KR870001151B1 - High strength polyamide fiber and it's making method - Google Patents

Abstract

This invention relates to the making method of high strength polyamide fiber with high fatigue resistance for reinforcing rubber. In this method, the double refraction ratio of the fiber satisfies the equation ΔnA-ΔnB>=0.5X10-3,and the double refraction ratio, Δn, is more than 50X10-3. The relative viscocity of the fiber, RV, is more than 4.0; the cutting strength more than 11g/d; the elongation limit more than 15%.

Description

Polyamide fiber having excellent strength and manufacturing method thereof

Figure 1 (a) is a schematic diagram showing the interference stripes that can be seen when observing the fibers of the present invention in an lateral direction with an interference microscope.

Figure 1 (b) is a schematic diagram of the fiber cross section.

FIG. 2 (a) is a schematic diagram showing the arrangement of a sample and a film surface in small angle X-ray diffraction axes.

Figure 2 (b) is a schematic diagram showing the small angle X-ray rotation pattern of the present invention fiber.

The present invention relates to an improved polyamide fiber and a method for producing the same, and more particularly, to a polyamide fiber and a method for producing the same, which have high strength and exhibit excellent fatigue resistance for reinforcing rubbers.

The polyamide, which is a raw material of the fiber intended in the present invention, has a relative degree measured at a polymer concentration of 10 mg / mι in a concentrated sulfuric acid solution at 20 ° C. and 96% of at least 3.5, preferably at least 4.0, such as polycadrolactam and polyhexa. Polyamines based on methyleneadipamide, polyhexamethylene sebakamide, copolymers of polyamides thereof, and condensation products of 1,4-cyclohexane bis (methylamine) and linear aliphatic dicarboxylic acid Drew and so on.

These polyamide materials are fiberized using melt spinning techniques. The present inventors have reached the present invention as a result of intensive studies on the relative viscosity and physical properties of these polyamides.

When the polyamide having a relative viscosity of less than 3.5 is fiberized using a conventional spinning lead technique, the distribution of the birefringence in the fiber cross section is very small, and the difference in the birefringence between the outermost layer and the innermost layer is almost negligible. It was also found that the cutting strength was only 10g / d.

On the other hand, if the relative viscosity is 3.5 or more, preferably 4.0 or more, it is quite difficult to make the fiber by a conventional spin-drawing technique, but it can be easily made into fiber if it is the spinning conditions specified in the present invention as described below.

In addition, the birefringence distribution in the fiber cross section of the obtained fiber decreases as the birefringence becomes smaller as the fiber goes from the outer layer to the inner layer.

0.5×10^-3(1)Δn _A -Δn _B

0.5 × 10 ^-3 (1)

Δn _A is the birefringence of the fiber at r / R = 0.9

Δn _B is the birefringence of the fiber at the position of r / R = 0.0

R: radius of fiber section

r: distance from the central axis of the fiber cross section

〕가 현저히 개선됨을 발견하고, 본발명에 이른 것이다. 폴리아미드는 이전부터 알려진 중합체이며, 폴리아미드섬유는 의료용 및 공업용섬유로서 광범위하게 사용되어 있으나, 그 큰 용도의 한가지로 타이어 코오드를 중심으로 하는 고무보강제를 들수있다.And the birefringence (Δn) of the fiber is 50 × 10 ⁻³ or more, and the cutting strength, nodule strength, and toughness (ie cutting strength X (cutting elongation))

] Is remarkably improved, and the present invention has been reached. Polyamide is a polymer known from the past, and polyamide fiber is widely used as a medical and industrial fiber, but one of its great uses is a rubber reinforcement centered on tire cords.

As a method for producing such a rubber-reinforced polyamide fiber, a method of multi-stretching (special public office 35-5113), a method of using a polymer having a high degree of polymerization (special public office 45-26572), and the like are limited.

By adopting such a method, the strength of the polyamide fiber itself or the strength deterioration at the time of high temperature vulcanization when used as a rubber reinforcement is slightly improved. However, since the elongation decreases, the toughness is hardly improved. Conditions required as such

9.58g/dCutting strength

9.58 g / d

46.0 ……(2)Cutting strength (g / d) X (cutting elongation (%))

46.0... … (2)

It is difficult to obtain a polyamide fiber that satisfies the requirements. Therefore, the effect that contributes to the improvement of the strength of the rubber solid (tire copper) obtained by using the fiber obtained by the method was inevitably said to be insufficient.

Moreover, as a method of manufacturing a high strength polyamide fiber by raising the relative viscosity of a polymer, the special services 48-12085, the special services 51-2528, and the special services 48-39369 are proposed.

By these methods, however, the upper limit of the relative viscosity (RV) is defined in the matter of ritual. For example, the RV of polycaprolactam fiber is 3.0-4.2 in the special office 48-12085 and 51-2528 in the special office. Ess. 3.32-4.01, and Special Forces 48-39369 stipulate that they are in the range of 3.00-4.50.

However, it is hard to think that the strength is hard to rise because the relative viscosity (RV) is too high, i.e., the molecular weight is too large when the principle of high strength of polyamide is considered. This is because the molecular weight is likely to increase the number of Thai molecules.

4.50)을 얻은 것이 사실상 불가능하게 되기 때문으로 생각된다.On the other hand, few examples of high-strength polyamide fibers with RV of 4.0 or higher are rarely seen. However, when RV is 4.0 or higher, the shear viscosity and elongation viscosity of the polymer are significantly increased. Drawing ratio is high enough in the drawing process.

4.50) is thought to be virtually impossible.

3.5의 폴리아미드이라도 아래식 :However, the inventors have conducted various studies, RV

Even polyamide of 3.5:

982g/sec·cm³……(3)Q / D ³

982 g / sec cm ³ . … (3)

12.8cm³/g ……(4)D ² V _W / Q

12.8 cm ³ / g... … (4)

100℃ ……(5)T ₂₀

100 ° C. … (5)

0.017 ……(6)△ n of undrawn gentleman

0.017... … (6)

Q: Discharge amount g / sec

D: Nozzle pore diameter cmø

V _W : Spinning Pulling Speed (cm / sec)

T ₂₀ : Ambient temperature [° C] of the discharge thread strand at a position 5 mm away from the thread strand at a position 20 mm in the thread strand discharge direction on the nozzle face.

Δn of undrawn yarn: Measured value after 30 ° C, 80% RH, 24 hours

It was found that a sufficiently high draw ratio can be obtained by the draw heat treatment step by setting the conditions satisfying.

3.5의 폴리아미드를 상기 (3)-(6)식을 만족하는 조건으로 방사하고 다시 연신열처리하므로서 (1)식을 만족하고, 터프니스〔절단강도 X {절단신도(%)

}가 46.0이상이며, 또한 RV

3.5이며, 고강도, 고결정강도를 가지는 종래의 폴리아미드섬유에는 없었던 전혀 신규한 구조특성을 가지는 폴리아미드섬유를 제공하는 것이다.In other words, the present inventors have a relative viscosity RV

The polyamide of 3.5 was spun under the conditions satisfying the above formulas (3)-(6) and stretched and heat treated again to satisfy the formula (1), and toughness [cutting strength X {cutting elongation (%)

} Is greater than or equal to 46.0 and also RV

The present invention provides a polyamide fiber having a novel structure characteristic, which is 3.5, which is not found in the conventional polyamide fiber having high strength and high crystal strength.

The novel structural properties described herein have a refractive index distribution in the fiber cross section which was not found in conventional polyamide fibers by using ultra-high RV polymer, which is difficult to increase the strength in the prior art, and in particular, the fiber length cycle by incineration X-ray scattering ( It is characterized by having a longer microstructure than ordinary polyamide fibers.

In particular, such structural properties are remarkably exhibited when using polyamides consisting mainly of polycaproamide or polyhexamethyleneamide. Among them, polyamide containing 75% by weight or more of polycaproamide is most suitable.

In addition, it is difficult to produce such refractive index distribution in fiber cross-section with a relative viscosity (RV) of less than 3.5 elongation viscosity level of polyamide, and in order to achieve the purpose, an RV of 3.5 or more, more preferably 4.0 or more, must be used.

In addition, it is difficult to produce such refractive index distributions in the fiber cross-section with a relative viscosity (RV) of less than 3.5 relative viscosity (RV) of polyamide, and in order to achieve the purpose, an RV of 3.5 or more and more preferably 4.0 or more should be used.

In addition, when the fiber length cycle by incineration X-ray scattering is 100 Hz or more, the high strength characteristic is further improved.

In addition, the short-fiber day level is less than 60d, the structure satisfying the formula (1) is more likely to be expressed, and the nodule strength is also high.

In addition, the birefringence (Δn) of the non-drawn yarn has a very large influence on the total draw ratio, and in order to secure a total draw ratio of 4.50 times or more, it is preferable to set the undrawn yarn to? 17 or less. (However, undrawn yarn Δn is a measured value after lapse of 30 ° C and 80% RH · 24hr).

The polyamide fiber having a unique microstructure according to the present invention satisfies the elongation characteristics of cutting strength of 11.0 g / d or more, crystal strength of 8.0 g / d or more and cutting elongation of 15% or more, which have been difficult to realize in the prior art. In addition, the effect of improving the cutting strength is thought to be due to the increase in the relative viscosity and the increase in the average molecular weight of the polymer, thereby increasing the probability of increasing the number of Thai molecules compared to those of ordinary molecular weight.

The improvement of the nodule strength is thought to be due to the fact that the distribution of the birefringence in the cross section of the fiber tends to increase the birefringence in comparison with the inner layer.

The high toughness of the polyamide fiber according to the present invention, i.e., the high breaking strength X (cutting elongation), is attributable to the fact that high strength is achieved without causing a decrease in stretching due to free stretching. That is to say, in manufacturing the polyamide fiber of the present invention,

982g/sec·㎤ (3)Q / D ³

982 g / sec · cm3 (3)

It is indispensable to set a spinning condition that satisfies the requirements of this condition. If this condition is not present, the polymer behavior at the nozzle orifice outlet becomes unstable at the time of spinning, and the yarn at the time of cutting or stretching the yarn at the time of spinning is unstable. A lot of cutting | disconnections generate | occur | produce, and even if it is extended | stretched, high strength thread cannot be obtained. Secondly,

12.8㎤/g (4)D ² V _W / Q

12.8 cm3 / g (4)

The requirement of is also an indispensable radiation condition. If this requirement is met, the radiation tension increases, the running of the emitter becomes unstable, and the thread is cut frequently.

Moreover, even if a diarrhea thread is not cut | disconnected, the draw ratio in an extending | stretching heat processing step falls, and high strength cannot be fully expressed even if the extending | stretching method by this invention is adopted as well as a normal drawing method.

This is thought to be due to the unstable thinning behavior of the emission chamber strands as the radiation tension increases, and to the increase in the birefringence (Δn) of the undrawn yarn. Third,

100℃ (5)T ² ₀

100 ℃ (5)

3.5이라는 고신장점도 종합체를 방사하므로 미연신사의 △n이 대단히 높아지기 쉽고, 상기 (6)식에 나타낸 바와같이 미연신사의 △n을 0.017이하로 억제하지 않으면 충분히 높은 연신배율을 확보하기 곤란케되고 고강도의 섬유를 얻을 수가 없다.Radiation conditions that do not meet the requirements of RV

Since the high elongation of 3.5 radiates the aggregate, it is very easy to increase? N of the undrawn yarn, and as shown in the above formula (6), it is difficult to secure a sufficiently high draw ratio unless the undrawn yarn of? N is suppressed to 0.017 or less. It is impossible to obtain a high strength fiber.

Particularly preferred among the above conditions is that in the range satisfying the requirements of the following formula (3 ')-(6')

500g/sec·㎤ (3')Q / D ³

500 g / sec cm 3 (3 ')

5.0㎤/g (4')D ² V _W / Q

5.0 cm 3 / g (4 ')

100℃ (5')T ₃₀₀

100 ℃ (5 ')

T ₃₀₀ : Atmosphere temperature [° C] of the discharge chamber strand at a position 5 mm away from the yarn strand at a position of 300 mm in the thread strand discharge direction from the nozzle face.

0.013 (6')△ n of undrawn gentleman

0.013 (6 ')

4.0의 중합체의 방사연신을 안정화시키는 효과가 현저히 발휘된다.Setting these radiation conditions, especially RV

The effect of stabilizing the radial stretching of the polymer of 4.0 is remarkably exhibited.

In carrying out the present invention, it is preferable to use polyamide having a relative viscosity of 4.0 or more. This is because it is desirable to increase the relative viscosity of the polymer in order to increase the distribution of the birefringence in the fiber cross section, which is an essential requirement of the present invention.

In the case where the distribution of the birefringence in the fiber cross section is increased by high-speed spinning, it is impossible to achieve a high Δn as in claim 1, and conversely, the cutting strength becomes small.

In addition, in the case of drawing a low-viscosity high-speed emission yarn, the fact as shown in the above paragraph (2) is not realized.

4.0의 중합체의 △n을 저하시키기 위하여 유효하며, 그 온도는 100℃ 이상으로 하는것이 바람직하다.In addition, raising the ambient temperature at a position 5 mm away from the thread strand at a position of 300 mm in the thread strand exit direction from the nozzle surface is particularly high RV RV.

It is effective in order to reduce (triangle | delta) n of the polymer of 4.0, and it is preferable to make the temperature into 100 degreeC or more.

In addition, when the nozzle pore diameter is 0.4 mm or less, the productivity can be increased as shown in the equations (3) and (4).

In the drawing of the undrawn yarn according to the present invention, the preliminary stretching of 1.10 times or less is performed, followed by the first stage stretching by a hot roller or a room temperature roller, or by the first stage stretching by a high-temperature pressurized steam at 200 ° C. or higher. In two-stage stretching, heat treatment is preferably performed at 100-200 ° C. Which one stage drawing method is adopted In order to stabilize the drawing behavior, it is necessary to draw more than 50% of the total drawing magnification by the first stage drawing, and it is preferable that the total drawing magnification is higher, and usually 4.5 times. Especially as mentioned above, it is preferable to set it as 5.0 times or more.

In addition, in the case of roller stretching, the stretching temperature in the first stage stretching must be 100 ° C or less. When 100 degreeC is added, a thread strand becomes unstable on a roller and a total draw ratio falls.

In case of applying the high-temperature pressurized steam to the first stage drawing, the distance between the thread strand and the steam jet hole should be within 50 mm, preferably within 20 mm, and the steam temperature in the steam jet hole should be 200 ° C or higher and 600 ° C or lower. There is.

Below 200 ° C, the drawing speed cannot be increased sufficiently and the drawing point cannot be fixed. Moreover, when it becomes 600 degreeC or more, the melting of a thread strand will arise easily, and will become unstable. If the distance between the thread strand and the steam jet ball falls by 50 mm or more, the temperature of the thread strand at the soft core point is considerably lowered, and it is difficult to fix the soft core point as long as the thread strand is not driven at an unusual low speed. In order to produce a polyamide fiber having an excellent strength, it is preferable to reduce the number of thread strand contacts in the stretching heat treatment step to be as small as possible. For example, in the second stage stretching heat treatment step, a heater of a non-contact type is effective.

In addition, three-stage stretching or four-stage stretching is effective as a method of stretching at a high draw ratio without generating voids or defects in the fiber. In the three-stage stretching, the stretching conditions of the second stage and the third stage are the points, and in the case of stretching the second stage and the third stage by a normal hot roller, a pin or a hot plate, the third stage is substantially more than the second stage. However, it is necessary to increase the heat treatment temperature, and it is most preferable to select the second stage stretching in the range of 100-200 캜 and the third stage stretching in the range of 160-220 캜.

Moreover, the method of extending | stretching by a high temperature pressurized steam at the 2nd stage is also effective. In the four-stage stretching, the four-stage stretching method is particularly effective in which the third stage stretching by high temperature and high pressure jet steam is performed after the second stage stretching by hot roller, pin, or hot plate is completed, and the high temperature treatment is performed after stretching. Do.

The fibers of the present invention are manufactured under special conditions as described above, and are characterized by high strength, nodular strength and high puffiness. The superiority of the physical properties of such fibers is closely related to the microstructure of the fibers, and is exhibited by a special microstructure that cannot be realized by conventionally known manufacturing methods.

When the fiber of the present invention is provided for reinforcement of rubber or the like, it is usually used in the form of pulpyfilament, but the use of the fiber of the present invention is not particularly limited, and thus, in the form of fiber, toving yarn, soup, chopped strand, etc. It may be.

The fiber of the present invention is suitably used for reinforcement cords of rubbers such as carcass cords and other reinforcing cords such as V-belts, flat belts and toothed belts in radial structural tires for heavy-weight vehicles. Of course, the temperature of the present invention is not limited to the above, and is used in the same manner as conventional polyamide fibers.

Below, the measuring method of the main parameter used for the measurement of the structure characteristic or physical property of the fiber of this invention is demonstrated.

<Method of Relative Viscosity>

Dissolve the sample in 96.3 ± 0.1% by weight reagent high sulfuric acid so that the polymer concentration is 10mg / ml, adjust the sample solution, and use the Ostwald viscometer with water dropping seconds of 6-7 seconds at a temperature of 20 ℃ ± 0.05 ℃. Measure the viscosity.

Use the same viscometer to measure the relative viscosity (RV) at the ratio of the drop time T ₀ (seconds) of 20 ml of sulfuric acid and the drop time T ₁ (seconds) of 20 ml of sample solution. It is calculated using the following equation.

RV = T ₁ / T ₀ (7)

<Measurement method of birefringence (Δn)>

A Nikon polarizing microscope POH type Leights Inc. Berecompensator was used, and a spectral light source starting device (Toshiba SLS-3-B type) was used as a light source (Na light source).

A sample cut at an angle of 45 ° with respect to the fiber side of 5-6 mm length is placed on the slide glass with the cut surface facing up.

Place the sample slide glass on the rotary stage, adjust it by rotating the sample to 45 ° with respect to the polarizer, insert the analyzer into the dark clock, and count the number of stripes with the compensator 30 (n). .

Turn the compensator to the right side of the screw to turn the sample darkest first (a), and turn the compensator to the left side of the screw to make the sample darker first. After measuring the scale (b) (read all to 1/10 scale), return the compensator to 30, remove the analyzer, measure the diameter (a) of the sample, and calculate the birefringence (Δn) according to the following formula. (Average of 20 measurements).

ε: Obtained from C / 10,000 and 1 in the instructions of Rights' comparator.

1 = (a-b) (: comparator's reading difference)

<Measurement method of Δn distribution in fiber cross section>

, O,N/,0) 및 의층굴절률(N―, 0.9, N//0,9)의치에 의하여 본발명의 섬유의 특이한 분자배향이 분명히되고, 본발명의 섬유의 우수한 강도와의 관련을 나타낼 수가 있다.Central refractive index obtained using transmission-quantity-type interference microscope (N

, O, N /, 0) and dendritic refractive index (N-, 0.9, N // 0,9) denaturing the specific molecular orientation of the fiber of the present invention and correlated with the excellent strength of the fiber of the present invention. Can be represented.

The distribution of the average refractive index observed from the side of the fiber can be measured by an interference stripe method obtained by using a transmission-quantity-type interference microscope (for example, an interference microscope interfacial obtained from East German Co., Ltd.). This method can be applied to fibers having a circular cross section.

)에 의하여 특징지어진다.The refractive index of the fiber is the refractive index (N //) for the polarized light oscillating in the parallel direction on the fiber side and the refractive index (N) for the polarized light oscillating in the vertical direction on the fiber side (N).

Is characterized by).

)을 사용하여 실시된다.All the measurements described herein use a xenon lamp as a light source, and a refractive index (N // and N obtained by using a green ray having a wavelength of 54 mL μ under polarized interference filter).

Is carried out using

(N

0 및 N

, 0.9)에 대하여도 동일하게 측정할 수 있다.Hereinafter, the measurement of N // and the N //, O and N //, 0.9 obtained at N // will be described in detail.

(N

0 and N

, 0.9) can also be measured in the same way.

The fiber to be tested is optically flat slide glass and cover glass, and is immersed in an inert encapsulation with respect to a fiber having a refractive index (NE) which gives a deviation of interference fringes in the range of 0.2-1 wavelength. The refractive index NE of the encapsulant is a value at 20 ° C. measured using Abbe's refractometer using green light (wavelength λ = 544 m / μ) as a light source.

This encapsulant is adjusted to have a refractive index of 1.48-1.65, for example, in a liquid mixture of liquid paraffin and α-bromnaphthalin. One fiber is immersed in this sealing agent.

The pattern of the interference fringe is photographed, and is analyzed by enlarging it 1000-2000 times. As shown in FIG. 1, the refractive index of the encapsulant of the fiber is N _E , the thickness between the S'-S 'of the fiber is t, the wavelength of the light used is λ, and the spacing of the parallel interference stripes of the backland (corresponding to 1λ). Is Dn and the deviation of the interference fringes by the fiber is dn, the optical path difference L is

It can be represented as. When the refractive index of the sample is NS, the refractive indices N ₁ and N ₂ of the encapsulating liquid are

N _S <N ₁

N _S ＞ N ₂

The two types of patterns are used to evaluate the pattern of the interference stripes as shown in FIG.

Therefore, the distribution of the average refractive index (N //) of the fiber at each position can be obtained from the optical path difference at each position from the center of the fiber to the outer circumference based on the expression (9). The thickness t can be calculated by calculation on the assumption that the fiber obtained is a circular cross section. However, it is also possible to consider a case where the circular cross section is not due to variations in manufacturing conditions or after-manufacturing accidents.

In order to eliminate such errors, it is appropriate to use the part where the deviation of the interference stripes is symmetrical with the fiber side as the axis of symmetry. When the radius of the fiber is R, the measurement is performed at intervals of 0.1 R between 0 and 0.9 R, and the average refractive index of each position can be obtained.

의 분포를 구할 수 있으므로 복굴절률분포는 △n(r/R)=N//, r/R-N

, r/R(10)에서 구할 수 있다. △n(r/R)은 적어도 3개의 필라멘트, 호적하게는 5-10개의 필라멘트의 대하여 측정한 것을 평균해서 얻을 수 있다.Similarly N

The birefringence distribution can be obtained by Δn (r / R) = N //, r / RN

, r / R (10). Δn (r / R) can be obtained by averaging at least three filaments, preferably those measured for 5-10 filaments.

<Measurement Method of Fiber's Elongation Properties>

SS curve of single fiber using Toyobouldwin's Pensilon under the conditions of 100mm of sample length (gauge length), elongation rate = 100% / min, recording speed 500mm / min, and super load 1 / 30g / d The cutting strength (g / d), the cutting elongation (%), and the young (g / d) were calculated.

Young's modulus was calculated from the maximum slope near the origin of the S-S curve. Regarding the calculation of each characteristic value, at least five filaments and a family register can be obtained by averaging the measurements relating to 10-20 filaments.

<Measurement method of crystal strength of fiber>

A sample made of 50 mm loops and other short fibers was attached to a hook fitted to a tensilon upper and lower chuck using Tensilon manufactured by Toyo Bouldwin, and the instrumentation length 50 mm, elongation rate = 100% / min, recording speed 500 mm The SS curve was measured at / min, and the nodule cut strength (g / d) and the nodule cut elongation (%) were calculated.

Averaged measurements of at least 5 filaments, preferably 10-20 filaments, are obtained.

<Method of Measuring Fiber Field Period by Incident X-ray Diffraction>

The measurement of the small angle X-ray scattering pattern is performed using, for example, an X-ray generator (Ru-3H type) manufactured by Science and Engineering.

For measurement, a tube voltage of 45 KV, a tube 70 mA, and a CUK (λX = 1.5418 kV) monochromated with a copper cathode nickel filter were used. Fiber samples are attached to the sample holder so that the single yarns are parallel to each other. The thickness of the sample should be about 0.5-1.0mm. X-rays were incident on the fiber side of the fibers arranged in parallel, and a diffractometer equipped with a Proportional Counter Probe (SPC-20) manufactured by Science and Electrical Engineering Co., Ltd. at 300 mm position for 2 seconds / Rotate at the rotational angular velocity in minutes and measure the diffraction intensity curve.

The long period small angle scattering angle 2α is read at the peak position or the show position of the diffraction intensity curve, and the fiber length period is calculated according to the equation (11) (see FIGS. 2A and 2B).

Experimental examples will be described below in detail the configuration and effect of the present invention. In addition, "part" and "%" in an experiment example show a "weight part" and "weight%" unless there is particular notice.

Experimental Example

The polycaproamide of the relative viscosity shown in Table 1 is used as a raw material, and spinning is carried out under the conditions shown in the table, and the birefringence (Δn) shown in the table (measured after 24 hours at 30 ° C. and 80% RH) and the relative viscosity Unstretched yarn of RV was obtained.

In addition, the heating table under the nozzle was disposed between the nozzle and the cooling table, and in spinning, an appropriate amount of spinning oil was attached to the yarn surface before the undrawn yarn was taken over.

Each obtained undrawn yarn was stretched under the conditions shown in Table 2 to obtain a drawn yarn of sand shown in Table 3.

TABLE 1

TABLE 2

TABLE 3

質)의 모든 것에 있어서 뛰어난 값이 얻어져 있다. 이에 대하여 비교예 1은 폴리카프 로아미드의 상대점도가 낮기 때문에 실가닥을 구성하는 평균분자쇄 길이가 짧아서 충분한 절단강도를 얻을 수 없다. 또 비교예 2는 T₂₀가 너무 낮아서 미연신사의 △n가 규정치를 넘기때문에 연신성이 저하하고 절단강도 및 결절강도를 만족할 수가 없다.As is clear from Tables 1-3, Examples 1-9, which meet the requirements of the present invention,

Excellent values are obtained for all of i). On the contrary, in Comparative Example 1, since the relative viscosity of polycaproamide is low, the average molecular chain length constituting the thread strand is short, and thus sufficient breaking strength cannot be obtained. In addition, in Comparative Example 2, T ₂₀ is too low and Δn of the undrawn yarn exceeds the prescribed value, so that the stretchability is lowered and the cutting strength and the nodule strength cannot be satisfied.

Claims (19)

Relative viscosity of the fiber itself in a 96% concentrated sulfuric acid aqueous solution at a polymer concentration of 10 mg / 10 ml at 20 ° C .: equal to or less than 3.5) and birefringence index in the fiber cross section: Δn _A -Δn _B

0.5 × 10 ^-3 (1) Δn _A is the birefringence of the fiber at the position r / R = 0.9 Δn _B is the birefringence of the fiber at the position of r / R = 0.0 R: radius of fiber section r: distance from the central axis of the fiber section The birefringence Δn of the fiber is 50 × 10 ⁻³ or more, Cutting strength (g / d) × [cutting elongation (%)]

Polyamide fiber having excellent strength, characterized in that 46.0 (2). The polyamide fiber of claim 1 wherein at least 75% by weight of the polyamide fiber is made of polycaproamide. The polyamide fiber according to claim 1 or 2, wherein the long fiber period by incineration X-ray diffraction is 100 ms or more. The polyamide fiber according to claim 1 or 2, wherein the relative viscosity of the fibers is at least 4.0. The polyamide fiber according to claim 1 or 2, wherein the short fibers are 60 denier or less. The polyamide fiber according to claim 1 or 2, wherein the breaking strength is 11.0 g / d or more. The polyamide fiber according to claim 1 or 2, wherein the nodule strength is 8.0 g / d or more. The polyamide fiber according to claim 1 or 2, wherein the elongation at break is 15% or more. When melt spinning the polyamide, the relative viscosity of the polyamide is 3.50 or more. Q / D ³

982 g / sec · cm3 (3) D ² V _W / Q

12.8 cm3 / g (4) T ₂₀

100 ℃ (5) △ n of undrawn gentleman

0.017 (6) Q: Nozzle stage factory discharge rate [g / sec] D: Nozzle pore diameter [cmø] Vw: Spinning Pulling Speed [cm / sec] T ₂₀ : Atmosphere temperature of the discharge thread strand at a position 5 mm away from the thread strand at a position 20 mm in the thread strand discharge direction from the nozzle surface [° C.] △ n of unstretched yarn: Measured value after standing for 30 hours at 80 ° C and 80% RH for 24 hours After melt spinning at the spinning conditions satisfying each of them, the polyamide discharged strand is cooled, and then emulsified, and then, once wound, the unstretched yarn is stretched or heat-treated without winding once. Method for producing a polyamide fiber having an excellent strength, characterized in that. 10. The method for producing a polyamide fiber according to claim 9, wherein at least 75% by weight of the polyamide fiber is made of polycaproamide. The method for producing a polyamide fiber according to claim 9 or 10, wherein the relative viscosity of the polyamide is 4.0 or more. The method for producing a polyamide fiber according to claim 9 or 10, wherein the atmosphere temperature at a position 5 mm away from the thread strand at a position of 300 mm of the thread strand discharge direction on the nozzle face is 100 ° C or more. The method of claim 9 or 10, wherein the melt viscosity of the polyamide, the relative viscosity of the polyamide is 4.0 or more, and the following formula: Q / D ³

500 g / sec · cm 3 (3 ') D ² Vw / Q

50 cm 3 / g (4 ') T ₃₀₀

100 ℃ (5 ') △ n of undrawn gentleman

0.013 (6 ') T ₃₀₀ : Atmosphere temperature [° C] of the discharge thread at a position 5 mm away from the thread strand at a position 300 mm from the nozzle strand discharge direction. Method for producing a polyamide fiber, characterized in that to satisfy each. The method according to claim 9 or 10, wherein, in the stretching heat treatment, a pre-expansion of not more than 1.10 times is provided between the undrawn yarn first supply roller and the undrawn yarn second supply roller maintained at 100 ° C or less. The first stage stretching of 50% or more of the total stretching ratio is performed between the first stretching roller, and the second stage stretching is performed at a temperature of 100-200 ° C between the second stretching roller. Method for producing polyamide fibers. 11. The method according to claim 9 or 10, wherein a pre-expansion of 1.10 times or less is applied between the undrawn yarn first supply roller and the undrawn yarn second supply roller maintained at 100 ° C or lower during the stretching heat treatment. However, in the case of performing the first stage stretching of 50% or more of the total stretching ratio between the stretching rollers and the division stretching of two or more stages, the process is performed at a temperature of 100-200 ° C between the stretching stages of the second stage stretching rollers. The polyamide fiber characterized in that the stretching is carried out two times, and the stretching at the temperature of 160-220 ° C and substantially higher than the second stretching is performed between the third drawing rollers. Manufacturing method. 11. The method according to claim 9 or 10, wherein the first stage stretching is performed after giving a pre-expansion of 1.10 times or less during the stretching heat treatment, and between the non-stretched second feeding roller and the first stage stretching roller at room temperature. A hot pressurized steam jet nozzle is installed in the nozzle and the nozzle temperature is set to 200 ° C. or higher to blow hot steam, and the first stage drawing point is fixed near the hot pressurized steam jet nozzle. The method according to claim 9 or 10, wherein the second stage stretched roller or the feed roller and the third stage stretch roller are subjected to high-temperature pressurization in continuing or stretching the heat treated again after winding once. After the steam blowing nozzle is installed and the high temperature steam is blown out by setting the nozzle temperature to 200 ° C or higher, the third stage drawing point is fixed near the hot pressurized steam jet, and then the third stage drawing roller and the fourth stage drawing roller The fourth stage stretching is performed at the temperature of 185-220 degreeC between, The manufacturing method of the polyamide fiber characterized by the above-mentioned. The method according to claim 9 or 10, wherein at the time of stretching heat treatment, a pre-expansion of not more than 1.10 times is provided between the unstretched first feed roller and the unstretched second feed roller maintained at 100 ° C or less. After the first stage stretching of 50% or more of the total stretching ratio between the first stage stretching roller and the second stage stretching roller, a hot pressurized steam jet nozzle is installed and the nozzle temperature is 200 ° C or higher. Polyamide characterized in that the second stage stretching is performed by ejecting the high temperature steam so that the second stage stretching point is in the vicinity of the hot pressurized steam ejection nozzle, and the third stage stretching is performed between the third stage stretching roller. Method of making fibers. The method for producing a polyamide fiber according to claim 9 or 10, wherein the stretching ratio is 4.5 times or more.

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