MXPA99005472A - Thermoplastic composite products and method of lining pipework - Google Patents

Abstract

A pipe (4) is rehabilitated by means of a tubular liner (5) which is introduced into the pipe in a contracted form, expanded into contact with the pipe wall, and hardened to retain its form. The liner (5) comprises composite material formed by knitting, braiding or weaving tows of intermingled filaments of thermoplastic and reinforcing fibre, the liner being heated during application to the pipe in order to melt the thermoplastic. The composite material may be created as a sleeve. Alternatively, a sheet of the material may be calendered and rolled up into a tubular form, overlapping edge margins of the sheet being bonded together after expansion of the tube into contact with the pipe wall.

Description

COMPOSITE OPLASTIC PRODUCTS AND METHOD FOR COATING TUBES BACKGROUND OF THE INVENTION This invention relates to the manufacture and use of products manufactured from reinforced thermoplastic composites, with fiber. In particular, the invention relates to methods of coating tubes and other ducts with such materials, and to the manufacture of duct and tube linings from such materials. Within the term "pipeline", when used herein, includes pipes, pipes and conduits, either to transport fluids (for example, a sewer) or for other purposes. Currently several different techniques are used to reconstruct existing pipe systems by coating the existing pipe instead of removing it and replacing it. Coating the existing pipe is generally cheaper and causes fewer interruptions than full replacement programs and is therefore widely used in the water and gas supply industries. For example, most of the main water streams in the United Kingdom are emptied of iron (most have a diameter of 150 mm or less). The fault REF .: 30485 of such pipes due to corrosion (both internal and external) becomes a growing problem with respect to the age of existing systems. Therefore, it is estimated that more than 50% of the main water flows in the United Kingdom have provided service for more than 40 years and that 20% have been in service for more than 80 years. Therefore, there is an increasing demand for the development of effective reconstruction techniques. Conventional methods for coating pipes include epoxy resin cement coating and spraying processes and "slip coating" processes. The latter involves inserting a pipe liner, typically made of polyethylene or PVC, e? "Sel existing tube. The slip coating is carried out in a variety of ways using various different forms of tube coating. For example, a type of slip coating widely used in the gas industry, referred to as "tube opening liner", which involves turning an MDPE tube liner into a tube in situ when first having to pull the liner through a tube. Die to reduce its diameter. Once in position, the coating expands and tries to revert to its original diameter. Therefore, after a period of 12 hours or similarly, the coating will expand and fit within the host tube. One advantage of the pipeline coating, and indeed of other slip coating processes, is that the coating can provide structural strength to the host tube to satisfy the high pressure regresses. However, when such structural coatings are used, precautions must be taken to reduce the diameter of the coating so that it can be removed within the tube if an adjustment is obtained between the coating and the wall of the tube. The turning loads used can be very high which can provide hazards in the installation. In addition, even with "fit" coating techniques, such as pipeline coating, the coating is not properly reversed to fit within the host tube along its entire length if there are variations in the pipe diameter. This can result in spaces that are free between the liner and the tube wall, which is undesirable. For example, if the coating fails, the fluid may slide between the coating and the tube wall before escaping and thus the externally observable manifestation of a leak or discharge in the coating may be a considerable distance from the actual point of contact. failure, which makes it difficult to identify the position of the fault.

An object of the present invention is to provide a new method for coating the pipe or other form of duct. According to a first aspect of the present invention, there is provided a duct coating method comprising: inserting into the duct a coating comprising a composite material consisting of filaments of thermoplastic material and filaments of reinforcing fiber; heating the coating to melt the thermoplastic filaments; apply pressure to the heated coating to press it in contact with the duct; and allowing the coating to cool while in contact with the duct in order to harden the thermoplastic / reinforcing fiber composite. A suitable composite material is available from Vetrotex International of 767 quai de Allobroges - BP 929, 73009, Chambery Cedex, France (a subsidiary of St. Gobain) under the registered trade name TWINTEX. TWINTEX is available, for example, as wound yarns or as woven fabrics or tows comprising long filaments homogeneously intermixed from thermoplastic materials such as polypropylene, polyethylene, polyethylene terephthalate (PET) and polybutyl terephthalate (PBT) with E glass, the content Fiberglass is typically 45 to 75% in weight (20 to 50% by volume). The manufacturing process of TWINTEX allows the thermoplastic and glass fiber filaments to be mixed in "dry" with a high degree of control over the distribution of the two filamentous fibers. The consolidation of the TWINTEX "prepreg" material in a rigid composite is obtained by heating the material under pressure to melt the thermoplastic and dispersing it between the glass fibers. The cooling of the material subsequently solidifies the thermoplastic which forms a solid matrix around the reinforcing glass fiber. The homogeneous distribution of the filaments in the TWINTEX product ensures favorable processing temperature conditions against the pressure and the resulting consolidated composite has good mechanical properties. Additional details of the TWINTEX product are readily available from the manufacturer. Prior to consolidation, the composite material is relatively flexible, therefore it can be inserted into a duct to be coated while in a collapsed configuration and subsequently expanded to make contact with the duct wall. During the installation process, pressure can be applied to the coating material to consolidate the composite material during the heating stage and / or between the heating stage and the cooling stage and / or during the cooling stage. A variety of different methods can be used to heat the coating, which include irradiating the coating with infrared radiation, or heating the coating using hot gas or steam. It is preferred that in the duct coating method according to the present invention, a coating consisting of glass reinforced fibers (for example TWINTEX) be used and that infrared radiation be used to heat the coating. It has been found that glass fibers are particularly sensitive / absorbent to short wave infrared radiation (i.e., wavelength less than 2 μm) at particular frequency ranges. The glass fibers are thus heated relatively quickly and melt the thermoplastic filaments interspersed therewith, with relatively little heat loss to the surrounding medium. This is particularly advantageous when the method is used to align thermally conductive pipes such as cast iron main pipes. As an additional means of limiting the heat loss from the coating to the duct and to the surrounding medium, the coating can be provided with an outer layer of insulating plastic material, for example a material thermoplastic such as that used in the composite material. Similarly, the coating can be provided with an inner layer of plastic materials, such as polypropylene or polyethylene, which provide the coating with an internal surface that meets the accepted standards for transmission of, for example, potable water supplies. The pipeline coating methods according to the present invention are not limited to in situ coatings, but must be applied to the coating of new pipes at the place of manufacture. Similarly, the methods according to the present invention are not restricted to providing inner tube liners, but can be adapted to provide external tube covers. In another of its aspects, the invention provides a method for applying a coating or cover, respectively, to an interior or exterior surface of a duct, comprising: applying a coating / cover to the duct which comprises composite material comprising fiber filaments thermoplastic and reinforcing fiber filaments; heating the composite material to melt the thermoplastic filaments; apply pressure to the liner / cover to press it and bring it into contact with the interior / exterior surface of the duct; and allowing the liner / cover to cool while in contact with the duct in order to harden the thermoplastic / reinforcing fiber composite. Furthermore, the present invention is not limited to providing tube liners and the coating of such tubes. In another of its aspects, the invention provides a method for manufacturing a product comprising knitting, braiding or weaving a composite material of intermingled filaments of thermoplastic and reinforcing fibers (for example TWINTEX). % "The use of such a method of interlocked filament tow (for example TWINTEX) allows the production of products having a wide variety of configurations, tubular or otherwise. For example, by weaving a wide variety of tubes in an appropriate pattern, devices and other products can be easily fabricated. Existing industrial knitting machines can be adapted to weave such materials in accordance with the present invention. By varying the diameters of interwoven fabric to suit the existing underground tubes that have a variety of tension and recovery properties have been produced using a variety of adherents and others sewing structures. This is coupled with changes in circular cylinder diameter and alternative calibers, which provides the corresponding preformed wall thicknesses and the stretching and resistance characteristics required to contend with pipe applications used in the water supply industry. In addition, various positive feeding methods incorporating "positive feeding tapes" and "storage feeder" methods have been used to provide a continuous prefabricated tube free of "protrusions" of better quality. The productivity of the machine has been improved by identifying a commercial match between gauge, diameter, speed, closing needle head and stop size, thread sag tension and suitability for operation. The position of the yarn feeder and the design in relation to the placement of the yarn in the head of the closing needle have been investigated and adjusted to assist in the ability to operate the "Twinter" yarn extracted from the package, both externally and externally. internally. Both electric and mechanical pattern systems are used to identify the simplest yet versatile fabric structure design. In addition, the use of infrared radiation to heat a composite material of thermoplastic fiber / reinforced fiber and particularly the use of infrared radiation of a wavelength at which the fiber reinforcement is particularly sensitive, provide advantages in the molding of products using a conventional fabric or similar fiber reinforced thermoplastic composites. Thus, according to a further aspect of the present invention, there is provided a method for manufacturing a product from a composite material comprising filaments of thermoplastic material and filaments of reinforcing fiber, the method comprising: irradiating the material with radiation infrared to melt the thermoplastic material; consolidate thermoplastic and reinforcing fibers; and allowing the thermoplastic to harden with the material in a desired manner. Preferably the reinforcing fibers are glass fibers. Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figures 1a and 1b are schematic cross sections of two forms of thermoplastic / fiber composite fiber tow. glass suitable for use in the present invention; - Figure 2 is a schematic illustration of a tube coating method according to the present invention; Figure 3 is a schematic illustration of a tube coating method according to a first preferred embodiment of the present invention; Figure 4 is a schematic illustration of a tube coating method according to a second preferred embodiment of the present invention; Figure 5 is a schematic cross-section through a tube coating according to the present invention; Figure 6 is a schematic cross section through an alternative tube liner according to the present invention; and Figure 7 is a schematic illustration of the manner in which a threaded plug side opening can be connected to a cladding tube in accordance with the present invention. It will be appreciated from the foregoing that all aspects of the present invention involve the use of a material comprising filaments of a thermoplastic material and filaments of reinforcing fibers. In particular, the preferred material for use in the present invention is one that is woven, braided or woven (or bonded in some other way) of tows comprising substantially continuous filaments of a thermoplastic material and similar continuous reinforcing fibers. More particularly, the preferred material that is available from Vetrotex International under the registered trade name TWINTEX. Figures 1a and 1b are cross sections through two preferred forms of the TWINTEX tops for use in the present invention. In both figures, the and lb, the ermoplastic filaments are shown as black dots 1 while the glass reinforcing fibers are shown as circles. The two tows differ from each other in that in the tow of Figure lb the intermixed filaments are collectively bonded by a layer 3 of thermoplastic wrap (which will generally be the same thermoplastic as that used for the filaments 1). Referring now to Figure 2, this is a general outline of a tube coating process according to the present invention. An underground host tube 4 is coated with a tube liner 5 comprising a hose (i.e., a sheath), interwoven, braided or woven of TWINTEX tow (generally the hose will be interwoven with TWINTEX tow twisted yarns). The liner 5 is stretched from the tube in a collapsed and folded configuration (a folded portion of the liner is illustrated with the reference number 5a) using a lathe (not shown). shown). Once in position within the host tube 4, the liner 5 is opened and pressed to come into contact with the wall of the tube. Heat and pressure is then applied to the coating to melt the thermoplastic filaments (for example, the coating must be heated to a temperature of about 148 ° C when the thermoplastic is polyethylene) and to compress the coating against the wall 4 of the tube to consolidate the composite material. The coating 5 is then allowed to cool while in contact with the tube wall, after which the thermoplastic hardens, forming a reinforced composite coating of substantially rigid fiber. Referring now to Figure 3, this illustrates the use of a robotic scraper or plug 6 in the coating process described in relation to Figure 2. The scraper 6 Robotic comprises positioning rollers 7 extending from its forward end, a heating means 8 located behind the positioning rollers 7, and cooling and consolidation rollers 9 extending from its rear end. When used, once the liner 5 has been inserted into the guest tube 4 in its folded configuration, the scraper 6 passes along the tube through the liner 5. As the scraper 6 advances through the liner 5, the first positioning rollers 7 open upwards of the covering 5a forward folding of the scraper 6 in the position of the coating 5 against the wall of the tube 4. A slight pressure of air will inflate the Twintex preform against the surface of the tube. Immediately behind the laying rollers, a heating means (which may be, for example, a radiant heater or a hot gas heater) then heat the coating 5 to a temperature sufficient to melt the thermoplastic. As the scraper advances further, the cooling and consolidating rollers 9 come into contact with the heated area of the coating 5 and compress the coating 5 against the surface of the tube 4 both to consolidate the composite material and to help cool the material for accelerate the hardening process, Therefore, as the scraper 6 moves along the tube 4, it effectively converts the flexible hose into a fully formed and hardened composite liner. As mentioned above, the heating medium is preferably a short wave infrared radiator. It has been found that the glass reinforcing fibers respond in particular to the radiation so that most of the energy emitted by the heater is absorbed by the glass fibers and subsequently transmitted to the thermoplastic material. This minimizes heat losses to the surrounding tube material and greatly reduces both the energy as the time needed to heat the coating to the required temperature. In Figure 4 there is illustrated an alternative method of installing the liner 5, while still following the general scheme described in relation to Figure 2. Here, an inflatable bag 10 is inserted into the liner 5 (for example a bag made of rubber of sylicon) . The bag 10 is then inflated with hot gas, both to heat the liner 5 and to compress it against the wall of the tube 4 to consolidate the thermoplastic and reinforcing fibers. The temperature and pressure inside the bag can be controlled as desired. Subsequently, either the gas within the bag 10 can be allowed to simply cool to allow the thermoplastic to harden, or cold gas can be blown into the bag 10 to replace the hot gas and accelerate the cooling process. As a modification of the above method, the gas supplied to the bag 10 can be at room temperature and the bag can be heated by another means. For example, electric heating elements or a system of heated tubes (eg, transporting hot oil) can be distributed through the wall of the bag 10. As mentioned arts, the heat loss to the surrounding tube and the earth can be substantial, which greatly increases the energy and / or time needed to heat the coating to the melting point of the thermoplastic. This problem can be particularly important in the lining of main cast iron water pipes. Accordingly, the coating can be provided with a coating layer of an insulating plastic material, for example, a thermoplastic equal to that which is incorporated in the composite material used to make the coating. In Figure 5 a cross section of such a coating is illustrated. The coating comprises a composite tube 11 provided with an outer sheath 12 of polypropylene or similar material. As a further modification, illustrated in Figure 6, the inner surface of the liner 11 can also be provided with a layer of plastic material 13, such as polyethylene or polypropylene. This is particularly desirable when the coating is to be used for coating main drinking water pipes. For example, HDPE is a material widely used to transport potable water and meets all the required standards, which may not necessarily coincide with the composite material used in the manufacture of the coating. Therefore, incorporating a layer of HDPE (or a similar material) on the inner surface of the coating provides a barrier between the composite material and the fluid to be transported through the coating.

It will be appreciated that the coating can be made with both an outer and an inner layer of thermoplastic material, such as HDPE. Because the coating is relatively flexible when inserted into the host tube, the insertion process is relatively simple. In addition, when the coating expands and is pressed against the surface of the tube, the flexibility of the coating can easily adapt to variations in the diameter of the host tube. The interweaving of the liner provides a convenient method for quickly fabricating coating in any desired shape, length, diameter and wall thicknesses. In addition, as mentioned above, by using new and existing interweaving techniques, the coating can be woven in a variety of configurations. For example, the branches can be interwoven within the liner so that a one-piece liner can be used to align both a main tube and a side connection. Coatings according to the present invention also have the advantage that they separate liner sections which can be easily connected together simply by heating and compressing ends together of respective liner sections to form a weld. Therefore, there is no need for the use of separate links.

In addition, with reference to Figure 7, the placement of side openings with a screw cap in a coated tube according to the present invention is a relatively simple procedure. That is, the inner flange 14a of a threaded cap side opening 14 can be easily fixed and sealed to the pipe covering using a layer 15 of thermoplastic substance or the like. It will be appreciated that the tube coating methods discussed above present only exemplary applications of the present invention. For example, the above methods can be easily adapted to coat or cover tubes at the point of manufacture. For example, modifications of the above methods can be used to provide an inner liner or outer shell to a new ductile iron pipe. Further, the invention is not limited to providing tubes and tube liners, but the interwoven process described herein can be used to make products of various shapes, tubular and otherwise. For example, a variety of tube devices and similar products can be prepared by weaving the composite material into an appropriate preform. In addition, although many aspects of the present invention involve the use of an interwoven material, the use of radiation can be advantageously applied. infrared of a particular wavelength to which the reinforcing fibers particularly respond, and the molding of any composite product of thermoplastic / reinforced fiber may be applied, whether the composite material is woven, woven or otherwise bonded , whether the composite material includes TWINTEX or not. The broad applicability of these and other aspects of the present invention will be readily apparent to a person appropriately familiar with the subject. As described so far, the coating produced within the tube is relatively flexible, even thermoplastic coatings applied to the inner and / or outer surface of the composite material. Although this allows the liner to collapse easily, in some circumstances it may be acceptable, or even advantageous, for the liner to be rigid and relatively inflexible for introduction into a duct. This can be accomplished by at least partially consolidating the composite material (by means of heat and pressure) to create a self-supporting and shaped preform prior to insertion into a duct. The preform may be in the form of a collapsed tube, the tube expands under heat and pressure to coat the tube. Alternatively, a sheet of composite material can be heated and calendered (between opposite chilled rollers) to create a consolidated sheet material. The rigid sheet material can then be rolled into a substantially tubular shape for insertion as a coating within a tube, the material roll is fixed, for example, by steel wire. By releasing the wire fasteners with the coating inside the tube, the roll tends to unwind to the inside diameter of the tube. The overlapping edge margins of the preform can then be joined together. A suitable attachment means for joining this may include electrical resistance wires which are incorporated into the composite sheet at their margins, or an adhesive tape which melts by heat. The tape can be heated, by means of, for example, included resistance wires or a metal filler material which can be heated by induction. A robotic scraper can be used to join the joint weld using, for example, a hot roller, ultrasound or infrared radiation, followed by a cooling roller. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (29)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A method for coating a duct, characterized in that it comprises: inserting into the duct a coating comprising a layer of composite material consisting of filaments of thermoplastic material and filaments of reinforcing fiber and an outer layer of thermoplastic material; heating the coating to melt the thermoplastic filaments; apply pressure to the heated coating to press it and put it in contact with the duct; and allowing the coating to cool while in contact with the duct in order to harden the thermoplastic / reinforcing fiber composite.

The method according to claim 1, characterized in that the coating is inserted into the duct in a collapsed configuration and subsequently expanded in contact with the duct.

3. The method according to claim 1 or 2, characterized in that pressure is applied to consolidate the composite material as the coating is heated.

4. The method according to any preceding claim, characterized in that pressure is applied to consolidate the composite material as the coating cools.

5. The method according to any preceding claim, characterized in that the coating is heated upon irradiation with infrared radiation.

The method according to any of claims 1 to 4, characterized in that the coating is heated by hot gas.

The method according to any of claims 1 to 4, characterized in that the coating is heated by steam.

The method according to any preceding claim, characterized in that subsequent to the insertion of the coating into the duct an apparatus is passed through the coating comprising at its forward end means for pressing the coating and bringing it into contact with the duct , a heating means placed on the back of the pressing medium to heat the coating, and a consolidation means placed at the rear of the heating means to apply pressure to the heated coating to consolidate the composite material.

The method according to claim 8, characterized in that the apparatus further includes a cooling means placed at the rear of the consolidation means to cool the consolidated coating.

The method according to any of claims 1 to 7, characterized in that subsequent to insertion of the coating into the duct, pressurized gas is introduced into the coating to press the coating against the duct, and the gas is heated to heat the coating.

The method according to claim 10, characterized in that an inflatable bag is inserted into the liner to receive the pressurized gas, the wall of the bag leans against the liner to press it against the duct.

A method for coating a duct, characterized in that it comprises: inserting into the duct a coating comprising a layer of composite material comprising filaments of thermoplastic material and filaments of reinforcing fiber; introduce pressurized gas into the liner to press the lining and put it in contact with the duct and heating the gas to melt the thermoplastic filaments; and it is preferred that the coating be cooled while in contact with the duct in order to harden the thermoplastic / reinforcing fiber composite.

The method according to claim 12, characterized in that the coating is inserted into the duct in a collapsed configuration and subsequently expanded in contact with the duct.

14. The method according to the claim 12 or claim 13, characterized in that the pressurized gas consolidates the composite material as the coating is heated.

15. The method according to any of claims 12 to 14, characterized in that pressure is applied to consolidate the composite material as the coating cools.

16. The method according to any of the preceding claims, characterized in that subsequent to the insertion of the coating in the duct is passed through the coating an apparatus having at its front end a means to press the coating and put it in contact with the duct, a heating medium to heat the gas and a means of consolidation towards the of the heating medium to apply pressure to the heated coating and consolidate the composite.

17. The method according to claim 16, characterized in that the apparatus further includes a cooling medium located at the rear of the consolidation means to cool the consolidated coating.

18. The method according to any of claims 12 to 17, characterized in that the coating also includes an outer layer of thermoplastic material.

The method according to any of the preceding claims, characterized in that the composite material is provided in the form of a sheath.

The method according to any of the preceding claim, characterized in that the composite material of the coating introduced into the duct is provided as a calendered sheet which has been rolled into a tubular form.

The method according to claim 20, characterized in that it includes the step of joining together superimposed margins of the sheet material to form a tube.

22. The method according to any of the preceding claim, characterized in that the reinforcing fiber comprises glass reinforcing fiber.

23. The method according to any of claims 19 to 23, characterized in that the material The composite is interwoven, braided or woven from tows comprising filaments interspersed heterogeneously of thermoplastic and reinforcing fibers.

24. The method according to claim 23, characterized in that the tows have from about 40o to about 75% reinforcing fiber by weight.

25. The method according to claim 23 or 24, characterized in that the tows have between about 20% and about 50% reinforcing fiber by volume.

26. The method according to any of claims 23 to 25, characterized in that each tow is wrapped in a thermoplastic cover.

27. The method according to any of claims 23 to 26, characterized in that the filaments of thermoplastic and reinforcing fibers are substantially continuous along the length of each tow.

28. The method according to any preceding claim, characterized in that the thermoplastic filaments comprise filaments of a polyolefin or a thermoplastic polyester.

29. The method according to any preceding claim, characterized in that the coating also includes an inner layer of a thermoplastic material.