Aramid original fiber and method for producing the same

Abstract

The present invention relates to an aramid dyed yarn and a manufacturing method thereof. The aramid dyed yarn is manufactured by blending and spinning a mixed solution containing a master batch stock solution containing a pigment and a meta-aramid stock solution obtained by polymerizing m-phenylenediamine (MPD) and isophthaloyl chloride (IPC), and the meta-aramid stock solution. Since the pigment is uniformly dispersed, there is little color shift, and the aramid dyed yarn has excellent light resistance.

Description

Technical Field

[0001] The present invention relates to aramid raw yarns and a method for producing the same, and more specifically, to meta-aramid raw yarns with less color bleeding and excellent light resistance and a method for producing the same.

Background Art

[0002] Generally, polyamide-based synthetic resins are classified into aliphatic polyamides and aromatic polyamides. Aliphatic polyamides are generally known under the trade name "nylon", and aromatic polyamides are well known under the trade name "aramid".

[0003] Among aliphatic polyamides, nylon 6, nylon 6,6, etc. are used as the most common thermoplastic engineering plastic materials and are utilized in various fields such as not only fibers but also various molding materials. Nylon resins used for molding are reinforced with mineral fibers or glass fibers in order to improve flame retardancy, impact resistance, price reduction, and mechanical properties such as elasticity, and are made into reinforced plastics as composite materials.

[0004] Aromatic polyamides, so-called "aramids", developed in the 1960s to improve the heat resistance of nylon, which is an aliphatic polyamide, are well known under trade names such as NOMEX (registered trademark) and KEVLAR (registered trademark). These aromatic polyamide materials have excellent heat resistance and high tensile strength and are used in fiber applications such as flame-retardant fiber fabrics and tire cords.

[0005] General aliphatic polyamides refer to synthetic resins containing aliphatic hydrocarbons bonded between amide groups, while aramids refer to synthetic resins in which benzene rings are bonded between two aromatic rings with 85% amide bonds between the amide groups. The aliphatic hydrocarbons of aliphatic polyamides easily cause molecular motion when heat is applied thereto. In contrast, the benzene rings of aromatic polyamides do not easily cause molecular motion even when heat is applied because the molecular chains are rigid. Therefore, they have thermal stability and high elasticity and exhibit characteristics greatly different from those of general aliphatic polyamides.

[0006] Aromatic polyamides are classified into para - aramids and meta - aramids. A representative example of para - aramids is Kevlar (registered trademark) developed by DuPont. Para - aramids are aramids characterized by the benzene ring being bonded to an amide group at the para - position. Due to their very rigid molecular chains and linear structures, they exhibit very high strength and particularly high elastic modulus. As a result, they have remarkable shock - absorbing ability and can be used in bulletproof vests, bulletproof helmets, safety gloves and boots, and fire - fighting suits. Furthermore, they are also used as materials for sports goods such as tennis rackets, boats, hockey sticks, fishing lines, and golf clubs. Industrially, they are used in fiber - reinforced plastics (FRP) and asbestos - substitute fibers. Representative examples of meta - aramids include Nomex (registered trademark) developed by DuPont and Conex (CONEX) (registered trademark) developed by Teijin. Meta - aramids are characterized by an amide group being bonded to the meta - position of the benzene ring. While having strength and elongation similar to those of ordinary nylon, they have extremely high thermal stability, are lightweight compared to other heat - resistant materials, and can absorb sweat to some extent, thus having the advantages of being refreshing and having a good touch. Initially, the color options were limited, but the latest meta - aramids are available in various colors including fluorescent colors. Meta - aramids are used not only in fire - fighting suits, racing driver uniforms, astronauts' suits, heat - resistant work clothes, but also in industrial applications such as high - temperature filters.

[0007] As one method of using such aramid fibers, there is a method of adding a pigment to a meta - aramid stock solution to produce a raw fiber. However, when producing a raw fiber using a meta - aramid stock solution, the added pigment may reduce the physical properties of the raw fiber. In particular, significant color deviation due to uneven dispersion of the pigment may occur, or the light resistance may decrease.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention was conceived to solve the above problems, and an object of the present invention is to provide an aramid original-dyed yarn in which a pigment added to a high-viscosity meta-aramid polymer is uniformly dispersed and the light resistance is improved, and a method for producing the same.

[0010] The above and other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments.

Means for Solving the Problems

[0011] The above object is achieved by an aramid original-dyed yarn produced by blend spinning a masterbatch stock solution containing a pigment and a meta-aramid stock solution obtained by polymerizing m-phenylenediamine (MPD) and isophthaloyl chloride (IPC); and a meta-aramid stock solution.

[0012] Preferably, the aramid original-dyed yarn may contain 0.01 to 2.5 parts by weight of a pigment based on 100 parts by weight of the meta-aramid fiber.

[0013] Preferably, the aramid original-dyed yarn can have a light resistance of grade 4 to 5 measured after being exposed to a xenon arc light source for 40 hours according to the KS K ISO105-B02 measurement method.

[0014] Preferably, the undegraded residue of the pigment at 350 °C is 95% or more.

[0015] Preferably, the strength of the aramid original-dyed yarn is 3.0 to 5.5 g / d.

[0016] Preferably, the aramid original-dyed yarn can have a single-filament fineness of 0.5 to 5.0 denier.

[0017] Furthermore, the above object is achieved by a method for manufacturing an aramid as-spun yarn, which includes a first step of polymerizing m-phenylenediamine (MPD) and isophthaloyl chloride (IPC) to produce a meta-aramid stock solution, a second step of dispersing and mixing a pigment and the meta-aramid stock solution to produce a masterbatch stock solution, a third step of mixing the meta-aramid stock solution and the masterbatch stock solution to produce a mixed stock solution, and a fourth step of spinning the mixed stock solution to produce an aramid as-spun yarn.

[0018] Preferably, the masterbatch stock solution in the second step can contain 0.1 to 10% by weight of the pigment.

[0019] Preferably, the solution viscosity of the masterbatch stock solution can be 5 to 50 poises at 25°C.

[0020] Preferably, the solution viscosity of the mixed stock solution can be 150 to 300 poises at 100°C and 350 to 650 poises at 80°C.

[0021] Preferably, the dispersed particle diameter of the pigment in the masterbatch stock solution can be less than 5 μm.

[0022] Preferably, the fourth step can be carried out by dry spinning.

Advantages of the Invention

[0023] According to the embodiments of the present invention, the aramid as-spun yarn and its manufacturing method can provide an aramid as-spun yarn with less color shift and excellent light resistance due to uniform pigment dispersion.

[0024] However, the effects of the present invention are not limited to the above effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

Brief Description of the Drawings

[0025]

Figure 1

Embodiments for Carrying Out the Invention

[0026] The present invention will be described in more detail with reference to the accompanying drawings in which exemplary embodiments of the present invention are shown. However, the present invention can be embodied in many different forms and should not be construed as limited to only the embodiments described herein.

[0027] In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Like reference numerals indicate like elements throughout the specification. When an element such as a layer, film, region, or substrate is referred to as being “on” another element, it will be understood that it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly” on another element, intervening elements are absent.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described herein.

[0029] FIG. 1 is a flowchart showing a method for manufacturing an aramid staple fiber according to an embodiment of the present invention.

[0030] Referring to FIG. 1, according to an embodiment of the present invention, a method for manufacturing an aramid original yarn includes a first step S101 of polymerizing m-phenylenediamine (MPD) and isophthaloyl chloride (IPC) to produce a meta-aramid stock solution, a second step S102 of dispersing and mixing a pigment and the meta-aramid stock solution to produce a masterbatch stock solution, a third step S103 of mixing the meta-aramid stock solution and the masterbatch stock solution to produce a mixed stock solution, and a fourth step S104 of spinning the mixed stock solution to produce an aramid original yarn.

[0031] As described above, in the present invention, instead of directly mixing a pigment with the meta-aramid stock solution polymerized in the first step, a masterbatch stock solution is produced by mixing the pigment with another meta-aramid stock solution (second step), and then an aramid original yarn is produced by mixing the masterbatch stock solution with the meta-aramid stock solution polymerized in the first step. If the second step (masterbatch step) is omitted and the pigment is directly dispersed in the meta-aramid polymer, since the viscosity of the meta-aramid polymer is high, dispersion becomes difficult. The physical and equipment requirements necessary to overcome this problem and achieve dispersion are large, requiring more equipment investment than necessary, leading to a decrease in economic feasibility. Therefore, by using a masterbatch stock solution designed to have a low viscosity, in the present invention, the pigment is preliminarily dispersed in the meta-aramid and at the same time the surface of the pigment is wetted with the meta-aramid. Thereby, in the subsequent third step of mixing the masterbatch and the meta-aramid, the maintenance of the dispersion state of the pigment in the masterbatch is strengthened.

[0032] In the first step S101 of polymerizing m-phenylenediamine (MPD) and isophthaloyl chloride (IPC) to produce a meta-aramid stock solution, the meta-aramid is polymerized via MPD and IPC to produce a meta-aramid stock solution.

[0033] The solution viscosity of the meta-aramid stock solution produced in the first step S101 is preferably 150 to 300 poises at 100 °C and 350 to 650 poises at 80 °C. Also, from the perspective of fiber physical properties, the molecular weight preferably ranges from 300,000 to 400,000 in terms of weight average molecular weight. If the weight average molecular weight of the meta-aramid stock solution is 300,000 or less, it will have an adverse effect on the strength and heat resistance of the fiber. On the other hand, if it exceeds 400,000, the spinning process will deteriorate, making it difficult to produce a uniform fiber product.

[0034] Next, in the second step S102 of producing a masterbatch stock solution by dispersing and mixing a pigment and a meta-aramid stock solution, a pigment is dispersed and mixed into the meta-aramid stock solution produced in the first step S101 to produce a masterbatch stock solution. In this case, the masterbatch preferably contains 0.1 to 10% by weight of the pigment. If the pigment content is less than 0.1% by weight, a shielding effect by the meta-aramid will occur in the fibrillation process of the high-viscosity meta-aramid polymer, making it difficult to achieve the desired color expression. As a result, the amount of pigment required to obtain the desired color increases, leading to an increase in manufacturing cost. On the other hand, if the pigment content exceeds 10% by weight, the risk of pigment re-aggregation becomes high, and it is highly likely to become unstable in the fibrillation process. In contrast, in the present invention, color expression is possible with a relatively low pigment content, which can reduce the cost burden and prevent a decrease in physical properties due to the pigment by uniform dispersion of the pigment.

[0035] The solution viscosity of the masterbatch stock solution produced in the second step S102 is preferably 5 to 50 poises at 25 °C. If the solution viscosity of the masterbatch stock solution at 25 °C is less than 5 poises, precipitation due to changes over time may occur after pigment dispersion, which may have an adverse effect on storage stability. On the other hand, if it exceeds 50 poises, a locally non-uniform dispersed phase may occur when producing the mixed stock solution. In this case, it is preferable to control the solution viscosity of the masterbatch stock solution with a polar amide-based solvent.

[0036] The dispersed particle size of the pigment in the masterbatch stock solution is preferably less than 5 μm. If the dispersed particle size of the pigment is 5 μm or more, in the fibrillation process (spinning, post-treatment), the pigment may act as a foreign substance and cause an imbalance in physical stress, which may lead to problems such as spinning defects and yarn breakage during the spinning process.

[0037] The pigment preferably contains at least one selected from organic pigments, inorganic pigments, and fluorescent pigments, and it is more preferable to use an organic pigment with a high melting point to enhance thermal stability.

[0038] Next, in the third step S103 of producing a mixed stock solution by mixing the meta-aramid stock solution and the masterbatch stock solution, the meta-aramid stock solution produced in the first step S101 and the masterbatch stock solution produced in the second step S102 are mixed.

[0039] At this time, it is preferable to mix 1,000 to 4,000 parts by weight of the meta-aramid stock solution with respect to 100 parts by weight of the masterbatch stock solution. If the content of the meta-aramid stock solution is less than 1,000 parts by weight, the viscosity of the mixed stock solution decreases and it becomes impractical for the spinning process. Also, if the content of the meta-aramid stock solution exceeds 4,000 parts by weight, a high-temperature spinning environment is required to ensure spinning, which causes economic inefficiency due to the addition of unnecessary heat sources. This may inhibit the uniformity of the final fiber product, further reduce the concentration of the meta-aramid, and may have an adverse effect on the color expression of the pigment due to the shielding effect of the meta-aramid.

[0040] The solution viscosity of the mixed stock solution is preferably 150 to 300 poises at 100 °C and 350 to 650 poises at 80 °C. If the solution viscosity of the mixed stock solution is less than 150 poises at 100 °C or less than 350 poises at 80 °C, there may occur a problem of poor spinning process that the fiber itself cannot withstand the tension received during the spinning process. On the other hand, if the solution viscosity exceeds 300 poises at 100 °C and 650 poises at 80 °C, it becomes difficult to achieve uniform discharge from the nozzle during the spinning process. By adding a polar amide solvent during the production of the master batch stock solution in the second step S102 and adjusting the mixing ratio of the master batch stock solution and the meta-aramid stock solution in the third step S103, the solution viscosity of the above mixed stock solution is controlled.

[0041] The master batch stock solution obtained by mixing a pigment into the meta-aramid stock solution has a melt viscosity at 25 °C of 5 to 50 poises as described above. Therefore, in the third step S103, through the step of mixing the meta-aramid stock solution and the master batch stock solution, the dispersion degree of the pigment is increased by mixing the relatively high-viscosity meta-aramid stock solution into the relatively low-viscosity master batch stock solution. Generally, the addition of a pigment results in a decrease in the strength of the yarn or fiber to be produced. However, through the above process, the dispersibility of the pigment is improved, so the amount of pigment required for color expression can be reduced, and ultimately, the reduction of the pigment can lead to an improvement in the strength of the fiber.

[0042] Next, in the fourth step S104 of spinning the mixed stock solution to produce an aramid as-spun yarn, the mixed stock solution produced in the third step S103 is spun to produce an aramid as-spun yarn. At this time, it is preferable to use dry spinning as the spinning method.

[0043] According to an embodiment of the present invention, the aramid as-spun yarn produced by the above method is produced by blend spinning a pigment and a meta-aramid obtained by polymerizing MPD and IPC.

[0044] The aramid base yarn produced by the above manufacturing method preferably contains 0.01 to 2.5 parts by weight of a pigment with respect to 100 parts by weight of the meta-aramid fiber. When the content of the pigment is less than 0.01 part by weight with respect to 100 parts by weight of the meta-aramid fiber, a shielding effect by the meta-aramid fiber occurs in the fibrillation process of the high-viscosity meta-aramid fiber, making it difficult to achieve the desired color expression. Furthermore, since the content of the pigment is decreasing, the burden of manufacturing cost for achieving the same color expression may increase. On the other hand, when the content of the pigment exceeds 2.5 parts by weight with respect to 100 parts by weight of the meta-aramid fiber, the risk of re-aggregation of the pigment becomes high, and the fibrillation process of the meta-aramid fiber is likely to become unstable.

[0045] In the aramid base yarn, it is preferable that the undegraded residue of the pigment at a high temperature of 350 °C is 95% or more. This property is related to the heat resistance of the organic pigment itself required for durability under high-temperature conditions in the fibrillation process. If the undegraded residue is less than 95%, it may lead to inconveniences such as variations in the color of the final product due to changes in content and color composition under the high-temperature conditions during the manufacturing process. Furthermore, in dry spinning, the risk of discoloration due to high-temperature spinning conditions and heat treatment conditions during post-processing increases.

[0046] The aramid base yarn preferably has a lightfastness of grade 4 to 5 measured after being exposed to a xenon arc light source for 40 hours according to the KS K ISO105 - B02 measurement method. Thus, the aramid base yarn according to the embodiment of the present invention can achieve high lightfastness by the uniform dispersion of the pigment itself.

[0047] Furthermore, the strength of the aramid dyed yarn is preferably 3.0 to 5.5 g / d. This corresponds to the strength of an aramid yarn (white aramid base yarn) that does not contain organic pigment particles. Generally, the strength of the base yarn decreases due to the addition of the pigment, but in the present invention, by minimizing the use of the pigment for color expression and enabling uniform dispersion of the pigment, it is possible to achieve a strength level that does not cause a physical property degradation comparable to that of an aramid yarn without pigment addition, despite containing organic pigment particles.

[0048] The single fiber fineness of the aramid original yarn is preferably 0.5 to 5.0 denier. Generally, the physical properties of the aramid original yarn are adversely affected by the added pigments, particularly by the pigment content. In the aramid original yarn according to the embodiment of the present invention, by improving the dispersibility of the pigment, even if a pigment for color expression is added, it is possible to make the single fiber fineness 0.5 to 5.0 denier. Since the amount of the pigment varies depending on the desired color, the spinning / post-treatment process may be different, but considering that the main use of the aramid original yarn is for clothing, it can be manufactured with a single fiber fineness of 0.5 to 5.0 denier by post-processing (weaving, knitting).

[0049] Hereinafter, the present invention will be described in more detail with reference to examples. The following examples are provided to further illustrate the present disclosure and are not intended to limit the scope of the present invention.

Examples

[0050] [Example 1] Meta-phenylenediamine (MPD) and isophthaloyl chloride (IPC) were polymerized to produce a meta-aramid stock solution (Arawin, Toray Advanced Materials Korea Inc.).

[0051] Next, 1% by weight of a pigment was mixed into the produced meta-aramid stock solution to produce a masterbatch stock solution. At this time, a dispersion treatment was performed so that the particle size distribution of the pigment in the masterbatch stock solution was less than 5 μm. Also, the solution viscosity of the masterbatch stock solution was 5 poise at 25°C.

[0052] Subsequently, 2,000 parts by weight of the meta-aramid stock solution was mixed with 100 parts by weight of the masterbatch stock solution to produce a mixed stock solution. At this time, the solution viscosity of the mixed stock solution was 150 poise at 100°C and 350 poise at 80°C.

[0053] Next, the produced mixed stock solution was subjected to dry spinning to produce an original yarn.

[0054] [Example 2] The original fiber was produced in the same manner as in Example 1, except that the pigment content for producing the masterbatch stock solution was 5% by weight.

[0055] [Example 3] The original fiber was produced in the same manner as in Example 1, except that the pigment content for producing the masterbatch stock solution was 10% by weight.

[0056] [Example 4] The original fiber was produced in the same manner as in Example 1, except that the pigment content for producing the masterbatch stock solution was 0.1% by weight.

[0057] [Example 5] The original fiber was produced in the same manner as in Example 1, except that the solution viscosity of the masterbatch stock solution was 50 poise at 25°C, and the solution viscosities of the mixed stock solution were 300 poise at 100°C and 650 poise at 80°C.

[0058] [Comparative Example] [Comparative Example 1] The original fiber was produced in the same manner as in Example 1, except that the dispersion treatment was not performed so that the particle size distribution of the pigment was less than 5 μm.

[0059] [Comparative Example 2] The original fiber was produced in the same manner as in Example 1, except that the pigment content for producing the masterbatch stock solution was 0.05% by weight.

[0060] [Comparative Example 3] The original fiber was produced in the same manner as in Example 1, except that the pigment content for producing the masterbatch stock solution was 11% by weight.

[0061] [Comparative Example 4] The original fiber was produced in the same manner as in Example 1, except that the solution viscosity of the masterbatch stock solution was 4 poise at 25°C, and the solution viscosities of the mixed stock solution were 140 poise at 100°C and 340 poise at 80°C.

[0062] [Comparative Example 5] The original fiber was produced in the same manner as in Example 1, except that the solution viscosity of the masterbatch stock solution was 51 poise at 25°C, the solution viscosity of the mixed stock solution was 310 poise at 100°C, and 660 poise at 80°C.

[0063] Using the original fibers produced in Examples 1 to 5 and Comparative Examples 1 to 5, the physical properties were measured according to the following experimental examples, and the results are shown in Tables 1 and 2 below.

[0064] [Experimental Example] (1) Visual observation of the presence or absence of precipitation The produced masterbatch stock solution was placed in a transparent container at a temperature of 25°C, and the interface due to precipitation was visually observed for 30 days. The occurrence of precipitation was recorded as "Yes" in Table 1, and "No" if no precipitation occurred. Intermediate cases were recorded as "Intermediate".

[0065] (2) Measurement of the dispersed particle size Regarding the produced original fiber, the dispersed particle size was measured for 30 days using an analog particle size analyzer (Grind Gauge).

[0066] (3) Measurement of color difference (ΔE) Regarding the produced masterbatch stock solution, using a color difference meter (manufactured by Konica Minolta, cm-3600a), based on the colorimetric method, the color difference for 30 days from the sampling date was measured.

[0067] (4) Measurement of light resistance Regarding the produced aramid original fiber, according to the KS K ISO105-B02 measurement method, the light resistance after exposure to a xenon arc light source for 40 hours was measured.

[0068] (5) Measurement of the single-filament fineness and strength The single-filament fineness and strength of the produced original fiber were measured using a vibroscope device under the conditions of 25°C and 65% RH.

[0069]

Table 1

[0070]

Table 2

[0071] As described above in Table 1 and Table 2, Examples 1 to 5 all satisfied the configuration of the present invention in terms of dispersed particle size, strength, single-filament fineness, and light resistance. Furthermore, in Examples 1 to 4, no precipitation was observed even after 30 days, the dispersed particle size was maintained below 5 μm, and the color difference over time was also small.

[0072] On the other hand, in Comparative Example 1 with a particle size distribution of 5 μm or more, precipitation occurred over time, the dispersion became excessive, and spinning into the aramid base fiber became impossible. In particular, in Comparative Example 1, there was no precipitation initially, but precipitation occurred after 5 days. The dispersed particle size was initially 5 μm or more, but it gradually increased over 30 days, and the color difference could not be measured after 5 days.

[0073] Furthermore, in Comparative Example 2 with insufficient pigment, an increase in the dispersed particle size was observed over time, and spinning into the aramid base fiber was impossible.

[0074] Similarly, in Comparative Example 3 with an excessive amount of pigment, precipitation occurred over time, the dispersed particle size became too large, and spinning into the aramid base fiber was impossible.

[0075] Also, in Comparative Example 4, both the masterbatch stock solution and the mixed stock solution had low viscosities, precipitation occurred over time, the dispersed particle size became too large, and spinning into the aramid base fiber was impossible.

[0076] Similarly, in Comparative Example 5, both the masterbatch stock solution and the mixed stock solution had high viscosities, but precipitation occurred immediately, the dispersed particle size became too large, and spinning into the aramid base fiber became impossible.

[0077] In addition, in all comparative examples except Comparative Example 2, precipitation and coagulation occurred over time, and the measured values became partially non-uniform during color difference measurement, making it impossible to ensure the reliability of the data. As a result, it was confirmed that the color difference could not be measured.

[0078] The present invention has been shown and described with reference to specific exemplary embodiments thereof, but the present invention should not be construed as being limited to the embodiments described herein, and various changes in form and detail may be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims

**Claim 1**: An aramid base yarn containing an organic pigment and a meta-aramid obtained by polymerizing m-phenylenediamine (MPD) and isophthaloyl chloride (IPC), wherein the undegraded residue of the organic pigment at a temperature of 350 °C is 95% or more, and the aramid base yarn has lightfastness of grades 4 to 5 measured after being exposed to a xenon arc light source for 40 hours according to the KS K ISO105-B02 measurement method. **Claim 2** The aramid base yarn according to claim 1, containing 0.01 to 2.5 parts by weight of an organic pigment with respect to 100 parts by weight of the meta-aramid fiber. **Claim 3** The aramid base yarn according to claim 1, wherein the strength of the aramid base yarn is 3.0 to 5.5 g / d. **Claim 4** The aramid base yarn according to claim 1, having a single-filament fineness of 0.5 to 5.0 denier. **Claim 5** A method for manufacturing an aramid base yarn, comprising: a first step of polymerizing m-phenylenediamine (MPD) and isophthaloyl chloride (IPC) to produce a meta-aramid stock solution; a second step of dispersing and mixing an organic pigment and the meta-aramid stock solution to produce a masterbatch stock solution; a third step of mixing the meta-aramid stock solution and the masterbatch stock solution to produce a mixed stock solution; and a fourth step of spinning the mixed stock solution to produce an aramid base yarn, wherein the solution viscosity of the masterbatch stock solution in the second step is 5 to 50 poise at 25 °C, the undegraded residue of the organic pigment at a temperature of 350 °C is 95% or more, and the manufacturing method is such that the aramid base yarn has lightfastness of grades 4 to 5 measured after being exposed to a xenon arc light source for 40 hours according to the KS K ISO105-B02 measurement method. **Claim 6** The method according to claim 5, wherein the masterbatch stock solution in the second step contains 0.1 to 10% by weight of an organic pigment. **Claim 7** The method according to claim 5, wherein the solution viscosity of the mixed stock solution is 150 to 300 poise at 100 °C and 350 to 650 poise at 80 °C. **Claim 8** The method according to claim 5, wherein the dispersion particle size of the organic pigment in the masterbatch stock solution is less than 5 μm. **Claim 9** The method according to claim 5, wherein the fourth step is performed by dry spinning.

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