KR101245890B1 - Aramide Fiber and Method for Manufacturing The Same - Google Patents

Abstract

The present invention relates to an aramid fiber and a method for producing the aramid fibers, each monofilament has a high roundness of the cross-sectional area is minimized, the method of producing an aramid fiber of the present invention comprises the steps of preparing an aromatic polyamide polymer; Dissolving the aromatic polyamide polymer in a sulfuric acid solvent to obtain spinning dope; Spinning the spin dope using a spinneret; Solidifying the spun spinning dope while remaining in a coagulation bath containing a coagulating solution for 0.10 to 0.50 seconds to form a filament; Washing the filament with water; And drying the washed filaments in a drying unit.

Aramid, coagulation tank, roundness

Description

TECHNICAL FIELD [0001] The present invention relates to an aramid fiber,

The present invention relates to aramid fibers and a method of manufacturing the same, and more particularly, to aramid fibers and a method for producing the same, each monofilament has a high roundness of the cross-sectional area is minimized.

Generally, the wholly aromatic polyamide fibers commonly referred to as aramid fibers include para-aramid fibers having a structure in which benzene rings are linearly connected through an amide group (CONH) and non-aramid fibers. Para-aramid fibers have excellent properties such as high strength, high elasticity and low shrinkage. They have a strong strength enough to lift 2 tons of automobile with a thin thread of 5mm thickness, Of-the-art industry. In addition, since the aramid fiber is carbonized at a temperature of 500 ° C or higher, the aramid fiber is also in the spotlight where high heat resistance is required.

Aramid fiber is a process for producing a wholly aromatic polyamide polymer by polymerizing an aromatic diamine and an aromatic dieside halide in a polymerization solvent containing N-methyl-2-pyrrolidone, dissolving this polymer in a concentrated sulfuric acid solvent to prepare a spinning dope After the step of spinning the spinning dope through the spinneret to pass through the non-coagulant fluid and coagulation bath sequentially to produce a filament, and the process of washing the filament, washing and drying and heat treatment .

The aramid fiber thus produced is required not only to have a high strength and a high modulus of elasticity but also to minimize its physical property variation. If the physical properties of the aramid fiber are deviated too much, the article made of the aramid fiber can not also be reliable. Therefore, the deviation of the properties of the aramid fiber is one of the important factors determining the commercial value of the aramid fiber.

However, the characteristics of the fibers themselves related to the variation of the physical properties of the aramid fibers and the process causes causing the deviations have not been clearly identified, and thus, a method for minimizing the variation of the physical properties of the fibers has not been presented until now.

The present invention was derived to solve the above problems, and an object of the present invention is to provide an aramid fiber and a method for producing the same, each monofilament has a high roundness of the cross section minimizes the variation in physical properties.

As an aspect of the present invention for achieving the above object, the aramid fiber of the present invention, including a plurality of monofilaments, the roundness of the monofilament cross section is 0.9 ~ 1.0.

According to another aspect of the present invention, there is provided a method for producing an aramid fiber according to the present invention, comprising the steps of: preparing an aromatic polyamide polymer; Dissolving the aromatic polyamide polymer in a sulfuric acid solvent to obtain spinning dope; Spinning the spin dope using a spinneret; Solidifying the spun spinning dope while remaining in a coagulation bath containing a coagulating solution for 0.10 to 0.50 seconds to form a filament; Washing the filament with water; And drying the washed filaments in a drying unit.

The method may further include measuring a roundness ratio of the dried filament, and adjusting a time for which the spun spinning dope stays in the coagulation bath according to the measured roundness ratio.

The step of adjusting the time the spinning dope stays in the coagulation bath may be performed by adjusting the size of the coagulation bath or the winding speed of the filament.

The coagulating solution is sulfuric acid is contained in water, ethylene glycol, glycerol, alcohol, or a mixture thereof, the concentration of sulfuric acid is preferably 4 to 10% by weight.

According to the aramid fiber according to the present invention and a manufacturing method thereof, the aramid fiber is composed of monofilaments having a high roundness cross section, not only has high strength and high modulus of elasticity but also minimizes the variation in physical properties.

In addition, it is possible to improve the reliability of the article made of the aramid fibers by minimizing the variation in physical properties of the aramid fibers. Thus, the product value of the aramid fibers can be maximized.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, one embodiment of an aramid fiber of the present invention and a method for producing the same will be described in detail with reference to the accompanying drawings.

To prepare the aramid fibers of the present invention, aromatic polyamide polymers are first prepared by the method described below.

An inorganic salt is added to the organic solvent to prepare a polymerization solvent. The organic solvent may be an amide organic solvent, a urea organic solvent or a mixed organic solvent thereof. Specific examples thereof include N-methyl-2-pyrrolidone (NMP), N, N'-dimethylacetate Amide (DMAc), hexamethylphosphoramide (HMPA), N, N, N ', N'-tetramethylurea (TMU), N, N-dimethylformamide (DMF) or mixtures thereof.

The inorganic salt is added to increase the degree of polymerization of the aromatic polyamide, and specific examples thereof include halogenated alkali metal salts or halogenated alkaline earth metal salts such as CaCl 2, LiCl, NaCl, KCl, LiBr and KBr, and these inorganic salts. Silver may be added alone or in the form of a mixture of two or more thereof. As the amount of the inorganic salt increases, the degree of polymerization of the aromatic polyamide increases, but when the inorganic salt is added in an excessive amount, there may be an inorganic salt that does not dissolve. Thus, the inorganic salt is 10% by weight or less based on the total amount of the polymerization solvent. It is preferable that it is the range of. Since the inorganic salt has poor solubility in organic solvents, the final polymerization solvent can be prepared by completely dissolving the inorganic salts by adding water and then removing the water through a dehydration process.

Next, an aromatic diamine is dissolved in the prepared polymerization solvent to prepare a mixed solution. Specific examples of aromatic diamines include para-phenylenediamine, 4,4'-diaminobiphenyl, 2,6-naphthalenediamine, 1,5-naphthalenediamine or 4,4'-diaminobenzanilide. However, the present invention is not limited thereto.

Subsequently, while stirring the mixed solution, a predetermined amount of aromatic dieside halide is added to the mixed solution to prepolymerize. Specific examples of aromatic dieside halides include, but are not limited to, terephthaloyl dichloride, 4,4'-benzoyl dichloride, 2,6-naphthalenedicarboxylic acid dichloride or 1,5-naphthalenedicarboxylic acid dichloride. It doesn't happen.

In the polymerization of the aromatic diamine and the aromatic dieside halide, the reaction proceeds at a high rate with exotherm. In this way, when the polymerization rate is high, there is a problem in that the degree of polymerization differs between the finally obtained polymers. More specifically, since the polymerization reaction does not proceed simultaneously in the entire mixed solution, the polymer that has first started the polymerization proceeds rapidly to form a long molecular chain, whereas the polymer that has started the polymerization first polymerizes first. There is no choice but to form shorter molecular chains than the polymer from which the reaction was initiated, and the higher the polymerization rate, the greater the difference. As described above, when the difference in degree of polymerization between the finally obtained polymers becomes large, the physical property deviation becomes large, which makes it difficult to realize the desired characteristics. Therefore, it is preferable to minimize the difference in degree of polymerization between the polymers finally obtained by preforming a prepolymer having a molecular chain of a predetermined length through a prepolymerization step, and then performing a polymerization step.

According to an embodiment of the present invention, the prepolymerization process is carried out at a reaction temperature of 0 to 45 ° C in a reactor, a reaction time is 3 to 15 minutes to give a sufficient polymerization time, and a wholly aromatic polyamide polymer It is preferable to add only 20 to 40% of the total amount of the aromatic diacid halide necessary for the production of the aromatic diacid halide in the prepolymerization step.

After the completion of the prepolymerization process, the temperature is lowered to 0 to 10 ° C. and an aromatic dieside halide is further added to the prepolymer to prepare a final polymer.

Since aromatic dieside halides react with aromatic diamines in a 1: 1 molar ratio when preparing an aromatic polyamide polymer, the amount of aromatic dieside halide added in the final polymerization is equal to the amount of molar equivalent to the aromatic diamine when added to the prepolymerization. mole). However, when preparing the polymerization solvent, a small amount of water added to assist in dissolving the inorganic salt may remain even after the dehydration process, in which case a small amount of water may react with the aromatic dieside halide to form an insoluble substance. Therefore, in view of the formation of such an insoluble substance, a small amount of aromatic dieside halide may be added more than aromatic diamine.

Specific examples of the aromatic polyamide polymer obtained by the polymerization step include poly (paraphenylene terephthal-amide: PPD-T), poly (4,4'-benzanilide terephthalamide), poly (paraphenylene-4, 4'-biphenylene-dicarboxylic acid amide) or poly (paraphenylene-2,6-naphthalenedicarboxylic acid amide).

Subsequently, the acid produced during the polymerization reaction is neutralized with an alkali compound.

Since the aromatic polyamide polymer obtained through the polymerization reaction is present in the form of bread crumb, the flowability of the aromatic polyamide solution is poor. Therefore, in order to improve the fluidity, it is preferable to proceed with the subsequent process in the state of making the slurry by adding water to the aromatic polyamide solution. On the other hand, the neutralization step can be carried out simultaneously by using water in which an alkali compound is dissolved when making the aromatic polyamide polymer slurry.

The inorganic alkali compound is an alkali metal of NaOH, Li2CO3, CaCO3, LiH, CaH2, LiOH, Ca (OH) 2, Li2O or CaO, carbonate of alkaline earth metal, hydride of alkaline earth metal, hydroxide of alkaline earth metal, or oxide of alkaline earth metal It is selected from the group consisting of.

When an inorganic alkali compound is added to an aromatic polyamide solution in a strong acid state containing a large amount of hydrochloric acid, the reaction rapidly reacts with hydrochloric acid, so that neutralization proceeds rapidly. The reaction rate is drastically reduced and the inorganic alkali compound remains in the neutralization solution in an unreacted state. This causes a problem that the insoluble inorganic alkali compound must be filtered through a filter after the neutralization is completed. Therefore, in order to prevent the formation of insoluble foreign matter in the aromatic polyamide solution, the neutralization process can be carried out at several times.

Subsequently, the aromatic polyamide polymer from which the acid is removed by the neutralization step is pulverized.

If the particle size of the polymer is too large in the extraction process described later, the polymerization solvent extraction process takes a lot of time and the polymerization solvent extraction efficiency is lowered, so that the grinding process is performed to reduce the particle size of the polymer before the extraction process.

Next, the polymerization solvent is extracted from the pulverized aromatic polyamide polymer. Since the polymerization solvent used for the polymerization step is contained in the aromatic polyamide polymer obtained by the polymerization, such a polymerization solvent must be extracted from the polymer, and the extracted polymerization solvent can be reused in the polymerization step. Such an extraction process is most effective and economical to perform using water. The extraction process may be performed by installing a filter in a bath having a discharge port, placing a polymer in the form of a crumb on the filter, and then pouring water to discharge the polymerization solvent contained in the polymer together with water to the discharge port.

Next, the remaining water after the extraction step is dehydrated, and then the drying process is completed to complete the production of the aromatic polyamide polymer. Thereafter, a classification process may be performed to classify the aromatic polyamide polymers by size for the spinning process.

Spinning dope is prepared by dissolving the aromatic polyamide polymer prepared as above in a concentrated sulfuric acid solvent having a concentration of 97 to 103%. Instead of the concentrated sulfuric acid, chloro sulfuric acid, fluoro sulfuric acid and the like may also be used.

The polymer concentration in the spin dope is preferably 10 to 25% by weight for the fiber properties. As the polyamide polymer concentration increases, the viscosity of the spin dope also increases, but beyond the critical concentration point, the viscosity of the spin dope rapidly decreases, while the spin dope does not form a solid phase. It changes from optically isotropic to optically anisotropic. Since the anisotropic spin dope can be made of high strength aramid fibers due to its structural and functional properties without a separate drawing process, it is preferable that the concentration of the polyamide polymer in the spinning dope exceeds the above critical concentration, but the concentration is excessively high. If large, the viscosity of the spinning dope is too low occurs.

1 shows a system for producing aramid fibers according to an embodiment of the present invention.

Spinning the spin dope using a spinneret 100 and then forming a filament by coagulating in a coagulation bath 200 through an air gap. .

The air gap may be mainly an air layer or an inert gas layer, the length of the air gap is 0.1 to 15 cm is preferable for improving the physical properties of the filament is produced.

The spinneret 100 has a plurality of capillaries having a diameter of 0.1 mm or less. If the diameter of the capillary formed in the spinneret exceeds 0.1 mm, the molecular orientation of the resulting filament is poor, resulting in a decrease in the strength of the filament.

As the coagulating solution, water, ethylene glycol, glycerol, alcohol, or a mixture thereof is used. The coagulating solution is maintained at -20 to 5 캜. When the radiation passing through the spinneret 100 passes through the coagulating solution, the sulfuric acid in the radiation is removed and filaments are formed. When the sulfuric acid is rapidly removed from the surface of the radiation, May be first solidified and the uniformity of the filament may be lowered. Therefore, it is preferable to add sulfuric acid to the coagulating solution in order to prevent sulfuric acid from leaking out rapidly from the surface of the radiation.

The sulfuric acid concentration of the coagulating solution is preferably 4 to 10% by weight. When the sulfuric acid concentration is less than 4% by weight, not only the rate of sulfuric acid escaped from the emission is high, but also the speed difference along the direction is reduced, thereby reducing the roundness of the monofilament. Here, the roundness means the ratio of the inscribed circle diameter to the circumscribed circle diameter of the monofilament cross section. It is preferable that the roundness of a monofilament cross section is 0.9-1.0. A roundness of less than 0.9 means that the rate of sulfuric acid exiting from the effluent is non-uniform, and aramid fibers composed of monofilaments with such low roundness have serious variation in properties.

On the other hand, when the concentration of sulfuric acid in the coagulation solution exceeds 10% by weight, the amount of sulfuric acid remaining in the filament formed by the coagulation of the spinning is high, which causes a problem that the physical properties of the aramid fibers are lowered.

On the other hand, the time for which the radiation substance stays in the coagulation bath is preferably 0.10 to 0.50 seconds. If the residence time is less than 0.10, since the spinning solidifies before the sulfuric acid is discharged out, the roundness of the monofilament cross section is improved, but the residual sulfuric acid is present, resulting in poor physical properties of the aramid fiber. On the other hand, if the residence time exceeds 0.50 seconds, a difference occurs in the degree of sulfuric acid escape in each part of the radiant, thereby reducing the roundness of the monofilament cross section.

Subsequently, the sulfuric acid remaining in the obtained filament is removed. The sulfuric acid used in the preparation of the radial dope may be largely removed while the radiation passes through the coagulation bath 200, but may remain without being completely removed. Also, when sulfuric acid is added to the coagulating solution of the coagulation bath 200 to uniformly remove sulfuric acid from the irradiator, there is a high probability that sulfuric acid remains in the obtained filament. It is very important to completely remove the sulfuric acid remaining in the filament, because the amount of sulfuric acid remaining in the filament may adversely affect the aramid fiber properties, even if the amount thereof is small.

The sulfuric acid remaining in the filament can be removed through a washing process using water or a mixed solution of water and an alkali solution. The washing process may be carried out in a multi-step, for example, the first washing in the first washing tank 300 containing 0.3 to 1.3% of an aqueous caustic solution of sulfuric acid-containing filament, and then The second washing in the second washing tank 400 containing 0.01 to 0.1% of the thinner caustic aqueous solution. First and second water wash rolls 310 and 410 are installed in the first and second water washing tanks 300 and 400 to move the filaments.

Then, a drying process for removing moisture remaining in the filament is performed in the drying unit 500. [ The drying process may control the moisture content of the filament by adjusting the time the filament touches the drying roll 510 in the drying unit 500 or by adjusting the temperature of the drying roll 510.

On the other hand, during the spinning, washing, neutralizing and drying processes, tension is applied to the filament. The optimum amount of tension applied to the filament during the drying process is about 3.0 to 7.0 gpd It is preferable to dry the filament under a tensile force of. When the tensile strength at the time of drying is less than 3.0 gpd, the degree of molecular orientation is decreased and ultimately the strength of the fiber is lowered. Conversely, if the tensile strength during drying exceeds 7.0 gpd, the filament may be cut, resulting in difficulty in manufacturing. On the other hand, the magnitude of the tension applied to the filament can be adjusted by appropriately controlling the surface speed of the roll moving the filament.

The drying roll 510 is heated by a predetermined means and the drying roll 510 is heated at least partially by means of heat shielding to prevent excessive heat from being emitted from the heated roll 510, It is preferable to surround it.

Subsequently, the dried filament is wound by the winder 600.

Meanwhile, according to one embodiment of the present invention, the method may further include measuring a roundness of the dried filament and adjusting the time for which the spun spinning dope stays in the coagulation bath according to the measured roundness. have. Adjusting the time that the spun spinning doped stays in the coagulation bath may be performed by adjusting the size of the coagulation bath or the winding speed of the filament. For example, when the roundness ratio of the monofilament is less than 0.9, the size of the coagulation bath is reduced or the winding speed of the filament is quickly adjusted.

Hereinafter, the present invention will be described in detail through examples and comparative examples. It should be noted, however, that the following examples are intended to assist the understanding of the present invention and should not limit the scope of the present invention.

Example  One

Spinning dope was prepared by dissolving 19 g of aromatic polyamide polymer in 100% sulfuric acid solvent. The filament was prepared by spinning the spinning dope using a spinneret and then solidifying it in a coagulation bath through an air gap. The air gap was an air layer having a length of 10 mm. The coagulation solution contained in the coagulation bath was the addition of 8% sulfuric acid to distilled water and maintained at about 5 캜 or lower during the spinning process. The time the filament stayed in the coagulation bath was 0.10 second. The filament was washed with water and dried, and then wound up with a winder to obtain aramid fibers.

Example  2 to 9

The aramid fibers were prepared in the same manner as in Example 1, except that the filaments stayed in the coagulation bath in 0.15 seconds, 0.20 seconds, 0.25 seconds, 0.30 seconds, 0.35 seconds, 0.40 seconds, 0.45 seconds, and 0.50 seconds, respectively. Each was prepared.

Comparative example  1 to 4

Aramid fibers were produced in the same manner as in Example 1, except that the filaments stayed in the coagulation bath, respectively, at 0.05 seconds, 0.09 seconds, 0.51 seconds, and 0.55 seconds.

The roundness of the monofilament of the aramid fibers obtained by the above examples and comparative examples and the strength deviation of the aramid fibers were measured by the following method to obtain the results shown in Table 1 below.

Monofilament  Cross section Roundness  Measure

After molding aramid fibers with vinyl chloride resin, the samples were rounded off with a knife. The sample was then adhered to the FE-SEM sample stage with the aramid fiber cross section facing up and sputtered Au to about 10 nm thick. Subsequently, the diameter of the inscribed circle and the circumscribed circle of the monofilament cross section was measured by observing the monofilament cross section under the conditions of an acceleration voltage of 7.00 KV and an operating distance of 31 mm with a scanning electron microscope manufactured by JEOL. The roundness of the monofilament cross section was calculated by calculating the ratio of the diameter of the inscribed circle to the diameter of the circumscribed circle.

Aramid  Measurement of strength deviation of fiber

The strength of the sample was determined by measuring the strength (g) when a 25 cm long sample was broken in an Instron tester (Instron Engineering Corp, Canton, Mass) and dividing it by the denier of the sample. At this time, the tensile speed was 300mm / min, the super-load was fineness × 1 / 30g. The strength deviation of aramid fibers was obtained by testing the strength of 50 samples prepared under the same conditions.

[Table 1]

Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Comparative Example 3 Comparative Example 4 Residence time in the coagulation tank
(second) 0.05 0.09 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.51 0.55 Mono
Roundness of the filament cross section 0.95 0.94 0.94 0.93 0.93 0.93 0.93 0.92 0.92 0.92 0.91 0.84 0.82 Of aramid fiber
Intensity deviation
(%) 19 14 9 7 4 4 3 5 6 7 8 12 13

As can be seen from Comparative Examples 1 and 2 of Table 1, when the residence time of the spinning dope in the coagulation bath is less than 0.10 seconds, the roundness of the monofilament cross section was good as 0.94 or more, but the strength deviation of the aramid fiber was in the industry. Did not meet the generally required 10%.

In addition, as can be seen from Comparative Examples 3 and 4, when the residence time of the spinning dope in the coagulation bath exceeds 0.50 seconds, the roundness of the monofilament cross-section was less than 0.90. The strength deviation of the fiber did not satisfy 10% or less.

1 shows a system for producing aramid fibers according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

100: spinneret 200: coagulation tank

300: first water washing tank 310: first water washing roll

400: 2nd water washing tank 410: 2nd water washing roll

500: drying unit 510: drying roll

600: winder

Claims (8)

Preparing an aromatic polyamide polymer; Dissolving the aromatic polyamide polymer in a sulfuric acid solvent to obtain spinning dope; Spinning the spin dope using a spinneret; Solidifying the spun spinning dope while remaining in a coagulation bath containing a coagulating solution for 0.10 to 0.50 seconds to form a filament; Washing the filament with water; And Method for producing aramid fibers, characterized in that it comprises the step of drying the washed filament in a drying unit. The method of claim 1, Method for producing aramid fibers, characterized in that further comprising the step of measuring the roundness of the dried filament. The method of claim 2, According to the measured roundness ratio, the method of producing aramid fiber, characterized in that further comprising the step of adjusting the time the spinning dope stay in the coagulation bath. The method of claim 3, wherein The step of adjusting the time the spinning spinning dope stays in the coagulation bath is performed by adjusting the size of the coagulation bath. The method of claim 3, wherein The step of adjusting the time the spinning dope stays in the coagulation bath is carried out by adjusting the winding speed of the filament. The method of claim 1, The coagulation solution is a method for producing aramid fibers, characterized in that it comprises water, ethylene glycol, glycerol, alcohol, or a mixture thereof. The method of claim 6, The coagulation solution is a method for producing aramid fibers, characterized in that further comprises 4 to 10% by weight of sulfuric acid. In an aramid fiber comprising a plurality of monofilaments, The roundness of the cross section of the monofilament is 0.9 to 1.0, Aramid fiber, characterized in that the strength deviation of the aramid fiber is 10% or less.

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