AQUEOUS POLYURETHANE DISPERSION

1 . An aqueous polyurethane dispersion, comprising a polyurethane having an anionic group dispersed therein, the polyurethane having a fusion enthalpy of 3 J/g-100 J/g at 20° C.-100° C. of the first temperature rising curve measured with the DSC according to DIN 65467, and a weight-average molecular weight of 31,000-95,000; wherein the aqueous polyurethane dispersion has an acid value of 0.5 mg KOH/g-8.5 mg KOH/g.

2 . The aqueous polyurethane dispersion of claim 1 , wherein the anionic group is located on a side chain of the polyurethane, and the anionic group is one or more of a sulfonate group and a carboxylate group.

3 . The aqueous polyurethane dispersion of claim 1 , wherein the polyurethane has a fusion enthalpy of 25 J/g-100 J/g at 20° C.-100° C. of the first temperature rising curve measured with the DSC according to DIN 65467.

4 . The aqueous polyurethane dispersion of claim 1 , wherein the polyurethane has a carboxyl group content of 0.1 wt %-1.5 wt %, on a basis that the amount of the polyurethane is 100 wt %.

5 . The aqueous polyurethane dispersion of claim 1 , wherein the polyurethane is obtained by reacting a system comprising the following components:

a. a polyisocyanate mixture containing hexamethylene diisocyanate;

b. an isocyanate-reactive group-containing mixture, comprising a polymer polyol having a number-average molecular weight of 400 g/mol-8,000 g/mol and a carboxyl group-containing isocyanate-reactive compound;

c. an emulsifier;

d. an optional solvent;

e. an optional reactive diluent; and

f. an optional stabilizer;

wherein the polymer polyol has a fusion enthalpy of 3 J/g-100 J/g at 20° C.-100° C. of the first temperature rising curve measured with the DSC according to DIN 65467,

wherein the amount of the carboxyl group-containing isocyanate-reactive compound is 0.1 wt %-1.5 wt % on a basis that the amount of the polyurethane is 100 wt %, and

wherein the neutralization degree of the carboxyl groups of the carboxyl group-containing isocyanate-reactive compound is 0-50%.

6 . The aqueous polyurethane dispersion of claim 5 , wherein the fusion enthalpy of the polymer polyol at 20° C.-100° C. of the first temperature rising curve measured with the DSC according to DIN 65467 is 25 J/g-100 J/g.

7 . The aqueous polyurethane dispersion of claim 5 , wherein the carboxyl group of the carboxyl group-containing isocyanate-reactive compound has a neutralization degree of 0.

8 . The aqueous polyurethane dispersion of claim 5 , wherein the polyisocyanate mixture comprises isocyanate groups and the isocyanate groups to the isocyanate-reactive groups in the system is 1.0-3.0.

9 . A process for preparing an aqueous polyurethane dispersion of claim 1 , comprising the steps of:

i. reacting some or all of a polyisocyanate mixture and an isocyanate-reactive group-containing mixture to obtain a prepolymer, the reaction is carried out in the presence of an optional solvent, or an optional solvent is added after the reaction to dissolve the prepolymer;

ii. reacting the prepolymer, an emulsifier, an optional reactive diluent, an optional stabilizer, the polyisocyanate mixture that is not added in the step i, and the isocyanate-reactive group-containing mixture that is not added in the step i to obtain the polyurethane; and

iii. introducing water and an optional emulsifier before, during or after step ii to obtain the aqueous polyurethane dispersion;

the aqueous polyurethane dispersion comprises a polyurethane having an anionic group dispersed therein, said polyurethane has a fusion enthalpy of 3 J/g-100 J/g at 20° C.-100° C. of the first temperature rising curve measured with the DSC according to DIN 65467, and a weight-average molecular weight of 31,000-95,000, the aqueous polyurethane dispersion has an acid value of 0.5 mg KOH/g-8.5 mg KOH/g.

10 . A composition comprising an aqueous polyurethane dispersion of claim 1 .

11 . The composition of claim 10 , wherein the composition is a coating, an adhesive, a sealant or a printing ink.

12 . An adhesive comprising an aqueous polyurethane dispersion of claim 1 .

13 . The adhesive of claim 12 , wherein the thermal activation temperature of the adhesive is 35° C.-70° C.

14 . The adhesive of claim 12 , further comprising a crosslinking agent having a carboxyl group-reactive group.

15 . An adhesion article having a substrate bonded with an adhesive of claim 12 .

16 . The adhesion article of claim 15 , wherein the substrate is one or more of a rubber, plastic, paper, cardboard, wood, textile, metal, alloy, fabric, fiber, artificial leather, leather, inorganic material, human or animal hair, and human or animal skin.

17 . The adhesion article of claim 15 , wherein the adhesion article is a shoe sole or a shoe shaft.

18 . The adhesion article of claim 15 , wherein the adhesion article is film or wood.

19 . A method of manufacturing an adhesion article, comprising the steps of:

A. applying the adhesive of claim 12 to at least one surface of a substrate;

B. heating and drying the surface of the substrate to which the adhesive is applied; and

C. contacting the surface of the substrate treated in step B with the substrate itself or the surface of an additional substrate to obtain the adhesion article.

20 . The method of claim 19 , further comprising step D between step B and step C: irradiating the surface of the substrate treated by step B with actinic radiation.

21 . (canceled)