KR20230139715A - Method for producing composite fiber - Google Patents

Abstract

The present invention relates to a method for producing composite fibers. The method for producing the composite fiber is a composite fiber in which para-aramid polymer, flexible chain polymer, and polyvinyl alcohol are homogeneously distributed, and some of the polyvinyl alcohol is cross-linked, showing excellent tensile properties, heat resistance, and post-processing properties. can be provided.

Description

Method for producing composite fibers {METHOD FOR PRODUCING COMPOSITE FIBER}

The present invention relates to a method for producing composite fibers.

Aramid is generally an amide-based synthetic polymer in which more than 85% of the amide bonds are directly linked to two aromatic groups, and is well known as an aromatic polyamide.

Aramid is divided into meta-aramid, which has flexible bending, and para-aramid, which has a rigid rod structure, depending on the structural characteristics of the molecular chain. In particular, poly(para-phenylene terephthalamide) fiber, one of the para-aramid fibers, has excellent properties such as high strength, high elasticity, and low shrinkage, and is widely used for industrial and medical purposes. However, the mechanical properties such as strength and elastic modulus of the fiber are not yet sufficient depending on the intended use, so efforts are being made to provide fibers with better physical properties.

As part of these efforts, a technology to improve the strength, dyeability, and heat resistance of the fiber by adding polyvinylpyrrolidone (PVP) to para-aramid fiber has been introduced. However, the optically anisotropic dope containing para-aramid and the PVP polymer solution had poor miscibility with each other, so it was insufficient to realize the effect resulting from the addition of PVP.

The present invention provides a method for producing composite fibers.

Hereinafter, a method for producing composite fibers according to specific embodiments of the invention and composite fibers manufactured therefrom will be described.

According to one embodiment of the invention, preparing a spinning dope containing a para-aramid polymer, a flexible chain polymer, and polyvinyl alcohol; manufacturing fibers by spinning the spinning dope; And a method for producing composite fibers is provided, including the step of crosslinking the fibers.

It is known that the use of polyvinylpyrrolidone (PVP) in the production of para-aramid fiber can improve the strength, dyeability, and heat resistance of the fiber, but optically anisotropic dope and PVP polymer solution containing para-aramid polymer are Due to poor miscibility with each other, it is very difficult to obtain a homogeneous solution, and as a result, there is a problem in that the desired physical properties are not properly realized.

As a result of continuous research by the present inventors to solve this problem, the present inventors have produced fibers by spinning flexible chain polymers such as para-aramid polymer and PVP together with polyvinyl alcohol, and then crosslinked the polyvinyl alcohol. The present invention was completed after confirming through experiments that composite fibers showing superior physical properties compared to composite fibers formed of para-aramid polymer and PVP could be provided.

Hereinafter, the manufacturing method of the composite fiber and the composite fiber manufactured therefrom will be described in detail.

In the manufacturing method according to the above embodiment, spinning dope is first manufactured. The spinning dope includes para-aramid polymer, flexible chain polymer, and polyvinyl alcohol.

The para-aramid polymer can be obtained by polymerizing aromatic diamine and aromatic diecid halide. Alternatively, an appropriate commercial product may be used as the para-aramid polymer.

As a non-limiting example, the aromatic diamine includes p-phenylenediamine, 4,4'-oxydianiline, 2,6-naphthalenediamine, 1,5-naphthalenediamine, and 4,4'-diaminobenzanilide. One or more species selected from the group consisting of may be used.

As a non-limiting example, the aromatic diecid halide includes terephthaloyl dichloride, [1,1'-biphenyl]-4,4'-dicarbonyl dichloride, and 4,4'-oxybis(benzoyl chloride). , naphthalene-2,6-dicarbonyl dichloride, naphthalene-1,5-dicarbonyl dichloride, etc. may be used.

For polymerization of the aromatic diamine and aromatic diecid halide, a polymerization solvent obtained by adding an inorganic salt to an organic solvent may be used.

The organic solvents include N-methyl-2-pyrrolidone (NMP), N,N'-dimethylacetamide (DMAc), hexamethylphosphoramide (HMPA), N,N,N',N'-tetra One or more selected from the group consisting of methyl urea (TMU), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) may be used.

The inorganic salt may be added for the purpose of increasing the degree of polymerization of aromatic polyamide. As the inorganic salt, a halogenated alkali metal salt or a halogenated alkaline earth metal salt may be used. As an example, the inorganic salt may include one or more selected from the group consisting of CaCl ₂ , LiCl, NaCl, KCl, LiBr, and KBr.

As the amount of the inorganic salt added increases, the degree of polymerization of the para-aramid polymer increases. However, if the inorganic salt is added in excess, polymerization may be inhibited due to the presence of inorganic salt that is not dissolved in the organic solvent. Therefore, it is preferable that the inorganic salt is added within 0.01 to 10% by weight based on the total weight of the polymerization solvent.

For polymerization of the aromatic diamine and aromatic diecid halide, a mixed solution can be prepared by dissolving the aromatic diamine in a polymerization solvent. Then, prepolymerization may be performed by adding a predetermined amount of the aromatic diecid halide to the mixed solution while stirring the mixed solution.

The polymerization reaction of the aromatic diamine and the aromatic diecid halide progresses at a rapid rate and generates heat. If the polymerization rate is too fast, the difference in degree of polymerization may increase between the final polymers obtained. Therefore, by pre-forming a polymer having a molecular chain of a predetermined length through the pre-polymerization and then performing the polymerization process, the difference in degree of polymerization between the polymers finally obtained can be minimized.

The prepolymerization may be performed by stirring at a temperature of 0°C to 45°C for 1 minute to 30 minutes or 5 minutes to 15 minutes. Then, the remaining amount of the aromatic diecid halide can be added to the obtained prepolymer solution and further polymerized to prepare a para-aramid polymer. The additional polymerization may be performed by stirring at a temperature of 0°C to 45°C for 5 minutes to 1 hour or 10 minutes to 40 minutes.

Since the aromatic diecid halide reacts with the aromatic diamine at a molar ratio of 1:1, the molar ratio of the aromatic diecid halide to the aromatic diamine may be about 0.9 to 1.1.

The para-aramid polymer may have an intrinsic viscosity of 4.0 dl/g or more, 5.0 dl/g or more, or 6.0 dl/g or more.

In this specification, intrinsic viscosity may be a value measured according to Equation 1 below.

[Equation 1]

IV = ln(η _rel )/C

In Equation 1, ln is a natural logarithmic function, C is the concentration of the polymer solution (e.g., a solution of 0.5 g of polymer dissolved in 100 mL of 95 to 98% by weight concentrated sulfuric acid), and the relative viscosity (η _rel ) is 30°C. is the ratio of the flow time between the polymer solution and the solvent measured with a capillary viscometer.

The para-aramid polymer includes poly(para-phenylene terephthalamide), poly(4,4'-benzanilide terephthalamide), poly(paraphenylene-4,4'-biphenylene-dicarbonyl amide), It may be poly(paraphenylene-2,6-naphthalenedicarbonyl amide) or a copolymer thereof. As an example, the para-aramid polymer may be poly(para-phenylene terephthalamide).

Sulfuric acid having a concentration of 97 to 102% by weight may be used as a solvent for the spinning dope. Instead of sulfuric acid, chlorosulfuric acid or fluorosulfuric acid may be used as the solvent.

The viscosity of the spinning dope for producing fibers increases as the concentration of para-aramid polymer in the spinning dope increases. However, when the concentration of para-aramid polymer exceeds the critical concentration, the viscosity of the spinning dope rapidly decreases. At this time, the radiation dope changes from optically isotropic to optically anisotropic without forming a solid phase. Due to its structural and functional properties, optically anisotropic dope can provide high-strength para-aramid fibers without a separate stretching process. Therefore, it is preferable that the concentration of the para-aramid polymer in the spinning dope exceeds the critical concentration, but if the concentration is too high, the viscosity of the spinning dope may be excessively low. Accordingly, the spinning dope may include a para-aramid polymer in an amount of 10 to 25% by weight based on the total weight of the spinning dope.

The spinning dope includes a flexible chain polymer and polyvinyl alcohol along with the para-aramid polymer. Strictly speaking, the polyvinyl alcohol may be called a flexible chain polymer, but in this specification, 'flexible chain polymer' and 'polyvinyl alcohol' refer to different components, and 'flexible chain polymer' refers to 'polyvinyl alcohol'. means ‘flexible chain polymer excluding alcohol’.

Such flexible chain polymers include polyvinylpyrrolidone-based polymers such as polyvinylpyrrolidone (PVP) or poly(vinylpyrrolidone-vinylacetate) (PVP/VA); Aliphatic polyamide polymers such as 6-nylon, 6,6-nylon, or 6,12-nylon; Polyaniline-based polymers such as substituted or unsubstituted polyaniline; Polyaryl ether ketone polymers such as polyether ketone ketone; and a meta-aramid polymer such as poly(meta-phenylene isophthalamide) (MPD-I) or poly(meta-phenylene isophthalamide/terephthalamide) (MPD-I/T). It may include more. For example, a polyvinylpyrrolidone-based polymer may be used as the flexible chain polymer to provide a composite fiber that exhibits excellent tensile properties and heat resistance.

The weight average molecular weight of the flexible chain polymer can be appropriately adjusted depending on the application field and purpose of the composite fiber. As an example, the weight average molecular weight of the flexible chain polymer may be 10,000 to 100,000 g/mol based on the converted value for standard polystyrene (PS Standard) measured using GPC (gel permeation chromatograph).

The flexible chain polymer may be included in an amount of 1 to 25 parts by weight based on 100 parts by weight of the para-aramid polymer.

Specifically, the flexible chain polymer is present in an amount of at least 1 part by weight, at least 3 parts by weight, at least 5 parts by weight, or at least 7 parts by weight, and at most 25 parts by weight, 22 parts by weight, and 20 parts by weight, based on 100 parts by weight of the para-aramid polymer. It may be included in less than or equal to 18 parts by weight. Within this range, the effect of improving tensile properties and heat resistance due to the flexible chain polymer can be maximized.

The polyvinyl alcohol is a polymer produced by saponifying a polymer obtained by polymerizing vinyl monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl trichloroacetate, vinyl trifluoroacetate, or vinyl pivalate.

The polyvinyl alcohol included in the composite fiber may have a saponification degree of 98 mol% or more or 99 mol% or more. Within this range, the miscibility of the para-aramid polymer and the flexible chain polymer can be improved and sufficient cross-linking can be formed without harming the intrinsic properties of the para-aramid fiber, thereby improving the tensile properties, heat resistance, and post-processing properties of the composite fiber. there is.

Additionally, the polyvinyl alcohol may have a molecular weight of 5,000 to 300,000 or 10,000 to 150,000. Within this range, the viscosity of the spinning dope can be controlled to an appropriate level to provide composite fibers with excellent tensile properties.

The polyvinyl alcohol may be included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the para-aramid polymer.

Specifically, the polyvinyl alcohol is present in an amount of at least 1 part by weight, at least 3 parts by weight, at least 5 parts by weight, or at least 7 parts by weight, and at least 30 parts by weight, 25 parts by weight, and 22 parts by weight, based on 100 parts by weight of the para-aramid polymer. parts or less, 20 parts by weight or less, or 18 parts by weight or less. By forming sufficient crosslinks within this range, the effects of improving tensile properties, heat resistance, and post-processing can be maximized.

In the step of preparing the spinning dope, a spinning dope containing all of a para-aramid polymer, a flexible chain polymer, and polyvinyl alcohol is prepared. Accordingly, para-aramid polymer, flexible chain polymer, and polyvinyl alcohol are all present from the center to the surface of the monofilament formed from the spinning dope. In the present specification, in order to distinguish the fiber according to one embodiment from the sheath-core type fiber in which the components constituting the fiber are not uniformly distributed from the center of the fiber to the surface, the para-aramid polymer constituting the fiber , it was expressed that flexible chain polymer and polyvinyl alcohol were present from the center of the fiber to the surface.

In the step of preparing the spinning dope, the order of mixing the para-aramid polymer, flexible chain polymer, and polyvinyl alcohol is not particularly limited. For example, the spinning dope is prepared by sequentially, randomly or simultaneously adding para-aramid polymer, flexible chain polymer and polyvinyl alcohol to a spinning solvent at 0 to 20° C. and mixing them through a mixer known in the art to which the present invention pertains. Alternatively, it can be prepared by heating to a temperature of 50 to 90 °C.

After the step of producing the spinning dope, a step of producing a fiber by spinning the spinning dope may be performed.

The step of producing the fiber can be performed under conventional conditions using a spinning device of conventional configuration, except for using the spinning dope.

For example, in the spinning step, the spinning dope may be spun in the form of a filament through mechanical wet spinning.

The air-gap wet spinning is a method of leaving an air-gap between the spinneret and the surface of the coagulation bath. According to this wet spinning method, the spinning dope can be spun into a coagulation tank containing a coagulating liquid through an air gap through a spinneret. The air gap may mainly be an air layer or an inert gas layer. The length of the air gap can be adjusted from 0.1 to 15 cm.

The spinneret may be provided with a plurality of capillaries having a diameter of 0.1 mm or less. If the diameter of the capillary tube formed in the spinneret exceeds 0.1 mm, the molecular orientation of the produced filament may deteriorate, resulting in lowered filament strength.

The dope spun through the spinneret is obtained as an unsolidified filament in which sulfuric acid is distributed on a matrix in which para-aramid polymer, flexible chain polymer, and polyvinyl alcohol are homogeneously distributed.

These uncoagulated filaments may be solidified by sequentially passing through an air gap, a coagulation tank containing a coagulating liquid, and a coagulation tube at the bottom of the coagulation tank.

The coagulation tank is located at the lower part of the spinneret and the coagulating liquid is stored therein, and a coagulation tube is formed at the lower part of the coagulation tank. Therefore, the dope that has passed through the capillary tube of the spinneret descends and is solidified while passing through the air gap, coagulation tank, and coagulation tube to form a filament, and this filament is discharged while passing through the coagulation tube.

The dope that has passed through the spinneret forms a filament as the sulfuric acid therein is removed in the process of passing through the coagulating liquid. At this time, if sulfuric acid is rapidly removed from the filament surface, the surface of the filament may solidify before the sulfuric acid contained therein escapes, which may reduce the uniformity of the filament.

Therefore, the coagulating solution may be an aqueous sulfuric acid solution in which sulfuric acid is added to water. More specifically, the coagulating liquid preferably contains 5 to 15% by weight of sulfuric acid. Additionally, the coagulating liquid may optionally contain a monohydric alcohol such as methanol, ethanol, or propanol; Dihydric alcohol (diol) such as ethylene glycol or propylene glycol; Alternatively, trihydric alcohol (triol) such as glycerol may be additionally added.

The temperature of the coagulating liquid may be 1 to 10 °C. If the temperature of the coagulating liquid is too low, it may be difficult for sulfuric acid to escape from the filament. If the temperature of the coagulating liquid is too high, sulfuric acid may rapidly escape from the filament and the uniformity of the filament may deteriorate.

The coagulation tube is connected to the coagulation tank, and a plurality of injection holes may be formed in the coagulation tube. In this case, the injection port is connected to a predetermined jet device, so that the coagulating liquid sprayed from the jet device is sprayed onto the filament passing through the coagulation tube through the injection port. It is preferable that the plurality of injection holes are aligned so that the coagulating liquid is sprayed symmetrically with respect to the filament. The spray angle of the coagulating liquid is preferably 0 to 85° with respect to the axial direction of the filament, and a spray angle of 20 to 40° is particularly suitable for commercial production processes.

In the step of manufacturing the fiber, the coagulation process may be followed by a water washing process to remove sulfuric acid remaining in the coagulated filament. Since sulfuric acid remaining in the coagulated filament may affect the cross-linking reaction of the fiber, the step of manufacturing the fiber preferably includes a water washing process, but if necessary, it may be performed after the step of cross-linking the fiber.

The water washing process may be performed by spraying water or a mixed solution of water and an alkaline solution onto the solidified filament.

The washing process may be performed in multiple steps. For example, the solidified filament may be first washed with a 0.1 to 1.5% by weight aqueous caustic solution, and then washed a second time with a more dilute caustic aqueous solution.

In the step of manufacturing the fiber, following the coagulation and washing processes, a drying process may be performed to control the moisture content remaining in the filament. However, it is not limited to this, and the drying process may be performed after the step of crosslinking the fiber.

The drying process may be performed by controlling the time the filament is in contact with a heated drying roll or by adjusting the temperature of the drying roll.

After producing the fiber, a step of crosslinking the produced fiber may be performed.

The step of cross-linking the fiber may be performed by a dipping method in which the fiber is immersed in the cross-linking agent solution and then taken out, or a spray method in which the cross-linking agent solution is sprayed on the fiber.

The cross-linking agent solution may include a compound having two or more aldehyde groups as a cross-linking agent capable of forming a cross-linking bond with polyvinyl alcohol.

As an example, a compound represented by the following formula (1) may be used as the crosslinking agent.

[Formula 1]

In Formula 1, A ¹ is C _1-30 alkylene substituted or unsubstituted with one or more selected from the group consisting of halogen, hydroxy, C _1-10 alkoxy, and C _6-20 aryl; or C _6-60 arylene substituted or unsubstituted with one or more selected from the group consisting of halogen, hydroxy, C _1-10 alkyl, and C _1-10 alkoxy.

Specifically, the crosslinking agent may be an aliphatic aldehyde compound such as glutaric dialdehyde or an aromatic aldehyde compound such as terephthalaldehyde. Considering the tensile properties of the composite fiber, an aromatic aldehyde compound may be used. You can.

The crosslinking agent may be used in an amount of 0.5 parts by weight or more or 1.0 parts by weight or less and 10 parts by weight or less, 5 parts by weight or less, or 2 parts by weight or less based on 100 parts by weight of the polyvinyl alcohol.

The crosslinking agent solution may include an acid catalyst as a crosslinking reaction catalyst between polyvinyl alcohol and the crosslinking agent. Specific examples of the acid catalyst include acetic acid, propionic acid, butyric acid, trichloroacetic acid, trifluoroacetic acid, or pivalic acid.

Additionally, the cross-linking agent solution may further contain alcohol to promote the cross-linking reaction between polyvinyl alcohol and the cross-linking agent. Specific examples of the alcohol include methanol, ethanol, or propanol.

Water can be used as a solvent for the crosslinking agent solution.

The crosslinking agent solution may include 0.5 to 5% by weight, 0.5 to 3% by weight, or 1.0 to 2.5% by weight of the crosslinking agent based on the total weight. The crosslinking agent solution may include 1 to 30% by weight, 3 to 20% by weight, or 5 to 15% by weight of the acid catalyst based on the total weight. The crosslinking agent solution may contain 1 to 30% by weight, 3 to 20% by weight, or 5 to 15% by weight of alcohol based on the total weight. The cross-linking agent solution includes a cross-linking agent, an acid catalyst, and an alcohol that can be added as needed in the content within the above-mentioned range, and may include a remaining amount of solvent.

In the step of cross-linking the fiber, the cross-linking agent solution is at a temperature higher than room temperature, for example, 30 to 90 ℃, 40 to 80 ℃, or 60 to 75 ℃ so that the cross-linking agent can smoothly penetrate and uniformly distribute within the fiber. can be maintained.

In the step of crosslinking the fiber, the contact time between the fiber and the crosslinking agent solution can be adjusted between 5 minutes to 120 minutes, 30 minutes to 90 minutes, or 40 to 100 minutes so that a sufficient crosslinking reaction can occur between polyvinyl alcohol and the crosslinking agent. there is.

In the step of crosslinking the fiber, a crosslinking reaction occurs between polyvinyl alcohol in the fiber and a compound having two or more aldehyde groups as a crosslinking agent, thereby improving the tensile properties, heat resistance, and post-processing properties of the composite fiber.

For example, in the step of crosslinking the fiber, at least a portion of the polyvinyl alcohol distributed within the fiber may form a crosslink of the form represented by the following formula (2).

[Formula 2]

In Formula 2, A ¹ is C _1-30 alkylene substituted or unsubstituted with one or more selected from the group consisting of halogen, hydroxy, C _1-10 alkoxy, and C _6-20 aryl; or C _6-60 arylene substituted or unsubstituted with one or more selected from the group consisting of halogen, hydroxy, C _1-10 alkyl, and C _1-10 alkoxy.

A ¹ in Formula 2 is the same as A ¹ in the crosslinking agent in Formula 1.

Composite fibers containing such crosslinks can exhibit improved tensile properties, heat resistance, and post-processing properties compared to composite fibers containing existing para-aramid polymers and PVP.

In the step of cross-linking the fiber, after the cross-linking reaction is completed, the cross-linking agent solution remaining in the cross-linked fiber can be washed with water and dried to provide a composite fiber.

The monofilament constituting the finally obtained composite fiber may have a fineness of 1.0 to 2.5 de (denier).

And, the composite fiber includes a plurality of the monofilaments and may have a total fineness of 600 to 10,000 de.

The composite fiber manufactured by the above-described method has para-aramid polymer, flexible chain polymer, and polyvinyl alcohol present from the center to the surface of the composite fiber, and at least a portion of the polyvinyl alcohol is connected through crosslinking. It can be obtained to exhibit excellent tensile properties, heat resistance, and post-processing properties.

For example, the composite fiber may exhibit excellent tensile properties, such as a tensile strength of 25 to 30 g/d, a Young's modulus of 600 to 900 g/d, and an elongation of 2.5 to 4.0%.

In addition, the composite fiber can exhibit excellent heat resistance with a heat aging strength retention rate of 85% or more.

In addition, in the case of existing para-aramid fibers formed by optically anisotropic dope, the surface (skin) part of the fiber with a fast solidification speed has a higher elastic modulus than the center (core) part of the fiber with a slow solidification speed, making para-aramid fibers more attractive. When stress was applied, the stress was concentrated on the surface area. However, since the composite fiber includes a cross-linked structure, even if stress is applied during the fiber processing process, it is possible to prevent fibrillation of the fine fiber or damage such as a kink band. Accordingly, the composite fiber can exhibit excellent post-processing properties.

As an example, the composite fiber has two or less bristles per 300 m, so it can have the advantage of not easily generating hair or cutting even due to friction generated in the manufacturing process of the composite fiber.

The tensile properties, heat aging strength retention rate, and hair number may be measured according to the method described in the test example described later.

In the method for producing composite fibers according to one embodiment of the invention, para-aramid polymer, flexible chain polymer, and polyvinyl alcohol are homogeneously distributed, and some of the polyvinyl alcohol is cross-linked, resulting in excellent tensile properties, heat resistance, and post-processing properties. It is possible to provide a composite fiber that can exhibit .

Hereinafter, the operation and effects of the invention will be described in more detail through specific examples of the invention. However, this is presented as an example of the invention, and the scope of the invention is not limited by this in any way.

Synthesis Example 1: Preparation of para-aramid polymer

A polymerization solvent was prepared by adding CaCl ₂ to N-methyl-2-pyrrolidone (NMP). A mixed solution was prepared by dissolving p-phenylenediamine (PPD) in the polymerization solvent.

While stirring the mixed solution, the same mole of terephthaloyl chloride (TPC) as PPD was added to the mixed solution in two portions to prepare poly(para-phenylene terephthalamide) (PPTA) with an intrinsic viscosity of 6.7. did.

Water and NaOH were added to the solution containing PPTA to neutralize the acid. Next, PPTA was pulverized, and the polymerization solvent contained in PPTA was extracted using water, and then dehydrated and dried to finally obtain PPTA.

Example 1: Preparation of composite fibers

PPTA obtained in Synthesis Example 1, polyvinylpyrrolidone (PVP, weight average molecular weight 40,000 g/mol), and polyvinyl alcohol (PVA) with a saponification degree of 99 mol% and a molecular weight of 50,000 to 85,000 were mixed in 99.8% by weight sulfuric acid. The spinning dope was prepared by dissolving. The PPTA was added at 20% by weight based on the total weight of the spinning dope, PVP was added at 12.0% by weight based on the weight of PPTA, and PVA was added at 12.0% by weight based on the weight of PPTA.

The spinning dope was spun through a spinneret and passed through an air gap into a coagulation tank containing a 10% by weight sulfuric acid aqueous solution at 5°C. Continuously passing through the coagulation tube at the bottom of the coagulation tank, coagulated filaments were obtained.

The solidified filaments were washed with water to remove sulfuric acid remaining on the filaments, then dried and wound.

Meanwhile, an immersion solution was prepared by dissolving 2% by weight of terephthalaldehyde, 10% by weight of acetic acid, and 10% by weight of methanol in water based on the total weight of the immersion solution.

To form cross-links between PVA within the filaments, the wound fibers were soaked in an immersion solution at 70° C. for 1 hour. Afterwards, the soaked fiber was taken out, washed with water, and dried to obtain a composite fiber with a monofilament fineness of 1.5 de and a total fineness of 1,500 de.

Comparative Example 1: Preparation of composite fiber

A spinning dope was prepared by dissolving PPTA and polyvinylpyrrolidone (PVP, weight average molecular weight 40,000 g/mol) obtained in Synthesis Example 1 in 99.8% by weight sulfuric acid. The PPTA was added at 20% by weight based on the total weight of the spinning dope, and PVP was added at 12.0% by weight based on the weight of PPTA.

The spinning dope was spun through a spinneret and passed through an air gap into a coagulation tank containing a 10% by weight sulfuric acid aqueous solution at 5°C. Continuously passing through the coagulation tube at the bottom of the coagulation tank, coagulated filaments were obtained.

The coagulated filaments were washed with water to remove sulfuric acid remaining on the filaments, then dried and wound to obtain composite fibers with a monofilament fineness of 1.5 de and a total fineness of 1,500 de.

Test example: Evaluation of physical properties of composite fibers

The physical properties of the composite fibers obtained in the above examples and comparative examples were measured according to the method described below, and the results are listed in Table 1.

(1) Fineness (denier, de)

Fineness was measured according to ASTM D 1577 as denier (de) expressed as weight (g) of 9000 m yarn.

(2) Tensile properties

For the composite fibers manufactured through Examples and Comparative Examples, ASTM D885 standard test method (sample length 250 mm, stretching speed 25 mm/min, ultra-load fineness Strength, Young's modulus, and elongation were measured according to 1/30 g). The tensile properties were measured after the composite fiber samples were stored for 14 hours at a relative humidity of 55% and a temperature of 23°C.

(3) Heat Aged Strength Retention (HASR)

HASR is a test to measure how much the initial strength of a fiber is maintained after heat aging.

Specifically, the initial strength was measured in the manner described in the tensile properties section above after the composite fiber samples were stored at a relative humidity of 55% and a temperature of 23 °C for 14 hours, heat treated at a temperature of 240 °C for 3 hours, and then reheated. The strength was measured in the manner described above, and the HASR was obtained by substituting the initial strength and the strength measured after heat aging into Equation 2 below.

[Equation 2]

HASR = (Strength after heat aging / Initial strength)

(4) Mow measurement

The number of hairs greater than 2 mm per 300 m of filament was measured while slowly traveling at 100 mpm along the composite fiber using a traveling hair measuring device (Techno-Mac, BT201).

Example 1 Comparative Example 1 Tensile Strength (g/d) 25.5 23.5 Young's modulus (g/d) 730 770 Elongation (%) 3.5 3.1 HASR (%) 93.5 87.5 Mou (Number) 2 4

Referring to Table 1, it was confirmed that the composite fiber according to the above example had superior tensile properties, heat resistance, and post-processing properties compared to the fiber according to Comparative Example 1.

Specifically, preparing a spinning dope containing a para-aramid polymer, a flexible chain polymer, and polyvinyl alcohol; manufacturing fibers by spinning the spinning dope; In the case of the composite fiber formed by the composite fiber manufacturing method of the present application, which includes the step of crosslinking the fiber, the tensile properties (tensile strength, Young's modulus, It was confirmed that the material had excellent elongation), had higher heat aging strength retention rate, had better heat resistance, and improved post-processing properties by preventing the generation of fuzz in the fiber.

Claims (15)

Preparing a spinning dope containing a para-aramid polymer, a flexible chain polymer, and polyvinyl alcohol;
manufacturing fibers by spinning the spinning dope; and
A method for producing composite fibers comprising the step of crosslinking the fibers.
The method of claim 1, wherein the para-aramid polymer is poly(para-phenylene terephthalamide), poly(4,4'-benzanilide terephthalamide), poly(paraphenylene-4,4'-biphenylene- A method for producing a composite fiber, comprising at least one selected from the group consisting of dicarbonyl amide), poly(paraphenylene-2,6-naphthalenedicarbonyl amide), or copolymers thereof.
The method of claim 1, wherein the flexible chain polymer comprises at least one selected from the group consisting of polyvinylpyrrolidone-based polymers, aliphatic polyamide polymers, polyaniline-based polymers, polyaryl ether ketone-based polymers, and meta-aramid polymers. , Method for producing composite fibers.
The method of claim 1, wherein the flexible chain polymer is a polyvinylpyrrolidone-based polymer.
The method of claim 1, wherein the flexible chain polymer has a weight average molecular weight of 10,000 to 100,000 g/mol.
The method of claim 1, wherein the flexible chain polymer is contained in an amount of 1 to 25 parts by weight based on 100 parts by weight of the para-aramid polymer.
The method of producing a composite fiber according to claim 1, wherein the polyvinyl alcohol has a degree of saponification of 98 mol% or more.
The method of claim 1, wherein the polyvinyl alcohol has a molecular weight of 5,000 to 300,000.
The method of claim 1, wherein the polyvinyl alcohol is contained in an amount of 1 to 30 parts by weight based on 100 parts by weight of the para-aramid polymer.
The method of manufacturing a composite fiber according to claim 1, wherein the step of cross-linking the fiber is performed by a dipping method in which the fiber is immersed in a cross-linking agent solution and then taken out, or a spray method in which the cross-linking agent solution is sprayed on the fiber.
The method of claim 10, wherein the cross-linking agent solution contains a compound represented by the following formula (1) as a cross-linking agent:
[Formula 1]

In Formula 1, A ¹ is C _1-30 alkylene substituted or unsubstituted with one or more selected from the group consisting of halogen, hydroxy, C _1-10 alkoxy, and C _6-20 aryl; or C _6-60 arylene substituted or unsubstituted with one or more selected from the group consisting of halogen, hydroxy, C _1-10 alkyl, and C _1-10 alkoxy.
The method of claim 11, wherein the crosslinking agent is used in an amount of 0.5 to 10 parts by weight based on 100 parts by weight of polyvinyl alcohol.
The method of claim 1, wherein the composite fiber has a tensile strength of 25 to 30 g/d, a Young's modulus of 600 to 900 g/d, and an elongation of 2.5 to 4.0%.
The method of producing a composite fiber according to claim 1, wherein the composite fiber has a heat aging strength retention rate of 85% or more.
The method of claim 1, wherein there are no more than 2 hairs per 300 m of the composite fiber.