Method for producing aqueous polyurethane dispersion and its application

Abstract

The present invention discloses a method for preparing an aqueous polyurethane dispersant and its application, which belongs to the field of polymer dispersants. The specific steps are as follows: weigh out an isocyanate group-containing compound as an initiator, and produce a polyurethane prepolymer with polyethylene glycol in the presence of nitrogen and a catalyst; add an organic solvent to the reaction system to control the viscosity; add chain extender 1 at 75-80°C to carry out a chain extension reaction for 2-2.5 h; add chain extender 2 at 75-80°C to carry out a chain extension reaction for 2-2.5 h; reduce the temperature to 50-55°C; add an end-capping agent to carry out an end-capping reaction for 1-1.5 h; after the reaction is completed, add triethylamine to carry out a neutralization reaction for 1 h; add deionized water to emulsify at high speed for 20-30 min; and remove the organic solvent by vacuum distillation at room temperature to obtain an aqueous polyurethane dispersant. The dispersant of this structure has high grinding efficiency when preparing liquid indigo dye, and the storage stability of the dye is good.

Description

[Technical Field]

[0001] The present invention is in the field of polymeric dispersants and relates to a method for producing an aqueous polyurethane dispersion and its application in the production of liquid indigo. [Background technology]

[0002] Indigo dye is a type of dye with a simple structure and very low water solubility, and is mainly used for dyeing and printing jeans. Currently, indigo dye is mainly in powder form. Powder disperse dyes have the advantages of simple packaging, easy transportation, good storage stability, strong adaptability to processing equipment, and simple operation. However, since indigo dye does not have a strong affinity for cotton fibers and is difficult to dye deep colors, most of the dye concentrates on the surface of the fibers. In fact, during the jeans production process in factories, more than 20 washing processes must be carried out to remove color floating and related auxiliaries from the fabric surface, which results in large amounts of water consumption and pollution. In addition, powder indigo dye has defects such as dust pollution during the chemical reaction process and inaccurate paste preparation or solution metering, posing certain risks to people's health.

[0003] As the global trend toward green environmental protection continues to grow, the concept of ecological environmental protection is gradually being incorporated into various industries, and the lifestyle of "returning to nature, green environmental protection, and ecological health" is increasingly being advocated by more people. The ecological pollution caused by the textile and apparel industry, a traditional industry on which people depend, has always been the focus of global attention. As the most polluting process in the textile and apparel industry, the dyeing and washing processes of denim products cause extremely serious environmental pollution. Liquid indigo dyes can overcome some of the shortcomings of powder disperse dyes, achieve good dispersion with less dispersant, improve dye utilization, and in dyeing or printing, their small dye particles improve dyeing rates and allow for deeper dyeing. At the same time, they facilitate dye diffusion into the interior of the fiber, reduce color floating on the surface of the fiber, and reduce the subsequent washing process, significantly reducing the discharge of printing and dyeing wastewater from the source. This reduces the amount of dye and related auxiliaries in the dyeing wastewater, reducing environmental damage caused by the dyeing process and realizing the development concept of energy-saving and environmental protection. Therefore, the production of liquid dyes has become a hot research topic in recent years. However, there are currently very few studies on the production of liquid indigo dyes, and problems exist such as low grinding efficiency during the production of liquid dyes, and the nanoscale liquid indigo dyes produced grow larger during storage, resulting in aggregation and precipitation, which leads to problems such as uneven dyeing and poor reproducibility.

[0004] The key to solving these problems is the structure of the dispersant. A suitable dispersant structure can not only improve the grinding efficiency of liquid dyes, but also provide good stability for the liquid dyes. Currently, most dispersants used to produce liquid indigo dyes are low-molecular-weight anionic and nonionic dispersants, such as naphthalene-based, lignin sulfonate salts, and various polyoxyethylene ether-type dispersants. While these can produce nanoscale liquid dyes, they still suffer from low grinding efficiency and poor stability. Polymeric dispersants have attracted attention because they have a special anchoring group structure that not only allows them to adsorb firmly to the particle surface but also provides stable solvation segments for the system. Current polymeric dispersants have achieved numerous beneficial results in the production of liquid pigments and paints. For example, the Chinese Patent Application for Invention with application number CN201910844629.7 (publication number CN110540639A) discloses a parallel-type polymeric aqueous pigment dispersant. The synthesized parallel-type polymeric aqueous pigment dispersant has a comb-shaped branched structure and contains a naphthalene ring and a peripheral ethylene oxide / propylene oxide polymer long chain. The parallel-type polymeric aqueous pigment dispersant has excellent dispersion stability, storage stability, and resolubility for organic pigments, high grinding efficiency, strong viscosity reduction, and good color development. The Chinese Patent Application for Invention with application number CN202110585011.0 (publication number CN113278111A) discloses a terpolymer dispersant. This dispersant has high grinding efficiency when producing liquid disperse dyes and good dye storage stability. However, there is currently little research on polymeric dispersants in the production of liquid indigo, and further research and development of new products is urgently needed. Summary of the Invention [Means for solving the problem]

[0005] The object of the present invention is to provide a method for preparing a designed and synthesized aqueous polyurethane dispersant and its application, specifically to successfully prepare a liquid indigo dye with good storage stability by mechanically grinding the synthesized dispersant and powdered indigo dye.

[0006] The technical solution is as follows: The method for producing an aqueous polyurethane dispersion according to the present invention, the specific operation steps of which are as follows: (1) Weigh out an isocyanate group-containing compound as an initiator, and react it with polyethylene glycol of a certain molecular weight at 75 to 80°C for 2 to 2.5 hours in the presence of nitrogen and a catalyst to produce a polyurethane prepolymer; Add an appropriate amount of organic solvent to the reaction system to control the viscosity, (2) The temperature was kept constant, and chain extender 1 was added to carry out the chain extension reaction for 2 to 2.5 hours. (3) The temperature is kept constant, chain extender 2 is added, and the chain extension reaction is continued for 2 to 2.5 hours. (4) The temperature is lowered to 50 to 55°C, a terminal blocking agent is added, and the terminal blocking reaction is carried out for 1 to 1.5 hours. (5) After the reaction is complete, add an equimolar amount of triethylamine to the chain extender 1 and carry out a neutralization reaction for 1 hour. Add an appropriate amount of deionized water and emulsify at high speed for 20 to 30 minutes. Then, remove the organic solvent by vacuum distillation at room temperature to finally obtain an aqueous polyurethane dispersion.

[0007] Furthermore, in step (1), the initiator is either hexamethylene diisocyanate or isophorone diisocyanate; the polyethylene glycol is either PEG 400 or PEG 600; The molar ratio of the initiator to polyethylene glycol is 4:1 to 1.2.

[0008] Further, in step (1), the catalyst is dibutyltin dilaurate; The amount used accounts for 2% to 3% by mass of the two types of monomers, the initiator and polyethylene glycol.

[0009] Furthermore, in step (1), the organic solvent is either acetone or butanone.

[0010] Furthermore, in step (2), the chain extender 1 is either 2,2-hydroxymethylpropionic acid or 2,2-hydroxymethylbutyric acid; The molar ratio of the initiator, polyethylene glycol, and chain extender 1 is 4:1 to 1.2:1.2 to 1.5.

[0011] Furthermore, in step (3), the chain extender 2 is 1-phenyl-1,2-ethylene glycol; The molar ratio of the initiator, polyethylene glycol, chain extender 1, and chain extender 2 is 4:1 to 1.2:1.2 to 1.5:1.2.

[0012] Furthermore, in step (4), the end-capping agent is methyl ethyl ketone oxime, The molar ratio of the initiator, polyethylene glycol, chain extender 1, chain extender 2, and end-capping agent is 4:1-1.2:1.2-1.5:1.2:0.2-1.2.

[0013] Furthermore, the aqueous polyurethane dispersion prepared by the above-mentioned method is applied to the preparation of liquid indigo dye.

[0014] Furthermore, the specific process includes the steps of mixing indigo dye, aqueous polyurethane dispersant and water, first pre-grinding in a grinding cup at 1500 r / min for 5-10 minutes, then adding zirconia beads, and then continuing to grind in a sand mill at 3000 r / min for 1-2 hours to obtain liquid indigo dye.

[0015] Furthermore, the aqueous polyurethane dispersant accounts for 25% to 35% of the dry weight of the indigo dye, the dye content in the liquid indigo dye is 25%, the rotation speed of the sand mill is 3000 to 3500 r / min, and the diameter of the zirconia beads is 1 to 2 mm.

[0016] The beneficial effects are as follows. Comparing the present invention with the prior art, the present invention has the following characteristics: 1. The aqueous polyurethane dispersant prepared in the present invention is transparent in appearance and only a very light pale yellow in color. However, the dispersants used in the liquid indigo production process in current relevant literature are naphthalene-based and lignin-based dispersants, which themselves have a certain color. The produced liquid indigo dye inevitably affects the color of textiles during subsequent dyeing or printing. The pale yellow and transparent aqueous polyurethane can greatly solve this problem. 2. The liquid indigo dye prepared in the present invention greatly improves the production environment in factories, solving the problems of conventional powder dyes, which are harmful to the environment and cannot accurately control the metering and rapid material blending when weighed, used, and transported in large quantities in factories. This ensures the physical health of workplace workers and lays the foundation for future clean, automated production in the workplace. 3. The aqueous polyurethane dispersant designed and synthesized in the present invention does not contain multiple COOs during the chain extension process. - The introduction of 1-phenyl-1,2-ethylene glycol as an anchoring group significantly improves the dye anchoring effect compared to the single-point anchoring of conventional dispersants. At the same time, the polyethylene glycol chain end is connected to the polyurethane dispersant as a solvation segment, and this chain end functions as a highly solvated chain end, providing good compatibility with aqueous media and creating sufficient steric hindrance to effectively prevent re-aggregation of dye particles. At the same time, the NH and C=O structures in the polyurethane carbamate structure form hydrogen bonds with the NH and C=O structures in the indigo dye structure, further improving the bonding strength between the dispersant and the dye particles. The introduction of 1-phenyl-1,2-ethylene glycol introduces a highly planar benzene ring structure containing π-π bonds, further increasing the steric hindrance of the dispersant, thereby preventing collision and aggregation between dye particles and achieving a stable system. 4. The dispersant designed and synthesized in this invention has high grinding efficiency when producing liquid disperse dyes, good storage stability for nanoscale dyes, and significantly improved dyeability compared to powder dyes. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is an operational flow chart of the present invention. [Figure 2] FIG. 2 is an infrared spectrum diagram of the aqueous polyurethane dispersion prepared in Example 1 of the present invention. [Figure 3] FIG. 3 is a particle size diagram and an SEM photograph of the liquid indigo dye particles according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will now be further described with reference to the drawings and specific examples.

[0019] As shown in the figure, the method for producing an aqueous polyurethane dispersion according to the present invention, the specific operation steps are as follows: (1) Weigh out an isocyanate group-containing compound as an initiator, and react it with polyethylene glycol of a certain molecular weight at 75 to 80°C for 2 to 2.5 hours in the presence of nitrogen and a catalyst to produce a polyurethane prepolymer; Add an appropriate amount of organic solvent to the reaction system to control the viscosity, (2) The temperature (75-80°C) is kept constant, and chain extender 1 is added to carry out the chain extension reaction for 2-2.5 hours. (3) The temperature (75-80°C) is kept constant, and chain extender 2 is added to continue the chain extension reaction for 2-2.5 hours. (4) The temperature (75-80°C) is lowered to 50-55°C, a terminal blocking agent is added, and the terminal blocking reaction is carried out for 1-1.5 hours. (5) After the reaction is completed, add an equimolar amount of triethylamine to the chain extender 1 and carry out a neutralization reaction for 1 hour. Add an appropriate amount of deionized water and emulsify at high speed for 20-30 minutes. Then, remove the organic solvent by vacuum distillation at room temperature (usually 25°C) to finally obtain an aqueous polyurethane dispersion.

[0020] Furthermore, in step (1), the initiator is either hexamethylene diisocyanate or isophorone diisocyanate, preferably isophorone diisocyanate; the polyethylene glycol is either PEG 400 or PEG 600, preferably PEG 400; The molar ratio of the initiator to polyethylene glycol is 4:1 to 1.2, and preferably 4:1.

[0021] Further, in step (1), the catalyst is dibutyltin dilaurate; The amount used is 2% to 3% by mass of the two monomers, the initiator and polyethylene glycol, and is preferably 2% by mass.

[0022] Furthermore, in step (1), the organic solvent is either acetone or butanone, preferably acetone.

[0023] Furthermore, in step (2), the chain extender 1 is either 2,2-hydroxymethylpropionic acid or 2,2-hydroxymethylbutyric acid, preferably 2,2-hydroxymethylbutyric acid; The molar ratio of the initiator, polyethylene glycol, and chain extender 1 is 4:1 to 1.2:1.2 to 1.5, and preferably 4:1:1.5.

[0024] Furthermore, in step (3), the chain extender 2 is 1-phenyl-1,2-ethylene glycol; The molar ratio of the initiator, polyethylene glycol, chain extender 1, and chain extender 2 is 4:1 to 1.2:1.2 to 1.5:1.2, and preferably 4:1:1.5:1.2.

[0025] Furthermore, in step (4), the end-capping agent is methyl ethyl ketone oxime, The molar ratio of the initiator, polyethylene glycol, chain extender 1, chain extender 2, and end-capping agent is 4:1-1.2:1.2-1.5:1.2:0.2-1.2, and preferably 4:1:1.5:1.2:0.6.

[0026] Furthermore, the aqueous polyurethane dispersion prepared by the above-mentioned method is applied to the preparation of liquid indigo dye.

[0027] Furthermore, the specific process includes the steps of mixing indigo dye, aqueous polyurethane dispersant and water, first pre-grinding in a grinding cup at 1500 r / min for 5-10 minutes, then adding zirconia beads, and then continuing to grind in a sand mill at 3000 r / min for 1-2 hours to obtain liquid indigo dye.

[0028] Furthermore, the aqueous polyurethane dispersant accounts for 25% to 35% of the dry weight of the indigo dye, preferably 27%, the dye content in the liquid indigo dye is 25%, the rotation speed of the sand mill is 3000 to 3500 r / min, preferably 3000 r / min, and the diameter of the zirconia beads is 1 to 2 mm, preferably 1 mm.

[0029] Example 1 (1) Synthesis of aqueous polyurethane dispersion The molar ratio of six monomers, initiator, polyethylene glycol, chain extender 1, chain extender 2, end capping agent, and neutralizer, was calculated to be 4:1:1.5:1.2:0.6:1.5. 1 mol of polyethylene glycol 400 was added to a three-necked flask equipped with a stirrer and a reflux condenser. The three-necked flask was then placed in an oil bath, the temperature was raised to 120°C, and the mixture was dehydrated under vacuum for 1 hour. The temperature was then lowered to 75°C, and 4 mol of isophorone diisocyanate and 2% by mass of dibutyltin dilaurate of the above two monomers were added. Nitrogen was blown in for 5 minutes, and the mixture was allowed to react for 2 hours to produce a polyurethane prepolymer. Add an appropriate amount of acetone to control the viscosity, keep the temperature constant, add 1.5 mol of chain extender 2,2-hydroxymethylbutyric acid and carry out chain extension reaction for 2 hours, add 1.2 mol of chain extender 1-phenyl-1,2-ethylene glycol and continue chain extension reaction for 2 hours at the same temperature, then reduce the temperature to 50°C, add 0.6 mol of methyl ethyl ketone oxime and carry out end-capping reaction for 1 hour, after the reaction is completed, add 1.5 mol of triethylamine and carry out neutralization reaction for 1 hour, add an appropriate amount of deionized water and carry out high-speed emulsification for 20 minutes, and remove acetone by vacuum distillation at room temperature to obtain an aqueous polyurethane dispersant.

[0030] The infrared spectrum of the aqueous polyurethane dispersion prepared in Example 1 is shown in FIG. 2. As can be seen from FIG. 2, -1 is the C=O stretching vibration peak of the urea bond, urethane bond, and DMBA, and is 2970 cm -1 belongs to the antisymmetric stretching vibration peak of CH in 1-phenyl-1,2-ethylene glycol and IPDI, and is at 1090 cm -1 The peak at 1460 cm corresponds to the C-O-C bond stretching vibration peak of polyethylene glycol. These characteristic peaks prove the existence of a carbamate structure. -1 The peak corresponds to the CH deformation vibration peak of the methyl group and the CH shear vibration peak of the methylene group, and is located at 1560 cm -1 The peak at 2260 cm corresponds to the mixed peak of CC stretching vibration, CN stretching vibration and NH in-plane bending vibration. -1The areas before and after this are characteristic absorption peaks of -NCO, and the peak values ​​are weak, indicating that -NCO in IPDI was almost completely involved in the reaction.

[0031] Comparing the aqueous polyurethane dispersion solution prepared in Example 1 with aqueous solutions of conventional dispersants, the aqueous polyurethane dispersion is generally transparent and pale yellow in appearance, while the naphthalene-based and lignin-based dispersants are dark brown in color.

[0032] (2) Application of aqueous polyurethane dispersion in the production of liquid indigo dye The polymer dispersant prepared in step (1) and deionized water were placed in a grinding cup and pre-ground at 1500 r / min for 10 minutes. After that, indigo dye and zirconia beads were added and ground at 3000 r / min for 1 hour to obtain a liquid indigo dye. The dry weight of the indigo dye was 15 g, and the aqueous polyurethane dispersant accounted for 27% of the dry weight of the indigo. Deionized water was added to make up to 60 g, so that the dye concentration in the liquid indigo was 25%, and the diameter of the zirconia beads was 1 mm.

[0033] For the liquid indigo dye prepared using the aqueous polyurethane dispersant in step (2), the particle size distribution diagram and SEM photograph of the dye particles are shown in Figure 3. The D90 of the liquid indigo suspension was approximately 280 nm, and the particle size distribution was uniform, with no large particles. The SEM photograph also revealed that the particles in the liquid indigo suspension were small and showed no obvious aggregation. The particle sizes of the prepared liquid indigo dye after storage at room temperature for 7 days and at 60°C for 7 days are shown in Table 1. It was found that the dispersant with this structure had high grinding efficiency when preparing the liquid disperse dye, and the storage stability of the dye was good, with the particle size of the dye particles not changing significantly before and after storage.

[0034] [Table 1]

[0035] The above are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above examples. All technical solutions within the concept of the present invention are within the scope of protection of the present invention. Furthermore, any improvements and modifications made by those skilled in the art without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an aqueous polyurethane dispersion for producing liquid indigo dye, the specific operation steps of which are as follows: (1) Weigh out an isocyanate group-containing compound as an initiator, and react it with polyethylene glycol of a certain molecular weight in the presence of nitrogen and a catalyst at 75 to 80°C for 2 to 2.5 hours to produce a polyurethane prepolymer; Add an appropriate amount of organic solvent to the reaction system to control the viscosity, (2) While maintaining a constant temperature, either 2,2-hydroxymethylpropionic acid or 2,2-hydroxymethylbutyric acid is added as a chain extender 1, and the chain extension reaction is carried out for 2 to 2.5 hours; (3) Keep the temperature constant, add 1-phenyl-1,2-ethylene glycol as chain extender 2, and continue the chain extension reaction for 2 to 2.5 hours; (4) The temperature is lowered to 50 to 55°C, a terminal blocking agent is added, and the terminal blocking reaction is carried out for 1 to 1.5 hours. (5) After the reaction is completed, the method for producing an aqueous polyurethane dispersant is characterized in that: triethylamine in an amount equimolar to the chain extender 1 is added, a neutralization reaction is carried out for 1 hour; deionized water is added, and high-speed emulsification is carried out for 20 to 30 minutes; and the organic solvent is removed by distillation under reduced pressure at room temperature, thereby finally obtaining an aqueous polyurethane dispersant.

2. In step (1), the initiator is either hexamethylene diisocyanate or isophorone diisocyanate; the polyethylene glycol is either PEG 400 or PEG 600; 2. The method for producing an aqueous polyurethane dispersion according to claim 1, wherein the molar ratio of the initiator to polyethylene glycol is 4:1 to 1.

2.

3. In step (1), the catalyst is dibutyltin dilaurate; The method for producing an aqueous polyurethane dispersion according to claim 1, characterized in that the amount of the initiator and polyethylene glycol used is 2% by mass to 3% by mass of the two monomers.

4. 2. The method for producing an aqueous polyurethane dispersion according to claim 1, wherein in step (1), the organic solvent is either acetone or butanone.

5. 2. The method for producing an aqueous polyurethane dispersion according to claim 1, wherein in step (2), the molar ratio of the initiator to the polyethylene glycol to the chain extender is 4:1-1.2:1.2-1.

5.

6. 2. The method for producing an aqueous polyurethane dispersion according to claim 1, wherein in step (3), the molar ratio of the initiator, polyethylene glycol, chain extender 1, and chain extender 2 is 4:1 to 1.2:1.2 to 1.5:1.

2.

7. In step (4), the end-capping agent is methyl ethyl ketone oxime; The method for producing an aqueous polyurethane dispersion according to claim 1, wherein the molar ratio of the initiator, polyethylene glycol, chain extender 1, chain extender 2, and end-capping agent is 4:1-1.2:1.2-1.5:1.2:0.2-1.

2.

8. The use of the method for producing aqueous polyurethane dispersions according to claims 1 to 7, characterized in that the specific process includes the steps of mixing indigo dye, aqueous polyurethane dispersion and water, first pre-grinding in a grinding cup at 1500 r / min for 5 to 10 minutes, then adding zirconia beads, and then continuing to grind in a sand mill at 3000 r / min for 1 to 2 hours to obtain liquid indigo dye.

9. The use according to claim 8, wherein the aqueous polyurethane dispersion accounts for 25% to 35% of the dry weight of the indigo dye, the dye content in the liquid indigo dye is 25%, the rotation speed of the sand mill is 3000 to 3500 r / min, and the diameter of the zirconia beads is 1 to 2 mm.

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