A method for preparing and using a low temperature cure waterborne amino baking enamel

Abstract

The application discloses a preparation method and application of a low-temperature curing water-based amino baking paint. The baking paint raw materials comprise methanol etherified amino resin, isobutanol etherified amino resin and organic silicon modified water-based polyurethane resin. The preparation method comprises the following steps: S1, preparation of the organic silicon modified water-based polyurethane resin; S2, mixing of the organic silicon modified water-based polyurethane resin and water, addition of adhesion additives and partial neutralizing agents, and stirring to obtain a first paint; S3, mixing of amino resin, leveling agents, wetting agents and defoaming agents, and stirring to obtain a second paint; S4, mixing and stirring of the first paint and the second paint to obtain a third paint; and S5, addition of a curing agent and residual neutralizing agents into the third paint to obtain the water-based amino baking paint. The water-based amino baking paint has good adhesion, good flexibility, excellent water resistance, low curing temperature, low VOC and other excellent performances, and is suitable for application on metal parts.

Description

Technical Field

[0001] This invention belongs to the field of water-based coating preparation technology, specifically relating to a method for preparing and applying a low-temperature curing water-based amino baking paint. Background Technology

[0002] Currently, environmental issues have become a major concern in Chinese society, especially in industries with the greatest environmental impact. The coatings industry, in particular, primarily emits volatile organic compounds (VOCs) during application. Traditional solvent-based coatings generate large amounts of VOCs during application, causing environmental pollution, resource waste, and harm to the health of construction workers. With increasing environmental awareness and increasingly stringent regulations, water-based coatings replacing solvent-based coatings is an inevitable trend. Current technologies require physical or chemical modification of water-based resins to address the performance shortcomings of water-based amino baking varnishes, gradually bringing their performance closer to that of solvent-based amino baking varnishes, in order to further expand the application market for water-based coatings. Summary of the Invention

[0003] This invention provides a method for preparing and applying a low-temperature curing waterborne amino baking paint, which solves the problems of existing waterborne amino baking paints being hard and brittle, having poor adhesion, and requiring high curing temperatures.

[0004] The content of this invention includes:

[0005] A method for preparing a low-temperature curing waterborne amino baking paint includes the following raw material components by weight percentage: 15-25% amino resin, 40-50% waterborne polyurethane resin, 5-10% curing agent, 5-10% neutralizing agent, 1-3% adhesion promoter, 1-2% leveling agent, 1-2% wetting agent, 1-2% defoamer, and 10-20% water; wherein the amino resin is a mixture of methanol-etherified amino resin and isobutanol-etherified amino resin; and the waterborne polyurethane resin is an organosilicon-modified waterborne polyurethane resin; the preparation method includes the following steps:

[0006] S1, Preparation of silicone-modified waterborne polyurethane resin: Weigh appropriate amounts of polydimethylsiloxane, toluene-2,4-diisocyanate, and catalyst, react at a certain temperature for a period of time, cool down, add chain extender N-isopropylethylenediamine, heat up, and continue to react for a period of time to obtain the product;

[0007] S2, mix silicone-modified waterborne polyurethane resin and water, add adhesion promoter and part of neutralizer, stir to obtain the first paint;

[0008] S3, mix amino resin, leveling agent, wetting agent and defoamer, stir to obtain the second paint;

[0009] S4. Mix the first paint and the second paint, and stir at high speed with a mixer to obtain the third paint;

[0010] S5, add curing agent and remaining neutralizing agent to the third paint, adjust the pH to 7.0-8.0, and obtain water-based amino baking paint.

[0011] Furthermore, the low-temperature curing waterborne amino baking paint comprises the following raw material components by weight percentage: 15% methanol etherified amino resin, 5% isobutanol etherified amino resin, 45% organosilicon modified waterborne polyurethane resin, 8% curing agent, 10% neutralizing agent, 2% adhesion promoter, 1% leveling agent, 1% wetting agent, 1% defoamer, and 12% water.

[0012] Furthermore, the mass ratio of the methanol etherified amino resin to the isobutanol etherified amino resin is 3:1-1.5.

[0013] Furthermore, the curing agent is an isocyanate curing agent; or, the molecular weight of the polydimethylsiloxane is 1000-2000.

[0014] Furthermore, the adhesion promoter is a phosphate ester adhesion promoter.

[0015] Furthermore, in step S1, the reaction is carried out at a certain temperature for a certain period of time, namely 3.5 hours at 75-80°C.

[0016] Furthermore, in step S1, the temperature is lowered to 50°C and then raised to 75-80°C.

[0017] Furthermore, in step S1, the reaction continues for a period of time, which is 3 hours.

[0018] Furthermore, the amount of neutralizing agent used in step S2 is 50-60%.

[0019] A low-temperature curing waterborne amino baking paint prepared by the above method is applied to metal parts.

[0020] The beneficial effects of this invention are:

[0021] 1) This application uses a mixture of two amino resins - methanol etherified amino resin and isobutanol etherified amino resin - and silicone-modified waterborne polyester resin to effectively improve the problems of poor adhesion, hardness and brittleness, and high curing temperature of single amino resins. This effectively improves the performance of waterborne amino baking paint. The waterborne amino baking paint of this application has excellent properties such as good adhesion, good flexibility, good water resistance, low curing temperature, and low VOC.

[0022] 2) Modifying waterborne polyurethane resin with silicone resin can improve the water resistance and corrosion resistance of waterborne polyurethane coatings;

[0023] 3) Processing the resin in stages helps to improve the crosslinking environment of the resin and further improve the mechanical properties of the coating.

[0024] 4) The use of low-temperature opening amino resin and low-temperature unsealing isocyanate curing agent realizes the low-temperature curing of water-based amino baking paint, with a curing temperature of <130℃, low energy consumption, and is more conducive to energy conservation and environmental protection. Detailed Implementation

[0025] Example 1

[0026] Weigh the following raw material components by weight percentage: 15g methanol etherified amino resin, 5g isobutanol etherified amino resin, 45g organosilicon modified waterborne polyurethane resin, 8g isocyanate curing agent, 10g neutralizer, 2g phosphate ester adhesion promoter, 1g leveling agent, 1g wetting agent, 1g defoamer, and 12g water.

[0027] Prepare according to the following steps:

[0028] S1, Preparation of silicone-modified waterborne polyurethane resin: Weigh 100.0g of polydimethylsiloxane with a molecular weight of 1000, 17.4g of toluene-2,4-diisocyanate, and 0.2g of dibutyltin dilaurate catalyst. React at 80℃ for 3.5h, cool to 50℃, add 0.2g of chain extender N-isopropylethylenediamine, heat to 80℃, and continue to react for 3h to obtain the product;

[0029] S2, mix organosilicon-modified waterborne polyurethane resin and water, add phosphate ester adhesion promoter and 50% neutralizer, stir at 400 r / min for 20 min to obtain the first paint;

[0030] S3, mix methanol etherified amino resin, isobutanol etherified amino resin, leveling agent, wetting agent, and defoamer, and stir in a mixer at 400 r / min for 20 min to obtain the second paint;

[0031] S4. Mix the first paint and the second paint, and stir at high speed of 800 r / min for 5 min to obtain the third paint;

[0032] S5, add isocyanate curing agent and remaining neutralizing agent to the third paint, and adjust the pH to 7.0-8.0 to obtain water-based amino baking paint.

[0033] Example 2

[0034] 10g methanol etherified amino resin, 5g isobutanol etherified amino resin, 50g organosilicon modified waterborne polyurethane resin, 8g isocyanate curing agent, 10g neutralizer, 2g phosphate ester adhesion promoter, 1g leveling agent, 1g wetting agent, 1g defoamer, and 12g water.

[0035] The rest is the same as in Example 1.

[0036] Example 3

[0037] Weigh the following raw material components by weight percentage: 15g methanol etherified amino resin, 5g isobutanol etherified amino resin, 45g organosilicon modified waterborne polyurethane resin, 8g isocyanate curing agent, 10g neutralizer, 2g phosphate ester adhesion promoter, 1g leveling agent, 1g wetting agent, 1g defoamer, and 12g water.

[0038] Prepare according to the following steps:

[0039] S1, Preparation of silicone-modified waterborne polyurethane resin: Weigh 200.0 g of polydimethylsiloxane with a molecular weight of 2000, 17.4 g of toluene-2,4-diisocyanate, and 0.2 g of dibutyltin dilaurate catalyst. React at 75°C for 3.5 h, cool to 50°C, add 0.2 g of chain extender N-isopropylethylenediamine, heat to 75°C, and continue to react for 3.5 h to obtain the product;

[0040] S2, mix organosilicon-modified waterborne polyurethane resin and water, add phosphate ester adhesion promoter and 50% neutralizer, stir at 500 r / min for 20 min to obtain the first paint;

[0041] S3, mix methanol etherified amino resin, isobutanol etherified amino resin, leveling agent, wetting agent and defoamer, and stir in a mixer at 500 r / min for 20 min to obtain the second paint;

[0042] S4. Mix the first paint and the second paint, and stir at a high speed of 700 r / min for 5 min to obtain the third paint;

[0043] S5, add isocyanate curing agent and remaining neutralizing agent to the third paint, and adjust the pH to 7.0-8.0 to obtain water-based amino baking paint.

[0044] Comparative Example 1

[0045] Weigh the following raw material components by weight percentage: 20g n-butanol etherified amino resin, 45g organosilicon modified waterborne polyurethane resin, 8g isocyanate curing agent, 10g neutralizer, 2g phosphate ester adhesion promoter, 1g leveling agent, 1g wetting agent, 1g defoamer, and 12g water.

[0046] The rest is the same as in Example 1.

[0047] Comparative Example 2

[0048] The unmodified waterborne polyurethane resin was used instead of the silicone-modified waterborne polyurethane resin, and the rest was the same as in Example 1.

[0049] Comparative Example 3

[0050] The content of each raw material component is the same as in Example 1.

[0051] Prepare according to the following steps:

[0052] S1, Preparation of silicone-modified waterborne polyurethane resin: Weigh 100.0g of polydimethylsiloxane with a molecular weight of 1000, 17.4g of toluene-2,4-diisocyanate, and 0.2g of dibutyltin dilaurate catalyst. React at 80℃ for 3.5h, cool to 50℃, add 0.2g of chain extender N-isopropylethylenediamine, heat to 80℃, and continue to react for 3h to obtain the product;

[0053] S2, mix the above raw materials, stir at 800r / min for 5min, adjust the pH to 7.0-8.0, and obtain water-based amino baking paint.

[0054] The coatings obtained in Examples 1-3 and Comparative Examples 1-3 were sprayed according to relevant methods, and the performance of the obtained coatings was tested. The test results are shown in Table 1.

[0055] Table 1 Performance Test Results

[0056]

[0057] Examples 1-3, using the formulation of this application, yielded paint coatings with good performance in all aspects. In Comparative Example 1, n-butanol etherified amino resin was used instead of the mixture of methanol etherified amino resin and isobutanol etherified amino resin, resulting in a coating with increased curing temperature and slightly poorer water resistance. In Comparative Example 2, unmodified waterborne polyurethane resin was used, resulting in a significant decrease in water resistance and impact resistance. In Comparative Example 3, the resin was not treated in steps, leading to a significant decrease in the adhesion, impact resistance, and salt water resistance of the obtained coating.

[0058] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0059] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A method for preparing a low-temperature curing waterborne amino baking paint, characterized in that, The raw material components include the following weight percentages: 15-25% amino resin, 40-50% waterborne polyurethane resin, 5-10% curing agent, 5-10% neutralizing agent, 1-3% adhesion promoter, 1-2% leveling agent, 1-2% wetting agent, 1-2% defoamer, and 10-20% water; wherein the amino resin is a mixture of methanol etherified amino resin and isobutanol etherified amino resin; The mass ratio of the methanol etherified amino resin to the isobutanol etherified amino resin is 3:1-1.5; The curing agent is an isocyanate curing agent; The adhesion promoter is a phosphate ester adhesion promoter; The waterborne polyurethane resin is an organosilicon-modified waterborne polyurethane resin; the preparation method includes the following steps: S1, Preparation of silicone-modified waterborne polyurethane resin: Weigh appropriate amounts of polydimethylsiloxane, toluene-2,4-diisocyanate, and catalyst, react at a certain temperature for a period of time, cool down, add chain extender N-isopropylethylenediamine, heat up, and continue to react for a period of time to obtain the product; S2, mix silicone-modified waterborne polyurethane resin and water, add adhesion promoter and part of neutralizer, stir to obtain the first paint; S3, mix amino resin, leveling agent, wetting agent and defoamer, stir to obtain the second paint; S4. Mix the first paint and the second paint, and stir at high speed with a mixer to obtain the third paint; S5, add curing agent and remaining neutralizing agent to the third paint, adjust the pH to 7.0-8.0, and obtain water-based amino baking paint; the molecular weight of the polydimethylsiloxane is 1000-2000.

2. The preparation method according to claim 1, characterized in that, The raw material components include the following weight percentages: 15% methanol etherified amino resin, 5% isobutanol etherified amino resin, 45% organosilicon modified waterborne polyurethane resin, 8% curing agent, 10% neutralizing agent, 2% adhesion promoter, 1% leveling agent, 1% wetting agent, 1% defoamer, and 12% water.

3. The preparation method according to claim 1, characterized in that, In step S1, the reaction is carried out at a certain temperature for a period of time, which is 3.5 hours at 75-80℃.

4. The preparation method according to claim 1, characterized in that, In step S1, the temperature is lowered to 50°C and then raised to 75-80°C.

5. The preparation method according to claim 3 or 4, characterized in that, In step S1, the reaction continues for a period of time, which is 3 hours.

6. The preparation method according to claim 3 or 4, characterized in that, The amount of neutralizing agent used in step S2 is 50-60%.

7. A low-temperature curing waterborne amino baking paint prepared by any one of claims 1-6 is applied to metal parts.

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