KR100930204B1 - Aramide fiber and method for manufacturing the same - Google Patents

Abstract

PURPOSE: Aramide fiber and a method for manufacturing the same are provided to improve intensity by intermolecular bonding through formation of strong hydrogen bond between polymer chains. CONSTITUTION: A method for manufacturing aramid fiber includes the followings: manufacturing an aromatic poly amide polymer; dissolving the aromatic poly amide polymer in a sulfuric acid solvent to gain sipping dope; spinning the spinning dope through a spinneret; forming filament by coagulating the spinning dope; washing the filament; drying the filament in a drying part(500); and measuring the hydrogen bond of the filament through infra-red spectroscopy. The drying part includes a front roll and a rear roll located successively. The manufacturing method of the aramid fiber further includes a step for adjusting rotation speed of the hydrogen bond, and a step for passing the spinning dope through an air gap.

Description

Aramide Fiber and Method for Manufacturing the Same

The present invention relates to aramid fibers and a method for manufacturing the same, and more particularly, to aramid fibers having an improved strength by strengthening the intermolecular bonds due to hydrogen bonding between the polymer chains and a method for producing the same.

Generally, wholly aromatic polyamide fibers, collectively referred to as aramid fibers, include para-aramid fibers and meta-aramid fibers having a structure in which the benzene rings are connected linearly through an amide group (CONH). Para-aramid fiber has excellent properties such as high strength, high elasticity, and low shrinkage. It is a thin thread of about 5mm thick and has a strong strength enough to lift 2 tons of cars. It is used in various industries in the high-tech industry. In addition, aramid fibers are carbonized at 500 ° C or higher, and thus are attracting attention in fields requiring high heat resistance.

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 fibers thus produced are required to have high strength and high modulus. The strength of aramid fibers is known to depend on the structure of the molecules themselves as well as the mode of bonding between the molecules. Since aramid fibers contain amide bonds in their molecular chains, if a hydrogen bond can be formed between the polymer chains, the aramid fibers may have high strength and high modulus due to the strong interaction between the polymer chains. However, there is no research on how to secure strong hydrogen bonds between polymer chains of aramid fibers.

The present invention was derived to solve the above problems, an object of the present invention, by providing a strong hydrogen bond between the polymer chains to provide aramid fibers having an improved strength according to the strengthening of the intermolecular bonds and a method for producing the same It is.

As an aspect of the present invention for achieving the above object, the aramid fiber of the present invention, including an amide bond, the stretching vibration absorption peak of the NH group of the amide bond is 3315 ~ 3295 cm ^-1 And the stretching vibration absorption peak of the C = O group of the amide bond appears at 1641 ~ 1627 cm ⁻¹ .

As another aspect of the present invention for achieving the above object, the aramid fiber manufacturing method 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 in a coagulation bath to form a filament; Washing the filament; And drying the washed filaments in a drying unit, wherein the drying unit includes a front roll and a rear end roll continuously positioned, and a ratio of the rotational speed of the rear end roll to the rotational speed of the front end roll is 1.00. Exceeding 1.20.

The hydrogen bonding degree of the dried filament may be measured by using an infrared spectroscopy, and adjusting the ratio of the rotation speed according to the measured hydrogen bonding degree may be further included.

According to the aramid fiber and the manufacturing method thereof according to the present invention, it is possible to form a strong hydrogen bond between the polymer chains of the aramid fiber. Such hydrogen bonds strengthen the intermolecular bonds, thereby making the aramid fibers have improved strength.

Hereinafter, an embodiment of the aramid fiber of the present invention and a manufacturing method thereof will be described in detail.

In order to make 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. As the organic solvent, an amide organic solvent, a urea organic solvent, or a mixed organic solvent thereof may be used. Specific examples thereof include N-methyl-2-pyrrolidone (NMP), N, and N'-dimethylacetate. Amide (DMAc), hexamethylphosphoramide (HMPA), N, N, N ', N'-tetramethyl urea (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. The inorganic salts 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 started the polymerization proceeds rapidly to form a long molecular chain, whereas the polymer that has started the polymerization first There is no choice but to form a shorter molecular chain than the polymer from which the polymerization was initiated, and the higher the polymerization rate, the greater the difference. As such, when the degree of polymerization difference between the polymers finally obtained increases, physical property variations also increase, making it difficult to achieve 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 one embodiment of the invention, the prepolymerization process is carried out while maintaining the reaction temperature at 0 ~ 45 ℃ in the reactor, the reaction time gives a sufficient polymerization time of about 3 to 15 minutes, the wholly aromatic polyamide polymer It is preferable to add only 20 to 40% of the total amount of the aromatic dieside halide necessary for the preparation during the prepolymerization process.

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 the aromatic polyamide polymer, the amount of aromatic dieside halides added during the final polymerization is equal to the amount of moles equivalent to the aromatic diamines 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 the 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 has been 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. This extraction process is most effective and economical to perform with 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.

The spinning dope is spinned using a spinneret 100 and then coagulated in a coagulation bath 200 through an air gap to form a filament.

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, alcohols, or mixtures thereof are used. The coagulating solution is maintained at -20 to 5 ℃. When the radioactive material passed through the spinneret 100 passes the coagulating solution, sulfuric acid in the radioactive material is removed to form a filament. This may solidify first and cause a problem of inferior uniformity of the filament. Therefore, it is preferable to add sulfuric acid to the coagulating liquid in order to prevent the sulfuric acid from escaping rapidly from the surface of the emission.

Next, sulfuric acid remaining in the obtained filament is removed.

Sulfuric acid used in the manufacture of the spinning dope may remain but is not removed completely, although most of the emissions are passed through the coagulation bath 200. Moreover, when sulfuric acid is added to the coagulating liquid of the coagulation tank 200 in order to make sulfuric acid escape uniformly from a effluent, it is highly likely that sulfuric acid will remain in the filament obtained. Since the amount of sulfuric acid remaining in the filament may adversely affect the aramid fiber properties no matter how small the amount, it is very important to completely remove the sulfuric acid remaining in the filament.

Sulfuric acid remaining in the filament can be removed through a washing process using water or a mixed solution of water and alkaline solution. The washing process may be carried out in a multi-step process, 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, then 0.01 The second washing in the second washing tank 400 containing 0.1 to 0.1% of the diluted caustic aqueous solution. First and second flushing rolls 310 and 410 are installed in the first and second flushing tanks 300 and 400, respectively, to move the filaments.

Subsequently, a drying process for removing moisture remaining in the filament is performed in the drying unit 500. In the drying process, the filament may reach the drying roll 510 in the drying unit 500, or the moisture content of the filament may be adjusted by controlling the temperature of the drying roll 510.

On the other hand, the drying unit 500 includes two or more drying rolls (510). The drying roll 510 is heated by a predetermined means. The drying rolls are preferably at least partly surrounded by heat shielding means in order to prevent excess heat from being released from the heated drying rolls and thereby causing heat loss.

The two or more drying rolls 510 include a front roll and a rear roll which are continuously positioned, and the ratio of the rotational speed of the rear roll to the rotational speed of the front roll is more than 1.00 but preferably 1.20 or less. When the rotational speed ratio is 1.00 or less, the degree of molecular orientation is reduced and the density between polymer chains is lowered, and as a result, intermolecular hydrogen bonds are weakened. In other words, the stretching vibration absorption peak of NH group appears at a higher frequency than 3315 cm ⁻¹ , and the stretching vibration absorption peak of C═O group is at a higher frequency than 1641 cm ⁻¹ . On the contrary, when the rotational speed ratio exceeds 1.20, the stretch vibration absorption peaks of NH group and C═O group appear at lower frequencies than 3315 cm ⁻¹ and 1641 cm ⁻¹ , respectively, but the monofilament is cut off, resulting in total aramid A decrease in strength of the fiber is caused.

The filament from which the water is removed is wound around the winder 600 while passing through the drying unit 500.

On the other hand, according to one embodiment of the present invention, after measuring the hydrogen bonding degree of the dried filament using infrared spectroscopy, it is possible to adjust the ratio of the rotational speed according to the measured hydrogen bonding degree. For example, when the elastic vibration absorption peaks of the NH group and the C═O group appear at a wavenumber higher than 3315 cm ⁻¹ and 1641 cm ⁻¹ , respectively, the ratio of the rotational speed is increased by a predetermined size, and the NH group and C When the elastic vibration absorption peak of the group = O appears at a wavenumber lower than 3315 cm ⁻¹ and 1641 cm ⁻¹ , respectively, the ratio of the rotational speed is lowered by a predetermined amount.

Hereinafter, the present invention will be described in detail through examples and comparative examples. However, the following examples are only intended to help the understanding of the present invention, and the scope of the present invention should not be limited thereto.

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 whose length was 10 mm. The coagulation solution contained in the coagulation bath was added with 8% sulfuric acid in distilled water. The filaments were washed with water and then dried by a plurality of drying rolls in a drying unit. At this time, the ratio of the rotational speed of the rear end roll to the rotational speed of the front end roll was 1.01. The aramid fiber was obtained by winding up the dried filament with a winder.

Example  2

When the filament was dried in the drying unit, aramid fibers were prepared in the same manner as in Example 1 except that the ratio of the rotational speed of the rear end rolls to the rotational speed of the front end rolls was 1.05.

Example  3

When the filaments were dried in the drying unit, aramid fibers were prepared in the same manner as in Example 1 except that the ratio of the rotational speed of the rear end rolls to the rotational speed of the front end rolls was 1.10.

Example  4

When the filaments were dried in the drying unit, aramid fibers were prepared in the same manner as in Example 1 except that the ratio of the rotational speed of the rear end rolls to the rotational speed of the front end rolls was 1.15.

Example  5

When the filaments were dried in the drying unit, aramid fibers were prepared in the same manner as in Example 1 except that the ratio of the rotational speed of the rear end rolls to the rotational speed of the front end rolls was 1.20.

Comparative example  One

When the filaments were dried in the drying unit, aramid fibers were prepared in the same manner as in Example 1 except that the ratio of the rotational speed of the rear end rolls to the rotational speed of the front end rolls was 0.95.

Comparative example  2

When the filaments were dried in the drying unit, aramid fibers were prepared in the same manner as in Example 1 except that the ratio of the rotational speed of the rear end rolls to the rotational speed of the front end rolls was 0.98.

Comparative example  3

When the filaments were dried in the drying unit, aramid fibers were prepared in the same manner as in Example 1 except that the ratio of the rotational speed of the rear end rolls to the rotational speed of the front end rolls was 1.00.

Comparative example  4

When the filaments were dried in the drying unit, aramid fibers were prepared in the same manner as in Example 1 except that the ratio of the rotational speed of the rear end rolls to the rotational speed of the front end rolls was 1.25.

The ATR spectrum and the strength of the aramid fibers obtained by the above Examples and Comparative Examples was measured by the following method to obtain the results shown in Table 1 below.

Aramid  Fibrous ATR  spectrum

The aramid fiber sample was washed sequentially with carbon tetrachloride and acetone to remove the emulsion, followed by vacuum drying at 60 ° C. for 4 hours. The dried sample was measured by FT-IR equipped with Ge ATR. As the FT-IR, Digilab's FTS-4000 was used. The measurement wavelength range was 4000-700 cm <-1>. Five samples obtained from one aramid fiber were repeatedly measured, and then the average value of the wave numbers showing the stretching vibration absorption peaks of the N-H and C═O groups was taken.

Aramid  Strength measurement 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 of the aramid fibers was obtained from the average value after testing five samples.

TABLE 1

Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 4 Vr / Vf ^{1 )} 0.95 0.98 1.00 1.01 1.05 1.10 1.15 1.20 1.25 Extension vibration absorption position of NH group (cm ^-1 ) 3348 3326 3318 3314 3310 3305 3301 3296 3293 Expansion vibration absorption peak position of C = O group (cm ^-1 ) 1653 1645 1644 1641 1634 1631 1630 1627 1625 Strength of aramid fiber (g / d) 21.20 21.70 21.80 22.80 24.30 24.30 24.60 24.70 21.90 ¹⁾ Ratio of the rotational speed Vr of the rear end roll to the rotational speed Vf of the front end roll

As can be seen from Table 1 above, when the ratio of the rotational speed of the rear end roll to the rotational speed of the front end roll is less than 1.00, the stretching vibration absorption peak of the NH group appears at a wavenumber higher than 3315 cm ^-1 , and the C = O group. The absorbing peaks of the stretching vibrations were higher than 1641 cm ^{-1, and the} absorbing peaks of the NH and C = O groups were higher than 3315 cm ^-1 and 1641 cm ^-1 when the rotational speed ratio exceeded 1.20. At low frequencies, respectively.

As such, when the elastic vibration absorption peaks of NH group and C = O group appear outside the wave range of 3315 ~ 3295 cm ^-1 and 1641 ~ 1627 cm ^-1 , respectively, the strength of aramid fiber is 22.00 which is generally required in the industry. It did not appear to satisfy g / d.

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

<Brief description of the symbols in the drawings>

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 in a coagulation bath to form a filament; Washing the filament; Drying the washed filaments in a drying unit-the drying unit includes a front roll and a rear end roll continuously positioned, and a ratio of the rotational speed of the rear end roll to the rotational speed of the front end roll exceeds 1.00 but not more than 1.20 Im-; And A method for producing aramid fiber, characterized in that it comprises the step of measuring the hydrogen bonding degree of the dried filament using infrared spectroscopy. delete The method of claim 1, Method for producing aramid fibers, characterized in that further comprising the step of adjusting the ratio of the rotational speed in accordance with the measured hydrogen bonding degree. The method of claim 1, The coagulating solution in the coagulation bath 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 4, wherein The coagulation solution is a method for producing aramid fibers, characterized in that further comprises sulfuric acid. The method of claim 1, And passing an air gap before solidifying the spun spin dope in a coagulation bath. The method of claim 1, wherein the washing of the filament comprises: Washing the filaments with 0.3-1.3% of an aqueous caustic solution; next, Method for producing aramid fibers comprising the step of washing with a caustic aqueous solution of 0.01 to 0.1%. Including amide bonds, Stretching vibration absorption peak of NH group of the amide bond is shown in 3315 ~ 3295 cm ^-1 , Stretching vibration absorption peak of the C = O group of the amide bond is aramid fiber, characterized in that appear in 1641 ~ 1627 cm ^-1 .

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