KR20110035206A - Aramid fiber and method for manufacturing the same - Google Patents

Abstract

PURPOSE: A method for fabricating aramid fiber is provided to prevent stress concentration at terminal groups and to improve strength and elongation rate. CONSTITUTION: A method for fabricating aramid fiber comprises: a step of preparing an aromatic polyamide polymer; a step of preparing a spinning dope using the aromatic polyamide polymers; a step of spinning the spinning dope to prepare an aramid filament; a step of washing the aramid filament; and a step of treating the aramid filament with a cross-linking agent.

Description

Aramid Fiber and Method for Manufacturing the Same

The present invention relates to aramid fibers and a method for producing the same, and more particularly, to a high-strength aramid fiber that can be used in bulletproof products and the like 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, the spinning material is passed through a non-coagulating fluid and a coagulation bath sequentially to produce a filament, and the filament is washed and dried.

However, the aramid fibers thus prepared include a plurality of end groups. If the aramid fibers are subjected to an external force, these end groups act as defects, ie, stress is concentrated on the end groups, so that breakage occurs easily at the end group portions, which causes the strength and elongation of the aramid filament to be significantly lower than the theoretical value. do.

Therefore, bulletproof products manufactured using such aramid fibers having low strength and elongation did not satisfy the level of bulletproof performance required by the industry.

Accordingly, the present invention relates to an aramid fiber and a method for producing the same that can prevent the problems caused by the above limitations and disadvantages of the related art.

One aspect of the present invention is to provide an aramid fiber and a method for producing the same having greatly improved strength and elongation.

Further features and advantages of the invention will be described below, and in part will be apparent from such techniques. Alternatively, other features and advantages of the present invention may be learned from the practice of the present invention. Objects and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

According to one aspect of the present invention as above, preparing an aramid filament; And it provides a method for producing aramid fibers comprising the step of treating the aramid filaments with a crosslinking agent.

In another aspect of the present invention, as an aramid fiber produced by spinning an aromatic polyamide polymer prepared by polymerization of an aromatic diamine and an aromatic dieside halide, an aramid fiber having a strength of at least 30 g / d and an elongation of at least 3.8% is provided. .

It is to be understood that both the foregoing general description and the following detailed description are intended to illustrate or explain the invention, and to provide a more detailed description of the invention in the claims.

According to the aramid fiber and the manufacturing method thereof according to the present invention, aramid fibers with improved strength and elongation can be obtained by bonding the end groups to each other by a crosslinking agent to prevent stress concentration in the end groups. Therefore, bulletproof products using such aramid fibers will have excellent ballistic performance.

As used herein, the term 'cross-linking agent' refers to a compound having a plurality of reactors capable of linking end groups in aramid fibers with each other.

Hereinafter, one Example of the manufacturing method of the aramid fiber of this invention is demonstrated concretely.

First, an inorganic salt is added to an 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. These 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 the aromatic diamine include para-phenylenediamine, 4,4'-diaminobiphenyl, 2,6-naphthalenediamine, 1,5-naphthalenediamine or 4,4'-diaminobenzanilide. However, it is not necessarily limited thereto.

Next, while stirring the mixed solution, a predetermined amount of aromatic dieside halide is added to the mixed solution and prepolymerized. Specific examples of the aromatic dieside halide include terephthaloyl dichloride, 4,4'-benzoyl dichloride, 2,6-naphthalenedicarboxylic acid dichloride or 1,5-naphthalenedicarboxylic acid dichloride, but are not necessarily It is not limited.

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 20-40% of the total amount of the aromatic dieside halide required 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. 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. The alkali compound is an alkali metal of NaOH, Li ₂ CO ₃ , CaCO ₃ , LiH, CaH ₂ , LiOH, Ca (OH) ₂ , Li ₂ O or CaO, carbonate of alkaline earth metal, hydride of alkaline earth metal, hydroxide of alkaline earth metal Or an oxide of an alkaline earth metal.

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 neutralization process is completed to grind the aromatic polyamide polymer from which the acid is removed. 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 process is dewatered, and then the aromatic polyamide polymer is manufactured through a drying process.

The polyamide polymer is then dissolved in concentrated sulfuric acid solvent having a concentration of 97-102% to produce spinning dope. Alternatively, chlorosulfuric acid, fluorosulfuric acid, or the like may be used instead of the concentrated sulfuric acid.

After spinning the spin dope using a spinneret, a filament is formed by coagulating in a coagulation bath in which a coagulating solution is received 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 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. The coagulating solution may be added sulfuric acid to water, ethylene glycol, glycerol, alcohol, or a mixture thereof, and is maintained at -20 to +90 ℃. When the radiation passed through the spinneret passes through the coagulating solution, the sulfuric acid in the emission is removed and filaments are formed. When sulfuric acid is rapidly removed from the surface, the surface is solidified before the sulfuric acid contained therein escapes. Since the problem of the uniformity of the filament may be lowered, sulfuric acid is added to the coagulating solution in order to prevent sulfuric acid from escaping rapidly from the surface of the radiant.

Next, sulfuric acid remaining in the obtained filament is removed. Sulfuric acid used in the manufacture of the spinning dope can remain but is not completely removed, although most of the emissions are passed through the coagulation bath. Moreover, when sulfuric acid is added to the coagulation liquid of a coagulation tank in order to make sulfuric acid escape | emit uniformly from a effluent, there is a high possibility 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 may be removed through a washing process using water or a mixed solution of water and an alkaline solution. The washing process may be carried out in a multi-step process, for example, after first washing the filament containing sulfuric acid with 0.3 to 1.3% of an aqueous caustic solution (water solution), 0.01 to 0.1% of the thinner caustic Secondary washing with an aqueous solution can be carried out.

Then, according to one embodiment of the present invention, the washed aramid filaments are treated with a crosslinking agent. As the crosslinking agent, dihydride or tetracarboxylic acid from which the dianhydride is hydrolyzed may be used, and a diacyl halide such as diacyl chloride or the diacyl halide may be used. Hydrolyzed dicarboxylic acids can be used.

In the crosslinking agent treatment process, all of the anhydride-containing dianhydride containing an aromatic group may be performed. Specific examples of the di-anhydride include 4,4'oxy diphthalic anhydride (ODPA), 4,4'carboxy diphthalic anhydride (4,4'carboxy diphthalic anhydride (4,4'oxy diphthalic anhydride (ODPA)) CDPA)), p-phthalic dianhydride (PPDA), and the like.

The dieside halide may be an aromatic dieside halide, and specific examples of the aromatic dieside halide include terephthaloyl dichloride, 4,4′benzoyl dichloride, 2,6-naphthalenedicarboxylic acid dichloride or 1,5 Naphthalenedicarboxylic acid dichloride and the like.

In addition, the dieside halide may be an aliphatic dieside halide, and specific examples of the aliphatic dieside halide include butanyl dichloride and hexaneyl dicloid, but are not necessarily limited thereto.

Such crosslinkers improve the strength and elongation of the final aramid fibers by acting to interconnect amine or acid end groups to prevent stress concentration at the end groups. The specific method of treating the washed aramid filament with a crosslinking agent is as follows.

In order to treat the washed aramid filaments with a crosslinking agent, a crosslinking agent composition must first be prepared. Such a crosslinking agent composition may be prepared by dissolving dianhydride or diacyl halide as a crosslinking agent in water as a solvent. If the crosslinking agent is difficult to dissolve in water, the crosslinking agent may be more uniformly dissolved by mixing a polar solvent. The concentration of the crosslinking agent may be adjusted in a conventional concentration range, for example, the concentration of the crosslinking agent may be in the range of 1 to 20% by weight. If the concentration of the crosslinking agent is less than 1% by weight, the desired strength and elongation may not be obtained as the terminal groups are not sufficiently bonded to each other. On the other hand, if the concentration of the crosslinking agent exceeds 20% by weight, the crosslinking agent may be added to the solvent. It may not be completely dissolved to obtain a uniform crosslinking reaction and the crosslinking agent which is not bonded with the end groups may be increased, resulting in waste of the crosslinking agent.

The process of treating the aramid filament with a crosslinking agent may be performed through a dipping process of dipping the filament in a treatment tank containing the crosslinking agent composition. It may be preferable to maintain the temperature of the treatment tank higher than room temperature so that the cross-linking agent can penetrate smoothly into the filament.

Alternatively, the process of treating the aramid filament with a crosslinking agent may be performed through a spray process of spraying the crosslinking agent composition maintained at a temperature higher than room temperature to the aramid filament using a nozzle or the like.

The process of treating the aramid filament with a crosslinking agent is preferably performed in the middle of washing and drying after spinning the spinning dope. This is because the filament after the washing process after spinning does not form a sufficient crystal orientation, so that the crosslinking agent can bind to the terminal groups to a sufficient degree by penetrating smoothly into the filament.

Optionally, washing the filament with a crosslinking agent and then removing the crosslinking agent attached to the surface of the filament may further comprise a washing step.

The aramid filament treated with the crosslinking agent undergoes a drying process, causing the crosslinking agents to crosslink. By controlling the time the filament is in contact with the heated drying roll, or by controlling the temperature of the drying roll, the moisture content of the filament can be adjusted, and the degree of reaction between the crosslinking agent and the aramid end group can be adjusted. The drying rolls are heated by some means, and the drying rolls are preferably at least partly surrounded by heat blocking means in order to prevent excessive heat from being released from the heated rolls and thereby causing heat loss.

Subsequently, the dried filament is wound on a branch pipe. Spinning speed is 300 to 1500 m / min.

The aramid filament thus prepared is a plurality of amine or acid end groups are bonded to each other by a crosslinking agent. In particular, the amine end groups are easily bound by the crosslinking agent. As such, the end groups are interconnected by a crosslinking agent, thereby preventing concentration of stress in the end groups when the aramid filaments are subjected to external stress. Thus, the aramid filaments produced have a good strength of at least 30 g / d. In addition, the prepared aramid filament has a high elongation of 3.8% or more because it can disperse the stress as the end group decreases.

In addition, as the end groups are interconnected by the crosslinking agent, the intrinsic viscosity (I.V) is greatly increased due to the effect of increasing the molecular weight.

In addition, as the aramid filament is treated with a crosslinking agent, voids formed on the surface are filled with the crosslinking agent, thereby increasing roughness and improving friction characteristics.

Thus, bulletproof products manufactured using aramid filaments having improved strength and elongation have better ballistic performance.

Optionally, instead of treating the washed aramid filaments with a crosslinking agent, the aramid filaments wound on the bobbin may be subjected to a washing and drying process, and then the dissociated aramid filaments may be treated with the crosslinking agent. Already dried aramid filaments are sufficiently crystallized, even if treated with a crosslinking agent, the effect of improving strength and elongation is insignificant, but it can improve the strength and elongation to some extent compared to aramid fibers without crosslinking agent treatment. It has an effect.

Also in this case, dianhydride or diacyl chloride may be used as the crosslinking agent, and the crosslinking agent is dissolved using water, an organic solvent or a mixed solvent thereof. It has a composition having a composition of 1 to 20% by weight and dipping the filament for a sufficient time to allow the crosslinking agent to penetrate into the filament into a solution maintained at a temperature higher than room temperature, or has a composition of the above concentration and room temperature A spray method may be applied in which the solution maintained at a higher temperature is sprayed onto the aramid filament.

Aramid filaments treated with a crosslinking agent undergo a drying process to induce a crosslinking reaction and remove moisture.

Optionally, products such as woven or knitted fabrics made using conventional aramid filaments can be treated with a crosslinking agent. At this time, the step of treating the crosslinking agent may be applied to the above-described dipping method or spray method, but is not necessarily limited thereto.

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 is not limited thereto.

Example  One

A mixed solution was prepared by dissolving 5.00 g of para-phenylenediamine in 100 ml of a polymerization solvent in which 7 wt% of CaCl _{2 was} added to N-methyl-2-pyrrolidone (NMP). Prepolymer was prepared by adding 3.18 g of terephthaloyl dichloride to the mixed solution and reacting at a rotational force of 500 rpm for 6 minutes. To this prepolymer, an additional 5.61 g of terephthaloyl dichloride was added and reacted for 15 minutes to prepare a poly (paraphenylene terephthal-amide: PPD-T) polymer, which was dissolved in 98% concentrated sulfuric acid solvent to form a spinning dope. (spinning dope) was prepared.

The spinning dope was spun using a spinneret and then coagulated in a coagulation bath through an air gap to obtain an aramid filament, which was washed with an alkaline solution.

In order to treat the washed aramid filaments with a crosslinking agent, 4,4 ′ oxydipsalic anhydride was used as a crosslinking agent, and the crosslinking agent was mixed with water and a N-methyl-2-pyrrolidone (NMP) mixed solvent (volume ratio 8: 2). The filament was dipped for 0.5 seconds in a solution having a composition having a composition of 5% by weight of the crosslinker prepared by dissolving in a) and maintained at a temperature of 50 ° C. Subsequently, the aramid filament treated with the crosslinking agent was dried at a temperature of 180 ° C. for 5 seconds and then wound in a bobbin to complete the aramid fiber.

Example 2

In treating the washed aramid filament with a crosslinking agent, an aramid fiber was prepared in the same manner as in Example 1 except that the spray method was applied rather than the dipping method.

Example 3

An aramid filament wound on the bobbin was obtained in the same manner as in Example 1 except that the step of treating the washed aramid filament with the crosslinking agent was omitted. Subsequently, after dissolving the aramid filament wound on the bobbin, the aramid filament was prepared by treating the dried aramid filament with a crosslinking agent and drying in the same manner as in Example 1.

Example 4

In treating the dissociated aramid filament with a crosslinking agent, an aramid fiber was prepared in the same manner as in Example 3 except that the spray method was applied instead of the dipping method.

Comparative example

Aramid fibers were prepared in the same manner as in Example 1, except that the step of treating the washed aramid with a crosslinking agent was omitted.

Inherent Viscosity (I.V.), strength, elongation, and roughness of each of the aramid fibers obtained by the above Examples and Comparative Examples were measured by the following method, and the results shown in Table 1 were obtained.

Inherent Viscosity (I.V.) Measurement of Aramid Fiber

Intrinsic viscosity (I.V.) was calculated by the following equation.

IV = ln (η _rel ) / C

Where C is the polymer concentration in sulfuric acid, and the relative viscosity η _rel is the ratio of the flow of the solution to the time of flow of the solvent, as measured by a capillary viscometer at 30 ° C.

Strength of aramid fibers (g / d) and Elongation (%) Measure

The strength of the sample was determined by measuring the strength (g) when the 25 cm long sample was broken in an Instron Engineering Corp. (Canton, Mass) and dividing it by the denier of the sample. At this time, the tensile speed was 300 mm / min, the ultra-load was fineness × 1 / 30g. The strength of the aramid fibers was determined by their average after testing five samples.

Roughness measurement of aramid fibers

Fiber roughness was measured using AFM (Atomic Force Microscopy), a surface roughness measuring device.

division Example 1 Example 2 Example 3 Example 4 Comparative example
Intrinsic Viscosity (I.V.) 8.5 8.3 7.9 7.6 5.5 Strength (g / d) 37 35 33 32 23 % Elongation 4.2 4.0 3.8 3.8 3.0 Roughness (㎛) 0.05 0.06 0.08 0.09 0.15

As can be seen from Examples 1 to 4 of the above table and Comparative Examples, Example 1, in which the washed aramid filaments were treated with a crosslinking agent using a dipping method, showed the highest intrinsic viscosity and the best strength and elongation.

Claims (8)

Preparing an aramid filament; And Method for producing aramid fibers comprising the step of treating the aramid filament with a crosslinking agent. The method of claim 1, wherein the preparing the aramid filaments, Preparing an aromatic polyamide polymer; Preparing a spin dope using the aromatic polyamide polymer; Spinning the spinning dope to obtain the aramid filament; And Method for producing aramid fibers comprising the step of washing the aramid filament. The method of claim 2, Drying the aramid filament treated with the crosslinking agent; And The method of claim 1, further comprising the step of winding the dried aramid filament (winding). The method of claim 1, Preparing the aramid filament is a method for producing aramid fiber, characterized in that comprising the step of unwinding the aramid filament wound in the bobbin. The method according to claim 2 or 4, The crosslinking agent treatment step is a method for producing aramid fibers, characterized in that carried out by a dipping (spray) method or a spray (spray) method. The method of claim 1, The crosslinking agent is a method of producing aramid fibers, characterized in that dihydride (dianhydride) or diacyl halide (diacyl halide). An aramid fiber produced by spinning an aromatic polyamide polymer produced by polymerization of an aromatic diamine and an aromatic dieside halide, wherein the aramid fiber has a strength of at least 30 g / d and an elongation of at least 3.8%. The method of claim 7, wherein The aramid fiber is characterized in that it has an intrinsic viscosity (I.V.) of 7.5 or more and a roughness of 0.1 μm or less.