Method for producing carbon fiber spun yarn

Abstract

To provide a method for producing carbon fiber spun yarn that can reduce variations in sliver thickness while suppressing breakage of carbon fibers.SOLUTION: This method for producing a carbon fiber spun yarn includes performing, a plurality of times, a kneading step for performing a kneading treatment while applying a load to a sliver composed of a plurality of carbon fibers. In the first kneading step, the load applied to the sliver is smaller than the load applied to the sliver in at least one of the second and subsequent kneading steps.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a carbon fiber spun yarn. [Background technology]

[0002] Patent Document 1 describes a method for producing a carbon fiber spun yarn. The method for producing a carbon fiber spun yarn includes multiple drawing steps. The drawing steps are steps in which a sliver made up of multiple carbon fibers is subjected to a drawing treatment.

[0003] Patent Document 2 describes that in the drawing process, a drawing treatment is carried out while applying a load to the sliver. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-179809 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-36554 Summary of the Invention [Problem to be solved by the invention]

[0005] When a sliver is made up of a plurality of carbon fibers, the carbon fibers may break when a drawing process is performed while applying a load to the sliver, which results in a decrease in material yield. [Means for solving the problem]

[0006] A method for manufacturing carbon fiber spun yarn to solve the above problems is a method for manufacturing carbon fiber spun yarn that includes multiple drawing processes in which a sliver made up of multiple carbon fibers is subjected to a drawing process while a load is applied to the sliver, and the load applied to the sliver in the first drawing process is smaller than the load applied to the sliver in at least one of the second or subsequent drawing processes.

[0007] In the second and subsequent drawing processes, the drawing treatment is performed on the sliver after the drawing process, so the carbon fibers in the sliver in the second and subsequent drawing processes are more aligned than in the sliver in the first drawing process. In other words, the carbon fibers in the sliver in the first drawing process are less aligned than in the sliver in the second and subsequent drawing processes.

[0008] When the carbon fibers are aligned, the contact area between the carbon fibers is large, which distributes the load applied to the sliver, making the carbon fibers less likely to break. On the other hand, when the carbon fibers are not aligned, the contact area between the carbon fibers is small, which causes the load applied to the sliver to be applied locally to the carbon fibers, making the carbon fibers more likely to break. Therefore, in the first drawing process, the carbon fibers are more likely to break than in the second or subsequent drawing processes. In other words, in the second or subsequent drawing processes, the carbon fibers are less likely to break than in the first drawing process.

[0009] According to the above configuration, the load applied to the sliver in the first drawing process is smaller than the load applied to the sliver in at least one of the second and subsequent drawing processes. In this way, by reducing the load applied to the sliver in the first drawing process, in which carbon fibers are likely to break, breakage of the carbon fibers can be suppressed. Furthermore, by increasing the load applied to the sliver in at least one of the second and subsequent drawing processes, in which carbon fibers are unlikely to break, variation in sliver thickness can be reduced. Therefore, variation in sliver thickness can be reduced while suppressing breakage of carbon fibers.

[0010] In the above-mentioned method for producing carbon fiber spun yarn, the drawing process may be performed three or more times, and the load applied to the sliver in each drawing process from the second drawing process onwards may be greater than the load applied to the sliver in the first drawing process.

[0011] According to the above configuration, the variation in sliver thickness can be further reduced compared to when the load applied to the sliver in only some of the multiple drawing processes performed from the second onwards is greater than the load applied to the sliver in the first drawing process.

[0012] In the method for producing a carbon fiber spun yarn, the load applied to the sliver in two consecutive drawing steps from the second drawing step onwards may be the same. According to the above configuration, the variation in sliver thickness can be further reduced compared to when the load applied to the sliver in one of two consecutive drawing processes from the second onwards is smaller than the load applied to the sliver in the other drawing process.

[0013] Furthermore, when the drawing processes are performed using the same drawing frame, if the loads applied to the sliver in two consecutive drawing processes are different, the worker needs to change the load applied to the sliver by replacing the load applying unit of the drawing frame. According to the above configuration, the load applied to the sliver in two consecutive drawing processes from the second onwards is the same. Therefore, it is possible to eliminate the need for the worker to replace the load applying unit of the drawing frame between two consecutive drawing processes from the second onwards. [Effects of the Invention]

[0014] According to the present invention, it is possible to reduce the variation in the thickness of the sliver while suppressing breakage of the carbon fiber. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a flowchart showing a method for producing a carbon fiber spun yarn. [Figure 2]FIG. 2 is a side view showing a drawing frame. [Figure 3] FIG. 3 is a schematic diagram showing the sliver in the first drawing step. [Figure 4] FIG. 4 is a schematic diagram showing the sliver in the second drawing step. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, one embodiment of a method for producing a carbon fiber spun yarn will be described with reference to FIGS. <Method for manufacturing carbon fiber spun yarn> As shown in Fig. 1, the method for producing carbon fiber spun yarn includes multiple drawing steps. The method for producing carbon fiber spun yarn of this embodiment includes three drawing steps as the multiple drawing steps. Of the three drawing steps, the drawing step carried out first is referred to as the first drawing step S1, the drawing step carried out second is referred to as the second drawing step S2, and the drawing step carried out third is referred to as the third drawing step S3. The second drawing step S2 and the third drawing step S3 are each the second or subsequent drawing steps. The second drawing step S2 and the third drawing step S3 are two consecutive drawing steps.

[0017] The first to third drawing steps S1 to S3 are steps in which a drawing process is performed while applying a load to a sliver S (see FIGS. 3 and 4) made up of a plurality of carbon fibers F. The drawing process is a process in which a plurality of slivers S are drafted while doubling them into a single sliver S. The drawing process is performed by a drawing frame 10, which will be described later. In this embodiment, the first to third drawing steps S1 to S3 are performed by the same drawing frame 10.

[0018] In the first drawing step S1, the drawing frame 10 performs a drawing process while applying a load to the card sliver. The card sliver is the sliver S that has been carded in the carding process, which is a process before the drawing process. In the second drawing step S2, the drawing frame 10 performs a drawing process while applying a load to the drawn sliver, which is the sliver S after the first drawing step S1. In the third drawing step S3, the drawing frame 10 performs a drawing process while applying a load to the drawn sliver, which is the sliver S after the second drawing step S2.

[0019] The load applied to the sliver S in the first drawing process is smaller than the load applied to the sliver S in the second and subsequent drawing processes. In this embodiment, the load applied to the sliver S in each step of the second and subsequent drawing processes is larger than the load applied to the sliver S in the first drawing process. In other words, the load applied to the sliver S in the second drawing process and the load applied to the sliver S in the third drawing process are each larger than the load applied to the sliver S in the first drawing process.

[0020] Specifically, the load W1 applied to the sliver S in the first drawing process S1 is smaller than the load W2 applied to the sliver S in the second drawing process S2. In other words, the load W2 applied to the sliver S in the second drawing process S2 is larger than the load W1 applied to the sliver S in the first drawing process S1.

[0021] The load W3 applied to the sliver S in the third drawing process S3 is larger than the load W1 applied to the sliver S in the first drawing process S1. In other words, the load W1 applied to the sliver S in the first drawing process S1 is smaller than the load W3 applied to the sliver S in the third drawing process S3.

[0022] In this embodiment, the load applied to the sliver S in two consecutive drawing processes from the second onwards is the same. Specifically, the load W2 applied to the sliver S in the second drawing process S2 and the load W3 applied to the sliver S in the third drawing process S3 are the same.

[0023] <Drawing machine> As shown in Fig. 2, the drawing frame 10 includes a plurality of roller pairs 11, guide rollers 12, and a load applying section 13. The drawing frame 10 of this embodiment includes a first roller pair 11a, a second roller pair 11b, a third roller pair 11c, and a fourth roller pair 11d as the plurality of roller pairs 11. The load applying section 13 of this embodiment is formed by a spring.

[0024] The second roller pair 11b is arranged downstream of the first roller pair 11a in the feed direction X of the sliver S. The third roller pair 11c is arranged downstream of the second roller pair 11b in the feed direction X of the sliver S. The fourth roller pair 11d is arranged downstream of the third roller pair 11c in the feed direction X of the sliver S. Each roller pair 11 has a lower roller 14 and an upper roller 15 provided above the lower roller 14. The guide roller 12 is arranged downstream of the upper roller 15 of the fourth roller pair 11d in the feed direction X of the sliver S.

[0025] In one drawing process, the sliver S passes between the lower roller 14 and the upper roller 15 of the first roller pair 11a, between the lower roller 14 and the upper roller 15 of the second roller pair 11b, between the lower roller 14 and the upper roller 15 of the third roller pair 11c, between the lower roller 14 and the upper roller 15 of the fourth roller pair 11d, and between the lower roller 14 and the guide roller 12 of the fourth roller pair 11d, in that order.

[0026] The roller pair 11 located more downstream in the feed direction X of the sliver S has a faster rotation speed. Specifically, the rotation speed of the second roller pair 11b is faster than the rotation speed of the first roller pair 11a. The rotation speed of the third roller pair 11c is faster than the rotation speed of the second roller pair 11b. The rotation speed of the fourth roller pair 11d is faster than the rotation speed of the third roller pair 11c. This causes the sliver S to be drafted. The guide roller 12 guides the sliver S drafted by the first to fourth roller pairs 11a to 11d in the feed direction X.

[0027] In this embodiment, the load applying section 13 is provided on the lower roller 14 and the upper roller 15 of each roller pair 11. The load applying section 13 provided on the lower roller 14 applies a load to the sliver S via the lower roller 14. The load applying section 13 provided on the upper roller 15 applies a load to the sliver S via the upper roller 15. The load that the load applying section 13 applies to the sliver S via the roller pair 11 is the same for each roller pair 11. In addition, the load applying section 13 is also provided on the guide roller 12. The load applying section 13 applies a load to the sliver S via the guide roller 12.

[0028] The drawing frame 10 of this embodiment is configured to be able to change the load applied to the sliver S. In this embodiment, an operator can change the load applied to the sliver S by the drawing frame 10 by replacing the spring serving as the load applying section 13.

[0029] As described above, in this embodiment, the first to third drawing steps S1 to S3 are performed by the same drawing frame 10. In this case, the operator first attaches the load applying section 13 to the drawing frame 10 so that the load applied to the sliver S is W1. In this state, the first drawing step S1 is performed.

[0030] The load W2 applied to the sliver S in the second drawing process S2 is larger than the load W1 applied to the sliver S in the first drawing process S1. Therefore, after the first drawing process S1, the worker changes the load applied by the drawing frame 10 to the sliver S by replacing the load applying unit 13. The worker replaces the load applying unit 13 so that the load applied to the sliver S becomes W2. After replacing the load applying unit 13, the second drawing process S2 is performed.

[0031] The load W2 applied to the sliver S in the second drawing process S2 is the same as the load W3 applied to the sliver S in the third drawing process S3. Therefore, after the second drawing process S2, the worker does not need to change the load applied by the drawing frame 10 to the sliver S by replacing the load applying unit 13. Therefore, the third drawing process S3 is performed without the worker replacing the load applying unit 13.

[0032] [Operation of this embodiment] The operation of this embodiment will be described. The method for producing carbon fiber spun yarn includes a drawing process in which a sliver S made of carbon fibers F is subjected to a drawing process while a load is applied thereto multiple times.

[0033] FIG. 3 shows the sliver S in the first drawing step S1, which is the first drawing step. FIG. 4 shows the sliver S in the second drawing step S2, which is the second drawing step. In the second drawing step S2, drawing treatment is performed on the sliver S after the first drawing step S1, so the carbon fibers F in the sliver S in the second drawing step S2 are more aligned than in the sliver S in the first drawing step S1. In other words, the carbon fibers F in the sliver S in the first drawing step S1 are less aligned than in the sliver S in the second drawing step S2. Although not shown, the carbon fibers F in the sliver S in the third drawing step S3, which is the third drawing step, are aligned to the same extent as in the sliver S in the second drawing step S2.

[0034] When the carbon fibers F are aligned, the contact area between the carbon fibers F is large, which distributes the load applied to the sliver S, making the carbon fibers F less likely to break. On the other hand, when the carbon fibers F are not aligned, the contact area between the carbon fibers F is small, which causes the load applied to the sliver S to be applied locally to the carbon fibers F, making the carbon fibers F more likely to break. Therefore, in the first drawing step S1, the carbon fibers F are more likely to break than in the second drawing step S2 and the third drawing step S3. In other words, in the second drawing step S2 and the third drawing step S3, the carbon fibers F are less likely to break than in the first drawing step S1.

[0035] In this embodiment, the load W1 applied to the sliver S in the first drawing process S1 is smaller than the load W2 applied to the sliver S in the second drawing process S2 and the load W3 applied to the sliver S in the third drawing process S3. In this way, in the first drawing process S1, where the carbon fibers F are prone to breakage, the load applied to the sliver S is reduced, thereby preventing breakage of the carbon fibers F. Furthermore, in the second drawing process S2 and the third drawing process S3, where the carbon fibers F are less prone to breakage, the load applied to the sliver S is increased, thereby reducing the variation in the thickness of the sliver S. Therefore, the variation in the thickness of the sliver S can be reduced while preventing breakage of the carbon fibers F.

[0036] [Effects of this embodiment] The effects of this embodiment will be described. (1) The load applied to the sliver S in the first drawing process is smaller than the load applied to the sliver S in the second and subsequent drawing processes. In this way, in the first drawing process, in which the carbon fiber F is prone to breakage, the load applied to the sliver S is reduced, thereby preventing breakage of the carbon fiber F. Furthermore, in the second and subsequent drawing processes, in which the carbon fiber F is less prone to breakage, the load applied to the sliver S is increased, thereby reducing the variation in the thickness of the sliver S. Therefore, the variation in the thickness of the sliver S can be reduced while preventing breakage of the carbon fiber F. By preventing breakage of the carbon fiber F, the material yield is improved. Furthermore, by reducing the variation in the thickness of the sliver S, the quality of the carbon fiber spun yarn is improved.

[0037] (2) The method for producing a carbon fiber spun yarn includes first to third drawing steps S1 to S3. The load W2 applied to the sliver S in the second drawing step S2 and the load W3 applied to the sliver S in the third drawing step S3 are each greater than the load W1 applied to the sliver S in the first drawing step S1.

[0038] According to this configuration, the variation in the thickness of the sliver S can be further reduced compared to when only one of the load W2 applied to the sliver S in the second drawing process S2 and the load W3 applied to the sliver S in the third drawing process S3 is greater than the load W1 applied to the sliver S in the first drawing process S1.

[0039] (3) The load W2 applied to the sliver S in the second drawing step S2 and the load W3 applied to the sliver S in the third drawing step S3 are the same. According to this configuration, the variation in the thickness of the sliver S can be further reduced compared to when one of the load W2 applied to the sliver S in the second drawing process S2 and the load W3 applied to the sliver S in the third drawing process S3 is smaller than the other.

[0040] In this embodiment, the first to third drawing processes S1 to S3 are performed by the same drawing frame 10. In this case, if the loads applied to the sliver S in two consecutive drawing processes are different, the worker needs to change the load applied to the sliver S by replacing the spring serving as the load applying unit 13. In this embodiment, the load W2 applied to the sliver S in the second drawing process S2 and the load W3 applied to the sliver S in the third drawing process S3 are the same. Therefore, it is possible to eliminate the need for the worker to replace the spring serving as the load applying unit 13 between the second drawing process S2 and the third drawing process S3.

[0041] (4) The carbon fibers F that make up the sliver S are not crimped, and therefore the carbon fibers F are less likely to tangle with each other. Furthermore, the carbon fibers F have low frictional resistance, and therefore tend to break apart. Furthermore, the carbon fibers F are brittle when bent. Therefore, the method for producing a carbon fiber spun yarn of this embodiment is effective in reducing the variation in the thickness of the sliver S while suppressing breakage of the carbon fibers F.

[0042] (5) As a method for suppressing breakage of the carbon fiber F, for example, omitting the drawing process can be considered. However, in this case, the sliver S is not doubled, and therefore the variation in the thickness of the sliver S is likely to increase. In contrast, in this embodiment, it is possible to suppress breakage of the carbon fiber F and reduce the variation in the thickness of the sliver S at the same time.

[0043] (6) As a method for suppressing breakage of the carbon fibers F, for example, blending the carbon fibers F with binder fibers is considered. The binder fibers are, for example, natural fibers or synthetic fibers. However, in this case, it is necessary to prepare the binder fibers separately. In contrast, in this embodiment, breakage of the carbon fibers F can be suppressed without using binder fibers.

[0044] [Example of change] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0045] The number of times the drawing step is performed does not have to be three. The number of times the drawing step is performed may be two, four or more, as long as it is a plurality of times. Only one of the load W2 applied to the sliver S in the second drawing step S2 and the load W3 applied to the sliver S in the third drawing step S3 may be greater than the load W1 applied to the sliver S in the first drawing step S1.

[0046] Specifically, the load W2 applied to the sliver S in the second drawing process S2 may be greater than the load W1 applied to the sliver S in the first drawing process S1, and the load W3 applied to the sliver S in the third drawing process S3 may be less than or equal to the load W1 applied to the sliver S in the first drawing process S1. Even in this case, the same effect as effect (1) of the above embodiment can be obtained.

[0047] The load W2 applied to the sliver S in the second drawing process S2 may be equal to or less than the load W1 applied to the sliver S in the first drawing process S1, and the load W3 applied to the sliver S in the third drawing process S3 may be greater than the load W1 applied to the sliver S in the first drawing process S1. Even in this case, the same effect as effect (1) of the above embodiment can be obtained.

[0048] In other words, if the load applied to the sliver S in the first drawing process is smaller than the load applied to the sliver S in at least one of the second and subsequent drawing processes, the same effect as effect (1) of the above embodiment can be obtained.

[0049] For example, if the drawing process is performed four times, the load applied to the sliver S in the first drawing process is set to be smaller than the load applied to the sliver S in at least one of the second, third, and fourth drawing processes.

[0050] For example, when the drawing process is performed four times, the load applied to the sliver S in each of the second to fourth drawing processes may be greater than the load applied to the sliver S in the first drawing process. In this case, the load applied to the sliver S in each of the second and subsequent drawing processes is greater than the load applied to the sliver S in the first drawing process, and therefore the same effect as effect (2) of the above embodiment can be obtained.

[0051] For example, when the drawing process is performed four times, the load applied to the sliver S in the third drawing process may be the same as the load applied to the sliver S in the fourth drawing process. In this case, the load applied to the sliver S in two consecutive drawing processes from the second onwards is the same, so that the same effect as effect (3) of the above embodiment can be obtained.

[0052] The load W2 applied to the sliver S in the second drawing step S2 and the load W3 applied to the sliver S in the third drawing step S3 may be different. In other words, the loads applied to the sliver S in two consecutive drawing steps from the second onwards may be different.

[0053] As an example, the load W2 applied to the sliver S in the second drawing process S2 may be greater than the load W1 applied to the sliver S in the first drawing process S1, and less than the load W3 applied to the sliver S in the third drawing process S3.

[0054] As another example, the load W3 applied to the sliver S in the third drawing process S3 may be greater than the load W1 applied to the sliver S in the first drawing process S1, and less than the load W2 applied to the sliver S in the second drawing process S2.

[0055] The first to third drawing steps S1 to S3 may be performed by different drawing frames 10. For example, the first drawing step S1 may be performed by a first drawing frame, the second drawing step S2 may be performed by a second drawing frame, and the third drawing step S3 may be performed by a third drawing frame.

[0056] The number of roller pairs 11 provided in the drawing frame 10 is not limited to four and may be changed as appropriate. The load applying portion 13 may be provided on only one of the lower roller 14 and the upper roller 15 .

[0057] <Definition> The phrase "at least one" as used herein means "one or more" of the desired options. As an example, the phrase "at least one" as used herein means "only one option" or "both of two options" when the number of options is two. As another example, the phrase "at least one" as used herein means "only one option" or "any combination of two or more options" when the number of options is three or more. [Explanation of symbols]

[0058] F...carbon fiber, S...sliver, S1...first drawing process as a drawing process, S2...second drawing process as a drawing process, S3...third drawing process as a drawing process.

Claims

1. A method for producing a carbon fiber spun yarn, the method including a drawing process for drawing a sliver made of a plurality of carbon fibers while applying a load to the sliver, A method for producing a carbon fiber spun yarn, wherein a load applied to the sliver in a first drawing step is smaller than a load applied to the sliver in at least one of the second or subsequent drawing steps.

2. The drawing step is repeated three or more times, 2. The method for producing carbon fiber spun yarn according to claim 1, wherein a load applied to the sliver in each of the second and subsequent drawing steps is greater than a load applied to the sliver in the first drawing step.

3. 3. The method for producing a carbon fiber spun yarn according to claim 2, wherein the load applied to the sliver in two consecutive drawing steps from the second drawing step onwards is the same.

Images