KR20210063096A - Short cut fiber for aramid paper, and aramide paper using the same - Google Patents

Abstract

The present invention relates to aramid paper with improved physical properties for a honeycomb, which comprises 40-60% by weight of meta-aramid short-cut fibers with a Y-shaped cross section and 40-60% by weight of meta-aramid fibrids to improve bonding strength between the meta-aramid short-cut fibers and the meta-aramid fibrids, and induces tissue densification to improve physical properties such as tensile strength, withstanding voltage, and the like.

Description

Short-cut fiber for aramid paper and aramid paper using the same {SHORT CUT FIBER FOR ARAMID PAPER, AND ARAMIDE PAPER USING THE SAME}

The present invention relates to a short-cut fiber for aramid paper and an aramid paper using the same, and to a short-cut fiber for aramid paper in which a sheath portion and a core portion are formed with meta-aramid dope having different concentrations, and aramid paper using the same.

Aramid fiber is a synthetic fiber made from aromatic polymer that DuPont of the United States succeeded in developing in 1965 with the goal of fiber having the strength of glass fiber and heat resistance of asbestos. was produced with In 1974, the U.S. Federal Trade Commission defined the term aramid as a general name for “aromatic polyamides in which 85% or more of amide bonds are directly bonded by two aromatic rings”. After that, ISO-2076, JIS L 0204-2 The name of Edo aramid was equally defined.

Aramid is divided into meta-type and para-type by the bonding unit of an amide-bonded aromatic ring. Meta-aramid fiber has excellent high-temperature heat resistance, and para-aramid fiber has high-strength and high elasticity as well as high-temperature heat resistance.

In the para-aramid, a benzene ring is bonded to an amide group at the para position. Because the molecular chain is very stiff and has a linear structure, it has very high strength and a particularly high modulus of elasticity, so it has excellent shock absorbing performance. It is used in bulletproof suits, bulletproof helmets, safety gloves or boots, firefighting suits, tennis rackets, boats, and hockey. As a material for sports equipment such as sticks, fishing lines, and golf clubs, it is also used for FRP (Fiber Reinforced Plastic) and asbestos replacement fibers for industry.

The meta-aramid is a benzene ring bonded to an amide group at the meta position, and the strength and elongation are similar to those of ordinary nylon, but the stability to heat is very good, and compared to other heat-resistant materials, it is lightweight and can absorb sweat to some extent, so it has the advantage of being comfortable. Have. Initially, only a few colors were limited, but recently, they are being made in various colors including fluorescent colors. It is used as a material for heat-resistant clothing such as firefighting suits, uniforms for racing car drivers, astronaut uniforms, and work clothes, and is used as a high-temperature filter for industrial purposes.

As described above, para-aramid and meta-aramid are manufactured in the form of paper as well as fibers and are used in many industrial fields.

The paper made of the meta-aramid is a fiber having a shorter length than the fibrid and staple fibers, which are polymerized meta-aramid and oriented into fine fibers and are non-granular pulp or film-like particles. The meta-aramid paper is produced through a floc.

Meta-aramid paper is a material mainly used as an electrical insulator and honeycomb structural material. As an electrical insulator, it is widely used in insulators of coils such as transformers and electric motors or printed circuit boards. It is used for heating elements and conductive tapes for electrostatic discharge.

Korean Patent Laid-Open No. 2007-0116139 discloses a porous sheet layer of a thermoplastic polymer having a melting point of 200° C. or less for use in capacitors, capacitors, and batteries, and fibrids or short fibers or fibrils of an organic compound having substantially no stable melting point. Disclosed is an insulating sheet in which meta-aramid paper manufactured by wet papermaking is laminated as a composite sheet having a layer structure of at least two or more layers in which a non-woven fabric-like sheet made of refined pulp is laminated.

As described above, meta-aramid paper is required to have a high level of physical properties such as strength, heat resistance, and flame retardancy as the industry develops, but meta-aramid paper is formed of meta-aramid floc and meta-aramid fibrid to greatly improve physical properties. There was a difficult problem.

As described above, the present invention was invented to solve the problems of the prior art as described above. In the form of a composite fiber of the sheath and the core, the sheath and the core are formed with meta-aramid dope having different concentrations to form short-cut fibers and meta An object of the present invention is to provide a short-cut fiber for aramid paper that can improve physical properties by improving bonding strength with aramid fibrid.

In addition, it aims to provide an aramid paper using the short-cut fiber for aramid paper of the present invention.

The present invention provides a short-cut fiber for aramid paper in the form of a composite fiber formed of a sheath portion and a core portion, wherein the core portion is formed with a high concentration of meta-aramid dope, and the sheath portion is formed with a low concentration of meta-aramid dope. .

In addition, the high-concentration meta-aramid dope of the core part has a concentration of 17 to 25 wt%, and the low-concentration meta-aramid dope of the sheath part provides a short-cut fiber for aramid paper, characterized in that the concentration is 5 to 10 wt%.

In addition, the concentration difference between the high concentration meta-aramid dope and the low concentration meta-aramid dope provides a short-cut fiber for aramid paper, characterized in that more than 10% by weight.

In addition, the short-cut fiber for aramid paper provides a short-cut fiber for aramid paper, characterized in that it has a flat cross-section.

In addition, it provides an aramid paper characterized in that the short-cut fiber for the aramid paper of any one of claims 1 to 4 is contained.

The short-cut fiber for aramid paper according to the present invention as described above is a composite fiber form of the sheath and core, and the sheath and core are formed with meta-aramid dope having different concentrations, so that the surface of the fiber is rough, so that the bonds between the short-cut fibers and meta-aramid It has the effect of improving the physical properties by improving the binding force with the fibrid.

In addition, there is an effect of providing an aramid paper using the short-cut fiber for aramid paper of the present invention.

Hereinafter, a preferred embodiment of the present invention will be described in detail. In describing the present invention, detailed descriptions of related known functions or configurations are omitted so as not to obscure the subject matter of the present invention.

As used herein, the terms 'about', 'substantially' and the like are used in a sense at or close to the numerical value when the manufacturing and material tolerances inherent in the stated meaning are presented, and provide an understanding of the present invention. To help, precise or absolute figures are used to prevent unfair use by unscrupulous infringers of the stated disclosure.

The present invention relates to a short-cut fiber for aramid paper in the form of a composite fiber formed of a sheath portion and a core portion, wherein the core portion is formed with a high concentration of meta-aramid dope, and the sheath portion is formed with a low concentration of meta-aramid dope.

As described above, the short-cut fiber for aramid paper of the present invention having a difference in the concentration of meta-aramid dope in the core part and the sheath part is produced by wet spinning, and the low-concentration sheath part is rapidly solidified to form a thin sheath part, and the high concentration of the core part The meta-aramid dope gradually solidifies.

As described above, the high-concentration meta-aramid dope of the core part penetrates the solidified sheath and gradually solidifies, forming numerous through holes in the sheath to roughen the fiber surface.

The short-cut fiber for aramid paper of the present invention, which has a rough surface as described above, enhances physical properties such as tensile strength of paper by strengthening the bonding between the short-cut fibers for aramid paper and the bonding force between the short-cut fibers and the meta-aramid fibrid when manufactured into paper. make it

The short-cut fibers for aramid paper of the present invention as described above may be formed in a circular cross-section, but when formed in a flat cross-section, the surface roughness of the sheath can be further improved, and fiber processability can be further improved.

When the short-cut fiber for aramid paper of the present invention is formed in a flat cross-section, it will be preferable to form an aspect ratio (long-axis length/short-axis length) of 2 to 5.

As the aspect ratio of the fiber of the flat cross-section increases, the roughness of the fiber surface can be improved, but if the aspect ratio is too large, the manufacturing processability is deteriorated, so that the aspect ratio is preferably 5 or less.

As described above, when the short-cut fibers are manufactured as flat yarns with a flat cross section, in the calendering process, between the meta-aramid short-cut fibers, between the meta-aramid short-cut simple fibers and the meta-aramid fibrids are reduced, and the structure becomes dense.

The sheath portion and the core portion of the present invention are preferably formed in a weight ratio of 30:80 to 20:70, more preferably 20:50 to 50:80.

The high concentration of the meta-aramid dope of the core part is 17 to 25% by weight, and the low concentration of the meta-aramid dope in the sheath part is preferably 5-10% by weight.

If the difference in concentration between the high-concentration meta-aramid dope and the low-concentration meta-aramid dope is too low, the roughness of the fiber surface may be insignificant. .

The short-cut fiber for the aramid paper has a fineness of 3 to 8 denier, and it will be preferable that the fiber length is 3 to 10 mm.

If the fineness of the short-cut fiber is too low or too high, the synergistic effect of the binding force between the short-cut fiber and the meta-aramid fibrid may be insignificant, and the manufacturing processability of the paper may be deteriorated.

By containing the short-cut fibers for aramid paper according to the present invention described above, it will be possible to form aramid paper with improved physical properties.

The aramid paper will preferably be formed by mixing short-cut fibers and meta-aramid fibrids in a weight ratio of 30:70 to 30:70.

When the short-cut fiber is contained in less than 30% by weight, it cannot be expected to improve the bonding strength between the short-cut fibers and between the short-cut fibers and the meta-aramid fibrid. can be

The aramid paper containing the short-cut fibers for the aramid paper of the present invention will be able to manufacture the paper by the generally used wetland papermaking method.

That is, the short-cut fiber and meta-aramid fibrid are uniformly mixed to form a web through a wet papermaking method with pulp, and then dehydrated through a nip roller and calendering. can do.

As an example according to the present invention below, a short-cut fiber and aramid paper for aramid paper of the present invention were prepared. The present invention is not limited to these examples.

Example 1

After preparing a meta-aramid resin with meta-phenylene diamine (MPD) and isophthaloyl chloride (IPC), it was dissolved in dimethylacetamide, a solvent, and 20 wt% and 8 wt% of meta-aramid dope (Dope) was prepared.

The 20 wt% meta-aramid dope was used as the core part and 8 wt% meta-aramid dope was used as the sheath part, and wet-spun into a composite fiber having a flat cross-section with a flatness of 2.5 to prepare a short-cut fiber for aramid paper of the present invention.

A pulp was prepared by mixing 40% by weight of the short-cut fibers of 6 mm in length and 2 denier fineness prepared above and 60% by weight of meta-aramid fibrid, and after forming a web by a wet papermaking method, it was dehydrated through a nip roller. and calendered at 280° C. to prepare aramid paper with improved physical properties of the present invention.

Example 2

It was prepared in the same manner as in Example 1, but by mixing 50% by weight of short-cut fibers and 50% by weight of meta-aramid fibrid, aramid paper with improved physical properties according to the present invention was prepared.

Example 3

It was prepared in the same manner as in Example 1, but by mixing 60% by weight of short-cut fibers and 40% by weight of meta-aramid fibrid, aramid paper with improved physical properties according to the present invention was prepared.

Comparative Example 1

Although prepared in the same manner as in Example 1, 50% by weight of meta-aramid floc having a circular cross-section having a fineness of 6 denier and 50% by weight of meta-aramid fibrid were mixed to prepare aramid paper.

◈ Evaluation of properties of aramid paper

The physical properties of the aramid paper prepared in Examples 1 to 3 and Comparative Example 1 as described above were measured and shown in Table 1.

* Tensile strength: It was measured using L&W's Tensile Tester according to ASTM D828 measurement method.

* Withstand voltage strength: According to ASTM D419, the voltage at which dielectric breakdown occurs (kV) is divided by the thickness (mm) of the insulating material.

division Example Comparative example One 2 3 One Tensile strength of base paper (N/cm) 26.2 26.9 27.5 20.5 Tensile strength of thermal paper (N/cm) 38.5 39.6 41.2 35.1 Withstand voltage strength (kV/mm) 24.0 24.1 23.5 20.5

As shown in Table 1, it can be seen that all of Examples 1 to 3 have improved tensile strength and withstand voltage strength compared to Comparative Example 1.

As in Examples 1 to 3, the higher the content of the short-cut fibers, the higher the tensile strength, but the withstand voltage strength decreases as the content increases. It will be preferable that the short-cut fibers of the present invention contain 40 to 60% by weight. .

Claims (5)

In the form of a composite fiber formed of a sheath part and a core part,
The core part is formed with a high concentration of meta-aramid dope,
The sheath portion is a short-cut fiber for aramid paper, characterized in that it is formed with a low concentration of meta-aramid dope.
The method of claim 1,
The high-concentration meta-aramid dope of the core part has a concentration of 17 to 25% by weight, and the low-concentration meta-aramid dope of the sheath part has a concentration of 5-10% by weight.
The method of claim 1,
A short-cut fiber for aramid paper, characterized in that the concentration difference between the high-concentration meta-aramid dope and the low-concentration meta-aramid dope is 10% by weight or more.
The method of claim 1,
The short-cut fiber for aramid paper is a short-cut fiber for aramid paper, characterized in that it has a flat cross-section.
Aramid paper, characterized in that it contains the short-cut fiber for aramid paper of any one of claims 1 to 4.