The current invention concerns a filament-wound liner-free pipe. It also concerns a process for manufacturing the same via a filament winding process. Furthermore, it concerns the production line and the mandrel and winding stations used therein. Background Art

Steel pipe is still used in the oil and gas industry. This type of pipe may be used, onshore and offshore, in the transport of fluids to or from the well such as oil and gas gathering lines, flow lines, and fluid and gas injection lines which may be installed on the surface or buried. Steel pipe may also be used for downhole applications such as drilling, intervention, or production including drill strings, coiled tubing, production tubing, casing, and velocity and heater strings, and the like. Carbon steels, however, may be susceptible to corrosion, may be severely affected by C02 or supercritical C02, sulphites and/or bacterial corrosion and by oilfield fluids, such as produced or injected water, brine, and dissolved acids, as well as well work-over fluids. Furthermore, steel pipelines, gathering lines or injection lines are usually installed using short (6-12 meter) sections. This requires additional labour. Moreover, in particular with rigid and heavy steel pipe this provides the possibility for fluid leakage at each fitting. Such labour intensive installation may also lead to lost revenues if production or transport of the fluids is suspended during the installation. To resist internal and external corrosion, filament-wound thermosetting resin pipes may be used. Nowadays, composite pipes and fittings (including flanges) are made of a combination of fibre, often glass-fibre, and a thermoset resin. A correct choice of this combination results in a laminate which can withstand relatively high pressure and can withstand highly corrosive chemicals. In some literature and design specifications these are referred to as glass-fibre reinforced plastic (GRP) pipeline and piping systems.

Obviously, the composite pipes and fittings must perform according to standard

specifications. For instance, according to ASTM F 1 173 - 95, "Standard Specification for Thermosetting Resin Fiberglass Pipe and Fittings to be Used for Marine Applications", the minimum heat distortion temperature of the thermosetting resin used should not be less than 80°C (176°F). In reality, the glass transition temperature should be greater than that of polyvinyl chloride at 105°C (221 °F) or polystyrene at 100°C (212°F). A pipe meeting the specification of ASTM F 1 173 is classified by type, grade, and class similar to Classification D 2310. The current invention concerns Type I - filament-wound (pipe and fittings). The grade covers Grade I - Epoxy/Epoxy Vinyl Ester Resin; Grade II - Polyester Resins, as well as Grade III - customer specified thermosetting Resin. Epoxy resins are a class of

5 thermosetting resins known to be useful for various applications including composites,

coatings, adhesives, films, and electrical laminates and thus particularly suitable for this application. Finally, the composite pipe and fitting of the present invention is Class A - No liner.

10 By way of example, Shell specifies the requirements for the purchase and use of GRP

pipeline and piping systems, with respect to onshore pipeline and piping systems and offshore piping systems for non-hydrocarbon application; onshore pipelines transporting oil and associated gas; pipeline and piping systems for chemicals; onshore and offshore piping systems for hydrocarbon liquids; and onshore pipeline systems for gas, see DEP

15 31 .40.10.19-Gen of February 201 1 . From this specification maximum allowable

temperatures are known:

Temperature limitations for GRP

Type GRP Maximum allowable Typical Tg value of operating temperature fully cured resin

Glass-fibre/epoxy (GRE)

- Aromatic-amine cured (MDA) 100 °C 140 °C

- Cyclo-aliphatic cured (IPD) 100 °C 140 °C

- Aliphatic-amine cured 85 °C 1 15 C

- Anhydride cured 85 °C 1 15 °C

Glass-fibre/vinyl ester (GRVE)

- Bisphenol A 90 °C 120 °c

- Novolac 100 °C 140 °c

Glass-fibre/polyester (GRUP)

- Isophthalic 60 °C 90 °C

Source: DEP 31 .40.10.19-Gen. The temperatures are for initial guidance

Kuwait Oil Company (K.S.C.) applies a similar maximum allowable operating temperature, of 1 10 °C for "epoxy"; 70 °C for "polyester", and 100 °C for "vinyl ester", as per BS EN ISO 14692-1 and ISO 14692-1 . Likewise the American petroleum Institute Subcommittee on Fiberglass and Plastic Tubulars provides a specification for the standards for fiberglass line pipe and fittings for use in conveying produced liquids including oil, gas, non-potable water and mixtures thereof in the oil and gas producing industries. See API specification 15LR, 7 ^th ed., August 2001 . Various minimum properties are defined as well as the test methods for qualification. A relatively high Tg value is therefore desirable.

The conventional production process for flexible pipes makes use of a thermoplastic liner onto which fibres are applied with a rotating mandrel or a thermoplastic liner as the basis mandrel (winding). Typically, the fibres go through a resin bath where they are impregnated before the fibre reaches the mandrel to form a so-called laminate. At the end of the winding process the pipe is transported into a curing oven for a (final) heat curing, to ensure that the glass transition temperature is sufficiently high. After the final cure the pipes are released, cut on the correct length, and both ends are machined for the joints necessary for connecting the pipes and possible fittings in the field. This process is very wasteful. Moreover, the wall of a filament-wound epoxy pipe may be fairly damage intolerant and may require careful handling, installation, and/or use of specific back-fill materials. Damage or cracks in the fibreglass-reinforced epoxy layer can lead to small leaks or "weeping" of the pipe under pressure. Furthermore, the thermoplastic liners used therein are susceptible to collapse by permeating gases trapped in the annulus between the liner and the outer pipe if the pressure inside rapidly decreases.

From US20030198562 a composite coiled tubing is known wherein a thermoplastic liner is used, that provides the body upon which the composite coiled tubing is constructed. Layered strips of carbon or other stiff material are provided between the outer layers to provide high axial stiffness and strength to the outer portion of the composite coiled tubing such that the composite coiled tubing has greater bending stiffness about the major axis as compared to the beninding stiffness about the minor axis to provide a preferred direction of bending about the axis of minimum bending stiffness when composite coiled tubing is spooled and unspooled.

Near all embodiments described in US5858003 have a solid inner liner, with one

embodiment using an inner weaved layer as inner liner. Onto this weaved layer an overlay of longitudinal fiber layer is applied. The composite coiled tubings of this reference are all made using a liner as moving 'mandrel' on which the composite material is wound.

A composite thermoplastic lined spoolable tube is known from e.g. W01997012166. The spoolable composite tube is capable of being spooled onto a reel for storage and for use in oil field applications. The spoolable composite tube comprises a composite layer having fibres embedded in a matrix and an inner liner enclosed by the composite layer that is formed from polymeric materials. The polymeric materials making up the inner liner can be thermoplastic or thermoset materials, and are preferably selected from a group of various polymers, such as polyvinylidene fluoride ("PVDF"), ethylene tetrafluoroethylene ("ETFE"), and polyethylene ("PE").The fibres in the composite layer are oriented to resist internal and external pressure and provide low bending stiffness. For example, the composite layer can comprise a helically extending (i.e., spiral) first fibre, a second fibre clockwise extending and helically oriented, and a third fibre counter clockwise extending and helically oriented. The first, second and third fibres may be oriented such that the first fibre is interwoven with either the second fibre or the third fibre or both.

One of the mechanical properties required for a cured thermoset resin to be suitable and useful in manufacturing spoolable pipe, is "high elongation". As indicated in

W01997012166, as the pipe is spooled, the top of the pipe must stretch and the bottom of the pipe must compress; and the pipe should be able to elongate and compress without developing any permanent change in shape or damage. A curable resin composition that, upon curing, provides a thermoset exhibiting high elongation while still maintaining its Tg is advantageous in the manufacture of a spoolable composite pipe. This is of particular relevance in common filament winding processes that require thermosetting resin

formulations to undergo multiple winding and resin impregnation stages; as well as intermediate curing stages.

The inventors set out to develop a superior pipe and to find a process for manufacturing a filament-wound pipe that does not require a liner, is flexible, can be made into spoolable pipes that outperform the spoolable pipes made with a thermoplastic inner lining and that does not suffer from cracks, as happens in the current spoolable pipes. Moreover, the inventors set out to find a method that allows the preparation of a liner free pipe, preferably a spoolable pipe, more preferably a pipe that is flexible. Also attention is paid to the loss of materials, which now is low. Moreover, safety at the production site is improved.

Summary of Invention

Accordingly the invention concerns a filament-wound liner-free pipe being flexible in at least one direction, having flexible sides in a bending direction and a rigid side or sides, with a core layer comprising a reinforcement material embedded in a matrix comprising a cured thermosetting resin, wherein the reinforcement material comprises one or more spiral fibre - - windings wrapped in a first direction, one or more spiral fibre cross-windings wrapped in a second direction, and one or more longitudinal fibre rovings extending along the length of the pipe, wherein more than 60% of the one or more longitudinal fibre rovings extending along the length of the pipe are located in the rigid side or sides. In line with the present invention, the spiral fibre windings and cross-windings are preferably provided as overlay on the longitudinal fibre rovings extending along the length of the pipe. Preferably, the filament- wound liner-free pipe comprises two or more layers comprising a reinforcement material embedded in a matrix comprising a cured thermosetting resin.

Moreover, the invention concerns a process for the manufacture of the above filament- wound liner-free pipe, comprising the steps of:

a) Winding a reinforcement material to form a dry wound reinforcement material;

b) Impregnating the dry wound reinforcement material with a thermosetting resin

system;

c) Curing the thermosetting resin system;

d) Removing the formed filament-wound liner-free pipe comprising a core layer from the mandrel by pultrusion;

e) Optionally applying additional layers by one or more steps of winding reinforcement material around the core layer and impregnating the winding reinforcement material either before or after winding with the same or a different thermosetting resin system and curing the resin system (B),

f) Optionally performing a final heat cure, and

g) Either

a. Cutting the formed filament-wound liner-free pipe on the correct length and machining the ends for joints necessary for connecting the pipes and possible fittings in the field, or

b. Winding the formed filament-wound liner-free pipe around a spool, wherein

I. the reinforcement material is wound in step a) directly on a hollow mandrel,

II. the reinforcement material comprises one or more spiral fibre windings wrapped in a first direction, one or more spiral fibre cross-windings wrapped in a second direction, and one or more longitudinal fibre rovings along the length of the pipe,

III. more than 60% of the one or more longitudinal fibre rovings along the length of the pipe are positioned in the rigid side or sides of the pipe,

IV. the or each thermosetting resin system is radiation curable, and

V. the thermosetting resin system in step b) is injected at least in part through a hollow mandrel. As indicated, the process can include several stages, i.e., the process can be a multistage process. Furthermore, step e) may be repeated for a number of times, with optional intermediate radiation curing, until the final dimensions are reached. The product may then be subjected to a final radiation curing or heat curing.

The invention also relates to the production line used to prepare the filament-wound liner- free pipe and the newly developed mandrel and winding stations that are part of the new production line. Description of the figure

For the purpose of illustrating the present invention, the figures show a schematic representation of a pipe according to the present invention and (parts of) the production line that may be used to form the same. However, it should be understood that the present invention is not limited to the embodiments shown in the figures.

Fig. 1 illustrates longitudinal rovings, preferably glass rovings, positioned at opposite sites along the mandrel. As shown by this figure, the longitudinal fibre rovings are therefore positioned first. These sides will become the less flexible sides. Also shown are the bobbins from which the fibres are drawn and the rotatable frame (also referred to as wrapping table) on which the bobbins are placed. The mandrel may be equipped with various means to keep the longitudinal fibre rovings in place prior to the application of the spiral fibre windings. On the right a cross section is shown, schematically illustrating the longitudinal rovings and the rigid sides wherein they are embedded.

Fig. 2 illustrates the situation of the longitudinal roving during the bending of the pipe. It shows that the bending is not hindered by the rigid sides.

Fig. 3 illustrates spiral winding. Obviously, the spiral fibre winding is at an angle value different from 0 or 180 degrees. Likewise Fig. 4 illustrates schematically the spiral windings and cross-windings in the pipe. Not shown in any of these figures is the resin matrix wherein the reinforcement material is embedded. These figures 3 and 4 show that the spiral windings and cross-windings in the core layer are overlaid onto the longitudinal fibre rovings.

Fig. 5, illustrates the first stations in the production line after the longitudinal rovings are applied along the mandrel. A first frame with bobbins is shown on the left, rotating in one direction around the mandrel and causing spiral windings in one direction. In the middle a second frame with bobbins is shown, rotating in the opposite direction and causing spiral windings in the opposite direction. On the right, schematically, an impregnation station and a radiation (UV) curing station is shown.

Fig. 6, illustrates the preferred hollow mandrel that is used in the production line of the present invention at the preferred impregnation station. Shown on the left and middle top is the introduction of the thermosetting resin system, which is injected into the reinforcement material. Fig. 7, illustrates the preferred impregnation station in greater detail. Schematically the seals and back-up seals are shown, as well as a resin chamber, wherein the wound reinforcement material is impregnated. This preferred station ensures no thermosetting resin system is lost due to leakage, which provides a safer workspace.

In Fig. 8 a schematic flowchart is shown of the production line according to the present invention. In this figure the production line for the embodiment concerning a spoolable pipe is presented. The production line comprises a roving station (1 ); mandrel station (2); supply for the longitudinal fibre rovings (3); winder station for the core layer (4); winder station(s) for additional layer(s) (5); impregnation station (6); (ultraviolet) curing station (7); pulling system (8); guide post (9); oven (10); cutting unit (1 1 ); product storage (12); guide column (13); steering unit (14); coil (15); resin supply and storage (16).

Description of embodiments

The inventor has developed a new pipe which may be distinguished from those known in the art. It is thermoplastic liner-free and entirely made of filament-wound thermosetting resin. Moreover, it has at least one longitudinal fibre roving along the length of the pipe, condensed in one or two opposite sides. This longitudinal fibre roving or roving(s) are preferably positioned first. It or they allow the pipe to be taken from the mandrel, which is not moving itself, and passed through the various stations by pulling. By having the longitudinal fibre roving(s) condensed in one side or two opposite sides, the flexibility of the pipe in the direction perpendicular to the plane formed by the rigid side(s) and the axis of the pipe in the length direction of the pipe is hardly affect, as can be seen in Fig. 2. Preferably, more than 80%, more preferably more than 90% of the one or more longitudinal fibre rovings extending along the pipe are located in the rigid side or sides. One longitudinal fibre roving in the core layer may suffice. However, preferably there are 2 longitudinal fibre rovings at opposite sides of the pipe. The more said rovings are condensed in the rigid sides, the more flexibility the pipe will retain in the bending direction(s). The pipe comprises a core layer of thermoset resin wherein the reinforcement material is embedded. Preferably the pipe comprises the core layer and additional layers. For instance, the pipe may comprise 1 to 20 additional layers, preferably 1 to 5, more preferably 2 to 4, most preferably 3 additional layers. By changing the number of layers the desired thickness of the wall of the pipe may be reached.

The composition of the thermosetting resin system, the nature of the reinforcement material and the orientation of the reinforcement material may each be different in each of the layers, provided the longitudinal rovings in a subsequent layer, if any, remain substantially within the same rigid side or sides of the pipe, to ensure flexibility of the pipe. Preferably, the longitudinal rovings are only present in the core layer. As the longitudinal roving or rovings are the first to be positioned on the mandrel, as shown in Fig. 1 , a distinguishing feature of the pipe of the present invention is that longitudinal rovings may be found at the inside of the pipe.

Thus, the thermosetting resin may be the same in each layer or a different thermosetting resin may be used. For instance, thermosetting resins with increased elongation at break may be selected for the outer layers. For practical purposes, the resin used for the core layer preferably has a glass transition temperature exceeding 1 10°, preferably exceeding 120 °C. With a Tg below 1 10°C, the pipe will be less suitable for employ as pipe for geothermal energy or district heating.

Many types of thermosetting resin may be used. Preferably radiation curable, more preferably UV curable resins or UV/heat curable resins are used. Radiation (UV) curable resins are known. These resins include alkyds, epoxy resins, acrylic resins, polyesters, vinylesters, novolacs, phenolics, polyurethanes, polyimides, silicones, and many others. Of particular interest are epoxy resins, which have been used water-borne, or solvent-borne as varnish or coating. Epoxy resins tend to have better hardness properties (as compared to polyesters), with improved adhesion and less shrinkage. The thermosetting resin system may therefore include curable epoxy resins that are commonly used to reinforce fibres and then cured to provide a composite article useful in the composite industry. Most commercial epoxy resins are based on epichlorohydrin and bisphenol A or a derivative thereof. Preferably the radiation curable resin is a liquid. Preferably, the dynamic viscosity (ASTM D- 445) at 25°C is between 1 ,000 and 20,000 mPa.s, more preferably between 5,000 and 15,000 mPa.s, even more preferably between 9,000 and 12,000 mPa.s. Viscosities above the upper limit make it difficult to properly impregnate the fibres. This problem may be partially addressed by employing application temperatures above room temperature.

However, this affects the economy of the process. Viscosities below the lower limit likewise may cause problems due to dripping of the resin and hence inadequate impregnation of the fibres.

There are many suppliers of radiation curable resins, in particular radiation curable epoxy resins. Of particular interest are liquid epoxy resins sold by DOW under the registered trademark D.E.R. Moreover, the radiation curable resin should cure quickly and result in a pipe that is relatively flexible. Curing and flexibility are also affected by the photoinitiator that is employed as well as by other additives. This is discussed hereafter. As indicated above, also a combination of different resin compositions may be used.

Thermosetting resins may exist both in single component and two-component formulations. Both may be used. An advantage of a two-component system (wherein part (a) is the resin and part (b) is the hardener) is a longer shelf life (the period of time which the resin can be stored without deterioration of properties). Single-component formulations may be easier to work with because they do not need to be mixed in the correct proportions before use. Solvent-free formulations are preferred, because they do not suffer from the problem of voids that may form during curing as a result of solvent evaporation. Moreover, solvent-free formulations do not require investments to handle evaporated solvents.

The consistency of the composition comprising the thermoset resin is an important consideration for efficient production. The composition used for the preparation of the core layer will be injected at least in part through the mandrel. It is therefore essential that the composition may flow easily between the individual fibres wrapped around or applied onto the mandrel. Radiation curable resins are typically cured with ultraviolet (UV) radiation or electron beam (EB) curing. UV curing is preferred, due to cost. Obviously, the radiation has to penetrate the resin, containing the fibres therein. LED lamps work very well as energy source. Preferably LED lamps are used, that generate > 95% UV and < 5% heat. Ideally, the resin or resins used are dual curable, meaning that they can be post-cured in an oven to reach their potential in terms of reduced monomer content, and elevated glass transition temperature and elongation at break. Indeed, as mentioned in the Shell specification referenced above, the pipe components and flanges must be post-cured.

As an example of a suitable resin for the matrix of the core-layer or any of the subsequent layers reference is made to Loctite® Product Accuset™ M. This is a UV light curable for resins that may be blended with recommended epoxy/amine matrix resin systems. Typical materials include standard bisphenol A resins and liquid amines such as isphorone diamine, Jeffamine™ t-430; Ancamine™ 2049, Jeffamine D-230 and HB Fuller # 7258. This product may be blended shortly before normal use. The blended systems should be used within the typical pot life of the epoxy/hardener system to avoid significant variations in the flow and wetting due to viscosity changes. When filament winding fibres impregnated with these matrix resins are passed under a UV light, the blend is instantly immobilized (i.e. "B- Staged"). According to the supplier this even removes the need for a final heat cure. On the other hand, a final heat cure is still preferred to achieve a high enough glass transition point.

Particularly suitable thermosetting resin systems are the dual cure thermosetting resins. Thus, it is known that thermoset systems employing low molecular weight resins and crosslinking agents may suffer from sagging, slumping, so-called fat edges and other problems because of the low viscosity during the curing bake. These rheology problems may be solved with a dual cure resin system. For instance, dual cure epoxies are used in applications that require a very quick initial handling strength, with full cure being achieved off-line or in a subsequent process when cycle time is not so critical. They are also suitable for applications that has shadowed area that cannot be cured with UV. An example of a dual cure resin system is UV15DC80 by Master Bond Inc., Tru-Bond™ DC 1000 UV by Devcon or AC A535-AT by Addison Clear Wave. A particularly suitable dual cure resin system is disclosed in US provisional patent application Serial No. 61/917,482, filed by Karanukaran et al. This resin system includes: (a) at least one epoxy resin; (b) at least one thermally reacting hardener; (c) at least one methacrylated or acrylated polyol; (d) at least one radiation reactive initiator; (e) optionally, at least one monomeric acrylate or at least one monomeric methacrylate; and (f) at least one thermally active free radical initiator.

In the preferred dual cure resin system, many different epoxy resins can be used as component (a). The epoxy resins useful in the present invention may be selected from any known epoxy resin in the art; and may include conventional and commercially available epoxy resins, which may be used alone or in combinations of two or more. For example, an extensive enumeration of epoxy resins useful in the curable resin composition of the present invention includes epoxides described in Pham et al., Epoxy Resins in the Kirk-Othmer Encyclopedia of Chemical Technology; John Wiley & Sons, Inc.: online December 04, 2004 and in the references therein; in Lee, H. and Neville, K., Handbook of Epoxy Resins, McGraw-Hill Book Company, New York, 1967, Chapter 2, pages 2-1 to 2-27, and in the references therein; May, C. A. Ed. Epoxy Resins: Chemistry and Technology, Marcel Dekker Inc., New York, 1988 and in the references therein; and in U.S. Patent No.

3,1 17,099; all which are incorporated herein by reference. In selecting epoxy resins for the preferred thermosetting resin system used in the process of the invention, consideration should not only be given to properties of the final product, but also to viscosity and other properties that may influence the processing of the thermosetting resin system. Particularly suitable epoxy resins useful in the present invention are based on reaction products of polyfunctional alcohols, polyglycols, phenols, cycloaliphatic carboxylic acids, aromatic amines, or aminophenols with epichlorohydrin. Other suitable epoxy resins useful for the compositions disclosed herein include reaction products of epichlorohydrin with o-cresol and epichlorohydrin with phenol novolacs. Component (a) may be selected from commercially available products, such as for example, D.E.R. ^® 330, D.E.R. 331 , D.E.R. 332, D.E.R. 324, D.E.R. 352, D.E.R. 354, D.E.R. 383, D.E.R. 542, D.E.R. 560, D.E.N. ^® 425, D.E.N. 431 , D.E.N. 438, D.E.R. 542, D.E.R. 560, D.E.R. 736, D.E.R. 732 or mixtures thereof. (D.E.R and D.E.N resins are commercially available from The Dow Chemical Company.)

The thermosetting resin system of the preferred embodiment may include at least one low viscosity epoxy resin compound as component (a) to form the epoxy matrix in a final curable formulation. For example, the low viscosity liquid epoxy resin compound useful in the present invention may include the epoxy compounds described in U.S. Patent No.

8,497,387; U.S. Provisional Patent Application Serial No. 61/660403, filed June 15, 2012, by Maurice Marks; and U.S. Provisional Patent Application Serial No. 61/718752, filed October 26, 2012, by Stephanie Potisek et al., all of which are incorporated herein by reference.

A few non-limiting embodiments of the epoxy resin useful as a compound in the curable epoxy resin formulation of the present invention may include, for example, epoxies selected from the group consisting of bisphenol-A based epoxy resins, bisphenol-F based epoxy resins, resorcinol based epoxy resins, methylolated phenol based epoxy resins, brominated and fluorinated epoxy resins, and combinations thereof. Examples of preferred

embodiments for the epoxy resin include bisphenol A diglycidyl ether, tetrabromobisphenol A diglycidyl ether, bisphenol F diglycidyl ether, resorcinol diglycidyl ether, triglycidyl ethers of para-aminophenols, epoxy novolacs, divinylarene dioxides, cycloaliphatic epoxy, and mixtures thereof.

Generally, the amount of epoxy resin used in the preferred dual cure thermosetting resin system must be of a sufficient amount to provide from about 0.9 to about 1 .5 epoxy groups for every active hydrogen in the hardener (component b). Component (b) can be any conventional hardener compound known to be suitable for curing an epoxy resin-based formulation. The curing agent for the above epoxy resin may include for example, one or more curing agents selected from the group consisting of amines (including aliphatic, cycloaliphatic, aromatic, dicyandiamide), polyamides, polyamidoamines, phenol- and amine-formaldehyde resins, carboxylic acid functional polyesters, anhydrides, polysulfides and polymercaptans; and mixtures thereof. Generally, the amount of hardener useful in the dual cure thermosetting resin may be for example, from 5 wt % to about 50 wt % based on the total weight of the composition.

The above described combination components (a) and (b) forms the thermally reactive portion of a dual cure curable resin system.

Component (c) of the preferred thermosetting resin system is a methacrylated or acrylated polyol compound useful for the curable resin formulation of the present invention may include for example at least one polyol capped with methacrylate or acrylate groups (i.e., "methacrylated or acrylated polyols"). Suitable examples include SR 644 and/or SR 603 from Sartomer.

Generally, the amount of (m)ethacrylated polyol useful in the preferred thermosetting resin system, may be for example, from 5 wt % to about 25 wt %, based on the total weight of the composition. At concentrations lower than 5 wt %, the cured thermoset might not show high elongation. At concentrations higher than 25 wt %, the mechanical properties of the curable formulation may start to drop.

Component (d) is the radiation reactive initiator, preferably a photoinitiator. Various photoinitiators are known. For instance, BASF is supplier of Irgacure® 819, Irgacure 907 and many phosphorous compounds that can be used as photoinitator. Generally, the amount of component (d) in the preferred thermosetting resin, may be for example, from 0.1 wt % to about 4 wt %, based on the total weight of the composition.

The above described combination of components (c) and (d) forms the radiation reactive resin portion of the preferred dual cure curable resin system.

Optionally, other useful compounds can be added to the preferred thermosetting resin system and may include for example one or more thermally activated free radical initiators. If present, a thermally activated free radical initiator may be present in an amount up to about 1 wt% based on the total weight of the composition. - -

The preferred thermosetting resin system may include, as component (f), in the form of one or more monomeric acrylates/methacrylates. They act as reactive diluent. Component (f), if present, may be present in an amount up to about 5 wt %, based on the total weight of the composition.

Various other optional component(s), compound(s) or additive(s) useful for their indented purpose and well known by those skilled in the art may be added to the thermosetting resin system or systems. For example, such additives may include inert fillers, dyes, pigments, colorants, thixotropic agents, surfactants, fluidity control agents, wetting and dispersing agents, flow and levelling additives, defoamers, rheology modifiers, stabilizers, diluents, adhesion promoters, flexibilizers, toughening agents, fire retardants, antioxidants, impregnation accelerators, impact modifiers, viscosity reducers, lubricants, compatibilizers, coupling agents, and antistatic agents and the like, and mixtures thereof. For instance, up to 5% by weight of carbon (as graphene, as powder or as fibre) may be used as antistatic. Any of the optional components described above may be added to the thermosetting resin system or systems so long as they do not adversely affect the curing reaction process or processes of the thermosetting resin system(s). Such optional components, if present, may be present in an amount up to about 10 wt %, based on the total weight of the composition. The process for preparing the thermosetting resin system or systems included admixing the various components. This is done at a suitable temperature, generally at about room temperature, using standard mixing equipment.

Various types fibres may be used. Suitable materials include boron, aluminium oxide, carbon (graphite), metal, polymers (e.g., aramid), ceramics and glass. A commonly used and preferred fibre is a glass fibre. Glass fibre or "fibreglass" is favoured for composite materials as it is relatively cheap, inert and gives reasonable properties. Glass fibres are available on continuous rolls, allowing the preparation of filament-wound spoolable pipes. Moreover, fibreglass comes in different sizes. They comprise continuous filaments bonded into a single strand and wound onto a bobbin shape. The filament diameter may differ from 13 to 17μη"ΐ, with a linear density, expressed as TEX, of 200 to 4800 gr/km. Preferably 1200 TEX, 2400 TEX and/or 4800 TEX fibreglass is used, more preferably with 1200 TEX fibreglass for the core layer and 4800 TEX fibreglass for the outer layer(s). Also mixtures of fibres may be used. Within the scope of the current invention is the use of fibres with different elasticity, whereby the more elastic fibres are used in the outside layers. The fibre and the radiation curable resin composition together form a composite. Typically, the amount of fibres is from 60 to 85 % by weight on the entire pipe. Preferably, the glass content (by weight) of the reinforced wall of the pipe or fitting may be determined in accordance with ASTM D 2584. In this procedure, three samples may be taken from three locations situated 120° apart in the same cross section of the component. The glass content is then preferably 65 to 80 % by weight for filament wound pipe and 65 to 75 % by weight for filament wound fittings.

The process for producing tubes and pipes is sometimes referred to as filament winding. Filament winding can also be described as the manufacture of parts with high fibre volume fractions and controlled fibre orientation. In a conventional process, fibre tows are immersed in a resin bath where they are coated (wet winding). The impregnated tows are then literally wound around a mandrel (mould core) in a controlled pattern to form the shape of the part, here a pipe. After winding, the resin is cured, ordinarily using heat. The mould core may be removed or may be left as an integral component of the part. This process is primarily used for hollow, generally circular or oval sectioned components, such as pipes and tanks. This common process has been combined with other fibre application methods, such as hand layup, pultrusion and braiding. Typically, the fibres may be impregnated before winding, but also pre-impregnated (dry winding) or post-impregnated.

In the process of the present invention, post-impregnation is preferred. Instead of wet winding, the thermosetting resin system is preferably at least in part injected into the dry fibers wound on a mandrel. The mandrel is similar in shape and functionality as common mandrels. However, in this case it is provided with an inlet and an outlet for the

thermosetting resin system. It is therefore a hollow mandrel. It may be provided with a heating means to control the temperature and hence viscosity of the thermosetting resin. Preferably the heating means keeps the mandrel at a steady temperature, preferably in the range of 40-60 °C. Different from e.g., US5828003, where the liner used as mandrel moves onward during the construction, here the mandrel is fixed. Whilst still being constructed, the core layer is taken from the mandrel, and pulled onwards. Preferably the mandrel is made sufficiently smooth to allow the core layer to be pulled therefrom without adverse effect on the pipe itself. Conveniently, the mandrel is provided with a smooth coating, e.g., a coating of Teflon®.

Fig. 6 provides a schematic presentation of the preferred mandrel. Fig 6 also provides a schematic presentation of impregnation of the reinforcement material both by internal impregnation, through the hollow mandrel, and by external impregnation. Part of the - 1 O - thermosetting resin system may be introduced by external impregnation, at the first impregnation station, as shown in Fig. 6 or at subsequent impregnation station(s) as shown in Fig. 7. A resin impregnating station typically has an inlet for receiving curable resin and an outlet discharging the thermosetting resin system in an impregnation chamber wherein the reinforcement material is impregnated. Pursuant to a preferred embodiment of the present invention, the new impregnation station is equipped with seals, to prevent leakage of the thermosetting resin system and thereby provides a safer workspace.

The pipe in preparation will be pulled onwards from mandrel to end station. Supports may be provided at various stages in the process to avoid sagging.

Following the impregnation station and preferably immediately following the impregnation station, is a curing station. This is preferably a UV curing station, as shown in Fig. 5, on the right.

Thus, the resin compositions used in the invention may be cured upon irradiation, preferably UV radiation, with a wavelength between 400 nm to 300 nm, for instance using long wavelength UV light at 365 nm. By way of example, a suitable UV source is LOCTITE® Zeta® 7200, which contains a 5 inch, 300 Watts/inch medium pressure mercury vapour bulb designed to emit in the UVA and UVB regions. Other equipment may be used. Optimum UV cure is dependent on UV exposure time and UV intensity. Resin suppliers will generally assist in the optimum dosage. Ideally, the resin that is in the matrix of the core layer produced according to the present invention is sufficiently cured within the time to move from the first station to the next winding station. This process and therefore this requirement repeats itself for any next applied layer.

UV cure may be sufficient to cure the thermosetting resin system. However, preferably a final heat cure is applied to achieve the full strength and required glass transition point of the pipes.

As a preferred embodiment of the present invention, the process step e) may be repeated a number of times. In this case the reinforcement material is applied onto the core layer prepared in the first part of the production line. Again this is preferably done by dry-winding with post-impregnation, rather than by wet winding.

In the process according to the present invention preferably pull-winding technology is used in combination with a filament winding apparatus. The filament winding apparatus may have a hoop winding device and a helical winding device and performs hoop winding and helical winding on a mandrel repeatedly by rotation so as to wind a fibre bundle around the mandrel, thereby forming an inner core layer of the pipe. The hoop winding device may have a wrapping table rotated around the axis of the mandrel. Preferably, the winders are computer-controlled, so as to apply the reinforcement material in different angles, axial and hoop. A bobbin is preferably rotatable attached to the wrapping table. By fixing the end of the fibre bundle to the mandrel and rotating the wrapping table around the axis of the mandrel, the fibre bundle is wound onto the mandrel forming the core layer of the pipe onto which additional fibres may be wound on the outer peripheral surface of the core layer. In this case, the bobbin is rotated by pulling out the fibre bundle toward the produced core layer. Preferably, the winders loaded with glass fibre bobbins automatically wind around the mandrel forming a pipe. Preferably, the pipe is formed by repeating the winding step in one or more subsequent winding stations, with intermediate curing stations. Preferably 10 to 18, suitably 14 winding stations are used, with 3 to 5, suitable 4 intermediate curing stations. The pipe is pulled through the winding stations at the end of the line. This enables production of variable or even continuous lengths of pipe.

The hoop winding device includes a wrapping table, and several bobbin support units.

Preferably 72 bobbins are used for each wrapping table. The winders preferably also include a braking unit, a slack removal unit, a detector and a controller. The latter helps in the event of a change in winding speed or rotation speed of the wrapping table. The wrapping table is rotated around an axis of the mandrel. The bobbin support unit is provided in the wrapping table and supports a bobbin of the fibre bundle. The braking unit brakes rotation of the bobbin supported by the bobbin support unit. The slack removal unit absorbs slack caused by difference between winding speed of the fibre bundle pulled out from the bobbin and wound onto the surface of the mandrel and unravelling speed of the fibre bundle unravelled from the bobbin by rotation of the bobbin. The detector detects that the slack absorbed by the slack removal units is more than a predetermined value or that the slack absorbed by the slack removal units is less than the predetermined value. The controller increases braking power of the braking unit based on a detection signal from the detector detecting that the slack absorbed by the slack removal units is not less than the predetermined value, and reduces braking power of the braking unit based on a detection signal from the detector detecting that the slack absorbed by the slack removal units is less than the predetermined value.

How the foregoing and other objects and advantages are attained will appear more fully from the following description referring to the accompanying drawings, in which: FIG. 8 is a schematic representation of a production line according to the present invention. The production line comprises a roving station (1 ) for applying longitudinal fibre rovings. These will help set the strength for pulling the core layer through the production line. Next is a mandrel station (2). The hollow mandrel is also shown in Fig. 6. It is provided with means to impregnate the fibres from the inside. Moreover, it is preferably provided with heating means, to keep the mandrel at a steady temperature, preferably in the range of 40-60 °C. The mandrel is preferably provided with a Teflon coating. Once the longitudinal fibre rovings are placed, fibre windings may be applied in various orientations. They may be supplied helically at various winding angle values, i.e., the angle to the pipe longitudinal axis, that can be either positive or negative. Winding patterns may be simple or complex, as discussed in WO2004007178 and the art described therein, included herein by reference. The longitudinal fibre rovings are supplied from supply (3) and preferably positioned first. By use of the winders (4) the core layer is prepared. The fibres may be wound and cross wound at a predetermined value (for example 5 to 85°, preferably 40 to 60°). This production line is believed to be new and hence forms part of the current invention.

Thus, the inventor has also developed a new production line and a new production process, whereby many of the disadvantages from the present discontinuous filament winding process can be eliminated. By introducing this new production process, herein referred to as "pull-winding", a products may be prepared with improved mechanical properties. Moreover, it is now feasible to make the pipe spoolable, which is a huge advance in the installation time and product cost (less joints).

Pull-winding is therefore a form of pultrusion. In a standard pultrusion process reinforcement materials like fibres or woven or braided strands are impregnated with resin, possibly followed by a separate preforming system, and pulled through a heated stationary die where the thermosetting resin undergoes polymerization. The impregnation is either done by pulling the reinforcement through a bath or by injecting the thermosetting resin into an injection chamber which typically is connected to the die. In a pull-winding process, the pultrusion is combined with the (cross) winding of reinforcement material.

The invention therefore provides for a production line for the process for the manufacture of a filament-wound liner-free pipe, comprising a roving station (1 ); a mandrel station (2) with a hollow mandrel; supply (3) for the longitudinal fibre rovings; a winder station (4) for the core layer; and a curing station. The production line may further comprise winder station(s) (5) for additional layer(s); impregnation station(s) (6); (ultraviolet) curing station(s) (7); pulling system (8); guide post (9); and, as curing station an oven (10) for heat cure. Preferably the - - production line further comprises cutting unit (1 1 ); product storage (12); guide column (13); steering unit (14); coil (15); and resin supply and storage (16). As indicated, supports may be provided at various stages in the process, not shown, to avoid sagging. The length of the pipes made according to the current invention may vary. Thus, pipes may be made with a length of from 4 to 25 meter, preferably from 6 to 12 meter, for instance about 9 meter. These are lengths typically found for filament-wound pipes. However, the pipes according to the present invention may also be used for fittings and hence be shorter. Likewise the thickness of the wall of the pipe may vary. Preferably, the core layer is at least about 2 mm thick. In order to provide sufficient robustness, the minimum wall thickness of is preferably not be less than 3 mm. Wall thickness may be achieved by the number of layers applied on the core layer, and also by the fibres included in the layers. For practical purposes the walls preferably are at most 30 mm thick. The thickness of the walls depend on the employ of the pipe and the amount of internal or external pressure it needs to be able to withstand. It also depends on the overall diameter of the pipe.

For instance, for qualification under the Shell specification, pipes, fittings and joints are tested through performance-based procedures. Schematically this may be presented as follows:

Source: DEP 31 .40.10.19-Gen. Table 3.

Pipes according to the present invention may have nominal diameter of 25 mm to 400 mm.

The pipes according to the invention are ideal for both onshore and offshore applications such as:

• Oilfield flow lines & gathering lines:

• Tubing & casing (API 8-round threaded joint);

· Injection and secondary recovery systems; • Gas gathering and transport lines;

• Sub-sea lines for liquids and multiphase flow;

• Riser pipes

• Short term or temporary and reusable surface lines;

· Unstable soil and swamp conditions;

• Raw water intake lines

• Brine lines;

• Geothermal and district heating; and

• Potable water.

The pipes are of particular interest as flexible riser. Thus, the pipes have a bending radius that is smaller than standard glass-filament-wound pipes (typically by at least 70% and up to 90% at the same working pressure). Moreover, the pipes according to the present invention may be spooled on a reel up to 4 to 5 km (depending on the diameter). Examples are enclosed below to illustrate the process of the current invention. The examples are not meant to limit the scope of the invention.

Experiments

Example 1

A spoolable pipe was made in equipment as described hereinabove with respect to Fig. 8. The filament-wound, liner-free pipe comprises a core layer and 3 additional layers. The thermosetting resin for each layer was the same, a dual cure UV thermosetting resin supplied by DOW. 1200 TEX fibreglass was used for the core layer and 4800 TEX fibreglass for the outer layers. The thermosetting resin was brought to a full cure by intermediate UV cure and a final heat cure.

The spoolable pipe was wound on a reel, and can therefore be transported on a reel to any jobsite. The pipe weighs about ½ of a steel pipe. It may be used at conditions ranging from -35°C to 1 10°C and with pressure service up to 500 bar (7,500 psi). Tg, as measured by DSC, was 140°C