. Polytetrafluoroethylene can be produced in a porous and expanded form as taught in U.S. Patent No. 3, 953,566, 3,962,153 and 4,187,390 Gore. The membranes and tubes described herein have a microstructure comprised of nodes interconnected by fibrils. The tube formation is performed by extruding a mixture of PTFE and liquid lubricant, removing the lubricant from the resulting tubular extrudate and expanding the extrudate by drawing at a suitable speed and at a temperature between about 100 ° C and 325 ° C. The resulting tube can preferably be subjected to amorphous immobilization while the tube is longitudinally restricted. This process creates the desirable orientation of the material and, correspondingly, the resistance, mainly in the longitudinal direction. However, for applications requiring tangential resistance or bursting resistance, such as those experiencing high internal pressure, these tubes may often not include sufficient strength in the circumferential wall to meet the desired performance needs.

P-.058 / 99 X Tubes formed from sheets or sheets of stacked layers of expanded PTFE have been formed by conventional tube seam sealing techniques, such as end-to-end butt sealing, recessing or beveling the ends for sealing and overlapping the ends to form a seam, as shown in Figures 1A, IB and IC, respectively. The ends are joined by any conventional sealing technique, such as, for example, by the use of an adhesive, by densifying and melting together the ends or the like. An example of tubes formed by recessing the ends of a flat sheet and adhering the recessed ends with an adhesive to form a bonded tube are the tubes available commercially from Helms Industrial Supply, Inc. and manufactured from flat sheets of stacked layers of expanded PTFE sold by WL Gore & Associates, Inc. (Elkton, MD), as GR SHEET® packaging material. These tubes have been incorporated as pipe connectors in industrial systems, whereby the joined pipes are placed between two pipes and fixed by means of a clamp at the ends of the pipes. Two exemplary configurations of this installation show hose clamps 50 and a coupling 52 P1058 / 99MX of pipe having screws 53 to hold and hold the pipe 54 in place, respectively, as shown in Figures 2A and 2B. PTF membranes? expanded porous tiener-fibrils oriented uniaxially, biaxially or multiaxially, as described in the aforementioned patents of the United States of America by Gore, have also been used in the manufacture of porous tubes by winding expanded PTFE membranes on a mandrel at a temperature above 1 = crystalline melting temperature of the PTFE during ur-period of time to achieve adhesion of the c = pas. This winding can be performed, for example, as an external helical shell over the expanded PTFE pipe described above to increase the tangential strength, such as is commercially available from W.L. Gore & Associates, Inc. (Flagstaff, AZ), as vascular grafts sold with the GORE-TEX® commercial label or as a wound layer between ur. internal expanded and an outer tube as disclosed in, for example, U.S. Patent No. 4,787,921 to Shibata. The flexible wound pipe and the expanded PTFE composite pipe produced in the aforementioned forms have been considered advantageous because they have resistance in both directions. longitudinal as in the P10S8 / 99MX circumferential, diametral flexibility, thin wall thickness up to 0.25 mm and small diameters up to 25.4 mm and its collapsible characteristics. It has been found that these tubes are suitable in various areas, such as intraluminal vascular grafts, filter elements or catheters, as described in PCT Publication No. WO 95/0555, gastroscope introducers as described in EPO Publication No. 0 605 243 and for gas permeation in applications such as degassing tubes as described in U.S. Patent No. 4,787, 921 to Shibata. Although tubular articles of the prior art work well in the applications for which they were designed, the prior art fails to obtain the improved tubes of the present invention that provide novel utility in a variety of industrial applications where a long life is required in flexion, high resistance, high thermal and chemical resistance and high purity. In accordance with the foregoing, it is a primary purpose of the present invention to provide novel tubes comprising expanded PTFE, which exhibit an improved flex life as compared to conventional flexible pipe materials. Another purpose of the present invention is P1058 / 99MX provide novel tubes comprising expanded PTFE, which exhibit an improved life in bending, while having wall thicknesses and diameters that to date could not be obtained based on the prior art teachings. It is a further purpose of the present invention to provide novel tubes comprising expanded PTFE, which incorporate surface textures, such as corrugations and the like, to provide improved performance in a wide variety of applications. It is a further purpose of the present invention to provide novel production techniques for manufacturing the novel tubes of the present invention. These and other purposes of the present invention will be apparent based on the following description.

SUMMARY OF THE INVENTION The present invention is a flexible tube comprising expanded PTFE and exhibiting excellent tensile and flexural strength, dimensional stability, non-chemical reactivity and utility at temperatures as high as approximately 280 ° C or higher and as low. as close to -273 ° C. In addition, the present invention provides novel techniques for P1058 / 99MX manufacture said tubes, whereby, for example, the tube is removable from the mandrel by applying a flow or burst of gas to separate the tube from the mandrel, the tube can be formed by blowing the mandrel tube into a mold or the similar. A preferred application for the novel flexible tubes of the present invention is as a connection between two or more members, such as tubes or the like. For example, the novel flexible fluoropolymer tubes can be placed around the periphery of a tubular member, such as a tube, having an outer diameter equal to or smaller than the inner diameter of the flexible tube. Alternatively, the tube in optional form may be stretched diametrically to fit around tubes having diameters greater than the inner diameter of the tube. Alternatively, the tubes may be provided with flared ends to allow connection or connection with standard tube flanges or the like. Furthermore, it is contemplated that alternate connecting means using the novel tubes of the present invention are also encompassed by the present invention. For example, the two or more elements that will be connected with the flexible tube of the present invention can practically be butted one after the other or they can be separated, either one in line with the other or P10S8 / 99MX with a certain angle between them, depending on the desired configuration of the final unit. The flexible tubes of the present invention can be used in a variety of industrial applications, including flexible connections or couplings to connect two conduits, ducts or pipe sections for the transport of gases, liquids, powders, granular materials and the like. As compared to the conventionally available connectors, the flexible tubes exhibit improved performance in applications between components of vibrating bulk solids transport equipment, screening and separation equipment, fluidized bed dryers and other processing equipment in which non-polluting tubular connections having an excellent flex life are desirable. In a further embodiment of the present invention, the novel flexible tubes of the present invention can be used as protective covers in, for example, mechanical components to protect said components from thermal, chemical, mechanical stresses as well as other stresses of the environment. For example, the hoses of the present invention can be used as tire covers of hydraulic or pneumatic cylinders, which undergo axial bending P10S8 / 99MX during use or, alternatively, as covers for industrial joints and automotive mechanics that suffer from angular bending or a twisting movement. The flexible tubes of the present invention may also exhibit utility in non-dynamic applications, such as in compressor connections, engine intake and exhaust manifolds and in vent duct connections. Additional applications of the novel tubes of the present invention, include the use as inner liners or liners for tubing or tubing sections or as tubular packing material around the peripheries of butted or abutted tubes, the tubes will be compressed against the walls of the tubing by any suitable means, such as, hose clamps, metal or plastic compression pipe couplings or the like. The flexible tube of the present invention can be formed in virtually any size and cross-sectional dimension important for industrial applications and can comprise any porous fluoropolymer membrane that provides the performance characteristics required. In a particularly preferred embodiment, the novel tube comprises expanded and porous PTFE membranes or combinations of expanded PTFE membranes produced by the methods described in, by P1058 / 99MX example, Patents of the United States of America No. 3,953,566, 3,962,153 and 4,187,390 Gore. Tube fabrication includes winding the porous fluoropolymer membrane around a cylindrical mandrel capable of withstanding such high temperatures as, for example, the crystalline melting point of PTFE or higher. The porous fluoropolymer membrane can be any thickness, width, etc. desired, and preferably has a microstructure comprised of nodes and fibrils, wherein the fibrils are oriented either in a single direction or in multiple directions. In a further embodiment, the novel tubes of the present invention can be shaped to incorporate unique geometries, such as conics, frusto or other geometries and can also be shaped to include corrugations or other desirable surface geometries in at least a portion of the tubes.

DESCRIPTION OF THE DRAWINGS OR FIGURES The detailed description of the present invention , it will be better understood when it is read together with the attached drawings. For the purpose of illustrating the invention, these are shown in the modalities of drawings that are currently preferred. However, it must be understood that the P1058 / 99MX invention is not limited to the precise arrangements and instrumentation shown. In the drawings: Figures 1A-1C are cross-sectional views of prior art tubes incorporating various seam sealing configurations to form the tubes. Figures 2A and 2B are side views of prior art tubes, such as those shown in Figure 1, used as pipe connectors, where the pipes are fixed to the pipes by hose clamps and a pipe coupling , respectively. Figure 3 is a 2500x electron scanning photomicrograph of an expanded PTFE membrane, longitudinally oriented, having a node and fibril structure. Figure 4 is a photomicrograph by electron scanning at 2500x of an expanded and axially oriented PTFE membrane having a structure of node and fibrils. Figure 5 is a photomicrograph by electron scanning at lOOOx of a multiaxially oriented expanded PTFE membrane having a node and fibril structure.

P1058 / 99MX Figure 6 is a perspective view of one embodiment of the present invention showing an exposed edge oriented longitudinally of the outer shell of the membrane. Figure 7 is a perspective view of another embodiment of the present invention, showing an exposed helically oriented edge of the outer shell of the membrane. Figure 8 is a perspective view of the perforated mandrel in which the porous fluoropolymer membrane is wound. Figure 9 is a perspective view of a coiled or wrapped membrane mandrel with hose clamps attached at the ends to hold the membrane in layers during a heating cycle. Figures 10A and 10B are perspective views of frusto and conical shaped tubes, respectively, of the present invention. Figure 11 is a side view of a tube of the present invention incorporating a helical rib. Figures 12A-12C are perspective views of tubes of the present invention having helical, circumferential and longitudinal corrugations, respectively. P1058 / 99 X Figures 13A-13C are partial, side and cross-sectional views of angular, rounded and square corrugation geometries, respectively, which may be formed in the corrugated tubes of the present invention. Figure 14 is a perspective view of one embodiment of a tube molding unit of the present invention. Figure 15 is a profile view of the modified apparatus for Newark bending tests, used to evaluate the bending life of the tubes during continuous compression / expansion cycles in the axial direction. Figure 16 is a perspective view of the layouts of the flexure testing facility used in the test materials in accordance with the present invention. Figure 17 is a perspective view of a tube placed in the flexure testing apparatus of Figure 15 in a flexed state.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The present invention is directed to a flexible fluoropolymer tube which exhibits excellent tensile and flexural strength, dimensional stability, non-chemical reactivity and utility at temperatures as high as approximately 280 ° C or P1058 / 99MX higher and as low as close to -273 ° C, in sizes and configurations that until now had not been possible to obtain based on the teachings of the prior art. In addition, the present invention provides novel techniques for manufacturing said tubes. For example, the tube can be removed from the mandrel by applying a flow or a burst of gas to separate the tube from the mandrel. In addition, novel forming techniques allow the formation of unique geometries that vary from conical configurations to bellows configurations and where the novel tubes have any number of desirable surfaces, such as corrugations, surface textures and the like. The novel flexible tubes of the present invention can be manufactured from fluoropolymeric materials that exhibit the desired performance characteristics described above. In a particularly preferred embodiment of the present invention, the novel fluoropolymer tubes are manufactured from a porous expanded polytetrafluoroethylene (PTFE) membrane, such as those taught in, for example, United States Patent No. 3,953,566 , 3,962,153 and 4,187,390 Gore, which are incorporated in their entirety as a reference here. The expanded porous PTFE can be loaded with P1058 / 99MX particulate fillers, coated on one or more surfaces or can be completely impregnated in at least a portion of the thickness of the membrane with polymeric materials before or during formation. Additionally, other components (e.g. sheet or film elements, reinforcing ribs, etc.) can be easily incorporated into the expanded PTFE membranes used to form the flexible tubes of the present invention. The fluoropolymer tubes of the present invention, which preferably comprise expanded PTFE, can be loaded with various fillers currently used to load expanded microporous PTFE films, as taught in U.S. Patent No. 4,096,227, to Gore and in US Pat. U.S. Patent No. 4,985,296, to Mortimer, Jr., incorporated herein by reference in its entirety. Suitable particulate fillers may include, for example, inorganic materials, such as metals, semimetals, metal oxides, glass, ceramics, catalysts and the like. Alternatively, other suitable particulate fillers may include, for example, organic materials selected from activated carbon, carbon black, polymeric resins such as ion exchange resins, chemical indicators that undergo a color change in P1058 / 99MX presence of other substances and the like. Furthermore, if a conductive charge is used to charge the expanded PTFE membrane and is present in sufficient quantity, the membrane and, thus, the tube itself, may exhibit static dissipating or conductive properties. The term "static dissipative", as used herein, is intended to include any material with a volume resistivity of less than 10 and greater than 10 ohm cm, as determined by ASTM D 257-90. The term "conductor", as used herein, is intended to include any material having a volume resistivity of 102 ohm cm or less, as determined by ASTM D257-90. The term "particulate" is defined herein to refer to individual particles of any dimensional relationship, including powders, fibers, etc. The tubes of the present invention may be fabricated from expanded PTFE that has been expanded monoaxially, biaxially or multiaxially, depending on the desired performance of the resulting flexible tubes. Figure 3 shows a photomicrograph by electron scanning at 2500x of a PTFE membrane longitudinally oriented (ie oriented in monoaxial form) having a structure of nodes and fibrils. In addition, Figure 4 is a photomicrograph by scanning with P1058 / 99MX electrons at 2500x of an expanded and axially oriented PTFE membrane having a node and fibril structure. In addition, Figure 5 is a photomicrograph by electron scanning at lOOOx of a multiaxially oriented expanded PTFE membrane having a node and fibril structure. In a particularly preferred embodiment of the present invention, as shown in Figure 6, a flexible fluoropolymer tube is produced by winding and axially expanding the expanded PTFE membrane 11 with the sides of layers 13 layered one in the upper part of the other around the mandrel 15, ending with the edge 12 of the outer layer of film longitudinally oriented along the outside of the tube. The multiple layers of the tube are preferably at least partially adhered to each other to minimize delamination during use. A preferred technique for adhesion of the layers is by heating, as described below. Depending on the desired final configuration of the tube, it may be desirable to substantially hold the porous film layers in place by holding them against the periphery of the mandrel to prevent the expanded PTFE membrane from contracting in the axial direction during the heating cycle. The mandrel wound with film is P10S8 / 99MX then heats up to a temperature above the crystalline melting point of the expanded PTFE for a sufficient period of time to obtain at least some coalescence of the nodes and the fibrils at the surface interface of each of the expanded PTFE layers, resulting in the adhesion of film layers. The degree or extent to which the expanded PTFE layers adhere to each other depends on the temperatures at which the expanded PTFE membrane is exposed and the period of time the membrane heated up, regardless of whether it is before, during or after the formation of the flexible tube. The preferred expanded PTFE membranes are usually those that have not been heated to temperatures above the crystalline melting point of the expanded PTFE prior to construction on the mandrel. The formed tube can then be heated to a temperature in excess of about 327 ° C, which results in amorphous immobilization as described in U.S. Patent No. 3,953,566, to Gore. Alternatively, the expanded microporous PTFE can be subjected to said amorphous immobilization before being wound onto the mandrel. The heating of the expanded PTFE can be carried out, for example, in a hot air convection oven, a radiant heat oven, a molten salt bath or any P10S8 / 99MX another heating medium able to reach the temperatures necessary to produce the adhesion between the layers of the expanded PTFE membrane. In an alternative embodiment of the present invention, as shown in Figure 7, the tubes can be created by helically winding a membrane strip 14 around a mandrel 15 and overlapping the adjacent edges of the membrane 17 to create a helically oriented edge 16 of the outer layer of the membrane. Multiple layers of membrane can be wound or coiled to obtain any wall thickness of the desired tube. The film wound mandrel can then be prepared and heated as described above to achieve membrane adhesion. In a further embodiment, the tubes of the present invention can be manufactured by combining the techniques described above. For example, the tubes can be manufactured by combining a helically wound interior and a coil or a longitudinally wound exterior, a coiled winding interior and a helically wound exterior, an interior and an exterior consisting of coil wound film and a middle region of helically wound film or, virtually any number of combinations of these rolling techniques. P1058 / 99MX In prior art tube constructions manufactured from expanded PTFE membranes and rolled, it has been observed that with heating, the inner surface of the tube can normally adhere to the surface of the mandrel as a result of the tightness or tightness of the rolled membrane and the adhesive properties of the expanded PTFE when it is heated to temperatures above its point of fusion. Expansion of the expanded FTFE membrane to the mandrel seemed to become a major problem as the number of membrane layers increased to produce tubes with higher wall thicknesses. Furthermore, adhesion to the mandrel appeared to be a great problem as the surface area of the membrane that comes into contact with the surface of the mandrel increases. Adhesion / friction of the tube in the mandrel when the tube is removed from the mandrel, can be easily overcome for small diameter and thin walled tubes. Thus, the prior art tube constructions of expanded PTFE membrane wound around a mandrel were limited to sizes up to 25.4 mm internal diameter and with a wall thickness of up to 0.25 mm. However, in prior art attempts to form tubes with a greater wall thickness and / or tubes having comparatively larger diameters when winding the membrane P1058 / 99MX PTFE expanded around a mandrel, the adhesion / friction forces tended to increase to the point where it was impossible to remove the tube from the mandrel without damaging the tube. A novel preferred technique in the manufacture of the tubes of the present invention is the use of a porous or perforated mandrel and the use of air pressure to force or push the inner wall of the tube and release it from the surface of the mandrel. Figure 8 shows an embodiment of the unit for removing the tube from the mandrel, in which a mandrel made from a tube 18 has holes 21 distributed over the surface of the mandrel to allow the pressurized gas to flow between the surface of the mandrel and the inner surface of the expanded PTFE membrane tube. The end caps 20 are attached to the ends of the mandrel by welding or the like to provide a watertight seal. In one of the end caps an orifice is provided for connection to a port or coupling 19. Figure 9 shows the mandrel of Figure 8 having a fluoropolymer membrane coil 22 wound around the mandrel where the edge 23 of the outer layer of the membrane is oriented longitudinally along the outside of the tube. The hose clamps 24 support the fluoropolymer membrane during the cycle P1058 / 99MX heating A pressurized gas line, such as an air line, may be attached or connected to the coupling, allowing pressurized air to enter the interior of the mandrel to provide the necessary internal air pressure required to overcome both the constriction forces the membrane layers of PTF? expanded as the adhesive bond of the inner layer of the membrane on the surface of the mandrel after the heating cycle. Alternatively, the mandrel may be equipped with an alternate means for supplying air to separate the tube from the mandrel. For example, a gas (for example air) can be blown through the entire inner length of the tube from a source at one or more ends of the tube / mandrel unit. The resulting tube may comprise at least partially porous construction resulting from the porous nature of the PTF membrane? expanded from which it was manufactured. If a non-porous tube is desired, can the PTFE membrane wound tube be heated above the crystalline melting temperature of the PTF? for a sufficient time to cause the contraction of the expanded porous PTFE membrane to the desired amount of porosity or practically until no porosity remains. The resulting PTF materials? expanded densified will exhibit remnants of a P1058 / 99MX structure of node and fibril, as evidenced by the peaks of the Differential Scanning Calorimetry (DSC) at 327 ° C and 380 ° C during a temperature increase of 10 ° C / min. For the DSC analysis of the materials of the present, by means of the use of the Differential Scanning Calorimeter a thermal analysis of a sample was determined. Approximately 10 mg of sample was placed on a Differential Scanning Calorimeter and the sample temperature was increased from 200 ° C to 400 ° C at a scanning speed of 10 ° C / min. Alternatively, compression of the expanded PTFE layers, whether at room temperature, below or above, prior to, during or after the heating step described above can greatly assist in the removal or removal of the porosity inside the tube wall. This compression can be achieved, for example, with a compression roller pressed against the expanded PTFE material or any other suitable compression means that decreases the porosity within the membrane layers. The present invention enables the formation of flexible fluoropolymer wound tubes of thicknesses and diameters that were not available until now, based on the teachings of the prior art. For example, P1B58 / 99MX wall thicknesses greater than 0.25 mm, and internal pipe diameters greater than 25.4 mm. and even larger, which were not taught or obtained in the prior art, are obtainable in the present invention. The preferred wall thicknesses can vary from greater than 0.25 mm to 1 mm, up to 2 mm, up to 5 m, and up to 10 mm or more. Preferred internal tube diameters can vary from greater than 25.4 mm, up to 51 mm, up to 76 mm, up to 101 mm, up to 127 mm, up to 152 mm, up to 203 mm and up to 254 mm or greater. As an alternative to the use of a perforated mandrel and air pressure to assist in the removal of the PTFE membrane tube, a collapsible mandrel can also be used, which allows the reduction of the circumference or perimeter which is adequate to assist in the removal of the mandrel tube. For example, the collapsible mandrel may be in the form of a coil of metal foil in which the expanded PTFE membrane is wound. After the heating cycle, the outer diameter of the coil can be reduced to assist in the removal of the expanded PTFE rolled tube. Alternatively, a collapsible segmented mandrel or other comparable collapsible mandrel geometry or configuration can be used. In an additional modaliaad of this P1058 / 99MX invention, one or more layers of one or more second materials having a different composition or configuration of the fluoropolymer membrane layer can be incorporated into the tubes of the present invention. For example, an alternate means to obtain at least partial adhesion of the fluoropolymer membrane layers is to use an adhesive to achieve intralayer bonding of the porous fluoropolymer membrane layers. A suitable class of adhesives may be in the form of thermoplastic polymer films having a melting point lower than the crystalline melting point of the expanded fluoropolymer membrane. The thermoplastic film can be wound where at least a portion of the PTFE membrane expanded in the mandrel so as to contact the adjacent membrane layers. Alternatively, the fluoropolymer membrane may be provided with an adhesive coating only on one surface thereof. These adhesive coated membranes can be oriented during winding around the mandrel, so that the adhesive coated side of the membrane is oriented away from the surface of the mandrel and, therefore, contacts only the adjacent membrane layers without make contact with the mandrel. The adhesive may be in the form of either a continuous or discontinuous coating. While the P1058 / 99MX thermoplastic fluoropolymers such as, for example, FEP or PFA, are preferred in the present invention, other polymers resistant to high temperature or with chemical resistance, such as liquid crystal polymers or polyetheretherketone can also be used. Alternatively, other materials including polypropylene, polyethylene terephthalate, polymethyl methacrylate, polycarbonate and the like, can provide good adhesion, depending on the conditions to which the tubes will be subjected during use. In a specific embodiment for forming membrane coated with adhesive to roll it into a tube of the present invention, an expanded PTFE membrane can be coated with a layer of, for example, FEP or other thermoplastic polymer, then the coated membrane is heated to a temperature above the melting point of the thermoplastic polymer and stretched while maintaining the temperature above the melting point of the thermoplastic polymer, then the coated membrane is cooled. The adhesive coating on the expanded PTFE membrane can be either continuous or discontinuous, depending mainly on the amount and speed of stretching, the temperature during stretching, the thickness of the adhesive, etc.

P1058 / 99MX Although it is a preferred embodiment of the invention to manufacture tubes having a circular cross-section using cylindrical mandrels, the mandrel can have any cross-sectional shape, including rectangular, triangular, oval, hexagonal and the like. In a further embodiment of the present invention, the mandrel can be conical or have a taper, as in a frusto, cone or the like, as shown in Figures 10A and 10B, respectively, to produce a tube having open ends of Different diameters from one end to the other. In a further embodiment of the present invention, the flexible fluoropolymer tube can optionally incorporate reinforcing ribs that serve as, for example, additional strength members or to prevent the tube from collapsing. The ribs may be oriented either longitudinally, in cases where additional axial strength may be desirable or, circumferentially or helically, in cases where diametral collapse is undesirable or an increase in diametral strength is required. Figure 11 shows a tube 57 of the present invention having helical ribs 55 incorporated therein. The circumferentially oriented ribs may be in the form of separate rings or fiber or coiled wire P1058 / 99MX helically. The reinforcing ribs can be of any material capable of withstanding the heating cycle required to manufacture the flexible fluoropolymer tube. Suitable rib compositions include, but are not limited to, metal, full density PTFE, expanded PTFE, expanded and densified PTFE, FEP, PFA, PEEK, polyimides and polyamides. These ribs can be incorporated into or joined to the tube during construction and can be located on the outer surface of the tube, on the inner surface of the tube or between the membrane layers. In a further embodiment, the reinforcing ribs can be attached to the fluoropolymer tube after formation. In a further alternative embodiment of the present invention, a reinforcing braid, such as, one or more expanded PTFE braided fibers circumferentially or helically wound, may be incorporated between the layers of the fluoropolymer membrane. In addition, depending on the final application, it may be desirable to provide any number of textures, surface geometries (eg, corrugations, tabs, etc.) to the flexible fluoropolymer tubing of the present invention. As mentioned earlier in this, P1058 / 99MX compression can be used to alter the porosity of the tube. These compression techniques can be applied selectively, such as, for example, by using a roller with a pattern, to incorporate surface textures, geometries, corrugations, etc. desired in the novel tubes of the present invention. The incorporation of corrugations, convolutions or other surface geometries in the tubes of the present invention can provide significant performance advantages in various end-use applications. For convenience, the term "corrugated" will be used herein to refer to any corrugations, convolutions, patterns or other geometries that may be incorporated into the tubes of the present invention. For example, the addition of circumferentially oriented corrugations can help maintain the inner diameter of the tube during axial, angular or lateral displacement of a part of the tube with respect to another part of the tube and can provide some radial resistance to collapse. Longitudinally oriented corrugations may be provided to assist in circumferential collapse. Figures 12A-12C show corrugated tubes having helical, circumferential and longitudinal corrugations, respectively, that can be manufactured in the present invention. These P1058 / 99MX corrugations could be incorporated into a PTF membrane tube? Expanded expansion, manufactured, as described above, by means of conventional compression techniques to form the corrugations in the tube wall. For example, as suggested above, corrugations can be added to the tube by compression between a pair of rollers having a series of interlacing grooves oriented around their circumference. Corrugations can also be added by creating circumferential folds or bends within the tube wall or by creating a helical crease in the wall of the tube. Depending on, for example, the compressive forces applied, the temperature of the tube, the means for imparting the corrugations and the like, the corrugated regions may be denser than the rest of the tube, thereby providing improved rigidity to the wall of the tube. tube. In addition, depending on the desired end use of the corrugated tubes of the present invention, the configuration of the corrugations may vary from corrugations at an angle to corrugations rounded to corrugations in a box, as shown in the partial lateral cross-sectional view of Figures 13A , 13B and 13C, respectively. In an embodiment for manufacturing a corrugated tube of the present invention, around a mandrel can P1058 / 99MZ placed a tube formed of fluoropolymer rolled and flexible, the mandrel has a series of grooves that surround its surface and a mold or cavity molds that have a pattern of groove coupling on the inside can be placed around the outside of the tube and used to compress the tube against the mandrel to form the corrugations in the wall of the tube. A preferred method for incorporating the corrugations into the novel tubes of the present invention is by first heating the tube wound with PTF? expanded until the intralayer union is achieved, followed by the expansion of the tube radially towards a mold having an internal geometry corresponding to the desired outer geometry of the tube. The radial expansion of the tube can preferably be obtained by creating a greater pressure between the wall of the tube and the mandrel at the pressure between the wall of the tube and the mold by means of the use of air pressure, vacuum or the like. For example, in a particularly preferred embodiment, a tube having corrugations in at least a portion thereof, such that it can be used as a bellows, conduit or the like, in an end-use application, can be formed by the following method . Specifically, an expanded PTFE membrane can be wound around a perforated mandrel and clamped in P1058 / 99 X its place around the ends, as described above. The mandrel wound with expanded PTFE can then be enclosed in a cylindrical mold chamber having a series of circumferentially oriented grooves in the inner wall of the mold chamber. The mold chamber unit and the expanded PTFE wound mandrel is heated to a temperature above about 327 CC for a period of time that facilitates intralayer bonding. Pressurized air is then applied to the interior of the tube through the perforated mandrel, which pushes the wall of the tube away from the surface of the mandrel and hits it against the surface of the mold having the circumferentially oriented grooves. Then the unit is cooled, preferably with the pressurized air that will be maintained during the cooling process until a temperature is reached where the tube maintains the geometries imparted by the mold and / or the mold has cooled to a temperature where It can be disassembled to remove the tube. Figure 14 illustrates an exemplary molding arrangement used to fabricate an expanded PTFE corrugated membrane corrugated tube of the present invention. The mandrel 18 wound with membrane and having perforations 21 and hose clamps 24 fitted at the ends, is enclosed in a mold that P1058 / 99MX comprises a two-part cylindrical female mold 60 having corrugations in the inner wall For purposes of alignment, an upper end cap 61 and a lower end cap 63 having pins 62 entering the mold ends are used female 60 for enclosing the ends of the mandrel 18. The upper end cap 61 has a hole that allows the passage of the interconnection 19 of the air line. The hose clamps 66 are tightened around the perimeter of the mold 60 to provide the circumferential support during the passage of the pressurization. The end caps 61, 63 and the mold 60 are held in the axial direction using annular flanges 67 screwed using threaded tie rods 68 and hex nuts 69. To the interconnection 19 for the air line an air line 70 is connected. Is the entire unit placed in an oven or stove where the temperature and duration of the heating cycle are adjusted to achieve the at least partial intralayer bond between the PTF layers? expanded and any other optional materials that may be incorporated into the wrapping such as adhesive or thermoplastic films. The pressurized air 72 is supplied to the interior of the mandrel via the air line 70, resulting in the expansion of the layered tube wall 71 away from the punched mandrel 18 and toward the P1058 / 99MX mold corrugations 60. The pressure is maintained while the mold and the article are cooled to a temperature where corrugations or other geometries imparted to the tube wall as a result of compaction against the mold surface are retained. The mold 60 and the end caps 61 and 63 are removed and the resulting corrugated tube is removed from the mandrel 18. In an alternative embodiment, the expanded PTFE membrane can be wound around a perforated mandrel having on its surface a desired geometry. A line and vacuum can be provided within the mandrel to evacuate the air and, with heating of the tube, the vacuum line could be used to suck the tube wound with expanded PTFE membrane against the surface of the mandrel and towards any recessed regions or indentations in the mandrel. the mandrel. After cooling, the tube could be removed from the mandrel by any suitable technique, such as by blowing air or sliding it over the surface of the mandrel, providing a collapsible mandrel as described hereinabove, etc. In an additional alternative embodiment of the present invention, as mentioned above, one or more layers of the flexible flucropolymer tube may comprise materials other than expanded PTFE for P1058 / 99MX provide desired properties to the flexible tube. For example, one or more sheet or sheet-like elements, such as polymeric films, metal flakes, metallic screens or the like, may be provided in the flexible tube or the like to provide improved properties to the resulting tube. Depending on the desired application of the novel tubes of the present invention, the properties of the tubes can be adapted or customized to meet any number of specific needs. For example, gas impermeability, liquid impermeability or improved resilience can be imparted to the tubes by any of several techniques. For example, a plastic material that tends to impermeability to gas and water can be applied to the tubes when coating the interior or exterior or, when impregnating the entire article after the formation of the tubes. These plastic materials may comprise, for example, FEP, fluorine resins, such as tetrafluoroethylene copolymer and perfluoroalkylvinylether, fluorinated and perfluorinated rubber, natural rubber rubber, natural latex rubber, polyurethane, silicone rubber, necprene, EPDM, polyimide, polyester , nylon, polyvinyl chloride, polyethylene and the like. In a further embodiment of the present invention, it has unexpectedly been discovered that at P1058 / 99MX incorporating one or more layers of a material having a lower porosity to that of the expanded PTFE membrane at suitable locations within the winding, pipe wall characteristics such as density and stiffness can be selectively imparted in regions variables within the cross section of the tube wall during the molding process. These strategically placed layers of material, referred to herein in general and for convenience as "shape-assisting layers" incorporated at some point during the rolling of the expanded PTFE membrane to form the tube, can provide a means for molding tubes that have improved shapes or properties. As mentioned above, the shape-assisting layer may comprise a layer of material having a porosity less than that of the expanded PTFE membrane wound around the mandrel. More specifically, the shape-assisting layers include materials that are thermally stable and conformable at the temperatures required for the molding process and that have or produce a layer or region with a porosity less than that of expanded PTFE membranes in layers or stratified. For example, the layers that help form and that substantially maintain their dimensional stability at the temperatures used for the formation P1058 / 99 X molded tube, include, but are not limited to, expanded and less porous PTFE films, full density PTFE, polyimide films, etc. Alternatively, the shape-assisting layer may comprise a FEP sheet or coating, PFA, liquid crystal polymer or other material that may be at least partially melted during the manufacturing process of the molded tube. The layer that helps the shape can have any thickness contemplated to obtain the desired final geometry. Without wishing to be bound by the theory, it is believed that the smaller the porosity of the layer that aids the form, the greater the compression force that is applied to the expanded PTFE layers during molding, thereby increasing the conformation. of the tube during the molding process. The shape-assisting layer may be present as an inner layer adjacent or close to the mandrel in which the expanded PTFE layers are wound for the fabrication of a substantially uniformly expanded expanded PTFE densified wall. Alternatively, for example, in a blow molding unit, the shape-assisting layer can be incorporated as an intermediate layer between a series of expanded PTFE membrane casings, resulting in tubes having smooth, optionally porous wall interiors. in the region between the mandrel and the P10S8 / 99MX form-aid layer, and, more defined molded exteriors with reduced porosity between the layer that helps form and the interior of the mold. Particularly, by providing the shape-assisting layer at some point within the expanded PTFE rolled film, it is believed that the shape-assisting layer improves compression of the outer layers of expanded PTFE during blow molding, whereas the inner layers of expanded PTFE wound into the interior of the shape-assisting layer are not compressed as strongly as the outer layers, thus resulting in minimal or no conformation or in the creation of less defined corrugations or other shapes on the inside of the tube. As described above, the novel tubes of the present invention can be fabricated to have virtually any desired surface geometries, density, stiffness or thickness, either in select portions or in the entire tube, to meet the specifications of an unlimited number of applications. desired end use and to provide improved performance during industrial service, mechanical service, etc. By optimizing the configuration of the expanded PTFE membranes used to form the tubes of the present invention, the thickness of the tube that will be formed based on the number of membrane shells P1058 / 99MX expanded PTFE, the processing conditions for the formation of the tubes, etc., it is possible to achieve virtually any desired combination of particularities to suit a specific need. The following examples are intended to illustrate but not limit the present invention.

EXAMPLE 1 A drilled mandrel was manufactured by drilling 675 uniformly spaced holes in the surface of a steel tube of 127 mm diameter and 406 mm in length, closing one end of the tube with a steel plate having an equal diameter and adjusting the other end a steel plate that has a central connection to connect an air line. A partially sintered porous expanded PTFE membrane produced by biaxial expansion, as described in US Pat. Nos. 3,953,566 and 3,962,153, by Gore, having a microstructure comprised of nodes interconnected by fibrils and having a thickness of 0.04 mm (0.0015). inches) was wound circumferentially around the mandrel until a thickness of layer 90 was obtained, while care was taken to ensure that no visible wrinkles appeared between the membrane layers during the winding or wrapping process, in order to obtain a bond P1058 / 99MX uniform surface. The partially sintered membrane was sticky in nature and the last layer of the envelope was uniformly pressed against the underlying layers to ensure contact during the heating cycle. Hose clamps were used to hold the porous film in place around the diameter of the mandrel at each end. The mandrel wound or wrapped with expanded PTFE was placed in an oven at a temperature of about 360 ° C for a period of one hour, then removed from the oven and a pressurized air line was connected to the port on the top of the mandrel. After allowing the material to cool to room temperature, air was supplied into the mandrel until a pressure of about 170 kPa was reached, resulting in the release of the expanded PTFE tube from the surface of the mandrel. The hose clamps were removed from the ends of the expanded PTFE rolled tube and the expanded porous PTFE film tube was easily removed from the mandrel. The flexible expanded PTFE tube had a wall thickness of 2.9 mm, an internal diameter of 127 mm and a density of 0.602 g / cm3.

EXAMPLE 2 A drilled mandrel was manufactured by drilling 99 P1058 / 99MX uniformly spaced holes in the surface of a steel tube 38 mm in diameter and 450 mm in length. A steel disk having an outer diameter close to the inner diameter of the steel tube was inserted into each end of the mandrel and welded in place. A 1/4 inch (6.4 mm) hole was drilled in the center of one of the discs and threaded with a standard national pipe thread in which an accessory was inserted and fixed in place for the connection of the line. air. A partially sintered porous expanded PTFE membrane having a thickness of 0.04 mm (0.0015 inches) and a width of about 560 mm and formed as described in Example 1, was wound around the aforementioned mandrel to an inch thickness. , while care was taken to ensure that there were no visible wrinkles between the membrane layers during the winding process in order to obtain a uniform surface bond. The membrane was sticky and the last layer of the wrapping or rolled was uniformly pressed against the underlying layers to ensure contact during the heating cycle. Hose clamps were used to hold the porous film in place around the diameter of the mandrel at each end. The mandrel rolled or wrapped with expanded PTFE was placed in an oven at a temperature of 360 CC for a period P1058 / 99MX of one hour. Then it was removed from the furnace and a pressurized air line was connected to the port on top of the mandrel. After allowing the material to cool at 23 ° C, air was supplied into the mandrel until a pressure of about 170 kPa was obtained, resulting in the release of the expanded PTFE tube from the surface of the mandrel. The tube wound with flexible expanded PTFE had a wall thickness of 1.03 mm, an internal diameter of 38 mm and a density of 0.584 g / cm3. This tube was cut in the four tubes used in the performance comparison by the flexure test described below. The flexible fluoropolymer tubes of the present invention demonstrate utility in high flex applications, where elastomeric materials are often used. Bending tests were conducted on porous expanded PTFE hoses compared to several elastomeric tubes (elastomers commonly used in high flexibility applications) on tube samples having a wall thickness between 1 mm and 1.5 mm, and a length of approximately 76 mm. The test was the most representative of axial compression and flexural recovery attested by tubular elements coupled in vibratory and transport industrial sieving equipment. P1058 / 99MX A Newark machine for bending tests was modified as shown in Figure 15 by the addition of piston units 38 that were connected to the original pistons 39 connected to the piston rod 36. Similar piston units were connected to the fixed pistons 40. The pistons of both the fixed piston units and those connected to the piston rod, were in axial alignment, produce regions between opposite pistons in which sections of pipe were coupled, a piston is fixed 41 and the other has axial movement capability with respect to the fixed piston 42. The motor 35 cyclically moves to the piston rod 36. and to the piston units 38 connected in axial direction, with a stroke length of 32 mm at a speed of approximately 8.7 cycles per second. The tolerance or resistance to bending of the samples was tested in accordance with ASTM D2097-69: Figure 16 is a diagram of the distances to connect the tube samples to the apparatus, which has a piston distance set to 15x the thickness of the specimen while in the closed position. The elastomeric samples tested were all cut from tube sections manufactured by The Belko Corporation (Kingsville, MD). Four 76 mm samples were cut from each of the seven elastomeric materials P1058 / 99MX tested, including styrene butadiene rubber (SBR) type 4597, ethylene propylene diene monomer (EPCM) type 3889, neoprene type 3854, urethane rubber type 3572, natural rubber type 4501, nitrile rubber type 3960 and silicone rubber type 4447. Samples were held in place around the pistons without stretching them using hose clamps at the maximum separation distance. The samples were thus flexed during 200,000 cycle intervals, among which the samples were examined for cracks and abrasion regions resulting from flexural fatigue. The samples were removed from the tester by bending when they exhibited cracks or holes that passed completely through the wall of the sample and were recorded as failed samples. Figure 17 shows an approach of one of the piston units of Figure 15 with a sample tube 27 fixed in the apparatus using hose clamps 28. The flexing action of the pistons results in a pattern of creases 25 in the sample of tube 27. Repeated bending results in regions of abrasion or cracking in the crease regions, which eventually leads to the formation of holes in the tube wall. Many polymeric and elastomeric materials were abraded during the course of bending witnessed during use. The particulates that are opened from the tube P1058 / 99MX are frequently a source of contamination for the products passing through the tube, as well as a source of contamination in the environment external to the tube. The chart below shows the performance results of a variety of materials when tested.

Flex Tube Testing of Expanded PTFE Film and Elastomeric Pipe (ASTM 2097-69 Modified) Material Strength% DeforRoughness in Thickness Number Terran Cycles Medium in the mation to the Durometer Sample Medium of Bending Peak (kPa) Rupture (Shore A) of the Wall Tube (-mi) Totals ASTM ASTM D638M-84 D638M-84 Rubber 1906 423 29 1 1.50 1,400,000 (failure) Natural 2 1.51 1,200,000 (failure) (Comp.4501) 3 1.50 800,000 (failure) 4 1.50 1,000,000 (failure) Heoprene 16250 431 61 1 1.05 2,600,000 (failure) (Comp.3845) 2 1.06 1,200,000 (failure) 3 1.04 1,000,000 (failure) 4 1.06 600,000 (failure) SBR 7449 408 48 1 1.05 200,000 (failure) (Comp.4597) 2 1.05 1,800,000 (failure) • 3 1,06 800,000 (failure) 4 1,06 1,400,000 (failure) EPDM 4265 534 46 1 1.01 200,000 (failure) (Comp.3889) 2 1.03 1,600,000 (failure) 3 1.02 800,000 (failure) 4 1.03 200,000 (failure) Rubber 25540 695 60 1 1.05 10,000, OOC (step) Urethane 2 1.05 400,000 (failure) (Comp.3572) 3 1.05 7,600,000 (failure) 4 1.06 1,200,000 (failure) Rubber 7500 524 52 1 1.04 600,000 (failure) Nitrile 2 1.04 600,000 (failure) (Comp.3960) 3 1.02 1,000,000 (failure) 4 1.04 1,400,000 (failure) Rubber 5796 242 55 1 .95 6,200,000 (failure) Silicone 2 .94 5,400,000 (failure) (Comp.4447) 3 .93 1,400,000 (failure) 4 .96 3,800,000 (failure) Tube of 24575 40.9 53 1 1.03 10, 000, OOC (step) Film of 2 1.03 10, 000, OOC (step) PTFE 3 1.02 10,000, OOC (step) Expanded 4 1.03 10, 000, OOC (step) P10S8 / 99MX It should be noted that when PTFE was manufactured at full density by pulp extrusion and with a wall thickness of 1.0 mm it was flexed manually in a way comparable to the tests established for the materials in the table, the density PTFE Full failed quickly due to its rigid nature.

EXAMPLE 3 A 0.04-mm expanded film with a PTFE thickness, as described in Examples 1 and 2, was wound around the 38 mm diameter mandrel described in Example 2, to a thickness of three layers. A two layer composite tape 44 mm wide and 0.09 mm thick, comprising an expanded PTFE membrane manufactured as described in US Pat. Nos. 3,953,566 and 3,962,153 Gore, and the FEP film obtained from E.l. du Pont de Nemours and Company (Wilmington, Delaware) under the tradename FEP film Teflon® 50A was wound helically around the mandrel with an overlap of approximately 15 mm between adjacent layers of wrap. The composite tape was manufactured: a) by contacting the expanded PTFE membrane with the FEP; b) heating the composition obtained in the P1058 / 99MX step from part a) to approximately 335 ° C; c) stretching the heated composition of the step of part b) while maintaining the temperature above the melting point of the thermoplastic polymer; and d) cooling to the product of step c). A second helical shell of the expanded FEP / PTFE composite was made in the opposite direction to the direction of the first layer of the composite, with an overlap of about 15 mm. Six more alternate envelopes of the composite film were made, each film was wound in the opposite direction to the previous windings. Hose clamps were used to hold the porous film in place around the diameter of the mandrel at each end. The mandrel wrapped with expanded PTFE was placed in an oven at a temperature of 340 ° C for a period of one hour, then removed from the oven and a pressurized air line was connected to the port on the top of the mandrel. After allowing the material to cool to approximately 23 ° C, pressurized air was supplied to the inside of the mandrel until a pressure of 170 kPa was obtained, resulting in the release of the expanded PTFE tube from the surface of the mandrel. The PTFE film tube had a wall thickness of 1.52 mm, an internal diameter of 38 mm and a P1058 / 99MX density of 0.766 g / cm, EXAMPLE 4 A coiled expanded fluoropolymer tube with a helically oriented internal reinforcing rib was produced using the perforated mandrel of Example 1. Fifty layers of a biaxially expanded PTFE film having a thickness of 0.04 mm produced using the methods taught in the Patents of US Pat. United States No. 3,953,566 and 3,962,153 were wrapped around the drilled mandrel. A single layer of PFA film 0.127 mm thick obtained from E.l. du Pont de Nemours and Company, under the trade name PFA Teflon 500LP film, was wound on top of the expanded PTFE with an overlap of approximately 40 mm. A 1.2 mm stainless steel wire was wound helically in a spring-like manner around the surface of the PFA film, each winding was about 15 mm apart. An additional layer of PFA film 0.127 mm thick was wound on the top of the wire, with an overlap of approximately 40 mm. Then at the top of the PFA film fifty layers of expanded PTFE 0.04 mm thick were rolled. Hose clamps were used to hold the layers in place around the diameter of the P1058 / 99MX mandrel on each end. The mandrel wrapped with porous expanded PTFE membrane was placed in an oven at a temperature of about 360 ° C for a period of one hour, then removed from the oven and a pressurized air line was connected to the port on the top of the mandrel . After cooling to approximately 200 ° C, pressurized air was supplied into the mandrel until a pressure of about 340 kPa was obtained, resulting in the release of the porous PTFE tube from the surface of the mandrel. From the ends of the mandrel wrapped with PTFE film, the hose clamps were removed and the porous PTFE coiled tube was easily removed from the mandrel. The resulting expanded PTFE tube had a wall thickness of 4.4 mm, an internal diameter of 38 mm and a length of 370 mm.

EXAMPLE 5 An expanded PTFE membrane 0.04 mm thick as described in Example 1 was continuously wound around the perforated mandrel described in Example 1 to a thickness of 60 layers. A mold is cut from an aluminum tube of 20.3 cm in external diameter, 15.2 cm in internal diameter which has 18 circumferential grooves with a "V" shape of 12.7 mm depth cut into the wall Internal P1058 / 99MX, as shown in the cross section of Figure 14. The aluminum tube was cut longitudinally in two halves, producing a two-part mold. End caps having inner diameters of approximately 20.3 cm were produced to fit in the mold when assembled, the top cap has a hole to expose the interconnection of the air line in the upper part of the mandrel. The rolled mandrel was placed in the lower end cap and the two-part corrugated mold and the upper end cap were assembled, encompassing the mandrel. To provide radial support during the molding process, three uniformly spaced hose clamps were added and surrounding the outer diameter of the mold. The mold and mandrel unit was clamped in the entire axial direction between two connected flanges using four threaded struts and hexagonal nuts. The mold and mandrel unit was placed in an oven and stainless steel air line tubing was connected to the interconnection in the mandrel through a hole in the upper part of the furnace. The oven was set at 365 ° C and the temperature inside the oven rose from about 23 ° C to 365 ° C in about 20 minutes. After 120 minutes at 365 ° C, pressurized air is supplied to the inside of the mandrel through the air line to reach a P1058 / 99MX internal pressure of 50, resulting in the expansion of the laminated film towards the mold grooves. The air pressure was maintained while the oven temperature fell to room temperature. When the mold and mandrel unit was cooled to less than about 50 ° C, it was removed from the oven and the air pressure was discontinued or interrupted. The mold was disassembled and the corrugated expanded PTFE tube formed was removed. The resulting tube had essentially the same dimensions external to the internal dimensions of the mold and a wall thickness of 1.75 mm. To determine the minimum internal void that the corrugated pipe could maintain before collapsing, both uncorrugated ends of the corrugated pipe of this example were fastened around the perimeter of aluminum cylinders of 15 cm in diameter, 16 cm apart. One of the 15 cm diameter cylinders had a hole through which air could be slowly evacuated from the inside of the corrugated tube and the amount of vacuum suctioned could be measured. The vacuum reading recorded at the collapse of the corrugated tube was approximately 12 cm of water.

EXAMPLE 6 A 0.04 mm expanded PTFE membrane, as described in Example 1, is continuously rolled P1058 / 99MX around the perforated mandrel, as described in Example 1, to a thickness of 25 layers. A sheet of PFA 0.127 mm thick, as described in Example 4, was wrapped around the porous PTFE film, with a longitudinal overlap region of 80 mm. On the mandrel on top of the PFA film twenty-five additional layers of the expanded PTFE membrane were wound. The layers were clamped in place around the ends of the mandrel using hose clamps and placed in the corrugated mold described in Example 5. The mold was clamped between the bd flanges, the air line was connected to the port in the part of the mandrel and the entire unit was placed in an oven, as described in Example 5. The oven was set at 365 ° C (the oven temperature rose from 23 ° C to 365 ° C in approximately 20 minutes). After 120 minutes at 365 ° C, pressurized air is delivered to the inside of the mandrel until an internal pressure of 50 is reached, resulting in the expansion of the tube into the mold grooves. The pressure was maintained while the mold was cooled to room temperature. The mold and mandrel unit were removed from the furnace and the air pressure was interrupted. The mold was dismantled and the resulting corrugated PTFE tube with the intermediate PFA layer was removed from the mandrel. The resulting tube had an inner region of P1058 / 99MX 0.6 mm thick straight wall, comprised of 25 internal coils of the expanded PTFE film and a 0.2 mm thick corrugated outer region, comprised of the PFA layer and the 25 outer PTFE film casings or coils tablets The tube had an internal diameter of approximately 150 mm and eighteen 12 mm corrugations with a "V" shape corresponding to the geometry of the mold.

EXAMPLE 7 An expanded PTFE membrane 0.04 mm thick and a PFA film 0.025 mm thick were wrapped together around the perforated mandrel described in Example 1. After three wraps or coils completed in this way, the PFA film only expanded PTFE film is wound around the perforated mandrel to provide 60 additional layers. The layers were held in place around the ends of the mandrel using hose clamps and placed in the corrugated mold. The mold was clamped between the bd flanges, the air line was connected to the port on the top of the mandrel and the entire unit was placed in an oven. The oven was adjusted to 365 ° C, requiring 20 minutes to ascend from 23 ° C to 365 ° C. After 120 minutes at 365 ° C, air was sent P1058 / 99MX pressurized inside the mandrel to obtain an internal pressure of 60, resulting in the expansion of the tube into the grooves of the mold. The pressure was maintained while the furnace temperature dropped to room temperature. When the mold and mandrel unit was cooled to room temperature, it was removed from the furnace and the air pressure was stopped, the mold was disassembled and the corrugated PTFE tube with co-coiled inner of PFA was removed. It was observed that the resulting tube was stiffer than the tubes produced in the previous examples. The tube formed in this example, when subjected to vacuum to determine collapse, was found to collapse to an internal vacuum of 64 cm of water using the vacuum test described in Example 5. The tube had a wall thickness of 0.71 mm, an internal diameter of approximately 150 mm and eighteen corrugations of 12 mm, with a "V" shape corresponding to the geometry of the mold.

EXAMPLE 8 An expanded PTFE corrugated tube loaded with carbon was fabricated using a 0.25 mm thick expanded PTFE film containing 5% carbon black by weight. The membrane was produced by the methods described in U.S. Patent No. 4,985,296 P1058 / 99MX by Mortimer, Jr. Fifteen layers of this material were wound around the perforated mandrel described in Example 1. The layers were clamped in place around the ends of the mandrel using hose clamps. The mandrel was placed in the corrugated mold and subjected to the same thermal cycle as described in Example 5. The resulting tube had a wall thickness of 2.5 mm, an internal diameter of approximately 150 mm and eighteen corrugations of 12 mm in shape of "V" corresponding to the geometry of the mold.

EXAMPLE 9 A corrugated pipe having an inner layer of full density PTFE and an expanded PTFE exterior was fabricated using extruded PTFE extruded dough tape, formed as described in U.S. Patent Nos. 3,953,566, 3,962,153, and 4,187,390 of Gore. The extruded PTFE tape having a density of 1.46 grams per cm, a thickness of 0.18 mm and a width of 150 cm, wound helically around the perforated mandrel described in Example 1 with a pitch of 3 cm.

Another extruded PTFE tape was wound helically in the opposite direction with a pitch of 3 cm above the first tape. In the upper part of the extruded they were rolled P1058 / 99MX longitudinally fifty layers of 0.04 mm biaxially expanded PTFE film, as described in Example 1. The films were held in place around the ends of the mandrel using hose clamps. The mandrel was then placed in the corrugated mold and subjected to the same thermal cycle as described in Example 5. The resulting tube had a wall thickness of 0.71 mm, an internal diameter of approximately 150 mm and eighteen corrugations of 12 mm with "V" shape corresponding to the geometry of the mold. This corrugated tube, to the visual observation, seemed to have a translucent inner layer at full density and a relatively more porous expanded PTFE exterior.

EXAMPLE 10 Two layers of 0.05 mm thick, 66 cm wide beveled and sintered PTFE obtained from Fluoroplastic, Inc. (Philadelphia, PA), were wound longitudinally around the perforated mandrel described in Example 1. On top of the beveled layers were longitudinally rolled up fifty layers of biaxially expanded 0.02 mm PTFE membrane, as described in Example 1. The films were held in place around the ends of the mandrel using hose clamps. The mandrel was placed in the P10S8 / 99MX corrugated mold and subjected to the same thermal cycle described in Example 5. The resultant had a wall thickness of 0.71 mm, an internal diameter of approximately 150 mm and eighteen 12 mm corrugations with a "V" shape corresponding to the mold geometry.

EXAMPLE 11 A composite tape consisting of longitudinally expanded PTFE and FEP manufactured as described in Example 3, having a thickness of 0.19 mm and a width of 105 mm, was wound helically as a first layer wherein the FEP side is oriented outward from the surface of the mandrel with a pitch of approximately 40 mm about the perforated mandrel described in Example 1. The second layer of the composite tape was wound helically with the FEP side down on the mandrel in the opposite direction to the first layer. Five more helical layers of the composite tape were wound on the mandrel with the same pitch of the first two, the FEP side down and with alternating winding directions. The composite tapes were held in place around the ends of the mandrel using hose clamps. The mandrel was placed in the corrugated mold as P1058 / 99MX described in Example 5. The furnace was set at 330 ° C, requiring seventeen minutes to ascend from about 23 ° C to 330 ° C. After 160 minutes at 330 ° C, pressurized air was sent into the mandrel to obtain an internal pressure of 45 ° C., resulting in the expansion of the laminated films towards the mold grooves. The pressure was maintained while the furnace temperature dropped to room temperature. When the mold and mandrel unit had cooled to room temperature, it was removed from the furnace and the air pressure was interrupted, the mold was disassembled and removed to the corrugated PTFE / FEP composite tube. The corrugated tube had a wall thickness of 1.2 mm, an internal diameter of approximately 150 mm and eighteen 12 mm corrugations with a "V" shape corresponding to the geometry of the mold.

METHODS OF TEST Measurement of density The densities were calculated in accordance with the Archimedes Principle, whereby the density of a solid body was determined using a liquid of known density. For this purpose, the article to be measured was first weighed in air and then immersed in the liquid of known density. Using these two weights, the density of the solid body was calculated by P1058 / 99MX next equation: A po where, A = Weight of the solid body in air, B = Weight of the solid body immersed in the test liquid, and C = Density of the test liquid at a given temperature, Although in the foregoing a few exemplary embodiments were described in detail of the present invention, those skilled in the art will readily appreciate that many modifications are possible without deviating materially from the novel teachings and advantages described herein. In accordance with the foregoing, it is intended that all such modifications be included within the scope of the present invention, as defined by the following claims.

P1058 / 99MX

Claims (37)

1. NOVELTY OF THE INVENCIOK Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1. A layered fluoropolymer membrane flexible tube, comprising: a first layer fluoropolymer membrane exhibiting a structure of nodes and fibrils, comprising an inner surface and an outer surface; at least one subsequent layer of fluoropolymer membrane exhibiting a node and fibril structure comprising an inner surface and an outer surface; wherein each subsequent layer surrounds at least a portion of the outer surface of the immediately preceding layer; and where the inner layer of the tube is larger than 25. 4 mm The flexible tube according to claim 1, wherein the layered fluropolymer membrane is wound in at least one configuration selected from the group consisting of helical coil and coiled coil. 3. The flexible tube according to claim 1, P1058 / 99MX where the tube has a wall thickness greater than 25.4 mm. The flexible tube according to claim 1, wherein the fluropolymer membrane comprises expanded polytetrafluoroethylene. The flexible tube according to claim 1, wherein the tube has at least one geometry selected from the group consisting of a tube of uniform diameter from one end to the other, a frustro geometry and a geometry with a non-uniform pattern. The flexible tube according to claim 1, wherein the tube comprises a flexible connection for connecting at least one set of selected members of conduits, ducts and tubing. The flexible tube according to claim 1, wherein the tube comprises a protective cover to protect the components from at least one of the thermal, chemical and mechanical stresses. The flexible tube according to claim 1, wherein the tube further comprises at least one load. The flexible tube according to claim 1, wherein the tube further comprises at least a second material interposed between at least one of the layers of the fluoropolymer membrane. 10. The flexible tube according to claim 1, P1058 / 99MX wherein the tube further comprises at least one reinforcing rib. A method for forming a layered fluoropolymer membrane flexible tube, comprising: providing a mandrel having a diameter greater than 25.4 mm with an outer surface and at least one outlet to allow gas to flow towards the outer surface of the mandrel; winding at least two layers of fluropolymer membrane exhibiting a node and fibril structure around the outer surface of the mandrel; heating the mandrel and the fluoropolymer membrane to a temperature above the crystalline melting point of the fluoropolymer for a sufficient time to induce the contraction and coalescence of the nodes and the fibrils at the surface interface of at least two layers, the contraction and coalescence result in the adhesion of the layers in a coherent tube of layered fluoropolymer membrane; blowing at least some gas through the outlet of the mandrel to separate the fluropolymer tube from the outer surface of the mandrel and withdraw the fluoropolymer tube from the mandrel. The method according to claim 11, wherein the winding of at least two layers of the film P1058 / 99MX fluoropolymer is made in at least one type of coil or helical winding. The flexible tube according to claim 11, further comprising providing at least a second material between the layers of the fluropolymer membrane. The flexible tube according to claim 11, wherein the fluoropolymer membrane comprises expanded polytetrafluoroethylene. 15. A corrugated flexible tube of layered fluropolymer membrane, comprising: a first fluoropolymer membrane layer comprising an inner surface and an outer surface; at least one subsequent layer of fluoropolymer membrane comprising an inner surface and an outer surface; wherein each subsequent layer surrounds at least a portion of the outer surface of the immediately preceding layer; and wherein the tube comprises at least one corrugation in at least a portion thereof. The corrugated flexible tube according to claim 15, wherein the layered fluropolymer membrane is wound in at least one configuration selected from the group consisting of winding P1058 / 99MX helical and coiled winding. 17. The corrugated flexible tube according to claim 15, wherein the fluropolymer membrane comprises expanded PTFE. 18. The corrugated flexible tube according to claim 17, the PTFE is at least partially densified. The corrugated flexible tube according to claim 15, wherein at least one corrugation has at least one geometry selected from the group consisting of angled corrugations, rounded corrugations and corrugations in frame. The corrugated flexible tube according to claim 15, wherein the density of the tube varies in one region of the tube with respect to another region of the tube. The corrugated flexible tube according to claim 15, wherein the tube further comprises a first end, a middle region and a second region and, wherein the middle region comprises corrugations and the first and second ends are not corrugated. The corrugated flexible tube according to claim 15, wherein the at least one corrugation is selected from the group consisting of longitudinal corrugations, helical corrugations and circumferential corrugations. P1058 / 99MX 23. The corrugated flexible tube according to claim 15, wherein the tube further comprises at least one load. The corrugated flexible tube according to claim 15, wherein the tube further comprises at least a second material interposed between at least one of the layers of the fluoropolymer membrane. The corrugated flexible tube according to claim 24, wherein the at least one second material has a porosity less than the porosity of the layers of fluropolymer material. The corrugated flexible tube according to claim 24, wherein the at least one second material comprises at least one material selected from the group consisting of FEP, PFA, liquid crystal polymer and PTFE having a porosity less than the porosity of the layers of the fluoropolymer material. The corrugated flexible tube according to claim 15, wherein the tube comprises a flexible connection for connecting at least one set of members selected from the group consisting of conduits, ducts and tubing. The corrugated flexible tube according to claim 15, wherein the tube comprises a protective cover for protecting the components of at least one of P1058 / 99MX the thermal, chemical and mechanical stresses. 29. The corrugated flexible tube according to claim 24, wherein the at least one second material is present on the outside of the tube. 30. The corrugated flexible tube according to claim 24, wherein at least one second material is present on the outside of the tube. 31. A corrugated flexible tube comprising: an outer region comprising corrugated layers comprising multiple coiled layers of expanded PTFE membrane; an internal region comprising multiple coiled layers of expanded PTFE membrane; and at least one layer of a second material sandwiched between the outer region and the inner region and adhered thereto, wherein the outer region has a porosity less than the porosity of the inner region. The corrugated flexible tube according to claim 31, wherein the at least one second material comprises at least one material having a porosity less than the porosity of the outer region. The corrugated flexible tube according to claim 31, wherein at least one second material comprises at least one material selected from the group consisting of FEP, PFA, liquid crystal polymer and PTFE P10S8 / 99MX which has a porosity lower than the porosity of the external region. 34. A method for forming a layered fluoropolymer membrane corrugated flexible tube, comprising: providing a mandrel with an outer surface and at least one outlet to allow gas to flow towards the outer surface of the mandrel; roll up at least two layers of expanded PTFE membrane that exhibit a structure of nodes and fibrils around the outer surface of the mandrel; heating the mandrel and the expanded PTFE membrane layers to a temperature above the crystalline melting point of the fluoropolymer for a sufficient time to induce contraction and coalescence of the nodes and fibrils at the surface interface of the at least two layers, with what the contraction and the coalescence result in the adhesion of the layers in a coherent tube of expanded PTFE membrane in layers; providing a mold having an internal geometry of corrugations spaced outwardly from the mandrel; blow at least some gas through the outlet of the mandrel to separate the expanded PTFE tube from the outer surface of the mandrel to force the tube towards the P1058 / 99MX internal geometry of the mold, forming in this way the corrugations in the expanded PTFE tube; and removing the flexible and corrugated expanded PTFE tube from the mold. 35. The method according to claim 34, wherein the wrapping or winding of the at least two layers of expanded PTFE membrane is carried out in at least one of the following winding types: coil or helical. 36. The method according to claim 34, further comprising providing at least one second material between two or more layers of expanded PTFE membrane. 37. The flexible tube according to claim 1, wherein the structure of nodes and fibrils of the first layer and the structure of nodes and fibrils of the at least one subsequent layer, coalesce in the surface interface of the layers. P1058 / 99MX