Aqueous polyurethane dispersion, preparation method therefor and use thereof

Abstract

Disclosed is an aqueous polyurethane dispersion. Raw materials for preparing the aqueous polyurethane dispersion comprise a combination of a prepolymer, a chain extender, and an external emulsifier. Raw materials for preparing the prepolymer comprise, in parts by weight, 7-15 parts of isocyanate, 25-43 parts of a polyol, and 0.2-2 parts of a reactive internal emulsifier, wherein the isocyanate comprises 1,5-pentamethylene diisocyanate, and the mass percentage of the 1,5-pentamethylene diisocyanate in the isocyanate is greater than or equal to 30%. The aqueous polyurethane dispersion has the viscosity less than 800 (23°C, mPa.s), the light transmittance greater than 89%, and the water absorption less than 4%.

Description

Aqueous polyurethane dispersion and its preparation method and application Technical Field

[0001] The present application relates to the field of polyurethane technology, for example, an aqueous polyurethane dispersion and its preparation method and application. Background Art

[0002] Waterborne polyurethane dispersion (PUD) is a common film-forming agent widely used in coatings, adhesives, textiles, and other fields. The film component can provide excellent mechanical properties as well as excellent surface decorative properties such as water resistance, wear resistance, and weather resistance.

[0003] During the preparation of conventional waterborne polyurethane dispersions, low-boiling-point solvents such as acetone and methyl ethyl ketone are added to reduce the viscosity of the prepolymer and facilitate its rapid dispersion in water. After dispersion, the low-boiling-point solvent is removed from the dispersion using vacuum distillation, resulting in a waterborne polyurethane dispersion with low solvent residue. However, this process not only requires large amounts of Class A solvents but also requires energy-intensive processes such as distillation and rectification.

[0004] A large number of water-based polyurethane dispersions (PUDs) utilize high-boiling-point, water-soluble aprotic solvents, such as N-methylpyrrolidone, N-ethylpyrrolidone, and dipropylene glycol dimethyl ether, as solvents during the prepolymerization reaction. After PUD preparation, these solvents are retained as a component of the PUD. This high-boiling-point solvent not only reduces the prepolymer viscosity but also, when retained in the dispersion, improves properties such as film-forming and gloss. However, PUDs prepared using this process often have disadvantages such as higher VOC levels, longer drying times, and the potential toxicity of the high-boiling-point solvent.

[0005] CN113039322A prepares a completely solvent-free aqueous polyurethane dispersion. This process utilizes a specialized emulsification process, requiring high-speed dispersion for both mixing the prepolymer with the emulsifier and emulsifying the mixture to produce a stable PUD. The emulsifier solution reacts readily with the prepolymer, causing an increase in viscosity and gelation.

[0006] CN113302221A disperses a prepolymer containing hydrophilic groups into an aqueous solution containing polyaminosulfonates, an alkali metal hydroxide or a non-volatile organic tertiary amine as a neutralizing agent, and other components to produce a high-solids PUD that is essentially free of volatile organic compounds. This preparation method offers advantages such as a simple process, high emulsion solids content, and extremely low TVOC. However, because the carboxyl groups in the PUD prepared by this process are neutralized with an alkali metal or a non-volatile tertiary amine, the carboxyl groups remain in the form of carboxylates after film formation, significantly reducing the water resistance of the coating. Furthermore, it prevents crosslinking with crosslinkers that react with carboxyl groups, such as epoxides, aziridines, and carbodiimides, significantly limiting the application range of this resin.

[0007] Because waterborne polyurethane dispersions in related technologies have problems such as requiring organic solvents for preparation, poor light transmittance, poor water resistance, and high viscosity, developing a waterborne polyurethane dispersion with low viscosity, high light transmittance, and low water absorption, which does not require organic solvents for preparation, is an urgent problem to be solved in this field.

[0008] Summary of the Invention

[0009] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0010] The present application provides an aqueous polyurethane dispersion, a preparation method, and an application thereof. The 1,5-pentamethylene diisocyanate (PDI) content in the isocyanate component of the aqueous polyurethane dispersion prepolymer is greater than 30%, the viscosity is less than 800 (23°C, mPa.s), the transmittance is greater than 89%, and the water absorption is less than 4%.

[0011] In a first aspect, the present application provides an aqueous polyurethane dispersion, wherein the raw materials for preparing the aqueous polyurethane dispersion include a combination of a prepolymer, a chain extender, and an external emulsifier, wherein the raw materials for preparing the prepolymer include, by weight: 7-15 parts of isocyanate (for example, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 13 parts, 15 parts, and specific values ​​between the above values; due to space limitations and for the sake of brevity, this application does not exhaustively list the specific values ​​within the range); 25-43 parts of polyol (for example, 25 parts, 26 parts, 28 parts, 30 parts, 35 parts, 40 parts, 43 parts, and specific values ​​between the above values; due to space limitations and for the sake of brevity, this application does not exhaustively list the specific values ​​within the range); 0.2-2 parts of reactive internal emulsifier (for example, it can be 0.2 parts, 0.3 parts, 0.5 parts, 1 parts, 1.5 parts, 2 parts, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application no longer exhaustively lists the specific values ​​included in the range), the isocyanate includes 1,5-pentamethylene diisocyanate; the mass percentage of 1,5-pentamethylene diisocyanate in the isocyanate is ≥30% (for example, it can be 30%, 35%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, this application no longer exhaustively lists the specific values ​​included in the range).

[0012] Preferably, the isocyanate further comprises any one of isophorone diisocyanate, hexamethylene diisocyanate (HDI) or dicyclohexylmethane diisocyanate, or a combination of at least two thereof.

[0013] PDI is a special linear, odd-numbered carbon diisocyanate with lower crystallinity than HDI. When used in the preparation of prepolymers for waterborne polyurethane dispersions, its relatively low crystallinity can reduce prepolymer viscosity and prevent the prepolymer from structuring and gelling during emulsification, which can lead to emulsification failure. PDI also has higher reactivity than other aliphatic diisocyanates, with its reactivity with water approaching that of aromatic diisocyanates. This high reactivity can accelerate the formation of emulsion particles during phase inversion.

[0014] Preferably, the polyol comprises any one or a combination of at least two of polyester polyol, polycaprolactone polyol, polycarbonate polyol, polyethylene oxide polyol, polypropylene oxide polyol, ethylene oxide-propylene oxide copolymer polyol, polytetramethylene glycol polyol, polypropylene glycol ether polyol, vegetable oil polyol, polyesteramide polyol, polythioether polyol, polyacetal polyol, polyolefin polyol or polysiloxane polyol.

[0015] Preferably, the polyol includes any one of polycarbonate diol, ethylene oxide propylene oxide copolymer diol, polypropylene oxide diol, polytetramethylene oxide diol, polycaprolactone diol, polybutylene adipate diol or polyethylene oxide diol, or a combination of at least two thereof.

[0016] Preferably, the number average molecular weight of the polyol is 300-5000, for example, it can be 300, 400, 500, 1000, 2000, 3000, 4000, 5000, and specific values ​​between the above points. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific points included in the range.

[0017] The number average molecular weight is calculated using the formula Mn = 56.1 * 1000 * f / (acid value + hydroxyl value), where f is the functionality of the polyol. The acid value of polyether polyols is determined using the method in GB / T 12008.5, and the hydroxyl value is determined using the phthalic anhydride method in Method A of GB / T 12008.3. The acid value of polyester polyols is determined using the method in HG / T 2708, and the hydroxyl value is determined using the acetic anhydride-pyridine method in Method A of HG / T 2709.

[0018] Preferably, the reactive internal emulsifier includes a hydrophilic polyol internal emulsifier and a water-soluble polyamine internal emulsifier.

[0019] Preferably, the reactive internal emulsifier includes any one or a combination of at least two of dimethylolpropionic acid, dimethylolbutanoic acid or polyethylene glycol monomethyl ether, sodium 2-[(2-aminoethyl)amino]ethanesulfonate, lysine, 3-(2-aminoethylamino)propane-1-sulfonic acid, 3-(2-aminoethylamino)propane-1-sulfonic acid or sodium N-(2-aminoethyl)-β-alanine.

[0020] Preferably, the raw materials for preparing the prepolymer also include 0-2000ppm of catalyst in parts by weight, for example, it can be 1ppm, 5ppm, 10ppm, 100ppm, 500ppm, 1000ppm, 2000ppm, and specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0021] Preferably, the catalyst comprises an organobismuth catalyst.

[0022] Preferably, the mass percentage of NCO groups in the prepolymer is 5-10%, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, and specific values ​​between the above points. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific points included in the range.

[0023] Preferably, the raw materials for preparing the aqueous polyurethane dispersion further include a neutralizer.

[0024] Preferably, the raw materials for preparing the aqueous polyurethane dispersion include, by weight, 40 parts of a prepolymer, 1.4-2.5 parts of a chain extender (for example, 1.4 parts, 1.5 parts, 1.8 parts, 2 parts, 2.2 parts, 2.5 parts, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application does not exhaustively list the specific values ​​included in the range), 0.1-0.8 parts of a neutralizer (for example, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.6 parts, 0.7 parts, 0.8 parts, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this application does not exhaustively list the specific values ​​included in the range). The specific point values ​​included in the range are exhaustively listed again), 0.2-1 parts of external emulsifier (for example, it can be 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 parts, and specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range), 38-60 parts of water (for example, it can be 38 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, and specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range).

[0025] Preferably, the chain extender comprises any one or a combination of at least two of hydrazine hydrate, ethylenediamine, triethylenetetramine, propylenediamine, butylenediamine, hexamethylenediamine, cyclohexanediamine, piperazine, 2-methylpiperazine, 5-amino-1,3,3-trimethyl-cyclohexanemethylamine or diethylenetriamine.

[0026] Preferably, the neutralizing agent comprises any one or a combination of at least two of alkali metal hydroxide, alkali metal carbonate, organic tertiary amine, alcoholamine, 2-amino-2-methyl-1-propanol, methyldiethanolamine, dimethylethanolamine, diethylethanolamine, triisopropanolamine, ammonia water or triethylamine.

[0027] Preferably, the external emulsifier includes any one of anionic surfactants, cationic surfactants, nonionic surfactants, polyvinyl alcohol or water-soluble cellulose, or a combination of at least two thereof.

[0028] Preferably, the external emulsifier includes any one of sodium salt of fatty alcohol ether sulfate, disodium alkyl polyoxyethylene succinate monoester sulfonate or sodium dodecylbenzenesulfonate, or a combination of at least two thereof.

[0029] In a second aspect, the present application provides a method for preparing the aqueous polyurethane dispersion according to the first aspect, the preparation method comprising:

[0030] (1) mixing isocyanate, polyol, and reactive internal emulsifier, and reacting them to obtain a prepolymer;

[0031] (2) mixing the prepolymer obtained in step (1), a chain extender and an external emulsifier, and reacting them to obtain the aqueous polyurethane dispersion.

[0032] Preferably, the preparation method specifically comprises:

[0033] (1) mixing isocyanate, polyol, reactive internal emulsifier and catalyst, and reacting to obtain a prepolymer;

[0034] (2) mixing the prepolymer obtained in step (1), a chain extender, a neutralizer and an external emulsifier, and reacting them to obtain the aqueous polyurethane dispersion.

[0035] Preferably, the reaction temperature in step (1) is 50-100°C, for example, it can be 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, and specific values ​​between the above points. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific points included in the range.

[0036] Preferably, the reaction time of step (1) is 2-10 h, for example, it can be 2 h, 3 h, 5 h, 8 h, 10 h, and specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0037] Preferably, the mixing in step (2) is carried out under stirring.

[0038] Preferably, the stirring rate is 200-800 rpm, for example, it can be 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, and specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0039] Preferably, the temperature of the reaction in step (2) is 15-40°C, for example, it can be 15°C, 16°C, 20°C, 25°C, 30°C, 35°C, 38°C, 40°C, and specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0040] Preferably, the reaction time of step (2) is 40-120 min, for example, it can be 40 min, 42 min, 45 min, 50 min, 60 min, 62 min, 65 min, 70 min, 75 min, 80 min, 90 min, 100 min, 110 min, 120 min, and specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0041] The introduction of hydrophilic groups into the polyurethane chain segments can impart a certain degree of water dispersibility to the polyurethane. This is achieved in the present application by adding a reactive internal emulsifier. The reactive internal emulsifier can be added in the form of a hydrophilic polyol during the prepolymer stage or in the form of a water-soluble polyamine during the chain extension stage.

[0042] The preparation method specifically comprises:

[0043] (1) reacting polyisocyanate, polyol, and hydrophilic polyol internal emulsifier at 50-100° C. to prepare a polyurethane prepolymer containing PDI, wherein the prepolymer has a low viscosity;

[0044] (2) The polyurethane prepolymer prepared by the above method is slowly added to a water mixture containing a chain extender, a neutralizer, a water-soluble polyamine internal emulsifier, an external emulsifier and other additives at a dispersion speed of 200-800 rpm within 40-120 minutes, and the reaction temperature is controlled below 40°C by the jacket and the prepolymer addition speed until the prepolymer is added, and then the temperature is continued to be controlled and dispersed for more than 60 minutes, and finally filtered and discharged.

[0045] In a third aspect, the present application provides an application of the aqueous polyurethane dispersion as described in the first aspect in coatings, adhesives, and textiles.

[0046] Compared with the related art, this application has the following beneficial effects:

[0047] The present application provides a waterborne polyurethane dispersion, preparation method, and application thereof. When the PDI content in the isocyanate component of the prepolymer is ≥30%, and the polyurethane prepolymer prepared using a high NCO / OH ratio and having a high free isocyanate NCO% content (5% to 10%), the prepolymer has a low viscosity at a lower temperature (50-100°C) and is easy to disperse. The resulting emulsion also has lower viscosity and particle size. When the solid content is 39.98-44.6%, the emulsion has a particle size distribution of 68-102nm and a viscosity of 217-463mPa.s; when the solid content is 55.09-59.3%, the emulsion has a particle size distribution of 186-201nm and a viscosity of 677-792mPa.s. When the PDI content in the isocyanate component of the prepolymer is ≥30%, the water absorption rate of the film is 2.2-3.8%, and the light transmittance is greater than 89%, reaching 89.1-92.1%. When the PDI content is ≥70% and ≤90%, the transmittance is greater than 91%, and can reach 91.1-92.1%.

[0048] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0049] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0050] The experimental materials used in the examples and comparative examples of this application are as follows:

[0051] (1) Polycarbonate diol, brand, UH200, manufacturer, UBE;

[0052] (2) Polypropylene oxide glycol, brand, PPG2000, manufacturer, Guodu Chemical;

[0053] (3) Polytetrahydrofuran diol, brand, PTMG2000, manufacturer, BASF;

[0054] (4) Polycaprolactone diol, brand CAPA2101A, manufacturer: Ingevity; brand CAPA2201A, manufacturer: Ingevity;

[0055] (5) Polybutylene adipate diol, brand, XCP-44, manufacturer, Asahikawa Chemical;

[0056] (6) Polyethylene oxide glycol, brand, PEG1000, manufacturer, Dongda Chemical;

[0057] (7) Dimethylolpropionic acid, manufacturer, Pasto;

[0058] (8) Linear difunctionalized polyethylene glycol monomethyl ether, brand, Ymer N120, manufacturer, Pasto;

[0059] (9) Isophorone diisocyanate, manufacturer: Covestro;

[0060] (10) Dicyclohexylmethane diisocyanate, manufacturer: Covestro;

[0061] (11) 1,6-hexamethylene diisocyanate, manufacturer: Covestro;

[0062] (12) 85% hydrazine hydrate solution, manufacturer: Sinopharm Reagent;

[0063] (13) 95% 2-amino-2-methyl-1-propanol solution, brand, AMP-95, manufacturer, Angus;

[0064] (14) Aqueous solution of disodium alkyl polyoxyethylene ether sulfonate succinate, brand: AEROSOL A-102, manufacturer: Solvay;

[0065] (15) Triethylamine, manufacturer: Sinopharm Reagent;

[0066] (16) Acetone, manufacturer: Sinopharm Reagent;

[0067] (17) Butanediol BDO, manufacturer: Sinopharm Reagent;

[0068] (18) Sodium 2-[(2-aminoethyl)amino]ethanesulfonate, Vestamin A95 (active ingredient 50%), manufacturer: Evonik.

[0069] Example 1

[0070] This embodiment provides an aqueous polyurethane dispersion and a preparation method thereof. The raw materials for preparing the aqueous polyurethane dispersion include: 100g of polycarbonate diol UH200, 300g of polytetramethylene ether glycol PTMEG2000, 10g of dimethylol propionic acid DMPA, 0.5g of organic bismuth catalyst Valikat Bi2010, 70g of 1,5-pentamethylene diisocyanate PDI, 30g of isophorone diisocyanate IPDI, 16.26g of 85% hydrazine hydrate, 6.65g of neutralizer AMP-95, 8g of AEROSOL A102, and 500g of deionized water.

[0071] The preparation method comprises:

[0072] In a flask equipped with a thermometer and mechanical stirring, polycarbonate diol UH200, polytetramethylene ether glycol PTMEG2000, dimethylol propionic acid DMPA, and organic bismuth catalyst Valikat Bi2010 were added, the temperature was raised to 80°C and stirred evenly, and then 1,5-pentamethylene diisocyanate PDI and isophorone diisocyanate IPDI were added. After stirring evenly, the temperature was slowly raised to 93-97°C. After the NCO content was determined to be <5.8% by the di-n-butylamine method, a prepolymer was obtained, and the temperature was lowered to 80°C.

[0073] 85% hydrazine hydrate, neutralizer AMP-95, AEROSOL A102, and deionized water were uniformly mixed and the mixture was temperature-controlled at 18°C. 400 g of the prepolymer prepared above was slowly added to the mixture at a dispersion speed of 450 rpm over 60 minutes while controlling the mixture temperature below 40°C. After the prepolymer was added, the mixture was dispersed for another 60 minutes and filtered through a 200-mesh filter to obtain a waterborne polyurethane dispersion.

[0074] Examples 2-9

[0075] Examples 2-9 provide an aqueous polyurethane dispersion and a preparation method thereof. The differences in the raw materials used in the preparation of the aqueous polyurethane dispersion and that of Example 1 are shown in Table 1. The preparation method is the same as that of Example 1.

[0076] Table 1

[0077] Comparative Example 1

[0078] This comparative example provides an aqueous polyurethane dispersion and a preparation method thereof. The raw materials for preparing the aqueous polyurethane dispersion include: 100g of polycarbonate diol UH200, 300g of polytetramethylene ether glycol PTMEG2000, 10g of dihydroxymethylpropionic acid DMPA, 0.5g of organic bismuth catalyst Valikat Bi2010, 30g of 1,5-pentamethylene diisocyanate PDI, 90g of isophorone diisocyanate IPDI, 16.11g of 85% hydrazine hydrate, 6.65g of neutralizer AMP-95, 8g of AEROSOL A102 and 500g of deionized water.

[0079] The preparation method comprises:

[0080] In a flask equipped with a thermometer and mechanical stirring, polycarbonate diol UH200, polytetramethylene ether glycol PTMEG2000, dimethylol propionic acid DMPA, and organic bismuth catalyst Valikat Bi2010 were added, the temperature was raised to 80°C and stirred evenly, and then 1,5-pentamethylene diisocyanate PDI and isophorone diisocyanate IPDI were added. After stirring evenly, the temperature was slowly raised to 93-97°C. After the NCO content was determined to be 5.8% by the di-n-butylamine method, the prepolymer preparation was completed and the temperature was lowered to 80°C.

[0081] 85% hydrazine hydrate, neutralizer AMP-95, AEROSOL A102, and deionized water were uniformly mixed and the mixture was temperature-controlled at 18°C. 400 g of the prepolymer prepared above was slowly added to the mixture at a dispersion speed of 450 rpm over 60 minutes while controlling the mixture temperature below 40°C. After the prepolymer was added, the mixture was dispersed for another 60 minutes and filtered through a 200-mesh filter to obtain a waterborne polyurethane dispersion.

[0082] Comparative Examples 2-5

[0083] Comparative Examples 2-5 provide an aqueous polyurethane dispersion and a preparation method thereof. The differences in the raw materials used in the preparation of the aqueous polyurethane dispersion and those of Comparative Example 1 are shown in Table 2, and the preparation method is the same as that of Comparative Example 1.

[0084] Table 2

[0085] The performance tests of the aqueous polyurethane dispersions provided in Examples 1-9 and Comparative Examples 1-5 were performed as follows:

[0086] (1) Viscosity: measured using Brookfield DV2T;

[0087] (2) Particle size: measured using a Malvern laser particle size analyzer;

[0088] (3) Water absorption: The dried and weighed film was immersed in water for 1 h, and the water absorption of the film was measured. Film preparation: The dispersion was applied to a glass slide with a thickness of 400-600 μm, and then dried at room temperature for 24 h, and then dried in an oven at 80 °C for 8 h to prepare a film with a dry film thickness of about 300 μm.

[0089] (4) Light transmittance: measured using the GB / T2410-2008 method;

[0090] (5) Solid content: determined according to GB-T1725-2007.

[0091] The performance tests were conducted on the aqueous polyurethane dispersions provided in Examples 1-9 and Comparative Examples 1-5. The test results are shown in Tables 3-4:

[0092] Table 3

[0093] Table 4

[0094] From the data in Tables 3-4, Examples 1-9 show that when the solid content is 39.98-49.83%, the particle size distribution of the emulsion is 68-118 nm, and the viscosity is 217-632 mPa.s; when the solid content is 50.42-59.3%, the particle size distribution of the emulsion is 136-201 nm, and the viscosity is 677-792 mPa.s. When the PDI content in the prepolymer isocyanate component is ≥30% and less than 90%, the transmittance of the film gradually increases from about 89% to 92% and has the highest transmittance of 92.1% when the PDI content is 75%. At the same time, as the amount of PDI increases, the water absorption rate of the film decreases rapidly and stabilizes at a lower level. When PDI is omitted from the formulation, the particle size of Comparative Example 1 is large, the viscosity of Comparative Example 2 is too high and the product lacks fluidity, the prepolymer of Comparative Example 3 is too viscous and cannot be dispersed, and the emulsion of Comparative Example 4 gels and fails when approximately 50% of the prepolymer is added during the emulsification process. In Comparative Example 5, the amount of internal emulsifier used exceeds the preferred range, and no external emulsifier is added, resulting in a relatively large particle size, high water absorption, and low light transmittance. Compared to the linear 1,6-hexamethylene diisocyanate with an even number of carbon atoms, the linear 1,5-pentamethylene diisocyanate with an odd number of carbon atoms used in the PUD of this application has low crystallinity. Furthermore, compared to isophorone diisocyanate and dicyclohexylmethane diisocyanate, it has higher crystallinity and shorter molecular segments. Shorter molecular segments and lower crystallinity can help the emulsion form smaller particles and lower viscosity at the same solids content. Smaller particle size and appropriate crystallinity can significantly improve the film-forming tightness of the resin, thereby achieving higher water resistance. When the PDI content is less than 30%, the phase inversion rate slows down, resulting in larger emulsion particle size. Compared with PDI, HDI's high crystallinity leads to severe crystallization during the prepolymer preparation process, resulting in extremely high prepolymer viscosity. When prepolymers containing a large amount of HDI are dispersed, the high crystallinity prevents phase inversion and causes gelation.

[0095] The applicant declares that while the above-mentioned embodiments are used to illustrate the aqueous polyurethane dispersion, preparation method, and application thereof, this application is not limited to the above-mentioned embodiments, and does not necessarily rely on the above-mentioned embodiments for implementation. Persons skilled in the art should understand that any improvements to this application, equivalent replacements for raw materials in the product, addition of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of this application.

Claims

1. An aqueous polyurethane dispersion, wherein: The raw materials for preparing the aqueous polyurethane dispersion include a combination of a prepolymer, a chain extender and an external emulsifier. The raw materials for preparing the prepolymer include, by weight, 7-15 parts of isocyanate, 25-43 parts of polyol, and 0.2-2 parts of a reactive internal emulsifier. The isocyanate includes 1,5-pentamethylene diisocyanate; the mass percentage of 1,5-pentamethylene diisocyanate in the isocyanate is ≥30%.

2. The aqueous polyurethane dispersion according to claim 1, wherein The isocyanate further comprises any one of isophorone diisocyanate, hexamethylene diisocyanate or dicyclohexylmethane diisocyanate or a combination of at least two thereof.

3. The aqueous polyurethane dispersion according to claim 1 or 2, wherein The polyol includes any one of polyester polyol, polycaprolactone polyol, polycarbonate polyol, polyethylene oxide polyol, polypropylene oxide polyol, ethylene oxide-propylene oxide copolymer polyol, polytetramethylene glycol polyol, polypropylene glycol ether polyol, vegetable oil polyol, polyesteramide polyol, polythioether polyol, polyacetal polyol, polyolefin polyol or polysiloxane polyol, or a combination of at least two thereof.

4. The aqueous polyurethane dispersion according to claim 3, wherein The polyol includes any one of polycarbonate diol, ethylene oxide propylene oxide copolymer diol, polypropylene oxide diol, polytetramethylene oxide diol, polycaprolactone diol, polybutylene adipate diol or polyethylene oxide diol, or a combination of at least two thereof.

5. The aqueous polyurethane dispersion according to any one of claims 1 to 4, wherein The number average molecular weight of the polyol is 300-5000; Preferably, the reactive internal emulsifier comprises any one of dimethylolpropionic acid, dimethylolbutyric acid, polyethylene glycol monomethyl ether, sodium 2-[(2-aminoethyl)amino]ethanesulfonate, lysine, 3-(2-aminoethylamino)propane-1-sulfonic acid, 3-(2-aminoethylamino)propane-1-sulfonic acid or sodium N-(2-aminoethyl)-β-alaninate, or a combination of at least two thereof; Preferably, the raw materials for preparing the prepolymer further include 0-2000 ppm of catalyst by weight; Preferably, the catalyst comprises an organobismuth catalyst; Preferably, the mass percentage of NCO groups in the prepolymer is 5-10%.

6. The aqueous polyurethane dispersion according to any one of claims 1 to 5, wherein The raw materials for preparing the waterborne polyurethane dispersion also include a neutralizer and a solvent; Preferably, the raw materials for preparing the aqueous polyurethane dispersion include, by weight: 40 parts of prepolymer, 1.4-2.5 parts of chain extender, 0.1-0.8 parts of neutralizer, 0.2-1 parts of external emulsifier, and 38-60 parts of water; Preferably, the chain extender comprises any one or a combination of at least two of hydrazine hydrate, ethylenediamine, triethylenetetramine, propylenediamine, butylenediamine, hexamethylenediamine, cyclohexanediamine, piperazine, 2-methylpiperazine, 5-amino-1,3,3-trimethyl-cyclohexanemethylamine or diethylenetriamine; Preferably, the neutralizing agent comprises any one of alkali metal hydroxide, alkali metal carbonate, organic tertiary amine, alcohol amine, 2-amino-2-methyl-1-propanol, methyldiethanolamine, dimethylethanolamine, diethylethanolamine, triisopropanolamine, ammonia water or triethylamine, or a combination of at least two thereof.

7. The aqueous polyurethane dispersion according to any one of claims 1 to 6, wherein The external emulsifier includes any one or a combination of at least two of anionic surfactants, cationic surfactants, nonionic surfactants, polyvinyl alcohol or water-soluble cellulose; Preferably, the external emulsifier includes any one of sodium salt of fatty alcohol ether sulfate, disodium alkyl polyoxyethylene succinate monoester sulfonate or sodium dodecylbenzene sulfonate, or a combination of at least two thereof.

8. A method for preparing an aqueous polyurethane dispersion as claimed in any one of claims 1 to 7, comprising: (1) mixing isocyanate, polyol and reactive internal emulsifier, reacting to obtain a prepolymer; (2) The prepolymer, chain extender and external emulsifier obtained in step (1) are mixed and reacted to obtain the aqueous polyurethane dispersion.

9. The preparation method according to claim 8, wherein: The preparation method specifically comprises: (1) mixing isocyanate, polyol, reactive internal emulsifier and catalyst, and reacting to obtain a prepolymer; (2) The prepolymer obtained in step (1), a chain extender, a neutralizer and an external emulsifier are mixed and reacted to obtain the aqueous polyurethane dispersion.

10. The preparation method according to claim 8 or 9, wherein: The reaction temperature in step (1) is 50-100°C; Preferably, the reaction time in step (1) is 2-20 hours.

11. The preparation method according to any one of claims 8 to 10, wherein: The mixing in step (2) is carried out under stirring; Preferably, the stirring rate is 200-800 rpm.

12. The preparation method according to any one of claims 8 to 11, wherein: The reaction temperature in step (2) is 15-40°C; Preferably, the reaction time in step (2) is 40-120 min.

13. Use of the aqueous polyurethane dispersion according to any one of claims 1 to 7 in coatings, adhesives and textiles.

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