JP2010106406A - Method for producing aromatic co-polyamide fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple method for producing an aromatic co-polyamide fiber by which even inorganic fine particles such as a high-specific gravity inorganic pigment can uniformly be dispersed in the fiber, with the result that the fiber has excellent mechanical characteristics such as strength without color unevenness. <P>SOLUTION: The aromatic co-polyamide fiber is produced. In the process, a slurry of the inorganic fine particles having ≥2 specific gravity, and dispersed in an amide-based solvent is added and mixed with 100 pts.wt. of an aromatic co-polyamide polymer solution dissolved in the amide-based solvent so as to provide ≤70 pts.wt. of the slurry. The resultant aromatic co-polyamide polymer solution mixed with the inorganic fine particles is further uniformly mixed with the aromatic co-polyamide polymer solution free from the inorganic fine particles. The obtained polymer dope is discharged from a spinneret, and passed through a coagulation step, water washing step, drying step, and hot-drawing step to provide the aromatic co-polyamide fiber. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing an aromatic copolyamide fiber excellent in dispersibility of inorganic fine particles having a high specific gravity and excellent in mechanical properties such as tensile strength.

Conventionally, an aramid fiber (fully aromatic polyamide fiber) mainly composed of an aromatic dicarboxylic acid component and an aromatic diamine component, particularly a para-type wholly aromatic polyamide fiber, has strength, high elastic modulus, high heat resistance, etc. Because of its characteristics, it is widely used in various industrial material applications and protective clothing applications such as fire-fighting clothes and bulletproof / bladeproof materials.
In recent years, in the field of protective clothing such as fire fighting clothes, in addition to the physical properties essential for protecting the life of firefighters such as strength and flame retardancy, design properties with various color variations are also an important factor. In order to add a color other than the original fiber color, there are a method of dyeing the fiber and a method of coloring the raw material at the stage of yarn production. In the case of polyparaphenylene terephthalamide (hereinafter referred to as “PPTA”) fiber, which is known as a typical para-type aramid fiber, an inorganic pigment that inhibits liquid crystallinity because it is produced using a liquid crystalline polymer dope Is difficult to add, so the fibers are colored mainly by dyeing. Various studies have been made so far regarding the dyeing of such PPTA fibers. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2007-16343) has a buckling portion (kink band) and this buckling. There have been reports on fiber structures containing para-type wholly aromatic polyamide fibers dyed partly with cationic or disperse dyes. However, in general, PPTA fiber is difficult to dye due to high chemical resistance, and by giving a higher buckling part physically by preferentially dyeing the buckling part in the fiber as in this publication, Although it dyes well without color unevenness, there is a problem in that mechanical properties such as strength are greatly impaired due to increased fiber defects.

On the other hand, in para-type aromatic copolyamide fibers that are produced using an isotropic polymer dope, addition of an inorganic pigment or the like to the polymer dope has no significant effect on crystallinity. Color the fibers with the following: Various studies have been made so far regarding such an original yarn. For example, in Patent Document 2 (Japanese Patent Application Laid-Open No. 2005-232642), a para type having a specific hue to which titanium oxide fine particles and the like are added. Fully aromatic polyamide fibers have been reported. Although it is possible to obtain a para-type wholly aromatic polyamide fiber having a certain hue by the method as described in this publication, there is no sufficient description regarding the production method, and the dispersibility in the fiber and the color of the fiber are not described. From the viewpoint of unevenness and the like, it is difficult to apply fine particles with high specific gravity, so that there are problems that the types of fine particles used are limited and the color of the resulting fiber is also limited.
In view of such a current situation, development of a simple method for producing an aromatic copolyamide fiber with little reduction in strength, even when various colors are used, and even when a pigment with a high specific gravity is used, has little color unevenness. It is highly desired.
JP 2007-16343 A JP-A-2005-232642

  The present invention has been made against the background of the above-described prior art, and in particular, even an inorganic pigment having a high specific gravity can be uniformly dispersed in a fiber. It aims at providing the simple manufacturing method of the aromatic copolyamide fiber excellent also in the mechanical characteristic.

  In the present invention, first, the sedimentation rate of a general powder in a solvent is expressed, and attention is paid to the Stokes equation shown as Equation 1.

  As shown in this equation, the sedimentation speed of the powder is proportional to the specific gravity difference between the powder and the solvent and inversely proportional to the viscosity of the solvent. When producing an aromatic copolyamide fiber containing fine particles, a slurry is prepared by dispersing fine particles in an amide solvent, which is a good solvent for the aromatic copolyamide polymer, and this is dissolved in an amide solvent. A method of mixing with a group copolyamide polymer solution is common. However, since the specific gravity of amide solvents is mostly around 1, and the viscosity is low, for example, in a slurry in which fine particles with a high specific gravity are dispersed, the surface of the fine particles is temporarily processed to increase the affinity with the solvent. However, the sedimentation of the fine particles easily occurs, and it is difficult to stably store the slurry. In addition, even if sufficient dispersibility of the slurry during storage can be achieved, for example, by sufficient agitation, it can easily settle out during transport until mixed with the aromatic copolyamide polymer solution, so The dispersion of the fine particles in the group copolyamide polymer solution becomes non-uniform, and as a result, the fine particles are segregated in the fiber, resulting in a significant decrease in mechanical properties. In addition, if the fine particles are fine particles intended for deposition, such as a pigment, there is a problem of color unevenness in the fibers. In addition, a method of directly dispersing fine particles in an aromatic copolyamide polymer solution and spinning it can be considered, but in this method as well, there is not only a concern of segregation of fine particles in the polymer solution and the resulting fiber. In order to obtain sufficient dispersibility, stirring for a long time is necessary, and it is difficult to prepare a large amount of polymer solution, which is not preferable from the viewpoint of productivity and work efficiency.

  Therefore, as a result of repeated studies to achieve a high dispersion of fine particles in the polymer solution and fiber more efficiently, first, the fine particle slurry dispersed in the amide solvent is added to the aromatic copolyamide polymer solution and mixed. Then, a polymer solution containing a high concentration of fine particles is prepared, and then a polymer solution containing the fine particles is mixed with a polymer solution not containing the fine particles, so that even inorganic fine particles having a high specific gravity are being stored. It was found that the segregation of fine particles in the polymer solution and fibers can be suppressed, and that an aromatic copolyamide fiber containing fine particles can be obtained efficiently without impairing mechanical properties.

  Thus, in the production of the aromatic copolyamide fiber, the present invention provides an inorganic fine particle slurry having a specific gravity of 2 or more dispersed in the amide solvent with respect to 100 parts by weight of the aromatic copolyamide polymer solution dissolved in the amide solvent. The polymer dope obtained by uniformly mixing the aromatic copolyamide polymer solution mixed with the inorganic fine particles and the aromatic copolyamide polymer solution not containing the inorganic fine particles was added and mixed so as to be less than or equal to parts by weight. It is related with the manufacturing method of the aromatic copolyamide fiber characterized by discharging through a nozzle | cap | die, and passing through a coagulation process, a water washing process, a drying process, and a heat | fever drawing process.

  According to the present invention, even inorganic fine particles having a high specific gravity can be dispersed efficiently and uniformly, and as a result, an aromatic copolyamide fiber with little color unevenness is obtained without impairing mechanical properties. be able to. The obtained aromatic copolyamide is usefully used in various fields such as industrial materials and the field of protective clothing such as fire fighting clothes.

Hereinafter, embodiments of the present invention will be described in detail.
The aromatic copolyamide in the present invention is a polymer in which two or more kinds of divalent aromatic groups are directly linked by an amide bond, and is generally an aromatic dicarboxylic acid in an amide polar solvent according to a known method. Obtained by polycondensation reaction of acid dichloride and aromatic diamine. At this time, the aromatic group may be one in which two aromatic rings are bonded with oxygen, sulfur, or an alkyl group. In addition, these divalent aromatic rings may be unsubstituted or substituted with a lower alkyl group such as a methyl group or a methyl group, or a halogen group such as a methoxy group or a chlorine group. The type and the number of substituents are not particularly limited.

  Examples of the aromatic dicarboxylic acid dichloride in the present invention include terephthalic acid dichloride, 2-chloroterephthalic acid dichloride, 3-methylterephthalic acid dichloride, 4,4′-biphenyldicarboxylic acid dichloride, 2,6-naphthalenedicarboxylic acid dichloride, and isophthalic acid. Acid dichloride and the like can be mentioned, but terephthalic acid dichloride is most preferable from the viewpoints of versatility and mechanical properties of the fiber. One or more of these aromatic dicarboxylic acid dichlorides can be used, and the composition ratio is not particularly limited.

Examples of the aromatic diamine in the present invention include paraphenylene diamine, 3,4'-diaminodiphenyl ether, parabiphenylene diamine, 5-amino-2- (4-aminophenylene) benzimidazole, 1,4-dichloroparaphenylene diamine, Examples include, but are not limited to, metaphenylenediamine, and the aromatic ring may have a substituent or other heterocyclic ring.
In the present invention, two or more of these aromatic diamines are used. The combination is most preferably a combination of paraphenylenediamine and 3,4′-diaminodiphenyl ether from the viewpoints of versatility and mechanical properties of the fiber, and the composition ratio is not particularly limited. 30 to 70 mol% and 70 to 30 mol% are preferred, respectively, more preferably 40 to 60 mol% and 60 to 40 mol%, most preferably 45 to 55 mol% and 55 to 55 mol%, respectively, with respect to the amount of the group diamine. 45 mol%.

  Examples of the amide solvent in the present invention include N-methyl-2-pyrrolidone (hereinafter referred to as “NMP”), N, N-dimethylformamide, N, N-dimethylacetamide, dimethylimidazolidinone and the like. NMP is most preferable from the viewpoints of versatility, harmfulness, handleability, and solubility in aromatic copolyamide polymers.

Examples of the inorganic fine particles in the present invention include fine particles of iron (III) oxide, cobalt blue, titanium oxide, barium sulfate, kaolin, graphite, calcium carbonate, wollastonite, mica, and the specific gravity is 2 or more. The specific gravity is preferably 3 to 10, and the average particle diameter (D50) is 0.05 to 2 μm, preferably 0.1 to 1.5 μm. Moreover, as long as it is an inorganic fine particle which satisfy | fills the above-mentioned specific gravity and average particle diameter (D50), it will not specifically limit to the composition and shape, the presence or absence of surface treatment, etc.
When the specific gravity is less than 2, since there is not much difference in specific gravity with the solvent, the dispersibility of the fine particles is maintained by stirring to some extent in the slurry in which the fine particles are dispersed in the solvent. By injecting this slurry into the polymer dope However, since segregation of the fine particles in the polymer dope is unlikely to occur, a method of dispersing the fine particles in the polymer dope first and mixing the polymer dope and the polymer dope not containing the fine particles as in the present invention. There is little need to take.

  In addition, when the average particle diameter (D50) of the inorganic fine particles is less than 0.05 μm, in order to disperse to such a size, stirring for a long time and / or high shear force is required, and considering productivity This is not preferable because it makes it difficult to prepare an efficient polymer dope. On the other hand, when the average particle diameter (D50) exceeds 2 μm, depending on the fiber diameter of the obtained fiber, when the average particle diameter is 5 to 20 μm, the size of the fine particles with respect to the fiber diameter increases. Since the continuous layer of the polymer in the fiber is inhibited by the fine particles, the portion where the fine particles are present becomes a defect, and the mechanical properties of the fiber are remarkably impaired.

  The average particle size (D50) mentioned here is measured using a laser diffraction type particle size distribution measuring device (device name: SALD-200VER, manufactured by Shimadzu Corporation) by dispersing fine particles in water. D50 is the 50th particle size counted from the smallest particle size when measuring the particle size of 100 samples, and means the average particle size of the measurement sample To do.

The polymer dope in the present invention refers to a polymer solution in which an aromatic copolyamide polymer is dissolved in a solvent that can be dissolved therein. If the solvent used in the polycondensation reaction between the aromatic dicarboxylic acid dichloride and the aromatic diamine is also a good solvent for the aromatic copolyamide polymer, the polymer after the polycondensation reaction is not isolated. It can be used as a polymer dope as it is.
In addition, an inorganic salt can also be used as a dissolution aid for the purpose of increasing the solubility of the polymer in the solvent. Examples of the inorganic salt include, but are not limited to, calcium chloride and lithium chloride. Although the amount of the inorganic salt added to the polymer dope is not particularly limited, it is 3 to 10% by weight based on the polymer dope weight from the viewpoint of the effect of improving the polymer solubility and the solubility of the inorganic salt in the solvent. preferable.

Next, the method of the present invention will be described.
In the present invention, an aromatic copolyamide polymer is first polymerized.
In this polymerization, a known polycondensation reaction is applied, an amide solvent such as NMP is added to the reaction vessel, and aromatic diamines such as paraphenylenediamine and 3,4′-diaminodiphenyl ether are dissolved therein, respectively. An aromatic dicarboxylic acid dichloride such as terephthalic acid dichloride is added to the polycondensation reaction. At this time, the amount of the aromatic diamine to be added is 30 to 70 mol% and 70 to 30 mol%, respectively, of paraphenylenediamine and 3,4'-diaminodiphenyl ether when the total amount of the aromatic diamine is 100 mol%. More preferably, they are 40-60 mol% and 60-40 mol%, respectively, Most preferably, they are 45-55 mol%, 55-45 mol%, respectively. Moreover, the quantity of the aromatic dicarboxylic acid dichloride to add is 95-105 mol% with respect to aromatic diamine. When the aromatic dicarboxylic acid dichloride is less than 95 mol% and exceeds 105 mol%, the reaction with the aromatic diamine does not proceed sufficiently, and a high degree of polymerization cannot be obtained.

  Thereafter, a polycondensation reaction between the aromatic diamine and the aromatic dicarboxylic acid dichloride is performed using a known stirrer. The reaction temperature and reaction time at this time vary greatly depending on the reaction temperature, and can be appropriately adjusted while watching the progress of the polymerization.

After completion of the reaction, hydrochloric acid is generated in the system due to the polycondensation reaction of aromatic diamine and aromatic dicarboxylic acid dichloride, and the system becomes acidic. For the purpose of neutralization, an alkali such as calcium hydroxide is added. . The amount of alkali added varies depending on the type of alkali and the amounts of aromatic diamine and aromatic dicarboxylic acid dichloride, but when calcium hydroxide is used, it is preferably 95 to 100 mol% with respect to the aromatic dicarboxylic acid dichloride. When calcium hydroxide is less than 95 mol%, neutralization cannot be carried out sufficiently, the inside of the system still shows acidity and causes depolymerization, which is not preferable. On the other hand, when it exceeds 100 mol%, the inside of the system shows an alkali, which is also not preferable because it causes depolymerization.
The calcium chloride generated by the neutralization reaction can be used as it is as a solubilizing agent that enhances the dissolution of the produced polymer in the solvent, and therefore does not need to be removed from the system.
The aromatic copolyamide polymer thus obtained is an isotropic polymer dope dissolved in NMP and can be used as it is in the spinning process without isolation. However, at this time, the concentration of the para-type wholly aromatic copolyamide polymer significantly affects the viscosity and stability of the polymer dope, and greatly affects the spinnability and the like in the subsequent spinning process. Therefore, the polymer concentration is preferably 2 to 10% by weight. Therefore, an appropriate amount of N-methyl-2-pyrrolidone can be added to the obtained polymer dope for the purpose of adjusting the polymer concentration and viscosity.

Next, the aromatic copolyamide polymer dope and the inorganic fine particles are mixed. The apparatus used for the mixing is not particularly limited, and any known mixing apparatus such as a planetary mixer, a mixer capable of uniformly dispersing fine particles in a polymer dope such as a kneader or a ruder may be used. The shape, output, and capacity are not particularly limited. Also, the mixing conditions such as output and time can be appropriately adjusted in consideration of the shape, output and capacity of the apparatus.
In order to efficiently disperse the inorganic fine particles in the polymer dope, it is preferable to mix a slurry in which the inorganic fine particles are previously dispersed in the amide solvent used for the polymer dope with the polymer dope. Further, the concentration of the inorganic fine particle slurry at that time is not particularly limited, but is preferably 1% by weight to 20% by weight, and more preferably 2% by weight from the viewpoints of dispersibility and handling of the fine particles in the slurry. % To 15% by weight, more preferably 3% to 10% by weight.

  Furthermore, the amount of the inorganic fine particle slurry mixed with the polymer dope is preferably 70 parts by weight or less, more preferably 5 to 60 parts by weight, and still more preferably 10 to 50 parts by weight with respect to 100 parts by weight of the polymer dope. The addition amount of the inorganic fine particle slurry can be appropriately adjusted within this range in consideration of the fine particle amount in the finally obtained fiber and the fine particle concentration in the inorganic fine particle slurry. When the addition amount of the inorganic fine particle slurry to the polymer dope exceeds 70 parts by weight, the amount of fine particles is too large, and in order to achieve uniform dispersion of the fine particles in the polymer dope, a long time and / or high shear force Is not preferable from the viewpoint of productivity.

  Next, a polymer dope in which inorganic fine particles are uniformly mixed and a polymer dope not containing inorganic fine particles are mixed. Regarding the mixing method, in consideration of workability, fiber productivity, etc., a known static mixer is most preferable, and its shape, type, length, etc. are particularly limited as long as they can be mixed uniformly. is not. In addition, as a method thereof, a pipe for feeding a polymer dope containing inorganic fine particles is joined to a pipe for feeding a polymer dope not containing inorganic fine particles, and various static mixers are provided on the downstream side where the pipes are joined. The method is preferred. The mixing ratio of the polymer dope in which the inorganic fine particles are uniformly mixed and the polymer dope not containing the inorganic fine particles varies depending on the concentration of the inorganic fine particles in the polymer dope in which the inorganic fine particles are uniformly mixed. It is preferable to adjust the amount of inorganic fine particles in the polyamide fiber to 0.1 to 10 parts by weight with respect to 100 parts by weight of the aromatic copolyamide polymer. When the amount of inorganic fine particles in the aromatic copolyamide fiber is less than 0.1 parts by weight with respect to 100 parts by weight of the aromatic copolyamide polymer, the effect of adding the added inorganic fine particles and the effect of adding other inorganic fine particles are It is not preferable because it hardly expresses. On the other hand, if the amount of the inorganic fine particles in the aromatic copolyamide fiber exceeds 10 parts by weight with respect to 100 parts by weight of the aromatic copolyamide polymer, the fiber may be dispersed even if the dispersion of the inorganic fine particles in the fiber is uniform. In particular, the amount of the aromatic copolyamide polymer itself that contributes to the strength is reduced, which makes it difficult to achieve a tensile strength of 18 cN / dtex or more. If the amount of inorganic fine particles in the aromatic copolyamide fiber can be adjusted to be in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the aromatic copolyamide polymer, the mixing ratio is not particularly limited. .

Next, spinning is performed using an aromatic copolyamide polymer dope mixed with inorganic fine particles.
First, the polymer dope is discharged from the spinneret. The hole diameter, nozzle length, number of holes, material, and the like of the spinneret used for discharging are not particularly limited, and can be appropriately adjusted in consideration of the fiber diameter, the number of single yarns, the spinnability, and the like of the obtained fiber. .
The temperature of the polymer dope when passing through the spinneret and the temperature of the spinneret are not particularly limited, but are preferably 80 to 120 ° C. from the viewpoint of spinnability and polymer dope discharge pressure.

  Next, the polymer dope discharged from the spinneret is coagulated in a coagulating liquid. At this time, when the temperatures of the spinneret and the coagulating liquid are greatly different, when the spinneret and the coagulating liquid come into contact with each other, the respective temperatures change and control becomes difficult. The length of the air gap at this time is not particularly limited, but is preferably 5 to 15 mm from the viewpoint of temperature controllability, stringiness, and the like. The coagulating liquid used here is an NMP aqueous solution, and the temperature and NMP concentration are not particularly limited, and are adjusted as appropriate within a range in which there is no problem in the coagulation state of the yarn taken out and the subsequent process passability. be able to.

  Next, the solidified yarn is washed with water. The purpose of this washing step is to remove NMP in the yarn as much as possible using water. The washing conditions are not particularly limited, and the number and temperature of the washing bath can be appropriately adjusted within a range in which NMP in the yarn can be sufficiently removed.

  Next, the washed fiber is dried. The drying conditions at this time are not particularly limited, and there is no problem as long as the moisture adhering to the fibers can be sufficiently removed. However, in consideration of workability and deterioration of the fibers due to heat, the temperature is 150 to 250 ° C. preferable. For drying, a known drying apparatus such as a contact-type drying apparatus such as a roller or a non-contact type drying apparatus in which fibers pass through a drying furnace can be used as it is.

  Next, the dried fiber is hot-drawn. In this step, the object is to highly orient polymer molecules in the fiber and impart strength by hot drawing of the fiber. The heat stretching temperature at this time is preferably 300 to 600 ° C, more preferably 320 ° C to 580 ° C, and most preferably 350 to 550 ° C. When the heat drawing temperature is less than 300 ° C., it is not preferable because the yarn cannot be sufficiently drawn and the strength of the fiber itself is not exhibited. On the other hand, when the temperature exceeds 600 ° C., the polymer is degraded due to thermal decomposition, and a high-strength yarn cannot be obtained. The draw ratio in this hot drawing step is preferably 5 to 15 times, but is not particularly limited to this range as long as sufficient high strength can be achieved. Further, in this heat stretching process, there is no particular problem even if it is performed in multiple stages as necessary.

  Then, if necessary, an oil agent is applied for the purpose of imparting charge suppression or lubricity to the fiber, and finally wound with a winder. There are no particular limitations on the type of oil agent to be applied and the amount to be applied, and the oil agent can be appropriately adjusted depending on the subsequent use. Moreover, about the winding method with a winder, it can wind up, adjusting a winding condition suitably using a well-known winder.

The aromatic copolyamide fiber thus obtained is excellent in dispersibility of the inorganic fine particles in the fiber, and when the inorganic fine particles are pigments, the color unevenness is small and the tensile strength is preferably 18 cN / dtex or more.
The tensile strength of the aromatic copolyamide fiber of the present invention is more preferably 20 to 25 cN / dtex, and is controlled by controlling, for example, the draw ratio and the proportion of inorganic fine particles to be dispersed with respect to the polymer component in the fiber. be able to.

The physical property items used in the examples were measured as follows.
<Average particle diameter of inorganic fine particles (D50)>
The fine particles were dispersed in water, and the particle size of the fine particles was measured using a laser diffraction particle size distribution analyzer (device name: SALD-200VER, manufactured by Shimadzu Corporation). The particle diameter of 100 samples was measured, and the particle diameter corresponding to the 50th particle from the smallest particle diameter was defined as “average particle diameter”.
<Color unevenness of fibers>
The fiber wound around the paper tube with a winder was visually observed, and evaluated according to the following three criteria: ○ / Δ / ×.
○: The number of places where the color is clearly different from others among the fibers wound around the paper tube is 0 to 5
Δ: The number of locations where the color is clearly different from the others among the fibers wound around the paper tube is 6 to 10
X: The number of locations where the color is clearly different from the others among the fibers wound around the paper tube is 11 or more. Table 1 shows the measurement results.

<Tensile strength of fiber>
Using a tensile tester (manufactured by INSTRON Co., Ltd., trade name: INSTRON, model: 5565 type), a tensile test was performed under the following conditions using a yarn test chuck in accordance with ASTM D885.
(Measurement condition)
Temperature: Room temperature Sample length: 75cm
Distance between chucks: 500 mm
Chuck tensile speed: 250 mm / min Initial load: 0.2 cN / dtex

[Example 1]
Nitrogen was fed into a stirring tank having a stirring blade and sufficiently substituted, and then 35 parts by weight of paraphenylenediamine and 65 parts by weight of 3,4'-diaminodiphenyl ether were added. When the total amount of the added aromatic diamine was 100 mol%, the molar ratio of paraphenylene diamine and 3,4′-diaminodiphenyl ether was 50 mol%. Next, 2,500 parts by weight of NMP was added, and the aromatic diamine was completely dissolved while stirring.
After the aromatic diamine was completely dissolved, 130 parts by weight of terephthalic acid dichloride was added to carry out a polycondensation reaction. In addition, the addition amount of a terephthalic-acid dichloride is 100 mol% with respect to aromatic diamine. Moreover, the reaction temperature and reaction time at this time were 80 degreeC and 30 minutes, respectively. By this polycondensation reaction, an aromatic copolyamide polymer was produced, and a polymer dope was obtained. Thereafter, for the purpose of neutralizing the polymer dope, 50 parts by weight of calcium hydroxide was added to the polymer dope to carry out a neutralization reaction, thereby obtaining an isotropic polymer dope used for yarn production. The polymer concentration of the obtained polymer dope was 6% by weight.

Next, 94 parts by weight of NMP and red iron oxide (III) fine particles (manufactured by Toda Kogyo Co., Ltd., product name: Toda Color 130ED, average particle diameter (D50) = 0.4 μm, specific gravity = 5.1) 6 Part by weight was added and stirred with a homogenizer to prepare a slurry having an iron (III) oxide fine particle concentration of 6% by weight.
Next, 30 parts by weight of an iron (III) oxide slurry was added to 70 parts by weight of the polymer dope previously polymerized and mixed for 1.5 hours with a planetary mixer to obtain a polymer dope containing iron (III) oxide fine particles. . In this case, the iron (III) oxide fine particles were 30% by weight with respect to the polymer.
Next, the polymer dope containing the iron (III) oxide fine particles and the polymer dope not containing the fine particles were stored in different tanks, and liquids were fed through the respective pipes. Each pipe is connected at a certain part, and a Kenex type static mixer is arranged at the end, and in the process of passing through it, the polymer dope containing iron (III) oxide fine particles and the polymer dope not containing fine particles are uniform To be mixed. In this case, the amount of each liquid fed was 5 parts by weight for the polymer dope containing the iron (III) oxide fine particles and 95 parts by weight for the polymer dope not containing the fine particles.

Next, a spinneret having a hole diameter of 0.3 mm and a hole number of 1,000 was heated to 105 ° C., and then the polymer dope heated to 105 ° C. was discharged, and the NMP concentration was 30 wt% through an air gap of 10 mm. And passed through a coagulation bath at 50 ° C. to obtain a coagulated yarn.
Subsequently, it washed with 50 degreeC water washing bath.
Next, after drying with a 200 ° C. drying roller, the first stage of thermal stretching was performed at 380 ° C. The draw ratio at this time was 2.4 times. Subsequently, the second stage of thermal stretching was performed at 530 ° C. The draw ratio at this time was 4 times.

  Finally, the fiber was wound around a paper tube with a winder to obtain the fiber. At this time, the fineness of the fibers was 1,670 dtex, the number of fibers was 1,000, and the content of the iron (III) oxide fine particles with respect to the fiber weight was 1.5% by weight. The results of visual color unevenness and tensile strength of the obtained fibers are shown in Table 1.

[Example 2]
An aromatic copolyamide copolymer dope was obtained by the same method as in Example 1. Separately, 10 parts by weight of the same red iron oxide (III) fine particles as in Example 1 were added to 90 parts by weight of NMP, and the mixture was stirred with a homogenizer and oxidized. A slurry having an iron (III) fine particle concentration of 10% by weight was prepared. Next, 11.4 parts by weight of an iron (III) oxide slurry was added to 88.6 parts by weight of the polymer dope and mixed for 1.5 hours with a planetary mixer to obtain a polymer dope containing iron (III) oxide fine particles. . At this time, the iron (III) oxide fine particles were 21.4% by weight based on the polymer.
Next, the polymer dope containing the iron (III) oxide fine particles and the polymer dope not containing the fine particles are stored and fed in the same manner as in Example 1, and the amount of the solution fed includes the iron (III) oxide fine particles. Fibers were obtained in the same manner as in Example 1 except that the polymer dope was 8 parts by weight / minute and the polymer dope not containing fine particles was 5 parts by weight / minute. The content of iron (III) fine particles with respect to the fiber weight at this time was 1.5% by weight. The results of visual color unevenness and tensile strength of the obtained fibers are shown in Table 1.

[Example 3]
An aromatic copolyamide copolymer dope was obtained by the same method as in Example 1, and further a polymer dope containing iron (III) oxide fine particles was obtained by the same method and mixing ratio as in Example 1. Next, a polymer dope containing iron (III) oxide fine particles and a polymer dope containing no fine particles are stored and fed in the same manner as in Example 1, and the amount of liquid fed is a polymer containing iron (III) oxide fine particles. Fibers were obtained in the same manner as in Example 1 except that the dope was 24 parts by weight / minute and the polymer dope not containing fine particles was 76 parts by weight / minute. The content of iron (III) oxide fine particles with respect to the fiber weight at this time was 7.2% by weight. The results of visual color unevenness and tensile strength of the obtained fibers are shown in Table 1.

[Example 4]
Fibers were obtained in the same manner as in Example 1 except that graphite (average particle diameter (D50) = 0.15 μm, specific gravity = 2.2) was used as the inorganic fine particles. The graphite fine particle content relative to the fiber weight at this time was 1.5% by weight. The results of visual color unevenness and tensile strength of the obtained fibers are shown in Table 1.

[Comparative Example 1]
A slurry of an aromatic copolyamide copolymer dope and iron (III) oxide fine particles was prepared in the same manner as in Example 1. The iron (III) oxide particulate slurry was then stored without prior mixing with the polymer dope. During storage, it was stored while suppressing sedimentation of fine particles with a stirrer. Next, a slurry of iron (III) fine particles and a polymer dope were fed in the same manner as in Example 1, and the amount of liquid fed was 1.5 parts by weight of the slurry of iron (III) fine particles / polymer dope. Were obtained in the same manner as in Example 1 except that the amount was 98.5 parts by weight / min. The content of iron (III) fine particles with respect to the fiber weight at this time was 1.5% by weight. The results of visual color unevenness and tensile strength of the obtained fibers are shown in Table 1.

[Comparative Example 2]
In the same manner as in Example 1, an aromatic copolyamide copolymer dope and iron (III) oxide fine particle slurry were prepared. Next, 44.4 parts by weight of iron oxide (III) slurry was added to 55.6 parts by weight of polymer dope, and mixed for 1.5 hours with a planetary mixer to obtain a polymer dope containing iron (III) oxide fine particles. . At this time, iron (III) fine particles were 44.4% by weight based on the polymer. Next, a polymer dope containing iron (III) oxide fine particles and a polymer dope not containing fine particles are stored and fed in the same manner as in Example 1, and the amount of the liquid fed is a polymer containing iron (III) oxide fine particles. Fibers were obtained in the same manner as in Example 1 except that the dope was 3.4 parts by weight / minute and the polymer dope not containing fine particles was 96.6 parts by weight / minute. The content of iron (III) fine particles with respect to the fiber weight at this time was 1.5% by weight. The results of visual color unevenness and tensile strength of the obtained fibers are shown in Table 1.

[Comparative Example 3]
Fibers were obtained in the same manner as in Comparative Example 1 except that graphite (average particle diameter (D50) = 0.15 μm, specific gravity = 2.2) was used as the inorganic fine particles. The graphite fine particle content relative to the fiber weight at this time was 1.5% by weight. The results of visual color unevenness and tensile strength of the obtained fibers are shown in Table 1.

[Comparative Example 4]
An aromatic copolyamide copolymer dope was obtained in the same manner as in Example 1, and the fiber was obtained by spinning it as it was under the same spinning conditions as in Example 1. Table 1 shows the results of tensile strength of the obtained fibers.

  The aromatic copolyamide fiber obtained by the present invention is particularly useful in various industrial material applications that require high strength, high elastic modulus, high heat resistance, etc., and protective clothing applications such as fire fighting clothes and bulletproof / bladeproof materials. .

Claims (6)

  In producing the aromatic copolyamide fiber, the slurry of inorganic fine particles having a specific gravity of 2 or more dispersed in the amide solvent is 70 parts by weight or less with respect to 100 parts by weight of the aromatic copolyamide polymer solution dissolved in the amide solvent. The aromatic copolyamide polymer solution mixed with the inorganic fine particles and the aromatic copolyamide polymer solution containing no inorganic fine particles are uniformly mixed, and the resulting polymer dope is discharged from the die. Then, a method for producing an aromatic copolyamide fiber, which is subjected to a coagulation step, a water washing step, a drying step, and a heat stretching step.   The method for producing an aromatic copolyamide fiber according to claim 1, wherein the inorganic fine particles contain at least iron (III) oxide fine particles.   The method for producing an aromatic copolyamide fiber according to claim 1 or 2, wherein the inorganic fine particles have an average particle diameter (D50) of 0.05 µm to 2 µm.   The method for producing an aromatic copolyamide fiber according to any one of claims 1 to 3, wherein the aromatic copolyamide fiber has a tensile strength of 18 cN / dtex or more.   The production of the aromatic copolyamide fiber according to any one of claims 1 to 4, wherein the inorganic fine particles contained in the aromatic copolyamide fiber are 0.1 to 10 parts by weight with respect to 100 parts by weight of the aromatic copolyamide polymer. Method. The method for producing an aromatic copolyamide fiber according to any one of claims 1 to 5, wherein the aromatic copolyamide is copolyparaphenylene 3,4'-oxydiphenylene terephthalamide.