Polypropylene fiber and method for manufacturing polypropylene fiber

Abstract

Obtained is a polypropylene fiber that selectively satisfies any of the following requirements: the degree of amorphous orientation being not lower than 85%; the degree of crystalline orientation being not lower than 90%; the degree of crystallinity being 60-75%; the strength being not lower than 7 cN/dtex; the initial elastic modulus being not lower than 100 cN/dtex; the rupture elongation being 10-30%; and the single fiber fineness being 3-20 dtex. This polypropylene fiber, in which a crystalline chain and an amorphous chain are highly oriented and that has high strength and high initial elastic modulus, is produced through a two-stage drawing method and by controlling the drawing tension of the final stage while maintaining production speed.

Claims

1. A polypropylene fiber, having an amorphous orientation degree of 88% or higher, wherein a strength is 7 cN/dtex or more, an initial elastic modulus is 100 cN/dtex or more, and a elongation at break is 10% to 30%.

2. The polypropylene fiber according to claim 1, wherein a single fiber fineness is 3 dtex to 20 dtex.

3. The polypropylene fiber according to claim 1, wherein a total fineness is 90 dtex to 900 dtex.

4. The polypropylene fiber according to claim 1, having an amorphous orientation degree of 90% to 92%.

5. A polypropylene fiber, having an amorphous orientation degree of 85% or higher and a crystallinity degree of 60% to 75% as determined by wide angle X-ray diffraction.

6. The polypropylene fiber according to claim 5, having an amorphous orientation degree of 88% to 98%.

7. The polypropylene fiber according to claim 5, wherein a single fiber fineness is 3 dtex to 20 dtex.

8. The polypropylene fiber according to claim 5, wherein a total fineness is 90 dtex to 900 dtex.

9. The polypropylene fiber according to claim 5, wherein a strength is 7 cN/dtex or more, an initial elastic modulus is 100 cN/dtex or more, and a elongation at break is 10% to 30%.

10. A polypropylene fiber, having an amorphous orientation degree of 85% or higher and an endothermic melting peak of 85 J/g to 12.0 J/g as determined by differential scanning calorimetry.

11. The polypropylene fiber according to claim 10, having an amorphous orientation degree of 88% to 98%.

12. The polypropylene fiber according to claim 10, wherein a single fiber fineness is 3 dtex to 20 dtex.

13. The polypropylene fiber according to claim 10, wherein a total fineness is 90 dtex to 900 dtex.

14. The polypropylene fiber according to claim 10, wherein a strength is 7 cN/dtex or more, an initial elastic modulus is 100 cN/dtex or more, and a elongation at break is 10% to 30%.

15. A polypropylene fiber, having an amorphous orientation degree of 85% or higher and a ratio of a scattering intensity in a meridian direction to a scattering intensity in an equatorial direction of 0.5 to 0.95 as determined by small angle X-ray scattering.

16. The polypropylene fiber according to claim 15, having an amorphous orientation degree of 90% to 98%.

17. The polypropylene fiber according to claim 15, wherein a single fiber fineness is 3 dtex to 20 dtex.

18. The polypropylene fiber according to claim 15, wherein a total fineness is 90 dtex to 900 dtex.

19. The polypropylene fiber according to claim 15, wherein a strength is 7 cN/dtex or more, an initial elastic modulus is 100 cN/dtex or more, and a elongation at break is 10% to 30%.

Description

EXAMPLES

(1) Hereinafter, the present invention will be described more specifically based on Examples 1 to 7 and Comparative Examples 1 to 3, however, the present invention is not limited to the following Examples at all. In these Examples and Comparative Examples, crystalline orientation degree, crystallinity degree, amorphous orientation degree, fiber strength and initial elastic modulus, elongation at break and single fiber fineness were measured by the following methods.

(2) (Melting Point of Polypropylene)

(3) A melting point of the polypropylene resin was calculated using a DSC apparatus (DSC 220 manufactured by SII NanoTechnology Inc.). Polypropylene resin pellets were finely cut and 10 mg of them were put in a sample pan. The measurement was carried out in a nitrogen atmosphere at a heating rate of 10 C./min and from the room temperature to 240 C. The temperature of the peak top of the obtained DSC curve was taken as the melting point.

(4) (Birefringence Value of Undrawn Yarn)

(5) A birefringence value of the undrawn yarn was calculated using a polarizing microscope (ECLIPSE E 600 manufactured by Nikon Corporation). An interference filter was used to have the wavelength of 546 nm, and a retardation measurement was carried out. The birefringence value was calculated by dividing the obtained retardation by a fiber diameter. The fiber diameter was calculated by the fineness and density (0.91 g/cm.sup.3) of the undrawn yarn. Five measurements were carried out and the average value was used.

(6) (Scattering Intensity Ratio in Meridian/Equatorial Direction by Small Angle X-Ray Scattering)

(7) A structural analysis of the process yarn at the time of completion of the first stage drawing was carried out by using the small angle X-ray scattering measurement apparatus (Ultrax 18, wavelength =1.54 , manufactured by Rigaku Corporation) and the DSC measurement apparatus (DSC 220 manufactured by SII NanoTechnology Inc.). In the small angle X-ray scattering measurement, the undrawn yarn was cut into approximately 5 cm and adjusted to be 50 mg. Fibers were aligned in one axis direction and attached to the sample holder. The measurement was carried out at the tube voltage of 40 kv, the tube current of 200 mA, and an irradiation time of 30 minutes. Regarding the obtained two-dimensional diffraction image, in the equatorial direction, a one-dimensional profile of was obtained in a range of 2=0.2 to 2. In the meridian direction, a one-dimensional profile of a range of =160 to 200 was obtained in a range of 2=0.2 to 2. For each 2, a maximum value obtained by dividing the one-dimensional profile in the meridian direction by the one-dimensional profile in the equatorial direction was taken as the intensity ratio in the meridian direction with respect to the intensity in the equatorial direction (intensity ratio by the small angle X-ray scattering).

(8) (DSC Peak Ratio)

(9) The DSC measurement of the process yarn at the time of completion of the first stage drawing was carried out by finely cutting the polypropylene process yarn and putting 10 mg into the sample pan. The measurement was carried out in a nitrogen atmosphere at a heating rate of 10 C./min and from the room temperature to 240 C. With respect to the obtained DSC profile, peaks were set between 168 C. and 174 C. and between 160 C. and 166 C., respectively, and waveform separation was performed to calculate the area ratio. For the function used for the waveform separation, Pseudo-Voigt function which is a superposition of Gaussian function and Lorenz function is used, and the ratio of the Gaussian function and the Lorenz function is fixed at 1:1.

(10) The DSC peak ratio was a value obtained by dividing the area of the melting peak at 160 C. to 166 C. by the area of the melting peak at 168 C. to 174 C.

(11) (Ratio of Crystalline Structure)

(12) A structural analysis of the undrawn yarn was carried out using the wide angle X-ray diffraction measurement apparatus (Ultrax 18, wavelength =1.54 , manufactured by Rigaku Corporation). The undrawn yarn was cut into approximately 5 cm and adjusted to be 30 mg. Fibers were aligned in one axis direction and attached to the sample holder. The measurement was carried out at the tube voltage or 40 kV, the tube current of 200 mA, and the irradiation time of 30 minutes.

(13) The one-dimensional profile in all directions were cut out from the obtained two-dimensional diffraction image, and the background was subtracted to obtain a final one-dimensional profile. The ratio of the crystalline component was measured by the above-described method. For the fitted peak function, Pseudo-Voigt function which is a superposition of Gaussian function and Lorenz function is used and the ratio of the Gaussian function and the Lorentz function is fixed at 1:1.

(14) <Method for Measuring Crystalline Orientation Degree and Crystallinity Degree>

(15) The crystalline orientation degree and crystallinity degree of the polypropylene fiber were measured using the wide angle X-ray diffraction measurement apparatus (Ultrax 18, wavelength =1.54 , manufactured by Rigaku Corporation). The drawn yarn was cut into approximately 5 cm and adjusted to be 30 mg. Fibers were aligned in one axis direction and attached to the sample holder. The measurement was carried out at the tube voltage of 40 kV, the tube current of 200 mA, and the irradiation time of 30 minutes.

(16) For the obtained two-dimensional diffraction image, a one-dimensional profile in 2 direction was cut out in a range of =175 to 185, and the background was subtracted to obtain a final one-dimensional profile. Peaks were set at diffraction angles of 14.1, 16.9, 18.6, 21.6 (crystalline component) and 16 (amorphous component), respectively, and a waveform separation was performed. The crystallinity degree was calculated by dividing the sum of the peak integral intensities of the crystalline component by all the peak integral intensities. For the fitted peak function, Pseudo-Voigt function which is a superposition of Gaussian function and Lorenz function is used and the ratio of the Gaussian function and the Lorentz function is fixed at 1:1.

(17) For the obtained two-dimensional image, a one-dimensional profile in a direction was cut out in a range of 2=16 to 17.5, and from a half value width of the peak at =90, the crystalline orientation degree=(180)100/180 was calculated.

(18) <Method of Measuring Amorphous Orientation Degree>

(19) The amorphous orientation degree, fa, of fibers, can be obtained by using an expression of fa=[nnc0.Math.fc.Math.c]/[(1c).Math.na0]100%. The n is an actually measured birefringence value, the nc0 is a crystal intrinsic birefringence, and 33.110.sup.3 is inserted. The na0 is an amorphous intrinsic birefringence, and 46.810.sup.3 is inserted. The fc is a crystalline orientation degree, and the c is a crystallinity degree. Values obtained by the wide angle X-ray diffraction measurement are used respectively. The birefringence value was calculated using a polarizing microscope (ECLIPSE E 600 manufactured by Nikon Corporation). An interference filter was used so as to have the wavelength of 546 nm, and a retardation measurement was carried out. The birefringence value was calculated by dividing the obtained retardation by a fiber diameter. The fiber diameter was calculated by the fineness and density (0.91 g/cm.sup.3) of the undrawn yarn. Five measurements were carried out and the average value was used.

(20) (Scattering Intensity Ratio in Meridian/Equatorial Direction by Small Angle X-Ray Scattering)

(21) The scattering intensity ratio in the meridian direction with respect to the scattering intensity in the equatorial direction of the polypropylene fiber by the small angle X-ray scattering measurement was calculated by a synchrotron radiation X-ray measurement (SPrin-8 BL 03 XU, wavelength 1 ). A two-dimensional scattering image was obtained by a detector: CCD, camera length: 4.0 m, and exposure time: 2 seconds. The polypropylene fiber was cut so as to have a size of about 5 cm and adjusted to be 10 mg to 50 mg. Fibers were aligned in one axis direction and attached to the sample holder. The analysis method was carried out by the same method as the scattering intensity ratio of the process yarns described above.

(22) <Method for Measuring Single Fiber Fineness and Total Fineness>

(23) A value obtained by sampling a polypropylene fiber bundle of 100 m and multiplying its mass (g) by 100 was taken as the total fineness. The single fiber fineness was calculated by dividing the total fineness by the number of filaments.

(24) <Method for Measuring Fiber Strength, Initial Elastic Modulus, and Elongation at Break>

(25) The fiber strength, the initial elastic modulus, and the elongation at break were measured in accordance with JIS L 1013. Using a tensile tester (AG-IS manufactured by Shimadzu Corporation) under conditions of a sample length of 200 mm and a tensile speed of 100 mm/min, strain-stress curves were measured under conditions of an atmosphere temperature of 20 C. and a relative humidity of 65%. The elongation at break was determined by the value of the rupture point, and the strength was determined by the stress at the rupture point. The initial elastic modulus was calculated by the inclination of the strain-stress curve. Five measurements were carried out and the average value was used.

(26) Various production conditions and properties of the polypropylene fibers in Examples 1 to 7 and Comparative Examples 1 to 3 are shown in Table 1.

Example 1

(27) Polypropylene resin (Y2000 GV, melting point of resin: 163.4 C., MFR=18 g/10 minutes (230 C., load: 2.16 kg, 10 min) manufactured by Prime Polymer Co., Ltd.) was charged into an extruder of a melt spinning apparatus, heated up to 280 C. to be melt kneaded, and discharged from a spinning nozzle having a discharge hole diameter of 0.5 mm and a discharge hole number of 36 holes at a mass flow of 45.3 g/min (1.26 g/min per hole). After cooling and solidifying by applying cold air at 20 C., an oil agent was applied, and the yarn was wound around a bobbin at a winding speed of 300 m/min to obtain an undrawn yarn having a crystalline structure ratio of 0 mass %, a meso-structure ratio of 49.1 mass %, an amorphous structure ratio of 50.9 mass % and a birefringence value of 0.7410.sup.3.

(28) With respect to the obtained undrawn yarn, preheating was carried out using the hot roll so as to have the yarn temperature of 85 C., and a hot plate drawing was performed in a first stage drawing at the yarn temperature of 145 C. and a draw ratio of 8 times. Preheating was continuously carried out further with the hot roll so as to have the yarn temperature of 120 C., and the hot plate drawing was performed in a second stage drawing at the yarn temperature of 155 C., the draw ratio of 1.20 times and a drawing velocity of 300 m/min to obtain a polypropylene fiber. The deformation rate and the drawing tension are as shown in Table 1.

(29) The strength and initial elastic modulus of the obtained polypropylene fiber are as shown in Table 1, and the polypropylene fiber having high strength and high initial elastic modulus was obtained. The elongation at break, fineness, crystalline orientation degree, amorphous orientation degree, and crystallinity degree of the polypropylene fiber are as shown in Table 1, and the fiber structure was highly oriented.

Example 2

(30) As shown in Table 1, a polypropylene fiber was obtained in the same manner as in Example 1 except that the yarn temperature was set to be 165 C. in the second stage drawing process. The deformation rate and the drawing tension are as shown in Table 1. The strength and initial elastic modulus of the obtained polypropylene fiber are as shown in Table 1, and a fiber having high strength and high initial elastic modulus was obtained. The elongation at break, fineness, crystalline orientation degree, amorphous orientation degree, and crystallinity degree are as shown in Table 1, and the fiber structure was highly oriented.

Example 3

(31) As shown in Table 1, a polypropylene fiber was obtained in the same manner as in Example 1 except that the yarn temperature was set to be 165 C. and the draw ratio was set to be 1.35 times in the second stage drawing process. The deformation rate and the drawing tension are as shown in Table 1. The strength and initial elastic modulus of the obtained polypropylene fiber are as shown in Table 1, and a fiber having high strength and high initial elastic modulus was obtained. The elongation at break, fineness, crystalline orientation degree, amorphous orientation degree, and crystallinity degree are as shown in Table 1, and the fiber structure was highly oriented.

Example 4

(32) As shown in Table 1, a polypropylene fiber was obtained in the same manner as in Example 1 except that the yarn temperature was set to be 175 C. and the draw ratio was set to be 1.35 times in the second stage drawing process. The deformation rate and the drawing tension are as shown in Table 1. The strength and initial elastic modulus of the obtained polypropylene fiber are as shown in Table 1, and a fiber having high strength and high initial elastic modulus was obtained. The elongation at break, fineness, crystalline orientation degree, amorphous orientation degree, and crystallinity degree are as shown in Table 1, and the fiber structure was highly oriented.

Example 5

(33) As shown in Table 1, a polypropylene fiber was obtained in the same manner as in Example 1 except that the yarn temperature was set to be 135 C. and the draw ratio was set to be 6 times in the first stage drawing process and that the yarn temperature was set to be 165 C. and the draw ratio was set to be 1.66 times in the second stage drawing process. The deformation rate and the drawing tension are as shown in Table 1. The strength and initial elastic modulus of the obtained polypropylene fiber are as shown in Table 1, and a fiber having high strength and high initial elastic modulus was obtained. The elongation at break, fineness, crystalline orientation degree, amorphous orientation degree, and crystallinity degree are as shown in Table 1, and the fiber structure was highly oriented.

Example 6

(34) As shown in Table 1, a polypropylene fiber Was obtained in the same manner as in Example 1 except that the yarn temperature was set to be 175 C. in the second stage drawing process. The deformation rate and the drawing tension were as shown in Table 1. The strength and initial elastic modulus of the obtained polypropylene fiber are as shown in Table 1, and a fiber having high strength and high initial elastic modulus was obtained. The elongation at break, fineness, crystalline orientation degree, amorphous orientation degree, and crystallinity degree are as shown in Table 1, and the fiber structure was highly oriented.

Example 7

(35) As shown in Table 1, a polypropylene fiber was obtained in the same manner as in Example 1 except that the yarn temperature was set to be 185 C. in the second stage drawing process. The deformation rate and the drawing tension were as shown in Table 1. The strength and initial elastic modulus of the obtained polypropylene fiber are as shown in Table 1, and a fiber having high strength and high initial elastic modulus was obtained. The elongation at break, fineness, crystalline orientation degree, amorphous orientation degree, and crystallinity degree are as shown in Table 1, and the fiber structure was highly oriented.

Comparative Example 1

(36) As shown in Table 1, a polypropylene fiber was obtained in the same manner as in Example 1 except that the yarn temperature was set to be 135 C. and the draw ratio was set to be 6 times in the first stage drawing process, and that the yarn temperature was set to be 175 C. and the draw ratio was set to be 1.50 times in the second stage drawing process. The deformation rate and the drawing tension are as shown in Table 1. The strength and initial elastic modulus of the obtained polypropylene fiber are as shown in Table 1, and high strength fiber was not obtained. The elongation at break, fineness, crystalline orientation degree, amorphous orientation degree, and crystallinity degree are as shown in Table 1, which resulted in low amorphous orientation degree.

Comparative Example 2

(37) As shown in Table 1, a polypropylene fiber was obtained in the same manner as in Example 1 except that the yarn temperature was set to be 155 C. and the draw ratio was set to be 6 times in the first stage drawing process, and that the yarn temperature was set to be 165 C. in the second stage drawing process. The deformation rate and the drawing tension are as shown in Table 1, and the drawing tension was low in the second stage drawing. The strength and initial elastic modulus of the obtained polypropylene fiber are as shown in Table 1, and a fiber having high strength and high initial elastic modulus was not obtained. The elongation at break, fineness, crystalline orientation degree, amorphous orientation degree, and crystallinity degree are as shown in Table 1, which resulted in low amorphous orientation degree.

Comparative Example 3

(38) As shown in Table 1, a polypropylene fiber was obtained in the same manner as is Example 1 except that the draw ratio was set to be 4 times in the first stage drawing process, and that the yarn temperature was set to be 165 C. and the draw ratio was set to be 1.80 times, in the second stage drawing process. The deformation rate and the drawing tension are as shown in Table 1, and the drawing tension was low in the second stage drawing. The strength and initial elastic modulus of the obtained polypropylene fiber are as shown in Table 1, and a fiber having high strength and high initial elastic modulus was not obtained. The elongation at break, fineness, crystalline orientation degree, amorphous orientation degree, and crystallinity degree are as shown in Table 1, which resulted in low amorphous orientation degree.

(39) TABLE-US-00001 TABLE 1 Second stage drawing condition Drawing Fiber physical property First stage drawing condition tention at the Total Initial Yarn Draw Deformation Yarn Draw Deformation time of final Draw elastic temperature ratio rate temperature ratio rate drawing ratio Strength modulus C. times l/sec C. times l/sec cN/dtex times cN/dtex cN/dtex Example 1 145 8 12.2 155 1.2 2.78 2.87 9.6 8.53 129.9 Example 2 145 8 12.2 165 1.2 2.78 2.31 9.6 8.54 127.6 Example 3 145 8 10.8 165 1.35 4.32 3.23 10.8 9.10 159.2 Example 4 145 8 10.8 175 1.35 4.32 2.74 10.8 8.64 149.8 Example 5 135 6 8.4 165 1.66 6.63 2.46 10.0 8.35 140.5 Example 6 145 8 12.2 175 1.2 2.78 1.62 9.6 7.39 118.6 Example 7 145 8 12.2 185 1.2 2.78 1.50 9.6 7.78 121.0 Comparative 135 6 9.3 175 1.5 5.56 1.49 9.0 6.91 108.6 Example 1 Comparative 155 6 11.6 165 1.2 2.78 1.03 7.2 6.50 82.3 Example 2 Comparative 145 4 69 165 1.8 7.41 0.98 7.2 4.53 65.4 Example 3 Fiber physical property Endothermic energy amount Scattering Single Crystalline Amorphous at melting intensity ratio Elongation Total fiber Crystallinity orientation orientation peak by DSC in meridian/ at break finess finess degree degree degree measurement equatorial % dtex dtex % % % J/g direction Example 1 16.4 159.8 4.4 67.7 93.2 98.4 111 0.69 Example 2 17.1 158.7 4.4 69.1 94.3 99.8 107 0.73 Example 3 13.1 141.4 3.9 66.1 95.2 91.8 109 0.66 Example 4 13.4 140.2 3.9 65.3 96.0 90.2 110 0.67 Example 5 15.0 153.5 4.3 70.9 95.9 97.3 108 0.78 Example 6 13.9 156.7 4.4 72.5 96.6 86.7 110 0.88 Example 7 15.3 157.8 4.4 71.8 95.1 88.9 112 0.94 Comparative 16.3 167.3 4.6 75.5 95.8 83.9 110 0.99 Example 1 Comparative 21.5 209.9 5.8 76.0 95.1 81.9 107 1.39 Example 2 Comparative 14.7 210.5 5.8 76.3 92.1 74.7 108 1.81 Example 3

Example 8

(40) Polypropylene resin (Y2000 GV, melting point of resin: 169.4 C., MFR=18 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Prime Polymer Co., Ltd.) was charged into an extruder of a melt spinning apparatus, melt kneaded at 280 C., and discharged at a mass flow of 34 g/min (1.4 g/min per hole) from a nozzle (0.4 mm, 24 holes) at 280 C. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min at room temperature to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 1.3010.sup.3, and the ratio of the crystalline structure was 0 mass %. A maximum draw ratio at break at 155 C. of this undrawn yarn was 11.6 times. When it is drawn at the preheating temperature of 85 C., the hot plate temperature of 155 C., 0.7 times of the maximum draw ratio at break, and the velocity of 300 m/min, the strength of the obtained polypropylene fiber was 7.9 cN/dtex, as shown in Table 2.

Example 9

(41) Polypropylene resin (Y2000 GV, melting point of resin: 169.4 C., MFR=18 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Prime Polymer Co., Ltd.) was charged into an extruder of a melt spinning apparatus, melt kneaded at 280 C., and discharged at a mass flow of 30 g/min (1.5 g/min per hole) from a nozzle (0.8 mm, 20 holes) at 280 C. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered and the yarn was wound around a bobbin at a take-up speed of 300 m/min at room temperature to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 0.9210.sup.3, and the ratio of the crystalline structure was 0 mass %. A maximum draw ratio at break at 155 C. of this undrawn yarn was 11.4 times. When it is drawn at the preheating temperature of 85 C., the hot plate temperature of 155 C., 0.7 times of the maximum draw ratio at break, and the velocity of 300 m/min, the strength of the obtained polypropylene fiber was 7.7 cN/dtex, as shown in Table 2.

Example 10

(42) Polypropylene resin (Y2000 GV, melting point of resin: 169.4 C., MFR=18 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Prime Polymer Co., Ltd.) was charged into an extruder of a melt spinning apparatus, melt kneaded at 280 C., and discharged at a mass flow of 46 g/min (2.3 g/min per hole) from a nozzle (0.5 mm, 20 holes) at 280 C. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min at room temperature to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 0.8810.sup.3, and the ratio of the crystalline structure was 0 mass %. A maximum draw ratio at break at 155 C. of this undrawn yarn was 11.9 times. When it is drawn at the preheating temperature of 85 C., the hot plate temperature of 155 C., 0.7 times of the maximum draw ratio at break, and the velocity of 300 m/min, the strength of the obtained polypropylene fiber was 7.4 cN/dtex, as shown in Table 2.

Example 11

(43) Polypropylene resin (Y2000 GV, melting point of resin: 169.4 C., MFR=18 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Prime Polymer Co., Ltd.) was charged into an extruder of a melt spinning apparatus, melt kneaded at 280 C., and discharged at a mass flow of 30 g/min (1.5 g/min per hole) from a nozzle (0.5 mm, 20 holes) at 280 C. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min at room temperature to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 0.8810.sup.3, and the ratio of the crystalline structure was 0 mass %. A maximum draw ratio at break at 135 C. of this undrawn yarn was 10.3 times. When it is drawn at the preheating temperature of 85 C., the hot plate temperature of 135 C., 0.7 times of the maximum draw ratio at break, and the velocity of 300 m/min, the strength of the obtained polypropylene fiber was 7.3 cN/dtex, as shown in Table 2.

Example 12

(44) Polypropylene resin (Y2000 GV, melting point of resin: 169.4 C., MFR=18 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Prime Polymer Co., Ltd.) was charged into an extruder of a melt spinning apparatus, melt kneaded at 280 C., and discharged at a mass flow of 30 g/min (1.5 g/min per hole) from a nozzle (0.5 mm, 20 holes) at 280 C. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min at room temperature to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 0.8810.sup.3, and the ratio of the crystalline structure was 0 mass %. A maximum draw ratio at break at 155 C. of this undrawn yarn was 10.9 times. When it is drawn at the preheating temperature of 85 C., the hot plate temperature of 155 C., 0.7 times of the maximum draw ratio at break, and the velocity of 300 m/min, the strength of the obtained polypropylene fiber was 7.1 cN/dtex, as shown in Table 2.

Example 13

(45) Polypropylene resin (Y2000 GV, melting point of resin: 169.4 C., MFR=18 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Prime Polymer Co., Ltd.) was charged into an extruder of a melt spinning apparatus, melt kneaded at 280 C., and discharged at a mass flow of 46 g/min (2.3 g/min per hole) from a nozzle (0.3 mm, 20 holes) at 280 C. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min at room temperature to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 0.7610.sup.3, and the ratio of the crystalline structure was 0 mass %. A maximum draw ratio at break at 155 C. of this undrawn yarn was 11.6 times. When it is drawn at the preheating temperature of 85 C., the hot plate temperature of 155 C., 0.7 times of the maximum draw ratio at break, and the velocity of 300 m/min, the strength of the obtained polypropylene fiber was 7.1 cN/dtex, as shown in Table 2.

Example 14

(46) Polypropylene resin (Y2000 GV, melting point of resin: 169.4 C., MFR=18 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Prime Polymer Co., Ltd.) was charged into an extruder of a melt spinning apparatus, melt kneaded at 280 C. and discharged at a mass flow of 34 g/min (1.4 g/min per hole) from a nozzle (0.4 mm, 24 holes) at 280 C. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min at room temperature to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 1.3010.sup.3, and the ratio of the crystalline structure was 0 mass %. A maximum draw ratio at break at 135 C. of this undrawn yarn was 10.4 times. When it is drawn at the preheating temperature of 85 C., the hot plate temperature of 135 C., 0.7 times of the maximum draw ratio at break, and the velocity of 300 m/min, the strength of the obtained polypropylene fiber was 7.1 cN/dtex, as shown in Table 2.

Example 15

(47) Polypropylene resin (Y2000 GV, melting point of resin: 169.4 C., MFR=18 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Prime Polymer Co., Ltd.) was charged into an extruder of a melt spinning apparatus, melt kneaded at 280 C., and discharged at a mass flow of 46 g/min (2.3 g/min per hole) from a nozzle (0.5 mm, 20 holes) at 280 C. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min at room temperature to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 0.8810.sup.3, and the ratio of the crystalline structure was 0 mass %. A maximum draw ratio at break at 135 C. of this undrawn yarn was 10.9 times. When it is drawn at the preheating temperature of 85 C., the hot plate temperature of 135 C., 0.7 times of the maximum draw ratio at break, and the velocity of 300 m/min, the strength of the obtained polypropylene fiber was 6.9 cN/dtex, as shown in Table 2.

Example 16

(48) Polypropylene resin (Y2000 GV, melting point of resin: 169.4 C., MFR=18 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Prime Polymer Co., Ltd.) was charged into an extruder of a melt spinning apparatus, melt kneaded at 250 C., and discharged at a mass flow of 30 g/min (1.5 g/min per hole) from a nozzle (0.3 mm, 20 holes) at 250 C. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min at room temperature to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 2.0210.sup.3, and the ratio of the crystalline structure was 16.0 mass %. A maximum draw ratio at break at 155 C. of this undrawn yarn was 10.1 times. When it is drawn at the preheating temperature of 85 C., the hot plate temperature of 155 C., 0.7 times of the maximum draw ratio at break, and the velocity of 300 m/min, the strength of the obtained polypropylene fiber was 7.3 cN/dtex, as shown in Table 2.

Example 17

(49) Polypropylene resin (Y2000 GV, melting point of resin: 169.4 C., MFR=18 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Prime Polymer Co., Ltd.) was charged into an extruder of a melt spinning apparatus, melt kneaded at 280 C., and discharged at a mass flow of 30 g/min (1.5 g/min per hole) from a nozzle (0.3 mm, 20 holes) at 280 C. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 600 m/min at room temperature to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 3.1510.sup.3, and the ratio of the crystalline structure was 0 mass %. A maximum draw ratio at break at 135 C. of this undrawn yarn was 9.3 times. When it is drawn at the preheating temperature of 85 C., the hot plate temperature of 135 C., 0.7 times of the maximum draw ratio at break, and the velocity of 300 m/min, the strength of the obtained polypropylene fiber was 6.7 cN/dtex, as shown in Table 2.

Comparative Example 4

(50) Polypropylene resin (SA01A, melting point of resin: 168.3 C., MFR=10 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Japan Polypropylene Corporation) was charged into an extruder of a melt spinning apparatus, melt kneaded at 280 C., and discharged at a mass flow of 34 g/min (1.4 g/min per hole) from a nozzle (0.4 mm, 24 holes) at 280 C. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min at room temperature to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 2.3610.sup.3, and the ratio of the crystalline structure was 46.0 mass %. A maximum draw ratio at break at 135 C. of this undrawn yarn was 9.3 times. When it is drawn at the preheating temperature of 85 C., the hot plate temperature of 135 C., 0.7 times of the maximum draw ratio at break, and the velocity of 300 m/min, the strength of the obtained polypropylene fiber was as low as 6.7 cN/dtex, as shown in Table 2. This is presumably because the MFR was as low as 10 g/10 min, the melt viscosity was high, and the tension of the resin on the spinning line became high, and consequently, the ratio of the crystalline structure of the obtained undrawn yarn increased, and the oriented crystallization of crystal was promoted.

Comparative Example 5

(51) Polypropylene resin (SA03A, melting point of resin: 168.7 C., MFR=30 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Japan Polypropylene Corporation) was charged into an extruder of a melt spinning apparatus, melt kneaded at 280 C., and discharged at a mass flow of 34 g/min (1.4 g/min per hole) from a nozzle (0.4 mm, 24 holes) at 280 C. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min at room temperature to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 1.0610.sup.3, and the ratio of the crystalline structure was 40.1 mass %. A maximum draw ratio at break at 135 C. of the undrawn yarn was 11.2 times. When it is drawn at the preheating temperature of 85 C., the hot plate temperature of 135 C., 0.7 times of the maximum draw ratio at break, and the velocity of 300 m/min, the strength of the obtained polypropylene fiber was 6.5 cN/dtex as shown in Table 2, which was lower than any of the above Examples 8 to 17. It is considered that despite the birefringence value was low, the desired strength was not able to be obtained because the crystalline structure was crystal and the MFR was extremely high.

Comparative Example 6

(52) Polypropylene resin (Y2000 GV, melting point of resin: 169.4 C., MFR=18 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Prime Polymer Co., Ltd.) was charged into an extruder of a melt spinning apparatus, melt kneaded at 220 C., and discharged at a mass flow of 30 g/min (1.5 g/min per hole) from a nozzle (0.3 mm, 20 holes) at 220 C. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min at room temperature to obtain an undrawn yarn. The birefringence value of the undrawn yarn was 3.3210.sup.3, and the ratio of the crystalline structure was 42.4 mass %. A maximum draw ratio at break at 155 C. of this undrawn yarn was 8.8 times. When it is drawn at the preheating temperature of 85 C., the hot plate temperature of 155 C., 0.7 times of the maximum draw ratio at break, and the velocity of 300 m/min, the strength of the obtained polypropylene fiber was 6.5 cN/dtex, as shown in Table 2. It is considered that despite the MFR is within the definition of the present invention, the strength of the obtained polypropylene fiber was as low as that of Comparative Example 5 since the spinning temperature was too low compared with other Examples and the birefringence value became too large.

(53) TABLE-US-00002 TABLE 2 Spinning condition of undrawn yarn Spinning Undrawn yarn Resin temperature Crystalline Spinning melting resin melting 1 hole Spinning Take-up Birefringence structure MFR temperature point point mass flow draft speed value ratio (g/min) ( C.) ( C.) ( C.) (g/min) (times) (m/min) (10.sup.-3) (%) Example 8 18 280 169.4 110.6 1.4 22 300 1.30 0 Example 9 18 280 169.4 110.6 1.5 12 300 0.93 0 Example 10 18 280 169.4 110.6 2.3 8 300 0.88 0 Example 11 18 280 169.4 110.6 1.5 12 300 0.88 0 Example 12 18 280 169.4 110.6 1.5 12 300 0.88 0 Example 13 18 280 169.4 110.6 2.3 8 300 0.76 0 Example 14 18 280 169.4 110.6 1.4 22 300 1.30 0 Example 15 18 280 169.4 110.6 2.3 12 300 0.88 6 Example 16 18 250 169.4 80.6 1.5 12 300 2.02 16.0 Example 17 18 280 169.4 110.6 1.5 24 600 31.5 0 Comparative 10 280 168.3 111.7 1.4 22 300 2.36 46.0 Example 4 Comparative 30 280 168.7 111.3 1.4 22 300 1.06 40.1 Example 5 Comparative 18 220 169.4 50.6 1.5 12 300 3.32 42.4 Example 6 Undrawn yarn Drawn yarn Meso- Amorphous Drawing condition of undrawn yarn Single structure structure Drawing fiber ratio ratio temperature Draw Ratio at fineness Strength Elongation (%) (%) ( C.) ratio break (dtex) (cN/dtex) (%) Example 8 54.3 45.7 155 8.1 11.6 5.3 7.9 23.4 Example 9 52.3 47.7 155 8.0 11.4 5.5 7.7 16.6 Example 10 49.6 50.4 155 8.3 11.9 7.8 7.4 15.3 Example 11 57.6 42.4 135 7.2 10.3 6 7.3 18 Example 12 57.6 42.4 155 7.6 10.9 5.7 7.1 16.4 Example 13 55.0 45.0 155 8.1 11.6 8.1 7.1 15.3 Example 14 54.3 45.7 135 7.3 10.4 5.9 7.1 23.8 Example 15 49.6 50.4 135 7.6 10.9 8.6 6.9 17.7 Example 16 48.0 36.0 155 7.1 10.1 6.4 7.3 18.3 Example 17 58.0 42.0 135 6.5 9.3 3.3 6.7 20.2 Comparative 0.0 54.0 135 6.5 9.3 6.3 6.7 29.2 Example 4 Comparative 0.0 59.9 135 7.8 11.2 5.5 6.5 21.6 Example 5 Comparative 0.0 57.6 155 6.2 8.8 7.3 6.5 18.2 Example 6

Example 18

(54) Polypropylene resin (Y2000 GV, MFR=18 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Prime Polymer Co., Ltd.) was charged into an extruder of a melt spinning apparatus, heated up to 280 C. and melt kneaded, and discharged at a mass flow of 30 g/min (1.5 g/min per hole) from a spinning nozzle having 20 discharge holes in which each discharge hole diameter is 0.5 mm. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and wound around a bobbin with a take-up speed of 300 m/min to obtain an undrawn yarn. This undrawn yarn has a crystalline structure ratio of 0%, a meso-structure ratio of 57.6%, an amorphous structure ratio of 42.4%, and a birefringence value of 0.8810.sup.3, which was low in crystallinity and orientation.

(55) With respect to the obtained undrawn yarn, preheating was carried out using the hot roll so as to have the yarn temperature of 85 C., and the hot plate drawing was performed in a first stage drawing at 9.1 times at a yarn temperature of 145 C., as shown in Table 4. Further, preheating was carried out continuously with the hot roll so as to have the yarn temperature of 120 C. further, and the hot plate drawing was performed in a second stage drawing at 1.1 times, at the yarn temperature at 165 C., a deformation rate of 1.52 (1/sec), and a drawing tension of 2.79 cN/dtex. As shown in Table 4, the drawing velocity in a final stage was 300 m/min. The obtained fiber had a strength of 9.4 cN/dtex, an initial elastic modulus of 142 cN/dtex, and a fiber having high strength and high initial elastic modulus was obtained. The elongation at break was 16.2%, and the single fiber fineness was 4.4 dtex.

Examples 19 to 22

(56) Polypropylene fibers were obtained using the same undrawn yarn as in Example 18 and in the same manner as in Example 18 except that the draw ratio of the first stage, the draw ratio of the second stage, the deformation rate, and the drawing tension were changed as shown in Table 4. The physical properties of the obtained polypropylene fibers are shown in Table 4.

Examples 23

(57) The same polypropylene resin as in Example 18 was discharged at a mass flow of 46 g/min (1.3 g/min per hole) from a spinning nozzle having 36 discharge holes in which each discharge hole diameter is 0.5 mm. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min to obtain an undrawn yarn. As shown in Table 3, the undrawn yarn has a crystalline structure ratio of 0%, a meso-structure ratio of 53.0%, an amorphous structure ratio of 47.0%, and a birefringence value of 1.0210.sup.3, which was low in crystallinity and orientation. With respect to the obtained undrawn yarn, preheating was carried out using the hot roll so as to have the yarn temperature of 85 C., and the hot plate drawing was performed in a first stage at 6.0 times at the yarn temperature of 135 C., as shown in Table 4. Further, preheating was carried out continuously with the hot roll so as to have the yarn temperature of 120 C., the hot plate drawing was performed in a second stage at 1.7 times, at the yarn temperature of 165 C., a deformation rate of 6.63 (1/second), and a drawing tension of 2.46 cN/dtex. A drawing velocity of the second stage was 300 m/min. The obtained fiber had a strength of 8.4 cN/dtex, an initial elastic modulus of 140 cN/dtex, and a fiber having high strength and high initial elastic modulus was obtained. A elongation at break was 15.0% and the single fiber fineness was 4.3 dtex (see Table 4).

Examples 24 to 25

(58) Polypropylene fibers were obtained using the same undrawn yarn as in Example 23 and in the same manner as in Example 23 except that the drawing temperature and the draw ratio of the first stage and the drawing temperature, the draw ratio, and the deformation rate of the second stage were as shown in Table 4. The physical properties of the obtained polypropylene fibers are shown in Table 4.

Comparative Example 7

(59) The same undrawn yarn as in Example 18 was preheated using the hot roll to have a yarn temperature of 85 C. and drawn in one stage as shown in Table 4. The hot plate drawing was performed at 7.2 times, at the yarn temperature of 135 C., a deformation rate of 14.4 (1/sec), and a drawing tension of 1.32 cN/dtex. The drawing velocity was 300 m/min. As shown in Table 4, the obtained fiber had a strength of 7.3 cN/dtex and an initial elastic modulus of 97 cN/dtex, which were lower than the Example. The elongation at break was 18.0%, and the single fiber fineness was 6.0 dtex.

Comparative Example 8

(60) The same undrawn yarn having low crystallinity and low orientation as in Example 18 was preheated using the hot roll to have a yarn temperature of 85 C. and drawn in one stage as shown in Table 4. The hot plate drawing was performed at 7.7 times, at the yarn temperature of 155 C., a deformation rate of 14.5 (1/sec), and a drawing tension of 1.28 cN/dtex. The drawing velocity was 300 m/min. As shown in Table 4, the obtained fiber had a strength of 7.1 cN/dtex and an initial elastic modulus of 91 cN/dtex, which were lower than the Example. The elongation at break was 16.4%, and the single fiber fineness was 5.7 dtex.

Comparative Example 9

(61) The same polymer as in Example 18 was charged into an extruder of a melt spinning apparatus, melt kneaded at 220 C., and discharged at a mass flow of 30 g/min (1.5 g/min per hole) from a nozzle (0.5 mm, 20 holes) at 220 C. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min at room temperature to obtain an undrawn yarn. The undrawn yarn had a crystal fraction of 42.4%, a meso fraction of 0%, an amorphous fraction of 57.6%, and a birefringence value of 3.3210.sup.3, which has high ratio of crystalline structure and high orientation. As shown in Table 4, with respect to the obtained undrawn yarn, preheating was performed so as to have a yarn temperature of 85 C. using the hot roll, and the hot plate drawing was performed in a first stage at 6.3 times at the yarn temperature of 145 C. Further, preheating was carried out continuously with the hot roll so as to have the yarn temperature of 120 C., the hot plate drawing was performed in a second stage at the yarn temperature of 165 C. and at 1.2 times, a deformation rate of 2.78 (1/second), and a drawing tension of 2.99 cN/dtex. The drawing velocity was 300 m/min. The obtained fiber had a strength of 7.0 cN/dtex and an initial elastic modulus of 103 cN/dtex, which were lower in strength and initial elastic modulus than those in the Example. The elongation at break was 17.2%, and the single fiber fineness was 6.3 dtex.

Comparative Example 10

(62) Polypropylene resin (SA01A, melting point of resin: 168.3 C., MFR=10 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Japan Polypropylene Corporation) was charged into an extruder of a melt spinning apparatus, melt kneaded at 280 C., and discharged at a mass flow of 34 g/min (1.4 g/min per hole) from a nozzle (0.4 mm, 24 holes) at 280 C., as shown in Table 3. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min at room temperature to obtain an undrawn yarn. As shown in Table 3, this undrawn yarn had a crystal fraction of 46.0%, a meso fraction of 0%, an amorphous fraction of 54.0%, and a birefringence value of 2.3610.sup.3, which was higher in crystallinity and orientation than the Example. With respect to the undrawn yarn, preheating was carried out using the hot roll so as to have a yarn temperature of 85 C. As shown in Table 4, the first stage drawing was performed at 6.3 times at a yarn temperature of 135 C. Further, preheating was carried out continuously with the hot roll so as to have a yarn temperature of 120 C., and the hot plate drawing was performed in a second stage at 1.2 times, at the yarn temperature of 160 C., a deformation rate of 3.06 (1/sec), and a drawing tension of 1.92 cN/dtex. The drawing velocity was 300 m/min. The obtained fiber had a strength of 8.0 cN/dtex and an initial elastic modulus of 85 cN/dtex, which were lower in the strength and the initial elastic modulus than those in the Example. The elongation at break was 24.6%, and the single fiber fineness was 5.6 dtex (see Table 4).

Comparative Example 11

(63) Polypropylene resin (SA03A, melting point of resin: 168.7 C., MFR=30 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Japan Polypropylene Corporation) was charged into an extruder of a melt spinning apparatus, melt kneaded at 280 C., and discharged at a mass flow of 34 g/min (1.4 g/min per hole) from a nozzle (0.4 mm, 24 holes) at 280 C. After cooling and solidifying by applying cold air at 20 C., an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min at room temperature to obtain an undrawn yarn (see Table 3). As shown in Table 3, the undrawn yarn had a birefringence value of 1.0610.sup.3, which was almost the same molecular orientation as in the Example, however, a crystal fraction of 40.1%, a meso fraction of 0%, and an amorphous fraction of 59.9%, which was higher in crystallinity than the Example. With respect to the obtained undrawn yarn, preheating was carried out using the hot roll so as to have a yarn temperature of 85 C. As shown in Table 4, the hot plate drawing was performed in a first stage at 7.9 times at the yarn temperature of 135 C. and. Further, preheating was carried out continuously with the hot roll so as to have the yarn temperature of 120 C., and the hot plate drawing was performed in a second stage at 1.2 times, at the yarn temperature of 160 C., a deformation rate of 3.06 (1/sec), a drawing tension of 1.72 cN/dtex. The drawing velocity was 300 m/min. The obtained fiber had a strength of 7.5 cN/dtex and an initial elastic modulus of 88 cN/dtex, which were lower than those in the Example. The elongation at break was 15.1%, and the single fiber fineness was 4.5 dtex.

(64) TABLE-US-00003 TABLE 3 Undrawn yarn Spinning Resin Resin temperature Take-up Polypro- Spinning melting Resin melting speed of Ratio of structure (mass %) Birefrin- pylene MFR temperature point point undrawn yarn Crystallinity Meso- Amorphous gence resin (g/min) ( C.) ( C.) ( C.) (m/min) structure structure structure value Example 18 Y2000GV 18 280 169.4 110.6 300 0.0 57.6 42.4 0.88 10.sup.3 Example 19 Y2000GV 18 280 169.4 110.6 300 0.0 57.6 42.4 0.88 10.sup.3 Example 20 Y2000GV 18 280 169.4 110.6 300 0.0 57.6 42.4 0.88 10.sup.3 Example 21 Y2000GV 18 280 169.4 110.6 300 0.0 57.6 42.4 0.88 10.sup.3 Example 22 Y2000GV 18 280 169.4 110.6 300 0.0 57.6 42.4 0.88 10.sup.3 Example 23 Y2000GV 18 280 169.4 110.6 300 0.0 53.0 47.0 1.02 10.sup.3 Example 24 Y2000GV 18 280 169.4 110.6 300 0.0 53.0 47.0 1.02 10.sup.3 Example 25 Y2000GV 18 280 169.4 110.6 300 0.0 53.0 47.0 1.02 10.sup.3 Comparative Y2000GV 18 280 169.4 110.6 300 0.0 57.6 42.4 0.88 10.sup.3 Example 7 Comparative Y2000GV 18 280 169.4 110.6 300 0.0 57.6 42.4 0.88 10.sup.3 Example 8 Comparative Y2000GV 18 220 169.4 50.6 300 42.4 0.0 57.6 3.32 10.sup.3 Example 9 Comparative SA01A 10 280 168.3 111.7 300 46.0 0.0 54.0 2.36 10.sup.3 Example 10 Comparative SA03A 30 280 168.7 111.3 300 40.1 0.0 59.9 1.06 10.sup.3 Example 11

(65) TABLE-US-00004 TABLE 4 Drawn yarn First stage Second stage Final stage Total Draw Draw Deformation draw Temperature ratio Temperature ratio rate Stages ratio ( C.) (times) ( C.) (times) (1/sec) Example 18 two stage 10.0 145 9.1 165 1.1 1.52 Example 19 two stage 10.0 145 8.4 165 1.2 2.78 Example 20 two stage 11.0 145 9.2 165 1.2 2.78 Example 21 two stage 11.0 145 8.5 165 1.3 3.85 Example 22 two stage 10.1 145 7.2 165 1.4 4.76 Example 23 two stage 10.0 135 6.0 165 1.7 6.63 Example 24 two stage 9.6 145 8.0 155 1.2 2.78 Example 25 two stage 10.8 145 8.0 175 1.35 4.32 Comparative two stage 7.2 135 7.2 14.4 Example 7 Comparative two stage 7.7 155 7.7 14.5 Example 8 Comparative two stage 7.5 145 6.3 165 1.2 2.78 Example 9 Comparative two stage 7.5 135 6.3 160 1.2 3.06 Example 10 Comparative two stage 9.6 135 7.9 160 1.2 3.06 Example 11 Drawn yarn Final stage Initial Drawing elastic Elongation Fineness(dtex) Tension velocity Strength modulus at break Single Total (cN/Dtex) (m/min) (cN/dtex) (cN/dtex) (%) fiber fineness Example 18 2.79 300 9.4 142 16.2 4.4 87.5 Example 19 2.79 300 9.2 143 15.5 4.4 88.6 Example 20 3.58 300 8.4 152 12.0 4.1 81.2 Example 21 3.63 300 8.9 151 12.9 4.1 81.1 Example 22 2.92 300 9.0 153 14.0 4.4 87.7 Example 23 2.46 300 8.4 140 15.0 4.3 153.5 Example 24 2.87 300 8.5 130 16.4 4.4 159.8 Example 25 2.74 300 8.6 150 13.4 3.9 140.2 Comparative 1.32 300 7.3 97 18.0 6.0 121.0 Example 7 Comparative 1.28 300 7.1 91 16.4 5.7 114.1 Example 8 Comparative 2.99 300 7.0 103 17.2 6.3 125.6 Example 9 Comparative 1.92 300 8.0 85 24.6 5.6 135.5 Example 10 Comparative 1.72 300 7.5 68 15.1 4.5 107.7 Example 11

Example 26

(66) As shown in Table 5, polypropylene resin (Y2000 GV, melting point of resin=169.8 C., MFR=18 g/10 min [230 C., load: 2.16 kg, 10 min] manufactured by Prime Polymer Co., Ltd.) was extruded from a melt spinning apparatus, melt kneaded at 280 C., and discharged from a spinning nozzle having 36 discharge holes in which each discharge hole diameter is 0.5 mm at a mass flow of 45.3 g/min (1.26 g/min). After cooling and solidifying by applying cold air at 20 C. to the fiber, an oil agent was adhered, and the yarn was wound around a bobbin at a take-up speed of 300 m/min to obtain an undrawn yarn. The undrawn yarn had a crystal structure ratio of 0%, a meso structure ratio of 53.0%, an amorphous structure ratio of 47.0%, and a birefringence value of 0.8810.sup.3, which was low in crystallinity and orientation. The obtained undrawn yarn was preheated with the hot roll so as to have a yarn temperature of 85 C., and the hot plate drawing in the first stage was performed at a yarn temperature of 145 C. and a draw ratio of 6.0 times. As a result of structural analysis of the process yarn at the completion of the first stage drawing, as shown in Table 5, an intensity ratio in the meridian direction with respect to an intensity in the equatorial direction by the small angle X scattering measurement was 1.45. An area ratio of the melting peak at 160 C. to 166 C. with respect to the melting peak at 168 C. to 174 C. was 54.6% by the DSC measurement, which was low in the inhomogeneous structure. Further, preheating was carried out continuously with the hot roll so as to have the yarn temperature of 120 C., and the hot plate drawing was performed in a second stage drawing so as to have the yarn temperature of 165 C., a draw ratio of 1.2 times, and a deformation rate of 2.78 (1/sec). The drawing velocity was 300 m/min, and a polypropylene fiber (see Table 6) was obtained. As shown in Table 6, the strength of the obtained polypropylene fiber was as high as 6.7 cN/dtex for fiber strength and 86.1 cN/dtex for initial elastic modulus, and the fiber was less fluffed. The elongation at break was 21.8%, and the single fiber fineness was 5.8 dtex.

Example 27

(67) A polypropylene fiber having a single fiber fineness of 4.2 dtex was obtained in the same manner as in Example 26 except that the second stage drawing was performed at a yarn temperature of 165 C., a draw ratio of 1.66 times, and a deformation rate of 6.63 (1/sec). The results are shown in Tables 5 and 6. The obtained polypropylene fiber had both high strength and initial elastic modulus and less fluffed.

Example 28

(68) A polypropylene fiber having a single fiber fineness of 4.4 dtex was obtained in the same manner as in Example 26 except that the first stage drawing was performed at a yarn temperature of 145 C. and a draw ratio of 8.0 times. The results are shown in Tables 5 and 6. The obtained polypropylene fiber had both high strength and initial elastic modulus and less fluffed.

Example 29

(69) A polypropylene fiber having a single fiber fineness of 4.7 dtex was obtained in the same manner as in Example 26 except that the second stage drawing was performed at a yarn temperature of 165 C., a draw ratio of 1.5 times, and a deformation rate of 5.56 (1/sec). The results are shown in Tables 5 and 6. The obtained polypropylene fiber had both high strength and initial elastic modulus and less fluffed.

Example 30

(70) A polypropylene fiber having a single fiber fineness of 4.6 dtex was obtained in the same manner as in Example 26 except that the first stage drawing was carried out at a yarn temperature of 135 C., and the second stage drawing was performed at a draw ratio of 1.5 times and a deformation race of 5.56 (1/second). The results are shown in Tables 5 and 6. The obtained polypropylene fiber had both high strength and initial elastic modulus and less fluffed.

Example 31

(71) A polypropylene fiber having a single fiber fineness of 3.9 dtex was obtained in the same manner as in Example 26 except that the hot plate drawing was performed in a first stage drawing at a draw ratio of 8.0 times, and the hot plate drawing was performed in a second stage drawing at a yarn temperature of 165 C., a draw ratio of 1.35 times, and a deformation rate of 4.32 (1/sec). The results are shown in Tables 5 and 6. The obtained polypropylene fiber had both high strength and initial elastic modulus and less fluffed.

Example 32

(72) A polypropylene fiber having a single fiber fineness of 4.4 dtex was obtained in the same manner as in Example 26 except that a yarn temperature was 155 C. and a draw ratio was 8.0 times in the first stage drawing. The results are shown in Tables 5 and 6. The obtained polypropylene fiber had both high strength and initial elastic modulus and less fluffed.

Comparative Example 12

(73) A polypropylene fiber having a single fiber fineness of 5.8 dtex was obtained in the same manner as in Example 26 except that a draw ratio was 4.0 times in the first stage drawing and a draw ratio was 1.8 times and a deformation rate was 7.41 (1/sec) in the second stage drawing. The results are shown in Tables 5 and 6. The obtained polypropylene fiber had a strength of 4.5 cN/dtex and the initial elastic modulus of 65.4 cN/dtex, which were both low in the strength and the initial elastic modulus, and is highly fluffed.

Comparative Example 13

(74) A polypropylene fiber having a single fiber fineness of 5.1 dtex was obtained in the same manner as in Example 26 except that a draw ratio was 4.0 times in the first stage drawing and a draw ratio was 2.0 times and a deformation rate was 8.33 (1/sec) in the second stage drawing. The results are shown in Tables 5 and 6. The obtained polypropylene fiber had a strength of 5.8 cN/dtex and an initial elastic modulus of 81.6 cN/dtex, which were both low in the strength and the initial elastic modulus, and is highly fluffed.

Comparative Example 14

(75) Although attempting to produce a polypropylene fiber in the same manner as in Example 26 except that a draw ratio was 4.0 times in the first stage drawing, and a draw ratio was 2.5 times and a deformation rate was 10 (1/sec) in the second stage drawing, yarn breakage occurred and a final fiber was not able to be obtained.

Comparative Example 15

(76) Although attempting to manufacture a polypropylene fiber in the same manner as in Example 26 except that a yarn temperature was 155 C. in the first stage drawing, and a draw ratio was 1.5 times and a deformation rate was 5.56 (1/sec) in the second stage drawing, yarn breakage occurred and a final fiber was not able to be obtained.

(77) TABLE-US-00005 TABLE 5 Preheating Second stage Single Initial in second Yarn Deformation Drawing Total fiber Total Elongation elastic stage temperature Draw rate velocity draw Spinning fineness fineness Strength at break modulus C. C. ratio 1/sec m/min ratio property dtex dtex cN/dtex % cN/dtex Example 26 120 165 1.2 2.78 300 7.2 favorable 5.8 209 6.7 21.8 86.1 Example 27 120 165 1.66 6.63 300 9.96 favorable 4.2 153 7.6 11.7 134.1 Example 28 120 165 1.2 2.78 300 9.6 favorable 4.4 159 8.5 17.1 127.6 Example 29 120 165 1.5 5.56 300 9 favorable 4.7 168 7.4 14.0 114.6 Example 30 120 165 1.5 5.56 300 9 favorable 4.6 167 8.0 15.5 126.7 Example 31 120 165 1.35 4.32 300 10.8 favorable 3.9 141 9.1 13.1 159.2 Example 32 120 165 1.2 2.78 300 9.6 favorable 4.4 158 7.8 15.5 130.2 Comparative 120 165 1.8 7.41 300 7.2 single yarn 5.8 210 4.5 14.7 65.4 Example 12 breakage, highly fluffed Comparative 120 165 2 8.33 300 8 highly fluffed 5.1 185 5.8 15.0 81.6 Example 13 Comparative 120 165 2.5 10 300 10 fiber bundle Example 14 breakage Comparative 120 165 1.5 5.56 300 9 fiber bundle Example 15 breakage

(78) TABLE-US-00006 TABLE 6 Preheating Second stage Single Initial in second Yarn Deformation Drawing Total fiber Total Elongation elastic stage temperature Draw rate velocity draw Spinning fineness fineness Strength at break modulus C. C. ratio l/sec m/min ratio property dtex dtex cN/dtex % cN/dtex Example 26 120 165 1.2 2.78 300 7.2 favorable 5.8 209 6.7 21.8 86.1 Example 27 120 165 1.66 6.63 300 9.96 favorable 4.2 153 7.6 11.7 134.1 Example 28 120 165 1.2 2.78 300 9.6 favorable 4.4 159 8.5 17.1 127.6 Example 29 120 165 1.5 5.56 300 9 favorable 4.7 168 7.4 14.0 114.6 Example 30 120 165 1.5 5.56 300 9 favorable 4.6 167 8.0 15.5 126.7 Example 31 120 165 1.35 4.32 300 10.8 favorable 3.9 141 9.1 13.1 159.2 Example 32 120 165 1.2 2.78 300 9.6 favorable 4.4 158 7.8 15.5 130.2 Comparative 120 165 1.8 7.41 300 7.2 single yarn 5.8 210 4.5 14.7 65.4 Example 12 breakage, highly fluffed Comparative 120 165 2 8.33 300 8 highly 5.1 185 5.8 15.0 81.6 Example 13 fluffed Comparative 120 165 2.5 10 300 10 fiber bundle Example 14 breakage Comparative 120 165 1.5 5.56 300 9 fiber bundle Example 15 breakage