Polyurethane waterproof coating and preparation method thereof

Abstract

The invention discloses a polyurethane waterproof coating and a preparation method thereof. Comprising the following steps: step 1, in a nitrogen atmosphere, mixing polytetrahydrofuran ether glycol with N-N-dimethylacetamide, raising the temperature, carrying out a stirring reaction, cooling, adding dibutyltin dilaurate, stirring, adding a modified monomer and 1, 4-butanediol, and carrying out a reaction to obtain modified polyurethane; and 2, transferring the modified polyurethane into a high-speed dispersion machine, adding the modified nano silicon dioxide, a defoaming agent, dipropylene glycol monomethyl ether, dibutyl phthalate, sodium dodecyl benzene sulfonate, hydroxyethyl cellulose and water, stirring at room temperature, and carrying out vacuum defoaming to obtain the polyurethane waterproof coating. The preparation method has the beneficial effects that a rigid modified monomer containing a phosphaphenanthrene group is synthesized, is chemically bonded into a polyurethane molecular chain segment and is used for carrying out surface chemical modification on nano silicon dioxide, so that dual functional integration is realized; the comprehensive performance of the polyurethane waterproof coating is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and in particular, relates to a polyurethane waterproof coating and a preparation method thereof. Background Art

[0002] Since its gradual development in the 1970s, polyurethane waterproof coatings have become one of the mainstream waterproof materials in the fields of construction, bridges, underground engineering, etc., with its high elasticity, seamless film formation and strong adhesion. Its core raw materials are composed of prepolymers generated by the reaction of isocyanate and polyol, which are cross-linked by moisture or curing agent to form a dense network structure, which can effectively adapt to the deformation of the substrate and resist water penetration.

[0003] With the acceleration of urbanization and the complexity of building structures, traditional polyurethane coatings have gradually exposed technical bottlenecks in long-term applications: on the one hand, inorganic fillers (such as calcium carbonate, talcum powder) and organic polyurethane matrices have insufficient compatibility due to polarity differences, which can easily cause interface peeling or stress concentration, reducing the strength of the coating; on the other hand, in terms of flame retardant properties, conventional flame retardants (such as aluminum hydroxide) have low compatibility with polyurethane and are easy to migrate or affect the elasticity of the coating after addition.

[0004] Therefore, in order to solve the above problems, the present invention provides a polyurethane waterproof coating and a preparation method thereof. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a polyurethane waterproof coating and a preparation method thereof.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a polyurethane waterproof coating comprises the following steps:

[0008] Step 1: Under a nitrogen atmosphere, polytetrahydrofuran ether diol and NN-dimethylacetamide are mixed, the temperature is raised to 80-90°C, stirred and reacted for 1-2h, the temperature is lowered to 60°C, dibutyltin dilaurate is added, stirred for 0.5-1h, modified monomers and 1,4-butanediol are added, and the reaction is carried out for 5-8h to obtain a modified polyurethane;

[0009] Step 2: Transfer the modified polyurethane to a high-speed disperser, add nano-silica, defoamer RKZ6008, dipropylene glycol methyl ether, dibutyl phthalate, sodium dodecylbenzene sulfonate, hydroxyethyl cellulose, and water, stir at room temperature for 20-30 minutes, and vacuum degas to obtain a polyurethane waterproof coating.

[0010] More optimally, the modified polyurethane comprises the following components: by weight, 30-40 parts of polytetramethylene ether glycol, 200-220 parts of NN-dimethylacetamide, 4-5 parts of dibutyltin dilaurate, 5-8 parts of modified monomers, and 2-3 parts of 1,4-butanediol.

[0011] More optimally, the polyurethane waterproof coating includes the following components: by weight, 50-60 parts of modified polyurethane, 3-4 parts of nano-silicon dioxide, 1-2 parts of defoamer RKZ6008, 1-2 parts of dipropylene glycol methyl ether, 1-2 parts of dibutyl phthalate, 2-6 parts of sodium dodecylbenzene sulfonate, 10-15 parts of hydroxyethyl cellulose, and 20-22 parts of water.

[0012] More optimally, the preparation process of the modified monomer is:

[0013] S1: diphenyl ether and dichlorophenylphosphine were mixed, aluminum chloride was added under nitrogen atmosphere, the temperature was raised to 20-30°C, the reaction was carried out for 15-18 hours, the mixture was cooled to room temperature, and a 10% by volume hydrochloric acid solution was used for hydrolysis, extraction, washing, and vacuum distillation to obtain intermediate 1;

[0014] S2: Add 3-allyl-2-hydroxybenzaldehyde, triethylamine and ethyl acetate into a three-necked flask, stir and mix, add intermediate 1, increase the temperature to 40-50°C, react for 4-5h, cool to room temperature, filter, wash and dry to obtain intermediate 2;

[0015] S3: Add intermediate 2 to anhydrous ethanol and stir to obtain solution A; add acetic acid and 2-aminobutanol to anhydrous ethanol to obtain solution B; under a protective atmosphere, add solution B dropwise to solution A, increase the temperature to 60-70°C, and react for 3-4 hours. After the reaction is completed, cool the mixture and stir it in deionized water to obtain a precipitate, filter, wash, and dry to obtain intermediate 3;

[0016] S4: Mix the intermediate 3, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and anhydrous ethanol, raise the temperature to 80-100°C, and react for 6-8 hours. After the reaction is completed, cool the mixture to room temperature, filter and wash with ethanol 10 times, and dry the obtained precipitate in vacuum at 70-80°C for 12-13 hours to obtain a modified monomer.

[0017] In the scheme, dichlorophenylphosphine is acylated on the aromatic ring of diphenyl ether under the catalysis of aluminum chloride (Lewis acid) to generate an intermediate 1 containing a phosphonate structure. The specific reaction process is as follows:

[0018]

[0019] In the scheme, in the presence of triethylamine, the phenolic hydroxyl group contained in 3-allyl-2-hydroxybenzaldehyde is deprotonated to generate a nucleophilic reagent, which reacts with intermediate 1. The specific reaction process is as follows:

[0020]

[0021] In the scheme, the aldehyde group of intermediate 2 undergoes nucleophilic addition with the amino group of 2-aminobutanol to form intermediate 3 with an imine structure. The specific reaction process is as follows:

[0022]

[0023] In the scheme, intermediate 3 undergoes an addition reaction with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO derivative) to introduce the phosphaphenanthrene group into the molecular structure. The structural formula of the obtained modified monomer is as follows:

[0024]

[0025] More optimally, the raw materials of intermediate 1 include the following substances, by weight: 17-20 parts of diphenyl ether, 45-50 parts of dichlorophenylphosphine, and 35-40 parts of aluminum chloride.

[0026] More optimally, the raw materials of intermediate 2 include the following substances, by weight: 20-25 parts of intermediate 1, 50-55 parts of 3-allyl-2-hydroxybenzaldehyde, 1-2 parts of triethylamine and 200-250 parts of ethyl acetate.

[0027] More optimally, the solution A comprises the following substances, by weight: 35-40 parts of intermediate 2 and 200-250 parts of anhydrous ethanol; the solution B comprises the following substances, by weight: 0.8-1 parts of acetic acid, 35-38 parts of 2-aminobutanol, and 100-150 parts of anhydrous ethanol.

[0028] More optimally, the modified monomer raw material includes the following substances, by weight: 40-42 parts of intermediate 3, 65-70 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and 300-350 parts of anhydrous ethanol.

[0029] More optimally, the preparation process of the modified nano-silica is as follows: (1) dispersing nano-silica in anhydrous ethanol, adding a mixture of 3-mercaptopropyltrimethoxysilane and methanol, reacting at 60-90°C with constant temperature stirring for 1-2h, adding ammonia water under a protective atmosphere, reacting for 4-8h, washing, and vacuum drying at 40-80°C for 6-24h to obtain thiolated nano-silica; (2) under a protective atmosphere, mixing thiolated nano-silica, anhydrous ethanol, and azobisisobutyronitrile, raising the temperature to 80-90°C, reacting for 3-4h, filtering, washing, and drying to obtain modified nano-silica.

[0030] More optimally, the thiolated nano-silica comprises the following components: by weight, 20-30 parts of nano-silica, 200-250 parts of anhydrous ethanol, 0.3-0.8 parts of 3-mercaptopropyltrimethoxysilane, 1-2 parts of methanol, and 0.1-0.2 parts of ammonia water; the modified nano-silica comprises the following components: by weight, 8-10 parts of thiolated nano-silica, 4-5 parts of modified monomers, 200-250 parts of anhydrous ethanol, and 0.01-0.02 parts of azobisisobutyronitrile.

[0031] Beneficial effects of the present invention:

[0032] The present invention synthesizes a rigid modified monomer containing a phosphophenanthrene group, chemically bonds it to a polyurethane molecular segment, and uses it to perform surface chemical modification on nano-silicon dioxide, thereby achieving dual functional integration and effectively improving the comprehensive performance of the polyurethane waterproof coating. The details are as follows:

[0033] First, the modified monomer embeds rigid groups such as benzene rings and allyl groups into the polyurethane hard segment through Friedel-Crafts acylation and nucleophilic substitution, forming a highly cross-linked three-dimensional network structure; this structure enhances the intermolecular force through hydrogen bonding and π-π stacking, thereby improving the tensile strength of the material; at the same time, the surface-modified nano-silica forms a strong chemical bond with the polyurethane matrix, effectively dispersing stress concentration and preventing crack propagation;

[0034] Second, polytetramethylene glycol (soft segment) provides flexibility, while the rigid segments of the modified monomer (containing phosphaphenanthrene groups) aggregate through hydrogen bonds to form hard segment micro-regions; this microphase separation structure significantly delays the fracture process through the synergistic effect of plastic deformation of the hard segment and elastic recovery of the soft segment when subjected to stress;

[0035] Third: Nano-silica and phosphaphenanthrene groups form a "carbon layer-inorganic matter" composite barrier; the high thermal stability of nano-silica promotes the formation of a dense carbon layer, blocking the transfer of oxygen and heat, while the phosphoric acid substances produced by the decomposition of phosphaphenanthrene catalyze the formation of carbon, and the two synergistically enhance the flame retardant effect. DETAILED DESCRIPTION

[0036] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Embodiment 1: A method for preparing a polyurethane waterproof coating, comprising the following steps:

[0038] Step 1: Under a nitrogen atmosphere, 30 parts of polytetramethylene glycol and 200 parts of NN-dimethylacetamide were mixed, the temperature was raised to 80°C, stirred and reacted for 1 hour, the temperature was lowered to 60°C, 4 parts of dibutyltin dilaurate were added, stirred for 0.5 hours, 5 parts of modified monomer and 2 parts of 1,4-butanediol were added, and the reaction was carried out for 5 hours to obtain a modified polyurethane;

[0039] Step 2: Transfer 50 parts of modified polyurethane to a high-speed disperser, add 3 parts of modified nano-silica, 1 part of defoamer RKZ6008, 1 part of dipropylene glycol methyl ether, 1 part of dibutyl phthalate, 2 parts of sodium dodecylbenzene sulfonate, 10 parts of hydroxyethyl cellulose, and 20 parts of water, stir at room temperature for 20 minutes, and vacuum degas to obtain a polyurethane waterproof coating;

[0040] Wherein, the preparation process of the modified monomer is:

[0041] S1: 17 parts of diphenyl ether and 45 parts of dichlorophenylphosphine were mixed, 35 parts of aluminum chloride were added under nitrogen atmosphere, the temperature was raised to 20°C, the reaction was carried out for 15 hours, the mixture was cooled to room temperature, hydrolyzed with 10% by volume hydrochloric acid solution, extracted, washed, and vacuum distilled to obtain intermediate 1;

[0042] S2: Add 50 parts of 3-allyl-2-hydroxybenzaldehyde, 1 part of triethylamine and 200 parts of ethyl acetate into a three-necked flask, stir and mix, add 20 parts of intermediate 1, raise the temperature to 40°C, react for 4 hours, cool to room temperature, filter, wash and dry to obtain intermediate 2;

[0043] S3: Add 35 parts of intermediate 2 to 200 parts of anhydrous ethanol, stir evenly, and obtain solution A; add 0.8 parts of acetic acid and 35 parts of 2-aminobutanol to 100 parts of anhydrous ethanol to obtain solution B; under a protective atmosphere, add solution B dropwise to solution A, increase the temperature to 60°C, and react for 3 hours. After the reaction is completed, cool the mixture and stir it in deionized water to obtain a precipitate, filter, wash, and dry to obtain intermediate 3;

[0044] S4: 40 parts of intermediate 3, 65 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 300 parts of anhydrous ethanol were mixed, the temperature was raised to 80°C, and the reaction was carried out for 6 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered and washed with ethanol 10 times, and the obtained precipitate was vacuum dried at 70°C for 12 hours to obtain a modified monomer;

[0045] The preparation process of modified nano-silica is as follows: (1) dispersing 20 parts of nano-silica into 200 parts of anhydrous ethanol, adding a mixture of 0.3 parts of 3-mercaptopropyltrimethoxysilane and 1 part of methanol, reacting at 60°C with constant temperature stirring for 1 hour, adding 0.1 parts of ammonia water under a protective atmosphere, reacting for 4 hours, washing, and vacuum drying at 40°C for 6 hours to obtain mercapto nano-silica; (2) under a protective atmosphere, mixing 8 parts of mercapto nano-silica, 4 parts of modified monomer, 200 parts of anhydrous ethanol, and 0.01 parts of azobisisobutyronitrile, raising the temperature to 80°C, reacting for 3 hours, filtering, washing, and drying to obtain modified nano-silica.

[0046] Embodiment 2: A method for preparing a polyurethane waterproof coating, comprising the following steps:

[0047] Step 1: Under a nitrogen atmosphere, 40 parts of polytetrahydrofuran ether diol and 220 parts of NN-dimethylacetamide were mixed, the temperature was raised to 90°C, stirred and reacted for 2 hours, the temperature was lowered to 60°C, 5 parts of dibutyltin dilaurate were added, stirred for 1 hour, 8 parts of modified monomer and 3 parts of 1,4-butanediol were added, and the reaction was carried out for 8 hours to obtain a modified polyurethane;

[0048] Step 2: Transfer 60 parts of modified polyurethane to a high-speed disperser, add 4 parts of modified nano-silica, 2 parts of defoamer RKZ6008, 2 parts of dipropylene glycol methyl ether, 2 parts of dibutyl phthalate, 6 parts of sodium dodecylbenzene sulfonate, 15 parts of hydroxyethyl cellulose, and 22 parts of water, stir at room temperature for 30 minutes, and vacuum degassing to obtain a polyurethane waterproof coating;

[0049] Wherein, the preparation process of the modified monomer is:

[0050] S1: 20 parts of diphenyl ether and 50 parts of dichlorophenylphosphine were mixed, 40 parts of aluminum chloride were added under nitrogen atmosphere, the temperature was raised to 30°C, the reaction was carried out for 18 hours, the mixture was cooled to room temperature, and a 10% by volume hydrochloric acid solution was used for hydrolysis, extraction, washing, and vacuum distillation to obtain intermediate 1;

[0051] S2: Add 55 parts of 3-allyl-2-hydroxybenzaldehyde, 2 parts of triethylamine and 250 parts of ethyl acetate into a three-necked flask, stir and mix, add 25 parts of intermediate 1, raise the temperature to 50°C, react for 5 hours, cool to room temperature, filter, wash and dry to obtain intermediate 2;

[0052] S3: Add 40 parts of intermediate 2 to 250 parts of anhydrous ethanol, stir evenly to obtain solution A; add 1 part of acetic acid and 38 parts of 2-aminobutanol to 150 parts of anhydrous ethanol to obtain solution B; under a protective atmosphere, add solution B dropwise to solution A, increase the temperature to 70°C, react for 4 hours, and after the reaction is completed, cool the mixture and stir in deionized water to obtain a precipitate, filter, wash, and dry to obtain intermediate 3;

[0053] S4: 42 parts of intermediate 3, 70 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 350 parts of anhydrous ethanol were mixed, the temperature was raised to 100° C., and the reaction was performed for 8 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered and washed with ethanol 10 times, and the obtained precipitate was vacuum dried at 80° C. for 13 hours to obtain a modified monomer;

[0054] The preparation process of modified nano-silica is as follows: (1) dispersing 20 parts of nano-silica into 200 parts of anhydrous ethanol, adding a mixture of 0.3 parts of 3-mercaptopropyltrimethoxysilane and 1 part of methanol, reacting at 60°C with constant temperature stirring for 1 hour, adding 0.1 parts of ammonia water under a protective atmosphere, reacting for 4 hours, washing, and vacuum drying at 40°C for 6 hours to obtain mercapto nano-silica; (2) under a protective atmosphere, mixing 8 parts of mercapto nano-silica, 4 parts of modified monomer, 200 parts of anhydrous ethanol, and 0.01 parts of azobisisobutyronitrile, raising the temperature to 80°C, reacting for 3 hours, filtering, washing, and drying to obtain modified nano-silica.

[0055] Embodiment 3: A method for preparing a polyurethane waterproof coating, comprising the following steps:

[0056] Step 1: Under a nitrogen atmosphere, 35 parts of polytetramethylene glycol and 210 parts of NN-dimethylacetamide were mixed, the temperature was raised to 85°C, stirred and reacted for 1.5 hours, the temperature was lowered to 60°C, 4.5 parts of dibutyltin dilaurate were added, stirred for 0.75 hours, 6.5 parts of modified monomer and 2.5 parts of 1,4-butanediol were added, and the reaction was carried out for 6.5 hours to obtain a modified polyurethane;

[0057] Step 2: Transfer 55 parts of modified polyurethane to a high-speed disperser, add 3.5 parts of modified nano-silica, 1.5 parts of defoamer RKZ6008, 1.5 parts of dipropylene glycol methyl ether, 1.5 parts of dibutyl phthalate, 4 parts of sodium dodecylbenzene sulfonate, 12.5 parts of hydroxyethyl cellulose, and 21 parts of water, stir at room temperature for 25 minutes, and vacuum degas to obtain a polyurethane waterproof coating;

[0058] Wherein, the preparation process of the modified monomer is:

[0059] S1: 18.5 parts of diphenyl ether and 47.5 parts of dichlorophenylphosphine were mixed, 37.5 parts of aluminum chloride were added under nitrogen atmosphere, the temperature was raised to 25°C, the reaction was carried out for 16.5 hours, the mixture was cooled to room temperature, hydrolyzed with 10% by volume hydrochloric acid solution, extracted, washed, and vacuum distilled to obtain intermediate 1;

[0060] S2: 52.5 parts of 3-allyl-2-hydroxybenzaldehyde, 1.5 parts of triethylamine and 225 parts of ethyl acetate were added to a three-necked flask, stirred and mixed, and 22.5 parts of intermediate 1 were added, the temperature was raised to 45°C, the reaction was carried out for 4.5 hours, and after cooling to room temperature, the intermediate 2 was obtained by filtering, washing and drying.

[0061] S3: Add 37.5 parts of intermediate 2 to 225 parts of anhydrous ethanol, stir evenly to obtain solution A; add 0.9 parts of acetic acid and 36.5 parts of 2-aminobutanol to 125 parts of anhydrous ethanol to obtain solution B; under a protective atmosphere, add solution B dropwise to solution A, increase the temperature to 65°C, and react for 3.5 hours. After the reaction is completed, cool the mixture and stir it in deionized water to obtain a precipitate, filter, wash, and dry to obtain intermediate 3;

[0062] S4: 41 parts of intermediate 3, 67.5 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 325 parts of anhydrous ethanol were mixed, the temperature was raised to 90°C, and the reaction was carried out for 7 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered and washed with ethanol 10 times, and the obtained precipitate was vacuum dried at 75°C for 12.5 hours to obtain a modified monomer;

[0063] The preparation process of modified nano-silica is as follows: (1) dispersing 20 parts of nano-silica into 200 parts of anhydrous ethanol, adding a mixture of 0.3 parts of 3-mercaptopropyltrimethoxysilane and 1 part of methanol, reacting at 60°C with constant temperature stirring for 1 hour, adding 0.1 parts of ammonia water under a protective atmosphere, reacting for 4 hours, washing, and vacuum drying at 40°C for 6 hours to obtain mercapto nano-silica; (2) under a protective atmosphere, mixing 8 parts of mercapto nano-silica, 4 parts of modified monomer, 200 parts of anhydrous ethanol, and 0.01 parts of azobisisobutyronitrile, raising the temperature to 80°C, reacting for 3 hours, filtering, washing, and drying to obtain modified nano-silica.

[0064] Comparative Example 1: No modified monomer is added, and the rest is the same as Example 3, as follows:

[0065] Step 1: Under a nitrogen atmosphere, 35 parts of polytetrahydrofuran ether glycol and 210 parts of NN-dimethylacetamide were mixed, the temperature was raised to 85°C, stirred and reacted for 1.5 hours, the temperature was lowered to 60°C, 4.5 parts of dibutyltin dilaurate were added, stirred for 0.75 hours, 6 parts of 1,4-butanediol were added, and the reaction was carried out for 6.5 hours to obtain a modified polyurethane;

[0066] Step 2: Transfer 55 parts of modified polyurethane to a high-speed disperser, add 3.5 parts of nano-silicon dioxide, 1.5 parts of defoamer RKZ6008, 1.5 parts of dipropylene glycol methyl ether, 1.5 parts of dibutyl phthalate, 4 parts of sodium dodecylbenzene sulfonate, 12.5 parts of hydroxyethyl cellulose, and 21 parts of water, stir at room temperature for 25 minutes, and vacuum degas to obtain a polyurethane waterproof coating.

[0067] Comparative Example 2: The nano-silicon dioxide is not modified, and the rest is the same as Example 3, as follows:

[0068] Step 1: Under a nitrogen atmosphere, 35 parts of polytetramethylene glycol and 210 parts of NN-dimethylacetamide were mixed, the temperature was raised to 85°C, stirred and reacted for 1.5 hours, the temperature was lowered to 60°C, 4.5 parts of dibutyltin dilaurate were added, stirred for 0.75 hours, 6.5 parts of modified monomer and 2.5 parts of 1,4-butanediol were added, and the reaction was carried out for 6.5 hours to obtain a modified polyurethane;

[0069] Step 2: Transfer 55 parts of modified polyurethane to a high-speed disperser, add 3.5 parts of nano-silicon dioxide, 1.5 parts of defoamer RKZ6008, 1.5 parts of dipropylene glycol methyl ether, 1.5 parts of dibutyl phthalate, 4 parts of sodium dodecylbenzene sulfonate, 12.5 parts of hydroxyethyl cellulose, and 21 parts of water, stir at room temperature for 25 minutes, and vacuum degas to obtain a polyurethane waterproof coating;

[0070] Wherein, the preparation process of the modified monomer is:

[0071] S1: 18.5 parts of diphenyl ether and 47.5 parts of dichlorophenylphosphine were mixed, 37.5 parts of aluminum chloride were added under nitrogen atmosphere, the temperature was raised to 25°C, the reaction was carried out for 16.5 hours, the mixture was cooled to room temperature, hydrolyzed with 10% by volume hydrochloric acid solution, extracted, washed, and vacuum distilled to obtain intermediate 1;

[0072] S2: 52.5 parts of 3-allyl-2-hydroxybenzaldehyde, 1.5 parts of triethylamine and 225 parts of ethyl acetate were added to a three-necked flask, stirred and mixed, and 22.5 parts of intermediate 1 were added, the temperature was raised to 45°C, the reaction was carried out for 4.5 hours, and after cooling to room temperature, the intermediate 2 was obtained by filtering, washing and drying.

[0073] S3: Add 37.5 parts of intermediate 2 to 225 parts of anhydrous ethanol, stir evenly to obtain solution A; add 0.9 parts of acetic acid and 36.5 parts of 2-aminobutanol to 125 parts of anhydrous ethanol to obtain solution B; under a protective atmosphere, add solution B dropwise to solution A, increase the temperature to 65°C, and react for 3.5 hours. After the reaction is completed, cool the mixture and stir it in deionized water to obtain a precipitate, filter, wash, and dry to obtain intermediate 3;

[0074] S4: Mix 41 parts of intermediate 3, 67.5 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 325 parts of anhydrous ethanol, raise the temperature to 90°C, and react for 7 hours. After the reaction is completed, cool the mixture to room temperature, filter and wash with ethanol 10 times, and dry the obtained precipitate in vacuum at 75°C for 12.5 hours to obtain a modified monomer.

[0075] Testing experiment: The polyurethane waterproof coating obtained in the embodiment and the comparative example was poured into a mold and cured at 85°C for 12 hours to prepare a cured product sample of 10 cm×10 cm×0.5 cm. The following test was performed:

[0076] (1) The tensile properties of the cured samples obtained in the examples and comparative examples were tested according to GB / T1040.1-2018 standard; (2) The oxygen index of the cured samples obtained in the examples and comparative examples was tested according to GB / T2406.1-2008 standard. The obtained data are shown in the following table:

[0077]

[0078] Conclusion: The present invention synthesizes a rigid modified monomer containing a phosphophanate group and introduces it into a polyurethane molecular chain, and uses the modified monomer to perform surface chemical modification on nano-silicon dioxide, thereby achieving dual functional integration and significantly improving the comprehensive performance of polyurethane waterproof coatings. Specifically, the modified monomer embeds rigid groups such as benzene rings and allyl groups into the polyurethane hard segment through Friedel-Crafts acylation and nucleophilic substitution reaction, forming a highly cross-linked three-dimensional network structure, enhancing the intermolecular force, thereby improving the tensile strength and elongation at break of the material. For example, the tensile strengths of Examples 1 to 3 are 55.8MPa, 56.7MPa, and 58.9MPa, respectively, which are significantly higher than Comparative Example 1 (45.9MPa) and Comparative Example 2 (48.8MPa), and the elongation at break also shows a similar trend, and the elongation at break of Example 3 reaches 912.4%, which is much higher than 729.9% of Comparative Example 1 and 800.9% of Comparative Example 2. In addition, the "carbon layer-inorganic matter" composite barrier formed by nano-silica and phosphaphenanthrene groups effectively blocks oxygen and heat transfer, significantly improving the flame retardant properties of the material. The limiting oxygen index of Example 3 reaches 33.9%, which is much higher than 22.7% of Comparative Example 1 and 27.1% of Comparative Example 2.

[0079] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0080] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing a polyurethane waterproof coating, characterized in that: The following steps are involved: Step 1: Under a nitrogen atmosphere, polytetrahydrofuran ether diol and NN-dimethylacetamide are mixed, the temperature is raised to 80-90°C, stirred and reacted for 1-2h, the temperature is lowered to 60°C, dibutyltin dilaurate is added, stirred for 0.5-1h, modified monomers and 1,4-butanediol are added, and the reaction is carried out for 5-8h to obtain a modified polyurethane; Step 2: Transfer the modified polyurethane to a high-speed disperser, add modified nano-silica, defoamer RKZ6008, dipropylene glycol methyl ether, dibutyl phthalate, sodium dodecylbenzene sulfonate, hydroxyethyl cellulose, and water, stir at room temperature for 20-30 minutes, and vacuum degas to obtain a polyurethane waterproof coating.

2. The method for preparing a polyurethane waterproof coating according to claim 1, characterized in that: The modified polyurethane comprises the following components: by weight, 30-40 parts of polytetramethylene ether glycol, 200-220 parts of NN-dimethylacetamide, 4-5 parts of dibutyltin dilaurate, 5-8 parts of modified monomers, and 2-3 parts of 1,4-butanediol.

3. The method for preparing a polyurethane waterproof coating according to claim 1, characterized in that: The polyurethane waterproof coating comprises the following components: by weight, 50-60 parts of modified polyurethane, 3-4 parts of modified nano silicon dioxide, 1-2 parts of defoamer RKZ6008, 1-2 parts of dipropylene glycol methyl ether, 1-2 parts of dibutyl phthalate, 2-6 parts of sodium dodecylbenzene sulfonate, 10-15 parts of hydroxyethyl cellulose, and 20-22 parts of water.

4. The method for preparing a polyurethane waterproof coating according to claim 1, characterized in that: The preparation process of the modified monomer is: S1: diphenyl ether and dichlorophenylphosphine were mixed, aluminum chloride was added under nitrogen atmosphere, the temperature was raised to 20-30°C, the reaction was carried out for 15-18 hours, the mixture was cooled to room temperature, and a 10% by volume hydrochloric acid solution was used for hydrolysis, extraction, washing, and vacuum distillation to obtain intermediate 1; S2: Add 3-allyl-2-hydroxybenzaldehyde, triethylamine and ethyl acetate into a three-necked flask, stir and mix, add intermediate 1, increase the temperature to 40-50°C, react for 4-5h, cool to room temperature, filter, wash and dry to obtain intermediate 2; S3: Add intermediate 2 to anhydrous ethanol and stir to obtain solution A; add acetic acid and 2-aminobutanol to anhydrous ethanol to obtain solution B; under a protective atmosphere, add solution B dropwise to solution A, increase the temperature to 60-70°C, and react for 3-4 hours. After the reaction is completed, cool the mixture and stir it in deionized water to obtain a precipitate, filter, wash, and dry to obtain intermediate 3; S4: Mix the intermediate 3, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and anhydrous ethanol, raise the temperature to 80-100°C, and react for 6-8 hours. After the reaction is completed, cool the mixture to room temperature, filter and wash with ethanol 10 times, and dry the obtained precipitate in vacuum at 70-80°C for 12-13 hours to obtain a modified monomer.

5. The method for preparing a polyurethane waterproof coating according to claim 4, characterized in that: The raw materials of the intermediate 1 include the following substances, by weight: 17-20 parts of diphenyl ether, 45-50 parts of dichlorophenylphosphine, and 35-40 parts of aluminum chloride.

6. The method for preparing a polyurethane waterproof coating according to claim 4, characterized in that: The raw materials of the intermediate 2 include the following substances, calculated by weight: 20-25 parts of the intermediate 1, 50-55 parts of 3-allyl-2-hydroxybenzaldehyde, 1-2 parts of triethylamine and 200-250 parts of ethyl acetate.

7. The method for preparing a polyurethane waterproof coating according to claim 4, characterized in that: The solution A comprises the following substances, calculated by weight: 35-40 parts of intermediate 2 and 200-250 parts of anhydrous ethanol; the solution B comprises the following substances, calculated by weight: 0.8-1 parts of acetic acid, 35-38 parts of 2-aminobutanol, and 100-150 parts of anhydrous ethanol.

8. The method for preparing a polyurethane waterproof coating according to claim 4, characterized in that: The modified monomer raw material comprises the following substances, by weight: 40-42 parts of intermediate 3, 65-70 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and 300-350 parts of anhydrous ethanol.

9. The method for preparing a polyurethane waterproof coating according to claim 1, characterized in that: The preparation process of the modified nano-silica is as follows: (1) dispersing nano-silica in anhydrous ethanol, adding a mixed solution of 3-mercaptopropyltrimethoxysilane and methanol, reacting at 60-90° C. with constant temperature stirring for 1-2 hours, adding ammonia water under a protective atmosphere, reacting for 4-8 hours, washing, and vacuum drying at 40-80° C. for 6-24 hours to obtain thiolated nano-silica; (2) under a protective atmosphere, mixing thiolated nano-silica, modified monomer, anhydrous ethanol, and azobisisobutyronitrile, raising the temperature to 80-90° C., reacting for 3-4 hours, filtering, washing, and drying to obtain modified nano-silica.

10. The method for preparing a polyurethane waterproof coating according to claim 9, characterized in that: The thiolated nano-silica comprises the following components: by weight, 20-30 parts of nano-silica, 200-250 parts of anhydrous ethanol, 0.3-0.8 parts of 3-mercaptopropyltrimethoxysilane, 1-2 parts of methanol, and 0.1-0.2 parts of ammonia water; the modified nano-silica comprises the following components: by weight, 8-10 parts of thiolated nano-silica, 4-5 parts of modified monomers, 200-250 parts of anhydrous ethanol, and 0.01-0.02 parts of azobisisobutyronitrile.

Images