WO2003059982A1

WO2003059982A1 - Aqueous polyurethane dispersions used as adhesives and coatings and its preparation

Info

Publication number: WO2003059982A1
Application number: PCT/CN2003/000051
Authority: WO
Inventors: Youlu Duan; Hexian Zou; Gang Duan
Original assignee: Youlu Duan; Hexian Zou; Gang Duan
Priority date: 2002-01-18
Filing date: 2003-01-20
Publication date: 2003-07-24
Also published as: CN100497429C; CN1362436A; AU2003203332A1

Abstract

The present invention relates to an organic macromolecule materials, i.e. aqueous polyurethane dispersions, their use for adhesives and coatings, and their preparation. The aqueous polyurethane dispersions are prepared by a process which use less organic solvent or even not use organic solvent and which use a mixture of three or more polyisocyanates composed of 1,6-hexane diisocyanate (HDI), tetramethylxylene diisocyanate (TMXDI) and other polyisocyanates. The dispersions are also nanometer-scale aqueous polyurethane dispersions. This new aqueous polyurethane dispersions have not only excellent binding property to be used as adhesives, but also good film-forming property to form a film with excellent mechanical property, so it can be used as coatings.

Description

Aqueous polyurethane dispersion used as adhesive and coating and preparation thereof

The present invention relates to an organic polymer material, that is, an aqueous polyurethane dispersion liquid that can be used as an adhesive and a coating, and a method for preparing the same.

Background technique

Aqueous polyurethane dispersions can be used as adhesives and coatings. Aqueous polyurethane dispersions are prepared by a four-step process: 1) The excess polyisocyanate is reacted with a polyol and a diol (or diamine) with a carboxyl group to form an isocyanate. Tailed prepolymer; 2) neutralization of the prepolymer; 3) dispersion of the neutralized prepolymer in water; 4) chain extension to form an aqueous polycyanate. Among polyisocyanates, 1,6-hexyl diisocyanate (HDI) is widely used to prepare water-based polyurethane adhesives and coatings.

US Patent ① USP. 6, 147,155 (Kenneth P Yonek and Yuliya Berezkill) pointed out that HDI can be used to prepare very soft, high strength and waterborne polyurethane coatings. However, only known prepolymer processes can be used with HDI and cannot be successfully prepared Aqueous polyurethane dispersions with carboxyl ion groups, because the viscosity of this HDI-based prepolymer dispersed in water rapidly increases to form a very thick paste, which cannot carry out chain extension reactions, or because amines are used During the chain extension reaction, insoluble polyurea agglomerated particles are formed, making the product unsuitable for commercial use. Therefore, the patent claims require that the first step is to use isophorone diisocyanate (IPDI) and dihydroxymethylpropionic acid (DMPA) to generate Isocyanate-terminated adduct. In the second step, HDI and polyester diol are reacted with the adduct produced in the first step to form a prepolymer, which is then neutralized and dispersed in water and reacts with water to extend the chain to form an aqueous polyurethane dispersion. The disadvantages of this method are: (1) the two-step method for preparing the prepolymer increases the number of process steps and complicates the process; (2) a large amount of solvent (N-fluorenyl-2- Pyrrolidone, that is, NMP); (3) The aqueous polyurethane dispersion prepared can only be used as a coating and is not suitable as an adhesive.

US patent ② USP. 4,870,129 (Wolfgang Henhin et al.) Invented a water-based polyamic acid adhesive prepared based on a mixture of HDI and IPDI, which has a low activation temperature and good adhesion properties. The water-based polyurethane amine adhesive products Dispercoll U-53 and U-54 developed by Bayer are the best water-based polyurethane adhesive products in the world today. The disadvantages of this patent are: (1) a special sulfonic acid diamine that is not commercialized is used as a chain extender to introduce ionic groups, so the preparation process must first extend the chain to form a polymer, and then Redispersion in water increases the difficulty of dispersing, so a large amount of acetone is used to reduce the viscosity of the polymer; (2) It follows that there must be a time-consuming, energy-consuming distillation of acetone from the product under reduced pressure And the steps of recovering acetone; (3) Dispercoll U-53 and U-54 products produced with this patent have poor film formation, sometimes crack, can only be used as adhesives, not suitable for coatings; (4) this patent also discloses A ternary mixed diisocyanate composed of HDI, IPDI and a third type of diisocyanate was used to prepare an aqueous polymer. Urethane adhesive, but diisocyanates with aromatic rings, such as tetramethylene diphenyl diisocyanate (TMXDI), toluene diisocyanate (TDI), and methylene diphenyl diisocyanate (MDI) are excluded from the third A kind of diisocyanate.

③ The product manual of Cytec company pointed out: Generally speaking, using TMXDI to prepare aqueous polyurethane dispersions, a solvent-free or less-solvent process can be used because the prepolymer based on TMXDI has a lower viscosity. However, compared to water-based polyurethanes prepared with TMXDI alone, compared with water-based polyurethanes prepared with IPDI or dicyclohexylmethane diisocyanate (H ₁₂ MDI), although it has higher elongation, it has lower strength and lower hardness. A very good coating. Compared with water-based polyurethane prepared with HDI, the water-based polyurethane prepared with TMXDI also reduces the crystallinity and crystallization speed. Used as an adhesive, the instant adhesive strength and final adhesive strength are also not good enough.

German patent ④ DE.4109477A1 (Hans et al.) Discloses a two-component aqueous polyurethane decomposition solution based on a mixture of TMXDI and other diisocyanates. In this mixture of isocyanates, the weight of TMXDI should be at least 30%, preferably at least 30%. 50%. According to this patent, this type of water-based polyurethane can be prepared by a solvent-free or low-solvent process, but the water-based polyurethane prepared in its experimental example has poor performance, and the surface of the resulting film is sticky. Only after reacting with the curing agent can it be made into a non-sticky film , Can only be used as an adhesive for flexible packaging composite film.

U.S. patents ⑤ USP. 5,608,000 (Youlu Duan et al.) And ⑥ USP. 5,637,639 (Youlu Duan et al.) Invented a sulfonic water-based polyurethane based on a mixture of two diisocyanates (such as HDI and IPDI, or HDI / TMXDI). These patents point out that in HDI / TMXDI, an increase in the content of TMXDI will reduce the crystallization rate of the resulting aqueous polyurethane, and when used as an adhesive, the instantaneous bonding strength and the final bonding strength are reduced.

The above patents and data show that: (1) HDI is a diisocyanate widely used in the preparation of aqueous polyurethane dispersions. HDI-based aqueous polyurethane dispersions can be used as coatings, and their films are soft and high in strength. The disadvantages are that: Aqueous polyurethane dispersions cannot be successfully prepared using HDI alone; (2) Prepolymers are prepared by two-step method using two diisocyanates of HDI and IPDI, and then neutralized, dispersed and diffused to successfully prepare aqueous polyamic acid coatings, but A large number of solvents must be used to prepare its prepolymer; (3) TMXDI, and its mixture with other diisocyanates, can be used to prepare aqueous polyurethane dispersions using a solvent-free or solvent-free process. The film is sticky, or the strength is not high enough to be suitable as a coating. And as an adhesive, its cohesiveness is not good enough; (4) Previous work has never told us that three or more diisocyanate mixture systems composed of HDI, TMXDI and other diisocyanates can be used to prepare aqueous polyurethane dispersions. liquid.

Therefore, the present invention will provide a new mixed system of three or more isocyanates composed of HDI, TMXDI and other diisoesters to prepare aqueous polyurethane aqueous dispersions. This new system will overcome the above-mentioned shortcomings. Summary of invention

The invention provides a new water-based polyurethane aqueous dispersion. The new water-based polyurethane dispersion is composed of

A mixture of three or more isocyanates composed of HDI, TMXDI and other polycyanates, prepared using a process with little or no organic solvents. This new water-based polyurethane dispersion has both good adhesive properties, can be used as an adhesive, and good film-forming properties. The film has good mechanical properties and can be used as a coating. With this new ternary or higher ternary isocyanate mixed system, it is also possible to prepare a new nano aqueous polyurethane dispersion.

The aqueous polyurethane dispersion of the present invention is composed of the reaction product of the following components:

A) An isocyanate composition composed of at least three different isocyanates composed of HDI, TMXDI and other polyisocyanates, wherein the weight percentages of the three isocyanates are 1-98: 1 to 98: 1 to 98;

B) A hydroxycarboxylic acid whose molecular formula is: (HO) xR (COOH) y, where R represents a straight or branched hydrocarbon group containing 1-12 carbon atoms, and X and Y represent the number of 1-3 ;

C) An organic polyhydroxy compound, including a polyester polyol, a polyether polyol, a sulfonic-type polypolyol, a poly (lipid-ether) polyol, or a physical mixture of the above-mentioned polyols;

D) optionally, an aliphatic diol having a molecular weight from 60 to 400;

E) A chain extender, which may be a polyamine compound or a mixture of polyamines, a hydrazine compound, water, or a mixture thereof.

Surprisingly, the properties of the aqueous polyurethane dispersion of the present invention are better than those of the best commercial water-based polyurethane products, Bayer's Dispercoll U-53 and U-54, and their bonding temperature resistance is better than U-53 and U- 54 high 30. Above C, its film-forming properties are better than U-53 and U-54, and its film's tensile strength is also better than U-53 and U-54. The aqueous polyurethane dispersion of the present invention can be used both as an adhesive and as a paint.

Furthermore, the present invention also provides a method for preparing a ternary and more than ternary isocyanate-based aqueous polyurethane dispersion such as HDI, TMXDI, and other isocyanates, including the following steps:

A) A mixture of HDI, TMXDI and other isocyanates, in the presence of no more than 2% of the total amount of the final aqueous polyurethane dispersion in water-soluble volatile organic solvents or in the absence of organic solvents, reacts with polyols and hydroxycarboxylic acids to produce Isocyanate-terminated prepolymers with carboxylic acid side groups;

B) disperse the resulting prepolymer in water;

C) reacting an isocyanate-terminated prepolymer dispersed in water with at least one amine chain extender to form a polyurethane polymer; D) The alkali metal hydroxide or tertiary amine is used to neutralize the carboxylic acid group of the hydroxy acid compound or prepolymer. This neutralization reaction can be performed before the prepolymer is formed, or it can be performed simultaneously with the prepolymerization reaction, or after the prepolymerization reaction is completed and the prepolymer is dispersed in water, or a neutralizing agent can be added to the water to react with The chain extension and chain termination reactions proceed simultaneously.

Compared with Bayer's method for preparing aqueous polyurethane dispersions Dispecoll U-53 and U-54, the method for preparing an aqueous polyurethane dispersion does not require the step of recovering the organic solvent by distillation.

Another feature of the method for preparing an aqueous polyurethane dispersion of the present invention is that the neutralization reaction can be performed before preparing the prepolymer. The method of the present invention can also prepare nano-aqueous polyurethane with a particle size less than 100 nanometers, which is smaller than that of Dispercoll U of Bayer -54 (particle size about 200 nm) is smaller than 1/2. Summary of the Invention

The term "polyurethane" in the present invention is defined as a polymer containing a urethane group, and also includes a polymer containing a urea group in addition to a carbamate group.

The aqueous polyurethane dispersion of the present invention is composed of three or more polyisocyanates, such as HDI, TMXDI, and other polyisocyanates. In the presence of a small amount or no organic solvent, it can be used with polyols, hydroxycarboxylic compounds, and may also contain It is prepared by reacting small molecule diols to form a prepolymer, and then dispersing it in water to extend the chain into a polymer. This new water-based polyurethane dispersion is compared with Bayer's water-based polyurethane dispersion products Dispercoll U-53 and U-54 based on a mixture of HDI and IPDI. It is used as an adhesive with a temperature-resistant ratio U-53. And U-54 high 3 (TC, used as a coating, its film formation is better than U-53 and U-54, and its film strength is also higher than U-53 and U-54. To prepare the aqueous polyurethane dispersion of the present invention, Compared with Bayer's method of preparing Dispercoll U-53 and U-54 with a large number of organic solvents (U.S. Patent No. 4,870,129), Bayer's process includes vacuum distillation recovery from an aqueous polyurethane dispersion. Organic solvent step, and the process of the present invention omits the step of distilling and recovering the organic solvent. The present invention can also prepare a nano-aqueous polyurethane dispersion with a particle size of less than 100 nanometers, which is also smaller than Dispercoll U-54 (particle size is about 200 nm).

For preparing the polyisocyanate of the aqueous polyurethane dispersion of the present invention, in addition to 1,6-hexyl diisocyanate (HDI) and tetramethylphenyl difluorenyl diisocyanate (TMXDI), other polyisocyanates may be aliphatic, or It can be aromatic or a mixture of aliphatic and aromatic polyisocyanates. Examples of suitable aliphatic diisocyanates are isophorone diisocyanate (IPDI), cyclopentyl diisocyanate, cyclohexyl diisocyanate, fluorenyl cyclohexyl diisocyanate, dicyclohexyl dioxane diisocyanate (H, ₂ MDI ), 1,4-tetrafluorenyl diisocyanate, 2,2,4-trifluorenyl-1,6-hexyl diisocyanate, 1,12-twelve Alkyl diisocyanate. Examples of suitable aromatic diisocyanates are benzene diisocyanate, terphenylene diisocyanate (TDI), diphenylbenzene diisocyanate, biphenyl diisocyanate, naphthalene diisocyanate, diphenylmethane diisocyanate (MDI). A better ternary combination is HDI and TMXDI with IPDI, or with H ₁₂ MDI, or with MDI, or with TDI. The best ternary combinations are HDI, TMXDI and IPDI, or HDI, TMXDI and MDI (or TDI). Wherein the weight ratio of HDI, TMXDI and the third polyisocyanate is 1 ~ 98: 1-98: 1 ~ 98 »

If desired, small amounts of monoisocyanate and polyisocyanate can also be used in the isocyanate combination to prepare the prepolymer of the present invention. The ratio of the monoisocyanate and the polyisocyanate used should be such that the average isocyanate group content of the resulting prepolymer is equal to or greater than two. Suitable monoisocyanates include methyl isocyanate, ethyl isocyanate, octadecyl isocyanate and the like. Suitable polyisocyanates include modified diisocyanates with isocyanate groups greater than 2, such as trimers of HDI, IPDI, TDI and the like. In addition, the modified polyisocyanate may contain groups such as urethane, biuret, and the like.

The polyol compound suitable for preparing the aqueous polyurethane dispersion of the present invention has a number average molecular weight from 400 to 10,000, and a molecular weight from 400 to 3000 is even better. These high molecular weight polyols include:

1. Polyester polyols are prepared by reacting polyhydric compounds, preferably diols, possibly by adding triols, and polyvalent carboxylic compounds, more preferably dicarboxylic acids.

In addition to these polycarboxylic acids, corresponding hepatic carboxylic acid compounds, or small molecular alcohol esters of these polycarboxylic acids, and mixtures thereof can also be used to prepare these polyester polyols. These polycarboxylic acid compounds may be aliphatic, alicyclic, aromatic, and / or heterocyclic. They may be unsaturated and / or substituted with halogen or the like. Examples of these carboxylic acids are: succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, trimellitic acid, terbium phthalate, tetrahydrophthalic anhydride, hexahydrophthalic anhydride , Tetrachlorophthalic anhydride, bridging tetrahydrophthalic acid§f, glutamic anhydride, maleic acid, maleic anhydride, trans-butenedioic acid, dimers and trimers of fatty acids, for example, can be mixed with fatty acids Dimer and trimer of oleic acid, difluorenyl terephthalate and diethylene terephthalate. Suitable polyhydric alcohol compounds include ethylene glycol, 1,2- and 1,3-propanediol, 1,3- and 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol , Neopentyl glycol, diethylene glycol, 2-fluorenyl-1,3-propanediol, 2,2-difluorenyl-1,3-propanediol, various isomers of dihydroxyfluorenyl cyclohexane, Glycerol and trimethylolpropane.

2. Polylactone polyols, such as polymers of caprolactone initiated with the above-mentioned polyols.

3. Polyhydroxyl-containing polycarbonate, such as the product of the aforementioned reaction of a polyol compound for the preparation of polyester polyols with phosgene and a diaryl carbonate. Also suitable are the reaction products of the aforementioned low molecular weight oligomers of polyesters or polylactones with phosgene, diaryl carbonates or cyclic carbonates. Among them, the polyhydric alcohol compound is preferably a dihydric alcohol compound, such as 1,3-propanediol, 1,4-butanediol, 1,4-dioxohydroxycyclohexane, 1,6-hexanedione Alcohol, diethylene glycol, triethylene glycol or tetraethylene glycol. The diaryl carbonate includes diphenyl carbonate, cyclic carbonate such as ethylene or propylene, and the like.

4. Polyether polyols, including polymers which are reacted with alkyl epoxy compounds initiated by compounds containing active hydrogen. These epoxy compounds include propylene oxide, butylene oxide, styrene epoxy, tetrahydrofuran, 3-chloro-1,2-propylene oxide, or a mixture of these epoxy compounds. If the weight content of ethylene oxide in the polyether does not exceed 10%, a certain proportion of ethylene oxide may be used. However, polyether polyols containing no ethylene epoxy are more suitable for use. Compounds containing at least one active hydrogen atom to initiate this reaction include water, methanol, ethanol, 1,2,6-hexanetriol, in addition to those polyol compounds suitable for the preparation of polyester polyols as described above, 1 , 2,4-butanetriol, tris-hydroxyethane, pentaerythritol, mannitol, sorbitol, fluorenyl rations, sucrose, phenol, isononylbenzene, resorcinol, hydroquinone, 1 1,1,1- or 1,1,2-tri (hydrocarbylphenyl) ethane. Polyether polyols started with amine-containing compounds can also be used, but used less often. Suitable amine-based compounds include ethylenediamine, diethylenetriamine, triethylenetetramine, 1,6-hexamethylenediamine, piperazine, and 2,5-difluorenylpiperidine. Qin, 1-amino-3-aminofluorenyl-3,5,5-trifluorenylcyclohexane, bis (4-aminocyclohexyl) methane, bis (4-amino-3-fluorenyl ring) Hexyl) pyrane, 1,4-cyclohexanediamine, 1,2-propanediamine, hydrazine, amino acid hydrazide, hydrazide of semi-carbabazine carboxylic acid, ammonia, amidine, tetramethylenediamine, Ethanolamine, diethanoldiamine, triethanoldiamine, aniline, phenylenediamine, 2,4 and 2,6-fluorenediphenylenediamine, polyphenyl polyfluorenyl polyamines obtained by the condensation reaction of aniline and formaldehyde, and their mixture. Phenol and acetol resins can also be used as starting compounds. The preferred starting compounds for the preparation of polyether polyols are compounds containing only hydroxyl groups, followed by compounds containing tertiary amines, followed by compounds containing NH groups that react with isocyanates.

5. Polythioether glycols, including 2,2'-dihydroxydiethylsulfide self-condensates, and polycondensates with other diols, dicarboxylic acids, formaldehyde, aminocarboxylic acids, or amino alcohols.

6. Polymeric polyols of the sulfonic type. Such polymeric polyols can be prepared from dicarboxylic acids, sulfonic acid diols, and sulfonic acid dicarboxylic acids. A better sulfonic polymer polyol is prepared by the condensation reaction of sodium 5-ophthalate isophthalic acid, adipic acid and 1,4-butanediol, and / or diethylene glycol.

If desired, monoalcohols and higher polyols can also be used to prepare the isocyanate-terminated prepolymers of the present invention. However, the ratio of the unit alcohol and the polyol should ensure that the average number of isocyanate groups of the prepolymer formed is equal to or less than two. Suitable examples include methanol, ethanol, n-propanol, isopropanol, hexanol, Octanol, Glycerol, Trimethylolpropane, 1,2,4-butanetriol, 1,2,6-hexanetriol, and mixtures thereof. In order for the isocyanate-terminated prepolymer to be dispersed in water to form a stable aqueous polyurethane dispersion of the present invention, it is necessary to embed a hydrophilic group, that is, an anionic group, a cationic group, or no, in the molecular structure of the prepolymer. Ionic hydrophilic group. Suitable hydrophilic components contain at least one (preferably at least two) isocyanate groups, or groups that are reactive with isocyanates, and contain at least one hydrophilic group or one potentially hydrophilic group. Examples of compounds that can be used to embed potential ionic groups include aliphatic hydroxycarboxylic acids, aliphatic or aromatic amine (primary or secondary amine) carboxylic acids, aliphatic hydroxysulfonic acids, aliphatic or aromatic Group amine (primary or secondary amine) sulfonic acid. The molecular weight of these acids is preferably less than 400.

According to the present invention, the preferred anionic group embedded in the polyurethane is a carboxylic acid group and a hydroxy acid of the following general formula:

(HO) xQ (COOH) _Y

Where Q contains a linear or branched alkane group of 1 to 12 carbon atoms, and X and Y represent numbers from 1 to 3. It is better that X equals 2. Preferably, the hydroxycarboxylic acid is a 2,2-dihydroxyfluorenyl alkyl acid represented by the following formula

ΟΗ, ΟΗ

R ¹ --COOH

CH ₂ OH

Wherein R ¹ represents hydrogen or an alkyl group having 1 to 9 carbon atoms. Examples of these compounds are 2,2-dihydroxyfluorenylacetic acid, 2,2-dihydroxyfluorenylpropionic acid, 2,2-dihydroxyfluorenylbutanoic acid, and 2,2-dihydroxyfluorenylvaleric acid. A better one is 2,2-dihydroxyamidinopropionic acid (DMPA).

The carboxylic acid group can be treated with a neutralizing agent to transform into a hydrophilic anionic group. Neutralizing agents include alkali metal salts, ammonia, primary amines, swollen amines, and preferably tertiary amines. Suitable alkali metal salts are sodium hydroxide, potassium hydroxide, sodium hydride, potassium hydride, sodium carbonate, potassium carbonate, sodium bicarbonate or potassium bicarbonate. It is better to use volatile organic amines, preferably tertiary amine compounds. Examples of suitable amine compounds are trimethylamine, triethylamine, triisopropylamine, tributylamine, N, N-dimethylcyclohexylamine, N, N-dioctadecylamine, Ν, Ν- Dimethylaniline, N-fluorenylmorpholine, N-ethylmorpholine, N-fluorenylpiperazine, N-fluorenylpyrrolidine, N-fluorenylpyridine, N, N-difluorenylethanolamine, N, N-Dimethylethanolamine, Triethanolamine, N-methyldiethanolamine, dimethylpropanolamine, 2-methoxyethyldiamine, N-hydroxyethylpyridine, 2- (2-dimethylethyl) (Oxyamine) ethanol or 5-diethylamine-2-fluorenone. The most preferred tertiary amines are those which do not contain isocyanate-reactive groups.

The carboxylic acid in the hydroxycarboxylic acid can be neutralized and then reacted with isocyanate to be embedded in the structure of the prepolymer. The hydroxyl group of the hydroxycarboxylic acid can also be reacted with the polyhydric alcohol and isocyanate to form a prepolymer with a carboxylic acid group, and then the alkali metal salt or a tertiary amine compound can be used to neutralize the carboxylic acid group in the prepolymer. Neutralization of carboxylic acid groups can also be partially Before the prepolymer is formed, and partly after the prepolymer is formed. The neutralized prepolymer is relatively easy to disperse in water. In some cases, especially polyester-based prepolymers based on HDI, the addition of a neutralizing agent will cause a sharp increase in the viscosity of the prepolymer. Then, the neutralizing agent can be mixed with water, and the unneutralized or The partially neutralized prepolymer is dispersed in this neutralizer-containing water. The amount of the neutralizing agent is 100% to 120% of the carboxylic acid equivalent.

In some cases, a small molecular weight diol may also be mixed with a polyhydric alcohol to prepare an isocyanate-terminated prepolymer. It is usually an aliphatic diol with a molecular weight from 60 to 400. Examples of small molecular weight diols are ethylene glycol, 1,3-propanediol, 1,4-butanediol or 1,6-hexanediol. The most commonly used is 1,4-butanediol. Small molecular weight diols can increase the strength, water resistance, and temperature resistance of polyurethanes.

The isocyanate-terminated prepolymer is prepared by reacting an excess of isocyanate with the above-mentioned active hydrogen-containing compound. The equivalent ratio of NCO in isocyanate to OH containing active hydrogen is 1-4.0: 1.0. The weight percentage of isocyanate groups in the resulting prepolymer is 1% to 10%. Among the above active hydrogen-containing compounds, the weight ratio of the polyhydric alcohol, the hydroxycarboxylic acid compound, and the small molecular weight diol is 50-98: 1-10: 0-20. The prepolymer preparation temperature is 25 ° C to 120 ° C, and the reaction time is 1 to 20 hours. The better reaction temperature is from 60'C to 100 ° C. The reaction temperature is lower than 25 ° C, the reaction time is too long, and the resulting prepolymer has a high viscosity, which is difficult to handle and difficult to disperse in water. Of course, co-solvents can also be used to reduce the viscosity of the prepolymer, but adding too much organic solvent will cause environmental protection, safety and health issues. On the other hand, a reaction temperature higher than 12CTC may cause side reactions, such as the reaction of isocyanate groups with carboxyl groups, the reaction of isocyanates with hydrogen on the amino group, etc., resulting in changes in the properties of the prepolymer and the resulting water Changes in the properties of polyurethane dispersions.

If necessary, a small amount of catalyst can be used to accelerate the synthesis of the prepolymer. Generally, the amount of the catalyst is 0.05% to 2.0% of the total weight of the prepolymer, and more preferably 0.1% to 0.2%. A commonly used catalyst is dibutyltin dilaurate.

If desired, the prepolymer can also be prepared in the presence of cosolvents, which must be volatile organic compounds that do not contain active hydrogen. Adding a co-solvent can reduce the viscosity of the prepolymer and make the synthesis reaction of the prepolymer more uniform. Suitable co-solvents include organic solvents such as ketones, esters, ethers and ketoesters. The more commonly used co-solvents are acetone and N-fluorenyl-2-pyrrolidone (NMP). The amount of co-solvent is generally 0% to 5% by weight of the prepolymer, that is, the weight content of the organic solvent in the resulting aqueous polyurethane dispersion does not exceed 2% (calculated based on 40% solids content).

If necessary, an external emulsifier containing no active hydrogen can also be used to increase the water-dispersing ability of the prepolymer and to improve the film-forming properties of the resulting aqueous polyurethane dispersion. The additional dispersant may be anionic, cationic, or non-ionic, depending on the ionic characteristics of the aqueous polyurethane dispersion. Added emulsification Agents, dispersants and surfactants can be added to the prepolymer or water before dispersing in water, or to the resulting aqueous polyurethane dispersion. If necessary, defoaming and leveling agents can also be added. Thickeners can also be added to adjust the viscosity of the aqueous polyurethane.

Once the isocyanate group-terminated prepolymer is formed, it can be dispersed in distilled or deionized water with stirring. The amount of water used to prepare a stable aqueous polyurethane dispersion is 80% to 40% of the total weight of the resulting aqueous polyurethane dispersion, and more preferably 65% to 50%. Water can be added to the prepolymer for dispersion, or the prepolymer can be added to water for dispersion, or the prepolymer stream and water stream can be continuously dispersed in the line through a high-speed dispersion device. The temperature of the prepolymer before dispersing is generally 35 ° C to 110 ° C. The preferred temperature is 45 ° C. C to 90 ° C, preferably 70 ° C to 80 ° C. The temperature of the water used for dispersion is 25 ° C to 90 ° C, preferably room temperature or 60-70 ° C.

After the prepolymer is dispersed in water and all its carboxylic acid groups are neutralized to become ionic groups, a chain extender is added to the dispersion of this prepolymer. The chain extender may be a known alcohol-based chain extender, but an amine or hydroxylamine-based chain extender is preferred. The chain extender can be added to the water before the prepolymer is dispersed, at the same time, or after the dispersion.

The amine chain extender is a polyamine or a mixture of polyamines. The average functionality of the amine chain extender, that is, the number of amine nitrogen atoms per molecule, should be about 1.8 to 6.0, more preferably 2.0 to 4.0, and most preferably 2.0 to 3.0. The required functionality can be achieved by mixing polyamines. For example, a functionality of 2.5 can be obtained using a mixture of equal moles of diamine and triamine.

Suitable amine chain extenders are hydrocarbon polyamine compounds having 2 to 6 amine genes, where the amines are primary or secondary amines. It may be aromatic, aliphatic, or alicyclic amine, and generally has 1-30 carbon atoms, more preferably 2-15 carbon atoms, and most preferably 2-10 carbon atoms. Examples of polyamines are diethylenetriamine, triethylenetetramine, tetraethylenepentamine, N- (2-piperazineethyl) ethylenediamine, Ν, Ν'-bis- (2-aminoethyl ) Pyrazine, Ν, Ν, Ν '-tris (2-aminoethyl) ethylenediamine, Ν- [Ν- (2-aminoethyl) -2-aminoethyl] -N'-(2 -Piperazineethyl) -ethylenediamine, N- (2-aminoethylene-N '-(2-piperazineethyl) amine, N, N-bis (2-piperazineethyl) amine, poly Ethyleneimine, iminodiamine guanidine, melamine, N- (2-aminoethyl) -1,3-propanediamine, 3,3'-diaminobenzidine, 2,4,6-triaminopyrimidine, Polypropylene oxide amine, tetrapropylene pentamine, tripropylene tetraamine, Ν, Ν-bis (6-aminohexyl) amine, Ν, Ν'-bis (3-aminopropyl) hexamethylene diamine, Or 2,4-bis (4'-aminophenyl) aniline. Better polyamines include isophorone diamine (IPDA), bis (4-aminocyclohexyl) pinene, bis (4-amino-3) -Fluorenylcyclohexyl) methane, 1,6-hexanediamine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine or pentaethylenehexamine. Use hydrazine as a chain extender Also better.

The amount of chain extender used depends on the number of ending isocyanate groups in the prepolymer. The equivalent ratio of the terminal isocyanate group in the prepolymer and the isocyanate active group in the chain extender is 1.0: 0.6 to 1.0: 1.1, A better ratio is 1.0: 0.8 to 1.0: 0.98.

Water can also act as a chain extender. The isocyanate group at the end of the prepolymer reacts with water to form an amine, which emits carbon dioxide. The resulting amine reacts with another isocyanate group to form a urea bond, and the prepolymer chain grows into a polymer. This chain extension reaction releases a large amount of carbon dioxide, causing the dispersion to form a foam, and ammonia water must be added to neutralize it, and a defoamer must be added to obtain a stable aqueous polyurethane dispersion.

The reaction between the prepolymer dispersed in water and the chain extender is generally performed in the range of 5-9 ° C, and it is preferably performed in the range of 20-80 ° C, and preferably in the range of 30-60'C. The reaction Conditions are generally carried out until the isocyanate groups of the prepolymer are substantially completely reacted.

The final product is an aqueous polyurethane dispersion of stable colloidal particles. Its particle size is generally less than 1.0 micron, such as 0.01 to 1.0 micron, preferably less than 0.5 micron, and most preferably 0.01 to 0.3 micron. The composition and preparation method of the aqueous polyurethane dispersion of the present invention can prepare a nano-aqueous polyurethane dispersion with a particle size of less than 100 nanometers (0.1 micron). Nano-aqueous polyurethane dispersion has good storage stability, good adhesion properties and good film-forming properties.

The aqueous polyurethane dispersion of the present invention generally has a solid content of 20% to 60%, and a better solid content of 35% to 50%.

The pH of the aqueous polyurethane dispersion of the present invention depends on its ionic type, and is anionic, cationic, or non-ionic. Generally, the aqueous polyurethane dispersion of the present invention is anionic, and its pH is 6-10, more preferably 7-9.5, and most preferably 7.5-9.5.

The viscosity of the aqueous polyurethane aqueous dispersion of the present invention is 10-10,000 centipoise, preferably 100-1,000 centipoise. Thickeners can be used to adjust the viscosity of aqueous polyurethanes. Typical thickeners are polyurethane dispersions, acrylic polymer emulsions, or aqueous cellulose dispersions.

The aqueous polyurethane dispersion of the present invention has good compatibility with other aqueous polymers, and their blends can improve certain properties of the aqueous polyurethane and reduce its cost. Examples of suitable waterborne polymers to be blended with are: polyacrylate emulsion, polystyrene-acrylate emulsion, polyvinyl acetate emulsion, polyethylene-vinyl acetate emulsion, polyvinyl chloride emulsion, synthetic rubber emulsion, natural Rubber latex, etc.

The aqueous polyurethane dispersion of the present invention can be used as a single component in many cases. In order to further improve its adhesive properties and coating film properties, such as improving its water resistance, solvent resistance and temperature resistance properties, water-dispersible curing agents can be added. Suitable curing agents include water-dispersible polyisocyanates, water-dispersible polyisocyanates, polycarbodiimides, polyaziridines, and water-based epoxy resins. The amount of this curing agent is generally 1% to 20% of the total weight of the two components, and more preferably 3% to 7%.

The aqueous polyurethane of the present invention can be used as an adhesive, an adhesive, a coating, a primer and a varnish. Available in various Such substrates include paper, wood, leather, metal, ceramics, cement, cloth, natural rubber, synthetic polymer materials, etc. Can be applied by brush, spray or roller.

The aqueous polyurethane dispersion of the present invention can also be modified by adding various additives. These additives include surfactants, defoamers, coalescents, fungicides, bactericides, plasticizers, thickeners, fillers, active pigments, UV stabilizers, flavorants, water-dispersible waxes, oils, Flame retardants and the like and mixtures thereof. Test Methods:

The following test methods are used to characterize the polymers of the present invention. Peel strength

Use a 0.25mm thick transparent PVC sheet as the substrate, cut into 250 x 300mm blocks with a paper cutter, and wipe the surface with ethanol. A fine-stripe metal rod was used to coat the aqueous polyurethane dispersion on the cleaned PVC with a length of 150 mm. The PVC coated with the aqueous polyurethane dispersion was allowed to dry at room temperature (usually more than 2 hours), and then two pieces of the same size coated PVC were compounded and cut into 25 X 150mm strip samples with a paper cutter. Use a heat sealer at 70 for this strip sample. C, heat activated at a pressure of 3.5 kg / cm ² for 30 seconds, and the T-peel strength was measured by Instron at a speed of 30 cm / minute. The instantaneous peel strength was measured within 15 minutes after the sample was thermally activated. The final peel strength was measured after the sample was thermally activated at room temperature for 7 days. The measurement method of the mechanical properties of the adhesive temperature resistance properties is as follows:

Bonding temperature resistance

Test sample preparation is the same as peel strength. Use a paper cutter to cut the sample into 50 X 25mm strips, and the glue area on one end is 25 X 25mm. Separate the uncoated 25 x 25mm composite PVC at the other end at 180 degrees. Hang one end with 100 g of missing code on the other end and hang the other end in a blast oven. From room temperature to 125 'C, the heating rate is 25. C / hour. Record the temperature at which the sample is pulled apart. If the sample is not pulled up to 125 ° C, record the peeling of the adhesive surface.

Determination of mechanical properties

The aqueous polyurethane dispersion was poured into a glass mold, dried at room temperature overnight, demoulded, left for 7 days, and the film was cut into dumbbell-shaped samples with a knife. Its thickness is controlled at 0.5-1.0mm. Using Intron, the stress-strain properties were measured at a speed of 5 cm / min, and the yield strength, tensile strength, and elongation were recorded. Preferred embodiment The following examples further illustrate the present invention, but the present invention is not limited to these examples. Unless otherwise specified, the proportions and percentages used in the examples are all weight ratios. Example 1-2

Examples 1 and 2 illustrate a prepolymer synthesized in one step by reacting a mixture of three diisocyanates composed of HDI and two ring-shaped diisocyanates (IPDI and TMXDI) in the presence of a small amount of solvent with DMPA and polyester diol. , Can successfully prepare stable aqueous polyurethane dispersions. Compared with US patent ① USP6147155, this patent describes the use of a mixture of HDI and cyclic diisocyanate (such as IPDI) with DMPA and polyester in the presence of a large amount of solvents (such as more than 20% of the total prepolymer NMP). Prepolymers synthesized by one-step diol reaction cannot successfully prepare stable aqueous polyurethane dispersions. Example 1

In a glass reaction axe equipped with a stirrer, a condenser tube, a thermocouple thermometer, and a calcium chloride drying tube, 219.2 g of polyesterdiol (prepared from 1,6-hexanediol, neopentyl glycol, and adipic acid) , Molecular weight 2000) and 12.1 g of DMPA and 9.1 g of triethylamine, 30.42 g of HDI, 19.98 g of IPDI and 21.96 g of TMXDI, reacted at 70'C for 3 hours in the presence of 16 g of acetone. The resulting neutralized isocyanate-terminated prepolymer was dispersed in 450 g of water with rapid stirring, and then a solution of 12.9 g of EDA in 22 g of water was slowly added. The dispersion was stirred at 60-65 ° C for 2 hours to obtain a stable, translucent, aqueous polyurethane dispersion with the following properties:

Solid content (%): 40.1

pH: 8.9

Viscosity (centipoise): 540

Particle size (nm): 89 Example 2

In the same glass reaction axe as in Example 1, 210 grams of polyesterdiol (prepared from 1,4-butanediol and adipic acid, molecular weight 2000), 14.1 grams of DMPA and 2.25 grams of 1,4-butanediol, With 42.34 grams of HDI, 23.31 grams of IPDI and 5.12 grams of TMXDI, at 70 in the presence of 17.8 grams of acetone. C was reacted for 3 hours, and then 10.1 g of triethylamine was added for neutralization for 15 minutes. The neutralized isocyanate-terminated prepolymer was dispersed in 529 g of water with rapid stirring, and then a solution of 7.6 g of EDA in 30 g of water was slowly added. This dispersion was stirred at 60-65 ° C for 2 hours to obtain a stable aqueous polyurethane dispersion with properties such as Down:

Solid content (%): 35.1

pH: 9.1

Viscosity (centipoise): 350

Particle size (nm): 180 Examples 3-4 and 5 (comparative example)

Examples 3 and 4 illustrate the use of a mixture of three diisocyanates, such as HDI, IPDI, and TMXDI, in the presence of a small amount of solvent (acetone), with triethylamine, 1,4-butanediol, DMPA, and polyesterdiol to form Prepolymer, which is dispersed in water, and the aqueous polyurethane dispersion produced by chain extension with diamine has better adhesive properties and better film-forming properties than Bayer's aqueous polyurethane products Dispercoll U-53 and U-54 Example 5 (Comparative Example) The properties of Dispercoll U-53 and U-54 were measured and compared with the aqueous polyurethane dispersion liquid phase prepared in Examples 3 and 4. U-53 and U-54 are products based on US Patent No. 4,870,129. They are a sulfonic acid-based aqueous polyurethane dispersion and are considered to be the best commercially available aqueous polyurethane dispersion adhesive products since the 1990s. Example 3

In the same glass reaction axe as in Example 1, 236.6 g of polyester diol (prepared from 1,6-hexanediol and adipic acid, molecular weight 2000), 2.6 g of 1,4-butanediol and 15.4 g of DMPA with 11.5 Triethylamine, 26.9 grams of HDI, 17.8 grams of IPDI, and 41.8 grams of TMXDI were reacted at 70 ° C for 3 hours in the presence of 18 grams of acetone. The resulting neutralized isocyanate-terminated prepolymer was dispersed in 500 grams of water with rapid stirring. Then slowly add a solution of 7.9 g of ethylenediamine in 22.7 g of water. This dispersion was further stirred at room temperature for 2 hours. The properties of the obtained stable, translucent aqueous polyurethane dispersion are shown in Table 1. Example 4

In the same glass reaction axe as in Example 1, 248.4 g of polyester diol (prepared from 1,4-butanediol and adipic acid, molecular weight 2000), 0.5 g of 1,4-butanediol and 16.1 g of DMPA with 12.9 g Triethylamine, 21.4 g of HDI, 30.3 g of IPDI and 15.6 g of TMXDI were reacted at 70 ° C for 3 hours in the presence of 17.6 g of acetone. The resulting neutralized isocyanate-terminated prepolymer was dispersed in 480 g of water with rapid stirring, and then a solution of 7 g of ethylenediamine in 30 g of water was slowly added. This dispersion was stirred at room temperature for 2 hours to obtain a stable translucent aqueous polyurethane dispersion.其结果见表 1。 Its performance is shown in Table 1. Example 5 (comparative example)

The properties of Dispercoll U-53 and U-54 were measured. A PVC / PVC adhesion test sample was prepared on the PVC coated with U-53 and U-54 by heat activated composite. Test its adhesive properties. Films were prepared by casting U-53 and U-54 in glass plate molds, and their mechanical properties were tested. Dispercoll U-53 and U-54, Bayer's water-based polyurethane products, based on US patent ② USR 4,870,129, use HDI and IPDI with polyester diols in a large amount of acetone (the total weight of the final aqueous polyurethane dispersion 40- 80% acetone) was used to prepare the prepolymer, and a sulfonate aliphatic diamine was used as a chain extender and a sulfonate ion group was introduced. The prepared aqueous polyurethane dispersion contains a large amount of acetone, and a vacuum distillation method is required to reduce the acetone content in the final product to less than 1%. All test results are shown in Table 1.

Example 6

Example 6 illustrates the use of a mixture of HDI, IPDI, and TMXDI in the absence of an organic solvent to react with a poly (ester-ether) glycol and other aqueous polyurethane dispersions. Agent. Compared with US patent ⑦ USP. 5,891,580 (Ficke et al.), This patent uses a mixture of 2,4-TDI and 2,6-TDI with polyether glycol, etc., in an aqueous polyurethane dispersion prepared in the presence of a large amount of acetone. It contains a large amount of acetone, and the water-based polyurethane product can be obtained after the acetone is distilled off. The product can be used as an adhesive for flexible packaging composite films.

In the same glass reaction axe as in Example 1, 280 grams of poly (ether) glycol (prepared from diethylene glycol and adipic acid, molecular weight 2000) and 15.4 grams of DMPA and 11.3 grams of triethylamine, 29.4 grams of HDI, 11.1 grams IPDI and 36.6 grams of TMXDI were reacted at 70 ° C for 3 hours. The neutralized isocyanate-terminated prepolymer was dispersed in 557 grams of water under rapid stirring, and then 3.05 grams of ethanolamine and 4.8 grams of ethylenediamine were slowly added. Solution in 30 grams of water. A stable, translucent aqueous polyurethane dispersion was obtained with the following properties:

Solid content (%): 40.1

pH: 8.9

Viscosity (centipoise): 350

Particle size (nm): 75

With this aqueous polyurethane dispersion, roller coated on the surface-treated films such as polypropylene, polyethylene, polyester and aluminum foil, dried, heat-composited, and has good adhesive properties. Example 7

Example 7 illustrates that an aqueous polyurethane dispersion prepared by using a mixture of HDI, IPDI, and TMXDI in the presence of a solvent without reacting with polyether glycol, etc., has good film-forming properties, and the film has good mechanical properties. It can be used as coating and can be used to make medical gloves and condoms.

In the same glass reaction axe as in Example 1, 238 grams of polyether glycol (prepared from propylene oxide, molecular weight 2000), 15.95 grams of DMPA and 2.14 grams of trimethylolpropane, and 12 grams of triethylamine, 28 grams HDI, 18.5 g of IPDI and 43.6 TMXDI, reacted at 70 ° C for 3 hours. The neutralized isocyanate-terminated prepolymer formed was dispersed in 522 g of water under rapid stirring, and then 6.1 g of hexamethylene diamine was slowly added. And 4.1 g of diethylenetriamine in 30 g of water. A stable, translucent, aqueous polyurethane dispersion was obtained with the following properties:

Solid content (%): 39.9

pH: 9.0

Viscosity (centipoise): 450

Particle size (nm): 95 实施例 8 The tensile strength of the film cast with this dispersion was 35Mpa, and the elongation was 850%. Example 8

Example 8 illustrates that an aqueous polyurethane dispersion prepared by using a mixture of HDI, H, ₂ MDI, and TMXDI with polyether glycol, etc., is a good coating.

In the same glass reaction axe as in Example 1, 238 grams of polyether glycol (prepared from propylene oxide, molecular weight 2000), 15.95 DMPA and 12 grams of triethylamine, 14 grams of HDI, 44 grams of H ₁₂ MDI, and 43.6 grams TMXDI, at 70. C was reacted for 3 hours. The resulting neutralized isocyanate-terminated prepolymer was dispersed in 665 g of water with rapid stirring, and then a solution of 7.85 g of ethylenediamine and 4.1 g of diethylenetriamine in 40 g of water was slowly added. . A stable, translucent, aqueous polyurethane dispersion was obtained. Its properties are as follows: Solid content (%): 35.1

pH: 9.1

Viscosity (centipoise): 550

Particle size (nm): 95

Tensile strength (Mpa): 45

Elongation (%): 750 Example 9

Example 9 shows that a mixture of HDI, TMXDI, and TDI is used in the presence of a small amount of solvent to react with a polyether diol and other aqueous polyurethane dispersions, which can be used as fabric treating agents.

In the same glass reaction axe as in Example 1, 218 grams of polyether glycol (molecular weight 2000 prepared from propylene oxide), 14.6 grams of DMPA and 1.8 grams of HDI, 2.7 grams of TMXDI and 64.9 grams of TDI, in the presence of 21 grams of acetone , At 60-70. C was reacted for 3 hours, 11 g of triethylamine was added and stirred for 15 minutes, and then immediately dispersed in 700 g of water with rapid stirring. A solution of 7 g of ethylenediamine in 25 g of water was slowly added with stirring. A milky white aqueous polyurethane dispersion was obtained. Its properties are as follows:

Solid content (%): 29.8

pH: 8.9

Viscosity (centipoise): 650

Particle size (nm): 195 Example 10 Example 10 illustrates that a mixture of HDI, TMXDI and MDI can be used to react with polyether glycol and the like in the presence of a small amount of organic solvent to obtain a stable aqueous polyurethane dispersion.

In the same glass reaction axe as in Example 1, a mixture of 89.9 g of MDI, 6.7 g of TMXDI and 1 g of HDI, and 14.6 g of DMPA and 218 g of poly (ester-ether) glycol (prepared from diethylene glycol and adipic acid, molecular weight) 2000), in the presence of 20 grams of acetone, react at 60-70 ° C for 3 hours, and then add 11.1 grams of triethylamine to neutralize the reaction for 15 minutes. With rapid stirring, 600 grams of water was added to form a dispersion of the prepolymer. A solution of 5.6 g of ethylenediamine and 3.3 g of ethanolamine in 30 g of water was added, and stirring was continued for 2 hours to obtain a stable aqueous polyurethane dispersion. Its properties are as follows:

Solid content (%): 35.2

pH: 8.7

Viscosity (centipoise): 720

Particle size (nm): 185

This dispersion has good adhesive properties on surface-treated polypropylene, polyethylene and polyester films, and can be used as an adhesive for flexible packaging composite films. This aqueous polyurethane dispersion also has good adhesion properties to fabrics, fibers, leather, etc.

Claims

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1. An aqueous polyurethane dispersion, wherein the polyimide ester is composed of the following reaction products;

(a) An isocyanate-terminated polyurethane prepolymer containing a carboxylate group, formed by the reaction of the following components:

(1) A polyisocyanate component composed of 1,6-hexyl diisocyanate, tetramethylphenyl diisocyanate, and a third polyisocyanate, and the third polyisocyanate component is isophorone Diisocyanate, dicyclohexylfluorene diisocyanate, methylene diphenyl diisocyanate, or pyrophenylene diisocyanate, of which 1,6-hexyl diisocyanate, tetramethylphenyl diisocyanate, and the third polyisocyanate The weight ratio is 1 to 98: 1 to 98: 1 to 98, and

(2) Long chain, each molecule containing two or more active hydrogens, molecular weight 400 to 10,000, including polyester polyols, polyether polyols, sulfonic-type polypolyols, poly

(Ester-ether) polyols, and organic polyols including mixtures thereof, and

(3) An organic hydroxycarboxylic acid compound having a molecular formula of (HO) xR (COOH) y, where R represents a straight or branched hydrocarbon group of 1-12 carbon atoms, and X and y represent integers of 1-3 ,with

(4) optionally, an aliphatic polyol having a molecular weight from 60 to 400,

The total OH equivalent ratio of the NCO equivalent of the isocyanate of (1) above to the organic polyhydroxy compound of (2), the hydroxycarboxylic acid compound of (3), and the aliphatic polyol of (4) is 1 to 4: 1.0. The weight percentage of isocyanate groups of the prepolymer formed after the reaction is 1 to 10%. The organic polyhydroxy compound (2), the hydroxycarboxylic acid compound (3), and the aliphatic polyol (4) Weight ratio is 50 ~ 98: 1 ~ 20: 0-20, and

(b) An active hydrogen-containing compound including water, ammonia, hydrazine or substituted hydrazine, aliphatic, alicyclic, aromatic or heterocyclic primary amines, secondary amines, polyamines, and alcohol amines. The equivalent ratio of the isocyanate reactive group in the chain extender except water to the isocyanate group in the prepolymer is from 0.6: 1.0 to 1.1: 1.

2. The aqueous polyurethane dispersion according to claim 1, wherein the molecular weight of the long-chain organic polyhydroxy compound is 400 to 3000, including ethylene glycol, butanediol, hexanediol, neopentyl A polyester diol consisting of alcohol, diethylene glycol, and a mixture thereof with adipic acid, or a polyether diol consisting of ethylene oxide, propylene oxide, and a mixture thereof.

3. The aqueous polyurethane dispersion according to claim 1, wherein the organic hydroxycarboxylic acid compound is 2,2-dimethylolpropionic acid, 2,3-dihydroxysuccinic acid, or dihydroxyl Butyric acid, glycolic acid, 2 -Hydroxypropionic acid, hydroxysuccinic acid, dihydroxysuccinic acid and dihydroxybenzoic acid.

4. The aqueous polyurethane dispersion according to claim 1, wherein the aliphatic polyol having a molecular weight of 60 to 400 is propylene glycol, butanediol, hexanediol, or trihydroxymethylpropane.

5. A method for preparing an aqueous polyurethane dispersion according to claim 1, comprising the following steps:

(a) a mixture of three diisocyanates having a weight ratio of 1,6-hexyl diisocyanate, tetramethylphenyl diisocyanate, and a third polyisocyanate of 1 to 98: 1 to 98: 1 to 99; In the presence of a water-soluble volatile organic solvent containing not more than 5% of the total amount of the finally produced aqueous polyurethane dispersion and the reaction temperature of 25 ° C to 120 ° C, the equivalent ratio of polyhydric alcohol and organic hydroxycarboxylic acid in NCO and OH When the ratio is 1.1 to 4.0: 1.0, the reaction is performed for 1 to 20 hours to form a prepolymer having an isocyanate group ending with a carboxylic acid side group. The other diisocyanates are isophorone diisocyanate, and dicyclohexyl dioxane di Isocyanate, fluorenyl diphenyl diisocyanate, or diphenyl diisocyanate;

(b) The resulting prepolymer or prepolymer after neutralization is dispersed in water;

(c) The prepolymer having isocyanate groups dispersed in water reacts with at least one amine chain extender to form a polyurethane polymer, wherein water is 40 to 80% of the total weight of the resulting aqueous polyurethane aqueous dispersion;

(d) Neutralize the carboxylic acid group of the hydroxycarboxylic acid compound or prepolymer with a neutralizer at 20 to 80'C. This neutralization reaction is performed before the formation of the prepolymer, at the same time as the prepolymerization reaction, after the completion of the prepolymerization reaction, and before the prepolymer is dispersed in water, or by adding a neutralizing agent to water and simultaneously with the chain extension reaction. The neutralizing agent is an alkali metal hydroxide or a salt thereof, ammonia, ammonia water, a primary amine, a secondary amine, or a tertiary amine.

6. The method for preparing an aqueous polyurethane dispersion according to claim 5, characterized in that the organic solvent is not more than 2% of the total amount of the finally produced aqueous polyurethane dispersion, and the organic solvent is acetone or N-fluorene -2-Pyrrolidone does not need to be distilled off from the resulting polyurethane dispersion.

The method for preparing an aqueous polyurethane dispersion according to claim 5, characterized in that the carboxyl group in the dihydroxymethylpropionic acid is neutralized with triethylamine before the formation of the prepolymer.

The aqueous polyurethane dispersion according to claim 1 or 5, wherein the aqueous polyurethane dispersion is an aqueous polyurethane having a particle diameter of less than 300 nanometers with improved adhesive properties and improved film properties.

The aqueous polyurethane dispersion according to claim 1 or 5, characterized in that the aqueous polyurethane dispersion is a nano-aqueous polyurethane dispersion with a particle size of less than 100 nanometers.