METHOD FOR SPLITTING CARBON FIBER TOW

Abstract

Provided is a method for splitting a carbon fiber tow, which comprises heating a carbon fiber tow sized with a first sizing material to soften the first sizing material and form a spread carbon fiber tow; passing the spread carbon fiber tow through at least one splitter and corresponding cutter to obtain multiple carbon fiber strands spaced apart; and sizing the carbon fiber strands with a second sizing material. With the method, multiple small carbon fiber tows having better tensile strength and/or modulus than the commercially available small carbon fiber tow products can be obtained. Products made of the small carbon fiber tows obtained by the present invention are lighter but stronger, and the production cost is relatively reduced. The present invention also achieves the purpose of energy saving and carbon reduction.

Claims

1. A method for splitting a carbon fiber tow, comprising: (A) providing a carbon fiber tow comprising multiple carbon filaments sized with a solution containing a first sizing material; (B) passing the carbon fiber tow through a first heating device to heat the carbon fiber tow at a temperature of between 45° C. and 140° C., so as to soften the first sizing material and form a spread carbon fiber tow; (C) adjusting the tension of the spread carbon fiber tow; (D) passing the spread carbon fiber tow through at least one splitter to obtain a plurality of multiple carbon fiber strands spaced apart; (E) passing the spread carbon fiber tow through at least one cutter to cut the carbon filaments connected between the carbon fiber strands; (F) adjusting the tension of the carbon fiber strands; (G) sizing the carbon fiber strands with a solution containing a second sizing material to obtain multiple sized carbon fiber strands; and (H) passing the multiple sized carbon fiber strands through a second heating device to heat the sized carbon fiber strands to obtain multiple split carbon fiber tows.

2. The method as claimed in claim 1, wherein the spread carbon fiber tow has a maximum width for the carbon fiber tow.

3. The method as claimed in claim 1, the step (B) is repeated multiple times to obtain the spread carbon fiber tow.

4. The method as claimed in claim 1, further comprising, in the step (H), passing the multiple sized carbon fiber strands through a cooling device after passing the multiple sized carbon fiber strands through a second heating device.

5. The method as claimed in claim 1, further comprising adjusting the width of the multiple sized carbon fiber tows.

6. The method as claimed in claim 4, further comprising adjusting the width of the multiple sized carbon fiber tows.

7. The method as claimed in claim 1, further comprising, after the step (E) and before the step (F), guiding each of the carbon fiber strands to one of guiding rollers respectively, wherein any two adjacent carbon fiber strands were guided to guiding rollers at different height level.

8. The method as claimed in claim 1, wherein the first sizing material is a thermosetting material.

9. The method as claimed in claim 1, wherein the second sizing material comprises a thermoplastic material or a thermosetting material.

10. The method as claimed in claim 9, wherein the thermoplastic material is selected from a group consisting of an acrylonitrile butadiene styrene (ABS), a polypropylene (PP), a polyethylene (PE), a polycarbonate (PC), a polyurethane (PU), a polystyrene (PS), a polyethylene terephthalate (PET), and a polyetheretherketone (PEEK).

11. The method as claimed in claim 9, wherein the thermosetting material is an epoxy resin.

12. The method as claimed in claim 1, wherein the carbon fiber tow is heated at a temperature of between 80° C. and 120° C. in Step (B).

13. The method as claimed in claim 1, wherein the multiple sized carbon fiber strands are heated at a temperature of between 80° C. and 120° C. in Step (H).

14. The method as claimed in claim 4, wherein the multiple sized carbon fiber strands are cooled at a temperature of between 2° C. and 10° C.

15. The method as claimed in claim 6, wherein the multiple sized carbon fiber strands are cooled at a temperature of between 2° C. and 10° C.

16. The method as claimed in claim 1, wherein the at least one splitter is made of metal.

17. The method as claimed in claim 1, wherein the at least one splitter is configured to equally split the spread carbon fiber tow.

18. The method as claimed in claim 1, wherein the at least one cutter is a circular saw blade.

19. The method as claimed in claim 1, wherein the split carbon fiber tow has a breaking strength of 16.0 kgf or higher and a breaking elongation of 4.8% or higher.

20. The method as claimed in claim 19, wherein the split carbon fiber tow has a length of about 5000 meters.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] FIG. 1 is a schematic diagram of a carbon fiber tow wound on a bobbin;

[0047] FIG. 2 is a schematic diagram showing the spreading of the carbon fiber tow;

[0048] FIG. 3 is a schematic diagram of guide roller assemblies;

[0049] FIG. 4 is a schematic diagram of a spread carbon fiber tow wound on a bobbin;

[0050] FIG. 5 is a schematic diagram showing the splitting and subsequent treatment of the carbon fiber tow;

[0051] FIG. 6 is a schematic diagram of a guide roller with eight grooves;

[0052] FIG. 7 is a schematic diagram of the carbon fiber tow produced by the method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] An example is exemplified below to illustrate the implementation of the method for splitting a carbon fiber tow of the present invention. A person skilled in the art can easily realize the advantages and effects of the present invention in accordance with the example and the accompanied drawings. It should be understood that the descriptions proposed herein are just preferable embodiments for the purpose of illustration only, not intended to limit the scope of the present invention. Various modifications and variations can be made to the present invention, without departing from the spirit and scope of the invention.

Example

[0054] As shown in FIG. 1, a commercial PAN carbon fiber tow 1 (manufacturer: Toray Industries, Inc., Japan; product no.: T700SC) having a width of W1, which was wound on a bobbin, was provided. The carbon fiber tow 1 had a length of 5000 meters (m) and a width (W1) of 7 millimeters (mm). The carbon fiber tow 1 contained 12000 carbon filaments (e.g. 12K), and was sized with an epoxy resin. In the following example, the 12K carbon fiber tow 1 was equally split and further sized into four split carbon fiber tows 21 by the method of the present invention, wherein each of the split carbon fiber tows 21 had a length of 5000 m and contained 3000 carbon filaments (e.g. 3K).

[0055] In the method of the present invention, the carbon fiber tow 1 was spread, split, and sized. The carbon fiber tow 1 was unwound and heated to be spread; the spread carbon fiber tow 7 was wound for further use first, and then unwound to be split and sized. The tension of the carbon fiber tow 1, the spread carbon fiber tow 7 and the split carbon fiber tows 21 was adjusted between steps for many times. The whole production line in the example is about 15 meters (m), and two spread carbon fiber tows 7 can be split at the same time to obtain eight split carbon fiber tows 21 because all rollers are wide enough to accommodate the tows and strands. The process was described in detail below.

[0056] First of all, an additional segment of sub-quality carbon fiber tow was stuck to the end of the carbon fiber tow 1 as a first guiding tow (not shown) by super glue. As shown in FIG. 2, the commercial carbon fiber tow 1 glued with the first guiding tow was provided on a feed creel 2. The free end of the first guiding tow was guided by hand from the feed creel 2 through a direction adjuster 3 to a tension device 4A first, and guided to a series of guide rollers 5 including a first guide roller 5A, multiple guide roller assemblies 5B and a second guide roller 5C. The feed creel 2 could regulate the tension of the carbon fiber tow 1 so that the carbon fiber tow 1 left the feed creel 2 with a constant tension. The direction adjuster 3 enabled the carbon fiber tow 1 to go straight to the tension device 4A and the series of guide rollers 5. The tension device 4A regulated the tension of the carbon fiber tow 1 before spreading, so that the carbon fiber tow 1 was not too tight, or too slack and sagged.

[0057] While the carbon fiber tow 1 arrived at the section between the first guide roller 5A and the second guide roller 5C, the carbon fiber tow 1 was guided to pass through an infrared heater 6 and heated at a temperature between 80° C. and 120° C., so as to soften the epoxy resin that sized the carbon fiber tow 1. As a result, the width of the carbon fiber tow 1 was gradually increased, as the tow schematically illustrated below between the two dashed lines in FIG. 2. Each of the plurality of guide roller assemblies 5B comprised a guide roller 51 and a track 52, as shown in FIG. 3. The position of the guide roller 51 was adjustable along the track 52 so as to adjust the route length of the carbon fiber tow 1 between the first guide roller 5A and the second guide roller 5C. As the vertical distance between two guide rollers 51 in adjacent guide roller assemblies 5B increased, the route length of the carbon fiber tow 1 increased, so that the heating time could be adjusted to sufficiently soften the epoxy resin that sized the carbon fiber tow 1. In order to further increase the heating time, the number of the plurality of guide roller assemblies 5B could be increased, which resulted in a longer route length of the carbon fiber tow 1. In this example, the number of the plurality of guide roller assemblies 5B is five; in other embodiments, the number of the plurality of guide roller assemblies 5B may be from four to twelve. In this example, the adjacent guide roller assemblies 5B are positioned at different height levels; in other embodiments, all guide roller assemblies 5B may be positioned at the same height level.

[0058] When the carbon fiber tow 1 was guided out of the second guide roller 5C, the 12K carbon fiber tow 1 had been spread into the spread carbon fiber tow 7 having a width (W2) of 16 mm. The tension of the spread carbon fiber tow 7 was further regulated by the tension device 4B, so that the spread carbon fiber tow 7 was not too tight, or too slack and sagged. After that, the spread carbon fiber tow 7 was further guided to a first winder 8. When the free end of the first guiding tow arrived at the first winder 8, the joint of the first guiding tow and the spread carbon fiber tow 7 left the feed creel 2. At this point, the first winder 8 started to operate at a winding speed of 25 meters per minute (m/min) so that the carbon fiber tow 1 was left the feed creel 2 at the same speed. Therefore, the feeding speed could be controlled by the first winder 8. When the spread carbon fiber tow 7 started to be wound on first the winder 8, the first guiding tow was removed. As shown in FIG. 4, the spread carbon fiber tow 7 having a width of W2 was wound on a bobbin. It is noted that W2 is larger than W1.

[0059] Similarly, an additional segment of sub-quality spread carbon fiber tow was stuck to the end of the spread carbon fiber tow 7 as a second guiding tow (not shown in figures) by super glue.

[0060] As shown in FIG. 5, a spread carbon fiber tow 7 was provided on a feed creel 9. In this example, two spread carbon fiber tows 7 spaced apart were provided in parallel to enhance product yield.

[0061] The free end of each second guiding tow was guided by hand to a tension device 10. The tension device 10 regulated the tension of each spread carbon fiber tow 7 so that the spread carbon fiber tows 7 were not too tight, or too slack and sagged.

[0062] Subsequently, the free end of each second guiding tow was guided by hand to a splitting device 11. In this example, the splitting device 11 comprised two sets of splitters 11A, wherein each of the sets contained three evenly spaced splitters 11A. The six splitters 11A were arranged on a hypothetical straight line perpendicular to the moving direction of the carbon fiber tows. When each spread carbon fiber tow 7 passed through one set of the splitters 11A, the spread carbon fiber tows 7 having 12000 carbon filaments were equally divided into four carbon fiber strands 20, each of which contained 3000 carbon filaments and had a width of 4 mm. The eight carbon fiber strands 20 were guided to eight grooves G on a first grooved guiding roller 11B and then to eight corresponding grooves G on a second grooved guiding roller 11D. Each groove G had a width of 4 mm, and the distance between two adjacent grooves G was 2 mm. The rollers arranged after the first grooved guiding roller 11B contained the same number of grooves G to accommodate the eight carbon fiber strands 20.

[0063] Since the carbon filaments comprised in the spread carbon fiber tows 7 might be skewed, not kept completely straight in the whole spread carbon fiber tows 7, there were carbon filaments connected between the carbon fiber strands 20 after splitting by the splitters 11A. Six cutters 11C were arranged on a hypothetical straight line perpendicular to the moving direction of the carbon fiber strands 20 between the first grooved guiding roller 11B and second grooved guiding roller 11D, to cut the carbon filaments connected between the carbon fiber strands 20.

[0064] After the second grooved guiding roller 11D, the eight carbon fiber strands 20 were then guided by hand to a third grooved guiding roller 11E, which also had eight grooves G as the first grooved guiding roller 11B, and arranged at a lower height level than the first grooved guiding roller 11B and second grooved guiding roller 11D. The difference of height level was advantageous to evenly transport the carbon fiber strands 20. FIG. 6 schematically shows the guide roller 11B which has eight grooves G. The first grooved guiding roller 11B, second grooved guiding roller 11D and third grooved guiding roller 11E contained the same number of grooves G to accommodate the carbon fiber strands 20.

[0065] The carbon fiber strands 20 were then sequentially guided to two sets of guide rollers 11F, wherein each set contained four guide rollers 11F at different height levels. Each of the carbon fiber strands 20 was guided to one of the guide rollers 11F to expand the distance between any of two adjacent carbon fiber strands 20. Any two adjacent guide rollers 11F were space apart by a vertical distance of 10 cm. Guide rollers 11F were not grooved. The horizontal distance between two carbon fiber strands 20 on two adjacent guide rollers 11F was about 5 mm. Therefore, the carbon fiber strands 20 are vertically and horizontally spaced apart.

[0066] The eight carbon fiber strands 20 were guided to a tension device 12. The route lengths of the carbon fiber strands 19 were different, so the tension device 12 was arranged to regulate the tension of the eight carbon fiber strands 20 so that the carbon fiber strands 20 were not too tight, or too slack and sagged. Since the carbon fiber strands 20 were split, cut and spaced apart with appropriate vertical and horizontal distances.

[0067] Subsequently, the eight carbon fiber strands 20 were then sized, heated and cooled.

[0068] After the tension device 12, the eight carbon fiber strands 20 were guided to a sizing device 13, which comprised a sizing bath 13A, a grooved guide roller 13B, a grooved guide roller 13C, and a roller 13D. The grooved guide roller 13B and the grooved guide roller 13C were made of stainless steel while the roller 13D was made of synthetic rubber. In this example, the sizing bath 13A was filled with a thermoplastic slurry comprising acrylonitrile butadiene styrene (ABS) polymer. The ABS polymer was dissolved in water to obtain the sizing solution with sizing content of 1%. After the eight carbon fiber strands 20 were guided through the sizing bath 13A, each of the eight carbon fiber strands 20 was sized with the sizing solution so as to eliminate carbon fiber fuzz and thus smooth the surfaces of the eight carbon fiber strands 20. When the eight carbon fiber strands 20 were guided through the grooved guide roller 13C, these carbon fiber strands 20 were pressed by the roller 13D in order to squeeze extra sizing solution. Eight carbon fiber strands 20 were sized.

[0069] Subsequently, the eight carbon fiber strands 20 were guided to a heating device 14, which comprised multiple grooved guide rollers 14A and multiple infrared heaters 14B. The temperature of the plurality of infrared heaters 14B was set between 120° C. and 140° C. so as to evaporate the water in the eight carbon fiber strands 20. The eight carbon fiber strands 20 were then guided to a tension device 15 to adjust the tension of the eight carbon fiber strands 20.

[0070] The eight carbon fiber strands 20 were then guided to a cooling chamber 16, which contained multiple grooved guide rollers 16A. The temperature of the cooling chamber 16 was set between 3° C. and 7° C. to cool the eight carbon fiber strands 20 and facilitate the cure of the thermoplastic sizing material (e.g. ABS polymer). The eight carbon fiber strands 20 were then guided to a tension device 17 to adjust the tension of the eight carbon fiber strands 20. After that, eight split carbon fiber tows 21 were obtained. The eight carbon fiber tows 21 could be optionally guided by hand to grooved roller 18 to adjust the width of the sized carbon fiber tows 21. The width of the grooves on the grooved roller 18 was 2.9 mm. After the width adjustment, the width of the eight split carbon fiber tows 21 was adjusted to 2.9 mm (W3). When the width of the split carbon fiber tows 21 was not adjusted, the grooves on the grooved roller 18 could be removed or replaced by another roller without grooves for width adjustment.

[0071] When the eight free ends of the split second guiding tows arrived at the eight winders 19A in a winding device 19, the winding device 19 started to operate at a winding speed of 12.5 m/min to pull the two spread carbon fiber tows 7. Therefore, the feeding speed of the spread carbon fiber tows 7 could be controlled by the winding device 19. After the strands split from the second guiding tows were totally wound, the second guiding tows were removed and the split carbon fiber tows 21 after the second guiding tows were wound. As shown in FIG. 7, the split carbon fiber tows 21 having a width of W3 were wound on a bobbin. As above, the width adjustment step is optional, and the split carbon fiber tows 21 without width adjustment had a width of W3′ (not shown). It is noted that W3 and W3′ are both smaller than W1, and W3 is smaller than W3′. In this example, there were eight split carbon fiber tows 21 produced from the two spread carbon fiber tows 7, wherein each of the carbon fiber tows 21 had a length of 5000 m and contained 3000 carbon filaments (e.g. 3K). In addition, the length of the eight split carbon fiber tows 21 was the same as that of the carbon fiber tow 1.

Test Example: Breaking Strength and Breaking Elongation of Produced 3K Carbon Fiber Tow

[0072] In this test example, a section of the carbon fiber strands 21 without width adjustment, which had a width of 4 mm, was used as a test sample.

[0073] Breaking strength and breaking elongation of the test sample were measured in accordance with ASTM D2256-2002, Option A1, wherein the test sample was loaded into grips, the gage length (length of thread between grips) was 25 cm, and the speed of testing was 30±1 centimeters per minute (cm/min).

[0074] For the test sample, the breaking strength was 16.0 kilogram-force (kgf) and the breaking elongation was 4.8%. From comparison of breaking strength and breaking elongation with the control test samples, it is found the test sample is the equivalent of T500 and T550 of the carbon fiber tow produced by Toray Industries, Inc.

[0075] With the method for splitting a carbon fiber tow of the present invention, a commercial 12K PAN carbon fiber tow, which has better tensile strength than other commercially available 3K carbon fiber tow, can be used to produce four 3K carbon fiber tows. The 3K carbon fiber tows obtained by splitting the 12K PAN carbon fiber tow have better tensile strength than other commercially available 3K carbon fiber tows. From the above description, a small carbon fiber tow (e.g. 1K to 6K) with higher tensile strength or modulus can be produced by the method for splitting a carbon fiber tow of the present invention. Thus, the products manufactured from the small carbon fiber tow obtained by the present invention have enhanced strength, and can be applied to many other technical fields.

[0076] In summary, the method for splitting a carbon fiber tow of the present invention can provide small carbon fiber tows (e.g. having 1000 to 6000 carbon filaments) with increased tensile strength and/or modulus than corresponding commercial products, and reduce the production cost thereof. The split carbon fiber tows produced by the present invention can be applied to many a variety of products, such as 3C products, sporting goods, wind power generation, new energy vehicles, drones, aerospace, aviation and military applications, and the like, and they can also be used as the raw material for 3D printing. The products produced from the small carbon fiber tows obtained by the present invention are lighter but stronger.

[0077] Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the features of the invention, the disclosure is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.