GB2597596A - Thermoplastic composite tape and pipe made therefrom - Google Patents

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 [0011 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. I ven more specifically, the present invention relates to thermoplastic composite pipes made using thermoplastic composite tapes coated in adhesive.

Background of the Invention

[0021 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 and a polymer is 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 slit to various widths.

[0031 These thermoplastic composite tapes are then wrapped or laid in a predetermined pattern to form a structure such as a pipe or pressure vessel etc. The thermoplastic composite tapes are joined together by heating the tape surfaces often with external radiation or heat such as hot gas/flame, infra-red or a laser etc. 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.

[0041 Whilst 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. I lence 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 that the product is made in a series of passes enabling layers time to cool, or apply additional air and/or water to the system to facilitate cooling.

[5] 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 layered thermoplastic composite pipe (TCP), they ideally would want 24 tape wrapping heads in a row and just 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 pipe passed backwards and forward through the wrapping machines either 6 or 4 times respectively.

[6] It is known in the field to create TCPs by simply wrapping unbondcd tapes, with this however, it is extremely difficult, if not impossible to control the positions of the tapes after spoolirig/unspoohrig the TCPs which greatly reduces the structural integrity of the TCPs. Short term properties such as tensile streng,th for example can drop around 17%.

[7] It is an object of the present invention to overcome this thermodynamic 25 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 layered 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 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 ai least one side of the thermoplastic composite tape.

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

[0101 An embodiment of the first aspect wherein the supporting polymer is polyethylene. The supporting polymer may alternatively be polypropylene, nylon, ':'()letrieittht rketune, Polyntlidene fluoride or pohivimilidene difluoride [011] An embodiment of the first aspect wherein both sides of the tape have been 20 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.

[0121 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 5 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; 5. 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°.

[017] 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.

[018] 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

[017] The invention will be described in more detail, by way of example, with reference to the following drawings: [018] Figure 1 depicts a generic thermoplastic composite tape; [019] Figure 2 depicts a schematic for producing adhesive coated thermoplastic composite tape; [020] Figure 3 depicts a prior art schematic of producing a thermoplastic composite pipe; [021] Figure 4 depicts a schematic for producing a thermoplastic composite pipe using adhesive coated thermoplastic composite tape.

[022] Figure 5 depicts a simplified cross section of a thermoplastic composite pipe made from adhesively coated thermoplastic composite tapes.

Detailed Description

[0231 Composite tapes in a general sense take the form as shown in figure 1. It consists of reinforcing fibres embedded in a polymer matrix. The polymer matrix provides inler aka 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 effected 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 which increase the materials mechanical properties enormously.

[024] 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 picks the appropriate materials etc for the specific purpose of the composite being created. Some corm-non reinforcing fibres include glass, carbon and aramid. Some common polymers used include PE (Polyethene), PE-la (Polyethene Raised Temperature resistance), PA (polyamide), and PVDF (Polyyinylidene Fluoride) etc. 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 etc. The thermoplastic composite tapes are joined together by heating the tape surfaces often with external radiation or heat such as hot gas/flame, infra-red or a laser etc. 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 therefore reduce the time needed to spend 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, they all having in common that the adhesives 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, completely remove the need for external heat/radiation. The adhesives can be structural adhesives like epoxides, acrylics etc, 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, polyurehanes, 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 based on acrylics or hot melt pressure sensitive adhesives based on but not limited to polyolefins, pol),Tarnides or polyesters.

[29] In another embodiment hot melt pressure sensitive adhesives could be used. 25 Such as 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] The specific components of thermoplastic composites can vary widely 5 within the general definition, this is because the specific components and structure are chosen to achieve specific physical properties specific to what the thermoplastic composite is desired to do.

[32] The present invention also encompasses a variety of different adhesives and application amounts dependent on the desired properties to be achieved by the end product. 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 meter. The various adhesives, the amounts applied, etc help control features such as, but not limited to, bond strength, strain capacity, temperature performance, environmental resistance etc. [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 etc. But any suitable surface treatment known to the skilled person to increase the surface energy of the thermoplastic composite tape can be used.

[034] Figure 2 depicts a preferred embodiment for the production of adhesively coated thermoplastic composite tape. It comprises having a 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 adhesively coated thermoplastic composite tape is then 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.

[0351 The adhesively 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.

[0361 As well as the improved efficiency due to reduced/removed requirement for 20 heat, and allowing for a wider variety of polymer matrix's to be used. When specifically creating, thermoplastic composite pipes the use of adhesively coated thermoplastic composite tape provides another advantage.

[0371 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 degrees and it is important that after spooling and unspooling the pipe off the drum that the tapes remain as close to +/-54 as possible.

[038] 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 length ways direction.

[0391 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 +/-54 Degree 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 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 that the adhesive will be based on is the operating temperature of the adhesive, which will affect the operating pressure of the pipe and flow medium/operating environment. The adhesive will also be selected on the ambient temperature of where spooling is carried out-for example the drum could be unspoolcd in Siberia where it is -50C or Saudi Arabia where it is +50C.

[0401 The benefit of this adhesive approach for manufacturing is that conventional pipes are made from either wrapping and fusing the thermoplastic composite tapes onto each other and an inner liner. The fusion process is usually either infra-red or lasers which results in the first tape layer welding to the pre heated 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 dis-similar polymers with different melt temperatures and affinity for each other. The use of pressure sensitive adhesive gets around this disadvantage.

[041] Figure 3 shows a simplified schematic of the conventional thermoplastic composite pipe construction line. At 31 you have a drum stand having an extruded pipe liner. The extruded pipe liner is then pulled off an guided to a preheating section 33, typically IR 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.

[0421 For high pressure pipe lines the number of layers could be very high (up to 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 ovahsation of the pipe or even collapse. Hence the wrapping machine will additionally require cooling units and time which limits production rate and increases cost and space required.

[0431 Figure 4 shows a simplified schematic of an embodiment of a production line for constructing thermoplastic composite pipes using adhesive coated thermoplastic composite tapes. Same as the traditional line it starts with an extruded pipe liner spooled around a drum stand 41 or the liner is extruded inline. The pipe liner is then passed by a plurality of adhesive coated thermoplastic composite tape winders, which remove the release film and wind the adhesively coated thermoplastic composite tapes around the pipe liner in a predetermined manner, the tapes bonding 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.

[044] By using adhesively coated tapes it becomes possible to simply have multiple wrapping units lined up limited only by the cost and size of the factory i.e make the pipe at high speed and in a single pass or at high speed and multiple passes if line is limited to say 8 wrapping machines. Either way the wrapping and bonding will be much faster and no need for lit or laser heaters or cooling system saving lot of capital cost and also utility cost-power and water. Apart from 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"A preferably greater than >5%) enables the tapes to move relative to one another, while being biased by the adhesive back to their original orientations. With this degree of flexibility between the tapes the thermoplastic composite pipe is made from, 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 degrees C. By using different adhesives, a user can customise the performance of the pipe and structures whilst improving processing efficiencies.

[045] A specific functioning embodiment of the current invention is made using a thermoplastic composite tape made form 62 weight "it uni-directional glass fibre reinforced polyethylene (the polyethylene making up the remaining 38% of the weight), the tape having a wight of 450g/m2. This is the preferred thermoplastic composite tape to be used but it is possible for a different thermoplastic composite tapes 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%. Alternates to glass fibres may also be used, for example carbon fibre or aramid fibre. Other polymers different to polyethylene can also be used, for example polypropylene, nylon, l'VDF (Polyvinylidene fluoride or polyvinylidene &fluoride), PREK (Poly-calieretherisetctic etc. [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 ther optastic composite tape is coated with a hotmelt pressure sensitive adhesive comprising styrenic thermoplastic rubber providing a strong permanent bond while also haying alap shear strength and strain capacity (elongation to break) above 5'('6, this allows for the final thermoplastic composite pipe to be able to be spooled and unspoolcd with little to no degradation to the composite pipe's structural integrity. One such IM), which adhesive that achieves this is commercially available as 2039(R is a 100% solid hot melt pressure sensitive adhesive based on styrenic thermoplastic rubber. In a preferred embodiment this adhesive is applied to one side of the surface treated thermoplastic composite tape at 40g/m2. Another trait of the adhesive used is although it needs to be heated when applied to the surface of the tape, it is not needed to be heated when forming the thermoplastic composite pipe unlike current methods for forming thermoplastic composite pipes.

[48] The thermoplastic composite pipe is formed by ping a plurality of the adhesively coated surface treated thermoplastic composite tapes trounds an inner 30 pipe liner at a predetermined angle (preferably 54"). Adhesion occurs due to the tape tension and the pressure as the tape is wrapped, no additional in-line heating is required, unlike current thermoplastic composite pipe production methods. Additional pressure may be added to the process to aid in 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 (1)

1. 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"A of the weight of the tape; a styrenic thermoplastic 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 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.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 Poi yvinylidene fluoride or polyvinyl idene difluoride.A tape according to any one of claims 1 to 4 wherein the supporting polymer is PoivetherethcActotiQ 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: 6. taking an inner pipe liner around a first spool or extruding an inner pipe liner in line; 7. 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 Ito 16; 8. 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; 9. 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; 10. 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.