Washable weather-resistant flame-retardant waterborne polyurethane finishing agent as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of polyurethane, and discloses a washable weather-resistant flame-retardant waterborne polyurethane finishing agent as well as a preparation method and application thereof. The preparation method comprises the following steps: adding functional additives (modified silicon carbide, a flame retardant, a free radical scavenger, epoxy resin and a chain extender) into a polyurethane prepolymer for reaction; then adding aliphatic diamine to carry out an end capping reaction, adding water to carry out phase inversion, and then adding a polyacrylate emulsion and a plasticizer to carry out emulsification. Through the synergistic interaction of the epoxy resin, the silane coupling agent modified silicon carbide and the polyacrylate, the flame-retardant waterborne polyurethane is endowed with excellent washing resistance.

Description

Technical Field

[0001] This invention relates to the field of polyurethane technology, and in particular to a water-washable, weather-resistant, flame-retardant waterborne polyurethane finishing agent, its preparation method, and its application. Background Technology

[0002] Waterborne polyurethane (WPU) is widely used in leather, microfiber leather, and functional finishing of textiles due to its low volatile organic compounds (VOCs), excellent chemical resistance, abrasion resistance, and wide substrate applicability. However, like most common organic polymers, polyurethane is flammable and decomposes very rapidly during combustion. To reduce safety hazards during use, flame-retardant functionalization modification of polyurethane is necessary.

[0003] Based on the mode of presence of flame-retardant components in waterborne polyurethane, it can be divided into additive flame-retardant waterborne polyurethane, which is physically bonded to waterborne polyurethane, and reactive flame-retardant waterborne polyurethane, which is part of the waterborne polyurethane chain. Additive flame-retardant waterborne polyurethane imparts flame-retardant properties by directly dispersing the flame retardant agent within the polyurethane matrix. This process is short and has low production costs, but it suffers from problems such as uneven dispersion and easy migration and aggregation of the flame-retardant components, leading to uneven flame-retardant effects in modified WPU products and susceptibility to detachment under external force and during washing. In contrast, in cross-linked modified flame-retardant WPU, the flame-retardant components are firmly bonded to the polyurethane polymer chain through chemical bonds, eliminating the problems of uneven dispersion and migration. This results in uniform flame-retardant properties in the modified product, and it is less affected by external force and washing.

[0004] In addition to its many advantages, waterborne polyurethane still suffers from poor water resistance, high-temperature stickiness, and low-temperature hardening. These problems severely limit the application scope of waterborne polyurethane finishing materials. Summary of the Invention

[0005] The purpose of this invention is to provide a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent, its preparation method, and its application, thereby solving the problems of poor water resistance, high-temperature stickiness, and low-temperature hardening of current waterborne flame-retardant polyurethanes.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent, comprising the following steps: Polydiol and diisocyanate are mixed to carry out a first reaction; after the first reaction is completed, a catalyst and acetone are added to carry out a second reaction to obtain a polyurethane prepolymer. Functional additives and acetone are added to the polyurethane prepolymer to carry out a third reaction; after the third reaction is completed, an aliphatic diamine is added to carry out a capping reaction to obtain a capped polyurethane. The end-capped polyurethane is cooled to a first temperature, and then defoamer and water are added for phase inversion. After phase inversion, polyacrylate emulsion and plasticizer are added for emulsification. After emulsification, acetone is removed by rotary evaporation to obtain the water-washable, weather-resistant, flame-retardant waterborne polyurethane finishing agent. The functional additive is a mixture of modified silicon carbide, flame retardant, free radical scavenger, epoxy resin, and chain extender.

[0007] Preferably, the modified silicon carbide is prepared by: carrying out a fourth reaction of nano-silicon carbide, silane coupling agent and toluene under nitrogen protection to obtain modified silicon carbide; The ratio of nano-silicon carbide, silane coupling agent, and toluene is 3-4 g: 6-10 g: 50 mL; the silane coupling agent is a mixture of trimethylmethoxysilane and dihydroxypolydimethylsiloxane in a molar ratio of 1:0.5-1; the temperature of the fourth reaction is 80-90 °C; and the time of the fourth reaction is 3-5 h.

[0008] Preferably, the flame retardant is a derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, with the following structural formula: .

[0009] Preferably, the free radical scavenger is one of hydroquinone dihydroxyethyl ether and resorcinol-bis(β-hydroxyethyl) ether.

[0010] Preferably, the mass ratio of the modified silicon carbide, flame retardant, free radical scavenger, epoxy resin, and chain extender is 2~3:4~6:0.5~1:2~3:3~5.

[0011] Preferably, the diisocyanate is at least two of hexamethylene diisocyanate, pentamethylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0012] Preferably, the mass ratio of the polydiol, diisocyanate, catalyst, functional additive, aliphatic diamine, and plasticizer is 20~30:25~40:0.3~0.5:15~25:3~5:3~5; and the mass ratio of the polyacrylate emulsion and the end-capped polyurethane is 1:1~1.5.

[0013] Preferably, the polyacrylate emulsion is prepared by: mixing a dispersant, an antifoaming agent, a monomer, and water for pre-emulsification to obtain a pre-emulsion; taking 20-30% of the volume of the pre-emulsion and heating it to 70-80°C, adding half of the initiator solution dropwise for the fifth reaction; when the fifth reaction turns blue, adding the remaining pre-emulsion dropwise over 1-2 hours; after the addition is complete, maintaining the temperature at 70-80°C for 20-30 minutes, then heating to 85-90°C, adding the remaining initiator solution dropwise over 3-5 minutes, maintaining the temperature at 85-90°C for 90-180 minutes, then cooling to 40°C, and adjusting the pH to 8-9 using ammonia water to obtain the polyacrylate emulsion. The monomer is a mixture of methyl methacrylate, isooctyl acrylate, styrene, and 4-vinylbenzaldehyde in a mass ratio of 1:1~1.2:0.3~0.5:0.5~0.8; the preemulsion contains 5~10% dispersant, 0.05% defoamer, and 15~30% monomer.

[0014] The present invention also provides a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent prepared by the above preparation method.

[0015] The present invention also provides the application of a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent prepared by the above preparation method in the finishing of microfiber synthetic leather.

[0016] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: 1) The main reason for the poor wash resistance of conventional polyurethane flame-retardant finished fabrics is that the polyurethane film easily absorbs moisture and swells, and has poor adhesion to the fibers, causing the formed flame-retardant polyurethane film to fall off during washing. Based on the systematic screening and compounding of diisocyanates, this invention endows flame-retardant waterborne polyurethane with excellent wash resistance through the synergistic effect of epoxy resin, silane coupling agent modified silicon carbide, and polyacrylate. First, the epoxy resin with excellent adhesion can improve the bonding force between polyurethane and the fiber matrix, while the silane coupling agent and polyacrylate can improve the hydrophobicity of the polyurethane film. Second, both modified silicon carbide and epoxy resin are polyhydroxy substances. When they participate in copolymerization, they can form a three-dimensional network structure of polyurethane, further improving the strength of the polyurethane film and improving the hydrophobicity of the polyurethane film and its bonding force with the fiber matrix. Finally, the aromatic aldehyde groups in polyacrylate can react with the amine groups in polyurethane during the drying process, further improving the crosslinking degree of the polyurethane film and improving the film's strength and wash resistance.

[0017] 2) The polyacrylate of this invention is an aromatic aldehyde copolymer polyacrylate, which can stably coexist with aliphatic diamine-terminated polyurethane in an aqueous medium, and undergoes a crosslinking reaction as water evaporates during the film-forming and drying process. This method does not affect the emulsification properties of the polyurethane prepolymer or the storage stability of the emulsion, and can improve the degree of crosslinking of the polyurethane film, thereby improving the film's strength and washability.

[0018] 3) The flame retardant, modified silicon carbide, phosphate ester plasticizer and free radical scavenger introduced in this invention have a synergistic effect, giving polyurethane excellent flame retardant properties.

[0019] The flame retardant is a derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. During combustion, the PO· produced can synergistically quench the HO· and H· produced by the free radical scavenger. At the same time, phosphorus-containing oxyacids are produced. When subjected to strong heat, the oxyacids will undergo a polymerization reaction to generate a dehydration catalyst, which catalyzes the formation of a carbon layer and delays the further combustion of the substrate.

[0020] Trimethylmethoxysilane and dihydroxypolydimethylsiloxane-modified silicon carbide are copolymerized and introduced into polyurethane. Silicon carbide, with its excellent high-temperature resistance, effectively improves the high-temperature resistance and flame retardant properties of the polyurethane film. Furthermore, the Si-O bond energy in trimethylmethoxysilane and dihydroxypolydimethylsiloxane is much greater than the CO and C-bond bonds that make up organic compounds, resulting in better high-temperature resistance than ordinary organic compounds. Moreover, the char layer formed by organosilicon at high temperatures is denser and more continuous, which can delay further combustion of the substrate. Organosilicon does not produce molten droplets during combustion, has a slow combustion rate, and does not emit toxic fumes.

[0021] Phosphate plasticizers not only improve the flexibility of polyurethane films at low temperatures but also enhance their flame retardancy. Furthermore, phosphate plasticizers and alkylsiloxanes have a synergistic effect, effectively improving the flexibility of polyurethane films at low temperatures. Detailed Implementation

[0022] This invention provides a method for preparing a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent, comprising the following steps: Polydiol and diisocyanate are mixed to carry out a first reaction; after the first reaction is completed, a catalyst and acetone are added to carry out a second reaction to obtain a polyurethane prepolymer. Functional additives and acetone are added to the polyurethane prepolymer to carry out a third reaction; after the third reaction is completed, an aliphatic diamine is added to carry out a capping reaction to obtain a capped polyurethane. The end-capped polyurethane is cooled to a first temperature, and then defoamer and water are added for phase inversion. After phase inversion, polyacrylate emulsion and plasticizer are added for emulsification. After emulsification, acetone is removed by rotary evaporation to obtain the water-washable, weather-resistant, flame-retardant waterborne polyurethane finishing agent.

[0023] In this invention, the polydiol is preferably a polyester diol; the polyester diol is preferably one of polyethylene glycol diol, poly(1,4-butanediol adipate) diol, poly(1,6-hexanediol adipate) diol, and poly(methyl-1,3-propanediol-1,6-hexanediol adipate) diol, and more preferably poly(1,4-butanediol adipate) diol.

[0024] In this invention, the diisocyanate is preferably at least two of hexamethylene diisocyanate, pentamethylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate, more preferably pentamethylene diisocyanate and 4,4'-dicyclohexylmethane diisocyanate in a molar ratio of 6:4. This invention uses raw materials without benzene ring structures in their molecular chains, which allows the polyurethane to have higher flexibility and prevents cracking of the hydrophobic polyurethane film during preparation. Therefore, compounding a certain amount of diisocyanate with a rigid cyclohexyl structure into a polydiol can appropriately improve the film's strength without affecting the polyurethane's flexibility.

[0025] In this invention, before the polydiol and diisocyanate are mixed, the polydiol is heated and melted, and then cooled to 45~50°C.

[0026] In this invention, the temperature of the first reaction is preferably 55~65℃, more preferably 60℃; the time of the first reaction is preferably 60~120min, more preferably 90min.

[0027] In this invention, the catalyst is preferably dibutyltin dilaurate.

[0028] In this invention, the temperature of the second reaction is preferably 70-80°C, more preferably 80°C; the time of the second reaction is preferably 60-90 min, more preferably 60 min.

[0029] In this invention, the functional additive is preferably a mixture of modified silicon carbide, flame retardant, free radical scavenger, epoxy resin, and chain extender; the mass ratio of the modified silicon carbide, flame retardant, free radical scavenger, epoxy resin, and chain extender is preferably 2~3:4~6:0.5~1:2~3:3~5, and more preferably 3:5:0.5:2.5:4.

[0030] In this invention, the flame retardant is preferably a derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, with the following structural formula: .

[0031] For details on the preparation method of the flame retardant used in this invention, please refer to patent CN202410907307.3.

[0032] In this invention, the free radical scavenger is preferably one of hydroquinone dihydroxyethyl ether and resorcinol-bis(β-hydroxyethyl) ether, and more preferably hydroquinone dihydroxyethyl ether.

[0033] In this invention, the epoxy resin is preferably a bisphenol A type epoxy resin, and more preferably epoxy resin E51.

[0034] In this invention, the chain extender is preferably 2,2-dihydroxymethylpropionic acid.

[0035] In this invention, the temperature of the third reaction is preferably 85~95℃, more preferably 90℃; the time of the third reaction is preferably 90~180min, more preferably 90min.

[0036] In this invention, the aliphatic diamine is preferably one of hexamethylenediamine, ethylenediamine, propylenediamine, and dimethylpentanediamine, and more preferably dimethylpentanediamine.

[0037] In this invention, the temperature of the end-capping reaction is preferably 85~95℃, more preferably 90℃; the time of the end-capping reaction is preferably 30~60min, more preferably 30min.

[0038] In this invention, the first temperature is preferably 40~50℃, and more preferably 40℃.

[0039] In this invention, the defoamer is preferably defoamer DM8317.

[0040] In this invention, the plasticizer is preferably a phosphate ester plasticizer; the phosphate ester plasticizer is preferably one of tri(2-ethylhexyl) phosphate, triisopropylphenyl phosphate, butyl diphenyl phosphate and toluene diphenyl phosphate, and more preferably tri(2-ethylhexyl) phosphate.

[0041] In this invention, the mass ratio of the polyacrylate emulsion to the end-capped polyurethane is preferably 1:1 to 1.5, more preferably 1:1.2. The end-capped polyurethane in this invention is the target end-capped polyurethane product in the mixed products obtained from the end-capping reaction.

[0042] In this invention, the emulsification time is preferably 120-180 min, and more preferably 120 min.

[0043] In this invention, the preferred mass ratio of the polydiol, diisocyanate, catalyst, functional additive, aliphatic diamine, and plasticizer is 20~30:25~40:0.3~0.5:15~25:3~5:3~5, and more preferably 25:35:0.4:20:5:4.

[0044] In this invention, the modified silicon carbide has the following structural diagram: ; in, For silicon carbide; x is a positive integer between 20 and 30; y is a positive integer between 20 and 30.

[0045] In this invention, the modified silicon carbide is prepared by: carrying out a fourth reaction of nano-silicon carbide, silane coupling agent, and toluene under nitrogen protection to obtain modified silicon carbide.

[0046] In this invention, the preferred ratio of nano-silicon carbide, silane coupling agent, and toluene is 3-4 g: 6-10 g: 50 mL, more preferably 3 g: 10 g: 50 mL; the preferred silane coupling agent is a mixture of trimethylmethoxysilane and dihydroxypolydimethylsiloxane in a molar ratio of 1:0.5-1, more preferably 1:0.8; the preferred temperature for the fourth reaction is 80-90°C, more preferably 80°C; the preferred reaction time is 3-5 h, more preferably 5 h. This invention uses a mixture of trimethylmethoxysilane and dihydroxypolydimethylsiloxane to modify silicon carbide. Trimethylmethoxysilane can block the hydroxyl groups on the surface of silicon carbide, improving its dispersibility in the polyurethane preparation system, while dihydroxypolydimethylsiloxane can impart suitable reactivity and good waterproof properties to silicon carbide.

[0047] In this invention, the preparation method of the polyacrylate emulsion is as follows: a dispersant, a defoamer, a monomer, and water are mixed and pre-emulsified to obtain a pre-emulsion; 20-30% of the volume of the pre-emulsion is heated to 70-80°C, and half of the initiator solution is added dropwise to carry out the fifth reaction. When the fifth reaction reaches the point where a blue color appears, the remaining pre-emulsion is added dropwise over 1-2 hours. After the addition is completed, the temperature is maintained at 70-80°C for 20-30 minutes, and then the temperature is raised to 85-90°C. The remaining initiator solution is added dropwise over 3-5 minutes, and the temperature is maintained at 85-90°C for 90-180 minutes. Then the temperature is lowered to 40°C, and the pH is adjusted to 8-9 using ammonia water to obtain the polyacrylate emulsion.

[0048] In this invention, the mass fraction of the dispersant in the preemulsion is preferably 5-10%, more preferably 8%, the mass fraction of the defoamer is preferably 0.05%, and the mass fraction of the monomer is preferably 15-30%, more preferably 25%; the monomer is preferably a mixture of methyl methacrylate, isooctyl acrylate, styrene, and 4-vinylbenzaldehyde in a mass ratio of 1:1-1.2:0.3-0.5:0.5-0.8, more preferably 1:1:0.4:0.6; the dispersant is preferably hexadecyltrimethylchloromethacrylate in a mass ratio of 1:1-2. The mixture of ammonium chloride and Span 60 is preferably 1:1.5; the defoamer is preferably defoamer DM8317; the initiator solution is preferably a potassium persulfate solution with a mass fraction of 10-15%, more preferably 10%; the volume ratio of the preemulsion to the initiator solution is preferably 30:1; the preemulsification temperature is preferably 30-40℃, more preferably 40℃; the preemulsification time is preferably 30-60 min, more preferably 40 min; the temperature of the fifth reaction is preferably 70-80℃, more preferably 70℃.

[0049] The present invention also provides a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent prepared by the above preparation method.

[0050] The present invention also provides the application of a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent prepared by the above preparation method in the finishing of microfiber synthetic leather.

[0051] 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.

[0052] Example 1

[0053] This embodiment provides a method for preparing a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent, comprising the following steps: 25g of poly(1,4-butanediol adipate) was melted by heating and then cooled to 50°C. 35g of diisocyanate (a mixture of pentamethylene diisocyanate and 4,4'-dicyclohexylmethane diisocyanate in a molar ratio of 6:4) was added, and the mixture was heated to 60°C and reacted for 90 min. Then, 0.4g of dibutyltin dilaurate and 10g of acetone were added, and the mixture was heated to 80°C and refluxed for 60 min to obtain a polyurethane prepolymer. Next, 20g of functional additives (modified silicon carbide, flame retardant, hydroquinone dihydroxyethyl ether, epoxy resin E51, and 2,2-dimethylolpropionic acid in a mass ratio of 3:5:0.5:2.5:4) and 20g of acetone were added, and the mixture was heated to 90°C and reacted at a constant temperature for 90 min. Then, 5g of dimethylpentanediamine was added for end-capping reaction for 30 min to obtain end-capped polyurethane. Finally, the end-capped polyurethane was cooled to 40°C, and 60g of acetone was slowly added dropwise. mL of deionized water containing 0.8 g / L of defoamer DM8317 was added. After the water-in-oil phase inversion was completed, polyacrylate emulsion (the mass ratio of polyacrylate emulsion to end-capped polyurethane was 1:1.2) and 4 g of tris(2-ethylhexyl) phosphate were quickly added. Emulsification was continued for 120 min. Acetone was removed by rotary evaporation to obtain a water-washable, weather-resistant, flame-retardant waterborne polyurethane finishing agent.

[0054] The modified silicon carbide is prepared as follows: 30g of nano silicon carbide powder is added to 500mL of toluene at room temperature, and after being ultrasonically dispersed evenly, 100g of silane coupling agent (trimethylmethoxysilane and dihydroxypolydimethylsiloxane in a molar ratio of 1:0.8) is added. The mixture is heated to 80℃ under a nitrogen gas flow and reacted at a constant temperature for 5h. After washing and drying, modified silicon carbide is obtained.

[0055] The preparation method of polyacrylate emulsion is as follows: In deionized water, add 8% by mass of dispersant (hexadecyltrimethylammonium chloride and Span 60 in a mass ratio of 1:1.5), 0.05% by mass of defoamer DM8317, and 25% by mass of monomers (methyl methacrylate, isooctyl acrylate, styrene, and 4-vinylbenzaldehyde in a mass ratio of 1:1:0.4:0.6). Pre-emulsify at 40°C for 40 min to obtain a pre-emulsion; take 80% of the pre-emulsion, and... The pre-emulsion was heated to 70°C. Half of the initiator solution (10% potassium persulfate solution) was added dropwise at a ratio of 30:1 (total volume of pre-emulsion to total volume of initiator solution). When the reaction turned blue, the collected pre-emulsion was added dropwise over 1.5 hours. After the addition was complete, the reaction was kept at a constant temperature for 30 minutes. The temperature was then raised to 90°C, and the remaining initiator solution was added dropwise over 4 minutes. The reaction was continued for 120 minutes. The temperature was then lowered to 40°C, and the pH was adjusted to 8 with ammonia to obtain a polyacrylate emulsion.

[0056] Comparative Example 1

[0057] This comparative example provides a method for preparing a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent, as detailed in Example 1, except that the diisocyanate is pentamethylene diisocyanate.

[0058] Comparative Example 2

[0059] This comparative example provides a method for preparing a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent, as detailed in Example 1, except that the diisocyanate is 4,4'-dicyclohexylmethane diisocyanate.

[0060] Comparative Example 3

[0061] This comparative example provides a method for preparing a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent, as detailed in Example 1, except that epoxy resin E51 is not added.

[0062] Comparative Example 4

[0063] This comparative example provides a method for preparing a water-washable, weather-resistant, flame-retardant waterborne polyurethane finishing agent, as detailed in Example 1, except that modified silicon carbide is not added.

[0064] Comparative Example 5

[0065] This comparative example provides a method for preparing a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent, as detailed in Example 1. The difference is that dimethylpentanediamine is not used to end-cap the polyurethane prepolymer, and aromatic aldehydes are not used in the copolymerization of the prepared polyacrylate (specifically, the monomers in the preparation method of the polyacrylate emulsion do not contain 4-vinylbenzaldehyde).

[0066] Comparative Example 6

[0067] This comparative example provides a method for preparing a water-washable, weather-resistant, flame-retardant waterborne polyurethane finishing agent, as detailed in Example 1, except that no flame retardant is added.

[0068] Comparative Example 7

[0069] This comparative example provides a method for preparing a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent, as detailed in Example 1, except that no phosphate ester plasticizer, tri(2-ethylhexyl) phosphate, is added.

[0070] Comparative Example 8

[0071] This comparative example provides a method for preparing a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent, as detailed in Example 1, except that a free radical scavenger, hydroquinone dihydroxyethyl ether, is not added.

[0072] The finishing agents obtained in Example 1 and Comparative Examples 1-8 were prepared to test their performance. The sample preparation method was as follows: (1) Preparation of polyurethane film: The finishing agent is evenly spread on polytetrafluoroethylene plate and cast into a film. Then it is dried at room temperature and finally placed in an oven at 110℃ for 10 min to obtain polyurethane film. The film thickness is controlled at 250±10μm.

[0073] (2) Effect of finishing agent application: The finishing agent was fixed onto the polyester fabric by the two dip and two nibble method. The mass concentration of the finishing agent was 80 g / L, the nibble rate was 60%, the pre-drying was at 80℃ for 5 min, and the baking was at 160℃ for 3 min.

[0074] The performance of polyester fabrics treated with the above-mentioned polyurethane films and finishing agents was tested. The results are shown in Tables 1, 2, 3, 4, and 5.

[0075] The main performance testing parameters and methods are as follows: (1) Water absorption test: Under room temperature conditions, the polyurethane film was cut into 5cm×5cm pieces, completely immersed in distilled water, and kept for 24 hours. After that, it was taken out, the water was absorbed with filter paper, and the water absorption rate was measured by weighing. The higher the water absorption rate, the worse the water resistance. Each sample was tested 3 times and the average value was taken.

[0076] (2) Washing method for washability: The washing method for fabrics treated with each finishing agent shall be in accordance with the standard specified in GB / T 19980-2025 Textiles - Evaluation method for appearance of textile products after household washing and drying.

[0077] (3) Limiting oxygen index test: Refer to GB / T 5454-1997 "Oxygen index method for testing the flammability of textiles".

[0078] (4) Flame retardant performance test: The test of damage length, smoldering time and afterflame time refers to GB / T 5455-2014 "Determination of vertical damage length, smoldering and afterflame time of textiles".

[0079] (5) Test method for low temperature resistance of polyurethane film: Place polyurethane film in a -20℃ environment for 2 hours, and analyze the flexibility of film by touch to judge the low temperature resistance of polyurethane film.

[0080] (6) Test method for high temperature resistance of polyurethane film: Place polyurethane film in an 80℃ environment for 2 hours, and analyze the flexibility of film by touch to judge the low temperature resistance of polyurethane film.

[0081] Table 1. Water Absorption of Polyurethane Membranes

[0082] Table 1 shows the water absorption of the polyurethane membranes prepared in Example 1 and Comparative Examples 1-5. The data in the table indicate that the water absorption rate of the polyurethane membrane prepared in Example 1 is significantly lower than that of the polyurethane membranes prepared in Comparative Examples 1-5. The order of influence on the water absorption rate of the polyurethane membranes, from largest to smallest, is: modified silicon carbide (Comparative Example 4), polyacrylate (Comparative Example 5), epoxy resin E51 (Comparative Example 3), and diisocyanate (Comparative Examples 1 and 2). This is because the hydroxyl groups in modified silicon carbide and the aromatic aldehyde groups in polyacrylate can not only undergo crosslinking reactions with polyurethane to form a three-dimensional network structure, but the dihydroxy polydimethylsiloxane and polyacrylate on the surface of silicon carbide can also impart excellent hydrophobicity to the polyurethane membrane.

[0083] Table 2 Flame retardancy of various polyurethane films

[0084] Table 2 shows the flame retardant properties of the polyurethane films prepared in Examples 1, 4, 6, and 7. The data in Table 2 indicate that the product with the simultaneous addition of modified silicon carbide, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivative, and tri(2-ethylhexyl) phosphate (Example 1) exhibits the best flame retardant effect. The order of influence on flame retardant effect is: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivative (Comparative Example 6), modified silicon carbide (Comparative Example 4), and tri(2-ethylhexyl) phosphate (Comparative Example 7). The flame retardant effect of Example 1 is superior to that of the comparative examples, indicating that modified silicon carbide, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivative, and tri(2-ethylhexyl) phosphate have a good synergistic flame retardant effect.

[0085] Table 3. Washability of fabrics treated with various flame retardants

[0086] Table 3 shows the wash resistance test results of the polyurethane-finished fabrics prepared in Example 1 and Comparative Examples 1-5. The data in the table show that the order of influence on the wash resistance of the flame retardant is modified silicon carbide, polyacrylate, epoxy resin E51, and diisocyanate.

[0087] The polyurethane flame retardant without modified silicon carbide (Comparative Example 4) not only has the lowest limiting oxygen index, but also the worst washability. This is because modified silicon carbide can not only react with polyurethane to form a three-dimensional network structure, giving the polyurethane film excellent hydrophobicity, but also improve the flame retardant properties of polyurethane.

[0088] Polyacrylate (Comparative Example 5) and epoxy resin E51 (Comparative Example 3) had no significant effect on the flame retardancy of the unwashed samples, but the limiting oxygen index decreased significantly after 10 washes, with polyacrylate showing the most significant effect. This is because polyacrylate undergoes a cross-linking reaction with polyurethane to form a three-dimensional network structure, giving the polyurethane film excellent hydrophobicity, while epoxy resin E51 can only improve the compactness of the polyurethane film through a cross-linking reaction.

[0089] Table 4 Low-temperature resistance of various polyurethane films

[0090] Table 4 shows the low-temperature resistance of the polyurethane films prepared in Example 1, Comparative Example 4, and Comparative Example 7. The data in the table show that the polyurethane film prepared in Example 1, after being placed in a -20℃ environment for 2 hours, does not become stiff to the touch and maintains good flexibility. However, the polyurethane films prepared in Comparative Examples 4 and 7 show significant changes in both feel and flexibility after being placed in a -20℃ environment for 2 hours.

[0091] Table 5. Heat resistance of various polyurethane films

[0092] Table 5 shows the effects of epoxy resin, modified silicon carbide, aromatic aldehyde copolymer polyacrylate, and free radical scavenger on the heat resistance of polyurethane films. The data in the table show that after being placed in an 80℃ environment for 2 hours, the polyurethane film prepared in Example 1 is not sticky, the polyurethane film prepared in Comparative Example 4 is relatively sticky, and the polyurethane films prepared in Comparative Examples 3, 5, and 8 are slightly sticky. This is because the crosslinking reaction between epoxy resin and aromatic aldehyde copolymer polyacrylate and the polyurethane prepolymer increases the degree of crosslinking of the polyurethane film, thus improving the problem of high-temperature stickiness. Modified silicon carbide not only undergoes a crosslinking reaction with the polyurethane prepolymer to increase the degree of crosslinking of the polyurethane film, but both polysiloxane and silicon carbide have excellent high-temperature resistance, effectively improving the high-temperature resistance of the polyurethane film. The free radical scavenger can absorb the free radicals generated by the polyurethane film under high-temperature conditions, slowing down the denaturation of the polyurethane.

[0093] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent, characterized in that, Includes the following steps: Polydiol and diisocyanate are mixed to carry out a first reaction; after the first reaction is completed, a catalyst and acetone are added to carry out a second reaction to obtain a polyurethane prepolymer. Functional additives and acetone are added to the polyurethane prepolymer to carry out a third reaction; after the third reaction is completed, an aliphatic diamine is added to carry out a capping reaction to obtain a capped polyurethane. The end-capped polyurethane is cooled to the first temperature, and then defoamer and water are added to initiate phase inversion. After phase inversion, polyacrylate emulsion and plasticizer are added for emulsification; after emulsification, acetone is removed by rotary evaporation to obtain the water-washable, weather-resistant, flame-retardant waterborne polyurethane finishing agent. The functional additive is a mixture of modified silicon carbide, flame retardant, free radical scavenger, epoxy resin, and chain extender.

2. The preparation method of a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent according to claim 1, characterized in that, The modified silicon carbide is prepared by: carrying out a fourth reaction of nano-silicon carbide, silane coupling agent, and toluene under nitrogen protection to obtain modified silicon carbide; The ratio of nano-silicon carbide, silane coupling agent, and toluene is 3-4 g: 6-10 g: 50 mL; the silane coupling agent is a mixture of trimethylmethoxysilane and dihydroxypolydimethylsiloxane in a molar ratio of 1:0.5-1; the temperature of the fourth reaction is 80-90 °C; and the time of the fourth reaction is 3-5 h.

3. The preparation method of a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent according to claim 1, characterized in that, The flame retardant is a derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and its structural formula is: 。 4. The preparation method of a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent according to claim 1, characterized in that, The free radical scavenger is one of hydroquinone dihydroxyethyl ether and resorcinol-bis(β-hydroxyethyl) ether.

5. The preparation method of a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent according to claim 1, characterized in that, The mass ratio of the modified silicon carbide, flame retardant, free radical scavenger, epoxy resin, and chain extender is 2~3:4~6:0.5~1:2~3:3~5.

6. The preparation method of a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent according to claim 1, characterized in that, The diisocyanate is at least two of hexamethylene diisocyanate, pentamethylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

7. The preparation method of a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent according to claim 1, characterized in that, The mass ratio of the polydiol, diisocyanate, catalyst, functional additive, aliphatic diamine, and plasticizer is 20~30:25~40:0.3~0.5:15~25:3~5:3~5; the mass ratio of the polyacrylate emulsion and the end-capped polyurethane is 1:1~1.

5.

8. The method for preparing a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent according to claim 1, characterized in that, The preparation method of the polyacrylate emulsion is as follows: a dispersant, a defoamer, a monomer, and water are mixed and pre-emulsified to obtain a pre-emulsion; 20-30% of the volume of the pre-emulsion is heated to 70-80°C, and half of the initiator solution is added dropwise to carry out the fifth reaction. When the fifth reaction turns blue, the remaining pre-emulsion is added dropwise over 1-2 hours. After the addition is completed, the temperature is maintained at 70-80°C for 20-30 minutes, then the temperature is raised to 85-90°C, and the remaining initiator solution is added dropwise over 3-5 minutes. The temperature is maintained at 85-90°C for 90-180 minutes, then the temperature is lowered to 40°C, and the pH is adjusted to 8-9 using ammonia water to obtain the polyacrylate emulsion. The monomer is a mixture of methyl methacrylate, isooctyl acrylate, styrene, and 4-vinylbenzaldehyde in a mass ratio of 1:1~1.2:0.3~0.5:0.5~0.8; the preemulsion contains 5~10% dispersant, 0.05% defoamer, and 15~30% monomer.

9. A water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent prepared by the preparation method according to any one of claims 1 to 8.

10. The application of a water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent prepared by the preparation method according to any one of claims 1 to 8, or the water-resistant, weather-resistant, flame-retardant waterborne polyurethane finishing agent according to claim 9, in the finishing of microfiber synthetic leather.

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