CN111138629A

CN111138629A - Waterborne polyurethane emulsion, coating, preparation method and application thereof

Info

Publication number: CN111138629A
Application number: CN202010042298.8A
Authority: CN
Inventors: 丁鹄岚; 李鸿越; 李炯
Original assignee: Guangzhou Kangdifu Environmental Protection Technology Co ltd
Current assignee: Guangzhou Kangdifu Environmental Protection Technology Co ltd
Priority date: 2020-01-15
Filing date: 2020-01-15
Publication date: 2020-05-12

Abstract

The invention relates to an aqueous polyurethane emulsion, a coating, and a preparation method and application thereof. The waterborne polyurethane emulsion is mainly prepared from the following components in parts by mass: polyol, isocyanate, a catalyst, a hydrophilic chain extender, a blocking agent, a neutralizer and water. Wherein the polyol comprises polyol a and polyol B; the polyol A is carbon dioxide copolymer polyol, and the polyol B is at least one of polycarbonate diol, polybutylene adipate diol and polytetrahydrofuran diol. The aqueous polyurethane emulsion has the advantages that the polyol A and the polyol B are mixed for use, and are matched with isocyanate, a catalyst, a hydrophilic chain extender, a blocking agent, a neutralizer and water, the mass parts of the components are controlled, so that the micro-phase separation of the aqueous polyurethane emulsion and the interaction between hydrogen bonds can be improved, and the aqueous polyurethane has good stability, water resistance and chemical reagent corrosion resistance.

Description

Waterborne polyurethane emulsion, coating, preparation method and application thereof

Technical Field

The invention relates to the technical field of high polymer materials, in particular to a waterborne polyurethane emulsion, a waterborne polyurethane coating, and a preparation method and application thereof.

Background

With the rapid development of economy, more and more materials are prepared and widely applied, and the development and the use of new materials bring great convenience to the life of people, but the problem of environmental pollution caused by the new materials is also increasingly serious. Such as solvent-based coatings, the use of solvent-based adhesives generate large amounts of Volatile Organic Compounds (VOCs) that have serious adverse effects on the environment. Therefore, the use of solvent-based paints and solvent-based adhesives is being restricted nationwide. Compared with solvent-based coatings and solvent-based adhesives, the waterborne polyurethane has the advantages of environmental friendliness, good toughness, high strength and the like. However, the stability and water resistance of products such as coatings, adhesives and the like prepared from the traditional waterborne polyurethane are poor, and the products are easily corroded by chemical agents, so that the application of the waterborne polyurethane is limited to a great extent.

Disclosure of Invention

Based on this, there is a need for an aqueous polyurethane emulsion. The waterborne polyurethane emulsion has good water resistance and chemical reagent corrosion resistance.

On the other hand, it is also necessary to provide a coating. The raw material components of the coating comprise the waterborne polyurethane emulsion, and the coating has good performance and is green and environment-friendly in use; and carbon dioxide is used as a raw material as a synthetic material, so that the method is green, low-carbon and environment-friendly.

The specific technical scheme is as follows:

the invention aims to provide a waterborne polyurethane emulsion which is mainly prepared from the following components in parts by mass:

the polyols comprise polyol A and polyol B; the polyol A is carbon dioxide copolymer polyol, and the polyol B is at least one of polycarbonate diol, polybutylene adipate diol and polytetrahydrofuran diol.

In one embodiment, the mass ratio of the polyol A to the polyol B is 1 (1.5-4).

In one embodiment, the carbon dioxide copolymer polyol has a number average molecular weight of 2000g/mol to 4000g/mol and a hydroxyl functionality of 2 to 6.

In one embodiment, the isocyanate is at least one of isophorone diisocyanate, hydrogenated methylene diphenyl diisocyanate, and hexamethylene diisocyanate.

In one embodiment, the catalyst is an organobismuth; and/or the presence of a gas in the gas,

the hydrophilic chain extender is at least one of dimethylol propionic acid, dimethylol butyric acid and ethylene diamino sodium sulfonate; and/or the presence of a gas in the gas,

the end-capping reagent is at least one of trimethylolpropane, pentaerythritol and glucose; and/or the presence of a gas in the gas,

the neutralizing agent is at least one of triethylamine, monoethanolamine, diethanolamine and triethanolamine.

Another object of the present invention is to provide a method for preparing an aqueous polyurethane emulsion, which comprises the following steps:

mixing polyol, isocyanate and a catalyst, and uniformly stirring at the temperature of 70-95 ℃;

adjusting the temperature to 60-70 ℃, adding a hydrophilic chain extender, and uniformly stirring at the temperature of 60-75 ℃;

adding an end-capping reagent, uniformly stirring at the temperature of 60-75 ℃, and then adding a neutralizing agent;

adjusting the temperature to 40-60 ℃, adding 95-105 parts by mass of solvent, and uniformly stirring to obtain a prepolymer;

dispersing the prepolymer in water at the temperature of 8-12 ℃ to obtain a preformed product of aqueous polyurethane emulsion;

and removing the solvent in the aqueous polyurethane emulsion preform.

In one embodiment, the solvent is at least one of acetone and butanone.

The invention also aims to provide application of the waterborne polyurethane emulsion in any one of the above embodiments in preparing a coating.

In addition to the above objects, it is also an object of the present invention to provide a coating material and a method for preparing said coating material.

The coating is mainly prepared from the following components in parts by mass: 95 to 105 parts of the aqueous polyurethane emulsion, 10 to 50 parts of amino resin and 0.5 to 1.6 parts of an auxiliary agent.

A preparation method of the coating comprises the following steps:

preparing the aqueous polyurethane emulsion by adopting the preparation method of the aqueous polyurethane emulsion in any embodiment;

and mixing the aqueous polyurethane emulsion with the auxiliary agent, and adding the amino resin.

The waterborne polyurethane emulsion is mainly prepared from the following components in parts by mass: 90 to 110 portions of polyol, 20 to 50 portions of isocyanate, 0.05 to 0.15 portion of catalyst, 5 to 10 portions of hydrophilic chain extender, 15 to 30 portions of end-capping reagent, 3.7 to 7.5 portions of neutralizer and 170 to 350 portions of water. Wherein the polyol comprises polyol A and polyol B; the polyol A is carbon dioxide copolymer polyol, and the polyol B is at least one of polycarbonate diol, polybutylene adipate diol and polytetrahydrofuran diol. The aqueous polyurethane emulsion takes the polyol A and the polyol B as raw materials, and the polyol A has an irregular internal structure and high disorder degree and can influence the arrangement of molecular chains. The polyol B has a symmetrical molecular internal structure, is easy to crystallize in the molecule, provides intramolecular hydrogen bonds, has high cohesive force, and can effectively improve intermolecular acting force. The combination of the polyol A and the polyol B can effectively improve the comprehensive performance of the waterborne polyurethane. Meanwhile, the polyol A and the polyol B are mixed for use, and are matched with isocyanate, a catalyst, a hydrophilic chain extender, a blocking agent, a neutralizer and water, the mass parts of the components are controlled, so that the micro-phase separation of the aqueous polyurethane emulsion and the interaction between hydrogen bonds can be improved, and the aqueous polyurethane has good stability, water resistance and chemical reagent corrosion resistance.

The coating is mainly prepared by the waterborne polyurethane emulsion, amino resin and an auxiliary agent. On the basis of good stability, water resistance and chemical corrosion resistance of the waterborne polyurethane, the coating has the characteristics of high hardness and good toughness through reasonable proportion of the waterborne polyurethane, amino resin and an auxiliary agent.

Detailed Description

In order that the invention may be more fully understood, reference will now be made to the accompanying examples. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The embodiment of the invention provides a waterborne polyurethane emulsion which is mainly prepared from the following components in parts by mass:

In the waterborne polyurethane, the main factors influencing the performance of the waterborne polyurethane are the selection and the proportion of a soft segment and a hard segment in the waterborne polyurethane. The soft segment is mainly composed of polyol, and the hard segment is mainly composed of isocyanate and other auxiliary agents. The selection of the polyol plays a key role in the performance of the waterborne polyurethane, and the polyol influences the molecular weight, stability, water resistance and corrosion resistance of the waterborne polyurethane. The performances of the waterborne polyurethane prepared by polymerizing different soft segments and isocyanate are greatly different, and the performances of the waterborne polyurethane prepared by polymerizing the same soft segments and isocyanate according to different proportions are also greatly different. Therefore, selecting a proper soft segment and determining the proportion of the soft segment to the hard segment are particularly important for improving the performance of the waterborne polyurethane. In the aqueous polyurethane emulsion of the embodiment, two types of polyols, namely polyol A and polyol B, are used as raw materials, and the polyol A has an irregular internal structure and high disorder degree and can influence the arrangement of molecular chains. The polyol B has a symmetrical molecular internal structure, is easy to crystallize in the molecule, provides intramolecular hydrogen bonds, has high cohesive force, and can effectively improve intermolecular acting force. The combination of the polyol A and the polyol B can effectively improve the comprehensive performance of the waterborne polyurethane. Meanwhile, the polyol A and the polyol B are mixed for use, and are matched with isocyanate, a catalyst, a hydrophilic chain extender, a blocking agent, a neutralizer and water, the mass parts of the components are controlled, so that the micro-phase separation of the aqueous polyurethane emulsion and the interaction between hydrogen bonds can be improved, and the aqueous polyurethane has good water resistance and chemical reagent corrosion resistance.

In a preferred embodiment, the mass ratio of the polyol A to the polyol B is 1 (1.5-4). The polyol A and the polyol B are matched according to the mass ratio of 1 (1.5-4), so that the isocyanate index of the waterborne polyurethane can be controlled to be less than 1, and the hydroxyl-terminated waterborne polyurethane can be obtained. Within the isocyanate index range, the waterborne polyurethane prepolymer has proper viscosity, is easy to emulsify, and can effectively improve the stability of waterborne polyurethane.

The isocyanate index is a ratio of the amount of isocyanate group (NCO) in the raw materials used in the polyurethane synthesis process to the sum of the amounts of NCO-reactive functional group-containing substances. In the conventional process for preparing the aqueous polyurethane, the isocyanate index is generally greater than 1, so that the aqueous polyurethane has a larger molecular weight. However, when the isocyanate index is greater than 1, the viscosity of the aqueous polyurethane prepolymer is too high, emulsification is difficult, and the stability of the product is poor.

In the embodiment, the appropriate polyol A and the appropriate polyol B are selected, and the mass ratio of the polyol A to the polyol B is controlled to be 1 (1.5-4), so that the isocyanate index of the waterborne polyurethane can be controlled to be less than 1, and the stability of the waterborne polyurethane can be effectively improved. Specifically, the polyol A is a carbon dioxide copolymer polyol, the carbon dioxide copolymer polyol contains more carbonate bonds and ether bonds and also contains a side methyl group, and the internal rotation of the carbonate bonds and the ether bonds is limited due to the existence of the side methyl group, so that the waterborne polyurethane product has high mechanical property and hardness. The polyol B is at least one of polycarbonate diol, polybutylene adipate diol and polytetrahydrofuran diol, the internal structure of the molecule of the polyol B is symmetrical, the cohesive force is large, and the disorder degree of the polyol A can be effectively reduced. By controlling the mass ratio of the polyol A to the polyol B to be 1 (1.5-4), the hydroxyl-terminated waterborne polyurethane with good comprehensive performance is obtained.

In a specific example, the aqueous polyurethane emulsion is prepared from the following components in parts by mass:

in a specific example, the aqueous polyurethane emulsion is mainly prepared from the following components in parts by mass:

specifically, the aqueous polyurethane emulsion is prepared from the following components in parts by mass:

in a particular example, the carbon dioxide copolymer polyol has a number average molecular weight of 2000g/mol to 4000g/mol and the carbon dioxide copolymer polyol has a hydroxyl functionality of 2 to 6. The polycarbonate diol has a number average molecular weight of 1000g/mol to 3000g/mol and a hydroxyl functionality of 2. The number average molecular weight of the polybutylene adipate glycol is 2000g/mol to 4000g/mol, and the hydroxyl functionality of the polybutylene adipate glycol is 2. The polytetrahydrofuran diol has a number average molecular weight of 1000g/mol to 3000g/mol and a hydroxyl functionality of 2.

In a specific example, the isocyanate is at least one of isophorone diisocyanate, hydrogenated methylene diphenyl diisocyanate, and hexamethylene diisocyanate. The catalyst is organic bismuth. The catalyst has great influence on the structure of the waterborne polyurethane. Polyol A mainly contains secondary hydroxyl groups and has low reactivity, and polyol B mainly contains primary hydroxyl groups and has high reactivity. The difference of the reactivity of the polyol A and the polyol B can cause the difference of the structures, and the organic bismuth catalyst can be adopted to ensure that the polyols are arranged in order, so that the waterborne polyurethane achieves excellent comprehensive performance. The hydrophilic chain extender is at least one of dimethylol propionic acid, dimethylol butyric acid and ethylene diamino sodium sulfonate. The blocking agent is at least one of trimethylolpropane, pentaerythritol and glucose. The neutralizing agent is at least one of triethylamine, monoethanolamine, diethanolamine and triethanolamine. The water is deionized water.

The invention also provides a preparation method of the waterborne polyurethane emulsion, which comprises the following steps:

mixing the polyol, the isocyanate, the catalyst, the hydrophilic chain extender, the end-capping agent, the neutralizer and the water according to the mass parts in the aqueous polyurethane emulsion;

mixing polyol, isocyanate and a catalyst, and stirring at the temperature of 70-95 ℃ for 2-5 h;

cooling to 60-70 ℃, adding a hydrophilic chain extender, and stirring for 1-3 h at the temperature of 60-75 ℃;

adding an end-capping reagent, stirring at 60-75 ℃ for 0.1-0.5 h, and adding a neutralizing agent;

cooling to 40-60 ℃, adding 95-105 parts by mass of solvent, and stirring for 0.1-1 h to obtain prepolymer;

the solvent in the aqueous polyurethane emulsion preform is removed.

In a specific example, the solvent is at least one of acetone and butanone.

In a specific example, the method of the dispersion processing is as follows: the prepolymer is mixed with water at a dispersing speed of 1200rpm to 2000 rpm. Specifically, the prepolymer is added into water at a dispersing speed of 1200rpm to 2000 rpm.

In a specific example, after the prepolymer is dispersed in water, the mixture obtained after dispersion is emulsified for 10 to 20 minutes.

In a specific example, the method for removing the solvent in the aqueous polyurethane emulsion preform is: the solvent was removed by reduced pressure.

In one specific example, the polyol is dehydrated before mixing the polyol, isocyanate, and catalyst. The dehydration treatment method comprises the following steps: stirring the polyhydric alcohol for 1.5 to 3 hours under the vacuum environment of 100 to 115 ℃.

The invention also provides an application of the waterborne polyurethane emulsion in preparing a coating.

In addition to the above embodiments, another embodiment of the present invention provides a coating material, which is mainly prepared from the following components in parts by mass: 95 to 105 parts of the aqueous polyurethane emulsion, 10 to 50 parts of amino resin and 0.5 to 1.6 parts of auxiliary agent.

Specifically, the amino resin is cyanamide resin 325 and/or cyanamide resin 303.

The auxiliary agent comprises 0.2-0.4 part of wetting agent, 0.1-0.4 part of defoaming agent and 0.2-0.8 part of thickening agent by mass.

The invention also provides a preparation method of the coating, which comprises the following steps:

preparing the aqueous polyurethane emulsion by adopting the preparation method of the aqueous polyurethane emulsion;

and mixing the aqueous polyurethane emulsion with an auxiliary agent, and adding amino resin.

The following are specific examples.

Example 1

Polyol a in this example is a carbon dioxide copolymer polyol having a number average molecular weight of 3000g/mol and a hydroxyl functionality of 2.

In this example, polyol B is a mixture of polycarbonate diol, polybutylene adipate diol, and polytetrahydrofuran diol. Wherein the polycarbonate diol has a number average molecular weight of 2000g/mol and a hydroxyl functionality of 2; the number average molecular weight of the polybutylene adipate glycol is 3000g/mol, and the hydroxyl functionality is 2; the polytetrahydrofuran diol has a number average molecular weight of 2000g/mol and a hydroxyl functionality of 2.

In this example, the isocyanate was isophorone diisocyanate. The catalyst is an organic bismuth catalyst. The hydrophilic chain extender is dimethylolpropionic acid. The end capping agent is trimethylolpropane. The neutralizing agent is triethylamine. The water is deionized water. The solvent is acetone.

The amino resin in this example is cyanamide resin 325. The auxiliary agent comprises 0.2 part by mass of wetting agent BYK, 0.1 part by mass of defoaming agent BYK024 and 0.5 part by mass of thickening agent Rohm and Haas 8 w.

The preparation method of the aqueous polyurethane emulsion in the embodiment comprises the following steps:

(1) 30 parts by mass of a carbon dioxide copolymer polyol, 30 parts by mass of polybutylene adipate diol, 20 parts by mass of polycarbonate diol and 20 parts by mass of polytetrahydrofuran diol are added into a reaction kettle. Stirring and dehydrating for 2h at the temperature of 100 ℃ in a vacuum environment. Then cooling to normal temperature, adding 35.52 parts by mass of isophorone diisocyanate and 0.1 part by mass of organic bismuth catalyst, heating to 80 ℃, and stirring and reacting for 4 hours at the temperature of 80 ℃. Then cooling to 70 ℃, adding 5.36 parts by mass of dimethylolpropionic acid, stirring and reacting at 70 ℃ for 1 hour, adding 21.44 parts by mass of trimethylolpropane, stirring for 0.2 hour, and then adding 4 parts by mass of triethylamine. Then, the temperature is reduced to 50 ℃, and 100 parts by mass of acetone is added and stirred for 0.5h, so as to obtain the prepolymer.

(2) And (2) adding the prepolymer obtained in the step (1) into 300 parts by mass of deionized water at the temperature of 10 ℃ at the dispersion speed of 1500rpm, and emulsifying for 15min to obtain the aqueous polyurethane emulsion preform.

(3) And (3) removing acetone from the aqueous polyurethane emulsion preform obtained in the step (2) under negative pressure to obtain the aqueous polyurethane emulsion in the embodiment.

In this example, the isocyanate index (0.16 × 2)/(0.01 × 2+0.01 × 2+0.01 × 2+0.04 × 2+0.16 × 3) is 0.5. The solid content of the aqueous polyurethane emulsion was 34.8%.

The preparation method of the coating in the embodiment comprises the following steps:

100 parts by mass of the aqueous polyurethane emulsion is taken, the auxiliary agent is added for dispersion, 35 parts by mass of the cyanamide-based resin 325 is added, and the mixture is uniformly stirred to obtain the coating in the embodiment.

Example 2

In this example, the isocyanate was isophorone diisocyanate. The catalyst is an organic bismuth catalyst. The hydrophilic chain extender is dimethylolbutyric acid. The end capping agent is trimethylolpropane. The neutralizing agent is triethylamine. The water is deionized water. The solvent is acetone.

(1) 20 parts by mass of a carbon dioxide copolymer polyol, 10 parts by mass of polybutylene adipate diol, 40 parts by mass of polycarbonate diol and 30 parts by mass of polytetrahydrofuran diol are added into a reaction kettle. Stirring and dehydrating for 2h at the temperature of 110 ℃ in a vacuum environment. Then cooling to normal temperature, adding 35.52 parts by mass of isophorone diisocyanate and 0.1 part by mass of organic bismuth catalyst, heating to 85 ℃, and stirring and reacting at 85 ℃ for 3 hours. Then cooling to 70 ℃, adding 5.92 parts by mass of dimethylolbutyric acid, stirring and reacting at 70 ℃ for 1 hour, adding 20.6 parts by mass of trimethylolpropane, and continuing stirring for 0.2 hour, and then adding 4 parts by mass of triethylamine. Then, the temperature is reduced to 50 ℃, and 100 parts by mass of acetone is added and stirred for 0.5h to obtain the prepolymer.

(2) And (2) adding the prepolymer obtained in the step (1) into 250 parts by mass of deionized water at the temperature of 10 ℃ at the dispersion speed of 1500rpm, and emulsifying for 15min to obtain the aqueous polyurethane emulsion preform.

(3) And (3) removing acetone from the aqueous polyurethane emulsion preform obtained in the step (2) under negative pressure to obtain the aqueous polyurethane emulsion in the embodiment. In this example, the isocyanate index (0.16 × 2)/(0.007 × 2+0.003 × 2+0.02 × 2+0.015 × 2+0.04 × 2+0.154 × 3) is 0.506. The solid content of the aqueous polyurethane emulsion was 38.9%.

Comparative example 1

In this comparative example polyol A was a polypropylene ether glycol having a number average molecular weight of 3000g/mol and a hydroxyl functionality of 2.

In this comparative example, polyol B is a mixture of polycarbonate diol, polybutylene adipate diol, and polytetrahydrofuran diol. Wherein the polycarbonate diol has a number average molecular weight of 2000g/mol and a hydroxyl functionality of 2; the number average molecular weight of the polybutylene adipate glycol is 3000g/mol, and the hydroxyl functionality is 2; the polytetrahydrofuran diol has a number average molecular weight of 2000g/mol and a hydroxyl functionality of 2.

The isocyanate in this comparative example was isophorone diisocyanate. The catalyst is an organic bismuth catalyst. The hydrophilic chain extender is dimethylolpropionic acid. The end capping agent is trimethylolpropane. The neutralizing agent is triethylamine. The water is deionized water. The solvent is acetone.

The amino resin in this comparative example was cyanotetramine 325. The auxiliary agent comprises 0.2 part by mass of wetting agent BYK, 0.1 part by mass of defoaming agent BYK024 and 0.5 part by mass of thickening agent Rohm and Haas 8 w.

The preparation method of the aqueous polyurethane emulsion in the comparative example comprises the following steps:

(1) 30 parts by mass of polypropylene ether glycol, 30 parts by mass of polybutylene adipate glycol, 20 parts by mass of polycarbonate glycol and 20 parts by mass of polytetrahydrofuran glycol are added to a reaction kettle. Stirring and dehydrating for 2h at the temperature of 100 ℃ in a vacuum environment. Then cooling to normal temperature, adding 35.52 parts by mass of isophorone diisocyanate and 0.1 part by mass of organic bismuth catalyst, heating to 80 ℃, and stirring and reacting for 4 hours at the temperature of 80 ℃. Then cooling to 70 ℃, adding 5.36 parts by mass of dimethylolpropionic acid, stirring and reacting at 70 ℃ for 1 hour, adding 21.44 parts by mass of trimethylolpropane, stirring for 0.2 hour, and then adding 4 parts by mass of triethylamine. Then, the temperature is reduced to 50 ℃, and 100 parts by mass of acetone is added and stirred for 0.5h, so as to obtain the prepolymer.

The preparation method of the coating in the comparative example was:

Comparative example 2

The polyol in this comparative example was a carbon dioxide copolymer polyol having a number average molecular weight of 3000g/mol and a hydroxyl functionality of 2, in 100 parts by mass.

(1) adding 100 parts by mass of carbon dioxide copolymer polyol into a reaction kettle. Stirring and dehydrating for 2h at the temperature of 100 ℃ in a vacuum environment. Then cooling to normal temperature, adding 35.52 parts by mass of isophorone diisocyanate and 0.1 part by mass of organic bismuth catalyst, heating to 80 ℃, and stirring and reacting for 4 hours at the temperature of 80 ℃. Then cooling to 70 ℃, adding 5.36 parts by mass of dimethylolpropionic acid, stirring and reacting at 70 ℃ for 1 hour, adding 21.44 parts by mass of trimethylolpropane, stirring for 0.2 hour, and then adding 4 parts by mass of triethylamine. Then, the temperature is reduced to 50 ℃, and 100 parts by mass of acetone is added and stirred for 0.5h, so as to obtain the prepolymer.

The preparation method of the coating in the comparative example was:

Comparative example 3

The polyol in this comparative example was 100 parts by mass of a polycarbonate diol having a number average molecular weight of 2000g/mol and a hydroxyl functionality of 2.

(1) 100 parts by mass of a polycarbonate diol was added to a reaction vessel. Stirring and dehydrating for 2h at the temperature of 100 ℃ in a vacuum environment. Then cooling to normal temperature, adding 35.52 parts by mass of isophorone diisocyanate and 0.1 part by mass of organic bismuth catalyst, heating to 80 ℃, and stirring and reacting for 4 hours at the temperature of 80 ℃. Then cooling to 70 ℃, adding 5.36 parts by mass of dimethylolpropionic acid, stirring and reacting at 70 ℃ for 1 hour, adding 21.44 parts by mass of trimethylolpropane, stirring for 0.2 hour, and then adding 4 parts by mass of triethylamine. Then, the temperature is reduced to 50 ℃, and 100 parts by mass of acetone is added and stirred for 0.5h, so as to obtain the prepolymer.

The preparation method of the coating in the comparative example was:

Comparative example 4

This comparative example differs from example 1 in that the polytetrahydrofuran diol of example 1 is replaced by a polypropylene ether glycol having a number average molecular weight of 2000g/mol and a hydroxyl functionality of 2. Meanwhile, the coating material in this comparative example was prepared in the same manner as in example 1.

Comparative example 5

This comparative example differs from example 1 in that no amino resin was added in the preparation of the coating. The coating in this comparative example was prepared in the same manner as in example 1.

Comparative example 6

This comparative example is different from example 1 in that, in the preparation of the coating material, the cyanamide resin 325 was replaced with the aqueous isocyanate curing agent 2547, and the mass ratio of the aqueous polyurethane emulsion to the aqueous isocyanate curing agent 2547 was 10: 1. The coating in this comparative example was prepared in the same manner as in example 1.

Comparative example 7

This comparative example differs from example 1 in that no auxiliary was added in the preparation of the coating.

Test example 1

The coatings of examples 1 to 2 and comparative examples 1 to 6 were applied to tinplate in accordance with GB/T1727-1992 "general paint film preparation method", the dry film thickness was controlled to 50 μm, the film was air-dried at room temperature for 1 hour, and the film was baked in an oven at 150 ℃ for 20 minutes. And then respectively carrying out a hardness test, a flexibility test, an adhesion test, an impact resistance test, a water resistance test, an acid resistance test, an alkali resistance test and an alcohol resistance test. The test results are shown in table 1.

The test method comprises the following steps:

(1) pencil hardness was determined according to the national standard GB/T6739-1996 method for measuring film pencil hardness.

(2) Flexibility the flexibility was determined using a spindle tester according to GB/T1731-93 "method for determination of flexibility of paint films", in which the greater the test data the poorer the flexibility.

(3) Adhesion testing was performed according to the cross-cut test of GB/T9286-1998 paint and varnish films.

(4) Impact resistance was measured according to GB/T1732-93 "determination of impact resistance of paint film".

(5) Water resistance according to the immersion boiling water method of the method B in GB/T1733-1993 'paint film water resistance determination', the rust spots are observed for more or less hours.

(6) The acid and alkali resistance is determined according to GB/T9274-1988 color paint and varnish liquid-resistant medium, the first method is adopted, the acid medium is 0.1mol/L sulfuric acid, the alkali medium is 0.1mol/L sodium hydroxide, the condition of the paint film is observed, and how many hours of rust spots appear.

(7) Alcohol resistance test the solvent was 99% alcohol according to GB/T23989-.

Table 1 results of performance testing

Test sample	Hardness of	Flexibility	Adhesion force	Impact resistance	Water resistance/h	Acid resistance/h	Alkali resistance/h	Resisting alcohol/time
									Example 1	5H	1	0	There was no abnormality	100	150	100	100
Example 2	5H	1	0	There was no abnormality	100	150	100	120
									Comparative example 1	2H	4	2	Partially fall off	50	70	60	50
Comparative example 2	4H	2	1	There was no abnormality	60	60	80	80
									Comparative example 3	4H	4	2	Falling off	70	80	90	100
Comparative example 4	2H	2	2	There was no abnormality	50	60	80	50
									Comparative example 5	-	-	-	-	-	-	-	-
Comparative example 6	1H	2	0	There was no abnormality	60	70	80	80
									Comparative example 7	3H	2	4	Partially spalling off	50	60	50	50

Note: representative properties were not detectable.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. An aqueous polyurethane emulsion, which is characterized in that: the adhesive is mainly prepared from the following components in parts by mass:

2. The aqueous polyurethane emulsion according to claim 1, characterized in that: the mass ratio of the polyol A to the polyol B is 1 (1.5-4).

3. The aqueous polyurethane emulsion according to claim 1, characterized in that: the number average molecular weight of the carbon dioxide copolymer polyol is 2000 g/mol-4000 g/mol, and the hydroxyl functionality of the carbon dioxide copolymer polyol is 2-6.

4. The aqueous polyurethane emulsion according to claim 1, characterized in that: the isocyanate is at least one of isophorone diisocyanate, hydrogenated methylene diphenyl diisocyanate and hexamethylene diisocyanate.

5. The aqueous polyurethane emulsion according to claim 1, characterized in that: the catalyst is organic bismuth; and/or the presence of a gas in the gas,

6. A preparation method of aqueous polyurethane emulsion is characterized in that: the method comprises the following steps:

and removing the solvent in the aqueous polyurethane emulsion preform.

7. The method of claim 6, wherein: the solvent is at least one of acetone and butanone.

8. Use of the aqueous polyurethane emulsion according to any one of claims 1 to 5 for the preparation of a coating.

9. A coating, characterized by: the adhesive is mainly prepared from the following components in parts by mass: the aqueous polyurethane emulsion according to any one of claims 1 to 5, which comprises 95 to 105 parts by weight of the aqueous polyurethane emulsion, 10 to 50 parts by weight of the amino resin, and 0.5 to 1.6 parts by weight of the auxiliary.

10. A method of preparing the coating of claim 9, wherein: the method comprises the following steps:

preparing the aqueous polyurethane emulsion by the preparation method of any one of claims 6 to 7;