Low-swelling waterborne polyurethane and preparation method thereof
By employing stepwise polymerization and controlling the amount of organic solvent, the problem of easy swelling of waterborne polyurethane in ester solvents was solved, resulting in better solvent resistance and chain segment uniformity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI JINQIANG ADHESIVE
- Filing Date
- 2026-03-03
- Publication Date
- 2026-05-12
AI Technical Summary
Existing waterborne polyurethanes are prone to swelling and dissolving in ester solvents, leading to adhesive failure. Furthermore, conventional preparation processes suffer from uneven chain segment structure and uneven cross-linking.
A stepwise polymerization method is adopted, first generating a prepolymer, then adding a hydrophilic chain extender and solvent, controlling the amount of organic solvent and crosslinking agent to ensure uniform distribution of the hydrophilic chain extender and form a uniform chain segment structure.
It significantly reduces the swelling rate of waterborne polyurethane in ester solvents, improves solvent resistance, and ensures the uniformity of chain segment structure and crosslinking structure.
Smart Images
Figure SMS_1 
Figure SMS_2
Abstract
Description
Technical Field
[0001] This invention relates to the field of waterborne polyurethane technology, and more particularly to a low-swelling waterborne polyurethane and its preparation method. Background Technology
[0002] Polyurethane is a class of polymers with urethane groups on its main molecular chain. It possesses excellent flexibility, strong anti-aging properties, adjustable hardness, and low-temperature flexural strength, making its overall characteristics superior to many other materials. Currently, it is widely used in coatings, elastomers, foams, and other fields. In recent years, with technological advancements and increasingly stringent requirements for material performance, the contradiction between low performance and high requirements has become increasingly prominent. Therefore, the research and development of high-performance and functional materials has become increasingly important and urgent. Simultaneously, with the tightening of environmental standards, the development of environmentally friendly materials has become increasingly crucial.
[0003] Waterborne polyurethane is a type of polyurethane prepared using water as the dispersion medium. It is non-flammable, low in VOCs, safe, and environmentally friendly, and can be widely used in various industrial fields. Chinese invention patent application CN106496514A uses polyester polyols and polyether polyols as the main chain for the preparation of waterborne polyurethane. However, using polycarbonate polyols, polyester polyols, and polyether polyols as the main chain results in extremely poor resistance to ester solvents due to the principle of "like dissolves like," making it highly susceptible to adhesion failure due to swelling and dissolution. Summary of the Invention
[0004] To address the solvent resistance issue of waterborne polyurethane, particularly carbonate solvents, the first aspect of this invention provides a method for preparing a low-swelling waterborne polyurethane, comprising at least the following steps: S1. Polyols, curing agents and catalysts are mixed and polymerized to generate prepolymers; S2. Add a hydrophilic chain extender and an organic solvent to the prepolymer to react and generate a hydrophilic polymer solution; S3. Cool the hydrophilic polymer solution, add an aqueous solution of neutralizing agent to carry out a neutralization reaction, and then add water to disperse the mixture. S4. After adding an aqueous solution of crosslinking agent to the mixture and stirring to react, the organic solvent is removed to obtain the low-swelling waterborne polyurethane. The organic solvent comprises 100%-140% of the total mass of the polyol, curing agent, hydrophilic chain extender, crosslinking agent, and neutralizing agent, with the total mass of the polyol, curing agent, hydrophilic chain extender, crosslinking agent, and neutralizing agent being 100%. The amount of the crosslinking agent is 0.1%-1.9% of the mass of the polyol.
[0005] In some embodiments, the amount of the crosslinking agent may be listed as 0.1%, 0.5%, 1%, 1.9%, or any value in the range of 0.1% to 1.9%.
[0006] In conventional waterborne polyurethane preparation processes, polyols, curing agents, chain extenders, and catalysts are typically added to the reaction system all at once, followed by reaction under specific conditions. While this process is simple, it suffers from poor reaction selectivity, uneven chain segment structure, uneven crosslinking structure, and poor solvent resistance. This invention innovatively employs a stepwise polymerization method. First, polyol resin, polyisocyanate curing agent, and catalyst react to generate a prepolymer, primarily forming the hard segment structure of polyurethane. Then, a hydrophilic chain extender and solvent are added to the prepolymer for further reaction. This stepwise addition method ensures that the hydrophilic chain extender is uniformly distributed within the prepolymer, forming a uniform polarity distribution. This uniform polarity distribution makes the polarity of the entire chain segment more consistent, less susceptible to penetration by ester solvents, and thus significantly reduces swelling.
[0007] On the other hand, the amount of organic solvent and crosslinking agent used in the preparation of waterborne polyurethane has a crucial impact on its performance. If the amount of organic solvent is too small, the viscosity rises rapidly during polymerization, leading to a decrease in the degree of reaction between isocyanate and active hydrogen, a lower polymer molecular weight, and an increased swelling rate. If the amount is too large, the overall concentration of active groups decreases, the degree of reaction is insufficient, the molecular weight is lower, and the swelling rate increases. In this invention, the total mass of polyol, curing agent, hydrophilic chain extender, crosslinking agent, and neutralizing agent is taken as 100%, and the mass of organic solvent is controlled at 100%-140%. This ensures the fluidity of the reaction system, allowing the crosslinking agent to be uniformly dispersed and effectively participate in the reaction. The appropriate amount of crosslinking agent ensures the formation of an ideal crosslinked structure in the favorable reaction environment provided by the organic solvent. The combined effect of these two factors results in waterborne polyurethane exhibiting excellent low swelling performance in ester solvents.
[0008] In some embodiments, the polymerization reaction conditions in S1 are: reaction temperature 80-90°C, reaction time 2-4 hours.
[0009] In some embodiments, the reaction conditions in S2 are: reaction temperature 65-75°C, reaction time 16-18h.
[0010] The reaction temperature can be listed as 65℃, 68℃, 70℃, 73℃, 75℃, or any value within the range of 65-75℃.
[0011] The reaction time can be listed as 16h, 17h, 18h, or any value within the range of 16-18h.
[0012] In this invention, the hydrophilic polymer solution generation stage is carried out at 65-75℃ for 16-18 hours, which is a longer reaction time than in conventional processes. This ensures that the hydrophilic chain extender and the prepolymer react fully to form a uniform chain segment structure, thereby significantly improving the solvent resistance of the final product.
[0013] In some embodiments, the cooling temperature in S3 is ≤30°C.
[0014] This invention controls the neutralization reaction temperature to ≤30℃, ensuring the uniformity of the neutralization reaction, avoiding excessive local pH changes, forming a uniform chain segment structure, significantly improving the solvent resistance of waterborne polyurethane, especially significantly reducing the swelling rate in ester solvents.
[0015] In some embodiments, the mass ratio of the neutralizing agent to water in the aqueous solution of the neutralizing agent is 1:(15-25).
[0016] In some embodiments, the amount of neutralizing agent in the aqueous solution of the neutralizing agent is 80%-100% of the amount of hydrophilic chain extender.
[0017] In some embodiments, the amount of catalyst is ≤800ppm, based on the total mass of the hydrophilic chain extender, polyol, and curing agent as 100%.
[0018] In some embodiments, the mass of the polyol is 58%-77% based on the total mass of the polyol, curing agent, hydrophilic chain extender, crosslinking agent and neutralizing agent as 100%.
[0019] In some embodiments, the mass of the hydrophilic chain extender is 3.9%-10% based on the total mass of the polyol, curing agent, hydrophilic chain extender, crosslinking agent and neutralizing agent as 100%.
[0020] In some embodiments, the mass of the curing agent is 18.9%-29% based on the total mass of the polyol, curing agent, hydrophilic chain extender, crosslinking agent and neutralizing agent as 100%.
[0021] In some embodiments, the polyol comprises hydrogenated hydroxyl-terminated polybutadiene.
[0022] In some embodiments, the hydrophilic chain extender includes at least one of D-glyceric acid, dimethylolpropionic acid, dimethylolacetic acid, trihydroxysulfonic acid, and dihydroxysuccinic acid.
[0023] In some embodiments, the crosslinking agent comprises a trifunctional polyamine.
[0024] Optionally, the trifunctional polyamine includes at least one of diethylenetriamine and di(hexamethylene)triamine.
[0025] In some embodiments, the curing agent includes aliphatic or alicyclic isocyanates.
[0026] Optionally, the curing agent includes one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and dicyclohexylmethane diisocyanate.
[0027] In some embodiments, the neutralizing agent includes a metal ion neutralizing agent.
[0028] Optionally, the metal ion neutralizing agent includes monovalent metal ion hydroxides.
[0029] In some embodiments, the catalyst includes an organotin catalyst.
[0030] Optionally, the organotin catalyst includes at least one of dimethyltin dinedecanoate, dibutyltin dilaurate, and dioctyltin dilaurate.
[0031] In some embodiments, the organic solvent includes at least one of acetone, butanone, ethyl acetate, propyl propionate, and ethyl propionate.
[0032] A second aspect of the present invention provides a low-swelling waterborne polyurethane, which is prepared by the above-described preparation method.
[0033] Beneficial effects: (1) The present invention, through a specific preparation process and by controlling the amount of raw materials, enables the prepared waterborne polyurethane to have excellent solvent resistance, especially with a low swelling rate in ester solvents.
[0034] (2) The present invention adopts a stepwise polymerization method, which makes the hydrophilic chain extender with strong polarity more evenly distributed in the chain segments, and uniformly improves the overall polarity of the chain segments, further reducing swelling and dissolution.
[0035] (3) The present invention uses hydrogenated hydroxyl-terminated polybutadiene as a polyol, which reduces the affinity between the main chain and ester solvents. At the same time, a large amount of hydrophilic chain extender is introduced to enhance the polarity of the chain segments, making the water solubility of the chain segments better, the oil solubility worse, and the solvent resistance increased.
[0036] (4) The present invention further enhances the water solubility and polarity of the chain segments by using a metal ion neutralizing agent, thereby reducing swelling and dissolution in ester solvents, especially carbonate solvents. Detailed Implementation
[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention. Experimental methods not specifically specified in the embodiments were performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the solvent for the solutions involved in this invention is water; the room temperature is 25°C; and the raw materials, consumables, and equipment used are all commercially available.
[0038] The raw material information used in each embodiment and comparative example is shown in Table 1 below: Table 1
[0039] Example 1 The first aspect of this example provides a method for preparing low-swelling waterborne polyurethane, comprising the following steps: S1. Place 50g of hydrogenated hydroxyl-terminated polybutadiene, 13.33g of dicyclohexylmethane diisocyanate, and 0.05g of dimethyltin dinecidate in a flask and seal it with nitrogen. React at 85°C for 3 hours to obtain the prepolymer. S2. Cool to 70°C, add 2.66g of dimethylolpropionic acid and 81g of butanone to the prepolymer and continue the reaction for 16 hours to generate a hydrophilic polymer solution. S3. Cool down to 30°C, add 14.7g of sodium hydroxide aqueous solution (0.7g sodium hydroxide, 14g pure water) to the hydrophilic polymer solution and stir to disperse for 5min; then add 154g of deionized water and stir to disperse for 15min to obtain a mixed solution; S4. Add 10.5g of diethylenetriamine aqueous solution (0.5g diethylenetriamine, 10g pure water) to the mixture and stir to disperse for 30min; remove the methyl ethyl ketone contained therein by vacuum distillation to obtain the low-swelling waterborne polyurethane product.
[0040] The second aspect of this example provides a low-swelling waterborne polyurethane, which is prepared by the above-described preparation method.
[0041] Example 2 The first aspect of this example provides a method for preparing low-swelling waterborne polyurethane, comprising the following steps: S1. Place 50g of hydrogenated hydroxyl-terminated polybutadiene, 18.37g of dicyclohexylmethane diisocyanate, and 0.05g of dimethyltin dinecidate in a flask and seal it with nitrogen. React at 85°C for 3 hours to obtain the prepolymer. S2. Cool to 70°C, add 5.18g of dimethylolpropionic acid and 92g of butanone to the prepolymer, and continue the reaction for 16 hours to generate a hydrophilic polymer solution. S3. Cool down to 30°C, add 29.39g of sodium hydroxide aqueous solution (1.39g sodium hydroxide, 28g pure water) to the hydrophilic polymer solution and stir to disperse for 5min; then add 172g of deionized water and stir to disperse for 15min to obtain a mixed solution; S4. Add 10.5g of diethylenetriamine aqueous solution (0.5g diethylenetriamine, 10g pure water) to the mixture and stir to disperse for 30min; remove the methyl ethyl ketone contained therein by vacuum distillation to obtain the low-swelling waterborne polyurethane product.
[0042] The second aspect of this example provides a low-swelling waterborne polyurethane, which is prepared by the above-described preparation method.
[0043] Example 3 The first aspect of this example provides a method for preparing low-swelling waterborne polyurethane, comprising the following steps: S1. Place 50g of hydrogenated hydroxyl-terminated polybutadiene, 24.7g of dicyclohexylmethane diisocyanate, and 0.06g of dimethyltin dinecidate in a flask and seal it with nitrogen. React at 85°C for 3 hours to obtain the prepolymer. S2. Cool to 70°C, add 8.35g of dimethylolpropionic acid and 104g of butanone to the prepolymer, and continue the reaction for 16 hours to generate a hydrophilic polymer solution. S3. Cool down to 30°C, add 47.24g of sodium hydroxide aqueous solution (2.24g sodium hydroxide, 45g pure water) to the hydrophilic polymer solution and stir to disperse for 5min; then add 194g of deionized water and stir to disperse for 15min to obtain a mixed solution; S4. Add 10.5g of diethylenetriamine aqueous solution (0.5g diethylenetriamine, 10g pure water) to the mixture and stir to disperse for 30min; remove the methyl ethyl ketone contained therein by vacuum distillation to obtain the low-swelling waterborne polyurethane product.
[0044] The second aspect of this example provides a low-swelling waterborne polyurethane, which is prepared by the above-described preparation method.
[0045] Comparative Example 1 This example provides a method for preparing waterborne polyurethane, including the following steps: 50g of hydrogenated hydroxyl-terminated polybutadiene, 18.37g of dicyclohexylmethane diisocyanate, 0.05g of dimethyltin dinecidate, 5.18g of dimethylolpropionic acid, and 88g of butanone were placed in a flask and sealed under nitrogen. The mixture was reacted at 70℃ for 16h. The temperature was then lowered to 30℃, and 29.39g of sodium hydroxide aqueous solution (1.39g of sodium hydroxide and 28g of pure water) was added and stirred and dispersed for 5min. 172g of deionized water was added and stirred and dispersed for 15min. 10.5g of diethylenetriamine aqueous solution (0.5g of diethylenetriamine and 10g of pure water) was added and stirred and dispersed for 30min. The butanone contained in the mixture was removed by vacuum distillation to obtain the waterborne polyurethane product.
[0046] Comparative Example 2 This example provides a method for preparing waterborne polyurethane, including the following steps: S1. Place 50g of hydrogenated hydroxyl-terminated polybutadiene, 10.37g of dicyclohexylmethane diisocyanate, 7.63g of 4,4'-methylenebis(phenyl isocyanate), and 0.06g of dimethyltin dinecidate in a flask and seal it with nitrogen. React at 85°C for 3h to obtain the prepolymer. S2. Cool to 70°C, add 5.18g of dimethylolpropionic acid and 92g of butanone to the prepolymer, and continue the reaction for 16 hours to generate a hydrophilic polymer solution. S3. Cool down to 30°C, add 29.39g of sodium hydroxide aqueous solution (1.39g sodium hydroxide, 28g pure water) to the hydrophilic polymer solution and stir to disperse for 5min; then add 170g of deionized water and stir to disperse for 15min to obtain a mixed solution; S4. Add 10.5g of diethylenetriamine aqueous solution (0.5g diethylenetriamine, 10g pure water) to the mixture and stir to disperse for 30min; remove the methyl ethyl ketone contained therein by vacuum distillation to obtain the waterborne polyurethane product.
[0047] Comparative Example 3 This example provides a method for preparing waterborne polyurethane, including the following steps: S1. Place 50g of hydrogenated hydroxyl-terminated polybutadiene, 18.37g of dicyclohexylmethane diisocyanate, and 0.06g of dimethyltin dinecidate in a flask and seal it with nitrogen. React at 85°C for 3 hours to obtain the prepolymer. S2. Cool to 70°C, add 5.18g of dimethylolpropionic acid and 92g of butanone to the prepolymer, and continue the reaction for 16 hours to generate a hydrophilic polymer solution. S3. Cool down to 30°C, add 29.39g of sodium hydroxide aqueous solution (1.39g sodium hydroxide, 28g pure water) to the hydrophilic polymer solution and stir to disperse for 5min; then add 172g of deionized water and stir to disperse for 15min to obtain a mixed solution; S4. Add 10.59g of crosslinking agent aqueous solution (0.4g of diethylenetriamine and 0.19g of di-n-butylamine dissolved in 10g of pure water) to the mixture and stir and disperse for 30min; remove the methyl ethyl ketone contained therein by vacuum distillation to obtain the waterborne polyurethane product.
[0048] Comparative Example 4 This example provides a method for preparing waterborne polyurethane, including the following steps: S1. Place 50g of hydrogenated hydroxyl-terminated polybutadiene, 18.37g of dicyclohexylmethane diisocyanate, and 0.06g of dimethyltin dinecidate in a flask and seal it with nitrogen. React at 85°C for 3 hours to obtain the prepolymer. S2. Cool to 70°C, add 5.18g of dimethylolpropionic acid and 92g of butanone to the prepolymer, and continue the reaction for 16 hours to generate a hydrophilic polymer solution. S3. Cool down to 30°C, add 29.39g of sodium hydroxide aqueous solution (1.39g sodium hydroxide, 28g pure water) to the hydrophilic polymer solution and stir to disperse for 5min; then add 172g of deionized water and stir to disperse for 15min to obtain a mixed solution; S4. Add 21g of diethylenetriamine aqueous solution (1g of diethylenetriamine dissolved in 20g of pure water) to the mixture and stir to disperse for 30min; remove the methyl ethyl ketone contained therein by vacuum distillation to obtain the waterborne polyurethane product.
[0049] Comparative Example 5 This example provides a method for preparing waterborne polyurethane, including the following steps: S1. Place 50g of hydrogenated hydroxyl-terminated polybutadiene, 18.37g of dicyclohexylmethane diisocyanate, and 0.05g of dimethyltin dinecidate in a flask and seal it with nitrogen. React at 85°C for 3 hours to obtain the prepolymer. S2. Cool to 70°C, add 5.18g of dimethylolbutyric acid and 92g of butanone to the prepolymer, and continue the reaction for 16 hours to generate a hydrophilic polymer solution. S3. Cool down to 30°C, add 29.39g of sodium hydroxide aqueous solution (1.39g sodium hydroxide, 28g pure water) to the hydrophilic polymer solution and stir to disperse for 5min; then add 172g of deionized water and stir to disperse for 15min to obtain a mixed solution; S4. Add 10.5g of diethylenetriamine aqueous solution (0.5g of diethylenetriamine dissolved in 10g of pure water) to the mixture and stir to disperse for 30min; remove the methyl ethyl ketone contained therein by vacuum distillation to obtain the waterborne polyurethane product.
[0050] Comparative Example 6 This example provides a method for preparing waterborne polyurethane, including the following steps: S1. Place 50g of polypropylene glycol (molecular weight 2000), 18.37g of dicyclohexylmethane diisocyanate and 0.05g of dimethyltin dinecidate in a flask and seal it with nitrogen. React at 85°C for 3 hours to obtain the prepolymer. S2. Cool to 70°C, add 5.18g of dimethylolpropionic acid and 88g of butanone to the prepolymer and continue the reaction for 16 hours to generate a hydrophilic polymer solution. S3. Cool down to 30°C, add 29.39g of sodium hydroxide aqueous solution (1.39g sodium hydroxide, 28g pure water) to the hydrophilic polymer solution and stir to disperse for 5min; then add 172g of deionized water and stir to disperse for 15min to obtain a mixed solution; S4. Add 10.5g of diethylenetriamine aqueous solution (0.5g of diethylenetriamine dissolved in 10g of pure water) to the mixture and stir to disperse for 30min; remove the methyl ethyl ketone contained therein by vacuum distillation to obtain the waterborne polyurethane product.
[0051] Comparative Example 7 This example provides a method for preparing low-swelling waterborne polyurethane, including the following steps: S1. Place 50g of hydrogenated hydroxyl-terminated polybutadiene, 18.37g of dicyclohexylmethane diisocyanate, and 0.05g of dimethyltin dinecidate in a flask and seal it with nitrogen. React at 85°C for 3 hours to obtain the prepolymer. S2. Cool to 70°C, add 5.18g of dimethylolpropionic acid and 92g of butanone to the prepolymer, and continue the reaction for 16 hours to generate a hydrophilic polymer solution. S3. Cool down to 30°C, add 29.39g of sodium hydroxide aqueous solution (1.39g sodium hydroxide, 28g pure water) to the hydrophilic polymer solution and stir to disperse for 5min; then add 172g of deionized water and stir to disperse for 15min to obtain a mixed solution; S4. Add 10.5g of triethylamine aqueous solution (0.5g of triethylamine dissolved in 10g of pure water) to the mixture and stir to disperse for 30min; remove the methyl ethyl ketone contained therein by vacuum distillation to obtain the waterborne polyurethane product.
[0052] Comparative Example 8 This example provides a method for preparing waterborne polyurethane, including the following steps: S1. Place 50g of hydrogenated hydroxyl-terminated polybutadiene, 18.37g of dicyclohexylmethane diisocyanate, and 0.05g of dimethyltin dinecidate in a flask and seal it with nitrogen. React at 85°C for 3 hours to obtain the prepolymer. S2. Cool to 70°C, add 5.18g of dimethylolpropionic acid and 74g of butanone to the prepolymer, and continue the reaction for 16 hours to generate a hydrophilic polymer solution. S3. Cool down to 30°C, add 29.39g of sodium hydroxide aqueous solution (1.39g sodium hydroxide, 28g pure water) to the hydrophilic polymer solution and stir to disperse for 5min; then add 172g of deionized water and stir to disperse for 15min to obtain a mixed solution; S4. Add 10.5g of diethylenetriamine aqueous solution (0.5g diethylenetriamine, 10g pure water) to the mixture and stir to disperse for 30min; remove the methyl ethyl ketone contained therein by vacuum distillation to obtain the waterborne polyurethane product.
[0053] Comparative Example 9 This example provides a method for preparing waterborne polyurethane, including the following steps: S1. Place 50g of hydrogenated hydroxyl-terminated polybutadiene, 18.37g of dicyclohexylmethane diisocyanate, and 0.05g of dimethyltin dinecidate in a flask and seal it with nitrogen. React at 85°C for 3 hours to obtain the prepolymer. S2. Cool to 70°C, add 5.18g of dimethylolpropionic acid and 140g of butanone to the prepolymer, and continue the reaction for 16 hours to generate a hydrophilic polymer solution. S3. Cool down to 30°C, add 29.39g of sodium hydroxide aqueous solution (1.39g sodium hydroxide, 28g pure water) to the hydrophilic polymer solution and stir to disperse for 5min; then add 172g of deionized water and stir to disperse for 15min to obtain a mixed solution; S4. Add 10.5g of diethylenetriamine aqueous solution (0.5g diethylenetriamine, 10g pure water) to the mixture and stir to disperse for 30min; remove the methyl ethyl ketone contained therein by vacuum distillation to obtain the waterborne polyurethane product.
[0054] Comparative Example 10 This example provides a method for preparing waterborne polyurethane, including the following steps: S1. Place 50g of hydroxyl-terminated polybutadiene, 13.33g of dicyclohexylmethane diisocyanate, and 0.05g of dimethyltin dinecidate in a flask and seal it with nitrogen. React at 85°C for 3 hours to obtain the prepolymer. S2. Cool to 70°C, add 2.66g of dimethylolpropionic acid and 81g of butanone to the prepolymer and continue the reaction for 16 hours to generate a hydrophilic polymer solution. S3. Cool down to 30°C, add 14.7g of sodium hydroxide aqueous solution (0.7g sodium hydroxide, 14g pure water) to the hydrophilic polymer solution and stir to disperse for 5min; then add 152g of deionized water and stir to disperse for 15min to obtain a mixed solution; S4. Add 10.5g of diethylenetriamine aqueous solution (0.5g diethylenetriamine, 10g pure water) to the mixture and stir to disperse for 30min; remove the methyl ethyl ketone contained therein by vacuum distillation to obtain the waterborne polyurethane product.
[0055] Performance testing Swelling test: 1. Prepare a mixed solution using a volume ratio of ethylene carbonate (EC): ethyl methyl carbonate (EMC): propylene carbonate (PC): ethyl acetate = 1:1:1:1.
[0056] 2. The aqueous polyurethane prepared in each embodiment and comparative example was made into a film with a thickness of about 500 micrometers in an oven at 60°C. Three strips of similar size were cut and the corresponding mass m1 was recorded.
[0057] 3. Place the strip in the mixed solution from step 1 and place it in an oven at 80°C for 12 hours. After removing the strip, wipe it with filter paper until it is surface dry and weigh it to obtain mass m2.
[0058] 4. Place the soaked strips in a 120℃ oven until constant weight, and record the mass m3.
[0059] Swelling rate = (m2 - m1) / m1, dissolution rate = (m1 - m3) / m1. The test results are shown in Table 2. Table 2
[0060] As shown in Table 2, the aqueous polyurethane prepared by Comparative Example 10 using unhydrogenated polybutadiene still exhibits significant swelling; Example 1 using hydrogenated hydroxyl-terminated polybutadiene effectively reduces swelling, which is due to the large number of "compliant" double bonds in the unhydrogenated polybutadiene.
[0061] Examples 2 and 3 are supplementary cases to Example 1 with increased hydrophilic chain extender content. They show that as the amount of hydrophilic chain extender increases, swelling decreases, but increasing the amount of hydrophilic chain extender also slightly increases dissolution. This is because an increase in small molecule chain extender leads to an increase in the number of small molecule chain segments that dissolve in the solution.
[0062] Comparative Example 1 was prepared using a one-pot method, but its poor solvent resistance was due to its poor segment uniformity and weak synthetic purpose.
[0063] Comparative Example 2 used a polyisocyanate with a benzene ring. Due to the low polarity of the benzene ring and its high compatibility with ester solvents, it had poor solvent resistance.
[0064] Comparative Example 3 used a difunctional crosslinking agent. Due to the poor degree of crosslinking, the degree of intermolecular crosslinking was insufficient, the intermolecular entanglement was poor, and its solvent resistance was poor.
[0065] Comparative Example 4 increased the crosslinking agent content, but its solution contained precipitates. Excessive crosslinking resulted in poor solubility of the waterborne polyurethane. The swelling and dissolution data were obtained from the supernatant. This comparative example is only used to illustrate that excessive crosslinking agent leads to poor preparation of waterborne polyurethane solution.
[0066] Comparative Example 5 changed the hydrophilic chain extender to DMBA. DMBA has higher solvent solubility than DMPA and cannot impart similar polarity to the chain segments as DMPA, resulting in poorer solvent resistance.
[0067] Comparative Example 6: The polyol is a polyether polyol. The chemical structure of polyether polyols makes them too compatible with solvents, making it difficult to form waterborne polyurethanes with good solvent resistance.
[0068] Comparative Example 7 used triethylamine as a neutralizing agent. As an organic base, it is not as polar as metal ions, and the overall chain segment is not polar enough, resulting in increased swelling.
[0069] Comparative Example 8 reduced the amount of butanone used, and the viscosity gradually increased during the polymerization process, which reduced the degree of reaction between isocyanate and active hydrogen, resulting in a lower polymer molecular weight and increased swelling compared to Example 2.
[0070] Comparative Example 9 increased the amount of butanone used, and the isocyanate content gradually decreased during the polymerization process. Excessive use of butanone led to a decrease in the overall concentration of active groups, a decrease in the degree of reaction, a lower molecular weight than in Example 2, and an increase in swelling.
[0071] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A method for preparing a low-swelling waterborne polyurethane, characterized in that, At least the following steps are included: S1. Polyols, curing agents and catalysts are mixed and polymerized to generate prepolymers; S2. Add a hydrophilic chain extender and an organic solvent to the prepolymer to react and generate a hydrophilic polymer solution; S3. Cool the hydrophilic polymer solution, add an aqueous solution of neutralizing agent to carry out a neutralization reaction, and then add water to disperse the mixture. S4. After adding an aqueous solution of crosslinking agent to the mixture and stirring to react, the organic solvent is removed to obtain the low-swelling waterborne polyurethane. The organic solvent comprises 100%-140% of the total mass of the polyol, curing agent, hydrophilic chain extender, crosslinking agent, and neutralizing agent, with the total mass of the polyol, curing agent, hydrophilic chain extender, crosslinking agent, and neutralizing agent being 100%. The amount of the crosslinking agent is 0.1%-1.9% of the mass of the polyol.
2. The preparation method according to claim 1, characterized in that, The polymerization conditions in S1 are: reaction temperature 80-90℃, reaction time 2-4h.
3. The preparation method according to claim 1, characterized in that, The reaction conditions in S2 are: reaction temperature 65-75℃, reaction time 16-18h.
4. The preparation method according to claim 1, characterized in that, The cooling temperature in S3 is ≤30℃.
5. The preparation method according to claim 1, characterized in that, The mass ratio of the neutralizing agent to water in the aqueous solution of the neutralizing agent is 1:(15-25).
6. The preparation method according to claim 1, characterized in that, The amount of neutralizing agent in the neutralizing agent aqueous solution is 80%-100% of the amount of hydrophilic chain extender.
7. The preparation method according to claim 1, characterized in that, Based on the total mass of the polyol, curing agent, hydrophilic chain extender, crosslinking agent and neutralizing agent being 100%, the mass of the hydrophilic chain extender is 3.9%-10%.
8. The preparation method according to claim 1, characterized in that, Based on the total mass of the hydrophilic chain extender, polyol, and curing agent as 100%, the amount of the catalyst is ≤800ppm.
9. The preparation method according to claim 1, characterized in that, Based on the total mass of the polyol, curing agent, hydrophilic chain extender, crosslinking agent and neutralizing agent being 100%, the mass of the curing agent is 18.9%-29%.
10. A low-swelling waterborne polyurethane, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.