Nano-enhanced self-crosslinking waterborne polyurethane emulsion, waterproof and moisture-permeable coating adhesive, and preparation method and application thereof

Abstract

The application discloses a self-crosslinking type water-based polyurethane emulsion, a nano-enhanced self-crosslinking type water-based polyurethane waterproof and moisture-permeable coating glue and a preparation method and application thereof. The self-crosslinking type water-based polyurethane emulsion comprises a polyurethane containing a ketone carbonyl group and free adipic acid dihydrazide. The adipic acid dihydrazide is added in the form of an aqueous solution after emulsification and chain extension is completed, exists in the form of a free small molecule in a water phase and is not covalently bonded with a polyurethane chain. The nano-enhanced self-crosslinking type water-based polyurethane waterproof and moisture-permeable coating glue comprises the self-crosslinking type water-based polyurethane emulsion, silane coupling agent modified nano silicon dioxide, a leveling agent, a defoaming agent and water. The coating glue is a single-component system, film forming and crosslinking can be simultaneously completed through one-step drying, and has high hydrostatic pressure resistance, high moisture permeation and excellent water washing resistance.

Description

Technical Field

[0001] This invention belongs to the technical field of textile chemicals and functional coating materials, specifically relating to a high-performance water-based waterproof and breathable coating adhesive, and more particularly to a single-component coating adhesive that achieves a balance between high water pressure resistance and high moisture permeability through nano-reinforcement and self-crosslinking technology, as well as its preparation method and application. Background Technology

[0002] Waterproof and breathable coatings can block liquid water penetration while allowing water vapor to pass through, making them a key technology for high-end textiles such as outdoor clothing and medical protective equipment. Currently, high-performance coatings mainly rely on solvent-based polyurethane systems, including wet-curing coatings. Although their performance is acceptable, they have inherent drawbacks such as heavy organic solvent pollution, complex processes, and high energy consumption, which do not align with the trend of green manufacturing.

[0003] Waterborne polyurethane coatings use water as the dispersion medium, which solves the safety problem at its source. However, their film density is poor and the coating strength is insufficient, resulting in low hydrostatic pressure resistance and poor durability, making it difficult to meet the requirements of harsh application environments. To compensate for these performance defects, existing technologies usually rely on the addition of external crosslinking agents or the introduction of complex processes in post-processing. This not only increases production steps and costs but also introduces new problems such as unstable coating performance and sensitivity to environmental humidity.

[0004] In the exploration of ways to improve the performance of water-based systems, existing solutions still have significant limitations. Chinese patent CN110983801A discloses a method for preparing waterproof and breathable cotton fabrics, which achieves functionality through physical blending of waterborne polyurethane with various modifying additives such as hydrophobic modified nano-silica and polyvinylpyrrolidone. However, this method requires the cotton fabric to first undergo water- and oil-repellent finishing and pre-drying and baking. After coating, it requires two more heating processes of pre-drying and baking, resulting in numerous steps, low production efficiency, and high energy consumption. Similarly, Chinese patent CN104727150A discloses a waterproof, breathable, antibacterial, and UV-resistant waterborne polyurethane material. This requires multiple steps to prepare the waterproof and breathable waterborne polyurethane resin, including prepolymerization, neutralization, emulsification, post-chain extension, and vacuum distillation to remove solvents. Then, functional components are introduced after surface modification of silver-loaded nano-titanium dioxide with a silane coupling agent. This preparation process involves many steps, high production costs, and complex process control.

[0005] Furthermore, in some existing aqueous polyurethane systems containing ketone hydrazide self-crosslinking, adipic acid diacid hydrazide (ADH) typically reacts with terminal isocyanate groups in the organic phase to covalently integrate into the polyurethane molecular chain, or it consumes the terminal isocyanate groups as a capping agent. Some existing technologies add adipic acid diacid hydrazide before emulsification, allowing it to react with the terminal isocyanate groups and thus covalently integrate into the polyurethane molecular chain. This introduction method fixes the hydrazide groups onto the polymer chain, restricting chain segment movement during film crosslinking, making it difficult to simultaneously achieve crosslinking uniformity and density, and resulting in a narrow synthesis process window, which can easily lead to system instability. Specifically:

[0006] If ADH participates in the reaction in the organic phase, its acylhydrazine group reacts with the isocyanate group (NCO) to generate acylurea, which consumes NCO and forms covalent bonds, causing ADH to lose its free crosslinking ability. It can only participate in subsequent ketone-hydrazine crosslinking with the acylhydrazine group on the chain segment. The distribution of crosslinking points is limited by the polymer chain structure, making it difficult to form a uniform network.

[0007] If ADH is added directly to the prepolymer mixture before emulsification, ADH will react rapidly with the residual NCO and will also be unable to remain in a free state.

[0008] If ADH is added in the early stage of emulsification, it will compete with water for NCO, which will affect the chain extension efficiency and make it difficult to control the crosslinking density.

[0009] Therefore, developing a single-component water-based coating adhesive that combines excellent waterproof and breathable properties with superior durability, while also being simple to process and suitable for efficient and green production, has become an urgent and challenging technical issue in this field. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art and provide a single-component nano-reinforced self-crosslinking waterborne polyurethane waterproof and breathable coating adhesive and its preparation method. This coating adhesive is a single-component system, and film formation and crosslinking can be completed simultaneously in a single drying step, greatly simplifying the process. Furthermore, the resulting coating exhibits excellent resistance to high hydrostatic pressure, high moisture permeability, and durable water washability.

[0011] To achieve the above objectives, the technical solution of the present invention is as follows:

[0012] A single-component, nano-reinforced, self-crosslinking, waterborne polyurethane waterproof and breathable coating adhesive, comprising the following components by weight:

[0013] Self-crosslinking waterborne polyurethane emulsion: 100 parts, on a solids basis;

[0014] Silane coupling agent modified nano-silica: 3-10 parts;

[0015] Leveling agent: 0.1–0.5 parts;

[0016] Defoamer: 0.1–0.3 parts;

[0017] Add deionized water: Add to the amount required for the coating adhesive to achieve an outflow time of 120±10s at 25℃ as determined by the Ford-4 viscosity cup method according to GB / T1723-1993;

[0018] The self-crosslinking aqueous polyurethane emulsion comprises:

[0019] Ketone carbonyl polyurethanes and free adipic acid dihydrazide;

[0020] The polyurethane containing ketone carbonyl is prepared by reacting polyether polyol, polyester polyol, diisocyanate, ketone carbonyl diol chain extender and hydrophilic chain extender.

[0021] The molar amount of the free adipic acid dihydrazide is 0.6 to 1.2 times the total molar amount of ketone carbonyl groups introduced by the ketone carbonyl-containing diol chain extender, and the adipic acid dihydrazide is added in the form of an aqueous solution after the emulsification chain extension is completed, and exists in the aqueous phase in the form of a free small molecule, without covalently bonding with the polyurethane chain.

[0022] in:

[0023] Based on the total mass of polyether polyols and polyester polyols as 100%, polyether polyols account for 75% to 90%, and polyester polyols account for 10% to 25%.

[0024] The polyether polyol is a polytetrahydrofuran ether diol with a number average molecular weight of 1500-2500.

[0025] The polyester polyol is polybutylene adipate diol with a number average molecular weight of 800-1500.

[0026] The amount of diisocyanate used is such that the molar ratio of its isocyanate groups (NCO) to the total hydroxyl groups of the polyether polyol and polyester polyol is 1.8 to 2.5:1.

[0027] The ketone carbonyl-containing diol chain extender is prepared by a Michael addition reaction of diacetone acrylamide and diethanolamine in a molar ratio of 1:1, and its dosage is 1.5 wt% to 2.5 wt% based on the total mass of polyether polyol, polyester polyol and diisocyanate.

[0028] The hydrophilic chain extender is dimethylolpropionic acid and / or dimethylolbutyric acid, whose carboxyl groups are neutralized into salts by a neutralizing agent, and its dosage is 3wt% to 6wt% based on the total mass of polyether polyol, polyester polyol and diisocyanate.

[0029] Further, the diisocyanate is at least one of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, or diphenylmethane diisocyanate.

[0030] Furthermore, the neutralizing agent is at least one of triethylamine, triethanolamine, or ammonia.

[0031] Furthermore, the degree of neutralization of the hydrophilic chain extender is 85% to 95%.

[0032] The silane coupling agent modified nano-silica is obtained by modifying nano-silica with an average particle size of 10-50 nm with at least one of aminosilane coupling agent, epoxysilane coupling agent or methacryloxysilane coupling agent, wherein the amount of silane coupling agent is 15%-25% of the mass of nano-silica;

[0033] Further, the aminosilane coupling agent is at least one of γ-aminopropyltriethoxysilane or γ-aminopropyltrimethoxysilane; the epoxysilane coupling agent is γ-glycidoxypropyltrimethoxysilane; and the methacryloyloxysilane coupling agent is γ-methacryloyloxypropyltrimethoxysilane.

[0034] Furthermore, the leveling agent is a polyether-modified silicone leveling agent; the defoamer is a silicone defoamer.

[0035] Furthermore, the solid content of the self-crosslinking waterborne polyurethane emulsion is 32% to 40%.

[0036] In this invention, the adipic acid dihydrazide is added in aqueous solution after emulsification and chain extension, and its amount is 0.6 to 1.2 times the total molar amount of ketone carbonyl groups introduced by the ketone carbonyl-containing diol chain extender. Since there is essentially no free NCO in the system upon addition, the adipic acid dihydrazide does not covalently bond with the polyurethane chain, but is uniformly dispersed in the aqueous phase as a free small molecule. During subsequent film formation, as water evaporates, the free adipic acid dihydrazide can diffuse freely and fully contact the ketone carbonyl groups on the polymer chain, undergoing a ketone-hydrazide crosslinking reaction to form a uniform crosslinked network. This design avoids the problems of covalent fixation and uneven crosslinking caused by introducing adipic acid dihydrazide in the organic phase or at the beginning of emulsification in existing technologies, making the crosslinking density easier to control and significantly improving overall performance.

[0037] The adipic acid dihydrazide exists in the aqueous phase in the form of a free small molecule, which can be verified by infrared spectroscopy and ultrafiltration / dialysis-liquid chromatography: before the addition of adipic acid dihydrazide, the isocyanate group absorption peak in the system (approximately 2270 cm⁻¹) is present. -1 The substance has disappeared; after its addition, the emulsion was separated into aqueous phase by ultrafiltration or dialysis, and the aqueous phase was detected by liquid chromatography. The retention time of adipic acid dihydrazide was consistent with that of the pure product, proving that it was not covalently bonded to the polyurethane chain.

[0038] The present invention also provides a method for preparing the self-crosslinking aqueous polyurethane emulsion, comprising the following steps:

[0039] (1) Under an inert atmosphere, polyether polyol, polyester polyol and diisocyanate are reacted at 75-85°C in the presence of a catalyst to obtain isocyanate-terminated polyurethane prepolymer.

[0040] (2) Add a ketone carbonyl diol chain extender and a hydrophilic chain extender to the prepolymer obtained in step (1) and continue the reaction to obtain a ketone carbonyl hydrophilic modified polyurethane prepolymer; react until the NCO content drops to the range of 0.5 to 2.0 wt%;

[0041] (3) The hydrophilic modified polyurethane prepolymer obtained in step (2) is neutralized into salt by a neutralizing agent and dispersed in deionized water under high-speed shearing for emulsification and chain extension; after the NCO content in the system is less than 0.1wt%, an aqueous solution of adipic acid dihydrazide is added and mixed evenly to obtain the self-crosslinking waterborne polyurethane emulsion.

[0042] The beneficial effects of this invention include:

[0043] The process is simple and efficient: The single-component self-crosslinking system of the present invention only requires conventional coating and one-step drying. While the moisture evaporates, the ketone-hydrazine crosslinking and nano-hybrid crosslinking are completed to form a high-performance coating film. No coagulation bath, multi-step coating or post-treatment is required, resulting in high production efficiency and low energy consumption.

[0044] Excellent waterproof and breathable properties: A dense and tough shielding layer is constructed through the synergistic effect of chemical cross-linking network and chemically bonded nano-silica, giving the coating high hydrostatic pressure resistance; at the same time, the hydrophilic segments in the polymer backbone are fixed in the cross-linking network, forming a stable moisture-permeable channel, achieving high moisture permeability.

[0045] Improved crosslinking uniformity: Adipic acid dihydrazide exists in the aqueous phase as a free small molecule. During film formation, it can diffuse freely and come into full contact with the ketone carbonyl group, avoiding the problem of uneven crosslinking caused by the covalent fixation of the hydrazide group in the prior art. This results in uniform crosslinking density of the coating film and stable overall performance.

[0046] Excellent durability: The three-dimensional cross-linked network and nanoparticle-reinforced structure effectively improve the coating's resistance to hydrolysis, solvents, and physical and mechanical strength, and maintain high performance after multiple washes or long-term use.

[0047] It is environmentally friendly: it uses water as a dispersion medium, has a low VOC content, and meets the requirements of green production. Attached Figure Description

[0048] none. Detailed Implementation

[0049] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0050] Preparation Example 1: Preparation of chain extenders containing ketone carbonyl diols

[0051] Equimolar amounts of diethanolamine and diacetone acrylamide were added to anhydrous ethanol to bring the total solid content to 30 wt%. The mixture was stirred at 70 °C for 5 hours. After the reaction was complete, the ethanol was removed under reduced pressure. The crude product was washed three times with acetone and dried under vacuum to obtain a diol chain extender containing a ketone carbonyl group. This chain extender was N,N-bis(2-hydroxyethyl)-3-[(2-methyl-4-oxopentan-2-yl)amino]propionamide.

[0052] The obtained chain extender was analyzed by infrared spectroscopy, and its concentration at 1715 cm⁻¹ was [missing value]. -1 The presence of a characteristic absorption peak of a ketone carbonyl group nearby; the disappearance of the proton signal of the carbon-carbon double bond in the proton NMR spectrum of diacetone acrylamide, proving that the Michael addition reaction was complete and that the chain extender molecule contains one ketone carbonyl group and two primary hydroxyl groups.

[0053] Example 1: Preparation of silane coupling agent modified nano-silica

[0054] 10 g of vapor-phase nano-SiO2 (average particle size 20 nm) was dispersed in 200 g of ethanol and sonicated for 30 minutes. 2 g of γ-aminopropyltriethoxysilane (KH550) was added, and the mixture was refluxed and stirred at 60 °C for 6 hours. After the reaction was complete, the mixture was centrifuged, washed three times with ethanol, and dried under vacuum at 80 °C to obtain aminosilane coupling agent modified nano-SiO2 powder.

[0055] This embodiment uses γ-aminopropyltriethoxysilane (KH550) as an example. When using γ-glycidoxypropyltrimethoxysilane or γ-methacryloyloxypropyltrimethoxysilane, the modification can be carried out by referring to the method of this embodiment.

[0056] Example 2: Synthesis of self-crosslinking waterborne polyurethane emulsion

[0057] Under dry nitrogen protection, 500g of polytetrahydrofuran ether glycol (number average molecular weight 2000) and 100g of polybutylene adipate glycol (number average molecular weight 1000) were added to the reactor, and the mixture was heated to 80℃ and dehydrated under vacuum for 1 hour. The temperature was then lowered to 75℃, and 155g of isophorone diisocyanate (NCO / OH molar ratio approximately 2.0) and 0.15g of dibutyltin dilaurate catalyst were added. The reaction was maintained at this temperature for 2 hours.

[0058] Then, 14 g of a ketone-containing carbonyl diol chain extender (refer to Preparation Example 1), prepared by reacting diacetone acrylamide with diethanolamine in a molar ratio of 1:1, was added. This amount was approximately 1.85 wt% of the prepolymer solids before the addition of the chain extender. 30 g of dimethylolpropionic acid (approximately 4.0 wt% of the prepolymer solids) was also added. The reaction was continued at 80 °C until the NCO content decreased to 0.6 wt% (titrated by the di-n-butylamine method). The temperature was lowered to 40 °C, and 20.4 g of triethylamine was added to neutralize and form a salt (90% neutralization).

[0059] The above-mentioned hydrophilic modified polyurethane prepolymer was slowly added to 2000g of deionized water under high-speed shear (3000-5000rpm) for emulsification and chain extension. Stirring was maintained for 30 minutes. The NCO content was determined to be below 0.1% using the di-n-butylamine method, and the 2270cm² content was confirmed by infrared spectroscopy. -1 The NCO absorption peak disappears.

[0060] Subsequently, 9g of adipic acid dihydrazide (1.0 times the molar amount of ketone carbonyl) was dissolved in 200g of deionized water and slowly added to the above emulsion. The mixture was stirred and mixed for 30 minutes to obtain a self-crosslinking waterborne polyurethane emulsion.

[0061] In this embodiment, by controlling the total amount of deionized water (2000g) added during emulsification and the amount of water in the neutralizing agent aqueous solution and the adipic acid dihydrazide aqueous solution, the final emulsion solid content is approximately 35%.

[0062] After separating the aqueous phase of the emulsion by ultrafiltration, the filtrate was analyzed by liquid chromatography. The retention time of adipic acid dihydrazide was consistent with that of the pure product, proving that it exists in the aqueous phase in the form of a free small molecule and is not covalently bonded to the polyurethane chain. The liquid chromatography conditions were: C18 column, mobile phase acetonitrile / water = 10 / 90, and detection wavelength 210 nm.

[0063] This embodiment uses isophorone diisocyanate as an example. When hexamethylene diisocyanate, toluene diisocyanate or diphenylmethane diisocyanate are used as substitutes, the synthesis can be carried out in accordance with the method of this embodiment.

[0064] This embodiment uses triethylamine as an example. When triethanolamine or ammonia is used as a substitute, the neutralization can be carried out in accordance with the method of this embodiment.

[0065] Example 3: Formulation of coating adhesive and fabric coating

[0066] Take 100g of the above-mentioned self-crosslinking waterborne polyurethane emulsion containing solids (e.g., about 286g when the solid content is 35%), add 5g of the modified nano-SiO2 obtained in Example 1, 0.3g of leveling agent (BYK-333), 0.2g of defoamer (BYK-024), and add about 30g of deionized water until the outflow time measured by the viscosity cup method of GB / T1723-1993 (4) at 25°C is 120±10s. Stir and mix at room temperature for 1 hour to obtain a one-component coating adhesive.

[0067] 210T nylon taffeta was selected as the base fabric. The coating adhesive was applied to the surface of the base fabric using a 100-mesh screen, and the dry coating amount was controlled to be 15g / m². The sample was then placed in an oven and dried at 120℃ for 4 minutes. After cooling, the coated fabric sample S1 was obtained.

[0068] Example 4: Different amounts of nano-silica

[0069] Following the preparation method of Example 3, only the amount of modified nano-SiO2 was adjusted to 3 parts and 10 parts, respectively, to obtain the coating adhesive; coated fabrics were prepared using the same coating process as in Example 3 (coating amount 15 g / m², drying at 120°C for 4 minutes). The resulting coated fabrics exhibited hydrostatic pressure resistance of 14800 mmH₂O and 17200 mmH₂O, respectively, and moisture permeability of 6800 g / m². 2 ·24h and 6100g / m 2 ·24h.

[0070] Example 5: Different coating amounts and drying conditions

[0071] The coating adhesive was prepared according to the formulation in Example 3. Coated fabrics were prepared by applying dry coating amounts of 10 g / m² and 20 g / m², respectively, and drying at 115°C for 4 minutes and 125°C for 3.5 minutes, respectively. The resulting samples exhibited hydrostatic pressure resistance ≥15000 mmH₂O and moisture permeability ≥6200 g / m². 2 ·24h.

[0072] Example 6: Storage Stability Test

[0073] The coating adhesive prepared in Example 3 was sealed and stored in a 50°C oven for 14 days. After being removed and brought to room temperature, the appearance was observed to show no gelation or delamination, and the viscosity change was less than 10%. The coating was then coated and dried using the same process as in Example 3. The hydrostatic pressure resistance retention rate of the coating film was measured to be greater than 95%, and the moisture permeability retention rate was greater than 90%.

[0074] Example 7: Validation of other silane coupling agents, diisocyanates, and neutralizing agents

[0075] Coating adhesives were prepared and coated onto fabrics using the methods of Examples 2 and 3, respectively, using γ-glycidoxypropyltrimethoxysilane-modified nano-silica, γ-methacryloyloxypropyltrimethoxysilane-modified nano-silica, hexamethylene diisocyanate instead of isophorone diisocyanate, and triethanolamine instead of triethylamine. The performance test results of the obtained samples are as follows:

[0076] Table 2 Validation Results of Alternative Raw Materials

[0077] Alternative raw materials <![CDATA[Hydrostatic pressure resistance (mmH₂O)]]> <![CDATA[Moisture vapor transmission rate (g / m 2 ·24h)]]> Hydrostatic pressure retention rate after hydrolysis (%) <![CDATA[γ-glycidoxypropyltrimethoxysilane modified nano-SiO₂]]> 15800 6400 90 <![CDATA[γ-methacryloyloxypropyltrimethoxysilane modified nano-SiO₂]]> 16200 6350 91 Hexamethylene diisocyanate as a substitute for isophorone diisocyanate 16000 6450 90 Triethanolamine instead of triethylamine 15900 6420 90

[0078] Based on this, the substitution effects of toluene diisocyanate, diphenylmethane diisocyanate, and ammonia were further verified, and the results are as follows:

[0079] Table 3 Validation Results of Supplemental Alternative Raw Materials

[0080] Alternative raw materials <![CDATA[Hydrostatic pressure resistance (mmH₂O)]]> <![CDATA[moisture vapor transmission rate (g / m 2 ·24h)]]> Hydrostatic pressure retention rate after hydrolysis (%) Toluene diisocyanate as a substitute for isophorone diisocyanate 15500 6300 88 Diphenylmethane diisocyanate as a substitute for isophorone diisocyanate 15300 6250 87 Ammonia as a substitute for triethylamine 15600 6380 89

[0081] Example 8: Water Washability Test

[0082] The coated fabric sample S1 obtained in Example 3 was subjected to 5 standard water washing cycles according to GB / T8629-2017. After water washing, the hydrostatic pressure retention rate was 88% and the moisture permeability retention rate was 85%, indicating that the coating has excellent water washing resistance.

[0083] Comparative Example 1

[0084] A control aqueous polyurethane emulsion without a ketone-hydrazine crosslinking system was prepared. Except for the absence of ketone-carbonyl diol chain extender and adipic acid dihydrazide, the raw materials and preparation steps of this control emulsion were the same as those in Example 2. The same base fabric was coated with the same process to obtain sample D1.

[0085] Comparative Example 2

[0086] Take 100g of the same emulsion as in Example 2, add 5g of unmodified nano-SiO2, and follow the same procedure as in Example 3 to obtain sample D2.

[0087] Comparative Example 3

[0088] Following the existing technique of reacting adipate dihydrazide with terminal isocyanate groups in an organic phase to covalently integrate it into the polyurethane molecular chain, an emulsion containing ketone hydrazide crosslinking groups was prepared. Modified nano-SiO2 was then added according to the formulation of Example 3 to obtain sample D3.

[0089] The specific preparation steps are as follows:

[0090] (1) Following steps (1) and (2) of Example 2, a polyurethane prepolymer with a ketone carbonyl terminal group was obtained, with an NCO content of 0.6 wt%;

[0091] (2) Cool the system to 60°C, add 9g of adipic acid dihydrazide (dissolved in 50g of N-methylpyrrolidone), stir and react for 1 hour to allow the adipic acid dihydrazide to react with the residual NCO and covalently attach to the polyurethane chain; after the reaction, the NCO content is less than 0.1wt%;

[0092] (3) Cool down to 40°C, add 20.4g of triethylamine to neutralize and form a salt, and then emulsify according to step (3) of Example 2, but without adding additional adipic acid dihydrazide;

[0093] (4) Add 5g of modified nano-SiO2, leveling agent, defoamer and deionized water according to the formulation of Example 3 to obtain sample D3.

[0094] Comparative Example 4

[0095] Before emulsification, adipic acid dihydrazide was directly added to the prepolymer mixture obtained in step (2) of Example 2. After stirring for 5 minutes, emulsification was carried out according to step (3) of Example 2. The remaining operations were the same as in Example 3, and sample D4 was obtained.

[0096] The specific preparation steps are as follows:

[0097] (1) Following steps (1) and (2) of Example 2, a hydrophilic modified polyurethane prepolymer containing ketone carbonyl groups was obtained;

[0098] (2) Cool to 40℃ and add 20.4g of triethylamine to neutralize and form a salt;

[0099] (3) Dissolve 9g of adipic dihydrazide in 200g of deionized water, add it to the prepolymer before high-speed shearing, stir rapidly for 5 minutes, and then immediately disperse the mixture in the remaining deionized water for emulsification; continue stirring for 30 minutes;

[0100] (4) Add 5g of modified nano-SiO2, leveling agent, defoamer and deionized water according to the formulation of Example 3 to obtain sample D4.

[0101] Performance Tests and Results

[0102] Test method:

[0103] Moisture permeability is measured according to GB / T12704.2-2009, in g / m³. 2 ·24h;

[0104] Hydrostatic pressure resistance refers to GB / T4744-2013, unit mmH2O;

[0105] Hydrolysis resistance is the performance retention rate after immersion in water at 70℃ for 72 hours.

[0106] Crosslinking uniformity is characterized by the swelling degree of the coating film. The lower the swelling degree, the higher and more uniform the crosslinking density.

[0107] Swelling test: Immerse the cross-linked coating sample in methyl ethyl ketone (MEK) at room temperature for 24 hours, remove it and wipe off the surface solvent, and calculate the swelling degree based on the mass change.

[0108] Table 1 Performance Test Results

[0109] Test Project Sample S1 Sample D1 Sample D2 Sample D3 Sample D4 <![CDATA[Moisture vapor transmission rate (g / m 2 ·24h)]]> 6500 4800 5200 5300 5100 <![CDATA[Hydrostatic pressure resistance (mmH2O)]]> 16500 8500 11000 12000 9500 Hydrostatic pressure retention rate after hydrolysis (%) 92 58 75 68 62 Hydrostatic pressure retention rate after 5 water washes (%) 88 — — — — Swelling degree (%) 1.8 4.5 3.2 3.8 4.2

[0110] Note: “—” in the table indicates that it has not been tested.

[0111] As shown in Table 1, sample S1 of the present invention is significantly superior to the comparative examples in terms of moisture permeability, hydrostatic pressure resistance, hydrolysis resistance retention rate, water wash resistance retention rate, and crosslinking uniformity. In particular, compared with comparative example 3, which uses covalently grafted ADH, and comparative example 4, which adds ADH before emulsification, the present invention adds ADH in the form of an aqueous solution after emulsification and chain extension, resulting in a more uniform crosslinking network and significantly improved water pressure resistance and durability, fully demonstrating the technical advantages of the present invention.

[0112] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A self-crosslinking waterborne polyurethane emulsion, characterized in that, This includes polyurethanes containing ketone carbonyl groups and free adipic acid dihydrazide; The polyurethane containing ketone carbonyl is prepared by reacting polyether polyol, polyester polyol, diisocyanate, ketone carbonyl diol chain extender and hydrophilic chain extender. Of which, based on the total mass of polyether polyols and polyester polyols as 100%, polyether polyols account for 75% to 90%, and polyester polyols account for 10% to 25%; The polyether polyol is a polytetrahydrofuran ether diol with a number average molecular weight of 1500-2500. The polyester polyol is polybutylene adipate diol with a number average molecular weight of 800-1500. The amount of diisocyanate used is such that the molar ratio of its isocyanate groups to the total hydroxyl groups of the polyether polyol and polyester polyol is 1.8 to 2.5:

1. The ketone carbonyl-containing diol chain extender is prepared by a Michael addition reaction of diacetone acrylamide and diethanolamine in a molar ratio of 1:1, and its dosage is 1.5 wt% to 2.5 wt% based on the total mass of polyether polyol, polyester polyol and diisocyanate. The hydrophilic chain extender is dimethylolpropionic acid and / or dimethylolbutyric acid, whose carboxyl groups are neutralized to form a salt by a neutralizing agent, and its dosage is 3wt% to 6wt% based on the total mass of polyether polyol, polyester polyol and diisocyanate; The molar amount of the free adipic acid dihydrazide is 0.6 to 1.2 times the total molar amount of ketone carbonyl groups introduced by the ketone carbonyl-containing diol chain extender. The adipic acid dihydrazide exists in the aqueous phase in the form of a free small molecule and does not covalently bond with the polyurethane chain.

2. The self-crosslinking aqueous polyurethane emulsion according to claim 1, characterized in that, The diisocyanate is at least one of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, or diphenylmethane diisocyanate.

3. The self-crosslinking aqueous polyurethane emulsion according to claim 1, characterized in that, The neutralizing agent is at least one of triethylamine, triethanolamine, or ammonia.

4. The self-crosslinking waterborne polyurethane emulsion according to claim 1, characterized in that, The degree of neutralization of the hydrophilic chain extender is 85% to 95%.

5. A method for preparing the self-crosslinking aqueous polyurethane emulsion according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Under an inert atmosphere, polyether polyol, polyester polyol and diisocyanate are reacted at 75-85°C in the presence of a catalyst to obtain isocyanate-terminated polyurethane prepolymer. (2) Add a ketone carbonyl diol chain extender and a hydrophilic chain extender to the prepolymer obtained in step (1) and continue the reaction to obtain a ketone carbonyl hydrophilic modified polyurethane prepolymer; react until the NCO content drops to the range of 0.5 to 2.0 wt%; (3) The hydrophilic modified polyurethane prepolymer obtained in step (2) is neutralized into salt by a neutralizing agent and dispersed in water under high-speed shearing for emulsification and chain extension; after the NCO content in the system is less than 0.1wt%, an aqueous solution of adipic acid dihydrazide is added and mixed evenly to obtain the self-crosslinking waterborne polyurethane emulsion.

6. A single-component, nano-reinforced, self-crosslinking, waterborne polyurethane waterproof and breathable coating adhesive, characterized in that, Based on parts by weight, it includes the following components: The self-crosslinking aqueous polyurethane emulsion according to any one of claims 1 to 4: 100 parts, based on solids; Silane coupling agent modified nano-silica: 3-10 parts; Leveling agent: 0.1–0.5 parts; Defoamer: 0.1–0.3 parts; Add deionized water: Add to the amount required for the coating adhesive to achieve an outflow time of 120±10s at 25℃ as determined by the Ford-4 viscosity cup method according to GB / T1723-1993; The silane coupling agent modified nano-silica is obtained by modifying nano-silica with an average particle size of 10-50 nm with at least one of aminosilane coupling agent, epoxysilane coupling agent or methacryloxysilane coupling agent, wherein the amount of silane coupling agent is 15%-25% of the mass of nano-silica.

7. The nano-reinforced self-crosslinking waterborne polyurethane waterproof and breathable coating adhesive according to claim 6, characterized in that, The solid content of the self-crosslinking waterborne polyurethane emulsion is 32% to 40%.

8. The nano-reinforced self-crosslinking waterborne polyurethane waterproof and breathable coating adhesive according to claim 6, characterized in that, The aminosilane coupling agent is at least one of γ-aminopropyltriethoxysilane or γ-aminopropyltrimethoxysilane; the epoxysilane coupling agent is γ-glycidoxypropyltrimethoxysilane; and the methacryloyloxysilane coupling agent is γ-methacryloyloxypropyltrimethoxysilane.

9. The nano-reinforced self-crosslinking waterborne polyurethane waterproof and breathable coating adhesive according to claim 6, characterized in that, The leveling agent is a polyether-modified silicone leveling agent; the defoamer is a silicone defoamer.

10. A method for preparing the nano-reinforced self-crosslinking waterborne polyurethane waterproof and breathable coating adhesive according to any one of claims 6 to 9, characterized in that, According to the components and weight parts described in any one of claims 6 to 9, 100 parts of self-crosslinking waterborne polyurethane emulsion (solids) are mixed with 3 to 10 parts of silane coupling agent modified nano-silica, 0.1 to 0.5 parts of leveling agent, 0.1 to 0.3 parts of defoamer, and added deionized water, and the mixture is brought up to a viscosity cup flow time of 120 ± 10 s at 25°C. The mixture is stirred and mixed at room temperature for 0.5 to 2 hours to obtain a single-component ready-to-use coating adhesive.

11. A method for preparing a waterproof and breathable fabric, characterized in that, Using the nano-reinforced self-crosslinking waterborne polyurethane waterproof and breathable coating adhesive according to any one of claims 6 to 9 includes the following steps: The coating adhesive is applied to the fabric surface, and the dry coating amount is 10-20 g / m². Drying at 115–125°C for 3.5–4.5 minutes completes film formation and cross-linking, resulting in a waterproof and breathable fabric.

12. A waterproof and breathable fabric, characterized in that, It is prepared by the method described in claim 11.