Spandex for air-permeable fabric and method for preparing the same

Abstract

The present application provides a kind of spandex for breathable fabric and its preparation method, which is the polyurethane-urea reaction product of polyurethane prepolymer and mixed amine, and the polyurethane prepolymer is obtained by the reaction of polyisocyanate and polyol; the preparation method comprises: prepolymerization: polyurethane prepolymer is obtained by the prepolymerization of polyisocyanate and polyol, then the polyurethane prepolymer is dissolved in solvent to obtain a solution containing polyurethane prepolymer; chain extension reaction: the solution containing polyurethane prepolymer is reacted with mixed amine solution to obtain a stock solution containing polyurethane-urea; aging spinning: the stock solution containing polyurethane-urea is aged, and a flow aid is added to the stock solution, and the aged polyurethane-urea stock solution is used as raw material to obtain spandex for breathable fabric by dry spinning. The spandex has low denier and good resilience, the preparation method is simple, conventional polymerization equipment for spandex can be used, and the spinning stability is good.

Description

Technical Field

[0001] This invention relates to the field of spandex, and more specifically to a type of spandex for breathable fabrics and its preparation method. Background Technology

[0002] Spandex fiber, due to its excellent elasticity, produces fabrics with a soft hand feel, good resilience, and comfortable wear when combined with yarns such as cotton, polyester, nylon, and silk. After years of development, the manufacturing cost of spandex fiber has gradually decreased, and it is now widely used in fabrics. However, because of its high denier and strong resilience, the fabrics made from it are not very comfortable, breathable, and have poor drape and wrinkle resistance. Therefore, its application in high-end fields is not as advanced as that of viscose fiber or cellulose acetate fiber.

[0003] Patent CN104651974A discloses an ultrafine denier spandex fiber and its preparation method. This fiber exhibits good drape and absorbency, thus improving the usability and comfort of the fabric. However, this spandex has a core-sheath structure, resulting in high production costs and low yields, making it unsuitable for mass production. Patent CN110331467A discloses an ultrafine denier spandex interwoven with polyester and its preparation method. This method improves the spinnability of the ultrafine denier spandex through composite spinning of polyether-type polyurethane and polyester-type polyurethane. This composite spandex is easily hydrolyzed under alkaline conditions, making the fabric more fluffy and improving fiber comfort. However, eliminating the polyester-type spandex with alkali can lead to uneven spandex thickness in the fabric, causing internal breakage due to varying stress levels, and also resulting in waste of the polyester-type spandex and increased costs. The ultra-fine denier spandex patents CN115710752A, CN102051705A, CN102021666A, etc., are all prepared by direct spinning and melt spinning. Their output is small, energy consumption is high, and cost is high, so they account for a small proportion in today's industrial production. Summary of the Invention

[0004] Technical Problem: To address the shortcomings of existing technologies, the present invention aims to provide a type of spandex for breathable fabrics and its preparation method. This spandex has a low denier, good resilience, and a simple preparation method that can be achieved using conventional spandex polymerization equipment. It also exhibits good spinning stability and is less prone to filament breakage during blending with other yarns. The resulting fabric has a soft hand feel, good comfort, and good breathability.

[0005] Technical solution: The present invention provides a spandex for breathable fabrics, wherein the spandex is a polyurethane-urea reaction product obtained by reacting polyurethane prepolymer and mixed amine, wherein the polyurethane prepolymer includes polyisocyanate and polyol.

[0006] The polyols include macromolecular polyether diols and small molecule polyols; the molar ratio of the macromolecular polyether diols to the small molecule polyols is 99.5:0.5 to 95:5.

[0007] The macromolecular polyether diols include polytetramethyl ether diols with a number average molecular weight of 1500–2500 g / mol.

[0008] The small molecule polyols described herein have a hydroxyl functionality of 3-5 and a carbon number of 3-5.

[0009] The small molecule polyols mentioned include one or more of glycerol, butanetetrol, pentaerythritol, and xylitol.

[0010] The polyisocyanates mentioned include diphenylmethane diisocyanate.

[0011] The NCO content of the polyurethane prepolymer is 2.2–3.5 wt%.

[0012] The mixed amine comprises a diamine chain extender and a monoamine end-capping agent. The diamine chain extender comprises one or more of ethylenediamine, propylenediamine, and 2-methyl-1,5-pentanediamine. The monoamine end-capping agent comprises one or more of diethylamine, dipropylamine, and n-hexylamine. The molar ratio of the diamine chain extender to the monoamine end-capping agent is 12:1 to 22:1.

[0013] The breathable fabric using performance spandex also contains less than 5% of a flow aid; the flow aid includes one or more of polyethylene glycol dimethacrylate, polypropylene glycol acrylate, and polybutylene glycol acrylate, with a number average molecular weight of 400-800 g / mol.

[0014] The method for preparing the breathable fabric spandex of the present invention uses polyurethane-urea reaction products as spinning raw materials and obtains them through dry spinning, specifically including the following steps:

[0015] Step 1, Prepolymerization reaction: The polyisocyanate and polyol are subjected to a prepolymerization reaction to obtain a polyurethane prepolymer, and then the polyurethane prepolymer is dissolved in a solvent to obtain a solution containing the polyurethane prepolymer.

[0016] Step 2, chain extension reaction: The polyurethane prepolymer solution is reacted with a mixed amine solution to obtain a stock solution containing polyurethane-urea;

[0017] Step 3, Curing and spinning: The polyurethane-urea stock solution is cured, and a flow aid is added to the stock solution. The cured polyurethane-urea stock solution is used as raw material to obtain breathable fabric through dry spinning, which is used to obtain spandex.

[0018] The polyols include macromolecular polyether diols and small molecule polyols; the molar ratio of the macromolecular polyether diols to the small molecule polyols is 99.5:0.5 to 95:5.

[0019] The mass concentration of the polyurethane-urea stock solution is 35wt% to 37wt%, and the viscosity of the stock solution is 3500 to 4500 poise (40℃); the mixed amine includes a diamine chain extender and a monoamine end-capping agent, and the molar ratio of the diamine chain extender to the monoamine end-capping agent is 12:1 to 22:1.

[0020] The flow aid is added to the stock solution during the curing and spinning step.

[0021] Beneficial effects: The spandex fiber prepared by this invention through a specific polymerization formula and spinning process has a low denier, good resilience, and a simple preparation method that can be used with conventional spandex polymerization equipment. It also exhibits good spinning stability and is less prone to breakage during blending with other yarns. The resulting fabric has a soft hand feel, good comfort, and excellent breathability. Due to its ultra-low linear density, it is particularly suitable for use in lightweight fabrics, providing excellent breathability and a cool, refreshing feel, while also imparting high resilience to the fabric. Detailed Implementation

[0022] The breathable fabric spandex contains a polyurethane-urea reaction product obtained from a polyurethane prepolymer and a mixed amine, wherein the polyurethane prepolymer is obtained by reacting a polyisocyanate and a polyol.

[0023] The polyols include a combination of macromolecular polyether diols and small molecule polyols, wherein the molar ratio of macromolecular polyether diols to small molecule polyols is 99.5:0.5 to 95:5.

[0024] The polyisocyanates mentioned include diphenylmethane diisocyanate;

[0025] The macromolecular polyether diols include polytetramethyl ether diols with a number average molecular weight of 1500–2500 g / mol, preferably 1500–2200 g / mol;

[0026] The hydroxyl functionality of the small molecule polyol is 3-5;

[0027] The small molecule polyols mentioned above have 3-5 carbon atoms;

[0028] Furthermore, the small molecule polyols include one or more of glycerol, butanetetrol, pentaerythritol, and xylitol;

[0029] The NCO content of the polyurethane prepolymer is 2.2–3.5 wt%.

[0030] The mixed amine comprises a diamine chain extender and a monoamine end-capping agent. The diamine chain extender comprises one or more of ethylenediamine, propylenediamine, and 2-methyl-1,5-pentanediamine. The monoamine end-capping agent comprises one or more of diethylamine, dipropylamine, and n-hexylamine.

[0031] The ratio of the diamine chain extender to the monoamine end-capping agent is 12:1 to 22:1.

[0032] The breathable fabric uses performance spandex and contains less than 5% flow aid.

[0033] Preferably, it contains 0.05% to 5% flow aid, calculated based on the mass of spandex;

[0034] The flow aid includes one or more of polyethylene glycol dimethacrylate, polypropylene glycol acrylate, and polybutylene glycol acrylate, with a number average molecular weight of 400-800 g / mol.

[0035] The spandex fiber has a denier of 3 to 10.

[0036] This invention provides a method for preparing spandex for breathable fabrics, which is obtained by dry spinning using the polyurethane-urea reaction product as the spinning raw material.

[0037] Specifically, the preparation method includes the following steps:

[0038] Prepolymerization reaction: The polyisocyanate and polyol are subjected to a prepolymerization reaction to obtain a polyurethane prepolymer, which is then dissolved in a solvent to obtain a solution containing the polyurethane prepolymer;

[0039] Chain extension reaction: A polyurethane prepolymer solution is reacted with a mixed amine solution to obtain a polyurethane-urea stock solution;

[0040] Curing and spinning: The raw solution is cured, and the breathable fabric is obtained by dry spinning using the cured polyurethane-urea raw solution as the raw material to obtain spandex; preferably, the mass concentration of the raw solution is 35% to 37%, and the viscosity of the raw solution is 3500 to 4500 poise (40°C).

[0041] Preferably, the flow aid is added to the stock solution during the curing and spinning step;

[0042] Preferably, the solvent includes N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), and dimethylformamide (DMF); as an example, the solvent is DMAc.

[0043] In some embodiments of the present invention, the mass concentration of the polyurethane prepolymer solution in step 1) is 30-40%, preferably 30-36%;

[0044] The concentration of the mixed amine solution in the chain extension reaction step is 3% to 10%;

[0045] The molar ratio of the total amine groups of the mixed amine to the isocyanate groups (NCO) of the polyurethane prepolymer in the chain extension reaction step is 1.10:1 to 1.40:1, preferably 1.25:1 to 1.35:1;

[0046] Diethylenetriamine may be selectively added during the chain extension reaction step, in an amount of 80–150 ppm, calculated based on the mass of spandex.

[0047] Furthermore, other functional additives may be added to the polyurethane-urea stock solution, as long as they do not degrade the product's performance. These may include one or more of the following: lubricants, antioxidants, UV stabilizers, matting agents, dyeing auxiliaries, chlorine-resistant auxiliaries, and lubricants.

[0048] In this invention, the dry spinning process includes the steps of spraying, stretching, drying, false twisting, and winding into filaments.

[0049] Furthermore, a spandex oil can be applied to the surface of the spandex after the false twisting step.

[0050] In some embodiments of the present invention, the method for preparing a breathable fabric using spandex specifically includes:

[0051] Prepolymerization reaction: Polyol and diisocyanate react in a molar ratio of 1:(1.56-1.75) to obtain 2.2-3.5 wt% NCO-terminated polyurethane prepolymer, wherein the polyol includes a combination of macromolecular polyether diol and small molecule polyol, and the molar ratio of macromolecular polyether diol to small molecule polyol is 99.5:0.5-95:5; the polyurethane prepolymer is dissolved in a solvent to form a polyurethane prepolymer solution with a mass concentration of 32-38%, wherein the solvent is dimethylacetamide (DMAc).

[0052] Chain extension reaction: The above polyurethane prepolymer solution is mixed with a mixed amine solution to obtain a polyurethane-urea stock solution with a mass concentration of 30-36%, wherein the molar ratio of total amine groups in the mixed amine to isocyanate groups (NCO) in the polyurethane prepolymer is (1.10-1.40):1; the mixed amine solution includes a diamine chain extender, a monoamine end-capping agent, diethylenetriamine and a solvent, and the mass concentration of the mixed amine solution is 4%-8%, wherein the molar ratio of the diamine chain extender to the monoamine end-capping agent is 12:1-22:1, and the amount of diethylenetriamine added is 80-150 ppm, calculated based on the mass of spandex.

[0053] Cured spinning: The above-mentioned polyurethane prepolymer solution is cured to form a spinning solution. The spinning solution is passed into a spinneret for extrusion, stretched, and dried to form a filament bundle. After false twisting and winding, it becomes a spandex filament cake. The spinning solution has a mass concentration of 30%–36% and a viscosity of 3500 poise–4500 poise.

[0054] Preferably, optional gliding agents or other functional additives are added during the curing process.

[0055] 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.

[0056] Viscosity testing method of embodiments and comparative examples of the present invention: The spinning solution is placed in a viscometer, and the apparent viscosity of the spinning solution is measured at 40°C.

[0057] Example 1

[0058] Prepolymerization reaction: Diphenylmethane diisocyanate (MDI) at a flow rate of 90 g / min and polyol at a flow rate of 407 g / min were mixed uniformly in a static mixer. The polyol included a mixture of polytetramethyl ether glycol (PTMG) and pentapentapentyl alcohol (PETP) in a molar ratio of 96:4. The mixture was heated to 90°C and reacted for 4 hours to obtain a polyurethane prepolymer with an NCO content of 2.62 wt%. The prepolymer was then dissolved to prepare a polyurethane prepolymer solution with a mass concentration of 36%.

[0059] Chain extension reaction: The polyurethane prepolymer solution and the mixed amine solution were placed in a second reactor for reaction. The mixed amine solution contained ethylenediamine, 2-methyl-1,5-pentanediamine and diethylamine in a molar ratio of 19:1:1.2. The molar ratio of the total amine groups in the mixed amine to the NCO of the polyurethane prepolymer was 1.30:1. The amount of diethylenetriamine added was 120 ppm. After chain extension in the mixing tank, a polyurethane-urea stock solution with a mass concentration of 35% was obtained.

[0060] Curing and spinning: The polyurethane-urea stock solution is cured in a storage tank to obtain a spinning solution. 0.2% of a flow aid, polyethylene glycol dimethacrylate, is added to the spinning solution. The spinning solution is then passed into a spinneret for extrusion, stretched, and dried to form a filament bundle. After false twisting and winding, it becomes a spandex filament cake. The spinning solution has a mass concentration of 34%, a viscosity of 4400 poise, a spinning speed of 550 m / min, and a pre-stretch of 9%, ultimately yielding 5 denier spandex fibers.

[0061] The preparation methods for Examples 2-9 are the same as those for Example 1. The types and amounts of raw materials used in each reaction step are shown in Table 1 below:

[0062] Table 1:

[0063]

[0064] Table 1 (continued):

[0065]

[0066]

[0067] Comparative Example 1

[0068] The difference from Example 1 is that the polyol includes a mixture of polytetramethyl ether glycol (PTMG) and pentapentapentyl alcohol (PETP) in a molar ratio of 90:10, while all other aspects remain the same.

[0069] Comparative Example 2

[0070] The difference from Example 4 is that an equimolar amount of (PTMG) was used to replace the original polyol pentanediol (PETP), and the polyol was pure polytetramethyl ether diol (PTMG), while everything else remained the same.

[0071] Comparative Example 3

[0072] The difference from Example 4 is that pentapentapentylene alcohol (PETP) in the polyol is not added in the prepolymerization step, but in the chain extension step, added to the mixed amine solution to react with the prepolymer. (Comparative Example 4)

[0073] The difference from Example 4 is that pentanediol (PETP) in the original polyol is replaced with an equimolar amount of pentanediol, while everything else remains the same.

[0074] Comparative Example 5

[0075] The difference from Example 4 is that an equimolar amount of D-mannitol is used to replace pentapentapentyl alcohol (PETP) in the original polyol, while everything else remains the same.

[0076] The above embodiments and comparative examples were subjected to the following performance tests, and the performance results are shown in Table 2 below:

[0077] Strength at 300% elongation: The stress of spandex yarn when stretched to 300% of its length.

[0078] Spinability: Summarize production line faults and calculate the average number of faults per unit per day. Less than 0.4 faults indicate excellent spinability, more than 0.4 but less than 0.8 faults indicate average spinability, more than 0.8 but less than 2.0 faults indicate poor spinability, and more than 2.0 faults indicate very poor spinability.

[0079] AA rate in 3.0-fold draft weaving: the percentage of unwound yarns without breakage under unwinding speed of 10m / min and 3.0-fold draft.

[0080] Fabric weight: Take a sample of finished fabric of the same area and calculate the weight per square meter.

[0081] Fabric air permeability: According to the national standard GB / T5453 "Determination of air permeability of textile fabrics", under the specified pressure difference conditions, the air flow rate passing vertically through a given area of ​​the sample within a certain time is measured, and the air permeability is calculated.

[0082] Table 2:

[0083]

Claims

1. A type of spandex for breathable fabrics, characterized in that... The spandex is a polyurethane urea reaction product obtained from polyurethane prepolymer and mixed amines. The polyurethane prepolymer is obtained by reacting polyisocyanate and polyol. The polyol includes macromolecular polyether diol and small molecule polyol. The hydroxyl functionality of the small molecule polyol is 3-5. The molar ratio of the macromolecular polyether diol to the small molecule polyol is 99.5:0.5-95:

5.

2. The spandex for breathable fabric according to claim 1, characterized in that, The macromolecular polyether diols include polytetramethyl ether diols with a number average molecular weight of 1500~2500 g / mol.

3. The spandex for breathable fabric according to claim 1, characterized in that, The small molecule polyols mentioned include one or more of glycerol, butanetetrol, pentaerythritol, and xylitol.

4. The spandex for breathable fabric according to claim 1, characterized in that, The polyisocyanates mentioned include diphenylmethane diisocyanate.

5. The spandex for breathable fabric according to claim 1, characterized in that, The NCO content of the polyurethane prepolymer is 2.2~3.5 wt%.

6. The spandex for breathable fabric according to claim 1, characterized in that, The mixed amine comprises a diamine chain extender and a monoamine end-capping agent. The diamine chain extender comprises one or more of ethylenediamine, propylenediamine, and 2-methyl-1,5-pentanediamine. The monoamine end-capping agent comprises one or more of diethylamine, dipropylamine, and n-hexylamine. The molar ratio of the diamine chain extender to the monoamine end-capping agent is 12:1 to 22:

1.

7. The spandex for breathable fabric according to claim 1, characterized in that, The breathable fabric using spandex also contains less than 5% of a flow aid; the flow aid includes one or more of polyethylene glycol dimethacrylate, polypropylene glycol acrylate, and polybutylene glycol acrylate, with a number average molecular weight of 400~800 g / mol.

8. A method for preparing spandex for breathable fabrics as described in claim 7, characterized in that, The polyurethane-urea reaction product is used as the spinning raw material and obtained by dry spinning, specifically including the following steps: Step 1, Prepolymerization reaction: The polyisocyanate and polyol are subjected to a prepolymerization reaction to obtain a polyurethane prepolymer, and then the polyurethane prepolymer is dissolved in a solvent to obtain a solution containing the polyurethane prepolymer. Step 2, chain extension reaction: The polyurethane prepolymer solution is reacted with a mixed amine solution to obtain a stock solution containing polyurethane-urea; Step 3, Curing and spinning: The polyurethane-urea stock solution is cured, and a flow aid is added to the stock solution. The cured polyurethane-urea stock solution is used as raw material to obtain breathable fabric through dry spinning, which is used to obtain spandex.

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