Aqueous polyurethane dispersions, processes for their preparation and use

Abstract

This invention relates to an aqueous polyurethane dispersion, its preparation method, and its application, belonging to the field of waterborne coatings technology. The aqueous polyurethane dispersion of this invention comprises the following raw materials: diisocyanate A, polyisocyanate sulfonic acid modified compound B, polyol C, and amino functional compound E. The aqueous polyurethane dispersion of this invention introduces sulfonic acid groups through polyisocyanate sulfonic acid modified compound B, and controls the proportion of sulfonic acid groups in the solids of the aqueous polyurethane dispersion to be 0.01-0.11 mmol / g, giving the aqueous polyurethane dispersion excellent storage stability. Waterborne two-component coatings formulated with this dispersion have the advantages of good water resistance and long service life.

Description

Technical Field

[0001] This invention relates to the field of waterborne coatings technology, and in particular to a waterborne polyurethane dispersion, its preparation method, and its application. Background Technology

[0002] With increasingly stringent environmental protection requirements in the coatings industry, the application of solvent-based coatings is facing more and more restrictions. Developing waterborne coatings with low volatile organic compounds (VOCs) has become an inevitable trend in the industry. Among them, waterborne coatings with waterborne polyurethane dispersions as the main film-forming substance stand out due to their unique advantages. The resulting coating film not only possesses excellent flexibility and feel but also outstanding weather resistance and chemical resistance. Therefore, it is widely used in coating various substrates such as textiles, leather, wood, and metals, becoming an important force driving the green transformation of the coatings industry.

[0003] The hydrophilic monomers commonly used in the synthesis of waterborne polyurethane dispersions are mainly classified into three categories: carboxylic acids, sulfonic acids, and polyethers. Among these, carboxylic acids and polyethers are primarily used to prepare waterborne polyurethane systems with a solids content of 30-45%. However, when using these two types of monomers to synthesize high-solids products (50-60%), it is often difficult to obtain waterborne polyurethane dispersions that combine good storage stability with uniform dispersion. In contrast, sulfonate groups have a much higher charge density than carboxylic acid groups, resulting in stronger electrostatic interactions with water molecules and the formation of a thicker and more stable hydration layer. Based on this characteristic, only a small amount of sulfonic acid groups needs to be introduced into the polyurethane molecular chain to impart sufficient hydrophilicity to the polymer, ensuring stable dispersion of the system. Therefore, sulfonic acid hydrophilic monomers have become the preferred materials for the synthesis of high-solids waterborne polyurethane dispersions.

[0004] Currently, the commonly used sulfonate hydrophilic agent is an aqueous solution of sodium ethylenediamine isosulfonate, such as Evonik Chemical's trade name VESTAMIN A 95, which typically contains about 50% water. However, when such sulfonate hydrophilic agents are used in the synthesis of aqueous polyurethane dispersions, there are two key problems: first, the water in the system can react with isocyanates; second, the chain extension reaction rate is extremely fast and difficult to control precisely. To alleviate these problems, a large amount of solvent (such as acetone) is usually added. For example, in the embodiments of patent CN101848952B (such as its embodiments 13 and 6), an aqueous polyurethane dispersion with a high solids content of more than 50 wt% was synthesized using an aqueous solution of sodium ethylenediamine isosulfonate as the hydrophilic agent. However, a large amount of acetone was used in the synthesis process, and the resulting aqueous dispersion needed to be deacetoneed under vacuum, which not only reduced production efficiency but also significantly increased energy consumption.

[0005] In summary, existing methods for synthesizing sulfonate-based waterborne polyurethane dispersions all have significant drawbacks. Therefore, developing novel sulfonate hydrophilic agents and applying them to the synthesis of waterborne polyurethane dispersions is of great theoretical and practical significance. Summary of the Invention

[0006] Based on this, the purpose of the present invention is to provide an aqueous polyurethane dispersion, its preparation method and application. The aqueous polyurethane dispersion has a high solids content and excellent storage stability. Waterborne coatings formulated using the aqueous polyurethane dispersion have the advantages of long service life and good water resistance.

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

[0008] This invention provides an aqueous polyurethane dispersion comprising the following raw materials:

[0009] 1) At least one diisocyanate A;

[0010] 2) At least one polyisocyanate sulfonic acid modified compound B;

[0011] 3) At least one polyol C;

[0012] 4) At least one amino-functional compound E;

[0013] in:

[0014] The number-average molecular weight of the polyol C is 500-8000 g / mol;

[0015] The polyisocyanate sulfonic acid modified compound B is obtained by reacting polyisocyanate T with aminosulfonic acid G, wherein the molar ratio of isocyanate groups in polyisocyanate T to the molar ratio of aminosulfonic acid G is 2.4-4.5:1; the aminosulfonic acid G is at least one of 2-cyclohexylaminoethanesulfonic acid, 3-cyclohexylaminopropanesulfonic acid, and 4-cyclohexylaminobutyric acid; and the proportion of sulfonic acid groups in the polyisocyanate sulfonic acid modified compound B to the solids of the aqueous polyurethane dispersion is 0.01-0.11 mmol / g.

[0016] Existing waterborne polyurethane dispersions in this field generally contain raw materials such as diisocyanate A, polyol C, and amino-functionalized compound E. First, diisocyanate A and polyol C are reacted to obtain a polyurethane prepolymer, and then the amino-functionalized compound is used to extend the chain of the polyurethane prepolymer. However, the waterborne polyurethane dispersion of this invention innovatively uses polyisocyanate sulfonic acid modified compound B as one of the raw materials. Introducing polyisocyanate sulfonic acid modified compound B into the polyurethane prepolymer imbues the prepolymer with sulfonic acid groups, resulting in a final waterborne polyurethane dispersion that exhibits both good storage stability and uniform dispersion.

[0017] This invention specifies that the polyisocyanate sulfonic acid modified compound B is obtained by reacting the polyisocyanate T with the aminosulfonic acid G, and specifies that the molar ratio of the isocyanate groups in the polyisocyanate T to the aminosulfonic acid G is 2.4-4.5:1. This ensures that a certain amount of sulfonic acid groups are introduced into the polyisocyanate sulfonic acid modified compound B, and also ensures that the polyisocyanate sulfonic acid modified compound B has an appropriate amount of isocyanate groups. This allows the isocyanate groups in the polyisocyanate sulfonic acid modified compound B to react with hydroxyl-containing substances (such as the polyol C mentioned above and the hydroxyl functional compound D described below) during the synthesis of polyurethane prepolymers, thereby introducing the polyisocyanate sulfonic acid modified compound B into the polyurethane prepolymer. If the ratio is too high, a large number of isocyanate groups in the polyisocyanate T will not be modified by aminosulfonic acid, resulting in the polyisocyanate sulfonic acid modified compound B having a large number of isocyanate groups. This leads to the formation of excessive cross-linking structures during the synthesis of polyurethane prepolymers, resulting in excessive viscosity, or even gelation, ultimately failing to obtain a storage-stable waterborne polyurethane dispersion. If the ratio is too low, a large number of isocyanate groups in the polyisocyanate T will be modified by aminosulfonic acid, resulting in the polyisocyanate sulfonic acid modified compound B having fewer isocyanate groups. That is, there are fewer isocyanate groups that can continue to react with hydroxyl-containing substances (such as the polyol C mentioned above and the hydroxyl functional compound D described below), causing the polyisocyanate sulfonic acid modified compound B to not be well integrated into the polyurethane prepolymer, thus affecting the application performance of the waterborne polyurethane dispersion in waterborne coatings (e.g., poor water resistance of the coating film).

[0018] This invention limits the proportion of sulfonic acid groups in the solids of the waterborne polyurethane dispersion in the polyisocyanate sulfonic acid modified compound B to 0.01-0.11 mmol / g, so that the final waterborne polyurethane dispersion has both good storage stability and dispersion uniformity. If this proportion is too low, too few sulfonic acid groups will be introduced into the polyurethane prepolymer, affecting the storage stability of the waterborne polyurethane dispersion; if this proportion is too high, too many sulfonic acid groups will be introduced, which will also affect the application performance of the waterborne polyurethane dispersion in waterborne coatings (e.g., poor water resistance of the coating film).

[0019] Furthermore, the raw materials for preparing the aqueous polyurethane dispersion also include: 5) hydroxyl functional compound D; the number-average molecular weight of hydroxyl functional compound D is 62-339 g / mol. By adding hydroxyl functional compound D, it can participate in the synthesis of polyurethane prepolymer and adjust the molecular chain structure of the polyurethane prepolymer. Those skilled in the art can choose to add or not add hydroxyl functional compound D according to actual needs. In addition, the structure of hydroxyl functional compound D is not particularly limited; in addition to containing hydroxyl groups, hydroxyl functional compound D may contain carboxyl groups or may not contain carboxyl groups.

[0020] Further, the weight ratio of the diisocyanate A, the polyisocyanate sulfonic acid modified B, the polyol C, the hydroxyl functional compound D, and the amino functional compound E is (4-20):(0.5-5):(20-30):(0-5):(0.2-2).

[0021] Furthermore, the polyisocyanate sulfonic acid modified compound B is obtained by reacting polyisocyanate T with aminosulfonic acid G. During the reaction, amine substances such as N,N-dimethylcyclohexylamine can be added to act as phase transfer catalysts and neutralizers.

[0022] As a preferred embodiment of the present invention, the diisocyanate A is at least one selected from hexamethylene diisocyanate, pentamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, naphthalene-1,5-diisocyanate, phenyl dimethyl diisocyanate, 4,4-dicyclohexylmethane diisocyanate, norbornene diisocyanate, and isophorone diisocyanate.

[0023] As a preferred embodiment of the present invention, the polyisocyanate T is at least one of the following: isocyanurate modified product, urea-formate modified product, and biuret modified product based on hexamethylene diisocyanate (HDI) and / or pentamethylene diisocyanate (PDI). It is clear that the polyisocyanate T is not a diisocyanate monomer, because after a diisocyanate monomer reacts with one molecule of aminosulfonic acid G, only one isocyanate group remains. It is difficult to introduce a sulfonic acid group into the side chain of the polyurethane prepolymer. Instead, the sulfonic acid group is introduced into the end position of the polyurethane prepolymer, which may result in the final polyisocyanate sulfonic acid modified product B failing to meet the requirement that the sulfonic acid group accounts for 0.01-0.11 mmol / g of the solids in the aqueous polyurethane dispersion.

[0024] As a preferred embodiment of the present invention, the number-average molecular weight of the polyol C is more preferably 1000-4000 g / mol.

[0025] As a preferred embodiment of the present invention, the polyol C is a variety of polyols such as polyester polyols, polyether polyols, polycarbonate polyols, polyesteramide polyols, polyacetal polyols, polysulfide polyols, and polybutadiene glycol polyols. These substances can be used alone or in combination of two or more. Polyol C is preferably a polyester polyol, polyether polyol, or polycarbonate polyol that is readily available industrially; the following are representative compounds as examples.

[0026] The aforementioned polyester polyol can be a substance obtained by esterification of a low molecular weight polyol and a polycarboxylic acid.

[0027] As the aforementioned low molecular weight polyols, examples include ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanediol, bisphenol A, hydrogenated bisphenol A, trimethylolpropane, trimethylolethane, pentaerythritol, sorbitol, etc. As polycarboxylic acids that can be used in the manufacture of the aforementioned polyester polyols, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic anhydride, fumaric acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalenedicarboxylic acid, biphenyl dicarboxylic acid, benzotriac, benzopyrene, and anhydrides or ester derivatives of these polycarboxylic acids can also be used. Furthermore, as the aforementioned polyester polyols, polyesters obtained through ring-opening polymerization of cyclic esters such as ε-caprolactone, and their copolyesters, can also be used.

[0028] Furthermore, as a polyether polyol, a substance obtained by addition polymerization of at least one of compounds such as ethylene oxide, propylene oxide, epibutylene oxide, styrene oxide, epichlorohydrin, tetrahydrofuran, and cyclohexane can be used, for example, as an initiator using a compound having at least two active hydrogen atoms as described later. As the aforementioned compound having at least two active hydrogen atoms, examples include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, sucrose, methyl glycol, glycerol, sorbitol, aconitic acid, benzotriic acid, triphenyltriic acid, phosphoric acid, ethylenediamine, propylenediamine, diethylenetriamine, triisopropanolamine, pyrogallol, dihydroxybenzoic acid, hydroxyphthalic acid, and 1,2,3-propanetrithiol.

[0029] In addition, polycarbonate polyols obtained by esterification reactions of carbonic acid and aliphatic polyols can be exemplified by diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol (PTMG), as well as reaction products of dialkyl carbonates such as dimethyl carbonate or cyclic carbonates such as ethylene carbonate.

[0030] As a preferred embodiment of the present invention, the hydroxyl functional compound D is a compound containing at least two hydroxyl groups, preferably at least one of the following: dimethylolpropionic acid, dimethylolbutyric acid, ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanediol, bisphenol A, hydrogenated bisphenol A, trimethylolpropane, trimethylolethane, pentaerythritol, and sorbitol.

[0031] As a preferred embodiment of the present invention, the amino-functional compound E is a compound containing at least one amino group. Preferably, the amino-functional compound E is at least one of ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine, 1,4-cyclohexanediamine, hydrazine, hydrazine hydrate, diethylenetriamine, triethylenetetramine, and hydroxyethylethylenediamine.

[0032] Furthermore, the waterborne polyurethane dispersion also includes a neutralizing agent, and the degree of neutralization of the waterborne polyurethane dispersion is 10-110%. Too low a degree of neutralization will result in poor storage stability of the waterborne polyurethane dispersion, making it prone to stratification and precipitation; too high a degree of neutralization will cause the waterborne polyurethane dispersion, when formulated with a crosslinking agent to form a waterborne coating, to catalyze the side reaction between the crosslinking agent (such as a polyisocyanate crosslinking agent) and water, resulting in a shorter usable time for the waterborne coating. Preferably, the neutralizing agent is at least one selected from N,N-dimethylethanolamine, triethylamine, ammonia, sodium hydroxide, and potassium hydroxide.

[0033] Furthermore, the aqueous polyurethane dispersion further includes water and an organic solvent; the solids content of the aqueous polyurethane dispersion is 30-60 wt%; the content of the organic solvent in the aqueous polyurethane dispersion is 0-10 wt%. The organic solvent may or may not be added. If an organic solvent is added, its content in the aqueous polyurethane dispersion shall not exceed 10 wt%. Excessive organic solvent will result in high VOC content in the aqueous polyurethane dispersion and its applied aqueous coatings, which is detrimental from an environmental perspective. As the organic solvent, any organic solvent that does not hinder the reaction can be used, such as ketones, ethers, acetates, hydrocarbons, chlorinated hydrocarbons, amides, and nitriles. Examples of ketones include acetone, diethyl ketone, methyl ethyl ketone, and methyl isobutyl ketone. Examples of ethers include diethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, tetrahydrofuran, and dioxane. Examples of acetates include ethyl acetate, butyl acetate, and propyl acetate. As hydrocarbons, n-pentane, n-hexane, cyclohexane, n-heptane, benzene, toluene, xylene, etc., can be used. As chlorinated hydrocarbons, carbon tetrachloride, dichloromethane, chloroform, trichloroethane, etc., can be used. As amides, dimethylformamide, N-methylpyrrolidone, N-ethylpyrrolidone, etc., can be used.

[0034] The present invention also provides a method for preparing any of the above-described aqueous polyurethane dispersions, comprising the following steps:

[0035] (1) Add 4-20 parts by weight of the diisocyanate A, 0.5-5 parts by weight of the polyisocyanate sulfonic acid modified B, 20-50 parts by weight of the polyol C, 0-5 parts by weight of the hydroxyl functional compound D, and 0-10 parts by weight of the organic solvent to the reaction vessel, mix evenly, and heat to 50-90℃ to carry out the reaction until the NCO value reaches the theoretical value to obtain the polyurethane prepolymer;

[0036] (2) Disperse the polyurethane prepolymer obtained in step (1) in water (preferably 30-70 parts by weight), and then add 0.2-2 parts by weight of the amino functional compound E to perform aqueous chain extension to obtain the aqueous polyurethane dispersion.

[0037] The method for preparing the aqueous polyurethane dispersion of the present invention includes the following steps: (1) reacting the diisocyanate A, the polyisocyanate sulfonic acid modified B, the polyol C, and the hydroxyl functional compound D to obtain a polyurethane prepolymer; and (2) chain-extending the polyurethane prepolymer with the amino functional compound E to finally obtain the aqueous polyurethane dispersion.

[0038] Furthermore, in step (2), during the process of dispersing the polyurethane prepolymer obtained in step (1) in water, emulsifiers, neutralizers, etc. may also be added. As a preferred method, in step (2), the polyurethane prepolymer obtained in step (1) is dispersed in a mixture of "water, emulsifier, and neutralizer".

[0039] Furthermore, in step (2), water may be added simultaneously when adding the amino-functional compound E. Preferably, in step (2), the amino-functional compound E is added in the form of a mixture of amino-functional compound E and water.

[0040] This invention also provides the application of any of the above-described waterborne polyurethane dispersions in waterborne coatings. Waterborne coatings using the aforementioned waterborne polyurethane dispersions as the main film-forming substance have the advantages of good water resistance and long service life.

[0041] Specifically, the present invention provides a water-based coating, specifically a water-based two-component coating, comprising component A and component B; component A comprises any of the water-based polyurethane dispersions described above; and component B comprises a crosslinking agent.

[0042] As a preferred embodiment of the present invention, the crosslinking agent is a polyisocyanate crosslinking agent containing free NCO groups.

[0043] The present invention also provides a coating film obtained by applying any of the above-described water-based coatings onto a substrate.

[0044] The advantages of this invention compared to existing technologies are as follows:

[0045] The waterborne polyurethane dispersion of the present invention has excellent storage stability, and the waterborne two-component coating formulated with polyisocyanate crosslinking agent has the advantages of good water resistance and long service life. Detailed Implementation

[0046] The present invention is further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention are within the scope of protection claimed by the present invention.

[0047] Example 1

[0048] This embodiment provides an aqueous polyurethane dispersion PU1, which is prepared through the following process:

[0049] (1) Preparation of polyisocyanate sulfonic acid modified compound B1:

[0050] Nitrogen gas was passed through the reaction flask, and 100.0g of Wannate HT-600 (polyisocyanate T, Wanhua Chemical's HDI-based isocyanurate modified product, NCO value 23.0%), 37.9g ​​of 3-cyclohexylaminopropanesulfonic acid (aminosulfonic acid G), and 22.9g of N,N-dimethylcyclohexylamine were added. The mixture was heated to 100℃ and reacted for 6h to obtain a pale yellow, viscous, transparent liquid polyisocyanate sulfonic acid modified product B1.

[0051] Among them, polyisocyanate sulfonic acid modified compound B1 is obtained by reacting polyisocyanate T (Wannate HT-600) with aminosulfonic acid G (3-cyclohexylaminopropanesulfonic acid), wherein the molar ratio of isocyanate groups in polyisocyanate T to aminosulfonic acid G is 3.2:1.

[0052] (2) Preparation of waterborne polyurethane dispersion PU1:

[0053] 500.0 g of polytetramethylene ether glycol (polyol C, number average molecular weight Mn of 2000 g / mol), 5.4 g of dimethylolpropionic acid (hydroxyl functional compound D), 15.2 g of neopentyl glycol (hydroxyl functional compound D), 162.3 g of isoflurane diisocyanate (diisocyanate A), 30.0 g of polyisocyanate sulfonic acid modified compound B1, and 70.0 g of N-ethylpyrrolidone (organic solvent) were added to a reaction vessel. The mixture was stirred and heated to 80 °C until the NCO value reached the theoretical value of 3.5%, thus obtaining a polyurethane prepolymer.

[0054] The above polyurethane prepolymer was dispersed in a mixture consisting of 591.0 g water, 15.0 g Sasol emulsifier Marlipal O13 / 90, and 4.0 g triethylamine. Then, a mixture consisting of 16.0 g hydrazine hydrate (amino-functional compound E) and 80.0 g water was added, and the mixture was stirred for another 30 min to obtain a milky white waterborne polyurethane dispersion PU1.

[0055] In this embodiment, the waterborne polyurethane dispersion PU1 has a solids content of 50 wt% and an organic solvent content of 4.7 wt%. In this embodiment, the sulfonic acid groups in the polyisocyanate sulfonic acid modified B1 account for 0.043 mmol / g of the solids in the waterborne polyurethane dispersion PU1.

[0056] The aqueous polyurethane dispersion PU1 in this embodiment showed no obvious precipitation or stratification after being stored in a 50°C oven for 2 weeks.

[0057] Example 2

[0058] This embodiment provides an aqueous polyurethane dispersion PU2, which is prepared through the following process:

[0059] (1) Preparation of polyisocyanate sulfonic acid modified compound B2:

[0060] Nitrogen gas was passed through the reaction flask, and 100.0 g of Desmodur eco N7300 (polyisocyanate T, Covestro's PDI-based isocyanurate modifier, NCO value 21.5%), 47.2 g of 3-cyclohexylaminoethanesulfonic acid (aminosulfonic acid G), and 30.4 g of N,N-dimethylcyclohexylamine were added. The mixture was heated to 100 °C and reacted for 6 h to obtain a pale yellow, viscous, transparent liquid polyisocyanate sulfonic acid modifier B2.

[0061] Among them, polyisocyanate sulfonic acid modified compound B2 is obtained by reacting polyisocyanate T (Desmodur eco N7300) with aminosulfonic acid G (3-cyclohexylaminoethanesulfonic acid), wherein the molar ratio of isocyanate groups in polyisocyanate T to aminosulfonic acid G is 2.25:1.

[0062] (2) Preparation of waterborne polyurethane dispersion PU2:

[0063] 396.4g of polyester polyol (polyol C, adipic acid / neopentyl glycol structure, number average molecular weight Mn of 1000 g / mol), 5.4g of dimethylolpropionic acid (hydroxyl functional compound D), 162.3g of isoflurane diisocyanate (diisocyanate A), 30.0g of polyisocyanate sulfonic acid modified compound B2, and 70.0g of N-ethylpyrrolidone (organic solvent) were added to the reaction vessel. The mixture was stirred and heated to 80℃ until the NCO value reached the theoretical value of 4.0%, thus obtaining a polyurethane prepolymer.

[0064] The above polyurethane prepolymer was dispersed in a mixture consisting of 472.0 g water, 15.0 g Sasol emulsifier Marlipal O13 / 90, and 4.0 g triethylamine. Then, a mixture consisting of 16.0 g hydrazine hydrate (amino-functional compound E) and 80.0 g water was added, and the mixture was stirred for another 30 min to obtain a milky white waterborne polyurethane dispersion PU2.

[0065] In this embodiment, the solids content of the aqueous polyurethane dispersion PU2 is 50 wt%, and the organic solvent content is 5.6 wt%. In this embodiment, the sulfonic acid groups in the polyisocyanate sulfonic acid modified B2 account for 0.061 mmol / g of the solids content of the aqueous polyurethane dispersion PU2.

[0066] The aqueous polyurethane dispersion PU2 in this embodiment showed no obvious precipitation or stratification after being stored in a 50°C oven for 2 weeks.

[0067] Example 3

[0068] This embodiment provides an aqueous polyurethane dispersion PU3, which is prepared through the following process:

[0069] (1) Preparation of polyisocyanate sulfonic acid modified compound B3:

[0070] Nitrogen gas was passed through the reaction flask, and 100.0 g of Desmodur N3200 (polyisocyanate T, a biuret modified by Covestro based on HDI, with an NCO value of 23.0%), 29.0 g of 3-cyclohexylaminobutyric acid (aminosulfonic acid G), and 16.4 g of N,N-dimethylcyclohexylamine were added. The mixture was heated to 100 °C and reacted for 6 h to obtain a pale yellow, viscous, transparent liquid polyisocyanate sulfonic acid modified compound B3.

[0071] Among them, the polyisocyanate sulfonic acid modified compound B3 is obtained by reacting polyisocyanate T (Desmodur N3200) with aminosulfonic acid G (3-cyclohexylaminobutyric acid), wherein the molar ratio of isocyanate groups in polyisocyanate T to aminosulfonic acid G is 4.45:1.

[0072] (2) Preparation of waterborne polyurethane dispersion PU3:

[0073] 600.0 g of polypropylene glycol (polyol C, number average molecular weight Mn of 4000 g / mol), 5.4 g of dimethylolpropionic acid (hydroxyl functional compound D), 25.7 g of neopentyl glycol (hydroxyl functional compound D), 191.5 g of 4,4-dicyclohexylmethane diisocyanate (diisocyanate A), and 30.0 g of polyisocyanate sulfonic acid modified compound B3 were added to a reaction vessel. The mixture was stirred and heated to 80 °C until the NCO value reached the theoretical value of 3.3%, thus obtaining a polyurethane prepolymer.

[0074] The above polyurethane prepolymer was dispersed in a mixture consisting of 801.0 g water, 15.0 g Sasol emulsifier Marlipal O13 / 90, and 4.0 g triethylamine. Then, a mixture consisting of 16.0 g hydrazine hydrate (amino-functional compound E) and 80.0 g water was added, and the mixture was stirred for another 30 min to obtain a milky white waterborne polyurethane dispersion PU3.

[0075] In this embodiment, the solids content of the aqueous polyurethane dispersion PU3 is 50 wt%, and the organic solvent content is 0 wt%. In this embodiment, the sulfonic acid groups in the polyisocyanate sulfonic acid modified B3 account for 0.029 mmol / g of the solids content of the aqueous polyurethane dispersion PU3.

[0076] The aqueous polyurethane dispersion PU3 in this embodiment showed no obvious precipitation or stratification after being stored in a 50°C oven for 2 weeks.

[0077] Example 4

[0078] This embodiment provides an aqueous polyurethane dispersion PU4, which is prepared through the following process:

[0079] 500.0 g of polytetramethylene ether glycol (polyol C, number average molecular weight Mn of 2000 g / mol), 5.4 g of dimethylolpropionic acid (hydroxyl functional compound D), 15.2 g of neopentyl glycol (hydroxyl functional compound D), 162.3 g of isoflurane diisocyanate (diisocyanate A), 8.0 g of polyisocyanate sulfonic acid modified compound B1, and 70.0 g of N-ethylpyrrolidone (organic solvent) were added to a reaction vessel. The mixture was stirred and heated to 80 °C until the NCO value reached the theoretical value of 3.3%, thus obtaining a polyurethane prepolymer.

[0080] The above polyurethane prepolymer was dispersed in a mixture consisting of 574.0 g water, 15.0 g Sasol emulsifier Marlipal O13 / 90, and 4.0 g triethylamine. Then, a mixture consisting of 14.8 g hydrazine hydrate (amino-functional compound E) and 74.0 g water was added, and the mixture was stirred for another 30 min to obtain a milky white waterborne polyurethane dispersion PU4.

[0081] In this embodiment, the solids content of the aqueous polyurethane dispersion PU4 is 50 wt%, and the organic solvent content is 4.9 wt%. In this embodiment, the sulfonic acid groups in the polyisocyanate sulfonic acid modified B1 account for 0.012 mmol / g of the solids content of the aqueous polyurethane dispersion PU4.

[0082] The aqueous polyurethane dispersion PU4 in this embodiment showed no obvious precipitation or stratification after being stored in a 50°C oven for 2 weeks.

[0083] Example 5

[0084] This embodiment provides an aqueous polyurethane dispersion PU5, which is prepared through the following process:

[0085] 500.0 g of polytetramethylene ether glycol (polyol C, number average molecular weight Mn of 2000 g / mol), 19.4 g of neopentyl glycol (hydroxyl functional compound D), 151.2 g of isoflurane diisocyanate (diisocyanate A), 79.0 g of polyisocyanate sulfonic acid modified compound B1, and 70.0 g of N-ethylpyrrolidone (organic solvent) were added to a reaction vessel. The mixture was stirred and heated to 80 °C until the NCO value reached the theoretical value of 3.4%, thus obtaining a polyurethane prepolymer.

[0086] The above polyurethane prepolymer was dispersed in a mixture consisting of 622.0 g water and 15.0 g Sasol emulsifier Marlipal O13 / 90. Then, a mixture consisting of 16.4 g hydrazine hydrate (amino-functional compound E) and 82.0 g water was added, and the mixture was stirred for 30 min to obtain a milky white waterborne polyurethane dispersion PU5.

[0087] In this embodiment, the waterborne polyurethane dispersion PU5 has a solids content of 50 wt% and an organic solvent content of 4.5 wt%. In this embodiment, the sulfonic acid groups in the polyisocyanate sulfonic acid modified B1 account for 0.108 mmol / g of the solids in the waterborne polyurethane dispersion PU5.

[0088] The aqueous polyurethane dispersion PU5 in this embodiment showed no obvious precipitation or stratification after being stored in a 50°C oven for 2 weeks.

[0089] Comparative Example 1

[0090] This comparative example provides an aqueous polyurethane dispersion CPU1, which is prepared by the following process:

[0091] 500.0 g of polytetramethylene ether glycol (polyol C, number average molecular weight Mn of 2000 g / mol), 5.4 g of dimethylolpropionic acid (hydroxyl functional compound D), 15.2 g of neopentyl glycol (hydroxyl functional compound D), 162.3 g of isoflurane diisocyanate (diisocyanate A), and 70.0 g of N-ethylpyrrolidone were added to a reaction vessel. The mixture was stirred and heated to 80 °C until the NCO value reached the theoretical value of 3.3%, thus obtaining a polyurethane prepolymer.

[0092] The above polyurethane prepolymer was dispersed in a mixture consisting of 561.0 g water, 15.0 g Sasol emulsifier Marlipal O13 / 90, and 4.0 g triethylamine. Then, a mixture consisting of 16.0 g hydrazine hydrate (amino-functional compound E) and 80.0 g water was added, and the mixture was stirred for another 30 min to obtain a milky white aqueous polyurethane dispersion CPU1.

[0093] The aqueous polyurethane dispersion CPU1 in this comparative example has a solids content of 50 wt% and an organic solvent content of 4.9 wt%. Polyisocyanate sulfonic acid modifier B was not used in this comparative example.

[0094] The aqueous polyurethane dispersion CPU1 in this comparative example quickly precipitated and separated into layers after standing, and could not form an aqueous dispersion that could be stored stably.

[0095] Comparative Example 2

[0096] This comparative example provides an aqueous polyurethane dispersion CPU2, which is prepared by the following process:

[0097] 500.0 g of polytetramethylene ether glycol (polyol C, number average molecular weight Mn of 2000 g / mol), 5.4 g of dimethylolpropionic acid (hydroxyl functional compound D), 15.2 g of neopentyl glycol (hydroxyl functional compound D), 162.3 g of isoflurane diisocyanate (diisocyanate A), 4.0 g of polyisocyanate sulfonic acid modified compound B1, and 70.0 g of N-ethylpyrrolidone (organic solvent) were added to a reaction vessel. The mixture was stirred and heated to 80 °C until the NCO value reached the theoretical value of 3.3%, thus obtaining a polyurethane prepolymer.

[0098] The above polyurethane prepolymer was dispersed in a mixture consisting of 561.0 g water, 15.0 g Sasol emulsifier Marlipal O13 / 90, and 4.0 g triethylamine. Then, a mixture consisting of 16.0 g hydrazine hydrate (amino-functional compound E) and 80.0 g water was added, and the mixture was stirred for another 30 min to obtain a milky white aqueous polyurethane dispersion, CPU2.

[0099] The aqueous polyurethane dispersion CPU2 in this comparative example has a solids content of 50 wt% and an organic solvent content of 4.9 wt%. In this comparative example, the sulfonic acid groups in the polyisocyanate sulfonic acid modified B1 account for 0.006 mmol / g of the solids in the aqueous polyurethane dispersion CPU2.

[0100] The aqueous polyurethane dispersion CPU2 in this comparative example quickly precipitated and separated into layers after standing, and could not form an aqueous dispersion that could be stored stably.

[0101] Comparative Example 3

[0102] This comparative example provides an aqueous polyurethane dispersion CPU3, which is prepared by the following process:

[0103] (1) Preparation of polyisocyanate sulfonic acid modified compound B4:

[0104] Nitrogen gas was passed through the reaction flask, and 100.0g of Wannate HT-600 (polyisocyanate T, Wanhua Chemical's HDI-based isocyanurate modified product, NCO value 23.0%), 60.6g of 3-cyclohexylaminopropanesulfonic acid (aminosulfonic acid G), and 36.6g of N,N-dimethylcyclohexylamine were added. The mixture was heated to 100℃ and reacted for 6h to obtain a pale yellow, viscous, transparent liquid polyisocyanate sulfonic acid modified product B4.

[0105] Among them, polyisocyanate sulfonic acid modified compound B4 is obtained by reacting polyisocyanate T (Wannate HT-600) with aminosulfonic acid G (3-cyclohexylaminopropanesulfonic acid), wherein the molar ratio of isocyanate groups in polyisocyanate T to aminosulfonic acid G is 2:1.

[0106] (2) Preparation of aqueous polyurethane dispersion CPU3:

[0107] 500.0 g of polytetramethylene ether glycol (polyol C, number average molecular weight Mn of 2000 g / mol), 5.4 g of dimethylolpropionic acid (hydroxyl functional compound D), 15.2 g of neopentyl glycol (hydroxyl functional compound D), 162.3 g of isoflurane diisocyanate (diisocyanate A), 30.0 g of polyisocyanate sulfonic acid modified compound B4, and 70.0 g of N-ethylpyrrolidone (organic solvent) were added to a reaction vessel. The mixture was stirred and heated to 80 °C until the NCO value reached the theoretical value of 3.5%, thus obtaining a polyurethane prepolymer.

[0108] The above polyurethane prepolymer was dispersed in a mixture consisting of 591.0 g water, 15.0 g Sasol emulsifier Marlipal O13 / 90, and 4.0 g triethylamine. Then, a mixture consisting of 16.0 g hydrazine hydrate and 80.0 g water was added, and the mixture was stirred for another 30 min to obtain a milky white aqueous polyurethane dispersion, CPU3.

[0109] The aqueous polyurethane dispersion CPU3 in this comparative example has a solids content of 50 wt% and an organic solvent content of 4.7 wt%. In this comparative example, the sulfonic acid groups in the polyisocyanate sulfonic acid modified B4 account for 0.056 mmol / g of the solids in the aqueous polyurethane dispersion CPU3.

[0110] The aqueous polyurethane dispersion CPU3 in this comparative example showed no obvious precipitation or stratification after being stored in a 50°C oven for 2 weeks.

[0111] Comparative Example 4

[0112] This comparative example provides an aqueous polyurethane dispersion CPU4, which is prepared by the following process:

[0113] (1) Preparation of polyisocyanate sulfonic acid modified compound B5:

[0114] Nitrogen gas was passed through the reaction flask, and 100.0g of Wannate HT-600 (polyisocyanate T, Wanhua Chemical's HDI-based isocyanurate modified product, NCO value 23.0%), 22.0g of 3-cyclohexylaminopropanesulfonic acid (aminosulfonic acid G), and 13.3g of N,N-dimethylcyclohexylamine were added. The mixture was heated to 100℃ and reacted for 6h to obtain a pale yellow, viscous, transparent liquid polyisocyanate sulfonic acid modified product B5.

[0115] Among them, polyisocyanate sulfonic acid modified compound B4 is obtained by reacting polyisocyanate T (Wannate HT-600) with aminosulfonic acid G (3-cyclohexylaminopropanesulfonic acid), wherein the molar ratio of isocyanate groups in polyisocyanate T to aminosulfonic acid G is 5.5:1.

[0116] (2) Preparation of aqueous polyurethane dispersion CPU4:

[0117] 500.0g of polytetramethylene ether glycol (polyol C, number average molecular weight Mn of 2000 g / mol), 5.4g of dimethylolpropionic acid (hydroxyl functional compound D), 15.2g of neopentyl glycol (hydroxyl functional compound D), 162.3g of isoflurane diisocyanate (diisocyanate A), 30.0g of polyisocyanate sulfonic acid modified compound B5, and 70.0g of N-ethylpyrrolidone (organic solvent) were added to the reaction vessel. The mixture was stirred and heated to 80℃ until the NCO value reached the theoretical value of 3.5%, resulting in a polyurethane prepolymer. At this point, a large amount of gel material had been produced.

[0118] The above polyurethane prepolymer was dispersed in a mixture consisting of 591.0 g water, 15.0 g Sasol emulsifier Marlipal O13 / 90, and 4.0 g triethylamine. A large amount of gel could not be emulsified uniformly, and a stable waterborne polyurethane dispersion could not be obtained.

[0119] Comparative Example 5

[0120] This comparative example provides an aqueous polyurethane dispersion CPU5, which is prepared by the following process:

[0121] 500.0 g of polytetramethylene ether glycol (polyol C, number average molecular weight Mn of 2000 g / mol), 5.4 g of dimethylolpropionic acid (hydroxyl functional compound D), 15.2 g of neopentyl glycol (hydroxyl functional compound D), 162.3 g of isoflurane diisocyanate (diisocyanate A), and 70.0 g of N-ethylpyrrolidone (organic solvent) were added to a reaction vessel. The mixture was stirred and heated to 80 °C until the NCO value reached the theoretical value of 3.3%, thus obtaining a polyurethane prepolymer. Then, the temperature was lowered to 45 °C, and 14.0 g of VESTAMIN A 95 (Evonik sulfonate chain extender, sodium ethylenediamine ethanesulfonate aqueous solution) was added and reacted at 45 °C for 30 min to obtain a polyurethane chain extender.

[0122] The above polyurethane chain extender was dispersed in a mixture consisting of 575.0 g water, 15.0 g Sasol emulsifier Marlipal O13 / 90, and 4.0 g triethylamine. Due to the very high viscosity of the polyurethane chain extender, it could not be dispersed and emulsified to obtain a storage-stable aqueous dispersion.

[0123] In this comparative example, polyisocyanate sulfonic acid modifier B was not used. Instead, VESTAMIN A 95 was used to introduce the polyurethane prepolymer into the polyurethane prepolymer before water dispersion, forming a polyurethane chain extender that was then dispersed in water. In this comparative example, the sulfonic acid groups in VESTAMIN A 95 accounted for 0.044 mmol / g of the solids in the aqueous polyurethane dispersion CPU5.

[0124] Comparative Example 6

[0125] This comparative example provides an aqueous polyurethane dispersion CPU6, which is prepared by the following process:

[0126] 500.0 g of polytetramethylene ether glycol (polyol C, number average molecular weight Mn of 2000 g / mol), 5.4 g of dimethylolpropionic acid (hydroxyl functional compound D), 15.2 g of neopentyl glycol (hydroxyl functional compound D), 162.3 g of isoflurane diisocyanate (diisocyanate A), and 70.0 g of N-ethylpyrrolidone (organic solvent) were added to a reaction vessel. The mixture was stirred and heated to 80 °C until the NCO value reached the theoretical value of 3.3%, thus obtaining a polyurethane prepolymer.

[0127] Then, the temperature was lowered to 45°C, and the above polyurethane prepolymer was dispersed in a mixture consisting of 575.0 g water, 14.0 g VESTAMIN A95 (Evonik sulfonate chain extender, sodium ethylenediamine ethanesulfonate aqueous solution), 15.0 g Sasol emulsifier Marlipal O13 / 90, and 4.0 g triethylamine. The mixture was then stirred for 30 min to obtain a milky white aqueous polyurethane dispersion, CPU6.

[0128] The solids content of the aqueous polyurethane dispersion CPU6 in this comparative example is 50 wt%, and the organic solvent content is 4.9 wt%.

[0129] In this comparative example, polyisocyanate sulfonic acid modifier B was not used; instead, the polyurethane prepolymer was directly dispersed in a mixture containing water, VESTAMIN A 95, emulsifier, and neutralizer. In this comparative example, the sulfonic acid groups in VESTAMIN A 95 accounted for 0.044 mmol / g of the solids in the aqueous polyurethane dispersion CPU6.

[0130] Example 6

[0131] This embodiment provides an application of a waterborne polyurethane dispersion in a waterborne two-component coating.

[0132] Specifically, a water-based two-component coating is provided, comprising component A and component B. Component A comprises 70 wt% of any one of the water-based polyurethane dispersions from Examples 1-5, 20 wt% white paste (75 wt% titanium dioxide content), 4 wt% co-solvent, 0.2 wt% wetting agent, 0.5 wt% wetting and defoaming agent, 0.2 wt% thickener, and 5.1 wt% pure water. Component B comprises 70 wt% polyisocyanate crosslinking agent and 30 wt% co-solvent. The selection of each component is shown in Table 1. Component A and component B are mixed at a weight ratio of 100:5 to obtain the final product.

[0133] This embodiment also provides a coating film obtained by applying the water-based two-component coating of this embodiment to the surface of a metal substrate.

[0134] Performance testing

[0135] The aqueous polyurethane dispersions of Examples 1-5, Comparative Examples 3 and 6, and the commercially available aqueous polyurethane dispersion PU-3822 were respectively used in combination with polyisocyanate crosslinking agents for aqueous two-component coatings.

[0136] Commercially available waterborne polyurethane dispersion PU-3822: Guangzhou Guanzhi New Materials, with a solids content of 60wt%, is a waterborne polyurethane dispersion prepared using sodium ethylenediamine ethanesulfonate chain extender.

[0137] Polyisocyanate crosslinking agent: OS-9014, Guangzhou Guanzhi New Materials, commercially available nonionic hydrophilic modified HDI type polyisocyanate, solid content: 100%, NCO value 19.0%.

[0138] Table 1. Formulations of water-based two-component coatings

[0139]

[0140] Specifically, the waterborne polyurethane dispersions of Examples 1-5, Comparative Examples 3 and 6, and the commercially available waterborne polyurethane dispersion PU-3822 were formulated into waterborne two-component coatings at 23±2℃ according to the formulations in Table 1, and the following performance tests were conducted:

[0141] (1) Usable time

[0142] Usable time test: After preparing the water-based two-component coating, observe the viscosity change every 0.5 hours. If the viscosity is more than twice the initial viscosity, it is considered to be outside the usable time.

[0143] (2) Water absorption rate of the coating

[0144] The curing conditions are as follows: apply the water-based two-component coating to the surface of the tinplate, leave it at room temperature for 20 minutes, then bake it in an 80℃ forced-air oven for 1 hour, and then leave it at room temperature for 3 days before conducting a water absorption test.

[0145] Water absorption test: The water absorption rate of the coating film was tested according to HG / T 3344-2012, and the film was immersed at 23±2℃ for 24 hours. The higher the water absorption rate, the worse the water resistance.

[0146] The performance test results are shown in Table 2:

[0147] Table 2 Performance Tests of Coatings

[0148]

[0149] According to the results of Examples 1-5 and Table 2, the waterborne polyurethane dispersions of Examples 1-5 of the present invention have a high solids content and good storage stability and dispersion uniformity. The waterborne two-component coatings formulated by combining the waterborne polyurethane dispersions of Examples 1-5 of the present invention with polyisocyanate crosslinking agents have excellent water resistance (low water absorption) and long service life.

[0150] In Comparative Example 1, the aqueous polyurethane dispersion CPU1 did not use polyisocyanate sulfonic acid modifier B as a raw material during the preparation process. As a result, no sulfonic acid groups were introduced into the aqueous polyurethane dispersion CPU1 of Comparative Example 1, and a storage-stable aqueous polyurethane dispersion could not be obtained.

[0151] In Comparative Example 2, the proportion of sulfonic acid groups in the polyisocyanate sulfonic acid modified B1 of the aqueous polyurethane dispersion CPU2 was too low, and thus a storage-stable aqueous polyurethane dispersion could not be obtained.

[0152] The aqueous polyurethane dispersion CPU3 of Comparative Example 3 uses a polyisocyanate sulfonic acid modified compound B4, which is obtained by reacting polyisocyanate T and aminosulfonic acid G in a ratio of 2:1 of the molar number of isocyanate groups of polyisocyanate T to the molar number of aminosulfonic acid G. This is not within the scope of the present invention (i.e., the polyisocyanate sulfonic acid modified compound B4 of Comparative Example 3 does not belong to the polyisocyanate sulfonic acid modified compound B as defined in the present invention). Although the aqueous polyurethane dispersion CPU3 of Comparative Example 3 has good storage stability, the water-based two-component coating film formed by the aqueous polyurethane dispersion CPU3 of Comparative Example 3 in combination with the polyisocyanate crosslinking agent exhibits poor water resistance. This is because during the preparation of polyisocyanate sulfonic acid modified compound B4, the molar ratio of isocyanate groups in polyisocyanate T to aminosulfonic acid G was too low. As a result, a large number of isocyanate groups in polyisocyanate T were modified by aminosulfonic acid, which in turn resulted in polyisocyanate sulfonic acid modified compound B4 having fewer isocyanate groups. That is, there were fewer isocyanate groups that could continue to react with polyol C and hydroxyl functional compound D. Consequently, polyisocyanate sulfonic acid modified compound B4 could not be well integrated into the polyurethane prepolymer, resulting in a higher water absorption rate of the water-based two-component coating film.

[0153] In Comparative Example 4, the aqueous polyurethane dispersion CPU4 uses a polyisocyanate sulfonic acid modified compound B5, which is obtained by reacting polyisocyanate T with aminosulfonic acid G at a ratio of 5.5:1 (the molar ratio of isocyanate groups in polyisocyanate T to aminosulfonic acid G). This is outside the scope of this invention (i.e., the polyisocyanate sulfonic acid modified compound B5 in Comparative Example 4 does not belong to the polyisocyanate sulfonic acid modified compound B as defined in this invention). During the synthesis of the aqueous polyurethane dispersion CPU4, gelation occurs, making it impossible to obtain a storage-stable aqueous dispersion. This is because during the preparation of the polyisocyanate sulfonic acid modified compound B5, the molar ratio of isocyanate groups in polyisocyanate T to aminosulfonic acid G is too high. This results in a large number of isocyanate groups in polyisocyanate T not being modified by aminosulfonic acid, leading to polyisocyanate sulfonic acid modified compound B5 having a large number of isocyanate groups. Consequently, excessive cross-linking structures are formed during the synthesis of the polyurethane prepolymer, resulting in gelation and preventing the formation of a storage-stable aqueous polyurethane dispersion.

[0154] Comparative Example 5, the aqueous polyurethane dispersion CPU5, did not use polyisocyanate sulfonic acid modifier B. Instead, VESTAMIN A 95 (Evonik sulfonate chain extender, sodium ethylenediamine ethanesulfonate aqueous solution) was added to the polyurethane prepolymer before it was dispersed in water to introduce the chain extension into the polyurethane prepolymer, forming a polyurethane chain extender. Then it was dispersed in water. In addition, a large amount of organic solvent was not used for dilution (unlike CN101848952B, which uses a very large amount of acetone for dilution). As a result, the viscosity of the polyurethane prepolymer was very high during the synthesis process, and it could not be dispersed and emulsified to obtain a storage-stable aqueous dispersion.

[0155] Comparative Example 6, the waterborne polyurethane dispersion CPU6, did not use polyisocyanate sulfonic acid modifier B. Instead, the polyurethane prepolymer was directly dispersed and emulsified in a mixture of "water, VESTAMIN A 95, emulsifier, and neutralizer". Although this avoided the problem of the polyurethane prepolymer not being able to disperse and emulsify, the waterborne two-component coating formed by the waterborne polyurethane dispersion CPU6 of Comparative Example 6 with the polyisocyanate crosslinking agent exhibited poor water resistance. This may be because VESTAMIN A 95 extends the chain in the aqueous phase, resulting in a large number of isocyanate groups reacting with water, leading to incomplete chain extension. Some of the chain extender failed to graft onto the polyurethane prepolymer and remained free in the coating, resulting in high water absorption of the coating.

[0156] The commercially available waterborne polyurethane dispersion PU-3822 is a sulfonate waterborne polyurethane dispersion using sodium ethylenediamine ethanesulfonate chain extender. It does not contain polyisocyanate sulfonic acid modifier B1, and its corresponding waterborne two-component coatings exhibit poor water resistance and short pot life.

[0157] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and the present invention also intends to include these modifications and variations.

Claims

1. An aqueous polyurethane dispersion, characterized in that: The following raw materials are included in the preparation: 1) At least one diisocyanate A; 2) At least one polyisocyanate sulfonic acid modified compound B; 3) At least one polyol C; 4) At least one amino-functional compound E; in: The number-average molecular weight of the polyol C is 500-8000 g / mol; The polyisocyanate sulfonic acid modified compound B is obtained by reacting polyisocyanate T with aminosulfonic acid G, wherein the molar ratio of isocyanate groups in polyisocyanate T to that in aminosulfonic acid G is 2.4-4.5:1; the polyisocyanate T is at least one of isocyanurate modified compound, urea carbamate modified compound, and biuret modified compound based on hexamethylene diisocyanate and / or pentamethylene diisocyanate, and the polyisocyanate T is not a diisocyanate monomer; the aminosulfonic acid G is at least one of 2-cyclohexylaminoethanesulfonic acid, 3-cyclohexylaminopropanesulfonic acid, and 4-cyclohexylaminobutyric acid; the proportion of sulfonic acid groups in the polyisocyanate sulfonic acid modified compound B to the solids of the aqueous polyurethane dispersion is 0.01-0.11 mmol / g; The amino-functional compound E is a compound containing at least one amino group, and the amino-functional compound E is used for aqueous chain extension.

2. The aqueous polyurethane dispersion according to claim 1, characterized in that: The raw materials for preparation also include: 5) hydroxyl functional compound D; the number average molecular weight of the hydroxyl functional compound D is 62-339 g / mol.

3. The aqueous polyurethane dispersion according to claim 1 or 2, characterized in that: The diisocyanate A is at least one of hexamethylene diisocyanate, pentamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, naphthalene-1,5-diisocyanate, phenyl dimethyl diisocyanate, 4,4-dicyclohexylmethane diisocyanate, norbornene diisocyanate, and isophorone diisocyanate.

4. The aqueous polyurethane dispersion according to claim 1 or 2, characterized in that: The number average molecular weight of the polyol C is 1000-4000 g / mol; the polyol C is at least one of polyether polyol, polyester polyol, and polycarbonate polyol.

5. The aqueous polyurethane dispersion according to claim 2, characterized in that: The hydroxyl functional compound D is a compound containing at least two hydroxyl groups, and the hydroxyl functional compound D is at least one of the following: dimethylolpropionic acid, dimethylolbutyric acid, ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanediol, bisphenol A, hydrogenated bisphenol A, trimethylolpropane, trimethylolethane, pentaerythritol, and sorbitol.

6. The aqueous polyurethane dispersion according to claim 1 or 2, characterized in that: The amino-functional compound E is at least one of ethylenediamine, 1,2-propanediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine, hydrazine, hydrazine hydrate, diethylenetriamine, triethylenetetramine, and hydroxyethylethylenediamine.

7. The aqueous polyurethane dispersion according to claim 1 or 2, characterized in that: It also includes water and organic solvents, wherein the solid content of the aqueous polyurethane dispersion is 30-60 wt%; and the content of the organic solvent in the aqueous polyurethane dispersion is 0-10 wt%.

8. A method for preparing an aqueous polyurethane dispersion according to any one of claims 1-7, characterized in that: Includes the following steps: (1) Add 4-20 parts by weight of diisocyanate A, 0.5-5 parts by weight of polyisocyanate sulfonic acid modified B, 20-50 parts by weight of polyol C, 0-5 parts by weight of hydroxyl functional compound D, and 0-10 parts by weight of organic solvent to the reaction vessel, mix evenly, and heat to 50-90℃ to carry out the reaction until the NCO value reaches the theoretical value to obtain polyurethane prepolymer; (2) Disperse the polyurethane prepolymer obtained in step (1) in water, and then add 0.2-2 parts by weight of amino functional compound E to carry out aqueous chain extension to obtain the aqueous polyurethane dispersion.

9. The use of an aqueous polyurethane dispersion as described in any one of claims 1-7 in an aqueous coating.

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