Patent Application
20210323786
This disclosure relates to an acrylic yarn package, and an acrylic yarn package having a good package shape and less troubles during transportation and unwinding. In particular, the package is suitable as an acrylic precursor yarn package used for production of carbon fibers.
Polyacrylonitrile long fibers have been used not only as clothing but also precursors of carbon fibers in recent years, and many improvement techniques have been disclosed to obtain carbon fibers having excellent performance and increase their productivity.
The carbon fibers are obtained by winding an acrylonitrile fiber yarn as a precursor once in a yarn-making process of spinning the acrylonitrile fiber yarn, and then sending the acrylonitrile fiber yarn to a carbonization process in which the fiber is heated in an air atmosphere at 200 to 300° C. to convert the fiber into an oxidized fiber (oxidation process), and the oxidized fiber is further heated to 300 to 3000° C. in an inert atmosphere such as nitrogen, argon, or helium to convert the oxidized fiber into a carbon fiber (carbonizing process). The carbon fibers are widely utilized as reinforcing fibers for composite materials in aerospace applications, sports applications, and general industrial applications and the like.
The carbon fiber generally includes a multifilament composed of filaments having 1000 or more monofilaments as one yarn unit, but because of a difference in production yarn speed between a yarn-making process and a carbonization process as a subsequent process, an acrylic yarn as a raw material is generally wound once in the yarn-making process, and then sent to the carbonization process. To increase productivity in the carbonization process, it is effective to increase the amount of an acrylic yarn that can be processed per one time. However, the acrylic yarn is usually wound around a core bobbin so that, if a large amount of yarn is wound around one bobbin, the bobbin may sag in a vertical direction during transportation of the bobbin to the carbonization process, or bulge in side surfaces may increase, to result in winding yarn collapse causing unwinding failure in the carbonization process.
Japanese Patent Laid-open Publication No. 11-263534 describes a technique for defining winding conditions such as a taper angle and winding tension in an acrylic yarn package for precursors of carbon fibers to obtain a good package shape during winding. However, JP '534 describes no winding yarn collapse during transportation. Japanese Patent Laid-open Publication No. 2002-3081 describes a technique for obtaining a good package shape by taking a specific yarn width and yarn shift ratio for a thick acrylic yarn of 33000 dtex or more. However, unless moisture is applied to the yarn before winding to improve the bundling property, deterioration in the package shape and trouble during unwinding cannot be completely prevented. This causes a problem that winding yarn collapse occurs even during transportation. Because of the application of moisture, the technique has the problem that the running cost increases and it is not suitable for long-distance movement due to an increase in mass.
Furthermore, Japanese Patent Laid-open Publication Nos. Sho51-23322 and 2005-273106 describe techniques for defining the hardness of a package for fibers having a total fineness of several tens to several hundreds dtex to prevent winding yarn collapse during transportation. However, those techniques cannot be directly applied to an acrylic yarn package for precursors of carbon fibers having a high total fineness exceeding 1000 dtex.
It could therefore be helpful to provide an acrylic yarn package that prevents winding yarn collapse during transportation when an acrylic yarn having a high total fineness is wound around a core bobbin.
We thus provide an acrylic yarn package including an acrylic yarn wound around a bobbin and having a total fineness of 8000 dtex or more, wherein the acrylic yarn on the package has a yarn width of 0.22 mm/1000 dtex or more and hardness of 60 or more.
Our acrylic yarn package has a good package shape and prevents collapse during transportation of an acrylic yarn package having a high total fineness to a next process when the acrylic yarn is wound around a core bobbin.
We considered the problems associated with a carbon fiber precursor acrylic thick yarn package having a good package shape without collapsing even during transportation when an acrylic yarn having a high total fineness is wound around a core bobbin as the above problems, and discovered that improvements are possible by setting the yarn width and hardness of the package to a certain level or higher.
The carbon fiber precursor acrylic yarn is composed of a so-called acrylic polymer, for example, preferably a polymer obtained by polymerizing 90% by mass or more of acrylicnitrile and less than 10% by mass of a comonomer. Examples of the comonomer include at least one selected from acrylic acid, methacrylic acid, itaconic acid, and methyl ester, ethyl ester, propyl ester, and butyl ester of these acids; alkali metal salt, ammonium salt, or allyl sulfonic acid, methallyl sulfonic acid, alkali metal salts thereof and the like.
Such an acrylic polymer can be obtained by using a known polymerization method, for example, a polymerization method such as emulsion polymerization, suspension polymerization, or solution polymerization. When an acrylic fiber is produced from these polymers, a polymer solution containing a solvent selected from, for example, dimethyl acetamide, dimethyl sulfoxide (DMSO), dimethylformamide, aqueous solutions of nitric acid, zinc chloride, and sodium rhodanide is used as a spinning raw yarn, and spinning is performed by a wet spinning method or a dry spinning method.
The spun yarn is then subjected to bath draw, but the spun-out yarn may be directly subjected to the bath draw, or the spun-out yarn may be washed with water once to remove the solvent, followed by subjecting the spun yarn to the bath draw. In such a bath draw, the spun yarn is preferably drawn about 2 to 6 times in a drawing bath at 50 to 98° C. After drawing, an oil agent is preferably applied to the spun yarn, and the spun yarn is subjected to drying and densification with a hot roller or the like. Then, the spun yarn is subjected to steam drawing, and then wound around a core bobbin to form a package.
When such a package is formed, a plurality of yarns may be combined, and then wound. It is effective to carbonize multifilament yarns at one time to improve productivity of carbon fibers. Therefore, the total fineness of the wound yarn is 8000 dtex or more. The moisture percentage of the yarn is preferably 3% or less to avoid an increase in mass during transportation. The total amount of the acrylic yarn obtained by subtracting bobbin mass and the amount of moisture from the mass of the entire package is preferably large, preferably 120 kg or more, and more preferably 200 kg or more to reduce the set number of the acrylic yarn in a carbonization process to improve efficiency.
It is important that the hardness of a bobbin end measured by a durometer is 60 or more to eliminate winding yarn collapse during transportation. If the hardness is less than 60, the package is apt to loosen, which can cause winding yarn collapse during transportation and yarn drop during unwinding to occur. The hardness of 60 or more can be achieved by setting the tension of the yarn during winding to an appropriate value. A large amount of yarn is commonly wound while a large tension is gradually attenuated, but the value may be an appropriate value depending on the fineness of the yarn and the number of filaments.
It is necessary to wind the acrylic yarn on the package with the yarn width of the acrylic yarn set to 0.22 mm/1000 dtex or more. If the yarn width is smaller than 0.22 mm/1000 dtex, the thickness of the yarn becomes large so that a gap causing yarn slip occurs between a yarn and another yarn adjacent to the yarn, which can cause winding yarn collapse during transportation. If the yarn width is more than 0.54 mm/1000 dtex, the yarn convergency deteriorates, which may cause trouble such as yarn drop and monofilament wrapping to occur during unwinding in the carbonization process, whereby the yarn width of the acrylic yarn on the package is preferably 0.22 mm to 0.54 mm/1000 dtex. The method of setting the yarn width on the package within the above range is not particularly limited, but when the yarn is wound with a winder, a method of winding the yarn after causing a group of free rollers for bundling to pass at a certain level or more is suitably used.
When the coefficient of static friction between the acrylic yarns is less than 0.13, a bulge in side surfaces may occur during winding even if the yarn width and the hardness are controlled to specific conditions to prevent the winding yarn collapse. Therefore, the coefficient of static friction is preferably 0.13 or more by applying an appropriate type and amount of an oil agent.
It is preferable to set a yarn shift ratio to 15 to 59% and a taper angle on the package to 6 to 14°. The yarn shift ratio is a ratio of a yarn shift length S to a yarn width T in two yarns passing through the closest points on the package in parallel. That is, this yarn shift ratio is obtained by (S/T)×100 shown in
As shown in
The yarn shift ratio and the taper angle can usually be controlled by setting the number of revolutions of a winder spindle per thread traverse, i.e., a so-called winding ratio to appropriate values. If the winding ratio is an integer, the yarn passes through the exactly same yarn passage before and after one traverse, whereby the yarn passage before and after one traverse can be shifted by setting the fractional portion of the winding ratio to an appropriate value, to control the yarn shift ratio. The taper angle can be controlled by setting the size of the entire winding ratio including an integer portion to an appropriate value.
If the yarn shift ratio is less than 15%, the package has large undulations. Even if a winding tension is increased, the hardness may be decreased, which can cause the winding yarn collapse to occur during transportation. When the yarn shift ratio is more than 59%, a contact surface between an inner layer yarn and an outer layer yarn is small so that the pressing of the outer layer yarn during winding causes the inner layer yarn to slip, to push out the inner layer yarn, which causes a bulge in side surfaces. Therefore, the yarn shift ratio is 15% to 59%, whereby both the hardness and the end face shape can have good values.
If the taper angle is less than 6°, the yarn drop during unwinding is likely to occur. If the taper angle is more than 14°, the bulge in side surfaces is large so that the taper angle is preferably 6 to 14°. When the yarn is wound with a constant winding ratio, the taper angle linearly decreases as the diameter of the package wound around the core bobbin increases, whereby the yarn can be wound while the taper angle is kept within a certain range by changing the winding ratio during winding depending on the winding amount of the yarn. For example, by providing a mechanism such that spindle drive and traverse drive are made to be independent from each other, the number of revolutions of the spindle is detected, calculation is performed to provide the set winding ratio, and then the number of revolutions of the traverse drive is controlled, the winding ratio can be freely set depending on the wilding amount in the winding process.
Hereinafter, our yarn packages will be described in detail with reference to Examples and Comparative Examples. Measurement methods used in Examples and Comparative Examples will be described below.
A sample yarn of 20 m was collected from a package to be measured, and a total fineness was determined by a method according to JIS L1013: 2010.
Coefficient of Static Friction
A sample yarn of 1.5 m was collected from a package to be measured, and wrapped around the collected package. At this time, the sample yarn was wound around the center of the package along the circumferential surface of the package. After the sample yarn was wound so that a contact angle with the package was 540°, a weight of 150 g was attached to each of both ends of the sample yarn. Then, the mass of the weight on one end side of the yarn was increased, and a mass of the weight when the yarn started to slip on a package was measured. A coefficient of static friction was calculated from the following formula:
Coefficient of static friction (μs)=3/π×Ln(T1/150)
π: Circumference ratio
T1: Mass of weight (g) when yarn starts to slip.
Using a caliper, the yarn width of the acrylic yarn on the package was measured at a total of five points of places within 2 cm from both ends of the package (both ends), a center of the package, a place between one of both the ends and the center, and a place between the other end and the center, and a value obtained by dividing the measured value with the total fineness was taken as the yarn width.
For two yarns passing through the closest points on the package in parallel, a yarn shift length (S) shown in
While the wound package was subjected to unwinding, an angle (θ) between a straight line (α) perpendicular to the axial direction of a core bobbin 2 shown in
Using HARDNESS TESTER “Type C” (for Cellular Rubber & Yarn Package) manufactured by KOBUNSHI KEIKI CO., LTD., values were measured at two places within 2 cm from both ends of the package, and the average value thereof was taken as the hardness of the yarn package.
Winding Yarn Collapse during Transportation
An acrylic yarn package was set at a trolley with a spindle, and one acrylic yarn package subjected to a transportation vibration test according to JIS Z 0232: 2004 once to determine the presence or absence of winding yarn collapse according to the following two levels: Good: No increase of 5.0 mm or more of bulge in side surfaces and no increase of 10 mm or more of warpage.
Poor: Increase of 5.0 mm or more of bulge in side surfaces and increase of 10 mm or more of warpage.
A distance (U) between a straight line 5 connecting both ends of an upper part of the package shown in
Bulge length in side surfaces (k1, k2), which was a height of a point where a side surface of the package bulges on the outermost side, with respect to a yarn traverse width (L) on the outermost surface of the package, as shown in
When the package was set on a creel, and the entire amount was subjected to unwinding, those that did not cause yarn drop or monofilament wrapping were taken as good, and those that caused yarn drop or monofilament wrapping were taken as poor.
Using a 19% DMSO solution of an acrylic polymer having an intrinsic viscosity [η] of 1.80 and containing 99.6% by mass of acrylonitrile and 0.4% by mass of itaconic acid as a raw spinning solution, and a spinneret having 6000 pores, semi-wet spinning was performed in a coagulation bath containing 30% of DMSO and 70% of water at 8° C. to obtain a coagulated yarn. The coagulated yarn was drawn 2.8 times in hot water while being washed with water. Furthermore, the remaining DMSO was washed with water until the DMSO amount became 0.01% or less in the yarn, and a silicone-based oil agent was then applied, followed by drying and densification at 150 to 160° C. Subsequently, the yarn was drawn 4.3 times in pressurized steam, and then dried again. Two 6000-filament yarns were combined, and a 12000-filament yarn having a total fineness of 13300 dtex was wound around an FRP core bobbin having an outer diameter of 145 mm with a winder so that the total amount of the acrylic yarn obtained by subtracting the bobbin mass and the amount of moisture from the mass of the entire package was 120 kg in a yarn width, a yarn shift ratio, and a taper angle range shown in Table 1. The amount of moisture was determined by collecting a yarn of about 12 m to be wound in advance, measuring a moisture percentage by a method according to JIS L1013: 2010, and multiplying the moisture percentage by the amount of the wound yarn.
As a result, as shown in Table 1, a good package which did not cause winding yarn collapse during transportation was provided.
An acrylic yarn was wound in a yarn width, a yarn shift ratio, and a taper angle range shown in Table 1 in the same manner as in Example 1 except that the total weight of the acrylic yarn obtained by subtracting a bobbin mass and an amount of moisture from the mass of an entire package was set to 240 kg, and a yarn width during winding, and a winding ratio and tension of a winder were changed.
As a result, as shown in Table 1, Examples 2 to 5 provided a good package that did not cause winding yarn collapse during transportation, but Example 4 caused a high yarn shift ratio of 60% or more during winding, to result in a small contact surface between an inner layer yarn and an outer layer yarn so that the outer layer yarn pressed the inner layer yarn during winding, and the inner layer yarn slid and was pushed out, to result in a package having a large bulge in side surfaces. Example 5 caused a large yarn width of 0.55 mm/1000 dtex or more to result in poor yarn convergency so that yarn drop and monofilament wrapping occurred during unwinding in a carbonization process. Comparative Examples 1 to 3 had hardness of less than 60 as compared to Example 2, and caused winding yarn collapse during transportation. Comparative Example 4 had a yarn width of less than 0.22 mm/1000 dtex as compared to Example 2, and caused winding yarn collapse during transportation.
A yarn was wound in a yarn width and a yarn shift ratio shown in Table 1 in the same manner as in Example 2 except that the amount of an oil agent deposited was adjusted to change the coefficient of static friction of the yarn. As a result, as shown in Table 1, a good package that did not cause winding yarn collapse during transportation was provided. Example 6 had a low coefficient of static friction of less than 0.13 and caused yarn lateral sliding during winding, to result in a package having large bulge in side surfaces.
A 24000-filament yarn having a total fineness of 26600 dtex was wound in a yarn width and a yarn shift ratio shown in Table 1 in the same manner as in Example 2 except that four 6000-filament yarns were combined.
As a result, as shown in Table 1, a good package that did not cause winding yarn collapse during transportation was provided.
A 24000-filament yarn having a total fineness of 29100 dtex was wound in a yarn width and a yarn shift ratio shown in Table 1 in the same manner as in Example 8 except that a drawing ratio in pressurized steam was 3.9.
As a result, as shown in Table 1, a good package that did not cause winding yarn collapse during transportation was provided.
A 36000-filament yarn having a total fineness of 26600 dtex was wound in a yarn width and a yarn shift ratio shown in Table 1 in the same manner as in Example 2 except that six 6000-filament yarns having a monofilament fineness of 0.74 dtex were combined.
As a result, as shown in Table 1, a good package that did not cause winding yarn collapse during transportation was provided.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-160115 | Aug 2018 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2019/032407 | 8/20/2019 | WO | 00 |
