FIELD OF THE INVENTION

The present invention relates to a method for cured-in-place pipe rehabilitation of a sewer line or pipe line, a liner for cured-in-pipe rehabilitation of a sewer line or pipe line used in this method, and use of a self-curing resin, in particular a frontal radical induced cationic polymerizable self-curing (FRICP) resin, for cured-in- pipe rehabilitation of a sewer line or pipe line according to the above method.

BACKGROUND OF THE INVENTION, PRIOR ART

Cured-in-place pipe rehabilitation (CIPP) refers to a trenchless method used to rehabilitate sewer-and pipe lines. This method was first described in US 4009063 by Eric Wood. It has been extensively used since many years. The CIPP technology allows two different operating procedures, these being the “Inversioninstallation method” and the “Pull-installation method”. In the “Inversion-installation method” a non-woven felt liner is first impregnated with a thermoset resin. Then the tubular liner is inverted by air or water pressure and pressed against the inner wall of the host pipe. In the “Pull-installation method “the resin impregnated liner is pulled into the pipe with a cable and then air or water is used to expand the liner to fit against the interior of the pipe.

A wide variety of thermoset resins are commercially available for CIPP, the most common being those consisting of UP (polyester and unsaturated polyester), VE (vinylester) and epoxy. Polyester and vinyl ester resin systems are normally used for the rehabilitation of sewers and for special waste applications while epoxy systems are used in pressure pipes and potable water pipes. The effectiveness of the CIPP method is in part determined by the mechanical performance of the composite comprised by thermoset resin system and the synthetic-fiber liner.

Epoxy thermosets are cured inside the host-and-damaged pipe by introducing hot water or steam. The impregnated liner is expanded, facing the inner walls of the damaged host pipe and cured at high temperatures. It is highly important that the polymerization temperature is kept constant and around 80 °C, to prevent surpassing the glass transition temperature (T _g ) of PVC (polyvinylchloride) pipe and ensuring the optimal mechanical performance of the epoxy thermoset. Low curing temperatures usually lead to inefficient curing and to an early-stage cessation in the polymerization reaction, leading to a drop in the glass transition temperature of the crosslinked thermoset and hence affecting its mechanical performance (A. C. Loos 1983, C. Wise et al. 1997).

Alternative to steam and hot water curing, CIPP technology allows the use of UV- curable resins for the rehabilitation of pipe and sewer systems. Here, a mobile robot supplemented with high-voltage (i.e. 100 — 2000 W) UV-lamps and/or UV-LED lamps is introduced inside the pipe containing an impregnated-and-inverted liner. Curing of the thermoset is concomitantly achieved as the UV/LED light source is moved along the pipe construct with a curing speed of 0.1 — 1 meters of liner per minute.

On the one hand, UV-curing resins shows many advantages over conventional condensation resins cured with steam and/or hot water. These mainly consist of:

1 . Time-saving technique: No need for resin premixing and faster curing-and-cool down times.

2. Environmentally friendly and lower energy consuming: No need to use benzinedependent steam generators, thus reducing the emissions of carbon monoxide. On the other hand, commercially available UV-curable resins for CIPP rehabilitation are one step beneath conventional epoxy amine/anhydride resin systems in terms of mechanical performance and adhesion to PVC host pipes. Most importantly, UV-light penetration plays a key role in determining the maximum allowable thickness of the composite, requiring the use of high-intensity LIV/LED lamps and/or high amounts of thermal initiators to achieve an appropriate thickness for CIPP rehabilitations, thus jeopardizing the shelf-life of the resin specimen highest mechanical, adhesion and chemical-resistance properties.

Appropriate thickness of CIPP rehabilitation requires high intensity LIV/LED lamps or high amounts of thermal initiators to achieve complete polymerization of the resin. In case of lateral pipe branched off the main pipe the lamps are difficult to apply to the lateral pipe.

SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to provide a method for cured-in- place pipe rehabilitation of a sewer line or pipe line that eases and improves curing of the liner.

This object is solved by a method for cured-in- place pipe rehabilitation of a sewer line or pipe line according to claim 1 . The method according to the invention comprises the following steps: a) a liner is impregnated with a resin b) the liner is applied to the inside of the sewer pipe or pipe line wherein c) the resin is a self-curing resin which cures following frontal polymerization d) curing of the self-curing resin is initiated by an energy source.

According to the invention, a self-curing epoxy resin is used to impregnate the liner. Curing of the self-curing resin is initiated by an energy source which initiates curing following frontal polymerization. This particularly involves the following advantages:

First, no continuous exposure of the resin impregnated liner to an energy source is required. Polymerization propagates independently of external stimulus once triggered. A relatively short application of energy is sufficient to initiate the self-curing process (i.e. frontal polymerization) Second, curing of thick liners (> 6mm) without high-intensity lamps is possible. The self-curing process of the resin propagates into the depth of the liner impregnated with the self-curing resin.

Third, the self-curing resin involves a multidirectional propagation of the curing front to lateral connections. This implies that in case of a pipe joint between a main pipe and a lateral pipe the energy source must be only positioned in the main pipe to reach curing of the lateral liner applied to the lateral pipe.

In one preferred embodiment, the self-curing resin is a frontal radical induced cationic polymerizable (FRICP) resin. Such self-curing resins are basically known in the art and particularly described in EP 3 344 679 B1 , the disclosure of which is herewith incorporated by reference.

Preferably, the self- curing resin may comprise epoxy monomers and /or prepolymers, in particular cycloaliphatic and/or aromatic epoxies such as 3,4- epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylate (ECC) and/or bisphenol A-diglycidyl ether (BADGE), respectively.

Preferably, the self-curing resin comprises cationically polymerizable polymers having at least one cationic polymerization initiator and at least one radical thermal initiator.

The cationic photo initiator may consist of onium salts, preferably diaryliodonium salts. Upon exposure to UV/LED light, carbocations will be formed amidst to light- induced cleavage. In a later stage, these reactive carbocations and/or subsequently abstracted hydrogen protons (H ⁺ ) will trigger the opening of oxirane rings thus releasing heat (i.e. exothermic reaction). The heat released from the exothermic opening of oxirane rings is used by RTI molecules leading to the formation of carbon-centered radicals that are later oxidized to carbocations in the presence of suitable cationic photoinitiators. These carbocations will induce the further opening of oxirane rings in epoxy monomers/prepolymers thus leading to a further release in energy and creating a self-sustaining polymerization front (Malik et al. 2020). In certain embodiments, the radical thermal initiator is benzopinacol and its deri- vates, azo-derivatives like AIBN or AMBN, and/or peroxide derivates like BPO and di-tert-butyl peroxide.

Preferably, the energy source comprises a UV/LED- curing device and/ or a heat curing device. Due to the self-curing properties of the resin, a relatively small energy source can be used.

The UV I LED curing device is preferably operating in the range of 360 to 500 nm.

The energy source may be moved along the pipe with constant speed or step-by- step to initiate polymerization of the self-curing resin.

In certain embodiments, the liner is applied by an inversion method or a pull-in installation method to the inside of the pipe.

Preferably, a packer, in particular a short packer, is used to apply the liner. Such packers having an inflatable bladder to press the line against the pipe wall are basically known in the art.

In a preferred embodiment, the liner is configured as a non-woven PES felt liner. Examples of non-woven PES felt-liners are described in US patent US9791088B2 and German utility model DE202012104166U1 . The thickness of the non-woven PES-felt material is generally found in the range of 3 — 6 mm for pipe diameters in the range of 70 — 250 mm.

The PES felt liner may be supplemented with a reinforcement yam, for example fiber glass. The felt liner may be as well supplemented with reinforcement yams, for example glass fiber.

Preferably, a coating of the non-woven PES-felt liners is provided usually comprised by an elastic thermoplastic that shows exceptional hydrolysis resistance properties and high temperature resistance. For UV/LED-curing applications, a coating consisting of polyurethane/polyester or polyurethane/polyether thermoplastic is preferred, ascribed to the low light attenuation coefficient they exhibit. In another embodiment, the liner is configured as a fiberglass mat. Examples of fiberglass mats used for this application include but are not limited to ECR-Glass fiber mats. The fiberglass mats are impregnated with self-curing epoxy resin and wrapped around the inflatable bladder of the packer. Examples of commercially available ECR-Glass fiber mats include but are not limited to those supplied by Saint-Gobain and Owens Coming.

According to a further aspect according to claim 15, the invention relates to a liner, in particular a non-woven PES felt liner or a fiberglass mat, for cured-in- pipe rehabilitation of a sewer line or pipe-line, used in the method according to one of the preceding claims, characterized in that the liner is impregnated with a self-curing resin, in particular a frontal radical induced cationic polymerizable (FRICP) resin.

According to a further aspect according to claim 16., the invention relates to the use of a self-curing resin, in particular a frontal radical induced cationic polymerizable (FRICP) resin, for cured-in- pipe rehabilitation of a sewer line or pipe line according to one of the preceding claims.

Other features and advantages of the present invention will become apparent from the following more detailed description of a preferred embodiment, which describes, by way of example, the principles of the invention. However, this embodiment should not be viewed as limiting the scope of the invention. The claims will serve to define the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 schematically shows a pipe line with a manhole for inserting a liner by inversion;

Fig. 2 schematically shows a pipe in which a liner is inserted f by means of a short packer comprising a light source; Fig 3 schematically shows a pipe line system having a main pipe and a lateral pipe in which a T-shaped liner is inserted by means of a packer comprising a light source.

DETAILED DESCRIPTION OF THE DRAWINGS

In the figures, the same reference numbers denote the same or similar components, unless stated to the contrary.

Fig. 1 schematically shows a sewer pipe line 10 comprising a man hole 11 . A liner 16 is applied to the inside of the main pipe 12 by means of an inversion-installation method basically known in the art. An inversion drum 13 is provided, which is connected with a pressure hose14. A tubular flange 15 is connected to the distal end of the pressure hose 14.The inversion drum 13 takes up a tubular liner 16, which is impregnated with a self-curing resin.

The self-curing resin is a frontal radical induced cationic polymerizable (FRICP) resin. Such self-curing resins are basically known in the art and particularly described in EP 3 344679 B1 , the disclosure of which is herewith incorporated by reference.

The liner 16 is guided through the pressure hose 14. The free end of the liner 16 is put over the outer circumference of the tubular flange 15 and fixed by bracket at the flange 15. If air pressure is applied to the liner through the pressure hose 14, the liner 16 is inverted into the pipe 12 and pressed to the inner wall of the pipe 12.

Afterward, a UV light source 17 is pushed by means of a flexible rod (not shown) into the liner 16. The light source 17 initiates self- curing of the resin which cures following frontal polymerization.

No continuous exposure of the resin impregnated liner 16 to the light source 17 is required. Polymerization propagates independently of external stimulus once triggered. A relatively short application of energy is sufficient to initiate the self-curing process (i.e. frontal polymerization). The self-curing process of the resin propagates into the depth of the liner impregnated with the self-curing resin.

Fig. 2 shows a further embodiment in which a packer 18 is used to apply a liner 16 to the inner wall of the pipe 12 being part of a pipe system 10. The packer 18 is inserted into the pipe 12 through a man hole 11 .

The packer 18 comprises a cylindrical main body 20. The main body 20 takes up a UV light source 17. The end portions of the packer 18 are provided with a clamping sleeve 26a, 26b for fixing a tubular bladder 22. The bladder 22 is made of a flexible light transparent material. An air pressure hose 28 is connected with the bladder 22.

To move the packer 18 within the pipe 12 wheels 19a, 19b are provided.

Commercially available UV/LED-curing packers include but are not limited to QuickPatch LED supplied by Sewertronics, UV-patch device supplied by IBG Hydrotech GmbH and QuickSeal curing device supplied by Cosmic Engineering GmbH among others.

A liner 16 is applied by means of the packer 18 to the inner wall of the pipe 12. The liner is impregnated with a self-curing resin as described in connection with Fig.1 . Curing of the self-curing resin is initiated by means of the light source 17. The light source 17 initiates self- curing of the resin which cures following frontal polymerization.

No continuous exposure of the resin impregnated liner 16 to the light source 17 is required. Polymerization propagates independently of external stimulus once triggered. A relatively short application of energy is sufficient to initiate the self-curing process (i.e. frontal polymerization).

The self-curing process of the resin propagates into the depth of the liner impregnated with the self-curing resin. Fig. 3 schematically shows a sewer pipe line 10 comprising a main pipe 12 and a lateral pipe 23 which are connected at a joint portion 24. The lateral pipe 23 may be connected with the sewer pipe system of a house.

A packer 18 (LIV/LED packer) is inserted in the main pipe 12 in order to apply a liner 34 for rehabilitation of a damaged portion the sewer pipe line 10 located at the joint portion 24. The liner 34 comprises a main liner 34a and a lateral liner 34b. The main liner 34a is positioned in the main line 12 and the lateral liner 34b in the lateral pipe 23. The liner 34 has a T-shape.

The packer 18 comprises a basic body 20 having a mainly tubular shape. The basic body 20 is surrounded by a bladder 22 made of a flexible transparent material. The bladder 22 comprises a main bladder 22a and a lateral bladder 22b. The end portions of the bladder 22 are fixed to the basic body 20 of the packer 18 by means of clamping sleeves 26a, 26b. For instance, a LIV/LED Hat packer as supplied by IBG Hydrotech can be used.

An opening 30 with a circular cross-section is provided in the basic body 20. The bladder 22 is connected with an air pressure hose 28 for applying air pressure to the bladder 22. Wheels 19a, 19b are provided to move the packer 18 within the sewer pipe line 10.

The liner 34 is configured as a non-woven PES felt liner which may be reinforced by a yam, for example fiber glass. Alternatively, the liner can be configured as fiber glass mat.

The liner 34 is impregnated with a self-curing resin which comprises cationically polymerizable polymers having a cationic polymerization initiator and a radical thermal initiator. Such a frontal radical induced cationic polymerizable (FRICP) resin is described in EP 3 344 679 B1 the disclosure of which is incorporated by reference.

In the following the cured-in-place pipe rehabilitation method will be described.

First, the liner 34 is impregnated with the self-curing resin outside the sewer pipe line 10. Afterwards, the liner is arranged at the outer circumference of the bladder 22 of the packer 18. In this phase, the lateral bladder 22b and the lateral liner are inserted within the basic body 20 of the packer 18.

The packer 18 is then inserted into the main line 12 and moved to the joint portion 16, where the liner 34 shall be applied to the damaged portion. After finding the position of the lateral pipe 23, air pressure is applied through the air pressure hose 28 into the bladder 22. The lateral bladder 22b is inverted through the opening 30 of the packer 18 into the lateral pipe 23 as shown in Fig. 3. In this position of the bladder 22 the main liner 34a is pressed against the inner wall of the main pipe 12. The lateral liner 22b and the lateral liner 34 b are pressed against the inner wall of the lateral line 23.

In the next step, the bladder 22 is deflated. The main bladder 22a and the lateral bladder 22b are moved from the liner 34. Then, the packer 18 is moved from the junction 16.

Curing of the resin takes place after the inversion of impregnated non-woven PES- felt liner in the target-and-damaged pipe.

The LIV/LED energy source 17 initiates curing of the self-curing resin of the liner 34. Due to the self-curing properties of the resin no continuous exposure of the resin is required. A relatively short application of light initiates the polymerization of the self-curing resin.

After initiating the curing process, the polymerization front migrates through the liner 34 and cures the same. The self-curing process of the resin propagates into the depth of the liner 34.

Since the self-curing resin involves a multi-directional propagation of the curing front, the lateral liner 34b arranged within the lateral pipe 23 is also cured. Usually, no introduction of the UV/LED curing device 36 into the lateral pipe 23 is necessary. A curing front can be triggered in the main pipe 12 and the curing front will proceed through the lateral pipe 23 without any external additional stimulus.

After initiating the self-curing process, the packer 18 is moved from the sewer pipe system 10 or moved to another position within the sewer pipe system 10. The curing of the resin may be triggered by exposure to LIV/LED light at the correct wavelength. Furthermore, it is possible to promote the polymerization of selfcuring epoxies by local exposure to heat.

The above-described methods for cured-in-place pipe rehabilitation imply that no continuous exposure of the resin impregnated liner to an inert energy source is required. A relatively short application of energy is sufficient to initiate the curing process of the self-curing resin. This implies that a relatively small energy source can be used in these methods.

Furthermore, the self-curing process of the resin propagates into the depth of the liner by its own. There is no need for high-intensity lamps.

EXAMPLES

Example 1 : Inversion -Installation Method (see Fig. 1 )

1. Liner: Non-woven PES felt liner 6 mm; Trelleborg UltraFlex, Multiflex

2. Self-curing resin:

2.1 BADGE or ECC frontal radical induced cationic polymerizable resin (FRICP) as described in EP3344679 B1 ; page 8, table 1 , example 1

2.2 Cationic initiator: IOC-8

2.3 Radical initiator: TPED

4. Light apparatus: Speedylight or LEDRig curing device, Sewertronics, Starlight UV-curing device supplied by Innovation Sewer technologies

5. Exposure time: 10 sec to 1 min

Example 2: Packer assisted liner application (see Fig. 2)

1 . Liner: Glass fiber mat, 3 — 6 mm

2.1 BADGE or ECC frontal radical induced cationic polymerizable resin (FRICP) as described in EP3344679 B1 ; page 8, table 1 , example 1

2.2 Cationic initiator: IOC-8

2.3 Radical initiator: TPED 3. Packer+Light apparatus: Quickseal curing device, Cosmic Engineering

GmbH

5. Exposure time: 10 sec to 5 min

Example 3: Packer assisted liner application (see Fig. 3)

1. Liner: Non-woven PES felt liner 6 mm; Trelleborg Multiflex, Ultraflex.

2. Self-curing resin:

2.1 BADGE or ECC frontal radical induced cationic polymerizable resin (FRICP) as described in EP3344679 B1 ; page 8, table 1 , example 1

2.2 Cationic initiator: IOC-8

2.3 Radical initiator: TPED

3. Packer with integrated light source: UV/LED Hat packer as supplied by IBG Hydrotech GmbH

5. Exposure time: 10 sec-1 min

LIST OF REFERENCE NUMBERS sewer pipe line man hole main pipe inversion drum pressure hose end flange liner energy source packer a, 19b wheel basic body bladder a main bladder b lateral bladder a, b clamping sleeve air pressure hose opening liner a main liner b lateral liner