A composite fishing line

Abstract

A composite fishing line 2 for flyfishing, comprises an inner core 4 and a buoyancy layer 6 disposed about the inner core. The buoyancy layer comprises a carrier material and hollow microspheres conta

Description

FIELD OF INVENTION

[001] The present disclosure relates to a composite fishing line, and in particular a floating flyfishing line having a core and a buoyancy layer. BACKGROUND

[002] Modern fly fishing lines are typically produced from polymers, with most of these lines being non-thermoplastic lines (e.g. PVC). Few manufacturers produce thermoplastic lines, with those that do resorting to thermoplastics with densities less than 1 g / cm3, such that the lines can float without the need for further processing of these materials to alter their buoyancy. It is desirable to use a braided core to increase the strength of the line. A thermoplastic layer is co-extruded over the core. However, the increased density of a braided core material means that the buoyancy of the outer thermoplastic material must be increased to compensate. This requires further processing of the thermoplastic material, with associated difficulties that arise when using buoyancy enhancement techniques such as gassing agents or buoyancy additives.

[003] Thermoplastic fly lines comprise a thermoplastic core, onto which a least one outer layer is applied. Typical core materials include polyamide or polyester, which are commonly provided in a braided or monofilament form. The core provides the base break strength for the fly line, typically between 121b - 501b depending on the fish being captured. The outer layer(s) commonly comprises PVC or polyurethane, which can be loaded with a variety of additives. However, the core has an increased density and as such the improved strength comes at the cost of reduced buoyancy.

[004] In a floating line a gassing (or foaming) agent can be added to the outer layer(s) to create voids that increase buoyancy. Such a layer may be referred to as a buoyancy layer, although it also provides other properties. The gassing / foaming agent produces a honeycomb or bubble-cell structure of voids in the material of the buoyancy layer. For polyurethane materials this results in the buoyancy layer having a specific gravity of over 0.9. This specific gravity requires the buoyancy layer to be relatively thick to offset the increased density of the core.

[005] Gassing of a material is inherently difficult to control and requires extensive set up and monitoring. When high levels of gassing / foaming agent are used, weak spots can occur in the buoyancy layer leading to failure that makes the resultant line unusable. Another issue that arises relates to inconsistency of gassing along the length of the buoyancy layer. Inconsistent distribution is common in gassed lines, with the number and size of voids differing over the length of the line. This can result in the line expanding and contracting at varying rates along and across its length. For example, sections of the line can contract more on one side than the other, resulting in snake-like coils when the line floats on the surface of the water. This coil effect is commonly known as line memory. Line memory is a distinct disadvantage, as the straighter the line lays on the surface, the more direct contact the fisherman has with a fish eating his fly. Line memory is more noticeable in cold conditions and contributes greatly to line tangles and frustration for the end user.

[006] A secondary coating may be added over the buoyancy layer to improve the performance of the line. The coating material may be provided with water repulsion additives and other agents that promote slickness, the latter of which is important to ensure that the line slides smoothly (for example over the rungs of a fishing rod). Alternatively, or in addition, the geometry of the outer layer can be altered to reduce the surface area available for sliding contact and / or to alter the frictional co-efficient of the line. PTFE / TPU coatings have been used to reduce the frictional co-efficient and / or water repulsion of lines. However, these materials are relatively dense leading to buoyancy issues. Consequently, even when the gassed layer is thick, the buoyancy of the PTFE / TPU coating must be increased to ensure the line floats appropriately. To date this has been achieved by the use of a gassing agent. The outer coating also protects the lower density buoyancy layer from tearing and protects the microspheres from damage.

[007] Microspheres are used to reduce density in PVC (i.e. non-thermoplastic) lines. However, due to the extrusion manufacturing processes required to produce thermoplastic lines microspheres are not seen as a viable solution. Microspheres cannot withstand the extreme pressure of the extrusion process and many are broken and therefore do not add to buoyancy. For example, PTFE has a melting point of 320°C and never passes beyond the gel stage, meaning that the pressures required to extrude PTFE would fracture the microspheres. Additionally, when microspheres are mixed into to PU they have a tendency to clump together. This results in a fly line with uneven distribution of the spheres, which in turn creates inconsistent buoyancy levels along the length of the fly line. Furthermore, the concentration of glass spheres required to attain the desired density, and hence buoyancy, significantly reduces the tensile strength of the PU material. Consequently it is difficult to achieve the required density whilst still maintaining requisite strength.

[008] The buoyancy layer may further comprise a flow modifier. The addition of a flow modifier further improves distribution of the microspheres. UHMWPE assists with microsphere distribution. However, it was unexpectantly discovered that the provision of a flow modifier, in combination with the UHMWPE, further improves distribution and entirely avoids clumping of microspheres at surface of line.

[009] The flow modifier may comprise fumed silica, which provides an improved reduction in clumping of microspheres. Additionally improves production of the line, and has limited effect on internal adhesion of the line.

[0010] The line may further comprise an additive configured to improve internal adhesion. Whilst the flow modifier improves distribution of microspheres, it also thins the material, which can introduce shape issues. Introducing an additive specifically configured to improve internal adhesion has a synergistic effect with the flow modifier, in that shape issues are significantly improved and durability also improves. This enables the production of reduced diameter lines and thus associated weight reduction benefits. By providing these two materials, the processing window is improved, resulting in improved repeatability and stability of the line. Additionally, set up times are reduced.

[0011] The additive configured to improve internal adhesion may comprise Ethylene Acrylic Acid (EAA). EAA is a co-polymer that further improves processibility, leading to a rounder and more stable line. The EAA acts as strong bonding agent between the outer layer and the core. EAA has ben found to result in ~30-40% improved durability of the line. Providing fumed silica and EAA has a synergistic effect, in that shape and durability are maximised.

[0012] It is therefore desirable to provide an improved fishing line, which addresses the above-described problems and / or which offers improvements generally. SUMMARY

[0013] According to the present disclosure there is provided a composite fishing line as described in the accompanying claims.

[0014] In an aspect of the disclosure there is provided a composite fishing line comprising an inner core; and a buoyancy layer disposed about the inner core, the buoyancy layer comprising a carrier material and hollow microspheres contained within the carrier material. The carrier material comprises a mixture of a thermoplastic material and ultra-high molecular weight polyethylene (UHMWPE). The use of the term "mixture" requires that the thermoplastic material and the UHMWPE are different materials. In other words, the carrier material comprises a mixture of a first thermoplastic material and a second thermoplastic material, where the first and second thermoplastic materials are different materials, and the second thermoplastic material is UHMWPE. The presence of UHMWPE in the carrier material increases the tensile strength of the line, and enables a higher concentration of microspheres to be added to the carrier material, thereby improving buoyancy. UHMWPE also enables a more uniform distribution of microspheres throughout the coating.

[0015] The buoyancy layer may contain microsphere loading by mass of 30%. The buoyancy layer may contain microsphere loading by mass of 20%. This mass loading ratio, combined with the use of UHMWPE, results in the buoyancy layer having an SG of less than 0.9.

[0016] The hollow microspheres may be glass microspheres. In an alternative embodiment they may be formed from a polymer.

[0017] The thermoplastic material of the carrier material may be polyurethane.

[0018] The fishing line may further comprise an outer coating disposed upon the buoyancy layer, which may comprise a water repellent material.

[0019] The outer coating may comprise a low friction material, which provides a smoother outer surface for better casting.

[0020] The outer coating may comprise UHMWPE. The outer coating may also comprise a thermoplastic polymer. The thermoplastic polymer of the outer coating may be polyurethane.

[0021] The outer coating may contain microspheres, which reduces the amount of microspheres needed in the buoyancy layer. The mass loading of microspheres in the buoyancy layer is preferably greater than the mass loading in the outer layer. The buoyancy layer still provides the majority of the floatation, whilst the outer layer assist buoyancy but contains less microspheres by weight and so is smoother for casting performance.

[0022] The core may comprise a thermoplastic material, which may be one or more of polyurethane, aramid fibres, polyester and polyamide. The core may be formed of multiple filaments. The multiple filaments may be braided.

[0023] A composite fishing line comprising an inner core; and a buoyancy layer disposed about the inner core, the buoyancy layer comprising a carrier material and a positively buoyant composition contained within the carrier material; wherein the carrier material comprises a mixture of a thermoplastic material and ultra-high-molecular-weight polyethylene. The positively buoyant composition may be a structured material, for example the positively buoyant composition may comprise microspheres. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present disclosure will now be described by way of example only with reference to the following illustrative figures in which: Figure 1 is a line in accordance with the present invention. Figure 2 is a compounding line in accordance with the present invention. Figure 3 is a first compounder screw configuration in accordance with the present invention. Figure 4 is a second compounder screw configuration in accordance with the present invention. Figure 5 is a fly line extrusion configuration in accordance with the present invention. DESCRIPTION OF EMBODIMENTS

[0025] The following description presents exemplary embodiments and, together with the drawings, serves to explain principles of the disclosure. The scope of the disclosure is not intended to be limited to the precise details of the embodiments or exact adherence with all method steps. Variations will be apparent to a skilled person and are deemed also to be covered by the description. Terms for features used herein should be given a broad interpretation that also encompasses equivalent functions and features. In some cases, several alternative terms (synonyms) for structural features have been provided but such terms are not intended to be exhaustive.

[0026] Descriptive terms should also be given the broadest possible interpretation; e.g. the term "comprising" as used in this specification means "consisting at least in part of" such that interpreting each statement in this specification that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner. Directional terms such as "vertical", "horizontal", "up", "down", "upper" and "lower" are relative terms that may be used for convenience of explanation usually with reference to the illustrations and are not intended to be ultimately limiting if an equivalent function can be achieved with an alternative dimension and / or direction.

[0027] The description herein refers to embodiments with particular combinations of configuration steps or features. However, it is envisaged that further combinations and cross-combinations of compatible steps or features between embodiments will be possible. The description of multiple features in relation to any specific embodiment is not an indication that such features are inextricably linked, and isolated features may function independently from other features and not necessarily require implementation as a complete combination.

[0028] Referring to Figure 1, a cross-section of a composite line 2 of the present invention is shown. The line 2 is suitable for flyfishing, but the present invention is not limited to this use. The line comprises a central core 4 around which a buoyancy layer 6 is formed. A coating layer 8 surrounds and encircles the buoyancy layer 6. The core 4 acts as the primary mechanical structure of the line. The core 4 is formed of braided polyester. A braided core is formed by taking individual strands of polymer and braiding them in a specific braid pattern to tailor tensile strength and stretch characteristics. For example, the angle of the braid can be varied to give differing stretch characteristics. However, the core can be formed of braided polyamide, monofilament polyamide, monofilament polyester or any other suitable thermoplastic. Braided polyester and polyamide notably improve tensile strength whilst reducing stretch.

[0029] The buoyancy layer 6 provides buoyancy and additional strength to the line. The buoyancy layer 6 is formed of a carrier material into which microspheres are mixed to increase buoyancy. The amount of microspheres may be varied to achieve the desired level of buoyancy. As an example, the microspheres may be glass microspheres having a particle size of 20 pm. However, microspheres produced from any suitable material may be used instead, for example polymeric microspheres can be used.

[0030] The carrier material comprises a mixture of polyurethane (PU) and ultra-high molecular weight polyethylene (UHMWPE). By mixing PU and UHMWPE the density of the carrier material is reduced compared to a pure PU carrier material. As such a thinner buoyancy layer is possible, resulting in a reduced quantity of microspheres. UHMWPE advantageously increases the tensile strength of the line 2, enabling the use of lower hardness base material, such as PU, which results in a more supple line. The PU may be supplemented for any other suitable base polymer. Furthermore, the increase strength provided by the UHMWPE enables a higher concentration of microspheres to be added to the carrier material if required as the increased strength counters the brittleness introduced by the microspheres.

[0031] The increased strength provided by the addition of UHMWPE also improves the processability of the carrier material. Through research and extensive experimentation it has been found that improved processibility can allow for a more uniform distribution of microspheres throughout the coating. The addition of UHMWPE enables uniform glass microsphere loading of the buoyancy layer 6. To improve the distribution of UHMWPE through the PU an anti-static agent is added to the carrier material.

[0032] The glass microspheres are preferably provided in a quantity of 5 to 30% by weight, depending on the floating and / or sinking characteristics required for the composite lines. In an alternative embodiment, polymeric microspheres may be provided in a quantity of 5 to 20% by weight. This has been determined to be the optimum range, with 20% by weight being the preferred maximum loading. Above 20% the mixture becomes rougher and increasingly brittle due to the presence of excess microspheres, and does not process as effectively through the compounding process during which the strand is cut into pellets in readiness for extrusion.

[0033] UHMWPE has low to negligible 'shape memory' i.e. it will readily return to its original shape. Combined with its other material properties it enables a line which remains supple and exhibits low shape memory down to -60°C. This is more than enough to ensure a memory free line at temperatures close to freezing point on the water, even when windchill and ground temperature is taken into account.

[0034] The coating layer 8 comprises PU, a lubricating agent, UHMWPE and an antistatic agent. Whilst UHMWPE provides low friction and water repellence, the addition of an anti-static agent advantageously lowers friction further and increases water repellence. The coating may be loaded with microspheres, in addition to the buoyancy layer 6. The coating provides water repulsion, slickness and is also provided with pigment to gives the line a desired colour. The coating layer may also be provided with microspheres to increase buoyancy. The increased surface area of the outer layer allows buoyancy to be improved with the use of a lower percentage by weight of microspheres.

[0035] In Figure 2 a compounding extrusion line 10 is shown, that is used for mixing the buoyancy layer-based material and microspheres and creating pelletised material for use in a coextruder for forming the line extruder, as described further below. The compounding extrusion line 10 comprises a compounding extrusion section including a twin screw extruder 12, a chilled water bath 14, and a pelletiser 16. The twin screw extruder 12 comprises a top feeder 18, a side feeder 20, and a vent port 21, positioned along the length of the conveyancing and mixing screws. Two compounding extrusion section configurations are described below.

[0036] In Figure 3 a first compounding screw section configuration 22 is shown. This first configuration comprises twin screws 24a, 24b having consecutive mixing sections 30,38 and conveyancing sections 34,40. A first feeder 26 is positioned to deliver the carrier material from the top feeder 18 to an initial conveyancing section 28. The conveyancing section 28 moves the carrier material deposited by the first feeder to a first mixing section 30 in a conveying direction 32. The first mixing section ensures the carrier material from the first feeder is blended homogenously. The carrier material then moves into an intermediate conveyancing section 34, where a second feeder 36 is located. The second feeder may be a side feeder. The second feeder deposits glass microspheres into the carrier material in the intermediate conveyancing section, which then conveys the glass microspheres and carrier material to a second mixing section 38. The second mixing section mixes the glass microspheres into the carrier material to produce an extrudate. The extrudate is then moved into a final conveyancing section 40. A vent port may be located in the final conveyancing section to relieve any gassing produced during the extrusion process.

[0037] It was initially it was considered that this first process may be unsuitable for producing a glass microsphere loaded extrudate, as the glass microspheres fractured when attempting to produce the extrudate in one pass. However, surprisingly it was found that mixing in the glass microspheres over two passes resulted in successful extrudate production. However, this inherently results in increased manufacturing time (compared to one pass) and also double processing of the material before it even reaches the co-extrusion step required to produce a line. However, this resulted in material degradation when compared to one pass of material.

[0038] In Figure 4 a second compounder screw configuration 42 is shown. This second configuration comprises twin screws 44a, 44b having consecutive mixing sections and conveyancing sections. A first feeder 46, fed by top feeder 18, is positioned to deliver the carrier material to an initial conveyancing section 48, which moves the carrier material deposited by the first feeder in a conveyancing direction 50 to a first mixing section 52. The first mixing section ensures the carrier material from the first feeder is blended homogenously. The carrier material then moves into a second mixing section 54 which further mixes the material. This improves the mixing of the UHMWPE and antistatic agent with the base polymer. From this second mixing section the carrier material moves into a final conveyancing section 56, along which a second feeder 58 is located. The second feeder 58 may be a side feeder. The second feeder deposits glass microspheres into the final conveyancing section, which conveys and mixes the glass microspheres and carrier material into an extrudate.

[0039] Advantageously, adding the microspheres downstream of the two mixing sections prevents mechanical damage to the microspheres by the mixers. As a result the spheres are better protected during manufacture, allowing an increase quantity of spheres to make it through the extrusion process intact, which improves the buoyancy properties of the material. Thus the extrudate can be processed in a single pass. Consequently, the carrier material experiences less degradation before being co-extruded and manufacturing time is reduced. The ability to process the materials in this manner is enabled by the addition of UHMWPE which improves processability. In a further advantage, locating the second mixing station immediately downstream of the first mixing station has been found to improve mixing of the carrier material prior to the introduction of the microspheres.

[0040] In Figure 5 a fly fishing line co-extruder 60 is shown. Core material 62 is passed into a die 64 in an extrusion direction 66. A buoyancy layer co-extruder 68, inner coating co-extruder 70 and outer coating co-extruder 72 are arranged around and connected to the die. The inner coating co-extruder 70 and outer coating co-extruder 72 together each form a separate layer that together form the coating 8. Alternatively, a single coating co-extruder could be used. The buoyancy layer co-extruder 68 is connected at the front of the die relative to the extrusion direction. The inner coating co-extruder 70 is connected to the middle of the die, and the outer coating co-extruder 72 is connected at the rear of the die. Thus, as the core 4 passes through the die, material from the buoyancy layer 6 is first formed onto the core 4, upon which the inner coating material is formed and finally upon which the outer coating material 8 is formed, to produce the finished line 2. The die is configured to allow for the material to be distributed in even layers over the core material as shown in Figure 1. The thickness of the extruded layers 4,6,8 is controlled by the machine controller and is governed by a combination of the line speed and the volume of material that is forced into the die.

Claims

1. A composite fishing line comprising:an inner core; anda buoyancy layer disposed about the inner core, the buoyancy layer comprising a carrier material and hollow microspheres contained within the carrier material;wherein the carrier material comprises a mixture of a thermoplastic material and ultra-high-molecular-weight polyethylene.

2. A composite fishing line according to claim 1 wherein the buoyancy layer contains microsphere loading by mass of 5% to 30%.

3. A composite fishing line according to claim 2 wherein the buoyancy layer contains microsphere loading by mass of 5% to 20%.

4. A composite fishing line according to claim 1 to 3 wherein the hollow microspheres are glass microspheres.

5. A composite fishing line according to any preceding claim, wherein the thermoplastic material of the carrier material is polyurethane.

6. A composite fishing line according to any preceding claim further comprising an outer coating disposed upon the buoyancy layer.

7. A composite fishing line according to claim 6 where in the outer coating comprises awater repellent material.

8. A composite fishing line according to claim 6 or 7 wherein the outer coatingcomprises low friction material.

9. A composite fishing line according to any one of claims 6 to 8 wherein the outer coating comprises ultra-high-molecular-weight polyethylene.

10. A composite fishing line according to any one of claims 6 to 9 wherein the outer coating contains microspheres.

11. A composite fishing line according to claim 10 wherein the mass loading of microspheres in the buoyancy layer is greater than the mass loading in the outer layer.

12. A composite fishing line according to any preceding claim wherein the inner core comprises a thermoplastic material.

13. A composite fishing line according to claim 12 wherein the thermoplastic material of the inner core comprises one or more of polyester, polyurethane, aramid fibres, and polyamide.

14. A composite fishing line according to any preceding claim wherein the inner core is formed of multiple filaments.

15. A composite fishing line according to any preceding claim, wherein the buoyancy layer further comprising a flow modifier.

16. A composite fishing line according to claim 15, wherein the flow modifier comprises fumed silica.

17. A composite fishing line according to claim 15 or 16, further comprising an additive configured to improve internal adhesion18. A composite fishing line according to claim 17, wherein the additive configured to improve internal adhesion comprises Ethylene Acrylic Acid (EAA)A

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