WO1990008034A1

WO1990008034A1 - Improved corrosion-resistant textiles

Info

Publication number: WO1990008034A1
Application number: PCT/US1990/000199
Authority: WO
Inventors: Stephen W. Tippett
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-01-19
Filing date: 1990-01-17
Publication date: 1990-07-26
Anticipated expiration: 1991-07-19
Also published as: AU5049090A

Abstract

A flexible, corrosion-resistant textile product comprising, in combination, first and second flexible textile substrates (10, 14), having a corrosion-resistant, film (12) sandwiched therebetween is described. In a preferred embodiment of the invention, the corrosion-resistant film comprises a gas-tight fluoropolymer film.

Description

IMPROVED CORROSION-RESISTANT TEXTILES BACKGROUND OF THE INVENTION

The present invention relates to new textile products having improved wear and corrosion resistance characteristics, and more particularly to textile products which are gas-tight, flexible and resistant to wear, abrasion and corrosion. The textile products of the present invention have particular utility for use in expansion joints for wet and/or dry flue duct seal service, and will be described in connection with such utility, although other uses are contemplated. Since their introduction in the early sixties, the use of non-metallic expansion joints for connecting the ends of large conduits have continuously grown. Large conduits are used to carry the combustion discharge, for example, from a power plant, to apparatus designed to remove noxious vapors and solids prior to discharging the remainder to the atmosphere. Expansion joints are subject to movement due to temperature variations and plant vibrations, and also are subject to high temperature exposure and exposure to highly corrosive materials. DESCRIPTION OF THE PRIOR ART One type of prior art non-πxietallic expans±On j&'in for use in high temperature and corrosive environments typically comprises a layered product that consists of various plies of material which are laid one over the other and usually mechanically fastened together in the clamp or flange area of the joint. This type of construction allows each material layer to function independently of the others. Typically, an expansion joint of this type is comprised of (1) one or more inner ply or plies capable of withstanding the high temperature (400°F+) of the flue gas; (2) one or more thermal insulating barrier plies to lower the temperature within the joint, and (3) one or more outer cover ply or plies. The expansion joint also may incorporate a gas seal ply as the inner ply, outer ply, or as an intermediate ply depending upon application requirements or manufacturer's design. Fluoropolymer coated flexible textile products such as polytetrafluoroethylene (PTFE) coated fiberglass or the like materials also are gaining increasing use in expansion joints due to their superior resistance to corrosion. Also, fluoropolymers have excellent electrical characteristics and physical properties, such as low coefficient of friction, low surface free energy and high degree of hydrophobiσity, which further favors their use in expansion joints. Fluoropolymers, and particularly perfluoropolymers such as polytetrafluoroethylene (PTFE) , fluoro (ethylene propylene) copolymer (FEP) , and σopolymers of tetrafluoroethylene and perfluoropropyl vinyl ether (PFA) are resistant to a wide variety of chemicals, even at elevated temperatures, making them widely useful in a variety of industrial applications. Fluoropolymers, such as polytetrafluoroethylene, are also well known for their low co-efficient of friction and relatively low surface-free energy which contributes to release behavior- ile they -exhibit outstanding chemical and thermal resistance, they are relatively soft waxy materials with relatively fragile surfaces easily damaged mechanically by scratching or wearing when rubbed against other materials. Increasing proportions of harder polymer components in the matrix may lead to improved mechanical wear characteristics, but with attendant loss of elongation (embrittlement) . While such compositions may reasonably be employed on relatively rigid substrates, when coated directly onto flexible substrates, such as woven cloth, they may result in products which are most frequently too brittle to serve as flexible coatings for conduits and may even crack when folded upon themselves. An object of the present invention is to provide a textile product which overcomes the aforesaid and other disadvantages of the prior art, and which is flexible, gas-tight, and possesses good environmental and surface wear resistance. Another object of the invention is to provide a gas-tight, non-metallic expansion joint which exhibits outstanding corrosion and surface wear resistant characteristics, and low co-efficient of friction. SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a laminated textile product comprising, in combination: (a) a load-bearing component consisting of a first flexible textile layer; (b) a mechanical barrier component comprising a second flexible textile layer; and (c) a chemically resistant, gas-tight film sandwiched between the load bearing component and the mechanical component, said chemically resistant, gas-tight film comprising a fluoropolymer-containing film. Other objects, advantages and features of the present invention will be apparent and readily understood from the following description of the invention, taken in conjunction with the -drawings, in -which like reference characters refer to like parts; and Wherein: DESCRIPTION OF THE DRAWINGS

Fig. 1 is a side elevational view, in cross section, of a laminated textile product made in accordance with the present invention; Fig. 2 is a vertical section of an expansion joint made using the laminated textile product in accordance with the present invention; and Fig. 3 is a view in cross section showing details of a 1 joint in a laminated textile product made in accordance

2 with the present invention.

3 DETAILED DESCRIPTION OF THE INVENTION

4 As used herein, the term textile shall include

5 naturally occurring and synthetic woven, non-woven,

6 matted, felted and knit fabric materials. Any suitable

7 textile material capable of withstanding processing

8 temperatures may be employed as the mechanical and load

9 bearing components in accordance with the present 0 invention. Examples, include, inter alia, glass, 1 fiberglass, ceramics, graphite (carbon), PBI 2 (polybenzimidazole) , PTFE, polyaramides such as Kevlar and 3 Nomex, polyolefins such as Tyvek, polyesters such as

14 Reemay, polyi ides, polyinides, thermoplastics such as

15 Kynar and Tefzel, polyethersulfones, polyetherimide,

16 polyetherketones, novolid phenolic fibers such as Kynol,

17 cotton, asbestos and other natural and synthetic fibers.

18 The fabric material may also comprise a metal such as

19 steel wire, mesh or wool, or the like. The fabric

20 substrate may comprise a yarn, filament, monofilament or

21 other fibrous material, either as such or assembled as a

22 textile, or any woven, non-woven, knitted, matted, felted,

23 et cetera, material.

2.4 Referring in particular to Figs. 1 and 2 of the -drawing, there is illustrated a -prefe red form of textile

26 material and expansion joint made in accordance with the

27 present invention. In accordance with the present

28 invention, a textile product comprises a first, load

29 bearing textile substrate layer 10, a second, mechanical

30 barrier textile layer 14, and a film layer 12 formed of a

31 corrosion-resistant, gas-tight (zero porosity) inert

32 material sandwiched between and bonded to load bearing

33 substrate layer 10, and mechanical barrier layer 14.

34 Depending on the nature of the substrate and the

35 intended end-use of the textile product, the textile

36 layers may be impregnated, either initially or simultaneously with a chemically resistant material such as of the type making up the gas-tight film. Also, depending on the nature of the textile layers and the envisioned end use, the textile may be treated with a 'bonding or coupling agent to enhance adhesion of the protective film to the textile, and/or a lubricant such as methylphenyl silicone oil, graphite, or other lubricating material which may be applied, for example, prior to, simultaneously with, or subsequent to the application of the bonding or coupling agent, to enhance flexibility of the textile. For example, one or both of load bearing substrate layer 10 and mechanical barrier layer 14 preferably will comprise fluoropolymer coated textile products, for example, PTFE coated fiberglass such as described in detail in U.S. Patent 4,654,235 which is incorporated herein by reference. The corrosion-resistant, gas-tight protective film preferably comprises one or a mixture of polyfluoropolymer materials such as PTFE, PFA and FEP, and may be preformed, or formed in situ by a variety of coating techniques such as dip coating or other well-known techniques. The textile product is formed as follows: load bearing substrate layer 10 and/or mechanical barrier layer 14 are impregnated or coated initially with a fluoropolymer such as PTFE, KALREZ (Dupont) , KEL-F (3M) or a blend thereof. Film layer 12 is then formed in situ such as by dip coating on one surface of load bearing substrate layer 10 and/or mechanical barrier layer 14, and substrate layer 10 and mechanical layer 14 are then laminated together with film layer 12 sandwiched therebetween, in a hot laminator. Alternatively, film layer 12 may be supplied as a separate pre-formed film which may be heat laminated between load bearing substrate layer 10 and mechanical barrier layer 14. Load bearing substrate layer 10 and mechanical barrier layer 14 preferably but not necessarily comprise the same or similar substrate materials, and may be the same or different thicknesses, depending on the intended use. Typically, substrate layer 10 and barrier layer 14 will be of a thickness of 5 to 60 mil. Film layer 12 should have a thickness of at least about 2 mil, and typically will have a thickness of 3 to 20 mil, preferably 5 to 10 mil. Referring in particular to Fig. 2, an expansion joint made using the laminated textile material of the present invention has two rectangular frames 16 of stock that are right angular in cross section with one wall of each frame bolted and sealed to the end flange of an appropriate one of the duct sections (not shown) that are to be interconnected by the joint. The outer edges 20 of the laminated textile material are seated against the other walls of the frame 16 and anchored to and sealed thereagainst utilizing threaded studs 22 or the like extending through the outer edges 20 and a hold-down frame 24 to receive anchoring nuts 26. The outer edges 20 may be otherwise secured to the frames or duct sections by any other means which results in an integral connection of the sections. As can be seen, the outer edges 20 of the material extending beyond hold-down frame 24 are located exteriorly of the flow of flue gases -through the expansion joints and thus will not be exposed to the corrosive gases contained therein. However, as can be seen in particular in Fig. 3, in the splice overlap area 30, material edges 28 would be exposed. In order to protect the exposed edges 28 in the splice overlap area 30, the exposed edges 28 of the composite material are encapsulated within a corrosion resistant, gas-tight barrier film 32 such as PFA or the like which may be heat sealed to the edges 28 of the cut composite material. A feature and advantage of the present invention is that the corrosion-resistant, gas-tight film is fully protected between two durable textile layers, thus 1 protecting the corrosion- resistant, gas-tight film from

2 damage during handling, and also from wear in use.

3 Moreover, the textile fabrics support the fluoropolymer

4 film and thus reinforce the film against stretching and

5 creasing. The load-bearing component, of course, is fully

6 protected from exposure to the flue gas thus extending the

7 life of the product, under use.

8 Various changes may be made in accordance with the

9 foregoing invention without departing from the spirit and

10 scope of the present invention. For example, while the

11 invention has been shown as comprising a single inert film

12 sandwiched between two textile layers, one or more

13 additional inert films and textile layers may be included

14 if desired.

15 Moreover, the laminated textile product of the present

16 is not limited for use in an expansion joint, but may be

17 advantageously used as a barrier product for other high 18. temperature and corrosive environments such as acid tank

19 liners. As will be appreciated, when used in such

20 environment, flexibility requirements are less.

21 Therefore, it typically is not necessary to consider the

22 inclusion of a lubricant in the load bearing and

23 mechanical barrier textile layers.

Claims

CLAIMS 1. A flexible, corrosion-resistant textile product charatcterized by comprising, in combination, first and second flexible textile substrates (10,14), having a corrosion-resistant, film (12) sandwiched therebetween. 2. A textile product according to claim 1 characterized in that said corrosion-resistant film comprises a gas-tight film, preferably a fluoropolymer- containing film, preferably having a thickness of 2 to 20 mil, more preferably 5 to 10 mil. 3. A textile product according to claim 1 or 2 characterized by one or more of the following features: (a) said textile substrates and film are heat laminated to one another; (b) at least one of said textile substrates is impregnated with a chemically-resistant material, preferably a fluoropolymer; (c) at least one of said textile substrates is impregnated with a lubricant, preferably silicone oil or graphite; (d) at least one of said flexible textile substrates comrises a material selected from glass, fiberglass, ceramic, graphite, carbon, a polybenzimidazole, a polytetrafluoroethylene, a polyaramide, a polyolefin, a polyester, a polimide, a polyinide, a polyethersulfone, a polyetherimide, a polyetherketone, a novolid, phenolic, cotton, asbestos, and a metal wire, mesh or wool. 4. In a flexible expansion joint for connecting the spaced ends of two conduits for conveying a corrosive fluid stream therebetween, said flexible expansion joint including framer members attached to end portions of each conduit for capturing the edges of a flexible corrosion- resistant textile, the improvement characterized in that said corrosion-resistant textile comprises a flexible textile product of claim 1. 5. A flexible expansion joint according to claim 4, wherein said flexible textile is spliced, the improvement characterized in that exposed edges (28) of the splice overlap area are encapsulated within a corrosion- resistant, barrier film (32). 6. The flexible expansion joint according to claim 5, characterized in that said corrosion-resistant, barrier film is heat sealed to said exposed edges. 7. A method of producing a flexible, corrosion- resistant textile product characterized by providing first and second flexible textile substrates, and laminating said substrates together with a corrosion-resistant, film sandwiched therebetween. 8. A method according to claim 7 characterized by one or more of the following features: (a) said corrosion-resistant film comprises a gas-tight film, preferably a fluoropolymer-containing film, preferably having a thickness of 2 to 20 mil, more preferably 5 to 10 mil; (b) including the step of heat laminating said textile substrates and film to one another; (c) including the step of encapsulating at least some of the exposed edges of said product within a corrosion-resistant barrier film, ^whe ein said corrosion- resistant barrier film preferably is heat sealed to said exposed edges; (d) at least one of said flexible textile substrates comprises a material selected from glass, fiberglass, ceramic, graphite, carbon, a polybenzimidazole, a polytetrafluoroethylene, a polyinide, a polyethersulfone, a polyetherimide, a polyetherketone, a novolid, phenolic, cotton, asbestos, and a metal wire, mesh or wool. 9. A method according to claim 7 characterized by one or both of the following features: (a) including the step of impregnating at least one of said textile substrates with a chemically-resistant material, preferably a fluoropolymer, prior to said lamination; or (b) including the step of impregnating at least one of said textile substrates with a lubricant, preferably silicone oil or graphite, prior to said lamination. 10. A method according to claim 9, characterized by (a) applying said chemically-resistant material and said lubricant simultaneously; or (b) applying said lubricant prior to said chemically-resistant impregnating material; or (c) applying said lubricant subsequent to said chemically-resistant impregnating material.