Cotton / spandex elastic fabric and preparation method thereof

Abstract

The invention relates to a cotton / spandex elastic fabric and a preparation method thereof, and belongs to the technical field of textile fabrics. A novel modified spandex fiber is adopted, octylene trichlorosilane and tetramethylpiperidinol react to obtain an intermediate, then the intermediate and dithiothreitol are subjected to a thiol-ene click reaction, and a modified alcohol monomer with huge hindered amine structures at the two ends and a flexible connection chain segment in the middle is prepared. The polyester fiber participates in copolymerization modification of spandex and is prepared into fiber through dry spinning; a large-volume hindered amine structure is stably introduced into a polyurethane main chain in a side chain form through copolymerization, and a uniform nanoscale physical entanglement network and a permanent anti-aging site are constructed in the fiber, so that the fiber is endowed with excellent creep resistance, high elastic recovery rate and lasting chlorine resistance and ultraviolet aging resistance in a synergistic manner. The elastic fabric prepared by blending the fiber and cotton has excellent lasting shape-preserving capability and wearing comfort, and overcomes the defect that the traditional product is easy to loosen and deform.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of textile fabrics, and in particular relates to a cotton / spandex stretch fabric and a preparation method thereof. BACKGROUND

[0002] Textiles are one of the basic needs of human life, and the comfort and functionality of fabrics are the core standards for measuring their quality. Among the numerous textile fibers, cotton and spandex represent two classic materials of different origins but complementary properties. Cotton fiber, as a widely sourced natural plant fiber, has long dominated the intimate and casual clothing market with its outstanding moisture absorption and ventilation, soft and skin-friendly touch, and non-allergic properties. However, the inherent wrinkles and lack of elasticity of pure cotton fabrics limit their application in modern clothing that seeks to fit the body shape and freedom of movement. Spandex, chemically known as polyurethane fiber, is a synthetic elastic fiber that is most notable for its high elongation at break and excellent elastic recovery. By core spinning or blending a small amount of spandex with cotton fibers, cotton / spandex stretch fabric can be prepared, which combines the comfort of cotton and the elasticity of spandex, effectively making up for the shortcomings of pure cotton fabrics, and thus is widely used in underwear, sportswear, jeans, T-shirts and other types of stretch clothing, greatly improving the comfort and aesthetics of wearing.

[0003] Despite the obvious advantages of cotton / spandex stretch fabric, its long-term durability, especially the loss of "shape retention," i.e., the fabric becomes loose, arches, and cannot fit the body after repeated wearing and washing, has always been a bottleneck restricting its performance. The root cause of this problem lies mainly in the material science defects of spandex fiber and its aging in service environment.

[0004] First, traditional spandex is a linear block copolymer composed of flexible long-chain polyether or polyester "soft segments" and rigid urethane "hard segments" arranged alternately. This structure gives it high elasticity, but as a linear polymer, it lacks permanent and stable lateral constraints between molecular chains. Under external forces (such as human activity, fabric hanging weight), the molecular chains are prone to relative slipping. Although the physical cross-linking network formed by hydrogen bonds in the hard segment can provide some recovery force, its strength is limited. This results in insufficient anti-creep and stress relaxation performance of traditional spandex fibers, which manifests as irreversible plastic deformation of the fabric after long-term static load (such as hanging) or repeated dynamic stretching, making it difficult to maintain the original fit version, especially in stress concentration areas such as elbows, knees, and waist openings.

[0005] Secondly, spandex molecular chains are extremely sensitive to external environmental factors, and their aging process will dramatically accelerate the above deformation problems. The two major aging inducers are ultraviolet rays and chlorine. Ultraviolet radiation in sunlight can directly cause photo-oxidative degradation of ether bonds or ester bonds in the soft segment of polyurethane, leading to molecular chain rupture. Chlorine-based bleaching agents contained in domestic water or chlorine in swimming pool water can attack the urethane bonds and soft segment structure of polyurethane, causing oxidation and chlorine substitution reactions, not only causing the yellowing of the fiber, but more seriously, leading to the degradation of the polymer backbone and the destruction of the cross-linked structure. These chemical aging processes cause the molecular weight of spandex to decrease, and the physical cross-linking points of the hard segment are destroyed, which directly leads to a significant decrease in fiber strength, modulus and elastic recovery rate, exacerbating the permanent deformation of the fabric and causing the clothes to quickly "collapse".

[0006] To address the above challenges, the existing technology mainly improves in two directions: one is to improve the anti-deformation ability by chemical cross-linking, and the other is to delay aging by adding antioxidants. In terms of anti-deformation, a common method is to introduce a cross-linking agent (such as a polyisocyanate or an epoxide compound) during the spinning process or after treatment to establish covalent bonds between spandex macromolecular chains to limit chain slipping. However, this method often "overcorrects", and excessive cross-linking severely limits the freedom of movement of molecular chain segments, leading to a significant decrease in fiber elongation at break and elasticity, a hard hand feel, and a sacrifice of the core comfort and elasticity of spandex. In terms of anti-aging, the industry generally uses physically blended small molecule hindered amine light stabilizers or antioxidants in the spinning solution. This method can indeed effectively capture free radicals and improve weather resistance in the early stage. However, its fundamental defect is insufficient durability: small molecule additives have limited compatibility with the polymer matrix, and are prone to migration and loss during long-term use, especially under the effects of washing, dry-wet alternating and heat. This leads to a rapid decay of the anti-aging effect with increasing washing and wearing times, and the migrated chemicals can also cause other problems.

[0007] In summary, the existing technology either sacrifices elasticity to achieve shape stability or cannot provide long-lasting and reliable anti-aging protection, and neither fundamentally solves the core problem of poor shape retention and durability of cotton / spandex stretch fabric. Therefore, developing a new type of spandex fiber that not only maintains excellent elasticity but also has inherent high anti-deformation ability and long-term anti-aging performance, and combining it with cotton, is the key to promoting the development of high-performance stretch fabric. SUMMARY

[0008] To solve the technical problems mentioned in the background art, the purpose of the present application is to provide a cotton / spandex stretch fabric and a preparation method thereof.

[0009] The purpose of the present application can be achieved by the following technical solutions: The cotton / spandex elastic fabric is made of a composite yarn with modified spandex fiber as the core and cotton fiber as the outer package; specifically, the modified spandex fiber is prepared by the following method: Step A1: Pre-mix tetramethylpiperidinol and anhydrous tetrahydrofuran, dry nitrogen atmosphere and cool to below 10℃, slowly add octene trichlorosilane and stir for 2h, then add triethylamine and control the temperature at 40-55℃ and continue to stir for 1-1.5h, filter out the salt after the reaction is completed, remove tetrahydrofuran by rotary evaporation, wash the substrate with deionized water and dry to obtain the intermediate; Further, the amount ratio of octene trichlorosilane, tetramethylpiperidinol, triethylamine and anhydrous tetrahydrofuran is 10mmol:30mmol:2-3mL:75-90mL, and the active alcohol hydroxyl group of tetramethylpiperidinol is substituted with octene trichlorosilane.

[0010] Step A2: Pre-mix the intermediate, dithiothreitol and ethanol, then add a photoinitiator and mix evenly, and then perform ultraviolet irradiation at 40-60mW / cm 2 Stir for 6-7h, remove ethanol by rotary evaporation after the reaction is completed, and obtain the modified alcohol monomer; Further, the amount ratio of the intermediate, dithiothreitol, photoinitiator and ethanol is 10mmol:5mmol:20-30mg:80-100mL, and the mercapto group of dithiothreitol is subjected to mercapto-alkene addition reaction with the alkenyl group on the intermediate molecule.

[0011] Step A3: Mix the modified alcohol monomer and dimethylacetamide, then pre-mix with polytetrahydrofuran ether glycol, then add diphenylmethane diisocyanate, stir at 80-90℃ for 1.8-2.2h, then cool to 50-55℃, add 1,4-butanediol and stannous octoate and continue to react and chain extend for 1-1.3h, then mature at 40℃ for 2h, and then vacuum degassing to obtain the spinning solution; Further, the -NCO and -OH molar ratio of diphenylmethane diisocyanate and polytetrahydrofuran ether glycol is 2.4-2.7:1, the amount of modified alcohol monomer is 1.5-2.2wt% of polytetrahydrofuran ether glycol, and the amount of stannous octoate is 0.015-0.02wt% of the prepolymer solution.

[0012] Step A4: The spinning solution is subjected to dry spinning, winding, hot drawing, oiling and bobbin winding in sequence to obtain the modified spandex fiber.

[0013] Further, the dry spinning drying temperature is 220-230℃, the winding speed is 700-800m / min, the hot drawing temperature is 80±2℃, and the drawing ratio is 3-3.5.

[0014] The application relates to a method for preparing a cotton / spandex elastic fabric, and particularly relates to the following steps: taking cotton fibers as outer cladding fibers, taking modified spandex fibers as core fibers, adopting a siro-spinning core-spun yarn process to prepare composite fibers, and then spinning the composite fibers into elastic fabrics.

[0015] Further, the cotton fibers have a micronaire value of 3.8-4.5.

[0016] Further, the content of the modified spandex fibers in the composite fibers is 8-12 wt%.

[0017] The application has the following beneficial effects: The application realizes synchronous and long-acting improvement of intrinsic properties of polyurethane fiber materials through an innovative molecular structure design.

[0018] Firstly, in terms of chemical stability, the hindered amine groups firmly anchored on the polymer chains through covalent bonds constitute uniformly distributed and intrinsic free radical capturing sites. Different from the fundamental defect of migration and loss of physically blended small molecule additives, the chemical bonding mode ensures the permanent existence under long-term use, multiple washing and heat processes. When the fiber is attacked by ultraviolet radiation or chlorine, the hindered amine structure on the side chain can efficiently and continuously quench the generated free radicals, interrupt the oxidative degradation chain reaction of the polymer, and thus provide the material with durable and reliable light oxidation and chlorine aging resistance.

[0019] Secondly, in terms of physical and mechanical properties, the unique side chain structure produces significant steric hindrance effect and physical entanglement enhancement. The huge hindered amine end group connected to the main chain, like the nanoscale reinforcing unit distributed between the molecular chains, greatly increases the interaction and entanglement density between the molecular chains. This effect forms a dynamic physical crosslinking network, which can effectively limit the excessive slippage and irreversible orientation of the molecular chains under external force, thereby significantly improving the anti-cree and stress relaxation resistance of the fiber, and showing lower permanent deformation rate and higher elastic recovery accuracy. Most importantly, the continuous flexible thioether-siloxane connecting segment ensures that the side chain itself has good activity freedom, avoids the huge side group from becoming a rigid structural defect or stress concentration point, and makes the flexibility of the polymer main chain be retained to the greatest extent.

[0020] In summary, the present application introduces a molecule structure unit with specific spatial conformation and reactivity into the polymer backbone in a chemical manner. The design achieves excellent long-term aging resistance and excellent anti-permanent deformation ability without sacrificing the inherent high elasticity and soft touch of the material. The elastic fabric prepared by compounding with cotton fibers has an unprecedented shape retention performance, completely overcoming the technical bottleneck of traditional cotton / spandex fabric that is prone to relaxation deformation and elasticity decay after long-term use, which has significant industrial progress significance. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0022] Embodiment 1, preparation of cotton / spandex elastic fabric, the specific implementation process is as follows: I. Preparation of modified spandex fiber Step A1: Take tetramethylpiperidinol and anhydrous tetrahydrofuran as raw materials, stir and pre-mix, and then pass dry nitrogen gas to protect it. At the same time, use an ice water bath to cool it to 5℃, slowly add octene trichlorosilane and control the temperature of the reaction system not to be higher than 20℃, continue to stir and react after complete addition, control the total addition reaction time to be 2h, then add triethylamine and heat to 40℃, stir and react for 1.5h. The amount ratio of octene trichlorosilane, tetramethylpiperidinol, triethylamine and anhydrous tetrahydrofuran is 10mmol:30mmol:2mL:75mL. After the reaction is completed, filter out the salt, remove tetrahydrofuran by rotary evaporation, wash the substrate with deionized water and dry it to obtain an intermediate.

[0023] Step A2: Take the intermediate, dithiothreitol and ethanol as raw materials, stir and pre-mix, then add a photoinitiator (2-hydroxy-2-methylbenzophenone) and mix uniformly, and then use a 365nm ultraviolet light source to irradiate, with an intensity of 40mW / cm 2 , and a temperature of room temperature, and a reaction time of 7h. The amount ratio of the intermediate, dithiothreitol, photoinitiator and ethanol is 10mmol:5mmol:20mg:80mL. After the reaction is completed, remove ethanol by rotary evaporation to obtain a modified alcohol monomer.

[0024] Step A3: Diphenylmethane diisocyanate and polytetrahydrofuran ether glycol (Mn=2000) were dosed according to a molar ratio of -NCO and -OH of 2.4:1, 1.5wt% of the modified alcohol monomer of polytetrahydrofuran ether glycol was metered, and 1,4-butanediol was taken according to a total R value (-NCO and -OH) of 1; first, the modified alcohol monomer and three times its mass of dimethylacetamide were mixed, then the polytetrahydrofuran ether glycol was premixed, and then the diphenylmethane diisocyanate was mixed, and the prepolymer was stirred at 80°C for 2.2h; after the prepolymerization was completed, the temperature was lowered to 50°C, 1,4-butanediol and 0.015wt% of stannous octoate of the prepolymer solution were added, and the reaction was continued for 1.3h; after the reaction was completed, the temperature was allowed to stand at 40°C for 2h, and then the spinning solution was obtained after vacuum degassing.

[0025] Step A4: The spinning solution was accurately metered by a gear pump and delivered to a dry spinning duct. The spinning solution was sprayed from the spinneret (72 holes, hole diameter 0.15mm) into the duct, and circulating hot nitrogen gas was introduced into the duct at a temperature of 220°C. The nascent fiber was collected at a speed of 700m / min, and the collected fiber was heat drawn on a heating roller at 80±2°C with a draw ratio of 3. Finally, the fiber was oiled, wound, and modified spandex fiber with a specification of 40D / 12f was prepared.

[0026] II. Preparation of cotton / spandex stretch fabric Raw material preparation: The cotton fiber was Xinjiang long-staple cotton treated by a comber process, with a fiber length of more than 35mm and a micronaire value of 3.8-4.2. The modified spandex fiber was a 40D / 12f product prepared by the above method.

[0027] Spinning: A siro-spinning core-spun yarn process was used, with cotton fiber as the outer covering fiber and the above modified spandex fiber as the core yarn. The specific parameters were as follows: the spandex pre-draw ratio was set to 3.4 times; the spinning twist was set to 850 twists per meter, and a composite fiber was prepared, in which the content of the modified spandex fiber was about 8wt%.

[0028] Weaving: The composite fiber was woven into a stretch fabric according to a warp density of 78 ends / cm and a weft density of 42 ends / cm.

[0029] Example 2, preparation of cotton / spandex stretch fabric, the specific implementation process is as follows: I. Preparation of modified spandex fiber Step A1: Take tetramethylpiperidinol and anhydrous tetrahydrofuran as raw materials, stir and mix, and protect with dry nitrogen. Cool to 5℃ with an ice water bath, slowly add octene trichlorosilane, and control the temperature of the reaction system not to exceed 20℃. After complete addition, continue to stir and react, control the total addition reaction time to be 2h, then add triethylamine and heat to 55℃. Stir and react for 1h. The amount ratio of octene trichlorosilane, tetramethylpiperidinol, triethylamine and anhydrous tetrahydrofuran is 10mmol:30mmol:3mL:90mL. After the reaction is completed, filter to remove salt, remove tetrahydrofuran by rotary evaporation, wash the substrate with deionized water and dry to obtain an intermediate.

[0030] Step A2: Take the intermediate, dithiothreitol and ethanol as raw materials, stir and mix, then add a photoinitiator (2-hydroxy-2-methylbenzophenone) and mix uniformly. Irradiate with a 365nm ultraviolet light source at an intensity of 60mW / cm 2 , at room temperature for 6h. The amount ratio of the intermediate, dithiothreitol, photoinitiator and ethanol is 10mmol:5mmol:30mg:100mL. After the reaction is completed, remove ethanol by rotary evaporation to obtain a modified alcohol monomer.

[0031] Step A3: Take diphenylmethane diisocyanate and polytetrahydrofuran ether glycol (Mn=2000) as raw materials, and dose the modified alcohol monomer at 1.8wt% of the polytetrahydrofuran ether glycol. According to the total R value (-NCO and -OH) of 1, take 1,4-butanediol. First, mix the modified alcohol monomer with three times its mass of dimethylacetamide, then pre-mix with the polytetrahydrofuran ether glycol, and then add the diphenylmethane diisocyanate. Stir and pre-polymerize at 90℃ for 1.8h. After the pre-polymerization is completed, cool to 55℃, add 1,4-butanediol and 0.02wt% of stannous octoate to the pre-polymer solution and continue to react for 1h. After the reaction is completed, age at 40℃ for 2h, and then vacuum degas to obtain a spinning solution.

[0032] Step A4: Accurately measure the spinning solution by a gear pump, and deliver it to a dry spinning duct. The spinning solution is sprayed from a spinneret (72 holes, hole diameter 0.15mm) into the duct. Circulating hot nitrogen is introduced into the duct at a temperature of 230℃. The nascent fiber is collected by winding at a speed of 800m / min. The wound fiber is heat drawn on a heating roller at 80±2℃ with a draw ratio of 3.5. Finally, the fiber is oiled and wound on a bobbin to obtain a modified spandex fiber with a specification of 40D / 12f.

[0033] II. Preparation of cotton / spandex stretch fabric Raw material preparation: the cotton fiber is Xinjiang long-staple cotton, which is treated by a carding process, the fiber length is greater than 35 mm, and the micronaire value is between 4.0-4.5. The modified spandex fiber is a 40D / 12f specification product prepared by the above method.

[0034] Spinning: using a siro spun core yarn process, taking cotton fiber as the outer covering fiber and the above modified spandex fiber as the core fiber. The specific parameters are: the spandex pre-drafting multiple is set to 3.8 times; the spinning twist is set to 900 twists per meter, and a composite fiber is prepared, in which the content of the modified spandex fiber is about 10wt%.

[0035] Textile: the composite fiber is formed by weaving according to the warp density of 78 roots per centimeter and the weft density of 42 roots per centimeter, and an elastic fabric is obtained.

[0036] Example 3, preparation of cotton / spandex elastic fabric, the specific implementation process is as follows: I. Preparation of modified spandex fiber Step A1: take tetramethylpiperidinol and anhydrous tetrahydrofuran, stir and pre-mix, and then pass dry nitrogen gas to protect it. At the same time, use an ice water bath to cool it to 5℃, slowly add octene trichlorosilane and control the reaction system temperature not to exceed 20℃, continue to stir and react after complete addition, control the total addition reaction time to be 2h, then add triethylamine and heat to 50℃, stir and react for 1.2h. The amount ratio of octene trichlorosilane, tetramethylpiperidinol, triethylamine and anhydrous tetrahydrofuran is 10mmol:30mmol:3mL:85mL. After the reaction is completed, filter out the salt, remove tetrahydrofuran by rotary evaporation, wash the substrate with deionized water and dry it to obtain an intermediate.

[0037] Step A2: take the intermediate, dithiothreitol and ethanol, stir and pre-mix, then add a photoinitiator (2-hydroxy-2-methylbenzophenone) and mix well, and then use a 365nm ultraviolet light source to irradiate it at an intensity of 50mW / cm 2 , at room temperature, for 6.5h. The amount ratio of the intermediate, dithiothreitol, photoinitiator and ethanol is 10mmol:5mmol:20mg:90mL. After the reaction is completed, remove ethanol by rotary evaporation to obtain a modified alcohol monomer.

[0038] Step A3: Diphenylmethane diisocyanate and polytetrahydrofuran ether glycol (Mn=2000) were dosed according to a molar ratio of -NCO and -OH of 2.7:1, 2.2wt% of the modified alcohol monomer of polytetrahydrofuran ether glycol was metered, and 1,4-butanediol was taken according to a total R value (-NCO and -OH) of 1; first, the modified alcohol monomer and three times its mass of dimethylacetamide were mixed, then the polytetrahydrofuran ether glycol was premixed, and then the diphenylmethane diisocyanate was mixed, and the pre-polymerization was stirred at 90°C for 2.0h; after the pre-polymerization was completed, the temperature was lowered to 50°C, 1,4-butanediol and 0.018wt% of stannous octoate of the pre-polymerization solution were added, and the reaction was continued for 1.2h; after the reaction was completed, the temperature was allowed to stand at 40°C for 2h, and then the spinning solution was obtained after vacuum degassing.

[0039] Step A4: The spinning solution was accurately metered by a gear pump and delivered to a dry spinning duct; the spinning solution was sprayed from the spinneret (72 holes, hole diameter 0.15mm) into the duct, and circulating hot nitrogen gas was introduced into the duct at a temperature of 220°C; the nascent fiber was wound and collected at a speed of 700m / min, the fiber after winding was heat drawn on a heating roller at 80±2°C with a draw ratio of 3.2, and finally the modified spandex fiber with a specification of 40D / 12f was obtained after oiling and winding.

[0040] II. Preparation of cotton / spandex stretch fabric Raw material preparation: The cotton fiber was Xinjiang long-staple cotton treated by a comber process, the fiber length was greater than 35mm, and the micronaire value was between 3.8-4.2; the modified spandex fiber was a 40D / 12f specification product prepared by the above method.

[0041] Spinning: A siro-spinning core-spun yarn process was used, with cotton fiber as the outer covering fiber and the above modified spandex fiber as the core yarn. The specific parameters were: the spandex pre-draw ratio was set to 3.5 times; the spinning twist was set to 850 twists per meter, and a composite fiber was prepared, in which the content of the modified spandex fiber was about 12wt%.

[0042] Weaving: The composite fiber was woven into a stretch fabric according to a warp density of 78 ends / cm and a weft density of 42 ends / cm.

[0043] Example 4, preparation of cotton / spandex stretch fabric, the specific implementation process is as follows: I. Preparation of modified spandex fiber Step A1: Take tetramethylpiperidinol and anhydrous tetrahydrofuran as raw materials, stir and mix, and protect with dry nitrogen. Cool to 5℃ with an ice water bath, slowly add octene trichlorosilane, and control the temperature of the reaction system not to exceed 20℃. After complete addition, continue to stir and react, control the total addition reaction time to be 2h, then add triethylamine and heat to 45℃. Stir and react for 1.5h. The amount ratio of octene trichlorosilane, tetramethylpiperidinol, triethylamine and anhydrous tetrahydrofuran is 10mmol:30mmol:2mL:80mL. After the reaction is completed, filter to remove salt, remove tetrahydrofuran by rotary evaporation, wash the substrate with deionized water and dry to obtain an intermediate.

[0044] Step A2: Take the intermediate, dithiothreitol and ethanol as raw materials, stir and mix, then add a photoinitiator (2-hydroxy-2-methylbenzophenone) and mix uniformly. Irradiate with a 365nm ultraviolet light source at an intensity of 50mW / cm 2 , at room temperature for 7h. The amount ratio of the intermediate, dithiothreitol, photoinitiator and ethanol is 10mmol:5mmol:25mg:90mL. After the reaction is completed, remove ethanol by rotary evaporation to obtain a modified alcohol monomer.

[0045] Step A3: Take diphenylmethane diisocyanate and polytetrahydrofuran ether glycol (Mn=2000) as raw materials, and the amount ratio of -NCO and -OH is 2.6:1. Measure 2.0wt% of the modified alcohol monomer in the polytetrahydrofuran ether glycol, and take 1,4-butanediol according to the total R value (-NCO and -OH) of 1. First, mix the modified alcohol monomer with three times its mass of dimethylacetamide, then pre-mix with the polytetrahydrofuran ether glycol, and then add the diphenylmethane diisocyanate. Stir and pre-polymerize at 90℃ for 2.0h. After the pre-polymerization is completed, cool to 55℃, add 1,4-butanediol and 0.02wt% of stannous octoate in the pre-polymer solution, and continue to react for 1.1h. After the reaction is completed, age at 40℃ for 2h. After vacuum degassing, a spinning solution is obtained.

[0046] Step A4: The spinning solution is accurately measured by a gear pump, and is delivered to a dry spinning duct. The spinning solution is sprayed from a spinneret (72 holes, hole diameter 0.15mm) into the duct. Circulating hot nitrogen is introduced into the duct at a temperature of 230℃. The nascent fiber is collected by winding at a speed of 800m / min. The wound fiber is hot drawn on a heating roller at 80±2℃ with a draw ratio of 3. Finally, the modified spandex fiber with a specification of 40D / 12f is obtained after oiling and winding.

[0047] II. Preparation of cotton / spandex stretch fabric Raw material preparation: the cotton fiber is Xinjiang long-staple cotton, which is treated by comber process, the fiber length is greater than 35 mm, and the micronaire value is between 3.8-4.2. The modified spandex fiber is a 40D / 12f product prepared by the above method.

[0048] Spinning: using the core-spun yarn process of siro spinning, taking cotton fiber as the outer covering fiber and the above modified spandex fiber as the core fiber. The specific parameters are: the spandex pre-drafting multiple is set to 3.6 times; the spinning twist is set to 880 twists per meter, and a composite fiber is prepared, in which the content of modified spandex fiber is about 11wt%.

[0049] Weaving: the composite fiber is woven into an elastic fabric according to the warp density of 78 roots per centimeter and the weft density of 42 roots per centimeter.

[0050] Comparative Example 1, referring to the elastic fabric manufacturing process of Example 4, the modified spandex fiber is replaced by 40D / 12f spandex fiber of INVISTA company, and the rest is the same.

[0051] Comparative Example 2, referring to the weaving preparation process of Example 4, no modified alcohol monomer is added, the molar ratio of -NCO and -OH of diphenyl methane diisocyanate and polytetrahydrofuran ether diol is 2:1, 2.2wt% of triphenyl methane triisocyanate is added to the prepolymer solution after prepolymerization, and at the same time, 0.15wt% of Tinuvin 765 anti-aging agent is added to the spinning solution, and the rest is the same.

[0052] Take the spandex fiber prepared above, refer to GB / T 3916-2013 standard, use electronic single yarn strength tester, clamp distance 500mm, tensile speed 500mm / min, test the breaking strength and breaking elongation of each spandex fiber sample; refer to FZ / T50007-2012 standard, stretch the fiber sample to 300% of its original length, keep for 5min, then let it freely recover for 2min, measure its remaining length, calculate the elastic recovery rate, and cycle this process for 50 times, calculate the permanent deformation rate; the specific test results are shown in Table 1: Table 1

[0053] Take the spandex fiber prepared above, immerse in a water solution with an effective concentration of 50mg / L for continuous stirring for 24h, drain for 2h, then place it in a xenon lamp aging test box, the temperature is 40℃, the cumulative irradiation energy reaches 200MJ / m 2, and the retention rate was calculated according to the data in Table 1; the stretch fabric prepared above was made into a standard pant piece according to the AATCC 128-2017 standard, and 5 million times of bending fatigue test was carried out on the elbow repeatedly bending simulator, after the test, the arch height of the elbow was measured, and the relaxation rate was calculated; at the same time, 100 clothing professionals were recruited to conduct blind evaluation on the style of the stretch fabric prepared above, the evaluation dimensions included hand feeling, fullness and fit, and the scores were given by 5-point scale; the specific test results are shown in Table 2: Table 2

[0054] From the above test data, it can be seen that the modified spandex fiber prepared in the example has high strength while maintaining good elasticity, especially under the simulated accelerated daily use aging conditions, the performance retention rate is high, and the fabric maintains good wearability.

[0055] In the description of the specification, the description of the reference terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are contained in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0056] The above is only an example and description of the present application, and those skilled in the art can make various modifications or supplements or use similar ways to replace the described specific embodiments, as long as they do not deviate from the invention or exceed the scope defined by the present claims, which shall belong to the protection scope of the present application.

Claims

1. A cotton / spandex elastic fabric, woven from a composite yarn with modified spandex fiber as the core and cotton fiber as the outer layer, characterized in that, Modified spandex fibers are prepared by the following method: Step A1: Premix tetramethylpiperidinol and anhydrous tetrahydrofuran, dry under nitrogen atmosphere and cool to below 10°C, slowly add octenetrichlorosilane and stir for 2 hours, then add triethylamine and control the temperature at 40-55°C and continue stirring for 1-1.5 hours to prepare the intermediate; Step A2: Premix the intermediate, dithiothreitol, and ethanol, then add the photoinitiator and mix thoroughly at room temperature with 40-60 mW / cm². 2 The modified alcohol monomer was prepared by stirring under ultraviolet irradiation for 6-7 hours. Step A3: After mixing the modified alcohol monomer and dimethylacetamide, premix it with polytetrahydrofuran ether diol, then add diphenylmethane diisocyanate and mix. Stir at 80-90℃ for 1.8-2.2h for prepolymerization. Then cool down to 50-55℃ and add 1,4-butanediol and stannous octoate to continue the reaction and chain extension for 1-1.3h. After aging and vacuum degassing, the spinning solution is obtained. Step A4: The spinning solution is subjected to dry spinning, winding, hot drawing, oiling, and winding in sequence to obtain modified spandex fiber.

2. The cotton / spandex elastic fabric according to claim 1, characterized in that, The ratio of octene trichlorosilane, tetramethylpiperidinol, triethylamine and anhydrous tetrahydrofuran is 10 mmol: 30 mmol: 2-3 mL: 75-90 mL.

3. The cotton / spandex elastic fabric according to claim 2, characterized in that, The ratio of intermediate, dithiothreitol, photoinitiator and ethanol is 10 mmol: 5 mmol: 20-30 mg: 80-100 mL.

4. The cotton / spandex elastic fabric according to claim 3, characterized in that, The molar ratio of -NCO to -OH in diphenylmethane diisocyanate and polytetrahydrofuran ether diol is 2.4-2.7:1, the amount of modified alcohol monomer is 1.5-2.2 wt% of polytetrahydrofuran ether diol, and the amount of stannous octoate is 0.015-0.02 wt% of the prepolymer solution.

5. The cotton / spandex elastic fabric according to claim 1, characterized in that, The dry spinning drying temperature is 220-230℃, the winding rate is 700-800m / min, the hot drawing temperature is 80±2℃, and the drawing ratio is 3-3.

5.

6. A method for preparing a cotton / spandex elastic fabric according to any one of claims 1-5, characterized in that, Specifically, the process involves using cotton fiber as the outer covering fiber and modified spandex fiber as the core yarn, employing Sirospun core-spun yarn technology to create composite fibers, which are then spun into elastic fabrics.

7. The method for preparing a cotton / spandex elastic fabric according to claim 6, characterized in that, The micronaire value of cotton fiber is 3.8-4.

5.

8. The method for preparing a cotton / spandex elastic fabric according to claim 6, characterized in that, The content of modified spandex fiber in the composite fiber is 8-12 wt%.

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