Spandex with good unwinding property and high cohesive force and preparation method thereof

Abstract

The invention relates to spandex with good unwinding property and high cohesive force and a preparation method thereof, the spandex comprises polyurethane-urea and a lubricant mixture, and the lubricant mixture comprises a lubricant and a dispersant; the lubricant comprises an organic lubricant and an inorganic lubricant, the dispersing agent comprises poly-alpha-cyanoacrylate, and the spandex also contains a crosslinking stabilizer and / or a functional additive. The preparation method comprises the following steps: reacting polymer polyol with polyisocyanate to obtain a polyurethane prepolymer, and dissolving the obtained polyurethane prepolymer in a solvent to obtain a polyurethane prepolymer solution; the obtained polyurethane prepolymer solution, a diamine chain extender and an amine chain terminator are subjected to a reaction, and a polyurethane-urea solution is obtained; a raw material is prepared from a polyurethane-urea solution, a lubricant mixture, a crosslinking stabilizer and a functional aid in the presence of a solvent, and the spandex fiber is obtained through dry spinning, the spandex fiber has the properties of excellent unwinding property, high cohesion, high resilience and high elongation.

Description

Technical Field

[0001] The invention relates to a spandex fiber with good unwinding property and high cohesion force and a preparation method thereof, belonging to the technical field of polyurethane elastic fiber manufacturing. Background Art

[0002] Spandex is the abbreviation of polyurethane fiber. Thanks to the high elasticity, high elongation, high recovery rate and other properties of spandex, the wearing comfort of the fabric is significantly improved. Spandex is generally composed of multiple filaments. Spandex fibers with a denier of 140D and above are widely used in elastic fabrics such as webbing, diaper waistbands, elastic bands, etc. With the development of productivity, the demand for improving production efficiency has put forward higher requirements on the performance of spandex products. The poor unwinding of spandex and the separation of fibers due to friction between fibers, metals, and plastic equipment under high-speed conditions are the two major problems that need to be solved in the high-speed unwinding process of this type of spandex products.

[0003] There are relevant patent reports on how to improve the cohesion of spandex fiber and the unwinding property of the yarn roll. Patent CN103339303A improves the adhesion between the yarns in the multifilament fiber by adding 0.01-10wt% of dialkyl sulfosuccinate. Patent CN107641847A improves the adhesion by adding 0.1-20wt% of liquid polyamide. Patent CN103109005A prepares spandex fiber by adding cellulose acetate butyrate, cellulose acetate propionate and their mixtures as soluble anti-adhesive compositions, and at least one calcium stearate, magnesium stearate, organic stearate, silicone oil, mineral oil and their mixtures. Patent CN108221076A improves the unwinding property of diaper spandex by adding polyhedral oligomeric silsesquioxane POSS. Patent CN106978650A introduces a polystyrene polymer with a number average molecular weight of 20,000 to 500,000 into the spinning solution of polyurethane urea to prevent irregular bulging and tension peaks occurring during the unwinding process and enhance the bonding properties with the hot melt adhesive.

[0004] It can be seen that the current methods mainly focus on improving the unwinding smoothness or the adhesion between the filaments. These methods still have some shortcomings, including but not limited to (1) the improvement of unwinding smoothness and the improvement of adhesion between the filaments are difficult to be compatible; (2) the unwinding improvement effect of a single organic or inorganic lubricant is limited; (3) the compatibility between inorganic additives such as matting agents and the polyurethane organic matrix is ​​poor, and they are easy to precipitate, resulting in powder loss or frictional separation; (4) additives may reduce the resilience of spandex fibers. Summary of the invention

[0005] Technical problem: The purpose of the present invention is to prepare a spandex fiber with good unwinding properties and high cohesion and a preparation method thereof. The spandex product takes into account both unwinding properties and cohesion, while maintaining the high resilience and high elongation properties of the spandex in this application.

[0006] Technical solution: The spandex with good unwinding property and high cohesive force of the present invention comprises polyurethane-urea and a lubricant mixture, wherein the lubricant mixture comprises a lubricant and a dispersant;

[0007] The lubricant includes an organic lubricant and an inorganic lubricant; the organic lubricant includes at least one of hydroxyethyl ethylene bisstearamide, lauric acid amide, and erucic acid amide; the inorganic lubricant includes at least one of hydrotalcite and mica powder; the organic lubricant accounts for 0.01 to 5 wt% of the total mass of the spandex, and the inorganic lubricant accounts for 0.1 to 5 wt% of the total mass of the spandex.

[0008] The dispersant comprises poly-α-cyanoacrylate, and the unit structure is as follows:

[0009]

[0010] Wherein R is a carbon skeleton having 1 to 8 carbon atoms;

[0011] The number average molecular weight of the poly-α-cyanoacrylate is 6000-60000 g / mol;

[0012] The poly-α-cyanoacrylate accounts for 0.1-20wt% of the total weight of the spandex.

[0013] The spandex further contains a crosslinking stabilizer and / or a functional additive, wherein the crosslinking stabilizer includes one or a mixture of inositol triphosphate and inositol hexaphosphate, and the crosslinking stabilizer accounts for 0.01 to 5 wt% of the total mass of the spandex; the functional additive includes one or more of an antioxidant, an anti-ultraviolet agent, a UV stabilizer, an anti-yellowing agent, a matting agent, a dyeing auxiliary, and a chlorine-resistant auxiliary;

[0014] The polyurethane-urea comprises the reaction product of a polymer polyol, a polyisocyanate, a diamine chain extender and an amine chain terminator;

[0015] The polymer polyol includes any one of polytetramethylene ether glycol, polyethylene glycol or polypropylene glycol or a combination of at least two thereof; the number average molecular weight of the polymer polyol is 1000 to 4000;

[0016] The polyisocyanate includes any one of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate or dicyclohexylmethane diisocyanate, or a combination of at least two thereof;

[0017] The diamine chain extender includes a diamine having 2 to 30 carbon atoms, and further includes any one or a combination of at least two of ethylenediamine, propylenediamine, butylenediamine, pentylenediamine, methylpentylenediamine, methylpropylenediamine, hexylenediamine, phenylenediamine, phenylenediamine, diaminocyclohexane or hexamethylenediamine;

[0018] The amine chain terminator includes a monoamine with a carbon number of 2 to 20, including any one of diethylamine, isopropylamine, n-butylamine, tert-butylamine, hexylamine, diethylamine, dimethylamine, di-n-butylamine, di-tert-butylamine, diisobutylamine, diisopropylamine, diethylamine, dipropylamine, cyclohexylamine or ethanolamine, or a combination of at least two thereof.

[0019] A method for preparing spandex with good unwinding property and high cohesive force of the present invention comprises:

[0020] Step 1. polymer polyol and polyisocyanate react to obtain a polyurethane prepolymer, and the obtained polyurethane prepolymer is dissolved in a solvent to obtain a polyurethane prepolymer solution; wherein the molar ratio of polyisocyanate to polymer polyol is (1.80-2.20):1;

[0021] Step 2. reacting the obtained polyurethane prepolymer solution, diamine chain extender and amine chain terminator to obtain a polyurethane-urea solution; wherein the molar ratio of the diamine chain extender to the amine chain terminator is (15.0-25.0):1;

[0022] The molar ratio of NCO in the polyurethane prepolymer to the amine groups in the diamine chain extender and the amine chain terminator is 1:(1.01-1.10);

[0023] Step 3. Prepare a raw material using a polyurethane-urea solution, a lubricant mixture, a cross-linking stabilizer, and a functional additive in the presence of a solvent, and obtain the spandex fiber by dry spinning;

[0024] The spandex fiber has a denier of ≥140D and contains 10 to 40 monofilaments.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0026] The invention adds a lubricant mixture containing poly-α-cyanoacrylate as a dispersant to the spandex, which can significantly improve the cohesion between the monofilaments in the spandex, and can also efficiently compound organic lubricants with organic lubricants to improve the unwinding effect of the spandex; further adding a cross-linking stabilizer can effectively avoid the poor compatibility of the additives with polyurethane when adding other powdered functional additives, solve the problems of easy precipitation of functional additives and frictional powder loss, and further reduce the surface friction coefficient of the filament bundle. DETAILED DESCRIPTION

[0027] The spandex with good unwinding property and high cohesive force comprises a polyurethane-urea and a lubricant mixture, and the lubricant mixture comprises a lubricant and a dispersant;

[0028] The lubricant includes an organic lubricant and an inorganic lubricant; the organic lubricant includes at least one of hydroxyethylethylene bisstearamide, lauric acid amide, and erucic acid amide; the inorganic lubricant includes at least one of hydrotalcite and mica powder;

[0029] Furthermore, the organic lubricant accounts for 0.01 to 5 wt% of the total mass of the spandex, and the inorganic lubricant accounts for 0.1 to 5 wt% of the total mass of the spandex;

[0030] The dispersant comprises poly-α-cyanoacrylate, and the unit structure is as follows:

[0031]

[0032] Wherein R is a carbon skeleton having 1 to 8 carbon atoms;

[0033] The number average molecular weight of the poly-α-cyanoacrylate is 6000-60000 g / mol;

[0034] Furthermore, the poly-α-cyanoacrylate accounts for 0.1 to 20 wt % of the total weight of the spandex.

[0035] Furthermore, the spandex further contains a cross-linking stabilizer, which includes one or a mixture of inositol triphosphate and inositol hexaphosphate, and the cross-linking stabilizer accounts for 0.01 to 5 wt% of the total mass of the spandex;

[0036] The spandex may optionally contain other functional additives commonly used in the spandex field, as long as they do not deteriorate the performance of the product, including one or more of antioxidants, anti-ultraviolet agents, UV stabilizers, anti-yellowing agents, matting agents, dyeing auxiliaries, and chlorine-resistant auxiliaries;

[0037] Preferably, the cross-linking stabilizer is mixed with an additive and then added to the spandex.

[0038] The polyurethane-urea comprises the reaction product of a polymer polyol, a polyisocyanate, a diamine chain extender and an amine chain terminator;

[0039] The polymer polyol includes any one of polytetramethylene ether glycol, polyethylene glycol or polypropylene glycol, or a combination of at least two thereof, and polytetramethylene ether glycol is further preferred;

[0040] The number average molecular weight of the polymer polyol is 1000 to 4000;

[0041] The polyisocyanate includes any one of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate or dicyclohexylmethane diisocyanate or a combination of at least two thereof, and diphenylmethane diisocyanate is more preferably used;

[0042] The diamine chain extender includes a diamine having 2 to 30 carbon atoms, and further includes any one or a combination of at least two of ethylenediamine, propylenediamine, butylenediamine, pentylenediamine, methylpentylenediamine, methylpropylenediamine, hexylenediamine, phenylenediamine, phenylenediamine, diaminocyclohexane or hexamethylenediamine;

[0043] The amine chain terminator includes a monoamine having 2 to 20 carbon atoms, and is more preferably any one of diethylamine, isopropylamine, n-butylamine, tert-butylamine, hexylamine, diethylamine, dimethylamine, di-n-butylamine, di-tert-butylamine, diisobutylamine, diisopropylamine, diethylamine, dipropylamine, cyclohexylamine or ethanolamine, or a combination of at least two thereof.

[0044] The polyurethane-urea is prepared by the following method, which comprises the following steps:

[0045] 1) reacting a polymer polyol with a polyisocyanate to obtain a polyurethane prepolymer, and dissolving the obtained polyurethane prepolymer in a solvent to obtain a polyurethane prepolymer solution;

[0046] 2) reacting the obtained polyurethane prepolymer solution, a diamine chain extender and an amine chain terminator to obtain a solution containing polyurethane-urea.

[0047] Preferably, in step 1), the molar ratio of polyisocyanate to polymer polyol is (1.80-2.20):1;

[0048] The molar ratio of the diamine chain extender to the amine chain terminator in the step 2) is (15.0-25.0):1;

[0049] Preferably, in the step 2), the molar ratio of NCO in the polyurethane prepolymer to the amine groups in the diamine chain extender and the amine chain terminator is 1:(1.01-1.10).

[0050] The solvent is N,N-dimethylformamide and / or N,N-dimethylacetamide. In some embodiments of the present invention, the solvent includes N,N-dimethylacetamide DMAc;

[0051] In some embodiments of the present invention, the reaction temperature of step 1) is 70-95°C;

[0052] The reaction temperature of the step 2) is 0-10°C;

[0053] There is no specific requirement for the reaction time, just ensure that all raw materials react fully.

[0054] The method for preparing spandex with good unwinding property and high cohesion force comprises: spinning the polyurethane-urea, lubricant mixture, optional crosslinking stabilizer and optional other functional additives as raw materials in the presence of a solvent to obtain the spandex fiber;

[0055] The spinning is dry spinning;

[0056] The dry spinning process includes the steps of spraying, stretching and drying;

[0057] Further, in some embodiments of the present invention, the spinning temperature is above 150°C; the temperature after the spinning is completed is below 50°C;

[0058] In some embodiments of the present invention, a solution containing polyurethane-urea, a solution containing a lubricant mixture, and a solution containing optional other functional additives and an optional cross-linking stabilizer can be prepared separately, and then mixed to obtain a spinning solution, and dry spinning is performed to obtain spandex fibers;

[0059] The lubricant-containing mixture solution is obtained by fully dispersing poly-α-cyanoacrylate, organic lubricant and inorganic lubricant into a solvent through ultrasonic stirring;

[0060] The solution containing optional other functional additives and optional crosslinking stabilizer is obtained by dispersing at least one additive selected from antioxidants, anti-ultraviolet agents, UV stabilizers, anti-yellowing agents, matting agents, dyeing additives, and chlorine-resistant additives into a solvent, and adding the crosslinking stabilizer and stirring thoroughly;

[0061] Wherein, if the other functional additives are in a solid state, they can be ground to obtain a particle size D95 of 2 to 10 μm;

[0062] Further, in some examples of the present invention, the solution containing optional other functional additives and optional crosslinking stabilizers is obtained by fully dispersing at least one of antioxidants, anti-ultraviolet agents, UV stabilizers, anti-yellowing agents, matting agents, dyeing additives, and chlorine-resistant additives into a solvent through cyclic grinding, adding a crosslinking stabilizer and stirring sufficiently, and the particle size D95 of the dispersed particles in the solution is 2 to 10 μm;

[0063] The mass percentage of the spinning solution is 30% to 40%, and the viscosity at a constant temperature of 40°C is 3000 to 10000 poise;

[0064] Furthermore, the spinning solution is subjected to aging treatment before spinning, and the aging temperature is 30-45°C.

[0065] The spandex fiber has a denier of ≥140D and contains 10 to 40 monofilaments.

[0066] The following examples are used to describe the production process of the present invention in detail, but these examples should not be construed as limiting the present invention in any sense.

[0067] Preparation of polyurethane-urea solution: adding polytetramethylene ether diol (number average molecular weight 1800) into a reaction kettle, stirring and heating to 50°C, adding diphenylmethane diisocyanate to react, and obtaining a polyurethane prepolymer terminated with isocyanate (-NCO); preparing ethylenediamine and diethylamine into a mixed amine solution with a mass percentage of 5% with DMAc, carrying out a chain extension reaction with the prepolymer, and adding DMAc to obtain a polyurethane-urea solution with a mass content of 35%;

[0068] Polyurethane-urea solution 1: the molar ratio of diphenylmethane diisocyanate to polytetramethylene ether glycol is 1.85:1, and the molar ratio of ethylenediamine to diethylamine is 20:1;

[0069] Polyurethane-urea solution 2: The molar ratio of diphenylmethane diisocyanate to polytetramethylene ether glycol is 1.95:1, and the molar ratio of ethylenediamine to diethylamine is 18:1.

[0070] Preparation of a lubricant-containing mixture solution: dispersing a lubricant and a dispersant into DMAc by ultrasonic stirring to obtain a lubricant-containing mixture solution with a mass content of 35%;

[0071] Wherein, the dispersant 1 is poly-α-cyanoacrylate 1, and the unit structure is as follows:

[0072]

[0073] Wherein R is ethyl, and the average number average molecular weight is 20000;

[0074] Dispersant 2 is poly-α-cyanoacrylate 2, and the unit structure is as follows:

[0075]

[0076] Where R is n-butyl, and the average number average molecular weight is 20000;

[0077] Dispersant 3 is polypropylene with an average number average molecular weight of 20,000.

[0078] Preparation of a solution containing other functional additives and a cross-linking stabilizer: The functional additives are fully dispersed in DMAc by circulating grinding. In the embodiments of the present invention and the comparative examples, the types and amounts of the functional additives are kept consistent: the antioxidant is antioxidant 245 (triethylene glycol bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate]), with a mass percentage of 0.5%; the UV stabilizer is a product of Solvay with a brand name of M535, with a mass percentage of 0.5%; the matting agent is titanium dioxide, with a mass percentage of 0.5%; the anti-yellowing agent is HN-150 (bis(N,N-dimethylhydrazideamino-4-phenyl)methane), with a mass percentage of 0.5%; the above mass percentages are all calculated based on the total mass of the prepared spandex fiber, and the total mass percentage of the functional additives is 2%;

[0079] Add a crosslinking stabilizer to the mixed solution, mix and stir thoroughly to obtain a solution containing other functional additives and a crosslinking stabilizer with a mass content of 30%.

[0080] Preparation of spandex fiber: After mixing a polyurethane-urea solution, a lubricant mixture solution, and a solution containing other functional additives and a cross-linking stabilizer, the mixture is aged at 50°C for 25 hours and dry-spun to obtain spandex fiber, wherein the spinning temperature is 260°C.

[0081] The spinning raw materials and the prepared spandex fibers of Examples 1 to 4 are shown in Table 1 below:

[0082] Table 1:

[0083]

[0084]

[0085] Example 5

[0086] The spinning raw material of Example 5 differs from that of Example 1 in that no organic lubricant is added, and an inorganic lubricant of equal mass, hydrotalcite, is used to replace the original organic lubricant. The spinning solution viscosity, spandex denier, and spandex filament number of the prepared spandex fiber 5 are the same as those of spandex fiber 1.

[0087] Example 6

[0088] The difference between the spinning raw materials of Example 6 and Example 1 is that no inorganic lubricant is added, and an equal mass of organic lubricant hydroxyethyl ethylene bisstearamide is used to replace the original inorganic lubricant. The spinning solution viscosity, spandex denier, and spandex filament number of the prepared spandex fiber 6 are the same as those of spandex fiber 1.

[0089] Example 7

[0090] The difference between the spinning raw material of Example 7 and Example 1 is that the dispersant 1 of Example 1 is replaced by the dispersant 3 of equal mass, and the spinning solution viscosity, spandex denier, and spandex filament number of the prepared spandex fiber 7 are the same as those of the spandex fiber 1.

[0091] Example 8

[0092] The difference between the spinning raw material of Example 8 and Example 2 is that no cross-linking stabilizer is added, and the spinning solution viscosity, spandex denier, and spandex filament number of the prepared spandex fiber 8 are the same as those of the spandex fiber 2.

[0093] Example 9

[0094] The difference between the spinning raw materials of Example 9 and Example 2 is that the same mass of polyethyleneimine is used to replace the inositol triphosphate of Example 1, and the spinning solution viscosity, spandex denier, and spandex filament number of the prepared spandex fiber 9 are the same as those of the spandex fiber 2.

[0095] Comparative Example 1

[0096] The spinning raw material of Example 1 is different from that of Example 1 in that no cross-linking dispersant is added, and the viscosity of the spinning solution, the denier of the spandex, and the number of spandex filaments of the prepared comparative spandex fiber 1 are the same as those of the spandex fiber 2.

[0097] The spandex fibers prepared in the above examples and comparative examples were subjected to the following performance tests, and the test results are compared in Table 2:

[0098] SS300 / DS / DE test method: FZ / T 50006-2013 "Test method for tensile properties of spandex yarn";

[0099] Elastic recovery rate RER310: It indicates the elastic recovery rate of the sample after repeated stretching 5 times to 300%, using F1 / Z50007-2012 "Spandex Elasticity Test";

[0100] Unwinding property: It indicates the degree of difficulty in unwinding the spandex yarn, and indicates the draft ratio when the spandex yarn adheres to the surface of the yarn roll in the unwinding state. The larger the value, the worse the unwinding property, and vice versa.

[0101] Unwinding property: It indicates the degree of difficulty in unwinding the spandex yarn, and indicates the draft ratio when the spandex yarn adheres to the surface of the yarn roll in the unwinding state. The larger the value, the worse the unwinding property, and vice versa.

[0102] Wire-to-wire friction coefficient: The ratio of the friction force between the wires to the vertical force acting on one surface, which reflects the roughness of the contact surface and has nothing to do with the size of the contact area. The larger the value, the greater the roughness, and vice versa.

[0103] Cohesion: The force when the fibers in contact with each other in a tow resist relative movement. The larger the value, the stronger the cohesion, and vice versa. FZ / T 50039-2018 "Test Method for Cohesion Performance of Spandex Filaments" is adopted.

[0104] Table 2:

[0105]

Claims

1. A spandex with good unwinding property and high cohesive force, characterized in that The spandex comprises polyurethane-urea and a lubricant mixture, wherein the lubricant mixture comprises a lubricant and a dispersant.

2. The spandex with good unwinding property and high cohesive force according to claim 1, characterized in that: The lubricant includes an organic lubricant and an inorganic lubricant; the organic lubricant includes at least one of hydroxyethyl ethylene bisstearamide, lauric acid amide, and erucic acid amide; the inorganic lubricant includes at least one of hydrotalcite and mica powder; the organic lubricant accounts for 0.01 to 5 wt% of the total mass of the spandex, and the inorganic lubricant accounts for 0.1 to 5 wt% of the total mass of the spandex.

3. The spandex with good unwinding property and high cohesive force according to claim 1, characterized in that: The dispersant comprises poly-α-cyanoacrylate, and the unit structure is as follows: Wherein R is a carbon skeleton having 1 to 8 carbon atoms; The number average molecular weight of the poly-α-cyanoacrylate is 6000-60000 g / mol; The poly-α-cyanoacrylate accounts for 0.1-20wt% of the total weight of the spandex.

4. The spandex with good unwinding property and high cohesive force according to claim 1, characterized in that: The spandex further contains a crosslinking stabilizer and / or a functional additive, wherein the crosslinking stabilizer includes one or a mixture of inositol triphosphate and inositol hexaphosphate, and the crosslinking stabilizer accounts for 0.01 to 5 wt% of the total mass of the spandex; the functional additive includes one or more of an antioxidant, an anti-ultraviolet agent, a UV stabilizer, an anti-yellowing agent, a matting agent, a dyeing auxiliary, and a chlorine-resistant auxiliary.

5. The spandex with good unwinding property and high cohesive force according to claim 1, characterized in that: The polyurethane-urea comprises the reaction product of a polymer polyol, a polyisocyanate, a diamine chain extender and an amine chain terminator.

6. The spandex with good unwinding property and high cohesive force according to claim 5, characterized in that: The polymer polyol includes any one of polytetramethylene ether glycol, polyethylene glycol or polypropylene glycol or a combination of at least two thereof; the number average molecular weight of the polymer polyol is 1000-4000.

7. The spandex with good unwinding property and high cohesive force according to claim 5, characterized in that: The polyisocyanate includes any one of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate or dicyclohexylmethane diisocyanate, or a combination of at least two thereof.

8. The spandex with good unwinding property and high cohesive force according to claim 5, characterized in that: The diamine chain extender includes a diamine with a carbon number of 2 to 30, and further includes any one or a combination of at least two of ethylenediamine, propylenediamine, butylenediamine, pentylenediamine, methylpentylenediamine, methylpropylenediamine, hexylenediamine, phenylenediamine, phenylenediamine, diaminocyclohexane or hexamethylenediamine.

9. The spandex with good unwinding property and high cohesive force according to claim 5, characterized in that: The amine chain terminator includes a monoamine with a carbon number of 2 to 20, including any one of diethylamine, isopropylamine, n-butylamine, tert-butylamine, hexylamine, diethylamine, dimethylamine, di-n-butylamine, di-tert-butylamine, diisobutylamine, diisopropylamine, diethylamine, dipropylamine, cyclohexylamine or ethanolamine, or a combination of at least two thereof.

10. A method for preparing a spandex with good unwinding property and high cohesive force as claimed in any one of claims 1 to 9, characterized in that: The preparation method comprises: Step 1. polymer polyol and polyisocyanate react to obtain a polyurethane prepolymer, and the obtained polyurethane prepolymer is dissolved in a solvent to obtain a polyurethane prepolymer solution; wherein the molar ratio of polyisocyanate to polymer polyol is (1.80-2.20):1; Step 2. reacting the obtained polyurethane prepolymer solution, diamine chain extender and amine chain terminator to obtain a polyurethane-urea solution; wherein the molar ratio of the diamine chain extender to the amine chain terminator is (15.0-25.0):1; and the molar ratio of NCO in the polyurethane prepolymer to the amine group in the diamine chain extender and the amine chain terminator is 1:(1.01-1.10); Step 3. Prepare a raw material using a polyurethane-urea solution, a lubricant mixture, a cross-linking stabilizer, and a functional additive in the presence of a solvent, and obtain the spandex fiber by dry spinning; The spandex fiber has a denier of ≥140D and contains 10 to 40 monofilaments.

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