Low-alkali high-uniform-dyeing process of polyester fabric

Abstract

The present application belongs to the field of low-alkali dyeing and finishing of textiles, and provides a low-alkali high-uniform-dyeing process for polyester fabrics, wherein a composite dispersion is constructed by dispersing dye particles and sodium sulfonate-based polyether copolyester, and is combined with anhydrous sodium carbonate and sodium bicarbonate to form a low-alkali dye bath, and the feeding temperature, the temperature rising rate, the dyeing temperature and the holding time are controlled in a closed high-temperature and high-pressure dyeing equipment, so that the high-temperature dispersion stability of the dye, the uniform dyeing of the fabric and the re-dispersion of the powder are considered, the problems of high-temperature agglomeration, dyeing obstruction and difficulty in unifying the re-dispersion stability are solved, and the low-alkali dyeing and finishing process is suitable for polyester fabrics.

Description

Technical Field

[0001] This invention relates to the field of low-alkali dyeing and finishing technology for textiles, specifically to a low-alkali, high-uniformity dyeing process for polyester fabrics. Background Technology

[0002] Polyester fabrics, primarily composed of polyethylene terephthalate (PET) fibers, are characterized by high strength, dimensional stability, abrasion resistance, and ease of care, making them widely used in clothing, home textiles, industrial textiles, and functional fabrics. High-temperature dyeing with disperse dyes remains a crucial processing method for achieving rich and durable colors in polyester fabrics. The dispersion stability of dye particles in the dye bath, the adsorption rate on the fiber surface, the diffusion rate within the fiber, and the post-dyeing washing burden all collectively affect the color difference, color variations, color spots, and production emissions of the finished product. With increasing demands for low liquor ratios, shorter processes, water conservation and emission reduction, and low-alkali processing, dyeing systems need to prevent dye particle agglomeration under high-temperature conditions while avoiding excessive dispersion or coating that hinders dye migration to polyester fibers. Therefore, developing processes that can balance high-temperature dispersion stability, dyeing performance, leveling, and powder redispersibility in low-alkali dye baths is of great significance for improving the dyeing quality of polyester fabrics and reducing post-processing pressure.

[0003] Existing technologies have proposed methods to improve the dyeing of disperse dyes on polyester fibers using high-temperature leveling agents, anionic or nonionic surfactants, amphiphilic polymer dispersants, and compounded auxiliaries. For example, Chinese Patent CN105970670A discloses a high-temperature, high-pressure dyeing leveling agent for disperse dye polyester fibers and its application. The background section points out that disperse dye dyeing often suffers from problems such as poor leveling, low dye uptake percentage, dye agglomeration, floating dye, and increased burden on subsequent reduction washing. Chinese Patent CN112663360A discloses a multifunctional dispersing leveling agent and its preparation method, and discusses issues such as insufficient dispersibility of nonionic surfactants under high-temperature conditions, the formation of secondary particles after high-temperature desorption of anionic dispersants, and operational and environmental shortcomings of carrier-based auxiliaries. While these solutions can improve some dispersion or migration problems, it remains difficult to simultaneously coordinate high-temperature, low-alkali dispersion stability, dye migration and uptake, powder redispersion, and process window stability. Summary of the Invention

[0004] The purpose of this invention is to provide a low-alkali, high-uniformity dyeing process for polyester fabrics, which solves the current problems of difficulty in balancing high-temperature dispersion stability and dyeing performance, as well as difficulty in balancing the redispersibility of composite dye powders and high-temperature, low-alkali stability.

[0005] This invention achieves a balance between dispersion stability, even dyeing, and powder redispersion by matching the sodium sulfonate-based polyether copolyester adsorption layer on the surface of disperse dye particles with low-alkali dyeing bath conditions. This allows the adsorption layer to both inhibit high-temperature aggregation and not excessively hinder dye migration. Furthermore, the redispersion hydrophilicity and high-temperature stability are adjusted through polyethylene glycol segments and sulfonate structural units.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A low-alkali, high-evenness dyeing process for polyester fabrics includes the following steps: S1. A composite dispersion is provided, wherein the composite dispersion is a disperse dye particle-sodium sulfonate-based polyether copolyester composite dispersion, comprising disperse dye particles, deionized water, and sodium sulfonate-based polyether copolyester adsorbed on the surface of the disperse dye particles; the disperse dye particles are composed of one or more of CI Disperse Red 60, CI Disperse Blue 56, and CI Disperse Yellow 54; the sodium sulfonate-based polyether copolyester is obtained by polycondensation of dimethyl terephthalate, ethylene glycol, polyethylene glycol with an average molecular weight of 400-1000, and sodium dimethyl 5-sulfoisophthalate under the catalysis of tetrabutyl titanate; the mass ratio of the disperse dye particles to the sodium sulfonate-based polyether copolyester is 100:(5-25), and the D50 of the disperse dye particles in the composite dispersion is 0.20-0.80 μm, and the D90 is 0.50-2.00 μm; S2. Prepare a low-alkali dye bath, wherein the low-alkali dye bath comprises deionized water, anhydrous sodium carbonate with a concentration of 0.30-1.20 g / L and sodium bicarbonate with a concentration of 0.10-0.80 g / L; S3. In a closed high-temperature and high-pressure dyeing equipment, polyester fabric is added to the low-alkali dye bath, and the mass ratio of the polyester fabric to the low-alkali dye bath is 1:(4-12); the composite dispersion is added at 50-70℃, so that the amount of disperse dye particles is 0.10-6.00wt% of the mass of the polyester fabric; the temperature is raised to 125-130℃ at a heating rate of 0.80-1.50℃ / min, held for 30-45min, then cooled, drained and washed to obtain a low-alkali, high-uniform dyed polyester fabric.

[0007] Furthermore, the polyester fabric is a polyethylene terephthalate fiber fabric.

[0008] Furthermore, the composite dispersion is prepared by the following steps: A1. Providing the sodium sulfonate-based polyether copolyester; A2. Add 100 parts by weight of the disperse dye particles, 5-25 parts by weight of the sodium sulfonate-based polyether copolyester and deionized water to a dispersion container and stir to obtain a pre-dispersion; A3. The pre-dispersion liquid is subjected to wet grinding or cyclic shear dispersion to form a sodium sulfonate-based polyether copolyester adsorption layer on the surface of the disperse dye particles; A4. When the D50 of the dispersed dye particles in the pre-dispersion solution is 0.20-0.80 μm and the D90 is 0.50-2.00 μm, stop grinding or cyclic shear dispersion; A5. Filter the pre-dispersion liquid after step A4 to obtain the composite dispersion; the apparent adsorption amount of sodium sulfonate-based polyether copolyester adsorbed on the surface of the disperse dye particles in the composite dispersion is 3.00-15.00 wt% relative to the disperse dye particles, and the apparent adsorption amount is not greater than the total content of sodium sulfonate-based polyether copolyester relative to the disperse dye particles, and the solid content is 10.00-35.00 wt%.

[0009] Furthermore, the sodium sulfonate-based polyether copolyester provided in step A1 is prepared through the following steps: B1. Raw material preparation: Based on 100 parts by weight of dimethyl terephthalate, add 70-160 parts by weight of ethylene glycol, 15-60 parts by weight of polyethylene glycol with an average molecular weight of 400-1000, 3-20 parts by weight of sodium 5-sulfoisophthalate and 0.02-0.20 parts by weight of tetrabutyl titanate; B2. Transesterification reaction: under nitrogen atmosphere, the reaction is carried out at 160-195℃ for 1.00-3.00h, and the low-boiling distillate containing methanol is removed; B3. Polycondensation reaction: The reactants obtained in step B2 are heated to 210-245℃ and reacted at a pressure of 0.0001-0.0050MPa for 2.00-5.00h; B4. Endpoint control: Stop the reaction when the acid value of the obtained polymer is 1.00-25.00 mg KOH / g.

[0010] B5. Cool down and discharge the material to obtain the sodium sulfonate-based polyether copolyester.

[0011] Furthermore, the composite dispersion is further prepared into a composite dye powder, as follows: C1. Adjust the solid content of the composite dispersion to 15.00-35.00 wt%; C2. Dry the material obtained in step C1 to obtain a composite dye powder with a moisture content of 1.00-6.00 wt%; the D90 of the disperse dye particles in the composite dispersion obtained after redispersing the composite dye powder with deionized water is 0.80-2.00 μm, and the redispersed composite dispersion is used as the composite dispersion in step S1 and in step S3.

[0012] Furthermore, the disperse dye particles are composed of two or three of CI Disperse Red 60, CI Disperse Blue 56 and CI Disperse Yellow 54, and each disperse dye is first mixed with the sodium sulfonate-based polyether copolyester to form a monochromatic composite dispersion according to a predetermined mass ratio.

[0013] Furthermore, during the process of heating from the temperature at which the composite dispersion is added to 90°C, the heating rate is 0.80-1.50°C / min, the heating rate is 0.80-1.20°C / min in the temperature range of 90-110°C, and the heating rate is 1.00-1.50°C / min in the temperature range of 110-130°C.

[0014] Furthermore, the sodium sulfonate-based polyether copolyester described in step S1 has an acid value of 1.00-25.00 mgKOH / g and contains polyethylene terephthalate segments, segments formed from polyethylene glycol with an average molecular weight of 400-1000, and structural units formed by the polycondensation of sodium 5-sulfoisophthalate.

[0015] Furthermore, the solid component of the composite dispersion is composed of the disperse dye particles and the sodium sulfonate-based polyether copolyester, wherein the disperse dye particles account for 80.00-95.24 wt% of the total mass of the solid component of the composite dispersion, the sodium sulfonate-based polyether copolyester accounts for 4.76-20.00 wt% of the total mass of the solid component of the composite dispersion, and the sum of the percentages of the disperse dye particles and the sodium sulfonate-based polyether copolyester in the total mass of the solid component of the composite dispersion is 100.00 wt%.

[0016] Furthermore, the composite dispersion described in step S1 is treated in an aqueous phase containing 0.30-1.20 g / L anhydrous sodium carbonate and 0.10-0.80 g / L sodium bicarbonate in a sealed pressure-resistant container at 125-130°C for 30-45 min. The average value of the dye filtration residue grade, determined by the double-layer filter paper filtration method of GB / T5541-2017, is 4.00-5.00.

[0017] Furthermore, after the composite dye powder is redispersed with deionized water, the solid content of the resulting composite dispersion is 10.00-30.00 wt%, and the D90 of the disperse dye particles in the composite dispersion is 0.80-2.00 μm.

[0018] Furthermore, when the disperse dye particles in step S1 are composed of three types of disperse dyes, namely CI Disperse Red 60, CI Disperse Blue 56 and CI Disperse Yellow 54, each disperse dye is mixed with the sodium sulfonate-based polyether copolyester to form a monochromatic composite dispersion according to a predetermined mass ratio.

[0019] Furthermore, when preparing the composite dispersion, 100 parts by weight of disperse dye particles, 5-25 parts by weight of sodium sulfonate-based polyether copolyester and deionized water are added to a dispersion container and stirred at 25-45°C for 20-60 minutes to obtain a pre-dispersion liquid for wet grinding or cyclic shear dispersion.

[0020] Furthermore, the pre-dispersion liquid is subjected to wet grinding or cyclic shear dispersion at 25-45℃ for 0.50-2.00h; when the D50 of the disperse dye particles in the pre-dispersion liquid is 0.20-0.80μm and the D90 is 0.50-2.00μm, the processing is stopped, and the mixture is filtered through 80-150 mesh to obtain the composite dispersion.

[0021] Furthermore, after the polycondensation reaction is completed, the reaction system is cooled to 80-120°C and discharged. The resulting sodium sulfonate-based polyether copolyester is used to mix with disperse dye particles and deionized water to form a pre-dispersion.

[0022] Further, the composite dispersion with a solid content of 15.00-35.00 wt% is fed into a drying device and dried under conditions of inlet air temperature of 120-160℃ and outlet air temperature of 70-95℃ to obtain a composite dye powder with a moisture content of 1.00-6.00 wt%. The composite dye powder is then redispersed with deionized water to obtain a composite dispersion with a solid content of 10.00-30.00 wt% and a disperse dye particle D90 of 0.80-2.00 μm.

[0023] Furthermore, the polyester fabric and low-alkali dye bath are placed in a closed high-temperature and high-pressure dyeing equipment. After adding the composite dispersion at 50-70℃, the temperature is raised to 125-130℃ at 0.80-1.50℃ / min and held for 30-45min. After the holding time is completed, the temperature is lowered, the liquid is drained, and the fabric is washed with deionized water to obtain the washed polyester fabric.

[0024] Furthermore, the composite dispersion was placed in an aqueous phase containing 0.30-1.20 g / L anhydrous sodium carbonate and 0.10-0.80 g / L sodium bicarbonate, and treated in a sealed pressure-resistant container at 125-130℃ for 30-45 min. The high-temperature dispersion stability was then determined using the double-layer filter paper filtration method according to GB / T5541-2017. The filtration time and dye residue level were recorded, and the results were used for the quality control of the high-temperature dispersion stability of the composite dispersion.

[0025] As a concept of this invention, the present invention employs a design that matches a disperse dye particle-sodium sulfonate-based polyether copolyester composite dispersion with a low-alkali dye bath, primarily to achieve a synergistic balance between high-temperature dispersion stability and dyeing performance. In existing technologies, to suppress the aggregation of disperse dye particles in high-temperature dye baths, the dispersion or coating effect on the particle surface is typically enhanced. However, an excessively strong adsorption layer can restrict the migration of dye from the aqueous phase to the polyester fiber. To improve dyeing performance, the dispersion layer is often weakened or the dye release rate is increased, which can cause particle instability under high-temperature, low-alkali conditions. This invention utilizes a sodium sulfonate-based polyether copolyester, formed by polyethylene terephthalate segments, polyethylene glycol segments, and sulfonate structural units, adsorbed onto the surface of disperse dye particles. This, combined with a low-alkali dye bath composed of anhydrous sodium carbonate and sodium bicarbonate and a controlled heating process, ensures stable adsorption, coordinated dye release, and fiber diffusion, thereby improving the problem of dual sacrifice in leveling dyeing.

[0026] Sodium sulfonate-based polyether copolyester and a low-alkali dye bath composed of anhydrous sodium carbonate and sodium bicarbonate jointly regulate the balance between high-temperature dispersion stability, dye migration, and powder redispersibility. Sodium sulfonate-based polyether copolyester mainly achieves compatibility with disperse dye particles and the polyester system through polyethylene terephthalate segments, and improves aqueous phase dispersion and redispersibility through polyethylene glycol segments and sulfonate structural units. However, excessively high apparent adsorption capacity may slow dye migration. The low-alkali dye bath helps provide a mild alkaline processing environment and reduces the pressure of strong alkali post-treatment, but insufficient buffering or temperature control may still induce high-temperature agglomeration or color difference. This invention achieves a balance between high-temperature dispersion stability, dyeing performance, leveling, and powder redispersibility by matching the proportions of sodium sulfonate-based polyether copolyester dosage, apparent adsorption capacity, particle size distribution, carbonate buffer concentration, and heating rate.

[0027] Beneficial technical effects 1. This invention enables the sodium sulfonate-based polyether copolyester to adsorb onto the surface of disperse dye particles, and controls the mass ratio of disperse dye particles to sodium sulfonate-based polyether copolyester, as well as D50 and D90, so that the composite dispersion has a good dispersion stability in a high-temperature, low-alkali dye bath, while avoiding excessive adsorption layer that would hinder dye migration.

[0028] 2. This invention uses a low-alkali dye bath composed of anhydrous sodium carbonate and sodium bicarbonate, and combines it with a process window of 50-70℃ feeding, 0.80-1.50℃ / min heating, and 125-130℃ holding, so that dye release, fiber diffusion and dye bath stability are coordinated, which helps to reduce color spots and color variations caused by high-temperature agglomeration.

[0029] 3. The sodium sulfonate-based polyether copolyester of the present invention contains polyethylene terephthalate segments, polyethylene glycol segments and sulfonate structural units, which can form a match between hydrophobic compatibility, hydrophilic redispersibility and electrical stability, which helps to maintain the particle size distribution after the composite dye powder is redispersed.

[0030] 4. This invention can prepare single-color composite dispersions separately and then mix them according to a predetermined mass ratio, so that multiple disperse dyes have formed a relatively uniform particle surface state before entering the low-alkali dyeing bath, which helps to reduce the impact of the dispersion difference of different dye particles on the color uniformity of the dyeing.

[0031] 5. This invention provides a continuous description of the conditions for pre-dispersion, wet grinding or cyclic shear dispersion, filtration, optional drying and powdering, redispersion, and closed high-temperature and high-pressure dyeing. This makes the key temperature, time, solid content, filtration mesh size, and quality control indicators clear, which is conducive to repeated industrialization. Attached Figure Description

[0032] Figure 1 This diagram illustrates the effect of sodium sulfonate-based polyether copolyester dosage on the filter residue level and dyeing rate in this scheme.

[0033] Figure 2 This diagram illustrates the effect of anhydrous sodium carbonate concentration on the filter residue grade and dyeing rate in this scheme.

[0034] Figure 3 This diagram illustrates the effect of dispersion D90 on the filter residue level and dye uptake rate in this scheme.

[0035] Figure 4 The graph shows the effect of the heat preservation time on the filter residue level and dyeing rate in this scheme.

[0036] Figure 5 This is a comparison chart of the apparent adsorption amounts of Example 1 and the comparative example of this scheme.

[0037] Figure 6 This is a comparison chart of the dyeing rate and evenness of Example 1 and the comparative example of this scheme.

[0038] Figure 7 This is a comparison chart of the redispersion D90 of Example 1 and the comparative example of this scheme.

[0039] Figure 8 These are macroscopic optical photographs comparing the final dyed polyester fabrics of Example 1 and Comparative Example 3; wherein, Figure 8 Figure a in the image is a macroscopic optical photograph of the low-alkali, high-level dyed polyester fabric from Example 1. Figure 8 Figure b in the image is a macroscopic optical photograph of the final dyed polyester fabric in Comparative Example 3.

[0040] Figure 9Comparison images of the SEM morphology and SEM-EDS surface scans of the final dyed polyester fabrics of Example 1 and Comparative Example 3 are shown; where, Figure 9 Figure a in the image is a low-magnification SEM image of the final dyed polyester fabric from Example 1; Figure 9 Figure b in the image is a low-magnification SEM image of the final dyed polyester fabric in Comparative Example 3. Figure 9 Figure c in the image is a magnified SEM image of the final dyed polyester fabric from Example 1. Figure 9 The d-image in the image is a magnified SEM image of the final dyed polyester fabric in Comparative Example 3. Figure 9 Figure e in the image is a high-magnification SEM image of the final dyed polyester fabric from Example 1. Figure 9 Figure f in the image is a high-magnification SEM image of the final dyed polyester fabric in Comparative Example 3. Figure 9 Figure g in the figure is a SEM-EDS surface scan of the final dyed polyester fabric from Example 1; Figure 9 The h-figure in the image is a SEM-EDS surface scan of the final dyed polyester fabric in Comparative Example 3. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0042] Example 1 S1: Preparation of sodium sulfonate-based polyether copolyester: Based on 100 parts by mass of dimethyl terephthalate, 70 parts by mass of ethylene glycol, 15 parts by mass of polyethylene glycol with an average molecular weight of 400, 3 parts by mass of sodium dimethyl 5-sulfoisophthalate, and 0.02 parts by mass of tetrabutyl titanate were added. All raw materials were commercially available chemically pure or analytically pure. The above raw materials were added to a polyester reaction apparatus equipped with a stirrer, condenser, and vacuum interface. Nitrogen gas with a purity ≥99.9% was introduced for 30 min to purge the mixture. The temperature was raised to 160℃ under mechanical stirring at 300 r / min, and the reaction was maintained at this temperature for 1.00 h. The low-boiling distillate containing methanol was continuously removed. Subsequently, the reactants were heated to 210℃ at 2℃ / min, the pressure was adjusted to 0.0050 MPa, and the reaction was continued for 2.00 h. The reaction was stopped when the acid value reached 1.00 mg KOH / g. The mixture was then cooled to 80°C and discharged to obtain sodium sulfonate-based polyether copolyester.

[0043] S2: Preparation of the composite dispersion: Using CI Disperse Red 60 as the dispersed dye particles, 100 parts by mass of CI Disperse Red 60, 5 parts by mass of sodium sulfonate-based polyether copolyester, and deionized water were added to a dispersion container. The material temperature was controlled at 25℃, and the mixture was mechanically stirred at 400 r / min for 20 min to obtain a pre-dispersion. The pre-dispersion was wet-milled at 25℃ for 0.50 h, with the circulating cooling water temperature maintained at 20℃ during the milling process. Before discharge, the particle size was monitored by laser diffraction particle size analysis. Wet milling was stopped when D50 was 0.20 μm and D90 was 0.50 μm. The mixture was then filtered through an 80-mesh filter to obtain a composite dispersion with a solid content of 10.00 wt%. The apparent adsorption amount of sodium sulfonate-based polyether copolyester adsorbed on the surface of disperse dye particles in the composite dispersion is 3.10 ± 0.20 wt% relative to the disperse dye particles. The disperse dye particles account for 95.24 wt% of the total solid component of the composite dispersion, and the sodium sulfonate-based polyether copolyester accounts for 4.76 wt% of the total solid component of the composite dispersion.

[0044] S3: Preparation and dyeing of the low-alkali dye bath. Take 100g of polyethylene terephthalate (PET) fiber fabric, and control the mass ratio of polyester fabric to low-alkali dye bath to 1:4. Add deionized water to the closed high-temperature and high-pressure dyeing equipment, add anhydrous sodium carbonate to make the concentration 0.30g / L, add sodium bicarbonate to make the concentration 0.10g / L, stir for 10min, and then add the polyester fabric. Add the composite dispersion at 50℃, so that the amount of disperse dye particles is 0.10wt% of the polyester fabric mass. The dyeing equipment heats up from 50℃ to 90℃ at 0.80℃ / min, from 90℃ to 110℃ at 0.80℃ / min, and from 110℃ to 125℃ at 1.00℃ / min, and holds at 125℃ for 30min. After the heat preservation is completed, the temperature is reduced to 80℃ at 2℃ / min, the liquid is drained, and the product is washed twice with 25℃ deionized water, with a bath ratio of 1:10 each time for 5 minutes. Then, it is dried in 60℃ hot air for 20 minutes to obtain a low-alkali, high-even-dyeing polyester fabric.

[0045] S4: Quality Inspection Methods and Results. The D50 and D90 of the composite dispersion were determined by laser diffraction particle size analysis. The dispersion medium was deionized water. After ultrasonic treatment for 1 min, the samples were cycled and tested, and the results were recorded three times and the average value was taken. High-temperature dispersion stability was tested using a double-layer filter paper filtration method. The composite dispersion was added to an aqueous phase containing 0.30 g / L anhydrous sodium carbonate and 0.10 g / L sodium bicarbonate, and treated at 125℃ for 30 min in a sealed pressure-resistant container before filtration. The filtration time was 58 ± 4 s, and the average dye filtration residue level was 4.30 ± 0.21. Color measurement of the fabric at 10 different locations showed an average comprehensive color difference ΔE of 0.72 ± 0.05, indicating a low comprehensive color difference.

[0046] Features and application scenarios of this embodiment: This embodiment adopts a relatively conservative low ratio scheme, with the amount of disperse dye particles, sodium sulfonate-based polyether copolyester, low alkali dye bath concentration and dyeing temperature in a relatively mild range, which is suitable for light-colored polyester fabrics, low auxiliary agent dosage and water-saving small liquor ratio dyeing scenarios.

[0047] Example 2 Raw materials and proportions: CI Disperse Red 60, CI Disperse Blue 56, and CI Disperse Yellow 54 are used as monochrome disperse dye particles, and are blended in a predetermined color ratio of 40:35:25 by mass. Based on 100 parts by mass of dimethyl terephthalate, the amount of ethylene glycol is 160 parts by mass, the amount of polyethylene glycol with an average molecular weight of 1000 is 60 parts by mass, the amount of sodium dimethyl 5-sulfoisophthalate is 20 parts by mass, and the amount of tetrabutyl titanate is 0.20 parts by mass. All raw materials are commercially available chemically pure or analytically pure grade.

[0048] Polyester component preparation process: The above-mentioned polyester synthesis raw materials were added to a reactor equipped with a condenser receiving device, and nitrogen was used for purging for 30 min (nitrogen purity ≥ 99.9%). The mechanical stirring speed was 350 r / min. The reactor was heated to 195℃ and held at that temperature for 3.00 h, and the low-boiling distillate containing methanol was removed. Subsequently, the system was heated to 245℃, the pressure was controlled at 0.0001 MPa, and the reaction was carried out for 5.00 h. Polycondensation was stopped when the acid value reached 25.00 mg KOH / g. The reaction system was cooled to 120℃ and discharged to obtain sodium sulfonate-based polyether copolyester.

[0049] Preparation process of monochrome composite dispersions and composite dye powders: 100 parts by mass of CI Disperse Red 60, 100 parts by mass of CI Disperse Blue 56, and 100 parts by mass of CI Disperse Yellow 54 were taken respectively, and 25 parts by mass of sodium sulfonate-based polyether copolyester and deionized water were added to each. The mixtures were stirred at 45℃ for 60 min to obtain three pre-dispersions. The three pre-dispersions were then subjected to cyclic shear dispersion at 45℃ for 2.00 h. Processing was stopped when the D50 of each monochrome composite dispersion reached 0.80 μm and the D90 reached 2.00 μm, and the mixtures were filtered through a 150-mesh filter. The solid content of the obtained monochrome composite dispersions was 35.00 wt%, the apparent adsorption capacity was 14.8 ± 0.5 wt%, the disperse dye particles accounted for 80.00 wt% of the total solid component mass, and the sodium sulfonate-based polyether copolyester accounted for 20.00 wt% of the total solid component mass. Three monochromatic composite dispersions were mixed in a mass ratio of 40:35:25 to obtain a composite dispersion to be dried. The solid content was adjusted to 35.00 wt%, and the mixture was dried at an inlet air temperature of 160℃ and an outlet air temperature of 95℃ to obtain a composite dye powder with a moisture content of 6.00 wt%. The composite dye powder was redispersed with deionized water to obtain a composite dispersion with a solid content of 30.00 wt% and a D90 of 2.00 μm.

[0050] Dyeing Process: 100g of polyethylene terephthalate (PET) fiber fabric was placed in a closed high-temperature, high-pressure dyeing apparatus. The mass ratio of polyester fabric to low-alkali dye bath was 1:12. The concentration of anhydrous sodium carbonate in the low-alkali dye bath was 1.20g / L, and the concentration of sodium bicarbonate was 0.80g / L. A composite dispersion obtained by redispersing the composite dye powder was added at 70℃, making the amount of disperse dye particles 6.00wt% of the polyester fabric mass. The dye bath temperature was increased from 70℃ to 90℃ at a rate of 1.50℃ / min, from 90℃ to 110℃ at a rate of 1.20℃ / min, and from 110℃ to 130℃ at a rate of 1.50℃ / min, and held at 130℃ for 45min. After holding, the temperature was lowered to 80℃, the liquid was drained, and the fabric was washed twice with deionized water at 25℃ for 5min each time, followed by drying in hot air at 60℃ for 20min.

[0051] Quality inspection or performance testing: The D50 and D90 of the composite dispersion were determined by laser diffraction particle size analysis, and the powder moisture content was determined by the 105℃ loss-in-weight method. High-temperature dispersion stability was tested using a double-layer filter paper filtration method. The composite dispersion was treated in an aqueous phase containing 1.20 g / L anhydrous sodium carbonate and 0.80 g / L sodium bicarbonate in a sealed pressure-resistant container at 130℃ for 45 min, followed by filtration. The filtration time was 70 ± 5 s, and the average dye filtration residue level was 4.80 ± 0.23. The average ΔE value of multi-point colorimetric measurements on the fabric was 0.86 ± 0.06.

[0052] The features of this embodiment are: This embodiment adopts an optimized scheme with a relatively high loading, with the average molecular weight of polyethylene glycol, the amount of sulfonate structural units, the amount of disperse dye particles, the solid content of the composite dispersion, and the powder drying conditions in a relatively high range, which is suitable for dark color blending, high dye usage, and redispersing and dyeing scenarios after storage and transportation of composite dye powder.

[0053] Example 3 In this embodiment, CI Disperse Red 60 and CI Disperse Blue 56 were used as disperse dye particles in a mass ratio of 60:40, with a preparation scale equivalent to 100 parts by mass of the total disperse dye particles. The sodium sulfonate-based polyether copolyester was synthesized using 100 parts by mass of dimethyl terephthalate, 110 parts by mass of ethylene glycol, 35 parts by mass of polyethylene glycol with an average molecular weight of 700, 12 parts by mass of sodium dimethyl 5-sulfoisophthalate, and 0.10 parts by mass of tetrabutyl titanate. After the above raw materials were added to the reactor, nitrogen gas with a purity ≥99.9% was introduced, the mechanical stirring speed was 320 r / min, and the temperature was raised to 175℃ for 2.00 h, while continuously removing the low-boiling distillate containing methanol. The reactants were then heated to 230℃, the pressure was controlled at 0.0010 MPa, and polycondensation was carried out for 3.50 h. The reaction was stopped when the acid value reached 13.00 mg KOH / g. The system was cooled to 100°C and then discharged to obtain sodium sulfonate-based polyether copolyester.

[0054] 100 parts by weight of disperse dye particles, 15 parts by weight of sodium sulfonate-based polyether copolyester, and deionized water were added to a dispersion container. The material temperature was controlled at 35°C, and the mixture was mechanically stirred at 450 rpm for 40 min to obtain a pre-dispersion. The pre-dispersion was then subjected to cyclic shear dispersion at 35°C for 1.20 h, with the shearing equipment speed set to 2500 rpm. During the process, the material temperature was controlled at 35°C through jacket cooling. The cyclic shear dispersion was stopped when D50 reached 0.50 μm and D90 reached 1.25 μm. The mixture was then filtered through a 120-mesh filter to obtain a composite dispersion with a solid content of 20.00 wt%. The apparent adsorption amount of sodium sulfonate-based polyether copolyester on the surface of the disperse dye particles relative to the disperse dye particles was 8.10 ± 0.30 wt%. The disperse dye particles accounted for 86.96 wt% of the total solid component, and the sodium sulfonate-based polyether copolyester accounted for 13.04 wt% of the total solid component.

[0055] 100g of polyethylene terephthalate (PET) fiber fabric was placed in a closed high-temperature, high-pressure dyeing apparatus. The mass ratio of polyester fabric to low-alkali dye bath was 1:8. The concentration of anhydrous sodium carbonate in the low-alkali dye bath was 0.75g / L, and the concentration of sodium bicarbonate was 0.45g / L. A composite dispersion was added at 60℃, making the amount of disperse dye particles 3.00wt% of the polyester fabric mass. The dye bath was heated from 60℃ to 90℃ at a rate of 1.10℃ / min, then from 90℃ to 110℃ at a rate of 1.00℃ / min, and finally from 110℃ to 128℃ at a rate of 1.25℃ / min, and held at 128℃ for 38min. After holding, the temperature was lowered to 80℃, the liquid was drained, and the fabric was washed twice with deionized water at a bath ratio of 1:10 for 5min each time. Finally, the fabric was dried in hot air at 60℃ for 20min.

[0056] Quality control records included particle size, adsorption capacity, solid content, and dyeing uniformity. Particle size was determined using laser diffraction particle size analysis. Adsorption capacity was determined by centrifugation followed by measurement and conversion of the free sodium sulfonate-based polyether copolyester content in the aqueous phase. Solid content was determined using the constant weight method at 105℃. The composite dispersion was treated in an aqueous phase containing 0.75 g / L anhydrous sodium carbonate and 0.45 g / L sodium bicarbonate in a sealed pressure-resistant container at 128℃ for 38 min, followed by double-layer filter paper filtration for 48 ± 3 s. The average dye residue level was 4.90 ± 0.10. The average ΔE value for multi-point color measurement of the fabric was 0.54 ± 0.04.

[0057] Applicable scenarios for this embodiment: This embodiment adopts intermediate ratio and segmented temperature control, taking into account the color stability of the two disperse dyes, the dispersion stability of the dye bath, and the dyeing process of polyester fibers. It is suitable for medium depth of color, batch dyeing, and fabric processing with high requirements for color difference control.

[0058] Example 4 I. Preparation Object and Polyester Components: CI Disperse Blue 56 and CI Disperse Yellow 54 were used as disperse dye particles in a mass ratio of 50:50, with a total disperse dye particle volume of 100 parts by mass. Sodium sulfonate-based polyether copolyester was prepared using 100 parts by mass of dimethyl terephthalate, 90 parts by mass of ethylene glycol, 45 parts by mass of polyethylene glycol with an average molecular weight of 900, 6 parts by mass of sodium dimethyl 5-sulfoisophthalate, and 0.05 parts by mass of tetrabutyl titanate as raw materials. The reaction was carried out under a nitrogen atmosphere with a nitrogen purity ≥99.9% and a stirring speed of 330 r / min. The reaction was first carried out at 185℃ for 1.50 h, and the low-boiling distillate containing methanol was removed. The temperature was then raised to 220℃, and polycondensation was performed at 0.0030 MPa for 4.00 h. The reaction was stopped when the acid value reached 8.00 mg KOH / g. The reaction system was cooled to 90℃ and discharged to obtain the sodium sulfonate-based polyether copolyester.

[0059] II. Composite Dispersion and Composite Dye Powder: 100 parts by weight of disperse dye particles, 20 parts by weight of sodium sulfonate-based polyether copolyester, and deionized water were added to a dispersion container and stirred at 420 r / min for 30 min at 30℃ to form a pre-dispersion. The pre-dispersion was wet-milled at 30℃ for 1.50 h, and the milling endpoint was controlled by particle size detection to obtain a dispersion system with D50 of 0.35 μm and D90 of 0.80 μm. The treated material was filtered through a 100-mesh filter to obtain a composite dispersion with a solid content of 15.00 wt%. The apparent adsorption capacity was 12.0 ± 0.4 wt%, with disperse dye particles accounting for 83.33 wt% of the total solid component and sodium sulfonate-based polyether copolyester accounting for 16.67 wt% of the total solid component. The composite dispersion was then sent to a drying device and dried at an inlet air temperature of 120℃ and an outlet air temperature of 70℃ to obtain a composite dye powder with a moisture content of 1.00 wt%. The composite dye powder was redispersed with deionized water to obtain a composite dispersion with a solid content of 10.00 wt% and a D90 of 0.80 μm.

[0060] III. Dye Bath Preparation and Dyeing: 100g of polyethylene terephthalate (PET) fiber fabric was placed in a closed high-temperature, high-pressure dyeing apparatus. The mass ratio of polyester fabric to low-alkali dye bath was 1:6. The concentration of anhydrous sodium carbonate in the low-alkali dye bath was 1.00g / L, and the concentration of sodium bicarbonate was 0.60g / L. A composite dispersion obtained by redispersing the composite dye powder was added at 65℃, making the amount of disperse dye particles 1.50wt% of the polyester fabric mass. The dye bath was heated from 65℃ to 90℃ at a rate of 1.30℃ / min, from 90℃ to 110℃ at a rate of 1.10℃ / min, and from 110℃ to 126℃ at a rate of 1.40℃ / min, and held at 126℃ for 42min. After holding, the temperature was lowered, the liquid drained, and the fabric was washed twice with deionized water for 5min each time, followed by drying in hot air at 60℃ for 20min.

[0061] IV. Quality Testing Methods and Results: The moisture content of the composite dye powder was determined by the 105℃ loss-in-weight method. The D90 of the redispersed composite dispersion was determined by laser diffraction particle size analysis. High-temperature dispersion stability was assessed using a double-layer filter paper filtration method. The redispersed composite dispersion was treated in an aqueous phase containing 1.00 g / L anhydrous sodium carbonate and 0.60 g / L sodium bicarbonate in a sealed pressure-resistant container at 126℃ for 42 min, followed by filtration. The filtration time was 52 ± 3 s, and the average dye filtration residue level was 4.40 ± 0.22. The average ΔE value of multi-point colorimetric measurements on the fabric was 0.63 ± 0.05.

[0062] V. Process characteristics and application direction of this embodiment: This embodiment adopts the composite dye powder redispersion path. The powder has a low moisture content and the particle size is in a small range after redispersion. It is suitable for processing polyester fabrics that require powder storage and transportation, on-site solution preparation and medium and light color blending and dyeing.

[0063] Comparative Example 1: Basically the same as Example 1, except that the amount of sodium sulfonate-based polyether copolyester used in preparing the composite dispersion was adjusted to 2 parts by mass; the other preparation conditions of sodium sulfonate-based polyether copolyester, preparation of composite dispersion and dyeing conditions were the same as in Example 1.

[0064] Comparative Example 2: It is basically the same as Example 1, except that the amount of sodium sulfonate-based polyether copolyester used in preparing the composite dispersion is adjusted to 30 parts by mass; the other preparation conditions of sodium sulfonate-based polyether copolyester, preparation of composite dispersion and dyeing conditions are the same as those in Example 1.

[0065] Comparative Example 3: It is basically the same as Example 1, except that the wet grinding time in step S2 is adjusted to 0.20h, so that the D50 of the disperse dye particles in the composite dispersion is 0.95μm and the D90 is 2.30μm; the preparation of sodium sulfonate-based polyether copolyester, the preparation of composite dispersion and dyeing conditions are the same as those in Example 1.

[0066] Comparative Example 4: Basically the same as Example 1, except that the concentration of anhydrous sodium carbonate in the low-alkali dye bath was adjusted to 0.10 g / L and the concentration of sodium bicarbonate was 0.10 g / L; the preparation of sodium sulfonate-based polyether copolyester, preparation of composite dispersion and dyeing conditions were the same as in Example 1.

[0067] Comparative Example 5: Basically the same as Example 1, except that the concentration of anhydrous sodium carbonate in the low-alkali dye bath was 0.30 g / L and the concentration of sodium bicarbonate was adjusted to 1.10 g / L; the preparation of sodium sulfonate-based polyether copolyester, preparation of composite dispersion and dyeing conditions were the same as in Example 1.

[0068] Comparative Example 6: It is basically the same as Example 1, except that the heating rate of the dye bath from 50°C to 125°C in step S3 is adjusted to 2.00°C / min; the preparation of sodium sulfonate-based polyether copolyester, preparation of composite dispersion and dyeing conditions are the same as in Example 1.

[0069] Comparative Example 7: Basically the same as Example 1, except that the dyeing temperature in step S3 was adjusted to 120°C, the dye bath was heated from 50°C to 90°C at 0.80°C / min, from 90°C to 110°C at 0.80°C / min, and then from 110°C to 120°C at 1.00°C / min and held at that temperature for 30 min; the preparation of sodium sulfonate-based polyether copolyester, the preparation of composite dispersion and the dyeing conditions were the same as in Example 1.

[0070] Comparative Example 8: It is basically the same as Example 1, except that the amount of sodium dimethyl 5-sulfonyl isophthalate in step B1 is adjusted to 1 part by mass; the preparation of sodium sulfonate-based polyether copolyester, preparation of composite dispersion and dyeing conditions are the same as in Example 1.

[0071] Comparative Example 9: Essentially the same as Example 1, except that polyethylene glycol was not added in step B1. A comparative copolyester without polyethylene glycol segments was prepared using 100 parts by weight of dimethyl terephthalate, 70 parts by weight of ethylene glycol, 3 parts by weight of sodium dimethyl 5-sulfoisophthalate, and 0.02 parts by weight of tetrabutyl titanate. The preparation of the remaining composite dispersion and dyeing conditions were the same as in Example 1. This comparative example was used to investigate the synergistic relationship between polyethylene glycol segments and sulfonate structural units.

[0072] Comparative Example 10: Essentially the same as Example 1, except that sodium 5-sulfoisophthalate was not added in step B1. Instead, a polyether copolyester without sulfonate structural units was prepared using 100 parts by mass of dimethyl terephthalate, 70 parts by mass of ethylene glycol, 15 parts by mass of polyethylene glycol with an average molecular weight of 400, and 0.02 parts by mass of tetrabutyl titanate. The preparation and dyeing conditions for the remaining composite dispersions were the same as in Example 1. This comparative example was used to investigate the synergistic relationship between the sulfonate structural units and the polyethylene glycol segments.

[0073] Comparative Example 11: This example is essentially the same as Example 1, except that in step S2, instead of wet grinding to form the sodium sulfonate-based polyether copolyester adsorption layer on the surface of the disperse dye particles, CI Disperse Red 60 is first ground in deionized water until D50 is 0.20 μm and D90 is 0.50 μm. Then, 5 parts by mass of the sodium sulfonate-based polyether copolyester are directly added to the low-alkali dye bath before dyeing. The remaining preparation and dyeing conditions for the sodium sulfonate-based polyether copolyester are the same as in Example 1. This comparative example is used to investigate the synergistic relationship between the disperse dye particles and the sodium sulfonate-based polyether copolyester adsorption layer.

[0074] Characterization and performance testing: The acid value of the sodium sulfonate-based polyether copolyester was determined by acid-base titration. The sample mass, titrant concentration, and titrant consumption volume were recorded and converted to mgKOH / g.

[0075] The test subjects were the composite dispersions of Examples 1-4 and Comparative Examples 1-11, with the aim of evaluating their dispersion stability under low-alkali and high-temperature conditions. The principle is that the less particle agglomeration after high-temperature treatment, the smoother the double-layer filter paper filtration and the higher the residue level. The method involved adding the corresponding anhydrous sodium carbonate and sodium bicarbonate aqueous phases to the sample, placing it in a sealed pressure-resistant container, and treating it at 125-130℃ for 30-45 min. The filtration time and dye residue level were recorded according to GB / T5541-2017 "Determination of High-Temperature Dispersion Stability of Disperse Dyes - Double-Layer Filter Paper Filtration Method". n=3. The average filtration time, standard deviation of filtration time, average residue level, and standard deviation of residue level were obtained. Shorter filtration time and higher residue level indicate better stability.

[0076] The test subjects were low-alkali dye bath residues before and after dyeing, and polyester fabrics after dyeing, with the aim of evaluating dyeing performance. The principle is that the absorbance of disperse dyes at their characteristic absorption wavelengths changes with the dye concentration in the residue. The method involved measuring the absorbance of the working solution before dyeing and the residue after dyeing, diluted with deionized water to the linear range of the corresponding calibration curve, establishing a dye concentration-absorbance calibration curve, and calculating the dyeing rate based on the difference between the initial dye amount and the residual dye amount. The test temperature was 25℃, and each sample was tested in triplicate. For working solutions and residues composed of two or three disperse dyes, the absorbance was measured at the characteristic absorption wavelength of each disperse dye, and multi-wavelength calculations were performed based on the concentration-absorbance calibration curves established using the corresponding monochromatic standard solutions to obtain the residual concentration of each disperse dye. The total dyeing rate was calculated as the ratio of the sum of the dyeing amounts of each component to the sum of the initial amounts of each component. The experiment yielded the average dyeing rate and the standard deviation of the dyeing rate, expressed as a percentage (%). Higher values ​​indicate a higher proportion of dye entering the polyester fabric.

[0077] The test subjects were polyester fabrics dyed in Examples 1-4 and Comparative Examples 1-11, with the aim of evaluating dyeing levelness. The principle is that color differences at different locations on the same fabric reflect the uniformity of dye distribution. The method involved equilibrating the fabrics at 25±2℃ and 50±5% relative humidity for 24 hours. Using an integrating sphere colorimeter, 10 locations were randomly selected on each fabric piece to measure the L*, a*, and b* values. The comprehensive color difference ΔE relative to the average chromaticity value was calculated and statistically analyzed. The average ΔE and standard deviation of ΔE were calculated based on the measurement results at the 10 locations. The experimentally obtained average ΔE and standard deviation of ΔE are dimensionless; lower values ​​indicate better dyeing levelness.

[0078] The test objects were composite dispersions and redispersible liquids of composite dye powders, with the aim of evaluating particle size control and powder redispersibility. The principle is that laser diffraction signals can be converted into particle volume distribution to obtain D50 and D90. The method involved diluting samples with deionized water to the instrument's specified shading range, sonicating for 1 min, circulating dispersion, and then measuring D50 and D90 using a laser diffraction particle size analyzer. Powder samples were first redispersed according to the target solid content before testing. (See Table 1 and...) Figure 7 The sample with a redispersible D90 was prepared by adjusting the corresponding composite dispersion to a solid content of 15.00-35.00 wt%, drying it at an inlet air temperature of 120-160℃ and an outlet air temperature of 70-95℃ to obtain composite dye powder, and then redispersing it with deionized water to a solid content of 10.00-30.00 wt% before particle size determination. The average D50, standard deviation of D50, average D90, and standard deviation of D90 were obtained from the experiment, in μm. The closer the D90 is to the designed particle size and the better the repeatability, the better the redispersibility.

[0079] The test object was sodium sulfonate-based polyether copolyester adsorbed on the surface of disperse dye particles in a composite dispersion, with the aim of evaluating the degree of adsorption layer formation. The principle was that the content of free sodium sulfonate-based polyether copolyester in the continuous phase after centrifugation could be compared with the feed amount and the adsorption amount calculated. The method involved high-speed centrifugation of a quantitative composite dispersion, collection of the supernatant, and determination of the free polyester content after blank correction using the total organic carbon method (based on calibration curves established for each sample's copolyester). The apparent adsorption amount was calculated by subtracting the free amount from the feed amount, with n=3. The experiment yielded the average and standard deviation of the apparent adsorption amount, in wt%. Values ​​within a reasonable range indicate controlled adsorption layer formation.

[0080] The test subjects were dyed polyester fabrics and undyed polyethylene terephthalate (PET) fiber fabrics. The purpose was to evaluate the strength retention of fabrics after low-alkali dyeing. The principle is that if low-alkali conditions cause less damage to the fibers, the fabric will have a higher breaking strength retention rate. The method involved equilibrating the samples at 25±2℃ and 50±5% relative humidity for 24 hours. Warp and weft samples were cut, and the breaking strength was measured using a fabric tensile testing machine at a constant tensile speed. Each warp and weft sample was tested in parallel three times. The warp and weft strength retention rates were calculated separately, and the average of the two values ​​was taken as the strength retention rate. The experiment yielded the average strength retention rate and the standard deviation of the strength retention rate, expressed as a percentage (%). Higher values ​​indicate less fabric processing damage.

[0081] Figures 1 to 4 The single-factor test samples shown were all prepared according to the basic preparation and staining process of Example 1. Except for the test factors listed in the description of each figure, the other conditions were kept consistent, and their parameter combinations did not correspond to all the conditions of a certain example or comparative example in Table 1.

[0082] To verify the synergistic relationship between "disperse dye particle surface adsorption layer - low-alkali dye bath conditions - particle size control" in this scheme, we first conducted a single-factor investigation on the key factors affecting high-temperature dispersion stability and dyeing performance based on Example 1. Figure 1The graph shows the effect of sodium sulfonate-based polyether copolyester dosage on the filter residue grade and dye uptake rate in this scheme. Under the conditions of fixed anhydrous sodium carbonate concentration of 0.30 g / L, dispersion D90 of 0.50 μm, and heat treatment at 125℃ for 30 min, only the dosage of sodium sulfonate-based polyether copolyester was varied from 2 to 30 parts by mass. The results show that when the dosage increased from 2 parts by mass to 15 parts by mass, the filter residue grade improved from 3.10 to 4.90, and the dye uptake rate increased from 81.5% to 91.0%. After further increasing to 30 parts by mass, the above indicators decreased. This result indicates that when the dosage of sodium sulfonate-based polyether copolyester is insufficient, it is difficult to form an effective adsorption protective layer, and dye particles are prone to agglomeration in the high-temperature dye bath; when the dosage is too high, it may enhance the spatial barrier effect of the particle surface, affecting the migration of dye into the polyester fiber. Therefore, an appropriate amount of adsorption layer is beneficial to achieve a balance between high-temperature dispersion stability and dye uptake ability.

[0083] Based on the established fact that the amount of adsorption layer has a significant impact on the stability of the system, the regulatory effect of low-alkali conditions on the staining behavior of the composite dispersion was further investigated. Figure 2 The diagram illustrates the effect of anhydrous sodium carbonate concentration on the filter residue grade and dyeing rate in this scheme. Based on Example 1, the amount of sodium sulfonate-based polyether copolyester was fixed at 5 parts by mass, the dispersion D90 was 0.50 μm, and the temperature was maintained at 125℃ for 30 min. Only the concentration of anhydrous sodium carbonate was varied from 0.10 to 1.50 g / L. The results show that when the concentration of anhydrous sodium carbonate was increased to 0.75 g / L, the filter residue grade reached 4.80, and the dyeing rate reached 90.5%. Further increasing the alkali concentration resulted in varying degrees of decrease in both indicators. This indicates that an appropriate amount of sodium carbonate can improve the ionic environment of the dye bath, allowing the dispersion effect of the sulfonate structural units to be realized. However, excessively high alkali concentrations can disrupt the stability of the dye bath, increasing the risk of particle aggregation and dyeing fluctuations. This demonstrates that the low-alkali conditions used in this scheme are not simply a reduction in the amount of alkali, but rather a match to the adsorption layer on the particle surface to maintain the high-temperature stability of the dye bath and the dyeing efficiency.

[0084] After the chemical composition and dye bath conditions are determined, the particle size of the dispersion becomes another key factor affecting the uniformity and stability of dyeing. Figure 3The diagram illustrates the effect of dispersion D90 on the filter residue level and dye uptake rate in this scheme. Based on Example 1, the amount of sodium sulfonate-based polyether copolyester was fixed at 5 parts by mass, the concentration of anhydrous sodium carbonate was 0.30 g / L, and the temperature was maintained at 125℃ for 30 min. Only the dispersion D90 was varied from 0.30 to 2.40 μm. The results show that when D90 is in the range of 0.80-1.25 μm, both the filter residue level and dye uptake rate remain at a high level, with the dye uptake rate reaching 90.2% when D90 is 1.25 μm. When the particle size is too large, dye particles are more likely to deposit or form localized enrichments in the dye bath; when the particle size is too small, the increased surface area may lead to an increased demand for surface auxiliaries, affecting dye release and migration. These results indicate that reasonably controlling the particle size of the composite dispersion helps reduce the risk of agglomeration and maintains good dye diffusion and dyeing ability.

[0085] The dyeing and heat preservation stage determines the extent to which the dye migrates from the dispersion system into the interior of the polyester fiber. Therefore, the rationality of the process window is further verified by using time variables. Figure 4 The diagram illustrates the effect of holding time on the filter residue grade and dyeing rate in this scheme. Using Example 1 as a baseline, the amount of sodium sulfonate-based polyether copolyester was fixed at 5 parts by mass, the concentration of anhydrous sodium carbonate was 0.30 g / L, and the dispersion D90 was 0.50 μm. Only the holding time at 125℃ was varied from 20 to 55 min. The results show that when the holding time was extended from 20 min to 38 min, the dyeing rate increased from 80.6% to 90.1%, and the filter residue grade improved to 4.70. However, when the holding time was further extended to 55 min, the relevant indicators decreased. This result indicates that appropriately extending the holding time is beneficial for establishing dye adsorption, diffusion, and dispersion equilibrium. However, excessively long holding times increase the possibility of particle collision, agglomeration, or decreased dye bath stability under high-temperature conditions. Therefore, this scheme achieves a synergistic effect of stable dispersion and sufficient dyeing through reasonable control of the holding time.

[0086] After single-factor results demonstrated that the key process parameters had clear adjustment rules, the structural role of the sodium sulfonate-based polyether copolyester adsorption layer was further verified by comparative analysis. Figure 5 The graph shows a comparison of the apparent adsorption amounts of Example 1 and the comparative examples. Example 1 has an apparent adsorption amount of 3.10 wt%, which is higher than that of Comparative Example 9 (2.60 wt%), Comparative Example 10 (2.10 wt%), and Comparative Example 11 (0.80 wt%). This result indicates that the sodium sulfonate-based polyether copolyester used in Example 1 can more effectively adsorb onto the surface of disperse dye particles, forming a composite adsorption layer with both hydrophilic dispersion and steric stabilization effects. This adsorption layer can reduce the tendency of dye particles to agglomerate secondaryly in a high-temperature, low-alkali dye bath, while maintaining the migration capability of dye particles during the dyeing process, laying the foundation for obtaining a higher dyeing rate and lower color difference.

[0087] Figure 6This diagram compares the dyeing rate and evenness of Example 1 with those of the comparative examples. Example 1 achieved a dyeing rate of 86.8% and an evenness ΔE of 0.72. Comparative Examples 4, 5, and 6 showed dyeing rates of 82.7%, 83.4%, and 84.1%, respectively, with ΔE values ​​of 1.25, 1.16, and 1.54. Compared to the comparative examples, Example 1 significantly reduced fabric color difference while increasing the dyeing rate, indicating that it did not excessively inhibit dye diffusion into the fiber due to enhanced dispersion stability, nor did it cause localized dye enrichment due to increased dyeing rate. This result demonstrates that this method can alleviate the contradiction in existing processes of "increased dispersion stability but limited dyeing" or "enhanced dyeing but insufficient evenness," achieving efficient and uniform dyeing under low-alkali conditions.

[0088] In addition to dispersion stability during the dyeing process, the redispersibility of composite dye powder is also an important indicator affecting the stability in practical applications. Figure 7 The diagram shows a comparison of the redispersion D90 values ​​of Example 1 and the comparative examples. The redispersion D90 of the composite dispersion in Example 1, after powdering and redispersion treatment, is 0.92 μm, significantly lower than that of Comparative Example 9 (1.88 μm), Comparative Example 10 (1.54 μm), and Comparative Example 11 (1.47 μm). This result indicates that the polyethylene glycol segments and sulfonate structural units in Example 1 can improve the hydrophilic wetting ability and particle separation ability of the powder after rehydration, and reduce irreversible agglomeration during the redispersion process after drying. This demonstrates that this method is not only suitable for stable dispersion at high temperatures and low alkali levels in dye baths, but also for improving the redispersion performance of composite dye powders, thereby solving the problem of particle size coarsening during powder storage, transportation, and reuse.

[0089] At the macroscopic fabric appearance level, the relationship between particle size control and low-alkali light-colored leveling effect was further verified. Figure 8 These are macroscopic optical photographs comparing the final dyed polyester fabrics of Example 1 and Comparative Example 3, in which... Figure 8 a is a macroscopic optical photograph of the low-alkali, high-even-dyeing polyester fabric of Example 1. It uses CI Disperse Red 60 / sodium sulfonate-based polyether copolyester composite dispersion with D50 of 0.20 μm and D90 of 0.50 μm, and is dyed under the conditions of anhydrous sodium carbonate 0.30 g / L, sodium bicarbonate 0.10 g / L, liquor ratio 1:4, and heat treatment at 125℃ for 30 min. The fabric exhibits a relatively continuous and uniform light red appearance. Figure 8 Figure b shows a macroscopic optical photograph of the final dyed polyester fabric from Comparative Example 3. In Comparative Example 3, the wet milling time was shortened to 0.20 h, resulting in an increase in dye particle D50 to 0.95 μm and D90 to 2.30 μm. This made it easier to observe localized color spots, color variations, or uneven color depth on the fabric surface. The appearance differences shown in this figure are consistent with the trend that fine-particle-size composite dispersions help reduce the risk of localized dye enrichment in low-alkali, light-colored dyeing.

[0090] To further explain the aforementioned macroscopic uniformity differences at the microscopic level, Figure 9 The images show the SEM morphology and SEM-EDS surface scan comparison of the final dyed polyester fabrics of Example 1 and Comparative Example 3. Figure 9 a and Figure 9 b are low-magnification SEM images of the final dyed polyester fabrics of Example 1 and Comparative Example 3, respectively, used to compare the overall morphology of yarns and fiber bundles of the dyed fabrics. Figure 9 c and Figure 9 d are medium magnification SEM images of the two, used to observe whether there are particles attached to the surface of the fiber bundle and monofilament; Figure 9 e and Figure 9 f represents high-magnification SEM images of both images, used to further determine the state of residual particles or aggregates on the fiber surface. Combined with... Figure 9 g and Figure 9 The SEM-EDS surface scan results of h show that the spatial distribution of elements such as C, O, N, Na, and S on the fiber surface can serve as a basis for comparing the distribution of residual components on the fiber surface. In Example 1, due to the smaller D50 and D90 of the composite dispersion, fewer local particle enrichments were observed on the fiber surface, and the surface scan distribution was more uniform. In contrast, in Comparative Example 3, due to the coarsening of particles, local deposition was more likely to form at fiber intersections or on the surface. The differences in morphology and elemental distribution shown in this figure are consistent with the trend that particle size control helps reduce the non-uniform deposition of dye particles on the fabric surface.

[0091] In conclusion, Figures 1 to 4 This indicates that there is a matching process window between the dosage of sodium sulfonate-based polyether copolyester, the low alkali concentration, the dispersion particle size, and the holding time. Figures 5 to 7 This demonstrates the correlation between the composite adsorption layer and the adsorption stability of dye particles, dyeing uniformity, and powder redispersibility. Figure 8 and Figure 9 The results, from both the macroscopic fabric appearance and microscopic surface distribution perspectives, demonstrate the promoting effect of fine-particle-size composite dispersions on low-alkali leveling dyeing. These results collectively indicate that this scheme effectively solves the problems of balancing high-temperature dispersion stability and dyeing performance, and the difficulty in balancing the redispersibility of composite dye powders with high-temperature and low-alkali stability, demonstrating good process rationality and implementation effectiveness.

[0092] Table 1 Performance of Examples and Comparative Examples As can be seen from the performance of the examples and comparative examples in Table 1, Examples 1-4 show a more coordinated trend in terms of filtration residue level, filtration time, dyeing rate, leveling performance ΔE, redispersion D90, and adsorption amount control. In the conventional single-variable comparative examples, when the polyester dosage is low, the particle size is large, the alkali component is low, or the dyeing temperature is deviated, the filtration time is prolonged, ΔE is increased, or the dyeing rate is reduced. In the synergistic comparative examples, when there is a lack of polyethylene glycol segments, a lack of sulfonate structural units, or no adsorption layer is formed, the redispersion and high-temperature filtration performance deteriorate simultaneously, indicating that the data trend corresponds to a balance between high-temperature dispersion stability, dyeing performance, and powder redispersion.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A low alkali high level dyeing process of polyester fabric, characterized by, Includes the following steps: S1. A composite dispersion is provided, wherein the composite dispersion is a disperse dye particle-sodium sulfonate-based polyether copolyester composite dispersion, comprising disperse dye particles, deionized water, and sodium sulfonate-based polyether copolyester adsorbed on the surface of the disperse dye particles; the disperse dye particles are composed of one or more of CI Disperse Red 60, CI Disperse Blue 56, and CI Disperse Yellow 54; the sodium sulfonate-based polyether copolyester is obtained by polycondensation of dimethyl terephthalate, ethylene glycol, polyethylene glycol with an average molecular weight of 400-1000, and sodium dimethyl 5-sulfoisophthalate under the catalysis of tetrabutyl titanate; the mass ratio of the disperse dye particles to the sodium sulfonate-based polyether copolyester is 100:(5-25), and the D50 of the disperse dye particles in the composite dispersion is 0.20-0.80 μm, and the D90 is 0.50-2.00 μm; S2. Prepare a low-alkali dye bath, wherein the low-alkali dye bath comprises deionized water, anhydrous sodium carbonate with a concentration of 0.30-1.20 g / L, and sodium bicarbonate with a concentration of 0.10-0.80 g / L; S3. In a closed high-temperature and high-pressure dyeing equipment, polyester fabric is added to the low-alkali dye bath, and the mass ratio of the polyester fabric to the low-alkali dye bath is 1:(4-12); the composite dispersion is added at 50-70℃, so that the amount of disperse dye particles is 0.10-6.00wt% of the mass of the polyester fabric; the temperature is raised to 125-130℃ at a heating rate of 0.80-1.50℃ / min, held for 30-45min, then cooled, drained and washed to obtain a low-alkali, high-uniform dyed polyester fabric.

2. The low alkali high level dyeing process of polyester fabric as claimed in claim 1, wherein, The polyester fabric is a polyethylene terephthalate fiber fabric.

3. The low alkali high level dyeing process of polyester fabric as claimed in claim 1, wherein, The composite dispersion is prepared by the following steps: A1. Providing the sodium sulfonate-based polyether copolyester; A2. Add 100 parts by weight of the disperse dye particles, 5-25 parts by weight of the sodium sulfonate-based polyether copolyester and deionized water to a dispersion container and stir to obtain a pre-dispersion; A3. The pre-dispersion liquid is subjected to wet grinding or cyclic shear dispersion to form a sodium sulfonate-based polyether copolyester adsorption layer on the surface of the disperse dye particles; A4. When the D50 of the dispersed dye particles in the pre-dispersion solution is 0.20-0.80 μm and the D90 is 0.50-2.00 μm, stop grinding or cyclic shear dispersion; A5. Filter the pre-dispersion liquid after step A4 to obtain the composite dispersion; the apparent adsorption amount of sodium sulfonate-based polyether copolyester adsorbed on the surface of the disperse dye particles in the composite dispersion is 3.00-15.00 wt% relative to the disperse dye particles, and the apparent adsorption amount is not greater than the total content of sodium sulfonate-based polyether copolyester relative to the disperse dye particles, and the solid content is 10.00-35.00 wt%.

4. The low-alkali, high-uniformity dyeing process for polyester fabrics according to claim 3, characterized in that, The sodium sulfonate-based polyether copolyester provided in step A1 is prepared by the following steps: B1. Raw material preparation: Based on 100 parts by weight of dimethyl terephthalate, add 70-160 parts by weight of ethylene glycol, 15-60 parts by weight of polyethylene glycol with an average molecular weight of 400-1000, 3-20 parts by weight of sodium 5-sulfoisophthalate and 0.02-0.20 parts by weight of tetrabutyl titanate; B2. Transesterification reaction: under nitrogen atmosphere, the reaction is carried out at 160-195℃ for 1.00-3.00h, and the low-boiling distillate containing methanol is removed; B3. Polycondensation reaction: The reactants obtained in step B2 are heated to 210-245℃ and reacted at a pressure of 0.0001-0.0050MPa for 2.00-5.00h; B4. Endpoint control: Stop the reaction when the acid value of the obtained polymer is 1.00-25.00 mg KOH / g; B5. Cool down and discharge the material to obtain the sodium sulfonate-based polyether copolyester.

5. The low-alkali, high-uniformity dyeing process for polyester fabrics according to claim 3, characterized in that, The composite dispersion is further prepared into a composite dye powder, as follows: C1. Adjust the solid content of the composite dispersion to 15.00-35.00 wt%; C2. Dry the material obtained in step C1 to obtain a composite dye powder with a moisture content of 1.00-6.00 wt%; the D90 of the disperse dye particles in the composite dispersion obtained after redispersing the composite dye powder with deionized water is 0.80-2.00 μm, and the redispersed composite dispersion is used as the composite dispersion in step S1 and in step S3.

6. The low-alkali, high-uniformity dyeing process for polyester fabrics according to claim 1, characterized in that, The disperse dye particles are composed of two or three of CI Disperse Red 60, CI Disperse Blue 56 and CI Disperse Yellow 54, and each disperse dye is first mixed with the sodium sulfonate-based polyether copolyester to form a monochromatic composite dispersion according to a predetermined mass ratio.

7. The low-alkali, high-uniformity dyeing process for polyester fabrics according to claim 1, characterized in that, The sodium sulfonate-based polyether copolyester described in step S1 has an acid value of 1.00-25.00 mgKOH / g and contains polyethylene terephthalate segments, segments formed from polyethylene glycol with an average molecular weight of 400-1000, and structural units formed by the polycondensation of sodium 5-sulfoisophthalate.

8. The low-alkali, high-uniformity dyeing process for polyester fabrics according to claim 7, characterized in that, In step S1, the apparent adsorption amount of sodium sulfonate-based polyether copolyester adsorbed on the surface of the disperse dye particles relative to the disperse dye particles is 3.00-15.00 wt%, and the apparent adsorption amount is not greater than the total content of sodium sulfonate-based polyether copolyester relative to the disperse dye particles. The solid content of the composite dispersion is 10.00-35.00 wt%, and the solid component of the composite dispersion is composed of the disperse dye particles and the sodium sulfonate-based polyether copolyester. The disperse dye particles account for 80.00-95.24 wt% of the total mass of the solid component of the composite dispersion, and the sodium sulfonate-based polyether copolyester accounts for 4.76-20.00 wt% of the total mass of the solid component of the composite dispersion. The sum of the percentages of the disperse dye particles and the sodium sulfonate-based polyether copolyester in the total mass of the solid component of the composite dispersion is 100.00 wt%.

9. The low-alkali, high-uniformity dyeing process for polyester fabrics according to claim 7, characterized in that, The composite dispersion described in step S1 was treated in an aqueous phase containing 0.30-1.20 g / L anhydrous sodium carbonate and 0.10-0.80 g / L sodium bicarbonate in a sealed pressure-resistant container at 125-130°C for 30-45 min. The average value of the dye filtration residue grade, determined by the double-layer filter paper filtration method of GB / T5541-2017, was 4.00-5.

00.

10. The low-alkali, high-uniformity dyeing process for polyester fabrics according to claim 7, characterized in that, The composite dispersion mentioned in step S1 is obtained by redispersing the composite dye powder with deionized water; the composite dye powder is obtained by drying the composite dispersion to be dried, the composite dispersion to be dried is a disperse dye particle-sodium sulfonate-based polyether copolyester composite dispersion with a solid content of 15.00-35.00wt%, the water content of the composite dye powder is 1.00-6.00wt%, the solid content of the composite dispersion is 10.00-30.00wt%, and the D90 of the disperse dye particles in the composite dispersion is 0.80-2.00μm.

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