A water-dispersible polyester material, its preparation and use

Abstract

The present application relates to the technical field of textiles, and particularly relates to a water-dispersible polyester material and a preparation method and application thereof. The method comprises the following steps: (1) the raw materials comprise an ester exchange catalyst, aromatic dimethyl ester, a dihydroxy compound and an alpha-hydroxy polycarboxylic acid; (2) the ester exchange catalyst, the aromatic dimethyl ester and the dihydroxy compound are reacted to obtain a water-dispersible polyester intermediate; and (3) the water-dispersible polyester intermediate is reacted with the alpha-hydroxy polycarboxylic acid to obtain the water-dispersible polyester material. The water-dispersible polyester material prepared by the method has multiple sulfonic acid groups and multiple carboxylic acid groups, so that the water-dispersible polyester material can exhibit significantly different and easily adjustable hydrophilicity and aggregation states in a wide pH or electrolyte concentration range, and can exhibit significantly different performance characteristics in different use environments.

Description

Technical Field

[0001] The present invention relates to the field of textile technology, and in particular to a water-dispersible polyester material and a preparation method and application thereof. Background Art

[0002] Currently, during the dyeing of polyester fibers with disperse dyes in a high-temperature, high-pressure dye bath, to inhibit the melting and aggregation of the disperse dyes, as well as their crystal transformation under alternating heating and cooling, and to ensure the thermal stability of the dye bath and the stability of the dye aggregates, high-temperature leveling agents based on a composite system of nonionic and anionic surfactants, or dispersants such as lignin, cardanol, polycarboxylic acids, and naphthalenesulfonic acid formaldehyde condensates, are often added to the dye bath. Among these, naphthalenesulfonic acid formaldehyde condensate dispersants have poor heat stability and high raw material costs, while polycarboxylic acid dispersants require harsh reaction conditions, complex processes, and high industrialization costs. Furthermore, the weakly hydrophilic polyester oligomers produced during the high-temperature, high-pressure dyeing process on polyester fibers require the assistance of surfactants (or dispersants) in a high-temperature, alkaline environment for relatively effective removal. Furthermore, to fully remove post-dyeing floating colors, the water-insoluble disperse dyes must be subjected to reduction soaping under alkaline, reducing conditions. These processes are not only energy-intensive, complex, and environmentally unfriendly, but also offer unsatisfactory results. Theoretically, the above confusion is due to the fact that traditional dispersants, leveling agents, and soaping agents have significantly insufficient affinity for polyester oligomers and disperse dyes, and their hydrophilicity / water solubility is sensitive to hard water and high temperature, and even become ineffective at high temperature.

[0003] Specifically, common dispersants and leveling agents related to polyester fibers or disperse dyes mainly include the following:

[0004] 1. Cardanol-based dispersants and high-temperature leveling agents for disperse dyes, mainly including cardanol sulfonates, cardanol sulfates, cardanol ethoxylates, cardanol carboxylates, cardanol quaternary ammonium salts and gemini surfactants.

[0005] For example, in "Preparation and Dyeing Properties of Highly Dispersible Hard Water Resistant High Temperature Leveling Agents" (Volume 37, Issue 8, 2020) written by Zhang Shenggang and Liu Yuqing, the complex of cardanol polyoxyethylene ether TF-n (EOn=3, 5, 7, 9, 10) and cardanol polyoxyethylene ether ammonium sulfonate was used for high temperature and high pressure dyeing of disperse dyes. The dispersion, slow dyeing, migration and dyeing effects (color yield, dyeing fastness, etc.) were found. It was found that the cardanol-based disperse dye high temperature leveling agent has better slow dyeing properties for disperse dyes than the traditional AB type high temperature leveling agent composed of glycerol polyoxyethylene ether oleate and styrylphenol polyoxyethylene ether sulfonate, and the difference in dyeing performance between the two under hard water conditions is more obvious; at the same time, the two are relatively close in migration performance.

[0006] The cashew phenol polyoxyethylene ether sulfate high temperature leveling agent is prepared by sulfonating the cashew phenol polyoxyethylene ether and amino sulfonic acid, and is disclosed in Biomass Cashew Phenol Polyoxyethylene Ether and Amino Sulfonic Acid Sulfonated to Generate Cashew Phenol Polyoxyethylene Ether Sulfate High Temperature Leveling Agent by Li Haonan and Wang Shugen (Journal of Xi'an University of Engineering, Vol. 29, No. 6, 2015). It is found that the cashew phenol polyoxyethylene ether sulfate has good dispersing capacity for disperse dyes, good leveling performance and migration for high temperature dyeing of polyester fabrics, and the leveling performance and migration of the polyester fabric dyed by the cashew phenol polyoxyethylene ether sulfate are roughly the same as those of the commercially available high temperature leveling agent.

[0007] However, although the high dispersion and hard water resistant high temperature leveling agent in the literature contains aromatic ring structure which has good affinity with polyester and disperse dyes, the composite surfactant type dispersant or high temperature leveling agent composed of "hydrophilic + hydrophobic" and "nonionic + anionic" structures still has problems of poor hard water resistance, poor high temperature resistance, weak dispersing and chelating capacity, and the like, due to the reasons of weak ionicity, lack of common structure with the dispersed objects (disperse dyes and polyester oligomers), lack of effective chelating structure, and serious deterioration of the hydrophilicity of the polyether chain segment which is important for dispersing force at high temperature.

[0008] 2. Lignin-based disperse dye dispersant and high temperature leveling agent, mainly including lignin sulfonate which is a byproduct of acid pulping and alkali lignin sulfonate which is a byproduct of alkali pulping.

[0009] The sulfomethylated alkali lignin is prepared by sulfomethylation reaction of formaldehyde and sodium bisulfite at high temperature and using acid-extracted alkali lignin as raw material, which is disclosed in Preparation and Performance of High Temperature Sulfomethylated Alkali Lignin Dye Dispersant by Zhang Zhiming, Zhou Mingsong and Yang Dongjie et al. (Fine Chemicals, Vol. 31, No. 12, 2014). It is found that the sulfomethylated alkali lignin has better comprehensive performance when the content of sulfonic acid group is 1.2-1.4 mmol / g, and the high temperature stability is obviously better than that of the traditional commercial dye dispersant, but it still has certain staining property to fibers.

[0010] The lignin-based dye dispersant is prepared by carboxymethylation of lignin, and then hydroxymethylation and sulfonation of formaldehyde and sodium bisulfite, which is disclosed in Preparation and Application Research of Lignin-based Dye Dispersant by Liu Zhipeng and Liu Minghua (Cellulose Science and Technology, Vol. 23, No. 3, 2015). It is found that the dispersing grade of the lignin-based dye dispersant for disperse dyes can reach 5.0 grade, and the dispersing performance meets the commercial requirements, and the product can maintain good dispersing performance at 150℃.

[0011] However, while lignin with a high sulfonic acid group content tends to have a lower staining rate on polyester fibers, its staining properties are still higher than those of traditional commercial dye dispersants. Furthermore, the sulfonation modification of lignin often requires the addition of formaldehyde, resulting in poor environmental performance. Similarly, because lignin sulfonates lack structural similarities and effective chelating properties with the dispersed materials (polyester oligomers and disperse dyes), they still cannot effectively clean dyed polyester fibers without the support of a reducing or alkaline environment.

[0012] 3. Polycarboxylic acid dispersants and soaping agents, mainly copolymers of maleic acid and acrylic acid or complexes based thereon.

[0013] For example, the copolymer of maleic anhydride and acrylic acid (acidic soaping agent) disclosed in "Acidic Soaping of Maleic Anhydride Acrylic Acid Polymer" ("Knitting Industry" 2013 Issue 1) by Song Qingshuang, Zheng Qingkang and Du Gaomin shows that after the dyed fabric is washed with acidic soaping agent, the K / S value, color saturation and various color fastness of the fabric are higher; compared with the traditional soaping process based on surfactants, the K / S value and color saturation of the fabric after washing with acidic soaping agent are higher, the dye hydrolysis is less, the various color fastness are improved or remain the same, and it has a significant water-saving effect.

[0014] As described in Yan Zi's article "Development and Application of a New Acidic Soaping Agent" (Journal of Xi'an Polytechnic University, Vol. 25, No. 6, 2011), a new acidic soaping agent was prepared by copolymerizing maleic anhydride, acrylic acid, and N-vinyl pyrrolidone, followed by compounding with carboxyethyl thiosuccinic acid and hydroxyethylidene diphosphonic acid. The study found that fabrics washed with the new acidic soaping agent exhibited brighter color and improved color fastness than those washed with conventional soaping agents. Furthermore, due to its strong acidity, it can be used as an alternative to acetic acid for neutralization, simplifying the soaping process.

[0015] However, despite their excellent dispersibility, foam-free nature, and low production cost, polycarboxylic acid acidic soaping agents lack ideal stain resistance. Similarly, due to their lack of structural commonality with polyester oligomers and disperse dyes, polycarboxylic acid acidic soaping agents cannot be used for disperse dye dyeing and soaping polyester fibers. Furthermore, they cannot effectively clean dyed polyester fibers from floating colors in the absence of a reducing or alkaline environment. Summary of the Invention

[0016] The present application aims to overcome the above-mentioned problems existing in the prior art and provides a water-dispersible polyester material, a preparation method and application thereof. The water-dispersible polyester material prepared by the method can be used as a high-temperature level dyeing agent and a reduction-free soaping agent for disperse dyeing, and can also be used for water-based dispersion of polyester material fine powder, surface hydrophilic modification and inhibition of aggregation tendency of water-based disperse dye, etc. The water-dispersible polyester material has multiple sulfonic acid groups and multiple carboxylic acid groups in the structure, which can exhibit significantly different and easily adjustable hydrophilicity and aggregation state in a wide range of pH or electrolyte concentration, and can exhibit significantly different performance characteristics in different use environments. Meanwhile, the multiple carboxylic groups on adjacent carbon atoms in the molecular structure also endow it with excellent dispersion and chelation capacity.

[0017] To achieve the above-mentioned purpose, the present application provides a method for preparing a water-dispersible polyester material, which comprises the following steps:

[0018] (1) Raw material preparation: the raw material comprises an ester exchange catalyst, an aromatic dimethyl ester, a dihydroxy compound and an α-hydroxy polycarboxylic acid;

[0019] The ester exchange catalyst is zinc acetate;

[0020] The aromatic dimethyl ester is dimethyl isophthalate-5-sodium sulfonate and dimethyl terephthalate;

[0021] The dihydroxy compound is selected from dihydric alcohol and optional polyethylene glycol; the dihydric alcohol is selected from one of ethylene glycol, 1,4-butanediol, 1,6-hexanediol and diethylene glycol;

[0022] The α-hydroxy polycarboxylic acid is citric acid;

[0023] The molar fractions of the components in the raw material are as follows: aromatic dimethyl ester 10, dihydroxy compound 5-9, α-hydroxy polycarboxylic acid 2-10, and the molar fraction of the α-hydroxy polycarboxylic acid = 2×(molar fraction of aromatic dimethyl ester-molar fraction of dihydroxy compound);

[0024] (2) Chain extension: the ester exchange catalyst, the aromatic dimethyl ester and the dihydroxy compound are reacted to prepare a water-dispersible polyester intermediate;

[0025] (3) End capping: the water-dispersible polyester intermediate is reacted with the α-hydroxy polycarboxylic acid to prepare the water-dispersible polyester material.

[0026] Preferably, the molar proportion of the dimethyl isophthalate-5-sodium sulfonate is 20-40% based on the total molar amount of the aromatic dimethyl ester.

[0027] Preferably, the amount of the transesterification catalyst used is 0.4 to 0.8% of the total weight of the aromatic dimethyl ester, the dihydroxy compound and the α-hydroxy polycarboxylic acid.

[0028] Preferably, the specific process of step (2) includes:

[0029] (2.1) Place the transesterification catalyst, aromatic dimethyl ester, and dihydroxy compound into the reactor, heat the reaction system to 150-200°C within 10-30 minutes, and maintain the temperature for 50-100 minutes under nitrogen protection, reflux, and stirring;

[0030] (2.2) The reaction system in step (2.1) is heated to 200-250° C. within 10-30 minutes, and the reaction is carried out for 50-100 minutes under nitrogen protection, condensation reflux and stirring to obtain a water-dispersible polyester macromolecular intermediate.

[0031] Preferably, the specific process of step (3) includes:

[0032] (3.1) adding α-hydroxy polycarboxylic acid to the reaction system obtained in step (2.2), maintaining the reaction conditions of step (2.2), and continuing the reaction for 30 to 60 minutes;

[0033] (3.2) Adjust the temperature of the reaction system obtained in step (3.1) to 230-280°C, and keep the reaction warm for 30-60 minutes under stirring and a vacuum degree of 0.02-0.05 MPa to obtain a water-dispersible polyester material.

[0034] Preferably, the molecular weight of the polyethylene glycol is 200-400.

[0035] The second aspect of the present invention provides a water-dispersible polyester material prepared according to the method described above.

[0036] The third aspect of the present invention provides the use of the water-dispersible polyester material described above in a disperse dye dyeing process.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The dispersed polyester material prepared by the method described herein has multiple sulfonic acid and carboxylic acid groups in its molecular structure, enabling it to exhibit significantly different and easily adjustable hydrophilicity and aggregation states over a wide range of pH or electrolyte concentrations, thus enabling it to exhibit significantly different performance characteristics under different usage environments. Specifically, by varying the pH of the applied medium, the degree of ionization of the multiple carboxyl groups in the molecular structure of the present invention product can be conveniently adjusted, thereby enabling the regulation of the interaction between the product and the dispersed object and the dispersion medium, thereby maximizing the effectiveness of the present invention product and expanding its application range. For example, in the dyeing process of polyester fibers with disperse dyes, to enhance its dispersion and "carrier-like" dye-promoting effects, the dye bath pH can be controlled to a low range. This suppresses its hydrophilicity / water solubility, thereby enhancing its dye solubilization and stabilization, as well as its adsorption capacity on the polyester fiber surface. During the post-dyeing rinsing stage, the dye bath pH can be controlled to a high range, thereby enhancing its water solubility, chelation, and dispersibility in the rinse bath, thereby enhancing its "soaping" ability.

[0039] 2. The dispersed polyester material prepared using the method described herein possesses a molecular structure (polyester structural units) that is universally compatible with disperse dyes and polyester molecules. Based on the principle of "like dissolves like," it exhibits excellent dyebath stabilization and leveling effects in disperse dye-on-polyester fiber dyeing systems, thereby simplifying the complex and inefficient dyeing heating process into a simple, direct, and efficient one. In particular, the product prepared using the method described herein exhibits a strong affinity for disperse dyes and polyester oligomers, coupled with its excellent chelating and dispersing properties, enabling effective cleaning of disperse dye-dyed fabrics without the aid of reducing agents or alkaline agents, resulting in a simple and environmentally friendly post-dye cleaning process.

[0040] 3. The dispersed polyester material prepared using the method described herein, characterized by multiple carboxyl groups (including the byproduct "polycitric acid") located on adjacent carbon atoms in its molecular structure, also imparts excellent dispersing and chelating capabilities. Specifically, the dispersing ability of the product of the present invention is not solely dependent on the water solubility of the "isolated" sulfonic acid groups in its molecular structure, but rather on the enhanced and complementary chelating dispersing power imparted by multiple carboxyl groups located on adjacent carbon atoms. This chelating dispersing ability is further enhanced in weakly alkaline environments. This structural design further enhances its dispersing, chelating, and cleaning properties, and has a broad range of applications. DETAILED DESCRIPTION

[0041] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0042] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0043] One aspect of the present invention provides a method for preparing a water-dispersible polyester material, the method comprising the following steps:

[0044] (1) Raw material preparation: The raw materials include an ester exchange catalyst, an aromatic dimethyl ester, a dihydroxy compound, and an α-hydroxy polycarboxylic acid;

[0045] The transesterification catalyst is zinc acetate;

[0046] The aromatic dimethyl esters are dimethyl 5-sulfonate sodium isophthalate and dimethyl terephthalate;

[0047] The dihydroxy compound is selected from diols and optionally polyethylene glycol; the diol is selected from one of ethylene glycol, 1,4-butanediol, 1,6-hexanediol and diethylene glycol;

[0048] The α-hydroxy polycarboxylic acid is citric acid;

[0049] The molar fractions of the components in the raw materials are: 10 aromatic dimethyl esters, 5-9 dihydroxy compounds, and 2-10 α-hydroxy polycarboxylic acids, where the molar fraction of the α-hydroxy polycarboxylic acid = 2×(the molar fraction of the aromatic dimethyl ester - the molar fraction of the dihydroxy compound);

[0050] (2) Chain extension: reacting an ester exchange catalyst, an aromatic dimethyl ester, and a dihydroxy compound to obtain a water-dispersible polyester intermediate;

[0051] (3) End-capping: reacting a water-dispersible polyester intermediate with an α-hydroxy polycarboxylic acid to obtain a water-dispersible polyester material.

[0052] According to some specific embodiments of the present invention, the molar fraction of the dihydroxy compound can be 5, 6, 7, 8 or 9.

[0053] According to some specific embodiments of the present invention, the molar fraction of the α-hydroxy polycarboxylic acid can be 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0054] In the present invention, the dihydroxy compound refers to an organic compound having two hydroxyl groups. It can be a diol, or a combination of a diol and polyethylene glycol. Preferably, the molecular weight of the polyethylene glycol is 200 to 400.

[0055] In the present invention, the aromatic dimethyl ester is composed of dimethyl 5-sulfoisophthalate sodium salt and dimethyl terephthalate. Preferably, the molar proportion of dimethyl 5-sulfoisophthalate sodium salt is 20-40% based on the total molar amount of the aromatic dimethyl ester.

[0056] In a preferred embodiment, the amount of the transesterification catalyst used is 0.4 to 0.8% of the total weight of the aromatic dimethyl ester, the dihydroxy compound and the α-hydroxy polycarboxylic acid.

[0057] In a preferred embodiment, the specific process of step (2) includes:

[0058] (2.1) Place the transesterification catalyst, aromatic dimethyl ester, and dihydroxy compound into the reactor, heat the reaction system to 150-200°C within 10-30 minutes, and maintain the temperature for 50-100 minutes under nitrogen protection, reflux, and stirring;

[0059] (2.2) The reaction system in step (2.1) is heated to 200-250° C. within 10-30 minutes, and the reaction is carried out for 50-100 minutes under nitrogen protection, condensation reflux and stirring to obtain a water-dispersible polyester macromolecular intermediate.

[0060] In the present invention, during steps (2.1) and (2.2), the distilled by-products may be separated.

[0061] In a preferred embodiment, the specific process of step (3) includes:

[0062] (3.1) adding α-hydroxy polycarboxylic acid to the reaction system obtained in step (2.2), maintaining the reaction conditions of step (2.2), and continuing the reaction for 30 to 60 minutes;

[0063] (3.2) Adjust the temperature of the reaction system obtained in step (3.1) to 230-280°C, and keep the reaction warm for 30-60 minutes under stirring and a vacuum degree of 0.02-0.05 MPa to obtain a water-dispersible polyester material.

[0064] In the present invention, in the step (3.1), maintaining the reaction conditions of step (2.2) means that the reaction temperature, nitrogen protection, condensation reflux and stirring conditions during the continued reaction remain consistent with those of step (2.2).

[0065] In the present invention, during step (3.2), the distilled by-products may be separated.

[0066] The second aspect of the present invention provides a water-dispersible polyester material prepared according to the method described above.

[0067] The third aspect of the present invention provides the use of the water-dispersible polyester material described above in a disperse dye dyeing process.

[0068] The water-dispersible polyester material prepared by the method described herein can be used as a high-temperature leveling agent and a reducing-free soaping agent for disperse dye dyeing. It can also be used for aqueous dispersion of polyester material micropowders, surface hydrophilic modification, and aggregation inhibition of water-based disperse dyes. The water-dispersible polyester material exhibits significantly different and easily adjustable hydrophilicity and aggregation states over a wide range of pH or electrolyte concentrations, enabling it to exhibit significantly different performance characteristics under different usage environments. Furthermore, it possesses excellent dispersing and chelating capabilities, greatly expanding its application range.

[0069] The finished product prepared by the method of the present invention must be stored in a cool, dry place in a sealed manner.

[0070] The present invention will be described in detail below through examples, but the protection scope of the present invention is not limited thereto.

[0071] Table 1

[0072]

[0073] Example 1

[0074] (1) Raw material preparation. The specific selection and amount of the raw materials are shown in Table 1.

[0075] (2) Chain extension: reacting an ester exchange catalyst, an aromatic dimethyl ester, and a dihydroxy compound to obtain a water-dispersible polyester macromolecular intermediate;

[0076] (2.1) Place the transesterification catalyst, aromatic dimethyl ester, and dihydroxy compound into the reactor. Raise the temperature of the reaction system to 155±1°C within 15 minutes. Maintain the temperature under nitrogen protection, reflux, and stirring for 65 minutes. During this time, separate the distilled by-products.

[0077] (2.2) heating the reaction system obtained in step (2.1) to 225±1°C within 15 minutes, and maintaining the temperature for 65 minutes under nitrogen protection, reflux, and stirring, during which the distilled by-products were separated to obtain a water-dispersible polyester macromolecular intermediate;

[0078] (3) End-capping: reacting a water-dispersible polyester macromolecular intermediate with an α-hydroxy polycarboxylic acid to obtain a water-dispersible polyester material.

[0079] (3.1) Add α-hydroxy polycarboxylic acid to the water-dispersible polyester macromolecular intermediate obtained in step (2.2), and continue the reaction at 225±1°C under nitrogen protection, reflux and stirring for 40 minutes;

[0080] (3.2) The temperature of the reaction system obtained in step (3.1) was adjusted to 255±1°C, and the reaction was carried out under a vacuum degree of 0.03-0.04 MPa with stirring for 35 minutes, during which the distilled by-products were separated to obtain a water-dispersible polyester material.

[0081] Example 2

[0082] (1) Raw material preparation. The specific selection and amount of the raw materials are shown in Table 1.

[0083] (2) Chain extension: reacting an ester exchange catalyst, an aromatic dimethyl ester, and a dihydroxy compound to obtain a water-dispersible polyester macromolecular intermediate;

[0084] (2.1) Add the transesterification catalyst, aromatic dimethyl ester, and dihydroxy compound to the reactor. Raise the temperature of the reaction system to 165±1°C within 20 minutes. Maintain the temperature under nitrogen protection, reflux, and stirring for 75 minutes. During this time, separate the distilled by-products.

[0085] (2.2) heating the reaction system obtained in step (2.1) to 235±1°C within 20 minutes, and maintaining the temperature for 75 minutes under nitrogen protection, reflux, and stirring, during which the distilled by-products were separated to obtain a water-dispersible polyester macromolecular intermediate;

[0086] (3) End-capping: reacting a water-dispersible polyester macromolecular intermediate with an α-hydroxy polycarboxylic acid to obtain a water-dispersible polyester material.

[0087] (3.1) Add α-hydroxy polycarboxylic acid to the water-dispersible polyester macromolecular intermediate obtained in step (2.2), and continue the reaction at 235±1°C under nitrogen protection, reflux and stirring for 50 minutes;

[0088] (3.2) The temperature of the reaction system obtained in step (2.1) was adjusted to 255±1°C, and the reaction was carried out under a vacuum degree of 0.02-0.03 MPa with stirring for 35 minutes, during which the distilled by-products were separated to obtain a water-dispersible polyester material.

[0089] Example 3

[0090] (1) Raw material preparation. The specific selection and amount of the raw materials are shown in Table 1.

[0091] (2) Chain extension: reacting an ester exchange catalyst, an aromatic dimethyl ester, and a dihydroxy compound to obtain a water-dispersible polyester macromolecular intermediate;

[0092] (2.1) Place the transesterification catalyst, aromatic dimethyl ester, and dihydroxy compound into the reactor, raise the temperature of the reaction system to 175±1°C within 25 minutes, and maintain the reaction temperature for 80-90 minutes under nitrogen protection, reflux, and stirring. During this time, separate the distilled by-products.

[0093] (2.2) heating the reaction system obtained in step (2.1) to 245±1°C within 25 minutes, and maintaining the temperature for 75 minutes under nitrogen protection, reflux, and stirring, during which the distilled by-products were separated to obtain a water-dispersible polyester macromolecular intermediate;

[0094] (3) End-capping: reacting a water-dispersible polyester macromolecular intermediate with an α-hydroxy polycarboxylic acid to obtain a water-dispersible polyester material.

[0095] (3.1) Add α-hydroxy polycarboxylic acid to the reaction system obtained in step (2.2), and continue the reaction at 245±1°C under nitrogen protection, reflux, and stirring for 55 minutes;

[0096] (3.2) The temperature of the reaction system obtained in step (3.1) was adjusted to 265±1°C, and the reaction was carried out under a vacuum degree of 0.025-0.035 MPa with stirring for 42 minutes, during which the distilled by-products were separated to obtain a water-dispersible polyester material.

[0097] The water-dispersible polyester material prepared in the embodiment can be used as a high-temperature leveling agent in the disperse dyeing process and as a reducing-free detergent for fabrics after dyeing.

[0098] ① In the process of dyeing polyester fibers with disperse dyes: there is no need to use a disperse dye high-temperature leveling agent composed of anionic / non-ionic surfactants, and the temperature rise control during the dyeing process does not need to be divided into three stages for different control as in the traditional process. It is only necessary to add the water-dispersible polyester material described in the present invention to the dyeing bath "in the same bath" (2-4 / L) to achieve the stabilization of the disperse dye dye bath and the one-step direct dyeing temperature increase process, making the high-temperature and high-pressure dyeing process of polyester fibers with disperse dyes easier to control.

[0099] ② After disperse dyeing polyester fibers, there is no need to wash away residual "floating" disperse dye on the fibers with sodium hydrosulfite and an alkali agent, as in conventional processes (process: sodium hydrosulfite 4-8 g / L, sodium carbonate 3-6 g / L, 75°C water washing for 10 minutes) to achieve good color fastness. Instead, the present invention only requires washing away residual "floating" disperse dye on the fibers with the water-dispersible polyester material (process: water-dispersible polyester 3-6 g / L, 75°C water washing for 10 minutes), achieving the same color fastness as conventional post-dyeing washing processes (all wet fastnesses are grade 4-5). Because the present invention's post-disperse dye washing process does not require the assistance of an alkali agent or sodium hydrosulfite, it offers improved environmental friendliness and ease of production.

[0100] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing a water-dispersible polyester material, characterized in that: The method comprises the following steps: (1) Raw material preparation: The raw materials include an ester exchange catalyst, an aromatic dimethyl ester, a dihydroxy compound, and an α-hydroxy polycarboxylic acid; The transesterification catalyst is zinc acetate; The aromatic dimethyl ester is dimethyl isophthalate-5-sodium sulfonate and dimethyl terephthalate; based on the total molar amount of the aromatic dimethyl ester, the molar proportion of dimethyl isophthalate-5-sodium sulfonate is 20-40%; The dihydroxy compound is selected from one of ethylene glycol, 1,4-butanediol, 1,6-hexanediol and diethylene glycol, or one of ethylene glycol, 1,4-butanediol, 1,6-hexanediol and diethylene glycol and polyethylene glycol; the molecular weight of the polyethylene glycol is 200-400; The α-hydroxy polycarboxylic acid is citric acid; The molar fractions of the components in the raw materials are: 10 aromatic dimethyl ester, 5-9 dihydroxy compound alcohols, and 2-10 α-hydroxy polycarboxylic acids, where the molar fraction of α-hydroxy polycarboxylic acid = 2×(molar fraction of aromatic dimethyl ester - molar fraction of dihydroxy compound); (2) Chain extension: reacting an ester exchange catalyst, an aromatic dimethyl ester, and a dihydroxy compound to obtain a water-dispersible polyester intermediate; (3) End-capping: The water-dispersible polyester intermediate is reacted with α-hydroxy polycarboxylic acid to obtain a water-dispersible polyester material.

2. The method according to claim 1, characterized in that The amount of the transesterification catalyst used is 0.4-0.8% of the total weight of the aromatic dimethyl ester, the dihydroxy compound and the α-hydroxy polycarboxylic acid.

3. The method according to claim 1, characterized in that The specific process of step (2) includes: (2.1) Place the transesterification catalyst, aromatic dimethyl ester, and dihydroxy compound into the reactor, heat the reaction system to 150-200°C within 10-30 minutes, and maintain the reaction temperature for 50-100 minutes under nitrogen protection, reflux, and stirring; (2.2) The reaction system in step (2.1) is heated to 200-250°C within 10-30 minutes, and the reaction is carried out at this temperature for 50-100 minutes under nitrogen protection, condensation reflux, and stirring to obtain a water-dispersible polyester macromolecular intermediate.

4. The method according to claim 3, characterized in that The specific process of step (3) includes: (3.1) Add α-hydroxy polycarboxylic acid to the reaction system obtained in step (2.2), maintain the reaction conditions of step (2.2), and continue the reaction for 30 to 60 minutes; (3.2) Adjust the temperature of the reaction system obtained in step (3.1) to 230-280°C, and carry out the reaction at this temperature for 30-60 minutes under stirring and a vacuum degree of 0.02-0.05 MPa to obtain a water-dispersible polyester material.

5. A water-dispersible polyester material prepared by the method according to any one of claims 1 to 4.

6. Use of the water-dispersible polyester material according to claim 5 in a disperse dyeing process.

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