KR102257811B1 - Aramid fiber with excellent light resistance and preparation method thereof - Google Patents

Abstract

The present invention relates to an aramid fiber having excellent light resistance and a method for manufacturing the same, wherein the method comprises: a step of preparing a polyimide precursor solution in which carbon black is dispersed; a step of coating a p-aramid fiber by impregnating the same with the polyimide precursor solution in which the carbon black is dispersed; and a step of heat-treating the p-aramid fiber coated with the polyimide precursor solution in which the carbon black is dispersed for imidization, thereby being able to manufacture the aramid fiber excellent in heat resistance and light resistance.

Description

Aramid fiber with excellent light resistance and preparation method thereof

The present invention relates to an aramid fiber excellent in light resistance and a method for producing the same.

Aromatic polyimide (PI) containing a benzene ring has high strength and excellent dimensional stability, insulation, weather resistance, and low thermal expansion properties. However, due to insolubility, processing and molding are difficult, and even if there is a technology for spinning high-strength fibers using PI, there have been limitations in that mass production is difficult.

On the other hand, aramid is generally distinguished from nylon of aliphatic polyamide, and is classified into meta (m)-aramid and para (p)-aramid depending on the position where the amide group (CO-NH) is bonded to the aromatic ring. Among them, p-aramid is structurally high in crystallinity and excellent in orientation, which is advantageous in forming an intermolecular attraction, so it is used in materials that require high strength, such as body armor.

However, since light corrosion and intensity decrease due to sunlight occurs, its use for outdoor use is limited due to poor light resistance and weather resistance.

Therefore, there is a need for a study on the production of p-aramid fibers with excellent light resistance and weather resistance properties using p-aramid.

1. Korean Patent Application Publication No. 10-2009-0040577 (published on April 27, 2009)

It is an object of the present invention to provide an aramid fiber having excellent mechanical properties and a method for producing the same without the effect of photocorrosion and photolysis even in UV light by coating a polyimide in which carbon black is dispersed on a p-aramid fiber.

In order to achieve the above object, the present invention comprises the steps of preparing a polyimide precursor solution in which carbon black is dispersed; coating p-aramid fibers by impregnating them with a polyimide precursor solution in which the carbon black is dispersed; And imidizing p-aramid fibers coated with a polyimide precursor solution in which the carbon black is dispersed by heat treatment. It provides a method for producing an aramid fiber excellent in light resistance comprising a.

In addition, the present invention provides an aramid fiber having excellent light resistance prepared according to the above manufacturing method.

The aramid fibers prepared according to the present invention are coated on the surface of p-aramid fibers by dispersing carbon black in polyamic acid, and thermally imidized at a high temperature to achieve heat resistance of polyimide, high strength properties of p-aramid, and carbon black. The light resistance due to can be expressed at the same time.

In particular, when carbon black is dispersed in an amount of 1% based on the weight of polyamic acid and coated on p-aramid fiber, the UV (ultraviolet) transmittance is less than 0.1%, and the photolysis effect is less than 3% even under UV (ultraviolet) for more than 140 hours. Can represent.

1 is a view showing the preparation of a polyamic acid (PAA) precursor solution in which 1% carbon black is dispersed according to an embodiment of the present invention.
2 is a view showing the production of p-aramid fibers and films coated with polyimide in which carbon black is dispersed according to an embodiment of the present invention.
3 is a diagram showing an FT-IR analysis of imidization of a polyimide film according to temperature.
4 is a view showing UV/Vis spectroscopy analysis of a polyimide film according to carbon black content.
5 is a view showing thermal properties analysis of p-aramid fibers, polyimide-coated p-aramid fibers, and polyimide-coated p-aramid fibers in which 1% carbon black is dispersed.
6 is a view showing the tensile strength characteristics analysis of p-aramid fibers, polyimide-coated p-aramid fibers, and polyimide-coated p-aramid fibers in which 1% carbon black is dispersed before and after UV irradiation.

Hereinafter, the present invention will be described in detail.

The present inventors disperse carbon black in polyamic acid to coat the surface of p-aramid fiber, and thermally imidize it at high temperature, so that the aramid has excellent heat resistance characteristics of polyimide, high strength characteristics of p-aramid, and light resistance characteristics due to carbon black. Fibers could be produced, and in particular, when carbon black was dispersed in an amount of 1% based on the weight of polyamic acid and coated on p-aramid fibers, the UV (ultraviolet) transmittance was 0.1% or less, and under UV (ultraviolet) for more than 140 hours. The present invention was completed by finding that it can exhibit a photolysis effect of less than 3%.

The present invention comprises the steps of preparing a polyimide precursor solution in which carbon black is dispersed; coating p-aramid fibers by impregnating them with a polyimide precursor solution in which the carbon black is dispersed; And imidizing p-aramid fibers coated with a polyimide precursor solution in which the carbon black is dispersed by heat treatment. It provides a method for producing an aramid fiber excellent in light resistance comprising a.

At this time, the polyimide precursor solution is obtained by dissolving a polyamic acid (PAA) polyimide precursor in a dimethylformamide (DMF) solvent, and the carbon black is dispersed in an amount of 0.25 to 2% based on the weight of the polyimide precursor. It is characterized in that, and preferably, carbon black may be dispersed in an amount of 1% based on the weight of the polyimide precursor, but is not limited thereto.

In addition, the heat treatment is imidized by performing at a temperature of 200 to 400° C. for 30 to 60 minutes, and may be imidized by performing at a temperature of 250° C. for 60 minutes, but is not limited thereto.

In addition, prior to the imidization heat treatment, the stabilization and solvent evaporation process may be further performed at a temperature of 50 to 100° C. for 20 to 40 minutes, and a stabilization and solvent evaporation process may be performed by performing the stabilization and solvent evaporation process at a temperature of 80° C. for 30 minutes. It can be, but is not limited thereto.

At this time, out of the above conditions, the aramid fiber having excellent thermal and light resistance properties according to the present invention is not formed properly, and thus a problem that cannot be used for outdoor fabrics or fibers that require light resistance and weather resistance may be caused.

In addition, the present invention provides an aramid fiber prepared according to the method for producing an aramid fiber excellent in light resistance.

At this time, the aramid fiber has a UV (ultraviolet) transmittance of 0.1% or less, and is characterized by showing less than 3% photolysis even under UV (ultraviolet) of 140 hours or more.

In the present invention, carbon black is dispersed in polyamic acid, coated on the surface of p-aramid, and thermally imidized at high temperature to simultaneously express the heat resistance of polyimide, high strength of p-aramid, and light resistance due to carbon black. An experiment was conducted on the coating yarn. p-aramid was impregnated in a polyamic acid solution in which 1%, 0.5%, and 0.25% of carbon black were dispersed, and padded with a mangle roller under conditions of a pickup rate of 23-25%, and then stabilized at 80° C., 250 Thermal imidization was performed at a high temperature of °C. Subsequently, an infrared spectrometer (FT-IR) was used to check the degree of imidation of the film according to the set condition value, and the light transmittance of the PI film in which carbon black was dispersed was measured by a UV-VIS spectrophotometer (Aglient, Cary). 5000) was used in the wavelength range of 200-800 nm. In addition, it was analyzed with a thermal gravimetric analyzer (TGA) to confirm the heat resistance of the coating yarn coated with polyimide in which carbon black was dispersed. In order to perform a test on the light resistance characteristics of the coating yarn due to the dispersed carbon black, UV treatment was performed for 144 hours, and then tensile strength measurement was performed.

Hereinafter, the present invention will be described in more detail through examples. These examples are only for describing the present invention in more detail, and that the scope of the present invention is not limited by these examples according to the gist of the present invention, to those of ordinary skill in the art to which the present invention pertains. It will be self-evident.

<Experimental material>

p - aramid (p -aramid) fibers were purchased from DuPont (Dupont) as 600De. Dimethylformamide (DMF) was purchased from Duksan, and polyamic acid (PAA) (solid content 18.75%), a precursor of polyimide (PI), was SKCKOLON PI varnish PMDA-ODA (Gumi, Gumi, Korea). I bought it in Korea).

Carbon Black, used for UV protection, was purchased from UL SCIENCE (Korea), and the thickness of the manufactured coating company is 805De.

< Example 1> Aramid Textile manufacturing

1-1. PAA And PAA /Carbon Black Blending Solution preparation

Solution A containing PAA and Solution B containing carbon black were prepared in order to prepare a coating solution having a viscosity suitable for the film and coating of the PI precursor.

Specifically, in order to prepare a PAA solution in which 1%, 0.5%, and 0.25% content of carbon black is dispersed, first, 25 g of DMF was added to 50 g of PAA to prepare a solution A having a lower viscosity, and then 1%, 0.5%, Solution B was prepared by adding 50g, 25g, and 12.5g of DMF to 0.5g, 0.25g, and 0.125g of carbon black corresponding to 0.25%, and then treatment three times for 15 minutes using an ultrasonic disperser (Sonicator).

Thereafter, the solution A and the solution B were mixed for 30 minutes using an ultrasonic disperser (Sonicator) to prepare a low viscosity PAA/Carbon black blending solution.

Thereafter, the air bubbles were removed by standing at 40° C. for 4 hours, and DMF was evaporated for 2 hours until the solution in a low viscosity state reached a viscosity suitable for film production and coating at 130° C. (FIG. 1).

1-2. PI, PI/Carbon Black Coating yarn And film manufacturing

The PAA solution and PAA/Carbon black solution prepared above were cast into a 10 mm film by a film maker, and the coating company impregnated the solution with p- aramid yarn in the PAA solution and PAA/Carbon black solution, respectively, to obtain a mangle roller. ) Under the conditions of 23-25% pickup rate, the PI was stabilized and the solvent evaporated at 80° C. for 30 minutes to prevent deformation of the film due to the condensation reaction. Then, it was prepared by performing heat treatment at a high temperature of 80 to 350° C. for 1 hour to perform imidization of PI (FIG. 2).

< Experimental example 1> PI film Imidization analysis

To determine the imidation of the polyamic acid in which carbon black was dispersed, the change in the functional group was measured through FT-IR.

The reaction of the chemical structural formula according to the imidization of the polyamic acid by heat treatment at 80-350° C. for 1 hour is shown in FIG. 3 and Table 1 below.

As a result, it was confirmed that the C=O stretching bond (1720cm ^-1 ) was shown at a high temperature of 250° C. or higher, and that the CNC bond (1377cm ^-1 ) appeared clearly and was imidized.

Therefore, the heat treatment conditions for imidization were fixed at 250°C.

division 80℃ 120℃ 160℃ 200℃ 250℃ 350℃ 1720 cm ^-One 64.57 61.41 48.85 45.63 37.29 37.13 1377 cm ^-One 58.68 57.23 48.33 46.72 41.51 41.36

< Experimental example 2> UV transmittance of PI film in which PI and Carbon black are dispersed

In order to find out the UV transmittance of the PI film according to the content of the dispersed carbon black, the transmittance was confirmed in the region of 600 nm to 800 nm through a UV/Vis spectrophotometer (FIG. 4, Table 2). The PI film in which the carbon black was not dispersed (FIG. 4(a)) showed a light transmittance of about 86-87%, but decreased as the content of carbon black increased. In particular, it was confirmed that the light transmittance hardly appeared in the PI film made of 1% dispersed carbon black.

division (a) (b) (c) (d) 600nm 86.2% 26.1% 21.7% 0.019% 700nm 87.6% 27.9% 23.4% 0.038% 800nm 87.8% 28.7% 24.2% 0.042%

< Experimental example 3> PI/ with carbon black dispersed p - aramid Coating Heat resistance properties

In order to measure the thermal decomposition temperature of the polyimide (PI) p -aramid coated yarn in which carbon black is dispersed, TG-DTA (SDT Q600, TA Instruments, USA) was used to set up to 800 °C at a rate of 10 °C/min in a nitrogen atmosphere. .

As a result, as shown in FIG. 5 and Table 3 below, the general p- Aramid yarn (control) starts pyrolysis at a relatively low temperature, and the PI-coated p- Aramid yarn is pyrolyzed at a higher about 530-550°C. I could confirm that.

In particular, p- Aramid yarn coated with PI in which 1% of carbon black was dispersed showed the highest temperature at 575.36°C at a weight loss of 10%, which is the initial thermal decomposition temperature of the coating company when carbon black coated on the surface of p-aramid fiber It is confirmed that it affected

division Control
( p - Aramid ) PI coated fiber PI coated fiber with Carbon black(1%) T _d (℃)
(5% weight loss) 492.13℃ 536.21℃ 549.89℃ T _d (℃)
(10% weight loss) 545.33℃ 553.69℃ 575.36℃

< Experimental example 4> PI/ in which carbon black is dispersed p - aramid Coating Light resistance characteristic

After exposing the PI/p- aramid coated yarn in which the prepared carbon black was dispersed to UV for 144 hours, a tensile strength experiment was conducted to determine the degree of photolysis, and PI according to the carbon black content in FIG. 6 and Table 4 below. It showed the mechanical properties before and after UV exposure of the coating company.

Existing p- aramid yarn when exposed to UV for 144 hours in the (control) the tensile strength decreased from 21.44 gf / denier to 18.13 gf / denier and showed a decreasing rate of about 15.44%, the p- aramid yarn was coated with PI When exposed to UV, it decreased from 16.17 gf/denier to 9.31 gf/denier, showing a higher reduction rate than the existing p-aramid yarn of about 42.42%. However, it was confirmed that the reduction rate due to photolysis of the coating company gradually decreased as the content of the dispersed carbon black increased.In particular, the p- aramid company coated with the final 1% content of carbon black decreased from 13.81 gf/denier to 13.49 gf/denier. It showed a relatively very low reduction rate of 2.31%, and the highest light resistance was confirmed in the 1% content of carbon black.

division p-Aramid
(control) PI coating PI+CB
(0.25%) PI+CB
(0.5%) PI+CB
(One%) Before UV treatment 21.44 (g/d) 16.17(g/d) 15.71(g/d) 14.26(g/d) 13.81(g/d) After UV treatment 18.13(g/d) 9.31(g/d) 9.33(g/d) 11.84(g/d) 13.49 (g/d) Reduction rate 15.44% 42.42% 40.61% 16.97% 2.31%

Claims (7)

Preparing a polyimide precursor solution in which carbon black is dispersed;
coating p-aramid fibers by impregnating them with a polyimide precursor solution in which the carbon black is dispersed; And
Imidizing p-aramid fibers coated with the polyimide precursor solution in which the carbon black is dispersed by heat treatment at a temperature of 250° C. for 60 minutes; Including,
The polyimide precursor solution dissolves a polyamic acid (PAA) polyimide precursor in a dimethylformamide (DMF) solvent,
The carbon black is dispersed in an amount of 1% based on the weight of the polyimide precursor,
A method for producing aramid fiber having excellent light resistance, characterized in that the transmittance is 0.1% or less at a wavelength of 500 to 800 nm and less than 3% photolysis even under UV (ultraviolet) for 140 hours or more. delete delete delete The method of claim 1,
A method for producing aramid fiber having excellent light resistance, characterized in that the stabilization and solvent evaporation process are further performed for 20 to 40 minutes at a temperature of 50 to 100° C. before the imidization heat treatment. delete delete

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