A method for producing fiber material, especially short cut fibers, to improve the performance of concrete

Abstract

A method for producing a fiber material, preferably heated fiber material, in particular a heated short cut fiber material, especially a heated short cut carbon fiber material, in particular to improve the performance of concrete, comprising the following steps: a) Softening fibers, b) Twisting the softened fibers, c) Toughening the twisted fibers by chemical treatment, d) Optionally, cutting the fiber material, especially the toughened fibers, to obtain a short cut fiber material, e) Optionally, heating the fiber material, especially the short cut fiber material, and f) Optionally, packing the fiber material, especially the heated fiber material, in particular the heated short cut fiber material.

Description

[0001] A method for producing fiber material, especially short cut fibers, to improve the performance of concrete

[0002] Technical Field

[0003] The present invention relates to the field of concrete reinforcement materials, in particular to a method for producing fiber material, especially short cut fibers, in particular to improve the performance of concrete.

[0004] Background Art

[0005] Currently, the traditional reinforcement materials for concrete are mainly steel fibers which have the following defects: Firstly, they are non corrosion-resistant which makes them unsuitable for applications in humid environments; secondly, due to their conductive effect, steel fibers can easily interfere with the conduction of telecommunication systems etc., which makes them unsuitable as reinforcement materials for concrete used in enclosed subways, tunnels etc.; thirdly, the surface of steel fibers is relatively stiff and it is difficult to smooth the steel wires on the reinforced concrete surface, which can easily damage tires of cars and cause traffic hazards on the road.

[0006] In recent years, due to the high strength and corrosion resistance of carbon fiber, it is gradually used to reinforce concrete. The manufacturing principle is simple, which is to cut high - strength carbon fiber yams into 6 - 50 mm short fibers directly, with an addition amount of 1 - 25 kg / m3concrete. The addition of carbon fibers as mentioned above improves the bending strength and comprehensive performance of concrete and / or mortar. However, due to the high modulus and surface inertness of carbon fibers, the poor bonding strength seriously affects the performance of carbon fiber reinforced concrete and its mechanical properties.

[0007] There is therefore still a need for improved solutions. Summary of the invention

[0008] It is therefore a task of the invention to provide a solution, which at least minimizes the disadvantages existing in the prior art. Especially, the task of the invention is to provide a method to improve fibers for improving the mechanical properties of concrete and / or mortar, especially to improve the bonding strength of fibers, especially carbon fibers, and to improve the dispersion and adhesion of fibers, especially carbon fibers, in concrete and / or mortar.

[0009] This task is solved by the features of the independent claim 1.

[0010] The invention therefore relates to a method for producing a fiber material, preferably heated fiber material, in particular a heated short cut fiber material, especially a heated short cut carbon fiber material, in particular to improve the performance of concrete, comprising the following steps: a) Softening fibers, b) Twisting the softened fibers, c) Toughening the twisted fibers by chemical treatment, d) Optionally, cutting the fiber material, especially the toughened fibers, to obtain a short cut fiber material, e) Optionally, heating the fiber material, especially the short cut fiber material and f) Optionally, packing the fiber material, especially the heated short cut fiber material.

[0011] Especially, the fibers are selected from carbon fibers, polyvinyl alcohol fibers, aramid fibers and / or liquid-crystal polymers (LCPs) fibers

[0012] In an especially preferred embodiment, the fibers are carbon fibers.

[0013] However, it is also possible that the fibers are polyvinyl alcohol fibers.

[0014] Preferably, the concrete and / or mortar referred to herein refer to cement based concrete and / or cement based mortar.

[0015] In particular, a K Grade of the carbon fibers is 6 K, 12 K or 24 K.

[0016] K-grades, or modulus grades, refer to the stiffness or modulus of carbon fibers used in a composite. Modulus is a measure of a material’s resistance to deformation under load and is expressed in terms of pressure or stress. In other words, the higher the modulus of a carbon fiber, the stiffer it is, and the more resistance it offers to bending and twisting. In another preferred embodiment, the carbon fibers are T300, T700 or T800 carbon fibers.

[0017] Preferably, after step b) the twisted fibers have a spiral shaped structure.

[0018] Step c) has the effect that the twisted fibers are structurally fixed.

[0019] In a preferred embodiment, in step a) the fibers are immersed in a softening agent, in particular before heating.

[0020] Especially, the softening agent comprises organic amid and / or organic silicone.

[0021] Especially, in step b) the softened fibers are twisted with 20 - 200 TPM, especially 25 - 100, in particular 30 - 50 TPM.

[0022] According to another embodiment, the fibers are twisted with 80 - 200 TPM, preferably with 90 - 190 TPM, in particular with 100 - 180 TPM.

[0023] The abbreviation TPM in this document stands for Turns per meter.

[0024] In another preferred embodiment, in step b) the softened fibers are twisted with an elastic twisting equipment.

[0025] In a special embodiment, in step c) the chemical treatment comprises the step of immersing the twisted fibers in a synthetic resin.

[0026] Especially, the synthetic resin an epoxy resin and / or a polyurethane resin, preferably a modified epoxy resin.

[0027] Especially, the epoxy resin is present in an amount of 3 - 10 wt. - %, referred to the total weight of the twisted fibers after step b).

[0028] Preferably, the epoxy resin comprises a toughening agent, in particular active glycerol enzyme, to toughen the epoxy resin.

[0029] In a special embodiment, the toughening agent is present in amount of 2 - 5 wt. - %, referred to the total weight of the epoxy resin. In a further preferred embodiment, in step c) the chemical treatment comprises the step of immersing the twisted fibers in modified epoxy resin, where the modified epoxy resin is present in an amount of 3 - 5 wt. - %, referred to the total weight of the twisted fibers after step b) and where the modified epoxy resin comprises active glycerol enzyme as a toughening agent in an amount of 2 - 5 wt. - %, referred to the total weight of the modified epoxy resin.

[0030] According to a further preferred embodiment, in a further step c'), during and / or after step c), the twisted fibers and / or the toughened fibers are coated with inorganic particles, especially calcium carbonate. This allows for improving a bonding with concrete and / or mortar.

[0031] Especially, the coating takes places before step d).

[0032] In particular, coating is performed by exposing the twisted fibers and / or the toughened fibers to an aerosol comprising the inorganic particles dispersed in a gas phase, especially air.

[0033] The inorganic particles preferably are calcium carbonate particles, especially with a particle size D50 of 1 - 1'000 nm, especially 2 - 800 nm, in particular 5 - 600 nm or 10 - 400 nm. The particle size can e.g. be measured by laser diffraction according to the method as described in standard ISO 13320-1:2009, preferably with a Mastersizer 2000 device (trademark of Malvern Instruments Ltd, GB).

[0034] In a special embodiment, step d) is carried out. Especially, in step d) the toughened fibers are cut to a length of 2 - 55 mm, preferably 4 - 53 mm, in particular 6 - 50 mm.

[0035] Step d) may take place right after step c) or step c'). However, it may also be performed at a later stage or omitted.

[0036] In a further special embodiment, in step e) is carried out. Thereby, preferably, the fiber material, especially the short cut fiber material is heated homogeneously.

[0037] The homogeneous heating procedure preferably comprises the steps of placing the fiber material, especially the short cut fiber material, in an oven with a constant temperature to reduce the surface stress of the fiber material, especially the short cut fiber material, and thereby achieve homogenization. In a preferred embodiment, in step e) the fiber material, especially the short cut fiber material, is heated to a temperature of 160 - 240 °C, preferably 170 - 230 °C, in particular 180 - 220 °C, especially 180 - 200°C, especially preferred 195 - 205 °C.

[0038] In particular, after coating the fibers with the inorganic particles in step c'), step e) carried out.

[0039] According to a further preferred embodiment, a step x) of surface structuring of an outer surface of the fiber material is performed, especially by forming particle shaped protrusions on the outer surface of the fiber material. This allows for obtaining high friction with mortar and / or concrete.

[0040] For surface structuring, preferably, the fiber material is subjected to a temperature of

[0041] 200 - 250°C, especially 220-240°C, in particular in a heating channel; and a polymeric material, especially a thermosetting resin, is applied on the surface of the fiber material to form a surface structure, especially particle shaped protrusions.

[0042] In particular, the polymeric material is sprayed onto the surface of the fiber material, especially at regular distances and / or evenly distributed over the surface of the fiber material, in particular to form the particle shaped protrusions.

[0043] The polymeric material may be an epoxy resin and / or a phenolic resin. However, other polymeric materials may be used as well.

[0044] Especially preferred, the surface structuring takes place after step c) or c'), in particular after step e).

[0045] Especially, the method further comprises a step y) of winding the fiber material onto a take-up device, especially a reel. This allows for collecting the fiber material for storage and / or transportation.

[0046] In a further preferred embodiment, step f) is carried out.

[0047] In the following, especially preferred implementations are described:

[0048] In a first especially preferred implementation, the following process steps are performed in the given order: a), b), c), d), e) and f). In a second especially preferred implementation, at least the process steps a), b), c), c') and e) are performed in the given order.

[0049] In a third especially preferred implementation, at least the process steps a), b), c), c'), e) and x) are performed in the given order.

[0050] In a fourth especially preferred implementation, at least the process steps a), b), c), c'), e), x) and y) are performed in the given order.

[0051] In a sixth especially preferred implementation, at least the process steps a), b), c), c'), e), x), y) and d) are performed in the given order.

[0052] In a sixth especially preferred implementation, at least the process steps a), b), c), c'), e), x), y), d) and f) are performed in the given order. Especially, the method according to the invention is carried out as a two or multi stage process with steps a), b), c), optionally step c'), optionally step x), optionally step y), and optionally step e) taking place in a first location and / or at a first time and the further steps taking place in at least one second location and / or at a later time.

[0053] In particular, the fiber material obtained in the process, especially the heated short cut fiber material, is mixed with concrete and / or mortar in an additional step g).

[0054] Especially, step f) is performed and after step f) the packed fiber material, especially the packed heated short cut fiber material, is mixed with concrete and / or mortar in the additional step g) .

[0055] Compared with existing technology, the beneficial effects of the present invention are as follows:

[0056] Compared with the prior art, the fiber material, especially the heated short cut fiber material, according to the invention has an increased adsorption capacity with the concrete by more than 28 %, and the dispersion of the fiber material, especially the heated short cut fiber material, in mortar has increased by more than 16 %. Using carbon fiber yams of equal strength to produce short cut carbon fiber material, the strength of the short cut carbon fiber material is increased by more than 12 %; The mechanical properties of concrete and mortar with the same amount of heated short cut carbon fiber material according to the invention are significantly optimized compared to traditional short cut carbon fiber material. Due to the steps of softening and twisting, a large amount of discarded carbon fibers or substandard carbon fibers on the market can be softened to facilitate twisting treatment, thus to achieve comprehensive utilization of waste and reduce carbon emissions.

[0057] Brief description of the drawings

[0058] The attached drawing is used to provide a further understanding of the present invention and form a part of the specification. It is used to explain the embodiments described below and does not constitute a limitation of the present invention.

[0059] In the attached drawing,

[0060] Fig. 1 shows the steps a) to f) of the method according to the invention.

[0061] Preferred embodiments

[0062] The following is a description of the preferred embodiments of the present invention based on the attached drawing. It should be understood that the preferred embodiments described here is only used to illustrate and explain the invention, and are not used to limit the scope of protection of the present invention.

[0063] Fig. 1 shows the method according to the invention for producing a short cut fiber material to improve the performance of concrete comprising the following steps: a) Softening fibers, b) Twisting the softened fibers, c) Toughening the twisted fibers by chemical treatment, d) Cutting the toughened fibers to obtain a short cut fiber material, e) Heating the short cut fiber material and f) Packing the heated short cut fiber material.

[0064] Embodiment 1

[0065] Soak T800 - 6K carbon fibers in a softener composed by 15 wt. - % organic amide and organic silicone, referred to the total weight of the carbon fibers, dry at 105 °C, then twist by 120 TPM, after that, soak them with toughened epoxy resin with a solid content of 55 wt. - %, referred to the total weight of the epoxy resin, and dry them at 230 °C, finally, cut them into short fibers with a length of 6 - 50mm by using a cutting machine and dry them in a 200 °C oven for 2 hours. This type of heated short cut carbon fiber is added to mortar at 4.5 vol. - %, referred to the total volume of the mortar. Compared with short cut carbon fibers that have not been softened, twisted and toughened, the bonding strength in mortar is increased by 21.2 %, the bending capacity is improved by 10.8 %, and the dispersion ability is improved by 11.2 %.

[0066] Embodiment 2

[0067] Soak T700 - 12K carbon fibers in a softener with 13 wt. - % silicone, referred to the total weight of the carbon fibers, then dry them. Twist the softened carbon fibers by 170 TPM, then soak the twisted carbon fibers in a modified epoxy resin with a solid content of 40 wt. - %, referred to the total weight of the epoxy resin, dry them again at 215 °C, and then cut them with a cutting machine into short fibers with a length of 6 - 25mm. By adding this type of heated short cut carbon fiber to mortar at 2.8 vol. - %, referred to the total weight of the mortar, compared with mortar without carbon fibers, the bending strength of concrete increased by 22 %, the splitting tensile strength increased by 19 %, and the Poisson's ratio decreased by 17 %.

[0068] Embodiment 3

[0069] In Embodiment 3, a method according to the invention for producing a fiber material comprises the following steps in the given order: a) Softening fibers, b) Twisting the softened fibers, c) Toughening the twisted fibers by chemical treatment, c') Coated the twisted fibers with inorganic particles, e) Heating the short cut fiber material, x) Surface structuring of an outer surface of the fiber material, y) Winding the fiber material onto a take-up device, especially a reel d) Cutting the fiber material to obtain a short cut fiber material f) Packing the heated short cut fiber material.

[0070] Steps a), b), c), d), e) and f were performed similar to embodiment 1 but in the order as described above.

[0071] Step c') was performed by exposing the twisted fibers to an aerosol of air and ultrafine calcium carbonate particles (D50 value in the nanometer range), In step x) the fiber material was subjected to a temperature of 220-240°C in a heating channel, and a polymeric material, e.g. in the form of epoxy, was applied on the surface of the fiber material to form evenly distributed particle shaped protrusions on the outer surface by spraying the polymeric material onto the outer surface of the fiber material. In step y), the fiber material was collected on a reel.

[0072] The above mentioned embodiments are only preferred embodiments of the invention and do not limit the scope of protection of the invention. Although the present invention is described in detail with reference to the aforementioned embodiments, it is still possible for a person skilled in the art to modify the technical solutions in the aforementioned embodiments or to equivalently replace some of their technical features. Any modifications, equivalent substitutions, improvements etc. made within the spirit and principles of the invention shall be included within the scope of protection of the invention.

[0073] Reference signs a) Step a): Softening fibers b) Step b): Twisting the softened fibers c) Step c): Toughening the twisted fibers by chemical treatment d) Step d): Cutting the toughened fibers to obtain a short cut fiber material e) Step e): Heating the short cut fiber material f) Step f): Packing the heated short cut fiber material

Claims

Claims1. A method for producing a fiber material, preferably heated fiber material, in particular a heated short cut fiber material, especially a heated short cut carbon fiber material, in particular to improve the performance of concrete, comprising the following steps: a) Softening fibers, b) Twisting the softened fibers, c) Toughening the twisted fibers by chemical treatment, d) Optionally, cutting the fiber material, especially the toughened fibers, to obtain a short cut fiber material, e) Optionally, heating the fiber material, especially the short cut fiber material, and f) Optionally, packing the fiber material, especially the heated fiber material, in particular the heated short cut fiber material.

2. The method according to claim 1, where the fibers are selected from carbon fibers, polyvinyl alcohol fibers, aramid fibers and / or liquid-crystal polymers (LCPs) fibers.

3. The method according to claim 2, where the fibers are carbon fibers.

4. The method according to any of the aforementioned claims, where in step a) the fibers are immersed in a softening agent.

5. The method according to claim 3, where the softening agent comprises organic amid and / or organic silicone.

6. The method according to any of the aforementioned claims, where in step b) the softened fibers are twisted with 20 - 200 TPM, especially 25 - 100, in particular 30 - 50 TPM.

7. The method according to any of the aforementioned claims, where in step c) the chemical treatment comprises the step of immersing the twisted fibers in a synthetic resin.

8. The method according to claim 7, whereby the synthetic resin is an epoxy resin and / or a polyurethane resin, preferably a modified epoxy resin.

9. The method according to any of the aforementioned claims, whereby in a further step c'), during and / or after step c), the twisted fibers and / or the toughened fibers are coated with inorganic particles, especially calcium carbonate.

10. The method according to claim 9, whereby coating is performed by exposing the twisted fibers and / or the toughened fibers to an aerosol comprising the inorganic particles dispersed in a gas phase, especially air.

11. The method according to any of claims 9 - 10, whereby the inorganic particles are calcium carbonate particles, especially with a particle size D50 of 1 - 1'000 nm, especially 2 - 800 nm, in particular 5 - 600 nm or 10 - 400 nm.

12. The method according to any of the aforementioned claims, where step d) is carried out.

13. The method according to claim 12 whereby, in step d) the toughened fibers are cut to a length of 2 - 55 mm, preferably 4 - 53 mm, in particular 6 - 50 mm.

14. The method according to any of the aforementioned claims, where step e) is carried out.

15. The method according to claim 14, where in step e) the fiber material, especially the short cut fiber material, is heated homogeneously.

16. The method according to any of claims 14 - 15, where in step e) the fiber material, especially the short cut fiber material, is heated to a temperature of 160 - 240 °C, preferably 170 - 230 °C, in particular 180 - 220 °C, especially 180 - 200°, especially preferred 195 - 205 °C.

17. The method according to any of claims 9 - 11, whereby after coating the fibers with the inorganic particles, step e) according to any of claims 12 - 15 is carried out.

18. The method according to any of the aforementioned claims, further comprising a step x) of surface structuring of an outer surface of the fiber material, especially by forming particle shaped protrusions on the outer surface of the fiber material.

19. The method according to claim 18, whereby for surface structuring, the fiber material is subjected to a temperature of 200 - 250°C, especially 220-240°C, and a polymeric material, especially a thermosetting resin, is applied on the surface of the fiber material to form a surface structure, especially particle shaped protrusions.

20. The method according to claim 19, whereby the polymeric material is sprayed onto the surface of the fiber material, especially at regular distances and / or evenly distributed over the surface of the fiber material, in particular to form the particle shaped protrusions.

21. The method according to any of claims 19 - 20, whereby the polymeric material is an epoxy resin and / or a phenolic resin.

22. The method according to any of claims 18 - 21, whereby the surface structuring takes place after step c) or c'), in particular after step e).

23. The method according to any of the aforementioned claims, further comprising a step y) of winding the fiber material onto a take-up device, especially a reel.

24. The method according to any of the aforementioned claims, where step f) is carried out.

25. The method according to any of the aforementioned claims whereby the following process steps are performed in the given order: a), b), c), d), e) and f).

26. The method according to any of claims 9 - 24, whereby at least the process steps a), b), c), c') and e) are performed in the given order.

27. The method according to any of claims 18 - 24, whereby at least the process steps a), b), c), c'), e) and x) are performed in the given order.

28. The method according to any of claims 18 - 24, whereby at least the process steps a), b), c), c'), e), x) and y) are performed in the given order.

29. The method according to any of claims 23 - 24, whereby at least the process steps a), b), c), c'), e), x), y) and d) are performed in the given order.

30. The method according to claim 24, whereby at least the process steps a), b), c), c'), e), x), y), d) and f) are performed in the given order.

31. The method according to any of the aforementioned claims, whereby the fiber material, especially the heated short cut fiber material, is mixed with concrete and / or mortar in an additional step g).

32. The method according to claim 31, whereby step f) is performed and after step f) the packed fiber material, especially the packed heated short cut fiber material, is mixed with concrete and / or mortar in the additional step g).

33. The method according to any of preceding claims, whereby the method is carried out as a two or multi stage process with steps a), b), c), optionally step c'), optionally step x), optionally step y), and optionally step e) taking place in a first location and / or at a first time and the further steps taking place in at least one second location and / or at a later time.

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