WO2009008600A1

WO2009008600A1 - Spandex fibers containing hydromagnesite

Info

Publication number: WO2009008600A1
Application number: PCT/KR2008/003476
Authority: WO
Inventors: Byung-Su Song; Hyun-Gee Jung; Ji-Hye Hong; Yeon-Soo Kang; Seung-Won Seo
Original assignee: Hyosung Corporation
Priority date: 2007-07-10
Filing date: 2008-06-19
Publication date: 2009-01-15
Also published as: KR20090005802A

Abstract

The present invention relates to spandex fiber excellent in resistance to chlorine without affecting intrinsic properties of the polyurethane polymer. The spandex fiber containing 0.1 to 10 wt% of hydromagnesite has a high resistance to chlorine and is therefore useful for underwear, socks, and particularly, sports apparel such as swimsuit.

Description

Description SPANDEX FIBERS CONTAINING HYDROMAGNESITE

Technical Field

[1] The present invention relates to a spandex fiber containing hydromagnesite. Particularly, the invention concerns a spandex fiber which has excellent chlorine-resistance as well as the intrinsic properties of the polyurethane polymer. Background Art

[2] Spandex fibers have high rubber- like elasticity and excellent physical properties such as tensile force, restoration force suitable for e.g. underwear, socks, sports apparel. Spandex fibers consist predominantly of polyurethane, whose physical properties deteriorate when exposed to chlorine water for washing. When swimsuit manufactured by warp-knitting spandex and polyamide is exposed to chlorinated water containing 0.5 to 3.5 ppm of active chlorine in a swimming pool, properties of spandex is also deteriorated

[3] In an attempt to improve the chlorine-resistance of spandex fibers, the use of aάϊtives as a chlorine resisting agent has been proposed For example, US Pat.No.4,340,527 suggest the use of zinc oxide; US Pat.No.5, 626,960, a mixture of huntite and hydromagnesitel; Korea Patent Publication No.92-3250, calcium carbonate or barium carbonate; JP Application Laid-Open No. H6-81215, MgO/ZnO solid solution; JP Application Laid-Open No. S59- 133248, magnesium oxide, magnesium hydroxide or hydrotalcite; and JP Application Laid-Open No. H3-292364, hydrotalcite treated with higher fatty acid and silane coupling agent.

[4] U.S.Pat.No.5,447,969, in particular discloses the use of hydrotalcite having crystallized water and being coated with a C₁₀-₃₀ fatty acid to improve dispersibility and thus prevent aggregation of hydrotalcite during the course of preparing spandex, thereby improving the problems in regard to a rise of discharge pressure and yarn breakage in the spinning process, the discoloration during tannin-solution treatment, and the swelling when immersed in chlorinated water. IVbre specifically, according to U.S.Pat.No.5,447,969, the dry spinning process of a polyurethane solution is conducted at a high temperature condition of 330 ⁰C to obtain spandex yarn. However, the use of hydrotalcite having crystallized water and being coated with a C ₁₀-₃₀ fatty acid causes the spandex yarn discoloration to yellow-brown during the dry spinning process conducted at a high temperature of 250 ⁰C.

[5] According to U.S. Patent No.6,692,828, a hydrotalcite, coated with melamine-based compounds having excellent heat-resistance, is used as a chlorine resisting agent in spandex fibers. However, even in the case of using the hydrotalcite, a spandex fiber is discolored almost equally as compared with U.S. Patent No.5,447,969 when dry spinning spandex fibers at 25O⁰C, although the degree of discoloration is less than that of U.S.Patent No.5,447,969.

[6] Europe Patent Publication No.l 262 499 Al discloses, as a chlorine assisting agent, the use of hydrotalcite milled to an average grain size of \μm or less to improve chlorine resistance of spandex fibers. Specifically, European Patent No. 1 262 499 Al discloses, in contrast to the conventional arts, a partially decarbonated hydrotalcite with a part of carbonic ions thereof decomposed into carbon dioxide and oxygen. The carbonic ion content in the hydrotalcite is important in imparting the chlorine resistance to spandex fibers. Accordingly, the hydrotalcite containing low carbonic ion content leads to poor resistance to chlorine of the spandex.

[7] Korea Patent Publication No. 2006-5814 discloses a method of preparing a spandex fiber excellent in resistance to discoloration and chlorine by using a hydrotalcite coated with melamine-based compounds and free of crystallized water, without dehy- droxylation- or decarbonation-treatment. However, the hydrotalcite from which only crystallized water removed should be carefully handled as it is highly hygroscopic, and therefore tends to return to the state of the original hydrotalcite having crystallized water. And even a hydrotalcite without crystallized water may absorb water in the preparing process of slurry or in the mixing process of slurry with polymer. For that reason, a spandex polymer according to Korea Patent Publication No.2006-5814 is discolored during dry spinning at 25O⁰C or higher.

[8] Korea Patent Publication 2006-66689 discloses the use of a partially dehydroxylated hydrotalcite to prepare a spandex fiber excellent in resistance to both discoloration and chlorine. The spandex yarn has better resistance to discoloration and chlorine as compared with that of Korea Pat. 2006-5814. Disclosure of Invention Technical Problem

[9] Accordingly, the object of the present invention is to provide a spandex fiber containing hydromagnesite and thereby having chlorine resistance. Technical Solution

[10] According to the preferred embodiment of the present invention, a spandex fiber contains 0.1 to 10 wt% of hydromagnesite based on the polyurethane polymer. [11] According to another preferred embodiment of the present invention, the hydro- magnesite is coated with 0.1 to 10 wt% of a coating agent based on the weight of a hy- dromagnesite may be used

[12] According to another preferred embodiment of the present invention, a coating agent include one or more compound selected from a group consisting of aliphatic alcohol, fatty acid, fatty acid salt, aliphatic ester, phosphoric acid ester, styrene/maleic acid anhydride copolymer and its derivatives, silane coupling agent, titanate coupling agent, polyorgano-siloxane, polyorganohydrogen-siloxane and melamine compounds.

[13] According to another preferred embodiment of the present invention, an uncoated hydromagnesite may be used

Advantageous Effects

[14] A spandex fiber according to the present invention has excellent resistance to chlorine and is therefore useful for underwear, socks and particularly, sports apparel such as swimsuit, etc.

Best Mode for Carrying Out the Invention

[15] Hereinafter, the present invention will be described in further detail.

[16] To achieve the above object, there is provided a spandex fiber containing 0.1 to 10 wt% of hydromagnesite. And the present invention has better chlorine-resistance, compared to U.S.Patent No. 5,626,960 using a mineral mixture of huntite and hydromagnesite. As a result of repeated experiments and researches, it has been found that hydromagnesite plays the most important role in improving chlorine resistance, and therefore spandex fiber with improved chlorine resistance may be achieved only with hydromagnesite, without huntite.

[17] The terms to describe the present invention are defined in consideration of features of the present invention, and may be subject to alteration, depending on the intentions and practices of one of ordinary skill in the art, and therefore should not be construed that the scope of the invention is limited thereto.

[18] The hydromagnesite according to the present invention is represented by the following formula (1):

[19] Mg₄(CO₃)₄Mg(OH)₂4H₂O (1)

[20] Hydromagnesite may be obtained from minerals or by synthesizing.

[21] The polyurethane polymer used in the preparation of the spandex fiber according to the present invention may be prepared, as a conventional method known in the art, by reacting an organic diisocyanate and a polymer diol to produce a polyurethane prepolymer, dissolving the polyurethane prepolymer in an organic solvent and reacting it with a diamine and a monoamine.

[22] The organic diisocyanate as used in the present invention may include diphenylmethane-4,4'-diisocyanate, hexamethylene diisocyanate, toluenediisocyanate, butylenediisocyanate, hydrogenated diphenylmethane-4,4'-diisocyanate, etc.

[23] The polymer diol as used in the present invention may include polytetramethylene etherglycol, polypropylene glycol, polycarbonate diol, etc.

[24] The diamine is used as a chain extender and may include ethylenediamine, propy- lenediamine, hydrazine, etc.

[25] The monoamine is used as a chain terminator and may include diethylamine, mo- noethanolamine, dimethylamine, etc.

[26] Stabilizers may be added into the polyurethane polymer to prevent discoloration and property deterioration of the spandex caused by UV, smog and heat treatment. Specific examples of the stabilizer may include hindered phenols, benzofuran-ones, semi- carbazides, benzotriazols, hindered amines, or polymeric tertiary amine stabilizer (such as polyurethane containing tertiary nitrogen, polydialkyl aminoalkyl methacrylate, etc.)

[27] The spandex fiber of the present invention may further include an additive such as titanium dioxide, magnesium stearate, etc. The titanium dioxide is used in an amount of 0.1 to 5wt% based on the weight of the spandex fiber, according to the whiteness of the spandex fiber. The magnesium stearate is used to enhance the unwinding capability of the spandex fiber and added in an amount of 0.1 to 2wt% based on the amount of the spandex fiber.

[28] The added amount of a hydromagnesite is desirably in the range of 0.1 to 10 wt% based on the polyurethane polymer. When the amount is less than 0.1wt%, the spandex fiber has little resistance to chlorine, and when the amount is higher than 10 wt%, the spandex fiber has a deterioration of strength, elongation and modulus due to excess inorganic compounds.

[29] In the preparation of spandex fiber according to the present invention, the hydromagnesite may be added to the polyurethane polymer at any convenient time. For example, a hydromagnesite may be added to the polyurethane polymer after mixing with other additives followed by sand-grinding or milling process, or after sand- grinding or milling process in the absence of other additives.

[30] In the present invention, the hydromagnesite may be coated or not coated with a coating agent conventionally used in the art, which does not affect the chlorine re- sistance of the spandex fiber.

[31] The coating process for hydromagnesite may be conducted by adding a coating agent to a solvent such as water, alcohol, ether, dioxane in an amount of 0.1 to 10wt% based on the weight of hydromagnesite to obtain a coating agent solution, adding a non- coated hydromagnesite thereto and coating the hydromagnesite with the solution at an elevated temperature of 50 to 17O⁰C (if necessary, using a high-pressure reactor) with stirring for about 10 minutes to 2 hours, and subjecting the resultant mixture to filtering and drying. Alternatively the coating process may be conducted by heat- melting a coating agent without solvent, and mixing the melted coating agent with a hydromagnesite in a high-speed mixer.

[32] The coating agent for the hyiromagnesite may comprise one or more selected from a group consisting of aliphatic alcohol, fatty acid, fatty acid salt, aliphatic ester, phosphoric acid ester, styrene/maleic acid anhydride copolymer and its derivatives, silane-based coupling agent, titanate-based coupling agent, polyorgano-siloxane, poly- organohydrogen-siloxane or melamine -based compounds. Preferably, a fatty acid, a fatty acid salt and melamine-based compounds may be used, and particularly, a fatty acid or a fatty acid salt exhibit excellent coating effect, compared to other coating materials.

[33] The fatty acids as a coating agent in the present invention are formed from mono- or poly-hydroxy fatty acids having straight- or branched- hydrocarbon chains of 3 to 40 carbon atoms. Specific examples of the fatty acids may include lauric acid, capronic acid, palmitic acid, and stearic acid

[34] The fatty acid salts as a coating agent in the present invention may include a metal selected from metals in Group I to III of the Periodic Table, or zinc. The fatty acids are formed from mono- or di-functional and saturated or unsaturated fatty acid having 6 to 30 carbon atoms. Examples of the fatty acid salts include lithium, sodium, magnesium, calcium, aluminium or zinc salts of oleic acid, palmitic acid or stearic acid, preferably, magnesium stearate, calcium stearate, or aluminium stearate, and more preferably, magnesium stearate.

[35] The melamine-based compounds used as a coating agent in the present invention include melamine compounds, phosphor-containing melamine compounds, melamine cyanurate compounds, melamine compounds substituted with an organic compound having a carboxyl group, phosphor-containing melamine compounds substituted with an organic compound having a carboxyl group, and melamine cyanurate compounds substituted with an organic compound having a carboxyl group, which may be used alone or in combination.

[36] Examples of the melamine compounds include methylene dimelamine, ethylene dimelamine, trimethylene dimelamine, tetramethylene dimelamine, hexamethylene dimelamine, decamethylene dimelamine, dodecamethylene dimelamine, l,3-c}clohexylene dimelamine, p-phenylene dimelamine, p-xylene dimelamine, di- ethylene trimelamine, triethylene tetramelamine, tetraethylene pentamelamine, hex- aethylene heptamelamine, and melamine formaldehyde.

[37] The phosphor-containing melamine compounds include any of the above-mentioned melamine compounds coupled with phosphoric acid or phosphate. Specific examples of the phosphor-containing melamine compounds include dimelamine pyrophosphate, melamine primary phosphate, melamine secondary phosphate, melamine polyphosphate, or melamine salt of bis-(pentaerythritol phosphate) phosphoric acid, etc.

[38] The melamine cyanurate compounds include melamine cyanurates substituted with at least one substituent, such as methyl, phenyl, carboxymethyl, 2-carboxyethyl, cyanomethyl and 2-cyanoethyl.

[39] It is preferred that the melamine-based compounds contain an organic compound having a carboxyl group. Specific examples of the organic compound having a carboxyl group include aliphatic monocarboxylic acids (e.g., caprylic , undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, eicosanoic acid or behenic acid); aliphatic dicarboxylic acids(e.g., malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebasic acid, 1,9-nonanedicarboylic acid, 1,10-decanedicarboxylic acid, 1,11-undecanedicarboxylic acid, 1,12-dcdecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid or 1,14-tetradecanedicarboxylic acid); aromatic monocarboxylic acids (e.g., benzoic acid, phenylacetic acid, α-naphthoic acid, β-naphthoic acid, cynnamic acid, p-amino hippuric acid and 4-(2-thiazoylsulfamyl)-phthalaninoic acid); aromatic dicarboxylic acids (e.g., terephthalic acid, isophthalic acid or phthalic acid); aromatic tricarboxylic acids (e.g., trimellitic acid, 1,3,5-benzenetricarboxylic acid or tris(2-carboxyethyl)isocyanurate); aromatic tetracarboxylic acids (e.g., pyromellitic acid or biphenyltetracarboxylic acid); aliphatic cyclic monocarboxylic acids (e.g., cy- clohexane carboxylic acid); or aliphatic cyclic dicarboxylic acids (e.g., l,2-c}clohexane dicarboxylic acid).

[40] The coating process using the melamine-based compounds in water should be conducted at a temperature of 15O⁰C or higher under pressure, due to a high melting point of the melamine -based compound

[41] The aliphatic alcohol is formed form mono- or poly- aliphatic alcohols having linear or branched hydrocarbon chains of 3 to 40 carbon atoms. The aliphatic alcohols preferably include at least one selected from a group consisting of alkanol, cy- cloalkanol, n-hexanol, n-heptanol, n-octanol, 2-ethylhexanol, isooctyl alcohol, octanol- 2, methyl heptanol, decyl alcohol, isodecyl alcohol, capryl alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, oleyl alcohol, benhenyl alcohol, cetyl alcohol, stearyl alcohol, cyclohexanol, methylcyclohexanol, alkandiol, propylene glycol, trimethylene glycol, 1,2-butylene glycol, 2,3-butylene glycol, 1,4- butylenes glycol, 1,6-hexanediol, pinacol, 1,2-pentanediol, 2-methyl-2,4-pentanediol, 1,3-butylene glycol, neopentyl glycol, 2-ethyl-l,3-hexanediol, 2,4-pentanediol, 2,4-heptanediol, 2,2-diethyle- 1 ,3-propanediol, 2-ethyl-2-butyl- 1 ,3-propanediol, 2-methyl-2-butyl-l,3-propanediol, pentaerythritol and dipentaerythritol. IVbre preferably, the aliphatic alcohols include one or more selected from stearyl alcohol, lauryl alcohol, caprylic alcohol, oleyl alcohol, or petaerylthritol.

[42] The coating process using the aliphatic alcohol is conducted by aάϊng the hydro- magnesite water or a solvent to prepare a solution, aάϊng the aliphatic alcohol to the solution in an amount of 0.1 to 20 wt% based on the weight of the hydromanesite, melting or dispersing the resultant mixture at 5O⁰C or higher and cooling it to the room temperature after stirring for more than 30 minutes. And through filtering and drying, the aliphatic alcohol is coated using electromagnetic waves. Energy sources of the electromagnetic waves are preferably from heat, gamma rays, X-rays, microwaves, ultrasonic waves or infrared

[43] If not treated by heat, gamma rays, X-rays, microwaves, ultrasonic waves or infrared after mixing the aliphatic alcohol with hydromagnesite followed by filtering and drying, the coating effect may be reduced The present invention, however, prepared the hydromagnesite with the aliphatic alcohol firmly attached by treating the hydromagnesite having the aliphatic alcohol with electromagnetic waves after mixing, filtering and drying.

[44] The coating agent enhances the dispersibility of the hydromagnesite in the spandex polymers, thereby maintaining the spinnability of the spandex.

[45] However, through sand-grinding and milling process, a non-coated hydromagnesite may also exhibit the same excellent spinnability as in the case of using a coated hydromagnesite. [46] The sand-grinding or milling process involves milling a mixture or slurry of the hy- dromagnesite, a solvent and a small amount of the polyurethane polymers using a conventional bead mill. The small amount of polyurethane polymers used enhances the dispersibility of the hydrotalcite. Examples of the solvents include dimethylacetamide, dimethylformamide and dimethylsulfoxide and a mixture thereof. The completion of the milling process is determined through filtering test, which is conducted as follows.

[47] After preparing the hydromagnesite slurry by milling process, 2kg samples thereof are taken. The 2kg slurry samples are inserted into an air tight container on which air pressure is put at the top. The bottom outlet of the air tight container has a diameter of 4cm and a stainless non- woven fabric sieve of 15/M. The slurry passes only through the sieve of the bottom outlet. The volume of slurry samples passing through for 2 minutes under air pressure of 1.5 kgf/cm² is measured The size of secondary aggregate particles of the slurry samples after passing through the sieve is considered to be below 15/M. When the 2kg slurry samples all pass through the sieve, that is considered to be passed in the test, and if not, failed

[48] Under the same condition as above, it turned out that when treated with milling process, a non-coated hydromagnesite may also bring the same results as in the case of using a coated hydromagnesite without causing problems in the manufacture of spandex. That is, when hydromagnesite is milled, there is almost no difference between the coated and non-coated hydromagnesite during the manufacture of spandex fibers.

[49] Hereinafter, the present invention will be described in further detail with reference to drawings and embodiments. But it should not be construed that the scope of the invention is limited thereto.

[50] Example

[51] Preparation of the hydromagnesite

[52] Preparation 1>

[53] The stearic acid was added to water in amount of 2 wt% based on the weight of the hydromagnesite, and the hydromagnesite was added thereto. The resulting mixture was stirred at 15O⁰C for 20 minutes, filtered and dried to obtain the hydromagnesite coated with stearic acid

[54] Preparation 2>

[55] The sodium stearate was added to water in amount of 2 wt% based on the weight of the hydromagnesite, and the hydromagnesite was added thereto. The resulting mixture was stirred at 15O⁰C for 20 minutes, filtered and dried to obtain the hydromagnesite coated with sodium stearate.

[56] <Preparation 3>

[57] The stearic acid and melamine polyphosphate were added to water and the hydro- magnesite was added thereto. The amount of the stearic acid and the melamine polyphosphate were 2 wt% and 1 wt%, respectively, based on the weight of hydro- magnesite. The resulting mixture was stirred at 16O⁰C for 30 minutes, filtered and dried to obtain the hydromagnesite coated with stearic acid and melamine polyphosphate.

[58] Preparation 4>

[59] The staryl alcohol was added to water in amount of 2 wt% based on the weight of the hydromagnesite, and the hydromagnesite was added thereto. The resulting mixture was stirred at 15O⁰C for 20 minutes, filtered, dried and treated with microwaves at 2450MHz for 7 minutes to obtain the hydromagnesite coated with stearyl alcohol.

[60] Preparation 5>

[61] The melamine phosphate was added to water in amount of 3 wt% based on the weight of the hydromagnesite, and the hydromagnesite was added thereto. The resulting mixture was stirred at 16O⁰C for 30 minutes, filtered and dried to obtain the hydromagnesite coated with melamine phosphate.

[62] Preparation 6>

[63] A non-coated hydromagnesite

[64] <Comparative preparation 1>

[65] Portafill H5, which is a mineral mixture of huntite and hydromagnesite.

(Ankerproort, Netherlands. According to the X-ray diffraction analysis, the ratio of huntite to hydromagnesite is 85:15)

[66] <Comparative preparation 2>

[67] Ultracarb U3, which is a mineral mixture of huntite and hydromagnesite. (Mnelco,

Great Britain. According to the X-ray diffraction analysis, the ratio of huntite to hydromagnesite is 80:20, and it is coated with the fatty acids).

[68] <Comparative preparation 3>

[69] Ultracarb U5, which is a mineral mixture of huntite and hydromagnesite. (Mnelco,

Great Britain. According to the x-ray diffraction analysis, the ratio of huntite to hydro- magensite is 45:55)

[70] <Comparative preparation 4>

[71] Ultracarb LH- 15, which is a mineral mixture of huntite and hydromagnesite.

(Mnelco, the Great Britain. According to the x-ray diffraction analysis, the ratio of huntite to hydromagnesite is 30:70).

[72] [Examples 1-6 and Comparative Examples 1-4]

[73] 518 g of dphenylmethane-4,4'-diisocyanate and 2,328 g of polytetramethylene ether glycol (Mw 1,800) were reacted with stirring at 8O⁰C in nitrogen atmosphere for 90 minutes to prepare a polyurethane prepolymer having isocyanate groups at both terminals. After cooling the prepolymer to the room temperature, 4,269 g of dimethy- lacetamide was added to obtain a polyurethane prepolymer solution. Subsequently, 34.4 g of ethylenediamine, 10.6 g of propylenediamine and 9.1 g of diethylamine were dissolved in 1,117 g of dimethylacetamid The resultant solution was added to the prepolymer solution at less than 10 ⁰C to prepare a polyurethane solution.

[74] Based on the total weight of the solid portion of the polymer, 1 wt% of ethylenebis(oxyethylene)bis-(3-(5-t-butyl-4-hydroxy-m-toyl)-propionate), 1 wt% of l,l,r,l'-tetramethyl-4,4'-(methylene-di-p-phenylene)disemicarbazide, 1 wt% of poly(N,N-diethyl-2-aminoethyl methacylate), 0.5 wt% of titanium dioxide and 0.5 wt% of magnesium stearate were mixed with 4 wt% of chorine resisting agents (prepared in the preparation 1 to 6 and Comparative preparation examples 1 to 4) to prepare a polyurethane spinning solution.

[75] Before adding the above additives to the polyurethane spinning solution, the additives were dispersed in the dimethylacetamide with Advantis V3 apparatus (Drais Mannheim, Germany) and grinded The resultant additives were then added to the polyurethane spinning solution after passing a filtering test.

[76] After defoaming the polyurethane spinning solution, the solution was dry spun at a spinning temperature of 25O⁰C to prepare a 4-filament 40-denier spandex fiber. The properties of the spandex fiber were measured The results are presented in Table 1.

[77] Table 1

[Table 1] [Table ]

[78] 1) Test for strength preservation rate in chlorinated water (chorine-resistance test)

[79] The spandex yarn subjected to 50% of stretching was treated with a water (pH 7, 97 to 98 ⁰C) for 1 hour and cooled down at the room temperature. After being dipped in 45L of chlorinated water (pH 7.5) containing 3.5 ppm of active chlorine for 24 hours, the spandex yarn was analyzed in regard to strength preservation rate.

[80] Strength preservation rate (%) = S/S ₀ x 100

[81] (S₀: strength before treatment, S: strength after treatment)

[82] An Instron 4301 (Instron Co., USA) was used for strength measurement, where the sample piece was 5 cm long and the cross head speed was 300 mm/min with a cell of 1 kg-

[83] As shown in Table 1, using hydromagnesite enhances chlorine resistance as compared with using a mineral mixture of huntite and hyiromagnesite. Industrial Applicability

[84] The present invention relates to a spandex fiber containing hydromagnesite. Particularly the invention concerns a spandex fiber which has excellent chlorine-resistance as well as the intrinsic properties of the polyurethane polymer. A spandex fiber according to the present invention has excellent resistance to chlorine and is therefore useful for underwear, socks and particularly, sports apparel such as swimsuit, etc.

Claims

[1] A spandex fiber containing hydromagnesite in an amount of 0.1 to 10 wt% based on the polyurethane polymer.

[2] A spandex fiber according to claim 1, wherein the hydromagnesite is coated with a coating agent in an amount of 0.1 to 10 wt% based on the weight of hydromagnesite.

[3] A spandex fiber according to claim 2, wherein the coating agent includes one or more compound selected from a group consisting of aliphatic alcohol, fatty acid, fatty acid salt, aliphatic ester, phosphoric acid ester, styrene/maleic acid anhydride copolymer and its derivatives, silane coupling agent, titanate coupling agent, polyorgano-siloxane, polyorganohydrogen-siloxane and melamine compounds.

[4] A spandex fiber according to claim 1, wherein the hydromagnesite uncoated is used