Polyhydroxy 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 polyhydroxy gemini quaternary ammonium salt cationic waterborne polyurethane emulsion and a preparation method thereof. Aiming at the problems that waterborne polyurethane is intruded by bacteria, the emulsion performance is poor, the film performance is poor and the like, the method comprises the following steps: reacting N-methyldiethanolamine with 1, 3-dichloro-2-propanol by using absolute ethyl alcohol as a solvent, and purifying to obtain gemini quaternary ammonium salt containing a pentahydroxy functional group; the preparation method comprises the following steps: mixing polyol, diisocyanate and a certain amount of gemini quaternary ammonium salt dissolved in a solvent, and carrying out heating and heat preservation reaction under stirring to obtain a polyurethane intermediate; adding an alcohol amine chain extender and a catalyst for reaction, completely reacting the residual amount of NCO, and cooling after the reaction is finished; and finally, adding water, and quickly and uniformly dispersing to obtain the waterborne polyurethane emulsion.

Description

Technical Field

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

[0002] Polyurethane (PU) has attracted attention from the scientific and industrial communities due to the multifunctionality of its original components. It is widely used in foams, composite materials, coatings, adhesives, inks, and other fields. However, polyurethane formulations are made with harmful organic solvents, and the release of large amounts of volatile organic compounds (VOCs) damages air quality and the environment. Waterborne polyurethane, on the other hand, introduces hydrophilic groups into the PU molecular chain. Utilizing the properties of these hydrophilic groups, PU can be uniformly dispersed in water under high-speed stirring. Only a small amount of organic solvent is used in the entire synthesis process, resulting in a product that uses water as a solvent and is virtually harmless to the environment. Waterborne polyurethane has been widely used in textile fabrics, coatings, interior leather, adhesives, and other industries. Pure wet polyurethane (WPU) currently lacks the ability to resist bacterial and viral attacks, thus limiting its application in certain fields. If antibacterial properties could be successfully imparted to WPU, it would have a much broader application prospect. Currently, methods for imparting antibacterial properties to waterborne polyurethanes often employ polyols containing tertiary amines or quaternary ammonium compounds on their main or side chains as cationic chain extenders introduced into the polyurethane molecular chain. The characteristics of these introduced cationic groups are utilized to endow cationic waterborne polyurethanes with antistatic, dustproof, and antibacterial properties. However, quaternary ammonium salts (QAS), as an important raw material for synthesizing cationic waterborne polyurethanes, have limited antibacterial properties, thus easily leading to bacterial growth in WPU. Meanwhile, traditional cationic hydrophilic chain extenders can only impart antibacterial properties to WPU, contain fewer hydrophilic groups, and have limited emulsifying properties, resulting in poor WPU emulsion performance. Therefore, some studies have chosen geminal quaternary ammonium salts (GQAS) as hydrophilic chain extenders to introduce into WPU. CN114409553B discloses a diol monomer containing quaternary ammonium salts with antibacterial function that is introduced into the polyurethane backbone as a chain extender, giving the polyurethane excellent antibacterial properties and effectively inhibiting the invasion of Staphylococcus aureus and Escherichia coli. However, this invention can only provide antibacterial properties to the polyurethane. Although it can ensure the stability of the emulsion, it cannot change the degree of crosslinking of the polyurethane, which will lead to poor performance of the subsequent polyurethane film, thus greatly reducing the service life of WPU.

[0003] Currently, the main method to improve the mechanical properties and water resistance of WPU is through crosslinking modification. Crosslinking modification mainly includes external crosslinking modification and internal crosslinking modification. External crosslinking modification is a modification method that involves adding crosslinking agents in practical applications. Internal crosslinking involves introducing multifunctional monomers into the WPU molecular chain to form a crosslinked or hyperbranched WPU single-component system, which can obtain WPU with a certain degree of branching and crosslinking, thereby improving the water resistance, mechanical properties, and chemical stability of WPU. Its disadvantage is that the viscosity is too high during the reaction process, which may require a large amount of organic solvent to reduce the viscosity. CN116041657B discloses a method for synthesizing an internally crosslinked cationic waterborne polyurethane emulsion. It uses glycidyl ether and diethanolamine to react to synthesize a tetrafunctional crosslinking agent containing a tertiary amino group for synthesizing cationic waterborne polyurethane. The resulting prepolymer has a moderate viscosity. After neutralization and dispersion, a transparent or semi-transparent emulsion with small particle size and good dispersion stability is obtained. At the same time, it can improve the mechanical properties of WPU film and improve water resistance and solvent resistance. However, the added tertiary amine crosslinking agent requires subsequent acid neutralization, which increases organic consumption and synthesis steps. Furthermore, the addition of tetrafunctional crosslinking agents and catalysts can easily lead to intense localized reactions, potentially causing systemic degradation. Summary of the Invention

[0004] To address the problems of bacterial contamination, poor emulsion performance, and poor membrane performance in waterborne polyurethane, this invention provides a polyhydroxy gemini quaternary ammonium salt cationic waterborne polyurethane emulsion and its preparation method. A pentafunctional gemini quaternary ammonium salt chain extender is synthesized and used to prepare WPU. This chain extender increases the crosslinking degree of WPU and imparts excellent antibacterial properties to WPU, resulting in excellent dispersibility of the WPU emulsion and good mechanical properties of the WPU membrane.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention provides a method for preparing a multi-hydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion, comprising the following steps:

[0007] Step 1: N-methyldiethanolamine and 1,3-dichloro-2-propanol are dissolved in a solvent and reacted. After the reaction is completed, the product is purified to obtain a white solid product, namely polyhydroxy gemini quaternary ammonium salt (GQAS).

[0008] The reaction formula for GQAS is:

[0009] .

[0010] Step 2: The dehydrated polyol, diisocyanate and solvent-dissolved polyhydroxy gemini quaternary ammonium salt are mixed and heated under stirring to prepare the isocyanate-terminated prepolymer.

[0011] Step 3: After the NCO% content is analyzed by di-n-butylamine back titration and reaches the theoretical value, a small molecule alcohol amine is added and a catalyst is added dropwise to completely react the remaining NCO. Then, the NCO% content is analyzed by di-n-butylamine back titration until the NCO content is completely reacted and then the temperature is lowered.

[0012] 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 the waterborne polyurethane emulsion.

[0013] This invention utilizes gemini quaternary ammonium salts as hydrophilic chain extenders in waterborne polyurethanes to increase their 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 and enhances the dispersibility of the waterborne polyurethane emulsion. 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, significantly reducing reaction time and organic matter consumption. This invention introduces novel pentafunctional gemini quaternary ammonium salts as hydrophilic chain extenders into waterborne polyurethanes (WPUs), endowing them with antibacterial capabilities while altering their linear crosslinking network.

[0014] Furthermore, in step 1, the molar ratio of N-methyldiethanolamine to 1,3-dichloro-2-propanol is 2:1.

[0015] Furthermore, in step 1, the solvent is one or more of anhydrous ethanol, deionized water, and dimethyl sulfoxide; the reaction temperature is 75°C and the reaction time is 15 hours.

[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 polyol has a molecular weight of 1000 and is one or more of polypropylene glycol, polytetrahydrofuran ether glycol, polyhexamethylene adipate, or polybutylene adipate; the diisocyanate is one or more of aromatic diisocyanates such as toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI), as well as isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), and methylene-dicyclohexyl-4,4-diisocyanate (HMDI).

[0018] Furthermore, in step 2, the solvent is dimethyl sulfoxide; the heating and holding temperature for the reaction is 80°C, and the time is 2–5 hours.

[0019] Furthermore, in step 3, the molar ratio of the small molecule alcohol amine to the polyhydroxy gemini quaternary ammonium salt in step 2 is 1:1.7 to 3.2; the amount of catalyst added is 5 to 50 ppm of the total amount of reactants.

[0020] Furthermore, in step 3, the small molecule alkanolamine is one of 1,4-butanediol, diethylene glycol, hexanediol, ethylenediamine, diethylenetriamine, or hexanediamine; the catalyst is one of dibutyltin dilaurate, stannous octoate, or triethylenediamine.

[0021] Furthermore, in step 3, the reaction temperature is 80°C, the time is 0.5 to 2 hours, and the cooling is performed by lowering the temperature to 40°C.

[0022] The present invention also provides a multi-hydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion, which is prepared by the above preparation method.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. The gemini quaternary ammonium salt synthesized in this invention is a gemini quaternary ammonium salt containing five functionalities. The operation is simple and the product is easy to purify. The product contains five functionalities and can be introduced into waterborne polyurethane as a hydrophilic chain extender to increase its crosslinking degree. No additional organic crosslinking agent is required. After the gemini quaternary ammonium salt is introduced into waterborne polyurethane, the hydrophilic groups of the gemini quaternary ammonium salt give the waterborne polyurethane emulsion good dispersibility and at the same time give the waterborne polyurethane membrane good mechanical properties.

[0025] 2. This invention differs from the traditional waterborne polyurethane synthesis process. Gemini quaternary ammonium salt is introduced as a hydrophilic chain extender into the hydropolymer film, resulting in a tensile strength of 4-13 MPa and an elongation at break of >300%.

[0026] 3. The raw materials of this invention are readily available and the synthesis process is simple. Detailed Implementation

[0027] To further illustrate the technical solution of the present invention, the present invention will be further described below through embodiments.

[0028] 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.

[0029] 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.

[0030] Performance tests in each embodiment:

[0031] (1) Particle size test: The particle size of the emulsion was measured by 90Plus PALS provided by Brook Haven, USA.

[0032] (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.

[0033] (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.

[0034] Example 1

[0035] A method for preparing a crosslinked cationic aqueous polyurethane emulsion using a polyhydroxy gemini quaternary ammonium salt includes the following steps:

[0036] Step 1: N-methyldiethanolamine and 1,3-dichloro-2-propanol were added to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser at a molar ratio of 2:1 and anhydrous ethanol (45% of the total reactants) as solvent. The mixture was reacted at 75 °C for 15 h. After purification, the target product, Gemini Quaternary Ammonium Salt (GQAS), was obtained as a white solid.

[0037] Step 2: 0.024 mol of dehydrated polytetrahydrofuran ether diol (PTMG, molecular weight 1000), 0.06 mol of isoflavone diisocyanate (IPDI), and 0.0082 mol of pentafunctional gemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide were added to the reactor. The mixture was heated to 80°C with stirring and kept at that temperature for 4 h to obtain an isocyanate-terminated intermediate. The NCO% content was determined to be 2.15% by di-n-butylamine back titration.

[0038] Step 3: Then add 0.016 mol of 1,4-butanediol chain extender and 40 ppm of dibutyltin dilaurate catalyst (T-12) to the total amount of reactants. React at 80°C for 1 h. After the reaction is complete, analyze the NCO reaction by di-n-butylamine back titration and then cool down to 40°C.

[0039] Step 4: Deionized water with a solid content of 20% is slowly added to the reaction system under rapid stirring and dispersed evenly to obtain a semi-transparent waterborne polyurethane emulsion.

[0040] Tests showed that the emulsion in this embodiment had a solid content of 20.8%, an average particle size of 66.67 nm, a tensile strength of 4.52 MPa at room temperature, an elongation at break of 367.43%, an inhibition rate of ≥99.56% against Escherichia coli, and an inhibition rate of ≥98.96% against Staphylococcus aureus.

[0041] Example 2

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

[0043] Step 1: N-methyldiethanolamine and 1,3-dichloro-2-propanol were added to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser at a molar ratio of 2:1 and anhydrous ethanol (45% of the total reactants) as solvent. The mixture was reacted at 75 °C for 15 h. After purification, the target product, Gemini Quaternary Ammonium Salt (GQAS), was obtained as a white solid.

[0044] Step 2: 0.02 mol of dehydrated polypropylene glycol (molecular weight 1000), 0.06 mol of isoflavone diisocyanate (IPDI), and 0.0082 mol of pentafunctional gemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide were added to the reactor. The mixture was heated to 80°C with stirring and kept at that temperature for 4 h to obtain an isocyanate-terminated intermediate. The NCO% content was determined to be 2.7 by di-n-butylamine back titration.

[0045] Step 3: Then add 0.0195 mol of 1,4-butanediol chain extender and 40 ppm of dibutyltin dilaurate catalyst (T-12) to the total amount of reactants. React at 80°C for 1 h. After the reaction is complete, analyze the NCO reaction by di-n-butylamine back titration and then 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 to obtain a semi-transparent waterborne polyurethane emulsion.

[0047] Tests showed that the emulsion in this embodiment had a solid content of 20.2%, an average particle size of 130.67 nm, a tensile strength of 6.27 MPa at room temperature, an elongation at break of 342.43%, an inhibition rate of ≥99.69% against Escherichia coli, and an inhibition rate of ≥98.56% against Staphylococcus aureus.

[0048] Example 3

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

[0050] Step 1: N-methyldiethanolamine and 1,3-dichloro-2-propanol were added to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser at a molar ratio of 2:1 and anhydrous ethanol (45% of the total reactants) as solvent. The mixture was reacted at 75 °C for 15 h. After purification, the target product, Gemini Quaternary Ammonium Salt (GQAS), was obtained as a white solid.

[0051] Step 2: 0.0171 mol of dehydrated polytetrahydrofuran ether diol (PTMG, molecular weight 1000), 0.06 mol of methylene-dicyclohexyl-4,4-diisocyanate (HMDI), and 0.0082 mol of pentafunctional gemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide were added to the reactor. The mixture was heated to 80°C with stirring and kept at that temperature for 4 h to obtain an isocyanate-terminated intermediate. The NCO% content was determined to be 3.1% by di-n-butylamine back titration.

[0052] Step 3: Then add 0.0224 mol hexanediol and 40 ppm dibutyltin dilaurate catalyst (T-12) of the total reactant amount, and react at 80℃ for 1 h. After the reaction is complete, analyze the NCO reaction by di-n-butylamine back titration and then cool down to 40℃.

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

[0054] Tests showed that the emulsion in this embodiment had a solid content of 20.6%, an average particle size of 205 nm, a tensile strength of 7.56 MPa at room temperature, an elongation at break of 210.31%, an inhibition rate of ≥99.31% against Escherichia coli, and an inhibition rate of ≥98.36% against Staphylococcus aureus.

[0055] Example 4

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

[0057] Step 1: N-methyldiethanolamine and 1,3-dichloro-2-propanol were added to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser at a molar ratio of 2:1 and anhydrous ethanol (45% of the total reactants) as solvent. The mixture was reacted at 75 °C for 15 h. After purification, the target product, Gemini Quaternary Ammonium Salt (GQAS), was obtained as a white solid.

[0058] Step 2: 0.0151 mol of dehydrated polytetrahydrofuran ether diol (PTMG, molecular weight 1000), 0.06 mol of hexamethylene diisocyanate (HDI), and 0.0082 mol of pentafunctional gemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide were added to the reactor. The mixture was heated to 80°C with stirring and kept at that temperature for 4 h to obtain an isocyanate-terminated intermediate. The NCO% content was determined to be 3.4% by di-n-butylamine back titration.

[0059] Step 3: Then add 0.0248 mol hexamethylenediamine chain extender and 40 ppm dibutyltin dilaurate catalyst (T-12) of the total reactant amount. React at 80℃ for 1 h. After the reaction is complete, analyze the NCO reaction by di-n-butylamine back titration and then cool down to 40℃.

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

[0061] Tests showed that the emulsion in this embodiment had a solid content of 20.6%, an average particle size of 279 nm, a tensile strength of 9.83 MPa at room temperature, an elongation at break of 100.43%, an inhibition rate of ≥99.87% against Escherichia coli, and an inhibition rate of ≥98.65% against Staphylococcus aureus.

[0062] Example 5

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

[0064] Step 1: N-methyldiethanolamine and 1,3-dichloro-2-propanol were added to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser at a molar ratio of 2:1 and anhydrous ethanol (45% of the total reactants) as solvent. The mixture was reacted at 75 °C for 15 h. After purification, the target product, Gemini Quaternary Ammonium Salt (GQAS), was obtained as a white solid.

[0065] Step 2: 0.02 mol of dehydrated polyhexanediol adipate (molecular weight 1000), 0.06 mol of isophorone diisocyanate (IPDI), and 0.0068 mol of pentafunctional gemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide were added to a reactor. The mixture was heated to 80°C with stirring and kept at that temperature for 4 h to obtain an isocyanate-terminated intermediate. The NCO% content was determined to be 3.2% by di-n-butylamine back titration.

[0066] Step 3: Then add 0.023 mol hexanediol chain extender and 40 ppm dibutyltin dilaurate catalyst (T-12) of the total reactant amount, and react at 80℃ for 1 h. After the reaction is complete, analyze the NCO reaction by di-n-butylamine back titration and then cool down to 40℃.

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

[0068] Tests showed that the emulsion in this embodiment had a solid content of 20.2%, an average particle size of 90.36 nm, a tensile strength of 4.27 MPa at room temperature, an elongation at break of 359.46%, an inhibition rate of ≥99.88% against Escherichia coli, and an inhibition rate of ≥98.16% against Staphylococcus aureus.

[0069] Example 6

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

[0071] Step 1: N-methyldiethanolamine and 1,3-dichloro-2-propanol were added to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser at a molar ratio of 2:1 and anhydrous ethanol (45% of the total reactants) as solvent. The mixture was reacted at 75 °C for 15 h. After purification, the target product, Gemini Quaternary Ammonium Salt (GQAS), was obtained as a white solid.

[0072] Step 2: 0.02 mol of dehydrated polytetrahydrofuran ether diol (PTMG, molecular weight 1000), 0.06 mol of toluene diisocyanate (TPDI), and 0.0075 mol of pentafunctional gemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide were added to the reactor. The mixture was heated to 80°C with stirring and kept at that temperature for 4 h to obtain an isocyanate-terminated intermediate. The NCO% content was determined to be 2.9% by di-n-butylamine back titration.

[0073] Step 3: Then add 0.0212 mol of diethylenetriamine chain extender and 40 ppm of dibutyltin dilaurate catalyst (T-12) to the total amount of reactants. React at 80℃ for 1 h. After the reaction is complete, analyze the NCO reaction by di-n-butylamine back titration and then cool down to 40℃.

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

[0075] Tests showed that the emulsion in this embodiment had a solid content of 20.52%, an average particle size of 90.36 nm, a tensile strength of 5.68 MPa at room temperature, an elongation at break of 336.46%, an inhibition rate of ≥99.77% against Escherichia coli, and an inhibition rate of ≥98.33% against Staphylococcus aureus.

[0076] Example 7

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

[0078] Step 1: N-methyldiethanolamine and 1,3-dichloro-2-propanol were added to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser at a molar ratio of 2:1 and anhydrous ethanol (45% of the total reactants) as solvent. The mixture was reacted at 75 °C for 15 h. After purification, the target product, Gemini Quaternary Ammonium Salt (GQAS), was obtained as a white solid.

[0079] Step 2: 0.02 mol of dehydrated polybutylene adipate (molecular weight 1000), 0.06 mol of isoflavone diisocyanate (IPDI), and 0.0089 mol of pentafunctional gemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide were added to the reactor. The mixture was heated to 80°C with stirring and kept at that temperature for 4 h to obtain an isocyanate-terminated intermediate. The NCO% content was determined to be 2.4% by di-n-butylamine back titration.

[0080] Step 3: Then add 0.0212 mol ethylenediamine chain extender and 40 ppm dibutyltin dilaurate catalyst (T-12) of the total reactant amount, and react at 80℃ for 1 h. After the reaction is complete, analyze the NCO reaction by di-n-butylamine back titration and then cool down to 40℃.

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

[0082] Tests showed that the emulsion in this embodiment had a solid content of 20.52%, an average particle size of 150.36 nm, a tensile strength of 10.65 MPa at room temperature, an elongation at break of 286.46%, an inhibition rate of ≥99.71% against Escherichia coli, and an inhibition rate of ≥98.99% against Staphylococcus aureus.

[0083] Example 8

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

[0085] Step 1: N-methyldiethanolamine and 1,3-dichloro-2-propanol were added to a 250 mL three-necked flask equipped with a thermometer, mechanical stirrer and reflux condenser at a molar ratio of 2:1 and anhydrous ethanol (45% of the total reactants) as solvent. The mixture was reacted at 75 °C for 15 h. After purification, the target product, Gemini Quaternary Ammonium Salt (GQAS), was obtained as a white solid.

[0086] Step 2: 0.02 mol of dehydrated polytetrahydrofuran ether diol (PTMG, molecular weight 1000), 0.06 mol of diphenylmethane diisocyanate (MDI), and 0.0095 mol of pentafunctional gemini quaternary ammonium salt dissolved in a certain amount of dimethyl sulfoxide were added to the reactor. The mixture was heated to 80°C with stirring and kept at that temperature for 4 h to obtain an isocyanate-terminated intermediate. The NCO% content was determined to be 2.25% by di-n-butylamine back titration.

[0087] Step 3: Then add 0.0212 mol of diethylene glycol chain extender and 40 ppm of dibutyltin dilaurate catalyst (T-12) to the total amount of reactants. React at 80°C for 1 h. After the reaction is complete, analyze the NCO reaction by di-n-butylamine back titration and then 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 to obtain a semi-transparent waterborne polyurethane emulsion.

[0089] Tests showed that the emulsion in this embodiment had a solid content of 20.52%, an average particle size of 180.96 nm, a tensile strength of 13.62 MPa at room temperature, an elongation at break of 190.46%, an inhibition rate of ≥99.29% against Escherichia coli, and an inhibition rate of ≥98.62% against Staphylococcus aureus.

[0090] Comparative Example

[0091] A method for preparing an aqueous polyurethane emulsion includes the following steps:

[0092] 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, thus obtaining an isocyanate-terminated intermediate. The NCO% content was determined to be 4.1% by di-n-butylamine back titration.

[0093] Step 2: Then add 0.0318 mol of 1,4-butanediol chain extender and 40 ppm of dibutyltin dilaurate catalyst (T-12) to the total amount of reactants. React at 80℃ for 1 h. After the reaction is completed, the NCO% content is analyzed by di-n-butylamine back titration and the temperature is lowered to 40℃ after it reaches the theoretical value.

[0094] 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.

[0095] 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.

[0096] Tests showed that the emulsion solid content was 20.2%, indicating poor emulsion stability (emulsion stability < 1 day).

[0097] 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.

[0098] 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 multi-hydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion, characterized in that, Includes the following steps: Step 1: N-methyldiethanolamine and 1,3-dichloro-2-propanol are dissolved in a solvent and reacted. After the reaction is completed, the product is purified to obtain a white solid product, namely polyhydroxy gemini quaternary ammonium salt. Step 2: The dehydrated polyol, diisocyanate and solvent-dissolved polyhydroxy gemini quaternary ammonium salt are mixed and heated under stirring to prepare the isocyanate-terminated prepolymer. Step 3: After the NCO% content reaches the theoretical value, add small molecule amines and add catalyst dropwise to react. After the remaining NCO% has reacted, 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 the waterborne polyurethane emulsion.

2. The method for preparing a multi-hydroxy 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-dichloro-2-propanol is 2:

1.

3. The method for preparing a polyhydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion according to claim 1, characterized in that, In step 1, the solvent is one or more of anhydrous ethanol, deionized water, and dimethyl sulfoxide; the reaction temperature is 75°C and the reaction time is 15 h.

4. The method for preparing a polyhydroxy 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.

5. The method for preparing a polyhydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion according to claim 1, characterized in that, In step 2, the polyol has a molecular weight of 1000 and is one or more of polypropylene glycol, polytetrahydrofuran ether glycol, polyhexamethylene adipate, or polybutylene adipate; the diisocyanate is an aromatic diisocyanate, and one or more of isophorone diisocyanate, hexamethylene diisocyanate, and methylene-dicyclohexyl-4,4-diisocyanate.

6. The method for preparing a polyhydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion according to claim 1, characterized in that, In step 2, the solvent is dimethyl sulfoxide; the heating and holding temperature for the reaction is 80°C, and the time is 2–5 h.

7. The method for preparing a polyhydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion according to claim 1, characterized in that, In step 3, the molar ratio of the small molecule alcohol amine to the polyhydroxy gemini quaternary ammonium salt in step 2 is 1:1.7 to 3.2; the amount of catalyst added is 5 to 50 ppm of the total amount of reactants.

8. The method for preparing a polyhydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion according to claim 1, characterized in that, In step 3, the small molecule alkanolamine is one of 1,4-butanediol, diethylene glycol, hexanediol, ethylenediamine, diethylenetriamine, or hexanediamine; the catalyst is one of dibutyltin dilaurate, stannous octoate, or triethylenediamine.

9. The method for preparing a polyhydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion according to claim 1, characterized in that, In step 3, the reaction temperature is 80℃ and the time is 0.5 to 2 hours. Cooling is performed by reducing the temperature to 40℃.

10. The multi-hydroxy gemini quaternary ammonium salt cationic aqueous polyurethane emulsion prepared by the preparation method according to any one of claims 1 to 9.