Preparation method of high-strength anticorrosive waterborne polyurethane material

Abstract

The invention belongs to the technical field of polyurethane material processing, and particularly relates to a preparation method of a high-strength anticorrosive waterborne polyurethane material. By using a unique polyol and isocyanate mixed system and using the compound chain extender and the cross-linking agent, the material forms a high-strength molecular structure, and compared with common waterborne polyurethane, the tensile strength and adhesive force of the material are remarkably improved, the material can bear larger external force, and the service life of the material is prolonged. The method is suitable for protection in a high-stress environment. Due to the addition of the modified biomass fibers and the special preservative and the compact cross-linked structure of the material, the corrosion resistance of the material is effectively improved. Through a salt spray test, the salt spray resistance time of the material reaches 1900 h or above, and the service life of a protected object can be remarkably prolonged. And the whole preparation process takes water as a dispersion medium, does not use a large amount of organic solvents, meets the environmental protection requirement, and has good social benefits and economic benefits.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyurethane material processing, and particularly relates to a preparation method of a high-strength anti-corrosion waterborne polyurethane material. Background Art

[0002] Waterborne polyurethane (WPU) is a polyurethane dispersion system with water as the dispersion medium. Different from traditional solvent-based polyurethanes, there are no organic solvents in the WPU system, which is non-toxic and does not pollute the environment. Therefore, during use, the emission of VOCs is effectively reduced, meeting the requirements of green environmental protection. At the same time, in addition to inheriting some excellent mechanical properties of solvent-based polyurethanes, WPU also has the advantages of low price, easy transportation and storage, good film-forming property at low temperature, relatively convenient use, good low-temperature resistance, wear resistance and adhesion. Thanks to its excellent properties, WPU has been widely used in all aspects of today's society and can be found in many scenarios. For various application scenarios, WPU can be designed with different molecular structures and properties to meet the actual use requirements. Among them, relatively common application fields include coatings, synthetic leather, adhesives, fiber treatment, etc.

[0003] Although WPU has received extensive attention in the research and application fields of coatings in recent years due to its controllable and adjustable molecular structure, green environmental protection and pollution-free, excellent mechanical properties, wear resistance, bonding properties and toughness, etc., compared with solvent-based polyurethanes, due to the presence of hydrophilic groups in the WPU molecular chain structure, the WPU material currently generally has disadvantages such as poor water resistance, poor chemical resistance, low solid content, slow film-forming speed, etc., which greatly limits the further development of WPU coatings. Therefore, it is necessary to modify WPU to further improve its comprehensive performance, broaden the application scope, enhance the strength and corrosion resistance of waterborne polyurethane, and extend the service life. This has become an important direction in the related research of WPU.

[0004] Based on this, we propose a preparation method of a high-strength anti-corrosion waterborne polyurethane material, hoping to solve the deficiencies in the existing technology. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of a high-strength anti-corrosion waterborne polyurethane material for the existing problems.

[0006] The present invention is achieved through the following technical solutions: A preparation method of a high-strength anti-corrosion waterborne polyurethane material, comprising the following steps: S1. Place the polyol after vacuum dehydration, modified biomass fiber, and nano-titanium dioxide together in a blender. Stir at 2000 - 3000 r / min for 30 - 40 min to form a homogeneous suspension, then add it to a reaction kettle. Heat up to 60 - 70 °C, add isocyanate, and stir and react for 2 - 3 h to obtain a prepolymer for standby; S2. Dissolve the chain extender in water, then add it to the prepolymer. Cool down to 40 - 50 °C and stir and react for 2 - 3 h; S3. Add a crosslinking agent to the system after chain extension in step S2. Heat up to 60 - 70 °C and continue to stir and react for 1 - 2 h to obtain a pre-emulsion; S4. Add a preservative to the pre-emulsion. Stir at 6000 - 8000 r / min for 40 - 60 min, then add deionized water. Continue to stir for 1 - 2 h and then perform vacuum degassing treatment. Adjust the pH to 7 - 8.

[0007] Furthermore, the polyol described in step S1 is a mixed system of polycarbonate diol and polyether polyol. The mass ratio of polycarbonate diol (number average molecular weight of 2000) to polyether polyol (number average molecular weight of 1800) is 1:0.5 - 1; The temperature of vacuum dehydration is 110 - 120 °C; The addition amount of nano-titanium dioxide is 0.6 - 1% of the mass of the polyol; The isocyanate is hexamethylene diisocyanate; The mass ratio of isocyanate to polyol is 1:1 - 2.

[0008] Furthermore, the addition amount of the modified biomass fiber described in step S1 is 3 - 4% of the mass of the polyol; The preparation of the modified biomass fiber includes the following steps: (1) Crush bamboo fiber to 100 - 200 mesh, then immerse it in a phosphate buffer solution containing 0.5 - 0.6% cellulase. Then place it in a shaker at 180 - 200 r / min and 38 - 40 °C and shake for 2 - 3 h, then filter. Then immerse it in a treatment agent, stir and mix evenly, and under the conditions of 365 nm and 50 W, perform ultraviolet light treatment for 20 - 30 min. Then add 3,4-dihydroxybenzaldehyde, heat up to 60 - 70 °C and react for 30 - 50 min, then filter, wash with deionized water 3 - 5 times, and place it in a vacuum drying oven and dry at 60 - 70 °C for 8 - 12 h to obtain activated fiber; (2) Add the above activated fiber to deionized water. The mass - volume ratio of activated fiber to deionized water is 1 g:9 - 10 mL. Under ultrasonic conditions, stir at 800 - 1000 r / min for 20 - 30 min to form a fiber suspension; (3) Add the fiber suspension into the reaction kettle, and successively add glycidyl methacrylate which is 0.2 - 0.3 times the mass of the activated fiber, maleic anhydride which is 0.1 - 0.16 times the mass of the activated fiber, and azobisisobutyronitrile which is 0.003 - 0.005 times the mass of the activated fiber. Stir at 600 - 800 r / min for 10 - 20 min, then heat up to 70 - 80 °C and continue stirring and reacting for 3 - 4 h; (4) After the reaction is completed, filter and wash with absolute ethanol 3 - 5 times, then place it in a vacuum drying oven and dry at 60 - 70 °C for 10 - 16 h.

[0009] Furthermore, in the treating agent described in step (1), the components and their corresponding weight percentages are: 1 - butyl - 3 - methylimidazolium acetate ionic liquid 70 - 80%, nano - titanium dioxide 0.6 - 0.9%, and the balance is deionized water.

[0010] Furthermore, the chain extender described in step S2 is a compounding agent of ethylenediamine and diethanolamine, and the molar ratio of ethylenediamine to diethanolamine is 1:1 - 2.

[0011] Furthermore, the cross - linker described in step S3 is trimethylolpropane, and the mass fraction of the cross - linker in the system is 3 - 5%.

[0012] Furthermore, the dosage of the preservative described in step S4 is 2 - 3% of the total system mass; The dosage of deionized water is 20 - 30% of the total system mass.

[0013] Furthermore, the preparation of the preservative includes the following steps: 1) Add it to 2 mg / mL dopamine hydrochloride, shake at 180 - 200 r / min and 40 - 46 °C for 5 - 6 h, then add zinc carbonate solution, react in a water bath at 60 - 70 °C for 2 - 3 h, filter, wash with deionized water 2 - 3 times, and then place it in a vacuum drying oven and dry at 60 - 70 °C for 6 - 8 h to obtain pre - modified nano - zinc oxide; 2) After subjecting the pre - modified nano - zinc oxide to corona treatment, immerse it in phytic acid solution, perform ultrasonic treatment for 30 - 40 min, then heat up to 60 - 70 °C, add epoxidized soybean oil, stir at 100 - 200 r / min for 2 - 3 h, filter, wash with deionized water 2 - 3 times, and then place it in a vacuum drying oven and dry at 60 - 70 °C for 6 - 8 h.

[0014] Furthermore, the voltage of the corona treatment described in step 2) is 10 - 15 kV, and the treatment time is 30 - 60 s.

[0015] The present invention has the following advantages compared with the prior art: 1. Through a unique polyol and isocyanate mixed system, as well as the use of compound chain extenders and crosslinking agents, the present invention enables the material to form a high-strength molecular structure. Compared with ordinary waterborne polyurethanes, the tensile strength and adhesion of the material are significantly improved, enabling it to withstand greater external forces and be suitable for protection in high-stress environments. The addition of modified biomass fibers and special preservatives, as well as the dense crosslinked structure of the material itself, effectively improves the anti-corrosion performance of the material. Through salt spray test, the salt spray resistance time of the material of the present invention reaches more than 1900 hours, which can significantly extend the service life of the protected object. And the entire preparation process uses water as the dispersion medium without using a large amount of organic solvents, meeting environmental protection requirements and having good social and economic benefits.

[0016] 2. The present invention combines bioenzymolysis, photocatalytic oxidation and dynamic covalent modification to activate bamboo fibers, realizing the efficient and directional activation of hydroxyl groups in bamboo fibers. Using a compound monomer of glycidyl methacrylate (GMA) and maleic anhydride (MAH), bifunctional groups are grafted onto the fiber surface through free radical polymerization. The epoxy group in glycidyl methacrylate can react with -NCO of the polyurethane prepolymer to form chemical crosslinking points. The anhydride group of maleic anhydride reacts with the hydroxyl groups of biomass fibers, enhancing the grafting stability and at the same time providing polar sites to interpenetrate the network with the polyurethane matrix. At the same time, the abundant hydroxyl groups in biomass fibers can react with the isocyanate groups in the polyurethane prepolymer to form chemical crosslinking points, enhancing the three-dimensional network structure and contributing to improving the mechanical strength and anti-corrosion performance of waterborne polyurethane materials. In the crosslinking stage, it interacts synergistically with the crosslinking agent to promote the formation of a ternary network of fiber-polyurethane-nanoparticles, further improving the comprehensive performance of waterborne polyurethane.

[0017] 3. The present invention disperses nano-zinc oxide in dopamine solution to form a polydopamine coating layer on the surface of nano-oxidation, effectively enhancing the dispersion of nano-zinc oxide and preventing its agglomeration. Then zinc carbonate treatment is carried out, which can play a role in inhibiting substrate corrosion. At this time, corona treatment is carried out. Through a high-voltage electric field, air is ionized to generate plasma (such as O - , OH - free radicals), introducing oxygen-containing functional groups (such as -OH, -COOH) on the ZnO surface, increasing the surface hydroxyl content, enhancing the reactivity with -NCO of the polyurethane prepolymer, reducing the surface energy, reducing nanoparticle agglomeration, and improving the dispersion stability in the aqueous system. In addition, by controlling the technical parameters of corona treatment, the nano-scale roughness is increased, enhancing the mechanical interlock with the substrate and promoting the loading of phytic acid. When it is used in waterborne polyurethane, it can release PO4 when the coating is damaged. 3-, passivate the surface of the substrate to further improve its corrosion resistance. After being treated with epoxidized soybean oil, the epoxy groups of epoxidized soybean oil undergo ring-opening grafting with the amino groups of the polydopamine layer to form a flexible interface layer. The long chains of epoxidized soybean oil can further enhance the compatibility between the preservative and polyurethane and improve the mechanical properties. Detailed implementation mode

[0018] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0019] Example 1

[0020] A preparation method of a high-strength anti-corrosion waterborne polyurethane material includes the following steps: S1. Put the vacuum-dehydrated polyol, modified biomass fiber, and nano-titanium dioxide into a blender together. After stirring at 2000 r / min for 30 min to form a homogeneous suspension, add it to a reaction kettle, heat up to 60 °C, add hexamethylene diisocyanate, and stir and react for 2 h to obtain a prepolymer for standby; The polyol is a mixed system of polycarbonate diol and polyether polyol, and the mass ratio of polycarbonate diol to polyether polyol is 1:0.5; The temperature of vacuum dehydration is 110 °C; The addition amount of nano-titanium dioxide is 0.6% of the mass of the polyol; The mass ratio of isocyanate to polyol is 1:1; The addition amount of the modified biomass fiber is 3% of the mass of the polyol; The preparation of the modified biomass fiber includes the following steps: (1) Crush bamboo fiber to 100 mesh, immerse it in a phosphate buffer solution containing 0.5% cellulase, then place it in a shaker at 180 r / min and 38 °C for shaking treatment for 2 h, then filter, immerse it in a treatment agent, stir and mix evenly, under the conditions of 365 nm and 50 W, perform ultraviolet light treatment for 20 min, add 3,4-dihydroxybenzaldehyde, heat up to 60 °C and react for 30 min, then filter, wash 3 times with deionized water, and place it in a vacuum drying oven, dry at 60 °C for 8 h to obtain activated fiber; the components and corresponding weight percentages in the treatment agent are 70% of 1-butyl-3-methylimidazolium acetate ionic liquid, 0.6% of nano-titanium dioxide, and the balance is deionized water; (2) Add the above-activated fibers to deionized water. The mass-volume ratio of the activated fibers to deionized water is 1 g:9 mL. Under ultrasonic conditions, stir at 800 r / min for 20 min to form a fiber suspension; (3) Add the fiber suspension to a reaction kettle, and sequentially add glycidyl methacrylate 0.2 times the mass of the activated fibers, maleic anhydride 0.1 times, and azobisisobutyronitrile 0.003 times. After stirring at 600 r / min for 10 min, raise the temperature to 70 °C and continue stirring and reacting for 3 h; (4) After the reaction is completed, filter and wash 3 times with absolute ethanol, then place it in a vacuum drying oven and dry at 60 °C for 10 h; S2. Dissolve ethylenediamine and diethanolamine in water according to a molar ratio of 1:1, then add it to the prepolymer, cool down to 40 °C, and stir and react for 2 h; S3. Add trimethylolpropane to the system after chain extension in step S2. After raising the temperature to 60 °C, continue stirring and reacting for 1 h to obtain a pre-emulsion; The mass fraction of the cross-linking agent in the system is 3%; S4. Add a preservative to the pre-emulsion, stir at 6000 r / min for 40 min, then add deionized water, continue stirring for 1 h, and then perform vacuum degassing treatment, and adjust the pH to 7; The dosage of the preservative is 2% of the total system mass; The dosage of deionized water is 20% of the total system mass; The preparation of the preservative includes the following steps: 1) Add it to 2 mg / mL of dopamine hydrochloride, shake at 180 r / min and 40 °C for 5 h, then add a zinc carbonate solution, react in a water bath at 60 °C for 2 h, filter, wash 2 times with deionized water, and then place it in a vacuum drying oven and dry at 60 °C for 6 h to obtain pre-modified nano-zinc oxide; 2) Subject the pre-modified nano-zinc oxide to corona treatment, then immerse it in a phytic acid solution, perform ultrasonic treatment for 30 min, then raise the temperature to 60 °C, add epoxidized soybean oil, stir at 100 r / min for 2 h, filter, wash 2 times with deionized water, and then place it in a vacuum drying oven and dry at 60 °C for 6 h; The voltage of the corona treatment is 10 kV and the treatment time is 30 s.

[0021] Example 2

[0022] A preparation method of a high-strength anti-corrosion waterborne polyurethane material, including the following steps: S1. Place the polyol after vacuum dehydration, the modified biomass fiber, and nano-titanium dioxide together in a blender. Stir at 2500 r / min for 35 min to form a homogeneous suspension, then add it to a reaction kettle. Heat up to 65 °C, add hexamethylene diisocyanate, and stir and react for 2.5 h to obtain a prepolymer for standby; The polyol is a mixed system of polycarbonate diol and polyether polyol, and the mass ratio of polycarbonate diol to polyether polyol is 1:0.75; The temperature of vacuum dehydration is 115 °C; The addition amount of nano-titanium dioxide is 0.8% of the mass of the polyol; The mass ratio of isocyanate to polyol is 1:1.5; The addition amount of the modified biomass fiber is 3.5% of the mass of the polyol; The preparation of the modified biomass fiber includes the following steps: (1) Crush bamboo fiber to 150 mesh, then immerse it in a phosphate buffer solution containing 0.55% cellulase, and then place it in a shaker at 190 r / min and 39 °C for shaking treatment for 2.5 h, then filter. Then immerse it in a treatment agent, stir and mix evenly, and under the conditions of 365 nm and 50 W, perform ultraviolet light treatment for 25 min. Then add 3,4-dihydroxybenzaldehyde, heat up to 65 °C and react for 40 min, then filter, wash 4 times with deionized water, and place it in a vacuum drying oven to dry at 65 °C for 10 h to obtain activated fiber; the components and corresponding weight percentages in the treatment agent are 75% of 1-butyl-3-methylimidazolium acetate ionic liquid, 0.7% of nano-titanium dioxide, and the balance is deionized water; (2) Add the above activated fiber to deionized water, and the mass-volume ratio of activated fiber to deionized water is 1 g:9.5 mL. Under ultrasonic conditions, stir at 900 r / min for 25 min to form a fiber suspension; (3) Add the fiber suspension to a reaction kettle, and successively add glycidyl methacrylate 0.25 times the mass of the activated fiber, maleic anhydride 0.13 times, and azobisisobutyronitrile 0.004 times. Stir at 700 r / min for 15 min, then heat up to 75 °C, and continue to stir and react for 3.5 h; (4) After the reaction is completed, filter and wash 4 times with absolute ethanol, and then place it in a vacuum drying oven to dry at 65 °C for 13 h; S2. Dissolve ethylenediamine and diethanolamine in water according to a molar ratio of 1:1.5, then add it to the prepolymer, cool down to 45 °C, and stir and react for 2.5 h; S3. Add trimethylolpropane to the system after chain extension in step S2, heat up to 65 °C, and continue to stir and react for 1.5 h to obtain a pre-emulsion; The mass fraction of the crosslinking agent in the system is 4%; S4. Add a preservative to the pre-emulsion, stir at 7000 r / min for 50 min, then add deionized water, continue to stir for 1.5 h, and then perform vacuum degassing, and adjust the pH to 7.5; The dosage of the preservative is 2.5% of the total system mass; The dosage of deionized water is 25% of the total system mass; The preparation of the preservative described above includes the following steps: 1) Add it to 2 mg / mL of dopamine hydrochloride, shake at 190 r / min and 43 °C for 5.5 h, then add a zinc carbonate solution, react at 65 °C in a water bath for 2.5 h, filter, wash twice with deionized water, and then place it in a vacuum drying oven, dry at 65 °C for 7 h to obtain pre-modified nano-zinc oxide; 2) Perform corona treatment on the pre-modified nano-zinc oxide, immerse it in phytic acid solution, ultrasonically treat for 35 min, then heat up to 65 °C, add epoxidized soybean oil, stir at 150 r / min for 2.5 h, filter, wash twice with deionized water, and then place it in a vacuum drying oven, dry at 65 °C for 7 h; The voltage of the corona treatment is 12 kV, and the treatment time is 45 s.

[0023] Example 3

[0024] A preparation method of a high-strength anti-corrosion waterborne polyurethane material includes the following steps: S1. Place the vacuum-dehydrated polyol, modified biomass fiber, and nano-titanium dioxide together in a blender, stir at 3000 r / min for 30 - 40 min to form a homogeneous suspension, add it to a reaction kettle, heat up to 70 °C, add hexamethylene diisocyanate, and stir and react for 3 h to obtain a prepolymer for standby; The polyol is a mixed system of polycarbonate diol and polyether polyol, and the mass ratio of polycarbonate diol to polyether polyol is 1:1; The temperature of vacuum dehydration is 120 °C; The addition amount of nano-titanium dioxide is 1% of the polyol mass; The mass ratio of isocyanate to polyol is 1:2; The addition amount of the modified biomass fiber is 4% of the polyol mass; The preparation of the modified biomass fiber described above includes the following steps: (1) Pulverize bamboo fiber to 200 mesh, immerse it in a phosphate buffer solution containing 0.6% cellulase, then place it in a shaker at 200 r / min and 40 °C for 3 h, filter, then immerse it in the treating agent, stir and mix evenly, under the conditions of 365 nm and 50 W, perform ultraviolet light treatment for 30 min, add 3,4-dihydroxybenzaldehyde, raise the temperature to 70 °C and react for 50 min, filter, wash with deionized water 3 - 5 times, then place it in a vacuum drying oven and dry at 70 °C for 12 h to obtain activated fiber; the components and corresponding weight percentages in the treating agent are 80% 1-butyl-3-methylimidazolium acetate ionic liquid, 0.9% nano-titanium dioxide, and the balance is deionized water; (2) Add the above activated fiber to deionized water, and the mass-volume ratio of the activated fiber to deionized water is 1 g:10 mL. Under ultrasonic conditions, stir at 1000 r / min for 30 min to form a fiber suspension; (3) Add the fiber suspension to a reaction kettle, and successively add glycidyl methacrylate 0.3 times the mass of the activated fiber, maleic anhydride 0.16 times, and azobisisobutyronitrile 0.005 times. Stir at 800 r / min for 20 min, then raise the temperature to 80 °C and continue stirring and reacting for 4 h; (4) After the reaction is completed, filter, wash with anhydrous ethanol 5 times, then place it in a vacuum drying oven and dry at 70 °C for 16 h; S2. Dissolve ethylenediamine and diethanolamine in water according to a molar ratio of 1:2, then add it to the prepolymer, cool down to 50 °C, and stir and react for 3 h; S3. Add trimethylolpropane to the system after chain extension in step S2, raise the temperature to 70 °C, and continue stirring and reacting for 2 h to obtain a pre-emulsion; The mass fraction of the cross-linking agent in the system is 5%; S4. Add a preservative to the pre-emulsion, stir at 8000 r / min for 60 min, then add deionized water, continue stirring for 2 h, then perform vacuum defoaming treatment, and adjust the pH to 8; The dosage of the preservative is 3% of the total system mass; The dosage of deionized water is 30% of the total system mass; The preparation of the preservative described above includes the following steps: 1) Add it to 2 mg / mL dopamine hydrochloride, shake at 200 r / min and 46 °C for 6 h, then add zinc carbonate solution, react in a water bath at 70 °C for 3 h, filter, wash with deionized water 3 times, then place it in a vacuum drying oven and dry at 70 °C for 8 h to obtain pre-modified nano-zinc oxide; 2) After subjecting the pre-modified nano-zinc oxide to corona treatment, immerse it in the phytic acid solution, perform ultrasonic treatment for 40 min, then raise the temperature to 70 °C, add epoxy soybean oil, stir at 200 r / min for 3 h, filter, wash with deionized water 3 times, and then place it in a vacuum drying oven and dry at 70 °C for 8 h; The voltage of the corona treatment is 15 kV, and the treatment time is 60 s.

[0025] Comparative Example 1 Compared with Example 2, in this Comparative Example 1, the modified biomass fiber in step S1 was replaced with untreated bamboo fiber, and the rest of the technical solutions were the same as those of Example 2.

[0026] Comparative Example 2 Compared with Example 2, in this Comparative Example 2, the modified biomass fiber in step S1 was omitted, and the rest of the technical solutions were the same as those of Example 2.

[0027] Comparative Example 3 Compared with Example 2, in this Comparative Example 3, the preservative described in step S4 was replaced with untreated nano-zinc oxide, and the rest of the technical solutions were the same as those of Example 2.

[0028] Performance Test 1. Coating Mechanical Property Test 1.1 Tensile Strength Test Referring to the method of GB / T 528-2009, make dumbbell-shaped specimens from the coating film samples of each group of waterborne polyurethane materials, and use a universal testing machine for testing. The tensile rate is 500 mm / min, and the whole test is carried out at room temperature. After testing three sets of data for each sample, perform processing. The calculation formula for tensile strength is as follows:

[0029] 1.2 Adhesion Test Referring to GB / T 5210-2006, use a coating adhesion detector with the model of LRTC-10S to test the adhesion of the coating film. Coating each group of waterborne polyurethane emulsions on the surface of the substrate, after completely curing to form a coating film, use a specific composite glue to firmly stick a circular forging die with a diameter of 5 cm to the above coating film, and let it stand for 12 h. Use the adhesion tester to apply a tensile force to the coating film and the forging die until they are separated. The ratio of the maximum tensile force Fmax to the area S of the circular forging die is the measured adhesion, and the calculation formula is as follows:

[0030] The specific test comparison data are shown in Table 1 below.

[0031] Table 1 Adhesion force (MPa) Tensile strength (MPa) Example 1 5.1 32.52 Example 2 5.6 33.56 Example 3 5.7 30.23 Comparative Example 1 4.5 27.25 Comparative Example 2 3.8 22.38 Comparative Example 3 5.1 39.25 As can be seen from Table 1 above, compared with Comparative Examples 1 to 3, the adhesion and tensile strength of the waterborne polyurethane materials prepared by the methods of Examples 1 to 3 of the present invention have been significantly improved.

[0032] 2. Salt spray test Referring to GB / T 10125-2012, the coated film specimen was fixed in a salt spray chamber at an angle of 15° to the vertical direction. The specimen was taken out every 240 h, rinsed with deionized water on the surface, and the corrosion situation was observed after drying. The salt solution was 5% NaCl with a pH of 6.5 - 7.2.

[0033] The salt spray resistance time of the waterborne polyurethane coating film of the present invention was extended to 1900 - 2100 h, effectively improving the anti-corrosion performance of the material and extending the service life of the protected object.

[0034] The above is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a high-strength anticorrosive waterborne polyurethane material, characterized in that: The steps include: S1. Put the vacuum dehydrated polyol, modified biomass fiber and nano titanium dioxide in a mixer, stir at 2000-3000 r / min for 30-40 min to form a homogeneous suspension, add it to a reactor, heat it to 60-70° C., add isocyanate, stir and react for 2-3 h to obtain a prepolymer for standby use; S2. After dissolving the chain extender in water, add it to the prepolymer, cool it to 40-50°C, and stir to react for 2-3 hours; S3, adding a crosslinking agent to the system after chain extension in step S2, heating to 60-70°C, and continuing to stir and react for 1-2h to obtain a pre-emulsion; S4. Add preservatives to the pre-emulsion, stir at 6000-8000 r / min for 40-60 min, add deionized water, continue stirring for 1-2 h, perform vacuum degassing, and adjust the pH to 7-8.

2. The method for preparing a high-strength anticorrosive waterborne polyurethane material according to claim 1, characterized in that: The polyol described in step S1 is a mixed system of polycarbonate diol and polyether polyol, and the mass ratio of polycarbonate diol to polyether polyol is 1:0.5-1; The temperature of vacuum dehydration is 110~120℃; The amount of nano titanium dioxide added is 0.6~1% of the mass of the polyol; The isocyanate is hexamethylene diisocyanate; The mass ratio of isocyanate to polyol is 1:1~2.

3. The method for preparing a high-strength anticorrosive waterborne polyurethane material according to claim 1, characterized in that: The amount of modified biomass fiber added in step S1 is 3-4% of the mass of the polyol; The preparation of modified biomass fiber comprises the following steps: (1) The bamboo fiber was crushed into 100-200 mesh and immersed in a phosphate buffer solution containing 0.5-0.6% cellulase, and then placed in a shaker at 180-200 r / min and 38-40°C for 2-3 hours and filtered. The fiber was then immersed in a treatment agent and stirred. After being evenly mixed, the fiber was treated with ultraviolet light at 365 nm and 50 W for 20-30 minutes. 3,4-dihydroxybenzaldehyde was added, the temperature was raised to 60-70°C and the reaction lasted for 30-50 minutes. The fiber was then filtered, washed with deionized water for 3-5 times, and placed in a vacuum drying oven. The fiber was dried at 60-70°C for 8-12 hours to obtain activated fiber. (2) adding the activated fiber to deionized water in a mass volume ratio of 1 g:9-10 mL, stirring at 800-1000 r / min for 20-30 min under ultrasonic conditions to form a fiber suspension; (3) Add the fiber suspension into the reactor, and add 0.2-0.3 times the mass of activated fiber glycidyl methacrylate, 0.1-0.16 times the mass of maleic anhydride, and 0.003-0.005 times the mass of azobisisobutyronitrile in sequence, stir at 600-800 r / min for 10-20 min, then heat to 70-80 °C and continue stirring for 3-4 h; (4) After the reaction is completed, filter and wash with anhydrous ethanol 3 to 5 times, place in a vacuum drying oven, and dry at 60 to 70°C for 10 to 16 hours.

4. The method for preparing a high-strength anticorrosive waterborne polyurethane material according to claim 3, characterized in that: The components and corresponding weight percentages of the treatment agent in step (1) are 70-80% of 1-butyl-3-methylimidazolium acetate ionic liquid, 0.6-0.9% of nano-titanium dioxide, and the balance is deionized water.

5. The method for preparing a high-strength anticorrosive waterborne polyurethane material according to claim 1, characterized in that: The chain extender described in step S2 is a compound of ethylenediamine and diethanolamine, and the molar ratio of ethylenediamine to diethanolamine is 1:1-2.

6. The method for preparing a high-strength anticorrosive waterborne polyurethane material according to claim 1, characterized in that: The cross-linking agent described in step S3 is trimethylolpropane, and the mass fraction of the cross-linking agent in the system is 3-5%.

7. The method for preparing a high-strength anticorrosive waterborne polyurethane material according to claim 1, characterized in that: The amount of the preservative in step S4 is 2-3% of the total system mass; The amount of deionized water used is 20~30% of the total system mass.

8. The method for preparing a high-strength anticorrosive waterborne polyurethane material according to claim 7, characterized in that: The preparation of the preservative comprises the following steps: 1) Add 2 mg / mL dopamine hydrochloride, shake at 180-200 r / min and 40-46°C for 5-6 hours, then add zinc carbonate solution, react in a water bath at 60-70°C for 2-3 hours, filter, wash with deionized water 2-3 times, place in a vacuum drying oven, and dry at 60-70°C for 6-8 hours to obtain pre-modified nano zinc oxide; 2) After corona treatment, the pre-modified nano-zinc oxide is immersed in a phytic acid solution and ultrasonically treated for 30-40 minutes. Then the temperature is raised to 60-70°C, epoxy soybean oil is added, and stirred at 100-200 r / min for 2-3 hours. After filtering, the pre-modified nano-zinc oxide is washed with deionized water for 2-3 times, and then placed in a vacuum drying oven and dried at 60-70°C for 6-8 hours.

9. The method for preparing a high-strength anticorrosive waterborne polyurethane material according to claim 8, characterized in that: The voltage of the corona treatment in step 2) is 10-15 kV, and the treatment time is 30-60 s.

10. A high-strength anti-corrosion water-based polyurethane material, characterized in that: The method is obtained by the preparation method according to any one of claims 1 to 9.

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