Tetrahydroxy gemini quaternary ammonium salt cationic waterborne polyurethane emulsion and preparation method thereof

Abstract

The invention belongs to the technical field of waterborne polyurethane, and particularly relates to a tetrahydroxy gemini quaternary ammonium salt cationic waterborne polyurethane emulsion and a preparation method thereof. Aiming at the problems that waterborne polyurethane is invaded by bacteria, the emulsion stability is poor, the mechanical property of a membrane is poor and the like, N-methyldiethanolamine and 1, 3-dichloropropane are used for synthesizing gemini quaternary ammonium salt containing 2N < + > / 4-OH as a hydrophilic chain extender, and the gemini quaternary ammonium salt is used for synthesizing the waterborne polyurethane. The waterborne polyurethane emulsion with small particle size and good dispersion stability and the waterborne polyurethane film with good mechanical property can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of waterborne polyurethane technology, specifically relating to a tetrahydroxy gemini quaternary ammonium salt cationic waterborne polyurethane emulsion and its preparation method. Background Technology

[0002] Polyurethane (PU) is widely used in coatings, adhesives, foams, plastics, rubber, and leather due to its excellent properties and wide tunability of structure-property ratio. However, solvent-based polyurethanes use organic solvents that generate large amounts of volatile organic compounds (VOCs), leading to increasing restrictions on their use. Waterborne polyurethanes, on the other hand, use water as a solvent, making them environmentally friendly. Their synthesis mainly involves introducing hydrophilic groups into the PU molecular chain segments. Utilizing the properties of these hydrophilic groups, the PU is uniformly dispersed in water, with little or no organic solvents used throughout the synthesis process. Waterborne polyurethane (WPU) has been widely used in textiles, coatings, interior leather, and adhesives, but it currently faces challenges such as bacterial contamination, poor emulsion stability, and poor membrane mechanical properties.

[0003] To address the bacterial infestation problem faced by waterborne polyurethanes (WPUs), common methods include adding antibiotics for sterilization. However, excessive antibiotic use can lead to a global antimicrobial resistance crisis. Currently, methods for imparting antibacterial properties to waterborne polyurethanes often involve introducing polyols containing tertiary amines or quaternary ammonium groups on the main chain or side chains as cationic chain extenders into the polyurethane molecular chain. The characteristics of the introduced cationic groups give cationic waterborne polyurethanes antistatic, dustproof, and antibacterial properties. Quaternary ammonium salts (QAS) are an important raw material for synthesizing cationic waterborne polyurethanes. As a well-known class of highly effective antibacterial agents, they exhibit persistence on treated surfaces, thus possessing broad-spectrum antibacterial activity and long-lasting efficiency. Furthermore, QAS also demonstrates advantages such as customizable molecular structures, high functionality, non-volatility, long lifespan, and chemical stability. Quaternary ammonium salts containing hydroxyl groups can be introduced into waterborne polyurethanes as hydrophilic chain extenders, thereby endowing them with antibacterial properties. Simultaneously, the N-hydroxyl groups in quaternary ammonium salts... +It possesses good hydrophilicity, which can improve the stability of WPU emulsions. For example, CN202410222638.3 discloses a quaternary ammonium salt-type waterborne polyurethane and its preparation method. Using dihydroxy silicone oil and isocyanate of different molecular weights as raw materials, and 3-dimethylamino-1,2-propanediol as a crosslinking agent, waterborne polyurethane materials are prepared through catalyst catalysis, quaternization, and other steps. This material is a long-chain quaternary ammonium salt compound that can penetrate and disrupt bacterial cell membranes, exhibiting antibacterial properties. CN202210109360.X discloses a bis-quaternary ammonium salt diol, its preparation method, and its application in antibacterial self-matting waterborne polyurethane coatings. Its antibacterial monomer is a monomer containing a bis-quaternary ammonium salt diol, with only two hydroxyl groups as active sites, reacting with isocyanate. The excellent hydrophilicity and antibacterial properties of the bis-quaternary ammonium salt structure endow WPU with self-emulsifying and antibacterial properties.

[0004] However, the aforementioned existing technologies all suffer from problems such as poor emulsion stability and poor membrane mechanical properties. Therefore, there is an urgent need in the field for a method to solve these problems. Summary of the Invention

[0005] To address the problems of bacterial contamination, poor emulsion stability, and poor mechanical properties of waterborne polyurethane films, this invention provides a method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic waterborne polyurethane emulsion. This invention synthesizes a 2N... + The method of using / 4-OH gemini quaternary ammonium salt as an emulsifier / chain extender / internal crosslinking agent to prepare WPU. This gemini quaternary ammonium salt increases the degree of crosslinking of WPU and imparts excellent antibacterial properties to WPU. The prepared WPU emulsion has excellent dispersibility and antibacterial properties, and the WPU membrane has good mechanical properties.

[0006] This invention utilizes N-methyldiethanolamine and 1,3-dichloropropane to synthesize a compound containing 2N... + Geminid quaternary ammonium salts with 4-OH can be used as hydrophilic chain extenders in the synthesis of waterborne polyurethanes to obtain waterborne polyurethane emulsions with small particle size and good dispersion stability, as well as waterborne polyurethane films with good mechanical properties.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion, comprising the following steps:

[0009] Step 1: N-methyldiethanolamine and 1,3-dichloropropane are dissolved in solvent A and reacted. After the reaction is completed, tetrahydroxygemini quaternary ammonium salt (GQAS) is obtained after purification.

[0010] The reaction formula for GQAS is:

[0011]

[0012] Step 2: The dehydrated polyol, diisocyanate and tetrahydroxy gemini quaternary ammonium salt dissolved in solvent B are mixed and heated under stirring to prepare an isocyanate-terminated prepolymer.

[0013] Step 3: After the isocyanate group content reaches the theoretical value, add small molecule alcohol amine and add catalyst dropwise to react the remaining isocyanate groups completely and then cool down.

[0014] Step 4: Deionized water is slowly added to the reaction system of step 3 under rapid stirring and dispersed evenly to obtain a transparent or semi-transparent emulsion, which is a waterborne polyurethane emulsion.

[0015] Furthermore, in step 1, the molar ratio of N-methyldiethanolamine to 1,3-dichloropropane is 2:1.

[0016] Furthermore, in step 2, the molar ratio of the dehydrated polyol to the diisocyanate is 1:2.5 to 4.

[0017] Furthermore, in step 2, the molar ratio of tetrahydroxygemini quaternary ammonium salt to small molecule alcohol amine in step 3 is 1:1.6 to 3.26, and in step 3, the amount of catalyst added is 5 to 50 ppm of the total reactants.

[0018] Furthermore, in step 2, the polyol is one of polypropylene glycol, polytetrahydrofuran glycol, polyhexamethylene adipate, or polybutylene adipate.

[0019] In step 2, the diisocyanate is one of aromatic diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, or methylene-dicyclohexyl-4,4-diisocyanate.

[0020] In step 3, the small molecule alcohol amine is one of 1,4-butanediol, diethylene glycol, hexanediol, ethylenediamine, diethylenetriamine, and hexanediamine;

[0021] The catalyst in step 3 is one or more of dibutyltin dilaurate, stannous octoate, or triethylenediamine.

[0022] Furthermore, the molecular weight of the polyol is 1000.

[0023] Furthermore, the reaction temperature in step 1 is 70~80℃, and the reaction time is 20h;

[0024] In step 2, the heating and heat preservation reaction temperature is 80-90℃, and the time is 2-5 hours.

[0025] In step 3, the reaction temperature is 60–80°C, the time is 0.5–2 hours, and the cooling process involves lowering the temperature to 40°C.

[0026] Furthermore, in step 1, solvent A is one or more of anhydrous ethanol, deionized water, and dimethyl sulfoxide; in step 2, solvent B is methyl sulfoxide.

[0027] Furthermore, in step 4, the amount of deionized water added is measured based on a solid content of 20%.

[0028] Secondly, the present invention also provides an aqueous polyurethane emulsion, which is prepared by the method of the first aspect.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. Raw materials are readily available, the synthesis scheme is simple, and the cost is low.

[0031] 2. In the traditional synthesis process of cationic waterborne polyurethane, acid needs to be added for neutralization after the addition of amine chain extenders. However, the present invention directly uses quaternary ammonium salt chain extenders, which eliminates the need for subsequent acid neutralization, thus greatly reducing reaction time and organic consumption.

[0032] 3. Emulsion stability > 6 months; film tensile strength 3–12 MPa; elongation at break > 300%. Inhibition rate against Escherichia coli ≥ 99%; inhibition rate against Staphylococcus aureus ≥ 98%.

[0033] 4. This invention uses 2N + Gemini quaternary ammonium salts with 4-OH groups are used as emulsifiers / chain extenders / internal crosslinking agents to modify WPU. Introducing these gemini quaternary ammonium salts as hydrophilic chain extenders into waterborne polyurethane increases its crosslinking degree, resulting in waterborne polyurethane films with excellent mechanical properties. This eliminates the need for additional organic crosslinking agents, reducing organic matter consumption. Furthermore, it imparts good antibacterial properties to the waterborne polyurethane, improves the dispersibility of the emulsion, and enhances the mechanical properties of the waterborne polyurethane film. In traditional cationic waterborne polyurethane synthesis, acid neutralization is required after adding amine chain extenders. However, this invention directly uses quaternary ammonium salt chain extenders, eliminating the need for subsequent acid neutralization, which significantly reduces reaction time and organic matter consumption. Detailed Implementation

[0034] To further illustrate the technical solution of the present invention, the present invention will be further described below through embodiments.

[0035] The polyols (polyester and polyether diol) used in each embodiment need to be dehydrated at 120°C and -0.09 to -0.095 MPa vacuum for 2 hours before use, and then sealed and stored for later use.

[0036] The solvents used in each embodiment were treated with molecular sieves for 3 hours before use. The reactor was equipped with a stirrer, thermometer and condenser.

[0037] Performance tests in each embodiment:

[0038] (1) Particle size test: The particle size of the emulsion was measured using a 90 Plus PALS provided by Brook Haven, USA;

[0039] (2) Antibacterial test: The antibacterial performance was measured by the BSP-150 biochemical incubator and the YXQ-LB-50SII pressure steam sterilizer produced by Shanghai Boxun Medical Biological Instrument Co., Ltd.

[0040] (3) Mechanical property test: 40-50g of the prepared emulsion was slowly poured into a 100×100×1.5mm glass mold and dried at room temperature for 24-48h. Then, it was placed in a vacuum oven at 30-60℃ and dried for 36-48h to obtain a WPU film with a thickness of 0.5-1.0mm. After being placed at room temperature for one to two weeks, its mechanical properties were tested according to the national standard GB / T528-1992.

[0041] Example 1

[0042] A method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion includes the following steps:

[0043] Step 1: Weigh N-methyldiethanolamine and 1,3-dichloropropane at a molar ratio of 2:1, dissolve them in anhydrous ethanol (45% of the total material), and add them to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser. React at 75 °C for 20 h and then stop the reaction. After purification, a white solid is obtained, which is the target product tetrahydroxygemini quaternary ammonium salt (GQAS).

[0044] Step 2: 0.024 mol of dehydrated polytetrahydrofuran ether diol (PTMG, molecular weight 1000), 0.06 mol of isophorone diisocyanate (IPDI), and 0.0082 mol of tetrahydroxygemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide are added to the reactor. The mixture is heated to 80°C under stirring and kept at that temperature for 4 h to obtain isocyanate-terminated polyurethane prepolymer.

[0045] Step 3: Analyze the NCO% reaction to 2.7% using di-n-butylamine titration. Add 0.016 mol of 1,4-butanediol chain extender and dibutyltin dilaurate catalyst (T-12, 40 ppm of the total reactants) to the above prepolymer. React at 80°C for 1 h. After the reaction is complete, analyze the NCO% reaction to 2.7% using di-n-butylamine back titration. After the reaction is complete, cool down to 40°C.

[0046] Step 4: Deionized water with a solid content of 20% is slowly added to the reaction system under rapid stirring and dispersed evenly. After 5 to 10 minutes, a semi-transparent waterborne polyurethane emulsion is obtained.

[0047] Tests showed that the emulsion in this embodiment had a solid content of 20.3%, an average particle size of 266.67 nm, a tensile strength of 3.52 MPa at room temperature, and an elongation at break of 347.43%. It exhibited an inhibition rate of ≥99.13% against Escherichia coli and ≥98.85% against Staphylococcus aureus.

[0048] Example 2

[0049] A method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion includes the following steps:

[0050] Step 1: Weigh N-methyldiethanolamine and 1,3-dichloropropane at a molar ratio of 2:1, dissolve them in anhydrous ethanol (45% of the total material), and add them to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser. React at room temperature (75°C) for 20 h and then stop the reaction. After purification, a white solid is obtained, which is the target product, tetrahydroxygemini quaternary ammonium salt (GQAS).

[0051] Step 2: 0.02 mol of dehydrated polypropylene glycol (molecular weight 1000), 0.06 mol of isoflavone diisocyanate (IPDI) and 0.0082 mol of tetrafunctional gemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide are added to the reactor, heated to 80°C under stirring and kept at the temperature for 4 h to obtain isocyanate-terminated polyurethane prepolymer.

[0052] Step 3: Analyze the NCO% reaction to 3.25% using di-n-butylamine titration. Add 0.0195 mol of 1,4-butanediol chain extender and dibutyltin dilaurate catalyst (T-12, 40 ppm of the total reactants) to the above prepolymer. React at 80°C for 1 h. After the reaction is complete, analyze the NCO% reaction to 3.25% using di-n-butylamine back titration. After the reaction is complete, cool down to 40°C.

[0053] Step 4: Deionized water with a solid content of 20% is slowly added to the reaction system under rapid stirring and dispersed evenly. After 5 to 10 minutes, a semi-transparent waterborne polyurethane emulsion is obtained.

[0054] The emulsion in this embodiment has a solid content of 20.2% and an average particle size of 296.33 nm. The tensile strength of the film at room temperature is 5.27 MPa, and the elongation at break is 298.56%. It exhibits an inhibition rate of ≥99.01% against Escherichia coli and ≥98.04% against Staphylococcus aureus.

[0055] Example 3

[0056] A method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion includes the following steps:

[0057] Step 1: Weigh N-methyldiethanolamine and 1,3-dichloropropane at a molar ratio of 2:1, dissolve them in anhydrous ethanol (45% of the total material), and add them to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser. React at 75 °C for 20 h and then stop the reaction. After purification, a white solid is obtained, which is the target product tetrahydroxygemini quaternary ammonium salt (GQAS).

[0058] Step 2: 0.0171 mol of dehydrated polyhexanediol adipate (molecular weight 1000), 0.06 mol of isoflavone diisocyanate (IPDI), and 0.0082 mol of tetrahydroxygemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide were added to the reactor. The mixture was heated to 80°C under stirring and kept at that temperature for 4 h to obtain isocyanate-terminated polyurethane prepolymer.

[0059] Step 3: Analyze the NCO% reaction to 3.65% using di-n-butylamine titration. Add 0.0265 mol of diethylenetriamine chain extender and dibutyltin dilaurate catalyst (T-12, 40 ppm of the total reactants) to the above prepolymer. React at 80°C for 1 h. After the reaction is complete, analyze the NCO% reaction to 3.65% using di-n-butylamine back titration. After the reaction is complete, cool down to 40°C.

[0060] Step 4: Deionized water with a solid content of 20% is slowly added to the reaction system under rapid stirring and dispersed evenly. After 5 to 10 minutes, a semi-transparent waterborne polyurethane emulsion is obtained.

[0061] The emulsion in this embodiment has a solid content of 20.2% and an average particle size of 341.21 nm. The tensile strength of the film at room temperature is 6.04 MPa, and the elongation at break is 232.63%. It exhibits an inhibition rate of ≥99.56% against Escherichia coli and ≥98.96% against Staphylococcus aureus.

[0062] Example 4

[0063] A method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion includes the following steps:

[0064] Step 1: Weigh N-methyldiethanolamine and 1,3-dichloropropane at a molar ratio of 2:1, dissolve them in anhydrous ethanol (45% of the total material), and add them to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser. React at 75 °C for 20 h and then stop the reaction. After purification, a white solid is obtained, which is the target product tetrahydroxygemini quaternary ammonium salt (GQAS).

[0065] Step 2: 0.0151 mol of dehydrated polytetrahydrofuran ether diol (PTMG, molecular weight 1000), 0.06 mol of aromatic diisocyanate (PDI), and 0.0082 mol of tetrahydroxygemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide are added to the reactor. The mixture is heated to 80°C under stirring and kept at that temperature for 4 hours to obtain isocyanate-terminated polyurethane prepolymer.

[0066] Step 3: Analyze the NCO% reaction to 3.9% using di-n-butylamine titration. Add 0.0285 mol of ethylenediamine chain extender and dibutyltin dilaurate catalyst (T-12, 40 ppm of the total reactants) to the above prepolymer. React at 60°C for 1 h. After the reaction is complete, analyze the NCO% reaction to 3.9% using di-n-butylamine back titration. After the reaction is complete, cool down to 40°C.

[0067] Step 4: Deionized water with a solid content of 20% is slowly added to the reaction system under rapid stirring and dispersed evenly. After 5 to 10 minutes, a semi-transparent waterborne polyurethane emulsion is obtained.

[0068] The emulsion in this embodiment has a solid content of 20.6% and an average particle size of 373.67 nm. The emulsion stability is >6 months. The tensile strength of the film at room temperature is 7.04 MPa, and the elongation at break is 100.43%. It exhibits an inhibition rate of ≥99.13% against Escherichia coli and ≥98.85% against Staphylococcus aureus.

[0069] Example 5

[0070] A method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion includes the following steps:

[0071] Step 1: Weigh N-methyldiethanolamine and 1,3-dichloropropane at a molar ratio of 2:1, dissolve them in anhydrous ethanol (45% of the total material), and add them to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser. Stop the reaction at 75 °C for 24 h to obtain a white solid, which is the target product tetrahydroxygemini quaternary ammonium salt (GQAS).

[0072] Step 2: 0.024 mol of dehydrated polybutylene adipate (molecular weight 1000), 0.06 mol of isophorone diisocyanate (IPDI) and 0.0071 mol of tetrafunctional gemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide are added to the reactor, heated to 80°C under stirring and kept at that temperature for 4 h to obtain isocyanate-terminated polyurethane prepolymer.

[0073] Step 3: Analyze NCO% by di-n-butylamine titration until the reaction reaches 3%. Add 0.0218 mol of diethylene glycol chain extender and dibutyltin dilaurate catalyst (T-12, 40 ppm of the total reactants) to the above prepolymer. React at 80°C for 1 h. After the reaction is complete, analyze NCO% by di-n-butylamine back titration. After the reaction is complete, cool down to 40°C.

[0074] Step 4: Deionized water with a solid content of 20% is slowly added to the reaction system under rapid stirring and dispersed evenly. After 5 to 10 minutes, a semi-transparent waterborne polyurethane emulsion is obtained.

[0075] The emulsion in this embodiment has a solid content of 20.3% and an average particle size of 371.23 nm. The film exhibits a tensile strength of 4.3 MPa and an elongation at break of 316.35% at room temperature; it demonstrates an inhibition rate of ≥99.46% against Escherichia coli and ≥98.63% against Staphylococcus aureus.

[0076] Example 6

[0077] A method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion includes the following steps:

[0078] Step 1: Weigh N-methyldiethanolamine and 1,3-dichloropropane at a molar ratio of 2:1, dissolve them in anhydrous ethanol (45% of the total material), and add them to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser. React at 75 °C for 20 h and then stop the reaction. After purification, a white solid is obtained, which is the target product tetrahydroxygemini quaternary ammonium salt (GQAS).

[0079] Step 2: 0.024 mol of dehydrated polytetrahydrofuran ether diol (PTMG, molecular weight 1000), 0.06 mol of methylene-dicyclohexyl-4,4-diisocyanate (MDI), and 0.0078 mol of tetrahydroxygemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide are added to the reactor. The mixture is heated to 80°C under stirring and kept at that temperature for 4 h to obtain an isocyanate-terminated polyurethane prepolymer.

[0080] Step 3: Analyze the NCO% reaction to 2.8% using di-n-butylamine titration. Add 0.0272 mol of ethylenediamine and dibutyltin dilaurate catalyst (T-12, 40 ppm of the total reactants) to the above prepolymer and react at 60°C for 1 h. After the reaction is complete, analyze the NCO% reaction to 2.8% using di-n-butylamine back titration. After the reaction is complete, cool down to 40°C.

[0081] Step 4: Deionized water with a solid content of 20% is slowly added to the reaction system under rapid stirring and dispersed evenly. After 5 to 10 minutes, a semi-transparent waterborne polyurethane emulsion is obtained.

[0082] The emulsion in this embodiment has a solid content of 20.6% and an average particle size of 393.67 nm. The emulsion stability is >6 months. The tensile strength of the film at room temperature is 5.04 MPa, and the elongation at break is 286.89%. It exhibits an inhibition rate of ≥99.73% against Escherichia coli and ≥98.86% against Staphylococcus aureus.

[0083] Example 7

[0084] A method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion includes the following steps:

[0085] Step 1: Weigh N-methyldiethanolamine and 1,3-dichloropropane at a molar ratio of 2:1, dissolve them in anhydrous ethanol (45% of the total material), and add them to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser. React at 75 °C for 20 h and then stop the reaction to obtain a white solid, which is the target product tetrahydroxygemini quaternary ammonium salt (GQAS).

[0086] Step 2: 0.024 mol of dehydrated polytetrahydrofuran ether diol (PTMG, molecular weight 1000), 0.06 mol of hexamethylene diisocyanate (HDI), and 0.0094 mol of tetrahydroxygemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide are added to the reactor. The mixture is heated to 80°C under stirring and kept at that temperature for 4 h to obtain isocyanate-terminated polyurethane prepolymer.

[0087] Step 3: Analyze the NCO% reaction to 2.3% using di-n-butylamine titration. Add 0.0172 mol hexanediol chain extender and dibutyltin dilaurate catalyst (T-12, 40 ppm of the total reactants) to the above polyurethane prepolymer. React at 80°C for 1 h. After the reaction is complete, analyze the NCO% reaction to 2.3% using di-n-butylamine back titration. After the reaction is complete, cool down to 40°C.

[0088] Step 4: Deionized water with a solid content of 20% is slowly added to the reaction system under rapid stirring and dispersed evenly. After 5 to 10 minutes, a semi-transparent waterborne polyurethane emulsion is obtained.

[0089] The emulsion in this embodiment has a solid content of 20.3% and an average particle size of 296.35 nm. The film exhibits a tensile strength of 8.52 MPa and an elongation at break of 221.69% at room temperature; it also demonstrates an inhibition rate of ≥99.03% against Escherichia coli and ≥99.01% against Staphylococcus aureus.

[0090] Example 8

[0091] A method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion includes the following steps:

[0092] Step 1: Weigh N-methyldiethanolamine and 1,3-dichloropropane at a molar ratio of 2:1, dissolve them in anhydrous ethanol (45% of the total material), and add them to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser. React at 75 °C for 20 h and then stop the reaction to obtain a white solid, which is the target product tetrahydroxygemini quaternary ammonium salt (GQAS).

[0093] Step 2: 0.024 mol of dehydrated polytetrahydrofuran ether diol (PTMG, molecular weight 1000), 0.06 mol of isophorone diisocyanate (IPDI), and 0.01 mol of tetrafunctional gemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide are added to the reactor. The mixture is heated to 80°C under stirring and kept at that temperature for 4 h to obtain isocyanate-terminated polyurethane prepolymer.

[0094] Step 3: Analyze NCO% by di-n-butylamine titration until the reaction reaches 2.2%. Add 0.016 mol hexamethylenediamine chain extender and dibutyltin dilaurate catalyst (T-12, 40 ppm of the total reactants) to the above prepolymer. React at 80°C for 1 h. After the reaction is complete, analyze NCO% by di-n-butylamine back titration. After the reaction is complete, cool down to 40°C.

[0095] Step 4: Deionized water with a solid content of 20% is slowly added to the reaction system under rapid stirring and dispersed evenly. After 5 to 10 minutes, a semi-transparent waterborne polyurethane emulsion is obtained.

[0096] The emulsion in this embodiment has a solid content of 20.3% and an average particle size of 296.35 nm. The tensile strength of the film at room temperature is 12.3 MPa, and the elongation at break is 169.32%. It exhibits an inhibition rate of ≥99.56% against Escherichia coli and ≥99.11% against Staphylococcus aureus.

[0097] Comparison Example 1

[0098] Step 1: 0.02 mol of dehydrated polytetrahydrofuran ether diol (PTMG, molecular weight 1000), 0.06 mol of isoflavone diisocyanate (IPDI), and 0.0082 mol of N-methyldiethanolamine were added to a reactor. The mixture was heated to 80°C with stirring and kept at that temperature for 4 hours. During the reaction, an appropriate amount of acetone was added to reduce the viscosity according to the viscosity, and an isocyanate-terminated polyurethane prepolymer was obtained. The NCO% was analyzed by di-n-butylamine titration to the theoretical value.

[0099] Step 2: Add 0.0318 mol of 1,4-butanediol chain extender and dibutyltin dilaurate catalyst (T-12, 40 ppm of the total reactants) to the above prepolymer, and react at 80°C for 1 h. After the reaction is completed, analyze the NCO% content by di-n-butylamine back titration. After it reaches the theoretical value, cool down to 40°C.

[0100] Step 3: Add 0.0082 mol of glacial acetic acid to the reaction system and neutralize the reaction at 40°C for 15 min. After the reaction is complete, cool down to 35°C.

[0101] Step 4: Deionized water with a solid content of 20% is slowly added to the reaction system under rapid stirring and dispersed evenly. The temperature is raised to 55°C, and the solvent is removed under vacuum at 55°C for 60 minutes to obtain the waterborne polyurethane emulsion.

[0102] The emulsion solids content of this comparative example was found to be 20.2%. The emulsion stability was poor, with a stability of <1 day.

[0103] The foregoing has shown and described the main features and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0104] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a tetrahydroxygemini quaternary ammonium salt cationic aqueous polyurethane emulsion, characterized in that, Includes the following steps: Step 1: N-methyldiethanolamine and 1,3-dichloropropane are dissolved in solvent A and reacted. After the reaction is completed, the tetrahydroxygemini quaternary ammonium salt is obtained after purification. Step 2: The dehydrated polyol, diisocyanate and tetrahydroxy gemini quaternary ammonium salt dissolved in solvent B are mixed and heated under stirring to prepare an isocyanate-terminated prepolymer. Step 3: After the isocyanate group content reaches the theoretical value, add small molecule alcohol amine and add catalyst dropwise to react the remaining isocyanate groups completely and then cool down. Step 4: Deionized water is slowly added to the reaction system of step 3 under rapid stirring and dispersed evenly to obtain a transparent or semi-transparent emulsion, which is a waterborne polyurethane emulsion.

2. The method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion according to claim 1, characterized in that, In step 1, the molar ratio of N-methyldiethanolamine to 1,3-dichloropropane is 2 to 2.5:

1.

3. The method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion according to claim 1, characterized in that, In step 2, the molar ratio of the dehydrated polyol to the diisocyanate is 1:2.5 to 4.

4. The method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion according to claim 1, characterized in that, In step 2, the molar ratio of tetrahydroxygemini quaternary ammonium salt to small molecule alcohol amine in step 3 is 1:1.6 to 3.49, and the amount of catalyst added in step 3 is 5 to 50 ppm of the total reactants.

5. The method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion according to claim 1, characterized in that, In step 2, the polyol is one or more of polypropylene glycol, polytetrahydrofuran glycol, polyhexamethylene adipate or polybutylene adipate. In step 2, the diisocyanate is an aromatic diisocyanate, and one or more of isophorone diisocyanate, hexamethylene diisocyanate, and methylene-dicyclohexyl-4,4-diisocyanate; In step 3, the small molecule alcohol amine is one or more of 1,4-butanediol, diethylene glycol, hexanediol, ethylenediamine, diethylenetriamine, hexanediamine, and isophorone diamine. The catalyst in step 3 is one or more of dibutyltin dilaurate, stannous octoate, or triethylenediamine.

6. The method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion according to claim 1, characterized in that, The polyol has a molecular weight of 1000.

7. The method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion according to claim 1, characterized in that, The reaction temperature in step 1 is 70-80℃, and the reaction time is 20h. In step 2, the heating and heat preservation reaction temperature is 80-90℃, and the time is 2-5 hours. In step 3, the reaction temperature is 60–80°C, the time is 0.5–2 hours, and the cooling process involves lowering the temperature to 40°C.

8. The method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion according to claim 1, characterized in that, In step 1, solvent A is one or more of anhydrous ethanol, deionized water, and dimethyl sulfoxide; in step 2, solvent B is methyl sulfoxide.

9. The method for preparing a tetrahydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion according to claim 1, characterized in that, In step 4, the amount of deionized water added is measured based on a solid content of 20%.

10. The aqueous polyurethane emulsion prepared by the preparation method according to any one of claims 1 to 9.

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