High-resistance waterborne polyurethane resin as well as preparation method and application thereof

Abstract

The invention discloses high-resistance waterborne polyurethane resin as well as a preparation method and application thereof, and belongs to the technical field of waterborne polyurethane resin. The resin comprises diisocyanate, polyol and other components, and has the key points that a surface migration agent is beta-cyclodextrin modified polydimethylsiloxane, and a response agent is adamantane modified nano silicon dioxide. The preparation method comprises the following steps: performing pre-polymerization, neutralization, emulsification and post-chain extension to obtain a basic emulsion, sequentially adding the response agent and the surface migration agent, adjusting the pH value, and curing. Controllable construction of the hydrophobic layer is achieved through the subject-object recognition effect, the bottleneck that existing waterborne polyurethane is poor in water resistance is solved, the problems of component agglomeration and low migration efficiency are solved, the protection performance of the coating is improved, the service life of the coating is prolonged, and the method can be used for preparing paint and is suitable for decoration and protection of various base materials.

Description

Technical Field

[0001] This invention belongs to the field of waterborne polyurethane resin technology, and relates to a high-durability waterborne polyurethane resin, its preparation method and application. Background Technology

[0002] Waterborne polyurethane resin is an environmentally friendly polymer material with outstanding advantages such as no VOC pollution, convenient construction, good film-forming properties, and strong adhesion. It has been widely used in the coatings field and can be used in various scenarios such as architectural coatings, wood coatings, and industrial protective coatings. It can provide decorative and protective functions for different substrates, which is in line with the current development trend of environmentally friendly coatings.

[0003] However, poor water resistance remains a key technical bottleneck restricting the further promotion and application of waterborne polyurethane resins in the coatings field. To achieve dispersibility or solubility in water, existing waterborne polyurethane resins must incorporate hydrophilic groups (such as carboxyl, hydroxyl, and urethane groups) into their molecular structure. The presence of these hydrophilic groups means that even after the resin cures to form a coating, a large number of hydrophilic sites remain on the surface, easily interacting with water. This leads to a decrease in the water contact angle and an increase in water absorption. Prolonged exposure to humid environments or contact with water can cause quality problems such as blistering, whitening, loss of gloss, peeling, and flaking. This not only damages the coating's appearance and decorative properties but also reduces its protective performance and service life, and may even cause damage to the substrate, failing to meet the actual application requirements of the coating. Summary of the Invention

[0004] The purpose of this invention is to provide a high-durability waterborne polyurethane resin, its preparation method and application. By using the host-guest recognition mechanism of surface migration agent and responsive agent, the hydrophobic layer is constructed in situ in the later stage of film formation, which significantly improves the water resistance and long-term stability of the coating.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a high-durability waterborne polyurethane resin comprising the following components: diisocyanate, polyol, small molecule chain extender, hydrophilic chain extender, post-chain extender, surface migration agent, responsive agent, neutralizing agent, catalyst, cosolvent, pH adjuster, and deionized water;

[0007] The surface migration agent is a polydimethylsiloxane modified with β-cyclodextrin;

[0008] The responsive agent is nano-silica modified with adamantane.

[0009] Preferably, the method for preparing the surface migration agent includes the following steps:

[0010] A1. β-Cyclodextrin and 3-isocyanate-propyltriethoxysilane are reacted at a mass ratio of 1:0.6-0.8 at 65-75°C for 5-7 hours to obtain an intermediate;

[0011] A2. Hydroxyl-terminated polydimethylsiloxane and an intermediate are reacted at a mass ratio of 1:0.4-0.6 at 75-85°C for 10-14 hours to obtain β-cyclodextrin-modified polydimethylsiloxane.

[0012] Preferably, the method for preparing the responsive agent includes the following steps:

[0013] B1. Nano-silica and aminosilane coupling agent are reacted at 65-75℃ for 10-14 hours at a mass ratio of 1:0.25-0.35 to obtain amino-modified nano-silica.

[0014] B2. Amino-modified nano-silica and adamantane carboxylic acid are reacted at a mass ratio of 1:0.15-0.25 at 25-35℃ for 22-26 hours to obtain adamantane-modified nano-silica.

[0015] Preferably, the composition comprises the following components in parts by weight: 35-50 parts diisocyanate, 40-60 parts polyol, 3-8 parts small molecule chain extender, 3-6 parts hydrophilic chain extender, 0.5-1.5 parts post-chain extender, 2-4 parts surface migration agent, 1-2.5 parts responsive agent, 2-5 parts neutralizer, 0.1-0.3 parts catalyst, 5-15 parts cosolvent, 0.3-0.6 parts pH adjuster, and 150-300 parts deionized water;

[0016] Preferably, the diisocyanate is isophorone diisocyanate; the polyol is a polyester polyol selected from one or more of poly(1,4-butanediol adipate), poly(1,6-hexanediol adipate), and polycaprolactone diol; the small molecule chain extender is 1,4-butanediol; the hydrophilic chain extender is dimethylolpropionic acid; the post-chain extender is ethylenediamine; the neutralizing agent is triethylamine; the catalyst is dibutyltin dilaurate; the cosolvent is N-methylpyrrolidone; and the pH adjuster is triethylamine.

[0017] In a second aspect, the present invention provides a method for preparing a high-durability waterborne polyurethane resin as described in the first aspect, comprising the following steps:

[0018] S1. Diisocyanate, polyol, small molecule chain extender, hydrophilic chain extender, catalyst and cosolvent are mixed and a prepolymerization reaction is carried out to obtain a prepolymer.

[0019] S2. Add a neutralizing agent to the prepolymer obtained in step S1 to carry out a neutralization reaction;

[0020] S3. The neutralized prepolymer is added to deionized water for emulsification, and then a chain extender is added to carry out a chain extension reaction to obtain an aqueous polyurethane resin base emulsion.

[0021] S4. Add the response agent to the base emulsion obtained in step S3 and disperse it evenly;

[0022] S5. After dissolving the surface migration agent in the solvent, add it to the mixture obtained in step S4;

[0023] S6. Add a pH adjuster to adjust the pH, let it stand and mature to obtain a high-durability waterborne polyurethane resin.

[0024] Preferably, the responsive agent in step S4 is added by ultrasonic dispersion, with an ultrasonic power of 200-400 W and a time of 10-20 min;

[0025] The surface migration agent mentioned in step S5 is added dropwise with ethanol as solvent at a stirring speed of 200-300 rpm;

[0026] In step S6, the pH is adjusted to 7.3-7.8, and the standing maturation time is 20-28 hours.

[0027] Preferably, the prepolymerization reaction temperature in step S1 is 75-85°C, and the reaction continues until the NCO content drops to 6.5-7.5%.

[0028] The emulsification temperature in step S3 is 40-45℃, and the stirring speed is 1000-1500 rpm.

[0029] Thirdly, the present invention provides a coating comprising a highly resistant waterborne polyurethane resin as described in the first aspect.

[0030] The beneficial effects of this invention are:

[0031] (1) In this invention, polydimethylsiloxane modified with β-cyclodextrin is used as a surface migration agent. The low surface energy of polydimethylsiloxane is utilized to drive the water evaporation in the early stage of film formation to migrate and accumulate on the coating surface. At the same time, nano-silica modified with adamantane is used as a response agent. Through the host-guest recognition between adamantane and β-cyclodextrin, it is actively captured and anchored on the coating surface by the surface migration agent in the later stage of film formation, thus realizing the controllable construction of the hydrophobic layer.

[0032] (2) In liquid coatings, the β-cyclodextrin cavities in the surface migration agent are encapsulated by polydimethylsiloxane segments and are in a "closed" state, unable to recognize the adamantane in the responsive agent. Therefore, the two remain stably coexisting during storage and application. As water evaporates, the pH of the system changes, and cross-linking occurs during film formation, the polydimethylsiloxane segments undergo conformational rearrangement, and the β-cyclodextrin cavities are gradually exposed and transformed into an "open" state. Only then can they recognize the responsive agent, which is uniformly dispersed in the coating, and capture it to the surface. This selective recognition mechanism ensures that the surface migration agent and the responsive agent do not interfere with each other in the liquid coating, but precisely synergize in the later stage of film formation, thereby achieving the in-situ construction of the hydrophobic layer.

[0033] (3) The present invention adopts a formulation sequence of adding the responsive agent first and then the surface migration agent, so that the responsive agent is first uniformly distributed in the resin matrix by ultrasonic dispersion, and the surface migration agent is added later to maintain its migration activity in the system, thus avoiding premature contact between the two in the liquid state, which would affect the migration and capture efficiency during the film formation process. This process design ensures that the surface migration agent can migrate smoothly to the surface, and the responsive agent can be uniformly dispersed in the bulk and effectively captured, thereby achieving excellent hydrophobic effect. Detailed Implementation

[0034] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0035] Example 1

[0036] A highly durable waterborne polyurethane resin comprises the following components in parts by weight:

[0037] 42 parts of isophorone diisocyanate, 50 parts of polyester polyol (poly(1,4-butanediol adipate, Mn=2000, hydroxyl value 56 mgKOH / g), 5 parts of 1,4-butanediol, 4.5 parts of dimethylolpropionic acid, 1.0 part of ethylenediamine, 3.0 parts of surface migration agent, 2.0 parts of response agent, 3.5 parts of triethylamine (for neutralization), 0.2 parts of dibutyltin dilaurate, 10 parts of N-methylpyrrolidone, 0.5 parts of triethylamine (for pH adjustment), and 200 parts of deionized water.

[0038] The preparation method of the surface migration agent includes the following steps:

[0039] A1. Dissolve β-cyclodextrin (25.0 g) in anhydrous ethanol (200 mL), add 3-isocyanopropyltriethoxysilane (18.0 g) and dibutyltin dilaurate (0.1 g), stir and reflux at 70 °C for 6 hours, remove the solvent by rotary evaporation after the reaction is completed to obtain the intermediate;

[0040] A2. Dissolve hydroxyl-terminated polydimethylsiloxane (Mn=20000, 50.0 g) in xylene (100 mL), add the intermediate obtained in step A1, stir and reflux at 80 °C for 12 hours, cool the reaction solution and add 200 mL of anhydrous ethanol, stir and centrifuge, wash 3 times, collect the precipitate, and vacuum dry at 60 °C for 24 hours to obtain β-cyclodextrin modified polydimethylsiloxane (surface migration agent).

[0041] The method for preparing the responsive agent includes the following steps:

[0042] B1. Disperse 100.0 g of nano-silica (particle size 20 nm) in anhydrous ethanol (500 mL), sonicate for 30 minutes (power 300 W, frequency 40 kHz), add 25.0 g of 3-aminopropyltriethoxysilane, heat to 70 °C, stir for 12 hours, centrifuge after cooling the reaction solution, wash 3 times with ethanol, and dry at 60 °C to obtain amino-modified nano-silica.

[0043] B2. Disperse the amino-modified nano silica (80.0 g) obtained in step B1 in anhydrous ethanol (400 mL), add 1-adamantane carboxylic acid (15.0 g), EDC·HCl (10.0 g) and NHS (5.0 g), stir the reaction at 30 °C for 24 hours, centrifuge the reaction solution, wash it three times each with ethanol and acetone, and dry it under vacuum at 60 °C for 24 hours to obtain adamantane-modified nano silica (response agent).

[0044] A method for preparing a high-durability waterborne polyurethane resin includes the following steps:

[0045] S1. Prepolymerization reaction: Add 50.0 g of poly(1,4-butanediol adipate) to the reactor and dehydrate it for 2 hours at 120℃ and vacuum degree -0.095 MPa. Cool down to 60℃ and add isophorone diisocyanate (42.0 g), 1,4-butanediol (5.0 g), dimethylolpropionic acid (4.5 g) and N-methylpyrrolidone (10.0 g). Stir and heat to 80℃, add dibutyltin dilaurate (0.2 g), and keep the reaction at this temperature. Take a sample every 30 minutes to determine the NCO content. Stop the prepolymerization reaction when the NCO content drops to 6.8%.

[0046] S2, Neutralization reaction: Cool the prepolymer obtained in step S1 to 45°C, add triethylamine (3.5 g), and stir for 30 minutes;

[0047] S3. Emulsification and Post-chain Extension: The neutralized prepolymer was transferred to an emulsification vessel, and deionized water (200 g, 40°C) was slowly added under high-speed stirring (1200 rpm) over a period of 30 minutes. After the water was added, ethylenediamine (1.0 g, pre-dissolved in 10 g of water) was added, and stirring was continued for another 30 minutes. The mixture was then distilled under reduced pressure at 50°C and a vacuum of -0.08 MPa. After cooling, the mixture was filtered to obtain an aqueous polyurethane resin base emulsion with a solid content of 30%.

[0048] S4. Add response agent: Take the base emulsion obtained in step S3, add the response agent (2.0 parts) prepared in step B2, and ultrasonically disperse for 15 minutes (power 300 W, frequency 40 kHz).

[0049] S5. Add surface migration agent: Dissolve the surface migration agent (3.0 parts) prepared in step A2 in anhydrous ethanol (5.0 parts), and slowly add it dropwise to the mixture obtained in step S4 under low speed stirring (250 rpm) at a dropping rate of 1 mL / min.

[0050] S6. pH adjustment and maturation: Add triethylamine (0.5 parts) to adjust the pH to 7.5, let stand for 24 hours to mature, and filter with a 200-mesh sieve to obtain a high-durability waterborne polyurethane resin.

[0051] Example 2

[0052] A highly durable waterborne polyurethane resin comprises the following components in parts by weight:

[0053] 42 parts of isophorone diisocyanate, 50 parts of polyester polyol (poly(1,4-butanediol adipate, Mn=2000, hydroxyl value 56 mgKOH / g), 5 parts of 1,4-butanediol, 4.5 parts of dimethylolpropionic acid, 1.0 part of ethylenediamine, 2.0 parts of surface migration agent, 1.0 part of response agent, 3.5 parts of triethylamine (for neutralization), 0.2 parts of dibutyltin dilaurate, 10 parts of N-methylpyrrolidone, 0.4 parts of triethylamine (for pH adjustment), and 200 parts of deionized water.

[0054] The preparation method of the surface migration agent includes the following steps:

[0055] A1. Dissolve β-cyclodextrin (25.0 g) in anhydrous ethanol (200 mL), add 3-isocyanopropyltriethoxysilane (15.0 g) and dibutyltin dilaurate (0.1 g), stir and reflux at 65 °C for 5 hours, remove the solvent by rotary evaporation after the reaction is completed to obtain the intermediate;

[0056] A2. Dissolve hydroxyl-terminated polydimethylsiloxane (Mn=20000, 50.0 g) in xylene (100 mL), add the intermediate obtained in step A1, stir and reflux at 75 °C for 10 hours, cool the reaction solution and add 200 mL of anhydrous ethanol, stir and centrifuge, wash 3 times, collect the precipitate, and vacuum dry at 60 °C for 24 hours to obtain β-cyclodextrin modified polydimethylsiloxane (surface migration agent).

[0057] The method for preparing the responsive agent includes the following steps:

[0058] B1. Disperse 100.0 g of nano-silica (30 nm particle size) in anhydrous ethanol (500 mL), sonicate for 30 minutes (300 W power, 40 kHz frequency), add 25.0 g of 3-aminopropyltriethoxysilane, heat to 65 °C, stir for 10 hours, centrifuge after cooling the reaction solution, wash 3 times with ethanol, and dry at 60 °C to obtain amino-modified nano-silica.

[0059] B2. Disperse the amino-modified nano silica (80.0 g) obtained in step B1 in anhydrous ethanol (400 mL), add 1-adamantanecarboxylic acid (12.0 g), EDC·HCl (8.0 g) and NHS (4.0 g), stir the reaction at 25 °C for 22 hours, centrifuge the reaction solution, wash it three times each with ethanol and acetone, and dry it under vacuum at 60 °C for 24 hours to obtain adamantane-modified nano silica (response agent).

[0060] A method for preparing a high-durability waterborne polyurethane resin includes the following steps:

[0061] S1. Prepolymerization reaction: Add 50.0 g of poly(1,4-butanediol adipate) to the reactor and dehydrate it for 2 hours at 120℃ and vacuum degree -0.095 MPa. Cool down to 60℃ and add isophorone diisocyanate (42.0 g), 1,4-butanediol (5.0 g), dimethylolpropionic acid (4.5 g) and N-methylpyrrolidone (10.0 g). Stir and heat to 75℃ and add dibutyltin dilaurate (0.2 g). Keep the reaction at this temperature and take samples every 30 minutes to determine the NCO content. After about 3.5 hours of reaction, when the NCO content drops to 7.2%, the prepolymerization reaction is ended.

[0062] S2, Neutralization reaction: Cool the prepolymer obtained in step S1 to 45°C, add triethylamine (3.5 g), and stir for 30 minutes;

[0063] S3. Emulsification and Post-chain Extension: The neutralized prepolymer was transferred to an emulsification vessel, and deionized water (200 g, 40°C) was slowly added under high-speed stirring (1000 rpm) over a period of 30 minutes. After the water was added, ethylenediamine (1.0 g, pre-dissolved in 10 g of water) was added, and stirring was continued for another 30 minutes. The mixture was then distilled under reduced pressure at 50°C and a vacuum of -0.08 MPa. After cooling, the mixture was filtered to obtain an aqueous polyurethane resin base emulsion with a solid content of 30%.

[0064] S4. Add response agent: Take the base emulsion obtained in step S3, add the response agent (1.0 part) prepared in step B2, and ultrasonically disperse for 15 minutes (power 200 W, frequency 40 kHz).

[0065] S5. Add surface migration agent: Dissolve the surface migration agent (2.0 parts) prepared in step A2 in anhydrous ethanol (4.0 parts), and slowly add it dropwise to the mixture obtained in step S4 under low speed stirring (200 rpm) at a dropping rate of 1 mL / min;

[0066] S6. pH adjustment and maturation: Add triethylamine (0.4 parts) to adjust the pH to 7.3, let stand for 20 hours to mature, and filter with a 200-mesh sieve to obtain a high-durability waterborne polyurethane resin.

[0067] Example 3

[0068] A highly durable waterborne polyurethane resin comprises the following components in parts by weight:

[0069] 42 parts isophorone diisocyanate, 50 parts polyester polyol (poly(1,4-butanediol adipate, Mn=2000, hydroxyl value 56 mgKOH / g), 5 parts 1,4-butanediol, 4.5 parts dimethylolpropionic acid, 1.0 part ethylenediamine, 4.0 parts surface migration agent, 2.5 parts response agent, 3.5 parts triethylamine (for neutralization), 0.2 parts dibutyltin dilaurate, 10 parts N-methylpyrrolidone, 0.4 parts triethylamine (for pH adjustment), and 200 parts deionized water.

[0070] The preparation method of the surface migration agent includes the following steps:

[0071] A1. Dissolve β-cyclodextrin (25.0 g) in anhydrous ethanol (200 mL), add 3-isocyanopropyltriethoxysilane (20.0 g) and dibutyltin dilaurate (0.1 g), stir and reflux at 75 °C for 7 hours, remove the solvent by rotary evaporation after the reaction is completed to obtain the intermediate;

[0072] A2. Dissolve hydroxyl-terminated polydimethylsiloxane (Mn=20000, 50.0 g) in xylene (100 mL), add the intermediate obtained in step A1, stir and reflux at 85 °C for 14 hours, cool the reaction solution and add 200 mL of anhydrous ethanol, stir and centrifuge, wash 3 times, collect the precipitate, and vacuum dry at 60 °C for 24 hours to obtain β-cyclodextrin modified polydimethylsiloxane (surface migration agent).

[0073] The method for preparing the responsive agent includes the following steps:

[0074] B1. Disperse 100.0 g of nano-silica (particle size 20 nm) in anhydrous ethanol (500 mL), sonicate for 30 minutes (power 300 W, frequency 40 kHz), add 3-aminopropyltriethoxysilane (35.0 g), heat to 75 °C, stir and react for 14 hours, centrifuge after cooling the reaction solution, wash 3 times with ethanol, and dry at 60 °C to obtain amino-modified nano-silica.

[0075] B2. Disperse the amino-modified nano silica (80.0 g) obtained in step B1 in anhydrous ethanol (400 mL), add 1-adamantanecarboxylic acid (20.0 g), EDC·HCl (12.0 g) and NHS (6.0 g), stir the reaction at 35 °C for 26 hours, centrifuge the reaction solution, wash it three times each with ethanol and acetone, and dry it under vacuum at 60 °C for 24 hours to obtain adamantane-modified nano silica (response agent).

[0076] A method for preparing a high-durability waterborne polyurethane resin includes the following steps:

[0077] S1. Prepolymerization reaction: Add 50.0 g of poly(1,4-butanediol adipate) to the reactor and dehydrate it for 2 hours at 120℃ and vacuum degree -0.095 MPa. Cool down to 60℃ and add isophorone diisocyanate (42.0 g), 1,4-butanediol (5.0 g), dimethylolpropionic acid (4.5 g) and N-methylpyrrolidone (10.0 g). Stir and heat to 85℃ and add dibutyltin dilaurate (0.2 g). Keep the reaction at this temperature and take samples every 30 minutes to determine the NCO content. After about 2.5 hours of reaction, when the NCO content drops to 6.5%, the prepolymerization reaction is ended.

[0078] S2, Neutralization reaction: Cool the prepolymer obtained in step S1 to 45°C, add triethylamine (3.5 g), and stir for 30 minutes;

[0079] S3. Emulsification and Post-chain Extension: The neutralized prepolymer was transferred to an emulsification vessel, and deionized water (200 g, 45°C) was slowly added under high-speed stirring (1500 rpm) over a period of 30 minutes. After the water was added, ethylenediamine (1.0 g, pre-dissolved in 10 g of water) was added, and stirring was continued for another 30 minutes. The mixture was then distilled under reduced pressure at 50°C and a vacuum of -0.08 MPa. After cooling, the mixture was filtered to obtain an aqueous polyurethane resin base emulsion with a solid content of 30%.

[0080] S4. Add response agent: Take the base emulsion obtained in step S3, add the response agent (2.5 parts) prepared in step B2, and ultrasonically disperse for 20 minutes (power 400 W, frequency 40 kHz).

[0081] S5. Add surface migration agent: Dissolve the surface migration agent (4.0 parts) prepared in step A2 in anhydrous ethanol (5.0 parts), and slowly add it dropwise to the mixture obtained in step S4 under low speed stirring (300 rpm) at a dropping rate of 1 mL / min.

[0082] S6. pH adjustment and maturation: Add triethylamine (0.6 parts) to adjust the pH to 7.8, let stand for 28 hours to mature, and filter with a 200-mesh sieve to obtain a high-durability waterborne polyurethane resin.

[0083] Comparative Example 1

[0084] The difference from Example 1 is that no surface migration agent and response agent are added, while the remaining components, weight parts, and preparation steps are completely consistent with Example 1.

[0085] Specifically, 3.0 parts of surface migration agent and 2.0 parts of response agent are removed from the components. Steps S4 (adding response agent and ultrasonically dispersing) and S5 (adding surface migration agent) are omitted in the preparation steps. The waterborne polyurethane resin base emulsion obtained in S3 is directly subjected to step S6 (adding pH adjuster to adjust pH to 7.5, standing for 24 hours to mature, and filtering with a 200-mesh sieve) to obtain waterborne polyurethane resin.

[0086] Comparative Example 2

[0087] The difference from Example 1 is that only a surface migration agent is added, and no response agent is added. The remaining components, weight parts, and preparation steps are completely consistent with Example 1.

[0088] Specifically, 2.0 parts of the responsive agent were removed from the composition, and 3.0 parts of the surface migration agent were retained. In the preparation steps, step S4 (adding the responsive agent and ultrasonically dispersing) was omitted, and the waterborne polyurethane resin base emulsion obtained in step S3 was directly subjected to step S5 (dissolving the surface migration agent in anhydrous ethanol and adding it dropwise under low-speed stirring). The subsequent step S6 remained unchanged, and the waterborne polyurethane resin was obtained.

[0089] Comparative Example 3

[0090] The difference from Example 1 is that only a response agent is added, and no surface migration agent is added. The remaining components, weight parts, and preparation steps are completely consistent with Example 1.

[0091] Specifically, 3.0 parts of surface migration agent were removed from the components, and 2.0 parts of response agent were retained; in the preparation steps, step S5 (adding surface migration agent) was omitted, and the mixture obtained in step S4 was directly subjected to step S6 (adding pH adjuster to adjust pH to 7.5, standing for 24 hours to mature, and filtering with a 200-mesh sieve) to obtain waterborne polyurethane resin.

[0092] Comparative Example 4

[0093] The difference from Example 1 is that the responsive agent was not modified with adamantane, and amino-modified nano-silica was used directly as the responsive agent. The remaining components, weight parts, and preparation steps were completely consistent with Example 1.

[0094] The preparation method of the responsive agent was modified as follows: only step B1 was performed, and step B2 was omitted. Specifically, 100.0 g of nano-silica (particle size 20 nm) was dispersed in anhydrous ethanol (500 mL), sonicated for 30 minutes (power 300 W, frequency 40 kHz), 25.0 g of 3-aminopropyltriethoxysilane was added, the temperature was raised to 70 °C, and the reaction was stirred for 12 hours. After the reaction solution was cooled, it was centrifuged, washed three times with ethanol, and dried at 60 °C to obtain amino-modified nano-silica, which was directly used as the responsive agent.

[0095] Comparative Example 5

[0096] The difference from Example 1 is that the order of adding the responsive agent and the surface migration agent is reversed, that is, the surface migration agent is added first and then the responsive agent is added. The remaining components, weight parts, and parameters of each step are completely consistent with Example 1.

[0097] The preparation steps have been modified as follows:

[0098] Steps S1, S2, and S3 are completely consistent with those in Example 1, resulting in an aqueous polyurethane resin base emulsion.

[0099] S4. Dissolve the surface migration agent (3.0 parts) in anhydrous ethanol (5.0 parts) and slowly add it dropwise to the base emulsion obtained in step S3 under low speed stirring (250 rpm) at a drop rate of 1 mL / min.

[0100] S5. Add the response agent (2.0 parts) to the mixture obtained in step S4 and ultrasonically disperse for 15 minutes (power 300 W, frequency 40 kHz).

[0101] S6. Add triethylamine (0.5 parts), adjust the pH to 7.5, let stand for 24 hours to mature, filter with a 200-mesh sieve to obtain waterborne polyurethane resin.

[0102] Performance testing

[0103] 1. Contact Angle Test

[0104] Samples from Examples 1-3 and Comparative Examples 1-5 were uniformly coated onto the surface of aluminum plates cleaned with acetone using a wire bar coater. The wet film thickness was controlled at 150 μm, and the films were dried at 25 ± 1 °C and 50 ± 5% RH. Contact angle measurements were taken at 10 min, 30 min, 60 min, 120 min, and 24 h after coating. For each measurement, 5 μL of deionized water was dropped onto the coating surface using a microsyringe, and the contact angle was read after 10 seconds to allow the droplet to stabilize. Measurements were taken at five different locations on the coating surface at each time point, and the average value was recorded. The contact angle at 24 h was used as the final water contact angle to evaluate the surface hydrophobicity.

[0105] 2. Water absorption rate test

[0106] Samples from Examples 1-3 and Comparative Examples 1-5 were coated onto polytetrafluoroethylene (PTFE) plates and dried to obtain individual coating films with a thickness of approximately 0.5 mm. The coating films were cut into 20 mm × 20 mm square samples, with three parallel samples prepared for each sample. The samples were dried in a 60°C oven for 2 hours, then removed and cooled to room temperature in a desiccator. The initial mass W0 (accurate to 0.1 mg) was weighed using an analytical balance. The samples were completely immersed in deionized water at 25 ± 1°C for 24 hours, then removed and quickly blotted dry with filter paper. The weight W1 (accurate to 0.1 mg) was immediately measured. The water absorption rate (%) was calculated using the formula: Water Absorption Rate (%) = [(W1 - W0) / W0] × 100%. The arithmetic mean of the three parallel samples was taken as the water absorption rate of that sample.

[0107] 3. Water immersion test

[0108] Samples from Examples 1-3 and Comparative Examples 1-5 were coated onto the surface of an aluminum plate using the method described in the contact angle test and allowed to dry and cure. The edges and back of the coated samples were sealed with paraffin wax. The sealed samples were then completely immersed in deionized water at 25±1℃, ensuring that the samples were completely submerged and not in contact with each other. The samples were removed at regular intervals (observed every 2 hours for the first 24 hours, and every 12 hours after 24 hours), and the surface moisture was blotted dry with filter paper. The surface condition of the coating was visually observed under natural light, and the time when whitening, blistering, loss of gloss, peeling, or flaking occurred was recorded. Three parallel samples were tested for each sample, and the shortest time when failure occurred was taken as the water immersion time of that sample.

[0109] The test results of each embodiment and comparative example are shown in Table 1.

[0110] Table 1

[0111]

[0112] As shown in Table 1, the contact angles of the coatings prepared in Examples 1-3 continuously increased during the film formation process, with the final contact angles all exceeding 151°, reaching as high as 156.2° in Example 1, while that of Comparative Example 1 was only 82.3°. Meanwhile, the 24-hour water absorption rate of Examples 1-3 was less than 4.5%, and the water immersion time exceeded 84 hours, with Example 1 exceeding 120 hours, far superior to Comparative Example 1's 16.8% and 2 hours. Comparative analysis showed that adding only a surface migration agent (Comparative Example 2) or only a responsive agent (Comparative Example 3) improved performance, but was far inferior to the examples; the absence of adamantane modification of the responsive agent (Comparative Example 4) or a change in the feeding order (Comparative Example 5) also led to a significant decrease in performance, confirming the crucial role of the host-guest recognition mechanism and specific process sequence in constructing a stable hydrophobic layer.

[0113] In summary, this invention utilizes β-cyclodextrin-modified polydimethylsiloxane as a surface migration agent and adamantane-modified nano-silica as a responsive agent, leveraging host-guest recognition in the later stages of film formation to achieve in-situ controllable construction of a hydrophobic layer. This significantly improves the hydrophobicity, water absorption resistance, and long-term water resistance of waterborne polyurethane coatings. Simultaneously, the optimized "add responsive agent first, then surface migration agent" process ensures efficient synergy among the components. This invention effectively solves the bottleneck of poor water resistance in traditional waterborne polyurethanes and can be used to prepare high-performance coatings, showing broad application prospects in the decoration and protection of various substrates.

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high-durability waterborne polyurethane resin, characterized in that, It includes the following components: diisocyanate, polyol, small molecule chain extender, hydrophilic chain extender, post-chain extender, surface migration agent, responsive agent, neutralizing agent, catalyst, cosolvent, pH adjuster and deionized water; The surface migration agent is a polydimethylsiloxane modified with β-cyclodextrin; The responsive agent is nano-silica modified with adamantane.

2. The high-durability waterborne polyurethane resin according to claim 1, characterized in that, The preparation method of the surface migration agent includes the following steps: A1. β-Cyclodextrin and 3-isocyanate-propyltriethoxysilane are reacted at a mass ratio of 1:0.6-0.8 at 65-75°C for 5-7 hours to obtain an intermediate; A2. Hydroxyl-terminated polydimethylsiloxane and an intermediate are reacted at a mass ratio of 1:0.4-0.6 at 75-85°C for 10-14 hours to obtain β-cyclodextrin-modified polydimethylsiloxane.

3. The high-durability waterborne polyurethane resin according to claim 1, characterized in that, The method for preparing the responsive agent includes the following steps: B1. Nano-silica and aminosilane coupling agent are reacted at 65-75℃ for 10-14 hours at a mass ratio of 1:0.25-0.35 to obtain amino-modified nano-silica. B2. Amino-modified nano-silica and adamantane carboxylic acid are reacted at a mass ratio of 1:0.15-0.25 at 25-35℃ for 22-26 hours to obtain adamantane-modified nano-silica.

4. A high-durability waterborne polyurethane resin according to claim 1 or 3, characterized in that, The particle size of the nano-silica is 20-30 nm.

5. The high-durability waterborne polyurethane resin according to claim 1, characterized in that, It comprises the following components in parts by weight: 35-50 parts diisocyanate, 40-60 parts polyol, 3-8 parts small molecule chain extender, 3-6 parts hydrophilic chain extender, 0.5-1.5 parts post-chain extender, 2-4 parts surface migration agent, 1-2.5 parts responsive agent, 2-5 parts neutralizer, 0.1-0.3 parts catalyst, 5-15 parts cosolvent, 0.3-0.6 parts pH adjuster, and 150-300 parts deionized water.

6. The high-durability waterborne polyurethane resin according to claim 5, characterized in that, The diisocyanate is isophorone diisocyanate; the polyol is a polyester polyol selected from one or more of poly(1,4-butanediol adipate), poly(1,6-hexanediol adipate), and polycaprolactone diol; the small molecule chain extender is 1,4-butanediol; the hydrophilic chain extender is dimethylolpropionic acid; the post-chain extender is ethylenediamine; the neutralizing agent is triethylamine; the catalyst is dibutyltin dilaurate; the cosolvent is N-methylpyrrolidone; and the pH adjuster is triethylamine.

7. A method for preparing a high-durability waterborne polyurethane resin as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Diisocyanate, polyol, small molecule chain extender, hydrophilic chain extender, catalyst and cosolvent are mixed and a prepolymerization reaction is carried out to obtain a prepolymer. S2. Add a neutralizing agent to the prepolymer obtained in step S1 to carry out a neutralization reaction; S3. The neutralized prepolymer is added to deionized water for emulsification, and then a chain extender is added to carry out a chain extension reaction to obtain an aqueous polyurethane resin base emulsion. S4. Add the response agent to the base emulsion obtained in step S3 and disperse it evenly; S5. After dissolving the surface migration agent in the solvent, add it to the mixture obtained in step S4; S6. Add a pH adjuster to adjust the pH, let it stand and mature to obtain a high-durability waterborne polyurethane resin.

8. The method for preparing a high-durability waterborne polyurethane resin according to claim 7, characterized in that, The response agent mentioned in step S4 is added by ultrasonic dispersion, with an ultrasonic power of 200-400 W and a time of 10-20 min; The surface migration agent mentioned in step S5 is added dropwise with ethanol as solvent at a stirring speed of 200-300 rpm; In step S6, the pH is adjusted to 7.3-7.8, and the standing maturation time is 20-28 hours.

9. The method for preparing a high-durability waterborne polyurethane resin according to claim 7, characterized in that, The prepolymerization reaction temperature in step S1 is 75-85℃, and the reaction continues until the NCO content drops to 6.5-7.5%. The emulsification temperature in step S3 is 40-45℃, and the stirring speed is 1000-1500 rpm.

10. A coating, characterized in that, The coating comprises a high-durability waterborne polyurethane resin as described in any one of claims 1-6.

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