Aqueous polyurethane dispersions, processes for their preparation and use

Abstract

The present application relates to a kind of aqueous polyurethane dispersions and its preparation method and application, the raw materials of the aqueous polyurethane dispersions include polyisocyanate, polyester polyol, hydrophilic chain extender containing sulfonic acid group, optionally small molecule chain extender;With the polyester polyol of specific structure as soft segment, it is prepared with the hydrophilic chain extender containing sulfonic acid group, and the soft and hard segments of molecular chain prepared contain hydrophilic group, and hydrophilic group distribution is more uniform, improves emulsion stability;The adhesive prepared by it is used for shoe glue, keeps initial adhesion while, and brushing is more excellent, also has broad application prospect in other fields requiring brushing.

Description

Technical Field

[0001] This invention belongs to the field of adhesives, specifically relating to an aqueous polyurethane dispersion, its preparation method, and its application. Background Technology

[0002] In shoe manufacturing, adhesives are essential for bonding the outsole and midsole, as well as the sole and upper, or the fabric of the upper itself. Currently, the primary application method is manual brushing. Therefore, brushability is a key indicator of adhesive quality. Smooth brushing reduces the frequency of brush changes, increasing shoemaking efficiency while minimizing costs associated with brush replacements. Conventional methods to improve brushability include reducing emulsion particle size and increasing emulsifier usage. However, reducing particle size leads to higher viscosity, lower yield, and limitations on thickener usage during adhesive preparation. Increasing emulsifier usage, on the other hand, results in decreased viscosity and reduced thickening efficiency – all undesirable outcomes.

[0003] CN120757744A discloses a highly brushable waterborne polyurethane-urea dispersion, its preparation method, and its applications. This method enriches the surface of latex particles with hydrophilic ionic groups by controlling the reaction sites of hydrophilic or hydrophilic-potential amine compounds with isocyanate groups. Specifically, it involves adding a portion of monofunctional hydrophilic compounds after dispersion, allowing more hydrophilic groups to be freely distributed on the particle surface. Combined with a specific structure of fatty alcohol polyoxyethylene ether, it increases emulsion stability, thereby improving the brushability of the product. However, because this patent incorporates monofunctional hydrophilic groups and has a small molecular weight, its performance may not meet the requirements in some fields where heat resistance is crucial.

[0004] Therefore, developing a waterborne polyurethane product with excellent brushability while maintaining other properties is an urgent problem to be solved in this field. Summary of the Invention

[0005] In view of the above-mentioned shortcomings in the prior art, the present invention aims to provide an aqueous polyurethane dispersion with excellent brushing performance, which can be used as an adhesive.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned aqueous polyurethane dispersion.

[0007] Another object of the present invention is to provide applications of the above-mentioned waterborne polyurethane dispersion.

[0008] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows:

[0009] In a first aspect, the present invention provides an aqueous polyurethane dispersion, wherein the raw materials for preparing the aqueous polyurethane dispersion include polyisocyanate, polyester polyol, hydrophilic chain extender containing sulfonic acid groups, and optionally small molecule chain extender.

[0010] The polyester polyol comprises the structural unit shown in Formula I, the structural unit shown in Formula II, the structural unit shown in Formula III, and optionally the structural unit shown in Formula IV:

[0011]

[0012] Formula I Formula II

[0013]

[0014] Formula III and Formula IV

[0015] In the waterborne polyurethane dispersion provided by the present invention, a polyester polyol with the above-mentioned specific structure is used as a soft segment, which makes the polymer soft segment have a certain degree of hydrophilicity, making the distribution of hydrophilic groups in the molecular chain more uniform and improving the overall stability of the particles.

[0016] In one embodiment, taking the total molar amount of structural units in the polyester polyol as 100%, the molar percentage of the structural unit shown in Formula I is denoted as a, the molar percentage of the structural unit shown in Formula II is denoted as b, the molar percentage of the structural unit shown in Formula III is denoted as c, and the molar percentage of the structural unit shown in Formula IV is denoted as d, wherein 0.1≤a / b≤0.25, d / c≤0.25;

[0017] Optionally, (c+d) > (a+b), and the structural unit shown in Equation IV is an optional structure. When d=0, c>(a+b).

[0018] In the polyester polyol described in this invention, sodium isophthalate sulfonate provides the hydrophilicity of the soft segments, while adipic acid provides the regularity of the chain ends. By controlling the ratio of sodium isophthalate sulfonate to adipic acid in the polyester polyol segments, especially within the range of 0.1 ≤ a / b ≤ 0.25, superior hydrophilicity and stability can be obtained. Furthermore, the introduction of butanediol and hexanediol can improve hydrolysis resistance. In particular, controlling the ratio of butanediol and hexanediol in the polyester polyol segments within the range of d / c ≤ 0.25, while possessing excellent hydrolysis resistance, suitable molecular weight regularity can be obtained, which is beneficial for activation during adhesive use and further improves initial tack.

[0019] The aqueous polyurethane dispersion provided by the present invention further includes the hydrophilic chain extender containing sulfonic acid groups. The presence of the hydrophilic chain extender with sulfonic acid structure in the aqueous polyurethane dispersion enables the polymer hard segments to also have a certain degree of hydrophilicity.

[0020] Compared to existing polyester, polyether, and polycarbonate polyurethanes, this invention is based on the structural design of a special polyester polyol, which gives the waterborne polyurethane dispersion a more uniform distribution of hydrophilic groups and better emulsion stability. The adhesive products prepared from it have better brushability while maintaining other properties, and have broad application prospects in the field of shoe adhesives.

[0021] The following are optional technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be achieved and realized through the following listed technical solutions.

[0022] In this invention, the molecular structure of the polyester polyol includes structural units of Formula I (derived from sodium isophthalate sulfonate), structural units of Formula II (derived from bisaccharide), structural units of Formula III (derived from 1,4-butanediol), and optionally structural units of Formula IV (derived from 1,6-hexanediol). Taking the total molar amount of structural units as 100%, the molar percentages of the four units are denoted as a, b, c, and d, respectively, wherein:

[0023] 0.1≤a / b≤0.25, where a / b can be 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.24 or 0.25, as well as specific point values ​​between the above points. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0024] d / c ≤ 0.25, where d / c can be 0, 0.05, 0.1, 0.15, 0.2 or 0.25, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0025] In one embodiment, the number average molecular weight of the polyester polyol is 1000-3000 g / mol, for example, it can be 1000 g / mol, 1200 g / mol, 1500 g / mol, 2000 g / mol, 2500 g / mol, 3000 g / mol, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0026] The polyester polyols described in this invention have no specific requirements regarding their source. Polyester polyols meeting the above structural requirements can be obtained through ordinary commercial purchases or custom-made methods; they can also be prepared by any feasible method, including conventional methods in the art, or improved methods based on conventional methods in the art. In specific applications, for example, they can be obtained by conventional esterification reactions of carboxylic acids (including sodium isophthalate sulfonate and adipic acid) and alcohols (including 1,4-butanediol and optionally 1,6-hexanediol). The esterification process, in which carboxylic acids and / or anhydrides are dehydrated with polyols in the presence of a catalyst to produce esters and water, is a well-known process in the art. Methods disclosed in patents CN121824930 and CN120888049 can also be referenced. Based on this, this invention obtains the polyester polyols of this invention by controlling process parameters and combining them with specific catalyst selection, such as tetraisopropyl titanate. Further details are omitted here.

[0027] In one embodiment, based on the total mass of the polyisocyanate, polyester polyol, hydrophilic chain extender containing sulfonic acid groups, and small molecule chain extender as 100%, the mass percentage of the polyisocyanate is 8.0-15.0%, for example, it can be 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5%, or 15.0%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but preferably 9.0-13.0%.

[0028] In one embodiment, based on the total mass of the polyisocyanate, polyester polyol, hydrophilic chain extender containing sulfonic acid groups, and small molecule chain extender as 100%, the mass percentage of the polyester polyol is 83-92%, for example, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, or 92%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but 84-91% is preferred.

[0029] In one embodiment, based on the total mass of the polyisocyanate, polyester polyol, hydrophilic chain extender containing sulfonic acid groups, and small molecule chain extender as 100%, the mass percentage of the hydrophilic chain extender containing sulfonic acid groups is 0.2-4%, for example, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.3%, 1.5%, 2%, 2.5%, 3%, 3.5%, 3.8%, or 4.0%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but preferably 0.3-3.5%.

[0030] In one embodiment, based on the total mass of the polyisocyanate, polyester polyol, hydrophilic chain extender containing sulfonic acid groups, and small molecule chain extender as 100%, the mass percentage of the small molecule chain extender is 0-3%, for example, it can be 0, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, or 3%, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but preferably 0-2%.

[0031] In one embodiment, the polyisocyanate is selected from one or more of hexamethylene diisocyanate, isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, pentamethylene diisocyanate, tetramethylene diisocyanate, 1,4-cyclohexane diisocyanate, 2,2-diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, and 2,4-diphenylmethane diisocyanate, preferably hexamethylene diisocyanate and / or isophorone diisocyanate.

[0032] In one embodiment, the hydrophilic chain extender containing a sulfonic acid group is selected from diaminosulfonic acid and its salts, preferably one or more of N-(2-aminoethyl)-2-aminoethanesulfonic acid and its alkali metal salts and / or ammonium salts, N-(2-aminoethyl)-2-aminobutyric acid and its alkali metal salts and / or ammonium salts, N-(2-aminoethyl)-3-aminopropanesulfonic acid and its alkali metal salts and / or ammonium salts, and more preferably sodium N-(2-aminoethyl)-2-aminoethanesulfonate.

[0033] In one embodiment, the small molecule chain extender is selected from one or more of ethylenediamine, isophorone diamine, 1,6-hexamethylenediamine, 4,4'-diaminodicyclohexylmethane, N-(2-hydroxyethyl)ethylenediamine, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, preferably N-(2-hydroxyethyl)ethylenediamine and / or N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0034] In one embodiment, the raw materials for preparing the aqueous polyurethane dispersion further include a catalyst.

[0035] In this invention, the type of catalyst is not specifically limited, and any catalyst known in the art that can catalyze the reaction of active hydrogen with NCO groups to generate carbamate groups is applicable to this invention;

[0036] Optionally, the catalyst is selected from organobismuth catalysts and / or organotin catalysts, including but not limited to: Bi@8108 (Leading Chemical Company), dimethyltin dinedecanoate, dibutyltin dilaurate, and dioctyltin dilaurate, with Bi@8108 (Leading Chemical Company) being preferred.

[0037] Optionally, based on the total mass of the polyisocyanate, polyester polyol, hydrophilic chain extender containing sulfonic acid groups, and small molecule chain extender, the mass percentage of the catalyst is ≤500ppm, for example, it can be 0, 5ppm, 10ppm, 50ppm, 100ppm, 150ppm, 200ppm, 250ppm, 300ppm, 350ppm, 400ppm, or 450ppm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0038] In one embodiment, the raw materials for preparing the aqueous polyurethane dispersion also include an organic solvent, which is removed from the aqueous polyurethane dispersion by conventional methods such as vacuum distillation after the reaction is completed.

[0039] Optionally, the boiling point of the organic solvent is 40-75°C, for example, it can be 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0040] Optionally, the organic solvent is selected from ketone solvents, preferably acetone and / or butanone, more preferably acetone.

[0041] Optionally, based on the total mass of the polyisocyanate, polyester polyol, hydrophilic chain extender containing sulfonic acid groups, and small molecule chain extender, the amount of organic solvent used is 100-300%, for example, 120%, 150%, 180%, 200%, 220%, 250%, or 280%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0042] In one embodiment, the raw materials for preparing the aqueous polyurethane dispersion include water;

[0043] Optionally, the amount of water used is such that the solid content of the aqueous polyurethane dispersion is 30-60 wt%, for example, 32 wt%, 35 wt%, 40 wt%, 45 wt%, 48 wt%, 50 wt%, 52 wt%, 55 wt%, or 58 wt%, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but preferably 43-53 wt%.

[0044] In one embodiment, the aqueous polyurethane dispersion contains water and has a solid content of 30-60 wt%.

[0045] In one embodiment, the particle size of the solids in the aqueous polyurethane dispersion is 100-500 nm, for example, it can be 120 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm or 450 nm, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but preferably 140-220 nm.

[0046] In a second aspect, the present invention provides a method for preparing an aqueous polyurethane dispersion as described in the first aspect, the preparation method comprising the following steps:

[0047] Polyisocyanate and polyester polyol are polymerized until NCO reaches the theoretical value to generate a diisocyanate-terminated prepolymer.

[0048] The diisocyanate-terminated prepolymer reacts with a hydrophilic chain extender containing sulfonic acid groups and optionally a small molecule chain extender, and is dispersed in water to obtain the aqueous polyurethane dispersion.

[0049] Optionally, the polymerization reaction is carried out in the presence of an organic solvent.

[0050] Optionally, the polymerization reaction is carried out in the presence of a catalyst.

[0051] In one specific embodiment, the preparation method includes the following steps:

[0052] S1: Polyisocyanate, polyester polyol, some organic solvent and catalyst are mixed and polymerized to obtain isocyanate-terminated prepolymer;

[0053] S2: After mixing the isocyanate-terminated prepolymer with the remaining organic solvent, it is then subjected to a chain extension reaction with a hydrophilic chain extender containing sulfonic acid groups and optionally a small molecule chain extender. Water is then added to disperse the mixture to obtain an emulsion. The organic solvent in the emulsion is removed to obtain the aqueous polyurethane dispersion.

[0054] In a preferred embodiment of the present invention, the organic solvent is added in two stages. The first stage serves as the solvent (medium) for the polymerization reaction. Optionally, based on a total organic solvent addition of 100%, the amount of organic solvent added in the polymerization reaction stage of step S1 is 2-30%, for example, 3%, 5%, 10%, 15%, 20%, 22%, 25%, or 28%, and specific values ​​between these values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range. In step S2, the remaining organic solvent is added and mixed with the prepolymer to dilute the prepolymer. For example, the isocyanate-terminated prepolymer can be cooled and then mixed and stirred to ensure complete dissolution.

[0055] In a preferred embodiment, the hydrophilic chain extender containing sulfonic acid groups and the small molecule chain extender mentioned in step S2 are added to the reaction system in solution form, such as an aqueous solution or an acetone solution. The solution concentration is not specifically limited and can be selected as 1-20 times the sum of the mass of the hydrophilic chain extender containing sulfonic acid groups and the small molecule chain extender.

[0056] Specifically, in practical applications, reaction solvents can be selected based on the solubility characteristics of hydrophilic chain extenders containing sulfonic acid groups and small molecule chain extenders. For example, hydrophilic chain extenders containing sulfonic acid groups, aliphatic chain extenders, and alicyclic chain extenders are readily soluble in water but poorly soluble in acetone. Water can be used as a solvent to achieve complete dissolution, ensuring that they participate in the chain extension reaction in a homogeneous manner. However, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is easily hydrolyzed in water. To avoid hydrolysis before the reaction, acetone is suitable as a solvent for dissolution before participating in the chain extension reaction.

[0057] Although water and acetone are miscible, the solvent systems suitable for the two types of chain extenders are significantly different. If they are mixed, some monomers may become ineffective or the dispersion and dissolution may be uneven, which will affect the uniformity of the chain extension reaction. Therefore, the conventional approach in this field is to prepare solutions separately and add them step by step. For example, the first chain extension uses an aqueous phase system and the second chain extension uses an acetone phase system. First, the aqueous phase chain extension introduces hydrophilic groups such as sulfonic acid and other aliphatic and alicyclic small molecule amine chain extenders to construct a hydrophilic macromolecular backbone. Then, the acetone phase chain extension introduces cross-linking structures such as silanes to improve the cross-linking degree of the resin and its heat resistance and hydrolysis resistance.

[0058] In a preferred embodiment, the polymerization reaction temperature in step S1 is 65-85°C, for example, 66°C, 70°C, 72°C, 75°C, 78°C, 80°C, 82°C or 84°C, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but 70-80°C is further preferred.

[0059] In a preferred embodiment, the polymerization reaction time in step S1 is the time required for the NCO groups of the product (diisocyanate-terminated prepolymer) to reach the theoretical value. The theoretical value of NCO groups refers to the mass fraction of NCO (NCO%, based on the total mass of polyisocyanate, polyester polyol, some organic solvent and catalyst) after the hydroxyl groups in the polyester polyol and the NCO in the isocyanate have completely reacted. In practical applications, due to some unavoidable side reactions during the polymerization reaction, the actual NCO value that can be achieved is often slightly lower than the theoretical value of NCO groups.

[0060] In one specific embodiment, the polymerization reaction described in step S1 is stopped when the NCO% in the isocyanate-terminated prepolymer reaches below the theoretical content of 2%. For example, it can be 2%, 1.9%, 1.8%, 1.6%, 1.4%, 1.2%, 1.0%, 0.8%, 0.6%, 0.4%, 0.2%, or 0.1%, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but it can be selected as 0.7-2%.

[0061] In a preferred embodiment, the temperature of the chain extension reaction in step S2 is 30-50°C, for example, 32°C, 35°C, 38°C, 40°C, 42°C, 45°C or 48°C, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but 35-45°C is preferred.

[0062] In a preferred embodiment, the chain extension reaction time in step S2 is 5-40 min, for example, it can be 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, 25 min, 30 min, or 35 min, as well as specific values ​​between the above values. For space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range; preferably, it is 15-25 min. In a preferred embodiment, the pH value of the emulsion in step S2 is 6 < pH < 9, for example, it can be 6.5, 6.8, 7.0, 7.2, 7.2, 7.5, 8, 8.2, 8.5, or 8.8, etc.

[0063] Step S2 of the present invention also includes the process of adding water to disperse and obtain an emulsion, and the process of removing organic solvents from the emulsion. These are conventional operating methods in the field. For example, emulsification methods with water added under high-speed shear conditions, separation methods such as vacuum distillation, etc. can be used.

[0064] It should be noted that the above-described method disclosed in this invention is only used as an example to illustrate one of the preparation methods used to obtain the waterborne polyurethane dispersion of this invention, and the preparation of the waterborne polyurethane dispersion of this invention should not be limited by the steps and parameters in the above method.

[0065] Thirdly, the present invention provides an application of the aqueous polyurethane dispersion as described in the first aspect, wherein the aqueous polyurethane dispersion is used in the field of adhesives, particularly as a shoe adhesive.

[0066] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0067] The waterborne polyurethane dispersion provided by this invention uses polyester polyols with specific structures and molecular weights as soft segments, while hydrophilic groups are also added to the hard segments. Through the structural design of the components and the synergistic effect between the compounded components, the particles of the waterborne polyurethane dispersion have a more uniform distribution of hydrophilic groups, resulting in higher dispersion stability. The adhesives prepared from it maintain their initial tack while exhibiting superior brushability, and have broad application prospects in the field of adhesives, especially shoe adhesives. Detailed Implementation

[0068] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0069] It should be noted that the endpoints and any values ​​of the ranges disclosed in this specification are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising,” “including,” “having,” “containing,” or any other variations thereof as used herein are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements and may also include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.

[0071] The terms "optionally," "optionally," or "any one" mean that the following item or event may or may not occur, and the description includes both scenarios where the event occurs and scenarios where the event does not occur. "And / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / " in this text generally indicates that the preceding and following related objects have an "or" relationship.

[0072] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0073] The main raw materials used in the various embodiments and comparative examples of this invention are sourced as follows. Unless otherwise specified, other raw materials and reagents were obtained through commercially available channels:

[0074] (1) Polyester polyols P1-P11, taking polyester polyol PI as an example, are prepared by the following method:

[0075] Under nitrogen protection, 1108.46g sodium isophthalate sulfonate, 2417.79g adipic acid, 1671.22g 1,4-butanediol, 547.84g 1,6-hexanediol, and 1.72g tetraisopropyl titanate catalyst were added to the polyester synthesis reactor. The material was heated to 140-160℃ and reacted at a constant temperature for 2 hours. Then, the temperature was raised to 220-230℃ and the reaction was continued for 4-6 hours while gradually increasing the vacuum to 10-100kPa(A). When the acid value was less than 0.5mgKOH / g and the hydroxyl value reached 56.1±3mgKOH / g, the reaction was stopped. Nitrogen gas was introduced to restore atmospheric pressure, and the material was cooled and discharged.

[0076] Polyester polyols P2-P11 can be prepared by technicians using the same method as polyester polyol P1, simply by adjusting the amounts of sodium isophthalate sulfonate, adipic acid, 1,4-butanediol, and 1,6-hexanediol, as well as the operating parameters.

[0077] The specific information of the obtained polyester polyols P1-P11 raw materials is shown in Table 1 below. In Table 1, a represents the molar percentage content of sodium isophthalic acid sulfonate polymeric structural unit, b represents the molar percentage content of adipic acid polymeric structural unit, c represents the molar percentage content of 1,4-butanediol polymeric structural unit, d represents the molar percentage content of 1,6-hexanediol polymeric structural unit, and Mn is the number average molecular weight.

[0078] Table 1

[0079] serial number a b c d a / b d / c Mn(g / mol) P1 9% 37% 44% 10% 0.24 0.23 2000 P2 8% 39% 44% 10% 0.20 0.23 2000 P3 8% 39% 44% 9% 0.20 0.2 2000 P4 6% 42% 43% 9% 0.14 0.21 3000 P5 5% 44% 44% 7% 0.1 0.16 3000 P6 4.5% 42% 48.5% 5% 0.1 0.1 1500 P7 4.5% 42% 53.5% 0 0.1 0 1500 P8 2% 45% 44% 9% 0.04 0.2 2000 P9 11% 36% 44% 9% 0.3 0.2 2000 P10 8% 39% 41% 12% 0.2 0.29 2000 P11 0 48% 52% 0 0 0 2000 P12 46% 0 43% 11% / 0.25 2000 P13 9% 38% 0 53% 0.25 / 2000

[0080] (2) Polyisocyanates

[0081] Hexamethylene diisocyanate (HDI): Industrial grade, Wanhua Chemical Group Co., Ltd.

[0082] Isophorone diisocyanate (IPDI): Industrial grade, Wanhua Chemical Group Co., Ltd.

[0083] (3) Hydrophilic chain extenders containing sulfonic acid groups

[0084] Sodium N-(2-aminoethyl)-2-aminoethanesulfonate (VESTAMIN) ® A95): Industrial grade, Evonik Chemicals.

[0085] (4) Small molecule chain extenders

[0086] N-(2-hydroxyethyl)ethylenediamine: Industrial grade, BASF;

[0087] N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane: Industrial grade, Hangzhou Jessica Chemical Co., Ltd.

[0088] (5) Catalyst

[0089] Bismuth neodecanoate, reagent grade, from a leading US chemical company.

[0090] (6) Organic solvents

[0091] Acetone, industrial grade, Wanhua Chemical Group Co., Ltd.

[0092] The testing methods for the basic physical properties of the prepolymer and polyurethane dispersion in the embodiments and comparative examples of this invention are as follows:

[0093] (1) NCO content of diisocyanate-terminated prepolymer: Take 0.5g of prepolymer, add 5mL of chlorobenzene to dissolve it initially, then add 20mL of di-n-butylamine standard solution quantitatively through an NCO titrator, sonicate for 10min, add 50mL of ethanol to the sample, then place the test electrode in the sample solution and use an NCO titrator to perform dilute hydrochloric acid titration test.

[0094] (2) Solid particle size of waterborne polyurethane dispersion: Take 0.1g of the sample to be tested, add it to 100g of deionized water, sonicate for 5min using an ultrasonic machine, and test the particle size using a Malvern particle size analyzer.

[0095] The following will use several embodiments as examples to describe in detail the specific components and preparation methods of the waterborne polyurethane dispersion of the present invention, but the components and preparation methods of the waterborne polyurethane dispersion of the present invention are not limited to these embodiments.

[0096] Example 1

[0097] The steps for preparing the aqueous polyurethane dispersion are as follows:

[0098] 1) Add 350g of polyester polyol P1, 44g of hexamethylene diisocyanate, 0.08g of bismuth neodecanoate, and 59g of acetone to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. React at 80℃. Take a sample every 1 hour to measure NCO%. After 3 hours, when the NCO% reaches below the theoretical content of 1.61%, stop the reaction to obtain the isocyanate-terminated prepolymer.

[0099] 2) Cool the isocyanate-terminated prepolymer to about 56°C, add 414g of acetone and stir to dissolve for 5 minutes. Then add a mixture of 4g of N-(2-hydroxyethyl)ethylenediamine, 2g of N-(2-aminoethyl)-2-aminoethanesulfonate sodium salt and 18g of deionized water. Perform chain extension reaction at 45°C for 20 minutes. Pour into a dispersion cup and add 470g of water under high-speed shear at 1500rpm to obtain a crude emulsion of aqueous polyurethane dispersion. Remove the acetone by vacuum distillation to obtain the aqueous polyurethane dispersion. Add water to make it have a solid content of 49%. The average particle size of the solids in the dispersed phase is measured to be 177nm.

[0100] Example 2

[0101] The steps for preparing the aqueous polyurethane dispersion are as follows:

[0102] 1) Add 320g of polyester polyol P2, 40g of hexamethylene diisocyanate, 0.07g of bismuth neodecanoate, and 37g of acetone to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. React at 85℃. Take a sample every 1 hour to measure NCO%. After 3 hours, when the NCO% reaches below the theoretical content of 2.1%, stop the reaction to obtain the isocyanate-terminated prepolymer.

[0103] 2) Cool the isocyanate-terminated prepolymer to about 56°C, add 511g of acetone and stir to dissolve for 5 minutes. Then add a mixture of 5g N-(2-hydroxyethyl)ethylenediamine, 4g N-(2-aminoethyl)-2-aminoethanesulfonate sodium salt and 30g deionized water. Perform chain extension reaction at 45°C for 10 minutes. Then add a mixture of 1g N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and 5g acetone and continue the reaction for 10 minutes. Pour into a dispersion cup and add 425g of water under high-speed shear at 1500rpm to obtain a crude emulsion of aqueous polyurethane dispersion. Remove the acetone by vacuum distillation to obtain an aqueous polyurethane dispersion. Add water to make it have a solid content of 49%. The average particle size of the solids in the dispersed phase is measured to be 183nm.

[0104] Example 3

[0105] The steps for preparing the aqueous polyurethane dispersion are as follows:

[0106] 1) Add 350g of polyester polyol P3, 23g of hexamethylene diisocyanate, 23g of isophorone diisocyanate, 0.07g of bismuth neodecanoate, and 59g of acetone to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. React at 80℃, taking samples every 1 hour to measure NCO%. After 3 hours, when the NCO% reaches below the theoretical content of 1.21%, stop the reaction to obtain the isocyanate-terminated prepolymer.

[0107] 2) The isocyanate-terminated prepolymer was cooled to about 56°C, and 495g of acetone was added and stirred for 5 minutes to dissolve. Then, a mixture of 2g of N-(2-hydroxyethyl)ethylenediamine, 1g of N-(2-aminoethyl)-2-aminoethanesulfonate sodium, and 12g of deionized water was added. The chain extension reaction was carried out at 40°C for 10 minutes. Then, a mixture of 1g of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and 5g of acetone was added, and the reaction was continued for 10 minutes. The mixture was poured into a dispersion cup, and 476g of water was added under high-speed shear at 1500rpm to obtain a crude emulsion of aqueous polyurethane dispersion. The acetone was removed by vacuum distillation to obtain an aqueous polyurethane dispersion. Water was added to make the solid content 49%. The average particle size of the solids in the dispersed phase was measured to be 187nm.

[0108] Example 4

[0109] The steps for preparing the aqueous polyurethane dispersion are as follows:

[0110] 1) Add 350g of polyester polyol P4, 18g of hexamethylene diisocyanate, 18g of isophorone diisocyanate, 0.08g of bismuth neodecanoate, and 77g of acetone to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. React at 75℃, taking samples every 1 hour to measure NCO%. After 3 hours, when the NCO% reaches below the theoretical content of 1.30%, stop the reaction to obtain the isocyanate-terminated prepolymer.

[0111] 2) The isocyanate-terminated prepolymer was cooled to about 56°C, and 618g of acetone was added and stirred for 5 minutes to dissolve. Then, a mixture of 2g of N-(2-hydroxyethyl)ethylenediamine, 2g of N-(2-aminoethyl)-2-aminoethanesulfonate sodium, and 15g of deionized water was added. The chain extension reaction was carried out at 38°C for 10 minutes. Then, a mixture of 1g of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and 5g of acetone was added, and the reaction was continued for 10 minutes. The mixture was poured into a dispersion cup, and 461g of water was added under high-speed shear at 1500 rpm to obtain a crude emulsion of aqueous polyurethane dispersion. The acetone was removed by vacuum distillation to obtain an aqueous polyurethane dispersion. Water was added to make the solid content 49%. The average particle size of the solids in the dispersed phase was measured to be 179nm.

[0112] Example 5

[0113] The steps for preparing the aqueous polyurethane dispersion are as follows:

[0114] 1) Add 350g of polyester polyol P5, 18g of hexamethylene diisocyanate, 18g of isophorone diisocyanate, 0.08g of bismuth neodecanoate, and 77g of acetone to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. React at 80℃, taking samples every 1 hour to measure NCO%. After 3 hours, when the NCO% reaches below the theoretical content of 1.30%, stop the reaction to obtain the isocyanate-terminated prepolymer.

[0115] 2) Cool the isocyanate-terminated prepolymer to about 56°C, add 618g of acetone and stir to dissolve for 5 minutes. Then add a mixture of 2g N-(2-hydroxyethyl)ethylenediamine, 2g N-(2-aminoethyl)-2-aminoethanesulfonate sodium salt and 15g deionized water. Perform chain extension reaction at 45°C for 15 minutes. Then add a mixture of 1g N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and 5g acetone and continue the reaction for 10 minutes. Pour into a dispersion cup and add 461g of water under high-speed shear at 1500rpm to obtain a crude emulsion of aqueous polyurethane dispersion. Remove the acetone by vacuum distillation to obtain the aqueous polyurethane dispersion. Add water to make it have a solid content of 49%. The average particle size of the solids in the dispersed phase is measured to be 175nm.

[0116] Example 6

[0117] The steps for preparing the aqueous polyurethane dispersion are as follows:

[0118] 1) Add 300g of polyester polyol P6, 45g of hexamethylene diisocyanate, 0.07g of bismuth neodecanoate, and 35g of acetone to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. React at 80℃. Take a sample every 1 hour to measure NCO%. After 3 hours, when the NCO% reaches below the theoretical content of 1.50%, stop the reaction to obtain the isocyanate-terminated prepolymer.

[0119] 2) Cool the isocyanate-terminated prepolymer to about 56°C, add 483g of acetone and stir to dissolve for 5 minutes. Then add a mixture of 12g of N-(2-aminoethyl)-2-aminoethanesulfonate sodium and 24g of deionized water. Perform chain extension reaction at 45°C for 20 minutes. Pour into a dispersion cup and add 404g of water under high-speed shear at 1500rpm to obtain a crude emulsion of aqueous polyurethane dispersion. Remove the acetone by vacuum distillation to obtain the aqueous polyurethane dispersion. Add water to make it have a solid content of 49%. The average particle size of the solids in the dispersed phase is measured to be 155nm.

[0120] Example 7

[0121] The steps for preparing the aqueous polyurethane dispersion are as follows:

[0122] 1) Add 300g of polyester polyol P7, 45g of hexamethylene diisocyanate, 0.07g of bismuth neodecanoate, and 35g of acetone to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. React at 75℃. Take a sample every 1 hour to measure NCO%. After 3 hours, when the NCO% reaches below the theoretical content of 1.50%, stop the reaction to obtain the isocyanate-terminated prepolymer.

[0123] 2) The isocyanate-terminated prepolymer was cooled to about 56°C, and 483g of acetone was added and stirred for 5 min to dissolve. Then, a mixture of 0.5g of N-(2-hydroxyethyl)ethylenediamine, 8g of N-(2-aminoethyl)-2-aminoethanesulfonate sodium, and 28g of deionized water was added. The chain extension reaction was carried out at 45°C for 10 min. Then, a mixture of 1g of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and 5g of acetone was added, and the reaction was continued for 10 min. The mixture was poured into a dispersion cup, and 400g of water was added under high-speed shearing conditions of 1500 rpm to obtain a crude emulsion of aqueous polyurethane dispersion. The acetone was removed by vacuum distillation to obtain an aqueous polyurethane dispersion. Water was added to make the solid content 49%. The average particle size of the solids in the dispersed phase was measured to be 173nm.

[0124] Example 8

[0125] The steps for preparing the aqueous polyurethane dispersion are as follows:

[0126] 1) Add 350g of polyester polyol P8, 44g of hexamethylene diisocyanate, 0.08g of bismuth neodecanoate, and 59g of acetone to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. React at 80℃. Take a sample every 1 hour to measure NCO%. After 3 hours, when the NCO% reaches below the theoretical content of 1.61%, stop the reaction to obtain the isocyanate-terminated prepolymer.

[0127] 2) The isocyanate-terminated prepolymer was cooled to about 56°C, and 414g of acetone was added and stirred for 5 minutes to dissolve. Then, a mixture of 2.5g of N-(2-hydroxyethyl)ethylenediamine, 8g of N-(2-aminoethyl)-2-aminoethanesulfonate sodium, and 32g of deionized water was added. The chain extension reaction was carried out at 45°C for 20 minutes. The mixture was poured into a dispersion cup, and 458g of water was added under high-speed shear at 1500rpm to obtain a crude emulsion of aqueous polyurethane dispersion. The acetone was removed by vacuum distillation to obtain an aqueous polyurethane dispersion. Water was added to make it have a solid content of 49%. The average particle size of the solids in the dispersed phase was measured to be 177nm.

[0128] Example 9

[0129] The steps for preparing the aqueous polyurethane dispersion are as follows:

[0130] 1) Add 350g of polyester polyol P9, 44g of hexamethylene diisocyanate, 0.08g of bismuth neodecanoate, and 59g of acetone to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. React at 80℃. Take a sample every 1 hour to measure NCO%. After 3 hours, when the NCO% reaches below the theoretical content of 1.61%, stop the reaction to obtain the isocyanate-terminated prepolymer.

[0131] 2) Cool the isocyanate-terminated prepolymer to about 56°C, add 414g of acetone and stir to dissolve for 5 minutes. Then add a mixture of 4.5g of N-(2-hydroxyethyl)ethylenediamine, 1g of N-(2-aminoethyl)-2-aminoethanesulfonate sodium salt and 17g of deionized water. Perform chain extension reaction at 45°C for 20 minutes. Pour into a dispersion cup and add 471g of water under high-speed shear at 1500rpm to obtain a crude emulsion of aqueous polyurethane dispersion. Remove the acetone by vacuum distillation to obtain the aqueous polyurethane dispersion. Add water to make it have a solid content of 49%. The average particle size of the solids in the dispersed phase is measured to be 179nm.

[0132] Example 10

[0133] The steps for preparing the aqueous polyurethane dispersion are as follows:

[0134] 1) Add 350g of polyester polyol P10, 44g of hexamethylene diisocyanate, 0.08g of bismuth neodecanoate, and 59g of acetone to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. React at 80℃. Take a sample every 1 hour to measure NCO%. After 3 hours, when the NCO% reaches below the theoretical content of 1.61%, stop the reaction to obtain the isocyanate-terminated prepolymer.

[0135] 2) The isocyanate-terminated prepolymer was cooled to about 56°C, and 414g of acetone was added and stirred for 5 minutes to dissolve. Then, a mixture of 4.5g of N-(2-hydroxyethyl)ethylenediamine, 1g of N-(2-aminoethyl)-2-aminoethanesulfonate sodium, and 17g of deionized water was added. The chain extension reaction was carried out at 45°C for 20 minutes. The mixture was poured into a dispersion cup, and 471g of water was added under high-speed shear at 1500rpm to obtain a crude emulsion of aqueous polyurethane dispersion. The acetone was removed by vacuum distillation to obtain an aqueous polyurethane dispersion. Water was added to make it have a solid content of 49%. The average particle size of the solids in the dispersed phase was measured to be 194nm.

[0136] Comparative Example 1

[0137] Aqueous polyurethane dispersions were prepared according to Example 1, except that polyester polyol P1 was replaced with polyester polyol P11 (a / b=0, d / c=0), and the mixture of 4g N-(2-hydroxyethyl)ethylenediamine and 2g N-(2-aminoethyl)-2-aminoethanesulfonate sodium with 18g deionized water in Example 1 was replaced with a mixture of 0.7g N-(2-hydroxyethyl)ethylenediamine and 14g N-(2-aminoethyl)-2-aminoethanesulfonate sodium with 18g deionized water. Other operations and conditions remained unchanged, and the particle size of the resulting dispersion was 182nm.

[0138] Comparative Example 2

[0139] Aqueous polyurethane dispersions were prepared according to Example 1, except that polyester polyol P1 was replaced with polyester polyol P12 (which has sodium isophthalate sulfonate structural units but no adipic acid structural units, d / c=0.25). Other operations and conditions remained unchanged. When water was added for dispersion, the dispersion was not achieved, and an aqueous polyurethane dispersion could not be obtained.

[0140] Comparative Example 3

[0141] Aqueous polyurethane dispersions were prepared according to Example 1, except that polyester polyol P1 was replaced with polyester polyol P13 (a / b=0.25, with 1,6-hexanediol structural units but no 1,4-butanediol polymerization units), while other operations and conditions remained unchanged. The resulting dispersion had a particle size of 191 nm.

[0142] Test method description:

[0143] The results of tests on brushability, initial tack, and heat resistance are shown in Table 2 below:

[0144] (1) Preparation of adhesive test samples:

[0145] Take 100g of each dispersion sample prepared in Examples 1-10 and Comparative Examples 1-3, add 0.05g of defoamer (BYK024), 0.2g of wetting agent (Tego245), and 0.15g of thickener (VesmodyU604), and stir evenly to prepare the adhesive test samples.

[0146] (2) Preparation of test strips:

[0147] Pretreatment of black rubber strips: After grinding the 60mm×20mm black rubber strips with a grinder, wipe them clean with methyl ethyl ketone (MEK), then wipe them four times with an acetone solution of 2wt% trichloroisocyanurate (oil-based bismuth powder), and bake them in a 70℃ oven for 2 minutes. Remove them and let them cool before use.

[0148] (3) Performance testing:

[0149] Brushability: Treat the rubber surface three times with a water-based treatment agent and dry it. Then place the rubber in an 80℃ oven for 5 minutes. Immediately after taking it out, add about 1g of adhesive to be tested and brush it. Test the number of brushes before particles appear or emulsion breaks.

[0150] Initial tack: Using a brush, the adhesive samples prepared by the dispersions of each embodiment and comparative example were gently brushed onto two pretreated black rubber strips, brushing back and forth three times each. Then, the two black rubber strips were placed in a 65°C oven and dried for 3 minutes. After drying, the two black rubber strips were folded into arcs and then gently touched together perpendicularly before being pulled apart. The tack was scored according to the force required to pull them apart (tack was scored from low to high as follows: A (weak tack, almost impossible to adhere), A+, A++, A+++, A++++, 6 levels).

[0151] Heat resistance: The adhesive samples obtained from the dispersion preparations of each embodiment and comparative example were evenly applied to two pretreated black rubber strips, activated in an oven at 65°C for 3 minutes, removed and bonded together by a press (20kgf×3s), holes were punched under the bonded strips and suspended in an oven at 180°C, 80°C×500g×0.5h, and the length of delamination within 0.5h was measured.

[0152] Table 2 Performance Comparison of Examples and Comparative Examples

[0153] Brushability (times) initial tack Heat resistance (mm) Example 1 30 times A++ 5mm Example 2 28 times A++ 3mm Example 3 28 times A+++ 4mm Example 4 26 times A+++ 2mm Example 5 25 times A+++ 5mm Example 6 26 times A++ 6mm Example 7 27 times A++++ 3mm Example 8 20 times A+++ 4mm Example 9 25 times A+ 9mm Example 10 27 times A+ 10mm Comparative Example 1 5 times A+++ 3mm Comparative Example 2 / / / Comparative Example 3 25 times A 3min full open

[0154] As can be seen from Table 2 above, the dispersion obtained in the embodiments of the present invention, when used as an adhesive, has good brushability and initial tack, while also having good heat resistance, and has great practical application value.

[0155] Compared with the examples, Comparative Example 1 has a soft segment that is not hydrophilic and has poor brushability. Compared with the examples, the small molecule alcohol polymerization units in the polyester polyol in Comparative Example 3 are all 1,6-hexanediol. Although the brushability is better, the adhesion is poor and the bonding is not strong because the molecular chain activation and movement ability is affected during activation. This also leads to poor heat resistance.

[0156] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An aqueous polyurethane dispersion, characterized in that, The raw materials for preparing the aqueous polyurethane dispersion include polyisocyanate, polyester polyol, hydrophilic chain extender containing sulfonic acid groups, and optionally small molecule chain extender. The polyester polyol comprises the structural unit shown in Formula I, the structural unit shown in Formula II, the structural unit shown in Formula III, and optionally the structural unit shown in Formula IV: 。 2. The aqueous polyurethane dispersion according to claim 1, characterized in that, Taking the total molar amount of structural units in the polyester polyol as 100%, the molar percentage of the structural unit shown in Formula I is denoted as a, the molar percentage of the structural unit shown in Formula II is denoted as b, the molar percentage of the structural unit shown in Formula III is denoted as c, and the molar percentage of the structural unit shown in Formula IV is denoted as d, where 0.1≤a / b≤0.25, d / c≤0.25; Optionally, (c+d) > (a+b); and / or, The number average molecular weight of the polyester polyol is 1000-3000 g / mol.

3. The aqueous polyurethane dispersion according to claim 1 or 2, characterized in that, Based on the total mass of the polyisocyanate, polyester polyol, hydrophilic chain extender containing sulfonic acid groups, and small molecule chain extender as 100%, the mass percentage of the polyisocyanate is 8.0-15.0%, preferably 9.0-13.0%; and / or, Based on the total mass of the polyisocyanate, polyester polyol, hydrophilic chain extender containing sulfonic acid groups, and small molecule chain extender as 100%, the mass percentage of the polyester polyol is 83-92%, preferably 84-91%; and / or, Based on the total mass of the polyisocyanate, polyester polyol, hydrophilic chain extender containing sulfonic acid groups, and small molecule chain extender as 100%, the mass percentage of the hydrophilic chain extender containing sulfonic acid groups is 0.2-4%, preferably 0.3-3.5%; and / or, Based on the total mass of the polyisocyanate, polyester polyol, hydrophilic chain extender containing sulfonic acid groups and small molecule chain extender as 100%, the mass percentage of the small molecule chain extender is 0-3%, preferably 0-2%.

4. The aqueous polyurethane dispersion according to any one of claims 1-3, characterized in that, The polyisocyanate is selected from one or more of hexamethylene diisocyanate, isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, pentamethylene diisocyanate, tetramethylene diisocyanate, 1,4-cyclohexane diisocyanate, 2,2-diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, and 2,4-diphenylmethane diisocyanate, preferably hexamethylene diisocyanate and / or isophorone diisocyanate; and / or, The hydrophilic chain extender containing a sulfonic acid group is selected from diaminosulfonic acid and its salts, preferably one or more of N-(2-aminoethyl)-2-aminoethanesulfonic acid and its alkali metal salts and / or ammonium salts, N-(2-aminoethyl)-2-aminobutyric acid and its alkali metal salts and / or ammonium salts, and N-(2-aminoethyl)-3-aminopropanesulfonic acid and its alkali metal salts and / or ammonium salts, more preferably sodium N-(2-aminoethyl)-2-aminoethanesulfonate; and / or, The small molecule chain extender is selected from one or more of ethylenediamine, isophorone diamine, 1,6-hexamethylenediamine, 4,4'-diaminodicyclohexylmethane, N-(2-hydroxyethyl)ethylenediamine, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, preferably N-(2-hydroxyethyl)ethylenediamine and / or N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

5. The aqueous polyurethane dispersion according to any one of claims 1-4, characterized in that, The raw materials for preparing the aqueous polyurethane dispersion include a catalyst; Optionally, the catalyst is selected from organobismuth catalysts and / or organotin catalysts, including but not limited to one or more of Bi@8108, dimethyltin dinedecanoate, dibutyltin dilaurate, and dioctyltin dilaurate, with Bi@8108 being preferred; Optionally, the mass percentage of the catalyst is ≤500 ppm, based on the total mass of the polyisocyanate, polyester polyol, hydrophilic chain extender containing sulfonic acid groups and small molecule chain extender.

6. The aqueous polyurethane dispersion according to any one of claims 1-5, characterized in that, The raw materials for preparing the aqueous polyurethane dispersion include an organic solvent; optionally, the boiling point of the organic solvent is 40-75°C; optionally, the organic solvent is selected from ketone solvents, preferably acetone and / or butanone, more preferably acetone; optionally, based on the total mass of the polyisocyanate, polyester polyol, hydrophilic chain extender containing sulfonic acid groups, and small molecule chain extender, the amount of the organic solvent is 100-300%; and / or, The raw materials for preparing the waterborne polyurethane dispersion include water; optionally, the amount of water used is such that the solid content of the waterborne polyurethane dispersion is 30-60 wt%, preferably 43-53 wt%.

7. A method for preparing the aqueous polyurethane dispersion according to any one of claims 1-6, characterized in that, Includes the following steps: Polyisocyanate and polyester polyol are polymerized until NCO reaches the theoretical value to generate a diisocyanate-terminated prepolymer. The diisocyanate-terminated prepolymer reacts with a hydrophilic chain extender containing sulfonic acid groups and optionally a small molecule chain extender, and is dispersed in water to obtain the aqueous polyurethane dispersion. Optionally, the polymerization reaction is carried out in the presence of an organic solvent; Optionally, the polymerization reaction is carried out in the presence of a catalyst.

8. The preparation method according to claim 7, characterized in that, Includes the following steps: S1: Polyisocyanate, polyester polyol, some organic solvent and catalyst are mixed and polymerized to obtain isocyanate-terminated prepolymer; S2: After mixing the isocyanate-terminated prepolymer with the remaining organic solvent, it is then subjected to a chain extension reaction with a hydrophilic chain extender containing sulfonic acid groups and optionally a small molecule chain extender. Water is then added to disperse the mixture to obtain an emulsion. The organic solvent in the emulsion is removed to obtain the aqueous polyurethane dispersion. Optionally, based on a total organic solvent addition of 100%, the amount of organic solvent added in the polymerization reaction stage of step S1 is 2-30%. Optionally, the hydrophilic chain extender containing sulfonic acid groups and the small molecule chain extender mentioned in step S2 are added to the reaction system in solution form, such as an aqueous solution or an acetone solution.

9. The preparation method according to claim 8, characterized in that, The polymerization reaction in step S1 is carried out at a temperature of 65-85°C, preferably 70-80°C; and / or, The polymerization reaction time in step S1 is the time required for the NCO groups in the product to reach the theoretical value; optionally, the polymerization reaction is stopped when the NCO% in the isocyanate-terminated prepolymer reaches below the theoretical content of 2%, preferably 0.7-2%; and / or, The chain extension reaction in step S2 is carried out at a temperature of 30-50°C, preferably 35-45°C; and / or, The chain extension reaction in step S2 takes 5-40 min, preferably 15-25 min; and / or, The pH value of the emulsion in step S2 is 6 < pH < 9.

10. The use of the aqueous polyurethane dispersion according to any one of claims 1-6 or the aqueous polyurethane dispersion prepared by the method according to any one of claims 7-9 in the field of adhesives, especially as a shoe adhesive.

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