JPH0754212A - Polyamide fiber - Google Patents

Abstract

PURPOSE:To provide a polyamide fiber reduced in the breakage of the fiber on its spinning, the occurrence of ling stages at the time of false-twisting processing, the occurrence of irregular dyeing, the deterioration of the physical properties due to fatigue operations, and high in the aggregating property of the amorphous regions of the fiber by maintaining the water content of the polymer in a melted state at a relative high level. CONSTITUTION:The water content of a polyamide in a melted state is maintained at a relatively high level to obtain a polyamide fiber high in the aggregating property of the amorphous regions and in the irregularity of the fiber structure due to the plasticizing effect, melting point lowering phenomenon and crystallizing temperature-lowering phenomenon of the water. The fiber satisfies viscoelastic properties of inequalities I-V [tandeltamax(alphaa) is the height of the maximum peak of main diffusion; Tmax(alphaa) is a temperature providing the peak of the main diffusion; tandeltamax(betaa) is the height of the maximum peak in beta diffusion zone; tandelta(20 deg.C) is the tandelta value at 20 deg.C; < > is the average value of values obtained by measuring the values of fibers spun under constant spinning conditions ten times, respectively] measured at a measuring frequency 35Hz.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide fiber in which variations in the fiber length direction and in the fiber structure between single yarns are suppressed and the cohesiveness of the amorphous region of the fiber is enhanced, and the variation in fiber structure. The most important purpose is to eliminate yarn breakage due to and to greatly improve the yield. Further, when the knitting process is performed because the fiber structure variation between the doffs is small, it is possible to suppress the ring step or the like which has been a problem in the past. In addition, since the amorphous region of the fiber has high cohesiveness and is uniform, if it is a clothing system, the variation in the structure does not become apparent due to the dyeing operation, etc. It can be suppressed. Industrial materials such as tire cords retain a highly cohesive fiber structure even after processing, so that the change in fiber structure due to fatigue operation or the like is small and the deterioration of fiber physical properties can be greatly suppressed.

[0002]

2. Description of the Related Art Polyamide fibers have long been used since they are excellent in strength, toughness, heat resistance, dyeability and color development.
Widely used as a material for industrial materials, interior bedding, and clothing. Generally, a polyamide fiber, especially a polyhexamethylene adipamide fiber has a high equilibrium constant when adjusting the raw material polymer, and is characterized by being easily polymerized as compared with polyethylene terephthalate. However, on the other hand, it has been believed that it is more appropriate to reduce the amount of water in the spun melt polymer as much as possible, because the presence of water easily causes hydrolysis and side reactions. This is also a reasonable idea in that it is easy to solubilize the water present in the melt system. If insoluble water is present, the surrounding polymer undergoes so-called microphase separation, and it is considered that the water content in the melt should be as low as possible even if estimated from the point of becoming nuclei of spherulites. In a sense, it can be taken for granted. For this reason, in melt spinning of polyamide, the maximum water content in the polymer chips and polymer melt is 1200.
ppm, generally around 500 ppm is adopted.
However, variations in water content when water content is controlled in this region directly adversely affect spinning stability.

In the process of spinning polyamide fibers, it is well known that so-called steaming (conditioning) is important for spinning stability and that the structure of the polyamide raw yarn is significantly changed by water content. ,
Moisture is an important factor that determines the yarn characteristics. Nevertheless, regarding the presence of water in the molten state of the polymer,
There is only a vague argument that "less is better" in terms of decomposition based on chemical equilibrium reactions. fact,
Most of the examples of the patent publications do not limit the water content. Even the few disclosed statements are up to 120
0 ppm, usually 500 to 700 ppm, is general, and there is no one that teaches the role or action effect of this water scientifically and in principle.

As a technique for reducing variations in physical properties of fibers, Japanese Unexamined Patent Publication No. 59-187639 discloses a single yarn fineness of 4
Discharge so that it is below denier, and after passing through the heating cylinder,
Although a spinning technique of uniform cooling is disclosed, this is merely a refinement of the cooling technique and nothing is said about polymer moisture. Further, even with this technique, it is not possible to obtain fibers having small variations in the physical properties of fibers as in the present invention.

[0005]

DISCLOSURE OF THE INVENTION An object of the present invention is to reduce variations in the fiber structure in order to suppress yarn breakage during spinning, ring stage during false twisting, dyeing unevenness, and deterioration of fiber physical properties due to fatigue operation. And to provide a polyamide fiber having a high cohesive property in an amorphous region, particularly a polyhexamethylene adipamide fiber and a poly ε-caproamide fiber.

[0006]

Means for Solving the Problems The present inventors have investigated the action of water in the spinning process of polyamide fibers, particularly polyhexamethylene adipamide fibers and poly ε-caproamide fibers, regarding melt flow characteristics and polymerization / depolymerization characteristics. In addition to scientifically grasping the thermal properties of the polymer and the polymer, we also conducted extensive studies through actual spinning experiments, and in the region where the amount of water in the molten state was higher than before, the plasticizing effect of water, the melting point lowering, and crystallization were achieved. As a result of the phenomenon of temperature decrease, it was found that the fiber structure of the obtained polyamide fiber is not easily affected by the spinning temperature and cooling conditions and has a high cohesive property in the amorphous region, thus completing the present invention.

That is, the polyamide fiber of the present invention has the following viscoelastic properties measured at a measurement frequency of 35 Hz (1).
It is a polyamide fiber characterized by satisfying the following expressions (5). <Tan δmax (αa)> -0.010 ≤ tan δmax (αa) ≤ <tan δmax (αa)> +0.010 (1) <Tmax (αa)> -5 ° C ≤ Tmax (αa) ≤ <Tmax (αa)> + 5 ° C (2) <tan δmax (βa)> −0.015 ≦ tan δmax (βa) ≦ <tan δmax (βa)> +0.015 (3) <tan δ (20 ° C)> −0.010 ≦ tan δ (20 ° C ) ≤ <tan δ (20 ℃) ＞ +0.010 (4) tan δ (20 ℃) ≦ 0.040 (5) (However, the main dispersion (αa) of the dynamic tangent (tan δ) -temperature (T) curve The maximum peak height is tan δma
x (αa), the temperature that gives the main dispersion (αa) peak is Tmax
(Αa), the maximum peak height in the β dispersion band is tanδmax
(Βa), and the tan δ value at 20 ° C. is tan δ (2
0 ° C). <Tanδmax (αa)>, <tanδma
x (βa)>, <tan δ (20 ° C)>, <Tmax (αa)
> Is the average value of the values obtained by measuring each value 10 times for each fiber spun under constant spinning conditions. ) Tan δ
-The temperature (T) analysis mainly reflects the structure of the amorphous portion of the fiber, and is a very important parameter for understanding the performance of the fiber. For example, 1 of “Techniques for measuring fibers and polymers (edited by the Textile Society of Japan)” by Shoichiro Yano (published by Asakura Shoten).
It is described on pages 94 to 203. The main dispersion peak (αa) reflects the thermal mobility of the entire amorphous portion of the fiber, and tan δmax and Tmax of this main dispersion peak
If the variation is out of the above ranges (1) and (2), it may cause yarn breakage during spinning or drawing, and stable spinning cannot be performed. Furthermore, the tan δ max of the β dispersion peak, 20
The variation in the tan δ value at ° C naturally contributes to the spinning stability, but is an important parameter for the change with time of the yarn during storage. For example, when the spun yarn is stored in a place controlled at 20 ° C. × 65% relative humidity, 20 ° C. represented by a mechanical tangent (tan δ) -temperature (T) curve
The amorphous part that can be moved below is always in a movable state and changes the fiber structure over time. β dispersion peak t
When the an δ max and the tan δ value at 20 ° C. deviate from the variation ranges (3) and (4), variations in the fiber structure after storage become apparent, causing problems such as ring steps during false twisting. The following range is more preferable for the variation range (4).

<Tan δ (20 ° C.)> −0.0070 ≦ tan δ (20 ° C.) ≦ <tan δ (20 ° C.)> + 0.0070 (4 ′) Further, the tan δ value at 20 ° C. indicates the cohesiveness of the fiber structure. It is an important parameter for judgment. If the tan δ value at 20 ° C. exceeds the above range (5), that is, the fiber having a low cohesiveness in the fiber structure is a clothing type, a fiber structure represented by a main dispersion peak (αa) by a dyeing operation or the like. Unevenness is likely to become apparent, causing problems such as staining spots. In the case of an industrial material such as a tire cord, the fiber structure is apt to move due to expansion and compression due to fatigue operation and the like, which causes deterioration of physical properties. Further, those which pass through the heat treatment step during processing have a bad effect such that the physical properties of the fiber are largely deteriorated after the processing and the settability is deteriorated. Note that the value of tan δ (20 ° C.) can take only a positive value.

Here, the measuring method and definition of the structure factor defined in the present invention will be shown. Further, FIG. 1 shows a model diagram of a tan δ-temperature (T) curve: Measuring method of tan δ-temperature (T) curve: DDV-01FP Rheovibron manufactured by Orientec Co. was used, measuring yarn length 2 cm, initial load 0.170 g / d, vibration amplitude 1
Fibers spun under a constant spinning condition at a vibration frequency of 35 Hz under the conditions of 6.0 μm and temperature rising rate of 5 ° C./min.
The measurement was repeated 0 times. (This corresponds to the "non-resonant forced vibration method" in the above book.) Definition of structure factor: (The position of each variance is shown in Fig. 1 as α a, α
b, β, γ) Tmax (αa): Temperature that gives the maximum tan δ value in αa dispersion of FIG. 1 (usually, several peaks may be given) tan δmax (αa): αa dispersion The maximum tan δ value in the band tan δ max (βa): the maximum tan δ value in the β dispersion band tan δ (20 ° C.): the tan δ value at the position of 20 ° C. Further, in the polyamide of the present invention, an additive usually used, for example, phosphorus Acid, inorganic phosphorus compounds such as sodium hypophosphite, phenylphosphonic acid, organic phosphorus compounds such as triphenylphosphite, phosphorus-nitrogen complex salts, polymerization catalysts such as phosphorus-nitrogen compounds, copper acetate, copper bromide, Copper iodide, 2
A copper compound such as a mercaptobenzimidazole copper complex salt,
2-mercaptobenzimidazole, thermal stabilizers such as tetrakis [methylene-3- (3,5di-t-butyl-4-hydroxyphenyl) -propionate] -methane, light stabilizers such as manganese lactate and manganese hypophosphite , A matting agent such as titanium dioxide and kaolin, a lubricant such as ethylene bisstearylamide, a methylol derivative of the same, a calcium stearate, a plasticizer, and a crystallization inhibitor.

The polyamide fiber of the present invention, particularly polyhexamethylene adipamide fiber and poly ε-caproamide fiber, is used in the polyamide melt or chips used for spinning in a saturated steam atmosphere in the melting temperature range of the polyamide polymer. The amount of water that can be stored at (1 atm) is not more than the maximum that can be stored under a saturated steam atmosphere (1 atm) in the temperature range of the cooling and solidification point of the polymer melt discharged from the spinneret. It is achieved by adjusting and melt spinning.

The water content of the polyamide polymer that can be stored in a saturated steam atmosphere in the melting temperature range is 1400 ppm or more for polyhexamethylene adipamide and poly ε-caproamide, although it strictly differs depending on the type of polyamide. This value is larger than the equilibrium water content in the polycondensation reaction of the polyamide having a polymerization degree of 50 or more obtained in the polycondensation reaction.
The ppm indication used here is the number of mg of water that can be contained in 1 kg of polymer. The upper limit of the amount of water is the amount of water that can be stored in a saturated steam atmosphere in the temperature range of the cooling and solidifying point of the discharged polymer melt. Cooling and solidifying temperature refers to the time when a polymer enclosed in a closed container with a scanning differential calorimeter (DSC) is once melted, held for a certain period of time (5 minutes), and then cooled at a certain rate (20 ° C./min). Is the crystallization temperature of. This naturally depends on the type of polyamide used and the amount of water contained in the polymer at that time, but it is in the range of 200 ° C. to 260 ° C., and for polyhexamethylene adipamide, it is around 245 ° C. at 1 atm. The maximum water content at this time is approximately 5000 ppm. The amount of water that can be accommodated under the saturated steam pressure in the melting temperature range is more than that in order to express the extensional viscosity decrease of the polymer melt with a sufficient plasticizing effect and to lower the cooling solidification point of the polymer. , The moisture-containing polymer melt is brought into a state as close as possible to the adsorption / desorption equilibrium of moisture with the atmosphere immediately after being discharged, and the adsorption / desorption phenomenon of water between the discharged filamentous material and the external atmosphere is apparently suppressed and then discharged. It also serves to inhibit the crystallization of the filamentous material. This effect is based on apparently impeding the mobility of the water in the extruded polymer melt, and thereby preventing rearrangement of the polymer molecules. Compared with the conventional low water content, the instability of spinning, which is caused by the relative dispersion of polymer water content, is significantly eliminated. Further, as in the conventional case, in the case of a small amount of melt water, the discharged filamentous material absorbs a relatively large amount of moisture with a decrease in the ambient temperature after the discharge, and crystallization is promoted through the movement of this water. There is also a concern. The solidifying point lowering effect and the crystallization inhibiting effect have a water content of 5000 pp.
It is effectively expressed up to m, and conversely, crystallization is rapidly promoted when it is higher than m. That is, for stable spinning, a water content of 1400 ppm to 5000 ppm is effective. Further, if the water content is in this region, it can be expected to spin a fiber having high toughness. FIG. 2 shows the solidification temperature and the heat of crystallization of the molten chips as a function of the water content of the chips. The effect of this water content is also reflected in the fiber structure of the discharged filamentous material. Tan δ max of a main dispersion peak (α dispersion peak) in a tan δ-temperature (T) curve of a fiber obtained by winding a melt polymer discharged at a linear velocity of 15 m / min at a winding speed of 150 m / min after cooling and solidification.
FIG. 3 shows the correlation between (αa) and the water content of chips.

Further, in the above-mentioned spinning method, due to the plasticizing effect of water and the effect of suppressing crystallization, it is possible to carry out spinning at a spinning temperature lower by 10 ° C. to 20 ° C. than before, and stable spinning is possible. Further, depending on the spinning conditions such as cooling conditions, winding speed, and spinneret discharge linear velocity, t of the obtained polyamide fiber may be increased.
Since the fiber structure observed by an δ-T analysis is almost the same without being affected by the difference in spinning temperature of about 10 ° C, the action effect of water is very significant in terms of spinning control for yield and quality. There is something. Furthermore, 10
Since it is possible to spin at a spinning temperature of 20 ° C to 20 ° C lower,
In addition to greatly improving whiteness in terms of quality, it is possible to realize energy-saving spinning by fundamentally improving the working environment based on heat and heat at the melt spinning site.

In actual spinning, there are two methods of giving the polymer melt system the water content specified in the present invention. 1
In other words, polymer chips can be manufactured separately and adjusted by conventional drying and moisture absorption methods. In particular, polymer chip manufacturing
Usually, the melt rope is extruded into a water bath and then cut. The water content in the melt rope at this time is 2500 to 3500 ppm, and the water content is controlled to a high water content. Is relatively easy. On the other hand, in the so-called continuous / continuous spinning system, in which polymer polymerization and spinning are interlocked, it is adjusted by supplying water in the process up to the spin head after adjusting to a predetermined degree of polymerization by post-polymerization. Since the amount of water in the melt system is higher than in the past, it may be necessary to apply a certain pressure or more to solubilize the water.
It is possible to cope with it by increasing / D or increasing the ejection linear velocity.

Hereinafter, the operation and effect of the present invention will be described with reference to examples, but the present invention is not limited thereto.

[0015]

EXAMPLES Prior to the description of the examples, polyamide chips,
In particular, the method for measuring the water content of polyhexamethylene adipamide thiop and poly ε-caproamide chips will be described. Using an electric titration type trace moisture analyzer (Mitsubishi CA-05 type) and moisture vaporizer (VA-05 type), set vaporization temperature: 208
° C, N2 carrier gas flow rate; 300 ml / min, E
ND SENS; 0.5 μg / sec, delay time; 5
Min, background; a value measured on a pellet having a sample weight of about 1 g under the condition of 0.05 or less.

[0016]

Examples 1-2 Poly of 90% formic acid relative viscosity 38 (acid concentration measured by acid-base titration method per 1 kg of polymer; 39 mmol, base concentration per 1 kg of polymer; 85 mmol) by a conventional polymerization method After polymerizing the hexamethylene adipamide polymer, the melt rope was extruded into a water bath at 20 ° C. and pelletized by an ordinary granulating equipment. The water content of the polymer at that time was 2800 ppm. The above pellets are treated by conventional drying method and moisture absorption method,
Pellets containing 0 ppm water were obtained. The pellets contained manganese lactate, 3000 ppm of titanium oxide, and 4 ppm of sodium pyrophosphate corresponding to 7 ppm in Mn content.

The above pellets were melted by an extruder, weighed by a gear pump, and then discharged from a spinneret. After cooling and solidification, a water-based finishing agent was applied, and at a winding speed of 4500 m / min, 15 denier / 5 filament polyhexamethylene adipamide fiber was obtained. The obtained polyhexamethylene adipamide fiber was treated at 20 ° C. and a relative humidity of 65.
% Cheese was stored in a temperature-controlled room for 7 days, and 10 cheeses having different spinning spindles were subjected to tan δ-temperature (T) analysis using 15 denier / 5 filament fibers. Table 1 shows the analysis results at that time, the spinning temperature, and the total number of cutting threads for 10 spinning spindles after spinning for 7 days. For reference, one piece of the obtained polyhexamethylene adipamide fiber was knitted, dyed at 97 ° C. for 45 minutes in an indefinite length state, and air-dried, and then dried at 20 ° C. × 65% relative humidity for 7 days.
The sample was stored in a temperature-controlled room controlled to 100% and analyzed by tan δ-temperature (T). The results are shown in Table 1. The analytical values described are the maximum and minimum values when measuring 10 cheeses. That is, the fiber structure varies within the above range.

Pellet water content 2000 ppm, 2800
The polyhexamethylene adipamide fiber spun at ppm has a small fiber structure variation, and the spinning yield is greatly improved. In addition, since it shows a highly cohesive fiber structure in the amorphous region, even if the dyed product has a pellet moisture content of 2
Polyhexamethylene adipamide fiber spun at 000 ppm and 2800 ppm has a small variation in fiber structure,
It also shows a highly cohesive fiber structure in the amorphous region.

[0019]

Comparative Example 1 Polyhexamethylene adipamide obtained by polymerization in the same manner as in Examples 1 and 2 was treated by a conventional drying method and moisture absorption method to obtain pellets containing 1200 ppm of water. The above pellets were tested in the same manner as in Examples 1 and 2. Table 2 shows the analysis results at that time.

Fibers spun with a pellet water content of 1200 ppm have pellet water content of 2000 ppm and 2800 pp.
Compared with the fiber spun by m, both the raw yarn and the dyed yarn have large structural variations in the amorphous portion and the number of cutting yarns is large.

[0021]

[Examples 3 to 4] A polyhexamethylene adipamide polymer having a relative viscosity of 90% formic acid of 80% was polymerized by a conventional polymerization method, and then the melt rope was extruded in a water bath at 20 ° C by a usual granulating equipment. Pelletized. The water content of the polymer at that time was 2800 ppm. The above pellets were treated by a conventional drying method and a moisture absorption method to obtain pellets containing 2000 ppm of water. This pellet has a copper content of 7
Copper iodide equivalent to 5 ppm and iodine content of 18
Potassium iodide equivalent to 00 ppm, and 15 ppm
It contains titanium oxide corresponding to.

The above pellets were spun and stretched by a conventional method as disclosed in JP-A-59-199812 to obtain 1260 denier / 208 filament polyhexamethylene adipamide fiber. The obtained polyhexamethylene adipamide fiber was stored in a thermostatic chamber controlled at 20 ° C. and a relative humidity of 65% for 7 days, and a tan δ-temperature (T) analysis was performed using 6 denier single yarn. Table 2 shows the analysis results at that time, the physical properties of the fiber, and the number of cutting threads after spinning for 7 days. The analytical values described are the maximum and minimum values when measured for 10 single yarns spun under constant conditions. That is, the fiber structure varies within the above range.

Next, the number of twists is 39 times / 10 cm for each yarn.
Twist the second twist, then twist each two twists 39 times / 10
cm was twisted to make a raw cord. This raw code is 3
The resorcinol-formaldehyde-latex solution was treated under the following conditions using an oven hot stretcher. Temperature / ° C Tension / kgf 1st zone 160 1.4 2nd zone 228 2.8 3rd zone 228 1.5 Treatment speed 15m / min Obtained treatment cord 20 ° C x relative humidity 65% controlled constant temperature Stored in the room for 7 days and tan with a single yarn
δ-Temperature (T) analysis was performed. Table 3 shows the analysis results at that time. The analysis values shown here are the same as those shown for the raw yarn.

Pellet water content 2000 ppm, 2800
The polyhexamethylene adipamide fiber spun at ppm has a small fiber structure variation, and the spinning yield is greatly improved. Furthermore, since it shows a highly cohesive fibrous structure in the amorphous region, the pellet water content of 2000 even when treated with resorcin-formaldehyde-latex solution
The polyhexamethylene adipamide fiber spun at -pm, 2800 ppm has a small fiber structure variation and a highly cohesive fiber structure in the amorphous region.

For reference, the treated cord was vulcanized under vulcanization conditions of 155 ° C. for 40 minutes, and a fatigue resistance test was conducted according to the Goodyear tube fatigue test. The results are shown in Table 2. The Goodyear tube fatigue test here is as follows. Method conforming to JISL-10173.2.2.1A Tube shape Inner diameter 12.5 mm Outer diameter 26 mm Length 230 mm Bending angle 90 degrees Internal pressure 3.5 kgf / cm ² Rotation speed 850 rpm Pellet water content 2000 ppm, 2800 ppm Polyhexamethylene spun Adipamide fiber exhibits a tube break time of over 1000 minutes.

[0026]

Comparative Example 2 Polyhexamethylene adipamide obtained by polymerization in the same manner as in Examples 3 and 4 was treated by a conventional drying method and moisture absorption method to obtain pellets containing 600 ppm of water. The above pellets were tested in the same manner as in Examples 3 and 4. Table 4 shows the analysis results at that time.

Fibers spun with a pellet water content of 600 ppm have pellet water content of 2000 ppm and 2800 ppm.
Compared with the fiber spun in (1), the irregular portion of the original yarn has a large structural variation and the number of cutting yarns is large. In addition, resorcin
There is a large structural variation in the amorphous portion of the formaldehyde-latex solution-treated yarn, and none of them shows a tube breaking time of more than 1000 minutes in the tube fatigue test.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

INDUSTRIAL APPLICABILITY The polyamide fiber of the present invention, particularly polyhexamethylene adipamide fiber and poly ε-caproamide fiber, has a small variation in the fiber structure observed by tan δ-temperature (T) analysis, and therefore the spinning yield is greatly improved. At the same time, it is possible to fundamentally improve the phenomenon caused by the fiber structure variation such as the ring step during false twisting.

Further, in addition to the small fiber structure variation, since the amorphous region has high cohesiveness, the fiber structure variation does not become apparent even when a processing operation is performed, and it is caused by the fiber structure variation such as dyeing spots. The phenomenon that occurs can be improved, and at the same time, the deterioration of physical properties can be suppressed.
Further, in the method for producing a polyamide fiber of the present invention, stable spinning is possible even if the spinning temperature is lowered from 10 ° C to 20 ° C. Therefore, the working environment based on heat and heat at the melt spinning site is fundamentally improved, and energy-saving spinning is performed. Can be realized.

[Brief description of drawings]

FIG. 1 shows a model diagram of a tan δ-temperature (T) curve of polyamide fiber.

FIG. 2 shows the water content dependence of the crystallization characteristics of polyhexamethylene adipamide.

FIG. 3 shows the water content dependency of the polyhexamethylene adipamide fiber structure.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigeru Morita 6-4100 Asahi-cho, Nobeoka-shi, Miyazaki Prefecture Asahi Kasei Kogyo Co., Ltd.

Claims (1)

[Claims] 1. A polyamide fiber characterized in that the viscoelastic property measured at a measurement frequency of 35 Hz satisfies the following expressions (1) to (5). <Tan δmax (αa)> -0.010 ≤ tan δmax (αa) ≤ <tan δmax (αa)> +0.010 (1) <Tmax (αa)> -5 ° C ≤ Tmax (αa) ≤ <Tmax (αa)> + 5 ° C (2) <tan δmax (βa)> −0.015 ≦ tan δmax (βa) ≦ <tan δmax (βa)> +0.015 (3) <tan δ (20 ° C)> −0.010 ≦ tan δ (20 ° C ) ≤ <tan δ (20 ℃) ＞ +0.010 (4) tan δ (20 ℃) ≦ 0.040 (5) (However, the main dispersion (αa) of the dynamic tangent (tan δ) -temperature (T) curve The maximum peak height is tan δma
x (αa), the temperature that gives the main dispersion (αa) peak is Tmax
(Αa), the maximum peak height in the β dispersion band is tanδmax
(Βa), and the tan δ value at 20 ° C. is tan δ (2
0 ° C). <Tanδmax (αa)>, <tanδma
x (βa)>, <tan δ (20 ° C)>, <Tmax (αa)
> Is the average value of the values obtained by measuring each value 10 times for each fiber spun under constant spinning conditions. )