KR102166023B1 - P-aramid fiber having excellent fatigue resistance and manufacturing method of the same - Google Patents

Abstract

The present invention is para-aramid; And it is made of a mixture containing 3 to 20% by weight of polyvinylpyrrolidone (PVP) based on the total weight of the para-aramid, it relates to a para-aramid fiber excellent in fatigue resistance of 95% or more.

Description

Para-aramid fiber with excellent fatigue resistance and its manufacturing method {P-ARAMID FIBER HAVING EXCELLENT FATIGUE RESISTANCE AND MANUFACTURING METHOD OF THE SAME}

The present invention relates to a para-aramid fiber composed of a mixture of para-aramid and polyvinylpyrrolidone, and to a method for producing the same.

Para-aramid fibers are used as various industrial materials because they show superior strength and modulus of elasticity than polyamide, polyester, and polyacrylonitrile fibers, which are general-purpose fibers, and are very excellent in heat resistance and chemical resistance.

In addition, in recent years, it has been widely used in optical cables, concrete reinforcing materials, rubber/plastic reinforcing materials, and aerospace/aviation fields, and has been researched and developed as a material with high applicability to new fields.

Meanwhile, in US Patent No. 5,073,440 issued to Lee on December 17, 1991, a fiber made of a mixture of paraphenylene terephthalamide (PPTA) and polyvinylpyrrolidone (PVP), a water-soluble polymer, It is disclosed. However, fibers containing para-aramid alone and fibers made of a mixture of PPTA and PVP of U.S. Patent No. 5,073,440 exhibit strong cotton bonds other than hydrogen bonds between chains and low Van der Waals force due to the unfolded chain structure. There is no power to form. Due to this, when there is little fatigue and friction, fibrillation of the surface of the filament easily occurs, resulting in lower strength and lower fatigue resistance.

For this reason, it is necessary to develop a para-aramid fiber that exhibits high strength properties while having excellent fatigue resistance.

An object of the present invention is to provide a para-aramid having excellent fatigue resistance and strength, and a method for producing the same.

Para-aramid fiber according to an embodiment of the present invention is para-aramid; And a mixture containing 3 to 20% by weight of polyvinylpyrrolidone (PVP) based on the total weight of the para-aramid, and the fatigue resistance may be 95% or more.

At this time, the polyvinylpyrrolidone may have a molecular weight of 10,000 to 360,000.

In addition, the para-aramid may be paraphenylene terephthalamide (PPTA).

In addition, the para-aramid fiber may have a strength of 20 g/d or more and a specific strength of 21 g/d or more.

In addition, the manufacturing method of para-aramid fiber according to an embodiment of the present invention is a spinning solution by dissolving 3 to 20% by weight of polyvinylpyrrolidone in a solvent based on the total weight of para-aramid and the para-aramid. Manufacturing steps; After spinning the spinning solution, winding the coagulated and washed fibers; And it may include the step of high-temperature treatment of the wound fiber under a strong alkali aqueous solution containing sodium hydroxide, ammonium persulfate or sodium phosphate.

The para-aramid fiber according to the embodiment of the present invention is made of a mixture of para-aramid and polyvinylpyrrolidone, and thus exhibits improved tensile properties compared to fibers produced only with para-aramid alone, and dyeability, UV stability, and rubber adhesion The back can be improved.

In addition, by crosslinking polyvinylpyrrolidone by heating a fiber made of a mixture of para-aramid and polyvinylpyrrolidone in a strong alkali aqueous solution, tensile strength and fatigue resistance may be improved.

In the present invention, various modifications may be made and various forms may be applied, and specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific form disclosed, it should be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

In describing each drawing, similar reference numerals have been used for similar elements. In the accompanying drawings, the dimensions of the structures are shown to be enlarged than actual for clarity of the present invention. Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are used only for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. Singular expressions include plural expressions unless the context clearly indicates otherwise.

In the present application, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof, does not preclude in advance the possibility of being added.

Hereinafter, an embodiment of the present invention will be described in more detail.

Para-aramid fibers according to an embodiment may be formed of a mixture containing para-aramid and polyvinylpyrrolidone.

At this time, the para-aramid fiber may contain 3 to 20% by weight of the polyvinylpyrrolidone based on the total weight of the para-aramid, preferably 6 to 15% by weight, more preferably It may contain 6 to 10% by weight. If it is out of the above range, it is difficult to express the desired effect, and if the content of the polyvinylpyrrolidone is less than 3% by weight, the resistance to fatigue of the fiber may decrease, and if it exceeds 20% by weight, the fiber Tensile strength may decrease.

In addition, the molecular weight of the polyvinylpyrrolidone is preferably 10,000 to 360,000, and the high molecular weight polyvinylpyrrolidone generates a high-viscosity spinning dope, so it may be more preferably 10,000 to 55,000.

Meanwhile, the para-aramid is preferably a paraphenylene terephthalamide (PPTA), but is not limited thereto.

As described above, the fiber containing para-aramid and polyvinylpyrrolidone may have improved tensile properties, rubber adhesion, and the like, compared to a fiber made with para-aramid alone, and particularly has an advantage of improving fatigue resistance. Specifically, the para-aramid fiber according to the present invention may have a strength of 20 g/d or more, a specific strength of 21 g/d or more, a fatigue resistance of 95% or more, and an adhesive force with a rubber of 20 kgf or more.

On the other hand, para-aramid fiber according to the present invention is prepared by dissolving para-aramid and polyvinylpyrrolidone in a solvent to prepare a homogenized spinning solution (dope); Extruding the spinning solution through a spinning nozzle, passing through an air layer, reaching a coagulation bath, and coagulating the spinning solution to obtain a multifilament; Winding the obtained multifilament by washing with water, drying and oiling; And treating the wound fiber at a high temperature in a strong alkali aqueous solution, but is not limited thereto.

Non-limiting examples of the para-aramid include paraphenylene terephthalamide (PPTA), poly(4,4'-benzanilide terephthalamide), poly(paraphenylene-4,4'-biphenylene-di Carboxylic acid amide), poly(paraphenylene-2,6-naphthalenedicarboxylic acid amide), or a mixture of two or more thereof, and more preferably, paraphenylene terephthalamide.

The para-aramid can be prepared by the following method.

First, a polymerization solvent is prepared by adding an inorganic salt to an organic solvent. As the organic solvent, N-methyl-2-pyrrolidone (NMP), N,N'-dimethylacetamide (DMAc), hexamethylphosphoamide (HMPA), N,N,N',N'-tetra Methyl urea (TMU), N,N-dimethylformamide (DMF) or mixtures thereof may be used. The inorganic salt is added to increase the degree of polymerization of para-aramid, and non-limiting examples thereof may be CaCl ₂ , LiCl, NaCl, KCl, LiBr, KBr, or a mixture thereof. However, when the inorganic salt is added in an excessive amount, an inorganic salt that is not dissolved may be present in the polymerization solvent, so the content of the inorganic salt in the polymerization solvent is preferably 10% by weight or less. Since the inorganic salt has poor solubility in an organic solvent, water is added to completely dissolve the inorganic salt, and then the water is removed through a dehydration step to prepare a final polymerization solvent.

Subsequently, a mixed solution is prepared by dissolving the aromatic diamine in the polymerization solvent. The aromatic diamine may be para-phenylenediamine, 4,4'-diaminobiphenyl, 2,6-naphthalenediamine, 1,5-naphthalenediamine, or 4,4'-diaminobenzanilide.

Then, while stirring the mixed solution, a first polymerization is performed by adding a predetermined amount of aromatic diecid halide to the mixed solution. The aromatic diecid halide may be terephthaloyl dichloride, 4,4'-benzoyl dichloride, 2,6-naphthalenedicarboxylic acid dichloride, or 1,5-naphthalenedicarboxylic acid dichloride. The prepolymer may be formed in the polymerization solvent through the first polymerization.

Subsequently, secondary polymerization is performed by additionally adding an aromatic diecid halide to the polymerization solvent, and para-aramid can be finally obtained through the secondary polymerization. The para-aramid may be polyparaphenylene terephthalamide (PPD-T), poly(4,4'-benzanilide terephthalamide), poly(paraphenylene-), depending on the type of aromatic diamine and aromatic diecid halide used. 4,4'-biphenylene-dicarboxylic acid amide), or poly(paraphenylene-2,6-naphthalenedicarboxylic acid amide).

Subsequently, alkali compounds such as NaOH, Li ₂ CO ₃ , CaCO ₃ , LiH, CaH ₂ , LiOH, Ca(OH) ₂ , Li ₂ O, and CaO are added to the polymerization solution to neutralize the hydrochloric acid generated during the polymerization reaction. can do. On the other hand, adding water to the polymerization solution obtained through the first and second polymerization processes to make it a slurry state to improve its fluidity may be advantageous in performing subsequent processes. At this time, the neutralization step and the slurry preparation step may be simultaneously performed by adding water in which an alkali compound is dissolved to the polymerization solution.

Subsequently, a polymerization solvent can be extracted from the polymerization solution. This extraction process is most effective and economical to perform using water. For example, by installing a filter in a bathtub equipped with an outlet, placing a polymer on the filter, and pouring water, the polymerization solvent contained in the polymer can be discharged to the outlet together with water. On the other hand, if the particle size of the aromatic polyamide present in the polymerization solution is too large, it takes a lot of time to extract the polymerization solvent, so that productivity may decrease. Therefore, before the polymerization solvent extraction process, the pulverization process of the aromatic polyamide may be performed.

Subsequently, by removing water remaining in the para-aramid through dehydration and drying processes, a para-aramid polymer can be obtained. The para-aramid polymer thus obtained preferably has an intrinsic viscosity in the range of 5.5 to 7.0. At this time, if the intrinsic viscosity is less than 5.5, it is difficult to obtain sufficient strength of the fiber, and if it exceeds 7.0, a problem of poor solubility may occur.

Meanwhile, the spinning solution may be an anisotropic solution of para-aramid and polyvinylpyrrolidone. As the spinning solvent, sulfuric acid having a concentration of 98 to 101% may be used, and it is preferably dissolved at 70 to 90°C. At this time, when the concentration and temperature of sulfuric acid are less than 98% by weight and 70°C, respectively, solubility is poor and a homogeneous solution cannot be obtained, and when the concentration and temperature of sulfuric acid exceeds 101% by weight and 90°C, physical properties of the polymer may be deteriorated.

Specifically, the spinning solution can be prepared by stirring finely ground para-aramid and polyvinylpyrrolidone in concentrated sulfuric acid. The spinning solution should be warmed to completely dissolve para-aramid and polyvinylpyrrolidone, but to minimize decomposition of the polymer, the temperature should be kept as low as possible.

The spinning solution effective in the present invention may generally contain about 35 to 45 g of a polymer (the total amount of para-aramid and polyvinylpyrrolidone) per 100 ml of a solvent. When 1.84 g/cm 3 of concentrated sulfuric acid is used, generally the spinning dope may contain 16 to 21% by weight of a para-aramid polymer. It is important that the total concentration of the polymer makes the spinning solution anisotropic. In order to show the advantages of the present invention, 3 to 20% by weight of polyvinylpyrrolidone is suitable based on the total weight of para-aramid in the spinning stock solution.

After the spinning solution prepared by the above method is provided as a spinneret through a dope supply unit, it may be extruded. At this time, the orifice having a diameter of 30 to 100 µm and a length of 80 to 300 µm is radiating including a plurality of orifices having a ratio (L/D) of 2 to 4 times the diameter and length, and a spacing between orifices of 0.5 to 5.0 mm. The spinning dope is extruded through a nozzle so that the fibrous spinning dope passes through the air layer to reach a coagulation bath, and then coagulated to obtain multifilaments.

The shape of the spinning nozzle used is usually circular, and the nozzle diameter may be 40 to 100 mm, more preferably 50 to 80 mm. If the nozzle diameter is less than 40mm, the distance between the orifices is too short to reduce the cooling efficiency of the solution, and adhesion may occur before the discharged solution solidifies.If it is more than 100mm, peripheral devices such as spinning packs and nozzles become large, which is disadvantageous to the facility. Do. In addition, if the diameter of the nozzle orifice is less than 30 µm or exceeds 100 µm, the spinning performance is adversely affected, such as a large number of threads during spinning. If the length of the nozzle orifice is less than 80 µm, the orientation of the solution is poor and the physical properties are poor. If it exceeds 300 µm, there is a disadvantage that excessive cost and effort are required to manufacture the nozzle orifice.

When the fibrous spinning dope that has passed through the spinning nozzle is coagulated in the coagulation solution, when the diameter of the fluid increases, the difference in coagulation rate between the surface and the inside increases, making it difficult to obtain fibers of a dense and uniform structure. Therefore, when spinning aramid solution, the spun fiber has a thinner diameter and can be obtained into the coagulation solution while maintaining an appropriate air layer even with the same discharge amount. If the distance of the air layer is too short, it is difficult to increase the spinning speed due to the increase in the fraction of micropores generated in the process of rapid solidification and desolvation of the surface layer, while the distance of the air layer too long is relatively affected by filament adhesion, ambient temperature, and humidity to maintain process stability. It's hard to do. In this case, the air layer may be preferably 3 to 20 mm, more preferably 5 to 15 mm.

The coagulation solution of the coagulation bath used in the present invention is preferably water containing 3 to 12% by weight of sulfuric acid. When the filament passes through the coagulation bath, the coagulation solution is vibrated by friction between the filament and the coagulation solution. In order to improve productivity by increasing excellent physical properties and spinning speed through stretching and orientation, this phenomenon is a factor that hinders process stability.Thus, the coagulation bath design takes into account the size and shape of the coagulation bath and the flow and amount of coagulation solution. It needs to be minimized.

As the filament passes through the coagulation bath, the desolvation and structure formation, which have a great influence on the formation of physical properties, are performed at the same time, so the temperature and concentration of the coagulation solution must be kept constant. The temperature of the coagulation bath may be 0 to 10°C, preferably 3 to 7°C. If it is less than 0℃, it is difficult to wash with sufficient water, and if it is more than 10℃, PPTA can rapidly escape from the aramid coagulated sand and pores may be generated, which may cause deterioration of physical properties. After coagulation is completed, washing is completed in a washing chamber at about 30°C.

The multi-filament after washing with water is continuously dried through a drying roller whose temperature is adjusted to 130 to 250°C, preferably 150 to 210°C. If the temperature is less than 130°C, sufficient drying is not possible. If the temperature is higher than 250°C, the filament may shrink rapidly and excessively, which may cause deterioration in physical properties. The dried filament may be wound by emulsion treatment according to a conventional method.

The wound para-aramid fiber can be treated at a high temperature under a strong alkali aqueous solution. The polyvinylpyrrolidone component can be crosslinked by heating the para-aramid fiber in a strong alkali aqueous solution containing sodium hydroxide, ammonium persulfate or sodium phosphate. At this time, the concentration of the strong alkali aqueous solution is preferably 2 to 10%, more preferably 2 to 5%, but is not limited thereto. In the fiber mixed with para-aramid and polyvinylpyrrolidone, it was not possible to confirm that the polyvinylpyrrolidone component was crosslinked by a general analysis method, but when polyvinylpyrrolidone alone was heated in a strong alkali aqueous solution, a gel was formed and crosslinked. I can confirm. For this reason, the effect can be inferred because the tensile strength and fatigue resistance are improved by heat treatment in a strong alkali aqueous solution.

Hereinafter, the present invention will be described in detail through examples. However, the following examples are only illustrative of the present invention, and the present invention is not limited by the following examples.

[Example 1]

Sulfuric acid with a concentration of 100.1% was cooled to 15℃ and transferred to a 2-inch twin extruder at a rate of 232.8 g/min, and PPTA with an intrinsic viscosity of 6.3 was transferred to a 2-inch twin at a rate of 56.4 g/min. Transferred to a twin extruder, mixed with sulfuric acid, transferred to a 5-inch twin extruder, completely dissolved at 85°C, and defoamed under reduced pressure of 720mmHg. After completely dissolving PVP with a molecular weight of 40,000 in 100.1% sulfuric acid at a concentration of 20% at 85°C, degassing under reduced pressure of 720mmHg, PVP is 10% by weight of PPTA, and the two solutions are mixed before the metering pump to orifice. It was extruded through a spinneret having 665 holes of 0.064 mm, and the extruded stock solution was discharged into a 10% sulfuric acid aqueous solution at 3° C. through an air gap of 7 mm length. The resulting fibers were washed with water, neutralized, and dried at 170° C. for 3 to 5 seconds, and 1,000 denier filaments were wound on a bobbin for dyeing filaments at 600 m/min. Thereafter, the fiber wound on the filament dyeing bobbin was mounted on a filament dyeing machine, and a 2% aqueous sodium hydroxide solution was circulated at a temperature of 100° C. to react for 30 minutes.

[Example 2]

Para-aramid fibers were prepared through the same procedure as in Example 1, except that 4% aqueous sodium hydroxide solution was used instead of 2% aqueous sodium hydroxide solution.

[Example 3]

Para-aramid fibers were prepared in the same manner as in Example 1, except that a 2% aqueous ammonium persulfate solution was used instead of a 2% aqueous sodium hydroxide solution.

[Example 4]

Para-aramid fibers were prepared through the same procedure as in Example 1, except that PVP was mixed at 6% by weight of PPTA to prepare a solution.

[Example 5]

Para-aramid fibers were prepared through the same procedure as in Example 1, except that PVP was mixed at 15% by weight of PPTA to prepare a solution.

[Comparative Example 1]

Sulfuric acid with a concentration of 100.1% was cooled to 15℃ and transferred to a 2-inch twin extruder at a rate of 232.8 g/min, and PPTA with an intrinsic viscosity of 6.3 was transferred to a 2-inch twin at a rate of 56.4 g/min. Transferred to a twin extruder, mixed with sulfuric acid, transferred to a 5-inch twin extruder, completely dissolved at 85°C, and defoamed under reduced pressure of 720 mmHg. Thereafter, it was extruded through a spinneret having 1000 holes having an orifice of 0.064 mm, and the extruded stock solution was discharged in a 10% sulfuric acid aqueous solution at 3° C. through an air gap of 7 mm. The resulting fibers were washed with water and neutralized, dried at 170° C. for 3 to 5 seconds, and wound at 600 m/min.

[Comparative Example 2]

Sulfuric acid with a concentration of 100.1% was cooled to 15℃ and transferred to a 2-inch twin extruder at a rate of 232.8 g/min, and PPTA with an intrinsic viscosity of 6.3 was transferred to a 2-inch twin at a rate of 56.4 g/min. After being transferred to a twin extruder, mixed with sulfuric acid, transferred to a 5-inch twin extruder, completely dissolved at 85°C, and defoamed under a reduced pressure of 720 mmHg. After completely dissolving PVP with a molecular weight of 40,000 in 100.1% sulfuric acid at a concentration of 20% at 85°C, degassing under reduced pressure of 720mmHg, PVP is 10% by weight of PPTA, and the two solutions are mixed before the metering pump to orifice. It was extruded through a spinneret having 1000 holes of 0.064 mm, and the extruded stock solution was discharged into a 10% sulfuric acid aqueous solution at 3°C through a 7 mm long airgap. The resulting fibers were washed with water and neutralized, dried at 170° C. for 3 to 5 seconds, and wound at 600 m/min.

[Experimental Example]

Physical properties of the para-aramid fibers according to Examples and Comparative Examples were evaluated using the following method, and the results are shown in Table 1 below.

1) tensile strength

Tensile strength was measured according to the ASTM D 7269 test method.

2) specific strength

It is the value obtained by dividing the breaking stress of the fiber by the linear density under the test corrected for the amount of PVP. Compared to PPTA, since PVP has little effect on the strength of the fiber, the strength of the fiber can be corrected for the presence of PVP. Specific strength is a measure of the strength of PPTA in the fiber and is determined by dividing the strength by the weight fraction of PPTA in the fiber.

3) rubber adhesion

The rubber adhesion test was used to evaluate only the adhesion (peel strength) between the unbent rubber and the reinforcing cord layer embedded in the rubber. The test specimen is the reinforced rubber product itself. The test method used is ASTM D 2630-71.

4) fatigue

The fatigue resistance was compared by measuring the residual strength after the fatigue test using a belt fatigue tester. The fatigue test condition was 80Kgf load, the spindle radius was 12.7mm, and the belt fatigue cycle was 37,500 times. After the fatigue test, the residual strength was measured using a tensile strength tester.

division Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 PVP/PPTA weight ratio (%) 10 10 10 6 15 0 10 alkali 2% sodium hydroxide 4% sodium hydroxide 2% ammonium persulfate 2% sodium hydroxide 2% sodium hydroxide - - Tensile strength (g/d) 23.1 23.0 23.0 22.5 21.7 23.2 21.3 Specific strength (g/d) 25.7 25.5 25.5 23.9 25.5 23.2 23.7 Peeling strength (Kgf) 23.3 22.8 22.2 20.0 20.2 10.2 15.7 Fatigue resistance (%) 98 98 97 96 95 90 91

Referring to Table 1, the fibers prepared according to the Examples have improved tensile properties, rubber adhesion, etc. compared to fibers prepared with para-aramid alone (Comparative Example 1) or fibers not treated with a strong alkali aqueous solution (Comparative Example 2). In particular, it can be seen that the fatigue resistance is improved. As a result, the para-aramid fiber according to the present invention has improved tensile strength and fatigue resistance by heat treatment in a strong alkali aqueous solution, and as a result, it can be inferred that a gel is formed and crosslinked as polyvinylpyrrolidone is heated in a strong alkali aqueous solution. I can.

Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art or those of ordinary skill in the art will not depart from the spirit and scope of the present invention described in the claims to be described later. It will be understood that various modifications and changes can be made to the present invention within the scope of the invention.

Therefore, the technical scope of the present invention should not be limited to the content described in the detailed description of the specification, but should be determined by the claims.

Claims (5)

delete delete delete delete Preparing a spinning solution by dissolving para-aramid and 6 to 15% by weight of polyvinylpyrrolidone in a solvent based on the total weight of the para-aramid;
After spinning the spinning solution, winding the coagulated and washed fibers; And
Comprising the step of preparing para-aramid fibers by treating the wound fibers at a high temperature of 100° C. in a strong alkali aqueous solution containing sodium hydroxide, ammonium persulfate or sodium phosphate,
The para-aramid fiber has a strength of 21.7 to 23.1 g/d, a specific strength of 23.9 to 25.7 g/d, and an anti-fatigue resistance of 85 to 98%.