Anionic, nonionic mixed modified waterborne polyisocyanate curing agent and preparation method thereof

Abstract

This invention provides an anionic and nonionic mixed-modified waterborne polyisocyanate curing agent and its preparation method. The raw materials for preparing the curing agent include the following components in parts by weight: 100 parts of isocyanate compound, 3-25 parts of anionic hydrophilic chain extender, 0-40 parts of nonionic hydrophilic chain extender, 60-90 parts of end-capping agent, and 1-30 parts of neutralizing agent, wherein the nonionic hydrophilic chain extender is not 0 parts. This anionic and nonionic mixed-modified waterborne polyisocyanate curing agent uses a combination of anionic and nonionic hydrophilic chain extenders as a mixed hydrophilic chain extender system, achieving a synergistic improvement in excellent water dispersibility, storage stability, low-temperature desealing performance, and curing film-forming performance. It does not require complex ionization treatment, and the preparation process is simple, overcoming the defects of single modified curing agents such as easy instability in alkaline environments and insufficient low-temperature performance.

Description

Technical Field

[0001] This invention belongs to the technical field of modified waterborne polyisocyanate curing agents, specifically relating to an anionic and nonionic mixed modified waterborne polyisocyanate curing agent and its preparation method. Background Technology

[0002] Polyisocyanate curing agents are cross-linking curing agents containing two or more active isocyanate groups (-NCO) in their molecules. They can react with compounds containing active hydrogen such as hydroxyl and amino groups to form a three-dimensional cross-linked network structure, making them a core curing component in polyurethane material systems. Primarily acting as a cross-linking agent, they react with matrix resins containing active hydrogen, such as polyols, significantly improving the mechanical strength, weather resistance, chemical corrosion resistance, and structural stability of the cured material. They are a key raw material for preparing high-performance polyurethane materials. Unmodified conventional polyisocyanates completely lack water dispersibility and cannot be uniformly mixed directly in aqueous systems. Forced stirring causes the NCO groups to react rapidly with water and become ineffective, preventing the formation of a uniformly cross-linked coating. Therefore, hydrophilic modification of polyisocyanates is necessary. After hydrophilic modification, the product can be stably dispersed in aqueous media, significantly improving dispersion stability in water, while suppressing side reactions between NCO groups and water, extending the system's pot life, and ultimately enabling the normal application and curing of environmentally friendly two-component waterborne coatings.

[0003] Hydrophilic modification techniques for polyisocyanate curing agents mainly include nonionic modification, ionic modification, and nanomaterial compound modification. Cationic modification involves introducing cationic substances (such as quaternary ammonium salts and imidazolium salts) into the polyisocyanate, which then reacts with acid to form a salt. However, cationically modified curing agents significantly accelerate the reaction between NCO groups and active hydrogen in alkaline environments, easily leading to premature crosslinking, a sharp increase in viscosity, or even gelation, resulting in poor storage stability and limited application time. Anionic modification typically involves introducing anionic groups such as carboxyl, sulfonic acid, or phosphate groups onto the molecular chain. Anionicly modified curing agents usually have a pH value less than 7, which helps to slow down the reaction rate of NCO groups with water, thereby extending their usable time. While anionicly modified curing agents offer advantages such as fast curing speed, suitability for humid conditions, and good film flexibility, they also suffer from insufficient low-temperature unsealing performance, poor long-term storage stability, and poor dispersion uniformity under extreme conditions. Nonionic modification methods often involve introducing hydrophilic groups containing ethylene oxide or propylene oxide to modify polyisocyanates, such as using polyethylene glycol monomethyl ether (MPEG) or polyethylene glycol PEG. The modified curing agent not only possesses hydrophilicity, but the remaining NCO groups are also encapsulated and protected, allowing it to exist stably in water. However, the introduction of numerous flexible hydrophilic segments not only severely reduces the water resistance of the coating film but also weakens the crosslinking density, leading to a significant decrease in the coating film's hardness, abrasion resistance, solvent resistance, and other mechanical properties, resulting in poor film-forming performance.

[0004] Therefore, current modification methods for polyisocyanate curing agents are all insufficient to simultaneously meet the requirements of high dispersibility, high stability, and high film-forming performance. Summary of the Invention

[0005] The technical problem solved by this invention is to provide an anionic and nonionic mixed modified waterborne polyisocyanate curing agent and its preparation method. It uses anionic and nonionic hydrophilic chain extenders as a mixed hydrophilic chain extender system, which achieves a synergistic improvement in excellent water dispersibility, storage stability, low-temperature unsealing performance and curing film-forming performance. It does not require complex ionization treatment, the preparation process is simple, and it overcomes the defects of single modified curing agents such as easy instability in alkaline environment and insufficient low-temperature performance.

[0006] To address the aforementioned problems, a first aspect of the present invention provides an anionic and nonionic mixed-modified waterborne polyisocyanate curing agent, the raw materials for which comprise the following components in parts by weight: The mixture contains 100 parts of isocyanate compound, 3-25 parts of anionic hydrophilic chain extender, 0-40 parts of nonionic hydrophilic chain extender, 60-90 parts of end-capping agent, and 1-30 parts of neutralizing agent, with the nonionic hydrophilic chain extender not being 0 parts.

[0007] Preferably, the raw materials for its preparation include the following components in parts by mass: 100 parts of isocyanate compound, 6-21 parts of anionic hydrophilic chain extender, 17-32 parts of nonionic hydrophilic chain extender, 66-85 parts of end-capping agent, and 4-29 parts of neutralizing agent.

[0008] Preferably, the molar ratio of the anionic hydrophilic chain extender to the nonionic hydrophilic chain extender is 1.5 to 9:1.

[0009] Preferably, the isocyanate compound is a combination of hexamethylene diisocyanate trimer and isophorone diisocyanate; the mass ratio of hexamethylene diisocyanate trimer to isophorone diisocyanate is 0.25~1.5:1.

[0010] Preferably, the anionic hydrophilic chain extender is one or a combination of several of dimethylolpropionic acid, dimethylolbutyric acid, and dihydroxysulfonate; The nonionic hydrophilic chain extender is one or a combination of several of the following: side-chain polyoxyethylene ether diol, polyethylene glycol, and trimethylolpropane polyethylene glycol monomethyl ether.

[0011] Preferably, the anionic hydrophilic chain extender is dimethylolpropionic acid; the nonionic hydrophilic chain extender is YMERN-120.

[0012] Preferably, the capping agent is methyl ethyl ketone oxime; and the neutralizing agent is triethylamine.

[0013] A second aspect of the present invention provides a method for preparing the above-mentioned anionic and nonionic mixed modified waterborne polyisocyanate curing agent, comprising the following steps: S1. Mix the anionic hydrophilic chain extender with the nonionic hydrophilic chain extender and heat to 60-70°C. C, to obtain a mixture of modifiers; S2. Dissolve the isocyanate compound in a solvent to obtain an isocyanate compound solution; S3. Add the isocyanate compound solution dropwise to the modifier mixture to obtain the reaction solution; S4. Add an end-capping agent to the reaction solution to carry out an end-capping reaction; then add a neutralizing agent to carry out a neutralization reaction to obtain the anionic and nonionic mixed modified waterborne polyisocyanate curing agent.

[0014] Preferably, a capping agent is added to the reaction solution to carry out a capping reaction, specifically including: measuring the NCO% of the reaction solution every 30 minutes; when the NCO% reaches the theoretical value, carrying out the capping reaction; and lowering the temperature of the reaction solution to 20-30°C. C, then add methyl ethyl ketone oxime solution.

[0015] Preferably, a neutralizing agent is added to carry out a neutralization reaction, specifically including: measuring NCO% every 30 minutes; when NCO% < 0.05%, carrying out the neutralization reaction; adding triethylamine to the reaction solution; reacting for 10-30 minutes; then adding water to make the solid content 25%-35%; and emulsifying for 10-30 minutes.

[0016] Compared with the prior art, the present invention has the following advantages: The modified waterborne polyisocyanate curing agent of this invention employs a mixture of anionic and nonionic hydrophilic chain extenders to modify isocyanate compounds. The anionic hydrophilic chain extender improves the dispersion stability, film hardness, and impact resistance of the curing agent; the nonionic hydrophilic chain extender, based on the polyether structure, improves the low-temperature desealing performance and long-term storage stability of the curing agent, reducing the impact of environmental temperature and pH fluctuations on the curing agent. The resulting modified waterborne polyisocyanate curing agent exhibits excellent stability and complete transparency at pH > 7; it also shows good dispersibility at pH 5-6. This invention solves the problem of instability of cationic modified curing agents in alkaline environments and compensates for the deficiencies in low-temperature performance and storage stability of anionic modified curing agents, achieving a synergistic improvement in water dispersibility, storage stability, low-temperature desealing performance, and film-forming performance. It also addresses the issue that a single modification method cannot simultaneously achieve comprehensive performance.

[0017] The modified waterborne polyisocyanate curing agent of the present invention uses anionic DMPA and nonionic YMER N-120 to achieve a synergistic improvement in water dispersibility, storage stability, low-temperature unsealing performance and film-forming performance, and solves the problem that a single modification method cannot take into account the comprehensive performance.

[0018] The modified waterborne polyisocyanate curing agent of this invention can form a stable waterborne dispersion system without complex ionization treatment. Anionic DMPA improves dispersion stability, film hardness, and impact resistance; nonionic YMER N-120, relying on its polyether structure, improves low-temperature unsealing performance and long-term storage stability, reducing the impact of environmental temperature and pH fluctuations. It exhibits excellent stability and complete transparency at pH > 7; it also demonstrates good dispersibility at pH 5-6.

[0019] The modified waterborne polyisocyanate curing agent of the present invention not only solves the problem of the instability of cationic modified curing agents in alkaline environment, but also makes up for the shortcomings of anionic modified curing agents in low temperature performance and storage stability.

[0020] The modified waterborne polyisocyanate curing agent of this invention has a moderate curing rate. After forming a film with hydroxyl acrylic resin, it achieves a hardness of 6H, an impact strength of 76 kg / cm², and an adhesion grade of 0; the initial unsealing temperature is 143.42°C. C, the end temperature of the endothermic peak is 171°C. C. Overall performance is balanced. Suitable for large-scale industrial production and applicable to waterborne polyurethane coatings, adhesives, coating materials, and other fields. Attached Figure Description

[0021] Figure 1 This is the DSC test curve of the modified waterborne polyisocyanate curing agent of Example 2 of the present invention; Detailed Implementation The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] An anionic and nonionic mixed-modified waterborne polyisocyanate curing agent according to an embodiment of the present invention comprises the following components in parts by weight: The mixture contains 100 parts of isocyanate compound, 3-25 parts of anionic hydrophilic chain extender, 0-40 parts of nonionic hydrophilic chain extender, 60-90 parts of end-capping agent, and 1-30 parts of neutralizing agent, with the nonionic hydrophilic chain extender not being 0 parts.

[0023] The modified waterborne polyisocyanate curing agent of this invention employs a mixture of anionic and nonionic hydrophilic chain extenders to modify isocyanate compounds. The anionic hydrophilic chain extender improves the dispersion stability, film hardness, and impact resistance of the curing agent. The nonionic hydrophilic chain extender, based on the polyether structure, improves the low-temperature desealing performance and long-term storage stability of the curing agent, reducing the impact of environmental temperature and pH fluctuations on the curing agent. The resulting modified waterborne polyisocyanate curing agent exhibits excellent stability and complete transparency at pH > 7, and also demonstrates good dispersibility at pH 5-6. This invention solves the problem of instability of cationic modified curing agents in alkaline environments and compensates for the deficiencies in low-temperature performance and storage stability of anionic modified curing agents. It achieves a synergistic improvement in water dispersibility, storage stability, low-temperature desealing performance, and film-forming performance, addressing the issue that a single modification method cannot simultaneously achieve comprehensive performance.

[0024] Preferably, the raw materials for its preparation include the following components in parts by mass: 100 parts of isocyanate compound, 6-21 parts of anionic hydrophilic chain extender, 17-32 parts of nonionic hydrophilic chain extender, 66-85 parts of end-capping agent, and 4-29 parts of neutralizing agent.

[0025] Within the above-mentioned preferred ratio range, the modified waterborne polyisocyanate curing agent can achieve better water dispersibility, storage stability, low-temperature unsealing performance, and film-forming performance.

[0026] Preferably, the molar ratio of the anionic hydrophilic chain extender to the nonionic hydrophilic chain extender is 1.5~9:1. A high proportion of nonionic hydrophilic segments in the system significantly improves the low-temperature storage stability and pH tolerance range of the curing agent. However, excessive nonionic hydrophilic segments introduce a large number of hydrophilic groups, leading to a significant decrease in the water resistance, hardness, and impact resistance of the cured film. Conversely, increasing the proportion of anionic hydrophilic groups results in smaller water-dispersible particle size of the curing agent, significantly improving the hardness and media resistance of the film. However, this greatly increases the system's sensitivity to pH fluctuations, making it prone to hydrophilic group aggregation and sedimentation at low temperatures, thus reducing storage stability. It also weakens the low-temperature unsealing advantage brought by nonionic segments, failing to meet the requirements for wide-temperature-range use. When the molar ratio of the two is within the above range, the two types of hydrophilic groups form a synergistic effect, which not only retains the advantages of high dispersion stability and high film strength brought by anionic modification, but also gives full play to the wide pH tolerance and high storage stability of nonionic modification. Ultimately, the curing agent is completely transparent and stable at pH>7, and still maintains good dispersibility in the pH range of 5~6. At the same time, it takes into account water dispersibility, low temperature desealing performance and film-forming comprehensive performance, and solves the performance shortcomings of single modification.

[0027] More preferably, the molar ratio of the anionic hydrophilic chain extender to the nonionic hydrophilic chain extender is 4:1.

[0028] Preferably, the isocyanate compound is a combination of hexamethylene diisocyanate trimer (3-HDI) and isophorone diisocyanate (IPDI); the mass ratio of hexamethylene diisocyanate trimer to isophorone diisocyanate is 0.25~1.5:1. An excessively high proportion of isophorone diisocyanate significantly reduces the crosslinking density of the system, resulting in a marked decrease in the hardness, weather resistance, gloss retention, and impact resistance of the final film, failing to meet the requirements for high-wear-resistant coatings. Hexamethylene diisocyanate trimer has higher functionality and can form a high-density crosslinking network, significantly improving the hardness, weather resistance, and media resistance of the film. However, when the content of hexamethylene diisocyanate trimer is too high, the system viscosity increases rapidly, making hydrophilic modification more difficult, and the dispersibility of the curing agent in water deteriorates, easily leading to stratification and sedimentation during long-term storage, making it unsuitable for applications with a wide pH range. When the molar ratio of the two is within a reasonable range, synergistic optimization of dispersibility, storage stability, and film mechanical properties can be achieved.

[0029] More preferably, the mass ratio of hexamethylene diisocyanate trimer to isophorone diisocyanate is 4:6, or 0.67:1.

[0030] Preferably, the anionic hydrophilic chain extender is one or a combination of several of dimethylolpropionic acid (DMPA), dimethylolbutyric acid (DMBA), and dihydroxysulfonate. More preferably, the anionic hydrophilic chain extender is dimethylolpropionic acid. The two hydroxyl groups of dimethylolpropionic acid react with the -NCO groups of the polyisocyanate, chemically bonding the dimethylolpropionic acid molecule into the polyisocyanate molecular backbone. The side-chain carboxyl groups of dimethylolpropionic acid are retained, and subsequently neutralized to form carboxylate anions, creating hydrophilic ionic groups. These anionic groups provide electrostatic repulsion in the aqueous phase, enabling the curing agent particles to disperse stably in water without agglomeration or precipitation. Compared to dimethylolbutyric acid, dimethylolpropionic acid has a smaller molecular weight, allowing for the introduction of more carboxyl groups for the same mass, resulting in stronger hydrophilicity and dispersion stability after neutralization. The design of the side-chain carboxyl groups does not affect the structural regularity of the molecular backbone, helping to maintain the crosslinking reactivity of the curing agent. Dihydroxysulfonates have poor compatibility with isocyanates. The strong polarity of sulfonate groups may lead to compatibility issues with polyisocyanate systems, affecting the uniformity of the reaction.

[0031] Preferably, the nonionic hydrophilic chain extender is one or a combination of several of the following: side-chain polyoxyethylene ether diol (YMER N-120, also known as bifunctional polyethylene glycol monomethyl ether), polyethylene glycol (PEG), and polyvinylpyrrolidone (PVP). More preferably, the nonionic hydrophilic chain extender is a side-chain polyoxyethylene ether diol, specifically YMER N-120. The hydroxyl groups at both ends of the molecule react with the -NCO groups of the polyisocyanate, chemically attaching the polyoxyethylene ether chain to the side chain positions of the polyisocyanate molecular backbone. The polyoxyethylene ether chain extends in water to form a hydration layer, preventing the aggregation and sedimentation of the curing agent particles through steric hindrance. The ether oxygen atoms in the polyoxyethylene ether chain form hydrogen bonds with water molecules, endowing the curing agent with nonionic hydrophilicity. This hydrophilic effect is pH-independent, therefore the curing agent can maintain stable dispersion over a wide pH range. YMER N-120's polyoxyethylene ether hydrophilic chains are located on the molecular side chains. This side-chain structure allows the hydrophilic segments to extend outward from the main chain, providing nonionic hydrophilic stabilization without excessively interfering with the main chain's crosslinking reaction. In contrast, ordinary PEG, used as a main chain extender, significantly reduces crosslinking density and coating hardness. Compared to PEG, YMER N-120 has a balanced ethoxylated chain length, allowing for precise control of performance requirements from rigid to flexible by adjusting its dosage. Its polyether segments exhibit flexibility and a low glass transition temperature, endowing the curing agent with excellent low-temperature performance and long-term storage stability, compensating for the instability of purely anionic curing agents under low-temperature conditions.

[0032] The combination of dimethylolpropionic acid (DMPA) and YMER N-120 is not a simple performance additive, but rather produces a significant synergistic effect. DMPA provides electrostatic repulsion stability, while YMER N-120 provides steric hindrance stability. This dual stabilization mechanism ensures stable dispersion of the curing agent over a wider pH range. DMPA contributes to hardness and rigidity, while YMER N-120 contributes to flexibility and low-temperature performance, achieving an optimal balance between hardness and toughness. The combination of DMPA and YMER N-120 moderately increases the unsealing temperature, resulting in better storage stability of the curing agent at room temperature. Simultaneously, the increased unsealing temperature ensures sufficient cross-linking reaction during high-temperature curing. Furthermore, the combination of DMPA and YMER N-120 results in a more suitable particle size for the curing agent, ensuring water dispersibility while avoiding storage instability caused by excessively small particle sizes or stratification and precipitation caused by excessively large particle sizes.

[0033] Preferably, the capping agent is methyl ethyl ketone oxime; and the neutralizing agent is triethylamine.

[0034] A second aspect of this invention provides a method for preparing the above-mentioned anionic and nonionic mixed modified waterborne polyisocyanate curing agent, comprising the following steps: S1. Mix anionic hydrophilic chain extender with nonionic hydrophilic chain extender and heat to 60~70℃ to obtain a modifier mixture; S2. Dissolve the isocyanate compound in a solvent to obtain an isocyanate compound solution; S3. Add the isocyanate compound solution dropwise to the modifier mixture to obtain the reaction solution; S4. Add an end-capping agent to the reaction solution to carry out an end-capping reaction; then add a neutralizing agent to carry out a neutralization reaction to obtain the anionic and nonionic mixed modified waterborne polyisocyanate curing agent.

[0035] Preferably, a capping agent is added to the reaction solution to carry out a capping reaction, specifically including: measuring the NCO% of the reaction solution every 30 minutes; when the NCO% reaches the theoretical value, carrying out the capping reaction; and lowering the temperature of the reaction solution to 20-30°C. C, then add methyl ethyl ketone oxime solution.

[0036] Preferably, a neutralizing agent is added to carry out a neutralization reaction, specifically including: measuring NCO% every 30 minutes, and when NCO% < 0.05%, carrying out a neutralization reaction, adding triethylamine to the reaction solution, reacting for 10-30 minutes, then adding water to make the solid content 25%-35%, and emulsifying for 10-30 minutes.

[0037] Example 1 The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent of this embodiment is prepared from the following components in parts by weight: 40 parts of hexamethylene diisocyanate trimer, 60 parts of isophorone diisocyanate, 20.9 parts of dimethylolpropionic acid, 17.4 parts of YMER N-120, 66.8 parts of butanone oxime, and 15.8 parts of triethylamine.

[0038] The preparation method of the anionic and nonionic mixed modified waterborne polyisocyanate curing agent in this embodiment is as follows: S1. Weigh out dimethylolpropionic acid and YMER N-120 and add them to a four-necked flask. Heat the flask in an oil bath to 120°C and remove water by vacuum for 3 hours. Then adjust the temperature to 70°C and install the reflux condenser, thermometer, mechanical stirrer, and dropping funnel on the four-necked flask.

[0039] S2. Weigh 3-HDI and IPDI and dissolve them in 10 mL of acetone to obtain a mixed solution of 3-HDI and IPDI. Add the solution to a dropping funnel and add the mixed solution of IPDI and 3-HDI dropwise, controlling the dropping rate to be completed within 20 min.

[0040] S3. After the addition is complete, measure NCO% every 30 min. When NCO% reaches the theoretical value, perform the end-capping reaction. Mix methyl ethyl ketone oxime with 5 mL of acetone to obtain methyl ethyl ketone oxime solution. Add the solution to a new dropping funnel, lower the oil bath temperature to room temperature, and add the methyl ethyl ketone oxime solution dropwise. The dropping rate should be controlled to be completed within 10 min.

[0041] S4. After the butanone oxime solution was added dropwise, the NCO% was measured every 30 minutes. When the NCO% was < 0.05%, the neutralization reaction was carried out, and the temperature was maintained at 25°C. C. Add triethylamine and react for 20 min. Then add deionized water to maintain a solid content of 30% and emulsify for 20 min. Remove acetone by rotary evaporation to obtain anionic and nonionic mixed modified waterborne polyisocyanate curing agent.

[0042] Example 2 The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent of this embodiment is prepared from the following components in parts by weight: 40 parts of hexamethylene diisocyanate trimer, 60 parts of isophorone diisocyanate, 13.4 parts of dimethylolpropionic acid, 24.9 parts of YMER N-120, 75.9 parts of butanone oxime, and 10.1 parts of triethylamine.

[0043] The preparation method of the anionic and nonionic mixed modified waterborne polyisocyanate curing agent in this embodiment is the same as that in Example 1.

[0044] Example 3 The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent of this embodiment is prepared from the following components in parts by weight: 40 parts of hexamethylene diisocyanate trimer, 60 parts of isophorone diisocyanate, 9.1 parts of dimethylolpropionic acid, 29.2 parts of YMER N-120, 81.1 parts of butanone oxime, and 6.9 parts of triethylamine.

[0045] The preparation method of the anionic and nonionic mixed modified waterborne polyisocyanate curing agent in this embodiment is the same as that in Example 1.

[0046] Example 4 The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent of this embodiment is prepared from the following components in parts by weight: 40 parts of hexamethylene diisocyanate trimer, 60 parts of isophorone diisocyanate, 6.4 parts of dimethylolpropionic acid, 31.9 parts of YMER N-120, 84.4 parts of butanone oxime, and 4.8 parts of triethylamine.

[0047] The preparation method of the anionic and nonionic mixed modified waterborne polyisocyanate curing agent in this embodiment is the same as that in Example 1.

[0048] Example 5 The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent of this embodiment is prepared from the following components in parts by weight: 40 parts of hexamethylene diisocyanate trimer, 60 parts of isophorone diisocyanate, 4.5 parts of dimethylolpropionic acid, 33.8 parts of YMER N-120, 86.7 parts of butanone oxime, and 3.4 parts of triethylamine.

[0049] The preparation method of the anionic and nonionic mixed modified waterborne polyisocyanate curing agent in this embodiment is the same as that in Example 1.

[0050] Example 6 The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent of this embodiment is prepared from the following components in parts by weight: 40 parts hexamethylene diisocyanate trimer, 60 parts isophorone diisocyanate, 3 parts dimethylolpropionic acid, 40 parts YMER N-120, 90 parts butanone oxime and 1 part triethylamine.

[0051] The preparation method of the anionic and nonionic mixed modified waterborne polyisocyanate curing agent in this embodiment is the same as that in Example 1.

[0052] Example 7 The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent of this embodiment is prepared from the following components in parts by weight: 40 parts of hexamethylene diisocyanate trimer, 60 parts of isophorone diisocyanate, 25 parts of dimethylolpropionic acid, 1 part of YMER N-120, 60 parts of butanone oxime, and 30 parts of triethylamine.

[0053] The preparation method of the anionic and nonionic mixed modified waterborne polyisocyanate curing agent in this embodiment is the same as that in Example 1.

[0054] Example 8 The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent of this embodiment is prepared from the following components in parts by weight: 100 parts of hexamethylene diisocyanate trimer, 13.4 parts of dimethylolpropionic acid, 24.9 parts of YMER N-120, 75.9 parts of butanone oxime, and 10.1 parts of triethylamine.

[0055] The preparation method of the anionic and nonionic mixed modified waterborne polyisocyanate curing agent in this embodiment is the same as that in Example 1.

[0056] Example 9 The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent of this embodiment is prepared from the following components in parts by weight: 80 parts of hexamethylene diisocyanate trimer, 20 parts of isophorone diisocyanate, 13.4 parts of dimethylolpropionic acid, 24.9 parts of YMER N-120, 75.9 parts of butanone oxime, and 10.1 parts of triethylamine.

[0057] The preparation method of the anionic and nonionic mixed modified waterborne polyisocyanate curing agent in this embodiment is the same as that in Example 1.

[0058] Example 10 The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent of this embodiment is prepared from the following components in parts by weight: 60 parts of hexamethylene diisocyanate trimer, 40 parts of isophorone diisocyanate, 13.4 parts of dimethylolpropionic acid, 24.9 parts of YMER N-120, 75.9 parts of butanone oxime, and 10.1 parts of triethylamine.

[0059] The preparation method of the anionic and nonionic mixed modified waterborne polyisocyanate curing agent in this embodiment is the same as that in Example 1.

[0060] Example 11 The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent of this embodiment is prepared from the following components in parts by weight: 20 parts of hexamethylene diisocyanate trimer, 80 parts of isophorone diisocyanate, 13.4 parts of dimethylolpropionic acid, 24.9 parts of YMER N-120, 75.9 parts of butanone oxime, and 10.1 parts of triethylamine.

[0061] The preparation method of the anionic and nonionic mixed modified waterborne polyisocyanate curing agent in this embodiment is the same as that in Example 1.

[0062] Example 12 The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent of this embodiment is prepared from the following components in parts by weight: 100 parts of isophorone diisocyanate, 13.4 parts of dimethylolpropionic acid, 24.9 parts of YMER N-120, 75.9 parts of butanone oxime, and 10.1 parts of triethylamine.

[0063] The preparation method of the anionic and nonionic mixed modified waterborne polyisocyanate curing agent in this embodiment is the same as that in Example 1.

[0064] Comparative Example 1 The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent of this comparative example is prepared from the following components in parts by weight: 40 parts of hexamethylene diisocyanate trimer, 60 parts of isophorone diisocyanate, 38.3 parts of dimethylolpropionic acid, 45.7 parts of butanone oxime, and 28.9 parts of triethylamine.

[0065] The preparation method of the anionic and nonionic mixed modified waterborne polyisocyanate curing agent in this comparative example is the same as that in Example 1.

[0066] Comparative Example 2 The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent of this comparative example is prepared from the following components in parts by weight: 40 parts of hexamethylene diisocyanate trimer, 60 parts of isophorone diisocyanate, 38.3 parts of YMER N-120, and 45.7 parts of butanone oxime.

[0067] The preparation method of the anionic and nonionic mixed modified waterborne polyisocyanate curing agent in this comparative example is the same as that in Example 1.

[0068] The particle size and appearance of the curing agents in the above embodiments and comparative examples were measured, and the results are shown in Table 1 below.

[0069] Table 1

[0070] The physical properties of the films formed by mixing the curing agent and hydroxyl acrylic resin in the above embodiments and comparative examples were measured. The mass ratio of curing agent to hydroxyl acrylic resin was 1:1. The results are shown in Table 2.

[0071] Table 2

[0072] As can be seen from Examples 1-7, as the molar ratio of DMPA to YMER gradually decreases and the content of YMER N-120 further increases, the particle size of the curing agent increases significantly (from 42 nm to 284.7 nm), and the appearance changes from colorless and transparent to milky white and turbid. This is because the increase in the amount of YMER N-120 leads to an increase in polar groups, resulting in stronger intermolecular forces, requiring greater shear force for emulsification, and thus making emulsification difficult. The hardness of the film gradually decreases (from 7H to 2H), and the impact strength first increases and then decreases (reaching 84 kg / cm in Example 4). 2 The adhesion and flexibility also change accordingly.

[0073] Compared to the preferred embodiments 1-5, the change in hardness is as follows: when n(DMPA) / n(YMER) is 9:1, the film hardness is the highest, reaching 7H, indicating that the film structure is relatively rigid at this ratio. As the proportion of YMER increases, the hardness gradually decreases. For example, in the embodiment, when n(DMPA) / n(YMER) is 5:5, the hardness drops to 3H. This decreasing trend is due to the increased amount of YMER N-120, which increases the molecular weight of the molecular chain, leading to stronger intermolecular forces. Furthermore, the increased number of ether bonds (COC) in the system, with lower rotational barriers within COC single bonds, facilitates rotation, resulting in a higher number of molecular chain conformations and thus reduced chain hardness. It is also related to the flexible structure of DMPA; increasing the DMPA proportion makes the film more flexible, thereby reducing hardness.

[0074] Impact strength variation: Impact strength increases with increasing YMER content. The highest impact strength, reaching 84 kg / cm², is achieved when n(DMPA) / n(YMER) = 6:4. 2 This indicates that a higher YMER content results in a film with stronger resistance to external forces. In contrast, when n(DMPA) / n(YMER) is 10:0, the impact strength is lower, only 34 kg / cm². 2 This indicates that the film is relatively brittle under these formulations.

[0075] Adhesion and flexibility variations: Adhesion was optimal at ratios of 9:1 to 7:3, indicating good adhesion performance of the film at these ratios. Adhesion at other ratios was 2-3, slightly inferior to the optimal ratio. Flexibility was best at ratios of 8:2 to 6:4, reaching grade 1, indicating greater flexibility and stronger adaptability to deformation at this ratio. As the DMPA ratio increased, the film's flexibility gradually increased, but its hardness decreased, which is related to the structural characteristics of DMPA. The optimal overall performance was achieved when the molar ratio of DMPA to YMER was 8:2 (Example 2): particle size 75 nm, colorless and transparent, film hardness 6H, and impact strength 75 kg / cm². 2 The adhesion was rated at 0, and the flexibility at 1. In contrast, Comparative Example 1, which used only anionic modification, had a smaller particle size (38 nm) and higher hardness (8H), but its impact strength was only 34 kg / cm². 2 The adhesion and flexibility of the sample were rated at level 3. In contrast, the control sample 2, which used nonionic modification alone, exhibited extremely large particle size (465.7 nm) and delamination, resulting in severely degraded mechanical properties of the film. This indicates that the combination of anionic and nonionic hydrophilic chain extenders produced a significant synergistic effect, achieving a balance between water dispersibility, storage stability, and overall film-forming performance.

[0076] In summary, compared to Examples 1-7, the mass fractions of each component differ. Among them, Examples 1-5 are preferred embodiments, with better overall performance than Examples 6 and 7. Examples 1-4 are further preferred embodiments. Example 2 is the most preferred embodiment.

[0077] Compared to Examples 2 and 8-12, the contents of other components remained unchanged, but the mass ratio of the two isocyanates differed. Based on the data in Tables 1 and 2, when the molar ratio of DMPA:YMER was fixed at 8:2, the following trends in performance were observed when the 3-HDI / IPDI mass ratio was changed (from 10:0 to 0:10): As the IPDI ratio increases (i.e., the HDI ratio decreases), the particle size generally increases, and the appearance changes from colorless and transparent to semi-transparent and opalescent. This indicates that an excessively high IPDI ratio reduces system compatibility and leads to poor dispersibility. However, the particle size in Example 2 (4:6) is smaller than that in 6:4, which may be because the interaction between the hydrophilic chain extender and the two isocyanates reaches an optimal balance at this ratio.

[0078] Hardness increases significantly with increasing HDI ratio, likely due to the high functionality and crosslinking density of HDI trimer; a certain proportion can enhance film hardness. Impact strength increases with increasing IPDI ratio, indicating that IPDI imparts better toughness to the film. This trend is opposite to the change in hardness, reflecting the trade-off between rigidity (HDI) and toughness (IPDI). Because the cyclic structure of IPDI provides a certain degree of flexibility, exceeding a certain ratio results in excessively low crosslinking density, leading to decreased impact strength. Adhesion is optimal at 6:4 and 4:6 (grade 0); excessively high or low ratios both deteriorate the adhesion. This suggests that an appropriate HDI / IPDI blend contributes to interfacial bonding. All examples (except Example 2 and Example 10, which are grade 1) show a flexibility grade of 1 with little variation, indicating that the flexibility in this system is less affected by the isocyanate ratio. Adjusting the mass fraction of 3-HDI can effectively optimize the water dispersibility of the curing agent. 20-60% exhibits the best water dispersibility, resulting in a uniform and transparent curing agent in water.

[0079] As can be seen from Examples 2 and 8-12, as the 3-HDI / IPDI mass ratio gradually decreases from 10:0 to 0:10, the particle size of the curing agent gradually increases (from 71.7 nm to 201.7 nm), the hardness of the adhesive film gradually decreases (from 7H to 4H), and the impact strength gradually increases (from 65 kg / cm²). 2 Increased to 80 kg / cm 2 The overall performance is optimal when the 3-HDI / IPDI mass ratio is 4:6 (Example 2).

[0080] Based on the above test results, an appropriate n(DMPA) / n(YMER) ratio can optimize the physical properties of the curing agent. When the 3-HDI / IPDI mass ratio is 4:6 and n(DMPA) / n(YMER) = 8:2, the emulsion particle size is 65 nm. The curing agent exhibits excellent stability and complete transparency at pH > 7, and also shows good dispersibility at pH 5-6. After forming a film with hydroxyl resin, the hardness is 6H and the impact strength is 76 kg / cm². 2 Adhesion level 0; Figure 1 DSC test curve of the curing agent when n(DMPA) / n(YMER) = 8:2.

[0081] Depend on Figure 1 It can be seen that the DSC curve of the curing agent has a large absorption peak, indicating that the curing agent is effective at absorption rates between 143 and 171 ppm. C will exhibit a significant endothermic phenomenon. From 143 C begins to appear, at 171 The maximum value is reached at temperature C. This indicates that the unsealing temperature range of the curing agent prepared by the reaction is 143–171°C. C, because YMER has a larger molecular weight, the polymerization forces on the molecular chain are stronger, resulting in a higher deblocking temperature than anionic YMER. This is consistent with the deblocking temperature described in the literature using methyl ethyl ketone oxime as the capping agent. Initial deblocking temperature: 143.42°C. C, the end temperature of the endothermic peak is 171°C. C, to achieve a balance in the properties of the curing agent. When the proportion of YMER is too high, the particle size increases and the water solubility decreases, but at the same time, the flexibility increases.

[0082] In summary, Examples 2, 10, and 11 are preferred embodiments, with Example 2 being the most preferred embodiment.

[0083] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A waterborne polyisocyanate curing agent with mixed anionic and nonionic modification, characterized in that, Its preparation raw materials include the following components in parts by mass: The mixture contains 100 parts of isocyanate compound, 3-25 parts of anionic hydrophilic chain extender, 0-40 parts of nonionic hydrophilic chain extender, 60-90 parts of end-capping agent, and 1-30 parts of neutralizing agent, with the nonionic hydrophilic chain extender not being 0 parts.

2. The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent according to claim 1, characterized in that, Its preparation raw materials include the following components in parts by mass: 100 parts of isocyanate compound, 6-21 parts of anionic hydrophilic chain extender, 17-32 parts of nonionic hydrophilic chain extender, 66-85 parts of end-capping agent, and 4-29 parts of neutralizing agent.

3. The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent according to claim 1, characterized in that: The molar ratio of the anionic hydrophilic chain extender to the nonionic hydrophilic chain extender is 1.5 to 9:

1.

4. The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent according to claim 1, characterized in that: The isocyanate compound is a combination of hexamethylene diisocyanate trimer and isophorone diisocyanate; the mass ratio of hexamethylene diisocyanate trimer to isophorone diisocyanate is 0.25~1.5:

1.

5. The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent according to claim 1, characterized in that: The anionic hydrophilic chain extender is one or a combination of several of dimethylolpropionic acid, dimethylolbutyric acid, and dihydroxysulfonate. The nonionic hydrophilic chain extender is one or a combination of several of the following: side-chain polyoxyethylene ether diol (bifunctional polyethylene glycol monomethyl ether), polyethylene glycol, and polyvinylpyrrolidone.

6. The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent according to claim 5, characterized in that: The anionic hydrophilic chain extender is dimethylolpropionic acid; the nonionic hydrophilic chain extender is YMER N-120.

7. The anionic and nonionic mixed-modified waterborne polyisocyanate curing agent according to claim 5, characterized in that: The capping agent is methyl ethyl ketone oxime; the neutralizing agent is triethylamine.

8. A method for preparing an anionic and nonionic mixed-modified waterborne polyisocyanate curing agent as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Mix the anionic hydrophilic chain extender with the nonionic hydrophilic chain extender and heat to 60-70°C. C, to obtain a mixture of modifiers; S2. Dissolve the isocyanate compound in a solvent to obtain an isocyanate compound solution; S3. Add the isocyanate compound solution dropwise to the modifier mixture to obtain the reaction solution; S4. Add an end-capping agent to the reaction solution to carry out an end-capping reaction; then add a neutralizing agent to carry out a neutralization reaction to obtain the anionic and nonionic mixed modified waterborne polyisocyanate curing agent.

9. The preparation method according to claim 8, characterized in that: Add a capping agent to the reaction solution to carry out the capping reaction, specifically including: measuring the NCO% of the reaction solution every 30 minutes; when the NCO% reaches the theoretical value, carrying out the capping reaction; and lowering the temperature of the reaction solution to 20-30 degrees Celsius. C, then add methyl ethyl ketone oxime solution.

10. The preparation method according to claim 9, characterized in that: Add a neutralizing agent and carry out a neutralization reaction, specifically including: measuring NCO% every 30 minutes; when NCO% < 0.05%, carry out the neutralization reaction; add triethylamine to the reaction solution; react for 10-30 minutes; then add water to make the solid content 25%-35%; and emulsify for 10-30 minutes.

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