JPH0571683B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD OF THE INVENTION The present invention relates to a method for producing high-strength, high-fatigue-resistant nylon 66 fibers. Conventional technology Nylon 66 fiber is characterized by its fatigue resistance, strength, elasticity,
Because it has superior resilience and adhesion to rubber, resin, and plastic compared to other fibers, it is widely applied in the field of industrial materials such as tire cords and carpets. However, the nylon that has traditionally been used
66 fibers had the disadvantage that those with high strength had poor fatigue resistance, and those with fatigue resistance had poor strength. That is, by conventionally known methods, it has not been possible to obtain nylon 66 fibers that are excellent in both fatigue resistance and strength. conventional nylon 66
The fibers can be cold-stretched or hot-stretched below their melting temperature (e.g., zone-stretch zone heat treatment (T. Kunugiet
al; Polymer Preprints, Japan31 (No. 4), 761
(1982)) to improve strength and elastic modulus.
However, this method increases the proportion of so-called tie molecular chains that connect crystal regions,
A study of the correlation between the microstructure of nylon 66 fibers and the mechanical properties of the fibers revealed that fatigue resistance is poor due to the increased tension in the amorphous region. Problems to be Solved by the Invention The present inventors studied the correlation between the microstructure of nylon 66 fibers, fatigue resistance, high strength, and high elastic modulus, and found that T _nax and (tan〓) _nax and fiber We found that there is a close relationship between the mechanical properties (strength, elastic modulus, fatigue resistance, etc.) of fibers, and found that the microstructure of highly strong and highly fatigue resistant fibers has a high ratio of extended chains and is amorphous. We found that a structure with low tension in the molecular chains inside the region is required, and based on this we completed the present invention. An object of the present invention is to provide a method for producing nylon 66 fibers that have high strength and excellent fatigue resistance. Means for Solving the Problems The method for producing high-strength, high-fatigue-resistant nylon 66 fibers according to the present invention includes: (1) when heat treating nylon 66 fibers spun at a spinning speed of 4000 m/min or more; The magnitude of the tension applied in the fiber axis direction is 0.5 (g/d) or more and 0.99T (g/d)
(However, T is the tensile strength of the fiber at break.) Below, (2) in an atmosphere substantially free of oxygen, (3) at a heat treatment temperature exceeding 240°C, Tm ₃ +
5/9×10 ² υ [However, Tm ₃ is the temperature at which the DSC melting curve returns to the baseline measured at a heating rate of 10°C/min (see Figure 3), υ is the processing speed (mm/min)
It is. ], (4) Length l (mm) in the fiber axis direction is 1≦l≦1+
4υ+5d/1.5θ (where, υ is the processing speed (mm/min), d is the denier of the fiber, and θ is the heat treatment temperature (℃)
), and then (5) cooling to a cooling temperature where the absolute value of the temperature gradient is |300|(°C/cm) or more and -60°C or less. In the present invention, "nylon 66 fiber" means a fiber substantially composed of polyhexamethylene adipamide polymerized from hexamethylene diamine and adipic acid, and the characteristics of polyhexamethylene adipamide It may be a copolyamide fiber containing a small amount of other copolymer components, or a fiber composed of a mixture with other polymers, as long as the properties are not impaired. The higher the polymerization degree of nylon 66 fibers, the higher the mechanical breaking strength, so it is desirable, especially the viscosity average molecular weight M〓 (measured in 95% concentrated sulfuric acid, according to the viscosity formula [η] = 2.5 + 0.0209M ^0.832 )
It is desirable that the value is 42000 or more. The first characteristic of the nylon fiber obtained by the manufacturing method according to the present invention is that the temperature (T _nax ) with respect to the peak value [(tan〓) _nax ] of the mechanical loss tangent at a measurement frequency of 110 Hz is less than 100°C, and the peak value [(tan〓) _na
x ] is greater than 0.06 and less than 0.10. In addition, the (tan〓) _nax of conventional clothing fibers is 0.09 to 0.13.
distribution, and T _nax is over 120℃. Furthermore, the (tan〓) _nax of the fiber obtained by cold drawing or zone drawing zone heat treatment method is 0.04 or less, and T _nax is 110° C. or more. When T _nax is less than 100°C, the ratio of tie molecular chains is small and the tension of the molecular chains inside the amorphous region is low. Due to this decrease in tension, T _nax <100℃
The fibers have excellent fatigue resistance. When T _nax is 100°C or higher, the tie molecular chain ratio increases, which increases the tension of the molecular chains inside the amorphous region, and this is probably the reason why fatigue resistance decreases. The fatigue resistance increases as T _nax decreases, but as T _nax decreases, the elastic modulus at 30°C tends to decrease. Therefore, the lower limit of T _nax is determined based on spinning and post-processing technology. In addition, the value of _nax , which reflects the amount of components capable of micro-Brownian motion of the main chain in the molecular chain inside the amorphous region (tan〓), exceeds 0.060 and exceeds 0.10.
Must be within the range below. (tan〓) If _{the nax} value is within this range, fatigue resistance is high and 30
It has excellent elastic modulus at °C and high strength. (tan〓)
When _nax is 0.060 or less, fatigue resistance is poor. Moreover, when (tan〓) _nax is 0.10 or more, the strength decreases significantly. A second feature of the nylon fiber obtained by the production method of the present invention is that the average birefringence (Δn ₍₀₎ ) in the central portion of the fiber is 5.8×10 ⁻² or more. The average birefringence strongly depends on the orientation of molecular chains in the crystalline and amorphous portions of the fiber. Δn ₍₀₎ is 5.8
If it is ×10 ^-2 or more, the ratio of elongated chains is high and the degree of orientation of the molecular chains in the fiber axis direction is also high, so the strength, elastic modulus, and fatigue resistance of the fiber are high. Δn ₍₀₎ is 5.8×
When it is less than 10 ^-2 , the ratio of fully extended chains decreases, and the strength and elastic modulus decrease significantly. Thus, it can be said that the nylon 66 fibers with high strength and excellent fatigue resistance obtained by the production method of the present invention have a unique microstructure different from conventionally known fibers. The first feature of the production method of the present invention is a spinning speed of 4000 m/
The point is to use high-speed spun fibers spun at a speed of min or more. Here, "spinning speed" means that in a commonly used spinning device as shown in FIG. This refers to the speed at which the yarn 1 that has passed through is taken up by the take-up roll 7. The basic principle underlying the present invention is to focus on the high-melting-point extended molecular chains contained in the fiber, and to elongate the molecular chains by locally heating and melting the other low-melting-point crystal parts under high tension. In the subsequent rapid cooling treatment, the elongated molecular chains are recrystallized, and at the same time, the amorphous region molecular chains are also immobilized. Therefore, the fibers used need to contain more extended molecular chains. For fibers with a spinning speed of less than 4000m/min,
4000m/
Fibers spun at min or more contain many elongated molecular chains. The higher the spinning speed, the more elongated molecular chains are included. This is why fibers spun at a spinning speed of 4000 m/min are used in the present invention. In addition, it is more preferable to use high-speed spun fibers spun at a spinning speed of 5500 m/min or more. The second feature of the manufacturing method of the present invention is that when the tension applied to the yarn during heat treatment is 0.5 (g/d) or more, the strength T at the time of tensile breakage of the yarn is multiplied by 0.99.
The point is to keep it below 0.99T (g/d). If the strength is less than 0.5 g/d, the molecular chains in the region melted by local heating will not be sufficiently stretched and will be fixed in the subsequent quenching zone, so no significant increase in strength or elastic modulus will occur. . Also, 0.99T
(g/d), yarn breakage occurs frequently during local heating, making processing impossible in many cases, and even if it is not impossible, macroscopic defects are likely to occur. On the contrary, the strength and elastic modulus decrease, and the fatigue resistance is also inferior. A third feature of the manufacturing method according to the invention is that the treatment is carried out in an atmosphere substantially free of oxygen. Since the treatment according to the present invention is carried out at a considerably high temperature as described above, the presence of oxygen in the atmosphere causes oxidative decomposition of the fibers, resulting in a decrease in strength and elastic modulus. Therefore, the heat treatment is performed under an inert gas atmosphere such as nitrogen gas. Furthermore, if the treatment is carried out in a vacuum, it will prevent the oxidative decomposition of the thread and increase the degree of polymerization of the thread.
This is more desirable because it improves the mechanical properties of the yarn. The fourth feature of the manufacturing method according to the present invention is that Tm ₃ +5/9×10 ² υ (where Tm ₃ is measured at a heating rate of 10°C/min as shown in Figure 3) at temperatures exceeding 240°C. Na
The temperature at which the DSC melting curve returns to the baseline G, υ, is the processing speed (mm/min). ) at the point of local heating. Here, "local heating" is an operation in which the fiber is heated in as narrow a region as possible to melt crystal regions other than the extended molecular chains. In order to heat the yarn as evenly as possible and to concentrate stress in the heating zone most efficiently, the length l (mm) in the fiber axis direction of the heating zone that heats the yarn is:
Relational expression consisting of processing speed υ (mm/min), processing temperature θ (°C), and yarn fineness d (denier): 1≦l≦1+
It is necessary to satisfy 4υ+5d/1.5θ. When the yarn is locally heated below 240 °C, the low melting temperature components such as folded chain crystals and other microcrystals are not substantially melted, and therefore the proportion of extended molecular chains does not increase, and the Tension in molecular chains, connecting crystals
This causes an increase in the tension of the tie molecular chains and macroscopic structural defects, resulting in a decrease in the fatigue resistance and strength of the yarn. When the heat treatment temperature exceeds 240℃ and is lower than Tm ₃ +5/9×10 ² υ, rearrangement of crystal components (growth of crystals in the direction of hydrogen bonds) occurs, resulting in the formation of extended chains, including amorphous regions. recrystallization is promoted, the ratio of extended chains increases, and the strength and elastic modulus increase significantly. In particular, heat treatment at temperatures above Tm ₃ and below Tm ₃ +5/9×10 ² υ, which was considered impossible in the past, is described in the fifth feature |300｜℃/
This was achieved for the first time by cooling with a sharp temperature gradient of cm or more, and the increase in the proportion of fully extended chains by heat treatment at this temperature is remarkable. If the heat treatment temperature is Tm ₃ +5/9×10 ² υ or more, the yarn will melt and break so much that the treatment becomes virtually impossible. The fifth feature of the production method according to the present invention is that after local heating, the temperature gradient is cooled to a cooling temperature of -60°C or less with an absolute value of |300|(°C/cm) or more. If there is a temperature gradient of ｜300｜ (°C/cm) or more, the orientation of the molecular chains melted by local heating in the fiber axis direction is immediately fixed (temperatures below Tm ₃ + 5/9×10 ² υ). (This is thought to be the reason why heat treatment can be performed at 30° C.), the degree of orientation increases significantly and the ratio of fully extended chains increases, resulting in an increase in strength and modulus of elasticity. In addition, by cooling to -60℃ or below, the molecular chains in the amorphous region have a low ratio of tie molecular chains, and although the degree of tension is low, they are instantly fixed in a state with a relatively high degree of orientation in the fiber axis direction. As a result, the fiber has high strength, modulus of elasticity, and fatigue resistance. If the temperature gradient is less than |300|(°C/cm), the stress concentration on the molecular chains melted by local heating will be small and the ratio of fully extended chains will not increase. Furthermore, at cooling temperatures higher than -60°C, the immobilization of molecular chains within the instantaneous amorphous region is insufficient.
The resulting yarn has poor strength, modulus and fatigue resistance. The structure and physical property values characterizing the fiber according to the present invention are measured as follows. [Mechanical loss tangent (tan〓) and dynamic modulus of elasticity (E′)] To measure the mechanical loss tangent (tan〓) and dynamic modulus of elasticity (E′), a Leo Vibron manufactured by Toyo Poldwin Co., Ltd. was used. (Rheo-Vibron) DDV-c type is used. Measurement frequency 110Hz, heating rate 10℃/
min, tan〓−temperature (T) characteristic in dry air, E′−
Measure temperature (T) characteristics. From tan〓−T curve
Read tan = peak height (tan =) _nax and tan = peak temperature (T _nax ). Note that the sample must be
Conditioned in an atmosphere of 0% relative humidity for 48 hours or more. [Average birefringence Δn ₍₀₎ ] Ernst Leitz Wetzlar polarizing microscope SM-LUX
- Berek using POL with light at a wavelength of 546 nm
The birefringence Δn ₍₀₎ at the center of the fiber was measured using the Compensator method. [Strong elongation] Manufactured by Toyo Baldwin, Tensilon-UM-
-20 type tensile testing machine, initial length 10cm, tensile speed 10cm/min under conditions of 20℃ 60%RH (relative humidity)
It was measured with [Fatigue resistance test] 48 on nylon 66 filament (840d/260f)
The fabric was twisted and pre-twisted once per 10cm, immersed in a resorcinol-formaldehyde-latex adhesive having the following composition, and then heat-treated at 230°C for 3 minutes. Ingredients by weight Resorcinol 11.0 Water 238.4 Formaldehyde 16.2 Sodium hydroxide 0.3 Styrene-butadiene-vinylpyridine copolymer latex (solid content 41% by weight) 244.0 509.9 The treatment code thus obtained was tested using a Gutdeyer tube fatigue tester. Using JISL-
1017 (tube fatigue strength method A), a tube fatigue test was conducted. EXAMPLES The present invention will be specifically described below with reference to Examples. Nylon 66 with a relative viscosity (UR) of 82 (25°C, concentrated sulfuric acid) was spun at 295°C from a spinneret with a pore diameter of 0.23 mm and 12 holes.
The fibers were melt-spun, cooled, added with an oil agent to give them convergence, and taken off at a take-off speed of 5500 m/min.
This sample was tested under a nitrogen atmosphere with a tension of 0.9T.
(g/d), heat treatment temperature 260, 265, 270
After local heating at (±1℃) for 0.7 seconds, rapid cooling to -196℃ with a temperature gradient of 450℃/cm or more, Example No. 2,
Fibers No. 3 and No. 4 obtained by the manufacturing method according to the present invention were obtained. For these samples, (tan〓) _nax, T _nax,
Δn _(0), storage modulus E′ _{30 at 30℃ and 150℃,}
E′ ₁₅₀ (GPa), fatigue resistance, strength (g/d), and elongation (%) were measured. The results are shown in Table 1. In addition, as a comparative example, untreated yarn (No. 1), 0.9T
(g/d) tension, heat treatment temperature 260℃, temperature gradient
Yarn obtained by cooling at 250℃/cm to a cooling temperature of 10℃ (No.
5), heat treatment temperature 230℃, temperature gradient 290℃/cm,
Thread obtained by cooling to -60℃ (No. 6), commercially available Asahi Kasei nylon 66 tire cord (1260d/210f)
Table 1 shows the numerical values of the structure and physical properties of (No. 7) in comparison with those of Examples.

[Table] * indicates comparative example. As can be seen from Table 1, Example Nos. 2, 3, and 4, which correspond to the fibers obtained by the manufacturing method of the present invention, are high strength and high fatigue resistant nylon 66 fibers. I understand that. In addition, the strength and elongation curves of the fiber (No. 4) obtained by the production method according to the present invention and comparative example products (No. 5) and (No. 6) are shown in FIG.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a comparison of strength and elongation curves of a fiber obtained by the production method according to the present invention (Example Sample No. 3) and a comparative example (Samples No. 5 and No. 6). Figure 2 shows
1 is a schematic diagram of an example of an apparatus for spinning nylon 66 high speed spun fibers used in the method of the present invention. In the figure,
1 is a yarn, 2 is a spinning head, 3 is a tubular heating area, 4
5 is a fluid suction device, 5 is an oil applying device, 6 is a focusing device, and 7 is a take-off roller. Figure 3 shows a typical DSC melting curve of nylon 66 fiber, with Tm ₁ ,
It is an explanatory diagram of Tm ₂ and Tm ₃ . In the figure, G is the baseline.

Claims (1)

[Claims] 1. Nylon spun at a spinning speed of 4000 m/min or more
66 When heat treating fibers, (1) the magnitude of the tension applied to the fiber axis in the fiber axis direction is 0.5 (g/d) or more and 0.99T (g/d)
(However, T is the tensile strength of the fiber at break.) Below, (2) in an atmosphere substantially free of oxygen, (3) at a heat treatment temperature exceeding 240°C, Tm ₃ +
5/9×10 ² υ [However, Tm ₃ is the temperature at which the DSC melting curve returns to the baseline measured at a heating rate of 10°C/min (see Figure 3), υ is the processing speed (mm/min)
It is. ], (4) Length l (mm) in the fiber axis direction is 1≦l≦1+
4υ + 5d/1.5θ (where υ is the processing speed (mm/min), d is the denier of the fiber, and θ is the heat treatment temperature (°C)), and then (5) the temperature gradient is A method for producing high-strength, high-fatigue-resistant nylon 66 fiber, characterized by having an absolute value of |300|(°C/cm) or more and cooling to a cooling temperature of -60°C or less.