The present invention relates to a method of making a laminated fabric for reinforcement of pipes and the actual fabric made thereby. The fabric is particularly useful when formed into a tube for reinforcing sewerage pipes.

It will be appreciated that pipes, as with other structural products, tend to age and wear over time. Thus, it is necessary to periodically inspect pipes for deterioration. With regard to sewerage pipes, this is particularly necessary as such pipes are located in inaccessible locations, usually underground where replacement would be difficult. It is far simpler to renovate a sewerage pipe by appropriate reinforcement than to replace this sewerage pipe.

Over recent years many techniques have been developed for pipe renovation, but the present invention relates to renovation using non- woven fabrics with an appropriate curable resin to provide reinforcement.

Essentially, a tube of non-woven fabric is formed by securing opposed longitudinal edges of a strip of fabric together in order to form a tube.

Commonly, the fabric also has laminated to one side a barrier layer eg provided by an impervious polymeric film to provide an environmental seal for the renovative pipeliner. The fabric is impregnated with a curable resin, which once cured provides a rigid reinforcement structure within the pipeline to be renovated.

The barrier layer in these known fabrics may be a Surlyn or other suitable plastics material laminated to the non-woven fabric using conventional techniques and in a molten state. An avantage of Surlyn over other known materials, for example previously known polypropylenes, is that it is generally more flexible once laminated to the non-woven fabric compare to a similar polypropylene assembly.

However, more recently, new polypropylenes have become available and these are generally more flexible. A problem with the polymeric film barrier layer eg previously known polypropylenes and, to a certain degree, Surlyn, is achieving, under acceptable conditions, an adequate bond between the polymeric film and the non-woven fabric on making a renovative pipeline. Further, stiffer pipeliner is more difficult to manipulate into a pipe to renovate it. Thus, the potential for wrinkling etc. is significantly greater with the known relatively stiff renovative pipeliner assemblies.

It is an object of the present invention to provide an improved method of making a laminated fabric material for reinforcement which substantially relieves at least some the above-mentioned problems.

Another object of the present invention is to provide an improved laminated material suitable for use in making a renovative pipeline.

The present invention, in one aspect, provides a method of making a laminated material suitable for use in renovation of pipes, the method including the following steps: a) forming a fibre fabric,

b) heating to a melting temperature a polyolefin plastics material having a melt-flow index of at least 5 grams per 10 minutes and providing a molten film of the plastics material, c) Presenting for lamination said molten film of polyolefm plastics material to said fabric through a calender arrangement, whereby the fabric and the film meet at the nip of the calender between its rollers.

In a preferred method it is arrange that said fabric and said film travel from a substantial perpendicular relative relationship, to a substantially compresse parallel relationship of the calender through the presentation of at least one of said fabric and said film about the curvature of a roller of said calender arrangement, said roller having a diameter of at least 40cm.

Preferably, the fabric is a non-woven fibre fabric made by a non- woven felt-making technique such as needle fibre entanglement of textile fibres.

Preferably the temperature of the polymeric material as it is formed into a film is about 210 ° C.

Preferably the film is made by extrusion of the polymeric material through a slit die having its outlet extending in a direction parallel with the axes of the calender rollers into the nip between a pair of the calender rollers.

The present invention also provides a laminated material suitable for use in the manufacture of a pipeliner, the material comprising a fibre fabric having a barrier layer melt-laminated thereto, the barrier layer comprising a film of polyolefin plastics material having a melt flow index of at least 5 grams per 10 minutes. A preferred material is made in accordance with the above method in accordance with the invention. A preferred material comprises a polyester fibre non-woven fabric having a weight from 600 to 1000 gsm and a polypropylene plastics material having a melt flow index of at least 6 gm per 10 minutes laminated to that fabric, for example Adflex C200F which has a melt flow index of about 7 gm per 10 minutes.

Melt flow index where mentioned herein is measured at 230 ° C under a load of 2.16kg with a standard nozzle of 2.095 mm by the ASTM D1238 method.

It is also preferred that the material of the barrier layer should be highly flexible, preferably having a flexural modulus less than 300 MPa measured by the ASTM D790 method.

The material of the barrier is preferably tough and very abrasion resistant. A material which has no break when subjected to a Notched IZOD test at-20°C under method ASTM D256 is preferred.

In carrying out the ASTM D790 and ASTM D256 tests, the tests are carried out on standard injection moulded specimens (ASTM D2146) conditioned at room temperature (ASTM D618-procedure A).

The physical nature of a polyolefin, especially polypropylene, means that few substances will adhere to its surface even for Surlyn which is an ionomeric polyolefm resin whose properties of adhesion are considerably better than most polyolefins; Surlyn is, also, quite expensive.

This low-adhesion effect has been considered in the past a possible drawback with regard to curable resin impregnation, an essential part of renovated pipeliner operation.

In the present invention the polyolefin polymer/fibre fabric interface bond is extremely good and so a renovative pipeliner formed from the laminated fabric material in accordance with invention is believed to be generally superior to previous laminate materials with Surlyn or high molecular weight conventional polypropylene barrier layer materials in respect of structural integrity and resistance to long term de-lamination between the barrier layer and the underlying fabric, after or during impregnation with curable resin.

In accordance with a preferred method embodying the present invention, a fibre fabric is made by known techniques. As indicated above, normally the fabric used for renovative pipeliner is of a non-woven nature. However, it will be appreciated that woven and knitted fabrics may also be used where the additional cost associated with such materials is acceptable. The techniques of making fabrics are well known to those skilled in the art and will not be outlined in this description.

An essential feature of the present invention is the use of a suitable polyolefin, preferably polypropylene, such as Adflex C200F supplie by Montell Polyolefins. Adflex C200F is a thermoplastic polyolefin which

has a high softness and a high fluidity. It is this high fluidity at an appropriate melting temperature which achieves the necessary performance. A most important property of the polypropylene plastics material used to form the barrier layer in accordance of the present invention is the melt flow index. In respect of Adflex C200F, the melt flow index"L"is 7 grams per 10 minutes. However, material with a lower melt flow index L can be used and therefore as a specified requirement the melt flow index of polypropylene preferred in the embodiments of the present invention should be at least 5 grams per 10 minutes at the test conditions defined above.

There now follows a description of methods of making a fabric embodying the present invention. It will be realised that these fabrics and methods have been selected for description to illustrate the invention by way of example.

In the accompanying drawings:- Figure 1 is a diagrammatic side view showing a laminator used in carrying out a method of making a laminated material embodying the invention.

In carrying out a method of making a laminated fabric material 26 comprising a fibre fabric 22 and a barrier layer 28 melt laminated thereto embodying the present invention, a non-woven textile fibre fabric 22 is made by known techniques and a polyolefm eg polypropylene, having a suitable melt flow index, normally in the form of granules, is heated in a hot melt screw extruder with slit die 18 which forms part of a laminator 10, to a melting temperature such that the plastics material is molten.

This molten plastics material is presented as a film 24 from the slit die 18 of the laminator.

In carrying out a preferred illustrative method the polyolefin is Adflex C200F (see above) and this is exposed to a maximum temperature of 240°C in the zoned extruder and lower temperatures of 230'or 225'in subsequent heating zones, the slit die 18 being maintained at a temperature of 220°C. The molten film 24 issuing from the die 18 is thus at a high temperature and in a fluid condition. However, it will be appreciated by those skilled in the art that alternative extruder temperatures may be necessary for other suitable polyolefin plastics materials.

An important aspect of a method of embodying the present invention is the presentation of the respective film 24 and fabric 22 in the laminator 10. The laminator inclues, as well as the extruder, a calender type arrangement of compressive rollers 12,16,20 in order to achieve the lamination between the fabric 22 and presented molten film 24. In accordance with a method embodying the present invention the relevant orientation or configuration of the film and fabric is such that their relative relationship traverses from a substantially perpendicular configuration to a substantially compressive horizontal parallel relationship in the rollers of the calender of the laminator assembly. In the illustrative method orientation occurs by presenting the fabric 22 about the upper roller 12 such that the curvature of that roller 12 achieves the necessary re- orientation of the respective fabric and film.

The slit die 18 of the extruder is positioned with the slit extending horizontally, parallel with the axes of rotation of the calender rollers. The

slit is positioned as closely as possible to a nip 14 between the carrier rollers 12,16 about 1 cm from the nip 14 to extrude the material generally horizontally into the nip 14 forming a thin molten film 24 on the lower roller 16 as it enters the nip 14 between the lower roller 16 and the upper roller 12. The fabric is fed round the upper roller 12 from a supply roll (not shown) positioned generally above the calender rolls (12,16,20), into engagement with the film on the lower roller 16. The calender rollers are kept at a suitable temperature, in the illustrative embodiment 60°C, to rapidly cool the molten film 24 to cause it to solidify from its molten condition after the film and non-woven fabric have been brought into engagement.

The diameter of the rollers 12,16,20 of the calender of the laminator assembly is important. In accordance with the present invention the roller 12 and roller 16 each have a diameter of at least 40cm. It will be understood by those skilled in the art that the diameter of the rollers that achieve the appropriate re-orientation of the film and fabric affects essentially the angle of attack or association between the film and fabric.

Thus, larger diameter rollers achieve a lower angle whilst lower diameter rollers achieve a more obtuse, higher angle.

It has been found that an angle of approximately 30° is acceptable for a typical fabric 650-850 gsm and about 4 mm thick with Adflex C200F molten film. However, it will be appreciated that alternative angles may be more appropriate for other material combinations. With a 30'angle of association about the calender roll using a polyester non-woven fabric and the Adflex C200F polypropylene plastics molten film it has been found

that the freezing time of the molten film upon the fabric is in the order 0.2 seconds.

This freezing time essentially provides the time period or window for association of the molten film and fabric. It is in this period that the film becomes embedded into the fabric. It has been noted that a high laminar bond strength is achieved using Adflex C200F and a polyester fabric as described above. This high lamination bond strength is believed to be achieved by the Adflex C200F plastics material when molten flowing into the surface of the fabric 22 where it encapsulates the fibres of that fabric and freezes about them. This freezing encapsulation of the fibres occurs at the same time as the material is compresse by the calender rollers of the lamination assembly to reduce its gauge.

As indicated above it is important that the plastic material used to form the barrier layer is projecte as a molten film 24 upon the fabric.

This ensures that the film profile is obtained relatively easily and the film appearance is both flat and free from blemishes. Those skilled in the art will understand that the gauge of the film should be as uniform as possible and inadequately molten plastics material will create significant gauge variations across the film as presented to the fabric.

The compression to which the molten film/fabric combination is subjected will also influence the penetration of the film into the fabric and in carrying out a process embodying the invention the nip 14 between the rollers 12,16 into which the molten film is extruded is set at a fixed minimumgap.

The gap is chosen to ensure that the molten film 24 penetrates only into a surface region of the non-woven fabric 22 sufficient to give satisfactory lamination strength but to leave part of the film on the surface of the non-woven fabric to provide the unbroken barrier layer 28 of the laminated fabric 26. Should the nip 14 gap be too small the molten film 24 will be forced too far into the non-woven fabric 22 resulting in a laminated fabric 26 which may be too stiff for convenient introduction into a pipe to be lined and also blocking interstices in the non-woven fabric.

Blocking of interstices militates against subsequent impregnation of sufficient curable resin into the non-woven fabric 22 for satisfactory performance as a renovation pipeline.

A pressure is applied to the upper roller 12 urging it towards the lower roller 16 which is fixed against vertical movement and the pressure is chosen to provide even lamination. It has surprisingly been found that somewhat lower pressures than have normally been employed for laminating Surlyn barrier layers to a particular fibre fabric can provide even and secure lamination across the whole width of the barrier layer.

Thus the nominal 2000 p. s. i. pressure employed for lamination of a Surlyn barrier layer may be reduced in carrying out the illustrative method; nevertheless it is also important to ensure that sufficient pressure is applied to achieve satisfactory lamination.

As mentioned above the cooling rate of the molten film is also important in controlling penetration of the molten film into the non-woven fabric. Cooling of the laminated material to a suitable temperature for subsequent handling or storage may be achieved by causing the laminated material to travel round a bottom roller 20 of the laminator.

In carrying out the illustrative method the calender stack of rollers used in the laminator 10 will have a temperature of 60°C to ensure controlled freezing or solidification of the plastics materials upon the fabric 22. Normally the polymer film 24 is in contact with at least one roller 16 during the calender process.

In one method embodying the invention using a polyester fibre non- woven fabric weighing about 600 gsm the roller nip 14 gap was set at 2.75 mm and the laminated fabric 26 had a weight of about 870 gsm with a gauge of about 4.6 mm, satisfactory for use in making a pipeline. The lamination strength of the barrier layer to non-woven fabric was satisfactory.

In another illustrative method using a similar fabric but weighing about 800 gsm, the gap of the nip 14 was set at an appropriate roll gap, suitably between 2.4 and 2.9 mm: the laminated fabric 26 had a weight of about 1020 gsm with a gauge of about 5.1 mm, satisfactory for use in making a pipeline. The lamination strength of the barrier layer to the non-woven fabric was satisfactory.

In yet another illustrative method, a similar fabric weighing about 1000 gsm was used and the laminated fabric 26 had a weight of about 1260 gsm.

The materials produced by these illustrative methods are themselves illustrative of the invention in its material aspects. In these illustrative materials the film weight is about 260 gsm but it may range fairly widely,

for example between 230 and 285 gsm. The thickness of this film is about 0.29 mm In order to compare the bond strength of a laminated fabric embodying the invention with a prior Surlyn laminated fabric used for renovative pipeliner, the following typical bond strengths are defined. For a Surlyn laminated fabric with a gauge of 3.7 mm, the typical bond strength is up to 30 Newtons per cm. Whilst the present combination of a similar fabric with an Adflex C200F plastics material barrier layer, to give a gauge of 3.6 mm will have a bond strength between the barrier layer 28 and fabric 22 in the upper thirties Newtons/per cm. Actual values for the Surlyn laminated fabric are between 29 and 25 Newtons per cm across the width of the laminated fabric and for the 3.6 mm Adflex laminated fabric 39 Newtons per cm. It will therefore be appreciated that there is at least a 20% increase in laminar bond strength in accordance with the present invention. However, also of importance is the fact that the polypropylene plastic materials employed in the illustrative methods generally have a softer nature and so pipelines including the illustrative materials are more easily installe for reinforcing renovation where required.