Modified polyurethane emulsion with flame-retardant and water-repellent effects and preparation method thereof

Abstract

The application relates to the field of textile auxiliaries, and specifically discloses a modified polyurethane emulsion with both flame-retardant and water-repellent effects and a preparation method thereof. A triazine compound with halogen is reacted with an amino acid at low temperature in the application, a hydrophilic carboxylate ion is introduced, the stability of the emulsion in the later stage is ensured, a triazine compound containing nitrogen is used to carry out a substitution reaction with a water-based polyurethane prepolymer capped with a small molecule amine, the prepared polyurethane emulsion not only has good storage stability, but also has improved content of nitrogen elements in the molecule due to the introduction of a large amount of triazine compounds, so that the flame retardance of the emulsion film material in the later stage is improved, and finally, seed emulsion polymerization is carried out on the polyurethane emulsion and an acrylate monomer to obtain the modified polyurethane emulsion with both flame-retardant and water-repellent properties, which has very great application prospect.

Description

Technical Field

[0001] This application relates to the technical field of textile auxiliaries, and more specifically, to a modified polyurethane emulsion with both flame-retardant and water-repellent properties and its preparation method. Background Technology

[0002] Waterborne polyurethane is an environmentally friendly material that uses water as a dispersion medium and does not pollute the environment during use, making it highly favored by the textile industry. While the application of waterborne polyurethane is becoming increasingly widespread, its flammability poses a serious threat to people's lives and property.

[0003] While traditional flame-retardant materials meet market demands to some extent, they still have many shortcomings in terms of environmental friendliness. To address this issue, environmentally friendly flame-retardant water-based polymer materials have been developed for the market, such as:

[0004] Patent CN119265933A describes the preparation of a flame-retardant and environmentally friendly textile sizing agent by adding resorcinol bis(diphenyl phosphate) and organomontmorillonite composite flame retardant to an aqueous polyurethane sizing agent. However, the flame-retardant sizing agent prepared by this composite method does not have durability or washability. In addition, due to the composite addition, it also has a certain impact on the stability of the emulsion.

[0005] Patent CN119264366A uses pentaerythritol to react with phosphorus oxychloride to prepare flame-retardant small molecules, and then reacts them with isocyanate and polyether polyol to prepare halogen-free flame-retardant waterborne polyurethane. However, the flame-retardant small molecules prepared by this method are not hydrophilic, which reduces the stability and hydrophilicity of the prepared modified waterborne polyurethane, thus resulting in a limited amount of flame retardant introduced and added.

[0006] Patent CN113754860A discloses a triazine charring agent, a flame-retardant polyurethane material, and a method for preparing the same. This patent involves reacting a triazine compound with dopamine to obtain a triazine compound with two or more hydroxyl groups. These hydroxyl groups are then grafted with isocyanates at 80°C to obtain a flame-retardant polyurethane material. This material is primarily used for flame retardancy of polymer fillers, and there are currently no records of its application in textile auxiliaries. Furthermore, while the triazine charring agent is rich in hydrophilic groups such as hydroxyl, carboxyl, and amino groups, which help enhance the flame-retardant effect, these hydrophilic groups weaken the water-repellent effect of waterborne polyurethane finishing agents.

[0007] Given the above, there are few reports in this field that can simultaneously optimize the flame retardancy and water repellency of waterborne polyurethane emulsions. Summary of the Invention

[0008] To address the issue that waterborne polyurethane additives cannot simultaneously optimize flame retardancy and water repellency, this application provides a modified polyurethane emulsion with both flame retardant and water repellent properties, and its preparation method.

[0009] In a first aspect, this application provides a modified polyurethane emulsion that combines flame retardancy and water repellency, employing the following technical solution:

[0010] A modified polyurethane emulsion with both flame-retardant and water-repellent properties is composed of the following weight percentages:

[0011]

[0012] Among them, the polyurethane emulsion is formed by grafting a flame-retardant small molecule chain extender onto an aqueous polyurethane prepolymer. The flame-retardant small molecule chain extender is obtained by reacting triazine compounds and amino acids.

[0013] Furthermore, the triazine compound is a halogenated triazine compound.

[0014] Furthermore, the halotriazine compound is selected from any one or more of 2,4,6-trichloro-1,3,5-triazine, 2,4,6-tribromo-1,3,5-triazine, and 2,4,6-trifluoro-1,3,5-triazine.

[0015] Furthermore, the amino acid is selected from any one or more of glycine, alanine, aminotaurine, leucine, phenylalanine, and lysine.

[0016] Furthermore, the waterborne polyurethane prepolymer is prepared by reacting isocyanate, polymeric diol, hydrophilic chain extender, and small molecule amine end-capping agent in a solvent.

[0017] Furthermore, the polymer diol is selected from any one or more of polyethylene oxide diol, 1,4-butanediol adipate diol, 1,6-butanediol adipate diol, ethylene adipate diol, diethylene adipate diol, propylene adipate diol, polytetrahydrofuran diol, polycarbonate diol, and polysiloxane diol.

[0018] Furthermore, the number-average molecular weight of the polymeric diol is 1000–1500.

[0019] Furthermore, the isocyanate is a diisocyanate.

[0020] Furthermore, the diisocyanate is selected from any one or more of toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, 1,12-dodecyl diisocyanate, phenyl dimethylene diisocyanate, dicyclohexylmethane diisocyanate, and diphenylmethane diisocyanate.

[0021] Furthermore, the hydrophilic chain extender is an anionic hydrophilic chain extender.

[0022] Furthermore, the anionic hydrophilic chain extender is selected from any one or more of dimethylolpropionic acid, dimethylolbutyric acid, and sodium 1,4-dihydroxy-2-butanesulfonate.

[0023] Furthermore, the small molecule amine end-capping agent is selected from any one or more of ethylenediamine, butanediamine, and isophoronediamine.

[0024] Furthermore, the number of carbon chains of the acrylate monomer is 5 to 25.

[0025] Furthermore, the acrylate monomer is selected from any one or more of octadecyl acrylate, ecicoacrylate, dodecyl acrylate, hydroxyethyl acrylate, and dimethylaminoethyl methacrylate.

[0026] Furthermore, the number of carbon chains of the acrylate monomer is 8 to 20.

[0027] Furthermore, the emulsifier is any one or more of octadecyltrimethylammonium chloride, octadecyldimethylbenzylammonium chloride, hexadecyltrimethylammonium bromide, fatty alcohol polyoxyethylene ether, and isomeric alcohol polyoxyethylene ether.

[0028] Furthermore, the initiator is any one or more of azobisisobutyramidine hydrochloride, azobisisobutyramimidazole hydrochloride, ammonium persulfate, and potassium persulfate.

[0029] Furthermore, the co-solvent is any one or more of tripropylene glycol, propylene glycol, and acetone.

[0030] Secondly, this application provides a method for preparing a modified polyurethane emulsion that has both flame-retardant and water-repellent properties, using the following technical solution:

[0031] A method for preparing a modified polyurethane emulsion with both flame-retardant and water-repellent properties includes the following steps:

[0032] Preparation of modified polyurethane emulsion: Emulsifier, polyurethane emulsion, acrylate monomer, cosolvent and water are mixed evenly and emulsified to obtain a pre-emulsion; a portion of the pre-emulsion is taken as the base liquid, and an initiator is added to the remaining pre-emulsion; the pre-emulsion containing the initiator is added dropwise to the base liquid, the temperature is raised to 80-85℃, and the reaction time is maintained for 6-8 hours to obtain the modified polyurethane emulsion.

[0033] Furthermore, in the modified polyurethane emulsion preparation step, the reaction system is cooled to 40-45°C, and the speed of the emulsifying disperser is 2000-3000 r / min.

[0034] Furthermore, the polyurethane emulsion is prepared according to the following steps: waterborne polyurethane prepolymer is added dropwise to a flame-retardant small molecule chain extender, the temperature is first raised to 40-45°C and the reaction continues for 2-3 hours, then the temperature is raised to 80-85°C and the reaction continues for 2-3 hours. During the reaction, the pH value of the reaction system is maintained at 5-6. After the reaction is completed, the temperature is lowered, a neutralizing agent and water are added to the system, and emulsification is carried out. After emulsification, the solvent is removed to obtain the flame-retardant waterborne polyurethane emulsion.

[0035] Furthermore, in the preparation step of the polyurethane emulsion, the solvent dilutes the aqueous polyurethane prepolymer to a solid content of 10-15 wt%.

[0036] Furthermore, in the preparation step of the polyurethane emulsion, the neutralizing agent is one of triethylamine, ammonia, sodium hydroxide, and potassium hydroxide.

[0037] Furthermore, the flame-retardant small molecule chain extender is prepared according to the following steps: a triazine compound is reacted with an amino acid in a solvent, the reaction temperature is controlled at 0-5°C, and the reaction time is 1-1.5 h.

[0038] In summary, this application has at least the following advantages:

[0039] 1. In this application, a flame-retardant small-molecule chain extender is obtained by reacting a triazine compound with amino acids. This flame-retardant small-molecule chain extender is then grafted onto an aqueous polyurethane prepolymer to obtain a polyurethane emulsion. The polyurethane emulsion is then polymerized with acrylate monomers to form a stable modified polyurethane emulsion. The modified polyurethane emulsion incorporates hydrophilic groups in its solid solution, which assist the flame retardant in exerting its flame-retardant effect. Simultaneously, the hydrophilic groups impart good dispersibility to the modified polyurethane emulsion, ensuring that the modified polyurethane emulsion particles are uniformly distributed on the surface of the coated object. Triazine compounds are rich in nitrogen and possess a triple nitrogen structure. At high temperatures, triazine compounds decompose endothermically, producing non-flammable gases, thus playing a flame-retardant role. The introduction of triazine compounds endows the modified polyurethane emulsion with good self-flame-retardant properties.

[0040] The double bonds of acrylates can react with the isocyanate groups of polyurethane under the action of an initiator, introducing long-chain, low-surface-energy alkyl groups into the modified polyurethane emulsion. In its emulsion state, the modified polyurethane emulsion consists of latex particles with hydrophilic groups on the outside and hydrophobic groups on the inside. This modified polyurethane emulsion overcomes the difficulty of applying polyurethane emulsions to fabrics. The hydrophilic groups on the surface of the modified polyurethane emulsion have the same polarity as the hydroxyl groups of the fiber, allowing it to adhere to the fiber. As moisture evaporates, the hydrophobic groups of the modified polyurethane emulsion particles extend towards the air interface, forming a self-repellent film with good water-repellent properties. Therefore, the modified polyurethane emulsion can simultaneously possess excellent flame retardancy and water repellency.

[0041] 2. In the process of synthesizing flame retardant small molecule chain extenders, amino acids are introduced. During the neutralization stage, amino acids can bring carboxylate ions, thereby increasing the hydrophilicity of waterborne polyurethane, which in turn increases the stability of modified polyurethane emulsion and increases the upper limit of the amount of flame retardant molecules introduced.

[0042] Meanwhile, although the raw materials for the synthesis of flame-retardant small molecule chain extenders are halogenated triazine compounds, some of the halogens on the halogenated triazine compounds are removed by substitution reaction with amino acids, and the other part is removed by substitution reaction with waterborne polyurethane prepolymers. The resulting modified polyurethane emulsion is halogen-free, safe and environmentally friendly, and suitable for textile finishing.

[0043] 3. This application optimizes the selection of acrylate monomers, emulsification parameters, isocyanate, number-average molecular weight of polymeric diols, and other related parameters to adjust the stability of modified polyurethane emulsions and avoid the large-scale introduction of acrylate monomers leading to a surge in particle size of modified polyurethane emulsions, thereby enhancing the storage stability and water-repellent properties of modified polyurethane emulsions. Detailed Implementation

[0044] This application is further illustrated by the following embodiments, comparative examples, and test data.

[0045] Example 1

[0046] A modified polyurethane emulsion with both flame-retardant and water-repellent properties is prepared according to the following steps:

[0047] (1) Preparation of prepolymer: 13.7g toluene diisocyanate, 35.1g polyethylene glycol 1000, 2.9g dimethylolpropionic acid and 15g ethylenediamine were thoroughly mixed in acetone, the temperature was raised to 80℃ and the reaction was carried out for 2h to obtain waterborne polyurethane prepolymer.

[0048] (2) Preparation of flame retardant small molecule chain extender: 23.8g of 2,4,6-trichloro-1,3,5-triazine and 9.5g of glycine were thoroughly mixed in acetone, and the reaction temperature was kept at 5℃ for 1.5h to obtain a flame retardant small molecule chain extender solution.

[0049] (3) Modification and emulsification of prepolymer: The prepolymer obtained in step (1) is diluted with acetone to 10% solid content and gradually added dropwise to the product obtained in step (2). The reaction temperature is maintained at 45°C for 2 hours. Then the temperature is raised to 85°C for 2 hours. Sodium carbonate is added as an acid-binding agent during the reaction to maintain the pH between 5 and 6. The product obtained above is cooled to 40°C, 2.2g of triethylamine is added for neutralization, and 200g of water is added for emulsification. The speed of the emulsification disperser is 2000r / min. The emulsion is then kept at 40°C and under vacuum conditions of -0.09Mpa to remove the solvent for 2 hours.

[0050] (4) Preparation of composite emulsion: 0.8g octadecyltrimethylammonium chloride, 12g polyurethane emulsion synthesized in step (3), 24g eicosinate, 8g tripropylene glycol and 55g water are mixed evenly and emulsified to obtain a pre-emulsion. 1 / 3 of the pre-emulsion is used as the base liquid. 0.2g azobisisobutyramidine hydrochloride is added to the remaining 2 / 3 of the pre-emulsion. After mixing evenly, it is gradually added dropwise to the base liquid and kept at 85℃ for 6h. After the reaction is completed, it is cooled to room temperature to obtain the modified polyurethane emulsion.

[0051] Example 2

[0052] A modified polyurethane emulsion with both flame retardant and water-repellent properties differs from Example 1 in that: in this example, isophorone diisocyanate is used in an equal weight ratio instead of toluene diisocyanate.

[0053] Example 3

[0054] A modified polyurethane emulsion with both flame retardant and water-repellent properties differs from Example 1 in that: in this example, 1,4-butanediol adipate is used in place of 1000 parts by weight of polyethylene oxide diol; wherein the number average molecular weight of 1,4-butanediol adipate is 1000.

[0055] Example 4

[0056] A modified polyurethane emulsion with both flame retardant and water-repellent properties differs from Example 1 in that: in this example, 2,4,6-tribromo-1,3,5-triazine is used in equal parts by weight instead of 2,4,6-trichloro-1,3,5-triazine.

[0057] Example 5

[0058] A modified polyurethane emulsion with both flame-retardant and water-repellent properties differs from Example 1 in that it uses a different acrylate monomer, as detailed below:

[0059] In Example 5, octadecyl acrylate was used in place of eicosinate acrylate in equal parts by weight;

[0060] In Example 6, dimethylaminoethyl methacrylate was used in place of eicosinate in equal parts by weight.

[0061] Example 7

[0062] A modified polyurethane emulsion with both flame-retardant and water-repellent properties is prepared according to the following steps:

[0063] (1) Preparation of prepolymer: 13.7g toluene diisocyanate, 35.1g polyethylene glycol 1000, 2.9g dimethylolpropionic acid and 15g ethylenediamine were thoroughly mixed in acetone, the temperature was raised to 80℃ and the reaction was carried out for 2h to obtain waterborne polyurethane prepolymer.

[0064] (2) Preparation of flame retardant small molecule chain extender: 23.8g of 2,4,6-trichloro-1,3,5-triazine and 9.5g of glycine were thoroughly mixed in acetone, and the reaction temperature was kept at 0℃ for 1h to obtain a flame retardant small molecule chain extender solution.

[0065] (3) Modification and emulsification of prepolymer: The prepolymer obtained in step (1) is diluted with acetone to a solid content of 12% and gradually added dropwise to the product obtained in step (2). The reaction temperature is maintained at 40°C for 3 hours. Then the temperature is raised to 80°C for 3 hours. Sodium carbonate is added as an acid-binding agent during the reaction to maintain the pH between 5 and 6. The product obtained above is cooled to 40°C, 2.2g of triethylamine is added for neutralization, and 200g of water is added for emulsification. The speed of the emulsification disperser is 2500r / min. The emulsion is then kept at 40°C and under vacuum conditions of -0.09Mpa to remove the solvent for 2 hours.

[0066] (4) Preparation of composite emulsion: 0.5g octadecyltrimethylammonium chloride, 15g polyurethane emulsion synthesized in step (3), 20g eicosinate, 9g tripropylene glycol and 55g water are mixed evenly and emulsified to obtain a pre-emulsion. 1 / 3 of the pre-emulsion is used as the base liquid. 0.5g azobisisobutyramidine hydrochloride is added to the remaining 2 / 3 of the pre-emulsion. After mixing evenly, it is gradually added dropwise to the base liquid and kept at 80℃ for 8h. After the reaction is completed, it is cooled to room temperature to obtain the modified polyurethane emulsion.

[0067] Example 8

[0068] A modified polyurethane emulsion with both flame-retardant and water-repellent properties is prepared according to the following steps:

[0069] (1) Preparation of prepolymer: 13.7g toluene diisocyanate, 35.1g polyethylene glycol 1000, 2.9g dimethylolpropionic acid and 15g ethylenediamine were thoroughly mixed in acetone, the temperature was raised to 80℃ and the reaction was carried out for 2h to obtain waterborne polyurethane prepolymer.

[0070] (2) Preparation of flame retardant small molecule chain extender: 23.8g of 2,4,6-trichloro-1,3,5-triazine and 9.5g of glycine were thoroughly mixed in acetone, and the reaction temperature was kept at 5℃ for 1.5h to obtain a flame retardant small molecule chain extender solution.

[0071] (3) Modification and emulsification of prepolymer: The prepolymer obtained in step (1) is diluted with acetone to a solid content of 15% and gradually added dropwise to the product obtained in step (2). The reaction temperature is maintained at 45°C for 2 hours. Then the temperature is raised to 85°C for 2 hours. Sodium carbonate is added as an acid-binding agent during the reaction to maintain the pH between 5 and 6. The product obtained above is cooled to 40°C, 2.2g of triethylamine is added for neutralization, and 200g of water is added for emulsification. The speed of the emulsification disperser is 2000r / min. The emulsion is then kept at 40°C and under vacuum conditions of -0.09Mpa to remove the solvent for 2 hours.

[0072] (4) Preparation of composite emulsion: 0.5g octadecyltrimethylammonium chloride, 10g polyurethane emulsion synthesized in step (3), 30g eicosinate, 7g tripropylene glycol and 52.4g water are mixed evenly and emulsified to obtain a pre-emulsion. 1 / 3 of the pre-emulsion is used as the base liquid. 0.1g azobisisobutyramidine hydrochloride is added to the remaining 2 / 3 of the pre-emulsion. After mixing evenly, it is gradually added dropwise to the base liquid and kept at 85℃ for 6h. After the reaction is completed, it is cooled to room temperature to obtain the modified polyurethane emulsion.

[0073] Comparative Example 1

[0074] A modified polyurethane emulsion with both flame retardant and water-repellent properties differs from Example 1 in that: in this comparative example, the waterborne polyurethane prepolymer is not modified with a small molecule triazine compound, but is directly compounded with an acrylate monomer after the waterborne polyurethane prepolymer is emulsified.

[0075] Comparative Example 2

[0076] A modified polyurethane emulsion with both flame retardant and water-repellent properties differs from Example 1 in that: this comparative example does not use an acrylate monomer composite modified polyurethane emulsion.

[0077] Comparative Example 3

[0078] A modified polyurethane emulsion with both flame retardant and water-repellent properties differs from Example 1 in that: in this comparative example, a small molecule triazine compound is used to modify the waterborne polyurethane prepolymer, but the triazine compound is not modified or neutralized by amino acids.

[0079] Performance testing

[0080] The modified polyurethane emulsions prepared in Examples 1-8 and Comparative Examples 1-3 were cast into films on silicone rubber plates and allowed to stand at room temperature for 4 days to obtain modified polyurethane films with a thickness of 1 mm. These films were then subjected to the following tests:

[0081] 1. Solid content determination: Take a certain amount of emulsion, keep it in an oven at 150℃ for 3 hours, and measure the weight before and after drying;

[0082] 2. Storage stability: Place the emulsion at room temperature for a period of time and observe the time it takes for the emulsion to separate into layers or gel.

[0083] 3. Membrane Mechanical Strength: The mechanical properties of the cast membrane were tested using an Instron 5567 universal testing machine (Instron Corporation, USA). According to the national standard GB / T1040.3-2006, the cast membrane was cut into dumbbell-shaped strips with a clamp spacing of 30 mm, a tensile speed of 100 mm / min, and a sensor sensitivity of 1 kN.

[0084] 4. Flame retardant and water repellency tests: Dilute the modified polyurethane emulsion from the examples or comparative examples to 50 g / L, dip and rub it twice into woven cotton fabric, dry at 100°C, heat-treat at 170°C for 40 seconds, cool to room temperature, and test the water repellency according to GB / T 4745-2012 Textiles - Test and evaluation of water resistance (water-dip method). Test the flame retardant properties according to GB / T5455-1997 Textiles - Test for flammability - Oxygen index method. Fabrics with flame retardant properties should have an oxygen index (LOI) value equal to or greater than 28%.

[0085] Table 1. Performance tests of the modified polyurethane emulsions obtained in Examples 1-8 and Comparative Examples 1-3

[0086]

[0087] in conclusion

[0088] Based on the above test data, it can be seen that:

[0089] Comparative Example 1 forms a single comparison with Example 1. In Comparative Example 1, the lack of triazine compounds to modify the waterborne polyurethane prepolymer resulted in a significant decrease in the oxygen index value of the modified polyurethane emulsion and poor flame retardant effect. At the same time, the mechanical strength of Comparative Example 1 also decreased significantly, indicating that the addition of flame retardant small molecule chain extenders can not only effectively improve the flame retardant properties of modified polyurethane emulsions, but also effectively improve the adhesion properties of modified polyurethane emulsions.

[0090] Comparative Example 2 was used as a single comparison with Example 1. Comparative Example 2 lacked the use of acrylate monomers to modify the polyurethane emulsion, resulting in a decreased water repellency and poorer water-repellent properties; simultaneously, the mechanical strength of the modified polyurethane emulsion decreased. Furthermore, optimization was performed on the type of acrylate monomer, specifically through a single comparison of Examples 1 and 5-6. The test data showed that the chain lengthening of the acrylate monomers helped improve the water repellency and mechanical strength of the modified polyurethane emulsion.

[0091] Comparative Example 3 forms a single comparison with Example 1. In Comparative Example 3, the flame retardant small molecule chain extender is not modified with amino acids but is directly grafted onto the waterborne polyurethane prepolymer. The storage stability of the resulting modified polyurethane emulsion is significantly reduced, not exceeding 3 months. The solids in the modified polyurethane emulsion are prone to flocculation and sedimentation, shortening its service life.

[0092] Examples 1 and 7-8 form a single comparison. In Examples 1 and 7-8, the increased ratio of acrylate monomer to polyurethane emulsion in Example 8 resulted in a slight increase in the oxygen index of the modified polyurethane emulsion and a significant improvement in its mechanical strength. This demonstrates that increasing the reaction ratio of acrylate monomer to polyurethane emulsion leads to a larger solids particle size in the modified polyurethane emulsion, which helps improve its mechanical strength and flame retardant properties. Simultaneously, maintaining the solids particle size within a suitable range does not affect the storage stability of the modified polyurethane emulsion.

[0093] In summary, the water repellency of Examples 1-5, 7, and 8 in this application all reach level 4 or above, and the oxygen index value reaches 28.5% or above, exhibiting excellent water repellency and flame retardant properties; furthermore, the storage time can reach 6 months or more, the mechanical strength is all above 5MPa, and the service life and performance are excellent.

[0094] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] Furthermore, the above-described embodiments merely illustrate several implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A modified polyurethane emulsion possessing both flame-retardant and water-repellent properties, characterized in that, Composed of the following weight percentages: Initiator 0.1-0.5% Emulsifier 0.5-1.5% Polyurethane emulsion 10-15% 20-30% acrylate monomers Cosolvent 7-9% Water content: 50-60%; Among them, the polyurethane emulsion is formed by grafting a flame-retardant small molecule chain extender onto an aqueous polyurethane prepolymer. The flame-retardant small molecule chain extender is obtained by reacting triazine compounds and amino acids in a solvent. The reaction temperature is controlled at 0-5℃ and the reaction time is 1-1.5h. The triazine compound is selected from any one or more of 2,4,6-trichloro-1,3,5-triazine, 2,4,6-tribromo-1,3,5-triazine, and 2,4,6-trifluoro-1,3,5-triazine; The amino acid is selected from any one or more of glycine, alanine, aminotaurine, leucine, phenylalanine, and lysine. The waterborne polyurethane prepolymer is prepared by reacting isocyanate, polymeric diol, hydrophilic chain extender, and small molecule amine end-capping agent in a solvent; the small molecule amine end-capping agent is selected from any one or more of ethylenediamine, butanediamine, and isophorone diamine; the hydrophilic chain extender is selected from any one or more of dimethylolpropionic acid, dimethylolbutyric acid, and sodium 1,4-dihydroxy-2-butanesulfonate. The acrylate monomer is selected from any one or more of octadecyl acrylate, ecicoacrylate, docosahexadecyl acrylate, hydroxyethyl acrylate, and dimethylaminoethyl methacrylate.

2. The modified polyurethane emulsion with both flame-retardant and water-repellent properties as described in claim 1, characterized in that: The emulsifier is any one or more of octadecyltrimethylammonium chloride, octadecyldimethylbenzylammonium chloride, hexadecyltrimethylammonium bromide, fatty alcohol polyoxyethylene ether, and isomeric alcohol polyoxyethylene ether.

3. The modified polyurethane emulsion with both flame-retardant and water-repellent properties as described in claim 1, characterized in that: The initiator is any one or more of azobisisobutyramidine hydrochloride, azobisisobutyramimidazole hydrochloride, ammonium persulfate, and potassium persulfate.

4. A method for preparing a modified polyurethane emulsion with both flame-retardant and water-repellent properties as described in any one of claims 1-3, characterized in that, The process includes the following steps: Preparation of modified polyurethane emulsion: Emulsifier, polyurethane emulsion, acrylate monomer, cosolvent and water are mixed evenly and emulsified to obtain a pre-emulsion; a portion of the pre-emulsion is taken as the base liquid, and an initiator is added to the remaining portion of the pre-emulsion; the pre-emulsion containing the initiator is added dropwise to the base liquid, the temperature is raised to 80-85℃, and the reaction time is maintained for 6-8 hours to obtain the modified polyurethane emulsion.

5. The method for preparing a modified polyurethane emulsion with both flame-retardant and water-repellent properties as described in claim 4, characterized in that: In the modified polyurethane emulsion preparation step, the reaction system is cooled to 40-45°C, and the speed of the emulsifying disperser is 2000-3000 r / min.

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