Aqueous polyurethane with meglumine as neutralizing agent, and preparation method and application thereof

Abstract

The application discloses aqueous polyurethane with meglumine as a neutralizing agent and a preparation method and application thereof. The application adopts bio-based meglumine as a neutralizing agent for preparing aqueous polyurethane, and the aqueous polyurethane is prepared through the steps of pre-polymerization, carboxylation chain extension, chain extension, neutralization, high-speed shearing emulsification, and pressure reduction desolventization, and has the characteristics of low VOC, no odor, storage stability, excellent mechanical properties and the like. The preparation process is mild and controllable, and the aqueous polyurethane can be widely applied to the fields of water-based paint, leather finishing, medical material, adhesive and the like, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of waterborne polymer materials technology, specifically relating to waterborne polyurethane with meglumine as a neutralizing agent, its preparation method and application. Background Technology

[0002] Waterborne polyurethane (WPU) uses water instead of organic solvents as the dispersion medium. It features low volatile organic compound (VOC) content, flame retardancy and safety, wide applicability, and excellent adhesion properties. It has been widely used in leather finishing, textile printing and dyeing, waterborne coatings, adhesives, medical materials and other fields. It is the mainstream environmentally friendly polymer material that replaces solvent-based polyurethane.

[0003] Currently, industrially mass-produced anionic waterborne polyurethane mainly involves introducing carboxyl-containing hydrophilic chain extenders such as dimethylolpropionic acid (DMPA) and dimethylolbutyric acid (DMBA) into the polyurethane molecular chain. Then, organic amine neutralizing agents are used to neutralize the carboxyl groups into carboxylate salts. The hydrophilicity of the ionic groups enables the stable dispersion of the polyurethane prepolymer in water. In existing technologies, commonly used neutralizing agents are mainly small-molecule organic amines such as triethylamine and ammonia. These neutralizing agents have several technical drawbacks in practical applications: First, triethylamine and ammonia are highly volatile, releasing large amounts of amine waste gas during the emulsification and coating curing processes, causing environmental pollution and impacting the production environment, making it difficult to meet the requirements of high-end environmentally friendly materials such as those used in the automotive industry. Second, small-molecule organic amines only have a single neutralization and salt-forming function and cannot participate in the chain extension and cross-linking reactions of the polyurethane molecular chain. Residual free amines reduce the water resistance, mechanical strength, and aging resistance of the waterborne polyurethane coating, limiting its application range.

[0004] Glucosamine (N-methyl-D-glucosamine) is a bio-based hydroxylamine compound with properties such as non-toxicity, high boiling point, low volatility, and excellent biocompatibility. Its molecular structure contains one secondary amine group and multiple hydroxyl groups. Currently, there is no technology that uses glutamic acid as a neutralizing agent for waterborne polyurethane, nor are there any related technical solutions for preparing waterborne polyurethane using it.

[0005] Therefore, developing a waterborne polyurethane with meglumine as a neutralizing agent, characterized by simple process, excellent environmental friendliness, and outstanding comprehensive performance, and its preparation method, is promising, addressing the shortcomings of existing neutralizing agents. Summary of the Invention

[0006] The first objective of this invention is to provide a waterborne polyurethane using meglumine as a neutralizing agent, thereby solving the technical problems of existing waterborne polyurethane neutralizing agents, such as high volatility, limited functionality, inability to participate in the chain extension and crosslinking reactions of polyurethane molecules, and poor coating performance. It also alleviates the technical problems of existing waterborne polyurethane neutralizing agents being derived from petrochemical resources, having high VOC emissions, and strong odor. The second objective of this invention is to provide a method for preparing and applying waterborne polyurethane using meglumine as a neutralizing agent.

[0007] According to a first aspect of the present invention, an aqueous polyurethane with meglumine as a neutralizing agent is provided, wherein, by weight, its raw materials are mainly composed of 100 parts of polymeric polyol, 25-42 parts of diisocyanate, 6-11 parts of hydrophilic chain extender, 0.08-0.25 parts of organometallic catalyst, 8-18 parts of cosolvent, 4-8.5 parts of meglumine, and 90-140 parts of deionized water.

[0008] This application reveals that meglumine has a high boiling point and is virtually non-volatile. Using bio-based meglumine instead of triethylamine as a neutralizing agent in the preparation of waterborne polyurethane solves the technical problems of high volatility and high VOC content associated with existing neutralizing agents such as triethylamine. The VOC content is far below the national standard, significantly improving environmental performance. It also eliminates amine odor, making it suitable for high-end environmental protection fields such as food and medical applications. Simultaneously, the secondary amine group of meglumine neutralizes the carboxyl group, achieving water dispersion. The hydroxyl groups bond to the NCO groups at the ends of the polyurethane prepolymer, integrating into the polyurethane molecular chain and increasing the crosslinking density, thus possessing the triple functions of neutralization, chain extension, and crosslinking. Because meglumine bonds with other raw materials, there is less residual free amine in the waterborne polyurethane after the reaction, which is beneficial for improving the water resistance, mechanical strength, and aging resistance of the waterborne polyurethane coating.

[0009] The waterborne polyurethane of this invention uses meglumine as a neutralizing agent to increase the crosslinking density of the molecular chain. This not only effectively solves the problem of high volatility of traditional neutralizing agents, but also significantly improves the emulsion stability, thermal stability, and aging resistance of the product. Furthermore, it alleviates the problems of high VOC content and strong amine odor that limit the application of traditional waterborne polyurethanes using neutralizing agents such as triethylamine in the environmental protection field. This waterborne polyurethane, prepared using polymeric polyols and aliphatic / alicyclic diisocyanates as main raw materials, features low VOC, no odor, stable storage, and excellent mechanical properties.

[0010] In some embodiments, the polymeric polyol is a polyether polyol or a polyester polyol, specifically a polyether diol or a polyester diol. Specifically, the polymeric polyol is selected from at least one of polybutylene adipate diol, polypropylene glycol, polytrimethylene ether diol, and polytetrahydrofuran polyether diol.

[0011] In some embodiments, the number average molecular weight of the polymeric polyol is 1000-2000.

[0012] In some embodiments, the diisocyanate is selected from at least one of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI), and 1,3-dimethylisocyanate cyclohexane (HXDI).

[0013] In some embodiments, the hydrophilic chain extender is prepared by the following steps: reacting serine alcohol with succinic anhydride at 50-70°C for 3-4 hours. The molar ratio of serine to succinic anhydride is 1:1 to 1:1.15.

[0014] In some embodiments, the organometallic catalyst is selected from at least one of dibutyltin dilaurate, stannous octoate, and organobismuth.

[0015] In some embodiments, the co-solvent is an organic solvent selected from at least one of acetone, butanone, and dimethylacetamide. The co-solvent is used to reduce the viscosity of the prepolymer, facilitating emulsification and dispersion.

[0016] In some embodiments, the aqueous polyurethane using meglumine as a neutralizing agent also includes 1.2 to 3.5 parts of a small molecule chain extender.

[0017] In some embodiments, the molar ratio of meglumine to the hydrophilic chain extender is (0.79~1.47):1.

[0018] In some embodiments, the small molecule chain extender is selected from rosin diol or modified hydrogenated rosin. Rosin diol can be obtained by purchasing commercially available product D-6011.

[0019] In some embodiments, the weight-average molecular weight of rosin diol is 800-1000, specifically, the weight-average molecular weight of rosin diol is 1000.

[0020] In some embodiments, the hydroxyl value of rosin glycol is 110-125 mg KOH / g. Preferably, the hydroxyl value of rosin glycol is 120 mg KOH / g. The hydroxyl value of D-6011 is 110-125 mg KOH / g.

[0021] In some embodiments, modified hydrogenated rosin is prepared by the following steps: (1) Hydrogenated rosin was mixed with glycidyl methacrylate (GMA), catalyst and polymerization inhibitor, and reacted at 110°C for 4 h to obtain GMA intermediate; (2) Add photoinitiator and mercaptoethanol to the GMA intermediate and react under ultraviolet light with an irradiation power of 100-300W for 45-180 min to obtain the product. The catalyst is triethylamine.

[0022] In some embodiments, the polymerization inhibitor is hydroquinone; the photoinitiator is selected from photoinitiator 1173 (2-hydroxy-2-methyl-1-phenyl-1-propanone).

[0023] In some embodiments, the molar ratio of hydrogenated rosin to glycidyl methacrylate is 1:(1~1.2). Preferably, the molar ratio of hydrogenated rosin to glycidyl methacrylate is 1:1.2.

[0024] In some embodiments, in step (1), the amount of catalyst used is 0.4% to 0.6% of the mass of hydrogenated rosin; the amount of polymerization inhibitor used is 0.15% to 0.3% of the mass of hydrogenated rosin.

[0025] In some embodiments, the amount of photoinitiator used is 1.5% to 3% of the total mass of GMA intermediate, photoinitiator and mercaptoethanol.

[0026] In some embodiments, the molar ratio of mercaptoethanol to the GMA intermediate is (1~1.1):1. Preferably, the molar ratio of mercaptoethanol to the GMA intermediate is 1.05:1.

[0027] In some embodiments, the hydrogenated rosin is dihydrorosin.

[0028] According to a second aspect of the present invention, a method for preparing an aqueous polyurethane using meglumine as a neutralizing agent is provided, comprising the following steps: S1. After vacuum dehydration of the polymer polyol, diisocyanate and organometallic catalyst are added to the polymer polyol at 70°C, and the reaction is carried out at 70~85°C under nitrogen atmosphere for 2~3 hours to obtain the prepolymer. S2. Cool down to 70℃, add hydrophilic chain extender, small molecule chain extender and cosolvent, and react at 70~85℃ for 3~4 h; S3. Cool the product from step S2 to 35~45℃, add an aqueous solution of meglumine at a speed of 600~1000 rpm, and react for 1-2 hours to obtain an aqueous polyurethane emulsion. S4. The aqueous polyurethane emulsion is obtained by vacuum distillation at 40~50℃.

[0029] The preparation method of the present invention first reacts a polymeric polyol with a diisocyanate under the action of a catalyst to obtain an NCO-terminated polyurethane prepolymer. Then, the prepolymer reacts with a hydrophilic chain extender and a small molecule chain extender to achieve carboxylation chain extension. Next, it is neutralized with meglumine as a neutralizing agent. Finally, the cosolvent is removed by high-speed shear emulsification and reduced pressure. The preparation process is mild and controllable.

[0030] In some embodiments, in step S1, vacuum dehydration is performed at 110~120°C for 1.5~2 hours.

[0031] According to a third aspect of the invention, the application of waterborne polyurethane with meglumine as a neutralizing agent is provided in waterborne coatings, leather finishing, medical materials, and adhesives.

[0032] The beneficial effects of this invention are as follows: (1) In this invention, bio-based meglumine is used to replace traditional volatile small molecule organic amines as a neutralizing agent to achieve neutralization, chain extension and cross-linking, and to prepare waterborne polyurethane materials with low VOC, good environmental performance, stable storage and excellent thermal stability.

[0033] (2) The present invention uses meglumine as a neutralizing agent, and the neutralization and crosslinking are carried out simultaneously, which simplifies the production process, shortens the reaction cycle, and the prepared waterborne polyurethane emulsion has uniform particle size, room temperature storage stability ≥6 months, and no layering, demulsification or precipitation.

[0034] (3) The preparation method of the present invention has mild process conditions, simple and controllable operation, no special production equipment required, and readily available raw materials. It is suitable for industrial mass production and has high economic value and application and promotion prospects. Attached Figure Description

[0035] Figure 1 The infrared spectra of waterborne polyurethane in Examples 4-6 and Comparative Example 1 of the present invention are shown below. Figure 2 These are appearance diagrams of the aqueous polyurethane emulsions of Examples 4-6 and Comparative Example 1 of the present invention; Figure 3 The particle size distribution diagrams are for the waterborne polyurethane of Examples 4-6 and Comparative Example 1 of this invention. Figure 4 The TGA curves of the waterborne polyurethane cured films of Examples 4-6 and Comparative Example 1 of this invention are shown. Figure 5 The DTG curves are for the waterborne polyurethane curing films of Examples 4-6 and Comparative Example 1 of the present invention. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings, but the embodiments of the present invention are not limited thereto. The raw materials and reagents involved in the following embodiments are all commercially available.

[0037] The hydrophilic chain extender SSA of the present invention is prepared by the following steps: reacting serine alcohol and succinic anhydride (the molar ratio of serine alcohol to succinic anhydride is 1:1) at 60°C for 3 hours to obtain the product.

[0038] The hydrophilic chain extender SSA is a bio-based raw material, which is green and environmentally friendly, and has highly active primary hydroxyl, carboxyl and amide bonds. SSA is liquid at room temperature and has a low melting point. It melts easily at the temperature (80~90℃) for preparing waterborne polyurethane. When SSA is used as a hydrophilic chain extender to prepare waterborne polyurethane, it is less likely to cause heterogeneous reactions and further improves the stability of the emulsion.

[0039] It should be noted that SSA is one of the hydrophilic chain extenders to choose from. Other commonly used hydrophilic chain extenders, such as dimethylolpropionic acid (DMPA) and dimethylolbutyric acid (DMBA), can also be selected.

[0040] In this invention, the small molecule chain extender is rosin glycol D-6011, which is obtained through purchase. It should be noted that rosin glycol is one option for small molecule chain extenders; other common small molecule chain extenders, such as 1,4-butanediol and 1,6-hexanediol, can also be selected.

[0041] In this invention, HHP is prepared through the following steps: (1) dihydrorosin (C 19 H 31 COOH), glycidyl methacrylate (GMA), hydroquinone as a polymerization inhibitor and triethylamine as a catalyst are mixed and reacted at 110°C for 4 hours to obtain GMA intermediate; (2) photoinitiator 1173 and mercaptoethanol are added to GMA intermediate and reacted under ultraviolet light with a power of 200W for 1 hour to obtain GMA intermediate; In step (1), the molar ratio of dihydrorosin to glycidyl methacrylate is 1:1.2, the amount of triethylamine is 0.5% of the mass of dihydrorosin, and the amount of hydroquinone is 0.2% of the mass of dihydrorosin.

[0042] In step (2), the molar ratio of mercaptoethanol to GMA intermediate is 1.05:1; the amount of photoinitiator 1173 is 2% of the total mass of GMA intermediate, photoinitiator 1173 and mercaptoethanol.

[0043] Example 1 This embodiment provides an aqueous polyurethane using meglumine as a neutralizing agent, comprising the following raw materials by weight: 35 parts of polybutylene adipate diol (number average molecular weight 2000), 25 parts of isophorone diisocyanate, 8 parts of SSA, 1.4 parts of D-6011, 0.14 parts of dibutyltin dilaurate, 12 parts of acetone, 9 parts of meglumine, and 120 parts of deionized water.

[0044] The preparation method includes the following steps: (1) Polybutylene adipate diol was dehydrated under vacuum at 115°C for 2 hours, then cooled to 75°C, and isophorone diisocyanate and dibutyltin dilaurate were added. The mixture was reacted at 75-85°C for 2.5 hours under nitrogen protection to obtain NCO-terminated prepolymer. (2) Cool down to 75°C, add hydrophilic chain extender SSA, D-6011 and acetone, and stir at 75 to 85°C for 3.5 h; (3) Cool down to 35°C, add an aqueous solution of meglumine to the product of step (2) within 25 min, add deionized water under high-speed shear at 600 r / min, and emulsify for 1-2 h. (4) Remove acetone by vacuum distillation at 45°C to obtain the product.

[0045] An aqueous solution of meglumine is prepared by the following steps: dissolving meglumine in deionized water.

[0046] Example 2 This embodiment provides an aqueous polyurethane using meglumine as a neutralizing agent, comprising the following raw materials by weight: 35 parts of polypropylene glycol (number average molecular weight of 2000), 30 parts of dicyclohexylmethane diisocyanate, 6.4 parts of SSA, 0.55 parts of HHP, 0.14 parts of organic bismuth catalyst (8108), 15 parts of acetone, 9.4 parts of meglumine, and 125 parts of deionized water.

[0047] The preparation method includes the following steps: (1) Polypropylene glycol was dehydrated under vacuum at 115°C for 2 hours, then cooled to 80°C, and dicyclohexylmethane diisocyanate and catalyst were added. The mixture was reacted at 75-85°C for 3 hours under nitrogen protection to obtain NCO-terminated prepolymer. (2) Cool down to 75°C, add hydrophilic chain extender SSA, HHP and acetone, and stir at 75-85°C for 3 hours; (3) Cool down to 35°C, add an aqueous solution of meglumine to the product of step (2) within 25 min, add deionized water under high-speed shear at 600 r / min, and emulsify for 1-2 h. (4) Remove acetone by vacuum distillation at 45°C to obtain the product.

[0048] Example 3 This embodiment provides an aqueous polyurethane using meglumine as a neutralizing agent, comprising the following raw materials by weight: 35 parts of polytetrahydrofuran polyether diol (number average molecular weight 2000), 28 parts of 1,3-dimethyl isocyanate cyclohexane, 11 parts of hydrophilic chain extender SSA, 0.9 parts of HHP, 0.13 parts of catalyst organic bismuth (8108), 15 parts of acetone, 12.5 parts of meglumine, and 125 parts of deionized water.

[0049] The preparation method includes the following steps: (1) Polytetrahydrofuran polyether diol was dehydrated under vacuum at 115°C for 2 hours, then cooled to 80°C, and 1,3-dimethyl isocyanate cyclohexane and catalyst were added. The mixture was reacted at 75-85°C for 3 hours under nitrogen protection to obtain NCO-terminated prepolymer. (2) Cool down to 75°C, add hydrophilic chain extender SSA, HHP and acetone, and stir at 75-85°C for 3 hours; (3) Cool down to 35°C, add an aqueous solution of meglumine to the product of step (2) within 25 min, add deionized water under high-speed shear at 600 r / min, and emulsify for 1-2 h. (4) Remove acetone by vacuum distillation at 45°C to obtain the product.

[0050] Example 4 This embodiment provides an aqueous polyurethane using meglumine as a neutralizing agent, comprising the following raw materials by weight: 35 parts of polytrimethylene ether glycol (number average molecular weight of 1500), 27 parts of isophorone diisocyanate, 5 parts of hydrophilic chain extender SSA, 1.5 parts of D-6011, 0.12 parts of catalyst organic bismuth (8108), 15 parts of acetone, 8.5 parts of meglumine, and 130 parts of deionized water.

[0051] The preparation method includes the following steps: (1) Polytrimethylene ether glycol was dehydrated under vacuum at 115°C for 2 hours, then cooled to 80°C, and isophorone diisocyanate and catalyst were added. The mixture was reacted at 75-85°C for 3 hours under nitrogen protection to obtain NCO-terminated prepolymer. (2) Cool down to 80°C, add hydrophilic chain extender SSA, D-6011 and acetone, and stir at 75-85°C for 3 hours; (3) Cool down to 35°C, add an aqueous solution of meglumine to the product of step (2) within 25 min, add deionized water under high-speed shear at 600 r / min, and emulsify for 1-2 h. (4) Remove acetone by vacuum distillation at 45°C to obtain the product.

[0052] Example 5 This embodiment provides an aqueous polyurethane using meglumine as a neutralizing agent, comprising the following raw materials by weight: 35 parts of polytrimethylene ether glycol (number average molecular weight of 2000), 27 parts of isophorone diisocyanate, 5 parts of hydrophilic chain extender SSA, 1.5 parts of D-6011, 0.12 parts of catalyst organic bismuth (8108), 15 parts of acetone, 12 parts of meglumine, and 130 parts of deionized water.

[0053] The preparation method includes the following steps: (1) Polytrimethylene ether glycol was dehydrated under vacuum at 115°C for 2 hours, then cooled to 80°C, and isophorone diisocyanate and catalyst were added. The mixture was reacted at 75-85°C for 3 hours under nitrogen protection to obtain NCO-terminated prepolymer. (2) Cool down to 75°C, add hydrophilic chain extender SSA, D-6011 and acetone, and stir at 75-85°C for 3 hours; (3) Cool down to 35°C, add an aqueous solution of meglumine to the product of step (2) within 25 min, add deionized water under high-speed shear at 600 r / min, and emulsify for 1-2 h. (4) Remove acetone by vacuum distillation at 45°C to obtain the product.

[0054] Example 6 35 parts of polytrimethylene ether glycol (number average molecular weight of 1500), 27 parts of isophorone diisocyanate, 5 parts of hydrophilic chain extender SSA, 1.5 parts of D-6011, 0.12 parts of catalyst organic bismuth (8108), 15 parts of acetone, 15.5 parts of meglumine, and 130 parts of deionized water.

[0055] The preparation method includes the following steps: (1) Polytrimethylene ether glycol was dehydrated under vacuum at 115°C for 2 hours, then cooled to 80°C, and dicyclohexylmethane diisocyanate and catalyst were added. The mixture was reacted at 75-85°C for 3 hours under nitrogen protection to obtain NCO-terminated prepolymer. (2) Cool down to 75°C, add hydrophilic chain extender SSA, rosin glycol D-6011 and acetone, and stir at 75-85°C for 3 hours; (3) Cool down to 35°C, add an aqueous solution of meglumine to the product of step (2) within 25 min, add deionized water under high-speed shear at 600 r / min, and emulsify for 1-2 h. (4) Remove acetone by vacuum distillation at 45°C to obtain the product.

[0056] Comparative Example 1 This comparative example provides an aqueous polyurethane comprising, by weight, the following raw materials: 35 parts of polytrimethylene ether glycol (number average molecular weight of 1500), 27 parts of isophorone diisocyanate, 5 parts of SSA, 1.5 parts of D-6011, 0.12 parts of catalyst organic bismuth (8108), 15 parts of acetone, 2.7 parts of triethylamine, and 130 parts of deionized water.

[0057] The preparation method includes the following steps: (1) Polytrimethylene ether glycol was dehydrated under vacuum at 115°C for 2 hours, then cooled to 80°C, and isophorone diisocyanate and organic bismuth were added. The mixture was reacted at 75-85°C for 3 hours under nitrogen protection to obtain NCO-terminated prepolymer. (2) Cool down to 75°C, add hydrophilic chain extender SSA, D-6011 and acetone, and stir at 75-85°C for 3 hours; (3) Cool down to 35°C, add triethylamine to the product of step (2) within 25 min, add deionized water under high-speed shear at 600 r / min, and emulsify for 1-2 h. (4) Remove acetone by vacuum distillation at 45°C to obtain the product.

[0058] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

[0059] The products of Examples 4-6 and Comparative Example 1 were solidified into films and used as samples for infrared spectroscopy experiments. The results are as follows: Figure 1 As shown. By Figure 1 It can be seen that all samples are 2270 cm. -1 The absence of the characteristic -NCO peak confirms that the isocyanate reaction was complete. (3348 and 1538 cm⁻¹) 1 The peaks are respectively attributed to N The stretching and bending vibrations of H, 2941 cm -1 The peak at that location is attributed to Stretching vibration of CH3, 2863 cm⁻¹ -1 The peak at that location is attributed to Stretching vibration of CH2, 1724 cm⁻¹ -1 The peak at 1650 cm⁻¹ is attributed to the stretching vibration of C=O. As a neutralizing agent, meglumine introduces a large number of -OH groups after neutralizing the carboxyl group in its amino group. In the example, the absorption valley in this region is much deeper than in the comparative example, and the hydrogen bonding effect continues to increase with increasing meglumine dosage; 1650 cm⁻¹ -1 1550 cm -1 The characteristic absorption of the urea bond was significantly deepened in the examples, due to the simultaneous participation of the amino group in the neutralization reaction with meglumine; 1000~1200 cm⁻¹ -1 The presence of strong characteristic absorptions at the COC and C-OH regions of the meglumine sugar ring, compared to weak signals in the comparative example, demonstrates that the absorption intensity increases with the amount of meglumine added, proving that meglumine has been successfully introduced into the polyurethane system.

[0060] Figure 2 The images shown are of the appearance of the aqueous polyurethane emulsions in Examples 4-6 and Comparative Example 1. Figure 3The particle size distribution diagrams, potential, and emulsion stability results for the aqueous polyurethane emulsions of Examples 4-6 and Comparative Example 1 are shown in Table 1. Particle size distribution test results ( Figure 3 The results showed that the waterborne polyurethane prepared in Comparative Example 1 had the largest particle size. When N-methyl-D-glucosamine (glucosamine) was used as a neutralizing agent, the peak particle size of the waterborne polyurethane emulsion decreased sequentially with increasing addition. The particle size of the waterborne polyurethane in Examples 4, 5, and 6 gradually decreased. Glucosamine molecules have secondary amino groups and a large number of hydrophilic hydroxyl groups. After neutralizing the carboxyl groups on the polyurethane molecular chain, more hydrophilic groups can be introduced on the particle surface, significantly improving the surface hydrophilicity and charge density of the particles, enhancing the electrostatic repulsion between particles, and inhibiting micelle aggregation. At the same time, the multi-hydroxyl structure can combine with water molecules through hydrogen bonds to form a more stable hydration layer, further reducing the tendency of particle aggregation and promoting the formation of smaller and narrower distributed emulsion particles. This indicates that glucosamine as a neutralizing agent can significantly optimize the dispersion stability of waterborne polyurethane emulsions, and the higher the dosage, the more prominent the effect of refining the particle size. Table 1 shows that the absolute values ​​of the zeta potentials of the waterborne polyurethane emulsions in Examples 4-6 are all greater than 35. Furthermore, the zeta potential values ​​increase with increasing meglumine content, indicating that the addition of meglumine improves the stability of the waterborne polyurethane emulsions. Centrifugal stability tests were performed on each waterborne polyurethane emulsion. An appropriate amount of WPU emulsion was placed in a test tube and centrifuged at 3000 r / min for 15 min at room temperature. If no obvious phase separation or precipitation occurred, the emulsion possessed storage stability for at least 6 months. After centrifugation, no visible layering or bottom sedimentation was observed in the waterborne polyurethane emulsions, indicating good storage stability.

[0061] Table 1 Potential and stability of waterborne polyurethane emulsions

[0062] Thermodynamic properties of the waterborne polyurethane cured films of Examples 4-6 and Comparative Example 1 were tested, and the results are as follows: Figure 4 and Figure 5As shown. The TGA and DTG curves indicate that all samples exhibit two thermal decomposition processes. The low-temperature decomposition stage of 200–320°C is attributed to the cleavage of the straight-chain side chains and hydrophilic groups of meglumine polyhydroxyl groups. Compared to Comparative Example 1, the initial decomposition temperature of the waterborne polyurethanes in Examples 4–6, which were neutralized with meglumine, was slightly earlier. However, thanks to the high-density hydrogen-bonded crosslinking network constructed after meglumine neutralization, the overall thermal decomposition range was controllable. The main decomposition range was 350–450°C, corresponding to the cleavage of the urethane and urea bonds in the polyurethane main chain. The urea bond hydrogen bond network generated by the waterborne polyurethanes in the examples effectively slowed down the main chain cleavage rate. The residual char at 800°C showed a clear pattern of Example 3 > Example 2 > Example 1 > Comparative Example 1. This may be because meglumine has a six-carbon polyhydroxyl straight-chain skeleton, which is prone to intramolecular cyclization during high-temperature processes to form oxygen-containing six-membered heterocycles. A large number of carbon structures can be rapidly cyclized and carbonized to form a dense carbon layer, significantly improving the char formation and heat-resistant barrier properties of the material. Considering the overall performance in char formation, flame retardancy, and heat resistance, all examples outperformed Comparative Example 1, which did not use meglumine as a neutralizing agent, and the performance gradually increased with the increase of meglumine addition. This indicates that the waterborne polyurethane film cured with meglumine as a neutralizing agent has superior thermal stability and good potential for flame retardant and heat-resistant applications.

[0063] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A waterborne polyurethane using meglumine as a neutralizing agent, characterized in that, By weight, its raw materials include: 30-45 parts of polymeric polyol, 23-42 parts of diisocyanate, 6-11 parts of hydrophilic chain extender, 0.55-1.5 parts of small molecule chain extender, 0.02-0.25 parts of organometallic catalyst, 8-18 parts of cosolvent, 8-20 parts of meglumine, and 80-140 parts of deionized water.

2. The waterborne polyurethane using meglumine as a neutralizing agent according to claim 1, characterized in that, The polymer polyol is selected from at least one of polybutylene adipate diol, polypropylene glycol, polytrimethylene ether diol, and polytetrahydrofuran polyether diol; the diisocyanate is selected from at least one of isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and 1,3-dimethylisocyanate cyclohexane; the organometallic catalyst is selected from at least one of dibutyltin dilaurate, stannous octoate, and organobismuth; and the cosolvent is selected from at least one of acetone, butanone, and dimethylacetamide.

3. The waterborne polyurethane using meglumine as a neutralizing agent according to claim 1, characterized in that, The small molecule chain extender is selected from rosin diol or modified hydrogenated rosin. Modified hydrogenated rosin is prepared through the following steps: (1) Hydrogenated rosin, glycidyl methacrylate, catalyst and polymerization inhibitor were mixed and reacted at 110°C for 4 h to obtain GMA intermediate; (2) Add photoinitiator and mercaptoethanol to the GMA intermediate and react under ultraviolet light with an irradiation power of 100-300W for 45-180 min to obtain the product. The catalyst is triethylamine.

4. The waterborne polyurethane using meglumine as a neutralizing agent according to claim 1 or 2, characterized in that, The number average molecular weight of the polymer polyol is 1000~2000.

5. The waterborne polyurethane using meglumine as a neutralizing agent according to claim 1, characterized in that, The hydrophilic chain extender is prepared by the following steps: The product is obtained by reacting serine alcohol with succinic anhydride at 50-70℃ for 3-4 hours. The molar ratio of serine to succinic anhydride is 1:1 to 1:1.

15.

6. The waterborne polyurethane using meglumine as a neutralizing agent according to claim 1, characterized in that, The hydrophilic chain extender is prepared by the following steps: The product is obtained by reacting serine alcohol with succinic anhydride at 50-70℃ for 3-4 hours. The molar ratio of serine to succinic anhydride is 1:1 to 1:1.

15.

7. The waterborne polyurethane using meglumine as a neutralizing agent according to claim 1, characterized in that, The molar ratio of meglumine to hydrophilic chain extender is (0.79~1.47):

1.

8. The method for preparing waterborne polyurethane using meglumine as a neutralizing agent as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. After vacuum dehydration of the polymer polyol, diisocyanate and organometallic catalyst are added to the polymer polyol at 70°C, and the reaction is carried out at 70~85°C under nitrogen atmosphere for 2~3 hours to obtain the prepolymer. S2. Cool down to 70~80℃, add hydrophilic chain extender, small molecule chain extender and cosolvent, and react at 70~85℃ for 3h; S3. Cool the product from step S2 to 35~45℃, add an aqueous solution of meglumine at a speed of 600~1000 rpm, and react for 1-2 hours to obtain an aqueous polyurethane emulsion. S4. The aqueous polyurethane emulsion is obtained by vacuum distillation at 40~50℃.

9. The method for preparing waterborne polyurethane using meglumine as a neutralizing agent according to claim 8, characterized in that, In step S1, vacuum dehydration is performed at 110~120℃ for 1.5~2 hours.

10. The application of waterborne polyurethane with meglumine as a neutralizing agent as described in any one of claims 1 to 7 in waterborne coatings, automotive applications, medical materials, and highly environmentally friendly adhesives.

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