KR20210138983A - Meta-Aramid Fibrid for High density nonwoven, and Method for Preparing the Same - Google Patents

Abstract

The present invention relates to a meta-aramid fibrid for a high-density non-woven fabric to increase tensile strength and withstand voltage strength of the high-density non-woven fabric and a manufacturing method thereof. According to the present invention, the method comprises: a dope forming step of dissolving meta-aramid in a polar amide-based solvent to form meta-aramid dope; a fibrid manufacturing step of manufacturing a meta-aramid fibrid with the dope; and a water washing step of washing the manufactured meta-aramid fibrid. The washing step includes a first water washing step of performing washing with water containing 5 to 50 wt% of a polar amide-based solvent at least three times and a second washing step of performing washing with water not containing the polar amide-based solvent. The content of the polar amide-based solvent in the washing water of first washing in the first water washing process is 20 to 50 wt% and is decreased by 5 to 10 wt% as water washing is repeated, wherein washing water used in the second water washing process is reused in the first water washing process during the water washing step.

Description

Meta-Aramid Fibrid for High density nonwoven, and Method for Preparing the Same

The present invention relates to a meta-aramid fibrid with improved physical properties and a method for manufacturing the same. By improving the physical properties of meta-aramid fibrid forming aramid paper, meta-aramid fibrid with improved physical properties that can produce aramid paper with excellent withstand voltage strength and whiteness It relates to a breed and a method for producing 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 term aramid was defined by the US Federal Trade Commission 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 a very high strength and a particularly high modulus of elasticity, so it has a very good impact absorbing performance. 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 has a benzene ring bonded to an amide group at the meta position, and has similar strength and elongation to normal nylon, but has very good heat stability, and is lightweight compared to other heat-resistant materials 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 non-woven fabrics as well as fibers and are used in many industrial fields.

The nonwoven fabric made of the meta-aramid polymerizes meta-aramid and oriented into fine fibers, and refers to fibers of a shorter length than fibrid and staple fibers, meaning non-granular pulp or film-like particles. A meta aramid nonwoven fabric is manufactured through a floc.

Meta aramid nonwoven fabric is mainly used as an electrical insulator and honeycomb structural material. As an electrical insulator, it is widely used as an insulator 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 Application 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 a meta-aramid nonwoven fabric manufactured by a wet papermaking method is laminated as a composite sheet having a layer structure of at least two or more layers in which a nonwoven fabric-like sheet made of a refined pulp is laminated.

As described above, when using meta-aramid nonwoven fabric as an electrical insulation material, withstand voltage strength is a very important factor, but the conventional meta aramid nonwoven fabric has micropores inside the meta aramid fibrid, making it difficult to manufacture it as a high-density nonwoven fabric. It is difficult to improve the withstand voltage strength. there was

As described above, the present invention is a meta-aramid fibrid for high-density non-woven fabric suitable for high-density non-woven fabric by suppressing micropores generated in the water washing process during the production of meta-aramid fibrid to solve the problems of the prior art as described above. An object of the present invention is to provide a manufacturing method.

In addition, an object of the present invention is to provide an eco-friendly method for manufacturing meta-aramid fibrids for high-density non-woven fabrics by recycling the washing water used for washing the meta-aramid fibrids.

In addition, an object of the present invention is to provide a meta-aramid fibrid that can improve the tensile strength and withstand voltage strength of the meta-aramid nonwoven fabric by suppressing micropores in the meta-aramid fibrid.

The present invention is a dope forming step of dissolving meta-aramid in a polar amide-based solvent to form a meta-aramid dope, a fibrid preparation step of preparing meta-aramid fibrids with the dope; And, in the method for producing meta-aramid fibrids for high-density non-woven fabric comprising a water washing step of washing the prepared meta-aramid fibrids with water, the washing step is performed 3 times or more with water washing containing 5 to 50% by weight of a polar amide-based solvent. a first water washing step of washing with water and a second washing step of washing with water that does not contain a polar amide solvent, wherein the content of the polar amide solvent in the first washing in the first washing step is 20 to 50 % by weight, and the content of the polar amide solvent in the washing water decreases by 5 to 10% by weight as the washing is repeated, but the washing water used in the second washing process in the washing step is recycled in the first washing process It provides a method for manufacturing meta-aramid fibrids for high-density non-woven fabrics.

In addition, the polar amide-based solvent provides a method for producing meta-aramid fibrids for high-density non-woven fabrics, characterized in that dimethylacetamide (DMAc).

In addition, it provides a method for producing meta-aramid fibrids for high-density non-woven fabrics, characterized in that the temperature of the washing water in the first washing step is 10 to 60°C.

In addition, there is provided a method for producing meta-aramid fibrids for high-density nonwoven fabrics, characterized in that the washing water containing the polar amide solvent used in the first washing process is recycled in the first washing process.

In addition, it provides a method for producing meta-aramid fibrids for high-density non-woven fabrics, characterized in that the washing with water that does not contain a polar amide solvent in the second washing step is performed twice or more.

In addition, in the second washing step, the temperature of the washing water at the time of the final washing provides a method for manufacturing a high-density non-woven meta-aramid fibrid, characterized in that 45 ~ 60 ℃.

In addition, it provides a meta-aramid fibrid for high-density nonwoven fabric, characterized in that the manufacturing method is prepared.

In addition, it provides a high-density nonwoven fabric comprising the meta-aramid fibrid.

The meta-aramid fibrid for high-density non-woven fabric according to the present invention as described above is the rapid solidification of meta-aramid in the water washing step and the formation of micropores through the washing water containing the solvent, which is formed by removing the solvent in the solidified state. It has the effect of providing a method for producing meta-aramid fibrids suitable for high-density non-woven fabrics.

In addition, the meta-aramid fibrid manufacturing method of the present invention has an eco-friendly effect by recycling the washing water used for washing.

In addition, the meta-aramid fibrid of the present invention has the effect of improving the tensile strength and the withstand voltage strength due to the small number of micropores formed therein.

1 is a process diagram showing a method for manufacturing meta-aramid fibrids for high-density non-woven fabrics according to the present invention.
2 is a diagram schematically illustrating the washing step of the method for manufacturing meta-aramid fibrids for high-density non-woven fabrics according to the present invention.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. First, it should be noted that in the drawings, the same components or parts are denoted by the same reference numerals whenever possible. In describing the present invention, detailed descriptions of related known functions or configurations are omitted so as not to obscure the gist of the present invention.

As used herein, the terms 'about', 'substantially' and the like are used in or close to the numerical value when 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.

1 is a process diagram showing a method for manufacturing meta-aramid fibrids for high-density non-woven fabrics according to the present invention, and FIG. 2 is a diagram schematically illustrating the washing step of the method for manufacturing meta-aramid fibrids for high-density non-woven fabrics according to the present invention.

The present invention relates to a method for producing meta-aramid fibrids capable of producing a high-density non-woven fabric, and relates to a method for producing meta-aramid fibrids for high-density non-woven fabric, including a dope forming step, a fibrid production step, and a water washing step, as shown in FIG. .

The dope forming step is a step of dissolving meta-aramid in a polar amide-based solvent to form a meta-aramid dope.

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

The meta-aramid dope will preferably be prepared with a dope having a solid content of 5 to 20% by weight.

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

The fibrid preparation step is a step of preparing the meta-aramid fibrid with the dope. As described in US Patent No. 3,756,908, the fibrid is a polymer solution in a non-solvent in a fibridater. It can be manufactured by subjecting it to precipitation and strong shear stress while in contact with it, and it may be manufactured through the manufacturing apparatus of Korean Patent Registration Nos. 1555986, 1541879, and 1544725.

The meta-aramid fibrid prepared as described above is washed with water through a water washing step to remove the solvent remaining in the fibrid.

The washing step is a process for removing the polar amide-based solvent in the meta-aramid fibrid by using it as washing water. do.

As described above, when washing with hot water that does not contain a polar amide solvent, the polar amide solvent is rapidly removed, and the meta-aramid fibrid is rapidly solidified, so that the spot where the polar amide solvent is removed is formed into micropores. Numerous micropores are formed inside the meta-aramid fibrid.

In addition, when the meta-aramid fibrid is washed with hot water that does not contain a polar amide-based solvent, the surface of the meta-aramid fibrid is rapidly solidified to form a skin layer, and the polar amide-based solvent is not easily removed. There is a problem that the amount of residual solvent is high even after washing with water.

The water washing step of the present invention includes a first water washing step of washing three or more times with water containing 5 to 50% by weight of a polar amide solvent as shown in FIG. 2 It is carried out including the washing process.

In the first washing step, the content of the polar amide solvent in the washing water at the time of first washing is 20 to 50% by weight, and as the washing is repeated, the content of the polar amide solvent in the washing water decreases by 5 to 10% by weight. am.

That is, as shown in FIG. 2, it is possible to wash the meta-aramid fibrid 100 by spraying the washing water through the injection hole 200. When the first washing process is washed three times, the polar amide When the solvent content is 30% by weight, the content of the polar amide solvent in the second washing is 20% by weight of washing water, and the content of the amide solvent in the polar solvent in the third washing is 10% by weight. will be.

If the water washing of the first water washing step is performed less than 3 times, the amount of residual solvent may increase, so it is preferable to perform it 3 times or more.

The polar amide-based solvent contained in the washing water is reduced by 5 to 10% by weight. If it is contained in an amount of less than 5% by weight, the number of times of washing may increase and the process time may be prolonged. If it exceeds 10% by weight, the occurrence of micropores is minimized. This is not possible, and the amount of residual solvent may increase.

If the temperature of the washing water in the first washing process is less than 10 ℃, the efficiency of solvent removal may be reduced, and if it exceeds 60 ℃, the solidification of meta-aramid fibrid may be rapidly increased, so the temperature of the washing water is 10 It is preferable that it is -60 degreeC, More preferably, it is 10-30 degreeC.

The first water washing process uses a washing water containing a polar amide solvent, and as the washing is repeated, the content of the polar amide solvent in the washing water is decreased to gradually solidify the meta-aramid fibrid while polar amide in the meta-aramid fibrid. By slowly removing the solvent, the formation of micropores generated when the polar amide solvent is removed is suppressed.

In addition, the solvent can be removed smoothly by preventing the formation of a skin layer on the surface of the meta-aramid fibrid due to the slow solidification of the meta-aramid fibrid, thereby lowering the amount of residual solvent of the meta-aramid fibrid.

The second washing process is a process of removing the polar amide solvent inside the meta aramid fibrid by washing with water that does not contain the polar amide solvent.

In the second washing step, in order to reliably remove the polar amide solvent from the meta aramid fibrid, it is preferable to wash with water that does not contain a polar amide solvent.

It is preferable that the temperature of the washing water in the second washing step is 10 to 60°C, and when the second washing step is performed two or more times, the washing water before the final washing is 10 to 30°C, and the number of times at the time of the final washing Washing at a temperature of 45 to 60 ° C will be able to minimize the residual amount of meta-aramid fibrid solvent.

By recycling the washing water used in the washing step as described above in the first washing process, it will be possible to reduce costs and increase affinity.

In the case of recycling the washing water, the washing water used in the washing process is stored in a storage 300 such as a liquid storage tank, as shown in FIG. 2, and a connection pipe 400 connecting the storage 300 and the injection port 200. ) and can be recycled.

Since the polar amide solvent is contained once the washing water is used, it is preferable not to use the recycled washing water in the second washing process.

As for the recycling of the washing water, the washing water used in the second washing process may be recycled in the first washing process, or the washing water used in the first washing process may be recycled in the first washing process.

When recycling the washing water, it is preferable to adjust the polar amide solvent content of the washing water and adjust the polar amide solvent content in the storage.

When the washing water is recycled, the washing water used in the second washing process may be used in the first washing process as shown in FIG. 2 .

When the washing water used in the first washing process is recycled in the first washing process, the washing water used in the subsequent washing can be recycled. For example, when the first washing process is washed three times, the third washing water is The second washing water can be recycled, and the second washing water can be recycled as the first washing water.

Alternatively, the washing water used in the previous washing can be recycled. For example, if the first washing process is washed three times, the first washing water is recycled as the second washing water, and the second washing water can be recycled as the third washing water. have.

The meta-aramid fibrid prepared as described above has a high density due to the small number of micropores inside, and the amount of residual solvent is also very low (500 ppm or less). The strength and withstand voltage strength will be improved.

The meta aramid fibrid for high-density nonwoven fabric according to the present invention can be used to prepare a meta aramid nonwoven fabric by a conventional method. After making the pulp in a slurry state, it will be possible to produce a nonwoven fabric by the wet papermaking method.

That is, after forming a web through the wet papermaking method of the prepared aramid pulp, it can be dehydrated through a nip roller and manufactured into a nonwoven fabric, including the steps of calendering.

The meta-aramid nonwoven fabric containing the meta-aramid fibrid according to the present invention as described above has a tensile strength of 35N/cm or more, and a withstand voltage strength of 20kV/mm or more, which will have very excellent properties and withstand voltage strength.

The meta aramid fibrid for high-density nonwoven fabric according to the present invention can be used to prepare a meta aramid nonwoven fabric by a conventional method. After making the pulp in a slurry state, it will be possible to produce a nonwoven fabric by the wet papermaking method.

That is, after forming a web through the wet papermaking method of the prepared aramid pulp, it can be dehydrated through a nip roller and manufactured into a nonwoven fabric, including the steps of calendering.

As an example according to the present invention below, a meta-aramid fibrid for high-density nonwoven fabric of the present invention was prepared. The present invention is not limited to these examples.

Example 1

Meta-aramid polymerized with M-phenylene diamine (MPD) and isophthaloyl chloride (IPC) was dissolved in a polar amide solvent, dimethyl acetamide (DMAc) to increase the concentration of meta-aramid. 8% by weight of meta aramid dope (Dope) was formed.

The meta-aramid fibrid prepared above was prepared by using the fibrid manufacturing apparatus of Korean Patent No. 1541879 with the meta-aramid dope.

The prepared meta aramid fibrid was washed with water in a first washing step of washing with water containing dimethylacetamide and a second washing step of washing with water not containing dimethylacetamide.

The first water washing process was washed with water 3 times. The dimethylacetamide content of the washing water for the first washing was 30% by weight, the dimethylacetamide content for the second washing was 20% by weight, and the dimethylacetamide content for the third washing was 10% by weight. Washing was used. In the first water washing process, all washing water at 30°C was used.

The second washing process was performed twice. The temperature of the washing water at the time of the first washing was 30 ℃, and the temperature of the washing water at the time of the second washing was 60 ℃.

The washing water was recycled as shown in FIG. 2, and the washing water used in the second washing process was used as the third washing water of the first washing process, the third washing water was recycled as the second washing water, and the second washing water was used as the first washing water. It can be recycled as washing water.

In the first water washing step, the dimethylacetamide content of the washing water was adjusted in the storage before use.

Example 2

Meta-aramid fibrid was prepared in the same manner as in Example 1, but the second washing process was washed once with water at 60°C.

Example 3

Meta-aramid fibrid was prepared in the same manner as in Example 1, but washing water was used as washing water at 60° C. in the first washing process.

comparative example

Meta-aramid fibrid was prepared in the same manner as in Example 1, but the washing step was performed 5 times using washing water not containing dimethylacetamide.

The residual DMAc content of the meta-aramid fibrids prepared in Examples 1 to 3 and Comparative Example 2 as described above was measured.

In addition, after mixing the meta aramid fibrid and meta aramid floc prepared in Examples 1 to 3 and Comparative Example 2 in a weight ratio of 1:1, a meta aramid nonwoven fabric was prepared by a wet papermaking method, and the basis weight and density of the prepared nonwoven fabric , tensile strength, and withstand voltage strength were measured and shown in Table 1.

*Tensile strength: Measured using L&W's Tensile Tester according to ASTM D 828 measurement method. It measures the force when breaking by applying tension to paper.

* Withstanding 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 1 Example 2 Example 3 comparative example Fibrid residual DMAc content (ppm) 2 230 64 2500 Nonwoven fabric basis weight (g/m2) 41.2 41 41.3 41 Non-woven fabric density (g/cm3) 0.73 0.64 0.69 0.58 Tensile strength (N/cm) 42.1 36.1 39.3 33.2 Withstand voltage strength (kV/mm) 25.2 20 21 16.3

As shown in Table 1, it can be seen that the meta aramid fibrids of Examples 1 to 3 washed with the water washing step of the present invention are significantly lower than the meta aramid fibrids of the comparative example in the residual DMAc content by the water washing step of the present invention. When washing with water, the amount of residual solvent can be significantly reduced.

Since the meta aramid fibrid of Example 1 has a lower residual DMAc content than the meta aramid fibrid of Example 3, it is preferable that the washing water in the first washing step be 30° C. or less.

In addition, as in Examples 1, 3 and 2, if water washing is performed only once in the second washing process, the residual DMAc content may increase, so it is preferable to wash the water twice or more in the second washing process.

In addition, Examples 1 to 3, which are nonwoven fabrics containing the meta aramid fibrid of the present invention, have a higher density than Comparative Examples at the same basis weight, and it can be seen that the density is high.

In addition, Examples 1 to 3, which are nonwoven fabrics containing the meta-aramid fibrid of the present invention, show higher tensile strength and withstand voltage strength than the comparative examples. It can be seen that the tensile strength is also improved.

Claims (8)

A dope forming step of dissolving meta-aramid in a polar amide-based solvent to form a meta-aramid dope, a fibrid manufacturing step of preparing meta-aramid fibrids with the dope; And, in the meta-aramid fibrid manufacturing method for high-density non-woven fabric comprising a water washing step of washing the prepared meta-aramid fibrid,
The water washing step includes a first water washing step of washing three or more times with water containing 5 to 50% by weight of a polar amide-based solvent and a second washing step of washing with water not containing a polar amide-based solvent,
In the first washing step, the content of the polar amide solvent in the washing water at the time of first washing is 20 to 50% by weight, and as the washing is repeated, the content of the polar amide solvent in the washing water decreases by 5 to 10% by weight,
Method for producing meta-aramid fibrid for high-density non-woven fabric, characterized in that the washing water used in the second washing process in the washing step is recycled in the first washing process. According to claim 1,
The method for producing meta-aramid fibrids for high-density non-woven fabrics, characterized in that the polar amide-based solvent is dimethylacetamide (DMAc). According to claim 1,
In the first washing step, the temperature of the washing water is 10 to 60° C. A method for producing meta-aramid fibrids for high-density non-woven fabrics. According to claim 1,
Method for producing meta-aramid fibrid for high-density nonwoven fabric, characterized in that the washing water containing the polar amide solvent used in the first washing process is recycled in the first washing process. According to claim 1,
The method for producing meta-aramid fibrid for high-density nonwoven fabric, characterized in that the washing with water that does not contain a polar amide solvent in the second washing step is performed twice or more. 6. The method of claim 5,
In the second washing step, the temperature of the washing water at the time of final washing is 45 to 60 ° C. Method for producing meta-aramid fibrids for high-density non-woven fabrics. A meta-aramid fibrid for high-density non-woven fabric, characterized in that the manufacturing method of any one of claims 1 to 6 is prepared. A high-density nonwoven fabric comprising the meta-aramid fibrid of claim 7.

Images