KR101961188B1 - Meta-aramid fiber having low thermal shrinkage and Manufacturing method thereof - Google Patents

Abstract

The present invention relates to a method for producing meta-aramid fibers having a reduced heat shrinkage, which is wet-radiated in a coagulation bath, comprising the steps of: wet-spinning in a coagulation bath having a polar amide solvent content of 45 to 50% step; A wet stretching step of wet-stretching the meta-aramid fiber at a stretching ratio of 2.5 to 3.3 in a coagulating bath having a polar amide solvent content of 30 to 40% by weight as a coagulating solution; A washing step of washing and drying the meta-aramid fiber; And a hot stretching step of hot-rolling the meta-aramid fiber at a stretching ratio of from 1.5 to 2.0 at 350 to 420 ° C.

Description

META-aramid fibers having reduced heat shrinkage and methods of making same

The present invention relates to a meta-aramid fiber having reduced heat shrinkage and a method for producing the same, and more particularly, to a meta-aramid fiber having a low heat shrinkage at a high temperature and having a reduced heat shrinkage rate,

Aromatic polyamides, developed in the 1960s, were developed to improve the heat resistance of nylon, an aliphatic polyamide. Aromatic polyamides, well known for their trade names such as Nomex and Kevlar, And has excellent heat resistance and high tensile strength which can be used for fibers such as cord.

Typical aliphatic polyamides are synthetic resins in which aliphatic hydrocarbons are bonded between amide groups, while aramid is a synthetic resin in which amide bonds are bonded between two aromatic rings. The aliphatic hydrocarbon of the aliphatic polyamide easily undergoes molecular motion when heat is applied, whereas the benzene ring of the aromatic polyamide is stable to heat and has a high elastic modulus because the molecular chain is rigid and the molecules do not easily move even when heat is applied. Exhibit many differences in characteristics.

Generally, when a typical aramid is stretched, high mechanical properties such as high strength and high tensile elastic modulus are exhibited. As a part of this, Korean Patent Laid-Open No. 10-2015-0017749 relates to a para-type wholly aromatic copolyamide stretched fiber and a method for producing the same, and specifically discloses a stretching method of an aramid fiber.

In particular, the meta-aramid is represented by Nomex developed by DuPont and Conex developed by Dejin. The meta-based aramid has a merit that the strength and elongation of the benzene ring are combined with the amide group at the meta-position, similar to ordinary nylon, but very good in heat stability, and light and sweat-absorbing compared to other heat-resistant materials. It is used as heat-resistant clothing materials such as fire fighting uniforms, uniforms for racing motorists, astronaut uniforms, and work clothes, and is used for high-temperature filters in industrial applications.

However, since the meta-aramid has a shrinkage ratio of about 5%, which is basically produced after the production, width shrinkage is caused in the post-processing such as nonwoven fabric production, spinning, dyeing, and the like. In particular, when the non-woven fabric formed of the meta-aramid fiber is used as a bag filter, the shrinkage of the meta-aramid fiber is increased as the shrinkage ratio of the bag filter increases, resulting in the detachment of the cage of the bag filter, The morphological stability of the filter at high temperature is important. Therefore, various methods are proposed to solve this problem.

For example, Korean Patent Registration No. 0462924 relates to a low shrinkage polyamide fiber for uncoated airbags and a method for producing the same, and more particularly, to a method for manufacturing a low shrinkage polyamide fiber for a nonwoven airbag, which comprises melting a polyhexamethylene adipamide chip having a relative viscosity of 2.5 or more, A step of extruding and cooling and solidifying the yarn by use of a cooling gas under a spinneret, and a step of winding the yarn at a total m / e ratio of 4.0 or more and performing multi-stage stretching, heat treatment and relaxation, . However, the heat shrinkability (160 DEG C, 30 minutes) of the above method was about 3 to 6%, and the heat shrinkability was not significantly improved.

 Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and provides a method for manufacturing a meta-aramid fiber with reduced heat shrinkage, which improves heat shrinkage through wet stretching and hot- .

Another object of the present invention is to provide a meta-aramid fiber having a reduced heat shrinkage, which is produced by the metha-aramid fiber production method with reduced heat shrinkage.

The present invention relates to a method for producing meta-aramid fibers having a reduced heat shrinkage, which is wet-radiated in a coagulation bath, comprising the steps of: wet-spinning in a coagulation bath having a polar amide solvent content of 45 to 50% step; A wet stretching step of wet-stretching the meta-aramid fiber at a stretch ratio of 2.5 to 3.3 in an elongation crease having a polar amide-based solvent content of 30 to 40% by weight as a coagulating liquid; A water washing step of washing and drying the meta-aramid fiber; And a hot stretching step of hot-rolling the meta-aramid fibers at a stretching ratio of 1.5 to 2.0 at 350 to 420 ° C, wherein the heat shrinkage ratio of the meta-aramid fibers is reduced.

The present invention also provides a method for producing a meta-aramid fiber with reduced heat shrinkage, wherein the stretching ratio (WDr) of the wet stretching step and the stretching ratio (HDr) of the hot stretching step satisfy the following formula.

1 < WDr / HDr < 2.5

Also provided is a meta-aramid fiber with reduced heat shrinkage, which is produced by the above process.

Also, the meta-aramid fiber has a heat shrinkage ratio of less than 2.5%.

As described above, the meta-aramid fibers with reduced heat shrinkage according to the present invention have an effect of reducing the heat shrinkage by minimizing the residual stress caused by the excessive elongation at the time of hot rolling, by increasing the wet heat mysterious ratio during manufacture.

In addition, the meta-aramid fibers with reduced heat shrinkage of the present invention have the effect of preventing the width contraction in the post-processing such as non-woven fabric production, spinning, dyeing and the like.

In addition, the meta-aramid fiber with reduced heat shrinkage of the present invention has an effect of having a stable value even when heat is applied, when it is used as a heat-resistant material such as a filter, a firefighter's suit,

1 is a process diagram of a method for producing meta-aramid fibers with reduced heat shrinkage according to the present invention.

Hereinafter, preferred embodiments 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 have the same reference numerals as much as possible. 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.

As used herein, the terms " about, " " substantially, " " etc. ", when used to refer to a manufacturing or material tolerance inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure.

1 is a process diagram of a method for producing meta-aramid fibers with reduced heat shrinkage according to the present invention.

The physical properties of general meta-aramid fibers vary depending on the coagulation, wet stretching, hot stretching, and open and defined conditions in wet spinning.

Conventional meta-aramid fibers have a softening ratio of about 1.5 to 2.0 and a hot-rolled ratio of about 2.5 to 3.3, and thus the hot-rolled steel sheet has a higher draw ratio than the wet-drawn steel sheet. The inventors of the present invention have found that the residual stress in the meta-aramid fiber is significantly increased due to excessive elongation at the time of hot rolling when the hot-melt ratio is made high, and the tendency to shrink when heat is applied after the fiber is produced is strong.

In the present invention, fibers are manufactured by increasing the mysterious mystery ratio to be higher than the hot mystery ratio in order to minimize the residual stress of the produced meta-aramid fibers.

The method of producing meta-aramid fibers with reduced heat shrinkage according to the present invention includes a spinning step, a wet stretching step, a washing step, and a hot rolling step as well as a general meta-aramid fiber.

The spinning step is a step of wet-spinning in a coagulation tank having a polar amide-based solvent content of 45 to 50% by weight to form meta-aramid fibers.

The spinning step is a wet spinning process in which meta-aramid dope dissolved in a polar amide solvent is radiated in a coagulating solution of a coagulation tank, and the polar amide solvent content contained in the coagulating solution is adjusted to 45 By weight to 50% by weight.

The polar amide solvent may be selected from the group consisting of dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethyl formamide (DMF), and dimethyl imidazolidinone Any one of the compounds may be used, and it is preferable to use dimethylacetamide having the most excellent effect.

The wet stretching step is a wet stretching step of stretching the meta-aramid fiber at a draw ratio of 2.5 to 3.3 in an elongation crease having a polar amide solvent content of 30 to 40% by weight as a coagulating solution, and is performed in the same manner as the wet stretching step of a general meta-aramid fiber , It is preferable that the polar amide-based solvent content of the coagulating solution is 30 to 40% by weight in order to prevent filing due to high stretching ratio.

The water washing step is a step of washing and drying the meta-aramid fiber, and may be carried out in the same manner as the washing and drying steps of a common meta-aramid fiber.

The hot stretching step is a step of stretching the meta-aramid fiber through a heating roller, wherein the meta-aramid fiber is hot-rolled at a stretching ratio of 1.5 to 2.0 at 350 to 420 ° C. It is preferable that the stretching ratio is set to be lower than the stretching ratio of wet stretching to minimize the residual stress of the stretched meta-aramid fiber.

As described above, the meta-aramid fiber of the present invention is manufactured by increasing the stretching ratio (WDr) of the wet stretching step to be higher than the stretching ratio (HDr) of the hot stretching step to minimize the residual stress inside the meta-aramid fiber after production, It is preferable to satisfy the following expression.

1 < WDr / HDr < 2.5

When the WDr / HDr value is less than 1, the stretching ratio HDr of the hot stretching step is larger than the stretching ratio WDr of the wet stretching step, so that the residual stress inside the meta-aramid fiber may increase, When the HDr value is 2.5 or more, the stretching ratio WDr of the wet stretching step becomes too large and the processability may be lowered.

The heat-shrinkable meta-aramid fiber according to the present invention produced by the above-described method has a heat shrinkage of less than 2.5% at 350 DEG C and is used as a heat-resistant material for filters, The shape stability can be improved by numerical values.

Hereinafter, an embodiment of a method for producing meta-aramid fibers with reduced heat shrinkage according to the present invention will be described, but the present invention is not limited to the examples.

Example 1

Metha aramid dopes having a meta-aramid concentration of 20% by weight dissolved in dimethylacetamide were wet-radiated in 50% by weight of dimethylacetamide and 50% by weight of water in a coagulation solution at 50 ° C, 20% by weight of dimethylacetamide, The mixture was dried at 80% by weight in a coagulating solution at about 50 캜 at a stretching ratio of 2.5, and then washed with water and dried.

The dried meta-aramid fibers were hot drawn at a draw ratio of 1.5 through a heating roller at about 380 ° C to produce meta-aramid fibers with reduced heat shrinkage according to the present invention.

Example  2

The wet stretching was carried out in the coagulation solution of 40% by weight of dimethylacetamide and 60% by weight of water to produce the meta-aramid fibers with reduced heat shrinkage according to the present invention.

Comparative Example  One

The wet spinning was carried out in a coagulating solution of 40% by weight of dimethylacetamide and 60% by weight of water. The wet stretching was conducted in the same manner as in Example 1 except that 20% by weight of dimethylacetamide and 1.5% And the hot rolled sheet was stretched at a stretching ratio of 3.3 to produce a meta-aramid fiber.

Comparative Example  2

The same procedure as in Comparative Example 1 was carried out except that the wet drawing was conducted at a draw ratio of 2.0 and the hot draw was conducted at a draw ratio of 2.5 to produce a meta-aramid fiber.

◈ Evaluation of Heat Shrinkage of Examples and Comparative Examples

The meta-aramid fibers prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were allowed to stand in an environment of 350 ° C. for 30 seconds, and the heat shrinkage ratio was measured and shown in Table 1.

division Example 1 Example 2 Comparative Example 1 Comparative Example 2 Coagulation bath DMAc concentration (wt%) 50 50 40 40 The wet-drawn DMAc concentration (wt%) 20 40 20 20 Stretching cost Wet stretching 2.5 2.5 1.5 2.0 Hot thread 1.5 1.5 3.3 2.5 Radiation fairness (point) 10 10 10 6 Heat shrinkage (%) 2 0.5 4 ㅡ

As shown in Table 1, the heat shrinkability of Examples 1 and 2, in which the heat shrinkage ratio of the present invention is reduced, is less than 2%, which indicates that the heat shrinkability of Comparative Example 1 is excellent.

In addition, as in Comparative Example 2, when the wet stretching ratio is increased without increasing the concentration of the polar amide-based solvent in the coagulation bath and the cremation crease, excessive threading by stretching occurs during the spinning process, and the processability is lowered.

In addition, the heat shrinkage ratio of Example 2 is the lowest. This is because, when the concentration of the polar amide solvent in the coagulation bath and the concentration of the polar amide solvent in the wet bath are increased, the metha aramide fiber having the lowest heat shrinkage rate is produced with good processability .

Claims (4)

A method for producing a meta-aramid fiber having a heat shrinkage reduced by wet-spinning in a coagulation bath,
A spinning step of wet-spinning in a coagulation bath containing 45 to 50% by weight of a coagulating solution of a polar amide solvent to form meta-aramid fibers;
A wet stretching step of wet-stretching the meta-aramid fiber at a stretch ratio of 2.5 to 3.3 in an elongation crease having a polar amide-based solvent content of 30 to 40% by weight as a coagulating liquid;
A washing step of washing and drying the meta-aramid fiber;
And a hot stretching step of hot-rolling the meta-aramid fiber at a stretching ratio of 1.5 to 2.0 at 350 to 420 ° C. The method of claim 1, wherein
Wherein the stretching ratio (WDr) of the wet stretching step and the stretching ratio (HDr) of the hot stretching step satisfy the following formula.
1 < WDr / HDr < 2.5 delete delete

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