A fibre-reinforced thermoplastic unidirectional tape, a method of manufacturing and use thereof and a reinforced thermoplastic pipe

Abstract

A fibre-reinforced thermoplastic unidirectional (UD) tape arranged for use in a reinforced thermoplastic pipe (RTP) configured for transporting fluids, wherein the UD tape comprises a thermoplastic matrix material and unidirectionally aligned reinforcing fibres dispersed within the thermoplastic matrix material, wherein said unidirectionally aligned reinforcing fibres extend in a longitudinal direction of the UD tape, wherein the thermoplastic matrix material comprises: - at least one non-polar polymer; - at least one polar polymer, and - at least one compatibilizer, wherein the thermoplastic matrix material comprises a non-polar polymer to polar polymer volume ratio of from 40:60 to 70:30. A method of manufacturing and use thereof and a reinforced thermoplastic pipe (RTP) comprising the UD tape.

Description

[0001] TITLE A fibre-reinforced thermoplastic unidirectional tape, a method of manufacturing and use thereof and a reinforced thermoplastic pipe

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a fibre-reinforced thermoplastic unidirectional (UD) tape, to a method of manufacturing the fibre-reinforced thermoplastic UD tape and to a use of the fibre-reinforced thermoplastic UD tape. The present disclosure further relates to a reinforced thermoplastic pipe (RTP) comprising the fibre-reinforced thermoplastic UD tape.

[0004] BACKGROUND

[0005] Introduced more than a half century ago, fibre-reinforced polymer compositions are composite materials with a wide range of applications in industry, for example in the automotive industry. The term "composite" can apply to any combination of individual materials, for example to a thermoplastic polymer (the matrix) in which fibres (reinforcing filler) have been dispersed. The reinforced plastics industry has used glass fibres in different forms for reinforcing polymer matrices to produce a diversity of products.

[0006] An example of the variety of products are fibre-reinforced thermoplastic unidirectional (UD) tapes. Fibre-reinforced thermoplastic UD tapes are reinforced with continuous fibres, wherein the fibres, e.g., glass, basalt, or carbon fibres, are unidirectionally aligned and embedded (dispersed) in a thermoplastic matrix material of the tape. UD tapes are often used in reinforced thermoplastic pipes (RTPs), for example for transporting fluids, like hydrocarbon fluids. An RTP usually comprises an inner liner, an outer jacket, and, positioned between the inner liner and the outer jacket, a reinforcement layer. The reinforcement layer comprises the UD tape.

[0007] RTPs have high strength due to the reinforcement of the fibres making it possible to use them instead of metallic pipes for a variety of applications in which metal pipes are currently used. Pipelines based on metallic materials have the drawbacks that they are highly sensitive to corrosion, that they are heavy and inflexible. Like the metal pipes, the RTPs are also exposed to corrosive acidic conditions (e.g., CO2and H2S in oil and gas) during operation, and hence must have long term resistance to these conditions. The combined effect of high temperature and corrosive conditions can be detrimental to the inner liner as well as the reinforcement layer, which reduces the overall service life of the pipe. To address this problem, RTPs based on polyamide (e.g., PA-11 or PA-12) and polyvinylidene fluoride (PVDF) have been proposed. However, most of these types of thermoplastic materials are relatively expensive.

[0008] Thermoplastic materials such as PEEK or PEKK (being aromatic polyketones), have excellent resistance to high temperatures and chemicals. RTPs comprising such thermoplastic materials make the RTPs suitable for transporting (hot) hydrocarbons fluids. Another benefit is that RTPs are flexible and hence spoolable on reels, enabling easy transportation, easy installation, and very low maintenance requirements. Another advantage is that these materials are lighter than metal allowing for easy and cheaper transport. A drawback of thermoplastic materials like PEEK or PEKK is that a relatively high processing temperature is required. Another disadvantage is that they are relatively even more expensive than PA-11 , PA-12 and PVDF solutions.

[0009] Relatively cheap and therefore, attractive alternatives, are thermoplastic materials like polyesters and polyolefins, such as polyethylene (PE) and polypropylene (PP). However, while resistant to hydrocarbons, polyesters are still too susceptible towards hydrolysis from water and acidic gases. A major drawback of polyolefins like PE and PP is that they have a relatively low melting temperature making them less suitable for applications that require materials with high temperature resistance, such as in the transportation of hot hydrocarbon fluids. Further, the operational temperature of current spoolable RTPs produced using economical materials, such as PE, is limited to relatively low temperatures: the polyolefin material softens above 70 °C and swells at temperatures above around 80°C when exposed to aliphatic and aromatic hydrocarbon liquids.

[0010] In addition, glass fibres present in the unidirectional (UD) tape of RTPs, are structurally affected by acidic gases that diffuse through the inner liner wall. This could lead to loss of strength of the glass fibres and premature fracture of the pipe, leading to liquid (oil) spillage.

[0011] There exists a need for a thermoplastic material for UD tape that is relatively low in life cycle cost but is resistant to relatively high temperatures, has improved chemical / hydrolysis resistance and has low diffusion rates of hydrocarbon liquids and water vapor.

[0012] OBJECTIVE

[0013] It is therefore an objective of the present invention to provide for a fibre-reinforced thermoplastic UD tape that has high-temperature resistance, improved chemical and hydrolysis resistance and low diffusion rates of hydrocarbons and water in combination with improved cost efficiency, making these UD tapes suitable for all types of applications.

[0014] SUMMARY

[0015] In a first aspect, the invention relates to a fibre-reinforced thermoplastic unidirectional (UD) tape arranged for use in a reinforced thermoplastic pipe (RTP) configured for transporting fluids, wherein the UD tape comprises a thermoplastic matrix material and unidirectionally aligned reinforcing fibres dispersed within the thermoplastic matrix material, wherein said unidirectionally aligned reinforcing fibres extend in a longitudinal direction of the UD tape, characterized in that the thermoplastic matrix material comprises: at least one non-polar polymer, at least one polar polymer, and at least one compatibilizer, wherein the thermoplastic matrix material comprises a non-polar polymer to polar polymer volume ratio of from 40:60 to 70:30. By combining the non-polar polymers and polar polymers, such as polyolefins combined with polyesters / polyamides, with the claimed weight ratio between the nonpolar and polar polymers in the thermoplastic matrix material into a blend with a compatibilizer, it is possible to take advantage of the strengths of each of the nonpolar and polar polymers and cover for their weaknesses. For example, PP, PE like polymers offer protection against water while the content of polyester PET reduces the effect of hydrocarbons (e.g., swelling) on PP, PE. So, they improve the performance of the blend with synergy of combining the advantages of each other.

[0016] Most polymer pairs are not miscible and they separate into domains, known as ‘islands in the sea’, that weakens the thermoplastic matrix material. Therefore, a co-continuous morphology of the polymer blend is required. A co-continuous morphology can be obtained when the amounts of non-polar polymers and the polar polymers by volume are in the ratios 40:60 to 70:30. Other ratios where one polymer is too much a minority leads to islands of one in the other. A co-continuous morphology increases tortuosity and improves the gas barrier properties.

[0017] In the present description, with “co-continuous morphology” is meant a non-equilibrium morphology that is generated during melt-mixing of two polymers, e.g. a non-polar polymer and a polar polymer. The co-continuous morphology is distinct from the “islands in the sea” morphology because there is an interpenetrating network of the two domains. As such, morphologies formed by two immiscible polymers are unstable, and they start changing through filament break-up and retraction as soon as the polymer blend comes out of the mixer, that is on cessation of shear and extensional flow. This phenomenon can be prevented by including a compatibilizer in the polymer blend.

[0018] The compatibilizer prevents demixing / delaminating, or segregation, for example during multiple meltings (that occur during tape formation and consolidation), of the polar and non-polar polymers. It improves the adhesion between the non-polar and polar polymers, thereby enabling the manufacture of a miscible blend of, for example, polyolefins and polyesters. Furthermore, impact and tensile properties improve by addition of the compatibilizer. In addition, the invention requires a compatibiliser to improve bonding of the domains on solidification and to prevent rapid de-mixing when the thermoplastic tape is remelted for consolidation after winding on the inner liner.

[0019] The UD tape according to the present invention does not soften up to about 115 °C. So it has good thermomechanical properties at working temperatures of 90 °C or higher.

[0020] Furthermore, the UD tape according to the present invention does not swell as much as a single polymer due to hydrocarbon liquids and is not severely affected by H2O, H2S, and CO2.

[0021] Another benefit is that the thermoplastic matrix material as used in the present invention has low diffusion rates of H2O, H2S, CO2, and hydrocarbons. These reduced diffusion rates protect the reinforcing fibres, embedded in the thermoplastic matrix material of the UD tape, from H2O and hydrocarbons and other corrosive chemicals like H2S and CO2, such that the UD tape’s strength is maintained throughout its service life.

[0022] Moreover, polyolefins like PE and PP are also readily available as cheaper recyclates. Polybutylene terephthalate (PBT) and polyamides, such as nylon 11 (PA11) and nylon 12 (PA12), are engineering thermoplastics that are more expensive; PBT is about twice as expensive as the polyolefins, and PA12 is up to 15 times more expensive than the polyolefins. However, by using them as a blend lowers their consumption and thus, reduces the costs of manufacturing the UD tape and products comprising such a UD tape.

[0023] In a second aspect, the invention relates to a method of manufacturing a fibre- reinforced thermoplastic unidirectional (UD) tape according to the first aspect of the present invention, comprising the steps of:

[0024] 1) providing a thermoplastic matrix material comprising at least one non-polar polymer, at least one polar polymer and at least one compatibilizer; 2) melt compounding the thermoplastic matrix material obtained in step 1) in an extruder, preferably at 230 to 360 °C, to obtain a molten thermoplastic matrix material;

[0025] 3) unidirectionally aligning reinforcing fibres;

[0026] 4) contacting the unidirectionally aligned reinforcing fibres obtained in step 3) with the molten thermoplastic matrix material obtained in step 2) and subsequently consolidating to obtain a fibre-reinforced thermoplastic UD tape.

[0027] In a third aspect, the invention relates to a use of a fibre-reinforced thermoplastic UD tape according to the first aspect of the present invention or manufactured according to the method according to the second aspect of the present invention for a reinforced thermoplastic pipe (RTP) configured for transporting of fluids.

[0028] In a fourth aspect, the invention relates to a reinforced thermoplastic pipe (RTP) comprising from a centre to a periphery:

[0029] - a thermoplastic inner liner;

[0030] - a reinforcing layer, comprising one or more layers of a fibre-reinforced thermoplastic unidirectional (UD) tape according to the first aspect of the present invention or manufactured according to the method according to the second aspect of the present invention; and

[0031] - a thermoplastic outer jacket.

[0032] Corresponding embodiments disclosed below for the first aspect are also applicable for the method of manufacturing the fibre-reinforced thermoplastic UD tape (second aspect), the use of the fibre-reinforced thermoplastic UD tape (third aspect), and to the RTP comprising the fibre-reinforced thermoplastic UD tape (fourth aspect) according to the present invention, unless stated otherwise.

[0033] DETAILED DESCRIPTION - EMBODIMENTS

[0034] The present invention is elucidated below with a detailed description.

[0035] Thermoplastic matrix material In the present description, with “thermoplastic matrix material” is meant a thermoplastic polymer material that forms the matrix of the fibre-reinforced thermoplastic composite.

[0036] Non-polar polymers

[0037] In the present description, with “non-polar polymer” is meant a type of polymer that lacks significant polar functional groups or has a symmetrical molecular structure that results in an even distribution of charge. In non-polar polymers, the electronegativity of the atoms involved is relatively balanced, leading to a lack of a net dipole moment within the polymer molecule.

[0038] Non-polar polymers typically exhibit properties such as low surface energy, resistance to polar solvents, and lower reactivity with other polar substances. They are often used in applications where these characteristics are advantageous, such as in packaging materials, insulating coatings, and non-stick surfaces.

[0039] The thermoplastic matrix material comprises at least one non-polar polymer, such as polyolefins, polytetrafluoroethylene, or polyphenylene sulphide.

[0040] In the present description, with “polyolefin” is meant a polymer of olefin monomers, having the general formula (CH2CHR)nwhere R is an alkyl group. Examples are polyethylene, polypropylene, and polymethylpentene.

[0041] In the present description, with “PE” is meant polyethylene which is according to the structure below:

[0042] PE is usually a mixture of similar polymers of ethylene, with various values of n. It is a thermoplastic, non-polar polymer and can be low-density or high-density and many variations thereof. PE is relatively cheap and therefore commonly employed in packaging materials, containers and various plastic products. In the present description, with “PP” is meant polypropylene which is according to the structure below:

[0043] PP is a thermoplastic, non-polar polymer and is very similar to PE, but a much stronger polymer. Like PE, it is a relatively cheap polymer making it a popular choice in manufacturing.

[0044] In the present description, with “PMP” is meant polymethylpentene which is according to the structure below:

[0045] PMP is a thermoplastic, non-polar polymer that has high heat resistance and low density. It has similar properties of PE and PP, although it is more brittle and more gas permeable.

[0046] In the present description, with “PTFE” is meant polytetrafluoroethylene according to the structure below:

[0047] Polytetrafluoroethylene is a fluorocarbon solid, as it is a high-molecular-weight polymer consisting wholly of carbon and fluorine.

[0048] In the present description, with “PPS” is meant polyphenylene sulphide according to the structure below:

[0049] This is a thermoplastic polymer consisting of aromatic rings linked by sulphides. In the present description, with “PPO” is meant polyphenylene oxide according to the structure below:

[0050] Polyphenylene oxide (PPO), also known as polyphenylene ether, also has the polar ether linkage. This polymer has high hydrolytic and chemical stability and creep resistance at high temperatures. Neat PPO is thermally unstable at melting and extrusion temperatures. It is modified with polystyrene (PS), a non-polar polymer. The modified PPO is used for extrusion purposes. The modified PPO, which is a blend of PPO and PS, is a miscible system. For the purpose of this invention, the miscible blend of PPO and PS is like a single polymer. The miscible blend of PPO and PS may be combined with an immiscible non-polar polymer like polypropylene to form a co- continuous structure.

[0051] In an embodiment, the at least one non-polar polymer is selected from the group consisting of a polyolefin, such as polyethylene (PE), polypropylene (PP) and polymethylpentene (PMP), polytetrafluoroethylene (PTFE), polyphenylene sulphide (PPS), polyphenylene oxide (PPO), and a combination of two or more thereof, preferably a polyolefin, such as polyethylene (PE) and polypropylene (PP).

[0052] Polar polymers

[0053] In the present description, with “polar polymer” is meant a type of polymer that contains polar functional groups and asymmetric structures, leading to an uneven distribution of charge within the polymer molecule. Polar functional groups typically involve electronegative atoms, such as oxygen, nitrogen, or fluorine, which create regions of partial negative and positive charges within the molecule.

[0054] In a polar polymer, the distribution of electrons is not uniform, resulting in a net dipole moment, at least in localised segments of the chain. This dipole moment gives the polymer certain properties, including enhanced interactions with other polar substances, higher surface energy, and specific electrical characteristics. In small molecules, the geometric arrangement of dipoles can lead to cancellation with no net dipole moment over the entire molecule, in polymers the local dipole moment of a polar functional group governs interactions between chains.

[0055] Polar polymers often exhibit different physical and chemical properties compared to non-polar polymers. They may have higher melting points, be more prone to interaction with polar solvents, and display different surface behaviours.

[0056] The thermoplastic matrix material comprises at least one polar polymer, such as polyester, polyamide, aliphatic polyketone, aromatic polyketone, polyurethane, polyether sulfone, polyetherimide, polyvinyl chloride, polyvinylidene fluoride, polyvinyl acetate, polyacrylonitrile, polycarbonate.

[0057] In the present description, with “polyester” is meant a polymer that contains an ester functional group in every repeat unit of their main chain and is according to the structure below:

[0058] Examples of polyesters are polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and liquid-crystal polyester.

[0059] In the present description, with “PET” is meant polyethylene terephthalate according to the structure below:

[0060] PET is a thermoplastic, polar polymer that consists of repeating (CI0H8O4) units. It was formerly produced from ethylene glycol (monoethylene glycol, MEG) and dimethyl terephthalate (DMT) but mostly produced now by the reaction of MEG with terephthalic acid (purified terephthalic acid, PTA). In the present description, with “PBT” is meant polybutylene terephthalate according to the structure below:

[0061] PBT is a thermoplastic, polar polymer that is closely related to PET. Compared to PET, PBT has slightly lower strength and rigidity, slightly better impact resistance, and a slightly lower glass transition temperature.

[0062] In the present description, with “PEN” is meant polyethylene naphthalate according to the structure below:

[0063] PEN is a thermoplastic, polar polymer derived from naphthalene-2,6-dicarboxylic acid and ethylene glycol (MEG). It is related to PET, but with superior barrier properties.

[0064] In the present description, with “LCP” is meant liquid-crystal polyester which is a polymer having the property of forming a liquid crystal melt, usually containing aromatic rings as mesogens. LCP is one that on melting forms a liquid crystal phase, a molten liquid state distinct from an isotropic melt, in that the liquid shows spontaneous parallel ordering of the chains in the melt, as opposed to the random entangled melt formed by most plastics on melting. The liquid crystal melt shows birefringence (a phenomenon wherein a material exhibits different refractive indices for light waves that have different polarization directions).

[0065] In the description, with “mesogen” is meant a compound that displays liquid crystal properties and can best be described liquids liquids that have orientational and some positional long-range order (that is, a property of crystals), yet it can flow like a liquid.

[0066] In the present description, with “polyamides” is meant a polymer comprising amide bonds. There are several types of polyamides, such as aliphatic polyamides, aromatic polyamides or polyphthalamides. Examples are polyamide 11 and polyamide 12. In the description, with “PA11 ” is meant polyamide 11 , also known as nylon 11 , according to the structure below:

[0067] PA11 is a type of synthetic polyamide known for its high strength, flexibility, and chemical resistance.

[0068] In the description, with “PA12” is meant polyamide 12, also known as nylon 12, according to the structure below:

[0069] PA12 is a versatile thermoplastic polymer valued for its flexibility, impact resistance, and chemical stability.

[0070] In the present description, with “aliphatic polyketone” is meant a polyketone comprising aliphatic comonomer(s) (POK), such as carbon monoxide, ethylene, and propylene monomers, according to the structure below:

[0071] In the present description, with “POK” is meant a polyketone polymer that is built from aliphatic comonomers. POKs are a family of thermoplastic polymers comprising polar ketone groups in the polymer backbone. They are prepared by polymerizing carbon monoxide with an olefin as comonomer (e.g., ethylene). POK come in different types depending on 1) the number of comonomers and; 2) the types of comonomer(s). When one olefin comonomer is used the term copolymer is often used and when two olefin comonomers are used the term terpolymer is often used.

[0072] The two most common types of aliphatic POK are copolymers built from the monomers carbon monoxide and ethylene (R being hydrogen), and terpolymers built from the monomers carbon monoxide, ethylene, and a second olefin comonomer which can be propylene, butylene (e.g. 1-butene), hexylene, octene, or dodecene (in the comonomers, R is methyl, butyl, hexyl, octyl, or dodecyl).

[0073] POKs have polar ketone groups in the polymer backbone and the presence of these ketone groups provides strong attraction between polymer chains, which increases the material’s melting point to about 260 °C for the copolymer (having carbon monoxide and ethylene monomers) and about 220 °C for the terpolymer (having carbon monoxide, ethylene, and propylene monomers).

[0074] In the present description, with “aromatic polyetherketone” is meant a polyetherketone comprising comonomer(s) having aromatic groups (PEK). PEKs are polymers whose backbone contain alternating ketone (R-CO-R) and ether (R-O-R) functionalities. The most common are PAEKs.

[0075] In the present description, with “PAEK” is meant polyaryletherketone. This is a family of PEK whose molecular backbone contains alternately ketone (Aryl-CO-Aryl) and ether groups (Aryl-O-Aryl), wherein Aryl is a 1 ,4-substutited aryl group. These polymers are semi-crystalline thermoplastics with high-temperature stability and high mechanical strength.

[0076] In the present description, with “PEEK” is meant polyetheretherketone according to the structure below:

[0077] PEEK is a PEK, more specifically of the PAEK family. PEEK is a semicrystalline thermoplastic with excellent mechanical and chemical resistance properties that are retained to high temperatures. The processing conditions used to mold PEEK can influence the crystallinity and hence the mechanical properties.

[0078] In the present description, with “PEKK” is meant polyetherketoneketone according to the structure below:

[0079] PEKK is also a PEK, more specifically of the PAEK family. PEKK is a semicrystalline thermoplastic with excellent mechanical and chemical resistance properties that are retained to high temperatures.

[0080] In an embodiment of the first aspect of the present invention, the thermoplastic matrix material of the UD tape comprises one or more aromatic polyketones (PEK), such as PEEK and PEKK. Due to the properties of these PEKs, they are suitable for use in reinforced thermoplastic pipes (RTPs).

[0081] In the present description, with “PU” is meant polyurethane, also often abbreviated as PUR. It is a class of polymers composed of organic units joined by carbamate (urethane) links. It can be produced from a wide range of starting materials leading to a variety of polyurethanes with different chemical structures and thus, different properties. An example of a PU is the structure below:

[0082] PU is typically produced by reacting an isocyanate with a polyol (resulting in the polyurethane structure above). Since a polyurethane contains two types of monomers, which polymerize one after the other, they are classed as alternating copolymers. Both the isocyanates and polyols used to make a polyurethane contain two or more functional groups per molecule.

[0083] In the present description, with “PES” is meant polyethersulfone according to the structure below. This is a thermoplastic polymer comprising ether bonds, aromatic rings, and sulfone bonds in the backbone: In the present description, with “PEI” is meant polyetherimide. This is a high- temperature thermoplastic polymer just like PEEK. Compared to PEEK, it has a lower impact strength. PEI contains phthalimide and bisphenol A subunits. It has the following structure:

[0084] In the present description, with “PVC” is meant polyvinylchloride according to the structure below:

[0085] PVC is produced by polymerization of the vinyl chloride monomer (VCM). The presence of the chloride groups gives the polymer very different properties from the structurally related PE.

[0086] In the present description, with “PVDF” is meant polyvinylidene fluoride, being a fluorinated type of polyolefin. It has the following structure:

[0087] PVDF is a thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride.

[0088] In the present description, with “PAN” is meant polyacrylonitrile according to the structure below: PAN is a synthetic, semicrystalline organic polymer resin. Almost all PAN are copolymers with acrylonitrile as the main monomer.

[0089] In the present description, with “PC” is meant polycarbonate according to the structure below:

[0090] PC is a group of thermoplastic polymers containing carbonate groups in their chemical structures. The main PC material is produced by the reaction of bisphenol A (BPA) and phosgene (COCI2). An alternative route to produce PC entails transesterification from BPA and diphenyl carbonate.

[0091] In an embodiment, the at least one polar polymer is selected from the group consisting of a polyester, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN) and liquid-crystal polyester (LCP), a polyamide, such as nylon 11 (PA11) and nylon 12 (PA12), aliphatic polyketone (POK), aromatic polyketone (PEK) such as a polyaryletherketone (PAEK), for example polyetheretherketone (PEEK) and polyetherketoneketone (PEKK), polyurethane (PU), polyether sulfone (PES), polyetherimide (PEI), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polycarbonate (PC), and a combination of two or more thereof, preferably a polyester, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN) and liquid-crystal polyester (LCP).

[0092] In a preferred embodiment, the at least one non-polar polymer is a polyolefin and the at least one polar polymer is a polyester, preferably the at least one non-polar polymer is polypropylene (PP) and the at least one polar polymer is polyethylene terephthalate (PET) or polybutylene terephthalate (PBT).

[0093] In another preferred embodiment, the non-polar polymer to polar polymer volume ratio is from 45:55 to 60:40, preferably 45:55 to 55:45. A volume ratio closer to 50:50 improves the co-continuous morphology of the thermoplastic matrix material, which results in a more constant quality of the UD tape. Co-continuous structures are three-dimensional interpenetrating and intertwining structures. The conditions for forming the co-continuous morphology is described in Petra Pbtschke and D. R. Paul,’ Formation of Co-continuous Structures in Melt-Mixed Immiscible Polymer Blends’ JOURNAL OF MACROMOLECULAR SCIENCE Part C— Polymer Reviews Vol. C43,No. 1 ,pp. 87-141 ,2003. Two important features are (1) equi volume composition and (2) equi viscosity of the two melts.

[0094] In the present disclosure, with “equi viscosity”, “equi melt viscosity” or “equi viscous” is meant that the respective melt, such as the melt of the thermoplastic matrix material, has a viscosity that is (more or less) constant throughout its volume.

[0095] In the present disclosure, with “equi volume” or “equi melt volume” is meant that the respective polymeric blend, such as the thermoplastic matrix material, comprises similar volumes of non-polar polymer and polar polymer. Hence, the volume ratio between the non-polar polymer and the polar polymer in such a blend is about 50:50.

[0096] The co-continuous range can be very narrow or quite wide but is centred around the phase inversion composition <Pi, which is also called the phase inversion point:

[0097] (cpi.Pi / cp2, Pi) X (T| I , PI / T| 2, PI) ~ 1, or ( pi, PI / <p2, PI) = (r| i ,H / r|2, PI) where r|i is the viscosity of component cp^ PI, is the volume fraction at phase inversion of the component i.

[0098] The interfacial tension of the two melts is also a determining factor in the stability of the co-continuous and its break up into a dispersed one. Low interfacial tension helps in the formation of co-continuous structures and reduces the rate of breakup. In blends with high interfacial tension, the phase inversion can occur at a single composition, whereas in blends with lower interfacial tension, the co-continuous composition range can be quite wide. Thus, while the optimal conditions for obtaining the co-continuous morphology is equi melt volume and equi melt viscosity, the article by Pbtschke and D. R. Paul, indicates there is a compositional range or band outside this exact point where the co-continuous morphology will form. Due to difficulty in measuring the melt volumes and volume ratio of both components (compared to the weight ratios of the components), and also measuring the interfacial tension for all the polymer compositions described herein, the exact compositional range for a particular combination of polymers which provides the co-continuous morphology can be established empirically by scanning electron microscopy, and this is documented in the scientific literature and is well known to those skilled in the art. But as a general starting point, such a range will be about 50:50 by melt volume and with both components preferably having a low viscosity of about 70 Pa s, the low viscosity and equi viscosity being selected to facilitate melt impregnation.

[0099] Preferably, the polar polymer is a fast crystallising polyester, the fastest one being the most preferable. This is because if one phase is a slow crystalliser, it would end up being amorphous and this would crystallise on reheating to the end-use temperature, leading to shrinkage of the re-crystallised domains with possible de-bonding from the second polymer. The crystallisation rate of the common polyesters follows the trend PBT > PET > PEN, hence PBT would be the most preferred.

[0100] Preferably, of the at least one non-polar polymer and the at least one polar polymer have similar viscosities, such as viscosities of at most 100 Pa s, such that the thermoplastic matrix material has an equi viscosity.

[0101] In an embodiment, the non-polar polymer is polypropylene (PP) and the polar polymer is polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), wherein the non-polar polymer to polar polymer volume ratio is from 45:55 to 55:45, and wherein the viscosity of the thermoplastic matrix material is at most 70 Pa s.

[0102] The thermoplastic matrix material may have: a melt mass-flow rate (MFR) of at least 60 g / 10min, preferably at least 100 g / 10min, more preferably at least 150 g / 10min, most preferably between 60 and 200 g / 10min measured at 240 °C with a load of 2.16 kg according to ASTM D1238-23; and / or a viscosity of at most 100 Pa s, preferably at most 70 Pa s, measured at 240 °C according to ISO 6721. A thermoplastic matrix material having such properties makes it extremely suitable for the application in UD tape, e.g., a thermoplastic material with a viscosity in this range improved impregnation of the fibres.

[0103] The MFR of a polyamide or polyester can be adjusted by controlling the moisture present in the melt by selecting the drying time of the polar polymer. The MFR of a PP can be adjusted by controlling its molecular weight by 'hydrolytic cracking' of the PP.

[0104] In order to blend the non-polar and the polar polymers, each of said non-polar and polar polymers must have a viscosity of from about 70 to about 200 Pa s, measured according to ISO 6721 at a temperature about 10 to 20 °C above the melting point of the higher melting polymer in the polymer blend. The melt viscosities of both polymers has to be low for impregnation, and they are preferably matched as that is a good condition for obtaining the co-continuous morphology.

[0105] Reinforcing fibres

[0106] Reinforcing fibres are dispersed in the thermoplastic material such that they are unidirectionally aligned in the thermoplastic material in order to obtain the fibre- reinforced thermoplastic UD tape according to the first aspect of the invention. The unidirectionally aligned reinforcing fibres may be selected from the group consisting of glass fibres, carbon fibres, basalt fibres, ceramic fibres, aramid fibres, hemp fibres, flax fibres, sisal fibres, and one or more combinations thereof, preferably glass fibres, carbon fibres, and / or basalt fibres. This broad range of types of fibres that are suitable for reinforcing the thermoplastic matrix material provides extra flexibility to the manufacturing process and makes it less dependent on one or a few types of fibres.

[0107] In the present description, with “unidirectionally aligned reinforcing fibres” is meant that substantially all fibres, preferably all fibres, are aligned in a single direction. In the present description, with “single direction” is meant the longitudinal direction of the UD tape, i.e., the machine direction in which the UD tape is manufactured. In the present description, with “parallel aligned continuous multifilament strands” is meant that the reinforcing fibres are continuous strands of fibres that are positioned in parallel to each other in the longitudinal direction of the UD tape. The fibres in the fibre-reinforced thermoplastic UD tape are generally supplied as a plurality of continuous, very long filaments, and can be in the form of strands, rovings, or yarns.

[0108] A filament is an individual fibre of reinforcing material. A strand is a plurality of bundled filaments. Yarns are collections of strands, for example strands twisted together. A roving refers to a collection of strands wound into a package.

[0109] In the present description, with “continuous” in connection with fibres, filaments, strands, yarns, or rovings is meant that the fibres, strands, filaments, yarns, or rovings generally have a significant length. However, it should not be understood to mean that the length of the fibres, strands, filaments, yarns, or rovings is perpetual or infinite. Continuous fibres, such as continuous filaments, strands, yarns, or rovings have a length of more than 100 mm, preferably more than 1000 mm, depending on the length of the of the UD tape. Most preferably, the fibres have the same length as the UD tape.

[0110] In the present description, with “reinforcing fibres” is meant fibres that are added to the thermoplastic matrix material with the purpose of improving the matrix material’s strength. In other words, fibres that reinforce the matrix material.

[0111] In the present description, with “glass fibres” is meant a material that consists of numerous extremely fine fibres of glass. Thin strands of silica-based or other formulation glass are extruded into many fibres with small diameters suitable for textile processing.

[0112] The most common type of glass fibre is E-glass, which is alumino-borosilicate glass. E-glass has less than 1 wt.% alkali oxides and is mainly used for glass-reinforced plastics. Other types of glass used are A-glass (alkali-lime glass with little or no boron oxide), E-CR-glass (Electrical / Chemical Resistance; alumino-lime silicate with less than 1 wt.% alkali oxides, with high acid resistance), C-glass (alkali-lime glass with high boron oxide content, used for glass staple fibres and insulation), D-glass (borosilicate glass, named for its low dielectric constant), R-glass (alumino silicate glass without MgO and CaO with high mechanical requirements as reinforcement), and S-glass (alumino silicate glass without CaO but with high MgO content with high tensile strength).

[0113] In the present description, with “carbon fibres” is meant carbon fibres (alternatively OF or graphite fibre) having a diameter of about 5 to 10 micrometres that are composed mostly of carbon atoms, arranged in a graphitic structure. Specifically, the graphene planes are oriented parallel to the carbon fibre’s axis. Carbon fibres have several advantages: high stiffness, high tensile strength, high strength to weight ratio, high chemical resistance, high-temperature tolerance, and low thermal expansion. However, they are relatively expensive compared to similar fibres, such as glass fibres and basalt fibres.

[0114] In the present description, with “basalt fibres” is meant fibres that are produced from basalt rocks by melting them and converting the melt into fibres. Basalt fibres, or more specifically basalt continuous fibres, can be used for the production of reinforcing materials and composite products. Basalt fibres are made from a single material, crushed basalt, from a carefully chosen quarry source. Basalt of high acidity (over 46% silica content) and low iron content is considered desirable for fibre production. Unlike with other composites, essentially no materials are added during its production: the basalt is simply washed and then melted. Basalt fibres are fire resistant and do not burn, which makes them very suitable as a reinforcing material in a fibre-reinforced thermoplastic UD tape that requires good flame retardancy.

[0115] Furthermore, when basalt fibres are used to strengthen polymers, its composites have good strength, high working temperature range, good chemical resistance, excellent heat and sound insulation properties and low water absorption. In addition, basalt fibres are easy to process, environmentally friendly, and relatively cheap.

[0116] In the present description, with “ceramic fibres” is meant fibres that are smalldimension filaments or threads composed of ceramic material, usually alumina and silica, used in lightweight units for electrical, thermal, and sound insulation. Mainly, ceramic fibres are of two types: ceramic oxide fibres and ceramic non-oxide fibres.

[0117] Ceramic oxide fibres mostly consist of alumina (AI2O3) and alumina-silica (AI2O3-SiO2) mixtures and are generally used for high-temperature applications due to their high melting points. Ceramic oxide fibres are used both as insulation and as reinforcement material. The mostly known examples for oxide ceramic fibres are composed of oxides such as silica (SiO2), mullite (3AI2O32SiO2), alumina (AI2O3), and zirconia (ZrO2) having different characteristic properties.

[0118] Production of non-oxide fibres is difficult due to their high melting points and resistance to densification. Oxidation resistance tends to be their main deficiency. Examples are silicon carbide-based fibres. Silicon carbide (SiC) fibres have an excellent combination of high strength, modulus, and thermal stability, including good oxidation resistance and mechanical properties (compressive-tensile strength) at high temperatures. Silicon carbide-based fibres are generally applied as continuous fibre in ceramic matrix. This type of ceramic matrix composites (CMCs) is used in hot section of engines for power, etc.

[0119] In the present description, with “aramid fibres” is meant aromatic polyamide fibres, which are a class of heat-resistant and strong synthetic fibres. The chain molecules in the fibres are highly oriented along the fibre axis. As a result, a higher proportion of the chemical bond contributes more to fibre strength than in many other synthetic fibres. Aramids have a very high melting point (>500 °C) and are spun from liquid crystalline solutions. “Aromatic” in the name refers to the presence of aromatic rings of six carbon atoms. In aramids these rings are connected via amide linkages each comprising a CO group attached to an NH group. Aramids are divided into two main types according to where the linkages attach to the rings: para-aramids and metaaramids. Numbering the carbon atoms sequentially around a ring, para-aramids have the linkages attached at positions 1 and 4, while meta-aramids have them at positions 1 and 3. That is, the attachment points are diametrically opposite each other in paraaramids, and two atoms apart in meta-aramids. In the present description, with “hemp fibres” is meant vegetable fibres that are generally based on arrangements of cellulose, often with lignin, derived from the hemp plant under the species Cannabis.

[0120] In the present description, with “flax fibres” is meant vegetable fibres that are extracted from the bast or skin of the stem of the flax plant (Linum usitatissimum L).

[0121] In the present description, with “sisal fibres” is meant vegetable fibres that are derived from the plant under the species Agave Sisalana.

[0122] Whichever the reinforcement fibre chosen, the fibres should have a suitable size applied to them. The size is selected to protect the fibre during handling, but also to provide good adhesion to the thermoplastic matrix polymer, thereby increasing the strength of the UD tape. The size on the fibre has to be selected according to the thermoplastic matrix material.

[0123] In the present description, with “distribution of fibres throughout the tape” is meant the distribution of the fibres over the width of the fibre-reinforced thermoplastic UD tape transverse to the longitudinal direction (i.e., machine direction) of the fibres. A relatively uneven distribution may result in the UD tape having undesirable and / or unpredictable structural characteristics. A relatively even distribution means that the continuous unidirectionally aligned fibres are evenly distributed in the UD tape and provides a UD tape having desirable and / or predictable structural characteristics. Preferably, the distribution of the fibres is relatively even.

[0124] In the present description, with “close to surface” is meant that the average distance between the top or bottom surface of the fibre-reinforced thermoplastic UD tape and the fibres embedded in the fibre-reinforced thermoplastic UD tape is between 5 and 20 % of the thickness of the fibre-reinforced thermoplastic UD tape.

[0125] Preferably, the unidirectionally aligned reinforcing fibres have a diameter of between 4 and 20 pm, preferably between 8 and 13 pm and / or a length of at least 100 mm, preferably at least 1000 mm. The fibres of this specific diameter and / or length provide sufficient strength to the UD tape over the whole length (in the longitudinal direction) of the UD tape. Furthermore, it also allows the preparation of a fibre-reinforced thermoplastic UD tape having a relatively low thickness.

[0126] Preferably, the unidirectionally aligned reinforcing fibres are aligned parallel to each other in the longitudinal direction. This improves the strength of the UD tape over the whole length (in the longitudinal direction) of the UD tape while maintaining the flexibility of the UD tape. In the present description, with “longitudinal direction” is meant the machine direction in which the UD tape is produced.

[0127] In another embodiment, the UD tape comprises between 10 and 74 wt.% of the unidirectionally aligned reinforcing fibres, between 25 and 89 wt.% of the thermoplastic matrix material, between 1 and 10 wt.% of the at least one compatibilizer, and between 0 and 10 wt.% of at least one additive, based on the total weight of the UD tape. The higher the fibre content in the UD tape, the higher the performance of the UD tape. However, a too high fibre content may lead to insufficient impregnation and / or problems with the mechanical strength of the UD tape, e.g., the integrity of the UD tape becomes poor, resulting in the UD tape falling apart.

[0128] The thermoplastic matrix material of the fibre-reinforced thermoplastic UD tape comprises one or more compatibilizers. In the present description, with “compatibilizers” is meant an additive that aids in the compatibility between different thermoplastic polymers. Most polymer pairs are immiscible and form domains, where the interface would be weak. Compatibilizer are polymers that have functional groups similar to both non-polar and polar polymers. Without them, immiscible polymers in the molten state when shearing is stopped would segregate into two layers like oil and water. One or more suitable compatibilizers are added to improve compatibility of the non-polar polymer(s) with the polar-polymer(s).

[0129] Block copolymers comprise of two or more homopolymer subunits linked by covalent bonds. They are made up of blocks of different polymerized monomers. Examples are diblock copolymers, which have two distinct blocks (e.g., ~A-A-A-A-A-B-B-B-B-B~), and triblock copolymers, which have three distinct blocks (e.g., ~A-A-A-A-B-B-B-B-C- C-C-C-).

[0130] Graft copolymers are segmented copolymers with a linear backbone of one chain segment and randomly distributed branches of another chain segment, which is structurally different from the former chain segment forming the linear backbone.

[0131] A terpolymer is a copolymer that contains three types of repeat units. Hence, a terpolymer is formed from the polymerization of three different monomers. The resulting polymer chain contains repeating units of all three monomers. An example is a random terpolymer of ethylene, acrylic ester, and glycidyl methacrylate.

[0132] In an embodiment, the compatibilizer is selected from the group consisting of block copolymers, graft copolymers, and terpolymers, for example, a styrene ethylene I butylene styrene triblock copolymer grafted with maleic anhydride (SEBSg-MA), a polypropylene-grafted maleic anhydride (PP-g-MA), a linear low density polyethylene grafted maleic anhydride (LLDPE-g-MA), a PP / ethylene-propylene copolymer, or mixtures of one or more thereof.

[0133] Additives

[0134] The thermoplastic matrix material may comprise one or more additives. The additive(s) are selected from the group consisting of adhesion-enhancing copromotors, stabilizers, impregnation agents, lubricants, antioxidants, and flame retardants.

[0135] In the present description, with “additives” is meant an additive for the thermoplastic polymers used that may be present in the thermoplastic matrix material. Additives are often used to improve the properties of the thermoplastic polymers.

[0136] In the present description, with “adhesion-enhancing copromotors” is meant a substance, being a copromotor, that enhances the adhesion of the thermoplastic matrix material and the reinforcing fibres dispersed within the thermoplastic matrix material. In an embodiment, the UD tape comprises an adhesion-enhancing copromotor as an additive. The adhesion-enhancing copromotor helps the thermoplastic matrix material bond with the reinforcing fibres dispersed in said matrix material.

[0137] In the present description, with “stabilizers” is meant an additive that aids in the prevention of heat, oxidation, and chemical degradation of the fibre-reinforced thermoplastic composite, specifically the thermoplastic matrix. Examples include phenolic alkylene dicarboxylates that provide stabilization against degradation with a reduced tendency to yellow discoloration and improved melt, processing performance over an extended period of time, aluminium phosphate or aluminium silicate treated with polyethylene glycol that improves the colour stability of the material, and zinc oxide or lead stabilizer that also improves the colour stability and furthermore improves the thermal stability of POK and its processing temperature window.

[0138] In the present description, with “impregnation agent” or "impregnating agent” is meant a material that is compatible with the thermoplastic polymer to be reinforced and may even be soluble in said polymer. The skilled person can select suitable combinations based on general knowledge, and may also find such combinations in the art.

[0139] Suitable examples of impregnating agents include low molar mass compounds, for example low molar mass or oligomeric polyurethanes, polyesters such as unsaturated polyesters, polycaprolactones, polyethylene terephthalate, poly(alpha-olefins), such as highly branched polyethylenes and polypropylenes, polyamides, such as nylons, and other hydrocarbon resins.

[0140] Preferably, the impregnating agent is non-volatile, and / or substantially solvent-free. In the context of the present invention, non-volatile means that the impregnating agent has a boiling point or range higher than the temperatures (about 230-240 °C) at which the polymer’s melt impregnation is conducted over the reinforcing fibres. In the context of present invention, "substantially solvent- free" means that impregnating agent contains less than 10 wt.% of solvent, preferably less than 5 wt.% of solvent based on the impregnating agent. In a preferred embodiment, the impregnating agent does not contain any organic solvent. In the present description, with “lubricants” is meant a material that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. Examples are stearamides and stearates, such as EBS, calcium stearate or magnesium stearate.

[0141] In the present description, with “antioxidants” is meant a compound that inhibits oxidation, a chemical reaction that can produce free radicals and cause chain scission. The antioxidant additive may comprise one, two or more phenolic groups. These phenolic antioxidant additives may be sterically hindered phenolic additives. Examples are tris(2,4-di-tert-butylphenyl)phosphite, commercially available as Irgafos 168, and octadecyl-3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate, available from BASF as Irganox 1076.

[0142] In the present description, with “flame retardants” is meant a material that is activated by the presence of an ignition source and is intended to prevent or slow the further development of ignition by a variety of different physical and chemical methods. They may be added as a copolymer during the polymerisation process, or later added to the polymer at a moulding or extrusion process or applied as a topical finish. Examples are minerals such as aluminium hydroxide (ATH), magnesium hydroxide (MDH), huntite and hydromagnesite, organohalogen compounds such as organochlorines, organobromines, and polymeric brominated compounds, organophosphorus compounds such as organophosphates, phosphonates, and phosphinates, and organic compounds such as carboxylic acid and dicarboxylic acid.

[0143] Unidirectional (UD) tapes

[0144] Preferably, the fibre-reinforced thermoplastic UD tape has a width of at least 2 cm, preferably between 5 and 20 cm, more preferably between 8 and 15 cm and / or has a thickness of between 0.10 and 0.80 mm, preferably between 0.15 and 0.50 mm, more preferably between 0.25 and 0.35 mm. A UD tape of these dimensions provides optimal balance between flexibility and applicability and strength. This makes them particularly suitable for the production of complex component shapes. Furthermore, the low thickness of the UD tape allows that the reinforced thermoplastic pipes only increase a very small amount in thickness.

[0145] In the present description, with “unidirectional (UD) tape” is meant a tape that comprises endless fibre-reinforced tapes of different widths with unidirectionally aligned reinforcing fibres. In UD tapes, fibres, such as glass fibres or carbon fibres, are embedded so ideally in a thermoplastic matrix that completely new possibilities arise in the production of components. Despite their low thickness, UD tapes have a high level of stability and are also particularly light. In addition, UD tapes can be processed efficiently and, depending on the combination and additives present, are flame retardant. Furthermore, the UD tape is collected and stored on rolls and hence it can be cut to length and width according to the application. Another important property of thermoplastic UD tape is the possibility of recycling.

[0146] Conversion from thermoplast to thermoset

[0147] For some applications, it is desirable to convert the thermoplastic material to a thermoset material. This can for example be done via heat-induced cross-linking. The cross-linking of the thermoplastic matrix material is performed after production (shaping or moulding) of the article comprising the fibre-reinforced thermoplastic UD tape. The conversion from thermoplastic to thermoset works only with a few polymers.

[0148] In an embodiment, the UD tape comprises at least one cross-linked non-polar polymer and / or at least one cross-linked polar polymer. This is beneficial, as the UD tape is more resistant to creep, and this allows for the use above the lowest melting point of the polymers in the UD tape for short periods of time.

[0149] Method of manufacturing fibre-reinforced thermoplastic UD tape

[0150] There exist various methods for producing fibre-reinforced thermoplastic UD tapes comprising non-polar and polar polymers. One potential manufacturing method is combining melt compounding with melt impregnating.

[0151] In step 1) of the method of manufacturing the fibre-reinforced thermoplastic UD tape, i.e., the providing of the thermoplastic matrix material comprising the non-polar and polar polymers and the compatibilizer, the detection of the co-continuous morphology in the blend of polar and non-polar polymers can be made empirically by the skilled person by microscopy, specifically Scanning Electron Microscopy (SEM).

[0152] The method of establishing the co-continuous range for a polymer combination is described here. First, as a starting point, the two polymers are blended by melt extrusion at approximately 50:50 by volume, without any compatibilizer. Extrusion without the compatibilizer aids in microscopic visualisation as the domain boundaries are sharper. The composition range by weight or volume where the co-continuous morphology is formed is mapped by changing the weight or volume ratios. Beyond these upper and lower composition boundaries, the polymers will form droplets of one in the other (‘island in the sea’ morphology); these composition ranges must be avoided for the purpose of this invention. Unless the polymers are self-compatibilizing, sharp domain boundaries reduce mechanical strength and impact resistance. Further, such a morphology is unstable in the melt and on cessation of shearing would lead to coalescence of domains of each polymer, leading to two melt layers. Hence, secondly, a composition in the range determined for the co-continuous morphology is selected and a co-compatibilizer is added, typically at 5-10% by weight. This improves the mechanical properties and stabilises the melt against rapid de-segregation. A good compatibilizer would lead to the domain boundaries seen in the microscope to become fuzzy.

[0153] Besides the classical co-continuous structure (see Fig. 1 d of the article of Petra Pbtschke and D.R. Paul, ‘Formation of Co-continuous Structures in Melt-Mixed Immiscible Polymer Blends’, 2003, Journal of Macromolecular Science Part C- Polymer Reviews No. 1 (1):87-141 , DOI:10.1081 / MC-120018022), structures other than the ‘island in the sea morphology’ can also be formed such as ‘matrix with fibres’ and ‘lamellar structure’ (see Fig. 1 b and 1 c of the above-referenced article). Both these morphologies are included for this invention.

[0154] According to Pbtschke and Paul, the most effective melt mixing to develop co- continuous structures is when the viscosities and the volume fractions of the two polymers are equal (equi volume, equi viscous). Equal-melt volume fractions maximize the opportunity for maintaining connectivity since neither component is present in a minor amount.

[0155] In an embodiment, compositions of a non-polar polymer and a polar polymer centring around equi volumes and / or equi viscosity are used. Besides seeking equi viscosity, low melt viscosity for the blend (about 70 Pa s) provides good impregnation of the glass fibres. This means selecting two polymers with low melt viscosities of about 70 to 200 Pa s.

[0156] The melt compounding of the thermoplastic matrix material obtained in step 1) of the method according to the second aspect is preferably done at a temperature from about 220 °C to about 360 °C, or between about 250 to about 330 °C, or between about 270 to about 300 °C. It is preferred that the melt compounding temperature is done at a temperature that is least 5 °C, preferably 10 °C, more preferably 15 °C above the melting point of higher melting polymer in the polymer blend.

[0157] Depending on the polar polymer type, after making the polymer blend for the thermoplastic matrix material, the viscosity of the polymer blend is measured at different drying times of the polar polymer and this generates a calibration curve. Based on this calibration curve, the drying time to reach desired level of viscosity of the polar polymer (and thus, resulting polymer blend) is determined. It may vary between no drying to a couple of hours, such as 3 or 5 hours.

[0158] The contacting of the unidirectionally aligned reinforcing fibres obtained in step 3) with the molten thermoplastic matrix material obtained in step 2) of the method according to the second aspect may be done for example by melt impregnation.

[0159] In an embodiment of the second aspect of the present invention, the method of manufacturing the UD tape may comprise a step 0) of drying the at least one polar polymer for 3 to 5 hours at a temperature of 100 to 150 °C prior to step 1).

[0160] Use In an embodiment of the third aspect of the present invention, the fibre-reinforced thermoplastic UD tape according to the first aspect or manufactured according to the second aspect is used for an RTP configured for transporting of hydrocarbon fluids, for example aromatic hydrocarbon fluids, CO2, and H2S. In the present description, with “fluids” is meant liquids, such as water, and gases, such as butane.

[0161] In the present description, with “reinforced thermoplastic pipe (RTP)” is meant a multilayer pipe of thermoplastic material that is reinforced. Other names used are Flexible Composite Pipes, Thermoplastic Composite Pipes, Flexible Flowline, Flexible Line Pipe, Spoolable Reinforced Plastic Line Pipe, Flexible Reinforced Pipe, Reinforced Line Pipe or Spoolable Composites. For offshore use, other names include Offshore Flexibles or Flexible Umbilical Risers. According to the present invention, an RTP includes from the centre of the RTP to the periphery of the RTP at least the following layers: a thermoplastic inner liner, a reinforcement layer, and a thermoplastic outer jacket. The outer jacket provides protection of the reinforcing UD tape windings from external mechanical damage.

[0162] In the present description, with “UD tape windings” is meant the fibre-reinforced thermoplastic UD tape that is provided on (wound around) the thermoplastic inner liner. With “fibre-reinforced thermoplastic UD tape” is meant the thermoplastic UD tape provided with fibres that reinforce the thermoplastic UD tape.

[0163] In the present description, with “thermoplastic inner liner” is meant the inner layer of the RTP that is made of a thermoplastic material, such as PVDF, PPS, POK, PA-11 , PA-12, PE, and PP. To prevent damage to the RTP, the thermoplastic inner liner must be made from a material that is resistant to chemicals, such as gaseous or liquid hydrocarbons, which are transported through the RTP. Preferably, the thermoplastic inner liner is also resistant to high temperatures. With “high temperatures” is meant the temperature of the fluids that flow through the RTP, being in the range of above 85 °C, preferably above 90 °C, more preferably above 100 °C, even more preferably above 115 °C. In the present description, with “reinforcement layer” is meant the layer between the thermoplastic inner liner and the thermoplastic outer jacket that is formed by the fibre- reinforced thermoplastic UD-tape. The reinforcement layer provides additional strength to the pipe, hence the name “reinforced thermoplastic pipe (RTP)”.

[0164] In the present description, with “thermoplastic outer jacket” is meant the outer jacket, layer, or cover of the RTP that is made of a thermoplastic material, such as PDVF, PPS, POK, PA-11 , PA-12, PE, and PP. To prevent damage to the RTP, the thermoplastic outer jacket must be made from a material that is resistant to impact and one or more of the following, UV light, high temperatures, water. With “high temperatures” is meant the temperature of the fluids that flow through the RTP, being in the range of above 85 °C, preferably above 90 °C, more preferably above 100 °C, even more preferably above 115 °C.

[0165] In addition, the thermoplastic outer jacket must be made of a material that is sufficiently strong to prevent damage from the surroundings to the RTP.

[0166] Thus, the RTP according to the fourth aspect of the present invention comprises from its centre to its periphery:

[0167] - a thermoplastic inner liner;

[0168] - a reinforcing layer, comprising one or more layers of a fibre-reinforced thermoplastic unidirectional (UD) tape arranged for use in an RTP configured for transporting fluids, wherein the UD tape comprises a thermoplastic matrix material and unidirectionally aligned reinforcing fibres dispersed within the thermoplastic matrix material, wherein said unidirectionally aligned reinforcing fibres extend in a longitudinal direction of the UD tape,

[0169] - a thermoplastic outer jacket, wherein the thermoplastic matrix material comprises: at least one non-polar polymer, at least one polar polymer, and at least one compatibilizer, wherein the thermoplastic matrix material comprises a non-polar polymer to polar polymer volume ratio of from 40:60 to 70:30. BRIEF DESCRIPTION OF DRAWINGS

[0170] The present invention is described hereinafter with reference to the accompanying drawings in which embodiments of the present invention are shown and in which like reference numbers indicate the same or similar elements. The invention is in no manner whatsoever limited to the embodiments disclosed therein.

[0171] Figure 1 shows a schematic representation of the morphology of a polymer blend in different ratios;

[0172] Figure 2 shows scanning electron microscopy (SEM) images showing the con- continuous phase of a polymer blend used in a thermoplastic matrix material according to the present invention;

[0173] Figure 3 shows a graph wherein the mass change is plotted against the time for different UD tape samples indication the moisture-uptake of the UD tape samples.

[0174] DETAILED DESCRIPTION OF DRAWINGS

[0175] Fig. 1 shows schematic representations of three blends of a non-polar polymer A (dark) and polar polymer B (light), each blend having a different polymer A to polymer B ratio. The two polymer are not miscible and after mixing, they separate into domains.

[0176] In the picture on the left, the polymer blend comprises 20 vol.% of polymer A and 80 vol.% of polymer B. Such a volume ratio results in the formation of islands of polymer B in the “sea” of polymer A.

[0177] In the picture on the right, the polymer blend comprises 80 vol.% of polymer B and 20 vol.% of polymer A. Such a volume ratio results in the formation of islands of polymer A in the “sea” of polymer B.

[0178] The picture in the middle shows a polymer blend having a co-continuous morphology. The polymer blend contains equal amounts of polymers A and B (both 50 vol.%) and after mixing, the form the morphology as shown in the picture in the middle of Fig. 1 . Fig. 2 shows scanning electron microscopy SEM) images of a thermoplastic polymer composite of PP (having a density of 0.91 g / cm3) and PET (having a density of 1.4 g / cm3). The two polymers were melt compounded. The thermoplastic polymer composite comprises 47 wt.% PP and 47 wt.% PET, which corresponds to a PP : PET volume ratio of 52 : 35 cm3. (The remaining 6 wt.% in the thermoplastic blend were a compatibilizer and additives, such as an adhesion improved copromotor.)

[0179] In the SEM images of Fig. 2, the white parts are the PET polymer and the dark parts are the PP polymer. It is clearly shown that the PP and PET form a co-continuous structure and due to the compatibilizer, the interface between the light and dark domains is fuzzy. This means that good adhesion between the two polymer types was established.

[0180] The graph in Fig. 3 shows the mass change over time for samples of different UD tapes. The dotted black line corresponds to a UD tape comprising a PE matrix having glass fibres (GF-PE). The solid black line with the circular dots corresponds to a UD tape comprising a PP matrix having glass fibres (GF-PP). The solid grey line with the square dots corresponds to a UD tape comprising a PP / PET matrix having glass fibres (GF-PP / PET), which is according to the present invention.

[0181] EXAMPLES

[0182] The present invention is further elucidated based on the examples below which are illustrative only and not considered limiting to the present invention. Those skilled in the art will readily recognize a variety of noncritical parameters that can be changed or modified to yield essentially the same results.

[0183] PP pellets (BJ356AI, a heterophasic copolymer characterized by very high flow, and optimum combination of high stiffness and impact strength; Melt Flow Rate (230 °C / 2.16 kg) 100 g / 10min measured according to ISO 1133; maleated) and PET pellets (a non-commercial grade from SABIC with intrinsic viscosity of 0.58 dL / g) were provided and melt compounded in an extruder at 270 °C, which is above the melting point of the higher melting polymer, viz. PET. The weight ratios were 47:47. To the blend, 5% of a compatibilizer (Lotader AX8900, from SK Chemicals) and 1 % of Orevac CA 100 (improves adhesion to glass fibres) were added. Prior to the step of melt compounding of the PP and PET, the PET was dried for 3 to 5 hours at 150 °C.

[0184] In the present description, with ‘maleated’ is meant that the polymer is treated with maleic anhydride.

[0185] For the impregnation of glass fibre tows, the zero-shear viscosity of the polymer blend should be low. The molecular weights of both the PP and PET were selected such that the melt viscosity of the blend was in the range 70 to 100 Pa s. The lower melt viscosity helps improving the impregnation quality, e.g., fibres are better wetted (surrounded by the thermoplastic resin).

[0186] These PP:PET pellets were finally used for making the GF-PP / PET tape. Ingredients and proportions, as provided in Table 1 , used to make compatibilized PP:PET is 1.47 : 1 by weight (which is a volume ratio of about 60:40). By volume, it is approximately 0.95 : 1 PP:PET.

[0187] Table 1.

[0188] Notes on Table 1 :

[0189] 1. Compatibiliser Lotader AZ 8900 gives finer domain morphology; without it, delamination with the 50:50 is likely on bending. Also without compatibilizer, second melting would lead to coalescence of domains. Hence, the compatibilizer must be used. 2. The Overac CA 100 is a coupling agent (adhesion-enhancing copromotor) for PP and glass fibres.

[0190] 3. The low l,V. PET was dried for 3 hours at 150 °C before extruding with the other ingredients.

[0191] As comparatives, polymer melts of 100% PP and 100% PE were prepared.

[0192] As reinforcing fibres, glass fibres (E-CR grade, 17 pm diameter, corrosion resistant grade) were used. The glass fibres were impregnated with the thermoplastic matrix material via extrusion of a molten web over the fibres with pulling over impregnation

[0193] Immersion of polymer materials in water

[0194] The moisture-uptake was compared of a UD tape prepared with a polypropylene matrix with glass fibres (GF-PP - Comparative Example 1), a UD tape prepared with a polyethylene matrix with glass fibres (GF-PE - Comparative Example 2), and a UD tape prepared with a polypropylene I polyethylene terephthalate matrix with glass fibres (GF-PP / PET) (Example 1).

[0195] As said, Fig. 3 shows the moisture uptake when the various samples are immersed in water with pH 5, at 93 °C for 10 and 77 days. From Fig. 3 it becomes clear that the Example 1 gives a lower moisture uptake compared to the Comparative Examples 1 and 2. The respective GF-PE and GF-PP samples take up about 3 and 2 times as much moisture compared to the GF-PP / PET sample. Since water may have a negative impact on the mechanical strength of the glass fibres, the GF-PP / PET UD tape is advantageous for RTPs carrying oil fluids due to its lower moisture uptake.

[0196] A further advantage of a PP-PET blend with co-continuous morphology is that its flow properties are dominated by the higher melting non-polar polymer. Thus, a moulded bar of the PP-PET with continuous morphology can be heated to 200°C (that is, well beyond the melting point of PP), and it will retain its shape. The same property is extended to a UD tape with the PP-PET matrix with co-continuous morphology, where the presence of the GF further reduces flow, facilitating short term high-temperature use of tapes and laminates. This is not possible with PP or PE where the bar would melt and become a transparent liquid at 200°C.

[0197] Mechanical properties of UD laminates

[0198] In this example, layers of GF-PP / PET UD tapes were laminated (Example 2) by compression moulding and compared with similar laminates made of GF-PP UD tapes (Comparative Example 3).

[0199] For Example 2, PP and PET pellets were provided and melt compounded in an extruder at 270°C which is above the melting point of the higher melting polymer, viz. PET. The PP was a high MFR (melt flow rate of 100 g / 10min). The molecular weights were selected so that the melt viscosity of the blend was in the range 70-100 Pa s at the high shear rates used for extrusion. The melt viscosity of both polymers was selected to be in the range of 70-100 Pa s. The impregnation of the GF with PP-PET was successful; the glass fibre content was 60 wt.% and the UD tape thickness was 300 pm.

[0200] The weight ratio of PP:PET was 47:47. To the blend, 5 wt.% of a compatibilizer (Lotader AX8900, from SK Chemicals) and 1 wt.% of Orevac CA 100 (for improving adhesion to glass fibres) were added. Prior to the step of melt compounding of the PP and PET, the PET pellets were dried for 3 to 5 hours at 150 °C. The drying time was adjusted to get the right melt viscosity for the PET. The melt compounded PP-PET blend with compatibilizer was stranded and pelletised. Microscopic examination had shown such a composition results in a co-continuous morphology. The compatibilized PP-PET pellets were then re-extruded at 280°C for impregnation into the glass fibres, to make the UD tape.

[0201] The GF-PP-PET tapes made as above were transformed to 3 mm thick laminates. O-direction UD laminates with ~3 mm thickness were produced from the UD tapes (10 plies each of ~300 pm were stacked and compression moulded at 270 °C). The mechanical properties of the laminates were tested. Comparative Example 3 used GF-PP UD tape with 63 wt.% GF, to make the laminates. The GF-PP laminates were moulded at 230 °C.

[0202] Mechanical testing was performed on the laminate, to obtain the inter-laminar shear strength (ILSS), which is a key material requirement for the composite.

[0203] The ILSS was measured using a composite bar with dimensions 30 mm x 10 mm x 3 mm (length x width x depth). The bending modulus and strength were measured using a composite bar with dimensions 80 mm x 10 mm x 3 mm. The results are shown in Table 2 below.

[0204] Table 2.

[0205] The ILSS value of the GF-PP / PET laminate was 25.8 MPa, which indicates a very good laminate quality. It was higher than the ILSS of the laminate from the GF-PP tape (23.68 MPa). From these results it becomes clear that the mechanical strength of the UD tape according to the present invention is at least similar to the mechanical strength of conventional UD tapes.

[0206] Furthermore, the melt viscosity of the PET melt decreased over time due to the absorption of moisture. With the PP melt and the PP-PET bend, this did not occur.

[0207] Modifications and additions to the methods and examples disclosed above are obvious to those skilled in the art and covered by the scope of the appended claims. Embodiments and examples of the first aspect of the present invention are also applicable to the second or further aspects of the present invention.

[0208] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope thereof. The scope of the present invention is defined by the appended claims. One or more of the objects of the invention are achieved by the appended claims.

Claims

CLAIMS1. A fibre-reinforced thermoplastic unidirectional (UD) tape arranged for use in a reinforced thermoplastic pipe (RTP) configured for transporting fluids, wherein the UD tape comprises a thermoplastic matrix material and unidirectionally aligned reinforcing fibres dispersed within the thermoplastic matrix material, wherein said unidirectionally aligned reinforcing fibres extend in a longitudinal direction of the UD tape, characterized in that the thermoplastic matrix material comprises: at least one non-polar polymer, wherein the at least one non-polar polymer is selected from a group comprising a polyolefin, such as polyethylene (PE), polypropylene (PP) and polymethylpentene (PMP), polytetrafluoroethylene (PTFE), polyphenylene sulphide (PPS), polyphenylene oxide (PPO), and a combination of two or more thereof; at least one polar polymer, wherein the at least one polar polymer is selected from a group comprising a polyester, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN) and liquid-crystal polyester (LCP), a polyamide, such as nylon 11 (PA11) and nylon 12 (PA12), aliphatic polyketone (POK), aromatic polyketone (PEK) such as a polyaryletherketone (PAEK), for example polyetheretherketone (PEEK) and polyetherketoneketone (PEKK), polyurethane (PU), polyether sulfone (PES), polyetherimide (PEI), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polycarbonate (PC), and a combination of two or more thereof, and at least one compatibilizer, wherein the thermoplastic matrix material comprises a non-polar polymer to polar polymer volume ratio of from 40:60 to 70:30.

2. The fibre-reinforced thermoplastic UD tape according to claim 1 , wherein the non-polar polymer to polar polymer volume ratio is from 45:55 to 60:40, preferably 45:55 to 55:45.

3. The fibre-reinforced thermoplastic UD tape according to claim 1 or 2, wherein the at least one non-polar polymer is selected from the group consisting of a polyolefin, such as polyethylene (PE), polypropylene (PP) and polymethylpentene (PMP), polytetrafluoroethylene (PTFE), polyphenylene sulphide (PPS), polyphenylene oxide (PPO), and a combination of two or more thereof, preferably a polyolefin, such as polyethylene (PE) and polypropylene (PP).

4. The fibre-reinforced thermoplastic UD tape according to any of the preceding claims, wherein the at least one polar polymer is selected from the group consisting of a polyester, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN) and liquid-crystal polyester (LCP), a polyamide, such as nylon 11 (PA11) and nylon 12 (PA12), aliphatic polyketone (POK), aromatic polyketone (PEK) such as a polyaryletherketone (PAEK), for example polyetheretherketone (PEEK) and polyetherketoneketone (PEKK), polyurethane (PU), polyether sulfone (PES), polyetherimide (PEI), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polycarbonate (PC), and a combination of two or more thereof, preferably a polyester, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN) and liquid-crystal polyester (LCP).

5. The fibre-reinforced thermoplastic UD tape according to any of the preceding claims, wherein the at least one non-polar polymer is a polyolefin and the at least one polar polymer is a polyester, preferably the at least one non-polar polymer is polypropylene (PP) and the at least one polar polymer is polyethylene terephthalate (PET) or polybutylene terephthalate (PBT).

6. The fibre-reinforced thermoplastic UD tape according to any of the preceding claims, wherein the at least one compatibilizer is selected from the group consisting of block copolymers, graft copolymers, and terpolymers, for example, a styrene ethylene I butylene styrene triblock copolymer grafted with maleic anhydride (SEBSg- MA), a polypropylene-grafted maleic anhydride (PP-g-MA), a linear low density polyethylene grafted maleic anhydride (LLDPE-g-MA), a PP / ethylene-propylene copolymer, or mixtures of one or more thereof.

7. The fibre-reinforced thermoplastic UD tape according to any of the preceding claims, further comprising an adhesion-enhancing copromotor as an additive.

8. The fibre-reinforced thermoplastic UD tape according to any of the preceding claims having a width of at least 2 cm, preferably between 5 and 20 cm, more preferably between 8 and 15 cm, and / or having a thickness of between 0.10 and 0.80 mm, preferably between 0.15 and 0.50 mm, more preferably between 0.25 and 0.35 mm.

9. The fibre-reinforced thermoplastic UD tape according to any of the preceding claims, wherein the thermoplastic matrix material has: a melt mass-flow rate (MFR) of at least 60 g / I Omin, preferably at least 100 g / 10min, more preferably at least 150 g / 10min, most preferably between 60 and 200 g / 10min measured at 240 °C with a load of 2.16 kg according to ASTM D1238-23; and / or a viscosity of at most 100 Pa s, preferably at most 70 Pa s, measured at 240 °C according to ISO 6721.

10. The fibre-reinforced thermoplastic UD tape according to any of the preceding claims, wherein the UD tape comprises between 10 and 74 wt.% of the unidirectionally aligned reinforcing fibres, between 25 and 89 wt.% of the thermoplastic matrix material, between 1 and 10 wt.% of the at least one compatibilizer, and between 0 and 10 wt.% of at least one additive, based on the total weight of the UD tape.

11. The fibre-reinforced thermoplastic UD tape according to any of the preceding claims, wherein the unidirectionally aligned reinforcing fibres are selected from the group consisting of glass fibres, carbon fibres, basalt fibres, ceramic fibres, aramid fibres, hemp fibres, flax fibres, sisal fibres, and one or more combinations thereof, preferably glass fibres, carbon fibres, and / or basalt fibres.

12. The fibre-reinforced thermoplastic UD tape according to any of the preceding claims, wherein the unidirectionally aligned reinforcing fibres have a diameter ofbetween 4 and 20 m, preferably between 8 and 13 pm and / or a length of at least 100 mm, preferably at least 1000 mm.

13. The fibre-reinforced thermoplastic UD tape according to any of the preceding claims, wherein the UD tape comprises at least one cross-linked non-polar polymer and / or at least one cross-linked polar polymer.

14. The fibre-reinforced thermoplastic UD tape according to any of the preceding claims, wherein the non-polar polymer is polypropylene (PP) and the polar polymer is polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), wherein the non-polar polymer to polar polymer volume ratio is from 45:55 to 55:45, and wherein the viscosity of the thermoplastic matrix material is at most 70 Pa s.

15. A method of manufacturing a fibre-reinforced thermoplastic unidirectional (UD) tape according to any of the preceding claims, comprising the steps of:1) providing a thermoplastic matrix material comprising at least one non-polar polymer, at least one polar polymer and at least one compatibilizer;2) melt compounding the thermoplastic matrix material obtained in step 1) in an extruder, preferably at 230 to 360 °C, to obtain a molten thermoplastic matrix material;3) unidirectionally aligning reinforcing fibres;4) contacting the unidirectionally aligned reinforcing fibres obtained in step 3) with the molten thermoplastic matrix material obtained in step 2) and subsequently consolidating to obtain a fibre-reinforced thermoplastic UD tape.

16. A use of a fibre-reinforced thermoplastic unidirectional (UD) tape according to any of the claims 1-14 or manufactured according to the method according to claim 15 for a reinforced thermoplastic pipe (RTP) configured for transporting of fluids, preferably hydrocarbon fluids.

17. A reinforced thermoplastic pipe (RTP) comprising from a centre to a periphery: - a thermoplastic inner liner;- a reinforcing layer, comprising one or more layers of a fibre-reinforced thermoplastic unidirectional (UD) tape according to any of the claims 1-14 or manufactured according to the method according to claim 15; and- a thermoplastic outer jacket.

18. A reinforced thermoplastic pipe (RTP) comprising from a centre to a periphery:- a thermoplastic inner liner;- a reinforcing layer, comprising one or more layers of a fibre-reinforced thermoplastic unidirectional (UD) tape arranged for use in an RTP configured for transporting fluids, wherein the UD tape comprises a thermoplastic matrix material and unidirectionally aligned reinforcing fibres dispersed within the thermoplastic matrix material, wherein said unidirectionally aligned reinforcing fibres extend in a longitudinal direction of the UD tape, wherein the thermoplastic matrix material comprises: at least one non-polar polymer, at least one polar polymer, and at least one compatibilizer, wherein the thermoplastic matrix material comprises a non-polar polymer to polar polymer volume ratio of from 40:60 to 70:30; and- a thermoplastic outer jacket.

Images