CN115433482A - A kind of preparation method of waterborne polyurethane water-resistant coating - Google Patents

Abstract

The invention discloses a preparation method of a water-based polyurethane water-resistant coating, belongs to the technical field of preparation of anticorrosive coatings, solves the problem of insufficient water resistance of the existing water-based polyurethane coating in anticorrosive property, and adopts the following specific technical scheme: the preparation method comprises two steps of preparation of a water-based coating and preparation of an anticorrosive coating, wherein the coating takes water-based polyurethane as a main matrix, the first step comprises preparation of a prepolymer of an emulsion and the water-based emulsion, and the second step is preparation of the anticorrosive coating.

Description

A kind of preparation method of waterborne polyurethane water-resistant coating

technical field

The invention belongs to the technical field of anticorrosion coating preparation, and in particular relates to a preparation method of a polymer material and a water-based polyurethane coating.

Background technique

Polyurethane coatings are prepolymers containing isocyanate groups formed by addition polymerization of oligomer diols, diisocyanates, etc., and are mixed with catalysts, leveling agents, defoamers, solvents, etc., and processed through mixing and other processes Made of one-component polyurethane waterproof coating. The coating film has beautiful appearance and good decorative properties, and has been widely used in buildings, bridges and concrete because of its good flexibility, impact resistance, corrosion resistance, chemical resistance and excellent low temperature resistance. Engineering and other fields.

Compared with traditional solvent-based coatings, water-based coatings are more environmentally friendly, safer, less polluting, have lower raw material costs, and are easy to use, so they have great application prospects. Water-based polyurethane coatings are a large category of water-based coatings. Its structural feature is the introduction of hydrophilic groups into the molecular chain of polyurethane, making it self-emulsifying. The existence of hydrophilic groups has an impact on the surface properties and long-term stability of the coating. At the same time, the water-based coating has a long curing time, low film-forming strength, and insufficient water resistance, which restrict its application range.

Contents of the invention

In order to solve the technical problem of insufficient water resistance in the anti-corrosion performance of existing water-based polyurethane coatings, the present invention provides a method for preparing water-based polyurethane water-resistant coatings. The invention constructs multiple cross-linked structures inside the coating through multi-component compound modification , improve its water resistance, thereby improving its ability to protect metal against corrosion.

In order to achieve the above object, the technical solution adopted in the present invention is: a method for preparing a water-based polyurethane water-resistant coating, comprising two steps of preparing an aqueous polyurethane emulsion and preparing an anti-corrosion coating;

1. The specific steps for the preparation of water-based polyurethane emulsion are as follows:

1.1. Preparation of water-based paint prepolymer: take oligomer polyol and dehydrate pretreatment under heating conditions in a vacuum drying oven to obtain oligomer diol; add catalyst, and then under inert gas conditions, 30-45 parts The oligomer diol reacts with 30-40 parts of diisocyanate at 70°C until the oligomer diol is completely reacted; add 2-6 parts of hydrophilic chain extender, react at 80°C for 2.5h, and continue to add 1-10 Parts of crosslinking agent were reacted for 1 hour, and organic solvent was added to reduce the viscosity of the system, and the viscosity of the system was reduced to the point where the mechanical stirring could operate normally, so as to obtain the water-based polyurethane prepolymer;

1.2. Preparation of water-based polyurethane emulsion: add 0.05-0.15 parts of polymerization inhibitor and 5-25 parts of end-capping agent to water-based polyurethane prepolymer, react at 60°C for 3 hours, cool down to 50°C, add 2-6 parts to neutralize Adding deionized water to the end-blocking prepolymer so that the solid content of the emulsion accounts for 30% of the mass fraction of the total emulsion, stirring at a high speed until the mixture is emulsified and dispersed, and distilling off the reactant under reduced pressure. organic solvents to finally obtain water-based polyurethane emulsions.

2. The specific steps of anti-corrosion coating preparation are as follows:

2.1. Drying: add the photoinitiator accounting for 4wt% of the end-capped prepolymer into the water-based polyurethane emulsion and mix evenly, place it in a polytetrafluoroethylene mold, let it stand at room temperature for two days, and fully dry;

2.2. Light-curing and cross-linking: Place the fully dried PTFE mold under a 200-1000W ultraviolet lamp, irradiate for 15 minutes to cure and cross-link, take it out after film formation, and obtain a water-resistant coating with multiple cross-linking and anti-corrosion functions.

The oligomer diol is one or any combination of polyester polyols, polyether polyols, polyolefin polyols, vegetable oil polyols, and epoxy resin polyols with a molecular weight of 500-3000.

The diisocyanate is one or any combination of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and hexamethylene diisocyanate.

The hydrophilic chain extender is one or any combination of dimethylolpropionic acid, dimethylolbutyric acid, sodium ethylenediaminoethanesulfonate, N-methyldiethanolamine, and triethanolamine.

The catalyst is an organotin reagent or a tertiary amine catalyst.

The crosslinking agent is one or any combination of trimethylolpropane and castor oil.

The polymerization inhibitor is one or any combination of p-methoxyphenol and hydroquinone.

The end-capping agent is one or any combination of hydroxyethyl methacrylate, hydroxypropyl methacrylate, pentaerythritol diacrylate, and pentaerythritol triacrylate.

The neutralizing agent is one or any combination of triethylamine, ammonia water, and sodium hydroxide.

The photoinitiator is one or any combination of photoinitiator 2959, benzophenone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and the photoinitiator and the end-blocking agent in the emulsion The mass proportion of the prepolymer is 1%~5%.

Compared with the prior art, the present invention has specific beneficial effects embodied in:

1. The present invention uses acrylate and castor oil to simultaneously modify the polyurethane chain structure, and the two complement each other, so that the storage stability of the water-based paint is improved.

2. The present invention uses acrylates with double bonds to cap chain polyurethane molecules, and cures them by ultraviolet light, so that the double bonds can be cross-linked, increasing the degree of internal cross-linking of the coating, and improving the protection of the coating against corrosion of metals. nature, and high production efficiency.

3. The water-based polyurethane coating finally prepared by the present invention also has excellent performance in terms of water resistance and mechanical strength.

Description of drawings

Fig. 1 is the reaction flow chart of the present invention.

Fig. 2 is a comparison table of the surface hardness, adhesion and transmittance of the water-resistant coating prepared in the present invention.

Fig. 3 is a comparison chart of the tensile properties of the water-resistant coating prepared in the present invention.

Fig. 4 is a comparison chart of the water absorption rate of the water-resistant coating prepared in the present invention.

Fig. 5 is a comparison diagram of the water contact angle of the water-resistant coating prepared in the present invention.

Fig. 6 is a polarization curve diagram of the water-resistant coating prepared by the present invention.

detailed description

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

As shown in Figure 1, a kind of preparation method of waterborne polyurethane water-resistant coating comprises two steps of waterborne polyurethane emulsion preparation and anticorrosion coating preparation;

Embodiment one

1. Preparation of water-based polyurethane emulsion

I, the preparation of waterborne polyurethane prepolymer: the polycarbonate diol (PCDL-1000) of 13.43mmol carries out dehydration pretreatment, then adds 25mmol parts of isophorone diisocyanate, and adds catalytic amount dibutyltin dilaurate, React at 70°C for 2 h; add 5.8 mmol parts of dimethylolpropionic acid (DMPA) and react at 80°C for 2.5 h.

II. Preparation of emulsion; prepare 11.5 mmol of pentaerythritol triacrylate, add it to the prepolymer for reaction, and react at 60 ° C for 3 h; then cool down to 50 ° C, add 5.8 mmol of triethylamine for neutralization reaction, The reaction time was 0.5 h; 55.48 ml of deionized water was added and the mechanical stirring speed was increased to 1000 r/min for emulsification for 20 min; finally, a water-based polyurethane emulsion was obtained.

(2) Preparation of photocured polyurethane film

1. Drying: add photocuring agent 2959, which accounts for 4% of the solid content of the emulsion, into the prepared emulsion, mix evenly, place it in a polytetrafluoroethylene mold, and let it stand at room temperature for 48h;

II. Photocuring: Place the finished emulsion under a 35w UV lamp for photocuring for 15 minutes, take it out after film formation, and obtain the final UV-cured waterborne polyurethane coating.

Finally, a waterborne polyurethane coating with 0% castor oil content was successfully prepared.

Embodiment two

1. Preparation of water-based polyurethane emulsion

I, the preparation of waterborne polyurethane prepolymer: the polycarbonate diol (PCDL-1000) of 11.3mmol carries out dehydration pretreatment, then adds 25mmol parts of isophorone diisocyanate, and adds catalytic amount dibutyltin dilaurate, React at 70°C for 2 h; add 5.8mmol parts of dimethylolpropionic acid (DMPA) and react at 80°C for 2.5h; then add 1.42mmol parts of castor oil and react at 70°C for 1 h; and add 2ml of acetone reduces the viscosity of the reaction system to the point where the mechanical stirring can operate normally.

II. Preparation of emulsion; prepare 11.5 mmol of pentaerythritol triacrylate, add it to the prepolymer for reaction, and react at 60 ° C for 3 h; then cool down to 50 ° C, add 5.8 mmol of triethylamine for neutralization reaction, The reaction time is 0.5 h; 51.54 ml of deionized water is added and the mechanical stirring speed is raised to 1000 r/min for emulsification for 20 min; finally, the acetone in the system is removed to obtain a water-based polyurethane emulsion.

(2) Preparation of photocured polyurethane film

I Drying: add light curing agent 2959, which accounts for 4% of the solid content of the emulsion, into the prepared emulsion, mix evenly, place it in a polytetrafluoroethylene mold, and let it stand at room temperature for 48 hours;

II Photocuring: Place the finished emulsion under a 35w UV lamp for photocuring for 15 minutes, take it out after film formation, and obtain the final UV-cured waterborne polyurethane coating.

Finally, a waterborne polyurethane coating with 2% castor oil was successfully prepared.

Embodiment three

1. Preparation of water-based polyurethane emulsion

I, the preparation of waterborne polyurethane prepolymer: the polycarbonate diol (PCDL-1000) of 9.45mmol carries out dehydration pretreatment, then adds 25mmol parts of isophorone diisocyanate, and adds catalytic amount dibutyltin dilaurate, React at 70°C for 2 h; add 5.8mmol parts of dimethylolpropionic acid (DMPA) and react at 80°C for 2.5h; then add 2.65mmol parts of castor oil and react at 70°C for 1 h; and add 2ml of acetone reduces the viscosity of the reaction system to the point where the mechanical stirring can operate normally.

II. Preparation of emulsion; prepare 11.5 mmol of pentaerythritol triacrylate, add it to the prepolymer for reaction, and react at 60 ° C for 3 h; then cool down to 50 ° C, add 5.8 mmol of triethylamine for neutralization reaction, The reaction time was 0.5 h; 50 ml of deionized water was added and the mechanical stirring speed was increased to 1000 r/min for emulsification for 20 min; finally, the acetone in the system was removed to obtain a water-based polyurethane emulsion.

(2) Preparation of photocured polyurethane film

I Drying: add light curing agent 2959, which accounts for 4% of the solid content of the emulsion, into the prepared emulsion, mix evenly, place it in a polytetrafluoroethylene mold, and let it stand at room temperature for 48 hours;

II Photocuring: Place the finished emulsion under a 35w UV lamp for photocuring for 15 minutes, take it out after film formation, and obtain the final UV-cured waterborne polyurethane coating.

Finally, a waterborne polyurethane coating with 4% castor oil was successfully prepared.

Embodiment four

1. Preparation of water-based polyurethane emulsion

I, the preparation of waterborne polyurethane prepolymer: the polycarbonate diol (PCDL-1000) of 6.4mmol carries out dehydration pretreatment, then adds 25mmol parts of isophorone diisocyanate, and adds catalytic amount dibutyltin dilaurate, React at 70 °C for 2 h; add 5.8 mmol parts of dimethylolpropionic acid (DMPA) and react at 80 °C for 2.5 h; add 4.69 mmol parts of castor oil and react at 70 °C for 1 h; and add 2ml of acetone reduces the viscosity of the reaction system to the point where the mechanical stirring can operate normally.

II. Preparation of emulsion; prepare 11.5 mmol of pentaerythritol triacrylate, add it to the prepolymer for reaction, and react at 60 ° C for 3 h; then cool down to 50 ° C, add 5.8 mmol of triethylamine for neutralization reaction, The reaction time was 0.5 h; 50 ml of deionized water was added and the mechanical stirring speed was increased to 1000 r/min for emulsification for 20 min; finally, the acetone in the system was removed to obtain a water-based polyurethane emulsion.

(2) Preparation of photocured polyurethane film

I Drying: add light curing agent 2959, which accounts for 4% of the solid content of the emulsion, into the prepared emulsion, mix evenly, place it in a polytetrafluoroethylene mold, and let it stand at room temperature for 48 hours;

II Photocuring: Place the finished emulsion under a 35w UV lamp for photocuring for 15 minutes, take it out after film formation, and obtain the final UV-cured waterborne polyurethane coating.

Finally, a waterborne polyurethane coating with 8% castor oil content was successfully prepared.

Use a universal tensile testing machine to test the tensile properties of the photocured film prepared according to GB/T1040.3-2006, and the results are shown in Figure 3; the film was cut into 20×20 mm samples and placed in deionized Soak in water for 24 h and 48 h, use filter paper to remove the surface moisture, measure the difference in mass before and after the film to calculate the water absorption, and evaluate the water resistance of the film, the results are shown in 4; the prepared coating was tested for water contact angle, the results are shown in Fig. 5; and carry out surface hardness, adhesion and transparency test to the prepared coating, the results are shown in Figure 2; the polarization curve test is carried out to the coating of 2%, 4% castor oil content, the result is shown in Figure 6 Show.

The prepared film was tested for performance, and the results are shown in Figure 1, showing that the prepared castor oil-based waterborne polyurethane anti-corrosion coating has good performance, especially when the castor oil content is 4%, the performance of the coating is the most excellent, The adhesion level to metal is 5B, the water absorption rate is 5%, the water contact angle is 90°, the corrosion current density is 1.063*10 ^-7 A/cm ^-2 , and the protection efficiency of Q235 steel plate substrate can reach 99.05%.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included within the scope of the present invention .

Claims (10)

1. A preparation method of a water-based polyurethane water-resistant coating is characterized by comprising two steps of preparing a water-based polyurethane emulsion and preparing an anticorrosive coating;

1. the preparation method of the waterborne polyurethane emulsion comprises the following specific steps:

1.1, preparation of a water-based paint prepolymer: dehydrating and pretreating oligomer polyol in a vacuum drying oven under the heating condition to obtain oligomer dihydric alcohol; adding 0.1-0.2 part of catalyst, and then reacting 30-45 parts of oligomer dihydric alcohol with 30-40 parts of diisocyanate at 70 ℃ under the condition of inert gas until the oligomer dihydric alcohol completely reacts; adding 2-6 parts of hydrophilic chain extender, reacting for 2.5 hours at 80 ℃, continuously adding 1-10 parts of cross-linking agent, reacting for 1 hour, and adding an organic solvent to reduce the viscosity of the system to obtain a waterborne polyurethane prepolymer;

1.2, preparing the aqueous polyurethane emulsion: adding 0.05 to 0.15 part of polymerization inhibitor and 5 to 25 parts of end-capping reagent into the waterborne polyurethane prepolymer, reacting for 3 hours at 60 ℃, cooling to 50 ℃, and adding 2 to 6 parts of neutralizer for reaction to obtain an end-capped prepolymer; adding deionized water into the end-capped prepolymer, stirring until the mixture is emulsified and dispersed, and distilling under reduced pressure to remove the organic solvent in the reactants to finally obtain the waterborne polyurethane emulsion;

2. the preparation method of the anticorrosive coating comprises the following specific steps:

2.1, drying: adding a photoinitiator accounting for 4wt% of the end-capped prepolymer into the aqueous polyurethane emulsion, uniformly mixing, placing the mixture into a polytetrafluoroethylene mold, and fully drying at room temperature;

2.2, photocuring and crosslinking: and (3) placing the fully dried polytetrafluoroethylene mold under an ultraviolet lamp of 200-1000W for photocuring, and taking out the mold after film forming to obtain the waterproof coating.

2. The method for preparing the water-resistant coating of waterborne polyurethane as claimed in claim 1, wherein the oligomer diol is one or more of polyester polyol, polyether polyol, polyolefin polyol, vegetable oil polyol and epoxy resin polyol with molecular weight of 500-3000.

3. The method for preparing the water-resistant coating of the waterborne polyurethane as claimed in claim 1, wherein the diisocyanate is one or a combination of any more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate and hexamethylene diisocyanate.

4. The method for preparing the water-resistant coating of the waterborne polyurethane as claimed in claim 1, wherein the hydrophilic chain extender is one or a combination of any more of dimethylolpropionic acid, dimethylolbutyric acid, sodium ethylene diamine ethanesulfonate, N-methyldiethanolamine and triethanolamine.

5. The method for preparing the water-resistant coating of the waterborne polyurethane as claimed in claim 1, wherein the catalyst is an organotin reagent or a tertiary amine catalyst.

6. The method for preparing the water-resistant coating of the waterborne polyurethane as claimed in claim 1, wherein the cross-linking agent is one or a combination of any more of trimethylolpropane and castor oil.

7. The method for preparing the water-resistant coating of the waterborne polyurethane as claimed in claim 1, wherein the polymerization inhibitor is one or a combination of any more of p-methoxyphenol and hydroquinone.

8. The method of claim 1, wherein the end-capping agent is one or a combination of more of hydroxyethyl methacrylate, hydroxypropyl methacrylate, pentaerythritol diacrylate and pentaerythritol triacrylate.

9. The method for preparing the water-resistant coating of the waterborne polyurethane as claimed in claim 1, wherein the neutralizing agent is one or a combination of any more of triethylamine, ammonia water and sodium hydroxide.

10. The method for preparing the water-resistant coating of the waterborne polyurethane as claimed in claim 1, wherein the photoinitiator is one or a combination of more of 2959, benzophenone and 2,4, 6-trimethylbenzoyldiphenylphosphine oxide, and the mass ratio of the photoinitiator to the blocked prepolymer in the emulsion is 1-5%.

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