WO2008029997A1

WO2008029997A1 - Chlorine resistant polyurethaneurea elastic fiber and preparation of thereof

Info

Publication number: WO2008029997A1
Application number: PCT/KR2007/003909
Authority: WO
Inventors: Okhyun Choi; Ickgy Shin; Inrak Jung; Jungbae Lee
Original assignee: Tae Kwang Ind. Co., Ltd.
Priority date: 2006-09-04
Filing date: 2007-08-16
Publication date: 2008-03-13
Also published as: KR100780395B1; TR200901601T1; CN101139751A; CN101139751B

Abstract

The present invention relates to a process for preparing polyurethaneurea elastic fiber, more specifically, to a process for preparing elastic fiber having excellent chlorine resistant property when being used for swimming wear after warp two-way knitting together with nylon fiber. The polyurethaneurea polymer of the invention comprises 1-10% by weight of chlorine resistant additive which is prepared by coating an inorganic chlorine resistant material with one or more substance (s) selected from fatty acids, fatty acid metal salts, fatty acid phosphoric esters, silica, silane, polyorganosiloxanes, and a polyorganosiloxane/polyorganohydrogensiloxane mixtures. The spandex obtained therefrom via conventional dry spinning is characterized to have excellent spinning stability, chlorine resistant property and uniformity.

Description

CHLORINE RESISTANT POLYURETHANEUREA ELASTIC FIBER AND

PREPARATION OF THEREOF

[Technical Field] The present invention relates to a polyurethaneurea elastic fiber having excellent chlorine resistance and uniformity, which is highly durable in chlorine-containing water of a swimming pool and provides excellent quality as a cloth material by means of mixture-knitting with Nylon, and a process for preparing the same.

[Background Art]

Polyurethaneurea elastic fiber is prepared by dry or melt spinning of a polymer obtained from chain extension of a prepolymer having isocyanate end groups, which was synthesized from a high molecular weight polyol and excess amount of organic diisocyanate,- and finds its use as an elastic functional material for various clothes such as foundation garments, socks, panty hoses and swimming wears by means of mixture-knitting with polyamide fiber, polyester fiber or a natural fiber.

The polyurethaneurea elastic fiber is deteriorated in physical properties, since the polyetherglycol structure constituting the soft segment of the polymer is decomposed by- bleach of chlorine-containing solution or active chlorine in a swimming pool for disinfection. Therefore, in order to improve chlorine resistant property of polyurethaneurea elastic fiber employed for a swimming wear, polyurethane elastic fibers using polyesterglycol have been developed. However, aliphatic esters, having high biological activity, are apt to be attacked by fungi, with insufficient chlorine resistance. In order to improve the chlorine resistance of polyether polyurethanes, various chlorine resistant additives have been used. Japanese Patent 1982-29609 and USP 4,340,527 used zinc oxide to improve the chlorine resistant property. However, zinc oxide is troublesome since it turns yellow upon reacting with an additive, and it is eluted under acidic dyeing condition at pH 3-4. In particular, zinc components cannot be used in Europe, being a regulatory substance for environment. Japanese Patent 1984-133248 employed hydrotalcite to improve chlorine resistant property. However, hydrotalcite used as a chlorine resistant additive was so hygroscopic that it caused problems of increasing gel formation of the polymer, increasing of filter pressure and reducing of spinning ability. Japanese Patent 1991-243446 employed a hydrotalcite coated with a fatty acid to prevent water absorption of the chlorine resistant additive and to improve dispersiveness, thus enhancing the chlorine resistant property of polyurethaneurea elastic fiber. However, the hydrotalcite reacts with an additive employed for light resistance and gas resistance of the polyurethaneurea elastic fiber, to convert the color of the product yellow during the spinning, as well as causing wave to the thread. USP 5,626,960 employed a mixture of Huntite and hydromagnesite to enhance chlorine resistant property. However, according to the patent, the chlorine resistant material was not coated so that problems of gel formation of the polymer due to hygroscopicity of the material and poor dispersion occurred to increase the filter pressure and fiber breakage rate, and the final product turned yellow.

[Disclosure] [Technical Problem]

An object of the present invention is to provide a polyether polyurethaneurea elastic fiber having excellent chlorine resistant property.

Another object of the present invention is to provide an additive to supplement anti-oxidation, light resistance and waste gas resistance of polyurethane elastic fiber, a chlorine resistant additive and an additive composition having good compatibility with polyurethaneurea.

Still another object of the invention is to employ basic magnesium carbonate as the chlorine resistant additive, to give a polyurethaneurea elastic fiber having excellent chlorine resistance, elastic resilience, strength retention and heat resistance.

[Technical Solution]

In order to achieve the objects as described above, the present invention provide a process for preparing a polyurethaneurea elastic fiber having chlorine resistant property, which comprises the steps of:

(a) mixing a polyhydric alcohol and an isocyanate compound to prepare a first polyurethane polymer;

(b) adding a chain extender, a chain terminator and a crosslinker to said first polymer to provide a second polymer;

(c) mixing basic magnesium carbonate as a chlorine resistant additive to said second polymer to prepare a spin dope; and

(d) spinning said spin dope to provide an elastic fiber. More specifically, the present invention provides a process for preparing polyurethaneurea elastic fiber having chlorine resistance, which comprises the steps of:

(a) mixing a monofunctional monoalcohol (500 ~ 2000 ppm) and an organic acid (5 ~ 20 ppm) with polytetramethylene ether glycol component, and mixing diphenylmethane-4 , 4 ' -diisocyanate component with said polytetramethylene ether glycol to make the equivalent (NCO/OH) of 1.5 ~ 2.0, to prepare a first polymer having 2.4 ~

3.5 mol% of unreacted diisocyanate at the end group and viscosity of 500 ~ 700 poise,-

(b) adding a chain extender solution, a chain terminator solution and a crosslinker to said first polymer mixture and stirring the resultant mixture to prepare a second polymer solution having apparent viscosity of 2000

3500 poise at 40^°C and 35% solid content;

(c) mixing basic magnesium carbonate (1 -10 wt%) coated with any one or more coating agent (s) as a chlorine resistant additive selected from fatty acids, fatty acid metal salts, fatty acid esters, fatty acid phosphoric esters, silica, silane, polyorganosiloxanes, and polyorganosiloxane/polyorganohydrogensiloxane mixtures, to prepare a spin dope having 3500 ~ 5000 poise (40^°C, 35% solid content); and

(d) spinning said spin dope to provide an elastic fiber. After step (a) , a step of dissolving the first polymer in N,N-dimethylacetamide to make the unreacted diisocyanate content uniform and prepare the first polymer mixture can be added . According to the present invention, one or more additive composition (s) selected from titanium dioxide, 1,1,1',1'- tetramethyl-4 , 4 ' (methylene-di-p-phenylene) disemicarbazide, magnesium stearate, diethylenetriamine, a dyeability enhancer and an anti-oxidant may be additionally employed in step c) . At this time, preferable contents of said additive compositions are 0.05-4.5% by weight of titanium dioxide, 0.2-3.5% by weight of 1, 1, 1' , 1' -tetramethyl-4 , 4 '- (methylene- di-p-phenylene) disemicarbazide, 0.1-2% by weight of magnesium stearate, 0.2-1.0% by weight of the dyeability enhancer, and 0.5-3.5% by weight of the anti-oxidant, based on the total dope composition.

Now, each step is specifically described. In the preparation of polyurethaneurea elastic fiber having enhanced chlorine resistant property according to the present invention, diphenylmethane-4, 4' -diisocyanate (p,p' - methylenediphenyldiisocyanate) and polytetramethylene ether glycol are continuously introduced to a cylindrical pipe reactor, to obtain a first polymer containing 2.4 - 3.5 mol% of unreacted diisocyanate at the terminal. The polymer is cooled to 40^°C, and completely dissolved to reduce the unreacted diisocyanate content sufficiently by using a high shear mixer just before being incorporated to a second reactor.

The mixture is introduced to the second polymerization reactor together with a chain extender solution (wherein ethylenediamine/1, 2-diaminopropane is dissolved in N, N- dimethylacetamide) , a chain terminator solution (wherein diethylamine is dissolved in N,N-dimethylacetamide) and a crosslinker (diethylenetriamine) , and the second reaction is performed with high-shear stirring to obtain polyurethaneurea polymer at 65~70^°C. The amount of the chain extender and the chain terminator to be introduced is preferably determined so that the equivalent of amine group is in 2-6 mol% excess based on isocyanate group being present in the first polymer. More specifically, ethylenediamine and 1, 2-diaminopropane as the chain extender are employed in a molar ratio of 70-90:30-10, more preferably 80:20; the chain terminator is employed in a ratio of 1/15-1/40, more preferably 1/26 with respect to the amine equivalent; and diethylenetriamine as the crosslinker is employed in an amount of 50-500 ppm, more preferably 150 ppm on the basis of said first polymer mixture.

If the amount of diethylenetriamine is less than 50 ppm, the effect of stabilizing the process viscosity of the dope is low, and the spinning process leads less crosslinking reaction, so that the expected effect of improvement in thermal resistance cannot be obtained. On the other hand, if the amount is more than 500 ppm, the raise of viscosity during the process slows down, so that much time is consumed to obtain desired viscosity; in addition, gel formation and ununiformity of polymer increase because of excess crosslinking reaction, to result in poor spinning ability.

The amount of amine introduced to the second polymerization is adjusted to give 10-60 meq/kg of terminal amine group being present in the final polymer. The stirring rate of the second polymerizer is adjusted to provide at least 80% reaction efficiency of the first polymer and the amine. Stirring efficiency is measured at the exit of the second polymerizer to determine an optimum stirring rate of the reaction. Polyurethaneurea polymer synthesized by chain extension and chain termination has about 30-40% of solid content, and the second polymer solution having about 2000-3500 poise of apparent viscosity at 40^°C was obtained. The inherent viscosity of this polymer measured with a solution (0.5 g/100 ml of N,N-dimethylacetamide) is 1.0.

The present invention is characterized in that basic magnesium carbonate is added to said composition in an amount of 0.1 -10% by weight to provide chlorine resistant property. The basic magnesium carbonate is preferably coated with any one or more substance (s) selected from fatty acids, fatty acid metal salts, fatty acid esters, fatty acid phosphoric esters, silica, silane, polyorganosiloxanes, and polyorganosiloxane/polyorganohydrogensiloxane mixtures in an amount of 1-20 parts by weight on the basis of 100 parts of basic magnesium carbonate.

When the basic magnesium carbonate is used without coating, the material is liable to absorb moisture. Thus, careful moisture control is required from the packing stage of the product to the use after storage in a storehouse. If an apparatus for drying the material is incorporated at the final usage, it may be utilized without coating. However, there remains the problem of second cohesion owing to surface charge of the chlorine resistant material, and more cost is needed for the moisture control as compared to the coated material.

Thus, it is preferable to coat the chlorine resistant material.

The basic magnesium carbonate can be selected from the compounds represented by Chemical Formulas 1~5, such as, specifically, hydromagnesite, dihydromagnesite and magnesite. Basic magnesium carbonate may be used after enhancing the activity by removing the surface water or crystal water partly via thermal treatment at 300^°C or less, or completely via thermal treatment at 400^°C or more.

4MgCO₃Mg(OH)₂- 4H₂O (1) 3MgCO₃Mg(OH)₂- 3H₂O (2)

4MgCO₃Mg(OH)₂ (3)

3MgCO₃Mg(OH)₂ (4)

MgCO₃ (5)

The surface of the basic magnesium carbonate employed according to the present invention is partly coated with acidic or neutral coating agent to lower the basicity, positive charge on the surface and the moisture absorption, simultaneously, thereby preventing re-cohesion of the material and enhancing the spinning ability of the dope, as well as inhibiting the coloring or discoloring of the fiber after spinning.

The coating of the material can be performed in a dry or a wet mode. According to the wet mode, the coating agent is added as an emulsion to the slurry of basic magnesium carbonate powder, and the mixture is sufficiently mixed, neutralized and dried. According to the dry mode, the coating agent is added as a liquid, emulsion or solid phase, while sufficiently stirring the basic magnesium carbonate particles by using a mixer such as super mixer and Henschel mixer, and the resultant mixture is fully mixed under heating or without heating.

The coating agent may be selected from fatty acids such as stearic acid, oleic acid, palmitic acid and lauric acid, alkaline metal salts thereof, higher alcohols, esters or the like, as well as silane, polyorganosiloxanes and polyorganosiloxane/polyorganohydrogen siloxane mixtures. Specific examples of alkaline salts of a higher fatty acid include sodium stearate, magnesium stearate, calcium stearate, sodium oleate, sodium palmitate, sodium laurate, sodium laurylsulfonate, and the like. A higher alcohol such as stearyl alcohol, oleyl alcohol, lauryl alcohol, or fatty acid ester such as glycerylmonostearate, stearyl oleate, lauryl oleate may be used. As the fatty acid phosphoric ester, stearyl phosphate, oleyl phosphate, lauryl phosphate or tridecyl phosphate having C₄..₃₀ linear or branched alkyl group may be used. As the silica, calcium silicate (Water-glass No.3 from DC Chemical Co., Ltd.) may be employed; as the silane, the compound represented by chemical formula (RO)₃SiR" (R' or R" represents same or different Ci_^40 aliphatic or aromatic hydrocarbon) ; as the polyorganosiloxane, polydimethylsiloxane, and as the polyorganohydrogensiloxane, polydimethylhydrogensiloxane.

If the basic magnesium carbonate is not coated in the present invention, required is keeping in a place provided with dehumidifying equipment for the storage of the material and moisture management. If it is stored in a usual place, problems of gel formation of the polymer owing to the moisture absorption of the material and poor dispersion may occur, to result in the raise of filter pressure during the process and increase of fiber breakage rate during the spinning. If the chlorine resistant material is coated in an amount less than 1 part by weight, sufficient prevention of moisture absorption or sufficient dispersion during the preparation of slurry cannot be expected, while if the amount is more than 20 parts by weight, no more increase in dispersive effect of the chlorine resistant material as compared to that using no more than 20 parts by weight. In terms of economy also, there is no need to use the material in an amount more than 20 parts by weight.

The basic magnesium carbonate thus coated is added in an amount of 0.1~10% by weight based on total dope solution. If the amount is less than 0.1% by weight, the chlorine resistant performance can not reach the expected value, while if it is more than 10% by weight, the chlorine resistant performance increases but mechanical properties such as strength, elongation and modulus of the fiber decreases. Thus, the above range is most preferable.

The basic magnesium carbonate added to the dope solution is preferably dispersed in N,N-dimethylacetamide solvent and pulverized and dispersed by using a wet pulverizer to make the size of 40 μm or less, more preferably 20 μ m or less before use .

According to the present invention, any one or more additive composition (s) selected from titanium dioxide, waste gas stabilizers, anti-oxidants, magnesium stearate, dyeability enhancers, UV stabilizers, or the like can be added, if required, in addition to the chlorine resistant additive.

Specifically, titanium dioxide serves as a matting agent, being preferably used in an amount of 0.05-4.5% by weight. If it is less than 0.05% by weight, the fiber glitters too much, while it is more than 4.5% by weight, excess amount of titanium dioxide promotes abrasion of the machine during the spinning and knitting process.

The waste gas stabilizer serves to prevent yellowing caused by nitrogen oxides. For example, 1, 1, 1' , 1' -tetramethyl- 4 , 4 ' - (methylene-di-p-phenylene) disemicarbazide can be employed. The preferable amount is 0.2 ~ 3.5% by weight of the dope solution. If the amount is less than 0.2% by weight of the dope solution, expected effect cannot be obtained, while if it is more than 3.5% by weight, the effect does not increase with increase of the amount added.

The anti-oxidant serves to capture the radicals inducing decomposition of polymers generated by heat or sun light. As the anti-oxidant, 1, 3 , 5-tris (4 ~t-butyl-3 -hydroxy-2, 6- dimethylbenzene) -1, 3, 5-triazine-2, 4 , 6- (IH, 3H, 5H) -trione may be used. The content is preferably from 0.5 to 3.5% by weight of the dope solution. If the amount is less than 0.5% by weight, sufficient anti-oxidant effect cannot be obtained, while if it is more than 3.5% by weight, the effect does not increase with the increase of the amount added.

Magnesium stearate is used to improve the spinning ability of the polymer, to reduce stickiness and enhance unwinding ability, with a preferable amount of 0.1-2% by weight of the dope solution. If the amount is less than 0.1% by weight, the spinning ability and unwinding ability is poor, while if it is more than 2% by weight, the fiber is too slippery to cause poor winding shape.

As the dyeability enhancer, poly (N,N-diethyl-2-aminoethyl methacrylate) is preferably used in an amount of 0.2-3.0% by weight of the dope solution. If the amount is less than 0.2% by weight, sufficient coloring cannot be obtained to result in severe glittering of the cloth material, while if it is more than 3.0% by weight, the excessive use may result in increase of production cost, or cause the accident of poor coloring owing to outflow of the olygomer during the dyeing process.

The additive composition according to the present invention is preferably added to the dope after preparing an additive slurry having not more than 10% by weight of solid content in DMAc as a solvent. It is preferably added to the dope after being pulverized and dispersed by using a high performance wet pulverizer to make the solid particle size 40 μ m or less. Then, the dope for spinning was spun by dry spinning to prepare polyurethaneurea chlorine resistant elastic fiber. It is preferably prepared at a temperature of 240~260^°C immediately downstream the spinning nozzle, and a spinning rate of 700-1200 m/min, during the spinning of the dope. Polyurethaneurea elastic fiber prepared according the process of the invention is also included in the scope of the invention.

Now, the process according to the present invention is described in more detail. Polytetramethylene ether glycol (PTMEG, Molecular weight 1815) , n-butanol (1200 ppm w/w based on PTMEG) and phosphoric acid (7 ppm w/w based on PTMEG) are sufficiently mixed, and diphenylmethane-4,4' -diisocyanate (MDI) is added thereto in a molar ratio of 1.70 based on PTMEG (NCO/OH = 1.70). The resultant mixture is polymerized to prepare a first polymer having 2.64 mol% of unreacted diisocyanate at the terminal. The first polymer is filtered through a filter (20μ m or less) , and uniformly and completely dissolved in N, N- dimethylacetamide (DMAc) in a high sheared mixer to give a first polymer mixture in which the content of unreacted diisocyanate has been sufficiently lowered. Ethylene diamine and 1, 2-diaminopropane as the chain extender and diethylamine as the chain terminator, and diethylenetriamine as the crosslinker are dissolved in N,N-dimethylacetamide so that the equivalent ratio of amine/isocyanate becomes 1.01-1.06. The solution thus obtained is charged to a second polymerizer together with the first polymer mixture, to obtain a second polymer (35% by weight) having the inherent viscosity of 1.0 with about 2000-3500 poise of viscosity as measured at 40^°C . To the second polymer, added is a slurry having not more than 10% by weight of solid content, which is comprised of titanium dioxide, 1,1,1' ,1' -tetramethyl-4 , 4' - (methylene-di-p-phenylene) disemicarbazide, 1, 3, 5-tris (4-t-butyl-3-hydroxy-2, 6- dimethylbenzene) -1,3, 5-triazine-2, 4 , 6- (IH, 3H, 5H) -trione, magnesium stearate, poly (N,N-diethyl-2-aminoethyl methacrylate) , Hydromagnesite and N,N-dimethylacetamide solvent. The slurry is incorporated to the process after a pulverizing and dispersing stage by using a wet pulverizing device to provide a particle size of the inorganic additives in the slurry of 40 μ m or less. The spin dope is passed through a static mixer of pipe shape to homogeneously mix the additive slurry with the second polymer, then the dope is spun with 700-1200 m/min of spin rate in a dry spinning mode to prepare a polyurethaneurea chlorine resistant fiber. After spinning, the residual solvent content in the spandex fiber is adjusted to 1.0% by weight or less. The spandex fiber thus prepared has inherent viscosity of 1.25 when measured in a solution in N,N-dimethylacetamide (0.5 g/100 ml)

[Advantageous Effects]

The polyurethaneurea chlorine resistant fiber prepared as described above has excellent uniformity and spinning ability, and provides excellent quality of cloth material having good elastic resilience, strength retention and chlorine resistant property.

[Mode for invention] Prior to the description of the Examples of the present invention, various methods of evaluation are described:

1) Measuring viscosity of a polymer

Viscosity of a polymer with chain extension and chain termination having been completed was measured at 40^°C by using a Brookfield Viscometer (B type), and reported in poise.

2) Measuring stirring efficiency of a polymer

A polymer is taken from the outlet of the secondary polymerization reactor. To measure the amine content in the dope and polymer terminal, each polymer is dissolved in N, N- dimethylacetamide solution, followed by titrating with 0.1 N HCl. Then, the mixing efficiency of the reactor is calculated from the proportion of amine content in the dope and polymer. 3) Measuring inherent viscosity

Viscosity of a solution prepared by dissolving 0.5 g of a polymer in 100 ml of N,N-dimethylacetamide is measured by Ubbelohde viscometer in a constant temperature bath at 30±0.5^°C, to obtain the inherent viscosity of the polymer. 4) Measuring pH of the chlorine resistant material

Two grams of sample is dispersed in 25 ml of ethyl alcohol, and pH of the material is measured by using a pH meter.

5) Tensile strength, Tensile elongation By using a tensile tester (manufactured by Instrong, UTM) , a sample having 5 cm length is stretched at a speed of 50 cm/min under the condition of 25^°C, 65% RH to measure Tensile strength (g/d) and Tensile elongation (%) .

6) Elastic recovery A 10 cm interval of a sample is marked, and the sample is stretched by 300%. After maintaining the stretching for 24 hours, the stretching is released. It is allowed as it is for 10 minutes, and the length recovered is measured. ER(%) = [(Ls - La) / (Ls - Lo)] x 100 In the formula, Lo is the length between the marks at the sample, Ls is the length of the sample when stretched by 300%, and La is the length after releasing the stretch.

7) Wet-heat elastic resilience A 10 cm interval of a sample is marked, and the sample is stretched by 100%. After treating the sample under steam atmosphere at 130^°C for 60 minutes, the stretch is released, and the length recovered (Lw) is measured. The resilience is expressed in a ratio to the untreated length of the sample. The high resilience represents high heat resistance but low thermal setting.

Wet-heat elastic resilience = [(20-Lw) /10] x 100

8) Dry-heat strength retention

A sample is treated with hot air at 180"C for 1 minute while it is stretched by 100%, and measured its strength in a tensile tester. The ratio of the strength after the dry-heat treatment to the strength of untreated fiber is the strength retention. The higher the strength retention is, the higher the heat resistance is. 9) Chlorine resistant property of fiber

A sample under 50% of stretching is impregnated in a bath having 20 ppm of effective chlorine concentration (pH 7) , and the ratios of the strength after 24, 48 and 72 hours is determined as the strength retention. The higher the strength retention is, the higher the chlorine resistant property is. The sample length before and after the chlorine treatment are measured to determine the elastic resilience. The higher the resilience is, the higher the chlorine resistant property is. (Criteria of fiber for chlorine resistance property: at least 70% of strength retention after 48 hr treatment)

10) Chlorine resistant property of cloth material The cloth material is cut along warp direction to give a test piece of 2cm x 20cm. While stretched by 50%, the test piece is impregnated in a bath having 200 ppm of effective chlorine concentration (pH 7) at 25^°C. The ratio of 50% stretch strength over time is determined as the strength retention. The higher the retention is, the higher the chlorine resistant property is .

Examples

Now the present invention is specifically described by means of Examples, but the invention is not restricted to those Examples by any means . [Example 1]

Polytetramethylene ether glycol (MW 1815, 305.13 g) , n- butanol (MW 74.12, 1200 ppm based on the weight of polytetramethylene ether glycol) and phosphoric acid (MW 98.0, 7 ppm based on the weight of polytetramethylene ether glycol) were mixed, and diphenylmethane-4 , 4 ' -diisocyanate {12. IS g) was continuously transported to a static mixer at 45 ^°C by using a quantitative pump. The mixture was introduced to a continuous polymerization tube having a cylindrical pipe shape at 70~90^°C, and reacted for 135 minutes to adjust the unreacted diisocyanate concentration at the terminal to 2.64 ±0.02 mol%. A first polymer having 620 poise of viscosity was synthesized.

The first polymer was cooled to 60^°C and stabilized within 24 hours, and continuously fed together with N, N- dimethylacetamide (600.65 g) to a high shear mixer at about 2500 rpm for 20 seconds immediately before being introduced to a second reactor. The first polymer was completely dissolved and cooled to provide a polyurethane prepolymer mixture containing about 40% of solid at 35~45^°C. The mixture was introduced to the second polymerization reactor together with a solution of a chain extender (ethylenediamine 5.72 g/ 1, 2-diaminopropane 1.76 g = molar ratio 80/20) , a solution of a chain terminator (diethylamine 0.70 g) and a crosslinker (diethylenetriamine, 150 ppm) , and the second polymerization was carried out with stirring at about 185 rpm for about 4 minutes to obtain polyurethaneurea compound at 65~85^°C.

The amount of diethylamine incorporated was 1/26 (amine equivalent ratio) based on the chain extender solution. The amount of amine incorporated was 4 mol% excess amount of the amine group (equivalent) based on the isocyanate group existing in the prepolymer. The quenching point of the polymerization was determined when the unreacted amine content reached not more than 2~6 mol%.

The second polyurethaneurea polymer polymerized with a chain extender and a chain terminator had about 35% of solid content, and about 2000-3500 poise of apparent viscosity at 40^°C. The inherent viscosity measured as a solution of the polymer (0.5 g) in N,N-dimethylacetamide (100 ml) was 1.0.

To the completely polymerized solution, following additives were added in order for the usual spandex to have durability while washing and using and maintain white color, to improve color-change resistance (prevent yellowing) and dyeability, to prevent or reduce deterioration of mechanical property and to enhance the durability against chlorine (the amount is based on total weight of the spun spandex fiber) : 0.50% by weight of titanium dioxide; 0.50% by weight of 1,1,1' ,1' -tetramethyl-4 , 4 ' - (methylene-di-p-phenylene) disemicarbazide as a waste gas stabilizer (HN-150, from Nippon Hydrazine); 1.44% by weight of a hindered phenolic compound, 1, 3, 5-tris (4-t-butyl-3-hydroxy-2, 6-dimethylbenzene) -1, 3, 5- triazine-2,4, 6- (IH, 3H, 5H) -trione [CYANOX 1790^® (from Cytec, United States)] as an anti-oxidant; 0.30% by weight of magnesium stearate (Nippon Oil and Fats, Japan) in order to improve the stickiness and unwinding ability; 0.51% by weight of poly (N,N-diethyl-2-aminoethyl methacrylate) as a dyeability enhancer; and 4.0% by weight of hydromagnesite (from Nanotech, Airlite-Sl) coated with 3% by weight (based on the chlorine resistant material) of stearic acid as a chlorine resistant additive. When preparing the additive slurry, inorganic particles were pulverized and dispersed by using a wet pulverizer to make the particle size not more than 10 μ m. A wet pulverizer was used to pulverize the inorganic additives among the additive slurry, to make the mean particle size of the inorganic substances not more than 10 μ m. Then, after performing a filter test of the slurry by using a 40 μ m filter, the slurry was introduced to the process. At this time, homogeneous mixing of the final polymer with the additives is important, so that a static mixer having a cylindrical pipe shape was employed for homogeneous mixing of the additives with the final polymer. The polyurethaneurea product thus prepared contained about 35% of solid, being a polymer solution having 4350 poise (40^°C) of viscosity, which is suitable for spinning.

The additive slurry to be mixed with the final polymer was maintained at 45^°C . The polymer solution for spinning thus prepared was subjected to dry spinning wherein the solution was constantly pumped by a gear pump to a spinning can having the atmosphere at 250 ^°C to evaporate the solvent, at a spinning rate of 900 m/min. The physical properties are shown in Table 2. [Example 2]

An elastic fiber was prepared according to the same procedure described in Example 1, but using hydromagnesite without coating.

[Example 3] An elastic fiber was prepared according to the same procedure described in Example 1, but using 2% by weight of hydromagnesite .

[Comparative Example 1]

An elastic fiber was prepared according to the same procedure described in Example I₇ but without adding hydromagnesite .

[Comparative Example 2]

An elastic fiber was prepared according to the same procedure described in Example 1, but hydrotalcite (DHT-4A, from Nippon Kyowa) was used instead of hydromagnesite in an amount of 4% by weight.

[Comparative Example 3]

An elastic fiber was prepared according to the same procedure described in Example I₇ but magnesium hydroxide was used instead of hydromagnesite in an amount of 4% by weight.

[Table 1]

[Table 2 ]

Note: b value: Yellowing is observed when it is 7 or more.

From the Examples and Comparative Examples, it is found that the elastic fiber according to the process of the invention using hydromagnesite coated with fatty acid exhibits higher strength retention after 48 hour treatment as compared to that using hydromagnesite without coating; the higher the content is, the better chlorine resistant property is.

In addition, when using other kinds of chlorine resistant substances such as hydrotalcite coated with fatty acid and magnesium hydroxide, the chlorine resistant property is significantly lowered as compared to that of the present invention. Further, in case of Comparative Example 3, the color of the fiber is kept to some extent, but has low viscosity stability and low tensile strength and tensile elongation.

Thus, when using hydromagnesite coated with fatty acid according to the present invention, obtained are excellent chlorine resistant property, heat resistance and spinning ability, as well as good quality of the cloth material after knitting and dyeing process.

[industrial Applicability]

The polyurethaneurea elastic fiber prepared according to the present invention has excellent chlorine resistant property and spinning ability, and provides, after dyeing process, a cloth material having excellent chlorine resistant property, elastic resilience and strength retention.

Claims

[CLAIMS]

[Claim l]

A process for preparing a polyurethaneurea elastic fiber having chlorine resistant property, which comprises the steps of:

(c) mixing basic magnesium carbonate as a chlorine resistant additive to said second polymer to prepare a spinning dope; and

(d) spinning the dope to prepare an elastic fiber.

[Claim 2]

A process for preparing a polyurethaneurea elastic fiber having chlorine resistant property according to claim 1, wherein, in step (a) , the first polymer is prepared by mixing a monofunctional monoalcohol (500 ~ 2000 ppm) and an organic acid (5 ~ 20 ppm) with polytetramethylene ether glycol component, and mixing diphenylmethane-4 , 4 ' -diisocyanate component to make the equivalent with respect to said polytetramethylene ether glycol (NCO/OH) of 1.5 ~ 2.0, to prepare a first polymer having 2.4 ~ 3.5 mol% of unreacted diisocyanate at the terminal and viscosity of 500 ~ 700 poise.

[Claim 3]

A process for preparing a polyurethaneurea elastic fiber having chlorine resistant property according to claim 1, wherein, in step (b) , the second polymer is prepared by adding a chain extender solution, a chain terminator solution and a crosslinker to said first polymer and stirring the resultant mixture to prepare a second polymer having apparent viscosity of 2000 ~ 3500 poise at 40^°C and 35% solid content.

[Claim 4]

A process for preparing a polyurethaneurea elastic fiber having chlorine resistant property according to claim 1, wherein, in step (c) , a basic magnesium carbonate, which is coated with any one or more coating agent (s) selected from fatty acids, fatty acid metal salts, fatty acid esters, fatty acid phosphoric esters, silica, silane, polyorganosiloxanes, and polyorganosiloxane/polyorganohydrogensiloxane mixtures, is mixed with said second polymer as a chlorine resistant additive in an amount from 1 to 10 % by weight based on total doping solution, to prepare a spin dope having 3500 ~ 5000 poise (at 40^°C, 35% solid content) of viscosity.

[Claim 5]

A process for preparing a polyurethaneurea elastic fiber having chlorine resistant property according to claim 4, wherein the coating agent is used for coating in an amount of 1 - 20 parts by weight based on the basic magnesium carbonate.

[Claim 6]

A process for preparing a polyurethaneurea elastic fiber having chlorine resistant property according to claim 1, wherein, in step (c) , the basic magnesium carbonate is characterized by one of Chemical Formulas (1) to (5) : 4MgCO₃Mg(OH)₂- 4H₂O (1)

3MgCO₃Mg(OH)₂- 3H₂O (2) 4MgCO₃Mg(OH)₂ (3)

3MgCO₃Mg(OH)₂ (4)

MgCO₃ (5)

[Claim 7]

A process for preparing a polyurethaneurea elastic fiber having chlorine resistant property according to claim 2, wherein said monofunctional monoalcohol is n-butanol, and said organic acid is phosphoric acid.

[Claim 8]

A process for preparing a polyurethaneurea elastic fiber having chlorine resistant property according to claim 3, wherein said chain extender solution is a solution of ethylenediamine/1, 2-diaminopropane dissolved in N₇N- dimethylacetamide, said chain terminator solution is a solution of diethylamine dissolved in N,N-dimethylacetamide, and said crosslinker is diethylenetriamine .

[Claim 9]

A process for preparing a polyurethaneurea elastic fiber having chlorine resistant property according to claim 8, wherein the amount of said chain extender and chain terminator amine incorporated is determined so that the equivalent of amine group is 2-6 mol% excess amount based on that of isocyanate group existing in the first polymer.

[Claim 10] A process for preparing a polyurethaneurea elastic fiber having chlorine resistant property according to claim 9, wherein ethylene diamine and 1, 2-diaminopropane are employed as said chain extender in a ratio of 70-90 : 30-10 mol%, the chain terminator is employed in an amount of 1/15 - 1/40 based on the amine equivalent of said chain extender, and diethylenetriamine as the crosslinker is employed in an amount of 50-500 ppm based on said first polymer mixture.

[Claim 11]

A process for preparing a polyurethaneurea elastic fiber having chlorine resistant property according to claim 10, wherein ethylene diamine and 1, 2-diaminopropane are employed in a ratio of 80:20 mol%, the chain terminator is employed in an amount of 1/26 based on the amine equivalent of said chain extender, and diethylenetriamine as the crosslinker is employed in an amount of 150 ppm based on said polymer.

[Claim 12]

A process for preparing a polyurethaneurea elastic fiber having chlorine resistant property according to claim 1, wherein, in step (a) , the first polymer is mixed by continuously transporting the components by means of a quantitative pump to a static mixer, and polymerized in a continuous polymerizing tube having a cylindrical pipe shape.

[Claim 13] A process for preparing a polyurethaneurea elastic fiber having chlorine resistant property according to claim 1, wherein, in step (c) , one or more additive composition (s) selected from titanium dioxide, a waste gas stabilizer, magnesium stearate, diethylenetriamine, a dyeability enhancer and an anti-oxidant , is (are) additionally employed in said spin dope .

[Claim 14]

A process for preparing a polyurethaneurea elastic fiber having chlorine resistant property according to claim 13, wherein, among said additive compositions, employed are 0.05-4.5% by weight of titanium dioxide, 0.2-3.5% by weight of 1,1,1' ,1' -tetramethyl-4 , 4 ' - (methylene-di-p- phenylene) disemicarbazide as the waste gas stabilizer, 0.1-2% by weight of magnesium stearate, 0.2-1.0% by weight of poly (N,N-diethyl-2-aminoethyl methacrylate) as the dyeability enhancer, and 0.5-3.5% by weight of 1, 3 , 5-tris (4-t-butyl-3- hydroxy-2, 6-dimethylbenzene) -1,3, 5-triazin-2, 4 , 6- (IH, 3H, 5H) - trione as the anti-oxidant .

[Claim 15]

A process for preparing a polyurethaneurea elastic fiber having chlorine resistant property according to any one of claims 1 to 14, wherein said spin dope is spun at a temperature of 240~260^°C immediately downstream the spinning nozzle, and a spinning rate of 700-1200 m/min.

[Claim 16]

A polyurethaneurea elastic fiber having chlorine resistant property which is prepared by a process according to any one of claims 1 to 14. [Claim 17]

A polyurethaneurea elastic fiber having chlorine resistant property which is prepared by a process according to claim 15.