KR20150079150A - Preparation method of Electrically-Conductive aramid film - Google Patents

Abstract

The present invention relates to a conductive aramid film, which has an improved thermal stability and an improved mechanical strength by using a raw sheet manufactured by mixing meta-aramid fibrid with flock and forming a meta-aramid/carbon nanotube layer which is electrospun on both surfaces of the manufactured raw sheet, so the film has a multilayered structure, thereby enabling the conductive aramid film to have good conductivity, and a manufacturing method thereof.

Description

Preparation method of Electrically-Conductive aramid film [0002]

The present invention relates to an aramid film which has high heat resistance and mechanical strength and exhibits electric conductivity and a method for producing the same.

The polyamide-based synthetic resin is classified into an aliphatic polyamide and an aromatic polyamide, an aliphatic polyamide is a trade name of nylon, and an aromatic polyamide is a trade name of aramid.

Aramid is well known for its trade names Nomex and Kevlar and has been developed to improve the heat resistance of nylon. It has excellent heat resistance and high tensile strength and is used for textile such as flame retardant textile fabric and tire cord. In addition, it is used in various applications in high-tech industries such as aerospace field, but it has a disadvantage of low electric conductivity.

Korean Patent Laid-Open Publication No. 2013-0076391 discloses that a methaarimide film having excellent mechanical strength is produced by preparing a raw material of meta-aramid and forming a meta-aramid layer on both sides of the raw paper. However, such a film has excellent mechanical strength It is not easy to apply to a display product or the like due to lack of electric conductivity.

Korean Patent Laid-Open Publication No. 2013-0001021 discloses a composite material having superior thermal stability and electrical conductivity than a meta-aramid single polymer by preparing a meta-aramid / carbon nanotube nanocomposite by mixing carbon nanotubes with meta-aramid. The same complex has a disadvantage in that the mechanical strength is lower than that of the meta-aramid single polymer.

The object of the present invention is to provide a method for producing a film based on a meta-aramid / carbon nanotube which exhibits excellent thermal stability, electrical conductivity and mechanical strength.

In order to accomplish the above object, the present invention provides a method for producing a paper composition, comprising: mixing meta-aramid fibrids and flocs at a ratio of 1: 9 to 3: 7 and adding a solvent; Forming a microporous structure on the paper by removing the solvent after preparing the paper with the ground composition; Mixing 0.01 to 5 parts by weight of carbon nanotubes with 100 parts by weight of the meta-aramid polymer in a solvent to prepare a spinning liquid; Forming a surface layer and a back layer based on aramid / carbon nanotubes by electrospinning the spinning solution on both sides of the raw paper; And a step of car-rendering the film. The present invention also provides a method for producing a conductive aramid film.

According to an embodiment of the present invention, any one of Ag, Au, ZnO, and SnO ₂ may be deposited on the surface of the raw paper prior to spinning the spinning solution on the raw paper.

According to another embodiment of the present invention, a magnetic field may be applied to the spinning solution for electrospinning to align the carbon nanotubes in the vertical direction of the raw paper.

According to another embodiment of the present invention, the thicknesses of the surface layer and the backside layer may be the same or different from each other, and may independently be 1 to 30 times the original thickness.

According to another embodiment of the present invention, the solvent may be at least one member selected from the group consisting of methyl acetamide, dimethyl formamide, N-methyl-2-pyrrolidone, dimethylsulfoxide,

The freeness of the fibrids may be 100 ml or less,

The meta-aramid polymer may be one prepared by polymerizing metaphenylenediamine and isophthaloyl chloride,

The knife rendering can be performed at 270-290 < 0 > C.

According to another embodiment of the present invention, the electrospinning method is characterized in that the spinning temperature is 25 to 100 占 폚, the distance between the nozzle of the electrospinning apparatus and the base paper is in the range of 4 to 10 cm, the radiation voltage is in the range of 10 to 20 kV And the spray solution is discharged to form a meta-aramid / carbon nanotube composite layer on both sides of the paper.

The conductive aramid film according to the present invention can be produced by preparing a raw paper in which meta-aramid fibrids and floc are mixed and forming a layer of electrospun meta-aramid / carbon nanotubes on both sides of the raw paper to produce a film having a multi- Improved stability and mechanical strength, and exhibited excellent electrical conductivity. The conductive aramid film according to the present invention can be manufactured by depositing metallic particles or metal oxides as a conductive material on a porous structure formed on a surface and a surface of raw paper and then applying a magnetic field during electrospinning of the spinning solution, The resulting amide / carbon nanotube coating layer can maximize electrical conductivity.

1 is a cross-sectional view of a conductive aramid film in which a metha-aramid / carbon nanotube layer is formed on both sides of a raw paper according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a conductive aramid film in which a metal or metal oxide is deposited on a surface of raw paper according to an embodiment of the present invention, and then a meta-aramid / carbon nanotube layer is formed.

Hereinafter, the present invention will be described in more detail.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted so as to avoid obscuring the subject matter of the present invention.

The present invention relates to a method for producing a floc composition, comprising mixing meta-aramid fibrids and flocs at a ratio of 1: 9 to 3: 7 and adding a solvent to produce a ground composition; Forming a microporous structure on the paper by removing the solvent after preparing the paper with the ground composition; Mixing 0.01 to 5 parts by weight of carbon nanotubes with 100 parts by weight of the meta-aramid polymer in an organic solvent to prepare a spinning liquid; Forming a surface layer and a backside layer based on meta-aramid / carbon nanotubes by electrospinning the spinning solution on both sides of the base paper; And a step of car-rendering the film. The present invention also provides a method for producing a conductive aramid film.

FIG. 1 is a cross-sectional view of a film produced by a method according to an embodiment of the present invention. Referring to FIG. 1, a meta-aramid green sheet 100 and a meta-aramid / carbon nanotube composite layer 200 formed on top and bottom of the green sheet . Hereinafter, the methacrylamide / carbon nanotube composite layer formed on the base paper is referred to as a surface layer 210, and the methacrylamide / carbon nanotube composite layer formed below the base paper is referred to as a backside layer 220 do.

Conventionally, composites composed only of meta-aramid and carbon nanotubes are effective for the production of fibers exhibiting conductivity by improving conductivity, but lack strength to produce films. In the present invention, a raw paper is prepared by mixing meta-aramid fibrids and floc, and both sides of the raw paper are coated with an aramid / carbon nanotube composite layer to produce a film having improved strength.

According to the present invention, a metal or a metal oxide, which is a conductive material, can be deposited on the surface of the raw paper before the spinning solution is electrospun. The metal or metal oxide may be Ag, Au, ZnO and SnO ₂ , And a film produced by applying the metal or metal oxide is shown in FIG.

The metal or metal oxide thin film layer may have a thickness of 1 to 100 mu m.

The raw paper is composed of fibrids and flocs, which causes a problem of deteriorating electrical conductivity. Therefore, in the present invention, a metal or a metal oxide, which is a conductive material, is deposited on the microstructure formed on the surface and inside of the raw paper by chemical vapor deposition, thereby solving the low electrical conductivity problem of the raw paper.

Further, in forming the aramid / carbon nanotube composite layer on the raw paper, the carbon nanotubes are aligned in a direction perpendicular to the paper to facilitate the movement of electrons, thereby further improving the electrical conductivity. In order to align the carbon nanotubes in a direction perpendicular to the paper, an electrospinning method was used. At this time, a magnetic field was applied to the spinning solution to form an aramid / carbon nanotube composite layer in which carbon nanotubes were arranged in a direction perpendicular to the paper there was.

Such a structure is preferable because it can hybridize with the metal or metal oxide structure deposited on the paper to improve the electrical conductivity.

The term " meta-aramid fibrids " in the present invention means film-like finely divided aramid polymers having length and width equal to or different from each other, independently from 100 to 1000 mu m, and thickness from 0.1 to 1 mu m, 2 to 25 mm and an aramid fiber having a diameter of 5 to 15 탆. If the length and diameter of the floc are less than the above range, the strength of the paper is lowered. If the length and diameter of the flock are more than the above range, it is difficult to form a uniform web by the wet method.

In the production of the raw paper, the ratio of fibrids to flocs may be from 1: 9 to 3: 7. When the ratio of the fibrids is increased, the strength is lowered. When the ratio of the flock is increased, the strength may be increased. However, when the meta-aramid / carbon nanotube composite is formed by electrospinning, It is not easy to align the nanotubes in the vertical direction to the raw paper, and there is a problem that the electrical conductivity may be deteriorated.

In the present invention, the thicknesses of the surface layer and the backside layer may be equal to or different from each other, and may independently be 1 to 30 times the thickness of the base paper. If the thickness of the base paper is thicker than the thickness of the surface layer and the backside layer, An aramid film having low conductivity can be produced due to conductivity. If the thickness of the surface layer and the backside layer exceeds 30 times the original thickness, the strength of the film is lowered, which is undesirable.

In the present invention, the freeness of the fibrids is 100 ml or less. If the freeness of the fibrids is low, the dehydration of the solvent during the production of the paper is lowered, and the solvent may block the microvoids of the paper. It is difficult to expect a film having improved electrical conductivity by interfering with the deposition of metal or metal oxide into the microporous structure of the paper.

In the present invention, a fibrid composition is prepared by dissolving the fibrids in the freeness range and mixing them with flocs and dissolving them in a solvent. The solvent may be selected from the group consisting of dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone (NMP), dimethylsulfoxide and water, preferably water. The concentration of the fibrids and the floc mixture dissolved in the solvent was preferably diluted to a concentration of 0.5 to 2% to prepare a raw paper.

The content of the carbon nanotubes of the meta-aramid / carbon nanotube composite is preferably 0.1 to 5% by weight based on the total weight of the composite. When the content of the carbon nanotubes is less than the above range, it is difficult to expect improvement of the conductivity of the composite. When the carbon nanotubes are in the above range, the dispersibility of the carbon nanotubes is inhibited and the dispersed carbon nanotubes can be re- , The transmittance may be deteriorated.

The carbon nanotube may be a single-walled carbon nanotube or a multi-walled carbon nanotube.

In the production of the meta-aramid / carbon nanotube composite, the mixing of the meta-aramid and the carbon nanotubes is preferably performed by a solvent mixture, and the carbon nanotubes can be dispersed by ultrasonic treatment or stirring.

In the present invention, the solvent may be any one selected from the group consisting of dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, dimethylsulfoxide and water,

When the solvent is mixed, a salt such as lithium chloride (LiCl) or calcium chloride (CaCl ₂ ) may be added in an amount of 1 to 10.0 wt% based on the weight of the total solution. The addition of the salt improves the solubility of the meta-aramid, Can be improved. When the content of the calcium chloride is less than the above range, there is a problem that the increase of the solid content becomes insignificant and it becomes unsuitable for the electrospinning. On the other hand, when the content exceeds the above range, the workability is deteriorated due to the corrosiveness of the salt, Can be.

Electrospinning is a modification of the electrostatic spray process in which fine filaments are released from the surface of a droplet when a high voltage is applied to a droplet suspended at the capillary end due to surface tension. When the polymer solution or melt is given an electrostatic amount, . Therefore, in order to induce an electrostatic force in the polymer solution, it is necessary to include a salt in order to have electrical characteristics in the polymer solution that has been spun.

The electrospinning step may be electrospinning at a spinning temperature of 25 to 100 DEG C, a viscosity of 50 to 500 poise, a spinning distance of 4 to 10 cm and a spinning voltage of 10 to 20 kV.

The above-mentioned spinning conditions allow optimal electrospinning during electrospinning using a spinning solution containing 10 to 20% by weight of meta-aramid / carbon nanotubes and 1 to 10% by weight of salt.

When the spinning temperature is lower than 25 ° C, the solution viscosity is too high, so that a high voltage is required for spinning, and the amount of spinning relative to the amount of spinning is reduced so that Taylor cone becomes large, There is a problem that the viscosity of the solution in the spinning solution is evaporated. In contrast, when the temperature exceeds 100 ° C, there is a problem that the viscosity of the solution changes as the water present in the spinning solution evaporates, making it difficult to ensure uniform radioactivity.

If the viscosity of the spinning solution is less than 20 poise, the viscosity of the composite nanofiber may be too low to lower the strength of the composite nanofibers produced. If the viscosity exceeds 500 poise, the spinning process may fail.

If the radiation distance is less than 4 cm, the solvent may not completely volatilize and the coating layer may not be formed well. On the other hand, if the radiation distance exceeds 10 cm, the electric field may be weakened, There may be a problem that the paper can not be focused on the paper 100 and fly.

On the other hand, the film formed with the raw paper 100 and the meta-aramid / carbon nanotube composite layer 200 may undergo car-rendering. The car rendering can be performed at a temperature range of 270 to 290 ° C. The temperature is in the range of 10 to 20 ° C lower than that of a conventional car rendering temperature. The reason is that the electroluminescent surface layer and the backside layer are melted at a relatively low temperature because they are not heat treated during the production of the film. This not only reduces the production cost but also has the advantage of physical characteristics while preventing sulfur change.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. It is to be understood, however, that these embodiments are provided for illustrative purposes only, and that the scope of the present invention is not limited thereto, and that various changes and modifications can be made within the scope and spirit of the present invention. It will be clear to those who have it.

Manufacturing example  One

Yeosu is also 80ml fibrids and 2De. 1 / 4inch flocs were mixed at a ratio of 2: 8 to form a stock. After that, the paper stock was diluted to 1% concentration so that the paper could be produced, and the paper was prepared with a basis weight of 41 g / m ² and the solvent was removed.

Example  One

1 part by weight of carbon nanotubes were mixed with 100 parts by weight of meta-aramid (solid content) of the meta-aramid solution, and a spinning solution having a concentration of 15% was prepared using DMAc (dimethyl acetamide) as a solvent. The spinning solution was ultrasonicated for 1 hour in order to increase the dispersibility of the carbon nanotubes. The prepared spinning solution was connected to a spinneret, a voltage of 10 to 20 kV was applied, and the spinneret was discharged at a rate of 0.05 to 1 cc / g per hole while maintaining a distance between the spinneret and the collector at 8 cm. Electrospinning was performed on both sides of the fabric, and a magnetic field was applied so that the carbon nanotubes were arranged perpendicular to the paper. After the electrospinning, calendering was carried out at a pressure of 100 kg / cm ² and a temperature of 290 ° C to produce a film.

Example  2

A film was prepared in the same manner as in Example 1 except that raw paper prepared by depositing ZnO on the raw paper prepared in Production Example 1 by chemical vapor deposition was used. The thickness of the deposited ZnO thin film layer was 50 탆.

Example  3

A film was prepared in the same manner as in Example 1 except that a magnetic field was not applied.

Comparative Example  One

Yeosu is also 80ml fibrids and 2De. A film was prepared in the same manner as in Example 1, except that the raw paper prepared in the ratio of 1/4 inch flock was used in a ratio of 1: 1.

Comparative Example  2

Yeosu is also 80ml fibrids and 2De. A film was prepared in the same manner as in Example 1 except that a raw paper prepared with a 1/4 inch flock at a ratio of 1:12 was used.

Comparative Example  3

A film was prepared by mixing meta-aramid / carbon nanotubes in solution without using paper.

Test Example  One

The manufactured product was conditioned in a constant temperature and humidity room at a temperature of 23 ° C and a relative humidity of 50% for 24 hours. The film thus prepared was cut into pieces of 25 cm to prepare samples. The tensile test was carried out using a tensile testing machine 1225A Respectively. The surface electrical resistance was measured using an electrical resistance meter (Keithley 8009 resistivity test fixture) to measure electrical conductivity. The results are shown in Table 1 below.

division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Strength (cN / dtex) 81 84 82 70 86 51 Surface electrical resistance
(Ω / sq) 4 × 10 ⁵ 8 x 10 ⁴ 7 x 10 ⁵ 5 × 10 ⁵ 6 × 10 ⁶ 7 × 10 ⁶

As shown in Table 1, in the production of the conductive film with the same content of the meta-aramid / carbon nanotube composite, the carbon nanotubes were arranged so as to be perpendicular to the raw paper by applying a magnetic field using a metal- The results show that the surface electric resistance is the lowest and the conductivity is the best. The comparison between Example 1 and Example 3 shows the effect of alignment of carbon nanotubes on electrical conductivity. When the carbon nanotubes were arranged by applying a magnetic field in the case of electrospinning, the film showed better conductivity than the film in which the carbon nanotubes were not arranged.

On the other hand, in Comparative Example 1, in which the content of fibrids and flocs was 1: 1, the strength was lower than that of Example 1, and the content of fibrids and flocs was 1:12 In one case, the strength was improved as compared with Example 1, but the surface electrical resistance was lowered.

Comparative Example 3 in which a film was prepared by a solvent mixing method according to the prior art showed low strength and no carbon nanotubes were arrayed, resulting in high surface electrical resistance. Thus, according to an embodiment of the present invention, It was confirmed that the resulting film was superior in strength and electrical conductivity to the comparative example.

100 origin
200 Aramid / carbon nanotube layer
210 surface layer 220,
300 metal or metal oxide layer

Claims (9)

Mixing meta aramid fibrids and floc in a ratio of 1: 9 to 3: 7 and adding a solvent to prepare a ground composition;
Forming a microporous structure on the paper by removing the solvent after preparing the paper with the ground composition;
Mixing 0.01 to 5 parts by weight of carbon nanotubes with 100 parts by weight of the meta-aramid polymer in a solvent to prepare a spinning liquid;
Forming a surface layer and a back layer based on aramid / carbon nanotubes by electrospinning the spinning solution on both sides of the raw paper;
And rendering the film car-rendered. The method according to claim 1,
And depositing any one of Ag, Au, ZnO, and SnO ₂ on the surface of the raw paper prior to spinning the spinning solution onto the raw paper. The method according to claim 1,
Wherein a magnetic field is applied to the spinning liquid during the electrospinning to align the carbon nanotubes in the vertical direction of the raw paper. The method according to claim 1,
Wherein the thickness of the surface layer and the thickness of the backside layer are the same or different from each other and independently from 1 to 30 times the thickness of the base paper. The method according to claim 1,
Wherein the solvent is at least one selected from the group consisting of dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, and water. The method according to claim 1,
Wherein the freeness of the fibrids is 100 ml or less. The method according to claim 1,
Wherein the meta-aramid polymer is prepared by polymerizing metaphenylenediamine and isophthaloyl chloride. The method according to claim 1,
Wherein the calendering is performed at 270 to 290 < RTI ID = 0.0 > C. ≪ / RTI > The method according to claim 1,
The electrospinning method is characterized in that the spinning solution is discharged at a spinning temperature of 25 to 100 占 폚 by adjusting the distance between the nozzle of the electrospinning apparatus and the raw paper to a range of 4 to 10 cm and the spinning voltage to a range of 10 to 20 kV Lt; RTI ID = 0.0 > Aramid < / RTI >

Images