JPH0115605B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an aromatic copolyamide fiber having high tenacity, high Young's modulus, and excellent abrasion resistance. More specifically, it is an aromatic copolyamide that uses a special aromatic diamine containing an ether bond as a copolymer component, has a specific microstructure, and has high strength, high Young's modulus, and excellent wear resistance. Relating to group copolyamide fibers. Prior Art It has been known that aromatic polyamides (PPTA-based polymers) with paraphenylene groups incorporated into the main chain, such as polyparaphenylene terephthalamide (PPTA), can easily be made into fibers with high strength and high Young's modulus. (See, for example, Japanese Patent Publication No. 47-2489), and attempts have already been made to put it to practical use as tire cords and plastic reinforcing materials. In addition to this PPTA-based polymer, polyamides mainly containing hard rings with para skeleton or parallel axis bonds,
It is also known that molded products with high strength and high Young's modulus can be obtained from polyamide hydrazide, aromatic polyamides containing rigid and linear heterocycles, and polyoxadiazole (for example, Black W, Preston
J.; “High-modulus wholly aromatic fibers”,
(See Marcel Dekker, Inc.). These polymers and PPTA-based polymers (hereinafter referred to as "rigid parallel axis bonded polyamides")
Polyheterocycles (called "polyheterocycles") are difficult to melt mold, and are mainly solution molded. Due to its rigidity, polyamide heterocycles with rigid and parallel axes bond can easily be formed into molded products having high strength and high Young's modulus, but on the other hand, they are difficult to form into stable solutions. When molding from a solution, generally the higher the concentration of the solution, the higher the productivity and the higher the strength. However, for example, PPTA-based polymers are only soluble at high concentrations (approximately 20%) in some mineral acids such as sulfuric acid, but using sulfuric acid, etc. is because the polymerization solvent and molding solvent are different. This not only complicates the process, but also causes significant disadvantages in terms of deterioration of the working environment, corrosion of equipment, disposal of waste liquid, etc. On the other hand, among organic solvents, aprotic polar solvents (N-methyl-2-pyrrolidone, N,
When solubilizing inorganic halogen salts (lithium chloride, calcium chloride, etc.) are added to N′ dimethylacetamide, etc., it is possible to dissolve only a few (weight)% to about 10 (weight)%, and the The performance is inferior to that when molded from a highly concentrated sulfuric acid solution. Therefore, in the molding of PPTA-based polymers, the following two methods are considered to be practical from both the ease of molding and the performance of molded products. (A) Using a highly concentrated sulfuric acid solution, a molded product with high strength, high Young's modulus, and good performance is obtained. -in this case,
Problems arise such as differences in solvents for polymerization and molding, deterioration of the working environment, corrosion of equipment, and disposal of waste liquid. (B) A slightly less well-produced molded article is obtained using a low-concentration organic solvent solution. -This case is superior to (A) above in terms of ease of operation, but under normal conditions only a molded product with low strength can be obtained. Rigid parallel axis bonded polyamide polyheterocycles other than PPTA systems also have the above-mentioned circumstances (A) and (B).
Since the rigid and parallel axis-bonded polyamide/polyheterocycles have a strong molecular cohesive force, it is very difficult to improve the defective structure once generated by heat treatment, stretching, etc. This means that the structure generated during the process of converting from solution to solid (ie, solidification) is a decisive strength controlling factor. In addition, polyamide polyheterocycles bonded with rigid and parallel axes often become optically anisotropic solutions at high concentrations, and this phenomenon is advantageous because it helps the structure to become more dense and highly oriented during the solidification process. However, there are very limited combinations of solution structure and solidification conditions that yield molded products with a strength exceeding 230 Kg/mm ² . At present, an optically anisotropic PPTA solution dissolved in 100% sulfuric acid at 80°C or higher to a concentration of 20% (by weight) is extruded into an air layer of about 0.5 to 1 cm.
After passing through this layer, a method of underflow tension spinning in an aqueous coagulation bath (Japanese Patent Application Laid-open No. 39458/1983) seems to be a practical method. However, this method, which falls within the scope of (A) above, involves the use of sulfuric acid, and it is doubtful whether it will be the most advantageous method industrially in the future. On the other hand, in the method that falls within the range of (B) above, the solution has a low concentration, and it is easy to make a molded product with low orientation and give low strength. Once such a structure is created, it becomes difficult to easily perform structural changes (for example, high-temperature stretching) to increase the strength. For the above-mentioned reasons, various difficulties are encountered in producing molded articles with high strength and high modulus from polyamide polyheterocycles bonded with rigid and parallel axes. On the other hand, a method is known to obtain a high-strength molded product by stretching a soft polymer chain at a high magnification (ultra-stretching) (for example, Cleak et.al., Polymer Eng. Sci. 14
[10] 682-686 (1974)). A flexible polymer chain entropically takes the form of a random coil in a molten or solution state, and tends to form crystals consisting of folded molecular chains during the crystallization process. The formation of folded crystals necessarily reduces the number of molecular chains penetrating the amorphous region, reducing the load-bearing efficiency and therefore the strength. Attempts have also been made to reduce the number of folded molecular chains in molded articles and to produce molded articles having a crystal structure consisting of extremely elongated molecular chains. For example, fibers with improved strength have been obtained by so-called super-stretching, which involves gradual stretching at high temperatures and extremely high stretching ratios. Examples of flexible polymers to which this method is applied include polyethylene, polypropylene, polyoxyethylene, and the like. These polymers are inexpensive and the stretching principle is simple, but the production speed is extremely slow;
Difficult to control operation when stretching near the limit.
Furthermore, since these flexible polymers have low melting points, they also have problems in terms of heat resistance. In recent years, a type of aromatic copolyamide fiber that incorporates a semi-flexible polymer component that is slightly rigid into an essentially rigid polymer component has been developed by ultra-stretching to achieve high strength, high Young's modulus, and heat resistance. A method for producing fibers with excellent properties has been proposed (Japanese Patent Application Laid-open Nos. 76386-1986, 136916-1980, and US Pat. No. 4,075,172). This method does not have the problems mentioned above and is industrially very advantageous in producing fibers with high strength and high Young's modulus. However, it was found that there was a drawback of poor abrasion resistance. OBJECT OF THE INVENTION An object of the present invention is to provide a heat-resistant aromatic copolyamide fiber that does not have the above-mentioned production problems, has high strength, high Young's modulus, and has excellent abrasion resistance. Structure of the Invention The present inventors have conducted research to improve the abrasion resistance of the above-mentioned aromatic copolyamide fibers without impairing their excellent properties such as excellent strength, Young's modulus, and heat resistance. In particular, by controlling the degree of crystallinity, crystal size, and crystal orientation, we succeeded in producing fibers with good wear resistance. That is, the present invention provides 80
At least mol% is composed of an aromatic copolyamide consisting of the following repeating units [] and [], (However, in [] and [] above,
Some or all of the hydrogen atoms of the aromatic residue may be substituted with a halogen atom and/or a lower alkyl group. ) An aromatic compound with high strength, high Young's modulus, and excellent wear resistance, characterized by a crystallinity of 50 to 70%, a crystal size of 18 to 40 Å, and a crystal orientation of 90% or more. It is a polyamide fiber. In the copolymer constituting the aromatic copolyamide fiber of the present invention, the portion that becomes the rigid skeleton is

[expression] and

[Formula], and the semi-flexible skeleton that is almost rigid is

It is a 3,4'-diaminodiphenyl residue represented by the formula, and these are copolymerized randomly or by copolymerizing 2 to 15 blocks of the above repeating units [] and [] each. forming a union. In this polymer, the copolymerization ratio of the repeating units [] and [] is suitably 1/3 to 3/1 in molar ratio []/[]. The degree of polymerization of the copolymer is 1.5 to 1.5 in terms of intrinsic viscosity.
7.0, especially a range of 2.0 to 5.0 is preferred. If necessary, the copolymer may be copolymerized with a small amount of other copolymer components or added with other polymers within a range that does not impair its properties. It may also contain additives such as modifiers. By introducing a 3,4'-diaminodiphenyl ether residue with an asymmetric structure into the main chain, this aromatic copolyamide can be dissolved in aprotic polar solvents and can be dissolved in aqueous coagulation baths. It has the advantage of being able to be stretched at a high magnification at high temperatures after being solidified. Furthermore, there is surprisingly little disturbance in the fiber structure, which is a concern due to the asymmetric structure, and it exhibits higher strength than PPTA, which is a homopolymer. In addition, the crystal structure is thought to be in the form of a collection of many microcrystals, with the crystal size generally becoming smaller due to the introduction of 3,4'-diaminodiphenyl ether residues. Such a reduction in crystal size prevents polarization separation between the crystalline phase and the amorphous phase, thereby improving wear resistance against continuous periodic external forces. However, the advantages mentioned above also depend on the microstructure of the fibers and cannot be obtained simply by using the above-mentioned aromatic copolyamides as polymers. According to the research conducted by the present inventors, the degree of crystallinity, crystal size, and degree of crystal orientation are particularly important for fibers made of the above-mentioned aromatic copolyamide, and when all of these are within a specific range, It was found that fibers with high tenacity, high Young's modulus, and excellent abrasion resistance can be obtained only by using this method. First, the crystallinity needs to be in the range of 50 to 70%, preferably in the range of 60 to 67%. Traditionally, in order to obtain fibers with high tenacity and high Young's modulus, it has been common practice to create a highly crystalline structure, and in the case of the aromatic copolyamide fibers mentioned above, the degree of crystallinity has been reduced as much as possible. Efforts have been made to increase the price. However, when the molecular structure is essentially rigid and a slightly flexible component (3,4'-diaminodiphenyl ether residue) is incorporated into it, as with the aromatic copolyamide mentioned above, , Firstly, increasing molecular orientation is important, and it is not desirable to preferentially increase crystallinity alone; in fact, when the crystallinity exceeds 70%, the abrasion resistance of the fiber tends to decrease. can be seen. In this sense, in the present invention, the upper limit of the degree of crystallinity must be suppressed to 70%, and the degree of crystallinity must be lower than this. On the other hand, if the degree of crystallinity is less than 50%, the strength of the obtained fiber will decrease significantly and it will be difficult to obtain a high-strength fiber. Next, the crystal size needs to be in the range of 18 to 40 Å, preferably in the range of 20 to 30 Å. If the crystal size is less than 18 Å, it will be too microcrystalline and the order of the entire crystal structure will decrease, resulting in a decrease in strength. On the other hand, when the crystal size exceeds 40 Å, the crystalline region becomes enlarged, polarization separation between the crystalline phase and the amorphous phase progresses, resulting in a so-called sea-island structure. Such a structure reduces the microcrystalline network structure and deteriorates wear resistance. Further, the degree of crystal orientation must be 90% or more, preferably 91 to 94%. A crystal orientation degree of less than 90% is unsuitable because the strength decreases. On the other hand, it is practically difficult to obtain a degree of crystal orientation of 95% or more, and it is considered that stretching with a considerably high degree of orientation is required. Method for measuring physical property values The crystallinity, crystal size, and crystal orientation described above are all measured by X-ray diffraction, and the method for measuring (calculating) these physical property values will be explained below. (i) Crystal size (D) An X-ray generator, wide-angle diffractometer, and counting circuit unit manufactured by Rigaku Denki Co., Ltd. are used. The sample is approximately 2.2g/
It is mounted on a 4.5 cm long holder so that the width density is 1 cm, and the stretching direction (machine direction) is perpendicular to the scan axis of the diffractometer. Perform wide-angle X-ray diffraction using Cu-Kα radiation (λ = 1.5418 Å). Most of the fibers of the invention then have substantially one or two overlapping main peaks in the range of 2θ=16 to 25° in the equatorial direction. Substantially one main peak is defined as the peak with the maximum intensity where two peaks are not recognized to overlap, or the depth of the valley between the two peaks even if it is recognized that two peaks overlap. The entire overlapped peak when the height (distance between the line segment connecting the tops of two peaks and the bottom of the valley) is less than 1/10 of the maximum height of the two peaks, or the height of the valley is the height of the two peaks. Refers to the higher of the two peaks when it is less than 1/10 of the maximum height. Two major peaks mean that the height of the valley between the two peaks is 1/10 or more of the maximum height of the two peaks, and the depth of the valley is 1/10 of the maximum height of the two peaks. It refers to the peak when the number is 10 or more. Crystal size (D) is calculated in Å by the following formula: D=0.94λ/(B-b)Cosθ In the above equation, 0.94 is what is called the Scherrer constant, B is the half-width of the measurement peak expressed in radians, and b is the broadening constant of the device (in radians). Yes, and in the case of the above device it is 0.0017rad. The following procedure is used to determine B from an X-ray diffraction chart. If there are two overlapping major peaks on the equator, separate each peak by assuming that each peak is in the shape of a Gaussian curve. Next, a curve obtained by dotting the heights of areas with no peaks obtained from the meridional diffraction curve is adopted as the baseline, and a straight line is drawn parallel to the baseline from the midpoint of the peak apex and the baseline, and the measured peak Find the width of the intersection (half width) in radians, and let this be B. In most of the fibers of the present invention, substantially one main peak is observed, and the value of B can be determined relatively easily. The detailed measurement conditions are as follows. Voltage 50KV Current 80mA Time constant 1 second Sweep speed 2°/min Chart speed 2cm/min Irradiation diameter of sample 2.8mmφ (ii) Degree of orientation (f) Same X-ray generator as used for crystal size measurement described above,
A wide-angle diffractometer and a counting circuit unit will be used, but a mechanical rotating sample stage will be installed to allow measurements in the azimuthal direction. The same applies to the sample density of the sample. The orientation diffraction peak is obtained by rotating in the azimuthal direction while maintaining the 2θ value with the maximum peak on the equator. It is easy to find the baseline, and a straight line parallel to the baseline is drawn from the midpoint of the perpendicular line drawn from the peak to this baseline, and the point of intersection with the shoulder of the peak is determined. If the length (half width) of the line segment formed by this intersection is H (degrees), the degree of crystal orientation (f) is determined by the following formula. f=180−H/180×100 (%) (iii) Crystallinity The apparatus was the same as described above. Sweep the diffractometer in the equator direction while rotating the sample in the vertical plane.
Take the total diffraction curve when the fibers are randomly oriented. Next, the diffraction charts in the meridian direction are superimposed to determine the reflections contributing to the amorphous portion. If the peak due to the crystal part in the meridian direction is excluded, a baseline due to reflection from the amorphous part is obtained. Furthermore, scattering due to air is determined. Calculate the degree of crystallinity X by determining the following C, T, and A in the range of 10°2θ40°. C = Area surrounded by (total diffraction line) and (baseline due to reflection of amorphous part) T = Area surrounded by (total diffraction line) and (zero height line) A = (Air scattering line) and (height Area surrounded by zero line) X=C/(TA)×100(%) The detailed measurement conditions are as follows. Voltage: 40KV Current: 30mA Time constant: 2 seconds Sweep speed: 2°/min Chart speed: 1cm/min Irradiation diameter on sample surface: 3.8mmφ Fiber manufacturing method Next, we will manufacture aromatic copolyamide fibers having the physical properties specified in the present invention. Explain the law. The aromatic copolyamide having the above-mentioned repeating units [] and [] can be produced by a polymerization method known per se, for example, US Pat.
Manufactured by the solution polymerization method described in No. 4075172. This aromatic copolyamide is soluble in aprotic polar solvents such as N,N'-dimethylacetamide and N-methyl-2-pyrrolidone, and in particular, metals from Groups 1 or 2 of the Periodic Table are soluble in the above solvents. It shows good solubility in solutions containing solubilized inorganic halogen salts (for example, lithium chloride, calcium chloride, etc.) consisting of halides, and can be used as a suitable spinning solution. The spinning solution generally has a polymer concentration of 4 to 4.
20 (wt)%, metal halide concentration 0.2-10
(weight)% is preferred. In addition, spinning uses a coagulation bath containing water, an aqueous solution of a polar solvent, or a metal halide therein, and the solution extruded from a spinneret is once extruded into an air layer, and then immediately introduced into the coagulation bath. It is preferable to adopt a method of coagulating it into a fibrous form. (A suitable method for preparing a spinning solution, spinning conditions, etc. are described in detail in U.S. Pat. No. 4,075,172.) The spun aromatic copolyamide fiber (undrawn fiber) is then subjected to drawing. However, in order to form the microstructure specified in the present invention, a stretching method that effectively increases molecular orientation prior to crystallization should be employed. Specifically, undrawn fibers are first drawn 2.0 to 6.0 times at a relatively low temperature of 400°C or lower, and then the remaining amount of drawing is performed at a high temperature exceeding 400°C to bring the total draw ratio to 8 to 15 times, preferably. teeth
It is necessary to employ multi-stage stretching such as 10 to 14 times. Among such multi-stage stretching, undrawn fibers are first stretched 1.1 to 2.0 times at a temperature of 100°C or lower (for example, in a hot water bath of 30 to 100°C), and then stretched at a temperature exceeding 100°C.
Stretched 1.5 to 3.0 times at a temperature not exceeding 400℃, and then 3.0 to 5.0 times at a temperature exceeding 400℃ but not exceeding 550℃.
A sequential stretching method is suitable, in which the film is stretched by 100% to 100%, and the total stretching ratio is 10 to 14 times. On the other hand, if undrawn fibers are drawn at once at a high magnification of about 10 to 14 times in a high temperature region around 500°C, as in the example of the above-mentioned US patent, crystallization will occur quickly due to the high temperature. fiber crystallinity is 70%
As a result, the fibers have a high altitude but poor abrasion resistance. In addition, when performing the above-mentioned multistage stretching, it is preferable to perform the stretching at 100° C. or lower in hot water, and to perform subsequent stretching using a hot plate and/or a superheated steam bath. Since the microstructure of the fibers of the present invention changes greatly depending on the conditions in the drawing process, the above-mentioned multi-stage drawing is adopted, and at the same time, the crystallinity, crystal size, and degree of crystal orientation of the final fibers are adjusted. It is necessary to appropriately adjust the stretching conditions so that all of the stretching conditions fall within the range specified in the present invention. Effects of the Invention The aromatic copolyamide fiber of the present invention having the microstructure as described above not only has high strength and Young's modulus, but also has the advantage of extremely high abrasion resistance. That is, the fiber typically has a tensile strength of 20 g/de or more and a Young's modulus of 500 g/de or more. Furthermore, the abrasion resistance is dramatically improved compared to conventionally known similar fibers, and shows an excellent value of 200 times the abrasion resistance measured by the measurement method described below. Furthermore, the aromatic copolyamide fiber of the present invention is
There are no manufacturing problems like PPTA fibers, and
Can be made with higher strength compared to PPTA fiber. It also has good heat resistance comparable to PPTA fiber. Therefore, the aromatic copolyamide fiber of the present invention can be effectively used in the fields of tire cords, other rubber products, reinforcing materials for resins, belts, lobes, heat-resistant filters, and the like. Examples Next, Examples and Comparative Examples of the present invention will be described in detail. The intrinsic viscosity and abrasion resistance shown in the examples are values measured as follows. (a) Intrinsic viscosity After washing off the solvent, the water-containing polymer was dried at 100℃ under vacuum for 3 hours, and then added to 97.5% concentrated sulfuric acid at 0.5 g/dl.
Measure using a conventional method using a solution containing a concentration of . (b) Abrasion resistance Two 1500 denier yarns are twisted and twisted four times per 10cm each to make a twisted cord. Two of these twisted cords are rubbed against each other in a perpendicular direction. At this time, the tension applied to each twisted yarn cord is
It is 0.2g/dl. Two twisted yarn cords are repeatedly rubbed together and the number of repetitions until one of them breaks is measured. Example 1 The following acid component (1 type) and amine component (2 types)
kinds) , N-methyl-2-pyrrolidone (hereinafter referred to as NMP)
) to obtain an aromatic copolyamide with an intrinsic viscosity of 3.2. Hydrochloric acid produced by the reaction was neutralized with calcium hydroxide, and a spinning solution (dope) was adjusted so that the concentration of the aromatic copolyamide was 6% (by weight). This spinning solution is extruded into an air layer through a spinneret with 1000 spinning holes (the discharge amount during spinning is adjusted so that the final drawn yarn is 1500 dl, and immediately introduced into a 30% (by weight) NMP aqueous solution and coagulated. After washing with water, it was stretched to 1.3 times in a hot water bath at 50°C, and dried under tension to 1.02 times on rollers at 120°C. Next, this dried yarn was subjected to the conditions shown in Table 1-1. 1-stage stretching or 2-stage stretching was performed on a hot plate.The physical properties of the resulting stretching were measured, and the results are shown in Table 1-2.
The results were obtained. Of these experiments, experiment No. 6 was conducted using NMP.
After coagulating in an aqueous solution and washing with water, it is dried in a fixed length without stretching in hot water, and then
It was stretched in one stage on a hot plate at 500°C.
This is a comparative example corresponding to No. 4 (Example).

[Table] Note: Experiments No. 3 to 5 are examples of the present invention, and the others are comparative examples.
In Experiments No. 1 to 2 and No. 4, only one stage of hot plate stretching was performed.

[Table] Note: Experiments No. 3 to 5 are examples of the present invention.
Experiment No. 1 is an experiment in which the degree of crystallinity, crystal size, and degree of crystal orientation are all outside the range specified by the present invention.
In Experiment No. 2, the crystal size and degree of crystal orientation were outside the range specified by the present invention, and both had low strength and poor wear resistance. Experiment No. 6 had an excessive degree of crystallinity and had good strength but poor wear resistance. Example 2 One type of component and two types of amine components were used as in Example 1, but the mixing ratio of the amine components during polymerization was varied within the following range as shown in Table 2-1. (However, the acid component and total amine component were balanced so that A + B = 50 parts below.) The above components were polymerized in NMP in the same manner as in Example 1, and the resulting polymer was spun. Since these polymers have different chemical compositions, they were stretched by the method shown in Table 2-1. Since the polymers of Experiment Nos. 7 and 8 were insoluble in NMP, they were dissolved in 99% concentrated sulfuric acid to prepare a spinning solution (polymer concentration 20% by weight), and the solution was spun into water to coagulate. Since these two examples could not be stretched at high magnification, they were each stretched in one step to 1.05 to 1.10 times on a hot plate at 500°C. In Experiment Nos. 9 to 13, stretching was performed in three stages. That is, first, it was stretched to 1.3 times in hot water at 50°C, then dried at a constant length, and then stretched to 2.0 times on the first hot plate set at 360°C, and the remaining stretching was 500 times.
80% of the stretching ratio at break on the second hot plate set at °C.
A drawn yarn was obtained by drawing at a drawing ratio of . When the physical properties of each drawn yarn thus obtained were measured, the results shown in Table 2-2 were obtained.

【table】

[Table] From the experimental results shown in Examples 1 and 2 above, only those with the polymer composition specified in the present invention and whose fiber crystallinity, crystal size, and crystal orientation are within specific ranges. However, it is clear that it has excellent strength and elongation properties, as well as excellent abrasion resistance.

Claims (1)

[Scope of Claims] 1. 80 mol% or more of the polymer repeating units are the following repeating units [] and [] [However, in [] and [] above,
Some or all of the hydrogen atoms of the aromatic residue may be substituted with a halogen atom and/or a lower alkyl group. ] A solution of an aromatic copolyamide composed of is extruded from a spinneret and coagulated in an aqueous coagulation bath to form an undrawn fiber, and the undrawn fiber is first drawn 1.1 to 2.0 times at a temperature of 100°C or less. Then, it is stretched 1.5 to 3.0 times at a temperature exceeding 100℃ but not exceeding 400℃,
Furthermore, at temperatures exceeding 400℃ but not exceeding 550℃, 3.0~
A method for producing an aromatic copolyamide fiber, which comprises stretching the fiber to 5.0 times and sequentially stretching the fiber at a total stretching ratio of 10 to 14 times.