KR102042592B1 - Meta-Aramid Paper Having Excellent Withstand Voltage and whiteness, and Method for Preparing the Same - Google Patents

Abstract

The present invention relates to a method for producing a meta-aramid paper formed from meta-aramid pulp containing meta-aramid fibrids, wherein the meta-aramid fibrids are washed with water of 60 to 70 ° C. before being formed into meta-aramid pulp, and the solvent remains. The present invention relates to a meta-aramid paper having improved withstand voltage strength and whiteness, and a method of manufacturing the same.

Description

Meta-Aramid Paper Having Excellent Withstand Voltage and whiteness, and Method for Preparing the Same}

The present invention relates to a meta-aramid paper having improved withstand voltage strength and whiteness, and a method of manufacturing the same. Aramid paper having excellent breakdown voltage strength and tensile strength that can withstand high voltages by improving the physical properties of the meta-aramid fibrid forming the aramid paper and its manufacture It is about a method.

Aramid fiber is a synthetic fiber based on aromatic polymer, which was developed in 1965 by Dupont, USA, with the goal of glass fiber strength and heat resistance of asbestos. In the late 1960s, Kevlar Was produced. In 1974, the Federal Trade Commission defined the term aramid as a generic name for "aromatic polyamides in which at least 85% of amide bonds were directly bonded to two aromatic rings." Since then, ISO-2076, JIS L 0204-2 Edo aramid is the same name.

Aramid is divided into a meta system and a para system by the coupling unit of the amide-bonded aromatic ring. Meta aramid fibers are excellent in high temperature heat resistance, para aramid fibers are characterized by high strength and high elasticity as well as high temperature heat resistance.

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

The meta aramid is a benzene ring is combined with an amide group in the meta position, the strength and elongation is similar to the normal nylon, but the heat stability is very good, compared to other heat-resistant materials, light and sweat absorption is possible to some extent, it is comfortable Have. Initially, the color was limited to a few, but recently, it is made of various colors including fluorescent colors. It is used as a heat-resistant garment material for fire fighting suits, uniforms for race car drivers, astronaut uniforms, and work clothes.

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

Paper made of meta aramid means fibers of shorter length than fibrid and staple fibers, which polymerize meta aramid and orient it into fine fibers and represent non-granular pulp or film-like particles. Meta aramid paper is prepared through floc.

Meta aramid paper is mainly used as an electric insulator and honeycomb structural material. It is widely used as an electric insulator for insulation of coils such as transformers and electric motors and printed boards. It is used for heating elements, conductive tapes for electrostatic discharge, and the like.

Korean Patent Laid-Open Publication No. 2007-0116139 discloses fibrid or short fibers or fibrils of an organic compound having substantially no melting point with a porous sheet layer of a thermoplastic polymer having a melting point of 200 ° C. or lower for use in a capacitor, a capacitor, and a battery. Disclosed is an insulating sheet obtained by laminating meta-aramid paper produced by the wet paper method with a composite sheet having a layer structure of at least two layers of laminated nonwoven fabric sheets made of pulverized pulp.

When meta-aramid paper is used as an electrical insulating material as described above, the breakdown voltage strength is a very important factor, but the conventional meta-aramid paper has a high residual amount of solvent which is not washed in the meta-aramid fibrid, and is formed between the meta-aramid floc and the meta-aramid fibrid. Since many voids are formed, it is difficult to improve the breakdown voltage strength.

As described above, the present invention has been invented to solve the problems of the prior art as described above. Aramid paper improves the breakdown voltage strength and whiteness of the aramid paper by minimizing the amount of solvent remaining in the meta-aramid fibrid forming the aramid paper. It is an object to provide a manufacturing method.

Another object of the present invention is to provide a meta-aramid paper having improved withstand voltage strength and whiteness, which is prepared by the method for producing meta-aramid paper having enhanced breakdown voltage strength and whiteness.

The present invention relates to a method for producing a meta-aramid paper formed from meta-aramid pulp containing meta-aramid fibrids, wherein the meta-aramid fibrids are washed with water of 60 to 70 ° C. before being formed into meta-aramid pulp, and the solvent remains. It provides a method for producing a meta-aramid paper with improved withstand voltage strength and whiteness, characterized in minimizing the amount.

In addition, the solvent remaining amount of the meta-aramid fibrid after washing with water to provide a method for producing meta-aramid paper with improved withstand voltage strength and whiteness, characterized in that less than 0.15% by weight.

The present invention also provides a method for producing meta-aramid paper having improved withstand voltage strength and whiteness, wherein the color-b value of meta-aramid fibrid is less than 2.5 after washing with water.

In addition, the solvent is dimethyl acetamide (dimethyl acetamide, DMAc) provides a method for producing a meta aramid paper with improved withstand voltage strength and whiteness.

In addition, it provides a meta-aramid paper with improved withstand voltage strength and whiteness is produced by the above production method.

In addition, the meta aramid paper provides a meta aramid paper with improved withstand voltage strength and whiteness, characterized in that the withstand voltage strength is 16kV / mm or more.

Meta-aramid paper with improved withstand voltage strength and whiteness according to the present invention is the amount of solvent remaining in the meta-aramid fibrid by controlling the temperature of the washing water used in the washing process of the meta-aramid fibrid forming the aramid paper By minimizing the effect of increasing the whiteness of meta-aramid fibrids.

In addition, the meta-aramid fibrids with a minimum amount of residual solvent are improved in homogeneity, and thus the withstand voltage strength of the meta-aramid paper is improved.

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

As used herein, the terms 'about', 'substantially', and the like, are used at, or in close proximity to, numerical values when manufacturing and material tolerances inherent in the stated meanings are set forth, and an understanding of the present invention may occur. Accurate or absolute figures are used to assist in the prevention of unfair use by unscrupulous infringers.

The present invention relates to a method for producing a meta-aramid paper formed from meta-aramid pulp containing meta-aramid fibrids, wherein the meta-aramid fibrids are controlled by flushing with water before being formed into meta-aramid pulp, thereby controlling the meta-aramid fibrids. The present invention relates to a method capable of improving the breakdown voltage strength and whiteness of meta-aramid paper by minimizing the remaining amount of solvent in the solvent.

The method for producing meta-aramid paper having improved withstand voltage strength and whiteness of the present invention prepares aramid paper including a fibrid manufacturing process, a pulp manufacturing process, and a paper manufacturing process.

The fibrid manufacturing step is a process for producing meta aramid fibrids with meta aramid dope (Dope).

The meta-aramid dope is formed by meta-aramid dope by dissolving meta-aramid polymerized with meta-phenylene diamine (MPD) and isophthaloyl chloride (IPC) in a polar amide solvent.

It is preferable that the meta aramid dope is prepared with a dope of 5 to 25% by weight of solids.

The polar amide solvents include dimethyl acetamide (DMAc), N-methylpyrrolidone (N-methylpyrrolidone, NMP), dimethyl formamide (DMF), dimethyl imidazolidinone, and the like. In the present invention, one selected from the above polar amide solvents may be used, and most preferably, dimethylacetamide (DMAc) is used.

The meta-aramid fibrids can be prepared by subjecting the polymer solution to precipitation and strong shear stress while contacting the non-solvent in the fibridater as described in US Patent No. 3,756,908. , May be manufactured through the manufacturing apparatus of Korean Patent Application No. 2014-0098919.

The meta-aramid fibrids prepared as described above are rinsed through a washing process before being contained in the pulp to remove the solvent remaining in the fibrids.

The washing process is a process for removing the polar amide solvent used as the solvent to remove impurities in the fibrids by using the washing water as meta-aramid fibrids.

When the residual amount of the solvent in the meta aramid fibrid is high, the whiteness of the meta aramid fibrid is lowered, thereby lowering the whiteness of the meta aramid paper.

In addition, the solvent remaining in the meta-aramid fibrids is discharged in the form of steam in the processing such as heat processing to form pores, thereby deteriorating the physical properties of the aramid paper, and if the residual amount of the solvent is high, the breakdown voltage strength may decrease the solvent. It is possible to improve the breakdown voltage strength and the whiteness by minimizing the remaining amount of.

The inventor of the present invention proved through experiments that the solvent residual amount in the meta-aramid fibrid can be changed by controlling the temperature of the washing water when washing the meta-aramid fibrid, and using the washing water of 60-70 ° C. It was found that the amount of solvent remaining in the meta-aramid fibrid can be minimized by washing with water.

Therefore, when washing meta-aramid fibrids, it is preferable that the temperature of the washing water is 60 to 70 ° C.

When the residual amount of solvent in the meta-aramid fibrid after washing with water exceeds 0.2% by weight, the increase in the breakdown voltage strength and whiteness is not so large, and the residual amount of the solvent in the meta-aramid fibrid is preferably 0.2% by weight or less, more preferably 0.15% by weight. Less than%.

As described above, when the amount of solvent remaining in the meta-aramid fibrid decreases, the whiteness of the meta-aramid fibrid increases, and the color-b value falls below 3.0. The meta-aramid fibrid of the present invention preferably has a color-b value of 3.0 or less, more preferably less than 2.5.

The pulp manufacturing step is a step of producing a meta aramid pulp by mixing the water washed meta aramid fibrid and meta aramid floc as described above.

In the pulp manufacturing process, the meta aramid fibrid and the meta aramid floc are mixed in a weight ratio of 30:70 to 70:30 to prepare a slurry pulp, which may be prepared by a general method for preparing aramid pulp.

The paper manufacturing process is a process for producing paper with meta-aramid pulp, it will be able to manufacture the paper by the wetland papermaking method generally used.

That is, the prepared aramid pulp may be formed into a paper by forming a web through a wet papermaking method, followed by dehydration and calendering through a nip roller.

The meta-aramid paper with improved withstand voltage strength and whiteness according to the present invention is excellent in whiteness and withstand voltage strength of 16kV / mm or more.

In the following Examples according to the present invention to prepare aramid paper excellent in the breakdown voltage strength and tensile strength of the present invention. The present invention is not limited to these examples.

Example  1 to 8

Meta aramid polymerized with M-phenylene diamine (MPD) and isophthaloyl chloride (IPC) was dissolved in dimethyl acetamide (DMAc), a polar amide solvent, A 20% by weight meta aramid dope was formed.

After preparing the meta aramid dopro meta aramid fibrids, the meta aramid fibrids were washed with water by controlling the temperature of the wash water.

The pulp was prepared by mixing the washed meta aramid fibrids and the meta aramid flocs in a weight ratio of 1 to 1, and the wet a method of preparing the meta aramid paper having improved withstand voltage strength and whiteness of the present invention.

According to the Examples, the temperature of the wash water and the solvent remaining amount (residual DMAc content) and Color B (measured with a color difference meter (CR-10, Minolta)) in the meta-aramid fibrid after washing were measured and shown in Table 1 below.

division Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Flush temperature
(℃) 10 20 30 40 50 60 70 80 Remaining DMAc content
(weight%) 0.52 0.40 0.38 0.32 0.25 0.12 0.08 0.08 Color b 3.5 3.2 2.8 2.5 2.5 2.2 2.0 2.0

As shown in Table 1, it can be seen that the residual DMAc content is lowered when the meta-aramid fibrid is washed with a high temperature wash water, and the remaining DMAc content is the lowest when the wash water temperature is 60 to 80 ° C. You can see the loss.

In the case of Example 8 where the temperature of the wash water is 80 ℃, the remaining DMAc content is not significantly different from Example 7 in which the temperature of the wash water is 70 ℃, the temperature of the wash water will be most preferable when 60 ~ 70 ℃ .

In addition, when the DMAc content remaining in the meta-aramid fibrid is low, it can be seen that the whiteness is improved by lowering the Color B value.

The tensile strength and withstand voltage strength of the aramid paper prepared in Examples 1 to 7 and Comparative Examples as described above are shown in Table 2.

Tensile strength: measured using the Tensile Tester of L & W according to ASTM D 828.

* Withstand voltage strength: The voltage (kV) in which dielectric breakdown occurs in accordance with ASTM D419 divided by the thickness (mm) of an insulating material.

division Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Basis weight (gsm) 40 40 40 40 40 40 40 40 The tensile strength
(MD, N /) 36.2 36.5 36.5 36.7 37.2 37.5 38.1 38.0 Withstand voltage
(kV / mm) 14.8 15.5 15.4 15.6 15.8 16.1 16.5 16.5

As shown in Table 2, when the content of DMAc remaining in the meta-aramid fibrid is low, the breakdown voltage strength is improved, and the tensile strength is also improved.

Claims (6)

In the method for producing meta-aramid paper formed of meta-aramid pulp containing meta-aramid fibrids,
The meta-aramid fibrids are washed with water at 60-70 ° C. before being formed into meta-aramid pulp, and the solvent resistance of meta-aramid fibrids is less than 0.15% by weight. Way.
delete The method of claim 1,
Method of producing a meta- aramid paper with improved withstand voltage strength and whiteness, characterized in that the color a-b value of the meta-aramid fibrid after washing with water washes less than 2.5.
The method of claim 1,
The solvent is dimethyl acetamide (dimethyl acetamide, DMAc), characterized in that the withstand voltage strength and whiteness enhanced meta aramid paper manufacturing method.
The meta-aramid paper having improved withstand voltage strength and whiteness, which is prepared by the method according to claim 1 or 3.
The method of claim 5,
The meta aramid paper is a meta aramid paper with improved withstand voltage strength and whiteness, characterized in that the withstand voltage strength of 16kV / ㎜ or more.