Porous and easily dyeable polyester fibers and their preparation methods

Abstract

This invention provides a porous, easily dyeable polyester fiber and its preparation method. The preparation process involves adding ethylene glycol, purified terephthalic acid, and a catalyst in a predetermined ratio to a high-pressure reactor for esterification. Next, a functional third monomer is added to the high-pressure reactor, and the reaction continues. After esterification, a polycondensation reaction is first carried out for a predetermined time under low vacuum, followed by continued vacuuming and then a polycondensation reaction for a predetermined time under high vacuum. Nitrogen gas is introduced for pressurization and discharge. The resulting liquid is water-cooled and pelletized to obtain a functional island-phase polyester masterbatch. The functional island-phase polymer is then blended with an incompatible marine polymer in a predetermined ratio, and melt-spun to obtain island-island fibers. Finally, the marine polymer is removed using an organic solvent to obtain the porous, easily dyeable polyester fiber. This invention achieves high-dyeing-performance polyester fibers through the synergistic effect of the rich and uniform pore structure of the porous, easily dyeable polyester fiber and the specific functional island-phase polyester masterbatch molecular structure.

Description

Technical Field

[0001] This invention relates to the field of fiber dyeing technology, and in particular to a porous, easily dyeable polyester fiber and its preparation method. Background Technology

[0002] With the development of science and technology and the improvement of people's living standards, consumers have increasingly higher requirements for clothing, demanding not only comfort but also vibrant colors and a natural feel. Therefore, chemical fibers need to be dyed in various colors to meet the increasingly competitive market demand. Currently, the main dyeing methods for fibers are high-temperature high-pressure dyeing and low-temperature dyeing. Low-temperature dyeing is usually carried out at lower temperatures. However, polyester (PET) fibers are highly hydrophobic, have a regular macromolecular chemical structure, and are prone to crystallization. Their high crystallinity and orientation make it difficult for dyes to penetrate the amorphous regions of the fiber. Furthermore, the presence of benzene rings on PET macromolecules and the lack of dye sites further complicate the dyeing process. Therefore, polyester fibers typically require high-temperature, high-pressure dyeing with a carrier, which not only complicates the dyeing process and results in poor dyeing quality, but also pollutes the environment with commonly used carriers such as phenol, chlorobenzene, biphenyl, and amines. Additionally, high-temperature high-pressure dyeing requires complex equipment, is costly, and easily generates static electricity during processing.

[0003] To better achieve the dyeing of polyester fibers, patent application number CN201811614008.1 discloses an easily dyeable porous modified polyester fiber and its preparation method. The method involves using a porous spinneret to melt-process modified polyester to obtain the easily dyeable porous modified polyester fiber using the FDY process. The preparation method of the modified polyester is as follows: terephthalic acid, ethylene glycol, a silicon-containing diol in the main chain, 2,2,3,4,5,5-hexamethyl-3,4-hexanediol, and Sb2O3 powder modified with metal oxides are mixed evenly and then subjected to esterification and polycondensation reactions to obtain the easily dyeable porous modified polyester fiber. The silicon-containing diol in the main chain is dimethylsilanediol, dimethyldiphenyldisiloxanediol, or tetramethyldisiloxanediol. This method of preparing polyester is relatively complex, and the dyeing temperature is relatively high. To a certain extent, the molecular structure of the fiber may be damaged, its strength reduced, thus affecting the durability of the fabric, and also changing the appearance and feel of the fiber.

[0004] In view of this, it is necessary to design an improved porous, easily dyeable polyester fiber and its preparation method to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a porous, easily dyeable polyester fiber and its preparation method. First, ethylene glycol, purified terephthalic acid, and a functional third monomer are subjected to an esterification reaction to obtain a functional island-phase polyester masterbatch with a specific structure. Then, utilizing the characteristics of island-state fibers, the functional island-phase polymer and the marine polymer are blended and melt-spun, and the marine polymer in the island-state fiber is removed, forming a uniform porous structure on the surface and inside of the fiber, increasing the specific surface area. Next, the porous fiber is dyed. Under the synergistic effect of the rich and uniform porous structure of the porous, easily dyeable polyester fiber and the molecular structure of the specific functional island-phase polyester masterbatch, a polyester fiber with high dyeing performance is obtained.

[0006] To achieve the above-mentioned objective, this invention provides a method for preparing porous, easily dyeable polyester fibers, comprising the following steps:

[0007] S1. Ethylene glycol, purified terephthalic acid and catalyst in a predetermined ratio are added to a high-pressure reactor and esterification reaction is carried out under a nitrogen atmosphere; then a functional third monomer is added to the high-pressure reactor and the reaction continues under a nitrogen atmosphere;

[0008] S2. After the esterification reaction is completed, the pressure is released to normal pressure, and the temperature is increased and the pressure is decreased. First, a polycondensation reaction of a preset time is carried out in the low vacuum stage, then the vacuum is continued, and then a polycondensation reaction of a preset time is carried out in the high vacuum stage. Nitrogen gas is introduced to pressurize and discharge the material. The liquid is cooled by water and pelletized to obtain functional island phase polyester masterbatch.

[0009] S3. The functional island polymer and the incompatible marine polymer are blended in a preset ratio, heated and melted, and then extruded and spun into fibers through a spinneret. After cooling, oiling, stretching, and heat setting, island fibers are obtained. Then, the marine polymer in the island fibers is removed with an organic solvent to obtain porous and easily dyeable polyester fibers.

[0010] As a further improvement of the present invention, in step S1, the functional third monomer includes one or more of compounds containing amide groups, polyols, and ester compounds.

[0011] As a further improvement of the present invention, the functional third monomer includes one or more of ethylene glycol isophthalate-5-sulfonate, polyamide, and tetrahydrofuran.

[0012] As a further improvement of the present invention, in step S1, the mass ratio of ethylene glycol to purified terephthalic acid is (1-1.5):1; the mass of the catalyst is 0.01%-1% of the total mass of ethylene glycol and purified terephthalic acid; the pressure of the esterification reaction is 300-400 kPa, and the temperature of the esterification reaction is 250-270°C.

[0013] The amount of the functional third monomer added accounts for 5%-15% of the total mass of the ethylene glycol and purified terephthalic acid. The reaction continues at a pressure of 300-400 kPa and a temperature of 250-270 °C.

[0014] As a further improvement of the present invention, in step S3, the mass ratio of the functional island polymer to the incompatible marine polymer is (1-3):(7-9); the marine polymer is one or more of polystyrene, polyethylene, and cellulose acetate.

[0015] As a further improvement of the present invention, the organic solvent is one or more of toluene, xylene, or acetone.

[0016] As a further improvement of the present invention, the heating and melting temperature is 260-280°C, the spinning speed is 3500-4000 m / min, the draw ratio is 3-5 times, and the heat setting temperature is 20-40°C.

[0017] As a further improvement of the present invention, in step S2, the pressure of the polycondensation reaction in the low vacuum stage is -(10-30) kPa, the reaction temperature is 275-285°C, and the reaction time is 10-20 min; the pressure of the polycondensation reaction in the high vacuum stage is -(90-100) kPa, the reaction temperature is 270-285°C, and the reaction time is 20-40 min.

[0018] As a further improvement to the present invention, the following steps are also included:

[0019] S4. The porous, easily dyeable polyester fiber is dyed in a dye solution with a mass concentration of 1%-5% disperse dye at a temperature of 60-80°C for 30-60 minutes.

[0020] The present invention also provides a porous, easily dyeable polyester fiber, which is prepared by the above-described method for preparing porous, easily dyeable polyester fibers.

[0021] The beneficial effects of this invention are:

[0022] (1) The method for preparing porous, easily dyeable polyester fibers provided by this invention first involves esterifying ethylene glycol, purified terephthalic acid, and a functional third monomer to bond the functional third monomer fragment structure into the polyester, thereby obtaining a functional island-phase polyester masterbatch. Then, utilizing the characteristics of island-island fibers, the functional island-phase polymer and the marine polymer are blended and melt-spun. The island-island fibers with a specific structure are placed in an organic solvent, allowing the marine polymer in the island-island fibers to dissolve in the organic solvent, forming a uniform porous structure on the surface and inside of the fiber, increasing the specific surface area and providing favorable conditions for subsequent dyeing processes. The porous fibers are then dyed. Under the synergistic effect of the rich and uniform porous structure of the porous, easily dyeable polyester fibers and the molecular structure of the specific functional island-phase polyester masterbatch, polyester fibers with high dyeing performance are obtained.

[0023] (2) This invention utilizes the island fiber method to prepare porous polyester fibers, which have good dyeing properties and allow dyes to easily penetrate the fiber interior, thereby achieving better coloring results. Simultaneously, during the dyeing process, the dye adsorption and diffusion rates on and inside the porous fiber are relatively fast, which helps improve dyeing uniformity and color saturation. The process is cost-effective and has broad application prospects. Attached Figure Description

[0024] Figure 1 The graph shows a comparison of the K / S values ​​of the porous, easily dyeable polyester fibers prepared in Example 1 and Comparative Example 18 after dyeing with Disperse Blue, Disperse Yellow, and Disperse Red, respectively. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0027] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0028] This invention provides a method for preparing porous, easily dyeable polyester fibers, comprising the following steps:

[0029] S1. Esterification reaction:

[0030] Ethylene glycol, purified terephthalic acid, and catalyst were added to a high-pressure reactor in a predetermined ratio and mixed evenly. The mixture was then purged with nitrogen three times to create a nitrogen atmosphere in the reactor. The esterification reaction was carried out under nitrogen atmosphere and slightly positive pressure conditions, which allowed ethylene glycol and purified terephthalic acid to bond together. The esterification reaction ended when the amount of water discharged during the esterification reaction reached 96% of the theoretical value, yielding a polyester prepolymer.

[0031] Specifically, the mass ratio of ethylene glycol to purified terephthalic acid is (1-1.5):1; the mass of the catalyst is 0.01%-1% of the total mass of ethylene glycol and purified terephthalic acid; the pressure of the esterification reaction is 300-400 kPa, the temperature of the esterification reaction is 250-270 °C; and the catalyst is Sb2O3 powder.

[0032] After depressurizing to atmospheric pressure, the functional third monomer is added to the high-pressure reactor and mixed evenly. The reactor is then purged with nitrogen three times to create a nitrogen atmosphere. The reaction continues under nitrogen atmosphere and slightly positive pressure to further bond the polyester prepolymer and the functional third monomer. The reaction ends when the amount of water distilled from the reaction reaches 96% of the theoretical value, yielding the functional prepolymer.

[0033] Specifically, the amount of the functional third monomer added accounts for 5%-15% of the total mass of ethylene glycol and purified terephthalic acid, and the pressure for continued reaction is 300-400 kPa and the temperature is 250-270 °C.

[0034] The functional third monomer includes one or more compounds containing amide groups, polyols, and ester compounds. Ester compounds are preferably compounds containing both ester and sulfonic acid groups. Specifically, the functional third monomer includes one or more of polyethylene isophthalate-5-sulfonate, polyamide, and tetrahydrofuran.

[0035] S2. Condensation reaction:

[0036] After the esterification reaction is completed, the pressure is released to atmospheric pressure, and the temperature is increased and the pressure is decreased. First, a polycondensation reaction is carried out in the low vacuum stage for a preset time. Then, the vacuum is continued, and a polycondensation reaction is carried out in the high vacuum stage for a preset time. The reaction endpoint is determined by the change in stirring current. When the reaction endpoint is reached, stirring is stopped, and nitrogen is introduced to pressurize and eliminate the vacuum. As nitrogen is continuously added, the material is pressurized and discharged. The liquid is cooled by water and pelletized to obtain functional island phase polyester masterbatch.

[0037] Specifically, the pressure of the polycondensation reaction in the low vacuum stage is -(10-30) kPa, the reaction temperature is 275-285℃, and the reaction time is 10-20 min; the pressure of the polycondensation reaction in the high vacuum stage is -(90-100) kPa, the reaction temperature is 270-285℃, and the reaction time is 20-40 min.

[0038] In this process, ethylene glycol, purified terephthalic acid, and the functional third monomer further bond with each other to obtain a functional island-phase polyester masterbatch. The presence of the functional third monomer fragment in the functional island-phase polyester masterbatch molecular chain not only increases the hydrophilicity of the subsequently produced fiber or weakens the rigidity of the macromolecular chain and increases the amorphous region, making it easier for dyes to enter the fiber and thus significantly improving the dyeing performance of the fiber; it also changes the gap between the functional island-phase polyester masterbatch molecular chains, further making it easier for dyes to enter the fiber and thus improving the dyeing performance of the fiber; in addition, it can also improve the fiber preparation process.

[0039] In some embodiments, the preparation of functional island-phase nylon masterbatch or functional island-phase polyolefin masterbatch can be achieved simply by replacing ethylene glycol and purified terephthalic acid with the corresponding first and second monomers. Other steps are basically similar and will not be described in detail here.

[0040] S3. Spinning:

[0041] The functional island polymer prepared in step S2 is blended with the incompatible marine polymer in a preset ratio, heated and melted, and then transported to a melt spinning machine through an independent flow channel. The nascent filament is then spun and formed by extrusion through a spinneret. The nascent filament is then cooled, oiled, drawn, and heat-set to obtain island-island fiber. The marine polymer in the island-island fiber is then removed with an organic solvent to obtain porous, easily dyeable polyester fiber.

[0042] Specifically, the mass ratio of the functional island polymer to the incompatible marine polymer is (1-3):(7-9); the marine polymer is one or more of polystyrene, polyethylene, and cellulose acetate.

[0043] The heating and melting temperature is 260-280℃, the spinning speed is 3500-4000m / min, the draw ratio is 3-5 times, and the heat setting temperature is 20-40℃.

[0044] The organic solvent is one or more of toluene, xylene, or acetone.

[0045] Island-island fiber is a high-functional fiber composed of a "marine phase" and an "island phase," where the marine phase component is soluble polyester and the island phase component is ordinary polyester. This invention utilizes the characteristics of island-island fiber to dissolve the marine phase component under a specific process, leaving the island phase component to obtain porous fibers with a specific structure. Specifically, in this process, functional island-phase polymers and marine-phase polymers are uniformly dispersed in a molten spinning solution and extruded through a spinneret to form nascent filaments. After cooling, oiling, stretching, and heat setting, the functional island-phase polymers and marine-phase polymers in the fiber are uniformly and firmly intercalated, resulting in island-island fibers with a specific structure. Next, the island-island fibers with this specific structure are placed in an organic solvent, allowing the marine-phase polymers in the fiber to dissolve, forming a uniform porous structure on the surface and inside the fiber. After drying, stable porous, easily dyeable polyester fibers are obtained. The resulting porous, easily dyeable polyester fibers are covered with surface depressions, increasing the specific surface area and providing favorable conditions for subsequent dyeing processes.

[0046] S4. Dyeing:

[0047] Porous, easily dyeable polyester fibers are dyed in a dye bath with a mass concentration of 1%-5% disperse dye at a temperature of 60-80℃ for 30-60 minutes.

[0048] In this process, firstly, the porous, easily dyeable polyester fiber has a large specific surface area, making it easier for disperse dyes to be adsorbed onto it. Then, the uniform and abundant pore structure on and inside the porous, easily dyeable polyester fiber allows a large amount of disperse dye to enter its pores. Simultaneously, the functional third monomer fragments in the functional island-phase polyester masterbatch molecular chains can increase the fiber's hydrophilicity or weaken the rigidity of the macromolecular chains, increasing the amorphous region. They can also alter the gaps between the functional island-phase polyester masterbatch molecular chains, making it easier for dyes to enter the fiber, thus significantly improving the fiber's dyeing performance. Finally, through the synergistic effect of the rich and uniform pore structure of the porous, easily dyeable polyester fiber and the specific functional island-phase polyester masterbatch molecular structure, a polyester fiber with high dyeing performance is obtained.

[0049] The present invention also provides a porous, easily dyeable polyester fiber, which is prepared by the above-described method for preparing porous, easily dyeable polyester fibers.

[0050] The present invention will now be described in detail through specific embodiments.

[0051] Example 1

[0052] A method for preparing porous, easily dyeable polyester fiber includes the following steps:

[0053] S1. Esterification reaction:

[0054] Ethylene glycol, purified terephthalic acid, and Sb2O3 catalyst in a predetermined ratio were added to a 5L high-pressure reactor and mixed evenly. The reactor was then purged with nitrogen three times to create a nitrogen atmosphere. The esterification reaction was carried out under nitrogen atmosphere and slightly positive pressure conditions, which allowed ethylene glycol and purified terephthalic acid to bond together. The esterification reaction ended when the amount of water distilled out during the esterification reaction reached 96% of the theoretical value, yielding a polyester prepolymer.

[0055] Specifically, the mass ratio of ethylene glycol, purified terephthalic acid, and catalyst is 1.2:1; the mass of catalyst is 0.01% of the total mass of ethylene glycol and purified terephthalic acid; the pressure of the esterification reaction is 350 kPa, and the temperature of the esterification reaction is 260 °C.

[0056] After depressurizing to atmospheric pressure, the functional third monomer is added to the high-pressure reactor and mixed evenly. The reactor is then purged with nitrogen three times to create a nitrogen atmosphere. The reaction continues under nitrogen atmosphere and slightly positive pressure to further bond the polyester prepolymer and the functional third monomer. The reaction ends when the amount of water distilled from the reaction reaches 96% of the theoretical value, yielding the functional prepolymer.

[0057] Specifically, the amount of the functional third monomer added accounts for 10% of the total mass of ethylene glycol and purified terephthalic acid, and the reaction continues at a pressure of 350 kPa and a temperature of 265 °C.

[0058] The functional third monomer is sodium ethylene glycol isophthalate-5-sulfonate.

[0059] S2. Condensation reaction:

[0060] After the esterification reaction is completed, the pressure is released to atmospheric pressure, and the temperature is increased and the pressure is decreased. First, a polycondensation reaction is carried out in the low vacuum stage for a preset time. Then, the vacuum is continued, and a polycondensation reaction is carried out in the high vacuum stage for a preset time. The reaction endpoint is judged according to the change of stirring current. When the reaction endpoint is reached, stirring is stopped, nitrogen is introduced to pressurize and eliminate the vacuum. As nitrogen is continuously added, the material is pressurized and discharged. The liquid is cooled by water and pelletized to obtain functional island phase polyester masterbatch.

[0061] Specifically, the pressure of the polycondensation reaction in the low vacuum stage is -20 kPa, the reaction temperature is 280°C, and the reaction time is 15 min; the pressure of the polycondensation reaction in the high vacuum stage is -100 kPa, the reaction temperature is 280°C, and the reaction time is 30 min.

[0062] S3. Spinning:

[0063] The functional island polymer prepared in step S2 is blended with the incompatible marine polymer in a preset ratio, heated and melted, and then transported to a melt spinning machine through an independent flow channel. The nascent filament is obtained by extrusion spinning through a spinneret. The nascent filament is then cooled, oiled, drawn, and heat-set to obtain island-island fiber. Toluene is then used to remove the marine polymer from the island-island fiber to obtain porous, easily dyeable polyester fiber.

[0064] Specifically, the mass ratio of the functional island polymer to the incompatible marine polymer is 2:8; the marine polymer is polyethylene.

[0065] The heating and melting temperature is 273℃, the spinning speed is 3600m / min, the draw ratio is 4 times, and the heat setting temperature is 30℃.

[0066] S4. Dyeing:

[0067] Porous, easily dyeable polyester fibers were dyed at 70°C in a 3% (w / w) disperse red dye solution for 45 minutes.

[0068] Examples 2-3 and Comparative Examples 1-2

[0069] A method for preparing porous, easily dyeable polyester fiber differs from Example 1 in that the amount of functional third monomer added in step S1 is different, while the rest is roughly the same as in Example 1, and will not be repeated here.

[0070] The porous, easily dyeable polyester fibers obtained in Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests, and the results are shown in Table 1.

[0071] The K / S value test is specifically conducted by using a colorimeter under conditions of D65 light source, 10° viewing angle, 8mm colorimetric aperture, including specular light and 100% UV light filtering to determine the K / S value of the fiber.

[0072] The staining rate was obtained by measuring the change in the K / S value before and after staining the sample.

[0073] The tensile strength test is conducted as follows: Prepare polyester fiber samples to be tested, ensuring that the samples are of uniform length and free from obvious damage or defects. Clamp the fiber samples securely using fixtures, ensuring that the stress points of the samples are within the fixtures. Set appropriate test parameters on the tensile testing machine, and then begin applying a load, gradually increasing the tensile force until the sample breaks. During the test, record the tensile force and elongation data in real time. Once the sample breaks, stop the test and record the maximum load-bearing capacity and maximum elongation. Calculate the tensile strength of the polyester fiber using the test data. Tensile strength is usually expressed as the maximum load-bearing capacity per unit area, i.e., tensile strength = maximum load-bearing capacity / sample cross-sectional area.

[0074] The elongation at break test is conducted as follows: Prepare a polyester fiber sample of a certain length. Clamp the sample using a fixture, ensuring a secure grip, uniform force distribution, and no skewing during the tensile test. Set appropriate test parameters on the tensile testing machine and begin the test, gradually increasing the load until the sample breaks. Record the tensile force and elongation data in real time during the test. Calculate the elongation at break of the polyester fiber based on the test data. Elongation at break is usually expressed as a percentage, and the formula is: Elongation at break = (Length at break - Initial length) / Initial length * 100%.

[0075] Table 1. Properties of porous, easily dyeable polyester fibers obtained in Examples 1-3 and Comparative Examples 1-2

[0076]

[0077] As shown in Table 1, with the increase of the content of the functional third monomer, the K / S value, dyeing rate, and breaking strength of the porous easy-to-dye polyester fiber all show a trend of first increasing and then decreasing, while the breaking elongation fluctuates within a certain range. When the content of the functional third monomer is 10%, the porous easy-to-dye polyester fiber obtained has the best performance in all aspects. This may be because, at this ratio, the functional island-phase polyester masterbatch obtained by the mutual bonding of ethylene glycol, purified terephthalic acid, and the functional third monomer can be better spun with the marine polymer to obtain island-island fibers with special structures. Furthermore, with the removal of the marine polymer, porous easy-to-dye polyester fibers with excellent structures are obtained.

[0078] Example 4 and Comparative Example 3

[0079] A method for preparing porous, easily dyeable polyester fiber differs from Example 1 in that the mass ratio of ethylene glycol and purified terephthalic acid in step S1 is different. Otherwise, it is largely the same as Example 1 and will not be described again here.

[0080] The porous, easily dyeable polyester fibers obtained in Example 4 and Comparative Example 3 were subjected to performance tests, and the results are shown in Table 2.

[0081] Table 2. Properties of the porous, easily dyeable polyester fibers obtained in Example 4 and Comparative Example 3.

[0082]

[0083] Table 2 shows that the porous, easily dyeable polyester fiber exhibits the best dyeing performance when the mass ratio of ethylene glycol to purified terephthalic acid is 1.2:1. When the content of purified terephthalic acid is relatively high, the performance of the resulting porous, easily dyeable polyester fiber is relatively poor. This may be because a relatively high content of purified terephthalic acid leads to acid residue after the reaction, which affects the inter-bonding structure of ethylene glycol, purified terephthalic acid, and the functional third monomer, thus affecting the structure and performance of the final porous, easily dyeable polyester fiber. Therefore, an excess of alcohol should be used in this esterification reaction to promote the acid-alcohol esterification reaction, reduce the formation of by-products, and improve the purity of the product.

[0084] Examples 5-8 and Comparative Examples 4-7

[0085] A method for preparing porous, easily dyeable polyester fiber differs from Example 1 in that the conditions of the polycondensation reaction in the low vacuum stage of step S2 are different. Otherwise, it is largely the same as Example 1 and will not be described again here.

[0086] The porous, easily dyeable polyester fibers obtained in Examples 5-8 and Comparative Examples 4-7 were subjected to performance tests, and the results are shown in Table 3.

[0087] Table 3. Properties of porous, easily dyeable polyester fibers obtained in Examples 5-8 and Comparative Examples 4-7

[0088]

[0089] As shown in Table 3, changing the temperature and pressure of the polycondensation reaction in the low vacuum stage alters the properties of the porous, easily dyeable polyester fiber. The porous, easily dyeable polyester fiber obtained at a pressure of -20 kPa and a temperature of 280 °C exhibits the best dyeing performance. This indicates that changes in temperature and pressure during the low vacuum stage affect the polycondensation reaction, thereby influencing the inter-bonding structure of ethylene glycol, purified terephthalic acid, and the functional third monomer, and consequently affecting the structure and properties of the final porous, easily dyeable polyester fiber.

[0090] Comparative Examples 8-9

[0091] A method for preparing porous, easily dyeable polyester fiber differs from Example 1 in that the conditions for the polycondensation reaction in the high vacuum stage of step S2 are different. Otherwise, it is largely the same as Example 1 and will not be described again here.

[0092] The porous, easily dyeable polyester fibers obtained in Examples 8-9 were subjected to performance tests, and the results are shown in Table 4.

[0093] Table 4 shows the properties of the porous, easily dyeable polyester fibers obtained in Comparative Examples 8-9.

[0094]

[0095] As shown in Table 4, changing the temperature and pressure of the polycondensation reaction in the high vacuum stage will change the properties of the porous and easily dyeable polyester fiber. When the polycondensation reaction pressure in the high vacuum stage is -100 kPa and the temperature is 280°C, the resulting porous and easily dyeable polyester fiber has the best dyeing performance.

[0096] Examples 9-10 and Comparative Examples 10-11

[0097] A method for preparing porous, easily dyeable polyester fiber differs from Example 1 in that the mass ratio of the functional island polymer to the incompatible marine polymer is different in step S3. Otherwise, it is largely the same as Example 1 and will not be repeated here.

[0098] The porous, easily dyeable polyester fibers obtained in Examples 9-10 and Comparative Examples 10-11 were subjected to performance tests, and the results are shown in Table 5.

[0099] Table 5. Properties of the porous, easily dyeable polyester fibers obtained in Examples 9-10 and Comparative Examples 10-11

[0100]

[0101] Table 5 shows that when the mass ratio of functional island polymer to incompatible marine polymer varies within a certain range, the properties of the resulting porous, easily dyeable polyester fiber fluctuate within a range. The porous, easily dyeable polyester fiber exhibits the best dyeing performance when the mass ratio of functional island polymer to incompatible marine polymer is 2:8. However, when the mass ratios of functional island polymer and incompatible marine polymer are the same, or when the content of functional island polymer is higher, all properties of the porous, easily dyeable polyester fiber decrease significantly. This may be because a relatively high content of functional island polymer leads to uneven internal fiber structure, reducing fiber strength and durability; it also results in rough fiber surface, affecting fiber softness and hand feel, and reducing comfort; furthermore, it affects the structure of the resulting porous, easily dyeable polyester fiber, thus impacting its properties.

[0102] Examples 11-12 and Comparative Examples 12-13

[0103] A method for preparing porous, easily dyeable polyester fiber differs from Example 1 in that the stretching speed in the melt spinning process of step S3 is different; otherwise, it is largely the same as Example 1 and will not be described again here.

[0104] The porous, easily dyeable polyester fibers obtained in Examples 11-12 and Comparative Examples 12-13 were subjected to performance tests, and the results are shown in Table 6.

[0105] Table 6. Properties of the porous, easily dyeable polyester fibers obtained in Examples 11-12 and Comparative Examples 12-13.

[0106]

[0107] As shown in Table 6, with the increase of the draw ratio in the melt spinning process, the K / S value, dyeing rate, breaking strength, and breaking elongation of the obtained porous, easily dyeable polyester fibers all show a trend of first increasing and then decreasing. When the draw speed in the melt spinning process is 4, the obtained porous, easily dyeable polyester fibers have the best dyeing performance. This is mainly because an excessively high draw ratio may cause the molecular chains inside the fiber to be arranged too tightly, resulting in uneven fiber strength, excessive stress, and easy local breakage, thus reducing the stability of the fiber. On the other hand, a too low draw ratio will result in an insufficiently ordered arrangement of molecular chains inside the fiber, reducing the fiber's strength and tensile properties. This will make the fiber surface less smooth, affecting the fiber's appearance quality and hand feel, and consequently affecting various properties.

[0108] Examples 13-14 and Comparative Examples 14-15

[0109] A method for preparing porous, easily dyeable polyester fiber differs from Example 1 in that the dyeing temperature in step S4 is different, while the rest is largely the same as in Example 1, and will not be repeated here.

[0110] The porous, easily dyeable polyester fibers obtained in Examples 13-14 and Comparative Examples 14-15 were subjected to performance tests, and the results are shown in Table 7.

[0111] Table 7. Properties of the porous, easily dyeable polyester fibers obtained in Examples 13-14 and Comparative Examples 14-15

[0112]

[0113] As shown in Table 7, the properties of the resulting porous, easily dyeable polyester fibers fluctuate within a certain range when the dyeing temperature varies. The best dyeing performance is achieved when the dyeing temperature is 70℃. Dyeing results are significantly worse when the dyeing temperature is too low or too high.

[0114] Examples 15-16

[0115] A method for preparing porous, easily dyeable polyester fiber differs from Example 1 in that the type of disperse dye used in step S4 is different, while the rest is largely the same as in Example 1 and will not be repeated here.

[0116] The porous, easily dyeable polyester fibers obtained in Examples 15-16 were subjected to performance tests, and the results are shown in Table 8.

[0117] Table 8. Properties of the porous, easily dyeable polyester fibers obtained in Examples 15-16

[0118]

[0119] As shown in Table 8, porous, easily dyeable polyester fibers can exhibit excellent performance for different dyes.

[0120] Comparative Example 16

[0121] A method for preparing porous, easily dyeable polyester fiber differs from Example 1 in that, in step S1, ethylene glycol, purified terephthalic acid, Sb2O3 catalyst, and a functional third monomer are directly blended. The other steps are largely the same as in Example 1 and will not be repeated here.

[0122] Comparative Example 17

[0123] A method for preparing porous, easily dyeable polyester fiber differs from Example 1 in that no functional third monomer is added in step S1. The rest is largely the same as in Example 1 and will not be described again here.

[0124] Comparative Example 18

[0125] A method for preparing porous, easily dyeable polyester fiber differs from Example 1 in that, in step S3, alkali solution is used instead of toluene. The rest is largely the same as in Example 1 and will not be described again here.

[0126] Comparative Example 19

[0127] A method for preparing porous, easily dyeable polyester fiber differs from Example 1 in that the functional third monomer in step S1 is replaced with graphene, which can promote dyeing. The rest is largely the same as in Example 1 and will not be described again here.

[0128] Comparative Example 20

[0129] A method for preparing porous, easily dyeable polyester fiber differs from Example 1 in that the raw materials used for esterification and polycondensation reactions are different, i.e., the preparation process of the functional island-phase polyester masterbatch is different. The preparation method of the functional island-phase polyester masterbatch is as follows: first, a modified polyester is prepared according to the method of Example 2 in application number CN201811614008.1, then the functional island-phase polyester masterbatch is obtained, and then the process of steps S3 and S4 in Example 1 of this invention is carried out.

[0130] The porous, easily dyeable polyester fibers obtained in Comparative Examples 16-20 were subjected to performance tests, and the results are shown in Table 9.

[0131] Table 9. Properties of the porous, easily dyeable polyester fibers obtained in Example 1 and Comparative Examples 16-20

[0132]

[0133] As can be seen from the data of Comparative Example 16, when the three monomers and catalyst are directly blended, the various properties of the resulting porous and easily dyeable polyester fiber are significantly worse. This may be because direct blending affects the molecular structure and distribution of the polymer. The order of addition of the third monomer affects the distribution and cross-linking degree of the polymer chain, which in turn affects the performance of the polymer. It can also generate unnecessary by-products or impurities, affecting the quality of the polymer, and thus affecting the structure and performance of the resulting porous and easily dyeable polyester fiber.

[0134] The data from Comparative Example 17 show that the staining effect is significantly worse when no functional third monomer is added, further illustrating the importance of the functional third monomer.

[0135] The data from Comparative Example 18 show that when alkali is used to replace toluene, the various properties of the resulting porous and easily dyeable polyester fibers are significantly worse. This may be because replacing toluene with alkali only creates tiny grooves or pores on the fiber surface through alkali treatment. The resulting fibers do not completely remove the marine components from the island fibers, thus affecting the structure and properties of the resulting porous and easily dyeable polyester fibers.

[0136] To further illustrate the poor dyeing performance after replacing toluene with alkaline solution, this application also compared various dyes, and the results are as follows: Figure 1 As shown. By Figure 1 It can be seen that when toluene is replaced with alkaline solution, the staining effect of disperse blue, disperse yellow and disperse red is worse than when toluene is used.

[0137] As can be seen from the data of Comparative Example 19, only the presence of a functional third monomer with a specific structure can better realize the interbonding structure of ethylene glycol, purified terephthalic acid and the functional third monomer, and obtain high-performance porous easy-dyeing polyester fibers.

[0138] As can be seen from the data of Comparative Example 20, changing the preparation process of functional island-phase polyester masterbatch will affect the structure and properties of porous easily dyeable polyester fiber, further illustrating that high-performance porous easily dyeable polyester fiber can only be obtained under the specific process flow of this invention.

[0139] In summary, the porous, easily dyeable polyester fibers prepared by the third monomer of this invention and the island fiber method have better dyeing properties than polyester fibers obtained by other methods.

[0140] In summary, the porous, easily dyeable polyester fiber and its preparation method provided by this invention first involve esterifying ethylene glycol, purified terephthalic acid, and a functional third monomer to obtain a functional island-phase polyester masterbatch with a specific structure. Next, utilizing the characteristics of island-sea fibers, the functional island-phase polymer and the marine polymer are blended and melt-spun, and the marine polymer in the island-sea fiber is removed, forming a uniform porous structure on the surface and inside of the fiber, increasing roughness and specific surface area. Then, the porous fiber is dyed. Through the synergistic effect of the rich and uniform porous structure of the porous, easily dyeable polyester fiber and the molecular structure of the specific functional island-phase polyester masterbatch, a polyester fiber with high dyeing performance is obtained. During the dyeing process, the dye adsorption and diffusion rates on the surface and inside the porous fiber are relatively fast, which helps to improve dyeing uniformity and color saturation. The process is low-cost and has broad application prospects.

[0141] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing porous, easily dyeable polyester fiber, characterized in that, Includes the following steps: S1. Ethylene glycol, purified terephthalic acid, and catalyst in a predetermined ratio are added to a high-pressure reactor, and an esterification reaction is carried out under a nitrogen atmosphere; then, a functional third monomer is added to the high-pressure reactor, and the reaction continues under a nitrogen atmosphere; the functional third monomer includes ethylene glycol isophthalate-5-sulfonate sodium; the amount of the functional third monomer added accounts for 5%-15% of the total mass of the ethylene glycol and purified terephthalic acid; S2. After the esterification reaction is completed, the pressure is released to atmospheric pressure, and the temperature is continued to rise and the pressure is reduced. First, a polycondensation reaction is carried out in a low vacuum stage for a preset time. Then, the vacuum is continued, and a polycondensation reaction is carried out in a high vacuum stage for a preset time. Nitrogen gas is introduced to pressurize and discharge the material. The liquid material is cooled by water and pelletized to obtain functional island-phase polyester masterbatch. The pressure of the polycondensation reaction in the low vacuum stage is -(10-30) kPa, the reaction temperature is 275-285℃, and the reaction time is 10-20 min. The pressure of the polycondensation reaction in the high vacuum stage is -(90-100) kPa, the reaction temperature is 270-285℃, and the reaction time is 20-40 min. S3. The functional island-phase polyester masterbatch is blended with an incompatible marine polymer in a preset ratio, heated and melted, and then extruded and spun through a spinneret. After cooling, oiling, stretching, and heat setting, island-sea fiber is obtained. Then, the marine polymer in the island-sea fiber is removed with an organic solvent to obtain porous and easily dyeable polyester fiber. The mass ratio of the functional island-phase polyester masterbatch to the incompatible marine polymer is (1-3):(7-9). The marine polymer is one or more of polystyrene, polyethylene, and cellulose acetate. The stretching ratio is 3-5 times.

2. The method for preparing porous, easily dyeable polyester fiber according to claim 1, characterized in that, In step S1, the mass ratio of ethylene glycol to purified terephthalic acid is (1-1.5):1; the mass of the catalyst is 0.01%-1% of the total mass of ethylene glycol and purified terephthalic acid; the pressure of the esterification reaction is 300-400 kPa, and the temperature of the esterification reaction is 250-270 °C. The pressure for the continued reaction is 300-400 kPa, and the temperature is 250-270 °C.

3. The method for preparing porous, easily dyeable polyester fiber according to claim 1, characterized in that, The organic solvent is one or more of toluene, xylene, or acetone.

4. The method for preparing porous, easily dyeable polyester fiber according to claim 1, characterized in that, The heating and melting temperature is 260-280℃, the spinning speed is 3500-4000m / min, and the heat setting temperature is 20-40℃.

5. The method for preparing porous, easily dyeable polyester fiber according to claim 1 further includes the following steps: S4. The porous, easily dyeable polyester fiber is dyed in a dye solution with a mass concentration of 1%-5% disperse dye at a temperature of 60-80℃ for 30-60 minutes.

6. A porous, easily dyeable polyester fiber, characterized in that, It is prepared by the method for preparing porous, easily dyeable polyester fibers according to any one of claims 1-5.

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