Water-resistant and high-adhesion two-component waterborne polyurethane coating and preparation method thereof

Abstract

The invention relates to the technical field of metal surface water-based coatings, and particularly discloses a water-resistant and high-adhesion two-component water-based polyurethane coating and a preparation method thereof. The invention relates to a water-resistant and high-adhesion double-component waterborne polyurethane coating which comprises a component A and a component B, the component A is prepared from the following components in parts by weight: 60 to 70 parts of modified acrylic resin; 6-8 parts of a cosolvent; 2-4 parts of solvent oil; 2-4 parts of a filler; 10 parts of water; 1.5 to 2.5 parts of wax slurry; the component B comprises the following components in parts by weight: 50-70 parts of an isocyanate curing agent; 40 parts of propylene glycol diethanol ester; the modified acrylic resin is prepared from the following raw materials: methyl 3, 4-dimethoxybenzoate, a mixed monomer, an initiator, a solvent and a neutralizer. The water-resistant and high-adhesion two-component waterborne polyurethane coating has the advantages of being high in water resistance and still good in adhesion after being soaked in water, and can be better suitable for the surface of a steel bridge in a water environment.

Description

Technical Field

[0001] The present application relates to the technical field of water-based coatings for metal surfaces, and more specifically, to a water-resistant, high-adhesion two-component water-based polyurethane coating and a preparation method thereof. Background Art

[0002] Steel structure bridges are widely used due to their advantages such as high strength, convenient manufacturing, fast construction speed and short construction period, but their easy corrosion has brought great losses to the construction industry. Water-based anti-corrosion coatings are one of the most economical and reasonable methods of anti-corrosion measures for steel structure bridges. In addition, for the environmental issues that people are increasingly concerned about, water-based anti-corrosion coatings can largely avoid the pollution caused by solvent volatilization to the environment.

[0003] Since the bottom of the steel beam is in a long-term humid and sealed environment, it is generally only about 3m away from the water surface, so the paint attached to the surface is easy to fall off; especially when the paint is a water-based acrylic film-forming substance, because it contains more hydroxyl groups and has excellent water absorption, moisture can easily penetrate, pass through the paint film and accumulate under the coating, which reduces the adhesion between the coating and the metal body, causing the paint film to peel off, thereby losing its protective effect on the steel bridge. Summary of the invention

[0004] In order to improve the water resistance of water-based coatings and reduce the effect of moisture on the adhesion of paint films, so that the paint films can better protect steel bridges in water environments, the present application provides a water-resistant, high-adhesion two-component water-based polyurethane coating and a preparation method thereof.

[0005] In the first aspect, the present application provides a water-resistant, high-adhesion two-component waterborne polyurethane coating, which adopts the following technical solution: A water-resistant, high-adhesion two-component waterborne polyurethane coating, comprising component A and component B; The component A comprises the following components in parts by weight: 60-70 parts of modified acrylic resin; 6-8 parts of cosolvent; 2-4 parts of solvent oil; 2-4 parts of filler; 10 parts of water; 1.5-2.5 parts of wax slurry; the component B comprises the following components in parts by weight: 50-70 parts of isocyanate curing agent; 40 parts of propylene glycol diethanol ester; The raw materials for preparing the modified acrylic resin include: methyl 3,4-dimethoxybenzoate, mixed monomers, an initiator, a solvent and a neutralizer.

[0006] By adopting the above technical solution: the acid monomer content in the acrylic resin determines its acid value. The larger the acid value, the easier it is to dissolve in water, but the poorer the water resistance. Therefore, in order to ensure the water solubility of the resin, the water resistance of the paint film is inevitably reduced. The modified acrylic resin prepared in this application is measured to have good water solubility, and when the paint film made with it as raw material is tested for water resistance, it can be maintained for more than 200 minutes to start whitening, and wrinkles only after 96 hours. The adhesion after immersion in water for 2 hours is still maintained at level three, which is far better than the performance of the paint film obtained using commercially available water-based acrylic resin.

[0007] The reason may be that the introduction of methyl 3,4-dimethoxybenzoate and the mixed monomers polymerize under the action of the initiator, and the rigid group benzene ring contained in methyl 3,4-dimethoxybenzoate shields the hydrophilic group, thereby improving the water resistance of the paint film. The polar groups contained in it can enhance the wettability of the copolymer on the metal surface and improve adhesion. Therefore, it not only has good water resistance, but also can ensure that the paint film plays a long-term protective role on the surface of the steel bridge in the water environment.

[0008] Optionally, the weight ratio of the methyl 3,4-dimethoxybenzoate to the mixed monomer is 0.1-0.14:1.

[0009] By adopting the above technical solution: when the weight ratio of methyl 3,4-dimethoxybenzoate to the mixed monomer is within the above range, the water resistance and water immersion adhesion of the paint film are both better.

[0010] Optionally, the preparation method of the modified acrylic resin is: Add methyl 3,4-dimethoxybenzoate, mixed monomers and initiator to the solvent, stir and mix, keep warm to react, add a neutralizer to adjust the pH of the system, add water, stir and mix, heat and react to obtain the product.

[0011] By adopting the above technical solution: compared with other monomers, such as epoxy acrylate, methyl 3,4-dimethoxybenzoate is not easy to form gel, so that the reaction can proceed normally, and thus the modified epoxy resin can be prepared by a one-step method.

[0012] Optionally, the mixed monomer is a mixture of methyl methacrylate, butyl acrylate, methacrylic acid, and β-hydroxyethyl methacrylate.

[0013] Optionally, the mixed monomer consists of the following components in weight percentage: Methyl methacrylate 40-50%; Butyl acrylate 35-40%; Methacrylic acid 5-10% β-Hydroxyethyl Methacrylate Remainder.

[0014] By adopting the above technical scheme: methyl methacrylate improves the hardness and adhesion of the paint film, butyl acrylate improves the flexibility of the paint film, methacrylic acid improves the solvent resistance of the paint film, and β-hydroxyethyl methacrylate improves the strength of the paint film, etc., through the reaction of the above monomers and controlling the amount of the above monomers, the modified acrylic resin obtained can effectively improve the comprehensive performance of the paint film.

[0015] Optionally, the solvent is ethanol or isopropanol.

[0016] Optionally, the initiator is azobisisobutyronitrile.

[0017] Optionally, the co-solvent consists of butyl ether and dipropylene glycol butyl ether in a weight ratio of 4:3.

[0018] Optionally, the weight ratio of component A to component B is 6:1.

[0019] In a second aspect, the present application provides a method for preparing a water-resistant, high-adhesion two-component waterborne polyurethane coating, using the following technical solution: A method for preparing a water-resistant, high-adhesion two-component waterborne polyurethane coating comprises the following steps: S1, blending modified acrylic resin, cosolvent, solvent oil, filler, water and wax slurry, grinding to obtain component A; S2, mixing isocyanate curing agent and propylene glycol diethanol to obtain component B; S3, mix component A and component B to obtain.

[0020] By adopting the above technical solution: the process steps are fewer, simple and efficient, which is conducive to the industrial scale-up of coating preparation, and the prepared coating has excellent water resistance and strong adhesion to the surface of the metal substrate in the water environment, and can be used to protect the surface of steel bridges in the water environment.

[0021] In summary, this application has the following beneficial effects: 1. The present application adopts a modified acrylic resin, which is polymerized with methyl 3,4-dimethoxybenzoate and a mixed monomer under the action of an initiator. The rigid group benzene ring contained in methyl 3,4-dimethoxybenzoate shields the hydrophilic group to improve the water resistance of the paint film, and the polar group contained in it can enhance the wettability of the copolymer on the metal surface and improve the adhesion. Therefore, it not only has good water resistance, but also can ensure that the paint film plays a long-term protective role on the steel surface in a water environment; 2. The modified acrylic resin in the present application is not easy to form gel during the preparation process, so that the reaction can proceed normally, and therefore can be prepared by a one-step method, which can simplify the process; 3. The preparation method of the present application has fewer process steps and is simple and efficient, which is conducive to the industrial scale-up of the preparation of coatings. The prepared coating has excellent water resistance and strong adhesion to the surface of the metal substrate in water environment, and can be used to protect the surface of steel bridges in water environment. DETAILED DESCRIPTION

[0022] The present application is further described in detail below in conjunction with the examples. The sources of the components are as follows, except for the following special instructions, the components are commercially available: Dispersant, brand is BASF, model 4290 dispersant; Rutile titanium dioxide, sourced from Zhengzhou Xinqishun Chemical Products Co., Ltd., model R-996; Water-based polyamide wax paste, brand: Hemmings, model: THIXATROL P2100W; Tego-4100, branded as Tego; Tego-450, branded as Tego; Isocyanate curing agent, brand is Asahi Chemical, model TLA-100.

[0023] Preparation Example 1 A modified acrylic resin is prepared by the following steps: Heat 10 kg of solvent (isopropanol) to 85°C, add 0.8 kg of methyl 3,4-dimethoxybenzoate, mixed monomers (4 kg of methyl methacrylate, 4 kg of butyl acrylate, 1 kg of methacrylic acid, 1 kg of β-hydroxyethyl methacrylate), and 1 kg of initiator (azobisisobutyronitrile), stir and mix, keep warm for 2.5 hours, cool to 50°C, add 25 wt% ammonia water to adjust the pH of the system to 7, let stand for 10 minutes, add water and stir and mix for 10 minutes, heat to 90°C and react for 40 minutes to obtain the product.

[0024] Preparation Example 2 A modified acrylic resin is prepared by the following steps: Heat 10 kg of solvent (isopropanol) to 85°C, add 0.8 kg of methyl 3,4-dimethoxybenzoate, mixed monomers (4.5 kg of methyl methacrylate, 3.8 kg of butyl acrylate, 0.75 kg of methacrylic acid, 0.95 kg of β-hydroxyethyl methacrylate), 1 kg of initiator (azobisisobutyronitrile), stir and mix, keep warm for 2.5 hours, cool to 50°C, add 25 wt% ammonia water to adjust the pH of the system to 7.5, let stand for 10 minutes, add water and stir and mix for 10 minutes, heat to 90°C and react for 40 minutes to obtain the product.

[0025] Preparation Example 3 A modified acrylic resin is prepared by the following steps: Heat 10 kg of solvent (ethanol) to 85°C, add 0.8 kg of methyl 3,4-dimethoxybenzoate, mixed monomers (5 kg of methyl methacrylate, 3.5 kg of butyl acrylate, 0.5 kg of methacrylic acid, 1 kg of β-hydroxyethyl methacrylate), 1 kg of initiator (azobisisobutyronitrile), stir and mix, keep warm for 2.5 hours, cool to 50°C, add 25 wt% ammonia water to adjust the pH of the system to 8, let stand for 10 minutes, add water and stir and mix for 10 minutes, heat to 90°C and react for 40 minutes to obtain the product.

[0026] Preparation Example 4-6 A modified acrylic resin, which is different from Preparation Example 2 in that the amount of methyl 3,4-dimethoxybenzoate is different, specifically as follows: Preparation Example 4: The weight ratio of methyl 3,4-dimethoxybenzoate to the mixed monomer is 0.1:1.

[0027] Preparation Example 5: The weight ratio of methyl 3,4-dimethoxybenzoate to the mixed monomers is 0.12:1.

[0028] Preparation Example 6: The weight ratio of methyl 3,4-dimethoxybenzoate to the mixed monomers is 0.14:1.

[0029] Comparative Preparation Example 1 An acrylic resin, which is different from Preparation Example 2 in that methyl 3,4-dimethoxybenzoate is not added.

[0030] Comparative Preparation Example 2 An acrylic resin, which is different from Preparation Example 2 in that an equal amount of epoxy acrylate is used instead of methyl 3,4-dimethoxybenzoate.

[0031] Epoxy acrylate, brand is Germany's Allnex, model EBECRYL 3700.

[0032] Water solubility test of modified acrylic resin The modified acrylic resins of the preparation examples and the comparative preparation examples were tested according to the national standard GB / T 1721-1979 to observe whether there was flocculent precipitation. If there was no flocculent precipitation, the water solubility was better.

[0033] Test results: The modified acrylic resins of Preparation Example and Comparative Preparation Example 1 have no flocculent precipitates, and the modified acrylic resin of Comparative Preparation Example 2 has no flocculent precipitates.

[0034] According to the water solubility test results, the modified acrylic resin of the present application has good water solubility and can be well applied to water-based coating systems; while the modified acrylic resin prepared by epoxy acrylate in Comparative Preparation Example 2 has poor water solubility. The reason for this may be that epoxy acrylate copolymerizes to form gel during the reaction process, which hinders the normal progress of the reaction.

[0035] Example 1 A water-resistant, high-adhesion two-component waterborne polyurethane coating is prepared by the following steps: S1, 20kg of modified acrylic resin (prepared in Preparation Example 1), 1kg of dispersant, 7.5kg of phthalocyanine green pigment, 2kg of rutile titanium dioxide, 1.5kg of water-based polyamide wax slurry, and 5kg of water were blended, stirred and mixed at 500rpm for 20min, and ground to a fineness of <15μm (the temperature was controlled not to exceed 70°C during the grinding process); then 40kg of modified acrylic resin (prepared in Preparation Example 1), cosolvent (3kg of butyl ether, 3kg of dipropylene glycol butyl ether), 2kg of solvent oil (100# aromatic hydrocarbon), 0.5kg of neutralizer N,N-dimethylethylamine, 0.3kg of Tego-4100, 0.2kg of Tego-450, and 5kg of water were added, and stirred at 500rpm for 20min to obtain component A; S2, blending 50 kg of isocyanate curing agent and 40 kg of propylene glycol diethanol ester, stirring and mixing at a speed of 300 rpm for 20 min to obtain component B; S3, blend 60kg of component A and 10kg of component B, and stir and mix at 300rpm for 20min to obtain.

[0036] It should be noted that the two-component waterborne polyurethane anti-corrosion coating of the present application can be stored with components A and B stored separately during storage, and can be mixed in proportion during use.

[0037] Example 2 A water-resistant, high-adhesion two-component waterborne polyurethane coating is prepared by the following steps: S1, 25kg of modified acrylic resin (prepared in Preparation Example 1), 1kg of dispersant, 7.5kg of phthalocyanine green pigment, 3kg of rutile titanium dioxide, 2kg of water-based polyamide wax slurry, and 5kg of water were blended, stirred and mixed at 500rpm for 20min, and ground to a fineness of <15μm (the temperature was controlled not to exceed 70°C during the grinding process); then 40kg of modified acrylic resin (prepared in Preparation Example 1), cosolvent (4kg of butyl ether, 3kg of dipropylene glycol butyl ether), 3kg of solvent oil (100# aromatic hydrocarbon), 0.5kg of neutralizer N,N-dimethylethylamine, 0.3kg of Tego-4100, 0.2kg of Tego-450, and 5kg of water were added, and stirred at 500rpm for 20min to obtain component A; S2, blending 60 kg of isocyanate curing agent and 40 kg of propylene glycol diethanol ester, stirring and mixing at a speed of 300 rpm for 20 min to obtain component B; S3, blend 60kg of component A and 10kg of component B, and stir and mix at 300rpm for 20min to obtain.

[0038] Example 3 A water-resistant, high-adhesion two-component waterborne polyurethane coating is prepared by the following steps: S1, 30kg of modified acrylic resin (prepared in Preparation Example 1), 1kg of dispersant, 7.5kg of phthalocyanine green pigment, 4kg of rutile titanium dioxide, 2.5kg of water-based polyamide wax slurry, and 5kg of water were blended, stirred and mixed at 500rpm for 20min, and ground to a fineness of <15μm (the temperature was controlled not to exceed 70°C during the grinding process); then 40kg of modified acrylic resin (prepared in Preparation Example 1), cosolvent (4kg of butyl ether, 4kg of dipropylene glycol butyl ether), 4kg of solvent oil (100# aromatic hydrocarbon), 0.5kg of neutralizer N,N-dimethylethylamine, 0.3kg of Tego-4100, 0.2kg of Tego-450, and 16kg of water were added, and stirred at 500rpm for 20min to obtain component A; S2, blending 70 kg of isocyanate curing agent and 40 kg of propylene glycol diethanol ester, stirring and mixing at a speed of 300 rpm for 20 min to obtain component B; S3, blend 60kg of component A and 10kg of component B, and stir and mix at 300rpm for 20min to obtain.

[0039] Comparative Example 1 A water-resistant, high-adhesion two-component waterborne polyurethane coating is prepared by the following steps: S1, 15kg of modified acrylic resin (prepared in Preparation Example 1), 1kg of dispersant, 7.5kg of phthalocyanine green pigment, 3kg of rutile titanium dioxide, 2kg of water-based polyamide wax slurry, and 5kg of water were mixed, stirred and mixed at 500rpm for 20min, and ground to a fineness of <15μm (the temperature was controlled not to exceed 70°C during the grinding process); then 40kg of modified acrylic resin (prepared in Preparation Example 1), cosolvent (4kg of butyl ether, 3kg of dipropylene glycol butyl ether), 3kg of solvent oil (100# aromatic hydrocarbon), 0.5kg of neutralizer N,N-dimethylethylamine, 0.3kg of Tego-4100, 0.2kg of Tego-450, and 5kg of water were added, and stirred at 500rpm for 20min to obtain component A; S2, blending 60 kg of isocyanate curing agent and 40 kg of propylene glycol diethanol ester, stirring and mixing at a speed of 300 rpm for 20 min to obtain component B; S3, blend 60kg of component A and 10kg of component B, and stir and mix at 300rpm for 20min to obtain.

[0040] Comparative Example 2 A water-resistant, high-adhesion two-component waterborne polyurethane coating is prepared by the following steps: S1, 35kg of modified acrylic resin (prepared in Preparation Example 1), 1kg of dispersant, 7.5kg of phthalocyanine green pigment, 3kg of rutile titanium dioxide, 2kg of water-based polyamide wax slurry, and 5kg of water were blended, stirred and mixed at 500rpm for 20min, and ground to a fineness of <15μm (the temperature was controlled not to exceed 70°C during the grinding process); then 40kg of modified acrylic resin (prepared in Preparation Example 1), cosolvent (4kg of butyl ether, 3kg of dipropylene glycol butyl ether), 3kg of solvent oil (100# aromatic hydrocarbon), 0.5kg of neutralizer N,N-dimethylethylamine, 0.3kg of Tego-4100, 0.2kg of Tego-450, and 5kg of water were added, and stirred at 500rpm for 20min to obtain component A; S2, blending 60 kg of isocyanate curing agent and 40 kg of propylene glycol diethanol ester, stirring and mixing at a speed of 300 rpm for 20 min to obtain component B; S3, blend 60kg of component A and 10kg of component B, and stir and mix at 300rpm for 20min to obtain.

[0041] Comparative Example 3 A water-resistant, high-adhesion two-component waterborne polyurethane coating, which differs from Example 1 in that an equal amount of waterborne acrylic resin is used instead of modified acrylic resin.

[0042] The water-based acrylic resin was obtained from Zhejiang Jinzhili Chemical Co., Ltd., model WZ-03.

[0043] Example 4-8, Comparative Example 4-5 A water-resistant, high-adhesion two-component waterborne polyurethane coating, which differs from Example 1 in that the use of the modified acrylic resin is referred to the following table, but the amount of the modified acrylic resin remains unchanged.

[0044] Table 1 Usage of modified acrylic resin in Examples 4-8 and Comparative Examples 4-5 Example 4 5 6 7 8 Preparation example of modified acrylic resin 2 3 4 5 6 Comparative Example 4 5 \ \ \ Comparative preparation example of modified acrylic resin 1 2 \ \ \ Performance Testing The following performance tests were conducted on the two-component waterborne polyurethane anticorrosive coatings prepared in the examples and comparative examples, and the test results are recorded in Table 2.

[0045] Detection Methods 1. Water resistance: Tested in accordance with national standard GB / T 1733-1993.

[0046] 2. Water immersion adhesion: The test panels that have been immersed in water for 2 hours in the above water resistance test process shall be tested according to the national standard GB / Tl720-1979.

[0047] Table 2 Performance test results Referring to the data in Table 2, in Examples 1-3, the prepared coatings have better water resistance because the modified acrylic resin prepared in Preparation Example 1 is used. The coatings start to turn white locally at about 230 minutes, turn white completely at about 290 minutes, and wrinkle after 96 hours. The adhesion after immersion in water for 2 hours still reaches Level 3. In Comparative Example 3, an equal amount of commercially available water-based acrylic resin is used instead of the modified acrylic resin. The prepared coatings start to turn white locally at 150 minutes, turn white completely at 180 minutes, and wrinkle after 48 hours. The water resistance cannot meet the higher use requirements. The difference between Comparative Example 4 and Example 2 is that methyl 3,4-dimethoxybenzoate is not added in the preparation process of the modified acrylic resin, and the performance is similar to that of Comparative Example 2. The difference between Comparative Example 5 and Example 2 is that an equal amount of epoxy acrylate is used instead of methyl 3,4-dimethoxybenzoate in the preparation process of the modified acrylic resin, and the performance of the prepared coating is lower than that of Example 2. This shows that only when the modified acrylic resin is prepared with methyl 3,4-dimethoxybenzoate as raw material can the water resistance of the coating be greatly improved, and it has long-term excellent adhesion in water environments, and can be better used to protect the surface of steel bridges.

[0048] The difference between Example 4-5 and Example 2 is that the ratio of each monomer in the mixed monomer is different, and Example 4 is a preferred example.

[0049] The difference between Example 6-8 and Example 4 is that the amount of methyl 3,4-dimethoxybenzoate used is different. When the amount is within the range of Example 6-8, the performance of the prepared coating is optimal.

[0050] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A water-resistant, high-adhesion two-component waterborne polyurethane coating, characterized in that: It includes component A and component B; The component A comprises the following components in parts by weight: 60-70 parts of modified acrylic resin; 6-8 parts of cosolvent; 2-4 parts of solvent oil; 2-4 parts of filler; 10 parts of water; 1.5-2.5 parts of wax slurry; the component B comprises the following components in parts by weight: 50-70 parts of isocyanate curing agent; 40 parts of propylene glycol diethanol ester; The raw materials for preparing the modified acrylic resin include: methyl 3,4-dimethoxybenzoate, mixed monomers, an initiator, a solvent and a neutralizer.

2. A water-resistant, high-adhesion two-component waterborne polyurethane coating according to claim 1, characterized in that: The weight ratio of the methyl 3,4-dimethoxybenzoate to the mixed monomer is 0.1-0.14:

1.

3. The water-resistant, high-adhesion two-component waterborne polyurethane coating according to claim 1, characterized in that: The preparation method of the modified acrylic resin is: Add methyl 3,4-dimethoxybenzoate, mixed monomers and initiator to the solvent, stir and mix, keep warm to react, add a neutralizer to adjust the pH of the system, add water, stir and mix, heat and react to obtain the product.

4. A water-resistant, high-adhesion two-component waterborne polyurethane coating according to claim 3, characterized in that: The mixed monomer is a mixture of methyl methacrylate, butyl acrylate, methacrylic acid and beta-hydroxyethyl methacrylate.

5. The water-resistant, high-adhesion two-component waterborne polyurethane coating according to claim 4, characterized in that: The mixed monomers are composed of the following components in percentage by weight: composition: Methyl methacrylate 40-50%; Butyl acrylate 35-40%; Methacrylic acid 5-10% β-Hydroxyethyl Methacrylate Remainder.

6. The water-resistant, high-adhesion two-component waterborne polyurethane coating according to claim 1, characterized in that: The solvent is ethanol or isopropanol.

7. The water-resistant, high-adhesion two-component waterborne polyurethane coating according to claim 1, characterized in that: The initiator is azobisisobutyronitrile.

8. The water-resistant, high-adhesion two-component waterborne polyurethane coating according to claim 1, characterized in that: The cosolvent is composed of butyl ether and dipropylene glycol butyl ether in a weight ratio of 4:

3.

9. The water-resistant, high-adhesion two-component waterborne polyurethane coating according to claim 1, characterized in that: The weight ratio of component A to component B is 6:

1.

10. A method for preparing a two-component waterborne polyurethane coating according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1, blending modified acrylic resin, cosolvent, solvent oil, filler and water wax slurry, grinding to obtain component A; S2, mixing isocyanate curing agent and propylene glycol diethanol to obtain component B; S3, mix component A and component B to obtain.

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