GB2618926A

GB2618926A - Thermoplastic composite tape and pipe made therefrom

Info

Publication number: GB2618926A
Application number: GB2312013.2A
Authority: GB
Inventors: Stephen Boyce Gerard; Andrew Finney Nigel; Richard Turner Matthew
Original assignee: Hive Composites Ltd
Current assignee: Hive Composites Ltd
Priority date: 2020-06-15
Filing date: 2021-06-15
Publication date: 2023-11-22
Also published as: GB202108506D0; GB202219718D0; GB2597596A; GB202312013D0

Abstract

A thermoplastic composite tape comprising: longitudinal unidirectional reinforcing fibres making up 55-75% of the weight of the tape embedded in a supporting polymer; a styrenic thermoplastic rubber based 100% solid hot melt pressure sensitive adhesive, the adhesive coating at least one side of the thermoplastic composite tape. The reinforcing fibres maybe glass fibres, carbon fibres or aramid fibres and the supporting polymer maybe polypropylene, nylon, polyvinylidene fluoride or polyvinylidene difluoride, or polyetheretherketone. Both sides of the tape may have been surface treated with a corona or plasma treatment. A method of manufacturing a thermoplastic composite pipe is also included, comprising the steps of: taking an inner pipe liner around a first spool or extruding an inner pipe liner in line, aligning a plurality of tape wrapping heads in front of the pipe liner, passing the pipe liner through the plurality of tape wrapping heads, spooling the formed thermoplastic composite pipe around a second spool or cutting into desired lengths.

Description

Thermoplastic Composite Tape and Pipe Made Therefrom [1] The present invention relates to thermoplastic composite pipes and the production thereof More specifically, the invention relates to the production of spoolable thermoplastic composite pipes. Even more specifically, the present invention relates to thermoplastic composite pipes made using thermoplastic composite tapes coated in adhesive.

Background of the Invention

[2] Thermoplastic composites are highly versatile materials that have a wide range of practical uses in the modern world. In the field there are currently a number of material suppliers who make uni-directional fibre reinforced thermoplastic tape. The most common way they do this is on a continuous basis by passing the reinforcement through a die with a polymer then being extruded into the fibres. Other types of thermoplastic composite tapes also exist, which are widely used; these include multi-axial/woven fibre reinforced thermoplastic tapes, short fibre reinforced tapes and self-reinforced thermoplastic composite tapes. The tapes can be made in narrow or wide strips, which are then split into various widths.

[003] These thermoplastic composite tapes are then wrapped or laid in a predetermined pattern to form a structure such as a pipe or pressure vessel. The thermoplastic composite tapes are joined together by heating the tape surfaces, often via external radiation or heat such as hot gas/flame, infrared or a laser. The external heat melts the surfaces of the tape, which are consolidated together and allowed to cool to form a fused or bonded laminated structure.

[004] While this is an effective and efficient way of joining the tapes together, it has a major limitation. During the joining process, one has to apply heat or energy and then cool the product. If numerous layers are being laminated together, the heat build-up can be substantial and because the materials are insulators, it takes a while to cool. Hence, in the production of a thermoplastic composite pipe, the tapes are wrapped around an inner extruded liner and by the time several layers have been added, the heat build-up accumulated can cause the liner/pipe to collapse. To overcome this problem, it is common practice for the product to be made in a series of passes, giving the layers time to cool, or to apply additional air and/or water to the system to facilitate cooling.

10051 The heating and cooling equipment involved in this is expensive, and the speed of production is limited by the heating and cooling rates. For example, if someone were making a 24-layer thermoplastic composite pipe (TCP), they ideally would want 24 tape wrapping heads in a row and would simply wrap and fuse the 24 layers of tape to form the reinforced pipe. In reality, because of the build-up of heat and cooling, usually only 4 or 6 wrapping machines will be in line, and the pipe will be passed backwards and forwards through the wrapping machines either 6 or 4 times respectively.

1006] It is known in the field that TCPs can be created by simply wrapping unbonded tapes; using this method, however, it is extremely difficult, if not impossible, to control the positions of the tapes after spooling/unspooling the TCPs, which greatly reduces the structural integrity of the TCPs. Short-term properties such as tensile strength, for example, can drop around 17%.

10071 It is an object of the present invention to overcome this thermodynamic limitation in the process by applying an adhesive in a predetermined and controlled amount onto either one or both sides of thermoplastic composite tape. The surface of the tapes may or may not be surface treated (to improve adhesion) with corona, flame or plasma prior to applying the adhesive. In this way, the thermoplastic composite tapes can be wrapped or laid down at high speed at ambient temperature and there is no need for any additional heating or cooling. This means a product such as a 24-layer pipe could be made in a single pass at higher speed and reduced cost.

Statement of Invention

[8] According to a first aspect of the invention, there is provided a thermoplastic composite tape comprising longitudinal uni-directional reinforcing fibres making up 55-75% of the weight of the tape embedded in a supporting polymer. This could be a styrenic thermoplastic rubber-based, 100% solid, hot-melt, pressure-sensitive adhesive, with the adhesive coating at least one side of the thermoplastic composite tape.

[9] An embodiment of the first aspect wherein the reinforcing fibres are glass 15 fibres. The reinforcing fibres may alternatively be carbon fibres or aramid fibres.

[10] An embodiment of the first aspect wherein the supporting polymer is polyethylene. The supporting polymer may alternatively be polypropylene, nylon, polyetheretherketone, polyvinylidene fluoride or potninylickne difluoride.

[11] An embodiment of the first aspect wherein both sides of the tape have been surface treated such that the surface energy is over 50 dynes. The surface treatment is preferably corona treatment, but may be plasma or flame treatment.

[012] An embodiment of the first aspect wherein the adhesive is applied at 40g/m2.

[013] An embodiment of the first aspect wherein the adhesive has an elongation percentage before break of over 5%.

[014] An embodiment of the first aspect wherein the total weight of the thermoplastic composite tape is 450g/m2.

[015] According to a second aspect there is provided a method of manufacturing a thermoplastic composite pipe comprising the steps of: 1 taking an inner pipe liner around a first spool or extruding an inner pipe liner in line; 2. aligning a plurality of tape wrapping heads in front of the pipe liner, each wrapping head holding one of a plurality of adhesively coated thermoplastic composite tapes according to any one of claims 1 to 16; 3 passing the pipe liner through the plurality of tape wrapping heads, each wrapping head wrapping an adhesively thermoplastic tape around the pipe liner under tension at a predetermined angle; 4 adhesion occurring between the thermoplastic tapes and the pipe liner and then subsequent layers of thermoplastic composite tape layers to each other due to the tension and the pressure as the tape is wrapped, without any in-line heating required; spooling the now formed thermoplastic composite pipe around a second spool or cutting into desired lengths.

[016] An embodiment of the method of the second aspect wherein the thermoplastic composite pipe is spooled around the second spool, further comprising the step of passing the pipe back through the wrapping heads, the wrapping heads adding additional layers of adhesively coated thermoplastic composite tape. The predetermined angle which the thermoplastic composite tapes are wrapped may be 54°.

1017] An embodiment of the method of the second aspect comprising the final step of applying an external thermoplastic coating to the outer surface of the thermoplastic composite pipe.

10181 According to a third aspect of the invention, there is provided a thermoplastic composite pipe made from thermoplastic composite tapes according to the first aspect.

Brief description of the drawings

1017] The invention will be described in more detail, by way of example, with reference to the following drawings: 10181 Figure 1 depicts a generic thermoplastic composite tape; 10191 Figure 2 depicts a schematic for producing adhesive-coated thermoplastic composite tape; 10201 Figure 3 depicts a prior art schematic of producing a thermoplastic composite pipe; 1021] Figure 4 depicts a schematic for producing a thermoplastic composite pipe using adhesive-coated thermoplastic composite tape; 1022] I igure 5 depicts a simplified cross-section of a thermoplastic composite pipe made from adhesive-coated thermoplastic composite tapes.

Detailed Description

10231 Composite tapes in a general sense take the form as shown in Figure 1. This consists of reinforcing fibres embedded in a polymer matrix. The polymer matrix provides inler alia resistance from environmental factors and transfers load into the reinforcing fibres, which provide strength and stiffness to the composite. The composites can have varied properties dependent on the components chosen and the orientation angle, length and concentration of the fibres in relation to the polymer matrix. The tensile strength is one feature greatly affected by the fibre orientation angle, length and concentration. Self-reinforced composites (SRCs), or single-polymer composites, in which a polymer matrix is reinforced with oriented fibres and tapes, or particles of the same polymer, for example, highly drawn thermoplastics, increase the material's mechanical properties enormously.

1024] Many different reinforcing fibre materials are known to the skilled person and all have their own properties. The same is also true for the polymer matrix. The skilled person will be aware of these and will pick the appropriate materials, etc., for the specific purpose of the composite being created. Some common reinforcing fibres include glass, carbon and aramid. Some common polymers used include PE (polyethene), PE-RT (polyethene raised temperature resistance), PA (polyamide), and PVDF (polyvinylidene fluoride).

10251 These thermoplastic composite tapes are then wrapped or laid in a predetermined pattern to form a structure such as a pipe or pressure vessel. The thermoplastic composite tapes are joined together by heating the tape surfaces, often with external radiation or heat such as hot gas/flame, infrared or a laser. The external heat melts the surfaces of the tape, which are consolidated together and allowed to cool to form a fused or bonded laminated structure.

[26] The present invention aims to greatly reduce or eliminate the need for heating and to therefore reduce the time needed to be spent cooling during manufacture. To achieve this, one or both sides of the thermoplastic composite tape is coated with a layer of adhesive, or treated to have a high enough surface energy so that they can adhere together with greatly reduced heating requirements.

[27] A variety-of adhesives can be used; all have in common the ability of the adhesives to enable layers of thermoplastic composite tapes to be bonded or fused together, with a greatly reduced need for external heat/radiation. Or in a preferred embodiment, the need for external heat/radiation can be completely removed. The adhesives can be structural adhesives like epoxides, acrylics, etc., or they can be semi-structural adhesives, for example, hot-melt, pressure-sensitive adhesives; or suitable liquid or powder-coating adhesives known to the skilled person can be used. The adhesives can be one part, two part or contact adhesives such as epoxides, polyurethanes, acrylics or cyanoacrylates.

[28] In a preferred embodiment, pressure-sensitive adhesive is used to cover one or both sides of the thermoplastic composite tape. In a preferred embodiment, pressure-sensitive adhesive is used to cover one or both sides of the thermoplastic composite tape. Suitable pressure-sensitive adhesives might be based on acrylics or hot-melt, pressure-sensitive adhesives might be based on but not limited to polyolefins, polyamides or polyesters.

[29] In another embodiment, hot-melt, pressure-sensitive adhesives could be 25 used. An example is Pressen (RTM), but once again any suitable hot-melt, pressure-sensitive adhesive known to the skilled person can be used. Suitable liquid adhesives known to the skilled person can also be used.

[30] The adhesive is applied to one or both surfaces of the tape to provide complete or partial coverage (for example, strip coating) of the tape surface(s).

[31] trhe specific components of thermoplastic composites can vary widely 5 within the general definition; this is because the specific components and structure are specifically chosen for their physical properties, which help the thermoplastic composite fulfil its desired function.

[32] The present invention also encompasses a variety of different adhesives and application amounts dependent on the end product's desired properties Depending on the desired properties of the tape, the adhesive will be applied to one or both surfaces of the thermoplastic composite tape at a predetermined, controlled amount of weight per square metre. The various adhesives, the amounts applied, etc., help control features such as, but not limited to, bond strength, strain capacity, temperature performance and environmental resistance.

[33] To increase the bond strength between the adhesive and the thermoplastic composite tape, the thermoplastic composite tape surfaces can be treated to increase surface energy. Some example methods of surface treatment to achieve this include corona treatment, flame treatment, chemical treatment and plasma treatment. I Iowever, any suitable surface treatment known to the skilled person to increase the surface energy of the thermoplastic composite tape can be used.

[34] Figure 2 depicts a preferred embodiment for the production of adhesive-coated thermoplastic composite tape. It comprises the source of a chosen thermoplastic tape at 21. The tape is then optionally passed through a surface treatment area at 22 such as corona, plasma, flame, etc., to increase the surface energy of one or both surfaces of the thermoplastic composite tape. From there, the thermoplastic composite tape is then passed through an adhesive applicator at 23; this will fully or partially cover one or both sides of the thermoplastic composite tape with a predetermined adhesive and predetermined amount of adhesive. From the adhesive applicator at 23, the tape is then passed through a release film applicator at 24, and then finally the completed adhesive-coated thermoplastic composite tape is spooled at 25, ready for use. In the preferred embodiment the tapes are treated and coated offline before they are used for their final purpose. But it is possible to treat and coat the tapes in line.

[35] The adhesive-coated thermoplastic composite tape provides a composite tape which can be secured together without the need for large amounts of heat to fuse/weld the thermoplastic composite tapes together. It also increases the variety of polymer matrixes that can be used together when multiple thermoplastic tapes are used. For example, in the traditional method of making thermoplastic composite pipes, the polymer matrix needs to be the same/similar polymer for a good-quality bond when fusing/welding together. The use of an adhesive allows for a wider range of polymers to be used.

[36] As well as the improved efficiency due to the reduced/removed requirement for heat, a wider variety of polymer matrixes can be used. When specifically 20 creating thermoplastic composite pipes, the use of adhesive-coated thermoplastic composite tape provides another advantage.

[37] The presence of pliable adhesive interlayers between the thermoplastic composite tapes aid in the spooling/unspooling of the pipe. This minimises any loss in pressure performance. This is because the pliability of the adhesive increases the ability to control the angles of the fibre reinforced thermoplastic composite tapes. The tapes are typically wound onto the pipe at +/-54° and it is important that after spooling and unspooling the pipe off the drum, the tapes remain as close to +/-54 as possible.

1038] During the process of spooling and unspooling, the tapes will 'want' to slip relative to each other as the pipe is spooled around a drum, especially at larger pipe diameters. The tapes on the inside diameter will be urged to compress and move more towards the hoop direction, and the tapes on the outer diameter stretch and go to a more longitudinal lengthways direction.

10391 After the spooled pipe drum is shipped to a site and deployed, which can take weeks, it is important that the tapes revert back to the +/-540 angle once unspooled. A high-strain (for example > 3%), high-strength adhesive can help ensure this. The amount of adhesive or thickness of adhesive layer is also another critical element, as too much will build up pipe thickness and cost and will not help with bond strength and spooling. 'therefore, the diameter of the pipe to be created dictates what strain, weight/thickness of adhesive is used. Another factor determining choice of adhesive is the operating temperature of the adhesive, which will affect the operating pressure of the pipe and flow medium/operating environment. Thc adhesive will also be selected according to the ambient temperature where the spooling is carried out; for example, the drum could be unspooled in Siberia where it is -50°C or Saudi Arabia where it is +50°C.

[040] The benefit of this adhesive approach for manufacturing is that conventional pipes are made from wrapping and fusing the thermoplastic composite tapes onto each other and an inner liner. The fusion process usually uses either infrared or lasers, which results in the first tape layer welding to the preheated surface of a polymer liner and subsequent tape layers to each other. It is best to have the same polymer system for the liner and tapes throughout, as the welding is easier than with dissimilar polymers with different melt temperatures and different affinities breach other. The use of pressure-sensitive adhesive overcomes this disadvantage.

1_041] Figure 3 shows a simplified schematic of the conventional thermoplastic composite pipe construction line. At 31 is a drum stand having an extruded pipe liner. The extruded pipe liner is then pulled off and guided to a preheating section 33, typically infrared heating. This primes the liner for application of traditional thermoplastic composite tapes. The thermoplastic composite tapes are held on a plurality of tape winders 34, which wrap the tapes around the liner at a predefined angle. In between each set of tape winders 34 are additional heat sources 35 and a final heat source 36 to bond the tape layers to each other and the liner. The now (at least partially) thermoplastic composite pipe is then spooled around a second drum stand 38.

I042] For high-pressure pipe lines the number of layers could be very high (up to 60 layers) so the pipes will require multiple passes through the machine. A typical pipe has around 24 layers. If a production line has 8 wrapping units, then the pipe will be passed through 3 times. In a single pass the heat build-up for 8 layers is large and can cause ovalisation of the pipe or even collapse. I lence the wrapping machine will additionally require cooling units and time, which limits production rate and increases cost and space required.

[043] Figure 4 shows a simplified schematic of an embodiment of a production line for constructing thermoplastic composite pipes using adhesive-coated thermoplastic composite tapes. In the same way as the traditional line, it starts with an extruded pipe liner spooled around a drum stand 41 or a liner being extruded in line. The pipe liner is then passed by a plurality of adhesive-coated thermoplastic composite tape winders, which remove the release film and wind the adhesive-coated thermoplastic composite tapes around the pipe liner in a predetermined manner; the tapes bond to the liner and each other respectively via the adhesive coatings. The pipe liner itself may be surface treated to increase surface energy and improve bonding prior to wrapping with the adhesive-coated tape.

[44] By using adhesive-coated tapes, it becomes possible to simply have multiple wrapping units lined up, limited only by the cost and size of the factory, that is, the pipe can be made at high speed and in a single pass or at high speed and multiple passes if the line is limited to, for example, 8 wrapping machines. Either way, the wrapping and bonding will be much faster and there will be no need for IR, laser heaters or a cooling system, with significant savings in terms of capital cost as well as in utility costs such as power and water. In addition to the process efficiency improvements/cost reductions, the introduction of the adhesive layer has another major technical benefit, which relates to the ability to spool the pipe around a drum. The current thermoplastic composite pipes are spoolable up to 6" diameter. By using a pliable, high-strain adhesive with a suitable lap shear strength and a strain capacity of (>3% preferably greater than >5"A), the tapes can move relative to one another, while being biased by the adhesive back to their original orientations. With this degree of flexibility between the tapes that make up the thermoplastic composite pipe, it is possible to produce a pipe up to 8" or more in diameter that can be spooled and unspooled up to ten times in temperatures ranging between -50 and +50°C. By using different adhesives, a user can customise the performance of the pipe and structures while improving processing efficiencies.

[45] A specific functioning embodiment of the current invention is made using a thermoplastic composite tape made from 62 weight % uni-directional glass fibre reinforced polyethylene (the polyethylene making up the remaining 38% of the weight), the tape having a weight of 450g/in2. This is the preferred thermoplastic composite tape to be used, but it is possible for a different thermoplastic composite tape to be used; or indeed, a plurality of different tapes can be used.

Any thermoplastic composite tape used will have a weight % of fibre between 60% and 70%. Alternatives to glass fibres may also be used, for example carbon fibre or ararnid fibre. Other polymers different to polyethylene can also be used, for example polypropylene, nylon, l'VOF (polyvinylidene fluoride or pohyviitylidene &fluoride), :PEEK. (polyetheretherketone).

[46] The thermoplastic composite tape has a surface energy of 32 dynes; this is then surface treated on both sides with corona treatment to increase the surface energy to over 50 dynes, which greatly increases the tape surface's ability-to bond.

Although corona treatment is preferable, other surface treatments such as plasma or flame treatment could be used to a similar effect, [47] After surface treatment, one side of the treated thermoplastic composite tape is coated with a hot-melt, pressure-sensitive adhesive comprising styrenic thermoplastic rubber, providing a strong permanent bond while also having a lap shear strength and strain capacity (elongation to break) above 5%. This allows for the final thermoplastic composite pipe to be spooled and unspooled with little to no degradation to the composite pipe's structural integrity. One such adhesive that achieves this is commercially available as Pressen 2039 (RTM), which is a 100% solid h, -melt, pre sure-sensitive adhesive based on styrenic thermoplastic rubber.

ill a preferred embodiment, this adhesive is applied to one side of file surface-treated thermoplastic composite tape at 40g/m2. Another trait of the adhesive used is that although it needs to be hefted when plied to the surface of the tape, it is not needed to be heated when fbrming the thermoplastic composite pipe, unlike current methods for fmming thermoplastic composite pipes [48] 'I 'he thermoplastic composite pipe is formed by wrapping a plurality of the adhesive-coated surface--treated thermoplastic composite tapes around an inner pipe liner at a predetermined angle (preferably 54"). Adhesion. occurs tape tension and the pressure as the tape is wrapped; no additional in-hue heating is required,unlike curreni thermoplastic composite pipe production methods.

Additional pressure may be added to the process to aid adhesion by using a consolidation roller.

[049] The invention has been described with reference to a preferred embodiment. The description is intended to enable a skilled person to make the invention, not to limit the scope of the invention. The scope of the invention is determined by the claims.

Claims

Claims 1. A thermoplastic composite tape comprising: longitudinal unidirectional reinforcing fibres making up 55-75% of the weight of the tape embedded in a supporting polymer making up 45-25% of the weight of the tape; a suirenic themloolastic rubber based 100% solid Hot melt pressure sensitive adhesive the adhesive coating at least one side of the thermoplastic composite tape. 2. 3. 4. 5. 6. 7. 8. 9.A tape according to any one of claims 1 to 4 wherein the supporting polymer is polypropylene.A tape according to any one of claims 1 to 4 wherein the supporting polymer is nylon.A tape according to any one of claims 1 to 4 wherein the supporting polymer is Polyvinylidene fluoride or pohivinylidene A tape according to any one of claims 1 to 4 wherein the supporting polymer is 0e1 cJLKJJMk.A tape according to claim 1 wherein the reinforcing fibres are glass fibres. A tape according to claim 1 wherein the reinforcing fibres are carbon fibres. A tape according to claim 1 wherein the reinforcing fibres are aramid fibres.A tape according to any preceding claim wherein the supporting polymer is polyethylene.10. A tape according to any preceding claim wherein both sides of the tape have been surface treated such that the surface energy is over 50 dynes.11.A tape according to claim 10 wherein the surface treatment was corona treatment.12.A tape according to claim 10 wherein the surface treatment was plasma treatment.13. A tape according to claim 10 wherein the surface treatment was flame treatment.14.A tape according to any preceding claim wherein the adhesive is applied at 40g/m2.15.A tape according to any preceding claim wherein the adhesive has an elongation percentage before break of over 5%.16.A tape according to any preceding claim wherein the total weight of the thermoplastic composite tape is 450g/m2.17. A method of manufacturing a thermoplastic composite pipe comprising the steps of: 1. taking an inner pipe liner around a first spool or extruding an inner pipe liner in line; 2. aligning a plurality of tape wrapping heads in front of the pipe liner; each wrapping head holding one of a plurality of adhesively coated thermoplastic composite tapes according to any one of claims 1 to 16; 3. passing the pipe liner through the plurality of tape wrapping heads; each wrapping head wrapping an adhesively thermoplastic tape around the pipe liner under tension at a predetermined angle; 4. adhesion occurring between the thermoplastic tapes and the pipe liner and then subsequent layers of thermoplastic composite tape layers to each other due to the tension and the pressure as the tape is wrapped, without any in line heating required; S 5. spooling the now formed thermoplastic composite pipe around a second spool or cutting into desired lengths.18.A method according to claim 17 wherein the thermoplastic composite pipe is spooled around the second spool, further comprising the step of passing the pipe back through the wrapping heads, the wrapping heads adding additional layers of adhesively coated thermoplastic composite tape.19.A method according to any one of claims 17 or 18 wherein the predetermined angle which the thermoplastic composite tapes are wrapped is 54°.20.A method according to any one of claims 17 to 19 comprising the final step of applying an external thermoplastic coating to the outer surface of the thermoplastic composite pipe.21. A thermoplastic composite pipe made from a plurality of thermoplastic composite tapes according to any one of claims 1 to 16.