KR20220094641A - Method for producing para-aramid fibers and para-aramid fibers producted thereform - Google Patents

Abstract

The present invention relates to a method for manufacturing para-aramid fibers, and a para-aramid manufactured thereby. The method for manufacturing para-aramid fibers comprises the steps of: spinning a core dope comprising a sulfonated aramid polymer and a sheath dope comprising a particulate additive in the form of a sheath-core filament; and performing a series of coagulation and washing processes to remove the particulate additive from the spun dope, thereby forming irregularities on the surface of the spun dope. Accordingly, the present invention can provide para-aramid fibers that exhibit improved rubber adhesion while maintaining, at an excellent level, or further improving the intrinsic properties of para-aramid fibers including mechanical properties.

Description

Para-aramid fiber manufacturing method and para-aramid prepared therefrom

The present invention relates to a method for producing para-aramid fibers and to para-aramid produced therefrom.

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

Aramid is classified into meta-aramid with flexible flexibility and para-aramid with rigid rod structure according to the structural characteristics of molecular chains. In particular, a poly(para-phenylene terephthalamide) fiber, which is one of the para-aramid fibers, has excellent mechanical properties, heat resistance, and flame retardancy while having a low density. Para-aramid fibers are mainly applied as reinforcing materials for various base materials such as rubber and resin in industrial fields requiring high performance.

In order to apply para-aramid fibers as reinforcing materials, appropriate pretreatment for para-aramid fibers is required in order to increase compatibility with the base material. For example, para-aramid fibers pretreated with a solution such as epoxy or isocyanate may be applied as a rubber reinforcing material.

However, there is a problem in that the interfacial adhesion with the pretreatment solution decreases due to the structural characteristics of the para-aramid fibers. In order to solve the above problem, a method of introducing a functional group to the surface of the para-aramid fiber through plasma treatment or generating irregularities on the surface of the para-aramid fiber through sand blasting has been attempted.

However, previously tried methods have resulted in a problem of lowering the mechanical strength, which is the strength of para-aramid fibers.

The present invention provides a method for producing para-aramid fibers.

The present invention also provides a para-aramid fiber prepared from the above manufacturing method.

Hereinafter, a method for producing a para-aramid fiber according to a specific embodiment of the present invention and a para-aramid fiber prepared through the manufacturing method will be described.

According to one embodiment of the invention, there is provided a method comprising: preparing a dope for a core comprising an aromatic polyamide polymer in which a functional group including sulfur is bonded to some aromatic nuclei; preparing a dope for a sheath comprising at least one particulate additive selected from the group consisting of water-soluble polymer particles and metal salt particles and an aromatic polyamide polymer; Spinning the dope for the core and the dope for the sheath in the form of a sheath-core filament; coagulating and washing the spun dope to obtain a filament having surface irregularities due to detachment of the particulate additive from the surface of the spun dope; And Para-aramid comprising the step of drying the filament is provided a method for producing an aramid fiber.

On the other hand, according to another embodiment of the invention, a core part comprising an aromatic polyamide polymer in which a functional group containing sulfur is bonded to some aromatic cores; and an aromatic polyamide polymer, and a para-aramid fiber comprising a sheath portion having an uneven surface.

Para-aramid fiber has excellent mechanical properties, heat resistance and flame retardancy while having a low density, so it is useful as a reinforcing material for various base materials such as rubber and resin, but has a disadvantage in that compatibility with the base material is not good.

As a result of continuous research to solve this problem, the present inventors have produced a core dope containing a sulfonated aromatic polyamide polymer and a sheath dope containing a particulate additive and an aromatic polyamide polymer in the form of a sheath-core filament. After solidification and washing with water, particulate additives are removed from the spun dope to form irregularities on the surface, thereby maintaining or further improving the intrinsic properties such as mechanical properties of para-aramid fibers at an excellent level or improving rubber adhesion It was confirmed through an experiment that it is possible to provide para-aramid fibers showing sex and completed the present invention.

Hereinafter, the method for producing the para-aramid fiber and the para-aramid fiber prepared therefrom will be described in detail.

In the method of manufacturing para-aramid fiber according to the embodiment, first dope for core and dope for sheath are prepared.

The dope for the sheath includes an aromatic polyamide polymer and a particulate additive.

The aromatic polyamide polymer may be obtained by polymerizing an aromatic diamine and an aromatic diecide halide. Alternatively, an appropriate commercial product may be used as the aromatic polyamide polymer.

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

As a non-limiting example, the aromatic diecide halide includes terephthaloyl dichloride, [1,1'-biphenyl]-4,4'-dicarbonyl dichloride, 4,4'-oxybis(benzoyl chloride) , at least one selected from the group consisting of naphthalene-2,6-dicarbonyl dichloride and naphthalene-1,5-dicarbonyl dichloride may be used.

A polymerization solvent in which an inorganic salt is added to an organic solvent may be used for polymerization of the aromatic diamine and the aromatic diecide halide.

Examples of the organic solvent include N-methyl-2-pyrrolidone (NMP), N,N'-dimethylacetamide (DMAc), hexamethylphosphoamide (HMPA), N,N,N',N'-tetra At least one 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 the aromatic polyamide. As the inorganic salt, a halogenated alkali metal salt or a halogenated alkaline earth metal salt may be used. For example, the inorganic salt may include at least one 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 aromatic polyamide polymer increases. However, when the inorganic salt is added in excess, an inorganic salt not dissolved in the organic solvent may exist to inhibit polymerization. Therefore, the inorganic salt is preferably added within 0.01 to 10% by weight based on the total weight of the polymerization solvent.

For polymerization of the aromatic diamine and the aromatic diecide halide, a mixed solution may be prepared by dissolving the aromatic diamine in a polymerization solvent. In addition, a predetermined amount of the aromatic diecide halide may be added to the mixed solution while stirring the mixed solution to perform preliminary polymerization.

The polymerization reaction of the aromatic diamine and the aromatic diecide halide proceeds rapidly with exotherm. If the polymerization rate is too fast, the degree of polymerization difference between the finally obtained polymers may become large. Accordingly, by pre-forming a polymer having a molecular chain of a predetermined length through the preliminary polymerization and then performing a polymerization process, a difference in polymerization degree between finally obtained polymers 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 residual amount of the aromatic diecide halide is added to the obtained prepolymer solution and further polymerization is performed to prepare an aromatic polyamide 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 diecide halide reacts with the aromatic diamine in a molar ratio of 1:1, the molar ratio of the aromatic diecide halide to the aromatic diamine may be about 0.9 to 1.1.

The aromatic polyamide polymer included in the dope for cis is poly(para-phenylene terephthalamide), poly(4,4'-benzanilide terephthalamide), poly(paraphenylene-4,4'-biphenylene- dicarbonyl amide), poly(paraphenylene-2,6-naphthalenedicarbonyl amide), or a copolymer thereof. For example, the aromatic polyamide polymer included in the dope for sheath may be poly(para-phenylene terephthalamide).

The particulate additive included in the dope for the sheath is at least one particle selected from the group consisting of water-soluble polymer particles and metal salt particles.

Specifically, the water-soluble polymer particles may be polyvinyl alcohol resin particles.

In addition, the metal salt particles may be one or more particles selected from the group consisting of iron sulfate (Fe ₂ (SO ₄ ) ₃ ) particles and aluminum sulfate (Al ₂ (SO ₄ ) ₃ ).

The particulate additive preferably has an average particle diameter of 0.01 to 1 μm. Specifically, the particulate additive may have an average particle diameter of 0.01 to 1 μm or 0.1 to 1 μm.

If the particle diameter of the particulate additive is too large, the surface unevenness due to the drop-off of the particulate additive in the coagulation and water washing process may deepen, thereby reducing mechanical properties of the filament. However, if the particle diameter of the particulate additive is too small, it is difficult to remove the particulate additive in the coagulation and water washing process, so that the target surface unevenness may not be formed.

The dope for the sheath may be prepared by dissolving the aromatic polyamide polymer in a solvent and then mixing the particulate additive.

As a solvent of the dope for the sheath, 97 to 100% by weight of sulfuric acid may be used. Alternatively, chlorosulfuric acid or fluorosulfuric acid may be used instead of sulfuric acid as the solvent.

As the concentration of the aromatic polyamide polymer in the spinning dope increases, the viscosity of the spinning dope also increases, but beyond 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 the structural and functional properties of the anisotropic spun dope, high-strength para-aramid fibers can be prepared without a separate stretching process. Accordingly, the concentration of the aromatic polyamide polymer in the dope for the sheath preferably exceeds the critical concentration, but if the concentration is too high, the viscosity of the dope for the sheath may become too low. Accordingly, the dope for the sheath may include the aromatic polyamide polymer in an amount of 10 to 25% by weight based on the total weight of the dope for the sheath.

The particulate additive is preferably included in the dope for the sheath in an amount of 0.01 wt % or more based on the weight of the aromatic polyamide polymer so that the effect of forming surface irregularities by the particulate additive can be expressed.

However, when the particulate additive is included in an excessive amount, the spinnability of the dope may be inhibited and mechanical properties of the filament may be deteriorated. Therefore, the particulate additive is preferably included in the dope in an amount of 5.0 wt% or less based on the weight of the aromatic polyamide polymer.

Specifically, the particulate additive is present in an amount of 0.01 to 5.0% by weight, or 0.1 to 3.0% by weight, or 0.1 to 2.0% by weight, or 0.1 to 1.5% by weight, or 0.5 to 1.0% by weight based on the weight of the aromatic polyamide polymer. It may be included in the dope for the sheath as a content.

On the other hand, a functional group containing sulfur is bonded to some aromatic nuclei of the aromatic polyamide polymer included in the dope for the core. Accordingly, the para-aramid fiber prepared according to the method of manufacturing the para-aramid fiber of the embodiment may exhibit improved rubber adhesion and excellent mechanical properties at the same time by including the core part having reinforced mechanical properties.

A functional group including sulfur may be bonded to the aromatic nucleus of the aromatic polyamide polymer included in the dope for the core through a sulfonation reaction.

Accordingly, the aromatic polyamide polymer in which a functional group containing sulfur is bonded to the partial aromatic nucleus may be referred to as a sulfonated aromatic polyamide polymer, and the functional group containing sulfur belongs to which the sulfonated aromatic polyamide polymer belongs. Depending on the environment, it may be a sulfonic acid group or a sulfonate group.

The sulfonated aromatic polyamide polymer contained in the dope for the core may be obtained by sulfonating the aromatic polyamide polymer described as being capable of being contained in the dope for the sheath.

In addition, the aromatic polyamide polymer included in the dope for sheath may also include a sulfonated aromatic polyamide polymer through a sulfonation reaction.

In the step of preparing the dope for the core, the dope for the core may be prepared by sulfonating the aromatic polyamide polymer through a separate process and then dissolving the sulfonated aromatic polyamide polymer in a spinning solvent. The aromatic polyamide polymer may be sulfonated in the process of preparing a dope for a core by employing sulfuric acid as a spinning solvent.

Specifically, after dissolving or dissolving the aromatic polyamide polymer in sulfuric acid, a sulfonation reaction between sulfuric acid and the aromatic polyamide polymer is induced to form an aromatic polyamide polymer in which a functional group containing sulfur is bonded to some aromatic nuclei. . Thereby, a dope for a core comprising a sulfonated aromatic polyamide polymer can be prepared.

The aromatic polyamide polymer may be dissolved in sulfuric acid by a freezing method. For example, after cooling sulfuric acid below its freezing point and blending with the aromatic polyamide polymer to obtain a solid mixture, the solid mixture may be melted to dissolve the aromatic polyamide polymer in sulfuric acid.

The sulfuric acid and the aromatic polyamide polymer may be mixed so that the dope for the core may include the sulfonated aromatic polyamide polymer in an amount of 10 to 25% by weight based on the total weight of the dope for the core.

The concentration of sulfuric acid used in the step of preparing the dope for the core may be 90 to 104.5 wt%. However, when a low concentration of sulfuric acid is used, the sulfonation reaction may not sufficiently occur. In addition, when a high concentration of sulfuric acid is used, there is a risk that all physical properties of the aromatic polyamide polymer exposed to the high concentration of sulfuric acid for a long time may be damaged. For example, when 100.5 to 102.5 wt% of high concentration sulfuric acid is used, the sulfonation reaction of the aromatic polyamide polymer can be induced by treatment at 70 to 80° C. for about 1 to 3 hours, but the aromatic polyamide polymer in high concentration sulfuric acid Physical properties such as intrinsic viscosity and tensile strength of the para-aramid fibers prepared by exposure for a long time may be reduced.

Accordingly, in the step of preparing the dope for the core, a sulfonation reaction may be induced by adding the aromatic polyamide polymer to a low concentration of sulfuric acid and then increasing the concentration of sulfuric acid during melting.

For example, 90 to 99.7 wt%, 95 to 98 wt% or 95 to 97 wt% of sulfuric acid is used as the low concentration of sulfuric acid, and the concentration of sulfuric acid at the time of melting is 99.8 to 104.5 wt%, 100 to 104 wt% , 100.5 to 103 wt%, 100.5 to 102.5 wt%, 99.8 to 103 wt%, 99.8 to 102 wt%, 99.8 to 101 wt%, or 99.8 to 100.7 wt%.

The concentration of the sulfuric acid may be increased by adding a high concentration of sulfuric acid in the melting process. The high concentration of sulfuric acid may be, for example, 99.8 to 104.5 wt% of sulfuric acid as oleum.

The melting temperature of the sulfuric acid and the aromatic polyamide polymer may be controlled within 70 to 95° C. depending on the concentration of sulfuric acid used and the degree of the sulfonation reaction.

For example, in the case of using the low concentration of sulfuric acid and increasing the concentration of sulfuric acid in the melting process, the melting temperature is 70 to 95 ℃, 75 to 95 ℃, 80 to 95 ℃, 85 to 95 ℃ or 85 to 90 ℃. can be adjusted. In the case of the method of using the low concentration of sulfuric acid and increasing the concentration of sulfuric acid in the melting process, even if the melting process is performed at a high temperature, the exposure time of the aromatic polyamide polymer to the high concentration of sulfuric acid is small, so there is little risk of deterioration in intrinsic properties. Accordingly, a sufficient sulfonation reaction can be induced by controlling the melting temperature to a high temperature as in the above-described range.

The melting time of the sulfuric acid and the aromatic polyamide polymer may be adjusted within 0.1 to 50 hours, depending on the concentration of sulfuric acid used and the degree of progress of the sulfonation reaction.

For example, in the case of using the low concentration of sulfuric acid and increasing the concentration of sulfuric acid in the melting process, the melting time is 0.1 to 5 hours, 0.1 to 4 hours, 0.1 to 3 hours, 0.1 to 2 hours, or 0.5 to 2 hours. can be adjusted.

In particular, the high concentration of sulfuric acid is added at a later stage of the melting process (at the end of the melting zone in the case of a continuous process) so that the exposure time of the aromatic polyamide polymer to the high concentration of sulfuric acid is from 0.05 to 2 hours, from 0.05 to 1.5 hours, from 0.05 to It may be adjusted to 1 hour or 0.05 to 0.5 hours.

The aromatic polyamide polymer sulfonated through the step of preparing the dope for the core may contain sulfur in an amount of 0.05 to 0.20 wt%, 0.07 to 0.18 wt%, or 0.09 to 0.16 wt% based on the total weight of the polymer.

Then, spinning the dope for the core and the dope for the sheath in the form of a sheath-core filament through a sheath-core spinning method; and coagulating and washing the spun dope to obtain a filament having surface irregularities due to detachment of the particulate additive from the surface of the spun dope.

The sheath-core spinning method may be performed under conventional conditions using a spinning apparatus having a conventional configuration except for using the dope. As a non-limiting example, the sheath-core spinning method may use the dope for the core and the dope for the sheath to be spun in the form of a sheath-core filament in which the core portion is not exposed, and solidified to obtain a filament.

In the spinning step, the dope for the core and the dope for the sheath may be spun in the form of a sheath-core filament through grit wet spinning.

The air-gap wet spinning involves placing an air-gap between the spinneret and the coagulation bath surface. According to such a wet spinning method, the dope for the core and the dope for the sheath may be spun into the coagulation tank containing the coagulating liquid through the air gap through the spinneret. The air gap may be mainly an air layer or an inert gas layer.

The spinneret may have a plurality of capillaries having a diameter of 0.1 mm or less. When the diameter of the capillary formed in the spinneret exceeds 0.1 mm, the molecular orientation of the produced filament is deteriorated, and as a result, the strength of the filament may be lowered.

Through the spinning step, an unsolidified filament in which the particulate additive and sulfuric acid are distributed on a matrix in which the sulfonated aromatic polyamide polymer and sulfuric acid are distributed in the core part and the aromatic polyamide polymer in the sheath part is obtained.

In the para-aramid fiber, the area ratio of the sheath portion to the core portion (area ratio of the sheath portion/core portion) is adjusted to 0.4/1 to 1.2/1, so that the core portion is not exposed and a stable sheath-core filament may be formed.

The dope spun in the spinning step may be coagulated by passing through the air gap and sequentially passing through the coagulation tank containing the coagulation solution and the coagulation tube under the coagulation tank.

The coagulation tank is located in the lower portion of the spinneret, the coagulation liquid is stored therein, and a coagulation tube is formed in the lower portion of the coagulation tank. Accordingly, the core dope and the sheath dope passing through the capillary tube of the spinneret are solidified while passing through the air gap, the coagulation bath and the coagulation tube to form a sheath-core filament, which is passed through the coagulation tube while being solidified. is emitted

The coagulation solution is water; monohydric alcohols such as methanol, ethanol or propanol; dihydric alcohols such as ethylene glycol or propylene glycol; triols such as glycerol; Or it may be a sulfuric acid solution in which sulfuric acid is added to a mixture thereof. The dope passing through the spinneret forms filaments while the sulfuric acid therein is removed while passing through the coagulating solution. At this time, if the sulfuric acid is rapidly removed from the filament surface, the filament surface may be solidified before the sulfuric acid contained therein goes crazy, and the uniformity of the filament may be deteriorated. Accordingly, the coagulating solution preferably contains 5 to 15% by weight of sulfuric acid. And, the temperature of the coagulating solution is preferably 1 to 10 ℃. If the temperature of the coagulating solution is too low, it may be difficult for the sulfuric acid to escape from the filament. If the temperature of the coagulating solution is too high, sulfuric acid may be rapidly escaped from the filament, thereby reducing the uniformity of the filament.

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 hole is connected to a predetermined jet device (jet device), the coagulation liquid injected from the injection device is injected into the filament passing through the coagulation tube through the injection hole. The plurality of injection holes are preferably arranged so that the coagulating liquid can be symmetrically injected with respect to the filament. The injection angle of the coagulating liquid is preferably 0 to 85° with respect to the axial direction of the filament, and in particular, an injection angle of 20 to 40° is suitable in a commercial production process.

In the coagulation process, at least a portion of the particulate additive present in the sheath portion of the filament may be removed from the surface of the filament.

After the solidification, water washing is performed. The washing with water is a process for removing at least a portion of the sulfuric acid remaining in the solidified filament and the particulate additive present on the surface of the filament. The water washing process may be performed by spraying water or a mixed solution of water and an alkali solution onto the coagulated filament.

The water washing process may be performed in multiple steps. For example, the coagulated filament may be first washed with 0.1 to 1.5% by weight of an aqueous caustic solution, followed by secondary washing with a thinner aqueous caustic solution.

At least a portion of the particulate additive present in the sheath portion of the filament is removed from the surface of the filament during the coagulation and washing process. In addition, the monofilament constituting the para-aramid fiber by the drop-off includes a core part including a sulfonated aromatic polyamide polymer and a sheath part surrounding the core part and having irregularities on the surface.

For example, the surface roughness of the sheath portion may be adjusted to 0.1 μm to 1.0 μm to exhibit excellent rubber adhesion while exhibiting various intrinsic physical properties of para-aramid fibers.

The surface roughness was measured using Atomic Force Microscopy (AFM). Specifically, the para-aramid fiber was fixed well in the V-groove of the substrate having the V-groove, and then the surface roughness was measured using a Nanoscope III a Multimode manufactured by Digital Instruments, UK.

Following the coagulation and washing process, a drying process for controlling the moisture content remaining in the filament is performed.

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

Para-aramid fiber manufacturing method according to the embodiment may further include the step of heat-treating the dried filament after the drying step.

The heat treatment process may be performed at about 250 to 500 °C. In addition, in the heat treatment process, the dried filament may be hot drawn by applying a predetermined tension. For example, in the heat treatment process, the filament may be hot-drawn by applying a tension of about 2000 to 4000 cN to the filament. Through such hot stretching, the mechanical properties of the para-aramid fibers can be further improved.

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

And, the para-aramid fiber according to another embodiment may include a plurality of the monofilaments, and may have a total fineness of 600 to 10,000 de.

The para-aramid fiber prepared by the above-described method may exhibit excellent adhesion performance to various pretreatment solutions or base materials through the surface unevenness while having excellent tensile strength.

A method for producing para-aramid fibers according to an embodiment of the present invention is a series of coagulation and washing after spinning a dope for a core containing a sulfonated aramid polymer and a dope for a sheath containing a particulate additive in the form of a sheath-core filament. Para-aramid fibers exhibiting improved rubber adhesion while maintaining or further improving intrinsic properties such as mechanical properties of para-aramid fibers at an excellent level by removing particulate additives from the spun dope through the process to form irregularities on the surface can provide

Hereinafter, the action and effect 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 in any way by this.

Synthesis Example 1: Preparation of aromatic polyamide 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, terephthaloyl chloride (TPC) of the same mole as PPD was added to the mixed solution in two portions to prepare poly(para-phenylene terephthalamide) (PPTA).

The acid was neutralized by adding water and NaOH to the solution containing PPTA. Then, after pulverizing the PPTA, the polymerization solvent contained in the PPTA was extracted using water, dehydrated and dried to finally obtain PPTA.

Example 1: Preparation of para-aramid fibers

After cooling 99% by weight of sulfuric acid below its freezing point, and mixing the cooled sulfuric acid and PPTA obtained in Synthesis Example 1 in a weight ratio of 80:20 to prepare a solid mixture, it is put into a kneader-mixer capable of melt kneading did

The temperature of the melting zone of the kneader-mixer was controlled to 88 ± 2 °C, and 20 wt% fuming sulfuric acid was added to the end of the melting zone to increase the concentration of sulfuric acid to about 102 wt%. At this time, by controlling the rate at which the solid mixture is fed into the kneader-mixer, the time for the solid mixture to stay in the entire melting region was adjusted to about 100 ± 10 minutes, and the exposure time to fuming sulfuric acid was adjusted to about 20 ± 5 minutes.

A portion of PPTA that passed through the melting region was sampled, and it was confirmed that a functional group containing sulfur was bonded to the aromatic nucleus of the PPTA so that about 0.15 wt% of sulfur was contained based on the total weight of the polymer.

Thereafter, the dope for the core was prepared by mixing the molten mixture passing through the melting region in the kneading region.

Separately, the PPTA obtained in Synthesis Example 1 was dissolved in 97 wt% sulfuric acid at 20 wt% based on the total weight of the cis dope, and 1.0 wt% of iron sulfate particles (Fe ₂ (SO ₄ ) ₃ , based on the weight of PPTA) An average particle diameter of 0.8 μm) was mixed with the solution to prepare a dope for a sheath.

The dope for the sheath and the dope for the core were spun by a sheath-core spinning method, and passed through an air gap through a coagulation bath containing 10 wt% sulfuric acid solution at 5 °C. At this time, the dopes were spun in the form of a sheath-core filament in which the core portion having an area ratio of the sheath portion/core portion of 1/1 was not exposed through a spinneret.

Subsequently, while passing the coagulation tube under the coagulation tank, coagulated filaments (monofilament fineness 1.5 de) were obtained.

The coagulated filaments were washed with water to remove sulfuric acid remaining on the filaments and iron sulfate particles present on the surface of the filaments.

The filaments were dried and then wound to obtain para-aramid fibers having a total fineness of 1,500 de.

Comparative Example 1: Preparation of para-aramid fibers

A dope for a sheath and a dope for a core were prepared by dissolving the PPTA obtained in Synthesis Example 1 in 99% by weight of sulfuric acid in a weight ratio of 80:20.

A para-aramid fiber having a total fineness of 1,500 de was obtained in the same manner as in Example 1, except that the dopes (ie, dope for sheath and dope for core that do not contain iron sulfate particles) were used.

Comparative Example 2: Preparation of para-aramid fibers

Para-aramid fibers having a total fineness of 1,500 de in the same manner as in Comparative Example 1, except that 1.0 wt% of silica particles (average particle diameter 0.8 μm) were added to the sheath dope of Comparative Example 1 based on the weight of PPTA. got it

Test Example: Evaluation of physical properties of para-aramid fibers

The physical properties of the para-aramid fibers obtained in Examples and Comparative Examples were measured according to the method described below, and the results are shown in Table 1.

(1) fineness (denier, de)

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

(2) Tensile strength (g/d)

Para-aramid fibers prepared in Examples and Comparative Examples were cut to a length of 250 mm to prepare a sample, and the sample was stored at a relative humidity of 55% and a temperature of 23° C. for 14 hours.

Then, according to the ASTM D885 standard test method, the sample was mounted on INSTRON's testing machine (Instron Engineering Corp, Canton, Mass), one side of the fiber was fixed, and a superload was applied to 1/30 g of the fineness (fineness X 1/30) g), the other side was tensioned at a rate of 25 mm/min, and the tensile load (g) when the fiber was broken was measured. The strength (g/d) was obtained by dividing the measured tensile load by the fineness.

(3) Rubber adhesion (kgf)

The para-aramid fibers obtained in Examples and Comparative Examples were respectively dipped in an epoxy solution in the same manner and dried to prepare samples. H-Test based on the standard test method of ASTM D 4776-98 was performed on the samples to measure rubber adhesion (kgf).

Example 1 Comparative Example 1 Comparative Example 2 Tensile strength (g/d) 28 24 26 Rubber adhesion (kgf) 20 13 18

Referring to Table 1, it was confirmed that the para-aramid fibers according to the examples exhibited superior tensile strength compared to the fibers according to Comparative Examples 1 and 2 while having improved rubber adhesion.

Claims (17)

Preparing a dope for a core comprising an aromatic polyamide polymer in which a functional group including sulfur is bonded to some aromatic cores;
preparing a dope for a sheath comprising at least one particulate additive selected from the group consisting of water-soluble polymer particles and metal salt particles and an aromatic polyamide polymer;
Spinning the dope for the core and the dope for the sheath in the form of a sheath-core filament;
coagulating and washing the spun dope to obtain a filament having surface irregularities due to detachment of the particulate additive from the surface of the spun dope; and
A method of producing a para-aramid fiber, comprising the step of drying the filament.
The method for producing para-aramid fibers according to claim 1, wherein the aromatic polyamide polymer contained in the dope for sheath is poly(para-phenylene terephthalamide).
The method of claim 1, wherein the water-soluble polymer particles are polyvinyl alcohol resin particles.
The para-aramid fiber according to claim 1, wherein the metal salt particles are at least one particle selected from the group consisting of iron sulfate (Fe ₂ (SO ₄ ) ₃ ) particles and aluminum sulfate (Al ₂ (SO ₄ ) ₃ ). manufacturing method.
The method of claim 1 , wherein the particulate additive has an average particle diameter of 0.01 to 1 μm.
The method according to claim 1, wherein the particulate additive is included in the dope for the sheath in an amount of 0.01 to 5.0% by weight based on the weight of the aromatic polyamide polymer included in the dope for the sheath.
The functional group containing sulfur in some aromatic cores by inducing a sulfonation reaction between sulfuric acid and the aromatic polyamide polymer according to claim 1, wherein, in the step of preparing the dope for the core, after or while dissolving the aromatic polyamide polymer in sulfuric acid A method for producing para-aramid fibers, wherein the aromatic polyamide polymers are bound.
According to claim 1, wherein in the step of preparing the dope for the core, after adding the aromatic polyamide polymer to 90 to 99.7 wt% of sulfuric acid, at a temperature of 70 to 95 °C, the concentration of sulfuric acid is increased to 99.8 to 104.5 wt% A method for producing a para-aramid fiber, wherein the aromatic polyamide polymer is bonded to an aromatic nucleus with a functional group containing sulfur.
According to claim 8, wherein in the step of preparing the dope for the core, the aromatic polyamide polymer stays at a temperature of 70 to 95 °C for 0.1 to 5 hours, para-aramid fiber production method.
The method for producing para-aramid fibers according to claim 8, wherein the exposure time of the aromatic polyamide polymer to 99.8 to 104.5 wt% of sulfuric acid in the step of preparing the dope for the core is 0.05 to 2 hours.
The method of claim 1, wherein the aromatic polyamide polymer to which a functional group containing sulfur is bonded to the partial aromatic nucleus contains 0.05 to 0.20 wt% of sulfur based on the total weight of the polymer.
a core part comprising an aromatic polyamide polymer in which a functional group including sulfur is bonded to some aromatic cores; and
A para-aramid fiber comprising an aromatic polyamide polymer and comprising a sheath portion having an uneven surface.
The para-aramid fiber according to claim 12, wherein the aromatic polyamide polymer to which a functional group containing sulfur is bonded to some aromatic nuclei contains 0.05 to 0.20 wt% of sulfur based on the total weight of the polymer.
The para-aramid fiber according to claim 12, wherein the area ratio of the sheath part/core part is 0.4/1 to 1.2/1.
The para-aramid fiber according to claim 12, wherein the sheath portion has a surface roughness of 0.1 μm to 1.0 μm.
The para-aramid fiber according to claim 12, wherein the monofilament constituting the para-aramid fiber has a fineness of 1.0 to 2.5 de.
13. The para-aramid fiber of claim 12, wherein the para-aramid fiber comprises a plurality of monofilaments and has a total fineness of 600 to 10,000 de.