TEXT OF THE DESCRIPTION

The present invention relates to a non-destructive in situ rehabilitation process of damaged and/or worn pipes (relining rehabilitation pipe) with tubular sleeves or sheaths (liner), impregnated with photoactivable hardening resins (carrier) by means of UV actinic light irradiation with emission comprised or mainly comprised in the range 360-420 nm, the sleeves used in said process and their use.

The sector of "relining" and of the so-called "CIPP" (Cured in place Pipe), that is the non-destructive rehabilitation/repair, in situ, of damaged pipes (tubes, downspouts, conduits, ducts, etc.) allows to carry out rehabilitation/repair interventions of worn and/or damaged pipes without having to resort to excavation and demolition.

In the current state of the art, systems are known which provide for the insertion inside the pipe of interest, of a sheath, also called sleeve, to be inverted or not, generally composed of a thermoplastic and flexible polymeric support (for instance polyolefin (polyethylene, polypropylene, etc.), polyurethane, polyester, PVC) reinforced with fabric, non-woven fabric or polyester felt or glass blend, impregnated with various types of hardening compositions (for instance, thermosetting orthophthalic polyester type). Once inserted, the sheath is mechanically made to adhere to the internal surfaces of the pipeline by the action of the pressure of the air blown by a special machine.

The air pressure is maintained until the impregnated sleeve, due to the resin hardening, acquires sufficient rigidity to remain positioned and consolidated on site and to make it possible to restart the pipeline itself.

There are different systems for obtaining the hardening of the resin impregnation of the sleeve which can be divided into two major subdivisions:

• Two-component ambient curing resins

• Two-component hot curing resins

The two-component ambient curing resins harden at room temperature in a certain time after the mixing between the two components (resin and ambient curing hardener) has taken place.

Such ambient curing systems have the main disadvantage that when the resin is activated at room temperature there is a limited working time (pot-life) to carry out the operations of impregnation of the sleeves, the insertion into the tube, the extroflexion and the swelling, then it is necessary to wait several hours before the impregnated sheath reaches sufficient rigidity (the greater the pot-life time, the greater the waiting time in hours before being able to put the restored pipeline into operation).

The two-component hot curing resins harden only when an activation temperature is reached or have a very slow hardening at room temperature and are then cross-linked with the application of a heat source (Hot curing resins).

The heat sources used for crosslinking hot curing resins are various and comprise hot air generators, water mass heating or steam generators.

However, these hot curing systems have innumerable disadvantages linked to the complexity of the equipment to be brought on site, to the energy cost necessary for heating large volumes of water which must be kept at temperature for a few hours if the resin is activated with hot water.

To overcome these problems, a type of hardening compositions used in the sector has been created, which comprises hardening compositions that can be photoactivated by irradiation with actinic light wherein stiffening occurs due to the effect of light on resins formulated to react to certain light frequencies.

The relining carried out with the photoactivable resins allows to obtain at the same time the necessary ease in terms of time to carry out the laying of the sleeves and at the same time make the stiffening and the return to work of the healed pipeline in a very short time from a few seconds to a few hours.

Within the category of photo-activated relining resins, two major subcategories can be distinguished:

• resins curable with broad spectrum UV lamps;

• UV resins for photoactivable relining through the use of UV LED sources.

However, resins that can be cured with broad spectrum UV lamps have the problem of generating a considerable amount of heat during irradiation, which is a problem due to the excessive temperature reached in the tubes by this hardening technique.

The photoactivable UV resins for relining allow, due to the narrowing of the amplitude of the frequencies emitted by the LEDs, significant energy savings. It is possible, in fact, to formulate the resins with photoinitiators that absorb specifically in the emission range of the LEDs, concentrating the light energy only in the absorbance field of the resin to be hardened, and at the same time have very low infrared emission of the LEDs from 360 to 420 nm with drastic decrease of temperatures inside the tube.

In general, it can be said that the irradiation LED system is more efficient because it does not emit and consume energy in the frequencies that would be useless and/or harmful for the hardening of that specific formulation of photoactivable resin and allows to contain temperatures during stiffening of the sleeve/resin.

In fact, frequencies below 360 nm start becoming dangerous for the health of operators and frequencies above 420 are very sensitive to visible light and make resin processing operations more complex during impregnation and in situ positioning operations.

Therefore, by using this light emission system combined with formulations of resins that have the absorbance of photoinitiators centered on these ranges 360 nm-420 nm, an efficient relining system is obtained as an advantage, with no danger for the operator, which does not produce infrared irradiation, low energy consumption and easy cooling of the diodes and at the same time the resin formulations used do not require darkness because they are not very sensitive to ambient light which would cause premature crosslinking.

There are several manufacturers on the market that offer specific sleeves to be impregnated for relining, but these sheaths have always been produced and used above all for ambient curing or hot curing systems, while for UV hardening systems the limit is represented by the hindrance of the same sleeve to the actinic light penetration.

In fact, a different behavior was noted in the experiments of light penetration into the impregnated felt. In particular, it was highlighted that, limited to the range of frequencies indicated, some felts on the market prevented the penetration of light more deeply, while other felts allowed a faster light penetration.

Where sleeves with a surface polymer liner that is too thick or opaque to light have been used, the final hardening results have been poor or insufficient.

Currently, a sleeve coated with a polymeric film which is fairly transparent to light is therefore chosen and in this way the penetration characteristics of the light radiation are improved.

Sheaths formed from glass fibers have also been proposed as suitable for UV curing systems, but such systems have a higher cost and often a limitation in the expansion flexibility of the sheath itself.

We have now surprisingly found that by eliminating or significantly reducing the presence of optical brighteners (also called optical whiteners) (OTB) (optical brightness), present inside the fibers that make up the felt, the depth of penetration and the efficiency of the system in terms of speed is no longer blocked or limited.

In fact, we have found that when a yarn containing optical brighteners is used to make relining sleeves that will be used with UV light-activated resins and operating in the frequency range from 360-420 nm, a significant problem is created that limits the effectiveness of the system for the characteristics of light reflection of the optical whitener present, in a way directly proportional to the quantity present in the yarn.

The present invention allows to solve the critical issues mentioned above by using a sleeve with the best light transmission capacity in the frequencies useful for hardening and allowing a saving in terms of energy required, with the same source and formulation of the photoinitiators internal to the resin, as well as the possibility of increasing the overall hardening speed and/or decreasing the radiated energy required to harden the resin.

For the purposes of the present invention in the description of the application:

• with the term "actinic light" or "actinic radiation" we mean an electromagnetic radiation having a wavelength between 100 and 600 nm;

• with "broad spectrum UV lamp" we mean from 200 to 450 nm;

• with "UV LED" we mean a light emitting diode in the wavelengths between 360 and 420 nm (possible with a mixture of different emission diodes on different frequencies);

• with "photo-activatable with/by actinic light" we mean a composition which, as a result of irradiation with an actinic light source, crosslinks thus becoming a "photoreticulated polymer composition".

Therefore, the aforementioned "photo-activatable with/by actinic light" compositions are also referred to as "photo-crosslinking" compositions.

• with "photoinitiator" we mean a chemical compound which, as a result of irradiation with actinic light, allows the activation and propagation of polymerization reactions by generating reactive species or generators of crosslinkers (Lewis acids, superbases etc.) with generally an absorbance spectrum that determines the efficiency limits during exposure to specific frequency ranges.

The process, object of the present invention, of in situ rehabilitation of damaged and/or worn pipes (relining rehabilitation pipe) with tubular sleeves or sheaths, both in extroversion and in direct application, impregnated with photo-activable hardening resins, by means of UV actinic light irradiation with emission comprised or mainly comprised in the range 360-420 nm, so that said actinic light generates outside said range 360-420 nm not more than 30%, preferably at most 15%, of its entire spectrum, is characterized in that said sleeves do not contain molecules that generate fluorescence with absorbance in the range 360-420 nm or that contain said molecules in such a quantity as not more than 30%, preferably not more than 10%, of the radiated energy is absorbed by said molecules and such that not more than 10% of the radiated energy is re-emitted outside said range.

The UV actinic light irradiation can have emission preferably comprised or mainly comprised in the range 380-410 nm, more preferably comprised in the range 385-405 nm, so that said actinic light generates respectively outside said 380-410 nm or from said range 385-405 nm, for a maximum of 10% of its entire spectrum.

The sources for UV actinic light irradiation are preferably chosen between those with UV LEDs and laser ones.

Among the substances that contain the molecules that generate fluorescence with absorbance we mention in particular the optical brightening agents (OTB) (also called optical whiteners) (optical brightness).

The sleeves contain a thermoplastic and flexible polymeric support, with low UV shielding, reinforced with fabric, non-woven fabric or felt containing variously oriented textile fibers and/or containing mainly synthetic fibers or containing mixed configurations of said textile fibers and/or said fibers of a mainly synthetic nature together with glass and/or carbon fibers.

The a posteriori explanation of the object of the invention could be the following.

The optical brighteners commonly used in plastics and synthetic yarns are molecules capable of absorbing light in a certain frequency range and reemitting it in a different frequency range in the visible range due to the effect of fluorescence.

The energy absorbed in these regions is re-emitted (swiffing) mostly from 420 nm upwards towards the visible light regions, resulting in useless energy for the curing of those photoreactive UV systems that operate mainly in a frequency range from 360 to 420 nm.

Absorption therefore represents an obstacle to the penetration of light and limits the depth reached by the frequencies in the range between 360 and 420 nm which are the most commonly used frequencies for the hardening of light-activated resins for relining.

In fact, when struck by certain wavelengths, specifically 360-420 nm, the molecules of the OTB are excited by absorbing UV radiation, the electrons lose part of their energy and re-emit a radiation, absorbed in the blue-violet field, in the visible light field that exceeds the range 360-420 nm: this phenomenon generates fluorescence.

So specifically, if the resinous system has an efficient absorption due to its efficient cross-linking in the 360-420 nm band, it will be obtained that the frequencies absorbed by the optical whitener from 360 to 420 will be shifted totally or partially towards higher frequencies in the visible range becoming useless for the purpose of crosslinking the system.

The part of light re-emitted in the visible range, when using a resin/emitter system comprised in the range 360-420 nm, is far from the absorbance peaks of the photoinitiators and is essentially wasted, no longer able to contribute to the crosslinking of the system: only the residual part that is not absorbed by the OTB and is able to pass will harden the resin in depth, but this will lead to a longer duration in seconds of the process, therefore to a lower speed of the relining process and an energy waste proportional to the emission efficiency of the specific OTB optical bleach and to its quantity contained in the yarn making up the felt.

Manufacturers of relining sleeves do not distinguish the quantity of optical brighteners present in the fiber making up the felt itself, which felt is composed of variously oriented textile fibers, mainly synthetic fibers obtained from yarns of polyester-like materials reinforced or not with fiber from various materials (glass, carbon, etc).

Unfortunately, the yarn that makes up the felt is not produced specifically to build sleeves for relining, but is part of the textile supply chain and when this is light in color, in some cases, it is improved by the initial manufacturer by adding optical brighteners which are used to obtain an effect of greater aesthetic value, but this effect in the application of relining is purely useless and as we have surprisingly found also harmful at least when using LED light sources in the range 360-420 nm.

Therefore, a felt made up using a yarn that contains any percentage of optical brightener will reflect by changing wavelength to a certain amount of absorbed light by re-emitting it in higher frequencies closer to visible light where they will no longer be able to harden the resin.

This harmful effect instead is absent or negligible if the felts themselves are subjected to the action of broad spectrum mercury UV lamps typical of broad spectrum lamp hardening systems.

Without wishing to bind to a specific theory, if the emission source is a broad spectrum lamp, it will generate a much larger range: generally a mercury lamp covers an emission range between 220 and 450 nm.

All frequencies in the range of UV C and UV B will not be intercepted by the OTB optical whitener, while those around 300 nm that will be intercepted will still be re-emitted with frequencies close to 400 nm still useful for hardening the resin system.

All this can represent the explanation why the presence or absence of optical brighteners inside the felts that are used for relining with UV hardening by means of visible lamps or LEDs, with frequencies higher than 420-450 nm, does not represent an appreciable obstacle to the efficiency of the relining system, while it represents it in the specific case of relining systems that use an emission system that produces a specific frequency range 360-420 nm for the hardening of the resin.

By way of non-exhaustive and non-binding example we can list some of the molecules that generate fluorescence with absorbance, used as optical brighteners:

• 2,5-thiophenediylbis (5-tert-butyl-l,3-benzoxazole);

• 4.4'-bis (benzoxazol-2-yl) stilbene;

• 4,4'-bis (2-methoxystyryl)-l,l'-biphenyl;

• 2.2 '-(1,4-naphthalenediyl) bisbenzoxazole;

• 4,4'-bis (2-sulfostyryl) biphenyl;

• tetrasodium 4,4'-bis[{4-[bis(2-hydroxyethyl)amino]-6-(4-sulphonato- anilino)-l,3,5-triazin-2-yl]amino} stilbene-2,2 '-disulphonate]

Looking at the absorption and re-emission curves in fluorescence of the OTBs listed above, and in particular of the 2,5-thiophenediylbis (5-tert-butyl- 1,3-benzoxazole) it can in fact be noted that the absorption of the OTB molecule takes place in the regions of the most useful frequencies for the hardening of photoactivable resins in use for relining and more specifically in UV LED hardening.

By looking for fluorescence, it will be possible to select the supply of the pre-made synthetic yarn/felt absolutely free of optical bleaches that does not emit any fluorescence when subjected to the light frequencies range 360-420 nm, or it is possible to find a synthetic fabric/felt already preconstituted that contains little optical whitener and/or that exhibits a very limited fluorescence and/orthat eventually re-emits especially in the frequencies still included in the range 360-420 nm useful for the hardening of the photoactive resinous system, but possibly not higher as it is no longer useful for crosslinking the photocrosslinking resinous system.

A second object of the present invention is the sleeve or sheath for damaged pipes rehabilitation, which contains a thermoplastic and flexible polymeric support, with low UV shielding, reinforced with fabric, non-woven fabric or felt containing variously oriented textile fibers and/or containing fibers of a mainly synthetic nature or containing mixed configurations of said textile fibers and/or of said fibers of a mainly synthetic nature together with glass and/or carbon fibers, which sleeve is suitable for being impregnated with a photo-hardening resin that can be photoactivated by irradiation with actinic UV light, and is characterized by the fact that said fabric, non-woven fabric or felt does not contain molecules that generate fluorescence with absorbance in the 360-420 nm range or contains said molecules in such quantities that not more than 30%, preferably not more than 10% of the radiated energy is absorbed by said molecules and such that not more than 10% of the radiated energy is reemitted outside said range.

Another object of the present invention is the tubular sleeve or sheath specified above impregnated with hardening resins that can be photoactivated by UV actinic light irradiation with emission comprised or mainly comprised in the 360-420 nm range.

A further object of the present invention is the process for producing the sleeve forthe non-destructive rehabilitation of a pipeline, suitable for being impregnated with a hardening resin that can be photoactivated by UV actinic light irradiation with an emission comprised or mainly comprised in the range between 360 nm and 420 nm, which comprises making available a substrate composed of a flexible thermoplastic or thermosetting polymeric film that is coated, laminated or glued on a felt containing variously oriented textile fibers and/or containing fibers of a mainly synthetic nature or containing mixed configurations of said textile fibers and/or of said fibers of a mainly synthetic nature together with glass and/or carbon fibers, and is characterized in that said felt does not contain molecules which generate fluorescence with absorbance in the 360-420 nm range or which contain said molecules in such quantities as not more than 30% of the energy already irradiated is absorbed by said molecules and such that not more than 10% of the radiated energy is re-emitted outside said field.

A further object of the present invention is the use of sleeves as described above in the in situ non-destructive rehabilitation procedures of damaged and/or worn pipes (relining rehabilitation pipe), both in extroversion and in direct application.

According to another aspect, the present invention refers to a kit consisting of: a tubular sleeve or sheath for the rehabilitation of damaged pipes, which sleeve or sheath contains a thermoplastic and flexible polymeric support, with low UV shielding, reinforced with fabric, non-woven fabric or felt containing variously oriented textile fibers and/or containing fibers of a mainly synthetic nature or containing mixed configurations of said textile fibers and/or of said fibers of a mainly synthetic nature together with glass and/or carbon fibers and characterized in that said fabric, non-woven fabric or felt does not contain molecules that generate fluorescence with absorbance in the range 360-420 nm or contains said molecules in an amount such that not more than 30% of the radiated energy is absorbed by said molecules and such that not more than 10% of the radiated energy is re-emitted outside said range; a resin for impregnating the material of said sleeve or sheath, which resin is a hardening resin, photoactivable by UV actinic light irradiation with emission comprised or mainly comprised in the 360-420 nm range; an emission source of said UV actinic light with emission comprised or mainly comprised in the range 360-420 nm.

In said Kit, the resin can be provided as a separate packaged element with respect to the sleeve and the actinic light source.

Alternatively, in said Kit, the resin can be in a form already previously applied to the material of the sleeve or sheath or to part of said material so as to impregnate it at least partially.