METHOD FOR PRODUCING A CONTINUOUS HYBRID YARN AND A CONTINUOUS HYBRID YARN PRODUCED BY SAID METHOD

Abstract

 The invention discloses a method for producing a continuous hybrid yarn from cut carbon fibres and polymer and/or inorganic fibres, preferably thermoplastic fibres, using textile techniques for this purpose. For this purpose, 10% of cut carbon fibres and at most 90% of polymer fibres are handled by means of opening and blending, a blend that is fed to a carding device with cylinders to produce a hybrid card sliver, which is subsequently subjected to folding, trimming, twisting and spinning to produce a continuous hybrid yarn produced by said method, which can be advantageously used to manufacture composites.

Description

OBJECT OF THE INVENTION

[0001] The present invention relates to a method for producing a continuous hybrid yarn produced from cut carbon fibres, which are stable fibres and fibres of different types. The continuous hybrid yarn produced by said method is also an object of the invention.

[0002] Advantageously, the disclosed method allows a hybrid yarn with the desired features to be produced by means of textile techniques from cut fibres, which cannot be processed directly by means of the known textile techniques.

BACKGROUND OF THE INVENTION

[0003] Hybrid yarns or fibres, produced from virgin carbon fibres, which are continuous filaments, are known in the prior art.

[0004] Moreover, there is a wide range of complex plastics and composites comprising carbon fibres and thermoplastic materials, which, at the end of their service life, are disposed of in composite landfills; therefore, their recycling and recovery are necessary to contribute to the sustainability of processes and materials and to the circular economy.

[0005] Virgin or short recycled carbon fibres (rCFs) exhibit rigidity and electrical conductivity; therefore, if not handled properly, they fragment and crumble, and furthermore, they can generate short circuits in machines without electrical insulation. For this reason, these short fibres cannot be processed directly by means of known textile techniques to produce yarns, which limits the practical application of cut carbon fibres.

[0006] Currently, these short carbon fibres can only be processed to produce webs or non-woven materials, which serve as intermediates in textile processes; however, the textiles or composites produced from these webs offer inferior mechanical properties compared to those produced by means of continuous yarns due to the random and non-directional distribution of the fibres in these webs or non-woven materials produced from cut fibres.

[0007] In this regard, the applicant for the present invention has found that there is a need to develop a method which enables spinning processes with cut carbon fibre, whether recycled or virgin, such that the fibres are arranged in parallel and aligned, improving the mechanical properties of current solutions (webs or non-woven materials).

DESCRIPTION OF THE INVENTION

[0008] The disclosed method enables hybrid yarns to be produced from cut carbon fibres, whether virgin or recycled, together with polymer fibres, which are preferably thermoplastic, and/or inorganic fibres, using textile fibre processing techniques for this purpose. In this sense, the invention is defined according to the set of claims attached to the present specification. In the proposed method, the parameters and technical modifications used in the carding process, card sliver trimming process, and spinning of the different combinations of fibres, are key factors.

[0009] Advantageously, using a textile spinning process, in which the fibres are arranged in parallel and aligned, starting from a blend including cut carbon fibres, allows transition from an anisotropic material (webs or non-woven materials) to an isotropic material (yarn). This improves the current solutions available on the market (webs or non-woven materials) such that the continuous hybrid yarn produced by the method of the present invention allows the mechanical properties to be maximised with respect to webs and non-woven materials, enabling the production of textile intermediates with a higher added value, as they offer superior mechanical properties as their fibres are directional.

[0010] Namely, the novelty of the invention lies in the use of cut carbon fibre, preferably sourced from recycled carbon fibres (rCFs), as there are no known devices and/or methods that allow producing hybrid yarns from polymer and/or inorganic fibres combined with cut carbon fibres.

[0011] According to the essence of the invention, the object of the present invention is the method for producing a continuous hybrid yarn from carbon fibres of a short length, between 20 mm and 120 mm, preferably between 30 mm and 80 mm, preferably using for this purpose a device with a carding machine with cylinders having a clothing with rigid or semi-rigid metallic teeth. To achieve a continuous hybrid yarn, the disclosed method is based on producing a hybrid card sliver which will be the precursor to the final continuous hybrid yarn produced.

[0012] In this sense, the method for producing a continuous hybrid yarn comprises the following steps:

• Handling at least 10% of cut carbon fibres (virgin or recycled) with a length between 20 mm and 120 mm, and at most 90% of polymer and/or inorganic fibres by means of fibre opening and blending technology. The cut carbon fibres can be sourced from a recycling process, such as a pyrolysis or solvolysis process applied to a composite. Optionally, during this first handling step, before and/or after blending the fibres, a sizing additive or binder and/or an oiling agent are added individually or in a combined manner and at a percentage of less than 5% of the total weight of the blend of fibres. The sizing additives can be organosilanes or matrix/reinforcement binding additives, while the oiling agents (fatty compounds that are added to facilitate the mechanical processing of the fibres and protect the brittle fibres, such as rCFs, from breaking) can be antistatic additives, additives improving fibre cohesion, or lubricating additives, among others;
• feeding the blend of open cut carbon fibres and polymer and/or inorganic fibres to the carding device with cylinders, having a rigid or semi-rigid clothing (metallic teeth), using different combinations of angles and teeth densities optimised according to the blend and length of fibres;
• carding (aligning and bonding of fibres) the blend of fibres and producing a hybrid card sliver of uniform thickness with a count between 2.0 and 8.0 kTex and a twist between 0 v/m and 50 v/m;
• folding and trimming at least one hybrid card sliver by means of a draw frame, applying drawing ratios between x1 and x10, producing a draw frame sliver;
• folding and twisting at least one draw frame sliver by means of a roving frame, producing a precursor roving with a count between 0.4 and 3.0 kTex and a false twist between 5 v/m and 50 v/m (an S- or Z-twist, interchangeably);
• spinning at least one precursor roving to produce the continuous hybrid yarn.

[0013] Following the described method, there is preferably produced a yarn with a spun yarn or ring yarn configuration, which in textile terminology refers to a yarn formed by cut fibre grouped together in the form a yarn by means of drawing and twisting.

[0014] The final spinning step can be carried out in different ways according the characteristics desired in the continuous hybrid yarn produced.

[0015] In this sense, in a preferred embodiment for yarns with thick counts, the spinning step is performed by means of a ring doubling-twisting machine, applying only twisting and/or plaiting on the precursor roving, producing the hybrid yarn from the roving/rovings with a yarn count of 100-3.200 Tex, with an S- or Z-twist of 25-500 v/m.

[0016] Alternatively, for yarns with fine counts, the spinning step can be carried out by means of a ring spinning machine, applying twisting and drawing on the precursor roving, producing the hybrid yarn with a yarn count of 5 - 150 Nm, with an S- or Z-twist of 350-1.500 v/m.

[0017] During the spinning step, it is possible to optionally incorporate a continuously spun core or a continuously spun cover yarn around the precursor roving or the spun hybrid yarn. Both the continuously spun core and the continuously spun cover can be a thermoplastic multifilament yarn, a thermoplastic monofilament yarn, a carbon multifilament yarn, a glass multifilament yarn, an aramide multifilament yarn, a metallic yarn or optical fibres.

[0018] Moreover, optionally, after the spinning step, the produced hybrid yarns are folded with opposite twisting and an equivalent number of twists to neutralise the continuous hybrid yarn. It should be noted in this regard that the yarns are Z- or S-twisted (clockwise or counterclockwise). When the yarn is plaited or folded (joining several strands), it is performed in the opposite direction with respect to the initial yarns and with a number of turns generally close to half of the initial number to neutralise same. In the context of the present invention, neutralising the yarn means leaving it untwisted (residual) such that the yarn is prevented from becoming twisted up during unwinding and handling, remaining loose.

[0019] The yarn produced is a hybrid yarn in the sense that it incorporates fibres of different types, such as the cut carbon fibres and the rest of the fibres used in the initial blend, which can be polymer fibres, inorganic fibres, or a combination thereof. Among polymer fibres, preferably thermoplastic fibres, such as PP (polypropylene), PA (polyamide), PET (polyethylene terephthalate), PPS (poly(phenylene sulphide)), and /or PBT (polybutylene terephthalate) fibres will be used. It is also possible to use thermoset fibres, such as aramides.

[0020] Also preferably, the polymer fibres are water-soluble fibres. Advantageously, this allows removing them in complementary subsequent processes for solubilising these embedded fibres, to leave a final yarn with the highest possible percentage of carbon fibre, as the latter does not dissolve.

[0021] The use of polymer fibres, thermoplastic fibres, or fibres of a similar nature contributes to the correct processing to produce a continuous yarn by means of the textile technologies described above. These polymer fibres act as a "matrix" element in the different final processes for producing composites in which the continuous hybrid yarn of the invention may be involved. In this sense, the yarn of the invention is particularly advantageous for manufacturing fabrics and the subsequent thermocompression, infusion, RTM (resin transfer moulding), lay-up process or similar for producing composites to create a preform or desired product. In the case of thermoplastic composites, the fibres become part of this matrix by means of fusion, after having chosen the adequate ratio of recycled or virgin cut carbon fibres to thermoplastic (TP) fibres. In the case of thermoset composites, the thermoplastic fibres may or may not be compatible with the thermoset resin to be used, such that they are dissolved during the infusion-curing process, or remain embedded between the matrix and the reinforcement.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] To complete the description that will be given below and for the purpose of helping to better understand the features of the invention, a set of drawings is attached as an integral part of said description, where the following is depicted in an illustrative and non-limiting manner:

Figure 1 shows a schematic side view of a device for producing a continuous hybrid yarn according to the object of the invention.

Figure 2 shows a perspective view of a detail of the device of Figure 1 further incorporating a conveyor belt.

Figure 3 shows a diagram of the detail of the clothing with teeth used in carding cylinders and the parameters defining same.

PREFERRED EMBODIMENT OF THE INVENTION

[0023] To carry out the method of the invention, a device comprising at least the following elements can be used:

• 1 pair of feed cylinders (1),
• 1 take-in cylinder (2),
• 1 pair of working cylinders (3)-cleaning cylinders (4),
• 1 central cylinder (5),
• 1 doffing cylinder (6),
• 1 comber-doffer (7),
• 1 conveyor belt (8),
• 1 draw box (9), and
• 1 sliver coiler (10),

[0024] Figure 1 shows a schematic side view of the device, which has a pair of feed rollers (1), a take-in cylinder (2), three pairs of working cylinders (3)-cleaning cylinders (4), a central cylinder (5), a doffing cylinder (6), a comber (7), a conveyor belt (8), a draw box (9) and a sliver coiler (10).

[0025] Moreover, Figure 2 illustrates a detail of the device of the invention according to a preferred embodiment thereof with the same number and type of cylinders in the carding machine but in which there is incorporated a conveyor belt (8), which is arranged between the area of the doffing cylinder or doffer (6) and the draw box (8) (the sliver formation area).

[0026] The conveyor belt (8) is synchronised with the speeds of the carding machine by means of pinions that maintain the cylinder traction ratios, which advantageously ensures the cohesion of the sliver and prevents same from breaking. Specifically, the working cylinders (3) maintain a fixed traction ratio with the doffing cylinder (6) and the conveyor belt (8) (assembly A), the cleaning cylinders (4) maintain a fixed traction ratio with the central cylinder (5) (assembly B), and the feed cylinders (1) (assembly C) have a variable speed. In this way, as a result of a control system, the speeds of assemblies A, B, and C can be modified from the device independently, but each assembly of elements has a fixed traction ratio (by means of a pinion configuration, which is not modified). Advantageously, the independent variation of the speeds of assemblies A, B, and C allows, on one hand, a stable production process by allowing the adjustment of asynchronous movements, and on the other hand, varying the output basis weight with respect to the input material, as well as increasing or decreasing the degree of carding the fibres at will, according the desired final product.

[0027] In the embodiment illustrated in Figure 2, it can be seen that the conveyor belt (8) incorporates triangular-shaped plates (15) with air blowers (16) to help the web of fibres converge in the form of a sliver, ensuring the cohesion thereof, which sliver is collected by means of a collector (18).

[0028] Figure 3 schematically shows in detail the different parameters of the teeth (11) referred to in the present specification.

[0029] The parameters for the clothings with teeth will be combined for each specific blend of fibres, such that adequate formation of a web is ensured first, which will give way to the sliver precursor to the final yarn. According to a preferred embodiment, the clothing with teeth (11) will be configured as follows:

• in the feed cylinders (1), the teeth (11) have a base (12) with a width between 1 mm and 5 mm and a height (13) between 5 and 8 mm, such that the teeth (11) are arranged with a front angle (17) between 50° and 80°, a pitch (14) between teeth (11) between 3.6 mm and 9 mm, and a density between 15 and 100 teeth;
• in the cleaning cylinders (4), the teeth (11) have a base (12) with a width between 1.1 mm and 3.2 mm and a height (13) between 4 and 5 mm, such that the teeth (11) are arranged with a front angle (17) between 50° and 80°, a pitch (14) between teeth (11) between 3.6 mm and 9 mm, and a density between 24 and 170 teeth per inch;
• in the working cylinders (3), the teeth (11) have a base (12) with a width between 1.3 mm and 4.25 mm and a height (13) between 5 and 7,5 mm, such that the teeth (11) are arranged with a front angle (17) between 50° and 65°, a pitch (14) between teeth (11) between 4 mm and 8.5 mm, and a density between 80 and 160 teeth per inch;
• in the central cylinder (5), the teeth (11) have a base (12) with a width between 0.9 mm and 3.2 mm and a height (13) between 3,5 and 5 mm, such that the teeth (11) are arranged with a front angle (17) between 50° and 80°, a pitch (14) between teeth (11) between 2.5 mm and 8.5 mm, and a density between 24 and 224 teeth per inch; and
• in the doffing cylinder (6), the teeth (11) have a base (12) with a width between 1.4 mm and 4.25 mm and a height (13) between 3.5 and 5 mm, such that the teeth (11) are arranged with a front angle (17) between 50° and 60°, a pitch (14) between teeth (11) between 4 mm and 8.5 mm, and a density between 18 and 160 teeth per inch.

[0030] In this sense, according to a preferred embodiment, to produce the continuous hybrid yarn starting from a blend of fibres with at least 10% of cut carbon fibres with a length between 20 mm and 120 mm and at most 90% of polymer thermoplastic fibres, the method below is followed:

• handling at least 10% of cut carbon fibres with a length between 20 mm and 120 mm and at most 90% of polymer thermoplastic fibres by means of fibre opening and blending technology, creating a blend of fibres in the form of a non-carded web;
• feeding the blend of open cut carbon fibres and polymer thermoplastic fibres to the carding device with cylinders;
• carding the blend of fibres and producing a hybrid card sliver of uniform thickness with a count between 2.0 and 8.0 kTex and a twist between 0 v/m and 50 v/m;
• folding and trimming at least one hybrid card sliver by means of a draw frame, applying drawing ratios between x1 and x10, producing a draw frame sliver;
• folding and twisting at least one draw frame sliver by means of a roving frame, producing a precursor roving with a count between 0.4 and 3.0 kTex and a false twist between 5 v/m and 50 v/m; and
• spinning at least one precursor roving to produce the continuous hybrid yarn.

[0031] According to a preferred embodiment of the invention, the spinning step is carried out by means of a ring doubling-twisting machine, applying only twisting and/or plaiting on the precursor roving, which creates a continuous hybrid yarn with a count between 100 and 3,200 Tex and an S- or Z-twist between 25 v/m and 500 v/m. In an alternative preferred embodiment, the spinning step is performed by means of a ring spinning machine, applying twisting and drawing on the precursor roving, which creates a continuous hybrid yarn with a count between 5 and 150 Nm and an S- or Z-twist between 350 v/m and 1500 v/m.

[0032] Finally, it should be noted that, optionally, after the spinning step, further hybridisation can be performed to improve the properties of the yarn, commonly known in the textile sector as commingling with thermoplastic continuous filaments and/or virgin carbon fibre. This further hybridisation can be performed by means of twisting, plaiting, folding, braiding, coating, etc., giving rise to, among others, the four common structure types for yarns produced by commingling: commingled yarn, cospined yarn, cowrapped yarn and cotwisted yarn.

Claims

1. A method for producing a continuous hybrid yarn, characterised in that it comprises the steps of:

- handling at least 10% of cut carbon fibres with a length between 20 mm and 120 mm, and at most 90% of polymer and/or inorganic fibres by means of fibre opening and blending technology;

- feeding the blend of open cut carbon fibres and polymer and/or inorganic fibres to the carding device with cylinders;

- carding the blend of fibres and producing a hybrid card sliver of uniform thickness with a count between 2.0 and 8.0 kTex and a twist between 0 v/m and 50 v/m;

- folding and trimming at least one hybrid card sliver by means of a draw frame applying drawing ratios between x1 and x10, producing a draw frame sliver;

- folding and twisting at least one draw frame sliver by means of a roving frame, producing a precursor roving with a count between 0.4 and 3.0 kTex and a false twist between 5 v/m and 50 v/m; and

- spinning at least one precursor roving to produce the continuous hybrid yarn.

2. The method for producing a continuous hybrid yarn according to claim 1, characterised in that a sizing additive and/or an oiling agent is added in the step of handling cut carbon fibres and polymer and/or inorganic fibres.

3. The method for producing a continuous hybrid yarn according to claim 1, characterised in that the polymer fibres are thermoplastic fibres or thermoset fibres.

4. The method for producing a continuous hybrid yarn according to claim 1, characterised in that the polymer fibres are water-soluble fibres.

5. The method for producing a continuous hybrid yarn according to claim 1, characterised in that the spinning step is performed by means of a ring doubling-twisting machine, applying only twisting and/or plaiting on the precursor roving.

6. The method for producing a continuous hybrid yarn according to claim 1, characterised in that the spinning step is performed by means of a ring spinning machine, applying twisting and drawing on the precursor roving.

7. The method for producing a continuous hybrid yarn according to claim 1, characterised in that a continuously spun core is incorporated during the spinning step.

8. The method for producing a continuous hybrid yarn according to claim 7, characterised in that the continuously spun core is a thermoplastic multifilament yarn, a thermoplastic monofilament yarn, a carbon multifilament yarn, a glass multifilament yarn, an aramide multifilament yarn, a metallic yarn or optical fibres.

9. The method for producing a continuous hybrid yarn according to claim 1, characterised in that a continuously spun cover yarn is incorporated around the precursor roving or hybrid yarn during the spinning step.

10. The method for producing a continuous hybrid yarn according to claim 9, characterised in that the continuously spun cover is a thermoplastic multifilament yarn, a thermoplastic monofilament yarn, a carbon multifilament yarn, a glass multifilament yarn, an aramide multifilament yarn, a metallic yarn or optical fibres.

11. The method for producing a continuous hybrid yarn according to claim 1, characterised in that after the spinning step, the produced hybrid yarns are folded with opposite twisting and an equivalent number of twists to neutralise the continuous hybrid yarn.

12. The method for producing a continuous hybrid yarn according to claim 1, characterised in that after the spinning step, hybridisation is performed with thermoplastic continuous filaments and/or virgin carbon fibre.

13. The method for producing a continuous hybrid yarn according to claim 12, characterised in that hybridisation is performed by means of twisting, plaiting, folding, braiding or coating.

14. A continuous hybrid yarn produced by the method according to claim 1, characterised in that it is produced from at least 10% of cut carbon fibres with a length between 20 mm and 120 mm and at most 90% of polymer and/or inorganic fibres.

15. The continuous hybrid yarn produced by the method according to claims 1 and 5, characterised in that it has a count between 100 and 3,200 Tex and an S- or Z-twist between 25 v/m and 500 v/m.

16. The continuous hybrid yarn produced by the method according to claims 1 and 6, characterised in that it has a count between 5 and 150 Nm and an S- or Z-twist between 350 v/m and 1500 v/m.

Drawing