KR101345071B1 - Aramid Fiber and Method for Manufacturing The Same - Google Patents

Abstract

The present invention relates to an aramid fiber having improved discoloration resistance and a method for producing the same so as to be less discolored even after exposure to an external environment such as sunlight, air, moisture, etc. for a long time, the aramid fiber manufacturing method of the present invention, aromatic polyamide Preparing a polymer; Measuring the molar ratio of the acid terminal to the amine terminal of the aromatic polyamide polymer; Classifying the aromatic polyamide polymer into a first aromatic polyamide polymer having a molar ratio of the acid terminal to the amine end of greater than 1.0 and a second aromatic polyamide polymer having a molar ratio of 1.0 or less; Preparing a dope using a dope polymer comprising the first and second aromatic polyamide polymers-the content of the first aromatic polyamide polymer of the dope polymer is greater than 50% by weight but less than 60% by weight Or less; And spinning the spinning dope.

Aramid, color change, amine end, acid end

Description

Technical Field The present invention relates to an aramid fiber,

The present invention relates to an aramid fiber and a method for manufacturing the same, and more particularly, to an aramid fiber having an improved discoloration resistance so as not to discolor even when exposed to external environment such as sunlight, air, moisture, etc. for a long time will be.

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 step of washing the filament, and drying and heat treatment .

The conventional aramid fibers prepared as described above are initially yellow, but have a problem of discoloration when exposed to external environments such as sunlight, air, and moisture for a long time. Such discoloration of aramid fibers is known not only to lower the customer attraction force of the aramid fibers alone, but also to impair the physical properties of the aramid fibers, in particular, the strength.

However, the cause of discoloration of aramid fibers has not been clearly identified to date, and thus there is no proposal for minimizing discoloration of aramid fibers.

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

The present invention is derived to solve the above problems, the advantage of the present invention is that the aramid fibers having improved discoloration resistance and its discoloration so that the discoloration does not become well even when exposed to external environment such as sunlight, air, moisture, etc. for a long time To provide a way.

Further features and advantages of the invention will be described hereinafter, and will in part be obvious from the description. Alternatively, other features and advantages of the invention may be learned through practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS The objects and other advantages of the present 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.

In order to achieve the above advantages, and in accordance with the object of the present invention, preparing an aromatic polyamide polymer; Measuring the molar ratio of the acid terminal to the amine terminal of the aromatic polyamide polymer; Classifying the aromatic polyamide polymer into a first aromatic polyamide polymer having a molar ratio of the acid terminal to the amine end of greater than 1.0 and a second aromatic polyamide polymer having a molar ratio of 1.0 or less; Preparing a dope using a dope polymer comprising the first and second aromatic polyamide polymers-the content of the first aromatic polyamide polymer of the dope polymer is greater than 50% by weight but less than 60% by weight Less than or equal to-; And it provides a method for producing aramid fibers comprising the step of spinning the spinning dope.

In another aspect of the present invention there is provided an aramid fiber comprising a polyamide polymer having amine and acid ends, wherein the molar ratio of the acid ends to the amine ends is greater than 1.0 but less than 1.9.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the invention as claimed.

According to the aramid fiber according to the present invention and a method for producing the same, the aramid fiber satisfies the strength required in the industry, that is, the intrinsic viscosity of the polyamide polymer, and its intrinsic color even when exposed to the external environment such as sunlight, air, moisture, etc. for a long time. Can be maintained. Therefore, it has an effect which can prevent the customer attraction force fall by the discoloration of aramid fiber.

The wholly aromatic polyamide polymer can be classified into three types according to the type of terminal group of the molecular chain. That is, the wholly aromatic polyamide polymer is classified as having amine end groups on both sides of the molecular chain, having amine end groups on one side and acidic end groups on the other side, and having acid end groups on both sides of the molecular chain. Can be. Typically, since the aromatic diamine and the aromatic dieside halide are reacted in a molar ratio of 1: 1 when preparing the aromatic polyamide polymer, the theoretical average molar ratio of the amine end groups and the acid end groups in the final polymerized wholly aromatic polyamide polymer is 1 Is 1:

A spinning dope is prepared by dissolving such an wholly aromatic polyamide polymer in sulfuric acid, and aramid fibers are produced by spinning, coagulation, washing with water, and drying the spinning dope. As mentioned above, aramid fibers are discolored under their influence from the external environment such as sunlight, air, moisture, etc. during use, and according to the present invention, the discoloration of such aramid fibers is significantly related to the end groups of the polyamide polymer. It turns out that there is. In other words, when the aramid fiber is exposed to the external environment, the amine group is more mutated than the acid group, and the amine group is found to be one of the important causes of discoloration of the aramid fiber.

Therefore, in order for the aromatic polyamide polymer contained in the aramid fibers to be stable even in the external environment, the acid end groups of the aromatic polyamide polymers must be excessive compared to the amine end groups. That is, according to the present invention, the aramid fiber comprises an aromatic polyamide polymer, wherein the molar ratio of the acid terminal to the amine end of the aromatic polyamide polymer is preferably greater than 1.0.

For this purpose, according to the invention, the molar ratio of the acid terminal to the amine terminal of the aromatic polyamide polymer is measured before dissolving the aromatic polyamide polymer in sulfuric acid. Based on this measurement result, an aromatic polyamide polymer is classified into a first aromatic polyamide polymer having a molar ratio of the acid terminal to an amine terminal exceeding 1.0 and a second aromatic polyamide polymer having a molar ratio of 1.0 or less. Subsequently, spinning dope is prepared by dissolving a dope polymer comprising the first and second aromatic polyamide polymers and having a content of the first aromatic polyamide polymer of more than 50 wt% but not more than 60 wt% in sulfuric acid.

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.

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 in order to increase the polymerization degree of the aromatic polyamide. Specific examples thereof include alkali metal halides such as CaCl ₂ , LiCl, NaCl, KCl, LiBr and KBr, or alkaline earth metal halides. The salts may be added alone or in the form of a mixture of two or more. As the addition amount of the inorganic salt increases, the degree of polymerization of the aromatic polyamide increases. However, since an inorganic salt which does not dissolve when the inorganic salt is added in an excessive amount may be present, the inorganic salt may be present in an amount of 10% . Since the inorganic salt has poor solubility in organic solvents, the final polymerization solvent may be prepared by completely dissolving the inorganic salt 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, the present invention is not 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 diacid halide include terephthaloyl dichloride, 4,4'-benzoyl dichloride, 2,6-naphthalene dicarboxylic acid dichloride and 1,5-naphthalene dicarboxylic acid dichloride, But is not limited thereto.

Polymerization of an aromatic diamine and an aromatic diacid halide proceeds at a rapid rate with the exothermic reaction. When the polymerization rate is increased as described above, there arises a problem that the difference in degree of polymerization between the finally obtained polymers increases. 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 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 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. 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).

According to the present invention, the amount of the aromatic dieside halide added during the final polymerization is preferably determined to be larger than the mole of the aromatic diamine when added to the amount added during the prepolymerization.

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

Since the aromatic polyamide polymer obtained through the polymerization reaction exists in powder form, the fluidity 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, when making an aromatic polyamide polymer slurry, the neutralization process can also be performed simultaneously by using water which melt | dissolved the alkali compound.

The inorganic alkaline compound may be at least one selected from the group consisting of alkaline metals such as NaOH, Li ₂ CO ₃ , CaCO ₃ , LiH, CaH ₂ , LiOH, Ca (OH) ₂ , Li ₂ O or CaO, carbonates of alkaline earth metals, hydrides of alkaline earth metals, Hydroxide, or an oxide of an alkaline earth metal.

When an inorganic alkaline compound is added to a strong acidic aromatic polyamide solution containing a large amount of hydrochloric acid, it quickly reacts with hydrochloric acid to rapidly neutralize. However, once the neutralization proceeds considerably and the pH approaches 7, The reaction rate is rapidly decreased and the inorganic alkaline compound is left in the neutralized solution in an unreacted state, which causes the problem that the insoluble inorganic alkaline compound must be filtered with the filter after 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. 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 process is dewatered, and then the aromatic polyamide polymer is manufactured through a drying process. Thereafter, a classification process may be performed to classify the aromatic polyamide polymers by size for the spinning process.

Subsequently, the molar ratio of the acid terminal to the amine terminal of the aromatic polyamide polymer prepared as described above is measured. Illustrating the molar ratio measurement method, i) 10 mg of an aromatic polyamide polymer sample was placed in an NMR tube and vacuum dried at about 60 ° C. for 4 hours to remove moisture, and ii) 0.5 ml of D ₂ SO ₄ was placed in the tube. Dissolve the sample at room temperature. iii) Subsequently, add 3 drops of TMS as reference material and measure 1 H-NMR at room temperature. iv) As a result, the area of the peak appearing at 7.5 ppm is calculated as the mole value of the amine terminus, and the area of the peak appearing at 7.9 ppm is calculated as the mole value of the acid terminus, whereby the acid terminal to the amine terminus of the aromatic polyamide polymer is Find the molar ratio of.

Based on this measurement result, an aromatic polyamide polymer is classified into a first aromatic polyamide polymer having a molar ratio of the acid terminal to an amine terminal exceeding 1.0 and a second aromatic polyamide polymer having a molar ratio of 1.0 or less.

Subsequently, a dope polymer including the first and second aromatic polyamide polymers was prepared so that the content of the first aromatic polyamide polymer was greater than 50% by weight but less than 60% by weight, and then a concentration of 97 to 102% was used. It is dissolved in a concentrated sulfuric acid solvent having a spinning dope (spinning dope) is prepared. 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 with sulfuric acid to water, ethylene glycol, glycerol, alcohol, or a mixture thereof, and is maintained at -20 to + 90 ° C. 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.

Subsequently, the 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. 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. For example, the filament containing sulfuric acid may be first washed with an aqueous caustic solution of 0.3 to 1.3%, and then a 0.01 to 0.1% dilute caustic aqueous solution The second wash can be done.

Then, a drying process is performed to adjust the moisture content remaining in the filament. The drying process may control the time for which the filament is in contact with the heated drying roll, or the moisture content of the filament by adjusting the temperature of the drying roll. 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.

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 1

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. A poly (paraphenylene terephthal-amide: PPD-T) polymer was prepared by further adding 5.61 g of terephthaloyl dichloride to the prepolymer thus prepared and reacting for 15 minutes. The molar ratio of the acid terminal to the amine terminal of the PPD-T polymer thus prepared was measured by the following method.

10 mg of PPD-T polymer sample was placed in an NMR tube to remove moisture by vacuum drying at about 60 ° C. for 4 hours, and 0.5 ml of D ₂ SO ₄ was added to the tube to dissolve the sample at room temperature. Subsequently, 3 drops of TMS was added as a reference material and 1 H-NMR was measured at room temperature. As a result, the molar ratio of the acid terminal to the amine terminal of the PPD-T polymer was calculated by calculating the area of the peak at 7.5 ppm by the mole value of the amine terminus and the area of the peak at 7.9 ppm by the mole value of the acid terminus. It was.

Based on this measurement result, the aromatic polyamide polymer was classified into a first polymer having a molar ratio of the acid terminal to an amine terminal exceeding 1.0 and a second polymer having a molar ratio of 1.0 or less.

Subsequently, a spinning dope was prepared by preparing a dope polymer including the first polymer and the second polymer but having a content of 60 wt% of the first polymer, and then dissolving it in 98% concentrated 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. Aramid fibers were prepared by washing the filaments with water and drying and winding them up with a winder.

Examples 2 to 4 and Comparative Examples 1 and 2

Doping polymers were prepared in the same manner as in Example 1, except that the content of the first polymer having a molar ratio of the acid terminal to the amine terminal exceeding 1.0 was as shown in Table 1 below. Using the same method as in Example 1 to prepare aramid fibers, respectively.

[Table 1]

Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Of the first polymer
Content (% by weight) 57 54 51 48 63

The molar ratio and intrinsic viscosity (Inherent Viscosity (IV)) of the acid terminal to the amine end of the dope polymer obtained by the above examples and comparative examples, the lowering of the intrinsic viscosity in the production of spinning dope, and the strength of the aramid fiber As a result of the measurement, the results shown in Table 2 were obtained.

Inherent Viscosity (I.V.) Determination of Doping Polymers

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

IV = ln (η _rel ) / C

Where C is the concentration of the polymer solution (solution in which 0.5 g of the polymer is dissolved in 100 ml of 98% concentrated sulfuric acid solvent), and the relative viscosity η _rel is the flow time ratio between the polymer solution and the solvent measured by a capillary viscometer at 30 ° C.

Color Change Measurement of Aramid Fiber

The color of the aramid fiber is defined as L value measured using KURABO's COLOR-7X, and “color change” refers to the aramid fiber whose initial color is L1, Black Panel Temperature (65 + 3 ° C), Exposure Light Source (Xenon). -Arc), Irradiance (0.35W / m ² @ 340nm), Exposure Cycle (102min of Light only / 18min Light and Water Spray) under the conditions of 24h when the color change occurs when △ L, Calculated as

% Change in color (L value) of aramid fibers = (ΔL / L1) × 100

Strength measurement of aramid fiber

The strength of the sample was determined by measuring the strength (g) when a 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 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 2]

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Molar ratio of the acid terminal to the amine terminal of the dope polymer 1.6 1.4 1.2 1.1 0.9 1.9 Dope polymer
Intrinsic Viscosity (IV) 5.6 6.0 6.1 6.2 6.2 5.4 Color (L value) change (%) of aramid fibers 5 7 7 8 11 4 Of aramid fiber
Strength (g / d) 22 22 23 23 23 20

As can be seen from Examples 1 to 4 and Comparative Example 1 of Table 2, aramid using a dope polymer having a content of the first polymer whose molar ratio of the acid terminal to the amine terminal is greater than 1.0 exceeds 50% by weight. When the fibers were prepared, the color change of the aramid fibers was found to decrease dramatically.

However, as can be seen from Comparative Example 2 of Table 2, the dope polymer having a content of the first polymer of more than 60% by weight has a problem that the intrinsic viscosity falls below 5.5, aramid made of such a dope polymer It can be seen that the fiber does not have the strength of 22 g / d required in the industry and its commerciality is remarkably inferior. That is, when the molar ratio of the acid terminal to the amine terminal is 1.9 or more, the problem of the strength of the aramid fibers is significantly lowered.

Claims (5)

Preparing an aromatic polyamide polymer; Measuring the molar ratio of acid end to amine end of the aromatic polyamide polymer; Classifying the aromatic polyamide polymer into a first aromatic polyamide polymer having a molar ratio of the acid terminal to the amine end of greater than 1.0 and a second aromatic polyamide polymer having a molar ratio of 1.0 or less; Preparing a dope using a dope polymer comprising the first and second aromatic polyamide polymers-the content of the first aromatic polyamide polymer of the dope polymer is greater than 50% by weight but less than 60% by weight Or less; And Method for producing aramid fibers comprising the step of spinning the spinning dope. The method of claim 1, The molar ratio of the acid terminal to the amine terminal is measured using NMR. The method of claim 1, Preparing the aromatic polyamide polymer, Dissolving an aromatic diamine in a polymerization solvent to prepare a mixed solution; Preparing a prepolymer by adding an aromatic dieside halide to the mixed solution; And A method for producing aramid fibers comprising the step of further adding an aromatic dieside halide to the prepolymer. The method of claim 3, wherein The sum of the moles of the aromatic dieside halide added to the mixed solution and the moles of the aromatic dieside halide added further to the prepolymer to prepare the prepolymer is greater than the mole of the aromatic diamine. A method for producing aramid fibers, characterized in that. delete