Waterborne polyurethane flame-retardant coating and preparation method thereof

Abstract

The invention discloses a waterborne polyurethane flame-retardant coating and a preparation method thereof, and relates to the technical field of coating materials. The waterborne polyurethane flame-retardant coating at least comprises the following raw materials in parts by mass: 100 parts of flame-retardant modified polyurethane emulsion; 2 to 3 parts of gamma-aminopropyl triethoxy silane; 0.5 to 1 part of fluorinated silicon dioxide nano particle dispersion liquid; 0.1 to 0.2 part of an organic tin catalyst; 0.2 to 0.3 part of a wetting leveling agent; 0.1 to 0.2 part of a defoaming agent; the flame-retardant modified polyurethane emulsion at least comprises the following raw materials in parts by mass: 20-30 parts of castor oil; 5 to 15 parts of polyester polyol; 15 to 25 parts of isophorone diisocyanate; 1.5 to 2.5 parts of dimethylolpropionic acid; 3 to 8 parts of a branched flame retardant containing phosphorus, nitrogen and silicon; 0.5 to 2 parts of gamma-(methacryloyloxy) propyl trimethoxy silane; 0.03 to 0.08 part of dibutyltin dilaurate; 1 to 2 parts of triethylamine; and 100 parts of deionized water. A coating prepared from the waterborne polyurethane flame-retardant coating has excellent flame retardance, durable stain resistance, self-cleaning performance and wear resistance.

Description

Technical Field

[0001] This invention relates to the field of coating materials technology, specifically to a water-based polyurethane flame-retardant coating and its preparation method. Background Technology

[0002] With the continuous improvement of the national economic level, people are paying more and more attention to sports and health, and flooring materials have broad development prospects. Polyurethane (PU), as one of the six major polymer synthetic materials, has the characteristics of high strength, high hardness, high modulus and high elongation. At the same time, it has good oil resistance, low temperature resistance and wear resistance. It can be used as an adhesive, coating, fiber, plastic, rubber and other fields, with a wide range of applications. Polyurethane flooring refers to the use of polyurethane flooring coatings combined with a new type of solvent-free or water-based, pollution-free floor functional construction technology, which provides anti-slip, anti-corrosion and wear-resistant flooring. Colored sand decorative flooring is a new type of non-solvent composite decorative flooring composed of colored quartz sand and resin. By freely combining one or more different colored quartz sands, a variety of decorative colors and patterns can be formed. Polyurethane colored sand flooring combines the advantages of polyurethane flooring and colored sand flooring, with good decorative effect, good mechanical, weather resistance, high and low temperature resistance and corrosion resistance. Its comprehensive performance is excellent and belongs to high-end flooring materials. It is suitable for places that require heavy-duty resistance and anti-slip, such as garages, warehouses, mold and machinery manufacturing workshops, etc.

[0003] The surface layer of cast-in-place polyurethane elastic colored sand plastic flooring is usually composed of polyurethane elastomer bonded with quartz sand. Although it has a certain toughness, it still has the following inherent defects: (1) The main chain of polyurethane polymer and organic colored sand are flammable substances, posing a fire hazard and making it difficult to meet the requirements of high flame retardant level places. (2) The porous and rough surface is very easy to adsorb dust, oil stains, pigments and other dirt, making cleaning difficult and affecting aesthetics and hygiene. (3) When exposed to ultraviolet rays, rainwater or daily cleaning agents for a long time, the surface is prone to yellowing, powdering or performance deterioration. At present, the surface performance of this type of flooring is mostly improved by applying solvent-based or water-based general-purpose topcoats. However, traditional topcoats have obvious shortcomings: physically added flame retardants are easy to migrate and precipitate, resulting in flame retardancy that is not lasting and affects mechanical properties; ordinary hydrophobic coatings have poor wear resistance and quickly fail under frequent trampling; the coefficient of thermal expansion and modulus of the coating and the polyurethane elastic substrate do not match, which easily causes cracking and peeling. Therefore, developing a surface coating that is durable, flame-retardant, stain-resistant, highly wear-resistant, and environmentally friendly has become a key technical challenge to improve the overall performance and added value of this type of flooring. Summary of the Invention

[0004] The purpose of this invention is to provide a water-based polyurethane flame-retardant coating and its preparation method, thereby solving the following technical problems:

[0005] Existing water-based polyurethane flame-retardant coatings used on cast-in-place polyurethane elastic colored sand plastic flooring have problems such as insufficient flame retardancy, poor stain resistance, and poor wear resistance.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A water-based polyurethane flame-retardant coating comprises at least the following raw materials in parts by weight:

[0008] 100 parts of flame-retardant modified polyurethane emulsion; 2-3 parts of γ-aminopropyltriethoxysilane; 0.5-1 parts of fluorinated silica nanoparticle dispersion; 0.1-0.2 parts of organotin catalyst; 0.2-0.3 parts of wetting and leveling agent; 0.1-0.2 parts of defoamer;

[0009] The flame-retardant modified polyurethane emulsion comprises at least the following raw materials in parts by weight: 20-30 parts castor oil; 5-15 parts polyester polyol; 15-25 parts isophorone diisocyanate; 1.5-2.5 parts dimethylolpropionic acid; 3-8 parts phosphorus-nitrogen-silicon branched flame retardant; 0.5-2 parts γ-(methacryloyloxy)propyltrimethoxysilane; 0.03-0.08 parts dibutyltin dilaurate; 1-2 parts triethylamine; and 100 parts deionized water.

[0010] As a further aspect of the present invention: the solid content of the flame-retardant modified polyurethane emulsion is 30-38 wt%, and the solid content of the fluorinated silica nanoparticle dispersion is 3-8 wt%.

[0011] As a further aspect of the present invention, the method for preparing the flame-retardant modified polyurethane emulsion includes at least the following steps:

[0012] Castor oil and polyester polyol were mixed and dehydrated, then isophorone diisocyanate and dibutyltin dilaurate were added, and the mixture was reacted at 70-80℃ for 1.5-2.5h to obtain a prepolymer.

[0013] Dimethylolpropionic acid was dissolved in acetone and added to the prepolymer. The mixture was reacted at 70-80°C for 1.5-2 hours. Then, a branched flame retardant containing phosphorus, nitrogen, and silicon was added, and the reaction was continued for 0.5-1.5 hours. The temperature was then lowered to 55-65°C, and γ-(methacryloyloxy)propyltrimethoxysilane was added. The mixture was reacted for 0.5-1.5 hours, and the temperature was lowered to 35-40°C. Triethylamine was added, and the mixture was reacted for 10-20 minutes. Finally, acetone was added to adjust the viscosity to obtain the modified prepolymer.

[0014] The modified prepolymer was added to deionized water, emulsified, and then distilled under reduced pressure to obtain a flame-retardant modified polyurethane emulsion.

[0015] As a further aspect of the present invention: the preparation method of the phosphorus-nitrogen-silicon branched flame retardant includes at least the following steps:

[0016] 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and 3,4-dihydroxybenzaldehyde were dissolved in a mixed solution of dimethyl sulfoxide and anhydrous ethanol. The mixture was heated to 40-50°C with stirring and reacted for 1.5-2.5 h. Diethyl phosphite and zinc chloride were added, and the mixture was heated to 75-85°C and refluxed for 7-9 h. The mixture was then cooled, washed, and dried to obtain a branched flame retardant containing phosphorus, nitrogen, and silicon.

[0017] As a further aspect of the present invention: the mass ratio of the 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, the 3,4-dihydroxybenzaldehyde, and the diethyl phosphite is 3-4:4-5:4-5.

[0018] As a further aspect of the present invention, the method for preparing the fluorinated silica nanoparticle dispersion includes at least the following steps:

[0019] Hydrophilic fumed silica nanoparticles were dispersed in a mixed solution of ethanol, ammonia and water, heated to 45-55℃, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane was added. The reaction was carried out for 11-13 hours, centrifuged and washed with alcohol to obtain a dispersion of fluorinated silica nanoparticles.

[0020] As a further aspect of the present invention: the mass ratio of the hydrophilic fumed silica nanoparticles to the 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is 1:1-1.5, the concentration of the ammonia water is 25-28wt%, and the mass ratio of the ethanol, the ammonia water and the water is 12-18:3-4:3-4.

[0021] As a further aspect of the present invention: the organotin catalyst is at least one of dibutyltin dilaurate, stannous octoate, or dibutyltin diacetate; the wetting and leveling agent is at least one of polyether-modified siloxane solution, nonionic acrylic copolymer solution, or ionic polyacrylate solution; and the defoamer is at least one of defoaming polysiloxane solution, polyether-modified polydimethylsiloxane solution, or silicone polyether emulsion.

[0022] The preparation method of the waterborne polyurethane flame-retardant coating described in any one of the above methods includes at least the following preparation steps:

[0023] Flame-retardant modified polyurethane emulsion, γ-aminopropyltriethoxysilane, fluorinated silica nanoparticle dispersion, organotin catalyst, wetting and leveling agent and defoamer are mixed, stirred and allowed to stand to defoam, to obtain waterborne polyurethane flame-retardant coating.

[0024] The beneficial effects of this invention are:

[0025] The waterborne polyurethane flame-retardant coating prepared in this invention is a compound of flame-retardant modified polyurethane emulsion and fluorinated silica nanoparticle dispersion. The flame-retardant modified polyurethane emulsion uses a mixture of castor oil and polyester polyol as the soft segment, ensuring the coating's elasticity and toughness. Isophorone diisocyanate serves as the hard segment raw material, imparting good weather resistance and mechanical strength to the coating. Further polymerization modification with a phosphorus-nitrogen-silicon branched flame retardant imparts high flame retardancy to the waterborne polyurethane. The compounded fluorinated silica nanoparticles are 1H,1H,2H,2H-perfluorodecyltrimethoxysilane grafted modified silica nanoparticles. The fluorocarbon chains grafted onto the surface of the silica nanoparticles disperse and anchor the nanoparticles within the waterborne polyurethane cross-linked network, providing the coating with extremely low surface energy. Furthermore, the nanoscale particles form a micro-nano secondary rough structure on the coating surface, achieving superhydrophobicity and adiaphragmity. The waterborne polyurethane coating prepared in this invention imparts excellent flame retardancy, durable stain resistance, self-cleaning properties, and wear resistance to floor surfaces.

[0026] The phosphorus-nitrogen-silicon branched flame retardant added to the flame-retardant modified polyurethane emulsion prepared in this invention is obtained by dehydration condensation of the terminal primary amino group of 1,3-bis(3-aminopropyl)tetramethyldisiloxane and the aldehyde group of 3,4-dihydroxybenzaldehyde, followed by grafting phosphate groups onto the ortho-position of the benzene ring. The hydroxyl groups (-OH) in the phosphorus-nitrogen-silicon branched flame retardant molecule undergo nucleophilic addition reactions with the isocyanate groups (-NCO) in the prepolymer, becoming part of the polyurethane molecular chain. This fundamentally avoids the migration and loss problems of traditional additive flame retardants, achieving intrinsic flame retardancy. The phosphorus, nitrogen, and silicon elements form a synergistic flame-retardant effect. Phosphorus promotes the formation of a dense char layer during combustion, nitrogen releases inert gases upon thermal decomposition to dilute combustible gases, and silicon forms an antioxidant silicate protective layer to enhance the stability of the char layer, achieving a high flame retardant rating.

[0027] In the flame-retardant modified polyurethane emulsion synthesis stage of this invention, γ-(methacryloyloxy)propyltrimethoxysilane is added for modification. γ-(methacryloyloxy)propyltrimethoxysilane and the aminosilane γ-aminopropyltriethoxysilane added to the coating undergo thorough hydrolysis and condensation, forming a dense three-dimensional Si-O-Si cross-linked network within the coating and at the interface between the coating and the floor substrate. This significantly improves the coating's adhesion, cohesive strength, hardness, and durability. The waterborne polyurethane coating prepared by this invention exhibits strong adhesion when applied to polyurethane elastic colored sand plastic flooring. Furthermore, the waterborne polyurethane coating, after film formation, possesses elasticity, matching the repeated deformation of the elastic layer and greatly reducing the problems of coating cracking and peeling caused by the elastic deformation of thermoplastic polyurethane elastic colored sand plastic flooring. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1: The preparation method of a branched flame retardant containing phosphorus, nitrogen, and silicon includes the following steps:

[0030] 3.73 g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (PATS) and 4.14 g of 3,4-dihydroxybenzaldehyde were dissolved in 30 mL of dimethyl sulfoxide and 60 mL of anhydrous ethanol. Under nitrogen protection, the mixture was magnetically stirred and heated to 45 °C for 2 h. Then, 4.14 g of diethyl phosphite and 0.1 g of zinc chloride were added, and the mixture was stirred for 10 min. The temperature was then raised to 80 °C and refluxed for another 8 h. After the reaction was completed, the mixture was allowed to cool naturally to room temperature and poured into 500 mL of petroleum ether and stirred for 0.5 h. Subsequently, the mixture was poured into 1000 mL of deionized water to precipitate the product. After washing, the product was dried under vacuum at 80 °C to obtain a branched flame retardant containing phosphorus, nitrogen, and silicon.

[0031] Example 2: The preparation method of the dispersion of fluorinated silica nanoparticles includes the following steps:

[0032] 10g of hydrophilic fumed silica nanoparticles were added to a mixed solution containing 150g of anhydrous ethanol, 30g of 25wt% ammonia and 30g of water. The mixture was stirred and dispersed at 25℃ for 1h. The temperature was then raised to 50℃, and 12g of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane was added dropwise. The reaction was continued for 12h. The mixture was then centrifuged and washed with alcohol until the residual ammonia was removed, resulting in a dispersion of fluorinated silica nanoparticles with a concentration of 5wt% ethanol.

[0033] Example 3: The preparation method of flame-retardant modified polyurethane emulsion includes the following steps:

[0034] 27 parts by weight of castor oil and 8 parts by weight of polyester polyol 2000 were mixed and heated to 115°C under nitrogen protection. The vacuum pump was turned on and the mixture was dehydrated at -0.095 MPa for 1.5 h. The mixture was then cooled to 75°C, and 22.5 parts by weight of isophorone diisocyanate and 0.06 parts by weight of dibutyltin dilaurate were added. The mixture was reacted at 75°C for 2 h to obtain the prepolymer.

[0035] 2.2 parts by mass of dimethylolpropionic acid were dissolved in 8 parts by mass of acetone and added to the above prepolymer. The mixture was reacted at 75°C for 1.5 h. Then, 6 parts by mass of the phosphorus-nitrogen-silicon branched flame retardant prepared in Example 1 were added and the reaction was continued for 1 h. The temperature was lowered to 60°C and 1.5 parts by mass of γ-(methacryloyloxy)propyltrimethoxysilane were added and the mixture was reacted for 1 h. The temperature was lowered to 38°C and 1.65 parts by mass of triethylamine were added and the mixture was reacted for 15 min. Then, 14 parts by mass of acetone were added to adjust the viscosity to obtain the modified prepolymer.

[0036] The modified prepolymer was added to 100 parts by mass of deionized water and emulsified for 30 min under high-speed shear at 1400 rpm. The emulsion was then distilled under reduced pressure in a 45°C water bath at -0.085 MPa to recover acetone and obtain a flame-retardant modified polyurethane emulsion with a solid content of approximately 34 wt%.

[0037] The preparation method of waterborne polyurethane flame-retardant coating includes the following steps:

[0038] 100 parts by weight of the above flame-retardant modified polyurethane emulsion, 2.8 parts by weight of γ-aminopropyltriethoxysilane, 1 part by weight of the dispersion of fluorinated silica nanoparticles prepared in Example 2, 0.12 parts by weight of dibutyltin dilaurate, 0.25 parts by weight of polysiloxane-polyether wetting and leveling agent and 0.15 parts by weight of polysiloxane-polyether defoamer were mixed and allowed to stand for defoaming for 20 minutes to obtain a waterborne polyurethane flame-retardant coating.

[0039] Example 4: The preparation method of flame-retardant modified polyurethane emulsion includes the following steps:

[0040] 25 parts by weight of castor oil and 10 parts by weight of polyester polyol 2000 were mixed and heated to 115°C under nitrogen protection. The vacuum pump was turned on and the mixture was dehydrated at -0.095 MPa for 1.5 h. The mixture was then cooled to 75°C, and 22 parts by weight of isophorone diisocyanate and 0.05 parts by weight of dibutyltin dilaurate were added. The mixture was reacted at 75°C for 2 h to obtain the prepolymer.

[0041] Two parts by mass of dimethylolpropionic acid were dissolved in five parts by mass of acetone and added to the prepolymer. The mixture was reacted at 75°C for 1.5 h. Then, eight parts by mass of the phosphorus-nitrogen-silicon branched flame retardant prepared in Example 1 were added, and the reaction was continued for 1 h. The temperature was lowered to 60°C, one part by mass of γ-(methacryloyloxy)propyltrimethoxysilane was added, and the mixture was reacted for 1 h. The temperature was lowered to 38°C, one part by mass of triethylamine was added, and the mixture was reacted for 15 min. Finally, 15 parts by mass of acetone were added to adjust the viscosity to obtain the modified prepolymer.

[0042] The modified prepolymer was added to 100 parts by weight of deionized water and emulsified at a high speed of 1400 rpm for 30 min. The emulsion was then distilled under reduced pressure in a water bath at 45°C and a vacuum of -0.085 MPa to recover acetone and obtain a flame-retardant modified polyurethane emulsion with a solid content of approximately 35 wt%.

[0043] The preparation method of waterborne polyurethane flame-retardant coating includes the following steps:

[0044] 100 parts by weight of the above flame-retardant modified polyurethane emulsion, 2.5 parts by weight of γ-aminopropyltriethoxysilane, 0.8 parts by weight of the dispersion of fluorinated silica nanoparticles prepared in Example 2, 0.15 parts by weight of dibutyltin dilaurate, 0.25 parts by weight of polysiloxane-polyether wetting and leveling agent and 0.15 parts by weight of polysiloxane-polyether defoamer were mixed and allowed to stand for defoaming for 20 minutes to obtain a waterborne polyurethane flame-retardant coating.

[0045] Example 5: The preparation method of flame-retardant modified polyurethane emulsion includes the following steps:

[0046] 28 parts by weight of castor oil and 7 parts by weight of polyester polyol 2000 were mixed and heated to 115°C under nitrogen protection. The vacuum pump was turned on and the mixture was dehydrated at -0.095 MPa for 1.5 h. The mixture was then cooled to 75°C, and 20 parts by weight of isophorone diisocyanate and 0.05 parts by weight of dibutyltin dilaurate were added. The mixture was reacted at 75°C for 2 h to obtain the prepolymer.

[0047] 2.2 parts by mass of dimethylolpropionic acid were dissolved in 8 parts by mass of acetone and added to the above prepolymer. The mixture was reacted at 75°C for 1.5 h. Then, 4 parts by mass of the phosphorus-nitrogen-silicon branched flame retardant prepared in Example 1 were added, and the reaction was continued for 1 h. The temperature was lowered to 60°C, and 1.8 parts by mass of γ-(methacryloyloxy)propyltrimethoxysilane were added. The mixture was reacted for 1 h, and the temperature was lowered to 38°C. Then, 1.65 parts by mass of triethylamine were added and the mixture was reacted for 15 min. Finally, 10 parts by mass of acetone were added to adjust the viscosity to obtain the modified prepolymer.

[0048] The modified prepolymer was added to 100 parts by mass of deionized water and emulsified for 30 min under high-speed shear at 1400 rpm. The emulsion was then distilled under reduced pressure in a 45°C water bath at -0.085 MPa to recover acetone and obtain a flame-retardant modified polyurethane emulsion with a solid content of approximately 34 wt%.

[0049] The preparation method of waterborne polyurethane flame-retardant coating includes the following steps:

[0050] 100 parts by weight of the above flame-retardant modified polyurethane emulsion, 3 parts by weight of γ-aminopropyltriethoxysilane, 1.5 parts by weight of the dispersion of fluorinated silica nanoparticles prepared in Example 2, 0.18 parts by weight of dibutyltin dilaurate, 0.25 parts by weight of polysiloxane-polyether wetting and leveling agent and 0.15 parts by weight of polysiloxane-polyether defoamer were mixed and allowed to stand for defoaming for 20 minutes to obtain a waterborne polyurethane flame-retardant coating.

[0051] Comparative Example 1: The preparation method of the modified polyurethane emulsion includes the following steps:

[0052] 27 parts by weight of castor oil and 13.5 parts by weight of polyester polyol 2000 were mixed and heated to 115°C under nitrogen protection. The vacuum pump was turned on and the mixture was dehydrated at -0.095 MPa for 1.5 h. The mixture was then cooled to 75°C, and 21.5 parts by weight of isophorone diisocyanate and 0.06 parts by weight of dibutyltin dilaurate were added. The mixture was reacted at 75°C for 2 h to obtain the prepolymer.

[0053] 2.2 parts by mass of dimethylolpropionic acid were dissolved in 8 parts by mass of acetone and added to the above prepolymer. The mixture was reacted at 75°C for 1.5 h, cooled to 60°C, and 1.5 parts by mass of γ-(methacryloyloxy)propyltrimethoxysilane were added. The mixture was reacted for 1 h, cooled to 38°C, and 1.65 parts by mass of triethylamine were added. The mixture was reacted for 15 min, and then 14 parts by mass of acetone were added to adjust the viscosity to obtain the modified prepolymer.

[0054] The modified prepolymer was added to 100 parts by mass of deionized water and emulsified for 30 min under high-speed shear at 1400 rpm. The emulsion was then distilled under reduced pressure in a 45°C water bath at -0.085 MPa to recover acetone and obtain a modified polyurethane emulsion with a solid content of approximately 34 wt%.

[0055] Compared with Example 3, in the preparation steps of the waterborne polyurethane flame retardant coating, the flame retardant modified polyurethane emulsion prepared in Example 3 was replaced by an equal mass of the modified polyurethane emulsion prepared in the cost comparison ratio, and the remaining components and preparation methods were completely consistent with Example 3.

[0056] Comparative Example 2: The preparation method of the modified polyurethane emulsion includes the following steps:

[0057] 27 parts by weight of castor oil and 8 parts by weight of polyester polyol 2000 were mixed and heated to 115°C under nitrogen protection. The vacuum pump was turned on and the mixture was dehydrated at -0.095 MPa for 1.5 h. The mixture was then cooled to 75°C, and 21.5 parts by weight of isophorone diisocyanate and 0.06 parts by weight of dibutyltin dilaurate were added. The mixture was reacted at 75°C for 2 h to obtain the prepolymer.

[0058] 2.2 parts by mass of dimethylolpropionic acid were dissolved in 8 parts by mass of acetone and added to the above prepolymer. The mixture was reacted at 75°C for 1.5 h. Then, 6 parts by mass of the phosphorus-nitrogen-silicon branched flame retardant prepared in Example 1 were added and the reaction was continued for 1 h. The temperature was lowered to 40°C, 0.5 parts by mass of 1,4-butanediol were added and the mixture was reacted for 1 h. The temperature was lowered to 38°C, 1.65 parts by mass of triethylamine were added and the mixture was reacted for 15 min. Then, 12 parts by mass of acetone were added to adjust the viscosity to obtain the modified prepolymer.

[0059] The modified prepolymer was added to 100 parts by mass of deionized water and emulsified at a high-speed shear of 1400 rpm for 30 min. The emulsion was then distilled under reduced pressure in a water bath at 45°C and a vacuum of -0.085 MPa to recover acetone and obtain a modified polyurethane emulsion with a solid content of approximately 34.5 wt%.

[0060] Compared with Example 3, in the preparation steps of the waterborne polyurethane flame retardant coating, the flame retardant modified polyurethane emulsion prepared in Example 3 was replaced by an equal mass of the modified polyurethane emulsion prepared in the cost comparison ratio, and the remaining components and preparation methods were completely consistent with Example 3.

[0061] Compared with Example 3, the preparation of flame-retardant modified polyurethane emulsion in Comparative Example 3 was the same as in Example 3. In the preparation steps of waterborne polyurethane flame-retardant coating, Comparative Example 3 only did not add the dispersion of fluorinated silica nanoparticles prepared in Example 2. The remaining components and preparation methods were completely consistent with those in Example 3.

[0062] Compared with Example 3, the preparation of flame-retardant modified polyurethane emulsion in Comparative Example 4 was the same as that in Example 3. In the preparation steps of waterborne polyurethane flame-retardant coating, Comparative Example 4 only did not add γ-aminopropyltriethoxysilane, and the remaining components and preparation methods were completely consistent with those in Example 3.

[0063] Performance testing

[0064] The waterborne polyurethane flame-retardant coatings prepared in Examples 3-5 and Comparative Examples 1-4 were poured into clean and dry PTFE molds and subjected to staged thermosetting treatment: First, they were left to stand at 25°C (room temperature) for 168 hours for preliminary crosslinking and moisture evaporation. Then, they were placed in a constant temperature oven at 60°C for 4 hours for further thermosetting to promote the full crosslinking reaction. Finally, they were allowed to cool naturally and slowly to room temperature in the oven before demolding to obtain flame-retardant samples for subsequent flame-retardant performance testing.

[0065] Limiting Oxygen Index (LOI): According to ASTM D2836-2017 standard, an oxygen index meter of model 5801-A was used to test the flame-retardant specimens. By adjusting the oxygen concentration, the flame-retardant specimens were made to continue to burn stably after the ignition source was removed, and the oxygen concentration value at this time was recorded as the LOI; the test results are shown in Table 1.

[0066] Vertical burning test (UL-94): The experiment was conducted using a vertical burning tester of model 5402-A according to ASTM D3801-2010 standard, and the duration of afterflame after two ignitions was recorded; the test results are shown in Table 1.

[0067] Tensile property test: According to the national standard GB / T 1040.3-2006 Test of tensile properties of plastics, the INSTRON-3365 double-arm universal testing machine was used to conduct tensile tests on the samples cut into type 5 dumbbell shapes. The tensile rate was 50 mm / min. Each group of samples was tested three times, and the average value was taken as the test result. The test results are shown in Table 1.

[0068] Anti-staining test: Soy sauce was dropped onto the tilted surface of the coated sample, and the sliding state of the droplet and whether there were any stains adhering to the droplet's path were observed; the test results are shown in Table 1;

[0069] Table 1: Statistical Table of Performance Test Data for Examples and Comparative Examples

[0070] LOI (%) UL-94 rating Tensile strength (MPa) Elongation at break (%) Stain resistance Example 3 30.5 V-0 12.5 350 No residue Example 4 32.0 V-0 14.0 320 No residue Example 5 28.0 V-0 11.0 380 No residue Comparative Example 1 22.0 Burning dripping 15.0 280 serious residue Comparative Example 2 29.8 V-1 8.5 450 Residue Comparative Example 3 30.3 V-0 12.0 340 Slight residue Comparative Example 4 30.1 V-0 10.5 400 Slight residue

[0071] The waterborne polyurethane flame-retardant coatings prepared in Examples 3-5 and Comparative Examples 1-4 were sprayed using a spray gun (0.3mm nozzle, 4 bar pressure) at a distance of approximately 15cm from the cast-in-place polyurethane elastic colored sand test panel, with spray patterns at 10cm intervals. 2 The dispersion was sprayed onto the surface of the test panel at a concentration of / mL, and then the sprayed test panel was cured at room temperature for 7 days. After three cycles of spraying and curing, a waterborne polyurethane flame-retardant coating was finally obtained for subsequent performance testing.

[0072] Contact angle: The contact angles (CA) of water and diiodomethane on the surface of the waterborne polyurethane flame retardant coating were measured using a DSA-30 optical contact angle meter. The volumes of water and diiodomethane droplets were 2.0 μL and 1.0 μL, respectively. The test results are shown in Table 2.

[0073] Abrasion resistance test: The sample surface was placed face down on sandpaper (1000 mesh), a pressure of 2.2 kPa was applied using a 200 g weight, and the sample was moved horizontally. The water contact angle of the coating was tested after 100 cycles (20 cm per cycle) of friction to evaluate the abrasion resistance of the coating; the test results are shown in Table 2.

[0074] Adhesion performance test: According to ASTM D3359 standard, the test coating was cut into a grid pattern using a cross-cutting tool with a tooth pitch of 1 mm, and the coating surface debris was cleaned. Then, 3M 600 transparent tape was used to repeatedly stick and peel off the grid area of ​​the coating. By observing the peeling of the coating, the coating adhesion performance was divided into six levels from 0 to 5; the test results are shown in Table 2.

[0075] Table 2: Statistical Table of Performance Test Data for Examples and Comparative Examples

[0076] Water contact angle (°) Diiodomethane contact angle (°) Water contact angle after wear (°) Adhesion Example 3 152 138 146 Level 0 Example 4 148 135 142 Level 0 Example 5 156 140 149 Level 0 Comparative Example 1 145 130 125 Level 1 Comparative Example 2 140 125 118 Level 2 Comparative Example 3 102 65 98 Level 0 Comparative Example 4 150 136 135 Level 1

[0077] As shown in Tables 1 and 2, the waterborne polyurethane flame-retardant coating prepared by this invention possesses high flame retardancy, superhydrophobicity, high adhesion, and good wear resistance. In Comparative Example 1, the waterborne polyurethane emulsion was not modified for flame retardancy, resulting in a coating that lacked flame retardancy and was more brittle. In Comparative Example 2, the waterborne polyurethane emulsion was not modified with a coupling agent, leading to decreased adhesion and wear resistance in the resulting coating. In Comparative Example 3, the waterborne polyurethane emulsion was not compounded with the fluorinated silica nanoparticle dispersion, resulting in a coating that lost its superhydrophobicity. In Comparative Example 4, the coating did not contain aminosilane, resulting in decreased adhesion and wear resistance.

[0078] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0079] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A water-based polyurethane flame-retardant coating, characterized in that, It shall include at least the following parts by weight of raw materials: 100 parts of flame-retardant modified polyurethane emulsion; 2-3 parts of γ-aminopropyltriethoxysilane; 0.5-1 parts of fluorinated silica nanoparticle dispersion; 0.1-0.2 parts of organotin catalyst; 0.2-0.3 parts of wetting and leveling agent; 0.1-0.2 parts of defoamer; The flame-retardant modified polyurethane emulsion comprises at least the following raw materials in parts by weight: 20-30 parts castor oil; 5-15 parts polyester polyol; 15-25 parts isophorone diisocyanate; 1.5-2.5 parts dimethylolpropionic acid; 3-8 parts phosphorus-nitrogen-silicon branched flame retardant; 0.5-2 parts γ-(methacryloyloxy)propyltrimethoxysilane; 0.03-0.08 parts dibutyltin dilaurate; 1-2 parts triethylamine; and 100 parts deionized water.

2. The waterborne polyurethane flame-retardant coating according to claim 1, characterized in that, The flame-retardant modified polyurethane emulsion has a solid content of 30-38 wt%, and the fluorinated silica nanoparticle dispersion has a solid content of 3-8 wt%.

3. The waterborne polyurethane flame-retardant coating according to claim 2, characterized in that, The preparation method of the flame-retardant modified polyurethane emulsion includes at least the following steps: Castor oil and polyester polyol were mixed and dehydrated, then isophorone diisocyanate and dibutyltin dilaurate were added, and the mixture was reacted at 70-80℃ for 1.5-2.5h to obtain a prepolymer. Dimethylolpropionic acid was dissolved in acetone and added to the prepolymer. The mixture was reacted at 70-80°C for 1.5-2 hours. Then, a branched flame retardant containing phosphorus, nitrogen, and silicon was added, and the reaction was continued for 0.5-1.5 hours. The temperature was then lowered to 55-65°C, and γ-(methacryloyloxy)propyltrimethoxysilane was added. The mixture was reacted for 0.5-1.5 hours, and the temperature was lowered to 35-40°C. Triethylamine was added, and the mixture was reacted for 10-20 minutes. Finally, acetone was added to adjust the viscosity to obtain the modified prepolymer. The modified prepolymer was added to deionized water, emulsified, and then distilled under reduced pressure to obtain a flame-retardant modified polyurethane emulsion.

4. The waterborne polyurethane flame-retardant coating according to claim 1, characterized in that, The preparation method of the phosphorus-nitrogen-silicon branched flame retardant includes at least the following steps: 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and 3,4-dihydroxybenzaldehyde were dissolved in a mixed solution of dimethyl sulfoxide and anhydrous ethanol. The mixture was heated to 40-50°C with stirring and reacted for 1.5-2.5 h. Diethyl phosphite and zinc chloride were added, and the mixture was heated to 75-85°C and refluxed for 7-9 h. The mixture was then cooled, washed, and dried to obtain a branched flame retardant containing phosphorus, nitrogen, and silicon.

5. The waterborne polyurethane flame-retardant coating according to claim 4, characterized in that, The mass ratio of the 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, the 3,4-dihydroxybenzaldehyde, and the diethyl phosphite is 3-4:4-5:4-5.

6. The waterborne polyurethane flame-retardant coating according to claim 1, characterized in that, The preparation method of the fluorinated silica nanoparticle dispersion includes at least the following steps: Hydrophilic fumed silica nanoparticles were dispersed in a mixed solution of ethanol, ammonia and water, heated to 45-55℃, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane was added. The reaction was carried out for 11-13 hours, centrifuged and washed with alcohol to obtain a dispersion of fluorinated silica nanoparticles.

7. The waterborne polyurethane flame-retardant coating according to claim 6, characterized in that, The mass ratio of the hydrophilic fumed silica nanoparticles to the 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is 1:1-1.5, the concentration of the ammonia is 25-28 wt%, and the mass ratio of the ethanol, the ammonia, and the water is 12-18:3-4:3-4.

8. The waterborne polyurethane flame-retardant coating according to claim 1, characterized in that, The organotin catalyst is at least one of dibutyltin dilaurate, stannous octoate, or dibutyltin diacetate; the wetting and leveling agent is at least one of polyether-modified siloxane solution, nonionic acrylic copolymer solution, or ionic polyacrylate solution; and the defoamer is at least one of defoaming polysiloxane solution, polyether-modified polydimethylsiloxane solution, or silicone oxide polyether emulsion.

9. A method for preparing a waterborne polyurethane flame-retardant coating according to any one of claims 1-8, characterized in that, It includes at least the following preparation steps: Flame-retardant modified polyurethane emulsion, γ-aminopropyltriethoxysilane, fluorinated silica nanoparticle dispersion, organotin catalyst, wetting and leveling agent and defoamer are mixed, stirred and allowed to stand to defoam, to obtain waterborne polyurethane flame-retardant coating.