WO2008007879A1

WO2008007879A1 - Polyurethaneurea elastic fiber and method for preparation thereof

Info

Publication number: WO2008007879A1
Application number: PCT/KR2007/003312
Authority: WO
Inventors: Okhyun Choi; Ickgy Shin; Inrak Jung
Original assignee: TAE KWANG IND CO Ltd
Current assignee: TAE KWANG IND CO Ltd
Priority date: 2006-07-11
Filing date: 2007-07-09
Publication date: 2008-01-17
Anticipated expiration: 2009-01-11
Also published as: CN101126181A; KR100780434B1

Abstract

The present invention relates to a preparation method of a polyurethaneurea elastic fiber, in which the sub-reaction and reaction speed are regulated during the prepolymer reaction by adding 1- functional monoalcohol and an organic acid in order to provide an elastic fiber exhibiting excellent uniformity during the weaving and processing of a synthetic fiber such as polyester or nylon, a static mixer having excellent stirring efficiency and a tubular reactor are used for constant even reaction to give a primary uniform polymer, the primary polymer is dissolved in a solvent using a high shear mixer, and a chain extender and chain terminator are added with regulation to give the secondary polymer having intrinsic viscosity of at least 1.0. In the present invention, a high shear mixer for the secondary polymerization exhibiting at least 80% of stirring efficiency and a cylindrical pipe shaped static mixer were used to inhibit sub-reaction and gelation to give a secondary polymer exhibiting stable spinning.

Description

[DESCRIPTION!

[invention Title]

POLYURETHANEUREA ELASTIC FIBER AND METHOD FOR PREPARATION THEREOF

[Technical Field]

The present invention relates to a polyurethaneurea elastic fiber having excellent uniformity and spinning property and providing excellent textile quality for cross- weaving with such synthetic fibers as polyester and nylon.

[Background Art]

To prepare the polyurethaneurea elastic fiber, prepolymer chain of isocyanate terminal synthesized from high molecular polyol and excessive organic diisocyanate was extended by using diamine to give a polymer, followed by dry spinning and melt spinning. The prepared polyurethaneurea elastic fiber is cross-weaved together with a polyamide fiber or polyester fiber and a natural fiber into various clothes requiring elasticity such as a foundation, socks, a panty stocking, a swim suit, etc.

In spite of its excellent elasticity resulted from hydrogen bonds of hard segments composed of bulky urea groups, the polyurethaneurea elastic fiber has a weakness in thermal durability because the hard segments therein are apt to move easily by the stimulation of high temperature. Thus, when the polyurethaneurea elastic fiber is cross-weaved with a synthetic fiber by high temperature dyeing or is secondarily dyed to prepare such clothes as a foundation requiring color combination, the elastic fiber of textile might loosen or become single ply threads, resulting in the decrease of elasticity and appearance of a product. This has been a common problem of whole polyurethane based elastic fibers including the polyurethaneurea elastic fiber.

Therefore, numbers of polyurethaneurea elastic fiber production companies have been tried various methods to improve heat resistance. Some of them produce polyurethaneurea elastic fiber products with improved heat resistance, but they are still in troubles of sacrificing other physical properties such as elastic recovery, settability, and elasticity in return and difficulty in regulating production processes.

To prepare polyurethaneurea keeping elasticity and heat resistance under dyeing process with a synthetic fiber or other secondary dyeing conditions, ethylenediamine has been used as an independent chain extender, resulting in the improved heat resistance owing to the linearity of ethylenediamine and strong coagulation between hard segments. However, it accelerates reaction speed very fast during chain extension, causing sub-reactions. In addition, the strong coagulation between hard segments causes gelation, making spinning difficult owing to the uneven and unstable viscosity and reducing the strength and elasticity of the elastic fiber. As a part of the effort to solve the above problems, Japanese Laid-Open Patent Publication No. S44 -22113 describes that a small amount of 1-functional monoalcohol is used in order to regulate the reaction speed of chain extension and inhibit sub-reaction. However, sacrifice of other physical properties of an elastic fiber such as strength and elasticity is inevitable according to this method, which has to be improved . The conventional methods to improve heat resistance of the polyurethane elastic fiber are described in Japanese Laid- Open Patent Publication No.S58-59213 and US Patent No. 5,100,999. According to these descriptions, heat resistance was improved by making the structure of crystalline cross- linking point stronger by using polycaprolactonediol and polycarbonatediol as polyol forming the soft segments of polyurethaneurea, but the improvement effect was not satisfactory and the elastic recovery was reduced, compared with the polyurethaneurea using polyetherpolyol . According to Japanese Laid-Open Patent Publication No. Hl-110520, diaminodiphenylurea was used as a chain extender to improve cross-linking density in the hard segments of urea group in the structure of diamine in order to improve heat resistance. However, this method might jeopardize spinning stability because crosslinks between polymers are formed in pre-spinning solution with consecutive changes of viscosity level.

Japanese Laid-Open Patent Publication No. H 4-100919 describes that triamines are polymerized, which will be used as an additive for pre-spinning in order to improve heat resistance. Since the introduction of this method designated to be conducted before spinning, numbers of polyurethaneurea elastic fiber production companies have been used triamine as a chain extender or an additive to improve heat resistance but the improvement effect has not been satisfactory. A co- extender has also been used as a supplement for reduced heat settability, viscosity and heat resistance, but the effect is still in question. Besides, the over-use of a cross- linking agent rather brought the problem of viscosity during the process.

[Disclosure] [Technical Problem]

It is an object of the present invention to provide a polyurethaneurea elastic fiber providing excellent textile qualities including elastic recovery, heat settability and strength even after weaving and dyeing processes (including high temperature dyeing) .

It is another object of the present invention to provide a polyurethaneurea elastic fiber by preparing the primary polymer first so as to reduce gelation and sub-reaction and thus facilitates the final spinning. It is a further object of the present invention to provide a polyurethaneurea elastic fiber having even physical properties prepared by making the additive composition for the secondary polymer and the resultant mixture stable for safe and easy spinning and for uniformity of the properties.

It is also an object of the present invention to provide a polymerization method providing excellent mixing efficiency and stability and a preparing method of the polyurethaneurea elastic fiber having excellent heat resistance, elastic recovery, heat settability and strength using the same.

It is also an object of the present invention to provide a polymerization apparatus for the reaction giving high mixing efficiency and stability.

[Technical Solution]

To achieve the above objects, the present invention provides a novel preparing method of an elastic fiber showing excellent heat resistance, heat settability, uniformity, elastic recovery, but no gelation, which comprises the following steps:

(a) Preparing polyurethaneprepolymer, the primary polymer, having the viscosity of 500 ~ 700 poise, in which non-reacted diisocyanate is contained at terminal up to 3 mol%, by mixing polytetramethyleneglycol (PTMEG) composed of 500 ~ 2000 ppm of 1-functional monoalcohol and 5 - 20 ppm of an organic acid and diphenylmethane-4, 4' -diisocyanate (MDI) in a static mixer at 40 ~ 50^°C, more preferably at 45°C, and polymerizing thereof in a cylindrical pipe shaped continuous polymerization tube at 70

~ 95^°C more preferably at 75 ~ 85°C;

(b) Preparing the secondary polymer solution having the apparent viscosity of 2000 ~ 3500 poise (solid content: 37%) by stirring the mixture of the primary polymer, a chain extender composed of ethylenediamine/l, 2- diaminopropane/diethylamine and a chain terminator in N, N- dimethylacetamide solvent at 40^°C; (c) Preparing a spinning dope having 3500 ~ 5000 poise (40^°C, solid content: 37%) by adding an additive composition to the polymer solution; and

(d) Preparing a polyurethaneurea elastic fiber by spinning the above spinning dope. The preparation of the primary polymer of the present invention has been designed for a monomer to be polymerized with keeping its properties evenly all through the continuous polymerization and thus for the final elastic fiber to have regular properties and at the same time for regulating the reaction speed by using 1- functional monoalcohol and an organic acid as a polymerization speed regulator. In general, the 1 -functional monoalcohol is added for polymerization to prevent the fast acceleration of urethane polymerization and gelation or excessive increase of viscosity. In the present invention, the 1-functional monoalcohol is used together with an organic acid, particularly phosphoric acid, to prevent rapid change of reaction speed and thus to secure stable polymerization. The 1-functional monoalcohol of the invention is preferably normal butanol and the preferable content of the normal butanol in polytetramethyleneetherglycol is 500 ~ 2000 ppm. If the content is less than 500 ppm, the regulation of reaction will be difficult, while the content is more than 2000 ppm, which means the 1-functional group is over-used with reducing molecular weight of a polymer, the physical properties of a textile will be reduced after spinning. In the present invention, an organic acid particularly phosphoric acid is used along with the 1-functional monoalcohol and at this time the content of the phosphoric acid in polytetramethyleneetherglycol is 5 ~ 20 ppm. If the content is within the above range, reaction speed will be properly regulated and physical properties of the final elastic fiber will be stably maintained.

According to the present invention, PTMEG was serially mixed with the mixture of an organic acid and the 1-functional monoalcohol and MDI, which were mixed by dosing pump, in a static mixer, followed by continuous polymerization in a cylindrical tube reactor. The mixing in the static mixer was performed at 40 ~ 50^°C to prevent unwanted polymerization. If the mixing is performed at a lower temperature than the above, the following polymerization will not be completely induced while if the mixing is performed at a higher temperature than the above, polymerization speed will be fast and gelation will occur. The fully mixed polymerization composition is polymerized in a cylindrical pipe shaped reactor at 70 ~ 95 ^°C for 100 ~ 200 minutes. The duration of the polymerization depends on the physical properties of a final product but 120 ~ 150 minute reaction is preferred. The final polyurethane prepolymer, the primary polymer, contains non-reacted isocyanate by up to 3 mol% at the terminal of the prepolymer and preferably has the viscosity of 500 ~ 700 poise for the wanted physical properties of the final elastic fiber and favorable production processes. If the content of the non- reacted isocyanate is more than 3 mol%, the formation of the primary polymer will not be successful and the molecular weight of the secondary polymerized polyurethaneurea will be too low to provide a proper level of viscosity, which means the physical properties of the secondary polymerization product will be poor.

The preparation process of the secondary polymer is described in detail hereinafter. The primary polymer prepared in the above was passed through a 10 ~ 20 μm filter to eliminate any composition remaining on the gel, followed by selection of a polymer. The polymer was loaded in a dissolver together with the solvent N,N-dimethylacetamide, followed by vigorous stirring for approximately 1 minute or preferably for 20 ~ 30 seconds for complete dissolving of non-reacted diisocyanate, which would be cooled to 15 ~ 45^°C for the following secondary reaction. The chain extender ethylenediamine and 1, 2-diaminopropane were added to the above solvent at the ratio of 70 - 90:30 ~ 10 mol%. And the primary polymer solution was simultaneously added to the secondary polymerization reactor equipped with a blade containing a cooling system. Polymerization was completed within 10 minutes. And the temperature of the polymerization reactor was under 85^°C.

The stirring speed of the blade in the secondary polymerization reactor was regulated by feed-back system in order for the mixing efficiency at the outlet to be at least 80%. The mixing efficiency is calculated by the percentage of the non-reacted chain extender amine group of the polymer terminal in the total preamine group included in the secondary polymer. If the mixing efficiency is lower than 80%, the mixing of the primary polymer with amine in the secondary reactor will not be satisfactory, resulting in irregular chain extension of the polymer, gelation, unsecured adhesion during the production procedure, and irregularity of textile properties after spinning. Excessive increase of the spinning speed to raise mixing efficiency causes sub-reaction and gelation by the raised stirring heat and reaction heat, and thereby increases viscosity instability of the dope and irregularity of textile properties. Therefore, it is the characteristic effect of the present invention to regulate the mixing efficiency to be at least 80%, more preferably 80 ~ 100% by high shear mixing. The mixing efficiency is calculated as follows,- 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. The polymer is prepared as a film and then dried. The polymer is dissolved again in N, N- dimethylacetamide solution, followed by titrating with 0.1 N HCl . The content of the terminal amine in the polymer is measured. The mixing efficiency of the reactor is calculated by the ratio of the terminal amine content in the polymer to the amine content in the dope .

The viscosity of a final polymer was regulated by adjusting the content of diethylamine in chain extender solution to be 1/20 (amine equivalence ratio) . The amount of amine added for the secondary polymerization is adjusted to let the amine at terminal of the final polymer to be 40 ~ 60 meq/kg. The stirring speed for the reaction was determined in order for the reaction efficiency between the primary polymer and amine to be at least 80% with measuring the mixing efficiency at the outlet of the secondary polymerization reactor.

The solid content of the polyurethaneurea polymer synthesized by chain extension and chain termination was approximately 32 ~ 37%, leading to the secondary polymer solution having the apparent viscosity of approximately 2800 poise at 40^°C. The intrinsic viscosity of the polymer at 0.5 g/100 ml of N,N-dimethylacetamide solution was approximately 1.0.

As explained hereinbefore, in the polymerization process, the preferable ratio of ethylenediamine (a chain extender) to 1, 2-diaminopropane is 70 ~ 90 : 30 10 mol%, and more preferably 80 : 20 mol%. The ratio of the chain terminator to the amine content used for the chain extender is 1/15 ~ 1/30 and more preferably 1/20. It is most preferred to mix ethylenediamine as a chain extender with 1, 2-diaminopropane at the ratio of 80 : 20 mol%. With the increase of ethylenediamine, hydrogen bonding force in the inside of the polymer increases, making viscosity unstable. With the increase of 1, 2-diaminopropane, viscosity becomes stable but heat resistance is not improved. In the meantime, the preferable ratio of a chain terminator, diethylamine, to the chain extender is 1/20, which is proper for preparing a polymer having stable viscosity and physical properties. If the content of diethylamine is too small, the secondary polymerization speed will not be regulated and the molecular weight of the polymer will be increased, resulting in unstably high viscosity. On the contrary, if the content of diethylamine is too high, the secondary polymerization speed will be reduced and thus the molecular weight of the polymer will be light, resulting in the low viscosity and poor textile properties after spinning.

The content of the chain extender and the chain terminator amine is 2 ~ 4 mol% for the non-reacted isocyanate group residing in prepolymer, the primary polymer. At this time, if the amine is used less than 2 mol%, the viscosity of the dope will increase with the increase of irregularity of the polymer. If the amine content is more than 4 mol%, which means the amine is used overdose, the molecular weight of the polymer will decrease along with the viscosity, resulting in the decrease of quality of the yarn obtained from spinning. The secondary polymer polyurethaneurea polymer preferably has the viscosity of 2000 ~ 3500 poise (40^°C, solid content: 37%) and more preferably has the viscosity of 2500 ~ 3000 poise. If the viscosity of the secondary polymer is up to 2000 poise, which means too low viscosity for a polymer and for the production of fiber, textile properties will be poor and spinning process cannot be stably performed. Therefore in that case, to form stable viscosity enough for spinning, extended aging time is required, which is not desirable in the aspects of economy and technology. In the meantime, if the viscosity is at least 3500 poise, which means too high viscosity for a polymer, viscosity regulation during the following procedure will be difficult and thus stable spinning will be still difficult. In addition, under the high viscosity condition, various additives added for the reaction will not be dispersed evenly, resulting in a poor quality product. The additive composition of the present invention is described in detail hereinafter. To help the conventional spandex maintain durability and white color and have improved anti-discoloration (prevention of yellowing) and dyeability as well as prevent damages of mechanical properties, a whitener, a waste gas stabilizer, an antioxidant, a viscosity and unwinding property enhancer, a dyeability enhancer and a spinning stabilizer are mixed and this mixture is added to the secondary polymer, polyurethaneurea.

In the present invention, each additive is added as follows to the total weight of spandex; diethylenediamine is added as a spinning stabilizer by 50 ~ 200 ppm, titanium dioxide is added by 0.1 ~ 5.0 weight%, 1, 1, 1' , 1' -tetramethyl- 4 , 4 ' (methylene-di-p-phenylene) disemicarbazide [HN-150] is added as a waste gas stabilizer by 0.1 ~ 5.0 weight%, 2- [4, 6- bis (2 , 4-dimethylphenyl) -1,3, 5-triazine-2-yl] -5- (octyloxy) phenol [CYASORB^® UV-1164D (Cynamid, USA)] is added as a photo-stabilizer by 0.1 ~ 3.0 weight%, 1, 3 , 5-tris (4-t-butyl- 3-hydroxy-2 , 6-dimethylbenzene) -1,3, 5-triazine-2, 4,6- (1H,3H,5H) -trion CYANOX 1790 (R) (Cynamid, USA) is added as an antioxidant by 0.1 ~ 5.0 weight%, magnesium stearate is added by 0.1 ~ 3.0 weight% to improve adhesion and unwinding property and poly (N,N-diethyl-2-aminoethyl methacrylate) is added as a dyeability enhancer by 0.1 ~ 3.0 weight%. Herein, diethylenetriamine is added not as a chain extender but as an additive for forming a cross-link during the high temperature spinning to improve heat resistance of an elastic fiber and for preventing precipitate resulted from the coagulation among inorganic additives, and at the same time to play a certain role in even mixing of the polymer and an additive . The even mixing between the final polymer and an additive is very important and a cylindrical pipe shaped static mixer is used for the even mixing of the polymer and an additive herein. The prepared polyurethaneurea solution (dope) contains 37% of solid content and the viscosity of 3500 ~ 5000 poise (at 40^°C), which is proper for spinning.

The storage temperature of the additive slurry which would be mixed with a final polymer is also very important. If the storage temperature of the additive slurry is over 60^°C, the increase of viscosity of the slurry will surpass the decrease of precipitation speed by a decreasing factor triggered by microbrown movement of each additive component, resulting in the coagulation of additive slurries and acceleration of precipitation speed with reducing the qualities of additive slurries. In addition, clogging cycle of an additive filter will also be short under the high temperature, resulting in the decrease of quality of a product. If the storage temperature of the additive slurry is lower than 40^°C, the comparative viscosity of the additive slurry will be increased with increasing the differential pressure of an additive filter, making the process unstable. In addition, microbrown movement of each additive component will be contracted under the low temperature, indicating that the coagulation will be accelerated, resulting in the decrease of additive quality and short clogging cycle of a filter. Therefore, the storage temperature of the additive slurry is preferably within the range of 40 ~ 50^°C .

[Best Mode]

The preparing method of the present invention is described hereinafter in detail with the preferable embodiments and additional explanations on specific components and contents are separately given. Before describing the preferable embodiments of the invention, various property evaluation methods are explained herein.

1) Measurement of the viscosity of a polymer Viscosity of a polymer which was through with chain extension and chain termination is measured at 40^°C by using a Brookfield Viscometer and is presented by the unit of poise.

2) Measurement of the gel particles in a polymer

A polymer is dissolved in 1% LiCl DMAc electrolyte at the concentration of 0.5% and the number of gel particles in the polymer is counted by using a coulter counter (Beckman) .

3) Measurement of mixing 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. The polymer is prepared as a film and then dried. The polymer is dissolved again in N,N-dimethylacetamide solution, followed by titrating with 0.1 N HCl. The content of the terminal amine in the polymer is measured. The mixing efficiency of the reactor is calculated by the ratio of the terminal amine content in the polymer to the amine content in the dope.

4) Measurement of intrinsic viscosity

0.5 g of the polymer is dissolved in 100 ml of N, N- dimethylacetamide solution and viscosity of the solution is measured by using an Ubbelohde viscometer to determine intrinsic viscosity of the polymer.

5) Breaking strength, breaking elongation

Breaking strength (g/d) and breaking elongation (%) are measured by using a Universal Tensile Machine (UTM, Instrong) at 20^°C under 65% RH (sample length: 5 cm, extension speed: 50cm/min) .

6) Elastic recovery

Samples are marked at 10 cm intervals and then extended 300%. Samples stand for 24 hours as extended and then are recovered from the extension. 10 minutes after the recovery, the recovered length is measured.

ER(%) = [(Ls - La) /(Ls - Lo)] x 100

(Wherein, Lo indicates the distance between marks on a sample, Ls indicates the length of a sample as 300% extended, La indicates the length of the sample after being recovered from the extension) 7) Moist heat elastic recovery

Samples are marked at 10 cm intervals. After being extended 100%, the samples are treated with water vapor for 60 minute at 130^°C and then let be recovered from the extension. The recovered length is measured and presented by the ratio to the length of a non-treated sample. The higher the elastic recovery, the higher heat resistance but the lower heat settability is.

Moist heat elastic recovery = [(Ls - Lt) /Lo] x 100 (Wherein, Lo indicates the distance between marks on a sample, Ls indicates the length of a sample as 100% extended, Lt indicates the recovered length from the extension of the sample)

8) Dry heat strength retention rate A sample is 100% extended and then treated with hot wind for 1 minute at 180°C . Strength is measured with a universal tensile machine and the ratio of the strength after dry heat- treatment to the strength of the non-treated sample is regarded as strength retention rate. The higher the strength retention rate, the higher heat resistance is.

Practical and presently preferred embodiments of the present invention are illustrative as shown in the following Examples and Comparative Examples . However, it will be appreciated that those skilled in the art, on consideration of this disclosure, may make modifications and improvements within the spirit and scope of the present invention.

Example 1 To 252.780 g of polytetramethyleneetherglycol (PTMEG, MW: 1815) were added 1150 ppm of normal butanol (n-Butanol, MW: 74.12) and 10 ppm of phosphoric acid, followed by mixing. 57.063 g of diphenylmethane-4,4' -diisocyanate was serially added to the 45^°C static mixer by using a dosing pump, which was loaded in a 85 90 ^°C cylindrical pipe shaped polymerization tube, followed by reaction for 130 minutes to adjust the non-reacted terminal diisocyanate as 2.33 ± 0.02 mol% to give a primary polymer having 700 poise.

The primary polymer was cooled at 40 "C, which was standing for 20 hours. Before adding the primary polymer to the secondary reactor, 456.663 g of N,N-dimethylacetamide was also serially loaded to the high shear mixer with stirring vigorously at approximately 2500 rpm for 20 seconds. The primary polymer was completely dissolved and cooled down at 15 °C to give polyurethane prepolymer mixture having the solid content of 40%.

The mixture was loaded to the secondary polymerization reactor along with a chain extender solution (ethylenediamine 4.00 g / 1, 2-diaminopropane 1.23 g = molar ratio 80/20) and a chain terminator solution (diethylamine 0.64g), followed by stirring at approximately 200 rpm for 4 minutes, leading to the secondary polymerization. As a result, polyurethaneurea compound was obtained at 65 ~ 70^°C. A polymer was recovered at the outlet of the secondary polymerization reactor and preamine and terminal amine residing in the dope and the polymer were measured to calculate the mixing efficiency of the secondary polymerization reactor. The stirring speed of the polymerization reactor and the content of amine and the temperature of the reactor were all regulated to lead the mixing efficiency to at least 80%. The amount of diethylamine was determined to be 1/20 (amine equivalence ratio) of the chain extender solution. The content of amine was determined to be 2 mol% for isocyanate group residing in the prepolymer. Herein, a polymerization terminator was not added and the termination time point was when the non-reacted amine content was reduced up to 1 ~ 5 mol%.

Polyurethaneurea secondary polymer polymerized with the addition of a chain extender and a chain terminator had the solid content of 37% and the apparent viscosity of 2500 poise at 40 °C . The intrinsic viscosity of this polymer dissolved in 100 ml of N,N-dimethylacetamide solution at the concentration of 0.5 g was 1.0.

In order for the conventional spandex not to lose durability and white color by washing or use, to have improved anti-discoloration (prevention of yellowing) and dyeability, and to be protected from being damaged in its properties, 0.12 weight% of titanium dioxide, 0.60 weight% of 1,1,1',1'- tetramethyl-4 , 4 ' (methylene-di-p-phenylene) disemicarbazide waste gas stabilizer [HN-150] , 0.1 ~ 3.0 weight% of 2- [4,6- bis (2,4-dimethylphenyl) -1,3, 5-triazine-2-yl] -5- (octyloxy) phenol photostabilizer [CYASORB^α>UV-1164D (Cynamid,

USA)], 1.44 weight% of 1, 3, 5-tris (4-t-butyl-3-hydroxy-2, 6- dimethylbenzene) -1, 3 , 5-triazine-2 , 4 , 6- (1H,3H,5H) -trion CYANOX

1790 (R) (Cynamid, USA), 0.50 weight% of magnesium stearate

(Nippon Oil & Fat, Japan) to improve viscosity and unwinding property, 0.6 weight% of poly (N,N-diethyl-2-aminoethyl methacrylate) dyeability enhancer and 100 ppm of diethylenetriamine, which were all the ratios to the total weight of the spinning spandex fiber, were added to the above polymerized solution. Herein, diethylenediamine was added not as a chain extender but as an additive to form a cross-link during the high temperature spinning to improve heat resistance of an elastic fiber and to prevent coagulation of inorganic additives from generating precipitate and at the same time to mix the polymer evenly with the additive. At this time, the even mixing of the final polymer with an additive is very important. To mix the final polymer with an additive evenly, a cylindrical pipe shaped static mixer was used. The prepared polyurethaneurea product contained the solid content of 37% and the viscosity of 4250 poise (40^°C), which was proper viscosity for spinning.

The additive slurry which would be mixed with a final polymer was maintained at 45 "C .

The prepared polymer solution for spinning was slowly driven through the spinning tube at 245 ~ 255 °C by using a gear pump, during which a solvent was evaporated. So, the polyurethaneurea elastic fiber was prepared by the above dry spinning at the speed of 900 m/min and the physical properties of the product are shown in Table 2.

Example 2

An elastic fiber was prepared by the same manner as described in Example 1 except that normal butanol was added by 1500 ppm for the total weight of polytetramethyleneetherglycol .

Comparative Example 1

An elastic fiber was prepared by the same manner as described in Example 1 except that a chain extender solution (ethylenediamine 3.92 g / 1, 2-diaminopropane 1.20 g = molar ratio 80/20) and a chain terminator solution (diethylamine 0.627 g) were added by the same equivalence ratio (amine equivalence ratio / diisocyanate equivalence ratio = 1.00) as terminal isocyanate group of the primary polymer. Comparative Example 2

An elastic fiber was prepared by the same manner as described in Comparative Example 1 except that the solid content was reduced 2% from 37% to 35% in order to reduce the viscosity by increasing the amount of N,N-dimethylacetamide added in the prepolymer solution before loading in the secondary polymerization reactor. Comparative Example 3

To 240.63 g of polytetramethyleneetherglycol (PTMEG, MW: 1815) were added 900 ppm of normal butanol (n-Butanol, MW: 74.12) and 10 ppm of phosphoric acid, followed by mixing. 57.04 g of diphenylmethane-4,4' -diisocyanate was serially added to the 45^°C static mixer by using the dosing pump, which was loaded in a 75 90 ^°C cylindrical pipe shaped polymerization tube, followed by reaction for 120 minutes to adjust the non-reacted terminal diisocyanate as 2.65 ± 0.02 mol%. An elastic fiber was prepared by the same manner as described in Comparative Example 1, except that the chain extender solution (ethylenediamine 4.29 g / 1, 2-diaminopropane 1.32 g) and the chain terminator solution (diethylamine 0.67 g) were reacted with the terminal isocyanate of the primary polymer and the solid content was 35%.

[Table 1]

[Table 2 ]

* Textile stripe grade (visual inspection, stripe grade per yard)

A(no stripes), B+(l~2 thin stripes), B(3~5 thin stripes), BC(5~10 thin stripes), C+(10~20 thin stripes), C(l~5 band like thick stripes) , D (at least 5 band like thick stripes) .

As explained hereinbefore, according to the method of the present invention, sub-reaction and gelation are inhibited by- even mixing during the primary polymerization, so the spinning elastic fiber has excellent uniformity, spinning property, elastic recovery, moist heat elastic recovery and strength retention rate, which results in the elastic fiber with good qualities including maintenance of strip pattern of textile and elegance after weaving and dyeing.

[industrial Applicability]

The present invention provides a polyurethaneurea elastic fiber having excellent textile qualities such as excellent uniformity and spinning property as well as elastic recovery and strength retention rate even after dyeing process.

Claims

[CLAIMS] [Claim l]

A preparing method of a polyurethaneurea elastic fiber comprising the following steps: A) Preparing the primary polymer by mixing 1-functional monoalcohol, organic acid, polytetramethyleneetherglycol and diphenylmethane-4,4' -diisocyanate in a static mixer and continuous reacting the mixture in a cylindrical pipe shaped reactor; and B) Preparing the secondary polymer solution by adding the amine mixture comprising ethylenediamine/1, 2- diaminopropane/diethylamine to the primary polymer and stirring the mixture in a stirring reactor with high shear stress.

[Claim 2]

The preparing method of a polyurethaneurea elastic fiber according to claim 1, wherein the primary polymer is dissolved in N,N-dimethylacetamide, resulting in the preliminary polymer mixture, the preliminary polymer mixture and the amine mixture comprising ethylenediamine/1, 2 -diaminopropane/diethylamine are stirred at a required speed set to give at least 80% of mixing efficiency, resulting in the secondary polymer solution wherein the apparent viscosity is 2000 ~ 3500 poise (solid content: 37%, 40^°C), an additive composition is added to the secondary polymer solution to prepare a spinning dope having the viscosity of 3500 ~ 5000 poise (40^°C, solid content: 37%), and the spinning dope is spun to prepare an elastic fiber in step B) .

[Claim 3]

The preparing method of a polyurethaneurea elastic fiber according to claim 1, wherein the 1-functional monoalcohol of step A) is normal butanol and the organic acid is phosphoric acid.

[Claim 4]

The preparing method of a polyurethaneurea elastic fiber according to claim 3, wherein the normal butanol, the 1- functional monoalcohol, is used at the concentration of 500 ~ 2000 ppm for the weight of polytetramethyleneetherglycol and the phosphoric acid, the organic acid, is used at the concentration of 5 ~ 20 ppm for the weight of polytetramethyleneetherglycol .

[Claim 5]

The preparing method of a polyurethaneurea elastic fiber according to claim 1, wherein the content of the amine mixture is determined as the amount that makes equivalence ratio of amine group to take 2 - 4 mol% excess for the isocyanate group in the primary polymer. [Claim 6]

The preparing method of a polyurethaneurea elastic fiber according to claim 5, wherein the amine mixture comprises ethylenediamine and 1, 2-diaminopropane, chain extenders, at the ratio of 70 ~ 90:30 ~ 10 mol% and diethylamine, a chain terminator, by the amount of 1/15 ~ 1/30 of the amine equivalence ratio of the chain extender.

[Claim 7] The preparing method of a polyurethaneurea elastic fiber according to claim 2, wherein the additive composition contains 0.05 ~ 4.5 weight% of titanium dioxide, 0.2 ~ 3.5 weight% of 1, 1, 1' , 1' -tetramethyl-4 , 4 ' (methylene-di-p- phenylene) disemicarbazide, 0.1 ~ 2 weight% of magnesium stearate, 0.2 ~ 1.0 weight% of poly (N,N-diethyl-2-aminoethyl methacrylate) dyeability enhancer, 0.1 ~ 3.0 weight% of 2-

[4, 6-bis (2,4-dimethylphenyl) -1,3, 5-triazine-2-yl] -5-

(octyloxy) phenol photostabilizer, 0.5 ~ 3.5 weight% of the antioxidant 1,3, 5-tris (4-t-butyl-3-hydroxy-2, 6- dimethylbenzene) -1, 3 , 5-triazine-2, 4, 6- (1H,3H,5H) -trion and 50 ~ 200 ppm of diethylenetriamine for the total weight of the dope composition.

[Claim 8] The preparing method of a polyurethaneurea elastic fiber according to claim 2, wherein the spinning is performed at the spinning nozzle fall down temperature of 240 ~ 255 ^°C and spinning speed of 700 - 1200 m/min.

[Claim 9] The preparing method of a polyurethaneurea elastic fiber according to claim 2, wherein the primary polymer is cooled down to 30 ~ 50^°C and loaded in a high shear mixer together with N,N-dimethylacetamide and dissolved for preparing the preliminary polymer mixture.

[Claim lθ]

The preparing method of a polyurethaneurea elastic fiber according to claim 2, wherein the preliminary polymer mixture is stirred with the amine mixture comprising ethylenediamine/1, 2-diaminopropane/diethylamine and then the polymer is taken from the outlet of the secondary polymerization reactor to measure the content of terminal group amine and preamine, and at this time the stirring speed of the polymerization reactor, the amine content and the temperature of the reactor are regulated to make the mixing efficiency at least 80%.

[Claim ll]

The preparing method of a polyurethaneurea elastic fiber according to claim 1, wherein the primary polymer of step A) contains non-reacted diisocyanate up to 3mol% at the terminal. [Claim 12 ]

The preparing method of a polyurethaneurea elastic fiber according to claim 4, wherein the temperature of the static mixer is 40 ~ 50 ^°C the temperature for the polymerization in the continuous polymerization tube is 70 ~ 95 ^°C and the resultant polyurethaneurea elastic fiber has the viscosity of 500 ~ 700 poise and contains the non-reacted diisocyanate by up to 3 mol% at the terminal.

[Claim 13]

A polyurethaneurea elastic fiber prepared by any method of claim 1 ~ claim 12.