Spandex fiber for free-cut fabric, and preparation method therefor and use thereof

Abstract

A spandex fiber for free-cut fabric, and a preparation method therefor and the use thereof. The raw materials used for preparing the spandex fiber comprise: isocyanate, a modified polyol, a bifunctional compound and a composite auxiliary agent. The prepared spandex fiber has great mechanical properties, including a strength of 2.01-2.18 d / g, a stress at a specified elongation of 13.0-13.7 cN, and an elongation at break of 522-557%. Efficient heat setting can be achieved at a temperature of 175°C or less, with a heat-setting efficiency of 87-92%. The spandex fiber also has good thermal stability, with the strength decreasing by only about 2% and the elongation at break decreasing by no more than 10% after undergoing a heat treatment. In addition, the spandex fiber has great adaptability; and, when blended together with fibers having relatively poor heat resistance such as cotton, silk and wool, fabrics made therefrom have good dimensional stability during cutting, do not curl nor fray, and can be cut freely.

Description

A spandex fiber for arbitrary cutting of fabrics, its preparation method and application Technical Field

[0001] This invention belongs to the field of fiber technology, specifically relating to a spandex fiber for fabrics that can be cut at will, its preparation method, and its application. Background Technology

[0002] Traditional textile and apparel design focuses on practicality and simplicity. However, with the continuous improvement and upgrading of consumers' quality of life and consumption concepts, textiles now exhibit characteristics such as health, comfort, aesthetics, fashion, and functionality.

[0003] Flexible fabrics are a relatively new type of fabric, typically made of synthetic fibers and spandex. Due to their excellent adaptability to cutting and edge stability, they can be freely cut and are less prone to curling, making them promising for future applications in emerging fabric development. Currently, heat setting is generally used to achieve dimensional stability during fabric cutting to some extent. Traditional spandex fibers require high temperatures for heat setting. However, if spandex is blended with fibers with poor heat resistance, such as cotton, silk, and wool, using the conventional 190-195℃ setting temperature will severely damage the dimensional and performance stability of these fibers. Fabrics made from such blends are prone to insufficient strength, curling, and unraveling during cutting, significantly reducing their processability. Conversely, if the setting temperature is lowered to protect the structure of cotton, silk, and wool, internal stress cannot be completely eliminated, resulting in a significant decrease in heat setting efficiency (HSE).

[0004] Therefore, in order to obtain high-performance fabrics with dimensional stability, cutting freedom, and resistance to curling, it is necessary to strictly control the heat setting temperature. Temperature adjustments may even be required depending on the type of fiber blended with spandex, as a single temperature cannot be used, resulting in waste of raw materials, time, and manpower. On the other hand, freely cut fabrics also have relatively poor strength, limiting their practical application in the textile industry.

[0005] Therefore, developing a spandex fiber that has high heat setting efficiency at low temperatures and good strength, so that the fabrics blended with it have excellent cut adaptability and edge stability, has broad application prospects in the textile field. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a spandex fiber for freely cut fabrics, its preparation method, and its application, achieving the invention's objective of providing fabrics with good dimensional stability, high strength, resistance to curling, no unraveling, and the ability to be freely cut.

[0007] To solve the above technical problems, the present invention adopts the following technical solution:

[0008] The first part of this invention provides a spandex fiber for fabrics that can be cut at will. The raw materials used to prepare the spandex fiber include: isocyanate, modified polyol, bifunctional compound, and composite auxiliaries.

[0009] Preferably, the molar ratio of the isocyanate to the modified polyol is 1.8 to 2:1.

[0010] Preferably, the isocyanate includes one or more of symmetrical isocyanates and asymmetrical isocyanates.

[0011] Further, the symmetrical isocyanate is selected from one or more of 4,4'-diphenylmethane diisocyanate, 2,2'-bis(4-isobutylisopentyl)propane, and 3,5'-diethyl-4-isobutylisopentylmethane.

[0012] Furthermore, the asymmetric isocyanate is selected from one or more of 2,4-diphenylmethane diisocyanate, isoflurone diisocyanate, and 1,4-phenylene diisocyanate.

[0013] More preferably, the isocyanate is 2,2'-bis(4-isobutylisopentyl)propane and 2,4-diphenylmethane diisocyanate in a molar ratio of 3:7.

[0014] Preferably, the modified polyol is prepared by:

[0015] S11, Activation

[0016] Dimeric glycerol was added to chloroform, followed by triethylamine and p-toluenesulfonyl chloride. The mixture was reacted at 0–5 °C for 12–16 h to replace one terminal hydroxyl group of the dimeric glycerol with a p-toluenesulfonate group. After the reaction was completed, 1 mol / L hydrochloric acid solution was added to the reaction solution to extract the organic phase. Excess anhydrous sodium carbonate was added to the organic phase, and the mixture was stirred thoroughly and then filtered. The filtrate was added to excess anhydrous diethyl ether, and the mixture was stirred thoroughly to precipitate a white precipitate. The precipitate was then filtered, dried, and activated dimeric glycerol was obtained.

[0017] S12, silane modification

[0018] Activated glycerol was added to DMSO, followed by potassium trimethylsilaneol. The nucleophilic substitution reaction was carried out at room temperature for 8–10 h. After the reaction was completed, the supernatant was collected by centrifugation and concentrated under reduced pressure to obtain the crude product. The crude product was extracted and dried with anhydrous sodium sulfate to obtain the glycerol-silane product.

[0019] S13, modification of pyridine

[0020] Dimeric glycerol-silane product was added to DMSO, followed by 2-pyridyl dithiocarbonate and potassium carbonate. The mixture was reacted at 40–50 °C for 6–8 h to graft pyridine groups onto the other terminal hydroxyl group of the dimeric glycerol-silane product. After the reaction was completed, the supernatant was collected by centrifugation and concentrated under reduced pressure to obtain a crude product. The crude product was extracted, dried with anhydrous sodium sulfate, and distilled under reduced pressure to obtain a modified polyol containing silane groups and pyridine groups.

[0021] Preferably, the molar ratio of dipolyglycerol to p-toluenesulfonyl chloride in S11 is 1:2 to 2.4.

[0022] Preferably, in S11, triethylamine is an alkaline catalyst, and the amount added is 1 to 2% of the mass of dipropylene glycol.

[0023] Preferably, the amount of potassium trimethylsilanol added in S12 is 20-30% of the mass of activated dipropylene glycol.

[0024] Preferably, the amount of 2-pyridyl dithiocarbonate added in S13 is 23-28% of the mass of the dipolyglycerol-silane product.

[0025] Preferably, the amount of potassium carbonate added in S13 is used to adjust the pH of the reaction system to 8-9.

[0026] The distribution ratio of hard and soft segments in spandex has a direct impact on its setting temperature. The applicant unexpectedly discovered that when using 2,2'-bis(4-isobutylisopentyl)propane, 2,4-diphenylmethane diisocyanate and modified polyol in a molar ratio of 3:7, the spandex molecules have a specific distribution ratio of hard and soft segments: (1) 2,2'-bis(4-isobutylisopentyl)propane and 2,4-diphenylmethane diisocyanate can introduce a certain proportion of rigid structure into the molecular structure of spandex. While ensuring the tensile stress and heat resistance of spandex, the steric hindrance effect is used to reduce the crystallinity of the hard segments in the molecular structure of spandex, reduce the restriction effect of the hard segments on the molecular chains of the soft segments, and improve the heat setting efficiency of spandex to a certain extent; (2) Dipropylene glycol contains four hydroxyl groups. After modification, one terminal hydroxyl group is grafted with a silane group and the other terminal hydroxyl group is grafted with a pyridine group. Modified polyols, as the soft segments of spandex molecular chains, have nitrogen atoms on the pyridine rings with high electronegativity, resulting in low electron cloud density. This leads to lower intermolecular forces between pyridine molecules and the molecular chain, thereby reducing molecular crystallinity, comprehensively improving the heat setting efficiency of spandex, and enhancing dimensional stability during fabric cutting.

[0027] Preferably, the bifunctional compound is one or more selected from 2-methyl-1,5-pentanediamine, 1,4-cyclohexanediol, neopentanediol, diethanolamine, and 3,5-dimethylthiotoluenediamine.

[0028] More preferably, the bifunctional group is 2-methyl-1,5-pentanediamine, and the molar fraction is 40-50% of the total amount of isocyanate and modified polyol.

[0029] The higher the crystallinity of the hard segments of spandex molecules, the more heat is required for the melting and recrystallization process of the crystalline regions, resulting in poor heat setting at lower temperatures. The hard segment structure formed by the reaction of 2-methyl-1,5-pentanediamine with 2,2'-bis(4-isobutylisopentyl)propane and 2,4-diphenylmethane diisocyanate in a molar ratio of 3:7 in this scheme has reduced intermolecular chain forces and is less likely to form an interlaced hydrogen bond network structure, resulting in low crystallinity of the hard segments. This allows for high-efficiency heat setting at low temperatures. When blended with fibers with poor heat resistance such as cotton, silk, and wool, the fabric made from it has good dimensional stability, does not curl or unravel, and can be cut at will.

[0030] Preferably, the composite additive is one or more of sodium benzoate, nano silica, and nano calcium carbonate; the amount of the composite additive added is 1 to 1.5% of the total mass of the spandex raw material.

[0031] Preferably, the composite additive is nano-silica and nano-calcium carbonate in a mass ratio of 3:1.5; the particle size of the nano-silica and nano-calcium carbonate is 50-100 nm.

[0032] The applicant discovered that when using the aforementioned isocyanate and 2-methyl-1,5-pentanediamine, the setting temperature of spandex is lowered by reducing the crystallinity of the hard segments in the spandex molecular chain. However, the reduced crystallinity leads to a decrease in the strength of the spandex. One end of the modified polyol is connected to a silane group. When a certain amount of nano-silica and nano-calcium carbonate in a mass ratio of 3:1.5 is added to the present invention, the hydroxyl groups on the surfaces of the nano-silica and nano-calcium carbonate can react with the silane groups on the surface of the modified polyol to form crosslinking points, thereby improving the strength and thermal stability of the spandex to a certain extent, giving the fabric excellent cutability and edge stability.

[0033] The second part of this invention provides a method for preparing spandex fibers for freely cut fabrics:

[0034] S21: After the modified polyol is dehydrated under reduced pressure at 115-125℃ for 2-3 hours, the composite additive is added and stirred evenly. The temperature is lowered to 80-85℃ and isocyanate is added. After stirring thoroughly, dibutyltin dilaurate is added and reacted for 2-3 hours. After cooling for 60-80 minutes, the prepolymer is obtained.

[0035] S22: Dissolve the prepolymer described in S21 in DMF to prepare a 20% concentration solution, add a bifunctional compound, react at 30-35℃ for 2-3 hours, and after aging, filtration, and degassing, obtain a spinning solution with a viscosity of 3000-4000 poise (40℃).

[0036] S23: The spinning solution described in S22 is metered by a metering pump, extruded from the spinneret, and enters the spinning tunnel. After being heated, the solvent evaporates and solidifies into a filament bundle. After stretching, oiling, and heat setting, the spandex fiber is obtained.

[0037] Preferably, the amount of dibutyltin dilaurate added in S21 is 0.08 to 0.12% of the total mass of the raw materials.

[0038] Preferably, the ripening temperature in S22 is 50-70°C, and the time is 12-24 hours.

[0039] Preferably, the temperature of the spinning channel in S23 is 230-270°C, and the speed is 700-800 m / min.

[0040] Preferably, the draw ratio in S23 is 2 to 3 times.

[0041] Preferably, the heat setting temperature in S23 is 170-175°C, and the time is 40-50 seconds.

[0042] The third part of this invention provides an application of spandex fibers for freely cut fabrics, which can be applied to the clothing industry, especially underwear and loungewear.

[0043] By adopting the above technical solution, the technical effect achieved by this invention is as follows:

[0044] 1. The spandex fiber prepared by this invention for use in fabrics that can be cut at will has excellent mechanical properties, including a strength of 2.01 to 2.18 d / g, a tensile stress of 13.0 to 13.7 cN, a breaking elongation of 522 to 557%, and a heat setting efficiency of 87 to 92%.

[0045] 2. The spandex prepared by this invention can achieve efficient heat setting below 175℃. On the one hand, it can optimize the elasticity of the fabric, making the elasticity more durable and stable, and it is not easy to deform even after multiple stretching, thus meeting the personalized needs of cutting at will. On the other hand, it enhances the dimensional stability of the fabric, preventing the fabric from deforming due to the release of internal stress of the spandex after cutting, ensuring that the shape after cutting meets expectations. It also has good adaptability. When blended with fibers with poor heat resistance such as cotton, silk, and wool, the fabric made from it has good dimensional stability during cutting, does not curl or unravel, and can be cut at will.

[0046] 3. The spandex prepared by this invention has good thermal stability. After heat treatment, the strength decreases by only about 2%, and the elongation at break decreases by no more than 10%. Detailed Implementation

[0047] The present invention will be further illustrated below with reference to specific embodiments.

[0048] Example 1: A spandex fiber for fabrics that can be cut at will, wherein the raw materials used to prepare the spandex fiber include: isocyanate, modified polyol, bifunctional compound, and composite auxiliaries.

[0049] The molar ratio of the isocyanate to the modified polyol is 1.9:1.

[0050] The isocyanate is 2,2'-bis(4-isobutylisopentyl)propane and 2,4-diphenylmethane diisocyanate in a molar ratio of 3:7.

[0051] The method for preparing the modified polyol is as follows:

[0052] S11, Activation

[0053] Dimeric glycerol was added to chloroform, followed by triethylamine and p-toluenesulfonyl chloride. The mixture was reacted at 3°C ​​for 14 hours to replace one terminal hydroxyl group of the dimeric glycerol with a p-toluenesulfonate group. After the reaction was completed, 1 mol / L hydrochloric acid solution was added to the reaction solution to extract the organic phase. Excess anhydrous sodium carbonate was added to the organic phase, and the mixture was stirred thoroughly and then filtered. The filtrate was added to excess anhydrous diethyl ether, and the mixture was stirred thoroughly to precipitate a white precipitate. The precipitate was then filtered, dried, and activated dimeric glycerol was obtained.

[0054] S12, silane modification

[0055] Activated glycerol was added to DMSO, followed by potassium trimethylsilaneol. The nucleophilic substitution reaction was carried out at room temperature for 9 hours. After the reaction was completed, the supernatant was collected by centrifugation and concentrated under reduced pressure to obtain the crude product. The crude product was extracted and dried with anhydrous sodium sulfate to obtain the glycerol-silane product.

[0056] S13, modification of pyridine

[0057] Dimeric glycerol-silane product was added to DMSO, followed by 2-pyridyl dithiocarbonate and potassium carbonate. The mixture was reacted at 45°C for 7 hours to graft pyridine groups onto the other terminal hydroxyl group of the dimeric glycerol-silane product. After the reaction was completed, the supernatant was collected by centrifugation and concentrated under reduced pressure to obtain a crude product. The crude product was extracted, dried with anhydrous sodium sulfate, and distilled under reduced pressure to obtain a modified polyol containing silane groups and pyridine groups.

[0058] The molar ratio of dipolyglycerol and p-toluenesulfonyl chloride in S11 is 1:2.2.

[0059] In S11, triethylamine is an alkaline catalyst, and the amount added is 1.5% of the mass of dipropylene glycol.

[0060] The amount of potassium trimethylsilanol added in S12 is 25% of the mass of activated dipropylene glycol.

[0061] The amount of 2-pyridyl dithiocarbonate added in S13 is 26% of the mass of the dipolyglycerol-silane product.

[0062] The amount of potassium carbonate added in S13 is to adjust the pH of the reaction system to 8.5.

[0063] The bifunctional compound is 2-methyl-1,5-pentanediamine, with a molar fraction of 45% of the total amount of isocyanate and modified polyol.

[0064] The composite additive is nano-silica and nano-calcium carbonate in a mass ratio of 3:1.5; the particle size of the nano-silica and nano-calcium carbonate is 50 nm.

[0065] The amount of the composite additive added is 1.2% of the total mass of the spandex raw material.

[0066] The second part of this invention provides a method for preparing spandex fibers for freely cut fabrics:

[0067] S21: After the modified polyol is dehydrated under reduced pressure at 120℃ for 2 hours, the composite additive is added and stirred evenly. The temperature is lowered to 80℃ and isocyanate is added. After stirring thoroughly, dibutyltin dilaurate is added and reacted for 2.5 hours. After cooling for 70 minutes, the prepolymer is obtained.

[0068] S22: Dissolve the prepolymer described in S21 in DMF to prepare a 20% concentration solution, add a bifunctional compound, react at 32°C for 2.5 h, and after aging, filtration, and degassing, obtain a spinning solution with a viscosity of 3600 poise (40°C).

[0069] S23: The spinning solution described in S22 is metered by a metering pump, extruded from the spinneret, and enters the spinning tunnel. After being heated, the solvent evaporates and solidifies into a filament bundle. After stretching, oiling, and heat setting, the spandex fiber is obtained.

[0070] The amount of dibutyltin dilaurate added in S21 is 0.1% of the total mass of the raw materials.

[0071] The ripening temperature in S22 is 60℃, and the time is 20h.

[0072] The temperature of the spinning channel in S23 is 250℃, and the speed is 750m / min.

[0073] The draw ratio in S23 is 2.5.

[0074] The heat setting temperature in S23 is 170℃, and the time is 50s.

[0075] Example 2: A spandex fiber for fabrics that can be cut at will, wherein the raw materials used to prepare the spandex fiber include: isocyanate, modified polyol, bifunctional compound, and composite auxiliaries.

[0076] The molar ratio of the isocyanate to the modified polyol is 2:1.

[0077] The isocyanate is 2,2'-bis(4-isobutylisopentyl)propane and 2,4-diphenylmethane diisocyanate in a molar ratio of 3:7.

[0078] The method for preparing the modified polyol is as follows:

[0079] S11, Activation

[0080] Dimeric glycerol was added to chloroform, followed by triethylamine and p-toluenesulfonyl chloride. The mixture was reacted at 0°C for 12 hours to replace one terminal hydroxyl group of the dimeric glycerol with a p-toluenesulfonate group. After the reaction was completed, 1 mol / L hydrochloric acid solution was added to the reaction solution to extract the organic phase. Excess anhydrous sodium carbonate was added to the organic phase, and the mixture was stirred thoroughly and then filtered. The filtrate was added to excess anhydrous diethyl ether, and the mixture was stirred thoroughly to precipitate a white precipitate. The precipitate was then filtered, dried, and activated dimeric glycerol was obtained.

[0081] S12, silane modification

[0082] Activated glycerol was added to DMSO, followed by potassium trimethylsilaneol. The nucleophilic substitution reaction was carried out at room temperature for 8 hours. After the reaction was completed, the supernatant was collected by centrifugation and concentrated under reduced pressure to obtain the crude product. The crude product was extracted and dried with anhydrous sodium sulfate to obtain the glycerol-silane product.

[0083] S13, modification of pyridine

[0084] Dimeric glycerol-silane product was added to DMSO, followed by 2-pyridyl dithiocarbonate and potassium carbonate. The mixture was reacted at 40°C for 6 hours to graft pyridine groups onto the other terminal hydroxyl group of the dimeric glycerol-silane product. After the reaction was completed, the supernatant was collected by centrifugation and concentrated under reduced pressure to obtain a crude product. The crude product was extracted, dried with anhydrous sodium sulfate, and distilled under reduced pressure to obtain a modified polyol containing silane groups and pyridine groups.

[0085] The molar ratio of dipolyglycerol to p-toluenesulfonyl chloride in S11 is 1:2.

[0086] In S11, triethylamine is an alkaline catalyst, and the amount added is 1% of the mass of dipropylene glycol.

[0087] The amount of potassium trimethylsilanol added in S12 is 20% of the mass of activated dipropylene glycol.

[0088] The amount of 2-pyridyl dithiocarbonate added in S13 is 23% of the mass of the dipolyglycerol-silane product.

[0089] The amount of potassium carbonate added in S13 is to adjust the pH of the reaction system to 8.

[0090] The bifunctional group is 2-methyl-1,5-pentanediamine, and its molar fraction is 40% of the total amount of isocyanate and modified polyol.

[0091] The composite additive is nano-silica and nano-calcium carbonate in a mass ratio of 3:1.5; the particle size of the nano-silica and nano-calcium carbonate is 100 nm.

[0092] The amount of the composite additive added is 1% of the total mass of the spandex raw material.

[0093] The method for preparing the spandex fiber for freely cut fabrics is as follows:

[0094] S21: After the modified polyol is dehydrated under reduced pressure at 115℃ for 3 hours, the composite additive is added and stirred evenly. The temperature is lowered to 85℃ and isocyanate is added. After stirring thoroughly, dibutyltin dilaurate is added and reacted for 2 hours. After cooling for 60 minutes, the prepolymer is obtained.

[0095] S22: Dissolve the prepolymer described in S21 in DMF to prepare a 20% concentration solution, add a bifunctional compound, react at 30°C for 3 hours, and after aging, filtration, and degassing, obtain a spinning solution with a viscosity of 3000 poise (40°C).

[0096] S23: The spinning solution described in S22 is metered by a metering pump, extruded from the spinneret, and enters the spinning tunnel. After being heated, the solvent evaporates and solidifies into a filament bundle. After stretching, oiling, and heat setting, the spandex fiber is obtained.

[0097] The amount of dibutyltin dilaurate added in S21 is 0.08% of the total mass of the raw materials.

[0098] The ripening temperature in S22 is 50℃, and the time is 12h.

[0099] The temperature of the spinning channel in S23 is 230℃, and the speed is 700m / min.

[0100] The draw ratio in S23 is 3.

[0101] The heat setting temperature in S23 is 170℃, and the time is 40s.

[0102] Example 3: A spandex fiber for fabrics that can be cut at will, wherein the raw materials used to prepare the spandex fiber include: isocyanate, modified polyol, bifunctional compound, and composite auxiliaries.

[0103] The molar ratio of the isocyanate to the modified polyol is 1.8:1.

[0104] The isocyanate is 2,2'-bis(4-isobutylisopentyl)propane and 2,4-diphenylmethane diisocyanate in a molar ratio of 3:7.

[0105] The method for preparing the modified polyol is as follows:

[0106] S11, Activation

[0107] Dimeric glycerol was added to chloroform, followed by triethylamine and p-toluenesulfonyl chloride. The mixture was reacted at 5°C for 16 hours to replace one terminal hydroxyl group of the dimeric glycerol with a p-toluenesulfonate group. After the reaction was completed, 1 mol / L hydrochloric acid solution was added to the reaction solution to extract the organic phase. Excess anhydrous sodium carbonate was added to the organic phase, and the mixture was stirred thoroughly and then filtered. The filtrate was added to excess anhydrous diethyl ether, and the mixture was stirred thoroughly to precipitate a white precipitate. The precipitate was then filtered, dried, and activated dimeric glycerol was obtained.

[0108] S12, silane modification

[0109] Activated glycerol was added to DMSO, followed by potassium trimethylsilaneol. The nucleophilic substitution reaction was carried out at room temperature for 10 h. After the reaction was completed, the supernatant was collected by centrifugation and concentrated under reduced pressure to obtain the crude product. The crude product was extracted and dried with anhydrous sodium sulfate to obtain the glycerol-silane product.

[0110] S13, modification of pyridine

[0111] Dimeric glycerol-silane product was added to DMSO, followed by 2-pyridyl dithiocarbonate and potassium carbonate. The mixture was reacted at 50°C for 8 hours to graft pyridine groups onto the other terminal hydroxyl group of the dimeric glycerol-silane product. After the reaction was completed, the supernatant was collected by centrifugation and concentrated under reduced pressure to obtain a crude product. The crude product was extracted, dried with anhydrous sodium sulfate, and distilled under reduced pressure to obtain a modified polyol containing silane groups and pyridine groups.

[0112] The molar ratio of dipolyglycerol and p-toluenesulfonyl chloride in S11 is 1:2.4.

[0113] In S11, triethylamine is an alkaline catalyst, and the amount added is 2% of the mass of dipropylene glycol.

[0114] The amount of potassium trimethylsilanol added in S12 is 30% of the mass of activated diglycerol.

[0115] The amount of 2-pyridyl dithiocarbonate added in S13 is 28% of the mass of the dipropylene glycol-silane product.

[0116] The amount of potassium carbonate added in S13 is to adjust the pH of the reaction system to 9.

[0117] The bifunctional group is 2-methyl-1,5-pentanediamine, and its molar fraction is 50% of the total amount of isocyanate and modified polyol.

[0118] The composite additive is nano-silica and nano-calcium carbonate in a mass ratio of 3:1.5; the particle size of the nano-silica and nano-calcium carbonate is 80 nm.

[0119] The amount of the composite additive added is 1.5% of the total mass of the spandex raw material.

[0120] The method for preparing the spandex fiber for freely cut fabrics is as follows:

[0121] S21: After the modified polyol is dehydrated under reduced pressure at 125℃ for 2.5h, the composite additive is added and stirred evenly. The temperature is lowered to 80℃ and isocyanate is added. After stirring thoroughly, dibutyltin dilaurate is added and reacted for 3h. After cooling for 80min, the prepolymer is obtained.

[0122] S22: Dissolve the prepolymer described in S21 in DMF to prepare a 20% concentration solution, add a bifunctional compound, react at 35°C for 2 hours, and after aging, filtration, and degassing, obtain a spinning solution with a viscosity of 4000 poise (40°C).

[0123] S23: The spinning solution described in S22 is metered by a metering pump, extruded from the spinneret, and enters the spinning tunnel. After being heated, the solvent evaporates and solidifies into a filament bundle. After stretching, oiling, and heat setting, the spandex fiber is obtained.

[0124] The amount of dibutyltin dilaurate added in S21 is 0.12% of the total mass of the raw materials.

[0125] The ripening temperature in S22 is 70℃, and the time is 12h.

[0126] The temperature of the spinning channel in S23 is 270℃, and the speed is 800m / min.

[0127] The draw ratio in S23 is 2.

[0128] The heat setting temperature in S23 is 175°C, and the time is 45 seconds.

[0129] Comparative Example 1: The difference between this example and Example 1 is that the isocyanate is 2,2'-bis(4-isobutylisopentyl)propane and 2,4-diphenylmethane diisocyanate in a molar ratio of 1:1. All other aspects are the same as in Example 1. This example serves as Comparative Example 1.

[0130] Comparative Example 2: The difference between this example and Example 1 is that the isocyanate is 2,2'-bis(4-isobutylisopentyl)propane and 2,4-diphenylmethane diisocyanate in a molar ratio of 2:6. All other aspects are the same as in Example 1, and this example serves as Comparative Example 2.

[0131] Comparative Example 3

[0132] Example 1, a representative example, was selected. Only the pyridine group was modified on the dipropylene glycol without modifying the silane, serving as the modified polyol. All other aspects were the same as in Example 1, serving as Comparative Example 3.

[0133] Comparative Example 4

[0134] Example 1, a representative example, was selected. Only the silane group on the dipropylene glycol was modified without modifying the pyridine group, serving as the modified polyol. All other aspects were the same as in Example 1, serving as Comparative Example 4.

[0135] The spandex fibers prepared in the examples and comparative examples were subjected to performance testing, and their strength reduction rate and elongation at break were tested after heat treatment at 140°C for two hours. The details are shown in Table 1.

[0136] Table 1

[0137]

[0138] As shown in Table 1, Examples 1-3 exhibit excellent mechanical properties, along with good heat setting efficiency and thermal stability. Comparative Examples 1 and 2 used isocyanates with different molar ratios, resulting in a slight decrease in all properties. This indicates that a molar ratio of 3:7 for 2,2'-bis(4-isobutylisopentyl)propane and 2,4-diphenylmethane diisocyanate provides better mechanical properties, heat resistance, and heat setting efficiency. Comparative Example 3 demonstrates that the silane groups on the modified polyol and the hydroxyl groups on the surface of the composite auxiliaries undergo chemical cross-linking, thus resulting in better mechanical properties and thermal stability. Comparative Example 4 shows that modified polyols with pyridine groups can improve the heat setting efficiency of fibers, lower the heat setting temperature, and also achieve good blending results with wool, silk, and other materials with poor heat resistance.

[0139] Unless otherwise specified, all proportions and percentages mentioned in this invention are mass proportions and mass percentages; all raw materials are commercially available.

[0140] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A spandex fiber for freely cut fabrics, characterized in that, The raw materials used in the preparation of the spandex fiber include: isocyanate, modified polyol, bifunctional compound, and composite auxiliaries; The modified polyol contains silane groups and pyridine groups.

2. The spandex fiber for freely cut fabrics according to claim 1, characterized in that, The molar ratio of the isocyanate to the modified polyol is 1.8 to 2:1; The isocyanate includes one or more of symmetrical isocyanates and asymmetrical isocyanates; The symmetrical isocyanate is selected from one or more of 4,4'-diphenylmethane diisocyanate, 2,2'-bis(4-isobutylisopentyl)propane, and 3,5'-diethyl-4-isobutylisopentylmethane; The asymmetric isocyanate is selected from one or more of 2,4-diphenylmethane diisocyanate, isoflurone diisocyanate, and 1,4-phenylene diisocyanate.

3. The spandex fiber for freely cut fabrics according to claim 1, characterized in that, The preparation method of the modified polyol includes activation, silane modification, and pyridine modification.

4. The spandex fiber for freely cut fabrics according to claim 3, characterized in that, The activation process involves adding dimeric glycerol to chloroform, then adding triethylamine and p-toluenesulfonyl chloride, reacting at 0–5°C for 12–16 h, extracting the organic phase with 1 mol / L hydrochloric acid solution after the reaction, adding excess anhydrous sodium carbonate to the organic phase, stirring thoroughly, filtering, adding excess anhydrous diethyl ether to the filtrate, stirring thoroughly to precipitate a white precipitate, filtering and drying to obtain activated dimeric glycerol. The molar ratio of dipolyglycerol to p-toluenesulfonyl chloride is 1:2 to 2.4; The triethylamine is an alkaline catalyst, and the amount added is 1 to 2% of the mass of dipropylene glycol.

5. The spandex fiber for freely cut fabrics according to claim 3, characterized in that, The modification of the silane is as follows: activated diglycerol is added to DMSO, then potassium trimethylsilane is added, and the nucleophilic substitution reaction is carried out at room temperature for 8-10 hours. After the reaction is completed, the supernatant is collected by centrifugation and concentrated under reduced pressure to obtain the crude product. The crude product is extracted and dried with anhydrous sodium sulfate to obtain the diglycerol-silane product. The amount of potassium trimethylsilanol added is 20-30% of the mass of activated dipropylene glycol.

6. The spandex fiber for freely cut fabrics according to claim 3, characterized in that, The modification of pyridine is as follows: adding dipolyglycerol-silane product to DMSO, then adding 2-pyridyl dithiocarbonate and potassium carbonate, reacting at 40-50℃ for 6-8 hours, centrifuging and taking the supernatant to concentrate under reduced pressure to obtain crude product, and extracting, drying with anhydrous sodium sulfate and distilling under reduced pressure to obtain modified polyol containing silane groups and pyridine groups. The amount of 2-pyridyl dithiocarbonate added in S13 is 23-28% of the mass of the dipropylene glycol-silane product; The amount of potassium carbonate added in S13 is to adjust the pH of the reaction system to 8-9.

7. The spandex fiber for arbitrary cutting of fabric according to claim 1, characterized in that, The bifunctional compound is one or more selected from 2-methyl-1,5-pentanediamine, 1,4-cyclohexanediol, neopentanediol, diethanolamine, and 3,5-dimethylthiotoluenediamine.

8. The spandex fiber for freely cut fabrics according to claim 1, characterized in that, The composite additive is one or more of sodium benzoate, nano silica, and nano calcium carbonate; the amount of the composite additive added is 1 to 1.5% of the total mass of the spandex raw material.

9. A method for preparing spandex fibers for freely cut fabrics, characterized in that, The preparation method includes the following steps: S21: After the modified polyol is dehydrated under reduced pressure at 115-125℃ for 2-3 hours, the composite additive is added and stirred evenly. The temperature is lowered to 80-85℃ and isocyanate is added. After stirring thoroughly, dibutyltin dilaurate is added and reacted for 2-3 hours. After cooling for 60-80 minutes, the prepolymer is obtained. S22: Dissolve the prepolymer described in S21 in DMF to prepare a 20% concentration solution, add a bifunctional compound, react at 30-35℃ for 2-3 hours, and after aging, filtration, and degassing, obtain a spinning solution with a viscosity of 3000-4000 poise (40℃). S23: The spinning solution described in S22 is metered by a metering pump, extruded from the spinneret, and enters the spinning tunnel. After being heated, the solvent evaporates and solidifies into a filament bundle. After stretching, oiling, and heat setting, the spandex fiber is obtained. The amount of dibutyltin dilaurate added in S21 accounts for 0.08-0.12% of the total mass of the raw materials; The heat setting temperature in S23 is 170-175℃, and the time is 40-50s.

10. A spandex fiber for arbitrary cutting of fabrics prepared by the method of claim 9, characterized in that, The spandex fiber can be used in the clothing industry, especially in underwear and loungewear.

Images