Spandex not easy to generate crease marks and fabric thereof

Abstract

The invention discloses spandex not easy to generate crease marks and a fabric thereof, the spandex contains a polyurethane urea polymer, the number-average molecular weight of the polyurethane urea polymer is 60000-100000 g / mol, and the relative molecular mass distribution is less than or equal to 1.60; the polymerization step of the polyurethane urea polymer in the preparation method comprises two times of chain extension. The preparation method comprises the following steps: step 1, primary chain extension: reacting a polyurethane prepolymer A with a diamine chain extender a to obtain a polyurethane urea prepolymer B; step 2, secondary chain extension: reacting the polyurethane-urea prepolymer B with a diamine chain extender a and a monoamine end-capping reagent b to obtain a polyurethane-urea polymer; the polyurethane urea polymer is used as a spinning raw material in the presence of a solvent, and the spandex fiber is obtained through spinning; the fabric contains the spandex or a mixture of the spandex and optional other fibers; the spandex is uniform in tension and good in rebound resilience, and the elastic fabric containing the spandex is not prone to generating creases.

Description

Technical Field

[0001] This invention relates to the field of polymer material preparation, and more specifically to a spandex and a fabric containing the spandex. Background Technology

[0002] Spandex is an elastic fiber with high elongation and high elastic recovery rate. Its breaking elongation can reach 500% to 700%, and its elastic recovery rate is greater than 90%, making it widely used in clothing and textiles. Spandex is a special textile fiber widely used in various covered yarns, circular knitting machines, warp-knitted fabrics, and other fabric-related fields. The dyeing and finishing process of fabrics is long and involves many processing steps. Poor control can easily lead to creases during production, especially in elastic fabrics containing spandex, which are more prone to creases, some of which are irreparable and negatively impact the appearance quality of the finished product. The formation of crease marks is an extremely complex process influenced by numerous factors, such as the stability of fabric tension, the rate of temperature rise and fall during dyeing and finishing, the dyeing time, and the liquor ratio. The properties of the spandex fiber itself are also a significant factor. Knitted fabrics containing spandex remain in a rope-like state during scouring, bleaching, and dyeing, causing the fibers to be continuously subjected to bending and deformation stress in the dyeing machine. If the molecular weight distribution of spandex is uneven, its tension is unstable, or its recovery ability after deformation is insufficient, creases are easily formed during the dyeing process.

[0003] Currently, there are few patents and literature reports on the preparation of spandex without crease marks, mainly focusing on improving the uniformity and resilience of spandex. Patent CN120425482A, through solution polymerization and pre-termining with diethylamine, improves the inhomogeneity of the prepolymerization and chain extension reactions of the spandex dope, effectively reducing gel formation and achieving efficient and highly uniform spandex dope preparation. However, pre-termining with diethylamine inevitably produces a large amount of low-molecular-weight polyurethane, which will inevitably affect the stability of the tension. Patent CN112281247A, through continuous polymerization and optimized spinning processes, solves the problem of insufficient spandex uniformity, achieving the preparation of highly uniform spandex, improving mechanical and temperature resistance properties, and reducing dynamic stress fluctuations and batch variations. However, this only improves uniformity to a certain extent through controlling the polymerization process and optimizing the spinning process, but it does not improve the structure and molecular weight distribution of the polyurethane molecular chains, thus having limited improvement on spandex crease marks. Patent CN105624822A addresses the issue of insufficient uniformity in spandex fibers by optimizing solvent purity, prepolymerization reaction, chain extender selection, and spinning process during fiber preparation. This results in a significant reduction in dynamic unwinding stress and improved uniformity. However, using a single amine chain extender without chain terminator makes it difficult to control the increase in polyurethane molecular weight. Patent CN116288767A achieves high elasticity, high temperature resistance, and hydrophilic oil repellency by using silica composite microspheres combined with 4-methacryloyloxytriphenyltriglyceridyl anhydride and salicylaniline in spandex fibers, improving the overall fabric performance. However, the auxiliaries are added to the polyurethane solution in slurry form, without improving the structure of the polyurethane molecular chain, resulting in very limited improvement on spandex crease marks. Summary of the Invention

[0004] Technical problem: The purpose of this invention is to provide a spandex and its fabric that are not prone to crease marks. The spandex prepared by this method has uniform tension and good resilience, and the elastic fabric containing this spandex is not prone to crease marks.

[0005] Technical solution: The spandex of the present invention that is not prone to crease marks contains a polyurethane urea polymer, wherein the number average molecular weight of the polyurethane urea polymer is between 60,000 and 100,000 g / mol and the relative molecular mass distribution is ≤1.60.

[0006] The spandex also contains a dispersant and a leveling agent; the dispersant accounts for 0.3% to 1% of the mass, calculated based on the mass of the spandex; the leveling agent accounts for 0.5% to 1% of the mass, calculated based on the mass of the spandex. The dispersant includes at least one of polyacrylamide salt and dodecylbenzene sulfonate; The leveling agent includes at least one of polyether-modified polysiloxane, polyester-modified polysiloxane, and alkyl-modified polysiloxane.

[0007] The present invention provides a method for preparing spandex that is less prone to crease marks, comprising using the polyurethane urea polymer as a spinning raw material in the presence of a solvent, and spinning to obtain the spandex fiber.

[0008] The preparation method of the polyurethane urea polymer of the present invention is as follows: the polyurethane urea polymer is obtained through a polymerization step, the polymerization step including two chain extension steps; including; Step 1, primary chain extension: react polyurethane prepolymer A with diamine chain extender a to obtain polyurethane urea prepolymer B; Step 2, secondary chain extension: The polyurethane urea prepolymer B is reacted with diamine chain extender a and monoamine end-capping agent b to obtain a polyurethane urea polymer. The types of diamine chain extender a in step 1 and diamine chain extender a in step 2 are the same.

[0009] in: In step 1, an amine solution containing diamine chain extender a is gradually added to a solution containing polyurethane prepolymer A to carry out an intermittent reaction. In step 2, a mixed amine solution containing diamine chain extender a and monoamine end-capping agent b is continuously added to the reactor along with a solution containing polyurethane urea prepolymer B for continuous reaction. The two chain extension steps are carried out in the presence of a solvent, which includes at least one of N,N-dimethylacetamide (DMAc) and N,N-dimethylformamide (DMF).

[0010] The polyurethane prepolymer A is obtained by reacting polyisocyanate and polymeric polyol, and the polyurethane prepolymer A contains 2.5% to 3% by mass of isocyanate groups NCO. The polyurethane urea prepolymer B contains 0.2% to 0.5% isocyanate groups (NCO) by mass.

[0011] The molar ratio of the diamine chain extender a in step 1 to step 2 is 3:1 to 5:1; In step 2, the molar ratio of the diamine chain extender a to the monoamine end-capping agent b is 3:1 to 1.5:1. In step 1, the molar ratio of the amine group of the diamine chain extender a to the NCO group of the polyurethane prepolymer A is 0.8:1 to 0.9:1. In step 2, the molar ratio of the amine groups of the diamine chain extender a and the monoamine end-capping agent b to the NCO groups of the polyurethane urea prepolymer B is 1.2:1 to 1.35:1. In step 2, the number-average molecular weight of the polyurethane urea polymer is between 60,000 and 100,000 g / mol, and the relative molecular mass distribution is ≤1.60.

[0012] The polyisocyanate includes any one or a combination of at least two of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate or dicyclohexylmethane diisocyanate, and is more preferably diphenylmethane diisocyanate (MDI). The polymeric polyol includes any one or a combination of at least two of polytetramethylene ether diol, polyethylene glycol, or polypropylene glycol, and is more preferably polytetramethylene ether diol PTMEG. The number average molecular weight of the polymer polyol is 1000-4000.

[0013] The diamine chain extender a comprises diamines having 2 to 30 carbon atoms, including any one or a combination of at least two of ethylenediamine, propylenediamine, butanediamine, pentanediamine, methylpentanediamine, methylpropylenediamine, hexanediamine, phenylenediamine, phenylenediamine, diaminocyclohexane, hexamethylenediamine, or 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, more preferably a combination of ethylenediamine and 3,3'-dimethyl-4,4-diaminodicyclohexylmethane; The monoamine end-capping agent b comprises a monoamine having 2 to 20 carbon atoms, including any one or a combination of at least two of the following: diethylamine, isopropylamine, n-butylamine, tert-butylamine, hexylamine diethylamine, dimethylamine, di-n-butylamine, di-tert-butylamine, diisobutylamine, diisopropylamine, diethylamine, dipropylamine, cyclohexylamine, or ethanolamine.

[0014] The fabric prepared from spandex that is not prone to crease marks according to the present invention contains the aforementioned spandex, or a mixture of the aforementioned spandex and optional other fibers; the other fibers include at least one selected from polyester fiber, polyamide fiber, viscose fiber, cotton fiber, silk fiber, and flax fiber.

[0015] Beneficial Effects: The preparation method of this invention employs a two-stage chain extension process during the polymerization of polyurethane urea polymer, which effectively reduces the molecular weight distribution of the polyurethane urea polymer and the coefficient of variation (CV) of the tension of the spandex fiber. The diamine chain extender first undergoes a chain extension reaction, preventing premature end-capping of the prepolymer to form low-molecular-weight polyurethane urea. The diamine chain extender and monoamine end-capping agent then undergo a second chain extension and chain termination reaction. The higher content of monoamine end-capping agent in the second chain extension prevents excessively rapid chain growth, avoiding the formation of very high-molecular-weight polyurethane urea, thus achieving the technical effect of narrow polyurethane molecular weight distribution and low tension fluctuation. The prepared spandex fiber exhibits good uniformity and resilience, and fabrics containing this spandex fiber are less prone to creases during subsequent processing. Detailed Implementation

[0016] The present invention will be further described below with reference to specific embodiments, providing a detailed explanation of the preparation method of spandex and the spandex itself. The advantages and features of the present invention will become clearer as the description unfolds. However, the embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention.

[0017] A type of spandex that is not prone to crease marks, comprising the polyurethane urea polymer, wherein the polyurethane urea polymer has a number-average molecular weight between 60,000 and 100,000 g / mol and a relative molecular mass distribution ≤1.60; The aforementioned spandex, which is not prone to crease marks, has a coefficient of variation (CV) of less than 2% and an elastic recovery rate of over 91%.

[0018] Furthermore, the spandex that is not prone to crease marks contains a polyurethane urea polymer, a dispersant, and a leveling agent. The dispersant includes at least one of polyacrylamide salt and dodecylbenzene sulfonate; The leveling agent includes at least one of polyether-modified polysiloxane, polyester-modified polysiloxane, and alkyl-modified polysiloxane; The dispersant has a mass percentage of 0.3% to 1%, calculated based on the mass of the spandex. The leveling agent has a mass percentage of 0.5% to 1%, calculated based on the mass of the spandex.

[0019] In this invention, spandex fibers obtained by spinning polyurethane urea polymers with a number-average molecular weight between 60,000 and 100,000 g / mol and a relative molecular mass distribution ≤1.60 can effectively reduce the coefficient of variation (CV) of spandex and maintain a high elastic recovery rate. Spandex prepared from polyurethane urea polymers with a narrow molecular weight distribution has small tension fluctuations and low CV values.

[0020] The method for preparing the spandex includes a polymerization step, wherein the polymerization step includes two chain extension steps.

[0021] The two chain extensions in the polymerization step include: (1) Primary chain extension: Polyurethane prepolymer A is reacted with diamine chain extender a to obtain polyurethane urea prepolymer B; (2) Secondary chain extension: The polyurethane urea prepolymer B is reacted with diamine chain extender a and monoamine end capping agent b to obtain polyurethane urea polymer.

[0022] The types of diamine chain extender a in step (1) and in step (2) are consistent; In this invention, by controlling the diamine chain extender a in step (1) and the diamine chain extender a in step (2) to be consistent, the resulting polyurethane molecular chain structure can be more stable and uniform, and the prepared spandex has better uniformity and more uniform tension.

[0023] Furthermore, the polyurethane prepolymer A in step (1) is obtained by reacting polyisocyanate and polymeric polyol, and the polyurethane prepolymer A contains 2.5% to 3% by mass of isocyanate groups (NCO). Furthermore, the polyurethane urea prepolymer B in step (1) contains 0.2% to 0.5% isocyanate groups (NCO) by mass.

[0024] Furthermore, the molar ratio of the diamine chain extender a in step (1) to step (2) is 3:1 to 5:1; Furthermore, the ratio of the total molar amount of diamine chain extender a in steps (1) and (2) to the molar amount of monoamine end-capping agent b in step (2) is 3:1 to 1.5:1; Furthermore, in step (1), the molar ratio of the amine group of the diamine chain extender a to the NCO group of the polyurethane prepolymer A is 0.8:1 to 0.9:1. Furthermore, in step (2), the molar ratio of the amine groups of the diamine chain extender a and the monoamine end-capping agent b to the NCO groups of the polyurethane urea prepolymer B is 1.2:1 to 1.35:1. Furthermore, in step (2), the number-average molecular weight of the polyurethane urea polymer is between 60,000 and 100,000 g / mol, and the relative molecular mass distribution is ≤1.60.

[0025] In this invention, the first chain extension in step (1) prevents the prepolymer from being prematurely capped to form low-molecular-weight polyurethane. In the second chain extension in step (2), the diamine chain extender and the monoamine capping agent simultaneously carry out chain extension and chain termination reactions. In addition, the content of the monoamine capping agent is relatively higher than that in the conventional spandex preparation process, and the amine group is much larger than the NCO group. During the second chain extension, the NCO will be quickly capped, avoiding the polyurethane with an excessively high molecular weight, resulting in a narrow molecular weight distribution and small tension fluctuation of the prepared polyurethane urea polymer.

[0026] Furthermore, the two chain extension steps are carried out in the presence of a solvent, which includes at least one of N,N-dimethylacetamide (DMAc) and N,N-dimethylformamide (DMF). The mass content of the solution containing polyurethane urea prepolymer B is 35-50%, and the mass content of the solution containing polyurethane urea polymer is 30-45%.

[0027] Furthermore, in step (1), an amine solution containing diamine chain extender a is gradually added to a solution containing polyurethane prepolymer A to carry out the reaction. Furthermore, in step (2), a mixed amine solution containing diamine chain extender a and monoamine end-capping agent b is simultaneously and continuously reacted with a solution containing polyurethane prepolymer A.

[0028] In some examples of the present invention, step (1) is carried out by an intermittent polymerization method, in which an amine solution containing a diamine chain extender a is gradually added to a solution containing polyurethane prepolymer A and mixed to obtain a solution containing polyurethane urea prepolymer B. Step (2) employs a continuous polymerization method, in which a solution containing polyurethane urea prepolymer B and a mixed amine solution containing diamine chain extender a and monoamine end-capping agent b are simultaneously and continuously added to a mixer for rapid mixing and reaction, thereby obtaining a solution containing polyurethane urea polymer.

[0029] In this invention, by controlling step (1) to adopt the intermittent polymerization method, the prepolymer A can react with the amine step by step, the reaction is relatively mild, and the resulting prepolymer B has a relatively uniform molecular weight; by controlling step (2) to adopt the continuous polymerization method, the prepolymer B is capped as early as possible, and a high molecular weight polyurethane urea polymer will not be formed.

[0030] As an example, the aggregation step of this invention specifically includes: (1) One-time chain extension: Amine solution containing diamine chain extender a is gradually added to the solution containing polyurethane prepolymer A and reacted at 10-40℃ for 0.5-1.5h to obtain polyurethane urea prepolymer B. After the reaction, the mass of the solution containing polyurethane urea prepolymer B is controlled to be 35-50%, that is, the mass percentage of polyurethane urea prepolymer B in the solution. The addition time of the amine solution is controlled within 30 to 60 minutes; The mass content of the amine solution is 2% to 3%, which is the mass percentage of the diamine chain extender a in the amine solution; The polyurethane prepolymer A is prepared by reacting polyisocyanate and polymeric polyol at 45-60°C for 1-3 hours in the presence of a solvent to obtain polyurethane prepolymer A. At the end of the reaction, the mass content of the solution containing polyurethane prepolymer A is controlled between 65% and 75%. (2) Secondary chain extension: At 10-40°C, a solution containing polyurethane urea prepolymer B and a mixed amine solution containing diamine chain extender a and monoamine end-capping agent b are simultaneously and continuously added to a dynamic mixer to react and obtain polyurethane urea polymer. After the reaction, the mass of the solution containing polyurethane urea polymer is controlled to be 30-45%. The mass content of the mixed amine solution is 0.5% to 1%, which is the percentage of the total mass of the diamine chain extender a and the monoamine end capping agent b in the mixed amine solution; In this invention, the solvent is DMAc.

[0031] In this invention, there are no special requirements for the specific structure of the dynamic mixer. It is only necessary to ensure that the reaction raw materials can be quickly stirred and mixed to react, and that they can be removed from the mixer in a timely manner after the reaction.

[0032] The polyisocyanate includes any one or a combination of at least two of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate or dicyclohexylmethane diisocyanate, and is more preferably diphenylmethane diisocyanate (MDI). The polymeric polyol includes any one or a combination of at least two of polytetramethylene ether diol, polyethylene glycol, or polypropylene glycol, and is more preferably polytetramethylene ether diol PTMEG. The number-average molecular weight of the polymer polyol is 1000-4000; Diamine chain extender a includes diamines having 2 to 30 carbon atoms, and more specifically, any one or a combination of at least two of ethylenediamine, propylenediamine, butanediamine, pentanediamine, methylpentanediamine, methylpropylenediamine, hexanediamine, phenylenediamine, phenylenediamine, diaminocyclohexane, hexamethylenediamine, or 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, and more preferably a combination of ethylenediamine and 3,3'-dimethyl-4,4-diaminodicyclohexylmethane; The monoamine end-capping agent b comprises a monoamine having 2 to 20 carbon atoms, and is more preferably any one or a combination of at least two of the following: diethylamine, isopropylamine, n-butylamine, tert-butylamine, hexylamine diethylamine, dimethylamine, di-n-butylamine, di-tert-butylamine, diisobutylamine, diisopropylamine, diethylamine, dipropylamine, cyclohexylamine, or ethanolamine.

[0033] In some embodiments of the present invention, the diamine chain extender a can be an aliphatic diamine alone, such as at least one of ethylenediamine, propylenediamine, butanediamine, pentanediamine, methylpentanediamine, methylpropylenediamine, and hexamethylenediamine. It can also be a compound of an aliphatic diamine with an alicyclic diamine or an aromatic diamine, such as ethylenediamine and phenylenediamine, ethylenediamine and diaminocyclohexane, ethylenediamine and 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, hexamethylenediamine and phenylenediamine, hexamethylenediamine and diaminocyclohexane, hexamethylenediamine and 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, methylpentanediamine and phenylenediamine, methylpentanediamine and diaminocyclohexane, methylpentanediamine and 3,3'-dimethyl-4,4-diaminodicyclohexylmethane; In some examples of the present invention, the molar ratio of aliphatic diamine to alicyclic diamine or aromatic diamine is 90:10 to 97:3.

[0034] The method for preparing the spandex includes a spinning step: using the polyurethane urea polymer as the spinning raw material in the presence of a solvent, the spandex fiber is obtained by spinning. The spinning process described is dry spinning; The dry spinning process includes the steps of spraying, stretching, and drying. Furthermore, the spinning temperature is above 150°C; the spinning speed is above 900 m / min.

[0035] Furthermore, the spinning raw materials are subjected to a curing treatment before spinning. The curing temperature is 30-60°C, and the curing time is not specifically required, as long as each raw material is fully cured.

[0036] Furthermore, dispersants and leveling agents are added to the solution containing polyurethane urea polymer; The dispersant includes at least one of polyacrylamide salt and dodecylbenzene sulfonate; The leveling agent includes at least one of polyether-modified polysiloxane, polyester-modified polysiloxane, and alkyl-modified polysiloxane; The dispersant has a mass percentage of 0.3% to 1%, calculated based on the mass of the spandex. The leveling agent has a mass percentage of 0.5% to 1%, calculated based on the mass of the spandex.

[0037] Furthermore, functional additives commonly used in the field of spandex are optionally added to the solution containing polyurethane-urea polymer, including one or more of antioxidants, UV stabilizers, UV inhibitors, anti-yellowing agents, matting agents, dyeing auxiliaries, and chlorine-resistant auxiliaries; In this invention, there is no particular limitation on the amount of functional additives added, as long as they do not degrade the performance of the spandex.

[0038] As an example, the spinning step of the present invention specifically includes: A solution containing a polyurethane urea polymer is used as the spinning raw material. The raw material is fed into a dry spinning system and subjected to spraying, stretching and drying steps to obtain uniform spandex. Furthermore, the spinning temperature is above 250°C; the spinning speed is above 900 m / min.

[0039] Furthermore, the spinning raw material is subjected to a curing treatment at 30-60°C before spinning. The spinning raw material includes a solution containing a polyurethane urea polymer and a slurry optionally containing additives. The slurry containing additives includes dispersants, leveling agents, and optionally functional additives.

[0040] In this invention, adding dispersants and leveling agents to the slurry containing additives can make the slurry more fluid and less prone to settling, and the additives can be more evenly dispersed in the spinning raw materials, thereby reducing the tension fluctuation of the spandex yarn.

[0041] The spandex fiber has a denier of ≥20D and contains 1 to 20 monofilaments.

[0042] A fabric comprising the aforementioned spandex and optionally other fibers; The other fibers mentioned include at least one of polyester fiber, polyamide fiber, viscose fiber, cotton fiber, silk fiber, and flax fiber.

[0043] As an example, the fabric includes spandex and polyester fibers, which are blended to obtain a polyester-spandex fabric. In some polyester / spandex fabrics of the present invention, the proportion of creases appearing after dyeing can be as low as 25% or even less than 3%; In some embodiments of this application, the proportion of creases is obtained through the following testing method: The fabric obtained by weaving spandex and 70D polyester fiber on a circular knitting machine was dyed using a high-temperature and high-pressure dyeing machine (program control: the temperature was raised to 130℃ at a rate of 1.5℃ / min, and dyed at a constant temperature of 130℃ for 60 minutes). The number of meters of fabric with creases after dyeing was counted to obtain the result.

[0044] The following embodiments are used to describe the production process of the present invention in detail, but these embodiments should not be construed as limiting the present invention in any way.

[0045] Preparation of polyurethane prepolymer A solution: Polyurethane prepolymer A1: 120 kg of solvent DMAc, 200 kg of PTMEG with a number average molecular weight of 1810 and 47.514 kg of MDI were added sequentially to the reactor. The reaction was carried out at 50 °C for 2 h to obtain a polyurethane prepolymer A1 solution with an NCO mass content of 2.70% and a mass concentration of 67.35%.

[0046] Polyurethane prepolymer A2: 105 kg of solvent DMAc, 200 kg of PTMEG with a number average molecular weight of 1900 and 45.297 kg of MDI were added sequentially to the first reactor. The reaction was carried out at 50 °C for 2 h to obtain a polyurethane prepolymer A2 solution with an NCO mass content of 2.60% and a mass concentration of 70.0%.

[0047] 1. Aggregation Steps Example 1

[0048] First chain extension: An amine solution containing 3.82 kg of ethylenediamine and 0.8 kg of 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane was gradually added to the polyurethane prepolymer A1 solution. The mass concentration of the amine solution was 2.5%. The reaction was carried out at 20°C for 45 min to obtain a polyurethane prepolymer B1 solution with an NCO mass content of 0.42% and a mass concentration of 45.7%. Second chain extension: The polyurethane prepolymer B1 solution and a mixed amine solution containing 0.716 kg of ethylenediamine, 0.149 kg of 3,3'-dimethyl-4,4-diaminodicyclohexylmethane and 0.551 kg of diethylamine were continuously added to a dynamic mixer to carry out chain extension and chain termination reactions to obtain polyurethane urea polymer 1 solution. The mass concentration of the mixed amine solution was 0.80%, and the mass concentration of polyurethane urea polymer 1 solution was 34.80%. Example 2

[0049] First chain extension: An amine solution containing 3.87 kg of ethylenediamine and 0.81 kg of 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane was gradually added to the polyurethane prepolymer A2 solution. The mass concentration of the amine solution was 2.5%. The reaction was carried out at 20°C for 45 min to obtain a polyurethane prepolymer B2 solution with an NCO mass content of 0.27% and a mass concentration of 44.3%. Second chain extension: A polyurethane prepolymer B2 solution and a mixed amine solution containing 0.474 kg of ethylenediamine, 0.099 kg of 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, and 0.304 kg of diethylamine were continuously and uninterruptedly added to a dynamic mixer to carry out chain extension and chain termination reactions, resulting in a polyurethane urea polymer 2 solution. The mass concentration of the mixed amine solution was 0.70%, and the mass concentration of the polyurethane urea polymer 2 solution was 36.40%. Example 3

[0050] First chain extension: An amine solution containing 3.82 kg of ethylenediamine and 0.8 kg of 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane was gradually added to the polyurethane prepolymer A1 solution. The mass concentration of the amine solution was 2.5%. The reaction was carried out at 20°C for 45 min to obtain a polyurethane prepolymer B3 solution with an NCO mass content of 0.42% and a mass concentration of 45.7%. Second chain extension: A mixed amine solution containing 0.716 kg of ethylenediamine, 0.149 kg of 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, and 0.551 kg of diethylamine was gradually added to the polyurethane prepolymer B3 solution to carry out chain extension and chain termination reactions, resulting in polyurethane urea polymer 3 solution. The mass concentration of the mixed amine solution was 0.80%, and the mass concentration of the polyurethane urea polymer 3 solution was 34.80%. Example 4

[0051] First chain extension: Polyurethane prepolymer A1 solution and an amine solution containing 3.82 kg of ethylenediamine and 0.8 kg of 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane were continuously added to a dynamic mixer to carry out the chain extension reaction, resulting in polyurethane prepolymer B4 with an NCO mass content of 0.42% and a biomass concentration of 45.7%, of which the amine solution had a mass concentration of 2.5%. Second chain extension: The polyurethane prepolymer B4 solution and a mixed amine solution containing 0.716 kg of ethylenediamine, 0.149 kg of 3,3'-dimethyl-4,4-diaminodicyclohexylmethane and 0.551 kg of diethylamine were continuously added to a dynamic mixer to carry out chain extension and chain termination reactions to obtain polyurethane urea polymer 4 solution. The mass concentration of the mixed amine solution was 0.80%, and the mass concentration of the polyurethane urea polymer 4 solution was 34.80%. Example 5

[0052] First chain extension: An amine solution containing 4.02 kg of ethylenediamine was gradually added to the polyurethane prepolymer A1 solution. The mass concentration of the amine solution was 2.5%. The reaction was carried out at 20°C for 45 min to obtain a polyurethane prepolymer B5 solution with an NCO mass content of 0.42% and a mass concentration of 45.7%. Second chain extension: The polyurethane prepolymer B5 solution and a mixed amine solution containing 0.754 kg of ethylenediamine and 0.551 kg of diethylamine were continuously added to a dynamic mixer to carry out chain extension and chain termination reactions to obtain polyurethane urea polymer 5 solution. The mass concentration of the mixed amine solution was 0.80%, and the mass concentration of the polyurethane urea polymer 5 solution was 34.80%. Example 6

[0053] First chain extension: An amine solution containing 7.773 kg of hexamethylenediamine was gradually added to the polyurethane prepolymer A1 solution. The mass concentration of the amine solution was 2.5%. The reaction was carried out at 20°C for 45 min to obtain a polyurethane prepolymer B6 solution with an NCO mass content of 0.42% and a mass concentration of 45.7%. Secondary chain extension: The polyurethane prepolymer B6 solution and a mixed amine solution containing 0.754 kg of ethylenediamine and 0.551 kg of diethylamine were continuously added to a dynamic mixer to carry out chain extension and chain termination reactions to obtain a polyurethane urea polymer 6 solution. The mass concentration of the mixed amine solution was 0.80%, and the mass concentration of the polyurethane urea polymer 6 solution was 34.80%.

[0054] Comparative Example 1

[0055] One-step intermittent chain extension: A mixed amine solution containing 4.536 kg of ethylenediamine, 0.949 kg of 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, and 0.551 kg of diethylamine was gradually added to the polyurethane prepolymer A1 solution. The mass concentration of the mixed amine solution was 2.0%. The reaction was carried out at 20°C for 45 min to obtain a control polyurethane urea polymer 1 solution with a mass concentration of 34.80%.

[0056] Comparative Example 2

[0057] One-step continuous chain extension: The polyurethane prepolymer A1 solution and a mixed amine solution containing 4.536 kg of ethylenediamine, 0.949 kg of 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, and 0.551 kg of diethylamine were continuously and uninterruptedly added to a dynamic mixer to carry out chain extension and chain termination reactions to obtain the comparative polyurethane urea polymer 2 solution. The mass concentration of the mixed amine solution was 2.0%, and the mass concentration of the comparative polyurethane urea polymer 2 solution was 34.80%.

[0058] Comparative Example 3

[0059] First chain extension: An amine solution containing 3.82 kg of ethylenediamine, 0.8 kg of 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, and 0.464 kg of diethylamine was gradually added to the polyurethane prepolymer A1 solution. The mass concentration of the amine solution was 2.5%. The reaction was carried out at 20°C for 45 min to obtain a control polyurethane prepolymer B3 solution with an NCO mass content of 0.31% and a mass concentration of 45.7%. Secondary chain extension: The comparative polyurethane prepolymer B3 solution and a mixed amine solution containing 0.716 kg of ethylenediamine, 0.149 kg of 3,3'-dimethyl-4,4-diaminodicyclohexylmethane and 0.087 kg of diethylamine were continuously added to a dynamic mixer to carry out chain extension and chain termination reactions to obtain the comparative polyurethane urea polymer 3 solution. The mass concentration of the mixed amine solution was 0.80%, and the mass concentration of the comparative polyurethane urea polymer 3 solution was 34.80%.

[0060] 2. Spinning steps Spandex fiber 1

[0061] The polyurethane urea polymer solution from Example 1 was transferred to a conical tank. A slurry containing 0.5% dispersant polyacrylamide salt, 0.5% leveling agent polyether-modified polysiloxane, 1.0% antioxidant 245, 0.5% matting agent TDO, 1.5% chlorine-resistant auxiliary hydrotalcite, 0.5% dyeing auxiliary SAS, and 0.3% cohesion auxiliary OT-100 was added to the conical tank. The mass percentage of the auxiliary agents in the slurry was calculated based on the mass of the spandex. The mixture was mixed and cured at 50°C for 26 hours. The cured solution was then sprayed, stretched, and dried into filaments using a dry spinning system to obtain spandex fiber 1 with a denier of 40D. Spandex fiber 2

[0062] The polyurethane urea polymer solution from Example 2 was transferred to a conical tank. A sizing agent containing 0.7% dispersant polyacrylamide salt, 0.9% leveling agent polyester modified polysiloxane, 1.0% antioxidant 245, 0.5% matting agent TDO, and 0.5% dyeing auxiliary agent SAS was added to the conical tank. The mass percentage of the auxiliary agents in the sizing agent was calculated based on the mass of the spandex. The mixture was mixed and matured at 50°C for 26 hours. The matured solution was sprayed, stretched, and dried into filaments using a dry spinning system to obtain spandex fiber 2 with a denier of 40D. Spandex fiber 3

[0063] The polyurethane urea polymer solution of Example 3 was transferred to a conical tank. A slurry containing 0.5% dispersant polyacrylamide salt, 0.5% leveling agent polyether modified polysiloxane, 1.0% antioxidant 245, 0.5% matting agent TDO, 1.5% chlorine-resistant auxiliary agent hydrotalcite, 0.5% dyeing auxiliary agent SAS, and 0.3% cohesion auxiliary agent OT-100 was added to the conical tank. The mass percentage of the auxiliary agents in the slurry was calculated based on the mass of the spandex. The mixture was mixed and cured at 50°C for 26 hours. The cured solution was sprayed, stretched, and dried into filaments using a dry spinning system to obtain spandex fiber 3 with a denier of 40D. Spandex fiber 4

[0064] The polyurethane urea polymer solution from Example 4 was transferred to a conical tank. A slurry containing 0.5% dispersant polyacrylamide salt, 0.5% leveling agent polyether-modified polysiloxane, 1.0% antioxidant 245, 0.5% matting agent TDO, 1.5% chlorine-resistant auxiliary agent hydrotalcite, 0.5% dyeing auxiliary agent SAS, and 0.3% cohesion auxiliary agent OT-100 was added to the conical tank. The mass percentage of the auxiliary agents in the slurry was calculated based on the mass of the spandex. The mixture was mixed and cured at 50°C for 26 hours. The cured solution was then sprayed, stretched, and dried into filaments using a dry spinning system to obtain spandex fiber 4 with a denier of 40D. Spandex fiber 5

[0065] The polyurethane urea polymer solution from Example 5 was transferred to a conical tank. A slurry containing 0.5% dispersant polyacrylamide salt, 0.5% leveling agent polyether-modified polysiloxane, 1.0% antioxidant 245, 0.5% matting agent TDO, 1.5% chlorine-resistant auxiliary agent hydrotalcite, 0.5% dyeing auxiliary agent SAS, and 0.3% cohesion auxiliary agent OT-100 was added to the conical tank. The mass percentage of the auxiliary agents in the slurry was calculated based on the mass of the spandex. The mixture was mixed and cured at 50°C for 26 hours. The cured solution was then sprayed, stretched, and dried into filaments using a dry spinning system to obtain spandex fiber 5 with a denier of 40D. Spandex fiber 6

[0066] The polyurethane urea polymer solution of Example 6 was transferred to a conical tank. A slurry containing 0.5% dispersant polyacrylamide salt, 0.5% leveling agent polyether modified polysiloxane, 1.0% antioxidant 245, 0.5% matting agent TDO, 1.5% chlorine-resistant auxiliary agent hydrotalcite, 0.5% dyeing auxiliary agent SAS, and 0.3% cohesion auxiliary agent OT-100 was added to the conical tank. The mass percentage of the auxiliary agents in the slurry was calculated based on the mass of the spandex. The mixture was mixed and matured at 50°C for 26 hours. The matured solution was sprayed, stretched, and dried into filaments using a dry spinning system to obtain spandex fiber 6 with a denier of 40D. Spandex fiber 7

[0067] The polyurethane urea polymer solution from Example 1 was transferred to a conical tank. A slurry containing 0.5% leveling agent polyether-modified polysiloxane, 1.0% antioxidant 245, 0.5% matting agent TDO, 1.5% chlorine-resistant auxiliary agent hydrotalcite, 0.5% dyeing auxiliary agent SAS, and 0.3% cohesion auxiliary agent OT-100 was added to the conical tank. The mass percentage of the auxiliary agents in the slurry was calculated based on the mass of the spandex. The mixture was mixed and cured at 50°C for 26 hours. The cured solution was then sprayed, stretched, and dried into filaments using a dry spinning system to obtain spandex fiber 7 with a denier of 40D. Spandex fiber 8

[0068] The polyurethane urea polymer solution from Example 1 was transferred to a conical tank. A slurry containing 0.5% dispersant polyacrylamide salt, 1.0% antioxidant 245, 0.5% matting agent TDO, 1.5% chlorine-resistant auxiliary agent hydrotalcite, 0.5% dyeing auxiliary agent SAS, and 0.3% cohesion auxiliary agent OT-100 was added to the conical tank. The mass percentage of the auxiliary agents in the slurry was calculated based on the mass of the spandex. The mixture was mixed and cured at 50°C for 26 hours. The cured solution was then sprayed, stretched, and dried into filaments using a dry spinning system to obtain spandex fiber 8 with a denier of 40D. Comparison with spandex fiber 1

[0069] The polyurethane urea polymer solution of Comparative Example 1 was transferred to a conical tank. A sizing agent containing 0.5% dispersant polyacrylamide salt, 0.5% leveling agent polyether modified polysiloxane, 0.2% antioxidant 245, 0.5% matting agent TDO, 0.2% chlorine-resistant auxiliary agent hydrotalcite, 0.5% dyeing auxiliary agent SAS, and 0.1% cohesion auxiliary agent OT-100 was added to the conical tank. The mass percentage of the auxiliary agents in the sizing agent was calculated based on the mass of the spandex. The mixture was mixed and cured at 50°C for 26 hours. The cured solution was sprayed, stretched, and dried into filaments using a dry spinning system to obtain comparative spandex fiber 1 with a denier of 40D. Comparison with spandex fiber 2

[0070] The polyurethane urea polymer solution of Comparative Example 2 was transferred to a conical tank. A slurry containing 0.5% dispersant polyacrylamide salt, 0.5% leveling agent polyether modified polysiloxane, 0.2% antioxidant 245, 0.5% matting agent TDO, 0.2% chlorine-resistant auxiliary hydrotalcite, 0.5% dyeing auxiliary SAS, and 0.1% cohesion auxiliary OT-100 was added to the conical tank. The mass percentage of the auxiliary agents in the slurry was calculated based on the mass of the spandex. The mixture was mixed and cured at 50°C for 26 hours. The cured solution was sprayed, stretched, and dried into filaments using a dry spinning system to obtain Comparative Spandex Fiber 2 with a denier of 40D. Comparison with spandex fiber 3

[0071] The polyurethane urea polymer solution of Comparative Example 3 was transferred to a conical tank. A sizing agent containing 0.5% dispersant polyacrylamide salt, 0.5% leveling agent polyether modified polysiloxane, 0.2% antioxidant 245, 0.5% matting agent TDO, 0.2% chlorine-resistant auxiliary agent hydrotalcite, 0.5% dyeing auxiliary agent SAS, and 0.1% cohesion auxiliary agent OT-100 was added to the conical tank. The mass percentage of the auxiliary agents in the sizing agent was calculated based on the mass of the spandex. The mixture was mixed and cured at 50°C for 26 hours. The cured solution was sprayed, stretched, and dried into filaments using a dry spinning system to obtain comparative spandex fiber 3 with a denier of 40D.

[0072] Preparation of spandex fabrics containing the present invention: The spandex fibers obtained above are woven with 70D polyester fibers on a circular knitting machine to obtain polyester-spandex blended fabrics.

[0073] The polyurethane urea polymer, spandex fiber, and spandex fabric prepared above were subjected to performance tests respectively: Tests on number-average molecular weight (Mn) and molecular weight distribution: After dissolving spandex fibers in DMAc, the molecular weight and molecular weight distribution of the polyurethane urea polymer were tested using a combination of laser light scattering and gel permeation chromatography. The relative molecular mass distribution is the ratio of number-average molecular weight (Mn) to weight-average molecular weight (Mw). R-value and CV testing: The spandex fiber filament cake was loaded into the first roller, the input speed of the first roller was set to 100m / min, and the output speed of the second roller was set to 350m / min, i.e., the draw ratio was 3.5 times. An electronic constant tension transmission system was used, and the fiber tension value was measured every 5 meters, for a total of 100 tension values. R value (range): represents the difference between the maximum and minimum tested tension of spandex yarn (R=XMAX-XMIN), where X is the tested tension, XMAX is the maximum tested tension, and XMIN is the minimum tested tension. CV (Coefficient of Variation of Tension): Represents the ratio of standard deviation to mean. The formula is as follows:

[0074] To detect the average tension value AVE.

[0075] RER310: Indicates the elastic recovery rate of spandex fiber, tested according to the method of FZ / T 50007-2012 "Test for Elasticity of Spandex Filament". The testing instrument is a microcomputer-controlled electronic universal testing machine, which measures the elastic recovery rate after stretching the spandex fiber to 300% five times.

[0076] Crease appearance rate: The percentage of creases in 1000 meters of dyed polyester / spandex fabric was calculated by dyeing the fabric in a high-temperature and high-pressure dyeing machine (program control: heating rate of 1.5℃ / min to 130℃, and dyeing at 130℃ for 60 minutes).

[0077] Specific performance data is shown in Table 1: Table 1

[0078] As can be seen from the data in Table 1, the spandex fibers prepared in the embodiments of the present invention have a narrow molecular weight distribution of polyurethane urea, small tension fluctuations, low R and CV values, and high elastic recovery rate. The proportion of crease marks appearing in the spandex blended fabric during subsequent dyeing is low. In contrast, the spandex filaments prepared in the comparative examples have a wide molecular weight distribution, large tension fluctuations, and a much higher proportion of crease marks compared to the examples.

Claims

1. A spandex that is less likely to produce crease marks, characterized in that, The spandex contains a polyurethane urea polymer, the number average molecular weight of the polyurethane urea polymer is between 60000-100000 g / mol, and the relative molecular mass distribution is ≤1.

60.

2. The spandex of claim 1, wherein, The spandex also contains a dispersing agent and a leveling agent; the mass percentage of the dispersing agent is 0.3%-1%, calculated based on the mass of the spandex; the mass percentage of the leveling agent is 0.5%-1%, calculated based on the mass of the spandex. Preferably, the dispersing agent includes at least one of polyacrylic amine salt, sodium dodecyl benzene sulfonate; Preferably, the leveling agent includes at least one of polyether modified polysiloxane, polyester modified polysiloxane, alkyl modified polysiloxane.

3. A method of producing spandex which is less likely to produce crease marks as claimed in claim 1 or 2, characterized in that, The preparation method includes that the polyurethane urea polymer is used as a spinning raw material in the presence of a solvent, and the spandex fiber is obtained through spinning.

4. A method for preparing a polyurethane urea polymer, characterized by, The polyurethane urea polymer is obtained through a polymerization step, and the polymerization step includes two chain extension steps. It includes Step 1, primary chain extension: a polyurethane urea prepolymer B is obtained by reacting a polyurethane prepolymer A with a diamine chain extender a; Step 2, secondary chain extension: a polyurethane urea polymer is obtained by reacting the polyurethane urea prepolymer B with the diamine chain extender a and a monoamine end-capping agent b; In the step 1, the diamine chain extender a and the diamine chain extender a in the step 2 are consistent in type.

5. The method of claim 4, wherein the polyurethane urea polymer is prepared by reacting a polyisocyanate with a polyol in the presence of a chain extender. In the step 1, an amine solution containing the diamine chain extender a is gradually added to a solution containing the polyurethane prepolymer A for intermittent reaction; In the step 2, a mixed amine solution containing the diamine chain extender a and the monoamine end-capping agent b is continuously and uninterruptedly added to a solution containing the polyurethane urea prepolymer B for continuous reaction; The two chain extension steps are carried out in the presence of a solvent, and the solvent includes at least one of N,N-dimethylacetamide DMAc and N,N-dimethylformamide DMF.

6. The method of claim 4, wherein the polyurethane urea polymer is prepared by reacting a polyisocyanate with a polyol in the presence of a chain extender. The polyurethane prepolymer A is obtained by reacting a polyisocyanate and a polymeric polyol, and the mass content of isocyanate groups NCO contained in the polyurethane prepolymer A is 2.5%-3%; The mass content of isocyanate groups NCO contained in the polyurethane urea prepolymer B is 0.2%-0.5%.

7. The method of claim 5, wherein the polyurethane urea polymer is prepared by reacting a polyisocyanate with a polyol in the presence of a chain extender. The molar ratio of the diamine chain extender a in the step 1 to the step 2 is 3:1-5:1; The molar ratio of the diamine chain extender a to the monoamine end-capping agent b in the step 2 is 3:1-1.5:1; The molar ratio of the amine groups of the diamine chain extender a to the NCO groups of the polyurethane prepolymer A in the step 1 is 0.8:1-0.9:1; The molar ratio of the amine groups of the diamine chain extender a and the monoamine end-capping agent b to the NCO groups of the polyurethane urea prepolymer B in the step 2 is 1.2:1-1.35:1; The number average molecular weight of the polyurethane urea polymer in the step 2 is between 60000-100000 g / mol, and the relative molecular mass distribution is ≤1.

60.

8. The method of claim 7, wherein the polyurethane urea polymer is prepared by reacting a polyisocyanate with a polyol in the presence of a chain extender. The polyisocyanate includes any one or a combination of at least two of diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate or dicyclohexylmethane diisocyanate, and is further preferably diphenylmethane diisocyanate MDI; The polymeric polyol includes any one or a combination of at least two of polytetramethylene ether glycol, polyethylene glycol or polypropylene glycol, and is further preferably polytetramethylene ether glycol PTMEG; The polymeric polyol has a number average molecular weight of 1000-4000.

9. The method of claim 8, wherein the polyurethane urea polymer is prepared by reacting a polyisocyanate with a polyol in the presence of a chain extender. The diamine chain extender a includes a diamine having a carbon atom number of 2-30, including any one or a combination of at least two of ethylenediamine, propylenediamine, butylenediamine, pentylenediamine, methylpentylenediamine, methylpropylenediamine, hexylenediamine, xylylenediamine, phenylenediamine, diaminocyclohexane, hexamethylenediamine or 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, and is further preferably a combination of ethylenediamine and 3,3'-dimethyl-4,4-diaminodicyclohexylmethane. The monoamine end-capping agent b includes a monoamine having a carbon atom number of 2-20, including any one or a combination of at least two of diethylamine, isopropylamine, n-butylamine, t-butylamine, hexylamine diethylamine, dimethylamine, di-n-butylamine, di-t-butylamine, diisobutylamine, diisopropylamine, diethylamine, dipropylamine, cyclohexylamine or ethanolamine.

10. A fabric prepared using the spandex of claim 1, wherein the fabric is characterized by, The fabric contains the spandex, or a mixture of the spandex and optional other fibers; the other fibers include at least one of polyester fiber, polyamide fiber, viscose fiber, cotton fiber, real silk fiber or linen fiber.

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