Patent Publication Number: US-2016245432-A1

Title: Tubes and methods of production and use thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application Ser. Nos. 61/642,172 and 61/642,181, both filed on May 3, 2012. The entire contents of each of these applications is hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     Tubes are used to transport variety of fluids in various applications. In the production of food, beverages, and pharmaceuticals, such tubes must remain sterile in order to prevent contamination of the end product. Accordingly, tubes are often steam cleaned, which can cause arcing of static electricity across tubing walls that damages the tubing. Existing tubing designed to withstand steam cleaning is convoluted, which inhibits the draining of condensed water and other fluids from the tubes. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention provides a tube including: a PTFE tube, a jacket circumferentially surrounding the PTFE tube, and a protective jacket circumferentially surrounding the jacket and the PTFE tube. The jacket is formed from a plurality of plaits of fiberglass lace. The fiberglass lace includes PTFE. 
     This aspect of the invention can have a variety of embodiments. The jacket can be a braided jacket. The jacket can be sintered to the PTFE tube. The fiberglass lace can be formed from a plurality of strands of PTFE-coated fiberglass. Each of the plurality of plaits can be coated with PTFE after braiding. 
     The jacket can include one or more metal plaits. Each of the one or more metal plaits can include a single metal wire. Each of the one or more metal plaits can include a plurality of metal wires. Each of the one or more metal plaits can include between 2 and 15 metal wires. Each of the one or more metal plaits can include 7 metal wires. The one or more metal plaits can lie substantially flat with respect to longitudinal axis of the tube. The one or more metal plaits can be spaced between every other plait and every 10 plaits. The one or more metal plaits can be spaced between every four plaits. 
     The fiberglass lace can include one or more reinforcing strands. The one or more reinforcing strands can be aramids. The one or more reinforcing strands can be para-aramids. The one or more reinforcing strands can be aromatic polyesters. One or more of the plaits can have a ratio of fiberglass strands to reinforcing strands between 1:1 and 20:1. One or more of the plaits can have a ratio of fiberglass strands to reinforcing strands of 7:1. 
     The PTFE tube can have an orientation index between 0.9 and 1.0. 
     The protective jacket can be an extruded protective jacket. The protective jacket can be an elastomeric protective jacket. The protective jacket can include one or more thermoplastic elastomers. The protective jacket can be a single-layer protective jacket. The protective jacket can be a multi-layer protective jacket. 
     The protective jacket can include a reinforcing member. The reinforcing member can be helically wound. The reinforcing member can be positioned between a first layer and a second layer of the protective jacket. The reinforcing member can be selected from the group consisting of: metal, fiberglass, and para-aramids. 
     The protective jacket can include one or more antimicrobial agents. 
     The fiberglass can be S-Glass. The fiberglass can be E-Glass. 
     Another aspect of the invention provides a method of producing a tube. The method includes: providing a PTFE tube, forming a jacket by circumferentially wrapping a plurality of plaits of fiberglass lace around the PTFE tube, and extruding a protective jacket over the jacket. The fiberglass lace includes PTFE. 
     This aspect of the invention can include a variety of embodiments. The forming step can include braiding the plurality of plaits around the PTFE tube. The fiberglass lace can be formed from a plurality of strands of PTFE-coated fiberglass. Each of the plurality of plaits can be coated with PTFE after braiding. 
     The PTFE tube can be formed by extrusion. The PTFE tube can be formed by vertical extrusion. The PTFE tube can have an orientation index between 0.9 and 1.0. The method can further include annealing the PTFE tube to increase the orientation index. The annealing step can be performed prior to the braiding step. 
     The method can include sintering the tube to bond the PTFE tube to the braided jacket. The sintering step can include introducing the tube into an oven so that the tube is heated to between about 700° F. and about 725° F. The tube can be exposed to the oven for a sufficient period of time to hold the tube at a temperature between about 700° F. and about 725° F. for about 3 minutes. 
     Another aspect of the invention provides a tube prepared by any of the methods described herein. 
     Another aspect of the invention provides a method of using a tube. The method includes: providing a tube as described herein and coupling one or more ends of the tube to one or more devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the nature and desired objects of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawing FIGS. wherein like reference characters denote corresponding parts throughout the several views and wherein: 
         FIG. 1  depicts a tube according to one embodiment of the invention; 
         FIG. 2  depicts a method of producing a tube according to an embodiment of the invention; 
         FIG. 3  depicts a method of using a tube according to an embodiment of the invention 
         FIG. 4A  provides a photograph of a cross-section of a wall of a tube according to an embodiment of the invention; and 
         FIG. 4B  provides a photograph of the braided jacket of a tube according to an embodiment of the invention 
     
    
    
     DEFINITIONS 
     The instant invention is most clearly understood with reference to the following definitions: 
     As used herein, the singular form “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. 
     Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from context, all numerical values provided herein are modified by the term about. 
     As used herein, the terms “comprises,” “comprising,” “containing,” “having,” and the like can have the meaning ascribed to them under U.S. patent law and can mean “includes,” “including,” and the like. 
     As used herein, the term “metal” refers to any chemical element that is a good conductor of electricity and/or heat. Examples of metals include, but are not limited to, aluminum, cadmium, niobium (also known as “columbium”), copper, gold, iron, nickel, platinum, silver, tantalum, titanium, zinc, zirconium, and the like. 
     Unless specifically stated or obvious from context, the term “or,” as used herein, is understood to be inclusive. 
     Ranges provided herein are understood to be shorthand for all of the values within the range. For example, a range of 1 to 50 is understood to include any number, combination of numbers, or sub-range from the group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, as well as all intervening decimal values between the aforementioned integers such as, for example, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. With respect to sub-ranges, “nested sub-ranges” that extend from either end point of the range are specifically contemplated. For example, a nested sub-range of an exemplary range of 1 to 50 may comprise 1 to 10, 1 to 20, 1 to 30, and 1 to 40 in one direction, or 50 to 40, 50 to 30, 50 to 20, and 50 to 10 in the other direction. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to  FIG. 1 , a length of tubing  100  according to one embodiment of the invention is provided. Tubing  100  includes an inner tube  102 , a jacket  104  circumferentially surrounding the inner tube  102 , and a protective jacket  108 . 
     Inner tube  102  can be composed of a polymer, for example, a fluoropolymer such as polytetrafluoroethylene (PTFE). In some embodiments, the PTFE is TEFLON® T62 available from E. I. du Pont de Nemours and Company of Wilmington, Del. 
     The inner tube  102  can, in some embodiments, have a high orientation index, which is a measure of the degree of orientation of the PTFE chains in the longitudinal direction versus that of the transverse direction. An orientation index of zero (0) means that the PTFE chains are randomly oriented. An orientation index of one (1) means that all of the PTFE chains are oriented in the longitudinal direction. 
     The inner tube  102  can be completely formed and/or cured before the jacket  104  is applied over the inner tube  102 . 
     Jacket  104  can be formed from a plurality of plaits  106  of fiberglass lace. The fiberglass lace, in turn, can incorporate PTFE. Suitable fiberglass lace is available under the A-A-52083 (Type IV) specification from a variety of sources including Breyden Products, Inc. of Columbia City, Indiana; Western Filament, Inc. of Grand Junction, Colo.; and W.F. Lake Corp. of Glens Falls, N.Y. 
     In some embodiments, the underlying fiberglass strands include of E-glass or S-glass. E-glass and S-glass are widely available from a variety of source. Generally speaking, E-glass is understood to refer to alumina-calcium-borosilicate glasses used as a general purpose reinforcement where strength and high electrical resistivity are desired, while S-glass is understood to refer to magnesium aluminosilicate glasses used for textile substrates or reinforcement in composite structural applications that require high strength, modulus, and durability under conditions of extreme temperature or corrosive environments. A variety of other types of fiberglass can be used including AR-glass, C-glass, D-glass, E-CR-glass, R-glass, and the like. 
     In some embodiments, the jacket  104  is braided as depicted in  FIG. 1 . In other embodiments, the jacket is formed by wrapping fiberglass plaits in a helical manner. 
     PTFE can be incorporated into the plaits  106  in a variety of manners. In one embodiments, each plait  106  is formed from a plurality of fiberglass strands, each of which individually coated with PTFE prior to braiding. In another embodiment, the braided plait  106  is dipped in PTFE to coat the braided plait  106 . 
     Each plait  106  can have a substantially rectangular cross-section. That is, each plait  106  can have a width substantially greater than a height. In such an embodiment, the plaits  106  can be arranged in the braided jacket such that the wider side of the plaits  106  contacted inner tube  102 . Such an arrangement minimizes the thickness of braided jacket  104  and provides more structural support to inner tube  102 . 
     Each plait  106  can be formed from a plurality of individual strands of fiberglass. For example, each plait  106  can be formed from between 5 and 19 strands. 
     One or more reinforcing strands can be incorporated one or more of the plaits  106 . For example, one or more aramid, para-aramid, or aromatic polyester strands can be braided along with the fiberglass strands. Suitable aramids and para-aramids are sold under the KEVLAR® brand by E. I. du Pont de Nemours and Company of Wilmington, Del., under the TECHNORA® brand by Teijin Limited of Osaka, Japan, and under the TWARON® brand by Teijin Aramid B.V. of Arnhem, The Netherlands. Suitable aromatic polyesters are available under the VECTRAN(r) and VECTRAN® EX brands from Kuraray America, Inc. of Fort Mill, S.C. The ratio of fiberglass strands to reinforcing strands can, for example, be between 1:1 and 20:1. 
     The jacket can also include one or more metal plaits  110  for additional strength. The metal plaits  110  can be incorporated into the jacket  104  in place of one or more fiberglass plaits  106 . For example, the spacing of metal plaits  110  can range from every other fiberglass plait  106  to every  10  fiberglass plaits  110  in order to optimize strength vs. stiffness of the tube  100 . The metal plaits  110  can include a one or more wires (e.g., between 1 and 15) that can lay flat or can be braided. For example, as seen in  FIG. 1 , six wires can be laid side-to-side so that each has a substantially uniform distance from the center of the tube  100 . The metal wires can be selected from a variety of metals including stainless steel. In one particular embodiment, a plait of seven . 0011 ″ diameter stainless steel wires is placed in every fourth bobbin. 
     The jacket  104  can be conductive. For example, the jacket  104  can include a plurality of conductive particles such as metal particles (e.g., copper, aluminum, gold, silver, nickel, and the like), carbon black, carbon fibers, or other conductive additives. Such particles can be present in the individual strands of fiberglass, applied to the fiberglass plaits  106 , and/or applied to the jacket  104  after formation. For example, any of the strands, plaits  106 , or jacket  104  can be dipped in a dispersion of conductive particles, which are then retained. 
     The jacket  104  can be sintered to the inner tube  102  to provide structural stability that prevents the inner tube  102  from collapsing, deforming, or bursting as will be discussed in greater detail below. 
     Protective jacket  108  can be a single layer jacket or a multi-layer jacket (the latter being depicted as an inner protective jacket layer  108   a  and outer protective jacket layer  108   b  in  FIG. 1 ). At its simplest, protective jacket  108  can be an elastomeric protective jacket that is extruded over jacket  104 . The protective jacket  108  can be formed from one or more thermoplastic elastomers. The protective jacket can include one or more reinforcing members  112  such as metal wires, fiberglass, aramids, para-aramids, and aromatic polyesters. In some embodiments, the one or more reinforcing members  112  are wrapped at a different pitch and/or direction than metal plaits  110 , thereby stiffening tube  100 . For example, reinforcing member can be a 0.0040″ diameter stainless steel wire wrapped at a W pitch (i.e., reinforcing member  112  advances ¼″ with each revolution around tube  100 ). 
     The protective jacket forms a chemical bond with the fiberglass jacket and reinforcing member  112  forms a further physical bond that holds protective jacket  108  against fiberglass jacket  104 . 
     In some embodiments, the protective jacket  108  includes one or more anti-microbial agents incorporated within the polymer. In some embodiments, one or more components of tube  100  are certified under Class VI by the U.S. Pharmacopeial Convention of Rockville, Md. 
     Additionally or alternatively, the protective jacket  108  can include one or more anti-blocking agents impart a waxy feel to the elastomer(s) in protective jacket  108 , thereby making the protective jacket  108  easier to clean. For example between about 0.5% and about 2.5% (by weight) of a mineral or metal salt can be added to the elastomer. 
     Referring now to  FIG. 2 , a method  200  of producing a tube according to an embodiment of the invention is provided. 
     In step S 202 , a PTFE tube is provided. The PTFE tube can be fabricated or can be obtained from a variety of sources. In some embodiments, the PTFE tube is formed by extrusion. For example, TEFLON® T62 PTFE can be mixed with ISOPAR™ G isoparaffin fluid available from ExxonMobile Chemical Company of Houston, Texas and extruded. Advantageously, PTFE tubes can be formed by vertical extrusion, in which the tube is extruded downward through a die (instead of the usual horizontal extrusion) in order to produce a tube with a high orientation index as discussed herein. Suitable vertically-extruded PTFE tubes are available from Titeflex Corporation of Springfield, Mass. Alternatively, the PTFE tube can be annealed (e.g., while hanging vertically) to increase the orientation index. This annealing step can be performed prior to the braiding step. 
     In step S 204 , a jacket is circumferentially wrapped around the PTFE tube. In some embodiments, the jacket is a braided. In other embodiments, the jacket is helically wrapped. The jacket can be formed from a plurality of plaits of fiberglass lace using standard braiding and rope making techniques and equipment. As discussed above, the fiberglass lace can include PTFE and/or one or more reinforcing strands. 
     In step S 206 , the assembled tube is optionally sintered to bond the PTFE tube to the braided jacket. The sintering step can include introducing the tube into an oven so that the tube is heated to between about 700° F. and about 725° F. The speed, length, and/or temperature of the oven can be controlled so that the tube is held at this temperature from between about 2 minutes and about 4 minutes (e.g., about 3 minutes). For example, the tube can pass through a 6′ oven at a rate of 24″/minute. 
     In step S 208 , a protective jacket is extruded over the fiberglass jacket using standard techniques and equipment such as a pressure die or a shrink die. 
     Referring now to  FIG. 3 , a method  300  of using a tube as described herein is provided. 
     In step S 302 , a tube is provided. The tube can be of the types described herein. 
     In step S 304 , one or more fittings can be coupled with one or more ends of the tube. The fittings can, for example, be of conventional types used in the automotive and aerospace industries. 
     In step S 306 , one or more ends of the tube are coupled to one or more devices. For example, a first end of a tube can be connected to a fluid source such as a tank and a second end of a tube can be connected to a fluid sink such as a mixer. 
     Referring now to  FIGS. 4A and 4B , exterior and cross-sectional views are provided of a tube  400  according to an embodiment of invention. The depicted tube  400  lacks a protective jacket, which can optionally be applied over tube  400 . 
       FIG. 4A  provides a photograph of a cross-section a wall of the tube  400 . The tube includes (moving outward from a central axis) a PTFE inner core layer  404  surrounded by a braided jacket  406 . 
       FIG. 4B  provides a photograph of the braided jacket  406  of the tube  400 . Although the depicted tube  400  has a dark pigment, individual plaits  408  of fiberglass lace are visible and an exemplary plait  408  is called out by a white rectangle. Within the plaits  408  of fiberglass lace, fiberglass strands  410  and aramid strands  412  are visible. The fiberglass strands  410  are darker than the aramid strands  412 . 
     Equivalents 
     While certain embodiments according to the invention have been described, the invention is not limited to just the described embodiments. Various changes and/or modifications can be made to any of the described embodiments without departing from the spirit or scope of the invention. Also, various combinations of elements, steps, features, and/or aspects of the described embodiments are possible and contemplated even if such combinations are not expressly identified herein. 
     Incorporation by Reference 
     The entire contents of all patents, published patent applications, and other references cited herein are hereby expressly incorporated herein in their entireties by reference.