WO1998051960A1

WO1998051960A1 - Improvements relating to curing of synthetic resin systems, for example, in the lining of pipelines and passageways

Info

Publication number: WO1998051960A1
Application number: PCT/GB1998/001267
Authority: WO
Inventors: Brian Chandler; Chris Davies
Original assignee: Sound Pipe Ltd.
Priority date: 1997-05-15
Filing date: 1998-05-14
Publication date: 1998-11-19
Also published as: AU7342198A

Abstract

The invention provides that a laser light used to cure synthetic resin systems, in particular those systems which are used in the lining of pipelines or passageways. The synthetic resin system is of the curable type, such as polyester or epoxy, and has a catalyst protected from causing premature curing of the resin by being contained in particles. Laser light is focussed so as to activate the particles which has the effect of releasing the catalyst so that it can commence doing its work of curing the resin, but there is no wastage of light energy, as is common with known systems in heating up the resin.

Description

Improvements Relating to Curing of Synthetic Resin Systems , for example, in the Lining of Pipelines and Passageways

This invention relates to the curing of curable synthetic resin systems which comprise a base resin and an agent (catalyst, accelerator, hardener or the like) referred to hereinafter simply as the catalyst, which causes curing of the resin. As a result of the curing, as will be appreciated, rigid articles or materials result.

Resin systems as indicated are used in many applications, a main one of which as far as our interest is concerned, is in the lining of pipelines and passageways. In such lining methods a tubular pipelining member (the liner, lining, lining tube or liner tube) is constructed from or includes a curable synthetic resin system, and usually, to give the liner handlability, has a filler or reinforcing material, for example fibrous material.

It is well known to form the liner from at least a layer of resin absorbent material such as felt or fabric or other fibrous material which is impregnated with the curable synthetic resin system. In another construction, the liner comprises a mixture of the resin system and fibres, which may be or include natural, acetylated fibres.

It is also known that some resin systems are curable by light radiation, especially ultraviolet (UV) light radiation.

Liners although tubular, are essentially of sheet material, and it is to be mentioned at this stage that the invention can be used also for sheet materials, of appropriate construction, which are not tubular.

Throughout the world and extensively are performed underground pipeline and passageway lining operations involving the use of liners formed of resin system impregnated felts, the methods practiced being for example as set forth in US Patents Nos . 4009063 and 406421 1.

As can be seen from said US patents, heat is used to cure the resin system of the liners after the liners have been put in position lining the pipeline or passageway surface. In practice, heat curing is performed by filling the inside of the liner when it is in place with hot water, the heat in the water serving to initiate and effect the curing of the resin system. The resin systems mainly used have polyester resin bases and benzyol peroxide catalyst and are of the heat cure type, but it is recognized that with different resin systems curing may be effected in other ways, by the selection of the appropriate resin system and curing means . Thus, it is known to use resin systems which can be cured by light radiation, for example as set forth in United States Patent 4581247 which sets out that light cure resin systems can be used in the lining of underground pipelines and passageways.

A main reason for adopting a resin system which can be selectively activated for example by light radiation, is to render the linings when impregnated with resin system capable of long shelf life, so that the linings can be impregnated at will, and utilised at a later date. Such resin systems are referred to in the art as "latent" systems insofar as the installer can control when the initiation and effecting of the cure takes place. This is highly desirable. The known heat curing resin systems do not have the same advantage, because these systems, usually based on polyester resin, are such that the polyester resins after mixing in of the catalyst, will cure ambiently in the course of time and over a relatively short period measured in hours and at most days, even if no heat is applied. In practice therefore when an installer is to insert a polyester resin system impregnated lining, he will mix the base resin and polyester and apply the resin system to the lining as close as possible in time to when he expects to install the lining. If the lining is installed for example overnight, the chances are that the lining will be resin impregnated during the preceding day.

Although the proposals for latent curing systems have been known for some time, as yet there does not appear to have been any general adoption of same by installers as practical problems arise in using the known latent curing resin systems . The search for an effective latent curing installation method nevertheless continues because if an effective latent curing method be provided, then considerable advantages will be attained compared to the heat curing system which is currently adopted.

With the heat curing system, the installer faces the difficulty of providing a boiler on site for heating water, and the boiler may be required to heat a very large volume of water, which is expensive. Secondly, the curing process tends to be slow when hot water is used and therefore the installer must remain on site for a longer period than he might wish. Certainly, when the installation is in a sewer, because the inside of the applied tube is filled with hot curing water, the sewage which normally flows through the sewer has to be diverted or "over-pumped" from a manhole upstream of the lining operation to a manhole downstream of the operation.

The present invention was made having regard to the need to endeavor to create a latent curing method in cured in place pipelining operations, and concerns the use of light radiation for effecting the initiation of cure which continues naturally. It is recognised however that the principle of the invention can be used in general for the curing of resin systems, especially when the resin forms or is embodied in a sheet structure, such as a liner tube.

It has already been suggested in Swiss Patent No 676029 A5 that light radiation can be used for curing flexible resin system impregnated liners when in place on a pipeline or passageway surface, and in that Swiss patent is disclosed that the light source, typically a UV light source, can be located at ground level, and the light can be transmitted through fibre optic means to a dispersing head inside the pipeline or passageway. The dispersing head projects the light onto the uncured resin system liner when it is in position, in order to effect cure of the resin system. The present invention in a preferred form is concerned with this method of application, but provides a method and apparatus which enable considerably increased advantages to be obtained.

When a UV light source is provided in for example a sewer, for the purposes of radiation curing a resin system liner tube, poor results are usually obtained due to the fact that if the sewage is also passing through the applied liner tube (which is desirable as it avoids overpumping) the sewage will cloud the atmosphere through which the light radiation must pass, and this leads to extremely poor results. In fact certain light cure development work which we have previously carried out using UV light sources, was suspended because of the difficulties of obtaining effective results. Such ineffective results comprised that the resin system failed to cure completely throughout the thickness of the lining tube.

With the present invention however, considerable improvement can be achieved, and in accordance with the invention in its most general aspect, a method for light curing of a resin system provides that a resin system comprises a base resin containing particles in which the catalyst is contained so as to be protected in that the catalyst is restrained from reacting with the resin to cause cure of the resin system, and a light source of selected wave length is used to impinge upon such particles with the effect of releasing the catalyst into the base resin which results in the curing of the resin system.

The particles may comprise microporous particles such as clay particles in which the catalyst is contained, and which react with the light from the source so as to open up, or disintegrate to release the catalyst into the resin base.

Such microporous particles may include a coating of a resinous substance to provide that the catalyst is additionally protected, to ensure that there will be no premature leaching out of the catalyst out of the particle pores.

The particles may be microcapsules in which the catalyst is contained.

Preferably, the resin system is contained in or comprises a sheet material, especially a tubular liner, which is applied to a pipeline or passageway.

The liner may be a felt impregnated with the resin system, or a mixture of resin system and fibres.

The preferred form of light source is a laser light source, as this provides the intense, focussed energy which can impinge upon the particles to cause same to react to release the catalyst, and the particular advantage is that the energy is not being wasted in heating up the mass of the entire resin system.

In one embodiment the laser light is transmitted via a fibre optic harness or cable comprising a first end adapted for presentation to or interfacing with a laser light radiation source, and a second end for presentation to the resin system, either directly or via a coupling device which enables the laser light energy which is applied to the resin system, to be caused to sweep over an area to be subjected to the light.

Thus, the second end may comprise a plurality of tails defining outlets, the outlets being arranged over the area to be treated. For example, the outlets may be arranged circumferentially in the manner of a chimney sweep's brush so as to face a tubular liner.

The apparatus for carrying out the method may be such as to enable liquid such as sewage to continue to flow through the pipeline or passageway whilst the said second end is located therein with the tails closely adjacent the lining surface.

In an alternative arrangement, the fibre optic harness may be in two sections, with an optical coupling therebetween, which enables the second section which has the second end, to be rotated so that the output light can be swept circumferentially over for example the inner surface of the liner, whilst the first section remains stationary.

In another arrangement, the second end is arranged to face the everting face of a liner as it is everted into the pipeline or passageway, and the second end moves along the pipeline or passageway along with the everting face. If desired, in this case the second end may be oscillated as it precedes the everting face, to ensure that the light falls most effectively on the everting face.

An advantage which the present invention provides when the light is applied to the liner after it has been positioned on the pipeline or passageway surface is that the liquid which is carried by the pipeline or passageway can continue to flow through the lining tube whilst curing is taking place, and therefore over pumping of the liquid is not required and indeed nor is a boiler for heating water.

The use of laser light to cure the resin technically need not involve fibre optic guides, but rather the laser light can be made to fall directly on the article or material to be cured. When curing a liner tube in this way, the laser light is caused to fall on the liner tube either by being caused to fall on the everting face, or by being passed along the inside of the tube. In the latter case, the light may be caused to pass along the tube axis and then be deflected to travel radially onto the tube inner surface. This deflection may be effected by a mirror or the like, and the mirror or the like may be rotatable to cause the beam to sweep circumferentially over the liner tube, to ensure that all of the tube is treated.

Alternatively, the laser may be arranged to direct its light beam directly in a radial fashion, onto the surface of the tube.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:-

Fig. 1 is a diagrammatic sectional view illustrating a lining installation;

Fig. 2 is an enlarged detailed view showing the application f the light to the liner; and

Figs. 3 and 4 are views similar to Fig. 2 showing two other embodiments of the invention.

Referring firstly to Figs. 1 and 2 of the drawings, shown therein is the application of a flexible liner tube to an underground sewer 10a. The tube illustrated by reference numeral 12a has been applied by any convenient method between manholes 14a and 16a extending from ground level G to the pipeline 10a.

Liner tube 12a comprises for example a resin absorbent layer or layers of felt or the like which is or are thoroughly saturated with the synthetic resin system to be cured. The system includes particles 1 1 a of the type described containing the catalyst, and coated with a resin if desired. To the inside is a membrane or film 13a which forms the means whereby the tube can be inflated, and which in the finished product forms a smooth surface enhancing flow through the cured lining. The application of these linings as is well known is for rehabilitation and/or repair of the sewer 10a.

In the example illustrated, at the upstream manhole 16a, there is a weir 15a which controls the flow of liquid, for example sewage, through the pipeline so that the liquid continues to flow through the pipeline, and at the same time maintains the tube 12a in inflated condition. The sewage level is indicated at 17a, and it continues to flow by passing over the weir 15a, the flow direction being indicated by the arrows .

The drawing illustrates one embodiment of the present invention in apparatus and in method. In the method, an apparatus 18a is pulled through the pipe in the direction of arrow 38a. This apparatus comprises a drive motor 19a having a shaft 20a which carries a mirror 22a and a radial section 24a of a fibre optic cable having another section 26a which is coupled to the apparatus 18a. The mirror is arranged at 45° to the pipeline axis but is rotated about such axis along with the section 24a, so that light transmitted along the section 26a falls on the mirror and is reflected into section 24a and is directed radially at the liner tube 12a.

The rotation of the section 24a causes the light to sweep circumferentially over the tube 12a inner surface and as the apparatus is moved along the pipeline in the direction of the arrows, so the whole inner surface of the liner tube 12a is treated. The ends of the section 24a may be adapted to contact and brush against the liner tube 12a. The said light is provided by a laser source 28a at ground level, and the section of fibre optic cable 26a has a front end 30a which faces the laser 28a to receive light thereform. The section 26a then extends into the pipeline as shown and has a stack portion 32a (preferably wrapped on a drum) to allow it to extend for the whole of the length of the liner as the apparatus 18a moves along the pipeline as curing or initiation of cure proceeds . Fig. 2 shows the apparatus 18a in greater detail, and also shows in dotted lines the section 24a at a diagrammatically opposite position during its rotation.

Operation of the method will be understood from the above, but in summary, what happens is that the laser light is focussed on the liner 12a, and falls thereon. As it does, it activates the particles 1 1 a, causing them to release their catalyst, and the surrounding resin base starts to cure. Once curing has started it continues in known manner without the need for further application of light energy and so the section 24a can be caused to rotate continuously and moved along the liner tube 12a, initiating cure as it goes along. The whole liner tube 12a is cured in this way. The advantage of using a laser is that the light is highly focussed and is of high energy, and only the particles 11 a are activated. There is no waste of energy laser in heating the whole of the resin system mass.

In the arrangement of Fig. 3, instead of splitting the fibre optic cable into two sections, only a single section 26a is used, and the second end is spread to lie radially, as shown at 34a in the form of a chimney sweep's brush so that the light distributed by the brush formation applies the light over the entire periphery of the tube 12a, and rotation of the fibre optic cable is not necessary. In Fig. 4 on the other hand, the liner tube 12a is shown as being applied to the pipeline 10a by being everted thereinto using fluid pressure as indicated by the arrows . Again a single section 26a of fibre optic cable is used, and the second end of the fibre optic cable is located facing the everting face 36a of the tube 12a, so that the laser light to initiate the cure falls on the tube 12a and activates the particles 11 a as described herein causing the subsequent cure of the tube 12a, after it has been applied to the pipeline surface. It may be noted here that the cure time is relatively long compared to the time it take the laser light to react with the particles, and so there is no danger of the liner tube 12a being cured after the initiation but before the tube is applied to the pipeline.

The speed of the apparatus 18a along the lining tube in the direction of arrows will be related to the speed at which the lining material cures, and typically the light will be arranged to fall on each part of the tube for at least 10 seconds, which means that the apparatus can be pulled through the pipeline quite fast, which is a considerable advantage

When the resin cure commences, it will be self continuing because resin curing is exothermic and heat will be generated to continue the cure. It is therefore simply a matter of initiating the cure using the laser energy in which case the apparatus can move along the pipeline or passageway at a fast rate.

Any suitable means such as energy deflectors or reflectors may be provided if necessary for causing the laser energy to deflect outwardly onto the tube 12a. The apparatus shown in Fig. 1 suitably will be winched through the pipeline or passageway by a winch and cable arrangement 40a from manhole 16a, and will typically include a transformer and electrical feed cable. To facilitate its movement, the equipment may be mounted on skids or rollers, and these skids or rollers will also maintain the apparatus reasonably centrally in the pipeline or passageway. Any suitable frequency of operation may be selected. With the progression of the apparatus through the lining tube, the lining will be heated progressively, and the interior of the lining in each case preferably will be held under pressure by the sewage as illustrated or by other pressure, typically air pressure up to 1 bar. If desired, flexible seal skirts may be used when the apparatus is used under water to keep the beam path clear of water, and water can be used for the inflation of the lining.

Suitable mechanical mounting of rotating parts can be effected by conventional arrangements .

The laser light may be any suitable, provided that the wavelengh is selected in relation to the resin system to cause liberation of the catalyst as described herein. Different laser sources may be needed for different resin systems, the most common of which are polyesters, epoxies, and phenolics . The laser may for example comprise a carbon dioxide laser which emits light in the far infra red spectrum (typically 10.6μ) .

Laser light in the infra red wavelength is particularly preferred when the resin system is an epoxy resin, or a composite material including epoxy resin. The laser may be a semiconductor laser or Nd.YAG, both of which have been used in tests. The wavelength of the semiconductor laser was 810 mm and that of the Nd.YAG laser was 1064 mm. Optical powers of the lasers ranged from 40 to 100 watts. In a laboratory test, a sample of epoxy resin composite was placed 10 cm from the output of a semiconductor laser, and the laser was switched on for a measured period of time and the temperature of the surface of the composite was measured at regular intervals. At an optical power of 40 watts, and a beam size of 3 x 5 cm, surface temperatures as high as 360°C were achieved within 20 seconds.

Similar temperatures were achieved within a much smaller time scale with the higher power laser system.

It was found that immediately after laser irradiation, the epoxy material became soft, but within an hour after heating, all the samples were substantially cured. Experiments were also carried out with a thin film of water over the samples. The water boiled during the tests, showing that the water absorbed some of the energy, but the samples cured again within a short time of removing the laser energy. Further experiments involved covering the samples with a glass sheet, which had no effect on the curing of the resin.

It was deduced that the water helps in the curing process, and protects the resin from excess damage and discoloration.

As seen herein, the invention can be applied where the laser is designed to travel along a pipe lined with a composite liner, as well as where the laser is used with optical fibres as mentioned above.

Where the laser is designed to be used in the pipe, with or without optical fibre transmission, a semiconductor laser is more likely, but they do have the disadvantage that they require significant electrical power, and it is not always possible or practical to take high electrical power devices into pipes where there may be a wet environment. Optical fibres on the other hand can be used to transmit significant optical powers over large distances e.g. more than a kilometer. For example, a fibre with a 960 μ core can transmit up to 450 watts continuous and 7M watts pulsed. Optical fibres have a peak transmission in the near infra red and they are therefore ideal for transmitting the optical energy from a semiconductor or Nd.YAG laser.

When a scanning system is used, it may be a galvanometric or rotating type, the effect of which is to paint the composite liner with a beam of energy.

As indicated, the main application for this invention will be for liner tubes which are cured in place (known as CIP tubes) , but it can be applied to thermoplastic tubes and sheet materials in general, for example to produce boat hulls, and bathroom articles such as shower trays and baths

If it is desired to monitor the temperature to which the linings or other articles are heated, infra red cameras could be used. The energy applied by the apparatus may be controlled by using pulsed mode operation.

As indicated herein, the method of applying the laser energy can be effected in various forms. In each case where tubes are being treated, it is desirable that the laser energy should be directed radially onto the liner tube, and this can be achieved in various ways.

The method can be applied where only a section of a sheet material is to be cured. By way of non limiting example, the following is given.

Liner tube details.

Resin base Polyester

Catlayst Benzyol Peroxide

Carrier particles for Catalyst Bentonite clay

Reinforcement Acetylated Natural Jute fibres.

Proportions.

Resin Matrix

Parts by weight of Catalyst to Clay Particles . 2 to 8

Parts by weight of clay including catalyst to Base resin 10 to 100

Parts by weight of Resin System to Fibres 100 to 100.

Such a material was extruded in sheet form and was subjected to laser light at a frequency as indicated herein for 10 seconds, and the material heated rapidly, and cured inside half an hour, showing that the curing can be initiated and effected in a rapid manner. Comparative samples which were of the same composition were not subjected to laser light and failed to show any signs of curing over a long period.

Claims

1. A method for light curing of a resin system wherein the resin system comprises a base resin containing particles in which the catalyst is contained so as to be protected in that the catalyst normally is restrained from reacting with the resin to cause cure of the resin system, and a light source of selected wave length is used to impinge upon such particles with the effect overcoming the protection and releasing the catalyst into the base resin which results in the curing of the resin system.

2. A method according to claim 1 , wherein the particles may comprise microporous particles in which the catalyst is contained, and which react with the light from the source so as to open up, or disintegrate to release the catalyst into the resin base.

3. A method according to claim 2, wherein the particles are clay particles.

4. A method according to claim 2 or 3, wherein the microporous particles include a coating of a resinous substance to provide that the catalyst is additionally protected, to ensure that there will be no premature leaching out of the catalyst from the particle pores.

5. A method according to claim 1 , wherein the particles are microcapsules in which the catalyst is contained.

6. A method according to any preceding claim, wherein the resin system is contained in or comprises a sheet material, especially a tubular liner, which is applied to a pipeline or passageway.

7. A method according to claim 6, wherein the liner is a felt impregnated with the resin system.

8. A method according to claim 6, wherein the liner is a mixture of resin system and fibres.

9. A method according to any preceding claim, wherein the light source is a laser source.

10. A method according to claim 9, wherein the laser light is transmitted via a fibre optic harness or cable comprising a first end adapted for presentation to or interfacing with a laser light radiation source, and a second end for presentation to the resin system, either directly or via a coupling device which enables the laser light energy which is applied to the resin system, to be caused to sweep over an area to be subjected to the light.

1 1. A method according to claim 10, wherein the second end comprises a plurality of tails defining outlets, the outlets being arranged over the area to be treated.

12. A method according to claim 1 1 , wherein the outlets are arranged in circular array in the manner of a chimney sweep's brush.

13. A method according to any preceding claim, as applied to the lining of a pipeline or passageway, wherein the apparatus for carrying out the method is such as to enable liquid such as sewage to continue to flow through the pipeline or passageway.