Methods for preparing waterborne polyurethane polymer dyes based on waste polyester and their application

Abstract

This invention relates to the field of dye preparation technology, specifically disclosing a method for preparing waterborne polyurethane polymer dyes based on waste polyester and its application. The preparation method includes: preparation of diethyl phthalate and synthesis of waterborne polyurethane polymer emulsion dyes. This invention ingeniously prepares waterborne polyurethane polymer dyes from waste polyester, utilizing waste polyester fabrics to prepare polymer dyes, and effectively avoiding the serious ecological and environmental hazards caused by traditional waste polyester disposal methods such as incineration or landfill. This method successfully promotes resource recycling, transforming what was originally "waste" into valuable resources, thereby significantly reducing the production cost of polymer dyes. It is not only environmentally friendly but also economically efficient, making this polymer dye easier to promote and utilize in the market.

Description

Technical Field

[0001] This invention belongs to the field of dye preparation technology, specifically relating to a method for preparing waterborne polyurethane polymer dyes based on waste polyester and its application. Background Technology

[0002] Human life is inseparable from "clothing, food, housing, and transportation," with "clothing" ranking first, highlighting its importance. Textiles are inseparable from fibers, which are broadly classified into natural fibers and chemical fibers. Natural fibers are derived from nature and can be obtained directly from it; chemical fibers are fibers produced through chemical treatment and processing. In industrial production, polyester fiber has advantages such as high modulus, high strength, high elasticity, resistance to deformation, insulation, and corrosion resistance; it is also relatively inexpensive; and it is the simplest of the three major synthetic fibers to process. Therefore, polyester fiber has become the most widely used, consumed, and used fiber in the market, accounting for as much as 90% of the use of chemical fibers. This has also led to a growing amount of waste polyester fabrics.

[0003] Currently, the methods for disposing of waste polyester fabrics remain quite limited, with incineration and landfill being the main approaches. However, both methods are not only inefficient but also cause severe environmental pollution. Incinerating waste polyester releases harmful gases and particulate matter, profoundly impacting air quality and the environment. Similarly, landfilling is an unsustainable method, consuming valuable land resources and potentially polluting soil and water sources, leading to long-term environmental problems.

[0004] In the textile and textile coating industry, while most traditional low-molecular-weight dyes or pigments are widely used, these materials have several shortcomings. For example, their heat resistance is generally poor, which limits the application range and service life of products to some extent. Furthermore, the production processes of these dyes are relatively complex, increasing production costs and reducing efficiency. More seriously, the production of these traditional dyes often generates large amounts of wastewater, which, if not treated promptly, will cause secondary pollution to the environment.

[0005] Meanwhile, although polymeric dyes offer superior performance, their high production costs hinder their widespread market adoption. This cost bottleneck limits their application in broader fields, deterring many businesses and individuals. Therefore, balancing performance and cost, and exploring more environmentally friendly and efficient methods for treating waste polyester, remain challenges facing the industry. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing waterborne polyurethane polymer dyes based on waste polyester and a method for using them, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing waterborne polyurethane polymer dyes based on waste polyester: S1, preparation of diethyl terephthalate (BHET): Choline chloride and zinc acetate in a molar ratio of 1:1 are mixed in a container and heated and stirred in a water bath at 60°C for 4 hours to obtain a transparent and homogeneous liquid, which will be used as a catalyst for the alcoholysis reaction.

[0009] Waste polyester textiles were washed, dried, and pulverized to obtain polyester fibers. The polyester fibers, ethylene glycol, and an alcoholysis catalyst were mixed in a three-necked flask at a mass ratio of 2:8:0.8 for alcoholysis reaction at 185℃-200℃ for 4-5 hours. After the reaction was complete, the alcoholysis liquid was poured off and quickly filtered while hot. The insoluble matter was the un-alcoholized polyester fibers. Excess boiling deionized water was added to the filtrate, and the mixture was filtered three times. The filtrate from the last filtration was placed in a refrigerator at 4℃ for recrystallization for 24 hours to obtain colorless needle-like crystals. The colorless needle-like crystals were washed, filtered, and dried to obtain the alcoholysis product, diethyl terephthalate (BHET).

[0010] S2. Synthesis of waterborne polyurethane polymer emulsion dyes: All reagents must be dried before the experiment. The entire experiment is carried out in a digital display oil bath. First, the dehydrated alcoholysis products, bis(hydroxyethyl) terephthalate (BHET) and 2,2-dimethylolpropionic acid (DMPA), are placed in a three-necked flask. Then, an appropriate amount of NMP is added as a solvent, with a solvent weight of 0.3-0.5g. The temperature is set at 90℃, and the mixture is mechanically stirred for 1 hour. During this time, it is necessary to observe whether the solid reagents are dispersed. When the inside of the flask is a transparent and homogeneous liquid with no solid residue, proceed to the next step.

[0011] Next, adjust the oil bath temperature to 85°C, add isophorone diisocyanate (5.8-6.0g) to the three-necked flask, and add the catalyst (0.04-0.1g of dibutyltin dilaurate). Set the temperature to 85°C and mechanically stir for 4 hours. During this time, pay attention to the viscosity of the reaction system. The viscosity will increase during the experiment, so add acetone intermittently to adjust it.

[0012] Then, while stirring continuously, wait for the oil bath temperature to drop to 60℃, add the chain extender BDO and 1,4-dihydroxyanthraquinone, where the mass ratio of the chain extender 1,4-butanediol to 1,4-dihydroxyanthraquinone is set to 7:3, 6:4, 5:5, 4:6, 3:7 and 1:0, maintain a constant temperature of 60℃, add the neutralizing agent TEA, and mechanically stir for 0.5h to adjust the pH of the system to 6-9;

[0013] Finally, after the reaction system has cooled to room temperature, the stirring speed is increased, and a mixture of deionized water and ethylene glycol is added dropwise to the flask. The weight ratio of deionized water to ethylene glycol is 1:1, and the mass of the mixture is 20-30 mL. Then, under the action of high-speed shearing of the rotor, waterborne polyurethane polymer emulsion dye is obtained.

[0014] The method for using water-based polyurethane polymer dyes is as follows: Prepare sized polyester fabric and cut it into 5 rectangular strips of 4cm x 8cm. Sonicate the water-based polyurethane polymer emulsion dye for 2 minutes to disperse it evenly. Immerse the polyester fabric in the evenly dispersed water-based polyurethane polymer emulsion dye and heat it in a water bath at 70℃-80℃ for 20-30 minutes. Then remove it from the emulsion dye and place it in a 190℃ forced-air drying oven for 2 minutes of high-temperature color fixing. Repeat the immersion and high-temperature color fixing process twice. Finally, remove the fabric strips, wash them, and dry them.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] This invention ingeniously prepares water-based polyurethane polymer dyes from waste polyester. This innovative method not only cleverly utilizes waste polyester fabrics to produce polymer dyes but also effectively avoids the serious environmental hazards caused by traditional waste polyester disposal methods, such as incineration or landfill. This approach successfully promotes resource recycling, transforming what was originally "waste" into valuable resources, thereby significantly reducing the production cost of polymer dyes. This innovation is not only environmentally friendly but also economically efficient, making these polymer dyes easier to promote and utilize in the market, and is expected to bring about a revolutionary change to the entire dye industry. Attached Figure Description

[0017] Figure 1 Scanning electron microscopy (SEM) images of bis(hydroxyethyl) terephthalate (BHET) and polyurethane polymer dyes;

[0018] Figure 2 Infrared spectra of polyurethane dyes, bis(hydroxyethyl) terephthalate, 1,4-butanediol, and 1,4-dihydroxyanthraquinone;

[0019] Figure 3 The image shows the ultraviolet spectrum of a waterborne polyurethane polymer dye.

[0020] Figure 4 XRD patterns of BHET and waterborne polyurethane polymer dyes;

[0021] Figure 5 The DSC spectrum of the waterborne polyurethane polymer dye;

[0022] Figure 6 The TG spectrum of waterborne polyurethane polymer dyes;

[0023] Figure 7 Scanning electron microscope image of undyed PET fabric;

[0024] Figure 8 This is a graph showing the color parameters related to the color of dyed polyester. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1:

[0027] Please see Figure 1 - Figure 8 As shown, a method for preparing waterborne polyurethane polymer dyes based on waste polyester fibers and its application method are described below:

[0028] A method for preparing waterborne polyurethane polymer dyes based on waste polyester.

[0029] S1. Preparation of dihydroxyethyl terephthalate (BHET): Choline chloride and zinc acetate in a molar ratio of 1:1 were mixed in a container and heated and stirred in a water bath at 60°C for 4 hours to obtain a transparent and homogeneous liquid, which will be used as a catalyst for the alcoholysis reaction.

[0030] Waste polyester textiles were washed, dried, and pulverized to obtain polyester fibers. The polyester fibers, ethylene glycol, and an alcoholysis catalyst were mixed in a three-necked flask at a mass ratio of 2:8:0.8 for alcoholysis reaction at 185℃-200℃ for 4-5 hours. After the reaction was complete, the alcoholysis liquid was poured off and quickly filtered while hot. The insoluble matter was the un-alcoholized polyester fibers. Excess boiling deionized water was added to the filtrate, and the mixture was filtered three times. The filtrate from the last filtration was placed in a refrigerator at 4℃ for recrystallization for 24 hours to obtain colorless needle-like crystals. The colorless needle-like crystals were washed, filtered, and dried to obtain the alcoholysis product, diethyl terephthalate (BHET).

[0031] S2. Synthesis of waterborne polyurethane polymer emulsion dyes: First, the dehydrated alcoholysis products, bis(hydroxyethyl) terephthalate (BHET) and 2,2-dimethylolpropionic acid (DMPA), are placed in a three-necked flask. Then, an appropriate amount of NMP is added as a solvent, with a solvent weight of 0.3-0.5g. The temperature is set at 90℃, and the mixture is mechanically stirred for 1 hour. During this time, it is necessary to observe whether the solid reagents are dispersed. When the inside of the flask shows a transparent and homogeneous liquid with no solid residue, proceed to the next step.

[0032] Next, adjust the oil bath temperature to 85°C, add isophorone diisocyanate (5.8-6.0g) to the three-necked flask, and add the catalyst (0.04-0.1g of dibutyltin dilaurate). Set the temperature to 85°C and mechanically stir for 4 hours. During this time, pay attention to the viscosity of the reaction system. The viscosity will increase during the experiment, so add acetone intermittently to adjust it.

[0033] Then, while stirring continuously, wait for the oil bath temperature to drop to 60℃, add the chain extender BDO and 1,4-dihydroxyanthraquinone, where the mass ratio of chain extender 1,4-butanediol to 1,4-dihydroxyanthraquinone is set to 7:3. Maintain a constant temperature of 60℃, add the neutralizing agent TEA, and mechanically stir for 0.5h to adjust the pH of the system to 6-9.

[0034] Finally, after the reaction system has cooled to room temperature, the stirring speed is increased, and a mixture of deionized water and ethylene glycol is added dropwise to the flask. The weight ratio of deionized water to ethylene glycol is 1:1, and the mass of the mixture is 20-30 mL. Then, under the action of high-speed shearing of the rotor, waterborne polyurethane polymer emulsion dye is obtained.

[0035] Example 2:

[0036] A method for preparing waterborne polyurethane polymer dyes based on waste polyester.

[0037] S1. The preparation steps for diethyl terephthalate are the same as in Example 1;

[0038] S2. The synthesis steps of the waterborne polyurethane polymer emulsion dye are the same as those in Example 1, except that the chain extender BDO and 1,4-dihydroxyanthraquinone are added, and the mass ratio of the chain extender 1,4-butanediol to 1,4-dihydroxyanthraquinone is 6:4.

[0039] Example 3:

[0040] A method for preparing waterborne polyurethane polymer dyes based on waste polyester.

[0041] S1. The preparation steps for diethyl terephthalate are the same as in Example 1;

[0042] S2. The synthesis steps of the waterborne polyurethane polymer emulsion dye are the same as those in Example 1, except that the chain extender BDO and 1,4-dihydroxyanthraquinone are added, and the mass ratio of the chain extender 1,4-butanediol to 1,4-dihydroxyanthraquinone is 6:4.

[0043] Example 4:

[0044] A method for preparing waterborne polyurethane polymer dyes based on waste polyester.

[0045] S1. The preparation steps for diethyl terephthalate are the same as in Example 1;

[0046] S2. The synthesis steps of the waterborne polyurethane polymer emulsion dye are the same as those in Example 1, except that the chain extender BDO and 1,4-dihydroxyanthraquinone are added, and the mass ratio of the chain extender 1,4-butanediol to 1,4-dihydroxyanthraquinone is 5:5.

[0047] Example 5:

[0048] A method for preparing waterborne polyurethane polymer dyes based on waste polyester.

[0049] S1. The preparation steps for diethyl terephthalate are the same as in Example 1;

[0050] S2. The synthesis steps of the waterborne polyurethane polymer emulsion dye are the same as those in Example 1, except that the chain extender BDO and 1,4-dihydroxyanthraquinone are added, and the mass ratio of chain extender 1,4-butanediol to 1,4-dihydroxyanthraquinone is 3:7.

[0051] Example 6:

[0052] A method for preparing waterborne polyurethane polymer dyes based on waste polyester.

[0053] S1. The preparation steps for diethyl terephthalate are the same as in Example 1;

[0054] S2. The synthesis steps of the waterborne polyurethane polymer emulsion dye are the same as those in Example 1, except that the chain extender BDO and 1,4-dihydroxyanthraquinone are added, and the mass ratio of chain extender 1,4-butanediol to 1,4-dihydroxyanthraquinone is 1:0.

[0055] Experimental testing, preparation of test samples

[0056] Waterborne polyurethane polymer emulsion dyes were labeled as Sample 1, Sample 2, Sample 3, Sample 4, Sample 5, and Sample 6 according to the mass ratios of BDO to 1,4-dihydroxyanthraquinone of 7:3, 6:4, 5:5, 4:6, 3:7, and 1:0, respectively. These samples were used to test viscosity, surface tension, and UV spectroscopy.

[0057] Dyeing method: Prepare sized polyester fabric and cut it into 5 rectangular strips of 4cm×8cm. Mark them as ①, ②, ③, ④, and ⑤ respectively. Sonicate the water-based polyurethane emulsion dye for 2 minutes to make the water-based polyurethane emulsion dye more evenly dispersed. Immerse the strips in water-based polyurethane emulsion dye samples 1, 2, 3, 4, and 5 in the order of ①, ②, ③, ④, and ⑤ respectively. Heat in a water bath at 70℃ for 20 minutes. Then remove them from the emulsion dye and place them in a 190℃ forced-air drying oven for high-temperature color fixing for 2 minutes. Repeat the immersion and high-temperature color fixing operation twice. Finally, remove the strips, wash and dry them.

[0058] Samples 1, 2, 3, 4, 5, and 6 were dropped into six glass petri dishes, respectively. All dishes were then placed in an oven to dry completely. After drying, the dried polyurethane polymer dye was removed from the petri dishes using a small sample spoon and placed into sample bags, designated as Sample I, Sample II, Sample III, Sample IV, Sample V, and Sample VI. The dried BHET was also placed into a sample bag and designated as Sample BHET. Samples I, II, III, IV, V, VI, and BHET were used for SEM, XRD, TG, DSC, and IR measurements.

[0059] The dyed fabric strips were labeled ①, ②, ③, ④, and ⑤, and were used to test SEM, KS, and dry / wet rubbing color fastness.

[0060] Surface morphology analysis of diethyl terephthalate and polyurethane polymer dyes:

[0061] Scanning electron microscopes can be used to observe and analyze the morphology, structure, and composition of an object's surface.

[0062] Figure 1 These are scanning electron microscope images of bis(hydroxyethyl) terephthalate (BHET) and polyurethane polymer dyes. Figure 1 (a) is an image of a sample of diethyl terephthalate prepared from waste polyester fibers by alcoholysis. Figure 1 (b) is a scanning electron microscope image of bis(hydroxyethyl) terephthalate, which shows that it exhibits needle-like crystal morphology. Figure 1 (c) is a polyurethane polymer dye prepared by polymerization of bis(hydroxyethyl) terephthalate. Figure 1 (d) is a scanning electron microscope image of the polyurethane polymer dye.

[0063] As shown in the figure, the polyurethane polymer dye obtained by polymerizing diethyl terephthalate exhibits a flake-like morphology, which is completely different from the morphology of diethyl terephthalate. This may be because the polyurethane polymer dye has the characteristics of a polymer and easily forms a polymer film.

[0064] Chemical structure testing and analysis:

[0065] Fourier transform infrared spectrometers can perform directional and quantitative analysis of samples.

[0066] Figure 2 These are the infrared spectra of waterborne polyurethane polymer dyes, diethyl terephthalate, 1,4-butanediol, and 1,4-dihydroxyanthraquinone. Figure 2 It can be seen that bis(hydroxyethyl) terephthalate (BHET) has a strong absorption peak at 3296.13035 cm⁻¹, which is a characteristic absorption peak caused by the stretching vibration of the free hydroxyl group -OH, indicating that the compound contains a free hydroxyl group; an alkyl-CH stretching vibration peak appears at 1714.86762 cm⁻¹; the absorption peaks at 1125.86558 cm⁻¹ and 1265.37172 cm⁻¹ correspond to the asymmetric and symmetric bending vibration peaks of COC, respectively, indicating the presence of ester bonds in the product.

[0067] The above analysis indicates that the alcoholysis products contain characteristic BHET groups such as hydroxyl, alkyl, and ester groups.

[0068] Figure 2 It is evident that 1,4-dihydroxyanthraquinone exhibits no significant absorption peak in the 1600-4000 cm⁻¹ range; the absorption peak of 1,4-butanediol at 3335.23422 cm⁻¹ is attributed to the stretching vibration of -OH; the absorption peak of waterborne polyurethane polymer dyes at 1727.08758 cm⁻¹ is attributed to the stretching vibration of C=O, and the absorption peak at 1243.17719 cm⁻¹ is attributed to the OCO stretching vibration in waterborne polyurethane. The appearance of these peaks indicates the formation of polyurethane chains. The disappearance of the -OH stretching vibration absorption peak at 600 cm⁻¹ is due to the reaction between the -OH groups of 1,4-butanediol and 1,4-dihydroxyanthraquinone and the -NCO group in polyurethane. The appearance and disappearance of these peaks suggest that 1,4-dihydroxyanthraquinone may be introduced into the polyurethane molecular chain.

[0069] Ultraviolet / visible spectrometers are mainly used for compound identification, purity testing, isomer determination, steric hindrance measurement, hydrogen bond strength determination, and other related quantitative analyses.

[0070] Figure 3 This is the UV spectrum of waterborne polyurethane polymer dyes. Lines 1, 2, 3, 4, 5, and 6 correspond to samples 1, 2, 3, 4, 5, and 6, respectively. When 1,4-dihydroxyanthraquinone is covalently introduced into the waterborne polyurethane polymer chain, its absorption spectrum type remains consistent overall. Figure 3It can be seen that absorption peaks related to the structure of waterborne polyurethane polymer dyes occurred in the ultraviolet-visible light range. This is mainly because waterborne polyurethane polymer dyes absorb light in the 330-600nm visible light range, which is why they generate color.

[0071] Phase analysis of materials:

[0072] X-ray diffraction is a primary method for studying the phases and crystal structures of matter. By performing X-ray diffraction on materials and analyzing their diffraction patterns, information such as the composition of the material and the structure or morphology of the atoms or molecules inside the material can be obtained.

[0073] Figure 4 These are the XRD patterns of waterborne polyurethane polymer dye samples I, II, III, IV, and V.

[0074] The waterborne polyurethane polymer dye obtained in the experiment is a polymer crystal. Figure 4 In the sample, a sharp peak can be seen in the waterborne polyurethane polymer dye 1, indicating that sample I has the best crystallinity. This suggests that the atoms in the crystal are arranged in a relatively orderly manner, with few or no structural defects or impurities.

[0075] Thermal performance test:

[0076] Differential scanning calorimetry is the most widely used thermal analysis technique. It is used to measure the relationship between the heat flow or thermal power difference between the sample end and the reference end of a sample under a certain atmosphere and programmed temperature, as a function of temperature and time.

[0077] Figure 5 These are the DSC temperature rise curves of waterborne polyurethane polymer dye samples I, II, III, IV, V, and VI. In the DSC temperature rise curves, samples I, II, and IV all exhibit a sharp endothermic melting peak at approximately 115℃; samples III and V exhibit a gentle endothermic melting peak at approximately 85℃. At this point, the glass transition temperature of the polyurethane polymer dye is reached, and the sample transitions from a glassy state to a rubbery state.

[0078] Thermal stability test:

[0079] Thermogravimetric analysis (TGA) is a thermal analysis technique that measures the relationship between the mass of a sample and temperature under programmed temperature control. It is generally used to study the thermal stability of materials.

[0080] Figure 6 The graph shows the TG curves of polyurethane polymer dye samples I, III, IV, V, and diethyl terephthalate. As can be seen from the graph, the weight of all polyurethane polymer dyes begins to decrease at 180℃, while the weight of diethyl terephthalate decreases at 250℃.

[0081] Viscosity and surface tension testing:

[0082] Table 1 shows that sample polyurethane polymer dye emulsion 1 has the highest viscosity, indicating that the solution molecules are more densely packed and more uniformly dispersed. This effectively prevents dye stratification, maintains its stability, and allows the dye to maintain good performance over a long period. The high viscosity also results in better dyeing effects for polyurethane polymer dye 1. Due to the high viscosity, its adhesion is stronger, and the dye is less likely to fall off the fabric during the dyeing process. However, excessively high viscosity may cause uneven dyeing, as described in polyurethane polymer dye emulsion 1. Appropriate viscosity conditions are beneficial for uniform dyeing of the emulsion, as in polyurethane polymer dye emulsion 5.

[0083] When the surface tension of a liquid is lower than the critical surface tension of a solid surface, the liquid will spread and wet the solid surface freely. Conversely, if the surface tension of the liquid is higher than the critical surface tension of the solid, the liquid will form discontinuous droplets with a contact angle greater than zero. The critical surface tension of polyester fabric is a specific value that determines what surface tension of liquid can spread freely on polyester. The critical surface tension of polyester fabric is 43 mN / m, while the surface tensions of polyurethane polymer dye emulsions are all lower than the critical surface tension of polyester fabric. This indicates that the polyurethane polymer dye emulsions prepared in the experiment can spread and wet the surface of polyester fabric freely, resulting in good dyeing effects.

[0084] Table 1. Viscosity test results of polyurethane polymer dyes

[0085]

[0086] Observing and analyzing the microscopic morphology of matter

[0087] Scanning electron microscope image of dyed PET fabric as shown Figure 7 As shown in (a), (b), (c), (d), and (e), these are scanning electron microscope images of undyed, sized polyester fabrics. Figure 7 (a) shows a scanning electron microscope image of the dyed PET fabric. Figure 7 As shown in (b), (c), (d), (e), and (f), the morphological characteristics of the polymer film on the surface of the dyed PET fabric can be clearly observed by comparison. However, the morphological characteristics of different samples are different. This may be because the content of dye molecules in the polyurethane polymer dye emulsion is different, which leads to different morphologies of the film on the surface of the dyed fabric in the figure.

[0088] Staining test

[0089] Figure 8The Lab value represents the color of a fabric dyed with polyurethane polymer dyes. Here, L* represents the brightness of the object, and the larger the L*, the more transparent the color; a* represents the red-green color of the object, with a positive a* indicating a reddish tint and a negative a* indicating a greenish tint; b* represents the yellow-blue color of the object, with a positive b* indicating a yellowish tint and a negative b* indicating a bluish tint.

[0090] Depend on Figure 8 It can be seen that, for the dyed polyester samples ①, ②, ③, ④, and ⑤, sample ③ has the highest brightness, and sample ④ has the lowest brightness; sample ① has the highest a* value, indicating a redder color; sample ⑤ has the highest b* value, indicating a yellowish color. Under visible light at 480 nm, the dyed polyester sample ⑤ has the highest K / S value, indicating that the more 1,4-dihydroxyanthraquinone added during the chain extension stage, the better the dyeing performance of the prepared polyurethane polymer dye.

[0091] Dry / wet rubbing color fastness test

[0092] For dry rubbing color fastness, the dyed polyester samples ①, ②, ③, ④, and ⑤ all achieved a grade of 5, while the wet rubbing color fastness was grade 4. This demonstrates that the polyester fabrics dyed with the five waterborne polyurethane polymer dyes prepared in this paper exhibit good color fastness. This is because 1,4-dihydroxyanthraquinone is covalently bonded to the polyurethane chain segments. As long as the molecular aggregate structure of the polyurethane is not destroyed, color fading will not occur, thus exhibiting excellent dry / wet rubbing color fastness.

[0093] The optimal experimental conditions for preparing diethyl terephthalate (BHET) by alcoholysis of waste polyester fibers were as follows: the catalyst was a transparent homogeneous liquid with a mass ratio of choline chloride and zinc acetate of 1:1; the mass ratio of ethylene glycol (EG) to polyester fibers was 4:1; and the alcoholysis was carried out at 185°C for 4 hours to obtain BHET monomer and its oligomer.

[0094] In the experiment for preparing waterborne polyurethane polymer dyes, four stages were established: prepolymerization, chain extension, neutralization, and emulsification. In the chain extension stage, 1,4-dihydroxyanthraquinone was used as a chain extender to replace part of the 1,4-butanediol, resulting in five waterborne polyurethane polymer dyes. Using the mass ratio of 1,4-butanediol to 1,4-dihydroxyanthraquinone as a variable, five ratios were set: 7:3, 6:4, 5:5, 4:6, and 3:7. The dyes were characterized by infrared and ultraviolet analysis, and their phase structure, thermal stability, thermal properties, viscosity, surface tension, and dyeing performance were tested.

[0095] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing waterborne polyurethane polymer dyes based on waste polyester, characterized in that, Including the following step: S1. Preparation of diethyl terephthalate (BHET): Choline chloride and... (The text abruptly ends here, so the translation stops as well.) Zinc acetate mixture was placed in a container and heated and stirred in a water bath at 60°C for 4 hours to obtain a transparent and homogeneous product. A liquid, which will act as a catalyst for the alcoholysis reaction; Waste polyester textiles were washed, dried, and pulverized to obtain polyester fibers. The polyester fibers, ethylene glycol, and the aforementioned alcoholysis catalyst were mixed in a three-necked flask at a mass ratio of 2:8:0.8 for alcoholysis reaction at 185℃-200℃ for 4-5 hours. After the reaction was complete, the alcoholysis liquid was poured off and quickly filtered while hot. The insoluble matter was the un-alcoholized polyester fibers. Excess boiling deionized water was added to the filtrate, and the mixture was filtered three times. The filtrate obtained from the last filtration was placed in a refrigerator at 4℃ for recrystallization for 24 hours to obtain colorless needle-like crystals. The colorless needle-like crystals were washed, filtered, and dried to obtain the alcoholysis product, diethyl terephthalate (BHET). S2. Synthesis of waterborne polyurethane polymer emulsion dyes: First, the dehydrated alcoholysis products, bis(hydroxyethyl) terephthalate (BHET) and 2,2-dimethylolpropionic acid (DMPA), are placed in a three-necked flask. Then, an appropriate amount of NMP is added as a solvent, with a solvent weight of 0.3-0.5g. The temperature is set at 90℃, and the mixture is mechanically stirred for 1 hour. During this time, it is necessary to observe whether the solid is dispersed. When the inside of the flask shows a transparent and homogeneous liquid with no solid residue, proceed to the next step. Next, adjust the oil bath temperature to 85°C, add isophorone diisocyanate (5.8-6.0g) to the three-necked flask, and add a catalyst (0.04-0.1g of dibutyltin dilaurate). Set the temperature to 85°C and stir mechanically for 4 hours. During this time, pay attention to the viscosity of the reaction system. The viscosity will increase during the experiment, and acetone will be added intermittently to adjust it. Then, while stirring continuously, wait for the oil bath temperature to drop to 60℃, add the chain extender BDO and 1,4-dihydroxyanthraquinone, where the mass ratio of chain extender 1,4-butanediol to 1,4-dihydroxyanthraquinone is set to 3:

7. Maintain a constant temperature of 60℃, add the neutralizing agent TEA, and mechanically stir for 0.5h. Adjust the pH of the system to 6-9. Finally, after the reaction system has cooled to room temperature, the stirring speed is increased, and a mixture of deionized water and ethylene glycol is added dropwise to the flask. The weight ratio of deionized water to ethylene glycol is 1:1, and the mass of the mixture is 20-30 mL. Then, under the action of high-speed shearing of the rotor, waterborne polyurethane polymer emulsion dye is obtained.

2. The method for using waterborne polyurethane polymer dyes prepared from waste polyester according to claim 1, characterized in that: Prepare the sized polyester fabric and cut it into 5 rectangular strips of 4cm x 8cm. Sonicate the water-based polyurethane emulsion dye for 2 minutes to disperse it evenly. Immerse the polyester fabric in the evenly dispersed water-based polyurethane emulsion dye and heat it in a water bath at 70℃-80℃ for 20-30 minutes. Then remove it from the emulsion dye and place it in a 190℃ forced-air drying oven for 2 minutes of high-temperature color fixing. Repeat the immersion and high-temperature color fixing process twice. Finally, remove the fabric strips, wash and dry them.

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