KR102545781B1 - Manufacturing method of sea-island complex fiber, manufacturing method of nonflammable resin including the same and sea-island complex fiber thereby - Google Patents

Abstract

In the method for producing the flame retardant resin of the present invention, as the water-soluble resin is included as the sea component, the weight reduction is possible through a non-alkali reduction process. Accordingly, there is an effect of maintaining excellent physical properties, dyeability, and flame retardancy of island component fibers.

Description

Manufacturing method of sea-island complex fiber, manufacturing method of nonflammable resin including the same and sea-island complex fiber thereby}

The present invention relates to a method for manufacturing fibers, and more particularly, to a method for manufacturing sea-island composite fibers, a method for manufacturing flame retardant resin fibers including the same, and sea-island composite fibers manufactured thereby.

In general, curtains, wallpaper, carpets, flame retardant non-woven fabrics, and other ornaments are made of flame retardant treated fabrics and non-woven fabrics for safety in places where people are densely populated, places with many electrical facilities, and places with many enclosed spaces. Therefore, conventional flame retardant yarns are prepared by melt-stretching chemical fiber yarn materials, and then the surface of each chemical fiber yarn is treated with a flame retardant to prevent burning due to a flame or the like. In addition, in the conventional flame retardant treatment method, the synthetic fiber yarn is woven or knitted using a loom or knitting machine to make a fabric, and then the surface of the fabric is treated with a flame retardant to prevent ignition by fire. However, conventionally, since flame retardant treatment is performed after manufacturing synthetic fiber yarns or fabrics, flame retardants are attached to the surface of synthetic fiber yarns or fabrics, so the flame retardant is likely to fall off depending on the time of use, and the flame retardant ability is improved by dropping the flame retardant. It had a downside.

In addition, in the case of flame retardant fibers, they tend to be used in high-quality fabric products, and in the case of products using high-quality fabrics, high color depth is required. / or make fibers. However, in the case of existing flame retardant fibers and/or resins for producing them, there is a problem in that physical properties of flame retardant fibers and/or fabrics prepared by additive compositions and processes for increasing color clarity are reduced. For example, Korean Patent Publication No. 2005-0103617 mentions a flame retardant polyester having excellent color development during dyeing by adding a complementary agent, but hydrolysis of the flame retardant by high-temperature hot water occurs during dyeing. Korean Patent Publication No. 2003-0028022 discloses a method for producing polyester using cationic dyes, which includes pretreatment of metal sulfonate salts to maintain spinning processability when preparing polyester compositions that can be dyed with cationic dyes. is required, which increases the process cost, and also causes a decrease in yarn properties and an increase in pack pressure during the process when the content of the modifier is increased to improve color clarity.

In addition, conventionally, as a flame retardant polyester sea-island type conjugate fiber, a sea-island type conjugate fiber using an alkali-soluble polyester polymer as a sea component and a flame retardant polyester as an island component has been disclosed. When the alkali reduction process is performed under strong base and high temperature conditions, hydrolysis and flame retardant dropout occur, resulting in deterioration in physical properties, dyeability, and flame retardancy of the final product.

KR 2005-0103617A KR 2003-0028022A

The present invention has been made to solve the above problems, and a method for producing sea-island type composite fibers capable of producing flame retardant resin fibers with excellent flame retardancy and dyeability, a method for manufacturing flame retardant resin fibers including the same, and sea-island manufactured thereby Its purpose is to provide a type composite fiber. In addition, a method for manufacturing sea-island composite fibers capable of preventing deterioration in dyeability, physical properties, and flame retardancy of flame retardant fibers even when weight loss is performed, a method for manufacturing flame retardant resin fibers including the same, and sea-island composite fibers manufactured thereby It has a different purpose to provide.

To solve the above problems, the present invention relates to a method for manufacturing a sea-island composite fiber, comprising the steps of preparing a flame retardant resin and a water-soluble polyester resin; a second step of drying the flame retardant resin and the water-soluble polyester resin; and Island in the Sea type composite fibers containing the water-soluble polyester resin as a sea component and the flame retardant resin as an island component by performing composite spinning on the dried flame retardant resin and the water-soluble polyester resin. 3 steps of preparing; including, wherein the flame retardant resin comprises 87.5 to 97.0 mol% of polyester, 2.5 to 4.5 mol% of a compound represented by Formula 1 below, and 0.5 to 8.0 mol% of a metal sulfonate, wherein the water-soluble The polyester resin includes 50 to 70 mol% of polyester, 20 to 30 mol% of an aromatic polyhydric carboxylic acid having 6 to 14 carbon atoms, 10 to 20 mol% of a metal sulfonate, and 10 to 20 mol% of an aliphatic diol.

[Formula 1]

In Formula 1, R ¹ is -OH, -COOH, -CH ₂ COOH, -CH ₂ CH ₂ COOH, -CH ₂ CH ₂ CH ₂ COOH, or -CH ₂ CH 2 CH _{2 CH 2 COOH} .

As a preferred embodiment of the present invention, the polyester may be a polyethylene terephthalate (PET) resin having a weight average molecular weight of 18,000 to 22,000.

As a preferred embodiment of the present invention, the composite spinning may be performed at a spinning temperature of 260 to 300 ° C and a spinning speed of 2,000 mpm or more.

As a preferred embodiment of the present invention, the flame retardant resin in the second step may be dried at 110 to 130 ° C, and the water-soluble polyester resin may be dried at 70 to 90 ° C.

As a preferred embodiment of the present invention, the compound represented by Formula 1 may be included in the flame retardant resin in an amount of 5,000 to 7,000 ppm (based on the P content of the compound).

As a preferred embodiment of the present invention, in the third step, the sea-island composite fiber may include the flame retardant resin and the water-soluble polyester resin in a weight ratio of 50:50 to 90:10.

As a preferred embodiment of the present invention, the metal sulfonate is 1 selected from the group consisting of dimethyl 5-sodiosulfo isophthalate, sodium 3,5-dicarbomethoxybenzenesulfonate and dicarbomethoxybenzenesulfonate. May include more than one species.

As a preferred embodiment of the present invention, the aromatic polyhydric carboxylic acid having 6 to 14 carbon atoms may include at least one selected from the group consisting of terephthalic acid, isophthalic acid and dimethyl terephthalate.

As a preferred embodiment of the present invention, the aliphatic diol may include an aliphatic diol having 2 to 20 carbon atoms.

As a preferred embodiment of the present invention, the aliphatic diol is ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, trimethyl glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, heptamethylene glycol, octamethylene glycol , It may include one or more selected from the group consisting of nonamethylene glycol, decamethylene glycol, undecamethylene glycol, dodecamethylene glycol, and tridecamethylene glycol.

Another aspect of the present invention provides a method for producing a flame retardant resin fiber. The manufacturing method includes the steps of manufacturing sea-island composite fibers by the manufacturing method of sea-island composite fibers of the present invention; and a fourth step of non-alkali reduction of the sea-island composite fibers.

As a preferred embodiment of the present invention, the above 4 steps may be performed in hot water at a temperature of 80 to 110 ° C for 10 to 50 minutes.

Another object of the present invention is an Island in the Sea composite fiber comprising a water-soluble polyester resin as a sea component and a flame retardant resin as an island component, wherein the flame retardant resin contains 87.5 to 97.0 mol% of polyester. , 0.5 to 8.0 mol% of a metal sulfonate and 2.5 to 4.5 mol% of a compound represented by Formula 1 below, wherein the water-soluble polyester resin contains 50 to 70 mol% of polyester and an aromatic polyvalent carboxyl group having 6 to 14 carbon atoms. To provide a sea-island composite fiber containing 20 to 30 mol% acid, 10 to 20 mol% metal sulfonate, and 10 to 20 mol% aliphatic diol.

[Formula 1]

In Formula 1, R ¹ is -OH, -COOH, -CH ₂ COOH, -CH ₂ CH ₂ COOH, -CH ₂ CH ₂ CH ₂ COOH, or -CH ₂ CH 2 CH _{2 CH 2 COOH} .

The flame retardant resin fiber prepared according to the present invention has improved flame retardancy and dyeability. In addition, the method for producing flame retardant ester fibers of the present invention has an effect of preventing deterioration of dyeability, physical properties, and flame retardancy of flame retardant fibers even if a weight loss process is performed.

1 is a cross-sectional view of an island-in-the-sea yarn according to an embodiment of the present invention.

Hereinafter, in order to explain the present invention in more detail, preferred embodiments according to the present invention will be described in more detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Like reference numbers indicate like elements throughout the specification.

A method for producing a flame retardant resin fiber according to an embodiment of the present invention includes a first step of preparing a flame retardant resin and a water-soluble polyester resin, a second step of drying the flame retardant resin and a water-soluble polyester resin, and the dried flame retardant resin and A third step of performing conjugate spinning on a water-soluble polyester resin to produce island-in-the-sea composite fibers containing the water-soluble polyester resin as a sea component and the flame retardant resin as an island component; and It includes four steps of non-alkali reduction of the sea-island composite fibers.

As the first step, a flame retardant resin and a water-soluble polyester resin are prepared. The flame retardant resin includes 87.5 to 97.0 mol% of polyester, 2.5 to 4.5 mol% of a compound represented by Formula 1 below, and 0.5 to 8.0 mol% of a metal sulfonate.

[Formula 1]

In Formula 1, R ¹ is -OH, -COOH, -CH ₂ COOH, -CH ₂ CH ₂ COOH, -CH ₂ CH ₂ CH ₂ COOH, or -CH ₂ CH 2 CH _{2 CH 2 COOH} .

The flame retardant resin is a composition formed from an island component, which is a fiber forming component, during the production of island-in-the-sea fibers, which will be described later, and corresponds to a composition that forms flame retardant resin fibers remaining after a non-reduction process described later.

In the flame retardant resin, when the polyester is less than 87.5 mol%, fiber formation may be difficult, and when the polyester fiber exceeds 97.0 mol%, the addition amount of the compound represented by Formula 1 and the metal sulfonate may be limited. . The polyester may be a polyethylene terephthalate (PET) resin having a weight average molecular weight of 18,000 to 22,000.

The compound represented by Formula 1 serves to increase flame retardancy. In the flame retardant resin, when the compound represented by Formula 1 is less than 2.5 mol%, the flame retardant synergistic effect by the compound represented by Formula 1 may be reduced, and when it exceeds 4.5 mol%, the polyester and metal are relatively The amount of added sulfonate may be limited.

The compound represented by Formula 1 is 5,000 to 7,000 ppm (based on the P content of the compound), preferably 5,200 to 6,500 ppm (based on the P content of the compound) in the flame retardant resin, more preferably 5,500 to 6,300 ppm ( Based on the P content of the compound), it is good to add it so that it becomes. At this time, if the input amount of the compound represented by Formula 1 is less than 5,000 ppm (based on the P content of the compound), sufficient flame retardancy may not be secured, and if it exceeds 7,000 ppm (based on the P content of the compound), polymerization due to excessive P content Poor reactivity may occur during the reaction, and problems such as a decrease in heat resistance and a decrease in viscosity of polymer chips may occur in a spinning process described later. In the final product, degradation of physical properties may occur, which may cause a problem of process passability due to yarn cutting during weaving and circular knitting, so it is recommended to use it within the above range.

The metal sulfonate serves to improve the dyeability of the flame retardant resin. In the flame retardant resin, when the metal sulfonate is less than 0.5 mol%, the effect of improving dyeability may be limited, and when the metal sulfonate exceeds 8.0 mol%, the amount of the polyester and the compound represented by Formula 1 is relatively added. this may be limited.

The metal sulfonate may include at least one selected from the group consisting of dimethyl 5-sodiosulfo isophthalate, sodium 3,5-dicarbomethoxybenzenesulfonate and dicarbomethoxybenzenesulfonate.

The water-soluble polyester resin is a component that forms a sea component, which is an extract component from sea-island fibers to be described later. The water-soluble polyester resin includes 50 to 70 mol% of polyester, 20 to 30 mol% of aromatic polycarboxylic acid having 6 to 14 carbon atoms, 10 to 20 mol% of metal sulfonate, and 10 to 20 mol% of aliphatic diol do.

The polyester may be a polyethylene terephthalate (PET) resin having a weight average molecular weight of 18,000 to 22,000. When the terephthalic acid is less than 60 mol% in the water-soluble polyester resin, the ratio of the sea component in the sea-island fibers described later may be smaller than the initial design value. In addition, when the terephthalic acid content exceeds 70 mol%, the content of other components may be limited.

The aromatic polyhydric carboxylic acid having 6 to 14 carbon atoms serves to reduce crystallinity. When the amount of the aromatic polyhydric carboxylic acid having 6 to 14 carbon atoms in the water-soluble polyester resin is less than 20 mol%, the effect of reducing the crystallinity may be reduced, and the aromatic polyhydric carboxylic acid having 6 to 14 carbon atoms may be less than 30 mol%. If exceeded, the content values of other components may be limited. The aromatic polyvalent carboxylic acid having 6 to 14 carbon atoms may include at least one selected from the group consisting of terephthalic acid, isophthalic acid and dimethyl terephthalate.

The metal sulfonate serves to induce adsorption of water molecules. That is, the water-soluble polyester resin is induced to have water solubility. In the water-soluble polyester resin, when the amount of the metal sulfonate is less than 10 mol%, the effect of inducing adsorption of water molecules is limited, so the reduction may not be sufficiently achieved by the non-alkali reduction described later, and the metal sulfonate is 20 mol%. If the % is exceeded, the content of other components may be relatively limited, and as the ratio of the amorphous region increases, spinning fairness such as yarn property degradation and pack pressure generation may be deteriorated.

The aliphatic diol may be esterified with the polyester to obtain a polyester resin. In the water-soluble polyester resin, when the aliphatic diol is less than 10 mol%, the yield of the water-soluble polyester resin may be low, and when it exceeds 20 mol%, unreacted aliphatic diol may be generated.

The aliphatic diol is an aliphatic diol having 2 to 20 carbon atoms, preferably ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, trimethyl glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, heptamethylene glycol, It may include at least one selected from the group consisting of octamethylene glycol, nonamethylene glycol, decamethylene glycol, undecamethylene glycol, dodecamethylene glycol, and tridecamethylene glycol. More preferably, at least one selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol and butylene glycol may be included.

In the second step, the flame retardant resin and the water-soluble polyester resin are dried. The drying step is to improve crystallinity by removing moisture so that the moisture content is less than 100 ppm, and the flame retardant resin can be dried at 110 ° C to 130 ° C, preferably at a low temperature of 110 ° C to 120 ° C. Drying can be done. At this time, if the drying temperature is less than 110 ° C., the resin may not be sufficiently dried, and if it exceeds 130 ° C., there may be a problem in that the intrinsic viscosity decreases, so it is preferable to perform drying at the above temperature.

The water-soluble polyester resin may be dried at 70° C. to 90° C., preferably at a low temperature of 70° C. to 80° C. At this time, if the drying temperature is less than 70 ° C., the resin may not be sufficiently dried, and if it exceeds 90 ° C., there may be problems in that chip fusion occurs and intrinsic viscosity decreases.

In the third step, composite spinning is performed on the dried flame retardant resin and the water-soluble polyester resin to include the water-soluble polyester resin as a sea component and the island in the sea including the flame retardant resin as an island component. ) to produce type composite fibers.

In addition, the spinning in the spinning step may be performed at a spinning temperature of 260 ° C to 300 ° C and a spinning speed of 2,000 mpm or more, preferably at a spinning temperature of 260 ° C to 290 ° C and a spinning speed of 3,500 mpm to 4,800 mpm. can also be performed. At this time, if the spinning temperature is less than 260 ° C, there may be a problem of dyeing (defective dyeing) due to unstretching due to insufficient alignment of the polymer, and if it exceeds 300 ° C, thermal decomposition due to high temperature occurs, resulting in yarn physical properties There may be issues with this degradation. And, if the spinning speed is less than 2,500 mpm, there may be a problem of dyeing (defective dyeing) due to unstretching due to lack of alignment of the polymer, and a cost increase due to a decrease in productivity may occur.

In addition, in the present invention, the spinning can be performed using a general sea-island composite spinneret used in the art, and a composite including a sea component spinneret 30 and an island component spinneret 31 as shown in FIG. 1 A spinneret may be used.

In this case, the flame retardant resin and the water-soluble polyester resin may be mixed in a weight ratio of 50:50 to 90:10. When the weight ratio of the flame retardant resin to the water-soluble polyester resin is less than 50%, the flame retardant effect by the compound represented by Chemical Formula 1 may be reduced, and when the flame retardant resin is 90% or more compared to the water-soluble polyester resin, sea-island fibers do not dissolve. Due to the low weight of the powder, a bonding problem with island components may occur during spinning, which may cause touch and dyeing defects in the final product after dissolution.

In the fourth step, the non-alkali reduction of the sea-island composite fibers. In this case, the non-alkali reduction is a reduction performed using water rather than alkali, and is possible because the above-described water-soluble polyester resin exhibits water solubility.

The non-alkali reduction may be performed in hot water at a temperature of 80 to 110 ° C for 10 to 50 minutes. When the temperature of the hot water is lower than 80° C. during weight loss, the rate of weight loss may slow down and the process time may slow down. When the temperature of the hot water exceeds 110° C., side reactions may occur. In addition, if the non-alkali reduction process time is less than 10 minutes, sufficient reduction may not be achieved, so that the sea component may not be completely extracted from the sea-island fibers, and side reactions may occur if the time exceeds 50 minutes.

As the flame retardant water resin fiber prepared by the above-described method for producing flame retardant water resin fiber is reduced by non-alkali reduction rather than alkali reduction, physical properties, dyeability, and flame retardancy of the flame retardant water resin fiber, which is an island component, are reduced. It is possible to provide a fiber having excellent physical properties, dyeability, and flame retardancy.

When the flame retardant water resin fiber of the present invention has an average diameter of 15 μm and an average fineness of 150 de, the rate of change in strength of the composite fiber may satisfy Equation 1 below.

[Equation 1]

In Equation 1, the strength of the composite fiber is measured according to the ASTM D2256 method, the unit of strength is g / d, and the strength change rate is 0.5% to 10%, more preferably 1% to 3% am.

Hereinafter, a preferred embodiment (example) is presented to help the understanding of the present invention. However, the following examples are only for helping understanding of the present invention, and the present invention is not limited by the following experimental examples.

[Example]

<Example 1 - Preparation of flame retardant resin fibers>

(1) Production of flame retardant resin (island component fiber composition)

After mixing 94.7 mol% of terephthalic acid and 1.30 mol% of dimethyl 5-sodiosulfo isophthalate, an esterification reaction was performed while removing water generated at 240° C. to prepare polyester.

Next, a compound represented by Chemical Formula 1-1 was added to the polyester and stirred to prepare a mixture. At this time, the compound represented by Formula 1 was added so as to be 6,020 ppm based on the P content in the total weight of the mixture.

Next, the mixture was polymerized at 278° C. to 280° C. and 1.5 torr or less to prepare a polymer to prepare a flame retardant resin (island component resin).

Further, the intrinsic viscosity (IV) of the prepared flame retardant water resin-forming composition (island component resin) was 0.670 dl/g when measured with an Ubbelohde viscometer.

[Formula 1-1]

In Formula 1-1, R ¹ is -CH ₂ CH ₂ COOH.

(2) Manufacture of resin for export (sea component fiber composition)

Mixing a heat-damaging component resin prepared by copolymerizing a mixture containing 60 mol% of polyethylene terephthalate, 20 mol% of isophthalic acid, 10 mol% of dimethyl 5-sodiosulfo isophthalate, and 10 mol% of diethylene glycol, The intrinsic viscosity (IV) of the prepared sheath resin was 0.820 dl/g.

(3) Manufacture of sea-island fibers

After adding the flame retardant resin to the island portion of the sea-island type composite spinneret and the water-soluble resin to the sea portion, spinning was performed under a spinning temperature of 280°C and a spinning speed of 4,200 mpm to island-island fibers (average diameter 15㎛, average fineness). 150 de, 70 wt% core, 30 wt% sheath).

(4) Weight loss process

The island-in-the-sea fibers were reduced in hot water at 98° C. for about 30 minutes to prepare phosphorus-based flame retardant polyester fibers.

<Example 2 - Preparation of dyed flame retardant resin fibers>

The phosphorus-based flame retardant polyester fiber prepared in Example 1 was improved with a dye and fiber at a bath ratio of 50: 1 using a disperse dye under the above disperse dye dyeing conditions (pH 4.5, temperature 130 ° C, dyeing treatment time 40 minutes) Dyeing was performed.

<Comparative Example 1>

Fibers were prepared in the same manner as in Example 1, except that the weight loss process was performed with a 5% aqueous solution of NaOH at a temperature of 98 ° C. for 30 minutes.

<Comparative Example 2>

Fibers were prepared in the same manner as in Example 2, except that the weight loss process was performed with a 5% NaOH aqueous solution at a temperature of 98 ° C. for 30 minutes.

Experimental Example: Measurement of physical properties of flame retardant fibers

(1) Intensity measurement

The strength of the fiber was measured using an automatic tensile tester (Textechno) at a speed of 50 cm/m and a gripping distance of 50 cm. Strength was defined as elongation as the value (g/de) obtained by dividing the applied load by denier when the fiber was elongated until it was cut by applying a constant force to the strength, and the value (%) expressed as a percentage of the initial length relative to the elongated length. .

And, the strength change rate (%) was measured based on Equation 1 below.

[Equation 1]

In Equation 1 above, the unit of intensity is g/d.

(2) Measurement of weight loss

The mass loss rate of the fiber was measured by measuring the mass of the fiber before and after the weight loss.

After performing the experiment as above, the results are shown in [Table 1].

Looking at the experimental results in Table 1, in the case of Examples 1 and 2 in which non-alkali reduction was performed, the strength and weight change rate were low, whereas in Comparative Examples 1 and 2 in which alkali reduction was performed, the strength and weight change rate were high can be seen.

In the above, the present invention has been described in detail with preferred embodiments and experimental examples, but the present invention is not limited by the above embodiments and experimental examples, and those skilled in the art within the technical spirit and scope of the present invention Various modifications and changes are possible by the person.

30: sea component 31: island component

Claims (13)

Step 1 of preparing a flame retardant resin and a water-soluble polyester resin;
a second step of drying the flame retardant resin and the water-soluble polyester resin; and
The dried flame retardant resin and the water-soluble polyester resin are subjected to composite spinning to produce Island in the Sea composite fibers containing the water-soluble polyester resin as a sea component and the flame retardant resin as an island component. 3 steps of manufacturing; including,
The flame retardant resin includes 87.5 to 97.0 mol% of polyester, 0.5 to 8.0 mol% of a metal sulfonate, and 2.5 to 4.5 mol% of a compound represented by Formula 1 below,
The water-soluble polyester resin includes 50 to 70 mol% of polyester, 20 to 30 mol% of an aromatic polyhydric carboxylic acid having 6 to 14 carbon atoms, 10 to 20 mol% of a metal sulfonate, and 10 to 20 mol% of an aliphatic diol Method for producing sea-island composite fibers.
[Formula 1]

In Formula 1, R ¹ is -OH, -COOH, -CH ₂ COOH, -CH ₂ CH ₂ COOH, -CH ₂ CH ₂ CH ₂ COOH, or -CH ₂ CH 2 CH _{2 CH 2 COOH} . According to claim 1,
The polyester is a polyethylene terephthalate (PET) resin having a weight average molecular weight of 18,000 to 22,000. Method for producing sea-island composite fibers. According to claim 1,
The composite spinning is a method for producing sea-island composite fibers performed at a spinning temperature of 260 to 300 ° C and a spinning speed of 2,000 mpm or more. According to claim 1,
The flame retardant resin in the second step is dried at 110 to 130 ° C, and the water-soluble polyester resin is dried at 70 to 90 ° C. According to claim 1,
The method for producing a sea-island composite fiber comprising the compound represented by Formula 1 in an amount of 5,000 to 7,000 ppm (based on the P content of the compound) in the flame retardant resin. According to claim 1,
In the third step, the sea-island composite fiber includes the flame retardant resin and the water-soluble polyester resin in a weight ratio of 50:50 to 90:10. According to claim 1,
The metal sulfonate is a sea-island composite fiber comprising at least one selected from the group consisting of dimethyl 5-sodiosulfo isophthalate, sodium 3,5-dicarbomethoxybenzenesulfonate and dicarbomethoxybenzenesulfonate. Manufacturing method of. According to claim 1,
The method of producing a sea-island composite fiber comprising at least one selected from the group consisting of terephthalic acid, isophthalic acid and dimethyl terephthalate, wherein the aromatic polyhydric carboxylic acid having 6 to 14 carbon atoms. According to claim 1,
The aliphatic diol is a method for producing a sea-island composite fiber comprising an aliphatic diol having 2 to 20 carbon atoms. According to claim 1,
The aliphatic diol is ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, trimethyl glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, heptamethylene glycol, octamethylene glycol, nonamethylene glycol, decamethylene glycol, A method for producing sea-island composite fibers comprising at least one selected from the group consisting of undecamethylene glycol, dodecamethylene glycol and tridecamethylene glycol. Manufacturing sea-island composite fibers by the method of manufacturing sea-island composite fibers according to any one of claims 1 to 10; and
A method for producing a flame retardant resin fiber comprising a fourth step of reducing the non-alkali of the sea-island composite fiber. According to claim 11,
The fourth step is a method for producing a flame retardant resin fiber performed for 10 to 50 minutes in hot water at a temperature of 80 to 110 ° C. In the island in the sea type composite fiber comprising a water-soluble polyester resin as a sea component and a flame retardant resin as an island component,
The flame retardant resin is copolymerized by including 87.5 to 97.0 mol% of polyester, 0.5 to 8.0 mol% of a metal sulfonate, and 2.5 to 4.5 mol% of a compound represented by Formula 1 below,
The water-soluble polyester resin includes 50 to 70 mol% of polyester, 20 to 30 mol% of an aromatic polyhydric carboxylic acid having 6 to 14 carbon atoms, 10 to 20 mol% of a metal sulfonate, and 10 to 20 mol% of an aliphatic diol sea-island type composite fiber copolymerized by
[Formula 1]

In Formula 1, R ¹ is -OH, -COOH, -CH ₂ COOH, -CH ₂ CH ₂ COOH, -CH ₂ CH ₂ CH ₂ COOH, or -CH ₂ CH 2 CH _{2 CH 2 COOH} .

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